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 You can set your program's working directory with the command
2061 @kbd{set cwd}. If you do not set any working directory with this
2062 command, your program will inherit @value{GDBN}'s working directory if
2063 native debugging, or the remote server's working directory if remote
2064 debugging. @xref{Working Directory, ,Your Program's Working
2067 @item The @emph{standard input and output.}
2068 Your program normally uses the same device for standard input and
2069 standard output as @value{GDBN} is using. You can redirect input and output
2070 in the @code{run} command line, or you can use the @code{tty} command to
2071 set a different device for your program.
2072 @xref{Input/Output, ,Your Program's Input and Output}.
2075 @emph{Warning:} While input and output redirection work, you cannot use
2076 pipes to pass the output of the program you are debugging to another
2077 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2081 When you issue the @code{run} command, your program begins to execute
2082 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2083 of how to arrange for your program to stop. Once your program has
2084 stopped, you may call functions in your program, using the @code{print}
2085 or @code{call} commands. @xref{Data, ,Examining Data}.
2087 If the modification time of your symbol file has changed since the last
2088 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2089 table, and reads it again. When it does this, @value{GDBN} tries to retain
2090 your current breakpoints.
2095 @cindex run to main procedure
2096 The name of the main procedure can vary from language to language.
2097 With C or C@t{++}, the main procedure name is always @code{main}, but
2098 other languages such as Ada do not require a specific name for their
2099 main procedure. The debugger provides a convenient way to start the
2100 execution of the program and to stop at the beginning of the main
2101 procedure, depending on the language used.
2103 The @samp{start} command does the equivalent of setting a temporary
2104 breakpoint at the beginning of the main procedure and then invoking
2105 the @samp{run} command.
2107 @cindex elaboration phase
2108 Some programs contain an @dfn{elaboration} phase where some startup code is
2109 executed before the main procedure is called. This depends on the
2110 languages used to write your program. In C@t{++}, for instance,
2111 constructors for static and global objects are executed before
2112 @code{main} is called. It is therefore possible that the debugger stops
2113 before reaching the main procedure. However, the temporary breakpoint
2114 will remain to halt execution.
2116 Specify the arguments to give to your program as arguments to the
2117 @samp{start} command. These arguments will be given verbatim to the
2118 underlying @samp{run} command. Note that the same arguments will be
2119 reused if no argument is provided during subsequent calls to
2120 @samp{start} or @samp{run}.
2122 It is sometimes necessary to debug the program during elaboration. In
2123 these cases, using the @code{start} command would stop the execution
2124 of your program too late, as the program would have already completed
2125 the elaboration phase. Under these circumstances, either insert
2126 breakpoints in your elaboration code before running your program or
2127 use the @code{starti} command.
2131 @cindex run to first instruction
2132 The @samp{starti} command does the equivalent of setting a temporary
2133 breakpoint at the first instruction of a program's execution and then
2134 invoking the @samp{run} command. For programs containing an
2135 elaboration phase, the @code{starti} command will stop execution at
2136 the start of the elaboration phase.
2138 @anchor{set exec-wrapper}
2139 @kindex set exec-wrapper
2140 @item set exec-wrapper @var{wrapper}
2141 @itemx show exec-wrapper
2142 @itemx unset exec-wrapper
2143 When @samp{exec-wrapper} is set, the specified wrapper is used to
2144 launch programs for debugging. @value{GDBN} starts your program
2145 with a shell command of the form @kbd{exec @var{wrapper}
2146 @var{program}}. Quoting is added to @var{program} and its
2147 arguments, but not to @var{wrapper}, so you should add quotes if
2148 appropriate for your shell. The wrapper runs until it executes
2149 your program, and then @value{GDBN} takes control.
2151 You can use any program that eventually calls @code{execve} with
2152 its arguments as a wrapper. Several standard Unix utilities do
2153 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2154 with @code{exec "$@@"} will also work.
2156 For example, you can use @code{env} to pass an environment variable to
2157 the debugged program, without setting the variable in your shell's
2161 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2165 This command is available when debugging locally on most targets, excluding
2166 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2168 @kindex set startup-with-shell
2169 @anchor{set startup-with-shell}
2170 @item set startup-with-shell
2171 @itemx set startup-with-shell on
2172 @itemx set startup-with-shell off
2173 @itemx show startup-with-shell
2174 On Unix systems, by default, if a shell is available on your target,
2175 @value{GDBN}) uses it to start your program. Arguments of the
2176 @code{run} command are passed to the shell, which does variable
2177 substitution, expands wildcard characters and performs redirection of
2178 I/O. In some circumstances, it may be useful to disable such use of a
2179 shell, for example, when debugging the shell itself or diagnosing
2180 startup failures such as:
2184 Starting program: ./a.out
2185 During startup program terminated with signal SIGSEGV, Segmentation fault.
2189 which indicates the shell or the wrapper specified with
2190 @samp{exec-wrapper} crashed, not your program. Most often, this is
2191 caused by something odd in your shell's non-interactive mode
2192 initialization file---such as @file{.cshrc} for C-shell,
2193 $@file{.zshenv} for the Z shell, or the file specified in the
2194 @samp{BASH_ENV} environment variable for BASH.
2196 @anchor{set auto-connect-native-target}
2197 @kindex set auto-connect-native-target
2198 @item set auto-connect-native-target
2199 @itemx set auto-connect-native-target on
2200 @itemx set auto-connect-native-target off
2201 @itemx show auto-connect-native-target
2203 By default, if not connected to any target yet (e.g., with
2204 @code{target remote}), the @code{run} command starts your program as a
2205 native process under @value{GDBN}, on your local machine. If you're
2206 sure you don't want to debug programs on your local machine, you can
2207 tell @value{GDBN} to not connect to the native target automatically
2208 with the @code{set auto-connect-native-target off} command.
2210 If @code{on}, which is the default, and if @value{GDBN} is not
2211 connected to a target already, the @code{run} command automaticaly
2212 connects to the native target, if one is available.
2214 If @code{off}, and if @value{GDBN} is not connected to a target
2215 already, the @code{run} command fails with an error:
2219 Don't know how to run. Try "help target".
2222 If @value{GDBN} is already connected to a target, @value{GDBN} always
2223 uses it with the @code{run} command.
2225 In any case, you can explicitly connect to the native target with the
2226 @code{target native} command. For example,
2229 (@value{GDBP}) set auto-connect-native-target off
2231 Don't know how to run. Try "help target".
2232 (@value{GDBP}) target native
2234 Starting program: ./a.out
2235 [Inferior 1 (process 10421) exited normally]
2238 In case you connected explicitly to the @code{native} target,
2239 @value{GDBN} remains connected even if all inferiors exit, ready for
2240 the next @code{run} command. Use the @code{disconnect} command to
2243 Examples of other commands that likewise respect the
2244 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2245 proc}, @code{info os}.
2247 @kindex set disable-randomization
2248 @item set disable-randomization
2249 @itemx set disable-randomization on
2250 This option (enabled by default in @value{GDBN}) will turn off the native
2251 randomization of the virtual address space of the started program. This option
2252 is useful for multiple debugging sessions to make the execution better
2253 reproducible and memory addresses reusable across debugging sessions.
2255 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2256 On @sc{gnu}/Linux you can get the same behavior using
2259 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2262 @item set disable-randomization off
2263 Leave the behavior of the started executable unchanged. Some bugs rear their
2264 ugly heads only when the program is loaded at certain addresses. If your bug
2265 disappears when you run the program under @value{GDBN}, that might be because
2266 @value{GDBN} by default disables the address randomization on platforms, such
2267 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2268 disable-randomization off} to try to reproduce such elusive bugs.
2270 On targets where it is available, virtual address space randomization
2271 protects the programs against certain kinds of security attacks. In these
2272 cases the attacker needs to know the exact location of a concrete executable
2273 code. Randomizing its location makes it impossible to inject jumps misusing
2274 a code at its expected addresses.
2276 Prelinking shared libraries provides a startup performance advantage but it
2277 makes addresses in these libraries predictable for privileged processes by
2278 having just unprivileged access at the target system. Reading the shared
2279 library binary gives enough information for assembling the malicious code
2280 misusing it. Still even a prelinked shared library can get loaded at a new
2281 random address just requiring the regular relocation process during the
2282 startup. Shared libraries not already prelinked are always loaded at
2283 a randomly chosen address.
2285 Position independent executables (PIE) contain position independent code
2286 similar to the shared libraries and therefore such executables get loaded at
2287 a randomly chosen address upon startup. PIE executables always load even
2288 already prelinked shared libraries at a random address. You can build such
2289 executable using @command{gcc -fPIE -pie}.
2291 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2292 (as long as the randomization is enabled).
2294 @item show disable-randomization
2295 Show the current setting of the explicit disable of the native randomization of
2296 the virtual address space of the started program.
2301 @section Your Program's Arguments
2303 @cindex arguments (to your program)
2304 The arguments to your program can be specified by the arguments of the
2306 They are passed to a shell, which expands wildcard characters and
2307 performs redirection of I/O, and thence to your program. Your
2308 @code{SHELL} environment variable (if it exists) specifies what shell
2309 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2310 the default shell (@file{/bin/sh} on Unix).
2312 On non-Unix systems, the program is usually invoked directly by
2313 @value{GDBN}, which emulates I/O redirection via the appropriate system
2314 calls, and the wildcard characters are expanded by the startup code of
2315 the program, not by the shell.
2317 @code{run} with no arguments uses the same arguments used by the previous
2318 @code{run}, or those set by the @code{set args} command.
2323 Specify the arguments to be used the next time your program is run. If
2324 @code{set args} has no arguments, @code{run} executes your program
2325 with no arguments. Once you have run your program with arguments,
2326 using @code{set args} before the next @code{run} is the only way to run
2327 it again without arguments.
2331 Show the arguments to give your program when it is started.
2335 @section Your Program's Environment
2337 @cindex environment (of your program)
2338 The @dfn{environment} consists of a set of environment variables and
2339 their values. Environment variables conventionally record such things as
2340 your user name, your home directory, your terminal type, and your search
2341 path for programs to run. Usually you set up environment variables with
2342 the shell and they are inherited by all the other programs you run. When
2343 debugging, it can be useful to try running your program with a modified
2344 environment without having to start @value{GDBN} over again.
2348 @item path @var{directory}
2349 Add @var{directory} to the front of the @code{PATH} environment variable
2350 (the search path for executables) that will be passed to your program.
2351 The value of @code{PATH} used by @value{GDBN} does not change.
2352 You may specify several directory names, separated by whitespace or by a
2353 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2354 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2355 is moved to the front, so it is searched sooner.
2357 You can use the string @samp{$cwd} to refer to whatever is the current
2358 working directory at the time @value{GDBN} searches the path. If you
2359 use @samp{.} instead, it refers to the directory where you executed the
2360 @code{path} command. @value{GDBN} replaces @samp{.} in the
2361 @var{directory} argument (with the current path) before adding
2362 @var{directory} to the search path.
2363 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2364 @c document that, since repeating it would be a no-op.
2368 Display the list of search paths for executables (the @code{PATH}
2369 environment variable).
2371 @kindex show environment
2372 @item show environment @r{[}@var{varname}@r{]}
2373 Print the value of environment variable @var{varname} to be given to
2374 your program when it starts. If you do not supply @var{varname},
2375 print the names and values of all environment variables to be given to
2376 your program. You can abbreviate @code{environment} as @code{env}.
2378 @kindex set environment
2379 @anchor{set environment}
2380 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2381 Set environment variable @var{varname} to @var{value}. The value
2382 changes for your program (and the shell @value{GDBN} uses to launch
2383 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2384 values of environment variables are just strings, and any
2385 interpretation is supplied by your program itself. The @var{value}
2386 parameter is optional; if it is eliminated, the variable is set to a
2388 @c "any string" here does not include leading, trailing
2389 @c blanks. Gnu asks: does anyone care?
2391 For example, this command:
2398 tells the debugged program, when subsequently run, that its user is named
2399 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2400 are not actually required.)
2402 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2403 which also inherits the environment set with @code{set environment}.
2404 If necessary, you can avoid that by using the @samp{env} program as a
2405 wrapper instead of using @code{set environment}. @xref{set
2406 exec-wrapper}, for an example doing just that.
2408 Environment variables that are set by the user are also transmitted to
2409 @command{gdbserver} to be used when starting the remote inferior.
2410 @pxref{QEnvironmentHexEncoded}.
2412 @kindex unset environment
2413 @anchor{unset environment}
2414 @item unset environment @var{varname}
2415 Remove variable @var{varname} from the environment to be passed to your
2416 program. This is different from @samp{set env @var{varname} =};
2417 @code{unset environment} removes the variable from the environment,
2418 rather than assigning it an empty value.
2420 Environment variables that are unset by the user are also unset on
2421 @command{gdbserver} when starting the remote inferior.
2422 @pxref{QEnvironmentUnset}.
2425 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2426 the shell indicated by your @code{SHELL} environment variable if it
2427 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2428 names a shell that runs an initialization file when started
2429 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2430 for the Z shell, or the file specified in the @samp{BASH_ENV}
2431 environment variable for BASH---any variables you set in that file
2432 affect your program. You may wish to move setting of environment
2433 variables to files that are only run when you sign on, such as
2434 @file{.login} or @file{.profile}.
2436 @node Working Directory
2437 @section Your Program's Working Directory
2439 @cindex working directory (of your program)
2440 Each time you start your program with @code{run}, the inferior will be
2441 initialized with the current working directory specified by the
2442 @kbd{set cwd} command. If no directory has been specified by this
2443 command, then the inferior will inherit @value{GDBN}'s current working
2444 directory as its working directory if native debugging, or it will
2445 inherit the remote server's current working directory if remote
2450 @cindex change inferior's working directory
2451 @anchor{set cwd command}
2452 @item set cwd @r{[}@var{directory}@r{]}
2453 Set the inferior's working directory to @var{directory}, which will be
2454 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2455 argument has been specified, the command clears the setting and resets
2456 it to an empty state. This setting has no effect on @value{GDBN}'s
2457 working directory, and it only takes effect the next time you start
2458 the inferior. The @file{~} in @var{directory} is a short for the
2459 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2460 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2461 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2464 You can also change @value{GDBN}'s current working directory by using
2465 the @code{cd} command.
2469 @cindex show inferior's working directory
2471 Show the inferior's working directory. If no directory has been
2472 specified by @kbd{set cwd}, then the default inferior's working
2473 directory is the same as @value{GDBN}'s working directory.
2476 @cindex change @value{GDBN}'s working directory
2478 @item cd @r{[}@var{directory}@r{]}
2479 Set the @value{GDBN} working directory to @var{directory}. If not
2480 given, @var{directory} uses @file{'~'}.
2482 The @value{GDBN} working directory serves as a default for the
2483 commands that specify files for @value{GDBN} to operate on.
2484 @xref{Files, ,Commands to Specify Files}.
2485 @xref{set cwd command}
2489 Print the @value{GDBN} working directory.
2492 It is generally impossible to find the current working directory of
2493 the process being debugged (since a program can change its directory
2494 during its run). If you work on a system where @value{GDBN} is
2495 configured with the @file{/proc} support, you can use the @code{info
2496 proc} command (@pxref{SVR4 Process Information}) to find out the
2497 current working directory of the debuggee.
2500 @section Your Program's Input and Output
2505 By default, the program you run under @value{GDBN} does input and output to
2506 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2507 to its own terminal modes to interact with you, but it records the terminal
2508 modes your program was using and switches back to them when you continue
2509 running your program.
2512 @kindex info terminal
2514 Displays information recorded by @value{GDBN} about the terminal modes your
2518 You can redirect your program's input and/or output using shell
2519 redirection with the @code{run} command. For example,
2526 starts your program, diverting its output to the file @file{outfile}.
2529 @cindex controlling terminal
2530 Another way to specify where your program should do input and output is
2531 with the @code{tty} command. This command accepts a file name as
2532 argument, and causes this file to be the default for future @code{run}
2533 commands. It also resets the controlling terminal for the child
2534 process, for future @code{run} commands. For example,
2541 directs that processes started with subsequent @code{run} commands
2542 default to do input and output on the terminal @file{/dev/ttyb} and have
2543 that as their controlling terminal.
2545 An explicit redirection in @code{run} overrides the @code{tty} command's
2546 effect on the input/output device, but not its effect on the controlling
2549 When you use the @code{tty} command or redirect input in the @code{run}
2550 command, only the input @emph{for your program} is affected. The input
2551 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2552 for @code{set inferior-tty}.
2554 @cindex inferior tty
2555 @cindex set inferior controlling terminal
2556 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2557 display the name of the terminal that will be used for future runs of your
2561 @item set inferior-tty [ @var{tty} ]
2562 @kindex set inferior-tty
2563 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2564 restores the default behavior, which is to use the same terminal as
2567 @item show inferior-tty
2568 @kindex show inferior-tty
2569 Show the current tty for the program being debugged.
2573 @section Debugging an Already-running Process
2578 @item attach @var{process-id}
2579 This command attaches to a running process---one that was started
2580 outside @value{GDBN}. (@code{info files} shows your active
2581 targets.) The command takes as argument a process ID. The usual way to
2582 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2583 or with the @samp{jobs -l} shell command.
2585 @code{attach} does not repeat if you press @key{RET} a second time after
2586 executing the command.
2589 To use @code{attach}, your program must be running in an environment
2590 which supports processes; for example, @code{attach} does not work for
2591 programs on bare-board targets that lack an operating system. You must
2592 also have permission to send the process a signal.
2594 When you use @code{attach}, the debugger finds the program running in
2595 the process first by looking in the current working directory, then (if
2596 the program is not found) by using the source file search path
2597 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2598 the @code{file} command to load the program. @xref{Files, ,Commands to
2601 The first thing @value{GDBN} does after arranging to debug the specified
2602 process is to stop it. You can examine and modify an attached process
2603 with all the @value{GDBN} commands that are ordinarily available when
2604 you start processes with @code{run}. You can insert breakpoints; you
2605 can step and continue; you can modify storage. If you would rather the
2606 process continue running, you may use the @code{continue} command after
2607 attaching @value{GDBN} to the process.
2612 When you have finished debugging the attached process, you can use the
2613 @code{detach} command to release it from @value{GDBN} control. Detaching
2614 the process continues its execution. After the @code{detach} command,
2615 that process and @value{GDBN} become completely independent once more, and you
2616 are ready to @code{attach} another process or start one with @code{run}.
2617 @code{detach} does not repeat if you press @key{RET} again after
2618 executing the command.
2621 If you exit @value{GDBN} while you have an attached process, you detach
2622 that process. If you use the @code{run} command, you kill that process.
2623 By default, @value{GDBN} asks for confirmation if you try to do either of these
2624 things; you can control whether or not you need to confirm by using the
2625 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2629 @section Killing the Child Process
2634 Kill the child process in which your program is running under @value{GDBN}.
2637 This command is useful if you wish to debug a core dump instead of a
2638 running process. @value{GDBN} ignores any core dump file while your program
2641 On some operating systems, a program cannot be executed outside @value{GDBN}
2642 while you have breakpoints set on it inside @value{GDBN}. You can use the
2643 @code{kill} command in this situation to permit running your program
2644 outside the debugger.
2646 The @code{kill} command is also useful if you wish to recompile and
2647 relink your program, since on many systems it is impossible to modify an
2648 executable file while it is running in a process. In this case, when you
2649 next type @code{run}, @value{GDBN} notices that the file has changed, and
2650 reads the symbol table again (while trying to preserve your current
2651 breakpoint settings).
2653 @node Inferiors and Programs
2654 @section Debugging Multiple Inferiors and Programs
2656 @value{GDBN} lets you run and debug multiple programs in a single
2657 session. In addition, @value{GDBN} on some systems may let you run
2658 several programs simultaneously (otherwise you have to exit from one
2659 before starting another). In the most general case, you can have
2660 multiple threads of execution in each of multiple processes, launched
2661 from multiple executables.
2664 @value{GDBN} represents the state of each program execution with an
2665 object called an @dfn{inferior}. An inferior typically corresponds to
2666 a process, but is more general and applies also to targets that do not
2667 have processes. Inferiors may be created before a process runs, and
2668 may be retained after a process exits. Inferiors have unique
2669 identifiers that are different from process ids. Usually each
2670 inferior will also have its own distinct address space, although some
2671 embedded targets may have several inferiors running in different parts
2672 of a single address space. Each inferior may in turn have multiple
2673 threads running in it.
2675 To find out what inferiors exist at any moment, use @w{@code{info
2679 @kindex info inferiors
2680 @item info inferiors
2681 Print a list of all inferiors currently being managed by @value{GDBN}.
2683 @value{GDBN} displays for each inferior (in this order):
2687 the inferior number assigned by @value{GDBN}
2690 the target system's inferior identifier
2693 the name of the executable the inferior is running.
2698 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2699 indicates the current inferior.
2703 @c end table here to get a little more width for example
2706 (@value{GDBP}) info inferiors
2707 Num Description Executable
2708 2 process 2307 hello
2709 * 1 process 3401 goodbye
2712 To switch focus between inferiors, use the @code{inferior} command:
2715 @kindex inferior @var{infno}
2716 @item inferior @var{infno}
2717 Make inferior number @var{infno} the current inferior. The argument
2718 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2719 in the first field of the @samp{info inferiors} display.
2722 @vindex $_inferior@r{, convenience variable}
2723 The debugger convenience variable @samp{$_inferior} contains the
2724 number of the current inferior. You may find this useful in writing
2725 breakpoint conditional expressions, command scripts, and so forth.
2726 @xref{Convenience Vars,, Convenience Variables}, for general
2727 information on convenience variables.
2729 You can get multiple executables into a debugging session via the
2730 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2731 systems @value{GDBN} can add inferiors to the debug session
2732 automatically by following calls to @code{fork} and @code{exec}. To
2733 remove inferiors from the debugging session use the
2734 @w{@code{remove-inferiors}} command.
2737 @kindex add-inferior
2738 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2739 Adds @var{n} inferiors to be run using @var{executable} as the
2740 executable; @var{n} defaults to 1. If no executable is specified,
2741 the inferiors begins empty, with no program. You can still assign or
2742 change the program assigned to the inferior at any time by using the
2743 @code{file} command with the executable name as its argument.
2745 @kindex clone-inferior
2746 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2747 Adds @var{n} inferiors ready to execute the same program as inferior
2748 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2749 number of the current inferior. This is a convenient command when you
2750 want to run another instance of the inferior you are debugging.
2753 (@value{GDBP}) info inferiors
2754 Num Description Executable
2755 * 1 process 29964 helloworld
2756 (@value{GDBP}) clone-inferior
2759 (@value{GDBP}) info inferiors
2760 Num Description Executable
2762 * 1 process 29964 helloworld
2765 You can now simply switch focus to inferior 2 and run it.
2767 @kindex remove-inferiors
2768 @item remove-inferiors @var{infno}@dots{}
2769 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2770 possible to remove an inferior that is running with this command. For
2771 those, use the @code{kill} or @code{detach} command first.
2775 To quit debugging one of the running inferiors that is not the current
2776 inferior, you can either detach from it by using the @w{@code{detach
2777 inferior}} command (allowing it to run independently), or kill it
2778 using the @w{@code{kill inferiors}} command:
2781 @kindex detach inferiors @var{infno}@dots{}
2782 @item detach inferior @var{infno}@dots{}
2783 Detach from the inferior or inferiors identified by @value{GDBN}
2784 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2785 still stays on the list of inferiors shown by @code{info inferiors},
2786 but its Description will show @samp{<null>}.
2788 @kindex kill inferiors @var{infno}@dots{}
2789 @item kill inferiors @var{infno}@dots{}
2790 Kill the inferior or inferiors identified by @value{GDBN} inferior
2791 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2792 stays on the list of inferiors shown by @code{info inferiors}, but its
2793 Description will show @samp{<null>}.
2796 After the successful completion of a command such as @code{detach},
2797 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2798 a normal process exit, the inferior is still valid and listed with
2799 @code{info inferiors}, ready to be restarted.
2802 To be notified when inferiors are started or exit under @value{GDBN}'s
2803 control use @w{@code{set print inferior-events}}:
2806 @kindex set print inferior-events
2807 @cindex print messages on inferior start and exit
2808 @item set print inferior-events
2809 @itemx set print inferior-events on
2810 @itemx set print inferior-events off
2811 The @code{set print inferior-events} command allows you to enable or
2812 disable printing of messages when @value{GDBN} notices that new
2813 inferiors have started or that inferiors have exited or have been
2814 detached. By default, these messages will not be printed.
2816 @kindex show print inferior-events
2817 @item show print inferior-events
2818 Show whether messages will be printed when @value{GDBN} detects that
2819 inferiors have started, exited or have been detached.
2822 Many commands will work the same with multiple programs as with a
2823 single program: e.g., @code{print myglobal} will simply display the
2824 value of @code{myglobal} in the current inferior.
2827 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2828 get more info about the relationship of inferiors, programs, address
2829 spaces in a debug session. You can do that with the @w{@code{maint
2830 info program-spaces}} command.
2833 @kindex maint info program-spaces
2834 @item maint info program-spaces
2835 Print a list of all program spaces currently being managed by
2838 @value{GDBN} displays for each program space (in this order):
2842 the program space number assigned by @value{GDBN}
2845 the name of the executable loaded into the program space, with e.g.,
2846 the @code{file} command.
2851 An asterisk @samp{*} preceding the @value{GDBN} program space number
2852 indicates the current program space.
2854 In addition, below each program space line, @value{GDBN} prints extra
2855 information that isn't suitable to display in tabular form. For
2856 example, the list of inferiors bound to the program space.
2859 (@value{GDBP}) maint info program-spaces
2863 Bound inferiors: ID 1 (process 21561)
2866 Here we can see that no inferior is running the program @code{hello},
2867 while @code{process 21561} is running the program @code{goodbye}. On
2868 some targets, it is possible that multiple inferiors are bound to the
2869 same program space. The most common example is that of debugging both
2870 the parent and child processes of a @code{vfork} call. For example,
2873 (@value{GDBP}) maint info program-spaces
2876 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2879 Here, both inferior 2 and inferior 1 are running in the same program
2880 space as a result of inferior 1 having executed a @code{vfork} call.
2884 @section Debugging Programs with Multiple Threads
2886 @cindex threads of execution
2887 @cindex multiple threads
2888 @cindex switching threads
2889 In some operating systems, such as GNU/Linux and Solaris, a single program
2890 may have more than one @dfn{thread} of execution. The precise semantics
2891 of threads differ from one operating system to another, but in general
2892 the threads of a single program are akin to multiple processes---except
2893 that they share one address space (that is, they can all examine and
2894 modify the same variables). On the other hand, each thread has its own
2895 registers and execution stack, and perhaps private memory.
2897 @value{GDBN} provides these facilities for debugging multi-thread
2901 @item automatic notification of new threads
2902 @item @samp{thread @var{thread-id}}, a command to switch among threads
2903 @item @samp{info threads}, a command to inquire about existing threads
2904 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2905 a command to apply a command to a list of threads
2906 @item thread-specific breakpoints
2907 @item @samp{set print thread-events}, which controls printing of
2908 messages on thread start and exit.
2909 @item @samp{set libthread-db-search-path @var{path}}, which lets
2910 the user specify which @code{libthread_db} to use if the default choice
2911 isn't compatible with the program.
2914 @cindex focus of debugging
2915 @cindex current thread
2916 The @value{GDBN} thread debugging facility allows you to observe all
2917 threads while your program runs---but whenever @value{GDBN} takes
2918 control, one thread in particular is always the focus of debugging.
2919 This thread is called the @dfn{current thread}. Debugging commands show
2920 program information from the perspective of the current thread.
2922 @cindex @code{New} @var{systag} message
2923 @cindex thread identifier (system)
2924 @c FIXME-implementors!! It would be more helpful if the [New...] message
2925 @c included GDB's numeric thread handle, so you could just go to that
2926 @c thread without first checking `info threads'.
2927 Whenever @value{GDBN} detects a new thread in your program, it displays
2928 the target system's identification for the thread with a message in the
2929 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2930 whose form varies depending on the particular system. For example, on
2931 @sc{gnu}/Linux, you might see
2934 [New Thread 0x41e02940 (LWP 25582)]
2938 when @value{GDBN} notices a new thread. In contrast, on other systems,
2939 the @var{systag} is simply something like @samp{process 368}, with no
2942 @c FIXME!! (1) Does the [New...] message appear even for the very first
2943 @c thread of a program, or does it only appear for the
2944 @c second---i.e.@: when it becomes obvious we have a multithread
2946 @c (2) *Is* there necessarily a first thread always? Or do some
2947 @c multithread systems permit starting a program with multiple
2948 @c threads ab initio?
2950 @anchor{thread numbers}
2951 @cindex thread number, per inferior
2952 @cindex thread identifier (GDB)
2953 For debugging purposes, @value{GDBN} associates its own thread number
2954 ---always a single integer---with each thread of an inferior. This
2955 number is unique between all threads of an inferior, but not unique
2956 between threads of different inferiors.
2958 @cindex qualified thread ID
2959 You can refer to a given thread in an inferior using the qualified
2960 @var{inferior-num}.@var{thread-num} syntax, also known as
2961 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2962 number and @var{thread-num} being the thread number of the given
2963 inferior. For example, thread @code{2.3} refers to thread number 3 of
2964 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2965 then @value{GDBN} infers you're referring to a thread of the current
2968 Until you create a second inferior, @value{GDBN} does not show the
2969 @var{inferior-num} part of thread IDs, even though you can always use
2970 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2971 of inferior 1, the initial inferior.
2973 @anchor{thread ID lists}
2974 @cindex thread ID lists
2975 Some commands accept a space-separated @dfn{thread ID list} as
2976 argument. A list element can be:
2980 A thread ID as shown in the first field of the @samp{info threads}
2981 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2985 A range of thread numbers, again with or without an inferior
2986 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2987 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2990 All threads of an inferior, specified with a star wildcard, with or
2991 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2992 @samp{1.*}) or @code{*}. The former refers to all threads of the
2993 given inferior, and the latter form without an inferior qualifier
2994 refers to all threads of the current inferior.
2998 For example, if the current inferior is 1, and inferior 7 has one
2999 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3000 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3001 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3002 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3006 @anchor{global thread numbers}
3007 @cindex global thread number
3008 @cindex global thread identifier (GDB)
3009 In addition to a @emph{per-inferior} number, each thread is also
3010 assigned a unique @emph{global} number, also known as @dfn{global
3011 thread ID}, a single integer. Unlike the thread number component of
3012 the thread ID, no two threads have the same global ID, even when
3013 you're debugging multiple inferiors.
3015 From @value{GDBN}'s perspective, a process always has at least one
3016 thread. In other words, @value{GDBN} assigns a thread number to the
3017 program's ``main thread'' even if the program is not multi-threaded.
3019 @vindex $_thread@r{, convenience variable}
3020 @vindex $_gthread@r{, convenience variable}
3021 The debugger convenience variables @samp{$_thread} and
3022 @samp{$_gthread} contain, respectively, the per-inferior thread number
3023 and the global thread number of the current thread. You may find this
3024 useful in writing breakpoint conditional expressions, command scripts,
3025 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3026 general information on convenience variables.
3028 If @value{GDBN} detects the program is multi-threaded, it augments the
3029 usual message about stopping at a breakpoint with the ID and name of
3030 the thread that hit the breakpoint.
3033 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3036 Likewise when the program receives a signal:
3039 Thread 1 "main" received signal SIGINT, Interrupt.
3043 @kindex info threads
3044 @item info threads @r{[}@var{thread-id-list}@r{]}
3046 Display information about one or more threads. With no arguments
3047 displays information about all threads. You can specify the list of
3048 threads that you want to display using the thread ID list syntax
3049 (@pxref{thread ID lists}).
3051 @value{GDBN} displays for each thread (in this order):
3055 the per-inferior thread number assigned by @value{GDBN}
3058 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3059 option was specified
3062 the target system's thread identifier (@var{systag})
3065 the thread's name, if one is known. A thread can either be named by
3066 the user (see @code{thread name}, below), or, in some cases, by the
3070 the current stack frame summary for that thread
3074 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3075 indicates the current thread.
3079 @c end table here to get a little more width for example
3082 (@value{GDBP}) info threads
3084 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3085 2 process 35 thread 23 0x34e5 in sigpause ()
3086 3 process 35 thread 27 0x34e5 in sigpause ()
3090 If you're debugging multiple inferiors, @value{GDBN} displays thread
3091 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3092 Otherwise, only @var{thread-num} is shown.
3094 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3095 indicating each thread's global thread ID:
3098 (@value{GDBP}) info threads
3099 Id GId Target Id Frame
3100 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3101 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3102 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3103 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3106 On Solaris, you can display more information about user threads with a
3107 Solaris-specific command:
3110 @item maint info sol-threads
3111 @kindex maint info sol-threads
3112 @cindex thread info (Solaris)
3113 Display info on Solaris user threads.
3117 @kindex thread @var{thread-id}
3118 @item thread @var{thread-id}
3119 Make thread ID @var{thread-id} the current thread. The command
3120 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3121 the first field of the @samp{info threads} display, with or without an
3122 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3124 @value{GDBN} responds by displaying the system identifier of the
3125 thread you selected, and its current stack frame summary:
3128 (@value{GDBP}) thread 2
3129 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3130 #0 some_function (ignore=0x0) at example.c:8
3131 8 printf ("hello\n");
3135 As with the @samp{[New @dots{}]} message, the form of the text after
3136 @samp{Switching to} depends on your system's conventions for identifying
3139 @kindex thread apply
3140 @cindex apply command to several threads
3141 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3142 The @code{thread apply} command allows you to apply the named
3143 @var{command} to one or more threads. Specify the threads that you
3144 want affected using the thread ID list syntax (@pxref{thread ID
3145 lists}), or specify @code{all} to apply to all threads. To apply a
3146 command to all threads in descending order, type @kbd{thread apply all
3147 @var{command}}. To apply a command to all threads in ascending order,
3148 type @kbd{thread apply all -ascending @var{command}}.
3152 @cindex name a thread
3153 @item thread name [@var{name}]
3154 This command assigns a name to the current thread. If no argument is
3155 given, any existing user-specified name is removed. The thread name
3156 appears in the @samp{info threads} display.
3158 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3159 determine the name of the thread as given by the OS. On these
3160 systems, a name specified with @samp{thread name} will override the
3161 system-give name, and removing the user-specified name will cause
3162 @value{GDBN} to once again display the system-specified name.
3165 @cindex search for a thread
3166 @item thread find [@var{regexp}]
3167 Search for and display thread ids whose name or @var{systag}
3168 matches the supplied regular expression.
3170 As well as being the complement to the @samp{thread name} command,
3171 this command also allows you to identify a thread by its target
3172 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3176 (@value{GDBN}) thread find 26688
3177 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3178 (@value{GDBN}) info thread 4
3180 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3183 @kindex set print thread-events
3184 @cindex print messages on thread start and exit
3185 @item set print thread-events
3186 @itemx set print thread-events on
3187 @itemx set print thread-events off
3188 The @code{set print thread-events} command allows you to enable or
3189 disable printing of messages when @value{GDBN} notices that new threads have
3190 started or that threads have exited. By default, these messages will
3191 be printed if detection of these events is supported by the target.
3192 Note that these messages cannot be disabled on all targets.
3194 @kindex show print thread-events
3195 @item show print thread-events
3196 Show whether messages will be printed when @value{GDBN} detects that threads
3197 have started and exited.
3200 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3201 more information about how @value{GDBN} behaves when you stop and start
3202 programs with multiple threads.
3204 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3205 watchpoints in programs with multiple threads.
3207 @anchor{set libthread-db-search-path}
3209 @kindex set libthread-db-search-path
3210 @cindex search path for @code{libthread_db}
3211 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3212 If this variable is set, @var{path} is a colon-separated list of
3213 directories @value{GDBN} will use to search for @code{libthread_db}.
3214 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3215 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3216 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3219 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3220 @code{libthread_db} library to obtain information about threads in the
3221 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3222 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3223 specific thread debugging library loading is enabled
3224 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3226 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3227 refers to the default system directories that are
3228 normally searched for loading shared libraries. The @samp{$sdir} entry
3229 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3230 (@pxref{libthread_db.so.1 file}).
3232 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3233 refers to the directory from which @code{libpthread}
3234 was loaded in the inferior process.
3236 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3237 @value{GDBN} attempts to initialize it with the current inferior process.
3238 If this initialization fails (which could happen because of a version
3239 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3240 will unload @code{libthread_db}, and continue with the next directory.
3241 If none of @code{libthread_db} libraries initialize successfully,
3242 @value{GDBN} will issue a warning and thread debugging will be disabled.
3244 Setting @code{libthread-db-search-path} is currently implemented
3245 only on some platforms.
3247 @kindex show libthread-db-search-path
3248 @item show libthread-db-search-path
3249 Display current libthread_db search path.
3251 @kindex set debug libthread-db
3252 @kindex show debug libthread-db
3253 @cindex debugging @code{libthread_db}
3254 @item set debug libthread-db
3255 @itemx show debug libthread-db
3256 Turns on or off display of @code{libthread_db}-related events.
3257 Use @code{1} to enable, @code{0} to disable.
3261 @section Debugging Forks
3263 @cindex fork, debugging programs which call
3264 @cindex multiple processes
3265 @cindex processes, multiple
3266 On most systems, @value{GDBN} has no special support for debugging
3267 programs which create additional processes using the @code{fork}
3268 function. When a program forks, @value{GDBN} will continue to debug the
3269 parent process and the child process will run unimpeded. If you have
3270 set a breakpoint in any code which the child then executes, the child
3271 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3272 will cause it to terminate.
3274 However, if you want to debug the child process there is a workaround
3275 which isn't too painful. Put a call to @code{sleep} in the code which
3276 the child process executes after the fork. It may be useful to sleep
3277 only if a certain environment variable is set, or a certain file exists,
3278 so that the delay need not occur when you don't want to run @value{GDBN}
3279 on the child. While the child is sleeping, use the @code{ps} program to
3280 get its process ID. Then tell @value{GDBN} (a new invocation of
3281 @value{GDBN} if you are also debugging the parent process) to attach to
3282 the child process (@pxref{Attach}). From that point on you can debug
3283 the child process just like any other process which you attached to.
3285 On some systems, @value{GDBN} provides support for debugging programs
3286 that create additional processes using the @code{fork} or @code{vfork}
3287 functions. On @sc{gnu}/Linux platforms, this feature is supported
3288 with kernel version 2.5.46 and later.
3290 The fork debugging commands are supported in native mode and when
3291 connected to @code{gdbserver} in either @code{target remote} mode or
3292 @code{target extended-remote} mode.
3294 By default, when a program forks, @value{GDBN} will continue to debug
3295 the parent process and the child process will run unimpeded.
3297 If you want to follow the child process instead of the parent process,
3298 use the command @w{@code{set follow-fork-mode}}.
3301 @kindex set follow-fork-mode
3302 @item set follow-fork-mode @var{mode}
3303 Set the debugger response to a program call of @code{fork} or
3304 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3305 process. The @var{mode} argument can be:
3309 The original process is debugged after a fork. The child process runs
3310 unimpeded. This is the default.
3313 The new process is debugged after a fork. The parent process runs
3318 @kindex show follow-fork-mode
3319 @item show follow-fork-mode
3320 Display the current debugger response to a @code{fork} or @code{vfork} call.
3323 @cindex debugging multiple processes
3324 On Linux, if you want to debug both the parent and child processes, use the
3325 command @w{@code{set detach-on-fork}}.
3328 @kindex set detach-on-fork
3329 @item set detach-on-fork @var{mode}
3330 Tells gdb whether to detach one of the processes after a fork, or
3331 retain debugger control over them both.
3335 The child process (or parent process, depending on the value of
3336 @code{follow-fork-mode}) will be detached and allowed to run
3337 independently. This is the default.
3340 Both processes will be held under the control of @value{GDBN}.
3341 One process (child or parent, depending on the value of
3342 @code{follow-fork-mode}) is debugged as usual, while the other
3347 @kindex show detach-on-fork
3348 @item show detach-on-fork
3349 Show whether detach-on-fork mode is on/off.
3352 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3353 will retain control of all forked processes (including nested forks).
3354 You can list the forked processes under the control of @value{GDBN} by
3355 using the @w{@code{info inferiors}} command, and switch from one fork
3356 to another by using the @code{inferior} command (@pxref{Inferiors and
3357 Programs, ,Debugging Multiple Inferiors and Programs}).
3359 To quit debugging one of the forked processes, you can either detach
3360 from it by using the @w{@code{detach inferiors}} command (allowing it
3361 to run independently), or kill it using the @w{@code{kill inferiors}}
3362 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3365 If you ask to debug a child process and a @code{vfork} is followed by an
3366 @code{exec}, @value{GDBN} executes the new target up to the first
3367 breakpoint in the new target. If you have a breakpoint set on
3368 @code{main} in your original program, the breakpoint will also be set on
3369 the child process's @code{main}.
3371 On some systems, when a child process is spawned by @code{vfork}, you
3372 cannot debug the child or parent until an @code{exec} call completes.
3374 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3375 call executes, the new target restarts. To restart the parent
3376 process, use the @code{file} command with the parent executable name
3377 as its argument. By default, after an @code{exec} call executes,
3378 @value{GDBN} discards the symbols of the previous executable image.
3379 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3383 @kindex set follow-exec-mode
3384 @item set follow-exec-mode @var{mode}
3386 Set debugger response to a program call of @code{exec}. An
3387 @code{exec} call replaces the program image of a process.
3389 @code{follow-exec-mode} can be:
3393 @value{GDBN} creates a new inferior and rebinds the process to this
3394 new inferior. The program the process was running before the
3395 @code{exec} call can be restarted afterwards by restarting the
3401 (@value{GDBP}) info inferiors
3403 Id Description Executable
3406 process 12020 is executing new program: prog2
3407 Program exited normally.
3408 (@value{GDBP}) info inferiors
3409 Id Description Executable
3415 @value{GDBN} keeps the process bound to the same inferior. The new
3416 executable image replaces the previous executable loaded in the
3417 inferior. Restarting the inferior after the @code{exec} call, with
3418 e.g., the @code{run} command, restarts the executable the process was
3419 running after the @code{exec} call. This is the default mode.
3424 (@value{GDBP}) info inferiors
3425 Id Description Executable
3428 process 12020 is executing new program: prog2
3429 Program exited normally.
3430 (@value{GDBP}) info inferiors
3431 Id Description Executable
3438 @code{follow-exec-mode} is supported in native mode and
3439 @code{target extended-remote} mode.
3441 You can use the @code{catch} command to make @value{GDBN} stop whenever
3442 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3443 Catchpoints, ,Setting Catchpoints}.
3445 @node Checkpoint/Restart
3446 @section Setting a @emph{Bookmark} to Return to Later
3451 @cindex snapshot of a process
3452 @cindex rewind program state
3454 On certain operating systems@footnote{Currently, only
3455 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3456 program's state, called a @dfn{checkpoint}, and come back to it
3459 Returning to a checkpoint effectively undoes everything that has
3460 happened in the program since the @code{checkpoint} was saved. This
3461 includes changes in memory, registers, and even (within some limits)
3462 system state. Effectively, it is like going back in time to the
3463 moment when the checkpoint was saved.
3465 Thus, if you're stepping thru a program and you think you're
3466 getting close to the point where things go wrong, you can save
3467 a checkpoint. Then, if you accidentally go too far and miss
3468 the critical statement, instead of having to restart your program
3469 from the beginning, you can just go back to the checkpoint and
3470 start again from there.
3472 This can be especially useful if it takes a lot of time or
3473 steps to reach the point where you think the bug occurs.
3475 To use the @code{checkpoint}/@code{restart} method of debugging:
3480 Save a snapshot of the debugged program's current execution state.
3481 The @code{checkpoint} command takes no arguments, but each checkpoint
3482 is assigned a small integer id, similar to a breakpoint id.
3484 @kindex info checkpoints
3485 @item info checkpoints
3486 List the checkpoints that have been saved in the current debugging
3487 session. For each checkpoint, the following information will be
3494 @item Source line, or label
3497 @kindex restart @var{checkpoint-id}
3498 @item restart @var{checkpoint-id}
3499 Restore the program state that was saved as checkpoint number
3500 @var{checkpoint-id}. All program variables, registers, stack frames
3501 etc.@: will be returned to the values that they had when the checkpoint
3502 was saved. In essence, gdb will ``wind back the clock'' to the point
3503 in time when the checkpoint was saved.
3505 Note that breakpoints, @value{GDBN} variables, command history etc.
3506 are not affected by restoring a checkpoint. In general, a checkpoint
3507 only restores things that reside in the program being debugged, not in
3510 @kindex delete checkpoint @var{checkpoint-id}
3511 @item delete checkpoint @var{checkpoint-id}
3512 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3516 Returning to a previously saved checkpoint will restore the user state
3517 of the program being debugged, plus a significant subset of the system
3518 (OS) state, including file pointers. It won't ``un-write'' data from
3519 a file, but it will rewind the file pointer to the previous location,
3520 so that the previously written data can be overwritten. For files
3521 opened in read mode, the pointer will also be restored so that the
3522 previously read data can be read again.
3524 Of course, characters that have been sent to a printer (or other
3525 external device) cannot be ``snatched back'', and characters received
3526 from eg.@: a serial device can be removed from internal program buffers,
3527 but they cannot be ``pushed back'' into the serial pipeline, ready to
3528 be received again. Similarly, the actual contents of files that have
3529 been changed cannot be restored (at this time).
3531 However, within those constraints, you actually can ``rewind'' your
3532 program to a previously saved point in time, and begin debugging it
3533 again --- and you can change the course of events so as to debug a
3534 different execution path this time.
3536 @cindex checkpoints and process id
3537 Finally, there is one bit of internal program state that will be
3538 different when you return to a checkpoint --- the program's process
3539 id. Each checkpoint will have a unique process id (or @var{pid}),
3540 and each will be different from the program's original @var{pid}.
3541 If your program has saved a local copy of its process id, this could
3542 potentially pose a problem.
3544 @subsection A Non-obvious Benefit of Using Checkpoints
3546 On some systems such as @sc{gnu}/Linux, address space randomization
3547 is performed on new processes for security reasons. This makes it
3548 difficult or impossible to set a breakpoint, or watchpoint, on an
3549 absolute address if you have to restart the program, since the
3550 absolute location of a symbol will change from one execution to the
3553 A checkpoint, however, is an @emph{identical} copy of a process.
3554 Therefore if you create a checkpoint at (eg.@:) the start of main,
3555 and simply return to that checkpoint instead of restarting the
3556 process, you can avoid the effects of address randomization and
3557 your symbols will all stay in the same place.
3560 @chapter Stopping and Continuing
3562 The principal purposes of using a debugger are so that you can stop your
3563 program before it terminates; or so that, if your program runs into
3564 trouble, you can investigate and find out why.
3566 Inside @value{GDBN}, your program may stop for any of several reasons,
3567 such as a signal, a breakpoint, or reaching a new line after a
3568 @value{GDBN} command such as @code{step}. You may then examine and
3569 change variables, set new breakpoints or remove old ones, and then
3570 continue execution. Usually, the messages shown by @value{GDBN} provide
3571 ample explanation of the status of your program---but you can also
3572 explicitly request this information at any time.
3575 @kindex info program
3577 Display information about the status of your program: whether it is
3578 running or not, what process it is, and why it stopped.
3582 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3583 * Continuing and Stepping:: Resuming execution
3584 * Skipping Over Functions and Files::
3585 Skipping over functions and files
3587 * Thread Stops:: Stopping and starting multi-thread programs
3591 @section Breakpoints, Watchpoints, and Catchpoints
3594 A @dfn{breakpoint} makes your program stop whenever a certain point in
3595 the program is reached. For each breakpoint, you can add conditions to
3596 control in finer detail whether your program stops. You can set
3597 breakpoints with the @code{break} command and its variants (@pxref{Set
3598 Breaks, ,Setting Breakpoints}), to specify the place where your program
3599 should stop by line number, function name or exact address in the
3602 On some systems, you can set breakpoints in shared libraries before
3603 the executable is run.
3606 @cindex data breakpoints
3607 @cindex memory tracing
3608 @cindex breakpoint on memory address
3609 @cindex breakpoint on variable modification
3610 A @dfn{watchpoint} is a special breakpoint that stops your program
3611 when the value of an expression changes. The expression may be a value
3612 of a variable, or it could involve values of one or more variables
3613 combined by operators, such as @samp{a + b}. This is sometimes called
3614 @dfn{data breakpoints}. You must use a different command to set
3615 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3616 from that, you can manage a watchpoint like any other breakpoint: you
3617 enable, disable, and delete both breakpoints and watchpoints using the
3620 You can arrange to have values from your program displayed automatically
3621 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3625 @cindex breakpoint on events
3626 A @dfn{catchpoint} is another special breakpoint that stops your program
3627 when a certain kind of event occurs, such as the throwing of a C@t{++}
3628 exception or the loading of a library. As with watchpoints, you use a
3629 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3630 Catchpoints}), but aside from that, you can manage a catchpoint like any
3631 other breakpoint. (To stop when your program receives a signal, use the
3632 @code{handle} command; see @ref{Signals, ,Signals}.)
3634 @cindex breakpoint numbers
3635 @cindex numbers for breakpoints
3636 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3637 catchpoint when you create it; these numbers are successive integers
3638 starting with one. In many of the commands for controlling various
3639 features of breakpoints you use the breakpoint number to say which
3640 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3641 @dfn{disabled}; if disabled, it has no effect on your program until you
3644 @cindex breakpoint ranges
3645 @cindex breakpoint lists
3646 @cindex ranges of breakpoints
3647 @cindex lists of breakpoints
3648 Some @value{GDBN} commands accept a space-separated list of breakpoints
3649 on which to operate. A list element can be either a single breakpoint number,
3650 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3651 When a breakpoint list is given to a command, all breakpoints in that list
3655 * Set Breaks:: Setting breakpoints
3656 * Set Watchpoints:: Setting watchpoints
3657 * Set Catchpoints:: Setting catchpoints
3658 * Delete Breaks:: Deleting breakpoints
3659 * Disabling:: Disabling breakpoints
3660 * Conditions:: Break conditions
3661 * Break Commands:: Breakpoint command lists
3662 * Dynamic Printf:: Dynamic printf
3663 * Save Breakpoints:: How to save breakpoints in a file
3664 * Static Probe Points:: Listing static probe points
3665 * Error in Breakpoints:: ``Cannot insert breakpoints''
3666 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3670 @subsection Setting Breakpoints
3672 @c FIXME LMB what does GDB do if no code on line of breakpt?
3673 @c consider in particular declaration with/without initialization.
3675 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3678 @kindex b @r{(@code{break})}
3679 @vindex $bpnum@r{, convenience variable}
3680 @cindex latest breakpoint
3681 Breakpoints are set with the @code{break} command (abbreviated
3682 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3683 number of the breakpoint you've set most recently; see @ref{Convenience
3684 Vars,, Convenience Variables}, for a discussion of what you can do with
3685 convenience variables.
3688 @item break @var{location}
3689 Set a breakpoint at the given @var{location}, which can specify a
3690 function name, a line number, or an address of an instruction.
3691 (@xref{Specify Location}, for a list of all the possible ways to
3692 specify a @var{location}.) The breakpoint will stop your program just
3693 before it executes any of the code in the specified @var{location}.
3695 When using source languages that permit overloading of symbols, such as
3696 C@t{++}, a function name may refer to more than one possible place to break.
3697 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3700 It is also possible to insert a breakpoint that will stop the program
3701 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3702 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3705 When called without any arguments, @code{break} sets a breakpoint at
3706 the next instruction to be executed in the selected stack frame
3707 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3708 innermost, this makes your program stop as soon as control
3709 returns to that frame. This is similar to the effect of a
3710 @code{finish} command in the frame inside the selected frame---except
3711 that @code{finish} does not leave an active breakpoint. If you use
3712 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3713 the next time it reaches the current location; this may be useful
3716 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3717 least one instruction has been executed. If it did not do this, you
3718 would be unable to proceed past a breakpoint without first disabling the
3719 breakpoint. This rule applies whether or not the breakpoint already
3720 existed when your program stopped.
3722 @item break @dots{} if @var{cond}
3723 Set a breakpoint with condition @var{cond}; evaluate the expression
3724 @var{cond} each time the breakpoint is reached, and stop only if the
3725 value is nonzero---that is, if @var{cond} evaluates as true.
3726 @samp{@dots{}} stands for one of the possible arguments described
3727 above (or no argument) specifying where to break. @xref{Conditions,
3728 ,Break Conditions}, for more information on breakpoint conditions.
3731 @item tbreak @var{args}
3732 Set a breakpoint enabled only for one stop. The @var{args} are the
3733 same as for the @code{break} command, and the breakpoint is set in the same
3734 way, but the breakpoint is automatically deleted after the first time your
3735 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3738 @cindex hardware breakpoints
3739 @item hbreak @var{args}
3740 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3741 @code{break} command and the breakpoint is set in the same way, but the
3742 breakpoint requires hardware support and some target hardware may not
3743 have this support. The main purpose of this is EPROM/ROM code
3744 debugging, so you can set a breakpoint at an instruction without
3745 changing the instruction. This can be used with the new trap-generation
3746 provided by SPARClite DSU and most x86-based targets. These targets
3747 will generate traps when a program accesses some data or instruction
3748 address that is assigned to the debug registers. However the hardware
3749 breakpoint registers can take a limited number of breakpoints. For
3750 example, on the DSU, only two data breakpoints can be set at a time, and
3751 @value{GDBN} will reject this command if more than two are used. Delete
3752 or disable unused hardware breakpoints before setting new ones
3753 (@pxref{Disabling, ,Disabling Breakpoints}).
3754 @xref{Conditions, ,Break Conditions}.
3755 For remote targets, you can restrict the number of hardware
3756 breakpoints @value{GDBN} will use, see @ref{set remote
3757 hardware-breakpoint-limit}.
3760 @item thbreak @var{args}
3761 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3762 are the same as for the @code{hbreak} command and the breakpoint is set in
3763 the same way. However, like the @code{tbreak} command,
3764 the breakpoint is automatically deleted after the
3765 first time your program stops there. Also, like the @code{hbreak}
3766 command, the breakpoint requires hardware support and some target hardware
3767 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3768 See also @ref{Conditions, ,Break Conditions}.
3771 @cindex regular expression
3772 @cindex breakpoints at functions matching a regexp
3773 @cindex set breakpoints in many functions
3774 @item rbreak @var{regex}
3775 Set breakpoints on all functions matching the regular expression
3776 @var{regex}. This command sets an unconditional breakpoint on all
3777 matches, printing a list of all breakpoints it set. Once these
3778 breakpoints are set, they are treated just like the breakpoints set with
3779 the @code{break} command. You can delete them, disable them, or make
3780 them conditional the same way as any other breakpoint.
3782 The syntax of the regular expression is the standard one used with tools
3783 like @file{grep}. Note that this is different from the syntax used by
3784 shells, so for instance @code{foo*} matches all functions that include
3785 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3786 @code{.*} leading and trailing the regular expression you supply, so to
3787 match only functions that begin with @code{foo}, use @code{^foo}.
3789 @cindex non-member C@t{++} functions, set breakpoint in
3790 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3791 breakpoints on overloaded functions that are not members of any special
3794 @cindex set breakpoints on all functions
3795 The @code{rbreak} command can be used to set breakpoints in
3796 @strong{all} the functions in a program, like this:
3799 (@value{GDBP}) rbreak .
3802 @item rbreak @var{file}:@var{regex}
3803 If @code{rbreak} is called with a filename qualification, it limits
3804 the search for functions matching the given regular expression to the
3805 specified @var{file}. This can be used, for example, to set breakpoints on
3806 every function in a given file:
3809 (@value{GDBP}) rbreak file.c:.
3812 The colon separating the filename qualifier from the regex may
3813 optionally be surrounded by spaces.
3815 @kindex info breakpoints
3816 @cindex @code{$_} and @code{info breakpoints}
3817 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3818 @itemx info break @r{[}@var{list}@dots{}@r{]}
3819 Print a table of all breakpoints, watchpoints, and catchpoints set and
3820 not deleted. Optional argument @var{n} means print information only
3821 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3822 For each breakpoint, following columns are printed:
3825 @item Breakpoint Numbers
3827 Breakpoint, watchpoint, or catchpoint.
3829 Whether the breakpoint is marked to be disabled or deleted when hit.
3830 @item Enabled or Disabled
3831 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3832 that are not enabled.
3834 Where the breakpoint is in your program, as a memory address. For a
3835 pending breakpoint whose address is not yet known, this field will
3836 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3837 library that has the symbol or line referred by breakpoint is loaded.
3838 See below for details. A breakpoint with several locations will
3839 have @samp{<MULTIPLE>} in this field---see below for details.
3841 Where the breakpoint is in the source for your program, as a file and
3842 line number. For a pending breakpoint, the original string passed to
3843 the breakpoint command will be listed as it cannot be resolved until
3844 the appropriate shared library is loaded in the future.
3848 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3849 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3850 @value{GDBN} on the host's side. If it is ``target'', then the condition
3851 is evaluated by the target. The @code{info break} command shows
3852 the condition on the line following the affected breakpoint, together with
3853 its condition evaluation mode in between parentheses.
3855 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3856 allowed to have a condition specified for it. The condition is not parsed for
3857 validity until a shared library is loaded that allows the pending
3858 breakpoint to resolve to a valid location.
3861 @code{info break} with a breakpoint
3862 number @var{n} as argument lists only that breakpoint. The
3863 convenience variable @code{$_} and the default examining-address for
3864 the @code{x} command are set to the address of the last breakpoint
3865 listed (@pxref{Memory, ,Examining Memory}).
3868 @code{info break} displays a count of the number of times the breakpoint
3869 has been hit. This is especially useful in conjunction with the
3870 @code{ignore} command. You can ignore a large number of breakpoint
3871 hits, look at the breakpoint info to see how many times the breakpoint
3872 was hit, and then run again, ignoring one less than that number. This
3873 will get you quickly to the last hit of that breakpoint.
3876 For a breakpoints with an enable count (xref) greater than 1,
3877 @code{info break} also displays that count.
3881 @value{GDBN} allows you to set any number of breakpoints at the same place in
3882 your program. There is nothing silly or meaningless about this. When
3883 the breakpoints are conditional, this is even useful
3884 (@pxref{Conditions, ,Break Conditions}).
3886 @cindex multiple locations, breakpoints
3887 @cindex breakpoints, multiple locations
3888 It is possible that a breakpoint corresponds to several locations
3889 in your program. Examples of this situation are:
3893 Multiple functions in the program may have the same name.
3896 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3897 instances of the function body, used in different cases.
3900 For a C@t{++} template function, a given line in the function can
3901 correspond to any number of instantiations.
3904 For an inlined function, a given source line can correspond to
3905 several places where that function is inlined.
3908 In all those cases, @value{GDBN} will insert a breakpoint at all
3909 the relevant locations.
3911 A breakpoint with multiple locations is displayed in the breakpoint
3912 table using several rows---one header row, followed by one row for
3913 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3914 address column. The rows for individual locations contain the actual
3915 addresses for locations, and show the functions to which those
3916 locations belong. The number column for a location is of the form
3917 @var{breakpoint-number}.@var{location-number}.
3922 Num Type Disp Enb Address What
3923 1 breakpoint keep y <MULTIPLE>
3925 breakpoint already hit 1 time
3926 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3927 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3930 Each location can be individually enabled or disabled by passing
3931 @var{breakpoint-number}.@var{location-number} as argument to the
3932 @code{enable} and @code{disable} commands. Note that you cannot
3933 delete the individual locations from the list, you can only delete the
3934 entire list of locations that belong to their parent breakpoint (with
3935 the @kbd{delete @var{num}} command, where @var{num} is the number of
3936 the parent breakpoint, 1 in the above example). Disabling or enabling
3937 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3938 that belong to that breakpoint.
3940 @cindex pending breakpoints
3941 It's quite common to have a breakpoint inside a shared library.
3942 Shared libraries can be loaded and unloaded explicitly,
3943 and possibly repeatedly, as the program is executed. To support
3944 this use case, @value{GDBN} updates breakpoint locations whenever
3945 any shared library is loaded or unloaded. Typically, you would
3946 set a breakpoint in a shared library at the beginning of your
3947 debugging session, when the library is not loaded, and when the
3948 symbols from the library are not available. When you try to set
3949 breakpoint, @value{GDBN} will ask you if you want to set
3950 a so called @dfn{pending breakpoint}---breakpoint whose address
3951 is not yet resolved.
3953 After the program is run, whenever a new shared library is loaded,
3954 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3955 shared library contains the symbol or line referred to by some
3956 pending breakpoint, that breakpoint is resolved and becomes an
3957 ordinary breakpoint. When a library is unloaded, all breakpoints
3958 that refer to its symbols or source lines become pending again.
3960 This logic works for breakpoints with multiple locations, too. For
3961 example, if you have a breakpoint in a C@t{++} template function, and
3962 a newly loaded shared library has an instantiation of that template,
3963 a new location is added to the list of locations for the breakpoint.
3965 Except for having unresolved address, pending breakpoints do not
3966 differ from regular breakpoints. You can set conditions or commands,
3967 enable and disable them and perform other breakpoint operations.
3969 @value{GDBN} provides some additional commands for controlling what
3970 happens when the @samp{break} command cannot resolve breakpoint
3971 address specification to an address:
3973 @kindex set breakpoint pending
3974 @kindex show breakpoint pending
3976 @item set breakpoint pending auto
3977 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3978 location, it queries you whether a pending breakpoint should be created.
3980 @item set breakpoint pending on
3981 This indicates that an unrecognized breakpoint location should automatically
3982 result in a pending breakpoint being created.
3984 @item set breakpoint pending off
3985 This indicates that pending breakpoints are not to be created. Any
3986 unrecognized breakpoint location results in an error. This setting does
3987 not affect any pending breakpoints previously created.
3989 @item show breakpoint pending
3990 Show the current behavior setting for creating pending breakpoints.
3993 The settings above only affect the @code{break} command and its
3994 variants. Once breakpoint is set, it will be automatically updated
3995 as shared libraries are loaded and unloaded.
3997 @cindex automatic hardware breakpoints
3998 For some targets, @value{GDBN} can automatically decide if hardware or
3999 software breakpoints should be used, depending on whether the
4000 breakpoint address is read-only or read-write. This applies to
4001 breakpoints set with the @code{break} command as well as to internal
4002 breakpoints set by commands like @code{next} and @code{finish}. For
4003 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4006 You can control this automatic behaviour with the following commands:
4008 @kindex set breakpoint auto-hw
4009 @kindex show breakpoint auto-hw
4011 @item set breakpoint auto-hw on
4012 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4013 will try to use the target memory map to decide if software or hardware
4014 breakpoint must be used.
4016 @item set breakpoint auto-hw off
4017 This indicates @value{GDBN} should not automatically select breakpoint
4018 type. If the target provides a memory map, @value{GDBN} will warn when
4019 trying to set software breakpoint at a read-only address.
4022 @value{GDBN} normally implements breakpoints by replacing the program code
4023 at the breakpoint address with a special instruction, which, when
4024 executed, given control to the debugger. By default, the program
4025 code is so modified only when the program is resumed. As soon as
4026 the program stops, @value{GDBN} restores the original instructions. This
4027 behaviour guards against leaving breakpoints inserted in the
4028 target should gdb abrubptly disconnect. However, with slow remote
4029 targets, inserting and removing breakpoint can reduce the performance.
4030 This behavior can be controlled with the following commands::
4032 @kindex set breakpoint always-inserted
4033 @kindex show breakpoint always-inserted
4035 @item set breakpoint always-inserted off
4036 All breakpoints, including newly added by the user, are inserted in
4037 the target only when the target is resumed. All breakpoints are
4038 removed from the target when it stops. This is the default mode.
4040 @item set breakpoint always-inserted on
4041 Causes all breakpoints to be inserted in the target at all times. If
4042 the user adds a new breakpoint, or changes an existing breakpoint, the
4043 breakpoints in the target are updated immediately. A breakpoint is
4044 removed from the target only when breakpoint itself is deleted.
4047 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4048 when a breakpoint breaks. If the condition is true, then the process being
4049 debugged stops, otherwise the process is resumed.
4051 If the target supports evaluating conditions on its end, @value{GDBN} may
4052 download the breakpoint, together with its conditions, to it.
4054 This feature can be controlled via the following commands:
4056 @kindex set breakpoint condition-evaluation
4057 @kindex show breakpoint condition-evaluation
4059 @item set breakpoint condition-evaluation host
4060 This option commands @value{GDBN} to evaluate the breakpoint
4061 conditions on the host's side. Unconditional breakpoints are sent to
4062 the target which in turn receives the triggers and reports them back to GDB
4063 for condition evaluation. This is the standard evaluation mode.
4065 @item set breakpoint condition-evaluation target
4066 This option commands @value{GDBN} to download breakpoint conditions
4067 to the target at the moment of their insertion. The target
4068 is responsible for evaluating the conditional expression and reporting
4069 breakpoint stop events back to @value{GDBN} whenever the condition
4070 is true. Due to limitations of target-side evaluation, some conditions
4071 cannot be evaluated there, e.g., conditions that depend on local data
4072 that is only known to the host. Examples include
4073 conditional expressions involving convenience variables, complex types
4074 that cannot be handled by the agent expression parser and expressions
4075 that are too long to be sent over to the target, specially when the
4076 target is a remote system. In these cases, the conditions will be
4077 evaluated by @value{GDBN}.
4079 @item set breakpoint condition-evaluation auto
4080 This is the default mode. If the target supports evaluating breakpoint
4081 conditions on its end, @value{GDBN} will download breakpoint conditions to
4082 the target (limitations mentioned previously apply). If the target does
4083 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4084 to evaluating all these conditions on the host's side.
4088 @cindex negative breakpoint numbers
4089 @cindex internal @value{GDBN} breakpoints
4090 @value{GDBN} itself sometimes sets breakpoints in your program for
4091 special purposes, such as proper handling of @code{longjmp} (in C
4092 programs). These internal breakpoints are assigned negative numbers,
4093 starting with @code{-1}; @samp{info breakpoints} does not display them.
4094 You can see these breakpoints with the @value{GDBN} maintenance command
4095 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4098 @node Set Watchpoints
4099 @subsection Setting Watchpoints
4101 @cindex setting watchpoints
4102 You can use a watchpoint to stop execution whenever the value of an
4103 expression changes, without having to predict a particular place where
4104 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4105 The expression may be as simple as the value of a single variable, or
4106 as complex as many variables combined by operators. Examples include:
4110 A reference to the value of a single variable.
4113 An address cast to an appropriate data type. For example,
4114 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4115 address (assuming an @code{int} occupies 4 bytes).
4118 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4119 expression can use any operators valid in the program's native
4120 language (@pxref{Languages}).
4123 You can set a watchpoint on an expression even if the expression can
4124 not be evaluated yet. For instance, you can set a watchpoint on
4125 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4126 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4127 the expression produces a valid value. If the expression becomes
4128 valid in some other way than changing a variable (e.g.@: if the memory
4129 pointed to by @samp{*global_ptr} becomes readable as the result of a
4130 @code{malloc} call), @value{GDBN} may not stop until the next time
4131 the expression changes.
4133 @cindex software watchpoints
4134 @cindex hardware watchpoints
4135 Depending on your system, watchpoints may be implemented in software or
4136 hardware. @value{GDBN} does software watchpointing by single-stepping your
4137 program and testing the variable's value each time, which is hundreds of
4138 times slower than normal execution. (But this may still be worth it, to
4139 catch errors where you have no clue what part of your program is the
4142 On some systems, such as most PowerPC or x86-based targets,
4143 @value{GDBN} includes support for hardware watchpoints, which do not
4144 slow down the running of your program.
4148 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4149 Set a watchpoint for an expression. @value{GDBN} will break when the
4150 expression @var{expr} is written into by the program and its value
4151 changes. The simplest (and the most popular) use of this command is
4152 to watch the value of a single variable:
4155 (@value{GDBP}) watch foo
4158 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4159 argument, @value{GDBN} breaks only when the thread identified by
4160 @var{thread-id} changes the value of @var{expr}. If any other threads
4161 change the value of @var{expr}, @value{GDBN} will not break. Note
4162 that watchpoints restricted to a single thread in this way only work
4163 with Hardware Watchpoints.
4165 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4166 (see below). The @code{-location} argument tells @value{GDBN} to
4167 instead watch the memory referred to by @var{expr}. In this case,
4168 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4169 and watch the memory at that address. The type of the result is used
4170 to determine the size of the watched memory. If the expression's
4171 result does not have an address, then @value{GDBN} will print an
4174 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4175 of masked watchpoints, if the current architecture supports this
4176 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4177 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4178 to an address to watch. The mask specifies that some bits of an address
4179 (the bits which are reset in the mask) should be ignored when matching
4180 the address accessed by the inferior against the watchpoint address.
4181 Thus, a masked watchpoint watches many addresses simultaneously---those
4182 addresses whose unmasked bits are identical to the unmasked bits in the
4183 watchpoint address. The @code{mask} argument implies @code{-location}.
4187 (@value{GDBP}) watch foo mask 0xffff00ff
4188 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4192 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4193 Set a watchpoint that will break when the value of @var{expr} is read
4197 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4198 Set a watchpoint that will break when @var{expr} is either read from
4199 or written into by the program.
4201 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4202 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4203 This command prints a list of watchpoints, using the same format as
4204 @code{info break} (@pxref{Set Breaks}).
4207 If you watch for a change in a numerically entered address you need to
4208 dereference it, as the address itself is just a constant number which will
4209 never change. @value{GDBN} refuses to create a watchpoint that watches
4210 a never-changing value:
4213 (@value{GDBP}) watch 0x600850
4214 Cannot watch constant value 0x600850.
4215 (@value{GDBP}) watch *(int *) 0x600850
4216 Watchpoint 1: *(int *) 6293584
4219 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4220 watchpoints execute very quickly, and the debugger reports a change in
4221 value at the exact instruction where the change occurs. If @value{GDBN}
4222 cannot set a hardware watchpoint, it sets a software watchpoint, which
4223 executes more slowly and reports the change in value at the next
4224 @emph{statement}, not the instruction, after the change occurs.
4226 @cindex use only software watchpoints
4227 You can force @value{GDBN} to use only software watchpoints with the
4228 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4229 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4230 the underlying system supports them. (Note that hardware-assisted
4231 watchpoints that were set @emph{before} setting
4232 @code{can-use-hw-watchpoints} to zero will still use the hardware
4233 mechanism of watching expression values.)
4236 @item set can-use-hw-watchpoints
4237 @kindex set can-use-hw-watchpoints
4238 Set whether or not to use hardware watchpoints.
4240 @item show can-use-hw-watchpoints
4241 @kindex show can-use-hw-watchpoints
4242 Show the current mode of using hardware watchpoints.
4245 For remote targets, you can restrict the number of hardware
4246 watchpoints @value{GDBN} will use, see @ref{set remote
4247 hardware-breakpoint-limit}.
4249 When you issue the @code{watch} command, @value{GDBN} reports
4252 Hardware watchpoint @var{num}: @var{expr}
4256 if it was able to set a hardware watchpoint.
4258 Currently, the @code{awatch} and @code{rwatch} commands can only set
4259 hardware watchpoints, because accesses to data that don't change the
4260 value of the watched expression cannot be detected without examining
4261 every instruction as it is being executed, and @value{GDBN} does not do
4262 that currently. If @value{GDBN} finds that it is unable to set a
4263 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4264 will print a message like this:
4267 Expression cannot be implemented with read/access watchpoint.
4270 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4271 data type of the watched expression is wider than what a hardware
4272 watchpoint on the target machine can handle. For example, some systems
4273 can only watch regions that are up to 4 bytes wide; on such systems you
4274 cannot set hardware watchpoints for an expression that yields a
4275 double-precision floating-point number (which is typically 8 bytes
4276 wide). As a work-around, it might be possible to break the large region
4277 into a series of smaller ones and watch them with separate watchpoints.
4279 If you set too many hardware watchpoints, @value{GDBN} might be unable
4280 to insert all of them when you resume the execution of your program.
4281 Since the precise number of active watchpoints is unknown until such
4282 time as the program is about to be resumed, @value{GDBN} might not be
4283 able to warn you about this when you set the watchpoints, and the
4284 warning will be printed only when the program is resumed:
4287 Hardware watchpoint @var{num}: Could not insert watchpoint
4291 If this happens, delete or disable some of the watchpoints.
4293 Watching complex expressions that reference many variables can also
4294 exhaust the resources available for hardware-assisted watchpoints.
4295 That's because @value{GDBN} needs to watch every variable in the
4296 expression with separately allocated resources.
4298 If you call a function interactively using @code{print} or @code{call},
4299 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4300 kind of breakpoint or the call completes.
4302 @value{GDBN} automatically deletes watchpoints that watch local
4303 (automatic) variables, or expressions that involve such variables, when
4304 they go out of scope, that is, when the execution leaves the block in
4305 which these variables were defined. In particular, when the program
4306 being debugged terminates, @emph{all} local variables go out of scope,
4307 and so only watchpoints that watch global variables remain set. If you
4308 rerun the program, you will need to set all such watchpoints again. One
4309 way of doing that would be to set a code breakpoint at the entry to the
4310 @code{main} function and when it breaks, set all the watchpoints.
4312 @cindex watchpoints and threads
4313 @cindex threads and watchpoints
4314 In multi-threaded programs, watchpoints will detect changes to the
4315 watched expression from every thread.
4318 @emph{Warning:} In multi-threaded programs, software watchpoints
4319 have only limited usefulness. If @value{GDBN} creates a software
4320 watchpoint, it can only watch the value of an expression @emph{in a
4321 single thread}. If you are confident that the expression can only
4322 change due to the current thread's activity (and if you are also
4323 confident that no other thread can become current), then you can use
4324 software watchpoints as usual. However, @value{GDBN} may not notice
4325 when a non-current thread's activity changes the expression. (Hardware
4326 watchpoints, in contrast, watch an expression in all threads.)
4329 @xref{set remote hardware-watchpoint-limit}.
4331 @node Set Catchpoints
4332 @subsection Setting Catchpoints
4333 @cindex catchpoints, setting
4334 @cindex exception handlers
4335 @cindex event handling
4337 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4338 kinds of program events, such as C@t{++} exceptions or the loading of a
4339 shared library. Use the @code{catch} command to set a catchpoint.
4343 @item catch @var{event}
4344 Stop when @var{event} occurs. The @var{event} can be any of the following:
4347 @item throw @r{[}@var{regexp}@r{]}
4348 @itemx rethrow @r{[}@var{regexp}@r{]}
4349 @itemx catch @r{[}@var{regexp}@r{]}
4351 @kindex catch rethrow
4353 @cindex stop on C@t{++} exceptions
4354 The throwing, re-throwing, or catching of a C@t{++} exception.
4356 If @var{regexp} is given, then only exceptions whose type matches the
4357 regular expression will be caught.
4359 @vindex $_exception@r{, convenience variable}
4360 The convenience variable @code{$_exception} is available at an
4361 exception-related catchpoint, on some systems. This holds the
4362 exception being thrown.
4364 There are currently some limitations to C@t{++} exception handling in
4369 The support for these commands is system-dependent. Currently, only
4370 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4374 The regular expression feature and the @code{$_exception} convenience
4375 variable rely on the presence of some SDT probes in @code{libstdc++}.
4376 If these probes are not present, then these features cannot be used.
4377 These probes were first available in the GCC 4.8 release, but whether
4378 or not they are available in your GCC also depends on how it was
4382 The @code{$_exception} convenience variable is only valid at the
4383 instruction at which an exception-related catchpoint is set.
4386 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4387 location in the system library which implements runtime exception
4388 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4389 (@pxref{Selection}) to get to your code.
4392 If you call a function interactively, @value{GDBN} normally returns
4393 control to you when the function has finished executing. If the call
4394 raises an exception, however, the call may bypass the mechanism that
4395 returns control to you and cause your program either to abort or to
4396 simply continue running until it hits a breakpoint, catches a signal
4397 that @value{GDBN} is listening for, or exits. This is the case even if
4398 you set a catchpoint for the exception; catchpoints on exceptions are
4399 disabled within interactive calls. @xref{Calling}, for information on
4400 controlling this with @code{set unwind-on-terminating-exception}.
4403 You cannot raise an exception interactively.
4406 You cannot install an exception handler interactively.
4410 @kindex catch exception
4411 @cindex Ada exception catching
4412 @cindex catch Ada exceptions
4413 An Ada exception being raised. If an exception name is specified
4414 at the end of the command (eg @code{catch exception Program_Error}),
4415 the debugger will stop only when this specific exception is raised.
4416 Otherwise, the debugger stops execution when any Ada exception is raised.
4418 When inserting an exception catchpoint on a user-defined exception whose
4419 name is identical to one of the exceptions defined by the language, the
4420 fully qualified name must be used as the exception name. Otherwise,
4421 @value{GDBN} will assume that it should stop on the pre-defined exception
4422 rather than the user-defined one. For instance, assuming an exception
4423 called @code{Constraint_Error} is defined in package @code{Pck}, then
4424 the command to use to catch such exceptions is @kbd{catch exception
4425 Pck.Constraint_Error}.
4427 @item exception unhandled
4428 @kindex catch exception unhandled
4429 An exception that was raised but is not handled by the program.
4432 @kindex catch assert
4433 A failed Ada assertion.
4437 @cindex break on fork/exec
4438 A call to @code{exec}.
4441 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4442 @kindex catch syscall
4443 @cindex break on a system call.
4444 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4445 syscall is a mechanism for application programs to request a service
4446 from the operating system (OS) or one of the OS system services.
4447 @value{GDBN} can catch some or all of the syscalls issued by the
4448 debuggee, and show the related information for each syscall. If no
4449 argument is specified, calls to and returns from all system calls
4452 @var{name} can be any system call name that is valid for the
4453 underlying OS. Just what syscalls are valid depends on the OS. On
4454 GNU and Unix systems, you can find the full list of valid syscall
4455 names on @file{/usr/include/asm/unistd.h}.
4457 @c For MS-Windows, the syscall names and the corresponding numbers
4458 @c can be found, e.g., on this URL:
4459 @c http://www.metasploit.com/users/opcode/syscalls.html
4460 @c but we don't support Windows syscalls yet.
4462 Normally, @value{GDBN} knows in advance which syscalls are valid for
4463 each OS, so you can use the @value{GDBN} command-line completion
4464 facilities (@pxref{Completion,, command completion}) to list the
4467 You may also specify the system call numerically. A syscall's
4468 number is the value passed to the OS's syscall dispatcher to
4469 identify the requested service. When you specify the syscall by its
4470 name, @value{GDBN} uses its database of syscalls to convert the name
4471 into the corresponding numeric code, but using the number directly
4472 may be useful if @value{GDBN}'s database does not have the complete
4473 list of syscalls on your system (e.g., because @value{GDBN} lags
4474 behind the OS upgrades).
4476 You may specify a group of related syscalls to be caught at once using
4477 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4478 instance, on some platforms @value{GDBN} allows you to catch all
4479 network related syscalls, by passing the argument @code{group:network}
4480 to @code{catch syscall}. Note that not all syscall groups are
4481 available in every system. You can use the command completion
4482 facilities (@pxref{Completion,, command completion}) to list the
4483 syscall groups available on your environment.
4485 The example below illustrates how this command works if you don't provide
4489 (@value{GDBP}) catch syscall
4490 Catchpoint 1 (syscall)
4492 Starting program: /tmp/catch-syscall
4494 Catchpoint 1 (call to syscall 'close'), \
4495 0xffffe424 in __kernel_vsyscall ()
4499 Catchpoint 1 (returned from syscall 'close'), \
4500 0xffffe424 in __kernel_vsyscall ()
4504 Here is an example of catching a system call by name:
4507 (@value{GDBP}) catch syscall chroot
4508 Catchpoint 1 (syscall 'chroot' [61])
4510 Starting program: /tmp/catch-syscall
4512 Catchpoint 1 (call to syscall 'chroot'), \
4513 0xffffe424 in __kernel_vsyscall ()
4517 Catchpoint 1 (returned from syscall 'chroot'), \
4518 0xffffe424 in __kernel_vsyscall ()
4522 An example of specifying a system call numerically. In the case
4523 below, the syscall number has a corresponding entry in the XML
4524 file, so @value{GDBN} finds its name and prints it:
4527 (@value{GDBP}) catch syscall 252
4528 Catchpoint 1 (syscall(s) 'exit_group')
4530 Starting program: /tmp/catch-syscall
4532 Catchpoint 1 (call to syscall 'exit_group'), \
4533 0xffffe424 in __kernel_vsyscall ()
4537 Program exited normally.
4541 Here is an example of catching a syscall group:
4544 (@value{GDBP}) catch syscall group:process
4545 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4546 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4547 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4549 Starting program: /tmp/catch-syscall
4551 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4552 from /lib64/ld-linux-x86-64.so.2
4558 However, there can be situations when there is no corresponding name
4559 in XML file for that syscall number. In this case, @value{GDBN} prints
4560 a warning message saying that it was not able to find the syscall name,
4561 but the catchpoint will be set anyway. See the example below:
4564 (@value{GDBP}) catch syscall 764
4565 warning: The number '764' does not represent a known syscall.
4566 Catchpoint 2 (syscall 764)
4570 If you configure @value{GDBN} using the @samp{--without-expat} option,
4571 it will not be able to display syscall names. Also, if your
4572 architecture does not have an XML file describing its system calls,
4573 you will not be able to see the syscall names. It is important to
4574 notice that these two features are used for accessing the syscall
4575 name database. In either case, you will see a warning like this:
4578 (@value{GDBP}) catch syscall
4579 warning: Could not open "syscalls/i386-linux.xml"
4580 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4581 GDB will not be able to display syscall names.
4582 Catchpoint 1 (syscall)
4586 Of course, the file name will change depending on your architecture and system.
4588 Still using the example above, you can also try to catch a syscall by its
4589 number. In this case, you would see something like:
4592 (@value{GDBP}) catch syscall 252
4593 Catchpoint 1 (syscall(s) 252)
4596 Again, in this case @value{GDBN} would not be able to display syscall's names.
4600 A call to @code{fork}.
4604 A call to @code{vfork}.
4606 @item load @r{[}regexp@r{]}
4607 @itemx unload @r{[}regexp@r{]}
4609 @kindex catch unload
4610 The loading or unloading of a shared library. If @var{regexp} is
4611 given, then the catchpoint will stop only if the regular expression
4612 matches one of the affected libraries.
4614 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4615 @kindex catch signal
4616 The delivery of a signal.
4618 With no arguments, this catchpoint will catch any signal that is not
4619 used internally by @value{GDBN}, specifically, all signals except
4620 @samp{SIGTRAP} and @samp{SIGINT}.
4622 With the argument @samp{all}, all signals, including those used by
4623 @value{GDBN}, will be caught. This argument cannot be used with other
4626 Otherwise, the arguments are a list of signal names as given to
4627 @code{handle} (@pxref{Signals}). Only signals specified in this list
4630 One reason that @code{catch signal} can be more useful than
4631 @code{handle} is that you can attach commands and conditions to the
4634 When a signal is caught by a catchpoint, the signal's @code{stop} and
4635 @code{print} settings, as specified by @code{handle}, are ignored.
4636 However, whether the signal is still delivered to the inferior depends
4637 on the @code{pass} setting; this can be changed in the catchpoint's
4642 @item tcatch @var{event}
4644 Set a catchpoint that is enabled only for one stop. The catchpoint is
4645 automatically deleted after the first time the event is caught.
4649 Use the @code{info break} command to list the current catchpoints.
4653 @subsection Deleting Breakpoints
4655 @cindex clearing breakpoints, watchpoints, catchpoints
4656 @cindex deleting breakpoints, watchpoints, catchpoints
4657 It is often necessary to eliminate a breakpoint, watchpoint, or
4658 catchpoint once it has done its job and you no longer want your program
4659 to stop there. This is called @dfn{deleting} the breakpoint. A
4660 breakpoint that has been deleted no longer exists; it is forgotten.
4662 With the @code{clear} command you can delete breakpoints according to
4663 where they are in your program. With the @code{delete} command you can
4664 delete individual breakpoints, watchpoints, or catchpoints by specifying
4665 their breakpoint numbers.
4667 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4668 automatically ignores breakpoints on the first instruction to be executed
4669 when you continue execution without changing the execution address.
4674 Delete any breakpoints at the next instruction to be executed in the
4675 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4676 the innermost frame is selected, this is a good way to delete a
4677 breakpoint where your program just stopped.
4679 @item clear @var{location}
4680 Delete any breakpoints set at the specified @var{location}.
4681 @xref{Specify Location}, for the various forms of @var{location}; the
4682 most useful ones are listed below:
4685 @item clear @var{function}
4686 @itemx clear @var{filename}:@var{function}
4687 Delete any breakpoints set at entry to the named @var{function}.
4689 @item clear @var{linenum}
4690 @itemx clear @var{filename}:@var{linenum}
4691 Delete any breakpoints set at or within the code of the specified
4692 @var{linenum} of the specified @var{filename}.
4695 @cindex delete breakpoints
4697 @kindex d @r{(@code{delete})}
4698 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4699 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4700 list specified as argument. If no argument is specified, delete all
4701 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4702 confirm off}). You can abbreviate this command as @code{d}.
4706 @subsection Disabling Breakpoints
4708 @cindex enable/disable a breakpoint
4709 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4710 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4711 it had been deleted, but remembers the information on the breakpoint so
4712 that you can @dfn{enable} it again later.
4714 You disable and enable breakpoints, watchpoints, and catchpoints with
4715 the @code{enable} and @code{disable} commands, optionally specifying
4716 one or more breakpoint numbers as arguments. Use @code{info break} to
4717 print a list of all breakpoints, watchpoints, and catchpoints if you
4718 do not know which numbers to use.
4720 Disabling and enabling a breakpoint that has multiple locations
4721 affects all of its locations.
4723 A breakpoint, watchpoint, or catchpoint can have any of several
4724 different states of enablement:
4728 Enabled. The breakpoint stops your program. A breakpoint set
4729 with the @code{break} command starts out in this state.
4731 Disabled. The breakpoint has no effect on your program.
4733 Enabled once. The breakpoint stops your program, but then becomes
4736 Enabled for a count. The breakpoint stops your program for the next
4737 N times, then becomes disabled.
4739 Enabled for deletion. The breakpoint stops your program, but
4740 immediately after it does so it is deleted permanently. A breakpoint
4741 set with the @code{tbreak} command starts out in this state.
4744 You can use the following commands to enable or disable breakpoints,
4745 watchpoints, and catchpoints:
4749 @kindex dis @r{(@code{disable})}
4750 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4751 Disable the specified breakpoints---or all breakpoints, if none are
4752 listed. A disabled breakpoint has no effect but is not forgotten. All
4753 options such as ignore-counts, conditions and commands are remembered in
4754 case the breakpoint is enabled again later. You may abbreviate
4755 @code{disable} as @code{dis}.
4758 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4759 Enable the specified breakpoints (or all defined breakpoints). They
4760 become effective once again in stopping your program.
4762 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4763 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4764 of these breakpoints immediately after stopping your program.
4766 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4767 Enable the specified breakpoints temporarily. @value{GDBN} records
4768 @var{count} with each of the specified breakpoints, and decrements a
4769 breakpoint's count when it is hit. When any count reaches 0,
4770 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4771 count (@pxref{Conditions, ,Break Conditions}), that will be
4772 decremented to 0 before @var{count} is affected.
4774 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4775 Enable the specified breakpoints to work once, then die. @value{GDBN}
4776 deletes any of these breakpoints as soon as your program stops there.
4777 Breakpoints set by the @code{tbreak} command start out in this state.
4780 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4781 @c confusing: tbreak is also initially enabled.
4782 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4783 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4784 subsequently, they become disabled or enabled only when you use one of
4785 the commands above. (The command @code{until} can set and delete a
4786 breakpoint of its own, but it does not change the state of your other
4787 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4791 @subsection Break Conditions
4792 @cindex conditional breakpoints
4793 @cindex breakpoint conditions
4795 @c FIXME what is scope of break condition expr? Context where wanted?
4796 @c in particular for a watchpoint?
4797 The simplest sort of breakpoint breaks every time your program reaches a
4798 specified place. You can also specify a @dfn{condition} for a
4799 breakpoint. A condition is just a Boolean expression in your
4800 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4801 a condition evaluates the expression each time your program reaches it,
4802 and your program stops only if the condition is @emph{true}.
4804 This is the converse of using assertions for program validation; in that
4805 situation, you want to stop when the assertion is violated---that is,
4806 when the condition is false. In C, if you want to test an assertion expressed
4807 by the condition @var{assert}, you should set the condition
4808 @samp{! @var{assert}} on the appropriate breakpoint.
4810 Conditions are also accepted for watchpoints; you may not need them,
4811 since a watchpoint is inspecting the value of an expression anyhow---but
4812 it might be simpler, say, to just set a watchpoint on a variable name,
4813 and specify a condition that tests whether the new value is an interesting
4816 Break conditions can have side effects, and may even call functions in
4817 your program. This can be useful, for example, to activate functions
4818 that log program progress, or to use your own print functions to
4819 format special data structures. The effects are completely predictable
4820 unless there is another enabled breakpoint at the same address. (In
4821 that case, @value{GDBN} might see the other breakpoint first and stop your
4822 program without checking the condition of this one.) Note that
4823 breakpoint commands are usually more convenient and flexible than break
4825 purpose of performing side effects when a breakpoint is reached
4826 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4828 Breakpoint conditions can also be evaluated on the target's side if
4829 the target supports it. Instead of evaluating the conditions locally,
4830 @value{GDBN} encodes the expression into an agent expression
4831 (@pxref{Agent Expressions}) suitable for execution on the target,
4832 independently of @value{GDBN}. Global variables become raw memory
4833 locations, locals become stack accesses, and so forth.
4835 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4836 when its condition evaluates to true. This mechanism may provide faster
4837 response times depending on the performance characteristics of the target
4838 since it does not need to keep @value{GDBN} informed about
4839 every breakpoint trigger, even those with false conditions.
4841 Break conditions can be specified when a breakpoint is set, by using
4842 @samp{if} in the arguments to the @code{break} command. @xref{Set
4843 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4844 with the @code{condition} command.
4846 You can also use the @code{if} keyword with the @code{watch} command.
4847 The @code{catch} command does not recognize the @code{if} keyword;
4848 @code{condition} is the only way to impose a further condition on a
4853 @item condition @var{bnum} @var{expression}
4854 Specify @var{expression} as the break condition for breakpoint,
4855 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4856 breakpoint @var{bnum} stops your program only if the value of
4857 @var{expression} is true (nonzero, in C). When you use
4858 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4859 syntactic correctness, and to determine whether symbols in it have
4860 referents in the context of your breakpoint. If @var{expression} uses
4861 symbols not referenced in the context of the breakpoint, @value{GDBN}
4862 prints an error message:
4865 No symbol "foo" in current context.
4870 not actually evaluate @var{expression} at the time the @code{condition}
4871 command (or a command that sets a breakpoint with a condition, like
4872 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4874 @item condition @var{bnum}
4875 Remove the condition from breakpoint number @var{bnum}. It becomes
4876 an ordinary unconditional breakpoint.
4879 @cindex ignore count (of breakpoint)
4880 A special case of a breakpoint condition is to stop only when the
4881 breakpoint has been reached a certain number of times. This is so
4882 useful that there is a special way to do it, using the @dfn{ignore
4883 count} of the breakpoint. Every breakpoint has an ignore count, which
4884 is an integer. Most of the time, the ignore count is zero, and
4885 therefore has no effect. But if your program reaches a breakpoint whose
4886 ignore count is positive, then instead of stopping, it just decrements
4887 the ignore count by one and continues. As a result, if the ignore count
4888 value is @var{n}, the breakpoint does not stop the next @var{n} times
4889 your program reaches it.
4893 @item ignore @var{bnum} @var{count}
4894 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4895 The next @var{count} times the breakpoint is reached, your program's
4896 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4899 To make the breakpoint stop the next time it is reached, specify
4902 When you use @code{continue} to resume execution of your program from a
4903 breakpoint, you can specify an ignore count directly as an argument to
4904 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4905 Stepping,,Continuing and Stepping}.
4907 If a breakpoint has a positive ignore count and a condition, the
4908 condition is not checked. Once the ignore count reaches zero,
4909 @value{GDBN} resumes checking the condition.
4911 You could achieve the effect of the ignore count with a condition such
4912 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4913 is decremented each time. @xref{Convenience Vars, ,Convenience
4917 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4920 @node Break Commands
4921 @subsection Breakpoint Command Lists
4923 @cindex breakpoint commands
4924 You can give any breakpoint (or watchpoint or catchpoint) a series of
4925 commands to execute when your program stops due to that breakpoint. For
4926 example, you might want to print the values of certain expressions, or
4927 enable other breakpoints.
4931 @kindex end@r{ (breakpoint commands)}
4932 @item commands @r{[}@var{list}@dots{}@r{]}
4933 @itemx @dots{} @var{command-list} @dots{}
4935 Specify a list of commands for the given breakpoints. The commands
4936 themselves appear on the following lines. Type a line containing just
4937 @code{end} to terminate the commands.
4939 To remove all commands from a breakpoint, type @code{commands} and
4940 follow it immediately with @code{end}; that is, give no commands.
4942 With no argument, @code{commands} refers to the last breakpoint,
4943 watchpoint, or catchpoint set (not to the breakpoint most recently
4944 encountered). If the most recent breakpoints were set with a single
4945 command, then the @code{commands} will apply to all the breakpoints
4946 set by that command. This applies to breakpoints set by
4947 @code{rbreak}, and also applies when a single @code{break} command
4948 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4952 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4953 disabled within a @var{command-list}.
4955 You can use breakpoint commands to start your program up again. Simply
4956 use the @code{continue} command, or @code{step}, or any other command
4957 that resumes execution.
4959 Any other commands in the command list, after a command that resumes
4960 execution, are ignored. This is because any time you resume execution
4961 (even with a simple @code{next} or @code{step}), you may encounter
4962 another breakpoint---which could have its own command list, leading to
4963 ambiguities about which list to execute.
4966 If the first command you specify in a command list is @code{silent}, the
4967 usual message about stopping at a breakpoint is not printed. This may
4968 be desirable for breakpoints that are to print a specific message and
4969 then continue. If none of the remaining commands print anything, you
4970 see no sign that the breakpoint was reached. @code{silent} is
4971 meaningful only at the beginning of a breakpoint command list.
4973 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4974 print precisely controlled output, and are often useful in silent
4975 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4977 For example, here is how you could use breakpoint commands to print the
4978 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4984 printf "x is %d\n",x
4989 One application for breakpoint commands is to compensate for one bug so
4990 you can test for another. Put a breakpoint just after the erroneous line
4991 of code, give it a condition to detect the case in which something
4992 erroneous has been done, and give it commands to assign correct values
4993 to any variables that need them. End with the @code{continue} command
4994 so that your program does not stop, and start with the @code{silent}
4995 command so that no output is produced. Here is an example:
5006 @node Dynamic Printf
5007 @subsection Dynamic Printf
5009 @cindex dynamic printf
5011 The dynamic printf command @code{dprintf} combines a breakpoint with
5012 formatted printing of your program's data to give you the effect of
5013 inserting @code{printf} calls into your program on-the-fly, without
5014 having to recompile it.
5016 In its most basic form, the output goes to the GDB console. However,
5017 you can set the variable @code{dprintf-style} for alternate handling.
5018 For instance, you can ask to format the output by calling your
5019 program's @code{printf} function. This has the advantage that the
5020 characters go to the program's output device, so they can recorded in
5021 redirects to files and so forth.
5023 If you are doing remote debugging with a stub or agent, you can also
5024 ask to have the printf handled by the remote agent. In addition to
5025 ensuring that the output goes to the remote program's device along
5026 with any other output the program might produce, you can also ask that
5027 the dprintf remain active even after disconnecting from the remote
5028 target. Using the stub/agent is also more efficient, as it can do
5029 everything without needing to communicate with @value{GDBN}.
5033 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5034 Whenever execution reaches @var{location}, print the values of one or
5035 more @var{expressions} under the control of the string @var{template}.
5036 To print several values, separate them with commas.
5038 @item set dprintf-style @var{style}
5039 Set the dprintf output to be handled in one of several different
5040 styles enumerated below. A change of style affects all existing
5041 dynamic printfs immediately. (If you need individual control over the
5042 print commands, simply define normal breakpoints with
5043 explicitly-supplied command lists.)
5047 @kindex dprintf-style gdb
5048 Handle the output using the @value{GDBN} @code{printf} command.
5051 @kindex dprintf-style call
5052 Handle the output by calling a function in your program (normally
5056 @kindex dprintf-style agent
5057 Have the remote debugging agent (such as @code{gdbserver}) handle
5058 the output itself. This style is only available for agents that
5059 support running commands on the target.
5062 @item set dprintf-function @var{function}
5063 Set the function to call if the dprintf style is @code{call}. By
5064 default its value is @code{printf}. You may set it to any expression.
5065 that @value{GDBN} can evaluate to a function, as per the @code{call}
5068 @item set dprintf-channel @var{channel}
5069 Set a ``channel'' for dprintf. If set to a non-empty value,
5070 @value{GDBN} will evaluate it as an expression and pass the result as
5071 a first argument to the @code{dprintf-function}, in the manner of
5072 @code{fprintf} and similar functions. Otherwise, the dprintf format
5073 string will be the first argument, in the manner of @code{printf}.
5075 As an example, if you wanted @code{dprintf} output to go to a logfile
5076 that is a standard I/O stream assigned to the variable @code{mylog},
5077 you could do the following:
5080 (gdb) set dprintf-style call
5081 (gdb) set dprintf-function fprintf
5082 (gdb) set dprintf-channel mylog
5083 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5084 Dprintf 1 at 0x123456: file main.c, line 25.
5086 1 dprintf keep y 0x00123456 in main at main.c:25
5087 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5092 Note that the @code{info break} displays the dynamic printf commands
5093 as normal breakpoint commands; you can thus easily see the effect of
5094 the variable settings.
5096 @item set disconnected-dprintf on
5097 @itemx set disconnected-dprintf off
5098 @kindex set disconnected-dprintf
5099 Choose whether @code{dprintf} commands should continue to run if
5100 @value{GDBN} has disconnected from the target. This only applies
5101 if the @code{dprintf-style} is @code{agent}.
5103 @item show disconnected-dprintf off
5104 @kindex show disconnected-dprintf
5105 Show the current choice for disconnected @code{dprintf}.
5109 @value{GDBN} does not check the validity of function and channel,
5110 relying on you to supply values that are meaningful for the contexts
5111 in which they are being used. For instance, the function and channel
5112 may be the values of local variables, but if that is the case, then
5113 all enabled dynamic prints must be at locations within the scope of
5114 those locals. If evaluation fails, @value{GDBN} will report an error.
5116 @node Save Breakpoints
5117 @subsection How to save breakpoints to a file
5119 To save breakpoint definitions to a file use the @w{@code{save
5120 breakpoints}} command.
5123 @kindex save breakpoints
5124 @cindex save breakpoints to a file for future sessions
5125 @item save breakpoints [@var{filename}]
5126 This command saves all current breakpoint definitions together with
5127 their commands and ignore counts, into a file @file{@var{filename}}
5128 suitable for use in a later debugging session. This includes all
5129 types of breakpoints (breakpoints, watchpoints, catchpoints,
5130 tracepoints). To read the saved breakpoint definitions, use the
5131 @code{source} command (@pxref{Command Files}). Note that watchpoints
5132 with expressions involving local variables may fail to be recreated
5133 because it may not be possible to access the context where the
5134 watchpoint is valid anymore. Because the saved breakpoint definitions
5135 are simply a sequence of @value{GDBN} commands that recreate the
5136 breakpoints, you can edit the file in your favorite editing program,
5137 and remove the breakpoint definitions you're not interested in, or
5138 that can no longer be recreated.
5141 @node Static Probe Points
5142 @subsection Static Probe Points
5144 @cindex static probe point, SystemTap
5145 @cindex static probe point, DTrace
5146 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5147 for Statically Defined Tracing, and the probes are designed to have a tiny
5148 runtime code and data footprint, and no dynamic relocations.
5150 Currently, the following types of probes are supported on
5151 ELF-compatible systems:
5155 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5156 @acronym{SDT} probes@footnote{See
5157 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5158 for more information on how to add @code{SystemTap} @acronym{SDT}
5159 probes in your applications.}. @code{SystemTap} probes are usable
5160 from assembly, C and C@t{++} languages@footnote{See
5161 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5162 for a good reference on how the @acronym{SDT} probes are implemented.}.
5164 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5165 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5169 @cindex semaphores on static probe points
5170 Some @code{SystemTap} probes have an associated semaphore variable;
5171 for instance, this happens automatically if you defined your probe
5172 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5173 @value{GDBN} will automatically enable it when you specify a
5174 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5175 breakpoint at a probe's location by some other method (e.g.,
5176 @code{break file:line}), then @value{GDBN} will not automatically set
5177 the semaphore. @code{DTrace} probes do not support semaphores.
5179 You can examine the available static static probes using @code{info
5180 probes}, with optional arguments:
5184 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5185 If given, @var{type} is either @code{stap} for listing
5186 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5187 probes. If omitted all probes are listed regardless of their types.
5189 If given, @var{provider} is a regular expression used to match against provider
5190 names when selecting which probes to list. If omitted, probes by all
5191 probes from all providers are listed.
5193 If given, @var{name} is a regular expression to match against probe names
5194 when selecting which probes to list. If omitted, probe names are not
5195 considered when deciding whether to display them.
5197 If given, @var{objfile} is a regular expression used to select which
5198 object files (executable or shared libraries) to examine. If not
5199 given, all object files are considered.
5201 @item info probes all
5202 List the available static probes, from all types.
5205 @cindex enabling and disabling probes
5206 Some probe points can be enabled and/or disabled. The effect of
5207 enabling or disabling a probe depends on the type of probe being
5208 handled. Some @code{DTrace} probes can be enabled or
5209 disabled, but @code{SystemTap} probes cannot be disabled.
5211 You can enable (or disable) one or more probes using the following
5212 commands, with optional arguments:
5215 @kindex enable probes
5216 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5217 If given, @var{provider} is a regular expression used to match against
5218 provider names when selecting which probes to enable. If omitted,
5219 all probes from all providers are enabled.
5221 If given, @var{name} is a regular expression to match against probe
5222 names when selecting which probes to enable. If omitted, probe names
5223 are not considered when deciding whether to enable them.
5225 If given, @var{objfile} is a regular expression used to select which
5226 object files (executable or shared libraries) to examine. If not
5227 given, all object files are considered.
5229 @kindex disable probes
5230 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5231 See the @code{enable probes} command above for a description of the
5232 optional arguments accepted by this command.
5235 @vindex $_probe_arg@r{, convenience variable}
5236 A probe may specify up to twelve arguments. These are available at the
5237 point at which the probe is defined---that is, when the current PC is
5238 at the probe's location. The arguments are available using the
5239 convenience variables (@pxref{Convenience Vars})
5240 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5241 probes each probe argument is an integer of the appropriate size;
5242 types are not preserved. In @code{DTrace} probes types are preserved
5243 provided that they are recognized as such by @value{GDBN}; otherwise
5244 the value of the probe argument will be a long integer. The
5245 convenience variable @code{$_probe_argc} holds the number of arguments
5246 at the current probe point.
5248 These variables are always available, but attempts to access them at
5249 any location other than a probe point will cause @value{GDBN} to give
5253 @c @ifclear BARETARGET
5254 @node Error in Breakpoints
5255 @subsection ``Cannot insert breakpoints''
5257 If you request too many active hardware-assisted breakpoints and
5258 watchpoints, you will see this error message:
5260 @c FIXME: the precise wording of this message may change; the relevant
5261 @c source change is not committed yet (Sep 3, 1999).
5263 Stopped; cannot insert breakpoints.
5264 You may have requested too many hardware breakpoints and watchpoints.
5268 This message is printed when you attempt to resume the program, since
5269 only then @value{GDBN} knows exactly how many hardware breakpoints and
5270 watchpoints it needs to insert.
5272 When this message is printed, you need to disable or remove some of the
5273 hardware-assisted breakpoints and watchpoints, and then continue.
5275 @node Breakpoint-related Warnings
5276 @subsection ``Breakpoint address adjusted...''
5277 @cindex breakpoint address adjusted
5279 Some processor architectures place constraints on the addresses at
5280 which breakpoints may be placed. For architectures thus constrained,
5281 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5282 with the constraints dictated by the architecture.
5284 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5285 a VLIW architecture in which a number of RISC-like instructions may be
5286 bundled together for parallel execution. The FR-V architecture
5287 constrains the location of a breakpoint instruction within such a
5288 bundle to the instruction with the lowest address. @value{GDBN}
5289 honors this constraint by adjusting a breakpoint's address to the
5290 first in the bundle.
5292 It is not uncommon for optimized code to have bundles which contain
5293 instructions from different source statements, thus it may happen that
5294 a breakpoint's address will be adjusted from one source statement to
5295 another. Since this adjustment may significantly alter @value{GDBN}'s
5296 breakpoint related behavior from what the user expects, a warning is
5297 printed when the breakpoint is first set and also when the breakpoint
5300 A warning like the one below is printed when setting a breakpoint
5301 that's been subject to address adjustment:
5304 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5307 Such warnings are printed both for user settable and @value{GDBN}'s
5308 internal breakpoints. If you see one of these warnings, you should
5309 verify that a breakpoint set at the adjusted address will have the
5310 desired affect. If not, the breakpoint in question may be removed and
5311 other breakpoints may be set which will have the desired behavior.
5312 E.g., it may be sufficient to place the breakpoint at a later
5313 instruction. A conditional breakpoint may also be useful in some
5314 cases to prevent the breakpoint from triggering too often.
5316 @value{GDBN} will also issue a warning when stopping at one of these
5317 adjusted breakpoints:
5320 warning: Breakpoint 1 address previously adjusted from 0x00010414
5324 When this warning is encountered, it may be too late to take remedial
5325 action except in cases where the breakpoint is hit earlier or more
5326 frequently than expected.
5328 @node Continuing and Stepping
5329 @section Continuing and Stepping
5333 @cindex resuming execution
5334 @dfn{Continuing} means resuming program execution until your program
5335 completes normally. In contrast, @dfn{stepping} means executing just
5336 one more ``step'' of your program, where ``step'' may mean either one
5337 line of source code, or one machine instruction (depending on what
5338 particular command you use). Either when continuing or when stepping,
5339 your program may stop even sooner, due to a breakpoint or a signal. (If
5340 it stops due to a signal, you may want to use @code{handle}, or use
5341 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5342 or you may step into the signal's handler (@pxref{stepping and signal
5347 @kindex c @r{(@code{continue})}
5348 @kindex fg @r{(resume foreground execution)}
5349 @item continue @r{[}@var{ignore-count}@r{]}
5350 @itemx c @r{[}@var{ignore-count}@r{]}
5351 @itemx fg @r{[}@var{ignore-count}@r{]}
5352 Resume program execution, at the address where your program last stopped;
5353 any breakpoints set at that address are bypassed. The optional argument
5354 @var{ignore-count} allows you to specify a further number of times to
5355 ignore a breakpoint at this location; its effect is like that of
5356 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5358 The argument @var{ignore-count} is meaningful only when your program
5359 stopped due to a breakpoint. At other times, the argument to
5360 @code{continue} is ignored.
5362 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5363 debugged program is deemed to be the foreground program) are provided
5364 purely for convenience, and have exactly the same behavior as
5368 To resume execution at a different place, you can use @code{return}
5369 (@pxref{Returning, ,Returning from a Function}) to go back to the
5370 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5371 Different Address}) to go to an arbitrary location in your program.
5373 A typical technique for using stepping is to set a breakpoint
5374 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5375 beginning of the function or the section of your program where a problem
5376 is believed to lie, run your program until it stops at that breakpoint,
5377 and then step through the suspect area, examining the variables that are
5378 interesting, until you see the problem happen.
5382 @kindex s @r{(@code{step})}
5384 Continue running your program until control reaches a different source
5385 line, then stop it and return control to @value{GDBN}. This command is
5386 abbreviated @code{s}.
5389 @c "without debugging information" is imprecise; actually "without line
5390 @c numbers in the debugging information". (gcc -g1 has debugging info but
5391 @c not line numbers). But it seems complex to try to make that
5392 @c distinction here.
5393 @emph{Warning:} If you use the @code{step} command while control is
5394 within a function that was compiled without debugging information,
5395 execution proceeds until control reaches a function that does have
5396 debugging information. Likewise, it will not step into a function which
5397 is compiled without debugging information. To step through functions
5398 without debugging information, use the @code{stepi} command, described
5402 The @code{step} command only stops at the first instruction of a source
5403 line. This prevents the multiple stops that could otherwise occur in
5404 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5405 to stop if a function that has debugging information is called within
5406 the line. In other words, @code{step} @emph{steps inside} any functions
5407 called within the line.
5409 Also, the @code{step} command only enters a function if there is line
5410 number information for the function. Otherwise it acts like the
5411 @code{next} command. This avoids problems when using @code{cc -gl}
5412 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5413 was any debugging information about the routine.
5415 @item step @var{count}
5416 Continue running as in @code{step}, but do so @var{count} times. If a
5417 breakpoint is reached, or a signal not related to stepping occurs before
5418 @var{count} steps, stepping stops right away.
5421 @kindex n @r{(@code{next})}
5422 @item next @r{[}@var{count}@r{]}
5423 Continue to the next source line in the current (innermost) stack frame.
5424 This is similar to @code{step}, but function calls that appear within
5425 the line of code are executed without stopping. Execution stops when
5426 control reaches a different line of code at the original stack level
5427 that was executing when you gave the @code{next} command. This command
5428 is abbreviated @code{n}.
5430 An argument @var{count} is a repeat count, as for @code{step}.
5433 @c FIX ME!! Do we delete this, or is there a way it fits in with
5434 @c the following paragraph? --- Vctoria
5436 @c @code{next} within a function that lacks debugging information acts like
5437 @c @code{step}, but any function calls appearing within the code of the
5438 @c function are executed without stopping.
5440 The @code{next} command only stops at the first instruction of a
5441 source line. This prevents multiple stops that could otherwise occur in
5442 @code{switch} statements, @code{for} loops, etc.
5444 @kindex set step-mode
5446 @cindex functions without line info, and stepping
5447 @cindex stepping into functions with no line info
5448 @itemx set step-mode on
5449 The @code{set step-mode on} command causes the @code{step} command to
5450 stop at the first instruction of a function which contains no debug line
5451 information rather than stepping over it.
5453 This is useful in cases where you may be interested in inspecting the
5454 machine instructions of a function which has no symbolic info and do not
5455 want @value{GDBN} to automatically skip over this function.
5457 @item set step-mode off
5458 Causes the @code{step} command to step over any functions which contains no
5459 debug information. This is the default.
5461 @item show step-mode
5462 Show whether @value{GDBN} will stop in or step over functions without
5463 source line debug information.
5466 @kindex fin @r{(@code{finish})}
5468 Continue running until just after function in the selected stack frame
5469 returns. Print the returned value (if any). This command can be
5470 abbreviated as @code{fin}.
5472 Contrast this with the @code{return} command (@pxref{Returning,
5473 ,Returning from a Function}).
5476 @kindex u @r{(@code{until})}
5477 @cindex run until specified location
5480 Continue running until a source line past the current line, in the
5481 current stack frame, is reached. This command is used to avoid single
5482 stepping through a loop more than once. It is like the @code{next}
5483 command, except that when @code{until} encounters a jump, it
5484 automatically continues execution until the program counter is greater
5485 than the address of the jump.
5487 This means that when you reach the end of a loop after single stepping
5488 though it, @code{until} makes your program continue execution until it
5489 exits the loop. In contrast, a @code{next} command at the end of a loop
5490 simply steps back to the beginning of the loop, which forces you to step
5491 through the next iteration.
5493 @code{until} always stops your program if it attempts to exit the current
5496 @code{until} may produce somewhat counterintuitive results if the order
5497 of machine code does not match the order of the source lines. For
5498 example, in the following excerpt from a debugging session, the @code{f}
5499 (@code{frame}) command shows that execution is stopped at line
5500 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5504 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5506 (@value{GDBP}) until
5507 195 for ( ; argc > 0; NEXTARG) @{
5510 This happened because, for execution efficiency, the compiler had
5511 generated code for the loop closure test at the end, rather than the
5512 start, of the loop---even though the test in a C @code{for}-loop is
5513 written before the body of the loop. The @code{until} command appeared
5514 to step back to the beginning of the loop when it advanced to this
5515 expression; however, it has not really gone to an earlier
5516 statement---not in terms of the actual machine code.
5518 @code{until} with no argument works by means of single
5519 instruction stepping, and hence is slower than @code{until} with an
5522 @item until @var{location}
5523 @itemx u @var{location}
5524 Continue running your program until either the specified @var{location} is
5525 reached, or the current stack frame returns. The location is any of
5526 the forms described in @ref{Specify Location}.
5527 This form of the command uses temporary breakpoints, and
5528 hence is quicker than @code{until} without an argument. The specified
5529 location is actually reached only if it is in the current frame. This
5530 implies that @code{until} can be used to skip over recursive function
5531 invocations. For instance in the code below, if the current location is
5532 line @code{96}, issuing @code{until 99} will execute the program up to
5533 line @code{99} in the same invocation of factorial, i.e., after the inner
5534 invocations have returned.
5537 94 int factorial (int value)
5539 96 if (value > 1) @{
5540 97 value *= factorial (value - 1);
5547 @kindex advance @var{location}
5548 @item advance @var{location}
5549 Continue running the program up to the given @var{location}. An argument is
5550 required, which should be of one of the forms described in
5551 @ref{Specify Location}.
5552 Execution will also stop upon exit from the current stack
5553 frame. This command is similar to @code{until}, but @code{advance} will
5554 not skip over recursive function calls, and the target location doesn't
5555 have to be in the same frame as the current one.
5559 @kindex si @r{(@code{stepi})}
5561 @itemx stepi @var{arg}
5563 Execute one machine instruction, then stop and return to the debugger.
5565 It is often useful to do @samp{display/i $pc} when stepping by machine
5566 instructions. This makes @value{GDBN} automatically display the next
5567 instruction to be executed, each time your program stops. @xref{Auto
5568 Display,, Automatic Display}.
5570 An argument is a repeat count, as in @code{step}.
5574 @kindex ni @r{(@code{nexti})}
5576 @itemx nexti @var{arg}
5578 Execute one machine instruction, but if it is a function call,
5579 proceed until the function returns.
5581 An argument is a repeat count, as in @code{next}.
5585 @anchor{range stepping}
5586 @cindex range stepping
5587 @cindex target-assisted range stepping
5588 By default, and if available, @value{GDBN} makes use of
5589 target-assisted @dfn{range stepping}. In other words, whenever you
5590 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5591 tells the target to step the corresponding range of instruction
5592 addresses instead of issuing multiple single-steps. This speeds up
5593 line stepping, particularly for remote targets. Ideally, there should
5594 be no reason you would want to turn range stepping off. However, it's
5595 possible that a bug in the debug info, a bug in the remote stub (for
5596 remote targets), or even a bug in @value{GDBN} could make line
5597 stepping behave incorrectly when target-assisted range stepping is
5598 enabled. You can use the following command to turn off range stepping
5602 @kindex set range-stepping
5603 @kindex show range-stepping
5604 @item set range-stepping
5605 @itemx show range-stepping
5606 Control whether range stepping is enabled.
5608 If @code{on}, and the target supports it, @value{GDBN} tells the
5609 target to step a range of addresses itself, instead of issuing
5610 multiple single-steps. If @code{off}, @value{GDBN} always issues
5611 single-steps, even if range stepping is supported by the target. The
5612 default is @code{on}.
5616 @node Skipping Over Functions and Files
5617 @section Skipping Over Functions and Files
5618 @cindex skipping over functions and files
5620 The program you are debugging may contain some functions which are
5621 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5622 skip a function, all functions in a file or a particular function in
5623 a particular file when stepping.
5625 For example, consider the following C function:
5636 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5637 are not interested in stepping through @code{boring}. If you run @code{step}
5638 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5639 step over both @code{foo} and @code{boring}!
5641 One solution is to @code{step} into @code{boring} and use the @code{finish}
5642 command to immediately exit it. But this can become tedious if @code{boring}
5643 is called from many places.
5645 A more flexible solution is to execute @kbd{skip boring}. This instructs
5646 @value{GDBN} never to step into @code{boring}. Now when you execute
5647 @code{step} at line 103, you'll step over @code{boring} and directly into
5650 Functions may be skipped by providing either a function name, linespec
5651 (@pxref{Specify Location}), regular expression that matches the function's
5652 name, file name or a @code{glob}-style pattern that matches the file name.
5654 On Posix systems the form of the regular expression is
5655 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5656 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5657 expression is whatever is provided by the @code{regcomp} function of
5658 the underlying system.
5659 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5660 description of @code{glob}-style patterns.
5664 @item skip @r{[}@var{options}@r{]}
5665 The basic form of the @code{skip} command takes zero or more options
5666 that specify what to skip.
5667 The @var{options} argument is any useful combination of the following:
5670 @item -file @var{file}
5671 @itemx -fi @var{file}
5672 Functions in @var{file} will be skipped over when stepping.
5674 @item -gfile @var{file-glob-pattern}
5675 @itemx -gfi @var{file-glob-pattern}
5676 @cindex skipping over files via glob-style patterns
5677 Functions in files matching @var{file-glob-pattern} will be skipped
5681 (gdb) skip -gfi utils/*.c
5684 @item -function @var{linespec}
5685 @itemx -fu @var{linespec}
5686 Functions named by @var{linespec} or the function containing the line
5687 named by @var{linespec} will be skipped over when stepping.
5688 @xref{Specify Location}.
5690 @item -rfunction @var{regexp}
5691 @itemx -rfu @var{regexp}
5692 @cindex skipping over functions via regular expressions
5693 Functions whose name matches @var{regexp} will be skipped over when stepping.
5695 This form is useful for complex function names.
5696 For example, there is generally no need to step into C@t{++} @code{std::string}
5697 constructors or destructors. Plus with C@t{++} templates it can be hard to
5698 write out the full name of the function, and often it doesn't matter what
5699 the template arguments are. Specifying the function to be skipped as a
5700 regular expression makes this easier.
5703 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5706 If you want to skip every templated C@t{++} constructor and destructor
5707 in the @code{std} namespace you can do:
5710 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5714 If no options are specified, the function you're currently debugging
5717 @kindex skip function
5718 @item skip function @r{[}@var{linespec}@r{]}
5719 After running this command, the function named by @var{linespec} or the
5720 function containing the line named by @var{linespec} will be skipped over when
5721 stepping. @xref{Specify Location}.
5723 If you do not specify @var{linespec}, the function you're currently debugging
5726 (If you have a function called @code{file} that you want to skip, use
5727 @kbd{skip function file}.)
5730 @item skip file @r{[}@var{filename}@r{]}
5731 After running this command, any function whose source lives in @var{filename}
5732 will be skipped over when stepping.
5735 (gdb) skip file boring.c
5736 File boring.c will be skipped when stepping.
5739 If you do not specify @var{filename}, functions whose source lives in the file
5740 you're currently debugging will be skipped.
5743 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5744 These are the commands for managing your list of skips:
5748 @item info skip @r{[}@var{range}@r{]}
5749 Print details about the specified skip(s). If @var{range} is not specified,
5750 print a table with details about all functions and files marked for skipping.
5751 @code{info skip} prints the following information about each skip:
5755 A number identifying this skip.
5756 @item Enabled or Disabled
5757 Enabled skips are marked with @samp{y}.
5758 Disabled skips are marked with @samp{n}.
5760 If the file name is a @samp{glob} pattern this is @samp{y}.
5761 Otherwise it is @samp{n}.
5763 The name or @samp{glob} pattern of the file to be skipped.
5764 If no file is specified this is @samp{<none>}.
5766 If the function name is a @samp{regular expression} this is @samp{y}.
5767 Otherwise it is @samp{n}.
5769 The name or regular expression of the function to skip.
5770 If no function is specified this is @samp{<none>}.
5774 @item skip delete @r{[}@var{range}@r{]}
5775 Delete the specified skip(s). If @var{range} is not specified, delete all
5779 @item skip enable @r{[}@var{range}@r{]}
5780 Enable the specified skip(s). If @var{range} is not specified, enable all
5783 @kindex skip disable
5784 @item skip disable @r{[}@var{range}@r{]}
5785 Disable the specified skip(s). If @var{range} is not specified, disable all
5794 A signal is an asynchronous event that can happen in a program. The
5795 operating system defines the possible kinds of signals, and gives each
5796 kind a name and a number. For example, in Unix @code{SIGINT} is the
5797 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5798 @code{SIGSEGV} is the signal a program gets from referencing a place in
5799 memory far away from all the areas in use; @code{SIGALRM} occurs when
5800 the alarm clock timer goes off (which happens only if your program has
5801 requested an alarm).
5803 @cindex fatal signals
5804 Some signals, including @code{SIGALRM}, are a normal part of the
5805 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5806 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5807 program has not specified in advance some other way to handle the signal.
5808 @code{SIGINT} does not indicate an error in your program, but it is normally
5809 fatal so it can carry out the purpose of the interrupt: to kill the program.
5811 @value{GDBN} has the ability to detect any occurrence of a signal in your
5812 program. You can tell @value{GDBN} in advance what to do for each kind of
5815 @cindex handling signals
5816 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5817 @code{SIGALRM} be silently passed to your program
5818 (so as not to interfere with their role in the program's functioning)
5819 but to stop your program immediately whenever an error signal happens.
5820 You can change these settings with the @code{handle} command.
5823 @kindex info signals
5827 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5828 handle each one. You can use this to see the signal numbers of all
5829 the defined types of signals.
5831 @item info signals @var{sig}
5832 Similar, but print information only about the specified signal number.
5834 @code{info handle} is an alias for @code{info signals}.
5836 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5837 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5838 for details about this command.
5841 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5842 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5843 can be the number of a signal or its name (with or without the
5844 @samp{SIG} at the beginning); a list of signal numbers of the form
5845 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5846 known signals. Optional arguments @var{keywords}, described below,
5847 say what change to make.
5851 The keywords allowed by the @code{handle} command can be abbreviated.
5852 Their full names are:
5856 @value{GDBN} should not stop your program when this signal happens. It may
5857 still print a message telling you that the signal has come in.
5860 @value{GDBN} should stop your program when this signal happens. This implies
5861 the @code{print} keyword as well.
5864 @value{GDBN} should print a message when this signal happens.
5867 @value{GDBN} should not mention the occurrence of the signal at all. This
5868 implies the @code{nostop} keyword as well.
5872 @value{GDBN} should allow your program to see this signal; your program
5873 can handle the signal, or else it may terminate if the signal is fatal
5874 and not handled. @code{pass} and @code{noignore} are synonyms.
5878 @value{GDBN} should not allow your program to see this signal.
5879 @code{nopass} and @code{ignore} are synonyms.
5883 When a signal stops your program, the signal is not visible to the
5885 continue. Your program sees the signal then, if @code{pass} is in
5886 effect for the signal in question @emph{at that time}. In other words,
5887 after @value{GDBN} reports a signal, you can use the @code{handle}
5888 command with @code{pass} or @code{nopass} to control whether your
5889 program sees that signal when you continue.
5891 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5892 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5893 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5896 You can also use the @code{signal} command to prevent your program from
5897 seeing a signal, or cause it to see a signal it normally would not see,
5898 or to give it any signal at any time. For example, if your program stopped
5899 due to some sort of memory reference error, you might store correct
5900 values into the erroneous variables and continue, hoping to see more
5901 execution; but your program would probably terminate immediately as
5902 a result of the fatal signal once it saw the signal. To prevent this,
5903 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5906 @cindex stepping and signal handlers
5907 @anchor{stepping and signal handlers}
5909 @value{GDBN} optimizes for stepping the mainline code. If a signal
5910 that has @code{handle nostop} and @code{handle pass} set arrives while
5911 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5912 in progress, @value{GDBN} lets the signal handler run and then resumes
5913 stepping the mainline code once the signal handler returns. In other
5914 words, @value{GDBN} steps over the signal handler. This prevents
5915 signals that you've specified as not interesting (with @code{handle
5916 nostop}) from changing the focus of debugging unexpectedly. Note that
5917 the signal handler itself may still hit a breakpoint, stop for another
5918 signal that has @code{handle stop} in effect, or for any other event
5919 that normally results in stopping the stepping command sooner. Also
5920 note that @value{GDBN} still informs you that the program received a
5921 signal if @code{handle print} is set.
5923 @anchor{stepping into signal handlers}
5925 If you set @code{handle pass} for a signal, and your program sets up a
5926 handler for it, then issuing a stepping command, such as @code{step}
5927 or @code{stepi}, when your program is stopped due to the signal will
5928 step @emph{into} the signal handler (if the target supports that).
5930 Likewise, if you use the @code{queue-signal} command to queue a signal
5931 to be delivered to the current thread when execution of the thread
5932 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5933 stepping command will step into the signal handler.
5935 Here's an example, using @code{stepi} to step to the first instruction
5936 of @code{SIGUSR1}'s handler:
5939 (@value{GDBP}) handle SIGUSR1
5940 Signal Stop Print Pass to program Description
5941 SIGUSR1 Yes Yes Yes User defined signal 1
5945 Program received signal SIGUSR1, User defined signal 1.
5946 main () sigusr1.c:28
5949 sigusr1_handler () at sigusr1.c:9
5953 The same, but using @code{queue-signal} instead of waiting for the
5954 program to receive the signal first:
5959 (@value{GDBP}) queue-signal SIGUSR1
5961 sigusr1_handler () at sigusr1.c:9
5966 @cindex extra signal information
5967 @anchor{extra signal information}
5969 On some targets, @value{GDBN} can inspect extra signal information
5970 associated with the intercepted signal, before it is actually
5971 delivered to the program being debugged. This information is exported
5972 by the convenience variable @code{$_siginfo}, and consists of data
5973 that is passed by the kernel to the signal handler at the time of the
5974 receipt of a signal. The data type of the information itself is
5975 target dependent. You can see the data type using the @code{ptype
5976 $_siginfo} command. On Unix systems, it typically corresponds to the
5977 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5980 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5981 referenced address that raised a segmentation fault.
5985 (@value{GDBP}) continue
5986 Program received signal SIGSEGV, Segmentation fault.
5987 0x0000000000400766 in main ()
5989 (@value{GDBP}) ptype $_siginfo
5996 struct @{...@} _kill;
5997 struct @{...@} _timer;
5999 struct @{...@} _sigchld;
6000 struct @{...@} _sigfault;
6001 struct @{...@} _sigpoll;
6004 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6008 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6009 $1 = (void *) 0x7ffff7ff7000
6013 Depending on target support, @code{$_siginfo} may also be writable.
6015 @cindex Intel MPX boundary violations
6016 @cindex boundary violations, Intel MPX
6017 On some targets, a @code{SIGSEGV} can be caused by a boundary
6018 violation, i.e., accessing an address outside of the allowed range.
6019 In those cases @value{GDBN} may displays additional information,
6020 depending on how @value{GDBN} has been told to handle the signal.
6021 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6022 kind: "Upper" or "Lower", the memory address accessed and the
6023 bounds, while with @code{handle nostop SIGSEGV} no additional
6024 information is displayed.
6026 The usual output of a segfault is:
6028 Program received signal SIGSEGV, Segmentation fault
6029 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6030 68 value = *(p + len);
6033 While a bound violation is presented as:
6035 Program received signal SIGSEGV, Segmentation fault
6036 Upper bound violation while accessing address 0x7fffffffc3b3
6037 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6038 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6039 68 value = *(p + len);
6043 @section Stopping and Starting Multi-thread Programs
6045 @cindex stopped threads
6046 @cindex threads, stopped
6048 @cindex continuing threads
6049 @cindex threads, continuing
6051 @value{GDBN} supports debugging programs with multiple threads
6052 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6053 are two modes of controlling execution of your program within the
6054 debugger. In the default mode, referred to as @dfn{all-stop mode},
6055 when any thread in your program stops (for example, at a breakpoint
6056 or while being stepped), all other threads in the program are also stopped by
6057 @value{GDBN}. On some targets, @value{GDBN} also supports
6058 @dfn{non-stop mode}, in which other threads can continue to run freely while
6059 you examine the stopped thread in the debugger.
6062 * All-Stop Mode:: All threads stop when GDB takes control
6063 * Non-Stop Mode:: Other threads continue to execute
6064 * Background Execution:: Running your program asynchronously
6065 * Thread-Specific Breakpoints:: Controlling breakpoints
6066 * Interrupted System Calls:: GDB may interfere with system calls
6067 * Observer Mode:: GDB does not alter program behavior
6071 @subsection All-Stop Mode
6073 @cindex all-stop mode
6075 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6076 @emph{all} threads of execution stop, not just the current thread. This
6077 allows you to examine the overall state of the program, including
6078 switching between threads, without worrying that things may change
6081 Conversely, whenever you restart the program, @emph{all} threads start
6082 executing. @emph{This is true even when single-stepping} with commands
6083 like @code{step} or @code{next}.
6085 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6086 Since thread scheduling is up to your debugging target's operating
6087 system (not controlled by @value{GDBN}), other threads may
6088 execute more than one statement while the current thread completes a
6089 single step. Moreover, in general other threads stop in the middle of a
6090 statement, rather than at a clean statement boundary, when the program
6093 You might even find your program stopped in another thread after
6094 continuing or even single-stepping. This happens whenever some other
6095 thread runs into a breakpoint, a signal, or an exception before the
6096 first thread completes whatever you requested.
6098 @cindex automatic thread selection
6099 @cindex switching threads automatically
6100 @cindex threads, automatic switching
6101 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6102 signal, it automatically selects the thread where that breakpoint or
6103 signal happened. @value{GDBN} alerts you to the context switch with a
6104 message such as @samp{[Switching to Thread @var{n}]} to identify the
6107 On some OSes, you can modify @value{GDBN}'s default behavior by
6108 locking the OS scheduler to allow only a single thread to run.
6111 @item set scheduler-locking @var{mode}
6112 @cindex scheduler locking mode
6113 @cindex lock scheduler
6114 Set the scheduler locking mode. It applies to normal execution,
6115 record mode, and replay mode. If it is @code{off}, then there is no
6116 locking and any thread may run at any time. If @code{on}, then only
6117 the current thread may run when the inferior is resumed. The
6118 @code{step} mode optimizes for single-stepping; it prevents other
6119 threads from preempting the current thread while you are stepping, so
6120 that the focus of debugging does not change unexpectedly. Other
6121 threads never get a chance to run when you step, and they are
6122 completely free to run when you use commands like @samp{continue},
6123 @samp{until}, or @samp{finish}. However, unless another thread hits a
6124 breakpoint during its timeslice, @value{GDBN} does not change the
6125 current thread away from the thread that you are debugging. The
6126 @code{replay} mode behaves like @code{off} in record mode and like
6127 @code{on} in replay mode.
6129 @item show scheduler-locking
6130 Display the current scheduler locking mode.
6133 @cindex resume threads of multiple processes simultaneously
6134 By default, when you issue one of the execution commands such as
6135 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6136 threads of the current inferior to run. For example, if @value{GDBN}
6137 is attached to two inferiors, each with two threads, the
6138 @code{continue} command resumes only the two threads of the current
6139 inferior. This is useful, for example, when you debug a program that
6140 forks and you want to hold the parent stopped (so that, for instance,
6141 it doesn't run to exit), while you debug the child. In other
6142 situations, you may not be interested in inspecting the current state
6143 of any of the processes @value{GDBN} is attached to, and you may want
6144 to resume them all until some breakpoint is hit. In the latter case,
6145 you can instruct @value{GDBN} to allow all threads of all the
6146 inferiors to run with the @w{@code{set schedule-multiple}} command.
6149 @kindex set schedule-multiple
6150 @item set schedule-multiple
6151 Set the mode for allowing threads of multiple processes to be resumed
6152 when an execution command is issued. When @code{on}, all threads of
6153 all processes are allowed to run. When @code{off}, only the threads
6154 of the current process are resumed. The default is @code{off}. The
6155 @code{scheduler-locking} mode takes precedence when set to @code{on},
6156 or while you are stepping and set to @code{step}.
6158 @item show schedule-multiple
6159 Display the current mode for resuming the execution of threads of
6164 @subsection Non-Stop Mode
6166 @cindex non-stop mode
6168 @c This section is really only a place-holder, and needs to be expanded
6169 @c with more details.
6171 For some multi-threaded targets, @value{GDBN} supports an optional
6172 mode of operation in which you can examine stopped program threads in
6173 the debugger while other threads continue to execute freely. This
6174 minimizes intrusion when debugging live systems, such as programs
6175 where some threads have real-time constraints or must continue to
6176 respond to external events. This is referred to as @dfn{non-stop} mode.
6178 In non-stop mode, when a thread stops to report a debugging event,
6179 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6180 threads as well, in contrast to the all-stop mode behavior. Additionally,
6181 execution commands such as @code{continue} and @code{step} apply by default
6182 only to the current thread in non-stop mode, rather than all threads as
6183 in all-stop mode. This allows you to control threads explicitly in
6184 ways that are not possible in all-stop mode --- for example, stepping
6185 one thread while allowing others to run freely, stepping
6186 one thread while holding all others stopped, or stepping several threads
6187 independently and simultaneously.
6189 To enter non-stop mode, use this sequence of commands before you run
6190 or attach to your program:
6193 # If using the CLI, pagination breaks non-stop.
6196 # Finally, turn it on!
6200 You can use these commands to manipulate the non-stop mode setting:
6203 @kindex set non-stop
6204 @item set non-stop on
6205 Enable selection of non-stop mode.
6206 @item set non-stop off
6207 Disable selection of non-stop mode.
6208 @kindex show non-stop
6210 Show the current non-stop enablement setting.
6213 Note these commands only reflect whether non-stop mode is enabled,
6214 not whether the currently-executing program is being run in non-stop mode.
6215 In particular, the @code{set non-stop} preference is only consulted when
6216 @value{GDBN} starts or connects to the target program, and it is generally
6217 not possible to switch modes once debugging has started. Furthermore,
6218 since not all targets support non-stop mode, even when you have enabled
6219 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6222 In non-stop mode, all execution commands apply only to the current thread
6223 by default. That is, @code{continue} only continues one thread.
6224 To continue all threads, issue @code{continue -a} or @code{c -a}.
6226 You can use @value{GDBN}'s background execution commands
6227 (@pxref{Background Execution}) to run some threads in the background
6228 while you continue to examine or step others from @value{GDBN}.
6229 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6230 always executed asynchronously in non-stop mode.
6232 Suspending execution is done with the @code{interrupt} command when
6233 running in the background, or @kbd{Ctrl-c} during foreground execution.
6234 In all-stop mode, this stops the whole process;
6235 but in non-stop mode the interrupt applies only to the current thread.
6236 To stop the whole program, use @code{interrupt -a}.
6238 Other execution commands do not currently support the @code{-a} option.
6240 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6241 that thread current, as it does in all-stop mode. This is because the
6242 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6243 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6244 changed to a different thread just as you entered a command to operate on the
6245 previously current thread.
6247 @node Background Execution
6248 @subsection Background Execution
6250 @cindex foreground execution
6251 @cindex background execution
6252 @cindex asynchronous execution
6253 @cindex execution, foreground, background and asynchronous
6255 @value{GDBN}'s execution commands have two variants: the normal
6256 foreground (synchronous) behavior, and a background
6257 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6258 the program to report that some thread has stopped before prompting for
6259 another command. In background execution, @value{GDBN} immediately gives
6260 a command prompt so that you can issue other commands while your program runs.
6262 If the target doesn't support async mode, @value{GDBN} issues an error
6263 message if you attempt to use the background execution commands.
6265 To specify background execution, add a @code{&} to the command. For example,
6266 the background form of the @code{continue} command is @code{continue&}, or
6267 just @code{c&}. The execution commands that accept background execution
6273 @xref{Starting, , Starting your Program}.
6277 @xref{Attach, , Debugging an Already-running Process}.
6281 @xref{Continuing and Stepping, step}.
6285 @xref{Continuing and Stepping, stepi}.
6289 @xref{Continuing and Stepping, next}.
6293 @xref{Continuing and Stepping, nexti}.
6297 @xref{Continuing and Stepping, continue}.
6301 @xref{Continuing and Stepping, finish}.
6305 @xref{Continuing and Stepping, until}.
6309 Background execution is especially useful in conjunction with non-stop
6310 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6311 However, you can also use these commands in the normal all-stop mode with
6312 the restriction that you cannot issue another execution command until the
6313 previous one finishes. Examples of commands that are valid in all-stop
6314 mode while the program is running include @code{help} and @code{info break}.
6316 You can interrupt your program while it is running in the background by
6317 using the @code{interrupt} command.
6324 Suspend execution of the running program. In all-stop mode,
6325 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6326 only the current thread. To stop the whole program in non-stop mode,
6327 use @code{interrupt -a}.
6330 @node Thread-Specific Breakpoints
6331 @subsection Thread-Specific Breakpoints
6333 When your program has multiple threads (@pxref{Threads,, Debugging
6334 Programs with Multiple Threads}), you can choose whether to set
6335 breakpoints on all threads, or on a particular thread.
6338 @cindex breakpoints and threads
6339 @cindex thread breakpoints
6340 @kindex break @dots{} thread @var{thread-id}
6341 @item break @var{location} thread @var{thread-id}
6342 @itemx break @var{location} thread @var{thread-id} if @dots{}
6343 @var{location} specifies source lines; there are several ways of
6344 writing them (@pxref{Specify Location}), but the effect is always to
6345 specify some source line.
6347 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6348 to specify that you only want @value{GDBN} to stop the program when a
6349 particular thread reaches this breakpoint. The @var{thread-id} specifier
6350 is one of the thread identifiers assigned by @value{GDBN}, shown
6351 in the first column of the @samp{info threads} display.
6353 If you do not specify @samp{thread @var{thread-id}} when you set a
6354 breakpoint, the breakpoint applies to @emph{all} threads of your
6357 You can use the @code{thread} qualifier on conditional breakpoints as
6358 well; in this case, place @samp{thread @var{thread-id}} before or
6359 after the breakpoint condition, like this:
6362 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6367 Thread-specific breakpoints are automatically deleted when
6368 @value{GDBN} detects the corresponding thread is no longer in the
6369 thread list. For example:
6373 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6376 There are several ways for a thread to disappear, such as a regular
6377 thread exit, but also when you detach from the process with the
6378 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6379 Process}), or if @value{GDBN} loses the remote connection
6380 (@pxref{Remote Debugging}), etc. Note that with some targets,
6381 @value{GDBN} is only able to detect a thread has exited when the user
6382 explictly asks for the thread list with the @code{info threads}
6385 @node Interrupted System Calls
6386 @subsection Interrupted System Calls
6388 @cindex thread breakpoints and system calls
6389 @cindex system calls and thread breakpoints
6390 @cindex premature return from system calls
6391 There is an unfortunate side effect when using @value{GDBN} to debug
6392 multi-threaded programs. If one thread stops for a
6393 breakpoint, or for some other reason, and another thread is blocked in a
6394 system call, then the system call may return prematurely. This is a
6395 consequence of the interaction between multiple threads and the signals
6396 that @value{GDBN} uses to implement breakpoints and other events that
6399 To handle this problem, your program should check the return value of
6400 each system call and react appropriately. This is good programming
6403 For example, do not write code like this:
6409 The call to @code{sleep} will return early if a different thread stops
6410 at a breakpoint or for some other reason.
6412 Instead, write this:
6417 unslept = sleep (unslept);
6420 A system call is allowed to return early, so the system is still
6421 conforming to its specification. But @value{GDBN} does cause your
6422 multi-threaded program to behave differently than it would without
6425 Also, @value{GDBN} uses internal breakpoints in the thread library to
6426 monitor certain events such as thread creation and thread destruction.
6427 When such an event happens, a system call in another thread may return
6428 prematurely, even though your program does not appear to stop.
6431 @subsection Observer Mode
6433 If you want to build on non-stop mode and observe program behavior
6434 without any chance of disruption by @value{GDBN}, you can set
6435 variables to disable all of the debugger's attempts to modify state,
6436 whether by writing memory, inserting breakpoints, etc. These operate
6437 at a low level, intercepting operations from all commands.
6439 When all of these are set to @code{off}, then @value{GDBN} is said to
6440 be @dfn{observer mode}. As a convenience, the variable
6441 @code{observer} can be set to disable these, plus enable non-stop
6444 Note that @value{GDBN} will not prevent you from making nonsensical
6445 combinations of these settings. For instance, if you have enabled
6446 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6447 then breakpoints that work by writing trap instructions into the code
6448 stream will still not be able to be placed.
6453 @item set observer on
6454 @itemx set observer off
6455 When set to @code{on}, this disables all the permission variables
6456 below (except for @code{insert-fast-tracepoints}), plus enables
6457 non-stop debugging. Setting this to @code{off} switches back to
6458 normal debugging, though remaining in non-stop mode.
6461 Show whether observer mode is on or off.
6463 @kindex may-write-registers
6464 @item set may-write-registers on
6465 @itemx set may-write-registers off
6466 This controls whether @value{GDBN} will attempt to alter the values of
6467 registers, such as with assignment expressions in @code{print}, or the
6468 @code{jump} command. It defaults to @code{on}.
6470 @item show may-write-registers
6471 Show the current permission to write registers.
6473 @kindex may-write-memory
6474 @item set may-write-memory on
6475 @itemx set may-write-memory off
6476 This controls whether @value{GDBN} will attempt to alter the contents
6477 of memory, such as with assignment expressions in @code{print}. It
6478 defaults to @code{on}.
6480 @item show may-write-memory
6481 Show the current permission to write memory.
6483 @kindex may-insert-breakpoints
6484 @item set may-insert-breakpoints on
6485 @itemx set may-insert-breakpoints off
6486 This controls whether @value{GDBN} will attempt to insert breakpoints.
6487 This affects all breakpoints, including internal breakpoints defined
6488 by @value{GDBN}. It defaults to @code{on}.
6490 @item show may-insert-breakpoints
6491 Show the current permission to insert breakpoints.
6493 @kindex may-insert-tracepoints
6494 @item set may-insert-tracepoints on
6495 @itemx set may-insert-tracepoints off
6496 This controls whether @value{GDBN} will attempt to insert (regular)
6497 tracepoints at the beginning of a tracing experiment. It affects only
6498 non-fast tracepoints, fast tracepoints being under the control of
6499 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6501 @item show may-insert-tracepoints
6502 Show the current permission to insert tracepoints.
6504 @kindex may-insert-fast-tracepoints
6505 @item set may-insert-fast-tracepoints on
6506 @itemx set may-insert-fast-tracepoints off
6507 This controls whether @value{GDBN} will attempt to insert fast
6508 tracepoints at the beginning of a tracing experiment. It affects only
6509 fast tracepoints, regular (non-fast) tracepoints being under the
6510 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6512 @item show may-insert-fast-tracepoints
6513 Show the current permission to insert fast tracepoints.
6515 @kindex may-interrupt
6516 @item set may-interrupt on
6517 @itemx set may-interrupt off
6518 This controls whether @value{GDBN} will attempt to interrupt or stop
6519 program execution. When this variable is @code{off}, the
6520 @code{interrupt} command will have no effect, nor will
6521 @kbd{Ctrl-c}. It defaults to @code{on}.
6523 @item show may-interrupt
6524 Show the current permission to interrupt or stop the program.
6528 @node Reverse Execution
6529 @chapter Running programs backward
6530 @cindex reverse execution
6531 @cindex running programs backward
6533 When you are debugging a program, it is not unusual to realize that
6534 you have gone too far, and some event of interest has already happened.
6535 If the target environment supports it, @value{GDBN} can allow you to
6536 ``rewind'' the program by running it backward.
6538 A target environment that supports reverse execution should be able
6539 to ``undo'' the changes in machine state that have taken place as the
6540 program was executing normally. Variables, registers etc.@: should
6541 revert to their previous values. Obviously this requires a great
6542 deal of sophistication on the part of the target environment; not
6543 all target environments can support reverse execution.
6545 When a program is executed in reverse, the instructions that
6546 have most recently been executed are ``un-executed'', in reverse
6547 order. The program counter runs backward, following the previous
6548 thread of execution in reverse. As each instruction is ``un-executed'',
6549 the values of memory and/or registers that were changed by that
6550 instruction are reverted to their previous states. After executing
6551 a piece of source code in reverse, all side effects of that code
6552 should be ``undone'', and all variables should be returned to their
6553 prior values@footnote{
6554 Note that some side effects are easier to undo than others. For instance,
6555 memory and registers are relatively easy, but device I/O is hard. Some
6556 targets may be able undo things like device I/O, and some may not.
6558 The contract between @value{GDBN} and the reverse executing target
6559 requires only that the target do something reasonable when
6560 @value{GDBN} tells it to execute backwards, and then report the
6561 results back to @value{GDBN}. Whatever the target reports back to
6562 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6563 assumes that the memory and registers that the target reports are in a
6564 consistant state, but @value{GDBN} accepts whatever it is given.
6567 If you are debugging in a target environment that supports
6568 reverse execution, @value{GDBN} provides the following commands.
6571 @kindex reverse-continue
6572 @kindex rc @r{(@code{reverse-continue})}
6573 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6574 @itemx rc @r{[}@var{ignore-count}@r{]}
6575 Beginning at the point where your program last stopped, start executing
6576 in reverse. Reverse execution will stop for breakpoints and synchronous
6577 exceptions (signals), just like normal execution. Behavior of
6578 asynchronous signals depends on the target environment.
6580 @kindex reverse-step
6581 @kindex rs @r{(@code{step})}
6582 @item reverse-step @r{[}@var{count}@r{]}
6583 Run the program backward until control reaches the start of a
6584 different source line; then stop it, and return control to @value{GDBN}.
6586 Like the @code{step} command, @code{reverse-step} will only stop
6587 at the beginning of a source line. It ``un-executes'' the previously
6588 executed source line. If the previous source line included calls to
6589 debuggable functions, @code{reverse-step} will step (backward) into
6590 the called function, stopping at the beginning of the @emph{last}
6591 statement in the called function (typically a return statement).
6593 Also, as with the @code{step} command, if non-debuggable functions are
6594 called, @code{reverse-step} will run thru them backward without stopping.
6596 @kindex reverse-stepi
6597 @kindex rsi @r{(@code{reverse-stepi})}
6598 @item reverse-stepi @r{[}@var{count}@r{]}
6599 Reverse-execute one machine instruction. Note that the instruction
6600 to be reverse-executed is @emph{not} the one pointed to by the program
6601 counter, but the instruction executed prior to that one. For instance,
6602 if the last instruction was a jump, @code{reverse-stepi} will take you
6603 back from the destination of the jump to the jump instruction itself.
6605 @kindex reverse-next
6606 @kindex rn @r{(@code{reverse-next})}
6607 @item reverse-next @r{[}@var{count}@r{]}
6608 Run backward to the beginning of the previous line executed in
6609 the current (innermost) stack frame. If the line contains function
6610 calls, they will be ``un-executed'' without stopping. Starting from
6611 the first line of a function, @code{reverse-next} will take you back
6612 to the caller of that function, @emph{before} the function was called,
6613 just as the normal @code{next} command would take you from the last
6614 line of a function back to its return to its caller
6615 @footnote{Unless the code is too heavily optimized.}.
6617 @kindex reverse-nexti
6618 @kindex rni @r{(@code{reverse-nexti})}
6619 @item reverse-nexti @r{[}@var{count}@r{]}
6620 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6621 in reverse, except that called functions are ``un-executed'' atomically.
6622 That is, if the previously executed instruction was a return from
6623 another function, @code{reverse-nexti} will continue to execute
6624 in reverse until the call to that function (from the current stack
6627 @kindex reverse-finish
6628 @item reverse-finish
6629 Just as the @code{finish} command takes you to the point where the
6630 current function returns, @code{reverse-finish} takes you to the point
6631 where it was called. Instead of ending up at the end of the current
6632 function invocation, you end up at the beginning.
6634 @kindex set exec-direction
6635 @item set exec-direction
6636 Set the direction of target execution.
6637 @item set exec-direction reverse
6638 @cindex execute forward or backward in time
6639 @value{GDBN} will perform all execution commands in reverse, until the
6640 exec-direction mode is changed to ``forward''. Affected commands include
6641 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6642 command cannot be used in reverse mode.
6643 @item set exec-direction forward
6644 @value{GDBN} will perform all execution commands in the normal fashion.
6645 This is the default.
6649 @node Process Record and Replay
6650 @chapter Recording Inferior's Execution and Replaying It
6651 @cindex process record and replay
6652 @cindex recording inferior's execution and replaying it
6654 On some platforms, @value{GDBN} provides a special @dfn{process record
6655 and replay} target that can record a log of the process execution, and
6656 replay it later with both forward and reverse execution commands.
6659 When this target is in use, if the execution log includes the record
6660 for the next instruction, @value{GDBN} will debug in @dfn{replay
6661 mode}. In the replay mode, the inferior does not really execute code
6662 instructions. Instead, all the events that normally happen during
6663 code execution are taken from the execution log. While code is not
6664 really executed in replay mode, the values of registers (including the
6665 program counter register) and the memory of the inferior are still
6666 changed as they normally would. Their contents are taken from the
6670 If the record for the next instruction is not in the execution log,
6671 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6672 inferior executes normally, and @value{GDBN} records the execution log
6675 The process record and replay target supports reverse execution
6676 (@pxref{Reverse Execution}), even if the platform on which the
6677 inferior runs does not. However, the reverse execution is limited in
6678 this case by the range of the instructions recorded in the execution
6679 log. In other words, reverse execution on platforms that don't
6680 support it directly can only be done in the replay mode.
6682 When debugging in the reverse direction, @value{GDBN} will work in
6683 replay mode as long as the execution log includes the record for the
6684 previous instruction; otherwise, it will work in record mode, if the
6685 platform supports reverse execution, or stop if not.
6687 For architecture environments that support process record and replay,
6688 @value{GDBN} provides the following commands:
6691 @kindex target record
6692 @kindex target record-full
6693 @kindex target record-btrace
6696 @kindex record btrace
6697 @kindex record btrace bts
6698 @kindex record btrace pt
6704 @kindex rec btrace bts
6705 @kindex rec btrace pt
6708 @item record @var{method}
6709 This command starts the process record and replay target. The
6710 recording method can be specified as parameter. Without a parameter
6711 the command uses the @code{full} recording method. The following
6712 recording methods are available:
6716 Full record/replay recording using @value{GDBN}'s software record and
6717 replay implementation. This method allows replaying and reverse
6720 @item btrace @var{format}
6721 Hardware-supported instruction recording. This method does not record
6722 data. Further, the data is collected in a ring buffer so old data will
6723 be overwritten when the buffer is full. It allows limited reverse
6724 execution. Variables and registers are not available during reverse
6725 execution. In remote debugging, recording continues on disconnect.
6726 Recorded data can be inspected after reconnecting. The recording may
6727 be stopped using @code{record stop}.
6729 The recording format can be specified as parameter. Without a parameter
6730 the command chooses the recording format. The following recording
6731 formats are available:
6735 @cindex branch trace store
6736 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6737 this format, the processor stores a from/to record for each executed
6738 branch in the btrace ring buffer.
6741 @cindex Intel Processor Trace
6742 Use the @dfn{Intel Processor Trace} recording format. In this
6743 format, the processor stores the execution trace in a compressed form
6744 that is afterwards decoded by @value{GDBN}.
6746 The trace can be recorded with very low overhead. The compressed
6747 trace format also allows small trace buffers to already contain a big
6748 number of instructions compared to @acronym{BTS}.
6750 Decoding the recorded execution trace, on the other hand, is more
6751 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6752 increased number of instructions to process. You should increase the
6753 buffer-size with care.
6756 Not all recording formats may be available on all processors.
6759 The process record and replay target can only debug a process that is
6760 already running. Therefore, you need first to start the process with
6761 the @kbd{run} or @kbd{start} commands, and then start the recording
6762 with the @kbd{record @var{method}} command.
6764 @cindex displaced stepping, and process record and replay
6765 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6766 will be automatically disabled when process record and replay target
6767 is started. That's because the process record and replay target
6768 doesn't support displaced stepping.
6770 @cindex non-stop mode, and process record and replay
6771 @cindex asynchronous execution, and process record and replay
6772 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6773 the asynchronous execution mode (@pxref{Background Execution}), not
6774 all recording methods are available. The @code{full} recording method
6775 does not support these two modes.
6780 Stop the process record and replay target. When process record and
6781 replay target stops, the entire execution log will be deleted and the
6782 inferior will either be terminated, or will remain in its final state.
6784 When you stop the process record and replay target in record mode (at
6785 the end of the execution log), the inferior will be stopped at the
6786 next instruction that would have been recorded. In other words, if
6787 you record for a while and then stop recording, the inferior process
6788 will be left in the same state as if the recording never happened.
6790 On the other hand, if the process record and replay target is stopped
6791 while in replay mode (that is, not at the end of the execution log,
6792 but at some earlier point), the inferior process will become ``live''
6793 at that earlier state, and it will then be possible to continue the
6794 usual ``live'' debugging of the process from that state.
6796 When the inferior process exits, or @value{GDBN} detaches from it,
6797 process record and replay target will automatically stop itself.
6801 Go to a specific location in the execution log. There are several
6802 ways to specify the location to go to:
6805 @item record goto begin
6806 @itemx record goto start
6807 Go to the beginning of the execution log.
6809 @item record goto end
6810 Go to the end of the execution log.
6812 @item record goto @var{n}
6813 Go to instruction number @var{n} in the execution log.
6817 @item record save @var{filename}
6818 Save the execution log to a file @file{@var{filename}}.
6819 Default filename is @file{gdb_record.@var{process_id}}, where
6820 @var{process_id} is the process ID of the inferior.
6822 This command may not be available for all recording methods.
6824 @kindex record restore
6825 @item record restore @var{filename}
6826 Restore the execution log from a file @file{@var{filename}}.
6827 File must have been created with @code{record save}.
6829 @kindex set record full
6830 @item set record full insn-number-max @var{limit}
6831 @itemx set record full insn-number-max unlimited
6832 Set the limit of instructions to be recorded for the @code{full}
6833 recording method. Default value is 200000.
6835 If @var{limit} is a positive number, then @value{GDBN} will start
6836 deleting instructions from the log once the number of the record
6837 instructions becomes greater than @var{limit}. For every new recorded
6838 instruction, @value{GDBN} will delete the earliest recorded
6839 instruction to keep the number of recorded instructions at the limit.
6840 (Since deleting recorded instructions loses information, @value{GDBN}
6841 lets you control what happens when the limit is reached, by means of
6842 the @code{stop-at-limit} option, described below.)
6844 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6845 delete recorded instructions from the execution log. The number of
6846 recorded instructions is limited only by the available memory.
6848 @kindex show record full
6849 @item show record full insn-number-max
6850 Show the limit of instructions to be recorded with the @code{full}
6853 @item set record full stop-at-limit
6854 Control the behavior of the @code{full} recording method when the
6855 number of recorded instructions reaches the limit. If ON (the
6856 default), @value{GDBN} will stop when the limit is reached for the
6857 first time and ask you whether you want to stop the inferior or
6858 continue running it and recording the execution log. If you decide
6859 to continue recording, each new recorded instruction will cause the
6860 oldest one to be deleted.
6862 If this option is OFF, @value{GDBN} will automatically delete the
6863 oldest record to make room for each new one, without asking.
6865 @item show record full stop-at-limit
6866 Show the current setting of @code{stop-at-limit}.
6868 @item set record full memory-query
6869 Control the behavior when @value{GDBN} is unable to record memory
6870 changes caused by an instruction for the @code{full} recording method.
6871 If ON, @value{GDBN} will query whether to stop the inferior in that
6874 If this option is OFF (the default), @value{GDBN} will automatically
6875 ignore the effect of such instructions on memory. Later, when
6876 @value{GDBN} replays this execution log, it will mark the log of this
6877 instruction as not accessible, and it will not affect the replay
6880 @item show record full memory-query
6881 Show the current setting of @code{memory-query}.
6883 @kindex set record btrace
6884 The @code{btrace} record target does not trace data. As a
6885 convenience, when replaying, @value{GDBN} reads read-only memory off
6886 the live program directly, assuming that the addresses of the
6887 read-only areas don't change. This for example makes it possible to
6888 disassemble code while replaying, but not to print variables.
6889 In some cases, being able to inspect variables might be useful.
6890 You can use the following command for that:
6892 @item set record btrace replay-memory-access
6893 Control the behavior of the @code{btrace} recording method when
6894 accessing memory during replay. If @code{read-only} (the default),
6895 @value{GDBN} will only allow accesses to read-only memory.
6896 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6897 and to read-write memory. Beware that the accessed memory corresponds
6898 to the live target and not necessarily to the current replay
6901 @kindex show record btrace
6902 @item show record btrace replay-memory-access
6903 Show the current setting of @code{replay-memory-access}.
6905 @kindex set record btrace bts
6906 @item set record btrace bts buffer-size @var{size}
6907 @itemx set record btrace bts buffer-size unlimited
6908 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6909 format. Default is 64KB.
6911 If @var{size} is a positive number, then @value{GDBN} will try to
6912 allocate a buffer of at least @var{size} bytes for each new thread
6913 that uses the btrace recording method and the @acronym{BTS} format.
6914 The actually obtained buffer size may differ from the requested
6915 @var{size}. Use the @code{info record} command to see the actual
6916 buffer size for each thread that uses the btrace recording method and
6917 the @acronym{BTS} format.
6919 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6920 allocate a buffer of 4MB.
6922 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6923 also need longer to process the branch trace data before it can be used.
6925 @item show record btrace bts buffer-size @var{size}
6926 Show the current setting of the requested ring buffer size for branch
6927 tracing in @acronym{BTS} format.
6929 @kindex set record btrace pt
6930 @item set record btrace pt buffer-size @var{size}
6931 @itemx set record btrace pt buffer-size unlimited
6932 Set the requested ring buffer size for branch tracing in Intel
6933 Processor Trace format. Default is 16KB.
6935 If @var{size} is a positive number, then @value{GDBN} will try to
6936 allocate a buffer of at least @var{size} bytes for each new thread
6937 that uses the btrace recording method and the Intel Processor Trace
6938 format. The actually obtained buffer size may differ from the
6939 requested @var{size}. Use the @code{info record} command to see the
6940 actual buffer size for each thread.
6942 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6943 allocate a buffer of 4MB.
6945 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6946 also need longer to process the branch trace data before it can be used.
6948 @item show record btrace pt buffer-size @var{size}
6949 Show the current setting of the requested ring buffer size for branch
6950 tracing in Intel Processor Trace format.
6954 Show various statistics about the recording depending on the recording
6959 For the @code{full} recording method, it shows the state of process
6960 record and its in-memory execution log buffer, including:
6964 Whether in record mode or replay mode.
6966 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6968 Highest recorded instruction number.
6970 Current instruction about to be replayed (if in replay mode).
6972 Number of instructions contained in the execution log.
6974 Maximum number of instructions that may be contained in the execution log.
6978 For the @code{btrace} recording method, it shows:
6984 Number of instructions that have been recorded.
6986 Number of blocks of sequential control-flow formed by the recorded
6989 Whether in record mode or replay mode.
6992 For the @code{bts} recording format, it also shows:
6995 Size of the perf ring buffer.
6998 For the @code{pt} recording format, it also shows:
7001 Size of the perf ring buffer.
7005 @kindex record delete
7008 When record target runs in replay mode (``in the past''), delete the
7009 subsequent execution log and begin to record a new execution log starting
7010 from the current address. This means you will abandon the previously
7011 recorded ``future'' and begin recording a new ``future''.
7013 @kindex record instruction-history
7014 @kindex rec instruction-history
7015 @item record instruction-history
7016 Disassembles instructions from the recorded execution log. By
7017 default, ten instructions are disassembled. This can be changed using
7018 the @code{set record instruction-history-size} command. Instructions
7019 are printed in execution order.
7021 It can also print mixed source+disassembly if you specify the the
7022 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7023 as well as in symbolic form by specifying the @code{/r} modifier.
7025 The current position marker is printed for the instruction at the
7026 current program counter value. This instruction can appear multiple
7027 times in the trace and the current position marker will be printed
7028 every time. To omit the current position marker, specify the
7031 To better align the printed instructions when the trace contains
7032 instructions from more than one function, the function name may be
7033 omitted by specifying the @code{/f} modifier.
7035 Speculatively executed instructions are prefixed with @samp{?}. This
7036 feature is not available for all recording formats.
7038 There are several ways to specify what part of the execution log to
7042 @item record instruction-history @var{insn}
7043 Disassembles ten instructions starting from instruction number
7046 @item record instruction-history @var{insn}, +/-@var{n}
7047 Disassembles @var{n} instructions around instruction number
7048 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7049 @var{n} instructions after instruction number @var{insn}. If
7050 @var{n} is preceded with @code{-}, disassembles @var{n}
7051 instructions before instruction number @var{insn}.
7053 @item record instruction-history
7054 Disassembles ten more instructions after the last disassembly.
7056 @item record instruction-history -
7057 Disassembles ten more instructions before the last disassembly.
7059 @item record instruction-history @var{begin}, @var{end}
7060 Disassembles instructions beginning with instruction number
7061 @var{begin} until instruction number @var{end}. The instruction
7062 number @var{end} is included.
7065 This command may not be available for all recording methods.
7068 @item set record instruction-history-size @var{size}
7069 @itemx set record instruction-history-size unlimited
7070 Define how many instructions to disassemble in the @code{record
7071 instruction-history} command. The default value is 10.
7072 A @var{size} of @code{unlimited} means unlimited instructions.
7075 @item show record instruction-history-size
7076 Show how many instructions to disassemble in the @code{record
7077 instruction-history} command.
7079 @kindex record function-call-history
7080 @kindex rec function-call-history
7081 @item record function-call-history
7082 Prints the execution history at function granularity. It prints one
7083 line for each sequence of instructions that belong to the same
7084 function giving the name of that function, the source lines
7085 for this instruction sequence (if the @code{/l} modifier is
7086 specified), and the instructions numbers that form the sequence (if
7087 the @code{/i} modifier is specified). The function names are indented
7088 to reflect the call stack depth if the @code{/c} modifier is
7089 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7093 (@value{GDBP}) @b{list 1, 10}
7104 (@value{GDBP}) @b{record function-call-history /ilc}
7105 1 bar inst 1,4 at foo.c:6,8
7106 2 foo inst 5,10 at foo.c:2,3
7107 3 bar inst 11,13 at foo.c:9,10
7110 By default, ten lines are printed. This can be changed using the
7111 @code{set record function-call-history-size} command. Functions are
7112 printed in execution order. There are several ways to specify what
7116 @item record function-call-history @var{func}
7117 Prints ten functions starting from function number @var{func}.
7119 @item record function-call-history @var{func}, +/-@var{n}
7120 Prints @var{n} functions around function number @var{func}. If
7121 @var{n} is preceded with @code{+}, prints @var{n} functions after
7122 function number @var{func}. If @var{n} is preceded with @code{-},
7123 prints @var{n} functions before function number @var{func}.
7125 @item record function-call-history
7126 Prints ten more functions after the last ten-line print.
7128 @item record function-call-history -
7129 Prints ten more functions before the last ten-line print.
7131 @item record function-call-history @var{begin}, @var{end}
7132 Prints functions beginning with function number @var{begin} until
7133 function number @var{end}. The function number @var{end} is included.
7136 This command may not be available for all recording methods.
7138 @item set record function-call-history-size @var{size}
7139 @itemx set record function-call-history-size unlimited
7140 Define how many lines to print in the
7141 @code{record function-call-history} command. The default value is 10.
7142 A size of @code{unlimited} means unlimited lines.
7144 @item show record function-call-history-size
7145 Show how many lines to print in the
7146 @code{record function-call-history} command.
7151 @chapter Examining the Stack
7153 When your program has stopped, the first thing you need to know is where it
7154 stopped and how it got there.
7157 Each time your program performs a function call, information about the call
7159 That information includes the location of the call in your program,
7160 the arguments of the call,
7161 and the local variables of the function being called.
7162 The information is saved in a block of data called a @dfn{stack frame}.
7163 The stack frames are allocated in a region of memory called the @dfn{call
7166 When your program stops, the @value{GDBN} commands for examining the
7167 stack allow you to see all of this information.
7169 @cindex selected frame
7170 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7171 @value{GDBN} commands refer implicitly to the selected frame. In
7172 particular, whenever you ask @value{GDBN} for the value of a variable in
7173 your program, the value is found in the selected frame. There are
7174 special @value{GDBN} commands to select whichever frame you are
7175 interested in. @xref{Selection, ,Selecting a Frame}.
7177 When your program stops, @value{GDBN} automatically selects the
7178 currently executing frame and describes it briefly, similar to the
7179 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7182 * Frames:: Stack frames
7183 * Backtrace:: Backtraces
7184 * Selection:: Selecting a frame
7185 * Frame Info:: Information on a frame
7186 * Frame Filter Management:: Managing frame filters
7191 @section Stack Frames
7193 @cindex frame, definition
7195 The call stack is divided up into contiguous pieces called @dfn{stack
7196 frames}, or @dfn{frames} for short; each frame is the data associated
7197 with one call to one function. The frame contains the arguments given
7198 to the function, the function's local variables, and the address at
7199 which the function is executing.
7201 @cindex initial frame
7202 @cindex outermost frame
7203 @cindex innermost frame
7204 When your program is started, the stack has only one frame, that of the
7205 function @code{main}. This is called the @dfn{initial} frame or the
7206 @dfn{outermost} frame. Each time a function is called, a new frame is
7207 made. Each time a function returns, the frame for that function invocation
7208 is eliminated. If a function is recursive, there can be many frames for
7209 the same function. The frame for the function in which execution is
7210 actually occurring is called the @dfn{innermost} frame. This is the most
7211 recently created of all the stack frames that still exist.
7213 @cindex frame pointer
7214 Inside your program, stack frames are identified by their addresses. A
7215 stack frame consists of many bytes, each of which has its own address; each
7216 kind of computer has a convention for choosing one byte whose
7217 address serves as the address of the frame. Usually this address is kept
7218 in a register called the @dfn{frame pointer register}
7219 (@pxref{Registers, $fp}) while execution is going on in that frame.
7221 @cindex frame number
7222 @value{GDBN} assigns numbers to all existing stack frames, starting with
7223 zero for the innermost frame, one for the frame that called it,
7224 and so on upward. These numbers do not really exist in your program;
7225 they are assigned by @value{GDBN} to give you a way of designating stack
7226 frames in @value{GDBN} commands.
7228 @c The -fomit-frame-pointer below perennially causes hbox overflow
7229 @c underflow problems.
7230 @cindex frameless execution
7231 Some compilers provide a way to compile functions so that they operate
7232 without stack frames. (For example, the @value{NGCC} option
7234 @samp{-fomit-frame-pointer}
7236 generates functions without a frame.)
7237 This is occasionally done with heavily used library functions to save
7238 the frame setup time. @value{GDBN} has limited facilities for dealing
7239 with these function invocations. If the innermost function invocation
7240 has no stack frame, @value{GDBN} nevertheless regards it as though
7241 it had a separate frame, which is numbered zero as usual, allowing
7242 correct tracing of the function call chain. However, @value{GDBN} has
7243 no provision for frameless functions elsewhere in the stack.
7249 @cindex call stack traces
7250 A backtrace is a summary of how your program got where it is. It shows one
7251 line per frame, for many frames, starting with the currently executing
7252 frame (frame zero), followed by its caller (frame one), and on up the
7255 @anchor{backtrace-command}
7258 @kindex bt @r{(@code{backtrace})}
7261 Print a backtrace of the entire stack: one line per frame for all
7262 frames in the stack.
7264 You can stop the backtrace at any time by typing the system interrupt
7265 character, normally @kbd{Ctrl-c}.
7267 @item backtrace @var{n}
7269 Similar, but print only the innermost @var{n} frames.
7271 @item backtrace -@var{n}
7273 Similar, but print only the outermost @var{n} frames.
7275 @item backtrace full
7277 @itemx bt full @var{n}
7278 @itemx bt full -@var{n}
7279 Print the values of the local variables also. As described above,
7280 @var{n} specifies the number of frames to print.
7282 @item backtrace no-filters
7283 @itemx bt no-filters
7284 @itemx bt no-filters @var{n}
7285 @itemx bt no-filters -@var{n}
7286 @itemx bt no-filters full
7287 @itemx bt no-filters full @var{n}
7288 @itemx bt no-filters full -@var{n}
7289 Do not run Python frame filters on this backtrace. @xref{Frame
7290 Filter API}, for more information. Additionally use @ref{disable
7291 frame-filter all} to turn off all frame filters. This is only
7292 relevant when @value{GDBN} has been configured with @code{Python}
7298 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7299 are additional aliases for @code{backtrace}.
7301 @cindex multiple threads, backtrace
7302 In a multi-threaded program, @value{GDBN} by default shows the
7303 backtrace only for the current thread. To display the backtrace for
7304 several or all of the threads, use the command @code{thread apply}
7305 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7306 apply all backtrace}, @value{GDBN} will display the backtrace for all
7307 the threads; this is handy when you debug a core dump of a
7308 multi-threaded program.
7310 Each line in the backtrace shows the frame number and the function name.
7311 The program counter value is also shown---unless you use @code{set
7312 print address off}. The backtrace also shows the source file name and
7313 line number, as well as the arguments to the function. The program
7314 counter value is omitted if it is at the beginning of the code for that
7317 Here is an example of a backtrace. It was made with the command
7318 @samp{bt 3}, so it shows the innermost three frames.
7322 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7324 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7325 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7327 (More stack frames follow...)
7332 The display for frame zero does not begin with a program counter
7333 value, indicating that your program has stopped at the beginning of the
7334 code for line @code{993} of @code{builtin.c}.
7337 The value of parameter @code{data} in frame 1 has been replaced by
7338 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7339 only if it is a scalar (integer, pointer, enumeration, etc). See command
7340 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7341 on how to configure the way function parameter values are printed.
7343 @cindex optimized out, in backtrace
7344 @cindex function call arguments, optimized out
7345 If your program was compiled with optimizations, some compilers will
7346 optimize away arguments passed to functions if those arguments are
7347 never used after the call. Such optimizations generate code that
7348 passes arguments through registers, but doesn't store those arguments
7349 in the stack frame. @value{GDBN} has no way of displaying such
7350 arguments in stack frames other than the innermost one. Here's what
7351 such a backtrace might look like:
7355 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7357 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7358 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7360 (More stack frames follow...)
7365 The values of arguments that were not saved in their stack frames are
7366 shown as @samp{<optimized out>}.
7368 If you need to display the values of such optimized-out arguments,
7369 either deduce that from other variables whose values depend on the one
7370 you are interested in, or recompile without optimizations.
7372 @cindex backtrace beyond @code{main} function
7373 @cindex program entry point
7374 @cindex startup code, and backtrace
7375 Most programs have a standard user entry point---a place where system
7376 libraries and startup code transition into user code. For C this is
7377 @code{main}@footnote{
7378 Note that embedded programs (the so-called ``free-standing''
7379 environment) are not required to have a @code{main} function as the
7380 entry point. They could even have multiple entry points.}.
7381 When @value{GDBN} finds the entry function in a backtrace
7382 it will terminate the backtrace, to avoid tracing into highly
7383 system-specific (and generally uninteresting) code.
7385 If you need to examine the startup code, or limit the number of levels
7386 in a backtrace, you can change this behavior:
7389 @item set backtrace past-main
7390 @itemx set backtrace past-main on
7391 @kindex set backtrace
7392 Backtraces will continue past the user entry point.
7394 @item set backtrace past-main off
7395 Backtraces will stop when they encounter the user entry point. This is the
7398 @item show backtrace past-main
7399 @kindex show backtrace
7400 Display the current user entry point backtrace policy.
7402 @item set backtrace past-entry
7403 @itemx set backtrace past-entry on
7404 Backtraces will continue past the internal entry point of an application.
7405 This entry point is encoded by the linker when the application is built,
7406 and is likely before the user entry point @code{main} (or equivalent) is called.
7408 @item set backtrace past-entry off
7409 Backtraces will stop when they encounter the internal entry point of an
7410 application. This is the default.
7412 @item show backtrace past-entry
7413 Display the current internal entry point backtrace policy.
7415 @item set backtrace limit @var{n}
7416 @itemx set backtrace limit 0
7417 @itemx set backtrace limit unlimited
7418 @cindex backtrace limit
7419 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7420 or zero means unlimited levels.
7422 @item show backtrace limit
7423 Display the current limit on backtrace levels.
7426 You can control how file names are displayed.
7429 @item set filename-display
7430 @itemx set filename-display relative
7431 @cindex filename-display
7432 Display file names relative to the compilation directory. This is the default.
7434 @item set filename-display basename
7435 Display only basename of a filename.
7437 @item set filename-display absolute
7438 Display an absolute filename.
7440 @item show filename-display
7441 Show the current way to display filenames.
7445 @section Selecting a Frame
7447 Most commands for examining the stack and other data in your program work on
7448 whichever stack frame is selected at the moment. Here are the commands for
7449 selecting a stack frame; all of them finish by printing a brief description
7450 of the stack frame just selected.
7453 @kindex frame@r{, selecting}
7454 @kindex f @r{(@code{frame})}
7457 Select frame number @var{n}. Recall that frame zero is the innermost
7458 (currently executing) frame, frame one is the frame that called the
7459 innermost one, and so on. The highest-numbered frame is the one for
7462 @item frame @var{stack-addr} [ @var{pc-addr} ]
7463 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7464 Select the frame at address @var{stack-addr}. This is useful mainly if the
7465 chaining of stack frames has been damaged by a bug, making it
7466 impossible for @value{GDBN} to assign numbers properly to all frames. In
7467 addition, this can be useful when your program has multiple stacks and
7468 switches between them. The optional @var{pc-addr} can also be given to
7469 specify the value of PC for the stack frame.
7473 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7474 numbers @var{n}, this advances toward the outermost frame, to higher
7475 frame numbers, to frames that have existed longer.
7478 @kindex do @r{(@code{down})}
7480 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7481 positive numbers @var{n}, this advances toward the innermost frame, to
7482 lower frame numbers, to frames that were created more recently.
7483 You may abbreviate @code{down} as @code{do}.
7486 All of these commands end by printing two lines of output describing the
7487 frame. The first line shows the frame number, the function name, the
7488 arguments, and the source file and line number of execution in that
7489 frame. The second line shows the text of that source line.
7497 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7499 10 read_input_file (argv[i]);
7503 After such a printout, the @code{list} command with no arguments
7504 prints ten lines centered on the point of execution in the frame.
7505 You can also edit the program at the point of execution with your favorite
7506 editing program by typing @code{edit}.
7507 @xref{List, ,Printing Source Lines},
7511 @kindex select-frame
7513 The @code{select-frame} command is a variant of @code{frame} that does
7514 not display the new frame after selecting it. This command is
7515 intended primarily for use in @value{GDBN} command scripts, where the
7516 output might be unnecessary and distracting.
7518 @kindex down-silently
7520 @item up-silently @var{n}
7521 @itemx down-silently @var{n}
7522 These two commands are variants of @code{up} and @code{down},
7523 respectively; they differ in that they do their work silently, without
7524 causing display of the new frame. They are intended primarily for use
7525 in @value{GDBN} command scripts, where the output might be unnecessary and
7530 @section Information About a Frame
7532 There are several other commands to print information about the selected
7538 When used without any argument, this command does not change which
7539 frame is selected, but prints a brief description of the currently
7540 selected stack frame. It can be abbreviated @code{f}. With an
7541 argument, this command is used to select a stack frame.
7542 @xref{Selection, ,Selecting a Frame}.
7545 @kindex info f @r{(@code{info frame})}
7548 This command prints a verbose description of the selected stack frame,
7553 the address of the frame
7555 the address of the next frame down (called by this frame)
7557 the address of the next frame up (caller of this frame)
7559 the language in which the source code corresponding to this frame is written
7561 the address of the frame's arguments
7563 the address of the frame's local variables
7565 the program counter saved in it (the address of execution in the caller frame)
7567 which registers were saved in the frame
7570 @noindent The verbose description is useful when
7571 something has gone wrong that has made the stack format fail to fit
7572 the usual conventions.
7574 @item info frame @var{addr}
7575 @itemx info f @var{addr}
7576 Print a verbose description of the frame at address @var{addr}, without
7577 selecting that frame. The selected frame remains unchanged by this
7578 command. This requires the same kind of address (more than one for some
7579 architectures) that you specify in the @code{frame} command.
7580 @xref{Selection, ,Selecting a Frame}.
7584 Print the arguments of the selected frame, each on a separate line.
7588 Print the local variables of the selected frame, each on a separate
7589 line. These are all variables (declared either static or automatic)
7590 accessible at the point of execution of the selected frame.
7594 @node Frame Filter Management
7595 @section Management of Frame Filters.
7596 @cindex managing frame filters
7598 Frame filters are Python based utilities to manage and decorate the
7599 output of frames. @xref{Frame Filter API}, for further information.
7601 Managing frame filters is performed by several commands available
7602 within @value{GDBN}, detailed here.
7605 @kindex info frame-filter
7606 @item info frame-filter
7607 Print a list of installed frame filters from all dictionaries, showing
7608 their name, priority and enabled status.
7610 @kindex disable frame-filter
7611 @anchor{disable frame-filter all}
7612 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7613 Disable a frame filter in the dictionary matching
7614 @var{filter-dictionary} and @var{filter-name}. The
7615 @var{filter-dictionary} may be @code{all}, @code{global},
7616 @code{progspace}, or the name of the object file where the frame filter
7617 dictionary resides. When @code{all} is specified, all frame filters
7618 across all dictionaries are disabled. The @var{filter-name} is the name
7619 of the frame filter and is used when @code{all} is not the option for
7620 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7621 may be enabled again later.
7623 @kindex enable frame-filter
7624 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7625 Enable a frame filter in the dictionary matching
7626 @var{filter-dictionary} and @var{filter-name}. The
7627 @var{filter-dictionary} may be @code{all}, @code{global},
7628 @code{progspace} or the name of the object file where the frame filter
7629 dictionary resides. When @code{all} is specified, all frame filters across
7630 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7631 filter and is used when @code{all} is not the option for
7632 @var{filter-dictionary}.
7637 (gdb) info frame-filter
7639 global frame-filters:
7640 Priority Enabled Name
7641 1000 No PrimaryFunctionFilter
7644 progspace /build/test frame-filters:
7645 Priority Enabled Name
7646 100 Yes ProgspaceFilter
7648 objfile /build/test frame-filters:
7649 Priority Enabled Name
7650 999 Yes BuildProgra Filter
7652 (gdb) disable frame-filter /build/test BuildProgramFilter
7653 (gdb) info frame-filter
7655 global frame-filters:
7656 Priority Enabled Name
7657 1000 No PrimaryFunctionFilter
7660 progspace /build/test frame-filters:
7661 Priority Enabled Name
7662 100 Yes ProgspaceFilter
7664 objfile /build/test frame-filters:
7665 Priority Enabled Name
7666 999 No BuildProgramFilter
7668 (gdb) enable frame-filter global PrimaryFunctionFilter
7669 (gdb) info frame-filter
7671 global frame-filters:
7672 Priority Enabled Name
7673 1000 Yes PrimaryFunctionFilter
7676 progspace /build/test frame-filters:
7677 Priority Enabled Name
7678 100 Yes ProgspaceFilter
7680 objfile /build/test frame-filters:
7681 Priority Enabled Name
7682 999 No BuildProgramFilter
7685 @kindex set frame-filter priority
7686 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7687 Set the @var{priority} of a frame filter in the dictionary matching
7688 @var{filter-dictionary}, and the frame filter name matching
7689 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7690 @code{progspace} or the name of the object file where the frame filter
7691 dictionary resides. The @var{priority} is an integer.
7693 @kindex show frame-filter priority
7694 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7695 Show the @var{priority} of a frame filter in the dictionary matching
7696 @var{filter-dictionary}, and the frame filter name matching
7697 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7698 @code{progspace} or the name of the object file where the frame filter
7704 (gdb) info frame-filter
7706 global frame-filters:
7707 Priority Enabled Name
7708 1000 Yes PrimaryFunctionFilter
7711 progspace /build/test frame-filters:
7712 Priority Enabled Name
7713 100 Yes ProgspaceFilter
7715 objfile /build/test frame-filters:
7716 Priority Enabled Name
7717 999 No BuildProgramFilter
7719 (gdb) set frame-filter priority global Reverse 50
7720 (gdb) info frame-filter
7722 global frame-filters:
7723 Priority Enabled Name
7724 1000 Yes PrimaryFunctionFilter
7727 progspace /build/test frame-filters:
7728 Priority Enabled Name
7729 100 Yes ProgspaceFilter
7731 objfile /build/test frame-filters:
7732 Priority Enabled Name
7733 999 No BuildProgramFilter
7738 @chapter Examining Source Files
7740 @value{GDBN} can print parts of your program's source, since the debugging
7741 information recorded in the program tells @value{GDBN} what source files were
7742 used to build it. When your program stops, @value{GDBN} spontaneously prints
7743 the line where it stopped. Likewise, when you select a stack frame
7744 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7745 execution in that frame has stopped. You can print other portions of
7746 source files by explicit command.
7748 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7749 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7750 @value{GDBN} under @sc{gnu} Emacs}.
7753 * List:: Printing source lines
7754 * Specify Location:: How to specify code locations
7755 * Edit:: Editing source files
7756 * Search:: Searching source files
7757 * Source Path:: Specifying source directories
7758 * Machine Code:: Source and machine code
7762 @section Printing Source Lines
7765 @kindex l @r{(@code{list})}
7766 To print lines from a source file, use the @code{list} command
7767 (abbreviated @code{l}). By default, ten lines are printed.
7768 There are several ways to specify what part of the file you want to
7769 print; see @ref{Specify Location}, for the full list.
7771 Here are the forms of the @code{list} command most commonly used:
7774 @item list @var{linenum}
7775 Print lines centered around line number @var{linenum} in the
7776 current source file.
7778 @item list @var{function}
7779 Print lines centered around the beginning of function
7783 Print more lines. If the last lines printed were printed with a
7784 @code{list} command, this prints lines following the last lines
7785 printed; however, if the last line printed was a solitary line printed
7786 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7787 Stack}), this prints lines centered around that line.
7790 Print lines just before the lines last printed.
7793 @cindex @code{list}, how many lines to display
7794 By default, @value{GDBN} prints ten source lines with any of these forms of
7795 the @code{list} command. You can change this using @code{set listsize}:
7798 @kindex set listsize
7799 @item set listsize @var{count}
7800 @itemx set listsize unlimited
7801 Make the @code{list} command display @var{count} source lines (unless
7802 the @code{list} argument explicitly specifies some other number).
7803 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7805 @kindex show listsize
7807 Display the number of lines that @code{list} prints.
7810 Repeating a @code{list} command with @key{RET} discards the argument,
7811 so it is equivalent to typing just @code{list}. This is more useful
7812 than listing the same lines again. An exception is made for an
7813 argument of @samp{-}; that argument is preserved in repetition so that
7814 each repetition moves up in the source file.
7816 In general, the @code{list} command expects you to supply zero, one or two
7817 @dfn{locations}. Locations specify source lines; there are several ways
7818 of writing them (@pxref{Specify Location}), but the effect is always
7819 to specify some source line.
7821 Here is a complete description of the possible arguments for @code{list}:
7824 @item list @var{location}
7825 Print lines centered around the line specified by @var{location}.
7827 @item list @var{first},@var{last}
7828 Print lines from @var{first} to @var{last}. Both arguments are
7829 locations. When a @code{list} command has two locations, and the
7830 source file of the second location is omitted, this refers to
7831 the same source file as the first location.
7833 @item list ,@var{last}
7834 Print lines ending with @var{last}.
7836 @item list @var{first},
7837 Print lines starting with @var{first}.
7840 Print lines just after the lines last printed.
7843 Print lines just before the lines last printed.
7846 As described in the preceding table.
7849 @node Specify Location
7850 @section Specifying a Location
7851 @cindex specifying location
7853 @cindex source location
7856 * Linespec Locations:: Linespec locations
7857 * Explicit Locations:: Explicit locations
7858 * Address Locations:: Address locations
7861 Several @value{GDBN} commands accept arguments that specify a location
7862 of your program's code. Since @value{GDBN} is a source-level
7863 debugger, a location usually specifies some line in the source code.
7864 Locations may be specified using three different formats:
7865 linespec locations, explicit locations, or address locations.
7867 @node Linespec Locations
7868 @subsection Linespec Locations
7869 @cindex linespec locations
7871 A @dfn{linespec} is a colon-separated list of source location parameters such
7872 as file name, function name, etc. Here are all the different ways of
7873 specifying a linespec:
7877 Specifies the line number @var{linenum} of the current source file.
7880 @itemx +@var{offset}
7881 Specifies the line @var{offset} lines before or after the @dfn{current
7882 line}. For the @code{list} command, the current line is the last one
7883 printed; for the breakpoint commands, this is the line at which
7884 execution stopped in the currently selected @dfn{stack frame}
7885 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7886 used as the second of the two linespecs in a @code{list} command,
7887 this specifies the line @var{offset} lines up or down from the first
7890 @item @var{filename}:@var{linenum}
7891 Specifies the line @var{linenum} in the source file @var{filename}.
7892 If @var{filename} is a relative file name, then it will match any
7893 source file name with the same trailing components. For example, if
7894 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7895 name of @file{/build/trunk/gcc/expr.c}, but not
7896 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7898 @item @var{function}
7899 Specifies the line that begins the body of the function @var{function}.
7900 For example, in C, this is the line with the open brace.
7902 @item @var{function}:@var{label}
7903 Specifies the line where @var{label} appears in @var{function}.
7905 @item @var{filename}:@var{function}
7906 Specifies the line that begins the body of the function @var{function}
7907 in the file @var{filename}. You only need the file name with a
7908 function name to avoid ambiguity when there are identically named
7909 functions in different source files.
7912 Specifies the line at which the label named @var{label} appears
7913 in the function corresponding to the currently selected stack frame.
7914 If there is no current selected stack frame (for instance, if the inferior
7915 is not running), then @value{GDBN} will not search for a label.
7917 @cindex breakpoint at static probe point
7918 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7919 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7920 applications to embed static probes. @xref{Static Probe Points}, for more
7921 information on finding and using static probes. This form of linespec
7922 specifies the location of such a static probe.
7924 If @var{objfile} is given, only probes coming from that shared library
7925 or executable matching @var{objfile} as a regular expression are considered.
7926 If @var{provider} is given, then only probes from that provider are considered.
7927 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7928 each one of those probes.
7931 @node Explicit Locations
7932 @subsection Explicit Locations
7933 @cindex explicit locations
7935 @dfn{Explicit locations} allow the user to directly specify the source
7936 location's parameters using option-value pairs.
7938 Explicit locations are useful when several functions, labels, or
7939 file names have the same name (base name for files) in the program's
7940 sources. In these cases, explicit locations point to the source
7941 line you meant more accurately and unambiguously. Also, using
7942 explicit locations might be faster in large programs.
7944 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7945 defined in the file named @file{foo} or the label @code{bar} in a function
7946 named @code{foo}. @value{GDBN} must search either the file system or
7947 the symbol table to know.
7949 The list of valid explicit location options is summarized in the
7953 @item -source @var{filename}
7954 The value specifies the source file name. To differentiate between
7955 files with the same base name, prepend as many directories as is necessary
7956 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7957 @value{GDBN} will use the first file it finds with the given base
7958 name. This option requires the use of either @code{-function} or @code{-line}.
7960 @item -function @var{function}
7961 The value specifies the name of a function. Operations
7962 on function locations unmodified by other options (such as @code{-label}
7963 or @code{-line}) refer to the line that begins the body of the function.
7964 In C, for example, this is the line with the open brace.
7966 @item -label @var{label}
7967 The value specifies the name of a label. When the function
7968 name is not specified, the label is searched in the function of the currently
7969 selected stack frame.
7971 @item -line @var{number}
7972 The value specifies a line offset for the location. The offset may either
7973 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7974 the command. When specified without any other options, the line offset is
7975 relative to the current line.
7978 Explicit location options may be abbreviated by omitting any non-unique
7979 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7981 @node Address Locations
7982 @subsection Address Locations
7983 @cindex address locations
7985 @dfn{Address locations} indicate a specific program address. They have
7986 the generalized form *@var{address}.
7988 For line-oriented commands, such as @code{list} and @code{edit}, this
7989 specifies a source line that contains @var{address}. For @code{break} and
7990 other breakpoint-oriented commands, this can be used to set breakpoints in
7991 parts of your program which do not have debugging information or
7994 Here @var{address} may be any expression valid in the current working
7995 language (@pxref{Languages, working language}) that specifies a code
7996 address. In addition, as a convenience, @value{GDBN} extends the
7997 semantics of expressions used in locations to cover several situations
7998 that frequently occur during debugging. Here are the various forms
8002 @item @var{expression}
8003 Any expression valid in the current working language.
8005 @item @var{funcaddr}
8006 An address of a function or procedure derived from its name. In C,
8007 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8008 simply the function's name @var{function} (and actually a special case
8009 of a valid expression). In Pascal and Modula-2, this is
8010 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8011 (although the Pascal form also works).
8013 This form specifies the address of the function's first instruction,
8014 before the stack frame and arguments have been set up.
8016 @item '@var{filename}':@var{funcaddr}
8017 Like @var{funcaddr} above, but also specifies the name of the source
8018 file explicitly. This is useful if the name of the function does not
8019 specify the function unambiguously, e.g., if there are several
8020 functions with identical names in different source files.
8024 @section Editing Source Files
8025 @cindex editing source files
8028 @kindex e @r{(@code{edit})}
8029 To edit the lines in a source file, use the @code{edit} command.
8030 The editing program of your choice
8031 is invoked with the current line set to
8032 the active line in the program.
8033 Alternatively, there are several ways to specify what part of the file you
8034 want to print if you want to see other parts of the program:
8037 @item edit @var{location}
8038 Edit the source file specified by @code{location}. Editing starts at
8039 that @var{location}, e.g., at the specified source line of the
8040 specified file. @xref{Specify Location}, for all the possible forms
8041 of the @var{location} argument; here are the forms of the @code{edit}
8042 command most commonly used:
8045 @item edit @var{number}
8046 Edit the current source file with @var{number} as the active line number.
8048 @item edit @var{function}
8049 Edit the file containing @var{function} at the beginning of its definition.
8054 @subsection Choosing your Editor
8055 You can customize @value{GDBN} to use any editor you want
8057 The only restriction is that your editor (say @code{ex}), recognizes the
8058 following command-line syntax:
8060 ex +@var{number} file
8062 The optional numeric value +@var{number} specifies the number of the line in
8063 the file where to start editing.}.
8064 By default, it is @file{@value{EDITOR}}, but you can change this
8065 by setting the environment variable @code{EDITOR} before using
8066 @value{GDBN}. For example, to configure @value{GDBN} to use the
8067 @code{vi} editor, you could use these commands with the @code{sh} shell:
8073 or in the @code{csh} shell,
8075 setenv EDITOR /usr/bin/vi
8080 @section Searching Source Files
8081 @cindex searching source files
8083 There are two commands for searching through the current source file for a
8088 @kindex forward-search
8089 @kindex fo @r{(@code{forward-search})}
8090 @item forward-search @var{regexp}
8091 @itemx search @var{regexp}
8092 The command @samp{forward-search @var{regexp}} checks each line,
8093 starting with the one following the last line listed, for a match for
8094 @var{regexp}. It lists the line that is found. You can use the
8095 synonym @samp{search @var{regexp}} or abbreviate the command name as
8098 @kindex reverse-search
8099 @item reverse-search @var{regexp}
8100 The command @samp{reverse-search @var{regexp}} checks each line, starting
8101 with the one before the last line listed and going backward, for a match
8102 for @var{regexp}. It lists the line that is found. You can abbreviate
8103 this command as @code{rev}.
8107 @section Specifying Source Directories
8110 @cindex directories for source files
8111 Executable programs sometimes do not record the directories of the source
8112 files from which they were compiled, just the names. Even when they do,
8113 the directories could be moved between the compilation and your debugging
8114 session. @value{GDBN} has a list of directories to search for source files;
8115 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8116 it tries all the directories in the list, in the order they are present
8117 in the list, until it finds a file with the desired name.
8119 For example, suppose an executable references the file
8120 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8121 @file{/mnt/cross}. The file is first looked up literally; if this
8122 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8123 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8124 message is printed. @value{GDBN} does not look up the parts of the
8125 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8126 Likewise, the subdirectories of the source path are not searched: if
8127 the source path is @file{/mnt/cross}, and the binary refers to
8128 @file{foo.c}, @value{GDBN} would not find it under
8129 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8131 Plain file names, relative file names with leading directories, file
8132 names containing dots, etc.@: are all treated as described above; for
8133 instance, if the source path is @file{/mnt/cross}, and the source file
8134 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8135 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8136 that---@file{/mnt/cross/foo.c}.
8138 Note that the executable search path is @emph{not} used to locate the
8141 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8142 any information it has cached about where source files are found and where
8143 each line is in the file.
8147 When you start @value{GDBN}, its source path includes only @samp{cdir}
8148 and @samp{cwd}, in that order.
8149 To add other directories, use the @code{directory} command.
8151 The search path is used to find both program source files and @value{GDBN}
8152 script files (read using the @samp{-command} option and @samp{source} command).
8154 In addition to the source path, @value{GDBN} provides a set of commands
8155 that manage a list of source path substitution rules. A @dfn{substitution
8156 rule} specifies how to rewrite source directories stored in the program's
8157 debug information in case the sources were moved to a different
8158 directory between compilation and debugging. A rule is made of
8159 two strings, the first specifying what needs to be rewritten in
8160 the path, and the second specifying how it should be rewritten.
8161 In @ref{set substitute-path}, we name these two parts @var{from} and
8162 @var{to} respectively. @value{GDBN} does a simple string replacement
8163 of @var{from} with @var{to} at the start of the directory part of the
8164 source file name, and uses that result instead of the original file
8165 name to look up the sources.
8167 Using the previous example, suppose the @file{foo-1.0} tree has been
8168 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8169 @value{GDBN} to replace @file{/usr/src} in all source path names with
8170 @file{/mnt/cross}. The first lookup will then be
8171 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8172 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8173 substitution rule, use the @code{set substitute-path} command
8174 (@pxref{set substitute-path}).
8176 To avoid unexpected substitution results, a rule is applied only if the
8177 @var{from} part of the directory name ends at a directory separator.
8178 For instance, a rule substituting @file{/usr/source} into
8179 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8180 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8181 is applied only at the beginning of the directory name, this rule will
8182 not be applied to @file{/root/usr/source/baz.c} either.
8184 In many cases, you can achieve the same result using the @code{directory}
8185 command. However, @code{set substitute-path} can be more efficient in
8186 the case where the sources are organized in a complex tree with multiple
8187 subdirectories. With the @code{directory} command, you need to add each
8188 subdirectory of your project. If you moved the entire tree while
8189 preserving its internal organization, then @code{set substitute-path}
8190 allows you to direct the debugger to all the sources with one single
8193 @code{set substitute-path} is also more than just a shortcut command.
8194 The source path is only used if the file at the original location no
8195 longer exists. On the other hand, @code{set substitute-path} modifies
8196 the debugger behavior to look at the rewritten location instead. So, if
8197 for any reason a source file that is not relevant to your executable is
8198 located at the original location, a substitution rule is the only
8199 method available to point @value{GDBN} at the new location.
8201 @cindex @samp{--with-relocated-sources}
8202 @cindex default source path substitution
8203 You can configure a default source path substitution rule by
8204 configuring @value{GDBN} with the
8205 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8206 should be the name of a directory under @value{GDBN}'s configured
8207 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8208 directory names in debug information under @var{dir} will be adjusted
8209 automatically if the installed @value{GDBN} is moved to a new
8210 location. This is useful if @value{GDBN}, libraries or executables
8211 with debug information and corresponding source code are being moved
8215 @item directory @var{dirname} @dots{}
8216 @item dir @var{dirname} @dots{}
8217 Add directory @var{dirname} to the front of the source path. Several
8218 directory names may be given to this command, separated by @samp{:}
8219 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8220 part of absolute file names) or
8221 whitespace. You may specify a directory that is already in the source
8222 path; this moves it forward, so @value{GDBN} searches it sooner.
8226 @vindex $cdir@r{, convenience variable}
8227 @vindex $cwd@r{, convenience variable}
8228 @cindex compilation directory
8229 @cindex current directory
8230 @cindex working directory
8231 @cindex directory, current
8232 @cindex directory, compilation
8233 You can use the string @samp{$cdir} to refer to the compilation
8234 directory (if one is recorded), and @samp{$cwd} to refer to the current
8235 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8236 tracks the current working directory as it changes during your @value{GDBN}
8237 session, while the latter is immediately expanded to the current
8238 directory at the time you add an entry to the source path.
8241 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8243 @c RET-repeat for @code{directory} is explicitly disabled, but since
8244 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8246 @item set directories @var{path-list}
8247 @kindex set directories
8248 Set the source path to @var{path-list}.
8249 @samp{$cdir:$cwd} are added if missing.
8251 @item show directories
8252 @kindex show directories
8253 Print the source path: show which directories it contains.
8255 @anchor{set substitute-path}
8256 @item set substitute-path @var{from} @var{to}
8257 @kindex set substitute-path
8258 Define a source path substitution rule, and add it at the end of the
8259 current list of existing substitution rules. If a rule with the same
8260 @var{from} was already defined, then the old rule is also deleted.
8262 For example, if the file @file{/foo/bar/baz.c} was moved to
8263 @file{/mnt/cross/baz.c}, then the command
8266 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8270 will tell @value{GDBN} to replace @samp{/foo/bar} with
8271 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8272 @file{baz.c} even though it was moved.
8274 In the case when more than one substitution rule have been defined,
8275 the rules are evaluated one by one in the order where they have been
8276 defined. The first one matching, if any, is selected to perform
8279 For instance, if we had entered the following commands:
8282 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8283 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8287 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8288 @file{/mnt/include/defs.h} by using the first rule. However, it would
8289 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8290 @file{/mnt/src/lib/foo.c}.
8293 @item unset substitute-path [path]
8294 @kindex unset substitute-path
8295 If a path is specified, search the current list of substitution rules
8296 for a rule that would rewrite that path. Delete that rule if found.
8297 A warning is emitted by the debugger if no rule could be found.
8299 If no path is specified, then all substitution rules are deleted.
8301 @item show substitute-path [path]
8302 @kindex show substitute-path
8303 If a path is specified, then print the source path substitution rule
8304 which would rewrite that path, if any.
8306 If no path is specified, then print all existing source path substitution
8311 If your source path is cluttered with directories that are no longer of
8312 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8313 versions of source. You can correct the situation as follows:
8317 Use @code{directory} with no argument to reset the source path to its default value.
8320 Use @code{directory} with suitable arguments to reinstall the
8321 directories you want in the source path. You can add all the
8322 directories in one command.
8326 @section Source and Machine Code
8327 @cindex source line and its code address
8329 You can use the command @code{info line} to map source lines to program
8330 addresses (and vice versa), and the command @code{disassemble} to display
8331 a range of addresses as machine instructions. You can use the command
8332 @code{set disassemble-next-line} to set whether to disassemble next
8333 source line when execution stops. When run under @sc{gnu} Emacs
8334 mode, the @code{info line} command causes the arrow to point to the
8335 line specified. Also, @code{info line} prints addresses in symbolic form as
8340 @item info line @var{location}
8341 Print the starting and ending addresses of the compiled code for
8342 source line @var{location}. You can specify source lines in any of
8343 the ways documented in @ref{Specify Location}.
8346 For example, we can use @code{info line} to discover the location of
8347 the object code for the first line of function
8348 @code{m4_changequote}:
8350 @c FIXME: I think this example should also show the addresses in
8351 @c symbolic form, as they usually would be displayed.
8353 (@value{GDBP}) info line m4_changequote
8354 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8358 @cindex code address and its source line
8359 We can also inquire (using @code{*@var{addr}} as the form for
8360 @var{location}) what source line covers a particular address:
8362 (@value{GDBP}) info line *0x63ff
8363 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8366 @cindex @code{$_} and @code{info line}
8367 @cindex @code{x} command, default address
8368 @kindex x@r{(examine), and} info line
8369 After @code{info line}, the default address for the @code{x} command
8370 is changed to the starting address of the line, so that @samp{x/i} is
8371 sufficient to begin examining the machine code (@pxref{Memory,
8372 ,Examining Memory}). Also, this address is saved as the value of the
8373 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8378 @cindex assembly instructions
8379 @cindex instructions, assembly
8380 @cindex machine instructions
8381 @cindex listing machine instructions
8383 @itemx disassemble /m
8384 @itemx disassemble /s
8385 @itemx disassemble /r
8386 This specialized command dumps a range of memory as machine
8387 instructions. It can also print mixed source+disassembly by specifying
8388 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8389 as well as in symbolic form by specifying the @code{/r} modifier.
8390 The default memory range is the function surrounding the
8391 program counter of the selected frame. A single argument to this
8392 command is a program counter value; @value{GDBN} dumps the function
8393 surrounding this value. When two arguments are given, they should
8394 be separated by a comma, possibly surrounded by whitespace. The
8395 arguments specify a range of addresses to dump, in one of two forms:
8398 @item @var{start},@var{end}
8399 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8400 @item @var{start},+@var{length}
8401 the addresses from @var{start} (inclusive) to
8402 @code{@var{start}+@var{length}} (exclusive).
8406 When 2 arguments are specified, the name of the function is also
8407 printed (since there could be several functions in the given range).
8409 The argument(s) can be any expression yielding a numeric value, such as
8410 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8412 If the range of memory being disassembled contains current program counter,
8413 the instruction at that location is shown with a @code{=>} marker.
8416 The following example shows the disassembly of a range of addresses of
8417 HP PA-RISC 2.0 code:
8420 (@value{GDBP}) disas 0x32c4, 0x32e4
8421 Dump of assembler code from 0x32c4 to 0x32e4:
8422 0x32c4 <main+204>: addil 0,dp
8423 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8424 0x32cc <main+212>: ldil 0x3000,r31
8425 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8426 0x32d4 <main+220>: ldo 0(r31),rp
8427 0x32d8 <main+224>: addil -0x800,dp
8428 0x32dc <main+228>: ldo 0x588(r1),r26
8429 0x32e0 <main+232>: ldil 0x3000,r31
8430 End of assembler dump.
8433 Here is an example showing mixed source+assembly for Intel x86
8434 with @code{/m} or @code{/s}, when the program is stopped just after
8435 function prologue in a non-optimized function with no inline code.
8438 (@value{GDBP}) disas /m main
8439 Dump of assembler code for function main:
8441 0x08048330 <+0>: push %ebp
8442 0x08048331 <+1>: mov %esp,%ebp
8443 0x08048333 <+3>: sub $0x8,%esp
8444 0x08048336 <+6>: and $0xfffffff0,%esp
8445 0x08048339 <+9>: sub $0x10,%esp
8447 6 printf ("Hello.\n");
8448 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8449 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8453 0x08048348 <+24>: mov $0x0,%eax
8454 0x0804834d <+29>: leave
8455 0x0804834e <+30>: ret
8457 End of assembler dump.
8460 The @code{/m} option is deprecated as its output is not useful when
8461 there is either inlined code or re-ordered code.
8462 The @code{/s} option is the preferred choice.
8463 Here is an example for AMD x86-64 showing the difference between
8464 @code{/m} output and @code{/s} output.
8465 This example has one inline function defined in a header file,
8466 and the code is compiled with @samp{-O2} optimization.
8467 Note how the @code{/m} output is missing the disassembly of
8468 several instructions that are present in the @code{/s} output.
8498 (@value{GDBP}) disas /m main
8499 Dump of assembler code for function main:
8503 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8504 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8508 0x000000000040041d <+29>: xor %eax,%eax
8509 0x000000000040041f <+31>: retq
8510 0x0000000000400420 <+32>: add %eax,%eax
8511 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8513 End of assembler dump.
8514 (@value{GDBP}) disas /s main
8515 Dump of assembler code for function main:
8519 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8523 0x0000000000400406 <+6>: test %eax,%eax
8524 0x0000000000400408 <+8>: js 0x400420 <main+32>
8529 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8530 0x000000000040040d <+13>: test %eax,%eax
8531 0x000000000040040f <+15>: mov $0x1,%eax
8532 0x0000000000400414 <+20>: cmovne %edx,%eax
8536 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8540 0x000000000040041d <+29>: xor %eax,%eax
8541 0x000000000040041f <+31>: retq
8545 0x0000000000400420 <+32>: add %eax,%eax
8546 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8547 End of assembler dump.
8550 Here is another example showing raw instructions in hex for AMD x86-64,
8553 (gdb) disas /r 0x400281,+10
8554 Dump of assembler code from 0x400281 to 0x40028b:
8555 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8556 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8557 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8558 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8559 End of assembler dump.
8562 Addresses cannot be specified as a location (@pxref{Specify Location}).
8563 So, for example, if you want to disassemble function @code{bar}
8564 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8565 and not @samp{disassemble foo.c:bar}.
8567 Some architectures have more than one commonly-used set of instruction
8568 mnemonics or other syntax.
8570 For programs that were dynamically linked and use shared libraries,
8571 instructions that call functions or branch to locations in the shared
8572 libraries might show a seemingly bogus location---it's actually a
8573 location of the relocation table. On some architectures, @value{GDBN}
8574 might be able to resolve these to actual function names.
8577 @kindex set disassembler-options
8578 @cindex disassembler options
8579 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8580 This command controls the passing of target specific information to
8581 the disassembler. For a list of valid options, please refer to the
8582 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8583 manual and/or the output of @kbd{objdump --help}
8584 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8585 The default value is the empty string.
8587 If it is necessary to specify more than one disassembler option, then
8588 multiple options can be placed together into a comma separated list.
8589 Currently this command is only supported on targets ARM, PowerPC
8592 @kindex show disassembler-options
8593 @item show disassembler-options
8594 Show the current setting of the disassembler options.
8598 @kindex set disassembly-flavor
8599 @cindex Intel disassembly flavor
8600 @cindex AT&T disassembly flavor
8601 @item set disassembly-flavor @var{instruction-set}
8602 Select the instruction set to use when disassembling the
8603 program via the @code{disassemble} or @code{x/i} commands.
8605 Currently this command is only defined for the Intel x86 family. You
8606 can set @var{instruction-set} to either @code{intel} or @code{att}.
8607 The default is @code{att}, the AT&T flavor used by default by Unix
8608 assemblers for x86-based targets.
8610 @kindex show disassembly-flavor
8611 @item show disassembly-flavor
8612 Show the current setting of the disassembly flavor.
8616 @kindex set disassemble-next-line
8617 @kindex show disassemble-next-line
8618 @item set disassemble-next-line
8619 @itemx show disassemble-next-line
8620 Control whether or not @value{GDBN} will disassemble the next source
8621 line or instruction when execution stops. If ON, @value{GDBN} will
8622 display disassembly of the next source line when execution of the
8623 program being debugged stops. This is @emph{in addition} to
8624 displaying the source line itself, which @value{GDBN} always does if
8625 possible. If the next source line cannot be displayed for some reason
8626 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8627 info in the debug info), @value{GDBN} will display disassembly of the
8628 next @emph{instruction} instead of showing the next source line. If
8629 AUTO, @value{GDBN} will display disassembly of next instruction only
8630 if the source line cannot be displayed. This setting causes
8631 @value{GDBN} to display some feedback when you step through a function
8632 with no line info or whose source file is unavailable. The default is
8633 OFF, which means never display the disassembly of the next line or
8639 @chapter Examining Data
8641 @cindex printing data
8642 @cindex examining data
8645 The usual way to examine data in your program is with the @code{print}
8646 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8647 evaluates and prints the value of an expression of the language your
8648 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8649 Different Languages}). It may also print the expression using a
8650 Python-based pretty-printer (@pxref{Pretty Printing}).
8653 @item print @var{expr}
8654 @itemx print /@var{f} @var{expr}
8655 @var{expr} is an expression (in the source language). By default the
8656 value of @var{expr} is printed in a format appropriate to its data type;
8657 you can choose a different format by specifying @samp{/@var{f}}, where
8658 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8662 @itemx print /@var{f}
8663 @cindex reprint the last value
8664 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8665 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8666 conveniently inspect the same value in an alternative format.
8669 A more low-level way of examining data is with the @code{x} command.
8670 It examines data in memory at a specified address and prints it in a
8671 specified format. @xref{Memory, ,Examining Memory}.
8673 If you are interested in information about types, or about how the
8674 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8675 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8678 @cindex exploring hierarchical data structures
8680 Another way of examining values of expressions and type information is
8681 through the Python extension command @code{explore} (available only if
8682 the @value{GDBN} build is configured with @code{--with-python}). It
8683 offers an interactive way to start at the highest level (or, the most
8684 abstract level) of the data type of an expression (or, the data type
8685 itself) and explore all the way down to leaf scalar values/fields
8686 embedded in the higher level data types.
8689 @item explore @var{arg}
8690 @var{arg} is either an expression (in the source language), or a type
8691 visible in the current context of the program being debugged.
8694 The working of the @code{explore} command can be illustrated with an
8695 example. If a data type @code{struct ComplexStruct} is defined in your
8705 struct ComplexStruct
8707 struct SimpleStruct *ss_p;
8713 followed by variable declarations as
8716 struct SimpleStruct ss = @{ 10, 1.11 @};
8717 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8721 then, the value of the variable @code{cs} can be explored using the
8722 @code{explore} command as follows.
8726 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8727 the following fields:
8729 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8730 arr = <Enter 1 to explore this field of type `int [10]'>
8732 Enter the field number of choice:
8736 Since the fields of @code{cs} are not scalar values, you are being
8737 prompted to chose the field you want to explore. Let's say you choose
8738 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8739 pointer, you will be asked if it is pointing to a single value. From
8740 the declaration of @code{cs} above, it is indeed pointing to a single
8741 value, hence you enter @code{y}. If you enter @code{n}, then you will
8742 be asked if it were pointing to an array of values, in which case this
8743 field will be explored as if it were an array.
8746 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8747 Continue exploring it as a pointer to a single value [y/n]: y
8748 The value of `*(cs.ss_p)' is a struct/class of type `struct
8749 SimpleStruct' with the following fields:
8751 i = 10 .. (Value of type `int')
8752 d = 1.1100000000000001 .. (Value of type `double')
8754 Press enter to return to parent value:
8758 If the field @code{arr} of @code{cs} was chosen for exploration by
8759 entering @code{1} earlier, then since it is as array, you will be
8760 prompted to enter the index of the element in the array that you want
8764 `cs.arr' is an array of `int'.
8765 Enter the index of the element you want to explore in `cs.arr': 5
8767 `(cs.arr)[5]' is a scalar value of type `int'.
8771 Press enter to return to parent value:
8774 In general, at any stage of exploration, you can go deeper towards the
8775 leaf values by responding to the prompts appropriately, or hit the
8776 return key to return to the enclosing data structure (the @i{higher}
8777 level data structure).
8779 Similar to exploring values, you can use the @code{explore} command to
8780 explore types. Instead of specifying a value (which is typically a
8781 variable name or an expression valid in the current context of the
8782 program being debugged), you specify a type name. If you consider the
8783 same example as above, your can explore the type
8784 @code{struct ComplexStruct} by passing the argument
8785 @code{struct ComplexStruct} to the @code{explore} command.
8788 (gdb) explore struct ComplexStruct
8792 By responding to the prompts appropriately in the subsequent interactive
8793 session, you can explore the type @code{struct ComplexStruct} in a
8794 manner similar to how the value @code{cs} was explored in the above
8797 The @code{explore} command also has two sub-commands,
8798 @code{explore value} and @code{explore type}. The former sub-command is
8799 a way to explicitly specify that value exploration of the argument is
8800 being invoked, while the latter is a way to explicitly specify that type
8801 exploration of the argument is being invoked.
8804 @item explore value @var{expr}
8805 @cindex explore value
8806 This sub-command of @code{explore} explores the value of the
8807 expression @var{expr} (if @var{expr} is an expression valid in the
8808 current context of the program being debugged). The behavior of this
8809 command is identical to that of the behavior of the @code{explore}
8810 command being passed the argument @var{expr}.
8812 @item explore type @var{arg}
8813 @cindex explore type
8814 This sub-command of @code{explore} explores the type of @var{arg} (if
8815 @var{arg} is a type visible in the current context of program being
8816 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8817 is an expression valid in the current context of the program being
8818 debugged). If @var{arg} is a type, then the behavior of this command is
8819 identical to that of the @code{explore} command being passed the
8820 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8821 this command will be identical to that of the @code{explore} command
8822 being passed the type of @var{arg} as the argument.
8826 * Expressions:: Expressions
8827 * Ambiguous Expressions:: Ambiguous Expressions
8828 * Variables:: Program variables
8829 * Arrays:: Artificial arrays
8830 * Output Formats:: Output formats
8831 * Memory:: Examining memory
8832 * Auto Display:: Automatic display
8833 * Print Settings:: Print settings
8834 * Pretty Printing:: Python pretty printing
8835 * Value History:: Value history
8836 * Convenience Vars:: Convenience variables
8837 * Convenience Funs:: Convenience functions
8838 * Registers:: Registers
8839 * Floating Point Hardware:: Floating point hardware
8840 * Vector Unit:: Vector Unit
8841 * OS Information:: Auxiliary data provided by operating system
8842 * Memory Region Attributes:: Memory region attributes
8843 * Dump/Restore Files:: Copy between memory and a file
8844 * Core File Generation:: Cause a program dump its core
8845 * Character Sets:: Debugging programs that use a different
8846 character set than GDB does
8847 * Caching Target Data:: Data caching for targets
8848 * Searching Memory:: Searching memory for a sequence of bytes
8849 * Value Sizes:: Managing memory allocated for values
8853 @section Expressions
8856 @code{print} and many other @value{GDBN} commands accept an expression and
8857 compute its value. Any kind of constant, variable or operator defined
8858 by the programming language you are using is valid in an expression in
8859 @value{GDBN}. This includes conditional expressions, function calls,
8860 casts, and string constants. It also includes preprocessor macros, if
8861 you compiled your program to include this information; see
8864 @cindex arrays in expressions
8865 @value{GDBN} supports array constants in expressions input by
8866 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8867 you can use the command @code{print @{1, 2, 3@}} to create an array
8868 of three integers. If you pass an array to a function or assign it
8869 to a program variable, @value{GDBN} copies the array to memory that
8870 is @code{malloc}ed in the target program.
8872 Because C is so widespread, most of the expressions shown in examples in
8873 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8874 Languages}, for information on how to use expressions in other
8877 In this section, we discuss operators that you can use in @value{GDBN}
8878 expressions regardless of your programming language.
8880 @cindex casts, in expressions
8881 Casts are supported in all languages, not just in C, because it is so
8882 useful to cast a number into a pointer in order to examine a structure
8883 at that address in memory.
8884 @c FIXME: casts supported---Mod2 true?
8886 @value{GDBN} supports these operators, in addition to those common
8887 to programming languages:
8891 @samp{@@} is a binary operator for treating parts of memory as arrays.
8892 @xref{Arrays, ,Artificial Arrays}, for more information.
8895 @samp{::} allows you to specify a variable in terms of the file or
8896 function where it is defined. @xref{Variables, ,Program Variables}.
8898 @cindex @{@var{type}@}
8899 @cindex type casting memory
8900 @cindex memory, viewing as typed object
8901 @cindex casts, to view memory
8902 @item @{@var{type}@} @var{addr}
8903 Refers to an object of type @var{type} stored at address @var{addr} in
8904 memory. The address @var{addr} may be any expression whose value is
8905 an integer or pointer (but parentheses are required around binary
8906 operators, just as in a cast). This construct is allowed regardless
8907 of what kind of data is normally supposed to reside at @var{addr}.
8910 @node Ambiguous Expressions
8911 @section Ambiguous Expressions
8912 @cindex ambiguous expressions
8914 Expressions can sometimes contain some ambiguous elements. For instance,
8915 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8916 a single function name to be defined several times, for application in
8917 different contexts. This is called @dfn{overloading}. Another example
8918 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8919 templates and is typically instantiated several times, resulting in
8920 the same function name being defined in different contexts.
8922 In some cases and depending on the language, it is possible to adjust
8923 the expression to remove the ambiguity. For instance in C@t{++}, you
8924 can specify the signature of the function you want to break on, as in
8925 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8926 qualified name of your function often makes the expression unambiguous
8929 When an ambiguity that needs to be resolved is detected, the debugger
8930 has the capability to display a menu of numbered choices for each
8931 possibility, and then waits for the selection with the prompt @samp{>}.
8932 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8933 aborts the current command. If the command in which the expression was
8934 used allows more than one choice to be selected, the next option in the
8935 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8938 For example, the following session excerpt shows an attempt to set a
8939 breakpoint at the overloaded symbol @code{String::after}.
8940 We choose three particular definitions of that function name:
8942 @c FIXME! This is likely to change to show arg type lists, at least
8945 (@value{GDBP}) b String::after
8948 [2] file:String.cc; line number:867
8949 [3] file:String.cc; line number:860
8950 [4] file:String.cc; line number:875
8951 [5] file:String.cc; line number:853
8952 [6] file:String.cc; line number:846
8953 [7] file:String.cc; line number:735
8955 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8956 Breakpoint 2 at 0xb344: file String.cc, line 875.
8957 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8958 Multiple breakpoints were set.
8959 Use the "delete" command to delete unwanted
8966 @kindex set multiple-symbols
8967 @item set multiple-symbols @var{mode}
8968 @cindex multiple-symbols menu
8970 This option allows you to adjust the debugger behavior when an expression
8973 By default, @var{mode} is set to @code{all}. If the command with which
8974 the expression is used allows more than one choice, then @value{GDBN}
8975 automatically selects all possible choices. For instance, inserting
8976 a breakpoint on a function using an ambiguous name results in a breakpoint
8977 inserted on each possible match. However, if a unique choice must be made,
8978 then @value{GDBN} uses the menu to help you disambiguate the expression.
8979 For instance, printing the address of an overloaded function will result
8980 in the use of the menu.
8982 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8983 when an ambiguity is detected.
8985 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8986 an error due to the ambiguity and the command is aborted.
8988 @kindex show multiple-symbols
8989 @item show multiple-symbols
8990 Show the current value of the @code{multiple-symbols} setting.
8994 @section Program Variables
8996 The most common kind of expression to use is the name of a variable
8999 Variables in expressions are understood in the selected stack frame
9000 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9004 global (or file-static)
9011 visible according to the scope rules of the
9012 programming language from the point of execution in that frame
9015 @noindent This means that in the function
9030 you can examine and use the variable @code{a} whenever your program is
9031 executing within the function @code{foo}, but you can only use or
9032 examine the variable @code{b} while your program is executing inside
9033 the block where @code{b} is declared.
9035 @cindex variable name conflict
9036 There is an exception: you can refer to a variable or function whose
9037 scope is a single source file even if the current execution point is not
9038 in this file. But it is possible to have more than one such variable or
9039 function with the same name (in different source files). If that
9040 happens, referring to that name has unpredictable effects. If you wish,
9041 you can specify a static variable in a particular function or file by
9042 using the colon-colon (@code{::}) notation:
9044 @cindex colon-colon, context for variables/functions
9046 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9047 @cindex @code{::}, context for variables/functions
9050 @var{file}::@var{variable}
9051 @var{function}::@var{variable}
9055 Here @var{file} or @var{function} is the name of the context for the
9056 static @var{variable}. In the case of file names, you can use quotes to
9057 make sure @value{GDBN} parses the file name as a single word---for example,
9058 to print a global value of @code{x} defined in @file{f2.c}:
9061 (@value{GDBP}) p 'f2.c'::x
9064 The @code{::} notation is normally used for referring to
9065 static variables, since you typically disambiguate uses of local variables
9066 in functions by selecting the appropriate frame and using the
9067 simple name of the variable. However, you may also use this notation
9068 to refer to local variables in frames enclosing the selected frame:
9077 process (a); /* Stop here */
9088 For example, if there is a breakpoint at the commented line,
9089 here is what you might see
9090 when the program stops after executing the call @code{bar(0)}:
9095 (@value{GDBP}) p bar::a
9098 #2 0x080483d0 in foo (a=5) at foobar.c:12
9101 (@value{GDBP}) p bar::a
9105 @cindex C@t{++} scope resolution
9106 These uses of @samp{::} are very rarely in conflict with the very
9107 similar use of the same notation in C@t{++}. When they are in
9108 conflict, the C@t{++} meaning takes precedence; however, this can be
9109 overridden by quoting the file or function name with single quotes.
9111 For example, suppose the program is stopped in a method of a class
9112 that has a field named @code{includefile}, and there is also an
9113 include file named @file{includefile} that defines a variable,
9117 (@value{GDBP}) p includefile
9119 (@value{GDBP}) p includefile::some_global
9120 A syntax error in expression, near `'.
9121 (@value{GDBP}) p 'includefile'::some_global
9125 @cindex wrong values
9126 @cindex variable values, wrong
9127 @cindex function entry/exit, wrong values of variables
9128 @cindex optimized code, wrong values of variables
9130 @emph{Warning:} Occasionally, a local variable may appear to have the
9131 wrong value at certain points in a function---just after entry to a new
9132 scope, and just before exit.
9134 You may see this problem when you are stepping by machine instructions.
9135 This is because, on most machines, it takes more than one instruction to
9136 set up a stack frame (including local variable definitions); if you are
9137 stepping by machine instructions, variables may appear to have the wrong
9138 values until the stack frame is completely built. On exit, it usually
9139 also takes more than one machine instruction to destroy a stack frame;
9140 after you begin stepping through that group of instructions, local
9141 variable definitions may be gone.
9143 This may also happen when the compiler does significant optimizations.
9144 To be sure of always seeing accurate values, turn off all optimization
9147 @cindex ``No symbol "foo" in current context''
9148 Another possible effect of compiler optimizations is to optimize
9149 unused variables out of existence, or assign variables to registers (as
9150 opposed to memory addresses). Depending on the support for such cases
9151 offered by the debug info format used by the compiler, @value{GDBN}
9152 might not be able to display values for such local variables. If that
9153 happens, @value{GDBN} will print a message like this:
9156 No symbol "foo" in current context.
9159 To solve such problems, either recompile without optimizations, or use a
9160 different debug info format, if the compiler supports several such
9161 formats. @xref{Compilation}, for more information on choosing compiler
9162 options. @xref{C, ,C and C@t{++}}, for more information about debug
9163 info formats that are best suited to C@t{++} programs.
9165 If you ask to print an object whose contents are unknown to
9166 @value{GDBN}, e.g., because its data type is not completely specified
9167 by the debug information, @value{GDBN} will say @samp{<incomplete
9168 type>}. @xref{Symbols, incomplete type}, for more about this.
9170 @cindex no debug info variables
9171 If you try to examine or use the value of a (global) variable for
9172 which @value{GDBN} has no type information, e.g., because the program
9173 includes no debug information, @value{GDBN} displays an error message.
9174 @xref{Symbols, unknown type}, for more about unknown types. If you
9175 cast the variable to its declared type, @value{GDBN} gets the
9176 variable's value using the cast-to type as the variable's type. For
9177 example, in a C program:
9180 (@value{GDBP}) p var
9181 'var' has unknown type; cast it to its declared type
9182 (@value{GDBP}) p (float) var
9186 If you append @kbd{@@entry} string to a function parameter name you get its
9187 value at the time the function got called. If the value is not available an
9188 error message is printed. Entry values are available only with some compilers.
9189 Entry values are normally also printed at the function parameter list according
9190 to @ref{set print entry-values}.
9193 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9199 (gdb) print i@@entry
9203 Strings are identified as arrays of @code{char} values without specified
9204 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9205 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9206 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9207 defines literal string type @code{"char"} as @code{char} without a sign.
9212 signed char var1[] = "A";
9215 You get during debugging
9220 $2 = @{65 'A', 0 '\0'@}
9224 @section Artificial Arrays
9226 @cindex artificial array
9228 @kindex @@@r{, referencing memory as an array}
9229 It is often useful to print out several successive objects of the
9230 same type in memory; a section of an array, or an array of
9231 dynamically determined size for which only a pointer exists in the
9234 You can do this by referring to a contiguous span of memory as an
9235 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9236 operand of @samp{@@} should be the first element of the desired array
9237 and be an individual object. The right operand should be the desired length
9238 of the array. The result is an array value whose elements are all of
9239 the type of the left argument. The first element is actually the left
9240 argument; the second element comes from bytes of memory immediately
9241 following those that hold the first element, and so on. Here is an
9242 example. If a program says
9245 int *array = (int *) malloc (len * sizeof (int));
9249 you can print the contents of @code{array} with
9255 The left operand of @samp{@@} must reside in memory. Array values made
9256 with @samp{@@} in this way behave just like other arrays in terms of
9257 subscripting, and are coerced to pointers when used in expressions.
9258 Artificial arrays most often appear in expressions via the value history
9259 (@pxref{Value History, ,Value History}), after printing one out.
9261 Another way to create an artificial array is to use a cast.
9262 This re-interprets a value as if it were an array.
9263 The value need not be in memory:
9265 (@value{GDBP}) p/x (short[2])0x12345678
9266 $1 = @{0x1234, 0x5678@}
9269 As a convenience, if you leave the array length out (as in
9270 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9271 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9273 (@value{GDBP}) p/x (short[])0x12345678
9274 $2 = @{0x1234, 0x5678@}
9277 Sometimes the artificial array mechanism is not quite enough; in
9278 moderately complex data structures, the elements of interest may not
9279 actually be adjacent---for example, if you are interested in the values
9280 of pointers in an array. One useful work-around in this situation is
9281 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9282 Variables}) as a counter in an expression that prints the first
9283 interesting value, and then repeat that expression via @key{RET}. For
9284 instance, suppose you have an array @code{dtab} of pointers to
9285 structures, and you are interested in the values of a field @code{fv}
9286 in each structure. Here is an example of what you might type:
9296 @node Output Formats
9297 @section Output Formats
9299 @cindex formatted output
9300 @cindex output formats
9301 By default, @value{GDBN} prints a value according to its data type. Sometimes
9302 this is not what you want. For example, you might want to print a number
9303 in hex, or a pointer in decimal. Or you might want to view data in memory
9304 at a certain address as a character string or as an instruction. To do
9305 these things, specify an @dfn{output format} when you print a value.
9307 The simplest use of output formats is to say how to print a value
9308 already computed. This is done by starting the arguments of the
9309 @code{print} command with a slash and a format letter. The format
9310 letters supported are:
9314 Regard the bits of the value as an integer, and print the integer in
9318 Print as integer in signed decimal.
9321 Print as integer in unsigned decimal.
9324 Print as integer in octal.
9327 Print as integer in binary. The letter @samp{t} stands for ``two''.
9328 @footnote{@samp{b} cannot be used because these format letters are also
9329 used with the @code{x} command, where @samp{b} stands for ``byte'';
9330 see @ref{Memory,,Examining Memory}.}
9333 @cindex unknown address, locating
9334 @cindex locate address
9335 Print as an address, both absolute in hexadecimal and as an offset from
9336 the nearest preceding symbol. You can use this format used to discover
9337 where (in what function) an unknown address is located:
9340 (@value{GDBP}) p/a 0x54320
9341 $3 = 0x54320 <_initialize_vx+396>
9345 The command @code{info symbol 0x54320} yields similar results.
9346 @xref{Symbols, info symbol}.
9349 Regard as an integer and print it as a character constant. This
9350 prints both the numerical value and its character representation. The
9351 character representation is replaced with the octal escape @samp{\nnn}
9352 for characters outside the 7-bit @sc{ascii} range.
9354 Without this format, @value{GDBN} displays @code{char},
9355 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9356 constants. Single-byte members of vectors are displayed as integer
9360 Regard the bits of the value as a floating point number and print
9361 using typical floating point syntax.
9364 @cindex printing strings
9365 @cindex printing byte arrays
9366 Regard as a string, if possible. With this format, pointers to single-byte
9367 data are displayed as null-terminated strings and arrays of single-byte data
9368 are displayed as fixed-length strings. Other values are displayed in their
9371 Without this format, @value{GDBN} displays pointers to and arrays of
9372 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9373 strings. Single-byte members of a vector are displayed as an integer
9377 Like @samp{x} formatting, the value is treated as an integer and
9378 printed as hexadecimal, but leading zeros are printed to pad the value
9379 to the size of the integer type.
9382 @cindex raw printing
9383 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9384 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9385 Printing}). This typically results in a higher-level display of the
9386 value's contents. The @samp{r} format bypasses any Python
9387 pretty-printer which might exist.
9390 For example, to print the program counter in hex (@pxref{Registers}), type
9397 Note that no space is required before the slash; this is because command
9398 names in @value{GDBN} cannot contain a slash.
9400 To reprint the last value in the value history with a different format,
9401 you can use the @code{print} command with just a format and no
9402 expression. For example, @samp{p/x} reprints the last value in hex.
9405 @section Examining Memory
9407 You can use the command @code{x} (for ``examine'') to examine memory in
9408 any of several formats, independently of your program's data types.
9410 @cindex examining memory
9412 @kindex x @r{(examine memory)}
9413 @item x/@var{nfu} @var{addr}
9416 Use the @code{x} command to examine memory.
9419 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9420 much memory to display and how to format it; @var{addr} is an
9421 expression giving the address where you want to start displaying memory.
9422 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9423 Several commands set convenient defaults for @var{addr}.
9426 @item @var{n}, the repeat count
9427 The repeat count is a decimal integer; the default is 1. It specifies
9428 how much memory (counting by units @var{u}) to display. If a negative
9429 number is specified, memory is examined backward from @var{addr}.
9430 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9433 @item @var{f}, the display format
9434 The display format is one of the formats used by @code{print}
9435 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9436 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9437 The default is @samp{x} (hexadecimal) initially. The default changes
9438 each time you use either @code{x} or @code{print}.
9440 @item @var{u}, the unit size
9441 The unit size is any of
9447 Halfwords (two bytes).
9449 Words (four bytes). This is the initial default.
9451 Giant words (eight bytes).
9454 Each time you specify a unit size with @code{x}, that size becomes the
9455 default unit the next time you use @code{x}. For the @samp{i} format,
9456 the unit size is ignored and is normally not written. For the @samp{s} format,
9457 the unit size defaults to @samp{b}, unless it is explicitly given.
9458 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9459 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9460 Note that the results depend on the programming language of the
9461 current compilation unit. If the language is C, the @samp{s}
9462 modifier will use the UTF-16 encoding while @samp{w} will use
9463 UTF-32. The encoding is set by the programming language and cannot
9466 @item @var{addr}, starting display address
9467 @var{addr} is the address where you want @value{GDBN} to begin displaying
9468 memory. The expression need not have a pointer value (though it may);
9469 it is always interpreted as an integer address of a byte of memory.
9470 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9471 @var{addr} is usually just after the last address examined---but several
9472 other commands also set the default address: @code{info breakpoints} (to
9473 the address of the last breakpoint listed), @code{info line} (to the
9474 starting address of a line), and @code{print} (if you use it to display
9475 a value from memory).
9478 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9479 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9480 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9481 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9482 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9484 You can also specify a negative repeat count to examine memory backward
9485 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9486 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9488 Since the letters indicating unit sizes are all distinct from the
9489 letters specifying output formats, you do not have to remember whether
9490 unit size or format comes first; either order works. The output
9491 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9492 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9494 Even though the unit size @var{u} is ignored for the formats @samp{s}
9495 and @samp{i}, you might still want to use a count @var{n}; for example,
9496 @samp{3i} specifies that you want to see three machine instructions,
9497 including any operands. For convenience, especially when used with
9498 the @code{display} command, the @samp{i} format also prints branch delay
9499 slot instructions, if any, beyond the count specified, which immediately
9500 follow the last instruction that is within the count. The command
9501 @code{disassemble} gives an alternative way of inspecting machine
9502 instructions; see @ref{Machine Code,,Source and Machine Code}.
9504 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9505 the command displays null-terminated strings or instructions before the given
9506 address as many as the absolute value of the given number. For the @samp{i}
9507 format, we use line number information in the debug info to accurately locate
9508 instruction boundaries while disassembling backward. If line info is not
9509 available, the command stops examining memory with an error message.
9511 All the defaults for the arguments to @code{x} are designed to make it
9512 easy to continue scanning memory with minimal specifications each time
9513 you use @code{x}. For example, after you have inspected three machine
9514 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9515 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9516 the repeat count @var{n} is used again; the other arguments default as
9517 for successive uses of @code{x}.
9519 When examining machine instructions, the instruction at current program
9520 counter is shown with a @code{=>} marker. For example:
9523 (@value{GDBP}) x/5i $pc-6
9524 0x804837f <main+11>: mov %esp,%ebp
9525 0x8048381 <main+13>: push %ecx
9526 0x8048382 <main+14>: sub $0x4,%esp
9527 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9528 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9531 @cindex @code{$_}, @code{$__}, and value history
9532 The addresses and contents printed by the @code{x} command are not saved
9533 in the value history because there is often too much of them and they
9534 would get in the way. Instead, @value{GDBN} makes these values available for
9535 subsequent use in expressions as values of the convenience variables
9536 @code{$_} and @code{$__}. After an @code{x} command, the last address
9537 examined is available for use in expressions in the convenience variable
9538 @code{$_}. The contents of that address, as examined, are available in
9539 the convenience variable @code{$__}.
9541 If the @code{x} command has a repeat count, the address and contents saved
9542 are from the last memory unit printed; this is not the same as the last
9543 address printed if several units were printed on the last line of output.
9545 @anchor{addressable memory unit}
9546 @cindex addressable memory unit
9547 Most targets have an addressable memory unit size of 8 bits. This means
9548 that to each memory address are associated 8 bits of data. Some
9549 targets, however, have other addressable memory unit sizes.
9550 Within @value{GDBN} and this document, the term
9551 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9552 when explicitly referring to a chunk of data of that size. The word
9553 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9554 the addressable memory unit size of the target. For most systems,
9555 addressable memory unit is a synonym of byte.
9557 @cindex remote memory comparison
9558 @cindex target memory comparison
9559 @cindex verify remote memory image
9560 @cindex verify target memory image
9561 When you are debugging a program running on a remote target machine
9562 (@pxref{Remote Debugging}), you may wish to verify the program's image
9563 in the remote machine's memory against the executable file you
9564 downloaded to the target. Or, on any target, you may want to check
9565 whether the program has corrupted its own read-only sections. The
9566 @code{compare-sections} command is provided for such situations.
9569 @kindex compare-sections
9570 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9571 Compare the data of a loadable section @var{section-name} in the
9572 executable file of the program being debugged with the same section in
9573 the target machine's memory, and report any mismatches. With no
9574 arguments, compares all loadable sections. With an argument of
9575 @code{-r}, compares all loadable read-only sections.
9577 Note: for remote targets, this command can be accelerated if the
9578 target supports computing the CRC checksum of a block of memory
9579 (@pxref{qCRC packet}).
9583 @section Automatic Display
9584 @cindex automatic display
9585 @cindex display of expressions
9587 If you find that you want to print the value of an expression frequently
9588 (to see how it changes), you might want to add it to the @dfn{automatic
9589 display list} so that @value{GDBN} prints its value each time your program stops.
9590 Each expression added to the list is given a number to identify it;
9591 to remove an expression from the list, you specify that number.
9592 The automatic display looks like this:
9596 3: bar[5] = (struct hack *) 0x3804
9600 This display shows item numbers, expressions and their current values. As with
9601 displays you request manually using @code{x} or @code{print}, you can
9602 specify the output format you prefer; in fact, @code{display} decides
9603 whether to use @code{print} or @code{x} depending your format
9604 specification---it uses @code{x} if you specify either the @samp{i}
9605 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9609 @item display @var{expr}
9610 Add the expression @var{expr} to the list of expressions to display
9611 each time your program stops. @xref{Expressions, ,Expressions}.
9613 @code{display} does not repeat if you press @key{RET} again after using it.
9615 @item display/@var{fmt} @var{expr}
9616 For @var{fmt} specifying only a display format and not a size or
9617 count, add the expression @var{expr} to the auto-display list but
9618 arrange to display it each time in the specified format @var{fmt}.
9619 @xref{Output Formats,,Output Formats}.
9621 @item display/@var{fmt} @var{addr}
9622 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9623 number of units, add the expression @var{addr} as a memory address to
9624 be examined each time your program stops. Examining means in effect
9625 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9628 For example, @samp{display/i $pc} can be helpful, to see the machine
9629 instruction about to be executed each time execution stops (@samp{$pc}
9630 is a common name for the program counter; @pxref{Registers, ,Registers}).
9633 @kindex delete display
9635 @item undisplay @var{dnums}@dots{}
9636 @itemx delete display @var{dnums}@dots{}
9637 Remove items from the list of expressions to display. Specify the
9638 numbers of the displays that you want affected with the command
9639 argument @var{dnums}. It can be a single display number, one of the
9640 numbers shown in the first field of the @samp{info display} display;
9641 or it could be a range of display numbers, as in @code{2-4}.
9643 @code{undisplay} does not repeat if you press @key{RET} after using it.
9644 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9646 @kindex disable display
9647 @item disable display @var{dnums}@dots{}
9648 Disable the display of item numbers @var{dnums}. A disabled display
9649 item is not printed automatically, but is not forgotten. It may be
9650 enabled again later. Specify the numbers of the displays that you
9651 want affected with the command argument @var{dnums}. It can be a
9652 single display number, one of the numbers shown in the first field of
9653 the @samp{info display} display; or it could be a range of display
9654 numbers, as in @code{2-4}.
9656 @kindex enable display
9657 @item enable display @var{dnums}@dots{}
9658 Enable display of item numbers @var{dnums}. It becomes effective once
9659 again in auto display of its expression, until you specify otherwise.
9660 Specify the numbers of the displays that you want affected with the
9661 command argument @var{dnums}. It can be a single display number, one
9662 of the numbers shown in the first field of the @samp{info display}
9663 display; or it could be a range of display numbers, as in @code{2-4}.
9666 Display the current values of the expressions on the list, just as is
9667 done when your program stops.
9669 @kindex info display
9671 Print the list of expressions previously set up to display
9672 automatically, each one with its item number, but without showing the
9673 values. This includes disabled expressions, which are marked as such.
9674 It also includes expressions which would not be displayed right now
9675 because they refer to automatic variables not currently available.
9678 @cindex display disabled out of scope
9679 If a display expression refers to local variables, then it does not make
9680 sense outside the lexical context for which it was set up. Such an
9681 expression is disabled when execution enters a context where one of its
9682 variables is not defined. For example, if you give the command
9683 @code{display last_char} while inside a function with an argument
9684 @code{last_char}, @value{GDBN} displays this argument while your program
9685 continues to stop inside that function. When it stops elsewhere---where
9686 there is no variable @code{last_char}---the display is disabled
9687 automatically. The next time your program stops where @code{last_char}
9688 is meaningful, you can enable the display expression once again.
9690 @node Print Settings
9691 @section Print Settings
9693 @cindex format options
9694 @cindex print settings
9695 @value{GDBN} provides the following ways to control how arrays, structures,
9696 and symbols are printed.
9699 These settings are useful for debugging programs in any language:
9703 @item set print address
9704 @itemx set print address on
9705 @cindex print/don't print memory addresses
9706 @value{GDBN} prints memory addresses showing the location of stack
9707 traces, structure values, pointer values, breakpoints, and so forth,
9708 even when it also displays the contents of those addresses. The default
9709 is @code{on}. For example, this is what a stack frame display looks like with
9710 @code{set print address on}:
9715 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9717 530 if (lquote != def_lquote)
9721 @item set print address off
9722 Do not print addresses when displaying their contents. For example,
9723 this is the same stack frame displayed with @code{set print address off}:
9727 (@value{GDBP}) set print addr off
9729 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9730 530 if (lquote != def_lquote)
9734 You can use @samp{set print address off} to eliminate all machine
9735 dependent displays from the @value{GDBN} interface. For example, with
9736 @code{print address off}, you should get the same text for backtraces on
9737 all machines---whether or not they involve pointer arguments.
9740 @item show print address
9741 Show whether or not addresses are to be printed.
9744 When @value{GDBN} prints a symbolic address, it normally prints the
9745 closest earlier symbol plus an offset. If that symbol does not uniquely
9746 identify the address (for example, it is a name whose scope is a single
9747 source file), you may need to clarify. One way to do this is with
9748 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9749 you can set @value{GDBN} to print the source file and line number when
9750 it prints a symbolic address:
9753 @item set print symbol-filename on
9754 @cindex source file and line of a symbol
9755 @cindex symbol, source file and line
9756 Tell @value{GDBN} to print the source file name and line number of a
9757 symbol in the symbolic form of an address.
9759 @item set print symbol-filename off
9760 Do not print source file name and line number of a symbol. This is the
9763 @item show print symbol-filename
9764 Show whether or not @value{GDBN} will print the source file name and
9765 line number of a symbol in the symbolic form of an address.
9768 Another situation where it is helpful to show symbol filenames and line
9769 numbers is when disassembling code; @value{GDBN} shows you the line
9770 number and source file that corresponds to each instruction.
9772 Also, you may wish to see the symbolic form only if the address being
9773 printed is reasonably close to the closest earlier symbol:
9776 @item set print max-symbolic-offset @var{max-offset}
9777 @itemx set print max-symbolic-offset unlimited
9778 @cindex maximum value for offset of closest symbol
9779 Tell @value{GDBN} to only display the symbolic form of an address if the
9780 offset between the closest earlier symbol and the address is less than
9781 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9782 to always print the symbolic form of an address if any symbol precedes
9783 it. Zero is equivalent to @code{unlimited}.
9785 @item show print max-symbolic-offset
9786 Ask how large the maximum offset is that @value{GDBN} prints in a
9790 @cindex wild pointer, interpreting
9791 @cindex pointer, finding referent
9792 If you have a pointer and you are not sure where it points, try
9793 @samp{set print symbol-filename on}. Then you can determine the name
9794 and source file location of the variable where it points, using
9795 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9796 For example, here @value{GDBN} shows that a variable @code{ptt} points
9797 at another variable @code{t}, defined in @file{hi2.c}:
9800 (@value{GDBP}) set print symbol-filename on
9801 (@value{GDBP}) p/a ptt
9802 $4 = 0xe008 <t in hi2.c>
9806 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9807 does not show the symbol name and filename of the referent, even with
9808 the appropriate @code{set print} options turned on.
9811 You can also enable @samp{/a}-like formatting all the time using
9812 @samp{set print symbol on}:
9815 @item set print symbol on
9816 Tell @value{GDBN} to print the symbol corresponding to an address, if
9819 @item set print symbol off
9820 Tell @value{GDBN} not to print the symbol corresponding to an
9821 address. In this mode, @value{GDBN} will still print the symbol
9822 corresponding to pointers to functions. This is the default.
9824 @item show print symbol
9825 Show whether @value{GDBN} will display the symbol corresponding to an
9829 Other settings control how different kinds of objects are printed:
9832 @item set print array
9833 @itemx set print array on
9834 @cindex pretty print arrays
9835 Pretty print arrays. This format is more convenient to read,
9836 but uses more space. The default is off.
9838 @item set print array off
9839 Return to compressed format for arrays.
9841 @item show print array
9842 Show whether compressed or pretty format is selected for displaying
9845 @cindex print array indexes
9846 @item set print array-indexes
9847 @itemx set print array-indexes on
9848 Print the index of each element when displaying arrays. May be more
9849 convenient to locate a given element in the array or quickly find the
9850 index of a given element in that printed array. The default is off.
9852 @item set print array-indexes off
9853 Stop printing element indexes when displaying arrays.
9855 @item show print array-indexes
9856 Show whether the index of each element is printed when displaying
9859 @item set print elements @var{number-of-elements}
9860 @itemx set print elements unlimited
9861 @cindex number of array elements to print
9862 @cindex limit on number of printed array elements
9863 Set a limit on how many elements of an array @value{GDBN} will print.
9864 If @value{GDBN} is printing a large array, it stops printing after it has
9865 printed the number of elements set by the @code{set print elements} command.
9866 This limit also applies to the display of strings.
9867 When @value{GDBN} starts, this limit is set to 200.
9868 Setting @var{number-of-elements} to @code{unlimited} or zero means
9869 that the number of elements to print is unlimited.
9871 @item show print elements
9872 Display the number of elements of a large array that @value{GDBN} will print.
9873 If the number is 0, then the printing is unlimited.
9875 @item set print frame-arguments @var{value}
9876 @kindex set print frame-arguments
9877 @cindex printing frame argument values
9878 @cindex print all frame argument values
9879 @cindex print frame argument values for scalars only
9880 @cindex do not print frame argument values
9881 This command allows to control how the values of arguments are printed
9882 when the debugger prints a frame (@pxref{Frames}). The possible
9887 The values of all arguments are printed.
9890 Print the value of an argument only if it is a scalar. The value of more
9891 complex arguments such as arrays, structures, unions, etc, is replaced
9892 by @code{@dots{}}. This is the default. Here is an example where
9893 only scalar arguments are shown:
9896 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9901 None of the argument values are printed. Instead, the value of each argument
9902 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9905 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9910 By default, only scalar arguments are printed. This command can be used
9911 to configure the debugger to print the value of all arguments, regardless
9912 of their type. However, it is often advantageous to not print the value
9913 of more complex parameters. For instance, it reduces the amount of
9914 information printed in each frame, making the backtrace more readable.
9915 Also, it improves performance when displaying Ada frames, because
9916 the computation of large arguments can sometimes be CPU-intensive,
9917 especially in large applications. Setting @code{print frame-arguments}
9918 to @code{scalars} (the default) or @code{none} avoids this computation,
9919 thus speeding up the display of each Ada frame.
9921 @item show print frame-arguments
9922 Show how the value of arguments should be displayed when printing a frame.
9924 @item set print raw frame-arguments on
9925 Print frame arguments in raw, non pretty-printed, form.
9927 @item set print raw frame-arguments off
9928 Print frame arguments in pretty-printed form, if there is a pretty-printer
9929 for the value (@pxref{Pretty Printing}),
9930 otherwise print the value in raw form.
9931 This is the default.
9933 @item show print raw frame-arguments
9934 Show whether to print frame arguments in raw form.
9936 @anchor{set print entry-values}
9937 @item set print entry-values @var{value}
9938 @kindex set print entry-values
9939 Set printing of frame argument values at function entry. In some cases
9940 @value{GDBN} can determine the value of function argument which was passed by
9941 the function caller, even if the value was modified inside the called function
9942 and therefore is different. With optimized code, the current value could be
9943 unavailable, but the entry value may still be known.
9945 The default value is @code{default} (see below for its description). Older
9946 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9947 this feature will behave in the @code{default} setting the same way as with the
9950 This functionality is currently supported only by DWARF 2 debugging format and
9951 the compiler has to produce @samp{DW_TAG_call_site} tags. With
9952 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9955 The @var{value} parameter can be one of the following:
9959 Print only actual parameter values, never print values from function entry
9963 #0 different (val=6)
9964 #0 lost (val=<optimized out>)
9966 #0 invalid (val=<optimized out>)
9970 Print only parameter values from function entry point. The actual parameter
9971 values are never printed.
9973 #0 equal (val@@entry=5)
9974 #0 different (val@@entry=5)
9975 #0 lost (val@@entry=5)
9976 #0 born (val@@entry=<optimized out>)
9977 #0 invalid (val@@entry=<optimized out>)
9981 Print only parameter values from function entry point. If value from function
9982 entry point is not known while the actual value is known, print the actual
9983 value for such parameter.
9985 #0 equal (val@@entry=5)
9986 #0 different (val@@entry=5)
9987 #0 lost (val@@entry=5)
9989 #0 invalid (val@@entry=<optimized out>)
9993 Print actual parameter values. If actual parameter value is not known while
9994 value from function entry point is known, print the entry point value for such
9998 #0 different (val=6)
9999 #0 lost (val@@entry=5)
10001 #0 invalid (val=<optimized out>)
10005 Always print both the actual parameter value and its value from function entry
10006 point, even if values of one or both are not available due to compiler
10009 #0 equal (val=5, val@@entry=5)
10010 #0 different (val=6, val@@entry=5)
10011 #0 lost (val=<optimized out>, val@@entry=5)
10012 #0 born (val=10, val@@entry=<optimized out>)
10013 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10017 Print the actual parameter value if it is known and also its value from
10018 function entry point if it is known. If neither is known, print for the actual
10019 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10020 values are known and identical, print the shortened
10021 @code{param=param@@entry=VALUE} notation.
10023 #0 equal (val=val@@entry=5)
10024 #0 different (val=6, val@@entry=5)
10025 #0 lost (val@@entry=5)
10027 #0 invalid (val=<optimized out>)
10031 Always print the actual parameter value. Print also its value from function
10032 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10033 if both values are known and identical, print the shortened
10034 @code{param=param@@entry=VALUE} notation.
10036 #0 equal (val=val@@entry=5)
10037 #0 different (val=6, val@@entry=5)
10038 #0 lost (val=<optimized out>, val@@entry=5)
10040 #0 invalid (val=<optimized out>)
10044 For analysis messages on possible failures of frame argument values at function
10045 entry resolution see @ref{set debug entry-values}.
10047 @item show print entry-values
10048 Show the method being used for printing of frame argument values at function
10051 @item set print repeats @var{number-of-repeats}
10052 @itemx set print repeats unlimited
10053 @cindex repeated array elements
10054 Set the threshold for suppressing display of repeated array
10055 elements. When the number of consecutive identical elements of an
10056 array exceeds the threshold, @value{GDBN} prints the string
10057 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10058 identical repetitions, instead of displaying the identical elements
10059 themselves. Setting the threshold to @code{unlimited} or zero will
10060 cause all elements to be individually printed. The default threshold
10063 @item show print repeats
10064 Display the current threshold for printing repeated identical
10067 @item set print null-stop
10068 @cindex @sc{null} elements in arrays
10069 Cause @value{GDBN} to stop printing the characters of an array when the first
10070 @sc{null} is encountered. This is useful when large arrays actually
10071 contain only short strings.
10072 The default is off.
10074 @item show print null-stop
10075 Show whether @value{GDBN} stops printing an array on the first
10076 @sc{null} character.
10078 @item set print pretty on
10079 @cindex print structures in indented form
10080 @cindex indentation in structure display
10081 Cause @value{GDBN} to print structures in an indented format with one member
10082 per line, like this:
10097 @item set print pretty off
10098 Cause @value{GDBN} to print structures in a compact format, like this:
10102 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10103 meat = 0x54 "Pork"@}
10108 This is the default format.
10110 @item show print pretty
10111 Show which format @value{GDBN} is using to print structures.
10113 @item set print sevenbit-strings on
10114 @cindex eight-bit characters in strings
10115 @cindex octal escapes in strings
10116 Print using only seven-bit characters; if this option is set,
10117 @value{GDBN} displays any eight-bit characters (in strings or
10118 character values) using the notation @code{\}@var{nnn}. This setting is
10119 best if you are working in English (@sc{ascii}) and you use the
10120 high-order bit of characters as a marker or ``meta'' bit.
10122 @item set print sevenbit-strings off
10123 Print full eight-bit characters. This allows the use of more
10124 international character sets, and is the default.
10126 @item show print sevenbit-strings
10127 Show whether or not @value{GDBN} is printing only seven-bit characters.
10129 @item set print union on
10130 @cindex unions in structures, printing
10131 Tell @value{GDBN} to print unions which are contained in structures
10132 and other unions. This is the default setting.
10134 @item set print union off
10135 Tell @value{GDBN} not to print unions which are contained in
10136 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10139 @item show print union
10140 Ask @value{GDBN} whether or not it will print unions which are contained in
10141 structures and other unions.
10143 For example, given the declarations
10146 typedef enum @{Tree, Bug@} Species;
10147 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10148 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10159 struct thing foo = @{Tree, @{Acorn@}@};
10163 with @code{set print union on} in effect @samp{p foo} would print
10166 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10170 and with @code{set print union off} in effect it would print
10173 $1 = @{it = Tree, form = @{...@}@}
10177 @code{set print union} affects programs written in C-like languages
10183 These settings are of interest when debugging C@t{++} programs:
10186 @cindex demangling C@t{++} names
10187 @item set print demangle
10188 @itemx set print demangle on
10189 Print C@t{++} names in their source form rather than in the encoded
10190 (``mangled'') form passed to the assembler and linker for type-safe
10191 linkage. The default is on.
10193 @item show print demangle
10194 Show whether C@t{++} names are printed in mangled or demangled form.
10196 @item set print asm-demangle
10197 @itemx set print asm-demangle on
10198 Print C@t{++} names in their source form rather than their mangled form, even
10199 in assembler code printouts such as instruction disassemblies.
10200 The default is off.
10202 @item show print asm-demangle
10203 Show whether C@t{++} names in assembly listings are printed in mangled
10206 @cindex C@t{++} symbol decoding style
10207 @cindex symbol decoding style, C@t{++}
10208 @kindex set demangle-style
10209 @item set demangle-style @var{style}
10210 Choose among several encoding schemes used by different compilers to
10211 represent C@t{++} names. The choices for @var{style} are currently:
10215 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10216 This is the default.
10219 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10222 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10225 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10228 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10229 @strong{Warning:} this setting alone is not sufficient to allow
10230 debugging @code{cfront}-generated executables. @value{GDBN} would
10231 require further enhancement to permit that.
10234 If you omit @var{style}, you will see a list of possible formats.
10236 @item show demangle-style
10237 Display the encoding style currently in use for decoding C@t{++} symbols.
10239 @item set print object
10240 @itemx set print object on
10241 @cindex derived type of an object, printing
10242 @cindex display derived types
10243 When displaying a pointer to an object, identify the @emph{actual}
10244 (derived) type of the object rather than the @emph{declared} type, using
10245 the virtual function table. Note that the virtual function table is
10246 required---this feature can only work for objects that have run-time
10247 type identification; a single virtual method in the object's declared
10248 type is sufficient. Note that this setting is also taken into account when
10249 working with variable objects via MI (@pxref{GDB/MI}).
10251 @item set print object off
10252 Display only the declared type of objects, without reference to the
10253 virtual function table. This is the default setting.
10255 @item show print object
10256 Show whether actual, or declared, object types are displayed.
10258 @item set print static-members
10259 @itemx set print static-members on
10260 @cindex static members of C@t{++} objects
10261 Print static members when displaying a C@t{++} object. The default is on.
10263 @item set print static-members off
10264 Do not print static members when displaying a C@t{++} object.
10266 @item show print static-members
10267 Show whether C@t{++} static members are printed or not.
10269 @item set print pascal_static-members
10270 @itemx set print pascal_static-members on
10271 @cindex static members of Pascal objects
10272 @cindex Pascal objects, static members display
10273 Print static members when displaying a Pascal object. The default is on.
10275 @item set print pascal_static-members off
10276 Do not print static members when displaying a Pascal object.
10278 @item show print pascal_static-members
10279 Show whether Pascal static members are printed or not.
10281 @c These don't work with HP ANSI C++ yet.
10282 @item set print vtbl
10283 @itemx set print vtbl on
10284 @cindex pretty print C@t{++} virtual function tables
10285 @cindex virtual functions (C@t{++}) display
10286 @cindex VTBL display
10287 Pretty print C@t{++} virtual function tables. The default is off.
10288 (The @code{vtbl} commands do not work on programs compiled with the HP
10289 ANSI C@t{++} compiler (@code{aCC}).)
10291 @item set print vtbl off
10292 Do not pretty print C@t{++} virtual function tables.
10294 @item show print vtbl
10295 Show whether C@t{++} virtual function tables are pretty printed, or not.
10298 @node Pretty Printing
10299 @section Pretty Printing
10301 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10302 Python code. It greatly simplifies the display of complex objects. This
10303 mechanism works for both MI and the CLI.
10306 * Pretty-Printer Introduction:: Introduction to pretty-printers
10307 * Pretty-Printer Example:: An example pretty-printer
10308 * Pretty-Printer Commands:: Pretty-printer commands
10311 @node Pretty-Printer Introduction
10312 @subsection Pretty-Printer Introduction
10314 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10315 registered for the value. If there is then @value{GDBN} invokes the
10316 pretty-printer to print the value. Otherwise the value is printed normally.
10318 Pretty-printers are normally named. This makes them easy to manage.
10319 The @samp{info pretty-printer} command will list all the installed
10320 pretty-printers with their names.
10321 If a pretty-printer can handle multiple data types, then its
10322 @dfn{subprinters} are the printers for the individual data types.
10323 Each such subprinter has its own name.
10324 The format of the name is @var{printer-name};@var{subprinter-name}.
10326 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10327 Typically they are automatically loaded and registered when the corresponding
10328 debug information is loaded, thus making them available without having to
10329 do anything special.
10331 There are three places where a pretty-printer can be registered.
10335 Pretty-printers registered globally are available when debugging
10339 Pretty-printers registered with a program space are available only
10340 when debugging that program.
10341 @xref{Progspaces In Python}, for more details on program spaces in Python.
10344 Pretty-printers registered with an objfile are loaded and unloaded
10345 with the corresponding objfile (e.g., shared library).
10346 @xref{Objfiles In Python}, for more details on objfiles in Python.
10349 @xref{Selecting Pretty-Printers}, for further information on how
10350 pretty-printers are selected,
10352 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10355 @node Pretty-Printer Example
10356 @subsection Pretty-Printer Example
10358 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10361 (@value{GDBP}) print s
10363 static npos = 4294967295,
10365 <std::allocator<char>> = @{
10366 <__gnu_cxx::new_allocator<char>> = @{
10367 <No data fields>@}, <No data fields>
10369 members of std::basic_string<char, std::char_traits<char>,
10370 std::allocator<char> >::_Alloc_hider:
10371 _M_p = 0x804a014 "abcd"
10376 With a pretty-printer for @code{std::string} only the contents are printed:
10379 (@value{GDBP}) print s
10383 @node Pretty-Printer Commands
10384 @subsection Pretty-Printer Commands
10385 @cindex pretty-printer commands
10388 @kindex info pretty-printer
10389 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10390 Print the list of installed pretty-printers.
10391 This includes disabled pretty-printers, which are marked as such.
10393 @var{object-regexp} is a regular expression matching the objects
10394 whose pretty-printers to list.
10395 Objects can be @code{global}, the program space's file
10396 (@pxref{Progspaces In Python}),
10397 and the object files within that program space (@pxref{Objfiles In Python}).
10398 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10399 looks up a printer from these three objects.
10401 @var{name-regexp} is a regular expression matching the name of the printers
10404 @kindex disable pretty-printer
10405 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10406 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10407 A disabled pretty-printer is not forgotten, it may be enabled again later.
10409 @kindex enable pretty-printer
10410 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10411 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10416 Suppose we have three pretty-printers installed: one from library1.so
10417 named @code{foo} that prints objects of type @code{foo}, and
10418 another from library2.so named @code{bar} that prints two types of objects,
10419 @code{bar1} and @code{bar2}.
10422 (gdb) info pretty-printer
10429 (gdb) info pretty-printer library2
10434 (gdb) disable pretty-printer library1
10436 2 of 3 printers enabled
10437 (gdb) info pretty-printer
10444 (gdb) disable pretty-printer library2 bar:bar1
10446 1 of 3 printers enabled
10447 (gdb) info pretty-printer library2
10454 (gdb) disable pretty-printer library2 bar
10456 0 of 3 printers enabled
10457 (gdb) info pretty-printer library2
10466 Note that for @code{bar} the entire printer can be disabled,
10467 as can each individual subprinter.
10469 @node Value History
10470 @section Value History
10472 @cindex value history
10473 @cindex history of values printed by @value{GDBN}
10474 Values printed by the @code{print} command are saved in the @value{GDBN}
10475 @dfn{value history}. This allows you to refer to them in other expressions.
10476 Values are kept until the symbol table is re-read or discarded
10477 (for example with the @code{file} or @code{symbol-file} commands).
10478 When the symbol table changes, the value history is discarded,
10479 since the values may contain pointers back to the types defined in the
10484 @cindex history number
10485 The values printed are given @dfn{history numbers} by which you can
10486 refer to them. These are successive integers starting with one.
10487 @code{print} shows you the history number assigned to a value by
10488 printing @samp{$@var{num} = } before the value; here @var{num} is the
10491 To refer to any previous value, use @samp{$} followed by the value's
10492 history number. The way @code{print} labels its output is designed to
10493 remind you of this. Just @code{$} refers to the most recent value in
10494 the history, and @code{$$} refers to the value before that.
10495 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10496 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10497 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10499 For example, suppose you have just printed a pointer to a structure and
10500 want to see the contents of the structure. It suffices to type
10506 If you have a chain of structures where the component @code{next} points
10507 to the next one, you can print the contents of the next one with this:
10514 You can print successive links in the chain by repeating this
10515 command---which you can do by just typing @key{RET}.
10517 Note that the history records values, not expressions. If the value of
10518 @code{x} is 4 and you type these commands:
10526 then the value recorded in the value history by the @code{print} command
10527 remains 4 even though the value of @code{x} has changed.
10530 @kindex show values
10532 Print the last ten values in the value history, with their item numbers.
10533 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10534 values} does not change the history.
10536 @item show values @var{n}
10537 Print ten history values centered on history item number @var{n}.
10539 @item show values +
10540 Print ten history values just after the values last printed. If no more
10541 values are available, @code{show values +} produces no display.
10544 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10545 same effect as @samp{show values +}.
10547 @node Convenience Vars
10548 @section Convenience Variables
10550 @cindex convenience variables
10551 @cindex user-defined variables
10552 @value{GDBN} provides @dfn{convenience variables} that you can use within
10553 @value{GDBN} to hold on to a value and refer to it later. These variables
10554 exist entirely within @value{GDBN}; they are not part of your program, and
10555 setting a convenience variable has no direct effect on further execution
10556 of your program. That is why you can use them freely.
10558 Convenience variables are prefixed with @samp{$}. Any name preceded by
10559 @samp{$} can be used for a convenience variable, unless it is one of
10560 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10561 (Value history references, in contrast, are @emph{numbers} preceded
10562 by @samp{$}. @xref{Value History, ,Value History}.)
10564 You can save a value in a convenience variable with an assignment
10565 expression, just as you would set a variable in your program.
10569 set $foo = *object_ptr
10573 would save in @code{$foo} the value contained in the object pointed to by
10576 Using a convenience variable for the first time creates it, but its
10577 value is @code{void} until you assign a new value. You can alter the
10578 value with another assignment at any time.
10580 Convenience variables have no fixed types. You can assign a convenience
10581 variable any type of value, including structures and arrays, even if
10582 that variable already has a value of a different type. The convenience
10583 variable, when used as an expression, has the type of its current value.
10586 @kindex show convenience
10587 @cindex show all user variables and functions
10588 @item show convenience
10589 Print a list of convenience variables used so far, and their values,
10590 as well as a list of the convenience functions.
10591 Abbreviated @code{show conv}.
10593 @kindex init-if-undefined
10594 @cindex convenience variables, initializing
10595 @item init-if-undefined $@var{variable} = @var{expression}
10596 Set a convenience variable if it has not already been set. This is useful
10597 for user-defined commands that keep some state. It is similar, in concept,
10598 to using local static variables with initializers in C (except that
10599 convenience variables are global). It can also be used to allow users to
10600 override default values used in a command script.
10602 If the variable is already defined then the expression is not evaluated so
10603 any side-effects do not occur.
10606 One of the ways to use a convenience variable is as a counter to be
10607 incremented or a pointer to be advanced. For example, to print
10608 a field from successive elements of an array of structures:
10612 print bar[$i++]->contents
10616 Repeat that command by typing @key{RET}.
10618 Some convenience variables are created automatically by @value{GDBN} and given
10619 values likely to be useful.
10622 @vindex $_@r{, convenience variable}
10624 The variable @code{$_} is automatically set by the @code{x} command to
10625 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10626 commands which provide a default address for @code{x} to examine also
10627 set @code{$_} to that address; these commands include @code{info line}
10628 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10629 except when set by the @code{x} command, in which case it is a pointer
10630 to the type of @code{$__}.
10632 @vindex $__@r{, convenience variable}
10634 The variable @code{$__} is automatically set by the @code{x} command
10635 to the value found in the last address examined. Its type is chosen
10636 to match the format in which the data was printed.
10639 @vindex $_exitcode@r{, convenience variable}
10640 When the program being debugged terminates normally, @value{GDBN}
10641 automatically sets this variable to the exit code of the program, and
10642 resets @code{$_exitsignal} to @code{void}.
10645 @vindex $_exitsignal@r{, convenience variable}
10646 When the program being debugged dies due to an uncaught signal,
10647 @value{GDBN} automatically sets this variable to that signal's number,
10648 and resets @code{$_exitcode} to @code{void}.
10650 To distinguish between whether the program being debugged has exited
10651 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10652 @code{$_exitsignal} is not @code{void}), the convenience function
10653 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10654 Functions}). For example, considering the following source code:
10657 #include <signal.h>
10660 main (int argc, char *argv[])
10667 A valid way of telling whether the program being debugged has exited
10668 or signalled would be:
10671 (@value{GDBP}) define has_exited_or_signalled
10672 Type commands for definition of ``has_exited_or_signalled''.
10673 End with a line saying just ``end''.
10674 >if $_isvoid ($_exitsignal)
10675 >echo The program has exited\n
10677 >echo The program has signalled\n
10683 Program terminated with signal SIGALRM, Alarm clock.
10684 The program no longer exists.
10685 (@value{GDBP}) has_exited_or_signalled
10686 The program has signalled
10689 As can be seen, @value{GDBN} correctly informs that the program being
10690 debugged has signalled, since it calls @code{raise} and raises a
10691 @code{SIGALRM} signal. If the program being debugged had not called
10692 @code{raise}, then @value{GDBN} would report a normal exit:
10695 (@value{GDBP}) has_exited_or_signalled
10696 The program has exited
10700 The variable @code{$_exception} is set to the exception object being
10701 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10704 @itemx $_probe_arg0@dots{}$_probe_arg11
10705 Arguments to a static probe. @xref{Static Probe Points}.
10708 @vindex $_sdata@r{, inspect, convenience variable}
10709 The variable @code{$_sdata} contains extra collected static tracepoint
10710 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10711 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10712 if extra static tracepoint data has not been collected.
10715 @vindex $_siginfo@r{, convenience variable}
10716 The variable @code{$_siginfo} contains extra signal information
10717 (@pxref{extra signal information}). Note that @code{$_siginfo}
10718 could be empty, if the application has not yet received any signals.
10719 For example, it will be empty before you execute the @code{run} command.
10722 @vindex $_tlb@r{, convenience variable}
10723 The variable @code{$_tlb} is automatically set when debugging
10724 applications running on MS-Windows in native mode or connected to
10725 gdbserver that supports the @code{qGetTIBAddr} request.
10726 @xref{General Query Packets}.
10727 This variable contains the address of the thread information block.
10730 The number of the current inferior. @xref{Inferiors and
10731 Programs, ,Debugging Multiple Inferiors and Programs}.
10734 The thread number of the current thread. @xref{thread numbers}.
10737 The global number of the current thread. @xref{global thread numbers}.
10741 @node Convenience Funs
10742 @section Convenience Functions
10744 @cindex convenience functions
10745 @value{GDBN} also supplies some @dfn{convenience functions}. These
10746 have a syntax similar to convenience variables. A convenience
10747 function can be used in an expression just like an ordinary function;
10748 however, a convenience function is implemented internally to
10751 These functions do not require @value{GDBN} to be configured with
10752 @code{Python} support, which means that they are always available.
10756 @item $_isvoid (@var{expr})
10757 @findex $_isvoid@r{, convenience function}
10758 Return one if the expression @var{expr} is @code{void}. Otherwise it
10761 A @code{void} expression is an expression where the type of the result
10762 is @code{void}. For example, you can examine a convenience variable
10763 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10767 (@value{GDBP}) print $_exitcode
10769 (@value{GDBP}) print $_isvoid ($_exitcode)
10772 Starting program: ./a.out
10773 [Inferior 1 (process 29572) exited normally]
10774 (@value{GDBP}) print $_exitcode
10776 (@value{GDBP}) print $_isvoid ($_exitcode)
10780 In the example above, we used @code{$_isvoid} to check whether
10781 @code{$_exitcode} is @code{void} before and after the execution of the
10782 program being debugged. Before the execution there is no exit code to
10783 be examined, therefore @code{$_exitcode} is @code{void}. After the
10784 execution the program being debugged returned zero, therefore
10785 @code{$_exitcode} is zero, which means that it is not @code{void}
10788 The @code{void} expression can also be a call of a function from the
10789 program being debugged. For example, given the following function:
10798 The result of calling it inside @value{GDBN} is @code{void}:
10801 (@value{GDBP}) print foo ()
10803 (@value{GDBP}) print $_isvoid (foo ())
10805 (@value{GDBP}) set $v = foo ()
10806 (@value{GDBP}) print $v
10808 (@value{GDBP}) print $_isvoid ($v)
10814 These functions require @value{GDBN} to be configured with
10815 @code{Python} support.
10819 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10820 @findex $_memeq@r{, convenience function}
10821 Returns one if the @var{length} bytes at the addresses given by
10822 @var{buf1} and @var{buf2} are equal.
10823 Otherwise it returns zero.
10825 @item $_regex(@var{str}, @var{regex})
10826 @findex $_regex@r{, convenience function}
10827 Returns one if the string @var{str} matches the regular expression
10828 @var{regex}. Otherwise it returns zero.
10829 The syntax of the regular expression is that specified by @code{Python}'s
10830 regular expression support.
10832 @item $_streq(@var{str1}, @var{str2})
10833 @findex $_streq@r{, convenience function}
10834 Returns one if the strings @var{str1} and @var{str2} are equal.
10835 Otherwise it returns zero.
10837 @item $_strlen(@var{str})
10838 @findex $_strlen@r{, convenience function}
10839 Returns the length of string @var{str}.
10841 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10842 @findex $_caller_is@r{, convenience function}
10843 Returns one if the calling function's name is equal to @var{name}.
10844 Otherwise it returns zero.
10846 If the optional argument @var{number_of_frames} is provided,
10847 it is the number of frames up in the stack to look.
10855 at testsuite/gdb.python/py-caller-is.c:21
10856 #1 0x00000000004005a0 in middle_func ()
10857 at testsuite/gdb.python/py-caller-is.c:27
10858 #2 0x00000000004005ab in top_func ()
10859 at testsuite/gdb.python/py-caller-is.c:33
10860 #3 0x00000000004005b6 in main ()
10861 at testsuite/gdb.python/py-caller-is.c:39
10862 (gdb) print $_caller_is ("middle_func")
10864 (gdb) print $_caller_is ("top_func", 2)
10868 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10869 @findex $_caller_matches@r{, convenience function}
10870 Returns one if the calling function's name matches the regular expression
10871 @var{regexp}. Otherwise it returns zero.
10873 If the optional argument @var{number_of_frames} is provided,
10874 it is the number of frames up in the stack to look.
10877 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10878 @findex $_any_caller_is@r{, convenience function}
10879 Returns one if any calling function's name is equal to @var{name}.
10880 Otherwise it returns zero.
10882 If the optional argument @var{number_of_frames} is provided,
10883 it is the number of frames up in the stack to look.
10886 This function differs from @code{$_caller_is} in that this function
10887 checks all stack frames from the immediate caller to the frame specified
10888 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10889 frame specified by @var{number_of_frames}.
10891 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10892 @findex $_any_caller_matches@r{, convenience function}
10893 Returns one if any calling function's name matches the regular expression
10894 @var{regexp}. Otherwise it returns zero.
10896 If the optional argument @var{number_of_frames} is provided,
10897 it is the number of frames up in the stack to look.
10900 This function differs from @code{$_caller_matches} in that this function
10901 checks all stack frames from the immediate caller to the frame specified
10902 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10903 frame specified by @var{number_of_frames}.
10905 @item $_as_string(@var{value})
10906 @findex $_as_string@r{, convenience function}
10907 Return the string representation of @var{value}.
10909 This function is useful to obtain the textual label (enumerator) of an
10910 enumeration value. For example, assuming the variable @var{node} is of
10911 an enumerated type:
10914 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10915 Visiting node of type NODE_INTEGER
10920 @value{GDBN} provides the ability to list and get help on
10921 convenience functions.
10924 @item help function
10925 @kindex help function
10926 @cindex show all convenience functions
10927 Print a list of all convenience functions.
10934 You can refer to machine register contents, in expressions, as variables
10935 with names starting with @samp{$}. The names of registers are different
10936 for each machine; use @code{info registers} to see the names used on
10940 @kindex info registers
10941 @item info registers
10942 Print the names and values of all registers except floating-point
10943 and vector registers (in the selected stack frame).
10945 @kindex info all-registers
10946 @cindex floating point registers
10947 @item info all-registers
10948 Print the names and values of all registers, including floating-point
10949 and vector registers (in the selected stack frame).
10951 @item info registers @var{regname} @dots{}
10952 Print the @dfn{relativized} value of each specified register @var{regname}.
10953 As discussed in detail below, register values are normally relative to
10954 the selected stack frame. The @var{regname} may be any register name valid on
10955 the machine you are using, with or without the initial @samp{$}.
10958 @anchor{standard registers}
10959 @cindex stack pointer register
10960 @cindex program counter register
10961 @cindex process status register
10962 @cindex frame pointer register
10963 @cindex standard registers
10964 @value{GDBN} has four ``standard'' register names that are available (in
10965 expressions) on most machines---whenever they do not conflict with an
10966 architecture's canonical mnemonics for registers. The register names
10967 @code{$pc} and @code{$sp} are used for the program counter register and
10968 the stack pointer. @code{$fp} is used for a register that contains a
10969 pointer to the current stack frame, and @code{$ps} is used for a
10970 register that contains the processor status. For example,
10971 you could print the program counter in hex with
10978 or print the instruction to be executed next with
10985 or add four to the stack pointer@footnote{This is a way of removing
10986 one word from the stack, on machines where stacks grow downward in
10987 memory (most machines, nowadays). This assumes that the innermost
10988 stack frame is selected; setting @code{$sp} is not allowed when other
10989 stack frames are selected. To pop entire frames off the stack,
10990 regardless of machine architecture, use @code{return};
10991 see @ref{Returning, ,Returning from a Function}.} with
10997 Whenever possible, these four standard register names are available on
10998 your machine even though the machine has different canonical mnemonics,
10999 so long as there is no conflict. The @code{info registers} command
11000 shows the canonical names. For example, on the SPARC, @code{info
11001 registers} displays the processor status register as @code{$psr} but you
11002 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11003 is an alias for the @sc{eflags} register.
11005 @value{GDBN} always considers the contents of an ordinary register as an
11006 integer when the register is examined in this way. Some machines have
11007 special registers which can hold nothing but floating point; these
11008 registers are considered to have floating point values. There is no way
11009 to refer to the contents of an ordinary register as floating point value
11010 (although you can @emph{print} it as a floating point value with
11011 @samp{print/f $@var{regname}}).
11013 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11014 means that the data format in which the register contents are saved by
11015 the operating system is not the same one that your program normally
11016 sees. For example, the registers of the 68881 floating point
11017 coprocessor are always saved in ``extended'' (raw) format, but all C
11018 programs expect to work with ``double'' (virtual) format. In such
11019 cases, @value{GDBN} normally works with the virtual format only (the format
11020 that makes sense for your program), but the @code{info registers} command
11021 prints the data in both formats.
11023 @cindex SSE registers (x86)
11024 @cindex MMX registers (x86)
11025 Some machines have special registers whose contents can be interpreted
11026 in several different ways. For example, modern x86-based machines
11027 have SSE and MMX registers that can hold several values packed
11028 together in several different formats. @value{GDBN} refers to such
11029 registers in @code{struct} notation:
11032 (@value{GDBP}) print $xmm1
11034 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11035 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11036 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11037 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11038 v4_int32 = @{0, 20657912, 11, 13@},
11039 v2_int64 = @{88725056443645952, 55834574859@},
11040 uint128 = 0x0000000d0000000b013b36f800000000
11045 To set values of such registers, you need to tell @value{GDBN} which
11046 view of the register you wish to change, as if you were assigning
11047 value to a @code{struct} member:
11050 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11053 Normally, register values are relative to the selected stack frame
11054 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11055 value that the register would contain if all stack frames farther in
11056 were exited and their saved registers restored. In order to see the
11057 true contents of hardware registers, you must select the innermost
11058 frame (with @samp{frame 0}).
11060 @cindex caller-saved registers
11061 @cindex call-clobbered registers
11062 @cindex volatile registers
11063 @cindex <not saved> values
11064 Usually ABIs reserve some registers as not needed to be saved by the
11065 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11066 registers). It may therefore not be possible for @value{GDBN} to know
11067 the value a register had before the call (in other words, in the outer
11068 frame), if the register value has since been changed by the callee.
11069 @value{GDBN} tries to deduce where the inner frame saved
11070 (``callee-saved'') registers, from the debug info, unwind info, or the
11071 machine code generated by your compiler. If some register is not
11072 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11073 its own knowledge of the ABI, or because the debug/unwind info
11074 explicitly says the register's value is undefined), @value{GDBN}
11075 displays @w{@samp{<not saved>}} as the register's value. With targets
11076 that @value{GDBN} has no knowledge of the register saving convention,
11077 if a register was not saved by the callee, then its value and location
11078 in the outer frame are assumed to be the same of the inner frame.
11079 This is usually harmless, because if the register is call-clobbered,
11080 the caller either does not care what is in the register after the
11081 call, or has code to restore the value that it does care about. Note,
11082 however, that if you change such a register in the outer frame, you
11083 may also be affecting the inner frame. Also, the more ``outer'' the
11084 frame is you're looking at, the more likely a call-clobbered
11085 register's value is to be wrong, in the sense that it doesn't actually
11086 represent the value the register had just before the call.
11088 @node Floating Point Hardware
11089 @section Floating Point Hardware
11090 @cindex floating point
11092 Depending on the configuration, @value{GDBN} may be able to give
11093 you more information about the status of the floating point hardware.
11098 Display hardware-dependent information about the floating
11099 point unit. The exact contents and layout vary depending on the
11100 floating point chip. Currently, @samp{info float} is supported on
11101 the ARM and x86 machines.
11105 @section Vector Unit
11106 @cindex vector unit
11108 Depending on the configuration, @value{GDBN} may be able to give you
11109 more information about the status of the vector unit.
11112 @kindex info vector
11114 Display information about the vector unit. The exact contents and
11115 layout vary depending on the hardware.
11118 @node OS Information
11119 @section Operating System Auxiliary Information
11120 @cindex OS information
11122 @value{GDBN} provides interfaces to useful OS facilities that can help
11123 you debug your program.
11125 @cindex auxiliary vector
11126 @cindex vector, auxiliary
11127 Some operating systems supply an @dfn{auxiliary vector} to programs at
11128 startup. This is akin to the arguments and environment that you
11129 specify for a program, but contains a system-dependent variety of
11130 binary values that tell system libraries important details about the
11131 hardware, operating system, and process. Each value's purpose is
11132 identified by an integer tag; the meanings are well-known but system-specific.
11133 Depending on the configuration and operating system facilities,
11134 @value{GDBN} may be able to show you this information. For remote
11135 targets, this functionality may further depend on the remote stub's
11136 support of the @samp{qXfer:auxv:read} packet, see
11137 @ref{qXfer auxiliary vector read}.
11142 Display the auxiliary vector of the inferior, which can be either a
11143 live process or a core dump file. @value{GDBN} prints each tag value
11144 numerically, and also shows names and text descriptions for recognized
11145 tags. Some values in the vector are numbers, some bit masks, and some
11146 pointers to strings or other data. @value{GDBN} displays each value in the
11147 most appropriate form for a recognized tag, and in hexadecimal for
11148 an unrecognized tag.
11151 On some targets, @value{GDBN} can access operating system-specific
11152 information and show it to you. The types of information available
11153 will differ depending on the type of operating system running on the
11154 target. The mechanism used to fetch the data is described in
11155 @ref{Operating System Information}. For remote targets, this
11156 functionality depends on the remote stub's support of the
11157 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11161 @item info os @var{infotype}
11163 Display OS information of the requested type.
11165 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11167 @anchor{linux info os infotypes}
11169 @kindex info os cpus
11171 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11172 the available fields from /proc/cpuinfo. For each supported architecture
11173 different fields are available. Two common entries are processor which gives
11174 CPU number and bogomips; a system constant that is calculated during
11175 kernel initialization.
11177 @kindex info os files
11179 Display the list of open file descriptors on the target. For each
11180 file descriptor, @value{GDBN} prints the identifier of the process
11181 owning the descriptor, the command of the owning process, the value
11182 of the descriptor, and the target of the descriptor.
11184 @kindex info os modules
11186 Display the list of all loaded kernel modules on the target. For each
11187 module, @value{GDBN} prints the module name, the size of the module in
11188 bytes, the number of times the module is used, the dependencies of the
11189 module, the status of the module, and the address of the loaded module
11192 @kindex info os msg
11194 Display the list of all System V message queues on the target. For each
11195 message queue, @value{GDBN} prints the message queue key, the message
11196 queue identifier, the access permissions, the current number of bytes
11197 on the queue, the current number of messages on the queue, the processes
11198 that last sent and received a message on the queue, the user and group
11199 of the owner and creator of the message queue, the times at which a
11200 message was last sent and received on the queue, and the time at which
11201 the message queue was last changed.
11203 @kindex info os processes
11205 Display the list of processes on the target. For each process,
11206 @value{GDBN} prints the process identifier, the name of the user, the
11207 command corresponding to the process, and the list of processor cores
11208 that the process is currently running on. (To understand what these
11209 properties mean, for this and the following info types, please consult
11210 the general @sc{gnu}/Linux documentation.)
11212 @kindex info os procgroups
11214 Display the list of process groups on the target. For each process,
11215 @value{GDBN} prints the identifier of the process group that it belongs
11216 to, the command corresponding to the process group leader, the process
11217 identifier, and the command line of the process. The list is sorted
11218 first by the process group identifier, then by the process identifier,
11219 so that processes belonging to the same process group are grouped together
11220 and the process group leader is listed first.
11222 @kindex info os semaphores
11224 Display the list of all System V semaphore sets on the target. For each
11225 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11226 set identifier, the access permissions, the number of semaphores in the
11227 set, the user and group of the owner and creator of the semaphore set,
11228 and the times at which the semaphore set was operated upon and changed.
11230 @kindex info os shm
11232 Display the list of all System V shared-memory regions on the target.
11233 For each shared-memory region, @value{GDBN} prints the region key,
11234 the shared-memory identifier, the access permissions, the size of the
11235 region, the process that created the region, the process that last
11236 attached to or detached from the region, the current number of live
11237 attaches to the region, and the times at which the region was last
11238 attached to, detach from, and changed.
11240 @kindex info os sockets
11242 Display the list of Internet-domain sockets on the target. For each
11243 socket, @value{GDBN} prints the address and port of the local and
11244 remote endpoints, the current state of the connection, the creator of
11245 the socket, the IP address family of the socket, and the type of the
11248 @kindex info os threads
11250 Display the list of threads running on the target. For each thread,
11251 @value{GDBN} prints the identifier of the process that the thread
11252 belongs to, the command of the process, the thread identifier, and the
11253 processor core that it is currently running on. The main thread of a
11254 process is not listed.
11258 If @var{infotype} is omitted, then list the possible values for
11259 @var{infotype} and the kind of OS information available for each
11260 @var{infotype}. If the target does not return a list of possible
11261 types, this command will report an error.
11264 @node Memory Region Attributes
11265 @section Memory Region Attributes
11266 @cindex memory region attributes
11268 @dfn{Memory region attributes} allow you to describe special handling
11269 required by regions of your target's memory. @value{GDBN} uses
11270 attributes to determine whether to allow certain types of memory
11271 accesses; whether to use specific width accesses; and whether to cache
11272 target memory. By default the description of memory regions is
11273 fetched from the target (if the current target supports this), but the
11274 user can override the fetched regions.
11276 Defined memory regions can be individually enabled and disabled. When a
11277 memory region is disabled, @value{GDBN} uses the default attributes when
11278 accessing memory in that region. Similarly, if no memory regions have
11279 been defined, @value{GDBN} uses the default attributes when accessing
11282 When a memory region is defined, it is given a number to identify it;
11283 to enable, disable, or remove a memory region, you specify that number.
11287 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11288 Define a memory region bounded by @var{lower} and @var{upper} with
11289 attributes @var{attributes}@dots{}, and add it to the list of regions
11290 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11291 case: it is treated as the target's maximum memory address.
11292 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11295 Discard any user changes to the memory regions and use target-supplied
11296 regions, if available, or no regions if the target does not support.
11299 @item delete mem @var{nums}@dots{}
11300 Remove memory regions @var{nums}@dots{} from the list of regions
11301 monitored by @value{GDBN}.
11303 @kindex disable mem
11304 @item disable mem @var{nums}@dots{}
11305 Disable monitoring of memory regions @var{nums}@dots{}.
11306 A disabled memory region is not forgotten.
11307 It may be enabled again later.
11310 @item enable mem @var{nums}@dots{}
11311 Enable monitoring of memory regions @var{nums}@dots{}.
11315 Print a table of all defined memory regions, with the following columns
11319 @item Memory Region Number
11320 @item Enabled or Disabled.
11321 Enabled memory regions are marked with @samp{y}.
11322 Disabled memory regions are marked with @samp{n}.
11325 The address defining the inclusive lower bound of the memory region.
11328 The address defining the exclusive upper bound of the memory region.
11331 The list of attributes set for this memory region.
11336 @subsection Attributes
11338 @subsubsection Memory Access Mode
11339 The access mode attributes set whether @value{GDBN} may make read or
11340 write accesses to a memory region.
11342 While these attributes prevent @value{GDBN} from performing invalid
11343 memory accesses, they do nothing to prevent the target system, I/O DMA,
11344 etc.@: from accessing memory.
11348 Memory is read only.
11350 Memory is write only.
11352 Memory is read/write. This is the default.
11355 @subsubsection Memory Access Size
11356 The access size attribute tells @value{GDBN} to use specific sized
11357 accesses in the memory region. Often memory mapped device registers
11358 require specific sized accesses. If no access size attribute is
11359 specified, @value{GDBN} may use accesses of any size.
11363 Use 8 bit memory accesses.
11365 Use 16 bit memory accesses.
11367 Use 32 bit memory accesses.
11369 Use 64 bit memory accesses.
11372 @c @subsubsection Hardware/Software Breakpoints
11373 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11374 @c will use hardware or software breakpoints for the internal breakpoints
11375 @c used by the step, next, finish, until, etc. commands.
11379 @c Always use hardware breakpoints
11380 @c @item swbreak (default)
11383 @subsubsection Data Cache
11384 The data cache attributes set whether @value{GDBN} will cache target
11385 memory. While this generally improves performance by reducing debug
11386 protocol overhead, it can lead to incorrect results because @value{GDBN}
11387 does not know about volatile variables or memory mapped device
11392 Enable @value{GDBN} to cache target memory.
11394 Disable @value{GDBN} from caching target memory. This is the default.
11397 @subsection Memory Access Checking
11398 @value{GDBN} can be instructed to refuse accesses to memory that is
11399 not explicitly described. This can be useful if accessing such
11400 regions has undesired effects for a specific target, or to provide
11401 better error checking. The following commands control this behaviour.
11404 @kindex set mem inaccessible-by-default
11405 @item set mem inaccessible-by-default [on|off]
11406 If @code{on} is specified, make @value{GDBN} treat memory not
11407 explicitly described by the memory ranges as non-existent and refuse accesses
11408 to such memory. The checks are only performed if there's at least one
11409 memory range defined. If @code{off} is specified, make @value{GDBN}
11410 treat the memory not explicitly described by the memory ranges as RAM.
11411 The default value is @code{on}.
11412 @kindex show mem inaccessible-by-default
11413 @item show mem inaccessible-by-default
11414 Show the current handling of accesses to unknown memory.
11418 @c @subsubsection Memory Write Verification
11419 @c The memory write verification attributes set whether @value{GDBN}
11420 @c will re-reads data after each write to verify the write was successful.
11424 @c @item noverify (default)
11427 @node Dump/Restore Files
11428 @section Copy Between Memory and a File
11429 @cindex dump/restore files
11430 @cindex append data to a file
11431 @cindex dump data to a file
11432 @cindex restore data from a file
11434 You can use the commands @code{dump}, @code{append}, and
11435 @code{restore} to copy data between target memory and a file. The
11436 @code{dump} and @code{append} commands write data to a file, and the
11437 @code{restore} command reads data from a file back into the inferior's
11438 memory. Files may be in binary, Motorola S-record, Intel hex,
11439 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11440 append to binary files, and cannot read from Verilog Hex files.
11445 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11446 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11447 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11448 or the value of @var{expr}, to @var{filename} in the given format.
11450 The @var{format} parameter may be any one of:
11457 Motorola S-record format.
11459 Tektronix Hex format.
11461 Verilog Hex format.
11464 @value{GDBN} uses the same definitions of these formats as the
11465 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11466 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11470 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11471 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11472 Append the contents of memory from @var{start_addr} to @var{end_addr},
11473 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11474 (@value{GDBN} can only append data to files in raw binary form.)
11477 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11478 Restore the contents of file @var{filename} into memory. The
11479 @code{restore} command can automatically recognize any known @sc{bfd}
11480 file format, except for raw binary. To restore a raw binary file you
11481 must specify the optional keyword @code{binary} after the filename.
11483 If @var{bias} is non-zero, its value will be added to the addresses
11484 contained in the file. Binary files always start at address zero, so
11485 they will be restored at address @var{bias}. Other bfd files have
11486 a built-in location; they will be restored at offset @var{bias}
11487 from that location.
11489 If @var{start} and/or @var{end} are non-zero, then only data between
11490 file offset @var{start} and file offset @var{end} will be restored.
11491 These offsets are relative to the addresses in the file, before
11492 the @var{bias} argument is applied.
11496 @node Core File Generation
11497 @section How to Produce a Core File from Your Program
11498 @cindex dump core from inferior
11500 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11501 image of a running process and its process status (register values
11502 etc.). Its primary use is post-mortem debugging of a program that
11503 crashed while it ran outside a debugger. A program that crashes
11504 automatically produces a core file, unless this feature is disabled by
11505 the user. @xref{Files}, for information on invoking @value{GDBN} in
11506 the post-mortem debugging mode.
11508 Occasionally, you may wish to produce a core file of the program you
11509 are debugging in order to preserve a snapshot of its state.
11510 @value{GDBN} has a special command for that.
11514 @kindex generate-core-file
11515 @item generate-core-file [@var{file}]
11516 @itemx gcore [@var{file}]
11517 Produce a core dump of the inferior process. The optional argument
11518 @var{file} specifies the file name where to put the core dump. If not
11519 specified, the file name defaults to @file{core.@var{pid}}, where
11520 @var{pid} is the inferior process ID.
11522 Note that this command is implemented only for some systems (as of
11523 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11525 On @sc{gnu}/Linux, this command can take into account the value of the
11526 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11527 dump (@pxref{set use-coredump-filter}).
11529 @kindex set use-coredump-filter
11530 @anchor{set use-coredump-filter}
11531 @item set use-coredump-filter on
11532 @itemx set use-coredump-filter off
11533 Enable or disable the use of the file
11534 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11535 files. This file is used by the Linux kernel to decide what types of
11536 memory mappings will be dumped or ignored when generating a core dump
11537 file. @var{pid} is the process ID of a currently running process.
11539 To make use of this feature, you have to write in the
11540 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11541 which is a bit mask representing the memory mapping types. If a bit
11542 is set in the bit mask, then the memory mappings of the corresponding
11543 types will be dumped; otherwise, they will be ignored. This
11544 configuration is inherited by child processes. For more information
11545 about the bits that can be set in the
11546 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11547 manpage of @code{core(5)}.
11549 By default, this option is @code{on}. If this option is turned
11550 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11551 and instead uses the same default value as the Linux kernel in order
11552 to decide which pages will be dumped in the core dump file. This
11553 value is currently @code{0x33}, which means that bits @code{0}
11554 (anonymous private mappings), @code{1} (anonymous shared mappings),
11555 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11556 This will cause these memory mappings to be dumped automatically.
11559 @node Character Sets
11560 @section Character Sets
11561 @cindex character sets
11563 @cindex translating between character sets
11564 @cindex host character set
11565 @cindex target character set
11567 If the program you are debugging uses a different character set to
11568 represent characters and strings than the one @value{GDBN} uses itself,
11569 @value{GDBN} can automatically translate between the character sets for
11570 you. The character set @value{GDBN} uses we call the @dfn{host
11571 character set}; the one the inferior program uses we call the
11572 @dfn{target character set}.
11574 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11575 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11576 remote protocol (@pxref{Remote Debugging}) to debug a program
11577 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11578 then the host character set is Latin-1, and the target character set is
11579 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11580 target-charset EBCDIC-US}, then @value{GDBN} translates between
11581 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11582 character and string literals in expressions.
11584 @value{GDBN} has no way to automatically recognize which character set
11585 the inferior program uses; you must tell it, using the @code{set
11586 target-charset} command, described below.
11588 Here are the commands for controlling @value{GDBN}'s character set
11592 @item set target-charset @var{charset}
11593 @kindex set target-charset
11594 Set the current target character set to @var{charset}. To display the
11595 list of supported target character sets, type
11596 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11598 @item set host-charset @var{charset}
11599 @kindex set host-charset
11600 Set the current host character set to @var{charset}.
11602 By default, @value{GDBN} uses a host character set appropriate to the
11603 system it is running on; you can override that default using the
11604 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11605 automatically determine the appropriate host character set. In this
11606 case, @value{GDBN} uses @samp{UTF-8}.
11608 @value{GDBN} can only use certain character sets as its host character
11609 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11610 @value{GDBN} will list the host character sets it supports.
11612 @item set charset @var{charset}
11613 @kindex set charset
11614 Set the current host and target character sets to @var{charset}. As
11615 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11616 @value{GDBN} will list the names of the character sets that can be used
11617 for both host and target.
11620 @kindex show charset
11621 Show the names of the current host and target character sets.
11623 @item show host-charset
11624 @kindex show host-charset
11625 Show the name of the current host character set.
11627 @item show target-charset
11628 @kindex show target-charset
11629 Show the name of the current target character set.
11631 @item set target-wide-charset @var{charset}
11632 @kindex set target-wide-charset
11633 Set the current target's wide character set to @var{charset}. This is
11634 the character set used by the target's @code{wchar_t} type. To
11635 display the list of supported wide character sets, type
11636 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11638 @item show target-wide-charset
11639 @kindex show target-wide-charset
11640 Show the name of the current target's wide character set.
11643 Here is an example of @value{GDBN}'s character set support in action.
11644 Assume that the following source code has been placed in the file
11645 @file{charset-test.c}:
11651 = @{72, 101, 108, 108, 111, 44, 32, 119,
11652 111, 114, 108, 100, 33, 10, 0@};
11653 char ibm1047_hello[]
11654 = @{200, 133, 147, 147, 150, 107, 64, 166,
11655 150, 153, 147, 132, 90, 37, 0@};
11659 printf ("Hello, world!\n");
11663 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11664 containing the string @samp{Hello, world!} followed by a newline,
11665 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11667 We compile the program, and invoke the debugger on it:
11670 $ gcc -g charset-test.c -o charset-test
11671 $ gdb -nw charset-test
11672 GNU gdb 2001-12-19-cvs
11673 Copyright 2001 Free Software Foundation, Inc.
11678 We can use the @code{show charset} command to see what character sets
11679 @value{GDBN} is currently using to interpret and display characters and
11683 (@value{GDBP}) show charset
11684 The current host and target character set is `ISO-8859-1'.
11688 For the sake of printing this manual, let's use @sc{ascii} as our
11689 initial character set:
11691 (@value{GDBP}) set charset ASCII
11692 (@value{GDBP}) show charset
11693 The current host and target character set is `ASCII'.
11697 Let's assume that @sc{ascii} is indeed the correct character set for our
11698 host system --- in other words, let's assume that if @value{GDBN} prints
11699 characters using the @sc{ascii} character set, our terminal will display
11700 them properly. Since our current target character set is also
11701 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11704 (@value{GDBP}) print ascii_hello
11705 $1 = 0x401698 "Hello, world!\n"
11706 (@value{GDBP}) print ascii_hello[0]
11711 @value{GDBN} uses the target character set for character and string
11712 literals you use in expressions:
11715 (@value{GDBP}) print '+'
11720 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11723 @value{GDBN} relies on the user to tell it which character set the
11724 target program uses. If we print @code{ibm1047_hello} while our target
11725 character set is still @sc{ascii}, we get jibberish:
11728 (@value{GDBP}) print ibm1047_hello
11729 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11730 (@value{GDBP}) print ibm1047_hello[0]
11735 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11736 @value{GDBN} tells us the character sets it supports:
11739 (@value{GDBP}) set target-charset
11740 ASCII EBCDIC-US IBM1047 ISO-8859-1
11741 (@value{GDBP}) set target-charset
11744 We can select @sc{ibm1047} as our target character set, and examine the
11745 program's strings again. Now the @sc{ascii} string is wrong, but
11746 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11747 target character set, @sc{ibm1047}, to the host character set,
11748 @sc{ascii}, and they display correctly:
11751 (@value{GDBP}) set target-charset IBM1047
11752 (@value{GDBP}) show charset
11753 The current host character set is `ASCII'.
11754 The current target character set is `IBM1047'.
11755 (@value{GDBP}) print ascii_hello
11756 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11757 (@value{GDBP}) print ascii_hello[0]
11759 (@value{GDBP}) print ibm1047_hello
11760 $8 = 0x4016a8 "Hello, world!\n"
11761 (@value{GDBP}) print ibm1047_hello[0]
11766 As above, @value{GDBN} uses the target character set for character and
11767 string literals you use in expressions:
11770 (@value{GDBP}) print '+'
11775 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11778 @node Caching Target Data
11779 @section Caching Data of Targets
11780 @cindex caching data of targets
11782 @value{GDBN} caches data exchanged between the debugger and a target.
11783 Each cache is associated with the address space of the inferior.
11784 @xref{Inferiors and Programs}, about inferior and address space.
11785 Such caching generally improves performance in remote debugging
11786 (@pxref{Remote Debugging}), because it reduces the overhead of the
11787 remote protocol by bundling memory reads and writes into large chunks.
11788 Unfortunately, simply caching everything would lead to incorrect results,
11789 since @value{GDBN} does not necessarily know anything about volatile
11790 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11791 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11793 Therefore, by default, @value{GDBN} only caches data
11794 known to be on the stack@footnote{In non-stop mode, it is moderately
11795 rare for a running thread to modify the stack of a stopped thread
11796 in a way that would interfere with a backtrace, and caching of
11797 stack reads provides a significant speed up of remote backtraces.} or
11798 in the code segment.
11799 Other regions of memory can be explicitly marked as
11800 cacheable; @pxref{Memory Region Attributes}.
11803 @kindex set remotecache
11804 @item set remotecache on
11805 @itemx set remotecache off
11806 This option no longer does anything; it exists for compatibility
11809 @kindex show remotecache
11810 @item show remotecache
11811 Show the current state of the obsolete remotecache flag.
11813 @kindex set stack-cache
11814 @item set stack-cache on
11815 @itemx set stack-cache off
11816 Enable or disable caching of stack accesses. When @code{on}, use
11817 caching. By default, this option is @code{on}.
11819 @kindex show stack-cache
11820 @item show stack-cache
11821 Show the current state of data caching for memory accesses.
11823 @kindex set code-cache
11824 @item set code-cache on
11825 @itemx set code-cache off
11826 Enable or disable caching of code segment accesses. When @code{on},
11827 use caching. By default, this option is @code{on}. This improves
11828 performance of disassembly in remote debugging.
11830 @kindex show code-cache
11831 @item show code-cache
11832 Show the current state of target memory cache for code segment
11835 @kindex info dcache
11836 @item info dcache @r{[}line@r{]}
11837 Print the information about the performance of data cache of the
11838 current inferior's address space. The information displayed
11839 includes the dcache width and depth, and for each cache line, its
11840 number, address, and how many times it was referenced. This
11841 command is useful for debugging the data cache operation.
11843 If a line number is specified, the contents of that line will be
11846 @item set dcache size @var{size}
11847 @cindex dcache size
11848 @kindex set dcache size
11849 Set maximum number of entries in dcache (dcache depth above).
11851 @item set dcache line-size @var{line-size}
11852 @cindex dcache line-size
11853 @kindex set dcache line-size
11854 Set number of bytes each dcache entry caches (dcache width above).
11855 Must be a power of 2.
11857 @item show dcache size
11858 @kindex show dcache size
11859 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11861 @item show dcache line-size
11862 @kindex show dcache line-size
11863 Show default size of dcache lines.
11867 @node Searching Memory
11868 @section Search Memory
11869 @cindex searching memory
11871 Memory can be searched for a particular sequence of bytes with the
11872 @code{find} command.
11876 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11877 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11878 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11879 etc. The search begins at address @var{start_addr} and continues for either
11880 @var{len} bytes or through to @var{end_addr} inclusive.
11883 @var{s} and @var{n} are optional parameters.
11884 They may be specified in either order, apart or together.
11887 @item @var{s}, search query size
11888 The size of each search query value.
11894 halfwords (two bytes)
11898 giant words (eight bytes)
11901 All values are interpreted in the current language.
11902 This means, for example, that if the current source language is C/C@t{++}
11903 then searching for the string ``hello'' includes the trailing '\0'.
11905 If the value size is not specified, it is taken from the
11906 value's type in the current language.
11907 This is useful when one wants to specify the search
11908 pattern as a mixture of types.
11909 Note that this means, for example, that in the case of C-like languages
11910 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11911 which is typically four bytes.
11913 @item @var{n}, maximum number of finds
11914 The maximum number of matches to print. The default is to print all finds.
11917 You can use strings as search values. Quote them with double-quotes
11919 The string value is copied into the search pattern byte by byte,
11920 regardless of the endianness of the target and the size specification.
11922 The address of each match found is printed as well as a count of the
11923 number of matches found.
11925 The address of the last value found is stored in convenience variable
11927 A count of the number of matches is stored in @samp{$numfound}.
11929 For example, if stopped at the @code{printf} in this function:
11935 static char hello[] = "hello-hello";
11936 static struct @{ char c; short s; int i; @}
11937 __attribute__ ((packed)) mixed
11938 = @{ 'c', 0x1234, 0x87654321 @};
11939 printf ("%s\n", hello);
11944 you get during debugging:
11947 (gdb) find &hello[0], +sizeof(hello), "hello"
11948 0x804956d <hello.1620+6>
11950 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11951 0x8049567 <hello.1620>
11952 0x804956d <hello.1620+6>
11954 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11955 0x8049567 <hello.1620>
11957 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11958 0x8049560 <mixed.1625>
11960 (gdb) print $numfound
11963 $2 = (void *) 0x8049560
11967 @section Value Sizes
11969 Whenever @value{GDBN} prints a value memory will be allocated within
11970 @value{GDBN} to hold the contents of the value. It is possible in
11971 some languages with dynamic typing systems, that an invalid program
11972 may indicate a value that is incorrectly large, this in turn may cause
11973 @value{GDBN} to try and allocate an overly large ammount of memory.
11976 @kindex set max-value-size
11977 @item set max-value-size @var{bytes}
11978 @itemx set max-value-size unlimited
11979 Set the maximum size of memory that @value{GDBN} will allocate for the
11980 contents of a value to @var{bytes}, trying to display a value that
11981 requires more memory than that will result in an error.
11983 Setting this variable does not effect values that have already been
11984 allocated within @value{GDBN}, only future allocations.
11986 There's a minimum size that @code{max-value-size} can be set to in
11987 order that @value{GDBN} can still operate correctly, this minimum is
11988 currently 16 bytes.
11990 The limit applies to the results of some subexpressions as well as to
11991 complete expressions. For example, an expression denoting a simple
11992 integer component, such as @code{x.y.z}, may fail if the size of
11993 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11994 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11995 @var{A} is an array variable with non-constant size, will generally
11996 succeed regardless of the bounds on @var{A}, as long as the component
11997 size is less than @var{bytes}.
11999 The default value of @code{max-value-size} is currently 64k.
12001 @kindex show max-value-size
12002 @item show max-value-size
12003 Show the maximum size of memory, in bytes, that @value{GDBN} will
12004 allocate for the contents of a value.
12007 @node Optimized Code
12008 @chapter Debugging Optimized Code
12009 @cindex optimized code, debugging
12010 @cindex debugging optimized code
12012 Almost all compilers support optimization. With optimization
12013 disabled, the compiler generates assembly code that corresponds
12014 directly to your source code, in a simplistic way. As the compiler
12015 applies more powerful optimizations, the generated assembly code
12016 diverges from your original source code. With help from debugging
12017 information generated by the compiler, @value{GDBN} can map from
12018 the running program back to constructs from your original source.
12020 @value{GDBN} is more accurate with optimization disabled. If you
12021 can recompile without optimization, it is easier to follow the
12022 progress of your program during debugging. But, there are many cases
12023 where you may need to debug an optimized version.
12025 When you debug a program compiled with @samp{-g -O}, remember that the
12026 optimizer has rearranged your code; the debugger shows you what is
12027 really there. Do not be too surprised when the execution path does not
12028 exactly match your source file! An extreme example: if you define a
12029 variable, but never use it, @value{GDBN} never sees that
12030 variable---because the compiler optimizes it out of existence.
12032 Some things do not work as well with @samp{-g -O} as with just
12033 @samp{-g}, particularly on machines with instruction scheduling. If in
12034 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12035 please report it to us as a bug (including a test case!).
12036 @xref{Variables}, for more information about debugging optimized code.
12039 * Inline Functions:: How @value{GDBN} presents inlining
12040 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12043 @node Inline Functions
12044 @section Inline Functions
12045 @cindex inline functions, debugging
12047 @dfn{Inlining} is an optimization that inserts a copy of the function
12048 body directly at each call site, instead of jumping to a shared
12049 routine. @value{GDBN} displays inlined functions just like
12050 non-inlined functions. They appear in backtraces. You can view their
12051 arguments and local variables, step into them with @code{step}, skip
12052 them with @code{next}, and escape from them with @code{finish}.
12053 You can check whether a function was inlined by using the
12054 @code{info frame} command.
12056 For @value{GDBN} to support inlined functions, the compiler must
12057 record information about inlining in the debug information ---
12058 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12059 other compilers do also. @value{GDBN} only supports inlined functions
12060 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12061 do not emit two required attributes (@samp{DW_AT_call_file} and
12062 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12063 function calls with earlier versions of @value{NGCC}. It instead
12064 displays the arguments and local variables of inlined functions as
12065 local variables in the caller.
12067 The body of an inlined function is directly included at its call site;
12068 unlike a non-inlined function, there are no instructions devoted to
12069 the call. @value{GDBN} still pretends that the call site and the
12070 start of the inlined function are different instructions. Stepping to
12071 the call site shows the call site, and then stepping again shows
12072 the first line of the inlined function, even though no additional
12073 instructions are executed.
12075 This makes source-level debugging much clearer; you can see both the
12076 context of the call and then the effect of the call. Only stepping by
12077 a single instruction using @code{stepi} or @code{nexti} does not do
12078 this; single instruction steps always show the inlined body.
12080 There are some ways that @value{GDBN} does not pretend that inlined
12081 function calls are the same as normal calls:
12085 Setting breakpoints at the call site of an inlined function may not
12086 work, because the call site does not contain any code. @value{GDBN}
12087 may incorrectly move the breakpoint to the next line of the enclosing
12088 function, after the call. This limitation will be removed in a future
12089 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12090 or inside the inlined function instead.
12093 @value{GDBN} cannot locate the return value of inlined calls after
12094 using the @code{finish} command. This is a limitation of compiler-generated
12095 debugging information; after @code{finish}, you can step to the next line
12096 and print a variable where your program stored the return value.
12100 @node Tail Call Frames
12101 @section Tail Call Frames
12102 @cindex tail call frames, debugging
12104 Function @code{B} can call function @code{C} in its very last statement. In
12105 unoptimized compilation the call of @code{C} is immediately followed by return
12106 instruction at the end of @code{B} code. Optimizing compiler may replace the
12107 call and return in function @code{B} into one jump to function @code{C}
12108 instead. Such use of a jump instruction is called @dfn{tail call}.
12110 During execution of function @code{C}, there will be no indication in the
12111 function call stack frames that it was tail-called from @code{B}. If function
12112 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12113 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12114 some cases @value{GDBN} can determine that @code{C} was tail-called from
12115 @code{B}, and it will then create fictitious call frame for that, with the
12116 return address set up as if @code{B} called @code{C} normally.
12118 This functionality is currently supported only by DWARF 2 debugging format and
12119 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12120 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12123 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12124 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12128 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12130 Stack level 1, frame at 0x7fffffffda30:
12131 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12132 tail call frame, caller of frame at 0x7fffffffda30
12133 source language c++.
12134 Arglist at unknown address.
12135 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12138 The detection of all the possible code path executions can find them ambiguous.
12139 There is no execution history stored (possible @ref{Reverse Execution} is never
12140 used for this purpose) and the last known caller could have reached the known
12141 callee by multiple different jump sequences. In such case @value{GDBN} still
12142 tries to show at least all the unambiguous top tail callers and all the
12143 unambiguous bottom tail calees, if any.
12146 @anchor{set debug entry-values}
12147 @item set debug entry-values
12148 @kindex set debug entry-values
12149 When set to on, enables printing of analysis messages for both frame argument
12150 values at function entry and tail calls. It will show all the possible valid
12151 tail calls code paths it has considered. It will also print the intersection
12152 of them with the final unambiguous (possibly partial or even empty) code path
12155 @item show debug entry-values
12156 @kindex show debug entry-values
12157 Show the current state of analysis messages printing for both frame argument
12158 values at function entry and tail calls.
12161 The analysis messages for tail calls can for example show why the virtual tail
12162 call frame for function @code{c} has not been recognized (due to the indirect
12163 reference by variable @code{x}):
12166 static void __attribute__((noinline, noclone)) c (void);
12167 void (*x) (void) = c;
12168 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12169 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12170 int main (void) @{ x (); return 0; @}
12172 Breakpoint 1, DW_OP_entry_value resolving cannot find
12173 DW_TAG_call_site 0x40039a in main
12175 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12178 #1 0x000000000040039a in main () at t.c:5
12181 Another possibility is an ambiguous virtual tail call frames resolution:
12185 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12186 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12187 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12188 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12189 static void __attribute__((noinline, noclone)) b (void)
12190 @{ if (i) c (); else e (); @}
12191 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12192 int main (void) @{ a (); return 0; @}
12194 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12195 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12196 tailcall: reduced: 0x4004d2(a) |
12199 #1 0x00000000004004d2 in a () at t.c:8
12200 #2 0x0000000000400395 in main () at t.c:9
12203 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12204 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12206 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12207 @ifset HAVE_MAKEINFO_CLICK
12208 @set ARROW @click{}
12209 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12210 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12212 @ifclear HAVE_MAKEINFO_CLICK
12214 @set CALLSEQ1B @value{CALLSEQ1A}
12215 @set CALLSEQ2B @value{CALLSEQ2A}
12218 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12219 The code can have possible execution paths @value{CALLSEQ1B} or
12220 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12222 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12223 has found. It then finds another possible calling sequcen - that one is
12224 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12225 printed as the @code{reduced:} calling sequence. That one could have many
12226 futher @code{compare:} and @code{reduced:} statements as long as there remain
12227 any non-ambiguous sequence entries.
12229 For the frame of function @code{b} in both cases there are different possible
12230 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12231 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12232 therefore this one is displayed to the user while the ambiguous frames are
12235 There can be also reasons why printing of frame argument values at function
12240 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12241 static void __attribute__((noinline, noclone)) a (int i);
12242 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12243 static void __attribute__((noinline, noclone)) a (int i)
12244 @{ if (i) b (i - 1); else c (0); @}
12245 int main (void) @{ a (5); return 0; @}
12248 #0 c (i=i@@entry=0) at t.c:2
12249 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12250 function "a" at 0x400420 can call itself via tail calls
12251 i=<optimized out>) at t.c:6
12252 #2 0x000000000040036e in main () at t.c:7
12255 @value{GDBN} cannot find out from the inferior state if and how many times did
12256 function @code{a} call itself (via function @code{b}) as these calls would be
12257 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12258 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12259 prints @code{<optimized out>} instead.
12262 @chapter C Preprocessor Macros
12264 Some languages, such as C and C@t{++}, provide a way to define and invoke
12265 ``preprocessor macros'' which expand into strings of tokens.
12266 @value{GDBN} can evaluate expressions containing macro invocations, show
12267 the result of macro expansion, and show a macro's definition, including
12268 where it was defined.
12270 You may need to compile your program specially to provide @value{GDBN}
12271 with information about preprocessor macros. Most compilers do not
12272 include macros in their debugging information, even when you compile
12273 with the @option{-g} flag. @xref{Compilation}.
12275 A program may define a macro at one point, remove that definition later,
12276 and then provide a different definition after that. Thus, at different
12277 points in the program, a macro may have different definitions, or have
12278 no definition at all. If there is a current stack frame, @value{GDBN}
12279 uses the macros in scope at that frame's source code line. Otherwise,
12280 @value{GDBN} uses the macros in scope at the current listing location;
12283 Whenever @value{GDBN} evaluates an expression, it always expands any
12284 macro invocations present in the expression. @value{GDBN} also provides
12285 the following commands for working with macros explicitly.
12289 @kindex macro expand
12290 @cindex macro expansion, showing the results of preprocessor
12291 @cindex preprocessor macro expansion, showing the results of
12292 @cindex expanding preprocessor macros
12293 @item macro expand @var{expression}
12294 @itemx macro exp @var{expression}
12295 Show the results of expanding all preprocessor macro invocations in
12296 @var{expression}. Since @value{GDBN} simply expands macros, but does
12297 not parse the result, @var{expression} need not be a valid expression;
12298 it can be any string of tokens.
12301 @item macro expand-once @var{expression}
12302 @itemx macro exp1 @var{expression}
12303 @cindex expand macro once
12304 @i{(This command is not yet implemented.)} Show the results of
12305 expanding those preprocessor macro invocations that appear explicitly in
12306 @var{expression}. Macro invocations appearing in that expansion are
12307 left unchanged. This command allows you to see the effect of a
12308 particular macro more clearly, without being confused by further
12309 expansions. Since @value{GDBN} simply expands macros, but does not
12310 parse the result, @var{expression} need not be a valid expression; it
12311 can be any string of tokens.
12314 @cindex macro definition, showing
12315 @cindex definition of a macro, showing
12316 @cindex macros, from debug info
12317 @item info macro [-a|-all] [--] @var{macro}
12318 Show the current definition or all definitions of the named @var{macro},
12319 and describe the source location or compiler command-line where that
12320 definition was established. The optional double dash is to signify the end of
12321 argument processing and the beginning of @var{macro} for non C-like macros where
12322 the macro may begin with a hyphen.
12324 @kindex info macros
12325 @item info macros @var{location}
12326 Show all macro definitions that are in effect at the location specified
12327 by @var{location}, and describe the source location or compiler
12328 command-line where those definitions were established.
12330 @kindex macro define
12331 @cindex user-defined macros
12332 @cindex defining macros interactively
12333 @cindex macros, user-defined
12334 @item macro define @var{macro} @var{replacement-list}
12335 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12336 Introduce a definition for a preprocessor macro named @var{macro},
12337 invocations of which are replaced by the tokens given in
12338 @var{replacement-list}. The first form of this command defines an
12339 ``object-like'' macro, which takes no arguments; the second form
12340 defines a ``function-like'' macro, which takes the arguments given in
12343 A definition introduced by this command is in scope in every
12344 expression evaluated in @value{GDBN}, until it is removed with the
12345 @code{macro undef} command, described below. The definition overrides
12346 all definitions for @var{macro} present in the program being debugged,
12347 as well as any previous user-supplied definition.
12349 @kindex macro undef
12350 @item macro undef @var{macro}
12351 Remove any user-supplied definition for the macro named @var{macro}.
12352 This command only affects definitions provided with the @code{macro
12353 define} command, described above; it cannot remove definitions present
12354 in the program being debugged.
12358 List all the macros defined using the @code{macro define} command.
12361 @cindex macros, example of debugging with
12362 Here is a transcript showing the above commands in action. First, we
12363 show our source files:
12368 #include "sample.h"
12371 #define ADD(x) (M + x)
12376 printf ("Hello, world!\n");
12378 printf ("We're so creative.\n");
12380 printf ("Goodbye, world!\n");
12387 Now, we compile the program using the @sc{gnu} C compiler,
12388 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12389 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12390 and @option{-gdwarf-4}; we recommend always choosing the most recent
12391 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12392 includes information about preprocessor macros in the debugging
12396 $ gcc -gdwarf-2 -g3 sample.c -o sample
12400 Now, we start @value{GDBN} on our sample program:
12404 GNU gdb 2002-05-06-cvs
12405 Copyright 2002 Free Software Foundation, Inc.
12406 GDB is free software, @dots{}
12410 We can expand macros and examine their definitions, even when the
12411 program is not running. @value{GDBN} uses the current listing position
12412 to decide which macro definitions are in scope:
12415 (@value{GDBP}) list main
12418 5 #define ADD(x) (M + x)
12423 10 printf ("Hello, world!\n");
12425 12 printf ("We're so creative.\n");
12426 (@value{GDBP}) info macro ADD
12427 Defined at /home/jimb/gdb/macros/play/sample.c:5
12428 #define ADD(x) (M + x)
12429 (@value{GDBP}) info macro Q
12430 Defined at /home/jimb/gdb/macros/play/sample.h:1
12431 included at /home/jimb/gdb/macros/play/sample.c:2
12433 (@value{GDBP}) macro expand ADD(1)
12434 expands to: (42 + 1)
12435 (@value{GDBP}) macro expand-once ADD(1)
12436 expands to: once (M + 1)
12440 In the example above, note that @code{macro expand-once} expands only
12441 the macro invocation explicit in the original text --- the invocation of
12442 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12443 which was introduced by @code{ADD}.
12445 Once the program is running, @value{GDBN} uses the macro definitions in
12446 force at the source line of the current stack frame:
12449 (@value{GDBP}) break main
12450 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12452 Starting program: /home/jimb/gdb/macros/play/sample
12454 Breakpoint 1, main () at sample.c:10
12455 10 printf ("Hello, world!\n");
12459 At line 10, the definition of the macro @code{N} at line 9 is in force:
12462 (@value{GDBP}) info macro N
12463 Defined at /home/jimb/gdb/macros/play/sample.c:9
12465 (@value{GDBP}) macro expand N Q M
12466 expands to: 28 < 42
12467 (@value{GDBP}) print N Q M
12472 As we step over directives that remove @code{N}'s definition, and then
12473 give it a new definition, @value{GDBN} finds the definition (or lack
12474 thereof) in force at each point:
12477 (@value{GDBP}) next
12479 12 printf ("We're so creative.\n");
12480 (@value{GDBP}) info macro N
12481 The symbol `N' has no definition as a C/C++ preprocessor macro
12482 at /home/jimb/gdb/macros/play/sample.c:12
12483 (@value{GDBP}) next
12485 14 printf ("Goodbye, world!\n");
12486 (@value{GDBP}) info macro N
12487 Defined at /home/jimb/gdb/macros/play/sample.c:13
12489 (@value{GDBP}) macro expand N Q M
12490 expands to: 1729 < 42
12491 (@value{GDBP}) print N Q M
12496 In addition to source files, macros can be defined on the compilation command
12497 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12498 such a way, @value{GDBN} displays the location of their definition as line zero
12499 of the source file submitted to the compiler.
12502 (@value{GDBP}) info macro __STDC__
12503 Defined at /home/jimb/gdb/macros/play/sample.c:0
12510 @chapter Tracepoints
12511 @c This chapter is based on the documentation written by Michael
12512 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12514 @cindex tracepoints
12515 In some applications, it is not feasible for the debugger to interrupt
12516 the program's execution long enough for the developer to learn
12517 anything helpful about its behavior. If the program's correctness
12518 depends on its real-time behavior, delays introduced by a debugger
12519 might cause the program to change its behavior drastically, or perhaps
12520 fail, even when the code itself is correct. It is useful to be able
12521 to observe the program's behavior without interrupting it.
12523 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12524 specify locations in the program, called @dfn{tracepoints}, and
12525 arbitrary expressions to evaluate when those tracepoints are reached.
12526 Later, using the @code{tfind} command, you can examine the values
12527 those expressions had when the program hit the tracepoints. The
12528 expressions may also denote objects in memory---structures or arrays,
12529 for example---whose values @value{GDBN} should record; while visiting
12530 a particular tracepoint, you may inspect those objects as if they were
12531 in memory at that moment. However, because @value{GDBN} records these
12532 values without interacting with you, it can do so quickly and
12533 unobtrusively, hopefully not disturbing the program's behavior.
12535 The tracepoint facility is currently available only for remote
12536 targets. @xref{Targets}. In addition, your remote target must know
12537 how to collect trace data. This functionality is implemented in the
12538 remote stub; however, none of the stubs distributed with @value{GDBN}
12539 support tracepoints as of this writing. The format of the remote
12540 packets used to implement tracepoints are described in @ref{Tracepoint
12543 It is also possible to get trace data from a file, in a manner reminiscent
12544 of corefiles; you specify the filename, and use @code{tfind} to search
12545 through the file. @xref{Trace Files}, for more details.
12547 This chapter describes the tracepoint commands and features.
12550 * Set Tracepoints::
12551 * Analyze Collected Data::
12552 * Tracepoint Variables::
12556 @node Set Tracepoints
12557 @section Commands to Set Tracepoints
12559 Before running such a @dfn{trace experiment}, an arbitrary number of
12560 tracepoints can be set. A tracepoint is actually a special type of
12561 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12562 standard breakpoint commands. For instance, as with breakpoints,
12563 tracepoint numbers are successive integers starting from one, and many
12564 of the commands associated with tracepoints take the tracepoint number
12565 as their argument, to identify which tracepoint to work on.
12567 For each tracepoint, you can specify, in advance, some arbitrary set
12568 of data that you want the target to collect in the trace buffer when
12569 it hits that tracepoint. The collected data can include registers,
12570 local variables, or global data. Later, you can use @value{GDBN}
12571 commands to examine the values these data had at the time the
12572 tracepoint was hit.
12574 Tracepoints do not support every breakpoint feature. Ignore counts on
12575 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12576 commands when they are hit. Tracepoints may not be thread-specific
12579 @cindex fast tracepoints
12580 Some targets may support @dfn{fast tracepoints}, which are inserted in
12581 a different way (such as with a jump instead of a trap), that is
12582 faster but possibly restricted in where they may be installed.
12584 @cindex static tracepoints
12585 @cindex markers, static tracepoints
12586 @cindex probing markers, static tracepoints
12587 Regular and fast tracepoints are dynamic tracing facilities, meaning
12588 that they can be used to insert tracepoints at (almost) any location
12589 in the target. Some targets may also support controlling @dfn{static
12590 tracepoints} from @value{GDBN}. With static tracing, a set of
12591 instrumentation points, also known as @dfn{markers}, are embedded in
12592 the target program, and can be activated or deactivated by name or
12593 address. These are usually placed at locations which facilitate
12594 investigating what the target is actually doing. @value{GDBN}'s
12595 support for static tracing includes being able to list instrumentation
12596 points, and attach them with @value{GDBN} defined high level
12597 tracepoints that expose the whole range of convenience of
12598 @value{GDBN}'s tracepoints support. Namely, support for collecting
12599 registers values and values of global or local (to the instrumentation
12600 point) variables; tracepoint conditions and trace state variables.
12601 The act of installing a @value{GDBN} static tracepoint on an
12602 instrumentation point, or marker, is referred to as @dfn{probing} a
12603 static tracepoint marker.
12605 @code{gdbserver} supports tracepoints on some target systems.
12606 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12608 This section describes commands to set tracepoints and associated
12609 conditions and actions.
12612 * Create and Delete Tracepoints::
12613 * Enable and Disable Tracepoints::
12614 * Tracepoint Passcounts::
12615 * Tracepoint Conditions::
12616 * Trace State Variables::
12617 * Tracepoint Actions::
12618 * Listing Tracepoints::
12619 * Listing Static Tracepoint Markers::
12620 * Starting and Stopping Trace Experiments::
12621 * Tracepoint Restrictions::
12624 @node Create and Delete Tracepoints
12625 @subsection Create and Delete Tracepoints
12628 @cindex set tracepoint
12630 @item trace @var{location}
12631 The @code{trace} command is very similar to the @code{break} command.
12632 Its argument @var{location} can be any valid location.
12633 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12634 which is a point in the target program where the debugger will briefly stop,
12635 collect some data, and then allow the program to continue. Setting a tracepoint
12636 or changing its actions takes effect immediately if the remote stub
12637 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12639 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12640 these changes don't take effect until the next @code{tstart}
12641 command, and once a trace experiment is running, further changes will
12642 not have any effect until the next trace experiment starts. In addition,
12643 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12644 address is not yet resolved. (This is similar to pending breakpoints.)
12645 Pending tracepoints are not downloaded to the target and not installed
12646 until they are resolved. The resolution of pending tracepoints requires
12647 @value{GDBN} support---when debugging with the remote target, and
12648 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12649 tracing}), pending tracepoints can not be resolved (and downloaded to
12650 the remote stub) while @value{GDBN} is disconnected.
12652 Here are some examples of using the @code{trace} command:
12655 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12657 (@value{GDBP}) @b{trace +2} // 2 lines forward
12659 (@value{GDBP}) @b{trace my_function} // first source line of function
12661 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12663 (@value{GDBP}) @b{trace *0x2117c4} // an address
12667 You can abbreviate @code{trace} as @code{tr}.
12669 @item trace @var{location} if @var{cond}
12670 Set a tracepoint with condition @var{cond}; evaluate the expression
12671 @var{cond} each time the tracepoint is reached, and collect data only
12672 if the value is nonzero---that is, if @var{cond} evaluates as true.
12673 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12674 information on tracepoint conditions.
12676 @item ftrace @var{location} [ if @var{cond} ]
12677 @cindex set fast tracepoint
12678 @cindex fast tracepoints, setting
12680 The @code{ftrace} command sets a fast tracepoint. For targets that
12681 support them, fast tracepoints will use a more efficient but possibly
12682 less general technique to trigger data collection, such as a jump
12683 instruction instead of a trap, or some sort of hardware support. It
12684 may not be possible to create a fast tracepoint at the desired
12685 location, in which case the command will exit with an explanatory
12688 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12691 On 32-bit x86-architecture systems, fast tracepoints normally need to
12692 be placed at an instruction that is 5 bytes or longer, but can be
12693 placed at 4-byte instructions if the low 64K of memory of the target
12694 program is available to install trampolines. Some Unix-type systems,
12695 such as @sc{gnu}/Linux, exclude low addresses from the program's
12696 address space; but for instance with the Linux kernel it is possible
12697 to let @value{GDBN} use this area by doing a @command{sysctl} command
12698 to set the @code{mmap_min_addr} kernel parameter, as in
12701 sudo sysctl -w vm.mmap_min_addr=32768
12705 which sets the low address to 32K, which leaves plenty of room for
12706 trampolines. The minimum address should be set to a page boundary.
12708 @item strace @var{location} [ if @var{cond} ]
12709 @cindex set static tracepoint
12710 @cindex static tracepoints, setting
12711 @cindex probe static tracepoint marker
12713 The @code{strace} command sets a static tracepoint. For targets that
12714 support it, setting a static tracepoint probes a static
12715 instrumentation point, or marker, found at @var{location}. It may not
12716 be possible to set a static tracepoint at the desired location, in
12717 which case the command will exit with an explanatory message.
12719 @value{GDBN} handles arguments to @code{strace} exactly as for
12720 @code{trace}, with the addition that the user can also specify
12721 @code{-m @var{marker}} as @var{location}. This probes the marker
12722 identified by the @var{marker} string identifier. This identifier
12723 depends on the static tracepoint backend library your program is
12724 using. You can find all the marker identifiers in the @samp{ID} field
12725 of the @code{info static-tracepoint-markers} command output.
12726 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12727 Markers}. For example, in the following small program using the UST
12733 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12738 the marker id is composed of joining the first two arguments to the
12739 @code{trace_mark} call with a slash, which translates to:
12742 (@value{GDBP}) info static-tracepoint-markers
12743 Cnt Enb ID Address What
12744 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12750 so you may probe the marker above with:
12753 (@value{GDBP}) strace -m ust/bar33
12756 Static tracepoints accept an extra collect action --- @code{collect
12757 $_sdata}. This collects arbitrary user data passed in the probe point
12758 call to the tracing library. In the UST example above, you'll see
12759 that the third argument to @code{trace_mark} is a printf-like format
12760 string. The user data is then the result of running that formating
12761 string against the following arguments. Note that @code{info
12762 static-tracepoint-markers} command output lists that format string in
12763 the @samp{Data:} field.
12765 You can inspect this data when analyzing the trace buffer, by printing
12766 the $_sdata variable like any other variable available to
12767 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12770 @cindex last tracepoint number
12771 @cindex recent tracepoint number
12772 @cindex tracepoint number
12773 The convenience variable @code{$tpnum} records the tracepoint number
12774 of the most recently set tracepoint.
12776 @kindex delete tracepoint
12777 @cindex tracepoint deletion
12778 @item delete tracepoint @r{[}@var{num}@r{]}
12779 Permanently delete one or more tracepoints. With no argument, the
12780 default is to delete all tracepoints. Note that the regular
12781 @code{delete} command can remove tracepoints also.
12786 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12788 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12792 You can abbreviate this command as @code{del tr}.
12795 @node Enable and Disable Tracepoints
12796 @subsection Enable and Disable Tracepoints
12798 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12801 @kindex disable tracepoint
12802 @item disable tracepoint @r{[}@var{num}@r{]}
12803 Disable tracepoint @var{num}, or all tracepoints if no argument
12804 @var{num} is given. A disabled tracepoint will have no effect during
12805 a trace experiment, but it is not forgotten. You can re-enable
12806 a disabled tracepoint using the @code{enable tracepoint} command.
12807 If the command is issued during a trace experiment and the debug target
12808 has support for disabling tracepoints during a trace experiment, then the
12809 change will be effective immediately. Otherwise, it will be applied to the
12810 next trace experiment.
12812 @kindex enable tracepoint
12813 @item enable tracepoint @r{[}@var{num}@r{]}
12814 Enable tracepoint @var{num}, or all tracepoints. If this command is
12815 issued during a trace experiment and the debug target supports enabling
12816 tracepoints during a trace experiment, then the enabled tracepoints will
12817 become effective immediately. Otherwise, they will become effective the
12818 next time a trace experiment is run.
12821 @node Tracepoint Passcounts
12822 @subsection Tracepoint Passcounts
12826 @cindex tracepoint pass count
12827 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12828 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12829 automatically stop a trace experiment. If a tracepoint's passcount is
12830 @var{n}, then the trace experiment will be automatically stopped on
12831 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12832 @var{num} is not specified, the @code{passcount} command sets the
12833 passcount of the most recently defined tracepoint. If no passcount is
12834 given, the trace experiment will run until stopped explicitly by the
12840 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12841 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12843 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12844 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12845 (@value{GDBP}) @b{trace foo}
12846 (@value{GDBP}) @b{pass 3}
12847 (@value{GDBP}) @b{trace bar}
12848 (@value{GDBP}) @b{pass 2}
12849 (@value{GDBP}) @b{trace baz}
12850 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12851 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12852 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12853 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12857 @node Tracepoint Conditions
12858 @subsection Tracepoint Conditions
12859 @cindex conditional tracepoints
12860 @cindex tracepoint conditions
12862 The simplest sort of tracepoint collects data every time your program
12863 reaches a specified place. You can also specify a @dfn{condition} for
12864 a tracepoint. A condition is just a Boolean expression in your
12865 programming language (@pxref{Expressions, ,Expressions}). A
12866 tracepoint with a condition evaluates the expression each time your
12867 program reaches it, and data collection happens only if the condition
12870 Tracepoint conditions can be specified when a tracepoint is set, by
12871 using @samp{if} in the arguments to the @code{trace} command.
12872 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12873 also be set or changed at any time with the @code{condition} command,
12874 just as with breakpoints.
12876 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12877 the conditional expression itself. Instead, @value{GDBN} encodes the
12878 expression into an agent expression (@pxref{Agent Expressions})
12879 suitable for execution on the target, independently of @value{GDBN}.
12880 Global variables become raw memory locations, locals become stack
12881 accesses, and so forth.
12883 For instance, suppose you have a function that is usually called
12884 frequently, but should not be called after an error has occurred. You
12885 could use the following tracepoint command to collect data about calls
12886 of that function that happen while the error code is propagating
12887 through the program; an unconditional tracepoint could end up
12888 collecting thousands of useless trace frames that you would have to
12892 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12895 @node Trace State Variables
12896 @subsection Trace State Variables
12897 @cindex trace state variables
12899 A @dfn{trace state variable} is a special type of variable that is
12900 created and managed by target-side code. The syntax is the same as
12901 that for GDB's convenience variables (a string prefixed with ``$''),
12902 but they are stored on the target. They must be created explicitly,
12903 using a @code{tvariable} command. They are always 64-bit signed
12906 Trace state variables are remembered by @value{GDBN}, and downloaded
12907 to the target along with tracepoint information when the trace
12908 experiment starts. There are no intrinsic limits on the number of
12909 trace state variables, beyond memory limitations of the target.
12911 @cindex convenience variables, and trace state variables
12912 Although trace state variables are managed by the target, you can use
12913 them in print commands and expressions as if they were convenience
12914 variables; @value{GDBN} will get the current value from the target
12915 while the trace experiment is running. Trace state variables share
12916 the same namespace as other ``$'' variables, which means that you
12917 cannot have trace state variables with names like @code{$23} or
12918 @code{$pc}, nor can you have a trace state variable and a convenience
12919 variable with the same name.
12923 @item tvariable $@var{name} [ = @var{expression} ]
12925 The @code{tvariable} command creates a new trace state variable named
12926 @code{$@var{name}}, and optionally gives it an initial value of
12927 @var{expression}. The @var{expression} is evaluated when this command is
12928 entered; the result will be converted to an integer if possible,
12929 otherwise @value{GDBN} will report an error. A subsequent
12930 @code{tvariable} command specifying the same name does not create a
12931 variable, but instead assigns the supplied initial value to the
12932 existing variable of that name, overwriting any previous initial
12933 value. The default initial value is 0.
12935 @item info tvariables
12936 @kindex info tvariables
12937 List all the trace state variables along with their initial values.
12938 Their current values may also be displayed, if the trace experiment is
12941 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12942 @kindex delete tvariable
12943 Delete the given trace state variables, or all of them if no arguments
12948 @node Tracepoint Actions
12949 @subsection Tracepoint Action Lists
12953 @cindex tracepoint actions
12954 @item actions @r{[}@var{num}@r{]}
12955 This command will prompt for a list of actions to be taken when the
12956 tracepoint is hit. If the tracepoint number @var{num} is not
12957 specified, this command sets the actions for the one that was most
12958 recently defined (so that you can define a tracepoint and then say
12959 @code{actions} without bothering about its number). You specify the
12960 actions themselves on the following lines, one action at a time, and
12961 terminate the actions list with a line containing just @code{end}. So
12962 far, the only defined actions are @code{collect}, @code{teval}, and
12963 @code{while-stepping}.
12965 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12966 Commands, ,Breakpoint Command Lists}), except that only the defined
12967 actions are allowed; any other @value{GDBN} command is rejected.
12969 @cindex remove actions from a tracepoint
12970 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12971 and follow it immediately with @samp{end}.
12974 (@value{GDBP}) @b{collect @var{data}} // collect some data
12976 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12978 (@value{GDBP}) @b{end} // signals the end of actions.
12981 In the following example, the action list begins with @code{collect}
12982 commands indicating the things to be collected when the tracepoint is
12983 hit. Then, in order to single-step and collect additional data
12984 following the tracepoint, a @code{while-stepping} command is used,
12985 followed by the list of things to be collected after each step in a
12986 sequence of single steps. The @code{while-stepping} command is
12987 terminated by its own separate @code{end} command. Lastly, the action
12988 list is terminated by an @code{end} command.
12991 (@value{GDBP}) @b{trace foo}
12992 (@value{GDBP}) @b{actions}
12993 Enter actions for tracepoint 1, one per line:
12996 > while-stepping 12
12997 > collect $pc, arr[i]
13002 @kindex collect @r{(tracepoints)}
13003 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13004 Collect values of the given expressions when the tracepoint is hit.
13005 This command accepts a comma-separated list of any valid expressions.
13006 In addition to global, static, or local variables, the following
13007 special arguments are supported:
13011 Collect all registers.
13014 Collect all function arguments.
13017 Collect all local variables.
13020 Collect the return address. This is helpful if you want to see more
13023 @emph{Note:} The return address location can not always be reliably
13024 determined up front, and the wrong address / registers may end up
13025 collected instead. On some architectures the reliability is higher
13026 for tracepoints at function entry, while on others it's the opposite.
13027 When this happens, backtracing will stop because the return address is
13028 found unavailable (unless another collect rule happened to match it).
13031 Collects the number of arguments from the static probe at which the
13032 tracepoint is located.
13033 @xref{Static Probe Points}.
13035 @item $_probe_arg@var{n}
13036 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13037 from the static probe at which the tracepoint is located.
13038 @xref{Static Probe Points}.
13041 @vindex $_sdata@r{, collect}
13042 Collect static tracepoint marker specific data. Only available for
13043 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13044 Lists}. On the UST static tracepoints library backend, an
13045 instrumentation point resembles a @code{printf} function call. The
13046 tracing library is able to collect user specified data formatted to a
13047 character string using the format provided by the programmer that
13048 instrumented the program. Other backends have similar mechanisms.
13049 Here's an example of a UST marker call:
13052 const char master_name[] = "$your_name";
13053 trace_mark(channel1, marker1, "hello %s", master_name)
13056 In this case, collecting @code{$_sdata} collects the string
13057 @samp{hello $yourname}. When analyzing the trace buffer, you can
13058 inspect @samp{$_sdata} like any other variable available to
13062 You can give several consecutive @code{collect} commands, each one
13063 with a single argument, or one @code{collect} command with several
13064 arguments separated by commas; the effect is the same.
13066 The optional @var{mods} changes the usual handling of the arguments.
13067 @code{s} requests that pointers to chars be handled as strings, in
13068 particular collecting the contents of the memory being pointed at, up
13069 to the first zero. The upper bound is by default the value of the
13070 @code{print elements} variable; if @code{s} is followed by a decimal
13071 number, that is the upper bound instead. So for instance
13072 @samp{collect/s25 mystr} collects as many as 25 characters at
13075 The command @code{info scope} (@pxref{Symbols, info scope}) is
13076 particularly useful for figuring out what data to collect.
13078 @kindex teval @r{(tracepoints)}
13079 @item teval @var{expr1}, @var{expr2}, @dots{}
13080 Evaluate the given expressions when the tracepoint is hit. This
13081 command accepts a comma-separated list of expressions. The results
13082 are discarded, so this is mainly useful for assigning values to trace
13083 state variables (@pxref{Trace State Variables}) without adding those
13084 values to the trace buffer, as would be the case if the @code{collect}
13087 @kindex while-stepping @r{(tracepoints)}
13088 @item while-stepping @var{n}
13089 Perform @var{n} single-step instruction traces after the tracepoint,
13090 collecting new data after each step. The @code{while-stepping}
13091 command is followed by the list of what to collect while stepping
13092 (followed by its own @code{end} command):
13095 > while-stepping 12
13096 > collect $regs, myglobal
13102 Note that @code{$pc} is not automatically collected by
13103 @code{while-stepping}; you need to explicitly collect that register if
13104 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13107 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13108 @kindex set default-collect
13109 @cindex default collection action
13110 This variable is a list of expressions to collect at each tracepoint
13111 hit. It is effectively an additional @code{collect} action prepended
13112 to every tracepoint action list. The expressions are parsed
13113 individually for each tracepoint, so for instance a variable named
13114 @code{xyz} may be interpreted as a global for one tracepoint, and a
13115 local for another, as appropriate to the tracepoint's location.
13117 @item show default-collect
13118 @kindex show default-collect
13119 Show the list of expressions that are collected by default at each
13124 @node Listing Tracepoints
13125 @subsection Listing Tracepoints
13128 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13129 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13130 @cindex information about tracepoints
13131 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13132 Display information about the tracepoint @var{num}. If you don't
13133 specify a tracepoint number, displays information about all the
13134 tracepoints defined so far. The format is similar to that used for
13135 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13136 command, simply restricting itself to tracepoints.
13138 A tracepoint's listing may include additional information specific to
13143 its passcount as given by the @code{passcount @var{n}} command
13146 the state about installed on target of each location
13150 (@value{GDBP}) @b{info trace}
13151 Num Type Disp Enb Address What
13152 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13154 collect globfoo, $regs
13159 2 tracepoint keep y <MULTIPLE>
13161 2.1 y 0x0804859c in func4 at change-loc.h:35
13162 installed on target
13163 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13164 installed on target
13165 2.3 y <PENDING> set_tracepoint
13166 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13167 not installed on target
13172 This command can be abbreviated @code{info tp}.
13175 @node Listing Static Tracepoint Markers
13176 @subsection Listing Static Tracepoint Markers
13179 @kindex info static-tracepoint-markers
13180 @cindex information about static tracepoint markers
13181 @item info static-tracepoint-markers
13182 Display information about all static tracepoint markers defined in the
13185 For each marker, the following columns are printed:
13189 An incrementing counter, output to help readability. This is not a
13192 The marker ID, as reported by the target.
13193 @item Enabled or Disabled
13194 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13195 that are not enabled.
13197 Where the marker is in your program, as a memory address.
13199 Where the marker is in the source for your program, as a file and line
13200 number. If the debug information included in the program does not
13201 allow @value{GDBN} to locate the source of the marker, this column
13202 will be left blank.
13206 In addition, the following information may be printed for each marker:
13210 User data passed to the tracing library by the marker call. In the
13211 UST backend, this is the format string passed as argument to the
13213 @item Static tracepoints probing the marker
13214 The list of static tracepoints attached to the marker.
13218 (@value{GDBP}) info static-tracepoint-markers
13219 Cnt ID Enb Address What
13220 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13221 Data: number1 %d number2 %d
13222 Probed by static tracepoints: #2
13223 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13229 @node Starting and Stopping Trace Experiments
13230 @subsection Starting and Stopping Trace Experiments
13233 @kindex tstart [ @var{notes} ]
13234 @cindex start a new trace experiment
13235 @cindex collected data discarded
13237 This command starts the trace experiment, and begins collecting data.
13238 It has the side effect of discarding all the data collected in the
13239 trace buffer during the previous trace experiment. If any arguments
13240 are supplied, they are taken as a note and stored with the trace
13241 experiment's state. The notes may be arbitrary text, and are
13242 especially useful with disconnected tracing in a multi-user context;
13243 the notes can explain what the trace is doing, supply user contact
13244 information, and so forth.
13246 @kindex tstop [ @var{notes} ]
13247 @cindex stop a running trace experiment
13249 This command stops the trace experiment. If any arguments are
13250 supplied, they are recorded with the experiment as a note. This is
13251 useful if you are stopping a trace started by someone else, for
13252 instance if the trace is interfering with the system's behavior and
13253 needs to be stopped quickly.
13255 @strong{Note}: a trace experiment and data collection may stop
13256 automatically if any tracepoint's passcount is reached
13257 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13260 @cindex status of trace data collection
13261 @cindex trace experiment, status of
13263 This command displays the status of the current trace data
13267 Here is an example of the commands we described so far:
13270 (@value{GDBP}) @b{trace gdb_c_test}
13271 (@value{GDBP}) @b{actions}
13272 Enter actions for tracepoint #1, one per line.
13273 > collect $regs,$locals,$args
13274 > while-stepping 11
13278 (@value{GDBP}) @b{tstart}
13279 [time passes @dots{}]
13280 (@value{GDBP}) @b{tstop}
13283 @anchor{disconnected tracing}
13284 @cindex disconnected tracing
13285 You can choose to continue running the trace experiment even if
13286 @value{GDBN} disconnects from the target, voluntarily or
13287 involuntarily. For commands such as @code{detach}, the debugger will
13288 ask what you want to do with the trace. But for unexpected
13289 terminations (@value{GDBN} crash, network outage), it would be
13290 unfortunate to lose hard-won trace data, so the variable
13291 @code{disconnected-tracing} lets you decide whether the trace should
13292 continue running without @value{GDBN}.
13295 @item set disconnected-tracing on
13296 @itemx set disconnected-tracing off
13297 @kindex set disconnected-tracing
13298 Choose whether a tracing run should continue to run if @value{GDBN}
13299 has disconnected from the target. Note that @code{detach} or
13300 @code{quit} will ask you directly what to do about a running trace no
13301 matter what this variable's setting, so the variable is mainly useful
13302 for handling unexpected situations, such as loss of the network.
13304 @item show disconnected-tracing
13305 @kindex show disconnected-tracing
13306 Show the current choice for disconnected tracing.
13310 When you reconnect to the target, the trace experiment may or may not
13311 still be running; it might have filled the trace buffer in the
13312 meantime, or stopped for one of the other reasons. If it is running,
13313 it will continue after reconnection.
13315 Upon reconnection, the target will upload information about the
13316 tracepoints in effect. @value{GDBN} will then compare that
13317 information to the set of tracepoints currently defined, and attempt
13318 to match them up, allowing for the possibility that the numbers may
13319 have changed due to creation and deletion in the meantime. If one of
13320 the target's tracepoints does not match any in @value{GDBN}, the
13321 debugger will create a new tracepoint, so that you have a number with
13322 which to specify that tracepoint. This matching-up process is
13323 necessarily heuristic, and it may result in useless tracepoints being
13324 created; you may simply delete them if they are of no use.
13326 @cindex circular trace buffer
13327 If your target agent supports a @dfn{circular trace buffer}, then you
13328 can run a trace experiment indefinitely without filling the trace
13329 buffer; when space runs out, the agent deletes already-collected trace
13330 frames, oldest first, until there is enough room to continue
13331 collecting. This is especially useful if your tracepoints are being
13332 hit too often, and your trace gets terminated prematurely because the
13333 buffer is full. To ask for a circular trace buffer, simply set
13334 @samp{circular-trace-buffer} to on. You can set this at any time,
13335 including during tracing; if the agent can do it, it will change
13336 buffer handling on the fly, otherwise it will not take effect until
13340 @item set circular-trace-buffer on
13341 @itemx set circular-trace-buffer off
13342 @kindex set circular-trace-buffer
13343 Choose whether a tracing run should use a linear or circular buffer
13344 for trace data. A linear buffer will not lose any trace data, but may
13345 fill up prematurely, while a circular buffer will discard old trace
13346 data, but it will have always room for the latest tracepoint hits.
13348 @item show circular-trace-buffer
13349 @kindex show circular-trace-buffer
13350 Show the current choice for the trace buffer. Note that this may not
13351 match the agent's current buffer handling, nor is it guaranteed to
13352 match the setting that might have been in effect during a past run,
13353 for instance if you are looking at frames from a trace file.
13358 @item set trace-buffer-size @var{n}
13359 @itemx set trace-buffer-size unlimited
13360 @kindex set trace-buffer-size
13361 Request that the target use a trace buffer of @var{n} bytes. Not all
13362 targets will honor the request; they may have a compiled-in size for
13363 the trace buffer, or some other limitation. Set to a value of
13364 @code{unlimited} or @code{-1} to let the target use whatever size it
13365 likes. This is also the default.
13367 @item show trace-buffer-size
13368 @kindex show trace-buffer-size
13369 Show the current requested size for the trace buffer. Note that this
13370 will only match the actual size if the target supports size-setting,
13371 and was able to handle the requested size. For instance, if the
13372 target can only change buffer size between runs, this variable will
13373 not reflect the change until the next run starts. Use @code{tstatus}
13374 to get a report of the actual buffer size.
13378 @item set trace-user @var{text}
13379 @kindex set trace-user
13381 @item show trace-user
13382 @kindex show trace-user
13384 @item set trace-notes @var{text}
13385 @kindex set trace-notes
13386 Set the trace run's notes.
13388 @item show trace-notes
13389 @kindex show trace-notes
13390 Show the trace run's notes.
13392 @item set trace-stop-notes @var{text}
13393 @kindex set trace-stop-notes
13394 Set the trace run's stop notes. The handling of the note is as for
13395 @code{tstop} arguments; the set command is convenient way to fix a
13396 stop note that is mistaken or incomplete.
13398 @item show trace-stop-notes
13399 @kindex show trace-stop-notes
13400 Show the trace run's stop notes.
13404 @node Tracepoint Restrictions
13405 @subsection Tracepoint Restrictions
13407 @cindex tracepoint restrictions
13408 There are a number of restrictions on the use of tracepoints. As
13409 described above, tracepoint data gathering occurs on the target
13410 without interaction from @value{GDBN}. Thus the full capabilities of
13411 the debugger are not available during data gathering, and then at data
13412 examination time, you will be limited by only having what was
13413 collected. The following items describe some common problems, but it
13414 is not exhaustive, and you may run into additional difficulties not
13420 Tracepoint expressions are intended to gather objects (lvalues). Thus
13421 the full flexibility of GDB's expression evaluator is not available.
13422 You cannot call functions, cast objects to aggregate types, access
13423 convenience variables or modify values (except by assignment to trace
13424 state variables). Some language features may implicitly call
13425 functions (for instance Objective-C fields with accessors), and therefore
13426 cannot be collected either.
13429 Collection of local variables, either individually or in bulk with
13430 @code{$locals} or @code{$args}, during @code{while-stepping} may
13431 behave erratically. The stepping action may enter a new scope (for
13432 instance by stepping into a function), or the location of the variable
13433 may change (for instance it is loaded into a register). The
13434 tracepoint data recorded uses the location information for the
13435 variables that is correct for the tracepoint location. When the
13436 tracepoint is created, it is not possible, in general, to determine
13437 where the steps of a @code{while-stepping} sequence will advance the
13438 program---particularly if a conditional branch is stepped.
13441 Collection of an incompletely-initialized or partially-destroyed object
13442 may result in something that @value{GDBN} cannot display, or displays
13443 in a misleading way.
13446 When @value{GDBN} displays a pointer to character it automatically
13447 dereferences the pointer to also display characters of the string
13448 being pointed to. However, collecting the pointer during tracing does
13449 not automatically collect the string. You need to explicitly
13450 dereference the pointer and provide size information if you want to
13451 collect not only the pointer, but the memory pointed to. For example,
13452 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13456 It is not possible to collect a complete stack backtrace at a
13457 tracepoint. Instead, you may collect the registers and a few hundred
13458 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13459 (adjust to use the name of the actual stack pointer register on your
13460 target architecture, and the amount of stack you wish to capture).
13461 Then the @code{backtrace} command will show a partial backtrace when
13462 using a trace frame. The number of stack frames that can be examined
13463 depends on the sizes of the frames in the collected stack. Note that
13464 if you ask for a block so large that it goes past the bottom of the
13465 stack, the target agent may report an error trying to read from an
13469 If you do not collect registers at a tracepoint, @value{GDBN} can
13470 infer that the value of @code{$pc} must be the same as the address of
13471 the tracepoint and use that when you are looking at a trace frame
13472 for that tracepoint. However, this cannot work if the tracepoint has
13473 multiple locations (for instance if it was set in a function that was
13474 inlined), or if it has a @code{while-stepping} loop. In those cases
13475 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13480 @node Analyze Collected Data
13481 @section Using the Collected Data
13483 After the tracepoint experiment ends, you use @value{GDBN} commands
13484 for examining the trace data. The basic idea is that each tracepoint
13485 collects a trace @dfn{snapshot} every time it is hit and another
13486 snapshot every time it single-steps. All these snapshots are
13487 consecutively numbered from zero and go into a buffer, and you can
13488 examine them later. The way you examine them is to @dfn{focus} on a
13489 specific trace snapshot. When the remote stub is focused on a trace
13490 snapshot, it will respond to all @value{GDBN} requests for memory and
13491 registers by reading from the buffer which belongs to that snapshot,
13492 rather than from @emph{real} memory or registers of the program being
13493 debugged. This means that @strong{all} @value{GDBN} commands
13494 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13495 behave as if we were currently debugging the program state as it was
13496 when the tracepoint occurred. Any requests for data that are not in
13497 the buffer will fail.
13500 * tfind:: How to select a trace snapshot
13501 * tdump:: How to display all data for a snapshot
13502 * save tracepoints:: How to save tracepoints for a future run
13506 @subsection @code{tfind @var{n}}
13509 @cindex select trace snapshot
13510 @cindex find trace snapshot
13511 The basic command for selecting a trace snapshot from the buffer is
13512 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13513 counting from zero. If no argument @var{n} is given, the next
13514 snapshot is selected.
13516 Here are the various forms of using the @code{tfind} command.
13520 Find the first snapshot in the buffer. This is a synonym for
13521 @code{tfind 0} (since 0 is the number of the first snapshot).
13524 Stop debugging trace snapshots, resume @emph{live} debugging.
13527 Same as @samp{tfind none}.
13530 No argument means find the next trace snapshot or find the first
13531 one if no trace snapshot is selected.
13534 Find the previous trace snapshot before the current one. This permits
13535 retracing earlier steps.
13537 @item tfind tracepoint @var{num}
13538 Find the next snapshot associated with tracepoint @var{num}. Search
13539 proceeds forward from the last examined trace snapshot. If no
13540 argument @var{num} is given, it means find the next snapshot collected
13541 for the same tracepoint as the current snapshot.
13543 @item tfind pc @var{addr}
13544 Find the next snapshot associated with the value @var{addr} of the
13545 program counter. Search proceeds forward from the last examined trace
13546 snapshot. If no argument @var{addr} is given, it means find the next
13547 snapshot with the same value of PC as the current snapshot.
13549 @item tfind outside @var{addr1}, @var{addr2}
13550 Find the next snapshot whose PC is outside the given range of
13551 addresses (exclusive).
13553 @item tfind range @var{addr1}, @var{addr2}
13554 Find the next snapshot whose PC is between @var{addr1} and
13555 @var{addr2} (inclusive).
13557 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13558 Find the next snapshot associated with the source line @var{n}. If
13559 the optional argument @var{file} is given, refer to line @var{n} in
13560 that source file. Search proceeds forward from the last examined
13561 trace snapshot. If no argument @var{n} is given, it means find the
13562 next line other than the one currently being examined; thus saying
13563 @code{tfind line} repeatedly can appear to have the same effect as
13564 stepping from line to line in a @emph{live} debugging session.
13567 The default arguments for the @code{tfind} commands are specifically
13568 designed to make it easy to scan through the trace buffer. For
13569 instance, @code{tfind} with no argument selects the next trace
13570 snapshot, and @code{tfind -} with no argument selects the previous
13571 trace snapshot. So, by giving one @code{tfind} command, and then
13572 simply hitting @key{RET} repeatedly you can examine all the trace
13573 snapshots in order. Or, by saying @code{tfind -} and then hitting
13574 @key{RET} repeatedly you can examine the snapshots in reverse order.
13575 The @code{tfind line} command with no argument selects the snapshot
13576 for the next source line executed. The @code{tfind pc} command with
13577 no argument selects the next snapshot with the same program counter
13578 (PC) as the current frame. The @code{tfind tracepoint} command with
13579 no argument selects the next trace snapshot collected by the same
13580 tracepoint as the current one.
13582 In addition to letting you scan through the trace buffer manually,
13583 these commands make it easy to construct @value{GDBN} scripts that
13584 scan through the trace buffer and print out whatever collected data
13585 you are interested in. Thus, if we want to examine the PC, FP, and SP
13586 registers from each trace frame in the buffer, we can say this:
13589 (@value{GDBP}) @b{tfind start}
13590 (@value{GDBP}) @b{while ($trace_frame != -1)}
13591 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13592 $trace_frame, $pc, $sp, $fp
13596 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13597 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13598 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13599 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13600 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13601 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13602 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13603 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13604 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13605 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13606 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13609 Or, if we want to examine the variable @code{X} at each source line in
13613 (@value{GDBP}) @b{tfind start}
13614 (@value{GDBP}) @b{while ($trace_frame != -1)}
13615 > printf "Frame %d, X == %d\n", $trace_frame, X
13625 @subsection @code{tdump}
13627 @cindex dump all data collected at tracepoint
13628 @cindex tracepoint data, display
13630 This command takes no arguments. It prints all the data collected at
13631 the current trace snapshot.
13634 (@value{GDBP}) @b{trace 444}
13635 (@value{GDBP}) @b{actions}
13636 Enter actions for tracepoint #2, one per line:
13637 > collect $regs, $locals, $args, gdb_long_test
13640 (@value{GDBP}) @b{tstart}
13642 (@value{GDBP}) @b{tfind line 444}
13643 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13645 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13647 (@value{GDBP}) @b{tdump}
13648 Data collected at tracepoint 2, trace frame 1:
13649 d0 0xc4aa0085 -995491707
13653 d4 0x71aea3d 119204413
13656 d7 0x380035 3670069
13657 a0 0x19e24a 1696330
13658 a1 0x3000668 50333288
13660 a3 0x322000 3284992
13661 a4 0x3000698 50333336
13662 a5 0x1ad3cc 1758156
13663 fp 0x30bf3c 0x30bf3c
13664 sp 0x30bf34 0x30bf34
13666 pc 0x20b2c8 0x20b2c8
13670 p = 0x20e5b4 "gdb-test"
13677 gdb_long_test = 17 '\021'
13682 @code{tdump} works by scanning the tracepoint's current collection
13683 actions and printing the value of each expression listed. So
13684 @code{tdump} can fail, if after a run, you change the tracepoint's
13685 actions to mention variables that were not collected during the run.
13687 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13688 uses the collected value of @code{$pc} to distinguish between trace
13689 frames that were collected at the tracepoint hit, and frames that were
13690 collected while stepping. This allows it to correctly choose whether
13691 to display the basic list of collections, or the collections from the
13692 body of the while-stepping loop. However, if @code{$pc} was not collected,
13693 then @code{tdump} will always attempt to dump using the basic collection
13694 list, and may fail if a while-stepping frame does not include all the
13695 same data that is collected at the tracepoint hit.
13696 @c This is getting pretty arcane, example would be good.
13698 @node save tracepoints
13699 @subsection @code{save tracepoints @var{filename}}
13700 @kindex save tracepoints
13701 @kindex save-tracepoints
13702 @cindex save tracepoints for future sessions
13704 This command saves all current tracepoint definitions together with
13705 their actions and passcounts, into a file @file{@var{filename}}
13706 suitable for use in a later debugging session. To read the saved
13707 tracepoint definitions, use the @code{source} command (@pxref{Command
13708 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13709 alias for @w{@code{save tracepoints}}
13711 @node Tracepoint Variables
13712 @section Convenience Variables for Tracepoints
13713 @cindex tracepoint variables
13714 @cindex convenience variables for tracepoints
13717 @vindex $trace_frame
13718 @item (int) $trace_frame
13719 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13720 snapshot is selected.
13722 @vindex $tracepoint
13723 @item (int) $tracepoint
13724 The tracepoint for the current trace snapshot.
13726 @vindex $trace_line
13727 @item (int) $trace_line
13728 The line number for the current trace snapshot.
13730 @vindex $trace_file
13731 @item (char []) $trace_file
13732 The source file for the current trace snapshot.
13734 @vindex $trace_func
13735 @item (char []) $trace_func
13736 The name of the function containing @code{$tracepoint}.
13739 Note: @code{$trace_file} is not suitable for use in @code{printf},
13740 use @code{output} instead.
13742 Here's a simple example of using these convenience variables for
13743 stepping through all the trace snapshots and printing some of their
13744 data. Note that these are not the same as trace state variables,
13745 which are managed by the target.
13748 (@value{GDBP}) @b{tfind start}
13750 (@value{GDBP}) @b{while $trace_frame != -1}
13751 > output $trace_file
13752 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13758 @section Using Trace Files
13759 @cindex trace files
13761 In some situations, the target running a trace experiment may no
13762 longer be available; perhaps it crashed, or the hardware was needed
13763 for a different activity. To handle these cases, you can arrange to
13764 dump the trace data into a file, and later use that file as a source
13765 of trace data, via the @code{target tfile} command.
13770 @item tsave [ -r ] @var{filename}
13771 @itemx tsave [-ctf] @var{dirname}
13772 Save the trace data to @var{filename}. By default, this command
13773 assumes that @var{filename} refers to the host filesystem, so if
13774 necessary @value{GDBN} will copy raw trace data up from the target and
13775 then save it. If the target supports it, you can also supply the
13776 optional argument @code{-r} (``remote'') to direct the target to save
13777 the data directly into @var{filename} in its own filesystem, which may be
13778 more efficient if the trace buffer is very large. (Note, however, that
13779 @code{target tfile} can only read from files accessible to the host.)
13780 By default, this command will save trace frame in tfile format.
13781 You can supply the optional argument @code{-ctf} to save data in CTF
13782 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13783 that can be shared by multiple debugging and tracing tools. Please go to
13784 @indicateurl{http://www.efficios.com/ctf} to get more information.
13786 @kindex target tfile
13790 @item target tfile @var{filename}
13791 @itemx target ctf @var{dirname}
13792 Use the file named @var{filename} or directory named @var{dirname} as
13793 a source of trace data. Commands that examine data work as they do with
13794 a live target, but it is not possible to run any new trace experiments.
13795 @code{tstatus} will report the state of the trace run at the moment
13796 the data was saved, as well as the current trace frame you are examining.
13797 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13801 (@value{GDBP}) target ctf ctf.ctf
13802 (@value{GDBP}) tfind
13803 Found trace frame 0, tracepoint 2
13804 39 ++a; /* set tracepoint 1 here */
13805 (@value{GDBP}) tdump
13806 Data collected at tracepoint 2, trace frame 0:
13810 c = @{"123", "456", "789", "123", "456", "789"@}
13811 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13819 @chapter Debugging Programs That Use Overlays
13822 If your program is too large to fit completely in your target system's
13823 memory, you can sometimes use @dfn{overlays} to work around this
13824 problem. @value{GDBN} provides some support for debugging programs that
13828 * How Overlays Work:: A general explanation of overlays.
13829 * Overlay Commands:: Managing overlays in @value{GDBN}.
13830 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13831 mapped by asking the inferior.
13832 * Overlay Sample Program:: A sample program using overlays.
13835 @node How Overlays Work
13836 @section How Overlays Work
13837 @cindex mapped overlays
13838 @cindex unmapped overlays
13839 @cindex load address, overlay's
13840 @cindex mapped address
13841 @cindex overlay area
13843 Suppose you have a computer whose instruction address space is only 64
13844 kilobytes long, but which has much more memory which can be accessed by
13845 other means: special instructions, segment registers, or memory
13846 management hardware, for example. Suppose further that you want to
13847 adapt a program which is larger than 64 kilobytes to run on this system.
13849 One solution is to identify modules of your program which are relatively
13850 independent, and need not call each other directly; call these modules
13851 @dfn{overlays}. Separate the overlays from the main program, and place
13852 their machine code in the larger memory. Place your main program in
13853 instruction memory, but leave at least enough space there to hold the
13854 largest overlay as well.
13856 Now, to call a function located in an overlay, you must first copy that
13857 overlay's machine code from the large memory into the space set aside
13858 for it in the instruction memory, and then jump to its entry point
13861 @c NB: In the below the mapped area's size is greater or equal to the
13862 @c size of all overlays. This is intentional to remind the developer
13863 @c that overlays don't necessarily need to be the same size.
13867 Data Instruction Larger
13868 Address Space Address Space Address Space
13869 +-----------+ +-----------+ +-----------+
13871 +-----------+ +-----------+ +-----------+<-- overlay 1
13872 | program | | main | .----| overlay 1 | load address
13873 | variables | | program | | +-----------+
13874 | and heap | | | | | |
13875 +-----------+ | | | +-----------+<-- overlay 2
13876 | | +-----------+ | | | load address
13877 +-----------+ | | | .-| overlay 2 |
13879 mapped --->+-----------+ | | +-----------+
13880 address | | | | | |
13881 | overlay | <-' | | |
13882 | area | <---' +-----------+<-- overlay 3
13883 | | <---. | | load address
13884 +-----------+ `--| overlay 3 |
13891 @anchor{A code overlay}A code overlay
13895 The diagram (@pxref{A code overlay}) shows a system with separate data
13896 and instruction address spaces. To map an overlay, the program copies
13897 its code from the larger address space to the instruction address space.
13898 Since the overlays shown here all use the same mapped address, only one
13899 may be mapped at a time. For a system with a single address space for
13900 data and instructions, the diagram would be similar, except that the
13901 program variables and heap would share an address space with the main
13902 program and the overlay area.
13904 An overlay loaded into instruction memory and ready for use is called a
13905 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13906 instruction memory. An overlay not present (or only partially present)
13907 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13908 is its address in the larger memory. The mapped address is also called
13909 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13910 called the @dfn{load memory address}, or @dfn{LMA}.
13912 Unfortunately, overlays are not a completely transparent way to adapt a
13913 program to limited instruction memory. They introduce a new set of
13914 global constraints you must keep in mind as you design your program:
13919 Before calling or returning to a function in an overlay, your program
13920 must make sure that overlay is actually mapped. Otherwise, the call or
13921 return will transfer control to the right address, but in the wrong
13922 overlay, and your program will probably crash.
13925 If the process of mapping an overlay is expensive on your system, you
13926 will need to choose your overlays carefully to minimize their effect on
13927 your program's performance.
13930 The executable file you load onto your system must contain each
13931 overlay's instructions, appearing at the overlay's load address, not its
13932 mapped address. However, each overlay's instructions must be relocated
13933 and its symbols defined as if the overlay were at its mapped address.
13934 You can use GNU linker scripts to specify different load and relocation
13935 addresses for pieces of your program; see @ref{Overlay Description,,,
13936 ld.info, Using ld: the GNU linker}.
13939 The procedure for loading executable files onto your system must be able
13940 to load their contents into the larger address space as well as the
13941 instruction and data spaces.
13945 The overlay system described above is rather simple, and could be
13946 improved in many ways:
13951 If your system has suitable bank switch registers or memory management
13952 hardware, you could use those facilities to make an overlay's load area
13953 contents simply appear at their mapped address in instruction space.
13954 This would probably be faster than copying the overlay to its mapped
13955 area in the usual way.
13958 If your overlays are small enough, you could set aside more than one
13959 overlay area, and have more than one overlay mapped at a time.
13962 You can use overlays to manage data, as well as instructions. In
13963 general, data overlays are even less transparent to your design than
13964 code overlays: whereas code overlays only require care when you call or
13965 return to functions, data overlays require care every time you access
13966 the data. Also, if you change the contents of a data overlay, you
13967 must copy its contents back out to its load address before you can copy a
13968 different data overlay into the same mapped area.
13973 @node Overlay Commands
13974 @section Overlay Commands
13976 To use @value{GDBN}'s overlay support, each overlay in your program must
13977 correspond to a separate section of the executable file. The section's
13978 virtual memory address and load memory address must be the overlay's
13979 mapped and load addresses. Identifying overlays with sections allows
13980 @value{GDBN} to determine the appropriate address of a function or
13981 variable, depending on whether the overlay is mapped or not.
13983 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13984 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13989 Disable @value{GDBN}'s overlay support. When overlay support is
13990 disabled, @value{GDBN} assumes that all functions and variables are
13991 always present at their mapped addresses. By default, @value{GDBN}'s
13992 overlay support is disabled.
13994 @item overlay manual
13995 @cindex manual overlay debugging
13996 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13997 relies on you to tell it which overlays are mapped, and which are not,
13998 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13999 commands described below.
14001 @item overlay map-overlay @var{overlay}
14002 @itemx overlay map @var{overlay}
14003 @cindex map an overlay
14004 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14005 be the name of the object file section containing the overlay. When an
14006 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14007 functions and variables at their mapped addresses. @value{GDBN} assumes
14008 that any other overlays whose mapped ranges overlap that of
14009 @var{overlay} are now unmapped.
14011 @item overlay unmap-overlay @var{overlay}
14012 @itemx overlay unmap @var{overlay}
14013 @cindex unmap an overlay
14014 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14015 must be the name of the object file section containing the overlay.
14016 When an overlay is unmapped, @value{GDBN} assumes it can find the
14017 overlay's functions and variables at their load addresses.
14020 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14021 consults a data structure the overlay manager maintains in the inferior
14022 to see which overlays are mapped. For details, see @ref{Automatic
14023 Overlay Debugging}.
14025 @item overlay load-target
14026 @itemx overlay load
14027 @cindex reloading the overlay table
14028 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14029 re-reads the table @value{GDBN} automatically each time the inferior
14030 stops, so this command should only be necessary if you have changed the
14031 overlay mapping yourself using @value{GDBN}. This command is only
14032 useful when using automatic overlay debugging.
14034 @item overlay list-overlays
14035 @itemx overlay list
14036 @cindex listing mapped overlays
14037 Display a list of the overlays currently mapped, along with their mapped
14038 addresses, load addresses, and sizes.
14042 Normally, when @value{GDBN} prints a code address, it includes the name
14043 of the function the address falls in:
14046 (@value{GDBP}) print main
14047 $3 = @{int ()@} 0x11a0 <main>
14050 When overlay debugging is enabled, @value{GDBN} recognizes code in
14051 unmapped overlays, and prints the names of unmapped functions with
14052 asterisks around them. For example, if @code{foo} is a function in an
14053 unmapped overlay, @value{GDBN} prints it this way:
14056 (@value{GDBP}) overlay list
14057 No sections are mapped.
14058 (@value{GDBP}) print foo
14059 $5 = @{int (int)@} 0x100000 <*foo*>
14062 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14066 (@value{GDBP}) overlay list
14067 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14068 mapped at 0x1016 - 0x104a
14069 (@value{GDBP}) print foo
14070 $6 = @{int (int)@} 0x1016 <foo>
14073 When overlay debugging is enabled, @value{GDBN} can find the correct
14074 address for functions and variables in an overlay, whether or not the
14075 overlay is mapped. This allows most @value{GDBN} commands, like
14076 @code{break} and @code{disassemble}, to work normally, even on unmapped
14077 code. However, @value{GDBN}'s breakpoint support has some limitations:
14081 @cindex breakpoints in overlays
14082 @cindex overlays, setting breakpoints in
14083 You can set breakpoints in functions in unmapped overlays, as long as
14084 @value{GDBN} can write to the overlay at its load address.
14086 @value{GDBN} can not set hardware or simulator-based breakpoints in
14087 unmapped overlays. However, if you set a breakpoint at the end of your
14088 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14089 you are using manual overlay management), @value{GDBN} will re-set its
14090 breakpoints properly.
14094 @node Automatic Overlay Debugging
14095 @section Automatic Overlay Debugging
14096 @cindex automatic overlay debugging
14098 @value{GDBN} can automatically track which overlays are mapped and which
14099 are not, given some simple co-operation from the overlay manager in the
14100 inferior. If you enable automatic overlay debugging with the
14101 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14102 looks in the inferior's memory for certain variables describing the
14103 current state of the overlays.
14105 Here are the variables your overlay manager must define to support
14106 @value{GDBN}'s automatic overlay debugging:
14110 @item @code{_ovly_table}:
14111 This variable must be an array of the following structures:
14116 /* The overlay's mapped address. */
14119 /* The size of the overlay, in bytes. */
14120 unsigned long size;
14122 /* The overlay's load address. */
14125 /* Non-zero if the overlay is currently mapped;
14127 unsigned long mapped;
14131 @item @code{_novlys}:
14132 This variable must be a four-byte signed integer, holding the total
14133 number of elements in @code{_ovly_table}.
14137 To decide whether a particular overlay is mapped or not, @value{GDBN}
14138 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14139 @code{lma} members equal the VMA and LMA of the overlay's section in the
14140 executable file. When @value{GDBN} finds a matching entry, it consults
14141 the entry's @code{mapped} member to determine whether the overlay is
14144 In addition, your overlay manager may define a function called
14145 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14146 will silently set a breakpoint there. If the overlay manager then
14147 calls this function whenever it has changed the overlay table, this
14148 will enable @value{GDBN} to accurately keep track of which overlays
14149 are in program memory, and update any breakpoints that may be set
14150 in overlays. This will allow breakpoints to work even if the
14151 overlays are kept in ROM or other non-writable memory while they
14152 are not being executed.
14154 @node Overlay Sample Program
14155 @section Overlay Sample Program
14156 @cindex overlay example program
14158 When linking a program which uses overlays, you must place the overlays
14159 at their load addresses, while relocating them to run at their mapped
14160 addresses. To do this, you must write a linker script (@pxref{Overlay
14161 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14162 since linker scripts are specific to a particular host system, target
14163 architecture, and target memory layout, this manual cannot provide
14164 portable sample code demonstrating @value{GDBN}'s overlay support.
14166 However, the @value{GDBN} source distribution does contain an overlaid
14167 program, with linker scripts for a few systems, as part of its test
14168 suite. The program consists of the following files from
14169 @file{gdb/testsuite/gdb.base}:
14173 The main program file.
14175 A simple overlay manager, used by @file{overlays.c}.
14180 Overlay modules, loaded and used by @file{overlays.c}.
14183 Linker scripts for linking the test program on the @code{d10v-elf}
14184 and @code{m32r-elf} targets.
14187 You can build the test program using the @code{d10v-elf} GCC
14188 cross-compiler like this:
14191 $ d10v-elf-gcc -g -c overlays.c
14192 $ d10v-elf-gcc -g -c ovlymgr.c
14193 $ d10v-elf-gcc -g -c foo.c
14194 $ d10v-elf-gcc -g -c bar.c
14195 $ d10v-elf-gcc -g -c baz.c
14196 $ d10v-elf-gcc -g -c grbx.c
14197 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14198 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14201 The build process is identical for any other architecture, except that
14202 you must substitute the appropriate compiler and linker script for the
14203 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14207 @chapter Using @value{GDBN} with Different Languages
14210 Although programming languages generally have common aspects, they are
14211 rarely expressed in the same manner. For instance, in ANSI C,
14212 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14213 Modula-2, it is accomplished by @code{p^}. Values can also be
14214 represented (and displayed) differently. Hex numbers in C appear as
14215 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14217 @cindex working language
14218 Language-specific information is built into @value{GDBN} for some languages,
14219 allowing you to express operations like the above in your program's
14220 native language, and allowing @value{GDBN} to output values in a manner
14221 consistent with the syntax of your program's native language. The
14222 language you use to build expressions is called the @dfn{working
14226 * Setting:: Switching between source languages
14227 * Show:: Displaying the language
14228 * Checks:: Type and range checks
14229 * Supported Languages:: Supported languages
14230 * Unsupported Languages:: Unsupported languages
14234 @section Switching Between Source Languages
14236 There are two ways to control the working language---either have @value{GDBN}
14237 set it automatically, or select it manually yourself. You can use the
14238 @code{set language} command for either purpose. On startup, @value{GDBN}
14239 defaults to setting the language automatically. The working language is
14240 used to determine how expressions you type are interpreted, how values
14243 In addition to the working language, every source file that
14244 @value{GDBN} knows about has its own working language. For some object
14245 file formats, the compiler might indicate which language a particular
14246 source file is in. However, most of the time @value{GDBN} infers the
14247 language from the name of the file. The language of a source file
14248 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14249 show each frame appropriately for its own language. There is no way to
14250 set the language of a source file from within @value{GDBN}, but you can
14251 set the language associated with a filename extension. @xref{Show, ,
14252 Displaying the Language}.
14254 This is most commonly a problem when you use a program, such
14255 as @code{cfront} or @code{f2c}, that generates C but is written in
14256 another language. In that case, make the
14257 program use @code{#line} directives in its C output; that way
14258 @value{GDBN} will know the correct language of the source code of the original
14259 program, and will display that source code, not the generated C code.
14262 * Filenames:: Filename extensions and languages.
14263 * Manually:: Setting the working language manually
14264 * Automatically:: Having @value{GDBN} infer the source language
14268 @subsection List of Filename Extensions and Languages
14270 If a source file name ends in one of the following extensions, then
14271 @value{GDBN} infers that its language is the one indicated.
14289 C@t{++} source file
14295 Objective-C source file
14299 Fortran source file
14302 Modula-2 source file
14306 Assembler source file. This actually behaves almost like C, but
14307 @value{GDBN} does not skip over function prologues when stepping.
14310 In addition, you may set the language associated with a filename
14311 extension. @xref{Show, , Displaying the Language}.
14314 @subsection Setting the Working Language
14316 If you allow @value{GDBN} to set the language automatically,
14317 expressions are interpreted the same way in your debugging session and
14320 @kindex set language
14321 If you wish, you may set the language manually. To do this, issue the
14322 command @samp{set language @var{lang}}, where @var{lang} is the name of
14323 a language, such as
14324 @code{c} or @code{modula-2}.
14325 For a list of the supported languages, type @samp{set language}.
14327 Setting the language manually prevents @value{GDBN} from updating the working
14328 language automatically. This can lead to confusion if you try
14329 to debug a program when the working language is not the same as the
14330 source language, when an expression is acceptable to both
14331 languages---but means different things. For instance, if the current
14332 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14340 might not have the effect you intended. In C, this means to add
14341 @code{b} and @code{c} and place the result in @code{a}. The result
14342 printed would be the value of @code{a}. In Modula-2, this means to compare
14343 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14345 @node Automatically
14346 @subsection Having @value{GDBN} Infer the Source Language
14348 To have @value{GDBN} set the working language automatically, use
14349 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14350 then infers the working language. That is, when your program stops in a
14351 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14352 working language to the language recorded for the function in that
14353 frame. If the language for a frame is unknown (that is, if the function
14354 or block corresponding to the frame was defined in a source file that
14355 does not have a recognized extension), the current working language is
14356 not changed, and @value{GDBN} issues a warning.
14358 This may not seem necessary for most programs, which are written
14359 entirely in one source language. However, program modules and libraries
14360 written in one source language can be used by a main program written in
14361 a different source language. Using @samp{set language auto} in this
14362 case frees you from having to set the working language manually.
14365 @section Displaying the Language
14367 The following commands help you find out which language is the
14368 working language, and also what language source files were written in.
14371 @item show language
14372 @anchor{show language}
14373 @kindex show language
14374 Display the current working language. This is the
14375 language you can use with commands such as @code{print} to
14376 build and compute expressions that may involve variables in your program.
14379 @kindex info frame@r{, show the source language}
14380 Display the source language for this frame. This language becomes the
14381 working language if you use an identifier from this frame.
14382 @xref{Frame Info, ,Information about a Frame}, to identify the other
14383 information listed here.
14386 @kindex info source@r{, show the source language}
14387 Display the source language of this source file.
14388 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14389 information listed here.
14392 In unusual circumstances, you may have source files with extensions
14393 not in the standard list. You can then set the extension associated
14394 with a language explicitly:
14397 @item set extension-language @var{ext} @var{language}
14398 @kindex set extension-language
14399 Tell @value{GDBN} that source files with extension @var{ext} are to be
14400 assumed as written in the source language @var{language}.
14402 @item info extensions
14403 @kindex info extensions
14404 List all the filename extensions and the associated languages.
14408 @section Type and Range Checking
14410 Some languages are designed to guard you against making seemingly common
14411 errors through a series of compile- and run-time checks. These include
14412 checking the type of arguments to functions and operators and making
14413 sure mathematical overflows are caught at run time. Checks such as
14414 these help to ensure a program's correctness once it has been compiled
14415 by eliminating type mismatches and providing active checks for range
14416 errors when your program is running.
14418 By default @value{GDBN} checks for these errors according to the
14419 rules of the current source language. Although @value{GDBN} does not check
14420 the statements in your program, it can check expressions entered directly
14421 into @value{GDBN} for evaluation via the @code{print} command, for example.
14424 * Type Checking:: An overview of type checking
14425 * Range Checking:: An overview of range checking
14428 @cindex type checking
14429 @cindex checks, type
14430 @node Type Checking
14431 @subsection An Overview of Type Checking
14433 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14434 arguments to operators and functions have to be of the correct type,
14435 otherwise an error occurs. These checks prevent type mismatch
14436 errors from ever causing any run-time problems. For example,
14439 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14441 (@value{GDBP}) print obj.my_method (0)
14444 (@value{GDBP}) print obj.my_method (0x1234)
14445 Cannot resolve method klass::my_method to any overloaded instance
14448 The second example fails because in C@t{++} the integer constant
14449 @samp{0x1234} is not type-compatible with the pointer parameter type.
14451 For the expressions you use in @value{GDBN} commands, you can tell
14452 @value{GDBN} to not enforce strict type checking or
14453 to treat any mismatches as errors and abandon the expression;
14454 When type checking is disabled, @value{GDBN} successfully evaluates
14455 expressions like the second example above.
14457 Even if type checking is off, there may be other reasons
14458 related to type that prevent @value{GDBN} from evaluating an expression.
14459 For instance, @value{GDBN} does not know how to add an @code{int} and
14460 a @code{struct foo}. These particular type errors have nothing to do
14461 with the language in use and usually arise from expressions which make
14462 little sense to evaluate anyway.
14464 @value{GDBN} provides some additional commands for controlling type checking:
14466 @kindex set check type
14467 @kindex show check type
14469 @item set check type on
14470 @itemx set check type off
14471 Set strict type checking on or off. If any type mismatches occur in
14472 evaluating an expression while type checking is on, @value{GDBN} prints a
14473 message and aborts evaluation of the expression.
14475 @item show check type
14476 Show the current setting of type checking and whether @value{GDBN}
14477 is enforcing strict type checking rules.
14480 @cindex range checking
14481 @cindex checks, range
14482 @node Range Checking
14483 @subsection An Overview of Range Checking
14485 In some languages (such as Modula-2), it is an error to exceed the
14486 bounds of a type; this is enforced with run-time checks. Such range
14487 checking is meant to ensure program correctness by making sure
14488 computations do not overflow, or indices on an array element access do
14489 not exceed the bounds of the array.
14491 For expressions you use in @value{GDBN} commands, you can tell
14492 @value{GDBN} to treat range errors in one of three ways: ignore them,
14493 always treat them as errors and abandon the expression, or issue
14494 warnings but evaluate the expression anyway.
14496 A range error can result from numerical overflow, from exceeding an
14497 array index bound, or when you type a constant that is not a member
14498 of any type. Some languages, however, do not treat overflows as an
14499 error. In many implementations of C, mathematical overflow causes the
14500 result to ``wrap around'' to lower values---for example, if @var{m} is
14501 the largest integer value, and @var{s} is the smallest, then
14504 @var{m} + 1 @result{} @var{s}
14507 This, too, is specific to individual languages, and in some cases
14508 specific to individual compilers or machines. @xref{Supported Languages, ,
14509 Supported Languages}, for further details on specific languages.
14511 @value{GDBN} provides some additional commands for controlling the range checker:
14513 @kindex set check range
14514 @kindex show check range
14516 @item set check range auto
14517 Set range checking on or off based on the current working language.
14518 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14521 @item set check range on
14522 @itemx set check range off
14523 Set range checking on or off, overriding the default setting for the
14524 current working language. A warning is issued if the setting does not
14525 match the language default. If a range error occurs and range checking is on,
14526 then a message is printed and evaluation of the expression is aborted.
14528 @item set check range warn
14529 Output messages when the @value{GDBN} range checker detects a range error,
14530 but attempt to evaluate the expression anyway. Evaluating the
14531 expression may still be impossible for other reasons, such as accessing
14532 memory that the process does not own (a typical example from many Unix
14536 Show the current setting of the range checker, and whether or not it is
14537 being set automatically by @value{GDBN}.
14540 @node Supported Languages
14541 @section Supported Languages
14543 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14544 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14545 @c This is false ...
14546 Some @value{GDBN} features may be used in expressions regardless of the
14547 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14548 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14549 ,Expressions}) can be used with the constructs of any supported
14552 The following sections detail to what degree each source language is
14553 supported by @value{GDBN}. These sections are not meant to be language
14554 tutorials or references, but serve only as a reference guide to what the
14555 @value{GDBN} expression parser accepts, and what input and output
14556 formats should look like for different languages. There are many good
14557 books written on each of these languages; please look to these for a
14558 language reference or tutorial.
14561 * C:: C and C@t{++}
14564 * Objective-C:: Objective-C
14565 * OpenCL C:: OpenCL C
14566 * Fortran:: Fortran
14569 * Modula-2:: Modula-2
14574 @subsection C and C@t{++}
14576 @cindex C and C@t{++}
14577 @cindex expressions in C or C@t{++}
14579 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14580 to both languages. Whenever this is the case, we discuss those languages
14584 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14585 @cindex @sc{gnu} C@t{++}
14586 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14587 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14588 effectively, you must compile your C@t{++} programs with a supported
14589 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14590 compiler (@code{aCC}).
14593 * C Operators:: C and C@t{++} operators
14594 * C Constants:: C and C@t{++} constants
14595 * C Plus Plus Expressions:: C@t{++} expressions
14596 * C Defaults:: Default settings for C and C@t{++}
14597 * C Checks:: C and C@t{++} type and range checks
14598 * Debugging C:: @value{GDBN} and C
14599 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14600 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14604 @subsubsection C and C@t{++} Operators
14606 @cindex C and C@t{++} operators
14608 Operators must be defined on values of specific types. For instance,
14609 @code{+} is defined on numbers, but not on structures. Operators are
14610 often defined on groups of types.
14612 For the purposes of C and C@t{++}, the following definitions hold:
14617 @emph{Integral types} include @code{int} with any of its storage-class
14618 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14621 @emph{Floating-point types} include @code{float}, @code{double}, and
14622 @code{long double} (if supported by the target platform).
14625 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14628 @emph{Scalar types} include all of the above.
14633 The following operators are supported. They are listed here
14634 in order of increasing precedence:
14638 The comma or sequencing operator. Expressions in a comma-separated list
14639 are evaluated from left to right, with the result of the entire
14640 expression being the last expression evaluated.
14643 Assignment. The value of an assignment expression is the value
14644 assigned. Defined on scalar types.
14647 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14648 and translated to @w{@code{@var{a} = @var{a op b}}}.
14649 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14650 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14651 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14654 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14655 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14656 should be of an integral type.
14659 Logical @sc{or}. Defined on integral types.
14662 Logical @sc{and}. Defined on integral types.
14665 Bitwise @sc{or}. Defined on integral types.
14668 Bitwise exclusive-@sc{or}. Defined on integral types.
14671 Bitwise @sc{and}. Defined on integral types.
14674 Equality and inequality. Defined on scalar types. The value of these
14675 expressions is 0 for false and non-zero for true.
14677 @item <@r{, }>@r{, }<=@r{, }>=
14678 Less than, greater than, less than or equal, greater than or equal.
14679 Defined on scalar types. The value of these expressions is 0 for false
14680 and non-zero for true.
14683 left shift, and right shift. Defined on integral types.
14686 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14689 Addition and subtraction. Defined on integral types, floating-point types and
14692 @item *@r{, }/@r{, }%
14693 Multiplication, division, and modulus. Multiplication and division are
14694 defined on integral and floating-point types. Modulus is defined on
14698 Increment and decrement. When appearing before a variable, the
14699 operation is performed before the variable is used in an expression;
14700 when appearing after it, the variable's value is used before the
14701 operation takes place.
14704 Pointer dereferencing. Defined on pointer types. Same precedence as
14708 Address operator. Defined on variables. Same precedence as @code{++}.
14710 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14711 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14712 to examine the address
14713 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14717 Negative. Defined on integral and floating-point types. Same
14718 precedence as @code{++}.
14721 Logical negation. Defined on integral types. Same precedence as
14725 Bitwise complement operator. Defined on integral types. Same precedence as
14730 Structure member, and pointer-to-structure member. For convenience,
14731 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14732 pointer based on the stored type information.
14733 Defined on @code{struct} and @code{union} data.
14736 Dereferences of pointers to members.
14739 Array indexing. @code{@var{a}[@var{i}]} is defined as
14740 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14743 Function parameter list. Same precedence as @code{->}.
14746 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14747 and @code{class} types.
14750 Doubled colons also represent the @value{GDBN} scope operator
14751 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14755 If an operator is redefined in the user code, @value{GDBN} usually
14756 attempts to invoke the redefined version instead of using the operator's
14757 predefined meaning.
14760 @subsubsection C and C@t{++} Constants
14762 @cindex C and C@t{++} constants
14764 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14769 Integer constants are a sequence of digits. Octal constants are
14770 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14771 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14772 @samp{l}, specifying that the constant should be treated as a
14776 Floating point constants are a sequence of digits, followed by a decimal
14777 point, followed by a sequence of digits, and optionally followed by an
14778 exponent. An exponent is of the form:
14779 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14780 sequence of digits. The @samp{+} is optional for positive exponents.
14781 A floating-point constant may also end with a letter @samp{f} or
14782 @samp{F}, specifying that the constant should be treated as being of
14783 the @code{float} (as opposed to the default @code{double}) type; or with
14784 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14788 Enumerated constants consist of enumerated identifiers, or their
14789 integral equivalents.
14792 Character constants are a single character surrounded by single quotes
14793 (@code{'}), or a number---the ordinal value of the corresponding character
14794 (usually its @sc{ascii} value). Within quotes, the single character may
14795 be represented by a letter or by @dfn{escape sequences}, which are of
14796 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14797 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14798 @samp{@var{x}} is a predefined special character---for example,
14799 @samp{\n} for newline.
14801 Wide character constants can be written by prefixing a character
14802 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14803 form of @samp{x}. The target wide character set is used when
14804 computing the value of this constant (@pxref{Character Sets}).
14807 String constants are a sequence of character constants surrounded by
14808 double quotes (@code{"}). Any valid character constant (as described
14809 above) may appear. Double quotes within the string must be preceded by
14810 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14813 Wide string constants can be written by prefixing a string constant
14814 with @samp{L}, as in C. The target wide character set is used when
14815 computing the value of this constant (@pxref{Character Sets}).
14818 Pointer constants are an integral value. You can also write pointers
14819 to constants using the C operator @samp{&}.
14822 Array constants are comma-separated lists surrounded by braces @samp{@{}
14823 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14824 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14825 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14828 @node C Plus Plus Expressions
14829 @subsubsection C@t{++} Expressions
14831 @cindex expressions in C@t{++}
14832 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14834 @cindex debugging C@t{++} programs
14835 @cindex C@t{++} compilers
14836 @cindex debug formats and C@t{++}
14837 @cindex @value{NGCC} and C@t{++}
14839 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14840 the proper compiler and the proper debug format. Currently,
14841 @value{GDBN} works best when debugging C@t{++} code that is compiled
14842 with the most recent version of @value{NGCC} possible. The DWARF
14843 debugging format is preferred; @value{NGCC} defaults to this on most
14844 popular platforms. Other compilers and/or debug formats are likely to
14845 work badly or not at all when using @value{GDBN} to debug C@t{++}
14846 code. @xref{Compilation}.
14851 @cindex member functions
14853 Member function calls are allowed; you can use expressions like
14856 count = aml->GetOriginal(x, y)
14859 @vindex this@r{, inside C@t{++} member functions}
14860 @cindex namespace in C@t{++}
14862 While a member function is active (in the selected stack frame), your
14863 expressions have the same namespace available as the member function;
14864 that is, @value{GDBN} allows implicit references to the class instance
14865 pointer @code{this} following the same rules as C@t{++}. @code{using}
14866 declarations in the current scope are also respected by @value{GDBN}.
14868 @cindex call overloaded functions
14869 @cindex overloaded functions, calling
14870 @cindex type conversions in C@t{++}
14872 You can call overloaded functions; @value{GDBN} resolves the function
14873 call to the right definition, with some restrictions. @value{GDBN} does not
14874 perform overload resolution involving user-defined type conversions,
14875 calls to constructors, or instantiations of templates that do not exist
14876 in the program. It also cannot handle ellipsis argument lists or
14879 It does perform integral conversions and promotions, floating-point
14880 promotions, arithmetic conversions, pointer conversions, conversions of
14881 class objects to base classes, and standard conversions such as those of
14882 functions or arrays to pointers; it requires an exact match on the
14883 number of function arguments.
14885 Overload resolution is always performed, unless you have specified
14886 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14887 ,@value{GDBN} Features for C@t{++}}.
14889 You must specify @code{set overload-resolution off} in order to use an
14890 explicit function signature to call an overloaded function, as in
14892 p 'foo(char,int)'('x', 13)
14895 The @value{GDBN} command-completion facility can simplify this;
14896 see @ref{Completion, ,Command Completion}.
14898 @cindex reference declarations
14900 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14901 references; you can use them in expressions just as you do in C@t{++}
14902 source---they are automatically dereferenced.
14904 In the parameter list shown when @value{GDBN} displays a frame, the values of
14905 reference variables are not displayed (unlike other variables); this
14906 avoids clutter, since references are often used for large structures.
14907 The @emph{address} of a reference variable is always shown, unless
14908 you have specified @samp{set print address off}.
14911 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14912 expressions can use it just as expressions in your program do. Since
14913 one scope may be defined in another, you can use @code{::} repeatedly if
14914 necessary, for example in an expression like
14915 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14916 resolving name scope by reference to source files, in both C and C@t{++}
14917 debugging (@pxref{Variables, ,Program Variables}).
14920 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14925 @subsubsection C and C@t{++} Defaults
14927 @cindex C and C@t{++} defaults
14929 If you allow @value{GDBN} to set range checking automatically, it
14930 defaults to @code{off} whenever the working language changes to
14931 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14932 selects the working language.
14934 If you allow @value{GDBN} to set the language automatically, it
14935 recognizes source files whose names end with @file{.c}, @file{.C}, or
14936 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14937 these files, it sets the working language to C or C@t{++}.
14938 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14939 for further details.
14942 @subsubsection C and C@t{++} Type and Range Checks
14944 @cindex C and C@t{++} checks
14946 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14947 checking is used. However, if you turn type checking off, @value{GDBN}
14948 will allow certain non-standard conversions, such as promoting integer
14949 constants to pointers.
14951 Range checking, if turned on, is done on mathematical operations. Array
14952 indices are not checked, since they are often used to index a pointer
14953 that is not itself an array.
14956 @subsubsection @value{GDBN} and C
14958 The @code{set print union} and @code{show print union} commands apply to
14959 the @code{union} type. When set to @samp{on}, any @code{union} that is
14960 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14961 appears as @samp{@{...@}}.
14963 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14964 with pointers and a memory allocation function. @xref{Expressions,
14967 @node Debugging C Plus Plus
14968 @subsubsection @value{GDBN} Features for C@t{++}
14970 @cindex commands for C@t{++}
14972 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14973 designed specifically for use with C@t{++}. Here is a summary:
14976 @cindex break in overloaded functions
14977 @item @r{breakpoint menus}
14978 When you want a breakpoint in a function whose name is overloaded,
14979 @value{GDBN} has the capability to display a menu of possible breakpoint
14980 locations to help you specify which function definition you want.
14981 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14983 @cindex overloading in C@t{++}
14984 @item rbreak @var{regex}
14985 Setting breakpoints using regular expressions is helpful for setting
14986 breakpoints on overloaded functions that are not members of any special
14988 @xref{Set Breaks, ,Setting Breakpoints}.
14990 @cindex C@t{++} exception handling
14992 @itemx catch rethrow
14994 Debug C@t{++} exception handling using these commands. @xref{Set
14995 Catchpoints, , Setting Catchpoints}.
14997 @cindex inheritance
14998 @item ptype @var{typename}
14999 Print inheritance relationships as well as other information for type
15001 @xref{Symbols, ,Examining the Symbol Table}.
15003 @item info vtbl @var{expression}.
15004 The @code{info vtbl} command can be used to display the virtual
15005 method tables of the object computed by @var{expression}. This shows
15006 one entry per virtual table; there may be multiple virtual tables when
15007 multiple inheritance is in use.
15009 @cindex C@t{++} demangling
15010 @item demangle @var{name}
15011 Demangle @var{name}.
15012 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15014 @cindex C@t{++} symbol display
15015 @item set print demangle
15016 @itemx show print demangle
15017 @itemx set print asm-demangle
15018 @itemx show print asm-demangle
15019 Control whether C@t{++} symbols display in their source form, both when
15020 displaying code as C@t{++} source and when displaying disassemblies.
15021 @xref{Print Settings, ,Print Settings}.
15023 @item set print object
15024 @itemx show print object
15025 Choose whether to print derived (actual) or declared types of objects.
15026 @xref{Print Settings, ,Print Settings}.
15028 @item set print vtbl
15029 @itemx show print vtbl
15030 Control the format for printing virtual function tables.
15031 @xref{Print Settings, ,Print Settings}.
15032 (The @code{vtbl} commands do not work on programs compiled with the HP
15033 ANSI C@t{++} compiler (@code{aCC}).)
15035 @kindex set overload-resolution
15036 @cindex overloaded functions, overload resolution
15037 @item set overload-resolution on
15038 Enable overload resolution for C@t{++} expression evaluation. The default
15039 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15040 and searches for a function whose signature matches the argument types,
15041 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15042 Expressions, ,C@t{++} Expressions}, for details).
15043 If it cannot find a match, it emits a message.
15045 @item set overload-resolution off
15046 Disable overload resolution for C@t{++} expression evaluation. For
15047 overloaded functions that are not class member functions, @value{GDBN}
15048 chooses the first function of the specified name that it finds in the
15049 symbol table, whether or not its arguments are of the correct type. For
15050 overloaded functions that are class member functions, @value{GDBN}
15051 searches for a function whose signature @emph{exactly} matches the
15054 @kindex show overload-resolution
15055 @item show overload-resolution
15056 Show the current setting of overload resolution.
15058 @item @r{Overloaded symbol names}
15059 You can specify a particular definition of an overloaded symbol, using
15060 the same notation that is used to declare such symbols in C@t{++}: type
15061 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15062 also use the @value{GDBN} command-line word completion facilities to list the
15063 available choices, or to finish the type list for you.
15064 @xref{Completion,, Command Completion}, for details on how to do this.
15067 @node Decimal Floating Point
15068 @subsubsection Decimal Floating Point format
15069 @cindex decimal floating point format
15071 @value{GDBN} can examine, set and perform computations with numbers in
15072 decimal floating point format, which in the C language correspond to the
15073 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15074 specified by the extension to support decimal floating-point arithmetic.
15076 There are two encodings in use, depending on the architecture: BID (Binary
15077 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15078 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15081 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15082 to manipulate decimal floating point numbers, it is not possible to convert
15083 (using a cast, for example) integers wider than 32-bit to decimal float.
15085 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15086 point computations, error checking in decimal float operations ignores
15087 underflow, overflow and divide by zero exceptions.
15089 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15090 to inspect @code{_Decimal128} values stored in floating point registers.
15091 See @ref{PowerPC,,PowerPC} for more details.
15097 @value{GDBN} can be used to debug programs written in D and compiled with
15098 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15099 specific feature --- dynamic arrays.
15104 @cindex Go (programming language)
15105 @value{GDBN} can be used to debug programs written in Go and compiled with
15106 @file{gccgo} or @file{6g} compilers.
15108 Here is a summary of the Go-specific features and restrictions:
15111 @cindex current Go package
15112 @item The current Go package
15113 The name of the current package does not need to be specified when
15114 specifying global variables and functions.
15116 For example, given the program:
15120 var myglob = "Shall we?"
15126 When stopped inside @code{main} either of these work:
15130 (gdb) p main.myglob
15133 @cindex builtin Go types
15134 @item Builtin Go types
15135 The @code{string} type is recognized by @value{GDBN} and is printed
15138 @cindex builtin Go functions
15139 @item Builtin Go functions
15140 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15141 function and handles it internally.
15143 @cindex restrictions on Go expressions
15144 @item Restrictions on Go expressions
15145 All Go operators are supported except @code{&^}.
15146 The Go @code{_} ``blank identifier'' is not supported.
15147 Automatic dereferencing of pointers is not supported.
15151 @subsection Objective-C
15153 @cindex Objective-C
15154 This section provides information about some commands and command
15155 options that are useful for debugging Objective-C code. See also
15156 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15157 few more commands specific to Objective-C support.
15160 * Method Names in Commands::
15161 * The Print Command with Objective-C::
15164 @node Method Names in Commands
15165 @subsubsection Method Names in Commands
15167 The following commands have been extended to accept Objective-C method
15168 names as line specifications:
15170 @kindex clear@r{, and Objective-C}
15171 @kindex break@r{, and Objective-C}
15172 @kindex info line@r{, and Objective-C}
15173 @kindex jump@r{, and Objective-C}
15174 @kindex list@r{, and Objective-C}
15178 @item @code{info line}
15183 A fully qualified Objective-C method name is specified as
15186 -[@var{Class} @var{methodName}]
15189 where the minus sign is used to indicate an instance method and a
15190 plus sign (not shown) is used to indicate a class method. The class
15191 name @var{Class} and method name @var{methodName} are enclosed in
15192 brackets, similar to the way messages are specified in Objective-C
15193 source code. For example, to set a breakpoint at the @code{create}
15194 instance method of class @code{Fruit} in the program currently being
15198 break -[Fruit create]
15201 To list ten program lines around the @code{initialize} class method,
15205 list +[NSText initialize]
15208 In the current version of @value{GDBN}, the plus or minus sign is
15209 required. In future versions of @value{GDBN}, the plus or minus
15210 sign will be optional, but you can use it to narrow the search. It
15211 is also possible to specify just a method name:
15217 You must specify the complete method name, including any colons. If
15218 your program's source files contain more than one @code{create} method,
15219 you'll be presented with a numbered list of classes that implement that
15220 method. Indicate your choice by number, or type @samp{0} to exit if
15223 As another example, to clear a breakpoint established at the
15224 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15227 clear -[NSWindow makeKeyAndOrderFront:]
15230 @node The Print Command with Objective-C
15231 @subsubsection The Print Command With Objective-C
15232 @cindex Objective-C, print objects
15233 @kindex print-object
15234 @kindex po @r{(@code{print-object})}
15236 The print command has also been extended to accept methods. For example:
15239 print -[@var{object} hash]
15242 @cindex print an Objective-C object description
15243 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15245 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15246 and print the result. Also, an additional command has been added,
15247 @code{print-object} or @code{po} for short, which is meant to print
15248 the description of an object. However, this command may only work
15249 with certain Objective-C libraries that have a particular hook
15250 function, @code{_NSPrintForDebugger}, defined.
15253 @subsection OpenCL C
15256 This section provides information about @value{GDBN}s OpenCL C support.
15259 * OpenCL C Datatypes::
15260 * OpenCL C Expressions::
15261 * OpenCL C Operators::
15264 @node OpenCL C Datatypes
15265 @subsubsection OpenCL C Datatypes
15267 @cindex OpenCL C Datatypes
15268 @value{GDBN} supports the builtin scalar and vector datatypes specified
15269 by OpenCL 1.1. In addition the half- and double-precision floating point
15270 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15271 extensions are also known to @value{GDBN}.
15273 @node OpenCL C Expressions
15274 @subsubsection OpenCL C Expressions
15276 @cindex OpenCL C Expressions
15277 @value{GDBN} supports accesses to vector components including the access as
15278 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15279 supported by @value{GDBN} can be used as well.
15281 @node OpenCL C Operators
15282 @subsubsection OpenCL C Operators
15284 @cindex OpenCL C Operators
15285 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15289 @subsection Fortran
15290 @cindex Fortran-specific support in @value{GDBN}
15292 @value{GDBN} can be used to debug programs written in Fortran, but it
15293 currently supports only the features of Fortran 77 language.
15295 @cindex trailing underscore, in Fortran symbols
15296 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15297 among them) append an underscore to the names of variables and
15298 functions. When you debug programs compiled by those compilers, you
15299 will need to refer to variables and functions with a trailing
15303 * Fortran Operators:: Fortran operators and expressions
15304 * Fortran Defaults:: Default settings for Fortran
15305 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15308 @node Fortran Operators
15309 @subsubsection Fortran Operators and Expressions
15311 @cindex Fortran operators and expressions
15313 Operators must be defined on values of specific types. For instance,
15314 @code{+} is defined on numbers, but not on characters or other non-
15315 arithmetic types. Operators are often defined on groups of types.
15319 The exponentiation operator. It raises the first operand to the power
15323 The range operator. Normally used in the form of array(low:high) to
15324 represent a section of array.
15327 The access component operator. Normally used to access elements in derived
15328 types. Also suitable for unions. As unions aren't part of regular Fortran,
15329 this can only happen when accessing a register that uses a gdbarch-defined
15333 @node Fortran Defaults
15334 @subsubsection Fortran Defaults
15336 @cindex Fortran Defaults
15338 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15339 default uses case-insensitive matches for Fortran symbols. You can
15340 change that with the @samp{set case-insensitive} command, see
15341 @ref{Symbols}, for the details.
15343 @node Special Fortran Commands
15344 @subsubsection Special Fortran Commands
15346 @cindex Special Fortran commands
15348 @value{GDBN} has some commands to support Fortran-specific features,
15349 such as displaying common blocks.
15352 @cindex @code{COMMON} blocks, Fortran
15353 @kindex info common
15354 @item info common @r{[}@var{common-name}@r{]}
15355 This command prints the values contained in the Fortran @code{COMMON}
15356 block whose name is @var{common-name}. With no argument, the names of
15357 all @code{COMMON} blocks visible at the current program location are
15364 @cindex Pascal support in @value{GDBN}, limitations
15365 Debugging Pascal programs which use sets, subranges, file variables, or
15366 nested functions does not currently work. @value{GDBN} does not support
15367 entering expressions, printing values, or similar features using Pascal
15370 The Pascal-specific command @code{set print pascal_static-members}
15371 controls whether static members of Pascal objects are displayed.
15372 @xref{Print Settings, pascal_static-members}.
15377 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15378 Programming Language}. Type- and value-printing, and expression
15379 parsing, are reasonably complete. However, there are a few
15380 peculiarities and holes to be aware of.
15384 Linespecs (@pxref{Specify Location}) are never relative to the current
15385 crate. Instead, they act as if there were a global namespace of
15386 crates, somewhat similar to the way @code{extern crate} behaves.
15388 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15389 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15390 to set a breakpoint in a function named @samp{f} in a crate named
15393 As a consequence of this approach, linespecs also cannot refer to
15394 items using @samp{self::} or @samp{super::}.
15397 Because @value{GDBN} implements Rust name-lookup semantics in
15398 expressions, it will sometimes prepend the current crate to a name.
15399 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15400 @samp{K}, then @code{print ::x::y} will try to find the symbol
15403 However, since it is useful to be able to refer to other crates when
15404 debugging, @value{GDBN} provides the @code{extern} extension to
15405 circumvent this. To use the extension, just put @code{extern} before
15406 a path expression to refer to the otherwise unavailable ``global''
15409 In the above example, if you wanted to refer to the symbol @samp{y} in
15410 the crate @samp{x}, you would use @code{print extern x::y}.
15413 The Rust expression evaluator does not support ``statement-like''
15414 expressions such as @code{if} or @code{match}, or lambda expressions.
15417 Tuple expressions are not implemented.
15420 The Rust expression evaluator does not currently implement the
15421 @code{Drop} trait. Objects that may be created by the evaluator will
15422 never be destroyed.
15425 @value{GDBN} does not implement type inference for generics. In order
15426 to call generic functions or otherwise refer to generic items, you
15427 will have to specify the type parameters manually.
15430 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15431 cases this does not cause any problems. However, in an expression
15432 context, completing a generic function name will give syntactically
15433 invalid results. This happens because Rust requires the @samp{::}
15434 operator between the function name and its generic arguments. For
15435 example, @value{GDBN} might provide a completion like
15436 @code{crate::f<u32>}, where the parser would require
15437 @code{crate::f::<u32>}.
15440 As of this writing, the Rust compiler (version 1.8) has a few holes in
15441 the debugging information it generates. These holes prevent certain
15442 features from being implemented by @value{GDBN}:
15446 Method calls cannot be made via traits.
15449 Trait objects cannot be created or inspected.
15452 Operator overloading is not implemented.
15455 When debugging in a monomorphized function, you cannot use the generic
15459 The type @code{Self} is not available.
15462 @code{use} statements are not available, so some names may not be
15463 available in the crate.
15468 @subsection Modula-2
15470 @cindex Modula-2, @value{GDBN} support
15472 The extensions made to @value{GDBN} to support Modula-2 only support
15473 output from the @sc{gnu} Modula-2 compiler (which is currently being
15474 developed). Other Modula-2 compilers are not currently supported, and
15475 attempting to debug executables produced by them is most likely
15476 to give an error as @value{GDBN} reads in the executable's symbol
15479 @cindex expressions in Modula-2
15481 * M2 Operators:: Built-in operators
15482 * Built-In Func/Proc:: Built-in functions and procedures
15483 * M2 Constants:: Modula-2 constants
15484 * M2 Types:: Modula-2 types
15485 * M2 Defaults:: Default settings for Modula-2
15486 * Deviations:: Deviations from standard Modula-2
15487 * M2 Checks:: Modula-2 type and range checks
15488 * M2 Scope:: The scope operators @code{::} and @code{.}
15489 * GDB/M2:: @value{GDBN} and Modula-2
15493 @subsubsection Operators
15494 @cindex Modula-2 operators
15496 Operators must be defined on values of specific types. For instance,
15497 @code{+} is defined on numbers, but not on structures. Operators are
15498 often defined on groups of types. For the purposes of Modula-2, the
15499 following definitions hold:
15504 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15508 @emph{Character types} consist of @code{CHAR} and its subranges.
15511 @emph{Floating-point types} consist of @code{REAL}.
15514 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15518 @emph{Scalar types} consist of all of the above.
15521 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15524 @emph{Boolean types} consist of @code{BOOLEAN}.
15528 The following operators are supported, and appear in order of
15529 increasing precedence:
15533 Function argument or array index separator.
15536 Assignment. The value of @var{var} @code{:=} @var{value} is
15540 Less than, greater than on integral, floating-point, or enumerated
15544 Less than or equal to, greater than or equal to
15545 on integral, floating-point and enumerated types, or set inclusion on
15546 set types. Same precedence as @code{<}.
15548 @item =@r{, }<>@r{, }#
15549 Equality and two ways of expressing inequality, valid on scalar types.
15550 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15551 available for inequality, since @code{#} conflicts with the script
15555 Set membership. Defined on set types and the types of their members.
15556 Same precedence as @code{<}.
15559 Boolean disjunction. Defined on boolean types.
15562 Boolean conjunction. Defined on boolean types.
15565 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15568 Addition and subtraction on integral and floating-point types, or union
15569 and difference on set types.
15572 Multiplication on integral and floating-point types, or set intersection
15576 Division on floating-point types, or symmetric set difference on set
15577 types. Same precedence as @code{*}.
15580 Integer division and remainder. Defined on integral types. Same
15581 precedence as @code{*}.
15584 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15587 Pointer dereferencing. Defined on pointer types.
15590 Boolean negation. Defined on boolean types. Same precedence as
15594 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15595 precedence as @code{^}.
15598 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15601 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15605 @value{GDBN} and Modula-2 scope operators.
15609 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15610 treats the use of the operator @code{IN}, or the use of operators
15611 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15612 @code{<=}, and @code{>=} on sets as an error.
15616 @node Built-In Func/Proc
15617 @subsubsection Built-in Functions and Procedures
15618 @cindex Modula-2 built-ins
15620 Modula-2 also makes available several built-in procedures and functions.
15621 In describing these, the following metavariables are used:
15626 represents an @code{ARRAY} variable.
15629 represents a @code{CHAR} constant or variable.
15632 represents a variable or constant of integral type.
15635 represents an identifier that belongs to a set. Generally used in the
15636 same function with the metavariable @var{s}. The type of @var{s} should
15637 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15640 represents a variable or constant of integral or floating-point type.
15643 represents a variable or constant of floating-point type.
15649 represents a variable.
15652 represents a variable or constant of one of many types. See the
15653 explanation of the function for details.
15656 All Modula-2 built-in procedures also return a result, described below.
15660 Returns the absolute value of @var{n}.
15663 If @var{c} is a lower case letter, it returns its upper case
15664 equivalent, otherwise it returns its argument.
15667 Returns the character whose ordinal value is @var{i}.
15670 Decrements the value in the variable @var{v} by one. Returns the new value.
15672 @item DEC(@var{v},@var{i})
15673 Decrements the value in the variable @var{v} by @var{i}. Returns the
15676 @item EXCL(@var{m},@var{s})
15677 Removes the element @var{m} from the set @var{s}. Returns the new
15680 @item FLOAT(@var{i})
15681 Returns the floating point equivalent of the integer @var{i}.
15683 @item HIGH(@var{a})
15684 Returns the index of the last member of @var{a}.
15687 Increments the value in the variable @var{v} by one. Returns the new value.
15689 @item INC(@var{v},@var{i})
15690 Increments the value in the variable @var{v} by @var{i}. Returns the
15693 @item INCL(@var{m},@var{s})
15694 Adds the element @var{m} to the set @var{s} if it is not already
15695 there. Returns the new set.
15698 Returns the maximum value of the type @var{t}.
15701 Returns the minimum value of the type @var{t}.
15704 Returns boolean TRUE if @var{i} is an odd number.
15707 Returns the ordinal value of its argument. For example, the ordinal
15708 value of a character is its @sc{ascii} value (on machines supporting
15709 the @sc{ascii} character set). The argument @var{x} must be of an
15710 ordered type, which include integral, character and enumerated types.
15712 @item SIZE(@var{x})
15713 Returns the size of its argument. The argument @var{x} can be a
15714 variable or a type.
15716 @item TRUNC(@var{r})
15717 Returns the integral part of @var{r}.
15719 @item TSIZE(@var{x})
15720 Returns the size of its argument. The argument @var{x} can be a
15721 variable or a type.
15723 @item VAL(@var{t},@var{i})
15724 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15728 @emph{Warning:} Sets and their operations are not yet supported, so
15729 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15733 @cindex Modula-2 constants
15735 @subsubsection Constants
15737 @value{GDBN} allows you to express the constants of Modula-2 in the following
15743 Integer constants are simply a sequence of digits. When used in an
15744 expression, a constant is interpreted to be type-compatible with the
15745 rest of the expression. Hexadecimal integers are specified by a
15746 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15749 Floating point constants appear as a sequence of digits, followed by a
15750 decimal point and another sequence of digits. An optional exponent can
15751 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15752 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15753 digits of the floating point constant must be valid decimal (base 10)
15757 Character constants consist of a single character enclosed by a pair of
15758 like quotes, either single (@code{'}) or double (@code{"}). They may
15759 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15760 followed by a @samp{C}.
15763 String constants consist of a sequence of characters enclosed by a
15764 pair of like quotes, either single (@code{'}) or double (@code{"}).
15765 Escape sequences in the style of C are also allowed. @xref{C
15766 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15770 Enumerated constants consist of an enumerated identifier.
15773 Boolean constants consist of the identifiers @code{TRUE} and
15777 Pointer constants consist of integral values only.
15780 Set constants are not yet supported.
15784 @subsubsection Modula-2 Types
15785 @cindex Modula-2 types
15787 Currently @value{GDBN} can print the following data types in Modula-2
15788 syntax: array types, record types, set types, pointer types, procedure
15789 types, enumerated types, subrange types and base types. You can also
15790 print the contents of variables declared using these type.
15791 This section gives a number of simple source code examples together with
15792 sample @value{GDBN} sessions.
15794 The first example contains the following section of code:
15803 and you can request @value{GDBN} to interrogate the type and value of
15804 @code{r} and @code{s}.
15807 (@value{GDBP}) print s
15809 (@value{GDBP}) ptype s
15811 (@value{GDBP}) print r
15813 (@value{GDBP}) ptype r
15818 Likewise if your source code declares @code{s} as:
15822 s: SET ['A'..'Z'] ;
15826 then you may query the type of @code{s} by:
15829 (@value{GDBP}) ptype s
15830 type = SET ['A'..'Z']
15834 Note that at present you cannot interactively manipulate set
15835 expressions using the debugger.
15837 The following example shows how you might declare an array in Modula-2
15838 and how you can interact with @value{GDBN} to print its type and contents:
15842 s: ARRAY [-10..10] OF CHAR ;
15846 (@value{GDBP}) ptype s
15847 ARRAY [-10..10] OF CHAR
15850 Note that the array handling is not yet complete and although the type
15851 is printed correctly, expression handling still assumes that all
15852 arrays have a lower bound of zero and not @code{-10} as in the example
15855 Here are some more type related Modula-2 examples:
15859 colour = (blue, red, yellow, green) ;
15860 t = [blue..yellow] ;
15868 The @value{GDBN} interaction shows how you can query the data type
15869 and value of a variable.
15872 (@value{GDBP}) print s
15874 (@value{GDBP}) ptype t
15875 type = [blue..yellow]
15879 In this example a Modula-2 array is declared and its contents
15880 displayed. Observe that the contents are written in the same way as
15881 their @code{C} counterparts.
15885 s: ARRAY [1..5] OF CARDINAL ;
15891 (@value{GDBP}) print s
15892 $1 = @{1, 0, 0, 0, 0@}
15893 (@value{GDBP}) ptype s
15894 type = ARRAY [1..5] OF CARDINAL
15897 The Modula-2 language interface to @value{GDBN} also understands
15898 pointer types as shown in this example:
15902 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15909 and you can request that @value{GDBN} describes the type of @code{s}.
15912 (@value{GDBP}) ptype s
15913 type = POINTER TO ARRAY [1..5] OF CARDINAL
15916 @value{GDBN} handles compound types as we can see in this example.
15917 Here we combine array types, record types, pointer types and subrange
15928 myarray = ARRAY myrange OF CARDINAL ;
15929 myrange = [-2..2] ;
15931 s: POINTER TO ARRAY myrange OF foo ;
15935 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15939 (@value{GDBP}) ptype s
15940 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15943 f3 : ARRAY [-2..2] OF CARDINAL;
15948 @subsubsection Modula-2 Defaults
15949 @cindex Modula-2 defaults
15951 If type and range checking are set automatically by @value{GDBN}, they
15952 both default to @code{on} whenever the working language changes to
15953 Modula-2. This happens regardless of whether you or @value{GDBN}
15954 selected the working language.
15956 If you allow @value{GDBN} to set the language automatically, then entering
15957 code compiled from a file whose name ends with @file{.mod} sets the
15958 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15959 Infer the Source Language}, for further details.
15962 @subsubsection Deviations from Standard Modula-2
15963 @cindex Modula-2, deviations from
15965 A few changes have been made to make Modula-2 programs easier to debug.
15966 This is done primarily via loosening its type strictness:
15970 Unlike in standard Modula-2, pointer constants can be formed by
15971 integers. This allows you to modify pointer variables during
15972 debugging. (In standard Modula-2, the actual address contained in a
15973 pointer variable is hidden from you; it can only be modified
15974 through direct assignment to another pointer variable or expression that
15975 returned a pointer.)
15978 C escape sequences can be used in strings and characters to represent
15979 non-printable characters. @value{GDBN} prints out strings with these
15980 escape sequences embedded. Single non-printable characters are
15981 printed using the @samp{CHR(@var{nnn})} format.
15984 The assignment operator (@code{:=}) returns the value of its right-hand
15988 All built-in procedures both modify @emph{and} return their argument.
15992 @subsubsection Modula-2 Type and Range Checks
15993 @cindex Modula-2 checks
15996 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15999 @c FIXME remove warning when type/range checks added
16001 @value{GDBN} considers two Modula-2 variables type equivalent if:
16005 They are of types that have been declared equivalent via a @code{TYPE
16006 @var{t1} = @var{t2}} statement
16009 They have been declared on the same line. (Note: This is true of the
16010 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16013 As long as type checking is enabled, any attempt to combine variables
16014 whose types are not equivalent is an error.
16016 Range checking is done on all mathematical operations, assignment, array
16017 index bounds, and all built-in functions and procedures.
16020 @subsubsection The Scope Operators @code{::} and @code{.}
16022 @cindex @code{.}, Modula-2 scope operator
16023 @cindex colon, doubled as scope operator
16025 @vindex colon-colon@r{, in Modula-2}
16026 @c Info cannot handle :: but TeX can.
16029 @vindex ::@r{, in Modula-2}
16032 There are a few subtle differences between the Modula-2 scope operator
16033 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16038 @var{module} . @var{id}
16039 @var{scope} :: @var{id}
16043 where @var{scope} is the name of a module or a procedure,
16044 @var{module} the name of a module, and @var{id} is any declared
16045 identifier within your program, except another module.
16047 Using the @code{::} operator makes @value{GDBN} search the scope
16048 specified by @var{scope} for the identifier @var{id}. If it is not
16049 found in the specified scope, then @value{GDBN} searches all scopes
16050 enclosing the one specified by @var{scope}.
16052 Using the @code{.} operator makes @value{GDBN} search the current scope for
16053 the identifier specified by @var{id} that was imported from the
16054 definition module specified by @var{module}. With this operator, it is
16055 an error if the identifier @var{id} was not imported from definition
16056 module @var{module}, or if @var{id} is not an identifier in
16060 @subsubsection @value{GDBN} and Modula-2
16062 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16063 Five subcommands of @code{set print} and @code{show print} apply
16064 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16065 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16066 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16067 analogue in Modula-2.
16069 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16070 with any language, is not useful with Modula-2. Its
16071 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16072 created in Modula-2 as they can in C or C@t{++}. However, because an
16073 address can be specified by an integral constant, the construct
16074 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16076 @cindex @code{#} in Modula-2
16077 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16078 interpreted as the beginning of a comment. Use @code{<>} instead.
16084 The extensions made to @value{GDBN} for Ada only support
16085 output from the @sc{gnu} Ada (GNAT) compiler.
16086 Other Ada compilers are not currently supported, and
16087 attempting to debug executables produced by them is most likely
16091 @cindex expressions in Ada
16093 * Ada Mode Intro:: General remarks on the Ada syntax
16094 and semantics supported by Ada mode
16096 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16097 * Additions to Ada:: Extensions of the Ada expression syntax.
16098 * Overloading support for Ada:: Support for expressions involving overloaded
16100 * Stopping Before Main Program:: Debugging the program during elaboration.
16101 * Ada Exceptions:: Ada Exceptions
16102 * Ada Tasks:: Listing and setting breakpoints in tasks.
16103 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16104 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16106 * Ada Glitches:: Known peculiarities of Ada mode.
16109 @node Ada Mode Intro
16110 @subsubsection Introduction
16111 @cindex Ada mode, general
16113 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16114 syntax, with some extensions.
16115 The philosophy behind the design of this subset is
16119 That @value{GDBN} should provide basic literals and access to operations for
16120 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16121 leaving more sophisticated computations to subprograms written into the
16122 program (which therefore may be called from @value{GDBN}).
16125 That type safety and strict adherence to Ada language restrictions
16126 are not particularly important to the @value{GDBN} user.
16129 That brevity is important to the @value{GDBN} user.
16132 Thus, for brevity, the debugger acts as if all names declared in
16133 user-written packages are directly visible, even if they are not visible
16134 according to Ada rules, thus making it unnecessary to fully qualify most
16135 names with their packages, regardless of context. Where this causes
16136 ambiguity, @value{GDBN} asks the user's intent.
16138 The debugger will start in Ada mode if it detects an Ada main program.
16139 As for other languages, it will enter Ada mode when stopped in a program that
16140 was translated from an Ada source file.
16142 While in Ada mode, you may use `@t{--}' for comments. This is useful
16143 mostly for documenting command files. The standard @value{GDBN} comment
16144 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16145 middle (to allow based literals).
16147 @node Omissions from Ada
16148 @subsubsection Omissions from Ada
16149 @cindex Ada, omissions from
16151 Here are the notable omissions from the subset:
16155 Only a subset of the attributes are supported:
16159 @t{'First}, @t{'Last}, and @t{'Length}
16160 on array objects (not on types and subtypes).
16163 @t{'Min} and @t{'Max}.
16166 @t{'Pos} and @t{'Val}.
16172 @t{'Range} on array objects (not subtypes), but only as the right
16173 operand of the membership (@code{in}) operator.
16176 @t{'Access}, @t{'Unchecked_Access}, and
16177 @t{'Unrestricted_Access} (a GNAT extension).
16185 @code{Characters.Latin_1} are not available and
16186 concatenation is not implemented. Thus, escape characters in strings are
16187 not currently available.
16190 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16191 equality of representations. They will generally work correctly
16192 for strings and arrays whose elements have integer or enumeration types.
16193 They may not work correctly for arrays whose element
16194 types have user-defined equality, for arrays of real values
16195 (in particular, IEEE-conformant floating point, because of negative
16196 zeroes and NaNs), and for arrays whose elements contain unused bits with
16197 indeterminate values.
16200 The other component-by-component array operations (@code{and}, @code{or},
16201 @code{xor}, @code{not}, and relational tests other than equality)
16202 are not implemented.
16205 @cindex array aggregates (Ada)
16206 @cindex record aggregates (Ada)
16207 @cindex aggregates (Ada)
16208 There is limited support for array and record aggregates. They are
16209 permitted only on the right sides of assignments, as in these examples:
16212 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16213 (@value{GDBP}) set An_Array := (1, others => 0)
16214 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16215 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16216 (@value{GDBP}) set A_Record := (1, "Peter", True);
16217 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16221 discriminant's value by assigning an aggregate has an
16222 undefined effect if that discriminant is used within the record.
16223 However, you can first modify discriminants by directly assigning to
16224 them (which normally would not be allowed in Ada), and then performing an
16225 aggregate assignment. For example, given a variable @code{A_Rec}
16226 declared to have a type such as:
16229 type Rec (Len : Small_Integer := 0) is record
16231 Vals : IntArray (1 .. Len);
16235 you can assign a value with a different size of @code{Vals} with two
16239 (@value{GDBP}) set A_Rec.Len := 4
16240 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16243 As this example also illustrates, @value{GDBN} is very loose about the usual
16244 rules concerning aggregates. You may leave out some of the
16245 components of an array or record aggregate (such as the @code{Len}
16246 component in the assignment to @code{A_Rec} above); they will retain their
16247 original values upon assignment. You may freely use dynamic values as
16248 indices in component associations. You may even use overlapping or
16249 redundant component associations, although which component values are
16250 assigned in such cases is not defined.
16253 Calls to dispatching subprograms are not implemented.
16256 The overloading algorithm is much more limited (i.e., less selective)
16257 than that of real Ada. It makes only limited use of the context in
16258 which a subexpression appears to resolve its meaning, and it is much
16259 looser in its rules for allowing type matches. As a result, some
16260 function calls will be ambiguous, and the user will be asked to choose
16261 the proper resolution.
16264 The @code{new} operator is not implemented.
16267 Entry calls are not implemented.
16270 Aside from printing, arithmetic operations on the native VAX floating-point
16271 formats are not supported.
16274 It is not possible to slice a packed array.
16277 The names @code{True} and @code{False}, when not part of a qualified name,
16278 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16280 Should your program
16281 redefine these names in a package or procedure (at best a dubious practice),
16282 you will have to use fully qualified names to access their new definitions.
16285 @node Additions to Ada
16286 @subsubsection Additions to Ada
16287 @cindex Ada, deviations from
16289 As it does for other languages, @value{GDBN} makes certain generic
16290 extensions to Ada (@pxref{Expressions}):
16294 If the expression @var{E} is a variable residing in memory (typically
16295 a local variable or array element) and @var{N} is a positive integer,
16296 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16297 @var{N}-1 adjacent variables following it in memory as an array. In
16298 Ada, this operator is generally not necessary, since its prime use is
16299 in displaying parts of an array, and slicing will usually do this in
16300 Ada. However, there are occasional uses when debugging programs in
16301 which certain debugging information has been optimized away.
16304 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16305 appears in function or file @var{B}.'' When @var{B} is a file name,
16306 you must typically surround it in single quotes.
16309 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16310 @var{type} that appears at address @var{addr}.''
16313 A name starting with @samp{$} is a convenience variable
16314 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16317 In addition, @value{GDBN} provides a few other shortcuts and outright
16318 additions specific to Ada:
16322 The assignment statement is allowed as an expression, returning
16323 its right-hand operand as its value. Thus, you may enter
16326 (@value{GDBP}) set x := y + 3
16327 (@value{GDBP}) print A(tmp := y + 1)
16331 The semicolon is allowed as an ``operator,'' returning as its value
16332 the value of its right-hand operand.
16333 This allows, for example,
16334 complex conditional breaks:
16337 (@value{GDBP}) break f
16338 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16342 Rather than use catenation and symbolic character names to introduce special
16343 characters into strings, one may instead use a special bracket notation,
16344 which is also used to print strings. A sequence of characters of the form
16345 @samp{["@var{XX}"]} within a string or character literal denotes the
16346 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16347 sequence of characters @samp{["""]} also denotes a single quotation mark
16348 in strings. For example,
16350 "One line.["0a"]Next line.["0a"]"
16353 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16357 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16358 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16362 (@value{GDBP}) print 'max(x, y)
16366 When printing arrays, @value{GDBN} uses positional notation when the
16367 array has a lower bound of 1, and uses a modified named notation otherwise.
16368 For example, a one-dimensional array of three integers with a lower bound
16369 of 3 might print as
16376 That is, in contrast to valid Ada, only the first component has a @code{=>}
16380 You may abbreviate attributes in expressions with any unique,
16381 multi-character subsequence of
16382 their names (an exact match gets preference).
16383 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16384 in place of @t{a'length}.
16387 @cindex quoting Ada internal identifiers
16388 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16389 to lower case. The GNAT compiler uses upper-case characters for
16390 some of its internal identifiers, which are normally of no interest to users.
16391 For the rare occasions when you actually have to look at them,
16392 enclose them in angle brackets to avoid the lower-case mapping.
16395 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16399 Printing an object of class-wide type or dereferencing an
16400 access-to-class-wide value will display all the components of the object's
16401 specific type (as indicated by its run-time tag). Likewise, component
16402 selection on such a value will operate on the specific type of the
16407 @node Overloading support for Ada
16408 @subsubsection Overloading support for Ada
16409 @cindex overloading, Ada
16411 The debugger supports limited overloading. Given a subprogram call in which
16412 the function symbol has multiple definitions, it will use the number of
16413 actual parameters and some information about their types to attempt to narrow
16414 the set of definitions. It also makes very limited use of context, preferring
16415 procedures to functions in the context of the @code{call} command, and
16416 functions to procedures elsewhere.
16418 If, after narrowing, the set of matching definitions still contains more than
16419 one definition, @value{GDBN} will display a menu to query which one it should
16423 (@value{GDBP}) print f(1)
16424 Multiple matches for f
16426 [1] foo.f (integer) return boolean at foo.adb:23
16427 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16431 In this case, just select one menu entry either to cancel expression evaluation
16432 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16433 instance (type the corresponding number and press @key{RET}).
16435 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16440 @kindex set ada print-signatures
16441 @item set ada print-signatures
16442 Control whether parameter types and return types are displayed in overloads
16443 selection menus. It is @code{on} by default.
16444 @xref{Overloading support for Ada}.
16446 @kindex show ada print-signatures
16447 @item show ada print-signatures
16448 Show the current setting for displaying parameter types and return types in
16449 overloads selection menu.
16450 @xref{Overloading support for Ada}.
16454 @node Stopping Before Main Program
16455 @subsubsection Stopping at the Very Beginning
16457 @cindex breakpointing Ada elaboration code
16458 It is sometimes necessary to debug the program during elaboration, and
16459 before reaching the main procedure.
16460 As defined in the Ada Reference
16461 Manual, the elaboration code is invoked from a procedure called
16462 @code{adainit}. To run your program up to the beginning of
16463 elaboration, simply use the following two commands:
16464 @code{tbreak adainit} and @code{run}.
16466 @node Ada Exceptions
16467 @subsubsection Ada Exceptions
16469 A command is provided to list all Ada exceptions:
16472 @kindex info exceptions
16473 @item info exceptions
16474 @itemx info exceptions @var{regexp}
16475 The @code{info exceptions} command allows you to list all Ada exceptions
16476 defined within the program being debugged, as well as their addresses.
16477 With a regular expression, @var{regexp}, as argument, only those exceptions
16478 whose names match @var{regexp} are listed.
16481 Below is a small example, showing how the command can be used, first
16482 without argument, and next with a regular expression passed as an
16486 (@value{GDBP}) info exceptions
16487 All defined Ada exceptions:
16488 constraint_error: 0x613da0
16489 program_error: 0x613d20
16490 storage_error: 0x613ce0
16491 tasking_error: 0x613ca0
16492 const.aint_global_e: 0x613b00
16493 (@value{GDBP}) info exceptions const.aint
16494 All Ada exceptions matching regular expression "const.aint":
16495 constraint_error: 0x613da0
16496 const.aint_global_e: 0x613b00
16499 It is also possible to ask @value{GDBN} to stop your program's execution
16500 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16503 @subsubsection Extensions for Ada Tasks
16504 @cindex Ada, tasking
16506 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16507 @value{GDBN} provides the following task-related commands:
16512 This command shows a list of current Ada tasks, as in the following example:
16519 (@value{GDBP}) info tasks
16520 ID TID P-ID Pri State Name
16521 1 8088000 0 15 Child Activation Wait main_task
16522 2 80a4000 1 15 Accept Statement b
16523 3 809a800 1 15 Child Activation Wait a
16524 * 4 80ae800 3 15 Runnable c
16529 In this listing, the asterisk before the last task indicates it to be the
16530 task currently being inspected.
16534 Represents @value{GDBN}'s internal task number.
16540 The parent's task ID (@value{GDBN}'s internal task number).
16543 The base priority of the task.
16546 Current state of the task.
16550 The task has been created but has not been activated. It cannot be
16554 The task is not blocked for any reason known to Ada. (It may be waiting
16555 for a mutex, though.) It is conceptually "executing" in normal mode.
16558 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16559 that were waiting on terminate alternatives have been awakened and have
16560 terminated themselves.
16562 @item Child Activation Wait
16563 The task is waiting for created tasks to complete activation.
16565 @item Accept Statement
16566 The task is waiting on an accept or selective wait statement.
16568 @item Waiting on entry call
16569 The task is waiting on an entry call.
16571 @item Async Select Wait
16572 The task is waiting to start the abortable part of an asynchronous
16576 The task is waiting on a select statement with only a delay
16579 @item Child Termination Wait
16580 The task is sleeping having completed a master within itself, and is
16581 waiting for the tasks dependent on that master to become terminated or
16582 waiting on a terminate Phase.
16584 @item Wait Child in Term Alt
16585 The task is sleeping waiting for tasks on terminate alternatives to
16586 finish terminating.
16588 @item Accepting RV with @var{taskno}
16589 The task is accepting a rendez-vous with the task @var{taskno}.
16593 Name of the task in the program.
16597 @kindex info task @var{taskno}
16598 @item info task @var{taskno}
16599 This command shows detailled informations on the specified task, as in
16600 the following example:
16605 (@value{GDBP}) info tasks
16606 ID TID P-ID Pri State Name
16607 1 8077880 0 15 Child Activation Wait main_task
16608 * 2 807c468 1 15 Runnable task_1
16609 (@value{GDBP}) info task 2
16610 Ada Task: 0x807c468
16613 Parent: 1 (main_task)
16619 @kindex task@r{ (Ada)}
16620 @cindex current Ada task ID
16621 This command prints the ID of the current task.
16627 (@value{GDBP}) info tasks
16628 ID TID P-ID Pri State Name
16629 1 8077870 0 15 Child Activation Wait main_task
16630 * 2 807c458 1 15 Runnable t
16631 (@value{GDBP}) task
16632 [Current task is 2]
16635 @item task @var{taskno}
16636 @cindex Ada task switching
16637 This command is like the @code{thread @var{thread-id}}
16638 command (@pxref{Threads}). It switches the context of debugging
16639 from the current task to the given task.
16645 (@value{GDBP}) info tasks
16646 ID TID P-ID Pri State Name
16647 1 8077870 0 15 Child Activation Wait main_task
16648 * 2 807c458 1 15 Runnable t
16649 (@value{GDBP}) task 1
16650 [Switching to task 1]
16651 #0 0x8067726 in pthread_cond_wait ()
16653 #0 0x8067726 in pthread_cond_wait ()
16654 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16655 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16656 #3 0x806153e in system.tasking.stages.activate_tasks ()
16657 #4 0x804aacc in un () at un.adb:5
16660 @item break @var{location} task @var{taskno}
16661 @itemx break @var{location} task @var{taskno} if @dots{}
16662 @cindex breakpoints and tasks, in Ada
16663 @cindex task breakpoints, in Ada
16664 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16665 These commands are like the @code{break @dots{} thread @dots{}}
16666 command (@pxref{Thread Stops}). The
16667 @var{location} argument specifies source lines, as described
16668 in @ref{Specify Location}.
16670 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16671 to specify that you only want @value{GDBN} to stop the program when a
16672 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16673 numeric task identifiers assigned by @value{GDBN}, shown in the first
16674 column of the @samp{info tasks} display.
16676 If you do not specify @samp{task @var{taskno}} when you set a
16677 breakpoint, the breakpoint applies to @emph{all} tasks of your
16680 You can use the @code{task} qualifier on conditional breakpoints as
16681 well; in this case, place @samp{task @var{taskno}} before the
16682 breakpoint condition (before the @code{if}).
16690 (@value{GDBP}) info tasks
16691 ID TID P-ID Pri State Name
16692 1 140022020 0 15 Child Activation Wait main_task
16693 2 140045060 1 15 Accept/Select Wait t2
16694 3 140044840 1 15 Runnable t1
16695 * 4 140056040 1 15 Runnable t3
16696 (@value{GDBP}) b 15 task 2
16697 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16698 (@value{GDBP}) cont
16703 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16705 (@value{GDBP}) info tasks
16706 ID TID P-ID Pri State Name
16707 1 140022020 0 15 Child Activation Wait main_task
16708 * 2 140045060 1 15 Runnable t2
16709 3 140044840 1 15 Runnable t1
16710 4 140056040 1 15 Delay Sleep t3
16714 @node Ada Tasks and Core Files
16715 @subsubsection Tasking Support when Debugging Core Files
16716 @cindex Ada tasking and core file debugging
16718 When inspecting a core file, as opposed to debugging a live program,
16719 tasking support may be limited or even unavailable, depending on
16720 the platform being used.
16721 For instance, on x86-linux, the list of tasks is available, but task
16722 switching is not supported.
16724 On certain platforms, the debugger needs to perform some
16725 memory writes in order to provide Ada tasking support. When inspecting
16726 a core file, this means that the core file must be opened with read-write
16727 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16728 Under these circumstances, you should make a backup copy of the core
16729 file before inspecting it with @value{GDBN}.
16731 @node Ravenscar Profile
16732 @subsubsection Tasking Support when using the Ravenscar Profile
16733 @cindex Ravenscar Profile
16735 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16736 specifically designed for systems with safety-critical real-time
16740 @kindex set ravenscar task-switching on
16741 @cindex task switching with program using Ravenscar Profile
16742 @item set ravenscar task-switching on
16743 Allows task switching when debugging a program that uses the Ravenscar
16744 Profile. This is the default.
16746 @kindex set ravenscar task-switching off
16747 @item set ravenscar task-switching off
16748 Turn off task switching when debugging a program that uses the Ravenscar
16749 Profile. This is mostly intended to disable the code that adds support
16750 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16751 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16752 To be effective, this command should be run before the program is started.
16754 @kindex show ravenscar task-switching
16755 @item show ravenscar task-switching
16756 Show whether it is possible to switch from task to task in a program
16757 using the Ravenscar Profile.
16762 @subsubsection Known Peculiarities of Ada Mode
16763 @cindex Ada, problems
16765 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16766 we know of several problems with and limitations of Ada mode in
16768 some of which will be fixed with planned future releases of the debugger
16769 and the GNU Ada compiler.
16773 Static constants that the compiler chooses not to materialize as objects in
16774 storage are invisible to the debugger.
16777 Named parameter associations in function argument lists are ignored (the
16778 argument lists are treated as positional).
16781 Many useful library packages are currently invisible to the debugger.
16784 Fixed-point arithmetic, conversions, input, and output is carried out using
16785 floating-point arithmetic, and may give results that only approximate those on
16789 The GNAT compiler never generates the prefix @code{Standard} for any of
16790 the standard symbols defined by the Ada language. @value{GDBN} knows about
16791 this: it will strip the prefix from names when you use it, and will never
16792 look for a name you have so qualified among local symbols, nor match against
16793 symbols in other packages or subprograms. If you have
16794 defined entities anywhere in your program other than parameters and
16795 local variables whose simple names match names in @code{Standard},
16796 GNAT's lack of qualification here can cause confusion. When this happens,
16797 you can usually resolve the confusion
16798 by qualifying the problematic names with package
16799 @code{Standard} explicitly.
16802 Older versions of the compiler sometimes generate erroneous debugging
16803 information, resulting in the debugger incorrectly printing the value
16804 of affected entities. In some cases, the debugger is able to work
16805 around an issue automatically. In other cases, the debugger is able
16806 to work around the issue, but the work-around has to be specifically
16809 @kindex set ada trust-PAD-over-XVS
16810 @kindex show ada trust-PAD-over-XVS
16813 @item set ada trust-PAD-over-XVS on
16814 Configure GDB to strictly follow the GNAT encoding when computing the
16815 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16816 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16817 a complete description of the encoding used by the GNAT compiler).
16818 This is the default.
16820 @item set ada trust-PAD-over-XVS off
16821 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16822 sometimes prints the wrong value for certain entities, changing @code{ada
16823 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16824 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16825 @code{off}, but this incurs a slight performance penalty, so it is
16826 recommended to leave this setting to @code{on} unless necessary.
16830 @cindex GNAT descriptive types
16831 @cindex GNAT encoding
16832 Internally, the debugger also relies on the compiler following a number
16833 of conventions known as the @samp{GNAT Encoding}, all documented in
16834 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16835 how the debugging information should be generated for certain types.
16836 In particular, this convention makes use of @dfn{descriptive types},
16837 which are artificial types generated purely to help the debugger.
16839 These encodings were defined at a time when the debugging information
16840 format used was not powerful enough to describe some of the more complex
16841 types available in Ada. Since DWARF allows us to express nearly all
16842 Ada features, the long-term goal is to slowly replace these descriptive
16843 types by their pure DWARF equivalent. To facilitate that transition,
16844 a new maintenance option is available to force the debugger to ignore
16845 those descriptive types. It allows the user to quickly evaluate how
16846 well @value{GDBN} works without them.
16850 @kindex maint ada set ignore-descriptive-types
16851 @item maintenance ada set ignore-descriptive-types [on|off]
16852 Control whether the debugger should ignore descriptive types.
16853 The default is not to ignore descriptives types (@code{off}).
16855 @kindex maint ada show ignore-descriptive-types
16856 @item maintenance ada show ignore-descriptive-types
16857 Show if descriptive types are ignored by @value{GDBN}.
16861 @node Unsupported Languages
16862 @section Unsupported Languages
16864 @cindex unsupported languages
16865 @cindex minimal language
16866 In addition to the other fully-supported programming languages,
16867 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16868 It does not represent a real programming language, but provides a set
16869 of capabilities close to what the C or assembly languages provide.
16870 This should allow most simple operations to be performed while debugging
16871 an application that uses a language currently not supported by @value{GDBN}.
16873 If the language is set to @code{auto}, @value{GDBN} will automatically
16874 select this language if the current frame corresponds to an unsupported
16878 @chapter Examining the Symbol Table
16880 The commands described in this chapter allow you to inquire about the
16881 symbols (names of variables, functions and types) defined in your
16882 program. This information is inherent in the text of your program and
16883 does not change as your program executes. @value{GDBN} finds it in your
16884 program's symbol table, in the file indicated when you started @value{GDBN}
16885 (@pxref{File Options, ,Choosing Files}), or by one of the
16886 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16888 @cindex symbol names
16889 @cindex names of symbols
16890 @cindex quoting names
16891 Occasionally, you may need to refer to symbols that contain unusual
16892 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16893 most frequent case is in referring to static variables in other
16894 source files (@pxref{Variables,,Program Variables}). File names
16895 are recorded in object files as debugging symbols, but @value{GDBN} would
16896 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16897 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16898 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16905 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16908 @cindex case-insensitive symbol names
16909 @cindex case sensitivity in symbol names
16910 @kindex set case-sensitive
16911 @item set case-sensitive on
16912 @itemx set case-sensitive off
16913 @itemx set case-sensitive auto
16914 Normally, when @value{GDBN} looks up symbols, it matches their names
16915 with case sensitivity determined by the current source language.
16916 Occasionally, you may wish to control that. The command @code{set
16917 case-sensitive} lets you do that by specifying @code{on} for
16918 case-sensitive matches or @code{off} for case-insensitive ones. If
16919 you specify @code{auto}, case sensitivity is reset to the default
16920 suitable for the source language. The default is case-sensitive
16921 matches for all languages except for Fortran, for which the default is
16922 case-insensitive matches.
16924 @kindex show case-sensitive
16925 @item show case-sensitive
16926 This command shows the current setting of case sensitivity for symbols
16929 @kindex set print type methods
16930 @item set print type methods
16931 @itemx set print type methods on
16932 @itemx set print type methods off
16933 Normally, when @value{GDBN} prints a class, it displays any methods
16934 declared in that class. You can control this behavior either by
16935 passing the appropriate flag to @code{ptype}, or using @command{set
16936 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16937 display the methods; this is the default. Specifying @code{off} will
16938 cause @value{GDBN} to omit the methods.
16940 @kindex show print type methods
16941 @item show print type methods
16942 This command shows the current setting of method display when printing
16945 @kindex set print type typedefs
16946 @item set print type typedefs
16947 @itemx set print type typedefs on
16948 @itemx set print type typedefs off
16950 Normally, when @value{GDBN} prints a class, it displays any typedefs
16951 defined in that class. You can control this behavior either by
16952 passing the appropriate flag to @code{ptype}, or using @command{set
16953 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16954 display the typedef definitions; this is the default. Specifying
16955 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16956 Note that this controls whether the typedef definition itself is
16957 printed, not whether typedef names are substituted when printing other
16960 @kindex show print type typedefs
16961 @item show print type typedefs
16962 This command shows the current setting of typedef display when
16965 @kindex info address
16966 @cindex address of a symbol
16967 @item info address @var{symbol}
16968 Describe where the data for @var{symbol} is stored. For a register
16969 variable, this says which register it is kept in. For a non-register
16970 local variable, this prints the stack-frame offset at which the variable
16973 Note the contrast with @samp{print &@var{symbol}}, which does not work
16974 at all for a register variable, and for a stack local variable prints
16975 the exact address of the current instantiation of the variable.
16977 @kindex info symbol
16978 @cindex symbol from address
16979 @cindex closest symbol and offset for an address
16980 @item info symbol @var{addr}
16981 Print the name of a symbol which is stored at the address @var{addr}.
16982 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16983 nearest symbol and an offset from it:
16986 (@value{GDBP}) info symbol 0x54320
16987 _initialize_vx + 396 in section .text
16991 This is the opposite of the @code{info address} command. You can use
16992 it to find out the name of a variable or a function given its address.
16994 For dynamically linked executables, the name of executable or shared
16995 library containing the symbol is also printed:
16998 (@value{GDBP}) info symbol 0x400225
16999 _start + 5 in section .text of /tmp/a.out
17000 (@value{GDBP}) info symbol 0x2aaaac2811cf
17001 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17006 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17007 Demangle @var{name}.
17008 If @var{language} is provided it is the name of the language to demangle
17009 @var{name} in. Otherwise @var{name} is demangled in the current language.
17011 The @samp{--} option specifies the end of options,
17012 and is useful when @var{name} begins with a dash.
17014 The parameter @code{demangle-style} specifies how to interpret the kind
17015 of mangling used. @xref{Print Settings}.
17018 @item whatis[/@var{flags}] [@var{arg}]
17019 Print the data type of @var{arg}, which can be either an expression
17020 or a name of a data type. With no argument, print the data type of
17021 @code{$}, the last value in the value history.
17023 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17024 is not actually evaluated, and any side-effecting operations (such as
17025 assignments or function calls) inside it do not take place.
17027 If @var{arg} is a variable or an expression, @code{whatis} prints its
17028 literal type as it is used in the source code. If the type was
17029 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17030 the data type underlying the @code{typedef}. If the type of the
17031 variable or the expression is a compound data type, such as
17032 @code{struct} or @code{class}, @code{whatis} never prints their
17033 fields or methods. It just prints the @code{struct}/@code{class}
17034 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17035 such a compound data type, use @code{ptype}.
17037 If @var{arg} is a type name that was defined using @code{typedef},
17038 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17039 Unrolling means that @code{whatis} will show the underlying type used
17040 in the @code{typedef} declaration of @var{arg}. However, if that
17041 underlying type is also a @code{typedef}, @code{whatis} will not
17044 For C code, the type names may also have the form @samp{class
17045 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17046 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17048 @var{flags} can be used to modify how the type is displayed.
17049 Available flags are:
17053 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17054 parameters and typedefs defined in a class when printing the class'
17055 members. The @code{/r} flag disables this.
17058 Do not print methods defined in the class.
17061 Print methods defined in the class. This is the default, but the flag
17062 exists in case you change the default with @command{set print type methods}.
17065 Do not print typedefs defined in the class. Note that this controls
17066 whether the typedef definition itself is printed, not whether typedef
17067 names are substituted when printing other types.
17070 Print typedefs defined in the class. This is the default, but the flag
17071 exists in case you change the default with @command{set print type typedefs}.
17075 @item ptype[/@var{flags}] [@var{arg}]
17076 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17077 detailed description of the type, instead of just the name of the type.
17078 @xref{Expressions, ,Expressions}.
17080 Contrary to @code{whatis}, @code{ptype} always unrolls any
17081 @code{typedef}s in its argument declaration, whether the argument is
17082 a variable, expression, or a data type. This means that @code{ptype}
17083 of a variable or an expression will not print literally its type as
17084 present in the source code---use @code{whatis} for that. @code{typedef}s at
17085 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17086 fields, methods and inner @code{class typedef}s of @code{struct}s,
17087 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17089 For example, for this variable declaration:
17092 typedef double real_t;
17093 struct complex @{ real_t real; double imag; @};
17094 typedef struct complex complex_t;
17096 real_t *real_pointer_var;
17100 the two commands give this output:
17104 (@value{GDBP}) whatis var
17106 (@value{GDBP}) ptype var
17107 type = struct complex @{
17111 (@value{GDBP}) whatis complex_t
17112 type = struct complex
17113 (@value{GDBP}) whatis struct complex
17114 type = struct complex
17115 (@value{GDBP}) ptype struct complex
17116 type = struct complex @{
17120 (@value{GDBP}) whatis real_pointer_var
17122 (@value{GDBP}) ptype real_pointer_var
17128 As with @code{whatis}, using @code{ptype} without an argument refers to
17129 the type of @code{$}, the last value in the value history.
17131 @cindex incomplete type
17132 Sometimes, programs use opaque data types or incomplete specifications
17133 of complex data structure. If the debug information included in the
17134 program does not allow @value{GDBN} to display a full declaration of
17135 the data type, it will say @samp{<incomplete type>}. For example,
17136 given these declarations:
17140 struct foo *fooptr;
17144 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17147 (@value{GDBP}) ptype foo
17148 $1 = <incomplete type>
17152 ``Incomplete type'' is C terminology for data types that are not
17153 completely specified.
17155 @cindex unknown type
17156 Othertimes, information about a variable's type is completely absent
17157 from the debug information included in the program. This most often
17158 happens when the program or library where the variable is defined
17159 includes no debug information at all. @value{GDBN} knows the variable
17160 exists from inspecting the linker/loader symbol table (e.g., the ELF
17161 dynamic symbol table), but such symbols do not contain type
17162 information. Inspecting the type of a (global) variable for which
17163 @value{GDBN} has no type information shows:
17166 (@value{GDBP}) ptype var
17167 type = <data variable, no debug info>
17170 @xref{Variables, no debug info variables}, for how to print the values
17174 @item info types @var{regexp}
17176 Print a brief description of all types whose names match the regular
17177 expression @var{regexp} (or all types in your program, if you supply
17178 no argument). Each complete typename is matched as though it were a
17179 complete line; thus, @samp{i type value} gives information on all
17180 types in your program whose names include the string @code{value}, but
17181 @samp{i type ^value$} gives information only on types whose complete
17182 name is @code{value}.
17184 This command differs from @code{ptype} in two ways: first, like
17185 @code{whatis}, it does not print a detailed description; second, it
17186 lists all source files where a type is defined.
17188 @kindex info type-printers
17189 @item info type-printers
17190 Versions of @value{GDBN} that ship with Python scripting enabled may
17191 have ``type printers'' available. When using @command{ptype} or
17192 @command{whatis}, these printers are consulted when the name of a type
17193 is needed. @xref{Type Printing API}, for more information on writing
17196 @code{info type-printers} displays all the available type printers.
17198 @kindex enable type-printer
17199 @kindex disable type-printer
17200 @item enable type-printer @var{name}@dots{}
17201 @item disable type-printer @var{name}@dots{}
17202 These commands can be used to enable or disable type printers.
17205 @cindex local variables
17206 @item info scope @var{location}
17207 List all the variables local to a particular scope. This command
17208 accepts a @var{location} argument---a function name, a source line, or
17209 an address preceded by a @samp{*}, and prints all the variables local
17210 to the scope defined by that location. (@xref{Specify Location}, for
17211 details about supported forms of @var{location}.) For example:
17214 (@value{GDBP}) @b{info scope command_line_handler}
17215 Scope for command_line_handler:
17216 Symbol rl is an argument at stack/frame offset 8, length 4.
17217 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17218 Symbol linelength is in static storage at address 0x150a1c, length 4.
17219 Symbol p is a local variable in register $esi, length 4.
17220 Symbol p1 is a local variable in register $ebx, length 4.
17221 Symbol nline is a local variable in register $edx, length 4.
17222 Symbol repeat is a local variable at frame offset -8, length 4.
17226 This command is especially useful for determining what data to collect
17227 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17230 @kindex info source
17232 Show information about the current source file---that is, the source file for
17233 the function containing the current point of execution:
17236 the name of the source file, and the directory containing it,
17238 the directory it was compiled in,
17240 its length, in lines,
17242 which programming language it is written in,
17244 if the debug information provides it, the program that compiled the file
17245 (which may include, e.g., the compiler version and command line arguments),
17247 whether the executable includes debugging information for that file, and
17248 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17250 whether the debugging information includes information about
17251 preprocessor macros.
17255 @kindex info sources
17257 Print the names of all source files in your program for which there is
17258 debugging information, organized into two lists: files whose symbols
17259 have already been read, and files whose symbols will be read when needed.
17261 @kindex info functions
17262 @item info functions
17263 Print the names and data types of all defined functions.
17265 @item info functions @var{regexp}
17266 Print the names and data types of all defined functions
17267 whose names contain a match for regular expression @var{regexp}.
17268 Thus, @samp{info fun step} finds all functions whose names
17269 include @code{step}; @samp{info fun ^step} finds those whose names
17270 start with @code{step}. If a function name contains characters
17271 that conflict with the regular expression language (e.g.@:
17272 @samp{operator*()}), they may be quoted with a backslash.
17274 @kindex info variables
17275 @item info variables
17276 Print the names and data types of all variables that are defined
17277 outside of functions (i.e.@: excluding local variables).
17279 @item info variables @var{regexp}
17280 Print the names and data types of all variables (except for local
17281 variables) whose names contain a match for regular expression
17284 @kindex info classes
17285 @cindex Objective-C, classes and selectors
17287 @itemx info classes @var{regexp}
17288 Display all Objective-C classes in your program, or
17289 (with the @var{regexp} argument) all those matching a particular regular
17292 @kindex info selectors
17293 @item info selectors
17294 @itemx info selectors @var{regexp}
17295 Display all Objective-C selectors in your program, or
17296 (with the @var{regexp} argument) all those matching a particular regular
17300 This was never implemented.
17301 @kindex info methods
17303 @itemx info methods @var{regexp}
17304 The @code{info methods} command permits the user to examine all defined
17305 methods within C@t{++} program, or (with the @var{regexp} argument) a
17306 specific set of methods found in the various C@t{++} classes. Many
17307 C@t{++} classes provide a large number of methods. Thus, the output
17308 from the @code{ptype} command can be overwhelming and hard to use. The
17309 @code{info-methods} command filters the methods, printing only those
17310 which match the regular-expression @var{regexp}.
17313 @cindex opaque data types
17314 @kindex set opaque-type-resolution
17315 @item set opaque-type-resolution on
17316 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17317 declared as a pointer to a @code{struct}, @code{class}, or
17318 @code{union}---for example, @code{struct MyType *}---that is used in one
17319 source file although the full declaration of @code{struct MyType} is in
17320 another source file. The default is on.
17322 A change in the setting of this subcommand will not take effect until
17323 the next time symbols for a file are loaded.
17325 @item set opaque-type-resolution off
17326 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17327 is printed as follows:
17329 @{<no data fields>@}
17332 @kindex show opaque-type-resolution
17333 @item show opaque-type-resolution
17334 Show whether opaque types are resolved or not.
17336 @kindex set print symbol-loading
17337 @cindex print messages when symbols are loaded
17338 @item set print symbol-loading
17339 @itemx set print symbol-loading full
17340 @itemx set print symbol-loading brief
17341 @itemx set print symbol-loading off
17342 The @code{set print symbol-loading} command allows you to control the
17343 printing of messages when @value{GDBN} loads symbol information.
17344 By default a message is printed for the executable and one for each
17345 shared library, and normally this is what you want. However, when
17346 debugging apps with large numbers of shared libraries these messages
17348 When set to @code{brief} a message is printed for each executable,
17349 and when @value{GDBN} loads a collection of shared libraries at once
17350 it will only print one message regardless of the number of shared
17351 libraries. When set to @code{off} no messages are printed.
17353 @kindex show print symbol-loading
17354 @item show print symbol-loading
17355 Show whether messages will be printed when a @value{GDBN} command
17356 entered from the keyboard causes symbol information to be loaded.
17358 @kindex maint print symbols
17359 @cindex symbol dump
17360 @kindex maint print psymbols
17361 @cindex partial symbol dump
17362 @kindex maint print msymbols
17363 @cindex minimal symbol dump
17364 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17365 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17366 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17367 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17368 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17369 Write a dump of debugging symbol data into the file @var{filename} or
17370 the terminal if @var{filename} is unspecified.
17371 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17373 If @code{-pc @var{address}} is specified, only dump symbols for the file
17374 with code at that address. Note that @var{address} may be a symbol like
17376 If @code{-source @var{source}} is specified, only dump symbols for that
17379 These commands are used to debug the @value{GDBN} symbol-reading code.
17380 These commands do not modify internal @value{GDBN} state, therefore
17381 @samp{maint print symbols} will only print symbols for already expanded symbol
17383 You can use the command @code{info sources} to find out which files these are.
17384 If you use @samp{maint print psymbols} instead, the dump shows information
17385 about symbols that @value{GDBN} only knows partially---that is, symbols
17386 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17387 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17390 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17391 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17393 @kindex maint info symtabs
17394 @kindex maint info psymtabs
17395 @cindex listing @value{GDBN}'s internal symbol tables
17396 @cindex symbol tables, listing @value{GDBN}'s internal
17397 @cindex full symbol tables, listing @value{GDBN}'s internal
17398 @cindex partial symbol tables, listing @value{GDBN}'s internal
17399 @item maint info symtabs @r{[} @var{regexp} @r{]}
17400 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17402 List the @code{struct symtab} or @code{struct partial_symtab}
17403 structures whose names match @var{regexp}. If @var{regexp} is not
17404 given, list them all. The output includes expressions which you can
17405 copy into a @value{GDBN} debugging this one to examine a particular
17406 structure in more detail. For example:
17409 (@value{GDBP}) maint info psymtabs dwarf2read
17410 @{ objfile /home/gnu/build/gdb/gdb
17411 ((struct objfile *) 0x82e69d0)
17412 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17413 ((struct partial_symtab *) 0x8474b10)
17416 text addresses 0x814d3c8 -- 0x8158074
17417 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17418 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17419 dependencies (none)
17422 (@value{GDBP}) maint info symtabs
17426 We see that there is one partial symbol table whose filename contains
17427 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17428 and we see that @value{GDBN} has not read in any symtabs yet at all.
17429 If we set a breakpoint on a function, that will cause @value{GDBN} to
17430 read the symtab for the compilation unit containing that function:
17433 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17434 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17436 (@value{GDBP}) maint info symtabs
17437 @{ objfile /home/gnu/build/gdb/gdb
17438 ((struct objfile *) 0x82e69d0)
17439 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17440 ((struct symtab *) 0x86c1f38)
17443 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17444 linetable ((struct linetable *) 0x8370fa0)
17445 debugformat DWARF 2
17451 @kindex maint info line-table
17452 @cindex listing @value{GDBN}'s internal line tables
17453 @cindex line tables, listing @value{GDBN}'s internal
17454 @item maint info line-table @r{[} @var{regexp} @r{]}
17456 List the @code{struct linetable} from all @code{struct symtab}
17457 instances whose name matches @var{regexp}. If @var{regexp} is not
17458 given, list the @code{struct linetable} from all @code{struct symtab}.
17460 @kindex maint set symbol-cache-size
17461 @cindex symbol cache size
17462 @item maint set symbol-cache-size @var{size}
17463 Set the size of the symbol cache to @var{size}.
17464 The default size is intended to be good enough for debugging
17465 most applications. This option exists to allow for experimenting
17466 with different sizes.
17468 @kindex maint show symbol-cache-size
17469 @item maint show symbol-cache-size
17470 Show the size of the symbol cache.
17472 @kindex maint print symbol-cache
17473 @cindex symbol cache, printing its contents
17474 @item maint print symbol-cache
17475 Print the contents of the symbol cache.
17476 This is useful when debugging symbol cache issues.
17478 @kindex maint print symbol-cache-statistics
17479 @cindex symbol cache, printing usage statistics
17480 @item maint print symbol-cache-statistics
17481 Print symbol cache usage statistics.
17482 This helps determine how well the cache is being utilized.
17484 @kindex maint flush-symbol-cache
17485 @cindex symbol cache, flushing
17486 @item maint flush-symbol-cache
17487 Flush the contents of the symbol cache, all entries are removed.
17488 This command is useful when debugging the symbol cache.
17489 It is also useful when collecting performance data.
17494 @chapter Altering Execution
17496 Once you think you have found an error in your program, you might want to
17497 find out for certain whether correcting the apparent error would lead to
17498 correct results in the rest of the run. You can find the answer by
17499 experiment, using the @value{GDBN} features for altering execution of the
17502 For example, you can store new values into variables or memory
17503 locations, give your program a signal, restart it at a different
17504 address, or even return prematurely from a function.
17507 * Assignment:: Assignment to variables
17508 * Jumping:: Continuing at a different address
17509 * Signaling:: Giving your program a signal
17510 * Returning:: Returning from a function
17511 * Calling:: Calling your program's functions
17512 * Patching:: Patching your program
17513 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17517 @section Assignment to Variables
17520 @cindex setting variables
17521 To alter the value of a variable, evaluate an assignment expression.
17522 @xref{Expressions, ,Expressions}. For example,
17529 stores the value 4 into the variable @code{x}, and then prints the
17530 value of the assignment expression (which is 4).
17531 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17532 information on operators in supported languages.
17534 @kindex set variable
17535 @cindex variables, setting
17536 If you are not interested in seeing the value of the assignment, use the
17537 @code{set} command instead of the @code{print} command. @code{set} is
17538 really the same as @code{print} except that the expression's value is
17539 not printed and is not put in the value history (@pxref{Value History,
17540 ,Value History}). The expression is evaluated only for its effects.
17542 If the beginning of the argument string of the @code{set} command
17543 appears identical to a @code{set} subcommand, use the @code{set
17544 variable} command instead of just @code{set}. This command is identical
17545 to @code{set} except for its lack of subcommands. For example, if your
17546 program has a variable @code{width}, you get an error if you try to set
17547 a new value with just @samp{set width=13}, because @value{GDBN} has the
17548 command @code{set width}:
17551 (@value{GDBP}) whatis width
17553 (@value{GDBP}) p width
17555 (@value{GDBP}) set width=47
17556 Invalid syntax in expression.
17560 The invalid expression, of course, is @samp{=47}. In
17561 order to actually set the program's variable @code{width}, use
17564 (@value{GDBP}) set var width=47
17567 Because the @code{set} command has many subcommands that can conflict
17568 with the names of program variables, it is a good idea to use the
17569 @code{set variable} command instead of just @code{set}. For example, if
17570 your program has a variable @code{g}, you run into problems if you try
17571 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17572 the command @code{set gnutarget}, abbreviated @code{set g}:
17576 (@value{GDBP}) whatis g
17580 (@value{GDBP}) set g=4
17584 The program being debugged has been started already.
17585 Start it from the beginning? (y or n) y
17586 Starting program: /home/smith/cc_progs/a.out
17587 "/home/smith/cc_progs/a.out": can't open to read symbols:
17588 Invalid bfd target.
17589 (@value{GDBP}) show g
17590 The current BFD target is "=4".
17595 The program variable @code{g} did not change, and you silently set the
17596 @code{gnutarget} to an invalid value. In order to set the variable
17600 (@value{GDBP}) set var g=4
17603 @value{GDBN} allows more implicit conversions in assignments than C; you can
17604 freely store an integer value into a pointer variable or vice versa,
17605 and you can convert any structure to any other structure that is the
17606 same length or shorter.
17607 @comment FIXME: how do structs align/pad in these conversions?
17608 @comment /doc@cygnus.com 18dec1990
17610 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17611 construct to generate a value of specified type at a specified address
17612 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17613 to memory location @code{0x83040} as an integer (which implies a certain size
17614 and representation in memory), and
17617 set @{int@}0x83040 = 4
17621 stores the value 4 into that memory location.
17624 @section Continuing at a Different Address
17626 Ordinarily, when you continue your program, you do so at the place where
17627 it stopped, with the @code{continue} command. You can instead continue at
17628 an address of your own choosing, with the following commands:
17632 @kindex j @r{(@code{jump})}
17633 @item jump @var{location}
17634 @itemx j @var{location}
17635 Resume execution at @var{location}. Execution stops again immediately
17636 if there is a breakpoint there. @xref{Specify Location}, for a description
17637 of the different forms of @var{location}. It is common
17638 practice to use the @code{tbreak} command in conjunction with
17639 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17641 The @code{jump} command does not change the current stack frame, or
17642 the stack pointer, or the contents of any memory location or any
17643 register other than the program counter. If @var{location} is in
17644 a different function from the one currently executing, the results may
17645 be bizarre if the two functions expect different patterns of arguments or
17646 of local variables. For this reason, the @code{jump} command requests
17647 confirmation if the specified line is not in the function currently
17648 executing. However, even bizarre results are predictable if you are
17649 well acquainted with the machine-language code of your program.
17652 On many systems, you can get much the same effect as the @code{jump}
17653 command by storing a new value into the register @code{$pc}. The
17654 difference is that this does not start your program running; it only
17655 changes the address of where it @emph{will} run when you continue. For
17663 makes the next @code{continue} command or stepping command execute at
17664 address @code{0x485}, rather than at the address where your program stopped.
17665 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17667 The most common occasion to use the @code{jump} command is to back
17668 up---perhaps with more breakpoints set---over a portion of a program
17669 that has already executed, in order to examine its execution in more
17674 @section Giving your Program a Signal
17675 @cindex deliver a signal to a program
17679 @item signal @var{signal}
17680 Resume execution where your program is stopped, but immediately give it the
17681 signal @var{signal}. The @var{signal} can be the name or the number of a
17682 signal. For example, on many systems @code{signal 2} and @code{signal
17683 SIGINT} are both ways of sending an interrupt signal.
17685 Alternatively, if @var{signal} is zero, continue execution without
17686 giving a signal. This is useful when your program stopped on account of
17687 a signal and would ordinarily see the signal when resumed with the
17688 @code{continue} command; @samp{signal 0} causes it to resume without a
17691 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17692 delivered to the currently selected thread, not the thread that last
17693 reported a stop. This includes the situation where a thread was
17694 stopped due to a signal. So if you want to continue execution
17695 suppressing the signal that stopped a thread, you should select that
17696 same thread before issuing the @samp{signal 0} command. If you issue
17697 the @samp{signal 0} command with another thread as the selected one,
17698 @value{GDBN} detects that and asks for confirmation.
17700 Invoking the @code{signal} command is not the same as invoking the
17701 @code{kill} utility from the shell. Sending a signal with @code{kill}
17702 causes @value{GDBN} to decide what to do with the signal depending on
17703 the signal handling tables (@pxref{Signals}). The @code{signal} command
17704 passes the signal directly to your program.
17706 @code{signal} does not repeat when you press @key{RET} a second time
17707 after executing the command.
17709 @kindex queue-signal
17710 @item queue-signal @var{signal}
17711 Queue @var{signal} to be delivered immediately to the current thread
17712 when execution of the thread resumes. The @var{signal} can be the name or
17713 the number of a signal. For example, on many systems @code{signal 2} and
17714 @code{signal SIGINT} are both ways of sending an interrupt signal.
17715 The handling of the signal must be set to pass the signal to the program,
17716 otherwise @value{GDBN} will report an error.
17717 You can control the handling of signals from @value{GDBN} with the
17718 @code{handle} command (@pxref{Signals}).
17720 Alternatively, if @var{signal} is zero, any currently queued signal
17721 for the current thread is discarded and when execution resumes no signal
17722 will be delivered. This is useful when your program stopped on account
17723 of a signal and would ordinarily see the signal when resumed with the
17724 @code{continue} command.
17726 This command differs from the @code{signal} command in that the signal
17727 is just queued, execution is not resumed. And @code{queue-signal} cannot
17728 be used to pass a signal whose handling state has been set to @code{nopass}
17733 @xref{stepping into signal handlers}, for information on how stepping
17734 commands behave when the thread has a signal queued.
17737 @section Returning from a Function
17740 @cindex returning from a function
17743 @itemx return @var{expression}
17744 You can cancel execution of a function call with the @code{return}
17745 command. If you give an
17746 @var{expression} argument, its value is used as the function's return
17750 When you use @code{return}, @value{GDBN} discards the selected stack frame
17751 (and all frames within it). You can think of this as making the
17752 discarded frame return prematurely. If you wish to specify a value to
17753 be returned, give that value as the argument to @code{return}.
17755 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17756 Frame}), and any other frames inside of it, leaving its caller as the
17757 innermost remaining frame. That frame becomes selected. The
17758 specified value is stored in the registers used for returning values
17761 The @code{return} command does not resume execution; it leaves the
17762 program stopped in the state that would exist if the function had just
17763 returned. In contrast, the @code{finish} command (@pxref{Continuing
17764 and Stepping, ,Continuing and Stepping}) resumes execution until the
17765 selected stack frame returns naturally.
17767 @value{GDBN} needs to know how the @var{expression} argument should be set for
17768 the inferior. The concrete registers assignment depends on the OS ABI and the
17769 type being returned by the selected stack frame. For example it is common for
17770 OS ABI to return floating point values in FPU registers while integer values in
17771 CPU registers. Still some ABIs return even floating point values in CPU
17772 registers. Larger integer widths (such as @code{long long int}) also have
17773 specific placement rules. @value{GDBN} already knows the OS ABI from its
17774 current target so it needs to find out also the type being returned to make the
17775 assignment into the right register(s).
17777 Normally, the selected stack frame has debug info. @value{GDBN} will always
17778 use the debug info instead of the implicit type of @var{expression} when the
17779 debug info is available. For example, if you type @kbd{return -1}, and the
17780 function in the current stack frame is declared to return a @code{long long
17781 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17782 into a @code{long long int}:
17785 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17787 (@value{GDBP}) return -1
17788 Make func return now? (y or n) y
17789 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17790 43 printf ("result=%lld\n", func ());
17794 However, if the selected stack frame does not have a debug info, e.g., if the
17795 function was compiled without debug info, @value{GDBN} has to find out the type
17796 to return from user. Specifying a different type by mistake may set the value
17797 in different inferior registers than the caller code expects. For example,
17798 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17799 of a @code{long long int} result for a debug info less function (on 32-bit
17800 architectures). Therefore the user is required to specify the return type by
17801 an appropriate cast explicitly:
17804 Breakpoint 2, 0x0040050b in func ()
17805 (@value{GDBP}) return -1
17806 Return value type not available for selected stack frame.
17807 Please use an explicit cast of the value to return.
17808 (@value{GDBP}) return (long long int) -1
17809 Make selected stack frame return now? (y or n) y
17810 #0 0x00400526 in main ()
17815 @section Calling Program Functions
17818 @cindex calling functions
17819 @cindex inferior functions, calling
17820 @item print @var{expr}
17821 Evaluate the expression @var{expr} and display the resulting value.
17822 The expression may include calls to functions in the program being
17826 @item call @var{expr}
17827 Evaluate the expression @var{expr} without displaying @code{void}
17830 You can use this variant of the @code{print} command if you want to
17831 execute a function from your program that does not return anything
17832 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17833 with @code{void} returned values that @value{GDBN} will otherwise
17834 print. If the result is not void, it is printed and saved in the
17838 It is possible for the function you call via the @code{print} or
17839 @code{call} command to generate a signal (e.g., if there's a bug in
17840 the function, or if you passed it incorrect arguments). What happens
17841 in that case is controlled by the @code{set unwindonsignal} command.
17843 Similarly, with a C@t{++} program it is possible for the function you
17844 call via the @code{print} or @code{call} command to generate an
17845 exception that is not handled due to the constraints of the dummy
17846 frame. In this case, any exception that is raised in the frame, but has
17847 an out-of-frame exception handler will not be found. GDB builds a
17848 dummy-frame for the inferior function call, and the unwinder cannot
17849 seek for exception handlers outside of this dummy-frame. What happens
17850 in that case is controlled by the
17851 @code{set unwind-on-terminating-exception} command.
17854 @item set unwindonsignal
17855 @kindex set unwindonsignal
17856 @cindex unwind stack in called functions
17857 @cindex call dummy stack unwinding
17858 Set unwinding of the stack if a signal is received while in a function
17859 that @value{GDBN} called in the program being debugged. If set to on,
17860 @value{GDBN} unwinds the stack it created for the call and restores
17861 the context to what it was before the call. If set to off (the
17862 default), @value{GDBN} stops in the frame where the signal was
17865 @item show unwindonsignal
17866 @kindex show unwindonsignal
17867 Show the current setting of stack unwinding in the functions called by
17870 @item set unwind-on-terminating-exception
17871 @kindex set unwind-on-terminating-exception
17872 @cindex unwind stack in called functions with unhandled exceptions
17873 @cindex call dummy stack unwinding on unhandled exception.
17874 Set unwinding of the stack if a C@t{++} exception is raised, but left
17875 unhandled while in a function that @value{GDBN} called in the program being
17876 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17877 it created for the call and restores the context to what it was before
17878 the call. If set to off, @value{GDBN} the exception is delivered to
17879 the default C@t{++} exception handler and the inferior terminated.
17881 @item show unwind-on-terminating-exception
17882 @kindex show unwind-on-terminating-exception
17883 Show the current setting of stack unwinding in the functions called by
17888 @subsection Calling functions with no debug info
17890 @cindex no debug info functions
17891 Sometimes, a function you wish to call is missing debug information.
17892 In such case, @value{GDBN} does not know the type of the function,
17893 including the types of the function's parameters. To avoid calling
17894 the inferior function incorrectly, which could result in the called
17895 function functioning erroneously and even crash, @value{GDBN} refuses
17896 to call the function unless you tell it the type of the function.
17898 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
17899 to do that. The simplest is to cast the call to the function's
17900 declared return type. For example:
17903 (@value{GDBP}) p getenv ("PATH")
17904 'getenv' has unknown return type; cast the call to its declared return type
17905 (@value{GDBP}) p (char *) getenv ("PATH")
17906 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
17909 Casting the return type of a no-debug function is equivalent to
17910 casting the function to a pointer to a prototyped function that has a
17911 prototype that matches the types of the passed-in arguments, and
17912 calling that. I.e., the call above is equivalent to:
17915 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
17919 and given this prototyped C or C++ function with float parameters:
17922 float multiply (float v1, float v2) @{ return v1 * v2; @}
17926 these calls are equivalent:
17929 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
17930 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
17933 If the function you wish to call is declared as unprototyped (i.e.@:
17934 old K&R style), you must use the cast-to-function-pointer syntax, so
17935 that @value{GDBN} knows that it needs to apply default argument
17936 promotions (promote float arguments to double). @xref{ABI, float
17937 promotion}. For example, given this unprototyped C function with
17938 float parameters, and no debug info:
17942 multiply_noproto (v1, v2)
17950 you call it like this:
17953 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
17957 @section Patching Programs
17959 @cindex patching binaries
17960 @cindex writing into executables
17961 @cindex writing into corefiles
17963 By default, @value{GDBN} opens the file containing your program's
17964 executable code (or the corefile) read-only. This prevents accidental
17965 alterations to machine code; but it also prevents you from intentionally
17966 patching your program's binary.
17968 If you'd like to be able to patch the binary, you can specify that
17969 explicitly with the @code{set write} command. For example, you might
17970 want to turn on internal debugging flags, or even to make emergency
17976 @itemx set write off
17977 If you specify @samp{set write on}, @value{GDBN} opens executable and
17978 core files for both reading and writing; if you specify @kbd{set write
17979 off} (the default), @value{GDBN} opens them read-only.
17981 If you have already loaded a file, you must load it again (using the
17982 @code{exec-file} or @code{core-file} command) after changing @code{set
17983 write}, for your new setting to take effect.
17987 Display whether executable files and core files are opened for writing
17988 as well as reading.
17991 @node Compiling and Injecting Code
17992 @section Compiling and injecting code in @value{GDBN}
17993 @cindex injecting code
17994 @cindex writing into executables
17995 @cindex compiling code
17997 @value{GDBN} supports on-demand compilation and code injection into
17998 programs running under @value{GDBN}. GCC 5.0 or higher built with
17999 @file{libcc1.so} must be installed for this functionality to be enabled.
18000 This functionality is implemented with the following commands.
18003 @kindex compile code
18004 @item compile code @var{source-code}
18005 @itemx compile code -raw @var{--} @var{source-code}
18006 Compile @var{source-code} with the compiler language found as the current
18007 language in @value{GDBN} (@pxref{Languages}). If compilation and
18008 injection is not supported with the current language specified in
18009 @value{GDBN}, or the compiler does not support this feature, an error
18010 message will be printed. If @var{source-code} compiles and links
18011 successfully, @value{GDBN} will load the object-code emitted,
18012 and execute it within the context of the currently selected inferior.
18013 It is important to note that the compiled code is executed immediately.
18014 After execution, the compiled code is removed from @value{GDBN} and any
18015 new types or variables you have defined will be deleted.
18017 The command allows you to specify @var{source-code} in two ways.
18018 The simplest method is to provide a single line of code to the command.
18022 compile code printf ("hello world\n");
18025 If you specify options on the command line as well as source code, they
18026 may conflict. The @samp{--} delimiter can be used to separate options
18027 from actual source code. E.g.:
18030 compile code -r -- printf ("hello world\n");
18033 Alternatively you can enter source code as multiple lines of text. To
18034 enter this mode, invoke the @samp{compile code} command without any text
18035 following the command. This will start the multiple-line editor and
18036 allow you to type as many lines of source code as required. When you
18037 have completed typing, enter @samp{end} on its own line to exit the
18042 >printf ("hello\n");
18043 >printf ("world\n");
18047 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18048 provided @var{source-code} in a callable scope. In this case, you must
18049 specify the entry point of the code by defining a function named
18050 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18051 inferior. Using @samp{-raw} option may be needed for example when
18052 @var{source-code} requires @samp{#include} lines which may conflict with
18053 inferior symbols otherwise.
18055 @kindex compile file
18056 @item compile file @var{filename}
18057 @itemx compile file -raw @var{filename}
18058 Like @code{compile code}, but take the source code from @var{filename}.
18061 compile file /home/user/example.c
18066 @item compile print @var{expr}
18067 @itemx compile print /@var{f} @var{expr}
18068 Compile and execute @var{expr} with the compiler language found as the
18069 current language in @value{GDBN} (@pxref{Languages}). By default the
18070 value of @var{expr} is printed in a format appropriate to its data type;
18071 you can choose a different format by specifying @samp{/@var{f}}, where
18072 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18075 @item compile print
18076 @itemx compile print /@var{f}
18077 @cindex reprint the last value
18078 Alternatively you can enter the expression (source code producing it) as
18079 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18080 command without any text following the command. This will start the
18081 multiple-line editor.
18085 The process of compiling and injecting the code can be inspected using:
18088 @anchor{set debug compile}
18089 @item set debug compile
18090 @cindex compile command debugging info
18091 Turns on or off display of @value{GDBN} process of compiling and
18092 injecting the code. The default is off.
18094 @item show debug compile
18095 Displays the current state of displaying @value{GDBN} process of
18096 compiling and injecting the code.
18099 @subsection Compilation options for the @code{compile} command
18101 @value{GDBN} needs to specify the right compilation options for the code
18102 to be injected, in part to make its ABI compatible with the inferior
18103 and in part to make the injected code compatible with @value{GDBN}'s
18107 The options used, in increasing precedence:
18110 @item target architecture and OS options (@code{gdbarch})
18111 These options depend on target processor type and target operating
18112 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18113 (@code{-m64}) compilation option.
18115 @item compilation options recorded in the target
18116 @value{NGCC} (since version 4.7) stores the options used for compilation
18117 into @code{DW_AT_producer} part of DWARF debugging information according
18118 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18119 explicitly specify @code{-g} during inferior compilation otherwise
18120 @value{NGCC} produces no DWARF. This feature is only relevant for
18121 platforms where @code{-g} produces DWARF by default, otherwise one may
18122 try to enforce DWARF by using @code{-gdwarf-4}.
18124 @item compilation options set by @code{set compile-args}
18128 You can override compilation options using the following command:
18131 @item set compile-args
18132 @cindex compile command options override
18133 Set compilation options used for compiling and injecting code with the
18134 @code{compile} commands. These options override any conflicting ones
18135 from the target architecture and/or options stored during inferior
18138 @item show compile-args
18139 Displays the current state of compilation options override.
18140 This does not show all the options actually used during compilation,
18141 use @ref{set debug compile} for that.
18144 @subsection Caveats when using the @code{compile} command
18146 There are a few caveats to keep in mind when using the @code{compile}
18147 command. As the caveats are different per language, the table below
18148 highlights specific issues on a per language basis.
18151 @item C code examples and caveats
18152 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18153 attempt to compile the source code with a @samp{C} compiler. The source
18154 code provided to the @code{compile} command will have much the same
18155 access to variables and types as it normally would if it were part of
18156 the program currently being debugged in @value{GDBN}.
18158 Below is a sample program that forms the basis of the examples that
18159 follow. This program has been compiled and loaded into @value{GDBN},
18160 much like any other normal debugging session.
18163 void function1 (void)
18166 printf ("function 1\n");
18169 void function2 (void)
18184 For the purposes of the examples in this section, the program above has
18185 been compiled, loaded into @value{GDBN}, stopped at the function
18186 @code{main}, and @value{GDBN} is awaiting input from the user.
18188 To access variables and types for any program in @value{GDBN}, the
18189 program must be compiled and packaged with debug information. The
18190 @code{compile} command is not an exception to this rule. Without debug
18191 information, you can still use the @code{compile} command, but you will
18192 be very limited in what variables and types you can access.
18194 So with that in mind, the example above has been compiled with debug
18195 information enabled. The @code{compile} command will have access to
18196 all variables and types (except those that may have been optimized
18197 out). Currently, as @value{GDBN} has stopped the program in the
18198 @code{main} function, the @code{compile} command would have access to
18199 the variable @code{k}. You could invoke the @code{compile} command
18200 and type some source code to set the value of @code{k}. You can also
18201 read it, or do anything with that variable you would normally do in
18202 @code{C}. Be aware that changes to inferior variables in the
18203 @code{compile} command are persistent. In the following example:
18206 compile code k = 3;
18210 the variable @code{k} is now 3. It will retain that value until
18211 something else in the example program changes it, or another
18212 @code{compile} command changes it.
18214 Normal scope and access rules apply to source code compiled and
18215 injected by the @code{compile} command. In the example, the variables
18216 @code{j} and @code{k} are not accessible yet, because the program is
18217 currently stopped in the @code{main} function, where these variables
18218 are not in scope. Therefore, the following command
18221 compile code j = 3;
18225 will result in a compilation error message.
18227 Once the program is continued, execution will bring these variables in
18228 scope, and they will become accessible; then the code you specify via
18229 the @code{compile} command will be able to access them.
18231 You can create variables and types with the @code{compile} command as
18232 part of your source code. Variables and types that are created as part
18233 of the @code{compile} command are not visible to the rest of the program for
18234 the duration of its run. This example is valid:
18237 compile code int ff = 5; printf ("ff is %d\n", ff);
18240 However, if you were to type the following into @value{GDBN} after that
18241 command has completed:
18244 compile code printf ("ff is %d\n'', ff);
18248 a compiler error would be raised as the variable @code{ff} no longer
18249 exists. Object code generated and injected by the @code{compile}
18250 command is removed when its execution ends. Caution is advised
18251 when assigning to program variables values of variables created by the
18252 code submitted to the @code{compile} command. This example is valid:
18255 compile code int ff = 5; k = ff;
18258 The value of the variable @code{ff} is assigned to @code{k}. The variable
18259 @code{k} does not require the existence of @code{ff} to maintain the value
18260 it has been assigned. However, pointers require particular care in
18261 assignment. If the source code compiled with the @code{compile} command
18262 changed the address of a pointer in the example program, perhaps to a
18263 variable created in the @code{compile} command, that pointer would point
18264 to an invalid location when the command exits. The following example
18265 would likely cause issues with your debugged program:
18268 compile code int ff = 5; p = &ff;
18271 In this example, @code{p} would point to @code{ff} when the
18272 @code{compile} command is executing the source code provided to it.
18273 However, as variables in the (example) program persist with their
18274 assigned values, the variable @code{p} would point to an invalid
18275 location when the command exists. A general rule should be followed
18276 in that you should either assign @code{NULL} to any assigned pointers,
18277 or restore a valid location to the pointer before the command exits.
18279 Similar caution must be exercised with any structs, unions, and typedefs
18280 defined in @code{compile} command. Types defined in the @code{compile}
18281 command will no longer be available in the next @code{compile} command.
18282 Therefore, if you cast a variable to a type defined in the
18283 @code{compile} command, care must be taken to ensure that any future
18284 need to resolve the type can be achieved.
18287 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18288 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18289 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18290 Compilation failed.
18291 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18295 Variables that have been optimized away by the compiler are not
18296 accessible to the code submitted to the @code{compile} command.
18297 Access to those variables will generate a compiler error which @value{GDBN}
18298 will print to the console.
18301 @subsection Compiler search for the @code{compile} command
18303 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18304 which may not be obvious for remote targets of different architecture
18305 than where @value{GDBN} is running. Environment variable @code{PATH} on
18306 @value{GDBN} host is searched for @value{NGCC} binary matching the
18307 target architecture and operating system. This search can be overriden
18308 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18309 taken from shell that executed @value{GDBN}, it is not the value set by
18310 @value{GDBN} command @code{set environment}). @xref{Environment}.
18313 Specifically @code{PATH} is searched for binaries matching regular expression
18314 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18315 debugged. @var{arch} is processor name --- multiarch is supported, so for
18316 example both @code{i386} and @code{x86_64} targets look for pattern
18317 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18318 for pattern @code{s390x?}. @var{os} is currently supported only for
18319 pattern @code{linux(-gnu)?}.
18321 On Posix hosts the compiler driver @value{GDBN} needs to find also
18322 shared library @file{libcc1.so} from the compiler. It is searched in
18323 default shared library search path (overridable with usual environment
18324 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18325 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18326 according to the installation of the found compiler --- as possibly
18327 specified by the @code{set compile-gcc} command.
18330 @item set compile-gcc
18331 @cindex compile command driver filename override
18332 Set compilation command used for compiling and injecting code with the
18333 @code{compile} commands. If this option is not set (it is set to
18334 an empty string), the search described above will occur --- that is the
18337 @item show compile-gcc
18338 Displays the current compile command @value{NGCC} driver filename.
18339 If set, it is the main command @command{gcc}, found usually for example
18340 under name @file{x86_64-linux-gnu-gcc}.
18344 @chapter @value{GDBN} Files
18346 @value{GDBN} needs to know the file name of the program to be debugged,
18347 both in order to read its symbol table and in order to start your
18348 program. To debug a core dump of a previous run, you must also tell
18349 @value{GDBN} the name of the core dump file.
18352 * Files:: Commands to specify files
18353 * File Caching:: Information about @value{GDBN}'s file caching
18354 * Separate Debug Files:: Debugging information in separate files
18355 * MiniDebugInfo:: Debugging information in a special section
18356 * Index Files:: Index files speed up GDB
18357 * Symbol Errors:: Errors reading symbol files
18358 * Data Files:: GDB data files
18362 @section Commands to Specify Files
18364 @cindex symbol table
18365 @cindex core dump file
18367 You may want to specify executable and core dump file names. The usual
18368 way to do this is at start-up time, using the arguments to
18369 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18370 Out of @value{GDBN}}).
18372 Occasionally it is necessary to change to a different file during a
18373 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18374 specify a file you want to use. Or you are debugging a remote target
18375 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18376 Program}). In these situations the @value{GDBN} commands to specify
18377 new files are useful.
18380 @cindex executable file
18382 @item file @var{filename}
18383 Use @var{filename} as the program to be debugged. It is read for its
18384 symbols and for the contents of pure memory. It is also the program
18385 executed when you use the @code{run} command. If you do not specify a
18386 directory and the file is not found in the @value{GDBN} working directory,
18387 @value{GDBN} uses the environment variable @code{PATH} as a list of
18388 directories to search, just as the shell does when looking for a program
18389 to run. You can change the value of this variable, for both @value{GDBN}
18390 and your program, using the @code{path} command.
18392 @cindex unlinked object files
18393 @cindex patching object files
18394 You can load unlinked object @file{.o} files into @value{GDBN} using
18395 the @code{file} command. You will not be able to ``run'' an object
18396 file, but you can disassemble functions and inspect variables. Also,
18397 if the underlying BFD functionality supports it, you could use
18398 @kbd{gdb -write} to patch object files using this technique. Note
18399 that @value{GDBN} can neither interpret nor modify relocations in this
18400 case, so branches and some initialized variables will appear to go to
18401 the wrong place. But this feature is still handy from time to time.
18404 @code{file} with no argument makes @value{GDBN} discard any information it
18405 has on both executable file and the symbol table.
18408 @item exec-file @r{[} @var{filename} @r{]}
18409 Specify that the program to be run (but not the symbol table) is found
18410 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18411 if necessary to locate your program. Omitting @var{filename} means to
18412 discard information on the executable file.
18414 @kindex symbol-file
18415 @item symbol-file @r{[} @var{filename} @r{]}
18416 Read symbol table information from file @var{filename}. @code{PATH} is
18417 searched when necessary. Use the @code{file} command to get both symbol
18418 table and program to run from the same file.
18420 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18421 program's symbol table.
18423 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18424 some breakpoints and auto-display expressions. This is because they may
18425 contain pointers to the internal data recording symbols and data types,
18426 which are part of the old symbol table data being discarded inside
18429 @code{symbol-file} does not repeat if you press @key{RET} again after
18432 When @value{GDBN} is configured for a particular environment, it
18433 understands debugging information in whatever format is the standard
18434 generated for that environment; you may use either a @sc{gnu} compiler, or
18435 other compilers that adhere to the local conventions.
18436 Best results are usually obtained from @sc{gnu} compilers; for example,
18437 using @code{@value{NGCC}} you can generate debugging information for
18440 For most kinds of object files, with the exception of old SVR3 systems
18441 using COFF, the @code{symbol-file} command does not normally read the
18442 symbol table in full right away. Instead, it scans the symbol table
18443 quickly to find which source files and which symbols are present. The
18444 details are read later, one source file at a time, as they are needed.
18446 The purpose of this two-stage reading strategy is to make @value{GDBN}
18447 start up faster. For the most part, it is invisible except for
18448 occasional pauses while the symbol table details for a particular source
18449 file are being read. (The @code{set verbose} command can turn these
18450 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18451 Warnings and Messages}.)
18453 We have not implemented the two-stage strategy for COFF yet. When the
18454 symbol table is stored in COFF format, @code{symbol-file} reads the
18455 symbol table data in full right away. Note that ``stabs-in-COFF''
18456 still does the two-stage strategy, since the debug info is actually
18460 @cindex reading symbols immediately
18461 @cindex symbols, reading immediately
18462 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18463 @itemx file @r{[} -readnow @r{]} @var{filename}
18464 You can override the @value{GDBN} two-stage strategy for reading symbol
18465 tables by using the @samp{-readnow} option with any of the commands that
18466 load symbol table information, if you want to be sure @value{GDBN} has the
18467 entire symbol table available.
18469 @c FIXME: for now no mention of directories, since this seems to be in
18470 @c flux. 13mar1992 status is that in theory GDB would look either in
18471 @c current dir or in same dir as myprog; but issues like competing
18472 @c GDB's, or clutter in system dirs, mean that in practice right now
18473 @c only current dir is used. FFish says maybe a special GDB hierarchy
18474 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18478 @item core-file @r{[}@var{filename}@r{]}
18480 Specify the whereabouts of a core dump file to be used as the ``contents
18481 of memory''. Traditionally, core files contain only some parts of the
18482 address space of the process that generated them; @value{GDBN} can access the
18483 executable file itself for other parts.
18485 @code{core-file} with no argument specifies that no core file is
18488 Note that the core file is ignored when your program is actually running
18489 under @value{GDBN}. So, if you have been running your program and you
18490 wish to debug a core file instead, you must kill the subprocess in which
18491 the program is running. To do this, use the @code{kill} command
18492 (@pxref{Kill Process, ,Killing the Child Process}).
18494 @kindex add-symbol-file
18495 @cindex dynamic linking
18496 @item add-symbol-file @var{filename} @var{address}
18497 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18498 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18499 The @code{add-symbol-file} command reads additional symbol table
18500 information from the file @var{filename}. You would use this command
18501 when @var{filename} has been dynamically loaded (by some other means)
18502 into the program that is running. The @var{address} should give the memory
18503 address at which the file has been loaded; @value{GDBN} cannot figure
18504 this out for itself. You can additionally specify an arbitrary number
18505 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18506 section name and base address for that section. You can specify any
18507 @var{address} as an expression.
18509 The symbol table of the file @var{filename} is added to the symbol table
18510 originally read with the @code{symbol-file} command. You can use the
18511 @code{add-symbol-file} command any number of times; the new symbol data
18512 thus read is kept in addition to the old.
18514 Changes can be reverted using the command @code{remove-symbol-file}.
18516 @cindex relocatable object files, reading symbols from
18517 @cindex object files, relocatable, reading symbols from
18518 @cindex reading symbols from relocatable object files
18519 @cindex symbols, reading from relocatable object files
18520 @cindex @file{.o} files, reading symbols from
18521 Although @var{filename} is typically a shared library file, an
18522 executable file, or some other object file which has been fully
18523 relocated for loading into a process, you can also load symbolic
18524 information from relocatable @file{.o} files, as long as:
18528 the file's symbolic information refers only to linker symbols defined in
18529 that file, not to symbols defined by other object files,
18531 every section the file's symbolic information refers to has actually
18532 been loaded into the inferior, as it appears in the file, and
18534 you can determine the address at which every section was loaded, and
18535 provide these to the @code{add-symbol-file} command.
18539 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18540 relocatable files into an already running program; such systems
18541 typically make the requirements above easy to meet. However, it's
18542 important to recognize that many native systems use complex link
18543 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18544 assembly, for example) that make the requirements difficult to meet. In
18545 general, one cannot assume that using @code{add-symbol-file} to read a
18546 relocatable object file's symbolic information will have the same effect
18547 as linking the relocatable object file into the program in the normal
18550 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18552 @kindex remove-symbol-file
18553 @item remove-symbol-file @var{filename}
18554 @item remove-symbol-file -a @var{address}
18555 Remove a symbol file added via the @code{add-symbol-file} command. The
18556 file to remove can be identified by its @var{filename} or by an @var{address}
18557 that lies within the boundaries of this symbol file in memory. Example:
18560 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18561 add symbol table from file "/home/user/gdb/mylib.so" at
18562 .text_addr = 0x7ffff7ff9480
18564 Reading symbols from /home/user/gdb/mylib.so...done.
18565 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18566 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18571 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18573 @kindex add-symbol-file-from-memory
18574 @cindex @code{syscall DSO}
18575 @cindex load symbols from memory
18576 @item add-symbol-file-from-memory @var{address}
18577 Load symbols from the given @var{address} in a dynamically loaded
18578 object file whose image is mapped directly into the inferior's memory.
18579 For example, the Linux kernel maps a @code{syscall DSO} into each
18580 process's address space; this DSO provides kernel-specific code for
18581 some system calls. The argument can be any expression whose
18582 evaluation yields the address of the file's shared object file header.
18583 For this command to work, you must have used @code{symbol-file} or
18584 @code{exec-file} commands in advance.
18587 @item section @var{section} @var{addr}
18588 The @code{section} command changes the base address of the named
18589 @var{section} of the exec file to @var{addr}. This can be used if the
18590 exec file does not contain section addresses, (such as in the
18591 @code{a.out} format), or when the addresses specified in the file
18592 itself are wrong. Each section must be changed separately. The
18593 @code{info files} command, described below, lists all the sections and
18597 @kindex info target
18600 @code{info files} and @code{info target} are synonymous; both print the
18601 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18602 including the names of the executable and core dump files currently in
18603 use by @value{GDBN}, and the files from which symbols were loaded. The
18604 command @code{help target} lists all possible targets rather than
18607 @kindex maint info sections
18608 @item maint info sections
18609 Another command that can give you extra information about program sections
18610 is @code{maint info sections}. In addition to the section information
18611 displayed by @code{info files}, this command displays the flags and file
18612 offset of each section in the executable and core dump files. In addition,
18613 @code{maint info sections} provides the following command options (which
18614 may be arbitrarily combined):
18618 Display sections for all loaded object files, including shared libraries.
18619 @item @var{sections}
18620 Display info only for named @var{sections}.
18621 @item @var{section-flags}
18622 Display info only for sections for which @var{section-flags} are true.
18623 The section flags that @value{GDBN} currently knows about are:
18626 Section will have space allocated in the process when loaded.
18627 Set for all sections except those containing debug information.
18629 Section will be loaded from the file into the child process memory.
18630 Set for pre-initialized code and data, clear for @code{.bss} sections.
18632 Section needs to be relocated before loading.
18634 Section cannot be modified by the child process.
18636 Section contains executable code only.
18638 Section contains data only (no executable code).
18640 Section will reside in ROM.
18642 Section contains data for constructor/destructor lists.
18644 Section is not empty.
18646 An instruction to the linker to not output the section.
18647 @item COFF_SHARED_LIBRARY
18648 A notification to the linker that the section contains
18649 COFF shared library information.
18651 Section contains common symbols.
18654 @kindex set trust-readonly-sections
18655 @cindex read-only sections
18656 @item set trust-readonly-sections on
18657 Tell @value{GDBN} that readonly sections in your object file
18658 really are read-only (i.e.@: that their contents will not change).
18659 In that case, @value{GDBN} can fetch values from these sections
18660 out of the object file, rather than from the target program.
18661 For some targets (notably embedded ones), this can be a significant
18662 enhancement to debugging performance.
18664 The default is off.
18666 @item set trust-readonly-sections off
18667 Tell @value{GDBN} not to trust readonly sections. This means that
18668 the contents of the section might change while the program is running,
18669 and must therefore be fetched from the target when needed.
18671 @item show trust-readonly-sections
18672 Show the current setting of trusting readonly sections.
18675 All file-specifying commands allow both absolute and relative file names
18676 as arguments. @value{GDBN} always converts the file name to an absolute file
18677 name and remembers it that way.
18679 @cindex shared libraries
18680 @anchor{Shared Libraries}
18681 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18682 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18683 DSBT (TIC6X) shared libraries.
18685 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18686 shared libraries. @xref{Expat}.
18688 @value{GDBN} automatically loads symbol definitions from shared libraries
18689 when you use the @code{run} command, or when you examine a core file.
18690 (Before you issue the @code{run} command, @value{GDBN} does not understand
18691 references to a function in a shared library, however---unless you are
18692 debugging a core file).
18694 @c FIXME: some @value{GDBN} release may permit some refs to undef
18695 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18696 @c FIXME...lib; check this from time to time when updating manual
18698 There are times, however, when you may wish to not automatically load
18699 symbol definitions from shared libraries, such as when they are
18700 particularly large or there are many of them.
18702 To control the automatic loading of shared library symbols, use the
18706 @kindex set auto-solib-add
18707 @item set auto-solib-add @var{mode}
18708 If @var{mode} is @code{on}, symbols from all shared object libraries
18709 will be loaded automatically when the inferior begins execution, you
18710 attach to an independently started inferior, or when the dynamic linker
18711 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18712 is @code{off}, symbols must be loaded manually, using the
18713 @code{sharedlibrary} command. The default value is @code{on}.
18715 @cindex memory used for symbol tables
18716 If your program uses lots of shared libraries with debug info that
18717 takes large amounts of memory, you can decrease the @value{GDBN}
18718 memory footprint by preventing it from automatically loading the
18719 symbols from shared libraries. To that end, type @kbd{set
18720 auto-solib-add off} before running the inferior, then load each
18721 library whose debug symbols you do need with @kbd{sharedlibrary
18722 @var{regexp}}, where @var{regexp} is a regular expression that matches
18723 the libraries whose symbols you want to be loaded.
18725 @kindex show auto-solib-add
18726 @item show auto-solib-add
18727 Display the current autoloading mode.
18730 @cindex load shared library
18731 To explicitly load shared library symbols, use the @code{sharedlibrary}
18735 @kindex info sharedlibrary
18737 @item info share @var{regex}
18738 @itemx info sharedlibrary @var{regex}
18739 Print the names of the shared libraries which are currently loaded
18740 that match @var{regex}. If @var{regex} is omitted then print
18741 all shared libraries that are loaded.
18744 @item info dll @var{regex}
18745 This is an alias of @code{info sharedlibrary}.
18747 @kindex sharedlibrary
18749 @item sharedlibrary @var{regex}
18750 @itemx share @var{regex}
18751 Load shared object library symbols for files matching a
18752 Unix regular expression.
18753 As with files loaded automatically, it only loads shared libraries
18754 required by your program for a core file or after typing @code{run}. If
18755 @var{regex} is omitted all shared libraries required by your program are
18758 @item nosharedlibrary
18759 @kindex nosharedlibrary
18760 @cindex unload symbols from shared libraries
18761 Unload all shared object library symbols. This discards all symbols
18762 that have been loaded from all shared libraries. Symbols from shared
18763 libraries that were loaded by explicit user requests are not
18767 Sometimes you may wish that @value{GDBN} stops and gives you control
18768 when any of shared library events happen. The best way to do this is
18769 to use @code{catch load} and @code{catch unload} (@pxref{Set
18772 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18773 command for this. This command exists for historical reasons. It is
18774 less useful than setting a catchpoint, because it does not allow for
18775 conditions or commands as a catchpoint does.
18778 @item set stop-on-solib-events
18779 @kindex set stop-on-solib-events
18780 This command controls whether @value{GDBN} should give you control
18781 when the dynamic linker notifies it about some shared library event.
18782 The most common event of interest is loading or unloading of a new
18785 @item show stop-on-solib-events
18786 @kindex show stop-on-solib-events
18787 Show whether @value{GDBN} stops and gives you control when shared
18788 library events happen.
18791 Shared libraries are also supported in many cross or remote debugging
18792 configurations. @value{GDBN} needs to have access to the target's libraries;
18793 this can be accomplished either by providing copies of the libraries
18794 on the host system, or by asking @value{GDBN} to automatically retrieve the
18795 libraries from the target. If copies of the target libraries are
18796 provided, they need to be the same as the target libraries, although the
18797 copies on the target can be stripped as long as the copies on the host are
18800 @cindex where to look for shared libraries
18801 For remote debugging, you need to tell @value{GDBN} where the target
18802 libraries are, so that it can load the correct copies---otherwise, it
18803 may try to load the host's libraries. @value{GDBN} has two variables
18804 to specify the search directories for target libraries.
18807 @cindex prefix for executable and shared library file names
18808 @cindex system root, alternate
18809 @kindex set solib-absolute-prefix
18810 @kindex set sysroot
18811 @item set sysroot @var{path}
18812 Use @var{path} as the system root for the program being debugged. Any
18813 absolute shared library paths will be prefixed with @var{path}; many
18814 runtime loaders store the absolute paths to the shared library in the
18815 target program's memory. When starting processes remotely, and when
18816 attaching to already-running processes (local or remote), their
18817 executable filenames will be prefixed with @var{path} if reported to
18818 @value{GDBN} as absolute by the operating system. If you use
18819 @code{set sysroot} to find executables and shared libraries, they need
18820 to be laid out in the same way that they are on the target, with
18821 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18824 If @var{path} starts with the sequence @file{target:} and the target
18825 system is remote then @value{GDBN} will retrieve the target binaries
18826 from the remote system. This is only supported when using a remote
18827 target that supports the @code{remote get} command (@pxref{File
18828 Transfer,,Sending files to a remote system}). The part of @var{path}
18829 following the initial @file{target:} (if present) is used as system
18830 root prefix on the remote file system. If @var{path} starts with the
18831 sequence @file{remote:} this is converted to the sequence
18832 @file{target:} by @code{set sysroot}@footnote{Historically the
18833 functionality to retrieve binaries from the remote system was
18834 provided by prefixing @var{path} with @file{remote:}}. If you want
18835 to specify a local system root using a directory that happens to be
18836 named @file{target:} or @file{remote:}, you need to use some
18837 equivalent variant of the name like @file{./target:}.
18839 For targets with an MS-DOS based filesystem, such as MS-Windows and
18840 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18841 absolute file name with @var{path}. But first, on Unix hosts,
18842 @value{GDBN} converts all backslash directory separators into forward
18843 slashes, because the backslash is not a directory separator on Unix:
18846 c:\foo\bar.dll @result{} c:/foo/bar.dll
18849 Then, @value{GDBN} attempts prefixing the target file name with
18850 @var{path}, and looks for the resulting file name in the host file
18854 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18857 If that does not find the binary, @value{GDBN} tries removing
18858 the @samp{:} character from the drive spec, both for convenience, and,
18859 for the case of the host file system not supporting file names with
18863 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18866 This makes it possible to have a system root that mirrors a target
18867 with more than one drive. E.g., you may want to setup your local
18868 copies of the target system shared libraries like so (note @samp{c} vs
18872 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18873 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18874 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18878 and point the system root at @file{/path/to/sysroot}, so that
18879 @value{GDBN} can find the correct copies of both
18880 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18882 If that still does not find the binary, @value{GDBN} tries
18883 removing the whole drive spec from the target file name:
18886 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18889 This last lookup makes it possible to not care about the drive name,
18890 if you don't want or need to.
18892 The @code{set solib-absolute-prefix} command is an alias for @code{set
18895 @cindex default system root
18896 @cindex @samp{--with-sysroot}
18897 You can set the default system root by using the configure-time
18898 @samp{--with-sysroot} option. If the system root is inside
18899 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18900 @samp{--exec-prefix}), then the default system root will be updated
18901 automatically if the installed @value{GDBN} is moved to a new
18904 @kindex show sysroot
18906 Display the current executable and shared library prefix.
18908 @kindex set solib-search-path
18909 @item set solib-search-path @var{path}
18910 If this variable is set, @var{path} is a colon-separated list of
18911 directories to search for shared libraries. @samp{solib-search-path}
18912 is used after @samp{sysroot} fails to locate the library, or if the
18913 path to the library is relative instead of absolute. If you want to
18914 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18915 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18916 finding your host's libraries. @samp{sysroot} is preferred; setting
18917 it to a nonexistent directory may interfere with automatic loading
18918 of shared library symbols.
18920 @kindex show solib-search-path
18921 @item show solib-search-path
18922 Display the current shared library search path.
18924 @cindex DOS file-name semantics of file names.
18925 @kindex set target-file-system-kind (unix|dos-based|auto)
18926 @kindex show target-file-system-kind
18927 @item set target-file-system-kind @var{kind}
18928 Set assumed file system kind for target reported file names.
18930 Shared library file names as reported by the target system may not
18931 make sense as is on the system @value{GDBN} is running on. For
18932 example, when remote debugging a target that has MS-DOS based file
18933 system semantics, from a Unix host, the target may be reporting to
18934 @value{GDBN} a list of loaded shared libraries with file names such as
18935 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18936 drive letters, so the @samp{c:\} prefix is not normally understood as
18937 indicating an absolute file name, and neither is the backslash
18938 normally considered a directory separator character. In that case,
18939 the native file system would interpret this whole absolute file name
18940 as a relative file name with no directory components. This would make
18941 it impossible to point @value{GDBN} at a copy of the remote target's
18942 shared libraries on the host using @code{set sysroot}, and impractical
18943 with @code{set solib-search-path}. Setting
18944 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18945 to interpret such file names similarly to how the target would, and to
18946 map them to file names valid on @value{GDBN}'s native file system
18947 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18948 to one of the supported file system kinds. In that case, @value{GDBN}
18949 tries to determine the appropriate file system variant based on the
18950 current target's operating system (@pxref{ABI, ,Configuring the
18951 Current ABI}). The supported file system settings are:
18955 Instruct @value{GDBN} to assume the target file system is of Unix
18956 kind. Only file names starting the forward slash (@samp{/}) character
18957 are considered absolute, and the directory separator character is also
18961 Instruct @value{GDBN} to assume the target file system is DOS based.
18962 File names starting with either a forward slash, or a drive letter
18963 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18964 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18965 considered directory separators.
18968 Instruct @value{GDBN} to use the file system kind associated with the
18969 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18970 This is the default.
18974 @cindex file name canonicalization
18975 @cindex base name differences
18976 When processing file names provided by the user, @value{GDBN}
18977 frequently needs to compare them to the file names recorded in the
18978 program's debug info. Normally, @value{GDBN} compares just the
18979 @dfn{base names} of the files as strings, which is reasonably fast
18980 even for very large programs. (The base name of a file is the last
18981 portion of its name, after stripping all the leading directories.)
18982 This shortcut in comparison is based upon the assumption that files
18983 cannot have more than one base name. This is usually true, but
18984 references to files that use symlinks or similar filesystem
18985 facilities violate that assumption. If your program records files
18986 using such facilities, or if you provide file names to @value{GDBN}
18987 using symlinks etc., you can set @code{basenames-may-differ} to
18988 @code{true} to instruct @value{GDBN} to completely canonicalize each
18989 pair of file names it needs to compare. This will make file-name
18990 comparisons accurate, but at a price of a significant slowdown.
18993 @item set basenames-may-differ
18994 @kindex set basenames-may-differ
18995 Set whether a source file may have multiple base names.
18997 @item show basenames-may-differ
18998 @kindex show basenames-may-differ
18999 Show whether a source file may have multiple base names.
19003 @section File Caching
19004 @cindex caching of opened files
19005 @cindex caching of bfd objects
19007 To speed up file loading, and reduce memory usage, @value{GDBN} will
19008 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19009 BFD, bfd, The Binary File Descriptor Library}. The following commands
19010 allow visibility and control of the caching behavior.
19013 @kindex maint info bfds
19014 @item maint info bfds
19015 This prints information about each @code{bfd} object that is known to
19018 @kindex maint set bfd-sharing
19019 @kindex maint show bfd-sharing
19020 @kindex bfd caching
19021 @item maint set bfd-sharing
19022 @item maint show bfd-sharing
19023 Control whether @code{bfd} objects can be shared. When sharing is
19024 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19025 than reopening the same file. Turning sharing off does not cause
19026 already shared @code{bfd} objects to be unshared, but all future files
19027 that are opened will create a new @code{bfd} object. Similarly,
19028 re-enabling sharing does not cause multiple existing @code{bfd}
19029 objects to be collapsed into a single shared @code{bfd} object.
19031 @kindex set debug bfd-cache @var{level}
19032 @kindex bfd caching
19033 @item set debug bfd-cache @var{level}
19034 Turns on debugging of the bfd cache, setting the level to @var{level}.
19036 @kindex show debug bfd-cache
19037 @kindex bfd caching
19038 @item show debug bfd-cache
19039 Show the current debugging level of the bfd cache.
19042 @node Separate Debug Files
19043 @section Debugging Information in Separate Files
19044 @cindex separate debugging information files
19045 @cindex debugging information in separate files
19046 @cindex @file{.debug} subdirectories
19047 @cindex debugging information directory, global
19048 @cindex global debugging information directories
19049 @cindex build ID, and separate debugging files
19050 @cindex @file{.build-id} directory
19052 @value{GDBN} allows you to put a program's debugging information in a
19053 file separate from the executable itself, in a way that allows
19054 @value{GDBN} to find and load the debugging information automatically.
19055 Since debugging information can be very large---sometimes larger
19056 than the executable code itself---some systems distribute debugging
19057 information for their executables in separate files, which users can
19058 install only when they need to debug a problem.
19060 @value{GDBN} supports two ways of specifying the separate debug info
19065 The executable contains a @dfn{debug link} that specifies the name of
19066 the separate debug info file. The separate debug file's name is
19067 usually @file{@var{executable}.debug}, where @var{executable} is the
19068 name of the corresponding executable file without leading directories
19069 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19070 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19071 checksum for the debug file, which @value{GDBN} uses to validate that
19072 the executable and the debug file came from the same build.
19075 The executable contains a @dfn{build ID}, a unique bit string that is
19076 also present in the corresponding debug info file. (This is supported
19077 only on some operating systems, when using the ELF or PE file formats
19078 for binary files and the @sc{gnu} Binutils.) For more details about
19079 this feature, see the description of the @option{--build-id}
19080 command-line option in @ref{Options, , Command Line Options, ld.info,
19081 The GNU Linker}. The debug info file's name is not specified
19082 explicitly by the build ID, but can be computed from the build ID, see
19086 Depending on the way the debug info file is specified, @value{GDBN}
19087 uses two different methods of looking for the debug file:
19091 For the ``debug link'' method, @value{GDBN} looks up the named file in
19092 the directory of the executable file, then in a subdirectory of that
19093 directory named @file{.debug}, and finally under each one of the global debug
19094 directories, in a subdirectory whose name is identical to the leading
19095 directories of the executable's absolute file name.
19098 For the ``build ID'' method, @value{GDBN} looks in the
19099 @file{.build-id} subdirectory of each one of the global debug directories for
19100 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19101 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19102 are the rest of the bit string. (Real build ID strings are 32 or more
19103 hex characters, not 10.)
19106 So, for example, suppose you ask @value{GDBN} to debug
19107 @file{/usr/bin/ls}, which has a debug link that specifies the
19108 file @file{ls.debug}, and a build ID whose value in hex is
19109 @code{abcdef1234}. If the list of the global debug directories includes
19110 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19111 debug information files, in the indicated order:
19115 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19117 @file{/usr/bin/ls.debug}
19119 @file{/usr/bin/.debug/ls.debug}
19121 @file{/usr/lib/debug/usr/bin/ls.debug}.
19124 @anchor{debug-file-directory}
19125 Global debugging info directories default to what is set by @value{GDBN}
19126 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19127 you can also set the global debugging info directories, and view the list
19128 @value{GDBN} is currently using.
19132 @kindex set debug-file-directory
19133 @item set debug-file-directory @var{directories}
19134 Set the directories which @value{GDBN} searches for separate debugging
19135 information files to @var{directory}. Multiple path components can be set
19136 concatenating them by a path separator.
19138 @kindex show debug-file-directory
19139 @item show debug-file-directory
19140 Show the directories @value{GDBN} searches for separate debugging
19145 @cindex @code{.gnu_debuglink} sections
19146 @cindex debug link sections
19147 A debug link is a special section of the executable file named
19148 @code{.gnu_debuglink}. The section must contain:
19152 A filename, with any leading directory components removed, followed by
19155 zero to three bytes of padding, as needed to reach the next four-byte
19156 boundary within the section, and
19158 a four-byte CRC checksum, stored in the same endianness used for the
19159 executable file itself. The checksum is computed on the debugging
19160 information file's full contents by the function given below, passing
19161 zero as the @var{crc} argument.
19164 Any executable file format can carry a debug link, as long as it can
19165 contain a section named @code{.gnu_debuglink} with the contents
19168 @cindex @code{.note.gnu.build-id} sections
19169 @cindex build ID sections
19170 The build ID is a special section in the executable file (and in other
19171 ELF binary files that @value{GDBN} may consider). This section is
19172 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19173 It contains unique identification for the built files---the ID remains
19174 the same across multiple builds of the same build tree. The default
19175 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19176 content for the build ID string. The same section with an identical
19177 value is present in the original built binary with symbols, in its
19178 stripped variant, and in the separate debugging information file.
19180 The debugging information file itself should be an ordinary
19181 executable, containing a full set of linker symbols, sections, and
19182 debugging information. The sections of the debugging information file
19183 should have the same names, addresses, and sizes as the original file,
19184 but they need not contain any data---much like a @code{.bss} section
19185 in an ordinary executable.
19187 The @sc{gnu} binary utilities (Binutils) package includes the
19188 @samp{objcopy} utility that can produce
19189 the separated executable / debugging information file pairs using the
19190 following commands:
19193 @kbd{objcopy --only-keep-debug foo foo.debug}
19198 These commands remove the debugging
19199 information from the executable file @file{foo} and place it in the file
19200 @file{foo.debug}. You can use the first, second or both methods to link the
19205 The debug link method needs the following additional command to also leave
19206 behind a debug link in @file{foo}:
19209 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19212 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19213 a version of the @code{strip} command such that the command @kbd{strip foo -f
19214 foo.debug} has the same functionality as the two @code{objcopy} commands and
19215 the @code{ln -s} command above, together.
19218 Build ID gets embedded into the main executable using @code{ld --build-id} or
19219 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19220 compatibility fixes for debug files separation are present in @sc{gnu} binary
19221 utilities (Binutils) package since version 2.18.
19226 @cindex CRC algorithm definition
19227 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19228 IEEE 802.3 using the polynomial:
19230 @c TexInfo requires naked braces for multi-digit exponents for Tex
19231 @c output, but this causes HTML output to barf. HTML has to be set using
19232 @c raw commands. So we end up having to specify this equation in 2
19237 <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>
19238 + <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
19244 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19245 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19249 The function is computed byte at a time, taking the least
19250 significant bit of each byte first. The initial pattern
19251 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19252 the final result is inverted to ensure trailing zeros also affect the
19255 @emph{Note:} This is the same CRC polynomial as used in handling the
19256 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19257 However in the case of the Remote Serial Protocol, the CRC is computed
19258 @emph{most} significant bit first, and the result is not inverted, so
19259 trailing zeros have no effect on the CRC value.
19261 To complete the description, we show below the code of the function
19262 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19263 initially supplied @code{crc} argument means that an initial call to
19264 this function passing in zero will start computing the CRC using
19267 @kindex gnu_debuglink_crc32
19270 gnu_debuglink_crc32 (unsigned long crc,
19271 unsigned char *buf, size_t len)
19273 static const unsigned long crc32_table[256] =
19275 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19276 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19277 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19278 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19279 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19280 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19281 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19282 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19283 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19284 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19285 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19286 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19287 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19288 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19289 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19290 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19291 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19292 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19293 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19294 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19295 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19296 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19297 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19298 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19299 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19300 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19301 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19302 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19303 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19304 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19305 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19306 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19307 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19308 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19309 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19310 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19311 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19312 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19313 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19314 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19315 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19316 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19317 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19318 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19319 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19320 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19321 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19322 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19323 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19324 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19325 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19328 unsigned char *end;
19330 crc = ~crc & 0xffffffff;
19331 for (end = buf + len; buf < end; ++buf)
19332 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19333 return ~crc & 0xffffffff;
19338 This computation does not apply to the ``build ID'' method.
19340 @node MiniDebugInfo
19341 @section Debugging information in a special section
19342 @cindex separate debug sections
19343 @cindex @samp{.gnu_debugdata} section
19345 Some systems ship pre-built executables and libraries that have a
19346 special @samp{.gnu_debugdata} section. This feature is called
19347 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19348 is used to supply extra symbols for backtraces.
19350 The intent of this section is to provide extra minimal debugging
19351 information for use in simple backtraces. It is not intended to be a
19352 replacement for full separate debugging information (@pxref{Separate
19353 Debug Files}). The example below shows the intended use; however,
19354 @value{GDBN} does not currently put restrictions on what sort of
19355 debugging information might be included in the section.
19357 @value{GDBN} has support for this extension. If the section exists,
19358 then it is used provided that no other source of debugging information
19359 can be found, and that @value{GDBN} was configured with LZMA support.
19361 This section can be easily created using @command{objcopy} and other
19362 standard utilities:
19365 # Extract the dynamic symbols from the main binary, there is no need
19366 # to also have these in the normal symbol table.
19367 nm -D @var{binary} --format=posix --defined-only \
19368 | awk '@{ print $1 @}' | sort > dynsyms
19370 # Extract all the text (i.e. function) symbols from the debuginfo.
19371 # (Note that we actually also accept "D" symbols, for the benefit
19372 # of platforms like PowerPC64 that use function descriptors.)
19373 nm @var{binary} --format=posix --defined-only \
19374 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19377 # Keep all the function symbols not already in the dynamic symbol
19379 comm -13 dynsyms funcsyms > keep_symbols
19381 # Separate full debug info into debug binary.
19382 objcopy --only-keep-debug @var{binary} debug
19384 # Copy the full debuginfo, keeping only a minimal set of symbols and
19385 # removing some unnecessary sections.
19386 objcopy -S --remove-section .gdb_index --remove-section .comment \
19387 --keep-symbols=keep_symbols debug mini_debuginfo
19389 # Drop the full debug info from the original binary.
19390 strip --strip-all -R .comment @var{binary}
19392 # Inject the compressed data into the .gnu_debugdata section of the
19395 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19399 @section Index Files Speed Up @value{GDBN}
19400 @cindex index files
19401 @cindex @samp{.gdb_index} section
19403 When @value{GDBN} finds a symbol file, it scans the symbols in the
19404 file in order to construct an internal symbol table. This lets most
19405 @value{GDBN} operations work quickly---at the cost of a delay early
19406 on. For large programs, this delay can be quite lengthy, so
19407 @value{GDBN} provides a way to build an index, which speeds up
19410 The index is stored as a section in the symbol file. @value{GDBN} can
19411 write the index to a file, then you can put it into the symbol file
19412 using @command{objcopy}.
19414 To create an index file, use the @code{save gdb-index} command:
19417 @item save gdb-index @var{directory}
19418 @kindex save gdb-index
19419 Create an index file for each symbol file currently known by
19420 @value{GDBN}. Each file is named after its corresponding symbol file,
19421 with @samp{.gdb-index} appended, and is written into the given
19425 Once you have created an index file you can merge it into your symbol
19426 file, here named @file{symfile}, using @command{objcopy}:
19429 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19430 --set-section-flags .gdb_index=readonly symfile symfile
19433 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19434 sections that have been deprecated. Usually they are deprecated because
19435 they are missing a new feature or have performance issues.
19436 To tell @value{GDBN} to use a deprecated index section anyway
19437 specify @code{set use-deprecated-index-sections on}.
19438 The default is @code{off}.
19439 This can speed up startup, but may result in some functionality being lost.
19440 @xref{Index Section Format}.
19442 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19443 must be done before gdb reads the file. The following will not work:
19446 $ gdb -ex "set use-deprecated-index-sections on" <program>
19449 Instead you must do, for example,
19452 $ gdb -iex "set use-deprecated-index-sections on" <program>
19455 There are currently some limitation on indices. They only work when
19456 for DWARF debugging information, not stabs. And, they do not
19457 currently work for programs using Ada.
19459 @node Symbol Errors
19460 @section Errors Reading Symbol Files
19462 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19463 such as symbol types it does not recognize, or known bugs in compiler
19464 output. By default, @value{GDBN} does not notify you of such problems, since
19465 they are relatively common and primarily of interest to people
19466 debugging compilers. If you are interested in seeing information
19467 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19468 only one message about each such type of problem, no matter how many
19469 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19470 to see how many times the problems occur, with the @code{set
19471 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19474 The messages currently printed, and their meanings, include:
19477 @item inner block not inside outer block in @var{symbol}
19479 The symbol information shows where symbol scopes begin and end
19480 (such as at the start of a function or a block of statements). This
19481 error indicates that an inner scope block is not fully contained
19482 in its outer scope blocks.
19484 @value{GDBN} circumvents the problem by treating the inner block as if it had
19485 the same scope as the outer block. In the error message, @var{symbol}
19486 may be shown as ``@code{(don't know)}'' if the outer block is not a
19489 @item block at @var{address} out of order
19491 The symbol information for symbol scope blocks should occur in
19492 order of increasing addresses. This error indicates that it does not
19495 @value{GDBN} does not circumvent this problem, and has trouble
19496 locating symbols in the source file whose symbols it is reading. (You
19497 can often determine what source file is affected by specifying
19498 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19501 @item bad block start address patched
19503 The symbol information for a symbol scope block has a start address
19504 smaller than the address of the preceding source line. This is known
19505 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19507 @value{GDBN} circumvents the problem by treating the symbol scope block as
19508 starting on the previous source line.
19510 @item bad string table offset in symbol @var{n}
19513 Symbol number @var{n} contains a pointer into the string table which is
19514 larger than the size of the string table.
19516 @value{GDBN} circumvents the problem by considering the symbol to have the
19517 name @code{foo}, which may cause other problems if many symbols end up
19520 @item unknown symbol type @code{0x@var{nn}}
19522 The symbol information contains new data types that @value{GDBN} does
19523 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19524 uncomprehended information, in hexadecimal.
19526 @value{GDBN} circumvents the error by ignoring this symbol information.
19527 This usually allows you to debug your program, though certain symbols
19528 are not accessible. If you encounter such a problem and feel like
19529 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19530 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19531 and examine @code{*bufp} to see the symbol.
19533 @item stub type has NULL name
19535 @value{GDBN} could not find the full definition for a struct or class.
19537 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19538 The symbol information for a C@t{++} member function is missing some
19539 information that recent versions of the compiler should have output for
19542 @item info mismatch between compiler and debugger
19544 @value{GDBN} could not parse a type specification output by the compiler.
19549 @section GDB Data Files
19551 @cindex prefix for data files
19552 @value{GDBN} will sometimes read an auxiliary data file. These files
19553 are kept in a directory known as the @dfn{data directory}.
19555 You can set the data directory's name, and view the name @value{GDBN}
19556 is currently using.
19559 @kindex set data-directory
19560 @item set data-directory @var{directory}
19561 Set the directory which @value{GDBN} searches for auxiliary data files
19562 to @var{directory}.
19564 @kindex show data-directory
19565 @item show data-directory
19566 Show the directory @value{GDBN} searches for auxiliary data files.
19569 @cindex default data directory
19570 @cindex @samp{--with-gdb-datadir}
19571 You can set the default data directory by using the configure-time
19572 @samp{--with-gdb-datadir} option. If the data directory is inside
19573 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19574 @samp{--exec-prefix}), then the default data directory will be updated
19575 automatically if the installed @value{GDBN} is moved to a new
19578 The data directory may also be specified with the
19579 @code{--data-directory} command line option.
19580 @xref{Mode Options}.
19583 @chapter Specifying a Debugging Target
19585 @cindex debugging target
19586 A @dfn{target} is the execution environment occupied by your program.
19588 Often, @value{GDBN} runs in the same host environment as your program;
19589 in that case, the debugging target is specified as a side effect when
19590 you use the @code{file} or @code{core} commands. When you need more
19591 flexibility---for example, running @value{GDBN} on a physically separate
19592 host, or controlling a standalone system over a serial port or a
19593 realtime system over a TCP/IP connection---you can use the @code{target}
19594 command to specify one of the target types configured for @value{GDBN}
19595 (@pxref{Target Commands, ,Commands for Managing Targets}).
19597 @cindex target architecture
19598 It is possible to build @value{GDBN} for several different @dfn{target
19599 architectures}. When @value{GDBN} is built like that, you can choose
19600 one of the available architectures with the @kbd{set architecture}
19604 @kindex set architecture
19605 @kindex show architecture
19606 @item set architecture @var{arch}
19607 This command sets the current target architecture to @var{arch}. The
19608 value of @var{arch} can be @code{"auto"}, in addition to one of the
19609 supported architectures.
19611 @item show architecture
19612 Show the current target architecture.
19614 @item set processor
19616 @kindex set processor
19617 @kindex show processor
19618 These are alias commands for, respectively, @code{set architecture}
19619 and @code{show architecture}.
19623 * Active Targets:: Active targets
19624 * Target Commands:: Commands for managing targets
19625 * Byte Order:: Choosing target byte order
19628 @node Active Targets
19629 @section Active Targets
19631 @cindex stacking targets
19632 @cindex active targets
19633 @cindex multiple targets
19635 There are multiple classes of targets such as: processes, executable files or
19636 recording sessions. Core files belong to the process class, making core file
19637 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19638 on multiple active targets, one in each class. This allows you to (for
19639 example) start a process and inspect its activity, while still having access to
19640 the executable file after the process finishes. Or if you start process
19641 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19642 presented a virtual layer of the recording target, while the process target
19643 remains stopped at the chronologically last point of the process execution.
19645 Use the @code{core-file} and @code{exec-file} commands to select a new core
19646 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19647 specify as a target a process that is already running, use the @code{attach}
19648 command (@pxref{Attach, ,Debugging an Already-running Process}).
19650 @node Target Commands
19651 @section Commands for Managing Targets
19654 @item target @var{type} @var{parameters}
19655 Connects the @value{GDBN} host environment to a target machine or
19656 process. A target is typically a protocol for talking to debugging
19657 facilities. You use the argument @var{type} to specify the type or
19658 protocol of the target machine.
19660 Further @var{parameters} are interpreted by the target protocol, but
19661 typically include things like device names or host names to connect
19662 with, process numbers, and baud rates.
19664 The @code{target} command does not repeat if you press @key{RET} again
19665 after executing the command.
19667 @kindex help target
19669 Displays the names of all targets available. To display targets
19670 currently selected, use either @code{info target} or @code{info files}
19671 (@pxref{Files, ,Commands to Specify Files}).
19673 @item help target @var{name}
19674 Describe a particular target, including any parameters necessary to
19677 @kindex set gnutarget
19678 @item set gnutarget @var{args}
19679 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19680 knows whether it is reading an @dfn{executable},
19681 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19682 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19683 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19686 @emph{Warning:} To specify a file format with @code{set gnutarget},
19687 you must know the actual BFD name.
19691 @xref{Files, , Commands to Specify Files}.
19693 @kindex show gnutarget
19694 @item show gnutarget
19695 Use the @code{show gnutarget} command to display what file format
19696 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19697 @value{GDBN} will determine the file format for each file automatically,
19698 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19701 @cindex common targets
19702 Here are some common targets (available, or not, depending on the GDB
19707 @item target exec @var{program}
19708 @cindex executable file target
19709 An executable file. @samp{target exec @var{program}} is the same as
19710 @samp{exec-file @var{program}}.
19712 @item target core @var{filename}
19713 @cindex core dump file target
19714 A core dump file. @samp{target core @var{filename}} is the same as
19715 @samp{core-file @var{filename}}.
19717 @item target remote @var{medium}
19718 @cindex remote target
19719 A remote system connected to @value{GDBN} via a serial line or network
19720 connection. This command tells @value{GDBN} to use its own remote
19721 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19723 For example, if you have a board connected to @file{/dev/ttya} on the
19724 machine running @value{GDBN}, you could say:
19727 target remote /dev/ttya
19730 @code{target remote} supports the @code{load} command. This is only
19731 useful if you have some other way of getting the stub to the target
19732 system, and you can put it somewhere in memory where it won't get
19733 clobbered by the download.
19735 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19736 @cindex built-in simulator target
19737 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19745 works; however, you cannot assume that a specific memory map, device
19746 drivers, or even basic I/O is available, although some simulators do
19747 provide these. For info about any processor-specific simulator details,
19748 see the appropriate section in @ref{Embedded Processors, ,Embedded
19751 @item target native
19752 @cindex native target
19753 Setup for local/native process debugging. Useful to make the
19754 @code{run} command spawn native processes (likewise @code{attach},
19755 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19756 (@pxref{set auto-connect-native-target}).
19760 Different targets are available on different configurations of @value{GDBN};
19761 your configuration may have more or fewer targets.
19763 Many remote targets require you to download the executable's code once
19764 you've successfully established a connection. You may wish to control
19765 various aspects of this process.
19770 @kindex set hash@r{, for remote monitors}
19771 @cindex hash mark while downloading
19772 This command controls whether a hash mark @samp{#} is displayed while
19773 downloading a file to the remote monitor. If on, a hash mark is
19774 displayed after each S-record is successfully downloaded to the
19778 @kindex show hash@r{, for remote monitors}
19779 Show the current status of displaying the hash mark.
19781 @item set debug monitor
19782 @kindex set debug monitor
19783 @cindex display remote monitor communications
19784 Enable or disable display of communications messages between
19785 @value{GDBN} and the remote monitor.
19787 @item show debug monitor
19788 @kindex show debug monitor
19789 Show the current status of displaying communications between
19790 @value{GDBN} and the remote monitor.
19795 @kindex load @var{filename} @var{offset}
19796 @item load @var{filename} @var{offset}
19798 Depending on what remote debugging facilities are configured into
19799 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19800 is meant to make @var{filename} (an executable) available for debugging
19801 on the remote system---by downloading, or dynamic linking, for example.
19802 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19803 the @code{add-symbol-file} command.
19805 If your @value{GDBN} does not have a @code{load} command, attempting to
19806 execute it gets the error message ``@code{You can't do that when your
19807 target is @dots{}}''
19809 The file is loaded at whatever address is specified in the executable.
19810 For some object file formats, you can specify the load address when you
19811 link the program; for other formats, like a.out, the object file format
19812 specifies a fixed address.
19813 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19815 It is also possible to tell @value{GDBN} to load the executable file at a
19816 specific offset described by the optional argument @var{offset}. When
19817 @var{offset} is provided, @var{filename} must also be provided.
19819 Depending on the remote side capabilities, @value{GDBN} may be able to
19820 load programs into flash memory.
19822 @code{load} does not repeat if you press @key{RET} again after using it.
19827 @kindex flash-erase
19829 @anchor{flash-erase}
19831 Erases all known flash memory regions on the target.
19836 @section Choosing Target Byte Order
19838 @cindex choosing target byte order
19839 @cindex target byte order
19841 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19842 offer the ability to run either big-endian or little-endian byte
19843 orders. Usually the executable or symbol will include a bit to
19844 designate the endian-ness, and you will not need to worry about
19845 which to use. However, you may still find it useful to adjust
19846 @value{GDBN}'s idea of processor endian-ness manually.
19850 @item set endian big
19851 Instruct @value{GDBN} to assume the target is big-endian.
19853 @item set endian little
19854 Instruct @value{GDBN} to assume the target is little-endian.
19856 @item set endian auto
19857 Instruct @value{GDBN} to use the byte order associated with the
19861 Display @value{GDBN}'s current idea of the target byte order.
19865 Note that these commands merely adjust interpretation of symbolic
19866 data on the host, and that they have absolutely no effect on the
19870 @node Remote Debugging
19871 @chapter Debugging Remote Programs
19872 @cindex remote debugging
19874 If you are trying to debug a program running on a machine that cannot run
19875 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19876 For example, you might use remote debugging on an operating system kernel,
19877 or on a small system which does not have a general purpose operating system
19878 powerful enough to run a full-featured debugger.
19880 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19881 to make this work with particular debugging targets. In addition,
19882 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19883 but not specific to any particular target system) which you can use if you
19884 write the remote stubs---the code that runs on the remote system to
19885 communicate with @value{GDBN}.
19887 Other remote targets may be available in your
19888 configuration of @value{GDBN}; use @code{help target} to list them.
19891 * Connecting:: Connecting to a remote target
19892 * File Transfer:: Sending files to a remote system
19893 * Server:: Using the gdbserver program
19894 * Remote Configuration:: Remote configuration
19895 * Remote Stub:: Implementing a remote stub
19899 @section Connecting to a Remote Target
19900 @cindex remote debugging, connecting
19901 @cindex @code{gdbserver}, connecting
19902 @cindex remote debugging, types of connections
19903 @cindex @code{gdbserver}, types of connections
19904 @cindex @code{gdbserver}, @code{target remote} mode
19905 @cindex @code{gdbserver}, @code{target extended-remote} mode
19907 This section describes how to connect to a remote target, including the
19908 types of connections and their differences, how to set up executable and
19909 symbol files on the host and target, and the commands used for
19910 connecting to and disconnecting from the remote target.
19912 @subsection Types of Remote Connections
19914 @value{GDBN} supports two types of remote connections, @code{target remote}
19915 mode and @code{target extended-remote} mode. Note that many remote targets
19916 support only @code{target remote} mode. There are several major
19917 differences between the two types of connections, enumerated here:
19921 @cindex remote debugging, detach and program exit
19922 @item Result of detach or program exit
19923 @strong{With target remote mode:} When the debugged program exits or you
19924 detach from it, @value{GDBN} disconnects from the target. When using
19925 @code{gdbserver}, @code{gdbserver} will exit.
19927 @strong{With target extended-remote mode:} When the debugged program exits or
19928 you detach from it, @value{GDBN} remains connected to the target, even
19929 though no program is running. You can rerun the program, attach to a
19930 running program, or use @code{monitor} commands specific to the target.
19932 When using @code{gdbserver} in this case, it does not exit unless it was
19933 invoked using the @option{--once} option. If the @option{--once} option
19934 was not used, you can ask @code{gdbserver} to exit using the
19935 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19937 @item Specifying the program to debug
19938 For both connection types you use the @code{file} command to specify the
19939 program on the host system. If you are using @code{gdbserver} there are
19940 some differences in how to specify the location of the program on the
19943 @strong{With target remote mode:} You must either specify the program to debug
19944 on the @code{gdbserver} command line or use the @option{--attach} option
19945 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19947 @cindex @option{--multi}, @code{gdbserver} option
19948 @strong{With target extended-remote mode:} You may specify the program to debug
19949 on the @code{gdbserver} command line, or you can load the program or attach
19950 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19952 @anchor{--multi Option in Types of Remote Connnections}
19953 You can start @code{gdbserver} without supplying an initial command to run
19954 or process ID to attach. To do this, use the @option{--multi} command line
19955 option. Then you can connect using @code{target extended-remote} and start
19956 the program you want to debug (see below for details on using the
19957 @code{run} command in this scenario). Note that the conditions under which
19958 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19959 (@code{target remote} or @code{target extended-remote}). The
19960 @option{--multi} option to @code{gdbserver} has no influence on that.
19962 @item The @code{run} command
19963 @strong{With target remote mode:} The @code{run} command is not
19964 supported. Once a connection has been established, you can use all
19965 the usual @value{GDBN} commands to examine and change data. The
19966 remote program is already running, so you can use commands like
19967 @kbd{step} and @kbd{continue}.
19969 @strong{With target extended-remote mode:} The @code{run} command is
19970 supported. The @code{run} command uses the value set by
19971 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19972 the program to run. Command line arguments are supported, except for
19973 wildcard expansion and I/O redirection (@pxref{Arguments}).
19975 If you specify the program to debug on the command line, then the
19976 @code{run} command is not required to start execution, and you can
19977 resume using commands like @kbd{step} and @kbd{continue} as with
19978 @code{target remote} mode.
19980 @anchor{Attaching in Types of Remote Connections}
19982 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19983 not supported. To attach to a running program using @code{gdbserver}, you
19984 must use the @option{--attach} option (@pxref{Running gdbserver}).
19986 @strong{With target extended-remote mode:} To attach to a running program,
19987 you may use the @code{attach} command after the connection has been
19988 established. If you are using @code{gdbserver}, you may also invoke
19989 @code{gdbserver} using the @option{--attach} option
19990 (@pxref{Running gdbserver}).
19994 @anchor{Host and target files}
19995 @subsection Host and Target Files
19996 @cindex remote debugging, symbol files
19997 @cindex symbol files, remote debugging
19999 @value{GDBN}, running on the host, needs access to symbol and debugging
20000 information for your program running on the target. This requires
20001 access to an unstripped copy of your program, and possibly any associated
20002 symbol files. Note that this section applies equally to both @code{target
20003 remote} mode and @code{target extended-remote} mode.
20005 Some remote targets (@pxref{qXfer executable filename read}, and
20006 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20007 the same connection used to communicate with @value{GDBN}. With such a
20008 target, if the remote program is unstripped, the only command you need is
20009 @code{target remote} (or @code{target extended-remote}).
20011 If the remote program is stripped, or the target does not support remote
20012 program file access, start up @value{GDBN} using the name of the local
20013 unstripped copy of your program as the first argument, or use the
20014 @code{file} command. Use @code{set sysroot} to specify the location (on
20015 the host) of target libraries (unless your @value{GDBN} was compiled with
20016 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20017 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20020 The symbol file and target libraries must exactly match the executable
20021 and libraries on the target, with one exception: the files on the host
20022 system should not be stripped, even if the files on the target system
20023 are. Mismatched or missing files will lead to confusing results
20024 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20025 files may also prevent @code{gdbserver} from debugging multi-threaded
20028 @subsection Remote Connection Commands
20029 @cindex remote connection commands
20030 @value{GDBN} can communicate with the target over a serial line, or
20031 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20032 each case, @value{GDBN} uses the same protocol for debugging your
20033 program; only the medium carrying the debugging packets varies. The
20034 @code{target remote} and @code{target extended-remote} commands
20035 establish a connection to the target. Both commands accept the same
20036 arguments, which indicate the medium to use:
20040 @item target remote @var{serial-device}
20041 @itemx target extended-remote @var{serial-device}
20042 @cindex serial line, @code{target remote}
20043 Use @var{serial-device} to communicate with the target. For example,
20044 to use a serial line connected to the device named @file{/dev/ttyb}:
20047 target remote /dev/ttyb
20050 If you're using a serial line, you may want to give @value{GDBN} the
20051 @samp{--baud} option, or use the @code{set serial baud} command
20052 (@pxref{Remote Configuration, set serial baud}) before the
20053 @code{target} command.
20055 @item target remote @code{@var{host}:@var{port}}
20056 @itemx target remote @code{tcp:@var{host}:@var{port}}
20057 @itemx target extended-remote @code{@var{host}:@var{port}}
20058 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20059 @cindex @acronym{TCP} port, @code{target remote}
20060 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20061 The @var{host} may be either a host name or a numeric @acronym{IP}
20062 address; @var{port} must be a decimal number. The @var{host} could be
20063 the target machine itself, if it is directly connected to the net, or
20064 it might be a terminal server which in turn has a serial line to the
20067 For example, to connect to port 2828 on a terminal server named
20071 target remote manyfarms:2828
20074 If your remote target is actually running on the same machine as your
20075 debugger session (e.g.@: a simulator for your target running on the
20076 same host), you can omit the hostname. For example, to connect to
20077 port 1234 on your local machine:
20080 target remote :1234
20084 Note that the colon is still required here.
20086 @item target remote @code{udp:@var{host}:@var{port}}
20087 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20088 @cindex @acronym{UDP} port, @code{target remote}
20089 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20090 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20093 target remote udp:manyfarms:2828
20096 When using a @acronym{UDP} connection for remote debugging, you should
20097 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20098 can silently drop packets on busy or unreliable networks, which will
20099 cause havoc with your debugging session.
20101 @item target remote | @var{command}
20102 @itemx target extended-remote | @var{command}
20103 @cindex pipe, @code{target remote} to
20104 Run @var{command} in the background and communicate with it using a
20105 pipe. The @var{command} is a shell command, to be parsed and expanded
20106 by the system's command shell, @code{/bin/sh}; it should expect remote
20107 protocol packets on its standard input, and send replies on its
20108 standard output. You could use this to run a stand-alone simulator
20109 that speaks the remote debugging protocol, to make net connections
20110 using programs like @code{ssh}, or for other similar tricks.
20112 If @var{command} closes its standard output (perhaps by exiting),
20113 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20114 program has already exited, this will have no effect.)
20118 @cindex interrupting remote programs
20119 @cindex remote programs, interrupting
20120 Whenever @value{GDBN} is waiting for the remote program, if you type the
20121 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20122 program. This may or may not succeed, depending in part on the hardware
20123 and the serial drivers the remote system uses. If you type the
20124 interrupt character once again, @value{GDBN} displays this prompt:
20127 Interrupted while waiting for the program.
20128 Give up (and stop debugging it)? (y or n)
20131 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20132 the remote debugging session. (If you decide you want to try again later,
20133 you can use @kbd{target remote} again to connect once more.) If you type
20134 @kbd{n}, @value{GDBN} goes back to waiting.
20136 In @code{target extended-remote} mode, typing @kbd{n} will leave
20137 @value{GDBN} connected to the target.
20140 @kindex detach (remote)
20142 When you have finished debugging the remote program, you can use the
20143 @code{detach} command to release it from @value{GDBN} control.
20144 Detaching from the target normally resumes its execution, but the results
20145 will depend on your particular remote stub. After the @code{detach}
20146 command in @code{target remote} mode, @value{GDBN} is free to connect to
20147 another target. In @code{target extended-remote} mode, @value{GDBN} is
20148 still connected to the target.
20152 The @code{disconnect} command closes the connection to the target, and
20153 the target is generally not resumed. It will wait for @value{GDBN}
20154 (this instance or another one) to connect and continue debugging. After
20155 the @code{disconnect} command, @value{GDBN} is again free to connect to
20158 @cindex send command to remote monitor
20159 @cindex extend @value{GDBN} for remote targets
20160 @cindex add new commands for external monitor
20162 @item monitor @var{cmd}
20163 This command allows you to send arbitrary commands directly to the
20164 remote monitor. Since @value{GDBN} doesn't care about the commands it
20165 sends like this, this command is the way to extend @value{GDBN}---you
20166 can add new commands that only the external monitor will understand
20170 @node File Transfer
20171 @section Sending files to a remote system
20172 @cindex remote target, file transfer
20173 @cindex file transfer
20174 @cindex sending files to remote systems
20176 Some remote targets offer the ability to transfer files over the same
20177 connection used to communicate with @value{GDBN}. This is convenient
20178 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20179 running @code{gdbserver} over a network interface. For other targets,
20180 e.g.@: embedded devices with only a single serial port, this may be
20181 the only way to upload or download files.
20183 Not all remote targets support these commands.
20187 @item remote put @var{hostfile} @var{targetfile}
20188 Copy file @var{hostfile} from the host system (the machine running
20189 @value{GDBN}) to @var{targetfile} on the target system.
20192 @item remote get @var{targetfile} @var{hostfile}
20193 Copy file @var{targetfile} from the target system to @var{hostfile}
20194 on the host system.
20196 @kindex remote delete
20197 @item remote delete @var{targetfile}
20198 Delete @var{targetfile} from the target system.
20203 @section Using the @code{gdbserver} Program
20206 @cindex remote connection without stubs
20207 @code{gdbserver} is a control program for Unix-like systems, which
20208 allows you to connect your program with a remote @value{GDBN} via
20209 @code{target remote} or @code{target extended-remote}---but without
20210 linking in the usual debugging stub.
20212 @code{gdbserver} is not a complete replacement for the debugging stubs,
20213 because it requires essentially the same operating-system facilities
20214 that @value{GDBN} itself does. In fact, a system that can run
20215 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20216 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20217 because it is a much smaller program than @value{GDBN} itself. It is
20218 also easier to port than all of @value{GDBN}, so you may be able to get
20219 started more quickly on a new system by using @code{gdbserver}.
20220 Finally, if you develop code for real-time systems, you may find that
20221 the tradeoffs involved in real-time operation make it more convenient to
20222 do as much development work as possible on another system, for example
20223 by cross-compiling. You can use @code{gdbserver} to make a similar
20224 choice for debugging.
20226 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20227 or a TCP connection, using the standard @value{GDBN} remote serial
20231 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20232 Do not run @code{gdbserver} connected to any public network; a
20233 @value{GDBN} connection to @code{gdbserver} provides access to the
20234 target system with the same privileges as the user running
20238 @anchor{Running gdbserver}
20239 @subsection Running @code{gdbserver}
20240 @cindex arguments, to @code{gdbserver}
20241 @cindex @code{gdbserver}, command-line arguments
20243 Run @code{gdbserver} on the target system. You need a copy of the
20244 program you want to debug, including any libraries it requires.
20245 @code{gdbserver} does not need your program's symbol table, so you can
20246 strip the program if necessary to save space. @value{GDBN} on the host
20247 system does all the symbol handling.
20249 To use the server, you must tell it how to communicate with @value{GDBN};
20250 the name of your program; and the arguments for your program. The usual
20254 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20257 @var{comm} is either a device name (to use a serial line), or a TCP
20258 hostname and portnumber, or @code{-} or @code{stdio} to use
20259 stdin/stdout of @code{gdbserver}.
20260 For example, to debug Emacs with the argument
20261 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20265 target> gdbserver /dev/com1 emacs foo.txt
20268 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20271 To use a TCP connection instead of a serial line:
20274 target> gdbserver host:2345 emacs foo.txt
20277 The only difference from the previous example is the first argument,
20278 specifying that you are communicating with the host @value{GDBN} via
20279 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20280 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20281 (Currently, the @samp{host} part is ignored.) You can choose any number
20282 you want for the port number as long as it does not conflict with any
20283 TCP ports already in use on the target system (for example, @code{23} is
20284 reserved for @code{telnet}).@footnote{If you choose a port number that
20285 conflicts with another service, @code{gdbserver} prints an error message
20286 and exits.} You must use the same port number with the host @value{GDBN}
20287 @code{target remote} command.
20289 The @code{stdio} connection is useful when starting @code{gdbserver}
20293 (gdb) target remote | ssh -T hostname gdbserver - hello
20296 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20297 and we don't want escape-character handling. Ssh does this by default when
20298 a command is provided, the flag is provided to make it explicit.
20299 You could elide it if you want to.
20301 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20302 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20303 display through a pipe connected to gdbserver.
20304 Both @code{stdout} and @code{stderr} use the same pipe.
20306 @anchor{Attaching to a program}
20307 @subsubsection Attaching to a Running Program
20308 @cindex attach to a program, @code{gdbserver}
20309 @cindex @option{--attach}, @code{gdbserver} option
20311 On some targets, @code{gdbserver} can also attach to running programs.
20312 This is accomplished via the @code{--attach} argument. The syntax is:
20315 target> gdbserver --attach @var{comm} @var{pid}
20318 @var{pid} is the process ID of a currently running process. It isn't
20319 necessary to point @code{gdbserver} at a binary for the running process.
20321 In @code{target extended-remote} mode, you can also attach using the
20322 @value{GDBN} attach command
20323 (@pxref{Attaching in Types of Remote Connections}).
20326 You can debug processes by name instead of process ID if your target has the
20327 @code{pidof} utility:
20330 target> gdbserver --attach @var{comm} `pidof @var{program}`
20333 In case more than one copy of @var{program} is running, or @var{program}
20334 has multiple threads, most versions of @code{pidof} support the
20335 @code{-s} option to only return the first process ID.
20337 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20339 This section applies only when @code{gdbserver} is run to listen on a TCP
20342 @code{gdbserver} normally terminates after all of its debugged processes have
20343 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20344 extended-remote}, @code{gdbserver} stays running even with no processes left.
20345 @value{GDBN} normally terminates the spawned debugged process on its exit,
20346 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20347 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20348 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20349 stays running even in the @kbd{target remote} mode.
20351 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20352 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20353 completeness, at most one @value{GDBN} can be connected at a time.
20355 @cindex @option{--once}, @code{gdbserver} option
20356 By default, @code{gdbserver} keeps the listening TCP port open, so that
20357 subsequent connections are possible. However, if you start @code{gdbserver}
20358 with the @option{--once} option, it will stop listening for any further
20359 connection attempts after connecting to the first @value{GDBN} session. This
20360 means no further connections to @code{gdbserver} will be possible after the
20361 first one. It also means @code{gdbserver} will terminate after the first
20362 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20363 connections and even in the @kbd{target extended-remote} mode. The
20364 @option{--once} option allows reusing the same port number for connecting to
20365 multiple instances of @code{gdbserver} running on the same host, since each
20366 instance closes its port after the first connection.
20368 @anchor{Other Command-Line Arguments for gdbserver}
20369 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20371 You can use the @option{--multi} option to start @code{gdbserver} without
20372 specifying a program to debug or a process to attach to. Then you can
20373 attach in @code{target extended-remote} mode and run or attach to a
20374 program. For more information,
20375 @pxref{--multi Option in Types of Remote Connnections}.
20377 @cindex @option{--debug}, @code{gdbserver} option
20378 The @option{--debug} option tells @code{gdbserver} to display extra
20379 status information about the debugging process.
20380 @cindex @option{--remote-debug}, @code{gdbserver} option
20381 The @option{--remote-debug} option tells @code{gdbserver} to display
20382 remote protocol debug output. These options are intended for
20383 @code{gdbserver} development and for bug reports to the developers.
20385 @cindex @option{--debug-format}, @code{gdbserver} option
20386 The @option{--debug-format=option1[,option2,...]} option tells
20387 @code{gdbserver} to include additional information in each output.
20388 Possible options are:
20392 Turn off all extra information in debugging output.
20394 Turn on all extra information in debugging output.
20396 Include a timestamp in each line of debugging output.
20399 Options are processed in order. Thus, for example, if @option{none}
20400 appears last then no additional information is added to debugging output.
20402 @cindex @option{--wrapper}, @code{gdbserver} option
20403 The @option{--wrapper} option specifies a wrapper to launch programs
20404 for debugging. The option should be followed by the name of the
20405 wrapper, then any command-line arguments to pass to the wrapper, then
20406 @kbd{--} indicating the end of the wrapper arguments.
20408 @code{gdbserver} runs the specified wrapper program with a combined
20409 command line including the wrapper arguments, then the name of the
20410 program to debug, then any arguments to the program. The wrapper
20411 runs until it executes your program, and then @value{GDBN} gains control.
20413 You can use any program that eventually calls @code{execve} with
20414 its arguments as a wrapper. Several standard Unix utilities do
20415 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20416 with @code{exec "$@@"} will also work.
20418 For example, you can use @code{env} to pass an environment variable to
20419 the debugged program, without setting the variable in @code{gdbserver}'s
20423 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20426 @cindex @option{--selftest}
20427 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20430 $ gdbserver --selftest
20431 Ran 2 unit tests, 0 failed
20434 These tests are disabled in release.
20435 @subsection Connecting to @code{gdbserver}
20437 The basic procedure for connecting to the remote target is:
20441 Run @value{GDBN} on the host system.
20444 Make sure you have the necessary symbol files
20445 (@pxref{Host and target files}).
20446 Load symbols for your application using the @code{file} command before you
20447 connect. Use @code{set sysroot} to locate target libraries (unless your
20448 @value{GDBN} was compiled with the correct sysroot using
20449 @code{--with-sysroot}).
20452 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20453 For TCP connections, you must start up @code{gdbserver} prior to using
20454 the @code{target} command. Otherwise you may get an error whose
20455 text depends on the host system, but which usually looks something like
20456 @samp{Connection refused}. Don't use the @code{load}
20457 command in @value{GDBN} when using @code{target remote} mode, since the
20458 program is already on the target.
20462 @anchor{Monitor Commands for gdbserver}
20463 @subsection Monitor Commands for @code{gdbserver}
20464 @cindex monitor commands, for @code{gdbserver}
20466 During a @value{GDBN} session using @code{gdbserver}, you can use the
20467 @code{monitor} command to send special requests to @code{gdbserver}.
20468 Here are the available commands.
20472 List the available monitor commands.
20474 @item monitor set debug 0
20475 @itemx monitor set debug 1
20476 Disable or enable general debugging messages.
20478 @item monitor set remote-debug 0
20479 @itemx monitor set remote-debug 1
20480 Disable or enable specific debugging messages associated with the remote
20481 protocol (@pxref{Remote Protocol}).
20483 @item monitor set debug-format option1@r{[},option2,...@r{]}
20484 Specify additional text to add to debugging messages.
20485 Possible options are:
20489 Turn off all extra information in debugging output.
20491 Turn on all extra information in debugging output.
20493 Include a timestamp in each line of debugging output.
20496 Options are processed in order. Thus, for example, if @option{none}
20497 appears last then no additional information is added to debugging output.
20499 @item monitor set libthread-db-search-path [PATH]
20500 @cindex gdbserver, search path for @code{libthread_db}
20501 When this command is issued, @var{path} is a colon-separated list of
20502 directories to search for @code{libthread_db} (@pxref{Threads,,set
20503 libthread-db-search-path}). If you omit @var{path},
20504 @samp{libthread-db-search-path} will be reset to its default value.
20506 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20507 not supported in @code{gdbserver}.
20510 Tell gdbserver to exit immediately. This command should be followed by
20511 @code{disconnect} to close the debugging session. @code{gdbserver} will
20512 detach from any attached processes and kill any processes it created.
20513 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20514 of a multi-process mode debug session.
20518 @subsection Tracepoints support in @code{gdbserver}
20519 @cindex tracepoints support in @code{gdbserver}
20521 On some targets, @code{gdbserver} supports tracepoints, fast
20522 tracepoints and static tracepoints.
20524 For fast or static tracepoints to work, a special library called the
20525 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20526 This library is built and distributed as an integral part of
20527 @code{gdbserver}. In addition, support for static tracepoints
20528 requires building the in-process agent library with static tracepoints
20529 support. At present, the UST (LTTng Userspace Tracer,
20530 @url{http://lttng.org/ust}) tracing engine is supported. This support
20531 is automatically available if UST development headers are found in the
20532 standard include path when @code{gdbserver} is built, or if
20533 @code{gdbserver} was explicitly configured using @option{--with-ust}
20534 to point at such headers. You can explicitly disable the support
20535 using @option{--with-ust=no}.
20537 There are several ways to load the in-process agent in your program:
20540 @item Specifying it as dependency at link time
20542 You can link your program dynamically with the in-process agent
20543 library. On most systems, this is accomplished by adding
20544 @code{-linproctrace} to the link command.
20546 @item Using the system's preloading mechanisms
20548 You can force loading the in-process agent at startup time by using
20549 your system's support for preloading shared libraries. Many Unixes
20550 support the concept of preloading user defined libraries. In most
20551 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20552 in the environment. See also the description of @code{gdbserver}'s
20553 @option{--wrapper} command line option.
20555 @item Using @value{GDBN} to force loading the agent at run time
20557 On some systems, you can force the inferior to load a shared library,
20558 by calling a dynamic loader function in the inferior that takes care
20559 of dynamically looking up and loading a shared library. On most Unix
20560 systems, the function is @code{dlopen}. You'll use the @code{call}
20561 command for that. For example:
20564 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20567 Note that on most Unix systems, for the @code{dlopen} function to be
20568 available, the program needs to be linked with @code{-ldl}.
20571 On systems that have a userspace dynamic loader, like most Unix
20572 systems, when you connect to @code{gdbserver} using @code{target
20573 remote}, you'll find that the program is stopped at the dynamic
20574 loader's entry point, and no shared library has been loaded in the
20575 program's address space yet, including the in-process agent. In that
20576 case, before being able to use any of the fast or static tracepoints
20577 features, you need to let the loader run and load the shared
20578 libraries. The simplest way to do that is to run the program to the
20579 main procedure. E.g., if debugging a C or C@t{++} program, start
20580 @code{gdbserver} like so:
20583 $ gdbserver :9999 myprogram
20586 Start GDB and connect to @code{gdbserver} like so, and run to main:
20590 (@value{GDBP}) target remote myhost:9999
20591 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20592 (@value{GDBP}) b main
20593 (@value{GDBP}) continue
20596 The in-process tracing agent library should now be loaded into the
20597 process; you can confirm it with the @code{info sharedlibrary}
20598 command, which will list @file{libinproctrace.so} as loaded in the
20599 process. You are now ready to install fast tracepoints, list static
20600 tracepoint markers, probe static tracepoints markers, and start
20603 @node Remote Configuration
20604 @section Remote Configuration
20607 @kindex show remote
20608 This section documents the configuration options available when
20609 debugging remote programs. For the options related to the File I/O
20610 extensions of the remote protocol, see @ref{system,
20611 system-call-allowed}.
20614 @item set remoteaddresssize @var{bits}
20615 @cindex address size for remote targets
20616 @cindex bits in remote address
20617 Set the maximum size of address in a memory packet to the specified
20618 number of bits. @value{GDBN} will mask off the address bits above
20619 that number, when it passes addresses to the remote target. The
20620 default value is the number of bits in the target's address.
20622 @item show remoteaddresssize
20623 Show the current value of remote address size in bits.
20625 @item set serial baud @var{n}
20626 @cindex baud rate for remote targets
20627 Set the baud rate for the remote serial I/O to @var{n} baud. The
20628 value is used to set the speed of the serial port used for debugging
20631 @item show serial baud
20632 Show the current speed of the remote connection.
20634 @item set serial parity @var{parity}
20635 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20636 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20638 @item show serial parity
20639 Show the current parity of the serial port.
20641 @item set remotebreak
20642 @cindex interrupt remote programs
20643 @cindex BREAK signal instead of Ctrl-C
20644 @anchor{set remotebreak}
20645 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20646 when you type @kbd{Ctrl-c} to interrupt the program running
20647 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20648 character instead. The default is off, since most remote systems
20649 expect to see @samp{Ctrl-C} as the interrupt signal.
20651 @item show remotebreak
20652 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20653 interrupt the remote program.
20655 @item set remoteflow on
20656 @itemx set remoteflow off
20657 @kindex set remoteflow
20658 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20659 on the serial port used to communicate to the remote target.
20661 @item show remoteflow
20662 @kindex show remoteflow
20663 Show the current setting of hardware flow control.
20665 @item set remotelogbase @var{base}
20666 Set the base (a.k.a.@: radix) of logging serial protocol
20667 communications to @var{base}. Supported values of @var{base} are:
20668 @code{ascii}, @code{octal}, and @code{hex}. The default is
20671 @item show remotelogbase
20672 Show the current setting of the radix for logging remote serial
20675 @item set remotelogfile @var{file}
20676 @cindex record serial communications on file
20677 Record remote serial communications on the named @var{file}. The
20678 default is not to record at all.
20680 @item show remotelogfile.
20681 Show the current setting of the file name on which to record the
20682 serial communications.
20684 @item set remotetimeout @var{num}
20685 @cindex timeout for serial communications
20686 @cindex remote timeout
20687 Set the timeout limit to wait for the remote target to respond to
20688 @var{num} seconds. The default is 2 seconds.
20690 @item show remotetimeout
20691 Show the current number of seconds to wait for the remote target
20694 @cindex limit hardware breakpoints and watchpoints
20695 @cindex remote target, limit break- and watchpoints
20696 @anchor{set remote hardware-watchpoint-limit}
20697 @anchor{set remote hardware-breakpoint-limit}
20698 @item set remote hardware-watchpoint-limit @var{limit}
20699 @itemx set remote hardware-breakpoint-limit @var{limit}
20700 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20701 watchpoints. A limit of -1, the default, is treated as unlimited.
20703 @cindex limit hardware watchpoints length
20704 @cindex remote target, limit watchpoints length
20705 @anchor{set remote hardware-watchpoint-length-limit}
20706 @item set remote hardware-watchpoint-length-limit @var{limit}
20707 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20708 a remote hardware watchpoint. A limit of -1, the default, is treated
20711 @item show remote hardware-watchpoint-length-limit
20712 Show the current limit (in bytes) of the maximum length of
20713 a remote hardware watchpoint.
20715 @item set remote exec-file @var{filename}
20716 @itemx show remote exec-file
20717 @anchor{set remote exec-file}
20718 @cindex executable file, for remote target
20719 Select the file used for @code{run} with @code{target
20720 extended-remote}. This should be set to a filename valid on the
20721 target system. If it is not set, the target will use a default
20722 filename (e.g.@: the last program run).
20724 @item set remote interrupt-sequence
20725 @cindex interrupt remote programs
20726 @cindex select Ctrl-C, BREAK or BREAK-g
20727 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20728 @samp{BREAK-g} as the
20729 sequence to the remote target in order to interrupt the execution.
20730 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20731 is high level of serial line for some certain time.
20732 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20733 It is @code{BREAK} signal followed by character @code{g}.
20735 @item show interrupt-sequence
20736 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20737 is sent by @value{GDBN} to interrupt the remote program.
20738 @code{BREAK-g} is BREAK signal followed by @code{g} and
20739 also known as Magic SysRq g.
20741 @item set remote interrupt-on-connect
20742 @cindex send interrupt-sequence on start
20743 Specify whether interrupt-sequence is sent to remote target when
20744 @value{GDBN} connects to it. This is mostly needed when you debug
20745 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20746 which is known as Magic SysRq g in order to connect @value{GDBN}.
20748 @item show interrupt-on-connect
20749 Show whether interrupt-sequence is sent
20750 to remote target when @value{GDBN} connects to it.
20754 @item set tcp auto-retry on
20755 @cindex auto-retry, for remote TCP target
20756 Enable auto-retry for remote TCP connections. This is useful if the remote
20757 debugging agent is launched in parallel with @value{GDBN}; there is a race
20758 condition because the agent may not become ready to accept the connection
20759 before @value{GDBN} attempts to connect. When auto-retry is
20760 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20761 to establish the connection using the timeout specified by
20762 @code{set tcp connect-timeout}.
20764 @item set tcp auto-retry off
20765 Do not auto-retry failed TCP connections.
20767 @item show tcp auto-retry
20768 Show the current auto-retry setting.
20770 @item set tcp connect-timeout @var{seconds}
20771 @itemx set tcp connect-timeout unlimited
20772 @cindex connection timeout, for remote TCP target
20773 @cindex timeout, for remote target connection
20774 Set the timeout for establishing a TCP connection to the remote target to
20775 @var{seconds}. The timeout affects both polling to retry failed connections
20776 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20777 that are merely slow to complete, and represents an approximate cumulative
20778 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20779 @value{GDBN} will keep attempting to establish a connection forever,
20780 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20782 @item show tcp connect-timeout
20783 Show the current connection timeout setting.
20786 @cindex remote packets, enabling and disabling
20787 The @value{GDBN} remote protocol autodetects the packets supported by
20788 your debugging stub. If you need to override the autodetection, you
20789 can use these commands to enable or disable individual packets. Each
20790 packet can be set to @samp{on} (the remote target supports this
20791 packet), @samp{off} (the remote target does not support this packet),
20792 or @samp{auto} (detect remote target support for this packet). They
20793 all default to @samp{auto}. For more information about each packet,
20794 see @ref{Remote Protocol}.
20796 During normal use, you should not have to use any of these commands.
20797 If you do, that may be a bug in your remote debugging stub, or a bug
20798 in @value{GDBN}. You may want to report the problem to the
20799 @value{GDBN} developers.
20801 For each packet @var{name}, the command to enable or disable the
20802 packet is @code{set remote @var{name}-packet}. The available settings
20805 @multitable @columnfractions 0.28 0.32 0.25
20808 @tab Related Features
20810 @item @code{fetch-register}
20812 @tab @code{info registers}
20814 @item @code{set-register}
20818 @item @code{binary-download}
20820 @tab @code{load}, @code{set}
20822 @item @code{read-aux-vector}
20823 @tab @code{qXfer:auxv:read}
20824 @tab @code{info auxv}
20826 @item @code{symbol-lookup}
20827 @tab @code{qSymbol}
20828 @tab Detecting multiple threads
20830 @item @code{attach}
20831 @tab @code{vAttach}
20834 @item @code{verbose-resume}
20836 @tab Stepping or resuming multiple threads
20842 @item @code{software-breakpoint}
20846 @item @code{hardware-breakpoint}
20850 @item @code{write-watchpoint}
20854 @item @code{read-watchpoint}
20858 @item @code{access-watchpoint}
20862 @item @code{pid-to-exec-file}
20863 @tab @code{qXfer:exec-file:read}
20864 @tab @code{attach}, @code{run}
20866 @item @code{target-features}
20867 @tab @code{qXfer:features:read}
20868 @tab @code{set architecture}
20870 @item @code{library-info}
20871 @tab @code{qXfer:libraries:read}
20872 @tab @code{info sharedlibrary}
20874 @item @code{memory-map}
20875 @tab @code{qXfer:memory-map:read}
20876 @tab @code{info mem}
20878 @item @code{read-sdata-object}
20879 @tab @code{qXfer:sdata:read}
20880 @tab @code{print $_sdata}
20882 @item @code{read-spu-object}
20883 @tab @code{qXfer:spu:read}
20884 @tab @code{info spu}
20886 @item @code{write-spu-object}
20887 @tab @code{qXfer:spu:write}
20888 @tab @code{info spu}
20890 @item @code{read-siginfo-object}
20891 @tab @code{qXfer:siginfo:read}
20892 @tab @code{print $_siginfo}
20894 @item @code{write-siginfo-object}
20895 @tab @code{qXfer:siginfo:write}
20896 @tab @code{set $_siginfo}
20898 @item @code{threads}
20899 @tab @code{qXfer:threads:read}
20900 @tab @code{info threads}
20902 @item @code{get-thread-local-@*storage-address}
20903 @tab @code{qGetTLSAddr}
20904 @tab Displaying @code{__thread} variables
20906 @item @code{get-thread-information-block-address}
20907 @tab @code{qGetTIBAddr}
20908 @tab Display MS-Windows Thread Information Block.
20910 @item @code{search-memory}
20911 @tab @code{qSearch:memory}
20914 @item @code{supported-packets}
20915 @tab @code{qSupported}
20916 @tab Remote communications parameters
20918 @item @code{catch-syscalls}
20919 @tab @code{QCatchSyscalls}
20920 @tab @code{catch syscall}
20922 @item @code{pass-signals}
20923 @tab @code{QPassSignals}
20924 @tab @code{handle @var{signal}}
20926 @item @code{program-signals}
20927 @tab @code{QProgramSignals}
20928 @tab @code{handle @var{signal}}
20930 @item @code{hostio-close-packet}
20931 @tab @code{vFile:close}
20932 @tab @code{remote get}, @code{remote put}
20934 @item @code{hostio-open-packet}
20935 @tab @code{vFile:open}
20936 @tab @code{remote get}, @code{remote put}
20938 @item @code{hostio-pread-packet}
20939 @tab @code{vFile:pread}
20940 @tab @code{remote get}, @code{remote put}
20942 @item @code{hostio-pwrite-packet}
20943 @tab @code{vFile:pwrite}
20944 @tab @code{remote get}, @code{remote put}
20946 @item @code{hostio-unlink-packet}
20947 @tab @code{vFile:unlink}
20948 @tab @code{remote delete}
20950 @item @code{hostio-readlink-packet}
20951 @tab @code{vFile:readlink}
20954 @item @code{hostio-fstat-packet}
20955 @tab @code{vFile:fstat}
20958 @item @code{hostio-setfs-packet}
20959 @tab @code{vFile:setfs}
20962 @item @code{noack-packet}
20963 @tab @code{QStartNoAckMode}
20964 @tab Packet acknowledgment
20966 @item @code{osdata}
20967 @tab @code{qXfer:osdata:read}
20968 @tab @code{info os}
20970 @item @code{query-attached}
20971 @tab @code{qAttached}
20972 @tab Querying remote process attach state.
20974 @item @code{trace-buffer-size}
20975 @tab @code{QTBuffer:size}
20976 @tab @code{set trace-buffer-size}
20978 @item @code{trace-status}
20979 @tab @code{qTStatus}
20980 @tab @code{tstatus}
20982 @item @code{traceframe-info}
20983 @tab @code{qXfer:traceframe-info:read}
20984 @tab Traceframe info
20986 @item @code{install-in-trace}
20987 @tab @code{InstallInTrace}
20988 @tab Install tracepoint in tracing
20990 @item @code{disable-randomization}
20991 @tab @code{QDisableRandomization}
20992 @tab @code{set disable-randomization}
20994 @item @code{startup-with-shell}
20995 @tab @code{QStartupWithShell}
20996 @tab @code{set startup-with-shell}
20998 @item @code{environment-hex-encoded}
20999 @tab @code{QEnvironmentHexEncoded}
21000 @tab @code{set environment}
21002 @item @code{environment-unset}
21003 @tab @code{QEnvironmentUnset}
21004 @tab @code{unset environment}
21006 @item @code{environment-reset}
21007 @tab @code{QEnvironmentReset}
21008 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21010 @item @code{set-working-dir}
21011 @tab @code{QSetWorkingDir}
21012 @tab @code{set cwd}
21014 @item @code{conditional-breakpoints-packet}
21015 @tab @code{Z0 and Z1}
21016 @tab @code{Support for target-side breakpoint condition evaluation}
21018 @item @code{multiprocess-extensions}
21019 @tab @code{multiprocess extensions}
21020 @tab Debug multiple processes and remote process PID awareness
21022 @item @code{swbreak-feature}
21023 @tab @code{swbreak stop reason}
21026 @item @code{hwbreak-feature}
21027 @tab @code{hwbreak stop reason}
21030 @item @code{fork-event-feature}
21031 @tab @code{fork stop reason}
21034 @item @code{vfork-event-feature}
21035 @tab @code{vfork stop reason}
21038 @item @code{exec-event-feature}
21039 @tab @code{exec stop reason}
21042 @item @code{thread-events}
21043 @tab @code{QThreadEvents}
21044 @tab Tracking thread lifetime.
21046 @item @code{no-resumed-stop-reply}
21047 @tab @code{no resumed thread left stop reply}
21048 @tab Tracking thread lifetime.
21053 @section Implementing a Remote Stub
21055 @cindex debugging stub, example
21056 @cindex remote stub, example
21057 @cindex stub example, remote debugging
21058 The stub files provided with @value{GDBN} implement the target side of the
21059 communication protocol, and the @value{GDBN} side is implemented in the
21060 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21061 these subroutines to communicate, and ignore the details. (If you're
21062 implementing your own stub file, you can still ignore the details: start
21063 with one of the existing stub files. @file{sparc-stub.c} is the best
21064 organized, and therefore the easiest to read.)
21066 @cindex remote serial debugging, overview
21067 To debug a program running on another machine (the debugging
21068 @dfn{target} machine), you must first arrange for all the usual
21069 prerequisites for the program to run by itself. For example, for a C
21074 A startup routine to set up the C runtime environment; these usually
21075 have a name like @file{crt0}. The startup routine may be supplied by
21076 your hardware supplier, or you may have to write your own.
21079 A C subroutine library to support your program's
21080 subroutine calls, notably managing input and output.
21083 A way of getting your program to the other machine---for example, a
21084 download program. These are often supplied by the hardware
21085 manufacturer, but you may have to write your own from hardware
21089 The next step is to arrange for your program to use a serial port to
21090 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21091 machine). In general terms, the scheme looks like this:
21095 @value{GDBN} already understands how to use this protocol; when everything
21096 else is set up, you can simply use the @samp{target remote} command
21097 (@pxref{Targets,,Specifying a Debugging Target}).
21099 @item On the target,
21100 you must link with your program a few special-purpose subroutines that
21101 implement the @value{GDBN} remote serial protocol. The file containing these
21102 subroutines is called a @dfn{debugging stub}.
21104 On certain remote targets, you can use an auxiliary program
21105 @code{gdbserver} instead of linking a stub into your program.
21106 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21109 The debugging stub is specific to the architecture of the remote
21110 machine; for example, use @file{sparc-stub.c} to debug programs on
21113 @cindex remote serial stub list
21114 These working remote stubs are distributed with @value{GDBN}:
21119 @cindex @file{i386-stub.c}
21122 For Intel 386 and compatible architectures.
21125 @cindex @file{m68k-stub.c}
21126 @cindex Motorola 680x0
21128 For Motorola 680x0 architectures.
21131 @cindex @file{sh-stub.c}
21134 For Renesas SH architectures.
21137 @cindex @file{sparc-stub.c}
21139 For @sc{sparc} architectures.
21141 @item sparcl-stub.c
21142 @cindex @file{sparcl-stub.c}
21145 For Fujitsu @sc{sparclite} architectures.
21149 The @file{README} file in the @value{GDBN} distribution may list other
21150 recently added stubs.
21153 * Stub Contents:: What the stub can do for you
21154 * Bootstrapping:: What you must do for the stub
21155 * Debug Session:: Putting it all together
21158 @node Stub Contents
21159 @subsection What the Stub Can Do for You
21161 @cindex remote serial stub
21162 The debugging stub for your architecture supplies these three
21166 @item set_debug_traps
21167 @findex set_debug_traps
21168 @cindex remote serial stub, initialization
21169 This routine arranges for @code{handle_exception} to run when your
21170 program stops. You must call this subroutine explicitly in your
21171 program's startup code.
21173 @item handle_exception
21174 @findex handle_exception
21175 @cindex remote serial stub, main routine
21176 This is the central workhorse, but your program never calls it
21177 explicitly---the setup code arranges for @code{handle_exception} to
21178 run when a trap is triggered.
21180 @code{handle_exception} takes control when your program stops during
21181 execution (for example, on a breakpoint), and mediates communications
21182 with @value{GDBN} on the host machine. This is where the communications
21183 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21184 representative on the target machine. It begins by sending summary
21185 information on the state of your program, then continues to execute,
21186 retrieving and transmitting any information @value{GDBN} needs, until you
21187 execute a @value{GDBN} command that makes your program resume; at that point,
21188 @code{handle_exception} returns control to your own code on the target
21192 @cindex @code{breakpoint} subroutine, remote
21193 Use this auxiliary subroutine to make your program contain a
21194 breakpoint. Depending on the particular situation, this may be the only
21195 way for @value{GDBN} to get control. For instance, if your target
21196 machine has some sort of interrupt button, you won't need to call this;
21197 pressing the interrupt button transfers control to
21198 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21199 simply receiving characters on the serial port may also trigger a trap;
21200 again, in that situation, you don't need to call @code{breakpoint} from
21201 your own program---simply running @samp{target remote} from the host
21202 @value{GDBN} session gets control.
21204 Call @code{breakpoint} if none of these is true, or if you simply want
21205 to make certain your program stops at a predetermined point for the
21206 start of your debugging session.
21209 @node Bootstrapping
21210 @subsection What You Must Do for the Stub
21212 @cindex remote stub, support routines
21213 The debugging stubs that come with @value{GDBN} are set up for a particular
21214 chip architecture, but they have no information about the rest of your
21215 debugging target machine.
21217 First of all you need to tell the stub how to communicate with the
21221 @item int getDebugChar()
21222 @findex getDebugChar
21223 Write this subroutine to read a single character from the serial port.
21224 It may be identical to @code{getchar} for your target system; a
21225 different name is used to allow you to distinguish the two if you wish.
21227 @item void putDebugChar(int)
21228 @findex putDebugChar
21229 Write this subroutine to write a single character to the serial port.
21230 It may be identical to @code{putchar} for your target system; a
21231 different name is used to allow you to distinguish the two if you wish.
21234 @cindex control C, and remote debugging
21235 @cindex interrupting remote targets
21236 If you want @value{GDBN} to be able to stop your program while it is
21237 running, you need to use an interrupt-driven serial driver, and arrange
21238 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21239 character). That is the character which @value{GDBN} uses to tell the
21240 remote system to stop.
21242 Getting the debugging target to return the proper status to @value{GDBN}
21243 probably requires changes to the standard stub; one quick and dirty way
21244 is to just execute a breakpoint instruction (the ``dirty'' part is that
21245 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21247 Other routines you need to supply are:
21250 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21251 @findex exceptionHandler
21252 Write this function to install @var{exception_address} in the exception
21253 handling tables. You need to do this because the stub does not have any
21254 way of knowing what the exception handling tables on your target system
21255 are like (for example, the processor's table might be in @sc{rom},
21256 containing entries which point to a table in @sc{ram}).
21257 The @var{exception_number} specifies the exception which should be changed;
21258 its meaning is architecture-dependent (for example, different numbers
21259 might represent divide by zero, misaligned access, etc). When this
21260 exception occurs, control should be transferred directly to
21261 @var{exception_address}, and the processor state (stack, registers,
21262 and so on) should be just as it is when a processor exception occurs. So if
21263 you want to use a jump instruction to reach @var{exception_address}, it
21264 should be a simple jump, not a jump to subroutine.
21266 For the 386, @var{exception_address} should be installed as an interrupt
21267 gate so that interrupts are masked while the handler runs. The gate
21268 should be at privilege level 0 (the most privileged level). The
21269 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21270 help from @code{exceptionHandler}.
21272 @item void flush_i_cache()
21273 @findex flush_i_cache
21274 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21275 instruction cache, if any, on your target machine. If there is no
21276 instruction cache, this subroutine may be a no-op.
21278 On target machines that have instruction caches, @value{GDBN} requires this
21279 function to make certain that the state of your program is stable.
21283 You must also make sure this library routine is available:
21286 @item void *memset(void *, int, int)
21288 This is the standard library function @code{memset} that sets an area of
21289 memory to a known value. If you have one of the free versions of
21290 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21291 either obtain it from your hardware manufacturer, or write your own.
21294 If you do not use the GNU C compiler, you may need other standard
21295 library subroutines as well; this varies from one stub to another,
21296 but in general the stubs are likely to use any of the common library
21297 subroutines which @code{@value{NGCC}} generates as inline code.
21300 @node Debug Session
21301 @subsection Putting it All Together
21303 @cindex remote serial debugging summary
21304 In summary, when your program is ready to debug, you must follow these
21309 Make sure you have defined the supporting low-level routines
21310 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21312 @code{getDebugChar}, @code{putDebugChar},
21313 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21317 Insert these lines in your program's startup code, before the main
21318 procedure is called:
21325 On some machines, when a breakpoint trap is raised, the hardware
21326 automatically makes the PC point to the instruction after the
21327 breakpoint. If your machine doesn't do that, you may need to adjust
21328 @code{handle_exception} to arrange for it to return to the instruction
21329 after the breakpoint on this first invocation, so that your program
21330 doesn't keep hitting the initial breakpoint instead of making
21334 For the 680x0 stub only, you need to provide a variable called
21335 @code{exceptionHook}. Normally you just use:
21338 void (*exceptionHook)() = 0;
21342 but if before calling @code{set_debug_traps}, you set it to point to a
21343 function in your program, that function is called when
21344 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21345 error). The function indicated by @code{exceptionHook} is called with
21346 one parameter: an @code{int} which is the exception number.
21349 Compile and link together: your program, the @value{GDBN} debugging stub for
21350 your target architecture, and the supporting subroutines.
21353 Make sure you have a serial connection between your target machine and
21354 the @value{GDBN} host, and identify the serial port on the host.
21357 @c The "remote" target now provides a `load' command, so we should
21358 @c document that. FIXME.
21359 Download your program to your target machine (or get it there by
21360 whatever means the manufacturer provides), and start it.
21363 Start @value{GDBN} on the host, and connect to the target
21364 (@pxref{Connecting,,Connecting to a Remote Target}).
21368 @node Configurations
21369 @chapter Configuration-Specific Information
21371 While nearly all @value{GDBN} commands are available for all native and
21372 cross versions of the debugger, there are some exceptions. This chapter
21373 describes things that are only available in certain configurations.
21375 There are three major categories of configurations: native
21376 configurations, where the host and target are the same, embedded
21377 operating system configurations, which are usually the same for several
21378 different processor architectures, and bare embedded processors, which
21379 are quite different from each other.
21384 * Embedded Processors::
21391 This section describes details specific to particular native
21395 * BSD libkvm Interface:: Debugging BSD kernel memory images
21396 * SVR4 Process Information:: SVR4 process information
21397 * DJGPP Native:: Features specific to the DJGPP port
21398 * Cygwin Native:: Features specific to the Cygwin port
21399 * Hurd Native:: Features specific to @sc{gnu} Hurd
21400 * Darwin:: Features specific to Darwin
21403 @node BSD libkvm Interface
21404 @subsection BSD libkvm Interface
21407 @cindex kernel memory image
21408 @cindex kernel crash dump
21410 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21411 interface that provides a uniform interface for accessing kernel virtual
21412 memory images, including live systems and crash dumps. @value{GDBN}
21413 uses this interface to allow you to debug live kernels and kernel crash
21414 dumps on many native BSD configurations. This is implemented as a
21415 special @code{kvm} debugging target. For debugging a live system, load
21416 the currently running kernel into @value{GDBN} and connect to the
21420 (@value{GDBP}) @b{target kvm}
21423 For debugging crash dumps, provide the file name of the crash dump as an
21427 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21430 Once connected to the @code{kvm} target, the following commands are
21436 Set current context from the @dfn{Process Control Block} (PCB) address.
21439 Set current context from proc address. This command isn't available on
21440 modern FreeBSD systems.
21443 @node SVR4 Process Information
21444 @subsection SVR4 Process Information
21446 @cindex examine process image
21447 @cindex process info via @file{/proc}
21449 Many versions of SVR4 and compatible systems provide a facility called
21450 @samp{/proc} that can be used to examine the image of a running
21451 process using file-system subroutines.
21453 If @value{GDBN} is configured for an operating system with this
21454 facility, the command @code{info proc} is available to report
21455 information about the process running your program, or about any
21456 process running on your system. This includes, as of this writing,
21457 @sc{gnu}/Linux and Solaris, for example.
21459 This command may also work on core files that were created on a system
21460 that has the @samp{/proc} facility.
21466 @itemx info proc @var{process-id}
21467 Summarize available information about any running process. If a
21468 process ID is specified by @var{process-id}, display information about
21469 that process; otherwise display information about the program being
21470 debugged. The summary includes the debugged process ID, the command
21471 line used to invoke it, its current working directory, and its
21472 executable file's absolute file name.
21474 On some systems, @var{process-id} can be of the form
21475 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21476 within a process. If the optional @var{pid} part is missing, it means
21477 a thread from the process being debugged (the leading @samp{/} still
21478 needs to be present, or else @value{GDBN} will interpret the number as
21479 a process ID rather than a thread ID).
21481 @item info proc cmdline
21482 @cindex info proc cmdline
21483 Show the original command line of the process. This command is
21484 specific to @sc{gnu}/Linux.
21486 @item info proc cwd
21487 @cindex info proc cwd
21488 Show the current working directory of the process. This command is
21489 specific to @sc{gnu}/Linux.
21491 @item info proc exe
21492 @cindex info proc exe
21493 Show the name of executable of the process. This command is specific
21496 @item info proc mappings
21497 @cindex memory address space mappings
21498 Report the memory address space ranges accessible in the program, with
21499 information on whether the process has read, write, or execute access
21500 rights to each range. On @sc{gnu}/Linux systems, each memory range
21501 includes the object file which is mapped to that range, instead of the
21502 memory access rights to that range.
21504 @item info proc stat
21505 @itemx info proc status
21506 @cindex process detailed status information
21507 These subcommands are specific to @sc{gnu}/Linux systems. They show
21508 the process-related information, including the user ID and group ID;
21509 how many threads are there in the process; its virtual memory usage;
21510 the signals that are pending, blocked, and ignored; its TTY; its
21511 consumption of system and user time; its stack size; its @samp{nice}
21512 value; etc. For more information, see the @samp{proc} man page
21513 (type @kbd{man 5 proc} from your shell prompt).
21515 @item info proc all
21516 Show all the information about the process described under all of the
21517 above @code{info proc} subcommands.
21520 @comment These sub-options of 'info proc' were not included when
21521 @comment procfs.c was re-written. Keep their descriptions around
21522 @comment against the day when someone finds the time to put them back in.
21523 @kindex info proc times
21524 @item info proc times
21525 Starting time, user CPU time, and system CPU time for your program and
21528 @kindex info proc id
21530 Report on the process IDs related to your program: its own process ID,
21531 the ID of its parent, the process group ID, and the session ID.
21534 @item set procfs-trace
21535 @kindex set procfs-trace
21536 @cindex @code{procfs} API calls
21537 This command enables and disables tracing of @code{procfs} API calls.
21539 @item show procfs-trace
21540 @kindex show procfs-trace
21541 Show the current state of @code{procfs} API call tracing.
21543 @item set procfs-file @var{file}
21544 @kindex set procfs-file
21545 Tell @value{GDBN} to write @code{procfs} API trace to the named
21546 @var{file}. @value{GDBN} appends the trace info to the previous
21547 contents of the file. The default is to display the trace on the
21550 @item show procfs-file
21551 @kindex show procfs-file
21552 Show the file to which @code{procfs} API trace is written.
21554 @item proc-trace-entry
21555 @itemx proc-trace-exit
21556 @itemx proc-untrace-entry
21557 @itemx proc-untrace-exit
21558 @kindex proc-trace-entry
21559 @kindex proc-trace-exit
21560 @kindex proc-untrace-entry
21561 @kindex proc-untrace-exit
21562 These commands enable and disable tracing of entries into and exits
21563 from the @code{syscall} interface.
21566 @kindex info pidlist
21567 @cindex process list, QNX Neutrino
21568 For QNX Neutrino only, this command displays the list of all the
21569 processes and all the threads within each process.
21572 @kindex info meminfo
21573 @cindex mapinfo list, QNX Neutrino
21574 For QNX Neutrino only, this command displays the list of all mapinfos.
21578 @subsection Features for Debugging @sc{djgpp} Programs
21579 @cindex @sc{djgpp} debugging
21580 @cindex native @sc{djgpp} debugging
21581 @cindex MS-DOS-specific commands
21584 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21585 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21586 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21587 top of real-mode DOS systems and their emulations.
21589 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21590 defines a few commands specific to the @sc{djgpp} port. This
21591 subsection describes those commands.
21596 This is a prefix of @sc{djgpp}-specific commands which print
21597 information about the target system and important OS structures.
21600 @cindex MS-DOS system info
21601 @cindex free memory information (MS-DOS)
21602 @item info dos sysinfo
21603 This command displays assorted information about the underlying
21604 platform: the CPU type and features, the OS version and flavor, the
21605 DPMI version, and the available conventional and DPMI memory.
21610 @cindex segment descriptor tables
21611 @cindex descriptor tables display
21613 @itemx info dos ldt
21614 @itemx info dos idt
21615 These 3 commands display entries from, respectively, Global, Local,
21616 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21617 tables are data structures which store a descriptor for each segment
21618 that is currently in use. The segment's selector is an index into a
21619 descriptor table; the table entry for that index holds the
21620 descriptor's base address and limit, and its attributes and access
21623 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21624 segment (used for both data and the stack), and a DOS segment (which
21625 allows access to DOS/BIOS data structures and absolute addresses in
21626 conventional memory). However, the DPMI host will usually define
21627 additional segments in order to support the DPMI environment.
21629 @cindex garbled pointers
21630 These commands allow to display entries from the descriptor tables.
21631 Without an argument, all entries from the specified table are
21632 displayed. An argument, which should be an integer expression, means
21633 display a single entry whose index is given by the argument. For
21634 example, here's a convenient way to display information about the
21635 debugged program's data segment:
21638 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21639 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21643 This comes in handy when you want to see whether a pointer is outside
21644 the data segment's limit (i.e.@: @dfn{garbled}).
21646 @cindex page tables display (MS-DOS)
21648 @itemx info dos pte
21649 These two commands display entries from, respectively, the Page
21650 Directory and the Page Tables. Page Directories and Page Tables are
21651 data structures which control how virtual memory addresses are mapped
21652 into physical addresses. A Page Table includes an entry for every
21653 page of memory that is mapped into the program's address space; there
21654 may be several Page Tables, each one holding up to 4096 entries. A
21655 Page Directory has up to 4096 entries, one each for every Page Table
21656 that is currently in use.
21658 Without an argument, @kbd{info dos pde} displays the entire Page
21659 Directory, and @kbd{info dos pte} displays all the entries in all of
21660 the Page Tables. An argument, an integer expression, given to the
21661 @kbd{info dos pde} command means display only that entry from the Page
21662 Directory table. An argument given to the @kbd{info dos pte} command
21663 means display entries from a single Page Table, the one pointed to by
21664 the specified entry in the Page Directory.
21666 @cindex direct memory access (DMA) on MS-DOS
21667 These commands are useful when your program uses @dfn{DMA} (Direct
21668 Memory Access), which needs physical addresses to program the DMA
21671 These commands are supported only with some DPMI servers.
21673 @cindex physical address from linear address
21674 @item info dos address-pte @var{addr}
21675 This command displays the Page Table entry for a specified linear
21676 address. The argument @var{addr} is a linear address which should
21677 already have the appropriate segment's base address added to it,
21678 because this command accepts addresses which may belong to @emph{any}
21679 segment. For example, here's how to display the Page Table entry for
21680 the page where a variable @code{i} is stored:
21683 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21684 @exdent @code{Page Table entry for address 0x11a00d30:}
21685 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21689 This says that @code{i} is stored at offset @code{0xd30} from the page
21690 whose physical base address is @code{0x02698000}, and shows all the
21691 attributes of that page.
21693 Note that you must cast the addresses of variables to a @code{char *},
21694 since otherwise the value of @code{__djgpp_base_address}, the base
21695 address of all variables and functions in a @sc{djgpp} program, will
21696 be added using the rules of C pointer arithmetics: if @code{i} is
21697 declared an @code{int}, @value{GDBN} will add 4 times the value of
21698 @code{__djgpp_base_address} to the address of @code{i}.
21700 Here's another example, it displays the Page Table entry for the
21704 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21705 @exdent @code{Page Table entry for address 0x29110:}
21706 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21710 (The @code{+ 3} offset is because the transfer buffer's address is the
21711 3rd member of the @code{_go32_info_block} structure.) The output
21712 clearly shows that this DPMI server maps the addresses in conventional
21713 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21714 linear (@code{0x29110}) addresses are identical.
21716 This command is supported only with some DPMI servers.
21719 @cindex DOS serial data link, remote debugging
21720 In addition to native debugging, the DJGPP port supports remote
21721 debugging via a serial data link. The following commands are specific
21722 to remote serial debugging in the DJGPP port of @value{GDBN}.
21725 @kindex set com1base
21726 @kindex set com1irq
21727 @kindex set com2base
21728 @kindex set com2irq
21729 @kindex set com3base
21730 @kindex set com3irq
21731 @kindex set com4base
21732 @kindex set com4irq
21733 @item set com1base @var{addr}
21734 This command sets the base I/O port address of the @file{COM1} serial
21737 @item set com1irq @var{irq}
21738 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21739 for the @file{COM1} serial port.
21741 There are similar commands @samp{set com2base}, @samp{set com3irq},
21742 etc.@: for setting the port address and the @code{IRQ} lines for the
21745 @kindex show com1base
21746 @kindex show com1irq
21747 @kindex show com2base
21748 @kindex show com2irq
21749 @kindex show com3base
21750 @kindex show com3irq
21751 @kindex show com4base
21752 @kindex show com4irq
21753 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21754 display the current settings of the base address and the @code{IRQ}
21755 lines used by the COM ports.
21758 @kindex info serial
21759 @cindex DOS serial port status
21760 This command prints the status of the 4 DOS serial ports. For each
21761 port, it prints whether it's active or not, its I/O base address and
21762 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21763 counts of various errors encountered so far.
21767 @node Cygwin Native
21768 @subsection Features for Debugging MS Windows PE Executables
21769 @cindex MS Windows debugging
21770 @cindex native Cygwin debugging
21771 @cindex Cygwin-specific commands
21773 @value{GDBN} supports native debugging of MS Windows programs, including
21774 DLLs with and without symbolic debugging information.
21776 @cindex Ctrl-BREAK, MS-Windows
21777 @cindex interrupt debuggee on MS-Windows
21778 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21779 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21780 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21781 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21782 sequence, which can be used to interrupt the debuggee even if it
21785 There are various additional Cygwin-specific commands, described in
21786 this section. Working with DLLs that have no debugging symbols is
21787 described in @ref{Non-debug DLL Symbols}.
21792 This is a prefix of MS Windows-specific commands which print
21793 information about the target system and important OS structures.
21795 @item info w32 selector
21796 This command displays information returned by
21797 the Win32 API @code{GetThreadSelectorEntry} function.
21798 It takes an optional argument that is evaluated to
21799 a long value to give the information about this given selector.
21800 Without argument, this command displays information
21801 about the six segment registers.
21803 @item info w32 thread-information-block
21804 This command displays thread specific information stored in the
21805 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21806 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21808 @kindex signal-event
21809 @item signal-event @var{id}
21810 This command signals an event with user-provided @var{id}. Used to resume
21811 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21813 To use it, create or edit the following keys in
21814 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21815 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21816 (for x86_64 versions):
21820 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21821 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21822 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21824 The first @code{%ld} will be replaced by the process ID of the
21825 crashing process, the second @code{%ld} will be replaced by the ID of
21826 the event that blocks the crashing process, waiting for @value{GDBN}
21830 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21831 make the system run debugger specified by the Debugger key
21832 automatically, @code{0} will cause a dialog box with ``OK'' and
21833 ``Cancel'' buttons to appear, which allows the user to either
21834 terminate the crashing process (OK) or debug it (Cancel).
21837 @kindex set cygwin-exceptions
21838 @cindex debugging the Cygwin DLL
21839 @cindex Cygwin DLL, debugging
21840 @item set cygwin-exceptions @var{mode}
21841 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21842 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21843 @value{GDBN} will delay recognition of exceptions, and may ignore some
21844 exceptions which seem to be caused by internal Cygwin DLL
21845 ``bookkeeping''. This option is meant primarily for debugging the
21846 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21847 @value{GDBN} users with false @code{SIGSEGV} signals.
21849 @kindex show cygwin-exceptions
21850 @item show cygwin-exceptions
21851 Displays whether @value{GDBN} will break on exceptions that happen
21852 inside the Cygwin DLL itself.
21854 @kindex set new-console
21855 @item set new-console @var{mode}
21856 If @var{mode} is @code{on} the debuggee will
21857 be started in a new console on next start.
21858 If @var{mode} is @code{off}, the debuggee will
21859 be started in the same console as the debugger.
21861 @kindex show new-console
21862 @item show new-console
21863 Displays whether a new console is used
21864 when the debuggee is started.
21866 @kindex set new-group
21867 @item set new-group @var{mode}
21868 This boolean value controls whether the debuggee should
21869 start a new group or stay in the same group as the debugger.
21870 This affects the way the Windows OS handles
21873 @kindex show new-group
21874 @item show new-group
21875 Displays current value of new-group boolean.
21877 @kindex set debugevents
21878 @item set debugevents
21879 This boolean value adds debug output concerning kernel events related
21880 to the debuggee seen by the debugger. This includes events that
21881 signal thread and process creation and exit, DLL loading and
21882 unloading, console interrupts, and debugging messages produced by the
21883 Windows @code{OutputDebugString} API call.
21885 @kindex set debugexec
21886 @item set debugexec
21887 This boolean value adds debug output concerning execute events
21888 (such as resume thread) seen by the debugger.
21890 @kindex set debugexceptions
21891 @item set debugexceptions
21892 This boolean value adds debug output concerning exceptions in the
21893 debuggee seen by the debugger.
21895 @kindex set debugmemory
21896 @item set debugmemory
21897 This boolean value adds debug output concerning debuggee memory reads
21898 and writes by the debugger.
21902 This boolean values specifies whether the debuggee is called
21903 via a shell or directly (default value is on).
21907 Displays if the debuggee will be started with a shell.
21912 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21915 @node Non-debug DLL Symbols
21916 @subsubsection Support for DLLs without Debugging Symbols
21917 @cindex DLLs with no debugging symbols
21918 @cindex Minimal symbols and DLLs
21920 Very often on windows, some of the DLLs that your program relies on do
21921 not include symbolic debugging information (for example,
21922 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21923 symbols in a DLL, it relies on the minimal amount of symbolic
21924 information contained in the DLL's export table. This section
21925 describes working with such symbols, known internally to @value{GDBN} as
21926 ``minimal symbols''.
21928 Note that before the debugged program has started execution, no DLLs
21929 will have been loaded. The easiest way around this problem is simply to
21930 start the program --- either by setting a breakpoint or letting the
21931 program run once to completion.
21933 @subsubsection DLL Name Prefixes
21935 In keeping with the naming conventions used by the Microsoft debugging
21936 tools, DLL export symbols are made available with a prefix based on the
21937 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21938 also entered into the symbol table, so @code{CreateFileA} is often
21939 sufficient. In some cases there will be name clashes within a program
21940 (particularly if the executable itself includes full debugging symbols)
21941 necessitating the use of the fully qualified name when referring to the
21942 contents of the DLL. Use single-quotes around the name to avoid the
21943 exclamation mark (``!'') being interpreted as a language operator.
21945 Note that the internal name of the DLL may be all upper-case, even
21946 though the file name of the DLL is lower-case, or vice-versa. Since
21947 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21948 some confusion. If in doubt, try the @code{info functions} and
21949 @code{info variables} commands or even @code{maint print msymbols}
21950 (@pxref{Symbols}). Here's an example:
21953 (@value{GDBP}) info function CreateFileA
21954 All functions matching regular expression "CreateFileA":
21956 Non-debugging symbols:
21957 0x77e885f4 CreateFileA
21958 0x77e885f4 KERNEL32!CreateFileA
21962 (@value{GDBP}) info function !
21963 All functions matching regular expression "!":
21965 Non-debugging symbols:
21966 0x6100114c cygwin1!__assert
21967 0x61004034 cygwin1!_dll_crt0@@0
21968 0x61004240 cygwin1!dll_crt0(per_process *)
21972 @subsubsection Working with Minimal Symbols
21974 Symbols extracted from a DLL's export table do not contain very much
21975 type information. All that @value{GDBN} can do is guess whether a symbol
21976 refers to a function or variable depending on the linker section that
21977 contains the symbol. Also note that the actual contents of the memory
21978 contained in a DLL are not available unless the program is running. This
21979 means that you cannot examine the contents of a variable or disassemble
21980 a function within a DLL without a running program.
21982 Variables are generally treated as pointers and dereferenced
21983 automatically. For this reason, it is often necessary to prefix a
21984 variable name with the address-of operator (``&'') and provide explicit
21985 type information in the command. Here's an example of the type of
21989 (@value{GDBP}) print 'cygwin1!__argv'
21990 'cygwin1!__argv' has unknown type; cast it to its declared type
21994 (@value{GDBP}) x 'cygwin1!__argv'
21995 'cygwin1!__argv' has unknown type; cast it to its declared type
21998 And two possible solutions:
22001 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22002 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22006 (@value{GDBP}) x/2x &'cygwin1!__argv'
22007 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22008 (@value{GDBP}) x/x 0x10021608
22009 0x10021608: 0x0022fd98
22010 (@value{GDBP}) x/s 0x0022fd98
22011 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22014 Setting a break point within a DLL is possible even before the program
22015 starts execution. However, under these circumstances, @value{GDBN} can't
22016 examine the initial instructions of the function in order to skip the
22017 function's frame set-up code. You can work around this by using ``*&''
22018 to set the breakpoint at a raw memory address:
22021 (@value{GDBP}) break *&'python22!PyOS_Readline'
22022 Breakpoint 1 at 0x1e04eff0
22025 The author of these extensions is not entirely convinced that setting a
22026 break point within a shared DLL like @file{kernel32.dll} is completely
22030 @subsection Commands Specific to @sc{gnu} Hurd Systems
22031 @cindex @sc{gnu} Hurd debugging
22033 This subsection describes @value{GDBN} commands specific to the
22034 @sc{gnu} Hurd native debugging.
22039 @kindex set signals@r{, Hurd command}
22040 @kindex set sigs@r{, Hurd command}
22041 This command toggles the state of inferior signal interception by
22042 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22043 affected by this command. @code{sigs} is a shorthand alias for
22048 @kindex show signals@r{, Hurd command}
22049 @kindex show sigs@r{, Hurd command}
22050 Show the current state of intercepting inferior's signals.
22052 @item set signal-thread
22053 @itemx set sigthread
22054 @kindex set signal-thread
22055 @kindex set sigthread
22056 This command tells @value{GDBN} which thread is the @code{libc} signal
22057 thread. That thread is run when a signal is delivered to a running
22058 process. @code{set sigthread} is the shorthand alias of @code{set
22061 @item show signal-thread
22062 @itemx show sigthread
22063 @kindex show signal-thread
22064 @kindex show sigthread
22065 These two commands show which thread will run when the inferior is
22066 delivered a signal.
22069 @kindex set stopped@r{, Hurd command}
22070 This commands tells @value{GDBN} that the inferior process is stopped,
22071 as with the @code{SIGSTOP} signal. The stopped process can be
22072 continued by delivering a signal to it.
22075 @kindex show stopped@r{, Hurd command}
22076 This command shows whether @value{GDBN} thinks the debuggee is
22079 @item set exceptions
22080 @kindex set exceptions@r{, Hurd command}
22081 Use this command to turn off trapping of exceptions in the inferior.
22082 When exception trapping is off, neither breakpoints nor
22083 single-stepping will work. To restore the default, set exception
22086 @item show exceptions
22087 @kindex show exceptions@r{, Hurd command}
22088 Show the current state of trapping exceptions in the inferior.
22090 @item set task pause
22091 @kindex set task@r{, Hurd commands}
22092 @cindex task attributes (@sc{gnu} Hurd)
22093 @cindex pause current task (@sc{gnu} Hurd)
22094 This command toggles task suspension when @value{GDBN} has control.
22095 Setting it to on takes effect immediately, and the task is suspended
22096 whenever @value{GDBN} gets control. Setting it to off will take
22097 effect the next time the inferior is continued. If this option is set
22098 to off, you can use @code{set thread default pause on} or @code{set
22099 thread pause on} (see below) to pause individual threads.
22101 @item show task pause
22102 @kindex show task@r{, Hurd commands}
22103 Show the current state of task suspension.
22105 @item set task detach-suspend-count
22106 @cindex task suspend count
22107 @cindex detach from task, @sc{gnu} Hurd
22108 This command sets the suspend count the task will be left with when
22109 @value{GDBN} detaches from it.
22111 @item show task detach-suspend-count
22112 Show the suspend count the task will be left with when detaching.
22114 @item set task exception-port
22115 @itemx set task excp
22116 @cindex task exception port, @sc{gnu} Hurd
22117 This command sets the task exception port to which @value{GDBN} will
22118 forward exceptions. The argument should be the value of the @dfn{send
22119 rights} of the task. @code{set task excp} is a shorthand alias.
22121 @item set noninvasive
22122 @cindex noninvasive task options
22123 This command switches @value{GDBN} to a mode that is the least
22124 invasive as far as interfering with the inferior is concerned. This
22125 is the same as using @code{set task pause}, @code{set exceptions}, and
22126 @code{set signals} to values opposite to the defaults.
22128 @item info send-rights
22129 @itemx info receive-rights
22130 @itemx info port-rights
22131 @itemx info port-sets
22132 @itemx info dead-names
22135 @cindex send rights, @sc{gnu} Hurd
22136 @cindex receive rights, @sc{gnu} Hurd
22137 @cindex port rights, @sc{gnu} Hurd
22138 @cindex port sets, @sc{gnu} Hurd
22139 @cindex dead names, @sc{gnu} Hurd
22140 These commands display information about, respectively, send rights,
22141 receive rights, port rights, port sets, and dead names of a task.
22142 There are also shorthand aliases: @code{info ports} for @code{info
22143 port-rights} and @code{info psets} for @code{info port-sets}.
22145 @item set thread pause
22146 @kindex set thread@r{, Hurd command}
22147 @cindex thread properties, @sc{gnu} Hurd
22148 @cindex pause current thread (@sc{gnu} Hurd)
22149 This command toggles current thread suspension when @value{GDBN} has
22150 control. Setting it to on takes effect immediately, and the current
22151 thread is suspended whenever @value{GDBN} gets control. Setting it to
22152 off will take effect the next time the inferior is continued.
22153 Normally, this command has no effect, since when @value{GDBN} has
22154 control, the whole task is suspended. However, if you used @code{set
22155 task pause off} (see above), this command comes in handy to suspend
22156 only the current thread.
22158 @item show thread pause
22159 @kindex show thread@r{, Hurd command}
22160 This command shows the state of current thread suspension.
22162 @item set thread run
22163 This command sets whether the current thread is allowed to run.
22165 @item show thread run
22166 Show whether the current thread is allowed to run.
22168 @item set thread detach-suspend-count
22169 @cindex thread suspend count, @sc{gnu} Hurd
22170 @cindex detach from thread, @sc{gnu} Hurd
22171 This command sets the suspend count @value{GDBN} will leave on a
22172 thread when detaching. This number is relative to the suspend count
22173 found by @value{GDBN} when it notices the thread; use @code{set thread
22174 takeover-suspend-count} to force it to an absolute value.
22176 @item show thread detach-suspend-count
22177 Show the suspend count @value{GDBN} will leave on the thread when
22180 @item set thread exception-port
22181 @itemx set thread excp
22182 Set the thread exception port to which to forward exceptions. This
22183 overrides the port set by @code{set task exception-port} (see above).
22184 @code{set thread excp} is the shorthand alias.
22186 @item set thread takeover-suspend-count
22187 Normally, @value{GDBN}'s thread suspend counts are relative to the
22188 value @value{GDBN} finds when it notices each thread. This command
22189 changes the suspend counts to be absolute instead.
22191 @item set thread default
22192 @itemx show thread default
22193 @cindex thread default settings, @sc{gnu} Hurd
22194 Each of the above @code{set thread} commands has a @code{set thread
22195 default} counterpart (e.g., @code{set thread default pause}, @code{set
22196 thread default exception-port}, etc.). The @code{thread default}
22197 variety of commands sets the default thread properties for all
22198 threads; you can then change the properties of individual threads with
22199 the non-default commands.
22206 @value{GDBN} provides the following commands specific to the Darwin target:
22209 @item set debug darwin @var{num}
22210 @kindex set debug darwin
22211 When set to a non zero value, enables debugging messages specific to
22212 the Darwin support. Higher values produce more verbose output.
22214 @item show debug darwin
22215 @kindex show debug darwin
22216 Show the current state of Darwin messages.
22218 @item set debug mach-o @var{num}
22219 @kindex set debug mach-o
22220 When set to a non zero value, enables debugging messages while
22221 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22222 file format used on Darwin for object and executable files.) Higher
22223 values produce more verbose output. This is a command to diagnose
22224 problems internal to @value{GDBN} and should not be needed in normal
22227 @item show debug mach-o
22228 @kindex show debug mach-o
22229 Show the current state of Mach-O file messages.
22231 @item set mach-exceptions on
22232 @itemx set mach-exceptions off
22233 @kindex set mach-exceptions
22234 On Darwin, faults are first reported as a Mach exception and are then
22235 mapped to a Posix signal. Use this command to turn on trapping of
22236 Mach exceptions in the inferior. This might be sometimes useful to
22237 better understand the cause of a fault. The default is off.
22239 @item show mach-exceptions
22240 @kindex show mach-exceptions
22241 Show the current state of exceptions trapping.
22246 @section Embedded Operating Systems
22248 This section describes configurations involving the debugging of
22249 embedded operating systems that are available for several different
22252 @value{GDBN} includes the ability to debug programs running on
22253 various real-time operating systems.
22255 @node Embedded Processors
22256 @section Embedded Processors
22258 This section goes into details specific to particular embedded
22261 @cindex send command to simulator
22262 Whenever a specific embedded processor has a simulator, @value{GDBN}
22263 allows to send an arbitrary command to the simulator.
22266 @item sim @var{command}
22267 @kindex sim@r{, a command}
22268 Send an arbitrary @var{command} string to the simulator. Consult the
22269 documentation for the specific simulator in use for information about
22270 acceptable commands.
22275 * ARC:: Synopsys ARC
22277 * M68K:: Motorola M68K
22278 * MicroBlaze:: Xilinx MicroBlaze
22279 * MIPS Embedded:: MIPS Embedded
22280 * PowerPC Embedded:: PowerPC Embedded
22283 * Super-H:: Renesas Super-H
22287 @subsection Synopsys ARC
22288 @cindex Synopsys ARC
22289 @cindex ARC specific commands
22295 @value{GDBN} provides the following ARC-specific commands:
22298 @item set debug arc
22299 @kindex set debug arc
22300 Control the level of ARC specific debug messages. Use 0 for no messages (the
22301 default), 1 for debug messages, and 2 for even more debug messages.
22303 @item show debug arc
22304 @kindex show debug arc
22305 Show the level of ARC specific debugging in operation.
22307 @item maint print arc arc-instruction @var{address}
22308 @kindex maint print arc arc-instruction
22309 Print internal disassembler information about instruction at a given address.
22316 @value{GDBN} provides the following ARM-specific commands:
22319 @item set arm disassembler
22321 This commands selects from a list of disassembly styles. The
22322 @code{"std"} style is the standard style.
22324 @item show arm disassembler
22326 Show the current disassembly style.
22328 @item set arm apcs32
22329 @cindex ARM 32-bit mode
22330 This command toggles ARM operation mode between 32-bit and 26-bit.
22332 @item show arm apcs32
22333 Display the current usage of the ARM 32-bit mode.
22335 @item set arm fpu @var{fputype}
22336 This command sets the ARM floating-point unit (FPU) type. The
22337 argument @var{fputype} can be one of these:
22341 Determine the FPU type by querying the OS ABI.
22343 Software FPU, with mixed-endian doubles on little-endian ARM
22346 GCC-compiled FPA co-processor.
22348 Software FPU with pure-endian doubles.
22354 Show the current type of the FPU.
22357 This command forces @value{GDBN} to use the specified ABI.
22360 Show the currently used ABI.
22362 @item set arm fallback-mode (arm|thumb|auto)
22363 @value{GDBN} uses the symbol table, when available, to determine
22364 whether instructions are ARM or Thumb. This command controls
22365 @value{GDBN}'s default behavior when the symbol table is not
22366 available. The default is @samp{auto}, which causes @value{GDBN} to
22367 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22370 @item show arm fallback-mode
22371 Show the current fallback instruction mode.
22373 @item set arm force-mode (arm|thumb|auto)
22374 This command overrides use of the symbol table to determine whether
22375 instructions are ARM or Thumb. The default is @samp{auto}, which
22376 causes @value{GDBN} to use the symbol table and then the setting
22377 of @samp{set arm fallback-mode}.
22379 @item show arm force-mode
22380 Show the current forced instruction mode.
22382 @item set debug arm
22383 Toggle whether to display ARM-specific debugging messages from the ARM
22384 target support subsystem.
22386 @item show debug arm
22387 Show whether ARM-specific debugging messages are enabled.
22391 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22392 The @value{GDBN} ARM simulator accepts the following optional arguments.
22395 @item --swi-support=@var{type}
22396 Tell the simulator which SWI interfaces to support. The argument
22397 @var{type} may be a comma separated list of the following values.
22398 The default value is @code{all}.
22413 The Motorola m68k configuration includes ColdFire support.
22416 @subsection MicroBlaze
22417 @cindex Xilinx MicroBlaze
22418 @cindex XMD, Xilinx Microprocessor Debugger
22420 The MicroBlaze is a soft-core processor supported on various Xilinx
22421 FPGAs, such as Spartan or Virtex series. Boards with these processors
22422 usually have JTAG ports which connect to a host system running the Xilinx
22423 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22424 This host system is used to download the configuration bitstream to
22425 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22426 communicates with the target board using the JTAG interface and
22427 presents a @code{gdbserver} interface to the board. By default
22428 @code{xmd} uses port @code{1234}. (While it is possible to change
22429 this default port, it requires the use of undocumented @code{xmd}
22430 commands. Contact Xilinx support if you need to do this.)
22432 Use these GDB commands to connect to the MicroBlaze target processor.
22435 @item target remote :1234
22436 Use this command to connect to the target if you are running @value{GDBN}
22437 on the same system as @code{xmd}.
22439 @item target remote @var{xmd-host}:1234
22440 Use this command to connect to the target if it is connected to @code{xmd}
22441 running on a different system named @var{xmd-host}.
22444 Use this command to download a program to the MicroBlaze target.
22446 @item set debug microblaze @var{n}
22447 Enable MicroBlaze-specific debugging messages if non-zero.
22449 @item show debug microblaze @var{n}
22450 Show MicroBlaze-specific debugging level.
22453 @node MIPS Embedded
22454 @subsection @acronym{MIPS} Embedded
22457 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22460 @item set mipsfpu double
22461 @itemx set mipsfpu single
22462 @itemx set mipsfpu none
22463 @itemx set mipsfpu auto
22464 @itemx show mipsfpu
22465 @kindex set mipsfpu
22466 @kindex show mipsfpu
22467 @cindex @acronym{MIPS} remote floating point
22468 @cindex floating point, @acronym{MIPS} remote
22469 If your target board does not support the @acronym{MIPS} floating point
22470 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22471 need this, you may wish to put the command in your @value{GDBN} init
22472 file). This tells @value{GDBN} how to find the return value of
22473 functions which return floating point values. It also allows
22474 @value{GDBN} to avoid saving the floating point registers when calling
22475 functions on the board. If you are using a floating point coprocessor
22476 with only single precision floating point support, as on the @sc{r4650}
22477 processor, use the command @samp{set mipsfpu single}. The default
22478 double precision floating point coprocessor may be selected using
22479 @samp{set mipsfpu double}.
22481 In previous versions the only choices were double precision or no
22482 floating point, so @samp{set mipsfpu on} will select double precision
22483 and @samp{set mipsfpu off} will select no floating point.
22485 As usual, you can inquire about the @code{mipsfpu} variable with
22486 @samp{show mipsfpu}.
22489 @node PowerPC Embedded
22490 @subsection PowerPC Embedded
22492 @cindex DVC register
22493 @value{GDBN} supports using the DVC (Data Value Compare) register to
22494 implement in hardware simple hardware watchpoint conditions of the form:
22497 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22498 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22501 The DVC register will be automatically used when @value{GDBN} detects
22502 such pattern in a condition expression, and the created watchpoint uses one
22503 debug register (either the @code{exact-watchpoints} option is on and the
22504 variable is scalar, or the variable has a length of one byte). This feature
22505 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22508 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22509 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22510 in which case watchpoints using only one debug register are created when
22511 watching variables of scalar types.
22513 You can create an artificial array to watch an arbitrary memory
22514 region using one of the following commands (@pxref{Expressions}):
22517 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22518 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22521 PowerPC embedded processors support masked watchpoints. See the discussion
22522 about the @code{mask} argument in @ref{Set Watchpoints}.
22524 @cindex ranged breakpoint
22525 PowerPC embedded processors support hardware accelerated
22526 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22527 the inferior whenever it executes an instruction at any address within
22528 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22529 use the @code{break-range} command.
22531 @value{GDBN} provides the following PowerPC-specific commands:
22534 @kindex break-range
22535 @item break-range @var{start-location}, @var{end-location}
22536 Set a breakpoint for an address range given by
22537 @var{start-location} and @var{end-location}, which can specify a function name,
22538 a line number, an offset of lines from the current line or from the start
22539 location, or an address of an instruction (see @ref{Specify Location},
22540 for a list of all the possible ways to specify a @var{location}.)
22541 The breakpoint will stop execution of the inferior whenever it
22542 executes an instruction at any address within the specified range,
22543 (including @var{start-location} and @var{end-location}.)
22545 @kindex set powerpc
22546 @item set powerpc soft-float
22547 @itemx show powerpc soft-float
22548 Force @value{GDBN} to use (or not use) a software floating point calling
22549 convention. By default, @value{GDBN} selects the calling convention based
22550 on the selected architecture and the provided executable file.
22552 @item set powerpc vector-abi
22553 @itemx show powerpc vector-abi
22554 Force @value{GDBN} to use the specified calling convention for vector
22555 arguments and return values. The valid options are @samp{auto};
22556 @samp{generic}, to avoid vector registers even if they are present;
22557 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22558 registers. By default, @value{GDBN} selects the calling convention
22559 based on the selected architecture and the provided executable file.
22561 @item set powerpc exact-watchpoints
22562 @itemx show powerpc exact-watchpoints
22563 Allow @value{GDBN} to use only one debug register when watching a variable
22564 of scalar type, thus assuming that the variable is accessed through the
22565 address of its first byte.
22570 @subsection Atmel AVR
22573 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22574 following AVR-specific commands:
22577 @item info io_registers
22578 @kindex info io_registers@r{, AVR}
22579 @cindex I/O registers (Atmel AVR)
22580 This command displays information about the AVR I/O registers. For
22581 each register, @value{GDBN} prints its number and value.
22588 When configured for debugging CRIS, @value{GDBN} provides the
22589 following CRIS-specific commands:
22592 @item set cris-version @var{ver}
22593 @cindex CRIS version
22594 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22595 The CRIS version affects register names and sizes. This command is useful in
22596 case autodetection of the CRIS version fails.
22598 @item show cris-version
22599 Show the current CRIS version.
22601 @item set cris-dwarf2-cfi
22602 @cindex DWARF-2 CFI and CRIS
22603 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22604 Change to @samp{off} when using @code{gcc-cris} whose version is below
22607 @item show cris-dwarf2-cfi
22608 Show the current state of using DWARF-2 CFI.
22610 @item set cris-mode @var{mode}
22612 Set the current CRIS mode to @var{mode}. It should only be changed when
22613 debugging in guru mode, in which case it should be set to
22614 @samp{guru} (the default is @samp{normal}).
22616 @item show cris-mode
22617 Show the current CRIS mode.
22621 @subsection Renesas Super-H
22624 For the Renesas Super-H processor, @value{GDBN} provides these
22628 @item set sh calling-convention @var{convention}
22629 @kindex set sh calling-convention
22630 Set the calling-convention used when calling functions from @value{GDBN}.
22631 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22632 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22633 convention. If the DWARF-2 information of the called function specifies
22634 that the function follows the Renesas calling convention, the function
22635 is called using the Renesas calling convention. If the calling convention
22636 is set to @samp{renesas}, the Renesas calling convention is always used,
22637 regardless of the DWARF-2 information. This can be used to override the
22638 default of @samp{gcc} if debug information is missing, or the compiler
22639 does not emit the DWARF-2 calling convention entry for a function.
22641 @item show sh calling-convention
22642 @kindex show sh calling-convention
22643 Show the current calling convention setting.
22648 @node Architectures
22649 @section Architectures
22651 This section describes characteristics of architectures that affect
22652 all uses of @value{GDBN} with the architecture, both native and cross.
22659 * HPPA:: HP PA architecture
22660 * SPU:: Cell Broadband Engine SPU architecture
22667 @subsection AArch64
22668 @cindex AArch64 support
22670 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22671 following special commands:
22674 @item set debug aarch64
22675 @kindex set debug aarch64
22676 This command determines whether AArch64 architecture-specific debugging
22677 messages are to be displayed.
22679 @item show debug aarch64
22680 Show whether AArch64 debugging messages are displayed.
22685 @subsection x86 Architecture-specific Issues
22688 @item set struct-convention @var{mode}
22689 @kindex set struct-convention
22690 @cindex struct return convention
22691 @cindex struct/union returned in registers
22692 Set the convention used by the inferior to return @code{struct}s and
22693 @code{union}s from functions to @var{mode}. Possible values of
22694 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22695 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22696 are returned on the stack, while @code{"reg"} means that a
22697 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22698 be returned in a register.
22700 @item show struct-convention
22701 @kindex show struct-convention
22702 Show the current setting of the convention to return @code{struct}s
22707 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22708 @cindex Intel Memory Protection Extensions (MPX).
22710 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22711 @footnote{The register named with capital letters represent the architecture
22712 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22713 which are the lower bound and upper bound. Bounds are effective addresses or
22714 memory locations. The upper bounds are architecturally represented in 1's
22715 complement form. A bound having lower bound = 0, and upper bound = 0
22716 (1's complement of all bits set) will allow access to the entire address space.
22718 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22719 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22720 display the upper bound performing the complement of one operation on the
22721 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22722 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22723 can also be noted that the upper bounds are inclusive.
22725 As an example, assume that the register BND0 holds bounds for a pointer having
22726 access allowed for the range between 0x32 and 0x71. The values present on
22727 bnd0raw and bnd registers are presented as follows:
22730 bnd0raw = @{0x32, 0xffffffff8e@}
22731 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22734 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22735 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22736 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22737 Python, the display includes the memory size, in bits, accessible to
22740 Bounds can also be stored in bounds tables, which are stored in
22741 application memory. These tables store bounds for pointers by specifying
22742 the bounds pointer's value along with its bounds. Evaluating and changing
22743 bounds located in bound tables is therefore interesting while investigating
22744 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22747 @item show mpx bound @var{pointer}
22748 @kindex show mpx bound
22749 Display bounds of the given @var{pointer}.
22751 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22752 @kindex set mpx bound
22753 Set the bounds of a pointer in the bound table.
22754 This command takes three parameters: @var{pointer} is the pointers
22755 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22756 for lower and upper bounds respectively.
22759 When you call an inferior function on an Intel MPX enabled program,
22760 GDB sets the inferior's bound registers to the init (disabled) state
22761 before calling the function. As a consequence, bounds checks for the
22762 pointer arguments passed to the function will always pass.
22764 This is necessary because when you call an inferior function, the
22765 program is usually in the middle of the execution of other function.
22766 Since at that point bound registers are in an arbitrary state, not
22767 clearing them would lead to random bound violations in the called
22770 You can still examine the influence of the bound registers on the
22771 execution of the called function by stopping the execution of the
22772 called function at its prologue, setting bound registers, and
22773 continuing the execution. For example:
22777 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
22778 $ print upper (a, b, c, d, 1)
22779 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
22781 @{lbound = 0x0, ubound = ffffffff@} : size -1
22784 At this last step the value of bnd0 can be changed for investigation of bound
22785 violations caused along the execution of the call. In order to know how to
22786 set the bound registers or bound table for the call consult the ABI.
22791 See the following section.
22794 @subsection @acronym{MIPS}
22796 @cindex stack on Alpha
22797 @cindex stack on @acronym{MIPS}
22798 @cindex Alpha stack
22799 @cindex @acronym{MIPS} stack
22800 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22801 sometimes requires @value{GDBN} to search backward in the object code to
22802 find the beginning of a function.
22804 @cindex response time, @acronym{MIPS} debugging
22805 To improve response time (especially for embedded applications, where
22806 @value{GDBN} may be restricted to a slow serial line for this search)
22807 you may want to limit the size of this search, using one of these
22811 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22812 @item set heuristic-fence-post @var{limit}
22813 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22814 search for the beginning of a function. A value of @var{0} (the
22815 default) means there is no limit. However, except for @var{0}, the
22816 larger the limit the more bytes @code{heuristic-fence-post} must search
22817 and therefore the longer it takes to run. You should only need to use
22818 this command when debugging a stripped executable.
22820 @item show heuristic-fence-post
22821 Display the current limit.
22825 These commands are available @emph{only} when @value{GDBN} is configured
22826 for debugging programs on Alpha or @acronym{MIPS} processors.
22828 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22832 @item set mips abi @var{arg}
22833 @kindex set mips abi
22834 @cindex set ABI for @acronym{MIPS}
22835 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22836 values of @var{arg} are:
22840 The default ABI associated with the current binary (this is the
22850 @item show mips abi
22851 @kindex show mips abi
22852 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22854 @item set mips compression @var{arg}
22855 @kindex set mips compression
22856 @cindex code compression, @acronym{MIPS}
22857 Tell @value{GDBN} which @acronym{MIPS} compressed
22858 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22859 inferior. @value{GDBN} uses this for code disassembly and other
22860 internal interpretation purposes. This setting is only referred to
22861 when no executable has been associated with the debugging session or
22862 the executable does not provide information about the encoding it uses.
22863 Otherwise this setting is automatically updated from information
22864 provided by the executable.
22866 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22867 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22868 executables containing @acronym{MIPS16} code frequently are not
22869 identified as such.
22871 This setting is ``sticky''; that is, it retains its value across
22872 debugging sessions until reset either explicitly with this command or
22873 implicitly from an executable.
22875 The compiler and/or assembler typically add symbol table annotations to
22876 identify functions compiled for the @acronym{MIPS16} or
22877 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22878 are present, @value{GDBN} uses them in preference to the global
22879 compressed @acronym{ISA} encoding setting.
22881 @item show mips compression
22882 @kindex show mips compression
22883 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22884 @value{GDBN} to debug the inferior.
22887 @itemx show mipsfpu
22888 @xref{MIPS Embedded, set mipsfpu}.
22890 @item set mips mask-address @var{arg}
22891 @kindex set mips mask-address
22892 @cindex @acronym{MIPS} addresses, masking
22893 This command determines whether the most-significant 32 bits of 64-bit
22894 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22895 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22896 setting, which lets @value{GDBN} determine the correct value.
22898 @item show mips mask-address
22899 @kindex show mips mask-address
22900 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22903 @item set remote-mips64-transfers-32bit-regs
22904 @kindex set remote-mips64-transfers-32bit-regs
22905 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22906 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22907 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22908 and 64 bits for other registers, set this option to @samp{on}.
22910 @item show remote-mips64-transfers-32bit-regs
22911 @kindex show remote-mips64-transfers-32bit-regs
22912 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22914 @item set debug mips
22915 @kindex set debug mips
22916 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22917 target code in @value{GDBN}.
22919 @item show debug mips
22920 @kindex show debug mips
22921 Show the current setting of @acronym{MIPS} debugging messages.
22927 @cindex HPPA support
22929 When @value{GDBN} is debugging the HP PA architecture, it provides the
22930 following special commands:
22933 @item set debug hppa
22934 @kindex set debug hppa
22935 This command determines whether HPPA architecture-specific debugging
22936 messages are to be displayed.
22938 @item show debug hppa
22939 Show whether HPPA debugging messages are displayed.
22941 @item maint print unwind @var{address}
22942 @kindex maint print unwind@r{, HPPA}
22943 This command displays the contents of the unwind table entry at the
22944 given @var{address}.
22950 @subsection Cell Broadband Engine SPU architecture
22951 @cindex Cell Broadband Engine
22954 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22955 it provides the following special commands:
22958 @item info spu event
22960 Display SPU event facility status. Shows current event mask
22961 and pending event status.
22963 @item info spu signal
22964 Display SPU signal notification facility status. Shows pending
22965 signal-control word and signal notification mode of both signal
22966 notification channels.
22968 @item info spu mailbox
22969 Display SPU mailbox facility status. Shows all pending entries,
22970 in order of processing, in each of the SPU Write Outbound,
22971 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22974 Display MFC DMA status. Shows all pending commands in the MFC
22975 DMA queue. For each entry, opcode, tag, class IDs, effective
22976 and local store addresses and transfer size are shown.
22978 @item info spu proxydma
22979 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22980 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22981 and local store addresses and transfer size are shown.
22985 When @value{GDBN} is debugging a combined PowerPC/SPU application
22986 on the Cell Broadband Engine, it provides in addition the following
22990 @item set spu stop-on-load @var{arg}
22992 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22993 will give control to the user when a new SPE thread enters its @code{main}
22994 function. The default is @code{off}.
22996 @item show spu stop-on-load
22998 Show whether to stop for new SPE threads.
23000 @item set spu auto-flush-cache @var{arg}
23001 Set whether to automatically flush the software-managed cache. When set to
23002 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23003 cache to be flushed whenever SPE execution stops. This provides a consistent
23004 view of PowerPC memory that is accessed via the cache. If an application
23005 does not use the software-managed cache, this option has no effect.
23007 @item show spu auto-flush-cache
23008 Show whether to automatically flush the software-managed cache.
23013 @subsection PowerPC
23014 @cindex PowerPC architecture
23016 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23017 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23018 numbers stored in the floating point registers. These values must be stored
23019 in two consecutive registers, always starting at an even register like
23020 @code{f0} or @code{f2}.
23022 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23023 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23024 @code{f2} and @code{f3} for @code{$dl1} and so on.
23026 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23027 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23030 @subsection Nios II
23031 @cindex Nios II architecture
23033 When @value{GDBN} is debugging the Nios II architecture,
23034 it provides the following special commands:
23038 @item set debug nios2
23039 @kindex set debug nios2
23040 This command turns on and off debugging messages for the Nios II
23041 target code in @value{GDBN}.
23043 @item show debug nios2
23044 @kindex show debug nios2
23045 Show the current setting of Nios II debugging messages.
23049 @subsection Sparc64
23050 @cindex Sparc64 support
23051 @cindex Application Data Integrity
23052 @subsubsection ADI Support
23054 The M7 processor supports an Application Data Integrity (ADI) feature that
23055 detects invalid data accesses. When software allocates memory and enables
23056 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23057 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23058 the 4-bit version in every cacheline of that data. Hardware saves the latter
23059 in spare bits in the cache and memory hierarchy. On each load and store,
23060 the processor compares the upper 4 VA (virtual address) bits to the
23061 cacheline's version. If there is a mismatch, the processor generates a
23062 version mismatch trap which can be either precise or disrupting. The trap
23063 is an error condition which the kernel delivers to the process as a SIGSEGV
23066 Note that only 64-bit applications can use ADI and need to be built with
23069 Values of the ADI version tags, which are in granularity of a
23070 cacheline (64 bytes), can be viewed or modified.
23074 @kindex adi examine
23075 @item adi (examine | x) [ / @var{n} ] @var{addr}
23077 The @code{adi examine} command displays the value of one ADI version tag per
23080 @var{n} is a decimal integer specifying the number in bytes; the default
23081 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23082 block size, to display.
23084 @var{addr} is the address in user address space where you want @value{GDBN}
23085 to begin displaying the ADI version tags.
23087 Below is an example of displaying ADI versions of variable "shmaddr".
23090 (@value{GDBP}) adi x/100 shmaddr
23091 0xfff800010002c000: 0 0
23095 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23097 The @code{adi assign} command is used to assign new ADI version tag
23100 @var{n} is a decimal integer specifying the number in bytes;
23101 the default is 1. It specifies how much ADI version information, at the
23102 ratio of 1:ADI block size, to modify.
23104 @var{addr} is the address in user address space where you want @value{GDBN}
23105 to begin modifying the ADI version tags.
23107 @var{tag} is the new ADI version tag.
23109 For example, do the following to modify then verify ADI versions of
23110 variable "shmaddr":
23113 (@value{GDBP}) adi a/100 shmaddr = 7
23114 (@value{GDBP}) adi x/100 shmaddr
23115 0xfff800010002c000: 7 7
23120 @node Controlling GDB
23121 @chapter Controlling @value{GDBN}
23123 You can alter the way @value{GDBN} interacts with you by using the
23124 @code{set} command. For commands controlling how @value{GDBN} displays
23125 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23130 * Editing:: Command editing
23131 * Command History:: Command history
23132 * Screen Size:: Screen size
23133 * Numbers:: Numbers
23134 * ABI:: Configuring the current ABI
23135 * Auto-loading:: Automatically loading associated files
23136 * Messages/Warnings:: Optional warnings and messages
23137 * Debugging Output:: Optional messages about internal happenings
23138 * Other Misc Settings:: Other Miscellaneous Settings
23146 @value{GDBN} indicates its readiness to read a command by printing a string
23147 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23148 can change the prompt string with the @code{set prompt} command. For
23149 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23150 the prompt in one of the @value{GDBN} sessions so that you can always tell
23151 which one you are talking to.
23153 @emph{Note:} @code{set prompt} does not add a space for you after the
23154 prompt you set. This allows you to set a prompt which ends in a space
23155 or a prompt that does not.
23159 @item set prompt @var{newprompt}
23160 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23162 @kindex show prompt
23164 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23167 Versions of @value{GDBN} that ship with Python scripting enabled have
23168 prompt extensions. The commands for interacting with these extensions
23172 @kindex set extended-prompt
23173 @item set extended-prompt @var{prompt}
23174 Set an extended prompt that allows for substitutions.
23175 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23176 substitution. Any escape sequences specified as part of the prompt
23177 string are replaced with the corresponding strings each time the prompt
23183 set extended-prompt Current working directory: \w (gdb)
23186 Note that when an extended-prompt is set, it takes control of the
23187 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23189 @kindex show extended-prompt
23190 @item show extended-prompt
23191 Prints the extended prompt. Any escape sequences specified as part of
23192 the prompt string with @code{set extended-prompt}, are replaced with the
23193 corresponding strings each time the prompt is displayed.
23197 @section Command Editing
23199 @cindex command line editing
23201 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23202 @sc{gnu} library provides consistent behavior for programs which provide a
23203 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23204 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23205 substitution, and a storage and recall of command history across
23206 debugging sessions.
23208 You may control the behavior of command line editing in @value{GDBN} with the
23209 command @code{set}.
23212 @kindex set editing
23215 @itemx set editing on
23216 Enable command line editing (enabled by default).
23218 @item set editing off
23219 Disable command line editing.
23221 @kindex show editing
23223 Show whether command line editing is enabled.
23226 @ifset SYSTEM_READLINE
23227 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23229 @ifclear SYSTEM_READLINE
23230 @xref{Command Line Editing},
23232 for more details about the Readline
23233 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23234 encouraged to read that chapter.
23236 @node Command History
23237 @section Command History
23238 @cindex command history
23240 @value{GDBN} can keep track of the commands you type during your
23241 debugging sessions, so that you can be certain of precisely what
23242 happened. Use these commands to manage the @value{GDBN} command
23245 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23246 package, to provide the history facility.
23247 @ifset SYSTEM_READLINE
23248 @xref{Using History Interactively, , , history, GNU History Library},
23250 @ifclear SYSTEM_READLINE
23251 @xref{Using History Interactively},
23253 for the detailed description of the History library.
23255 To issue a command to @value{GDBN} without affecting certain aspects of
23256 the state which is seen by users, prefix it with @samp{server }
23257 (@pxref{Server Prefix}). This
23258 means that this command will not affect the command history, nor will it
23259 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23260 pressed on a line by itself.
23262 @cindex @code{server}, command prefix
23263 The server prefix does not affect the recording of values into the value
23264 history; to print a value without recording it into the value history,
23265 use the @code{output} command instead of the @code{print} command.
23267 Here is the description of @value{GDBN} commands related to command
23271 @cindex history substitution
23272 @cindex history file
23273 @kindex set history filename
23274 @cindex @env{GDBHISTFILE}, environment variable
23275 @item set history filename @var{fname}
23276 Set the name of the @value{GDBN} command history file to @var{fname}.
23277 This is the file where @value{GDBN} reads an initial command history
23278 list, and where it writes the command history from this session when it
23279 exits. You can access this list through history expansion or through
23280 the history command editing characters listed below. This file defaults
23281 to the value of the environment variable @code{GDBHISTFILE}, or to
23282 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23285 @cindex save command history
23286 @kindex set history save
23287 @item set history save
23288 @itemx set history save on
23289 Record command history in a file, whose name may be specified with the
23290 @code{set history filename} command. By default, this option is disabled.
23292 @item set history save off
23293 Stop recording command history in a file.
23295 @cindex history size
23296 @kindex set history size
23297 @cindex @env{GDBHISTSIZE}, environment variable
23298 @item set history size @var{size}
23299 @itemx set history size unlimited
23300 Set the number of commands which @value{GDBN} keeps in its history list.
23301 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23302 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23303 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23304 either a negative number or the empty string, then the number of commands
23305 @value{GDBN} keeps in the history list is unlimited.
23307 @cindex remove duplicate history
23308 @kindex set history remove-duplicates
23309 @item set history remove-duplicates @var{count}
23310 @itemx set history remove-duplicates unlimited
23311 Control the removal of duplicate history entries in the command history list.
23312 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23313 history entries and remove the first entry that is a duplicate of the current
23314 entry being added to the command history list. If @var{count} is
23315 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23316 removal of duplicate history entries is disabled.
23318 Only history entries added during the current session are considered for
23319 removal. This option is set to 0 by default.
23323 History expansion assigns special meaning to the character @kbd{!}.
23324 @ifset SYSTEM_READLINE
23325 @xref{Event Designators, , , history, GNU History Library},
23327 @ifclear SYSTEM_READLINE
23328 @xref{Event Designators},
23332 @cindex history expansion, turn on/off
23333 Since @kbd{!} is also the logical not operator in C, history expansion
23334 is off by default. If you decide to enable history expansion with the
23335 @code{set history expansion on} command, you may sometimes need to
23336 follow @kbd{!} (when it is used as logical not, in an expression) with
23337 a space or a tab to prevent it from being expanded. The readline
23338 history facilities do not attempt substitution on the strings
23339 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23341 The commands to control history expansion are:
23344 @item set history expansion on
23345 @itemx set history expansion
23346 @kindex set history expansion
23347 Enable history expansion. History expansion is off by default.
23349 @item set history expansion off
23350 Disable history expansion.
23353 @kindex show history
23355 @itemx show history filename
23356 @itemx show history save
23357 @itemx show history size
23358 @itemx show history expansion
23359 These commands display the state of the @value{GDBN} history parameters.
23360 @code{show history} by itself displays all four states.
23365 @kindex show commands
23366 @cindex show last commands
23367 @cindex display command history
23368 @item show commands
23369 Display the last ten commands in the command history.
23371 @item show commands @var{n}
23372 Print ten commands centered on command number @var{n}.
23374 @item show commands +
23375 Print ten commands just after the commands last printed.
23379 @section Screen Size
23380 @cindex size of screen
23381 @cindex screen size
23384 @cindex pauses in output
23386 Certain commands to @value{GDBN} may produce large amounts of
23387 information output to the screen. To help you read all of it,
23388 @value{GDBN} pauses and asks you for input at the end of each page of
23389 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23390 to discard the remaining output. Also, the screen width setting
23391 determines when to wrap lines of output. Depending on what is being
23392 printed, @value{GDBN} tries to break the line at a readable place,
23393 rather than simply letting it overflow onto the following line.
23395 Normally @value{GDBN} knows the size of the screen from the terminal
23396 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23397 together with the value of the @code{TERM} environment variable and the
23398 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23399 you can override it with the @code{set height} and @code{set
23406 @kindex show height
23407 @item set height @var{lpp}
23408 @itemx set height unlimited
23410 @itemx set width @var{cpl}
23411 @itemx set width unlimited
23413 These @code{set} commands specify a screen height of @var{lpp} lines and
23414 a screen width of @var{cpl} characters. The associated @code{show}
23415 commands display the current settings.
23417 If you specify a height of either @code{unlimited} or zero lines,
23418 @value{GDBN} does not pause during output no matter how long the
23419 output is. This is useful if output is to a file or to an editor
23422 Likewise, you can specify @samp{set width unlimited} or @samp{set
23423 width 0} to prevent @value{GDBN} from wrapping its output.
23425 @item set pagination on
23426 @itemx set pagination off
23427 @kindex set pagination
23428 Turn the output pagination on or off; the default is on. Turning
23429 pagination off is the alternative to @code{set height unlimited}. Note that
23430 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23431 Options, -batch}) also automatically disables pagination.
23433 @item show pagination
23434 @kindex show pagination
23435 Show the current pagination mode.
23440 @cindex number representation
23441 @cindex entering numbers
23443 You can always enter numbers in octal, decimal, or hexadecimal in
23444 @value{GDBN} by the usual conventions: octal numbers begin with
23445 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23446 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23447 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23448 10; likewise, the default display for numbers---when no particular
23449 format is specified---is base 10. You can change the default base for
23450 both input and output with the commands described below.
23453 @kindex set input-radix
23454 @item set input-radix @var{base}
23455 Set the default base for numeric input. Supported choices
23456 for @var{base} are decimal 8, 10, or 16. The base must itself be
23457 specified either unambiguously or using the current input radix; for
23461 set input-radix 012
23462 set input-radix 10.
23463 set input-radix 0xa
23467 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23468 leaves the input radix unchanged, no matter what it was, since
23469 @samp{10}, being without any leading or trailing signs of its base, is
23470 interpreted in the current radix. Thus, if the current radix is 16,
23471 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23474 @kindex set output-radix
23475 @item set output-radix @var{base}
23476 Set the default base for numeric display. Supported choices
23477 for @var{base} are decimal 8, 10, or 16. The base must itself be
23478 specified either unambiguously or using the current input radix.
23480 @kindex show input-radix
23481 @item show input-radix
23482 Display the current default base for numeric input.
23484 @kindex show output-radix
23485 @item show output-radix
23486 Display the current default base for numeric display.
23488 @item set radix @r{[}@var{base}@r{]}
23492 These commands set and show the default base for both input and output
23493 of numbers. @code{set radix} sets the radix of input and output to
23494 the same base; without an argument, it resets the radix back to its
23495 default value of 10.
23500 @section Configuring the Current ABI
23502 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23503 application automatically. However, sometimes you need to override its
23504 conclusions. Use these commands to manage @value{GDBN}'s view of the
23510 @cindex Newlib OS ABI and its influence on the longjmp handling
23512 One @value{GDBN} configuration can debug binaries for multiple operating
23513 system targets, either via remote debugging or native emulation.
23514 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23515 but you can override its conclusion using the @code{set osabi} command.
23516 One example where this is useful is in debugging of binaries which use
23517 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23518 not have the same identifying marks that the standard C library for your
23521 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23522 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23523 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23524 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23528 Show the OS ABI currently in use.
23531 With no argument, show the list of registered available OS ABI's.
23533 @item set osabi @var{abi}
23534 Set the current OS ABI to @var{abi}.
23537 @cindex float promotion
23539 Generally, the way that an argument of type @code{float} is passed to a
23540 function depends on whether the function is prototyped. For a prototyped
23541 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23542 according to the architecture's convention for @code{float}. For unprototyped
23543 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23544 @code{double} and then passed.
23546 Unfortunately, some forms of debug information do not reliably indicate whether
23547 a function is prototyped. If @value{GDBN} calls a function that is not marked
23548 as prototyped, it consults @kbd{set coerce-float-to-double}.
23551 @kindex set coerce-float-to-double
23552 @item set coerce-float-to-double
23553 @itemx set coerce-float-to-double on
23554 Arguments of type @code{float} will be promoted to @code{double} when passed
23555 to an unprototyped function. This is the default setting.
23557 @item set coerce-float-to-double off
23558 Arguments of type @code{float} will be passed directly to unprototyped
23561 @kindex show coerce-float-to-double
23562 @item show coerce-float-to-double
23563 Show the current setting of promoting @code{float} to @code{double}.
23567 @kindex show cp-abi
23568 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23569 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23570 used to build your application. @value{GDBN} only fully supports
23571 programs with a single C@t{++} ABI; if your program contains code using
23572 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23573 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23574 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23575 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23576 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23577 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23582 Show the C@t{++} ABI currently in use.
23585 With no argument, show the list of supported C@t{++} ABI's.
23587 @item set cp-abi @var{abi}
23588 @itemx set cp-abi auto
23589 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23593 @section Automatically loading associated files
23594 @cindex auto-loading
23596 @value{GDBN} sometimes reads files with commands and settings automatically,
23597 without being explicitly told so by the user. We call this feature
23598 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23599 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23600 results or introduce security risks (e.g., if the file comes from untrusted
23604 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23605 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23607 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23608 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23611 There are various kinds of files @value{GDBN} can automatically load.
23612 In addition to these files, @value{GDBN} supports auto-loading code written
23613 in various extension languages. @xref{Auto-loading extensions}.
23615 Note that loading of these associated files (including the local @file{.gdbinit}
23616 file) requires accordingly configured @code{auto-load safe-path}
23617 (@pxref{Auto-loading safe path}).
23619 For these reasons, @value{GDBN} includes commands and options to let you
23620 control when to auto-load files and which files should be auto-loaded.
23623 @anchor{set auto-load off}
23624 @kindex set auto-load off
23625 @item set auto-load off
23626 Globally disable loading of all auto-loaded files.
23627 You may want to use this command with the @samp{-iex} option
23628 (@pxref{Option -init-eval-command}) such as:
23630 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23633 Be aware that system init file (@pxref{System-wide configuration})
23634 and init files from your home directory (@pxref{Home Directory Init File})
23635 still get read (as they come from generally trusted directories).
23636 To prevent @value{GDBN} from auto-loading even those init files, use the
23637 @option{-nx} option (@pxref{Mode Options}), in addition to
23638 @code{set auto-load no}.
23640 @anchor{show auto-load}
23641 @kindex show auto-load
23642 @item show auto-load
23643 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23647 (gdb) show auto-load
23648 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23649 libthread-db: Auto-loading of inferior specific libthread_db is on.
23650 local-gdbinit: Auto-loading of .gdbinit script from current directory
23652 python-scripts: Auto-loading of Python scripts is on.
23653 safe-path: List of directories from which it is safe to auto-load files
23654 is $debugdir:$datadir/auto-load.
23655 scripts-directory: List of directories from which to load auto-loaded scripts
23656 is $debugdir:$datadir/auto-load.
23659 @anchor{info auto-load}
23660 @kindex info auto-load
23661 @item info auto-load
23662 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23666 (gdb) info auto-load
23669 Yes /home/user/gdb/gdb-gdb.gdb
23670 libthread-db: No auto-loaded libthread-db.
23671 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23675 Yes /home/user/gdb/gdb-gdb.py
23679 These are @value{GDBN} control commands for the auto-loading:
23681 @multitable @columnfractions .5 .5
23682 @item @xref{set auto-load off}.
23683 @tab Disable auto-loading globally.
23684 @item @xref{show auto-load}.
23685 @tab Show setting of all kinds of files.
23686 @item @xref{info auto-load}.
23687 @tab Show state of all kinds of files.
23688 @item @xref{set auto-load gdb-scripts}.
23689 @tab Control for @value{GDBN} command scripts.
23690 @item @xref{show auto-load gdb-scripts}.
23691 @tab Show setting of @value{GDBN} command scripts.
23692 @item @xref{info auto-load gdb-scripts}.
23693 @tab Show state of @value{GDBN} command scripts.
23694 @item @xref{set auto-load python-scripts}.
23695 @tab Control for @value{GDBN} Python scripts.
23696 @item @xref{show auto-load python-scripts}.
23697 @tab Show setting of @value{GDBN} Python scripts.
23698 @item @xref{info auto-load python-scripts}.
23699 @tab Show state of @value{GDBN} Python scripts.
23700 @item @xref{set auto-load guile-scripts}.
23701 @tab Control for @value{GDBN} Guile scripts.
23702 @item @xref{show auto-load guile-scripts}.
23703 @tab Show setting of @value{GDBN} Guile scripts.
23704 @item @xref{info auto-load guile-scripts}.
23705 @tab Show state of @value{GDBN} Guile scripts.
23706 @item @xref{set auto-load scripts-directory}.
23707 @tab Control for @value{GDBN} auto-loaded scripts location.
23708 @item @xref{show auto-load scripts-directory}.
23709 @tab Show @value{GDBN} auto-loaded scripts location.
23710 @item @xref{add-auto-load-scripts-directory}.
23711 @tab Add directory for auto-loaded scripts location list.
23712 @item @xref{set auto-load local-gdbinit}.
23713 @tab Control for init file in the current directory.
23714 @item @xref{show auto-load local-gdbinit}.
23715 @tab Show setting of init file in the current directory.
23716 @item @xref{info auto-load local-gdbinit}.
23717 @tab Show state of init file in the current directory.
23718 @item @xref{set auto-load libthread-db}.
23719 @tab Control for thread debugging library.
23720 @item @xref{show auto-load libthread-db}.
23721 @tab Show setting of thread debugging library.
23722 @item @xref{info auto-load libthread-db}.
23723 @tab Show state of thread debugging library.
23724 @item @xref{set auto-load safe-path}.
23725 @tab Control directories trusted for automatic loading.
23726 @item @xref{show auto-load safe-path}.
23727 @tab Show directories trusted for automatic loading.
23728 @item @xref{add-auto-load-safe-path}.
23729 @tab Add directory trusted for automatic loading.
23732 @node Init File in the Current Directory
23733 @subsection Automatically loading init file in the current directory
23734 @cindex auto-loading init file in the current directory
23736 By default, @value{GDBN} reads and executes the canned sequences of commands
23737 from init file (if any) in the current working directory,
23738 see @ref{Init File in the Current Directory during Startup}.
23740 Note that loading of this local @file{.gdbinit} file also requires accordingly
23741 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23744 @anchor{set auto-load local-gdbinit}
23745 @kindex set auto-load local-gdbinit
23746 @item set auto-load local-gdbinit [on|off]
23747 Enable or disable the auto-loading of canned sequences of commands
23748 (@pxref{Sequences}) found in init file in the current directory.
23750 @anchor{show auto-load local-gdbinit}
23751 @kindex show auto-load local-gdbinit
23752 @item show auto-load local-gdbinit
23753 Show whether auto-loading of canned sequences of commands from init file in the
23754 current directory is enabled or disabled.
23756 @anchor{info auto-load local-gdbinit}
23757 @kindex info auto-load local-gdbinit
23758 @item info auto-load local-gdbinit
23759 Print whether canned sequences of commands from init file in the
23760 current directory have been auto-loaded.
23763 @node libthread_db.so.1 file
23764 @subsection Automatically loading thread debugging library
23765 @cindex auto-loading libthread_db.so.1
23767 This feature is currently present only on @sc{gnu}/Linux native hosts.
23769 @value{GDBN} reads in some cases thread debugging library from places specific
23770 to the inferior (@pxref{set libthread-db-search-path}).
23772 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23773 without checking this @samp{set auto-load libthread-db} switch as system
23774 libraries have to be trusted in general. In all other cases of
23775 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23776 auto-load libthread-db} is enabled before trying to open such thread debugging
23779 Note that loading of this debugging library also requires accordingly configured
23780 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23783 @anchor{set auto-load libthread-db}
23784 @kindex set auto-load libthread-db
23785 @item set auto-load libthread-db [on|off]
23786 Enable or disable the auto-loading of inferior specific thread debugging library.
23788 @anchor{show auto-load libthread-db}
23789 @kindex show auto-load libthread-db
23790 @item show auto-load libthread-db
23791 Show whether auto-loading of inferior specific thread debugging library is
23792 enabled or disabled.
23794 @anchor{info auto-load libthread-db}
23795 @kindex info auto-load libthread-db
23796 @item info auto-load libthread-db
23797 Print the list of all loaded inferior specific thread debugging libraries and
23798 for each such library print list of inferior @var{pid}s using it.
23801 @node Auto-loading safe path
23802 @subsection Security restriction for auto-loading
23803 @cindex auto-loading safe-path
23805 As the files of inferior can come from untrusted source (such as submitted by
23806 an application user) @value{GDBN} does not always load any files automatically.
23807 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23808 directories trusted for loading files not explicitly requested by user.
23809 Each directory can also be a shell wildcard pattern.
23811 If the path is not set properly you will see a warning and the file will not
23816 Reading symbols from /home/user/gdb/gdb...done.
23817 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23818 declined by your `auto-load safe-path' set
23819 to "$debugdir:$datadir/auto-load".
23820 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23821 declined by your `auto-load safe-path' set
23822 to "$debugdir:$datadir/auto-load".
23826 To instruct @value{GDBN} to go ahead and use the init files anyway,
23827 invoke @value{GDBN} like this:
23830 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23833 The list of trusted directories is controlled by the following commands:
23836 @anchor{set auto-load safe-path}
23837 @kindex set auto-load safe-path
23838 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23839 Set the list of directories (and their subdirectories) trusted for automatic
23840 loading and execution of scripts. You can also enter a specific trusted file.
23841 Each directory can also be a shell wildcard pattern; wildcards do not match
23842 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23843 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23844 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23845 its default value as specified during @value{GDBN} compilation.
23847 The list of directories uses path separator (@samp{:} on GNU and Unix
23848 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23849 to the @env{PATH} environment variable.
23851 @anchor{show auto-load safe-path}
23852 @kindex show auto-load safe-path
23853 @item show auto-load safe-path
23854 Show the list of directories trusted for automatic loading and execution of
23857 @anchor{add-auto-load-safe-path}
23858 @kindex add-auto-load-safe-path
23859 @item add-auto-load-safe-path
23860 Add an entry (or list of entries) to the list of directories trusted for
23861 automatic loading and execution of scripts. Multiple entries may be delimited
23862 by the host platform path separator in use.
23865 This variable defaults to what @code{--with-auto-load-dir} has been configured
23866 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23867 substitution applies the same as for @ref{set auto-load scripts-directory}.
23868 The default @code{set auto-load safe-path} value can be also overriden by
23869 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23871 Setting this variable to @file{/} disables this security protection,
23872 corresponding @value{GDBN} configuration option is
23873 @option{--without-auto-load-safe-path}.
23874 This variable is supposed to be set to the system directories writable by the
23875 system superuser only. Users can add their source directories in init files in
23876 their home directories (@pxref{Home Directory Init File}). See also deprecated
23877 init file in the current directory
23878 (@pxref{Init File in the Current Directory during Startup}).
23880 To force @value{GDBN} to load the files it declined to load in the previous
23881 example, you could use one of the following ways:
23884 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23885 Specify this trusted directory (or a file) as additional component of the list.
23886 You have to specify also any existing directories displayed by
23887 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23889 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23890 Specify this directory as in the previous case but just for a single
23891 @value{GDBN} session.
23893 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23894 Disable auto-loading safety for a single @value{GDBN} session.
23895 This assumes all the files you debug during this @value{GDBN} session will come
23896 from trusted sources.
23898 @item @kbd{./configure --without-auto-load-safe-path}
23899 During compilation of @value{GDBN} you may disable any auto-loading safety.
23900 This assumes all the files you will ever debug with this @value{GDBN} come from
23904 On the other hand you can also explicitly forbid automatic files loading which
23905 also suppresses any such warning messages:
23908 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23909 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23911 @item @file{~/.gdbinit}: @samp{set auto-load no}
23912 Disable auto-loading globally for the user
23913 (@pxref{Home Directory Init File}). While it is improbable, you could also
23914 use system init file instead (@pxref{System-wide configuration}).
23917 This setting applies to the file names as entered by user. If no entry matches
23918 @value{GDBN} tries as a last resort to also resolve all the file names into
23919 their canonical form (typically resolving symbolic links) and compare the
23920 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23921 own before starting the comparison so a canonical form of directories is
23922 recommended to be entered.
23924 @node Auto-loading verbose mode
23925 @subsection Displaying files tried for auto-load
23926 @cindex auto-loading verbose mode
23928 For better visibility of all the file locations where you can place scripts to
23929 be auto-loaded with inferior --- or to protect yourself against accidental
23930 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23931 all the files attempted to be loaded. Both existing and non-existing files may
23934 For example the list of directories from which it is safe to auto-load files
23935 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23936 may not be too obvious while setting it up.
23939 (gdb) set debug auto-load on
23940 (gdb) file ~/src/t/true
23941 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23942 for objfile "/tmp/true".
23943 auto-load: Updating directories of "/usr:/opt".
23944 auto-load: Using directory "/usr".
23945 auto-load: Using directory "/opt".
23946 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23947 by your `auto-load safe-path' set to "/usr:/opt".
23951 @anchor{set debug auto-load}
23952 @kindex set debug auto-load
23953 @item set debug auto-load [on|off]
23954 Set whether to print the filenames attempted to be auto-loaded.
23956 @anchor{show debug auto-load}
23957 @kindex show debug auto-load
23958 @item show debug auto-load
23959 Show whether printing of the filenames attempted to be auto-loaded is turned
23963 @node Messages/Warnings
23964 @section Optional Warnings and Messages
23966 @cindex verbose operation
23967 @cindex optional warnings
23968 By default, @value{GDBN} is silent about its inner workings. If you are
23969 running on a slow machine, you may want to use the @code{set verbose}
23970 command. This makes @value{GDBN} tell you when it does a lengthy
23971 internal operation, so you will not think it has crashed.
23973 Currently, the messages controlled by @code{set verbose} are those
23974 which announce that the symbol table for a source file is being read;
23975 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23978 @kindex set verbose
23979 @item set verbose on
23980 Enables @value{GDBN} output of certain informational messages.
23982 @item set verbose off
23983 Disables @value{GDBN} output of certain informational messages.
23985 @kindex show verbose
23987 Displays whether @code{set verbose} is on or off.
23990 By default, if @value{GDBN} encounters bugs in the symbol table of an
23991 object file, it is silent; but if you are debugging a compiler, you may
23992 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23997 @kindex set complaints
23998 @item set complaints @var{limit}
23999 Permits @value{GDBN} to output @var{limit} complaints about each type of
24000 unusual symbols before becoming silent about the problem. Set
24001 @var{limit} to zero to suppress all complaints; set it to a large number
24002 to prevent complaints from being suppressed.
24004 @kindex show complaints
24005 @item show complaints
24006 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24010 @anchor{confirmation requests}
24011 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24012 lot of stupid questions to confirm certain commands. For example, if
24013 you try to run a program which is already running:
24017 The program being debugged has been started already.
24018 Start it from the beginning? (y or n)
24021 If you are willing to unflinchingly face the consequences of your own
24022 commands, you can disable this ``feature'':
24026 @kindex set confirm
24028 @cindex confirmation
24029 @cindex stupid questions
24030 @item set confirm off
24031 Disables confirmation requests. Note that running @value{GDBN} with
24032 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24033 automatically disables confirmation requests.
24035 @item set confirm on
24036 Enables confirmation requests (the default).
24038 @kindex show confirm
24040 Displays state of confirmation requests.
24044 @cindex command tracing
24045 If you need to debug user-defined commands or sourced files you may find it
24046 useful to enable @dfn{command tracing}. In this mode each command will be
24047 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24048 quantity denoting the call depth of each command.
24051 @kindex set trace-commands
24052 @cindex command scripts, debugging
24053 @item set trace-commands on
24054 Enable command tracing.
24055 @item set trace-commands off
24056 Disable command tracing.
24057 @item show trace-commands
24058 Display the current state of command tracing.
24061 @node Debugging Output
24062 @section Optional Messages about Internal Happenings
24063 @cindex optional debugging messages
24065 @value{GDBN} has commands that enable optional debugging messages from
24066 various @value{GDBN} subsystems; normally these commands are of
24067 interest to @value{GDBN} maintainers, or when reporting a bug. This
24068 section documents those commands.
24071 @kindex set exec-done-display
24072 @item set exec-done-display
24073 Turns on or off the notification of asynchronous commands'
24074 completion. When on, @value{GDBN} will print a message when an
24075 asynchronous command finishes its execution. The default is off.
24076 @kindex show exec-done-display
24077 @item show exec-done-display
24078 Displays the current setting of asynchronous command completion
24081 @cindex ARM AArch64
24082 @item set debug aarch64
24083 Turns on or off display of debugging messages related to ARM AArch64.
24084 The default is off.
24086 @item show debug aarch64
24087 Displays the current state of displaying debugging messages related to
24089 @cindex gdbarch debugging info
24090 @cindex architecture debugging info
24091 @item set debug arch
24092 Turns on or off display of gdbarch debugging info. The default is off
24093 @item show debug arch
24094 Displays the current state of displaying gdbarch debugging info.
24095 @item set debug aix-solib
24096 @cindex AIX shared library debugging
24097 Control display of debugging messages from the AIX shared library
24098 support module. The default is off.
24099 @item show debug aix-thread
24100 Show the current state of displaying AIX shared library debugging messages.
24101 @item set debug aix-thread
24102 @cindex AIX threads
24103 Display debugging messages about inner workings of the AIX thread
24105 @item show debug aix-thread
24106 Show the current state of AIX thread debugging info display.
24107 @item set debug check-physname
24109 Check the results of the ``physname'' computation. When reading DWARF
24110 debugging information for C@t{++}, @value{GDBN} attempts to compute
24111 each entity's name. @value{GDBN} can do this computation in two
24112 different ways, depending on exactly what information is present.
24113 When enabled, this setting causes @value{GDBN} to compute the names
24114 both ways and display any discrepancies.
24115 @item show debug check-physname
24116 Show the current state of ``physname'' checking.
24117 @item set debug coff-pe-read
24118 @cindex COFF/PE exported symbols
24119 Control display of debugging messages related to reading of COFF/PE
24120 exported symbols. The default is off.
24121 @item show debug coff-pe-read
24122 Displays the current state of displaying debugging messages related to
24123 reading of COFF/PE exported symbols.
24124 @item set debug dwarf-die
24126 Dump DWARF DIEs after they are read in.
24127 The value is the number of nesting levels to print.
24128 A value of zero turns off the display.
24129 @item show debug dwarf-die
24130 Show the current state of DWARF DIE debugging.
24131 @item set debug dwarf-line
24132 @cindex DWARF Line Tables
24133 Turns on or off display of debugging messages related to reading
24134 DWARF line tables. The default is 0 (off).
24135 A value of 1 provides basic information.
24136 A value greater than 1 provides more verbose information.
24137 @item show debug dwarf-line
24138 Show the current state of DWARF line table debugging.
24139 @item set debug dwarf-read
24140 @cindex DWARF Reading
24141 Turns on or off display of debugging messages related to reading
24142 DWARF debug info. The default is 0 (off).
24143 A value of 1 provides basic information.
24144 A value greater than 1 provides more verbose information.
24145 @item show debug dwarf-read
24146 Show the current state of DWARF reader debugging.
24147 @item set debug displaced
24148 @cindex displaced stepping debugging info
24149 Turns on or off display of @value{GDBN} debugging info for the
24150 displaced stepping support. The default is off.
24151 @item show debug displaced
24152 Displays the current state of displaying @value{GDBN} debugging info
24153 related to displaced stepping.
24154 @item set debug event
24155 @cindex event debugging info
24156 Turns on or off display of @value{GDBN} event debugging info. The
24158 @item show debug event
24159 Displays the current state of displaying @value{GDBN} event debugging
24161 @item set debug expression
24162 @cindex expression debugging info
24163 Turns on or off display of debugging info about @value{GDBN}
24164 expression parsing. The default is off.
24165 @item show debug expression
24166 Displays the current state of displaying debugging info about
24167 @value{GDBN} expression parsing.
24168 @item set debug fbsd-lwp
24169 @cindex FreeBSD LWP debug messages
24170 Turns on or off debugging messages from the FreeBSD LWP debug support.
24171 @item show debug fbsd-lwp
24172 Show the current state of FreeBSD LWP debugging messages.
24173 @item set debug frame
24174 @cindex frame debugging info
24175 Turns on or off display of @value{GDBN} frame debugging info. The
24177 @item show debug frame
24178 Displays the current state of displaying @value{GDBN} frame debugging
24180 @item set debug gnu-nat
24181 @cindex @sc{gnu}/Hurd debug messages
24182 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24183 @item show debug gnu-nat
24184 Show the current state of @sc{gnu}/Hurd debugging messages.
24185 @item set debug infrun
24186 @cindex inferior debugging info
24187 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24188 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24189 for implementing operations such as single-stepping the inferior.
24190 @item show debug infrun
24191 Displays the current state of @value{GDBN} inferior debugging.
24192 @item set debug jit
24193 @cindex just-in-time compilation, debugging messages
24194 Turn on or off debugging messages from JIT debug support.
24195 @item show debug jit
24196 Displays the current state of @value{GDBN} JIT debugging.
24197 @item set debug lin-lwp
24198 @cindex @sc{gnu}/Linux LWP debug messages
24199 @cindex Linux lightweight processes
24200 Turn on or off debugging messages from the Linux LWP debug support.
24201 @item show debug lin-lwp
24202 Show the current state of Linux LWP debugging messages.
24203 @item set debug linux-namespaces
24204 @cindex @sc{gnu}/Linux namespaces debug messages
24205 Turn on or off debugging messages from the Linux namespaces debug support.
24206 @item show debug linux-namespaces
24207 Show the current state of Linux namespaces debugging messages.
24208 @item set debug mach-o
24209 @cindex Mach-O symbols processing
24210 Control display of debugging messages related to Mach-O symbols
24211 processing. The default is off.
24212 @item show debug mach-o
24213 Displays the current state of displaying debugging messages related to
24214 reading of COFF/PE exported symbols.
24215 @item set debug notification
24216 @cindex remote async notification debugging info
24217 Turn on or off debugging messages about remote async notification.
24218 The default is off.
24219 @item show debug notification
24220 Displays the current state of remote async notification debugging messages.
24221 @item set debug observer
24222 @cindex observer debugging info
24223 Turns on or off display of @value{GDBN} observer debugging. This
24224 includes info such as the notification of observable events.
24225 @item show debug observer
24226 Displays the current state of observer debugging.
24227 @item set debug overload
24228 @cindex C@t{++} overload debugging info
24229 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24230 info. This includes info such as ranking of functions, etc. The default
24232 @item show debug overload
24233 Displays the current state of displaying @value{GDBN} C@t{++} overload
24235 @cindex expression parser, debugging info
24236 @cindex debug expression parser
24237 @item set debug parser
24238 Turns on or off the display of expression parser debugging output.
24239 Internally, this sets the @code{yydebug} variable in the expression
24240 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24241 details. The default is off.
24242 @item show debug parser
24243 Show the current state of expression parser debugging.
24244 @cindex packets, reporting on stdout
24245 @cindex serial connections, debugging
24246 @cindex debug remote protocol
24247 @cindex remote protocol debugging
24248 @cindex display remote packets
24249 @item set debug remote
24250 Turns on or off display of reports on all packets sent back and forth across
24251 the serial line to the remote machine. The info is printed on the
24252 @value{GDBN} standard output stream. The default is off.
24253 @item show debug remote
24254 Displays the state of display of remote packets.
24256 @item set debug separate-debug-file
24257 Turns on or off display of debug output about separate debug file search.
24258 @item show debug separate-debug-file
24259 Displays the state of separate debug file search debug output.
24261 @item set debug serial
24262 Turns on or off display of @value{GDBN} serial debugging info. The
24264 @item show debug serial
24265 Displays the current state of displaying @value{GDBN} serial debugging
24267 @item set debug solib-frv
24268 @cindex FR-V shared-library debugging
24269 Turn on or off debugging messages for FR-V shared-library code.
24270 @item show debug solib-frv
24271 Display the current state of FR-V shared-library code debugging
24273 @item set debug symbol-lookup
24274 @cindex symbol lookup
24275 Turns on or off display of debugging messages related to symbol lookup.
24276 The default is 0 (off).
24277 A value of 1 provides basic information.
24278 A value greater than 1 provides more verbose information.
24279 @item show debug symbol-lookup
24280 Show the current state of symbol lookup debugging messages.
24281 @item set debug symfile
24282 @cindex symbol file functions
24283 Turns on or off display of debugging messages related to symbol file functions.
24284 The default is off. @xref{Files}.
24285 @item show debug symfile
24286 Show the current state of symbol file debugging messages.
24287 @item set debug symtab-create
24288 @cindex symbol table creation
24289 Turns on or off display of debugging messages related to symbol table creation.
24290 The default is 0 (off).
24291 A value of 1 provides basic information.
24292 A value greater than 1 provides more verbose information.
24293 @item show debug symtab-create
24294 Show the current state of symbol table creation debugging.
24295 @item set debug target
24296 @cindex target debugging info
24297 Turns on or off display of @value{GDBN} target debugging info. This info
24298 includes what is going on at the target level of GDB, as it happens. The
24299 default is 0. Set it to 1 to track events, and to 2 to also track the
24300 value of large memory transfers.
24301 @item show debug target
24302 Displays the current state of displaying @value{GDBN} target debugging
24304 @item set debug timestamp
24305 @cindex timestampping debugging info
24306 Turns on or off display of timestamps with @value{GDBN} debugging info.
24307 When enabled, seconds and microseconds are displayed before each debugging
24309 @item show debug timestamp
24310 Displays the current state of displaying timestamps with @value{GDBN}
24312 @item set debug varobj
24313 @cindex variable object debugging info
24314 Turns on or off display of @value{GDBN} variable object debugging
24315 info. The default is off.
24316 @item show debug varobj
24317 Displays the current state of displaying @value{GDBN} variable object
24319 @item set debug xml
24320 @cindex XML parser debugging
24321 Turn on or off debugging messages for built-in XML parsers.
24322 @item show debug xml
24323 Displays the current state of XML debugging messages.
24326 @node Other Misc Settings
24327 @section Other Miscellaneous Settings
24328 @cindex miscellaneous settings
24331 @kindex set interactive-mode
24332 @item set interactive-mode
24333 If @code{on}, forces @value{GDBN} to assume that GDB was started
24334 in a terminal. In practice, this means that @value{GDBN} should wait
24335 for the user to answer queries generated by commands entered at
24336 the command prompt. If @code{off}, forces @value{GDBN} to operate
24337 in the opposite mode, and it uses the default answers to all queries.
24338 If @code{auto} (the default), @value{GDBN} tries to determine whether
24339 its standard input is a terminal, and works in interactive-mode if it
24340 is, non-interactively otherwise.
24342 In the vast majority of cases, the debugger should be able to guess
24343 correctly which mode should be used. But this setting can be useful
24344 in certain specific cases, such as running a MinGW @value{GDBN}
24345 inside a cygwin window.
24347 @kindex show interactive-mode
24348 @item show interactive-mode
24349 Displays whether the debugger is operating in interactive mode or not.
24352 @node Extending GDB
24353 @chapter Extending @value{GDBN}
24354 @cindex extending GDB
24356 @value{GDBN} provides several mechanisms for extension.
24357 @value{GDBN} also provides the ability to automatically load
24358 extensions when it reads a file for debugging. This allows the
24359 user to automatically customize @value{GDBN} for the program
24363 * Sequences:: Canned Sequences of @value{GDBN} Commands
24364 * Python:: Extending @value{GDBN} using Python
24365 * Guile:: Extending @value{GDBN} using Guile
24366 * Auto-loading extensions:: Automatically loading extensions
24367 * Multiple Extension Languages:: Working with multiple extension languages
24368 * Aliases:: Creating new spellings of existing commands
24371 To facilitate the use of extension languages, @value{GDBN} is capable
24372 of evaluating the contents of a file. When doing so, @value{GDBN}
24373 can recognize which extension language is being used by looking at
24374 the filename extension. Files with an unrecognized filename extension
24375 are always treated as a @value{GDBN} Command Files.
24376 @xref{Command Files,, Command files}.
24378 You can control how @value{GDBN} evaluates these files with the following
24382 @kindex set script-extension
24383 @kindex show script-extension
24384 @item set script-extension off
24385 All scripts are always evaluated as @value{GDBN} Command Files.
24387 @item set script-extension soft
24388 The debugger determines the scripting language based on filename
24389 extension. If this scripting language is supported, @value{GDBN}
24390 evaluates the script using that language. Otherwise, it evaluates
24391 the file as a @value{GDBN} Command File.
24393 @item set script-extension strict
24394 The debugger determines the scripting language based on filename
24395 extension, and evaluates the script using that language. If the
24396 language is not supported, then the evaluation fails.
24398 @item show script-extension
24399 Display the current value of the @code{script-extension} option.
24404 @section Canned Sequences of Commands
24406 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24407 Command Lists}), @value{GDBN} provides two ways to store sequences of
24408 commands for execution as a unit: user-defined commands and command
24412 * Define:: How to define your own commands
24413 * Hooks:: Hooks for user-defined commands
24414 * Command Files:: How to write scripts of commands to be stored in a file
24415 * Output:: Commands for controlled output
24416 * Auto-loading sequences:: Controlling auto-loaded command files
24420 @subsection User-defined Commands
24422 @cindex user-defined command
24423 @cindex arguments, to user-defined commands
24424 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24425 which you assign a new name as a command. This is done with the
24426 @code{define} command. User commands may accept an unlimited number of arguments
24427 separated by whitespace. Arguments are accessed within the user command
24428 via @code{$arg0@dots{}$argN}. A trivial example:
24432 print $arg0 + $arg1 + $arg2
24437 To execute the command use:
24444 This defines the command @code{adder}, which prints the sum of
24445 its three arguments. Note the arguments are text substitutions, so they may
24446 reference variables, use complex expressions, or even perform inferior
24449 @cindex argument count in user-defined commands
24450 @cindex how many arguments (user-defined commands)
24451 In addition, @code{$argc} may be used to find out how many arguments have
24457 print $arg0 + $arg1
24460 print $arg0 + $arg1 + $arg2
24465 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24466 to process a variable number of arguments:
24473 eval "set $sum = $sum + $arg%d", $i
24483 @item define @var{commandname}
24484 Define a command named @var{commandname}. If there is already a command
24485 by that name, you are asked to confirm that you want to redefine it.
24486 The argument @var{commandname} may be a bare command name consisting of letters,
24487 numbers, dashes, and underscores. It may also start with any predefined
24488 prefix command. For example, @samp{define target my-target} creates
24489 a user-defined @samp{target my-target} command.
24491 The definition of the command is made up of other @value{GDBN} command lines,
24492 which are given following the @code{define} command. The end of these
24493 commands is marked by a line containing @code{end}.
24496 @kindex end@r{ (user-defined commands)}
24497 @item document @var{commandname}
24498 Document the user-defined command @var{commandname}, so that it can be
24499 accessed by @code{help}. The command @var{commandname} must already be
24500 defined. This command reads lines of documentation just as @code{define}
24501 reads the lines of the command definition, ending with @code{end}.
24502 After the @code{document} command is finished, @code{help} on command
24503 @var{commandname} displays the documentation you have written.
24505 You may use the @code{document} command again to change the
24506 documentation of a command. Redefining the command with @code{define}
24507 does not change the documentation.
24509 @kindex dont-repeat
24510 @cindex don't repeat command
24512 Used inside a user-defined command, this tells @value{GDBN} that this
24513 command should not be repeated when the user hits @key{RET}
24514 (@pxref{Command Syntax, repeat last command}).
24516 @kindex help user-defined
24517 @item help user-defined
24518 List all user-defined commands and all python commands defined in class
24519 COMAND_USER. The first line of the documentation or docstring is
24524 @itemx show user @var{commandname}
24525 Display the @value{GDBN} commands used to define @var{commandname} (but
24526 not its documentation). If no @var{commandname} is given, display the
24527 definitions for all user-defined commands.
24528 This does not work for user-defined python commands.
24530 @cindex infinite recursion in user-defined commands
24531 @kindex show max-user-call-depth
24532 @kindex set max-user-call-depth
24533 @item show max-user-call-depth
24534 @itemx set max-user-call-depth
24535 The value of @code{max-user-call-depth} controls how many recursion
24536 levels are allowed in user-defined commands before @value{GDBN} suspects an
24537 infinite recursion and aborts the command.
24538 This does not apply to user-defined python commands.
24541 In addition to the above commands, user-defined commands frequently
24542 use control flow commands, described in @ref{Command Files}.
24544 When user-defined commands are executed, the
24545 commands of the definition are not printed. An error in any command
24546 stops execution of the user-defined command.
24548 If used interactively, commands that would ask for confirmation proceed
24549 without asking when used inside a user-defined command. Many @value{GDBN}
24550 commands that normally print messages to say what they are doing omit the
24551 messages when used in a user-defined command.
24554 @subsection User-defined Command Hooks
24555 @cindex command hooks
24556 @cindex hooks, for commands
24557 @cindex hooks, pre-command
24560 You may define @dfn{hooks}, which are a special kind of user-defined
24561 command. Whenever you run the command @samp{foo}, if the user-defined
24562 command @samp{hook-foo} exists, it is executed (with no arguments)
24563 before that command.
24565 @cindex hooks, post-command
24567 A hook may also be defined which is run after the command you executed.
24568 Whenever you run the command @samp{foo}, if the user-defined command
24569 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24570 that command. Post-execution hooks may exist simultaneously with
24571 pre-execution hooks, for the same command.
24573 It is valid for a hook to call the command which it hooks. If this
24574 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24576 @c It would be nice if hookpost could be passed a parameter indicating
24577 @c if the command it hooks executed properly or not. FIXME!
24579 @kindex stop@r{, a pseudo-command}
24580 In addition, a pseudo-command, @samp{stop} exists. Defining
24581 (@samp{hook-stop}) makes the associated commands execute every time
24582 execution stops in your program: before breakpoint commands are run,
24583 displays are printed, or the stack frame is printed.
24585 For example, to ignore @code{SIGALRM} signals while
24586 single-stepping, but treat them normally during normal execution,
24591 handle SIGALRM nopass
24595 handle SIGALRM pass
24598 define hook-continue
24599 handle SIGALRM pass
24603 As a further example, to hook at the beginning and end of the @code{echo}
24604 command, and to add extra text to the beginning and end of the message,
24612 define hookpost-echo
24616 (@value{GDBP}) echo Hello World
24617 <<<---Hello World--->>>
24622 You can define a hook for any single-word command in @value{GDBN}, but
24623 not for command aliases; you should define a hook for the basic command
24624 name, e.g.@: @code{backtrace} rather than @code{bt}.
24625 @c FIXME! So how does Joe User discover whether a command is an alias
24627 You can hook a multi-word command by adding @code{hook-} or
24628 @code{hookpost-} to the last word of the command, e.g.@:
24629 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24631 If an error occurs during the execution of your hook, execution of
24632 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24633 (before the command that you actually typed had a chance to run).
24635 If you try to define a hook which does not match any known command, you
24636 get a warning from the @code{define} command.
24638 @node Command Files
24639 @subsection Command Files
24641 @cindex command files
24642 @cindex scripting commands
24643 A command file for @value{GDBN} is a text file made of lines that are
24644 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24645 also be included. An empty line in a command file does nothing; it
24646 does not mean to repeat the last command, as it would from the
24649 You can request the execution of a command file with the @code{source}
24650 command. Note that the @code{source} command is also used to evaluate
24651 scripts that are not Command Files. The exact behavior can be configured
24652 using the @code{script-extension} setting.
24653 @xref{Extending GDB,, Extending GDB}.
24657 @cindex execute commands from a file
24658 @item source [-s] [-v] @var{filename}
24659 Execute the command file @var{filename}.
24662 The lines in a command file are generally executed sequentially,
24663 unless the order of execution is changed by one of the
24664 @emph{flow-control commands} described below. The commands are not
24665 printed as they are executed. An error in any command terminates
24666 execution of the command file and control is returned to the console.
24668 @value{GDBN} first searches for @var{filename} in the current directory.
24669 If the file is not found there, and @var{filename} does not specify a
24670 directory, then @value{GDBN} also looks for the file on the source search path
24671 (specified with the @samp{directory} command);
24672 except that @file{$cdir} is not searched because the compilation directory
24673 is not relevant to scripts.
24675 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24676 on the search path even if @var{filename} specifies a directory.
24677 The search is done by appending @var{filename} to each element of the
24678 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24679 and the search path contains @file{/home/user} then @value{GDBN} will
24680 look for the script @file{/home/user/mylib/myscript}.
24681 The search is also done if @var{filename} is an absolute path.
24682 For example, if @var{filename} is @file{/tmp/myscript} and
24683 the search path contains @file{/home/user} then @value{GDBN} will
24684 look for the script @file{/home/user/tmp/myscript}.
24685 For DOS-like systems, if @var{filename} contains a drive specification,
24686 it is stripped before concatenation. For example, if @var{filename} is
24687 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24688 will look for the script @file{c:/tmp/myscript}.
24690 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24691 each command as it is executed. The option must be given before
24692 @var{filename}, and is interpreted as part of the filename anywhere else.
24694 Commands that would ask for confirmation if used interactively proceed
24695 without asking when used in a command file. Many @value{GDBN} commands that
24696 normally print messages to say what they are doing omit the messages
24697 when called from command files.
24699 @value{GDBN} also accepts command input from standard input. In this
24700 mode, normal output goes to standard output and error output goes to
24701 standard error. Errors in a command file supplied on standard input do
24702 not terminate execution of the command file---execution continues with
24706 gdb < cmds > log 2>&1
24709 (The syntax above will vary depending on the shell used.) This example
24710 will execute commands from the file @file{cmds}. All output and errors
24711 would be directed to @file{log}.
24713 Since commands stored on command files tend to be more general than
24714 commands typed interactively, they frequently need to deal with
24715 complicated situations, such as different or unexpected values of
24716 variables and symbols, changes in how the program being debugged is
24717 built, etc. @value{GDBN} provides a set of flow-control commands to
24718 deal with these complexities. Using these commands, you can write
24719 complex scripts that loop over data structures, execute commands
24720 conditionally, etc.
24727 This command allows to include in your script conditionally executed
24728 commands. The @code{if} command takes a single argument, which is an
24729 expression to evaluate. It is followed by a series of commands that
24730 are executed only if the expression is true (its value is nonzero).
24731 There can then optionally be an @code{else} line, followed by a series
24732 of commands that are only executed if the expression was false. The
24733 end of the list is marked by a line containing @code{end}.
24737 This command allows to write loops. Its syntax is similar to
24738 @code{if}: the command takes a single argument, which is an expression
24739 to evaluate, and must be followed by the commands to execute, one per
24740 line, terminated by an @code{end}. These commands are called the
24741 @dfn{body} of the loop. The commands in the body of @code{while} are
24742 executed repeatedly as long as the expression evaluates to true.
24746 This command exits the @code{while} loop in whose body it is included.
24747 Execution of the script continues after that @code{while}s @code{end}
24750 @kindex loop_continue
24751 @item loop_continue
24752 This command skips the execution of the rest of the body of commands
24753 in the @code{while} loop in whose body it is included. Execution
24754 branches to the beginning of the @code{while} loop, where it evaluates
24755 the controlling expression.
24757 @kindex end@r{ (if/else/while commands)}
24759 Terminate the block of commands that are the body of @code{if},
24760 @code{else}, or @code{while} flow-control commands.
24765 @subsection Commands for Controlled Output
24767 During the execution of a command file or a user-defined command, normal
24768 @value{GDBN} output is suppressed; the only output that appears is what is
24769 explicitly printed by the commands in the definition. This section
24770 describes three commands useful for generating exactly the output you
24775 @item echo @var{text}
24776 @c I do not consider backslash-space a standard C escape sequence
24777 @c because it is not in ANSI.
24778 Print @var{text}. Nonprinting characters can be included in
24779 @var{text} using C escape sequences, such as @samp{\n} to print a
24780 newline. @strong{No newline is printed unless you specify one.}
24781 In addition to the standard C escape sequences, a backslash followed
24782 by a space stands for a space. This is useful for displaying a
24783 string with spaces at the beginning or the end, since leading and
24784 trailing spaces are otherwise trimmed from all arguments.
24785 To print @samp{@w{ }and foo =@w{ }}, use the command
24786 @samp{echo \@w{ }and foo = \@w{ }}.
24788 A backslash at the end of @var{text} can be used, as in C, to continue
24789 the command onto subsequent lines. For example,
24792 echo This is some text\n\
24793 which is continued\n\
24794 onto several lines.\n
24797 produces the same output as
24800 echo This is some text\n
24801 echo which is continued\n
24802 echo onto several lines.\n
24806 @item output @var{expression}
24807 Print the value of @var{expression} and nothing but that value: no
24808 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24809 value history either. @xref{Expressions, ,Expressions}, for more information
24812 @item output/@var{fmt} @var{expression}
24813 Print the value of @var{expression} in format @var{fmt}. You can use
24814 the same formats as for @code{print}. @xref{Output Formats,,Output
24815 Formats}, for more information.
24818 @item printf @var{template}, @var{expressions}@dots{}
24819 Print the values of one or more @var{expressions} under the control of
24820 the string @var{template}. To print several values, make
24821 @var{expressions} be a comma-separated list of individual expressions,
24822 which may be either numbers or pointers. Their values are printed as
24823 specified by @var{template}, exactly as a C program would do by
24824 executing the code below:
24827 printf (@var{template}, @var{expressions}@dots{});
24830 As in @code{C} @code{printf}, ordinary characters in @var{template}
24831 are printed verbatim, while @dfn{conversion specification} introduced
24832 by the @samp{%} character cause subsequent @var{expressions} to be
24833 evaluated, their values converted and formatted according to type and
24834 style information encoded in the conversion specifications, and then
24837 For example, you can print two values in hex like this:
24840 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24843 @code{printf} supports all the standard @code{C} conversion
24844 specifications, including the flags and modifiers between the @samp{%}
24845 character and the conversion letter, with the following exceptions:
24849 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24852 The modifier @samp{*} is not supported for specifying precision or
24856 The @samp{'} flag (for separation of digits into groups according to
24857 @code{LC_NUMERIC'}) is not supported.
24860 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24864 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24867 The conversion letters @samp{a} and @samp{A} are not supported.
24871 Note that the @samp{ll} type modifier is supported only if the
24872 underlying @code{C} implementation used to build @value{GDBN} supports
24873 the @code{long long int} type, and the @samp{L} type modifier is
24874 supported only if @code{long double} type is available.
24876 As in @code{C}, @code{printf} supports simple backslash-escape
24877 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24878 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24879 single character. Octal and hexadecimal escape sequences are not
24882 Additionally, @code{printf} supports conversion specifications for DFP
24883 (@dfn{Decimal Floating Point}) types using the following length modifiers
24884 together with a floating point specifier.
24889 @samp{H} for printing @code{Decimal32} types.
24892 @samp{D} for printing @code{Decimal64} types.
24895 @samp{DD} for printing @code{Decimal128} types.
24898 If the underlying @code{C} implementation used to build @value{GDBN} has
24899 support for the three length modifiers for DFP types, other modifiers
24900 such as width and precision will also be available for @value{GDBN} to use.
24902 In case there is no such @code{C} support, no additional modifiers will be
24903 available and the value will be printed in the standard way.
24905 Here's an example of printing DFP types using the above conversion letters:
24907 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24912 @item eval @var{template}, @var{expressions}@dots{}
24913 Convert the values of one or more @var{expressions} under the control of
24914 the string @var{template} to a command line, and call it.
24918 @node Auto-loading sequences
24919 @subsection Controlling auto-loading native @value{GDBN} scripts
24920 @cindex native script auto-loading
24922 When a new object file is read (for example, due to the @code{file}
24923 command, or because the inferior has loaded a shared library),
24924 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24925 @xref{Auto-loading extensions}.
24927 Auto-loading can be enabled or disabled,
24928 and the list of auto-loaded scripts can be printed.
24931 @anchor{set auto-load gdb-scripts}
24932 @kindex set auto-load gdb-scripts
24933 @item set auto-load gdb-scripts [on|off]
24934 Enable or disable the auto-loading of canned sequences of commands scripts.
24936 @anchor{show auto-load gdb-scripts}
24937 @kindex show auto-load gdb-scripts
24938 @item show auto-load gdb-scripts
24939 Show whether auto-loading of canned sequences of commands scripts is enabled or
24942 @anchor{info auto-load gdb-scripts}
24943 @kindex info auto-load gdb-scripts
24944 @cindex print list of auto-loaded canned sequences of commands scripts
24945 @item info auto-load gdb-scripts [@var{regexp}]
24946 Print the list of all canned sequences of commands scripts that @value{GDBN}
24950 If @var{regexp} is supplied only canned sequences of commands scripts with
24951 matching names are printed.
24953 @c Python docs live in a separate file.
24954 @include python.texi
24956 @c Guile docs live in a separate file.
24957 @include guile.texi
24959 @node Auto-loading extensions
24960 @section Auto-loading extensions
24961 @cindex auto-loading extensions
24963 @value{GDBN} provides two mechanisms for automatically loading extensions
24964 when a new object file is read (for example, due to the @code{file}
24965 command, or because the inferior has loaded a shared library):
24966 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24967 section of modern file formats like ELF.
24970 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24971 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24972 * Which flavor to choose?::
24975 The auto-loading feature is useful for supplying application-specific
24976 debugging commands and features.
24978 Auto-loading can be enabled or disabled,
24979 and the list of auto-loaded scripts can be printed.
24980 See the @samp{auto-loading} section of each extension language
24981 for more information.
24982 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24983 For Python files see @ref{Python Auto-loading}.
24985 Note that loading of this script file also requires accordingly configured
24986 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24988 @node objfile-gdbdotext file
24989 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24990 @cindex @file{@var{objfile}-gdb.gdb}
24991 @cindex @file{@var{objfile}-gdb.py}
24992 @cindex @file{@var{objfile}-gdb.scm}
24994 When a new object file is read, @value{GDBN} looks for a file named
24995 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24996 where @var{objfile} is the object file's name and
24997 where @var{ext} is the file extension for the extension language:
25000 @item @file{@var{objfile}-gdb.gdb}
25001 GDB's own command language
25002 @item @file{@var{objfile}-gdb.py}
25004 @item @file{@var{objfile}-gdb.scm}
25008 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25009 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25010 components, and appending the @file{-gdb.@var{ext}} suffix.
25011 If this file exists and is readable, @value{GDBN} will evaluate it as a
25012 script in the specified extension language.
25014 If this file does not exist, then @value{GDBN} will look for
25015 @var{script-name} file in all of the directories as specified below.
25017 Note that loading of these files requires an accordingly configured
25018 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25020 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25021 scripts normally according to its @file{.exe} filename. But if no scripts are
25022 found @value{GDBN} also tries script filenames matching the object file without
25023 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25024 is attempted on any platform. This makes the script filenames compatible
25025 between Unix and MS-Windows hosts.
25028 @anchor{set auto-load scripts-directory}
25029 @kindex set auto-load scripts-directory
25030 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25031 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25032 may be delimited by the host platform path separator in use
25033 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25035 Each entry here needs to be covered also by the security setting
25036 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25038 @anchor{with-auto-load-dir}
25039 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25040 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25041 configuration option @option{--with-auto-load-dir}.
25043 Any reference to @file{$debugdir} will get replaced by
25044 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25045 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25046 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25047 @file{$datadir} must be placed as a directory component --- either alone or
25048 delimited by @file{/} or @file{\} directory separators, depending on the host
25051 The list of directories uses path separator (@samp{:} on GNU and Unix
25052 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25053 to the @env{PATH} environment variable.
25055 @anchor{show auto-load scripts-directory}
25056 @kindex show auto-load scripts-directory
25057 @item show auto-load scripts-directory
25058 Show @value{GDBN} auto-loaded scripts location.
25060 @anchor{add-auto-load-scripts-directory}
25061 @kindex add-auto-load-scripts-directory
25062 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25063 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25064 Multiple entries may be delimited by the host platform path separator in use.
25067 @value{GDBN} does not track which files it has already auto-loaded this way.
25068 @value{GDBN} will load the associated script every time the corresponding
25069 @var{objfile} is opened.
25070 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25071 is evaluated more than once.
25073 @node dotdebug_gdb_scripts section
25074 @subsection The @code{.debug_gdb_scripts} section
25075 @cindex @code{.debug_gdb_scripts} section
25077 For systems using file formats like ELF and COFF,
25078 when @value{GDBN} loads a new object file
25079 it will look for a special section named @code{.debug_gdb_scripts}.
25080 If this section exists, its contents is a list of null-terminated entries
25081 specifying scripts to load. Each entry begins with a non-null prefix byte that
25082 specifies the kind of entry, typically the extension language and whether the
25083 script is in a file or inlined in @code{.debug_gdb_scripts}.
25085 The following entries are supported:
25088 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25089 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25090 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25091 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25094 @subsubsection Script File Entries
25096 If the entry specifies a file, @value{GDBN} will look for the file first
25097 in the current directory and then along the source search path
25098 (@pxref{Source Path, ,Specifying Source Directories}),
25099 except that @file{$cdir} is not searched, since the compilation
25100 directory is not relevant to scripts.
25102 File entries can be placed in section @code{.debug_gdb_scripts} with,
25103 for example, this GCC macro for Python scripts.
25106 /* Note: The "MS" section flags are to remove duplicates. */
25107 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25109 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25110 .byte 1 /* Python */\n\
25111 .asciz \"" script_name "\"\n\
25117 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25118 Then one can reference the macro in a header or source file like this:
25121 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25124 The script name may include directories if desired.
25126 Note that loading of this script file also requires accordingly configured
25127 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25129 If the macro invocation is put in a header, any application or library
25130 using this header will get a reference to the specified script,
25131 and with the use of @code{"MS"} attributes on the section, the linker
25132 will remove duplicates.
25134 @subsubsection Script Text Entries
25136 Script text entries allow to put the executable script in the entry
25137 itself instead of loading it from a file.
25138 The first line of the entry, everything after the prefix byte and up to
25139 the first newline (@code{0xa}) character, is the script name, and must not
25140 contain any kind of space character, e.g., spaces or tabs.
25141 The rest of the entry, up to the trailing null byte, is the script to
25142 execute in the specified language. The name needs to be unique among
25143 all script names, as @value{GDBN} executes each script only once based
25146 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25150 #include "symcat.h"
25151 #include "gdb/section-scripts.h"
25153 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25154 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25155 ".ascii \"gdb.inlined-script\\n\"\n"
25156 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25157 ".ascii \" def __init__ (self):\\n\"\n"
25158 ".ascii \" super (test_cmd, self).__init__ ("
25159 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25160 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25161 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25162 ".ascii \"test_cmd ()\\n\"\n"
25168 Loading of inlined scripts requires a properly configured
25169 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25170 The path to specify in @code{auto-load safe-path} is the path of the file
25171 containing the @code{.debug_gdb_scripts} section.
25173 @node Which flavor to choose?
25174 @subsection Which flavor to choose?
25176 Given the multiple ways of auto-loading extensions, it might not always
25177 be clear which one to choose. This section provides some guidance.
25180 Benefits of the @file{-gdb.@var{ext}} way:
25184 Can be used with file formats that don't support multiple sections.
25187 Ease of finding scripts for public libraries.
25189 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25190 in the source search path.
25191 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25192 isn't a source directory in which to find the script.
25195 Doesn't require source code additions.
25199 Benefits of the @code{.debug_gdb_scripts} way:
25203 Works with static linking.
25205 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25206 trigger their loading. When an application is statically linked the only
25207 objfile available is the executable, and it is cumbersome to attach all the
25208 scripts from all the input libraries to the executable's
25209 @file{-gdb.@var{ext}} script.
25212 Works with classes that are entirely inlined.
25214 Some classes can be entirely inlined, and thus there may not be an associated
25215 shared library to attach a @file{-gdb.@var{ext}} script to.
25218 Scripts needn't be copied out of the source tree.
25220 In some circumstances, apps can be built out of large collections of internal
25221 libraries, and the build infrastructure necessary to install the
25222 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25223 cumbersome. It may be easier to specify the scripts in the
25224 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25225 top of the source tree to the source search path.
25228 @node Multiple Extension Languages
25229 @section Multiple Extension Languages
25231 The Guile and Python extension languages do not share any state,
25232 and generally do not interfere with each other.
25233 There are some things to be aware of, however.
25235 @subsection Python comes first
25237 Python was @value{GDBN}'s first extension language, and to avoid breaking
25238 existing behaviour Python comes first. This is generally solved by the
25239 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25240 extension languages, and when it makes a call to an extension language,
25241 (say to pretty-print a value), it tries each in turn until an extension
25242 language indicates it has performed the request (e.g., has returned the
25243 pretty-printed form of a value).
25244 This extends to errors while performing such requests: If an error happens
25245 while, for example, trying to pretty-print an object then the error is
25246 reported and any following extension languages are not tried.
25249 @section Creating new spellings of existing commands
25250 @cindex aliases for commands
25252 It is often useful to define alternate spellings of existing commands.
25253 For example, if a new @value{GDBN} command defined in Python has
25254 a long name to type, it is handy to have an abbreviated version of it
25255 that involves less typing.
25257 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25258 of the @samp{step} command even though it is otherwise an ambiguous
25259 abbreviation of other commands like @samp{set} and @samp{show}.
25261 Aliases are also used to provide shortened or more common versions
25262 of multi-word commands. For example, @value{GDBN} provides the
25263 @samp{tty} alias of the @samp{set inferior-tty} command.
25265 You can define a new alias with the @samp{alias} command.
25270 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25274 @var{ALIAS} specifies the name of the new alias.
25275 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25278 @var{COMMAND} specifies the name of an existing command
25279 that is being aliased.
25281 The @samp{-a} option specifies that the new alias is an abbreviation
25282 of the command. Abbreviations are not shown in command
25283 lists displayed by the @samp{help} command.
25285 The @samp{--} option specifies the end of options,
25286 and is useful when @var{ALIAS} begins with a dash.
25288 Here is a simple example showing how to make an abbreviation
25289 of a command so that there is less to type.
25290 Suppose you were tired of typing @samp{disas}, the current
25291 shortest unambiguous abbreviation of the @samp{disassemble} command
25292 and you wanted an even shorter version named @samp{di}.
25293 The following will accomplish this.
25296 (gdb) alias -a di = disas
25299 Note that aliases are different from user-defined commands.
25300 With a user-defined command, you also need to write documentation
25301 for it with the @samp{document} command.
25302 An alias automatically picks up the documentation of the existing command.
25304 Here is an example where we make @samp{elms} an abbreviation of
25305 @samp{elements} in the @samp{set print elements} command.
25306 This is to show that you can make an abbreviation of any part
25310 (gdb) alias -a set print elms = set print elements
25311 (gdb) alias -a show print elms = show print elements
25312 (gdb) set p elms 20
25314 Limit on string chars or array elements to print is 200.
25317 Note that if you are defining an alias of a @samp{set} command,
25318 and you want to have an alias for the corresponding @samp{show}
25319 command, then you need to define the latter separately.
25321 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25322 @var{ALIAS}, just as they are normally.
25325 (gdb) alias -a set pr elms = set p ele
25328 Finally, here is an example showing the creation of a one word
25329 alias for a more complex command.
25330 This creates alias @samp{spe} of the command @samp{set print elements}.
25333 (gdb) alias spe = set print elements
25338 @chapter Command Interpreters
25339 @cindex command interpreters
25341 @value{GDBN} supports multiple command interpreters, and some command
25342 infrastructure to allow users or user interface writers to switch
25343 between interpreters or run commands in other interpreters.
25345 @value{GDBN} currently supports two command interpreters, the console
25346 interpreter (sometimes called the command-line interpreter or @sc{cli})
25347 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25348 describes both of these interfaces in great detail.
25350 By default, @value{GDBN} will start with the console interpreter.
25351 However, the user may choose to start @value{GDBN} with another
25352 interpreter by specifying the @option{-i} or @option{--interpreter}
25353 startup options. Defined interpreters include:
25357 @cindex console interpreter
25358 The traditional console or command-line interpreter. This is the most often
25359 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25360 @value{GDBN} will use this interpreter.
25363 @cindex mi interpreter
25364 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25365 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25366 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25370 @cindex mi2 interpreter
25371 The current @sc{gdb/mi} interface.
25374 @cindex mi1 interpreter
25375 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25379 @cindex invoke another interpreter
25381 @kindex interpreter-exec
25382 You may execute commands in any interpreter from the current
25383 interpreter using the appropriate command. If you are running the
25384 console interpreter, simply use the @code{interpreter-exec} command:
25387 interpreter-exec mi "-data-list-register-names"
25390 @sc{gdb/mi} has a similar command, although it is only available in versions of
25391 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25393 Note that @code{interpreter-exec} only changes the interpreter for the
25394 duration of the specified command. It does not change the interpreter
25397 @cindex start a new independent interpreter
25399 Although you may only choose a single interpreter at startup, it is
25400 possible to run an independent interpreter on a specified input/output
25401 device (usually a tty).
25403 For example, consider a debugger GUI or IDE that wants to provide a
25404 @value{GDBN} console view. It may do so by embedding a terminal
25405 emulator widget in its GUI, starting @value{GDBN} in the traditional
25406 command-line mode with stdin/stdout/stderr redirected to that
25407 terminal, and then creating an MI interpreter running on a specified
25408 input/output device. The console interpreter created by @value{GDBN}
25409 at startup handles commands the user types in the terminal widget,
25410 while the GUI controls and synchronizes state with @value{GDBN} using
25411 the separate MI interpreter.
25413 To start a new secondary @dfn{user interface} running MI, use the
25414 @code{new-ui} command:
25417 @cindex new user interface
25419 new-ui @var{interpreter} @var{tty}
25422 The @var{interpreter} parameter specifies the interpreter to run.
25423 This accepts the same values as the @code{interpreter-exec} command.
25424 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25425 @var{tty} parameter specifies the name of the bidirectional file the
25426 interpreter uses for input/output, usually the name of a
25427 pseudoterminal slave on Unix systems. For example:
25430 (@value{GDBP}) new-ui mi /dev/pts/9
25434 runs an MI interpreter on @file{/dev/pts/9}.
25437 @chapter @value{GDBN} Text User Interface
25439 @cindex Text User Interface
25442 * TUI Overview:: TUI overview
25443 * TUI Keys:: TUI key bindings
25444 * TUI Single Key Mode:: TUI single key mode
25445 * TUI Commands:: TUI-specific commands
25446 * TUI Configuration:: TUI configuration variables
25449 The @value{GDBN} Text User Interface (TUI) is a terminal
25450 interface which uses the @code{curses} library to show the source
25451 file, the assembly output, the program registers and @value{GDBN}
25452 commands in separate text windows. The TUI mode is supported only
25453 on platforms where a suitable version of the @code{curses} library
25456 The TUI mode is enabled by default when you invoke @value{GDBN} as
25457 @samp{@value{GDBP} -tui}.
25458 You can also switch in and out of TUI mode while @value{GDBN} runs by
25459 using various TUI commands and key bindings, such as @command{tui
25460 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25461 @ref{TUI Keys, ,TUI Key Bindings}.
25464 @section TUI Overview
25466 In TUI mode, @value{GDBN} can display several text windows:
25470 This window is the @value{GDBN} command window with the @value{GDBN}
25471 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25472 managed using readline.
25475 The source window shows the source file of the program. The current
25476 line and active breakpoints are displayed in this window.
25479 The assembly window shows the disassembly output of the program.
25482 This window shows the processor registers. Registers are highlighted
25483 when their values change.
25486 The source and assembly windows show the current program position
25487 by highlighting the current line and marking it with a @samp{>} marker.
25488 Breakpoints are indicated with two markers. The first marker
25489 indicates the breakpoint type:
25493 Breakpoint which was hit at least once.
25496 Breakpoint which was never hit.
25499 Hardware breakpoint which was hit at least once.
25502 Hardware breakpoint which was never hit.
25505 The second marker indicates whether the breakpoint is enabled or not:
25509 Breakpoint is enabled.
25512 Breakpoint is disabled.
25515 The source, assembly and register windows are updated when the current
25516 thread changes, when the frame changes, or when the program counter
25519 These windows are not all visible at the same time. The command
25520 window is always visible. The others can be arranged in several
25531 source and assembly,
25534 source and registers, or
25537 assembly and registers.
25540 A status line above the command window shows the following information:
25544 Indicates the current @value{GDBN} target.
25545 (@pxref{Targets, ,Specifying a Debugging Target}).
25548 Gives the current process or thread number.
25549 When no process is being debugged, this field is set to @code{No process}.
25552 Gives the current function name for the selected frame.
25553 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25554 When there is no symbol corresponding to the current program counter,
25555 the string @code{??} is displayed.
25558 Indicates the current line number for the selected frame.
25559 When the current line number is not known, the string @code{??} is displayed.
25562 Indicates the current program counter address.
25566 @section TUI Key Bindings
25567 @cindex TUI key bindings
25569 The TUI installs several key bindings in the readline keymaps
25570 @ifset SYSTEM_READLINE
25571 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25573 @ifclear SYSTEM_READLINE
25574 (@pxref{Command Line Editing}).
25576 The following key bindings are installed for both TUI mode and the
25577 @value{GDBN} standard mode.
25586 Enter or leave the TUI mode. When leaving the TUI mode,
25587 the curses window management stops and @value{GDBN} operates using
25588 its standard mode, writing on the terminal directly. When reentering
25589 the TUI mode, control is given back to the curses windows.
25590 The screen is then refreshed.
25594 Use a TUI layout with only one window. The layout will
25595 either be @samp{source} or @samp{assembly}. When the TUI mode
25596 is not active, it will switch to the TUI mode.
25598 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25602 Use a TUI layout with at least two windows. When the current
25603 layout already has two windows, the next layout with two windows is used.
25604 When a new layout is chosen, one window will always be common to the
25605 previous layout and the new one.
25607 Think of it as the Emacs @kbd{C-x 2} binding.
25611 Change the active window. The TUI associates several key bindings
25612 (like scrolling and arrow keys) with the active window. This command
25613 gives the focus to the next TUI window.
25615 Think of it as the Emacs @kbd{C-x o} binding.
25619 Switch in and out of the TUI SingleKey mode that binds single
25620 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25623 The following key bindings only work in the TUI mode:
25628 Scroll the active window one page up.
25632 Scroll the active window one page down.
25636 Scroll the active window one line up.
25640 Scroll the active window one line down.
25644 Scroll the active window one column left.
25648 Scroll the active window one column right.
25652 Refresh the screen.
25655 Because the arrow keys scroll the active window in the TUI mode, they
25656 are not available for their normal use by readline unless the command
25657 window has the focus. When another window is active, you must use
25658 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25659 and @kbd{C-f} to control the command window.
25661 @node TUI Single Key Mode
25662 @section TUI Single Key Mode
25663 @cindex TUI single key mode
25665 The TUI also provides a @dfn{SingleKey} mode, which binds several
25666 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25667 switch into this mode, where the following key bindings are used:
25670 @kindex c @r{(SingleKey TUI key)}
25674 @kindex d @r{(SingleKey TUI key)}
25678 @kindex f @r{(SingleKey TUI key)}
25682 @kindex n @r{(SingleKey TUI key)}
25686 @kindex o @r{(SingleKey TUI key)}
25688 nexti. The shortcut letter @samp{o} stands for ``step Over''.
25690 @kindex q @r{(SingleKey TUI key)}
25692 exit the SingleKey mode.
25694 @kindex r @r{(SingleKey TUI key)}
25698 @kindex s @r{(SingleKey TUI key)}
25702 @kindex i @r{(SingleKey TUI key)}
25704 stepi. The shortcut letter @samp{i} stands for ``step Into''.
25706 @kindex u @r{(SingleKey TUI key)}
25710 @kindex v @r{(SingleKey TUI key)}
25714 @kindex w @r{(SingleKey TUI key)}
25719 Other keys temporarily switch to the @value{GDBN} command prompt.
25720 The key that was pressed is inserted in the editing buffer so that
25721 it is possible to type most @value{GDBN} commands without interaction
25722 with the TUI SingleKey mode. Once the command is entered the TUI
25723 SingleKey mode is restored. The only way to permanently leave
25724 this mode is by typing @kbd{q} or @kbd{C-x s}.
25728 @section TUI-specific Commands
25729 @cindex TUI commands
25731 The TUI has specific commands to control the text windows.
25732 These commands are always available, even when @value{GDBN} is not in
25733 the TUI mode. When @value{GDBN} is in the standard mode, most
25734 of these commands will automatically switch to the TUI mode.
25736 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25737 terminal, or @value{GDBN} has been started with the machine interface
25738 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25739 these commands will fail with an error, because it would not be
25740 possible or desirable to enable curses window management.
25745 Activate TUI mode. The last active TUI window layout will be used if
25746 TUI mode has prevsiouly been used in the current debugging session,
25747 otherwise a default layout is used.
25750 @kindex tui disable
25751 Disable TUI mode, returning to the console interpreter.
25755 List and give the size of all displayed windows.
25757 @item layout @var{name}
25759 Changes which TUI windows are displayed. In each layout the command
25760 window is always displayed, the @var{name} parameter controls which
25761 additional windows are displayed, and can be any of the following:
25765 Display the next layout.
25768 Display the previous layout.
25771 Display the source and command windows.
25774 Display the assembly and command windows.
25777 Display the source, assembly, and command windows.
25780 When in @code{src} layout display the register, source, and command
25781 windows. When in @code{asm} or @code{split} layout display the
25782 register, assembler, and command windows.
25785 @item focus @var{name}
25787 Changes which TUI window is currently active for scrolling. The
25788 @var{name} parameter can be any of the following:
25792 Make the next window active for scrolling.
25795 Make the previous window active for scrolling.
25798 Make the source window active for scrolling.
25801 Make the assembly window active for scrolling.
25804 Make the register window active for scrolling.
25807 Make the command window active for scrolling.
25812 Refresh the screen. This is similar to typing @kbd{C-L}.
25814 @item tui reg @var{group}
25816 Changes the register group displayed in the tui register window to
25817 @var{group}. If the register window is not currently displayed this
25818 command will cause the register window to be displayed. The list of
25819 register groups, as well as their order is target specific. The
25820 following groups are available on most targets:
25823 Repeatedly selecting this group will cause the display to cycle
25824 through all of the available register groups.
25827 Repeatedly selecting this group will cause the display to cycle
25828 through all of the available register groups in the reverse order to
25832 Display the general registers.
25834 Display the floating point registers.
25836 Display the system registers.
25838 Display the vector registers.
25840 Display all registers.
25845 Update the source window and the current execution point.
25847 @item winheight @var{name} +@var{count}
25848 @itemx winheight @var{name} -@var{count}
25850 Change the height of the window @var{name} by @var{count}
25851 lines. Positive counts increase the height, while negative counts
25852 decrease it. The @var{name} parameter can be one of @code{src} (the
25853 source window), @code{cmd} (the command window), @code{asm} (the
25854 disassembly window), or @code{regs} (the register display window).
25856 @item tabset @var{nchars}
25858 Set the width of tab stops to be @var{nchars} characters. This
25859 setting affects the display of TAB characters in the source and
25863 @node TUI Configuration
25864 @section TUI Configuration Variables
25865 @cindex TUI configuration variables
25867 Several configuration variables control the appearance of TUI windows.
25870 @item set tui border-kind @var{kind}
25871 @kindex set tui border-kind
25872 Select the border appearance for the source, assembly and register windows.
25873 The possible values are the following:
25876 Use a space character to draw the border.
25879 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25882 Use the Alternate Character Set to draw the border. The border is
25883 drawn using character line graphics if the terminal supports them.
25886 @item set tui border-mode @var{mode}
25887 @kindex set tui border-mode
25888 @itemx set tui active-border-mode @var{mode}
25889 @kindex set tui active-border-mode
25890 Select the display attributes for the borders of the inactive windows
25891 or the active window. The @var{mode} can be one of the following:
25894 Use normal attributes to display the border.
25900 Use reverse video mode.
25903 Use half bright mode.
25905 @item half-standout
25906 Use half bright and standout mode.
25909 Use extra bright or bold mode.
25911 @item bold-standout
25912 Use extra bright or bold and standout mode.
25917 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25920 @cindex @sc{gnu} Emacs
25921 A special interface allows you to use @sc{gnu} Emacs to view (and
25922 edit) the source files for the program you are debugging with
25925 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25926 executable file you want to debug as an argument. This command starts
25927 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25928 created Emacs buffer.
25929 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25931 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25936 All ``terminal'' input and output goes through an Emacs buffer, called
25939 This applies both to @value{GDBN} commands and their output, and to the input
25940 and output done by the program you are debugging.
25942 This is useful because it means that you can copy the text of previous
25943 commands and input them again; you can even use parts of the output
25946 All the facilities of Emacs' Shell mode are available for interacting
25947 with your program. In particular, you can send signals the usual
25948 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25952 @value{GDBN} displays source code through Emacs.
25954 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25955 source file for that frame and puts an arrow (@samp{=>}) at the
25956 left margin of the current line. Emacs uses a separate buffer for
25957 source display, and splits the screen to show both your @value{GDBN} session
25960 Explicit @value{GDBN} @code{list} or search commands still produce output as
25961 usual, but you probably have no reason to use them from Emacs.
25964 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25965 a graphical mode, enabled by default, which provides further buffers
25966 that can control the execution and describe the state of your program.
25967 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25969 If you specify an absolute file name when prompted for the @kbd{M-x
25970 gdb} argument, then Emacs sets your current working directory to where
25971 your program resides. If you only specify the file name, then Emacs
25972 sets your current working directory to the directory associated
25973 with the previous buffer. In this case, @value{GDBN} may find your
25974 program by searching your environment's @code{PATH} variable, but on
25975 some operating systems it might not find the source. So, although the
25976 @value{GDBN} input and output session proceeds normally, the auxiliary
25977 buffer does not display the current source and line of execution.
25979 The initial working directory of @value{GDBN} is printed on the top
25980 line of the GUD buffer and this serves as a default for the commands
25981 that specify files for @value{GDBN} to operate on. @xref{Files,
25982 ,Commands to Specify Files}.
25984 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25985 need to call @value{GDBN} by a different name (for example, if you
25986 keep several configurations around, with different names) you can
25987 customize the Emacs variable @code{gud-gdb-command-name} to run the
25990 In the GUD buffer, you can use these special Emacs commands in
25991 addition to the standard Shell mode commands:
25995 Describe the features of Emacs' GUD Mode.
25998 Execute to another source line, like the @value{GDBN} @code{step} command; also
25999 update the display window to show the current file and location.
26002 Execute to next source line in this function, skipping all function
26003 calls, like the @value{GDBN} @code{next} command. Then update the display window
26004 to show the current file and location.
26007 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26008 display window accordingly.
26011 Execute until exit from the selected stack frame, like the @value{GDBN}
26012 @code{finish} command.
26015 Continue execution of your program, like the @value{GDBN} @code{continue}
26019 Go up the number of frames indicated by the numeric argument
26020 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26021 like the @value{GDBN} @code{up} command.
26024 Go down the number of frames indicated by the numeric argument, like the
26025 @value{GDBN} @code{down} command.
26028 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26029 tells @value{GDBN} to set a breakpoint on the source line point is on.
26031 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26032 separate frame which shows a backtrace when the GUD buffer is current.
26033 Move point to any frame in the stack and type @key{RET} to make it
26034 become the current frame and display the associated source in the
26035 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26036 selected frame become the current one. In graphical mode, the
26037 speedbar displays watch expressions.
26039 If you accidentally delete the source-display buffer, an easy way to get
26040 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26041 request a frame display; when you run under Emacs, this recreates
26042 the source buffer if necessary to show you the context of the current
26045 The source files displayed in Emacs are in ordinary Emacs buffers
26046 which are visiting the source files in the usual way. You can edit
26047 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26048 communicates with Emacs in terms of line numbers. If you add or
26049 delete lines from the text, the line numbers that @value{GDBN} knows cease
26050 to correspond properly with the code.
26052 A more detailed description of Emacs' interaction with @value{GDBN} is
26053 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26057 @chapter The @sc{gdb/mi} Interface
26059 @unnumberedsec Function and Purpose
26061 @cindex @sc{gdb/mi}, its purpose
26062 @sc{gdb/mi} is a line based machine oriented text interface to
26063 @value{GDBN} and is activated by specifying using the
26064 @option{--interpreter} command line option (@pxref{Mode Options}). It
26065 is specifically intended to support the development of systems which
26066 use the debugger as just one small component of a larger system.
26068 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26069 in the form of a reference manual.
26071 Note that @sc{gdb/mi} is still under construction, so some of the
26072 features described below are incomplete and subject to change
26073 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26075 @unnumberedsec Notation and Terminology
26077 @cindex notational conventions, for @sc{gdb/mi}
26078 This chapter uses the following notation:
26082 @code{|} separates two alternatives.
26085 @code{[ @var{something} ]} indicates that @var{something} is optional:
26086 it may or may not be given.
26089 @code{( @var{group} )*} means that @var{group} inside the parentheses
26090 may repeat zero or more times.
26093 @code{( @var{group} )+} means that @var{group} inside the parentheses
26094 may repeat one or more times.
26097 @code{"@var{string}"} means a literal @var{string}.
26101 @heading Dependencies
26105 * GDB/MI General Design::
26106 * GDB/MI Command Syntax::
26107 * GDB/MI Compatibility with CLI::
26108 * GDB/MI Development and Front Ends::
26109 * GDB/MI Output Records::
26110 * GDB/MI Simple Examples::
26111 * GDB/MI Command Description Format::
26112 * GDB/MI Breakpoint Commands::
26113 * GDB/MI Catchpoint Commands::
26114 * GDB/MI Program Context::
26115 * GDB/MI Thread Commands::
26116 * GDB/MI Ada Tasking Commands::
26117 * GDB/MI Program Execution::
26118 * GDB/MI Stack Manipulation::
26119 * GDB/MI Variable Objects::
26120 * GDB/MI Data Manipulation::
26121 * GDB/MI Tracepoint Commands::
26122 * GDB/MI Symbol Query::
26123 * GDB/MI File Commands::
26125 * GDB/MI Kod Commands::
26126 * GDB/MI Memory Overlay Commands::
26127 * GDB/MI Signal Handling Commands::
26129 * GDB/MI Target Manipulation::
26130 * GDB/MI File Transfer Commands::
26131 * GDB/MI Ada Exceptions Commands::
26132 * GDB/MI Support Commands::
26133 * GDB/MI Miscellaneous Commands::
26136 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26137 @node GDB/MI General Design
26138 @section @sc{gdb/mi} General Design
26139 @cindex GDB/MI General Design
26141 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26142 parts---commands sent to @value{GDBN}, responses to those commands
26143 and notifications. Each command results in exactly one response,
26144 indicating either successful completion of the command, or an error.
26145 For the commands that do not resume the target, the response contains the
26146 requested information. For the commands that resume the target, the
26147 response only indicates whether the target was successfully resumed.
26148 Notifications is the mechanism for reporting changes in the state of the
26149 target, or in @value{GDBN} state, that cannot conveniently be associated with
26150 a command and reported as part of that command response.
26152 The important examples of notifications are:
26156 Exec notifications. These are used to report changes in
26157 target state---when a target is resumed, or stopped. It would not
26158 be feasible to include this information in response of resuming
26159 commands, because one resume commands can result in multiple events in
26160 different threads. Also, quite some time may pass before any event
26161 happens in the target, while a frontend needs to know whether the resuming
26162 command itself was successfully executed.
26165 Console output, and status notifications. Console output
26166 notifications are used to report output of CLI commands, as well as
26167 diagnostics for other commands. Status notifications are used to
26168 report the progress of a long-running operation. Naturally, including
26169 this information in command response would mean no output is produced
26170 until the command is finished, which is undesirable.
26173 General notifications. Commands may have various side effects on
26174 the @value{GDBN} or target state beyond their official purpose. For example,
26175 a command may change the selected thread. Although such changes can
26176 be included in command response, using notification allows for more
26177 orthogonal frontend design.
26181 There's no guarantee that whenever an MI command reports an error,
26182 @value{GDBN} or the target are in any specific state, and especially,
26183 the state is not reverted to the state before the MI command was
26184 processed. Therefore, whenever an MI command results in an error,
26185 we recommend that the frontend refreshes all the information shown in
26186 the user interface.
26190 * Context management::
26191 * Asynchronous and non-stop modes::
26195 @node Context management
26196 @subsection Context management
26198 @subsubsection Threads and Frames
26200 In most cases when @value{GDBN} accesses the target, this access is
26201 done in context of a specific thread and frame (@pxref{Frames}).
26202 Often, even when accessing global data, the target requires that a thread
26203 be specified. The CLI interface maintains the selected thread and frame,
26204 and supplies them to target on each command. This is convenient,
26205 because a command line user would not want to specify that information
26206 explicitly on each command, and because user interacts with
26207 @value{GDBN} via a single terminal, so no confusion is possible as
26208 to what thread and frame are the current ones.
26210 In the case of MI, the concept of selected thread and frame is less
26211 useful. First, a frontend can easily remember this information
26212 itself. Second, a graphical frontend can have more than one window,
26213 each one used for debugging a different thread, and the frontend might
26214 want to access additional threads for internal purposes. This
26215 increases the risk that by relying on implicitly selected thread, the
26216 frontend may be operating on a wrong one. Therefore, each MI command
26217 should explicitly specify which thread and frame to operate on. To
26218 make it possible, each MI command accepts the @samp{--thread} and
26219 @samp{--frame} options, the value to each is @value{GDBN} global
26220 identifier for thread and frame to operate on.
26222 Usually, each top-level window in a frontend allows the user to select
26223 a thread and a frame, and remembers the user selection for further
26224 operations. However, in some cases @value{GDBN} may suggest that the
26225 current thread or frame be changed. For example, when stopping on a
26226 breakpoint it is reasonable to switch to the thread where breakpoint is
26227 hit. For another example, if the user issues the CLI @samp{thread} or
26228 @samp{frame} commands via the frontend, it is desirable to change the
26229 frontend's selection to the one specified by user. @value{GDBN}
26230 communicates the suggestion to change current thread and frame using the
26231 @samp{=thread-selected} notification.
26233 Note that historically, MI shares the selected thread with CLI, so
26234 frontends used the @code{-thread-select} to execute commands in the
26235 right context. However, getting this to work right is cumbersome. The
26236 simplest way is for frontend to emit @code{-thread-select} command
26237 before every command. This doubles the number of commands that need
26238 to be sent. The alternative approach is to suppress @code{-thread-select}
26239 if the selected thread in @value{GDBN} is supposed to be identical to the
26240 thread the frontend wants to operate on. However, getting this
26241 optimization right can be tricky. In particular, if the frontend
26242 sends several commands to @value{GDBN}, and one of the commands changes the
26243 selected thread, then the behaviour of subsequent commands will
26244 change. So, a frontend should either wait for response from such
26245 problematic commands, or explicitly add @code{-thread-select} for
26246 all subsequent commands. No frontend is known to do this exactly
26247 right, so it is suggested to just always pass the @samp{--thread} and
26248 @samp{--frame} options.
26250 @subsubsection Language
26252 The execution of several commands depends on which language is selected.
26253 By default, the current language (@pxref{show language}) is used.
26254 But for commands known to be language-sensitive, it is recommended
26255 to use the @samp{--language} option. This option takes one argument,
26256 which is the name of the language to use while executing the command.
26260 -data-evaluate-expression --language c "sizeof (void*)"
26265 The valid language names are the same names accepted by the
26266 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26267 @samp{local} or @samp{unknown}.
26269 @node Asynchronous and non-stop modes
26270 @subsection Asynchronous command execution and non-stop mode
26272 On some targets, @value{GDBN} is capable of processing MI commands
26273 even while the target is running. This is called @dfn{asynchronous
26274 command execution} (@pxref{Background Execution}). The frontend may
26275 specify a preferrence for asynchronous execution using the
26276 @code{-gdb-set mi-async 1} command, which should be emitted before
26277 either running the executable or attaching to the target. After the
26278 frontend has started the executable or attached to the target, it can
26279 find if asynchronous execution is enabled using the
26280 @code{-list-target-features} command.
26283 @item -gdb-set mi-async on
26284 @item -gdb-set mi-async off
26285 Set whether MI is in asynchronous mode.
26287 When @code{off}, which is the default, MI execution commands (e.g.,
26288 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26289 for the program to stop before processing further commands.
26291 When @code{on}, MI execution commands are background execution
26292 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26293 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26294 MI commands even while the target is running.
26296 @item -gdb-show mi-async
26297 Show whether MI asynchronous mode is enabled.
26300 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26301 @code{target-async} instead of @code{mi-async}, and it had the effect
26302 of both putting MI in asynchronous mode and making CLI background
26303 commands possible. CLI background commands are now always possible
26304 ``out of the box'' if the target supports them. The old spelling is
26305 kept as a deprecated alias for backwards compatibility.
26307 Even if @value{GDBN} can accept a command while target is running,
26308 many commands that access the target do not work when the target is
26309 running. Therefore, asynchronous command execution is most useful
26310 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26311 it is possible to examine the state of one thread, while other threads
26314 When a given thread is running, MI commands that try to access the
26315 target in the context of that thread may not work, or may work only on
26316 some targets. In particular, commands that try to operate on thread's
26317 stack will not work, on any target. Commands that read memory, or
26318 modify breakpoints, may work or not work, depending on the target. Note
26319 that even commands that operate on global state, such as @code{print},
26320 @code{set}, and breakpoint commands, still access the target in the
26321 context of a specific thread, so frontend should try to find a
26322 stopped thread and perform the operation on that thread (using the
26323 @samp{--thread} option).
26325 Which commands will work in the context of a running thread is
26326 highly target dependent. However, the two commands
26327 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26328 to find the state of a thread, will always work.
26330 @node Thread groups
26331 @subsection Thread groups
26332 @value{GDBN} may be used to debug several processes at the same time.
26333 On some platfroms, @value{GDBN} may support debugging of several
26334 hardware systems, each one having several cores with several different
26335 processes running on each core. This section describes the MI
26336 mechanism to support such debugging scenarios.
26338 The key observation is that regardless of the structure of the
26339 target, MI can have a global list of threads, because most commands that
26340 accept the @samp{--thread} option do not need to know what process that
26341 thread belongs to. Therefore, it is not necessary to introduce
26342 neither additional @samp{--process} option, nor an notion of the
26343 current process in the MI interface. The only strictly new feature
26344 that is required is the ability to find how the threads are grouped
26347 To allow the user to discover such grouping, and to support arbitrary
26348 hierarchy of machines/cores/processes, MI introduces the concept of a
26349 @dfn{thread group}. Thread group is a collection of threads and other
26350 thread groups. A thread group always has a string identifier, a type,
26351 and may have additional attributes specific to the type. A new
26352 command, @code{-list-thread-groups}, returns the list of top-level
26353 thread groups, which correspond to processes that @value{GDBN} is
26354 debugging at the moment. By passing an identifier of a thread group
26355 to the @code{-list-thread-groups} command, it is possible to obtain
26356 the members of specific thread group.
26358 To allow the user to easily discover processes, and other objects, he
26359 wishes to debug, a concept of @dfn{available thread group} is
26360 introduced. Available thread group is an thread group that
26361 @value{GDBN} is not debugging, but that can be attached to, using the
26362 @code{-target-attach} command. The list of available top-level thread
26363 groups can be obtained using @samp{-list-thread-groups --available}.
26364 In general, the content of a thread group may be only retrieved only
26365 after attaching to that thread group.
26367 Thread groups are related to inferiors (@pxref{Inferiors and
26368 Programs}). Each inferior corresponds to a thread group of a special
26369 type @samp{process}, and some additional operations are permitted on
26370 such thread groups.
26372 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26373 @node GDB/MI Command Syntax
26374 @section @sc{gdb/mi} Command Syntax
26377 * GDB/MI Input Syntax::
26378 * GDB/MI Output Syntax::
26381 @node GDB/MI Input Syntax
26382 @subsection @sc{gdb/mi} Input Syntax
26384 @cindex input syntax for @sc{gdb/mi}
26385 @cindex @sc{gdb/mi}, input syntax
26387 @item @var{command} @expansion{}
26388 @code{@var{cli-command} | @var{mi-command}}
26390 @item @var{cli-command} @expansion{}
26391 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26392 @var{cli-command} is any existing @value{GDBN} CLI command.
26394 @item @var{mi-command} @expansion{}
26395 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26396 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26398 @item @var{token} @expansion{}
26399 "any sequence of digits"
26401 @item @var{option} @expansion{}
26402 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26404 @item @var{parameter} @expansion{}
26405 @code{@var{non-blank-sequence} | @var{c-string}}
26407 @item @var{operation} @expansion{}
26408 @emph{any of the operations described in this chapter}
26410 @item @var{non-blank-sequence} @expansion{}
26411 @emph{anything, provided it doesn't contain special characters such as
26412 "-", @var{nl}, """ and of course " "}
26414 @item @var{c-string} @expansion{}
26415 @code{""" @var{seven-bit-iso-c-string-content} """}
26417 @item @var{nl} @expansion{}
26426 The CLI commands are still handled by the @sc{mi} interpreter; their
26427 output is described below.
26430 The @code{@var{token}}, when present, is passed back when the command
26434 Some @sc{mi} commands accept optional arguments as part of the parameter
26435 list. Each option is identified by a leading @samp{-} (dash) and may be
26436 followed by an optional argument parameter. Options occur first in the
26437 parameter list and can be delimited from normal parameters using
26438 @samp{--} (this is useful when some parameters begin with a dash).
26445 We want easy access to the existing CLI syntax (for debugging).
26448 We want it to be easy to spot a @sc{mi} operation.
26451 @node GDB/MI Output Syntax
26452 @subsection @sc{gdb/mi} Output Syntax
26454 @cindex output syntax of @sc{gdb/mi}
26455 @cindex @sc{gdb/mi}, output syntax
26456 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26457 followed, optionally, by a single result record. This result record
26458 is for the most recent command. The sequence of output records is
26459 terminated by @samp{(gdb)}.
26461 If an input command was prefixed with a @code{@var{token}} then the
26462 corresponding output for that command will also be prefixed by that same
26466 @item @var{output} @expansion{}
26467 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26469 @item @var{result-record} @expansion{}
26470 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26472 @item @var{out-of-band-record} @expansion{}
26473 @code{@var{async-record} | @var{stream-record}}
26475 @item @var{async-record} @expansion{}
26476 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26478 @item @var{exec-async-output} @expansion{}
26479 @code{[ @var{token} ] "*" @var{async-output nl}}
26481 @item @var{status-async-output} @expansion{}
26482 @code{[ @var{token} ] "+" @var{async-output nl}}
26484 @item @var{notify-async-output} @expansion{}
26485 @code{[ @var{token} ] "=" @var{async-output nl}}
26487 @item @var{async-output} @expansion{}
26488 @code{@var{async-class} ( "," @var{result} )*}
26490 @item @var{result-class} @expansion{}
26491 @code{"done" | "running" | "connected" | "error" | "exit"}
26493 @item @var{async-class} @expansion{}
26494 @code{"stopped" | @var{others}} (where @var{others} will be added
26495 depending on the needs---this is still in development).
26497 @item @var{result} @expansion{}
26498 @code{ @var{variable} "=" @var{value}}
26500 @item @var{variable} @expansion{}
26501 @code{ @var{string} }
26503 @item @var{value} @expansion{}
26504 @code{ @var{const} | @var{tuple} | @var{list} }
26506 @item @var{const} @expansion{}
26507 @code{@var{c-string}}
26509 @item @var{tuple} @expansion{}
26510 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26512 @item @var{list} @expansion{}
26513 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26514 @var{result} ( "," @var{result} )* "]" }
26516 @item @var{stream-record} @expansion{}
26517 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26519 @item @var{console-stream-output} @expansion{}
26520 @code{"~" @var{c-string nl}}
26522 @item @var{target-stream-output} @expansion{}
26523 @code{"@@" @var{c-string nl}}
26525 @item @var{log-stream-output} @expansion{}
26526 @code{"&" @var{c-string nl}}
26528 @item @var{nl} @expansion{}
26531 @item @var{token} @expansion{}
26532 @emph{any sequence of digits}.
26540 All output sequences end in a single line containing a period.
26543 The @code{@var{token}} is from the corresponding request. Note that
26544 for all async output, while the token is allowed by the grammar and
26545 may be output by future versions of @value{GDBN} for select async
26546 output messages, it is generally omitted. Frontends should treat
26547 all async output as reporting general changes in the state of the
26548 target and there should be no need to associate async output to any
26552 @cindex status output in @sc{gdb/mi}
26553 @var{status-async-output} contains on-going status information about the
26554 progress of a slow operation. It can be discarded. All status output is
26555 prefixed by @samp{+}.
26558 @cindex async output in @sc{gdb/mi}
26559 @var{exec-async-output} contains asynchronous state change on the target
26560 (stopped, started, disappeared). All async output is prefixed by
26564 @cindex notify output in @sc{gdb/mi}
26565 @var{notify-async-output} contains supplementary information that the
26566 client should handle (e.g., a new breakpoint information). All notify
26567 output is prefixed by @samp{=}.
26570 @cindex console output in @sc{gdb/mi}
26571 @var{console-stream-output} is output that should be displayed as is in the
26572 console. It is the textual response to a CLI command. All the console
26573 output is prefixed by @samp{~}.
26576 @cindex target output in @sc{gdb/mi}
26577 @var{target-stream-output} is the output produced by the target program.
26578 All the target output is prefixed by @samp{@@}.
26581 @cindex log output in @sc{gdb/mi}
26582 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26583 instance messages that should be displayed as part of an error log. All
26584 the log output is prefixed by @samp{&}.
26587 @cindex list output in @sc{gdb/mi}
26588 New @sc{gdb/mi} commands should only output @var{lists} containing
26594 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26595 details about the various output records.
26597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26598 @node GDB/MI Compatibility with CLI
26599 @section @sc{gdb/mi} Compatibility with CLI
26601 @cindex compatibility, @sc{gdb/mi} and CLI
26602 @cindex @sc{gdb/mi}, compatibility with CLI
26604 For the developers convenience CLI commands can be entered directly,
26605 but there may be some unexpected behaviour. For example, commands
26606 that query the user will behave as if the user replied yes, breakpoint
26607 command lists are not executed and some CLI commands, such as
26608 @code{if}, @code{when} and @code{define}, prompt for further input with
26609 @samp{>}, which is not valid MI output.
26611 This feature may be removed at some stage in the future and it is
26612 recommended that front ends use the @code{-interpreter-exec} command
26613 (@pxref{-interpreter-exec}).
26615 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26616 @node GDB/MI Development and Front Ends
26617 @section @sc{gdb/mi} Development and Front Ends
26618 @cindex @sc{gdb/mi} development
26620 The application which takes the MI output and presents the state of the
26621 program being debugged to the user is called a @dfn{front end}.
26623 Although @sc{gdb/mi} is still incomplete, it is currently being used
26624 by a variety of front ends to @value{GDBN}. This makes it difficult
26625 to introduce new functionality without breaking existing usage. This
26626 section tries to minimize the problems by describing how the protocol
26629 Some changes in MI need not break a carefully designed front end, and
26630 for these the MI version will remain unchanged. The following is a
26631 list of changes that may occur within one level, so front ends should
26632 parse MI output in a way that can handle them:
26636 New MI commands may be added.
26639 New fields may be added to the output of any MI command.
26642 The range of values for fields with specified values, e.g.,
26643 @code{in_scope} (@pxref{-var-update}) may be extended.
26645 @c The format of field's content e.g type prefix, may change so parse it
26646 @c at your own risk. Yes, in general?
26648 @c The order of fields may change? Shouldn't really matter but it might
26649 @c resolve inconsistencies.
26652 If the changes are likely to break front ends, the MI version level
26653 will be increased by one. This will allow the front end to parse the
26654 output according to the MI version. Apart from mi0, new versions of
26655 @value{GDBN} will not support old versions of MI and it will be the
26656 responsibility of the front end to work with the new one.
26658 @c Starting with mi3, add a new command -mi-version that prints the MI
26661 The best way to avoid unexpected changes in MI that might break your front
26662 end is to make your project known to @value{GDBN} developers and
26663 follow development on @email{gdb@@sourceware.org} and
26664 @email{gdb-patches@@sourceware.org}.
26665 @cindex mailing lists
26667 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26668 @node GDB/MI Output Records
26669 @section @sc{gdb/mi} Output Records
26672 * GDB/MI Result Records::
26673 * GDB/MI Stream Records::
26674 * GDB/MI Async Records::
26675 * GDB/MI Breakpoint Information::
26676 * GDB/MI Frame Information::
26677 * GDB/MI Thread Information::
26678 * GDB/MI Ada Exception Information::
26681 @node GDB/MI Result Records
26682 @subsection @sc{gdb/mi} Result Records
26684 @cindex result records in @sc{gdb/mi}
26685 @cindex @sc{gdb/mi}, result records
26686 In addition to a number of out-of-band notifications, the response to a
26687 @sc{gdb/mi} command includes one of the following result indications:
26691 @item "^done" [ "," @var{results} ]
26692 The synchronous operation was successful, @code{@var{results}} are the return
26697 This result record is equivalent to @samp{^done}. Historically, it
26698 was output instead of @samp{^done} if the command has resumed the
26699 target. This behaviour is maintained for backward compatibility, but
26700 all frontends should treat @samp{^done} and @samp{^running}
26701 identically and rely on the @samp{*running} output record to determine
26702 which threads are resumed.
26706 @value{GDBN} has connected to a remote target.
26708 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26710 The operation failed. The @code{msg=@var{c-string}} variable contains
26711 the corresponding error message.
26713 If present, the @code{code=@var{c-string}} variable provides an error
26714 code on which consumers can rely on to detect the corresponding
26715 error condition. At present, only one error code is defined:
26718 @item "undefined-command"
26719 Indicates that the command causing the error does not exist.
26724 @value{GDBN} has terminated.
26728 @node GDB/MI Stream Records
26729 @subsection @sc{gdb/mi} Stream Records
26731 @cindex @sc{gdb/mi}, stream records
26732 @cindex stream records in @sc{gdb/mi}
26733 @value{GDBN} internally maintains a number of output streams: the console, the
26734 target, and the log. The output intended for each of these streams is
26735 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26737 Each stream record begins with a unique @dfn{prefix character} which
26738 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26739 Syntax}). In addition to the prefix, each stream record contains a
26740 @code{@var{string-output}}. This is either raw text (with an implicit new
26741 line) or a quoted C string (which does not contain an implicit newline).
26744 @item "~" @var{string-output}
26745 The console output stream contains text that should be displayed in the
26746 CLI console window. It contains the textual responses to CLI commands.
26748 @item "@@" @var{string-output}
26749 The target output stream contains any textual output from the running
26750 target. This is only present when GDB's event loop is truly
26751 asynchronous, which is currently only the case for remote targets.
26753 @item "&" @var{string-output}
26754 The log stream contains debugging messages being produced by @value{GDBN}'s
26758 @node GDB/MI Async Records
26759 @subsection @sc{gdb/mi} Async Records
26761 @cindex async records in @sc{gdb/mi}
26762 @cindex @sc{gdb/mi}, async records
26763 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26764 additional changes that have occurred. Those changes can either be a
26765 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26766 target activity (e.g., target stopped).
26768 The following is the list of possible async records:
26772 @item *running,thread-id="@var{thread}"
26773 The target is now running. The @var{thread} field can be the global
26774 thread ID of the the thread that is now running, and it can be
26775 @samp{all} if all threads are running. The frontend should assume
26776 that no interaction with a running thread is possible after this
26777 notification is produced. The frontend should not assume that this
26778 notification is output only once for any command. @value{GDBN} may
26779 emit this notification several times, either for different threads,
26780 because it cannot resume all threads together, or even for a single
26781 thread, if the thread must be stepped though some code before letting
26784 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26785 The target has stopped. The @var{reason} field can have one of the
26789 @item breakpoint-hit
26790 A breakpoint was reached.
26791 @item watchpoint-trigger
26792 A watchpoint was triggered.
26793 @item read-watchpoint-trigger
26794 A read watchpoint was triggered.
26795 @item access-watchpoint-trigger
26796 An access watchpoint was triggered.
26797 @item function-finished
26798 An -exec-finish or similar CLI command was accomplished.
26799 @item location-reached
26800 An -exec-until or similar CLI command was accomplished.
26801 @item watchpoint-scope
26802 A watchpoint has gone out of scope.
26803 @item end-stepping-range
26804 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26805 similar CLI command was accomplished.
26806 @item exited-signalled
26807 The inferior exited because of a signal.
26809 The inferior exited.
26810 @item exited-normally
26811 The inferior exited normally.
26812 @item signal-received
26813 A signal was received by the inferior.
26815 The inferior has stopped due to a library being loaded or unloaded.
26816 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26817 set or when a @code{catch load} or @code{catch unload} catchpoint is
26818 in use (@pxref{Set Catchpoints}).
26820 The inferior has forked. This is reported when @code{catch fork}
26821 (@pxref{Set Catchpoints}) has been used.
26823 The inferior has vforked. This is reported in when @code{catch vfork}
26824 (@pxref{Set Catchpoints}) has been used.
26825 @item syscall-entry
26826 The inferior entered a system call. This is reported when @code{catch
26827 syscall} (@pxref{Set Catchpoints}) has been used.
26828 @item syscall-return
26829 The inferior returned from a system call. This is reported when
26830 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26832 The inferior called @code{exec}. This is reported when @code{catch exec}
26833 (@pxref{Set Catchpoints}) has been used.
26836 The @var{id} field identifies the global thread ID of the thread
26837 that directly caused the stop -- for example by hitting a breakpoint.
26838 Depending on whether all-stop
26839 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26840 stop all threads, or only the thread that directly triggered the stop.
26841 If all threads are stopped, the @var{stopped} field will have the
26842 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26843 field will be a list of thread identifiers. Presently, this list will
26844 always include a single thread, but frontend should be prepared to see
26845 several threads in the list. The @var{core} field reports the
26846 processor core on which the stop event has happened. This field may be absent
26847 if such information is not available.
26849 @item =thread-group-added,id="@var{id}"
26850 @itemx =thread-group-removed,id="@var{id}"
26851 A thread group was either added or removed. The @var{id} field
26852 contains the @value{GDBN} identifier of the thread group. When a thread
26853 group is added, it generally might not be associated with a running
26854 process. When a thread group is removed, its id becomes invalid and
26855 cannot be used in any way.
26857 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26858 A thread group became associated with a running program,
26859 either because the program was just started or the thread group
26860 was attached to a program. The @var{id} field contains the
26861 @value{GDBN} identifier of the thread group. The @var{pid} field
26862 contains process identifier, specific to the operating system.
26864 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26865 A thread group is no longer associated with a running program,
26866 either because the program has exited, or because it was detached
26867 from. The @var{id} field contains the @value{GDBN} identifier of the
26868 thread group. The @var{code} field is the exit code of the inferior; it exists
26869 only when the inferior exited with some code.
26871 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26872 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26873 A thread either was created, or has exited. The @var{id} field
26874 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26875 field identifies the thread group this thread belongs to.
26877 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26878 Informs that the selected thread or frame were changed. This notification
26879 is not emitted as result of the @code{-thread-select} or
26880 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26881 that is not documented to change the selected thread and frame actually
26882 changes them. In particular, invoking, directly or indirectly
26883 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26884 will generate this notification. Changing the thread or frame from another
26885 user interface (see @ref{Interpreters}) will also generate this notification.
26887 The @var{frame} field is only present if the newly selected thread is
26888 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
26890 We suggest that in response to this notification, front ends
26891 highlight the selected thread and cause subsequent commands to apply to
26894 @item =library-loaded,...
26895 Reports that a new library file was loaded by the program. This
26896 notification has 5 fields---@var{id}, @var{target-name},
26897 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
26898 opaque identifier of the library. For remote debugging case,
26899 @var{target-name} and @var{host-name} fields give the name of the
26900 library file on the target, and on the host respectively. For native
26901 debugging, both those fields have the same value. The
26902 @var{symbols-loaded} field is emitted only for backward compatibility
26903 and should not be relied on to convey any useful information. The
26904 @var{thread-group} field, if present, specifies the id of the thread
26905 group in whose context the library was loaded. If the field is
26906 absent, it means the library was loaded in the context of all present
26907 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
26910 @item =library-unloaded,...
26911 Reports that a library was unloaded by the program. This notification
26912 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26913 the same meaning as for the @code{=library-loaded} notification.
26914 The @var{thread-group} field, if present, specifies the id of the
26915 thread group in whose context the library was unloaded. If the field is
26916 absent, it means the library was unloaded in the context of all present
26919 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26920 @itemx =traceframe-changed,end
26921 Reports that the trace frame was changed and its new number is
26922 @var{tfnum}. The number of the tracepoint associated with this trace
26923 frame is @var{tpnum}.
26925 @item =tsv-created,name=@var{name},initial=@var{initial}
26926 Reports that the new trace state variable @var{name} is created with
26927 initial value @var{initial}.
26929 @item =tsv-deleted,name=@var{name}
26930 @itemx =tsv-deleted
26931 Reports that the trace state variable @var{name} is deleted or all
26932 trace state variables are deleted.
26934 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26935 Reports that the trace state variable @var{name} is modified with
26936 the initial value @var{initial}. The current value @var{current} of
26937 trace state variable is optional and is reported if the current
26938 value of trace state variable is known.
26940 @item =breakpoint-created,bkpt=@{...@}
26941 @itemx =breakpoint-modified,bkpt=@{...@}
26942 @itemx =breakpoint-deleted,id=@var{number}
26943 Reports that a breakpoint was created, modified, or deleted,
26944 respectively. Only user-visible breakpoints are reported to the MI
26947 The @var{bkpt} argument is of the same form as returned by the various
26948 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26949 @var{number} is the ordinal number of the breakpoint.
26951 Note that if a breakpoint is emitted in the result record of a
26952 command, then it will not also be emitted in an async record.
26954 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26955 @itemx =record-stopped,thread-group="@var{id}"
26956 Execution log recording was either started or stopped on an
26957 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26958 group corresponding to the affected inferior.
26960 The @var{method} field indicates the method used to record execution. If the
26961 method in use supports multiple recording formats, @var{format} will be present
26962 and contain the currently used format. @xref{Process Record and Replay},
26963 for existing method and format values.
26965 @item =cmd-param-changed,param=@var{param},value=@var{value}
26966 Reports that a parameter of the command @code{set @var{param}} is
26967 changed to @var{value}. In the multi-word @code{set} command,
26968 the @var{param} is the whole parameter list to @code{set} command.
26969 For example, In command @code{set check type on}, @var{param}
26970 is @code{check type} and @var{value} is @code{on}.
26972 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26973 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26974 written in an inferior. The @var{id} is the identifier of the
26975 thread group corresponding to the affected inferior. The optional
26976 @code{type="code"} part is reported if the memory written to holds
26980 @node GDB/MI Breakpoint Information
26981 @subsection @sc{gdb/mi} Breakpoint Information
26983 When @value{GDBN} reports information about a breakpoint, a
26984 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26989 The breakpoint number. For a breakpoint that represents one location
26990 of a multi-location breakpoint, this will be a dotted pair, like
26994 The type of the breakpoint. For ordinary breakpoints this will be
26995 @samp{breakpoint}, but many values are possible.
26998 If the type of the breakpoint is @samp{catchpoint}, then this
26999 indicates the exact type of catchpoint.
27002 This is the breakpoint disposition---either @samp{del}, meaning that
27003 the breakpoint will be deleted at the next stop, or @samp{keep},
27004 meaning that the breakpoint will not be deleted.
27007 This indicates whether the breakpoint is enabled, in which case the
27008 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27009 Note that this is not the same as the field @code{enable}.
27012 The address of the breakpoint. This may be a hexidecimal number,
27013 giving the address; or the string @samp{<PENDING>}, for a pending
27014 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27015 multiple locations. This field will not be present if no address can
27016 be determined. For example, a watchpoint does not have an address.
27019 If known, the function in which the breakpoint appears.
27020 If not known, this field is not present.
27023 The name of the source file which contains this function, if known.
27024 If not known, this field is not present.
27027 The full file name of the source file which contains this function, if
27028 known. If not known, this field is not present.
27031 The line number at which this breakpoint appears, if known.
27032 If not known, this field is not present.
27035 If the source file is not known, this field may be provided. If
27036 provided, this holds the address of the breakpoint, possibly followed
27040 If this breakpoint is pending, this field is present and holds the
27041 text used to set the breakpoint, as entered by the user.
27044 Where this breakpoint's condition is evaluated, either @samp{host} or
27048 If this is a thread-specific breakpoint, then this identifies the
27049 thread in which the breakpoint can trigger.
27052 If this breakpoint is restricted to a particular Ada task, then this
27053 field will hold the task identifier.
27056 If the breakpoint is conditional, this is the condition expression.
27059 The ignore count of the breakpoint.
27062 The enable count of the breakpoint.
27064 @item traceframe-usage
27067 @item static-tracepoint-marker-string-id
27068 For a static tracepoint, the name of the static tracepoint marker.
27071 For a masked watchpoint, this is the mask.
27074 A tracepoint's pass count.
27076 @item original-location
27077 The location of the breakpoint as originally specified by the user.
27078 This field is optional.
27081 The number of times the breakpoint has been hit.
27084 This field is only given for tracepoints. This is either @samp{y},
27085 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27089 Some extra data, the exact contents of which are type-dependent.
27093 For example, here is what the output of @code{-break-insert}
27094 (@pxref{GDB/MI Breakpoint Commands}) might be:
27097 -> -break-insert main
27098 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27099 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27100 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27105 @node GDB/MI Frame Information
27106 @subsection @sc{gdb/mi} Frame Information
27108 Response from many MI commands includes an information about stack
27109 frame. This information is a tuple that may have the following
27114 The level of the stack frame. The innermost frame has the level of
27115 zero. This field is always present.
27118 The name of the function corresponding to the frame. This field may
27119 be absent if @value{GDBN} is unable to determine the function name.
27122 The code address for the frame. This field is always present.
27125 The name of the source files that correspond to the frame's code
27126 address. This field may be absent.
27129 The source line corresponding to the frames' code address. This field
27133 The name of the binary file (either executable or shared library) the
27134 corresponds to the frame's code address. This field may be absent.
27138 @node GDB/MI Thread Information
27139 @subsection @sc{gdb/mi} Thread Information
27141 Whenever @value{GDBN} has to report an information about a thread, it
27142 uses a tuple with the following fields. The fields are always present unless
27147 The global numeric id assigned to the thread by @value{GDBN}.
27150 The target-specific string identifying the thread.
27153 Additional information about the thread provided by the target.
27154 It is supposed to be human-readable and not interpreted by the
27155 frontend. This field is optional.
27158 The name of the thread. If the user specified a name using the
27159 @code{thread name} command, then this name is given. Otherwise, if
27160 @value{GDBN} can extract the thread name from the target, then that
27161 name is given. If @value{GDBN} cannot find the thread name, then this
27165 The execution state of the thread, either @samp{stopped} or @samp{running},
27166 depending on whether the thread is presently running.
27169 The stack frame currently executing in the thread. This field is only present
27170 if the thread is stopped. Its format is documented in
27171 @ref{GDB/MI Frame Information}.
27174 The value of this field is an integer number of the processor core the
27175 thread was last seen on. This field is optional.
27178 @node GDB/MI Ada Exception Information
27179 @subsection @sc{gdb/mi} Ada Exception Information
27181 Whenever a @code{*stopped} record is emitted because the program
27182 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27183 @value{GDBN} provides the name of the exception that was raised via
27184 the @code{exception-name} field.
27186 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27187 @node GDB/MI Simple Examples
27188 @section Simple Examples of @sc{gdb/mi} Interaction
27189 @cindex @sc{gdb/mi}, simple examples
27191 This subsection presents several simple examples of interaction using
27192 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27193 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27194 the output received from @sc{gdb/mi}.
27196 Note the line breaks shown in the examples are here only for
27197 readability, they don't appear in the real output.
27199 @subheading Setting a Breakpoint
27201 Setting a breakpoint generates synchronous output which contains detailed
27202 information of the breakpoint.
27205 -> -break-insert main
27206 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27207 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27208 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27213 @subheading Program Execution
27215 Program execution generates asynchronous records and MI gives the
27216 reason that execution stopped.
27222 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27223 frame=@{addr="0x08048564",func="main",
27224 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27225 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27230 <- *stopped,reason="exited-normally"
27234 @subheading Quitting @value{GDBN}
27236 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27244 Please note that @samp{^exit} is printed immediately, but it might
27245 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27246 performs necessary cleanups, including killing programs being debugged
27247 or disconnecting from debug hardware, so the frontend should wait till
27248 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27249 fails to exit in reasonable time.
27251 @subheading A Bad Command
27253 Here's what happens if you pass a non-existent command:
27257 <- ^error,msg="Undefined MI command: rubbish"
27262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27263 @node GDB/MI Command Description Format
27264 @section @sc{gdb/mi} Command Description Format
27266 The remaining sections describe blocks of commands. Each block of
27267 commands is laid out in a fashion similar to this section.
27269 @subheading Motivation
27271 The motivation for this collection of commands.
27273 @subheading Introduction
27275 A brief introduction to this collection of commands as a whole.
27277 @subheading Commands
27279 For each command in the block, the following is described:
27281 @subsubheading Synopsis
27284 -command @var{args}@dots{}
27287 @subsubheading Result
27289 @subsubheading @value{GDBN} Command
27291 The corresponding @value{GDBN} CLI command(s), if any.
27293 @subsubheading Example
27295 Example(s) formatted for readability. Some of the described commands have
27296 not been implemented yet and these are labeled N.A.@: (not available).
27299 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27300 @node GDB/MI Breakpoint Commands
27301 @section @sc{gdb/mi} Breakpoint Commands
27303 @cindex breakpoint commands for @sc{gdb/mi}
27304 @cindex @sc{gdb/mi}, breakpoint commands
27305 This section documents @sc{gdb/mi} commands for manipulating
27308 @subheading The @code{-break-after} Command
27309 @findex -break-after
27311 @subsubheading Synopsis
27314 -break-after @var{number} @var{count}
27317 The breakpoint number @var{number} is not in effect until it has been
27318 hit @var{count} times. To see how this is reflected in the output of
27319 the @samp{-break-list} command, see the description of the
27320 @samp{-break-list} command below.
27322 @subsubheading @value{GDBN} Command
27324 The corresponding @value{GDBN} command is @samp{ignore}.
27326 @subsubheading Example
27331 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27332 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27333 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27341 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27342 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27343 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27344 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27345 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27346 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27347 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27348 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27349 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27350 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27355 @subheading The @code{-break-catch} Command
27356 @findex -break-catch
27359 @subheading The @code{-break-commands} Command
27360 @findex -break-commands
27362 @subsubheading Synopsis
27365 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27368 Specifies the CLI commands that should be executed when breakpoint
27369 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27370 are the commands. If no command is specified, any previously-set
27371 commands are cleared. @xref{Break Commands}. Typical use of this
27372 functionality is tracing a program, that is, printing of values of
27373 some variables whenever breakpoint is hit and then continuing.
27375 @subsubheading @value{GDBN} Command
27377 The corresponding @value{GDBN} command is @samp{commands}.
27379 @subsubheading Example
27384 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27385 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27386 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27389 -break-commands 1 "print v" "continue"
27394 @subheading The @code{-break-condition} Command
27395 @findex -break-condition
27397 @subsubheading Synopsis
27400 -break-condition @var{number} @var{expr}
27403 Breakpoint @var{number} will stop the program only if the condition in
27404 @var{expr} is true. The condition becomes part of the
27405 @samp{-break-list} output (see the description of the @samp{-break-list}
27408 @subsubheading @value{GDBN} Command
27410 The corresponding @value{GDBN} command is @samp{condition}.
27412 @subsubheading Example
27416 -break-condition 1 1
27420 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27421 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27422 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27423 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27424 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27425 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27426 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27427 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27428 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27429 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27433 @subheading The @code{-break-delete} Command
27434 @findex -break-delete
27436 @subsubheading Synopsis
27439 -break-delete ( @var{breakpoint} )+
27442 Delete the breakpoint(s) whose number(s) are specified in the argument
27443 list. This is obviously reflected in the breakpoint list.
27445 @subsubheading @value{GDBN} Command
27447 The corresponding @value{GDBN} command is @samp{delete}.
27449 @subsubheading Example
27457 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27458 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27459 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27460 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27461 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27462 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27463 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27468 @subheading The @code{-break-disable} Command
27469 @findex -break-disable
27471 @subsubheading Synopsis
27474 -break-disable ( @var{breakpoint} )+
27477 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27478 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27480 @subsubheading @value{GDBN} Command
27482 The corresponding @value{GDBN} command is @samp{disable}.
27484 @subsubheading Example
27492 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27493 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27494 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27495 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27496 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27497 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27498 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27499 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27500 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27501 line="5",thread-groups=["i1"],times="0"@}]@}
27505 @subheading The @code{-break-enable} Command
27506 @findex -break-enable
27508 @subsubheading Synopsis
27511 -break-enable ( @var{breakpoint} )+
27514 Enable (previously disabled) @var{breakpoint}(s).
27516 @subsubheading @value{GDBN} Command
27518 The corresponding @value{GDBN} command is @samp{enable}.
27520 @subsubheading Example
27528 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27529 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27530 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27531 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27532 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27533 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27534 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27535 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27536 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27537 line="5",thread-groups=["i1"],times="0"@}]@}
27541 @subheading The @code{-break-info} Command
27542 @findex -break-info
27544 @subsubheading Synopsis
27547 -break-info @var{breakpoint}
27551 Get information about a single breakpoint.
27553 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27554 Information}, for details on the format of each breakpoint in the
27557 @subsubheading @value{GDBN} Command
27559 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27561 @subsubheading Example
27564 @subheading The @code{-break-insert} Command
27565 @findex -break-insert
27566 @anchor{-break-insert}
27568 @subsubheading Synopsis
27571 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27572 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27573 [ -p @var{thread-id} ] [ @var{location} ]
27577 If specified, @var{location}, can be one of:
27580 @item linespec location
27581 A linespec location. @xref{Linespec Locations}.
27583 @item explicit location
27584 An explicit location. @sc{gdb/mi} explicit locations are
27585 analogous to the CLI's explicit locations using the option names
27586 listed below. @xref{Explicit Locations}.
27589 @item --source @var{filename}
27590 The source file name of the location. This option requires the use
27591 of either @samp{--function} or @samp{--line}.
27593 @item --function @var{function}
27594 The name of a function or method.
27596 @item --label @var{label}
27597 The name of a label.
27599 @item --line @var{lineoffset}
27600 An absolute or relative line offset from the start of the location.
27603 @item address location
27604 An address location, *@var{address}. @xref{Address Locations}.
27608 The possible optional parameters of this command are:
27612 Insert a temporary breakpoint.
27614 Insert a hardware breakpoint.
27616 If @var{location} cannot be parsed (for example if it
27617 refers to unknown files or functions), create a pending
27618 breakpoint. Without this flag, @value{GDBN} will report
27619 an error, and won't create a breakpoint, if @var{location}
27622 Create a disabled breakpoint.
27624 Create a tracepoint. @xref{Tracepoints}. When this parameter
27625 is used together with @samp{-h}, a fast tracepoint is created.
27626 @item -c @var{condition}
27627 Make the breakpoint conditional on @var{condition}.
27628 @item -i @var{ignore-count}
27629 Initialize the @var{ignore-count}.
27630 @item -p @var{thread-id}
27631 Restrict the breakpoint to the thread with the specified global
27635 @subsubheading Result
27637 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27638 resulting breakpoint.
27640 Note: this format is open to change.
27641 @c An out-of-band breakpoint instead of part of the result?
27643 @subsubheading @value{GDBN} Command
27645 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27646 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27648 @subsubheading Example
27653 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27654 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27657 -break-insert -t foo
27658 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27659 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27663 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27664 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27665 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27666 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27667 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27668 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27669 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27670 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27671 addr="0x0001072c", func="main",file="recursive2.c",
27672 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27674 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27675 addr="0x00010774",func="foo",file="recursive2.c",
27676 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27679 @c -break-insert -r foo.*
27680 @c ~int foo(int, int);
27681 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27682 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27687 @subheading The @code{-dprintf-insert} Command
27688 @findex -dprintf-insert
27690 @subsubheading Synopsis
27693 -dprintf-insert [ -t ] [ -f ] [ -d ]
27694 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27695 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27700 If supplied, @var{location} may be specified the same way as for
27701 the @code{-break-insert} command. @xref{-break-insert}.
27703 The possible optional parameters of this command are:
27707 Insert a temporary breakpoint.
27709 If @var{location} cannot be parsed (for example, if it
27710 refers to unknown files or functions), create a pending
27711 breakpoint. Without this flag, @value{GDBN} will report
27712 an error, and won't create a breakpoint, if @var{location}
27715 Create a disabled breakpoint.
27716 @item -c @var{condition}
27717 Make the breakpoint conditional on @var{condition}.
27718 @item -i @var{ignore-count}
27719 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27720 to @var{ignore-count}.
27721 @item -p @var{thread-id}
27722 Restrict the breakpoint to the thread with the specified global
27726 @subsubheading Result
27728 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27729 resulting breakpoint.
27731 @c An out-of-band breakpoint instead of part of the result?
27733 @subsubheading @value{GDBN} Command
27735 The corresponding @value{GDBN} command is @samp{dprintf}.
27737 @subsubheading Example
27741 4-dprintf-insert foo "At foo entry\n"
27742 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27743 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27744 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27745 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27746 original-location="foo"@}
27748 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27749 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27750 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27751 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27752 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27753 original-location="mi-dprintf.c:26"@}
27757 @subheading The @code{-break-list} Command
27758 @findex -break-list
27760 @subsubheading Synopsis
27766 Displays the list of inserted breakpoints, showing the following fields:
27770 number of the breakpoint
27772 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27774 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27777 is the breakpoint enabled or no: @samp{y} or @samp{n}
27779 memory location at which the breakpoint is set
27781 logical location of the breakpoint, expressed by function name, file
27783 @item Thread-groups
27784 list of thread groups to which this breakpoint applies
27786 number of times the breakpoint has been hit
27789 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27790 @code{body} field is an empty list.
27792 @subsubheading @value{GDBN} Command
27794 The corresponding @value{GDBN} command is @samp{info break}.
27796 @subsubheading Example
27801 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27802 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27803 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27804 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27805 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27806 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27807 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27808 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27809 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27811 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27812 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27813 line="13",thread-groups=["i1"],times="0"@}]@}
27817 Here's an example of the result when there are no breakpoints:
27822 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27823 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27824 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27825 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27826 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27827 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27828 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27833 @subheading The @code{-break-passcount} Command
27834 @findex -break-passcount
27836 @subsubheading Synopsis
27839 -break-passcount @var{tracepoint-number} @var{passcount}
27842 Set the passcount for tracepoint @var{tracepoint-number} to
27843 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27844 is not a tracepoint, error is emitted. This corresponds to CLI
27845 command @samp{passcount}.
27847 @subheading The @code{-break-watch} Command
27848 @findex -break-watch
27850 @subsubheading Synopsis
27853 -break-watch [ -a | -r ]
27856 Create a watchpoint. With the @samp{-a} option it will create an
27857 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27858 read from or on a write to the memory location. With the @samp{-r}
27859 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27860 trigger only when the memory location is accessed for reading. Without
27861 either of the options, the watchpoint created is a regular watchpoint,
27862 i.e., it will trigger when the memory location is accessed for writing.
27863 @xref{Set Watchpoints, , Setting Watchpoints}.
27865 Note that @samp{-break-list} will report a single list of watchpoints and
27866 breakpoints inserted.
27868 @subsubheading @value{GDBN} Command
27870 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27873 @subsubheading Example
27875 Setting a watchpoint on a variable in the @code{main} function:
27880 ^done,wpt=@{number="2",exp="x"@}
27885 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27886 value=@{old="-268439212",new="55"@},
27887 frame=@{func="main",args=[],file="recursive2.c",
27888 fullname="/home/foo/bar/recursive2.c",line="5"@}
27892 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27893 the program execution twice: first for the variable changing value, then
27894 for the watchpoint going out of scope.
27899 ^done,wpt=@{number="5",exp="C"@}
27904 *stopped,reason="watchpoint-trigger",
27905 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27906 frame=@{func="callee4",args=[],
27907 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27908 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27913 *stopped,reason="watchpoint-scope",wpnum="5",
27914 frame=@{func="callee3",args=[@{name="strarg",
27915 value="0x11940 \"A string argument.\""@}],
27916 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27917 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27921 Listing breakpoints and watchpoints, at different points in the program
27922 execution. Note that once the watchpoint goes out of scope, it is
27928 ^done,wpt=@{number="2",exp="C"@}
27931 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27932 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27933 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27934 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27935 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27936 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27937 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27938 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27939 addr="0x00010734",func="callee4",
27940 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27941 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27943 bkpt=@{number="2",type="watchpoint",disp="keep",
27944 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27949 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27950 value=@{old="-276895068",new="3"@},
27951 frame=@{func="callee4",args=[],
27952 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27953 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27956 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27957 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27958 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27959 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27960 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27961 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27962 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27963 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27964 addr="0x00010734",func="callee4",
27965 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27966 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27968 bkpt=@{number="2",type="watchpoint",disp="keep",
27969 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27973 ^done,reason="watchpoint-scope",wpnum="2",
27974 frame=@{func="callee3",args=[@{name="strarg",
27975 value="0x11940 \"A string argument.\""@}],
27976 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27977 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27980 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27981 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27982 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27983 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27984 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27985 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27986 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27987 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27988 addr="0x00010734",func="callee4",
27989 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27990 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27991 thread-groups=["i1"],times="1"@}]@}
27996 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27997 @node GDB/MI Catchpoint Commands
27998 @section @sc{gdb/mi} Catchpoint Commands
28000 This section documents @sc{gdb/mi} commands for manipulating
28004 * Shared Library GDB/MI Catchpoint Commands::
28005 * Ada Exception GDB/MI Catchpoint Commands::
28008 @node Shared Library GDB/MI Catchpoint Commands
28009 @subsection Shared Library @sc{gdb/mi} Catchpoints
28011 @subheading The @code{-catch-load} Command
28012 @findex -catch-load
28014 @subsubheading Synopsis
28017 -catch-load [ -t ] [ -d ] @var{regexp}
28020 Add a catchpoint for library load events. If the @samp{-t} option is used,
28021 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28022 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28023 in a disabled state. The @samp{regexp} argument is a regular
28024 expression used to match the name of the loaded library.
28027 @subsubheading @value{GDBN} Command
28029 The corresponding @value{GDBN} command is @samp{catch load}.
28031 @subsubheading Example
28034 -catch-load -t foo.so
28035 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28036 what="load of library matching foo.so",catch-type="load",times="0"@}
28041 @subheading The @code{-catch-unload} Command
28042 @findex -catch-unload
28044 @subsubheading Synopsis
28047 -catch-unload [ -t ] [ -d ] @var{regexp}
28050 Add a catchpoint for library unload events. If the @samp{-t} option is
28051 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28052 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28053 created in a disabled state. The @samp{regexp} argument is a regular
28054 expression used to match the name of the unloaded library.
28056 @subsubheading @value{GDBN} Command
28058 The corresponding @value{GDBN} command is @samp{catch unload}.
28060 @subsubheading Example
28063 -catch-unload -d bar.so
28064 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28065 what="load of library matching bar.so",catch-type="unload",times="0"@}
28069 @node Ada Exception GDB/MI Catchpoint Commands
28070 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28072 The following @sc{gdb/mi} commands can be used to create catchpoints
28073 that stop the execution when Ada exceptions are being raised.
28075 @subheading The @code{-catch-assert} Command
28076 @findex -catch-assert
28078 @subsubheading Synopsis
28081 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28084 Add a catchpoint for failed Ada assertions.
28086 The possible optional parameters for this command are:
28089 @item -c @var{condition}
28090 Make the catchpoint conditional on @var{condition}.
28092 Create a disabled catchpoint.
28094 Create a temporary catchpoint.
28097 @subsubheading @value{GDBN} Command
28099 The corresponding @value{GDBN} command is @samp{catch assert}.
28101 @subsubheading Example
28105 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28106 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28107 thread-groups=["i1"],times="0",
28108 original-location="__gnat_debug_raise_assert_failure"@}
28112 @subheading The @code{-catch-exception} Command
28113 @findex -catch-exception
28115 @subsubheading Synopsis
28118 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28122 Add a catchpoint stopping when Ada exceptions are raised.
28123 By default, the command stops the program when any Ada exception
28124 gets raised. But it is also possible, by using some of the
28125 optional parameters described below, to create more selective
28128 The possible optional parameters for this command are:
28131 @item -c @var{condition}
28132 Make the catchpoint conditional on @var{condition}.
28134 Create a disabled catchpoint.
28135 @item -e @var{exception-name}
28136 Only stop when @var{exception-name} is raised. This option cannot
28137 be used combined with @samp{-u}.
28139 Create a temporary catchpoint.
28141 Stop only when an unhandled exception gets raised. This option
28142 cannot be used combined with @samp{-e}.
28145 @subsubheading @value{GDBN} Command
28147 The corresponding @value{GDBN} commands are @samp{catch exception}
28148 and @samp{catch exception unhandled}.
28150 @subsubheading Example
28153 -catch-exception -e Program_Error
28154 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28155 enabled="y",addr="0x0000000000404874",
28156 what="`Program_Error' Ada exception", thread-groups=["i1"],
28157 times="0",original-location="__gnat_debug_raise_exception"@}
28161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28162 @node GDB/MI Program Context
28163 @section @sc{gdb/mi} Program Context
28165 @subheading The @code{-exec-arguments} Command
28166 @findex -exec-arguments
28169 @subsubheading Synopsis
28172 -exec-arguments @var{args}
28175 Set the inferior program arguments, to be used in the next
28178 @subsubheading @value{GDBN} Command
28180 The corresponding @value{GDBN} command is @samp{set args}.
28182 @subsubheading Example
28186 -exec-arguments -v word
28193 @subheading The @code{-exec-show-arguments} Command
28194 @findex -exec-show-arguments
28196 @subsubheading Synopsis
28199 -exec-show-arguments
28202 Print the arguments of the program.
28204 @subsubheading @value{GDBN} Command
28206 The corresponding @value{GDBN} command is @samp{show args}.
28208 @subsubheading Example
28213 @subheading The @code{-environment-cd} Command
28214 @findex -environment-cd
28216 @subsubheading Synopsis
28219 -environment-cd @var{pathdir}
28222 Set @value{GDBN}'s working directory.
28224 @subsubheading @value{GDBN} Command
28226 The corresponding @value{GDBN} command is @samp{cd}.
28228 @subsubheading Example
28232 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28238 @subheading The @code{-environment-directory} Command
28239 @findex -environment-directory
28241 @subsubheading Synopsis
28244 -environment-directory [ -r ] [ @var{pathdir} ]+
28247 Add directories @var{pathdir} to beginning of search path for source files.
28248 If the @samp{-r} option is used, the search path is reset to the default
28249 search path. If directories @var{pathdir} are supplied in addition to the
28250 @samp{-r} option, the search path is first reset and then addition
28252 Multiple directories may be specified, separated by blanks. Specifying
28253 multiple directories in a single command
28254 results in the directories added to the beginning of the
28255 search path in the same order they were presented in the command.
28256 If blanks are needed as
28257 part of a directory name, double-quotes should be used around
28258 the name. In the command output, the path will show up separated
28259 by the system directory-separator character. The directory-separator
28260 character must not be used
28261 in any directory name.
28262 If no directories are specified, the current search path is displayed.
28264 @subsubheading @value{GDBN} Command
28266 The corresponding @value{GDBN} command is @samp{dir}.
28268 @subsubheading Example
28272 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28273 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28275 -environment-directory ""
28276 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28278 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28279 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28281 -environment-directory -r
28282 ^done,source-path="$cdir:$cwd"
28287 @subheading The @code{-environment-path} Command
28288 @findex -environment-path
28290 @subsubheading Synopsis
28293 -environment-path [ -r ] [ @var{pathdir} ]+
28296 Add directories @var{pathdir} to beginning of search path for object files.
28297 If the @samp{-r} option is used, the search path is reset to the original
28298 search path that existed at gdb start-up. If directories @var{pathdir} are
28299 supplied in addition to the
28300 @samp{-r} option, the search path is first reset and then addition
28302 Multiple directories may be specified, separated by blanks. Specifying
28303 multiple directories in a single command
28304 results in the directories added to the beginning of the
28305 search path in the same order they were presented in the command.
28306 If blanks are needed as
28307 part of a directory name, double-quotes should be used around
28308 the name. In the command output, the path will show up separated
28309 by the system directory-separator character. The directory-separator
28310 character must not be used
28311 in any directory name.
28312 If no directories are specified, the current path is displayed.
28315 @subsubheading @value{GDBN} Command
28317 The corresponding @value{GDBN} command is @samp{path}.
28319 @subsubheading Example
28324 ^done,path="/usr/bin"
28326 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28327 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28329 -environment-path -r /usr/local/bin
28330 ^done,path="/usr/local/bin:/usr/bin"
28335 @subheading The @code{-environment-pwd} Command
28336 @findex -environment-pwd
28338 @subsubheading Synopsis
28344 Show the current working directory.
28346 @subsubheading @value{GDBN} Command
28348 The corresponding @value{GDBN} command is @samp{pwd}.
28350 @subsubheading Example
28355 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28359 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28360 @node GDB/MI Thread Commands
28361 @section @sc{gdb/mi} Thread Commands
28364 @subheading The @code{-thread-info} Command
28365 @findex -thread-info
28367 @subsubheading Synopsis
28370 -thread-info [ @var{thread-id} ]
28373 Reports information about either a specific thread, if the
28374 @var{thread-id} parameter is present, or about all threads.
28375 @var{thread-id} is the thread's global thread ID. When printing
28376 information about all threads, also reports the global ID of the
28379 @subsubheading @value{GDBN} Command
28381 The @samp{info thread} command prints the same information
28384 @subsubheading Result
28386 The result contains the following attributes:
28390 A list of threads. The format of the elements of the list is described in
28391 @ref{GDB/MI Thread Information}.
28393 @item current-thread-id
28394 The global id of the currently selected thread. This field is omitted if there
28395 is no selected thread (for example, when the selected inferior is not running,
28396 and therefore has no threads) or if a @var{thread-id} argument was passed to
28401 @subsubheading Example
28406 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28407 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28408 args=[]@},state="running"@},
28409 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28410 frame=@{level="0",addr="0x0804891f",func="foo",
28411 args=[@{name="i",value="10"@}],
28412 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28413 state="running"@}],
28414 current-thread-id="1"
28418 @subheading The @code{-thread-list-ids} Command
28419 @findex -thread-list-ids
28421 @subsubheading Synopsis
28427 Produces a list of the currently known global @value{GDBN} thread ids.
28428 At the end of the list it also prints the total number of such
28431 This command is retained for historical reasons, the
28432 @code{-thread-info} command should be used instead.
28434 @subsubheading @value{GDBN} Command
28436 Part of @samp{info threads} supplies the same information.
28438 @subsubheading Example
28443 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28444 current-thread-id="1",number-of-threads="3"
28449 @subheading The @code{-thread-select} Command
28450 @findex -thread-select
28452 @subsubheading Synopsis
28455 -thread-select @var{thread-id}
28458 Make thread with global thread number @var{thread-id} the current
28459 thread. It prints the number of the new current thread, and the
28460 topmost frame for that thread.
28462 This command is deprecated in favor of explicitly using the
28463 @samp{--thread} option to each command.
28465 @subsubheading @value{GDBN} Command
28467 The corresponding @value{GDBN} command is @samp{thread}.
28469 @subsubheading Example
28476 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28477 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28481 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28482 number-of-threads="3"
28485 ^done,new-thread-id="3",
28486 frame=@{level="0",func="vprintf",
28487 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28488 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28492 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28493 @node GDB/MI Ada Tasking Commands
28494 @section @sc{gdb/mi} Ada Tasking Commands
28496 @subheading The @code{-ada-task-info} Command
28497 @findex -ada-task-info
28499 @subsubheading Synopsis
28502 -ada-task-info [ @var{task-id} ]
28505 Reports information about either a specific Ada task, if the
28506 @var{task-id} parameter is present, or about all Ada tasks.
28508 @subsubheading @value{GDBN} Command
28510 The @samp{info tasks} command prints the same information
28511 about all Ada tasks (@pxref{Ada Tasks}).
28513 @subsubheading Result
28515 The result is a table of Ada tasks. The following columns are
28516 defined for each Ada task:
28520 This field exists only for the current thread. It has the value @samp{*}.
28523 The identifier that @value{GDBN} uses to refer to the Ada task.
28526 The identifier that the target uses to refer to the Ada task.
28529 The global thread identifier of the thread corresponding to the Ada
28532 This field should always exist, as Ada tasks are always implemented
28533 on top of a thread. But if @value{GDBN} cannot find this corresponding
28534 thread for any reason, the field is omitted.
28537 This field exists only when the task was created by another task.
28538 In this case, it provides the ID of the parent task.
28541 The base priority of the task.
28544 The current state of the task. For a detailed description of the
28545 possible states, see @ref{Ada Tasks}.
28548 The name of the task.
28552 @subsubheading Example
28556 ^done,tasks=@{nr_rows="3",nr_cols="8",
28557 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28558 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28559 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28560 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28561 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28562 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28563 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28564 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28565 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28566 state="Child Termination Wait",name="main_task"@}]@}
28570 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28571 @node GDB/MI Program Execution
28572 @section @sc{gdb/mi} Program Execution
28574 These are the asynchronous commands which generate the out-of-band
28575 record @samp{*stopped}. Currently @value{GDBN} only really executes
28576 asynchronously with remote targets and this interaction is mimicked in
28579 @subheading The @code{-exec-continue} Command
28580 @findex -exec-continue
28582 @subsubheading Synopsis
28585 -exec-continue [--reverse] [--all|--thread-group N]
28588 Resumes the execution of the inferior program, which will continue
28589 to execute until it reaches a debugger stop event. If the
28590 @samp{--reverse} option is specified, execution resumes in reverse until
28591 it reaches a stop event. Stop events may include
28594 breakpoints or watchpoints
28596 signals or exceptions
28598 the end of the process (or its beginning under @samp{--reverse})
28600 the end or beginning of a replay log if one is being used.
28602 In all-stop mode (@pxref{All-Stop
28603 Mode}), may resume only one thread, or all threads, depending on the
28604 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28605 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28606 ignored in all-stop mode. If the @samp{--thread-group} options is
28607 specified, then all threads in that thread group are resumed.
28609 @subsubheading @value{GDBN} Command
28611 The corresponding @value{GDBN} corresponding is @samp{continue}.
28613 @subsubheading Example
28620 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28621 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28627 @subheading The @code{-exec-finish} Command
28628 @findex -exec-finish
28630 @subsubheading Synopsis
28633 -exec-finish [--reverse]
28636 Resumes the execution of the inferior program until the current
28637 function is exited. Displays the results returned by the function.
28638 If the @samp{--reverse} option is specified, resumes the reverse
28639 execution of the inferior program until the point where current
28640 function was called.
28642 @subsubheading @value{GDBN} Command
28644 The corresponding @value{GDBN} command is @samp{finish}.
28646 @subsubheading Example
28648 Function returning @code{void}.
28655 *stopped,reason="function-finished",frame=@{func="main",args=[],
28656 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28660 Function returning other than @code{void}. The name of the internal
28661 @value{GDBN} variable storing the result is printed, together with the
28668 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28669 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28670 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28671 gdb-result-var="$1",return-value="0"
28676 @subheading The @code{-exec-interrupt} Command
28677 @findex -exec-interrupt
28679 @subsubheading Synopsis
28682 -exec-interrupt [--all|--thread-group N]
28685 Interrupts the background execution of the target. Note how the token
28686 associated with the stop message is the one for the execution command
28687 that has been interrupted. The token for the interrupt itself only
28688 appears in the @samp{^done} output. If the user is trying to
28689 interrupt a non-running program, an error message will be printed.
28691 Note that when asynchronous execution is enabled, this command is
28692 asynchronous just like other execution commands. That is, first the
28693 @samp{^done} response will be printed, and the target stop will be
28694 reported after that using the @samp{*stopped} notification.
28696 In non-stop mode, only the context thread is interrupted by default.
28697 All threads (in all inferiors) will be interrupted if the
28698 @samp{--all} option is specified. If the @samp{--thread-group}
28699 option is specified, all threads in that group will be interrupted.
28701 @subsubheading @value{GDBN} Command
28703 The corresponding @value{GDBN} command is @samp{interrupt}.
28705 @subsubheading Example
28716 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28717 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28718 fullname="/home/foo/bar/try.c",line="13"@}
28723 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28727 @subheading The @code{-exec-jump} Command
28730 @subsubheading Synopsis
28733 -exec-jump @var{location}
28736 Resumes execution of the inferior program at the location specified by
28737 parameter. @xref{Specify Location}, for a description of the
28738 different forms of @var{location}.
28740 @subsubheading @value{GDBN} Command
28742 The corresponding @value{GDBN} command is @samp{jump}.
28744 @subsubheading Example
28747 -exec-jump foo.c:10
28748 *running,thread-id="all"
28753 @subheading The @code{-exec-next} Command
28756 @subsubheading Synopsis
28759 -exec-next [--reverse]
28762 Resumes execution of the inferior program, stopping when the beginning
28763 of the next source line is reached.
28765 If the @samp{--reverse} option is specified, resumes reverse execution
28766 of the inferior program, stopping at the beginning of the previous
28767 source line. If you issue this command on the first line of a
28768 function, it will take you back to the caller of that function, to the
28769 source line where the function was called.
28772 @subsubheading @value{GDBN} Command
28774 The corresponding @value{GDBN} command is @samp{next}.
28776 @subsubheading Example
28782 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28787 @subheading The @code{-exec-next-instruction} Command
28788 @findex -exec-next-instruction
28790 @subsubheading Synopsis
28793 -exec-next-instruction [--reverse]
28796 Executes one machine instruction. If the instruction is a function
28797 call, continues until the function returns. If the program stops at an
28798 instruction in the middle of a source line, the address will be
28801 If the @samp{--reverse} option is specified, resumes reverse execution
28802 of the inferior program, stopping at the previous instruction. If the
28803 previously executed instruction was a return from another function,
28804 it will continue to execute in reverse until the call to that function
28805 (from the current stack frame) is reached.
28807 @subsubheading @value{GDBN} Command
28809 The corresponding @value{GDBN} command is @samp{nexti}.
28811 @subsubheading Example
28815 -exec-next-instruction
28819 *stopped,reason="end-stepping-range",
28820 addr="0x000100d4",line="5",file="hello.c"
28825 @subheading The @code{-exec-return} Command
28826 @findex -exec-return
28828 @subsubheading Synopsis
28834 Makes current function return immediately. Doesn't execute the inferior.
28835 Displays the new current frame.
28837 @subsubheading @value{GDBN} Command
28839 The corresponding @value{GDBN} command is @samp{return}.
28841 @subsubheading Example
28845 200-break-insert callee4
28846 200^done,bkpt=@{number="1",addr="0x00010734",
28847 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28852 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28853 frame=@{func="callee4",args=[],
28854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28855 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28861 111^done,frame=@{level="0",func="callee3",
28862 args=[@{name="strarg",
28863 value="0x11940 \"A string argument.\""@}],
28864 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28865 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28870 @subheading The @code{-exec-run} Command
28873 @subsubheading Synopsis
28876 -exec-run [ --all | --thread-group N ] [ --start ]
28879 Starts execution of the inferior from the beginning. The inferior
28880 executes until either a breakpoint is encountered or the program
28881 exits. In the latter case the output will include an exit code, if
28882 the program has exited exceptionally.
28884 When neither the @samp{--all} nor the @samp{--thread-group} option
28885 is specified, the current inferior is started. If the
28886 @samp{--thread-group} option is specified, it should refer to a thread
28887 group of type @samp{process}, and that thread group will be started.
28888 If the @samp{--all} option is specified, then all inferiors will be started.
28890 Using the @samp{--start} option instructs the debugger to stop
28891 the execution at the start of the inferior's main subprogram,
28892 following the same behavior as the @code{start} command
28893 (@pxref{Starting}).
28895 @subsubheading @value{GDBN} Command
28897 The corresponding @value{GDBN} command is @samp{run}.
28899 @subsubheading Examples
28904 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28909 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28910 frame=@{func="main",args=[],file="recursive2.c",
28911 fullname="/home/foo/bar/recursive2.c",line="4"@}
28916 Program exited normally:
28924 *stopped,reason="exited-normally"
28929 Program exited exceptionally:
28937 *stopped,reason="exited",exit-code="01"
28941 Another way the program can terminate is if it receives a signal such as
28942 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28946 *stopped,reason="exited-signalled",signal-name="SIGINT",
28947 signal-meaning="Interrupt"
28951 @c @subheading -exec-signal
28954 @subheading The @code{-exec-step} Command
28957 @subsubheading Synopsis
28960 -exec-step [--reverse]
28963 Resumes execution of the inferior program, stopping when the beginning
28964 of the next source line is reached, if the next source line is not a
28965 function call. If it is, stop at the first instruction of the called
28966 function. If the @samp{--reverse} option is specified, resumes reverse
28967 execution of the inferior program, stopping at the beginning of the
28968 previously executed source line.
28970 @subsubheading @value{GDBN} Command
28972 The corresponding @value{GDBN} command is @samp{step}.
28974 @subsubheading Example
28976 Stepping into a function:
28982 *stopped,reason="end-stepping-range",
28983 frame=@{func="foo",args=[@{name="a",value="10"@},
28984 @{name="b",value="0"@}],file="recursive2.c",
28985 fullname="/home/foo/bar/recursive2.c",line="11"@}
28995 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29000 @subheading The @code{-exec-step-instruction} Command
29001 @findex -exec-step-instruction
29003 @subsubheading Synopsis
29006 -exec-step-instruction [--reverse]
29009 Resumes the inferior which executes one machine instruction. If the
29010 @samp{--reverse} option is specified, resumes reverse execution of the
29011 inferior program, stopping at the previously executed instruction.
29012 The output, once @value{GDBN} has stopped, will vary depending on
29013 whether we have stopped in the middle of a source line or not. In the
29014 former case, the address at which the program stopped will be printed
29017 @subsubheading @value{GDBN} Command
29019 The corresponding @value{GDBN} command is @samp{stepi}.
29021 @subsubheading Example
29025 -exec-step-instruction
29029 *stopped,reason="end-stepping-range",
29030 frame=@{func="foo",args=[],file="try.c",
29031 fullname="/home/foo/bar/try.c",line="10"@}
29033 -exec-step-instruction
29037 *stopped,reason="end-stepping-range",
29038 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29039 fullname="/home/foo/bar/try.c",line="10"@}
29044 @subheading The @code{-exec-until} Command
29045 @findex -exec-until
29047 @subsubheading Synopsis
29050 -exec-until [ @var{location} ]
29053 Executes the inferior until the @var{location} specified in the
29054 argument is reached. If there is no argument, the inferior executes
29055 until a source line greater than the current one is reached. The
29056 reason for stopping in this case will be @samp{location-reached}.
29058 @subsubheading @value{GDBN} Command
29060 The corresponding @value{GDBN} command is @samp{until}.
29062 @subsubheading Example
29066 -exec-until recursive2.c:6
29070 *stopped,reason="location-reached",frame=@{func="main",args=[],
29071 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29076 @subheading -file-clear
29077 Is this going away????
29080 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29081 @node GDB/MI Stack Manipulation
29082 @section @sc{gdb/mi} Stack Manipulation Commands
29084 @subheading The @code{-enable-frame-filters} Command
29085 @findex -enable-frame-filters
29088 -enable-frame-filters
29091 @value{GDBN} allows Python-based frame filters to affect the output of
29092 the MI commands relating to stack traces. As there is no way to
29093 implement this in a fully backward-compatible way, a front end must
29094 request that this functionality be enabled.
29096 Once enabled, this feature cannot be disabled.
29098 Note that if Python support has not been compiled into @value{GDBN},
29099 this command will still succeed (and do nothing).
29101 @subheading The @code{-stack-info-frame} Command
29102 @findex -stack-info-frame
29104 @subsubheading Synopsis
29110 Get info on the selected frame.
29112 @subsubheading @value{GDBN} Command
29114 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29115 (without arguments).
29117 @subsubheading Example
29122 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29123 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29124 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29128 @subheading The @code{-stack-info-depth} Command
29129 @findex -stack-info-depth
29131 @subsubheading Synopsis
29134 -stack-info-depth [ @var{max-depth} ]
29137 Return the depth of the stack. If the integer argument @var{max-depth}
29138 is specified, do not count beyond @var{max-depth} frames.
29140 @subsubheading @value{GDBN} Command
29142 There's no equivalent @value{GDBN} command.
29144 @subsubheading Example
29146 For a stack with frame levels 0 through 11:
29153 -stack-info-depth 4
29156 -stack-info-depth 12
29159 -stack-info-depth 11
29162 -stack-info-depth 13
29167 @anchor{-stack-list-arguments}
29168 @subheading The @code{-stack-list-arguments} Command
29169 @findex -stack-list-arguments
29171 @subsubheading Synopsis
29174 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29175 [ @var{low-frame} @var{high-frame} ]
29178 Display a list of the arguments for the frames between @var{low-frame}
29179 and @var{high-frame} (inclusive). If @var{low-frame} and
29180 @var{high-frame} are not provided, list the arguments for the whole
29181 call stack. If the two arguments are equal, show the single frame
29182 at the corresponding level. It is an error if @var{low-frame} is
29183 larger than the actual number of frames. On the other hand,
29184 @var{high-frame} may be larger than the actual number of frames, in
29185 which case only existing frames will be returned.
29187 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29188 the variables; if it is 1 or @code{--all-values}, print also their
29189 values; and if it is 2 or @code{--simple-values}, print the name,
29190 type and value for simple data types, and the name and type for arrays,
29191 structures and unions. If the option @code{--no-frame-filters} is
29192 supplied, then Python frame filters will not be executed.
29194 If the @code{--skip-unavailable} option is specified, arguments that
29195 are not available are not listed. Partially available arguments
29196 are still displayed, however.
29198 Use of this command to obtain arguments in a single frame is
29199 deprecated in favor of the @samp{-stack-list-variables} command.
29201 @subsubheading @value{GDBN} Command
29203 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29204 @samp{gdb_get_args} command which partially overlaps with the
29205 functionality of @samp{-stack-list-arguments}.
29207 @subsubheading Example
29214 frame=@{level="0",addr="0x00010734",func="callee4",
29215 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29216 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29217 frame=@{level="1",addr="0x0001076c",func="callee3",
29218 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29219 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29220 frame=@{level="2",addr="0x0001078c",func="callee2",
29221 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29222 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29223 frame=@{level="3",addr="0x000107b4",func="callee1",
29224 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29225 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29226 frame=@{level="4",addr="0x000107e0",func="main",
29227 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29228 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29230 -stack-list-arguments 0
29233 frame=@{level="0",args=[]@},
29234 frame=@{level="1",args=[name="strarg"]@},
29235 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29236 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29237 frame=@{level="4",args=[]@}]
29239 -stack-list-arguments 1
29242 frame=@{level="0",args=[]@},
29244 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29245 frame=@{level="2",args=[
29246 @{name="intarg",value="2"@},
29247 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29248 @{frame=@{level="3",args=[
29249 @{name="intarg",value="2"@},
29250 @{name="strarg",value="0x11940 \"A string argument.\""@},
29251 @{name="fltarg",value="3.5"@}]@},
29252 frame=@{level="4",args=[]@}]
29254 -stack-list-arguments 0 2 2
29255 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29257 -stack-list-arguments 1 2 2
29258 ^done,stack-args=[frame=@{level="2",
29259 args=[@{name="intarg",value="2"@},
29260 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29264 @c @subheading -stack-list-exception-handlers
29267 @anchor{-stack-list-frames}
29268 @subheading The @code{-stack-list-frames} Command
29269 @findex -stack-list-frames
29271 @subsubheading Synopsis
29274 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29277 List the frames currently on the stack. For each frame it displays the
29282 The frame number, 0 being the topmost frame, i.e., the innermost function.
29284 The @code{$pc} value for that frame.
29288 File name of the source file where the function lives.
29289 @item @var{fullname}
29290 The full file name of the source file where the function lives.
29292 Line number corresponding to the @code{$pc}.
29294 The shared library where this function is defined. This is only given
29295 if the frame's function is not known.
29298 If invoked without arguments, this command prints a backtrace for the
29299 whole stack. If given two integer arguments, it shows the frames whose
29300 levels are between the two arguments (inclusive). If the two arguments
29301 are equal, it shows the single frame at the corresponding level. It is
29302 an error if @var{low-frame} is larger than the actual number of
29303 frames. On the other hand, @var{high-frame} may be larger than the
29304 actual number of frames, in which case only existing frames will be
29305 returned. If the option @code{--no-frame-filters} is supplied, then
29306 Python frame filters will not be executed.
29308 @subsubheading @value{GDBN} Command
29310 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29312 @subsubheading Example
29314 Full stack backtrace:
29320 [frame=@{level="0",addr="0x0001076c",func="foo",
29321 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29322 frame=@{level="1",addr="0x000107a4",func="foo",
29323 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29324 frame=@{level="2",addr="0x000107a4",func="foo",
29325 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29326 frame=@{level="3",addr="0x000107a4",func="foo",
29327 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29328 frame=@{level="4",addr="0x000107a4",func="foo",
29329 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29330 frame=@{level="5",addr="0x000107a4",func="foo",
29331 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29332 frame=@{level="6",addr="0x000107a4",func="foo",
29333 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29334 frame=@{level="7",addr="0x000107a4",func="foo",
29335 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29336 frame=@{level="8",addr="0x000107a4",func="foo",
29337 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29338 frame=@{level="9",addr="0x000107a4",func="foo",
29339 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29340 frame=@{level="10",addr="0x000107a4",func="foo",
29341 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29342 frame=@{level="11",addr="0x00010738",func="main",
29343 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29347 Show frames between @var{low_frame} and @var{high_frame}:
29351 -stack-list-frames 3 5
29353 [frame=@{level="3",addr="0x000107a4",func="foo",
29354 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29355 frame=@{level="4",addr="0x000107a4",func="foo",
29356 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29357 frame=@{level="5",addr="0x000107a4",func="foo",
29358 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29362 Show a single frame:
29366 -stack-list-frames 3 3
29368 [frame=@{level="3",addr="0x000107a4",func="foo",
29369 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29374 @subheading The @code{-stack-list-locals} Command
29375 @findex -stack-list-locals
29376 @anchor{-stack-list-locals}
29378 @subsubheading Synopsis
29381 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29384 Display the local variable names for the selected frame. If
29385 @var{print-values} is 0 or @code{--no-values}, print only the names of
29386 the variables; if it is 1 or @code{--all-values}, print also their
29387 values; and if it is 2 or @code{--simple-values}, print the name,
29388 type and value for simple data types, and the name and type for arrays,
29389 structures and unions. In this last case, a frontend can immediately
29390 display the value of simple data types and create variable objects for
29391 other data types when the user wishes to explore their values in
29392 more detail. If the option @code{--no-frame-filters} is supplied, then
29393 Python frame filters will not be executed.
29395 If the @code{--skip-unavailable} option is specified, local variables
29396 that are not available are not listed. Partially available local
29397 variables are still displayed, however.
29399 This command is deprecated in favor of the
29400 @samp{-stack-list-variables} command.
29402 @subsubheading @value{GDBN} Command
29404 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29406 @subsubheading Example
29410 -stack-list-locals 0
29411 ^done,locals=[name="A",name="B",name="C"]
29413 -stack-list-locals --all-values
29414 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29415 @{name="C",value="@{1, 2, 3@}"@}]
29416 -stack-list-locals --simple-values
29417 ^done,locals=[@{name="A",type="int",value="1"@},
29418 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29422 @anchor{-stack-list-variables}
29423 @subheading The @code{-stack-list-variables} Command
29424 @findex -stack-list-variables
29426 @subsubheading Synopsis
29429 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29432 Display the names of local variables and function arguments for the selected frame. If
29433 @var{print-values} is 0 or @code{--no-values}, print only the names of
29434 the variables; if it is 1 or @code{--all-values}, print also their
29435 values; and if it is 2 or @code{--simple-values}, print the name,
29436 type and value for simple data types, and the name and type for arrays,
29437 structures and unions. If the option @code{--no-frame-filters} is
29438 supplied, then Python frame filters will not be executed.
29440 If the @code{--skip-unavailable} option is specified, local variables
29441 and arguments that are not available are not listed. Partially
29442 available arguments and local variables are still displayed, however.
29444 @subsubheading Example
29448 -stack-list-variables --thread 1 --frame 0 --all-values
29449 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29454 @subheading The @code{-stack-select-frame} Command
29455 @findex -stack-select-frame
29457 @subsubheading Synopsis
29460 -stack-select-frame @var{framenum}
29463 Change the selected frame. Select a different frame @var{framenum} on
29466 This command in deprecated in favor of passing the @samp{--frame}
29467 option to every command.
29469 @subsubheading @value{GDBN} Command
29471 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29472 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29474 @subsubheading Example
29478 -stack-select-frame 2
29483 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29484 @node GDB/MI Variable Objects
29485 @section @sc{gdb/mi} Variable Objects
29489 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29491 For the implementation of a variable debugger window (locals, watched
29492 expressions, etc.), we are proposing the adaptation of the existing code
29493 used by @code{Insight}.
29495 The two main reasons for that are:
29499 It has been proven in practice (it is already on its second generation).
29502 It will shorten development time (needless to say how important it is
29506 The original interface was designed to be used by Tcl code, so it was
29507 slightly changed so it could be used through @sc{gdb/mi}. This section
29508 describes the @sc{gdb/mi} operations that will be available and gives some
29509 hints about their use.
29511 @emph{Note}: In addition to the set of operations described here, we
29512 expect the @sc{gui} implementation of a variable window to require, at
29513 least, the following operations:
29516 @item @code{-gdb-show} @code{output-radix}
29517 @item @code{-stack-list-arguments}
29518 @item @code{-stack-list-locals}
29519 @item @code{-stack-select-frame}
29524 @subheading Introduction to Variable Objects
29526 @cindex variable objects in @sc{gdb/mi}
29528 Variable objects are "object-oriented" MI interface for examining and
29529 changing values of expressions. Unlike some other MI interfaces that
29530 work with expressions, variable objects are specifically designed for
29531 simple and efficient presentation in the frontend. A variable object
29532 is identified by string name. When a variable object is created, the
29533 frontend specifies the expression for that variable object. The
29534 expression can be a simple variable, or it can be an arbitrary complex
29535 expression, and can even involve CPU registers. After creating a
29536 variable object, the frontend can invoke other variable object
29537 operations---for example to obtain or change the value of a variable
29538 object, or to change display format.
29540 Variable objects have hierarchical tree structure. Any variable object
29541 that corresponds to a composite type, such as structure in C, has
29542 a number of child variable objects, for example corresponding to each
29543 element of a structure. A child variable object can itself have
29544 children, recursively. Recursion ends when we reach
29545 leaf variable objects, which always have built-in types. Child variable
29546 objects are created only by explicit request, so if a frontend
29547 is not interested in the children of a particular variable object, no
29548 child will be created.
29550 For a leaf variable object it is possible to obtain its value as a
29551 string, or set the value from a string. String value can be also
29552 obtained for a non-leaf variable object, but it's generally a string
29553 that only indicates the type of the object, and does not list its
29554 contents. Assignment to a non-leaf variable object is not allowed.
29556 A frontend does not need to read the values of all variable objects each time
29557 the program stops. Instead, MI provides an update command that lists all
29558 variable objects whose values has changed since the last update
29559 operation. This considerably reduces the amount of data that must
29560 be transferred to the frontend. As noted above, children variable
29561 objects are created on demand, and only leaf variable objects have a
29562 real value. As result, gdb will read target memory only for leaf
29563 variables that frontend has created.
29565 The automatic update is not always desirable. For example, a frontend
29566 might want to keep a value of some expression for future reference,
29567 and never update it. For another example, fetching memory is
29568 relatively slow for embedded targets, so a frontend might want
29569 to disable automatic update for the variables that are either not
29570 visible on the screen, or ``closed''. This is possible using so
29571 called ``frozen variable objects''. Such variable objects are never
29572 implicitly updated.
29574 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29575 fixed variable object, the expression is parsed when the variable
29576 object is created, including associating identifiers to specific
29577 variables. The meaning of expression never changes. For a floating
29578 variable object the values of variables whose names appear in the
29579 expressions are re-evaluated every time in the context of the current
29580 frame. Consider this example:
29585 struct work_state state;
29592 If a fixed variable object for the @code{state} variable is created in
29593 this function, and we enter the recursive call, the variable
29594 object will report the value of @code{state} in the top-level
29595 @code{do_work} invocation. On the other hand, a floating variable
29596 object will report the value of @code{state} in the current frame.
29598 If an expression specified when creating a fixed variable object
29599 refers to a local variable, the variable object becomes bound to the
29600 thread and frame in which the variable object is created. When such
29601 variable object is updated, @value{GDBN} makes sure that the
29602 thread/frame combination the variable object is bound to still exists,
29603 and re-evaluates the variable object in context of that thread/frame.
29605 The following is the complete set of @sc{gdb/mi} operations defined to
29606 access this functionality:
29608 @multitable @columnfractions .4 .6
29609 @item @strong{Operation}
29610 @tab @strong{Description}
29612 @item @code{-enable-pretty-printing}
29613 @tab enable Python-based pretty-printing
29614 @item @code{-var-create}
29615 @tab create a variable object
29616 @item @code{-var-delete}
29617 @tab delete the variable object and/or its children
29618 @item @code{-var-set-format}
29619 @tab set the display format of this variable
29620 @item @code{-var-show-format}
29621 @tab show the display format of this variable
29622 @item @code{-var-info-num-children}
29623 @tab tells how many children this object has
29624 @item @code{-var-list-children}
29625 @tab return a list of the object's children
29626 @item @code{-var-info-type}
29627 @tab show the type of this variable object
29628 @item @code{-var-info-expression}
29629 @tab print parent-relative expression that this variable object represents
29630 @item @code{-var-info-path-expression}
29631 @tab print full expression that this variable object represents
29632 @item @code{-var-show-attributes}
29633 @tab is this variable editable? does it exist here?
29634 @item @code{-var-evaluate-expression}
29635 @tab get the value of this variable
29636 @item @code{-var-assign}
29637 @tab set the value of this variable
29638 @item @code{-var-update}
29639 @tab update the variable and its children
29640 @item @code{-var-set-frozen}
29641 @tab set frozeness attribute
29642 @item @code{-var-set-update-range}
29643 @tab set range of children to display on update
29646 In the next subsection we describe each operation in detail and suggest
29647 how it can be used.
29649 @subheading Description And Use of Operations on Variable Objects
29651 @subheading The @code{-enable-pretty-printing} Command
29652 @findex -enable-pretty-printing
29655 -enable-pretty-printing
29658 @value{GDBN} allows Python-based visualizers to affect the output of the
29659 MI variable object commands. However, because there was no way to
29660 implement this in a fully backward-compatible way, a front end must
29661 request that this functionality be enabled.
29663 Once enabled, this feature cannot be disabled.
29665 Note that if Python support has not been compiled into @value{GDBN},
29666 this command will still succeed (and do nothing).
29668 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29669 may work differently in future versions of @value{GDBN}.
29671 @subheading The @code{-var-create} Command
29672 @findex -var-create
29674 @subsubheading Synopsis
29677 -var-create @{@var{name} | "-"@}
29678 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29681 This operation creates a variable object, which allows the monitoring of
29682 a variable, the result of an expression, a memory cell or a CPU
29685 The @var{name} parameter is the string by which the object can be
29686 referenced. It must be unique. If @samp{-} is specified, the varobj
29687 system will generate a string ``varNNNNNN'' automatically. It will be
29688 unique provided that one does not specify @var{name} of that format.
29689 The command fails if a duplicate name is found.
29691 The frame under which the expression should be evaluated can be
29692 specified by @var{frame-addr}. A @samp{*} indicates that the current
29693 frame should be used. A @samp{@@} indicates that a floating variable
29694 object must be created.
29696 @var{expression} is any expression valid on the current language set (must not
29697 begin with a @samp{*}), or one of the following:
29701 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29704 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29707 @samp{$@var{regname}} --- a CPU register name
29710 @cindex dynamic varobj
29711 A varobj's contents may be provided by a Python-based pretty-printer. In this
29712 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29713 have slightly different semantics in some cases. If the
29714 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29715 will never create a dynamic varobj. This ensures backward
29716 compatibility for existing clients.
29718 @subsubheading Result
29720 This operation returns attributes of the newly-created varobj. These
29725 The name of the varobj.
29728 The number of children of the varobj. This number is not necessarily
29729 reliable for a dynamic varobj. Instead, you must examine the
29730 @samp{has_more} attribute.
29733 The varobj's scalar value. For a varobj whose type is some sort of
29734 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29735 will not be interesting.
29738 The varobj's type. This is a string representation of the type, as
29739 would be printed by the @value{GDBN} CLI. If @samp{print object}
29740 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29741 @emph{actual} (derived) type of the object is shown rather than the
29742 @emph{declared} one.
29745 If a variable object is bound to a specific thread, then this is the
29746 thread's global identifier.
29749 For a dynamic varobj, this indicates whether there appear to be any
29750 children available. For a non-dynamic varobj, this will be 0.
29753 This attribute will be present and have the value @samp{1} if the
29754 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29755 then this attribute will not be present.
29758 A dynamic varobj can supply a display hint to the front end. The
29759 value comes directly from the Python pretty-printer object's
29760 @code{display_hint} method. @xref{Pretty Printing API}.
29763 Typical output will look like this:
29766 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29767 has_more="@var{has_more}"
29771 @subheading The @code{-var-delete} Command
29772 @findex -var-delete
29774 @subsubheading Synopsis
29777 -var-delete [ -c ] @var{name}
29780 Deletes a previously created variable object and all of its children.
29781 With the @samp{-c} option, just deletes the children.
29783 Returns an error if the object @var{name} is not found.
29786 @subheading The @code{-var-set-format} Command
29787 @findex -var-set-format
29789 @subsubheading Synopsis
29792 -var-set-format @var{name} @var{format-spec}
29795 Sets the output format for the value of the object @var{name} to be
29798 @anchor{-var-set-format}
29799 The syntax for the @var{format-spec} is as follows:
29802 @var{format-spec} @expansion{}
29803 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29806 The natural format is the default format choosen automatically
29807 based on the variable type (like decimal for an @code{int}, hex
29808 for pointers, etc.).
29810 The zero-hexadecimal format has a representation similar to hexadecimal
29811 but with padding zeroes to the left of the value. For example, a 32-bit
29812 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29813 zero-hexadecimal format.
29815 For a variable with children, the format is set only on the
29816 variable itself, and the children are not affected.
29818 @subheading The @code{-var-show-format} Command
29819 @findex -var-show-format
29821 @subsubheading Synopsis
29824 -var-show-format @var{name}
29827 Returns the format used to display the value of the object @var{name}.
29830 @var{format} @expansion{}
29835 @subheading The @code{-var-info-num-children} Command
29836 @findex -var-info-num-children
29838 @subsubheading Synopsis
29841 -var-info-num-children @var{name}
29844 Returns the number of children of a variable object @var{name}:
29850 Note that this number is not completely reliable for a dynamic varobj.
29851 It will return the current number of children, but more children may
29855 @subheading The @code{-var-list-children} Command
29856 @findex -var-list-children
29858 @subsubheading Synopsis
29861 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29863 @anchor{-var-list-children}
29865 Return a list of the children of the specified variable object and
29866 create variable objects for them, if they do not already exist. With
29867 a single argument or if @var{print-values} has a value of 0 or
29868 @code{--no-values}, print only the names of the variables; if
29869 @var{print-values} is 1 or @code{--all-values}, also print their
29870 values; and if it is 2 or @code{--simple-values} print the name and
29871 value for simple data types and just the name for arrays, structures
29874 @var{from} and @var{to}, if specified, indicate the range of children
29875 to report. If @var{from} or @var{to} is less than zero, the range is
29876 reset and all children will be reported. Otherwise, children starting
29877 at @var{from} (zero-based) and up to and excluding @var{to} will be
29880 If a child range is requested, it will only affect the current call to
29881 @code{-var-list-children}, but not future calls to @code{-var-update}.
29882 For this, you must instead use @code{-var-set-update-range}. The
29883 intent of this approach is to enable a front end to implement any
29884 update approach it likes; for example, scrolling a view may cause the
29885 front end to request more children with @code{-var-list-children}, and
29886 then the front end could call @code{-var-set-update-range} with a
29887 different range to ensure that future updates are restricted to just
29890 For each child the following results are returned:
29895 Name of the variable object created for this child.
29898 The expression to be shown to the user by the front end to designate this child.
29899 For example this may be the name of a structure member.
29901 For a dynamic varobj, this value cannot be used to form an
29902 expression. There is no way to do this at all with a dynamic varobj.
29904 For C/C@t{++} structures there are several pseudo children returned to
29905 designate access qualifiers. For these pseudo children @var{exp} is
29906 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29907 type and value are not present.
29909 A dynamic varobj will not report the access qualifying
29910 pseudo-children, regardless of the language. This information is not
29911 available at all with a dynamic varobj.
29914 Number of children this child has. For a dynamic varobj, this will be
29918 The type of the child. If @samp{print object}
29919 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29920 @emph{actual} (derived) type of the object is shown rather than the
29921 @emph{declared} one.
29924 If values were requested, this is the value.
29927 If this variable object is associated with a thread, this is the
29928 thread's global thread id. Otherwise this result is not present.
29931 If the variable object is frozen, this variable will be present with a value of 1.
29934 A dynamic varobj can supply a display hint to the front end. The
29935 value comes directly from the Python pretty-printer object's
29936 @code{display_hint} method. @xref{Pretty Printing API}.
29939 This attribute will be present and have the value @samp{1} if the
29940 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29941 then this attribute will not be present.
29945 The result may have its own attributes:
29949 A dynamic varobj can supply a display hint to the front end. The
29950 value comes directly from the Python pretty-printer object's
29951 @code{display_hint} method. @xref{Pretty Printing API}.
29954 This is an integer attribute which is nonzero if there are children
29955 remaining after the end of the selected range.
29958 @subsubheading Example
29962 -var-list-children n
29963 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29964 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29966 -var-list-children --all-values n
29967 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29968 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29972 @subheading The @code{-var-info-type} Command
29973 @findex -var-info-type
29975 @subsubheading Synopsis
29978 -var-info-type @var{name}
29981 Returns the type of the specified variable @var{name}. The type is
29982 returned as a string in the same format as it is output by the
29986 type=@var{typename}
29990 @subheading The @code{-var-info-expression} Command
29991 @findex -var-info-expression
29993 @subsubheading Synopsis
29996 -var-info-expression @var{name}
29999 Returns a string that is suitable for presenting this
30000 variable object in user interface. The string is generally
30001 not valid expression in the current language, and cannot be evaluated.
30003 For example, if @code{a} is an array, and variable object
30004 @code{A} was created for @code{a}, then we'll get this output:
30007 (gdb) -var-info-expression A.1
30008 ^done,lang="C",exp="1"
30012 Here, the value of @code{lang} is the language name, which can be
30013 found in @ref{Supported Languages}.
30015 Note that the output of the @code{-var-list-children} command also
30016 includes those expressions, so the @code{-var-info-expression} command
30019 @subheading The @code{-var-info-path-expression} Command
30020 @findex -var-info-path-expression
30022 @subsubheading Synopsis
30025 -var-info-path-expression @var{name}
30028 Returns an expression that can be evaluated in the current
30029 context and will yield the same value that a variable object has.
30030 Compare this with the @code{-var-info-expression} command, which
30031 result can be used only for UI presentation. Typical use of
30032 the @code{-var-info-path-expression} command is creating a
30033 watchpoint from a variable object.
30035 This command is currently not valid for children of a dynamic varobj,
30036 and will give an error when invoked on one.
30038 For example, suppose @code{C} is a C@t{++} class, derived from class
30039 @code{Base}, and that the @code{Base} class has a member called
30040 @code{m_size}. Assume a variable @code{c} is has the type of
30041 @code{C} and a variable object @code{C} was created for variable
30042 @code{c}. Then, we'll get this output:
30044 (gdb) -var-info-path-expression C.Base.public.m_size
30045 ^done,path_expr=((Base)c).m_size)
30048 @subheading The @code{-var-show-attributes} Command
30049 @findex -var-show-attributes
30051 @subsubheading Synopsis
30054 -var-show-attributes @var{name}
30057 List attributes of the specified variable object @var{name}:
30060 status=@var{attr} [ ( ,@var{attr} )* ]
30064 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30066 @subheading The @code{-var-evaluate-expression} Command
30067 @findex -var-evaluate-expression
30069 @subsubheading Synopsis
30072 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30075 Evaluates the expression that is represented by the specified variable
30076 object and returns its value as a string. The format of the string
30077 can be specified with the @samp{-f} option. The possible values of
30078 this option are the same as for @code{-var-set-format}
30079 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30080 the current display format will be used. The current display format
30081 can be changed using the @code{-var-set-format} command.
30087 Note that one must invoke @code{-var-list-children} for a variable
30088 before the value of a child variable can be evaluated.
30090 @subheading The @code{-var-assign} Command
30091 @findex -var-assign
30093 @subsubheading Synopsis
30096 -var-assign @var{name} @var{expression}
30099 Assigns the value of @var{expression} to the variable object specified
30100 by @var{name}. The object must be @samp{editable}. If the variable's
30101 value is altered by the assign, the variable will show up in any
30102 subsequent @code{-var-update} list.
30104 @subsubheading Example
30112 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30116 @subheading The @code{-var-update} Command
30117 @findex -var-update
30119 @subsubheading Synopsis
30122 -var-update [@var{print-values}] @{@var{name} | "*"@}
30125 Reevaluate the expressions corresponding to the variable object
30126 @var{name} and all its direct and indirect children, and return the
30127 list of variable objects whose values have changed; @var{name} must
30128 be a root variable object. Here, ``changed'' means that the result of
30129 @code{-var-evaluate-expression} before and after the
30130 @code{-var-update} is different. If @samp{*} is used as the variable
30131 object names, all existing variable objects are updated, except
30132 for frozen ones (@pxref{-var-set-frozen}). The option
30133 @var{print-values} determines whether both names and values, or just
30134 names are printed. The possible values of this option are the same
30135 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30136 recommended to use the @samp{--all-values} option, to reduce the
30137 number of MI commands needed on each program stop.
30139 With the @samp{*} parameter, if a variable object is bound to a
30140 currently running thread, it will not be updated, without any
30143 If @code{-var-set-update-range} was previously used on a varobj, then
30144 only the selected range of children will be reported.
30146 @code{-var-update} reports all the changed varobjs in a tuple named
30149 Each item in the change list is itself a tuple holding:
30153 The name of the varobj.
30156 If values were requested for this update, then this field will be
30157 present and will hold the value of the varobj.
30160 @anchor{-var-update}
30161 This field is a string which may take one of three values:
30165 The variable object's current value is valid.
30168 The variable object does not currently hold a valid value but it may
30169 hold one in the future if its associated expression comes back into
30173 The variable object no longer holds a valid value.
30174 This can occur when the executable file being debugged has changed,
30175 either through recompilation or by using the @value{GDBN} @code{file}
30176 command. The front end should normally choose to delete these variable
30180 In the future new values may be added to this list so the front should
30181 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30184 This is only present if the varobj is still valid. If the type
30185 changed, then this will be the string @samp{true}; otherwise it will
30188 When a varobj's type changes, its children are also likely to have
30189 become incorrect. Therefore, the varobj's children are automatically
30190 deleted when this attribute is @samp{true}. Also, the varobj's update
30191 range, when set using the @code{-var-set-update-range} command, is
30195 If the varobj's type changed, then this field will be present and will
30198 @item new_num_children
30199 For a dynamic varobj, if the number of children changed, or if the
30200 type changed, this will be the new number of children.
30202 The @samp{numchild} field in other varobj responses is generally not
30203 valid for a dynamic varobj -- it will show the number of children that
30204 @value{GDBN} knows about, but because dynamic varobjs lazily
30205 instantiate their children, this will not reflect the number of
30206 children which may be available.
30208 The @samp{new_num_children} attribute only reports changes to the
30209 number of children known by @value{GDBN}. This is the only way to
30210 detect whether an update has removed children (which necessarily can
30211 only happen at the end of the update range).
30214 The display hint, if any.
30217 This is an integer value, which will be 1 if there are more children
30218 available outside the varobj's update range.
30221 This attribute will be present and have the value @samp{1} if the
30222 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30223 then this attribute will not be present.
30226 If new children were added to a dynamic varobj within the selected
30227 update range (as set by @code{-var-set-update-range}), then they will
30228 be listed in this attribute.
30231 @subsubheading Example
30238 -var-update --all-values var1
30239 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30240 type_changed="false"@}]
30244 @subheading The @code{-var-set-frozen} Command
30245 @findex -var-set-frozen
30246 @anchor{-var-set-frozen}
30248 @subsubheading Synopsis
30251 -var-set-frozen @var{name} @var{flag}
30254 Set the frozenness flag on the variable object @var{name}. The
30255 @var{flag} parameter should be either @samp{1} to make the variable
30256 frozen or @samp{0} to make it unfrozen. If a variable object is
30257 frozen, then neither itself, nor any of its children, are
30258 implicitly updated by @code{-var-update} of
30259 a parent variable or by @code{-var-update *}. Only
30260 @code{-var-update} of the variable itself will update its value and
30261 values of its children. After a variable object is unfrozen, it is
30262 implicitly updated by all subsequent @code{-var-update} operations.
30263 Unfreezing a variable does not update it, only subsequent
30264 @code{-var-update} does.
30266 @subsubheading Example
30270 -var-set-frozen V 1
30275 @subheading The @code{-var-set-update-range} command
30276 @findex -var-set-update-range
30277 @anchor{-var-set-update-range}
30279 @subsubheading Synopsis
30282 -var-set-update-range @var{name} @var{from} @var{to}
30285 Set the range of children to be returned by future invocations of
30286 @code{-var-update}.
30288 @var{from} and @var{to} indicate the range of children to report. If
30289 @var{from} or @var{to} is less than zero, the range is reset and all
30290 children will be reported. Otherwise, children starting at @var{from}
30291 (zero-based) and up to and excluding @var{to} will be reported.
30293 @subsubheading Example
30297 -var-set-update-range V 1 2
30301 @subheading The @code{-var-set-visualizer} command
30302 @findex -var-set-visualizer
30303 @anchor{-var-set-visualizer}
30305 @subsubheading Synopsis
30308 -var-set-visualizer @var{name} @var{visualizer}
30311 Set a visualizer for the variable object @var{name}.
30313 @var{visualizer} is the visualizer to use. The special value
30314 @samp{None} means to disable any visualizer in use.
30316 If not @samp{None}, @var{visualizer} must be a Python expression.
30317 This expression must evaluate to a callable object which accepts a
30318 single argument. @value{GDBN} will call this object with the value of
30319 the varobj @var{name} as an argument (this is done so that the same
30320 Python pretty-printing code can be used for both the CLI and MI).
30321 When called, this object must return an object which conforms to the
30322 pretty-printing interface (@pxref{Pretty Printing API}).
30324 The pre-defined function @code{gdb.default_visualizer} may be used to
30325 select a visualizer by following the built-in process
30326 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30327 a varobj is created, and so ordinarily is not needed.
30329 This feature is only available if Python support is enabled. The MI
30330 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30331 can be used to check this.
30333 @subsubheading Example
30335 Resetting the visualizer:
30339 -var-set-visualizer V None
30343 Reselecting the default (type-based) visualizer:
30347 -var-set-visualizer V gdb.default_visualizer
30351 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30352 can be used to instantiate this class for a varobj:
30356 -var-set-visualizer V "lambda val: SomeClass()"
30360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30361 @node GDB/MI Data Manipulation
30362 @section @sc{gdb/mi} Data Manipulation
30364 @cindex data manipulation, in @sc{gdb/mi}
30365 @cindex @sc{gdb/mi}, data manipulation
30366 This section describes the @sc{gdb/mi} commands that manipulate data:
30367 examine memory and registers, evaluate expressions, etc.
30369 For details about what an addressable memory unit is,
30370 @pxref{addressable memory unit}.
30372 @c REMOVED FROM THE INTERFACE.
30373 @c @subheading -data-assign
30374 @c Change the value of a program variable. Plenty of side effects.
30375 @c @subsubheading GDB Command
30377 @c @subsubheading Example
30380 @subheading The @code{-data-disassemble} Command
30381 @findex -data-disassemble
30383 @subsubheading Synopsis
30387 [ -s @var{start-addr} -e @var{end-addr} ]
30388 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30396 @item @var{start-addr}
30397 is the beginning address (or @code{$pc})
30398 @item @var{end-addr}
30400 @item @var{filename}
30401 is the name of the file to disassemble
30402 @item @var{linenum}
30403 is the line number to disassemble around
30405 is the number of disassembly lines to be produced. If it is -1,
30406 the whole function will be disassembled, in case no @var{end-addr} is
30407 specified. If @var{end-addr} is specified as a non-zero value, and
30408 @var{lines} is lower than the number of disassembly lines between
30409 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30410 displayed; if @var{lines} is higher than the number of lines between
30411 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30416 @item 0 disassembly only
30417 @item 1 mixed source and disassembly (deprecated)
30418 @item 2 disassembly with raw opcodes
30419 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30420 @item 4 mixed source and disassembly
30421 @item 5 mixed source and disassembly with raw opcodes
30424 Modes 1 and 3 are deprecated. The output is ``source centric''
30425 which hasn't proved useful in practice.
30426 @xref{Machine Code}, for a discussion of the difference between
30427 @code{/m} and @code{/s} output of the @code{disassemble} command.
30430 @subsubheading Result
30432 The result of the @code{-data-disassemble} command will be a list named
30433 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30434 used with the @code{-data-disassemble} command.
30436 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30441 The address at which this instruction was disassembled.
30444 The name of the function this instruction is within.
30447 The decimal offset in bytes from the start of @samp{func-name}.
30450 The text disassembly for this @samp{address}.
30453 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30454 bytes for the @samp{inst} field.
30458 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30459 @samp{src_and_asm_line}, each of which has the following fields:
30463 The line number within @samp{file}.
30466 The file name from the compilation unit. This might be an absolute
30467 file name or a relative file name depending on the compile command
30471 Absolute file name of @samp{file}. It is converted to a canonical form
30472 using the source file search path
30473 (@pxref{Source Path, ,Specifying Source Directories})
30474 and after resolving all the symbolic links.
30476 If the source file is not found this field will contain the path as
30477 present in the debug information.
30479 @item line_asm_insn
30480 This is a list of tuples containing the disassembly for @samp{line} in
30481 @samp{file}. The fields of each tuple are the same as for
30482 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30483 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30488 Note that whatever included in the @samp{inst} field, is not
30489 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30492 @subsubheading @value{GDBN} Command
30494 The corresponding @value{GDBN} command is @samp{disassemble}.
30496 @subsubheading Example
30498 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30502 -data-disassemble -s $pc -e "$pc + 20" -- 0
30505 @{address="0x000107c0",func-name="main",offset="4",
30506 inst="mov 2, %o0"@},
30507 @{address="0x000107c4",func-name="main",offset="8",
30508 inst="sethi %hi(0x11800), %o2"@},
30509 @{address="0x000107c8",func-name="main",offset="12",
30510 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30511 @{address="0x000107cc",func-name="main",offset="16",
30512 inst="sethi %hi(0x11800), %o2"@},
30513 @{address="0x000107d0",func-name="main",offset="20",
30514 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30518 Disassemble the whole @code{main} function. Line 32 is part of
30522 -data-disassemble -f basics.c -l 32 -- 0
30524 @{address="0x000107bc",func-name="main",offset="0",
30525 inst="save %sp, -112, %sp"@},
30526 @{address="0x000107c0",func-name="main",offset="4",
30527 inst="mov 2, %o0"@},
30528 @{address="0x000107c4",func-name="main",offset="8",
30529 inst="sethi %hi(0x11800), %o2"@},
30531 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30532 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30536 Disassemble 3 instructions from the start of @code{main}:
30540 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30542 @{address="0x000107bc",func-name="main",offset="0",
30543 inst="save %sp, -112, %sp"@},
30544 @{address="0x000107c0",func-name="main",offset="4",
30545 inst="mov 2, %o0"@},
30546 @{address="0x000107c4",func-name="main",offset="8",
30547 inst="sethi %hi(0x11800), %o2"@}]
30551 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30555 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30557 src_and_asm_line=@{line="31",
30558 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30559 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30560 line_asm_insn=[@{address="0x000107bc",
30561 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30562 src_and_asm_line=@{line="32",
30563 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30564 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30565 line_asm_insn=[@{address="0x000107c0",
30566 func-name="main",offset="4",inst="mov 2, %o0"@},
30567 @{address="0x000107c4",func-name="main",offset="8",
30568 inst="sethi %hi(0x11800), %o2"@}]@}]
30573 @subheading The @code{-data-evaluate-expression} Command
30574 @findex -data-evaluate-expression
30576 @subsubheading Synopsis
30579 -data-evaluate-expression @var{expr}
30582 Evaluate @var{expr} as an expression. The expression could contain an
30583 inferior function call. The function call will execute synchronously.
30584 If the expression contains spaces, it must be enclosed in double quotes.
30586 @subsubheading @value{GDBN} Command
30588 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30589 @samp{call}. In @code{gdbtk} only, there's a corresponding
30590 @samp{gdb_eval} command.
30592 @subsubheading Example
30594 In the following example, the numbers that precede the commands are the
30595 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30596 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30600 211-data-evaluate-expression A
30603 311-data-evaluate-expression &A
30604 311^done,value="0xefffeb7c"
30606 411-data-evaluate-expression A+3
30609 511-data-evaluate-expression "A + 3"
30615 @subheading The @code{-data-list-changed-registers} Command
30616 @findex -data-list-changed-registers
30618 @subsubheading Synopsis
30621 -data-list-changed-registers
30624 Display a list of the registers that have changed.
30626 @subsubheading @value{GDBN} Command
30628 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30629 has the corresponding command @samp{gdb_changed_register_list}.
30631 @subsubheading Example
30633 On a PPC MBX board:
30641 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30642 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30645 -data-list-changed-registers
30646 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30647 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30648 "24","25","26","27","28","30","31","64","65","66","67","69"]
30653 @subheading The @code{-data-list-register-names} Command
30654 @findex -data-list-register-names
30656 @subsubheading Synopsis
30659 -data-list-register-names [ ( @var{regno} )+ ]
30662 Show a list of register names for the current target. If no arguments
30663 are given, it shows a list of the names of all the registers. If
30664 integer numbers are given as arguments, it will print a list of the
30665 names of the registers corresponding to the arguments. To ensure
30666 consistency between a register name and its number, the output list may
30667 include empty register names.
30669 @subsubheading @value{GDBN} Command
30671 @value{GDBN} does not have a command which corresponds to
30672 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30673 corresponding command @samp{gdb_regnames}.
30675 @subsubheading Example
30677 For the PPC MBX board:
30680 -data-list-register-names
30681 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30682 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30683 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30684 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30685 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30686 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30687 "", "pc","ps","cr","lr","ctr","xer"]
30689 -data-list-register-names 1 2 3
30690 ^done,register-names=["r1","r2","r3"]
30694 @subheading The @code{-data-list-register-values} Command
30695 @findex -data-list-register-values
30697 @subsubheading Synopsis
30700 -data-list-register-values
30701 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30704 Display the registers' contents. The format according to which the
30705 registers' contents are to be returned is given by @var{fmt}, followed
30706 by an optional list of numbers specifying the registers to display. A
30707 missing list of numbers indicates that the contents of all the
30708 registers must be returned. The @code{--skip-unavailable} option
30709 indicates that only the available registers are to be returned.
30711 Allowed formats for @var{fmt} are:
30728 @subsubheading @value{GDBN} Command
30730 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30731 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30733 @subsubheading Example
30735 For a PPC MBX board (note: line breaks are for readability only, they
30736 don't appear in the actual output):
30740 -data-list-register-values r 64 65
30741 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30742 @{number="65",value="0x00029002"@}]
30744 -data-list-register-values x
30745 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30746 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30747 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30748 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30749 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30750 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30751 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30752 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30753 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30754 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30755 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30756 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30757 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30758 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30759 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30760 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30761 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30762 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30763 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30764 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30765 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30766 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30767 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30768 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30769 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30770 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30771 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30772 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30773 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30774 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30775 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30776 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30777 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30778 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30779 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30780 @{number="69",value="0x20002b03"@}]
30785 @subheading The @code{-data-read-memory} Command
30786 @findex -data-read-memory
30788 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30790 @subsubheading Synopsis
30793 -data-read-memory [ -o @var{byte-offset} ]
30794 @var{address} @var{word-format} @var{word-size}
30795 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30802 @item @var{address}
30803 An expression specifying the address of the first memory word to be
30804 read. Complex expressions containing embedded white space should be
30805 quoted using the C convention.
30807 @item @var{word-format}
30808 The format to be used to print the memory words. The notation is the
30809 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30812 @item @var{word-size}
30813 The size of each memory word in bytes.
30815 @item @var{nr-rows}
30816 The number of rows in the output table.
30818 @item @var{nr-cols}
30819 The number of columns in the output table.
30822 If present, indicates that each row should include an @sc{ascii} dump. The
30823 value of @var{aschar} is used as a padding character when a byte is not a
30824 member of the printable @sc{ascii} character set (printable @sc{ascii}
30825 characters are those whose code is between 32 and 126, inclusively).
30827 @item @var{byte-offset}
30828 An offset to add to the @var{address} before fetching memory.
30831 This command displays memory contents as a table of @var{nr-rows} by
30832 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30833 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30834 (returned as @samp{total-bytes}). Should less than the requested number
30835 of bytes be returned by the target, the missing words are identified
30836 using @samp{N/A}. The number of bytes read from the target is returned
30837 in @samp{nr-bytes} and the starting address used to read memory in
30840 The address of the next/previous row or page is available in
30841 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30844 @subsubheading @value{GDBN} Command
30846 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30847 @samp{gdb_get_mem} memory read command.
30849 @subsubheading Example
30851 Read six bytes of memory starting at @code{bytes+6} but then offset by
30852 @code{-6} bytes. Format as three rows of two columns. One byte per
30853 word. Display each word in hex.
30857 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30858 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30859 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30860 prev-page="0x0000138a",memory=[
30861 @{addr="0x00001390",data=["0x00","0x01"]@},
30862 @{addr="0x00001392",data=["0x02","0x03"]@},
30863 @{addr="0x00001394",data=["0x04","0x05"]@}]
30867 Read two bytes of memory starting at address @code{shorts + 64} and
30868 display as a single word formatted in decimal.
30872 5-data-read-memory shorts+64 d 2 1 1
30873 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30874 next-row="0x00001512",prev-row="0x0000150e",
30875 next-page="0x00001512",prev-page="0x0000150e",memory=[
30876 @{addr="0x00001510",data=["128"]@}]
30880 Read thirty two bytes of memory starting at @code{bytes+16} and format
30881 as eight rows of four columns. Include a string encoding with @samp{x}
30882 used as the non-printable character.
30886 4-data-read-memory bytes+16 x 1 8 4 x
30887 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30888 next-row="0x000013c0",prev-row="0x0000139c",
30889 next-page="0x000013c0",prev-page="0x00001380",memory=[
30890 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30891 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30892 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30893 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30894 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30895 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30896 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30897 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30901 @subheading The @code{-data-read-memory-bytes} Command
30902 @findex -data-read-memory-bytes
30904 @subsubheading Synopsis
30907 -data-read-memory-bytes [ -o @var{offset} ]
30908 @var{address} @var{count}
30915 @item @var{address}
30916 An expression specifying the address of the first addressable memory unit
30917 to be read. Complex expressions containing embedded white space should be
30918 quoted using the C convention.
30921 The number of addressable memory units to read. This should be an integer
30925 The offset relative to @var{address} at which to start reading. This
30926 should be an integer literal. This option is provided so that a frontend
30927 is not required to first evaluate address and then perform address
30928 arithmetics itself.
30932 This command attempts to read all accessible memory regions in the
30933 specified range. First, all regions marked as unreadable in the memory
30934 map (if one is defined) will be skipped. @xref{Memory Region
30935 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30936 regions. For each one, if reading full region results in an errors,
30937 @value{GDBN} will try to read a subset of the region.
30939 In general, every single memory unit in the region may be readable or not,
30940 and the only way to read every readable unit is to try a read at
30941 every address, which is not practical. Therefore, @value{GDBN} will
30942 attempt to read all accessible memory units at either beginning or the end
30943 of the region, using a binary division scheme. This heuristic works
30944 well for reading accross a memory map boundary. Note that if a region
30945 has a readable range that is neither at the beginning or the end,
30946 @value{GDBN} will not read it.
30948 The result record (@pxref{GDB/MI Result Records}) that is output of
30949 the command includes a field named @samp{memory} whose content is a
30950 list of tuples. Each tuple represent a successfully read memory block
30951 and has the following fields:
30955 The start address of the memory block, as hexadecimal literal.
30958 The end address of the memory block, as hexadecimal literal.
30961 The offset of the memory block, as hexadecimal literal, relative to
30962 the start address passed to @code{-data-read-memory-bytes}.
30965 The contents of the memory block, in hex.
30971 @subsubheading @value{GDBN} Command
30973 The corresponding @value{GDBN} command is @samp{x}.
30975 @subsubheading Example
30979 -data-read-memory-bytes &a 10
30980 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30982 contents="01000000020000000300"@}]
30987 @subheading The @code{-data-write-memory-bytes} Command
30988 @findex -data-write-memory-bytes
30990 @subsubheading Synopsis
30993 -data-write-memory-bytes @var{address} @var{contents}
30994 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31001 @item @var{address}
31002 An expression specifying the address of the first addressable memory unit
31003 to be written. Complex expressions containing embedded white space should
31004 be quoted using the C convention.
31006 @item @var{contents}
31007 The hex-encoded data to write. It is an error if @var{contents} does
31008 not represent an integral number of addressable memory units.
31011 Optional argument indicating the number of addressable memory units to be
31012 written. If @var{count} is greater than @var{contents}' length,
31013 @value{GDBN} will repeatedly write @var{contents} until it fills
31014 @var{count} memory units.
31018 @subsubheading @value{GDBN} Command
31020 There's no corresponding @value{GDBN} command.
31022 @subsubheading Example
31026 -data-write-memory-bytes &a "aabbccdd"
31033 -data-write-memory-bytes &a "aabbccdd" 16e
31038 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31039 @node GDB/MI Tracepoint Commands
31040 @section @sc{gdb/mi} Tracepoint Commands
31042 The commands defined in this section implement MI support for
31043 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31045 @subheading The @code{-trace-find} Command
31046 @findex -trace-find
31048 @subsubheading Synopsis
31051 -trace-find @var{mode} [@var{parameters}@dots{}]
31054 Find a trace frame using criteria defined by @var{mode} and
31055 @var{parameters}. The following table lists permissible
31056 modes and their parameters. For details of operation, see @ref{tfind}.
31061 No parameters are required. Stops examining trace frames.
31064 An integer is required as parameter. Selects tracepoint frame with
31067 @item tracepoint-number
31068 An integer is required as parameter. Finds next
31069 trace frame that corresponds to tracepoint with the specified number.
31072 An address is required as parameter. Finds
31073 next trace frame that corresponds to any tracepoint at the specified
31076 @item pc-inside-range
31077 Two addresses are required as parameters. Finds next trace
31078 frame that corresponds to a tracepoint at an address inside the
31079 specified range. Both bounds are considered to be inside the range.
31081 @item pc-outside-range
31082 Two addresses are required as parameters. Finds
31083 next trace frame that corresponds to a tracepoint at an address outside
31084 the specified range. Both bounds are considered to be inside the range.
31087 Line specification is required as parameter. @xref{Specify Location}.
31088 Finds next trace frame that corresponds to a tracepoint at
31089 the specified location.
31093 If @samp{none} was passed as @var{mode}, the response does not
31094 have fields. Otherwise, the response may have the following fields:
31098 This field has either @samp{0} or @samp{1} as the value, depending
31099 on whether a matching tracepoint was found.
31102 The index of the found traceframe. This field is present iff
31103 the @samp{found} field has value of @samp{1}.
31106 The index of the found tracepoint. This field is present iff
31107 the @samp{found} field has value of @samp{1}.
31110 The information about the frame corresponding to the found trace
31111 frame. This field is present only if a trace frame was found.
31112 @xref{GDB/MI Frame Information}, for description of this field.
31116 @subsubheading @value{GDBN} Command
31118 The corresponding @value{GDBN} command is @samp{tfind}.
31120 @subheading -trace-define-variable
31121 @findex -trace-define-variable
31123 @subsubheading Synopsis
31126 -trace-define-variable @var{name} [ @var{value} ]
31129 Create trace variable @var{name} if it does not exist. If
31130 @var{value} is specified, sets the initial value of the specified
31131 trace variable to that value. Note that the @var{name} should start
31132 with the @samp{$} character.
31134 @subsubheading @value{GDBN} Command
31136 The corresponding @value{GDBN} command is @samp{tvariable}.
31138 @subheading The @code{-trace-frame-collected} Command
31139 @findex -trace-frame-collected
31141 @subsubheading Synopsis
31144 -trace-frame-collected
31145 [--var-print-values @var{var_pval}]
31146 [--comp-print-values @var{comp_pval}]
31147 [--registers-format @var{regformat}]
31148 [--memory-contents]
31151 This command returns the set of collected objects, register names,
31152 trace state variable names, memory ranges and computed expressions
31153 that have been collected at a particular trace frame. The optional
31154 parameters to the command affect the output format in different ways.
31155 See the output description table below for more details.
31157 The reported names can be used in the normal manner to create
31158 varobjs and inspect the objects themselves. The items returned by
31159 this command are categorized so that it is clear which is a variable,
31160 which is a register, which is a trace state variable, which is a
31161 memory range and which is a computed expression.
31163 For instance, if the actions were
31165 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31166 collect *(int*)0xaf02bef0@@40
31170 the object collected in its entirety would be @code{myVar}. The
31171 object @code{myArray} would be partially collected, because only the
31172 element at index @code{myIndex} would be collected. The remaining
31173 objects would be computed expressions.
31175 An example output would be:
31179 -trace-frame-collected
31181 explicit-variables=[@{name="myVar",value="1"@}],
31182 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31183 @{name="myObj.field",value="0"@},
31184 @{name="myPtr->field",value="1"@},
31185 @{name="myCount + 2",value="3"@},
31186 @{name="$tvar1 + 1",value="43970027"@}],
31187 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31188 @{number="1",value="0x0"@},
31189 @{number="2",value="0x4"@},
31191 @{number="125",value="0x0"@}],
31192 tvars=[@{name="$tvar1",current="43970026"@}],
31193 memory=[@{address="0x0000000000602264",length="4"@},
31194 @{address="0x0000000000615bc0",length="4"@}]
31201 @item explicit-variables
31202 The set of objects that have been collected in their entirety (as
31203 opposed to collecting just a few elements of an array or a few struct
31204 members). For each object, its name and value are printed.
31205 The @code{--var-print-values} option affects how or whether the value
31206 field is output. If @var{var_pval} is 0, then print only the names;
31207 if it is 1, print also their values; and if it is 2, print the name,
31208 type and value for simple data types, and the name and type for
31209 arrays, structures and unions.
31211 @item computed-expressions
31212 The set of computed expressions that have been collected at the
31213 current trace frame. The @code{--comp-print-values} option affects
31214 this set like the @code{--var-print-values} option affects the
31215 @code{explicit-variables} set. See above.
31218 The registers that have been collected at the current trace frame.
31219 For each register collected, the name and current value are returned.
31220 The value is formatted according to the @code{--registers-format}
31221 option. See the @command{-data-list-register-values} command for a
31222 list of the allowed formats. The default is @samp{x}.
31225 The trace state variables that have been collected at the current
31226 trace frame. For each trace state variable collected, the name and
31227 current value are returned.
31230 The set of memory ranges that have been collected at the current trace
31231 frame. Its content is a list of tuples. Each tuple represents a
31232 collected memory range and has the following fields:
31236 The start address of the memory range, as hexadecimal literal.
31239 The length of the memory range, as decimal literal.
31242 The contents of the memory block, in hex. This field is only present
31243 if the @code{--memory-contents} option is specified.
31249 @subsubheading @value{GDBN} Command
31251 There is no corresponding @value{GDBN} command.
31253 @subsubheading Example
31255 @subheading -trace-list-variables
31256 @findex -trace-list-variables
31258 @subsubheading Synopsis
31261 -trace-list-variables
31264 Return a table of all defined trace variables. Each element of the
31265 table has the following fields:
31269 The name of the trace variable. This field is always present.
31272 The initial value. This is a 64-bit signed integer. This
31273 field is always present.
31276 The value the trace variable has at the moment. This is a 64-bit
31277 signed integer. This field is absent iff current value is
31278 not defined, for example if the trace was never run, or is
31283 @subsubheading @value{GDBN} Command
31285 The corresponding @value{GDBN} command is @samp{tvariables}.
31287 @subsubheading Example
31291 -trace-list-variables
31292 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31293 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31294 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31295 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31296 body=[variable=@{name="$trace_timestamp",initial="0"@}
31297 variable=@{name="$foo",initial="10",current="15"@}]@}
31301 @subheading -trace-save
31302 @findex -trace-save
31304 @subsubheading Synopsis
31307 -trace-save [ -r ] [ -ctf ] @var{filename}
31310 Saves the collected trace data to @var{filename}. Without the
31311 @samp{-r} option, the data is downloaded from the target and saved
31312 in a local file. With the @samp{-r} option the target is asked
31313 to perform the save.
31315 By default, this command will save the trace in the tfile format. You can
31316 supply the optional @samp{-ctf} argument to save it the CTF format. See
31317 @ref{Trace Files} for more information about CTF.
31319 @subsubheading @value{GDBN} Command
31321 The corresponding @value{GDBN} command is @samp{tsave}.
31324 @subheading -trace-start
31325 @findex -trace-start
31327 @subsubheading Synopsis
31333 Starts a tracing experiment. The result of this command does not
31336 @subsubheading @value{GDBN} Command
31338 The corresponding @value{GDBN} command is @samp{tstart}.
31340 @subheading -trace-status
31341 @findex -trace-status
31343 @subsubheading Synopsis
31349 Obtains the status of a tracing experiment. The result may include
31350 the following fields:
31355 May have a value of either @samp{0}, when no tracing operations are
31356 supported, @samp{1}, when all tracing operations are supported, or
31357 @samp{file} when examining trace file. In the latter case, examining
31358 of trace frame is possible but new tracing experiement cannot be
31359 started. This field is always present.
31362 May have a value of either @samp{0} or @samp{1} depending on whether
31363 tracing experiement is in progress on target. This field is present
31364 if @samp{supported} field is not @samp{0}.
31367 Report the reason why the tracing was stopped last time. This field
31368 may be absent iff tracing was never stopped on target yet. The
31369 value of @samp{request} means the tracing was stopped as result of
31370 the @code{-trace-stop} command. The value of @samp{overflow} means
31371 the tracing buffer is full. The value of @samp{disconnection} means
31372 tracing was automatically stopped when @value{GDBN} has disconnected.
31373 The value of @samp{passcount} means tracing was stopped when a
31374 tracepoint was passed a maximal number of times for that tracepoint.
31375 This field is present if @samp{supported} field is not @samp{0}.
31377 @item stopping-tracepoint
31378 The number of tracepoint whose passcount as exceeded. This field is
31379 present iff the @samp{stop-reason} field has the value of
31383 @itemx frames-created
31384 The @samp{frames} field is a count of the total number of trace frames
31385 in the trace buffer, while @samp{frames-created} is the total created
31386 during the run, including ones that were discarded, such as when a
31387 circular trace buffer filled up. Both fields are optional.
31391 These fields tell the current size of the tracing buffer and the
31392 remaining space. These fields are optional.
31395 The value of the circular trace buffer flag. @code{1} means that the
31396 trace buffer is circular and old trace frames will be discarded if
31397 necessary to make room, @code{0} means that the trace buffer is linear
31401 The value of the disconnected tracing flag. @code{1} means that
31402 tracing will continue after @value{GDBN} disconnects, @code{0} means
31403 that the trace run will stop.
31406 The filename of the trace file being examined. This field is
31407 optional, and only present when examining a trace file.
31411 @subsubheading @value{GDBN} Command
31413 The corresponding @value{GDBN} command is @samp{tstatus}.
31415 @subheading -trace-stop
31416 @findex -trace-stop
31418 @subsubheading Synopsis
31424 Stops a tracing experiment. The result of this command has the same
31425 fields as @code{-trace-status}, except that the @samp{supported} and
31426 @samp{running} fields are not output.
31428 @subsubheading @value{GDBN} Command
31430 The corresponding @value{GDBN} command is @samp{tstop}.
31433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31434 @node GDB/MI Symbol Query
31435 @section @sc{gdb/mi} Symbol Query Commands
31439 @subheading The @code{-symbol-info-address} Command
31440 @findex -symbol-info-address
31442 @subsubheading Synopsis
31445 -symbol-info-address @var{symbol}
31448 Describe where @var{symbol} is stored.
31450 @subsubheading @value{GDBN} Command
31452 The corresponding @value{GDBN} command is @samp{info address}.
31454 @subsubheading Example
31458 @subheading The @code{-symbol-info-file} Command
31459 @findex -symbol-info-file
31461 @subsubheading Synopsis
31467 Show the file for the symbol.
31469 @subsubheading @value{GDBN} Command
31471 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31472 @samp{gdb_find_file}.
31474 @subsubheading Example
31478 @subheading The @code{-symbol-info-function} Command
31479 @findex -symbol-info-function
31481 @subsubheading Synopsis
31484 -symbol-info-function
31487 Show which function the symbol lives in.
31489 @subsubheading @value{GDBN} Command
31491 @samp{gdb_get_function} in @code{gdbtk}.
31493 @subsubheading Example
31497 @subheading The @code{-symbol-info-line} Command
31498 @findex -symbol-info-line
31500 @subsubheading Synopsis
31506 Show the core addresses of the code for a source line.
31508 @subsubheading @value{GDBN} Command
31510 The corresponding @value{GDBN} command is @samp{info line}.
31511 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31513 @subsubheading Example
31517 @subheading The @code{-symbol-info-symbol} Command
31518 @findex -symbol-info-symbol
31520 @subsubheading Synopsis
31523 -symbol-info-symbol @var{addr}
31526 Describe what symbol is at location @var{addr}.
31528 @subsubheading @value{GDBN} Command
31530 The corresponding @value{GDBN} command is @samp{info symbol}.
31532 @subsubheading Example
31536 @subheading The @code{-symbol-list-functions} Command
31537 @findex -symbol-list-functions
31539 @subsubheading Synopsis
31542 -symbol-list-functions
31545 List the functions in the executable.
31547 @subsubheading @value{GDBN} Command
31549 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31550 @samp{gdb_search} in @code{gdbtk}.
31552 @subsubheading Example
31557 @subheading The @code{-symbol-list-lines} Command
31558 @findex -symbol-list-lines
31560 @subsubheading Synopsis
31563 -symbol-list-lines @var{filename}
31566 Print the list of lines that contain code and their associated program
31567 addresses for the given source filename. The entries are sorted in
31568 ascending PC order.
31570 @subsubheading @value{GDBN} Command
31572 There is no corresponding @value{GDBN} command.
31574 @subsubheading Example
31577 -symbol-list-lines basics.c
31578 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31584 @subheading The @code{-symbol-list-types} Command
31585 @findex -symbol-list-types
31587 @subsubheading Synopsis
31593 List all the type names.
31595 @subsubheading @value{GDBN} Command
31597 The corresponding commands are @samp{info types} in @value{GDBN},
31598 @samp{gdb_search} in @code{gdbtk}.
31600 @subsubheading Example
31604 @subheading The @code{-symbol-list-variables} Command
31605 @findex -symbol-list-variables
31607 @subsubheading Synopsis
31610 -symbol-list-variables
31613 List all the global and static variable names.
31615 @subsubheading @value{GDBN} Command
31617 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31619 @subsubheading Example
31623 @subheading The @code{-symbol-locate} Command
31624 @findex -symbol-locate
31626 @subsubheading Synopsis
31632 @subsubheading @value{GDBN} Command
31634 @samp{gdb_loc} in @code{gdbtk}.
31636 @subsubheading Example
31640 @subheading The @code{-symbol-type} Command
31641 @findex -symbol-type
31643 @subsubheading Synopsis
31646 -symbol-type @var{variable}
31649 Show type of @var{variable}.
31651 @subsubheading @value{GDBN} Command
31653 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31654 @samp{gdb_obj_variable}.
31656 @subsubheading Example
31661 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31662 @node GDB/MI File Commands
31663 @section @sc{gdb/mi} File Commands
31665 This section describes the GDB/MI commands to specify executable file names
31666 and to read in and obtain symbol table information.
31668 @subheading The @code{-file-exec-and-symbols} Command
31669 @findex -file-exec-and-symbols
31671 @subsubheading Synopsis
31674 -file-exec-and-symbols @var{file}
31677 Specify the executable file to be debugged. This file is the one from
31678 which the symbol table is also read. If no file is specified, the
31679 command clears the executable and symbol information. If breakpoints
31680 are set when using this command with no arguments, @value{GDBN} will produce
31681 error messages. Otherwise, no output is produced, except a completion
31684 @subsubheading @value{GDBN} Command
31686 The corresponding @value{GDBN} command is @samp{file}.
31688 @subsubheading Example
31692 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31698 @subheading The @code{-file-exec-file} Command
31699 @findex -file-exec-file
31701 @subsubheading Synopsis
31704 -file-exec-file @var{file}
31707 Specify the executable file to be debugged. Unlike
31708 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31709 from this file. If used without argument, @value{GDBN} clears the information
31710 about the executable file. No output is produced, except a completion
31713 @subsubheading @value{GDBN} Command
31715 The corresponding @value{GDBN} command is @samp{exec-file}.
31717 @subsubheading Example
31721 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31728 @subheading The @code{-file-list-exec-sections} Command
31729 @findex -file-list-exec-sections
31731 @subsubheading Synopsis
31734 -file-list-exec-sections
31737 List the sections of the current executable file.
31739 @subsubheading @value{GDBN} Command
31741 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31742 information as this command. @code{gdbtk} has a corresponding command
31743 @samp{gdb_load_info}.
31745 @subsubheading Example
31750 @subheading The @code{-file-list-exec-source-file} Command
31751 @findex -file-list-exec-source-file
31753 @subsubheading Synopsis
31756 -file-list-exec-source-file
31759 List the line number, the current source file, and the absolute path
31760 to the current source file for the current executable. The macro
31761 information field has a value of @samp{1} or @samp{0} depending on
31762 whether or not the file includes preprocessor macro information.
31764 @subsubheading @value{GDBN} Command
31766 The @value{GDBN} equivalent is @samp{info source}
31768 @subsubheading Example
31772 123-file-list-exec-source-file
31773 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31778 @subheading The @code{-file-list-exec-source-files} Command
31779 @findex -file-list-exec-source-files
31781 @subsubheading Synopsis
31784 -file-list-exec-source-files
31787 List the source files for the current executable.
31789 It will always output both the filename and fullname (absolute file
31790 name) of a source file.
31792 @subsubheading @value{GDBN} Command
31794 The @value{GDBN} equivalent is @samp{info sources}.
31795 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31797 @subsubheading Example
31800 -file-list-exec-source-files
31802 @{file=foo.c,fullname=/home/foo.c@},
31803 @{file=/home/bar.c,fullname=/home/bar.c@},
31804 @{file=gdb_could_not_find_fullpath.c@}]
31808 @subheading The @code{-file-list-shared-libraries} Command
31809 @findex -file-list-shared-libraries
31811 @subsubheading Synopsis
31814 -file-list-shared-libraries [ @var{regexp} ]
31817 List the shared libraries in the program.
31818 With a regular expression @var{regexp}, only those libraries whose
31819 names match @var{regexp} are listed.
31821 @subsubheading @value{GDBN} Command
31823 The corresponding @value{GDBN} command is @samp{info shared}. The fields
31824 have a similar meaning to the @code{=library-loaded} notification.
31825 The @code{ranges} field specifies the multiple segments belonging to this
31826 library. Each range has the following fields:
31830 The address defining the inclusive lower bound of the segment.
31832 The address defining the exclusive upper bound of the segment.
31835 @subsubheading Example
31838 -file-list-exec-source-files
31839 ^done,shared-libraries=[
31840 @{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
31841 @{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
31847 @subheading The @code{-file-list-symbol-files} Command
31848 @findex -file-list-symbol-files
31850 @subsubheading Synopsis
31853 -file-list-symbol-files
31858 @subsubheading @value{GDBN} Command
31860 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31862 @subsubheading Example
31867 @subheading The @code{-file-symbol-file} Command
31868 @findex -file-symbol-file
31870 @subsubheading Synopsis
31873 -file-symbol-file @var{file}
31876 Read symbol table info from the specified @var{file} argument. When
31877 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31878 produced, except for a completion notification.
31880 @subsubheading @value{GDBN} Command
31882 The corresponding @value{GDBN} command is @samp{symbol-file}.
31884 @subsubheading Example
31888 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31894 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31895 @node GDB/MI Memory Overlay Commands
31896 @section @sc{gdb/mi} Memory Overlay Commands
31898 The memory overlay commands are not implemented.
31900 @c @subheading -overlay-auto
31902 @c @subheading -overlay-list-mapping-state
31904 @c @subheading -overlay-list-overlays
31906 @c @subheading -overlay-map
31908 @c @subheading -overlay-off
31910 @c @subheading -overlay-on
31912 @c @subheading -overlay-unmap
31914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31915 @node GDB/MI Signal Handling Commands
31916 @section @sc{gdb/mi} Signal Handling Commands
31918 Signal handling commands are not implemented.
31920 @c @subheading -signal-handle
31922 @c @subheading -signal-list-handle-actions
31924 @c @subheading -signal-list-signal-types
31928 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31929 @node GDB/MI Target Manipulation
31930 @section @sc{gdb/mi} Target Manipulation Commands
31933 @subheading The @code{-target-attach} Command
31934 @findex -target-attach
31936 @subsubheading Synopsis
31939 -target-attach @var{pid} | @var{gid} | @var{file}
31942 Attach to a process @var{pid} or a file @var{file} outside of
31943 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31944 group, the id previously returned by
31945 @samp{-list-thread-groups --available} must be used.
31947 @subsubheading @value{GDBN} Command
31949 The corresponding @value{GDBN} command is @samp{attach}.
31951 @subsubheading Example
31955 =thread-created,id="1"
31956 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31962 @subheading The @code{-target-compare-sections} Command
31963 @findex -target-compare-sections
31965 @subsubheading Synopsis
31968 -target-compare-sections [ @var{section} ]
31971 Compare data of section @var{section} on target to the exec file.
31972 Without the argument, all sections are compared.
31974 @subsubheading @value{GDBN} Command
31976 The @value{GDBN} equivalent is @samp{compare-sections}.
31978 @subsubheading Example
31983 @subheading The @code{-target-detach} Command
31984 @findex -target-detach
31986 @subsubheading Synopsis
31989 -target-detach [ @var{pid} | @var{gid} ]
31992 Detach from the remote target which normally resumes its execution.
31993 If either @var{pid} or @var{gid} is specified, detaches from either
31994 the specified process, or specified thread group. There's no output.
31996 @subsubheading @value{GDBN} Command
31998 The corresponding @value{GDBN} command is @samp{detach}.
32000 @subsubheading Example
32010 @subheading The @code{-target-disconnect} Command
32011 @findex -target-disconnect
32013 @subsubheading Synopsis
32019 Disconnect from the remote target. There's no output and the target is
32020 generally not resumed.
32022 @subsubheading @value{GDBN} Command
32024 The corresponding @value{GDBN} command is @samp{disconnect}.
32026 @subsubheading Example
32036 @subheading The @code{-target-download} Command
32037 @findex -target-download
32039 @subsubheading Synopsis
32045 Loads the executable onto the remote target.
32046 It prints out an update message every half second, which includes the fields:
32050 The name of the section.
32052 The size of what has been sent so far for that section.
32054 The size of the section.
32056 The total size of what was sent so far (the current and the previous sections).
32058 The size of the overall executable to download.
32062 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32063 @sc{gdb/mi} Output Syntax}).
32065 In addition, it prints the name and size of the sections, as they are
32066 downloaded. These messages include the following fields:
32070 The name of the section.
32072 The size of the section.
32074 The size of the overall executable to download.
32078 At the end, a summary is printed.
32080 @subsubheading @value{GDBN} Command
32082 The corresponding @value{GDBN} command is @samp{load}.
32084 @subsubheading Example
32086 Note: each status message appears on a single line. Here the messages
32087 have been broken down so that they can fit onto a page.
32092 +download,@{section=".text",section-size="6668",total-size="9880"@}
32093 +download,@{section=".text",section-sent="512",section-size="6668",
32094 total-sent="512",total-size="9880"@}
32095 +download,@{section=".text",section-sent="1024",section-size="6668",
32096 total-sent="1024",total-size="9880"@}
32097 +download,@{section=".text",section-sent="1536",section-size="6668",
32098 total-sent="1536",total-size="9880"@}
32099 +download,@{section=".text",section-sent="2048",section-size="6668",
32100 total-sent="2048",total-size="9880"@}
32101 +download,@{section=".text",section-sent="2560",section-size="6668",
32102 total-sent="2560",total-size="9880"@}
32103 +download,@{section=".text",section-sent="3072",section-size="6668",
32104 total-sent="3072",total-size="9880"@}
32105 +download,@{section=".text",section-sent="3584",section-size="6668",
32106 total-sent="3584",total-size="9880"@}
32107 +download,@{section=".text",section-sent="4096",section-size="6668",
32108 total-sent="4096",total-size="9880"@}
32109 +download,@{section=".text",section-sent="4608",section-size="6668",
32110 total-sent="4608",total-size="9880"@}
32111 +download,@{section=".text",section-sent="5120",section-size="6668",
32112 total-sent="5120",total-size="9880"@}
32113 +download,@{section=".text",section-sent="5632",section-size="6668",
32114 total-sent="5632",total-size="9880"@}
32115 +download,@{section=".text",section-sent="6144",section-size="6668",
32116 total-sent="6144",total-size="9880"@}
32117 +download,@{section=".text",section-sent="6656",section-size="6668",
32118 total-sent="6656",total-size="9880"@}
32119 +download,@{section=".init",section-size="28",total-size="9880"@}
32120 +download,@{section=".fini",section-size="28",total-size="9880"@}
32121 +download,@{section=".data",section-size="3156",total-size="9880"@}
32122 +download,@{section=".data",section-sent="512",section-size="3156",
32123 total-sent="7236",total-size="9880"@}
32124 +download,@{section=".data",section-sent="1024",section-size="3156",
32125 total-sent="7748",total-size="9880"@}
32126 +download,@{section=".data",section-sent="1536",section-size="3156",
32127 total-sent="8260",total-size="9880"@}
32128 +download,@{section=".data",section-sent="2048",section-size="3156",
32129 total-sent="8772",total-size="9880"@}
32130 +download,@{section=".data",section-sent="2560",section-size="3156",
32131 total-sent="9284",total-size="9880"@}
32132 +download,@{section=".data",section-sent="3072",section-size="3156",
32133 total-sent="9796",total-size="9880"@}
32134 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32141 @subheading The @code{-target-exec-status} Command
32142 @findex -target-exec-status
32144 @subsubheading Synopsis
32147 -target-exec-status
32150 Provide information on the state of the target (whether it is running or
32151 not, for instance).
32153 @subsubheading @value{GDBN} Command
32155 There's no equivalent @value{GDBN} command.
32157 @subsubheading Example
32161 @subheading The @code{-target-list-available-targets} Command
32162 @findex -target-list-available-targets
32164 @subsubheading Synopsis
32167 -target-list-available-targets
32170 List the possible targets to connect to.
32172 @subsubheading @value{GDBN} Command
32174 The corresponding @value{GDBN} command is @samp{help target}.
32176 @subsubheading Example
32180 @subheading The @code{-target-list-current-targets} Command
32181 @findex -target-list-current-targets
32183 @subsubheading Synopsis
32186 -target-list-current-targets
32189 Describe the current target.
32191 @subsubheading @value{GDBN} Command
32193 The corresponding information is printed by @samp{info file} (among
32196 @subsubheading Example
32200 @subheading The @code{-target-list-parameters} Command
32201 @findex -target-list-parameters
32203 @subsubheading Synopsis
32206 -target-list-parameters
32212 @subsubheading @value{GDBN} Command
32216 @subsubheading Example
32219 @subheading The @code{-target-flash-erase} Command
32220 @findex -target-flash-erase
32222 @subsubheading Synopsis
32225 -target-flash-erase
32228 Erases all known flash memory regions on the target.
32230 The corresponding @value{GDBN} command is @samp{flash-erase}.
32232 The output is a list of flash regions that have been erased, with starting
32233 addresses and memory region sizes.
32237 -target-flash-erase
32238 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32242 @subheading The @code{-target-select} Command
32243 @findex -target-select
32245 @subsubheading Synopsis
32248 -target-select @var{type} @var{parameters @dots{}}
32251 Connect @value{GDBN} to the remote target. This command takes two args:
32255 The type of target, for instance @samp{remote}, etc.
32256 @item @var{parameters}
32257 Device names, host names and the like. @xref{Target Commands, ,
32258 Commands for Managing Targets}, for more details.
32261 The output is a connection notification, followed by the address at
32262 which the target program is, in the following form:
32265 ^connected,addr="@var{address}",func="@var{function name}",
32266 args=[@var{arg list}]
32269 @subsubheading @value{GDBN} Command
32271 The corresponding @value{GDBN} command is @samp{target}.
32273 @subsubheading Example
32277 -target-select remote /dev/ttya
32278 ^connected,addr="0xfe00a300",func="??",args=[]
32282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32283 @node GDB/MI File Transfer Commands
32284 @section @sc{gdb/mi} File Transfer Commands
32287 @subheading The @code{-target-file-put} Command
32288 @findex -target-file-put
32290 @subsubheading Synopsis
32293 -target-file-put @var{hostfile} @var{targetfile}
32296 Copy file @var{hostfile} from the host system (the machine running
32297 @value{GDBN}) to @var{targetfile} on the target system.
32299 @subsubheading @value{GDBN} Command
32301 The corresponding @value{GDBN} command is @samp{remote put}.
32303 @subsubheading Example
32307 -target-file-put localfile remotefile
32313 @subheading The @code{-target-file-get} Command
32314 @findex -target-file-get
32316 @subsubheading Synopsis
32319 -target-file-get @var{targetfile} @var{hostfile}
32322 Copy file @var{targetfile} from the target system to @var{hostfile}
32323 on the host system.
32325 @subsubheading @value{GDBN} Command
32327 The corresponding @value{GDBN} command is @samp{remote get}.
32329 @subsubheading Example
32333 -target-file-get remotefile localfile
32339 @subheading The @code{-target-file-delete} Command
32340 @findex -target-file-delete
32342 @subsubheading Synopsis
32345 -target-file-delete @var{targetfile}
32348 Delete @var{targetfile} from the target system.
32350 @subsubheading @value{GDBN} Command
32352 The corresponding @value{GDBN} command is @samp{remote delete}.
32354 @subsubheading Example
32358 -target-file-delete remotefile
32364 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32365 @node GDB/MI Ada Exceptions Commands
32366 @section Ada Exceptions @sc{gdb/mi} Commands
32368 @subheading The @code{-info-ada-exceptions} Command
32369 @findex -info-ada-exceptions
32371 @subsubheading Synopsis
32374 -info-ada-exceptions [ @var{regexp}]
32377 List all Ada exceptions defined within the program being debugged.
32378 With a regular expression @var{regexp}, only those exceptions whose
32379 names match @var{regexp} are listed.
32381 @subsubheading @value{GDBN} Command
32383 The corresponding @value{GDBN} command is @samp{info exceptions}.
32385 @subsubheading Result
32387 The result is a table of Ada exceptions. The following columns are
32388 defined for each exception:
32392 The name of the exception.
32395 The address of the exception.
32399 @subsubheading Example
32402 -info-ada-exceptions aint
32403 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32404 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32405 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32406 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32407 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32410 @subheading Catching Ada Exceptions
32412 The commands describing how to ask @value{GDBN} to stop when a program
32413 raises an exception are described at @ref{Ada Exception GDB/MI
32414 Catchpoint Commands}.
32417 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32418 @node GDB/MI Support Commands
32419 @section @sc{gdb/mi} Support Commands
32421 Since new commands and features get regularly added to @sc{gdb/mi},
32422 some commands are available to help front-ends query the debugger
32423 about support for these capabilities. Similarly, it is also possible
32424 to query @value{GDBN} about target support of certain features.
32426 @subheading The @code{-info-gdb-mi-command} Command
32427 @cindex @code{-info-gdb-mi-command}
32428 @findex -info-gdb-mi-command
32430 @subsubheading Synopsis
32433 -info-gdb-mi-command @var{cmd_name}
32436 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32438 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32439 is technically not part of the command name (@pxref{GDB/MI Input
32440 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32441 for ease of use, this command also accepts the form with the leading
32444 @subsubheading @value{GDBN} Command
32446 There is no corresponding @value{GDBN} command.
32448 @subsubheading Result
32450 The result is a tuple. There is currently only one field:
32454 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32455 @code{"false"} otherwise.
32459 @subsubheading Example
32461 Here is an example where the @sc{gdb/mi} command does not exist:
32464 -info-gdb-mi-command unsupported-command
32465 ^done,command=@{exists="false"@}
32469 And here is an example where the @sc{gdb/mi} command is known
32473 -info-gdb-mi-command symbol-list-lines
32474 ^done,command=@{exists="true"@}
32477 @subheading The @code{-list-features} Command
32478 @findex -list-features
32479 @cindex supported @sc{gdb/mi} features, list
32481 Returns a list of particular features of the MI protocol that
32482 this version of gdb implements. A feature can be a command,
32483 or a new field in an output of some command, or even an
32484 important bugfix. While a frontend can sometimes detect presence
32485 of a feature at runtime, it is easier to perform detection at debugger
32488 The command returns a list of strings, with each string naming an
32489 available feature. Each returned string is just a name, it does not
32490 have any internal structure. The list of possible feature names
32496 (gdb) -list-features
32497 ^done,result=["feature1","feature2"]
32500 The current list of features is:
32503 @item frozen-varobjs
32504 Indicates support for the @code{-var-set-frozen} command, as well
32505 as possible presense of the @code{frozen} field in the output
32506 of @code{-varobj-create}.
32507 @item pending-breakpoints
32508 Indicates support for the @option{-f} option to the @code{-break-insert}
32511 Indicates Python scripting support, Python-based
32512 pretty-printing commands, and possible presence of the
32513 @samp{display_hint} field in the output of @code{-var-list-children}
32515 Indicates support for the @code{-thread-info} command.
32516 @item data-read-memory-bytes
32517 Indicates support for the @code{-data-read-memory-bytes} and the
32518 @code{-data-write-memory-bytes} commands.
32519 @item breakpoint-notifications
32520 Indicates that changes to breakpoints and breakpoints created via the
32521 CLI will be announced via async records.
32522 @item ada-task-info
32523 Indicates support for the @code{-ada-task-info} command.
32524 @item language-option
32525 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32526 option (@pxref{Context management}).
32527 @item info-gdb-mi-command
32528 Indicates support for the @code{-info-gdb-mi-command} command.
32529 @item undefined-command-error-code
32530 Indicates support for the "undefined-command" error code in error result
32531 records, produced when trying to execute an undefined @sc{gdb/mi} command
32532 (@pxref{GDB/MI Result Records}).
32533 @item exec-run-start-option
32534 Indicates that the @code{-exec-run} command supports the @option{--start}
32535 option (@pxref{GDB/MI Program Execution}).
32538 @subheading The @code{-list-target-features} Command
32539 @findex -list-target-features
32541 Returns a list of particular features that are supported by the
32542 target. Those features affect the permitted MI commands, but
32543 unlike the features reported by the @code{-list-features} command, the
32544 features depend on which target GDB is using at the moment. Whenever
32545 a target can change, due to commands such as @code{-target-select},
32546 @code{-target-attach} or @code{-exec-run}, the list of target features
32547 may change, and the frontend should obtain it again.
32551 (gdb) -list-target-features
32552 ^done,result=["async"]
32555 The current list of features is:
32559 Indicates that the target is capable of asynchronous command
32560 execution, which means that @value{GDBN} will accept further commands
32561 while the target is running.
32564 Indicates that the target is capable of reverse execution.
32565 @xref{Reverse Execution}, for more information.
32569 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32570 @node GDB/MI Miscellaneous Commands
32571 @section Miscellaneous @sc{gdb/mi} Commands
32573 @c @subheading -gdb-complete
32575 @subheading The @code{-gdb-exit} Command
32578 @subsubheading Synopsis
32584 Exit @value{GDBN} immediately.
32586 @subsubheading @value{GDBN} Command
32588 Approximately corresponds to @samp{quit}.
32590 @subsubheading Example
32600 @subheading The @code{-exec-abort} Command
32601 @findex -exec-abort
32603 @subsubheading Synopsis
32609 Kill the inferior running program.
32611 @subsubheading @value{GDBN} Command
32613 The corresponding @value{GDBN} command is @samp{kill}.
32615 @subsubheading Example
32620 @subheading The @code{-gdb-set} Command
32623 @subsubheading Synopsis
32629 Set an internal @value{GDBN} variable.
32630 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32632 @subsubheading @value{GDBN} Command
32634 The corresponding @value{GDBN} command is @samp{set}.
32636 @subsubheading Example
32646 @subheading The @code{-gdb-show} Command
32649 @subsubheading Synopsis
32655 Show the current value of a @value{GDBN} variable.
32657 @subsubheading @value{GDBN} Command
32659 The corresponding @value{GDBN} command is @samp{show}.
32661 @subsubheading Example
32670 @c @subheading -gdb-source
32673 @subheading The @code{-gdb-version} Command
32674 @findex -gdb-version
32676 @subsubheading Synopsis
32682 Show version information for @value{GDBN}. Used mostly in testing.
32684 @subsubheading @value{GDBN} Command
32686 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32687 default shows this information when you start an interactive session.
32689 @subsubheading Example
32691 @c This example modifies the actual output from GDB to avoid overfull
32697 ~Copyright 2000 Free Software Foundation, Inc.
32698 ~GDB is free software, covered by the GNU General Public License, and
32699 ~you are welcome to change it and/or distribute copies of it under
32700 ~ certain conditions.
32701 ~Type "show copying" to see the conditions.
32702 ~There is absolutely no warranty for GDB. Type "show warranty" for
32704 ~This GDB was configured as
32705 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32710 @subheading The @code{-list-thread-groups} Command
32711 @findex -list-thread-groups
32713 @subheading Synopsis
32716 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32719 Lists thread groups (@pxref{Thread groups}). When a single thread
32720 group is passed as the argument, lists the children of that group.
32721 When several thread group are passed, lists information about those
32722 thread groups. Without any parameters, lists information about all
32723 top-level thread groups.
32725 Normally, thread groups that are being debugged are reported.
32726 With the @samp{--available} option, @value{GDBN} reports thread groups
32727 available on the target.
32729 The output of this command may have either a @samp{threads} result or
32730 a @samp{groups} result. The @samp{thread} result has a list of tuples
32731 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32732 Information}). The @samp{groups} result has a list of tuples as value,
32733 each tuple describing a thread group. If top-level groups are
32734 requested (that is, no parameter is passed), or when several groups
32735 are passed, the output always has a @samp{groups} result. The format
32736 of the @samp{group} result is described below.
32738 To reduce the number of roundtrips it's possible to list thread groups
32739 together with their children, by passing the @samp{--recurse} option
32740 and the recursion depth. Presently, only recursion depth of 1 is
32741 permitted. If this option is present, then every reported thread group
32742 will also include its children, either as @samp{group} or
32743 @samp{threads} field.
32745 In general, any combination of option and parameters is permitted, with
32746 the following caveats:
32750 When a single thread group is passed, the output will typically
32751 be the @samp{threads} result. Because threads may not contain
32752 anything, the @samp{recurse} option will be ignored.
32755 When the @samp{--available} option is passed, limited information may
32756 be available. In particular, the list of threads of a process might
32757 be inaccessible. Further, specifying specific thread groups might
32758 not give any performance advantage over listing all thread groups.
32759 The frontend should assume that @samp{-list-thread-groups --available}
32760 is always an expensive operation and cache the results.
32764 The @samp{groups} result is a list of tuples, where each tuple may
32765 have the following fields:
32769 Identifier of the thread group. This field is always present.
32770 The identifier is an opaque string; frontends should not try to
32771 convert it to an integer, even though it might look like one.
32774 The type of the thread group. At present, only @samp{process} is a
32778 The target-specific process identifier. This field is only present
32779 for thread groups of type @samp{process} and only if the process exists.
32782 The exit code of this group's last exited thread, formatted in octal.
32783 This field is only present for thread groups of type @samp{process} and
32784 only if the process is not running.
32787 The number of children this thread group has. This field may be
32788 absent for an available thread group.
32791 This field has a list of tuples as value, each tuple describing a
32792 thread. It may be present if the @samp{--recurse} option is
32793 specified, and it's actually possible to obtain the threads.
32796 This field is a list of integers, each identifying a core that one
32797 thread of the group is running on. This field may be absent if
32798 such information is not available.
32801 The name of the executable file that corresponds to this thread group.
32802 The field is only present for thread groups of type @samp{process},
32803 and only if there is a corresponding executable file.
32807 @subheading Example
32811 -list-thread-groups
32812 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32813 -list-thread-groups 17
32814 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32815 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32816 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32817 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32818 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32819 -list-thread-groups --available
32820 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32821 -list-thread-groups --available --recurse 1
32822 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32823 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32824 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32825 -list-thread-groups --available --recurse 1 17 18
32826 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32827 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32828 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32831 @subheading The @code{-info-os} Command
32834 @subsubheading Synopsis
32837 -info-os [ @var{type} ]
32840 If no argument is supplied, the command returns a table of available
32841 operating-system-specific information types. If one of these types is
32842 supplied as an argument @var{type}, then the command returns a table
32843 of data of that type.
32845 The types of information available depend on the target operating
32848 @subsubheading @value{GDBN} Command
32850 The corresponding @value{GDBN} command is @samp{info os}.
32852 @subsubheading Example
32854 When run on a @sc{gnu}/Linux system, the output will look something
32860 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32861 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32862 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32863 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32864 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32866 item=@{col0="files",col1="Listing of all file descriptors",
32867 col2="File descriptors"@},
32868 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32869 col2="Kernel modules"@},
32870 item=@{col0="msg",col1="Listing of all message queues",
32871 col2="Message queues"@},
32872 item=@{col0="processes",col1="Listing of all processes",
32873 col2="Processes"@},
32874 item=@{col0="procgroups",col1="Listing of all process groups",
32875 col2="Process groups"@},
32876 item=@{col0="semaphores",col1="Listing of all semaphores",
32877 col2="Semaphores"@},
32878 item=@{col0="shm",col1="Listing of all shared-memory regions",
32879 col2="Shared-memory regions"@},
32880 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32882 item=@{col0="threads",col1="Listing of all threads",
32886 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32887 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32888 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32889 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32890 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32891 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32892 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32893 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32895 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32896 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32900 (Note that the MI output here includes a @code{"Title"} column that
32901 does not appear in command-line @code{info os}; this column is useful
32902 for MI clients that want to enumerate the types of data, such as in a
32903 popup menu, but is needless clutter on the command line, and
32904 @code{info os} omits it.)
32906 @subheading The @code{-add-inferior} Command
32907 @findex -add-inferior
32909 @subheading Synopsis
32915 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32916 inferior is not associated with any executable. Such association may
32917 be established with the @samp{-file-exec-and-symbols} command
32918 (@pxref{GDB/MI File Commands}). The command response has a single
32919 field, @samp{inferior}, whose value is the identifier of the
32920 thread group corresponding to the new inferior.
32922 @subheading Example
32927 ^done,inferior="i3"
32930 @subheading The @code{-interpreter-exec} Command
32931 @findex -interpreter-exec
32933 @subheading Synopsis
32936 -interpreter-exec @var{interpreter} @var{command}
32938 @anchor{-interpreter-exec}
32940 Execute the specified @var{command} in the given @var{interpreter}.
32942 @subheading @value{GDBN} Command
32944 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32946 @subheading Example
32950 -interpreter-exec console "break main"
32951 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32952 &"During symbol reading, bad structure-type format.\n"
32953 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32958 @subheading The @code{-inferior-tty-set} Command
32959 @findex -inferior-tty-set
32961 @subheading Synopsis
32964 -inferior-tty-set /dev/pts/1
32967 Set terminal for future runs of the program being debugged.
32969 @subheading @value{GDBN} Command
32971 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32973 @subheading Example
32977 -inferior-tty-set /dev/pts/1
32982 @subheading The @code{-inferior-tty-show} Command
32983 @findex -inferior-tty-show
32985 @subheading Synopsis
32991 Show terminal for future runs of program being debugged.
32993 @subheading @value{GDBN} Command
32995 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32997 @subheading Example
33001 -inferior-tty-set /dev/pts/1
33005 ^done,inferior_tty_terminal="/dev/pts/1"
33009 @subheading The @code{-enable-timings} Command
33010 @findex -enable-timings
33012 @subheading Synopsis
33015 -enable-timings [yes | no]
33018 Toggle the printing of the wallclock, user and system times for an MI
33019 command as a field in its output. This command is to help frontend
33020 developers optimize the performance of their code. No argument is
33021 equivalent to @samp{yes}.
33023 @subheading @value{GDBN} Command
33027 @subheading Example
33035 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33036 addr="0x080484ed",func="main",file="myprog.c",
33037 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33039 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33047 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33048 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33049 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33050 fullname="/home/nickrob/myprog.c",line="73"@}
33055 @chapter @value{GDBN} Annotations
33057 This chapter describes annotations in @value{GDBN}. Annotations were
33058 designed to interface @value{GDBN} to graphical user interfaces or other
33059 similar programs which want to interact with @value{GDBN} at a
33060 relatively high level.
33062 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33066 This is Edition @value{EDITION}, @value{DATE}.
33070 * Annotations Overview:: What annotations are; the general syntax.
33071 * Server Prefix:: Issuing a command without affecting user state.
33072 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33073 * Errors:: Annotations for error messages.
33074 * Invalidation:: Some annotations describe things now invalid.
33075 * Annotations for Running::
33076 Whether the program is running, how it stopped, etc.
33077 * Source Annotations:: Annotations describing source code.
33080 @node Annotations Overview
33081 @section What is an Annotation?
33082 @cindex annotations
33084 Annotations start with a newline character, two @samp{control-z}
33085 characters, and the name of the annotation. If there is no additional
33086 information associated with this annotation, the name of the annotation
33087 is followed immediately by a newline. If there is additional
33088 information, the name of the annotation is followed by a space, the
33089 additional information, and a newline. The additional information
33090 cannot contain newline characters.
33092 Any output not beginning with a newline and two @samp{control-z}
33093 characters denotes literal output from @value{GDBN}. Currently there is
33094 no need for @value{GDBN} to output a newline followed by two
33095 @samp{control-z} characters, but if there was such a need, the
33096 annotations could be extended with an @samp{escape} annotation which
33097 means those three characters as output.
33099 The annotation @var{level}, which is specified using the
33100 @option{--annotate} command line option (@pxref{Mode Options}), controls
33101 how much information @value{GDBN} prints together with its prompt,
33102 values of expressions, source lines, and other types of output. Level 0
33103 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33104 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33105 for programs that control @value{GDBN}, and level 2 annotations have
33106 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33107 Interface, annotate, GDB's Obsolete Annotations}).
33110 @kindex set annotate
33111 @item set annotate @var{level}
33112 The @value{GDBN} command @code{set annotate} sets the level of
33113 annotations to the specified @var{level}.
33115 @item show annotate
33116 @kindex show annotate
33117 Show the current annotation level.
33120 This chapter describes level 3 annotations.
33122 A simple example of starting up @value{GDBN} with annotations is:
33125 $ @kbd{gdb --annotate=3}
33127 Copyright 2003 Free Software Foundation, Inc.
33128 GDB is free software, covered by the GNU General Public License,
33129 and you are welcome to change it and/or distribute copies of it
33130 under certain conditions.
33131 Type "show copying" to see the conditions.
33132 There is absolutely no warranty for GDB. Type "show warranty"
33134 This GDB was configured as "i386-pc-linux-gnu"
33145 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33146 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33147 denotes a @samp{control-z} character) are annotations; the rest is
33148 output from @value{GDBN}.
33150 @node Server Prefix
33151 @section The Server Prefix
33152 @cindex server prefix
33154 If you prefix a command with @samp{server } then it will not affect
33155 the command history, nor will it affect @value{GDBN}'s notion of which
33156 command to repeat if @key{RET} is pressed on a line by itself. This
33157 means that commands can be run behind a user's back by a front-end in
33158 a transparent manner.
33160 The @code{server } prefix does not affect the recording of values into
33161 the value history; to print a value without recording it into the
33162 value history, use the @code{output} command instead of the
33163 @code{print} command.
33165 Using this prefix also disables confirmation requests
33166 (@pxref{confirmation requests}).
33169 @section Annotation for @value{GDBN} Input
33171 @cindex annotations for prompts
33172 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33173 to know when to send output, when the output from a given command is
33176 Different kinds of input each have a different @dfn{input type}. Each
33177 input type has three annotations: a @code{pre-} annotation, which
33178 denotes the beginning of any prompt which is being output, a plain
33179 annotation, which denotes the end of the prompt, and then a @code{post-}
33180 annotation which denotes the end of any echo which may (or may not) be
33181 associated with the input. For example, the @code{prompt} input type
33182 features the following annotations:
33190 The input types are
33193 @findex pre-prompt annotation
33194 @findex prompt annotation
33195 @findex post-prompt annotation
33197 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33199 @findex pre-commands annotation
33200 @findex commands annotation
33201 @findex post-commands annotation
33203 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33204 command. The annotations are repeated for each command which is input.
33206 @findex pre-overload-choice annotation
33207 @findex overload-choice annotation
33208 @findex post-overload-choice annotation
33209 @item overload-choice
33210 When @value{GDBN} wants the user to select between various overloaded functions.
33212 @findex pre-query annotation
33213 @findex query annotation
33214 @findex post-query annotation
33216 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33218 @findex pre-prompt-for-continue annotation
33219 @findex prompt-for-continue annotation
33220 @findex post-prompt-for-continue annotation
33221 @item prompt-for-continue
33222 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33223 expect this to work well; instead use @code{set height 0} to disable
33224 prompting. This is because the counting of lines is buggy in the
33225 presence of annotations.
33230 @cindex annotations for errors, warnings and interrupts
33232 @findex quit annotation
33237 This annotation occurs right before @value{GDBN} responds to an interrupt.
33239 @findex error annotation
33244 This annotation occurs right before @value{GDBN} responds to an error.
33246 Quit and error annotations indicate that any annotations which @value{GDBN} was
33247 in the middle of may end abruptly. For example, if a
33248 @code{value-history-begin} annotation is followed by a @code{error}, one
33249 cannot expect to receive the matching @code{value-history-end}. One
33250 cannot expect not to receive it either, however; an error annotation
33251 does not necessarily mean that @value{GDBN} is immediately returning all the way
33254 @findex error-begin annotation
33255 A quit or error annotation may be preceded by
33261 Any output between that and the quit or error annotation is the error
33264 Warning messages are not yet annotated.
33265 @c If we want to change that, need to fix warning(), type_error(),
33266 @c range_error(), and possibly other places.
33269 @section Invalidation Notices
33271 @cindex annotations for invalidation messages
33272 The following annotations say that certain pieces of state may have
33276 @findex frames-invalid annotation
33277 @item ^Z^Zframes-invalid
33279 The frames (for example, output from the @code{backtrace} command) may
33282 @findex breakpoints-invalid annotation
33283 @item ^Z^Zbreakpoints-invalid
33285 The breakpoints may have changed. For example, the user just added or
33286 deleted a breakpoint.
33289 @node Annotations for Running
33290 @section Running the Program
33291 @cindex annotations for running programs
33293 @findex starting annotation
33294 @findex stopping annotation
33295 When the program starts executing due to a @value{GDBN} command such as
33296 @code{step} or @code{continue},
33302 is output. When the program stops,
33308 is output. Before the @code{stopped} annotation, a variety of
33309 annotations describe how the program stopped.
33312 @findex exited annotation
33313 @item ^Z^Zexited @var{exit-status}
33314 The program exited, and @var{exit-status} is the exit status (zero for
33315 successful exit, otherwise nonzero).
33317 @findex signalled annotation
33318 @findex signal-name annotation
33319 @findex signal-name-end annotation
33320 @findex signal-string annotation
33321 @findex signal-string-end annotation
33322 @item ^Z^Zsignalled
33323 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33324 annotation continues:
33330 ^Z^Zsignal-name-end
33334 ^Z^Zsignal-string-end
33339 where @var{name} is the name of the signal, such as @code{SIGILL} or
33340 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33341 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33342 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33343 user's benefit and have no particular format.
33345 @findex signal annotation
33347 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33348 just saying that the program received the signal, not that it was
33349 terminated with it.
33351 @findex breakpoint annotation
33352 @item ^Z^Zbreakpoint @var{number}
33353 The program hit breakpoint number @var{number}.
33355 @findex watchpoint annotation
33356 @item ^Z^Zwatchpoint @var{number}
33357 The program hit watchpoint number @var{number}.
33360 @node Source Annotations
33361 @section Displaying Source
33362 @cindex annotations for source display
33364 @findex source annotation
33365 The following annotation is used instead of displaying source code:
33368 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33371 where @var{filename} is an absolute file name indicating which source
33372 file, @var{line} is the line number within that file (where 1 is the
33373 first line in the file), @var{character} is the character position
33374 within the file (where 0 is the first character in the file) (for most
33375 debug formats this will necessarily point to the beginning of a line),
33376 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33377 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33378 @var{addr} is the address in the target program associated with the
33379 source which is being displayed. The @var{addr} is in the form @samp{0x}
33380 followed by one or more lowercase hex digits (note that this does not
33381 depend on the language).
33383 @node JIT Interface
33384 @chapter JIT Compilation Interface
33385 @cindex just-in-time compilation
33386 @cindex JIT compilation interface
33388 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33389 interface. A JIT compiler is a program or library that generates native
33390 executable code at runtime and executes it, usually in order to achieve good
33391 performance while maintaining platform independence.
33393 Programs that use JIT compilation are normally difficult to debug because
33394 portions of their code are generated at runtime, instead of being loaded from
33395 object files, which is where @value{GDBN} normally finds the program's symbols
33396 and debug information. In order to debug programs that use JIT compilation,
33397 @value{GDBN} has an interface that allows the program to register in-memory
33398 symbol files with @value{GDBN} at runtime.
33400 If you are using @value{GDBN} to debug a program that uses this interface, then
33401 it should work transparently so long as you have not stripped the binary. If
33402 you are developing a JIT compiler, then the interface is documented in the rest
33403 of this chapter. At this time, the only known client of this interface is the
33406 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33407 JIT compiler communicates with @value{GDBN} by writing data into a global
33408 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33409 attaches, it reads a linked list of symbol files from the global variable to
33410 find existing code, and puts a breakpoint in the function so that it can find
33411 out about additional code.
33414 * Declarations:: Relevant C struct declarations
33415 * Registering Code:: Steps to register code
33416 * Unregistering Code:: Steps to unregister code
33417 * Custom Debug Info:: Emit debug information in a custom format
33421 @section JIT Declarations
33423 These are the relevant struct declarations that a C program should include to
33424 implement the interface:
33434 struct jit_code_entry
33436 struct jit_code_entry *next_entry;
33437 struct jit_code_entry *prev_entry;
33438 const char *symfile_addr;
33439 uint64_t symfile_size;
33442 struct jit_descriptor
33445 /* This type should be jit_actions_t, but we use uint32_t
33446 to be explicit about the bitwidth. */
33447 uint32_t action_flag;
33448 struct jit_code_entry *relevant_entry;
33449 struct jit_code_entry *first_entry;
33452 /* GDB puts a breakpoint in this function. */
33453 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33455 /* Make sure to specify the version statically, because the
33456 debugger may check the version before we can set it. */
33457 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33460 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33461 modifications to this global data properly, which can easily be done by putting
33462 a global mutex around modifications to these structures.
33464 @node Registering Code
33465 @section Registering Code
33467 To register code with @value{GDBN}, the JIT should follow this protocol:
33471 Generate an object file in memory with symbols and other desired debug
33472 information. The file must include the virtual addresses of the sections.
33475 Create a code entry for the file, which gives the start and size of the symbol
33479 Add it to the linked list in the JIT descriptor.
33482 Point the relevant_entry field of the descriptor at the entry.
33485 Set @code{action_flag} to @code{JIT_REGISTER} and call
33486 @code{__jit_debug_register_code}.
33489 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33490 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33491 new code. However, the linked list must still be maintained in order to allow
33492 @value{GDBN} to attach to a running process and still find the symbol files.
33494 @node Unregistering Code
33495 @section Unregistering Code
33497 If code is freed, then the JIT should use the following protocol:
33501 Remove the code entry corresponding to the code from the linked list.
33504 Point the @code{relevant_entry} field of the descriptor at the code entry.
33507 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33508 @code{__jit_debug_register_code}.
33511 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33512 and the JIT will leak the memory used for the associated symbol files.
33514 @node Custom Debug Info
33515 @section Custom Debug Info
33516 @cindex custom JIT debug info
33517 @cindex JIT debug info reader
33519 Generating debug information in platform-native file formats (like ELF
33520 or COFF) may be an overkill for JIT compilers; especially if all the
33521 debug info is used for is displaying a meaningful backtrace. The
33522 issue can be resolved by having the JIT writers decide on a debug info
33523 format and also provide a reader that parses the debug info generated
33524 by the JIT compiler. This section gives a brief overview on writing
33525 such a parser. More specific details can be found in the source file
33526 @file{gdb/jit-reader.in}, which is also installed as a header at
33527 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33529 The reader is implemented as a shared object (so this functionality is
33530 not available on platforms which don't allow loading shared objects at
33531 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33532 @code{jit-reader-unload} are provided, to be used to load and unload
33533 the readers from a preconfigured directory. Once loaded, the shared
33534 object is used the parse the debug information emitted by the JIT
33538 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33539 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33542 @node Using JIT Debug Info Readers
33543 @subsection Using JIT Debug Info Readers
33544 @kindex jit-reader-load
33545 @kindex jit-reader-unload
33547 Readers can be loaded and unloaded using the @code{jit-reader-load}
33548 and @code{jit-reader-unload} commands.
33551 @item jit-reader-load @var{reader}
33552 Load the JIT reader named @var{reader}, which is a shared
33553 object specified as either an absolute or a relative file name. In
33554 the latter case, @value{GDBN} will try to load the reader from a
33555 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33556 system (here @var{libdir} is the system library directory, often
33557 @file{/usr/local/lib}).
33559 Only one reader can be active at a time; trying to load a second
33560 reader when one is already loaded will result in @value{GDBN}
33561 reporting an error. A new JIT reader can be loaded by first unloading
33562 the current one using @code{jit-reader-unload} and then invoking
33563 @code{jit-reader-load}.
33565 @item jit-reader-unload
33566 Unload the currently loaded JIT reader.
33570 @node Writing JIT Debug Info Readers
33571 @subsection Writing JIT Debug Info Readers
33572 @cindex writing JIT debug info readers
33574 As mentioned, a reader is essentially a shared object conforming to a
33575 certain ABI. This ABI is described in @file{jit-reader.h}.
33577 @file{jit-reader.h} defines the structures, macros and functions
33578 required to write a reader. It is installed (along with
33579 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33580 the system include directory.
33582 Readers need to be released under a GPL compatible license. A reader
33583 can be declared as released under such a license by placing the macro
33584 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33586 The entry point for readers is the symbol @code{gdb_init_reader},
33587 which is expected to be a function with the prototype
33589 @findex gdb_init_reader
33591 extern struct gdb_reader_funcs *gdb_init_reader (void);
33594 @cindex @code{struct gdb_reader_funcs}
33596 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33597 functions. These functions are executed to read the debug info
33598 generated by the JIT compiler (@code{read}), to unwind stack frames
33599 (@code{unwind}) and to create canonical frame IDs
33600 (@code{get_Frame_id}). It also has a callback that is called when the
33601 reader is being unloaded (@code{destroy}). The struct looks like this
33604 struct gdb_reader_funcs
33606 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33607 int reader_version;
33609 /* For use by the reader. */
33612 gdb_read_debug_info *read;
33613 gdb_unwind_frame *unwind;
33614 gdb_get_frame_id *get_frame_id;
33615 gdb_destroy_reader *destroy;
33619 @cindex @code{struct gdb_symbol_callbacks}
33620 @cindex @code{struct gdb_unwind_callbacks}
33622 The callbacks are provided with another set of callbacks by
33623 @value{GDBN} to do their job. For @code{read}, these callbacks are
33624 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33625 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33626 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33627 files and new symbol tables inside those object files. @code{struct
33628 gdb_unwind_callbacks} has callbacks to read registers off the current
33629 frame and to write out the values of the registers in the previous
33630 frame. Both have a callback (@code{target_read}) to read bytes off the
33631 target's address space.
33633 @node In-Process Agent
33634 @chapter In-Process Agent
33635 @cindex debugging agent
33636 The traditional debugging model is conceptually low-speed, but works fine,
33637 because most bugs can be reproduced in debugging-mode execution. However,
33638 as multi-core or many-core processors are becoming mainstream, and
33639 multi-threaded programs become more and more popular, there should be more
33640 and more bugs that only manifest themselves at normal-mode execution, for
33641 example, thread races, because debugger's interference with the program's
33642 timing may conceal the bugs. On the other hand, in some applications,
33643 it is not feasible for the debugger to interrupt the program's execution
33644 long enough for the developer to learn anything helpful about its behavior.
33645 If the program's correctness depends on its real-time behavior, delays
33646 introduced by a debugger might cause the program to fail, even when the
33647 code itself is correct. It is useful to be able to observe the program's
33648 behavior without interrupting it.
33650 Therefore, traditional debugging model is too intrusive to reproduce
33651 some bugs. In order to reduce the interference with the program, we can
33652 reduce the number of operations performed by debugger. The
33653 @dfn{In-Process Agent}, a shared library, is running within the same
33654 process with inferior, and is able to perform some debugging operations
33655 itself. As a result, debugger is only involved when necessary, and
33656 performance of debugging can be improved accordingly. Note that
33657 interference with program can be reduced but can't be removed completely,
33658 because the in-process agent will still stop or slow down the program.
33660 The in-process agent can interpret and execute Agent Expressions
33661 (@pxref{Agent Expressions}) during performing debugging operations. The
33662 agent expressions can be used for different purposes, such as collecting
33663 data in tracepoints, and condition evaluation in breakpoints.
33665 @anchor{Control Agent}
33666 You can control whether the in-process agent is used as an aid for
33667 debugging with the following commands:
33670 @kindex set agent on
33672 Causes the in-process agent to perform some operations on behalf of the
33673 debugger. Just which operations requested by the user will be done
33674 by the in-process agent depends on the its capabilities. For example,
33675 if you request to evaluate breakpoint conditions in the in-process agent,
33676 and the in-process agent has such capability as well, then breakpoint
33677 conditions will be evaluated in the in-process agent.
33679 @kindex set agent off
33680 @item set agent off
33681 Disables execution of debugging operations by the in-process agent. All
33682 of the operations will be performed by @value{GDBN}.
33686 Display the current setting of execution of debugging operations by
33687 the in-process agent.
33691 * In-Process Agent Protocol::
33694 @node In-Process Agent Protocol
33695 @section In-Process Agent Protocol
33696 @cindex in-process agent protocol
33698 The in-process agent is able to communicate with both @value{GDBN} and
33699 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33700 used for communications between @value{GDBN} or GDBserver and the IPA.
33701 In general, @value{GDBN} or GDBserver sends commands
33702 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33703 in-process agent replies back with the return result of the command, or
33704 some other information. The data sent to in-process agent is composed
33705 of primitive data types, such as 4-byte or 8-byte type, and composite
33706 types, which are called objects (@pxref{IPA Protocol Objects}).
33709 * IPA Protocol Objects::
33710 * IPA Protocol Commands::
33713 @node IPA Protocol Objects
33714 @subsection IPA Protocol Objects
33715 @cindex ipa protocol objects
33717 The commands sent to and results received from agent may contain some
33718 complex data types called @dfn{objects}.
33720 The in-process agent is running on the same machine with @value{GDBN}
33721 or GDBserver, so it doesn't have to handle as much differences between
33722 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33723 However, there are still some differences of two ends in two processes:
33727 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33728 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33730 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33731 GDBserver is compiled with one, and in-process agent is compiled with
33735 Here are the IPA Protocol Objects:
33739 agent expression object. It represents an agent expression
33740 (@pxref{Agent Expressions}).
33741 @anchor{agent expression object}
33743 tracepoint action object. It represents a tracepoint action
33744 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33745 memory, static trace data and to evaluate expression.
33746 @anchor{tracepoint action object}
33748 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33749 @anchor{tracepoint object}
33753 The following table describes important attributes of each IPA protocol
33756 @multitable @columnfractions .30 .20 .50
33757 @headitem Name @tab Size @tab Description
33758 @item @emph{agent expression object} @tab @tab
33759 @item length @tab 4 @tab length of bytes code
33760 @item byte code @tab @var{length} @tab contents of byte code
33761 @item @emph{tracepoint action for collecting memory} @tab @tab
33762 @item 'M' @tab 1 @tab type of tracepoint action
33763 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33764 address of the lowest byte to collect, otherwise @var{addr} is the offset
33765 of @var{basereg} for memory collecting.
33766 @item len @tab 8 @tab length of memory for collecting
33767 @item basereg @tab 4 @tab the register number containing the starting
33768 memory address for collecting.
33769 @item @emph{tracepoint action for collecting registers} @tab @tab
33770 @item 'R' @tab 1 @tab type of tracepoint action
33771 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33772 @item 'L' @tab 1 @tab type of tracepoint action
33773 @item @emph{tracepoint action for expression evaluation} @tab @tab
33774 @item 'X' @tab 1 @tab type of tracepoint action
33775 @item agent expression @tab length of @tab @ref{agent expression object}
33776 @item @emph{tracepoint object} @tab @tab
33777 @item number @tab 4 @tab number of tracepoint
33778 @item address @tab 8 @tab address of tracepoint inserted on
33779 @item type @tab 4 @tab type of tracepoint
33780 @item enabled @tab 1 @tab enable or disable of tracepoint
33781 @item step_count @tab 8 @tab step
33782 @item pass_count @tab 8 @tab pass
33783 @item numactions @tab 4 @tab number of tracepoint actions
33784 @item hit count @tab 8 @tab hit count
33785 @item trace frame usage @tab 8 @tab trace frame usage
33786 @item compiled_cond @tab 8 @tab compiled condition
33787 @item orig_size @tab 8 @tab orig size
33788 @item condition @tab 4 if condition is NULL otherwise length of
33789 @ref{agent expression object}
33790 @tab zero if condition is NULL, otherwise is
33791 @ref{agent expression object}
33792 @item actions @tab variable
33793 @tab numactions number of @ref{tracepoint action object}
33796 @node IPA Protocol Commands
33797 @subsection IPA Protocol Commands
33798 @cindex ipa protocol commands
33800 The spaces in each command are delimiters to ease reading this commands
33801 specification. They don't exist in real commands.
33805 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33806 Installs a new fast tracepoint described by @var{tracepoint_object}
33807 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33808 head of @dfn{jumppad}, which is used to jump to data collection routine
33813 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33814 @var{target_address} is address of tracepoint in the inferior.
33815 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33816 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33817 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33818 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33825 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33826 is about to kill inferiors.
33834 @item probe_marker_at:@var{address}
33835 Asks in-process agent to probe the marker at @var{address}.
33842 @item unprobe_marker_at:@var{address}
33843 Asks in-process agent to unprobe the marker at @var{address}.
33847 @chapter Reporting Bugs in @value{GDBN}
33848 @cindex bugs in @value{GDBN}
33849 @cindex reporting bugs in @value{GDBN}
33851 Your bug reports play an essential role in making @value{GDBN} reliable.
33853 Reporting a bug may help you by bringing a solution to your problem, or it
33854 may not. But in any case the principal function of a bug report is to help
33855 the entire community by making the next version of @value{GDBN} work better. Bug
33856 reports are your contribution to the maintenance of @value{GDBN}.
33858 In order for a bug report to serve its purpose, you must include the
33859 information that enables us to fix the bug.
33862 * Bug Criteria:: Have you found a bug?
33863 * Bug Reporting:: How to report bugs
33867 @section Have You Found a Bug?
33868 @cindex bug criteria
33870 If you are not sure whether you have found a bug, here are some guidelines:
33873 @cindex fatal signal
33874 @cindex debugger crash
33875 @cindex crash of debugger
33877 If the debugger gets a fatal signal, for any input whatever, that is a
33878 @value{GDBN} bug. Reliable debuggers never crash.
33880 @cindex error on valid input
33882 If @value{GDBN} produces an error message for valid input, that is a
33883 bug. (Note that if you're cross debugging, the problem may also be
33884 somewhere in the connection to the target.)
33886 @cindex invalid input
33888 If @value{GDBN} does not produce an error message for invalid input,
33889 that is a bug. However, you should note that your idea of
33890 ``invalid input'' might be our idea of ``an extension'' or ``support
33891 for traditional practice''.
33894 If you are an experienced user of debugging tools, your suggestions
33895 for improvement of @value{GDBN} are welcome in any case.
33898 @node Bug Reporting
33899 @section How to Report Bugs
33900 @cindex bug reports
33901 @cindex @value{GDBN} bugs, reporting
33903 A number of companies and individuals offer support for @sc{gnu} products.
33904 If you obtained @value{GDBN} from a support organization, we recommend you
33905 contact that organization first.
33907 You can find contact information for many support companies and
33908 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33910 @c should add a web page ref...
33913 @ifset BUGURL_DEFAULT
33914 In any event, we also recommend that you submit bug reports for
33915 @value{GDBN}. The preferred method is to submit them directly using
33916 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33917 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33920 @strong{Do not send bug reports to @samp{info-gdb}, or to
33921 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33922 not want to receive bug reports. Those that do have arranged to receive
33925 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33926 serves as a repeater. The mailing list and the newsgroup carry exactly
33927 the same messages. Often people think of posting bug reports to the
33928 newsgroup instead of mailing them. This appears to work, but it has one
33929 problem which can be crucial: a newsgroup posting often lacks a mail
33930 path back to the sender. Thus, if we need to ask for more information,
33931 we may be unable to reach you. For this reason, it is better to send
33932 bug reports to the mailing list.
33934 @ifclear BUGURL_DEFAULT
33935 In any event, we also recommend that you submit bug reports for
33936 @value{GDBN} to @value{BUGURL}.
33940 The fundamental principle of reporting bugs usefully is this:
33941 @strong{report all the facts}. If you are not sure whether to state a
33942 fact or leave it out, state it!
33944 Often people omit facts because they think they know what causes the
33945 problem and assume that some details do not matter. Thus, you might
33946 assume that the name of the variable you use in an example does not matter.
33947 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33948 stray memory reference which happens to fetch from the location where that
33949 name is stored in memory; perhaps, if the name were different, the contents
33950 of that location would fool the debugger into doing the right thing despite
33951 the bug. Play it safe and give a specific, complete example. That is the
33952 easiest thing for you to do, and the most helpful.
33954 Keep in mind that the purpose of a bug report is to enable us to fix the
33955 bug. It may be that the bug has been reported previously, but neither
33956 you nor we can know that unless your bug report is complete and
33959 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33960 bell?'' Those bug reports are useless, and we urge everyone to
33961 @emph{refuse to respond to them} except to chide the sender to report
33964 To enable us to fix the bug, you should include all these things:
33968 The version of @value{GDBN}. @value{GDBN} announces it if you start
33969 with no arguments; you can also print it at any time using @code{show
33972 Without this, we will not know whether there is any point in looking for
33973 the bug in the current version of @value{GDBN}.
33976 The type of machine you are using, and the operating system name and
33980 The details of the @value{GDBN} build-time configuration.
33981 @value{GDBN} shows these details if you invoke it with the
33982 @option{--configuration} command-line option, or if you type
33983 @code{show configuration} at @value{GDBN}'s prompt.
33986 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33987 ``@value{GCC}--2.8.1''.
33990 What compiler (and its version) was used to compile the program you are
33991 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33992 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33993 to get this information; for other compilers, see the documentation for
33997 The command arguments you gave the compiler to compile your example and
33998 observe the bug. For example, did you use @samp{-O}? To guarantee
33999 you will not omit something important, list them all. A copy of the
34000 Makefile (or the output from make) is sufficient.
34002 If we were to try to guess the arguments, we would probably guess wrong
34003 and then we might not encounter the bug.
34006 A complete input script, and all necessary source files, that will
34010 A description of what behavior you observe that you believe is
34011 incorrect. For example, ``It gets a fatal signal.''
34013 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34014 will certainly notice it. But if the bug is incorrect output, we might
34015 not notice unless it is glaringly wrong. You might as well not give us
34016 a chance to make a mistake.
34018 Even if the problem you experience is a fatal signal, you should still
34019 say so explicitly. Suppose something strange is going on, such as, your
34020 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34021 the C library on your system. (This has happened!) Your copy might
34022 crash and ours would not. If you told us to expect a crash, then when
34023 ours fails to crash, we would know that the bug was not happening for
34024 us. If you had not told us to expect a crash, then we would not be able
34025 to draw any conclusion from our observations.
34028 @cindex recording a session script
34029 To collect all this information, you can use a session recording program
34030 such as @command{script}, which is available on many Unix systems.
34031 Just run your @value{GDBN} session inside @command{script} and then
34032 include the @file{typescript} file with your bug report.
34034 Another way to record a @value{GDBN} session is to run @value{GDBN}
34035 inside Emacs and then save the entire buffer to a file.
34038 If you wish to suggest changes to the @value{GDBN} source, send us context
34039 diffs. If you even discuss something in the @value{GDBN} source, refer to
34040 it by context, not by line number.
34042 The line numbers in our development sources will not match those in your
34043 sources. Your line numbers would convey no useful information to us.
34047 Here are some things that are not necessary:
34051 A description of the envelope of the bug.
34053 Often people who encounter a bug spend a lot of time investigating
34054 which changes to the input file will make the bug go away and which
34055 changes will not affect it.
34057 This is often time consuming and not very useful, because the way we
34058 will find the bug is by running a single example under the debugger
34059 with breakpoints, not by pure deduction from a series of examples.
34060 We recommend that you save your time for something else.
34062 Of course, if you can find a simpler example to report @emph{instead}
34063 of the original one, that is a convenience for us. Errors in the
34064 output will be easier to spot, running under the debugger will take
34065 less time, and so on.
34067 However, simplification is not vital; if you do not want to do this,
34068 report the bug anyway and send us the entire test case you used.
34071 A patch for the bug.
34073 A patch for the bug does help us if it is a good one. But do not omit
34074 the necessary information, such as the test case, on the assumption that
34075 a patch is all we need. We might see problems with your patch and decide
34076 to fix the problem another way, or we might not understand it at all.
34078 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34079 construct an example that will make the program follow a certain path
34080 through the code. If you do not send us the example, we will not be able
34081 to construct one, so we will not be able to verify that the bug is fixed.
34083 And if we cannot understand what bug you are trying to fix, or why your
34084 patch should be an improvement, we will not install it. A test case will
34085 help us to understand.
34088 A guess about what the bug is or what it depends on.
34090 Such guesses are usually wrong. Even we cannot guess right about such
34091 things without first using the debugger to find the facts.
34094 @c The readline documentation is distributed with the readline code
34095 @c and consists of the two following files:
34098 @c Use -I with makeinfo to point to the appropriate directory,
34099 @c environment var TEXINPUTS with TeX.
34100 @ifclear SYSTEM_READLINE
34101 @include rluser.texi
34102 @include hsuser.texi
34106 @appendix In Memoriam
34108 The @value{GDBN} project mourns the loss of the following long-time
34113 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34114 to Free Software in general. Outside of @value{GDBN}, he was known in
34115 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34117 @item Michael Snyder
34118 Michael was one of the Global Maintainers of the @value{GDBN} project,
34119 with contributions recorded as early as 1996, until 2011. In addition
34120 to his day to day participation, he was a large driving force behind
34121 adding Reverse Debugging to @value{GDBN}.
34124 Beyond their technical contributions to the project, they were also
34125 enjoyable members of the Free Software Community. We will miss them.
34127 @node Formatting Documentation
34128 @appendix Formatting Documentation
34130 @cindex @value{GDBN} reference card
34131 @cindex reference card
34132 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34133 for printing with PostScript or Ghostscript, in the @file{gdb}
34134 subdirectory of the main source directory@footnote{In
34135 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34136 release.}. If you can use PostScript or Ghostscript with your printer,
34137 you can print the reference card immediately with @file{refcard.ps}.
34139 The release also includes the source for the reference card. You
34140 can format it, using @TeX{}, by typing:
34146 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34147 mode on US ``letter'' size paper;
34148 that is, on a sheet 11 inches wide by 8.5 inches
34149 high. You will need to specify this form of printing as an option to
34150 your @sc{dvi} output program.
34152 @cindex documentation
34154 All the documentation for @value{GDBN} comes as part of the machine-readable
34155 distribution. The documentation is written in Texinfo format, which is
34156 a documentation system that uses a single source file to produce both
34157 on-line information and a printed manual. You can use one of the Info
34158 formatting commands to create the on-line version of the documentation
34159 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34161 @value{GDBN} includes an already formatted copy of the on-line Info
34162 version of this manual in the @file{gdb} subdirectory. The main Info
34163 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34164 subordinate files matching @samp{gdb.info*} in the same directory. If
34165 necessary, you can print out these files, or read them with any editor;
34166 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34167 Emacs or the standalone @code{info} program, available as part of the
34168 @sc{gnu} Texinfo distribution.
34170 If you want to format these Info files yourself, you need one of the
34171 Info formatting programs, such as @code{texinfo-format-buffer} or
34174 If you have @code{makeinfo} installed, and are in the top level
34175 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34176 version @value{GDBVN}), you can make the Info file by typing:
34183 If you want to typeset and print copies of this manual, you need @TeX{},
34184 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34185 Texinfo definitions file.
34187 @TeX{} is a typesetting program; it does not print files directly, but
34188 produces output files called @sc{dvi} files. To print a typeset
34189 document, you need a program to print @sc{dvi} files. If your system
34190 has @TeX{} installed, chances are it has such a program. The precise
34191 command to use depends on your system; @kbd{lpr -d} is common; another
34192 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34193 require a file name without any extension or a @samp{.dvi} extension.
34195 @TeX{} also requires a macro definitions file called
34196 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34197 written in Texinfo format. On its own, @TeX{} cannot either read or
34198 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34199 and is located in the @file{gdb-@var{version-number}/texinfo}
34202 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34203 typeset and print this manual. First switch to the @file{gdb}
34204 subdirectory of the main source directory (for example, to
34205 @file{gdb-@value{GDBVN}/gdb}) and type:
34211 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34213 @node Installing GDB
34214 @appendix Installing @value{GDBN}
34215 @cindex installation
34218 * Requirements:: Requirements for building @value{GDBN}
34219 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34220 * Separate Objdir:: Compiling @value{GDBN} in another directory
34221 * Config Names:: Specifying names for hosts and targets
34222 * Configure Options:: Summary of options for configure
34223 * System-wide configuration:: Having a system-wide init file
34227 @section Requirements for Building @value{GDBN}
34228 @cindex building @value{GDBN}, requirements for
34230 Building @value{GDBN} requires various tools and packages to be available.
34231 Other packages will be used only if they are found.
34233 @heading Tools/Packages Necessary for Building @value{GDBN}
34235 @item ISO C90 compiler
34236 @value{GDBN} is written in ISO C90. It should be buildable with any
34237 working C90 compiler, e.g.@: GCC.
34241 @heading Tools/Packages Optional for Building @value{GDBN}
34245 @value{GDBN} can use the Expat XML parsing library. This library may be
34246 included with your operating system distribution; if it is not, you
34247 can get the latest version from @url{http://expat.sourceforge.net}.
34248 The @file{configure} script will search for this library in several
34249 standard locations; if it is installed in an unusual path, you can
34250 use the @option{--with-libexpat-prefix} option to specify its location.
34256 Remote protocol memory maps (@pxref{Memory Map Format})
34258 Target descriptions (@pxref{Target Descriptions})
34260 Remote shared library lists (@xref{Library List Format},
34261 or alternatively @pxref{Library List Format for SVR4 Targets})
34263 MS-Windows shared libraries (@pxref{Shared Libraries})
34265 Traceframe info (@pxref{Traceframe Info Format})
34267 Branch trace (@pxref{Branch Trace Format},
34268 @pxref{Branch Trace Configuration Format})
34272 @cindex compressed debug sections
34273 @value{GDBN} will use the @samp{zlib} library, if available, to read
34274 compressed debug sections. Some linkers, such as GNU gold, are capable
34275 of producing binaries with compressed debug sections. If @value{GDBN}
34276 is compiled with @samp{zlib}, it will be able to read the debug
34277 information in such binaries.
34279 The @samp{zlib} library is likely included with your operating system
34280 distribution; if it is not, you can get the latest version from
34281 @url{http://zlib.net}.
34284 @value{GDBN}'s features related to character sets (@pxref{Character
34285 Sets}) require a functioning @code{iconv} implementation. If you are
34286 on a GNU system, then this is provided by the GNU C Library. Some
34287 other systems also provide a working @code{iconv}.
34289 If @value{GDBN} is using the @code{iconv} program which is installed
34290 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34291 This is done with @option{--with-iconv-bin} which specifies the
34292 directory that contains the @code{iconv} program.
34294 On systems without @code{iconv}, you can install GNU Libiconv. If you
34295 have previously installed Libiconv, you can use the
34296 @option{--with-libiconv-prefix} option to configure.
34298 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34299 arrange to build Libiconv if a directory named @file{libiconv} appears
34300 in the top-most source directory. If Libiconv is built this way, and
34301 if the operating system does not provide a suitable @code{iconv}
34302 implementation, then the just-built library will automatically be used
34303 by @value{GDBN}. One easy way to set this up is to download GNU
34304 Libiconv, unpack it, and then rename the directory holding the
34305 Libiconv source code to @samp{libiconv}.
34308 @node Running Configure
34309 @section Invoking the @value{GDBN} @file{configure} Script
34310 @cindex configuring @value{GDBN}
34311 @value{GDBN} comes with a @file{configure} script that automates the process
34312 of preparing @value{GDBN} for installation; you can then use @code{make} to
34313 build the @code{gdb} program.
34315 @c irrelevant in info file; it's as current as the code it lives with.
34316 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34317 look at the @file{README} file in the sources; we may have improved the
34318 installation procedures since publishing this manual.}
34321 The @value{GDBN} distribution includes all the source code you need for
34322 @value{GDBN} in a single directory, whose name is usually composed by
34323 appending the version number to @samp{gdb}.
34325 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34326 @file{gdb-@value{GDBVN}} directory. That directory contains:
34329 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34330 script for configuring @value{GDBN} and all its supporting libraries
34332 @item gdb-@value{GDBVN}/gdb
34333 the source specific to @value{GDBN} itself
34335 @item gdb-@value{GDBVN}/bfd
34336 source for the Binary File Descriptor library
34338 @item gdb-@value{GDBVN}/include
34339 @sc{gnu} include files
34341 @item gdb-@value{GDBVN}/libiberty
34342 source for the @samp{-liberty} free software library
34344 @item gdb-@value{GDBVN}/opcodes
34345 source for the library of opcode tables and disassemblers
34347 @item gdb-@value{GDBVN}/readline
34348 source for the @sc{gnu} command-line interface
34350 @item gdb-@value{GDBVN}/glob
34351 source for the @sc{gnu} filename pattern-matching subroutine
34353 @item gdb-@value{GDBVN}/mmalloc
34354 source for the @sc{gnu} memory-mapped malloc package
34357 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34358 from the @file{gdb-@var{version-number}} source directory, which in
34359 this example is the @file{gdb-@value{GDBVN}} directory.
34361 First switch to the @file{gdb-@var{version-number}} source directory
34362 if you are not already in it; then run @file{configure}. Pass the
34363 identifier for the platform on which @value{GDBN} will run as an
34369 cd gdb-@value{GDBVN}
34370 ./configure @var{host}
34375 where @var{host} is an identifier such as @samp{sun4} or
34376 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34377 (You can often leave off @var{host}; @file{configure} tries to guess the
34378 correct value by examining your system.)
34380 Running @samp{configure @var{host}} and then running @code{make} builds the
34381 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34382 libraries, then @code{gdb} itself. The configured source files, and the
34383 binaries, are left in the corresponding source directories.
34386 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34387 system does not recognize this automatically when you run a different
34388 shell, you may need to run @code{sh} on it explicitly:
34391 sh configure @var{host}
34394 If you run @file{configure} from a directory that contains source
34395 directories for multiple libraries or programs, such as the
34396 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34398 creates configuration files for every directory level underneath (unless
34399 you tell it not to, with the @samp{--norecursion} option).
34401 You should run the @file{configure} script from the top directory in the
34402 source tree, the @file{gdb-@var{version-number}} directory. If you run
34403 @file{configure} from one of the subdirectories, you will configure only
34404 that subdirectory. That is usually not what you want. In particular,
34405 if you run the first @file{configure} from the @file{gdb} subdirectory
34406 of the @file{gdb-@var{version-number}} directory, you will omit the
34407 configuration of @file{bfd}, @file{readline}, and other sibling
34408 directories of the @file{gdb} subdirectory. This leads to build errors
34409 about missing include files such as @file{bfd/bfd.h}.
34411 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34412 However, you should make sure that the shell on your path (named by
34413 the @samp{SHELL} environment variable) is publicly readable. Remember
34414 that @value{GDBN} uses the shell to start your program---some systems refuse to
34415 let @value{GDBN} debug child processes whose programs are not readable.
34417 @node Separate Objdir
34418 @section Compiling @value{GDBN} in Another Directory
34420 If you want to run @value{GDBN} versions for several host or target machines,
34421 you need a different @code{gdb} compiled for each combination of
34422 host and target. @file{configure} is designed to make this easy by
34423 allowing you to generate each configuration in a separate subdirectory,
34424 rather than in the source directory. If your @code{make} program
34425 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34426 @code{make} in each of these directories builds the @code{gdb}
34427 program specified there.
34429 To build @code{gdb} in a separate directory, run @file{configure}
34430 with the @samp{--srcdir} option to specify where to find the source.
34431 (You also need to specify a path to find @file{configure}
34432 itself from your working directory. If the path to @file{configure}
34433 would be the same as the argument to @samp{--srcdir}, you can leave out
34434 the @samp{--srcdir} option; it is assumed.)
34436 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34437 separate directory for a Sun 4 like this:
34441 cd gdb-@value{GDBVN}
34444 ../gdb-@value{GDBVN}/configure sun4
34449 When @file{configure} builds a configuration using a remote source
34450 directory, it creates a tree for the binaries with the same structure
34451 (and using the same names) as the tree under the source directory. In
34452 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34453 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34454 @file{gdb-sun4/gdb}.
34456 Make sure that your path to the @file{configure} script has just one
34457 instance of @file{gdb} in it. If your path to @file{configure} looks
34458 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34459 one subdirectory of @value{GDBN}, not the whole package. This leads to
34460 build errors about missing include files such as @file{bfd/bfd.h}.
34462 One popular reason to build several @value{GDBN} configurations in separate
34463 directories is to configure @value{GDBN} for cross-compiling (where
34464 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34465 programs that run on another machine---the @dfn{target}).
34466 You specify a cross-debugging target by
34467 giving the @samp{--target=@var{target}} option to @file{configure}.
34469 When you run @code{make} to build a program or library, you must run
34470 it in a configured directory---whatever directory you were in when you
34471 called @file{configure} (or one of its subdirectories).
34473 The @code{Makefile} that @file{configure} generates in each source
34474 directory also runs recursively. If you type @code{make} in a source
34475 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34476 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34477 will build all the required libraries, and then build GDB.
34479 When you have multiple hosts or targets configured in separate
34480 directories, you can run @code{make} on them in parallel (for example,
34481 if they are NFS-mounted on each of the hosts); they will not interfere
34485 @section Specifying Names for Hosts and Targets
34487 The specifications used for hosts and targets in the @file{configure}
34488 script are based on a three-part naming scheme, but some short predefined
34489 aliases are also supported. The full naming scheme encodes three pieces
34490 of information in the following pattern:
34493 @var{architecture}-@var{vendor}-@var{os}
34496 For example, you can use the alias @code{sun4} as a @var{host} argument,
34497 or as the value for @var{target} in a @code{--target=@var{target}}
34498 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34500 The @file{configure} script accompanying @value{GDBN} does not provide
34501 any query facility to list all supported host and target names or
34502 aliases. @file{configure} calls the Bourne shell script
34503 @code{config.sub} to map abbreviations to full names; you can read the
34504 script, if you wish, or you can use it to test your guesses on
34505 abbreviations---for example:
34508 % sh config.sub i386-linux
34510 % sh config.sub alpha-linux
34511 alpha-unknown-linux-gnu
34512 % sh config.sub hp9k700
34514 % sh config.sub sun4
34515 sparc-sun-sunos4.1.1
34516 % sh config.sub sun3
34517 m68k-sun-sunos4.1.1
34518 % sh config.sub i986v
34519 Invalid configuration `i986v': machine `i986v' not recognized
34523 @code{config.sub} is also distributed in the @value{GDBN} source
34524 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34526 @node Configure Options
34527 @section @file{configure} Options
34529 Here is a summary of the @file{configure} options and arguments that
34530 are most often useful for building @value{GDBN}. @file{configure} also has
34531 several other options not listed here. @inforef{What Configure
34532 Does,,configure.info}, for a full explanation of @file{configure}.
34535 configure @r{[}--help@r{]}
34536 @r{[}--prefix=@var{dir}@r{]}
34537 @r{[}--exec-prefix=@var{dir}@r{]}
34538 @r{[}--srcdir=@var{dirname}@r{]}
34539 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34540 @r{[}--target=@var{target}@r{]}
34545 You may introduce options with a single @samp{-} rather than
34546 @samp{--} if you prefer; but you may abbreviate option names if you use
34551 Display a quick summary of how to invoke @file{configure}.
34553 @item --prefix=@var{dir}
34554 Configure the source to install programs and files under directory
34557 @item --exec-prefix=@var{dir}
34558 Configure the source to install programs under directory
34561 @c avoid splitting the warning from the explanation:
34563 @item --srcdir=@var{dirname}
34564 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34565 @code{make} that implements the @code{VPATH} feature.}@*
34566 Use this option to make configurations in directories separate from the
34567 @value{GDBN} source directories. Among other things, you can use this to
34568 build (or maintain) several configurations simultaneously, in separate
34569 directories. @file{configure} writes configuration-specific files in
34570 the current directory, but arranges for them to use the source in the
34571 directory @var{dirname}. @file{configure} creates directories under
34572 the working directory in parallel to the source directories below
34575 @item --norecursion
34576 Configure only the directory level where @file{configure} is executed; do not
34577 propagate configuration to subdirectories.
34579 @item --target=@var{target}
34580 Configure @value{GDBN} for cross-debugging programs running on the specified
34581 @var{target}. Without this option, @value{GDBN} is configured to debug
34582 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34584 There is no convenient way to generate a list of all available targets.
34586 @item @var{host} @dots{}
34587 Configure @value{GDBN} to run on the specified @var{host}.
34589 There is no convenient way to generate a list of all available hosts.
34592 There are many other options available as well, but they are generally
34593 needed for special purposes only.
34595 @node System-wide configuration
34596 @section System-wide configuration and settings
34597 @cindex system-wide init file
34599 @value{GDBN} can be configured to have a system-wide init file;
34600 this file will be read and executed at startup (@pxref{Startup, , What
34601 @value{GDBN} does during startup}).
34603 Here is the corresponding configure option:
34606 @item --with-system-gdbinit=@var{file}
34607 Specify that the default location of the system-wide init file is
34611 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34612 it may be subject to relocation. Two possible cases:
34616 If the default location of this init file contains @file{$prefix},
34617 it will be subject to relocation. Suppose that the configure options
34618 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34619 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34620 init file is looked for as @file{$install/etc/gdbinit} instead of
34621 @file{$prefix/etc/gdbinit}.
34624 By contrast, if the default location does not contain the prefix,
34625 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34626 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34627 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34628 wherever @value{GDBN} is installed.
34631 If the configured location of the system-wide init file (as given by the
34632 @option{--with-system-gdbinit} option at configure time) is in the
34633 data-directory (as specified by @option{--with-gdb-datadir} at configure
34634 time) or in one of its subdirectories, then @value{GDBN} will look for the
34635 system-wide init file in the directory specified by the
34636 @option{--data-directory} command-line option.
34637 Note that the system-wide init file is only read once, during @value{GDBN}
34638 initialization. If the data-directory is changed after @value{GDBN} has
34639 started with the @code{set data-directory} command, the file will not be
34643 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34646 @node System-wide Configuration Scripts
34647 @subsection Installed System-wide Configuration Scripts
34648 @cindex system-wide configuration scripts
34650 The @file{system-gdbinit} directory, located inside the data-directory
34651 (as specified by @option{--with-gdb-datadir} at configure time) contains
34652 a number of scripts which can be used as system-wide init files. To
34653 automatically source those scripts at startup, @value{GDBN} should be
34654 configured with @option{--with-system-gdbinit}. Otherwise, any user
34655 should be able to source them by hand as needed.
34657 The following scripts are currently available:
34660 @item @file{elinos.py}
34662 @cindex ELinOS system-wide configuration script
34663 This script is useful when debugging a program on an ELinOS target.
34664 It takes advantage of the environment variables defined in a standard
34665 ELinOS environment in order to determine the location of the system
34666 shared libraries, and then sets the @samp{solib-absolute-prefix}
34667 and @samp{solib-search-path} variables appropriately.
34669 @item @file{wrs-linux.py}
34670 @pindex wrs-linux.py
34671 @cindex Wind River Linux system-wide configuration script
34672 This script is useful when debugging a program on a target running
34673 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34674 the host-side sysroot used by the target system.
34678 @node Maintenance Commands
34679 @appendix Maintenance Commands
34680 @cindex maintenance commands
34681 @cindex internal commands
34683 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34684 includes a number of commands intended for @value{GDBN} developers,
34685 that are not documented elsewhere in this manual. These commands are
34686 provided here for reference. (For commands that turn on debugging
34687 messages, see @ref{Debugging Output}.)
34690 @kindex maint agent
34691 @kindex maint agent-eval
34692 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34693 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34694 Translate the given @var{expression} into remote agent bytecodes.
34695 This command is useful for debugging the Agent Expression mechanism
34696 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34697 expression useful for data collection, such as by tracepoints, while
34698 @samp{maint agent-eval} produces an expression that evaluates directly
34699 to a result. For instance, a collection expression for @code{globa +
34700 globb} will include bytecodes to record four bytes of memory at each
34701 of the addresses of @code{globa} and @code{globb}, while discarding
34702 the result of the addition, while an evaluation expression will do the
34703 addition and return the sum.
34704 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34705 If not, generate remote agent bytecode for current frame PC address.
34707 @kindex maint agent-printf
34708 @item maint agent-printf @var{format},@var{expr},...
34709 Translate the given format string and list of argument expressions
34710 into remote agent bytecodes and display them as a disassembled list.
34711 This command is useful for debugging the agent version of dynamic
34712 printf (@pxref{Dynamic Printf}).
34714 @kindex maint info breakpoints
34715 @item @anchor{maint info breakpoints}maint info breakpoints
34716 Using the same format as @samp{info breakpoints}, display both the
34717 breakpoints you've set explicitly, and those @value{GDBN} is using for
34718 internal purposes. Internal breakpoints are shown with negative
34719 breakpoint numbers. The type column identifies what kind of breakpoint
34724 Normal, explicitly set breakpoint.
34727 Normal, explicitly set watchpoint.
34730 Internal breakpoint, used to handle correctly stepping through
34731 @code{longjmp} calls.
34733 @item longjmp resume
34734 Internal breakpoint at the target of a @code{longjmp}.
34737 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34740 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34743 Shared library events.
34747 @kindex maint info btrace
34748 @item maint info btrace
34749 Pint information about raw branch tracing data.
34751 @kindex maint btrace packet-history
34752 @item maint btrace packet-history
34753 Print the raw branch trace packets that are used to compute the
34754 execution history for the @samp{record btrace} command. Both the
34755 information and the format in which it is printed depend on the btrace
34760 For the BTS recording format, print a list of blocks of sequential
34761 code. For each block, the following information is printed:
34765 Newer blocks have higher numbers. The oldest block has number zero.
34766 @item Lowest @samp{PC}
34767 @item Highest @samp{PC}
34771 For the Intel Processor Trace recording format, print a list of
34772 Intel Processor Trace packets. For each packet, the following
34773 information is printed:
34776 @item Packet number
34777 Newer packets have higher numbers. The oldest packet has number zero.
34779 The packet's offset in the trace stream.
34780 @item Packet opcode and payload
34784 @kindex maint btrace clear-packet-history
34785 @item maint btrace clear-packet-history
34786 Discards the cached packet history printed by the @samp{maint btrace
34787 packet-history} command. The history will be computed again when
34790 @kindex maint btrace clear
34791 @item maint btrace clear
34792 Discard the branch trace data. The data will be fetched anew and the
34793 branch trace will be recomputed when needed.
34795 This implicitly truncates the branch trace to a single branch trace
34796 buffer. When updating branch trace incrementally, the branch trace
34797 available to @value{GDBN} may be bigger than a single branch trace
34800 @kindex maint set btrace pt skip-pad
34801 @item maint set btrace pt skip-pad
34802 @kindex maint show btrace pt skip-pad
34803 @item maint show btrace pt skip-pad
34804 Control whether @value{GDBN} will skip PAD packets when computing the
34807 @kindex set displaced-stepping
34808 @kindex show displaced-stepping
34809 @cindex displaced stepping support
34810 @cindex out-of-line single-stepping
34811 @item set displaced-stepping
34812 @itemx show displaced-stepping
34813 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34814 if the target supports it. Displaced stepping is a way to single-step
34815 over breakpoints without removing them from the inferior, by executing
34816 an out-of-line copy of the instruction that was originally at the
34817 breakpoint location. It is also known as out-of-line single-stepping.
34820 @item set displaced-stepping on
34821 If the target architecture supports it, @value{GDBN} will use
34822 displaced stepping to step over breakpoints.
34824 @item set displaced-stepping off
34825 @value{GDBN} will not use displaced stepping to step over breakpoints,
34826 even if such is supported by the target architecture.
34828 @cindex non-stop mode, and @samp{set displaced-stepping}
34829 @item set displaced-stepping auto
34830 This is the default mode. @value{GDBN} will use displaced stepping
34831 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34832 architecture supports displaced stepping.
34835 @kindex maint check-psymtabs
34836 @item maint check-psymtabs
34837 Check the consistency of currently expanded psymtabs versus symtabs.
34838 Use this to check, for example, whether a symbol is in one but not the other.
34840 @kindex maint check-symtabs
34841 @item maint check-symtabs
34842 Check the consistency of currently expanded symtabs.
34844 @kindex maint expand-symtabs
34845 @item maint expand-symtabs [@var{regexp}]
34846 Expand symbol tables.
34847 If @var{regexp} is specified, only expand symbol tables for file
34848 names matching @var{regexp}.
34850 @kindex maint set catch-demangler-crashes
34851 @kindex maint show catch-demangler-crashes
34852 @cindex demangler crashes
34853 @item maint set catch-demangler-crashes [on|off]
34854 @itemx maint show catch-demangler-crashes
34855 Control whether @value{GDBN} should attempt to catch crashes in the
34856 symbol name demangler. The default is to attempt to catch crashes.
34857 If enabled, the first time a crash is caught, a core file is created,
34858 the offending symbol is displayed and the user is presented with the
34859 option to terminate the current session.
34861 @kindex maint cplus first_component
34862 @item maint cplus first_component @var{name}
34863 Print the first C@t{++} class/namespace component of @var{name}.
34865 @kindex maint cplus namespace
34866 @item maint cplus namespace
34867 Print the list of possible C@t{++} namespaces.
34869 @kindex maint deprecate
34870 @kindex maint undeprecate
34871 @cindex deprecated commands
34872 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34873 @itemx maint undeprecate @var{command}
34874 Deprecate or undeprecate the named @var{command}. Deprecated commands
34875 cause @value{GDBN} to issue a warning when you use them. The optional
34876 argument @var{replacement} says which newer command should be used in
34877 favor of the deprecated one; if it is given, @value{GDBN} will mention
34878 the replacement as part of the warning.
34880 @kindex maint dump-me
34881 @item maint dump-me
34882 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34883 Cause a fatal signal in the debugger and force it to dump its core.
34884 This is supported only on systems which support aborting a program
34885 with the @code{SIGQUIT} signal.
34887 @kindex maint internal-error
34888 @kindex maint internal-warning
34889 @kindex maint demangler-warning
34890 @cindex demangler crashes
34891 @item maint internal-error @r{[}@var{message-text}@r{]}
34892 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34893 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34895 Cause @value{GDBN} to call the internal function @code{internal_error},
34896 @code{internal_warning} or @code{demangler_warning} and hence behave
34897 as though an internal problem has been detected. In addition to
34898 reporting the internal problem, these functions give the user the
34899 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34900 and @code{internal_warning}) create a core file of the current
34901 @value{GDBN} session.
34903 These commands take an optional parameter @var{message-text} that is
34904 used as the text of the error or warning message.
34906 Here's an example of using @code{internal-error}:
34909 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34910 @dots{}/maint.c:121: internal-error: testing, 1, 2
34911 A problem internal to GDB has been detected. Further
34912 debugging may prove unreliable.
34913 Quit this debugging session? (y or n) @kbd{n}
34914 Create a core file? (y or n) @kbd{n}
34918 @cindex @value{GDBN} internal error
34919 @cindex internal errors, control of @value{GDBN} behavior
34920 @cindex demangler crashes
34922 @kindex maint set internal-error
34923 @kindex maint show internal-error
34924 @kindex maint set internal-warning
34925 @kindex maint show internal-warning
34926 @kindex maint set demangler-warning
34927 @kindex maint show demangler-warning
34928 @item maint set internal-error @var{action} [ask|yes|no]
34929 @itemx maint show internal-error @var{action}
34930 @itemx maint set internal-warning @var{action} [ask|yes|no]
34931 @itemx maint show internal-warning @var{action}
34932 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34933 @itemx maint show demangler-warning @var{action}
34934 When @value{GDBN} reports an internal problem (error or warning) it
34935 gives the user the opportunity to both quit @value{GDBN} and create a
34936 core file of the current @value{GDBN} session. These commands let you
34937 override the default behaviour for each particular @var{action},
34938 described in the table below.
34942 You can specify that @value{GDBN} should always (yes) or never (no)
34943 quit. The default is to ask the user what to do.
34946 You can specify that @value{GDBN} should always (yes) or never (no)
34947 create a core file. The default is to ask the user what to do. Note
34948 that there is no @code{corefile} option for @code{demangler-warning}:
34949 demangler warnings always create a core file and this cannot be
34953 @kindex maint packet
34954 @item maint packet @var{text}
34955 If @value{GDBN} is talking to an inferior via the serial protocol,
34956 then this command sends the string @var{text} to the inferior, and
34957 displays the response packet. @value{GDBN} supplies the initial
34958 @samp{$} character, the terminating @samp{#} character, and the
34961 @kindex maint print architecture
34962 @item maint print architecture @r{[}@var{file}@r{]}
34963 Print the entire architecture configuration. The optional argument
34964 @var{file} names the file where the output goes.
34966 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
34967 @item maint print c-tdesc
34968 Print the target description (@pxref{Target Descriptions}) as
34969 a C source file. By default, the target description is for the current
34970 target, but if the optional argument @var{file} is provided, that file
34971 is used to produce the description. The @var{file} should be an XML
34972 document, of the form described in @ref{Target Description Format}.
34973 The created source file is built into @value{GDBN} when @value{GDBN} is
34974 built again. This command is used by developers after they add or
34975 modify XML target descriptions.
34977 @kindex maint check xml-descriptions
34978 @item maint check xml-descriptions @var{dir}
34979 Check that the target descriptions dynamically created by @value{GDBN}
34980 equal the descriptions created from XML files found in @var{dir}.
34982 @kindex maint print dummy-frames
34983 @item maint print dummy-frames
34984 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34987 (@value{GDBP}) @kbd{b add}
34989 (@value{GDBP}) @kbd{print add(2,3)}
34990 Breakpoint 2, add (a=2, b=3) at @dots{}
34992 The program being debugged stopped while in a function called from GDB.
34994 (@value{GDBP}) @kbd{maint print dummy-frames}
34995 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34999 Takes an optional file parameter.
35001 @kindex maint print registers
35002 @kindex maint print raw-registers
35003 @kindex maint print cooked-registers
35004 @kindex maint print register-groups
35005 @kindex maint print remote-registers
35006 @item maint print registers @r{[}@var{file}@r{]}
35007 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35008 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35009 @itemx maint print register-groups @r{[}@var{file}@r{]}
35010 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35011 Print @value{GDBN}'s internal register data structures.
35013 The command @code{maint print raw-registers} includes the contents of
35014 the raw register cache; the command @code{maint print
35015 cooked-registers} includes the (cooked) value of all registers,
35016 including registers which aren't available on the target nor visible
35017 to user; the command @code{maint print register-groups} includes the
35018 groups that each register is a member of; and the command @code{maint
35019 print remote-registers} includes the remote target's register numbers
35020 and offsets in the `G' packets.
35022 These commands take an optional parameter, a file name to which to
35023 write the information.
35025 @kindex maint print reggroups
35026 @item maint print reggroups @r{[}@var{file}@r{]}
35027 Print @value{GDBN}'s internal register group data structures. The
35028 optional argument @var{file} tells to what file to write the
35031 The register groups info looks like this:
35034 (@value{GDBP}) @kbd{maint print reggroups}
35047 This command forces @value{GDBN} to flush its internal register cache.
35049 @kindex maint print objfiles
35050 @cindex info for known object files
35051 @item maint print objfiles @r{[}@var{regexp}@r{]}
35052 Print a dump of all known object files.
35053 If @var{regexp} is specified, only print object files whose names
35054 match @var{regexp}. For each object file, this command prints its name,
35055 address in memory, and all of its psymtabs and symtabs.
35057 @kindex maint print user-registers
35058 @cindex user registers
35059 @item maint print user-registers
35060 List all currently available @dfn{user registers}. User registers
35061 typically provide alternate names for actual hardware registers. They
35062 include the four ``standard'' registers @code{$fp}, @code{$pc},
35063 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35064 registers can be used in expressions in the same way as the canonical
35065 register names, but only the latter are listed by the @code{info
35066 registers} and @code{maint print registers} commands.
35068 @kindex maint print section-scripts
35069 @cindex info for known .debug_gdb_scripts-loaded scripts
35070 @item maint print section-scripts [@var{regexp}]
35071 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35072 If @var{regexp} is specified, only print scripts loaded by object files
35073 matching @var{regexp}.
35074 For each script, this command prints its name as specified in the objfile,
35075 and the full path if known.
35076 @xref{dotdebug_gdb_scripts section}.
35078 @kindex maint print statistics
35079 @cindex bcache statistics
35080 @item maint print statistics
35081 This command prints, for each object file in the program, various data
35082 about that object file followed by the byte cache (@dfn{bcache})
35083 statistics for the object file. The objfile data includes the number
35084 of minimal, partial, full, and stabs symbols, the number of types
35085 defined by the objfile, the number of as yet unexpanded psym tables,
35086 the number of line tables and string tables, and the amount of memory
35087 used by the various tables. The bcache statistics include the counts,
35088 sizes, and counts of duplicates of all and unique objects, max,
35089 average, and median entry size, total memory used and its overhead and
35090 savings, and various measures of the hash table size and chain
35093 @kindex maint print target-stack
35094 @cindex target stack description
35095 @item maint print target-stack
35096 A @dfn{target} is an interface between the debugger and a particular
35097 kind of file or process. Targets can be stacked in @dfn{strata},
35098 so that more than one target can potentially respond to a request.
35099 In particular, memory accesses will walk down the stack of targets
35100 until they find a target that is interested in handling that particular
35103 This command prints a short description of each layer that was pushed on
35104 the @dfn{target stack}, starting from the top layer down to the bottom one.
35106 @kindex maint print type
35107 @cindex type chain of a data type
35108 @item maint print type @var{expr}
35109 Print the type chain for a type specified by @var{expr}. The argument
35110 can be either a type name or a symbol. If it is a symbol, the type of
35111 that symbol is described. The type chain produced by this command is
35112 a recursive definition of the data type as stored in @value{GDBN}'s
35113 data structures, including its flags and contained types.
35115 @kindex maint selftest
35117 @item maint selftest @r{[}@var{filter}@r{]}
35118 Run any self tests that were compiled in to @value{GDBN}. This will
35119 print a message showing how many tests were run, and how many failed.
35120 If a @var{filter} is passed, only the tests with @var{filter} in their
35123 @kindex "maint info selftests"
35125 @item maint info selftests
35126 List the selftests compiled in to @value{GDBN}.
35128 @kindex maint set dwarf always-disassemble
35129 @kindex maint show dwarf always-disassemble
35130 @item maint set dwarf always-disassemble
35131 @item maint show dwarf always-disassemble
35132 Control the behavior of @code{info address} when using DWARF debugging
35135 The default is @code{off}, which means that @value{GDBN} should try to
35136 describe a variable's location in an easily readable format. When
35137 @code{on}, @value{GDBN} will instead display the DWARF location
35138 expression in an assembly-like format. Note that some locations are
35139 too complex for @value{GDBN} to describe simply; in this case you will
35140 always see the disassembly form.
35142 Here is an example of the resulting disassembly:
35145 (gdb) info addr argc
35146 Symbol "argc" is a complex DWARF expression:
35150 For more information on these expressions, see
35151 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35153 @kindex maint set dwarf max-cache-age
35154 @kindex maint show dwarf max-cache-age
35155 @item maint set dwarf max-cache-age
35156 @itemx maint show dwarf max-cache-age
35157 Control the DWARF compilation unit cache.
35159 @cindex DWARF compilation units cache
35160 In object files with inter-compilation-unit references, such as those
35161 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35162 reader needs to frequently refer to previously read compilation units.
35163 This setting controls how long a compilation unit will remain in the
35164 cache if it is not referenced. A higher limit means that cached
35165 compilation units will be stored in memory longer, and more total
35166 memory will be used. Setting it to zero disables caching, which will
35167 slow down @value{GDBN} startup, but reduce memory consumption.
35169 @kindex maint set profile
35170 @kindex maint show profile
35171 @cindex profiling GDB
35172 @item maint set profile
35173 @itemx maint show profile
35174 Control profiling of @value{GDBN}.
35176 Profiling will be disabled until you use the @samp{maint set profile}
35177 command to enable it. When you enable profiling, the system will begin
35178 collecting timing and execution count data; when you disable profiling or
35179 exit @value{GDBN}, the results will be written to a log file. Remember that
35180 if you use profiling, @value{GDBN} will overwrite the profiling log file
35181 (often called @file{gmon.out}). If you have a record of important profiling
35182 data in a @file{gmon.out} file, be sure to move it to a safe location.
35184 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35185 compiled with the @samp{-pg} compiler option.
35187 @kindex maint set show-debug-regs
35188 @kindex maint show show-debug-regs
35189 @cindex hardware debug registers
35190 @item maint set show-debug-regs
35191 @itemx maint show show-debug-regs
35192 Control whether to show variables that mirror the hardware debug
35193 registers. Use @code{on} to enable, @code{off} to disable. If
35194 enabled, the debug registers values are shown when @value{GDBN} inserts or
35195 removes a hardware breakpoint or watchpoint, and when the inferior
35196 triggers a hardware-assisted breakpoint or watchpoint.
35198 @kindex maint set show-all-tib
35199 @kindex maint show show-all-tib
35200 @item maint set show-all-tib
35201 @itemx maint show show-all-tib
35202 Control whether to show all non zero areas within a 1k block starting
35203 at thread local base, when using the @samp{info w32 thread-information-block}
35206 @kindex maint set target-async
35207 @kindex maint show target-async
35208 @item maint set target-async
35209 @itemx maint show target-async
35210 This controls whether @value{GDBN} targets operate in synchronous or
35211 asynchronous mode (@pxref{Background Execution}). Normally the
35212 default is asynchronous, if it is available; but this can be changed
35213 to more easily debug problems occurring only in synchronous mode.
35215 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35216 @kindex maint show target-non-stop
35217 @item maint set target-non-stop
35218 @itemx maint show target-non-stop
35220 This controls whether @value{GDBN} targets always operate in non-stop
35221 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35222 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35223 if supported by the target.
35226 @item maint set target-non-stop auto
35227 This is the default mode. @value{GDBN} controls the target in
35228 non-stop mode if the target supports it.
35230 @item maint set target-non-stop on
35231 @value{GDBN} controls the target in non-stop mode even if the target
35232 does not indicate support.
35234 @item maint set target-non-stop off
35235 @value{GDBN} does not control the target in non-stop mode even if the
35236 target supports it.
35239 @kindex maint set per-command
35240 @kindex maint show per-command
35241 @item maint set per-command
35242 @itemx maint show per-command
35243 @cindex resources used by commands
35245 @value{GDBN} can display the resources used by each command.
35246 This is useful in debugging performance problems.
35249 @item maint set per-command space [on|off]
35250 @itemx maint show per-command space
35251 Enable or disable the printing of the memory used by GDB for each command.
35252 If enabled, @value{GDBN} will display how much memory each command
35253 took, following the command's own output.
35254 This can also be requested by invoking @value{GDBN} with the
35255 @option{--statistics} command-line switch (@pxref{Mode Options}).
35257 @item maint set per-command time [on|off]
35258 @itemx maint show per-command time
35259 Enable or disable the printing of the execution time of @value{GDBN}
35261 If enabled, @value{GDBN} will display how much time it
35262 took to execute each command, following the command's own output.
35263 Both CPU time and wallclock time are printed.
35264 Printing both is useful when trying to determine whether the cost is
35265 CPU or, e.g., disk/network latency.
35266 Note that the CPU time printed is for @value{GDBN} only, it does not include
35267 the execution time of the inferior because there's no mechanism currently
35268 to compute how much time was spent by @value{GDBN} and how much time was
35269 spent by the program been debugged.
35270 This can also be requested by invoking @value{GDBN} with the
35271 @option{--statistics} command-line switch (@pxref{Mode Options}).
35273 @item maint set per-command symtab [on|off]
35274 @itemx maint show per-command symtab
35275 Enable or disable the printing of basic symbol table statistics
35277 If enabled, @value{GDBN} will display the following information:
35281 number of symbol tables
35283 number of primary symbol tables
35285 number of blocks in the blockvector
35289 @kindex maint space
35290 @cindex memory used by commands
35291 @item maint space @var{value}
35292 An alias for @code{maint set per-command space}.
35293 A non-zero value enables it, zero disables it.
35296 @cindex time of command execution
35297 @item maint time @var{value}
35298 An alias for @code{maint set per-command time}.
35299 A non-zero value enables it, zero disables it.
35301 @kindex maint translate-address
35302 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35303 Find the symbol stored at the location specified by the address
35304 @var{addr} and an optional section name @var{section}. If found,
35305 @value{GDBN} prints the name of the closest symbol and an offset from
35306 the symbol's location to the specified address. This is similar to
35307 the @code{info address} command (@pxref{Symbols}), except that this
35308 command also allows to find symbols in other sections.
35310 If section was not specified, the section in which the symbol was found
35311 is also printed. For dynamically linked executables, the name of
35312 executable or shared library containing the symbol is printed as well.
35316 The following command is useful for non-interactive invocations of
35317 @value{GDBN}, such as in the test suite.
35320 @item set watchdog @var{nsec}
35321 @kindex set watchdog
35322 @cindex watchdog timer
35323 @cindex timeout for commands
35324 Set the maximum number of seconds @value{GDBN} will wait for the
35325 target operation to finish. If this time expires, @value{GDBN}
35326 reports and error and the command is aborted.
35328 @item show watchdog
35329 Show the current setting of the target wait timeout.
35332 @node Remote Protocol
35333 @appendix @value{GDBN} Remote Serial Protocol
35338 * Stop Reply Packets::
35339 * General Query Packets::
35340 * Architecture-Specific Protocol Details::
35341 * Tracepoint Packets::
35342 * Host I/O Packets::
35344 * Notification Packets::
35345 * Remote Non-Stop::
35346 * Packet Acknowledgment::
35348 * File-I/O Remote Protocol Extension::
35349 * Library List Format::
35350 * Library List Format for SVR4 Targets::
35351 * Memory Map Format::
35352 * Thread List Format::
35353 * Traceframe Info Format::
35354 * Branch Trace Format::
35355 * Branch Trace Configuration Format::
35361 There may be occasions when you need to know something about the
35362 protocol---for example, if there is only one serial port to your target
35363 machine, you might want your program to do something special if it
35364 recognizes a packet meant for @value{GDBN}.
35366 In the examples below, @samp{->} and @samp{<-} are used to indicate
35367 transmitted and received data, respectively.
35369 @cindex protocol, @value{GDBN} remote serial
35370 @cindex serial protocol, @value{GDBN} remote
35371 @cindex remote serial protocol
35372 All @value{GDBN} commands and responses (other than acknowledgments
35373 and notifications, see @ref{Notification Packets}) are sent as a
35374 @var{packet}. A @var{packet} is introduced with the character
35375 @samp{$}, the actual @var{packet-data}, and the terminating character
35376 @samp{#} followed by a two-digit @var{checksum}:
35379 @code{$}@var{packet-data}@code{#}@var{checksum}
35383 @cindex checksum, for @value{GDBN} remote
35385 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35386 characters between the leading @samp{$} and the trailing @samp{#} (an
35387 eight bit unsigned checksum).
35389 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35390 specification also included an optional two-digit @var{sequence-id}:
35393 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35396 @cindex sequence-id, for @value{GDBN} remote
35398 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35399 has never output @var{sequence-id}s. Stubs that handle packets added
35400 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35402 When either the host or the target machine receives a packet, the first
35403 response expected is an acknowledgment: either @samp{+} (to indicate
35404 the package was received correctly) or @samp{-} (to request
35408 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35413 The @samp{+}/@samp{-} acknowledgments can be disabled
35414 once a connection is established.
35415 @xref{Packet Acknowledgment}, for details.
35417 The host (@value{GDBN}) sends @var{command}s, and the target (the
35418 debugging stub incorporated in your program) sends a @var{response}. In
35419 the case of step and continue @var{command}s, the response is only sent
35420 when the operation has completed, and the target has again stopped all
35421 threads in all attached processes. This is the default all-stop mode
35422 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35423 execution mode; see @ref{Remote Non-Stop}, for details.
35425 @var{packet-data} consists of a sequence of characters with the
35426 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35429 @cindex remote protocol, field separator
35430 Fields within the packet should be separated using @samp{,} @samp{;} or
35431 @samp{:}. Except where otherwise noted all numbers are represented in
35432 @sc{hex} with leading zeros suppressed.
35434 Implementors should note that prior to @value{GDBN} 5.0, the character
35435 @samp{:} could not appear as the third character in a packet (as it
35436 would potentially conflict with the @var{sequence-id}).
35438 @cindex remote protocol, binary data
35439 @anchor{Binary Data}
35440 Binary data in most packets is encoded either as two hexadecimal
35441 digits per byte of binary data. This allowed the traditional remote
35442 protocol to work over connections which were only seven-bit clean.
35443 Some packets designed more recently assume an eight-bit clean
35444 connection, and use a more efficient encoding to send and receive
35447 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35448 as an escape character. Any escaped byte is transmitted as the escape
35449 character followed by the original character XORed with @code{0x20}.
35450 For example, the byte @code{0x7d} would be transmitted as the two
35451 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35452 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35453 @samp{@}}) must always be escaped. Responses sent by the stub
35454 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35455 is not interpreted as the start of a run-length encoded sequence
35458 Response @var{data} can be run-length encoded to save space.
35459 Run-length encoding replaces runs of identical characters with one
35460 instance of the repeated character, followed by a @samp{*} and a
35461 repeat count. The repeat count is itself sent encoded, to avoid
35462 binary characters in @var{data}: a value of @var{n} is sent as
35463 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35464 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35465 code 32) for a repeat count of 3. (This is because run-length
35466 encoding starts to win for counts 3 or more.) Thus, for example,
35467 @samp{0* } is a run-length encoding of ``0000'': the space character
35468 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35471 The printable characters @samp{#} and @samp{$} or with a numeric value
35472 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35473 seven repeats (@samp{$}) can be expanded using a repeat count of only
35474 five (@samp{"}). For example, @samp{00000000} can be encoded as
35477 The error response returned for some packets includes a two character
35478 error number. That number is not well defined.
35480 @cindex empty response, for unsupported packets
35481 For any @var{command} not supported by the stub, an empty response
35482 (@samp{$#00}) should be returned. That way it is possible to extend the
35483 protocol. A newer @value{GDBN} can tell if a packet is supported based
35486 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35487 commands for register access, and the @samp{m} and @samp{M} commands
35488 for memory access. Stubs that only control single-threaded targets
35489 can implement run control with the @samp{c} (continue), and @samp{s}
35490 (step) commands. Stubs that support multi-threading targets should
35491 support the @samp{vCont} command. All other commands are optional.
35496 The following table provides a complete list of all currently defined
35497 @var{command}s and their corresponding response @var{data}.
35498 @xref{File-I/O Remote Protocol Extension}, for details about the File
35499 I/O extension of the remote protocol.
35501 Each packet's description has a template showing the packet's overall
35502 syntax, followed by an explanation of the packet's meaning. We
35503 include spaces in some of the templates for clarity; these are not
35504 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35505 separate its components. For example, a template like @samp{foo
35506 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35507 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35508 @var{baz}. @value{GDBN} does not transmit a space character between the
35509 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35512 @cindex @var{thread-id}, in remote protocol
35513 @anchor{thread-id syntax}
35514 Several packets and replies include a @var{thread-id} field to identify
35515 a thread. Normally these are positive numbers with a target-specific
35516 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35517 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35520 In addition, the remote protocol supports a multiprocess feature in
35521 which the @var{thread-id} syntax is extended to optionally include both
35522 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35523 The @var{pid} (process) and @var{tid} (thread) components each have the
35524 format described above: a positive number with target-specific
35525 interpretation formatted as a big-endian hex string, literal @samp{-1}
35526 to indicate all processes or threads (respectively), or @samp{0} to
35527 indicate an arbitrary process or thread. Specifying just a process, as
35528 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35529 error to specify all processes but a specific thread, such as
35530 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35531 for those packets and replies explicitly documented to include a process
35532 ID, rather than a @var{thread-id}.
35534 The multiprocess @var{thread-id} syntax extensions are only used if both
35535 @value{GDBN} and the stub report support for the @samp{multiprocess}
35536 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35539 Note that all packet forms beginning with an upper- or lower-case
35540 letter, other than those described here, are reserved for future use.
35542 Here are the packet descriptions.
35547 @cindex @samp{!} packet
35548 @anchor{extended mode}
35549 Enable extended mode. In extended mode, the remote server is made
35550 persistent. The @samp{R} packet is used to restart the program being
35556 The remote target both supports and has enabled extended mode.
35560 @cindex @samp{?} packet
35562 Indicate the reason the target halted. The reply is the same as for
35563 step and continue. This packet has a special interpretation when the
35564 target is in non-stop mode; see @ref{Remote Non-Stop}.
35567 @xref{Stop Reply Packets}, for the reply specifications.
35569 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35570 @cindex @samp{A} packet
35571 Initialized @code{argv[]} array passed into program. @var{arglen}
35572 specifies the number of bytes in the hex encoded byte stream
35573 @var{arg}. See @code{gdbserver} for more details.
35578 The arguments were set.
35584 @cindex @samp{b} packet
35585 (Don't use this packet; its behavior is not well-defined.)
35586 Change the serial line speed to @var{baud}.
35588 JTC: @emph{When does the transport layer state change? When it's
35589 received, or after the ACK is transmitted. In either case, there are
35590 problems if the command or the acknowledgment packet is dropped.}
35592 Stan: @emph{If people really wanted to add something like this, and get
35593 it working for the first time, they ought to modify ser-unix.c to send
35594 some kind of out-of-band message to a specially-setup stub and have the
35595 switch happen "in between" packets, so that from remote protocol's point
35596 of view, nothing actually happened.}
35598 @item B @var{addr},@var{mode}
35599 @cindex @samp{B} packet
35600 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35601 breakpoint at @var{addr}.
35603 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35604 (@pxref{insert breakpoint or watchpoint packet}).
35606 @cindex @samp{bc} packet
35609 Backward continue. Execute the target system in reverse. No parameter.
35610 @xref{Reverse Execution}, for more information.
35613 @xref{Stop Reply Packets}, for the reply specifications.
35615 @cindex @samp{bs} packet
35618 Backward single step. Execute one instruction in reverse. No parameter.
35619 @xref{Reverse Execution}, for more information.
35622 @xref{Stop Reply Packets}, for the reply specifications.
35624 @item c @r{[}@var{addr}@r{]}
35625 @cindex @samp{c} packet
35626 Continue at @var{addr}, which is the address to resume. If @var{addr}
35627 is omitted, resume at current address.
35629 This packet is deprecated for multi-threading support. @xref{vCont
35633 @xref{Stop Reply Packets}, for the reply specifications.
35635 @item C @var{sig}@r{[};@var{addr}@r{]}
35636 @cindex @samp{C} packet
35637 Continue with signal @var{sig} (hex signal number). If
35638 @samp{;@var{addr}} is omitted, resume at same address.
35640 This packet is deprecated for multi-threading support. @xref{vCont
35644 @xref{Stop Reply Packets}, for the reply specifications.
35647 @cindex @samp{d} packet
35650 Don't use this packet; instead, define a general set packet
35651 (@pxref{General Query Packets}).
35655 @cindex @samp{D} packet
35656 The first form of the packet is used to detach @value{GDBN} from the
35657 remote system. It is sent to the remote target
35658 before @value{GDBN} disconnects via the @code{detach} command.
35660 The second form, including a process ID, is used when multiprocess
35661 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35662 detach only a specific process. The @var{pid} is specified as a
35663 big-endian hex string.
35673 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35674 @cindex @samp{F} packet
35675 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35676 This is part of the File-I/O protocol extension. @xref{File-I/O
35677 Remote Protocol Extension}, for the specification.
35680 @anchor{read registers packet}
35681 @cindex @samp{g} packet
35682 Read general registers.
35686 @item @var{XX@dots{}}
35687 Each byte of register data is described by two hex digits. The bytes
35688 with the register are transmitted in target byte order. The size of
35689 each register and their position within the @samp{g} packet are
35690 determined by the @value{GDBN} internal gdbarch functions
35691 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35693 When reading registers from a trace frame (@pxref{Analyze Collected
35694 Data,,Using the Collected Data}), the stub may also return a string of
35695 literal @samp{x}'s in place of the register data digits, to indicate
35696 that the corresponding register has not been collected, thus its value
35697 is unavailable. For example, for an architecture with 4 registers of
35698 4 bytes each, the following reply indicates to @value{GDBN} that
35699 registers 0 and 2 have not been collected, while registers 1 and 3
35700 have been collected, and both have zero value:
35704 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35711 @item G @var{XX@dots{}}
35712 @cindex @samp{G} packet
35713 Write general registers. @xref{read registers packet}, for a
35714 description of the @var{XX@dots{}} data.
35724 @item H @var{op} @var{thread-id}
35725 @cindex @samp{H} packet
35726 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35727 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35728 should be @samp{c} for step and continue operations (note that this
35729 is deprecated, supporting the @samp{vCont} command is a better
35730 option), and @samp{g} for other operations. The thread designator
35731 @var{thread-id} has the format and interpretation described in
35732 @ref{thread-id syntax}.
35743 @c 'H': How restrictive (or permissive) is the thread model. If a
35744 @c thread is selected and stopped, are other threads allowed
35745 @c to continue to execute? As I mentioned above, I think the
35746 @c semantics of each command when a thread is selected must be
35747 @c described. For example:
35749 @c 'g': If the stub supports threads and a specific thread is
35750 @c selected, returns the register block from that thread;
35751 @c otherwise returns current registers.
35753 @c 'G' If the stub supports threads and a specific thread is
35754 @c selected, sets the registers of the register block of
35755 @c that thread; otherwise sets current registers.
35757 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35758 @anchor{cycle step packet}
35759 @cindex @samp{i} packet
35760 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35761 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35762 step starting at that address.
35765 @cindex @samp{I} packet
35766 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35770 @cindex @samp{k} packet
35773 The exact effect of this packet is not specified.
35775 For a bare-metal target, it may power cycle or reset the target
35776 system. For that reason, the @samp{k} packet has no reply.
35778 For a single-process target, it may kill that process if possible.
35780 A multiple-process target may choose to kill just one process, or all
35781 that are under @value{GDBN}'s control. For more precise control, use
35782 the vKill packet (@pxref{vKill packet}).
35784 If the target system immediately closes the connection in response to
35785 @samp{k}, @value{GDBN} does not consider the lack of packet
35786 acknowledgment to be an error, and assumes the kill was successful.
35788 If connected using @kbd{target extended-remote}, and the target does
35789 not close the connection in response to a kill request, @value{GDBN}
35790 probes the target state as if a new connection was opened
35791 (@pxref{? packet}).
35793 @item m @var{addr},@var{length}
35794 @cindex @samp{m} packet
35795 Read @var{length} addressable memory units starting at address @var{addr}
35796 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35797 any particular boundary.
35799 The stub need not use any particular size or alignment when gathering
35800 data from memory for the response; even if @var{addr} is word-aligned
35801 and @var{length} is a multiple of the word size, the stub is free to
35802 use byte accesses, or not. For this reason, this packet may not be
35803 suitable for accessing memory-mapped I/O devices.
35804 @cindex alignment of remote memory accesses
35805 @cindex size of remote memory accesses
35806 @cindex memory, alignment and size of remote accesses
35810 @item @var{XX@dots{}}
35811 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35812 The reply may contain fewer addressable memory units than requested if the
35813 server was able to read only part of the region of memory.
35818 @item M @var{addr},@var{length}:@var{XX@dots{}}
35819 @cindex @samp{M} packet
35820 Write @var{length} addressable memory units starting at address @var{addr}
35821 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35822 byte is transmitted as a two-digit hexadecimal number.
35829 for an error (this includes the case where only part of the data was
35834 @cindex @samp{p} packet
35835 Read the value of register @var{n}; @var{n} is in hex.
35836 @xref{read registers packet}, for a description of how the returned
35837 register value is encoded.
35841 @item @var{XX@dots{}}
35842 the register's value
35846 Indicating an unrecognized @var{query}.
35849 @item P @var{n@dots{}}=@var{r@dots{}}
35850 @anchor{write register packet}
35851 @cindex @samp{P} packet
35852 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35853 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35854 digits for each byte in the register (target byte order).
35864 @item q @var{name} @var{params}@dots{}
35865 @itemx Q @var{name} @var{params}@dots{}
35866 @cindex @samp{q} packet
35867 @cindex @samp{Q} packet
35868 General query (@samp{q}) and set (@samp{Q}). These packets are
35869 described fully in @ref{General Query Packets}.
35872 @cindex @samp{r} packet
35873 Reset the entire system.
35875 Don't use this packet; use the @samp{R} packet instead.
35878 @cindex @samp{R} packet
35879 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35880 This packet is only available in extended mode (@pxref{extended mode}).
35882 The @samp{R} packet has no reply.
35884 @item s @r{[}@var{addr}@r{]}
35885 @cindex @samp{s} packet
35886 Single step, resuming at @var{addr}. If
35887 @var{addr} is omitted, resume at same address.
35889 This packet is deprecated for multi-threading support. @xref{vCont
35893 @xref{Stop Reply Packets}, for the reply specifications.
35895 @item S @var{sig}@r{[};@var{addr}@r{]}
35896 @anchor{step with signal packet}
35897 @cindex @samp{S} packet
35898 Step with signal. This is analogous to the @samp{C} packet, but
35899 requests a single-step, rather than a normal resumption of execution.
35901 This packet is deprecated for multi-threading support. @xref{vCont
35905 @xref{Stop Reply Packets}, for the reply specifications.
35907 @item t @var{addr}:@var{PP},@var{MM}
35908 @cindex @samp{t} packet
35909 Search backwards starting at address @var{addr} for a match with pattern
35910 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35911 There must be at least 3 digits in @var{addr}.
35913 @item T @var{thread-id}
35914 @cindex @samp{T} packet
35915 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35920 thread is still alive
35926 Packets starting with @samp{v} are identified by a multi-letter name,
35927 up to the first @samp{;} or @samp{?} (or the end of the packet).
35929 @item vAttach;@var{pid}
35930 @cindex @samp{vAttach} packet
35931 Attach to a new process with the specified process ID @var{pid}.
35932 The process ID is a
35933 hexadecimal integer identifying the process. In all-stop mode, all
35934 threads in the attached process are stopped; in non-stop mode, it may be
35935 attached without being stopped if that is supported by the target.
35937 @c In non-stop mode, on a successful vAttach, the stub should set the
35938 @c current thread to a thread of the newly-attached process. After
35939 @c attaching, GDB queries for the attached process's thread ID with qC.
35940 @c Also note that, from a user perspective, whether or not the
35941 @c target is stopped on attach in non-stop mode depends on whether you
35942 @c use the foreground or background version of the attach command, not
35943 @c on what vAttach does; GDB does the right thing with respect to either
35944 @c stopping or restarting threads.
35946 This packet is only available in extended mode (@pxref{extended mode}).
35952 @item @r{Any stop packet}
35953 for success in all-stop mode (@pxref{Stop Reply Packets})
35955 for success in non-stop mode (@pxref{Remote Non-Stop})
35958 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35959 @cindex @samp{vCont} packet
35960 @anchor{vCont packet}
35961 Resume the inferior, specifying different actions for each thread.
35963 For each inferior thread, the leftmost action with a matching
35964 @var{thread-id} is applied. Threads that don't match any action
35965 remain in their current state. Thread IDs are specified using the
35966 syntax described in @ref{thread-id syntax}. If multiprocess
35967 extensions (@pxref{multiprocess extensions}) are supported, actions
35968 can be specified to match all threads in a process by using the
35969 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
35970 @var{thread-id} matches all threads. Specifying no actions is an
35973 Currently supported actions are:
35979 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35983 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35986 @item r @var{start},@var{end}
35987 Step once, and then keep stepping as long as the thread stops at
35988 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35989 The remote stub reports a stop reply when either the thread goes out
35990 of the range or is stopped due to an unrelated reason, such as hitting
35991 a breakpoint. @xref{range stepping}.
35993 If the range is empty (@var{start} == @var{end}), then the action
35994 becomes equivalent to the @samp{s} action. In other words,
35995 single-step once, and report the stop (even if the stepped instruction
35996 jumps to @var{start}).
35998 (A stop reply may be sent at any point even if the PC is still within
35999 the stepping range; for example, it is valid to implement this packet
36000 in a degenerate way as a single instruction step operation.)
36004 The optional argument @var{addr} normally associated with the
36005 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36006 not supported in @samp{vCont}.
36008 The @samp{t} action is only relevant in non-stop mode
36009 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36010 A stop reply should be generated for any affected thread not already stopped.
36011 When a thread is stopped by means of a @samp{t} action,
36012 the corresponding stop reply should indicate that the thread has stopped with
36013 signal @samp{0}, regardless of whether the target uses some other signal
36014 as an implementation detail.
36016 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36017 @samp{r} actions for threads that are already running. Conversely,
36018 the server must ignore @samp{t} actions for threads that are already
36021 @emph{Note:} In non-stop mode, a thread is considered running until
36022 @value{GDBN} acknowleges an asynchronous stop notification for it with
36023 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36025 The stub must support @samp{vCont} if it reports support for
36026 multiprocess extensions (@pxref{multiprocess extensions}).
36029 @xref{Stop Reply Packets}, for the reply specifications.
36032 @cindex @samp{vCont?} packet
36033 Request a list of actions supported by the @samp{vCont} packet.
36037 @item vCont@r{[};@var{action}@dots{}@r{]}
36038 The @samp{vCont} packet is supported. Each @var{action} is a supported
36039 command in the @samp{vCont} packet.
36041 The @samp{vCont} packet is not supported.
36044 @anchor{vCtrlC packet}
36046 @cindex @samp{vCtrlC} packet
36047 Interrupt remote target as if a control-C was pressed on the remote
36048 terminal. This is the equivalent to reacting to the @code{^C}
36049 (@samp{\003}, the control-C character) character in all-stop mode
36050 while the target is running, except this works in non-stop mode.
36051 @xref{interrupting remote targets}, for more info on the all-stop
36062 @item vFile:@var{operation}:@var{parameter}@dots{}
36063 @cindex @samp{vFile} packet
36064 Perform a file operation on the target system. For details,
36065 see @ref{Host I/O Packets}.
36067 @item vFlashErase:@var{addr},@var{length}
36068 @cindex @samp{vFlashErase} packet
36069 Direct the stub to erase @var{length} bytes of flash starting at
36070 @var{addr}. The region may enclose any number of flash blocks, but
36071 its start and end must fall on block boundaries, as indicated by the
36072 flash block size appearing in the memory map (@pxref{Memory Map
36073 Format}). @value{GDBN} groups flash memory programming operations
36074 together, and sends a @samp{vFlashDone} request after each group; the
36075 stub is allowed to delay erase operation until the @samp{vFlashDone}
36076 packet is received.
36086 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36087 @cindex @samp{vFlashWrite} packet
36088 Direct the stub to write data to flash address @var{addr}. The data
36089 is passed in binary form using the same encoding as for the @samp{X}
36090 packet (@pxref{Binary Data}). The memory ranges specified by
36091 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36092 not overlap, and must appear in order of increasing addresses
36093 (although @samp{vFlashErase} packets for higher addresses may already
36094 have been received; the ordering is guaranteed only between
36095 @samp{vFlashWrite} packets). If a packet writes to an address that was
36096 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36097 target-specific method, the results are unpredictable.
36105 for vFlashWrite addressing non-flash memory
36111 @cindex @samp{vFlashDone} packet
36112 Indicate to the stub that flash programming operation is finished.
36113 The stub is permitted to delay or batch the effects of a group of
36114 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36115 @samp{vFlashDone} packet is received. The contents of the affected
36116 regions of flash memory are unpredictable until the @samp{vFlashDone}
36117 request is completed.
36119 @item vKill;@var{pid}
36120 @cindex @samp{vKill} packet
36121 @anchor{vKill packet}
36122 Kill the process with the specified process ID @var{pid}, which is a
36123 hexadecimal integer identifying the process. This packet is used in
36124 preference to @samp{k} when multiprocess protocol extensions are
36125 supported; see @ref{multiprocess extensions}.
36135 @item vMustReplyEmpty
36136 @cindex @samp{vMustReplyEmpty} packet
36137 The correct reply to an unknown @samp{v} packet is to return the empty
36138 string, however, some older versions of @command{gdbserver} would
36139 incorrectly return @samp{OK} for unknown @samp{v} packets.
36141 The @samp{vMustReplyEmpty} is used as a feature test to check how
36142 @command{gdbserver} handles unknown packets, it is important that this
36143 packet be handled in the same way as other unknown @samp{v} packets.
36144 If this packet is handled differently to other unknown @samp{v}
36145 packets then it is possile that @value{GDBN} may run into problems in
36146 other areas, specifically around use of @samp{vFile:setfs:}.
36148 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36149 @cindex @samp{vRun} packet
36150 Run the program @var{filename}, passing it each @var{argument} on its
36151 command line. The file and arguments are hex-encoded strings. If
36152 @var{filename} is an empty string, the stub may use a default program
36153 (e.g.@: the last program run). The program is created in the stopped
36156 @c FIXME: What about non-stop mode?
36158 This packet is only available in extended mode (@pxref{extended mode}).
36164 @item @r{Any stop packet}
36165 for success (@pxref{Stop Reply Packets})
36169 @cindex @samp{vStopped} packet
36170 @xref{Notification Packets}.
36172 @item X @var{addr},@var{length}:@var{XX@dots{}}
36174 @cindex @samp{X} packet
36175 Write data to memory, where the data is transmitted in binary.
36176 Memory is specified by its address @var{addr} and number of addressable memory
36177 units @var{length} (@pxref{addressable memory unit});
36178 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36188 @item z @var{type},@var{addr},@var{kind}
36189 @itemx Z @var{type},@var{addr},@var{kind}
36190 @anchor{insert breakpoint or watchpoint packet}
36191 @cindex @samp{z} packet
36192 @cindex @samp{Z} packets
36193 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36194 watchpoint starting at address @var{address} of kind @var{kind}.
36196 Each breakpoint and watchpoint packet @var{type} is documented
36199 @emph{Implementation notes: A remote target shall return an empty string
36200 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36201 remote target shall support either both or neither of a given
36202 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36203 avoid potential problems with duplicate packets, the operations should
36204 be implemented in an idempotent way.}
36206 @item z0,@var{addr},@var{kind}
36207 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36208 @cindex @samp{z0} packet
36209 @cindex @samp{Z0} packet
36210 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36211 @var{addr} of type @var{kind}.
36213 A software breakpoint is implemented by replacing the instruction at
36214 @var{addr} with a software breakpoint or trap instruction. The
36215 @var{kind} is target-specific and typically indicates the size of the
36216 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36217 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36218 architectures have additional meanings for @var{kind}
36219 (@pxref{Architecture-Specific Protocol Details}); if no
36220 architecture-specific value is being used, it should be @samp{0}.
36221 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36222 conditional expressions in bytecode form that should be evaluated on
36223 the target's side. These are the conditions that should be taken into
36224 consideration when deciding if the breakpoint trigger should be
36225 reported back to @value{GDBN}.
36227 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36228 for how to best report a software breakpoint event to @value{GDBN}.
36230 The @var{cond_list} parameter is comprised of a series of expressions,
36231 concatenated without separators. Each expression has the following form:
36235 @item X @var{len},@var{expr}
36236 @var{len} is the length of the bytecode expression and @var{expr} is the
36237 actual conditional expression in bytecode form.
36241 The optional @var{cmd_list} parameter introduces commands that may be
36242 run on the target, rather than being reported back to @value{GDBN}.
36243 The parameter starts with a numeric flag @var{persist}; if the flag is
36244 nonzero, then the breakpoint may remain active and the commands
36245 continue to be run even when @value{GDBN} disconnects from the target.
36246 Following this flag is a series of expressions concatenated with no
36247 separators. Each expression has the following form:
36251 @item X @var{len},@var{expr}
36252 @var{len} is the length of the bytecode expression and @var{expr} is the
36253 actual commands expression in bytecode form.
36257 @emph{Implementation note: It is possible for a target to copy or move
36258 code that contains software breakpoints (e.g., when implementing
36259 overlays). The behavior of this packet, in the presence of such a
36260 target, is not defined.}
36272 @item z1,@var{addr},@var{kind}
36273 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36274 @cindex @samp{z1} packet
36275 @cindex @samp{Z1} packet
36276 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36277 address @var{addr}.
36279 A hardware breakpoint is implemented using a mechanism that is not
36280 dependent on being able to modify the target's memory. The
36281 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36282 same meaning as in @samp{Z0} packets.
36284 @emph{Implementation note: A hardware breakpoint is not affected by code
36297 @item z2,@var{addr},@var{kind}
36298 @itemx Z2,@var{addr},@var{kind}
36299 @cindex @samp{z2} packet
36300 @cindex @samp{Z2} packet
36301 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36302 The number of bytes to watch is specified by @var{kind}.
36314 @item z3,@var{addr},@var{kind}
36315 @itemx Z3,@var{addr},@var{kind}
36316 @cindex @samp{z3} packet
36317 @cindex @samp{Z3} packet
36318 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36319 The number of bytes to watch is specified by @var{kind}.
36331 @item z4,@var{addr},@var{kind}
36332 @itemx Z4,@var{addr},@var{kind}
36333 @cindex @samp{z4} packet
36334 @cindex @samp{Z4} packet
36335 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36336 The number of bytes to watch is specified by @var{kind}.
36350 @node Stop Reply Packets
36351 @section Stop Reply Packets
36352 @cindex stop reply packets
36354 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36355 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36356 receive any of the below as a reply. Except for @samp{?}
36357 and @samp{vStopped}, that reply is only returned
36358 when the target halts. In the below the exact meaning of @dfn{signal
36359 number} is defined by the header @file{include/gdb/signals.h} in the
36360 @value{GDBN} source code.
36362 In non-stop mode, the server will simply reply @samp{OK} to commands
36363 such as @samp{vCont}; any stop will be the subject of a future
36364 notification. @xref{Remote Non-Stop}.
36366 As in the description of request packets, we include spaces in the
36367 reply templates for clarity; these are not part of the reply packet's
36368 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36374 The program received signal number @var{AA} (a two-digit hexadecimal
36375 number). This is equivalent to a @samp{T} response with no
36376 @var{n}:@var{r} pairs.
36378 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36379 @cindex @samp{T} packet reply
36380 The program received signal number @var{AA} (a two-digit hexadecimal
36381 number). This is equivalent to an @samp{S} response, except that the
36382 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36383 and other information directly in the stop reply packet, reducing
36384 round-trip latency. Single-step and breakpoint traps are reported
36385 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36389 If @var{n} is a hexadecimal number, it is a register number, and the
36390 corresponding @var{r} gives that register's value. The data @var{r} is a
36391 series of bytes in target byte order, with each byte given by a
36392 two-digit hex number.
36395 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36396 the stopped thread, as specified in @ref{thread-id syntax}.
36399 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36400 the core on which the stop event was detected.
36403 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36404 specific event that stopped the target. The currently defined stop
36405 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36406 signal. At most one stop reason should be present.
36409 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36410 and go on to the next; this allows us to extend the protocol in the
36414 The currently defined stop reasons are:
36420 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36423 @item syscall_entry
36424 @itemx syscall_return
36425 The packet indicates a syscall entry or return, and @var{r} is the
36426 syscall number, in hex.
36428 @cindex shared library events, remote reply
36430 The packet indicates that the loaded libraries have changed.
36431 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36432 list of loaded libraries. The @var{r} part is ignored.
36434 @cindex replay log events, remote reply
36436 The packet indicates that the target cannot continue replaying
36437 logged execution events, because it has reached the end (or the
36438 beginning when executing backward) of the log. The value of @var{r}
36439 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36440 for more information.
36443 @anchor{swbreak stop reason}
36444 The packet indicates a software breakpoint instruction was executed,
36445 irrespective of whether it was @value{GDBN} that planted the
36446 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36447 part must be left empty.
36449 On some architectures, such as x86, at the architecture level, when a
36450 breakpoint instruction executes the program counter points at the
36451 breakpoint address plus an offset. On such targets, the stub is
36452 responsible for adjusting the PC to point back at the breakpoint
36455 This packet should not be sent by default; older @value{GDBN} versions
36456 did not support it. @value{GDBN} requests it, by supplying an
36457 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36458 remote stub must also supply the appropriate @samp{qSupported} feature
36459 indicating support.
36461 This packet is required for correct non-stop mode operation.
36464 The packet indicates the target stopped for a hardware breakpoint.
36465 The @var{r} part must be left empty.
36467 The same remarks about @samp{qSupported} and non-stop mode above
36470 @cindex fork events, remote reply
36472 The packet indicates that @code{fork} was called, and @var{r}
36473 is the thread ID of the new child process. Refer to
36474 @ref{thread-id syntax} for the format of the @var{thread-id}
36475 field. This packet is only applicable to targets that support
36478 This packet should not be sent by default; older @value{GDBN} versions
36479 did not support it. @value{GDBN} requests it, by supplying an
36480 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36481 remote stub must also supply the appropriate @samp{qSupported} feature
36482 indicating support.
36484 @cindex vfork events, remote reply
36486 The packet indicates that @code{vfork} was called, and @var{r}
36487 is the thread ID of the new child process. Refer to
36488 @ref{thread-id syntax} for the format of the @var{thread-id}
36489 field. This packet is only applicable to targets that support
36492 This packet should not be sent by default; older @value{GDBN} versions
36493 did not support it. @value{GDBN} requests it, by supplying an
36494 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36495 remote stub must also supply the appropriate @samp{qSupported} feature
36496 indicating support.
36498 @cindex vforkdone events, remote reply
36500 The packet indicates that a child process created by a vfork
36501 has either called @code{exec} or terminated, so that the
36502 address spaces of the parent and child process are no longer
36503 shared. The @var{r} part is ignored. This packet is only
36504 applicable to targets that support vforkdone events.
36506 This packet should not be sent by default; older @value{GDBN} versions
36507 did not support it. @value{GDBN} requests it, by supplying an
36508 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36509 remote stub must also supply the appropriate @samp{qSupported} feature
36510 indicating support.
36512 @cindex exec events, remote reply
36514 The packet indicates that @code{execve} was called, and @var{r}
36515 is the absolute pathname of the file that was executed, in hex.
36516 This packet is only applicable to targets that support exec events.
36518 This packet should not be sent by default; older @value{GDBN} versions
36519 did not support it. @value{GDBN} requests it, by supplying an
36520 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36521 remote stub must also supply the appropriate @samp{qSupported} feature
36522 indicating support.
36524 @cindex thread create event, remote reply
36525 @anchor{thread create event}
36527 The packet indicates that the thread was just created. The new thread
36528 is stopped until @value{GDBN} sets it running with a resumption packet
36529 (@pxref{vCont packet}). This packet should not be sent by default;
36530 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36531 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36532 @var{r} part is ignored.
36537 @itemx W @var{AA} ; process:@var{pid}
36538 The process exited, and @var{AA} is the exit status. This is only
36539 applicable to certain targets.
36541 The second form of the response, including the process ID of the
36542 exited process, can be used only when @value{GDBN} has reported
36543 support for multiprocess protocol extensions; see @ref{multiprocess
36544 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36548 @itemx X @var{AA} ; process:@var{pid}
36549 The process terminated with signal @var{AA}.
36551 The second form of the response, including the process ID of the
36552 terminated process, can be used only when @value{GDBN} has reported
36553 support for multiprocess protocol extensions; see @ref{multiprocess
36554 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36557 @anchor{thread exit event}
36558 @cindex thread exit event, remote reply
36559 @item w @var{AA} ; @var{tid}
36561 The thread exited, and @var{AA} is the exit status. This response
36562 should not be sent by default; @value{GDBN} requests it with the
36563 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36564 @var{AA} is formatted as a big-endian hex string.
36567 There are no resumed threads left in the target. In other words, even
36568 though the process is alive, the last resumed thread has exited. For
36569 example, say the target process has two threads: thread 1 and thread
36570 2. The client leaves thread 1 stopped, and resumes thread 2, which
36571 subsequently exits. At this point, even though the process is still
36572 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36573 executing either. The @samp{N} stop reply thus informs the client
36574 that it can stop waiting for stop replies. This packet should not be
36575 sent by default; older @value{GDBN} versions did not support it.
36576 @value{GDBN} requests it, by supplying an appropriate
36577 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36578 also supply the appropriate @samp{qSupported} feature indicating
36581 @item O @var{XX}@dots{}
36582 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36583 written as the program's console output. This can happen at any time
36584 while the program is running and the debugger should continue to wait
36585 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36587 @item F @var{call-id},@var{parameter}@dots{}
36588 @var{call-id} is the identifier which says which host system call should
36589 be called. This is just the name of the function. Translation into the
36590 correct system call is only applicable as it's defined in @value{GDBN}.
36591 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36594 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36595 this very system call.
36597 The target replies with this packet when it expects @value{GDBN} to
36598 call a host system call on behalf of the target. @value{GDBN} replies
36599 with an appropriate @samp{F} packet and keeps up waiting for the next
36600 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36601 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36602 Protocol Extension}, for more details.
36606 @node General Query Packets
36607 @section General Query Packets
36608 @cindex remote query requests
36610 Packets starting with @samp{q} are @dfn{general query packets};
36611 packets starting with @samp{Q} are @dfn{general set packets}. General
36612 query and set packets are a semi-unified form for retrieving and
36613 sending information to and from the stub.
36615 The initial letter of a query or set packet is followed by a name
36616 indicating what sort of thing the packet applies to. For example,
36617 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36618 definitions with the stub. These packet names follow some
36623 The name must not contain commas, colons or semicolons.
36625 Most @value{GDBN} query and set packets have a leading upper case
36628 The names of custom vendor packets should use a company prefix, in
36629 lower case, followed by a period. For example, packets designed at
36630 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36631 foos) or @samp{Qacme.bar} (for setting bars).
36634 The name of a query or set packet should be separated from any
36635 parameters by a @samp{:}; the parameters themselves should be
36636 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36637 full packet name, and check for a separator or the end of the packet,
36638 in case two packet names share a common prefix. New packets should not begin
36639 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36640 packets predate these conventions, and have arguments without any terminator
36641 for the packet name; we suspect they are in widespread use in places that
36642 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36643 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36646 Like the descriptions of the other packets, each description here
36647 has a template showing the packet's overall syntax, followed by an
36648 explanation of the packet's meaning. We include spaces in some of the
36649 templates for clarity; these are not part of the packet's syntax. No
36650 @value{GDBN} packet uses spaces to separate its components.
36652 Here are the currently defined query and set packets:
36658 Turn on or off the agent as a helper to perform some debugging operations
36659 delegated from @value{GDBN} (@pxref{Control Agent}).
36661 @item QAllow:@var{op}:@var{val}@dots{}
36662 @cindex @samp{QAllow} packet
36663 Specify which operations @value{GDBN} expects to request of the
36664 target, as a semicolon-separated list of operation name and value
36665 pairs. Possible values for @var{op} include @samp{WriteReg},
36666 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36667 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36668 indicating that @value{GDBN} will not request the operation, or 1,
36669 indicating that it may. (The target can then use this to set up its
36670 own internals optimally, for instance if the debugger never expects to
36671 insert breakpoints, it may not need to install its own trap handler.)
36674 @cindex current thread, remote request
36675 @cindex @samp{qC} packet
36676 Return the current thread ID.
36680 @item QC @var{thread-id}
36681 Where @var{thread-id} is a thread ID as documented in
36682 @ref{thread-id syntax}.
36683 @item @r{(anything else)}
36684 Any other reply implies the old thread ID.
36687 @item qCRC:@var{addr},@var{length}
36688 @cindex CRC of memory block, remote request
36689 @cindex @samp{qCRC} packet
36690 @anchor{qCRC packet}
36691 Compute the CRC checksum of a block of memory using CRC-32 defined in
36692 IEEE 802.3. The CRC is computed byte at a time, taking the most
36693 significant bit of each byte first. The initial pattern code
36694 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36696 @emph{Note:} This is the same CRC used in validating separate debug
36697 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36698 Files}). However the algorithm is slightly different. When validating
36699 separate debug files, the CRC is computed taking the @emph{least}
36700 significant bit of each byte first, and the final result is inverted to
36701 detect trailing zeros.
36706 An error (such as memory fault)
36707 @item C @var{crc32}
36708 The specified memory region's checksum is @var{crc32}.
36711 @item QDisableRandomization:@var{value}
36712 @cindex disable address space randomization, remote request
36713 @cindex @samp{QDisableRandomization} packet
36714 Some target operating systems will randomize the virtual address space
36715 of the inferior process as a security feature, but provide a feature
36716 to disable such randomization, e.g.@: to allow for a more deterministic
36717 debugging experience. On such systems, this packet with a @var{value}
36718 of 1 directs the target to disable address space randomization for
36719 processes subsequently started via @samp{vRun} packets, while a packet
36720 with a @var{value} of 0 tells the target to enable address space
36723 This packet is only available in extended mode (@pxref{extended mode}).
36728 The request succeeded.
36731 An error occurred. The error number @var{nn} is given as hex digits.
36734 An empty reply indicates that @samp{QDisableRandomization} is not supported
36738 This packet is not probed by default; the remote stub must request it,
36739 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36740 This should only be done on targets that actually support disabling
36741 address space randomization.
36743 @item QStartupWithShell:@var{value}
36744 @cindex startup with shell, remote request
36745 @cindex @samp{QStartupWithShell} packet
36746 On UNIX-like targets, it is possible to start the inferior using a
36747 shell program. This is the default behavior on both @value{GDBN} and
36748 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
36749 used to inform @command{gdbserver} whether it should start the
36750 inferior using a shell or not.
36752 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
36753 to start the inferior. If @var{value} is @samp{1},
36754 @command{gdbserver} will use a shell to start the inferior. All other
36755 values are considered an error.
36757 This packet is only available in extended mode (@pxref{extended
36763 The request succeeded.
36766 An error occurred. The error number @var{nn} is given as hex digits.
36769 This packet is not probed by default; the remote stub must request it,
36770 by supplying an appropriate @samp{qSupported} response
36771 (@pxref{qSupported}). This should only be done on targets that
36772 actually support starting the inferior using a shell.
36774 Use of this packet is controlled by the @code{set startup-with-shell}
36775 command; @pxref{set startup-with-shell}.
36777 @item QEnvironmentHexEncoded:@var{hex-value}
36778 @anchor{QEnvironmentHexEncoded}
36779 @cindex set environment variable, remote request
36780 @cindex @samp{QEnvironmentHexEncoded} packet
36781 On UNIX-like targets, it is possible to set environment variables that
36782 will be passed to the inferior during the startup process. This
36783 packet is used to inform @command{gdbserver} of an environment
36784 variable that has been defined by the user on @value{GDBN} (@pxref{set
36787 The packet is composed by @var{hex-value}, an hex encoded
36788 representation of the @var{name=value} format representing an
36789 environment variable. The name of the environment variable is
36790 represented by @var{name}, and the value to be assigned to the
36791 environment variable is represented by @var{value}. If the variable
36792 has no value (i.e., the value is @code{null}), then @var{value} will
36795 This packet is only available in extended mode (@pxref{extended
36801 The request succeeded.
36804 This packet is not probed by default; the remote stub must request it,
36805 by supplying an appropriate @samp{qSupported} response
36806 (@pxref{qSupported}). This should only be done on targets that
36807 actually support passing environment variables to the starting
36810 This packet is related to the @code{set environment} command;
36811 @pxref{set environment}.
36813 @item QEnvironmentUnset:@var{hex-value}
36814 @anchor{QEnvironmentUnset}
36815 @cindex unset environment variable, remote request
36816 @cindex @samp{QEnvironmentUnset} packet
36817 On UNIX-like targets, it is possible to unset environment variables
36818 before starting the inferior in the remote target. This packet is
36819 used to inform @command{gdbserver} of an environment variable that has
36820 been unset by the user on @value{GDBN} (@pxref{unset environment}).
36822 The packet is composed by @var{hex-value}, an hex encoded
36823 representation of the name of the environment variable to be unset.
36825 This packet is only available in extended mode (@pxref{extended
36831 The request succeeded.
36834 This packet is not probed by default; the remote stub must request it,
36835 by supplying an appropriate @samp{qSupported} response
36836 (@pxref{qSupported}). This should only be done on targets that
36837 actually support passing environment variables to the starting
36840 This packet is related to the @code{unset environment} command;
36841 @pxref{unset environment}.
36843 @item QEnvironmentReset
36844 @anchor{QEnvironmentReset}
36845 @cindex reset environment, remote request
36846 @cindex @samp{QEnvironmentReset} packet
36847 On UNIX-like targets, this packet is used to reset the state of
36848 environment variables in the remote target before starting the
36849 inferior. In this context, reset means unsetting all environment
36850 variables that were previously set by the user (i.e., were not
36851 initially present in the environment). It is sent to
36852 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
36853 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
36854 (@pxref{QEnvironmentUnset}) packets.
36856 This packet is only available in extended mode (@pxref{extended
36862 The request succeeded.
36865 This packet is not probed by default; the remote stub must request it,
36866 by supplying an appropriate @samp{qSupported} response
36867 (@pxref{qSupported}). This should only be done on targets that
36868 actually support passing environment variables to the starting
36871 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
36872 @anchor{QSetWorkingDir packet}
36873 @cindex set working directory, remote request
36874 @cindex @samp{QSetWorkingDir} packet
36875 This packet is used to inform the remote server of the intended
36876 current working directory for programs that are going to be executed.
36878 The packet is composed by @var{directory}, an hex encoded
36879 representation of the directory that the remote inferior will use as
36880 its current working directory. If @var{directory} is an empty string,
36881 the remote server should reset the inferior's current working
36882 directory to its original, empty value.
36884 This packet is only available in extended mode (@pxref{extended
36890 The request succeeded.
36894 @itemx qsThreadInfo
36895 @cindex list active threads, remote request
36896 @cindex @samp{qfThreadInfo} packet
36897 @cindex @samp{qsThreadInfo} packet
36898 Obtain a list of all active thread IDs from the target (OS). Since there
36899 may be too many active threads to fit into one reply packet, this query
36900 works iteratively: it may require more than one query/reply sequence to
36901 obtain the entire list of threads. The first query of the sequence will
36902 be the @samp{qfThreadInfo} query; subsequent queries in the
36903 sequence will be the @samp{qsThreadInfo} query.
36905 NOTE: This packet replaces the @samp{qL} query (see below).
36909 @item m @var{thread-id}
36911 @item m @var{thread-id},@var{thread-id}@dots{}
36912 a comma-separated list of thread IDs
36914 (lower case letter @samp{L}) denotes end of list.
36917 In response to each query, the target will reply with a list of one or
36918 more thread IDs, separated by commas.
36919 @value{GDBN} will respond to each reply with a request for more thread
36920 ids (using the @samp{qs} form of the query), until the target responds
36921 with @samp{l} (lower-case ell, for @dfn{last}).
36922 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36925 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36926 initial connection with the remote target, and the very first thread ID
36927 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36928 message. Therefore, the stub should ensure that the first thread ID in
36929 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36931 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36932 @cindex get thread-local storage address, remote request
36933 @cindex @samp{qGetTLSAddr} packet
36934 Fetch the address associated with thread local storage specified
36935 by @var{thread-id}, @var{offset}, and @var{lm}.
36937 @var{thread-id} is the thread ID associated with the
36938 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36940 @var{offset} is the (big endian, hex encoded) offset associated with the
36941 thread local variable. (This offset is obtained from the debug
36942 information associated with the variable.)
36944 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36945 load module associated with the thread local storage. For example,
36946 a @sc{gnu}/Linux system will pass the link map address of the shared
36947 object associated with the thread local storage under consideration.
36948 Other operating environments may choose to represent the load module
36949 differently, so the precise meaning of this parameter will vary.
36953 @item @var{XX}@dots{}
36954 Hex encoded (big endian) bytes representing the address of the thread
36955 local storage requested.
36958 An error occurred. The error number @var{nn} is given as hex digits.
36961 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36964 @item qGetTIBAddr:@var{thread-id}
36965 @cindex get thread information block address
36966 @cindex @samp{qGetTIBAddr} packet
36967 Fetch address of the Windows OS specific Thread Information Block.
36969 @var{thread-id} is the thread ID associated with the thread.
36973 @item @var{XX}@dots{}
36974 Hex encoded (big endian) bytes representing the linear address of the
36975 thread information block.
36978 An error occured. This means that either the thread was not found, or the
36979 address could not be retrieved.
36982 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36985 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36986 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36987 digit) is one to indicate the first query and zero to indicate a
36988 subsequent query; @var{threadcount} (two hex digits) is the maximum
36989 number of threads the response packet can contain; and @var{nextthread}
36990 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36991 returned in the response as @var{argthread}.
36993 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36997 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36998 Where: @var{count} (two hex digits) is the number of threads being
36999 returned; @var{done} (one hex digit) is zero to indicate more threads
37000 and one indicates no further threads; @var{argthreadid} (eight hex
37001 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37002 is a sequence of thread IDs, @var{threadid} (eight hex
37003 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37007 @cindex section offsets, remote request
37008 @cindex @samp{qOffsets} packet
37009 Get section offsets that the target used when relocating the downloaded
37014 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37015 Relocate the @code{Text} section by @var{xxx} from its original address.
37016 Relocate the @code{Data} section by @var{yyy} from its original address.
37017 If the object file format provides segment information (e.g.@: @sc{elf}
37018 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37019 segments by the supplied offsets.
37021 @emph{Note: while a @code{Bss} offset may be included in the response,
37022 @value{GDBN} ignores this and instead applies the @code{Data} offset
37023 to the @code{Bss} section.}
37025 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37026 Relocate the first segment of the object file, which conventionally
37027 contains program code, to a starting address of @var{xxx}. If
37028 @samp{DataSeg} is specified, relocate the second segment, which
37029 conventionally contains modifiable data, to a starting address of
37030 @var{yyy}. @value{GDBN} will report an error if the object file
37031 does not contain segment information, or does not contain at least
37032 as many segments as mentioned in the reply. Extra segments are
37033 kept at fixed offsets relative to the last relocated segment.
37036 @item qP @var{mode} @var{thread-id}
37037 @cindex thread information, remote request
37038 @cindex @samp{qP} packet
37039 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37040 encoded 32 bit mode; @var{thread-id} is a thread ID
37041 (@pxref{thread-id syntax}).
37043 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37046 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37050 @cindex non-stop mode, remote request
37051 @cindex @samp{QNonStop} packet
37053 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37054 @xref{Remote Non-Stop}, for more information.
37059 The request succeeded.
37062 An error occurred. The error number @var{nn} is given as hex digits.
37065 An empty reply indicates that @samp{QNonStop} is not supported by
37069 This packet is not probed by default; the remote stub must request it,
37070 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37071 Use of this packet is controlled by the @code{set non-stop} command;
37072 @pxref{Non-Stop Mode}.
37074 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37075 @itemx QCatchSyscalls:0
37076 @cindex catch syscalls from inferior, remote request
37077 @cindex @samp{QCatchSyscalls} packet
37078 @anchor{QCatchSyscalls}
37079 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37080 catching syscalls from the inferior process.
37082 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37083 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37084 is listed, every system call should be reported.
37086 Note that if a syscall not in the list is reported, @value{GDBN} will
37087 still filter the event according to its own list from all corresponding
37088 @code{catch syscall} commands. However, it is more efficient to only
37089 report the requested syscalls.
37091 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37092 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37094 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37095 kept for the new process too. On targets where exec may affect syscall
37096 numbers, for example with exec between 32 and 64-bit processes, the
37097 client should send a new packet with the new syscall list.
37102 The request succeeded.
37105 An error occurred. @var{nn} are hex digits.
37108 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37112 Use of this packet is controlled by the @code{set remote catch-syscalls}
37113 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37114 This packet is not probed by default; the remote stub must request it,
37115 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37117 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37118 @cindex pass signals to inferior, remote request
37119 @cindex @samp{QPassSignals} packet
37120 @anchor{QPassSignals}
37121 Each listed @var{signal} should be passed directly to the inferior process.
37122 Signals are numbered identically to continue packets and stop replies
37123 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37124 strictly greater than the previous item. These signals do not need to stop
37125 the inferior, or be reported to @value{GDBN}. All other signals should be
37126 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37127 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37128 new list. This packet improves performance when using @samp{handle
37129 @var{signal} nostop noprint pass}.
37134 The request succeeded.
37137 An error occurred. The error number @var{nn} is given as hex digits.
37140 An empty reply indicates that @samp{QPassSignals} is not supported by
37144 Use of this packet is controlled by the @code{set remote pass-signals}
37145 command (@pxref{Remote Configuration, set remote pass-signals}).
37146 This packet is not probed by default; the remote stub must request it,
37147 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37149 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37150 @cindex signals the inferior may see, remote request
37151 @cindex @samp{QProgramSignals} packet
37152 @anchor{QProgramSignals}
37153 Each listed @var{signal} may be delivered to the inferior process.
37154 Others should be silently discarded.
37156 In some cases, the remote stub may need to decide whether to deliver a
37157 signal to the program or not without @value{GDBN} involvement. One
37158 example of that is while detaching --- the program's threads may have
37159 stopped for signals that haven't yet had a chance of being reported to
37160 @value{GDBN}, and so the remote stub can use the signal list specified
37161 by this packet to know whether to deliver or ignore those pending
37164 This does not influence whether to deliver a signal as requested by a
37165 resumption packet (@pxref{vCont packet}).
37167 Signals are numbered identically to continue packets and stop replies
37168 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37169 strictly greater than the previous item. Multiple
37170 @samp{QProgramSignals} packets do not combine; any earlier
37171 @samp{QProgramSignals} list is completely replaced by the new list.
37176 The request succeeded.
37179 An error occurred. The error number @var{nn} is given as hex digits.
37182 An empty reply indicates that @samp{QProgramSignals} is not supported
37186 Use of this packet is controlled by the @code{set remote program-signals}
37187 command (@pxref{Remote Configuration, set remote program-signals}).
37188 This packet is not probed by default; the remote stub must request it,
37189 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37191 @anchor{QThreadEvents}
37192 @item QThreadEvents:1
37193 @itemx QThreadEvents:0
37194 @cindex thread create/exit events, remote request
37195 @cindex @samp{QThreadEvents} packet
37197 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37198 reporting of thread create and exit events. @xref{thread create
37199 event}, for the reply specifications. For example, this is used in
37200 non-stop mode when @value{GDBN} stops a set of threads and
37201 synchronously waits for the their corresponding stop replies. Without
37202 exit events, if one of the threads exits, @value{GDBN} would hang
37203 forever not knowing that it should no longer expect a stop for that
37204 same thread. @value{GDBN} does not enable this feature unless the
37205 stub reports that it supports it by including @samp{QThreadEvents+} in
37206 its @samp{qSupported} reply.
37211 The request succeeded.
37214 An error occurred. The error number @var{nn} is given as hex digits.
37217 An empty reply indicates that @samp{QThreadEvents} is not supported by
37221 Use of this packet is controlled by the @code{set remote thread-events}
37222 command (@pxref{Remote Configuration, set remote thread-events}).
37224 @item qRcmd,@var{command}
37225 @cindex execute remote command, remote request
37226 @cindex @samp{qRcmd} packet
37227 @var{command} (hex encoded) is passed to the local interpreter for
37228 execution. Invalid commands should be reported using the output
37229 string. Before the final result packet, the target may also respond
37230 with a number of intermediate @samp{O@var{output}} console output
37231 packets. @emph{Implementors should note that providing access to a
37232 stubs's interpreter may have security implications}.
37237 A command response with no output.
37239 A command response with the hex encoded output string @var{OUTPUT}.
37241 Indicate a badly formed request.
37243 An empty reply indicates that @samp{qRcmd} is not recognized.
37246 (Note that the @code{qRcmd} packet's name is separated from the
37247 command by a @samp{,}, not a @samp{:}, contrary to the naming
37248 conventions above. Please don't use this packet as a model for new
37251 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37252 @cindex searching memory, in remote debugging
37254 @cindex @samp{qSearch:memory} packet
37256 @cindex @samp{qSearch memory} packet
37257 @anchor{qSearch memory}
37258 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37259 Both @var{address} and @var{length} are encoded in hex;
37260 @var{search-pattern} is a sequence of bytes, also hex encoded.
37265 The pattern was not found.
37267 The pattern was found at @var{address}.
37269 A badly formed request or an error was encountered while searching memory.
37271 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37274 @item QStartNoAckMode
37275 @cindex @samp{QStartNoAckMode} packet
37276 @anchor{QStartNoAckMode}
37277 Request that the remote stub disable the normal @samp{+}/@samp{-}
37278 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37283 The stub has switched to no-acknowledgment mode.
37284 @value{GDBN} acknowledges this reponse,
37285 but neither the stub nor @value{GDBN} shall send or expect further
37286 @samp{+}/@samp{-} acknowledgments in the current connection.
37288 An empty reply indicates that the stub does not support no-acknowledgment mode.
37291 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37292 @cindex supported packets, remote query
37293 @cindex features of the remote protocol
37294 @cindex @samp{qSupported} packet
37295 @anchor{qSupported}
37296 Tell the remote stub about features supported by @value{GDBN}, and
37297 query the stub for features it supports. This packet allows
37298 @value{GDBN} and the remote stub to take advantage of each others'
37299 features. @samp{qSupported} also consolidates multiple feature probes
37300 at startup, to improve @value{GDBN} performance---a single larger
37301 packet performs better than multiple smaller probe packets on
37302 high-latency links. Some features may enable behavior which must not
37303 be on by default, e.g.@: because it would confuse older clients or
37304 stubs. Other features may describe packets which could be
37305 automatically probed for, but are not. These features must be
37306 reported before @value{GDBN} will use them. This ``default
37307 unsupported'' behavior is not appropriate for all packets, but it
37308 helps to keep the initial connection time under control with new
37309 versions of @value{GDBN} which support increasing numbers of packets.
37313 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37314 The stub supports or does not support each returned @var{stubfeature},
37315 depending on the form of each @var{stubfeature} (see below for the
37318 An empty reply indicates that @samp{qSupported} is not recognized,
37319 or that no features needed to be reported to @value{GDBN}.
37322 The allowed forms for each feature (either a @var{gdbfeature} in the
37323 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37327 @item @var{name}=@var{value}
37328 The remote protocol feature @var{name} is supported, and associated
37329 with the specified @var{value}. The format of @var{value} depends
37330 on the feature, but it must not include a semicolon.
37332 The remote protocol feature @var{name} is supported, and does not
37333 need an associated value.
37335 The remote protocol feature @var{name} is not supported.
37337 The remote protocol feature @var{name} may be supported, and
37338 @value{GDBN} should auto-detect support in some other way when it is
37339 needed. This form will not be used for @var{gdbfeature} notifications,
37340 but may be used for @var{stubfeature} responses.
37343 Whenever the stub receives a @samp{qSupported} request, the
37344 supplied set of @value{GDBN} features should override any previous
37345 request. This allows @value{GDBN} to put the stub in a known
37346 state, even if the stub had previously been communicating with
37347 a different version of @value{GDBN}.
37349 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37354 This feature indicates whether @value{GDBN} supports multiprocess
37355 extensions to the remote protocol. @value{GDBN} does not use such
37356 extensions unless the stub also reports that it supports them by
37357 including @samp{multiprocess+} in its @samp{qSupported} reply.
37358 @xref{multiprocess extensions}, for details.
37361 This feature indicates that @value{GDBN} supports the XML target
37362 description. If the stub sees @samp{xmlRegisters=} with target
37363 specific strings separated by a comma, it will report register
37367 This feature indicates whether @value{GDBN} supports the
37368 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37369 instruction reply packet}).
37372 This feature indicates whether @value{GDBN} supports the swbreak stop
37373 reason in stop replies. @xref{swbreak stop reason}, for details.
37376 This feature indicates whether @value{GDBN} supports the hwbreak stop
37377 reason in stop replies. @xref{swbreak stop reason}, for details.
37380 This feature indicates whether @value{GDBN} supports fork event
37381 extensions to the remote protocol. @value{GDBN} does not use such
37382 extensions unless the stub also reports that it supports them by
37383 including @samp{fork-events+} in its @samp{qSupported} reply.
37386 This feature indicates whether @value{GDBN} supports vfork event
37387 extensions to the remote protocol. @value{GDBN} does not use such
37388 extensions unless the stub also reports that it supports them by
37389 including @samp{vfork-events+} in its @samp{qSupported} reply.
37392 This feature indicates whether @value{GDBN} supports exec event
37393 extensions to the remote protocol. @value{GDBN} does not use such
37394 extensions unless the stub also reports that it supports them by
37395 including @samp{exec-events+} in its @samp{qSupported} reply.
37397 @item vContSupported
37398 This feature indicates whether @value{GDBN} wants to know the
37399 supported actions in the reply to @samp{vCont?} packet.
37402 Stubs should ignore any unknown values for
37403 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37404 packet supports receiving packets of unlimited length (earlier
37405 versions of @value{GDBN} may reject overly long responses). Additional values
37406 for @var{gdbfeature} may be defined in the future to let the stub take
37407 advantage of new features in @value{GDBN}, e.g.@: incompatible
37408 improvements in the remote protocol---the @samp{multiprocess} feature is
37409 an example of such a feature. The stub's reply should be independent
37410 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37411 describes all the features it supports, and then the stub replies with
37412 all the features it supports.
37414 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37415 responses, as long as each response uses one of the standard forms.
37417 Some features are flags. A stub which supports a flag feature
37418 should respond with a @samp{+} form response. Other features
37419 require values, and the stub should respond with an @samp{=}
37422 Each feature has a default value, which @value{GDBN} will use if
37423 @samp{qSupported} is not available or if the feature is not mentioned
37424 in the @samp{qSupported} response. The default values are fixed; a
37425 stub is free to omit any feature responses that match the defaults.
37427 Not all features can be probed, but for those which can, the probing
37428 mechanism is useful: in some cases, a stub's internal
37429 architecture may not allow the protocol layer to know some information
37430 about the underlying target in advance. This is especially common in
37431 stubs which may be configured for multiple targets.
37433 These are the currently defined stub features and their properties:
37435 @multitable @columnfractions 0.35 0.2 0.12 0.2
37436 @c NOTE: The first row should be @headitem, but we do not yet require
37437 @c a new enough version of Texinfo (4.7) to use @headitem.
37439 @tab Value Required
37443 @item @samp{PacketSize}
37448 @item @samp{qXfer:auxv:read}
37453 @item @samp{qXfer:btrace:read}
37458 @item @samp{qXfer:btrace-conf:read}
37463 @item @samp{qXfer:exec-file:read}
37468 @item @samp{qXfer:features:read}
37473 @item @samp{qXfer:libraries:read}
37478 @item @samp{qXfer:libraries-svr4:read}
37483 @item @samp{augmented-libraries-svr4-read}
37488 @item @samp{qXfer:memory-map:read}
37493 @item @samp{qXfer:sdata:read}
37498 @item @samp{qXfer:spu:read}
37503 @item @samp{qXfer:spu:write}
37508 @item @samp{qXfer:siginfo:read}
37513 @item @samp{qXfer:siginfo:write}
37518 @item @samp{qXfer:threads:read}
37523 @item @samp{qXfer:traceframe-info:read}
37528 @item @samp{qXfer:uib:read}
37533 @item @samp{qXfer:fdpic:read}
37538 @item @samp{Qbtrace:off}
37543 @item @samp{Qbtrace:bts}
37548 @item @samp{Qbtrace:pt}
37553 @item @samp{Qbtrace-conf:bts:size}
37558 @item @samp{Qbtrace-conf:pt:size}
37563 @item @samp{QNonStop}
37568 @item @samp{QCatchSyscalls}
37573 @item @samp{QPassSignals}
37578 @item @samp{QStartNoAckMode}
37583 @item @samp{multiprocess}
37588 @item @samp{ConditionalBreakpoints}
37593 @item @samp{ConditionalTracepoints}
37598 @item @samp{ReverseContinue}
37603 @item @samp{ReverseStep}
37608 @item @samp{TracepointSource}
37613 @item @samp{QAgent}
37618 @item @samp{QAllow}
37623 @item @samp{QDisableRandomization}
37628 @item @samp{EnableDisableTracepoints}
37633 @item @samp{QTBuffer:size}
37638 @item @samp{tracenz}
37643 @item @samp{BreakpointCommands}
37648 @item @samp{swbreak}
37653 @item @samp{hwbreak}
37658 @item @samp{fork-events}
37663 @item @samp{vfork-events}
37668 @item @samp{exec-events}
37673 @item @samp{QThreadEvents}
37678 @item @samp{no-resumed}
37685 These are the currently defined stub features, in more detail:
37688 @cindex packet size, remote protocol
37689 @item PacketSize=@var{bytes}
37690 The remote stub can accept packets up to at least @var{bytes} in
37691 length. @value{GDBN} will send packets up to this size for bulk
37692 transfers, and will never send larger packets. This is a limit on the
37693 data characters in the packet, including the frame and checksum.
37694 There is no trailing NUL byte in a remote protocol packet; if the stub
37695 stores packets in a NUL-terminated format, it should allow an extra
37696 byte in its buffer for the NUL. If this stub feature is not supported,
37697 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37699 @item qXfer:auxv:read
37700 The remote stub understands the @samp{qXfer:auxv:read} packet
37701 (@pxref{qXfer auxiliary vector read}).
37703 @item qXfer:btrace:read
37704 The remote stub understands the @samp{qXfer:btrace:read}
37705 packet (@pxref{qXfer btrace read}).
37707 @item qXfer:btrace-conf:read
37708 The remote stub understands the @samp{qXfer:btrace-conf:read}
37709 packet (@pxref{qXfer btrace-conf read}).
37711 @item qXfer:exec-file:read
37712 The remote stub understands the @samp{qXfer:exec-file:read} packet
37713 (@pxref{qXfer executable filename read}).
37715 @item qXfer:features:read
37716 The remote stub understands the @samp{qXfer:features:read} packet
37717 (@pxref{qXfer target description read}).
37719 @item qXfer:libraries:read
37720 The remote stub understands the @samp{qXfer:libraries:read} packet
37721 (@pxref{qXfer library list read}).
37723 @item qXfer:libraries-svr4:read
37724 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37725 (@pxref{qXfer svr4 library list read}).
37727 @item augmented-libraries-svr4-read
37728 The remote stub understands the augmented form of the
37729 @samp{qXfer:libraries-svr4:read} packet
37730 (@pxref{qXfer svr4 library list read}).
37732 @item qXfer:memory-map:read
37733 The remote stub understands the @samp{qXfer:memory-map:read} packet
37734 (@pxref{qXfer memory map read}).
37736 @item qXfer:sdata:read
37737 The remote stub understands the @samp{qXfer:sdata:read} packet
37738 (@pxref{qXfer sdata read}).
37740 @item qXfer:spu:read
37741 The remote stub understands the @samp{qXfer:spu:read} packet
37742 (@pxref{qXfer spu read}).
37744 @item qXfer:spu:write
37745 The remote stub understands the @samp{qXfer:spu:write} packet
37746 (@pxref{qXfer spu write}).
37748 @item qXfer:siginfo:read
37749 The remote stub understands the @samp{qXfer:siginfo:read} packet
37750 (@pxref{qXfer siginfo read}).
37752 @item qXfer:siginfo:write
37753 The remote stub understands the @samp{qXfer:siginfo:write} packet
37754 (@pxref{qXfer siginfo write}).
37756 @item qXfer:threads:read
37757 The remote stub understands the @samp{qXfer:threads:read} packet
37758 (@pxref{qXfer threads read}).
37760 @item qXfer:traceframe-info:read
37761 The remote stub understands the @samp{qXfer:traceframe-info:read}
37762 packet (@pxref{qXfer traceframe info read}).
37764 @item qXfer:uib:read
37765 The remote stub understands the @samp{qXfer:uib:read}
37766 packet (@pxref{qXfer unwind info block}).
37768 @item qXfer:fdpic:read
37769 The remote stub understands the @samp{qXfer:fdpic:read}
37770 packet (@pxref{qXfer fdpic loadmap read}).
37773 The remote stub understands the @samp{QNonStop} packet
37774 (@pxref{QNonStop}).
37776 @item QCatchSyscalls
37777 The remote stub understands the @samp{QCatchSyscalls} packet
37778 (@pxref{QCatchSyscalls}).
37781 The remote stub understands the @samp{QPassSignals} packet
37782 (@pxref{QPassSignals}).
37784 @item QStartNoAckMode
37785 The remote stub understands the @samp{QStartNoAckMode} packet and
37786 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37789 @anchor{multiprocess extensions}
37790 @cindex multiprocess extensions, in remote protocol
37791 The remote stub understands the multiprocess extensions to the remote
37792 protocol syntax. The multiprocess extensions affect the syntax of
37793 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37794 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37795 replies. Note that reporting this feature indicates support for the
37796 syntactic extensions only, not that the stub necessarily supports
37797 debugging of more than one process at a time. The stub must not use
37798 multiprocess extensions in packet replies unless @value{GDBN} has also
37799 indicated it supports them in its @samp{qSupported} request.
37801 @item qXfer:osdata:read
37802 The remote stub understands the @samp{qXfer:osdata:read} packet
37803 ((@pxref{qXfer osdata read}).
37805 @item ConditionalBreakpoints
37806 The target accepts and implements evaluation of conditional expressions
37807 defined for breakpoints. The target will only report breakpoint triggers
37808 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37810 @item ConditionalTracepoints
37811 The remote stub accepts and implements conditional expressions defined
37812 for tracepoints (@pxref{Tracepoint Conditions}).
37814 @item ReverseContinue
37815 The remote stub accepts and implements the reverse continue packet
37819 The remote stub accepts and implements the reverse step packet
37822 @item TracepointSource
37823 The remote stub understands the @samp{QTDPsrc} packet that supplies
37824 the source form of tracepoint definitions.
37827 The remote stub understands the @samp{QAgent} packet.
37830 The remote stub understands the @samp{QAllow} packet.
37832 @item QDisableRandomization
37833 The remote stub understands the @samp{QDisableRandomization} packet.
37835 @item StaticTracepoint
37836 @cindex static tracepoints, in remote protocol
37837 The remote stub supports static tracepoints.
37839 @item InstallInTrace
37840 @anchor{install tracepoint in tracing}
37841 The remote stub supports installing tracepoint in tracing.
37843 @item EnableDisableTracepoints
37844 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37845 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37846 to be enabled and disabled while a trace experiment is running.
37848 @item QTBuffer:size
37849 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37850 packet that allows to change the size of the trace buffer.
37853 @cindex string tracing, in remote protocol
37854 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37855 See @ref{Bytecode Descriptions} for details about the bytecode.
37857 @item BreakpointCommands
37858 @cindex breakpoint commands, in remote protocol
37859 The remote stub supports running a breakpoint's command list itself,
37860 rather than reporting the hit to @value{GDBN}.
37863 The remote stub understands the @samp{Qbtrace:off} packet.
37866 The remote stub understands the @samp{Qbtrace:bts} packet.
37869 The remote stub understands the @samp{Qbtrace:pt} packet.
37871 @item Qbtrace-conf:bts:size
37872 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37874 @item Qbtrace-conf:pt:size
37875 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37878 The remote stub reports the @samp{swbreak} stop reason for memory
37882 The remote stub reports the @samp{hwbreak} stop reason for hardware
37886 The remote stub reports the @samp{fork} stop reason for fork events.
37889 The remote stub reports the @samp{vfork} stop reason for vfork events
37890 and vforkdone events.
37893 The remote stub reports the @samp{exec} stop reason for exec events.
37895 @item vContSupported
37896 The remote stub reports the supported actions in the reply to
37897 @samp{vCont?} packet.
37899 @item QThreadEvents
37900 The remote stub understands the @samp{QThreadEvents} packet.
37903 The remote stub reports the @samp{N} stop reply.
37908 @cindex symbol lookup, remote request
37909 @cindex @samp{qSymbol} packet
37910 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37911 requests. Accept requests from the target for the values of symbols.
37916 The target does not need to look up any (more) symbols.
37917 @item qSymbol:@var{sym_name}
37918 The target requests the value of symbol @var{sym_name} (hex encoded).
37919 @value{GDBN} may provide the value by using the
37920 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37924 @item qSymbol:@var{sym_value}:@var{sym_name}
37925 Set the value of @var{sym_name} to @var{sym_value}.
37927 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37928 target has previously requested.
37930 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37931 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37937 The target does not need to look up any (more) symbols.
37938 @item qSymbol:@var{sym_name}
37939 The target requests the value of a new symbol @var{sym_name} (hex
37940 encoded). @value{GDBN} will continue to supply the values of symbols
37941 (if available), until the target ceases to request them.
37946 @itemx QTDisconnected
37953 @itemx qTMinFTPILen
37955 @xref{Tracepoint Packets}.
37957 @item qThreadExtraInfo,@var{thread-id}
37958 @cindex thread attributes info, remote request
37959 @cindex @samp{qThreadExtraInfo} packet
37960 Obtain from the target OS a printable string description of thread
37961 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37962 for the forms of @var{thread-id}. This
37963 string may contain anything that the target OS thinks is interesting
37964 for @value{GDBN} to tell the user about the thread. The string is
37965 displayed in @value{GDBN}'s @code{info threads} display. Some
37966 examples of possible thread extra info strings are @samp{Runnable}, or
37967 @samp{Blocked on Mutex}.
37971 @item @var{XX}@dots{}
37972 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37973 comprising the printable string containing the extra information about
37974 the thread's attributes.
37977 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37978 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37979 conventions above. Please don't use this packet as a model for new
37998 @xref{Tracepoint Packets}.
38000 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38001 @cindex read special object, remote request
38002 @cindex @samp{qXfer} packet
38003 @anchor{qXfer read}
38004 Read uninterpreted bytes from the target's special data area
38005 identified by the keyword @var{object}. Request @var{length} bytes
38006 starting at @var{offset} bytes into the data. The content and
38007 encoding of @var{annex} is specific to @var{object}; it can supply
38008 additional details about what data to access.
38013 Data @var{data} (@pxref{Binary Data}) has been read from the
38014 target. There may be more data at a higher address (although
38015 it is permitted to return @samp{m} even for the last valid
38016 block of data, as long as at least one byte of data was read).
38017 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38021 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38022 There is no more data to be read. It is possible for @var{data} to
38023 have fewer bytes than the @var{length} in the request.
38026 The @var{offset} in the request is at the end of the data.
38027 There is no more data to be read.
38030 The request was malformed, or @var{annex} was invalid.
38033 The offset was invalid, or there was an error encountered reading the data.
38034 The @var{nn} part is a hex-encoded @code{errno} value.
38037 An empty reply indicates the @var{object} string was not recognized by
38038 the stub, or that the object does not support reading.
38041 Here are the specific requests of this form defined so far. All the
38042 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38043 formats, listed above.
38046 @item qXfer:auxv:read::@var{offset},@var{length}
38047 @anchor{qXfer auxiliary vector read}
38048 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38049 auxiliary vector}. Note @var{annex} must be empty.
38051 This packet is not probed by default; the remote stub must request it,
38052 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38054 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38055 @anchor{qXfer btrace read}
38057 Return a description of the current branch trace.
38058 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38059 packet may have one of the following values:
38063 Returns all available branch trace.
38066 Returns all available branch trace if the branch trace changed since
38067 the last read request.
38070 Returns the new branch trace since the last read request. Adds a new
38071 block to the end of the trace that begins at zero and ends at the source
38072 location of the first branch in the trace buffer. This extra block is
38073 used to stitch traces together.
38075 If the trace buffer overflowed, returns an error indicating the overflow.
38078 This packet is not probed by default; the remote stub must request it
38079 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38081 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38082 @anchor{qXfer btrace-conf read}
38084 Return a description of the current branch trace configuration.
38085 @xref{Branch Trace Configuration Format}.
38087 This packet is not probed by default; the remote stub must request it
38088 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38090 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38091 @anchor{qXfer executable filename read}
38092 Return the full absolute name of the file that was executed to create
38093 a process running on the remote system. The annex specifies the
38094 numeric process ID of the process to query, encoded as a hexadecimal
38095 number. If the annex part is empty the remote stub should return the
38096 filename corresponding to the currently executing process.
38098 This packet is not probed by default; the remote stub must request it,
38099 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38101 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38102 @anchor{qXfer target description read}
38103 Access the @dfn{target description}. @xref{Target Descriptions}. The
38104 annex specifies which XML document to access. The main description is
38105 always loaded from the @samp{target.xml} annex.
38107 This packet is not probed by default; the remote stub must request it,
38108 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38110 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38111 @anchor{qXfer library list read}
38112 Access the target's list of loaded libraries. @xref{Library List Format}.
38113 The annex part of the generic @samp{qXfer} packet must be empty
38114 (@pxref{qXfer read}).
38116 Targets which maintain a list of libraries in the program's memory do
38117 not need to implement this packet; it is designed for platforms where
38118 the operating system manages the list of loaded libraries.
38120 This packet is not probed by default; the remote stub must request it,
38121 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38123 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38124 @anchor{qXfer svr4 library list read}
38125 Access the target's list of loaded libraries when the target is an SVR4
38126 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38127 of the generic @samp{qXfer} packet must be empty unless the remote
38128 stub indicated it supports the augmented form of this packet
38129 by supplying an appropriate @samp{qSupported} response
38130 (@pxref{qXfer read}, @ref{qSupported}).
38132 This packet is optional for better performance on SVR4 targets.
38133 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38135 This packet is not probed by default; the remote stub must request it,
38136 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38138 If the remote stub indicates it supports the augmented form of this
38139 packet then the annex part of the generic @samp{qXfer} packet may
38140 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38141 arguments. The currently supported arguments are:
38144 @item start=@var{address}
38145 A hexadecimal number specifying the address of the @samp{struct
38146 link_map} to start reading the library list from. If unset or zero
38147 then the first @samp{struct link_map} in the library list will be
38148 chosen as the starting point.
38150 @item prev=@var{address}
38151 A hexadecimal number specifying the address of the @samp{struct
38152 link_map} immediately preceding the @samp{struct link_map}
38153 specified by the @samp{start} argument. If unset or zero then
38154 the remote stub will expect that no @samp{struct link_map}
38155 exists prior to the starting point.
38159 Arguments that are not understood by the remote stub will be silently
38162 @item qXfer:memory-map:read::@var{offset},@var{length}
38163 @anchor{qXfer memory map read}
38164 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38165 annex part of the generic @samp{qXfer} packet must be empty
38166 (@pxref{qXfer read}).
38168 This packet is not probed by default; the remote stub must request it,
38169 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38171 @item qXfer:sdata:read::@var{offset},@var{length}
38172 @anchor{qXfer sdata read}
38174 Read contents of the extra collected static tracepoint marker
38175 information. The annex part of the generic @samp{qXfer} packet must
38176 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38179 This packet is not probed by default; the remote stub must request it,
38180 by supplying an appropriate @samp{qSupported} response
38181 (@pxref{qSupported}).
38183 @item qXfer:siginfo:read::@var{offset},@var{length}
38184 @anchor{qXfer siginfo read}
38185 Read contents of the extra signal information on the target
38186 system. The annex part of the generic @samp{qXfer} packet must be
38187 empty (@pxref{qXfer read}).
38189 This packet is not probed by default; the remote stub must request it,
38190 by supplying an appropriate @samp{qSupported} response
38191 (@pxref{qSupported}).
38193 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38194 @anchor{qXfer spu read}
38195 Read contents of an @code{spufs} file on the target system. The
38196 annex specifies which file to read; it must be of the form
38197 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38198 in the target process, and @var{name} identifes the @code{spufs} file
38199 in that context to be accessed.
38201 This packet is not probed by default; the remote stub must request it,
38202 by supplying an appropriate @samp{qSupported} response
38203 (@pxref{qSupported}).
38205 @item qXfer:threads:read::@var{offset},@var{length}
38206 @anchor{qXfer threads read}
38207 Access the list of threads on target. @xref{Thread List Format}. The
38208 annex part of the generic @samp{qXfer} packet must be empty
38209 (@pxref{qXfer read}).
38211 This packet is not probed by default; the remote stub must request it,
38212 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38214 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38215 @anchor{qXfer traceframe info read}
38217 Return a description of the current traceframe's contents.
38218 @xref{Traceframe Info Format}. The annex part of the generic
38219 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38221 This packet is not probed by default; the remote stub must request it,
38222 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38224 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38225 @anchor{qXfer unwind info block}
38227 Return the unwind information block for @var{pc}. This packet is used
38228 on OpenVMS/ia64 to ask the kernel unwind information.
38230 This packet is not probed by default.
38232 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38233 @anchor{qXfer fdpic loadmap read}
38234 Read contents of @code{loadmap}s on the target system. The
38235 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38236 executable @code{loadmap} or interpreter @code{loadmap} to read.
38238 This packet is not probed by default; the remote stub must request it,
38239 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38241 @item qXfer:osdata:read::@var{offset},@var{length}
38242 @anchor{qXfer osdata read}
38243 Access the target's @dfn{operating system information}.
38244 @xref{Operating System Information}.
38248 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38249 @cindex write data into object, remote request
38250 @anchor{qXfer write}
38251 Write uninterpreted bytes into the target's special data area
38252 identified by the keyword @var{object}, starting at @var{offset} bytes
38253 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38254 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38255 is specific to @var{object}; it can supply additional details about what data
38261 @var{nn} (hex encoded) is the number of bytes written.
38262 This may be fewer bytes than supplied in the request.
38265 The request was malformed, or @var{annex} was invalid.
38268 The offset was invalid, or there was an error encountered writing the data.
38269 The @var{nn} part is a hex-encoded @code{errno} value.
38272 An empty reply indicates the @var{object} string was not
38273 recognized by the stub, or that the object does not support writing.
38276 Here are the specific requests of this form defined so far. All the
38277 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38278 formats, listed above.
38281 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38282 @anchor{qXfer siginfo write}
38283 Write @var{data} to the extra signal information on the target system.
38284 The annex part of the generic @samp{qXfer} packet must be
38285 empty (@pxref{qXfer write}).
38287 This packet is not probed by default; the remote stub must request it,
38288 by supplying an appropriate @samp{qSupported} response
38289 (@pxref{qSupported}).
38291 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38292 @anchor{qXfer spu write}
38293 Write @var{data} to an @code{spufs} file on the target system. The
38294 annex specifies which file to write; it must be of the form
38295 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38296 in the target process, and @var{name} identifes the @code{spufs} file
38297 in that context to be accessed.
38299 This packet is not probed by default; the remote stub must request it,
38300 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38303 @item qXfer:@var{object}:@var{operation}:@dots{}
38304 Requests of this form may be added in the future. When a stub does
38305 not recognize the @var{object} keyword, or its support for
38306 @var{object} does not recognize the @var{operation} keyword, the stub
38307 must respond with an empty packet.
38309 @item qAttached:@var{pid}
38310 @cindex query attached, remote request
38311 @cindex @samp{qAttached} packet
38312 Return an indication of whether the remote server attached to an
38313 existing process or created a new process. When the multiprocess
38314 protocol extensions are supported (@pxref{multiprocess extensions}),
38315 @var{pid} is an integer in hexadecimal format identifying the target
38316 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38317 the query packet will be simplified as @samp{qAttached}.
38319 This query is used, for example, to know whether the remote process
38320 should be detached or killed when a @value{GDBN} session is ended with
38321 the @code{quit} command.
38326 The remote server attached to an existing process.
38328 The remote server created a new process.
38330 A badly formed request or an error was encountered.
38334 Enable branch tracing for the current thread using Branch Trace Store.
38339 Branch tracing has been enabled.
38341 A badly formed request or an error was encountered.
38345 Enable branch tracing for the current thread using Intel Processor Trace.
38350 Branch tracing has been enabled.
38352 A badly formed request or an error was encountered.
38356 Disable branch tracing for the current thread.
38361 Branch tracing has been disabled.
38363 A badly formed request or an error was encountered.
38366 @item Qbtrace-conf:bts:size=@var{value}
38367 Set the requested ring buffer size for new threads that use the
38368 btrace recording method in bts format.
38373 The ring buffer size has been set.
38375 A badly formed request or an error was encountered.
38378 @item Qbtrace-conf:pt:size=@var{value}
38379 Set the requested ring buffer size for new threads that use the
38380 btrace recording method in pt format.
38385 The ring buffer size has been set.
38387 A badly formed request or an error was encountered.
38392 @node Architecture-Specific Protocol Details
38393 @section Architecture-Specific Protocol Details
38395 This section describes how the remote protocol is applied to specific
38396 target architectures. Also see @ref{Standard Target Features}, for
38397 details of XML target descriptions for each architecture.
38400 * ARM-Specific Protocol Details::
38401 * MIPS-Specific Protocol Details::
38404 @node ARM-Specific Protocol Details
38405 @subsection @acronym{ARM}-specific Protocol Details
38408 * ARM Breakpoint Kinds::
38411 @node ARM Breakpoint Kinds
38412 @subsubsection @acronym{ARM} Breakpoint Kinds
38413 @cindex breakpoint kinds, @acronym{ARM}
38415 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38420 16-bit Thumb mode breakpoint.
38423 32-bit Thumb mode (Thumb-2) breakpoint.
38426 32-bit @acronym{ARM} mode breakpoint.
38430 @node MIPS-Specific Protocol Details
38431 @subsection @acronym{MIPS}-specific Protocol Details
38434 * MIPS Register packet Format::
38435 * MIPS Breakpoint Kinds::
38438 @node MIPS Register packet Format
38439 @subsubsection @acronym{MIPS} Register Packet Format
38440 @cindex register packet format, @acronym{MIPS}
38442 The following @code{g}/@code{G} packets have previously been defined.
38443 In the below, some thirty-two bit registers are transferred as
38444 sixty-four bits. Those registers should be zero/sign extended (which?)
38445 to fill the space allocated. Register bytes are transferred in target
38446 byte order. The two nibbles within a register byte are transferred
38447 most-significant -- least-significant.
38452 All registers are transferred as thirty-two bit quantities in the order:
38453 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38454 registers; fsr; fir; fp.
38457 All registers are transferred as sixty-four bit quantities (including
38458 thirty-two bit registers such as @code{sr}). The ordering is the same
38463 @node MIPS Breakpoint Kinds
38464 @subsubsection @acronym{MIPS} Breakpoint Kinds
38465 @cindex breakpoint kinds, @acronym{MIPS}
38467 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38472 16-bit @acronym{MIPS16} mode breakpoint.
38475 16-bit @acronym{microMIPS} mode breakpoint.
38478 32-bit standard @acronym{MIPS} mode breakpoint.
38481 32-bit @acronym{microMIPS} mode breakpoint.
38485 @node Tracepoint Packets
38486 @section Tracepoint Packets
38487 @cindex tracepoint packets
38488 @cindex packets, tracepoint
38490 Here we describe the packets @value{GDBN} uses to implement
38491 tracepoints (@pxref{Tracepoints}).
38495 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38496 @cindex @samp{QTDP} packet
38497 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38498 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38499 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38500 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38501 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38502 the number of bytes that the target should copy elsewhere to make room
38503 for the tracepoint. If an @samp{X} is present, it introduces a
38504 tracepoint condition, which consists of a hexadecimal length, followed
38505 by a comma and hex-encoded bytes, in a manner similar to action
38506 encodings as described below. If the trailing @samp{-} is present,
38507 further @samp{QTDP} packets will follow to specify this tracepoint's
38513 The packet was understood and carried out.
38515 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38517 The packet was not recognized.
38520 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38521 Define actions to be taken when a tracepoint is hit. The @var{n} and
38522 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38523 this tracepoint. This packet may only be sent immediately after
38524 another @samp{QTDP} packet that ended with a @samp{-}. If the
38525 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38526 specifying more actions for this tracepoint.
38528 In the series of action packets for a given tracepoint, at most one
38529 can have an @samp{S} before its first @var{action}. If such a packet
38530 is sent, it and the following packets define ``while-stepping''
38531 actions. Any prior packets define ordinary actions --- that is, those
38532 taken when the tracepoint is first hit. If no action packet has an
38533 @samp{S}, then all the packets in the series specify ordinary
38534 tracepoint actions.
38536 The @samp{@var{action}@dots{}} portion of the packet is a series of
38537 actions, concatenated without separators. Each action has one of the
38543 Collect the registers whose bits are set in @var{mask},
38544 a hexadecimal number whose @var{i}'th bit is set if register number
38545 @var{i} should be collected. (The least significant bit is numbered
38546 zero.) Note that @var{mask} may be any number of digits long; it may
38547 not fit in a 32-bit word.
38549 @item M @var{basereg},@var{offset},@var{len}
38550 Collect @var{len} bytes of memory starting at the address in register
38551 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38552 @samp{-1}, then the range has a fixed address: @var{offset} is the
38553 address of the lowest byte to collect. The @var{basereg},
38554 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38555 values (the @samp{-1} value for @var{basereg} is a special case).
38557 @item X @var{len},@var{expr}
38558 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38559 it directs. The agent expression @var{expr} is as described in
38560 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38561 two-digit hex number in the packet; @var{len} is the number of bytes
38562 in the expression (and thus one-half the number of hex digits in the
38567 Any number of actions may be packed together in a single @samp{QTDP}
38568 packet, as long as the packet does not exceed the maximum packet
38569 length (400 bytes, for many stubs). There may be only one @samp{R}
38570 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38571 actions. Any registers referred to by @samp{M} and @samp{X} actions
38572 must be collected by a preceding @samp{R} action. (The
38573 ``while-stepping'' actions are treated as if they were attached to a
38574 separate tracepoint, as far as these restrictions are concerned.)
38579 The packet was understood and carried out.
38581 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38583 The packet was not recognized.
38586 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38587 @cindex @samp{QTDPsrc} packet
38588 Specify a source string of tracepoint @var{n} at address @var{addr}.
38589 This is useful to get accurate reproduction of the tracepoints
38590 originally downloaded at the beginning of the trace run. The @var{type}
38591 is the name of the tracepoint part, such as @samp{cond} for the
38592 tracepoint's conditional expression (see below for a list of types), while
38593 @var{bytes} is the string, encoded in hexadecimal.
38595 @var{start} is the offset of the @var{bytes} within the overall source
38596 string, while @var{slen} is the total length of the source string.
38597 This is intended for handling source strings that are longer than will
38598 fit in a single packet.
38599 @c Add detailed example when this info is moved into a dedicated
38600 @c tracepoint descriptions section.
38602 The available string types are @samp{at} for the location,
38603 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38604 @value{GDBN} sends a separate packet for each command in the action
38605 list, in the same order in which the commands are stored in the list.
38607 The target does not need to do anything with source strings except
38608 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38611 Although this packet is optional, and @value{GDBN} will only send it
38612 if the target replies with @samp{TracepointSource} @xref{General
38613 Query Packets}, it makes both disconnected tracing and trace files
38614 much easier to use. Otherwise the user must be careful that the
38615 tracepoints in effect while looking at trace frames are identical to
38616 the ones in effect during the trace run; even a small discrepancy
38617 could cause @samp{tdump} not to work, or a particular trace frame not
38620 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38621 @cindex define trace state variable, remote request
38622 @cindex @samp{QTDV} packet
38623 Create a new trace state variable, number @var{n}, with an initial
38624 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38625 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38626 the option of not using this packet for initial values of zero; the
38627 target should simply create the trace state variables as they are
38628 mentioned in expressions. The value @var{builtin} should be 1 (one)
38629 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38630 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38631 @samp{qTsV} packet had it set. The contents of @var{name} is the
38632 hex-encoded name (without the leading @samp{$}) of the trace state
38635 @item QTFrame:@var{n}
38636 @cindex @samp{QTFrame} packet
38637 Select the @var{n}'th tracepoint frame from the buffer, and use the
38638 register and memory contents recorded there to answer subsequent
38639 request packets from @value{GDBN}.
38641 A successful reply from the stub indicates that the stub has found the
38642 requested frame. The response is a series of parts, concatenated
38643 without separators, describing the frame we selected. Each part has
38644 one of the following forms:
38648 The selected frame is number @var{n} in the trace frame buffer;
38649 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38650 was no frame matching the criteria in the request packet.
38653 The selected trace frame records a hit of tracepoint number @var{t};
38654 @var{t} is a hexadecimal number.
38658 @item QTFrame:pc:@var{addr}
38659 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38660 currently selected frame whose PC is @var{addr};
38661 @var{addr} is a hexadecimal number.
38663 @item QTFrame:tdp:@var{t}
38664 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38665 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38666 is a hexadecimal number.
38668 @item QTFrame:range:@var{start}:@var{end}
38669 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38670 currently selected frame whose PC is between @var{start} (inclusive)
38671 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38674 @item QTFrame:outside:@var{start}:@var{end}
38675 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38676 frame @emph{outside} the given range of addresses (exclusive).
38679 @cindex @samp{qTMinFTPILen} packet
38680 This packet requests the minimum length of instruction at which a fast
38681 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38682 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38683 it depends on the target system being able to create trampolines in
38684 the first 64K of memory, which might or might not be possible for that
38685 system. So the reply to this packet will be 4 if it is able to
38692 The minimum instruction length is currently unknown.
38694 The minimum instruction length is @var{length}, where @var{length}
38695 is a hexadecimal number greater or equal to 1. A reply
38696 of 1 means that a fast tracepoint may be placed on any instruction
38697 regardless of size.
38699 An error has occurred.
38701 An empty reply indicates that the request is not supported by the stub.
38705 @cindex @samp{QTStart} packet
38706 Begin the tracepoint experiment. Begin collecting data from
38707 tracepoint hits in the trace frame buffer. This packet supports the
38708 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38709 instruction reply packet}).
38712 @cindex @samp{QTStop} packet
38713 End the tracepoint experiment. Stop collecting trace frames.
38715 @item QTEnable:@var{n}:@var{addr}
38717 @cindex @samp{QTEnable} packet
38718 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38719 experiment. If the tracepoint was previously disabled, then collection
38720 of data from it will resume.
38722 @item QTDisable:@var{n}:@var{addr}
38724 @cindex @samp{QTDisable} packet
38725 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38726 experiment. No more data will be collected from the tracepoint unless
38727 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38730 @cindex @samp{QTinit} packet
38731 Clear the table of tracepoints, and empty the trace frame buffer.
38733 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38734 @cindex @samp{QTro} packet
38735 Establish the given ranges of memory as ``transparent''. The stub
38736 will answer requests for these ranges from memory's current contents,
38737 if they were not collected as part of the tracepoint hit.
38739 @value{GDBN} uses this to mark read-only regions of memory, like those
38740 containing program code. Since these areas never change, they should
38741 still have the same contents they did when the tracepoint was hit, so
38742 there's no reason for the stub to refuse to provide their contents.
38744 @item QTDisconnected:@var{value}
38745 @cindex @samp{QTDisconnected} packet
38746 Set the choice to what to do with the tracing run when @value{GDBN}
38747 disconnects from the target. A @var{value} of 1 directs the target to
38748 continue the tracing run, while 0 tells the target to stop tracing if
38749 @value{GDBN} is no longer in the picture.
38752 @cindex @samp{qTStatus} packet
38753 Ask the stub if there is a trace experiment running right now.
38755 The reply has the form:
38759 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38760 @var{running} is a single digit @code{1} if the trace is presently
38761 running, or @code{0} if not. It is followed by semicolon-separated
38762 optional fields that an agent may use to report additional status.
38766 If the trace is not running, the agent may report any of several
38767 explanations as one of the optional fields:
38772 No trace has been run yet.
38774 @item tstop[:@var{text}]:0
38775 The trace was stopped by a user-originated stop command. The optional
38776 @var{text} field is a user-supplied string supplied as part of the
38777 stop command (for instance, an explanation of why the trace was
38778 stopped manually). It is hex-encoded.
38781 The trace stopped because the trace buffer filled up.
38783 @item tdisconnected:0
38784 The trace stopped because @value{GDBN} disconnected from the target.
38786 @item tpasscount:@var{tpnum}
38787 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38789 @item terror:@var{text}:@var{tpnum}
38790 The trace stopped because tracepoint @var{tpnum} had an error. The
38791 string @var{text} is available to describe the nature of the error
38792 (for instance, a divide by zero in the condition expression); it
38796 The trace stopped for some other reason.
38800 Additional optional fields supply statistical and other information.
38801 Although not required, they are extremely useful for users monitoring
38802 the progress of a trace run. If a trace has stopped, and these
38803 numbers are reported, they must reflect the state of the just-stopped
38808 @item tframes:@var{n}
38809 The number of trace frames in the buffer.
38811 @item tcreated:@var{n}
38812 The total number of trace frames created during the run. This may
38813 be larger than the trace frame count, if the buffer is circular.
38815 @item tsize:@var{n}
38816 The total size of the trace buffer, in bytes.
38818 @item tfree:@var{n}
38819 The number of bytes still unused in the buffer.
38821 @item circular:@var{n}
38822 The value of the circular trace buffer flag. @code{1} means that the
38823 trace buffer is circular and old trace frames will be discarded if
38824 necessary to make room, @code{0} means that the trace buffer is linear
38827 @item disconn:@var{n}
38828 The value of the disconnected tracing flag. @code{1} means that
38829 tracing will continue after @value{GDBN} disconnects, @code{0} means
38830 that the trace run will stop.
38834 @item qTP:@var{tp}:@var{addr}
38835 @cindex tracepoint status, remote request
38836 @cindex @samp{qTP} packet
38837 Ask the stub for the current state of tracepoint number @var{tp} at
38838 address @var{addr}.
38842 @item V@var{hits}:@var{usage}
38843 The tracepoint has been hit @var{hits} times so far during the trace
38844 run, and accounts for @var{usage} in the trace buffer. Note that
38845 @code{while-stepping} steps are not counted as separate hits, but the
38846 steps' space consumption is added into the usage number.
38850 @item qTV:@var{var}
38851 @cindex trace state variable value, remote request
38852 @cindex @samp{qTV} packet
38853 Ask the stub for the value of the trace state variable number @var{var}.
38858 The value of the variable is @var{value}. This will be the current
38859 value of the variable if the user is examining a running target, or a
38860 saved value if the variable was collected in the trace frame that the
38861 user is looking at. Note that multiple requests may result in
38862 different reply values, such as when requesting values while the
38863 program is running.
38866 The value of the variable is unknown. This would occur, for example,
38867 if the user is examining a trace frame in which the requested variable
38872 @cindex @samp{qTfP} packet
38874 @cindex @samp{qTsP} packet
38875 These packets request data about tracepoints that are being used by
38876 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38877 of data, and multiple @code{qTsP} to get additional pieces. Replies
38878 to these packets generally take the form of the @code{QTDP} packets
38879 that define tracepoints. (FIXME add detailed syntax)
38882 @cindex @samp{qTfV} packet
38884 @cindex @samp{qTsV} packet
38885 These packets request data about trace state variables that are on the
38886 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38887 and multiple @code{qTsV} to get additional variables. Replies to
38888 these packets follow the syntax of the @code{QTDV} packets that define
38889 trace state variables.
38895 @cindex @samp{qTfSTM} packet
38896 @cindex @samp{qTsSTM} packet
38897 These packets request data about static tracepoint markers that exist
38898 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38899 first piece of data, and multiple @code{qTsSTM} to get additional
38900 pieces. Replies to these packets take the following form:
38904 @item m @var{address}:@var{id}:@var{extra}
38906 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38907 a comma-separated list of markers
38909 (lower case letter @samp{L}) denotes end of list.
38911 An error occurred. The error number @var{nn} is given as hex digits.
38913 An empty reply indicates that the request is not supported by the
38917 The @var{address} is encoded in hex;
38918 @var{id} and @var{extra} are strings encoded in hex.
38920 In response to each query, the target will reply with a list of one or
38921 more markers, separated by commas. @value{GDBN} will respond to each
38922 reply with a request for more markers (using the @samp{qs} form of the
38923 query), until the target responds with @samp{l} (lower-case ell, for
38926 @item qTSTMat:@var{address}
38928 @cindex @samp{qTSTMat} packet
38929 This packets requests data about static tracepoint markers in the
38930 target program at @var{address}. Replies to this packet follow the
38931 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38932 tracepoint markers.
38934 @item QTSave:@var{filename}
38935 @cindex @samp{QTSave} packet
38936 This packet directs the target to save trace data to the file name
38937 @var{filename} in the target's filesystem. The @var{filename} is encoded
38938 as a hex string; the interpretation of the file name (relative vs
38939 absolute, wild cards, etc) is up to the target.
38941 @item qTBuffer:@var{offset},@var{len}
38942 @cindex @samp{qTBuffer} packet
38943 Return up to @var{len} bytes of the current contents of trace buffer,
38944 starting at @var{offset}. The trace buffer is treated as if it were
38945 a contiguous collection of traceframes, as per the trace file format.
38946 The reply consists as many hex-encoded bytes as the target can deliver
38947 in a packet; it is not an error to return fewer than were asked for.
38948 A reply consisting of just @code{l} indicates that no bytes are
38951 @item QTBuffer:circular:@var{value}
38952 This packet directs the target to use a circular trace buffer if
38953 @var{value} is 1, or a linear buffer if the value is 0.
38955 @item QTBuffer:size:@var{size}
38956 @anchor{QTBuffer-size}
38957 @cindex @samp{QTBuffer size} packet
38958 This packet directs the target to make the trace buffer be of size
38959 @var{size} if possible. A value of @code{-1} tells the target to
38960 use whatever size it prefers.
38962 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38963 @cindex @samp{QTNotes} packet
38964 This packet adds optional textual notes to the trace run. Allowable
38965 types include @code{user}, @code{notes}, and @code{tstop}, the
38966 @var{text} fields are arbitrary strings, hex-encoded.
38970 @subsection Relocate instruction reply packet
38971 When installing fast tracepoints in memory, the target may need to
38972 relocate the instruction currently at the tracepoint address to a
38973 different address in memory. For most instructions, a simple copy is
38974 enough, but, for example, call instructions that implicitly push the
38975 return address on the stack, and relative branches or other
38976 PC-relative instructions require offset adjustment, so that the effect
38977 of executing the instruction at a different address is the same as if
38978 it had executed in the original location.
38980 In response to several of the tracepoint packets, the target may also
38981 respond with a number of intermediate @samp{qRelocInsn} request
38982 packets before the final result packet, to have @value{GDBN} handle
38983 this relocation operation. If a packet supports this mechanism, its
38984 documentation will explicitly say so. See for example the above
38985 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38986 format of the request is:
38989 @item qRelocInsn:@var{from};@var{to}
38991 This requests @value{GDBN} to copy instruction at address @var{from}
38992 to address @var{to}, possibly adjusted so that executing the
38993 instruction at @var{to} has the same effect as executing it at
38994 @var{from}. @value{GDBN} writes the adjusted instruction to target
38995 memory starting at @var{to}.
39000 @item qRelocInsn:@var{adjusted_size}
39001 Informs the stub the relocation is complete. The @var{adjusted_size} is
39002 the length in bytes of resulting relocated instruction sequence.
39004 A badly formed request was detected, or an error was encountered while
39005 relocating the instruction.
39008 @node Host I/O Packets
39009 @section Host I/O Packets
39010 @cindex Host I/O, remote protocol
39011 @cindex file transfer, remote protocol
39013 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39014 operations on the far side of a remote link. For example, Host I/O is
39015 used to upload and download files to a remote target with its own
39016 filesystem. Host I/O uses the same constant values and data structure
39017 layout as the target-initiated File-I/O protocol. However, the
39018 Host I/O packets are structured differently. The target-initiated
39019 protocol relies on target memory to store parameters and buffers.
39020 Host I/O requests are initiated by @value{GDBN}, and the
39021 target's memory is not involved. @xref{File-I/O Remote Protocol
39022 Extension}, for more details on the target-initiated protocol.
39024 The Host I/O request packets all encode a single operation along with
39025 its arguments. They have this format:
39029 @item vFile:@var{operation}: @var{parameter}@dots{}
39030 @var{operation} is the name of the particular request; the target
39031 should compare the entire packet name up to the second colon when checking
39032 for a supported operation. The format of @var{parameter} depends on
39033 the operation. Numbers are always passed in hexadecimal. Negative
39034 numbers have an explicit minus sign (i.e.@: two's complement is not
39035 used). Strings (e.g.@: filenames) are encoded as a series of
39036 hexadecimal bytes. The last argument to a system call may be a
39037 buffer of escaped binary data (@pxref{Binary Data}).
39041 The valid responses to Host I/O packets are:
39045 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39046 @var{result} is the integer value returned by this operation, usually
39047 non-negative for success and -1 for errors. If an error has occured,
39048 @var{errno} will be included in the result specifying a
39049 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39050 operations which return data, @var{attachment} supplies the data as a
39051 binary buffer. Binary buffers in response packets are escaped in the
39052 normal way (@pxref{Binary Data}). See the individual packet
39053 documentation for the interpretation of @var{result} and
39057 An empty response indicates that this operation is not recognized.
39061 These are the supported Host I/O operations:
39064 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39065 Open a file at @var{filename} and return a file descriptor for it, or
39066 return -1 if an error occurs. The @var{filename} is a string,
39067 @var{flags} is an integer indicating a mask of open flags
39068 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39069 of mode bits to use if the file is created (@pxref{mode_t Values}).
39070 @xref{open}, for details of the open flags and mode values.
39072 @item vFile:close: @var{fd}
39073 Close the open file corresponding to @var{fd} and return 0, or
39074 -1 if an error occurs.
39076 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39077 Read data from the open file corresponding to @var{fd}. Up to
39078 @var{count} bytes will be read from the file, starting at @var{offset}
39079 relative to the start of the file. The target may read fewer bytes;
39080 common reasons include packet size limits and an end-of-file
39081 condition. The number of bytes read is returned. Zero should only be
39082 returned for a successful read at the end of the file, or if
39083 @var{count} was zero.
39085 The data read should be returned as a binary attachment on success.
39086 If zero bytes were read, the response should include an empty binary
39087 attachment (i.e.@: a trailing semicolon). The return value is the
39088 number of target bytes read; the binary attachment may be longer if
39089 some characters were escaped.
39091 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39092 Write @var{data} (a binary buffer) to the open file corresponding
39093 to @var{fd}. Start the write at @var{offset} from the start of the
39094 file. Unlike many @code{write} system calls, there is no
39095 separate @var{count} argument; the length of @var{data} in the
39096 packet is used. @samp{vFile:write} returns the number of bytes written,
39097 which may be shorter than the length of @var{data}, or -1 if an
39100 @item vFile:fstat: @var{fd}
39101 Get information about the open file corresponding to @var{fd}.
39102 On success the information is returned as a binary attachment
39103 and the return value is the size of this attachment in bytes.
39104 If an error occurs the return value is -1. The format of the
39105 returned binary attachment is as described in @ref{struct stat}.
39107 @item vFile:unlink: @var{filename}
39108 Delete the file at @var{filename} on the target. Return 0,
39109 or -1 if an error occurs. The @var{filename} is a string.
39111 @item vFile:readlink: @var{filename}
39112 Read value of symbolic link @var{filename} on the target. Return
39113 the number of bytes read, or -1 if an error occurs.
39115 The data read should be returned as a binary attachment on success.
39116 If zero bytes were read, the response should include an empty binary
39117 attachment (i.e.@: a trailing semicolon). The return value is the
39118 number of target bytes read; the binary attachment may be longer if
39119 some characters were escaped.
39121 @item vFile:setfs: @var{pid}
39122 Select the filesystem on which @code{vFile} operations with
39123 @var{filename} arguments will operate. This is required for
39124 @value{GDBN} to be able to access files on remote targets where
39125 the remote stub does not share a common filesystem with the
39128 If @var{pid} is nonzero, select the filesystem as seen by process
39129 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39130 the remote stub. Return 0 on success, or -1 if an error occurs.
39131 If @code{vFile:setfs:} indicates success, the selected filesystem
39132 remains selected until the next successful @code{vFile:setfs:}
39138 @section Interrupts
39139 @cindex interrupts (remote protocol)
39140 @anchor{interrupting remote targets}
39142 In all-stop mode, when a program on the remote target is running,
39143 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39144 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39145 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39147 The precise meaning of @code{BREAK} is defined by the transport
39148 mechanism and may, in fact, be undefined. @value{GDBN} does not
39149 currently define a @code{BREAK} mechanism for any of the network
39150 interfaces except for TCP, in which case @value{GDBN} sends the
39151 @code{telnet} BREAK sequence.
39153 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39154 transport mechanisms. It is represented by sending the single byte
39155 @code{0x03} without any of the usual packet overhead described in
39156 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39157 transmitted as part of a packet, it is considered to be packet data
39158 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39159 (@pxref{X packet}), used for binary downloads, may include an unescaped
39160 @code{0x03} as part of its packet.
39162 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39163 When Linux kernel receives this sequence from serial port,
39164 it stops execution and connects to gdb.
39166 In non-stop mode, because packet resumptions are asynchronous
39167 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39168 command to the remote stub, even when the target is running. For that
39169 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39170 packet}) with the usual packet framing instead of the single byte
39173 Stubs are not required to recognize these interrupt mechanisms and the
39174 precise meaning associated with receipt of the interrupt is
39175 implementation defined. If the target supports debugging of multiple
39176 threads and/or processes, it should attempt to interrupt all
39177 currently-executing threads and processes.
39178 If the stub is successful at interrupting the
39179 running program, it should send one of the stop
39180 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39181 of successfully stopping the program in all-stop mode, and a stop reply
39182 for each stopped thread in non-stop mode.
39183 Interrupts received while the
39184 program is stopped are queued and the program will be interrupted when
39185 it is resumed next time.
39187 @node Notification Packets
39188 @section Notification Packets
39189 @cindex notification packets
39190 @cindex packets, notification
39192 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39193 packets that require no acknowledgment. Both the GDB and the stub
39194 may send notifications (although the only notifications defined at
39195 present are sent by the stub). Notifications carry information
39196 without incurring the round-trip latency of an acknowledgment, and so
39197 are useful for low-impact communications where occasional packet loss
39200 A notification packet has the form @samp{% @var{data} #
39201 @var{checksum}}, where @var{data} is the content of the notification,
39202 and @var{checksum} is a checksum of @var{data}, computed and formatted
39203 as for ordinary @value{GDBN} packets. A notification's @var{data}
39204 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39205 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39206 to acknowledge the notification's receipt or to report its corruption.
39208 Every notification's @var{data} begins with a name, which contains no
39209 colon characters, followed by a colon character.
39211 Recipients should silently ignore corrupted notifications and
39212 notifications they do not understand. Recipients should restart
39213 timeout periods on receipt of a well-formed notification, whether or
39214 not they understand it.
39216 Senders should only send the notifications described here when this
39217 protocol description specifies that they are permitted. In the
39218 future, we may extend the protocol to permit existing notifications in
39219 new contexts; this rule helps older senders avoid confusing newer
39222 (Older versions of @value{GDBN} ignore bytes received until they see
39223 the @samp{$} byte that begins an ordinary packet, so new stubs may
39224 transmit notifications without fear of confusing older clients. There
39225 are no notifications defined for @value{GDBN} to send at the moment, but we
39226 assume that most older stubs would ignore them, as well.)
39228 Each notification is comprised of three parts:
39230 @item @var{name}:@var{event}
39231 The notification packet is sent by the side that initiates the
39232 exchange (currently, only the stub does that), with @var{event}
39233 carrying the specific information about the notification, and
39234 @var{name} specifying the name of the notification.
39236 The acknowledge sent by the other side, usually @value{GDBN}, to
39237 acknowledge the exchange and request the event.
39240 The purpose of an asynchronous notification mechanism is to report to
39241 @value{GDBN} that something interesting happened in the remote stub.
39243 The remote stub may send notification @var{name}:@var{event}
39244 at any time, but @value{GDBN} acknowledges the notification when
39245 appropriate. The notification event is pending before @value{GDBN}
39246 acknowledges. Only one notification at a time may be pending; if
39247 additional events occur before @value{GDBN} has acknowledged the
39248 previous notification, they must be queued by the stub for later
39249 synchronous transmission in response to @var{ack} packets from
39250 @value{GDBN}. Because the notification mechanism is unreliable,
39251 the stub is permitted to resend a notification if it believes
39252 @value{GDBN} may not have received it.
39254 Specifically, notifications may appear when @value{GDBN} is not
39255 otherwise reading input from the stub, or when @value{GDBN} is
39256 expecting to read a normal synchronous response or a
39257 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39258 Notification packets are distinct from any other communication from
39259 the stub so there is no ambiguity.
39261 After receiving a notification, @value{GDBN} shall acknowledge it by
39262 sending a @var{ack} packet as a regular, synchronous request to the
39263 stub. Such acknowledgment is not required to happen immediately, as
39264 @value{GDBN} is permitted to send other, unrelated packets to the
39265 stub first, which the stub should process normally.
39267 Upon receiving a @var{ack} packet, if the stub has other queued
39268 events to report to @value{GDBN}, it shall respond by sending a
39269 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39270 packet to solicit further responses; again, it is permitted to send
39271 other, unrelated packets as well which the stub should process
39274 If the stub receives a @var{ack} packet and there are no additional
39275 @var{event} to report, the stub shall return an @samp{OK} response.
39276 At this point, @value{GDBN} has finished processing a notification
39277 and the stub has completed sending any queued events. @value{GDBN}
39278 won't accept any new notifications until the final @samp{OK} is
39279 received . If further notification events occur, the stub shall send
39280 a new notification, @value{GDBN} shall accept the notification, and
39281 the process shall be repeated.
39283 The process of asynchronous notification can be illustrated by the
39286 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39289 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39291 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39296 The following notifications are defined:
39297 @multitable @columnfractions 0.12 0.12 0.38 0.38
39306 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39307 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39308 for information on how these notifications are acknowledged by
39310 @tab Report an asynchronous stop event in non-stop mode.
39314 @node Remote Non-Stop
39315 @section Remote Protocol Support for Non-Stop Mode
39317 @value{GDBN}'s remote protocol supports non-stop debugging of
39318 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39319 supports non-stop mode, it should report that to @value{GDBN} by including
39320 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39322 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39323 establishing a new connection with the stub. Entering non-stop mode
39324 does not alter the state of any currently-running threads, but targets
39325 must stop all threads in any already-attached processes when entering
39326 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39327 probe the target state after a mode change.
39329 In non-stop mode, when an attached process encounters an event that
39330 would otherwise be reported with a stop reply, it uses the
39331 asynchronous notification mechanism (@pxref{Notification Packets}) to
39332 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39333 in all processes are stopped when a stop reply is sent, in non-stop
39334 mode only the thread reporting the stop event is stopped. That is,
39335 when reporting a @samp{S} or @samp{T} response to indicate completion
39336 of a step operation, hitting a breakpoint, or a fault, only the
39337 affected thread is stopped; any other still-running threads continue
39338 to run. When reporting a @samp{W} or @samp{X} response, all running
39339 threads belonging to other attached processes continue to run.
39341 In non-stop mode, the target shall respond to the @samp{?} packet as
39342 follows. First, any incomplete stop reply notification/@samp{vStopped}
39343 sequence in progress is abandoned. The target must begin a new
39344 sequence reporting stop events for all stopped threads, whether or not
39345 it has previously reported those events to @value{GDBN}. The first
39346 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39347 subsequent stop replies are sent as responses to @samp{vStopped} packets
39348 using the mechanism described above. The target must not send
39349 asynchronous stop reply notifications until the sequence is complete.
39350 If all threads are running when the target receives the @samp{?} packet,
39351 or if the target is not attached to any process, it shall respond
39354 If the stub supports non-stop mode, it should also support the
39355 @samp{swbreak} stop reason if software breakpoints are supported, and
39356 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39357 (@pxref{swbreak stop reason}). This is because given the asynchronous
39358 nature of non-stop mode, between the time a thread hits a breakpoint
39359 and the time the event is finally processed by @value{GDBN}, the
39360 breakpoint may have already been removed from the target. Due to
39361 this, @value{GDBN} needs to be able to tell whether a trap stop was
39362 caused by a delayed breakpoint event, which should be ignored, as
39363 opposed to a random trap signal, which should be reported to the user.
39364 Note the @samp{swbreak} feature implies that the target is responsible
39365 for adjusting the PC when a software breakpoint triggers, if
39366 necessary, such as on the x86 architecture.
39368 @node Packet Acknowledgment
39369 @section Packet Acknowledgment
39371 @cindex acknowledgment, for @value{GDBN} remote
39372 @cindex packet acknowledgment, for @value{GDBN} remote
39373 By default, when either the host or the target machine receives a packet,
39374 the first response expected is an acknowledgment: either @samp{+} (to indicate
39375 the package was received correctly) or @samp{-} (to request retransmission).
39376 This mechanism allows the @value{GDBN} remote protocol to operate over
39377 unreliable transport mechanisms, such as a serial line.
39379 In cases where the transport mechanism is itself reliable (such as a pipe or
39380 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39381 It may be desirable to disable them in that case to reduce communication
39382 overhead, or for other reasons. This can be accomplished by means of the
39383 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39385 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39386 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39387 and response format still includes the normal checksum, as described in
39388 @ref{Overview}, but the checksum may be ignored by the receiver.
39390 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39391 no-acknowledgment mode, it should report that to @value{GDBN}
39392 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39393 @pxref{qSupported}.
39394 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39395 disabled via the @code{set remote noack-packet off} command
39396 (@pxref{Remote Configuration}),
39397 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39398 Only then may the stub actually turn off packet acknowledgments.
39399 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39400 response, which can be safely ignored by the stub.
39402 Note that @code{set remote noack-packet} command only affects negotiation
39403 between @value{GDBN} and the stub when subsequent connections are made;
39404 it does not affect the protocol acknowledgment state for any current
39406 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39407 new connection is established,
39408 there is also no protocol request to re-enable the acknowledgments
39409 for the current connection, once disabled.
39414 Example sequence of a target being re-started. Notice how the restart
39415 does not get any direct output:
39420 @emph{target restarts}
39423 <- @code{T001:1234123412341234}
39427 Example sequence of a target being stepped by a single instruction:
39430 -> @code{G1445@dots{}}
39435 <- @code{T001:1234123412341234}
39439 <- @code{1455@dots{}}
39443 @node File-I/O Remote Protocol Extension
39444 @section File-I/O Remote Protocol Extension
39445 @cindex File-I/O remote protocol extension
39448 * File-I/O Overview::
39449 * Protocol Basics::
39450 * The F Request Packet::
39451 * The F Reply Packet::
39452 * The Ctrl-C Message::
39454 * List of Supported Calls::
39455 * Protocol-specific Representation of Datatypes::
39457 * File-I/O Examples::
39460 @node File-I/O Overview
39461 @subsection File-I/O Overview
39462 @cindex file-i/o overview
39464 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39465 target to use the host's file system and console I/O to perform various
39466 system calls. System calls on the target system are translated into a
39467 remote protocol packet to the host system, which then performs the needed
39468 actions and returns a response packet to the target system.
39469 This simulates file system operations even on targets that lack file systems.
39471 The protocol is defined to be independent of both the host and target systems.
39472 It uses its own internal representation of datatypes and values. Both
39473 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39474 translating the system-dependent value representations into the internal
39475 protocol representations when data is transmitted.
39477 The communication is synchronous. A system call is possible only when
39478 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39479 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39480 the target is stopped to allow deterministic access to the target's
39481 memory. Therefore File-I/O is not interruptible by target signals. On
39482 the other hand, it is possible to interrupt File-I/O by a user interrupt
39483 (@samp{Ctrl-C}) within @value{GDBN}.
39485 The target's request to perform a host system call does not finish
39486 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39487 after finishing the system call, the target returns to continuing the
39488 previous activity (continue, step). No additional continue or step
39489 request from @value{GDBN} is required.
39492 (@value{GDBP}) continue
39493 <- target requests 'system call X'
39494 target is stopped, @value{GDBN} executes system call
39495 -> @value{GDBN} returns result
39496 ... target continues, @value{GDBN} returns to wait for the target
39497 <- target hits breakpoint and sends a Txx packet
39500 The protocol only supports I/O on the console and to regular files on
39501 the host file system. Character or block special devices, pipes,
39502 named pipes, sockets or any other communication method on the host
39503 system are not supported by this protocol.
39505 File I/O is not supported in non-stop mode.
39507 @node Protocol Basics
39508 @subsection Protocol Basics
39509 @cindex protocol basics, file-i/o
39511 The File-I/O protocol uses the @code{F} packet as the request as well
39512 as reply packet. Since a File-I/O system call can only occur when
39513 @value{GDBN} is waiting for a response from the continuing or stepping target,
39514 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39515 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39516 This @code{F} packet contains all information needed to allow @value{GDBN}
39517 to call the appropriate host system call:
39521 A unique identifier for the requested system call.
39524 All parameters to the system call. Pointers are given as addresses
39525 in the target memory address space. Pointers to strings are given as
39526 pointer/length pair. Numerical values are given as they are.
39527 Numerical control flags are given in a protocol-specific representation.
39531 At this point, @value{GDBN} has to perform the following actions.
39535 If the parameters include pointer values to data needed as input to a
39536 system call, @value{GDBN} requests this data from the target with a
39537 standard @code{m} packet request. This additional communication has to be
39538 expected by the target implementation and is handled as any other @code{m}
39542 @value{GDBN} translates all value from protocol representation to host
39543 representation as needed. Datatypes are coerced into the host types.
39546 @value{GDBN} calls the system call.
39549 It then coerces datatypes back to protocol representation.
39552 If the system call is expected to return data in buffer space specified
39553 by pointer parameters to the call, the data is transmitted to the
39554 target using a @code{M} or @code{X} packet. This packet has to be expected
39555 by the target implementation and is handled as any other @code{M} or @code{X}
39560 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39561 necessary information for the target to continue. This at least contains
39568 @code{errno}, if has been changed by the system call.
39575 After having done the needed type and value coercion, the target continues
39576 the latest continue or step action.
39578 @node The F Request Packet
39579 @subsection The @code{F} Request Packet
39580 @cindex file-i/o request packet
39581 @cindex @code{F} request packet
39583 The @code{F} request packet has the following format:
39586 @item F@var{call-id},@var{parameter@dots{}}
39588 @var{call-id} is the identifier to indicate the host system call to be called.
39589 This is just the name of the function.
39591 @var{parameter@dots{}} are the parameters to the system call.
39592 Parameters are hexadecimal integer values, either the actual values in case
39593 of scalar datatypes, pointers to target buffer space in case of compound
39594 datatypes and unspecified memory areas, or pointer/length pairs in case
39595 of string parameters. These are appended to the @var{call-id} as a
39596 comma-delimited list. All values are transmitted in ASCII
39597 string representation, pointer/length pairs separated by a slash.
39603 @node The F Reply Packet
39604 @subsection The @code{F} Reply Packet
39605 @cindex file-i/o reply packet
39606 @cindex @code{F} reply packet
39608 The @code{F} reply packet has the following format:
39612 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39614 @var{retcode} is the return code of the system call as hexadecimal value.
39616 @var{errno} is the @code{errno} set by the call, in protocol-specific
39618 This parameter can be omitted if the call was successful.
39620 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39621 case, @var{errno} must be sent as well, even if the call was successful.
39622 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39629 or, if the call was interrupted before the host call has been performed:
39636 assuming 4 is the protocol-specific representation of @code{EINTR}.
39641 @node The Ctrl-C Message
39642 @subsection The @samp{Ctrl-C} Message
39643 @cindex ctrl-c message, in file-i/o protocol
39645 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39646 reply packet (@pxref{The F Reply Packet}),
39647 the target should behave as if it had
39648 gotten a break message. The meaning for the target is ``system call
39649 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39650 (as with a break message) and return to @value{GDBN} with a @code{T02}
39653 It's important for the target to know in which
39654 state the system call was interrupted. There are two possible cases:
39658 The system call hasn't been performed on the host yet.
39661 The system call on the host has been finished.
39665 These two states can be distinguished by the target by the value of the
39666 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39667 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39668 on POSIX systems. In any other case, the target may presume that the
39669 system call has been finished --- successfully or not --- and should behave
39670 as if the break message arrived right after the system call.
39672 @value{GDBN} must behave reliably. If the system call has not been called
39673 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39674 @code{errno} in the packet. If the system call on the host has been finished
39675 before the user requests a break, the full action must be finished by
39676 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39677 The @code{F} packet may only be sent when either nothing has happened
39678 or the full action has been completed.
39681 @subsection Console I/O
39682 @cindex console i/o as part of file-i/o
39684 By default and if not explicitly closed by the target system, the file
39685 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39686 on the @value{GDBN} console is handled as any other file output operation
39687 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39688 by @value{GDBN} so that after the target read request from file descriptor
39689 0 all following typing is buffered until either one of the following
39694 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39696 system call is treated as finished.
39699 The user presses @key{RET}. This is treated as end of input with a trailing
39703 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39704 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39708 If the user has typed more characters than fit in the buffer given to
39709 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39710 either another @code{read(0, @dots{})} is requested by the target, or debugging
39711 is stopped at the user's request.
39714 @node List of Supported Calls
39715 @subsection List of Supported Calls
39716 @cindex list of supported file-i/o calls
39733 @unnumberedsubsubsec open
39734 @cindex open, file-i/o system call
39739 int open(const char *pathname, int flags);
39740 int open(const char *pathname, int flags, mode_t mode);
39744 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39747 @var{flags} is the bitwise @code{OR} of the following values:
39751 If the file does not exist it will be created. The host
39752 rules apply as far as file ownership and time stamps
39756 When used with @code{O_CREAT}, if the file already exists it is
39757 an error and open() fails.
39760 If the file already exists and the open mode allows
39761 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39762 truncated to zero length.
39765 The file is opened in append mode.
39768 The file is opened for reading only.
39771 The file is opened for writing only.
39774 The file is opened for reading and writing.
39778 Other bits are silently ignored.
39782 @var{mode} is the bitwise @code{OR} of the following values:
39786 User has read permission.
39789 User has write permission.
39792 Group has read permission.
39795 Group has write permission.
39798 Others have read permission.
39801 Others have write permission.
39805 Other bits are silently ignored.
39808 @item Return value:
39809 @code{open} returns the new file descriptor or -1 if an error
39816 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39819 @var{pathname} refers to a directory.
39822 The requested access is not allowed.
39825 @var{pathname} was too long.
39828 A directory component in @var{pathname} does not exist.
39831 @var{pathname} refers to a device, pipe, named pipe or socket.
39834 @var{pathname} refers to a file on a read-only filesystem and
39835 write access was requested.
39838 @var{pathname} is an invalid pointer value.
39841 No space on device to create the file.
39844 The process already has the maximum number of files open.
39847 The limit on the total number of files open on the system
39851 The call was interrupted by the user.
39857 @unnumberedsubsubsec close
39858 @cindex close, file-i/o system call
39867 @samp{Fclose,@var{fd}}
39869 @item Return value:
39870 @code{close} returns zero on success, or -1 if an error occurred.
39876 @var{fd} isn't a valid open file descriptor.
39879 The call was interrupted by the user.
39885 @unnumberedsubsubsec read
39886 @cindex read, file-i/o system call
39891 int read(int fd, void *buf, unsigned int count);
39895 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39897 @item Return value:
39898 On success, the number of bytes read is returned.
39899 Zero indicates end of file. If count is zero, read
39900 returns zero as well. On error, -1 is returned.
39906 @var{fd} is not a valid file descriptor or is not open for
39910 @var{bufptr} is an invalid pointer value.
39913 The call was interrupted by the user.
39919 @unnumberedsubsubsec write
39920 @cindex write, file-i/o system call
39925 int write(int fd, const void *buf, unsigned int count);
39929 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39931 @item Return value:
39932 On success, the number of bytes written are returned.
39933 Zero indicates nothing was written. On error, -1
39940 @var{fd} is not a valid file descriptor or is not open for
39944 @var{bufptr} is an invalid pointer value.
39947 An attempt was made to write a file that exceeds the
39948 host-specific maximum file size allowed.
39951 No space on device to write the data.
39954 The call was interrupted by the user.
39960 @unnumberedsubsubsec lseek
39961 @cindex lseek, file-i/o system call
39966 long lseek (int fd, long offset, int flag);
39970 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39972 @var{flag} is one of:
39976 The offset is set to @var{offset} bytes.
39979 The offset is set to its current location plus @var{offset}
39983 The offset is set to the size of the file plus @var{offset}
39987 @item Return value:
39988 On success, the resulting unsigned offset in bytes from
39989 the beginning of the file is returned. Otherwise, a
39990 value of -1 is returned.
39996 @var{fd} is not a valid open file descriptor.
39999 @var{fd} is associated with the @value{GDBN} console.
40002 @var{flag} is not a proper value.
40005 The call was interrupted by the user.
40011 @unnumberedsubsubsec rename
40012 @cindex rename, file-i/o system call
40017 int rename(const char *oldpath, const char *newpath);
40021 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40023 @item Return value:
40024 On success, zero is returned. On error, -1 is returned.
40030 @var{newpath} is an existing directory, but @var{oldpath} is not a
40034 @var{newpath} is a non-empty directory.
40037 @var{oldpath} or @var{newpath} is a directory that is in use by some
40041 An attempt was made to make a directory a subdirectory
40045 A component used as a directory in @var{oldpath} or new
40046 path is not a directory. Or @var{oldpath} is a directory
40047 and @var{newpath} exists but is not a directory.
40050 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40053 No access to the file or the path of the file.
40057 @var{oldpath} or @var{newpath} was too long.
40060 A directory component in @var{oldpath} or @var{newpath} does not exist.
40063 The file is on a read-only filesystem.
40066 The device containing the file has no room for the new
40070 The call was interrupted by the user.
40076 @unnumberedsubsubsec unlink
40077 @cindex unlink, file-i/o system call
40082 int unlink(const char *pathname);
40086 @samp{Funlink,@var{pathnameptr}/@var{len}}
40088 @item Return value:
40089 On success, zero is returned. On error, -1 is returned.
40095 No access to the file or the path of the file.
40098 The system does not allow unlinking of directories.
40101 The file @var{pathname} cannot be unlinked because it's
40102 being used by another process.
40105 @var{pathnameptr} is an invalid pointer value.
40108 @var{pathname} was too long.
40111 A directory component in @var{pathname} does not exist.
40114 A component of the path is not a directory.
40117 The file is on a read-only filesystem.
40120 The call was interrupted by the user.
40126 @unnumberedsubsubsec stat/fstat
40127 @cindex fstat, file-i/o system call
40128 @cindex stat, file-i/o system call
40133 int stat(const char *pathname, struct stat *buf);
40134 int fstat(int fd, struct stat *buf);
40138 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40139 @samp{Ffstat,@var{fd},@var{bufptr}}
40141 @item Return value:
40142 On success, zero is returned. On error, -1 is returned.
40148 @var{fd} is not a valid open file.
40151 A directory component in @var{pathname} does not exist or the
40152 path is an empty string.
40155 A component of the path is not a directory.
40158 @var{pathnameptr} is an invalid pointer value.
40161 No access to the file or the path of the file.
40164 @var{pathname} was too long.
40167 The call was interrupted by the user.
40173 @unnumberedsubsubsec gettimeofday
40174 @cindex gettimeofday, file-i/o system call
40179 int gettimeofday(struct timeval *tv, void *tz);
40183 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40185 @item Return value:
40186 On success, 0 is returned, -1 otherwise.
40192 @var{tz} is a non-NULL pointer.
40195 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40201 @unnumberedsubsubsec isatty
40202 @cindex isatty, file-i/o system call
40207 int isatty(int fd);
40211 @samp{Fisatty,@var{fd}}
40213 @item Return value:
40214 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40220 The call was interrupted by the user.
40225 Note that the @code{isatty} call is treated as a special case: it returns
40226 1 to the target if the file descriptor is attached
40227 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40228 would require implementing @code{ioctl} and would be more complex than
40233 @unnumberedsubsubsec system
40234 @cindex system, file-i/o system call
40239 int system(const char *command);
40243 @samp{Fsystem,@var{commandptr}/@var{len}}
40245 @item Return value:
40246 If @var{len} is zero, the return value indicates whether a shell is
40247 available. A zero return value indicates a shell is not available.
40248 For non-zero @var{len}, the value returned is -1 on error and the
40249 return status of the command otherwise. Only the exit status of the
40250 command is returned, which is extracted from the host's @code{system}
40251 return value by calling @code{WEXITSTATUS(retval)}. In case
40252 @file{/bin/sh} could not be executed, 127 is returned.
40258 The call was interrupted by the user.
40263 @value{GDBN} takes over the full task of calling the necessary host calls
40264 to perform the @code{system} call. The return value of @code{system} on
40265 the host is simplified before it's returned
40266 to the target. Any termination signal information from the child process
40267 is discarded, and the return value consists
40268 entirely of the exit status of the called command.
40270 Due to security concerns, the @code{system} call is by default refused
40271 by @value{GDBN}. The user has to allow this call explicitly with the
40272 @code{set remote system-call-allowed 1} command.
40275 @item set remote system-call-allowed
40276 @kindex set remote system-call-allowed
40277 Control whether to allow the @code{system} calls in the File I/O
40278 protocol for the remote target. The default is zero (disabled).
40280 @item show remote system-call-allowed
40281 @kindex show remote system-call-allowed
40282 Show whether the @code{system} calls are allowed in the File I/O
40286 @node Protocol-specific Representation of Datatypes
40287 @subsection Protocol-specific Representation of Datatypes
40288 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40291 * Integral Datatypes::
40293 * Memory Transfer::
40298 @node Integral Datatypes
40299 @unnumberedsubsubsec Integral Datatypes
40300 @cindex integral datatypes, in file-i/o protocol
40302 The integral datatypes used in the system calls are @code{int},
40303 @code{unsigned int}, @code{long}, @code{unsigned long},
40304 @code{mode_t}, and @code{time_t}.
40306 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40307 implemented as 32 bit values in this protocol.
40309 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40311 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40312 in @file{limits.h}) to allow range checking on host and target.
40314 @code{time_t} datatypes are defined as seconds since the Epoch.
40316 All integral datatypes transferred as part of a memory read or write of a
40317 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40320 @node Pointer Values
40321 @unnumberedsubsubsec Pointer Values
40322 @cindex pointer values, in file-i/o protocol
40324 Pointers to target data are transmitted as they are. An exception
40325 is made for pointers to buffers for which the length isn't
40326 transmitted as part of the function call, namely strings. Strings
40327 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40334 which is a pointer to data of length 18 bytes at position 0x1aaf.
40335 The length is defined as the full string length in bytes, including
40336 the trailing null byte. For example, the string @code{"hello world"}
40337 at address 0x123456 is transmitted as
40343 @node Memory Transfer
40344 @unnumberedsubsubsec Memory Transfer
40345 @cindex memory transfer, in file-i/o protocol
40347 Structured data which is transferred using a memory read or write (for
40348 example, a @code{struct stat}) is expected to be in a protocol-specific format
40349 with all scalar multibyte datatypes being big endian. Translation to
40350 this representation needs to be done both by the target before the @code{F}
40351 packet is sent, and by @value{GDBN} before
40352 it transfers memory to the target. Transferred pointers to structured
40353 data should point to the already-coerced data at any time.
40357 @unnumberedsubsubsec struct stat
40358 @cindex struct stat, in file-i/o protocol
40360 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40361 is defined as follows:
40365 unsigned int st_dev; /* device */
40366 unsigned int st_ino; /* inode */
40367 mode_t st_mode; /* protection */
40368 unsigned int st_nlink; /* number of hard links */
40369 unsigned int st_uid; /* user ID of owner */
40370 unsigned int st_gid; /* group ID of owner */
40371 unsigned int st_rdev; /* device type (if inode device) */
40372 unsigned long st_size; /* total size, in bytes */
40373 unsigned long st_blksize; /* blocksize for filesystem I/O */
40374 unsigned long st_blocks; /* number of blocks allocated */
40375 time_t st_atime; /* time of last access */
40376 time_t st_mtime; /* time of last modification */
40377 time_t st_ctime; /* time of last change */
40381 The integral datatypes conform to the definitions given in the
40382 appropriate section (see @ref{Integral Datatypes}, for details) so this
40383 structure is of size 64 bytes.
40385 The values of several fields have a restricted meaning and/or
40391 A value of 0 represents a file, 1 the console.
40394 No valid meaning for the target. Transmitted unchanged.
40397 Valid mode bits are described in @ref{Constants}. Any other
40398 bits have currently no meaning for the target.
40403 No valid meaning for the target. Transmitted unchanged.
40408 These values have a host and file system dependent
40409 accuracy. Especially on Windows hosts, the file system may not
40410 support exact timing values.
40413 The target gets a @code{struct stat} of the above representation and is
40414 responsible for coercing it to the target representation before
40417 Note that due to size differences between the host, target, and protocol
40418 representations of @code{struct stat} members, these members could eventually
40419 get truncated on the target.
40421 @node struct timeval
40422 @unnumberedsubsubsec struct timeval
40423 @cindex struct timeval, in file-i/o protocol
40425 The buffer of type @code{struct timeval} used by the File-I/O protocol
40426 is defined as follows:
40430 time_t tv_sec; /* second */
40431 long tv_usec; /* microsecond */
40435 The integral datatypes conform to the definitions given in the
40436 appropriate section (see @ref{Integral Datatypes}, for details) so this
40437 structure is of size 8 bytes.
40440 @subsection Constants
40441 @cindex constants, in file-i/o protocol
40443 The following values are used for the constants inside of the
40444 protocol. @value{GDBN} and target are responsible for translating these
40445 values before and after the call as needed.
40456 @unnumberedsubsubsec Open Flags
40457 @cindex open flags, in file-i/o protocol
40459 All values are given in hexadecimal representation.
40471 @node mode_t Values
40472 @unnumberedsubsubsec mode_t Values
40473 @cindex mode_t values, in file-i/o protocol
40475 All values are given in octal representation.
40492 @unnumberedsubsubsec Errno Values
40493 @cindex errno values, in file-i/o protocol
40495 All values are given in decimal representation.
40520 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40521 any error value not in the list of supported error numbers.
40524 @unnumberedsubsubsec Lseek Flags
40525 @cindex lseek flags, in file-i/o protocol
40534 @unnumberedsubsubsec Limits
40535 @cindex limits, in file-i/o protocol
40537 All values are given in decimal representation.
40540 INT_MIN -2147483648
40542 UINT_MAX 4294967295
40543 LONG_MIN -9223372036854775808
40544 LONG_MAX 9223372036854775807
40545 ULONG_MAX 18446744073709551615
40548 @node File-I/O Examples
40549 @subsection File-I/O Examples
40550 @cindex file-i/o examples
40552 Example sequence of a write call, file descriptor 3, buffer is at target
40553 address 0x1234, 6 bytes should be written:
40556 <- @code{Fwrite,3,1234,6}
40557 @emph{request memory read from target}
40560 @emph{return "6 bytes written"}
40564 Example sequence of a read call, file descriptor 3, buffer is at target
40565 address 0x1234, 6 bytes should be read:
40568 <- @code{Fread,3,1234,6}
40569 @emph{request memory write to target}
40570 -> @code{X1234,6:XXXXXX}
40571 @emph{return "6 bytes read"}
40575 Example sequence of a read call, call fails on the host due to invalid
40576 file descriptor (@code{EBADF}):
40579 <- @code{Fread,3,1234,6}
40583 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40587 <- @code{Fread,3,1234,6}
40592 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40596 <- @code{Fread,3,1234,6}
40597 -> @code{X1234,6:XXXXXX}
40601 @node Library List Format
40602 @section Library List Format
40603 @cindex library list format, remote protocol
40605 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40606 same process as your application to manage libraries. In this case,
40607 @value{GDBN} can use the loader's symbol table and normal memory
40608 operations to maintain a list of shared libraries. On other
40609 platforms, the operating system manages loaded libraries.
40610 @value{GDBN} can not retrieve the list of currently loaded libraries
40611 through memory operations, so it uses the @samp{qXfer:libraries:read}
40612 packet (@pxref{qXfer library list read}) instead. The remote stub
40613 queries the target's operating system and reports which libraries
40616 The @samp{qXfer:libraries:read} packet returns an XML document which
40617 lists loaded libraries and their offsets. Each library has an
40618 associated name and one or more segment or section base addresses,
40619 which report where the library was loaded in memory.
40621 For the common case of libraries that are fully linked binaries, the
40622 library should have a list of segments. If the target supports
40623 dynamic linking of a relocatable object file, its library XML element
40624 should instead include a list of allocated sections. The segment or
40625 section bases are start addresses, not relocation offsets; they do not
40626 depend on the library's link-time base addresses.
40628 @value{GDBN} must be linked with the Expat library to support XML
40629 library lists. @xref{Expat}.
40631 A simple memory map, with one loaded library relocated by a single
40632 offset, looks like this:
40636 <library name="/lib/libc.so.6">
40637 <segment address="0x10000000"/>
40642 Another simple memory map, with one loaded library with three
40643 allocated sections (.text, .data, .bss), looks like this:
40647 <library name="sharedlib.o">
40648 <section address="0x10000000"/>
40649 <section address="0x20000000"/>
40650 <section address="0x30000000"/>
40655 The format of a library list is described by this DTD:
40658 <!-- library-list: Root element with versioning -->
40659 <!ELEMENT library-list (library)*>
40660 <!ATTLIST library-list version CDATA #FIXED "1.0">
40661 <!ELEMENT library (segment*, section*)>
40662 <!ATTLIST library name CDATA #REQUIRED>
40663 <!ELEMENT segment EMPTY>
40664 <!ATTLIST segment address CDATA #REQUIRED>
40665 <!ELEMENT section EMPTY>
40666 <!ATTLIST section address CDATA #REQUIRED>
40669 In addition, segments and section descriptors cannot be mixed within a
40670 single library element, and you must supply at least one segment or
40671 section for each library.
40673 @node Library List Format for SVR4 Targets
40674 @section Library List Format for SVR4 Targets
40675 @cindex library list format, remote protocol
40677 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40678 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40679 shared libraries. Still a special library list provided by this packet is
40680 more efficient for the @value{GDBN} remote protocol.
40682 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40683 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40684 target, the following parameters are reported:
40688 @code{name}, the absolute file name from the @code{l_name} field of
40689 @code{struct link_map}.
40691 @code{lm} with address of @code{struct link_map} used for TLS
40692 (Thread Local Storage) access.
40694 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40695 @code{struct link_map}. For prelinked libraries this is not an absolute
40696 memory address. It is a displacement of absolute memory address against
40697 address the file was prelinked to during the library load.
40699 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40702 Additionally the single @code{main-lm} attribute specifies address of
40703 @code{struct link_map} used for the main executable. This parameter is used
40704 for TLS access and its presence is optional.
40706 @value{GDBN} must be linked with the Expat library to support XML
40707 SVR4 library lists. @xref{Expat}.
40709 A simple memory map, with two loaded libraries (which do not use prelink),
40713 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40714 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40716 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40718 </library-list-svr>
40721 The format of an SVR4 library list is described by this DTD:
40724 <!-- library-list-svr4: Root element with versioning -->
40725 <!ELEMENT library-list-svr4 (library)*>
40726 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40727 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40728 <!ELEMENT library EMPTY>
40729 <!ATTLIST library name CDATA #REQUIRED>
40730 <!ATTLIST library lm CDATA #REQUIRED>
40731 <!ATTLIST library l_addr CDATA #REQUIRED>
40732 <!ATTLIST library l_ld CDATA #REQUIRED>
40735 @node Memory Map Format
40736 @section Memory Map Format
40737 @cindex memory map format
40739 To be able to write into flash memory, @value{GDBN} needs to obtain a
40740 memory map from the target. This section describes the format of the
40743 The memory map is obtained using the @samp{qXfer:memory-map:read}
40744 (@pxref{qXfer memory map read}) packet and is an XML document that
40745 lists memory regions.
40747 @value{GDBN} must be linked with the Expat library to support XML
40748 memory maps. @xref{Expat}.
40750 The top-level structure of the document is shown below:
40753 <?xml version="1.0"?>
40754 <!DOCTYPE memory-map
40755 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40756 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40762 Each region can be either:
40767 A region of RAM starting at @var{addr} and extending for @var{length}
40771 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40776 A region of read-only memory:
40779 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40784 A region of flash memory, with erasure blocks @var{blocksize}
40788 <memory type="flash" start="@var{addr}" length="@var{length}">
40789 <property name="blocksize">@var{blocksize}</property>
40795 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40796 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40797 packets to write to addresses in such ranges.
40799 The formal DTD for memory map format is given below:
40802 <!-- ................................................... -->
40803 <!-- Memory Map XML DTD ................................ -->
40804 <!-- File: memory-map.dtd .............................. -->
40805 <!-- .................................... .............. -->
40806 <!-- memory-map.dtd -->
40807 <!-- memory-map: Root element with versioning -->
40808 <!ELEMENT memory-map (memory | property)>
40809 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40810 <!ELEMENT memory (property)>
40811 <!-- memory: Specifies a memory region,
40812 and its type, or device. -->
40813 <!ATTLIST memory type CDATA #REQUIRED
40814 start CDATA #REQUIRED
40815 length CDATA #REQUIRED
40816 device CDATA #IMPLIED>
40817 <!-- property: Generic attribute tag -->
40818 <!ELEMENT property (#PCDATA | property)*>
40819 <!ATTLIST property name CDATA #REQUIRED>
40822 @node Thread List Format
40823 @section Thread List Format
40824 @cindex thread list format
40826 To efficiently update the list of threads and their attributes,
40827 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40828 (@pxref{qXfer threads read}) and obtains the XML document with
40829 the following structure:
40832 <?xml version="1.0"?>
40834 <thread id="id" core="0" name="name">
40835 ... description ...
40840 Each @samp{thread} element must have the @samp{id} attribute that
40841 identifies the thread (@pxref{thread-id syntax}). The
40842 @samp{core} attribute, if present, specifies which processor core
40843 the thread was last executing on. The @samp{name} attribute, if
40844 present, specifies the human-readable name of the thread. The content
40845 of the of @samp{thread} element is interpreted as human-readable
40846 auxiliary information. The @samp{handle} attribute, if present,
40847 is a hex encoded representation of the thread handle.
40850 @node Traceframe Info Format
40851 @section Traceframe Info Format
40852 @cindex traceframe info format
40854 To be able to know which objects in the inferior can be examined when
40855 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40856 memory ranges, registers and trace state variables that have been
40857 collected in a traceframe.
40859 This list is obtained using the @samp{qXfer:traceframe-info:read}
40860 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40862 @value{GDBN} must be linked with the Expat library to support XML
40863 traceframe info discovery. @xref{Expat}.
40865 The top-level structure of the document is shown below:
40868 <?xml version="1.0"?>
40869 <!DOCTYPE traceframe-info
40870 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40871 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40877 Each traceframe block can be either:
40882 A region of collected memory starting at @var{addr} and extending for
40883 @var{length} bytes from there:
40886 <memory start="@var{addr}" length="@var{length}"/>
40890 A block indicating trace state variable numbered @var{number} has been
40894 <tvar id="@var{number}"/>
40899 The formal DTD for the traceframe info format is given below:
40902 <!ELEMENT traceframe-info (memory | tvar)* >
40903 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40905 <!ELEMENT memory EMPTY>
40906 <!ATTLIST memory start CDATA #REQUIRED
40907 length CDATA #REQUIRED>
40909 <!ATTLIST tvar id CDATA #REQUIRED>
40912 @node Branch Trace Format
40913 @section Branch Trace Format
40914 @cindex branch trace format
40916 In order to display the branch trace of an inferior thread,
40917 @value{GDBN} needs to obtain the list of branches. This list is
40918 represented as list of sequential code blocks that are connected via
40919 branches. The code in each block has been executed sequentially.
40921 This list is obtained using the @samp{qXfer:btrace:read}
40922 (@pxref{qXfer btrace read}) packet and is an XML document.
40924 @value{GDBN} must be linked with the Expat library to support XML
40925 traceframe info discovery. @xref{Expat}.
40927 The top-level structure of the document is shown below:
40930 <?xml version="1.0"?>
40932 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40933 "http://sourceware.org/gdb/gdb-btrace.dtd">
40942 A block of sequentially executed instructions starting at @var{begin}
40943 and ending at @var{end}:
40946 <block begin="@var{begin}" end="@var{end}"/>
40951 The formal DTD for the branch trace format is given below:
40954 <!ELEMENT btrace (block* | pt) >
40955 <!ATTLIST btrace version CDATA #FIXED "1.0">
40957 <!ELEMENT block EMPTY>
40958 <!ATTLIST block begin CDATA #REQUIRED
40959 end CDATA #REQUIRED>
40961 <!ELEMENT pt (pt-config?, raw?)>
40963 <!ELEMENT pt-config (cpu?)>
40965 <!ELEMENT cpu EMPTY>
40966 <!ATTLIST cpu vendor CDATA #REQUIRED
40967 family CDATA #REQUIRED
40968 model CDATA #REQUIRED
40969 stepping CDATA #REQUIRED>
40971 <!ELEMENT raw (#PCDATA)>
40974 @node Branch Trace Configuration Format
40975 @section Branch Trace Configuration Format
40976 @cindex branch trace configuration format
40978 For each inferior thread, @value{GDBN} can obtain the branch trace
40979 configuration using the @samp{qXfer:btrace-conf:read}
40980 (@pxref{qXfer btrace-conf read}) packet.
40982 The configuration describes the branch trace format and configuration
40983 settings for that format. The following information is described:
40987 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40990 The size of the @acronym{BTS} ring buffer in bytes.
40993 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40997 The size of the @acronym{Intel PT} ring buffer in bytes.
41001 @value{GDBN} must be linked with the Expat library to support XML
41002 branch trace configuration discovery. @xref{Expat}.
41004 The formal DTD for the branch trace configuration format is given below:
41007 <!ELEMENT btrace-conf (bts?, pt?)>
41008 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41010 <!ELEMENT bts EMPTY>
41011 <!ATTLIST bts size CDATA #IMPLIED>
41013 <!ELEMENT pt EMPTY>
41014 <!ATTLIST pt size CDATA #IMPLIED>
41017 @include agentexpr.texi
41019 @node Target Descriptions
41020 @appendix Target Descriptions
41021 @cindex target descriptions
41023 One of the challenges of using @value{GDBN} to debug embedded systems
41024 is that there are so many minor variants of each processor
41025 architecture in use. It is common practice for vendors to start with
41026 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41027 and then make changes to adapt it to a particular market niche. Some
41028 architectures have hundreds of variants, available from dozens of
41029 vendors. This leads to a number of problems:
41033 With so many different customized processors, it is difficult for
41034 the @value{GDBN} maintainers to keep up with the changes.
41036 Since individual variants may have short lifetimes or limited
41037 audiences, it may not be worthwhile to carry information about every
41038 variant in the @value{GDBN} source tree.
41040 When @value{GDBN} does support the architecture of the embedded system
41041 at hand, the task of finding the correct architecture name to give the
41042 @command{set architecture} command can be error-prone.
41045 To address these problems, the @value{GDBN} remote protocol allows a
41046 target system to not only identify itself to @value{GDBN}, but to
41047 actually describe its own features. This lets @value{GDBN} support
41048 processor variants it has never seen before --- to the extent that the
41049 descriptions are accurate, and that @value{GDBN} understands them.
41051 @value{GDBN} must be linked with the Expat library to support XML
41052 target descriptions. @xref{Expat}.
41055 * Retrieving Descriptions:: How descriptions are fetched from a target.
41056 * Target Description Format:: The contents of a target description.
41057 * Predefined Target Types:: Standard types available for target
41059 * Enum Target Types:: How to define enum target types.
41060 * Standard Target Features:: Features @value{GDBN} knows about.
41063 @node Retrieving Descriptions
41064 @section Retrieving Descriptions
41066 Target descriptions can be read from the target automatically, or
41067 specified by the user manually. The default behavior is to read the
41068 description from the target. @value{GDBN} retrieves it via the remote
41069 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41070 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41071 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41072 XML document, of the form described in @ref{Target Description
41075 Alternatively, you can specify a file to read for the target description.
41076 If a file is set, the target will not be queried. The commands to
41077 specify a file are:
41080 @cindex set tdesc filename
41081 @item set tdesc filename @var{path}
41082 Read the target description from @var{path}.
41084 @cindex unset tdesc filename
41085 @item unset tdesc filename
41086 Do not read the XML target description from a file. @value{GDBN}
41087 will use the description supplied by the current target.
41089 @cindex show tdesc filename
41090 @item show tdesc filename
41091 Show the filename to read for a target description, if any.
41095 @node Target Description Format
41096 @section Target Description Format
41097 @cindex target descriptions, XML format
41099 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41100 document which complies with the Document Type Definition provided in
41101 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41102 means you can use generally available tools like @command{xmllint} to
41103 check that your feature descriptions are well-formed and valid.
41104 However, to help people unfamiliar with XML write descriptions for
41105 their targets, we also describe the grammar here.
41107 Target descriptions can identify the architecture of the remote target
41108 and (for some architectures) provide information about custom register
41109 sets. They can also identify the OS ABI of the remote target.
41110 @value{GDBN} can use this information to autoconfigure for your
41111 target, or to warn you if you connect to an unsupported target.
41113 Here is a simple target description:
41116 <target version="1.0">
41117 <architecture>i386:x86-64</architecture>
41122 This minimal description only says that the target uses
41123 the x86-64 architecture.
41125 A target description has the following overall form, with [ ] marking
41126 optional elements and @dots{} marking repeatable elements. The elements
41127 are explained further below.
41130 <?xml version="1.0"?>
41131 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41132 <target version="1.0">
41133 @r{[}@var{architecture}@r{]}
41134 @r{[}@var{osabi}@r{]}
41135 @r{[}@var{compatible}@r{]}
41136 @r{[}@var{feature}@dots{}@r{]}
41141 The description is generally insensitive to whitespace and line
41142 breaks, under the usual common-sense rules. The XML version
41143 declaration and document type declaration can generally be omitted
41144 (@value{GDBN} does not require them), but specifying them may be
41145 useful for XML validation tools. The @samp{version} attribute for
41146 @samp{<target>} may also be omitted, but we recommend
41147 including it; if future versions of @value{GDBN} use an incompatible
41148 revision of @file{gdb-target.dtd}, they will detect and report
41149 the version mismatch.
41151 @subsection Inclusion
41152 @cindex target descriptions, inclusion
41155 @cindex <xi:include>
41158 It can sometimes be valuable to split a target description up into
41159 several different annexes, either for organizational purposes, or to
41160 share files between different possible target descriptions. You can
41161 divide a description into multiple files by replacing any element of
41162 the target description with an inclusion directive of the form:
41165 <xi:include href="@var{document}"/>
41169 When @value{GDBN} encounters an element of this form, it will retrieve
41170 the named XML @var{document}, and replace the inclusion directive with
41171 the contents of that document. If the current description was read
41172 using @samp{qXfer}, then so will be the included document;
41173 @var{document} will be interpreted as the name of an annex. If the
41174 current description was read from a file, @value{GDBN} will look for
41175 @var{document} as a file in the same directory where it found the
41176 original description.
41178 @subsection Architecture
41179 @cindex <architecture>
41181 An @samp{<architecture>} element has this form:
41184 <architecture>@var{arch}</architecture>
41187 @var{arch} is one of the architectures from the set accepted by
41188 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41191 @cindex @code{<osabi>}
41193 This optional field was introduced in @value{GDBN} version 7.0.
41194 Previous versions of @value{GDBN} ignore it.
41196 An @samp{<osabi>} element has this form:
41199 <osabi>@var{abi-name}</osabi>
41202 @var{abi-name} is an OS ABI name from the same selection accepted by
41203 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41205 @subsection Compatible Architecture
41206 @cindex @code{<compatible>}
41208 This optional field was introduced in @value{GDBN} version 7.0.
41209 Previous versions of @value{GDBN} ignore it.
41211 A @samp{<compatible>} element has this form:
41214 <compatible>@var{arch}</compatible>
41217 @var{arch} is one of the architectures from the set accepted by
41218 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41220 A @samp{<compatible>} element is used to specify that the target
41221 is able to run binaries in some other than the main target architecture
41222 given by the @samp{<architecture>} element. For example, on the
41223 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41224 or @code{powerpc:common64}, but the system is able to run binaries
41225 in the @code{spu} architecture as well. The way to describe this
41226 capability with @samp{<compatible>} is as follows:
41229 <architecture>powerpc:common</architecture>
41230 <compatible>spu</compatible>
41233 @subsection Features
41236 Each @samp{<feature>} describes some logical portion of the target
41237 system. Features are currently used to describe available CPU
41238 registers and the types of their contents. A @samp{<feature>} element
41242 <feature name="@var{name}">
41243 @r{[}@var{type}@dots{}@r{]}
41249 Each feature's name should be unique within the description. The name
41250 of a feature does not matter unless @value{GDBN} has some special
41251 knowledge of the contents of that feature; if it does, the feature
41252 should have its standard name. @xref{Standard Target Features}.
41256 Any register's value is a collection of bits which @value{GDBN} must
41257 interpret. The default interpretation is a two's complement integer,
41258 but other types can be requested by name in the register description.
41259 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41260 Target Types}), and the description can define additional composite
41263 Each type element must have an @samp{id} attribute, which gives
41264 a unique (within the containing @samp{<feature>}) name to the type.
41265 Types must be defined before they are used.
41268 Some targets offer vector registers, which can be treated as arrays
41269 of scalar elements. These types are written as @samp{<vector>} elements,
41270 specifying the array element type, @var{type}, and the number of elements,
41274 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41278 If a register's value is usefully viewed in multiple ways, define it
41279 with a union type containing the useful representations. The
41280 @samp{<union>} element contains one or more @samp{<field>} elements,
41281 each of which has a @var{name} and a @var{type}:
41284 <union id="@var{id}">
41285 <field name="@var{name}" type="@var{type}"/>
41292 If a register's value is composed from several separate values, define
41293 it with either a structure type or a flags type.
41294 A flags type may only contain bitfields.
41295 A structure type may either contain only bitfields or contain no bitfields.
41296 If the value contains only bitfields, its total size in bytes must be
41299 Non-bitfield values have a @var{name} and @var{type}.
41302 <struct id="@var{id}">
41303 <field name="@var{name}" type="@var{type}"/>
41308 Both @var{name} and @var{type} values are required.
41309 No implicit padding is added.
41311 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41314 <struct id="@var{id}" size="@var{size}">
41315 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41321 <flags id="@var{id}" size="@var{size}">
41322 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41327 The @var{name} value is required.
41328 Bitfield values may be named with the empty string, @samp{""},
41329 in which case the field is ``filler'' and its value is not printed.
41330 Not all bits need to be specified, so ``filler'' fields are optional.
41332 The @var{start} and @var{end} values are required, and @var{type}
41334 The field's @var{start} must be less than or equal to its @var{end},
41335 and zero represents the least significant bit.
41337 The default value of @var{type} is @code{bool} for single bit fields,
41338 and an unsigned integer otherwise.
41340 Which to choose? Structures or flags?
41342 Registers defined with @samp{flags} have these advantages over
41343 defining them with @samp{struct}:
41347 Arithmetic may be performed on them as if they were integers.
41349 They are printed in a more readable fashion.
41352 Registers defined with @samp{struct} have one advantage over
41353 defining them with @samp{flags}:
41357 One can fetch individual fields like in @samp{C}.
41360 (gdb) print $my_struct_reg.field3
41366 @subsection Registers
41369 Each register is represented as an element with this form:
41372 <reg name="@var{name}"
41373 bitsize="@var{size}"
41374 @r{[}regnum="@var{num}"@r{]}
41375 @r{[}save-restore="@var{save-restore}"@r{]}
41376 @r{[}type="@var{type}"@r{]}
41377 @r{[}group="@var{group}"@r{]}/>
41381 The components are as follows:
41386 The register's name; it must be unique within the target description.
41389 The register's size, in bits.
41392 The register's number. If omitted, a register's number is one greater
41393 than that of the previous register (either in the current feature or in
41394 a preceding feature); the first register in the target description
41395 defaults to zero. This register number is used to read or write
41396 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41397 packets, and registers appear in the @code{g} and @code{G} packets
41398 in order of increasing register number.
41401 Whether the register should be preserved across inferior function
41402 calls; this must be either @code{yes} or @code{no}. The default is
41403 @code{yes}, which is appropriate for most registers except for
41404 some system control registers; this is not related to the target's
41408 The type of the register. It may be a predefined type, a type
41409 defined in the current feature, or one of the special types @code{int}
41410 and @code{float}. @code{int} is an integer type of the correct size
41411 for @var{bitsize}, and @code{float} is a floating point type (in the
41412 architecture's normal floating point format) of the correct size for
41413 @var{bitsize}. The default is @code{int}.
41416 The register group to which this register belongs. It must
41417 be either @code{general}, @code{float}, or @code{vector}. If no
41418 @var{group} is specified, @value{GDBN} will not display the register
41419 in @code{info registers}.
41423 @node Predefined Target Types
41424 @section Predefined Target Types
41425 @cindex target descriptions, predefined types
41427 Type definitions in the self-description can build up composite types
41428 from basic building blocks, but can not define fundamental types. Instead,
41429 standard identifiers are provided by @value{GDBN} for the fundamental
41430 types. The currently supported types are:
41435 Boolean type, occupying a single bit.
41442 Signed integer types holding the specified number of bits.
41449 Unsigned integer types holding the specified number of bits.
41453 Pointers to unspecified code and data. The program counter and
41454 any dedicated return address register may be marked as code
41455 pointers; printing a code pointer converts it into a symbolic
41456 address. The stack pointer and any dedicated address registers
41457 may be marked as data pointers.
41460 Single precision IEEE floating point.
41463 Double precision IEEE floating point.
41466 The 12-byte extended precision format used by ARM FPA registers.
41469 The 10-byte extended precision format used by x87 registers.
41472 32bit @sc{eflags} register used by x86.
41475 32bit @sc{mxcsr} register used by x86.
41479 @node Enum Target Types
41480 @section Enum Target Types
41481 @cindex target descriptions, enum types
41483 Enum target types are useful in @samp{struct} and @samp{flags}
41484 register descriptions. @xref{Target Description Format}.
41486 Enum types have a name, size and a list of name/value pairs.
41489 <enum id="@var{id}" size="@var{size}">
41490 <evalue name="@var{name}" value="@var{value}"/>
41495 Enums must be defined before they are used.
41498 <enum id="levels_type" size="4">
41499 <evalue name="low" value="0"/>
41500 <evalue name="high" value="1"/>
41502 <flags id="flags_type" size="4">
41503 <field name="X" start="0"/>
41504 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41506 <reg name="flags" bitsize="32" type="flags_type"/>
41509 Given that description, a value of 3 for the @samp{flags} register
41510 would be printed as:
41513 (gdb) info register flags
41514 flags 0x3 [ X LEVEL=high ]
41517 @node Standard Target Features
41518 @section Standard Target Features
41519 @cindex target descriptions, standard features
41521 A target description must contain either no registers or all the
41522 target's registers. If the description contains no registers, then
41523 @value{GDBN} will assume a default register layout, selected based on
41524 the architecture. If the description contains any registers, the
41525 default layout will not be used; the standard registers must be
41526 described in the target description, in such a way that @value{GDBN}
41527 can recognize them.
41529 This is accomplished by giving specific names to feature elements
41530 which contain standard registers. @value{GDBN} will look for features
41531 with those names and verify that they contain the expected registers;
41532 if any known feature is missing required registers, or if any required
41533 feature is missing, @value{GDBN} will reject the target
41534 description. You can add additional registers to any of the
41535 standard features --- @value{GDBN} will display them just as if
41536 they were added to an unrecognized feature.
41538 This section lists the known features and their expected contents.
41539 Sample XML documents for these features are included in the
41540 @value{GDBN} source tree, in the directory @file{gdb/features}.
41542 Names recognized by @value{GDBN} should include the name of the
41543 company or organization which selected the name, and the overall
41544 architecture to which the feature applies; so e.g.@: the feature
41545 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41547 The names of registers are not case sensitive for the purpose
41548 of recognizing standard features, but @value{GDBN} will only display
41549 registers using the capitalization used in the description.
41552 * AArch64 Features::
41556 * MicroBlaze Features::
41560 * Nios II Features::
41561 * PowerPC Features::
41562 * S/390 and System z Features::
41568 @node AArch64 Features
41569 @subsection AArch64 Features
41570 @cindex target descriptions, AArch64 features
41572 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41573 targets. It should contain registers @samp{x0} through @samp{x30},
41574 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41576 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41577 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41581 @subsection ARC Features
41582 @cindex target descriptions, ARC Features
41584 ARC processors are highly configurable, so even core registers and their number
41585 are not completely predetermined. In addition flags and PC registers which are
41586 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41587 that one of the core registers features is present.
41588 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41590 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41591 targets with a normal register file. It should contain registers @samp{r0}
41592 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41593 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41594 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41595 @samp{ilink} and extension core registers are not available to read/write, when
41596 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41598 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41599 ARC HS targets with a reduced register file. It should contain registers
41600 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41601 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41602 This feature may contain register @samp{ilink} and any of extension core
41603 registers @samp{r32} through @samp{r59/acch}.
41605 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41606 targets with a normal register file. It should contain registers @samp{r0}
41607 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41608 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41609 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41610 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41611 registers are not available when debugging GNU/Linux applications. The only
41612 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41613 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41614 ARC v2, but @samp{ilink2} is optional on ARCompact.
41616 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41617 targets. It should contain registers @samp{pc} and @samp{status32}.
41620 @subsection ARM Features
41621 @cindex target descriptions, ARM features
41623 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41625 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41626 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41628 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41629 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41630 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41633 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41634 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41636 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41637 it should contain at least registers @samp{wR0} through @samp{wR15} and
41638 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41639 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41641 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41642 should contain at least registers @samp{d0} through @samp{d15}. If
41643 they are present, @samp{d16} through @samp{d31} should also be included.
41644 @value{GDBN} will synthesize the single-precision registers from
41645 halves of the double-precision registers.
41647 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41648 need to contain registers; it instructs @value{GDBN} to display the
41649 VFP double-precision registers as vectors and to synthesize the
41650 quad-precision registers from pairs of double-precision registers.
41651 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41652 be present and include 32 double-precision registers.
41654 @node i386 Features
41655 @subsection i386 Features
41656 @cindex target descriptions, i386 features
41658 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41659 targets. It should describe the following registers:
41663 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41665 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41667 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41668 @samp{fs}, @samp{gs}
41670 @samp{st0} through @samp{st7}
41672 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41673 @samp{foseg}, @samp{fooff} and @samp{fop}
41676 The register sets may be different, depending on the target.
41678 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41679 describe registers:
41683 @samp{xmm0} through @samp{xmm7} for i386
41685 @samp{xmm0} through @samp{xmm15} for amd64
41690 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41691 @samp{org.gnu.gdb.i386.sse} feature. It should
41692 describe the upper 128 bits of @sc{ymm} registers:
41696 @samp{ymm0h} through @samp{ymm7h} for i386
41698 @samp{ymm0h} through @samp{ymm15h} for amd64
41701 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41702 Memory Protection Extension (MPX). It should describe the following registers:
41706 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41708 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41711 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41712 describe a single register, @samp{orig_eax}.
41714 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41715 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41717 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41718 @samp{org.gnu.gdb.i386.avx} feature. It should
41719 describe additional @sc{xmm} registers:
41723 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41726 It should describe the upper 128 bits of additional @sc{ymm} registers:
41730 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41734 describe the upper 256 bits of @sc{zmm} registers:
41738 @samp{zmm0h} through @samp{zmm7h} for i386.
41740 @samp{zmm0h} through @samp{zmm15h} for amd64.
41744 describe the additional @sc{zmm} registers:
41748 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41751 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
41752 describe a single register, @samp{pkru}. It is a 32-bit register
41753 valid for i386 and amd64.
41755 @node MicroBlaze Features
41756 @subsection MicroBlaze Features
41757 @cindex target descriptions, MicroBlaze features
41759 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41760 targets. It should contain registers @samp{r0} through @samp{r31},
41761 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41762 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41763 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41765 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41766 If present, it should contain registers @samp{rshr} and @samp{rslr}
41768 @node MIPS Features
41769 @subsection @acronym{MIPS} Features
41770 @cindex target descriptions, @acronym{MIPS} features
41772 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41773 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41774 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41777 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41778 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41779 registers. They may be 32-bit or 64-bit depending on the target.
41781 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41782 it may be optional in a future version of @value{GDBN}. It should
41783 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41784 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41786 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41787 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41788 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41789 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41791 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41792 contain a single register, @samp{restart}, which is used by the
41793 Linux kernel to control restartable syscalls.
41795 @node M68K Features
41796 @subsection M68K Features
41797 @cindex target descriptions, M68K features
41800 @item @samp{org.gnu.gdb.m68k.core}
41801 @itemx @samp{org.gnu.gdb.coldfire.core}
41802 @itemx @samp{org.gnu.gdb.fido.core}
41803 One of those features must be always present.
41804 The feature that is present determines which flavor of m68k is
41805 used. The feature that is present should contain registers
41806 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41807 @samp{sp}, @samp{ps} and @samp{pc}.
41809 @item @samp{org.gnu.gdb.coldfire.fp}
41810 This feature is optional. If present, it should contain registers
41811 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41815 @node NDS32 Features
41816 @subsection NDS32 Features
41817 @cindex target descriptions, NDS32 features
41819 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41820 targets. It should contain at least registers @samp{r0} through
41821 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41824 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41825 it should contain 64-bit double-precision floating-point registers
41826 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41827 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41829 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41830 registers are overlapped with the thirty-two 32-bit single-precision
41831 floating-point registers. The 32-bit single-precision registers, if
41832 not being listed explicitly, will be synthesized from halves of the
41833 overlapping 64-bit double-precision registers. Listing 32-bit
41834 single-precision registers explicitly is deprecated, and the
41835 support to it could be totally removed some day.
41837 @node Nios II Features
41838 @subsection Nios II Features
41839 @cindex target descriptions, Nios II features
41841 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41842 targets. It should contain the 32 core registers (@samp{zero},
41843 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41844 @samp{pc}, and the 16 control registers (@samp{status} through
41847 @node PowerPC Features
41848 @subsection PowerPC Features
41849 @cindex target descriptions, PowerPC features
41851 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41852 targets. It should contain registers @samp{r0} through @samp{r31},
41853 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41854 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41856 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41857 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41859 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41860 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41863 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41864 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41865 will combine these registers with the floating point registers
41866 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41867 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41868 through @samp{vs63}, the set of vector registers for POWER7.
41870 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41871 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41872 @samp{spefscr}. SPE targets should provide 32-bit registers in
41873 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41874 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41875 these to present registers @samp{ev0} through @samp{ev31} to the
41878 @node S/390 and System z Features
41879 @subsection S/390 and System z Features
41880 @cindex target descriptions, S/390 features
41881 @cindex target descriptions, System z features
41883 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41884 System z targets. It should contain the PSW and the 16 general
41885 registers. In particular, System z targets should provide the 64-bit
41886 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41887 S/390 targets should provide the 32-bit versions of these registers.
41888 A System z target that runs in 31-bit addressing mode should provide
41889 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41890 register's upper halves @samp{r0h} through @samp{r15h}, and their
41891 lower halves @samp{r0l} through @samp{r15l}.
41893 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41894 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41897 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41898 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41900 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41901 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41902 targets and 32-bit otherwise. In addition, the feature may contain
41903 the @samp{last_break} register, whose width depends on the addressing
41904 mode, as well as the @samp{system_call} register, which is always
41907 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41908 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41909 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41911 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41912 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41913 combined by @value{GDBN} with the floating point registers @samp{f0}
41914 through @samp{f15} to present the 128-bit wide vector registers
41915 @samp{v0} through @samp{v15}. In addition, this feature should
41916 contain the 128-bit wide vector registers @samp{v16} through
41919 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
41920 the 64-bit wide guarded-storage-control registers @samp{gsd},
41921 @samp{gssm}, and @samp{gsepla}.
41923 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
41924 the 64-bit wide guarded-storage broadcast control registers
41925 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
41927 @node Sparc Features
41928 @subsection Sparc Features
41929 @cindex target descriptions, sparc32 features
41930 @cindex target descriptions, sparc64 features
41931 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
41932 targets. It should describe the following registers:
41936 @samp{g0} through @samp{g7}
41938 @samp{o0} through @samp{o7}
41940 @samp{l0} through @samp{l7}
41942 @samp{i0} through @samp{i7}
41945 They may be 32-bit or 64-bit depending on the target.
41947 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
41948 targets. It should describe the following registers:
41952 @samp{f0} through @samp{f31}
41954 @samp{f32} through @samp{f62} for sparc64
41957 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
41958 targets. It should describe the following registers:
41962 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
41963 @samp{fsr}, and @samp{csr} for sparc32
41965 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
41969 @node TIC6x Features
41970 @subsection TMS320C6x Features
41971 @cindex target descriptions, TIC6x features
41972 @cindex target descriptions, TMS320C6x features
41973 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41974 targets. It should contain registers @samp{A0} through @samp{A15},
41975 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41977 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41978 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41979 through @samp{B31}.
41981 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41982 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41984 @node Operating System Information
41985 @appendix Operating System Information
41986 @cindex operating system information
41992 Users of @value{GDBN} often wish to obtain information about the state of
41993 the operating system running on the target---for example the list of
41994 processes, or the list of open files. This section describes the
41995 mechanism that makes it possible. This mechanism is similar to the
41996 target features mechanism (@pxref{Target Descriptions}), but focuses
41997 on a different aspect of target.
41999 Operating system information is retrived from the target via the
42000 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42001 read}). The object name in the request should be @samp{osdata}, and
42002 the @var{annex} identifies the data to be fetched.
42005 @appendixsection Process list
42006 @cindex operating system information, process list
42008 When requesting the process list, the @var{annex} field in the
42009 @samp{qXfer} request should be @samp{processes}. The returned data is
42010 an XML document. The formal syntax of this document is defined in
42011 @file{gdb/features/osdata.dtd}.
42013 An example document is:
42016 <?xml version="1.0"?>
42017 <!DOCTYPE target SYSTEM "osdata.dtd">
42018 <osdata type="processes">
42020 <column name="pid">1</column>
42021 <column name="user">root</column>
42022 <column name="command">/sbin/init</column>
42023 <column name="cores">1,2,3</column>
42028 Each item should include a column whose name is @samp{pid}. The value
42029 of that column should identify the process on the target. The
42030 @samp{user} and @samp{command} columns are optional, and will be
42031 displayed by @value{GDBN}. The @samp{cores} column, if present,
42032 should contain a comma-separated list of cores that this process
42033 is running on. Target may provide additional columns,
42034 which @value{GDBN} currently ignores.
42036 @node Trace File Format
42037 @appendix Trace File Format
42038 @cindex trace file format
42040 The trace file comes in three parts: a header, a textual description
42041 section, and a trace frame section with binary data.
42043 The header has the form @code{\x7fTRACE0\n}. The first byte is
42044 @code{0x7f} so as to indicate that the file contains binary data,
42045 while the @code{0} is a version number that may have different values
42048 The description section consists of multiple lines of @sc{ascii} text
42049 separated by newline characters (@code{0xa}). The lines may include a
42050 variety of optional descriptive or context-setting information, such
42051 as tracepoint definitions or register set size. @value{GDBN} will
42052 ignore any line that it does not recognize. An empty line marks the end
42057 Specifies the size of a register block in bytes. This is equal to the
42058 size of a @code{g} packet payload in the remote protocol. @var{size}
42059 is an ascii decimal number. There should be only one such line in
42060 a single trace file.
42062 @item status @var{status}
42063 Trace status. @var{status} has the same format as a @code{qTStatus}
42064 remote packet reply. There should be only one such line in a single trace
42067 @item tp @var{payload}
42068 Tracepoint definition. The @var{payload} has the same format as
42069 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42070 may take multiple lines of definition, corresponding to the multiple
42073 @item tsv @var{payload}
42074 Trace state variable definition. The @var{payload} has the same format as
42075 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42076 may take multiple lines of definition, corresponding to the multiple
42079 @item tdesc @var{payload}
42080 Target description in XML format. The @var{payload} is a single line of
42081 the XML file. All such lines should be concatenated together to get
42082 the original XML file. This file is in the same format as @code{qXfer}
42083 @code{features} payload, and corresponds to the main @code{target.xml}
42084 file. Includes are not allowed.
42088 The trace frame section consists of a number of consecutive frames.
42089 Each frame begins with a two-byte tracepoint number, followed by a
42090 four-byte size giving the amount of data in the frame. The data in
42091 the frame consists of a number of blocks, each introduced by a
42092 character indicating its type (at least register, memory, and trace
42093 state variable). The data in this section is raw binary, not a
42094 hexadecimal or other encoding; its endianness matches the target's
42097 @c FIXME bi-arch may require endianness/arch info in description section
42100 @item R @var{bytes}
42101 Register block. The number and ordering of bytes matches that of a
42102 @code{g} packet in the remote protocol. Note that these are the
42103 actual bytes, in target order, not a hexadecimal encoding.
42105 @item M @var{address} @var{length} @var{bytes}...
42106 Memory block. This is a contiguous block of memory, at the 8-byte
42107 address @var{address}, with a 2-byte length @var{length}, followed by
42108 @var{length} bytes.
42110 @item V @var{number} @var{value}
42111 Trace state variable block. This records the 8-byte signed value
42112 @var{value} of trace state variable numbered @var{number}.
42116 Future enhancements of the trace file format may include additional types
42119 @node Index Section Format
42120 @appendix @code{.gdb_index} section format
42121 @cindex .gdb_index section format
42122 @cindex index section format
42124 This section documents the index section that is created by @code{save
42125 gdb-index} (@pxref{Index Files}). The index section is
42126 DWARF-specific; some knowledge of DWARF is assumed in this
42129 The mapped index file format is designed to be directly
42130 @code{mmap}able on any architecture. In most cases, a datum is
42131 represented using a little-endian 32-bit integer value, called an
42132 @code{offset_type}. Big endian machines must byte-swap the values
42133 before using them. Exceptions to this rule are noted. The data is
42134 laid out such that alignment is always respected.
42136 A mapped index consists of several areas, laid out in order.
42140 The file header. This is a sequence of values, of @code{offset_type}
42141 unless otherwise noted:
42145 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42146 Version 4 uses a different hashing function from versions 5 and 6.
42147 Version 6 includes symbols for inlined functions, whereas versions 4
42148 and 5 do not. Version 7 adds attributes to the CU indices in the
42149 symbol table. Version 8 specifies that symbols from DWARF type units
42150 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42151 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42153 @value{GDBN} will only read version 4, 5, or 6 indices
42154 by specifying @code{set use-deprecated-index-sections on}.
42155 GDB has a workaround for potentially broken version 7 indices so it is
42156 currently not flagged as deprecated.
42159 The offset, from the start of the file, of the CU list.
42162 The offset, from the start of the file, of the types CU list. Note
42163 that this area can be empty, in which case this offset will be equal
42164 to the next offset.
42167 The offset, from the start of the file, of the address area.
42170 The offset, from the start of the file, of the symbol table.
42173 The offset, from the start of the file, of the constant pool.
42177 The CU list. This is a sequence of pairs of 64-bit little-endian
42178 values, sorted by the CU offset. The first element in each pair is
42179 the offset of a CU in the @code{.debug_info} section. The second
42180 element in each pair is the length of that CU. References to a CU
42181 elsewhere in the map are done using a CU index, which is just the
42182 0-based index into this table. Note that if there are type CUs, then
42183 conceptually CUs and type CUs form a single list for the purposes of
42187 The types CU list. This is a sequence of triplets of 64-bit
42188 little-endian values. In a triplet, the first value is the CU offset,
42189 the second value is the type offset in the CU, and the third value is
42190 the type signature. The types CU list is not sorted.
42193 The address area. The address area consists of a sequence of address
42194 entries. Each address entry has three elements:
42198 The low address. This is a 64-bit little-endian value.
42201 The high address. This is a 64-bit little-endian value. Like
42202 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42205 The CU index. This is an @code{offset_type} value.
42209 The symbol table. This is an open-addressed hash table. The size of
42210 the hash table is always a power of 2.
42212 Each slot in the hash table consists of a pair of @code{offset_type}
42213 values. The first value is the offset of the symbol's name in the
42214 constant pool. The second value is the offset of the CU vector in the
42217 If both values are 0, then this slot in the hash table is empty. This
42218 is ok because while 0 is a valid constant pool index, it cannot be a
42219 valid index for both a string and a CU vector.
42221 The hash value for a table entry is computed by applying an
42222 iterative hash function to the symbol's name. Starting with an
42223 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42224 the string is incorporated into the hash using the formula depending on the
42229 The formula is @code{r = r * 67 + c - 113}.
42231 @item Versions 5 to 7
42232 The formula is @code{r = r * 67 + tolower (c) - 113}.
42235 The terminating @samp{\0} is not incorporated into the hash.
42237 The step size used in the hash table is computed via
42238 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42239 value, and @samp{size} is the size of the hash table. The step size
42240 is used to find the next candidate slot when handling a hash
42243 The names of C@t{++} symbols in the hash table are canonicalized. We
42244 don't currently have a simple description of the canonicalization
42245 algorithm; if you intend to create new index sections, you must read
42249 The constant pool. This is simply a bunch of bytes. It is organized
42250 so that alignment is correct: CU vectors are stored first, followed by
42253 A CU vector in the constant pool is a sequence of @code{offset_type}
42254 values. The first value is the number of CU indices in the vector.
42255 Each subsequent value is the index and symbol attributes of a CU in
42256 the CU list. This element in the hash table is used to indicate which
42257 CUs define the symbol and how the symbol is used.
42258 See below for the format of each CU index+attributes entry.
42260 A string in the constant pool is zero-terminated.
42263 Attributes were added to CU index values in @code{.gdb_index} version 7.
42264 If a symbol has multiple uses within a CU then there is one
42265 CU index+attributes value for each use.
42267 The format of each CU index+attributes entry is as follows
42273 This is the index of the CU in the CU list.
42275 These bits are reserved for future purposes and must be zero.
42277 The kind of the symbol in the CU.
42281 This value is reserved and should not be used.
42282 By reserving zero the full @code{offset_type} value is backwards compatible
42283 with previous versions of the index.
42285 The symbol is a type.
42287 The symbol is a variable or an enum value.
42289 The symbol is a function.
42291 Any other kind of symbol.
42293 These values are reserved.
42297 This bit is zero if the value is global and one if it is static.
42299 The determination of whether a symbol is global or static is complicated.
42300 The authorative reference is the file @file{dwarf2read.c} in
42301 @value{GDBN} sources.
42305 This pseudo-code describes the computation of a symbol's kind and
42306 global/static attributes in the index.
42309 is_external = get_attribute (die, DW_AT_external);
42310 language = get_attribute (cu_die, DW_AT_language);
42313 case DW_TAG_typedef:
42314 case DW_TAG_base_type:
42315 case DW_TAG_subrange_type:
42319 case DW_TAG_enumerator:
42321 is_static = language != CPLUS;
42323 case DW_TAG_subprogram:
42325 is_static = ! (is_external || language == ADA);
42327 case DW_TAG_constant:
42329 is_static = ! is_external;
42331 case DW_TAG_variable:
42333 is_static = ! is_external;
42335 case DW_TAG_namespace:
42339 case DW_TAG_class_type:
42340 case DW_TAG_interface_type:
42341 case DW_TAG_structure_type:
42342 case DW_TAG_union_type:
42343 case DW_TAG_enumeration_type:
42345 is_static = language != CPLUS;
42353 @appendix Manual pages
42357 * gdb man:: The GNU Debugger man page
42358 * gdbserver man:: Remote Server for the GNU Debugger man page
42359 * gcore man:: Generate a core file of a running program
42360 * gdbinit man:: gdbinit scripts
42366 @c man title gdb The GNU Debugger
42368 @c man begin SYNOPSIS gdb
42369 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42370 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42371 [@option{-b}@w{ }@var{bps}]
42372 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42373 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42374 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42375 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42376 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42379 @c man begin DESCRIPTION gdb
42380 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42381 going on ``inside'' another program while it executes -- or what another
42382 program was doing at the moment it crashed.
42384 @value{GDBN} can do four main kinds of things (plus other things in support of
42385 these) to help you catch bugs in the act:
42389 Start your program, specifying anything that might affect its behavior.
42392 Make your program stop on specified conditions.
42395 Examine what has happened, when your program has stopped.
42398 Change things in your program, so you can experiment with correcting the
42399 effects of one bug and go on to learn about another.
42402 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42405 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42406 commands from the terminal until you tell it to exit with the @value{GDBN}
42407 command @code{quit}. You can get online help from @value{GDBN} itself
42408 by using the command @code{help}.
42410 You can run @code{gdb} with no arguments or options; but the most
42411 usual way to start @value{GDBN} is with one argument or two, specifying an
42412 executable program as the argument:
42418 You can also start with both an executable program and a core file specified:
42424 You can, instead, specify a process ID as a second argument, if you want
42425 to debug a running process:
42433 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42434 named @file{1234}; @value{GDBN} does check for a core file first).
42435 With option @option{-p} you can omit the @var{program} filename.
42437 Here are some of the most frequently needed @value{GDBN} commands:
42439 @c pod2man highlights the right hand side of the @item lines.
42441 @item break [@var{file}:]@var{function}
42442 Set a breakpoint at @var{function} (in @var{file}).
42444 @item run [@var{arglist}]
42445 Start your program (with @var{arglist}, if specified).
42448 Backtrace: display the program stack.
42450 @item print @var{expr}
42451 Display the value of an expression.
42454 Continue running your program (after stopping, e.g. at a breakpoint).
42457 Execute next program line (after stopping); step @emph{over} any
42458 function calls in the line.
42460 @item edit [@var{file}:]@var{function}
42461 look at the program line where it is presently stopped.
42463 @item list [@var{file}:]@var{function}
42464 type the text of the program in the vicinity of where it is presently stopped.
42467 Execute next program line (after stopping); step @emph{into} any
42468 function calls in the line.
42470 @item help [@var{name}]
42471 Show information about @value{GDBN} command @var{name}, or general information
42472 about using @value{GDBN}.
42475 Exit from @value{GDBN}.
42479 For full details on @value{GDBN},
42480 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42481 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42482 as the @code{gdb} entry in the @code{info} program.
42486 @c man begin OPTIONS gdb
42487 Any arguments other than options specify an executable
42488 file and core file (or process ID); that is, the first argument
42489 encountered with no
42490 associated option flag is equivalent to a @option{-se} option, and the second,
42491 if any, is equivalent to a @option{-c} option if it's the name of a file.
42493 both long and short forms; both are shown here. The long forms are also
42494 recognized if you truncate them, so long as enough of the option is
42495 present to be unambiguous. (If you prefer, you can flag option
42496 arguments with @option{+} rather than @option{-}, though we illustrate the
42497 more usual convention.)
42499 All the options and command line arguments you give are processed
42500 in sequential order. The order makes a difference when the @option{-x}
42506 List all options, with brief explanations.
42508 @item -symbols=@var{file}
42509 @itemx -s @var{file}
42510 Read symbol table from file @var{file}.
42513 Enable writing into executable and core files.
42515 @item -exec=@var{file}
42516 @itemx -e @var{file}
42517 Use file @var{file} as the executable file to execute when
42518 appropriate, and for examining pure data in conjunction with a core
42521 @item -se=@var{file}
42522 Read symbol table from file @var{file} and use it as the executable
42525 @item -core=@var{file}
42526 @itemx -c @var{file}
42527 Use file @var{file} as a core dump to examine.
42529 @item -command=@var{file}
42530 @itemx -x @var{file}
42531 Execute @value{GDBN} commands from file @var{file}.
42533 @item -ex @var{command}
42534 Execute given @value{GDBN} @var{command}.
42536 @item -directory=@var{directory}
42537 @itemx -d @var{directory}
42538 Add @var{directory} to the path to search for source files.
42541 Do not execute commands from @file{~/.gdbinit}.
42545 Do not execute commands from any @file{.gdbinit} initialization files.
42549 ``Quiet''. Do not print the introductory and copyright messages. These
42550 messages are also suppressed in batch mode.
42553 Run in batch mode. Exit with status @code{0} after processing all the command
42554 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42555 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42556 commands in the command files.
42558 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42559 download and run a program on another computer; in order to make this
42560 more useful, the message
42563 Program exited normally.
42567 (which is ordinarily issued whenever a program running under @value{GDBN} control
42568 terminates) is not issued when running in batch mode.
42570 @item -cd=@var{directory}
42571 Run @value{GDBN} using @var{directory} as its working directory,
42572 instead of the current directory.
42576 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42577 @value{GDBN} to output the full file name and line number in a standard,
42578 recognizable fashion each time a stack frame is displayed (which
42579 includes each time the program stops). This recognizable format looks
42580 like two @samp{\032} characters, followed by the file name, line number
42581 and character position separated by colons, and a newline. The
42582 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42583 characters as a signal to display the source code for the frame.
42586 Set the line speed (baud rate or bits per second) of any serial
42587 interface used by @value{GDBN} for remote debugging.
42589 @item -tty=@var{device}
42590 Run using @var{device} for your program's standard input and output.
42594 @c man begin SEEALSO gdb
42596 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42597 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42598 documentation are properly installed at your site, the command
42605 should give you access to the complete manual.
42607 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42608 Richard M. Stallman and Roland H. Pesch, July 1991.
42612 @node gdbserver man
42613 @heading gdbserver man
42615 @c man title gdbserver Remote Server for the GNU Debugger
42617 @c man begin SYNOPSIS gdbserver
42618 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42620 gdbserver --attach @var{comm} @var{pid}
42622 gdbserver --multi @var{comm}
42626 @c man begin DESCRIPTION gdbserver
42627 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42628 than the one which is running the program being debugged.
42631 @subheading Usage (server (target) side)
42634 Usage (server (target) side):
42637 First, you need to have a copy of the program you want to debug put onto
42638 the target system. The program can be stripped to save space if needed, as
42639 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42640 the @value{GDBN} running on the host system.
42642 To use the server, you log on to the target system, and run the @command{gdbserver}
42643 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42644 your program, and (c) its arguments. The general syntax is:
42647 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42650 For example, using a serial port, you might say:
42654 @c @file would wrap it as F</dev/com1>.
42655 target> gdbserver /dev/com1 emacs foo.txt
42658 target> gdbserver @file{/dev/com1} emacs foo.txt
42662 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42663 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42664 waits patiently for the host @value{GDBN} to communicate with it.
42666 To use a TCP connection, you could say:
42669 target> gdbserver host:2345 emacs foo.txt
42672 This says pretty much the same thing as the last example, except that we are
42673 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42674 that we are expecting to see a TCP connection from @code{host} to local TCP port
42675 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42676 want for the port number as long as it does not conflict with any existing TCP
42677 ports on the target system. This same port number must be used in the host
42678 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42679 you chose a port number that conflicts with another service, @command{gdbserver} will
42680 print an error message and exit.
42682 @command{gdbserver} can also attach to running programs.
42683 This is accomplished via the @option{--attach} argument. The syntax is:
42686 target> gdbserver --attach @var{comm} @var{pid}
42689 @var{pid} is the process ID of a currently running process. It isn't
42690 necessary to point @command{gdbserver} at a binary for the running process.
42692 To start @code{gdbserver} without supplying an initial command to run
42693 or process ID to attach, use the @option{--multi} command line option.
42694 In such case you should connect using @kbd{target extended-remote} to start
42695 the program you want to debug.
42698 target> gdbserver --multi @var{comm}
42702 @subheading Usage (host side)
42708 You need an unstripped copy of the target program on your host system, since
42709 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42710 would, with the target program as the first argument. (You may need to use the
42711 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42712 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42713 new command you need to know about is @code{target remote}
42714 (or @code{target extended-remote}). Its argument is either
42715 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42716 descriptor. For example:
42720 @c @file would wrap it as F</dev/ttyb>.
42721 (gdb) target remote /dev/ttyb
42724 (gdb) target remote @file{/dev/ttyb}
42729 communicates with the server via serial line @file{/dev/ttyb}, and:
42732 (gdb) target remote the-target:2345
42736 communicates via a TCP connection to port 2345 on host `the-target', where
42737 you previously started up @command{gdbserver} with the same port number. Note that for
42738 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42739 command, otherwise you may get an error that looks something like
42740 `Connection refused'.
42742 @command{gdbserver} can also debug multiple inferiors at once,
42745 the @value{GDBN} manual in node @code{Inferiors and Programs}
42746 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42749 @ref{Inferiors and Programs}.
42751 In such case use the @code{extended-remote} @value{GDBN} command variant:
42754 (gdb) target extended-remote the-target:2345
42757 The @command{gdbserver} option @option{--multi} may or may not be used in such
42761 @c man begin OPTIONS gdbserver
42762 There are three different modes for invoking @command{gdbserver}:
42767 Debug a specific program specified by its program name:
42770 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42773 The @var{comm} parameter specifies how should the server communicate
42774 with @value{GDBN}; it is either a device name (to use a serial line),
42775 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42776 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42777 debug in @var{prog}. Any remaining arguments will be passed to the
42778 program verbatim. When the program exits, @value{GDBN} will close the
42779 connection, and @code{gdbserver} will exit.
42782 Debug a specific program by specifying the process ID of a running
42786 gdbserver --attach @var{comm} @var{pid}
42789 The @var{comm} parameter is as described above. Supply the process ID
42790 of a running program in @var{pid}; @value{GDBN} will do everything
42791 else. Like with the previous mode, when the process @var{pid} exits,
42792 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42795 Multi-process mode -- debug more than one program/process:
42798 gdbserver --multi @var{comm}
42801 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42802 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42803 close the connection when a process being debugged exits, so you can
42804 debug several processes in the same session.
42807 In each of the modes you may specify these options:
42812 List all options, with brief explanations.
42815 This option causes @command{gdbserver} to print its version number and exit.
42818 @command{gdbserver} will attach to a running program. The syntax is:
42821 target> gdbserver --attach @var{comm} @var{pid}
42824 @var{pid} is the process ID of a currently running process. It isn't
42825 necessary to point @command{gdbserver} at a binary for the running process.
42828 To start @code{gdbserver} without supplying an initial command to run
42829 or process ID to attach, use this command line option.
42830 Then you can connect using @kbd{target extended-remote} and start
42831 the program you want to debug. The syntax is:
42834 target> gdbserver --multi @var{comm}
42838 Instruct @code{gdbserver} to display extra status information about the debugging
42840 This option is intended for @code{gdbserver} development and for bug reports to
42843 @item --remote-debug
42844 Instruct @code{gdbserver} to display remote protocol debug output.
42845 This option is intended for @code{gdbserver} development and for bug reports to
42848 @item --debug-format=option1@r{[},option2,...@r{]}
42849 Instruct @code{gdbserver} to include extra information in each line
42850 of debugging output.
42851 @xref{Other Command-Line Arguments for gdbserver}.
42854 Specify a wrapper to launch programs
42855 for debugging. The option should be followed by the name of the
42856 wrapper, then any command-line arguments to pass to the wrapper, then
42857 @kbd{--} indicating the end of the wrapper arguments.
42860 By default, @command{gdbserver} keeps the listening TCP port open, so that
42861 additional connections are possible. However, if you start @code{gdbserver}
42862 with the @option{--once} option, it will stop listening for any further
42863 connection attempts after connecting to the first @value{GDBN} session.
42865 @c --disable-packet is not documented for users.
42867 @c --disable-randomization and --no-disable-randomization are superseded by
42868 @c QDisableRandomization.
42873 @c man begin SEEALSO gdbserver
42875 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42876 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42877 documentation are properly installed at your site, the command
42883 should give you access to the complete manual.
42885 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42886 Richard M. Stallman and Roland H. Pesch, July 1991.
42893 @c man title gcore Generate a core file of a running program
42896 @c man begin SYNOPSIS gcore
42897 gcore [-o @var{filename}] @var{pid}
42901 @c man begin DESCRIPTION gcore
42902 Generate a core dump of a running program with process ID @var{pid}.
42903 Produced file is equivalent to a kernel produced core file as if the process
42904 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42905 limit). Unlike after a crash, after @command{gcore} the program remains
42906 running without any change.
42909 @c man begin OPTIONS gcore
42911 @item -o @var{filename}
42912 The optional argument
42913 @var{filename} specifies the file name where to put the core dump.
42914 If not specified, the file name defaults to @file{core.@var{pid}},
42915 where @var{pid} is the running program process ID.
42919 @c man begin SEEALSO gcore
42921 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42922 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42923 documentation are properly installed at your site, the command
42930 should give you access to the complete manual.
42932 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42933 Richard M. Stallman and Roland H. Pesch, July 1991.
42940 @c man title gdbinit GDB initialization scripts
42943 @c man begin SYNOPSIS gdbinit
42944 @ifset SYSTEM_GDBINIT
42945 @value{SYSTEM_GDBINIT}
42954 @c man begin DESCRIPTION gdbinit
42955 These files contain @value{GDBN} commands to automatically execute during
42956 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42959 the @value{GDBN} manual in node @code{Sequences}
42960 -- shell command @code{info -f gdb -n Sequences}.
42966 Please read more in
42968 the @value{GDBN} manual in node @code{Startup}
42969 -- shell command @code{info -f gdb -n Startup}.
42976 @ifset SYSTEM_GDBINIT
42977 @item @value{SYSTEM_GDBINIT}
42979 @ifclear SYSTEM_GDBINIT
42980 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42982 System-wide initialization file. It is executed unless user specified
42983 @value{GDBN} option @code{-nx} or @code{-n}.
42986 the @value{GDBN} manual in node @code{System-wide configuration}
42987 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42990 @ref{System-wide configuration}.
42994 User initialization file. It is executed unless user specified
42995 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42998 Initialization file for current directory. It may need to be enabled with
42999 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43002 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43003 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43006 @ref{Init File in the Current Directory}.
43011 @c man begin SEEALSO gdbinit
43013 gdb(1), @code{info -f gdb -n Startup}
43015 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43016 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43017 documentation are properly installed at your site, the command
43023 should give you access to the complete manual.
43025 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43026 Richard M. Stallman and Roland H. Pesch, July 1991.
43032 @node GNU Free Documentation License
43033 @appendix GNU Free Documentation License
43036 @node Concept Index
43037 @unnumbered Concept Index
43041 @node Command and Variable Index
43042 @unnumbered Command, Variable, and Function Index
43047 % I think something like @@colophon should be in texinfo. In the
43049 \long\def\colophon{\hbox to0pt{}\vfill
43050 \centerline{The body of this manual is set in}
43051 \centerline{\fontname\tenrm,}
43052 \centerline{with headings in {\bf\fontname\tenbf}}
43053 \centerline{and examples in {\tt\fontname\tentt}.}
43054 \centerline{{\it\fontname\tenit\/},}
43055 \centerline{{\bf\fontname\tenbf}, and}
43056 \centerline{{\sl\fontname\tensl\/}}
43057 \centerline{are used for emphasis.}\vfill}
43059 % Blame: doc@@cygnus.com, 1991.