1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2017 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2017 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
550 @chapter A Sample @value{GDBN} Session
552 You can use this manual at your leisure to read all about @value{GDBN}.
553 However, a handful of commands are enough to get started using the
554 debugger. This chapter illustrates those commands.
557 In this sample session, we emphasize user input like this: @b{input},
558 to make it easier to pick out from the surrounding output.
561 @c FIXME: this example may not be appropriate for some configs, where
562 @c FIXME...primary interest is in remote use.
564 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
565 processor) exhibits the following bug: sometimes, when we change its
566 quote strings from the default, the commands used to capture one macro
567 definition within another stop working. In the following short @code{m4}
568 session, we define a macro @code{foo} which expands to @code{0000}; we
569 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
570 same thing. However, when we change the open quote string to
571 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
572 procedure fails to define a new synonym @code{baz}:
581 @b{define(bar,defn(`foo'))}
585 @b{changequote(<QUOTE>,<UNQUOTE>)}
587 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
590 m4: End of input: 0: fatal error: EOF in string
594 Let us use @value{GDBN} to try to see what is going on.
597 $ @b{@value{GDBP} m4}
598 @c FIXME: this falsifies the exact text played out, to permit smallbook
599 @c FIXME... format to come out better.
600 @value{GDBN} is free software and you are welcome to distribute copies
601 of it under certain conditions; type "show copying" to see
603 There is absolutely no warranty for @value{GDBN}; type "show warranty"
606 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
611 @value{GDBN} reads only enough symbol data to know where to find the
612 rest when needed; as a result, the first prompt comes up very quickly.
613 We now tell @value{GDBN} to use a narrower display width than usual, so
614 that examples fit in this manual.
617 (@value{GDBP}) @b{set width 70}
621 We need to see how the @code{m4} built-in @code{changequote} works.
622 Having looked at the source, we know the relevant subroutine is
623 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
624 @code{break} command.
627 (@value{GDBP}) @b{break m4_changequote}
628 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
632 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
633 control; as long as control does not reach the @code{m4_changequote}
634 subroutine, the program runs as usual:
637 (@value{GDBP}) @b{run}
638 Starting program: /work/Editorial/gdb/gnu/m4/m4
646 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
647 suspends execution of @code{m4}, displaying information about the
648 context where it stops.
651 @b{changequote(<QUOTE>,<UNQUOTE>)}
653 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
655 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
659 Now we use the command @code{n} (@code{next}) to advance execution to
660 the next line of the current function.
664 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
669 @code{set_quotes} looks like a promising subroutine. We can go into it
670 by using the command @code{s} (@code{step}) instead of @code{next}.
671 @code{step} goes to the next line to be executed in @emph{any}
672 subroutine, so it steps into @code{set_quotes}.
676 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 530 if (lquote != def_lquote)
682 The display that shows the subroutine where @code{m4} is now
683 suspended (and its arguments) is called a stack frame display. It
684 shows a summary of the stack. We can use the @code{backtrace}
685 command (which can also be spelled @code{bt}), to see where we are
686 in the stack as a whole: the @code{backtrace} command displays a
687 stack frame for each active subroutine.
690 (@value{GDBP}) @b{bt}
691 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
695 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
696 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
698 #4 0x79dc in expand_input () at macro.c:40
699 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
703 We step through a few more lines to see what happens. The first two
704 times, we can use @samp{s}; the next two times we use @code{n} to avoid
705 falling into the @code{xstrdup} subroutine.
709 0x3b5c 532 if (rquote != def_rquote)
711 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
712 def_lquote : xstrdup(lq);
714 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
717 538 len_lquote = strlen(rquote);
721 The last line displayed looks a little odd; we can examine the variables
722 @code{lquote} and @code{rquote} to see if they are in fact the new left
723 and right quotes we specified. We use the command @code{p}
724 (@code{print}) to see their values.
727 (@value{GDBP}) @b{p lquote}
728 $1 = 0x35d40 "<QUOTE>"
729 (@value{GDBP}) @b{p rquote}
730 $2 = 0x35d50 "<UNQUOTE>"
734 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
735 To look at some context, we can display ten lines of source
736 surrounding the current line with the @code{l} (@code{list}) command.
742 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
744 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
747 538 len_lquote = strlen(rquote);
748 539 len_rquote = strlen(lquote);
755 Let us step past the two lines that set @code{len_lquote} and
756 @code{len_rquote}, and then examine the values of those variables.
760 539 len_rquote = strlen(lquote);
763 (@value{GDBP}) @b{p len_lquote}
765 (@value{GDBP}) @b{p len_rquote}
770 That certainly looks wrong, assuming @code{len_lquote} and
771 @code{len_rquote} are meant to be the lengths of @code{lquote} and
772 @code{rquote} respectively. We can set them to better values using
773 the @code{p} command, since it can print the value of
774 any expression---and that expression can include subroutine calls and
778 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
780 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
785 Is that enough to fix the problem of using the new quotes with the
786 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
787 executing with the @code{c} (@code{continue}) command, and then try the
788 example that caused trouble initially:
794 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
801 Success! The new quotes now work just as well as the default ones. The
802 problem seems to have been just the two typos defining the wrong
803 lengths. We allow @code{m4} exit by giving it an EOF as input:
807 Program exited normally.
811 The message @samp{Program exited normally.} is from @value{GDBN}; it
812 indicates @code{m4} has finished executing. We can end our @value{GDBN}
813 session with the @value{GDBN} @code{quit} command.
816 (@value{GDBP}) @b{quit}
820 @chapter Getting In and Out of @value{GDBN}
822 This chapter discusses how to start @value{GDBN}, and how to get out of it.
826 type @samp{@value{GDBP}} to start @value{GDBN}.
828 type @kbd{quit} or @kbd{Ctrl-d} to exit.
832 * Invoking GDB:: How to start @value{GDBN}
833 * Quitting GDB:: How to quit @value{GDBN}
834 * Shell Commands:: How to use shell commands inside @value{GDBN}
835 * Logging Output:: How to log @value{GDBN}'s output to a file
839 @section Invoking @value{GDBN}
841 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
842 @value{GDBN} reads commands from the terminal until you tell it to exit.
844 You can also run @code{@value{GDBP}} with a variety of arguments and options,
845 to specify more of your debugging environment at the outset.
847 The command-line options described here are designed
848 to cover a variety of situations; in some environments, some of these
849 options may effectively be unavailable.
851 The most usual way to start @value{GDBN} is with one argument,
852 specifying an executable program:
855 @value{GDBP} @var{program}
859 You can also start with both an executable program and a core file
863 @value{GDBP} @var{program} @var{core}
866 You can, instead, specify a process ID as a second argument, if you want
867 to debug a running process:
870 @value{GDBP} @var{program} 1234
874 would attach @value{GDBN} to process @code{1234} (unless you also have a file
875 named @file{1234}; @value{GDBN} does check for a core file first).
877 Taking advantage of the second command-line argument requires a fairly
878 complete operating system; when you use @value{GDBN} as a remote
879 debugger attached to a bare board, there may not be any notion of
880 ``process'', and there is often no way to get a core dump. @value{GDBN}
881 will warn you if it is unable to attach or to read core dumps.
883 You can optionally have @code{@value{GDBP}} pass any arguments after the
884 executable file to the inferior using @code{--args}. This option stops
887 @value{GDBP} --args gcc -O2 -c foo.c
889 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
890 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
892 You can run @code{@value{GDBP}} without printing the front material, which describes
893 @value{GDBN}'s non-warranty, by specifying @code{--silent}
894 (or @code{-q}/@code{--quiet}):
897 @value{GDBP} --silent
901 You can further control how @value{GDBN} starts up by using command-line
902 options. @value{GDBN} itself can remind you of the options available.
912 to display all available options and briefly describe their use
913 (@samp{@value{GDBP} -h} is a shorter equivalent).
915 All options and command line arguments you give are processed
916 in sequential order. The order makes a difference when the
917 @samp{-x} option is used.
921 * File Options:: Choosing files
922 * Mode Options:: Choosing modes
923 * Startup:: What @value{GDBN} does during startup
927 @subsection Choosing Files
929 When @value{GDBN} starts, it reads any arguments other than options as
930 specifying an executable file and core file (or process ID). This is
931 the same as if the arguments were specified by the @samp{-se} and
932 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
933 first argument that does not have an associated option flag as
934 equivalent to the @samp{-se} option followed by that argument; and the
935 second argument that does not have an associated option flag, if any, as
936 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
937 If the second argument begins with a decimal digit, @value{GDBN} will
938 first attempt to attach to it as a process, and if that fails, attempt
939 to open it as a corefile. If you have a corefile whose name begins with
940 a digit, you can prevent @value{GDBN} from treating it as a pid by
941 prefixing it with @file{./}, e.g.@: @file{./12345}.
943 If @value{GDBN} has not been configured to included core file support,
944 such as for most embedded targets, then it will complain about a second
945 argument and ignore it.
947 Many options have both long and short forms; both are shown in the
948 following list. @value{GDBN} also recognizes the long forms if you truncate
949 them, so long as enough of the option is present to be unambiguous.
950 (If you prefer, you can flag option arguments with @samp{--} rather
951 than @samp{-}, though we illustrate the more usual convention.)
953 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
954 @c way, both those who look for -foo and --foo in the index, will find
958 @item -symbols @var{file}
960 @cindex @code{--symbols}
962 Read symbol table from file @var{file}.
964 @item -exec @var{file}
966 @cindex @code{--exec}
968 Use file @var{file} as the executable file to execute when appropriate,
969 and for examining pure data in conjunction with a core dump.
973 Read symbol table from file @var{file} and use it as the executable
976 @item -core @var{file}
978 @cindex @code{--core}
980 Use file @var{file} as a core dump to examine.
982 @item -pid @var{number}
983 @itemx -p @var{number}
986 Connect to process ID @var{number}, as with the @code{attach} command.
988 @item -command @var{file}
990 @cindex @code{--command}
992 Execute commands from file @var{file}. The contents of this file is
993 evaluated exactly as the @code{source} command would.
994 @xref{Command Files,, Command files}.
996 @item -eval-command @var{command}
997 @itemx -ex @var{command}
998 @cindex @code{--eval-command}
1000 Execute a single @value{GDBN} command.
1002 This option may be used multiple times to call multiple commands. It may
1003 also be interleaved with @samp{-command} as required.
1006 @value{GDBP} -ex 'target sim' -ex 'load' \
1007 -x setbreakpoints -ex 'run' a.out
1010 @item -init-command @var{file}
1011 @itemx -ix @var{file}
1012 @cindex @code{--init-command}
1014 Execute commands from file @var{file} before loading the inferior (but
1015 after loading gdbinit files).
1018 @item -init-eval-command @var{command}
1019 @itemx -iex @var{command}
1020 @cindex @code{--init-eval-command}
1022 Execute a single @value{GDBN} command before loading the inferior (but
1023 after loading gdbinit files).
1026 @item -directory @var{directory}
1027 @itemx -d @var{directory}
1028 @cindex @code{--directory}
1030 Add @var{directory} to the path to search for source and script files.
1034 @cindex @code{--readnow}
1036 Read each symbol file's entire symbol table immediately, rather than
1037 the default, which is to read it incrementally as it is needed.
1038 This makes startup slower, but makes future operations faster.
1043 @subsection Choosing Modes
1045 You can run @value{GDBN} in various alternative modes---for example, in
1046 batch mode or quiet mode.
1054 Do not execute commands found in any initialization file.
1055 There are three init files, loaded in the following order:
1058 @item @file{system.gdbinit}
1059 This is the system-wide init file.
1060 Its location is specified with the @code{--with-system-gdbinit}
1061 configure option (@pxref{System-wide configuration}).
1062 It is loaded first when @value{GDBN} starts, before command line options
1063 have been processed.
1064 @item @file{~/.gdbinit}
1065 This is the init file in your home directory.
1066 It is loaded next, after @file{system.gdbinit}, and before
1067 command options have been processed.
1068 @item @file{./.gdbinit}
1069 This is the init file in the current directory.
1070 It is loaded last, after command line options other than @code{-x} and
1071 @code{-ex} have been processed. Command line options @code{-x} and
1072 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1075 For further documentation on startup processing, @xref{Startup}.
1076 For documentation on how to write command files,
1077 @xref{Command Files,,Command Files}.
1082 Do not execute commands found in @file{~/.gdbinit}, the init file
1083 in your home directory.
1089 @cindex @code{--quiet}
1090 @cindex @code{--silent}
1092 ``Quiet''. Do not print the introductory and copyright messages. These
1093 messages are also suppressed in batch mode.
1096 @cindex @code{--batch}
1097 Run in batch mode. Exit with status @code{0} after processing all the
1098 command files specified with @samp{-x} (and all commands from
1099 initialization files, if not inhibited with @samp{-n}). Exit with
1100 nonzero status if an error occurs in executing the @value{GDBN} commands
1101 in the command files. Batch mode also disables pagination, sets unlimited
1102 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1103 off} were in effect (@pxref{Messages/Warnings}).
1105 Batch mode may be useful for running @value{GDBN} as a filter, for
1106 example to download and run a program on another computer; in order to
1107 make this more useful, the message
1110 Program exited normally.
1114 (which is ordinarily issued whenever a program running under
1115 @value{GDBN} control terminates) is not issued when running in batch
1119 @cindex @code{--batch-silent}
1120 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1121 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1122 unaffected). This is much quieter than @samp{-silent} and would be useless
1123 for an interactive session.
1125 This is particularly useful when using targets that give @samp{Loading section}
1126 messages, for example.
1128 Note that targets that give their output via @value{GDBN}, as opposed to
1129 writing directly to @code{stdout}, will also be made silent.
1131 @item -return-child-result
1132 @cindex @code{--return-child-result}
1133 The return code from @value{GDBN} will be the return code from the child
1134 process (the process being debugged), with the following exceptions:
1138 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1139 internal error. In this case the exit code is the same as it would have been
1140 without @samp{-return-child-result}.
1142 The user quits with an explicit value. E.g., @samp{quit 1}.
1144 The child process never runs, or is not allowed to terminate, in which case
1145 the exit code will be -1.
1148 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1149 when @value{GDBN} is being used as a remote program loader or simulator
1154 @cindex @code{--nowindows}
1156 ``No windows''. If @value{GDBN} comes with a graphical user interface
1157 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1158 interface. If no GUI is available, this option has no effect.
1162 @cindex @code{--windows}
1164 If @value{GDBN} includes a GUI, then this option requires it to be
1167 @item -cd @var{directory}
1169 Run @value{GDBN} using @var{directory} as its working directory,
1170 instead of the current directory.
1172 @item -data-directory @var{directory}
1173 @itemx -D @var{directory}
1174 @cindex @code{--data-directory}
1176 Run @value{GDBN} using @var{directory} as its data directory.
1177 The data directory is where @value{GDBN} searches for its
1178 auxiliary files. @xref{Data Files}.
1182 @cindex @code{--fullname}
1184 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1185 subprocess. It tells @value{GDBN} to output the full file name and line
1186 number in a standard, recognizable fashion each time a stack frame is
1187 displayed (which includes each time your program stops). This
1188 recognizable format looks like two @samp{\032} characters, followed by
1189 the file name, line number and character position separated by colons,
1190 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1191 @samp{\032} characters as a signal to display the source code for the
1194 @item -annotate @var{level}
1195 @cindex @code{--annotate}
1196 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1197 effect is identical to using @samp{set annotate @var{level}}
1198 (@pxref{Annotations}). The annotation @var{level} controls how much
1199 information @value{GDBN} prints together with its prompt, values of
1200 expressions, source lines, and other types of output. Level 0 is the
1201 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1202 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1203 that control @value{GDBN}, and level 2 has been deprecated.
1205 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1209 @cindex @code{--args}
1210 Change interpretation of command line so that arguments following the
1211 executable file are passed as command line arguments to the inferior.
1212 This option stops option processing.
1214 @item -baud @var{bps}
1216 @cindex @code{--baud}
1218 Set the line speed (baud rate or bits per second) of any serial
1219 interface used by @value{GDBN} for remote debugging.
1221 @item -l @var{timeout}
1223 Set the timeout (in seconds) of any communication used by @value{GDBN}
1224 for remote debugging.
1226 @item -tty @var{device}
1227 @itemx -t @var{device}
1228 @cindex @code{--tty}
1230 Run using @var{device} for your program's standard input and output.
1231 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1233 @c resolve the situation of these eventually
1235 @cindex @code{--tui}
1236 Activate the @dfn{Text User Interface} when starting. The Text User
1237 Interface manages several text windows on the terminal, showing
1238 source, assembly, registers and @value{GDBN} command outputs
1239 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1240 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1241 Using @value{GDBN} under @sc{gnu} Emacs}).
1243 @item -interpreter @var{interp}
1244 @cindex @code{--interpreter}
1245 Use the interpreter @var{interp} for interface with the controlling
1246 program or device. This option is meant to be set by programs which
1247 communicate with @value{GDBN} using it as a back end.
1248 @xref{Interpreters, , Command Interpreters}.
1250 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1251 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1252 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1253 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1254 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1255 @sc{gdb/mi} interfaces are no longer supported.
1258 @cindex @code{--write}
1259 Open the executable and core files for both reading and writing. This
1260 is equivalent to the @samp{set write on} command inside @value{GDBN}
1264 @cindex @code{--statistics}
1265 This option causes @value{GDBN} to print statistics about time and
1266 memory usage after it completes each command and returns to the prompt.
1269 @cindex @code{--version}
1270 This option causes @value{GDBN} to print its version number and
1271 no-warranty blurb, and exit.
1273 @item -configuration
1274 @cindex @code{--configuration}
1275 This option causes @value{GDBN} to print details about its build-time
1276 configuration parameters, and then exit. These details can be
1277 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1282 @subsection What @value{GDBN} Does During Startup
1283 @cindex @value{GDBN} startup
1285 Here's the description of what @value{GDBN} does during session startup:
1289 Sets up the command interpreter as specified by the command line
1290 (@pxref{Mode Options, interpreter}).
1294 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1295 used when building @value{GDBN}; @pxref{System-wide configuration,
1296 ,System-wide configuration and settings}) and executes all the commands in
1299 @anchor{Home Directory Init File}
1301 Reads the init file (if any) in your home directory@footnote{On
1302 DOS/Windows systems, the home directory is the one pointed to by the
1303 @code{HOME} environment variable.} and executes all the commands in
1306 @anchor{Option -init-eval-command}
1308 Executes commands and command files specified by the @samp{-iex} and
1309 @samp{-ix} options in their specified order. Usually you should use the
1310 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1311 settings before @value{GDBN} init files get executed and before inferior
1315 Processes command line options and operands.
1317 @anchor{Init File in the Current Directory during Startup}
1319 Reads and executes the commands from init file (if any) in the current
1320 working directory as long as @samp{set auto-load local-gdbinit} is set to
1321 @samp{on} (@pxref{Init File in the Current Directory}).
1322 This is only done if the current directory is
1323 different from your home directory. Thus, you can have more than one
1324 init file, one generic in your home directory, and another, specific
1325 to the program you are debugging, in the directory where you invoke
1329 If the command line specified a program to debug, or a process to
1330 attach to, or a core file, @value{GDBN} loads any auto-loaded
1331 scripts provided for the program or for its loaded shared libraries.
1332 @xref{Auto-loading}.
1334 If you wish to disable the auto-loading during startup,
1335 you must do something like the following:
1338 $ gdb -iex "set auto-load python-scripts off" myprogram
1341 Option @samp{-ex} does not work because the auto-loading is then turned
1345 Executes commands and command files specified by the @samp{-ex} and
1346 @samp{-x} options in their specified order. @xref{Command Files}, for
1347 more details about @value{GDBN} command files.
1350 Reads the command history recorded in the @dfn{history file}.
1351 @xref{Command History}, for more details about the command history and the
1352 files where @value{GDBN} records it.
1355 Init files use the same syntax as @dfn{command files} (@pxref{Command
1356 Files}) and are processed by @value{GDBN} in the same way. The init
1357 file in your home directory can set options (such as @samp{set
1358 complaints}) that affect subsequent processing of command line options
1359 and operands. Init files are not executed if you use the @samp{-nx}
1360 option (@pxref{Mode Options, ,Choosing Modes}).
1362 To display the list of init files loaded by gdb at startup, you
1363 can use @kbd{gdb --help}.
1365 @cindex init file name
1366 @cindex @file{.gdbinit}
1367 @cindex @file{gdb.ini}
1368 The @value{GDBN} init files are normally called @file{.gdbinit}.
1369 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1370 the limitations of file names imposed by DOS filesystems. The Windows
1371 port of @value{GDBN} uses the standard name, but if it finds a
1372 @file{gdb.ini} file in your home directory, it warns you about that
1373 and suggests to rename the file to the standard name.
1377 @section Quitting @value{GDBN}
1378 @cindex exiting @value{GDBN}
1379 @cindex leaving @value{GDBN}
1382 @kindex quit @r{[}@var{expression}@r{]}
1383 @kindex q @r{(@code{quit})}
1384 @item quit @r{[}@var{expression}@r{]}
1386 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1387 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1388 do not supply @var{expression}, @value{GDBN} will terminate normally;
1389 otherwise it will terminate using the result of @var{expression} as the
1394 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1395 terminates the action of any @value{GDBN} command that is in progress and
1396 returns to @value{GDBN} command level. It is safe to type the interrupt
1397 character at any time because @value{GDBN} does not allow it to take effect
1398 until a time when it is safe.
1400 If you have been using @value{GDBN} to control an attached process or
1401 device, you can release it with the @code{detach} command
1402 (@pxref{Attach, ,Debugging an Already-running Process}).
1404 @node Shell Commands
1405 @section Shell Commands
1407 If you need to execute occasional shell commands during your
1408 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1409 just use the @code{shell} command.
1414 @cindex shell escape
1415 @item shell @var{command-string}
1416 @itemx !@var{command-string}
1417 Invoke a standard shell to execute @var{command-string}.
1418 Note that no space is needed between @code{!} and @var{command-string}.
1419 If it exists, the environment variable @code{SHELL} determines which
1420 shell to run. Otherwise @value{GDBN} uses the default shell
1421 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1424 The utility @code{make} is often needed in development environments.
1425 You do not have to use the @code{shell} command for this purpose in
1430 @cindex calling make
1431 @item make @var{make-args}
1432 Execute the @code{make} program with the specified
1433 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1436 @node Logging Output
1437 @section Logging Output
1438 @cindex logging @value{GDBN} output
1439 @cindex save @value{GDBN} output to a file
1441 You may want to save the output of @value{GDBN} commands to a file.
1442 There are several commands to control @value{GDBN}'s logging.
1446 @item set logging on
1448 @item set logging off
1450 @cindex logging file name
1451 @item set logging file @var{file}
1452 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1453 @item set logging overwrite [on|off]
1454 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1455 you want @code{set logging on} to overwrite the logfile instead.
1456 @item set logging redirect [on|off]
1457 By default, @value{GDBN} output will go to both the terminal and the logfile.
1458 Set @code{redirect} if you want output to go only to the log file.
1459 @kindex show logging
1461 Show the current values of the logging settings.
1465 @chapter @value{GDBN} Commands
1467 You can abbreviate a @value{GDBN} command to the first few letters of the command
1468 name, if that abbreviation is unambiguous; and you can repeat certain
1469 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1470 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1471 show you the alternatives available, if there is more than one possibility).
1474 * Command Syntax:: How to give commands to @value{GDBN}
1475 * Completion:: Command completion
1476 * Help:: How to ask @value{GDBN} for help
1479 @node Command Syntax
1480 @section Command Syntax
1482 A @value{GDBN} command is a single line of input. There is no limit on
1483 how long it can be. It starts with a command name, which is followed by
1484 arguments whose meaning depends on the command name. For example, the
1485 command @code{step} accepts an argument which is the number of times to
1486 step, as in @samp{step 5}. You can also use the @code{step} command
1487 with no arguments. Some commands do not allow any arguments.
1489 @cindex abbreviation
1490 @value{GDBN} command names may always be truncated if that abbreviation is
1491 unambiguous. Other possible command abbreviations are listed in the
1492 documentation for individual commands. In some cases, even ambiguous
1493 abbreviations are allowed; for example, @code{s} is specially defined as
1494 equivalent to @code{step} even though there are other commands whose
1495 names start with @code{s}. You can test abbreviations by using them as
1496 arguments to the @code{help} command.
1498 @cindex repeating commands
1499 @kindex RET @r{(repeat last command)}
1500 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1501 repeat the previous command. Certain commands (for example, @code{run})
1502 will not repeat this way; these are commands whose unintentional
1503 repetition might cause trouble and which you are unlikely to want to
1504 repeat. User-defined commands can disable this feature; see
1505 @ref{Define, dont-repeat}.
1507 The @code{list} and @code{x} commands, when you repeat them with
1508 @key{RET}, construct new arguments rather than repeating
1509 exactly as typed. This permits easy scanning of source or memory.
1511 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1512 output, in a way similar to the common utility @code{more}
1513 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1514 @key{RET} too many in this situation, @value{GDBN} disables command
1515 repetition after any command that generates this sort of display.
1517 @kindex # @r{(a comment)}
1519 Any text from a @kbd{#} to the end of the line is a comment; it does
1520 nothing. This is useful mainly in command files (@pxref{Command
1521 Files,,Command Files}).
1523 @cindex repeating command sequences
1524 @kindex Ctrl-o @r{(operate-and-get-next)}
1525 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1526 commands. This command accepts the current line, like @key{RET}, and
1527 then fetches the next line relative to the current line from the history
1531 @section Command Completion
1534 @cindex word completion
1535 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1536 only one possibility; it can also show you what the valid possibilities
1537 are for the next word in a command, at any time. This works for @value{GDBN}
1538 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1540 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1541 of a word. If there is only one possibility, @value{GDBN} fills in the
1542 word, and waits for you to finish the command (or press @key{RET} to
1543 enter it). For example, if you type
1545 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1546 @c complete accuracy in these examples; space introduced for clarity.
1547 @c If texinfo enhancements make it unnecessary, it would be nice to
1548 @c replace " @key" by "@key" in the following...
1550 (@value{GDBP}) info bre @key{TAB}
1554 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1555 the only @code{info} subcommand beginning with @samp{bre}:
1558 (@value{GDBP}) info breakpoints
1562 You can either press @key{RET} at this point, to run the @code{info
1563 breakpoints} command, or backspace and enter something else, if
1564 @samp{breakpoints} does not look like the command you expected. (If you
1565 were sure you wanted @code{info breakpoints} in the first place, you
1566 might as well just type @key{RET} immediately after @samp{info bre},
1567 to exploit command abbreviations rather than command completion).
1569 If there is more than one possibility for the next word when you press
1570 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1571 characters and try again, or just press @key{TAB} a second time;
1572 @value{GDBN} displays all the possible completions for that word. For
1573 example, you might want to set a breakpoint on a subroutine whose name
1574 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1575 just sounds the bell. Typing @key{TAB} again displays all the
1576 function names in your program that begin with those characters, for
1580 (@value{GDBP}) b make_ @key{TAB}
1581 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1582 make_a_section_from_file make_environ
1583 make_abs_section make_function_type
1584 make_blockvector make_pointer_type
1585 make_cleanup make_reference_type
1586 make_command make_symbol_completion_list
1587 (@value{GDBP}) b make_
1591 After displaying the available possibilities, @value{GDBN} copies your
1592 partial input (@samp{b make_} in the example) so you can finish the
1595 If you just want to see the list of alternatives in the first place, you
1596 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1597 means @kbd{@key{META} ?}. You can type this either by holding down a
1598 key designated as the @key{META} shift on your keyboard (if there is
1599 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1601 If the number of possible completions is large, @value{GDBN} will
1602 print as much of the list as it has collected, as well as a message
1603 indicating that the list may be truncated.
1606 (@value{GDBP}) b m@key{TAB}@key{TAB}
1608 <... the rest of the possible completions ...>
1609 *** List may be truncated, max-completions reached. ***
1614 This behavior can be controlled with the following commands:
1617 @kindex set max-completions
1618 @item set max-completions @var{limit}
1619 @itemx set max-completions unlimited
1620 Set the maximum number of completion candidates. @value{GDBN} will
1621 stop looking for more completions once it collects this many candidates.
1622 This is useful when completing on things like function names as collecting
1623 all the possible candidates can be time consuming.
1624 The default value is 200. A value of zero disables tab-completion.
1625 Note that setting either no limit or a very large limit can make
1627 @kindex show max-completions
1628 @item show max-completions
1629 Show the maximum number of candidates that @value{GDBN} will collect and show
1633 @cindex quotes in commands
1634 @cindex completion of quoted strings
1635 Sometimes the string you need, while logically a ``word'', may contain
1636 parentheses or other characters that @value{GDBN} normally excludes from
1637 its notion of a word. To permit word completion to work in this
1638 situation, you may enclose words in @code{'} (single quote marks) in
1639 @value{GDBN} commands.
1641 The most likely situation where you might need this is in typing the
1642 name of a C@t{++} function. This is because C@t{++} allows function
1643 overloading (multiple definitions of the same function, distinguished
1644 by argument type). For example, when you want to set a breakpoint you
1645 may need to distinguish whether you mean the version of @code{name}
1646 that takes an @code{int} parameter, @code{name(int)}, or the version
1647 that takes a @code{float} parameter, @code{name(float)}. To use the
1648 word-completion facilities in this situation, type a single quote
1649 @code{'} at the beginning of the function name. This alerts
1650 @value{GDBN} that it may need to consider more information than usual
1651 when you press @key{TAB} or @kbd{M-?} to request word completion:
1654 (@value{GDBP}) b 'bubble( @kbd{M-?}
1655 bubble(double,double) bubble(int,int)
1656 (@value{GDBP}) b 'bubble(
1659 In some cases, @value{GDBN} can tell that completing a name requires using
1660 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1661 completing as much as it can) if you do not type the quote in the first
1665 (@value{GDBP}) b bub @key{TAB}
1666 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1667 (@value{GDBP}) b 'bubble(
1671 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1672 you have not yet started typing the argument list when you ask for
1673 completion on an overloaded symbol.
1675 For more information about overloaded functions, see @ref{C Plus Plus
1676 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1677 overload-resolution off} to disable overload resolution;
1678 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1680 @cindex completion of structure field names
1681 @cindex structure field name completion
1682 @cindex completion of union field names
1683 @cindex union field name completion
1684 When completing in an expression which looks up a field in a
1685 structure, @value{GDBN} also tries@footnote{The completer can be
1686 confused by certain kinds of invalid expressions. Also, it only
1687 examines the static type of the expression, not the dynamic type.} to
1688 limit completions to the field names available in the type of the
1692 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1693 magic to_fputs to_rewind
1694 to_data to_isatty to_write
1695 to_delete to_put to_write_async_safe
1700 This is because the @code{gdb_stdout} is a variable of the type
1701 @code{struct ui_file} that is defined in @value{GDBN} sources as
1708 ui_file_flush_ftype *to_flush;
1709 ui_file_write_ftype *to_write;
1710 ui_file_write_async_safe_ftype *to_write_async_safe;
1711 ui_file_fputs_ftype *to_fputs;
1712 ui_file_read_ftype *to_read;
1713 ui_file_delete_ftype *to_delete;
1714 ui_file_isatty_ftype *to_isatty;
1715 ui_file_rewind_ftype *to_rewind;
1716 ui_file_put_ftype *to_put;
1723 @section Getting Help
1724 @cindex online documentation
1727 You can always ask @value{GDBN} itself for information on its commands,
1728 using the command @code{help}.
1731 @kindex h @r{(@code{help})}
1734 You can use @code{help} (abbreviated @code{h}) with no arguments to
1735 display a short list of named classes of commands:
1739 List of classes of commands:
1741 aliases -- Aliases of other commands
1742 breakpoints -- Making program stop at certain points
1743 data -- Examining data
1744 files -- Specifying and examining files
1745 internals -- Maintenance commands
1746 obscure -- Obscure features
1747 running -- Running the program
1748 stack -- Examining the stack
1749 status -- Status inquiries
1750 support -- Support facilities
1751 tracepoints -- Tracing of program execution without
1752 stopping the program
1753 user-defined -- User-defined commands
1755 Type "help" followed by a class name for a list of
1756 commands in that class.
1757 Type "help" followed by command name for full
1759 Command name abbreviations are allowed if unambiguous.
1762 @c the above line break eliminates huge line overfull...
1764 @item help @var{class}
1765 Using one of the general help classes as an argument, you can get a
1766 list of the individual commands in that class. For example, here is the
1767 help display for the class @code{status}:
1770 (@value{GDBP}) help status
1775 @c Line break in "show" line falsifies real output, but needed
1776 @c to fit in smallbook page size.
1777 info -- Generic command for showing things
1778 about the program being debugged
1779 show -- Generic command for showing things
1782 Type "help" followed by command name for full
1784 Command name abbreviations are allowed if unambiguous.
1788 @item help @var{command}
1789 With a command name as @code{help} argument, @value{GDBN} displays a
1790 short paragraph on how to use that command.
1793 @item apropos @var{args}
1794 The @code{apropos} command searches through all of the @value{GDBN}
1795 commands, and their documentation, for the regular expression specified in
1796 @var{args}. It prints out all matches found. For example:
1807 alias -- Define a new command that is an alias of an existing command
1808 aliases -- Aliases of other commands
1809 d -- Delete some breakpoints or auto-display expressions
1810 del -- Delete some breakpoints or auto-display expressions
1811 delete -- Delete some breakpoints or auto-display expressions
1816 @item complete @var{args}
1817 The @code{complete @var{args}} command lists all the possible completions
1818 for the beginning of a command. Use @var{args} to specify the beginning of the
1819 command you want completed. For example:
1825 @noindent results in:
1836 @noindent This is intended for use by @sc{gnu} Emacs.
1839 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1840 and @code{show} to inquire about the state of your program, or the state
1841 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1842 manual introduces each of them in the appropriate context. The listings
1843 under @code{info} and under @code{show} in the Command, Variable, and
1844 Function Index point to all the sub-commands. @xref{Command and Variable
1850 @kindex i @r{(@code{info})}
1852 This command (abbreviated @code{i}) is for describing the state of your
1853 program. For example, you can show the arguments passed to a function
1854 with @code{info args}, list the registers currently in use with @code{info
1855 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1856 You can get a complete list of the @code{info} sub-commands with
1857 @w{@code{help info}}.
1861 You can assign the result of an expression to an environment variable with
1862 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1863 @code{set prompt $}.
1867 In contrast to @code{info}, @code{show} is for describing the state of
1868 @value{GDBN} itself.
1869 You can change most of the things you can @code{show}, by using the
1870 related command @code{set}; for example, you can control what number
1871 system is used for displays with @code{set radix}, or simply inquire
1872 which is currently in use with @code{show radix}.
1875 To display all the settable parameters and their current
1876 values, you can use @code{show} with no arguments; you may also use
1877 @code{info set}. Both commands produce the same display.
1878 @c FIXME: "info set" violates the rule that "info" is for state of
1879 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1880 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1884 Here are several miscellaneous @code{show} subcommands, all of which are
1885 exceptional in lacking corresponding @code{set} commands:
1888 @kindex show version
1889 @cindex @value{GDBN} version number
1891 Show what version of @value{GDBN} is running. You should include this
1892 information in @value{GDBN} bug-reports. If multiple versions of
1893 @value{GDBN} are in use at your site, you may need to determine which
1894 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1895 commands are introduced, and old ones may wither away. Also, many
1896 system vendors ship variant versions of @value{GDBN}, and there are
1897 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1898 The version number is the same as the one announced when you start
1901 @kindex show copying
1902 @kindex info copying
1903 @cindex display @value{GDBN} copyright
1906 Display information about permission for copying @value{GDBN}.
1908 @kindex show warranty
1909 @kindex info warranty
1911 @itemx info warranty
1912 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1913 if your version of @value{GDBN} comes with one.
1915 @kindex show configuration
1916 @item show configuration
1917 Display detailed information about the way @value{GDBN} was configured
1918 when it was built. This displays the optional arguments passed to the
1919 @file{configure} script and also configuration parameters detected
1920 automatically by @command{configure}. When reporting a @value{GDBN}
1921 bug (@pxref{GDB Bugs}), it is important to include this information in
1927 @chapter Running Programs Under @value{GDBN}
1929 When you run a program under @value{GDBN}, you must first generate
1930 debugging information when you compile it.
1932 You may start @value{GDBN} with its arguments, if any, in an environment
1933 of your choice. If you are doing native debugging, you may redirect
1934 your program's input and output, debug an already running process, or
1935 kill a child process.
1938 * Compilation:: Compiling for debugging
1939 * Starting:: Starting your program
1940 * Arguments:: Your program's arguments
1941 * Environment:: Your program's environment
1943 * Working Directory:: Your program's working directory
1944 * Input/Output:: Your program's input and output
1945 * Attach:: Debugging an already-running process
1946 * Kill Process:: Killing the child process
1948 * Inferiors and Programs:: Debugging multiple inferiors and programs
1949 * Threads:: Debugging programs with multiple threads
1950 * Forks:: Debugging forks
1951 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1955 @section Compiling for Debugging
1957 In order to debug a program effectively, you need to generate
1958 debugging information when you compile it. This debugging information
1959 is stored in the object file; it describes the data type of each
1960 variable or function and the correspondence between source line numbers
1961 and addresses in the executable code.
1963 To request debugging information, specify the @samp{-g} option when you run
1966 Programs that are to be shipped to your customers are compiled with
1967 optimizations, using the @samp{-O} compiler option. However, some
1968 compilers are unable to handle the @samp{-g} and @samp{-O} options
1969 together. Using those compilers, you cannot generate optimized
1970 executables containing debugging information.
1972 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1973 without @samp{-O}, making it possible to debug optimized code. We
1974 recommend that you @emph{always} use @samp{-g} whenever you compile a
1975 program. You may think your program is correct, but there is no sense
1976 in pushing your luck. For more information, see @ref{Optimized Code}.
1978 Older versions of the @sc{gnu} C compiler permitted a variant option
1979 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1980 format; if your @sc{gnu} C compiler has this option, do not use it.
1982 @value{GDBN} knows about preprocessor macros and can show you their
1983 expansion (@pxref{Macros}). Most compilers do not include information
1984 about preprocessor macros in the debugging information if you specify
1985 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1986 the @sc{gnu} C compiler, provides macro information if you are using
1987 the DWARF debugging format, and specify the option @option{-g3}.
1989 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1990 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1991 information on @value{NGCC} options affecting debug information.
1993 You will have the best debugging experience if you use the latest
1994 version of the DWARF debugging format that your compiler supports.
1995 DWARF is currently the most expressive and best supported debugging
1996 format in @value{GDBN}.
2000 @section Starting your Program
2006 @kindex r @r{(@code{run})}
2009 Use the @code{run} command to start your program under @value{GDBN}.
2010 You must first specify the program name with an argument to
2011 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2012 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2013 command (@pxref{Files, ,Commands to Specify Files}).
2017 If you are running your program in an execution environment that
2018 supports processes, @code{run} creates an inferior process and makes
2019 that process run your program. In some environments without processes,
2020 @code{run} jumps to the start of your program. Other targets,
2021 like @samp{remote}, are always running. If you get an error
2022 message like this one:
2025 The "remote" target does not support "run".
2026 Try "help target" or "continue".
2030 then use @code{continue} to run your program. You may need @code{load}
2031 first (@pxref{load}).
2033 The execution of a program is affected by certain information it
2034 receives from its superior. @value{GDBN} provides ways to specify this
2035 information, which you must do @emph{before} starting your program. (You
2036 can change it after starting your program, but such changes only affect
2037 your program the next time you start it.) This information may be
2038 divided into four categories:
2041 @item The @emph{arguments.}
2042 Specify the arguments to give your program as the arguments of the
2043 @code{run} command. If a shell is available on your target, the shell
2044 is used to pass the arguments, so that you may use normal conventions
2045 (such as wildcard expansion or variable substitution) in describing
2047 In Unix systems, you can control which shell is used with the
2048 @code{SHELL} environment variable. If you do not define @code{SHELL},
2049 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2050 use of any shell with the @code{set startup-with-shell} command (see
2053 @item The @emph{environment.}
2054 Your program normally inherits its environment from @value{GDBN}, but you can
2055 use the @value{GDBN} commands @code{set environment} and @code{unset
2056 environment} to change parts of the environment that affect
2057 your program. @xref{Environment, ,Your Program's Environment}.
2059 @item The @emph{working directory.}
2060 Your program inherits its working directory from @value{GDBN}. You can set
2061 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2062 @xref{Working Directory, ,Your Program's Working Directory}.
2064 @item The @emph{standard input and output.}
2065 Your program normally uses the same device for standard input and
2066 standard output as @value{GDBN} is using. You can redirect input and output
2067 in the @code{run} command line, or you can use the @code{tty} command to
2068 set a different device for your program.
2069 @xref{Input/Output, ,Your Program's Input and Output}.
2072 @emph{Warning:} While input and output redirection work, you cannot use
2073 pipes to pass the output of the program you are debugging to another
2074 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2078 When you issue the @code{run} command, your program begins to execute
2079 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2080 of how to arrange for your program to stop. Once your program has
2081 stopped, you may call functions in your program, using the @code{print}
2082 or @code{call} commands. @xref{Data, ,Examining Data}.
2084 If the modification time of your symbol file has changed since the last
2085 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2086 table, and reads it again. When it does this, @value{GDBN} tries to retain
2087 your current breakpoints.
2092 @cindex run to main procedure
2093 The name of the main procedure can vary from language to language.
2094 With C or C@t{++}, the main procedure name is always @code{main}, but
2095 other languages such as Ada do not require a specific name for their
2096 main procedure. The debugger provides a convenient way to start the
2097 execution of the program and to stop at the beginning of the main
2098 procedure, depending on the language used.
2100 The @samp{start} command does the equivalent of setting a temporary
2101 breakpoint at the beginning of the main procedure and then invoking
2102 the @samp{run} command.
2104 @cindex elaboration phase
2105 Some programs contain an @dfn{elaboration} phase where some startup code is
2106 executed before the main procedure is called. This depends on the
2107 languages used to write your program. In C@t{++}, for instance,
2108 constructors for static and global objects are executed before
2109 @code{main} is called. It is therefore possible that the debugger stops
2110 before reaching the main procedure. However, the temporary breakpoint
2111 will remain to halt execution.
2113 Specify the arguments to give to your program as arguments to the
2114 @samp{start} command. These arguments will be given verbatim to the
2115 underlying @samp{run} command. Note that the same arguments will be
2116 reused if no argument is provided during subsequent calls to
2117 @samp{start} or @samp{run}.
2119 It is sometimes necessary to debug the program during elaboration. In
2120 these cases, using the @code{start} command would stop the execution of
2121 your program too late, as the program would have already completed the
2122 elaboration phase. Under these circumstances, insert breakpoints in your
2123 elaboration code before running your program.
2125 @anchor{set exec-wrapper}
2126 @kindex set exec-wrapper
2127 @item set exec-wrapper @var{wrapper}
2128 @itemx show exec-wrapper
2129 @itemx unset exec-wrapper
2130 When @samp{exec-wrapper} is set, the specified wrapper is used to
2131 launch programs for debugging. @value{GDBN} starts your program
2132 with a shell command of the form @kbd{exec @var{wrapper}
2133 @var{program}}. Quoting is added to @var{program} and its
2134 arguments, but not to @var{wrapper}, so you should add quotes if
2135 appropriate for your shell. The wrapper runs until it executes
2136 your program, and then @value{GDBN} takes control.
2138 You can use any program that eventually calls @code{execve} with
2139 its arguments as a wrapper. Several standard Unix utilities do
2140 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2141 with @code{exec "$@@"} will also work.
2143 For example, you can use @code{env} to pass an environment variable to
2144 the debugged program, without setting the variable in your shell's
2148 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2152 This command is available when debugging locally on most targets, excluding
2153 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2155 @kindex set startup-with-shell
2156 @anchor{set startup-with-shell}
2157 @item set startup-with-shell
2158 @itemx set startup-with-shell on
2159 @itemx set startup-with-shell off
2160 @itemx show startup-with-shell
2161 On Unix systems, by default, if a shell is available on your target,
2162 @value{GDBN}) uses it to start your program. Arguments of the
2163 @code{run} command are passed to the shell, which does variable
2164 substitution, expands wildcard characters and performs redirection of
2165 I/O. In some circumstances, it may be useful to disable such use of a
2166 shell, for example, when debugging the shell itself or diagnosing
2167 startup failures such as:
2171 Starting program: ./a.out
2172 During startup program terminated with signal SIGSEGV, Segmentation fault.
2176 which indicates the shell or the wrapper specified with
2177 @samp{exec-wrapper} crashed, not your program. Most often, this is
2178 caused by something odd in your shell's non-interactive mode
2179 initialization file---such as @file{.cshrc} for C-shell,
2180 $@file{.zshenv} for the Z shell, or the file specified in the
2181 @samp{BASH_ENV} environment variable for BASH.
2183 @anchor{set auto-connect-native-target}
2184 @kindex set auto-connect-native-target
2185 @item set auto-connect-native-target
2186 @itemx set auto-connect-native-target on
2187 @itemx set auto-connect-native-target off
2188 @itemx show auto-connect-native-target
2190 By default, if not connected to any target yet (e.g., with
2191 @code{target remote}), the @code{run} command starts your program as a
2192 native process under @value{GDBN}, on your local machine. If you're
2193 sure you don't want to debug programs on your local machine, you can
2194 tell @value{GDBN} to not connect to the native target automatically
2195 with the @code{set auto-connect-native-target off} command.
2197 If @code{on}, which is the default, and if @value{GDBN} is not
2198 connected to a target already, the @code{run} command automaticaly
2199 connects to the native target, if one is available.
2201 If @code{off}, and if @value{GDBN} is not connected to a target
2202 already, the @code{run} command fails with an error:
2206 Don't know how to run. Try "help target".
2209 If @value{GDBN} is already connected to a target, @value{GDBN} always
2210 uses it with the @code{run} command.
2212 In any case, you can explicitly connect to the native target with the
2213 @code{target native} command. For example,
2216 (@value{GDBP}) set auto-connect-native-target off
2218 Don't know how to run. Try "help target".
2219 (@value{GDBP}) target native
2221 Starting program: ./a.out
2222 [Inferior 1 (process 10421) exited normally]
2225 In case you connected explicitly to the @code{native} target,
2226 @value{GDBN} remains connected even if all inferiors exit, ready for
2227 the next @code{run} command. Use the @code{disconnect} command to
2230 Examples of other commands that likewise respect the
2231 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2232 proc}, @code{info os}.
2234 @kindex set disable-randomization
2235 @item set disable-randomization
2236 @itemx set disable-randomization on
2237 This option (enabled by default in @value{GDBN}) will turn off the native
2238 randomization of the virtual address space of the started program. This option
2239 is useful for multiple debugging sessions to make the execution better
2240 reproducible and memory addresses reusable across debugging sessions.
2242 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2243 On @sc{gnu}/Linux you can get the same behavior using
2246 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2249 @item set disable-randomization off
2250 Leave the behavior of the started executable unchanged. Some bugs rear their
2251 ugly heads only when the program is loaded at certain addresses. If your bug
2252 disappears when you run the program under @value{GDBN}, that might be because
2253 @value{GDBN} by default disables the address randomization on platforms, such
2254 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2255 disable-randomization off} to try to reproduce such elusive bugs.
2257 On targets where it is available, virtual address space randomization
2258 protects the programs against certain kinds of security attacks. In these
2259 cases the attacker needs to know the exact location of a concrete executable
2260 code. Randomizing its location makes it impossible to inject jumps misusing
2261 a code at its expected addresses.
2263 Prelinking shared libraries provides a startup performance advantage but it
2264 makes addresses in these libraries predictable for privileged processes by
2265 having just unprivileged access at the target system. Reading the shared
2266 library binary gives enough information for assembling the malicious code
2267 misusing it. Still even a prelinked shared library can get loaded at a new
2268 random address just requiring the regular relocation process during the
2269 startup. Shared libraries not already prelinked are always loaded at
2270 a randomly chosen address.
2272 Position independent executables (PIE) contain position independent code
2273 similar to the shared libraries and therefore such executables get loaded at
2274 a randomly chosen address upon startup. PIE executables always load even
2275 already prelinked shared libraries at a random address. You can build such
2276 executable using @command{gcc -fPIE -pie}.
2278 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2279 (as long as the randomization is enabled).
2281 @item show disable-randomization
2282 Show the current setting of the explicit disable of the native randomization of
2283 the virtual address space of the started program.
2288 @section Your Program's Arguments
2290 @cindex arguments (to your program)
2291 The arguments to your program can be specified by the arguments of the
2293 They are passed to a shell, which expands wildcard characters and
2294 performs redirection of I/O, and thence to your program. Your
2295 @code{SHELL} environment variable (if it exists) specifies what shell
2296 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2297 the default shell (@file{/bin/sh} on Unix).
2299 On non-Unix systems, the program is usually invoked directly by
2300 @value{GDBN}, which emulates I/O redirection via the appropriate system
2301 calls, and the wildcard characters are expanded by the startup code of
2302 the program, not by the shell.
2304 @code{run} with no arguments uses the same arguments used by the previous
2305 @code{run}, or those set by the @code{set args} command.
2310 Specify the arguments to be used the next time your program is run. If
2311 @code{set args} has no arguments, @code{run} executes your program
2312 with no arguments. Once you have run your program with arguments,
2313 using @code{set args} before the next @code{run} is the only way to run
2314 it again without arguments.
2318 Show the arguments to give your program when it is started.
2322 @section Your Program's Environment
2324 @cindex environment (of your program)
2325 The @dfn{environment} consists of a set of environment variables and
2326 their values. Environment variables conventionally record such things as
2327 your user name, your home directory, your terminal type, and your search
2328 path for programs to run. Usually you set up environment variables with
2329 the shell and they are inherited by all the other programs you run. When
2330 debugging, it can be useful to try running your program with a modified
2331 environment without having to start @value{GDBN} over again.
2335 @item path @var{directory}
2336 Add @var{directory} to the front of the @code{PATH} environment variable
2337 (the search path for executables) that will be passed to your program.
2338 The value of @code{PATH} used by @value{GDBN} does not change.
2339 You may specify several directory names, separated by whitespace or by a
2340 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2341 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2342 is moved to the front, so it is searched sooner.
2344 You can use the string @samp{$cwd} to refer to whatever is the current
2345 working directory at the time @value{GDBN} searches the path. If you
2346 use @samp{.} instead, it refers to the directory where you executed the
2347 @code{path} command. @value{GDBN} replaces @samp{.} in the
2348 @var{directory} argument (with the current path) before adding
2349 @var{directory} to the search path.
2350 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2351 @c document that, since repeating it would be a no-op.
2355 Display the list of search paths for executables (the @code{PATH}
2356 environment variable).
2358 @kindex show environment
2359 @item show environment @r{[}@var{varname}@r{]}
2360 Print the value of environment variable @var{varname} to be given to
2361 your program when it starts. If you do not supply @var{varname},
2362 print the names and values of all environment variables to be given to
2363 your program. You can abbreviate @code{environment} as @code{env}.
2365 @kindex set environment
2366 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2367 Set environment variable @var{varname} to @var{value}. The value
2368 changes for your program (and the shell @value{GDBN} uses to launch
2369 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2370 values of environment variables are just strings, and any
2371 interpretation is supplied by your program itself. The @var{value}
2372 parameter is optional; if it is eliminated, the variable is set to a
2374 @c "any string" here does not include leading, trailing
2375 @c blanks. Gnu asks: does anyone care?
2377 For example, this command:
2384 tells the debugged program, when subsequently run, that its user is named
2385 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2386 are not actually required.)
2388 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2389 which also inherits the environment set with @code{set environment}.
2390 If necessary, you can avoid that by using the @samp{env} program as a
2391 wrapper instead of using @code{set environment}. @xref{set
2392 exec-wrapper}, for an example doing just that.
2394 @kindex unset environment
2395 @item unset environment @var{varname}
2396 Remove variable @var{varname} from the environment to be passed to your
2397 program. This is different from @samp{set env @var{varname} =};
2398 @code{unset environment} removes the variable from the environment,
2399 rather than assigning it an empty value.
2402 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2403 the shell indicated by your @code{SHELL} environment variable if it
2404 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2405 names a shell that runs an initialization file when started
2406 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2407 for the Z shell, or the file specified in the @samp{BASH_ENV}
2408 environment variable for BASH---any variables you set in that file
2409 affect your program. You may wish to move setting of environment
2410 variables to files that are only run when you sign on, such as
2411 @file{.login} or @file{.profile}.
2413 @node Working Directory
2414 @section Your Program's Working Directory
2416 @cindex working directory (of your program)
2417 Each time you start your program with @code{run}, it inherits its
2418 working directory from the current working directory of @value{GDBN}.
2419 The @value{GDBN} working directory is initially whatever it inherited
2420 from its parent process (typically the shell), but you can specify a new
2421 working directory in @value{GDBN} with the @code{cd} command.
2423 The @value{GDBN} working directory also serves as a default for the commands
2424 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2429 @cindex change working directory
2430 @item cd @r{[}@var{directory}@r{]}
2431 Set the @value{GDBN} working directory to @var{directory}. If not
2432 given, @var{directory} uses @file{'~'}.
2436 Print the @value{GDBN} working directory.
2439 It is generally impossible to find the current working directory of
2440 the process being debugged (since a program can change its directory
2441 during its run). If you work on a system where @value{GDBN} is
2442 configured with the @file{/proc} support, you can use the @code{info
2443 proc} command (@pxref{SVR4 Process Information}) to find out the
2444 current working directory of the debuggee.
2447 @section Your Program's Input and Output
2452 By default, the program you run under @value{GDBN} does input and output to
2453 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2454 to its own terminal modes to interact with you, but it records the terminal
2455 modes your program was using and switches back to them when you continue
2456 running your program.
2459 @kindex info terminal
2461 Displays information recorded by @value{GDBN} about the terminal modes your
2465 You can redirect your program's input and/or output using shell
2466 redirection with the @code{run} command. For example,
2473 starts your program, diverting its output to the file @file{outfile}.
2476 @cindex controlling terminal
2477 Another way to specify where your program should do input and output is
2478 with the @code{tty} command. This command accepts a file name as
2479 argument, and causes this file to be the default for future @code{run}
2480 commands. It also resets the controlling terminal for the child
2481 process, for future @code{run} commands. For example,
2488 directs that processes started with subsequent @code{run} commands
2489 default to do input and output on the terminal @file{/dev/ttyb} and have
2490 that as their controlling terminal.
2492 An explicit redirection in @code{run} overrides the @code{tty} command's
2493 effect on the input/output device, but not its effect on the controlling
2496 When you use the @code{tty} command or redirect input in the @code{run}
2497 command, only the input @emph{for your program} is affected. The input
2498 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2499 for @code{set inferior-tty}.
2501 @cindex inferior tty
2502 @cindex set inferior controlling terminal
2503 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2504 display the name of the terminal that will be used for future runs of your
2508 @item set inferior-tty [ @var{tty} ]
2509 @kindex set inferior-tty
2510 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2511 restores the default behavior, which is to use the same terminal as
2514 @item show inferior-tty
2515 @kindex show inferior-tty
2516 Show the current tty for the program being debugged.
2520 @section Debugging an Already-running Process
2525 @item attach @var{process-id}
2526 This command attaches to a running process---one that was started
2527 outside @value{GDBN}. (@code{info files} shows your active
2528 targets.) The command takes as argument a process ID. The usual way to
2529 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2530 or with the @samp{jobs -l} shell command.
2532 @code{attach} does not repeat if you press @key{RET} a second time after
2533 executing the command.
2536 To use @code{attach}, your program must be running in an environment
2537 which supports processes; for example, @code{attach} does not work for
2538 programs on bare-board targets that lack an operating system. You must
2539 also have permission to send the process a signal.
2541 When you use @code{attach}, the debugger finds the program running in
2542 the process first by looking in the current working directory, then (if
2543 the program is not found) by using the source file search path
2544 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2545 the @code{file} command to load the program. @xref{Files, ,Commands to
2548 The first thing @value{GDBN} does after arranging to debug the specified
2549 process is to stop it. You can examine and modify an attached process
2550 with all the @value{GDBN} commands that are ordinarily available when
2551 you start processes with @code{run}. You can insert breakpoints; you
2552 can step and continue; you can modify storage. If you would rather the
2553 process continue running, you may use the @code{continue} command after
2554 attaching @value{GDBN} to the process.
2559 When you have finished debugging the attached process, you can use the
2560 @code{detach} command to release it from @value{GDBN} control. Detaching
2561 the process continues its execution. After the @code{detach} command,
2562 that process and @value{GDBN} become completely independent once more, and you
2563 are ready to @code{attach} another process or start one with @code{run}.
2564 @code{detach} does not repeat if you press @key{RET} again after
2565 executing the command.
2568 If you exit @value{GDBN} while you have an attached process, you detach
2569 that process. If you use the @code{run} command, you kill that process.
2570 By default, @value{GDBN} asks for confirmation if you try to do either of these
2571 things; you can control whether or not you need to confirm by using the
2572 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2576 @section Killing the Child Process
2581 Kill the child process in which your program is running under @value{GDBN}.
2584 This command is useful if you wish to debug a core dump instead of a
2585 running process. @value{GDBN} ignores any core dump file while your program
2588 On some operating systems, a program cannot be executed outside @value{GDBN}
2589 while you have breakpoints set on it inside @value{GDBN}. You can use the
2590 @code{kill} command in this situation to permit running your program
2591 outside the debugger.
2593 The @code{kill} command is also useful if you wish to recompile and
2594 relink your program, since on many systems it is impossible to modify an
2595 executable file while it is running in a process. In this case, when you
2596 next type @code{run}, @value{GDBN} notices that the file has changed, and
2597 reads the symbol table again (while trying to preserve your current
2598 breakpoint settings).
2600 @node Inferiors and Programs
2601 @section Debugging Multiple Inferiors and Programs
2603 @value{GDBN} lets you run and debug multiple programs in a single
2604 session. In addition, @value{GDBN} on some systems may let you run
2605 several programs simultaneously (otherwise you have to exit from one
2606 before starting another). In the most general case, you can have
2607 multiple threads of execution in each of multiple processes, launched
2608 from multiple executables.
2611 @value{GDBN} represents the state of each program execution with an
2612 object called an @dfn{inferior}. An inferior typically corresponds to
2613 a process, but is more general and applies also to targets that do not
2614 have processes. Inferiors may be created before a process runs, and
2615 may be retained after a process exits. Inferiors have unique
2616 identifiers that are different from process ids. Usually each
2617 inferior will also have its own distinct address space, although some
2618 embedded targets may have several inferiors running in different parts
2619 of a single address space. Each inferior may in turn have multiple
2620 threads running in it.
2622 To find out what inferiors exist at any moment, use @w{@code{info
2626 @kindex info inferiors
2627 @item info inferiors
2628 Print a list of all inferiors currently being managed by @value{GDBN}.
2630 @value{GDBN} displays for each inferior (in this order):
2634 the inferior number assigned by @value{GDBN}
2637 the target system's inferior identifier
2640 the name of the executable the inferior is running.
2645 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2646 indicates the current inferior.
2650 @c end table here to get a little more width for example
2653 (@value{GDBP}) info inferiors
2654 Num Description Executable
2655 2 process 2307 hello
2656 * 1 process 3401 goodbye
2659 To switch focus between inferiors, use the @code{inferior} command:
2662 @kindex inferior @var{infno}
2663 @item inferior @var{infno}
2664 Make inferior number @var{infno} the current inferior. The argument
2665 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2666 in the first field of the @samp{info inferiors} display.
2669 @vindex $_inferior@r{, convenience variable}
2670 The debugger convenience variable @samp{$_inferior} contains the
2671 number of the current inferior. You may find this useful in writing
2672 breakpoint conditional expressions, command scripts, and so forth.
2673 @xref{Convenience Vars,, Convenience Variables}, for general
2674 information on convenience variables.
2676 You can get multiple executables into a debugging session via the
2677 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2678 systems @value{GDBN} can add inferiors to the debug session
2679 automatically by following calls to @code{fork} and @code{exec}. To
2680 remove inferiors from the debugging session use the
2681 @w{@code{remove-inferiors}} command.
2684 @kindex add-inferior
2685 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2686 Adds @var{n} inferiors to be run using @var{executable} as the
2687 executable; @var{n} defaults to 1. If no executable is specified,
2688 the inferiors begins empty, with no program. You can still assign or
2689 change the program assigned to the inferior at any time by using the
2690 @code{file} command with the executable name as its argument.
2692 @kindex clone-inferior
2693 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2694 Adds @var{n} inferiors ready to execute the same program as inferior
2695 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2696 number of the current inferior. This is a convenient command when you
2697 want to run another instance of the inferior you are debugging.
2700 (@value{GDBP}) info inferiors
2701 Num Description Executable
2702 * 1 process 29964 helloworld
2703 (@value{GDBP}) clone-inferior
2706 (@value{GDBP}) info inferiors
2707 Num Description Executable
2709 * 1 process 29964 helloworld
2712 You can now simply switch focus to inferior 2 and run it.
2714 @kindex remove-inferiors
2715 @item remove-inferiors @var{infno}@dots{}
2716 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2717 possible to remove an inferior that is running with this command. For
2718 those, use the @code{kill} or @code{detach} command first.
2722 To quit debugging one of the running inferiors that is not the current
2723 inferior, you can either detach from it by using the @w{@code{detach
2724 inferior}} command (allowing it to run independently), or kill it
2725 using the @w{@code{kill inferiors}} command:
2728 @kindex detach inferiors @var{infno}@dots{}
2729 @item detach inferior @var{infno}@dots{}
2730 Detach from the inferior or inferiors identified by @value{GDBN}
2731 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2732 still stays on the list of inferiors shown by @code{info inferiors},
2733 but its Description will show @samp{<null>}.
2735 @kindex kill inferiors @var{infno}@dots{}
2736 @item kill inferiors @var{infno}@dots{}
2737 Kill the inferior or inferiors identified by @value{GDBN} inferior
2738 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2739 stays on the list of inferiors shown by @code{info inferiors}, but its
2740 Description will show @samp{<null>}.
2743 After the successful completion of a command such as @code{detach},
2744 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2745 a normal process exit, the inferior is still valid and listed with
2746 @code{info inferiors}, ready to be restarted.
2749 To be notified when inferiors are started or exit under @value{GDBN}'s
2750 control use @w{@code{set print inferior-events}}:
2753 @kindex set print inferior-events
2754 @cindex print messages on inferior start and exit
2755 @item set print inferior-events
2756 @itemx set print inferior-events on
2757 @itemx set print inferior-events off
2758 The @code{set print inferior-events} command allows you to enable or
2759 disable printing of messages when @value{GDBN} notices that new
2760 inferiors have started or that inferiors have exited or have been
2761 detached. By default, these messages will not be printed.
2763 @kindex show print inferior-events
2764 @item show print inferior-events
2765 Show whether messages will be printed when @value{GDBN} detects that
2766 inferiors have started, exited or have been detached.
2769 Many commands will work the same with multiple programs as with a
2770 single program: e.g., @code{print myglobal} will simply display the
2771 value of @code{myglobal} in the current inferior.
2774 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2775 get more info about the relationship of inferiors, programs, address
2776 spaces in a debug session. You can do that with the @w{@code{maint
2777 info program-spaces}} command.
2780 @kindex maint info program-spaces
2781 @item maint info program-spaces
2782 Print a list of all program spaces currently being managed by
2785 @value{GDBN} displays for each program space (in this order):
2789 the program space number assigned by @value{GDBN}
2792 the name of the executable loaded into the program space, with e.g.,
2793 the @code{file} command.
2798 An asterisk @samp{*} preceding the @value{GDBN} program space number
2799 indicates the current program space.
2801 In addition, below each program space line, @value{GDBN} prints extra
2802 information that isn't suitable to display in tabular form. For
2803 example, the list of inferiors bound to the program space.
2806 (@value{GDBP}) maint info program-spaces
2810 Bound inferiors: ID 1 (process 21561)
2813 Here we can see that no inferior is running the program @code{hello},
2814 while @code{process 21561} is running the program @code{goodbye}. On
2815 some targets, it is possible that multiple inferiors are bound to the
2816 same program space. The most common example is that of debugging both
2817 the parent and child processes of a @code{vfork} call. For example,
2820 (@value{GDBP}) maint info program-spaces
2823 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2826 Here, both inferior 2 and inferior 1 are running in the same program
2827 space as a result of inferior 1 having executed a @code{vfork} call.
2831 @section Debugging Programs with Multiple Threads
2833 @cindex threads of execution
2834 @cindex multiple threads
2835 @cindex switching threads
2836 In some operating systems, such as GNU/Linux and Solaris, a single program
2837 may have more than one @dfn{thread} of execution. The precise semantics
2838 of threads differ from one operating system to another, but in general
2839 the threads of a single program are akin to multiple processes---except
2840 that they share one address space (that is, they can all examine and
2841 modify the same variables). On the other hand, each thread has its own
2842 registers and execution stack, and perhaps private memory.
2844 @value{GDBN} provides these facilities for debugging multi-thread
2848 @item automatic notification of new threads
2849 @item @samp{thread @var{thread-id}}, a command to switch among threads
2850 @item @samp{info threads}, a command to inquire about existing threads
2851 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2852 a command to apply a command to a list of threads
2853 @item thread-specific breakpoints
2854 @item @samp{set print thread-events}, which controls printing of
2855 messages on thread start and exit.
2856 @item @samp{set libthread-db-search-path @var{path}}, which lets
2857 the user specify which @code{libthread_db} to use if the default choice
2858 isn't compatible with the program.
2861 @cindex focus of debugging
2862 @cindex current thread
2863 The @value{GDBN} thread debugging facility allows you to observe all
2864 threads while your program runs---but whenever @value{GDBN} takes
2865 control, one thread in particular is always the focus of debugging.
2866 This thread is called the @dfn{current thread}. Debugging commands show
2867 program information from the perspective of the current thread.
2869 @cindex @code{New} @var{systag} message
2870 @cindex thread identifier (system)
2871 @c FIXME-implementors!! It would be more helpful if the [New...] message
2872 @c included GDB's numeric thread handle, so you could just go to that
2873 @c thread without first checking `info threads'.
2874 Whenever @value{GDBN} detects a new thread in your program, it displays
2875 the target system's identification for the thread with a message in the
2876 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2877 whose form varies depending on the particular system. For example, on
2878 @sc{gnu}/Linux, you might see
2881 [New Thread 0x41e02940 (LWP 25582)]
2885 when @value{GDBN} notices a new thread. In contrast, on other systems,
2886 the @var{systag} is simply something like @samp{process 368}, with no
2889 @c FIXME!! (1) Does the [New...] message appear even for the very first
2890 @c thread of a program, or does it only appear for the
2891 @c second---i.e.@: when it becomes obvious we have a multithread
2893 @c (2) *Is* there necessarily a first thread always? Or do some
2894 @c multithread systems permit starting a program with multiple
2895 @c threads ab initio?
2897 @anchor{thread numbers}
2898 @cindex thread number, per inferior
2899 @cindex thread identifier (GDB)
2900 For debugging purposes, @value{GDBN} associates its own thread number
2901 ---always a single integer---with each thread of an inferior. This
2902 number is unique between all threads of an inferior, but not unique
2903 between threads of different inferiors.
2905 @cindex qualified thread ID
2906 You can refer to a given thread in an inferior using the qualified
2907 @var{inferior-num}.@var{thread-num} syntax, also known as
2908 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2909 number and @var{thread-num} being the thread number of the given
2910 inferior. For example, thread @code{2.3} refers to thread number 3 of
2911 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2912 then @value{GDBN} infers you're referring to a thread of the current
2915 Until you create a second inferior, @value{GDBN} does not show the
2916 @var{inferior-num} part of thread IDs, even though you can always use
2917 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2918 of inferior 1, the initial inferior.
2920 @anchor{thread ID lists}
2921 @cindex thread ID lists
2922 Some commands accept a space-separated @dfn{thread ID list} as
2923 argument. A list element can be:
2927 A thread ID as shown in the first field of the @samp{info threads}
2928 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2932 A range of thread numbers, again with or without an inferior
2933 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2934 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2937 All threads of an inferior, specified with a star wildcard, with or
2938 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2939 @samp{1.*}) or @code{*}. The former refers to all threads of the
2940 given inferior, and the latter form without an inferior qualifier
2941 refers to all threads of the current inferior.
2945 For example, if the current inferior is 1, and inferior 7 has one
2946 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2947 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2948 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2949 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2953 @anchor{global thread numbers}
2954 @cindex global thread number
2955 @cindex global thread identifier (GDB)
2956 In addition to a @emph{per-inferior} number, each thread is also
2957 assigned a unique @emph{global} number, also known as @dfn{global
2958 thread ID}, a single integer. Unlike the thread number component of
2959 the thread ID, no two threads have the same global ID, even when
2960 you're debugging multiple inferiors.
2962 From @value{GDBN}'s perspective, a process always has at least one
2963 thread. In other words, @value{GDBN} assigns a thread number to the
2964 program's ``main thread'' even if the program is not multi-threaded.
2966 @vindex $_thread@r{, convenience variable}
2967 @vindex $_gthread@r{, convenience variable}
2968 The debugger convenience variables @samp{$_thread} and
2969 @samp{$_gthread} contain, respectively, the per-inferior thread number
2970 and the global thread number of the current thread. You may find this
2971 useful in writing breakpoint conditional expressions, command scripts,
2972 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2973 general information on convenience variables.
2975 If @value{GDBN} detects the program is multi-threaded, it augments the
2976 usual message about stopping at a breakpoint with the ID and name of
2977 the thread that hit the breakpoint.
2980 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2983 Likewise when the program receives a signal:
2986 Thread 1 "main" received signal SIGINT, Interrupt.
2990 @kindex info threads
2991 @item info threads @r{[}@var{thread-id-list}@r{]}
2993 Display information about one or more threads. With no arguments
2994 displays information about all threads. You can specify the list of
2995 threads that you want to display using the thread ID list syntax
2996 (@pxref{thread ID lists}).
2998 @value{GDBN} displays for each thread (in this order):
3002 the per-inferior thread number assigned by @value{GDBN}
3005 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3006 option was specified
3009 the target system's thread identifier (@var{systag})
3012 the thread's name, if one is known. A thread can either be named by
3013 the user (see @code{thread name}, below), or, in some cases, by the
3017 the current stack frame summary for that thread
3021 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3022 indicates the current thread.
3026 @c end table here to get a little more width for example
3029 (@value{GDBP}) info threads
3031 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3032 2 process 35 thread 23 0x34e5 in sigpause ()
3033 3 process 35 thread 27 0x34e5 in sigpause ()
3037 If you're debugging multiple inferiors, @value{GDBN} displays thread
3038 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3039 Otherwise, only @var{thread-num} is shown.
3041 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3042 indicating each thread's global thread ID:
3045 (@value{GDBP}) info threads
3046 Id GId Target Id Frame
3047 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3048 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3049 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3050 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3053 On Solaris, you can display more information about user threads with a
3054 Solaris-specific command:
3057 @item maint info sol-threads
3058 @kindex maint info sol-threads
3059 @cindex thread info (Solaris)
3060 Display info on Solaris user threads.
3064 @kindex thread @var{thread-id}
3065 @item thread @var{thread-id}
3066 Make thread ID @var{thread-id} the current thread. The command
3067 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3068 the first field of the @samp{info threads} display, with or without an
3069 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3071 @value{GDBN} responds by displaying the system identifier of the
3072 thread you selected, and its current stack frame summary:
3075 (@value{GDBP}) thread 2
3076 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3077 #0 some_function (ignore=0x0) at example.c:8
3078 8 printf ("hello\n");
3082 As with the @samp{[New @dots{}]} message, the form of the text after
3083 @samp{Switching to} depends on your system's conventions for identifying
3086 @kindex thread apply
3087 @cindex apply command to several threads
3088 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3089 The @code{thread apply} command allows you to apply the named
3090 @var{command} to one or more threads. Specify the threads that you
3091 want affected using the thread ID list syntax (@pxref{thread ID
3092 lists}), or specify @code{all} to apply to all threads. To apply a
3093 command to all threads in descending order, type @kbd{thread apply all
3094 @var{command}}. To apply a command to all threads in ascending order,
3095 type @kbd{thread apply all -ascending @var{command}}.
3099 @cindex name a thread
3100 @item thread name [@var{name}]
3101 This command assigns a name to the current thread. If no argument is
3102 given, any existing user-specified name is removed. The thread name
3103 appears in the @samp{info threads} display.
3105 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3106 determine the name of the thread as given by the OS. On these
3107 systems, a name specified with @samp{thread name} will override the
3108 system-give name, and removing the user-specified name will cause
3109 @value{GDBN} to once again display the system-specified name.
3112 @cindex search for a thread
3113 @item thread find [@var{regexp}]
3114 Search for and display thread ids whose name or @var{systag}
3115 matches the supplied regular expression.
3117 As well as being the complement to the @samp{thread name} command,
3118 this command also allows you to identify a thread by its target
3119 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3123 (@value{GDBN}) thread find 26688
3124 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3125 (@value{GDBN}) info thread 4
3127 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3130 @kindex set print thread-events
3131 @cindex print messages on thread start and exit
3132 @item set print thread-events
3133 @itemx set print thread-events on
3134 @itemx set print thread-events off
3135 The @code{set print thread-events} command allows you to enable or
3136 disable printing of messages when @value{GDBN} notices that new threads have
3137 started or that threads have exited. By default, these messages will
3138 be printed if detection of these events is supported by the target.
3139 Note that these messages cannot be disabled on all targets.
3141 @kindex show print thread-events
3142 @item show print thread-events
3143 Show whether messages will be printed when @value{GDBN} detects that threads
3144 have started and exited.
3147 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3148 more information about how @value{GDBN} behaves when you stop and start
3149 programs with multiple threads.
3151 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3152 watchpoints in programs with multiple threads.
3154 @anchor{set libthread-db-search-path}
3156 @kindex set libthread-db-search-path
3157 @cindex search path for @code{libthread_db}
3158 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3159 If this variable is set, @var{path} is a colon-separated list of
3160 directories @value{GDBN} will use to search for @code{libthread_db}.
3161 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3162 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3163 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3166 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3167 @code{libthread_db} library to obtain information about threads in the
3168 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3169 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3170 specific thread debugging library loading is enabled
3171 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3173 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3174 refers to the default system directories that are
3175 normally searched for loading shared libraries. The @samp{$sdir} entry
3176 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3177 (@pxref{libthread_db.so.1 file}).
3179 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3180 refers to the directory from which @code{libpthread}
3181 was loaded in the inferior process.
3183 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3184 @value{GDBN} attempts to initialize it with the current inferior process.
3185 If this initialization fails (which could happen because of a version
3186 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3187 will unload @code{libthread_db}, and continue with the next directory.
3188 If none of @code{libthread_db} libraries initialize successfully,
3189 @value{GDBN} will issue a warning and thread debugging will be disabled.
3191 Setting @code{libthread-db-search-path} is currently implemented
3192 only on some platforms.
3194 @kindex show libthread-db-search-path
3195 @item show libthread-db-search-path
3196 Display current libthread_db search path.
3198 @kindex set debug libthread-db
3199 @kindex show debug libthread-db
3200 @cindex debugging @code{libthread_db}
3201 @item set debug libthread-db
3202 @itemx show debug libthread-db
3203 Turns on or off display of @code{libthread_db}-related events.
3204 Use @code{1} to enable, @code{0} to disable.
3208 @section Debugging Forks
3210 @cindex fork, debugging programs which call
3211 @cindex multiple processes
3212 @cindex processes, multiple
3213 On most systems, @value{GDBN} has no special support for debugging
3214 programs which create additional processes using the @code{fork}
3215 function. When a program forks, @value{GDBN} will continue to debug the
3216 parent process and the child process will run unimpeded. If you have
3217 set a breakpoint in any code which the child then executes, the child
3218 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3219 will cause it to terminate.
3221 However, if you want to debug the child process there is a workaround
3222 which isn't too painful. Put a call to @code{sleep} in the code which
3223 the child process executes after the fork. It may be useful to sleep
3224 only if a certain environment variable is set, or a certain file exists,
3225 so that the delay need not occur when you don't want to run @value{GDBN}
3226 on the child. While the child is sleeping, use the @code{ps} program to
3227 get its process ID. Then tell @value{GDBN} (a new invocation of
3228 @value{GDBN} if you are also debugging the parent process) to attach to
3229 the child process (@pxref{Attach}). From that point on you can debug
3230 the child process just like any other process which you attached to.
3232 On some systems, @value{GDBN} provides support for debugging programs
3233 that create additional processes using the @code{fork} or @code{vfork}
3234 functions. On @sc{gnu}/Linux platforms, this feature is supported
3235 with kernel version 2.5.46 and later.
3237 The fork debugging commands are supported in native mode and when
3238 connected to @code{gdbserver} in either @code{target remote} mode or
3239 @code{target extended-remote} mode.
3241 By default, when a program forks, @value{GDBN} will continue to debug
3242 the parent process and the child process will run unimpeded.
3244 If you want to follow the child process instead of the parent process,
3245 use the command @w{@code{set follow-fork-mode}}.
3248 @kindex set follow-fork-mode
3249 @item set follow-fork-mode @var{mode}
3250 Set the debugger response to a program call of @code{fork} or
3251 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3252 process. The @var{mode} argument can be:
3256 The original process is debugged after a fork. The child process runs
3257 unimpeded. This is the default.
3260 The new process is debugged after a fork. The parent process runs
3265 @kindex show follow-fork-mode
3266 @item show follow-fork-mode
3267 Display the current debugger response to a @code{fork} or @code{vfork} call.
3270 @cindex debugging multiple processes
3271 On Linux, if you want to debug both the parent and child processes, use the
3272 command @w{@code{set detach-on-fork}}.
3275 @kindex set detach-on-fork
3276 @item set detach-on-fork @var{mode}
3277 Tells gdb whether to detach one of the processes after a fork, or
3278 retain debugger control over them both.
3282 The child process (or parent process, depending on the value of
3283 @code{follow-fork-mode}) will be detached and allowed to run
3284 independently. This is the default.
3287 Both processes will be held under the control of @value{GDBN}.
3288 One process (child or parent, depending on the value of
3289 @code{follow-fork-mode}) is debugged as usual, while the other
3294 @kindex show detach-on-fork
3295 @item show detach-on-fork
3296 Show whether detach-on-fork mode is on/off.
3299 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3300 will retain control of all forked processes (including nested forks).
3301 You can list the forked processes under the control of @value{GDBN} by
3302 using the @w{@code{info inferiors}} command, and switch from one fork
3303 to another by using the @code{inferior} command (@pxref{Inferiors and
3304 Programs, ,Debugging Multiple Inferiors and Programs}).
3306 To quit debugging one of the forked processes, you can either detach
3307 from it by using the @w{@code{detach inferiors}} command (allowing it
3308 to run independently), or kill it using the @w{@code{kill inferiors}}
3309 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3312 If you ask to debug a child process and a @code{vfork} is followed by an
3313 @code{exec}, @value{GDBN} executes the new target up to the first
3314 breakpoint in the new target. If you have a breakpoint set on
3315 @code{main} in your original program, the breakpoint will also be set on
3316 the child process's @code{main}.
3318 On some systems, when a child process is spawned by @code{vfork}, you
3319 cannot debug the child or parent until an @code{exec} call completes.
3321 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3322 call executes, the new target restarts. To restart the parent
3323 process, use the @code{file} command with the parent executable name
3324 as its argument. By default, after an @code{exec} call executes,
3325 @value{GDBN} discards the symbols of the previous executable image.
3326 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3330 @kindex set follow-exec-mode
3331 @item set follow-exec-mode @var{mode}
3333 Set debugger response to a program call of @code{exec}. An
3334 @code{exec} call replaces the program image of a process.
3336 @code{follow-exec-mode} can be:
3340 @value{GDBN} creates a new inferior and rebinds the process to this
3341 new inferior. The program the process was running before the
3342 @code{exec} call can be restarted afterwards by restarting the
3348 (@value{GDBP}) info inferiors
3350 Id Description Executable
3353 process 12020 is executing new program: prog2
3354 Program exited normally.
3355 (@value{GDBP}) info inferiors
3356 Id Description Executable
3362 @value{GDBN} keeps the process bound to the same inferior. The new
3363 executable image replaces the previous executable loaded in the
3364 inferior. Restarting the inferior after the @code{exec} call, with
3365 e.g., the @code{run} command, restarts the executable the process was
3366 running after the @code{exec} call. This is the default mode.
3371 (@value{GDBP}) info inferiors
3372 Id Description Executable
3375 process 12020 is executing new program: prog2
3376 Program exited normally.
3377 (@value{GDBP}) info inferiors
3378 Id Description Executable
3385 @code{follow-exec-mode} is supported in native mode and
3386 @code{target extended-remote} mode.
3388 You can use the @code{catch} command to make @value{GDBN} stop whenever
3389 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3390 Catchpoints, ,Setting Catchpoints}.
3392 @node Checkpoint/Restart
3393 @section Setting a @emph{Bookmark} to Return to Later
3398 @cindex snapshot of a process
3399 @cindex rewind program state
3401 On certain operating systems@footnote{Currently, only
3402 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3403 program's state, called a @dfn{checkpoint}, and come back to it
3406 Returning to a checkpoint effectively undoes everything that has
3407 happened in the program since the @code{checkpoint} was saved. This
3408 includes changes in memory, registers, and even (within some limits)
3409 system state. Effectively, it is like going back in time to the
3410 moment when the checkpoint was saved.
3412 Thus, if you're stepping thru a program and you think you're
3413 getting close to the point where things go wrong, you can save
3414 a checkpoint. Then, if you accidentally go too far and miss
3415 the critical statement, instead of having to restart your program
3416 from the beginning, you can just go back to the checkpoint and
3417 start again from there.
3419 This can be especially useful if it takes a lot of time or
3420 steps to reach the point where you think the bug occurs.
3422 To use the @code{checkpoint}/@code{restart} method of debugging:
3427 Save a snapshot of the debugged program's current execution state.
3428 The @code{checkpoint} command takes no arguments, but each checkpoint
3429 is assigned a small integer id, similar to a breakpoint id.
3431 @kindex info checkpoints
3432 @item info checkpoints
3433 List the checkpoints that have been saved in the current debugging
3434 session. For each checkpoint, the following information will be
3441 @item Source line, or label
3444 @kindex restart @var{checkpoint-id}
3445 @item restart @var{checkpoint-id}
3446 Restore the program state that was saved as checkpoint number
3447 @var{checkpoint-id}. All program variables, registers, stack frames
3448 etc.@: will be returned to the values that they had when the checkpoint
3449 was saved. In essence, gdb will ``wind back the clock'' to the point
3450 in time when the checkpoint was saved.
3452 Note that breakpoints, @value{GDBN} variables, command history etc.
3453 are not affected by restoring a checkpoint. In general, a checkpoint
3454 only restores things that reside in the program being debugged, not in
3457 @kindex delete checkpoint @var{checkpoint-id}
3458 @item delete checkpoint @var{checkpoint-id}
3459 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3463 Returning to a previously saved checkpoint will restore the user state
3464 of the program being debugged, plus a significant subset of the system
3465 (OS) state, including file pointers. It won't ``un-write'' data from
3466 a file, but it will rewind the file pointer to the previous location,
3467 so that the previously written data can be overwritten. For files
3468 opened in read mode, the pointer will also be restored so that the
3469 previously read data can be read again.
3471 Of course, characters that have been sent to a printer (or other
3472 external device) cannot be ``snatched back'', and characters received
3473 from eg.@: a serial device can be removed from internal program buffers,
3474 but they cannot be ``pushed back'' into the serial pipeline, ready to
3475 be received again. Similarly, the actual contents of files that have
3476 been changed cannot be restored (at this time).
3478 However, within those constraints, you actually can ``rewind'' your
3479 program to a previously saved point in time, and begin debugging it
3480 again --- and you can change the course of events so as to debug a
3481 different execution path this time.
3483 @cindex checkpoints and process id
3484 Finally, there is one bit of internal program state that will be
3485 different when you return to a checkpoint --- the program's process
3486 id. Each checkpoint will have a unique process id (or @var{pid}),
3487 and each will be different from the program's original @var{pid}.
3488 If your program has saved a local copy of its process id, this could
3489 potentially pose a problem.
3491 @subsection A Non-obvious Benefit of Using Checkpoints
3493 On some systems such as @sc{gnu}/Linux, address space randomization
3494 is performed on new processes for security reasons. This makes it
3495 difficult or impossible to set a breakpoint, or watchpoint, on an
3496 absolute address if you have to restart the program, since the
3497 absolute location of a symbol will change from one execution to the
3500 A checkpoint, however, is an @emph{identical} copy of a process.
3501 Therefore if you create a checkpoint at (eg.@:) the start of main,
3502 and simply return to that checkpoint instead of restarting the
3503 process, you can avoid the effects of address randomization and
3504 your symbols will all stay in the same place.
3507 @chapter Stopping and Continuing
3509 The principal purposes of using a debugger are so that you can stop your
3510 program before it terminates; or so that, if your program runs into
3511 trouble, you can investigate and find out why.
3513 Inside @value{GDBN}, your program may stop for any of several reasons,
3514 such as a signal, a breakpoint, or reaching a new line after a
3515 @value{GDBN} command such as @code{step}. You may then examine and
3516 change variables, set new breakpoints or remove old ones, and then
3517 continue execution. Usually, the messages shown by @value{GDBN} provide
3518 ample explanation of the status of your program---but you can also
3519 explicitly request this information at any time.
3522 @kindex info program
3524 Display information about the status of your program: whether it is
3525 running or not, what process it is, and why it stopped.
3529 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3530 * Continuing and Stepping:: Resuming execution
3531 * Skipping Over Functions and Files::
3532 Skipping over functions and files
3534 * Thread Stops:: Stopping and starting multi-thread programs
3538 @section Breakpoints, Watchpoints, and Catchpoints
3541 A @dfn{breakpoint} makes your program stop whenever a certain point in
3542 the program is reached. For each breakpoint, you can add conditions to
3543 control in finer detail whether your program stops. You can set
3544 breakpoints with the @code{break} command and its variants (@pxref{Set
3545 Breaks, ,Setting Breakpoints}), to specify the place where your program
3546 should stop by line number, function name or exact address in the
3549 On some systems, you can set breakpoints in shared libraries before
3550 the executable is run.
3553 @cindex data breakpoints
3554 @cindex memory tracing
3555 @cindex breakpoint on memory address
3556 @cindex breakpoint on variable modification
3557 A @dfn{watchpoint} is a special breakpoint that stops your program
3558 when the value of an expression changes. The expression may be a value
3559 of a variable, or it could involve values of one or more variables
3560 combined by operators, such as @samp{a + b}. This is sometimes called
3561 @dfn{data breakpoints}. You must use a different command to set
3562 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3563 from that, you can manage a watchpoint like any other breakpoint: you
3564 enable, disable, and delete both breakpoints and watchpoints using the
3567 You can arrange to have values from your program displayed automatically
3568 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3572 @cindex breakpoint on events
3573 A @dfn{catchpoint} is another special breakpoint that stops your program
3574 when a certain kind of event occurs, such as the throwing of a C@t{++}
3575 exception or the loading of a library. As with watchpoints, you use a
3576 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3577 Catchpoints}), but aside from that, you can manage a catchpoint like any
3578 other breakpoint. (To stop when your program receives a signal, use the
3579 @code{handle} command; see @ref{Signals, ,Signals}.)
3581 @cindex breakpoint numbers
3582 @cindex numbers for breakpoints
3583 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3584 catchpoint when you create it; these numbers are successive integers
3585 starting with one. In many of the commands for controlling various
3586 features of breakpoints you use the breakpoint number to say which
3587 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3588 @dfn{disabled}; if disabled, it has no effect on your program until you
3591 @cindex breakpoint ranges
3592 @cindex breakpoint lists
3593 @cindex ranges of breakpoints
3594 @cindex lists of breakpoints
3595 Some @value{GDBN} commands accept a space-separated list of breakpoints
3596 on which to operate. A list element can be either a single breakpoint number,
3597 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3598 When a breakpoint list is given to a command, all breakpoints in that list
3602 * Set Breaks:: Setting breakpoints
3603 * Set Watchpoints:: Setting watchpoints
3604 * Set Catchpoints:: Setting catchpoints
3605 * Delete Breaks:: Deleting breakpoints
3606 * Disabling:: Disabling breakpoints
3607 * Conditions:: Break conditions
3608 * Break Commands:: Breakpoint command lists
3609 * Dynamic Printf:: Dynamic printf
3610 * Save Breakpoints:: How to save breakpoints in a file
3611 * Static Probe Points:: Listing static probe points
3612 * Error in Breakpoints:: ``Cannot insert breakpoints''
3613 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3617 @subsection Setting Breakpoints
3619 @c FIXME LMB what does GDB do if no code on line of breakpt?
3620 @c consider in particular declaration with/without initialization.
3622 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3625 @kindex b @r{(@code{break})}
3626 @vindex $bpnum@r{, convenience variable}
3627 @cindex latest breakpoint
3628 Breakpoints are set with the @code{break} command (abbreviated
3629 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3630 number of the breakpoint you've set most recently; see @ref{Convenience
3631 Vars,, Convenience Variables}, for a discussion of what you can do with
3632 convenience variables.
3635 @item break @var{location}
3636 Set a breakpoint at the given @var{location}, which can specify a
3637 function name, a line number, or an address of an instruction.
3638 (@xref{Specify Location}, for a list of all the possible ways to
3639 specify a @var{location}.) The breakpoint will stop your program just
3640 before it executes any of the code in the specified @var{location}.
3642 When using source languages that permit overloading of symbols, such as
3643 C@t{++}, a function name may refer to more than one possible place to break.
3644 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3647 It is also possible to insert a breakpoint that will stop the program
3648 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3649 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3652 When called without any arguments, @code{break} sets a breakpoint at
3653 the next instruction to be executed in the selected stack frame
3654 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3655 innermost, this makes your program stop as soon as control
3656 returns to that frame. This is similar to the effect of a
3657 @code{finish} command in the frame inside the selected frame---except
3658 that @code{finish} does not leave an active breakpoint. If you use
3659 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3660 the next time it reaches the current location; this may be useful
3663 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3664 least one instruction has been executed. If it did not do this, you
3665 would be unable to proceed past a breakpoint without first disabling the
3666 breakpoint. This rule applies whether or not the breakpoint already
3667 existed when your program stopped.
3669 @item break @dots{} if @var{cond}
3670 Set a breakpoint with condition @var{cond}; evaluate the expression
3671 @var{cond} each time the breakpoint is reached, and stop only if the
3672 value is nonzero---that is, if @var{cond} evaluates as true.
3673 @samp{@dots{}} stands for one of the possible arguments described
3674 above (or no argument) specifying where to break. @xref{Conditions,
3675 ,Break Conditions}, for more information on breakpoint conditions.
3678 @item tbreak @var{args}
3679 Set a breakpoint enabled only for one stop. The @var{args} are the
3680 same as for the @code{break} command, and the breakpoint is set in the same
3681 way, but the breakpoint is automatically deleted after the first time your
3682 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3685 @cindex hardware breakpoints
3686 @item hbreak @var{args}
3687 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3688 @code{break} command and the breakpoint is set in the same way, but the
3689 breakpoint requires hardware support and some target hardware may not
3690 have this support. The main purpose of this is EPROM/ROM code
3691 debugging, so you can set a breakpoint at an instruction without
3692 changing the instruction. This can be used with the new trap-generation
3693 provided by SPARClite DSU and most x86-based targets. These targets
3694 will generate traps when a program accesses some data or instruction
3695 address that is assigned to the debug registers. However the hardware
3696 breakpoint registers can take a limited number of breakpoints. For
3697 example, on the DSU, only two data breakpoints can be set at a time, and
3698 @value{GDBN} will reject this command if more than two are used. Delete
3699 or disable unused hardware breakpoints before setting new ones
3700 (@pxref{Disabling, ,Disabling Breakpoints}).
3701 @xref{Conditions, ,Break Conditions}.
3702 For remote targets, you can restrict the number of hardware
3703 breakpoints @value{GDBN} will use, see @ref{set remote
3704 hardware-breakpoint-limit}.
3707 @item thbreak @var{args}
3708 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3709 are the same as for the @code{hbreak} command and the breakpoint is set in
3710 the same way. However, like the @code{tbreak} command,
3711 the breakpoint is automatically deleted after the
3712 first time your program stops there. Also, like the @code{hbreak}
3713 command, the breakpoint requires hardware support and some target hardware
3714 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3715 See also @ref{Conditions, ,Break Conditions}.
3718 @cindex regular expression
3719 @cindex breakpoints at functions matching a regexp
3720 @cindex set breakpoints in many functions
3721 @item rbreak @var{regex}
3722 Set breakpoints on all functions matching the regular expression
3723 @var{regex}. This command sets an unconditional breakpoint on all
3724 matches, printing a list of all breakpoints it set. Once these
3725 breakpoints are set, they are treated just like the breakpoints set with
3726 the @code{break} command. You can delete them, disable them, or make
3727 them conditional the same way as any other breakpoint.
3729 The syntax of the regular expression is the standard one used with tools
3730 like @file{grep}. Note that this is different from the syntax used by
3731 shells, so for instance @code{foo*} matches all functions that include
3732 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3733 @code{.*} leading and trailing the regular expression you supply, so to
3734 match only functions that begin with @code{foo}, use @code{^foo}.
3736 @cindex non-member C@t{++} functions, set breakpoint in
3737 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3738 breakpoints on overloaded functions that are not members of any special
3741 @cindex set breakpoints on all functions
3742 The @code{rbreak} command can be used to set breakpoints in
3743 @strong{all} the functions in a program, like this:
3746 (@value{GDBP}) rbreak .
3749 @item rbreak @var{file}:@var{regex}
3750 If @code{rbreak} is called with a filename qualification, it limits
3751 the search for functions matching the given regular expression to the
3752 specified @var{file}. This can be used, for example, to set breakpoints on
3753 every function in a given file:
3756 (@value{GDBP}) rbreak file.c:.
3759 The colon separating the filename qualifier from the regex may
3760 optionally be surrounded by spaces.
3762 @kindex info breakpoints
3763 @cindex @code{$_} and @code{info breakpoints}
3764 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3765 @itemx info break @r{[}@var{list}@dots{}@r{]}
3766 Print a table of all breakpoints, watchpoints, and catchpoints set and
3767 not deleted. Optional argument @var{n} means print information only
3768 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3769 For each breakpoint, following columns are printed:
3772 @item Breakpoint Numbers
3774 Breakpoint, watchpoint, or catchpoint.
3776 Whether the breakpoint is marked to be disabled or deleted when hit.
3777 @item Enabled or Disabled
3778 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3779 that are not enabled.
3781 Where the breakpoint is in your program, as a memory address. For a
3782 pending breakpoint whose address is not yet known, this field will
3783 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3784 library that has the symbol or line referred by breakpoint is loaded.
3785 See below for details. A breakpoint with several locations will
3786 have @samp{<MULTIPLE>} in this field---see below for details.
3788 Where the breakpoint is in the source for your program, as a file and
3789 line number. For a pending breakpoint, the original string passed to
3790 the breakpoint command will be listed as it cannot be resolved until
3791 the appropriate shared library is loaded in the future.
3795 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3796 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3797 @value{GDBN} on the host's side. If it is ``target'', then the condition
3798 is evaluated by the target. The @code{info break} command shows
3799 the condition on the line following the affected breakpoint, together with
3800 its condition evaluation mode in between parentheses.
3802 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3803 allowed to have a condition specified for it. The condition is not parsed for
3804 validity until a shared library is loaded that allows the pending
3805 breakpoint to resolve to a valid location.
3808 @code{info break} with a breakpoint
3809 number @var{n} as argument lists only that breakpoint. The
3810 convenience variable @code{$_} and the default examining-address for
3811 the @code{x} command are set to the address of the last breakpoint
3812 listed (@pxref{Memory, ,Examining Memory}).
3815 @code{info break} displays a count of the number of times the breakpoint
3816 has been hit. This is especially useful in conjunction with the
3817 @code{ignore} command. You can ignore a large number of breakpoint
3818 hits, look at the breakpoint info to see how many times the breakpoint
3819 was hit, and then run again, ignoring one less than that number. This
3820 will get you quickly to the last hit of that breakpoint.
3823 For a breakpoints with an enable count (xref) greater than 1,
3824 @code{info break} also displays that count.
3828 @value{GDBN} allows you to set any number of breakpoints at the same place in
3829 your program. There is nothing silly or meaningless about this. When
3830 the breakpoints are conditional, this is even useful
3831 (@pxref{Conditions, ,Break Conditions}).
3833 @cindex multiple locations, breakpoints
3834 @cindex breakpoints, multiple locations
3835 It is possible that a breakpoint corresponds to several locations
3836 in your program. Examples of this situation are:
3840 Multiple functions in the program may have the same name.
3843 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3844 instances of the function body, used in different cases.
3847 For a C@t{++} template function, a given line in the function can
3848 correspond to any number of instantiations.
3851 For an inlined function, a given source line can correspond to
3852 several places where that function is inlined.
3855 In all those cases, @value{GDBN} will insert a breakpoint at all
3856 the relevant locations.
3858 A breakpoint with multiple locations is displayed in the breakpoint
3859 table using several rows---one header row, followed by one row for
3860 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3861 address column. The rows for individual locations contain the actual
3862 addresses for locations, and show the functions to which those
3863 locations belong. The number column for a location is of the form
3864 @var{breakpoint-number}.@var{location-number}.
3869 Num Type Disp Enb Address What
3870 1 breakpoint keep y <MULTIPLE>
3872 breakpoint already hit 1 time
3873 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3874 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3877 Each location can be individually enabled or disabled by passing
3878 @var{breakpoint-number}.@var{location-number} as argument to the
3879 @code{enable} and @code{disable} commands. Note that you cannot
3880 delete the individual locations from the list, you can only delete the
3881 entire list of locations that belong to their parent breakpoint (with
3882 the @kbd{delete @var{num}} command, where @var{num} is the number of
3883 the parent breakpoint, 1 in the above example). Disabling or enabling
3884 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3885 that belong to that breakpoint.
3887 @cindex pending breakpoints
3888 It's quite common to have a breakpoint inside a shared library.
3889 Shared libraries can be loaded and unloaded explicitly,
3890 and possibly repeatedly, as the program is executed. To support
3891 this use case, @value{GDBN} updates breakpoint locations whenever
3892 any shared library is loaded or unloaded. Typically, you would
3893 set a breakpoint in a shared library at the beginning of your
3894 debugging session, when the library is not loaded, and when the
3895 symbols from the library are not available. When you try to set
3896 breakpoint, @value{GDBN} will ask you if you want to set
3897 a so called @dfn{pending breakpoint}---breakpoint whose address
3898 is not yet resolved.
3900 After the program is run, whenever a new shared library is loaded,
3901 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3902 shared library contains the symbol or line referred to by some
3903 pending breakpoint, that breakpoint is resolved and becomes an
3904 ordinary breakpoint. When a library is unloaded, all breakpoints
3905 that refer to its symbols or source lines become pending again.
3907 This logic works for breakpoints with multiple locations, too. For
3908 example, if you have a breakpoint in a C@t{++} template function, and
3909 a newly loaded shared library has an instantiation of that template,
3910 a new location is added to the list of locations for the breakpoint.
3912 Except for having unresolved address, pending breakpoints do not
3913 differ from regular breakpoints. You can set conditions or commands,
3914 enable and disable them and perform other breakpoint operations.
3916 @value{GDBN} provides some additional commands for controlling what
3917 happens when the @samp{break} command cannot resolve breakpoint
3918 address specification to an address:
3920 @kindex set breakpoint pending
3921 @kindex show breakpoint pending
3923 @item set breakpoint pending auto
3924 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3925 location, it queries you whether a pending breakpoint should be created.
3927 @item set breakpoint pending on
3928 This indicates that an unrecognized breakpoint location should automatically
3929 result in a pending breakpoint being created.
3931 @item set breakpoint pending off
3932 This indicates that pending breakpoints are not to be created. Any
3933 unrecognized breakpoint location results in an error. This setting does
3934 not affect any pending breakpoints previously created.
3936 @item show breakpoint pending
3937 Show the current behavior setting for creating pending breakpoints.
3940 The settings above only affect the @code{break} command and its
3941 variants. Once breakpoint is set, it will be automatically updated
3942 as shared libraries are loaded and unloaded.
3944 @cindex automatic hardware breakpoints
3945 For some targets, @value{GDBN} can automatically decide if hardware or
3946 software breakpoints should be used, depending on whether the
3947 breakpoint address is read-only or read-write. This applies to
3948 breakpoints set with the @code{break} command as well as to internal
3949 breakpoints set by commands like @code{next} and @code{finish}. For
3950 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3953 You can control this automatic behaviour with the following commands:
3955 @kindex set breakpoint auto-hw
3956 @kindex show breakpoint auto-hw
3958 @item set breakpoint auto-hw on
3959 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3960 will try to use the target memory map to decide if software or hardware
3961 breakpoint must be used.
3963 @item set breakpoint auto-hw off
3964 This indicates @value{GDBN} should not automatically select breakpoint
3965 type. If the target provides a memory map, @value{GDBN} will warn when
3966 trying to set software breakpoint at a read-only address.
3969 @value{GDBN} normally implements breakpoints by replacing the program code
3970 at the breakpoint address with a special instruction, which, when
3971 executed, given control to the debugger. By default, the program
3972 code is so modified only when the program is resumed. As soon as
3973 the program stops, @value{GDBN} restores the original instructions. This
3974 behaviour guards against leaving breakpoints inserted in the
3975 target should gdb abrubptly disconnect. However, with slow remote
3976 targets, inserting and removing breakpoint can reduce the performance.
3977 This behavior can be controlled with the following commands::
3979 @kindex set breakpoint always-inserted
3980 @kindex show breakpoint always-inserted
3982 @item set breakpoint always-inserted off
3983 All breakpoints, including newly added by the user, are inserted in
3984 the target only when the target is resumed. All breakpoints are
3985 removed from the target when it stops. This is the default mode.
3987 @item set breakpoint always-inserted on
3988 Causes all breakpoints to be inserted in the target at all times. If
3989 the user adds a new breakpoint, or changes an existing breakpoint, the
3990 breakpoints in the target are updated immediately. A breakpoint is
3991 removed from the target only when breakpoint itself is deleted.
3994 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3995 when a breakpoint breaks. If the condition is true, then the process being
3996 debugged stops, otherwise the process is resumed.
3998 If the target supports evaluating conditions on its end, @value{GDBN} may
3999 download the breakpoint, together with its conditions, to it.
4001 This feature can be controlled via the following commands:
4003 @kindex set breakpoint condition-evaluation
4004 @kindex show breakpoint condition-evaluation
4006 @item set breakpoint condition-evaluation host
4007 This option commands @value{GDBN} to evaluate the breakpoint
4008 conditions on the host's side. Unconditional breakpoints are sent to
4009 the target which in turn receives the triggers and reports them back to GDB
4010 for condition evaluation. This is the standard evaluation mode.
4012 @item set breakpoint condition-evaluation target
4013 This option commands @value{GDBN} to download breakpoint conditions
4014 to the target at the moment of their insertion. The target
4015 is responsible for evaluating the conditional expression and reporting
4016 breakpoint stop events back to @value{GDBN} whenever the condition
4017 is true. Due to limitations of target-side evaluation, some conditions
4018 cannot be evaluated there, e.g., conditions that depend on local data
4019 that is only known to the host. Examples include
4020 conditional expressions involving convenience variables, complex types
4021 that cannot be handled by the agent expression parser and expressions
4022 that are too long to be sent over to the target, specially when the
4023 target is a remote system. In these cases, the conditions will be
4024 evaluated by @value{GDBN}.
4026 @item set breakpoint condition-evaluation auto
4027 This is the default mode. If the target supports evaluating breakpoint
4028 conditions on its end, @value{GDBN} will download breakpoint conditions to
4029 the target (limitations mentioned previously apply). If the target does
4030 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4031 to evaluating all these conditions on the host's side.
4035 @cindex negative breakpoint numbers
4036 @cindex internal @value{GDBN} breakpoints
4037 @value{GDBN} itself sometimes sets breakpoints in your program for
4038 special purposes, such as proper handling of @code{longjmp} (in C
4039 programs). These internal breakpoints are assigned negative numbers,
4040 starting with @code{-1}; @samp{info breakpoints} does not display them.
4041 You can see these breakpoints with the @value{GDBN} maintenance command
4042 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4045 @node Set Watchpoints
4046 @subsection Setting Watchpoints
4048 @cindex setting watchpoints
4049 You can use a watchpoint to stop execution whenever the value of an
4050 expression changes, without having to predict a particular place where
4051 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4052 The expression may be as simple as the value of a single variable, or
4053 as complex as many variables combined by operators. Examples include:
4057 A reference to the value of a single variable.
4060 An address cast to an appropriate data type. For example,
4061 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4062 address (assuming an @code{int} occupies 4 bytes).
4065 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4066 expression can use any operators valid in the program's native
4067 language (@pxref{Languages}).
4070 You can set a watchpoint on an expression even if the expression can
4071 not be evaluated yet. For instance, you can set a watchpoint on
4072 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4073 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4074 the expression produces a valid value. If the expression becomes
4075 valid in some other way than changing a variable (e.g.@: if the memory
4076 pointed to by @samp{*global_ptr} becomes readable as the result of a
4077 @code{malloc} call), @value{GDBN} may not stop until the next time
4078 the expression changes.
4080 @cindex software watchpoints
4081 @cindex hardware watchpoints
4082 Depending on your system, watchpoints may be implemented in software or
4083 hardware. @value{GDBN} does software watchpointing by single-stepping your
4084 program and testing the variable's value each time, which is hundreds of
4085 times slower than normal execution. (But this may still be worth it, to
4086 catch errors where you have no clue what part of your program is the
4089 On some systems, such as most PowerPC or x86-based targets,
4090 @value{GDBN} includes support for hardware watchpoints, which do not
4091 slow down the running of your program.
4095 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4096 Set a watchpoint for an expression. @value{GDBN} will break when the
4097 expression @var{expr} is written into by the program and its value
4098 changes. The simplest (and the most popular) use of this command is
4099 to watch the value of a single variable:
4102 (@value{GDBP}) watch foo
4105 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4106 argument, @value{GDBN} breaks only when the thread identified by
4107 @var{thread-id} changes the value of @var{expr}. If any other threads
4108 change the value of @var{expr}, @value{GDBN} will not break. Note
4109 that watchpoints restricted to a single thread in this way only work
4110 with Hardware Watchpoints.
4112 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4113 (see below). The @code{-location} argument tells @value{GDBN} to
4114 instead watch the memory referred to by @var{expr}. In this case,
4115 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4116 and watch the memory at that address. The type of the result is used
4117 to determine the size of the watched memory. If the expression's
4118 result does not have an address, then @value{GDBN} will print an
4121 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4122 of masked watchpoints, if the current architecture supports this
4123 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4124 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4125 to an address to watch. The mask specifies that some bits of an address
4126 (the bits which are reset in the mask) should be ignored when matching
4127 the address accessed by the inferior against the watchpoint address.
4128 Thus, a masked watchpoint watches many addresses simultaneously---those
4129 addresses whose unmasked bits are identical to the unmasked bits in the
4130 watchpoint address. The @code{mask} argument implies @code{-location}.
4134 (@value{GDBP}) watch foo mask 0xffff00ff
4135 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4139 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4140 Set a watchpoint that will break when the value of @var{expr} is read
4144 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4145 Set a watchpoint that will break when @var{expr} is either read from
4146 or written into by the program.
4148 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4149 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4150 This command prints a list of watchpoints, using the same format as
4151 @code{info break} (@pxref{Set Breaks}).
4154 If you watch for a change in a numerically entered address you need to
4155 dereference it, as the address itself is just a constant number which will
4156 never change. @value{GDBN} refuses to create a watchpoint that watches
4157 a never-changing value:
4160 (@value{GDBP}) watch 0x600850
4161 Cannot watch constant value 0x600850.
4162 (@value{GDBP}) watch *(int *) 0x600850
4163 Watchpoint 1: *(int *) 6293584
4166 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4167 watchpoints execute very quickly, and the debugger reports a change in
4168 value at the exact instruction where the change occurs. If @value{GDBN}
4169 cannot set a hardware watchpoint, it sets a software watchpoint, which
4170 executes more slowly and reports the change in value at the next
4171 @emph{statement}, not the instruction, after the change occurs.
4173 @cindex use only software watchpoints
4174 You can force @value{GDBN} to use only software watchpoints with the
4175 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4176 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4177 the underlying system supports them. (Note that hardware-assisted
4178 watchpoints that were set @emph{before} setting
4179 @code{can-use-hw-watchpoints} to zero will still use the hardware
4180 mechanism of watching expression values.)
4183 @item set can-use-hw-watchpoints
4184 @kindex set can-use-hw-watchpoints
4185 Set whether or not to use hardware watchpoints.
4187 @item show can-use-hw-watchpoints
4188 @kindex show can-use-hw-watchpoints
4189 Show the current mode of using hardware watchpoints.
4192 For remote targets, you can restrict the number of hardware
4193 watchpoints @value{GDBN} will use, see @ref{set remote
4194 hardware-breakpoint-limit}.
4196 When you issue the @code{watch} command, @value{GDBN} reports
4199 Hardware watchpoint @var{num}: @var{expr}
4203 if it was able to set a hardware watchpoint.
4205 Currently, the @code{awatch} and @code{rwatch} commands can only set
4206 hardware watchpoints, because accesses to data that don't change the
4207 value of the watched expression cannot be detected without examining
4208 every instruction as it is being executed, and @value{GDBN} does not do
4209 that currently. If @value{GDBN} finds that it is unable to set a
4210 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4211 will print a message like this:
4214 Expression cannot be implemented with read/access watchpoint.
4217 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4218 data type of the watched expression is wider than what a hardware
4219 watchpoint on the target machine can handle. For example, some systems
4220 can only watch regions that are up to 4 bytes wide; on such systems you
4221 cannot set hardware watchpoints for an expression that yields a
4222 double-precision floating-point number (which is typically 8 bytes
4223 wide). As a work-around, it might be possible to break the large region
4224 into a series of smaller ones and watch them with separate watchpoints.
4226 If you set too many hardware watchpoints, @value{GDBN} might be unable
4227 to insert all of them when you resume the execution of your program.
4228 Since the precise number of active watchpoints is unknown until such
4229 time as the program is about to be resumed, @value{GDBN} might not be
4230 able to warn you about this when you set the watchpoints, and the
4231 warning will be printed only when the program is resumed:
4234 Hardware watchpoint @var{num}: Could not insert watchpoint
4238 If this happens, delete or disable some of the watchpoints.
4240 Watching complex expressions that reference many variables can also
4241 exhaust the resources available for hardware-assisted watchpoints.
4242 That's because @value{GDBN} needs to watch every variable in the
4243 expression with separately allocated resources.
4245 If you call a function interactively using @code{print} or @code{call},
4246 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4247 kind of breakpoint or the call completes.
4249 @value{GDBN} automatically deletes watchpoints that watch local
4250 (automatic) variables, or expressions that involve such variables, when
4251 they go out of scope, that is, when the execution leaves the block in
4252 which these variables were defined. In particular, when the program
4253 being debugged terminates, @emph{all} local variables go out of scope,
4254 and so only watchpoints that watch global variables remain set. If you
4255 rerun the program, you will need to set all such watchpoints again. One
4256 way of doing that would be to set a code breakpoint at the entry to the
4257 @code{main} function and when it breaks, set all the watchpoints.
4259 @cindex watchpoints and threads
4260 @cindex threads and watchpoints
4261 In multi-threaded programs, watchpoints will detect changes to the
4262 watched expression from every thread.
4265 @emph{Warning:} In multi-threaded programs, software watchpoints
4266 have only limited usefulness. If @value{GDBN} creates a software
4267 watchpoint, it can only watch the value of an expression @emph{in a
4268 single thread}. If you are confident that the expression can only
4269 change due to the current thread's activity (and if you are also
4270 confident that no other thread can become current), then you can use
4271 software watchpoints as usual. However, @value{GDBN} may not notice
4272 when a non-current thread's activity changes the expression. (Hardware
4273 watchpoints, in contrast, watch an expression in all threads.)
4276 @xref{set remote hardware-watchpoint-limit}.
4278 @node Set Catchpoints
4279 @subsection Setting Catchpoints
4280 @cindex catchpoints, setting
4281 @cindex exception handlers
4282 @cindex event handling
4284 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4285 kinds of program events, such as C@t{++} exceptions or the loading of a
4286 shared library. Use the @code{catch} command to set a catchpoint.
4290 @item catch @var{event}
4291 Stop when @var{event} occurs. The @var{event} can be any of the following:
4294 @item throw @r{[}@var{regexp}@r{]}
4295 @itemx rethrow @r{[}@var{regexp}@r{]}
4296 @itemx catch @r{[}@var{regexp}@r{]}
4298 @kindex catch rethrow
4300 @cindex stop on C@t{++} exceptions
4301 The throwing, re-throwing, or catching of a C@t{++} exception.
4303 If @var{regexp} is given, then only exceptions whose type matches the
4304 regular expression will be caught.
4306 @vindex $_exception@r{, convenience variable}
4307 The convenience variable @code{$_exception} is available at an
4308 exception-related catchpoint, on some systems. This holds the
4309 exception being thrown.
4311 There are currently some limitations to C@t{++} exception handling in
4316 The support for these commands is system-dependent. Currently, only
4317 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4321 The regular expression feature and the @code{$_exception} convenience
4322 variable rely on the presence of some SDT probes in @code{libstdc++}.
4323 If these probes are not present, then these features cannot be used.
4324 These probes were first available in the GCC 4.8 release, but whether
4325 or not they are available in your GCC also depends on how it was
4329 The @code{$_exception} convenience variable is only valid at the
4330 instruction at which an exception-related catchpoint is set.
4333 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4334 location in the system library which implements runtime exception
4335 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4336 (@pxref{Selection}) to get to your code.
4339 If you call a function interactively, @value{GDBN} normally returns
4340 control to you when the function has finished executing. If the call
4341 raises an exception, however, the call may bypass the mechanism that
4342 returns control to you and cause your program either to abort or to
4343 simply continue running until it hits a breakpoint, catches a signal
4344 that @value{GDBN} is listening for, or exits. This is the case even if
4345 you set a catchpoint for the exception; catchpoints on exceptions are
4346 disabled within interactive calls. @xref{Calling}, for information on
4347 controlling this with @code{set unwind-on-terminating-exception}.
4350 You cannot raise an exception interactively.
4353 You cannot install an exception handler interactively.
4357 @kindex catch exception
4358 @cindex Ada exception catching
4359 @cindex catch Ada exceptions
4360 An Ada exception being raised. If an exception name is specified
4361 at the end of the command (eg @code{catch exception Program_Error}),
4362 the debugger will stop only when this specific exception is raised.
4363 Otherwise, the debugger stops execution when any Ada exception is raised.
4365 When inserting an exception catchpoint on a user-defined exception whose
4366 name is identical to one of the exceptions defined by the language, the
4367 fully qualified name must be used as the exception name. Otherwise,
4368 @value{GDBN} will assume that it should stop on the pre-defined exception
4369 rather than the user-defined one. For instance, assuming an exception
4370 called @code{Constraint_Error} is defined in package @code{Pck}, then
4371 the command to use to catch such exceptions is @kbd{catch exception
4372 Pck.Constraint_Error}.
4374 @item exception unhandled
4375 @kindex catch exception unhandled
4376 An exception that was raised but is not handled by the program.
4379 @kindex catch assert
4380 A failed Ada assertion.
4384 @cindex break on fork/exec
4385 A call to @code{exec}.
4388 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4389 @kindex catch syscall
4390 @cindex break on a system call.
4391 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4392 syscall is a mechanism for application programs to request a service
4393 from the operating system (OS) or one of the OS system services.
4394 @value{GDBN} can catch some or all of the syscalls issued by the
4395 debuggee, and show the related information for each syscall. If no
4396 argument is specified, calls to and returns from all system calls
4399 @var{name} can be any system call name that is valid for the
4400 underlying OS. Just what syscalls are valid depends on the OS. On
4401 GNU and Unix systems, you can find the full list of valid syscall
4402 names on @file{/usr/include/asm/unistd.h}.
4404 @c For MS-Windows, the syscall names and the corresponding numbers
4405 @c can be found, e.g., on this URL:
4406 @c http://www.metasploit.com/users/opcode/syscalls.html
4407 @c but we don't support Windows syscalls yet.
4409 Normally, @value{GDBN} knows in advance which syscalls are valid for
4410 each OS, so you can use the @value{GDBN} command-line completion
4411 facilities (@pxref{Completion,, command completion}) to list the
4414 You may also specify the system call numerically. A syscall's
4415 number is the value passed to the OS's syscall dispatcher to
4416 identify the requested service. When you specify the syscall by its
4417 name, @value{GDBN} uses its database of syscalls to convert the name
4418 into the corresponding numeric code, but using the number directly
4419 may be useful if @value{GDBN}'s database does not have the complete
4420 list of syscalls on your system (e.g., because @value{GDBN} lags
4421 behind the OS upgrades).
4423 You may specify a group of related syscalls to be caught at once using
4424 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4425 instance, on some platforms @value{GDBN} allows you to catch all
4426 network related syscalls, by passing the argument @code{group:network}
4427 to @code{catch syscall}. Note that not all syscall groups are
4428 available in every system. You can use the command completion
4429 facilities (@pxref{Completion,, command completion}) to list the
4430 syscall groups available on your environment.
4432 The example below illustrates how this command works if you don't provide
4436 (@value{GDBP}) catch syscall
4437 Catchpoint 1 (syscall)
4439 Starting program: /tmp/catch-syscall
4441 Catchpoint 1 (call to syscall 'close'), \
4442 0xffffe424 in __kernel_vsyscall ()
4446 Catchpoint 1 (returned from syscall 'close'), \
4447 0xffffe424 in __kernel_vsyscall ()
4451 Here is an example of catching a system call by name:
4454 (@value{GDBP}) catch syscall chroot
4455 Catchpoint 1 (syscall 'chroot' [61])
4457 Starting program: /tmp/catch-syscall
4459 Catchpoint 1 (call to syscall 'chroot'), \
4460 0xffffe424 in __kernel_vsyscall ()
4464 Catchpoint 1 (returned from syscall 'chroot'), \
4465 0xffffe424 in __kernel_vsyscall ()
4469 An example of specifying a system call numerically. In the case
4470 below, the syscall number has a corresponding entry in the XML
4471 file, so @value{GDBN} finds its name and prints it:
4474 (@value{GDBP}) catch syscall 252
4475 Catchpoint 1 (syscall(s) 'exit_group')
4477 Starting program: /tmp/catch-syscall
4479 Catchpoint 1 (call to syscall 'exit_group'), \
4480 0xffffe424 in __kernel_vsyscall ()
4484 Program exited normally.
4488 Here is an example of catching a syscall group:
4491 (@value{GDBP}) catch syscall group:process
4492 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4493 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4494 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4496 Starting program: /tmp/catch-syscall
4498 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4499 from /lib64/ld-linux-x86-64.so.2
4505 However, there can be situations when there is no corresponding name
4506 in XML file for that syscall number. In this case, @value{GDBN} prints
4507 a warning message saying that it was not able to find the syscall name,
4508 but the catchpoint will be set anyway. See the example below:
4511 (@value{GDBP}) catch syscall 764
4512 warning: The number '764' does not represent a known syscall.
4513 Catchpoint 2 (syscall 764)
4517 If you configure @value{GDBN} using the @samp{--without-expat} option,
4518 it will not be able to display syscall names. Also, if your
4519 architecture does not have an XML file describing its system calls,
4520 you will not be able to see the syscall names. It is important to
4521 notice that these two features are used for accessing the syscall
4522 name database. In either case, you will see a warning like this:
4525 (@value{GDBP}) catch syscall
4526 warning: Could not open "syscalls/i386-linux.xml"
4527 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4528 GDB will not be able to display syscall names.
4529 Catchpoint 1 (syscall)
4533 Of course, the file name will change depending on your architecture and system.
4535 Still using the example above, you can also try to catch a syscall by its
4536 number. In this case, you would see something like:
4539 (@value{GDBP}) catch syscall 252
4540 Catchpoint 1 (syscall(s) 252)
4543 Again, in this case @value{GDBN} would not be able to display syscall's names.
4547 A call to @code{fork}.
4551 A call to @code{vfork}.
4553 @item load @r{[}regexp@r{]}
4554 @itemx unload @r{[}regexp@r{]}
4556 @kindex catch unload
4557 The loading or unloading of a shared library. If @var{regexp} is
4558 given, then the catchpoint will stop only if the regular expression
4559 matches one of the affected libraries.
4561 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4562 @kindex catch signal
4563 The delivery of a signal.
4565 With no arguments, this catchpoint will catch any signal that is not
4566 used internally by @value{GDBN}, specifically, all signals except
4567 @samp{SIGTRAP} and @samp{SIGINT}.
4569 With the argument @samp{all}, all signals, including those used by
4570 @value{GDBN}, will be caught. This argument cannot be used with other
4573 Otherwise, the arguments are a list of signal names as given to
4574 @code{handle} (@pxref{Signals}). Only signals specified in this list
4577 One reason that @code{catch signal} can be more useful than
4578 @code{handle} is that you can attach commands and conditions to the
4581 When a signal is caught by a catchpoint, the signal's @code{stop} and
4582 @code{print} settings, as specified by @code{handle}, are ignored.
4583 However, whether the signal is still delivered to the inferior depends
4584 on the @code{pass} setting; this can be changed in the catchpoint's
4589 @item tcatch @var{event}
4591 Set a catchpoint that is enabled only for one stop. The catchpoint is
4592 automatically deleted after the first time the event is caught.
4596 Use the @code{info break} command to list the current catchpoints.
4600 @subsection Deleting Breakpoints
4602 @cindex clearing breakpoints, watchpoints, catchpoints
4603 @cindex deleting breakpoints, watchpoints, catchpoints
4604 It is often necessary to eliminate a breakpoint, watchpoint, or
4605 catchpoint once it has done its job and you no longer want your program
4606 to stop there. This is called @dfn{deleting} the breakpoint. A
4607 breakpoint that has been deleted no longer exists; it is forgotten.
4609 With the @code{clear} command you can delete breakpoints according to
4610 where they are in your program. With the @code{delete} command you can
4611 delete individual breakpoints, watchpoints, or catchpoints by specifying
4612 their breakpoint numbers.
4614 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4615 automatically ignores breakpoints on the first instruction to be executed
4616 when you continue execution without changing the execution address.
4621 Delete any breakpoints at the next instruction to be executed in the
4622 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4623 the innermost frame is selected, this is a good way to delete a
4624 breakpoint where your program just stopped.
4626 @item clear @var{location}
4627 Delete any breakpoints set at the specified @var{location}.
4628 @xref{Specify Location}, for the various forms of @var{location}; the
4629 most useful ones are listed below:
4632 @item clear @var{function}
4633 @itemx clear @var{filename}:@var{function}
4634 Delete any breakpoints set at entry to the named @var{function}.
4636 @item clear @var{linenum}
4637 @itemx clear @var{filename}:@var{linenum}
4638 Delete any breakpoints set at or within the code of the specified
4639 @var{linenum} of the specified @var{filename}.
4642 @cindex delete breakpoints
4644 @kindex d @r{(@code{delete})}
4645 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4646 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4647 list specified as argument. If no argument is specified, delete all
4648 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4649 confirm off}). You can abbreviate this command as @code{d}.
4653 @subsection Disabling Breakpoints
4655 @cindex enable/disable a breakpoint
4656 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4657 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4658 it had been deleted, but remembers the information on the breakpoint so
4659 that you can @dfn{enable} it again later.
4661 You disable and enable breakpoints, watchpoints, and catchpoints with
4662 the @code{enable} and @code{disable} commands, optionally specifying
4663 one or more breakpoint numbers as arguments. Use @code{info break} to
4664 print a list of all breakpoints, watchpoints, and catchpoints if you
4665 do not know which numbers to use.
4667 Disabling and enabling a breakpoint that has multiple locations
4668 affects all of its locations.
4670 A breakpoint, watchpoint, or catchpoint can have any of several
4671 different states of enablement:
4675 Enabled. The breakpoint stops your program. A breakpoint set
4676 with the @code{break} command starts out in this state.
4678 Disabled. The breakpoint has no effect on your program.
4680 Enabled once. The breakpoint stops your program, but then becomes
4683 Enabled for a count. The breakpoint stops your program for the next
4684 N times, then becomes disabled.
4686 Enabled for deletion. The breakpoint stops your program, but
4687 immediately after it does so it is deleted permanently. A breakpoint
4688 set with the @code{tbreak} command starts out in this state.
4691 You can use the following commands to enable or disable breakpoints,
4692 watchpoints, and catchpoints:
4696 @kindex dis @r{(@code{disable})}
4697 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4698 Disable the specified breakpoints---or all breakpoints, if none are
4699 listed. A disabled breakpoint has no effect but is not forgotten. All
4700 options such as ignore-counts, conditions and commands are remembered in
4701 case the breakpoint is enabled again later. You may abbreviate
4702 @code{disable} as @code{dis}.
4705 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4706 Enable the specified breakpoints (or all defined breakpoints). They
4707 become effective once again in stopping your program.
4709 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4710 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4711 of these breakpoints immediately after stopping your program.
4713 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4714 Enable the specified breakpoints temporarily. @value{GDBN} records
4715 @var{count} with each of the specified breakpoints, and decrements a
4716 breakpoint's count when it is hit. When any count reaches 0,
4717 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4718 count (@pxref{Conditions, ,Break Conditions}), that will be
4719 decremented to 0 before @var{count} is affected.
4721 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4722 Enable the specified breakpoints to work once, then die. @value{GDBN}
4723 deletes any of these breakpoints as soon as your program stops there.
4724 Breakpoints set by the @code{tbreak} command start out in this state.
4727 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4728 @c confusing: tbreak is also initially enabled.
4729 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4730 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4731 subsequently, they become disabled or enabled only when you use one of
4732 the commands above. (The command @code{until} can set and delete a
4733 breakpoint of its own, but it does not change the state of your other
4734 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4738 @subsection Break Conditions
4739 @cindex conditional breakpoints
4740 @cindex breakpoint conditions
4742 @c FIXME what is scope of break condition expr? Context where wanted?
4743 @c in particular for a watchpoint?
4744 The simplest sort of breakpoint breaks every time your program reaches a
4745 specified place. You can also specify a @dfn{condition} for a
4746 breakpoint. A condition is just a Boolean expression in your
4747 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4748 a condition evaluates the expression each time your program reaches it,
4749 and your program stops only if the condition is @emph{true}.
4751 This is the converse of using assertions for program validation; in that
4752 situation, you want to stop when the assertion is violated---that is,
4753 when the condition is false. In C, if you want to test an assertion expressed
4754 by the condition @var{assert}, you should set the condition
4755 @samp{! @var{assert}} on the appropriate breakpoint.
4757 Conditions are also accepted for watchpoints; you may not need them,
4758 since a watchpoint is inspecting the value of an expression anyhow---but
4759 it might be simpler, say, to just set a watchpoint on a variable name,
4760 and specify a condition that tests whether the new value is an interesting
4763 Break conditions can have side effects, and may even call functions in
4764 your program. This can be useful, for example, to activate functions
4765 that log program progress, or to use your own print functions to
4766 format special data structures. The effects are completely predictable
4767 unless there is another enabled breakpoint at the same address. (In
4768 that case, @value{GDBN} might see the other breakpoint first and stop your
4769 program without checking the condition of this one.) Note that
4770 breakpoint commands are usually more convenient and flexible than break
4772 purpose of performing side effects when a breakpoint is reached
4773 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4775 Breakpoint conditions can also be evaluated on the target's side if
4776 the target supports it. Instead of evaluating the conditions locally,
4777 @value{GDBN} encodes the expression into an agent expression
4778 (@pxref{Agent Expressions}) suitable for execution on the target,
4779 independently of @value{GDBN}. Global variables become raw memory
4780 locations, locals become stack accesses, and so forth.
4782 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4783 when its condition evaluates to true. This mechanism may provide faster
4784 response times depending on the performance characteristics of the target
4785 since it does not need to keep @value{GDBN} informed about
4786 every breakpoint trigger, even those with false conditions.
4788 Break conditions can be specified when a breakpoint is set, by using
4789 @samp{if} in the arguments to the @code{break} command. @xref{Set
4790 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4791 with the @code{condition} command.
4793 You can also use the @code{if} keyword with the @code{watch} command.
4794 The @code{catch} command does not recognize the @code{if} keyword;
4795 @code{condition} is the only way to impose a further condition on a
4800 @item condition @var{bnum} @var{expression}
4801 Specify @var{expression} as the break condition for breakpoint,
4802 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4803 breakpoint @var{bnum} stops your program only if the value of
4804 @var{expression} is true (nonzero, in C). When you use
4805 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4806 syntactic correctness, and to determine whether symbols in it have
4807 referents in the context of your breakpoint. If @var{expression} uses
4808 symbols not referenced in the context of the breakpoint, @value{GDBN}
4809 prints an error message:
4812 No symbol "foo" in current context.
4817 not actually evaluate @var{expression} at the time the @code{condition}
4818 command (or a command that sets a breakpoint with a condition, like
4819 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4821 @item condition @var{bnum}
4822 Remove the condition from breakpoint number @var{bnum}. It becomes
4823 an ordinary unconditional breakpoint.
4826 @cindex ignore count (of breakpoint)
4827 A special case of a breakpoint condition is to stop only when the
4828 breakpoint has been reached a certain number of times. This is so
4829 useful that there is a special way to do it, using the @dfn{ignore
4830 count} of the breakpoint. Every breakpoint has an ignore count, which
4831 is an integer. Most of the time, the ignore count is zero, and
4832 therefore has no effect. But if your program reaches a breakpoint whose
4833 ignore count is positive, then instead of stopping, it just decrements
4834 the ignore count by one and continues. As a result, if the ignore count
4835 value is @var{n}, the breakpoint does not stop the next @var{n} times
4836 your program reaches it.
4840 @item ignore @var{bnum} @var{count}
4841 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4842 The next @var{count} times the breakpoint is reached, your program's
4843 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4846 To make the breakpoint stop the next time it is reached, specify
4849 When you use @code{continue} to resume execution of your program from a
4850 breakpoint, you can specify an ignore count directly as an argument to
4851 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4852 Stepping,,Continuing and Stepping}.
4854 If a breakpoint has a positive ignore count and a condition, the
4855 condition is not checked. Once the ignore count reaches zero,
4856 @value{GDBN} resumes checking the condition.
4858 You could achieve the effect of the ignore count with a condition such
4859 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4860 is decremented each time. @xref{Convenience Vars, ,Convenience
4864 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4867 @node Break Commands
4868 @subsection Breakpoint Command Lists
4870 @cindex breakpoint commands
4871 You can give any breakpoint (or watchpoint or catchpoint) a series of
4872 commands to execute when your program stops due to that breakpoint. For
4873 example, you might want to print the values of certain expressions, or
4874 enable other breakpoints.
4878 @kindex end@r{ (breakpoint commands)}
4879 @item commands @r{[}@var{list}@dots{}@r{]}
4880 @itemx @dots{} @var{command-list} @dots{}
4882 Specify a list of commands for the given breakpoints. The commands
4883 themselves appear on the following lines. Type a line containing just
4884 @code{end} to terminate the commands.
4886 To remove all commands from a breakpoint, type @code{commands} and
4887 follow it immediately with @code{end}; that is, give no commands.
4889 With no argument, @code{commands} refers to the last breakpoint,
4890 watchpoint, or catchpoint set (not to the breakpoint most recently
4891 encountered). If the most recent breakpoints were set with a single
4892 command, then the @code{commands} will apply to all the breakpoints
4893 set by that command. This applies to breakpoints set by
4894 @code{rbreak}, and also applies when a single @code{break} command
4895 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4899 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4900 disabled within a @var{command-list}.
4902 You can use breakpoint commands to start your program up again. Simply
4903 use the @code{continue} command, or @code{step}, or any other command
4904 that resumes execution.
4906 Any other commands in the command list, after a command that resumes
4907 execution, are ignored. This is because any time you resume execution
4908 (even with a simple @code{next} or @code{step}), you may encounter
4909 another breakpoint---which could have its own command list, leading to
4910 ambiguities about which list to execute.
4913 If the first command you specify in a command list is @code{silent}, the
4914 usual message about stopping at a breakpoint is not printed. This may
4915 be desirable for breakpoints that are to print a specific message and
4916 then continue. If none of the remaining commands print anything, you
4917 see no sign that the breakpoint was reached. @code{silent} is
4918 meaningful only at the beginning of a breakpoint command list.
4920 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4921 print precisely controlled output, and are often useful in silent
4922 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4924 For example, here is how you could use breakpoint commands to print the
4925 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4931 printf "x is %d\n",x
4936 One application for breakpoint commands is to compensate for one bug so
4937 you can test for another. Put a breakpoint just after the erroneous line
4938 of code, give it a condition to detect the case in which something
4939 erroneous has been done, and give it commands to assign correct values
4940 to any variables that need them. End with the @code{continue} command
4941 so that your program does not stop, and start with the @code{silent}
4942 command so that no output is produced. Here is an example:
4953 @node Dynamic Printf
4954 @subsection Dynamic Printf
4956 @cindex dynamic printf
4958 The dynamic printf command @code{dprintf} combines a breakpoint with
4959 formatted printing of your program's data to give you the effect of
4960 inserting @code{printf} calls into your program on-the-fly, without
4961 having to recompile it.
4963 In its most basic form, the output goes to the GDB console. However,
4964 you can set the variable @code{dprintf-style} for alternate handling.
4965 For instance, you can ask to format the output by calling your
4966 program's @code{printf} function. This has the advantage that the
4967 characters go to the program's output device, so they can recorded in
4968 redirects to files and so forth.
4970 If you are doing remote debugging with a stub or agent, you can also
4971 ask to have the printf handled by the remote agent. In addition to
4972 ensuring that the output goes to the remote program's device along
4973 with any other output the program might produce, you can also ask that
4974 the dprintf remain active even after disconnecting from the remote
4975 target. Using the stub/agent is also more efficient, as it can do
4976 everything without needing to communicate with @value{GDBN}.
4980 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4981 Whenever execution reaches @var{location}, print the values of one or
4982 more @var{expressions} under the control of the string @var{template}.
4983 To print several values, separate them with commas.
4985 @item set dprintf-style @var{style}
4986 Set the dprintf output to be handled in one of several different
4987 styles enumerated below. A change of style affects all existing
4988 dynamic printfs immediately. (If you need individual control over the
4989 print commands, simply define normal breakpoints with
4990 explicitly-supplied command lists.)
4994 @kindex dprintf-style gdb
4995 Handle the output using the @value{GDBN} @code{printf} command.
4998 @kindex dprintf-style call
4999 Handle the output by calling a function in your program (normally
5003 @kindex dprintf-style agent
5004 Have the remote debugging agent (such as @code{gdbserver}) handle
5005 the output itself. This style is only available for agents that
5006 support running commands on the target.
5009 @item set dprintf-function @var{function}
5010 Set the function to call if the dprintf style is @code{call}. By
5011 default its value is @code{printf}. You may set it to any expression.
5012 that @value{GDBN} can evaluate to a function, as per the @code{call}
5015 @item set dprintf-channel @var{channel}
5016 Set a ``channel'' for dprintf. If set to a non-empty value,
5017 @value{GDBN} will evaluate it as an expression and pass the result as
5018 a first argument to the @code{dprintf-function}, in the manner of
5019 @code{fprintf} and similar functions. Otherwise, the dprintf format
5020 string will be the first argument, in the manner of @code{printf}.
5022 As an example, if you wanted @code{dprintf} output to go to a logfile
5023 that is a standard I/O stream assigned to the variable @code{mylog},
5024 you could do the following:
5027 (gdb) set dprintf-style call
5028 (gdb) set dprintf-function fprintf
5029 (gdb) set dprintf-channel mylog
5030 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5031 Dprintf 1 at 0x123456: file main.c, line 25.
5033 1 dprintf keep y 0x00123456 in main at main.c:25
5034 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5039 Note that the @code{info break} displays the dynamic printf commands
5040 as normal breakpoint commands; you can thus easily see the effect of
5041 the variable settings.
5043 @item set disconnected-dprintf on
5044 @itemx set disconnected-dprintf off
5045 @kindex set disconnected-dprintf
5046 Choose whether @code{dprintf} commands should continue to run if
5047 @value{GDBN} has disconnected from the target. This only applies
5048 if the @code{dprintf-style} is @code{agent}.
5050 @item show disconnected-dprintf off
5051 @kindex show disconnected-dprintf
5052 Show the current choice for disconnected @code{dprintf}.
5056 @value{GDBN} does not check the validity of function and channel,
5057 relying on you to supply values that are meaningful for the contexts
5058 in which they are being used. For instance, the function and channel
5059 may be the values of local variables, but if that is the case, then
5060 all enabled dynamic prints must be at locations within the scope of
5061 those locals. If evaluation fails, @value{GDBN} will report an error.
5063 @node Save Breakpoints
5064 @subsection How to save breakpoints to a file
5066 To save breakpoint definitions to a file use the @w{@code{save
5067 breakpoints}} command.
5070 @kindex save breakpoints
5071 @cindex save breakpoints to a file for future sessions
5072 @item save breakpoints [@var{filename}]
5073 This command saves all current breakpoint definitions together with
5074 their commands and ignore counts, into a file @file{@var{filename}}
5075 suitable for use in a later debugging session. This includes all
5076 types of breakpoints (breakpoints, watchpoints, catchpoints,
5077 tracepoints). To read the saved breakpoint definitions, use the
5078 @code{source} command (@pxref{Command Files}). Note that watchpoints
5079 with expressions involving local variables may fail to be recreated
5080 because it may not be possible to access the context where the
5081 watchpoint is valid anymore. Because the saved breakpoint definitions
5082 are simply a sequence of @value{GDBN} commands that recreate the
5083 breakpoints, you can edit the file in your favorite editing program,
5084 and remove the breakpoint definitions you're not interested in, or
5085 that can no longer be recreated.
5088 @node Static Probe Points
5089 @subsection Static Probe Points
5091 @cindex static probe point, SystemTap
5092 @cindex static probe point, DTrace
5093 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5094 for Statically Defined Tracing, and the probes are designed to have a tiny
5095 runtime code and data footprint, and no dynamic relocations.
5097 Currently, the following types of probes are supported on
5098 ELF-compatible systems:
5102 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5103 @acronym{SDT} probes@footnote{See
5104 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5105 for more information on how to add @code{SystemTap} @acronym{SDT}
5106 probes in your applications.}. @code{SystemTap} probes are usable
5107 from assembly, C and C@t{++} languages@footnote{See
5108 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5109 for a good reference on how the @acronym{SDT} probes are implemented.}.
5111 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5112 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5116 @cindex semaphores on static probe points
5117 Some @code{SystemTap} probes have an associated semaphore variable;
5118 for instance, this happens automatically if you defined your probe
5119 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5120 @value{GDBN} will automatically enable it when you specify a
5121 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5122 breakpoint at a probe's location by some other method (e.g.,
5123 @code{break file:line}), then @value{GDBN} will not automatically set
5124 the semaphore. @code{DTrace} probes do not support semaphores.
5126 You can examine the available static static probes using @code{info
5127 probes}, with optional arguments:
5131 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5132 If given, @var{type} is either @code{stap} for listing
5133 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5134 probes. If omitted all probes are listed regardless of their types.
5136 If given, @var{provider} is a regular expression used to match against provider
5137 names when selecting which probes to list. If omitted, probes by all
5138 probes from all providers are listed.
5140 If given, @var{name} is a regular expression to match against probe names
5141 when selecting which probes to list. If omitted, probe names are not
5142 considered when deciding whether to display them.
5144 If given, @var{objfile} is a regular expression used to select which
5145 object files (executable or shared libraries) to examine. If not
5146 given, all object files are considered.
5148 @item info probes all
5149 List the available static probes, from all types.
5152 @cindex enabling and disabling probes
5153 Some probe points can be enabled and/or disabled. The effect of
5154 enabling or disabling a probe depends on the type of probe being
5155 handled. Some @code{DTrace} probes can be enabled or
5156 disabled, but @code{SystemTap} probes cannot be disabled.
5158 You can enable (or disable) one or more probes using the following
5159 commands, with optional arguments:
5162 @kindex enable probes
5163 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5164 If given, @var{provider} is a regular expression used to match against
5165 provider names when selecting which probes to enable. If omitted,
5166 all probes from all providers are enabled.
5168 If given, @var{name} is a regular expression to match against probe
5169 names when selecting which probes to enable. If omitted, probe names
5170 are not considered when deciding whether to enable them.
5172 If given, @var{objfile} is a regular expression used to select which
5173 object files (executable or shared libraries) to examine. If not
5174 given, all object files are considered.
5176 @kindex disable probes
5177 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5178 See the @code{enable probes} command above for a description of the
5179 optional arguments accepted by this command.
5182 @vindex $_probe_arg@r{, convenience variable}
5183 A probe may specify up to twelve arguments. These are available at the
5184 point at which the probe is defined---that is, when the current PC is
5185 at the probe's location. The arguments are available using the
5186 convenience variables (@pxref{Convenience Vars})
5187 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5188 probes each probe argument is an integer of the appropriate size;
5189 types are not preserved. In @code{DTrace} probes types are preserved
5190 provided that they are recognized as such by @value{GDBN}; otherwise
5191 the value of the probe argument will be a long integer. The
5192 convenience variable @code{$_probe_argc} holds the number of arguments
5193 at the current probe point.
5195 These variables are always available, but attempts to access them at
5196 any location other than a probe point will cause @value{GDBN} to give
5200 @c @ifclear BARETARGET
5201 @node Error in Breakpoints
5202 @subsection ``Cannot insert breakpoints''
5204 If you request too many active hardware-assisted breakpoints and
5205 watchpoints, you will see this error message:
5207 @c FIXME: the precise wording of this message may change; the relevant
5208 @c source change is not committed yet (Sep 3, 1999).
5210 Stopped; cannot insert breakpoints.
5211 You may have requested too many hardware breakpoints and watchpoints.
5215 This message is printed when you attempt to resume the program, since
5216 only then @value{GDBN} knows exactly how many hardware breakpoints and
5217 watchpoints it needs to insert.
5219 When this message is printed, you need to disable or remove some of the
5220 hardware-assisted breakpoints and watchpoints, and then continue.
5222 @node Breakpoint-related Warnings
5223 @subsection ``Breakpoint address adjusted...''
5224 @cindex breakpoint address adjusted
5226 Some processor architectures place constraints on the addresses at
5227 which breakpoints may be placed. For architectures thus constrained,
5228 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5229 with the constraints dictated by the architecture.
5231 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5232 a VLIW architecture in which a number of RISC-like instructions may be
5233 bundled together for parallel execution. The FR-V architecture
5234 constrains the location of a breakpoint instruction within such a
5235 bundle to the instruction with the lowest address. @value{GDBN}
5236 honors this constraint by adjusting a breakpoint's address to the
5237 first in the bundle.
5239 It is not uncommon for optimized code to have bundles which contain
5240 instructions from different source statements, thus it may happen that
5241 a breakpoint's address will be adjusted from one source statement to
5242 another. Since this adjustment may significantly alter @value{GDBN}'s
5243 breakpoint related behavior from what the user expects, a warning is
5244 printed when the breakpoint is first set and also when the breakpoint
5247 A warning like the one below is printed when setting a breakpoint
5248 that's been subject to address adjustment:
5251 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5254 Such warnings are printed both for user settable and @value{GDBN}'s
5255 internal breakpoints. If you see one of these warnings, you should
5256 verify that a breakpoint set at the adjusted address will have the
5257 desired affect. If not, the breakpoint in question may be removed and
5258 other breakpoints may be set which will have the desired behavior.
5259 E.g., it may be sufficient to place the breakpoint at a later
5260 instruction. A conditional breakpoint may also be useful in some
5261 cases to prevent the breakpoint from triggering too often.
5263 @value{GDBN} will also issue a warning when stopping at one of these
5264 adjusted breakpoints:
5267 warning: Breakpoint 1 address previously adjusted from 0x00010414
5271 When this warning is encountered, it may be too late to take remedial
5272 action except in cases where the breakpoint is hit earlier or more
5273 frequently than expected.
5275 @node Continuing and Stepping
5276 @section Continuing and Stepping
5280 @cindex resuming execution
5281 @dfn{Continuing} means resuming program execution until your program
5282 completes normally. In contrast, @dfn{stepping} means executing just
5283 one more ``step'' of your program, where ``step'' may mean either one
5284 line of source code, or one machine instruction (depending on what
5285 particular command you use). Either when continuing or when stepping,
5286 your program may stop even sooner, due to a breakpoint or a signal. (If
5287 it stops due to a signal, you may want to use @code{handle}, or use
5288 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5289 or you may step into the signal's handler (@pxref{stepping and signal
5294 @kindex c @r{(@code{continue})}
5295 @kindex fg @r{(resume foreground execution)}
5296 @item continue @r{[}@var{ignore-count}@r{]}
5297 @itemx c @r{[}@var{ignore-count}@r{]}
5298 @itemx fg @r{[}@var{ignore-count}@r{]}
5299 Resume program execution, at the address where your program last stopped;
5300 any breakpoints set at that address are bypassed. The optional argument
5301 @var{ignore-count} allows you to specify a further number of times to
5302 ignore a breakpoint at this location; its effect is like that of
5303 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5305 The argument @var{ignore-count} is meaningful only when your program
5306 stopped due to a breakpoint. At other times, the argument to
5307 @code{continue} is ignored.
5309 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5310 debugged program is deemed to be the foreground program) are provided
5311 purely for convenience, and have exactly the same behavior as
5315 To resume execution at a different place, you can use @code{return}
5316 (@pxref{Returning, ,Returning from a Function}) to go back to the
5317 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5318 Different Address}) to go to an arbitrary location in your program.
5320 A typical technique for using stepping is to set a breakpoint
5321 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5322 beginning of the function or the section of your program where a problem
5323 is believed to lie, run your program until it stops at that breakpoint,
5324 and then step through the suspect area, examining the variables that are
5325 interesting, until you see the problem happen.
5329 @kindex s @r{(@code{step})}
5331 Continue running your program until control reaches a different source
5332 line, then stop it and return control to @value{GDBN}. This command is
5333 abbreviated @code{s}.
5336 @c "without debugging information" is imprecise; actually "without line
5337 @c numbers in the debugging information". (gcc -g1 has debugging info but
5338 @c not line numbers). But it seems complex to try to make that
5339 @c distinction here.
5340 @emph{Warning:} If you use the @code{step} command while control is
5341 within a function that was compiled without debugging information,
5342 execution proceeds until control reaches a function that does have
5343 debugging information. Likewise, it will not step into a function which
5344 is compiled without debugging information. To step through functions
5345 without debugging information, use the @code{stepi} command, described
5349 The @code{step} command only stops at the first instruction of a source
5350 line. This prevents the multiple stops that could otherwise occur in
5351 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5352 to stop if a function that has debugging information is called within
5353 the line. In other words, @code{step} @emph{steps inside} any functions
5354 called within the line.
5356 Also, the @code{step} command only enters a function if there is line
5357 number information for the function. Otherwise it acts like the
5358 @code{next} command. This avoids problems when using @code{cc -gl}
5359 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5360 was any debugging information about the routine.
5362 @item step @var{count}
5363 Continue running as in @code{step}, but do so @var{count} times. If a
5364 breakpoint is reached, or a signal not related to stepping occurs before
5365 @var{count} steps, stepping stops right away.
5368 @kindex n @r{(@code{next})}
5369 @item next @r{[}@var{count}@r{]}
5370 Continue to the next source line in the current (innermost) stack frame.
5371 This is similar to @code{step}, but function calls that appear within
5372 the line of code are executed without stopping. Execution stops when
5373 control reaches a different line of code at the original stack level
5374 that was executing when you gave the @code{next} command. This command
5375 is abbreviated @code{n}.
5377 An argument @var{count} is a repeat count, as for @code{step}.
5380 @c FIX ME!! Do we delete this, or is there a way it fits in with
5381 @c the following paragraph? --- Vctoria
5383 @c @code{next} within a function that lacks debugging information acts like
5384 @c @code{step}, but any function calls appearing within the code of the
5385 @c function are executed without stopping.
5387 The @code{next} command only stops at the first instruction of a
5388 source line. This prevents multiple stops that could otherwise occur in
5389 @code{switch} statements, @code{for} loops, etc.
5391 @kindex set step-mode
5393 @cindex functions without line info, and stepping
5394 @cindex stepping into functions with no line info
5395 @itemx set step-mode on
5396 The @code{set step-mode on} command causes the @code{step} command to
5397 stop at the first instruction of a function which contains no debug line
5398 information rather than stepping over it.
5400 This is useful in cases where you may be interested in inspecting the
5401 machine instructions of a function which has no symbolic info and do not
5402 want @value{GDBN} to automatically skip over this function.
5404 @item set step-mode off
5405 Causes the @code{step} command to step over any functions which contains no
5406 debug information. This is the default.
5408 @item show step-mode
5409 Show whether @value{GDBN} will stop in or step over functions without
5410 source line debug information.
5413 @kindex fin @r{(@code{finish})}
5415 Continue running until just after function in the selected stack frame
5416 returns. Print the returned value (if any). This command can be
5417 abbreviated as @code{fin}.
5419 Contrast this with the @code{return} command (@pxref{Returning,
5420 ,Returning from a Function}).
5423 @kindex u @r{(@code{until})}
5424 @cindex run until specified location
5427 Continue running until a source line past the current line, in the
5428 current stack frame, is reached. This command is used to avoid single
5429 stepping through a loop more than once. It is like the @code{next}
5430 command, except that when @code{until} encounters a jump, it
5431 automatically continues execution until the program counter is greater
5432 than the address of the jump.
5434 This means that when you reach the end of a loop after single stepping
5435 though it, @code{until} makes your program continue execution until it
5436 exits the loop. In contrast, a @code{next} command at the end of a loop
5437 simply steps back to the beginning of the loop, which forces you to step
5438 through the next iteration.
5440 @code{until} always stops your program if it attempts to exit the current
5443 @code{until} may produce somewhat counterintuitive results if the order
5444 of machine code does not match the order of the source lines. For
5445 example, in the following excerpt from a debugging session, the @code{f}
5446 (@code{frame}) command shows that execution is stopped at line
5447 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5451 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5453 (@value{GDBP}) until
5454 195 for ( ; argc > 0; NEXTARG) @{
5457 This happened because, for execution efficiency, the compiler had
5458 generated code for the loop closure test at the end, rather than the
5459 start, of the loop---even though the test in a C @code{for}-loop is
5460 written before the body of the loop. The @code{until} command appeared
5461 to step back to the beginning of the loop when it advanced to this
5462 expression; however, it has not really gone to an earlier
5463 statement---not in terms of the actual machine code.
5465 @code{until} with no argument works by means of single
5466 instruction stepping, and hence is slower than @code{until} with an
5469 @item until @var{location}
5470 @itemx u @var{location}
5471 Continue running your program until either the specified @var{location} is
5472 reached, or the current stack frame returns. The location is any of
5473 the forms described in @ref{Specify Location}.
5474 This form of the command uses temporary breakpoints, and
5475 hence is quicker than @code{until} without an argument. The specified
5476 location is actually reached only if it is in the current frame. This
5477 implies that @code{until} can be used to skip over recursive function
5478 invocations. For instance in the code below, if the current location is
5479 line @code{96}, issuing @code{until 99} will execute the program up to
5480 line @code{99} in the same invocation of factorial, i.e., after the inner
5481 invocations have returned.
5484 94 int factorial (int value)
5486 96 if (value > 1) @{
5487 97 value *= factorial (value - 1);
5494 @kindex advance @var{location}
5495 @item advance @var{location}
5496 Continue running the program up to the given @var{location}. An argument is
5497 required, which should be of one of the forms described in
5498 @ref{Specify Location}.
5499 Execution will also stop upon exit from the current stack
5500 frame. This command is similar to @code{until}, but @code{advance} will
5501 not skip over recursive function calls, and the target location doesn't
5502 have to be in the same frame as the current one.
5506 @kindex si @r{(@code{stepi})}
5508 @itemx stepi @var{arg}
5510 Execute one machine instruction, then stop and return to the debugger.
5512 It is often useful to do @samp{display/i $pc} when stepping by machine
5513 instructions. This makes @value{GDBN} automatically display the next
5514 instruction to be executed, each time your program stops. @xref{Auto
5515 Display,, Automatic Display}.
5517 An argument is a repeat count, as in @code{step}.
5521 @kindex ni @r{(@code{nexti})}
5523 @itemx nexti @var{arg}
5525 Execute one machine instruction, but if it is a function call,
5526 proceed until the function returns.
5528 An argument is a repeat count, as in @code{next}.
5532 @anchor{range stepping}
5533 @cindex range stepping
5534 @cindex target-assisted range stepping
5535 By default, and if available, @value{GDBN} makes use of
5536 target-assisted @dfn{range stepping}. In other words, whenever you
5537 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5538 tells the target to step the corresponding range of instruction
5539 addresses instead of issuing multiple single-steps. This speeds up
5540 line stepping, particularly for remote targets. Ideally, there should
5541 be no reason you would want to turn range stepping off. However, it's
5542 possible that a bug in the debug info, a bug in the remote stub (for
5543 remote targets), or even a bug in @value{GDBN} could make line
5544 stepping behave incorrectly when target-assisted range stepping is
5545 enabled. You can use the following command to turn off range stepping
5549 @kindex set range-stepping
5550 @kindex show range-stepping
5551 @item set range-stepping
5552 @itemx show range-stepping
5553 Control whether range stepping is enabled.
5555 If @code{on}, and the target supports it, @value{GDBN} tells the
5556 target to step a range of addresses itself, instead of issuing
5557 multiple single-steps. If @code{off}, @value{GDBN} always issues
5558 single-steps, even if range stepping is supported by the target. The
5559 default is @code{on}.
5563 @node Skipping Over Functions and Files
5564 @section Skipping Over Functions and Files
5565 @cindex skipping over functions and files
5567 The program you are debugging may contain some functions which are
5568 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5569 skip a function, all functions in a file or a particular function in
5570 a particular file when stepping.
5572 For example, consider the following C function:
5583 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5584 are not interested in stepping through @code{boring}. If you run @code{step}
5585 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5586 step over both @code{foo} and @code{boring}!
5588 One solution is to @code{step} into @code{boring} and use the @code{finish}
5589 command to immediately exit it. But this can become tedious if @code{boring}
5590 is called from many places.
5592 A more flexible solution is to execute @kbd{skip boring}. This instructs
5593 @value{GDBN} never to step into @code{boring}. Now when you execute
5594 @code{step} at line 103, you'll step over @code{boring} and directly into
5597 Functions may be skipped by providing either a function name, linespec
5598 (@pxref{Specify Location}), regular expression that matches the function's
5599 name, file name or a @code{glob}-style pattern that matches the file name.
5601 On Posix systems the form of the regular expression is
5602 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5603 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5604 expression is whatever is provided by the @code{regcomp} function of
5605 the underlying system.
5606 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5607 description of @code{glob}-style patterns.
5611 @item skip @r{[}@var{options}@r{]}
5612 The basic form of the @code{skip} command takes zero or more options
5613 that specify what to skip.
5614 The @var{options} argument is any useful combination of the following:
5617 @item -file @var{file}
5618 @itemx -fi @var{file}
5619 Functions in @var{file} will be skipped over when stepping.
5621 @item -gfile @var{file-glob-pattern}
5622 @itemx -gfi @var{file-glob-pattern}
5623 @cindex skipping over files via glob-style patterns
5624 Functions in files matching @var{file-glob-pattern} will be skipped
5628 (gdb) skip -gfi utils/*.c
5631 @item -function @var{linespec}
5632 @itemx -fu @var{linespec}
5633 Functions named by @var{linespec} or the function containing the line
5634 named by @var{linespec} will be skipped over when stepping.
5635 @xref{Specify Location}.
5637 @item -rfunction @var{regexp}
5638 @itemx -rfu @var{regexp}
5639 @cindex skipping over functions via regular expressions
5640 Functions whose name matches @var{regexp} will be skipped over when stepping.
5642 This form is useful for complex function names.
5643 For example, there is generally no need to step into C@t{++} @code{std::string}
5644 constructors or destructors. Plus with C@t{++} templates it can be hard to
5645 write out the full name of the function, and often it doesn't matter what
5646 the template arguments are. Specifying the function to be skipped as a
5647 regular expression makes this easier.
5650 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5653 If you want to skip every templated C@t{++} constructor and destructor
5654 in the @code{std} namespace you can do:
5657 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5661 If no options are specified, the function you're currently debugging
5664 @kindex skip function
5665 @item skip function @r{[}@var{linespec}@r{]}
5666 After running this command, the function named by @var{linespec} or the
5667 function containing the line named by @var{linespec} will be skipped over when
5668 stepping. @xref{Specify Location}.
5670 If you do not specify @var{linespec}, the function you're currently debugging
5673 (If you have a function called @code{file} that you want to skip, use
5674 @kbd{skip function file}.)
5677 @item skip file @r{[}@var{filename}@r{]}
5678 After running this command, any function whose source lives in @var{filename}
5679 will be skipped over when stepping.
5682 (gdb) skip file boring.c
5683 File boring.c will be skipped when stepping.
5686 If you do not specify @var{filename}, functions whose source lives in the file
5687 you're currently debugging will be skipped.
5690 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5691 These are the commands for managing your list of skips:
5695 @item info skip @r{[}@var{range}@r{]}
5696 Print details about the specified skip(s). If @var{range} is not specified,
5697 print a table with details about all functions and files marked for skipping.
5698 @code{info skip} prints the following information about each skip:
5702 A number identifying this skip.
5703 @item Enabled or Disabled
5704 Enabled skips are marked with @samp{y}.
5705 Disabled skips are marked with @samp{n}.
5707 If the file name is a @samp{glob} pattern this is @samp{y}.
5708 Otherwise it is @samp{n}.
5710 The name or @samp{glob} pattern of the file to be skipped.
5711 If no file is specified this is @samp{<none>}.
5713 If the function name is a @samp{regular expression} this is @samp{y}.
5714 Otherwise it is @samp{n}.
5716 The name or regular expression of the function to skip.
5717 If no function is specified this is @samp{<none>}.
5721 @item skip delete @r{[}@var{range}@r{]}
5722 Delete the specified skip(s). If @var{range} is not specified, delete all
5726 @item skip enable @r{[}@var{range}@r{]}
5727 Enable the specified skip(s). If @var{range} is not specified, enable all
5730 @kindex skip disable
5731 @item skip disable @r{[}@var{range}@r{]}
5732 Disable the specified skip(s). If @var{range} is not specified, disable all
5741 A signal is an asynchronous event that can happen in a program. The
5742 operating system defines the possible kinds of signals, and gives each
5743 kind a name and a number. For example, in Unix @code{SIGINT} is the
5744 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5745 @code{SIGSEGV} is the signal a program gets from referencing a place in
5746 memory far away from all the areas in use; @code{SIGALRM} occurs when
5747 the alarm clock timer goes off (which happens only if your program has
5748 requested an alarm).
5750 @cindex fatal signals
5751 Some signals, including @code{SIGALRM}, are a normal part of the
5752 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5753 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5754 program has not specified in advance some other way to handle the signal.
5755 @code{SIGINT} does not indicate an error in your program, but it is normally
5756 fatal so it can carry out the purpose of the interrupt: to kill the program.
5758 @value{GDBN} has the ability to detect any occurrence of a signal in your
5759 program. You can tell @value{GDBN} in advance what to do for each kind of
5762 @cindex handling signals
5763 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5764 @code{SIGALRM} be silently passed to your program
5765 (so as not to interfere with their role in the program's functioning)
5766 but to stop your program immediately whenever an error signal happens.
5767 You can change these settings with the @code{handle} command.
5770 @kindex info signals
5774 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5775 handle each one. You can use this to see the signal numbers of all
5776 the defined types of signals.
5778 @item info signals @var{sig}
5779 Similar, but print information only about the specified signal number.
5781 @code{info handle} is an alias for @code{info signals}.
5783 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5784 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5785 for details about this command.
5788 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5789 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5790 can be the number of a signal or its name (with or without the
5791 @samp{SIG} at the beginning); a list of signal numbers of the form
5792 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5793 known signals. Optional arguments @var{keywords}, described below,
5794 say what change to make.
5798 The keywords allowed by the @code{handle} command can be abbreviated.
5799 Their full names are:
5803 @value{GDBN} should not stop your program when this signal happens. It may
5804 still print a message telling you that the signal has come in.
5807 @value{GDBN} should stop your program when this signal happens. This implies
5808 the @code{print} keyword as well.
5811 @value{GDBN} should print a message when this signal happens.
5814 @value{GDBN} should not mention the occurrence of the signal at all. This
5815 implies the @code{nostop} keyword as well.
5819 @value{GDBN} should allow your program to see this signal; your program
5820 can handle the signal, or else it may terminate if the signal is fatal
5821 and not handled. @code{pass} and @code{noignore} are synonyms.
5825 @value{GDBN} should not allow your program to see this signal.
5826 @code{nopass} and @code{ignore} are synonyms.
5830 When a signal stops your program, the signal is not visible to the
5832 continue. Your program sees the signal then, if @code{pass} is in
5833 effect for the signal in question @emph{at that time}. In other words,
5834 after @value{GDBN} reports a signal, you can use the @code{handle}
5835 command with @code{pass} or @code{nopass} to control whether your
5836 program sees that signal when you continue.
5838 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5839 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5840 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5843 You can also use the @code{signal} command to prevent your program from
5844 seeing a signal, or cause it to see a signal it normally would not see,
5845 or to give it any signal at any time. For example, if your program stopped
5846 due to some sort of memory reference error, you might store correct
5847 values into the erroneous variables and continue, hoping to see more
5848 execution; but your program would probably terminate immediately as
5849 a result of the fatal signal once it saw the signal. To prevent this,
5850 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5853 @cindex stepping and signal handlers
5854 @anchor{stepping and signal handlers}
5856 @value{GDBN} optimizes for stepping the mainline code. If a signal
5857 that has @code{handle nostop} and @code{handle pass} set arrives while
5858 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5859 in progress, @value{GDBN} lets the signal handler run and then resumes
5860 stepping the mainline code once the signal handler returns. In other
5861 words, @value{GDBN} steps over the signal handler. This prevents
5862 signals that you've specified as not interesting (with @code{handle
5863 nostop}) from changing the focus of debugging unexpectedly. Note that
5864 the signal handler itself may still hit a breakpoint, stop for another
5865 signal that has @code{handle stop} in effect, or for any other event
5866 that normally results in stopping the stepping command sooner. Also
5867 note that @value{GDBN} still informs you that the program received a
5868 signal if @code{handle print} is set.
5870 @anchor{stepping into signal handlers}
5872 If you set @code{handle pass} for a signal, and your program sets up a
5873 handler for it, then issuing a stepping command, such as @code{step}
5874 or @code{stepi}, when your program is stopped due to the signal will
5875 step @emph{into} the signal handler (if the target supports that).
5877 Likewise, if you use the @code{queue-signal} command to queue a signal
5878 to be delivered to the current thread when execution of the thread
5879 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5880 stepping command will step into the signal handler.
5882 Here's an example, using @code{stepi} to step to the first instruction
5883 of @code{SIGUSR1}'s handler:
5886 (@value{GDBP}) handle SIGUSR1
5887 Signal Stop Print Pass to program Description
5888 SIGUSR1 Yes Yes Yes User defined signal 1
5892 Program received signal SIGUSR1, User defined signal 1.
5893 main () sigusr1.c:28
5896 sigusr1_handler () at sigusr1.c:9
5900 The same, but using @code{queue-signal} instead of waiting for the
5901 program to receive the signal first:
5906 (@value{GDBP}) queue-signal SIGUSR1
5908 sigusr1_handler () at sigusr1.c:9
5913 @cindex extra signal information
5914 @anchor{extra signal information}
5916 On some targets, @value{GDBN} can inspect extra signal information
5917 associated with the intercepted signal, before it is actually
5918 delivered to the program being debugged. This information is exported
5919 by the convenience variable @code{$_siginfo}, and consists of data
5920 that is passed by the kernel to the signal handler at the time of the
5921 receipt of a signal. The data type of the information itself is
5922 target dependent. You can see the data type using the @code{ptype
5923 $_siginfo} command. On Unix systems, it typically corresponds to the
5924 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5927 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5928 referenced address that raised a segmentation fault.
5932 (@value{GDBP}) continue
5933 Program received signal SIGSEGV, Segmentation fault.
5934 0x0000000000400766 in main ()
5936 (@value{GDBP}) ptype $_siginfo
5943 struct @{...@} _kill;
5944 struct @{...@} _timer;
5946 struct @{...@} _sigchld;
5947 struct @{...@} _sigfault;
5948 struct @{...@} _sigpoll;
5951 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5955 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5956 $1 = (void *) 0x7ffff7ff7000
5960 Depending on target support, @code{$_siginfo} may also be writable.
5962 @cindex Intel MPX boundary violations
5963 @cindex boundary violations, Intel MPX
5964 On some targets, a @code{SIGSEGV} can be caused by a boundary
5965 violation, i.e., accessing an address outside of the allowed range.
5966 In those cases @value{GDBN} may displays additional information,
5967 depending on how @value{GDBN} has been told to handle the signal.
5968 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5969 kind: "Upper" or "Lower", the memory address accessed and the
5970 bounds, while with @code{handle nostop SIGSEGV} no additional
5971 information is displayed.
5973 The usual output of a segfault is:
5975 Program received signal SIGSEGV, Segmentation fault
5976 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5977 68 value = *(p + len);
5980 While a bound violation is presented as:
5982 Program received signal SIGSEGV, Segmentation fault
5983 Upper bound violation while accessing address 0x7fffffffc3b3
5984 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5985 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5986 68 value = *(p + len);
5990 @section Stopping and Starting Multi-thread Programs
5992 @cindex stopped threads
5993 @cindex threads, stopped
5995 @cindex continuing threads
5996 @cindex threads, continuing
5998 @value{GDBN} supports debugging programs with multiple threads
5999 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6000 are two modes of controlling execution of your program within the
6001 debugger. In the default mode, referred to as @dfn{all-stop mode},
6002 when any thread in your program stops (for example, at a breakpoint
6003 or while being stepped), all other threads in the program are also stopped by
6004 @value{GDBN}. On some targets, @value{GDBN} also supports
6005 @dfn{non-stop mode}, in which other threads can continue to run freely while
6006 you examine the stopped thread in the debugger.
6009 * All-Stop Mode:: All threads stop when GDB takes control
6010 * Non-Stop Mode:: Other threads continue to execute
6011 * Background Execution:: Running your program asynchronously
6012 * Thread-Specific Breakpoints:: Controlling breakpoints
6013 * Interrupted System Calls:: GDB may interfere with system calls
6014 * Observer Mode:: GDB does not alter program behavior
6018 @subsection All-Stop Mode
6020 @cindex all-stop mode
6022 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6023 @emph{all} threads of execution stop, not just the current thread. This
6024 allows you to examine the overall state of the program, including
6025 switching between threads, without worrying that things may change
6028 Conversely, whenever you restart the program, @emph{all} threads start
6029 executing. @emph{This is true even when single-stepping} with commands
6030 like @code{step} or @code{next}.
6032 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6033 Since thread scheduling is up to your debugging target's operating
6034 system (not controlled by @value{GDBN}), other threads may
6035 execute more than one statement while the current thread completes a
6036 single step. Moreover, in general other threads stop in the middle of a
6037 statement, rather than at a clean statement boundary, when the program
6040 You might even find your program stopped in another thread after
6041 continuing or even single-stepping. This happens whenever some other
6042 thread runs into a breakpoint, a signal, or an exception before the
6043 first thread completes whatever you requested.
6045 @cindex automatic thread selection
6046 @cindex switching threads automatically
6047 @cindex threads, automatic switching
6048 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6049 signal, it automatically selects the thread where that breakpoint or
6050 signal happened. @value{GDBN} alerts you to the context switch with a
6051 message such as @samp{[Switching to Thread @var{n}]} to identify the
6054 On some OSes, you can modify @value{GDBN}'s default behavior by
6055 locking the OS scheduler to allow only a single thread to run.
6058 @item set scheduler-locking @var{mode}
6059 @cindex scheduler locking mode
6060 @cindex lock scheduler
6061 Set the scheduler locking mode. It applies to normal execution,
6062 record mode, and replay mode. If it is @code{off}, then there is no
6063 locking and any thread may run at any time. If @code{on}, then only
6064 the current thread may run when the inferior is resumed. The
6065 @code{step} mode optimizes for single-stepping; it prevents other
6066 threads from preempting the current thread while you are stepping, so
6067 that the focus of debugging does not change unexpectedly. Other
6068 threads never get a chance to run when you step, and they are
6069 completely free to run when you use commands like @samp{continue},
6070 @samp{until}, or @samp{finish}. However, unless another thread hits a
6071 breakpoint during its timeslice, @value{GDBN} does not change the
6072 current thread away from the thread that you are debugging. The
6073 @code{replay} mode behaves like @code{off} in record mode and like
6074 @code{on} in replay mode.
6076 @item show scheduler-locking
6077 Display the current scheduler locking mode.
6080 @cindex resume threads of multiple processes simultaneously
6081 By default, when you issue one of the execution commands such as
6082 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6083 threads of the current inferior to run. For example, if @value{GDBN}
6084 is attached to two inferiors, each with two threads, the
6085 @code{continue} command resumes only the two threads of the current
6086 inferior. This is useful, for example, when you debug a program that
6087 forks and you want to hold the parent stopped (so that, for instance,
6088 it doesn't run to exit), while you debug the child. In other
6089 situations, you may not be interested in inspecting the current state
6090 of any of the processes @value{GDBN} is attached to, and you may want
6091 to resume them all until some breakpoint is hit. In the latter case,
6092 you can instruct @value{GDBN} to allow all threads of all the
6093 inferiors to run with the @w{@code{set schedule-multiple}} command.
6096 @kindex set schedule-multiple
6097 @item set schedule-multiple
6098 Set the mode for allowing threads of multiple processes to be resumed
6099 when an execution command is issued. When @code{on}, all threads of
6100 all processes are allowed to run. When @code{off}, only the threads
6101 of the current process are resumed. The default is @code{off}. The
6102 @code{scheduler-locking} mode takes precedence when set to @code{on},
6103 or while you are stepping and set to @code{step}.
6105 @item show schedule-multiple
6106 Display the current mode for resuming the execution of threads of
6111 @subsection Non-Stop Mode
6113 @cindex non-stop mode
6115 @c This section is really only a place-holder, and needs to be expanded
6116 @c with more details.
6118 For some multi-threaded targets, @value{GDBN} supports an optional
6119 mode of operation in which you can examine stopped program threads in
6120 the debugger while other threads continue to execute freely. This
6121 minimizes intrusion when debugging live systems, such as programs
6122 where some threads have real-time constraints or must continue to
6123 respond to external events. This is referred to as @dfn{non-stop} mode.
6125 In non-stop mode, when a thread stops to report a debugging event,
6126 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6127 threads as well, in contrast to the all-stop mode behavior. Additionally,
6128 execution commands such as @code{continue} and @code{step} apply by default
6129 only to the current thread in non-stop mode, rather than all threads as
6130 in all-stop mode. This allows you to control threads explicitly in
6131 ways that are not possible in all-stop mode --- for example, stepping
6132 one thread while allowing others to run freely, stepping
6133 one thread while holding all others stopped, or stepping several threads
6134 independently and simultaneously.
6136 To enter non-stop mode, use this sequence of commands before you run
6137 or attach to your program:
6140 # If using the CLI, pagination breaks non-stop.
6143 # Finally, turn it on!
6147 You can use these commands to manipulate the non-stop mode setting:
6150 @kindex set non-stop
6151 @item set non-stop on
6152 Enable selection of non-stop mode.
6153 @item set non-stop off
6154 Disable selection of non-stop mode.
6155 @kindex show non-stop
6157 Show the current non-stop enablement setting.
6160 Note these commands only reflect whether non-stop mode is enabled,
6161 not whether the currently-executing program is being run in non-stop mode.
6162 In particular, the @code{set non-stop} preference is only consulted when
6163 @value{GDBN} starts or connects to the target program, and it is generally
6164 not possible to switch modes once debugging has started. Furthermore,
6165 since not all targets support non-stop mode, even when you have enabled
6166 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6169 In non-stop mode, all execution commands apply only to the current thread
6170 by default. That is, @code{continue} only continues one thread.
6171 To continue all threads, issue @code{continue -a} or @code{c -a}.
6173 You can use @value{GDBN}'s background execution commands
6174 (@pxref{Background Execution}) to run some threads in the background
6175 while you continue to examine or step others from @value{GDBN}.
6176 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6177 always executed asynchronously in non-stop mode.
6179 Suspending execution is done with the @code{interrupt} command when
6180 running in the background, or @kbd{Ctrl-c} during foreground execution.
6181 In all-stop mode, this stops the whole process;
6182 but in non-stop mode the interrupt applies only to the current thread.
6183 To stop the whole program, use @code{interrupt -a}.
6185 Other execution commands do not currently support the @code{-a} option.
6187 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6188 that thread current, as it does in all-stop mode. This is because the
6189 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6190 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6191 changed to a different thread just as you entered a command to operate on the
6192 previously current thread.
6194 @node Background Execution
6195 @subsection Background Execution
6197 @cindex foreground execution
6198 @cindex background execution
6199 @cindex asynchronous execution
6200 @cindex execution, foreground, background and asynchronous
6202 @value{GDBN}'s execution commands have two variants: the normal
6203 foreground (synchronous) behavior, and a background
6204 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6205 the program to report that some thread has stopped before prompting for
6206 another command. In background execution, @value{GDBN} immediately gives
6207 a command prompt so that you can issue other commands while your program runs.
6209 If the target doesn't support async mode, @value{GDBN} issues an error
6210 message if you attempt to use the background execution commands.
6212 To specify background execution, add a @code{&} to the command. For example,
6213 the background form of the @code{continue} command is @code{continue&}, or
6214 just @code{c&}. The execution commands that accept background execution
6220 @xref{Starting, , Starting your Program}.
6224 @xref{Attach, , Debugging an Already-running Process}.
6228 @xref{Continuing and Stepping, step}.
6232 @xref{Continuing and Stepping, stepi}.
6236 @xref{Continuing and Stepping, next}.
6240 @xref{Continuing and Stepping, nexti}.
6244 @xref{Continuing and Stepping, continue}.
6248 @xref{Continuing and Stepping, finish}.
6252 @xref{Continuing and Stepping, until}.
6256 Background execution is especially useful in conjunction with non-stop
6257 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6258 However, you can also use these commands in the normal all-stop mode with
6259 the restriction that you cannot issue another execution command until the
6260 previous one finishes. Examples of commands that are valid in all-stop
6261 mode while the program is running include @code{help} and @code{info break}.
6263 You can interrupt your program while it is running in the background by
6264 using the @code{interrupt} command.
6271 Suspend execution of the running program. In all-stop mode,
6272 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6273 only the current thread. To stop the whole program in non-stop mode,
6274 use @code{interrupt -a}.
6277 @node Thread-Specific Breakpoints
6278 @subsection Thread-Specific Breakpoints
6280 When your program has multiple threads (@pxref{Threads,, Debugging
6281 Programs with Multiple Threads}), you can choose whether to set
6282 breakpoints on all threads, or on a particular thread.
6285 @cindex breakpoints and threads
6286 @cindex thread breakpoints
6287 @kindex break @dots{} thread @var{thread-id}
6288 @item break @var{location} thread @var{thread-id}
6289 @itemx break @var{location} thread @var{thread-id} if @dots{}
6290 @var{location} specifies source lines; there are several ways of
6291 writing them (@pxref{Specify Location}), but the effect is always to
6292 specify some source line.
6294 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6295 to specify that you only want @value{GDBN} to stop the program when a
6296 particular thread reaches this breakpoint. The @var{thread-id} specifier
6297 is one of the thread identifiers assigned by @value{GDBN}, shown
6298 in the first column of the @samp{info threads} display.
6300 If you do not specify @samp{thread @var{thread-id}} when you set a
6301 breakpoint, the breakpoint applies to @emph{all} threads of your
6304 You can use the @code{thread} qualifier on conditional breakpoints as
6305 well; in this case, place @samp{thread @var{thread-id}} before or
6306 after the breakpoint condition, like this:
6309 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6314 Thread-specific breakpoints are automatically deleted when
6315 @value{GDBN} detects the corresponding thread is no longer in the
6316 thread list. For example:
6320 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6323 There are several ways for a thread to disappear, such as a regular
6324 thread exit, but also when you detach from the process with the
6325 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6326 Process}), or if @value{GDBN} loses the remote connection
6327 (@pxref{Remote Debugging}), etc. Note that with some targets,
6328 @value{GDBN} is only able to detect a thread has exited when the user
6329 explictly asks for the thread list with the @code{info threads}
6332 @node Interrupted System Calls
6333 @subsection Interrupted System Calls
6335 @cindex thread breakpoints and system calls
6336 @cindex system calls and thread breakpoints
6337 @cindex premature return from system calls
6338 There is an unfortunate side effect when using @value{GDBN} to debug
6339 multi-threaded programs. If one thread stops for a
6340 breakpoint, or for some other reason, and another thread is blocked in a
6341 system call, then the system call may return prematurely. This is a
6342 consequence of the interaction between multiple threads and the signals
6343 that @value{GDBN} uses to implement breakpoints and other events that
6346 To handle this problem, your program should check the return value of
6347 each system call and react appropriately. This is good programming
6350 For example, do not write code like this:
6356 The call to @code{sleep} will return early if a different thread stops
6357 at a breakpoint or for some other reason.
6359 Instead, write this:
6364 unslept = sleep (unslept);
6367 A system call is allowed to return early, so the system is still
6368 conforming to its specification. But @value{GDBN} does cause your
6369 multi-threaded program to behave differently than it would without
6372 Also, @value{GDBN} uses internal breakpoints in the thread library to
6373 monitor certain events such as thread creation and thread destruction.
6374 When such an event happens, a system call in another thread may return
6375 prematurely, even though your program does not appear to stop.
6378 @subsection Observer Mode
6380 If you want to build on non-stop mode and observe program behavior
6381 without any chance of disruption by @value{GDBN}, you can set
6382 variables to disable all of the debugger's attempts to modify state,
6383 whether by writing memory, inserting breakpoints, etc. These operate
6384 at a low level, intercepting operations from all commands.
6386 When all of these are set to @code{off}, then @value{GDBN} is said to
6387 be @dfn{observer mode}. As a convenience, the variable
6388 @code{observer} can be set to disable these, plus enable non-stop
6391 Note that @value{GDBN} will not prevent you from making nonsensical
6392 combinations of these settings. For instance, if you have enabled
6393 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6394 then breakpoints that work by writing trap instructions into the code
6395 stream will still not be able to be placed.
6400 @item set observer on
6401 @itemx set observer off
6402 When set to @code{on}, this disables all the permission variables
6403 below (except for @code{insert-fast-tracepoints}), plus enables
6404 non-stop debugging. Setting this to @code{off} switches back to
6405 normal debugging, though remaining in non-stop mode.
6408 Show whether observer mode is on or off.
6410 @kindex may-write-registers
6411 @item set may-write-registers on
6412 @itemx set may-write-registers off
6413 This controls whether @value{GDBN} will attempt to alter the values of
6414 registers, such as with assignment expressions in @code{print}, or the
6415 @code{jump} command. It defaults to @code{on}.
6417 @item show may-write-registers
6418 Show the current permission to write registers.
6420 @kindex may-write-memory
6421 @item set may-write-memory on
6422 @itemx set may-write-memory off
6423 This controls whether @value{GDBN} will attempt to alter the contents
6424 of memory, such as with assignment expressions in @code{print}. It
6425 defaults to @code{on}.
6427 @item show may-write-memory
6428 Show the current permission to write memory.
6430 @kindex may-insert-breakpoints
6431 @item set may-insert-breakpoints on
6432 @itemx set may-insert-breakpoints off
6433 This controls whether @value{GDBN} will attempt to insert breakpoints.
6434 This affects all breakpoints, including internal breakpoints defined
6435 by @value{GDBN}. It defaults to @code{on}.
6437 @item show may-insert-breakpoints
6438 Show the current permission to insert breakpoints.
6440 @kindex may-insert-tracepoints
6441 @item set may-insert-tracepoints on
6442 @itemx set may-insert-tracepoints off
6443 This controls whether @value{GDBN} will attempt to insert (regular)
6444 tracepoints at the beginning of a tracing experiment. It affects only
6445 non-fast tracepoints, fast tracepoints being under the control of
6446 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6448 @item show may-insert-tracepoints
6449 Show the current permission to insert tracepoints.
6451 @kindex may-insert-fast-tracepoints
6452 @item set may-insert-fast-tracepoints on
6453 @itemx set may-insert-fast-tracepoints off
6454 This controls whether @value{GDBN} will attempt to insert fast
6455 tracepoints at the beginning of a tracing experiment. It affects only
6456 fast tracepoints, regular (non-fast) tracepoints being under the
6457 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6459 @item show may-insert-fast-tracepoints
6460 Show the current permission to insert fast tracepoints.
6462 @kindex may-interrupt
6463 @item set may-interrupt on
6464 @itemx set may-interrupt off
6465 This controls whether @value{GDBN} will attempt to interrupt or stop
6466 program execution. When this variable is @code{off}, the
6467 @code{interrupt} command will have no effect, nor will
6468 @kbd{Ctrl-c}. It defaults to @code{on}.
6470 @item show may-interrupt
6471 Show the current permission to interrupt or stop the program.
6475 @node Reverse Execution
6476 @chapter Running programs backward
6477 @cindex reverse execution
6478 @cindex running programs backward
6480 When you are debugging a program, it is not unusual to realize that
6481 you have gone too far, and some event of interest has already happened.
6482 If the target environment supports it, @value{GDBN} can allow you to
6483 ``rewind'' the program by running it backward.
6485 A target environment that supports reverse execution should be able
6486 to ``undo'' the changes in machine state that have taken place as the
6487 program was executing normally. Variables, registers etc.@: should
6488 revert to their previous values. Obviously this requires a great
6489 deal of sophistication on the part of the target environment; not
6490 all target environments can support reverse execution.
6492 When a program is executed in reverse, the instructions that
6493 have most recently been executed are ``un-executed'', in reverse
6494 order. The program counter runs backward, following the previous
6495 thread of execution in reverse. As each instruction is ``un-executed'',
6496 the values of memory and/or registers that were changed by that
6497 instruction are reverted to their previous states. After executing
6498 a piece of source code in reverse, all side effects of that code
6499 should be ``undone'', and all variables should be returned to their
6500 prior values@footnote{
6501 Note that some side effects are easier to undo than others. For instance,
6502 memory and registers are relatively easy, but device I/O is hard. Some
6503 targets may be able undo things like device I/O, and some may not.
6505 The contract between @value{GDBN} and the reverse executing target
6506 requires only that the target do something reasonable when
6507 @value{GDBN} tells it to execute backwards, and then report the
6508 results back to @value{GDBN}. Whatever the target reports back to
6509 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6510 assumes that the memory and registers that the target reports are in a
6511 consistant state, but @value{GDBN} accepts whatever it is given.
6514 If you are debugging in a target environment that supports
6515 reverse execution, @value{GDBN} provides the following commands.
6518 @kindex reverse-continue
6519 @kindex rc @r{(@code{reverse-continue})}
6520 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6521 @itemx rc @r{[}@var{ignore-count}@r{]}
6522 Beginning at the point where your program last stopped, start executing
6523 in reverse. Reverse execution will stop for breakpoints and synchronous
6524 exceptions (signals), just like normal execution. Behavior of
6525 asynchronous signals depends on the target environment.
6527 @kindex reverse-step
6528 @kindex rs @r{(@code{step})}
6529 @item reverse-step @r{[}@var{count}@r{]}
6530 Run the program backward until control reaches the start of a
6531 different source line; then stop it, and return control to @value{GDBN}.
6533 Like the @code{step} command, @code{reverse-step} will only stop
6534 at the beginning of a source line. It ``un-executes'' the previously
6535 executed source line. If the previous source line included calls to
6536 debuggable functions, @code{reverse-step} will step (backward) into
6537 the called function, stopping at the beginning of the @emph{last}
6538 statement in the called function (typically a return statement).
6540 Also, as with the @code{step} command, if non-debuggable functions are
6541 called, @code{reverse-step} will run thru them backward without stopping.
6543 @kindex reverse-stepi
6544 @kindex rsi @r{(@code{reverse-stepi})}
6545 @item reverse-stepi @r{[}@var{count}@r{]}
6546 Reverse-execute one machine instruction. Note that the instruction
6547 to be reverse-executed is @emph{not} the one pointed to by the program
6548 counter, but the instruction executed prior to that one. For instance,
6549 if the last instruction was a jump, @code{reverse-stepi} will take you
6550 back from the destination of the jump to the jump instruction itself.
6552 @kindex reverse-next
6553 @kindex rn @r{(@code{reverse-next})}
6554 @item reverse-next @r{[}@var{count}@r{]}
6555 Run backward to the beginning of the previous line executed in
6556 the current (innermost) stack frame. If the line contains function
6557 calls, they will be ``un-executed'' without stopping. Starting from
6558 the first line of a function, @code{reverse-next} will take you back
6559 to the caller of that function, @emph{before} the function was called,
6560 just as the normal @code{next} command would take you from the last
6561 line of a function back to its return to its caller
6562 @footnote{Unless the code is too heavily optimized.}.
6564 @kindex reverse-nexti
6565 @kindex rni @r{(@code{reverse-nexti})}
6566 @item reverse-nexti @r{[}@var{count}@r{]}
6567 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6568 in reverse, except that called functions are ``un-executed'' atomically.
6569 That is, if the previously executed instruction was a return from
6570 another function, @code{reverse-nexti} will continue to execute
6571 in reverse until the call to that function (from the current stack
6574 @kindex reverse-finish
6575 @item reverse-finish
6576 Just as the @code{finish} command takes you to the point where the
6577 current function returns, @code{reverse-finish} takes you to the point
6578 where it was called. Instead of ending up at the end of the current
6579 function invocation, you end up at the beginning.
6581 @kindex set exec-direction
6582 @item set exec-direction
6583 Set the direction of target execution.
6584 @item set exec-direction reverse
6585 @cindex execute forward or backward in time
6586 @value{GDBN} will perform all execution commands in reverse, until the
6587 exec-direction mode is changed to ``forward''. Affected commands include
6588 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6589 command cannot be used in reverse mode.
6590 @item set exec-direction forward
6591 @value{GDBN} will perform all execution commands in the normal fashion.
6592 This is the default.
6596 @node Process Record and Replay
6597 @chapter Recording Inferior's Execution and Replaying It
6598 @cindex process record and replay
6599 @cindex recording inferior's execution and replaying it
6601 On some platforms, @value{GDBN} provides a special @dfn{process record
6602 and replay} target that can record a log of the process execution, and
6603 replay it later with both forward and reverse execution commands.
6606 When this target is in use, if the execution log includes the record
6607 for the next instruction, @value{GDBN} will debug in @dfn{replay
6608 mode}. In the replay mode, the inferior does not really execute code
6609 instructions. Instead, all the events that normally happen during
6610 code execution are taken from the execution log. While code is not
6611 really executed in replay mode, the values of registers (including the
6612 program counter register) and the memory of the inferior are still
6613 changed as they normally would. Their contents are taken from the
6617 If the record for the next instruction is not in the execution log,
6618 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6619 inferior executes normally, and @value{GDBN} records the execution log
6622 The process record and replay target supports reverse execution
6623 (@pxref{Reverse Execution}), even if the platform on which the
6624 inferior runs does not. However, the reverse execution is limited in
6625 this case by the range of the instructions recorded in the execution
6626 log. In other words, reverse execution on platforms that don't
6627 support it directly can only be done in the replay mode.
6629 When debugging in the reverse direction, @value{GDBN} will work in
6630 replay mode as long as the execution log includes the record for the
6631 previous instruction; otherwise, it will work in record mode, if the
6632 platform supports reverse execution, or stop if not.
6634 For architecture environments that support process record and replay,
6635 @value{GDBN} provides the following commands:
6638 @kindex target record
6639 @kindex target record-full
6640 @kindex target record-btrace
6643 @kindex record btrace
6644 @kindex record btrace bts
6645 @kindex record btrace pt
6651 @kindex rec btrace bts
6652 @kindex rec btrace pt
6655 @item record @var{method}
6656 This command starts the process record and replay target. The
6657 recording method can be specified as parameter. Without a parameter
6658 the command uses the @code{full} recording method. The following
6659 recording methods are available:
6663 Full record/replay recording using @value{GDBN}'s software record and
6664 replay implementation. This method allows replaying and reverse
6667 @item btrace @var{format}
6668 Hardware-supported instruction recording. This method does not record
6669 data. Further, the data is collected in a ring buffer so old data will
6670 be overwritten when the buffer is full. It allows limited reverse
6671 execution. Variables and registers are not available during reverse
6672 execution. In remote debugging, recording continues on disconnect.
6673 Recorded data can be inspected after reconnecting. The recording may
6674 be stopped using @code{record stop}.
6676 The recording format can be specified as parameter. Without a parameter
6677 the command chooses the recording format. The following recording
6678 formats are available:
6682 @cindex branch trace store
6683 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6684 this format, the processor stores a from/to record for each executed
6685 branch in the btrace ring buffer.
6688 @cindex Intel Processor Trace
6689 Use the @dfn{Intel Processor Trace} recording format. In this
6690 format, the processor stores the execution trace in a compressed form
6691 that is afterwards decoded by @value{GDBN}.
6693 The trace can be recorded with very low overhead. The compressed
6694 trace format also allows small trace buffers to already contain a big
6695 number of instructions compared to @acronym{BTS}.
6697 Decoding the recorded execution trace, on the other hand, is more
6698 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6699 increased number of instructions to process. You should increase the
6700 buffer-size with care.
6703 Not all recording formats may be available on all processors.
6706 The process record and replay target can only debug a process that is
6707 already running. Therefore, you need first to start the process with
6708 the @kbd{run} or @kbd{start} commands, and then start the recording
6709 with the @kbd{record @var{method}} command.
6711 @cindex displaced stepping, and process record and replay
6712 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6713 will be automatically disabled when process record and replay target
6714 is started. That's because the process record and replay target
6715 doesn't support displaced stepping.
6717 @cindex non-stop mode, and process record and replay
6718 @cindex asynchronous execution, and process record and replay
6719 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6720 the asynchronous execution mode (@pxref{Background Execution}), not
6721 all recording methods are available. The @code{full} recording method
6722 does not support these two modes.
6727 Stop the process record and replay target. When process record and
6728 replay target stops, the entire execution log will be deleted and the
6729 inferior will either be terminated, or will remain in its final state.
6731 When you stop the process record and replay target in record mode (at
6732 the end of the execution log), the inferior will be stopped at the
6733 next instruction that would have been recorded. In other words, if
6734 you record for a while and then stop recording, the inferior process
6735 will be left in the same state as if the recording never happened.
6737 On the other hand, if the process record and replay target is stopped
6738 while in replay mode (that is, not at the end of the execution log,
6739 but at some earlier point), the inferior process will become ``live''
6740 at that earlier state, and it will then be possible to continue the
6741 usual ``live'' debugging of the process from that state.
6743 When the inferior process exits, or @value{GDBN} detaches from it,
6744 process record and replay target will automatically stop itself.
6748 Go to a specific location in the execution log. There are several
6749 ways to specify the location to go to:
6752 @item record goto begin
6753 @itemx record goto start
6754 Go to the beginning of the execution log.
6756 @item record goto end
6757 Go to the end of the execution log.
6759 @item record goto @var{n}
6760 Go to instruction number @var{n} in the execution log.
6764 @item record save @var{filename}
6765 Save the execution log to a file @file{@var{filename}}.
6766 Default filename is @file{gdb_record.@var{process_id}}, where
6767 @var{process_id} is the process ID of the inferior.
6769 This command may not be available for all recording methods.
6771 @kindex record restore
6772 @item record restore @var{filename}
6773 Restore the execution log from a file @file{@var{filename}}.
6774 File must have been created with @code{record save}.
6776 @kindex set record full
6777 @item set record full insn-number-max @var{limit}
6778 @itemx set record full insn-number-max unlimited
6779 Set the limit of instructions to be recorded for the @code{full}
6780 recording method. Default value is 200000.
6782 If @var{limit} is a positive number, then @value{GDBN} will start
6783 deleting instructions from the log once the number of the record
6784 instructions becomes greater than @var{limit}. For every new recorded
6785 instruction, @value{GDBN} will delete the earliest recorded
6786 instruction to keep the number of recorded instructions at the limit.
6787 (Since deleting recorded instructions loses information, @value{GDBN}
6788 lets you control what happens when the limit is reached, by means of
6789 the @code{stop-at-limit} option, described below.)
6791 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6792 delete recorded instructions from the execution log. The number of
6793 recorded instructions is limited only by the available memory.
6795 @kindex show record full
6796 @item show record full insn-number-max
6797 Show the limit of instructions to be recorded with the @code{full}
6800 @item set record full stop-at-limit
6801 Control the behavior of the @code{full} recording method when the
6802 number of recorded instructions reaches the limit. If ON (the
6803 default), @value{GDBN} will stop when the limit is reached for the
6804 first time and ask you whether you want to stop the inferior or
6805 continue running it and recording the execution log. If you decide
6806 to continue recording, each new recorded instruction will cause the
6807 oldest one to be deleted.
6809 If this option is OFF, @value{GDBN} will automatically delete the
6810 oldest record to make room for each new one, without asking.
6812 @item show record full stop-at-limit
6813 Show the current setting of @code{stop-at-limit}.
6815 @item set record full memory-query
6816 Control the behavior when @value{GDBN} is unable to record memory
6817 changes caused by an instruction for the @code{full} recording method.
6818 If ON, @value{GDBN} will query whether to stop the inferior in that
6821 If this option is OFF (the default), @value{GDBN} will automatically
6822 ignore the effect of such instructions on memory. Later, when
6823 @value{GDBN} replays this execution log, it will mark the log of this
6824 instruction as not accessible, and it will not affect the replay
6827 @item show record full memory-query
6828 Show the current setting of @code{memory-query}.
6830 @kindex set record btrace
6831 The @code{btrace} record target does not trace data. As a
6832 convenience, when replaying, @value{GDBN} reads read-only memory off
6833 the live program directly, assuming that the addresses of the
6834 read-only areas don't change. This for example makes it possible to
6835 disassemble code while replaying, but not to print variables.
6836 In some cases, being able to inspect variables might be useful.
6837 You can use the following command for that:
6839 @item set record btrace replay-memory-access
6840 Control the behavior of the @code{btrace} recording method when
6841 accessing memory during replay. If @code{read-only} (the default),
6842 @value{GDBN} will only allow accesses to read-only memory.
6843 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6844 and to read-write memory. Beware that the accessed memory corresponds
6845 to the live target and not necessarily to the current replay
6848 @kindex show record btrace
6849 @item show record btrace replay-memory-access
6850 Show the current setting of @code{replay-memory-access}.
6852 @kindex set record btrace bts
6853 @item set record btrace bts buffer-size @var{size}
6854 @itemx set record btrace bts buffer-size unlimited
6855 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6856 format. Default is 64KB.
6858 If @var{size} is a positive number, then @value{GDBN} will try to
6859 allocate a buffer of at least @var{size} bytes for each new thread
6860 that uses the btrace recording method and the @acronym{BTS} format.
6861 The actually obtained buffer size may differ from the requested
6862 @var{size}. Use the @code{info record} command to see the actual
6863 buffer size for each thread that uses the btrace recording method and
6864 the @acronym{BTS} format.
6866 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6867 allocate a buffer of 4MB.
6869 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6870 also need longer to process the branch trace data before it can be used.
6872 @item show record btrace bts buffer-size @var{size}
6873 Show the current setting of the requested ring buffer size for branch
6874 tracing in @acronym{BTS} format.
6876 @kindex set record btrace pt
6877 @item set record btrace pt buffer-size @var{size}
6878 @itemx set record btrace pt buffer-size unlimited
6879 Set the requested ring buffer size for branch tracing in Intel
6880 Processor Trace format. Default is 16KB.
6882 If @var{size} is a positive number, then @value{GDBN} will try to
6883 allocate a buffer of at least @var{size} bytes for each new thread
6884 that uses the btrace recording method and the Intel Processor Trace
6885 format. The actually obtained buffer size may differ from the
6886 requested @var{size}. Use the @code{info record} command to see the
6887 actual buffer size for each thread.
6889 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6890 allocate a buffer of 4MB.
6892 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6893 also need longer to process the branch trace data before it can be used.
6895 @item show record btrace pt buffer-size @var{size}
6896 Show the current setting of the requested ring buffer size for branch
6897 tracing in Intel Processor Trace format.
6901 Show various statistics about the recording depending on the recording
6906 For the @code{full} recording method, it shows the state of process
6907 record and its in-memory execution log buffer, including:
6911 Whether in record mode or replay mode.
6913 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6915 Highest recorded instruction number.
6917 Current instruction about to be replayed (if in replay mode).
6919 Number of instructions contained in the execution log.
6921 Maximum number of instructions that may be contained in the execution log.
6925 For the @code{btrace} recording method, it shows:
6931 Number of instructions that have been recorded.
6933 Number of blocks of sequential control-flow formed by the recorded
6936 Whether in record mode or replay mode.
6939 For the @code{bts} recording format, it also shows:
6942 Size of the perf ring buffer.
6945 For the @code{pt} recording format, it also shows:
6948 Size of the perf ring buffer.
6952 @kindex record delete
6955 When record target runs in replay mode (``in the past''), delete the
6956 subsequent execution log and begin to record a new execution log starting
6957 from the current address. This means you will abandon the previously
6958 recorded ``future'' and begin recording a new ``future''.
6960 @kindex record instruction-history
6961 @kindex rec instruction-history
6962 @item record instruction-history
6963 Disassembles instructions from the recorded execution log. By
6964 default, ten instructions are disassembled. This can be changed using
6965 the @code{set record instruction-history-size} command. Instructions
6966 are printed in execution order.
6968 It can also print mixed source+disassembly if you specify the the
6969 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6970 as well as in symbolic form by specifying the @code{/r} modifier.
6972 The current position marker is printed for the instruction at the
6973 current program counter value. This instruction can appear multiple
6974 times in the trace and the current position marker will be printed
6975 every time. To omit the current position marker, specify the
6978 To better align the printed instructions when the trace contains
6979 instructions from more than one function, the function name may be
6980 omitted by specifying the @code{/f} modifier.
6982 Speculatively executed instructions are prefixed with @samp{?}. This
6983 feature is not available for all recording formats.
6985 There are several ways to specify what part of the execution log to
6989 @item record instruction-history @var{insn}
6990 Disassembles ten instructions starting from instruction number
6993 @item record instruction-history @var{insn}, +/-@var{n}
6994 Disassembles @var{n} instructions around instruction number
6995 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6996 @var{n} instructions after instruction number @var{insn}. If
6997 @var{n} is preceded with @code{-}, disassembles @var{n}
6998 instructions before instruction number @var{insn}.
7000 @item record instruction-history
7001 Disassembles ten more instructions after the last disassembly.
7003 @item record instruction-history -
7004 Disassembles ten more instructions before the last disassembly.
7006 @item record instruction-history @var{begin}, @var{end}
7007 Disassembles instructions beginning with instruction number
7008 @var{begin} until instruction number @var{end}. The instruction
7009 number @var{end} is included.
7012 This command may not be available for all recording methods.
7015 @item set record instruction-history-size @var{size}
7016 @itemx set record instruction-history-size unlimited
7017 Define how many instructions to disassemble in the @code{record
7018 instruction-history} command. The default value is 10.
7019 A @var{size} of @code{unlimited} means unlimited instructions.
7022 @item show record instruction-history-size
7023 Show how many instructions to disassemble in the @code{record
7024 instruction-history} command.
7026 @kindex record function-call-history
7027 @kindex rec function-call-history
7028 @item record function-call-history
7029 Prints the execution history at function granularity. It prints one
7030 line for each sequence of instructions that belong to the same
7031 function giving the name of that function, the source lines
7032 for this instruction sequence (if the @code{/l} modifier is
7033 specified), and the instructions numbers that form the sequence (if
7034 the @code{/i} modifier is specified). The function names are indented
7035 to reflect the call stack depth if the @code{/c} modifier is
7036 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7040 (@value{GDBP}) @b{list 1, 10}
7051 (@value{GDBP}) @b{record function-call-history /ilc}
7052 1 bar inst 1,4 at foo.c:6,8
7053 2 foo inst 5,10 at foo.c:2,3
7054 3 bar inst 11,13 at foo.c:9,10
7057 By default, ten lines are printed. This can be changed using the
7058 @code{set record function-call-history-size} command. Functions are
7059 printed in execution order. There are several ways to specify what
7063 @item record function-call-history @var{func}
7064 Prints ten functions starting from function number @var{func}.
7066 @item record function-call-history @var{func}, +/-@var{n}
7067 Prints @var{n} functions around function number @var{func}. If
7068 @var{n} is preceded with @code{+}, prints @var{n} functions after
7069 function number @var{func}. If @var{n} is preceded with @code{-},
7070 prints @var{n} functions before function number @var{func}.
7072 @item record function-call-history
7073 Prints ten more functions after the last ten-line print.
7075 @item record function-call-history -
7076 Prints ten more functions before the last ten-line print.
7078 @item record function-call-history @var{begin}, @var{end}
7079 Prints functions beginning with function number @var{begin} until
7080 function number @var{end}. The function number @var{end} is included.
7083 This command may not be available for all recording methods.
7085 @item set record function-call-history-size @var{size}
7086 @itemx set record function-call-history-size unlimited
7087 Define how many lines to print in the
7088 @code{record function-call-history} command. The default value is 10.
7089 A size of @code{unlimited} means unlimited lines.
7091 @item show record function-call-history-size
7092 Show how many lines to print in the
7093 @code{record function-call-history} command.
7098 @chapter Examining the Stack
7100 When your program has stopped, the first thing you need to know is where it
7101 stopped and how it got there.
7104 Each time your program performs a function call, information about the call
7106 That information includes the location of the call in your program,
7107 the arguments of the call,
7108 and the local variables of the function being called.
7109 The information is saved in a block of data called a @dfn{stack frame}.
7110 The stack frames are allocated in a region of memory called the @dfn{call
7113 When your program stops, the @value{GDBN} commands for examining the
7114 stack allow you to see all of this information.
7116 @cindex selected frame
7117 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7118 @value{GDBN} commands refer implicitly to the selected frame. In
7119 particular, whenever you ask @value{GDBN} for the value of a variable in
7120 your program, the value is found in the selected frame. There are
7121 special @value{GDBN} commands to select whichever frame you are
7122 interested in. @xref{Selection, ,Selecting a Frame}.
7124 When your program stops, @value{GDBN} automatically selects the
7125 currently executing frame and describes it briefly, similar to the
7126 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7129 * Frames:: Stack frames
7130 * Backtrace:: Backtraces
7131 * Selection:: Selecting a frame
7132 * Frame Info:: Information on a frame
7133 * Frame Filter Management:: Managing frame filters
7138 @section Stack Frames
7140 @cindex frame, definition
7142 The call stack is divided up into contiguous pieces called @dfn{stack
7143 frames}, or @dfn{frames} for short; each frame is the data associated
7144 with one call to one function. The frame contains the arguments given
7145 to the function, the function's local variables, and the address at
7146 which the function is executing.
7148 @cindex initial frame
7149 @cindex outermost frame
7150 @cindex innermost frame
7151 When your program is started, the stack has only one frame, that of the
7152 function @code{main}. This is called the @dfn{initial} frame or the
7153 @dfn{outermost} frame. Each time a function is called, a new frame is
7154 made. Each time a function returns, the frame for that function invocation
7155 is eliminated. If a function is recursive, there can be many frames for
7156 the same function. The frame for the function in which execution is
7157 actually occurring is called the @dfn{innermost} frame. This is the most
7158 recently created of all the stack frames that still exist.
7160 @cindex frame pointer
7161 Inside your program, stack frames are identified by their addresses. A
7162 stack frame consists of many bytes, each of which has its own address; each
7163 kind of computer has a convention for choosing one byte whose
7164 address serves as the address of the frame. Usually this address is kept
7165 in a register called the @dfn{frame pointer register}
7166 (@pxref{Registers, $fp}) while execution is going on in that frame.
7168 @cindex frame number
7169 @value{GDBN} assigns numbers to all existing stack frames, starting with
7170 zero for the innermost frame, one for the frame that called it,
7171 and so on upward. These numbers do not really exist in your program;
7172 they are assigned by @value{GDBN} to give you a way of designating stack
7173 frames in @value{GDBN} commands.
7175 @c The -fomit-frame-pointer below perennially causes hbox overflow
7176 @c underflow problems.
7177 @cindex frameless execution
7178 Some compilers provide a way to compile functions so that they operate
7179 without stack frames. (For example, the @value{NGCC} option
7181 @samp{-fomit-frame-pointer}
7183 generates functions without a frame.)
7184 This is occasionally done with heavily used library functions to save
7185 the frame setup time. @value{GDBN} has limited facilities for dealing
7186 with these function invocations. If the innermost function invocation
7187 has no stack frame, @value{GDBN} nevertheless regards it as though
7188 it had a separate frame, which is numbered zero as usual, allowing
7189 correct tracing of the function call chain. However, @value{GDBN} has
7190 no provision for frameless functions elsewhere in the stack.
7196 @cindex call stack traces
7197 A backtrace is a summary of how your program got where it is. It shows one
7198 line per frame, for many frames, starting with the currently executing
7199 frame (frame zero), followed by its caller (frame one), and on up the
7202 @anchor{backtrace-command}
7205 @kindex bt @r{(@code{backtrace})}
7208 Print a backtrace of the entire stack: one line per frame for all
7209 frames in the stack.
7211 You can stop the backtrace at any time by typing the system interrupt
7212 character, normally @kbd{Ctrl-c}.
7214 @item backtrace @var{n}
7216 Similar, but print only the innermost @var{n} frames.
7218 @item backtrace -@var{n}
7220 Similar, but print only the outermost @var{n} frames.
7222 @item backtrace full
7224 @itemx bt full @var{n}
7225 @itemx bt full -@var{n}
7226 Print the values of the local variables also. As described above,
7227 @var{n} specifies the number of frames to print.
7229 @item backtrace no-filters
7230 @itemx bt no-filters
7231 @itemx bt no-filters @var{n}
7232 @itemx bt no-filters -@var{n}
7233 @itemx bt no-filters full
7234 @itemx bt no-filters full @var{n}
7235 @itemx bt no-filters full -@var{n}
7236 Do not run Python frame filters on this backtrace. @xref{Frame
7237 Filter API}, for more information. Additionally use @ref{disable
7238 frame-filter all} to turn off all frame filters. This is only
7239 relevant when @value{GDBN} has been configured with @code{Python}
7245 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7246 are additional aliases for @code{backtrace}.
7248 @cindex multiple threads, backtrace
7249 In a multi-threaded program, @value{GDBN} by default shows the
7250 backtrace only for the current thread. To display the backtrace for
7251 several or all of the threads, use the command @code{thread apply}
7252 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7253 apply all backtrace}, @value{GDBN} will display the backtrace for all
7254 the threads; this is handy when you debug a core dump of a
7255 multi-threaded program.
7257 Each line in the backtrace shows the frame number and the function name.
7258 The program counter value is also shown---unless you use @code{set
7259 print address off}. The backtrace also shows the source file name and
7260 line number, as well as the arguments to the function. The program
7261 counter value is omitted if it is at the beginning of the code for that
7264 Here is an example of a backtrace. It was made with the command
7265 @samp{bt 3}, so it shows the innermost three frames.
7269 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7271 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7272 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7274 (More stack frames follow...)
7279 The display for frame zero does not begin with a program counter
7280 value, indicating that your program has stopped at the beginning of the
7281 code for line @code{993} of @code{builtin.c}.
7284 The value of parameter @code{data} in frame 1 has been replaced by
7285 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7286 only if it is a scalar (integer, pointer, enumeration, etc). See command
7287 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7288 on how to configure the way function parameter values are printed.
7290 @cindex optimized out, in backtrace
7291 @cindex function call arguments, optimized out
7292 If your program was compiled with optimizations, some compilers will
7293 optimize away arguments passed to functions if those arguments are
7294 never used after the call. Such optimizations generate code that
7295 passes arguments through registers, but doesn't store those arguments
7296 in the stack frame. @value{GDBN} has no way of displaying such
7297 arguments in stack frames other than the innermost one. Here's what
7298 such a backtrace might look like:
7302 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7304 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7305 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7307 (More stack frames follow...)
7312 The values of arguments that were not saved in their stack frames are
7313 shown as @samp{<optimized out>}.
7315 If you need to display the values of such optimized-out arguments,
7316 either deduce that from other variables whose values depend on the one
7317 you are interested in, or recompile without optimizations.
7319 @cindex backtrace beyond @code{main} function
7320 @cindex program entry point
7321 @cindex startup code, and backtrace
7322 Most programs have a standard user entry point---a place where system
7323 libraries and startup code transition into user code. For C this is
7324 @code{main}@footnote{
7325 Note that embedded programs (the so-called ``free-standing''
7326 environment) are not required to have a @code{main} function as the
7327 entry point. They could even have multiple entry points.}.
7328 When @value{GDBN} finds the entry function in a backtrace
7329 it will terminate the backtrace, to avoid tracing into highly
7330 system-specific (and generally uninteresting) code.
7332 If you need to examine the startup code, or limit the number of levels
7333 in a backtrace, you can change this behavior:
7336 @item set backtrace past-main
7337 @itemx set backtrace past-main on
7338 @kindex set backtrace
7339 Backtraces will continue past the user entry point.
7341 @item set backtrace past-main off
7342 Backtraces will stop when they encounter the user entry point. This is the
7345 @item show backtrace past-main
7346 @kindex show backtrace
7347 Display the current user entry point backtrace policy.
7349 @item set backtrace past-entry
7350 @itemx set backtrace past-entry on
7351 Backtraces will continue past the internal entry point of an application.
7352 This entry point is encoded by the linker when the application is built,
7353 and is likely before the user entry point @code{main} (or equivalent) is called.
7355 @item set backtrace past-entry off
7356 Backtraces will stop when they encounter the internal entry point of an
7357 application. This is the default.
7359 @item show backtrace past-entry
7360 Display the current internal entry point backtrace policy.
7362 @item set backtrace limit @var{n}
7363 @itemx set backtrace limit 0
7364 @itemx set backtrace limit unlimited
7365 @cindex backtrace limit
7366 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7367 or zero means unlimited levels.
7369 @item show backtrace limit
7370 Display the current limit on backtrace levels.
7373 You can control how file names are displayed.
7376 @item set filename-display
7377 @itemx set filename-display relative
7378 @cindex filename-display
7379 Display file names relative to the compilation directory. This is the default.
7381 @item set filename-display basename
7382 Display only basename of a filename.
7384 @item set filename-display absolute
7385 Display an absolute filename.
7387 @item show filename-display
7388 Show the current way to display filenames.
7392 @section Selecting a Frame
7394 Most commands for examining the stack and other data in your program work on
7395 whichever stack frame is selected at the moment. Here are the commands for
7396 selecting a stack frame; all of them finish by printing a brief description
7397 of the stack frame just selected.
7400 @kindex frame@r{, selecting}
7401 @kindex f @r{(@code{frame})}
7404 Select frame number @var{n}. Recall that frame zero is the innermost
7405 (currently executing) frame, frame one is the frame that called the
7406 innermost one, and so on. The highest-numbered frame is the one for
7409 @item frame @var{stack-addr} [ @var{pc-addr} ]
7410 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7411 Select the frame at address @var{stack-addr}. This is useful mainly if the
7412 chaining of stack frames has been damaged by a bug, making it
7413 impossible for @value{GDBN} to assign numbers properly to all frames. In
7414 addition, this can be useful when your program has multiple stacks and
7415 switches between them. The optional @var{pc-addr} can also be given to
7416 specify the value of PC for the stack frame.
7420 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7421 numbers @var{n}, this advances toward the outermost frame, to higher
7422 frame numbers, to frames that have existed longer.
7425 @kindex do @r{(@code{down})}
7427 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7428 positive numbers @var{n}, this advances toward the innermost frame, to
7429 lower frame numbers, to frames that were created more recently.
7430 You may abbreviate @code{down} as @code{do}.
7433 All of these commands end by printing two lines of output describing the
7434 frame. The first line shows the frame number, the function name, the
7435 arguments, and the source file and line number of execution in that
7436 frame. The second line shows the text of that source line.
7444 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7446 10 read_input_file (argv[i]);
7450 After such a printout, the @code{list} command with no arguments
7451 prints ten lines centered on the point of execution in the frame.
7452 You can also edit the program at the point of execution with your favorite
7453 editing program by typing @code{edit}.
7454 @xref{List, ,Printing Source Lines},
7458 @kindex select-frame
7460 The @code{select-frame} command is a variant of @code{frame} that does
7461 not display the new frame after selecting it. This command is
7462 intended primarily for use in @value{GDBN} command scripts, where the
7463 output might be unnecessary and distracting.
7465 @kindex down-silently
7467 @item up-silently @var{n}
7468 @itemx down-silently @var{n}
7469 These two commands are variants of @code{up} and @code{down},
7470 respectively; they differ in that they do their work silently, without
7471 causing display of the new frame. They are intended primarily for use
7472 in @value{GDBN} command scripts, where the output might be unnecessary and
7477 @section Information About a Frame
7479 There are several other commands to print information about the selected
7485 When used without any argument, this command does not change which
7486 frame is selected, but prints a brief description of the currently
7487 selected stack frame. It can be abbreviated @code{f}. With an
7488 argument, this command is used to select a stack frame.
7489 @xref{Selection, ,Selecting a Frame}.
7492 @kindex info f @r{(@code{info frame})}
7495 This command prints a verbose description of the selected stack frame,
7500 the address of the frame
7502 the address of the next frame down (called by this frame)
7504 the address of the next frame up (caller of this frame)
7506 the language in which the source code corresponding to this frame is written
7508 the address of the frame's arguments
7510 the address of the frame's local variables
7512 the program counter saved in it (the address of execution in the caller frame)
7514 which registers were saved in the frame
7517 @noindent The verbose description is useful when
7518 something has gone wrong that has made the stack format fail to fit
7519 the usual conventions.
7521 @item info frame @var{addr}
7522 @itemx info f @var{addr}
7523 Print a verbose description of the frame at address @var{addr}, without
7524 selecting that frame. The selected frame remains unchanged by this
7525 command. This requires the same kind of address (more than one for some
7526 architectures) that you specify in the @code{frame} command.
7527 @xref{Selection, ,Selecting a Frame}.
7531 Print the arguments of the selected frame, each on a separate line.
7535 Print the local variables of the selected frame, each on a separate
7536 line. These are all variables (declared either static or automatic)
7537 accessible at the point of execution of the selected frame.
7541 @node Frame Filter Management
7542 @section Management of Frame Filters.
7543 @cindex managing frame filters
7545 Frame filters are Python based utilities to manage and decorate the
7546 output of frames. @xref{Frame Filter API}, for further information.
7548 Managing frame filters is performed by several commands available
7549 within @value{GDBN}, detailed here.
7552 @kindex info frame-filter
7553 @item info frame-filter
7554 Print a list of installed frame filters from all dictionaries, showing
7555 their name, priority and enabled status.
7557 @kindex disable frame-filter
7558 @anchor{disable frame-filter all}
7559 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7560 Disable a frame filter in the dictionary matching
7561 @var{filter-dictionary} and @var{filter-name}. The
7562 @var{filter-dictionary} may be @code{all}, @code{global},
7563 @code{progspace}, or the name of the object file where the frame filter
7564 dictionary resides. When @code{all} is specified, all frame filters
7565 across all dictionaries are disabled. The @var{filter-name} is the name
7566 of the frame filter and is used when @code{all} is not the option for
7567 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7568 may be enabled again later.
7570 @kindex enable frame-filter
7571 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7572 Enable a frame filter in the dictionary matching
7573 @var{filter-dictionary} and @var{filter-name}. The
7574 @var{filter-dictionary} may be @code{all}, @code{global},
7575 @code{progspace} or the name of the object file where the frame filter
7576 dictionary resides. When @code{all} is specified, all frame filters across
7577 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7578 filter and is used when @code{all} is not the option for
7579 @var{filter-dictionary}.
7584 (gdb) info frame-filter
7586 global frame-filters:
7587 Priority Enabled Name
7588 1000 No PrimaryFunctionFilter
7591 progspace /build/test frame-filters:
7592 Priority Enabled Name
7593 100 Yes ProgspaceFilter
7595 objfile /build/test frame-filters:
7596 Priority Enabled Name
7597 999 Yes BuildProgra Filter
7599 (gdb) disable frame-filter /build/test BuildProgramFilter
7600 (gdb) info frame-filter
7602 global frame-filters:
7603 Priority Enabled Name
7604 1000 No PrimaryFunctionFilter
7607 progspace /build/test frame-filters:
7608 Priority Enabled Name
7609 100 Yes ProgspaceFilter
7611 objfile /build/test frame-filters:
7612 Priority Enabled Name
7613 999 No BuildProgramFilter
7615 (gdb) enable frame-filter global PrimaryFunctionFilter
7616 (gdb) info frame-filter
7618 global frame-filters:
7619 Priority Enabled Name
7620 1000 Yes PrimaryFunctionFilter
7623 progspace /build/test frame-filters:
7624 Priority Enabled Name
7625 100 Yes ProgspaceFilter
7627 objfile /build/test frame-filters:
7628 Priority Enabled Name
7629 999 No BuildProgramFilter
7632 @kindex set frame-filter priority
7633 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7634 Set the @var{priority} of a frame filter in the dictionary matching
7635 @var{filter-dictionary}, and the frame filter name matching
7636 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7637 @code{progspace} or the name of the object file where the frame filter
7638 dictionary resides. The @var{priority} is an integer.
7640 @kindex show frame-filter priority
7641 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7642 Show the @var{priority} of a frame filter in the dictionary matching
7643 @var{filter-dictionary}, and the frame filter name matching
7644 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7645 @code{progspace} or the name of the object file where the frame filter
7651 (gdb) info frame-filter
7653 global frame-filters:
7654 Priority Enabled Name
7655 1000 Yes PrimaryFunctionFilter
7658 progspace /build/test frame-filters:
7659 Priority Enabled Name
7660 100 Yes ProgspaceFilter
7662 objfile /build/test frame-filters:
7663 Priority Enabled Name
7664 999 No BuildProgramFilter
7666 (gdb) set frame-filter priority global Reverse 50
7667 (gdb) info frame-filter
7669 global frame-filters:
7670 Priority Enabled Name
7671 1000 Yes PrimaryFunctionFilter
7674 progspace /build/test frame-filters:
7675 Priority Enabled Name
7676 100 Yes ProgspaceFilter
7678 objfile /build/test frame-filters:
7679 Priority Enabled Name
7680 999 No BuildProgramFilter
7685 @chapter Examining Source Files
7687 @value{GDBN} can print parts of your program's source, since the debugging
7688 information recorded in the program tells @value{GDBN} what source files were
7689 used to build it. When your program stops, @value{GDBN} spontaneously prints
7690 the line where it stopped. Likewise, when you select a stack frame
7691 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7692 execution in that frame has stopped. You can print other portions of
7693 source files by explicit command.
7695 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7696 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7697 @value{GDBN} under @sc{gnu} Emacs}.
7700 * List:: Printing source lines
7701 * Specify Location:: How to specify code locations
7702 * Edit:: Editing source files
7703 * Search:: Searching source files
7704 * Source Path:: Specifying source directories
7705 * Machine Code:: Source and machine code
7709 @section Printing Source Lines
7712 @kindex l @r{(@code{list})}
7713 To print lines from a source file, use the @code{list} command
7714 (abbreviated @code{l}). By default, ten lines are printed.
7715 There are several ways to specify what part of the file you want to
7716 print; see @ref{Specify Location}, for the full list.
7718 Here are the forms of the @code{list} command most commonly used:
7721 @item list @var{linenum}
7722 Print lines centered around line number @var{linenum} in the
7723 current source file.
7725 @item list @var{function}
7726 Print lines centered around the beginning of function
7730 Print more lines. If the last lines printed were printed with a
7731 @code{list} command, this prints lines following the last lines
7732 printed; however, if the last line printed was a solitary line printed
7733 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7734 Stack}), this prints lines centered around that line.
7737 Print lines just before the lines last printed.
7740 @cindex @code{list}, how many lines to display
7741 By default, @value{GDBN} prints ten source lines with any of these forms of
7742 the @code{list} command. You can change this using @code{set listsize}:
7745 @kindex set listsize
7746 @item set listsize @var{count}
7747 @itemx set listsize unlimited
7748 Make the @code{list} command display @var{count} source lines (unless
7749 the @code{list} argument explicitly specifies some other number).
7750 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7752 @kindex show listsize
7754 Display the number of lines that @code{list} prints.
7757 Repeating a @code{list} command with @key{RET} discards the argument,
7758 so it is equivalent to typing just @code{list}. This is more useful
7759 than listing the same lines again. An exception is made for an
7760 argument of @samp{-}; that argument is preserved in repetition so that
7761 each repetition moves up in the source file.
7763 In general, the @code{list} command expects you to supply zero, one or two
7764 @dfn{locations}. Locations specify source lines; there are several ways
7765 of writing them (@pxref{Specify Location}), but the effect is always
7766 to specify some source line.
7768 Here is a complete description of the possible arguments for @code{list}:
7771 @item list @var{location}
7772 Print lines centered around the line specified by @var{location}.
7774 @item list @var{first},@var{last}
7775 Print lines from @var{first} to @var{last}. Both arguments are
7776 locations. When a @code{list} command has two locations, and the
7777 source file of the second location is omitted, this refers to
7778 the same source file as the first location.
7780 @item list ,@var{last}
7781 Print lines ending with @var{last}.
7783 @item list @var{first},
7784 Print lines starting with @var{first}.
7787 Print lines just after the lines last printed.
7790 Print lines just before the lines last printed.
7793 As described in the preceding table.
7796 @node Specify Location
7797 @section Specifying a Location
7798 @cindex specifying location
7800 @cindex source location
7803 * Linespec Locations:: Linespec locations
7804 * Explicit Locations:: Explicit locations
7805 * Address Locations:: Address locations
7808 Several @value{GDBN} commands accept arguments that specify a location
7809 of your program's code. Since @value{GDBN} is a source-level
7810 debugger, a location usually specifies some line in the source code.
7811 Locations may be specified using three different formats:
7812 linespec locations, explicit locations, or address locations.
7814 @node Linespec Locations
7815 @subsection Linespec Locations
7816 @cindex linespec locations
7818 A @dfn{linespec} is a colon-separated list of source location parameters such
7819 as file name, function name, etc. Here are all the different ways of
7820 specifying a linespec:
7824 Specifies the line number @var{linenum} of the current source file.
7827 @itemx +@var{offset}
7828 Specifies the line @var{offset} lines before or after the @dfn{current
7829 line}. For the @code{list} command, the current line is the last one
7830 printed; for the breakpoint commands, this is the line at which
7831 execution stopped in the currently selected @dfn{stack frame}
7832 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7833 used as the second of the two linespecs in a @code{list} command,
7834 this specifies the line @var{offset} lines up or down from the first
7837 @item @var{filename}:@var{linenum}
7838 Specifies the line @var{linenum} in the source file @var{filename}.
7839 If @var{filename} is a relative file name, then it will match any
7840 source file name with the same trailing components. For example, if
7841 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7842 name of @file{/build/trunk/gcc/expr.c}, but not
7843 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7845 @item @var{function}
7846 Specifies the line that begins the body of the function @var{function}.
7847 For example, in C, this is the line with the open brace.
7849 @item @var{function}:@var{label}
7850 Specifies the line where @var{label} appears in @var{function}.
7852 @item @var{filename}:@var{function}
7853 Specifies the line that begins the body of the function @var{function}
7854 in the file @var{filename}. You only need the file name with a
7855 function name to avoid ambiguity when there are identically named
7856 functions in different source files.
7859 Specifies the line at which the label named @var{label} appears
7860 in the function corresponding to the currently selected stack frame.
7861 If there is no current selected stack frame (for instance, if the inferior
7862 is not running), then @value{GDBN} will not search for a label.
7864 @cindex breakpoint at static probe point
7865 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7866 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7867 applications to embed static probes. @xref{Static Probe Points}, for more
7868 information on finding and using static probes. This form of linespec
7869 specifies the location of such a static probe.
7871 If @var{objfile} is given, only probes coming from that shared library
7872 or executable matching @var{objfile} as a regular expression are considered.
7873 If @var{provider} is given, then only probes from that provider are considered.
7874 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7875 each one of those probes.
7878 @node Explicit Locations
7879 @subsection Explicit Locations
7880 @cindex explicit locations
7882 @dfn{Explicit locations} allow the user to directly specify the source
7883 location's parameters using option-value pairs.
7885 Explicit locations are useful when several functions, labels, or
7886 file names have the same name (base name for files) in the program's
7887 sources. In these cases, explicit locations point to the source
7888 line you meant more accurately and unambiguously. Also, using
7889 explicit locations might be faster in large programs.
7891 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7892 defined in the file named @file{foo} or the label @code{bar} in a function
7893 named @code{foo}. @value{GDBN} must search either the file system or
7894 the symbol table to know.
7896 The list of valid explicit location options is summarized in the
7900 @item -source @var{filename}
7901 The value specifies the source file name. To differentiate between
7902 files with the same base name, prepend as many directories as is necessary
7903 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7904 @value{GDBN} will use the first file it finds with the given base
7905 name. This option requires the use of either @code{-function} or @code{-line}.
7907 @item -function @var{function}
7908 The value specifies the name of a function. Operations
7909 on function locations unmodified by other options (such as @code{-label}
7910 or @code{-line}) refer to the line that begins the body of the function.
7911 In C, for example, this is the line with the open brace.
7913 @item -label @var{label}
7914 The value specifies the name of a label. When the function
7915 name is not specified, the label is searched in the function of the currently
7916 selected stack frame.
7918 @item -line @var{number}
7919 The value specifies a line offset for the location. The offset may either
7920 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7921 the command. When specified without any other options, the line offset is
7922 relative to the current line.
7925 Explicit location options may be abbreviated by omitting any non-unique
7926 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7928 @node Address Locations
7929 @subsection Address Locations
7930 @cindex address locations
7932 @dfn{Address locations} indicate a specific program address. They have
7933 the generalized form *@var{address}.
7935 For line-oriented commands, such as @code{list} and @code{edit}, this
7936 specifies a source line that contains @var{address}. For @code{break} and
7937 other breakpoint-oriented commands, this can be used to set breakpoints in
7938 parts of your program which do not have debugging information or
7941 Here @var{address} may be any expression valid in the current working
7942 language (@pxref{Languages, working language}) that specifies a code
7943 address. In addition, as a convenience, @value{GDBN} extends the
7944 semantics of expressions used in locations to cover several situations
7945 that frequently occur during debugging. Here are the various forms
7949 @item @var{expression}
7950 Any expression valid in the current working language.
7952 @item @var{funcaddr}
7953 An address of a function or procedure derived from its name. In C,
7954 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
7955 simply the function's name @var{function} (and actually a special case
7956 of a valid expression). In Pascal and Modula-2, this is
7957 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7958 (although the Pascal form also works).
7960 This form specifies the address of the function's first instruction,
7961 before the stack frame and arguments have been set up.
7963 @item '@var{filename}':@var{funcaddr}
7964 Like @var{funcaddr} above, but also specifies the name of the source
7965 file explicitly. This is useful if the name of the function does not
7966 specify the function unambiguously, e.g., if there are several
7967 functions with identical names in different source files.
7971 @section Editing Source Files
7972 @cindex editing source files
7975 @kindex e @r{(@code{edit})}
7976 To edit the lines in a source file, use the @code{edit} command.
7977 The editing program of your choice
7978 is invoked with the current line set to
7979 the active line in the program.
7980 Alternatively, there are several ways to specify what part of the file you
7981 want to print if you want to see other parts of the program:
7984 @item edit @var{location}
7985 Edit the source file specified by @code{location}. Editing starts at
7986 that @var{location}, e.g., at the specified source line of the
7987 specified file. @xref{Specify Location}, for all the possible forms
7988 of the @var{location} argument; here are the forms of the @code{edit}
7989 command most commonly used:
7992 @item edit @var{number}
7993 Edit the current source file with @var{number} as the active line number.
7995 @item edit @var{function}
7996 Edit the file containing @var{function} at the beginning of its definition.
8001 @subsection Choosing your Editor
8002 You can customize @value{GDBN} to use any editor you want
8004 The only restriction is that your editor (say @code{ex}), recognizes the
8005 following command-line syntax:
8007 ex +@var{number} file
8009 The optional numeric value +@var{number} specifies the number of the line in
8010 the file where to start editing.}.
8011 By default, it is @file{@value{EDITOR}}, but you can change this
8012 by setting the environment variable @code{EDITOR} before using
8013 @value{GDBN}. For example, to configure @value{GDBN} to use the
8014 @code{vi} editor, you could use these commands with the @code{sh} shell:
8020 or in the @code{csh} shell,
8022 setenv EDITOR /usr/bin/vi
8027 @section Searching Source Files
8028 @cindex searching source files
8030 There are two commands for searching through the current source file for a
8035 @kindex forward-search
8036 @kindex fo @r{(@code{forward-search})}
8037 @item forward-search @var{regexp}
8038 @itemx search @var{regexp}
8039 The command @samp{forward-search @var{regexp}} checks each line,
8040 starting with the one following the last line listed, for a match for
8041 @var{regexp}. It lists the line that is found. You can use the
8042 synonym @samp{search @var{regexp}} or abbreviate the command name as
8045 @kindex reverse-search
8046 @item reverse-search @var{regexp}
8047 The command @samp{reverse-search @var{regexp}} checks each line, starting
8048 with the one before the last line listed and going backward, for a match
8049 for @var{regexp}. It lists the line that is found. You can abbreviate
8050 this command as @code{rev}.
8054 @section Specifying Source Directories
8057 @cindex directories for source files
8058 Executable programs sometimes do not record the directories of the source
8059 files from which they were compiled, just the names. Even when they do,
8060 the directories could be moved between the compilation and your debugging
8061 session. @value{GDBN} has a list of directories to search for source files;
8062 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8063 it tries all the directories in the list, in the order they are present
8064 in the list, until it finds a file with the desired name.
8066 For example, suppose an executable references the file
8067 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8068 @file{/mnt/cross}. The file is first looked up literally; if this
8069 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8070 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8071 message is printed. @value{GDBN} does not look up the parts of the
8072 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8073 Likewise, the subdirectories of the source path are not searched: if
8074 the source path is @file{/mnt/cross}, and the binary refers to
8075 @file{foo.c}, @value{GDBN} would not find it under
8076 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8078 Plain file names, relative file names with leading directories, file
8079 names containing dots, etc.@: are all treated as described above; for
8080 instance, if the source path is @file{/mnt/cross}, and the source file
8081 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8082 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8083 that---@file{/mnt/cross/foo.c}.
8085 Note that the executable search path is @emph{not} used to locate the
8088 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8089 any information it has cached about where source files are found and where
8090 each line is in the file.
8094 When you start @value{GDBN}, its source path includes only @samp{cdir}
8095 and @samp{cwd}, in that order.
8096 To add other directories, use the @code{directory} command.
8098 The search path is used to find both program source files and @value{GDBN}
8099 script files (read using the @samp{-command} option and @samp{source} command).
8101 In addition to the source path, @value{GDBN} provides a set of commands
8102 that manage a list of source path substitution rules. A @dfn{substitution
8103 rule} specifies how to rewrite source directories stored in the program's
8104 debug information in case the sources were moved to a different
8105 directory between compilation and debugging. A rule is made of
8106 two strings, the first specifying what needs to be rewritten in
8107 the path, and the second specifying how it should be rewritten.
8108 In @ref{set substitute-path}, we name these two parts @var{from} and
8109 @var{to} respectively. @value{GDBN} does a simple string replacement
8110 of @var{from} with @var{to} at the start of the directory part of the
8111 source file name, and uses that result instead of the original file
8112 name to look up the sources.
8114 Using the previous example, suppose the @file{foo-1.0} tree has been
8115 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8116 @value{GDBN} to replace @file{/usr/src} in all source path names with
8117 @file{/mnt/cross}. The first lookup will then be
8118 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8119 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8120 substitution rule, use the @code{set substitute-path} command
8121 (@pxref{set substitute-path}).
8123 To avoid unexpected substitution results, a rule is applied only if the
8124 @var{from} part of the directory name ends at a directory separator.
8125 For instance, a rule substituting @file{/usr/source} into
8126 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8127 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8128 is applied only at the beginning of the directory name, this rule will
8129 not be applied to @file{/root/usr/source/baz.c} either.
8131 In many cases, you can achieve the same result using the @code{directory}
8132 command. However, @code{set substitute-path} can be more efficient in
8133 the case where the sources are organized in a complex tree with multiple
8134 subdirectories. With the @code{directory} command, you need to add each
8135 subdirectory of your project. If you moved the entire tree while
8136 preserving its internal organization, then @code{set substitute-path}
8137 allows you to direct the debugger to all the sources with one single
8140 @code{set substitute-path} is also more than just a shortcut command.
8141 The source path is only used if the file at the original location no
8142 longer exists. On the other hand, @code{set substitute-path} modifies
8143 the debugger behavior to look at the rewritten location instead. So, if
8144 for any reason a source file that is not relevant to your executable is
8145 located at the original location, a substitution rule is the only
8146 method available to point @value{GDBN} at the new location.
8148 @cindex @samp{--with-relocated-sources}
8149 @cindex default source path substitution
8150 You can configure a default source path substitution rule by
8151 configuring @value{GDBN} with the
8152 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8153 should be the name of a directory under @value{GDBN}'s configured
8154 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8155 directory names in debug information under @var{dir} will be adjusted
8156 automatically if the installed @value{GDBN} is moved to a new
8157 location. This is useful if @value{GDBN}, libraries or executables
8158 with debug information and corresponding source code are being moved
8162 @item directory @var{dirname} @dots{}
8163 @item dir @var{dirname} @dots{}
8164 Add directory @var{dirname} to the front of the source path. Several
8165 directory names may be given to this command, separated by @samp{:}
8166 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8167 part of absolute file names) or
8168 whitespace. You may specify a directory that is already in the source
8169 path; this moves it forward, so @value{GDBN} searches it sooner.
8173 @vindex $cdir@r{, convenience variable}
8174 @vindex $cwd@r{, convenience variable}
8175 @cindex compilation directory
8176 @cindex current directory
8177 @cindex working directory
8178 @cindex directory, current
8179 @cindex directory, compilation
8180 You can use the string @samp{$cdir} to refer to the compilation
8181 directory (if one is recorded), and @samp{$cwd} to refer to the current
8182 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8183 tracks the current working directory as it changes during your @value{GDBN}
8184 session, while the latter is immediately expanded to the current
8185 directory at the time you add an entry to the source path.
8188 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8190 @c RET-repeat for @code{directory} is explicitly disabled, but since
8191 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8193 @item set directories @var{path-list}
8194 @kindex set directories
8195 Set the source path to @var{path-list}.
8196 @samp{$cdir:$cwd} are added if missing.
8198 @item show directories
8199 @kindex show directories
8200 Print the source path: show which directories it contains.
8202 @anchor{set substitute-path}
8203 @item set substitute-path @var{from} @var{to}
8204 @kindex set substitute-path
8205 Define a source path substitution rule, and add it at the end of the
8206 current list of existing substitution rules. If a rule with the same
8207 @var{from} was already defined, then the old rule is also deleted.
8209 For example, if the file @file{/foo/bar/baz.c} was moved to
8210 @file{/mnt/cross/baz.c}, then the command
8213 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8217 will tell @value{GDBN} to replace @samp{/foo/bar} with
8218 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8219 @file{baz.c} even though it was moved.
8221 In the case when more than one substitution rule have been defined,
8222 the rules are evaluated one by one in the order where they have been
8223 defined. The first one matching, if any, is selected to perform
8226 For instance, if we had entered the following commands:
8229 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8230 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8234 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8235 @file{/mnt/include/defs.h} by using the first rule. However, it would
8236 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8237 @file{/mnt/src/lib/foo.c}.
8240 @item unset substitute-path [path]
8241 @kindex unset substitute-path
8242 If a path is specified, search the current list of substitution rules
8243 for a rule that would rewrite that path. Delete that rule if found.
8244 A warning is emitted by the debugger if no rule could be found.
8246 If no path is specified, then all substitution rules are deleted.
8248 @item show substitute-path [path]
8249 @kindex show substitute-path
8250 If a path is specified, then print the source path substitution rule
8251 which would rewrite that path, if any.
8253 If no path is specified, then print all existing source path substitution
8258 If your source path is cluttered with directories that are no longer of
8259 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8260 versions of source. You can correct the situation as follows:
8264 Use @code{directory} with no argument to reset the source path to its default value.
8267 Use @code{directory} with suitable arguments to reinstall the
8268 directories you want in the source path. You can add all the
8269 directories in one command.
8273 @section Source and Machine Code
8274 @cindex source line and its code address
8276 You can use the command @code{info line} to map source lines to program
8277 addresses (and vice versa), and the command @code{disassemble} to display
8278 a range of addresses as machine instructions. You can use the command
8279 @code{set disassemble-next-line} to set whether to disassemble next
8280 source line when execution stops. When run under @sc{gnu} Emacs
8281 mode, the @code{info line} command causes the arrow to point to the
8282 line specified. Also, @code{info line} prints addresses in symbolic form as
8287 @item info line @var{location}
8288 Print the starting and ending addresses of the compiled code for
8289 source line @var{location}. You can specify source lines in any of
8290 the ways documented in @ref{Specify Location}.
8293 For example, we can use @code{info line} to discover the location of
8294 the object code for the first line of function
8295 @code{m4_changequote}:
8297 @c FIXME: I think this example should also show the addresses in
8298 @c symbolic form, as they usually would be displayed.
8300 (@value{GDBP}) info line m4_changequote
8301 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8305 @cindex code address and its source line
8306 We can also inquire (using @code{*@var{addr}} as the form for
8307 @var{location}) what source line covers a particular address:
8309 (@value{GDBP}) info line *0x63ff
8310 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8313 @cindex @code{$_} and @code{info line}
8314 @cindex @code{x} command, default address
8315 @kindex x@r{(examine), and} info line
8316 After @code{info line}, the default address for the @code{x} command
8317 is changed to the starting address of the line, so that @samp{x/i} is
8318 sufficient to begin examining the machine code (@pxref{Memory,
8319 ,Examining Memory}). Also, this address is saved as the value of the
8320 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8325 @cindex assembly instructions
8326 @cindex instructions, assembly
8327 @cindex machine instructions
8328 @cindex listing machine instructions
8330 @itemx disassemble /m
8331 @itemx disassemble /s
8332 @itemx disassemble /r
8333 This specialized command dumps a range of memory as machine
8334 instructions. It can also print mixed source+disassembly by specifying
8335 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8336 as well as in symbolic form by specifying the @code{/r} modifier.
8337 The default memory range is the function surrounding the
8338 program counter of the selected frame. A single argument to this
8339 command is a program counter value; @value{GDBN} dumps the function
8340 surrounding this value. When two arguments are given, they should
8341 be separated by a comma, possibly surrounded by whitespace. The
8342 arguments specify a range of addresses to dump, in one of two forms:
8345 @item @var{start},@var{end}
8346 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8347 @item @var{start},+@var{length}
8348 the addresses from @var{start} (inclusive) to
8349 @code{@var{start}+@var{length}} (exclusive).
8353 When 2 arguments are specified, the name of the function is also
8354 printed (since there could be several functions in the given range).
8356 The argument(s) can be any expression yielding a numeric value, such as
8357 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8359 If the range of memory being disassembled contains current program counter,
8360 the instruction at that location is shown with a @code{=>} marker.
8363 The following example shows the disassembly of a range of addresses of
8364 HP PA-RISC 2.0 code:
8367 (@value{GDBP}) disas 0x32c4, 0x32e4
8368 Dump of assembler code from 0x32c4 to 0x32e4:
8369 0x32c4 <main+204>: addil 0,dp
8370 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8371 0x32cc <main+212>: ldil 0x3000,r31
8372 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8373 0x32d4 <main+220>: ldo 0(r31),rp
8374 0x32d8 <main+224>: addil -0x800,dp
8375 0x32dc <main+228>: ldo 0x588(r1),r26
8376 0x32e0 <main+232>: ldil 0x3000,r31
8377 End of assembler dump.
8380 Here is an example showing mixed source+assembly for Intel x86
8381 with @code{/m} or @code{/s}, when the program is stopped just after
8382 function prologue in a non-optimized function with no inline code.
8385 (@value{GDBP}) disas /m main
8386 Dump of assembler code for function main:
8388 0x08048330 <+0>: push %ebp
8389 0x08048331 <+1>: mov %esp,%ebp
8390 0x08048333 <+3>: sub $0x8,%esp
8391 0x08048336 <+6>: and $0xfffffff0,%esp
8392 0x08048339 <+9>: sub $0x10,%esp
8394 6 printf ("Hello.\n");
8395 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8396 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8400 0x08048348 <+24>: mov $0x0,%eax
8401 0x0804834d <+29>: leave
8402 0x0804834e <+30>: ret
8404 End of assembler dump.
8407 The @code{/m} option is deprecated as its output is not useful when
8408 there is either inlined code or re-ordered code.
8409 The @code{/s} option is the preferred choice.
8410 Here is an example for AMD x86-64 showing the difference between
8411 @code{/m} output and @code{/s} output.
8412 This example has one inline function defined in a header file,
8413 and the code is compiled with @samp{-O2} optimization.
8414 Note how the @code{/m} output is missing the disassembly of
8415 several instructions that are present in the @code{/s} output.
8445 (@value{GDBP}) disas /m main
8446 Dump of assembler code for function main:
8450 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8451 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8455 0x000000000040041d <+29>: xor %eax,%eax
8456 0x000000000040041f <+31>: retq
8457 0x0000000000400420 <+32>: add %eax,%eax
8458 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8460 End of assembler dump.
8461 (@value{GDBP}) disas /s main
8462 Dump of assembler code for function main:
8466 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8470 0x0000000000400406 <+6>: test %eax,%eax
8471 0x0000000000400408 <+8>: js 0x400420 <main+32>
8476 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8477 0x000000000040040d <+13>: test %eax,%eax
8478 0x000000000040040f <+15>: mov $0x1,%eax
8479 0x0000000000400414 <+20>: cmovne %edx,%eax
8483 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8487 0x000000000040041d <+29>: xor %eax,%eax
8488 0x000000000040041f <+31>: retq
8492 0x0000000000400420 <+32>: add %eax,%eax
8493 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8494 End of assembler dump.
8497 Here is another example showing raw instructions in hex for AMD x86-64,
8500 (gdb) disas /r 0x400281,+10
8501 Dump of assembler code from 0x400281 to 0x40028b:
8502 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8503 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8504 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8505 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8506 End of assembler dump.
8509 Addresses cannot be specified as a location (@pxref{Specify Location}).
8510 So, for example, if you want to disassemble function @code{bar}
8511 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8512 and not @samp{disassemble foo.c:bar}.
8514 Some architectures have more than one commonly-used set of instruction
8515 mnemonics or other syntax.
8517 For programs that were dynamically linked and use shared libraries,
8518 instructions that call functions or branch to locations in the shared
8519 libraries might show a seemingly bogus location---it's actually a
8520 location of the relocation table. On some architectures, @value{GDBN}
8521 might be able to resolve these to actual function names.
8524 @kindex set disassembler-options
8525 @cindex disassembler options
8526 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8527 This command controls the passing of target specific information to
8528 the disassembler. For a list of valid options, please refer to the
8529 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8530 manual and/or the output of @kbd{objdump --help}
8531 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8532 The default value is the empty string.
8534 If it is necessary to specify more than one disassembler option, then
8535 multiple options can be placed together into a comma separated list.
8536 Currently this command is only supported on targets ARM, PowerPC
8539 @kindex show disassembler-options
8540 @item show disassembler-options
8541 Show the current setting of the disassembler options.
8545 @kindex set disassembly-flavor
8546 @cindex Intel disassembly flavor
8547 @cindex AT&T disassembly flavor
8548 @item set disassembly-flavor @var{instruction-set}
8549 Select the instruction set to use when disassembling the
8550 program via the @code{disassemble} or @code{x/i} commands.
8552 Currently this command is only defined for the Intel x86 family. You
8553 can set @var{instruction-set} to either @code{intel} or @code{att}.
8554 The default is @code{att}, the AT&T flavor used by default by Unix
8555 assemblers for x86-based targets.
8557 @kindex show disassembly-flavor
8558 @item show disassembly-flavor
8559 Show the current setting of the disassembly flavor.
8563 @kindex set disassemble-next-line
8564 @kindex show disassemble-next-line
8565 @item set disassemble-next-line
8566 @itemx show disassemble-next-line
8567 Control whether or not @value{GDBN} will disassemble the next source
8568 line or instruction when execution stops. If ON, @value{GDBN} will
8569 display disassembly of the next source line when execution of the
8570 program being debugged stops. This is @emph{in addition} to
8571 displaying the source line itself, which @value{GDBN} always does if
8572 possible. If the next source line cannot be displayed for some reason
8573 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8574 info in the debug info), @value{GDBN} will display disassembly of the
8575 next @emph{instruction} instead of showing the next source line. If
8576 AUTO, @value{GDBN} will display disassembly of next instruction only
8577 if the source line cannot be displayed. This setting causes
8578 @value{GDBN} to display some feedback when you step through a function
8579 with no line info or whose source file is unavailable. The default is
8580 OFF, which means never display the disassembly of the next line or
8586 @chapter Examining Data
8588 @cindex printing data
8589 @cindex examining data
8592 The usual way to examine data in your program is with the @code{print}
8593 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8594 evaluates and prints the value of an expression of the language your
8595 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8596 Different Languages}). It may also print the expression using a
8597 Python-based pretty-printer (@pxref{Pretty Printing}).
8600 @item print @var{expr}
8601 @itemx print /@var{f} @var{expr}
8602 @var{expr} is an expression (in the source language). By default the
8603 value of @var{expr} is printed in a format appropriate to its data type;
8604 you can choose a different format by specifying @samp{/@var{f}}, where
8605 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8609 @itemx print /@var{f}
8610 @cindex reprint the last value
8611 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8612 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8613 conveniently inspect the same value in an alternative format.
8616 A more low-level way of examining data is with the @code{x} command.
8617 It examines data in memory at a specified address and prints it in a
8618 specified format. @xref{Memory, ,Examining Memory}.
8620 If you are interested in information about types, or about how the
8621 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8622 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8625 @cindex exploring hierarchical data structures
8627 Another way of examining values of expressions and type information is
8628 through the Python extension command @code{explore} (available only if
8629 the @value{GDBN} build is configured with @code{--with-python}). It
8630 offers an interactive way to start at the highest level (or, the most
8631 abstract level) of the data type of an expression (or, the data type
8632 itself) and explore all the way down to leaf scalar values/fields
8633 embedded in the higher level data types.
8636 @item explore @var{arg}
8637 @var{arg} is either an expression (in the source language), or a type
8638 visible in the current context of the program being debugged.
8641 The working of the @code{explore} command can be illustrated with an
8642 example. If a data type @code{struct ComplexStruct} is defined in your
8652 struct ComplexStruct
8654 struct SimpleStruct *ss_p;
8660 followed by variable declarations as
8663 struct SimpleStruct ss = @{ 10, 1.11 @};
8664 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8668 then, the value of the variable @code{cs} can be explored using the
8669 @code{explore} command as follows.
8673 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8674 the following fields:
8676 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8677 arr = <Enter 1 to explore this field of type `int [10]'>
8679 Enter the field number of choice:
8683 Since the fields of @code{cs} are not scalar values, you are being
8684 prompted to chose the field you want to explore. Let's say you choose
8685 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8686 pointer, you will be asked if it is pointing to a single value. From
8687 the declaration of @code{cs} above, it is indeed pointing to a single
8688 value, hence you enter @code{y}. If you enter @code{n}, then you will
8689 be asked if it were pointing to an array of values, in which case this
8690 field will be explored as if it were an array.
8693 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8694 Continue exploring it as a pointer to a single value [y/n]: y
8695 The value of `*(cs.ss_p)' is a struct/class of type `struct
8696 SimpleStruct' with the following fields:
8698 i = 10 .. (Value of type `int')
8699 d = 1.1100000000000001 .. (Value of type `double')
8701 Press enter to return to parent value:
8705 If the field @code{arr} of @code{cs} was chosen for exploration by
8706 entering @code{1} earlier, then since it is as array, you will be
8707 prompted to enter the index of the element in the array that you want
8711 `cs.arr' is an array of `int'.
8712 Enter the index of the element you want to explore in `cs.arr': 5
8714 `(cs.arr)[5]' is a scalar value of type `int'.
8718 Press enter to return to parent value:
8721 In general, at any stage of exploration, you can go deeper towards the
8722 leaf values by responding to the prompts appropriately, or hit the
8723 return key to return to the enclosing data structure (the @i{higher}
8724 level data structure).
8726 Similar to exploring values, you can use the @code{explore} command to
8727 explore types. Instead of specifying a value (which is typically a
8728 variable name or an expression valid in the current context of the
8729 program being debugged), you specify a type name. If you consider the
8730 same example as above, your can explore the type
8731 @code{struct ComplexStruct} by passing the argument
8732 @code{struct ComplexStruct} to the @code{explore} command.
8735 (gdb) explore struct ComplexStruct
8739 By responding to the prompts appropriately in the subsequent interactive
8740 session, you can explore the type @code{struct ComplexStruct} in a
8741 manner similar to how the value @code{cs} was explored in the above
8744 The @code{explore} command also has two sub-commands,
8745 @code{explore value} and @code{explore type}. The former sub-command is
8746 a way to explicitly specify that value exploration of the argument is
8747 being invoked, while the latter is a way to explicitly specify that type
8748 exploration of the argument is being invoked.
8751 @item explore value @var{expr}
8752 @cindex explore value
8753 This sub-command of @code{explore} explores the value of the
8754 expression @var{expr} (if @var{expr} is an expression valid in the
8755 current context of the program being debugged). The behavior of this
8756 command is identical to that of the behavior of the @code{explore}
8757 command being passed the argument @var{expr}.
8759 @item explore type @var{arg}
8760 @cindex explore type
8761 This sub-command of @code{explore} explores the type of @var{arg} (if
8762 @var{arg} is a type visible in the current context of program being
8763 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8764 is an expression valid in the current context of the program being
8765 debugged). If @var{arg} is a type, then the behavior of this command is
8766 identical to that of the @code{explore} command being passed the
8767 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8768 this command will be identical to that of the @code{explore} command
8769 being passed the type of @var{arg} as the argument.
8773 * Expressions:: Expressions
8774 * Ambiguous Expressions:: Ambiguous Expressions
8775 * Variables:: Program variables
8776 * Arrays:: Artificial arrays
8777 * Output Formats:: Output formats
8778 * Memory:: Examining memory
8779 * Auto Display:: Automatic display
8780 * Print Settings:: Print settings
8781 * Pretty Printing:: Python pretty printing
8782 * Value History:: Value history
8783 * Convenience Vars:: Convenience variables
8784 * Convenience Funs:: Convenience functions
8785 * Registers:: Registers
8786 * Floating Point Hardware:: Floating point hardware
8787 * Vector Unit:: Vector Unit
8788 * OS Information:: Auxiliary data provided by operating system
8789 * Memory Region Attributes:: Memory region attributes
8790 * Dump/Restore Files:: Copy between memory and a file
8791 * Core File Generation:: Cause a program dump its core
8792 * Character Sets:: Debugging programs that use a different
8793 character set than GDB does
8794 * Caching Target Data:: Data caching for targets
8795 * Searching Memory:: Searching memory for a sequence of bytes
8796 * Value Sizes:: Managing memory allocated for values
8800 @section Expressions
8803 @code{print} and many other @value{GDBN} commands accept an expression and
8804 compute its value. Any kind of constant, variable or operator defined
8805 by the programming language you are using is valid in an expression in
8806 @value{GDBN}. This includes conditional expressions, function calls,
8807 casts, and string constants. It also includes preprocessor macros, if
8808 you compiled your program to include this information; see
8811 @cindex arrays in expressions
8812 @value{GDBN} supports array constants in expressions input by
8813 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8814 you can use the command @code{print @{1, 2, 3@}} to create an array
8815 of three integers. If you pass an array to a function or assign it
8816 to a program variable, @value{GDBN} copies the array to memory that
8817 is @code{malloc}ed in the target program.
8819 Because C is so widespread, most of the expressions shown in examples in
8820 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8821 Languages}, for information on how to use expressions in other
8824 In this section, we discuss operators that you can use in @value{GDBN}
8825 expressions regardless of your programming language.
8827 @cindex casts, in expressions
8828 Casts are supported in all languages, not just in C, because it is so
8829 useful to cast a number into a pointer in order to examine a structure
8830 at that address in memory.
8831 @c FIXME: casts supported---Mod2 true?
8833 @value{GDBN} supports these operators, in addition to those common
8834 to programming languages:
8838 @samp{@@} is a binary operator for treating parts of memory as arrays.
8839 @xref{Arrays, ,Artificial Arrays}, for more information.
8842 @samp{::} allows you to specify a variable in terms of the file or
8843 function where it is defined. @xref{Variables, ,Program Variables}.
8845 @cindex @{@var{type}@}
8846 @cindex type casting memory
8847 @cindex memory, viewing as typed object
8848 @cindex casts, to view memory
8849 @item @{@var{type}@} @var{addr}
8850 Refers to an object of type @var{type} stored at address @var{addr} in
8851 memory. The address @var{addr} may be any expression whose value is
8852 an integer or pointer (but parentheses are required around binary
8853 operators, just as in a cast). This construct is allowed regardless
8854 of what kind of data is normally supposed to reside at @var{addr}.
8857 @node Ambiguous Expressions
8858 @section Ambiguous Expressions
8859 @cindex ambiguous expressions
8861 Expressions can sometimes contain some ambiguous elements. For instance,
8862 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8863 a single function name to be defined several times, for application in
8864 different contexts. This is called @dfn{overloading}. Another example
8865 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8866 templates and is typically instantiated several times, resulting in
8867 the same function name being defined in different contexts.
8869 In some cases and depending on the language, it is possible to adjust
8870 the expression to remove the ambiguity. For instance in C@t{++}, you
8871 can specify the signature of the function you want to break on, as in
8872 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8873 qualified name of your function often makes the expression unambiguous
8876 When an ambiguity that needs to be resolved is detected, the debugger
8877 has the capability to display a menu of numbered choices for each
8878 possibility, and then waits for the selection with the prompt @samp{>}.
8879 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8880 aborts the current command. If the command in which the expression was
8881 used allows more than one choice to be selected, the next option in the
8882 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8885 For example, the following session excerpt shows an attempt to set a
8886 breakpoint at the overloaded symbol @code{String::after}.
8887 We choose three particular definitions of that function name:
8889 @c FIXME! This is likely to change to show arg type lists, at least
8892 (@value{GDBP}) b String::after
8895 [2] file:String.cc; line number:867
8896 [3] file:String.cc; line number:860
8897 [4] file:String.cc; line number:875
8898 [5] file:String.cc; line number:853
8899 [6] file:String.cc; line number:846
8900 [7] file:String.cc; line number:735
8902 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8903 Breakpoint 2 at 0xb344: file String.cc, line 875.
8904 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8905 Multiple breakpoints were set.
8906 Use the "delete" command to delete unwanted
8913 @kindex set multiple-symbols
8914 @item set multiple-symbols @var{mode}
8915 @cindex multiple-symbols menu
8917 This option allows you to adjust the debugger behavior when an expression
8920 By default, @var{mode} is set to @code{all}. If the command with which
8921 the expression is used allows more than one choice, then @value{GDBN}
8922 automatically selects all possible choices. For instance, inserting
8923 a breakpoint on a function using an ambiguous name results in a breakpoint
8924 inserted on each possible match. However, if a unique choice must be made,
8925 then @value{GDBN} uses the menu to help you disambiguate the expression.
8926 For instance, printing the address of an overloaded function will result
8927 in the use of the menu.
8929 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8930 when an ambiguity is detected.
8932 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8933 an error due to the ambiguity and the command is aborted.
8935 @kindex show multiple-symbols
8936 @item show multiple-symbols
8937 Show the current value of the @code{multiple-symbols} setting.
8941 @section Program Variables
8943 The most common kind of expression to use is the name of a variable
8946 Variables in expressions are understood in the selected stack frame
8947 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8951 global (or file-static)
8958 visible according to the scope rules of the
8959 programming language from the point of execution in that frame
8962 @noindent This means that in the function
8977 you can examine and use the variable @code{a} whenever your program is
8978 executing within the function @code{foo}, but you can only use or
8979 examine the variable @code{b} while your program is executing inside
8980 the block where @code{b} is declared.
8982 @cindex variable name conflict
8983 There is an exception: you can refer to a variable or function whose
8984 scope is a single source file even if the current execution point is not
8985 in this file. But it is possible to have more than one such variable or
8986 function with the same name (in different source files). If that
8987 happens, referring to that name has unpredictable effects. If you wish,
8988 you can specify a static variable in a particular function or file by
8989 using the colon-colon (@code{::}) notation:
8991 @cindex colon-colon, context for variables/functions
8993 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8994 @cindex @code{::}, context for variables/functions
8997 @var{file}::@var{variable}
8998 @var{function}::@var{variable}
9002 Here @var{file} or @var{function} is the name of the context for the
9003 static @var{variable}. In the case of file names, you can use quotes to
9004 make sure @value{GDBN} parses the file name as a single word---for example,
9005 to print a global value of @code{x} defined in @file{f2.c}:
9008 (@value{GDBP}) p 'f2.c'::x
9011 The @code{::} notation is normally used for referring to
9012 static variables, since you typically disambiguate uses of local variables
9013 in functions by selecting the appropriate frame and using the
9014 simple name of the variable. However, you may also use this notation
9015 to refer to local variables in frames enclosing the selected frame:
9024 process (a); /* Stop here */
9035 For example, if there is a breakpoint at the commented line,
9036 here is what you might see
9037 when the program stops after executing the call @code{bar(0)}:
9042 (@value{GDBP}) p bar::a
9045 #2 0x080483d0 in foo (a=5) at foobar.c:12
9048 (@value{GDBP}) p bar::a
9052 @cindex C@t{++} scope resolution
9053 These uses of @samp{::} are very rarely in conflict with the very
9054 similar use of the same notation in C@t{++}. When they are in
9055 conflict, the C@t{++} meaning takes precedence; however, this can be
9056 overridden by quoting the file or function name with single quotes.
9058 For example, suppose the program is stopped in a method of a class
9059 that has a field named @code{includefile}, and there is also an
9060 include file named @file{includefile} that defines a variable,
9064 (@value{GDBP}) p includefile
9066 (@value{GDBP}) p includefile::some_global
9067 A syntax error in expression, near `'.
9068 (@value{GDBP}) p 'includefile'::some_global
9072 @cindex wrong values
9073 @cindex variable values, wrong
9074 @cindex function entry/exit, wrong values of variables
9075 @cindex optimized code, wrong values of variables
9077 @emph{Warning:} Occasionally, a local variable may appear to have the
9078 wrong value at certain points in a function---just after entry to a new
9079 scope, and just before exit.
9081 You may see this problem when you are stepping by machine instructions.
9082 This is because, on most machines, it takes more than one instruction to
9083 set up a stack frame (including local variable definitions); if you are
9084 stepping by machine instructions, variables may appear to have the wrong
9085 values until the stack frame is completely built. On exit, it usually
9086 also takes more than one machine instruction to destroy a stack frame;
9087 after you begin stepping through that group of instructions, local
9088 variable definitions may be gone.
9090 This may also happen when the compiler does significant optimizations.
9091 To be sure of always seeing accurate values, turn off all optimization
9094 @cindex ``No symbol "foo" in current context''
9095 Another possible effect of compiler optimizations is to optimize
9096 unused variables out of existence, or assign variables to registers (as
9097 opposed to memory addresses). Depending on the support for such cases
9098 offered by the debug info format used by the compiler, @value{GDBN}
9099 might not be able to display values for such local variables. If that
9100 happens, @value{GDBN} will print a message like this:
9103 No symbol "foo" in current context.
9106 To solve such problems, either recompile without optimizations, or use a
9107 different debug info format, if the compiler supports several such
9108 formats. @xref{Compilation}, for more information on choosing compiler
9109 options. @xref{C, ,C and C@t{++}}, for more information about debug
9110 info formats that are best suited to C@t{++} programs.
9112 If you ask to print an object whose contents are unknown to
9113 @value{GDBN}, e.g., because its data type is not completely specified
9114 by the debug information, @value{GDBN} will say @samp{<incomplete
9115 type>}. @xref{Symbols, incomplete type}, for more about this.
9117 If you append @kbd{@@entry} string to a function parameter name you get its
9118 value at the time the function got called. If the value is not available an
9119 error message is printed. Entry values are available only with some compilers.
9120 Entry values are normally also printed at the function parameter list according
9121 to @ref{set print entry-values}.
9124 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9130 (gdb) print i@@entry
9134 Strings are identified as arrays of @code{char} values without specified
9135 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9136 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9137 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9138 defines literal string type @code{"char"} as @code{char} without a sign.
9143 signed char var1[] = "A";
9146 You get during debugging
9151 $2 = @{65 'A', 0 '\0'@}
9155 @section Artificial Arrays
9157 @cindex artificial array
9159 @kindex @@@r{, referencing memory as an array}
9160 It is often useful to print out several successive objects of the
9161 same type in memory; a section of an array, or an array of
9162 dynamically determined size for which only a pointer exists in the
9165 You can do this by referring to a contiguous span of memory as an
9166 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9167 operand of @samp{@@} should be the first element of the desired array
9168 and be an individual object. The right operand should be the desired length
9169 of the array. The result is an array value whose elements are all of
9170 the type of the left argument. The first element is actually the left
9171 argument; the second element comes from bytes of memory immediately
9172 following those that hold the first element, and so on. Here is an
9173 example. If a program says
9176 int *array = (int *) malloc (len * sizeof (int));
9180 you can print the contents of @code{array} with
9186 The left operand of @samp{@@} must reside in memory. Array values made
9187 with @samp{@@} in this way behave just like other arrays in terms of
9188 subscripting, and are coerced to pointers when used in expressions.
9189 Artificial arrays most often appear in expressions via the value history
9190 (@pxref{Value History, ,Value History}), after printing one out.
9192 Another way to create an artificial array is to use a cast.
9193 This re-interprets a value as if it were an array.
9194 The value need not be in memory:
9196 (@value{GDBP}) p/x (short[2])0x12345678
9197 $1 = @{0x1234, 0x5678@}
9200 As a convenience, if you leave the array length out (as in
9201 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9202 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9204 (@value{GDBP}) p/x (short[])0x12345678
9205 $2 = @{0x1234, 0x5678@}
9208 Sometimes the artificial array mechanism is not quite enough; in
9209 moderately complex data structures, the elements of interest may not
9210 actually be adjacent---for example, if you are interested in the values
9211 of pointers in an array. One useful work-around in this situation is
9212 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9213 Variables}) as a counter in an expression that prints the first
9214 interesting value, and then repeat that expression via @key{RET}. For
9215 instance, suppose you have an array @code{dtab} of pointers to
9216 structures, and you are interested in the values of a field @code{fv}
9217 in each structure. Here is an example of what you might type:
9227 @node Output Formats
9228 @section Output Formats
9230 @cindex formatted output
9231 @cindex output formats
9232 By default, @value{GDBN} prints a value according to its data type. Sometimes
9233 this is not what you want. For example, you might want to print a number
9234 in hex, or a pointer in decimal. Or you might want to view data in memory
9235 at a certain address as a character string or as an instruction. To do
9236 these things, specify an @dfn{output format} when you print a value.
9238 The simplest use of output formats is to say how to print a value
9239 already computed. This is done by starting the arguments of the
9240 @code{print} command with a slash and a format letter. The format
9241 letters supported are:
9245 Regard the bits of the value as an integer, and print the integer in
9249 Print as integer in signed decimal.
9252 Print as integer in unsigned decimal.
9255 Print as integer in octal.
9258 Print as integer in binary. The letter @samp{t} stands for ``two''.
9259 @footnote{@samp{b} cannot be used because these format letters are also
9260 used with the @code{x} command, where @samp{b} stands for ``byte'';
9261 see @ref{Memory,,Examining Memory}.}
9264 @cindex unknown address, locating
9265 @cindex locate address
9266 Print as an address, both absolute in hexadecimal and as an offset from
9267 the nearest preceding symbol. You can use this format used to discover
9268 where (in what function) an unknown address is located:
9271 (@value{GDBP}) p/a 0x54320
9272 $3 = 0x54320 <_initialize_vx+396>
9276 The command @code{info symbol 0x54320} yields similar results.
9277 @xref{Symbols, info symbol}.
9280 Regard as an integer and print it as a character constant. This
9281 prints both the numerical value and its character representation. The
9282 character representation is replaced with the octal escape @samp{\nnn}
9283 for characters outside the 7-bit @sc{ascii} range.
9285 Without this format, @value{GDBN} displays @code{char},
9286 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9287 constants. Single-byte members of vectors are displayed as integer
9291 Regard the bits of the value as a floating point number and print
9292 using typical floating point syntax.
9295 @cindex printing strings
9296 @cindex printing byte arrays
9297 Regard as a string, if possible. With this format, pointers to single-byte
9298 data are displayed as null-terminated strings and arrays of single-byte data
9299 are displayed as fixed-length strings. Other values are displayed in their
9302 Without this format, @value{GDBN} displays pointers to and arrays of
9303 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9304 strings. Single-byte members of a vector are displayed as an integer
9308 Like @samp{x} formatting, the value is treated as an integer and
9309 printed as hexadecimal, but leading zeros are printed to pad the value
9310 to the size of the integer type.
9313 @cindex raw printing
9314 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9315 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9316 Printing}). This typically results in a higher-level display of the
9317 value's contents. The @samp{r} format bypasses any Python
9318 pretty-printer which might exist.
9321 For example, to print the program counter in hex (@pxref{Registers}), type
9328 Note that no space is required before the slash; this is because command
9329 names in @value{GDBN} cannot contain a slash.
9331 To reprint the last value in the value history with a different format,
9332 you can use the @code{print} command with just a format and no
9333 expression. For example, @samp{p/x} reprints the last value in hex.
9336 @section Examining Memory
9338 You can use the command @code{x} (for ``examine'') to examine memory in
9339 any of several formats, independently of your program's data types.
9341 @cindex examining memory
9343 @kindex x @r{(examine memory)}
9344 @item x/@var{nfu} @var{addr}
9347 Use the @code{x} command to examine memory.
9350 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9351 much memory to display and how to format it; @var{addr} is an
9352 expression giving the address where you want to start displaying memory.
9353 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9354 Several commands set convenient defaults for @var{addr}.
9357 @item @var{n}, the repeat count
9358 The repeat count is a decimal integer; the default is 1. It specifies
9359 how much memory (counting by units @var{u}) to display. If a negative
9360 number is specified, memory is examined backward from @var{addr}.
9361 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9364 @item @var{f}, the display format
9365 The display format is one of the formats used by @code{print}
9366 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9367 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9368 The default is @samp{x} (hexadecimal) initially. The default changes
9369 each time you use either @code{x} or @code{print}.
9371 @item @var{u}, the unit size
9372 The unit size is any of
9378 Halfwords (two bytes).
9380 Words (four bytes). This is the initial default.
9382 Giant words (eight bytes).
9385 Each time you specify a unit size with @code{x}, that size becomes the
9386 default unit the next time you use @code{x}. For the @samp{i} format,
9387 the unit size is ignored and is normally not written. For the @samp{s} format,
9388 the unit size defaults to @samp{b}, unless it is explicitly given.
9389 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9390 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9391 Note that the results depend on the programming language of the
9392 current compilation unit. If the language is C, the @samp{s}
9393 modifier will use the UTF-16 encoding while @samp{w} will use
9394 UTF-32. The encoding is set by the programming language and cannot
9397 @item @var{addr}, starting display address
9398 @var{addr} is the address where you want @value{GDBN} to begin displaying
9399 memory. The expression need not have a pointer value (though it may);
9400 it is always interpreted as an integer address of a byte of memory.
9401 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9402 @var{addr} is usually just after the last address examined---but several
9403 other commands also set the default address: @code{info breakpoints} (to
9404 the address of the last breakpoint listed), @code{info line} (to the
9405 starting address of a line), and @code{print} (if you use it to display
9406 a value from memory).
9409 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9410 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9411 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9412 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9413 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9415 You can also specify a negative repeat count to examine memory backward
9416 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9417 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9419 Since the letters indicating unit sizes are all distinct from the
9420 letters specifying output formats, you do not have to remember whether
9421 unit size or format comes first; either order works. The output
9422 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9423 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9425 Even though the unit size @var{u} is ignored for the formats @samp{s}
9426 and @samp{i}, you might still want to use a count @var{n}; for example,
9427 @samp{3i} specifies that you want to see three machine instructions,
9428 including any operands. For convenience, especially when used with
9429 the @code{display} command, the @samp{i} format also prints branch delay
9430 slot instructions, if any, beyond the count specified, which immediately
9431 follow the last instruction that is within the count. The command
9432 @code{disassemble} gives an alternative way of inspecting machine
9433 instructions; see @ref{Machine Code,,Source and Machine Code}.
9435 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9436 the command displays null-terminated strings or instructions before the given
9437 address as many as the absolute value of the given number. For the @samp{i}
9438 format, we use line number information in the debug info to accurately locate
9439 instruction boundaries while disassembling backward. If line info is not
9440 available, the command stops examining memory with an error message.
9442 All the defaults for the arguments to @code{x} are designed to make it
9443 easy to continue scanning memory with minimal specifications each time
9444 you use @code{x}. For example, after you have inspected three machine
9445 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9446 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9447 the repeat count @var{n} is used again; the other arguments default as
9448 for successive uses of @code{x}.
9450 When examining machine instructions, the instruction at current program
9451 counter is shown with a @code{=>} marker. For example:
9454 (@value{GDBP}) x/5i $pc-6
9455 0x804837f <main+11>: mov %esp,%ebp
9456 0x8048381 <main+13>: push %ecx
9457 0x8048382 <main+14>: sub $0x4,%esp
9458 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9459 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9462 @cindex @code{$_}, @code{$__}, and value history
9463 The addresses and contents printed by the @code{x} command are not saved
9464 in the value history because there is often too much of them and they
9465 would get in the way. Instead, @value{GDBN} makes these values available for
9466 subsequent use in expressions as values of the convenience variables
9467 @code{$_} and @code{$__}. After an @code{x} command, the last address
9468 examined is available for use in expressions in the convenience variable
9469 @code{$_}. The contents of that address, as examined, are available in
9470 the convenience variable @code{$__}.
9472 If the @code{x} command has a repeat count, the address and contents saved
9473 are from the last memory unit printed; this is not the same as the last
9474 address printed if several units were printed on the last line of output.
9476 @anchor{addressable memory unit}
9477 @cindex addressable memory unit
9478 Most targets have an addressable memory unit size of 8 bits. This means
9479 that to each memory address are associated 8 bits of data. Some
9480 targets, however, have other addressable memory unit sizes.
9481 Within @value{GDBN} and this document, the term
9482 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9483 when explicitly referring to a chunk of data of that size. The word
9484 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9485 the addressable memory unit size of the target. For most systems,
9486 addressable memory unit is a synonym of byte.
9488 @cindex remote memory comparison
9489 @cindex target memory comparison
9490 @cindex verify remote memory image
9491 @cindex verify target memory image
9492 When you are debugging a program running on a remote target machine
9493 (@pxref{Remote Debugging}), you may wish to verify the program's image
9494 in the remote machine's memory against the executable file you
9495 downloaded to the target. Or, on any target, you may want to check
9496 whether the program has corrupted its own read-only sections. The
9497 @code{compare-sections} command is provided for such situations.
9500 @kindex compare-sections
9501 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9502 Compare the data of a loadable section @var{section-name} in the
9503 executable file of the program being debugged with the same section in
9504 the target machine's memory, and report any mismatches. With no
9505 arguments, compares all loadable sections. With an argument of
9506 @code{-r}, compares all loadable read-only sections.
9508 Note: for remote targets, this command can be accelerated if the
9509 target supports computing the CRC checksum of a block of memory
9510 (@pxref{qCRC packet}).
9514 @section Automatic Display
9515 @cindex automatic display
9516 @cindex display of expressions
9518 If you find that you want to print the value of an expression frequently
9519 (to see how it changes), you might want to add it to the @dfn{automatic
9520 display list} so that @value{GDBN} prints its value each time your program stops.
9521 Each expression added to the list is given a number to identify it;
9522 to remove an expression from the list, you specify that number.
9523 The automatic display looks like this:
9527 3: bar[5] = (struct hack *) 0x3804
9531 This display shows item numbers, expressions and their current values. As with
9532 displays you request manually using @code{x} or @code{print}, you can
9533 specify the output format you prefer; in fact, @code{display} decides
9534 whether to use @code{print} or @code{x} depending your format
9535 specification---it uses @code{x} if you specify either the @samp{i}
9536 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9540 @item display @var{expr}
9541 Add the expression @var{expr} to the list of expressions to display
9542 each time your program stops. @xref{Expressions, ,Expressions}.
9544 @code{display} does not repeat if you press @key{RET} again after using it.
9546 @item display/@var{fmt} @var{expr}
9547 For @var{fmt} specifying only a display format and not a size or
9548 count, add the expression @var{expr} to the auto-display list but
9549 arrange to display it each time in the specified format @var{fmt}.
9550 @xref{Output Formats,,Output Formats}.
9552 @item display/@var{fmt} @var{addr}
9553 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9554 number of units, add the expression @var{addr} as a memory address to
9555 be examined each time your program stops. Examining means in effect
9556 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9559 For example, @samp{display/i $pc} can be helpful, to see the machine
9560 instruction about to be executed each time execution stops (@samp{$pc}
9561 is a common name for the program counter; @pxref{Registers, ,Registers}).
9564 @kindex delete display
9566 @item undisplay @var{dnums}@dots{}
9567 @itemx delete display @var{dnums}@dots{}
9568 Remove items from the list of expressions to display. Specify the
9569 numbers of the displays that you want affected with the command
9570 argument @var{dnums}. It can be a single display number, one of the
9571 numbers shown in the first field of the @samp{info display} display;
9572 or it could be a range of display numbers, as in @code{2-4}.
9574 @code{undisplay} does not repeat if you press @key{RET} after using it.
9575 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9577 @kindex disable display
9578 @item disable display @var{dnums}@dots{}
9579 Disable the display of item numbers @var{dnums}. A disabled display
9580 item is not printed automatically, but is not forgotten. It may be
9581 enabled again later. Specify the numbers of the displays that you
9582 want affected with the command argument @var{dnums}. It can be a
9583 single display number, one of the numbers shown in the first field of
9584 the @samp{info display} display; or it could be a range of display
9585 numbers, as in @code{2-4}.
9587 @kindex enable display
9588 @item enable display @var{dnums}@dots{}
9589 Enable display of item numbers @var{dnums}. It becomes effective once
9590 again in auto display of its expression, until you specify otherwise.
9591 Specify the numbers of the displays that you want affected with the
9592 command argument @var{dnums}. It can be a single display number, one
9593 of the numbers shown in the first field of the @samp{info display}
9594 display; or it could be a range of display numbers, as in @code{2-4}.
9597 Display the current values of the expressions on the list, just as is
9598 done when your program stops.
9600 @kindex info display
9602 Print the list of expressions previously set up to display
9603 automatically, each one with its item number, but without showing the
9604 values. This includes disabled expressions, which are marked as such.
9605 It also includes expressions which would not be displayed right now
9606 because they refer to automatic variables not currently available.
9609 @cindex display disabled out of scope
9610 If a display expression refers to local variables, then it does not make
9611 sense outside the lexical context for which it was set up. Such an
9612 expression is disabled when execution enters a context where one of its
9613 variables is not defined. For example, if you give the command
9614 @code{display last_char} while inside a function with an argument
9615 @code{last_char}, @value{GDBN} displays this argument while your program
9616 continues to stop inside that function. When it stops elsewhere---where
9617 there is no variable @code{last_char}---the display is disabled
9618 automatically. The next time your program stops where @code{last_char}
9619 is meaningful, you can enable the display expression once again.
9621 @node Print Settings
9622 @section Print Settings
9624 @cindex format options
9625 @cindex print settings
9626 @value{GDBN} provides the following ways to control how arrays, structures,
9627 and symbols are printed.
9630 These settings are useful for debugging programs in any language:
9634 @item set print address
9635 @itemx set print address on
9636 @cindex print/don't print memory addresses
9637 @value{GDBN} prints memory addresses showing the location of stack
9638 traces, structure values, pointer values, breakpoints, and so forth,
9639 even when it also displays the contents of those addresses. The default
9640 is @code{on}. For example, this is what a stack frame display looks like with
9641 @code{set print address on}:
9646 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9648 530 if (lquote != def_lquote)
9652 @item set print address off
9653 Do not print addresses when displaying their contents. For example,
9654 this is the same stack frame displayed with @code{set print address off}:
9658 (@value{GDBP}) set print addr off
9660 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9661 530 if (lquote != def_lquote)
9665 You can use @samp{set print address off} to eliminate all machine
9666 dependent displays from the @value{GDBN} interface. For example, with
9667 @code{print address off}, you should get the same text for backtraces on
9668 all machines---whether or not they involve pointer arguments.
9671 @item show print address
9672 Show whether or not addresses are to be printed.
9675 When @value{GDBN} prints a symbolic address, it normally prints the
9676 closest earlier symbol plus an offset. If that symbol does not uniquely
9677 identify the address (for example, it is a name whose scope is a single
9678 source file), you may need to clarify. One way to do this is with
9679 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9680 you can set @value{GDBN} to print the source file and line number when
9681 it prints a symbolic address:
9684 @item set print symbol-filename on
9685 @cindex source file and line of a symbol
9686 @cindex symbol, source file and line
9687 Tell @value{GDBN} to print the source file name and line number of a
9688 symbol in the symbolic form of an address.
9690 @item set print symbol-filename off
9691 Do not print source file name and line number of a symbol. This is the
9694 @item show print symbol-filename
9695 Show whether or not @value{GDBN} will print the source file name and
9696 line number of a symbol in the symbolic form of an address.
9699 Another situation where it is helpful to show symbol filenames and line
9700 numbers is when disassembling code; @value{GDBN} shows you the line
9701 number and source file that corresponds to each instruction.
9703 Also, you may wish to see the symbolic form only if the address being
9704 printed is reasonably close to the closest earlier symbol:
9707 @item set print max-symbolic-offset @var{max-offset}
9708 @itemx set print max-symbolic-offset unlimited
9709 @cindex maximum value for offset of closest symbol
9710 Tell @value{GDBN} to only display the symbolic form of an address if the
9711 offset between the closest earlier symbol and the address is less than
9712 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9713 to always print the symbolic form of an address if any symbol precedes
9714 it. Zero is equivalent to @code{unlimited}.
9716 @item show print max-symbolic-offset
9717 Ask how large the maximum offset is that @value{GDBN} prints in a
9721 @cindex wild pointer, interpreting
9722 @cindex pointer, finding referent
9723 If you have a pointer and you are not sure where it points, try
9724 @samp{set print symbol-filename on}. Then you can determine the name
9725 and source file location of the variable where it points, using
9726 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9727 For example, here @value{GDBN} shows that a variable @code{ptt} points
9728 at another variable @code{t}, defined in @file{hi2.c}:
9731 (@value{GDBP}) set print symbol-filename on
9732 (@value{GDBP}) p/a ptt
9733 $4 = 0xe008 <t in hi2.c>
9737 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9738 does not show the symbol name and filename of the referent, even with
9739 the appropriate @code{set print} options turned on.
9742 You can also enable @samp{/a}-like formatting all the time using
9743 @samp{set print symbol on}:
9746 @item set print symbol on
9747 Tell @value{GDBN} to print the symbol corresponding to an address, if
9750 @item set print symbol off
9751 Tell @value{GDBN} not to print the symbol corresponding to an
9752 address. In this mode, @value{GDBN} will still print the symbol
9753 corresponding to pointers to functions. This is the default.
9755 @item show print symbol
9756 Show whether @value{GDBN} will display the symbol corresponding to an
9760 Other settings control how different kinds of objects are printed:
9763 @item set print array
9764 @itemx set print array on
9765 @cindex pretty print arrays
9766 Pretty print arrays. This format is more convenient to read,
9767 but uses more space. The default is off.
9769 @item set print array off
9770 Return to compressed format for arrays.
9772 @item show print array
9773 Show whether compressed or pretty format is selected for displaying
9776 @cindex print array indexes
9777 @item set print array-indexes
9778 @itemx set print array-indexes on
9779 Print the index of each element when displaying arrays. May be more
9780 convenient to locate a given element in the array or quickly find the
9781 index of a given element in that printed array. The default is off.
9783 @item set print array-indexes off
9784 Stop printing element indexes when displaying arrays.
9786 @item show print array-indexes
9787 Show whether the index of each element is printed when displaying
9790 @item set print elements @var{number-of-elements}
9791 @itemx set print elements unlimited
9792 @cindex number of array elements to print
9793 @cindex limit on number of printed array elements
9794 Set a limit on how many elements of an array @value{GDBN} will print.
9795 If @value{GDBN} is printing a large array, it stops printing after it has
9796 printed the number of elements set by the @code{set print elements} command.
9797 This limit also applies to the display of strings.
9798 When @value{GDBN} starts, this limit is set to 200.
9799 Setting @var{number-of-elements} to @code{unlimited} or zero means
9800 that the number of elements to print is unlimited.
9802 @item show print elements
9803 Display the number of elements of a large array that @value{GDBN} will print.
9804 If the number is 0, then the printing is unlimited.
9806 @item set print frame-arguments @var{value}
9807 @kindex set print frame-arguments
9808 @cindex printing frame argument values
9809 @cindex print all frame argument values
9810 @cindex print frame argument values for scalars only
9811 @cindex do not print frame argument values
9812 This command allows to control how the values of arguments are printed
9813 when the debugger prints a frame (@pxref{Frames}). The possible
9818 The values of all arguments are printed.
9821 Print the value of an argument only if it is a scalar. The value of more
9822 complex arguments such as arrays, structures, unions, etc, is replaced
9823 by @code{@dots{}}. This is the default. Here is an example where
9824 only scalar arguments are shown:
9827 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9832 None of the argument values are printed. Instead, the value of each argument
9833 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9836 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9841 By default, only scalar arguments are printed. This command can be used
9842 to configure the debugger to print the value of all arguments, regardless
9843 of their type. However, it is often advantageous to not print the value
9844 of more complex parameters. For instance, it reduces the amount of
9845 information printed in each frame, making the backtrace more readable.
9846 Also, it improves performance when displaying Ada frames, because
9847 the computation of large arguments can sometimes be CPU-intensive,
9848 especially in large applications. Setting @code{print frame-arguments}
9849 to @code{scalars} (the default) or @code{none} avoids this computation,
9850 thus speeding up the display of each Ada frame.
9852 @item show print frame-arguments
9853 Show how the value of arguments should be displayed when printing a frame.
9855 @item set print raw frame-arguments on
9856 Print frame arguments in raw, non pretty-printed, form.
9858 @item set print raw frame-arguments off
9859 Print frame arguments in pretty-printed form, if there is a pretty-printer
9860 for the value (@pxref{Pretty Printing}),
9861 otherwise print the value in raw form.
9862 This is the default.
9864 @item show print raw frame-arguments
9865 Show whether to print frame arguments in raw form.
9867 @anchor{set print entry-values}
9868 @item set print entry-values @var{value}
9869 @kindex set print entry-values
9870 Set printing of frame argument values at function entry. In some cases
9871 @value{GDBN} can determine the value of function argument which was passed by
9872 the function caller, even if the value was modified inside the called function
9873 and therefore is different. With optimized code, the current value could be
9874 unavailable, but the entry value may still be known.
9876 The default value is @code{default} (see below for its description). Older
9877 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9878 this feature will behave in the @code{default} setting the same way as with the
9881 This functionality is currently supported only by DWARF 2 debugging format and
9882 the compiler has to produce @samp{DW_TAG_call_site} tags. With
9883 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9886 The @var{value} parameter can be one of the following:
9890 Print only actual parameter values, never print values from function entry
9894 #0 different (val=6)
9895 #0 lost (val=<optimized out>)
9897 #0 invalid (val=<optimized out>)
9901 Print only parameter values from function entry point. The actual parameter
9902 values are never printed.
9904 #0 equal (val@@entry=5)
9905 #0 different (val@@entry=5)
9906 #0 lost (val@@entry=5)
9907 #0 born (val@@entry=<optimized out>)
9908 #0 invalid (val@@entry=<optimized out>)
9912 Print only parameter values from function entry point. If value from function
9913 entry point is not known while the actual value is known, print the actual
9914 value for such parameter.
9916 #0 equal (val@@entry=5)
9917 #0 different (val@@entry=5)
9918 #0 lost (val@@entry=5)
9920 #0 invalid (val@@entry=<optimized out>)
9924 Print actual parameter values. If actual parameter value is not known while
9925 value from function entry point is known, print the entry point value for such
9929 #0 different (val=6)
9930 #0 lost (val@@entry=5)
9932 #0 invalid (val=<optimized out>)
9936 Always print both the actual parameter value and its value from function entry
9937 point, even if values of one or both are not available due to compiler
9940 #0 equal (val=5, val@@entry=5)
9941 #0 different (val=6, val@@entry=5)
9942 #0 lost (val=<optimized out>, val@@entry=5)
9943 #0 born (val=10, val@@entry=<optimized out>)
9944 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9948 Print the actual parameter value if it is known and also its value from
9949 function entry point if it is known. If neither is known, print for the actual
9950 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9951 values are known and identical, print the shortened
9952 @code{param=param@@entry=VALUE} notation.
9954 #0 equal (val=val@@entry=5)
9955 #0 different (val=6, val@@entry=5)
9956 #0 lost (val@@entry=5)
9958 #0 invalid (val=<optimized out>)
9962 Always print the actual parameter value. Print also its value from function
9963 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9964 if both values are known and identical, print the shortened
9965 @code{param=param@@entry=VALUE} notation.
9967 #0 equal (val=val@@entry=5)
9968 #0 different (val=6, val@@entry=5)
9969 #0 lost (val=<optimized out>, val@@entry=5)
9971 #0 invalid (val=<optimized out>)
9975 For analysis messages on possible failures of frame argument values at function
9976 entry resolution see @ref{set debug entry-values}.
9978 @item show print entry-values
9979 Show the method being used for printing of frame argument values at function
9982 @item set print repeats @var{number-of-repeats}
9983 @itemx set print repeats unlimited
9984 @cindex repeated array elements
9985 Set the threshold for suppressing display of repeated array
9986 elements. When the number of consecutive identical elements of an
9987 array exceeds the threshold, @value{GDBN} prints the string
9988 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9989 identical repetitions, instead of displaying the identical elements
9990 themselves. Setting the threshold to @code{unlimited} or zero will
9991 cause all elements to be individually printed. The default threshold
9994 @item show print repeats
9995 Display the current threshold for printing repeated identical
9998 @item set print null-stop
9999 @cindex @sc{null} elements in arrays
10000 Cause @value{GDBN} to stop printing the characters of an array when the first
10001 @sc{null} is encountered. This is useful when large arrays actually
10002 contain only short strings.
10003 The default is off.
10005 @item show print null-stop
10006 Show whether @value{GDBN} stops printing an array on the first
10007 @sc{null} character.
10009 @item set print pretty on
10010 @cindex print structures in indented form
10011 @cindex indentation in structure display
10012 Cause @value{GDBN} to print structures in an indented format with one member
10013 per line, like this:
10028 @item set print pretty off
10029 Cause @value{GDBN} to print structures in a compact format, like this:
10033 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10034 meat = 0x54 "Pork"@}
10039 This is the default format.
10041 @item show print pretty
10042 Show which format @value{GDBN} is using to print structures.
10044 @item set print sevenbit-strings on
10045 @cindex eight-bit characters in strings
10046 @cindex octal escapes in strings
10047 Print using only seven-bit characters; if this option is set,
10048 @value{GDBN} displays any eight-bit characters (in strings or
10049 character values) using the notation @code{\}@var{nnn}. This setting is
10050 best if you are working in English (@sc{ascii}) and you use the
10051 high-order bit of characters as a marker or ``meta'' bit.
10053 @item set print sevenbit-strings off
10054 Print full eight-bit characters. This allows the use of more
10055 international character sets, and is the default.
10057 @item show print sevenbit-strings
10058 Show whether or not @value{GDBN} is printing only seven-bit characters.
10060 @item set print union on
10061 @cindex unions in structures, printing
10062 Tell @value{GDBN} to print unions which are contained in structures
10063 and other unions. This is the default setting.
10065 @item set print union off
10066 Tell @value{GDBN} not to print unions which are contained in
10067 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10070 @item show print union
10071 Ask @value{GDBN} whether or not it will print unions which are contained in
10072 structures and other unions.
10074 For example, given the declarations
10077 typedef enum @{Tree, Bug@} Species;
10078 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10079 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10090 struct thing foo = @{Tree, @{Acorn@}@};
10094 with @code{set print union on} in effect @samp{p foo} would print
10097 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10101 and with @code{set print union off} in effect it would print
10104 $1 = @{it = Tree, form = @{...@}@}
10108 @code{set print union} affects programs written in C-like languages
10114 These settings are of interest when debugging C@t{++} programs:
10117 @cindex demangling C@t{++} names
10118 @item set print demangle
10119 @itemx set print demangle on
10120 Print C@t{++} names in their source form rather than in the encoded
10121 (``mangled'') form passed to the assembler and linker for type-safe
10122 linkage. The default is on.
10124 @item show print demangle
10125 Show whether C@t{++} names are printed in mangled or demangled form.
10127 @item set print asm-demangle
10128 @itemx set print asm-demangle on
10129 Print C@t{++} names in their source form rather than their mangled form, even
10130 in assembler code printouts such as instruction disassemblies.
10131 The default is off.
10133 @item show print asm-demangle
10134 Show whether C@t{++} names in assembly listings are printed in mangled
10137 @cindex C@t{++} symbol decoding style
10138 @cindex symbol decoding style, C@t{++}
10139 @kindex set demangle-style
10140 @item set demangle-style @var{style}
10141 Choose among several encoding schemes used by different compilers to
10142 represent C@t{++} names. The choices for @var{style} are currently:
10146 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10147 This is the default.
10150 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10153 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10156 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10159 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10160 @strong{Warning:} this setting alone is not sufficient to allow
10161 debugging @code{cfront}-generated executables. @value{GDBN} would
10162 require further enhancement to permit that.
10165 If you omit @var{style}, you will see a list of possible formats.
10167 @item show demangle-style
10168 Display the encoding style currently in use for decoding C@t{++} symbols.
10170 @item set print object
10171 @itemx set print object on
10172 @cindex derived type of an object, printing
10173 @cindex display derived types
10174 When displaying a pointer to an object, identify the @emph{actual}
10175 (derived) type of the object rather than the @emph{declared} type, using
10176 the virtual function table. Note that the virtual function table is
10177 required---this feature can only work for objects that have run-time
10178 type identification; a single virtual method in the object's declared
10179 type is sufficient. Note that this setting is also taken into account when
10180 working with variable objects via MI (@pxref{GDB/MI}).
10182 @item set print object off
10183 Display only the declared type of objects, without reference to the
10184 virtual function table. This is the default setting.
10186 @item show print object
10187 Show whether actual, or declared, object types are displayed.
10189 @item set print static-members
10190 @itemx set print static-members on
10191 @cindex static members of C@t{++} objects
10192 Print static members when displaying a C@t{++} object. The default is on.
10194 @item set print static-members off
10195 Do not print static members when displaying a C@t{++} object.
10197 @item show print static-members
10198 Show whether C@t{++} static members are printed or not.
10200 @item set print pascal_static-members
10201 @itemx set print pascal_static-members on
10202 @cindex static members of Pascal objects
10203 @cindex Pascal objects, static members display
10204 Print static members when displaying a Pascal object. The default is on.
10206 @item set print pascal_static-members off
10207 Do not print static members when displaying a Pascal object.
10209 @item show print pascal_static-members
10210 Show whether Pascal static members are printed or not.
10212 @c These don't work with HP ANSI C++ yet.
10213 @item set print vtbl
10214 @itemx set print vtbl on
10215 @cindex pretty print C@t{++} virtual function tables
10216 @cindex virtual functions (C@t{++}) display
10217 @cindex VTBL display
10218 Pretty print C@t{++} virtual function tables. The default is off.
10219 (The @code{vtbl} commands do not work on programs compiled with the HP
10220 ANSI C@t{++} compiler (@code{aCC}).)
10222 @item set print vtbl off
10223 Do not pretty print C@t{++} virtual function tables.
10225 @item show print vtbl
10226 Show whether C@t{++} virtual function tables are pretty printed, or not.
10229 @node Pretty Printing
10230 @section Pretty Printing
10232 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10233 Python code. It greatly simplifies the display of complex objects. This
10234 mechanism works for both MI and the CLI.
10237 * Pretty-Printer Introduction:: Introduction to pretty-printers
10238 * Pretty-Printer Example:: An example pretty-printer
10239 * Pretty-Printer Commands:: Pretty-printer commands
10242 @node Pretty-Printer Introduction
10243 @subsection Pretty-Printer Introduction
10245 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10246 registered for the value. If there is then @value{GDBN} invokes the
10247 pretty-printer to print the value. Otherwise the value is printed normally.
10249 Pretty-printers are normally named. This makes them easy to manage.
10250 The @samp{info pretty-printer} command will list all the installed
10251 pretty-printers with their names.
10252 If a pretty-printer can handle multiple data types, then its
10253 @dfn{subprinters} are the printers for the individual data types.
10254 Each such subprinter has its own name.
10255 The format of the name is @var{printer-name};@var{subprinter-name}.
10257 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10258 Typically they are automatically loaded and registered when the corresponding
10259 debug information is loaded, thus making them available without having to
10260 do anything special.
10262 There are three places where a pretty-printer can be registered.
10266 Pretty-printers registered globally are available when debugging
10270 Pretty-printers registered with a program space are available only
10271 when debugging that program.
10272 @xref{Progspaces In Python}, for more details on program spaces in Python.
10275 Pretty-printers registered with an objfile are loaded and unloaded
10276 with the corresponding objfile (e.g., shared library).
10277 @xref{Objfiles In Python}, for more details on objfiles in Python.
10280 @xref{Selecting Pretty-Printers}, for further information on how
10281 pretty-printers are selected,
10283 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10286 @node Pretty-Printer Example
10287 @subsection Pretty-Printer Example
10289 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10292 (@value{GDBP}) print s
10294 static npos = 4294967295,
10296 <std::allocator<char>> = @{
10297 <__gnu_cxx::new_allocator<char>> = @{
10298 <No data fields>@}, <No data fields>
10300 members of std::basic_string<char, std::char_traits<char>,
10301 std::allocator<char> >::_Alloc_hider:
10302 _M_p = 0x804a014 "abcd"
10307 With a pretty-printer for @code{std::string} only the contents are printed:
10310 (@value{GDBP}) print s
10314 @node Pretty-Printer Commands
10315 @subsection Pretty-Printer Commands
10316 @cindex pretty-printer commands
10319 @kindex info pretty-printer
10320 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10321 Print the list of installed pretty-printers.
10322 This includes disabled pretty-printers, which are marked as such.
10324 @var{object-regexp} is a regular expression matching the objects
10325 whose pretty-printers to list.
10326 Objects can be @code{global}, the program space's file
10327 (@pxref{Progspaces In Python}),
10328 and the object files within that program space (@pxref{Objfiles In Python}).
10329 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10330 looks up a printer from these three objects.
10332 @var{name-regexp} is a regular expression matching the name of the printers
10335 @kindex disable pretty-printer
10336 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10337 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10338 A disabled pretty-printer is not forgotten, it may be enabled again later.
10340 @kindex enable pretty-printer
10341 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10342 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10347 Suppose we have three pretty-printers installed: one from library1.so
10348 named @code{foo} that prints objects of type @code{foo}, and
10349 another from library2.so named @code{bar} that prints two types of objects,
10350 @code{bar1} and @code{bar2}.
10353 (gdb) info pretty-printer
10360 (gdb) info pretty-printer library2
10365 (gdb) disable pretty-printer library1
10367 2 of 3 printers enabled
10368 (gdb) info pretty-printer
10375 (gdb) disable pretty-printer library2 bar:bar1
10377 1 of 3 printers enabled
10378 (gdb) info pretty-printer library2
10385 (gdb) disable pretty-printer library2 bar
10387 0 of 3 printers enabled
10388 (gdb) info pretty-printer library2
10397 Note that for @code{bar} the entire printer can be disabled,
10398 as can each individual subprinter.
10400 @node Value History
10401 @section Value History
10403 @cindex value history
10404 @cindex history of values printed by @value{GDBN}
10405 Values printed by the @code{print} command are saved in the @value{GDBN}
10406 @dfn{value history}. This allows you to refer to them in other expressions.
10407 Values are kept until the symbol table is re-read or discarded
10408 (for example with the @code{file} or @code{symbol-file} commands).
10409 When the symbol table changes, the value history is discarded,
10410 since the values may contain pointers back to the types defined in the
10415 @cindex history number
10416 The values printed are given @dfn{history numbers} by which you can
10417 refer to them. These are successive integers starting with one.
10418 @code{print} shows you the history number assigned to a value by
10419 printing @samp{$@var{num} = } before the value; here @var{num} is the
10422 To refer to any previous value, use @samp{$} followed by the value's
10423 history number. The way @code{print} labels its output is designed to
10424 remind you of this. Just @code{$} refers to the most recent value in
10425 the history, and @code{$$} refers to the value before that.
10426 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10427 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10428 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10430 For example, suppose you have just printed a pointer to a structure and
10431 want to see the contents of the structure. It suffices to type
10437 If you have a chain of structures where the component @code{next} points
10438 to the next one, you can print the contents of the next one with this:
10445 You can print successive links in the chain by repeating this
10446 command---which you can do by just typing @key{RET}.
10448 Note that the history records values, not expressions. If the value of
10449 @code{x} is 4 and you type these commands:
10457 then the value recorded in the value history by the @code{print} command
10458 remains 4 even though the value of @code{x} has changed.
10461 @kindex show values
10463 Print the last ten values in the value history, with their item numbers.
10464 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10465 values} does not change the history.
10467 @item show values @var{n}
10468 Print ten history values centered on history item number @var{n}.
10470 @item show values +
10471 Print ten history values just after the values last printed. If no more
10472 values are available, @code{show values +} produces no display.
10475 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10476 same effect as @samp{show values +}.
10478 @node Convenience Vars
10479 @section Convenience Variables
10481 @cindex convenience variables
10482 @cindex user-defined variables
10483 @value{GDBN} provides @dfn{convenience variables} that you can use within
10484 @value{GDBN} to hold on to a value and refer to it later. These variables
10485 exist entirely within @value{GDBN}; they are not part of your program, and
10486 setting a convenience variable has no direct effect on further execution
10487 of your program. That is why you can use them freely.
10489 Convenience variables are prefixed with @samp{$}. Any name preceded by
10490 @samp{$} can be used for a convenience variable, unless it is one of
10491 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10492 (Value history references, in contrast, are @emph{numbers} preceded
10493 by @samp{$}. @xref{Value History, ,Value History}.)
10495 You can save a value in a convenience variable with an assignment
10496 expression, just as you would set a variable in your program.
10500 set $foo = *object_ptr
10504 would save in @code{$foo} the value contained in the object pointed to by
10507 Using a convenience variable for the first time creates it, but its
10508 value is @code{void} until you assign a new value. You can alter the
10509 value with another assignment at any time.
10511 Convenience variables have no fixed types. You can assign a convenience
10512 variable any type of value, including structures and arrays, even if
10513 that variable already has a value of a different type. The convenience
10514 variable, when used as an expression, has the type of its current value.
10517 @kindex show convenience
10518 @cindex show all user variables and functions
10519 @item show convenience
10520 Print a list of convenience variables used so far, and their values,
10521 as well as a list of the convenience functions.
10522 Abbreviated @code{show conv}.
10524 @kindex init-if-undefined
10525 @cindex convenience variables, initializing
10526 @item init-if-undefined $@var{variable} = @var{expression}
10527 Set a convenience variable if it has not already been set. This is useful
10528 for user-defined commands that keep some state. It is similar, in concept,
10529 to using local static variables with initializers in C (except that
10530 convenience variables are global). It can also be used to allow users to
10531 override default values used in a command script.
10533 If the variable is already defined then the expression is not evaluated so
10534 any side-effects do not occur.
10537 One of the ways to use a convenience variable is as a counter to be
10538 incremented or a pointer to be advanced. For example, to print
10539 a field from successive elements of an array of structures:
10543 print bar[$i++]->contents
10547 Repeat that command by typing @key{RET}.
10549 Some convenience variables are created automatically by @value{GDBN} and given
10550 values likely to be useful.
10553 @vindex $_@r{, convenience variable}
10555 The variable @code{$_} is automatically set by the @code{x} command to
10556 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10557 commands which provide a default address for @code{x} to examine also
10558 set @code{$_} to that address; these commands include @code{info line}
10559 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10560 except when set by the @code{x} command, in which case it is a pointer
10561 to the type of @code{$__}.
10563 @vindex $__@r{, convenience variable}
10565 The variable @code{$__} is automatically set by the @code{x} command
10566 to the value found in the last address examined. Its type is chosen
10567 to match the format in which the data was printed.
10570 @vindex $_exitcode@r{, convenience variable}
10571 When the program being debugged terminates normally, @value{GDBN}
10572 automatically sets this variable to the exit code of the program, and
10573 resets @code{$_exitsignal} to @code{void}.
10576 @vindex $_exitsignal@r{, convenience variable}
10577 When the program being debugged dies due to an uncaught signal,
10578 @value{GDBN} automatically sets this variable to that signal's number,
10579 and resets @code{$_exitcode} to @code{void}.
10581 To distinguish between whether the program being debugged has exited
10582 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10583 @code{$_exitsignal} is not @code{void}), the convenience function
10584 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10585 Functions}). For example, considering the following source code:
10588 #include <signal.h>
10591 main (int argc, char *argv[])
10598 A valid way of telling whether the program being debugged has exited
10599 or signalled would be:
10602 (@value{GDBP}) define has_exited_or_signalled
10603 Type commands for definition of ``has_exited_or_signalled''.
10604 End with a line saying just ``end''.
10605 >if $_isvoid ($_exitsignal)
10606 >echo The program has exited\n
10608 >echo The program has signalled\n
10614 Program terminated with signal SIGALRM, Alarm clock.
10615 The program no longer exists.
10616 (@value{GDBP}) has_exited_or_signalled
10617 The program has signalled
10620 As can be seen, @value{GDBN} correctly informs that the program being
10621 debugged has signalled, since it calls @code{raise} and raises a
10622 @code{SIGALRM} signal. If the program being debugged had not called
10623 @code{raise}, then @value{GDBN} would report a normal exit:
10626 (@value{GDBP}) has_exited_or_signalled
10627 The program has exited
10631 The variable @code{$_exception} is set to the exception object being
10632 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10635 @itemx $_probe_arg0@dots{}$_probe_arg11
10636 Arguments to a static probe. @xref{Static Probe Points}.
10639 @vindex $_sdata@r{, inspect, convenience variable}
10640 The variable @code{$_sdata} contains extra collected static tracepoint
10641 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10642 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10643 if extra static tracepoint data has not been collected.
10646 @vindex $_siginfo@r{, convenience variable}
10647 The variable @code{$_siginfo} contains extra signal information
10648 (@pxref{extra signal information}). Note that @code{$_siginfo}
10649 could be empty, if the application has not yet received any signals.
10650 For example, it will be empty before you execute the @code{run} command.
10653 @vindex $_tlb@r{, convenience variable}
10654 The variable @code{$_tlb} is automatically set when debugging
10655 applications running on MS-Windows in native mode or connected to
10656 gdbserver that supports the @code{qGetTIBAddr} request.
10657 @xref{General Query Packets}.
10658 This variable contains the address of the thread information block.
10661 The number of the current inferior. @xref{Inferiors and
10662 Programs, ,Debugging Multiple Inferiors and Programs}.
10665 The thread number of the current thread. @xref{thread numbers}.
10668 The global number of the current thread. @xref{global thread numbers}.
10672 @node Convenience Funs
10673 @section Convenience Functions
10675 @cindex convenience functions
10676 @value{GDBN} also supplies some @dfn{convenience functions}. These
10677 have a syntax similar to convenience variables. A convenience
10678 function can be used in an expression just like an ordinary function;
10679 however, a convenience function is implemented internally to
10682 These functions do not require @value{GDBN} to be configured with
10683 @code{Python} support, which means that they are always available.
10687 @item $_isvoid (@var{expr})
10688 @findex $_isvoid@r{, convenience function}
10689 Return one if the expression @var{expr} is @code{void}. Otherwise it
10692 A @code{void} expression is an expression where the type of the result
10693 is @code{void}. For example, you can examine a convenience variable
10694 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10698 (@value{GDBP}) print $_exitcode
10700 (@value{GDBP}) print $_isvoid ($_exitcode)
10703 Starting program: ./a.out
10704 [Inferior 1 (process 29572) exited normally]
10705 (@value{GDBP}) print $_exitcode
10707 (@value{GDBP}) print $_isvoid ($_exitcode)
10711 In the example above, we used @code{$_isvoid} to check whether
10712 @code{$_exitcode} is @code{void} before and after the execution of the
10713 program being debugged. Before the execution there is no exit code to
10714 be examined, therefore @code{$_exitcode} is @code{void}. After the
10715 execution the program being debugged returned zero, therefore
10716 @code{$_exitcode} is zero, which means that it is not @code{void}
10719 The @code{void} expression can also be a call of a function from the
10720 program being debugged. For example, given the following function:
10729 The result of calling it inside @value{GDBN} is @code{void}:
10732 (@value{GDBP}) print foo ()
10734 (@value{GDBP}) print $_isvoid (foo ())
10736 (@value{GDBP}) set $v = foo ()
10737 (@value{GDBP}) print $v
10739 (@value{GDBP}) print $_isvoid ($v)
10745 These functions require @value{GDBN} to be configured with
10746 @code{Python} support.
10750 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10751 @findex $_memeq@r{, convenience function}
10752 Returns one if the @var{length} bytes at the addresses given by
10753 @var{buf1} and @var{buf2} are equal.
10754 Otherwise it returns zero.
10756 @item $_regex(@var{str}, @var{regex})
10757 @findex $_regex@r{, convenience function}
10758 Returns one if the string @var{str} matches the regular expression
10759 @var{regex}. Otherwise it returns zero.
10760 The syntax of the regular expression is that specified by @code{Python}'s
10761 regular expression support.
10763 @item $_streq(@var{str1}, @var{str2})
10764 @findex $_streq@r{, convenience function}
10765 Returns one if the strings @var{str1} and @var{str2} are equal.
10766 Otherwise it returns zero.
10768 @item $_strlen(@var{str})
10769 @findex $_strlen@r{, convenience function}
10770 Returns the length of string @var{str}.
10772 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10773 @findex $_caller_is@r{, convenience function}
10774 Returns one if the calling function's name is equal to @var{name}.
10775 Otherwise it returns zero.
10777 If the optional argument @var{number_of_frames} is provided,
10778 it is the number of frames up in the stack to look.
10786 at testsuite/gdb.python/py-caller-is.c:21
10787 #1 0x00000000004005a0 in middle_func ()
10788 at testsuite/gdb.python/py-caller-is.c:27
10789 #2 0x00000000004005ab in top_func ()
10790 at testsuite/gdb.python/py-caller-is.c:33
10791 #3 0x00000000004005b6 in main ()
10792 at testsuite/gdb.python/py-caller-is.c:39
10793 (gdb) print $_caller_is ("middle_func")
10795 (gdb) print $_caller_is ("top_func", 2)
10799 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10800 @findex $_caller_matches@r{, convenience function}
10801 Returns one if the calling function's name matches the regular expression
10802 @var{regexp}. Otherwise it returns zero.
10804 If the optional argument @var{number_of_frames} is provided,
10805 it is the number of frames up in the stack to look.
10808 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10809 @findex $_any_caller_is@r{, convenience function}
10810 Returns one if any calling function's name is equal to @var{name}.
10811 Otherwise it returns zero.
10813 If the optional argument @var{number_of_frames} is provided,
10814 it is the number of frames up in the stack to look.
10817 This function differs from @code{$_caller_is} in that this function
10818 checks all stack frames from the immediate caller to the frame specified
10819 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10820 frame specified by @var{number_of_frames}.
10822 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10823 @findex $_any_caller_matches@r{, convenience function}
10824 Returns one if any calling function's name matches the regular expression
10825 @var{regexp}. Otherwise it returns zero.
10827 If the optional argument @var{number_of_frames} is provided,
10828 it is the number of frames up in the stack to look.
10831 This function differs from @code{$_caller_matches} in that this function
10832 checks all stack frames from the immediate caller to the frame specified
10833 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10834 frame specified by @var{number_of_frames}.
10836 @item $_as_string(@var{value})
10837 @findex $_as_string@r{, convenience function}
10838 Return the string representation of @var{value}.
10840 This function is useful to obtain the textual label (enumerator) of an
10841 enumeration value. For example, assuming the variable @var{node} is of
10842 an enumerated type:
10845 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10846 Visiting node of type NODE_INTEGER
10851 @value{GDBN} provides the ability to list and get help on
10852 convenience functions.
10855 @item help function
10856 @kindex help function
10857 @cindex show all convenience functions
10858 Print a list of all convenience functions.
10865 You can refer to machine register contents, in expressions, as variables
10866 with names starting with @samp{$}. The names of registers are different
10867 for each machine; use @code{info registers} to see the names used on
10871 @kindex info registers
10872 @item info registers
10873 Print the names and values of all registers except floating-point
10874 and vector registers (in the selected stack frame).
10876 @kindex info all-registers
10877 @cindex floating point registers
10878 @item info all-registers
10879 Print the names and values of all registers, including floating-point
10880 and vector registers (in the selected stack frame).
10882 @item info registers @var{regname} @dots{}
10883 Print the @dfn{relativized} value of each specified register @var{regname}.
10884 As discussed in detail below, register values are normally relative to
10885 the selected stack frame. The @var{regname} may be any register name valid on
10886 the machine you are using, with or without the initial @samp{$}.
10889 @anchor{standard registers}
10890 @cindex stack pointer register
10891 @cindex program counter register
10892 @cindex process status register
10893 @cindex frame pointer register
10894 @cindex standard registers
10895 @value{GDBN} has four ``standard'' register names that are available (in
10896 expressions) on most machines---whenever they do not conflict with an
10897 architecture's canonical mnemonics for registers. The register names
10898 @code{$pc} and @code{$sp} are used for the program counter register and
10899 the stack pointer. @code{$fp} is used for a register that contains a
10900 pointer to the current stack frame, and @code{$ps} is used for a
10901 register that contains the processor status. For example,
10902 you could print the program counter in hex with
10909 or print the instruction to be executed next with
10916 or add four to the stack pointer@footnote{This is a way of removing
10917 one word from the stack, on machines where stacks grow downward in
10918 memory (most machines, nowadays). This assumes that the innermost
10919 stack frame is selected; setting @code{$sp} is not allowed when other
10920 stack frames are selected. To pop entire frames off the stack,
10921 regardless of machine architecture, use @code{return};
10922 see @ref{Returning, ,Returning from a Function}.} with
10928 Whenever possible, these four standard register names are available on
10929 your machine even though the machine has different canonical mnemonics,
10930 so long as there is no conflict. The @code{info registers} command
10931 shows the canonical names. For example, on the SPARC, @code{info
10932 registers} displays the processor status register as @code{$psr} but you
10933 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10934 is an alias for the @sc{eflags} register.
10936 @value{GDBN} always considers the contents of an ordinary register as an
10937 integer when the register is examined in this way. Some machines have
10938 special registers which can hold nothing but floating point; these
10939 registers are considered to have floating point values. There is no way
10940 to refer to the contents of an ordinary register as floating point value
10941 (although you can @emph{print} it as a floating point value with
10942 @samp{print/f $@var{regname}}).
10944 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10945 means that the data format in which the register contents are saved by
10946 the operating system is not the same one that your program normally
10947 sees. For example, the registers of the 68881 floating point
10948 coprocessor are always saved in ``extended'' (raw) format, but all C
10949 programs expect to work with ``double'' (virtual) format. In such
10950 cases, @value{GDBN} normally works with the virtual format only (the format
10951 that makes sense for your program), but the @code{info registers} command
10952 prints the data in both formats.
10954 @cindex SSE registers (x86)
10955 @cindex MMX registers (x86)
10956 Some machines have special registers whose contents can be interpreted
10957 in several different ways. For example, modern x86-based machines
10958 have SSE and MMX registers that can hold several values packed
10959 together in several different formats. @value{GDBN} refers to such
10960 registers in @code{struct} notation:
10963 (@value{GDBP}) print $xmm1
10965 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10966 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10967 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10968 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10969 v4_int32 = @{0, 20657912, 11, 13@},
10970 v2_int64 = @{88725056443645952, 55834574859@},
10971 uint128 = 0x0000000d0000000b013b36f800000000
10976 To set values of such registers, you need to tell @value{GDBN} which
10977 view of the register you wish to change, as if you were assigning
10978 value to a @code{struct} member:
10981 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10984 Normally, register values are relative to the selected stack frame
10985 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10986 value that the register would contain if all stack frames farther in
10987 were exited and their saved registers restored. In order to see the
10988 true contents of hardware registers, you must select the innermost
10989 frame (with @samp{frame 0}).
10991 @cindex caller-saved registers
10992 @cindex call-clobbered registers
10993 @cindex volatile registers
10994 @cindex <not saved> values
10995 Usually ABIs reserve some registers as not needed to be saved by the
10996 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10997 registers). It may therefore not be possible for @value{GDBN} to know
10998 the value a register had before the call (in other words, in the outer
10999 frame), if the register value has since been changed by the callee.
11000 @value{GDBN} tries to deduce where the inner frame saved
11001 (``callee-saved'') registers, from the debug info, unwind info, or the
11002 machine code generated by your compiler. If some register is not
11003 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11004 its own knowledge of the ABI, or because the debug/unwind info
11005 explicitly says the register's value is undefined), @value{GDBN}
11006 displays @w{@samp{<not saved>}} as the register's value. With targets
11007 that @value{GDBN} has no knowledge of the register saving convention,
11008 if a register was not saved by the callee, then its value and location
11009 in the outer frame are assumed to be the same of the inner frame.
11010 This is usually harmless, because if the register is call-clobbered,
11011 the caller either does not care what is in the register after the
11012 call, or has code to restore the value that it does care about. Note,
11013 however, that if you change such a register in the outer frame, you
11014 may also be affecting the inner frame. Also, the more ``outer'' the
11015 frame is you're looking at, the more likely a call-clobbered
11016 register's value is to be wrong, in the sense that it doesn't actually
11017 represent the value the register had just before the call.
11019 @node Floating Point Hardware
11020 @section Floating Point Hardware
11021 @cindex floating point
11023 Depending on the configuration, @value{GDBN} may be able to give
11024 you more information about the status of the floating point hardware.
11029 Display hardware-dependent information about the floating
11030 point unit. The exact contents and layout vary depending on the
11031 floating point chip. Currently, @samp{info float} is supported on
11032 the ARM and x86 machines.
11036 @section Vector Unit
11037 @cindex vector unit
11039 Depending on the configuration, @value{GDBN} may be able to give you
11040 more information about the status of the vector unit.
11043 @kindex info vector
11045 Display information about the vector unit. The exact contents and
11046 layout vary depending on the hardware.
11049 @node OS Information
11050 @section Operating System Auxiliary Information
11051 @cindex OS information
11053 @value{GDBN} provides interfaces to useful OS facilities that can help
11054 you debug your program.
11056 @cindex auxiliary vector
11057 @cindex vector, auxiliary
11058 Some operating systems supply an @dfn{auxiliary vector} to programs at
11059 startup. This is akin to the arguments and environment that you
11060 specify for a program, but contains a system-dependent variety of
11061 binary values that tell system libraries important details about the
11062 hardware, operating system, and process. Each value's purpose is
11063 identified by an integer tag; the meanings are well-known but system-specific.
11064 Depending on the configuration and operating system facilities,
11065 @value{GDBN} may be able to show you this information. For remote
11066 targets, this functionality may further depend on the remote stub's
11067 support of the @samp{qXfer:auxv:read} packet, see
11068 @ref{qXfer auxiliary vector read}.
11073 Display the auxiliary vector of the inferior, which can be either a
11074 live process or a core dump file. @value{GDBN} prints each tag value
11075 numerically, and also shows names and text descriptions for recognized
11076 tags. Some values in the vector are numbers, some bit masks, and some
11077 pointers to strings or other data. @value{GDBN} displays each value in the
11078 most appropriate form for a recognized tag, and in hexadecimal for
11079 an unrecognized tag.
11082 On some targets, @value{GDBN} can access operating system-specific
11083 information and show it to you. The types of information available
11084 will differ depending on the type of operating system running on the
11085 target. The mechanism used to fetch the data is described in
11086 @ref{Operating System Information}. For remote targets, this
11087 functionality depends on the remote stub's support of the
11088 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11092 @item info os @var{infotype}
11094 Display OS information of the requested type.
11096 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11098 @anchor{linux info os infotypes}
11100 @kindex info os cpus
11102 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11103 the available fields from /proc/cpuinfo. For each supported architecture
11104 different fields are available. Two common entries are processor which gives
11105 CPU number and bogomips; a system constant that is calculated during
11106 kernel initialization.
11108 @kindex info os files
11110 Display the list of open file descriptors on the target. For each
11111 file descriptor, @value{GDBN} prints the identifier of the process
11112 owning the descriptor, the command of the owning process, the value
11113 of the descriptor, and the target of the descriptor.
11115 @kindex info os modules
11117 Display the list of all loaded kernel modules on the target. For each
11118 module, @value{GDBN} prints the module name, the size of the module in
11119 bytes, the number of times the module is used, the dependencies of the
11120 module, the status of the module, and the address of the loaded module
11123 @kindex info os msg
11125 Display the list of all System V message queues on the target. For each
11126 message queue, @value{GDBN} prints the message queue key, the message
11127 queue identifier, the access permissions, the current number of bytes
11128 on the queue, the current number of messages on the queue, the processes
11129 that last sent and received a message on the queue, the user and group
11130 of the owner and creator of the message queue, the times at which a
11131 message was last sent and received on the queue, and the time at which
11132 the message queue was last changed.
11134 @kindex info os processes
11136 Display the list of processes on the target. For each process,
11137 @value{GDBN} prints the process identifier, the name of the user, the
11138 command corresponding to the process, and the list of processor cores
11139 that the process is currently running on. (To understand what these
11140 properties mean, for this and the following info types, please consult
11141 the general @sc{gnu}/Linux documentation.)
11143 @kindex info os procgroups
11145 Display the list of process groups on the target. For each process,
11146 @value{GDBN} prints the identifier of the process group that it belongs
11147 to, the command corresponding to the process group leader, the process
11148 identifier, and the command line of the process. The list is sorted
11149 first by the process group identifier, then by the process identifier,
11150 so that processes belonging to the same process group are grouped together
11151 and the process group leader is listed first.
11153 @kindex info os semaphores
11155 Display the list of all System V semaphore sets on the target. For each
11156 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11157 set identifier, the access permissions, the number of semaphores in the
11158 set, the user and group of the owner and creator of the semaphore set,
11159 and the times at which the semaphore set was operated upon and changed.
11161 @kindex info os shm
11163 Display the list of all System V shared-memory regions on the target.
11164 For each shared-memory region, @value{GDBN} prints the region key,
11165 the shared-memory identifier, the access permissions, the size of the
11166 region, the process that created the region, the process that last
11167 attached to or detached from the region, the current number of live
11168 attaches to the region, and the times at which the region was last
11169 attached to, detach from, and changed.
11171 @kindex info os sockets
11173 Display the list of Internet-domain sockets on the target. For each
11174 socket, @value{GDBN} prints the address and port of the local and
11175 remote endpoints, the current state of the connection, the creator of
11176 the socket, the IP address family of the socket, and the type of the
11179 @kindex info os threads
11181 Display the list of threads running on the target. For each thread,
11182 @value{GDBN} prints the identifier of the process that the thread
11183 belongs to, the command of the process, the thread identifier, and the
11184 processor core that it is currently running on. The main thread of a
11185 process is not listed.
11189 If @var{infotype} is omitted, then list the possible values for
11190 @var{infotype} and the kind of OS information available for each
11191 @var{infotype}. If the target does not return a list of possible
11192 types, this command will report an error.
11195 @node Memory Region Attributes
11196 @section Memory Region Attributes
11197 @cindex memory region attributes
11199 @dfn{Memory region attributes} allow you to describe special handling
11200 required by regions of your target's memory. @value{GDBN} uses
11201 attributes to determine whether to allow certain types of memory
11202 accesses; whether to use specific width accesses; and whether to cache
11203 target memory. By default the description of memory regions is
11204 fetched from the target (if the current target supports this), but the
11205 user can override the fetched regions.
11207 Defined memory regions can be individually enabled and disabled. When a
11208 memory region is disabled, @value{GDBN} uses the default attributes when
11209 accessing memory in that region. Similarly, if no memory regions have
11210 been defined, @value{GDBN} uses the default attributes when accessing
11213 When a memory region is defined, it is given a number to identify it;
11214 to enable, disable, or remove a memory region, you specify that number.
11218 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11219 Define a memory region bounded by @var{lower} and @var{upper} with
11220 attributes @var{attributes}@dots{}, and add it to the list of regions
11221 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11222 case: it is treated as the target's maximum memory address.
11223 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11226 Discard any user changes to the memory regions and use target-supplied
11227 regions, if available, or no regions if the target does not support.
11230 @item delete mem @var{nums}@dots{}
11231 Remove memory regions @var{nums}@dots{} from the list of regions
11232 monitored by @value{GDBN}.
11234 @kindex disable mem
11235 @item disable mem @var{nums}@dots{}
11236 Disable monitoring of memory regions @var{nums}@dots{}.
11237 A disabled memory region is not forgotten.
11238 It may be enabled again later.
11241 @item enable mem @var{nums}@dots{}
11242 Enable monitoring of memory regions @var{nums}@dots{}.
11246 Print a table of all defined memory regions, with the following columns
11250 @item Memory Region Number
11251 @item Enabled or Disabled.
11252 Enabled memory regions are marked with @samp{y}.
11253 Disabled memory regions are marked with @samp{n}.
11256 The address defining the inclusive lower bound of the memory region.
11259 The address defining the exclusive upper bound of the memory region.
11262 The list of attributes set for this memory region.
11267 @subsection Attributes
11269 @subsubsection Memory Access Mode
11270 The access mode attributes set whether @value{GDBN} may make read or
11271 write accesses to a memory region.
11273 While these attributes prevent @value{GDBN} from performing invalid
11274 memory accesses, they do nothing to prevent the target system, I/O DMA,
11275 etc.@: from accessing memory.
11279 Memory is read only.
11281 Memory is write only.
11283 Memory is read/write. This is the default.
11286 @subsubsection Memory Access Size
11287 The access size attribute tells @value{GDBN} to use specific sized
11288 accesses in the memory region. Often memory mapped device registers
11289 require specific sized accesses. If no access size attribute is
11290 specified, @value{GDBN} may use accesses of any size.
11294 Use 8 bit memory accesses.
11296 Use 16 bit memory accesses.
11298 Use 32 bit memory accesses.
11300 Use 64 bit memory accesses.
11303 @c @subsubsection Hardware/Software Breakpoints
11304 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11305 @c will use hardware or software breakpoints for the internal breakpoints
11306 @c used by the step, next, finish, until, etc. commands.
11310 @c Always use hardware breakpoints
11311 @c @item swbreak (default)
11314 @subsubsection Data Cache
11315 The data cache attributes set whether @value{GDBN} will cache target
11316 memory. While this generally improves performance by reducing debug
11317 protocol overhead, it can lead to incorrect results because @value{GDBN}
11318 does not know about volatile variables or memory mapped device
11323 Enable @value{GDBN} to cache target memory.
11325 Disable @value{GDBN} from caching target memory. This is the default.
11328 @subsection Memory Access Checking
11329 @value{GDBN} can be instructed to refuse accesses to memory that is
11330 not explicitly described. This can be useful if accessing such
11331 regions has undesired effects for a specific target, or to provide
11332 better error checking. The following commands control this behaviour.
11335 @kindex set mem inaccessible-by-default
11336 @item set mem inaccessible-by-default [on|off]
11337 If @code{on} is specified, make @value{GDBN} treat memory not
11338 explicitly described by the memory ranges as non-existent and refuse accesses
11339 to such memory. The checks are only performed if there's at least one
11340 memory range defined. If @code{off} is specified, make @value{GDBN}
11341 treat the memory not explicitly described by the memory ranges as RAM.
11342 The default value is @code{on}.
11343 @kindex show mem inaccessible-by-default
11344 @item show mem inaccessible-by-default
11345 Show the current handling of accesses to unknown memory.
11349 @c @subsubsection Memory Write Verification
11350 @c The memory write verification attributes set whether @value{GDBN}
11351 @c will re-reads data after each write to verify the write was successful.
11355 @c @item noverify (default)
11358 @node Dump/Restore Files
11359 @section Copy Between Memory and a File
11360 @cindex dump/restore files
11361 @cindex append data to a file
11362 @cindex dump data to a file
11363 @cindex restore data from a file
11365 You can use the commands @code{dump}, @code{append}, and
11366 @code{restore} to copy data between target memory and a file. The
11367 @code{dump} and @code{append} commands write data to a file, and the
11368 @code{restore} command reads data from a file back into the inferior's
11369 memory. Files may be in binary, Motorola S-record, Intel hex,
11370 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11371 append to binary files, and cannot read from Verilog Hex files.
11376 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11377 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11378 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11379 or the value of @var{expr}, to @var{filename} in the given format.
11381 The @var{format} parameter may be any one of:
11388 Motorola S-record format.
11390 Tektronix Hex format.
11392 Verilog Hex format.
11395 @value{GDBN} uses the same definitions of these formats as the
11396 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11397 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11401 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11402 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11403 Append the contents of memory from @var{start_addr} to @var{end_addr},
11404 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11405 (@value{GDBN} can only append data to files in raw binary form.)
11408 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11409 Restore the contents of file @var{filename} into memory. The
11410 @code{restore} command can automatically recognize any known @sc{bfd}
11411 file format, except for raw binary. To restore a raw binary file you
11412 must specify the optional keyword @code{binary} after the filename.
11414 If @var{bias} is non-zero, its value will be added to the addresses
11415 contained in the file. Binary files always start at address zero, so
11416 they will be restored at address @var{bias}. Other bfd files have
11417 a built-in location; they will be restored at offset @var{bias}
11418 from that location.
11420 If @var{start} and/or @var{end} are non-zero, then only data between
11421 file offset @var{start} and file offset @var{end} will be restored.
11422 These offsets are relative to the addresses in the file, before
11423 the @var{bias} argument is applied.
11427 @node Core File Generation
11428 @section How to Produce a Core File from Your Program
11429 @cindex dump core from inferior
11431 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11432 image of a running process and its process status (register values
11433 etc.). Its primary use is post-mortem debugging of a program that
11434 crashed while it ran outside a debugger. A program that crashes
11435 automatically produces a core file, unless this feature is disabled by
11436 the user. @xref{Files}, for information on invoking @value{GDBN} in
11437 the post-mortem debugging mode.
11439 Occasionally, you may wish to produce a core file of the program you
11440 are debugging in order to preserve a snapshot of its state.
11441 @value{GDBN} has a special command for that.
11445 @kindex generate-core-file
11446 @item generate-core-file [@var{file}]
11447 @itemx gcore [@var{file}]
11448 Produce a core dump of the inferior process. The optional argument
11449 @var{file} specifies the file name where to put the core dump. If not
11450 specified, the file name defaults to @file{core.@var{pid}}, where
11451 @var{pid} is the inferior process ID.
11453 Note that this command is implemented only for some systems (as of
11454 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11456 On @sc{gnu}/Linux, this command can take into account the value of the
11457 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11458 dump (@pxref{set use-coredump-filter}).
11460 @kindex set use-coredump-filter
11461 @anchor{set use-coredump-filter}
11462 @item set use-coredump-filter on
11463 @itemx set use-coredump-filter off
11464 Enable or disable the use of the file
11465 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11466 files. This file is used by the Linux kernel to decide what types of
11467 memory mappings will be dumped or ignored when generating a core dump
11468 file. @var{pid} is the process ID of a currently running process.
11470 To make use of this feature, you have to write in the
11471 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11472 which is a bit mask representing the memory mapping types. If a bit
11473 is set in the bit mask, then the memory mappings of the corresponding
11474 types will be dumped; otherwise, they will be ignored. This
11475 configuration is inherited by child processes. For more information
11476 about the bits that can be set in the
11477 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11478 manpage of @code{core(5)}.
11480 By default, this option is @code{on}. If this option is turned
11481 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11482 and instead uses the same default value as the Linux kernel in order
11483 to decide which pages will be dumped in the core dump file. This
11484 value is currently @code{0x33}, which means that bits @code{0}
11485 (anonymous private mappings), @code{1} (anonymous shared mappings),
11486 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11487 This will cause these memory mappings to be dumped automatically.
11490 @node Character Sets
11491 @section Character Sets
11492 @cindex character sets
11494 @cindex translating between character sets
11495 @cindex host character set
11496 @cindex target character set
11498 If the program you are debugging uses a different character set to
11499 represent characters and strings than the one @value{GDBN} uses itself,
11500 @value{GDBN} can automatically translate between the character sets for
11501 you. The character set @value{GDBN} uses we call the @dfn{host
11502 character set}; the one the inferior program uses we call the
11503 @dfn{target character set}.
11505 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11506 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11507 remote protocol (@pxref{Remote Debugging}) to debug a program
11508 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11509 then the host character set is Latin-1, and the target character set is
11510 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11511 target-charset EBCDIC-US}, then @value{GDBN} translates between
11512 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11513 character and string literals in expressions.
11515 @value{GDBN} has no way to automatically recognize which character set
11516 the inferior program uses; you must tell it, using the @code{set
11517 target-charset} command, described below.
11519 Here are the commands for controlling @value{GDBN}'s character set
11523 @item set target-charset @var{charset}
11524 @kindex set target-charset
11525 Set the current target character set to @var{charset}. To display the
11526 list of supported target character sets, type
11527 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11529 @item set host-charset @var{charset}
11530 @kindex set host-charset
11531 Set the current host character set to @var{charset}.
11533 By default, @value{GDBN} uses a host character set appropriate to the
11534 system it is running on; you can override that default using the
11535 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11536 automatically determine the appropriate host character set. In this
11537 case, @value{GDBN} uses @samp{UTF-8}.
11539 @value{GDBN} can only use certain character sets as its host character
11540 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11541 @value{GDBN} will list the host character sets it supports.
11543 @item set charset @var{charset}
11544 @kindex set charset
11545 Set the current host and target character sets to @var{charset}. As
11546 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11547 @value{GDBN} will list the names of the character sets that can be used
11548 for both host and target.
11551 @kindex show charset
11552 Show the names of the current host and target character sets.
11554 @item show host-charset
11555 @kindex show host-charset
11556 Show the name of the current host character set.
11558 @item show target-charset
11559 @kindex show target-charset
11560 Show the name of the current target character set.
11562 @item set target-wide-charset @var{charset}
11563 @kindex set target-wide-charset
11564 Set the current target's wide character set to @var{charset}. This is
11565 the character set used by the target's @code{wchar_t} type. To
11566 display the list of supported wide character sets, type
11567 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11569 @item show target-wide-charset
11570 @kindex show target-wide-charset
11571 Show the name of the current target's wide character set.
11574 Here is an example of @value{GDBN}'s character set support in action.
11575 Assume that the following source code has been placed in the file
11576 @file{charset-test.c}:
11582 = @{72, 101, 108, 108, 111, 44, 32, 119,
11583 111, 114, 108, 100, 33, 10, 0@};
11584 char ibm1047_hello[]
11585 = @{200, 133, 147, 147, 150, 107, 64, 166,
11586 150, 153, 147, 132, 90, 37, 0@};
11590 printf ("Hello, world!\n");
11594 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11595 containing the string @samp{Hello, world!} followed by a newline,
11596 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11598 We compile the program, and invoke the debugger on it:
11601 $ gcc -g charset-test.c -o charset-test
11602 $ gdb -nw charset-test
11603 GNU gdb 2001-12-19-cvs
11604 Copyright 2001 Free Software Foundation, Inc.
11609 We can use the @code{show charset} command to see what character sets
11610 @value{GDBN} is currently using to interpret and display characters and
11614 (@value{GDBP}) show charset
11615 The current host and target character set is `ISO-8859-1'.
11619 For the sake of printing this manual, let's use @sc{ascii} as our
11620 initial character set:
11622 (@value{GDBP}) set charset ASCII
11623 (@value{GDBP}) show charset
11624 The current host and target character set is `ASCII'.
11628 Let's assume that @sc{ascii} is indeed the correct character set for our
11629 host system --- in other words, let's assume that if @value{GDBN} prints
11630 characters using the @sc{ascii} character set, our terminal will display
11631 them properly. Since our current target character set is also
11632 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11635 (@value{GDBP}) print ascii_hello
11636 $1 = 0x401698 "Hello, world!\n"
11637 (@value{GDBP}) print ascii_hello[0]
11642 @value{GDBN} uses the target character set for character and string
11643 literals you use in expressions:
11646 (@value{GDBP}) print '+'
11651 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11654 @value{GDBN} relies on the user to tell it which character set the
11655 target program uses. If we print @code{ibm1047_hello} while our target
11656 character set is still @sc{ascii}, we get jibberish:
11659 (@value{GDBP}) print ibm1047_hello
11660 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11661 (@value{GDBP}) print ibm1047_hello[0]
11666 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11667 @value{GDBN} tells us the character sets it supports:
11670 (@value{GDBP}) set target-charset
11671 ASCII EBCDIC-US IBM1047 ISO-8859-1
11672 (@value{GDBP}) set target-charset
11675 We can select @sc{ibm1047} as our target character set, and examine the
11676 program's strings again. Now the @sc{ascii} string is wrong, but
11677 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11678 target character set, @sc{ibm1047}, to the host character set,
11679 @sc{ascii}, and they display correctly:
11682 (@value{GDBP}) set target-charset IBM1047
11683 (@value{GDBP}) show charset
11684 The current host character set is `ASCII'.
11685 The current target character set is `IBM1047'.
11686 (@value{GDBP}) print ascii_hello
11687 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11688 (@value{GDBP}) print ascii_hello[0]
11690 (@value{GDBP}) print ibm1047_hello
11691 $8 = 0x4016a8 "Hello, world!\n"
11692 (@value{GDBP}) print ibm1047_hello[0]
11697 As above, @value{GDBN} uses the target character set for character and
11698 string literals you use in expressions:
11701 (@value{GDBP}) print '+'
11706 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11709 @node Caching Target Data
11710 @section Caching Data of Targets
11711 @cindex caching data of targets
11713 @value{GDBN} caches data exchanged between the debugger and a target.
11714 Each cache is associated with the address space of the inferior.
11715 @xref{Inferiors and Programs}, about inferior and address space.
11716 Such caching generally improves performance in remote debugging
11717 (@pxref{Remote Debugging}), because it reduces the overhead of the
11718 remote protocol by bundling memory reads and writes into large chunks.
11719 Unfortunately, simply caching everything would lead to incorrect results,
11720 since @value{GDBN} does not necessarily know anything about volatile
11721 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11722 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11724 Therefore, by default, @value{GDBN} only caches data
11725 known to be on the stack@footnote{In non-stop mode, it is moderately
11726 rare for a running thread to modify the stack of a stopped thread
11727 in a way that would interfere with a backtrace, and caching of
11728 stack reads provides a significant speed up of remote backtraces.} or
11729 in the code segment.
11730 Other regions of memory can be explicitly marked as
11731 cacheable; @pxref{Memory Region Attributes}.
11734 @kindex set remotecache
11735 @item set remotecache on
11736 @itemx set remotecache off
11737 This option no longer does anything; it exists for compatibility
11740 @kindex show remotecache
11741 @item show remotecache
11742 Show the current state of the obsolete remotecache flag.
11744 @kindex set stack-cache
11745 @item set stack-cache on
11746 @itemx set stack-cache off
11747 Enable or disable caching of stack accesses. When @code{on}, use
11748 caching. By default, this option is @code{on}.
11750 @kindex show stack-cache
11751 @item show stack-cache
11752 Show the current state of data caching for memory accesses.
11754 @kindex set code-cache
11755 @item set code-cache on
11756 @itemx set code-cache off
11757 Enable or disable caching of code segment accesses. When @code{on},
11758 use caching. By default, this option is @code{on}. This improves
11759 performance of disassembly in remote debugging.
11761 @kindex show code-cache
11762 @item show code-cache
11763 Show the current state of target memory cache for code segment
11766 @kindex info dcache
11767 @item info dcache @r{[}line@r{]}
11768 Print the information about the performance of data cache of the
11769 current inferior's address space. The information displayed
11770 includes the dcache width and depth, and for each cache line, its
11771 number, address, and how many times it was referenced. This
11772 command is useful for debugging the data cache operation.
11774 If a line number is specified, the contents of that line will be
11777 @item set dcache size @var{size}
11778 @cindex dcache size
11779 @kindex set dcache size
11780 Set maximum number of entries in dcache (dcache depth above).
11782 @item set dcache line-size @var{line-size}
11783 @cindex dcache line-size
11784 @kindex set dcache line-size
11785 Set number of bytes each dcache entry caches (dcache width above).
11786 Must be a power of 2.
11788 @item show dcache size
11789 @kindex show dcache size
11790 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11792 @item show dcache line-size
11793 @kindex show dcache line-size
11794 Show default size of dcache lines.
11798 @node Searching Memory
11799 @section Search Memory
11800 @cindex searching memory
11802 Memory can be searched for a particular sequence of bytes with the
11803 @code{find} command.
11807 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11808 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11809 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11810 etc. The search begins at address @var{start_addr} and continues for either
11811 @var{len} bytes or through to @var{end_addr} inclusive.
11814 @var{s} and @var{n} are optional parameters.
11815 They may be specified in either order, apart or together.
11818 @item @var{s}, search query size
11819 The size of each search query value.
11825 halfwords (two bytes)
11829 giant words (eight bytes)
11832 All values are interpreted in the current language.
11833 This means, for example, that if the current source language is C/C@t{++}
11834 then searching for the string ``hello'' includes the trailing '\0'.
11836 If the value size is not specified, it is taken from the
11837 value's type in the current language.
11838 This is useful when one wants to specify the search
11839 pattern as a mixture of types.
11840 Note that this means, for example, that in the case of C-like languages
11841 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11842 which is typically four bytes.
11844 @item @var{n}, maximum number of finds
11845 The maximum number of matches to print. The default is to print all finds.
11848 You can use strings as search values. Quote them with double-quotes
11850 The string value is copied into the search pattern byte by byte,
11851 regardless of the endianness of the target and the size specification.
11853 The address of each match found is printed as well as a count of the
11854 number of matches found.
11856 The address of the last value found is stored in convenience variable
11858 A count of the number of matches is stored in @samp{$numfound}.
11860 For example, if stopped at the @code{printf} in this function:
11866 static char hello[] = "hello-hello";
11867 static struct @{ char c; short s; int i; @}
11868 __attribute__ ((packed)) mixed
11869 = @{ 'c', 0x1234, 0x87654321 @};
11870 printf ("%s\n", hello);
11875 you get during debugging:
11878 (gdb) find &hello[0], +sizeof(hello), "hello"
11879 0x804956d <hello.1620+6>
11881 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11882 0x8049567 <hello.1620>
11883 0x804956d <hello.1620+6>
11885 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11886 0x8049567 <hello.1620>
11888 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11889 0x8049560 <mixed.1625>
11891 (gdb) print $numfound
11894 $2 = (void *) 0x8049560
11898 @section Value Sizes
11900 Whenever @value{GDBN} prints a value memory will be allocated within
11901 @value{GDBN} to hold the contents of the value. It is possible in
11902 some languages with dynamic typing systems, that an invalid program
11903 may indicate a value that is incorrectly large, this in turn may cause
11904 @value{GDBN} to try and allocate an overly large ammount of memory.
11907 @kindex set max-value-size
11908 @item set max-value-size @var{bytes}
11909 @itemx set max-value-size unlimited
11910 Set the maximum size of memory that @value{GDBN} will allocate for the
11911 contents of a value to @var{bytes}, trying to display a value that
11912 requires more memory than that will result in an error.
11914 Setting this variable does not effect values that have already been
11915 allocated within @value{GDBN}, only future allocations.
11917 There's a minimum size that @code{max-value-size} can be set to in
11918 order that @value{GDBN} can still operate correctly, this minimum is
11919 currently 16 bytes.
11921 The limit applies to the results of some subexpressions as well as to
11922 complete expressions. For example, an expression denoting a simple
11923 integer component, such as @code{x.y.z}, may fail if the size of
11924 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11925 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11926 @var{A} is an array variable with non-constant size, will generally
11927 succeed regardless of the bounds on @var{A}, as long as the component
11928 size is less than @var{bytes}.
11930 The default value of @code{max-value-size} is currently 64k.
11932 @kindex show max-value-size
11933 @item show max-value-size
11934 Show the maximum size of memory, in bytes, that @value{GDBN} will
11935 allocate for the contents of a value.
11938 @node Optimized Code
11939 @chapter Debugging Optimized Code
11940 @cindex optimized code, debugging
11941 @cindex debugging optimized code
11943 Almost all compilers support optimization. With optimization
11944 disabled, the compiler generates assembly code that corresponds
11945 directly to your source code, in a simplistic way. As the compiler
11946 applies more powerful optimizations, the generated assembly code
11947 diverges from your original source code. With help from debugging
11948 information generated by the compiler, @value{GDBN} can map from
11949 the running program back to constructs from your original source.
11951 @value{GDBN} is more accurate with optimization disabled. If you
11952 can recompile without optimization, it is easier to follow the
11953 progress of your program during debugging. But, there are many cases
11954 where you may need to debug an optimized version.
11956 When you debug a program compiled with @samp{-g -O}, remember that the
11957 optimizer has rearranged your code; the debugger shows you what is
11958 really there. Do not be too surprised when the execution path does not
11959 exactly match your source file! An extreme example: if you define a
11960 variable, but never use it, @value{GDBN} never sees that
11961 variable---because the compiler optimizes it out of existence.
11963 Some things do not work as well with @samp{-g -O} as with just
11964 @samp{-g}, particularly on machines with instruction scheduling. If in
11965 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11966 please report it to us as a bug (including a test case!).
11967 @xref{Variables}, for more information about debugging optimized code.
11970 * Inline Functions:: How @value{GDBN} presents inlining
11971 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11974 @node Inline Functions
11975 @section Inline Functions
11976 @cindex inline functions, debugging
11978 @dfn{Inlining} is an optimization that inserts a copy of the function
11979 body directly at each call site, instead of jumping to a shared
11980 routine. @value{GDBN} displays inlined functions just like
11981 non-inlined functions. They appear in backtraces. You can view their
11982 arguments and local variables, step into them with @code{step}, skip
11983 them with @code{next}, and escape from them with @code{finish}.
11984 You can check whether a function was inlined by using the
11985 @code{info frame} command.
11987 For @value{GDBN} to support inlined functions, the compiler must
11988 record information about inlining in the debug information ---
11989 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11990 other compilers do also. @value{GDBN} only supports inlined functions
11991 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11992 do not emit two required attributes (@samp{DW_AT_call_file} and
11993 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11994 function calls with earlier versions of @value{NGCC}. It instead
11995 displays the arguments and local variables of inlined functions as
11996 local variables in the caller.
11998 The body of an inlined function is directly included at its call site;
11999 unlike a non-inlined function, there are no instructions devoted to
12000 the call. @value{GDBN} still pretends that the call site and the
12001 start of the inlined function are different instructions. Stepping to
12002 the call site shows the call site, and then stepping again shows
12003 the first line of the inlined function, even though no additional
12004 instructions are executed.
12006 This makes source-level debugging much clearer; you can see both the
12007 context of the call and then the effect of the call. Only stepping by
12008 a single instruction using @code{stepi} or @code{nexti} does not do
12009 this; single instruction steps always show the inlined body.
12011 There are some ways that @value{GDBN} does not pretend that inlined
12012 function calls are the same as normal calls:
12016 Setting breakpoints at the call site of an inlined function may not
12017 work, because the call site does not contain any code. @value{GDBN}
12018 may incorrectly move the breakpoint to the next line of the enclosing
12019 function, after the call. This limitation will be removed in a future
12020 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12021 or inside the inlined function instead.
12024 @value{GDBN} cannot locate the return value of inlined calls after
12025 using the @code{finish} command. This is a limitation of compiler-generated
12026 debugging information; after @code{finish}, you can step to the next line
12027 and print a variable where your program stored the return value.
12031 @node Tail Call Frames
12032 @section Tail Call Frames
12033 @cindex tail call frames, debugging
12035 Function @code{B} can call function @code{C} in its very last statement. In
12036 unoptimized compilation the call of @code{C} is immediately followed by return
12037 instruction at the end of @code{B} code. Optimizing compiler may replace the
12038 call and return in function @code{B} into one jump to function @code{C}
12039 instead. Such use of a jump instruction is called @dfn{tail call}.
12041 During execution of function @code{C}, there will be no indication in the
12042 function call stack frames that it was tail-called from @code{B}. If function
12043 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12044 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12045 some cases @value{GDBN} can determine that @code{C} was tail-called from
12046 @code{B}, and it will then create fictitious call frame for that, with the
12047 return address set up as if @code{B} called @code{C} normally.
12049 This functionality is currently supported only by DWARF 2 debugging format and
12050 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12051 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12054 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12055 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12059 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12061 Stack level 1, frame at 0x7fffffffda30:
12062 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12063 tail call frame, caller of frame at 0x7fffffffda30
12064 source language c++.
12065 Arglist at unknown address.
12066 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12069 The detection of all the possible code path executions can find them ambiguous.
12070 There is no execution history stored (possible @ref{Reverse Execution} is never
12071 used for this purpose) and the last known caller could have reached the known
12072 callee by multiple different jump sequences. In such case @value{GDBN} still
12073 tries to show at least all the unambiguous top tail callers and all the
12074 unambiguous bottom tail calees, if any.
12077 @anchor{set debug entry-values}
12078 @item set debug entry-values
12079 @kindex set debug entry-values
12080 When set to on, enables printing of analysis messages for both frame argument
12081 values at function entry and tail calls. It will show all the possible valid
12082 tail calls code paths it has considered. It will also print the intersection
12083 of them with the final unambiguous (possibly partial or even empty) code path
12086 @item show debug entry-values
12087 @kindex show debug entry-values
12088 Show the current state of analysis messages printing for both frame argument
12089 values at function entry and tail calls.
12092 The analysis messages for tail calls can for example show why the virtual tail
12093 call frame for function @code{c} has not been recognized (due to the indirect
12094 reference by variable @code{x}):
12097 static void __attribute__((noinline, noclone)) c (void);
12098 void (*x) (void) = c;
12099 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12100 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12101 int main (void) @{ x (); return 0; @}
12103 Breakpoint 1, DW_OP_entry_value resolving cannot find
12104 DW_TAG_call_site 0x40039a in main
12106 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12109 #1 0x000000000040039a in main () at t.c:5
12112 Another possibility is an ambiguous virtual tail call frames resolution:
12116 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12117 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12118 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12119 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12120 static void __attribute__((noinline, noclone)) b (void)
12121 @{ if (i) c (); else e (); @}
12122 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12123 int main (void) @{ a (); return 0; @}
12125 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12126 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12127 tailcall: reduced: 0x4004d2(a) |
12130 #1 0x00000000004004d2 in a () at t.c:8
12131 #2 0x0000000000400395 in main () at t.c:9
12134 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12135 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12137 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12138 @ifset HAVE_MAKEINFO_CLICK
12139 @set ARROW @click{}
12140 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12141 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12143 @ifclear HAVE_MAKEINFO_CLICK
12145 @set CALLSEQ1B @value{CALLSEQ1A}
12146 @set CALLSEQ2B @value{CALLSEQ2A}
12149 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12150 The code can have possible execution paths @value{CALLSEQ1B} or
12151 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12153 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12154 has found. It then finds another possible calling sequcen - that one is
12155 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12156 printed as the @code{reduced:} calling sequence. That one could have many
12157 futher @code{compare:} and @code{reduced:} statements as long as there remain
12158 any non-ambiguous sequence entries.
12160 For the frame of function @code{b} in both cases there are different possible
12161 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12162 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12163 therefore this one is displayed to the user while the ambiguous frames are
12166 There can be also reasons why printing of frame argument values at function
12171 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12172 static void __attribute__((noinline, noclone)) a (int i);
12173 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12174 static void __attribute__((noinline, noclone)) a (int i)
12175 @{ if (i) b (i - 1); else c (0); @}
12176 int main (void) @{ a (5); return 0; @}
12179 #0 c (i=i@@entry=0) at t.c:2
12180 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12181 function "a" at 0x400420 can call itself via tail calls
12182 i=<optimized out>) at t.c:6
12183 #2 0x000000000040036e in main () at t.c:7
12186 @value{GDBN} cannot find out from the inferior state if and how many times did
12187 function @code{a} call itself (via function @code{b}) as these calls would be
12188 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12189 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12190 prints @code{<optimized out>} instead.
12193 @chapter C Preprocessor Macros
12195 Some languages, such as C and C@t{++}, provide a way to define and invoke
12196 ``preprocessor macros'' which expand into strings of tokens.
12197 @value{GDBN} can evaluate expressions containing macro invocations, show
12198 the result of macro expansion, and show a macro's definition, including
12199 where it was defined.
12201 You may need to compile your program specially to provide @value{GDBN}
12202 with information about preprocessor macros. Most compilers do not
12203 include macros in their debugging information, even when you compile
12204 with the @option{-g} flag. @xref{Compilation}.
12206 A program may define a macro at one point, remove that definition later,
12207 and then provide a different definition after that. Thus, at different
12208 points in the program, a macro may have different definitions, or have
12209 no definition at all. If there is a current stack frame, @value{GDBN}
12210 uses the macros in scope at that frame's source code line. Otherwise,
12211 @value{GDBN} uses the macros in scope at the current listing location;
12214 Whenever @value{GDBN} evaluates an expression, it always expands any
12215 macro invocations present in the expression. @value{GDBN} also provides
12216 the following commands for working with macros explicitly.
12220 @kindex macro expand
12221 @cindex macro expansion, showing the results of preprocessor
12222 @cindex preprocessor macro expansion, showing the results of
12223 @cindex expanding preprocessor macros
12224 @item macro expand @var{expression}
12225 @itemx macro exp @var{expression}
12226 Show the results of expanding all preprocessor macro invocations in
12227 @var{expression}. Since @value{GDBN} simply expands macros, but does
12228 not parse the result, @var{expression} need not be a valid expression;
12229 it can be any string of tokens.
12232 @item macro expand-once @var{expression}
12233 @itemx macro exp1 @var{expression}
12234 @cindex expand macro once
12235 @i{(This command is not yet implemented.)} Show the results of
12236 expanding those preprocessor macro invocations that appear explicitly in
12237 @var{expression}. Macro invocations appearing in that expansion are
12238 left unchanged. This command allows you to see the effect of a
12239 particular macro more clearly, without being confused by further
12240 expansions. Since @value{GDBN} simply expands macros, but does not
12241 parse the result, @var{expression} need not be a valid expression; it
12242 can be any string of tokens.
12245 @cindex macro definition, showing
12246 @cindex definition of a macro, showing
12247 @cindex macros, from debug info
12248 @item info macro [-a|-all] [--] @var{macro}
12249 Show the current definition or all definitions of the named @var{macro},
12250 and describe the source location or compiler command-line where that
12251 definition was established. The optional double dash is to signify the end of
12252 argument processing and the beginning of @var{macro} for non C-like macros where
12253 the macro may begin with a hyphen.
12255 @kindex info macros
12256 @item info macros @var{location}
12257 Show all macro definitions that are in effect at the location specified
12258 by @var{location}, and describe the source location or compiler
12259 command-line where those definitions were established.
12261 @kindex macro define
12262 @cindex user-defined macros
12263 @cindex defining macros interactively
12264 @cindex macros, user-defined
12265 @item macro define @var{macro} @var{replacement-list}
12266 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12267 Introduce a definition for a preprocessor macro named @var{macro},
12268 invocations of which are replaced by the tokens given in
12269 @var{replacement-list}. The first form of this command defines an
12270 ``object-like'' macro, which takes no arguments; the second form
12271 defines a ``function-like'' macro, which takes the arguments given in
12274 A definition introduced by this command is in scope in every
12275 expression evaluated in @value{GDBN}, until it is removed with the
12276 @code{macro undef} command, described below. The definition overrides
12277 all definitions for @var{macro} present in the program being debugged,
12278 as well as any previous user-supplied definition.
12280 @kindex macro undef
12281 @item macro undef @var{macro}
12282 Remove any user-supplied definition for the macro named @var{macro}.
12283 This command only affects definitions provided with the @code{macro
12284 define} command, described above; it cannot remove definitions present
12285 in the program being debugged.
12289 List all the macros defined using the @code{macro define} command.
12292 @cindex macros, example of debugging with
12293 Here is a transcript showing the above commands in action. First, we
12294 show our source files:
12299 #include "sample.h"
12302 #define ADD(x) (M + x)
12307 printf ("Hello, world!\n");
12309 printf ("We're so creative.\n");
12311 printf ("Goodbye, world!\n");
12318 Now, we compile the program using the @sc{gnu} C compiler,
12319 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12320 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12321 and @option{-gdwarf-4}; we recommend always choosing the most recent
12322 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12323 includes information about preprocessor macros in the debugging
12327 $ gcc -gdwarf-2 -g3 sample.c -o sample
12331 Now, we start @value{GDBN} on our sample program:
12335 GNU gdb 2002-05-06-cvs
12336 Copyright 2002 Free Software Foundation, Inc.
12337 GDB is free software, @dots{}
12341 We can expand macros and examine their definitions, even when the
12342 program is not running. @value{GDBN} uses the current listing position
12343 to decide which macro definitions are in scope:
12346 (@value{GDBP}) list main
12349 5 #define ADD(x) (M + x)
12354 10 printf ("Hello, world!\n");
12356 12 printf ("We're so creative.\n");
12357 (@value{GDBP}) info macro ADD
12358 Defined at /home/jimb/gdb/macros/play/sample.c:5
12359 #define ADD(x) (M + x)
12360 (@value{GDBP}) info macro Q
12361 Defined at /home/jimb/gdb/macros/play/sample.h:1
12362 included at /home/jimb/gdb/macros/play/sample.c:2
12364 (@value{GDBP}) macro expand ADD(1)
12365 expands to: (42 + 1)
12366 (@value{GDBP}) macro expand-once ADD(1)
12367 expands to: once (M + 1)
12371 In the example above, note that @code{macro expand-once} expands only
12372 the macro invocation explicit in the original text --- the invocation of
12373 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12374 which was introduced by @code{ADD}.
12376 Once the program is running, @value{GDBN} uses the macro definitions in
12377 force at the source line of the current stack frame:
12380 (@value{GDBP}) break main
12381 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12383 Starting program: /home/jimb/gdb/macros/play/sample
12385 Breakpoint 1, main () at sample.c:10
12386 10 printf ("Hello, world!\n");
12390 At line 10, the definition of the macro @code{N} at line 9 is in force:
12393 (@value{GDBP}) info macro N
12394 Defined at /home/jimb/gdb/macros/play/sample.c:9
12396 (@value{GDBP}) macro expand N Q M
12397 expands to: 28 < 42
12398 (@value{GDBP}) print N Q M
12403 As we step over directives that remove @code{N}'s definition, and then
12404 give it a new definition, @value{GDBN} finds the definition (or lack
12405 thereof) in force at each point:
12408 (@value{GDBP}) next
12410 12 printf ("We're so creative.\n");
12411 (@value{GDBP}) info macro N
12412 The symbol `N' has no definition as a C/C++ preprocessor macro
12413 at /home/jimb/gdb/macros/play/sample.c:12
12414 (@value{GDBP}) next
12416 14 printf ("Goodbye, world!\n");
12417 (@value{GDBP}) info macro N
12418 Defined at /home/jimb/gdb/macros/play/sample.c:13
12420 (@value{GDBP}) macro expand N Q M
12421 expands to: 1729 < 42
12422 (@value{GDBP}) print N Q M
12427 In addition to source files, macros can be defined on the compilation command
12428 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12429 such a way, @value{GDBN} displays the location of their definition as line zero
12430 of the source file submitted to the compiler.
12433 (@value{GDBP}) info macro __STDC__
12434 Defined at /home/jimb/gdb/macros/play/sample.c:0
12441 @chapter Tracepoints
12442 @c This chapter is based on the documentation written by Michael
12443 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12445 @cindex tracepoints
12446 In some applications, it is not feasible for the debugger to interrupt
12447 the program's execution long enough for the developer to learn
12448 anything helpful about its behavior. If the program's correctness
12449 depends on its real-time behavior, delays introduced by a debugger
12450 might cause the program to change its behavior drastically, or perhaps
12451 fail, even when the code itself is correct. It is useful to be able
12452 to observe the program's behavior without interrupting it.
12454 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12455 specify locations in the program, called @dfn{tracepoints}, and
12456 arbitrary expressions to evaluate when those tracepoints are reached.
12457 Later, using the @code{tfind} command, you can examine the values
12458 those expressions had when the program hit the tracepoints. The
12459 expressions may also denote objects in memory---structures or arrays,
12460 for example---whose values @value{GDBN} should record; while visiting
12461 a particular tracepoint, you may inspect those objects as if they were
12462 in memory at that moment. However, because @value{GDBN} records these
12463 values without interacting with you, it can do so quickly and
12464 unobtrusively, hopefully not disturbing the program's behavior.
12466 The tracepoint facility is currently available only for remote
12467 targets. @xref{Targets}. In addition, your remote target must know
12468 how to collect trace data. This functionality is implemented in the
12469 remote stub; however, none of the stubs distributed with @value{GDBN}
12470 support tracepoints as of this writing. The format of the remote
12471 packets used to implement tracepoints are described in @ref{Tracepoint
12474 It is also possible to get trace data from a file, in a manner reminiscent
12475 of corefiles; you specify the filename, and use @code{tfind} to search
12476 through the file. @xref{Trace Files}, for more details.
12478 This chapter describes the tracepoint commands and features.
12481 * Set Tracepoints::
12482 * Analyze Collected Data::
12483 * Tracepoint Variables::
12487 @node Set Tracepoints
12488 @section Commands to Set Tracepoints
12490 Before running such a @dfn{trace experiment}, an arbitrary number of
12491 tracepoints can be set. A tracepoint is actually a special type of
12492 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12493 standard breakpoint commands. For instance, as with breakpoints,
12494 tracepoint numbers are successive integers starting from one, and many
12495 of the commands associated with tracepoints take the tracepoint number
12496 as their argument, to identify which tracepoint to work on.
12498 For each tracepoint, you can specify, in advance, some arbitrary set
12499 of data that you want the target to collect in the trace buffer when
12500 it hits that tracepoint. The collected data can include registers,
12501 local variables, or global data. Later, you can use @value{GDBN}
12502 commands to examine the values these data had at the time the
12503 tracepoint was hit.
12505 Tracepoints do not support every breakpoint feature. Ignore counts on
12506 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12507 commands when they are hit. Tracepoints may not be thread-specific
12510 @cindex fast tracepoints
12511 Some targets may support @dfn{fast tracepoints}, which are inserted in
12512 a different way (such as with a jump instead of a trap), that is
12513 faster but possibly restricted in where they may be installed.
12515 @cindex static tracepoints
12516 @cindex markers, static tracepoints
12517 @cindex probing markers, static tracepoints
12518 Regular and fast tracepoints are dynamic tracing facilities, meaning
12519 that they can be used to insert tracepoints at (almost) any location
12520 in the target. Some targets may also support controlling @dfn{static
12521 tracepoints} from @value{GDBN}. With static tracing, a set of
12522 instrumentation points, also known as @dfn{markers}, are embedded in
12523 the target program, and can be activated or deactivated by name or
12524 address. These are usually placed at locations which facilitate
12525 investigating what the target is actually doing. @value{GDBN}'s
12526 support for static tracing includes being able to list instrumentation
12527 points, and attach them with @value{GDBN} defined high level
12528 tracepoints that expose the whole range of convenience of
12529 @value{GDBN}'s tracepoints support. Namely, support for collecting
12530 registers values and values of global or local (to the instrumentation
12531 point) variables; tracepoint conditions and trace state variables.
12532 The act of installing a @value{GDBN} static tracepoint on an
12533 instrumentation point, or marker, is referred to as @dfn{probing} a
12534 static tracepoint marker.
12536 @code{gdbserver} supports tracepoints on some target systems.
12537 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12539 This section describes commands to set tracepoints and associated
12540 conditions and actions.
12543 * Create and Delete Tracepoints::
12544 * Enable and Disable Tracepoints::
12545 * Tracepoint Passcounts::
12546 * Tracepoint Conditions::
12547 * Trace State Variables::
12548 * Tracepoint Actions::
12549 * Listing Tracepoints::
12550 * Listing Static Tracepoint Markers::
12551 * Starting and Stopping Trace Experiments::
12552 * Tracepoint Restrictions::
12555 @node Create and Delete Tracepoints
12556 @subsection Create and Delete Tracepoints
12559 @cindex set tracepoint
12561 @item trace @var{location}
12562 The @code{trace} command is very similar to the @code{break} command.
12563 Its argument @var{location} can be any valid location.
12564 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12565 which is a point in the target program where the debugger will briefly stop,
12566 collect some data, and then allow the program to continue. Setting a tracepoint
12567 or changing its actions takes effect immediately if the remote stub
12568 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12570 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12571 these changes don't take effect until the next @code{tstart}
12572 command, and once a trace experiment is running, further changes will
12573 not have any effect until the next trace experiment starts. In addition,
12574 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12575 address is not yet resolved. (This is similar to pending breakpoints.)
12576 Pending tracepoints are not downloaded to the target and not installed
12577 until they are resolved. The resolution of pending tracepoints requires
12578 @value{GDBN} support---when debugging with the remote target, and
12579 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12580 tracing}), pending tracepoints can not be resolved (and downloaded to
12581 the remote stub) while @value{GDBN} is disconnected.
12583 Here are some examples of using the @code{trace} command:
12586 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12588 (@value{GDBP}) @b{trace +2} // 2 lines forward
12590 (@value{GDBP}) @b{trace my_function} // first source line of function
12592 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12594 (@value{GDBP}) @b{trace *0x2117c4} // an address
12598 You can abbreviate @code{trace} as @code{tr}.
12600 @item trace @var{location} if @var{cond}
12601 Set a tracepoint with condition @var{cond}; evaluate the expression
12602 @var{cond} each time the tracepoint is reached, and collect data only
12603 if the value is nonzero---that is, if @var{cond} evaluates as true.
12604 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12605 information on tracepoint conditions.
12607 @item ftrace @var{location} [ if @var{cond} ]
12608 @cindex set fast tracepoint
12609 @cindex fast tracepoints, setting
12611 The @code{ftrace} command sets a fast tracepoint. For targets that
12612 support them, fast tracepoints will use a more efficient but possibly
12613 less general technique to trigger data collection, such as a jump
12614 instruction instead of a trap, or some sort of hardware support. It
12615 may not be possible to create a fast tracepoint at the desired
12616 location, in which case the command will exit with an explanatory
12619 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12622 On 32-bit x86-architecture systems, fast tracepoints normally need to
12623 be placed at an instruction that is 5 bytes or longer, but can be
12624 placed at 4-byte instructions if the low 64K of memory of the target
12625 program is available to install trampolines. Some Unix-type systems,
12626 such as @sc{gnu}/Linux, exclude low addresses from the program's
12627 address space; but for instance with the Linux kernel it is possible
12628 to let @value{GDBN} use this area by doing a @command{sysctl} command
12629 to set the @code{mmap_min_addr} kernel parameter, as in
12632 sudo sysctl -w vm.mmap_min_addr=32768
12636 which sets the low address to 32K, which leaves plenty of room for
12637 trampolines. The minimum address should be set to a page boundary.
12639 @item strace @var{location} [ if @var{cond} ]
12640 @cindex set static tracepoint
12641 @cindex static tracepoints, setting
12642 @cindex probe static tracepoint marker
12644 The @code{strace} command sets a static tracepoint. For targets that
12645 support it, setting a static tracepoint probes a static
12646 instrumentation point, or marker, found at @var{location}. It may not
12647 be possible to set a static tracepoint at the desired location, in
12648 which case the command will exit with an explanatory message.
12650 @value{GDBN} handles arguments to @code{strace} exactly as for
12651 @code{trace}, with the addition that the user can also specify
12652 @code{-m @var{marker}} as @var{location}. This probes the marker
12653 identified by the @var{marker} string identifier. This identifier
12654 depends on the static tracepoint backend library your program is
12655 using. You can find all the marker identifiers in the @samp{ID} field
12656 of the @code{info static-tracepoint-markers} command output.
12657 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12658 Markers}. For example, in the following small program using the UST
12664 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12669 the marker id is composed of joining the first two arguments to the
12670 @code{trace_mark} call with a slash, which translates to:
12673 (@value{GDBP}) info static-tracepoint-markers
12674 Cnt Enb ID Address What
12675 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12681 so you may probe the marker above with:
12684 (@value{GDBP}) strace -m ust/bar33
12687 Static tracepoints accept an extra collect action --- @code{collect
12688 $_sdata}. This collects arbitrary user data passed in the probe point
12689 call to the tracing library. In the UST example above, you'll see
12690 that the third argument to @code{trace_mark} is a printf-like format
12691 string. The user data is then the result of running that formating
12692 string against the following arguments. Note that @code{info
12693 static-tracepoint-markers} command output lists that format string in
12694 the @samp{Data:} field.
12696 You can inspect this data when analyzing the trace buffer, by printing
12697 the $_sdata variable like any other variable available to
12698 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12701 @cindex last tracepoint number
12702 @cindex recent tracepoint number
12703 @cindex tracepoint number
12704 The convenience variable @code{$tpnum} records the tracepoint number
12705 of the most recently set tracepoint.
12707 @kindex delete tracepoint
12708 @cindex tracepoint deletion
12709 @item delete tracepoint @r{[}@var{num}@r{]}
12710 Permanently delete one or more tracepoints. With no argument, the
12711 default is to delete all tracepoints. Note that the regular
12712 @code{delete} command can remove tracepoints also.
12717 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12719 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12723 You can abbreviate this command as @code{del tr}.
12726 @node Enable and Disable Tracepoints
12727 @subsection Enable and Disable Tracepoints
12729 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12732 @kindex disable tracepoint
12733 @item disable tracepoint @r{[}@var{num}@r{]}
12734 Disable tracepoint @var{num}, or all tracepoints if no argument
12735 @var{num} is given. A disabled tracepoint will have no effect during
12736 a trace experiment, but it is not forgotten. You can re-enable
12737 a disabled tracepoint using the @code{enable tracepoint} command.
12738 If the command is issued during a trace experiment and the debug target
12739 has support for disabling tracepoints during a trace experiment, then the
12740 change will be effective immediately. Otherwise, it will be applied to the
12741 next trace experiment.
12743 @kindex enable tracepoint
12744 @item enable tracepoint @r{[}@var{num}@r{]}
12745 Enable tracepoint @var{num}, or all tracepoints. If this command is
12746 issued during a trace experiment and the debug target supports enabling
12747 tracepoints during a trace experiment, then the enabled tracepoints will
12748 become effective immediately. Otherwise, they will become effective the
12749 next time a trace experiment is run.
12752 @node Tracepoint Passcounts
12753 @subsection Tracepoint Passcounts
12757 @cindex tracepoint pass count
12758 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12759 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12760 automatically stop a trace experiment. If a tracepoint's passcount is
12761 @var{n}, then the trace experiment will be automatically stopped on
12762 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12763 @var{num} is not specified, the @code{passcount} command sets the
12764 passcount of the most recently defined tracepoint. If no passcount is
12765 given, the trace experiment will run until stopped explicitly by the
12771 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12772 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12774 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12775 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12776 (@value{GDBP}) @b{trace foo}
12777 (@value{GDBP}) @b{pass 3}
12778 (@value{GDBP}) @b{trace bar}
12779 (@value{GDBP}) @b{pass 2}
12780 (@value{GDBP}) @b{trace baz}
12781 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12782 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12783 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12784 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12788 @node Tracepoint Conditions
12789 @subsection Tracepoint Conditions
12790 @cindex conditional tracepoints
12791 @cindex tracepoint conditions
12793 The simplest sort of tracepoint collects data every time your program
12794 reaches a specified place. You can also specify a @dfn{condition} for
12795 a tracepoint. A condition is just a Boolean expression in your
12796 programming language (@pxref{Expressions, ,Expressions}). A
12797 tracepoint with a condition evaluates the expression each time your
12798 program reaches it, and data collection happens only if the condition
12801 Tracepoint conditions can be specified when a tracepoint is set, by
12802 using @samp{if} in the arguments to the @code{trace} command.
12803 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12804 also be set or changed at any time with the @code{condition} command,
12805 just as with breakpoints.
12807 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12808 the conditional expression itself. Instead, @value{GDBN} encodes the
12809 expression into an agent expression (@pxref{Agent Expressions})
12810 suitable for execution on the target, independently of @value{GDBN}.
12811 Global variables become raw memory locations, locals become stack
12812 accesses, and so forth.
12814 For instance, suppose you have a function that is usually called
12815 frequently, but should not be called after an error has occurred. You
12816 could use the following tracepoint command to collect data about calls
12817 of that function that happen while the error code is propagating
12818 through the program; an unconditional tracepoint could end up
12819 collecting thousands of useless trace frames that you would have to
12823 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12826 @node Trace State Variables
12827 @subsection Trace State Variables
12828 @cindex trace state variables
12830 A @dfn{trace state variable} is a special type of variable that is
12831 created and managed by target-side code. The syntax is the same as
12832 that for GDB's convenience variables (a string prefixed with ``$''),
12833 but they are stored on the target. They must be created explicitly,
12834 using a @code{tvariable} command. They are always 64-bit signed
12837 Trace state variables are remembered by @value{GDBN}, and downloaded
12838 to the target along with tracepoint information when the trace
12839 experiment starts. There are no intrinsic limits on the number of
12840 trace state variables, beyond memory limitations of the target.
12842 @cindex convenience variables, and trace state variables
12843 Although trace state variables are managed by the target, you can use
12844 them in print commands and expressions as if they were convenience
12845 variables; @value{GDBN} will get the current value from the target
12846 while the trace experiment is running. Trace state variables share
12847 the same namespace as other ``$'' variables, which means that you
12848 cannot have trace state variables with names like @code{$23} or
12849 @code{$pc}, nor can you have a trace state variable and a convenience
12850 variable with the same name.
12854 @item tvariable $@var{name} [ = @var{expression} ]
12856 The @code{tvariable} command creates a new trace state variable named
12857 @code{$@var{name}}, and optionally gives it an initial value of
12858 @var{expression}. The @var{expression} is evaluated when this command is
12859 entered; the result will be converted to an integer if possible,
12860 otherwise @value{GDBN} will report an error. A subsequent
12861 @code{tvariable} command specifying the same name does not create a
12862 variable, but instead assigns the supplied initial value to the
12863 existing variable of that name, overwriting any previous initial
12864 value. The default initial value is 0.
12866 @item info tvariables
12867 @kindex info tvariables
12868 List all the trace state variables along with their initial values.
12869 Their current values may also be displayed, if the trace experiment is
12872 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12873 @kindex delete tvariable
12874 Delete the given trace state variables, or all of them if no arguments
12879 @node Tracepoint Actions
12880 @subsection Tracepoint Action Lists
12884 @cindex tracepoint actions
12885 @item actions @r{[}@var{num}@r{]}
12886 This command will prompt for a list of actions to be taken when the
12887 tracepoint is hit. If the tracepoint number @var{num} is not
12888 specified, this command sets the actions for the one that was most
12889 recently defined (so that you can define a tracepoint and then say
12890 @code{actions} without bothering about its number). You specify the
12891 actions themselves on the following lines, one action at a time, and
12892 terminate the actions list with a line containing just @code{end}. So
12893 far, the only defined actions are @code{collect}, @code{teval}, and
12894 @code{while-stepping}.
12896 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12897 Commands, ,Breakpoint Command Lists}), except that only the defined
12898 actions are allowed; any other @value{GDBN} command is rejected.
12900 @cindex remove actions from a tracepoint
12901 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12902 and follow it immediately with @samp{end}.
12905 (@value{GDBP}) @b{collect @var{data}} // collect some data
12907 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12909 (@value{GDBP}) @b{end} // signals the end of actions.
12912 In the following example, the action list begins with @code{collect}
12913 commands indicating the things to be collected when the tracepoint is
12914 hit. Then, in order to single-step and collect additional data
12915 following the tracepoint, a @code{while-stepping} command is used,
12916 followed by the list of things to be collected after each step in a
12917 sequence of single steps. The @code{while-stepping} command is
12918 terminated by its own separate @code{end} command. Lastly, the action
12919 list is terminated by an @code{end} command.
12922 (@value{GDBP}) @b{trace foo}
12923 (@value{GDBP}) @b{actions}
12924 Enter actions for tracepoint 1, one per line:
12927 > while-stepping 12
12928 > collect $pc, arr[i]
12933 @kindex collect @r{(tracepoints)}
12934 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12935 Collect values of the given expressions when the tracepoint is hit.
12936 This command accepts a comma-separated list of any valid expressions.
12937 In addition to global, static, or local variables, the following
12938 special arguments are supported:
12942 Collect all registers.
12945 Collect all function arguments.
12948 Collect all local variables.
12951 Collect the return address. This is helpful if you want to see more
12954 @emph{Note:} The return address location can not always be reliably
12955 determined up front, and the wrong address / registers may end up
12956 collected instead. On some architectures the reliability is higher
12957 for tracepoints at function entry, while on others it's the opposite.
12958 When this happens, backtracing will stop because the return address is
12959 found unavailable (unless another collect rule happened to match it).
12962 Collects the number of arguments from the static probe at which the
12963 tracepoint is located.
12964 @xref{Static Probe Points}.
12966 @item $_probe_arg@var{n}
12967 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12968 from the static probe at which the tracepoint is located.
12969 @xref{Static Probe Points}.
12972 @vindex $_sdata@r{, collect}
12973 Collect static tracepoint marker specific data. Only available for
12974 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12975 Lists}. On the UST static tracepoints library backend, an
12976 instrumentation point resembles a @code{printf} function call. The
12977 tracing library is able to collect user specified data formatted to a
12978 character string using the format provided by the programmer that
12979 instrumented the program. Other backends have similar mechanisms.
12980 Here's an example of a UST marker call:
12983 const char master_name[] = "$your_name";
12984 trace_mark(channel1, marker1, "hello %s", master_name)
12987 In this case, collecting @code{$_sdata} collects the string
12988 @samp{hello $yourname}. When analyzing the trace buffer, you can
12989 inspect @samp{$_sdata} like any other variable available to
12993 You can give several consecutive @code{collect} commands, each one
12994 with a single argument, or one @code{collect} command with several
12995 arguments separated by commas; the effect is the same.
12997 The optional @var{mods} changes the usual handling of the arguments.
12998 @code{s} requests that pointers to chars be handled as strings, in
12999 particular collecting the contents of the memory being pointed at, up
13000 to the first zero. The upper bound is by default the value of the
13001 @code{print elements} variable; if @code{s} is followed by a decimal
13002 number, that is the upper bound instead. So for instance
13003 @samp{collect/s25 mystr} collects as many as 25 characters at
13006 The command @code{info scope} (@pxref{Symbols, info scope}) is
13007 particularly useful for figuring out what data to collect.
13009 @kindex teval @r{(tracepoints)}
13010 @item teval @var{expr1}, @var{expr2}, @dots{}
13011 Evaluate the given expressions when the tracepoint is hit. This
13012 command accepts a comma-separated list of expressions. The results
13013 are discarded, so this is mainly useful for assigning values to trace
13014 state variables (@pxref{Trace State Variables}) without adding those
13015 values to the trace buffer, as would be the case if the @code{collect}
13018 @kindex while-stepping @r{(tracepoints)}
13019 @item while-stepping @var{n}
13020 Perform @var{n} single-step instruction traces after the tracepoint,
13021 collecting new data after each step. The @code{while-stepping}
13022 command is followed by the list of what to collect while stepping
13023 (followed by its own @code{end} command):
13026 > while-stepping 12
13027 > collect $regs, myglobal
13033 Note that @code{$pc} is not automatically collected by
13034 @code{while-stepping}; you need to explicitly collect that register if
13035 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13038 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13039 @kindex set default-collect
13040 @cindex default collection action
13041 This variable is a list of expressions to collect at each tracepoint
13042 hit. It is effectively an additional @code{collect} action prepended
13043 to every tracepoint action list. The expressions are parsed
13044 individually for each tracepoint, so for instance a variable named
13045 @code{xyz} may be interpreted as a global for one tracepoint, and a
13046 local for another, as appropriate to the tracepoint's location.
13048 @item show default-collect
13049 @kindex show default-collect
13050 Show the list of expressions that are collected by default at each
13055 @node Listing Tracepoints
13056 @subsection Listing Tracepoints
13059 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13060 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13061 @cindex information about tracepoints
13062 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13063 Display information about the tracepoint @var{num}. If you don't
13064 specify a tracepoint number, displays information about all the
13065 tracepoints defined so far. The format is similar to that used for
13066 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13067 command, simply restricting itself to tracepoints.
13069 A tracepoint's listing may include additional information specific to
13074 its passcount as given by the @code{passcount @var{n}} command
13077 the state about installed on target of each location
13081 (@value{GDBP}) @b{info trace}
13082 Num Type Disp Enb Address What
13083 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13085 collect globfoo, $regs
13090 2 tracepoint keep y <MULTIPLE>
13092 2.1 y 0x0804859c in func4 at change-loc.h:35
13093 installed on target
13094 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13095 installed on target
13096 2.3 y <PENDING> set_tracepoint
13097 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13098 not installed on target
13103 This command can be abbreviated @code{info tp}.
13106 @node Listing Static Tracepoint Markers
13107 @subsection Listing Static Tracepoint Markers
13110 @kindex info static-tracepoint-markers
13111 @cindex information about static tracepoint markers
13112 @item info static-tracepoint-markers
13113 Display information about all static tracepoint markers defined in the
13116 For each marker, the following columns are printed:
13120 An incrementing counter, output to help readability. This is not a
13123 The marker ID, as reported by the target.
13124 @item Enabled or Disabled
13125 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13126 that are not enabled.
13128 Where the marker is in your program, as a memory address.
13130 Where the marker is in the source for your program, as a file and line
13131 number. If the debug information included in the program does not
13132 allow @value{GDBN} to locate the source of the marker, this column
13133 will be left blank.
13137 In addition, the following information may be printed for each marker:
13141 User data passed to the tracing library by the marker call. In the
13142 UST backend, this is the format string passed as argument to the
13144 @item Static tracepoints probing the marker
13145 The list of static tracepoints attached to the marker.
13149 (@value{GDBP}) info static-tracepoint-markers
13150 Cnt ID Enb Address What
13151 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13152 Data: number1 %d number2 %d
13153 Probed by static tracepoints: #2
13154 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13160 @node Starting and Stopping Trace Experiments
13161 @subsection Starting and Stopping Trace Experiments
13164 @kindex tstart [ @var{notes} ]
13165 @cindex start a new trace experiment
13166 @cindex collected data discarded
13168 This command starts the trace experiment, and begins collecting data.
13169 It has the side effect of discarding all the data collected in the
13170 trace buffer during the previous trace experiment. If any arguments
13171 are supplied, they are taken as a note and stored with the trace
13172 experiment's state. The notes may be arbitrary text, and are
13173 especially useful with disconnected tracing in a multi-user context;
13174 the notes can explain what the trace is doing, supply user contact
13175 information, and so forth.
13177 @kindex tstop [ @var{notes} ]
13178 @cindex stop a running trace experiment
13180 This command stops the trace experiment. If any arguments are
13181 supplied, they are recorded with the experiment as a note. This is
13182 useful if you are stopping a trace started by someone else, for
13183 instance if the trace is interfering with the system's behavior and
13184 needs to be stopped quickly.
13186 @strong{Note}: a trace experiment and data collection may stop
13187 automatically if any tracepoint's passcount is reached
13188 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13191 @cindex status of trace data collection
13192 @cindex trace experiment, status of
13194 This command displays the status of the current trace data
13198 Here is an example of the commands we described so far:
13201 (@value{GDBP}) @b{trace gdb_c_test}
13202 (@value{GDBP}) @b{actions}
13203 Enter actions for tracepoint #1, one per line.
13204 > collect $regs,$locals,$args
13205 > while-stepping 11
13209 (@value{GDBP}) @b{tstart}
13210 [time passes @dots{}]
13211 (@value{GDBP}) @b{tstop}
13214 @anchor{disconnected tracing}
13215 @cindex disconnected tracing
13216 You can choose to continue running the trace experiment even if
13217 @value{GDBN} disconnects from the target, voluntarily or
13218 involuntarily. For commands such as @code{detach}, the debugger will
13219 ask what you want to do with the trace. But for unexpected
13220 terminations (@value{GDBN} crash, network outage), it would be
13221 unfortunate to lose hard-won trace data, so the variable
13222 @code{disconnected-tracing} lets you decide whether the trace should
13223 continue running without @value{GDBN}.
13226 @item set disconnected-tracing on
13227 @itemx set disconnected-tracing off
13228 @kindex set disconnected-tracing
13229 Choose whether a tracing run should continue to run if @value{GDBN}
13230 has disconnected from the target. Note that @code{detach} or
13231 @code{quit} will ask you directly what to do about a running trace no
13232 matter what this variable's setting, so the variable is mainly useful
13233 for handling unexpected situations, such as loss of the network.
13235 @item show disconnected-tracing
13236 @kindex show disconnected-tracing
13237 Show the current choice for disconnected tracing.
13241 When you reconnect to the target, the trace experiment may or may not
13242 still be running; it might have filled the trace buffer in the
13243 meantime, or stopped for one of the other reasons. If it is running,
13244 it will continue after reconnection.
13246 Upon reconnection, the target will upload information about the
13247 tracepoints in effect. @value{GDBN} will then compare that
13248 information to the set of tracepoints currently defined, and attempt
13249 to match them up, allowing for the possibility that the numbers may
13250 have changed due to creation and deletion in the meantime. If one of
13251 the target's tracepoints does not match any in @value{GDBN}, the
13252 debugger will create a new tracepoint, so that you have a number with
13253 which to specify that tracepoint. This matching-up process is
13254 necessarily heuristic, and it may result in useless tracepoints being
13255 created; you may simply delete them if they are of no use.
13257 @cindex circular trace buffer
13258 If your target agent supports a @dfn{circular trace buffer}, then you
13259 can run a trace experiment indefinitely without filling the trace
13260 buffer; when space runs out, the agent deletes already-collected trace
13261 frames, oldest first, until there is enough room to continue
13262 collecting. This is especially useful if your tracepoints are being
13263 hit too often, and your trace gets terminated prematurely because the
13264 buffer is full. To ask for a circular trace buffer, simply set
13265 @samp{circular-trace-buffer} to on. You can set this at any time,
13266 including during tracing; if the agent can do it, it will change
13267 buffer handling on the fly, otherwise it will not take effect until
13271 @item set circular-trace-buffer on
13272 @itemx set circular-trace-buffer off
13273 @kindex set circular-trace-buffer
13274 Choose whether a tracing run should use a linear or circular buffer
13275 for trace data. A linear buffer will not lose any trace data, but may
13276 fill up prematurely, while a circular buffer will discard old trace
13277 data, but it will have always room for the latest tracepoint hits.
13279 @item show circular-trace-buffer
13280 @kindex show circular-trace-buffer
13281 Show the current choice for the trace buffer. Note that this may not
13282 match the agent's current buffer handling, nor is it guaranteed to
13283 match the setting that might have been in effect during a past run,
13284 for instance if you are looking at frames from a trace file.
13289 @item set trace-buffer-size @var{n}
13290 @itemx set trace-buffer-size unlimited
13291 @kindex set trace-buffer-size
13292 Request that the target use a trace buffer of @var{n} bytes. Not all
13293 targets will honor the request; they may have a compiled-in size for
13294 the trace buffer, or some other limitation. Set to a value of
13295 @code{unlimited} or @code{-1} to let the target use whatever size it
13296 likes. This is also the default.
13298 @item show trace-buffer-size
13299 @kindex show trace-buffer-size
13300 Show the current requested size for the trace buffer. Note that this
13301 will only match the actual size if the target supports size-setting,
13302 and was able to handle the requested size. For instance, if the
13303 target can only change buffer size between runs, this variable will
13304 not reflect the change until the next run starts. Use @code{tstatus}
13305 to get a report of the actual buffer size.
13309 @item set trace-user @var{text}
13310 @kindex set trace-user
13312 @item show trace-user
13313 @kindex show trace-user
13315 @item set trace-notes @var{text}
13316 @kindex set trace-notes
13317 Set the trace run's notes.
13319 @item show trace-notes
13320 @kindex show trace-notes
13321 Show the trace run's notes.
13323 @item set trace-stop-notes @var{text}
13324 @kindex set trace-stop-notes
13325 Set the trace run's stop notes. The handling of the note is as for
13326 @code{tstop} arguments; the set command is convenient way to fix a
13327 stop note that is mistaken or incomplete.
13329 @item show trace-stop-notes
13330 @kindex show trace-stop-notes
13331 Show the trace run's stop notes.
13335 @node Tracepoint Restrictions
13336 @subsection Tracepoint Restrictions
13338 @cindex tracepoint restrictions
13339 There are a number of restrictions on the use of tracepoints. As
13340 described above, tracepoint data gathering occurs on the target
13341 without interaction from @value{GDBN}. Thus the full capabilities of
13342 the debugger are not available during data gathering, and then at data
13343 examination time, you will be limited by only having what was
13344 collected. The following items describe some common problems, but it
13345 is not exhaustive, and you may run into additional difficulties not
13351 Tracepoint expressions are intended to gather objects (lvalues). Thus
13352 the full flexibility of GDB's expression evaluator is not available.
13353 You cannot call functions, cast objects to aggregate types, access
13354 convenience variables or modify values (except by assignment to trace
13355 state variables). Some language features may implicitly call
13356 functions (for instance Objective-C fields with accessors), and therefore
13357 cannot be collected either.
13360 Collection of local variables, either individually or in bulk with
13361 @code{$locals} or @code{$args}, during @code{while-stepping} may
13362 behave erratically. The stepping action may enter a new scope (for
13363 instance by stepping into a function), or the location of the variable
13364 may change (for instance it is loaded into a register). The
13365 tracepoint data recorded uses the location information for the
13366 variables that is correct for the tracepoint location. When the
13367 tracepoint is created, it is not possible, in general, to determine
13368 where the steps of a @code{while-stepping} sequence will advance the
13369 program---particularly if a conditional branch is stepped.
13372 Collection of an incompletely-initialized or partially-destroyed object
13373 may result in something that @value{GDBN} cannot display, or displays
13374 in a misleading way.
13377 When @value{GDBN} displays a pointer to character it automatically
13378 dereferences the pointer to also display characters of the string
13379 being pointed to. However, collecting the pointer during tracing does
13380 not automatically collect the string. You need to explicitly
13381 dereference the pointer and provide size information if you want to
13382 collect not only the pointer, but the memory pointed to. For example,
13383 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13387 It is not possible to collect a complete stack backtrace at a
13388 tracepoint. Instead, you may collect the registers and a few hundred
13389 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13390 (adjust to use the name of the actual stack pointer register on your
13391 target architecture, and the amount of stack you wish to capture).
13392 Then the @code{backtrace} command will show a partial backtrace when
13393 using a trace frame. The number of stack frames that can be examined
13394 depends on the sizes of the frames in the collected stack. Note that
13395 if you ask for a block so large that it goes past the bottom of the
13396 stack, the target agent may report an error trying to read from an
13400 If you do not collect registers at a tracepoint, @value{GDBN} can
13401 infer that the value of @code{$pc} must be the same as the address of
13402 the tracepoint and use that when you are looking at a trace frame
13403 for that tracepoint. However, this cannot work if the tracepoint has
13404 multiple locations (for instance if it was set in a function that was
13405 inlined), or if it has a @code{while-stepping} loop. In those cases
13406 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13411 @node Analyze Collected Data
13412 @section Using the Collected Data
13414 After the tracepoint experiment ends, you use @value{GDBN} commands
13415 for examining the trace data. The basic idea is that each tracepoint
13416 collects a trace @dfn{snapshot} every time it is hit and another
13417 snapshot every time it single-steps. All these snapshots are
13418 consecutively numbered from zero and go into a buffer, and you can
13419 examine them later. The way you examine them is to @dfn{focus} on a
13420 specific trace snapshot. When the remote stub is focused on a trace
13421 snapshot, it will respond to all @value{GDBN} requests for memory and
13422 registers by reading from the buffer which belongs to that snapshot,
13423 rather than from @emph{real} memory or registers of the program being
13424 debugged. This means that @strong{all} @value{GDBN} commands
13425 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13426 behave as if we were currently debugging the program state as it was
13427 when the tracepoint occurred. Any requests for data that are not in
13428 the buffer will fail.
13431 * tfind:: How to select a trace snapshot
13432 * tdump:: How to display all data for a snapshot
13433 * save tracepoints:: How to save tracepoints for a future run
13437 @subsection @code{tfind @var{n}}
13440 @cindex select trace snapshot
13441 @cindex find trace snapshot
13442 The basic command for selecting a trace snapshot from the buffer is
13443 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13444 counting from zero. If no argument @var{n} is given, the next
13445 snapshot is selected.
13447 Here are the various forms of using the @code{tfind} command.
13451 Find the first snapshot in the buffer. This is a synonym for
13452 @code{tfind 0} (since 0 is the number of the first snapshot).
13455 Stop debugging trace snapshots, resume @emph{live} debugging.
13458 Same as @samp{tfind none}.
13461 No argument means find the next trace snapshot or find the first
13462 one if no trace snapshot is selected.
13465 Find the previous trace snapshot before the current one. This permits
13466 retracing earlier steps.
13468 @item tfind tracepoint @var{num}
13469 Find the next snapshot associated with tracepoint @var{num}. Search
13470 proceeds forward from the last examined trace snapshot. If no
13471 argument @var{num} is given, it means find the next snapshot collected
13472 for the same tracepoint as the current snapshot.
13474 @item tfind pc @var{addr}
13475 Find the next snapshot associated with the value @var{addr} of the
13476 program counter. Search proceeds forward from the last examined trace
13477 snapshot. If no argument @var{addr} is given, it means find the next
13478 snapshot with the same value of PC as the current snapshot.
13480 @item tfind outside @var{addr1}, @var{addr2}
13481 Find the next snapshot whose PC is outside the given range of
13482 addresses (exclusive).
13484 @item tfind range @var{addr1}, @var{addr2}
13485 Find the next snapshot whose PC is between @var{addr1} and
13486 @var{addr2} (inclusive).
13488 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13489 Find the next snapshot associated with the source line @var{n}. If
13490 the optional argument @var{file} is given, refer to line @var{n} in
13491 that source file. Search proceeds forward from the last examined
13492 trace snapshot. If no argument @var{n} is given, it means find the
13493 next line other than the one currently being examined; thus saying
13494 @code{tfind line} repeatedly can appear to have the same effect as
13495 stepping from line to line in a @emph{live} debugging session.
13498 The default arguments for the @code{tfind} commands are specifically
13499 designed to make it easy to scan through the trace buffer. For
13500 instance, @code{tfind} with no argument selects the next trace
13501 snapshot, and @code{tfind -} with no argument selects the previous
13502 trace snapshot. So, by giving one @code{tfind} command, and then
13503 simply hitting @key{RET} repeatedly you can examine all the trace
13504 snapshots in order. Or, by saying @code{tfind -} and then hitting
13505 @key{RET} repeatedly you can examine the snapshots in reverse order.
13506 The @code{tfind line} command with no argument selects the snapshot
13507 for the next source line executed. The @code{tfind pc} command with
13508 no argument selects the next snapshot with the same program counter
13509 (PC) as the current frame. The @code{tfind tracepoint} command with
13510 no argument selects the next trace snapshot collected by the same
13511 tracepoint as the current one.
13513 In addition to letting you scan through the trace buffer manually,
13514 these commands make it easy to construct @value{GDBN} scripts that
13515 scan through the trace buffer and print out whatever collected data
13516 you are interested in. Thus, if we want to examine the PC, FP, and SP
13517 registers from each trace frame in the buffer, we can say this:
13520 (@value{GDBP}) @b{tfind start}
13521 (@value{GDBP}) @b{while ($trace_frame != -1)}
13522 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13523 $trace_frame, $pc, $sp, $fp
13527 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13528 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13529 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13530 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13531 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13532 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13533 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13534 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13535 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13536 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13537 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13540 Or, if we want to examine the variable @code{X} at each source line in
13544 (@value{GDBP}) @b{tfind start}
13545 (@value{GDBP}) @b{while ($trace_frame != -1)}
13546 > printf "Frame %d, X == %d\n", $trace_frame, X
13556 @subsection @code{tdump}
13558 @cindex dump all data collected at tracepoint
13559 @cindex tracepoint data, display
13561 This command takes no arguments. It prints all the data collected at
13562 the current trace snapshot.
13565 (@value{GDBP}) @b{trace 444}
13566 (@value{GDBP}) @b{actions}
13567 Enter actions for tracepoint #2, one per line:
13568 > collect $regs, $locals, $args, gdb_long_test
13571 (@value{GDBP}) @b{tstart}
13573 (@value{GDBP}) @b{tfind line 444}
13574 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13576 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13578 (@value{GDBP}) @b{tdump}
13579 Data collected at tracepoint 2, trace frame 1:
13580 d0 0xc4aa0085 -995491707
13584 d4 0x71aea3d 119204413
13587 d7 0x380035 3670069
13588 a0 0x19e24a 1696330
13589 a1 0x3000668 50333288
13591 a3 0x322000 3284992
13592 a4 0x3000698 50333336
13593 a5 0x1ad3cc 1758156
13594 fp 0x30bf3c 0x30bf3c
13595 sp 0x30bf34 0x30bf34
13597 pc 0x20b2c8 0x20b2c8
13601 p = 0x20e5b4 "gdb-test"
13608 gdb_long_test = 17 '\021'
13613 @code{tdump} works by scanning the tracepoint's current collection
13614 actions and printing the value of each expression listed. So
13615 @code{tdump} can fail, if after a run, you change the tracepoint's
13616 actions to mention variables that were not collected during the run.
13618 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13619 uses the collected value of @code{$pc} to distinguish between trace
13620 frames that were collected at the tracepoint hit, and frames that were
13621 collected while stepping. This allows it to correctly choose whether
13622 to display the basic list of collections, or the collections from the
13623 body of the while-stepping loop. However, if @code{$pc} was not collected,
13624 then @code{tdump} will always attempt to dump using the basic collection
13625 list, and may fail if a while-stepping frame does not include all the
13626 same data that is collected at the tracepoint hit.
13627 @c This is getting pretty arcane, example would be good.
13629 @node save tracepoints
13630 @subsection @code{save tracepoints @var{filename}}
13631 @kindex save tracepoints
13632 @kindex save-tracepoints
13633 @cindex save tracepoints for future sessions
13635 This command saves all current tracepoint definitions together with
13636 their actions and passcounts, into a file @file{@var{filename}}
13637 suitable for use in a later debugging session. To read the saved
13638 tracepoint definitions, use the @code{source} command (@pxref{Command
13639 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13640 alias for @w{@code{save tracepoints}}
13642 @node Tracepoint Variables
13643 @section Convenience Variables for Tracepoints
13644 @cindex tracepoint variables
13645 @cindex convenience variables for tracepoints
13648 @vindex $trace_frame
13649 @item (int) $trace_frame
13650 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13651 snapshot is selected.
13653 @vindex $tracepoint
13654 @item (int) $tracepoint
13655 The tracepoint for the current trace snapshot.
13657 @vindex $trace_line
13658 @item (int) $trace_line
13659 The line number for the current trace snapshot.
13661 @vindex $trace_file
13662 @item (char []) $trace_file
13663 The source file for the current trace snapshot.
13665 @vindex $trace_func
13666 @item (char []) $trace_func
13667 The name of the function containing @code{$tracepoint}.
13670 Note: @code{$trace_file} is not suitable for use in @code{printf},
13671 use @code{output} instead.
13673 Here's a simple example of using these convenience variables for
13674 stepping through all the trace snapshots and printing some of their
13675 data. Note that these are not the same as trace state variables,
13676 which are managed by the target.
13679 (@value{GDBP}) @b{tfind start}
13681 (@value{GDBP}) @b{while $trace_frame != -1}
13682 > output $trace_file
13683 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13689 @section Using Trace Files
13690 @cindex trace files
13692 In some situations, the target running a trace experiment may no
13693 longer be available; perhaps it crashed, or the hardware was needed
13694 for a different activity. To handle these cases, you can arrange to
13695 dump the trace data into a file, and later use that file as a source
13696 of trace data, via the @code{target tfile} command.
13701 @item tsave [ -r ] @var{filename}
13702 @itemx tsave [-ctf] @var{dirname}
13703 Save the trace data to @var{filename}. By default, this command
13704 assumes that @var{filename} refers to the host filesystem, so if
13705 necessary @value{GDBN} will copy raw trace data up from the target and
13706 then save it. If the target supports it, you can also supply the
13707 optional argument @code{-r} (``remote'') to direct the target to save
13708 the data directly into @var{filename} in its own filesystem, which may be
13709 more efficient if the trace buffer is very large. (Note, however, that
13710 @code{target tfile} can only read from files accessible to the host.)
13711 By default, this command will save trace frame in tfile format.
13712 You can supply the optional argument @code{-ctf} to save data in CTF
13713 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13714 that can be shared by multiple debugging and tracing tools. Please go to
13715 @indicateurl{http://www.efficios.com/ctf} to get more information.
13717 @kindex target tfile
13721 @item target tfile @var{filename}
13722 @itemx target ctf @var{dirname}
13723 Use the file named @var{filename} or directory named @var{dirname} as
13724 a source of trace data. Commands that examine data work as they do with
13725 a live target, but it is not possible to run any new trace experiments.
13726 @code{tstatus} will report the state of the trace run at the moment
13727 the data was saved, as well as the current trace frame you are examining.
13728 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13732 (@value{GDBP}) target ctf ctf.ctf
13733 (@value{GDBP}) tfind
13734 Found trace frame 0, tracepoint 2
13735 39 ++a; /* set tracepoint 1 here */
13736 (@value{GDBP}) tdump
13737 Data collected at tracepoint 2, trace frame 0:
13741 c = @{"123", "456", "789", "123", "456", "789"@}
13742 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13750 @chapter Debugging Programs That Use Overlays
13753 If your program is too large to fit completely in your target system's
13754 memory, you can sometimes use @dfn{overlays} to work around this
13755 problem. @value{GDBN} provides some support for debugging programs that
13759 * How Overlays Work:: A general explanation of overlays.
13760 * Overlay Commands:: Managing overlays in @value{GDBN}.
13761 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13762 mapped by asking the inferior.
13763 * Overlay Sample Program:: A sample program using overlays.
13766 @node How Overlays Work
13767 @section How Overlays Work
13768 @cindex mapped overlays
13769 @cindex unmapped overlays
13770 @cindex load address, overlay's
13771 @cindex mapped address
13772 @cindex overlay area
13774 Suppose you have a computer whose instruction address space is only 64
13775 kilobytes long, but which has much more memory which can be accessed by
13776 other means: special instructions, segment registers, or memory
13777 management hardware, for example. Suppose further that you want to
13778 adapt a program which is larger than 64 kilobytes to run on this system.
13780 One solution is to identify modules of your program which are relatively
13781 independent, and need not call each other directly; call these modules
13782 @dfn{overlays}. Separate the overlays from the main program, and place
13783 their machine code in the larger memory. Place your main program in
13784 instruction memory, but leave at least enough space there to hold the
13785 largest overlay as well.
13787 Now, to call a function located in an overlay, you must first copy that
13788 overlay's machine code from the large memory into the space set aside
13789 for it in the instruction memory, and then jump to its entry point
13792 @c NB: In the below the mapped area's size is greater or equal to the
13793 @c size of all overlays. This is intentional to remind the developer
13794 @c that overlays don't necessarily need to be the same size.
13798 Data Instruction Larger
13799 Address Space Address Space Address Space
13800 +-----------+ +-----------+ +-----------+
13802 +-----------+ +-----------+ +-----------+<-- overlay 1
13803 | program | | main | .----| overlay 1 | load address
13804 | variables | | program | | +-----------+
13805 | and heap | | | | | |
13806 +-----------+ | | | +-----------+<-- overlay 2
13807 | | +-----------+ | | | load address
13808 +-----------+ | | | .-| overlay 2 |
13810 mapped --->+-----------+ | | +-----------+
13811 address | | | | | |
13812 | overlay | <-' | | |
13813 | area | <---' +-----------+<-- overlay 3
13814 | | <---. | | load address
13815 +-----------+ `--| overlay 3 |
13822 @anchor{A code overlay}A code overlay
13826 The diagram (@pxref{A code overlay}) shows a system with separate data
13827 and instruction address spaces. To map an overlay, the program copies
13828 its code from the larger address space to the instruction address space.
13829 Since the overlays shown here all use the same mapped address, only one
13830 may be mapped at a time. For a system with a single address space for
13831 data and instructions, the diagram would be similar, except that the
13832 program variables and heap would share an address space with the main
13833 program and the overlay area.
13835 An overlay loaded into instruction memory and ready for use is called a
13836 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13837 instruction memory. An overlay not present (or only partially present)
13838 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13839 is its address in the larger memory. The mapped address is also called
13840 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13841 called the @dfn{load memory address}, or @dfn{LMA}.
13843 Unfortunately, overlays are not a completely transparent way to adapt a
13844 program to limited instruction memory. They introduce a new set of
13845 global constraints you must keep in mind as you design your program:
13850 Before calling or returning to a function in an overlay, your program
13851 must make sure that overlay is actually mapped. Otherwise, the call or
13852 return will transfer control to the right address, but in the wrong
13853 overlay, and your program will probably crash.
13856 If the process of mapping an overlay is expensive on your system, you
13857 will need to choose your overlays carefully to minimize their effect on
13858 your program's performance.
13861 The executable file you load onto your system must contain each
13862 overlay's instructions, appearing at the overlay's load address, not its
13863 mapped address. However, each overlay's instructions must be relocated
13864 and its symbols defined as if the overlay were at its mapped address.
13865 You can use GNU linker scripts to specify different load and relocation
13866 addresses for pieces of your program; see @ref{Overlay Description,,,
13867 ld.info, Using ld: the GNU linker}.
13870 The procedure for loading executable files onto your system must be able
13871 to load their contents into the larger address space as well as the
13872 instruction and data spaces.
13876 The overlay system described above is rather simple, and could be
13877 improved in many ways:
13882 If your system has suitable bank switch registers or memory management
13883 hardware, you could use those facilities to make an overlay's load area
13884 contents simply appear at their mapped address in instruction space.
13885 This would probably be faster than copying the overlay to its mapped
13886 area in the usual way.
13889 If your overlays are small enough, you could set aside more than one
13890 overlay area, and have more than one overlay mapped at a time.
13893 You can use overlays to manage data, as well as instructions. In
13894 general, data overlays are even less transparent to your design than
13895 code overlays: whereas code overlays only require care when you call or
13896 return to functions, data overlays require care every time you access
13897 the data. Also, if you change the contents of a data overlay, you
13898 must copy its contents back out to its load address before you can copy a
13899 different data overlay into the same mapped area.
13904 @node Overlay Commands
13905 @section Overlay Commands
13907 To use @value{GDBN}'s overlay support, each overlay in your program must
13908 correspond to a separate section of the executable file. The section's
13909 virtual memory address and load memory address must be the overlay's
13910 mapped and load addresses. Identifying overlays with sections allows
13911 @value{GDBN} to determine the appropriate address of a function or
13912 variable, depending on whether the overlay is mapped or not.
13914 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13915 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13920 Disable @value{GDBN}'s overlay support. When overlay support is
13921 disabled, @value{GDBN} assumes that all functions and variables are
13922 always present at their mapped addresses. By default, @value{GDBN}'s
13923 overlay support is disabled.
13925 @item overlay manual
13926 @cindex manual overlay debugging
13927 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13928 relies on you to tell it which overlays are mapped, and which are not,
13929 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13930 commands described below.
13932 @item overlay map-overlay @var{overlay}
13933 @itemx overlay map @var{overlay}
13934 @cindex map an overlay
13935 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13936 be the name of the object file section containing the overlay. When an
13937 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13938 functions and variables at their mapped addresses. @value{GDBN} assumes
13939 that any other overlays whose mapped ranges overlap that of
13940 @var{overlay} are now unmapped.
13942 @item overlay unmap-overlay @var{overlay}
13943 @itemx overlay unmap @var{overlay}
13944 @cindex unmap an overlay
13945 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13946 must be the name of the object file section containing the overlay.
13947 When an overlay is unmapped, @value{GDBN} assumes it can find the
13948 overlay's functions and variables at their load addresses.
13951 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13952 consults a data structure the overlay manager maintains in the inferior
13953 to see which overlays are mapped. For details, see @ref{Automatic
13954 Overlay Debugging}.
13956 @item overlay load-target
13957 @itemx overlay load
13958 @cindex reloading the overlay table
13959 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13960 re-reads the table @value{GDBN} automatically each time the inferior
13961 stops, so this command should only be necessary if you have changed the
13962 overlay mapping yourself using @value{GDBN}. This command is only
13963 useful when using automatic overlay debugging.
13965 @item overlay list-overlays
13966 @itemx overlay list
13967 @cindex listing mapped overlays
13968 Display a list of the overlays currently mapped, along with their mapped
13969 addresses, load addresses, and sizes.
13973 Normally, when @value{GDBN} prints a code address, it includes the name
13974 of the function the address falls in:
13977 (@value{GDBP}) print main
13978 $3 = @{int ()@} 0x11a0 <main>
13981 When overlay debugging is enabled, @value{GDBN} recognizes code in
13982 unmapped overlays, and prints the names of unmapped functions with
13983 asterisks around them. For example, if @code{foo} is a function in an
13984 unmapped overlay, @value{GDBN} prints it this way:
13987 (@value{GDBP}) overlay list
13988 No sections are mapped.
13989 (@value{GDBP}) print foo
13990 $5 = @{int (int)@} 0x100000 <*foo*>
13993 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13997 (@value{GDBP}) overlay list
13998 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13999 mapped at 0x1016 - 0x104a
14000 (@value{GDBP}) print foo
14001 $6 = @{int (int)@} 0x1016 <foo>
14004 When overlay debugging is enabled, @value{GDBN} can find the correct
14005 address for functions and variables in an overlay, whether or not the
14006 overlay is mapped. This allows most @value{GDBN} commands, like
14007 @code{break} and @code{disassemble}, to work normally, even on unmapped
14008 code. However, @value{GDBN}'s breakpoint support has some limitations:
14012 @cindex breakpoints in overlays
14013 @cindex overlays, setting breakpoints in
14014 You can set breakpoints in functions in unmapped overlays, as long as
14015 @value{GDBN} can write to the overlay at its load address.
14017 @value{GDBN} can not set hardware or simulator-based breakpoints in
14018 unmapped overlays. However, if you set a breakpoint at the end of your
14019 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14020 you are using manual overlay management), @value{GDBN} will re-set its
14021 breakpoints properly.
14025 @node Automatic Overlay Debugging
14026 @section Automatic Overlay Debugging
14027 @cindex automatic overlay debugging
14029 @value{GDBN} can automatically track which overlays are mapped and which
14030 are not, given some simple co-operation from the overlay manager in the
14031 inferior. If you enable automatic overlay debugging with the
14032 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14033 looks in the inferior's memory for certain variables describing the
14034 current state of the overlays.
14036 Here are the variables your overlay manager must define to support
14037 @value{GDBN}'s automatic overlay debugging:
14041 @item @code{_ovly_table}:
14042 This variable must be an array of the following structures:
14047 /* The overlay's mapped address. */
14050 /* The size of the overlay, in bytes. */
14051 unsigned long size;
14053 /* The overlay's load address. */
14056 /* Non-zero if the overlay is currently mapped;
14058 unsigned long mapped;
14062 @item @code{_novlys}:
14063 This variable must be a four-byte signed integer, holding the total
14064 number of elements in @code{_ovly_table}.
14068 To decide whether a particular overlay is mapped or not, @value{GDBN}
14069 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14070 @code{lma} members equal the VMA and LMA of the overlay's section in the
14071 executable file. When @value{GDBN} finds a matching entry, it consults
14072 the entry's @code{mapped} member to determine whether the overlay is
14075 In addition, your overlay manager may define a function called
14076 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14077 will silently set a breakpoint there. If the overlay manager then
14078 calls this function whenever it has changed the overlay table, this
14079 will enable @value{GDBN} to accurately keep track of which overlays
14080 are in program memory, and update any breakpoints that may be set
14081 in overlays. This will allow breakpoints to work even if the
14082 overlays are kept in ROM or other non-writable memory while they
14083 are not being executed.
14085 @node Overlay Sample Program
14086 @section Overlay Sample Program
14087 @cindex overlay example program
14089 When linking a program which uses overlays, you must place the overlays
14090 at their load addresses, while relocating them to run at their mapped
14091 addresses. To do this, you must write a linker script (@pxref{Overlay
14092 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14093 since linker scripts are specific to a particular host system, target
14094 architecture, and target memory layout, this manual cannot provide
14095 portable sample code demonstrating @value{GDBN}'s overlay support.
14097 However, the @value{GDBN} source distribution does contain an overlaid
14098 program, with linker scripts for a few systems, as part of its test
14099 suite. The program consists of the following files from
14100 @file{gdb/testsuite/gdb.base}:
14104 The main program file.
14106 A simple overlay manager, used by @file{overlays.c}.
14111 Overlay modules, loaded and used by @file{overlays.c}.
14114 Linker scripts for linking the test program on the @code{d10v-elf}
14115 and @code{m32r-elf} targets.
14118 You can build the test program using the @code{d10v-elf} GCC
14119 cross-compiler like this:
14122 $ d10v-elf-gcc -g -c overlays.c
14123 $ d10v-elf-gcc -g -c ovlymgr.c
14124 $ d10v-elf-gcc -g -c foo.c
14125 $ d10v-elf-gcc -g -c bar.c
14126 $ d10v-elf-gcc -g -c baz.c
14127 $ d10v-elf-gcc -g -c grbx.c
14128 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14129 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14132 The build process is identical for any other architecture, except that
14133 you must substitute the appropriate compiler and linker script for the
14134 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14138 @chapter Using @value{GDBN} with Different Languages
14141 Although programming languages generally have common aspects, they are
14142 rarely expressed in the same manner. For instance, in ANSI C,
14143 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14144 Modula-2, it is accomplished by @code{p^}. Values can also be
14145 represented (and displayed) differently. Hex numbers in C appear as
14146 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14148 @cindex working language
14149 Language-specific information is built into @value{GDBN} for some languages,
14150 allowing you to express operations like the above in your program's
14151 native language, and allowing @value{GDBN} to output values in a manner
14152 consistent with the syntax of your program's native language. The
14153 language you use to build expressions is called the @dfn{working
14157 * Setting:: Switching between source languages
14158 * Show:: Displaying the language
14159 * Checks:: Type and range checks
14160 * Supported Languages:: Supported languages
14161 * Unsupported Languages:: Unsupported languages
14165 @section Switching Between Source Languages
14167 There are two ways to control the working language---either have @value{GDBN}
14168 set it automatically, or select it manually yourself. You can use the
14169 @code{set language} command for either purpose. On startup, @value{GDBN}
14170 defaults to setting the language automatically. The working language is
14171 used to determine how expressions you type are interpreted, how values
14174 In addition to the working language, every source file that
14175 @value{GDBN} knows about has its own working language. For some object
14176 file formats, the compiler might indicate which language a particular
14177 source file is in. However, most of the time @value{GDBN} infers the
14178 language from the name of the file. The language of a source file
14179 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14180 show each frame appropriately for its own language. There is no way to
14181 set the language of a source file from within @value{GDBN}, but you can
14182 set the language associated with a filename extension. @xref{Show, ,
14183 Displaying the Language}.
14185 This is most commonly a problem when you use a program, such
14186 as @code{cfront} or @code{f2c}, that generates C but is written in
14187 another language. In that case, make the
14188 program use @code{#line} directives in its C output; that way
14189 @value{GDBN} will know the correct language of the source code of the original
14190 program, and will display that source code, not the generated C code.
14193 * Filenames:: Filename extensions and languages.
14194 * Manually:: Setting the working language manually
14195 * Automatically:: Having @value{GDBN} infer the source language
14199 @subsection List of Filename Extensions and Languages
14201 If a source file name ends in one of the following extensions, then
14202 @value{GDBN} infers that its language is the one indicated.
14220 C@t{++} source file
14226 Objective-C source file
14230 Fortran source file
14233 Modula-2 source file
14237 Assembler source file. This actually behaves almost like C, but
14238 @value{GDBN} does not skip over function prologues when stepping.
14241 In addition, you may set the language associated with a filename
14242 extension. @xref{Show, , Displaying the Language}.
14245 @subsection Setting the Working Language
14247 If you allow @value{GDBN} to set the language automatically,
14248 expressions are interpreted the same way in your debugging session and
14251 @kindex set language
14252 If you wish, you may set the language manually. To do this, issue the
14253 command @samp{set language @var{lang}}, where @var{lang} is the name of
14254 a language, such as
14255 @code{c} or @code{modula-2}.
14256 For a list of the supported languages, type @samp{set language}.
14258 Setting the language manually prevents @value{GDBN} from updating the working
14259 language automatically. This can lead to confusion if you try
14260 to debug a program when the working language is not the same as the
14261 source language, when an expression is acceptable to both
14262 languages---but means different things. For instance, if the current
14263 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14271 might not have the effect you intended. In C, this means to add
14272 @code{b} and @code{c} and place the result in @code{a}. The result
14273 printed would be the value of @code{a}. In Modula-2, this means to compare
14274 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14276 @node Automatically
14277 @subsection Having @value{GDBN} Infer the Source Language
14279 To have @value{GDBN} set the working language automatically, use
14280 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14281 then infers the working language. That is, when your program stops in a
14282 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14283 working language to the language recorded for the function in that
14284 frame. If the language for a frame is unknown (that is, if the function
14285 or block corresponding to the frame was defined in a source file that
14286 does not have a recognized extension), the current working language is
14287 not changed, and @value{GDBN} issues a warning.
14289 This may not seem necessary for most programs, which are written
14290 entirely in one source language. However, program modules and libraries
14291 written in one source language can be used by a main program written in
14292 a different source language. Using @samp{set language auto} in this
14293 case frees you from having to set the working language manually.
14296 @section Displaying the Language
14298 The following commands help you find out which language is the
14299 working language, and also what language source files were written in.
14302 @item show language
14303 @anchor{show language}
14304 @kindex show language
14305 Display the current working language. This is the
14306 language you can use with commands such as @code{print} to
14307 build and compute expressions that may involve variables in your program.
14310 @kindex info frame@r{, show the source language}
14311 Display the source language for this frame. This language becomes the
14312 working language if you use an identifier from this frame.
14313 @xref{Frame Info, ,Information about a Frame}, to identify the other
14314 information listed here.
14317 @kindex info source@r{, show the source language}
14318 Display the source language of this source file.
14319 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14320 information listed here.
14323 In unusual circumstances, you may have source files with extensions
14324 not in the standard list. You can then set the extension associated
14325 with a language explicitly:
14328 @item set extension-language @var{ext} @var{language}
14329 @kindex set extension-language
14330 Tell @value{GDBN} that source files with extension @var{ext} are to be
14331 assumed as written in the source language @var{language}.
14333 @item info extensions
14334 @kindex info extensions
14335 List all the filename extensions and the associated languages.
14339 @section Type and Range Checking
14341 Some languages are designed to guard you against making seemingly common
14342 errors through a series of compile- and run-time checks. These include
14343 checking the type of arguments to functions and operators and making
14344 sure mathematical overflows are caught at run time. Checks such as
14345 these help to ensure a program's correctness once it has been compiled
14346 by eliminating type mismatches and providing active checks for range
14347 errors when your program is running.
14349 By default @value{GDBN} checks for these errors according to the
14350 rules of the current source language. Although @value{GDBN} does not check
14351 the statements in your program, it can check expressions entered directly
14352 into @value{GDBN} for evaluation via the @code{print} command, for example.
14355 * Type Checking:: An overview of type checking
14356 * Range Checking:: An overview of range checking
14359 @cindex type checking
14360 @cindex checks, type
14361 @node Type Checking
14362 @subsection An Overview of Type Checking
14364 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14365 arguments to operators and functions have to be of the correct type,
14366 otherwise an error occurs. These checks prevent type mismatch
14367 errors from ever causing any run-time problems. For example,
14370 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14372 (@value{GDBP}) print obj.my_method (0)
14375 (@value{GDBP}) print obj.my_method (0x1234)
14376 Cannot resolve method klass::my_method to any overloaded instance
14379 The second example fails because in C@t{++} the integer constant
14380 @samp{0x1234} is not type-compatible with the pointer parameter type.
14382 For the expressions you use in @value{GDBN} commands, you can tell
14383 @value{GDBN} to not enforce strict type checking or
14384 to treat any mismatches as errors and abandon the expression;
14385 When type checking is disabled, @value{GDBN} successfully evaluates
14386 expressions like the second example above.
14388 Even if type checking is off, there may be other reasons
14389 related to type that prevent @value{GDBN} from evaluating an expression.
14390 For instance, @value{GDBN} does not know how to add an @code{int} and
14391 a @code{struct foo}. These particular type errors have nothing to do
14392 with the language in use and usually arise from expressions which make
14393 little sense to evaluate anyway.
14395 @value{GDBN} provides some additional commands for controlling type checking:
14397 @kindex set check type
14398 @kindex show check type
14400 @item set check type on
14401 @itemx set check type off
14402 Set strict type checking on or off. If any type mismatches occur in
14403 evaluating an expression while type checking is on, @value{GDBN} prints a
14404 message and aborts evaluation of the expression.
14406 @item show check type
14407 Show the current setting of type checking and whether @value{GDBN}
14408 is enforcing strict type checking rules.
14411 @cindex range checking
14412 @cindex checks, range
14413 @node Range Checking
14414 @subsection An Overview of Range Checking
14416 In some languages (such as Modula-2), it is an error to exceed the
14417 bounds of a type; this is enforced with run-time checks. Such range
14418 checking is meant to ensure program correctness by making sure
14419 computations do not overflow, or indices on an array element access do
14420 not exceed the bounds of the array.
14422 For expressions you use in @value{GDBN} commands, you can tell
14423 @value{GDBN} to treat range errors in one of three ways: ignore them,
14424 always treat them as errors and abandon the expression, or issue
14425 warnings but evaluate the expression anyway.
14427 A range error can result from numerical overflow, from exceeding an
14428 array index bound, or when you type a constant that is not a member
14429 of any type. Some languages, however, do not treat overflows as an
14430 error. In many implementations of C, mathematical overflow causes the
14431 result to ``wrap around'' to lower values---for example, if @var{m} is
14432 the largest integer value, and @var{s} is the smallest, then
14435 @var{m} + 1 @result{} @var{s}
14438 This, too, is specific to individual languages, and in some cases
14439 specific to individual compilers or machines. @xref{Supported Languages, ,
14440 Supported Languages}, for further details on specific languages.
14442 @value{GDBN} provides some additional commands for controlling the range checker:
14444 @kindex set check range
14445 @kindex show check range
14447 @item set check range auto
14448 Set range checking on or off based on the current working language.
14449 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14452 @item set check range on
14453 @itemx set check range off
14454 Set range checking on or off, overriding the default setting for the
14455 current working language. A warning is issued if the setting does not
14456 match the language default. If a range error occurs and range checking is on,
14457 then a message is printed and evaluation of the expression is aborted.
14459 @item set check range warn
14460 Output messages when the @value{GDBN} range checker detects a range error,
14461 but attempt to evaluate the expression anyway. Evaluating the
14462 expression may still be impossible for other reasons, such as accessing
14463 memory that the process does not own (a typical example from many Unix
14467 Show the current setting of the range checker, and whether or not it is
14468 being set automatically by @value{GDBN}.
14471 @node Supported Languages
14472 @section Supported Languages
14474 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14475 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14476 @c This is false ...
14477 Some @value{GDBN} features may be used in expressions regardless of the
14478 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14479 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14480 ,Expressions}) can be used with the constructs of any supported
14483 The following sections detail to what degree each source language is
14484 supported by @value{GDBN}. These sections are not meant to be language
14485 tutorials or references, but serve only as a reference guide to what the
14486 @value{GDBN} expression parser accepts, and what input and output
14487 formats should look like for different languages. There are many good
14488 books written on each of these languages; please look to these for a
14489 language reference or tutorial.
14492 * C:: C and C@t{++}
14495 * Objective-C:: Objective-C
14496 * OpenCL C:: OpenCL C
14497 * Fortran:: Fortran
14500 * Modula-2:: Modula-2
14505 @subsection C and C@t{++}
14507 @cindex C and C@t{++}
14508 @cindex expressions in C or C@t{++}
14510 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14511 to both languages. Whenever this is the case, we discuss those languages
14515 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14516 @cindex @sc{gnu} C@t{++}
14517 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14518 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14519 effectively, you must compile your C@t{++} programs with a supported
14520 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14521 compiler (@code{aCC}).
14524 * C Operators:: C and C@t{++} operators
14525 * C Constants:: C and C@t{++} constants
14526 * C Plus Plus Expressions:: C@t{++} expressions
14527 * C Defaults:: Default settings for C and C@t{++}
14528 * C Checks:: C and C@t{++} type and range checks
14529 * Debugging C:: @value{GDBN} and C
14530 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14531 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14535 @subsubsection C and C@t{++} Operators
14537 @cindex C and C@t{++} operators
14539 Operators must be defined on values of specific types. For instance,
14540 @code{+} is defined on numbers, but not on structures. Operators are
14541 often defined on groups of types.
14543 For the purposes of C and C@t{++}, the following definitions hold:
14548 @emph{Integral types} include @code{int} with any of its storage-class
14549 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14552 @emph{Floating-point types} include @code{float}, @code{double}, and
14553 @code{long double} (if supported by the target platform).
14556 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14559 @emph{Scalar types} include all of the above.
14564 The following operators are supported. They are listed here
14565 in order of increasing precedence:
14569 The comma or sequencing operator. Expressions in a comma-separated list
14570 are evaluated from left to right, with the result of the entire
14571 expression being the last expression evaluated.
14574 Assignment. The value of an assignment expression is the value
14575 assigned. Defined on scalar types.
14578 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14579 and translated to @w{@code{@var{a} = @var{a op b}}}.
14580 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14581 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14582 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14585 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14586 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14587 should be of an integral type.
14590 Logical @sc{or}. Defined on integral types.
14593 Logical @sc{and}. Defined on integral types.
14596 Bitwise @sc{or}. Defined on integral types.
14599 Bitwise exclusive-@sc{or}. Defined on integral types.
14602 Bitwise @sc{and}. Defined on integral types.
14605 Equality and inequality. Defined on scalar types. The value of these
14606 expressions is 0 for false and non-zero for true.
14608 @item <@r{, }>@r{, }<=@r{, }>=
14609 Less than, greater than, less than or equal, greater than or equal.
14610 Defined on scalar types. The value of these expressions is 0 for false
14611 and non-zero for true.
14614 left shift, and right shift. Defined on integral types.
14617 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14620 Addition and subtraction. Defined on integral types, floating-point types and
14623 @item *@r{, }/@r{, }%
14624 Multiplication, division, and modulus. Multiplication and division are
14625 defined on integral and floating-point types. Modulus is defined on
14629 Increment and decrement. When appearing before a variable, the
14630 operation is performed before the variable is used in an expression;
14631 when appearing after it, the variable's value is used before the
14632 operation takes place.
14635 Pointer dereferencing. Defined on pointer types. Same precedence as
14639 Address operator. Defined on variables. Same precedence as @code{++}.
14641 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14642 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14643 to examine the address
14644 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14648 Negative. Defined on integral and floating-point types. Same
14649 precedence as @code{++}.
14652 Logical negation. Defined on integral types. Same precedence as
14656 Bitwise complement operator. Defined on integral types. Same precedence as
14661 Structure member, and pointer-to-structure member. For convenience,
14662 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14663 pointer based on the stored type information.
14664 Defined on @code{struct} and @code{union} data.
14667 Dereferences of pointers to members.
14670 Array indexing. @code{@var{a}[@var{i}]} is defined as
14671 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14674 Function parameter list. Same precedence as @code{->}.
14677 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14678 and @code{class} types.
14681 Doubled colons also represent the @value{GDBN} scope operator
14682 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14686 If an operator is redefined in the user code, @value{GDBN} usually
14687 attempts to invoke the redefined version instead of using the operator's
14688 predefined meaning.
14691 @subsubsection C and C@t{++} Constants
14693 @cindex C and C@t{++} constants
14695 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14700 Integer constants are a sequence of digits. Octal constants are
14701 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14702 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14703 @samp{l}, specifying that the constant should be treated as a
14707 Floating point constants are a sequence of digits, followed by a decimal
14708 point, followed by a sequence of digits, and optionally followed by an
14709 exponent. An exponent is of the form:
14710 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14711 sequence of digits. The @samp{+} is optional for positive exponents.
14712 A floating-point constant may also end with a letter @samp{f} or
14713 @samp{F}, specifying that the constant should be treated as being of
14714 the @code{float} (as opposed to the default @code{double}) type; or with
14715 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14719 Enumerated constants consist of enumerated identifiers, or their
14720 integral equivalents.
14723 Character constants are a single character surrounded by single quotes
14724 (@code{'}), or a number---the ordinal value of the corresponding character
14725 (usually its @sc{ascii} value). Within quotes, the single character may
14726 be represented by a letter or by @dfn{escape sequences}, which are of
14727 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14728 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14729 @samp{@var{x}} is a predefined special character---for example,
14730 @samp{\n} for newline.
14732 Wide character constants can be written by prefixing a character
14733 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14734 form of @samp{x}. The target wide character set is used when
14735 computing the value of this constant (@pxref{Character Sets}).
14738 String constants are a sequence of character constants surrounded by
14739 double quotes (@code{"}). Any valid character constant (as described
14740 above) may appear. Double quotes within the string must be preceded by
14741 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14744 Wide string constants can be written by prefixing a string constant
14745 with @samp{L}, as in C. The target wide character set is used when
14746 computing the value of this constant (@pxref{Character Sets}).
14749 Pointer constants are an integral value. You can also write pointers
14750 to constants using the C operator @samp{&}.
14753 Array constants are comma-separated lists surrounded by braces @samp{@{}
14754 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14755 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14756 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14759 @node C Plus Plus Expressions
14760 @subsubsection C@t{++} Expressions
14762 @cindex expressions in C@t{++}
14763 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14765 @cindex debugging C@t{++} programs
14766 @cindex C@t{++} compilers
14767 @cindex debug formats and C@t{++}
14768 @cindex @value{NGCC} and C@t{++}
14770 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14771 the proper compiler and the proper debug format. Currently,
14772 @value{GDBN} works best when debugging C@t{++} code that is compiled
14773 with the most recent version of @value{NGCC} possible. The DWARF
14774 debugging format is preferred; @value{NGCC} defaults to this on most
14775 popular platforms. Other compilers and/or debug formats are likely to
14776 work badly or not at all when using @value{GDBN} to debug C@t{++}
14777 code. @xref{Compilation}.
14782 @cindex member functions
14784 Member function calls are allowed; you can use expressions like
14787 count = aml->GetOriginal(x, y)
14790 @vindex this@r{, inside C@t{++} member functions}
14791 @cindex namespace in C@t{++}
14793 While a member function is active (in the selected stack frame), your
14794 expressions have the same namespace available as the member function;
14795 that is, @value{GDBN} allows implicit references to the class instance
14796 pointer @code{this} following the same rules as C@t{++}. @code{using}
14797 declarations in the current scope are also respected by @value{GDBN}.
14799 @cindex call overloaded functions
14800 @cindex overloaded functions, calling
14801 @cindex type conversions in C@t{++}
14803 You can call overloaded functions; @value{GDBN} resolves the function
14804 call to the right definition, with some restrictions. @value{GDBN} does not
14805 perform overload resolution involving user-defined type conversions,
14806 calls to constructors, or instantiations of templates that do not exist
14807 in the program. It also cannot handle ellipsis argument lists or
14810 It does perform integral conversions and promotions, floating-point
14811 promotions, arithmetic conversions, pointer conversions, conversions of
14812 class objects to base classes, and standard conversions such as those of
14813 functions or arrays to pointers; it requires an exact match on the
14814 number of function arguments.
14816 Overload resolution is always performed, unless you have specified
14817 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14818 ,@value{GDBN} Features for C@t{++}}.
14820 You must specify @code{set overload-resolution off} in order to use an
14821 explicit function signature to call an overloaded function, as in
14823 p 'foo(char,int)'('x', 13)
14826 The @value{GDBN} command-completion facility can simplify this;
14827 see @ref{Completion, ,Command Completion}.
14829 @cindex reference declarations
14831 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14832 references; you can use them in expressions just as you do in C@t{++}
14833 source---they are automatically dereferenced.
14835 In the parameter list shown when @value{GDBN} displays a frame, the values of
14836 reference variables are not displayed (unlike other variables); this
14837 avoids clutter, since references are often used for large structures.
14838 The @emph{address} of a reference variable is always shown, unless
14839 you have specified @samp{set print address off}.
14842 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14843 expressions can use it just as expressions in your program do. Since
14844 one scope may be defined in another, you can use @code{::} repeatedly if
14845 necessary, for example in an expression like
14846 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14847 resolving name scope by reference to source files, in both C and C@t{++}
14848 debugging (@pxref{Variables, ,Program Variables}).
14851 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14856 @subsubsection C and C@t{++} Defaults
14858 @cindex C and C@t{++} defaults
14860 If you allow @value{GDBN} to set range checking automatically, it
14861 defaults to @code{off} whenever the working language changes to
14862 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14863 selects the working language.
14865 If you allow @value{GDBN} to set the language automatically, it
14866 recognizes source files whose names end with @file{.c}, @file{.C}, or
14867 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14868 these files, it sets the working language to C or C@t{++}.
14869 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14870 for further details.
14873 @subsubsection C and C@t{++} Type and Range Checks
14875 @cindex C and C@t{++} checks
14877 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14878 checking is used. However, if you turn type checking off, @value{GDBN}
14879 will allow certain non-standard conversions, such as promoting integer
14880 constants to pointers.
14882 Range checking, if turned on, is done on mathematical operations. Array
14883 indices are not checked, since they are often used to index a pointer
14884 that is not itself an array.
14887 @subsubsection @value{GDBN} and C
14889 The @code{set print union} and @code{show print union} commands apply to
14890 the @code{union} type. When set to @samp{on}, any @code{union} that is
14891 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14892 appears as @samp{@{...@}}.
14894 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14895 with pointers and a memory allocation function. @xref{Expressions,
14898 @node Debugging C Plus Plus
14899 @subsubsection @value{GDBN} Features for C@t{++}
14901 @cindex commands for C@t{++}
14903 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14904 designed specifically for use with C@t{++}. Here is a summary:
14907 @cindex break in overloaded functions
14908 @item @r{breakpoint menus}
14909 When you want a breakpoint in a function whose name is overloaded,
14910 @value{GDBN} has the capability to display a menu of possible breakpoint
14911 locations to help you specify which function definition you want.
14912 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14914 @cindex overloading in C@t{++}
14915 @item rbreak @var{regex}
14916 Setting breakpoints using regular expressions is helpful for setting
14917 breakpoints on overloaded functions that are not members of any special
14919 @xref{Set Breaks, ,Setting Breakpoints}.
14921 @cindex C@t{++} exception handling
14923 @itemx catch rethrow
14925 Debug C@t{++} exception handling using these commands. @xref{Set
14926 Catchpoints, , Setting Catchpoints}.
14928 @cindex inheritance
14929 @item ptype @var{typename}
14930 Print inheritance relationships as well as other information for type
14932 @xref{Symbols, ,Examining the Symbol Table}.
14934 @item info vtbl @var{expression}.
14935 The @code{info vtbl} command can be used to display the virtual
14936 method tables of the object computed by @var{expression}. This shows
14937 one entry per virtual table; there may be multiple virtual tables when
14938 multiple inheritance is in use.
14940 @cindex C@t{++} demangling
14941 @item demangle @var{name}
14942 Demangle @var{name}.
14943 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14945 @cindex C@t{++} symbol display
14946 @item set print demangle
14947 @itemx show print demangle
14948 @itemx set print asm-demangle
14949 @itemx show print asm-demangle
14950 Control whether C@t{++} symbols display in their source form, both when
14951 displaying code as C@t{++} source and when displaying disassemblies.
14952 @xref{Print Settings, ,Print Settings}.
14954 @item set print object
14955 @itemx show print object
14956 Choose whether to print derived (actual) or declared types of objects.
14957 @xref{Print Settings, ,Print Settings}.
14959 @item set print vtbl
14960 @itemx show print vtbl
14961 Control the format for printing virtual function tables.
14962 @xref{Print Settings, ,Print Settings}.
14963 (The @code{vtbl} commands do not work on programs compiled with the HP
14964 ANSI C@t{++} compiler (@code{aCC}).)
14966 @kindex set overload-resolution
14967 @cindex overloaded functions, overload resolution
14968 @item set overload-resolution on
14969 Enable overload resolution for C@t{++} expression evaluation. The default
14970 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14971 and searches for a function whose signature matches the argument types,
14972 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14973 Expressions, ,C@t{++} Expressions}, for details).
14974 If it cannot find a match, it emits a message.
14976 @item set overload-resolution off
14977 Disable overload resolution for C@t{++} expression evaluation. For
14978 overloaded functions that are not class member functions, @value{GDBN}
14979 chooses the first function of the specified name that it finds in the
14980 symbol table, whether or not its arguments are of the correct type. For
14981 overloaded functions that are class member functions, @value{GDBN}
14982 searches for a function whose signature @emph{exactly} matches the
14985 @kindex show overload-resolution
14986 @item show overload-resolution
14987 Show the current setting of overload resolution.
14989 @item @r{Overloaded symbol names}
14990 You can specify a particular definition of an overloaded symbol, using
14991 the same notation that is used to declare such symbols in C@t{++}: type
14992 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14993 also use the @value{GDBN} command-line word completion facilities to list the
14994 available choices, or to finish the type list for you.
14995 @xref{Completion,, Command Completion}, for details on how to do this.
14998 @node Decimal Floating Point
14999 @subsubsection Decimal Floating Point format
15000 @cindex decimal floating point format
15002 @value{GDBN} can examine, set and perform computations with numbers in
15003 decimal floating point format, which in the C language correspond to the
15004 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15005 specified by the extension to support decimal floating-point arithmetic.
15007 There are two encodings in use, depending on the architecture: BID (Binary
15008 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15009 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15012 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15013 to manipulate decimal floating point numbers, it is not possible to convert
15014 (using a cast, for example) integers wider than 32-bit to decimal float.
15016 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15017 point computations, error checking in decimal float operations ignores
15018 underflow, overflow and divide by zero exceptions.
15020 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15021 to inspect @code{_Decimal128} values stored in floating point registers.
15022 See @ref{PowerPC,,PowerPC} for more details.
15028 @value{GDBN} can be used to debug programs written in D and compiled with
15029 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15030 specific feature --- dynamic arrays.
15035 @cindex Go (programming language)
15036 @value{GDBN} can be used to debug programs written in Go and compiled with
15037 @file{gccgo} or @file{6g} compilers.
15039 Here is a summary of the Go-specific features and restrictions:
15042 @cindex current Go package
15043 @item The current Go package
15044 The name of the current package does not need to be specified when
15045 specifying global variables and functions.
15047 For example, given the program:
15051 var myglob = "Shall we?"
15057 When stopped inside @code{main} either of these work:
15061 (gdb) p main.myglob
15064 @cindex builtin Go types
15065 @item Builtin Go types
15066 The @code{string} type is recognized by @value{GDBN} and is printed
15069 @cindex builtin Go functions
15070 @item Builtin Go functions
15071 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15072 function and handles it internally.
15074 @cindex restrictions on Go expressions
15075 @item Restrictions on Go expressions
15076 All Go operators are supported except @code{&^}.
15077 The Go @code{_} ``blank identifier'' is not supported.
15078 Automatic dereferencing of pointers is not supported.
15082 @subsection Objective-C
15084 @cindex Objective-C
15085 This section provides information about some commands and command
15086 options that are useful for debugging Objective-C code. See also
15087 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15088 few more commands specific to Objective-C support.
15091 * Method Names in Commands::
15092 * The Print Command with Objective-C::
15095 @node Method Names in Commands
15096 @subsubsection Method Names in Commands
15098 The following commands have been extended to accept Objective-C method
15099 names as line specifications:
15101 @kindex clear@r{, and Objective-C}
15102 @kindex break@r{, and Objective-C}
15103 @kindex info line@r{, and Objective-C}
15104 @kindex jump@r{, and Objective-C}
15105 @kindex list@r{, and Objective-C}
15109 @item @code{info line}
15114 A fully qualified Objective-C method name is specified as
15117 -[@var{Class} @var{methodName}]
15120 where the minus sign is used to indicate an instance method and a
15121 plus sign (not shown) is used to indicate a class method. The class
15122 name @var{Class} and method name @var{methodName} are enclosed in
15123 brackets, similar to the way messages are specified in Objective-C
15124 source code. For example, to set a breakpoint at the @code{create}
15125 instance method of class @code{Fruit} in the program currently being
15129 break -[Fruit create]
15132 To list ten program lines around the @code{initialize} class method,
15136 list +[NSText initialize]
15139 In the current version of @value{GDBN}, the plus or minus sign is
15140 required. In future versions of @value{GDBN}, the plus or minus
15141 sign will be optional, but you can use it to narrow the search. It
15142 is also possible to specify just a method name:
15148 You must specify the complete method name, including any colons. If
15149 your program's source files contain more than one @code{create} method,
15150 you'll be presented with a numbered list of classes that implement that
15151 method. Indicate your choice by number, or type @samp{0} to exit if
15154 As another example, to clear a breakpoint established at the
15155 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15158 clear -[NSWindow makeKeyAndOrderFront:]
15161 @node The Print Command with Objective-C
15162 @subsubsection The Print Command With Objective-C
15163 @cindex Objective-C, print objects
15164 @kindex print-object
15165 @kindex po @r{(@code{print-object})}
15167 The print command has also been extended to accept methods. For example:
15170 print -[@var{object} hash]
15173 @cindex print an Objective-C object description
15174 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15176 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15177 and print the result. Also, an additional command has been added,
15178 @code{print-object} or @code{po} for short, which is meant to print
15179 the description of an object. However, this command may only work
15180 with certain Objective-C libraries that have a particular hook
15181 function, @code{_NSPrintForDebugger}, defined.
15184 @subsection OpenCL C
15187 This section provides information about @value{GDBN}s OpenCL C support.
15190 * OpenCL C Datatypes::
15191 * OpenCL C Expressions::
15192 * OpenCL C Operators::
15195 @node OpenCL C Datatypes
15196 @subsubsection OpenCL C Datatypes
15198 @cindex OpenCL C Datatypes
15199 @value{GDBN} supports the builtin scalar and vector datatypes specified
15200 by OpenCL 1.1. In addition the half- and double-precision floating point
15201 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15202 extensions are also known to @value{GDBN}.
15204 @node OpenCL C Expressions
15205 @subsubsection OpenCL C Expressions
15207 @cindex OpenCL C Expressions
15208 @value{GDBN} supports accesses to vector components including the access as
15209 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15210 supported by @value{GDBN} can be used as well.
15212 @node OpenCL C Operators
15213 @subsubsection OpenCL C Operators
15215 @cindex OpenCL C Operators
15216 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15220 @subsection Fortran
15221 @cindex Fortran-specific support in @value{GDBN}
15223 @value{GDBN} can be used to debug programs written in Fortran, but it
15224 currently supports only the features of Fortran 77 language.
15226 @cindex trailing underscore, in Fortran symbols
15227 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15228 among them) append an underscore to the names of variables and
15229 functions. When you debug programs compiled by those compilers, you
15230 will need to refer to variables and functions with a trailing
15234 * Fortran Operators:: Fortran operators and expressions
15235 * Fortran Defaults:: Default settings for Fortran
15236 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15239 @node Fortran Operators
15240 @subsubsection Fortran Operators and Expressions
15242 @cindex Fortran operators and expressions
15244 Operators must be defined on values of specific types. For instance,
15245 @code{+} is defined on numbers, but not on characters or other non-
15246 arithmetic types. Operators are often defined on groups of types.
15250 The exponentiation operator. It raises the first operand to the power
15254 The range operator. Normally used in the form of array(low:high) to
15255 represent a section of array.
15258 The access component operator. Normally used to access elements in derived
15259 types. Also suitable for unions. As unions aren't part of regular Fortran,
15260 this can only happen when accessing a register that uses a gdbarch-defined
15264 @node Fortran Defaults
15265 @subsubsection Fortran Defaults
15267 @cindex Fortran Defaults
15269 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15270 default uses case-insensitive matches for Fortran symbols. You can
15271 change that with the @samp{set case-insensitive} command, see
15272 @ref{Symbols}, for the details.
15274 @node Special Fortran Commands
15275 @subsubsection Special Fortran Commands
15277 @cindex Special Fortran commands
15279 @value{GDBN} has some commands to support Fortran-specific features,
15280 such as displaying common blocks.
15283 @cindex @code{COMMON} blocks, Fortran
15284 @kindex info common
15285 @item info common @r{[}@var{common-name}@r{]}
15286 This command prints the values contained in the Fortran @code{COMMON}
15287 block whose name is @var{common-name}. With no argument, the names of
15288 all @code{COMMON} blocks visible at the current program location are
15295 @cindex Pascal support in @value{GDBN}, limitations
15296 Debugging Pascal programs which use sets, subranges, file variables, or
15297 nested functions does not currently work. @value{GDBN} does not support
15298 entering expressions, printing values, or similar features using Pascal
15301 The Pascal-specific command @code{set print pascal_static-members}
15302 controls whether static members of Pascal objects are displayed.
15303 @xref{Print Settings, pascal_static-members}.
15308 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15309 Programming Language}. Type- and value-printing, and expression
15310 parsing, are reasonably complete. However, there are a few
15311 peculiarities and holes to be aware of.
15315 Linespecs (@pxref{Specify Location}) are never relative to the current
15316 crate. Instead, they act as if there were a global namespace of
15317 crates, somewhat similar to the way @code{extern crate} behaves.
15319 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15320 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15321 to set a breakpoint in a function named @samp{f} in a crate named
15324 As a consequence of this approach, linespecs also cannot refer to
15325 items using @samp{self::} or @samp{super::}.
15328 Because @value{GDBN} implements Rust name-lookup semantics in
15329 expressions, it will sometimes prepend the current crate to a name.
15330 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15331 @samp{K}, then @code{print ::x::y} will try to find the symbol
15334 However, since it is useful to be able to refer to other crates when
15335 debugging, @value{GDBN} provides the @code{extern} extension to
15336 circumvent this. To use the extension, just put @code{extern} before
15337 a path expression to refer to the otherwise unavailable ``global''
15340 In the above example, if you wanted to refer to the symbol @samp{y} in
15341 the crate @samp{x}, you would use @code{print extern x::y}.
15344 The Rust expression evaluator does not support ``statement-like''
15345 expressions such as @code{if} or @code{match}, or lambda expressions.
15348 Tuple expressions are not implemented.
15351 The Rust expression evaluator does not currently implement the
15352 @code{Drop} trait. Objects that may be created by the evaluator will
15353 never be destroyed.
15356 @value{GDBN} does not implement type inference for generics. In order
15357 to call generic functions or otherwise refer to generic items, you
15358 will have to specify the type parameters manually.
15361 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15362 cases this does not cause any problems. However, in an expression
15363 context, completing a generic function name will give syntactically
15364 invalid results. This happens because Rust requires the @samp{::}
15365 operator between the function name and its generic arguments. For
15366 example, @value{GDBN} might provide a completion like
15367 @code{crate::f<u32>}, where the parser would require
15368 @code{crate::f::<u32>}.
15371 As of this writing, the Rust compiler (version 1.8) has a few holes in
15372 the debugging information it generates. These holes prevent certain
15373 features from being implemented by @value{GDBN}:
15377 Method calls cannot be made via traits.
15380 Trait objects cannot be created or inspected.
15383 Operator overloading is not implemented.
15386 When debugging in a monomorphized function, you cannot use the generic
15390 The type @code{Self} is not available.
15393 @code{use} statements are not available, so some names may not be
15394 available in the crate.
15399 @subsection Modula-2
15401 @cindex Modula-2, @value{GDBN} support
15403 The extensions made to @value{GDBN} to support Modula-2 only support
15404 output from the @sc{gnu} Modula-2 compiler (which is currently being
15405 developed). Other Modula-2 compilers are not currently supported, and
15406 attempting to debug executables produced by them is most likely
15407 to give an error as @value{GDBN} reads in the executable's symbol
15410 @cindex expressions in Modula-2
15412 * M2 Operators:: Built-in operators
15413 * Built-In Func/Proc:: Built-in functions and procedures
15414 * M2 Constants:: Modula-2 constants
15415 * M2 Types:: Modula-2 types
15416 * M2 Defaults:: Default settings for Modula-2
15417 * Deviations:: Deviations from standard Modula-2
15418 * M2 Checks:: Modula-2 type and range checks
15419 * M2 Scope:: The scope operators @code{::} and @code{.}
15420 * GDB/M2:: @value{GDBN} and Modula-2
15424 @subsubsection Operators
15425 @cindex Modula-2 operators
15427 Operators must be defined on values of specific types. For instance,
15428 @code{+} is defined on numbers, but not on structures. Operators are
15429 often defined on groups of types. For the purposes of Modula-2, the
15430 following definitions hold:
15435 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15439 @emph{Character types} consist of @code{CHAR} and its subranges.
15442 @emph{Floating-point types} consist of @code{REAL}.
15445 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15449 @emph{Scalar types} consist of all of the above.
15452 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15455 @emph{Boolean types} consist of @code{BOOLEAN}.
15459 The following operators are supported, and appear in order of
15460 increasing precedence:
15464 Function argument or array index separator.
15467 Assignment. The value of @var{var} @code{:=} @var{value} is
15471 Less than, greater than on integral, floating-point, or enumerated
15475 Less than or equal to, greater than or equal to
15476 on integral, floating-point and enumerated types, or set inclusion on
15477 set types. Same precedence as @code{<}.
15479 @item =@r{, }<>@r{, }#
15480 Equality and two ways of expressing inequality, valid on scalar types.
15481 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15482 available for inequality, since @code{#} conflicts with the script
15486 Set membership. Defined on set types and the types of their members.
15487 Same precedence as @code{<}.
15490 Boolean disjunction. Defined on boolean types.
15493 Boolean conjunction. Defined on boolean types.
15496 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15499 Addition and subtraction on integral and floating-point types, or union
15500 and difference on set types.
15503 Multiplication on integral and floating-point types, or set intersection
15507 Division on floating-point types, or symmetric set difference on set
15508 types. Same precedence as @code{*}.
15511 Integer division and remainder. Defined on integral types. Same
15512 precedence as @code{*}.
15515 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15518 Pointer dereferencing. Defined on pointer types.
15521 Boolean negation. Defined on boolean types. Same precedence as
15525 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15526 precedence as @code{^}.
15529 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15532 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15536 @value{GDBN} and Modula-2 scope operators.
15540 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15541 treats the use of the operator @code{IN}, or the use of operators
15542 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15543 @code{<=}, and @code{>=} on sets as an error.
15547 @node Built-In Func/Proc
15548 @subsubsection Built-in Functions and Procedures
15549 @cindex Modula-2 built-ins
15551 Modula-2 also makes available several built-in procedures and functions.
15552 In describing these, the following metavariables are used:
15557 represents an @code{ARRAY} variable.
15560 represents a @code{CHAR} constant or variable.
15563 represents a variable or constant of integral type.
15566 represents an identifier that belongs to a set. Generally used in the
15567 same function with the metavariable @var{s}. The type of @var{s} should
15568 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15571 represents a variable or constant of integral or floating-point type.
15574 represents a variable or constant of floating-point type.
15580 represents a variable.
15583 represents a variable or constant of one of many types. See the
15584 explanation of the function for details.
15587 All Modula-2 built-in procedures also return a result, described below.
15591 Returns the absolute value of @var{n}.
15594 If @var{c} is a lower case letter, it returns its upper case
15595 equivalent, otherwise it returns its argument.
15598 Returns the character whose ordinal value is @var{i}.
15601 Decrements the value in the variable @var{v} by one. Returns the new value.
15603 @item DEC(@var{v},@var{i})
15604 Decrements the value in the variable @var{v} by @var{i}. Returns the
15607 @item EXCL(@var{m},@var{s})
15608 Removes the element @var{m} from the set @var{s}. Returns the new
15611 @item FLOAT(@var{i})
15612 Returns the floating point equivalent of the integer @var{i}.
15614 @item HIGH(@var{a})
15615 Returns the index of the last member of @var{a}.
15618 Increments the value in the variable @var{v} by one. Returns the new value.
15620 @item INC(@var{v},@var{i})
15621 Increments the value in the variable @var{v} by @var{i}. Returns the
15624 @item INCL(@var{m},@var{s})
15625 Adds the element @var{m} to the set @var{s} if it is not already
15626 there. Returns the new set.
15629 Returns the maximum value of the type @var{t}.
15632 Returns the minimum value of the type @var{t}.
15635 Returns boolean TRUE if @var{i} is an odd number.
15638 Returns the ordinal value of its argument. For example, the ordinal
15639 value of a character is its @sc{ascii} value (on machines supporting
15640 the @sc{ascii} character set). The argument @var{x} must be of an
15641 ordered type, which include integral, character and enumerated types.
15643 @item SIZE(@var{x})
15644 Returns the size of its argument. The argument @var{x} can be a
15645 variable or a type.
15647 @item TRUNC(@var{r})
15648 Returns the integral part of @var{r}.
15650 @item TSIZE(@var{x})
15651 Returns the size of its argument. The argument @var{x} can be a
15652 variable or a type.
15654 @item VAL(@var{t},@var{i})
15655 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15659 @emph{Warning:} Sets and their operations are not yet supported, so
15660 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15664 @cindex Modula-2 constants
15666 @subsubsection Constants
15668 @value{GDBN} allows you to express the constants of Modula-2 in the following
15674 Integer constants are simply a sequence of digits. When used in an
15675 expression, a constant is interpreted to be type-compatible with the
15676 rest of the expression. Hexadecimal integers are specified by a
15677 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15680 Floating point constants appear as a sequence of digits, followed by a
15681 decimal point and another sequence of digits. An optional exponent can
15682 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15683 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15684 digits of the floating point constant must be valid decimal (base 10)
15688 Character constants consist of a single character enclosed by a pair of
15689 like quotes, either single (@code{'}) or double (@code{"}). They may
15690 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15691 followed by a @samp{C}.
15694 String constants consist of a sequence of characters enclosed by a
15695 pair of like quotes, either single (@code{'}) or double (@code{"}).
15696 Escape sequences in the style of C are also allowed. @xref{C
15697 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15701 Enumerated constants consist of an enumerated identifier.
15704 Boolean constants consist of the identifiers @code{TRUE} and
15708 Pointer constants consist of integral values only.
15711 Set constants are not yet supported.
15715 @subsubsection Modula-2 Types
15716 @cindex Modula-2 types
15718 Currently @value{GDBN} can print the following data types in Modula-2
15719 syntax: array types, record types, set types, pointer types, procedure
15720 types, enumerated types, subrange types and base types. You can also
15721 print the contents of variables declared using these type.
15722 This section gives a number of simple source code examples together with
15723 sample @value{GDBN} sessions.
15725 The first example contains the following section of code:
15734 and you can request @value{GDBN} to interrogate the type and value of
15735 @code{r} and @code{s}.
15738 (@value{GDBP}) print s
15740 (@value{GDBP}) ptype s
15742 (@value{GDBP}) print r
15744 (@value{GDBP}) ptype r
15749 Likewise if your source code declares @code{s} as:
15753 s: SET ['A'..'Z'] ;
15757 then you may query the type of @code{s} by:
15760 (@value{GDBP}) ptype s
15761 type = SET ['A'..'Z']
15765 Note that at present you cannot interactively manipulate set
15766 expressions using the debugger.
15768 The following example shows how you might declare an array in Modula-2
15769 and how you can interact with @value{GDBN} to print its type and contents:
15773 s: ARRAY [-10..10] OF CHAR ;
15777 (@value{GDBP}) ptype s
15778 ARRAY [-10..10] OF CHAR
15781 Note that the array handling is not yet complete and although the type
15782 is printed correctly, expression handling still assumes that all
15783 arrays have a lower bound of zero and not @code{-10} as in the example
15786 Here are some more type related Modula-2 examples:
15790 colour = (blue, red, yellow, green) ;
15791 t = [blue..yellow] ;
15799 The @value{GDBN} interaction shows how you can query the data type
15800 and value of a variable.
15803 (@value{GDBP}) print s
15805 (@value{GDBP}) ptype t
15806 type = [blue..yellow]
15810 In this example a Modula-2 array is declared and its contents
15811 displayed. Observe that the contents are written in the same way as
15812 their @code{C} counterparts.
15816 s: ARRAY [1..5] OF CARDINAL ;
15822 (@value{GDBP}) print s
15823 $1 = @{1, 0, 0, 0, 0@}
15824 (@value{GDBP}) ptype s
15825 type = ARRAY [1..5] OF CARDINAL
15828 The Modula-2 language interface to @value{GDBN} also understands
15829 pointer types as shown in this example:
15833 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15840 and you can request that @value{GDBN} describes the type of @code{s}.
15843 (@value{GDBP}) ptype s
15844 type = POINTER TO ARRAY [1..5] OF CARDINAL
15847 @value{GDBN} handles compound types as we can see in this example.
15848 Here we combine array types, record types, pointer types and subrange
15859 myarray = ARRAY myrange OF CARDINAL ;
15860 myrange = [-2..2] ;
15862 s: POINTER TO ARRAY myrange OF foo ;
15866 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15870 (@value{GDBP}) ptype s
15871 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15874 f3 : ARRAY [-2..2] OF CARDINAL;
15879 @subsubsection Modula-2 Defaults
15880 @cindex Modula-2 defaults
15882 If type and range checking are set automatically by @value{GDBN}, they
15883 both default to @code{on} whenever the working language changes to
15884 Modula-2. This happens regardless of whether you or @value{GDBN}
15885 selected the working language.
15887 If you allow @value{GDBN} to set the language automatically, then entering
15888 code compiled from a file whose name ends with @file{.mod} sets the
15889 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15890 Infer the Source Language}, for further details.
15893 @subsubsection Deviations from Standard Modula-2
15894 @cindex Modula-2, deviations from
15896 A few changes have been made to make Modula-2 programs easier to debug.
15897 This is done primarily via loosening its type strictness:
15901 Unlike in standard Modula-2, pointer constants can be formed by
15902 integers. This allows you to modify pointer variables during
15903 debugging. (In standard Modula-2, the actual address contained in a
15904 pointer variable is hidden from you; it can only be modified
15905 through direct assignment to another pointer variable or expression that
15906 returned a pointer.)
15909 C escape sequences can be used in strings and characters to represent
15910 non-printable characters. @value{GDBN} prints out strings with these
15911 escape sequences embedded. Single non-printable characters are
15912 printed using the @samp{CHR(@var{nnn})} format.
15915 The assignment operator (@code{:=}) returns the value of its right-hand
15919 All built-in procedures both modify @emph{and} return their argument.
15923 @subsubsection Modula-2 Type and Range Checks
15924 @cindex Modula-2 checks
15927 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15930 @c FIXME remove warning when type/range checks added
15932 @value{GDBN} considers two Modula-2 variables type equivalent if:
15936 They are of types that have been declared equivalent via a @code{TYPE
15937 @var{t1} = @var{t2}} statement
15940 They have been declared on the same line. (Note: This is true of the
15941 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15944 As long as type checking is enabled, any attempt to combine variables
15945 whose types are not equivalent is an error.
15947 Range checking is done on all mathematical operations, assignment, array
15948 index bounds, and all built-in functions and procedures.
15951 @subsubsection The Scope Operators @code{::} and @code{.}
15953 @cindex @code{.}, Modula-2 scope operator
15954 @cindex colon, doubled as scope operator
15956 @vindex colon-colon@r{, in Modula-2}
15957 @c Info cannot handle :: but TeX can.
15960 @vindex ::@r{, in Modula-2}
15963 There are a few subtle differences between the Modula-2 scope operator
15964 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15969 @var{module} . @var{id}
15970 @var{scope} :: @var{id}
15974 where @var{scope} is the name of a module or a procedure,
15975 @var{module} the name of a module, and @var{id} is any declared
15976 identifier within your program, except another module.
15978 Using the @code{::} operator makes @value{GDBN} search the scope
15979 specified by @var{scope} for the identifier @var{id}. If it is not
15980 found in the specified scope, then @value{GDBN} searches all scopes
15981 enclosing the one specified by @var{scope}.
15983 Using the @code{.} operator makes @value{GDBN} search the current scope for
15984 the identifier specified by @var{id} that was imported from the
15985 definition module specified by @var{module}. With this operator, it is
15986 an error if the identifier @var{id} was not imported from definition
15987 module @var{module}, or if @var{id} is not an identifier in
15991 @subsubsection @value{GDBN} and Modula-2
15993 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15994 Five subcommands of @code{set print} and @code{show print} apply
15995 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15996 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15997 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15998 analogue in Modula-2.
16000 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16001 with any language, is not useful with Modula-2. Its
16002 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16003 created in Modula-2 as they can in C or C@t{++}. However, because an
16004 address can be specified by an integral constant, the construct
16005 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16007 @cindex @code{#} in Modula-2
16008 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16009 interpreted as the beginning of a comment. Use @code{<>} instead.
16015 The extensions made to @value{GDBN} for Ada only support
16016 output from the @sc{gnu} Ada (GNAT) compiler.
16017 Other Ada compilers are not currently supported, and
16018 attempting to debug executables produced by them is most likely
16022 @cindex expressions in Ada
16024 * Ada Mode Intro:: General remarks on the Ada syntax
16025 and semantics supported by Ada mode
16027 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16028 * Additions to Ada:: Extensions of the Ada expression syntax.
16029 * Overloading support for Ada:: Support for expressions involving overloaded
16031 * Stopping Before Main Program:: Debugging the program during elaboration.
16032 * Ada Exceptions:: Ada Exceptions
16033 * Ada Tasks:: Listing and setting breakpoints in tasks.
16034 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16035 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16037 * Ada Glitches:: Known peculiarities of Ada mode.
16040 @node Ada Mode Intro
16041 @subsubsection Introduction
16042 @cindex Ada mode, general
16044 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16045 syntax, with some extensions.
16046 The philosophy behind the design of this subset is
16050 That @value{GDBN} should provide basic literals and access to operations for
16051 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16052 leaving more sophisticated computations to subprograms written into the
16053 program (which therefore may be called from @value{GDBN}).
16056 That type safety and strict adherence to Ada language restrictions
16057 are not particularly important to the @value{GDBN} user.
16060 That brevity is important to the @value{GDBN} user.
16063 Thus, for brevity, the debugger acts as if all names declared in
16064 user-written packages are directly visible, even if they are not visible
16065 according to Ada rules, thus making it unnecessary to fully qualify most
16066 names with their packages, regardless of context. Where this causes
16067 ambiguity, @value{GDBN} asks the user's intent.
16069 The debugger will start in Ada mode if it detects an Ada main program.
16070 As for other languages, it will enter Ada mode when stopped in a program that
16071 was translated from an Ada source file.
16073 While in Ada mode, you may use `@t{--}' for comments. This is useful
16074 mostly for documenting command files. The standard @value{GDBN} comment
16075 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16076 middle (to allow based literals).
16078 @node Omissions from Ada
16079 @subsubsection Omissions from Ada
16080 @cindex Ada, omissions from
16082 Here are the notable omissions from the subset:
16086 Only a subset of the attributes are supported:
16090 @t{'First}, @t{'Last}, and @t{'Length}
16091 on array objects (not on types and subtypes).
16094 @t{'Min} and @t{'Max}.
16097 @t{'Pos} and @t{'Val}.
16103 @t{'Range} on array objects (not subtypes), but only as the right
16104 operand of the membership (@code{in}) operator.
16107 @t{'Access}, @t{'Unchecked_Access}, and
16108 @t{'Unrestricted_Access} (a GNAT extension).
16116 @code{Characters.Latin_1} are not available and
16117 concatenation is not implemented. Thus, escape characters in strings are
16118 not currently available.
16121 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16122 equality of representations. They will generally work correctly
16123 for strings and arrays whose elements have integer or enumeration types.
16124 They may not work correctly for arrays whose element
16125 types have user-defined equality, for arrays of real values
16126 (in particular, IEEE-conformant floating point, because of negative
16127 zeroes and NaNs), and for arrays whose elements contain unused bits with
16128 indeterminate values.
16131 The other component-by-component array operations (@code{and}, @code{or},
16132 @code{xor}, @code{not}, and relational tests other than equality)
16133 are not implemented.
16136 @cindex array aggregates (Ada)
16137 @cindex record aggregates (Ada)
16138 @cindex aggregates (Ada)
16139 There is limited support for array and record aggregates. They are
16140 permitted only on the right sides of assignments, as in these examples:
16143 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16144 (@value{GDBP}) set An_Array := (1, others => 0)
16145 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16146 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16147 (@value{GDBP}) set A_Record := (1, "Peter", True);
16148 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16152 discriminant's value by assigning an aggregate has an
16153 undefined effect if that discriminant is used within the record.
16154 However, you can first modify discriminants by directly assigning to
16155 them (which normally would not be allowed in Ada), and then performing an
16156 aggregate assignment. For example, given a variable @code{A_Rec}
16157 declared to have a type such as:
16160 type Rec (Len : Small_Integer := 0) is record
16162 Vals : IntArray (1 .. Len);
16166 you can assign a value with a different size of @code{Vals} with two
16170 (@value{GDBP}) set A_Rec.Len := 4
16171 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16174 As this example also illustrates, @value{GDBN} is very loose about the usual
16175 rules concerning aggregates. You may leave out some of the
16176 components of an array or record aggregate (such as the @code{Len}
16177 component in the assignment to @code{A_Rec} above); they will retain their
16178 original values upon assignment. You may freely use dynamic values as
16179 indices in component associations. You may even use overlapping or
16180 redundant component associations, although which component values are
16181 assigned in such cases is not defined.
16184 Calls to dispatching subprograms are not implemented.
16187 The overloading algorithm is much more limited (i.e., less selective)
16188 than that of real Ada. It makes only limited use of the context in
16189 which a subexpression appears to resolve its meaning, and it is much
16190 looser in its rules for allowing type matches. As a result, some
16191 function calls will be ambiguous, and the user will be asked to choose
16192 the proper resolution.
16195 The @code{new} operator is not implemented.
16198 Entry calls are not implemented.
16201 Aside from printing, arithmetic operations on the native VAX floating-point
16202 formats are not supported.
16205 It is not possible to slice a packed array.
16208 The names @code{True} and @code{False}, when not part of a qualified name,
16209 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16211 Should your program
16212 redefine these names in a package or procedure (at best a dubious practice),
16213 you will have to use fully qualified names to access their new definitions.
16216 @node Additions to Ada
16217 @subsubsection Additions to Ada
16218 @cindex Ada, deviations from
16220 As it does for other languages, @value{GDBN} makes certain generic
16221 extensions to Ada (@pxref{Expressions}):
16225 If the expression @var{E} is a variable residing in memory (typically
16226 a local variable or array element) and @var{N} is a positive integer,
16227 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16228 @var{N}-1 adjacent variables following it in memory as an array. In
16229 Ada, this operator is generally not necessary, since its prime use is
16230 in displaying parts of an array, and slicing will usually do this in
16231 Ada. However, there are occasional uses when debugging programs in
16232 which certain debugging information has been optimized away.
16235 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16236 appears in function or file @var{B}.'' When @var{B} is a file name,
16237 you must typically surround it in single quotes.
16240 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16241 @var{type} that appears at address @var{addr}.''
16244 A name starting with @samp{$} is a convenience variable
16245 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16248 In addition, @value{GDBN} provides a few other shortcuts and outright
16249 additions specific to Ada:
16253 The assignment statement is allowed as an expression, returning
16254 its right-hand operand as its value. Thus, you may enter
16257 (@value{GDBP}) set x := y + 3
16258 (@value{GDBP}) print A(tmp := y + 1)
16262 The semicolon is allowed as an ``operator,'' returning as its value
16263 the value of its right-hand operand.
16264 This allows, for example,
16265 complex conditional breaks:
16268 (@value{GDBP}) break f
16269 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16273 Rather than use catenation and symbolic character names to introduce special
16274 characters into strings, one may instead use a special bracket notation,
16275 which is also used to print strings. A sequence of characters of the form
16276 @samp{["@var{XX}"]} within a string or character literal denotes the
16277 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16278 sequence of characters @samp{["""]} also denotes a single quotation mark
16279 in strings. For example,
16281 "One line.["0a"]Next line.["0a"]"
16284 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16288 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16289 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16293 (@value{GDBP}) print 'max(x, y)
16297 When printing arrays, @value{GDBN} uses positional notation when the
16298 array has a lower bound of 1, and uses a modified named notation otherwise.
16299 For example, a one-dimensional array of three integers with a lower bound
16300 of 3 might print as
16307 That is, in contrast to valid Ada, only the first component has a @code{=>}
16311 You may abbreviate attributes in expressions with any unique,
16312 multi-character subsequence of
16313 their names (an exact match gets preference).
16314 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16315 in place of @t{a'length}.
16318 @cindex quoting Ada internal identifiers
16319 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16320 to lower case. The GNAT compiler uses upper-case characters for
16321 some of its internal identifiers, which are normally of no interest to users.
16322 For the rare occasions when you actually have to look at them,
16323 enclose them in angle brackets to avoid the lower-case mapping.
16326 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16330 Printing an object of class-wide type or dereferencing an
16331 access-to-class-wide value will display all the components of the object's
16332 specific type (as indicated by its run-time tag). Likewise, component
16333 selection on such a value will operate on the specific type of the
16338 @node Overloading support for Ada
16339 @subsubsection Overloading support for Ada
16340 @cindex overloading, Ada
16342 The debugger supports limited overloading. Given a subprogram call in which
16343 the function symbol has multiple definitions, it will use the number of
16344 actual parameters and some information about their types to attempt to narrow
16345 the set of definitions. It also makes very limited use of context, preferring
16346 procedures to functions in the context of the @code{call} command, and
16347 functions to procedures elsewhere.
16349 If, after narrowing, the set of matching definitions still contains more than
16350 one definition, @value{GDBN} will display a menu to query which one it should
16354 (@value{GDBP}) print f(1)
16355 Multiple matches for f
16357 [1] foo.f (integer) return boolean at foo.adb:23
16358 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16362 In this case, just select one menu entry either to cancel expression evaluation
16363 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16364 instance (type the corresponding number and press @key{RET}).
16366 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16371 @kindex set ada print-signatures
16372 @item set ada print-signatures
16373 Control whether parameter types and return types are displayed in overloads
16374 selection menus. It is @code{on} by default.
16375 @xref{Overloading support for Ada}.
16377 @kindex show ada print-signatures
16378 @item show ada print-signatures
16379 Show the current setting for displaying parameter types and return types in
16380 overloads selection menu.
16381 @xref{Overloading support for Ada}.
16385 @node Stopping Before Main Program
16386 @subsubsection Stopping at the Very Beginning
16388 @cindex breakpointing Ada elaboration code
16389 It is sometimes necessary to debug the program during elaboration, and
16390 before reaching the main procedure.
16391 As defined in the Ada Reference
16392 Manual, the elaboration code is invoked from a procedure called
16393 @code{adainit}. To run your program up to the beginning of
16394 elaboration, simply use the following two commands:
16395 @code{tbreak adainit} and @code{run}.
16397 @node Ada Exceptions
16398 @subsubsection Ada Exceptions
16400 A command is provided to list all Ada exceptions:
16403 @kindex info exceptions
16404 @item info exceptions
16405 @itemx info exceptions @var{regexp}
16406 The @code{info exceptions} command allows you to list all Ada exceptions
16407 defined within the program being debugged, as well as their addresses.
16408 With a regular expression, @var{regexp}, as argument, only those exceptions
16409 whose names match @var{regexp} are listed.
16412 Below is a small example, showing how the command can be used, first
16413 without argument, and next with a regular expression passed as an
16417 (@value{GDBP}) info exceptions
16418 All defined Ada exceptions:
16419 constraint_error: 0x613da0
16420 program_error: 0x613d20
16421 storage_error: 0x613ce0
16422 tasking_error: 0x613ca0
16423 const.aint_global_e: 0x613b00
16424 (@value{GDBP}) info exceptions const.aint
16425 All Ada exceptions matching regular expression "const.aint":
16426 constraint_error: 0x613da0
16427 const.aint_global_e: 0x613b00
16430 It is also possible to ask @value{GDBN} to stop your program's execution
16431 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16434 @subsubsection Extensions for Ada Tasks
16435 @cindex Ada, tasking
16437 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16438 @value{GDBN} provides the following task-related commands:
16443 This command shows a list of current Ada tasks, as in the following example:
16450 (@value{GDBP}) info tasks
16451 ID TID P-ID Pri State Name
16452 1 8088000 0 15 Child Activation Wait main_task
16453 2 80a4000 1 15 Accept Statement b
16454 3 809a800 1 15 Child Activation Wait a
16455 * 4 80ae800 3 15 Runnable c
16460 In this listing, the asterisk before the last task indicates it to be the
16461 task currently being inspected.
16465 Represents @value{GDBN}'s internal task number.
16471 The parent's task ID (@value{GDBN}'s internal task number).
16474 The base priority of the task.
16477 Current state of the task.
16481 The task has been created but has not been activated. It cannot be
16485 The task is not blocked for any reason known to Ada. (It may be waiting
16486 for a mutex, though.) It is conceptually "executing" in normal mode.
16489 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16490 that were waiting on terminate alternatives have been awakened and have
16491 terminated themselves.
16493 @item Child Activation Wait
16494 The task is waiting for created tasks to complete activation.
16496 @item Accept Statement
16497 The task is waiting on an accept or selective wait statement.
16499 @item Waiting on entry call
16500 The task is waiting on an entry call.
16502 @item Async Select Wait
16503 The task is waiting to start the abortable part of an asynchronous
16507 The task is waiting on a select statement with only a delay
16510 @item Child Termination Wait
16511 The task is sleeping having completed a master within itself, and is
16512 waiting for the tasks dependent on that master to become terminated or
16513 waiting on a terminate Phase.
16515 @item Wait Child in Term Alt
16516 The task is sleeping waiting for tasks on terminate alternatives to
16517 finish terminating.
16519 @item Accepting RV with @var{taskno}
16520 The task is accepting a rendez-vous with the task @var{taskno}.
16524 Name of the task in the program.
16528 @kindex info task @var{taskno}
16529 @item info task @var{taskno}
16530 This command shows detailled informations on the specified task, as in
16531 the following example:
16536 (@value{GDBP}) info tasks
16537 ID TID P-ID Pri State Name
16538 1 8077880 0 15 Child Activation Wait main_task
16539 * 2 807c468 1 15 Runnable task_1
16540 (@value{GDBP}) info task 2
16541 Ada Task: 0x807c468
16544 Parent: 1 (main_task)
16550 @kindex task@r{ (Ada)}
16551 @cindex current Ada task ID
16552 This command prints the ID of the current task.
16558 (@value{GDBP}) info tasks
16559 ID TID P-ID Pri State Name
16560 1 8077870 0 15 Child Activation Wait main_task
16561 * 2 807c458 1 15 Runnable t
16562 (@value{GDBP}) task
16563 [Current task is 2]
16566 @item task @var{taskno}
16567 @cindex Ada task switching
16568 This command is like the @code{thread @var{thread-id}}
16569 command (@pxref{Threads}). It switches the context of debugging
16570 from the current task to the given task.
16576 (@value{GDBP}) info tasks
16577 ID TID P-ID Pri State Name
16578 1 8077870 0 15 Child Activation Wait main_task
16579 * 2 807c458 1 15 Runnable t
16580 (@value{GDBP}) task 1
16581 [Switching to task 1]
16582 #0 0x8067726 in pthread_cond_wait ()
16584 #0 0x8067726 in pthread_cond_wait ()
16585 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16586 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16587 #3 0x806153e in system.tasking.stages.activate_tasks ()
16588 #4 0x804aacc in un () at un.adb:5
16591 @item break @var{location} task @var{taskno}
16592 @itemx break @var{location} task @var{taskno} if @dots{}
16593 @cindex breakpoints and tasks, in Ada
16594 @cindex task breakpoints, in Ada
16595 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16596 These commands are like the @code{break @dots{} thread @dots{}}
16597 command (@pxref{Thread Stops}). The
16598 @var{location} argument specifies source lines, as described
16599 in @ref{Specify Location}.
16601 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16602 to specify that you only want @value{GDBN} to stop the program when a
16603 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16604 numeric task identifiers assigned by @value{GDBN}, shown in the first
16605 column of the @samp{info tasks} display.
16607 If you do not specify @samp{task @var{taskno}} when you set a
16608 breakpoint, the breakpoint applies to @emph{all} tasks of your
16611 You can use the @code{task} qualifier on conditional breakpoints as
16612 well; in this case, place @samp{task @var{taskno}} before the
16613 breakpoint condition (before the @code{if}).
16621 (@value{GDBP}) info tasks
16622 ID TID P-ID Pri State Name
16623 1 140022020 0 15 Child Activation Wait main_task
16624 2 140045060 1 15 Accept/Select Wait t2
16625 3 140044840 1 15 Runnable t1
16626 * 4 140056040 1 15 Runnable t3
16627 (@value{GDBP}) b 15 task 2
16628 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16629 (@value{GDBP}) cont
16634 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16636 (@value{GDBP}) info tasks
16637 ID TID P-ID Pri State Name
16638 1 140022020 0 15 Child Activation Wait main_task
16639 * 2 140045060 1 15 Runnable t2
16640 3 140044840 1 15 Runnable t1
16641 4 140056040 1 15 Delay Sleep t3
16645 @node Ada Tasks and Core Files
16646 @subsubsection Tasking Support when Debugging Core Files
16647 @cindex Ada tasking and core file debugging
16649 When inspecting a core file, as opposed to debugging a live program,
16650 tasking support may be limited or even unavailable, depending on
16651 the platform being used.
16652 For instance, on x86-linux, the list of tasks is available, but task
16653 switching is not supported.
16655 On certain platforms, the debugger needs to perform some
16656 memory writes in order to provide Ada tasking support. When inspecting
16657 a core file, this means that the core file must be opened with read-write
16658 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16659 Under these circumstances, you should make a backup copy of the core
16660 file before inspecting it with @value{GDBN}.
16662 @node Ravenscar Profile
16663 @subsubsection Tasking Support when using the Ravenscar Profile
16664 @cindex Ravenscar Profile
16666 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16667 specifically designed for systems with safety-critical real-time
16671 @kindex set ravenscar task-switching on
16672 @cindex task switching with program using Ravenscar Profile
16673 @item set ravenscar task-switching on
16674 Allows task switching when debugging a program that uses the Ravenscar
16675 Profile. This is the default.
16677 @kindex set ravenscar task-switching off
16678 @item set ravenscar task-switching off
16679 Turn off task switching when debugging a program that uses the Ravenscar
16680 Profile. This is mostly intended to disable the code that adds support
16681 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16682 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16683 To be effective, this command should be run before the program is started.
16685 @kindex show ravenscar task-switching
16686 @item show ravenscar task-switching
16687 Show whether it is possible to switch from task to task in a program
16688 using the Ravenscar Profile.
16693 @subsubsection Known Peculiarities of Ada Mode
16694 @cindex Ada, problems
16696 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16697 we know of several problems with and limitations of Ada mode in
16699 some of which will be fixed with planned future releases of the debugger
16700 and the GNU Ada compiler.
16704 Static constants that the compiler chooses not to materialize as objects in
16705 storage are invisible to the debugger.
16708 Named parameter associations in function argument lists are ignored (the
16709 argument lists are treated as positional).
16712 Many useful library packages are currently invisible to the debugger.
16715 Fixed-point arithmetic, conversions, input, and output is carried out using
16716 floating-point arithmetic, and may give results that only approximate those on
16720 The GNAT compiler never generates the prefix @code{Standard} for any of
16721 the standard symbols defined by the Ada language. @value{GDBN} knows about
16722 this: it will strip the prefix from names when you use it, and will never
16723 look for a name you have so qualified among local symbols, nor match against
16724 symbols in other packages or subprograms. If you have
16725 defined entities anywhere in your program other than parameters and
16726 local variables whose simple names match names in @code{Standard},
16727 GNAT's lack of qualification here can cause confusion. When this happens,
16728 you can usually resolve the confusion
16729 by qualifying the problematic names with package
16730 @code{Standard} explicitly.
16733 Older versions of the compiler sometimes generate erroneous debugging
16734 information, resulting in the debugger incorrectly printing the value
16735 of affected entities. In some cases, the debugger is able to work
16736 around an issue automatically. In other cases, the debugger is able
16737 to work around the issue, but the work-around has to be specifically
16740 @kindex set ada trust-PAD-over-XVS
16741 @kindex show ada trust-PAD-over-XVS
16744 @item set ada trust-PAD-over-XVS on
16745 Configure GDB to strictly follow the GNAT encoding when computing the
16746 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16747 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16748 a complete description of the encoding used by the GNAT compiler).
16749 This is the default.
16751 @item set ada trust-PAD-over-XVS off
16752 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16753 sometimes prints the wrong value for certain entities, changing @code{ada
16754 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16755 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16756 @code{off}, but this incurs a slight performance penalty, so it is
16757 recommended to leave this setting to @code{on} unless necessary.
16761 @cindex GNAT descriptive types
16762 @cindex GNAT encoding
16763 Internally, the debugger also relies on the compiler following a number
16764 of conventions known as the @samp{GNAT Encoding}, all documented in
16765 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16766 how the debugging information should be generated for certain types.
16767 In particular, this convention makes use of @dfn{descriptive types},
16768 which are artificial types generated purely to help the debugger.
16770 These encodings were defined at a time when the debugging information
16771 format used was not powerful enough to describe some of the more complex
16772 types available in Ada. Since DWARF allows us to express nearly all
16773 Ada features, the long-term goal is to slowly replace these descriptive
16774 types by their pure DWARF equivalent. To facilitate that transition,
16775 a new maintenance option is available to force the debugger to ignore
16776 those descriptive types. It allows the user to quickly evaluate how
16777 well @value{GDBN} works without them.
16781 @kindex maint ada set ignore-descriptive-types
16782 @item maintenance ada set ignore-descriptive-types [on|off]
16783 Control whether the debugger should ignore descriptive types.
16784 The default is not to ignore descriptives types (@code{off}).
16786 @kindex maint ada show ignore-descriptive-types
16787 @item maintenance ada show ignore-descriptive-types
16788 Show if descriptive types are ignored by @value{GDBN}.
16792 @node Unsupported Languages
16793 @section Unsupported Languages
16795 @cindex unsupported languages
16796 @cindex minimal language
16797 In addition to the other fully-supported programming languages,
16798 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16799 It does not represent a real programming language, but provides a set
16800 of capabilities close to what the C or assembly languages provide.
16801 This should allow most simple operations to be performed while debugging
16802 an application that uses a language currently not supported by @value{GDBN}.
16804 If the language is set to @code{auto}, @value{GDBN} will automatically
16805 select this language if the current frame corresponds to an unsupported
16809 @chapter Examining the Symbol Table
16811 The commands described in this chapter allow you to inquire about the
16812 symbols (names of variables, functions and types) defined in your
16813 program. This information is inherent in the text of your program and
16814 does not change as your program executes. @value{GDBN} finds it in your
16815 program's symbol table, in the file indicated when you started @value{GDBN}
16816 (@pxref{File Options, ,Choosing Files}), or by one of the
16817 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16819 @cindex symbol names
16820 @cindex names of symbols
16821 @cindex quoting names
16822 Occasionally, you may need to refer to symbols that contain unusual
16823 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16824 most frequent case is in referring to static variables in other
16825 source files (@pxref{Variables,,Program Variables}). File names
16826 are recorded in object files as debugging symbols, but @value{GDBN} would
16827 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16828 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16829 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16836 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16839 @cindex case-insensitive symbol names
16840 @cindex case sensitivity in symbol names
16841 @kindex set case-sensitive
16842 @item set case-sensitive on
16843 @itemx set case-sensitive off
16844 @itemx set case-sensitive auto
16845 Normally, when @value{GDBN} looks up symbols, it matches their names
16846 with case sensitivity determined by the current source language.
16847 Occasionally, you may wish to control that. The command @code{set
16848 case-sensitive} lets you do that by specifying @code{on} for
16849 case-sensitive matches or @code{off} for case-insensitive ones. If
16850 you specify @code{auto}, case sensitivity is reset to the default
16851 suitable for the source language. The default is case-sensitive
16852 matches for all languages except for Fortran, for which the default is
16853 case-insensitive matches.
16855 @kindex show case-sensitive
16856 @item show case-sensitive
16857 This command shows the current setting of case sensitivity for symbols
16860 @kindex set print type methods
16861 @item set print type methods
16862 @itemx set print type methods on
16863 @itemx set print type methods off
16864 Normally, when @value{GDBN} prints a class, it displays any methods
16865 declared in that class. You can control this behavior either by
16866 passing the appropriate flag to @code{ptype}, or using @command{set
16867 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16868 display the methods; this is the default. Specifying @code{off} will
16869 cause @value{GDBN} to omit the methods.
16871 @kindex show print type methods
16872 @item show print type methods
16873 This command shows the current setting of method display when printing
16876 @kindex set print type typedefs
16877 @item set print type typedefs
16878 @itemx set print type typedefs on
16879 @itemx set print type typedefs off
16881 Normally, when @value{GDBN} prints a class, it displays any typedefs
16882 defined in that class. You can control this behavior either by
16883 passing the appropriate flag to @code{ptype}, or using @command{set
16884 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16885 display the typedef definitions; this is the default. Specifying
16886 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16887 Note that this controls whether the typedef definition itself is
16888 printed, not whether typedef names are substituted when printing other
16891 @kindex show print type typedefs
16892 @item show print type typedefs
16893 This command shows the current setting of typedef display when
16896 @kindex info address
16897 @cindex address of a symbol
16898 @item info address @var{symbol}
16899 Describe where the data for @var{symbol} is stored. For a register
16900 variable, this says which register it is kept in. For a non-register
16901 local variable, this prints the stack-frame offset at which the variable
16904 Note the contrast with @samp{print &@var{symbol}}, which does not work
16905 at all for a register variable, and for a stack local variable prints
16906 the exact address of the current instantiation of the variable.
16908 @kindex info symbol
16909 @cindex symbol from address
16910 @cindex closest symbol and offset for an address
16911 @item info symbol @var{addr}
16912 Print the name of a symbol which is stored at the address @var{addr}.
16913 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16914 nearest symbol and an offset from it:
16917 (@value{GDBP}) info symbol 0x54320
16918 _initialize_vx + 396 in section .text
16922 This is the opposite of the @code{info address} command. You can use
16923 it to find out the name of a variable or a function given its address.
16925 For dynamically linked executables, the name of executable or shared
16926 library containing the symbol is also printed:
16929 (@value{GDBP}) info symbol 0x400225
16930 _start + 5 in section .text of /tmp/a.out
16931 (@value{GDBP}) info symbol 0x2aaaac2811cf
16932 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16937 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16938 Demangle @var{name}.
16939 If @var{language} is provided it is the name of the language to demangle
16940 @var{name} in. Otherwise @var{name} is demangled in the current language.
16942 The @samp{--} option specifies the end of options,
16943 and is useful when @var{name} begins with a dash.
16945 The parameter @code{demangle-style} specifies how to interpret the kind
16946 of mangling used. @xref{Print Settings}.
16949 @item whatis[/@var{flags}] [@var{arg}]
16950 Print the data type of @var{arg}, which can be either an expression
16951 or a name of a data type. With no argument, print the data type of
16952 @code{$}, the last value in the value history.
16954 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16955 is not actually evaluated, and any side-effecting operations (such as
16956 assignments or function calls) inside it do not take place.
16958 If @var{arg} is a variable or an expression, @code{whatis} prints its
16959 literal type as it is used in the source code. If the type was
16960 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16961 the data type underlying the @code{typedef}. If the type of the
16962 variable or the expression is a compound data type, such as
16963 @code{struct} or @code{class}, @code{whatis} never prints their
16964 fields or methods. It just prints the @code{struct}/@code{class}
16965 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16966 such a compound data type, use @code{ptype}.
16968 If @var{arg} is a type name that was defined using @code{typedef},
16969 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16970 Unrolling means that @code{whatis} will show the underlying type used
16971 in the @code{typedef} declaration of @var{arg}. However, if that
16972 underlying type is also a @code{typedef}, @code{whatis} will not
16975 For C code, the type names may also have the form @samp{class
16976 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16977 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16979 @var{flags} can be used to modify how the type is displayed.
16980 Available flags are:
16984 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16985 parameters and typedefs defined in a class when printing the class'
16986 members. The @code{/r} flag disables this.
16989 Do not print methods defined in the class.
16992 Print methods defined in the class. This is the default, but the flag
16993 exists in case you change the default with @command{set print type methods}.
16996 Do not print typedefs defined in the class. Note that this controls
16997 whether the typedef definition itself is printed, not whether typedef
16998 names are substituted when printing other types.
17001 Print typedefs defined in the class. This is the default, but the flag
17002 exists in case you change the default with @command{set print type typedefs}.
17006 @item ptype[/@var{flags}] [@var{arg}]
17007 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17008 detailed description of the type, instead of just the name of the type.
17009 @xref{Expressions, ,Expressions}.
17011 Contrary to @code{whatis}, @code{ptype} always unrolls any
17012 @code{typedef}s in its argument declaration, whether the argument is
17013 a variable, expression, or a data type. This means that @code{ptype}
17014 of a variable or an expression will not print literally its type as
17015 present in the source code---use @code{whatis} for that. @code{typedef}s at
17016 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17017 fields, methods and inner @code{class typedef}s of @code{struct}s,
17018 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17020 For example, for this variable declaration:
17023 typedef double real_t;
17024 struct complex @{ real_t real; double imag; @};
17025 typedef struct complex complex_t;
17027 real_t *real_pointer_var;
17031 the two commands give this output:
17035 (@value{GDBP}) whatis var
17037 (@value{GDBP}) ptype var
17038 type = struct complex @{
17042 (@value{GDBP}) whatis complex_t
17043 type = struct complex
17044 (@value{GDBP}) whatis struct complex
17045 type = struct complex
17046 (@value{GDBP}) ptype struct complex
17047 type = struct complex @{
17051 (@value{GDBP}) whatis real_pointer_var
17053 (@value{GDBP}) ptype real_pointer_var
17059 As with @code{whatis}, using @code{ptype} without an argument refers to
17060 the type of @code{$}, the last value in the value history.
17062 @cindex incomplete type
17063 Sometimes, programs use opaque data types or incomplete specifications
17064 of complex data structure. If the debug information included in the
17065 program does not allow @value{GDBN} to display a full declaration of
17066 the data type, it will say @samp{<incomplete type>}. For example,
17067 given these declarations:
17071 struct foo *fooptr;
17075 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17078 (@value{GDBP}) ptype foo
17079 $1 = <incomplete type>
17083 ``Incomplete type'' is C terminology for data types that are not
17084 completely specified.
17087 @item info types @var{regexp}
17089 Print a brief description of all types whose names match the regular
17090 expression @var{regexp} (or all types in your program, if you supply
17091 no argument). Each complete typename is matched as though it were a
17092 complete line; thus, @samp{i type value} gives information on all
17093 types in your program whose names include the string @code{value}, but
17094 @samp{i type ^value$} gives information only on types whose complete
17095 name is @code{value}.
17097 This command differs from @code{ptype} in two ways: first, like
17098 @code{whatis}, it does not print a detailed description; second, it
17099 lists all source files where a type is defined.
17101 @kindex info type-printers
17102 @item info type-printers
17103 Versions of @value{GDBN} that ship with Python scripting enabled may
17104 have ``type printers'' available. When using @command{ptype} or
17105 @command{whatis}, these printers are consulted when the name of a type
17106 is needed. @xref{Type Printing API}, for more information on writing
17109 @code{info type-printers} displays all the available type printers.
17111 @kindex enable type-printer
17112 @kindex disable type-printer
17113 @item enable type-printer @var{name}@dots{}
17114 @item disable type-printer @var{name}@dots{}
17115 These commands can be used to enable or disable type printers.
17118 @cindex local variables
17119 @item info scope @var{location}
17120 List all the variables local to a particular scope. This command
17121 accepts a @var{location} argument---a function name, a source line, or
17122 an address preceded by a @samp{*}, and prints all the variables local
17123 to the scope defined by that location. (@xref{Specify Location}, for
17124 details about supported forms of @var{location}.) For example:
17127 (@value{GDBP}) @b{info scope command_line_handler}
17128 Scope for command_line_handler:
17129 Symbol rl is an argument at stack/frame offset 8, length 4.
17130 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17131 Symbol linelength is in static storage at address 0x150a1c, length 4.
17132 Symbol p is a local variable in register $esi, length 4.
17133 Symbol p1 is a local variable in register $ebx, length 4.
17134 Symbol nline is a local variable in register $edx, length 4.
17135 Symbol repeat is a local variable at frame offset -8, length 4.
17139 This command is especially useful for determining what data to collect
17140 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17143 @kindex info source
17145 Show information about the current source file---that is, the source file for
17146 the function containing the current point of execution:
17149 the name of the source file, and the directory containing it,
17151 the directory it was compiled in,
17153 its length, in lines,
17155 which programming language it is written in,
17157 if the debug information provides it, the program that compiled the file
17158 (which may include, e.g., the compiler version and command line arguments),
17160 whether the executable includes debugging information for that file, and
17161 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17163 whether the debugging information includes information about
17164 preprocessor macros.
17168 @kindex info sources
17170 Print the names of all source files in your program for which there is
17171 debugging information, organized into two lists: files whose symbols
17172 have already been read, and files whose symbols will be read when needed.
17174 @kindex info functions
17175 @item info functions
17176 Print the names and data types of all defined functions.
17178 @item info functions @var{regexp}
17179 Print the names and data types of all defined functions
17180 whose names contain a match for regular expression @var{regexp}.
17181 Thus, @samp{info fun step} finds all functions whose names
17182 include @code{step}; @samp{info fun ^step} finds those whose names
17183 start with @code{step}. If a function name contains characters
17184 that conflict with the regular expression language (e.g.@:
17185 @samp{operator*()}), they may be quoted with a backslash.
17187 @kindex info variables
17188 @item info variables
17189 Print the names and data types of all variables that are defined
17190 outside of functions (i.e.@: excluding local variables).
17192 @item info variables @var{regexp}
17193 Print the names and data types of all variables (except for local
17194 variables) whose names contain a match for regular expression
17197 @kindex info classes
17198 @cindex Objective-C, classes and selectors
17200 @itemx info classes @var{regexp}
17201 Display all Objective-C classes in your program, or
17202 (with the @var{regexp} argument) all those matching a particular regular
17205 @kindex info selectors
17206 @item info selectors
17207 @itemx info selectors @var{regexp}
17208 Display all Objective-C selectors in your program, or
17209 (with the @var{regexp} argument) all those matching a particular regular
17213 This was never implemented.
17214 @kindex info methods
17216 @itemx info methods @var{regexp}
17217 The @code{info methods} command permits the user to examine all defined
17218 methods within C@t{++} program, or (with the @var{regexp} argument) a
17219 specific set of methods found in the various C@t{++} classes. Many
17220 C@t{++} classes provide a large number of methods. Thus, the output
17221 from the @code{ptype} command can be overwhelming and hard to use. The
17222 @code{info-methods} command filters the methods, printing only those
17223 which match the regular-expression @var{regexp}.
17226 @cindex opaque data types
17227 @kindex set opaque-type-resolution
17228 @item set opaque-type-resolution on
17229 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17230 declared as a pointer to a @code{struct}, @code{class}, or
17231 @code{union}---for example, @code{struct MyType *}---that is used in one
17232 source file although the full declaration of @code{struct MyType} is in
17233 another source file. The default is on.
17235 A change in the setting of this subcommand will not take effect until
17236 the next time symbols for a file are loaded.
17238 @item set opaque-type-resolution off
17239 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17240 is printed as follows:
17242 @{<no data fields>@}
17245 @kindex show opaque-type-resolution
17246 @item show opaque-type-resolution
17247 Show whether opaque types are resolved or not.
17249 @kindex set print symbol-loading
17250 @cindex print messages when symbols are loaded
17251 @item set print symbol-loading
17252 @itemx set print symbol-loading full
17253 @itemx set print symbol-loading brief
17254 @itemx set print symbol-loading off
17255 The @code{set print symbol-loading} command allows you to control the
17256 printing of messages when @value{GDBN} loads symbol information.
17257 By default a message is printed for the executable and one for each
17258 shared library, and normally this is what you want. However, when
17259 debugging apps with large numbers of shared libraries these messages
17261 When set to @code{brief} a message is printed for each executable,
17262 and when @value{GDBN} loads a collection of shared libraries at once
17263 it will only print one message regardless of the number of shared
17264 libraries. When set to @code{off} no messages are printed.
17266 @kindex show print symbol-loading
17267 @item show print symbol-loading
17268 Show whether messages will be printed when a @value{GDBN} command
17269 entered from the keyboard causes symbol information to be loaded.
17271 @kindex maint print symbols
17272 @cindex symbol dump
17273 @kindex maint print psymbols
17274 @cindex partial symbol dump
17275 @kindex maint print msymbols
17276 @cindex minimal symbol dump
17277 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17278 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17279 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17280 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17281 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17282 Write a dump of debugging symbol data into the file @var{filename} or
17283 the terminal if @var{filename} is unspecified.
17284 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17286 If @code{-pc @var{address}} is specified, only dump symbols for the file
17287 with code at that address. Note that @var{address} may be a symbol like
17289 If @code{-source @var{source}} is specified, only dump symbols for that
17292 These commands are used to debug the @value{GDBN} symbol-reading code.
17293 These commands do not modify internal @value{GDBN} state, therefore
17294 @samp{maint print symbols} will only print symbols for already expanded symbol
17296 You can use the command @code{info sources} to find out which files these are.
17297 If you use @samp{maint print psymbols} instead, the dump shows information
17298 about symbols that @value{GDBN} only knows partially---that is, symbols
17299 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17300 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17303 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17304 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17306 @kindex maint info symtabs
17307 @kindex maint info psymtabs
17308 @cindex listing @value{GDBN}'s internal symbol tables
17309 @cindex symbol tables, listing @value{GDBN}'s internal
17310 @cindex full symbol tables, listing @value{GDBN}'s internal
17311 @cindex partial symbol tables, listing @value{GDBN}'s internal
17312 @item maint info symtabs @r{[} @var{regexp} @r{]}
17313 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17315 List the @code{struct symtab} or @code{struct partial_symtab}
17316 structures whose names match @var{regexp}. If @var{regexp} is not
17317 given, list them all. The output includes expressions which you can
17318 copy into a @value{GDBN} debugging this one to examine a particular
17319 structure in more detail. For example:
17322 (@value{GDBP}) maint info psymtabs dwarf2read
17323 @{ objfile /home/gnu/build/gdb/gdb
17324 ((struct objfile *) 0x82e69d0)
17325 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17326 ((struct partial_symtab *) 0x8474b10)
17329 text addresses 0x814d3c8 -- 0x8158074
17330 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17331 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17332 dependencies (none)
17335 (@value{GDBP}) maint info symtabs
17339 We see that there is one partial symbol table whose filename contains
17340 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17341 and we see that @value{GDBN} has not read in any symtabs yet at all.
17342 If we set a breakpoint on a function, that will cause @value{GDBN} to
17343 read the symtab for the compilation unit containing that function:
17346 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17347 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17349 (@value{GDBP}) maint info symtabs
17350 @{ objfile /home/gnu/build/gdb/gdb
17351 ((struct objfile *) 0x82e69d0)
17352 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17353 ((struct symtab *) 0x86c1f38)
17356 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17357 linetable ((struct linetable *) 0x8370fa0)
17358 debugformat DWARF 2
17364 @kindex maint info line-table
17365 @cindex listing @value{GDBN}'s internal line tables
17366 @cindex line tables, listing @value{GDBN}'s internal
17367 @item maint info line-table @r{[} @var{regexp} @r{]}
17369 List the @code{struct linetable} from all @code{struct symtab}
17370 instances whose name matches @var{regexp}. If @var{regexp} is not
17371 given, list the @code{struct linetable} from all @code{struct symtab}.
17373 @kindex maint set symbol-cache-size
17374 @cindex symbol cache size
17375 @item maint set symbol-cache-size @var{size}
17376 Set the size of the symbol cache to @var{size}.
17377 The default size is intended to be good enough for debugging
17378 most applications. This option exists to allow for experimenting
17379 with different sizes.
17381 @kindex maint show symbol-cache-size
17382 @item maint show symbol-cache-size
17383 Show the size of the symbol cache.
17385 @kindex maint print symbol-cache
17386 @cindex symbol cache, printing its contents
17387 @item maint print symbol-cache
17388 Print the contents of the symbol cache.
17389 This is useful when debugging symbol cache issues.
17391 @kindex maint print symbol-cache-statistics
17392 @cindex symbol cache, printing usage statistics
17393 @item maint print symbol-cache-statistics
17394 Print symbol cache usage statistics.
17395 This helps determine how well the cache is being utilized.
17397 @kindex maint flush-symbol-cache
17398 @cindex symbol cache, flushing
17399 @item maint flush-symbol-cache
17400 Flush the contents of the symbol cache, all entries are removed.
17401 This command is useful when debugging the symbol cache.
17402 It is also useful when collecting performance data.
17407 @chapter Altering Execution
17409 Once you think you have found an error in your program, you might want to
17410 find out for certain whether correcting the apparent error would lead to
17411 correct results in the rest of the run. You can find the answer by
17412 experiment, using the @value{GDBN} features for altering execution of the
17415 For example, you can store new values into variables or memory
17416 locations, give your program a signal, restart it at a different
17417 address, or even return prematurely from a function.
17420 * Assignment:: Assignment to variables
17421 * Jumping:: Continuing at a different address
17422 * Signaling:: Giving your program a signal
17423 * Returning:: Returning from a function
17424 * Calling:: Calling your program's functions
17425 * Patching:: Patching your program
17426 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17430 @section Assignment to Variables
17433 @cindex setting variables
17434 To alter the value of a variable, evaluate an assignment expression.
17435 @xref{Expressions, ,Expressions}. For example,
17442 stores the value 4 into the variable @code{x}, and then prints the
17443 value of the assignment expression (which is 4).
17444 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17445 information on operators in supported languages.
17447 @kindex set variable
17448 @cindex variables, setting
17449 If you are not interested in seeing the value of the assignment, use the
17450 @code{set} command instead of the @code{print} command. @code{set} is
17451 really the same as @code{print} except that the expression's value is
17452 not printed and is not put in the value history (@pxref{Value History,
17453 ,Value History}). The expression is evaluated only for its effects.
17455 If the beginning of the argument string of the @code{set} command
17456 appears identical to a @code{set} subcommand, use the @code{set
17457 variable} command instead of just @code{set}. This command is identical
17458 to @code{set} except for its lack of subcommands. For example, if your
17459 program has a variable @code{width}, you get an error if you try to set
17460 a new value with just @samp{set width=13}, because @value{GDBN} has the
17461 command @code{set width}:
17464 (@value{GDBP}) whatis width
17466 (@value{GDBP}) p width
17468 (@value{GDBP}) set width=47
17469 Invalid syntax in expression.
17473 The invalid expression, of course, is @samp{=47}. In
17474 order to actually set the program's variable @code{width}, use
17477 (@value{GDBP}) set var width=47
17480 Because the @code{set} command has many subcommands that can conflict
17481 with the names of program variables, it is a good idea to use the
17482 @code{set variable} command instead of just @code{set}. For example, if
17483 your program has a variable @code{g}, you run into problems if you try
17484 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17485 the command @code{set gnutarget}, abbreviated @code{set g}:
17489 (@value{GDBP}) whatis g
17493 (@value{GDBP}) set g=4
17497 The program being debugged has been started already.
17498 Start it from the beginning? (y or n) y
17499 Starting program: /home/smith/cc_progs/a.out
17500 "/home/smith/cc_progs/a.out": can't open to read symbols:
17501 Invalid bfd target.
17502 (@value{GDBP}) show g
17503 The current BFD target is "=4".
17508 The program variable @code{g} did not change, and you silently set the
17509 @code{gnutarget} to an invalid value. In order to set the variable
17513 (@value{GDBP}) set var g=4
17516 @value{GDBN} allows more implicit conversions in assignments than C; you can
17517 freely store an integer value into a pointer variable or vice versa,
17518 and you can convert any structure to any other structure that is the
17519 same length or shorter.
17520 @comment FIXME: how do structs align/pad in these conversions?
17521 @comment /doc@cygnus.com 18dec1990
17523 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17524 construct to generate a value of specified type at a specified address
17525 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17526 to memory location @code{0x83040} as an integer (which implies a certain size
17527 and representation in memory), and
17530 set @{int@}0x83040 = 4
17534 stores the value 4 into that memory location.
17537 @section Continuing at a Different Address
17539 Ordinarily, when you continue your program, you do so at the place where
17540 it stopped, with the @code{continue} command. You can instead continue at
17541 an address of your own choosing, with the following commands:
17545 @kindex j @r{(@code{jump})}
17546 @item jump @var{location}
17547 @itemx j @var{location}
17548 Resume execution at @var{location}. Execution stops again immediately
17549 if there is a breakpoint there. @xref{Specify Location}, for a description
17550 of the different forms of @var{location}. It is common
17551 practice to use the @code{tbreak} command in conjunction with
17552 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17554 The @code{jump} command does not change the current stack frame, or
17555 the stack pointer, or the contents of any memory location or any
17556 register other than the program counter. If @var{location} is in
17557 a different function from the one currently executing, the results may
17558 be bizarre if the two functions expect different patterns of arguments or
17559 of local variables. For this reason, the @code{jump} command requests
17560 confirmation if the specified line is not in the function currently
17561 executing. However, even bizarre results are predictable if you are
17562 well acquainted with the machine-language code of your program.
17565 On many systems, you can get much the same effect as the @code{jump}
17566 command by storing a new value into the register @code{$pc}. The
17567 difference is that this does not start your program running; it only
17568 changes the address of where it @emph{will} run when you continue. For
17576 makes the next @code{continue} command or stepping command execute at
17577 address @code{0x485}, rather than at the address where your program stopped.
17578 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17580 The most common occasion to use the @code{jump} command is to back
17581 up---perhaps with more breakpoints set---over a portion of a program
17582 that has already executed, in order to examine its execution in more
17587 @section Giving your Program a Signal
17588 @cindex deliver a signal to a program
17592 @item signal @var{signal}
17593 Resume execution where your program is stopped, but immediately give it the
17594 signal @var{signal}. The @var{signal} can be the name or the number of a
17595 signal. For example, on many systems @code{signal 2} and @code{signal
17596 SIGINT} are both ways of sending an interrupt signal.
17598 Alternatively, if @var{signal} is zero, continue execution without
17599 giving a signal. This is useful when your program stopped on account of
17600 a signal and would ordinarily see the signal when resumed with the
17601 @code{continue} command; @samp{signal 0} causes it to resume without a
17604 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17605 delivered to the currently selected thread, not the thread that last
17606 reported a stop. This includes the situation where a thread was
17607 stopped due to a signal. So if you want to continue execution
17608 suppressing the signal that stopped a thread, you should select that
17609 same thread before issuing the @samp{signal 0} command. If you issue
17610 the @samp{signal 0} command with another thread as the selected one,
17611 @value{GDBN} detects that and asks for confirmation.
17613 Invoking the @code{signal} command is not the same as invoking the
17614 @code{kill} utility from the shell. Sending a signal with @code{kill}
17615 causes @value{GDBN} to decide what to do with the signal depending on
17616 the signal handling tables (@pxref{Signals}). The @code{signal} command
17617 passes the signal directly to your program.
17619 @code{signal} does not repeat when you press @key{RET} a second time
17620 after executing the command.
17622 @kindex queue-signal
17623 @item queue-signal @var{signal}
17624 Queue @var{signal} to be delivered immediately to the current thread
17625 when execution of the thread resumes. The @var{signal} can be the name or
17626 the number of a signal. For example, on many systems @code{signal 2} and
17627 @code{signal SIGINT} are both ways of sending an interrupt signal.
17628 The handling of the signal must be set to pass the signal to the program,
17629 otherwise @value{GDBN} will report an error.
17630 You can control the handling of signals from @value{GDBN} with the
17631 @code{handle} command (@pxref{Signals}).
17633 Alternatively, if @var{signal} is zero, any currently queued signal
17634 for the current thread is discarded and when execution resumes no signal
17635 will be delivered. This is useful when your program stopped on account
17636 of a signal and would ordinarily see the signal when resumed with the
17637 @code{continue} command.
17639 This command differs from the @code{signal} command in that the signal
17640 is just queued, execution is not resumed. And @code{queue-signal} cannot
17641 be used to pass a signal whose handling state has been set to @code{nopass}
17646 @xref{stepping into signal handlers}, for information on how stepping
17647 commands behave when the thread has a signal queued.
17650 @section Returning from a Function
17653 @cindex returning from a function
17656 @itemx return @var{expression}
17657 You can cancel execution of a function call with the @code{return}
17658 command. If you give an
17659 @var{expression} argument, its value is used as the function's return
17663 When you use @code{return}, @value{GDBN} discards the selected stack frame
17664 (and all frames within it). You can think of this as making the
17665 discarded frame return prematurely. If you wish to specify a value to
17666 be returned, give that value as the argument to @code{return}.
17668 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17669 Frame}), and any other frames inside of it, leaving its caller as the
17670 innermost remaining frame. That frame becomes selected. The
17671 specified value is stored in the registers used for returning values
17674 The @code{return} command does not resume execution; it leaves the
17675 program stopped in the state that would exist if the function had just
17676 returned. In contrast, the @code{finish} command (@pxref{Continuing
17677 and Stepping, ,Continuing and Stepping}) resumes execution until the
17678 selected stack frame returns naturally.
17680 @value{GDBN} needs to know how the @var{expression} argument should be set for
17681 the inferior. The concrete registers assignment depends on the OS ABI and the
17682 type being returned by the selected stack frame. For example it is common for
17683 OS ABI to return floating point values in FPU registers while integer values in
17684 CPU registers. Still some ABIs return even floating point values in CPU
17685 registers. Larger integer widths (such as @code{long long int}) also have
17686 specific placement rules. @value{GDBN} already knows the OS ABI from its
17687 current target so it needs to find out also the type being returned to make the
17688 assignment into the right register(s).
17690 Normally, the selected stack frame has debug info. @value{GDBN} will always
17691 use the debug info instead of the implicit type of @var{expression} when the
17692 debug info is available. For example, if you type @kbd{return -1}, and the
17693 function in the current stack frame is declared to return a @code{long long
17694 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17695 into a @code{long long int}:
17698 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17700 (@value{GDBP}) return -1
17701 Make func return now? (y or n) y
17702 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17703 43 printf ("result=%lld\n", func ());
17707 However, if the selected stack frame does not have a debug info, e.g., if the
17708 function was compiled without debug info, @value{GDBN} has to find out the type
17709 to return from user. Specifying a different type by mistake may set the value
17710 in different inferior registers than the caller code expects. For example,
17711 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17712 of a @code{long long int} result for a debug info less function (on 32-bit
17713 architectures). Therefore the user is required to specify the return type by
17714 an appropriate cast explicitly:
17717 Breakpoint 2, 0x0040050b in func ()
17718 (@value{GDBP}) return -1
17719 Return value type not available for selected stack frame.
17720 Please use an explicit cast of the value to return.
17721 (@value{GDBP}) return (long long int) -1
17722 Make selected stack frame return now? (y or n) y
17723 #0 0x00400526 in main ()
17728 @section Calling Program Functions
17731 @cindex calling functions
17732 @cindex inferior functions, calling
17733 @item print @var{expr}
17734 Evaluate the expression @var{expr} and display the resulting value.
17735 The expression may include calls to functions in the program being
17739 @item call @var{expr}
17740 Evaluate the expression @var{expr} without displaying @code{void}
17743 You can use this variant of the @code{print} command if you want to
17744 execute a function from your program that does not return anything
17745 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17746 with @code{void} returned values that @value{GDBN} will otherwise
17747 print. If the result is not void, it is printed and saved in the
17751 It is possible for the function you call via the @code{print} or
17752 @code{call} command to generate a signal (e.g., if there's a bug in
17753 the function, or if you passed it incorrect arguments). What happens
17754 in that case is controlled by the @code{set unwindonsignal} command.
17756 Similarly, with a C@t{++} program it is possible for the function you
17757 call via the @code{print} or @code{call} command to generate an
17758 exception that is not handled due to the constraints of the dummy
17759 frame. In this case, any exception that is raised in the frame, but has
17760 an out-of-frame exception handler will not be found. GDB builds a
17761 dummy-frame for the inferior function call, and the unwinder cannot
17762 seek for exception handlers outside of this dummy-frame. What happens
17763 in that case is controlled by the
17764 @code{set unwind-on-terminating-exception} command.
17767 @item set unwindonsignal
17768 @kindex set unwindonsignal
17769 @cindex unwind stack in called functions
17770 @cindex call dummy stack unwinding
17771 Set unwinding of the stack if a signal is received while in a function
17772 that @value{GDBN} called in the program being debugged. If set to on,
17773 @value{GDBN} unwinds the stack it created for the call and restores
17774 the context to what it was before the call. If set to off (the
17775 default), @value{GDBN} stops in the frame where the signal was
17778 @item show unwindonsignal
17779 @kindex show unwindonsignal
17780 Show the current setting of stack unwinding in the functions called by
17783 @item set unwind-on-terminating-exception
17784 @kindex set unwind-on-terminating-exception
17785 @cindex unwind stack in called functions with unhandled exceptions
17786 @cindex call dummy stack unwinding on unhandled exception.
17787 Set unwinding of the stack if a C@t{++} exception is raised, but left
17788 unhandled while in a function that @value{GDBN} called in the program being
17789 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17790 it created for the call and restores the context to what it was before
17791 the call. If set to off, @value{GDBN} the exception is delivered to
17792 the default C@t{++} exception handler and the inferior terminated.
17794 @item show unwind-on-terminating-exception
17795 @kindex show unwind-on-terminating-exception
17796 Show the current setting of stack unwinding in the functions called by
17801 @cindex weak alias functions
17802 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17803 for another function. In such case, @value{GDBN} might not pick up
17804 the type information, including the types of the function arguments,
17805 which causes @value{GDBN} to call the inferior function incorrectly.
17806 As a result, the called function will function erroneously and may
17807 even crash. A solution to that is to use the name of the aliased
17811 @section Patching Programs
17813 @cindex patching binaries
17814 @cindex writing into executables
17815 @cindex writing into corefiles
17817 By default, @value{GDBN} opens the file containing your program's
17818 executable code (or the corefile) read-only. This prevents accidental
17819 alterations to machine code; but it also prevents you from intentionally
17820 patching your program's binary.
17822 If you'd like to be able to patch the binary, you can specify that
17823 explicitly with the @code{set write} command. For example, you might
17824 want to turn on internal debugging flags, or even to make emergency
17830 @itemx set write off
17831 If you specify @samp{set write on}, @value{GDBN} opens executable and
17832 core files for both reading and writing; if you specify @kbd{set write
17833 off} (the default), @value{GDBN} opens them read-only.
17835 If you have already loaded a file, you must load it again (using the
17836 @code{exec-file} or @code{core-file} command) after changing @code{set
17837 write}, for your new setting to take effect.
17841 Display whether executable files and core files are opened for writing
17842 as well as reading.
17845 @node Compiling and Injecting Code
17846 @section Compiling and injecting code in @value{GDBN}
17847 @cindex injecting code
17848 @cindex writing into executables
17849 @cindex compiling code
17851 @value{GDBN} supports on-demand compilation and code injection into
17852 programs running under @value{GDBN}. GCC 5.0 or higher built with
17853 @file{libcc1.so} must be installed for this functionality to be enabled.
17854 This functionality is implemented with the following commands.
17857 @kindex compile code
17858 @item compile code @var{source-code}
17859 @itemx compile code -raw @var{--} @var{source-code}
17860 Compile @var{source-code} with the compiler language found as the current
17861 language in @value{GDBN} (@pxref{Languages}). If compilation and
17862 injection is not supported with the current language specified in
17863 @value{GDBN}, or the compiler does not support this feature, an error
17864 message will be printed. If @var{source-code} compiles and links
17865 successfully, @value{GDBN} will load the object-code emitted,
17866 and execute it within the context of the currently selected inferior.
17867 It is important to note that the compiled code is executed immediately.
17868 After execution, the compiled code is removed from @value{GDBN} and any
17869 new types or variables you have defined will be deleted.
17871 The command allows you to specify @var{source-code} in two ways.
17872 The simplest method is to provide a single line of code to the command.
17876 compile code printf ("hello world\n");
17879 If you specify options on the command line as well as source code, they
17880 may conflict. The @samp{--} delimiter can be used to separate options
17881 from actual source code. E.g.:
17884 compile code -r -- printf ("hello world\n");
17887 Alternatively you can enter source code as multiple lines of text. To
17888 enter this mode, invoke the @samp{compile code} command without any text
17889 following the command. This will start the multiple-line editor and
17890 allow you to type as many lines of source code as required. When you
17891 have completed typing, enter @samp{end} on its own line to exit the
17896 >printf ("hello\n");
17897 >printf ("world\n");
17901 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17902 provided @var{source-code} in a callable scope. In this case, you must
17903 specify the entry point of the code by defining a function named
17904 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17905 inferior. Using @samp{-raw} option may be needed for example when
17906 @var{source-code} requires @samp{#include} lines which may conflict with
17907 inferior symbols otherwise.
17909 @kindex compile file
17910 @item compile file @var{filename}
17911 @itemx compile file -raw @var{filename}
17912 Like @code{compile code}, but take the source code from @var{filename}.
17915 compile file /home/user/example.c
17920 @item compile print @var{expr}
17921 @itemx compile print /@var{f} @var{expr}
17922 Compile and execute @var{expr} with the compiler language found as the
17923 current language in @value{GDBN} (@pxref{Languages}). By default the
17924 value of @var{expr} is printed in a format appropriate to its data type;
17925 you can choose a different format by specifying @samp{/@var{f}}, where
17926 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17929 @item compile print
17930 @itemx compile print /@var{f}
17931 @cindex reprint the last value
17932 Alternatively you can enter the expression (source code producing it) as
17933 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17934 command without any text following the command. This will start the
17935 multiple-line editor.
17939 The process of compiling and injecting the code can be inspected using:
17942 @anchor{set debug compile}
17943 @item set debug compile
17944 @cindex compile command debugging info
17945 Turns on or off display of @value{GDBN} process of compiling and
17946 injecting the code. The default is off.
17948 @item show debug compile
17949 Displays the current state of displaying @value{GDBN} process of
17950 compiling and injecting the code.
17953 @subsection Compilation options for the @code{compile} command
17955 @value{GDBN} needs to specify the right compilation options for the code
17956 to be injected, in part to make its ABI compatible with the inferior
17957 and in part to make the injected code compatible with @value{GDBN}'s
17961 The options used, in increasing precedence:
17964 @item target architecture and OS options (@code{gdbarch})
17965 These options depend on target processor type and target operating
17966 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17967 (@code{-m64}) compilation option.
17969 @item compilation options recorded in the target
17970 @value{NGCC} (since version 4.7) stores the options used for compilation
17971 into @code{DW_AT_producer} part of DWARF debugging information according
17972 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17973 explicitly specify @code{-g} during inferior compilation otherwise
17974 @value{NGCC} produces no DWARF. This feature is only relevant for
17975 platforms where @code{-g} produces DWARF by default, otherwise one may
17976 try to enforce DWARF by using @code{-gdwarf-4}.
17978 @item compilation options set by @code{set compile-args}
17982 You can override compilation options using the following command:
17985 @item set compile-args
17986 @cindex compile command options override
17987 Set compilation options used for compiling and injecting code with the
17988 @code{compile} commands. These options override any conflicting ones
17989 from the target architecture and/or options stored during inferior
17992 @item show compile-args
17993 Displays the current state of compilation options override.
17994 This does not show all the options actually used during compilation,
17995 use @ref{set debug compile} for that.
17998 @subsection Caveats when using the @code{compile} command
18000 There are a few caveats to keep in mind when using the @code{compile}
18001 command. As the caveats are different per language, the table below
18002 highlights specific issues on a per language basis.
18005 @item C code examples and caveats
18006 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18007 attempt to compile the source code with a @samp{C} compiler. The source
18008 code provided to the @code{compile} command will have much the same
18009 access to variables and types as it normally would if it were part of
18010 the program currently being debugged in @value{GDBN}.
18012 Below is a sample program that forms the basis of the examples that
18013 follow. This program has been compiled and loaded into @value{GDBN},
18014 much like any other normal debugging session.
18017 void function1 (void)
18020 printf ("function 1\n");
18023 void function2 (void)
18038 For the purposes of the examples in this section, the program above has
18039 been compiled, loaded into @value{GDBN}, stopped at the function
18040 @code{main}, and @value{GDBN} is awaiting input from the user.
18042 To access variables and types for any program in @value{GDBN}, the
18043 program must be compiled and packaged with debug information. The
18044 @code{compile} command is not an exception to this rule. Without debug
18045 information, you can still use the @code{compile} command, but you will
18046 be very limited in what variables and types you can access.
18048 So with that in mind, the example above has been compiled with debug
18049 information enabled. The @code{compile} command will have access to
18050 all variables and types (except those that may have been optimized
18051 out). Currently, as @value{GDBN} has stopped the program in the
18052 @code{main} function, the @code{compile} command would have access to
18053 the variable @code{k}. You could invoke the @code{compile} command
18054 and type some source code to set the value of @code{k}. You can also
18055 read it, or do anything with that variable you would normally do in
18056 @code{C}. Be aware that changes to inferior variables in the
18057 @code{compile} command are persistent. In the following example:
18060 compile code k = 3;
18064 the variable @code{k} is now 3. It will retain that value until
18065 something else in the example program changes it, or another
18066 @code{compile} command changes it.
18068 Normal scope and access rules apply to source code compiled and
18069 injected by the @code{compile} command. In the example, the variables
18070 @code{j} and @code{k} are not accessible yet, because the program is
18071 currently stopped in the @code{main} function, where these variables
18072 are not in scope. Therefore, the following command
18075 compile code j = 3;
18079 will result in a compilation error message.
18081 Once the program is continued, execution will bring these variables in
18082 scope, and they will become accessible; then the code you specify via
18083 the @code{compile} command will be able to access them.
18085 You can create variables and types with the @code{compile} command as
18086 part of your source code. Variables and types that are created as part
18087 of the @code{compile} command are not visible to the rest of the program for
18088 the duration of its run. This example is valid:
18091 compile code int ff = 5; printf ("ff is %d\n", ff);
18094 However, if you were to type the following into @value{GDBN} after that
18095 command has completed:
18098 compile code printf ("ff is %d\n'', ff);
18102 a compiler error would be raised as the variable @code{ff} no longer
18103 exists. Object code generated and injected by the @code{compile}
18104 command is removed when its execution ends. Caution is advised
18105 when assigning to program variables values of variables created by the
18106 code submitted to the @code{compile} command. This example is valid:
18109 compile code int ff = 5; k = ff;
18112 The value of the variable @code{ff} is assigned to @code{k}. The variable
18113 @code{k} does not require the existence of @code{ff} to maintain the value
18114 it has been assigned. However, pointers require particular care in
18115 assignment. If the source code compiled with the @code{compile} command
18116 changed the address of a pointer in the example program, perhaps to a
18117 variable created in the @code{compile} command, that pointer would point
18118 to an invalid location when the command exits. The following example
18119 would likely cause issues with your debugged program:
18122 compile code int ff = 5; p = &ff;
18125 In this example, @code{p} would point to @code{ff} when the
18126 @code{compile} command is executing the source code provided to it.
18127 However, as variables in the (example) program persist with their
18128 assigned values, the variable @code{p} would point to an invalid
18129 location when the command exists. A general rule should be followed
18130 in that you should either assign @code{NULL} to any assigned pointers,
18131 or restore a valid location to the pointer before the command exits.
18133 Similar caution must be exercised with any structs, unions, and typedefs
18134 defined in @code{compile} command. Types defined in the @code{compile}
18135 command will no longer be available in the next @code{compile} command.
18136 Therefore, if you cast a variable to a type defined in the
18137 @code{compile} command, care must be taken to ensure that any future
18138 need to resolve the type can be achieved.
18141 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18142 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18143 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18144 Compilation failed.
18145 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18149 Variables that have been optimized away by the compiler are not
18150 accessible to the code submitted to the @code{compile} command.
18151 Access to those variables will generate a compiler error which @value{GDBN}
18152 will print to the console.
18155 @subsection Compiler search for the @code{compile} command
18157 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18158 which may not be obvious for remote targets of different architecture
18159 than where @value{GDBN} is running. Environment variable @code{PATH} on
18160 @value{GDBN} host is searched for @value{NGCC} binary matching the
18161 target architecture and operating system. This search can be overriden
18162 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18163 taken from shell that executed @value{GDBN}, it is not the value set by
18164 @value{GDBN} command @code{set environment}). @xref{Environment}.
18167 Specifically @code{PATH} is searched for binaries matching regular expression
18168 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18169 debugged. @var{arch} is processor name --- multiarch is supported, so for
18170 example both @code{i386} and @code{x86_64} targets look for pattern
18171 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18172 for pattern @code{s390x?}. @var{os} is currently supported only for
18173 pattern @code{linux(-gnu)?}.
18175 On Posix hosts the compiler driver @value{GDBN} needs to find also
18176 shared library @file{libcc1.so} from the compiler. It is searched in
18177 default shared library search path (overridable with usual environment
18178 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18179 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18180 according to the installation of the found compiler --- as possibly
18181 specified by the @code{set compile-gcc} command.
18184 @item set compile-gcc
18185 @cindex compile command driver filename override
18186 Set compilation command used for compiling and injecting code with the
18187 @code{compile} commands. If this option is not set (it is set to
18188 an empty string), the search described above will occur --- that is the
18191 @item show compile-gcc
18192 Displays the current compile command @value{NGCC} driver filename.
18193 If set, it is the main command @command{gcc}, found usually for example
18194 under name @file{x86_64-linux-gnu-gcc}.
18198 @chapter @value{GDBN} Files
18200 @value{GDBN} needs to know the file name of the program to be debugged,
18201 both in order to read its symbol table and in order to start your
18202 program. To debug a core dump of a previous run, you must also tell
18203 @value{GDBN} the name of the core dump file.
18206 * Files:: Commands to specify files
18207 * File Caching:: Information about @value{GDBN}'s file caching
18208 * Separate Debug Files:: Debugging information in separate files
18209 * MiniDebugInfo:: Debugging information in a special section
18210 * Index Files:: Index files speed up GDB
18211 * Symbol Errors:: Errors reading symbol files
18212 * Data Files:: GDB data files
18216 @section Commands to Specify Files
18218 @cindex symbol table
18219 @cindex core dump file
18221 You may want to specify executable and core dump file names. The usual
18222 way to do this is at start-up time, using the arguments to
18223 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18224 Out of @value{GDBN}}).
18226 Occasionally it is necessary to change to a different file during a
18227 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18228 specify a file you want to use. Or you are debugging a remote target
18229 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18230 Program}). In these situations the @value{GDBN} commands to specify
18231 new files are useful.
18234 @cindex executable file
18236 @item file @var{filename}
18237 Use @var{filename} as the program to be debugged. It is read for its
18238 symbols and for the contents of pure memory. It is also the program
18239 executed when you use the @code{run} command. If you do not specify a
18240 directory and the file is not found in the @value{GDBN} working directory,
18241 @value{GDBN} uses the environment variable @code{PATH} as a list of
18242 directories to search, just as the shell does when looking for a program
18243 to run. You can change the value of this variable, for both @value{GDBN}
18244 and your program, using the @code{path} command.
18246 @cindex unlinked object files
18247 @cindex patching object files
18248 You can load unlinked object @file{.o} files into @value{GDBN} using
18249 the @code{file} command. You will not be able to ``run'' an object
18250 file, but you can disassemble functions and inspect variables. Also,
18251 if the underlying BFD functionality supports it, you could use
18252 @kbd{gdb -write} to patch object files using this technique. Note
18253 that @value{GDBN} can neither interpret nor modify relocations in this
18254 case, so branches and some initialized variables will appear to go to
18255 the wrong place. But this feature is still handy from time to time.
18258 @code{file} with no argument makes @value{GDBN} discard any information it
18259 has on both executable file and the symbol table.
18262 @item exec-file @r{[} @var{filename} @r{]}
18263 Specify that the program to be run (but not the symbol table) is found
18264 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18265 if necessary to locate your program. Omitting @var{filename} means to
18266 discard information on the executable file.
18268 @kindex symbol-file
18269 @item symbol-file @r{[} @var{filename} @r{]}
18270 Read symbol table information from file @var{filename}. @code{PATH} is
18271 searched when necessary. Use the @code{file} command to get both symbol
18272 table and program to run from the same file.
18274 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18275 program's symbol table.
18277 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18278 some breakpoints and auto-display expressions. This is because they may
18279 contain pointers to the internal data recording symbols and data types,
18280 which are part of the old symbol table data being discarded inside
18283 @code{symbol-file} does not repeat if you press @key{RET} again after
18286 When @value{GDBN} is configured for a particular environment, it
18287 understands debugging information in whatever format is the standard
18288 generated for that environment; you may use either a @sc{gnu} compiler, or
18289 other compilers that adhere to the local conventions.
18290 Best results are usually obtained from @sc{gnu} compilers; for example,
18291 using @code{@value{NGCC}} you can generate debugging information for
18294 For most kinds of object files, with the exception of old SVR3 systems
18295 using COFF, the @code{symbol-file} command does not normally read the
18296 symbol table in full right away. Instead, it scans the symbol table
18297 quickly to find which source files and which symbols are present. The
18298 details are read later, one source file at a time, as they are needed.
18300 The purpose of this two-stage reading strategy is to make @value{GDBN}
18301 start up faster. For the most part, it is invisible except for
18302 occasional pauses while the symbol table details for a particular source
18303 file are being read. (The @code{set verbose} command can turn these
18304 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18305 Warnings and Messages}.)
18307 We have not implemented the two-stage strategy for COFF yet. When the
18308 symbol table is stored in COFF format, @code{symbol-file} reads the
18309 symbol table data in full right away. Note that ``stabs-in-COFF''
18310 still does the two-stage strategy, since the debug info is actually
18314 @cindex reading symbols immediately
18315 @cindex symbols, reading immediately
18316 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18317 @itemx file @r{[} -readnow @r{]} @var{filename}
18318 You can override the @value{GDBN} two-stage strategy for reading symbol
18319 tables by using the @samp{-readnow} option with any of the commands that
18320 load symbol table information, if you want to be sure @value{GDBN} has the
18321 entire symbol table available.
18323 @c FIXME: for now no mention of directories, since this seems to be in
18324 @c flux. 13mar1992 status is that in theory GDB would look either in
18325 @c current dir or in same dir as myprog; but issues like competing
18326 @c GDB's, or clutter in system dirs, mean that in practice right now
18327 @c only current dir is used. FFish says maybe a special GDB hierarchy
18328 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18332 @item core-file @r{[}@var{filename}@r{]}
18334 Specify the whereabouts of a core dump file to be used as the ``contents
18335 of memory''. Traditionally, core files contain only some parts of the
18336 address space of the process that generated them; @value{GDBN} can access the
18337 executable file itself for other parts.
18339 @code{core-file} with no argument specifies that no core file is
18342 Note that the core file is ignored when your program is actually running
18343 under @value{GDBN}. So, if you have been running your program and you
18344 wish to debug a core file instead, you must kill the subprocess in which
18345 the program is running. To do this, use the @code{kill} command
18346 (@pxref{Kill Process, ,Killing the Child Process}).
18348 @kindex add-symbol-file
18349 @cindex dynamic linking
18350 @item add-symbol-file @var{filename} @var{address}
18351 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18352 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18353 The @code{add-symbol-file} command reads additional symbol table
18354 information from the file @var{filename}. You would use this command
18355 when @var{filename} has been dynamically loaded (by some other means)
18356 into the program that is running. The @var{address} should give the memory
18357 address at which the file has been loaded; @value{GDBN} cannot figure
18358 this out for itself. You can additionally specify an arbitrary number
18359 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18360 section name and base address for that section. You can specify any
18361 @var{address} as an expression.
18363 The symbol table of the file @var{filename} is added to the symbol table
18364 originally read with the @code{symbol-file} command. You can use the
18365 @code{add-symbol-file} command any number of times; the new symbol data
18366 thus read is kept in addition to the old.
18368 Changes can be reverted using the command @code{remove-symbol-file}.
18370 @cindex relocatable object files, reading symbols from
18371 @cindex object files, relocatable, reading symbols from
18372 @cindex reading symbols from relocatable object files
18373 @cindex symbols, reading from relocatable object files
18374 @cindex @file{.o} files, reading symbols from
18375 Although @var{filename} is typically a shared library file, an
18376 executable file, or some other object file which has been fully
18377 relocated for loading into a process, you can also load symbolic
18378 information from relocatable @file{.o} files, as long as:
18382 the file's symbolic information refers only to linker symbols defined in
18383 that file, not to symbols defined by other object files,
18385 every section the file's symbolic information refers to has actually
18386 been loaded into the inferior, as it appears in the file, and
18388 you can determine the address at which every section was loaded, and
18389 provide these to the @code{add-symbol-file} command.
18393 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18394 relocatable files into an already running program; such systems
18395 typically make the requirements above easy to meet. However, it's
18396 important to recognize that many native systems use complex link
18397 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18398 assembly, for example) that make the requirements difficult to meet. In
18399 general, one cannot assume that using @code{add-symbol-file} to read a
18400 relocatable object file's symbolic information will have the same effect
18401 as linking the relocatable object file into the program in the normal
18404 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18406 @kindex remove-symbol-file
18407 @item remove-symbol-file @var{filename}
18408 @item remove-symbol-file -a @var{address}
18409 Remove a symbol file added via the @code{add-symbol-file} command. The
18410 file to remove can be identified by its @var{filename} or by an @var{address}
18411 that lies within the boundaries of this symbol file in memory. Example:
18414 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18415 add symbol table from file "/home/user/gdb/mylib.so" at
18416 .text_addr = 0x7ffff7ff9480
18418 Reading symbols from /home/user/gdb/mylib.so...done.
18419 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18420 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18425 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18427 @kindex add-symbol-file-from-memory
18428 @cindex @code{syscall DSO}
18429 @cindex load symbols from memory
18430 @item add-symbol-file-from-memory @var{address}
18431 Load symbols from the given @var{address} in a dynamically loaded
18432 object file whose image is mapped directly into the inferior's memory.
18433 For example, the Linux kernel maps a @code{syscall DSO} into each
18434 process's address space; this DSO provides kernel-specific code for
18435 some system calls. The argument can be any expression whose
18436 evaluation yields the address of the file's shared object file header.
18437 For this command to work, you must have used @code{symbol-file} or
18438 @code{exec-file} commands in advance.
18441 @item section @var{section} @var{addr}
18442 The @code{section} command changes the base address of the named
18443 @var{section} of the exec file to @var{addr}. This can be used if the
18444 exec file does not contain section addresses, (such as in the
18445 @code{a.out} format), or when the addresses specified in the file
18446 itself are wrong. Each section must be changed separately. The
18447 @code{info files} command, described below, lists all the sections and
18451 @kindex info target
18454 @code{info files} and @code{info target} are synonymous; both print the
18455 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18456 including the names of the executable and core dump files currently in
18457 use by @value{GDBN}, and the files from which symbols were loaded. The
18458 command @code{help target} lists all possible targets rather than
18461 @kindex maint info sections
18462 @item maint info sections
18463 Another command that can give you extra information about program sections
18464 is @code{maint info sections}. In addition to the section information
18465 displayed by @code{info files}, this command displays the flags and file
18466 offset of each section in the executable and core dump files. In addition,
18467 @code{maint info sections} provides the following command options (which
18468 may be arbitrarily combined):
18472 Display sections for all loaded object files, including shared libraries.
18473 @item @var{sections}
18474 Display info only for named @var{sections}.
18475 @item @var{section-flags}
18476 Display info only for sections for which @var{section-flags} are true.
18477 The section flags that @value{GDBN} currently knows about are:
18480 Section will have space allocated in the process when loaded.
18481 Set for all sections except those containing debug information.
18483 Section will be loaded from the file into the child process memory.
18484 Set for pre-initialized code and data, clear for @code{.bss} sections.
18486 Section needs to be relocated before loading.
18488 Section cannot be modified by the child process.
18490 Section contains executable code only.
18492 Section contains data only (no executable code).
18494 Section will reside in ROM.
18496 Section contains data for constructor/destructor lists.
18498 Section is not empty.
18500 An instruction to the linker to not output the section.
18501 @item COFF_SHARED_LIBRARY
18502 A notification to the linker that the section contains
18503 COFF shared library information.
18505 Section contains common symbols.
18508 @kindex set trust-readonly-sections
18509 @cindex read-only sections
18510 @item set trust-readonly-sections on
18511 Tell @value{GDBN} that readonly sections in your object file
18512 really are read-only (i.e.@: that their contents will not change).
18513 In that case, @value{GDBN} can fetch values from these sections
18514 out of the object file, rather than from the target program.
18515 For some targets (notably embedded ones), this can be a significant
18516 enhancement to debugging performance.
18518 The default is off.
18520 @item set trust-readonly-sections off
18521 Tell @value{GDBN} not to trust readonly sections. This means that
18522 the contents of the section might change while the program is running,
18523 and must therefore be fetched from the target when needed.
18525 @item show trust-readonly-sections
18526 Show the current setting of trusting readonly sections.
18529 All file-specifying commands allow both absolute and relative file names
18530 as arguments. @value{GDBN} always converts the file name to an absolute file
18531 name and remembers it that way.
18533 @cindex shared libraries
18534 @anchor{Shared Libraries}
18535 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18536 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18537 DSBT (TIC6X) shared libraries.
18539 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18540 shared libraries. @xref{Expat}.
18542 @value{GDBN} automatically loads symbol definitions from shared libraries
18543 when you use the @code{run} command, or when you examine a core file.
18544 (Before you issue the @code{run} command, @value{GDBN} does not understand
18545 references to a function in a shared library, however---unless you are
18546 debugging a core file).
18548 @c FIXME: some @value{GDBN} release may permit some refs to undef
18549 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18550 @c FIXME...lib; check this from time to time when updating manual
18552 There are times, however, when you may wish to not automatically load
18553 symbol definitions from shared libraries, such as when they are
18554 particularly large or there are many of them.
18556 To control the automatic loading of shared library symbols, use the
18560 @kindex set auto-solib-add
18561 @item set auto-solib-add @var{mode}
18562 If @var{mode} is @code{on}, symbols from all shared object libraries
18563 will be loaded automatically when the inferior begins execution, you
18564 attach to an independently started inferior, or when the dynamic linker
18565 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18566 is @code{off}, symbols must be loaded manually, using the
18567 @code{sharedlibrary} command. The default value is @code{on}.
18569 @cindex memory used for symbol tables
18570 If your program uses lots of shared libraries with debug info that
18571 takes large amounts of memory, you can decrease the @value{GDBN}
18572 memory footprint by preventing it from automatically loading the
18573 symbols from shared libraries. To that end, type @kbd{set
18574 auto-solib-add off} before running the inferior, then load each
18575 library whose debug symbols you do need with @kbd{sharedlibrary
18576 @var{regexp}}, where @var{regexp} is a regular expression that matches
18577 the libraries whose symbols you want to be loaded.
18579 @kindex show auto-solib-add
18580 @item show auto-solib-add
18581 Display the current autoloading mode.
18584 @cindex load shared library
18585 To explicitly load shared library symbols, use the @code{sharedlibrary}
18589 @kindex info sharedlibrary
18591 @item info share @var{regex}
18592 @itemx info sharedlibrary @var{regex}
18593 Print the names of the shared libraries which are currently loaded
18594 that match @var{regex}. If @var{regex} is omitted then print
18595 all shared libraries that are loaded.
18598 @item info dll @var{regex}
18599 This is an alias of @code{info sharedlibrary}.
18601 @kindex sharedlibrary
18603 @item sharedlibrary @var{regex}
18604 @itemx share @var{regex}
18605 Load shared object library symbols for files matching a
18606 Unix regular expression.
18607 As with files loaded automatically, it only loads shared libraries
18608 required by your program for a core file or after typing @code{run}. If
18609 @var{regex} is omitted all shared libraries required by your program are
18612 @item nosharedlibrary
18613 @kindex nosharedlibrary
18614 @cindex unload symbols from shared libraries
18615 Unload all shared object library symbols. This discards all symbols
18616 that have been loaded from all shared libraries. Symbols from shared
18617 libraries that were loaded by explicit user requests are not
18621 Sometimes you may wish that @value{GDBN} stops and gives you control
18622 when any of shared library events happen. The best way to do this is
18623 to use @code{catch load} and @code{catch unload} (@pxref{Set
18626 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18627 command for this. This command exists for historical reasons. It is
18628 less useful than setting a catchpoint, because it does not allow for
18629 conditions or commands as a catchpoint does.
18632 @item set stop-on-solib-events
18633 @kindex set stop-on-solib-events
18634 This command controls whether @value{GDBN} should give you control
18635 when the dynamic linker notifies it about some shared library event.
18636 The most common event of interest is loading or unloading of a new
18639 @item show stop-on-solib-events
18640 @kindex show stop-on-solib-events
18641 Show whether @value{GDBN} stops and gives you control when shared
18642 library events happen.
18645 Shared libraries are also supported in many cross or remote debugging
18646 configurations. @value{GDBN} needs to have access to the target's libraries;
18647 this can be accomplished either by providing copies of the libraries
18648 on the host system, or by asking @value{GDBN} to automatically retrieve the
18649 libraries from the target. If copies of the target libraries are
18650 provided, they need to be the same as the target libraries, although the
18651 copies on the target can be stripped as long as the copies on the host are
18654 @cindex where to look for shared libraries
18655 For remote debugging, you need to tell @value{GDBN} where the target
18656 libraries are, so that it can load the correct copies---otherwise, it
18657 may try to load the host's libraries. @value{GDBN} has two variables
18658 to specify the search directories for target libraries.
18661 @cindex prefix for executable and shared library file names
18662 @cindex system root, alternate
18663 @kindex set solib-absolute-prefix
18664 @kindex set sysroot
18665 @item set sysroot @var{path}
18666 Use @var{path} as the system root for the program being debugged. Any
18667 absolute shared library paths will be prefixed with @var{path}; many
18668 runtime loaders store the absolute paths to the shared library in the
18669 target program's memory. When starting processes remotely, and when
18670 attaching to already-running processes (local or remote), their
18671 executable filenames will be prefixed with @var{path} if reported to
18672 @value{GDBN} as absolute by the operating system. If you use
18673 @code{set sysroot} to find executables and shared libraries, they need
18674 to be laid out in the same way that they are on the target, with
18675 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18678 If @var{path} starts with the sequence @file{target:} and the target
18679 system is remote then @value{GDBN} will retrieve the target binaries
18680 from the remote system. This is only supported when using a remote
18681 target that supports the @code{remote get} command (@pxref{File
18682 Transfer,,Sending files to a remote system}). The part of @var{path}
18683 following the initial @file{target:} (if present) is used as system
18684 root prefix on the remote file system. If @var{path} starts with the
18685 sequence @file{remote:} this is converted to the sequence
18686 @file{target:} by @code{set sysroot}@footnote{Historically the
18687 functionality to retrieve binaries from the remote system was
18688 provided by prefixing @var{path} with @file{remote:}}. If you want
18689 to specify a local system root using a directory that happens to be
18690 named @file{target:} or @file{remote:}, you need to use some
18691 equivalent variant of the name like @file{./target:}.
18693 For targets with an MS-DOS based filesystem, such as MS-Windows and
18694 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18695 absolute file name with @var{path}. But first, on Unix hosts,
18696 @value{GDBN} converts all backslash directory separators into forward
18697 slashes, because the backslash is not a directory separator on Unix:
18700 c:\foo\bar.dll @result{} c:/foo/bar.dll
18703 Then, @value{GDBN} attempts prefixing the target file name with
18704 @var{path}, and looks for the resulting file name in the host file
18708 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18711 If that does not find the binary, @value{GDBN} tries removing
18712 the @samp{:} character from the drive spec, both for convenience, and,
18713 for the case of the host file system not supporting file names with
18717 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18720 This makes it possible to have a system root that mirrors a target
18721 with more than one drive. E.g., you may want to setup your local
18722 copies of the target system shared libraries like so (note @samp{c} vs
18726 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18727 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18728 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18732 and point the system root at @file{/path/to/sysroot}, so that
18733 @value{GDBN} can find the correct copies of both
18734 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18736 If that still does not find the binary, @value{GDBN} tries
18737 removing the whole drive spec from the target file name:
18740 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18743 This last lookup makes it possible to not care about the drive name,
18744 if you don't want or need to.
18746 The @code{set solib-absolute-prefix} command is an alias for @code{set
18749 @cindex default system root
18750 @cindex @samp{--with-sysroot}
18751 You can set the default system root by using the configure-time
18752 @samp{--with-sysroot} option. If the system root is inside
18753 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18754 @samp{--exec-prefix}), then the default system root will be updated
18755 automatically if the installed @value{GDBN} is moved to a new
18758 @kindex show sysroot
18760 Display the current executable and shared library prefix.
18762 @kindex set solib-search-path
18763 @item set solib-search-path @var{path}
18764 If this variable is set, @var{path} is a colon-separated list of
18765 directories to search for shared libraries. @samp{solib-search-path}
18766 is used after @samp{sysroot} fails to locate the library, or if the
18767 path to the library is relative instead of absolute. If you want to
18768 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18769 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18770 finding your host's libraries. @samp{sysroot} is preferred; setting
18771 it to a nonexistent directory may interfere with automatic loading
18772 of shared library symbols.
18774 @kindex show solib-search-path
18775 @item show solib-search-path
18776 Display the current shared library search path.
18778 @cindex DOS file-name semantics of file names.
18779 @kindex set target-file-system-kind (unix|dos-based|auto)
18780 @kindex show target-file-system-kind
18781 @item set target-file-system-kind @var{kind}
18782 Set assumed file system kind for target reported file names.
18784 Shared library file names as reported by the target system may not
18785 make sense as is on the system @value{GDBN} is running on. For
18786 example, when remote debugging a target that has MS-DOS based file
18787 system semantics, from a Unix host, the target may be reporting to
18788 @value{GDBN} a list of loaded shared libraries with file names such as
18789 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18790 drive letters, so the @samp{c:\} prefix is not normally understood as
18791 indicating an absolute file name, and neither is the backslash
18792 normally considered a directory separator character. In that case,
18793 the native file system would interpret this whole absolute file name
18794 as a relative file name with no directory components. This would make
18795 it impossible to point @value{GDBN} at a copy of the remote target's
18796 shared libraries on the host using @code{set sysroot}, and impractical
18797 with @code{set solib-search-path}. Setting
18798 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18799 to interpret such file names similarly to how the target would, and to
18800 map them to file names valid on @value{GDBN}'s native file system
18801 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18802 to one of the supported file system kinds. In that case, @value{GDBN}
18803 tries to determine the appropriate file system variant based on the
18804 current target's operating system (@pxref{ABI, ,Configuring the
18805 Current ABI}). The supported file system settings are:
18809 Instruct @value{GDBN} to assume the target file system is of Unix
18810 kind. Only file names starting the forward slash (@samp{/}) character
18811 are considered absolute, and the directory separator character is also
18815 Instruct @value{GDBN} to assume the target file system is DOS based.
18816 File names starting with either a forward slash, or a drive letter
18817 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18818 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18819 considered directory separators.
18822 Instruct @value{GDBN} to use the file system kind associated with the
18823 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18824 This is the default.
18828 @cindex file name canonicalization
18829 @cindex base name differences
18830 When processing file names provided by the user, @value{GDBN}
18831 frequently needs to compare them to the file names recorded in the
18832 program's debug info. Normally, @value{GDBN} compares just the
18833 @dfn{base names} of the files as strings, which is reasonably fast
18834 even for very large programs. (The base name of a file is the last
18835 portion of its name, after stripping all the leading directories.)
18836 This shortcut in comparison is based upon the assumption that files
18837 cannot have more than one base name. This is usually true, but
18838 references to files that use symlinks or similar filesystem
18839 facilities violate that assumption. If your program records files
18840 using such facilities, or if you provide file names to @value{GDBN}
18841 using symlinks etc., you can set @code{basenames-may-differ} to
18842 @code{true} to instruct @value{GDBN} to completely canonicalize each
18843 pair of file names it needs to compare. This will make file-name
18844 comparisons accurate, but at a price of a significant slowdown.
18847 @item set basenames-may-differ
18848 @kindex set basenames-may-differ
18849 Set whether a source file may have multiple base names.
18851 @item show basenames-may-differ
18852 @kindex show basenames-may-differ
18853 Show whether a source file may have multiple base names.
18857 @section File Caching
18858 @cindex caching of opened files
18859 @cindex caching of bfd objects
18861 To speed up file loading, and reduce memory usage, @value{GDBN} will
18862 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18863 BFD, bfd, The Binary File Descriptor Library}. The following commands
18864 allow visibility and control of the caching behavior.
18867 @kindex maint info bfds
18868 @item maint info bfds
18869 This prints information about each @code{bfd} object that is known to
18872 @kindex maint set bfd-sharing
18873 @kindex maint show bfd-sharing
18874 @kindex bfd caching
18875 @item maint set bfd-sharing
18876 @item maint show bfd-sharing
18877 Control whether @code{bfd} objects can be shared. When sharing is
18878 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18879 than reopening the same file. Turning sharing off does not cause
18880 already shared @code{bfd} objects to be unshared, but all future files
18881 that are opened will create a new @code{bfd} object. Similarly,
18882 re-enabling sharing does not cause multiple existing @code{bfd}
18883 objects to be collapsed into a single shared @code{bfd} object.
18885 @kindex set debug bfd-cache @var{level}
18886 @kindex bfd caching
18887 @item set debug bfd-cache @var{level}
18888 Turns on debugging of the bfd cache, setting the level to @var{level}.
18890 @kindex show debug bfd-cache
18891 @kindex bfd caching
18892 @item show debug bfd-cache
18893 Show the current debugging level of the bfd cache.
18896 @node Separate Debug Files
18897 @section Debugging Information in Separate Files
18898 @cindex separate debugging information files
18899 @cindex debugging information in separate files
18900 @cindex @file{.debug} subdirectories
18901 @cindex debugging information directory, global
18902 @cindex global debugging information directories
18903 @cindex build ID, and separate debugging files
18904 @cindex @file{.build-id} directory
18906 @value{GDBN} allows you to put a program's debugging information in a
18907 file separate from the executable itself, in a way that allows
18908 @value{GDBN} to find and load the debugging information automatically.
18909 Since debugging information can be very large---sometimes larger
18910 than the executable code itself---some systems distribute debugging
18911 information for their executables in separate files, which users can
18912 install only when they need to debug a problem.
18914 @value{GDBN} supports two ways of specifying the separate debug info
18919 The executable contains a @dfn{debug link} that specifies the name of
18920 the separate debug info file. The separate debug file's name is
18921 usually @file{@var{executable}.debug}, where @var{executable} is the
18922 name of the corresponding executable file without leading directories
18923 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18924 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18925 checksum for the debug file, which @value{GDBN} uses to validate that
18926 the executable and the debug file came from the same build.
18929 The executable contains a @dfn{build ID}, a unique bit string that is
18930 also present in the corresponding debug info file. (This is supported
18931 only on some operating systems, when using the ELF or PE file formats
18932 for binary files and the @sc{gnu} Binutils.) For more details about
18933 this feature, see the description of the @option{--build-id}
18934 command-line option in @ref{Options, , Command Line Options, ld.info,
18935 The GNU Linker}. The debug info file's name is not specified
18936 explicitly by the build ID, but can be computed from the build ID, see
18940 Depending on the way the debug info file is specified, @value{GDBN}
18941 uses two different methods of looking for the debug file:
18945 For the ``debug link'' method, @value{GDBN} looks up the named file in
18946 the directory of the executable file, then in a subdirectory of that
18947 directory named @file{.debug}, and finally under each one of the global debug
18948 directories, in a subdirectory whose name is identical to the leading
18949 directories of the executable's absolute file name.
18952 For the ``build ID'' method, @value{GDBN} looks in the
18953 @file{.build-id} subdirectory of each one of the global debug directories for
18954 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18955 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18956 are the rest of the bit string. (Real build ID strings are 32 or more
18957 hex characters, not 10.)
18960 So, for example, suppose you ask @value{GDBN} to debug
18961 @file{/usr/bin/ls}, which has a debug link that specifies the
18962 file @file{ls.debug}, and a build ID whose value in hex is
18963 @code{abcdef1234}. If the list of the global debug directories includes
18964 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18965 debug information files, in the indicated order:
18969 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18971 @file{/usr/bin/ls.debug}
18973 @file{/usr/bin/.debug/ls.debug}
18975 @file{/usr/lib/debug/usr/bin/ls.debug}.
18978 @anchor{debug-file-directory}
18979 Global debugging info directories default to what is set by @value{GDBN}
18980 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18981 you can also set the global debugging info directories, and view the list
18982 @value{GDBN} is currently using.
18986 @kindex set debug-file-directory
18987 @item set debug-file-directory @var{directories}
18988 Set the directories which @value{GDBN} searches for separate debugging
18989 information files to @var{directory}. Multiple path components can be set
18990 concatenating them by a path separator.
18992 @kindex show debug-file-directory
18993 @item show debug-file-directory
18994 Show the directories @value{GDBN} searches for separate debugging
18999 @cindex @code{.gnu_debuglink} sections
19000 @cindex debug link sections
19001 A debug link is a special section of the executable file named
19002 @code{.gnu_debuglink}. The section must contain:
19006 A filename, with any leading directory components removed, followed by
19009 zero to three bytes of padding, as needed to reach the next four-byte
19010 boundary within the section, and
19012 a four-byte CRC checksum, stored in the same endianness used for the
19013 executable file itself. The checksum is computed on the debugging
19014 information file's full contents by the function given below, passing
19015 zero as the @var{crc} argument.
19018 Any executable file format can carry a debug link, as long as it can
19019 contain a section named @code{.gnu_debuglink} with the contents
19022 @cindex @code{.note.gnu.build-id} sections
19023 @cindex build ID sections
19024 The build ID is a special section in the executable file (and in other
19025 ELF binary files that @value{GDBN} may consider). This section is
19026 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19027 It contains unique identification for the built files---the ID remains
19028 the same across multiple builds of the same build tree. The default
19029 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19030 content for the build ID string. The same section with an identical
19031 value is present in the original built binary with symbols, in its
19032 stripped variant, and in the separate debugging information file.
19034 The debugging information file itself should be an ordinary
19035 executable, containing a full set of linker symbols, sections, and
19036 debugging information. The sections of the debugging information file
19037 should have the same names, addresses, and sizes as the original file,
19038 but they need not contain any data---much like a @code{.bss} section
19039 in an ordinary executable.
19041 The @sc{gnu} binary utilities (Binutils) package includes the
19042 @samp{objcopy} utility that can produce
19043 the separated executable / debugging information file pairs using the
19044 following commands:
19047 @kbd{objcopy --only-keep-debug foo foo.debug}
19052 These commands remove the debugging
19053 information from the executable file @file{foo} and place it in the file
19054 @file{foo.debug}. You can use the first, second or both methods to link the
19059 The debug link method needs the following additional command to also leave
19060 behind a debug link in @file{foo}:
19063 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19066 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19067 a version of the @code{strip} command such that the command @kbd{strip foo -f
19068 foo.debug} has the same functionality as the two @code{objcopy} commands and
19069 the @code{ln -s} command above, together.
19072 Build ID gets embedded into the main executable using @code{ld --build-id} or
19073 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19074 compatibility fixes for debug files separation are present in @sc{gnu} binary
19075 utilities (Binutils) package since version 2.18.
19080 @cindex CRC algorithm definition
19081 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19082 IEEE 802.3 using the polynomial:
19084 @c TexInfo requires naked braces for multi-digit exponents for Tex
19085 @c output, but this causes HTML output to barf. HTML has to be set using
19086 @c raw commands. So we end up having to specify this equation in 2
19091 <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>
19092 + <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
19098 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19099 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19103 The function is computed byte at a time, taking the least
19104 significant bit of each byte first. The initial pattern
19105 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19106 the final result is inverted to ensure trailing zeros also affect the
19109 @emph{Note:} This is the same CRC polynomial as used in handling the
19110 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19111 However in the case of the Remote Serial Protocol, the CRC is computed
19112 @emph{most} significant bit first, and the result is not inverted, so
19113 trailing zeros have no effect on the CRC value.
19115 To complete the description, we show below the code of the function
19116 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19117 initially supplied @code{crc} argument means that an initial call to
19118 this function passing in zero will start computing the CRC using
19121 @kindex gnu_debuglink_crc32
19124 gnu_debuglink_crc32 (unsigned long crc,
19125 unsigned char *buf, size_t len)
19127 static const unsigned long crc32_table[256] =
19129 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19130 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19131 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19132 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19133 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19134 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19135 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19136 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19137 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19138 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19139 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19140 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19141 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19142 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19143 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19144 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19145 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19146 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19147 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19148 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19149 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19150 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19151 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19152 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19153 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19154 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19155 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19156 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19157 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19158 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19159 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19160 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19161 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19162 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19163 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19164 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19165 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19166 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19167 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19168 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19169 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19170 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19171 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19172 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19173 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19174 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19175 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19176 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19177 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19178 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19179 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19182 unsigned char *end;
19184 crc = ~crc & 0xffffffff;
19185 for (end = buf + len; buf < end; ++buf)
19186 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19187 return ~crc & 0xffffffff;
19192 This computation does not apply to the ``build ID'' method.
19194 @node MiniDebugInfo
19195 @section Debugging information in a special section
19196 @cindex separate debug sections
19197 @cindex @samp{.gnu_debugdata} section
19199 Some systems ship pre-built executables and libraries that have a
19200 special @samp{.gnu_debugdata} section. This feature is called
19201 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19202 is used to supply extra symbols for backtraces.
19204 The intent of this section is to provide extra minimal debugging
19205 information for use in simple backtraces. It is not intended to be a
19206 replacement for full separate debugging information (@pxref{Separate
19207 Debug Files}). The example below shows the intended use; however,
19208 @value{GDBN} does not currently put restrictions on what sort of
19209 debugging information might be included in the section.
19211 @value{GDBN} has support for this extension. If the section exists,
19212 then it is used provided that no other source of debugging information
19213 can be found, and that @value{GDBN} was configured with LZMA support.
19215 This section can be easily created using @command{objcopy} and other
19216 standard utilities:
19219 # Extract the dynamic symbols from the main binary, there is no need
19220 # to also have these in the normal symbol table.
19221 nm -D @var{binary} --format=posix --defined-only \
19222 | awk '@{ print $1 @}' | sort > dynsyms
19224 # Extract all the text (i.e. function) symbols from the debuginfo.
19225 # (Note that we actually also accept "D" symbols, for the benefit
19226 # of platforms like PowerPC64 that use function descriptors.)
19227 nm @var{binary} --format=posix --defined-only \
19228 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19231 # Keep all the function symbols not already in the dynamic symbol
19233 comm -13 dynsyms funcsyms > keep_symbols
19235 # Separate full debug info into debug binary.
19236 objcopy --only-keep-debug @var{binary} debug
19238 # Copy the full debuginfo, keeping only a minimal set of symbols and
19239 # removing some unnecessary sections.
19240 objcopy -S --remove-section .gdb_index --remove-section .comment \
19241 --keep-symbols=keep_symbols debug mini_debuginfo
19243 # Drop the full debug info from the original binary.
19244 strip --strip-all -R .comment @var{binary}
19246 # Inject the compressed data into the .gnu_debugdata section of the
19249 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19253 @section Index Files Speed Up @value{GDBN}
19254 @cindex index files
19255 @cindex @samp{.gdb_index} section
19257 When @value{GDBN} finds a symbol file, it scans the symbols in the
19258 file in order to construct an internal symbol table. This lets most
19259 @value{GDBN} operations work quickly---at the cost of a delay early
19260 on. For large programs, this delay can be quite lengthy, so
19261 @value{GDBN} provides a way to build an index, which speeds up
19264 The index is stored as a section in the symbol file. @value{GDBN} can
19265 write the index to a file, then you can put it into the symbol file
19266 using @command{objcopy}.
19268 To create an index file, use the @code{save gdb-index} command:
19271 @item save gdb-index @var{directory}
19272 @kindex save gdb-index
19273 Create an index file for each symbol file currently known by
19274 @value{GDBN}. Each file is named after its corresponding symbol file,
19275 with @samp{.gdb-index} appended, and is written into the given
19279 Once you have created an index file you can merge it into your symbol
19280 file, here named @file{symfile}, using @command{objcopy}:
19283 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19284 --set-section-flags .gdb_index=readonly symfile symfile
19287 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19288 sections that have been deprecated. Usually they are deprecated because
19289 they are missing a new feature or have performance issues.
19290 To tell @value{GDBN} to use a deprecated index section anyway
19291 specify @code{set use-deprecated-index-sections on}.
19292 The default is @code{off}.
19293 This can speed up startup, but may result in some functionality being lost.
19294 @xref{Index Section Format}.
19296 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19297 must be done before gdb reads the file. The following will not work:
19300 $ gdb -ex "set use-deprecated-index-sections on" <program>
19303 Instead you must do, for example,
19306 $ gdb -iex "set use-deprecated-index-sections on" <program>
19309 There are currently some limitation on indices. They only work when
19310 for DWARF debugging information, not stabs. And, they do not
19311 currently work for programs using Ada.
19313 @node Symbol Errors
19314 @section Errors Reading Symbol Files
19316 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19317 such as symbol types it does not recognize, or known bugs in compiler
19318 output. By default, @value{GDBN} does not notify you of such problems, since
19319 they are relatively common and primarily of interest to people
19320 debugging compilers. If you are interested in seeing information
19321 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19322 only one message about each such type of problem, no matter how many
19323 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19324 to see how many times the problems occur, with the @code{set
19325 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19328 The messages currently printed, and their meanings, include:
19331 @item inner block not inside outer block in @var{symbol}
19333 The symbol information shows where symbol scopes begin and end
19334 (such as at the start of a function or a block of statements). This
19335 error indicates that an inner scope block is not fully contained
19336 in its outer scope blocks.
19338 @value{GDBN} circumvents the problem by treating the inner block as if it had
19339 the same scope as the outer block. In the error message, @var{symbol}
19340 may be shown as ``@code{(don't know)}'' if the outer block is not a
19343 @item block at @var{address} out of order
19345 The symbol information for symbol scope blocks should occur in
19346 order of increasing addresses. This error indicates that it does not
19349 @value{GDBN} does not circumvent this problem, and has trouble
19350 locating symbols in the source file whose symbols it is reading. (You
19351 can often determine what source file is affected by specifying
19352 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19355 @item bad block start address patched
19357 The symbol information for a symbol scope block has a start address
19358 smaller than the address of the preceding source line. This is known
19359 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19361 @value{GDBN} circumvents the problem by treating the symbol scope block as
19362 starting on the previous source line.
19364 @item bad string table offset in symbol @var{n}
19367 Symbol number @var{n} contains a pointer into the string table which is
19368 larger than the size of the string table.
19370 @value{GDBN} circumvents the problem by considering the symbol to have the
19371 name @code{foo}, which may cause other problems if many symbols end up
19374 @item unknown symbol type @code{0x@var{nn}}
19376 The symbol information contains new data types that @value{GDBN} does
19377 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19378 uncomprehended information, in hexadecimal.
19380 @value{GDBN} circumvents the error by ignoring this symbol information.
19381 This usually allows you to debug your program, though certain symbols
19382 are not accessible. If you encounter such a problem and feel like
19383 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19384 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19385 and examine @code{*bufp} to see the symbol.
19387 @item stub type has NULL name
19389 @value{GDBN} could not find the full definition for a struct or class.
19391 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19392 The symbol information for a C@t{++} member function is missing some
19393 information that recent versions of the compiler should have output for
19396 @item info mismatch between compiler and debugger
19398 @value{GDBN} could not parse a type specification output by the compiler.
19403 @section GDB Data Files
19405 @cindex prefix for data files
19406 @value{GDBN} will sometimes read an auxiliary data file. These files
19407 are kept in a directory known as the @dfn{data directory}.
19409 You can set the data directory's name, and view the name @value{GDBN}
19410 is currently using.
19413 @kindex set data-directory
19414 @item set data-directory @var{directory}
19415 Set the directory which @value{GDBN} searches for auxiliary data files
19416 to @var{directory}.
19418 @kindex show data-directory
19419 @item show data-directory
19420 Show the directory @value{GDBN} searches for auxiliary data files.
19423 @cindex default data directory
19424 @cindex @samp{--with-gdb-datadir}
19425 You can set the default data directory by using the configure-time
19426 @samp{--with-gdb-datadir} option. If the data directory is inside
19427 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19428 @samp{--exec-prefix}), then the default data directory will be updated
19429 automatically if the installed @value{GDBN} is moved to a new
19432 The data directory may also be specified with the
19433 @code{--data-directory} command line option.
19434 @xref{Mode Options}.
19437 @chapter Specifying a Debugging Target
19439 @cindex debugging target
19440 A @dfn{target} is the execution environment occupied by your program.
19442 Often, @value{GDBN} runs in the same host environment as your program;
19443 in that case, the debugging target is specified as a side effect when
19444 you use the @code{file} or @code{core} commands. When you need more
19445 flexibility---for example, running @value{GDBN} on a physically separate
19446 host, or controlling a standalone system over a serial port or a
19447 realtime system over a TCP/IP connection---you can use the @code{target}
19448 command to specify one of the target types configured for @value{GDBN}
19449 (@pxref{Target Commands, ,Commands for Managing Targets}).
19451 @cindex target architecture
19452 It is possible to build @value{GDBN} for several different @dfn{target
19453 architectures}. When @value{GDBN} is built like that, you can choose
19454 one of the available architectures with the @kbd{set architecture}
19458 @kindex set architecture
19459 @kindex show architecture
19460 @item set architecture @var{arch}
19461 This command sets the current target architecture to @var{arch}. The
19462 value of @var{arch} can be @code{"auto"}, in addition to one of the
19463 supported architectures.
19465 @item show architecture
19466 Show the current target architecture.
19468 @item set processor
19470 @kindex set processor
19471 @kindex show processor
19472 These are alias commands for, respectively, @code{set architecture}
19473 and @code{show architecture}.
19477 * Active Targets:: Active targets
19478 * Target Commands:: Commands for managing targets
19479 * Byte Order:: Choosing target byte order
19482 @node Active Targets
19483 @section Active Targets
19485 @cindex stacking targets
19486 @cindex active targets
19487 @cindex multiple targets
19489 There are multiple classes of targets such as: processes, executable files or
19490 recording sessions. Core files belong to the process class, making core file
19491 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19492 on multiple active targets, one in each class. This allows you to (for
19493 example) start a process and inspect its activity, while still having access to
19494 the executable file after the process finishes. Or if you start process
19495 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19496 presented a virtual layer of the recording target, while the process target
19497 remains stopped at the chronologically last point of the process execution.
19499 Use the @code{core-file} and @code{exec-file} commands to select a new core
19500 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19501 specify as a target a process that is already running, use the @code{attach}
19502 command (@pxref{Attach, ,Debugging an Already-running Process}).
19504 @node Target Commands
19505 @section Commands for Managing Targets
19508 @item target @var{type} @var{parameters}
19509 Connects the @value{GDBN} host environment to a target machine or
19510 process. A target is typically a protocol for talking to debugging
19511 facilities. You use the argument @var{type} to specify the type or
19512 protocol of the target machine.
19514 Further @var{parameters} are interpreted by the target protocol, but
19515 typically include things like device names or host names to connect
19516 with, process numbers, and baud rates.
19518 The @code{target} command does not repeat if you press @key{RET} again
19519 after executing the command.
19521 @kindex help target
19523 Displays the names of all targets available. To display targets
19524 currently selected, use either @code{info target} or @code{info files}
19525 (@pxref{Files, ,Commands to Specify Files}).
19527 @item help target @var{name}
19528 Describe a particular target, including any parameters necessary to
19531 @kindex set gnutarget
19532 @item set gnutarget @var{args}
19533 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19534 knows whether it is reading an @dfn{executable},
19535 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19536 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19537 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19540 @emph{Warning:} To specify a file format with @code{set gnutarget},
19541 you must know the actual BFD name.
19545 @xref{Files, , Commands to Specify Files}.
19547 @kindex show gnutarget
19548 @item show gnutarget
19549 Use the @code{show gnutarget} command to display what file format
19550 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19551 @value{GDBN} will determine the file format for each file automatically,
19552 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19555 @cindex common targets
19556 Here are some common targets (available, or not, depending on the GDB
19561 @item target exec @var{program}
19562 @cindex executable file target
19563 An executable file. @samp{target exec @var{program}} is the same as
19564 @samp{exec-file @var{program}}.
19566 @item target core @var{filename}
19567 @cindex core dump file target
19568 A core dump file. @samp{target core @var{filename}} is the same as
19569 @samp{core-file @var{filename}}.
19571 @item target remote @var{medium}
19572 @cindex remote target
19573 A remote system connected to @value{GDBN} via a serial line or network
19574 connection. This command tells @value{GDBN} to use its own remote
19575 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19577 For example, if you have a board connected to @file{/dev/ttya} on the
19578 machine running @value{GDBN}, you could say:
19581 target remote /dev/ttya
19584 @code{target remote} supports the @code{load} command. This is only
19585 useful if you have some other way of getting the stub to the target
19586 system, and you can put it somewhere in memory where it won't get
19587 clobbered by the download.
19589 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19590 @cindex built-in simulator target
19591 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19599 works; however, you cannot assume that a specific memory map, device
19600 drivers, or even basic I/O is available, although some simulators do
19601 provide these. For info about any processor-specific simulator details,
19602 see the appropriate section in @ref{Embedded Processors, ,Embedded
19605 @item target native
19606 @cindex native target
19607 Setup for local/native process debugging. Useful to make the
19608 @code{run} command spawn native processes (likewise @code{attach},
19609 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19610 (@pxref{set auto-connect-native-target}).
19614 Different targets are available on different configurations of @value{GDBN};
19615 your configuration may have more or fewer targets.
19617 Many remote targets require you to download the executable's code once
19618 you've successfully established a connection. You may wish to control
19619 various aspects of this process.
19624 @kindex set hash@r{, for remote monitors}
19625 @cindex hash mark while downloading
19626 This command controls whether a hash mark @samp{#} is displayed while
19627 downloading a file to the remote monitor. If on, a hash mark is
19628 displayed after each S-record is successfully downloaded to the
19632 @kindex show hash@r{, for remote monitors}
19633 Show the current status of displaying the hash mark.
19635 @item set debug monitor
19636 @kindex set debug monitor
19637 @cindex display remote monitor communications
19638 Enable or disable display of communications messages between
19639 @value{GDBN} and the remote monitor.
19641 @item show debug monitor
19642 @kindex show debug monitor
19643 Show the current status of displaying communications between
19644 @value{GDBN} and the remote monitor.
19649 @kindex load @var{filename} @var{offset}
19650 @item load @var{filename} @var{offset}
19652 Depending on what remote debugging facilities are configured into
19653 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19654 is meant to make @var{filename} (an executable) available for debugging
19655 on the remote system---by downloading, or dynamic linking, for example.
19656 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19657 the @code{add-symbol-file} command.
19659 If your @value{GDBN} does not have a @code{load} command, attempting to
19660 execute it gets the error message ``@code{You can't do that when your
19661 target is @dots{}}''
19663 The file is loaded at whatever address is specified in the executable.
19664 For some object file formats, you can specify the load address when you
19665 link the program; for other formats, like a.out, the object file format
19666 specifies a fixed address.
19667 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19669 It is also possible to tell @value{GDBN} to load the executable file at a
19670 specific offset described by the optional argument @var{offset}. When
19671 @var{offset} is provided, @var{filename} must also be provided.
19673 Depending on the remote side capabilities, @value{GDBN} may be able to
19674 load programs into flash memory.
19676 @code{load} does not repeat if you press @key{RET} again after using it.
19681 @kindex flash-erase
19683 @anchor{flash-erase}
19685 Erases all known flash memory regions on the target.
19690 @section Choosing Target Byte Order
19692 @cindex choosing target byte order
19693 @cindex target byte order
19695 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19696 offer the ability to run either big-endian or little-endian byte
19697 orders. Usually the executable or symbol will include a bit to
19698 designate the endian-ness, and you will not need to worry about
19699 which to use. However, you may still find it useful to adjust
19700 @value{GDBN}'s idea of processor endian-ness manually.
19704 @item set endian big
19705 Instruct @value{GDBN} to assume the target is big-endian.
19707 @item set endian little
19708 Instruct @value{GDBN} to assume the target is little-endian.
19710 @item set endian auto
19711 Instruct @value{GDBN} to use the byte order associated with the
19715 Display @value{GDBN}'s current idea of the target byte order.
19719 Note that these commands merely adjust interpretation of symbolic
19720 data on the host, and that they have absolutely no effect on the
19724 @node Remote Debugging
19725 @chapter Debugging Remote Programs
19726 @cindex remote debugging
19728 If you are trying to debug a program running on a machine that cannot run
19729 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19730 For example, you might use remote debugging on an operating system kernel,
19731 or on a small system which does not have a general purpose operating system
19732 powerful enough to run a full-featured debugger.
19734 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19735 to make this work with particular debugging targets. In addition,
19736 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19737 but not specific to any particular target system) which you can use if you
19738 write the remote stubs---the code that runs on the remote system to
19739 communicate with @value{GDBN}.
19741 Other remote targets may be available in your
19742 configuration of @value{GDBN}; use @code{help target} to list them.
19745 * Connecting:: Connecting to a remote target
19746 * File Transfer:: Sending files to a remote system
19747 * Server:: Using the gdbserver program
19748 * Remote Configuration:: Remote configuration
19749 * Remote Stub:: Implementing a remote stub
19753 @section Connecting to a Remote Target
19754 @cindex remote debugging, connecting
19755 @cindex @code{gdbserver}, connecting
19756 @cindex remote debugging, types of connections
19757 @cindex @code{gdbserver}, types of connections
19758 @cindex @code{gdbserver}, @code{target remote} mode
19759 @cindex @code{gdbserver}, @code{target extended-remote} mode
19761 This section describes how to connect to a remote target, including the
19762 types of connections and their differences, how to set up executable and
19763 symbol files on the host and target, and the commands used for
19764 connecting to and disconnecting from the remote target.
19766 @subsection Types of Remote Connections
19768 @value{GDBN} supports two types of remote connections, @code{target remote}
19769 mode and @code{target extended-remote} mode. Note that many remote targets
19770 support only @code{target remote} mode. There are several major
19771 differences between the two types of connections, enumerated here:
19775 @cindex remote debugging, detach and program exit
19776 @item Result of detach or program exit
19777 @strong{With target remote mode:} When the debugged program exits or you
19778 detach from it, @value{GDBN} disconnects from the target. When using
19779 @code{gdbserver}, @code{gdbserver} will exit.
19781 @strong{With target extended-remote mode:} When the debugged program exits or
19782 you detach from it, @value{GDBN} remains connected to the target, even
19783 though no program is running. You can rerun the program, attach to a
19784 running program, or use @code{monitor} commands specific to the target.
19786 When using @code{gdbserver} in this case, it does not exit unless it was
19787 invoked using the @option{--once} option. If the @option{--once} option
19788 was not used, you can ask @code{gdbserver} to exit using the
19789 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19791 @item Specifying the program to debug
19792 For both connection types you use the @code{file} command to specify the
19793 program on the host system. If you are using @code{gdbserver} there are
19794 some differences in how to specify the location of the program on the
19797 @strong{With target remote mode:} You must either specify the program to debug
19798 on the @code{gdbserver} command line or use the @option{--attach} option
19799 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19801 @cindex @option{--multi}, @code{gdbserver} option
19802 @strong{With target extended-remote mode:} You may specify the program to debug
19803 on the @code{gdbserver} command line, or you can load the program or attach
19804 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19806 @anchor{--multi Option in Types of Remote Connnections}
19807 You can start @code{gdbserver} without supplying an initial command to run
19808 or process ID to attach. To do this, use the @option{--multi} command line
19809 option. Then you can connect using @code{target extended-remote} and start
19810 the program you want to debug (see below for details on using the
19811 @code{run} command in this scenario). Note that the conditions under which
19812 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19813 (@code{target remote} or @code{target extended-remote}). The
19814 @option{--multi} option to @code{gdbserver} has no influence on that.
19816 @item The @code{run} command
19817 @strong{With target remote mode:} The @code{run} command is not
19818 supported. Once a connection has been established, you can use all
19819 the usual @value{GDBN} commands to examine and change data. The
19820 remote program is already running, so you can use commands like
19821 @kbd{step} and @kbd{continue}.
19823 @strong{With target extended-remote mode:} The @code{run} command is
19824 supported. The @code{run} command uses the value set by
19825 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19826 the program to run. Command line arguments are supported, except for
19827 wildcard expansion and I/O redirection (@pxref{Arguments}).
19829 If you specify the program to debug on the command line, then the
19830 @code{run} command is not required to start execution, and you can
19831 resume using commands like @kbd{step} and @kbd{continue} as with
19832 @code{target remote} mode.
19834 @anchor{Attaching in Types of Remote Connections}
19836 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19837 not supported. To attach to a running program using @code{gdbserver}, you
19838 must use the @option{--attach} option (@pxref{Running gdbserver}).
19840 @strong{With target extended-remote mode:} To attach to a running program,
19841 you may use the @code{attach} command after the connection has been
19842 established. If you are using @code{gdbserver}, you may also invoke
19843 @code{gdbserver} using the @option{--attach} option
19844 (@pxref{Running gdbserver}).
19848 @anchor{Host and target files}
19849 @subsection Host and Target Files
19850 @cindex remote debugging, symbol files
19851 @cindex symbol files, remote debugging
19853 @value{GDBN}, running on the host, needs access to symbol and debugging
19854 information for your program running on the target. This requires
19855 access to an unstripped copy of your program, and possibly any associated
19856 symbol files. Note that this section applies equally to both @code{target
19857 remote} mode and @code{target extended-remote} mode.
19859 Some remote targets (@pxref{qXfer executable filename read}, and
19860 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19861 the same connection used to communicate with @value{GDBN}. With such a
19862 target, if the remote program is unstripped, the only command you need is
19863 @code{target remote} (or @code{target extended-remote}).
19865 If the remote program is stripped, or the target does not support remote
19866 program file access, start up @value{GDBN} using the name of the local
19867 unstripped copy of your program as the first argument, or use the
19868 @code{file} command. Use @code{set sysroot} to specify the location (on
19869 the host) of target libraries (unless your @value{GDBN} was compiled with
19870 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19871 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19874 The symbol file and target libraries must exactly match the executable
19875 and libraries on the target, with one exception: the files on the host
19876 system should not be stripped, even if the files on the target system
19877 are. Mismatched or missing files will lead to confusing results
19878 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19879 files may also prevent @code{gdbserver} from debugging multi-threaded
19882 @subsection Remote Connection Commands
19883 @cindex remote connection commands
19884 @value{GDBN} can communicate with the target over a serial line, or
19885 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19886 each case, @value{GDBN} uses the same protocol for debugging your
19887 program; only the medium carrying the debugging packets varies. The
19888 @code{target remote} and @code{target extended-remote} commands
19889 establish a connection to the target. Both commands accept the same
19890 arguments, which indicate the medium to use:
19894 @item target remote @var{serial-device}
19895 @itemx target extended-remote @var{serial-device}
19896 @cindex serial line, @code{target remote}
19897 Use @var{serial-device} to communicate with the target. For example,
19898 to use a serial line connected to the device named @file{/dev/ttyb}:
19901 target remote /dev/ttyb
19904 If you're using a serial line, you may want to give @value{GDBN} the
19905 @samp{--baud} option, or use the @code{set serial baud} command
19906 (@pxref{Remote Configuration, set serial baud}) before the
19907 @code{target} command.
19909 @item target remote @code{@var{host}:@var{port}}
19910 @itemx target remote @code{tcp:@var{host}:@var{port}}
19911 @itemx target extended-remote @code{@var{host}:@var{port}}
19912 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19913 @cindex @acronym{TCP} port, @code{target remote}
19914 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19915 The @var{host} may be either a host name or a numeric @acronym{IP}
19916 address; @var{port} must be a decimal number. The @var{host} could be
19917 the target machine itself, if it is directly connected to the net, or
19918 it might be a terminal server which in turn has a serial line to the
19921 For example, to connect to port 2828 on a terminal server named
19925 target remote manyfarms:2828
19928 If your remote target is actually running on the same machine as your
19929 debugger session (e.g.@: a simulator for your target running on the
19930 same host), you can omit the hostname. For example, to connect to
19931 port 1234 on your local machine:
19934 target remote :1234
19938 Note that the colon is still required here.
19940 @item target remote @code{udp:@var{host}:@var{port}}
19941 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19942 @cindex @acronym{UDP} port, @code{target remote}
19943 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19944 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19947 target remote udp:manyfarms:2828
19950 When using a @acronym{UDP} connection for remote debugging, you should
19951 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19952 can silently drop packets on busy or unreliable networks, which will
19953 cause havoc with your debugging session.
19955 @item target remote | @var{command}
19956 @itemx target extended-remote | @var{command}
19957 @cindex pipe, @code{target remote} to
19958 Run @var{command} in the background and communicate with it using a
19959 pipe. The @var{command} is a shell command, to be parsed and expanded
19960 by the system's command shell, @code{/bin/sh}; it should expect remote
19961 protocol packets on its standard input, and send replies on its
19962 standard output. You could use this to run a stand-alone simulator
19963 that speaks the remote debugging protocol, to make net connections
19964 using programs like @code{ssh}, or for other similar tricks.
19966 If @var{command} closes its standard output (perhaps by exiting),
19967 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19968 program has already exited, this will have no effect.)
19972 @cindex interrupting remote programs
19973 @cindex remote programs, interrupting
19974 Whenever @value{GDBN} is waiting for the remote program, if you type the
19975 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19976 program. This may or may not succeed, depending in part on the hardware
19977 and the serial drivers the remote system uses. If you type the
19978 interrupt character once again, @value{GDBN} displays this prompt:
19981 Interrupted while waiting for the program.
19982 Give up (and stop debugging it)? (y or n)
19985 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19986 the remote debugging session. (If you decide you want to try again later,
19987 you can use @kbd{target remote} again to connect once more.) If you type
19988 @kbd{n}, @value{GDBN} goes back to waiting.
19990 In @code{target extended-remote} mode, typing @kbd{n} will leave
19991 @value{GDBN} connected to the target.
19994 @kindex detach (remote)
19996 When you have finished debugging the remote program, you can use the
19997 @code{detach} command to release it from @value{GDBN} control.
19998 Detaching from the target normally resumes its execution, but the results
19999 will depend on your particular remote stub. After the @code{detach}
20000 command in @code{target remote} mode, @value{GDBN} is free to connect to
20001 another target. In @code{target extended-remote} mode, @value{GDBN} is
20002 still connected to the target.
20006 The @code{disconnect} command closes the connection to the target, and
20007 the target is generally not resumed. It will wait for @value{GDBN}
20008 (this instance or another one) to connect and continue debugging. After
20009 the @code{disconnect} command, @value{GDBN} is again free to connect to
20012 @cindex send command to remote monitor
20013 @cindex extend @value{GDBN} for remote targets
20014 @cindex add new commands for external monitor
20016 @item monitor @var{cmd}
20017 This command allows you to send arbitrary commands directly to the
20018 remote monitor. Since @value{GDBN} doesn't care about the commands it
20019 sends like this, this command is the way to extend @value{GDBN}---you
20020 can add new commands that only the external monitor will understand
20024 @node File Transfer
20025 @section Sending files to a remote system
20026 @cindex remote target, file transfer
20027 @cindex file transfer
20028 @cindex sending files to remote systems
20030 Some remote targets offer the ability to transfer files over the same
20031 connection used to communicate with @value{GDBN}. This is convenient
20032 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20033 running @code{gdbserver} over a network interface. For other targets,
20034 e.g.@: embedded devices with only a single serial port, this may be
20035 the only way to upload or download files.
20037 Not all remote targets support these commands.
20041 @item remote put @var{hostfile} @var{targetfile}
20042 Copy file @var{hostfile} from the host system (the machine running
20043 @value{GDBN}) to @var{targetfile} on the target system.
20046 @item remote get @var{targetfile} @var{hostfile}
20047 Copy file @var{targetfile} from the target system to @var{hostfile}
20048 on the host system.
20050 @kindex remote delete
20051 @item remote delete @var{targetfile}
20052 Delete @var{targetfile} from the target system.
20057 @section Using the @code{gdbserver} Program
20060 @cindex remote connection without stubs
20061 @code{gdbserver} is a control program for Unix-like systems, which
20062 allows you to connect your program with a remote @value{GDBN} via
20063 @code{target remote} or @code{target extended-remote}---but without
20064 linking in the usual debugging stub.
20066 @code{gdbserver} is not a complete replacement for the debugging stubs,
20067 because it requires essentially the same operating-system facilities
20068 that @value{GDBN} itself does. In fact, a system that can run
20069 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20070 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20071 because it is a much smaller program than @value{GDBN} itself. It is
20072 also easier to port than all of @value{GDBN}, so you may be able to get
20073 started more quickly on a new system by using @code{gdbserver}.
20074 Finally, if you develop code for real-time systems, you may find that
20075 the tradeoffs involved in real-time operation make it more convenient to
20076 do as much development work as possible on another system, for example
20077 by cross-compiling. You can use @code{gdbserver} to make a similar
20078 choice for debugging.
20080 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20081 or a TCP connection, using the standard @value{GDBN} remote serial
20085 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20086 Do not run @code{gdbserver} connected to any public network; a
20087 @value{GDBN} connection to @code{gdbserver} provides access to the
20088 target system with the same privileges as the user running
20092 @anchor{Running gdbserver}
20093 @subsection Running @code{gdbserver}
20094 @cindex arguments, to @code{gdbserver}
20095 @cindex @code{gdbserver}, command-line arguments
20097 Run @code{gdbserver} on the target system. You need a copy of the
20098 program you want to debug, including any libraries it requires.
20099 @code{gdbserver} does not need your program's symbol table, so you can
20100 strip the program if necessary to save space. @value{GDBN} on the host
20101 system does all the symbol handling.
20103 To use the server, you must tell it how to communicate with @value{GDBN};
20104 the name of your program; and the arguments for your program. The usual
20108 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20111 @var{comm} is either a device name (to use a serial line), or a TCP
20112 hostname and portnumber, or @code{-} or @code{stdio} to use
20113 stdin/stdout of @code{gdbserver}.
20114 For example, to debug Emacs with the argument
20115 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20119 target> gdbserver /dev/com1 emacs foo.txt
20122 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20125 To use a TCP connection instead of a serial line:
20128 target> gdbserver host:2345 emacs foo.txt
20131 The only difference from the previous example is the first argument,
20132 specifying that you are communicating with the host @value{GDBN} via
20133 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20134 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20135 (Currently, the @samp{host} part is ignored.) You can choose any number
20136 you want for the port number as long as it does not conflict with any
20137 TCP ports already in use on the target system (for example, @code{23} is
20138 reserved for @code{telnet}).@footnote{If you choose a port number that
20139 conflicts with another service, @code{gdbserver} prints an error message
20140 and exits.} You must use the same port number with the host @value{GDBN}
20141 @code{target remote} command.
20143 The @code{stdio} connection is useful when starting @code{gdbserver}
20147 (gdb) target remote | ssh -T hostname gdbserver - hello
20150 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20151 and we don't want escape-character handling. Ssh does this by default when
20152 a command is provided, the flag is provided to make it explicit.
20153 You could elide it if you want to.
20155 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20156 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20157 display through a pipe connected to gdbserver.
20158 Both @code{stdout} and @code{stderr} use the same pipe.
20160 @anchor{Attaching to a program}
20161 @subsubsection Attaching to a Running Program
20162 @cindex attach to a program, @code{gdbserver}
20163 @cindex @option{--attach}, @code{gdbserver} option
20165 On some targets, @code{gdbserver} can also attach to running programs.
20166 This is accomplished via the @code{--attach} argument. The syntax is:
20169 target> gdbserver --attach @var{comm} @var{pid}
20172 @var{pid} is the process ID of a currently running process. It isn't
20173 necessary to point @code{gdbserver} at a binary for the running process.
20175 In @code{target extended-remote} mode, you can also attach using the
20176 @value{GDBN} attach command
20177 (@pxref{Attaching in Types of Remote Connections}).
20180 You can debug processes by name instead of process ID if your target has the
20181 @code{pidof} utility:
20184 target> gdbserver --attach @var{comm} `pidof @var{program}`
20187 In case more than one copy of @var{program} is running, or @var{program}
20188 has multiple threads, most versions of @code{pidof} support the
20189 @code{-s} option to only return the first process ID.
20191 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20193 This section applies only when @code{gdbserver} is run to listen on a TCP
20196 @code{gdbserver} normally terminates after all of its debugged processes have
20197 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20198 extended-remote}, @code{gdbserver} stays running even with no processes left.
20199 @value{GDBN} normally terminates the spawned debugged process on its exit,
20200 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20201 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20202 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20203 stays running even in the @kbd{target remote} mode.
20205 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20206 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20207 completeness, at most one @value{GDBN} can be connected at a time.
20209 @cindex @option{--once}, @code{gdbserver} option
20210 By default, @code{gdbserver} keeps the listening TCP port open, so that
20211 subsequent connections are possible. However, if you start @code{gdbserver}
20212 with the @option{--once} option, it will stop listening for any further
20213 connection attempts after connecting to the first @value{GDBN} session. This
20214 means no further connections to @code{gdbserver} will be possible after the
20215 first one. It also means @code{gdbserver} will terminate after the first
20216 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20217 connections and even in the @kbd{target extended-remote} mode. The
20218 @option{--once} option allows reusing the same port number for connecting to
20219 multiple instances of @code{gdbserver} running on the same host, since each
20220 instance closes its port after the first connection.
20222 @anchor{Other Command-Line Arguments for gdbserver}
20223 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20225 You can use the @option{--multi} option to start @code{gdbserver} without
20226 specifying a program to debug or a process to attach to. Then you can
20227 attach in @code{target extended-remote} mode and run or attach to a
20228 program. For more information,
20229 @pxref{--multi Option in Types of Remote Connnections}.
20231 @cindex @option{--debug}, @code{gdbserver} option
20232 The @option{--debug} option tells @code{gdbserver} to display extra
20233 status information about the debugging process.
20234 @cindex @option{--remote-debug}, @code{gdbserver} option
20235 The @option{--remote-debug} option tells @code{gdbserver} to display
20236 remote protocol debug output. These options are intended for
20237 @code{gdbserver} development and for bug reports to the developers.
20239 @cindex @option{--debug-format}, @code{gdbserver} option
20240 The @option{--debug-format=option1[,option2,...]} option tells
20241 @code{gdbserver} to include additional information in each output.
20242 Possible options are:
20246 Turn off all extra information in debugging output.
20248 Turn on all extra information in debugging output.
20250 Include a timestamp in each line of debugging output.
20253 Options are processed in order. Thus, for example, if @option{none}
20254 appears last then no additional information is added to debugging output.
20256 @cindex @option{--wrapper}, @code{gdbserver} option
20257 The @option{--wrapper} option specifies a wrapper to launch programs
20258 for debugging. The option should be followed by the name of the
20259 wrapper, then any command-line arguments to pass to the wrapper, then
20260 @kbd{--} indicating the end of the wrapper arguments.
20262 @code{gdbserver} runs the specified wrapper program with a combined
20263 command line including the wrapper arguments, then the name of the
20264 program to debug, then any arguments to the program. The wrapper
20265 runs until it executes your program, and then @value{GDBN} gains control.
20267 You can use any program that eventually calls @code{execve} with
20268 its arguments as a wrapper. Several standard Unix utilities do
20269 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20270 with @code{exec "$@@"} will also work.
20272 For example, you can use @code{env} to pass an environment variable to
20273 the debugged program, without setting the variable in @code{gdbserver}'s
20277 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20280 @cindex @option{--selftest}
20281 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20284 $ gdbserver --selftest
20285 Ran 2 unit tests, 0 failed
20288 These tests are disabled in release.
20289 @subsection Connecting to @code{gdbserver}
20291 The basic procedure for connecting to the remote target is:
20295 Run @value{GDBN} on the host system.
20298 Make sure you have the necessary symbol files
20299 (@pxref{Host and target files}).
20300 Load symbols for your application using the @code{file} command before you
20301 connect. Use @code{set sysroot} to locate target libraries (unless your
20302 @value{GDBN} was compiled with the correct sysroot using
20303 @code{--with-sysroot}).
20306 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20307 For TCP connections, you must start up @code{gdbserver} prior to using
20308 the @code{target} command. Otherwise you may get an error whose
20309 text depends on the host system, but which usually looks something like
20310 @samp{Connection refused}. Don't use the @code{load}
20311 command in @value{GDBN} when using @code{target remote} mode, since the
20312 program is already on the target.
20316 @anchor{Monitor Commands for gdbserver}
20317 @subsection Monitor Commands for @code{gdbserver}
20318 @cindex monitor commands, for @code{gdbserver}
20320 During a @value{GDBN} session using @code{gdbserver}, you can use the
20321 @code{monitor} command to send special requests to @code{gdbserver}.
20322 Here are the available commands.
20326 List the available monitor commands.
20328 @item monitor set debug 0
20329 @itemx monitor set debug 1
20330 Disable or enable general debugging messages.
20332 @item monitor set remote-debug 0
20333 @itemx monitor set remote-debug 1
20334 Disable or enable specific debugging messages associated with the remote
20335 protocol (@pxref{Remote Protocol}).
20337 @item monitor set debug-format option1@r{[},option2,...@r{]}
20338 Specify additional text to add to debugging messages.
20339 Possible options are:
20343 Turn off all extra information in debugging output.
20345 Turn on all extra information in debugging output.
20347 Include a timestamp in each line of debugging output.
20350 Options are processed in order. Thus, for example, if @option{none}
20351 appears last then no additional information is added to debugging output.
20353 @item monitor set libthread-db-search-path [PATH]
20354 @cindex gdbserver, search path for @code{libthread_db}
20355 When this command is issued, @var{path} is a colon-separated list of
20356 directories to search for @code{libthread_db} (@pxref{Threads,,set
20357 libthread-db-search-path}). If you omit @var{path},
20358 @samp{libthread-db-search-path} will be reset to its default value.
20360 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20361 not supported in @code{gdbserver}.
20364 Tell gdbserver to exit immediately. This command should be followed by
20365 @code{disconnect} to close the debugging session. @code{gdbserver} will
20366 detach from any attached processes and kill any processes it created.
20367 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20368 of a multi-process mode debug session.
20372 @subsection Tracepoints support in @code{gdbserver}
20373 @cindex tracepoints support in @code{gdbserver}
20375 On some targets, @code{gdbserver} supports tracepoints, fast
20376 tracepoints and static tracepoints.
20378 For fast or static tracepoints to work, a special library called the
20379 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20380 This library is built and distributed as an integral part of
20381 @code{gdbserver}. In addition, support for static tracepoints
20382 requires building the in-process agent library with static tracepoints
20383 support. At present, the UST (LTTng Userspace Tracer,
20384 @url{http://lttng.org/ust}) tracing engine is supported. This support
20385 is automatically available if UST development headers are found in the
20386 standard include path when @code{gdbserver} is built, or if
20387 @code{gdbserver} was explicitly configured using @option{--with-ust}
20388 to point at such headers. You can explicitly disable the support
20389 using @option{--with-ust=no}.
20391 There are several ways to load the in-process agent in your program:
20394 @item Specifying it as dependency at link time
20396 You can link your program dynamically with the in-process agent
20397 library. On most systems, this is accomplished by adding
20398 @code{-linproctrace} to the link command.
20400 @item Using the system's preloading mechanisms
20402 You can force loading the in-process agent at startup time by using
20403 your system's support for preloading shared libraries. Many Unixes
20404 support the concept of preloading user defined libraries. In most
20405 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20406 in the environment. See also the description of @code{gdbserver}'s
20407 @option{--wrapper} command line option.
20409 @item Using @value{GDBN} to force loading the agent at run time
20411 On some systems, you can force the inferior to load a shared library,
20412 by calling a dynamic loader function in the inferior that takes care
20413 of dynamically looking up and loading a shared library. On most Unix
20414 systems, the function is @code{dlopen}. You'll use the @code{call}
20415 command for that. For example:
20418 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20421 Note that on most Unix systems, for the @code{dlopen} function to be
20422 available, the program needs to be linked with @code{-ldl}.
20425 On systems that have a userspace dynamic loader, like most Unix
20426 systems, when you connect to @code{gdbserver} using @code{target
20427 remote}, you'll find that the program is stopped at the dynamic
20428 loader's entry point, and no shared library has been loaded in the
20429 program's address space yet, including the in-process agent. In that
20430 case, before being able to use any of the fast or static tracepoints
20431 features, you need to let the loader run and load the shared
20432 libraries. The simplest way to do that is to run the program to the
20433 main procedure. E.g., if debugging a C or C@t{++} program, start
20434 @code{gdbserver} like so:
20437 $ gdbserver :9999 myprogram
20440 Start GDB and connect to @code{gdbserver} like so, and run to main:
20444 (@value{GDBP}) target remote myhost:9999
20445 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20446 (@value{GDBP}) b main
20447 (@value{GDBP}) continue
20450 The in-process tracing agent library should now be loaded into the
20451 process; you can confirm it with the @code{info sharedlibrary}
20452 command, which will list @file{libinproctrace.so} as loaded in the
20453 process. You are now ready to install fast tracepoints, list static
20454 tracepoint markers, probe static tracepoints markers, and start
20457 @node Remote Configuration
20458 @section Remote Configuration
20461 @kindex show remote
20462 This section documents the configuration options available when
20463 debugging remote programs. For the options related to the File I/O
20464 extensions of the remote protocol, see @ref{system,
20465 system-call-allowed}.
20468 @item set remoteaddresssize @var{bits}
20469 @cindex address size for remote targets
20470 @cindex bits in remote address
20471 Set the maximum size of address in a memory packet to the specified
20472 number of bits. @value{GDBN} will mask off the address bits above
20473 that number, when it passes addresses to the remote target. The
20474 default value is the number of bits in the target's address.
20476 @item show remoteaddresssize
20477 Show the current value of remote address size in bits.
20479 @item set serial baud @var{n}
20480 @cindex baud rate for remote targets
20481 Set the baud rate for the remote serial I/O to @var{n} baud. The
20482 value is used to set the speed of the serial port used for debugging
20485 @item show serial baud
20486 Show the current speed of the remote connection.
20488 @item set serial parity @var{parity}
20489 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20490 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20492 @item show serial parity
20493 Show the current parity of the serial port.
20495 @item set remotebreak
20496 @cindex interrupt remote programs
20497 @cindex BREAK signal instead of Ctrl-C
20498 @anchor{set remotebreak}
20499 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20500 when you type @kbd{Ctrl-c} to interrupt the program running
20501 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20502 character instead. The default is off, since most remote systems
20503 expect to see @samp{Ctrl-C} as the interrupt signal.
20505 @item show remotebreak
20506 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20507 interrupt the remote program.
20509 @item set remoteflow on
20510 @itemx set remoteflow off
20511 @kindex set remoteflow
20512 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20513 on the serial port used to communicate to the remote target.
20515 @item show remoteflow
20516 @kindex show remoteflow
20517 Show the current setting of hardware flow control.
20519 @item set remotelogbase @var{base}
20520 Set the base (a.k.a.@: radix) of logging serial protocol
20521 communications to @var{base}. Supported values of @var{base} are:
20522 @code{ascii}, @code{octal}, and @code{hex}. The default is
20525 @item show remotelogbase
20526 Show the current setting of the radix for logging remote serial
20529 @item set remotelogfile @var{file}
20530 @cindex record serial communications on file
20531 Record remote serial communications on the named @var{file}. The
20532 default is not to record at all.
20534 @item show remotelogfile.
20535 Show the current setting of the file name on which to record the
20536 serial communications.
20538 @item set remotetimeout @var{num}
20539 @cindex timeout for serial communications
20540 @cindex remote timeout
20541 Set the timeout limit to wait for the remote target to respond to
20542 @var{num} seconds. The default is 2 seconds.
20544 @item show remotetimeout
20545 Show the current number of seconds to wait for the remote target
20548 @cindex limit hardware breakpoints and watchpoints
20549 @cindex remote target, limit break- and watchpoints
20550 @anchor{set remote hardware-watchpoint-limit}
20551 @anchor{set remote hardware-breakpoint-limit}
20552 @item set remote hardware-watchpoint-limit @var{limit}
20553 @itemx set remote hardware-breakpoint-limit @var{limit}
20554 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20555 watchpoints. A limit of -1, the default, is treated as unlimited.
20557 @cindex limit hardware watchpoints length
20558 @cindex remote target, limit watchpoints length
20559 @anchor{set remote hardware-watchpoint-length-limit}
20560 @item set remote hardware-watchpoint-length-limit @var{limit}
20561 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20562 a remote hardware watchpoint. A limit of -1, the default, is treated
20565 @item show remote hardware-watchpoint-length-limit
20566 Show the current limit (in bytes) of the maximum length of
20567 a remote hardware watchpoint.
20569 @item set remote exec-file @var{filename}
20570 @itemx show remote exec-file
20571 @anchor{set remote exec-file}
20572 @cindex executable file, for remote target
20573 Select the file used for @code{run} with @code{target
20574 extended-remote}. This should be set to a filename valid on the
20575 target system. If it is not set, the target will use a default
20576 filename (e.g.@: the last program run).
20578 @item set remote interrupt-sequence
20579 @cindex interrupt remote programs
20580 @cindex select Ctrl-C, BREAK or BREAK-g
20581 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20582 @samp{BREAK-g} as the
20583 sequence to the remote target in order to interrupt the execution.
20584 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20585 is high level of serial line for some certain time.
20586 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20587 It is @code{BREAK} signal followed by character @code{g}.
20589 @item show interrupt-sequence
20590 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20591 is sent by @value{GDBN} to interrupt the remote program.
20592 @code{BREAK-g} is BREAK signal followed by @code{g} and
20593 also known as Magic SysRq g.
20595 @item set remote interrupt-on-connect
20596 @cindex send interrupt-sequence on start
20597 Specify whether interrupt-sequence is sent to remote target when
20598 @value{GDBN} connects to it. This is mostly needed when you debug
20599 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20600 which is known as Magic SysRq g in order to connect @value{GDBN}.
20602 @item show interrupt-on-connect
20603 Show whether interrupt-sequence is sent
20604 to remote target when @value{GDBN} connects to it.
20608 @item set tcp auto-retry on
20609 @cindex auto-retry, for remote TCP target
20610 Enable auto-retry for remote TCP connections. This is useful if the remote
20611 debugging agent is launched in parallel with @value{GDBN}; there is a race
20612 condition because the agent may not become ready to accept the connection
20613 before @value{GDBN} attempts to connect. When auto-retry is
20614 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20615 to establish the connection using the timeout specified by
20616 @code{set tcp connect-timeout}.
20618 @item set tcp auto-retry off
20619 Do not auto-retry failed TCP connections.
20621 @item show tcp auto-retry
20622 Show the current auto-retry setting.
20624 @item set tcp connect-timeout @var{seconds}
20625 @itemx set tcp connect-timeout unlimited
20626 @cindex connection timeout, for remote TCP target
20627 @cindex timeout, for remote target connection
20628 Set the timeout for establishing a TCP connection to the remote target to
20629 @var{seconds}. The timeout affects both polling to retry failed connections
20630 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20631 that are merely slow to complete, and represents an approximate cumulative
20632 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20633 @value{GDBN} will keep attempting to establish a connection forever,
20634 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20636 @item show tcp connect-timeout
20637 Show the current connection timeout setting.
20640 @cindex remote packets, enabling and disabling
20641 The @value{GDBN} remote protocol autodetects the packets supported by
20642 your debugging stub. If you need to override the autodetection, you
20643 can use these commands to enable or disable individual packets. Each
20644 packet can be set to @samp{on} (the remote target supports this
20645 packet), @samp{off} (the remote target does not support this packet),
20646 or @samp{auto} (detect remote target support for this packet). They
20647 all default to @samp{auto}. For more information about each packet,
20648 see @ref{Remote Protocol}.
20650 During normal use, you should not have to use any of these commands.
20651 If you do, that may be a bug in your remote debugging stub, or a bug
20652 in @value{GDBN}. You may want to report the problem to the
20653 @value{GDBN} developers.
20655 For each packet @var{name}, the command to enable or disable the
20656 packet is @code{set remote @var{name}-packet}. The available settings
20659 @multitable @columnfractions 0.28 0.32 0.25
20662 @tab Related Features
20664 @item @code{fetch-register}
20666 @tab @code{info registers}
20668 @item @code{set-register}
20672 @item @code{binary-download}
20674 @tab @code{load}, @code{set}
20676 @item @code{read-aux-vector}
20677 @tab @code{qXfer:auxv:read}
20678 @tab @code{info auxv}
20680 @item @code{symbol-lookup}
20681 @tab @code{qSymbol}
20682 @tab Detecting multiple threads
20684 @item @code{attach}
20685 @tab @code{vAttach}
20688 @item @code{verbose-resume}
20690 @tab Stepping or resuming multiple threads
20696 @item @code{software-breakpoint}
20700 @item @code{hardware-breakpoint}
20704 @item @code{write-watchpoint}
20708 @item @code{read-watchpoint}
20712 @item @code{access-watchpoint}
20716 @item @code{pid-to-exec-file}
20717 @tab @code{qXfer:exec-file:read}
20718 @tab @code{attach}, @code{run}
20720 @item @code{target-features}
20721 @tab @code{qXfer:features:read}
20722 @tab @code{set architecture}
20724 @item @code{library-info}
20725 @tab @code{qXfer:libraries:read}
20726 @tab @code{info sharedlibrary}
20728 @item @code{memory-map}
20729 @tab @code{qXfer:memory-map:read}
20730 @tab @code{info mem}
20732 @item @code{read-sdata-object}
20733 @tab @code{qXfer:sdata:read}
20734 @tab @code{print $_sdata}
20736 @item @code{read-spu-object}
20737 @tab @code{qXfer:spu:read}
20738 @tab @code{info spu}
20740 @item @code{write-spu-object}
20741 @tab @code{qXfer:spu:write}
20742 @tab @code{info spu}
20744 @item @code{read-siginfo-object}
20745 @tab @code{qXfer:siginfo:read}
20746 @tab @code{print $_siginfo}
20748 @item @code{write-siginfo-object}
20749 @tab @code{qXfer:siginfo:write}
20750 @tab @code{set $_siginfo}
20752 @item @code{threads}
20753 @tab @code{qXfer:threads:read}
20754 @tab @code{info threads}
20756 @item @code{get-thread-local-@*storage-address}
20757 @tab @code{qGetTLSAddr}
20758 @tab Displaying @code{__thread} variables
20760 @item @code{get-thread-information-block-address}
20761 @tab @code{qGetTIBAddr}
20762 @tab Display MS-Windows Thread Information Block.
20764 @item @code{search-memory}
20765 @tab @code{qSearch:memory}
20768 @item @code{supported-packets}
20769 @tab @code{qSupported}
20770 @tab Remote communications parameters
20772 @item @code{catch-syscalls}
20773 @tab @code{QCatchSyscalls}
20774 @tab @code{catch syscall}
20776 @item @code{pass-signals}
20777 @tab @code{QPassSignals}
20778 @tab @code{handle @var{signal}}
20780 @item @code{program-signals}
20781 @tab @code{QProgramSignals}
20782 @tab @code{handle @var{signal}}
20784 @item @code{hostio-close-packet}
20785 @tab @code{vFile:close}
20786 @tab @code{remote get}, @code{remote put}
20788 @item @code{hostio-open-packet}
20789 @tab @code{vFile:open}
20790 @tab @code{remote get}, @code{remote put}
20792 @item @code{hostio-pread-packet}
20793 @tab @code{vFile:pread}
20794 @tab @code{remote get}, @code{remote put}
20796 @item @code{hostio-pwrite-packet}
20797 @tab @code{vFile:pwrite}
20798 @tab @code{remote get}, @code{remote put}
20800 @item @code{hostio-unlink-packet}
20801 @tab @code{vFile:unlink}
20802 @tab @code{remote delete}
20804 @item @code{hostio-readlink-packet}
20805 @tab @code{vFile:readlink}
20808 @item @code{hostio-fstat-packet}
20809 @tab @code{vFile:fstat}
20812 @item @code{hostio-setfs-packet}
20813 @tab @code{vFile:setfs}
20816 @item @code{noack-packet}
20817 @tab @code{QStartNoAckMode}
20818 @tab Packet acknowledgment
20820 @item @code{osdata}
20821 @tab @code{qXfer:osdata:read}
20822 @tab @code{info os}
20824 @item @code{query-attached}
20825 @tab @code{qAttached}
20826 @tab Querying remote process attach state.
20828 @item @code{trace-buffer-size}
20829 @tab @code{QTBuffer:size}
20830 @tab @code{set trace-buffer-size}
20832 @item @code{trace-status}
20833 @tab @code{qTStatus}
20834 @tab @code{tstatus}
20836 @item @code{traceframe-info}
20837 @tab @code{qXfer:traceframe-info:read}
20838 @tab Traceframe info
20840 @item @code{install-in-trace}
20841 @tab @code{InstallInTrace}
20842 @tab Install tracepoint in tracing
20844 @item @code{disable-randomization}
20845 @tab @code{QDisableRandomization}
20846 @tab @code{set disable-randomization}
20848 @item @code{startup-with-shell}
20849 @tab @code{QStartupWithShell}
20850 @tab @code{set startup-with-shell}
20852 @item @code{conditional-breakpoints-packet}
20853 @tab @code{Z0 and Z1}
20854 @tab @code{Support for target-side breakpoint condition evaluation}
20856 @item @code{multiprocess-extensions}
20857 @tab @code{multiprocess extensions}
20858 @tab Debug multiple processes and remote process PID awareness
20860 @item @code{swbreak-feature}
20861 @tab @code{swbreak stop reason}
20864 @item @code{hwbreak-feature}
20865 @tab @code{hwbreak stop reason}
20868 @item @code{fork-event-feature}
20869 @tab @code{fork stop reason}
20872 @item @code{vfork-event-feature}
20873 @tab @code{vfork stop reason}
20876 @item @code{exec-event-feature}
20877 @tab @code{exec stop reason}
20880 @item @code{thread-events}
20881 @tab @code{QThreadEvents}
20882 @tab Tracking thread lifetime.
20884 @item @code{no-resumed-stop-reply}
20885 @tab @code{no resumed thread left stop reply}
20886 @tab Tracking thread lifetime.
20891 @section Implementing a Remote Stub
20893 @cindex debugging stub, example
20894 @cindex remote stub, example
20895 @cindex stub example, remote debugging
20896 The stub files provided with @value{GDBN} implement the target side of the
20897 communication protocol, and the @value{GDBN} side is implemented in the
20898 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20899 these subroutines to communicate, and ignore the details. (If you're
20900 implementing your own stub file, you can still ignore the details: start
20901 with one of the existing stub files. @file{sparc-stub.c} is the best
20902 organized, and therefore the easiest to read.)
20904 @cindex remote serial debugging, overview
20905 To debug a program running on another machine (the debugging
20906 @dfn{target} machine), you must first arrange for all the usual
20907 prerequisites for the program to run by itself. For example, for a C
20912 A startup routine to set up the C runtime environment; these usually
20913 have a name like @file{crt0}. The startup routine may be supplied by
20914 your hardware supplier, or you may have to write your own.
20917 A C subroutine library to support your program's
20918 subroutine calls, notably managing input and output.
20921 A way of getting your program to the other machine---for example, a
20922 download program. These are often supplied by the hardware
20923 manufacturer, but you may have to write your own from hardware
20927 The next step is to arrange for your program to use a serial port to
20928 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20929 machine). In general terms, the scheme looks like this:
20933 @value{GDBN} already understands how to use this protocol; when everything
20934 else is set up, you can simply use the @samp{target remote} command
20935 (@pxref{Targets,,Specifying a Debugging Target}).
20937 @item On the target,
20938 you must link with your program a few special-purpose subroutines that
20939 implement the @value{GDBN} remote serial protocol. The file containing these
20940 subroutines is called a @dfn{debugging stub}.
20942 On certain remote targets, you can use an auxiliary program
20943 @code{gdbserver} instead of linking a stub into your program.
20944 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20947 The debugging stub is specific to the architecture of the remote
20948 machine; for example, use @file{sparc-stub.c} to debug programs on
20951 @cindex remote serial stub list
20952 These working remote stubs are distributed with @value{GDBN}:
20957 @cindex @file{i386-stub.c}
20960 For Intel 386 and compatible architectures.
20963 @cindex @file{m68k-stub.c}
20964 @cindex Motorola 680x0
20966 For Motorola 680x0 architectures.
20969 @cindex @file{sh-stub.c}
20972 For Renesas SH architectures.
20975 @cindex @file{sparc-stub.c}
20977 For @sc{sparc} architectures.
20979 @item sparcl-stub.c
20980 @cindex @file{sparcl-stub.c}
20983 For Fujitsu @sc{sparclite} architectures.
20987 The @file{README} file in the @value{GDBN} distribution may list other
20988 recently added stubs.
20991 * Stub Contents:: What the stub can do for you
20992 * Bootstrapping:: What you must do for the stub
20993 * Debug Session:: Putting it all together
20996 @node Stub Contents
20997 @subsection What the Stub Can Do for You
20999 @cindex remote serial stub
21000 The debugging stub for your architecture supplies these three
21004 @item set_debug_traps
21005 @findex set_debug_traps
21006 @cindex remote serial stub, initialization
21007 This routine arranges for @code{handle_exception} to run when your
21008 program stops. You must call this subroutine explicitly in your
21009 program's startup code.
21011 @item handle_exception
21012 @findex handle_exception
21013 @cindex remote serial stub, main routine
21014 This is the central workhorse, but your program never calls it
21015 explicitly---the setup code arranges for @code{handle_exception} to
21016 run when a trap is triggered.
21018 @code{handle_exception} takes control when your program stops during
21019 execution (for example, on a breakpoint), and mediates communications
21020 with @value{GDBN} on the host machine. This is where the communications
21021 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21022 representative on the target machine. It begins by sending summary
21023 information on the state of your program, then continues to execute,
21024 retrieving and transmitting any information @value{GDBN} needs, until you
21025 execute a @value{GDBN} command that makes your program resume; at that point,
21026 @code{handle_exception} returns control to your own code on the target
21030 @cindex @code{breakpoint} subroutine, remote
21031 Use this auxiliary subroutine to make your program contain a
21032 breakpoint. Depending on the particular situation, this may be the only
21033 way for @value{GDBN} to get control. For instance, if your target
21034 machine has some sort of interrupt button, you won't need to call this;
21035 pressing the interrupt button transfers control to
21036 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21037 simply receiving characters on the serial port may also trigger a trap;
21038 again, in that situation, you don't need to call @code{breakpoint} from
21039 your own program---simply running @samp{target remote} from the host
21040 @value{GDBN} session gets control.
21042 Call @code{breakpoint} if none of these is true, or if you simply want
21043 to make certain your program stops at a predetermined point for the
21044 start of your debugging session.
21047 @node Bootstrapping
21048 @subsection What You Must Do for the Stub
21050 @cindex remote stub, support routines
21051 The debugging stubs that come with @value{GDBN} are set up for a particular
21052 chip architecture, but they have no information about the rest of your
21053 debugging target machine.
21055 First of all you need to tell the stub how to communicate with the
21059 @item int getDebugChar()
21060 @findex getDebugChar
21061 Write this subroutine to read a single character from the serial port.
21062 It may be identical to @code{getchar} for your target system; a
21063 different name is used to allow you to distinguish the two if you wish.
21065 @item void putDebugChar(int)
21066 @findex putDebugChar
21067 Write this subroutine to write a single character to the serial port.
21068 It may be identical to @code{putchar} for your target system; a
21069 different name is used to allow you to distinguish the two if you wish.
21072 @cindex control C, and remote debugging
21073 @cindex interrupting remote targets
21074 If you want @value{GDBN} to be able to stop your program while it is
21075 running, you need to use an interrupt-driven serial driver, and arrange
21076 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21077 character). That is the character which @value{GDBN} uses to tell the
21078 remote system to stop.
21080 Getting the debugging target to return the proper status to @value{GDBN}
21081 probably requires changes to the standard stub; one quick and dirty way
21082 is to just execute a breakpoint instruction (the ``dirty'' part is that
21083 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21085 Other routines you need to supply are:
21088 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21089 @findex exceptionHandler
21090 Write this function to install @var{exception_address} in the exception
21091 handling tables. You need to do this because the stub does not have any
21092 way of knowing what the exception handling tables on your target system
21093 are like (for example, the processor's table might be in @sc{rom},
21094 containing entries which point to a table in @sc{ram}).
21095 The @var{exception_number} specifies the exception which should be changed;
21096 its meaning is architecture-dependent (for example, different numbers
21097 might represent divide by zero, misaligned access, etc). When this
21098 exception occurs, control should be transferred directly to
21099 @var{exception_address}, and the processor state (stack, registers,
21100 and so on) should be just as it is when a processor exception occurs. So if
21101 you want to use a jump instruction to reach @var{exception_address}, it
21102 should be a simple jump, not a jump to subroutine.
21104 For the 386, @var{exception_address} should be installed as an interrupt
21105 gate so that interrupts are masked while the handler runs. The gate
21106 should be at privilege level 0 (the most privileged level). The
21107 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21108 help from @code{exceptionHandler}.
21110 @item void flush_i_cache()
21111 @findex flush_i_cache
21112 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21113 instruction cache, if any, on your target machine. If there is no
21114 instruction cache, this subroutine may be a no-op.
21116 On target machines that have instruction caches, @value{GDBN} requires this
21117 function to make certain that the state of your program is stable.
21121 You must also make sure this library routine is available:
21124 @item void *memset(void *, int, int)
21126 This is the standard library function @code{memset} that sets an area of
21127 memory to a known value. If you have one of the free versions of
21128 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21129 either obtain it from your hardware manufacturer, or write your own.
21132 If you do not use the GNU C compiler, you may need other standard
21133 library subroutines as well; this varies from one stub to another,
21134 but in general the stubs are likely to use any of the common library
21135 subroutines which @code{@value{NGCC}} generates as inline code.
21138 @node Debug Session
21139 @subsection Putting it All Together
21141 @cindex remote serial debugging summary
21142 In summary, when your program is ready to debug, you must follow these
21147 Make sure you have defined the supporting low-level routines
21148 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21150 @code{getDebugChar}, @code{putDebugChar},
21151 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21155 Insert these lines in your program's startup code, before the main
21156 procedure is called:
21163 On some machines, when a breakpoint trap is raised, the hardware
21164 automatically makes the PC point to the instruction after the
21165 breakpoint. If your machine doesn't do that, you may need to adjust
21166 @code{handle_exception} to arrange for it to return to the instruction
21167 after the breakpoint on this first invocation, so that your program
21168 doesn't keep hitting the initial breakpoint instead of making
21172 For the 680x0 stub only, you need to provide a variable called
21173 @code{exceptionHook}. Normally you just use:
21176 void (*exceptionHook)() = 0;
21180 but if before calling @code{set_debug_traps}, you set it to point to a
21181 function in your program, that function is called when
21182 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21183 error). The function indicated by @code{exceptionHook} is called with
21184 one parameter: an @code{int} which is the exception number.
21187 Compile and link together: your program, the @value{GDBN} debugging stub for
21188 your target architecture, and the supporting subroutines.
21191 Make sure you have a serial connection between your target machine and
21192 the @value{GDBN} host, and identify the serial port on the host.
21195 @c The "remote" target now provides a `load' command, so we should
21196 @c document that. FIXME.
21197 Download your program to your target machine (or get it there by
21198 whatever means the manufacturer provides), and start it.
21201 Start @value{GDBN} on the host, and connect to the target
21202 (@pxref{Connecting,,Connecting to a Remote Target}).
21206 @node Configurations
21207 @chapter Configuration-Specific Information
21209 While nearly all @value{GDBN} commands are available for all native and
21210 cross versions of the debugger, there are some exceptions. This chapter
21211 describes things that are only available in certain configurations.
21213 There are three major categories of configurations: native
21214 configurations, where the host and target are the same, embedded
21215 operating system configurations, which are usually the same for several
21216 different processor architectures, and bare embedded processors, which
21217 are quite different from each other.
21222 * Embedded Processors::
21229 This section describes details specific to particular native
21233 * BSD libkvm Interface:: Debugging BSD kernel memory images
21234 * SVR4 Process Information:: SVR4 process information
21235 * DJGPP Native:: Features specific to the DJGPP port
21236 * Cygwin Native:: Features specific to the Cygwin port
21237 * Hurd Native:: Features specific to @sc{gnu} Hurd
21238 * Darwin:: Features specific to Darwin
21241 @node BSD libkvm Interface
21242 @subsection BSD libkvm Interface
21245 @cindex kernel memory image
21246 @cindex kernel crash dump
21248 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21249 interface that provides a uniform interface for accessing kernel virtual
21250 memory images, including live systems and crash dumps. @value{GDBN}
21251 uses this interface to allow you to debug live kernels and kernel crash
21252 dumps on many native BSD configurations. This is implemented as a
21253 special @code{kvm} debugging target. For debugging a live system, load
21254 the currently running kernel into @value{GDBN} and connect to the
21258 (@value{GDBP}) @b{target kvm}
21261 For debugging crash dumps, provide the file name of the crash dump as an
21265 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21268 Once connected to the @code{kvm} target, the following commands are
21274 Set current context from the @dfn{Process Control Block} (PCB) address.
21277 Set current context from proc address. This command isn't available on
21278 modern FreeBSD systems.
21281 @node SVR4 Process Information
21282 @subsection SVR4 Process Information
21284 @cindex examine process image
21285 @cindex process info via @file{/proc}
21287 Many versions of SVR4 and compatible systems provide a facility called
21288 @samp{/proc} that can be used to examine the image of a running
21289 process using file-system subroutines.
21291 If @value{GDBN} is configured for an operating system with this
21292 facility, the command @code{info proc} is available to report
21293 information about the process running your program, or about any
21294 process running on your system. This includes, as of this writing,
21295 @sc{gnu}/Linux and Solaris, for example.
21297 This command may also work on core files that were created on a system
21298 that has the @samp{/proc} facility.
21304 @itemx info proc @var{process-id}
21305 Summarize available information about any running process. If a
21306 process ID is specified by @var{process-id}, display information about
21307 that process; otherwise display information about the program being
21308 debugged. The summary includes the debugged process ID, the command
21309 line used to invoke it, its current working directory, and its
21310 executable file's absolute file name.
21312 On some systems, @var{process-id} can be of the form
21313 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21314 within a process. If the optional @var{pid} part is missing, it means
21315 a thread from the process being debugged (the leading @samp{/} still
21316 needs to be present, or else @value{GDBN} will interpret the number as
21317 a process ID rather than a thread ID).
21319 @item info proc cmdline
21320 @cindex info proc cmdline
21321 Show the original command line of the process. This command is
21322 specific to @sc{gnu}/Linux.
21324 @item info proc cwd
21325 @cindex info proc cwd
21326 Show the current working directory of the process. This command is
21327 specific to @sc{gnu}/Linux.
21329 @item info proc exe
21330 @cindex info proc exe
21331 Show the name of executable of the process. This command is specific
21334 @item info proc mappings
21335 @cindex memory address space mappings
21336 Report the memory address space ranges accessible in the program, with
21337 information on whether the process has read, write, or execute access
21338 rights to each range. On @sc{gnu}/Linux systems, each memory range
21339 includes the object file which is mapped to that range, instead of the
21340 memory access rights to that range.
21342 @item info proc stat
21343 @itemx info proc status
21344 @cindex process detailed status information
21345 These subcommands are specific to @sc{gnu}/Linux systems. They show
21346 the process-related information, including the user ID and group ID;
21347 how many threads are there in the process; its virtual memory usage;
21348 the signals that are pending, blocked, and ignored; its TTY; its
21349 consumption of system and user time; its stack size; its @samp{nice}
21350 value; etc. For more information, see the @samp{proc} man page
21351 (type @kbd{man 5 proc} from your shell prompt).
21353 @item info proc all
21354 Show all the information about the process described under all of the
21355 above @code{info proc} subcommands.
21358 @comment These sub-options of 'info proc' were not included when
21359 @comment procfs.c was re-written. Keep their descriptions around
21360 @comment against the day when someone finds the time to put them back in.
21361 @kindex info proc times
21362 @item info proc times
21363 Starting time, user CPU time, and system CPU time for your program and
21366 @kindex info proc id
21368 Report on the process IDs related to your program: its own process ID,
21369 the ID of its parent, the process group ID, and the session ID.
21372 @item set procfs-trace
21373 @kindex set procfs-trace
21374 @cindex @code{procfs} API calls
21375 This command enables and disables tracing of @code{procfs} API calls.
21377 @item show procfs-trace
21378 @kindex show procfs-trace
21379 Show the current state of @code{procfs} API call tracing.
21381 @item set procfs-file @var{file}
21382 @kindex set procfs-file
21383 Tell @value{GDBN} to write @code{procfs} API trace to the named
21384 @var{file}. @value{GDBN} appends the trace info to the previous
21385 contents of the file. The default is to display the trace on the
21388 @item show procfs-file
21389 @kindex show procfs-file
21390 Show the file to which @code{procfs} API trace is written.
21392 @item proc-trace-entry
21393 @itemx proc-trace-exit
21394 @itemx proc-untrace-entry
21395 @itemx proc-untrace-exit
21396 @kindex proc-trace-entry
21397 @kindex proc-trace-exit
21398 @kindex proc-untrace-entry
21399 @kindex proc-untrace-exit
21400 These commands enable and disable tracing of entries into and exits
21401 from the @code{syscall} interface.
21404 @kindex info pidlist
21405 @cindex process list, QNX Neutrino
21406 For QNX Neutrino only, this command displays the list of all the
21407 processes and all the threads within each process.
21410 @kindex info meminfo
21411 @cindex mapinfo list, QNX Neutrino
21412 For QNX Neutrino only, this command displays the list of all mapinfos.
21416 @subsection Features for Debugging @sc{djgpp} Programs
21417 @cindex @sc{djgpp} debugging
21418 @cindex native @sc{djgpp} debugging
21419 @cindex MS-DOS-specific commands
21422 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21423 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21424 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21425 top of real-mode DOS systems and their emulations.
21427 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21428 defines a few commands specific to the @sc{djgpp} port. This
21429 subsection describes those commands.
21434 This is a prefix of @sc{djgpp}-specific commands which print
21435 information about the target system and important OS structures.
21438 @cindex MS-DOS system info
21439 @cindex free memory information (MS-DOS)
21440 @item info dos sysinfo
21441 This command displays assorted information about the underlying
21442 platform: the CPU type and features, the OS version and flavor, the
21443 DPMI version, and the available conventional and DPMI memory.
21448 @cindex segment descriptor tables
21449 @cindex descriptor tables display
21451 @itemx info dos ldt
21452 @itemx info dos idt
21453 These 3 commands display entries from, respectively, Global, Local,
21454 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21455 tables are data structures which store a descriptor for each segment
21456 that is currently in use. The segment's selector is an index into a
21457 descriptor table; the table entry for that index holds the
21458 descriptor's base address and limit, and its attributes and access
21461 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21462 segment (used for both data and the stack), and a DOS segment (which
21463 allows access to DOS/BIOS data structures and absolute addresses in
21464 conventional memory). However, the DPMI host will usually define
21465 additional segments in order to support the DPMI environment.
21467 @cindex garbled pointers
21468 These commands allow to display entries from the descriptor tables.
21469 Without an argument, all entries from the specified table are
21470 displayed. An argument, which should be an integer expression, means
21471 display a single entry whose index is given by the argument. For
21472 example, here's a convenient way to display information about the
21473 debugged program's data segment:
21476 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21477 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21481 This comes in handy when you want to see whether a pointer is outside
21482 the data segment's limit (i.e.@: @dfn{garbled}).
21484 @cindex page tables display (MS-DOS)
21486 @itemx info dos pte
21487 These two commands display entries from, respectively, the Page
21488 Directory and the Page Tables. Page Directories and Page Tables are
21489 data structures which control how virtual memory addresses are mapped
21490 into physical addresses. A Page Table includes an entry for every
21491 page of memory that is mapped into the program's address space; there
21492 may be several Page Tables, each one holding up to 4096 entries. A
21493 Page Directory has up to 4096 entries, one each for every Page Table
21494 that is currently in use.
21496 Without an argument, @kbd{info dos pde} displays the entire Page
21497 Directory, and @kbd{info dos pte} displays all the entries in all of
21498 the Page Tables. An argument, an integer expression, given to the
21499 @kbd{info dos pde} command means display only that entry from the Page
21500 Directory table. An argument given to the @kbd{info dos pte} command
21501 means display entries from a single Page Table, the one pointed to by
21502 the specified entry in the Page Directory.
21504 @cindex direct memory access (DMA) on MS-DOS
21505 These commands are useful when your program uses @dfn{DMA} (Direct
21506 Memory Access), which needs physical addresses to program the DMA
21509 These commands are supported only with some DPMI servers.
21511 @cindex physical address from linear address
21512 @item info dos address-pte @var{addr}
21513 This command displays the Page Table entry for a specified linear
21514 address. The argument @var{addr} is a linear address which should
21515 already have the appropriate segment's base address added to it,
21516 because this command accepts addresses which may belong to @emph{any}
21517 segment. For example, here's how to display the Page Table entry for
21518 the page where a variable @code{i} is stored:
21521 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21522 @exdent @code{Page Table entry for address 0x11a00d30:}
21523 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21527 This says that @code{i} is stored at offset @code{0xd30} from the page
21528 whose physical base address is @code{0x02698000}, and shows all the
21529 attributes of that page.
21531 Note that you must cast the addresses of variables to a @code{char *},
21532 since otherwise the value of @code{__djgpp_base_address}, the base
21533 address of all variables and functions in a @sc{djgpp} program, will
21534 be added using the rules of C pointer arithmetics: if @code{i} is
21535 declared an @code{int}, @value{GDBN} will add 4 times the value of
21536 @code{__djgpp_base_address} to the address of @code{i}.
21538 Here's another example, it displays the Page Table entry for the
21542 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21543 @exdent @code{Page Table entry for address 0x29110:}
21544 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21548 (The @code{+ 3} offset is because the transfer buffer's address is the
21549 3rd member of the @code{_go32_info_block} structure.) The output
21550 clearly shows that this DPMI server maps the addresses in conventional
21551 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21552 linear (@code{0x29110}) addresses are identical.
21554 This command is supported only with some DPMI servers.
21557 @cindex DOS serial data link, remote debugging
21558 In addition to native debugging, the DJGPP port supports remote
21559 debugging via a serial data link. The following commands are specific
21560 to remote serial debugging in the DJGPP port of @value{GDBN}.
21563 @kindex set com1base
21564 @kindex set com1irq
21565 @kindex set com2base
21566 @kindex set com2irq
21567 @kindex set com3base
21568 @kindex set com3irq
21569 @kindex set com4base
21570 @kindex set com4irq
21571 @item set com1base @var{addr}
21572 This command sets the base I/O port address of the @file{COM1} serial
21575 @item set com1irq @var{irq}
21576 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21577 for the @file{COM1} serial port.
21579 There are similar commands @samp{set com2base}, @samp{set com3irq},
21580 etc.@: for setting the port address and the @code{IRQ} lines for the
21583 @kindex show com1base
21584 @kindex show com1irq
21585 @kindex show com2base
21586 @kindex show com2irq
21587 @kindex show com3base
21588 @kindex show com3irq
21589 @kindex show com4base
21590 @kindex show com4irq
21591 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21592 display the current settings of the base address and the @code{IRQ}
21593 lines used by the COM ports.
21596 @kindex info serial
21597 @cindex DOS serial port status
21598 This command prints the status of the 4 DOS serial ports. For each
21599 port, it prints whether it's active or not, its I/O base address and
21600 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21601 counts of various errors encountered so far.
21605 @node Cygwin Native
21606 @subsection Features for Debugging MS Windows PE Executables
21607 @cindex MS Windows debugging
21608 @cindex native Cygwin debugging
21609 @cindex Cygwin-specific commands
21611 @value{GDBN} supports native debugging of MS Windows programs, including
21612 DLLs with and without symbolic debugging information.
21614 @cindex Ctrl-BREAK, MS-Windows
21615 @cindex interrupt debuggee on MS-Windows
21616 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21617 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21618 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21619 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21620 sequence, which can be used to interrupt the debuggee even if it
21623 There are various additional Cygwin-specific commands, described in
21624 this section. Working with DLLs that have no debugging symbols is
21625 described in @ref{Non-debug DLL Symbols}.
21630 This is a prefix of MS Windows-specific commands which print
21631 information about the target system and important OS structures.
21633 @item info w32 selector
21634 This command displays information returned by
21635 the Win32 API @code{GetThreadSelectorEntry} function.
21636 It takes an optional argument that is evaluated to
21637 a long value to give the information about this given selector.
21638 Without argument, this command displays information
21639 about the six segment registers.
21641 @item info w32 thread-information-block
21642 This command displays thread specific information stored in the
21643 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21644 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21646 @kindex signal-event
21647 @item signal-event @var{id}
21648 This command signals an event with user-provided @var{id}. Used to resume
21649 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21651 To use it, create or edit the following keys in
21652 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21653 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21654 (for x86_64 versions):
21658 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21659 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21660 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21662 The first @code{%ld} will be replaced by the process ID of the
21663 crashing process, the second @code{%ld} will be replaced by the ID of
21664 the event that blocks the crashing process, waiting for @value{GDBN}
21668 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21669 make the system run debugger specified by the Debugger key
21670 automatically, @code{0} will cause a dialog box with ``OK'' and
21671 ``Cancel'' buttons to appear, which allows the user to either
21672 terminate the crashing process (OK) or debug it (Cancel).
21675 @kindex set cygwin-exceptions
21676 @cindex debugging the Cygwin DLL
21677 @cindex Cygwin DLL, debugging
21678 @item set cygwin-exceptions @var{mode}
21679 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21680 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21681 @value{GDBN} will delay recognition of exceptions, and may ignore some
21682 exceptions which seem to be caused by internal Cygwin DLL
21683 ``bookkeeping''. This option is meant primarily for debugging the
21684 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21685 @value{GDBN} users with false @code{SIGSEGV} signals.
21687 @kindex show cygwin-exceptions
21688 @item show cygwin-exceptions
21689 Displays whether @value{GDBN} will break on exceptions that happen
21690 inside the Cygwin DLL itself.
21692 @kindex set new-console
21693 @item set new-console @var{mode}
21694 If @var{mode} is @code{on} the debuggee will
21695 be started in a new console on next start.
21696 If @var{mode} is @code{off}, the debuggee will
21697 be started in the same console as the debugger.
21699 @kindex show new-console
21700 @item show new-console
21701 Displays whether a new console is used
21702 when the debuggee is started.
21704 @kindex set new-group
21705 @item set new-group @var{mode}
21706 This boolean value controls whether the debuggee should
21707 start a new group or stay in the same group as the debugger.
21708 This affects the way the Windows OS handles
21711 @kindex show new-group
21712 @item show new-group
21713 Displays current value of new-group boolean.
21715 @kindex set debugevents
21716 @item set debugevents
21717 This boolean value adds debug output concerning kernel events related
21718 to the debuggee seen by the debugger. This includes events that
21719 signal thread and process creation and exit, DLL loading and
21720 unloading, console interrupts, and debugging messages produced by the
21721 Windows @code{OutputDebugString} API call.
21723 @kindex set debugexec
21724 @item set debugexec
21725 This boolean value adds debug output concerning execute events
21726 (such as resume thread) seen by the debugger.
21728 @kindex set debugexceptions
21729 @item set debugexceptions
21730 This boolean value adds debug output concerning exceptions in the
21731 debuggee seen by the debugger.
21733 @kindex set debugmemory
21734 @item set debugmemory
21735 This boolean value adds debug output concerning debuggee memory reads
21736 and writes by the debugger.
21740 This boolean values specifies whether the debuggee is called
21741 via a shell or directly (default value is on).
21745 Displays if the debuggee will be started with a shell.
21750 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21753 @node Non-debug DLL Symbols
21754 @subsubsection Support for DLLs without Debugging Symbols
21755 @cindex DLLs with no debugging symbols
21756 @cindex Minimal symbols and DLLs
21758 Very often on windows, some of the DLLs that your program relies on do
21759 not include symbolic debugging information (for example,
21760 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21761 symbols in a DLL, it relies on the minimal amount of symbolic
21762 information contained in the DLL's export table. This section
21763 describes working with such symbols, known internally to @value{GDBN} as
21764 ``minimal symbols''.
21766 Note that before the debugged program has started execution, no DLLs
21767 will have been loaded. The easiest way around this problem is simply to
21768 start the program --- either by setting a breakpoint or letting the
21769 program run once to completion.
21771 @subsubsection DLL Name Prefixes
21773 In keeping with the naming conventions used by the Microsoft debugging
21774 tools, DLL export symbols are made available with a prefix based on the
21775 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21776 also entered into the symbol table, so @code{CreateFileA} is often
21777 sufficient. In some cases there will be name clashes within a program
21778 (particularly if the executable itself includes full debugging symbols)
21779 necessitating the use of the fully qualified name when referring to the
21780 contents of the DLL. Use single-quotes around the name to avoid the
21781 exclamation mark (``!'') being interpreted as a language operator.
21783 Note that the internal name of the DLL may be all upper-case, even
21784 though the file name of the DLL is lower-case, or vice-versa. Since
21785 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21786 some confusion. If in doubt, try the @code{info functions} and
21787 @code{info variables} commands or even @code{maint print msymbols}
21788 (@pxref{Symbols}). Here's an example:
21791 (@value{GDBP}) info function CreateFileA
21792 All functions matching regular expression "CreateFileA":
21794 Non-debugging symbols:
21795 0x77e885f4 CreateFileA
21796 0x77e885f4 KERNEL32!CreateFileA
21800 (@value{GDBP}) info function !
21801 All functions matching regular expression "!":
21803 Non-debugging symbols:
21804 0x6100114c cygwin1!__assert
21805 0x61004034 cygwin1!_dll_crt0@@0
21806 0x61004240 cygwin1!dll_crt0(per_process *)
21810 @subsubsection Working with Minimal Symbols
21812 Symbols extracted from a DLL's export table do not contain very much
21813 type information. All that @value{GDBN} can do is guess whether a symbol
21814 refers to a function or variable depending on the linker section that
21815 contains the symbol. Also note that the actual contents of the memory
21816 contained in a DLL are not available unless the program is running. This
21817 means that you cannot examine the contents of a variable or disassemble
21818 a function within a DLL without a running program.
21820 Variables are generally treated as pointers and dereferenced
21821 automatically. For this reason, it is often necessary to prefix a
21822 variable name with the address-of operator (``&'') and provide explicit
21823 type information in the command. Here's an example of the type of
21827 (@value{GDBP}) print 'cygwin1!__argv'
21832 (@value{GDBP}) x 'cygwin1!__argv'
21833 0x10021610: "\230y\""
21836 And two possible solutions:
21839 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21840 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21844 (@value{GDBP}) x/2x &'cygwin1!__argv'
21845 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21846 (@value{GDBP}) x/x 0x10021608
21847 0x10021608: 0x0022fd98
21848 (@value{GDBP}) x/s 0x0022fd98
21849 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21852 Setting a break point within a DLL is possible even before the program
21853 starts execution. However, under these circumstances, @value{GDBN} can't
21854 examine the initial instructions of the function in order to skip the
21855 function's frame set-up code. You can work around this by using ``*&''
21856 to set the breakpoint at a raw memory address:
21859 (@value{GDBP}) break *&'python22!PyOS_Readline'
21860 Breakpoint 1 at 0x1e04eff0
21863 The author of these extensions is not entirely convinced that setting a
21864 break point within a shared DLL like @file{kernel32.dll} is completely
21868 @subsection Commands Specific to @sc{gnu} Hurd Systems
21869 @cindex @sc{gnu} Hurd debugging
21871 This subsection describes @value{GDBN} commands specific to the
21872 @sc{gnu} Hurd native debugging.
21877 @kindex set signals@r{, Hurd command}
21878 @kindex set sigs@r{, Hurd command}
21879 This command toggles the state of inferior signal interception by
21880 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21881 affected by this command. @code{sigs} is a shorthand alias for
21886 @kindex show signals@r{, Hurd command}
21887 @kindex show sigs@r{, Hurd command}
21888 Show the current state of intercepting inferior's signals.
21890 @item set signal-thread
21891 @itemx set sigthread
21892 @kindex set signal-thread
21893 @kindex set sigthread
21894 This command tells @value{GDBN} which thread is the @code{libc} signal
21895 thread. That thread is run when a signal is delivered to a running
21896 process. @code{set sigthread} is the shorthand alias of @code{set
21899 @item show signal-thread
21900 @itemx show sigthread
21901 @kindex show signal-thread
21902 @kindex show sigthread
21903 These two commands show which thread will run when the inferior is
21904 delivered a signal.
21907 @kindex set stopped@r{, Hurd command}
21908 This commands tells @value{GDBN} that the inferior process is stopped,
21909 as with the @code{SIGSTOP} signal. The stopped process can be
21910 continued by delivering a signal to it.
21913 @kindex show stopped@r{, Hurd command}
21914 This command shows whether @value{GDBN} thinks the debuggee is
21917 @item set exceptions
21918 @kindex set exceptions@r{, Hurd command}
21919 Use this command to turn off trapping of exceptions in the inferior.
21920 When exception trapping is off, neither breakpoints nor
21921 single-stepping will work. To restore the default, set exception
21924 @item show exceptions
21925 @kindex show exceptions@r{, Hurd command}
21926 Show the current state of trapping exceptions in the inferior.
21928 @item set task pause
21929 @kindex set task@r{, Hurd commands}
21930 @cindex task attributes (@sc{gnu} Hurd)
21931 @cindex pause current task (@sc{gnu} Hurd)
21932 This command toggles task suspension when @value{GDBN} has control.
21933 Setting it to on takes effect immediately, and the task is suspended
21934 whenever @value{GDBN} gets control. Setting it to off will take
21935 effect the next time the inferior is continued. If this option is set
21936 to off, you can use @code{set thread default pause on} or @code{set
21937 thread pause on} (see below) to pause individual threads.
21939 @item show task pause
21940 @kindex show task@r{, Hurd commands}
21941 Show the current state of task suspension.
21943 @item set task detach-suspend-count
21944 @cindex task suspend count
21945 @cindex detach from task, @sc{gnu} Hurd
21946 This command sets the suspend count the task will be left with when
21947 @value{GDBN} detaches from it.
21949 @item show task detach-suspend-count
21950 Show the suspend count the task will be left with when detaching.
21952 @item set task exception-port
21953 @itemx set task excp
21954 @cindex task exception port, @sc{gnu} Hurd
21955 This command sets the task exception port to which @value{GDBN} will
21956 forward exceptions. The argument should be the value of the @dfn{send
21957 rights} of the task. @code{set task excp} is a shorthand alias.
21959 @item set noninvasive
21960 @cindex noninvasive task options
21961 This command switches @value{GDBN} to a mode that is the least
21962 invasive as far as interfering with the inferior is concerned. This
21963 is the same as using @code{set task pause}, @code{set exceptions}, and
21964 @code{set signals} to values opposite to the defaults.
21966 @item info send-rights
21967 @itemx info receive-rights
21968 @itemx info port-rights
21969 @itemx info port-sets
21970 @itemx info dead-names
21973 @cindex send rights, @sc{gnu} Hurd
21974 @cindex receive rights, @sc{gnu} Hurd
21975 @cindex port rights, @sc{gnu} Hurd
21976 @cindex port sets, @sc{gnu} Hurd
21977 @cindex dead names, @sc{gnu} Hurd
21978 These commands display information about, respectively, send rights,
21979 receive rights, port rights, port sets, and dead names of a task.
21980 There are also shorthand aliases: @code{info ports} for @code{info
21981 port-rights} and @code{info psets} for @code{info port-sets}.
21983 @item set thread pause
21984 @kindex set thread@r{, Hurd command}
21985 @cindex thread properties, @sc{gnu} Hurd
21986 @cindex pause current thread (@sc{gnu} Hurd)
21987 This command toggles current thread suspension when @value{GDBN} has
21988 control. Setting it to on takes effect immediately, and the current
21989 thread is suspended whenever @value{GDBN} gets control. Setting it to
21990 off will take effect the next time the inferior is continued.
21991 Normally, this command has no effect, since when @value{GDBN} has
21992 control, the whole task is suspended. However, if you used @code{set
21993 task pause off} (see above), this command comes in handy to suspend
21994 only the current thread.
21996 @item show thread pause
21997 @kindex show thread@r{, Hurd command}
21998 This command shows the state of current thread suspension.
22000 @item set thread run
22001 This command sets whether the current thread is allowed to run.
22003 @item show thread run
22004 Show whether the current thread is allowed to run.
22006 @item set thread detach-suspend-count
22007 @cindex thread suspend count, @sc{gnu} Hurd
22008 @cindex detach from thread, @sc{gnu} Hurd
22009 This command sets the suspend count @value{GDBN} will leave on a
22010 thread when detaching. This number is relative to the suspend count
22011 found by @value{GDBN} when it notices the thread; use @code{set thread
22012 takeover-suspend-count} to force it to an absolute value.
22014 @item show thread detach-suspend-count
22015 Show the suspend count @value{GDBN} will leave on the thread when
22018 @item set thread exception-port
22019 @itemx set thread excp
22020 Set the thread exception port to which to forward exceptions. This
22021 overrides the port set by @code{set task exception-port} (see above).
22022 @code{set thread excp} is the shorthand alias.
22024 @item set thread takeover-suspend-count
22025 Normally, @value{GDBN}'s thread suspend counts are relative to the
22026 value @value{GDBN} finds when it notices each thread. This command
22027 changes the suspend counts to be absolute instead.
22029 @item set thread default
22030 @itemx show thread default
22031 @cindex thread default settings, @sc{gnu} Hurd
22032 Each of the above @code{set thread} commands has a @code{set thread
22033 default} counterpart (e.g., @code{set thread default pause}, @code{set
22034 thread default exception-port}, etc.). The @code{thread default}
22035 variety of commands sets the default thread properties for all
22036 threads; you can then change the properties of individual threads with
22037 the non-default commands.
22044 @value{GDBN} provides the following commands specific to the Darwin target:
22047 @item set debug darwin @var{num}
22048 @kindex set debug darwin
22049 When set to a non zero value, enables debugging messages specific to
22050 the Darwin support. Higher values produce more verbose output.
22052 @item show debug darwin
22053 @kindex show debug darwin
22054 Show the current state of Darwin messages.
22056 @item set debug mach-o @var{num}
22057 @kindex set debug mach-o
22058 When set to a non zero value, enables debugging messages while
22059 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22060 file format used on Darwin for object and executable files.) Higher
22061 values produce more verbose output. This is a command to diagnose
22062 problems internal to @value{GDBN} and should not be needed in normal
22065 @item show debug mach-o
22066 @kindex show debug mach-o
22067 Show the current state of Mach-O file messages.
22069 @item set mach-exceptions on
22070 @itemx set mach-exceptions off
22071 @kindex set mach-exceptions
22072 On Darwin, faults are first reported as a Mach exception and are then
22073 mapped to a Posix signal. Use this command to turn on trapping of
22074 Mach exceptions in the inferior. This might be sometimes useful to
22075 better understand the cause of a fault. The default is off.
22077 @item show mach-exceptions
22078 @kindex show mach-exceptions
22079 Show the current state of exceptions trapping.
22084 @section Embedded Operating Systems
22086 This section describes configurations involving the debugging of
22087 embedded operating systems that are available for several different
22090 @value{GDBN} includes the ability to debug programs running on
22091 various real-time operating systems.
22093 @node Embedded Processors
22094 @section Embedded Processors
22096 This section goes into details specific to particular embedded
22099 @cindex send command to simulator
22100 Whenever a specific embedded processor has a simulator, @value{GDBN}
22101 allows to send an arbitrary command to the simulator.
22104 @item sim @var{command}
22105 @kindex sim@r{, a command}
22106 Send an arbitrary @var{command} string to the simulator. Consult the
22107 documentation for the specific simulator in use for information about
22108 acceptable commands.
22113 * ARC:: Synopsys ARC
22115 * M68K:: Motorola M68K
22116 * MicroBlaze:: Xilinx MicroBlaze
22117 * MIPS Embedded:: MIPS Embedded
22118 * PowerPC Embedded:: PowerPC Embedded
22121 * Super-H:: Renesas Super-H
22125 @subsection Synopsys ARC
22126 @cindex Synopsys ARC
22127 @cindex ARC specific commands
22133 @value{GDBN} provides the following ARC-specific commands:
22136 @item set debug arc
22137 @kindex set debug arc
22138 Control the level of ARC specific debug messages. Use 0 for no messages (the
22139 default), 1 for debug messages, and 2 for even more debug messages.
22141 @item show debug arc
22142 @kindex show debug arc
22143 Show the level of ARC specific debugging in operation.
22145 @item maint print arc arc-instruction @var{address}
22146 @kindex maint print arc arc-instruction
22147 Print internal disassembler information about instruction at a given address.
22154 @value{GDBN} provides the following ARM-specific commands:
22157 @item set arm disassembler
22159 This commands selects from a list of disassembly styles. The
22160 @code{"std"} style is the standard style.
22162 @item show arm disassembler
22164 Show the current disassembly style.
22166 @item set arm apcs32
22167 @cindex ARM 32-bit mode
22168 This command toggles ARM operation mode between 32-bit and 26-bit.
22170 @item show arm apcs32
22171 Display the current usage of the ARM 32-bit mode.
22173 @item set arm fpu @var{fputype}
22174 This command sets the ARM floating-point unit (FPU) type. The
22175 argument @var{fputype} can be one of these:
22179 Determine the FPU type by querying the OS ABI.
22181 Software FPU, with mixed-endian doubles on little-endian ARM
22184 GCC-compiled FPA co-processor.
22186 Software FPU with pure-endian doubles.
22192 Show the current type of the FPU.
22195 This command forces @value{GDBN} to use the specified ABI.
22198 Show the currently used ABI.
22200 @item set arm fallback-mode (arm|thumb|auto)
22201 @value{GDBN} uses the symbol table, when available, to determine
22202 whether instructions are ARM or Thumb. This command controls
22203 @value{GDBN}'s default behavior when the symbol table is not
22204 available. The default is @samp{auto}, which causes @value{GDBN} to
22205 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22208 @item show arm fallback-mode
22209 Show the current fallback instruction mode.
22211 @item set arm force-mode (arm|thumb|auto)
22212 This command overrides use of the symbol table to determine whether
22213 instructions are ARM or Thumb. The default is @samp{auto}, which
22214 causes @value{GDBN} to use the symbol table and then the setting
22215 of @samp{set arm fallback-mode}.
22217 @item show arm force-mode
22218 Show the current forced instruction mode.
22220 @item set debug arm
22221 Toggle whether to display ARM-specific debugging messages from the ARM
22222 target support subsystem.
22224 @item show debug arm
22225 Show whether ARM-specific debugging messages are enabled.
22229 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22230 The @value{GDBN} ARM simulator accepts the following optional arguments.
22233 @item --swi-support=@var{type}
22234 Tell the simulator which SWI interfaces to support. The argument
22235 @var{type} may be a comma separated list of the following values.
22236 The default value is @code{all}.
22251 The Motorola m68k configuration includes ColdFire support.
22254 @subsection MicroBlaze
22255 @cindex Xilinx MicroBlaze
22256 @cindex XMD, Xilinx Microprocessor Debugger
22258 The MicroBlaze is a soft-core processor supported on various Xilinx
22259 FPGAs, such as Spartan or Virtex series. Boards with these processors
22260 usually have JTAG ports which connect to a host system running the Xilinx
22261 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22262 This host system is used to download the configuration bitstream to
22263 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22264 communicates with the target board using the JTAG interface and
22265 presents a @code{gdbserver} interface to the board. By default
22266 @code{xmd} uses port @code{1234}. (While it is possible to change
22267 this default port, it requires the use of undocumented @code{xmd}
22268 commands. Contact Xilinx support if you need to do this.)
22270 Use these GDB commands to connect to the MicroBlaze target processor.
22273 @item target remote :1234
22274 Use this command to connect to the target if you are running @value{GDBN}
22275 on the same system as @code{xmd}.
22277 @item target remote @var{xmd-host}:1234
22278 Use this command to connect to the target if it is connected to @code{xmd}
22279 running on a different system named @var{xmd-host}.
22282 Use this command to download a program to the MicroBlaze target.
22284 @item set debug microblaze @var{n}
22285 Enable MicroBlaze-specific debugging messages if non-zero.
22287 @item show debug microblaze @var{n}
22288 Show MicroBlaze-specific debugging level.
22291 @node MIPS Embedded
22292 @subsection @acronym{MIPS} Embedded
22295 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22298 @item set mipsfpu double
22299 @itemx set mipsfpu single
22300 @itemx set mipsfpu none
22301 @itemx set mipsfpu auto
22302 @itemx show mipsfpu
22303 @kindex set mipsfpu
22304 @kindex show mipsfpu
22305 @cindex @acronym{MIPS} remote floating point
22306 @cindex floating point, @acronym{MIPS} remote
22307 If your target board does not support the @acronym{MIPS} floating point
22308 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22309 need this, you may wish to put the command in your @value{GDBN} init
22310 file). This tells @value{GDBN} how to find the return value of
22311 functions which return floating point values. It also allows
22312 @value{GDBN} to avoid saving the floating point registers when calling
22313 functions on the board. If you are using a floating point coprocessor
22314 with only single precision floating point support, as on the @sc{r4650}
22315 processor, use the command @samp{set mipsfpu single}. The default
22316 double precision floating point coprocessor may be selected using
22317 @samp{set mipsfpu double}.
22319 In previous versions the only choices were double precision or no
22320 floating point, so @samp{set mipsfpu on} will select double precision
22321 and @samp{set mipsfpu off} will select no floating point.
22323 As usual, you can inquire about the @code{mipsfpu} variable with
22324 @samp{show mipsfpu}.
22327 @node PowerPC Embedded
22328 @subsection PowerPC Embedded
22330 @cindex DVC register
22331 @value{GDBN} supports using the DVC (Data Value Compare) register to
22332 implement in hardware simple hardware watchpoint conditions of the form:
22335 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22336 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22339 The DVC register will be automatically used when @value{GDBN} detects
22340 such pattern in a condition expression, and the created watchpoint uses one
22341 debug register (either the @code{exact-watchpoints} option is on and the
22342 variable is scalar, or the variable has a length of one byte). This feature
22343 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22346 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22347 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22348 in which case watchpoints using only one debug register are created when
22349 watching variables of scalar types.
22351 You can create an artificial array to watch an arbitrary memory
22352 region using one of the following commands (@pxref{Expressions}):
22355 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22356 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22359 PowerPC embedded processors support masked watchpoints. See the discussion
22360 about the @code{mask} argument in @ref{Set Watchpoints}.
22362 @cindex ranged breakpoint
22363 PowerPC embedded processors support hardware accelerated
22364 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22365 the inferior whenever it executes an instruction at any address within
22366 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22367 use the @code{break-range} command.
22369 @value{GDBN} provides the following PowerPC-specific commands:
22372 @kindex break-range
22373 @item break-range @var{start-location}, @var{end-location}
22374 Set a breakpoint for an address range given by
22375 @var{start-location} and @var{end-location}, which can specify a function name,
22376 a line number, an offset of lines from the current line or from the start
22377 location, or an address of an instruction (see @ref{Specify Location},
22378 for a list of all the possible ways to specify a @var{location}.)
22379 The breakpoint will stop execution of the inferior whenever it
22380 executes an instruction at any address within the specified range,
22381 (including @var{start-location} and @var{end-location}.)
22383 @kindex set powerpc
22384 @item set powerpc soft-float
22385 @itemx show powerpc soft-float
22386 Force @value{GDBN} to use (or not use) a software floating point calling
22387 convention. By default, @value{GDBN} selects the calling convention based
22388 on the selected architecture and the provided executable file.
22390 @item set powerpc vector-abi
22391 @itemx show powerpc vector-abi
22392 Force @value{GDBN} to use the specified calling convention for vector
22393 arguments and return values. The valid options are @samp{auto};
22394 @samp{generic}, to avoid vector registers even if they are present;
22395 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22396 registers. By default, @value{GDBN} selects the calling convention
22397 based on the selected architecture and the provided executable file.
22399 @item set powerpc exact-watchpoints
22400 @itemx show powerpc exact-watchpoints
22401 Allow @value{GDBN} to use only one debug register when watching a variable
22402 of scalar type, thus assuming that the variable is accessed through the
22403 address of its first byte.
22408 @subsection Atmel AVR
22411 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22412 following AVR-specific commands:
22415 @item info io_registers
22416 @kindex info io_registers@r{, AVR}
22417 @cindex I/O registers (Atmel AVR)
22418 This command displays information about the AVR I/O registers. For
22419 each register, @value{GDBN} prints its number and value.
22426 When configured for debugging CRIS, @value{GDBN} provides the
22427 following CRIS-specific commands:
22430 @item set cris-version @var{ver}
22431 @cindex CRIS version
22432 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22433 The CRIS version affects register names and sizes. This command is useful in
22434 case autodetection of the CRIS version fails.
22436 @item show cris-version
22437 Show the current CRIS version.
22439 @item set cris-dwarf2-cfi
22440 @cindex DWARF-2 CFI and CRIS
22441 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22442 Change to @samp{off} when using @code{gcc-cris} whose version is below
22445 @item show cris-dwarf2-cfi
22446 Show the current state of using DWARF-2 CFI.
22448 @item set cris-mode @var{mode}
22450 Set the current CRIS mode to @var{mode}. It should only be changed when
22451 debugging in guru mode, in which case it should be set to
22452 @samp{guru} (the default is @samp{normal}).
22454 @item show cris-mode
22455 Show the current CRIS mode.
22459 @subsection Renesas Super-H
22462 For the Renesas Super-H processor, @value{GDBN} provides these
22466 @item set sh calling-convention @var{convention}
22467 @kindex set sh calling-convention
22468 Set the calling-convention used when calling functions from @value{GDBN}.
22469 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22470 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22471 convention. If the DWARF-2 information of the called function specifies
22472 that the function follows the Renesas calling convention, the function
22473 is called using the Renesas calling convention. If the calling convention
22474 is set to @samp{renesas}, the Renesas calling convention is always used,
22475 regardless of the DWARF-2 information. This can be used to override the
22476 default of @samp{gcc} if debug information is missing, or the compiler
22477 does not emit the DWARF-2 calling convention entry for a function.
22479 @item show sh calling-convention
22480 @kindex show sh calling-convention
22481 Show the current calling convention setting.
22486 @node Architectures
22487 @section Architectures
22489 This section describes characteristics of architectures that affect
22490 all uses of @value{GDBN} with the architecture, both native and cross.
22497 * HPPA:: HP PA architecture
22498 * SPU:: Cell Broadband Engine SPU architecture
22505 @subsection AArch64
22506 @cindex AArch64 support
22508 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22509 following special commands:
22512 @item set debug aarch64
22513 @kindex set debug aarch64
22514 This command determines whether AArch64 architecture-specific debugging
22515 messages are to be displayed.
22517 @item show debug aarch64
22518 Show whether AArch64 debugging messages are displayed.
22523 @subsection x86 Architecture-specific Issues
22526 @item set struct-convention @var{mode}
22527 @kindex set struct-convention
22528 @cindex struct return convention
22529 @cindex struct/union returned in registers
22530 Set the convention used by the inferior to return @code{struct}s and
22531 @code{union}s from functions to @var{mode}. Possible values of
22532 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22533 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22534 are returned on the stack, while @code{"reg"} means that a
22535 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22536 be returned in a register.
22538 @item show struct-convention
22539 @kindex show struct-convention
22540 Show the current setting of the convention to return @code{struct}s
22545 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22546 @cindex Intel Memory Protection Extensions (MPX).
22548 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22549 @footnote{The register named with capital letters represent the architecture
22550 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22551 which are the lower bound and upper bound. Bounds are effective addresses or
22552 memory locations. The upper bounds are architecturally represented in 1's
22553 complement form. A bound having lower bound = 0, and upper bound = 0
22554 (1's complement of all bits set) will allow access to the entire address space.
22556 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22557 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22558 display the upper bound performing the complement of one operation on the
22559 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22560 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22561 can also be noted that the upper bounds are inclusive.
22563 As an example, assume that the register BND0 holds bounds for a pointer having
22564 access allowed for the range between 0x32 and 0x71. The values present on
22565 bnd0raw and bnd registers are presented as follows:
22568 bnd0raw = @{0x32, 0xffffffff8e@}
22569 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22572 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22573 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22574 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22575 Python, the display includes the memory size, in bits, accessible to
22578 Bounds can also be stored in bounds tables, which are stored in
22579 application memory. These tables store bounds for pointers by specifying
22580 the bounds pointer's value along with its bounds. Evaluating and changing
22581 bounds located in bound tables is therefore interesting while investigating
22582 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22585 @item show mpx bound @var{pointer}
22586 @kindex show mpx bound
22587 Display bounds of the given @var{pointer}.
22589 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22590 @kindex set mpx bound
22591 Set the bounds of a pointer in the bound table.
22592 This command takes three parameters: @var{pointer} is the pointers
22593 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22594 for lower and upper bounds respectively.
22597 When you call an inferior function on an Intel MPX enabled program,
22598 GDB sets the inferior's bound registers to the init (disabled) state
22599 before calling the function. As a consequence, bounds checks for the
22600 pointer arguments passed to the function will always pass.
22602 This is necessary because when you call an inferior function, the
22603 program is usually in the middle of the execution of other function.
22604 Since at that point bound registers are in an arbitrary state, not
22605 clearing them would lead to random bound violations in the called
22608 You can still examine the influence of the bound registers on the
22609 execution of the called function by stopping the execution of the
22610 called function at its prologue, setting bound registers, and
22611 continuing the execution. For example:
22615 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
22616 $ print upper (a, b, c, d, 1)
22617 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
22619 @{lbound = 0x0, ubound = ffffffff@} : size -1
22622 At this last step the value of bnd0 can be changed for investigation of bound
22623 violations caused along the execution of the call. In order to know how to
22624 set the bound registers or bound table for the call consult the ABI.
22629 See the following section.
22632 @subsection @acronym{MIPS}
22634 @cindex stack on Alpha
22635 @cindex stack on @acronym{MIPS}
22636 @cindex Alpha stack
22637 @cindex @acronym{MIPS} stack
22638 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22639 sometimes requires @value{GDBN} to search backward in the object code to
22640 find the beginning of a function.
22642 @cindex response time, @acronym{MIPS} debugging
22643 To improve response time (especially for embedded applications, where
22644 @value{GDBN} may be restricted to a slow serial line for this search)
22645 you may want to limit the size of this search, using one of these
22649 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22650 @item set heuristic-fence-post @var{limit}
22651 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22652 search for the beginning of a function. A value of @var{0} (the
22653 default) means there is no limit. However, except for @var{0}, the
22654 larger the limit the more bytes @code{heuristic-fence-post} must search
22655 and therefore the longer it takes to run. You should only need to use
22656 this command when debugging a stripped executable.
22658 @item show heuristic-fence-post
22659 Display the current limit.
22663 These commands are available @emph{only} when @value{GDBN} is configured
22664 for debugging programs on Alpha or @acronym{MIPS} processors.
22666 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22670 @item set mips abi @var{arg}
22671 @kindex set mips abi
22672 @cindex set ABI for @acronym{MIPS}
22673 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22674 values of @var{arg} are:
22678 The default ABI associated with the current binary (this is the
22688 @item show mips abi
22689 @kindex show mips abi
22690 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22692 @item set mips compression @var{arg}
22693 @kindex set mips compression
22694 @cindex code compression, @acronym{MIPS}
22695 Tell @value{GDBN} which @acronym{MIPS} compressed
22696 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22697 inferior. @value{GDBN} uses this for code disassembly and other
22698 internal interpretation purposes. This setting is only referred to
22699 when no executable has been associated with the debugging session or
22700 the executable does not provide information about the encoding it uses.
22701 Otherwise this setting is automatically updated from information
22702 provided by the executable.
22704 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22705 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22706 executables containing @acronym{MIPS16} code frequently are not
22707 identified as such.
22709 This setting is ``sticky''; that is, it retains its value across
22710 debugging sessions until reset either explicitly with this command or
22711 implicitly from an executable.
22713 The compiler and/or assembler typically add symbol table annotations to
22714 identify functions compiled for the @acronym{MIPS16} or
22715 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22716 are present, @value{GDBN} uses them in preference to the global
22717 compressed @acronym{ISA} encoding setting.
22719 @item show mips compression
22720 @kindex show mips compression
22721 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22722 @value{GDBN} to debug the inferior.
22725 @itemx show mipsfpu
22726 @xref{MIPS Embedded, set mipsfpu}.
22728 @item set mips mask-address @var{arg}
22729 @kindex set mips mask-address
22730 @cindex @acronym{MIPS} addresses, masking
22731 This command determines whether the most-significant 32 bits of 64-bit
22732 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22733 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22734 setting, which lets @value{GDBN} determine the correct value.
22736 @item show mips mask-address
22737 @kindex show mips mask-address
22738 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22741 @item set remote-mips64-transfers-32bit-regs
22742 @kindex set remote-mips64-transfers-32bit-regs
22743 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22744 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22745 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22746 and 64 bits for other registers, set this option to @samp{on}.
22748 @item show remote-mips64-transfers-32bit-regs
22749 @kindex show remote-mips64-transfers-32bit-regs
22750 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22752 @item set debug mips
22753 @kindex set debug mips
22754 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22755 target code in @value{GDBN}.
22757 @item show debug mips
22758 @kindex show debug mips
22759 Show the current setting of @acronym{MIPS} debugging messages.
22765 @cindex HPPA support
22767 When @value{GDBN} is debugging the HP PA architecture, it provides the
22768 following special commands:
22771 @item set debug hppa
22772 @kindex set debug hppa
22773 This command determines whether HPPA architecture-specific debugging
22774 messages are to be displayed.
22776 @item show debug hppa
22777 Show whether HPPA debugging messages are displayed.
22779 @item maint print unwind @var{address}
22780 @kindex maint print unwind@r{, HPPA}
22781 This command displays the contents of the unwind table entry at the
22782 given @var{address}.
22788 @subsection Cell Broadband Engine SPU architecture
22789 @cindex Cell Broadband Engine
22792 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22793 it provides the following special commands:
22796 @item info spu event
22798 Display SPU event facility status. Shows current event mask
22799 and pending event status.
22801 @item info spu signal
22802 Display SPU signal notification facility status. Shows pending
22803 signal-control word and signal notification mode of both signal
22804 notification channels.
22806 @item info spu mailbox
22807 Display SPU mailbox facility status. Shows all pending entries,
22808 in order of processing, in each of the SPU Write Outbound,
22809 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22812 Display MFC DMA status. Shows all pending commands in the MFC
22813 DMA queue. For each entry, opcode, tag, class IDs, effective
22814 and local store addresses and transfer size are shown.
22816 @item info spu proxydma
22817 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22818 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22819 and local store addresses and transfer size are shown.
22823 When @value{GDBN} is debugging a combined PowerPC/SPU application
22824 on the Cell Broadband Engine, it provides in addition the following
22828 @item set spu stop-on-load @var{arg}
22830 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22831 will give control to the user when a new SPE thread enters its @code{main}
22832 function. The default is @code{off}.
22834 @item show spu stop-on-load
22836 Show whether to stop for new SPE threads.
22838 @item set spu auto-flush-cache @var{arg}
22839 Set whether to automatically flush the software-managed cache. When set to
22840 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22841 cache to be flushed whenever SPE execution stops. This provides a consistent
22842 view of PowerPC memory that is accessed via the cache. If an application
22843 does not use the software-managed cache, this option has no effect.
22845 @item show spu auto-flush-cache
22846 Show whether to automatically flush the software-managed cache.
22851 @subsection PowerPC
22852 @cindex PowerPC architecture
22854 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22855 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22856 numbers stored in the floating point registers. These values must be stored
22857 in two consecutive registers, always starting at an even register like
22858 @code{f0} or @code{f2}.
22860 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22861 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22862 @code{f2} and @code{f3} for @code{$dl1} and so on.
22864 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22865 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22868 @subsection Nios II
22869 @cindex Nios II architecture
22871 When @value{GDBN} is debugging the Nios II architecture,
22872 it provides the following special commands:
22876 @item set debug nios2
22877 @kindex set debug nios2
22878 This command turns on and off debugging messages for the Nios II
22879 target code in @value{GDBN}.
22881 @item show debug nios2
22882 @kindex show debug nios2
22883 Show the current setting of Nios II debugging messages.
22887 @subsection Sparc64
22888 @cindex Sparc64 support
22889 @cindex Application Data Integrity
22890 @subsubsection ADI Support
22892 The M7 processor supports an Application Data Integrity (ADI) feature that
22893 detects invalid data accesses. When software allocates memory and enables
22894 ADI on the allocated memory, it chooses a 4-bit version number, sets the
22895 version in the upper 4 bits of the 64-bit pointer to that data, and stores
22896 the 4-bit version in every cacheline of that data. Hardware saves the latter
22897 in spare bits in the cache and memory hierarchy. On each load and store,
22898 the processor compares the upper 4 VA (virtual address) bits to the
22899 cacheline's version. If there is a mismatch, the processor generates a
22900 version mismatch trap which can be either precise or disrupting. The trap
22901 is an error condition which the kernel delivers to the process as a SIGSEGV
22904 Note that only 64-bit applications can use ADI and need to be built with
22907 Values of the ADI version tags, which are in granularity of a
22908 cacheline (64 bytes), can be viewed or modified.
22912 @kindex adi examine
22913 @item adi (examine | x) [ / @var{n} ] @var{addr}
22915 The @code{adi examine} command displays the value of one ADI version tag per
22918 @var{n} is a decimal integer specifying the number in bytes; the default
22919 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
22920 block size, to display.
22922 @var{addr} is the address in user address space where you want @value{GDBN}
22923 to begin displaying the ADI version tags.
22925 Below is an example of displaying ADI versions of variable "shmaddr".
22928 (@value{GDBP}) adi x/100 shmaddr
22929 0xfff800010002c000: 0 0
22933 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
22935 The @code{adi assign} command is used to assign new ADI version tag
22938 @var{n} is a decimal integer specifying the number in bytes;
22939 the default is 1. It specifies how much ADI version information, at the
22940 ratio of 1:ADI block size, to modify.
22942 @var{addr} is the address in user address space where you want @value{GDBN}
22943 to begin modifying the ADI version tags.
22945 @var{tag} is the new ADI version tag.
22947 For example, do the following to modify then verify ADI versions of
22948 variable "shmaddr":
22951 (@value{GDBP}) adi a/100 shmaddr = 7
22952 (@value{GDBP}) adi x/100 shmaddr
22953 0xfff800010002c000: 7 7
22958 @node Controlling GDB
22959 @chapter Controlling @value{GDBN}
22961 You can alter the way @value{GDBN} interacts with you by using the
22962 @code{set} command. For commands controlling how @value{GDBN} displays
22963 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22968 * Editing:: Command editing
22969 * Command History:: Command history
22970 * Screen Size:: Screen size
22971 * Numbers:: Numbers
22972 * ABI:: Configuring the current ABI
22973 * Auto-loading:: Automatically loading associated files
22974 * Messages/Warnings:: Optional warnings and messages
22975 * Debugging Output:: Optional messages about internal happenings
22976 * Other Misc Settings:: Other Miscellaneous Settings
22984 @value{GDBN} indicates its readiness to read a command by printing a string
22985 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22986 can change the prompt string with the @code{set prompt} command. For
22987 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22988 the prompt in one of the @value{GDBN} sessions so that you can always tell
22989 which one you are talking to.
22991 @emph{Note:} @code{set prompt} does not add a space for you after the
22992 prompt you set. This allows you to set a prompt which ends in a space
22993 or a prompt that does not.
22997 @item set prompt @var{newprompt}
22998 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23000 @kindex show prompt
23002 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23005 Versions of @value{GDBN} that ship with Python scripting enabled have
23006 prompt extensions. The commands for interacting with these extensions
23010 @kindex set extended-prompt
23011 @item set extended-prompt @var{prompt}
23012 Set an extended prompt that allows for substitutions.
23013 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23014 substitution. Any escape sequences specified as part of the prompt
23015 string are replaced with the corresponding strings each time the prompt
23021 set extended-prompt Current working directory: \w (gdb)
23024 Note that when an extended-prompt is set, it takes control of the
23025 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23027 @kindex show extended-prompt
23028 @item show extended-prompt
23029 Prints the extended prompt. Any escape sequences specified as part of
23030 the prompt string with @code{set extended-prompt}, are replaced with the
23031 corresponding strings each time the prompt is displayed.
23035 @section Command Editing
23037 @cindex command line editing
23039 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23040 @sc{gnu} library provides consistent behavior for programs which provide a
23041 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23042 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23043 substitution, and a storage and recall of command history across
23044 debugging sessions.
23046 You may control the behavior of command line editing in @value{GDBN} with the
23047 command @code{set}.
23050 @kindex set editing
23053 @itemx set editing on
23054 Enable command line editing (enabled by default).
23056 @item set editing off
23057 Disable command line editing.
23059 @kindex show editing
23061 Show whether command line editing is enabled.
23064 @ifset SYSTEM_READLINE
23065 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23067 @ifclear SYSTEM_READLINE
23068 @xref{Command Line Editing},
23070 for more details about the Readline
23071 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23072 encouraged to read that chapter.
23074 @node Command History
23075 @section Command History
23076 @cindex command history
23078 @value{GDBN} can keep track of the commands you type during your
23079 debugging sessions, so that you can be certain of precisely what
23080 happened. Use these commands to manage the @value{GDBN} command
23083 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23084 package, to provide the history facility.
23085 @ifset SYSTEM_READLINE
23086 @xref{Using History Interactively, , , history, GNU History Library},
23088 @ifclear SYSTEM_READLINE
23089 @xref{Using History Interactively},
23091 for the detailed description of the History library.
23093 To issue a command to @value{GDBN} without affecting certain aspects of
23094 the state which is seen by users, prefix it with @samp{server }
23095 (@pxref{Server Prefix}). This
23096 means that this command will not affect the command history, nor will it
23097 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23098 pressed on a line by itself.
23100 @cindex @code{server}, command prefix
23101 The server prefix does not affect the recording of values into the value
23102 history; to print a value without recording it into the value history,
23103 use the @code{output} command instead of the @code{print} command.
23105 Here is the description of @value{GDBN} commands related to command
23109 @cindex history substitution
23110 @cindex history file
23111 @kindex set history filename
23112 @cindex @env{GDBHISTFILE}, environment variable
23113 @item set history filename @var{fname}
23114 Set the name of the @value{GDBN} command history file to @var{fname}.
23115 This is the file where @value{GDBN} reads an initial command history
23116 list, and where it writes the command history from this session when it
23117 exits. You can access this list through history expansion or through
23118 the history command editing characters listed below. This file defaults
23119 to the value of the environment variable @code{GDBHISTFILE}, or to
23120 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23123 @cindex save command history
23124 @kindex set history save
23125 @item set history save
23126 @itemx set history save on
23127 Record command history in a file, whose name may be specified with the
23128 @code{set history filename} command. By default, this option is disabled.
23130 @item set history save off
23131 Stop recording command history in a file.
23133 @cindex history size
23134 @kindex set history size
23135 @cindex @env{GDBHISTSIZE}, environment variable
23136 @item set history size @var{size}
23137 @itemx set history size unlimited
23138 Set the number of commands which @value{GDBN} keeps in its history list.
23139 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23140 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23141 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23142 either a negative number or the empty string, then the number of commands
23143 @value{GDBN} keeps in the history list is unlimited.
23145 @cindex remove duplicate history
23146 @kindex set history remove-duplicates
23147 @item set history remove-duplicates @var{count}
23148 @itemx set history remove-duplicates unlimited
23149 Control the removal of duplicate history entries in the command history list.
23150 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23151 history entries and remove the first entry that is a duplicate of the current
23152 entry being added to the command history list. If @var{count} is
23153 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23154 removal of duplicate history entries is disabled.
23156 Only history entries added during the current session are considered for
23157 removal. This option is set to 0 by default.
23161 History expansion assigns special meaning to the character @kbd{!}.
23162 @ifset SYSTEM_READLINE
23163 @xref{Event Designators, , , history, GNU History Library},
23165 @ifclear SYSTEM_READLINE
23166 @xref{Event Designators},
23170 @cindex history expansion, turn on/off
23171 Since @kbd{!} is also the logical not operator in C, history expansion
23172 is off by default. If you decide to enable history expansion with the
23173 @code{set history expansion on} command, you may sometimes need to
23174 follow @kbd{!} (when it is used as logical not, in an expression) with
23175 a space or a tab to prevent it from being expanded. The readline
23176 history facilities do not attempt substitution on the strings
23177 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23179 The commands to control history expansion are:
23182 @item set history expansion on
23183 @itemx set history expansion
23184 @kindex set history expansion
23185 Enable history expansion. History expansion is off by default.
23187 @item set history expansion off
23188 Disable history expansion.
23191 @kindex show history
23193 @itemx show history filename
23194 @itemx show history save
23195 @itemx show history size
23196 @itemx show history expansion
23197 These commands display the state of the @value{GDBN} history parameters.
23198 @code{show history} by itself displays all four states.
23203 @kindex show commands
23204 @cindex show last commands
23205 @cindex display command history
23206 @item show commands
23207 Display the last ten commands in the command history.
23209 @item show commands @var{n}
23210 Print ten commands centered on command number @var{n}.
23212 @item show commands +
23213 Print ten commands just after the commands last printed.
23217 @section Screen Size
23218 @cindex size of screen
23219 @cindex screen size
23222 @cindex pauses in output
23224 Certain commands to @value{GDBN} may produce large amounts of
23225 information output to the screen. To help you read all of it,
23226 @value{GDBN} pauses and asks you for input at the end of each page of
23227 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23228 to discard the remaining output. Also, the screen width setting
23229 determines when to wrap lines of output. Depending on what is being
23230 printed, @value{GDBN} tries to break the line at a readable place,
23231 rather than simply letting it overflow onto the following line.
23233 Normally @value{GDBN} knows the size of the screen from the terminal
23234 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23235 together with the value of the @code{TERM} environment variable and the
23236 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23237 you can override it with the @code{set height} and @code{set
23244 @kindex show height
23245 @item set height @var{lpp}
23246 @itemx set height unlimited
23248 @itemx set width @var{cpl}
23249 @itemx set width unlimited
23251 These @code{set} commands specify a screen height of @var{lpp} lines and
23252 a screen width of @var{cpl} characters. The associated @code{show}
23253 commands display the current settings.
23255 If you specify a height of either @code{unlimited} or zero lines,
23256 @value{GDBN} does not pause during output no matter how long the
23257 output is. This is useful if output is to a file or to an editor
23260 Likewise, you can specify @samp{set width unlimited} or @samp{set
23261 width 0} to prevent @value{GDBN} from wrapping its output.
23263 @item set pagination on
23264 @itemx set pagination off
23265 @kindex set pagination
23266 Turn the output pagination on or off; the default is on. Turning
23267 pagination off is the alternative to @code{set height unlimited}. Note that
23268 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23269 Options, -batch}) also automatically disables pagination.
23271 @item show pagination
23272 @kindex show pagination
23273 Show the current pagination mode.
23278 @cindex number representation
23279 @cindex entering numbers
23281 You can always enter numbers in octal, decimal, or hexadecimal in
23282 @value{GDBN} by the usual conventions: octal numbers begin with
23283 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23284 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23285 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23286 10; likewise, the default display for numbers---when no particular
23287 format is specified---is base 10. You can change the default base for
23288 both input and output with the commands described below.
23291 @kindex set input-radix
23292 @item set input-radix @var{base}
23293 Set the default base for numeric input. Supported choices
23294 for @var{base} are decimal 8, 10, or 16. The base must itself be
23295 specified either unambiguously or using the current input radix; for
23299 set input-radix 012
23300 set input-radix 10.
23301 set input-radix 0xa
23305 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23306 leaves the input radix unchanged, no matter what it was, since
23307 @samp{10}, being without any leading or trailing signs of its base, is
23308 interpreted in the current radix. Thus, if the current radix is 16,
23309 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23312 @kindex set output-radix
23313 @item set output-radix @var{base}
23314 Set the default base for numeric display. Supported choices
23315 for @var{base} are decimal 8, 10, or 16. The base must itself be
23316 specified either unambiguously or using the current input radix.
23318 @kindex show input-radix
23319 @item show input-radix
23320 Display the current default base for numeric input.
23322 @kindex show output-radix
23323 @item show output-radix
23324 Display the current default base for numeric display.
23326 @item set radix @r{[}@var{base}@r{]}
23330 These commands set and show the default base for both input and output
23331 of numbers. @code{set radix} sets the radix of input and output to
23332 the same base; without an argument, it resets the radix back to its
23333 default value of 10.
23338 @section Configuring the Current ABI
23340 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23341 application automatically. However, sometimes you need to override its
23342 conclusions. Use these commands to manage @value{GDBN}'s view of the
23348 @cindex Newlib OS ABI and its influence on the longjmp handling
23350 One @value{GDBN} configuration can debug binaries for multiple operating
23351 system targets, either via remote debugging or native emulation.
23352 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23353 but you can override its conclusion using the @code{set osabi} command.
23354 One example where this is useful is in debugging of binaries which use
23355 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23356 not have the same identifying marks that the standard C library for your
23359 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23360 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23361 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23362 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23366 Show the OS ABI currently in use.
23369 With no argument, show the list of registered available OS ABI's.
23371 @item set osabi @var{abi}
23372 Set the current OS ABI to @var{abi}.
23375 @cindex float promotion
23377 Generally, the way that an argument of type @code{float} is passed to a
23378 function depends on whether the function is prototyped. For a prototyped
23379 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23380 according to the architecture's convention for @code{float}. For unprototyped
23381 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23382 @code{double} and then passed.
23384 Unfortunately, some forms of debug information do not reliably indicate whether
23385 a function is prototyped. If @value{GDBN} calls a function that is not marked
23386 as prototyped, it consults @kbd{set coerce-float-to-double}.
23389 @kindex set coerce-float-to-double
23390 @item set coerce-float-to-double
23391 @itemx set coerce-float-to-double on
23392 Arguments of type @code{float} will be promoted to @code{double} when passed
23393 to an unprototyped function. This is the default setting.
23395 @item set coerce-float-to-double off
23396 Arguments of type @code{float} will be passed directly to unprototyped
23399 @kindex show coerce-float-to-double
23400 @item show coerce-float-to-double
23401 Show the current setting of promoting @code{float} to @code{double}.
23405 @kindex show cp-abi
23406 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23407 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23408 used to build your application. @value{GDBN} only fully supports
23409 programs with a single C@t{++} ABI; if your program contains code using
23410 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23411 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23412 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23413 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23414 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23415 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23420 Show the C@t{++} ABI currently in use.
23423 With no argument, show the list of supported C@t{++} ABI's.
23425 @item set cp-abi @var{abi}
23426 @itemx set cp-abi auto
23427 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23431 @section Automatically loading associated files
23432 @cindex auto-loading
23434 @value{GDBN} sometimes reads files with commands and settings automatically,
23435 without being explicitly told so by the user. We call this feature
23436 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23437 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23438 results or introduce security risks (e.g., if the file comes from untrusted
23442 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23443 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23445 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23446 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23449 There are various kinds of files @value{GDBN} can automatically load.
23450 In addition to these files, @value{GDBN} supports auto-loading code written
23451 in various extension languages. @xref{Auto-loading extensions}.
23453 Note that loading of these associated files (including the local @file{.gdbinit}
23454 file) requires accordingly configured @code{auto-load safe-path}
23455 (@pxref{Auto-loading safe path}).
23457 For these reasons, @value{GDBN} includes commands and options to let you
23458 control when to auto-load files and which files should be auto-loaded.
23461 @anchor{set auto-load off}
23462 @kindex set auto-load off
23463 @item set auto-load off
23464 Globally disable loading of all auto-loaded files.
23465 You may want to use this command with the @samp{-iex} option
23466 (@pxref{Option -init-eval-command}) such as:
23468 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23471 Be aware that system init file (@pxref{System-wide configuration})
23472 and init files from your home directory (@pxref{Home Directory Init File})
23473 still get read (as they come from generally trusted directories).
23474 To prevent @value{GDBN} from auto-loading even those init files, use the
23475 @option{-nx} option (@pxref{Mode Options}), in addition to
23476 @code{set auto-load no}.
23478 @anchor{show auto-load}
23479 @kindex show auto-load
23480 @item show auto-load
23481 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23485 (gdb) show auto-load
23486 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23487 libthread-db: Auto-loading of inferior specific libthread_db is on.
23488 local-gdbinit: Auto-loading of .gdbinit script from current directory
23490 python-scripts: Auto-loading of Python scripts is on.
23491 safe-path: List of directories from which it is safe to auto-load files
23492 is $debugdir:$datadir/auto-load.
23493 scripts-directory: List of directories from which to load auto-loaded scripts
23494 is $debugdir:$datadir/auto-load.
23497 @anchor{info auto-load}
23498 @kindex info auto-load
23499 @item info auto-load
23500 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23504 (gdb) info auto-load
23507 Yes /home/user/gdb/gdb-gdb.gdb
23508 libthread-db: No auto-loaded libthread-db.
23509 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23513 Yes /home/user/gdb/gdb-gdb.py
23517 These are @value{GDBN} control commands for the auto-loading:
23519 @multitable @columnfractions .5 .5
23520 @item @xref{set auto-load off}.
23521 @tab Disable auto-loading globally.
23522 @item @xref{show auto-load}.
23523 @tab Show setting of all kinds of files.
23524 @item @xref{info auto-load}.
23525 @tab Show state of all kinds of files.
23526 @item @xref{set auto-load gdb-scripts}.
23527 @tab Control for @value{GDBN} command scripts.
23528 @item @xref{show auto-load gdb-scripts}.
23529 @tab Show setting of @value{GDBN} command scripts.
23530 @item @xref{info auto-load gdb-scripts}.
23531 @tab Show state of @value{GDBN} command scripts.
23532 @item @xref{set auto-load python-scripts}.
23533 @tab Control for @value{GDBN} Python scripts.
23534 @item @xref{show auto-load python-scripts}.
23535 @tab Show setting of @value{GDBN} Python scripts.
23536 @item @xref{info auto-load python-scripts}.
23537 @tab Show state of @value{GDBN} Python scripts.
23538 @item @xref{set auto-load guile-scripts}.
23539 @tab Control for @value{GDBN} Guile scripts.
23540 @item @xref{show auto-load guile-scripts}.
23541 @tab Show setting of @value{GDBN} Guile scripts.
23542 @item @xref{info auto-load guile-scripts}.
23543 @tab Show state of @value{GDBN} Guile scripts.
23544 @item @xref{set auto-load scripts-directory}.
23545 @tab Control for @value{GDBN} auto-loaded scripts location.
23546 @item @xref{show auto-load scripts-directory}.
23547 @tab Show @value{GDBN} auto-loaded scripts location.
23548 @item @xref{add-auto-load-scripts-directory}.
23549 @tab Add directory for auto-loaded scripts location list.
23550 @item @xref{set auto-load local-gdbinit}.
23551 @tab Control for init file in the current directory.
23552 @item @xref{show auto-load local-gdbinit}.
23553 @tab Show setting of init file in the current directory.
23554 @item @xref{info auto-load local-gdbinit}.
23555 @tab Show state of init file in the current directory.
23556 @item @xref{set auto-load libthread-db}.
23557 @tab Control for thread debugging library.
23558 @item @xref{show auto-load libthread-db}.
23559 @tab Show setting of thread debugging library.
23560 @item @xref{info auto-load libthread-db}.
23561 @tab Show state of thread debugging library.
23562 @item @xref{set auto-load safe-path}.
23563 @tab Control directories trusted for automatic loading.
23564 @item @xref{show auto-load safe-path}.
23565 @tab Show directories trusted for automatic loading.
23566 @item @xref{add-auto-load-safe-path}.
23567 @tab Add directory trusted for automatic loading.
23570 @node Init File in the Current Directory
23571 @subsection Automatically loading init file in the current directory
23572 @cindex auto-loading init file in the current directory
23574 By default, @value{GDBN} reads and executes the canned sequences of commands
23575 from init file (if any) in the current working directory,
23576 see @ref{Init File in the Current Directory during Startup}.
23578 Note that loading of this local @file{.gdbinit} file also requires accordingly
23579 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23582 @anchor{set auto-load local-gdbinit}
23583 @kindex set auto-load local-gdbinit
23584 @item set auto-load local-gdbinit [on|off]
23585 Enable or disable the auto-loading of canned sequences of commands
23586 (@pxref{Sequences}) found in init file in the current directory.
23588 @anchor{show auto-load local-gdbinit}
23589 @kindex show auto-load local-gdbinit
23590 @item show auto-load local-gdbinit
23591 Show whether auto-loading of canned sequences of commands from init file in the
23592 current directory is enabled or disabled.
23594 @anchor{info auto-load local-gdbinit}
23595 @kindex info auto-load local-gdbinit
23596 @item info auto-load local-gdbinit
23597 Print whether canned sequences of commands from init file in the
23598 current directory have been auto-loaded.
23601 @node libthread_db.so.1 file
23602 @subsection Automatically loading thread debugging library
23603 @cindex auto-loading libthread_db.so.1
23605 This feature is currently present only on @sc{gnu}/Linux native hosts.
23607 @value{GDBN} reads in some cases thread debugging library from places specific
23608 to the inferior (@pxref{set libthread-db-search-path}).
23610 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23611 without checking this @samp{set auto-load libthread-db} switch as system
23612 libraries have to be trusted in general. In all other cases of
23613 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23614 auto-load libthread-db} is enabled before trying to open such thread debugging
23617 Note that loading of this debugging library also requires accordingly configured
23618 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23621 @anchor{set auto-load libthread-db}
23622 @kindex set auto-load libthread-db
23623 @item set auto-load libthread-db [on|off]
23624 Enable or disable the auto-loading of inferior specific thread debugging library.
23626 @anchor{show auto-load libthread-db}
23627 @kindex show auto-load libthread-db
23628 @item show auto-load libthread-db
23629 Show whether auto-loading of inferior specific thread debugging library is
23630 enabled or disabled.
23632 @anchor{info auto-load libthread-db}
23633 @kindex info auto-load libthread-db
23634 @item info auto-load libthread-db
23635 Print the list of all loaded inferior specific thread debugging libraries and
23636 for each such library print list of inferior @var{pid}s using it.
23639 @node Auto-loading safe path
23640 @subsection Security restriction for auto-loading
23641 @cindex auto-loading safe-path
23643 As the files of inferior can come from untrusted source (such as submitted by
23644 an application user) @value{GDBN} does not always load any files automatically.
23645 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23646 directories trusted for loading files not explicitly requested by user.
23647 Each directory can also be a shell wildcard pattern.
23649 If the path is not set properly you will see a warning and the file will not
23654 Reading symbols from /home/user/gdb/gdb...done.
23655 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23656 declined by your `auto-load safe-path' set
23657 to "$debugdir:$datadir/auto-load".
23658 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23659 declined by your `auto-load safe-path' set
23660 to "$debugdir:$datadir/auto-load".
23664 To instruct @value{GDBN} to go ahead and use the init files anyway,
23665 invoke @value{GDBN} like this:
23668 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23671 The list of trusted directories is controlled by the following commands:
23674 @anchor{set auto-load safe-path}
23675 @kindex set auto-load safe-path
23676 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23677 Set the list of directories (and their subdirectories) trusted for automatic
23678 loading and execution of scripts. You can also enter a specific trusted file.
23679 Each directory can also be a shell wildcard pattern; wildcards do not match
23680 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23681 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23682 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23683 its default value as specified during @value{GDBN} compilation.
23685 The list of directories uses path separator (@samp{:} on GNU and Unix
23686 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23687 to the @env{PATH} environment variable.
23689 @anchor{show auto-load safe-path}
23690 @kindex show auto-load safe-path
23691 @item show auto-load safe-path
23692 Show the list of directories trusted for automatic loading and execution of
23695 @anchor{add-auto-load-safe-path}
23696 @kindex add-auto-load-safe-path
23697 @item add-auto-load-safe-path
23698 Add an entry (or list of entries) to the list of directories trusted for
23699 automatic loading and execution of scripts. Multiple entries may be delimited
23700 by the host platform path separator in use.
23703 This variable defaults to what @code{--with-auto-load-dir} has been configured
23704 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23705 substitution applies the same as for @ref{set auto-load scripts-directory}.
23706 The default @code{set auto-load safe-path} value can be also overriden by
23707 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23709 Setting this variable to @file{/} disables this security protection,
23710 corresponding @value{GDBN} configuration option is
23711 @option{--without-auto-load-safe-path}.
23712 This variable is supposed to be set to the system directories writable by the
23713 system superuser only. Users can add their source directories in init files in
23714 their home directories (@pxref{Home Directory Init File}). See also deprecated
23715 init file in the current directory
23716 (@pxref{Init File in the Current Directory during Startup}).
23718 To force @value{GDBN} to load the files it declined to load in the previous
23719 example, you could use one of the following ways:
23722 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23723 Specify this trusted directory (or a file) as additional component of the list.
23724 You have to specify also any existing directories displayed by
23725 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23727 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23728 Specify this directory as in the previous case but just for a single
23729 @value{GDBN} session.
23731 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23732 Disable auto-loading safety for a single @value{GDBN} session.
23733 This assumes all the files you debug during this @value{GDBN} session will come
23734 from trusted sources.
23736 @item @kbd{./configure --without-auto-load-safe-path}
23737 During compilation of @value{GDBN} you may disable any auto-loading safety.
23738 This assumes all the files you will ever debug with this @value{GDBN} come from
23742 On the other hand you can also explicitly forbid automatic files loading which
23743 also suppresses any such warning messages:
23746 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23747 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23749 @item @file{~/.gdbinit}: @samp{set auto-load no}
23750 Disable auto-loading globally for the user
23751 (@pxref{Home Directory Init File}). While it is improbable, you could also
23752 use system init file instead (@pxref{System-wide configuration}).
23755 This setting applies to the file names as entered by user. If no entry matches
23756 @value{GDBN} tries as a last resort to also resolve all the file names into
23757 their canonical form (typically resolving symbolic links) and compare the
23758 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23759 own before starting the comparison so a canonical form of directories is
23760 recommended to be entered.
23762 @node Auto-loading verbose mode
23763 @subsection Displaying files tried for auto-load
23764 @cindex auto-loading verbose mode
23766 For better visibility of all the file locations where you can place scripts to
23767 be auto-loaded with inferior --- or to protect yourself against accidental
23768 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23769 all the files attempted to be loaded. Both existing and non-existing files may
23772 For example the list of directories from which it is safe to auto-load files
23773 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23774 may not be too obvious while setting it up.
23777 (gdb) set debug auto-load on
23778 (gdb) file ~/src/t/true
23779 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23780 for objfile "/tmp/true".
23781 auto-load: Updating directories of "/usr:/opt".
23782 auto-load: Using directory "/usr".
23783 auto-load: Using directory "/opt".
23784 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23785 by your `auto-load safe-path' set to "/usr:/opt".
23789 @anchor{set debug auto-load}
23790 @kindex set debug auto-load
23791 @item set debug auto-load [on|off]
23792 Set whether to print the filenames attempted to be auto-loaded.
23794 @anchor{show debug auto-load}
23795 @kindex show debug auto-load
23796 @item show debug auto-load
23797 Show whether printing of the filenames attempted to be auto-loaded is turned
23801 @node Messages/Warnings
23802 @section Optional Warnings and Messages
23804 @cindex verbose operation
23805 @cindex optional warnings
23806 By default, @value{GDBN} is silent about its inner workings. If you are
23807 running on a slow machine, you may want to use the @code{set verbose}
23808 command. This makes @value{GDBN} tell you when it does a lengthy
23809 internal operation, so you will not think it has crashed.
23811 Currently, the messages controlled by @code{set verbose} are those
23812 which announce that the symbol table for a source file is being read;
23813 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23816 @kindex set verbose
23817 @item set verbose on
23818 Enables @value{GDBN} output of certain informational messages.
23820 @item set verbose off
23821 Disables @value{GDBN} output of certain informational messages.
23823 @kindex show verbose
23825 Displays whether @code{set verbose} is on or off.
23828 By default, if @value{GDBN} encounters bugs in the symbol table of an
23829 object file, it is silent; but if you are debugging a compiler, you may
23830 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23835 @kindex set complaints
23836 @item set complaints @var{limit}
23837 Permits @value{GDBN} to output @var{limit} complaints about each type of
23838 unusual symbols before becoming silent about the problem. Set
23839 @var{limit} to zero to suppress all complaints; set it to a large number
23840 to prevent complaints from being suppressed.
23842 @kindex show complaints
23843 @item show complaints
23844 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23848 @anchor{confirmation requests}
23849 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23850 lot of stupid questions to confirm certain commands. For example, if
23851 you try to run a program which is already running:
23855 The program being debugged has been started already.
23856 Start it from the beginning? (y or n)
23859 If you are willing to unflinchingly face the consequences of your own
23860 commands, you can disable this ``feature'':
23864 @kindex set confirm
23866 @cindex confirmation
23867 @cindex stupid questions
23868 @item set confirm off
23869 Disables confirmation requests. Note that running @value{GDBN} with
23870 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23871 automatically disables confirmation requests.
23873 @item set confirm on
23874 Enables confirmation requests (the default).
23876 @kindex show confirm
23878 Displays state of confirmation requests.
23882 @cindex command tracing
23883 If you need to debug user-defined commands or sourced files you may find it
23884 useful to enable @dfn{command tracing}. In this mode each command will be
23885 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23886 quantity denoting the call depth of each command.
23889 @kindex set trace-commands
23890 @cindex command scripts, debugging
23891 @item set trace-commands on
23892 Enable command tracing.
23893 @item set trace-commands off
23894 Disable command tracing.
23895 @item show trace-commands
23896 Display the current state of command tracing.
23899 @node Debugging Output
23900 @section Optional Messages about Internal Happenings
23901 @cindex optional debugging messages
23903 @value{GDBN} has commands that enable optional debugging messages from
23904 various @value{GDBN} subsystems; normally these commands are of
23905 interest to @value{GDBN} maintainers, or when reporting a bug. This
23906 section documents those commands.
23909 @kindex set exec-done-display
23910 @item set exec-done-display
23911 Turns on or off the notification of asynchronous commands'
23912 completion. When on, @value{GDBN} will print a message when an
23913 asynchronous command finishes its execution. The default is off.
23914 @kindex show exec-done-display
23915 @item show exec-done-display
23916 Displays the current setting of asynchronous command completion
23919 @cindex ARM AArch64
23920 @item set debug aarch64
23921 Turns on or off display of debugging messages related to ARM AArch64.
23922 The default is off.
23924 @item show debug aarch64
23925 Displays the current state of displaying debugging messages related to
23927 @cindex gdbarch debugging info
23928 @cindex architecture debugging info
23929 @item set debug arch
23930 Turns on or off display of gdbarch debugging info. The default is off
23931 @item show debug arch
23932 Displays the current state of displaying gdbarch debugging info.
23933 @item set debug aix-solib
23934 @cindex AIX shared library debugging
23935 Control display of debugging messages from the AIX shared library
23936 support module. The default is off.
23937 @item show debug aix-thread
23938 Show the current state of displaying AIX shared library debugging messages.
23939 @item set debug aix-thread
23940 @cindex AIX threads
23941 Display debugging messages about inner workings of the AIX thread
23943 @item show debug aix-thread
23944 Show the current state of AIX thread debugging info display.
23945 @item set debug check-physname
23947 Check the results of the ``physname'' computation. When reading DWARF
23948 debugging information for C@t{++}, @value{GDBN} attempts to compute
23949 each entity's name. @value{GDBN} can do this computation in two
23950 different ways, depending on exactly what information is present.
23951 When enabled, this setting causes @value{GDBN} to compute the names
23952 both ways and display any discrepancies.
23953 @item show debug check-physname
23954 Show the current state of ``physname'' checking.
23955 @item set debug coff-pe-read
23956 @cindex COFF/PE exported symbols
23957 Control display of debugging messages related to reading of COFF/PE
23958 exported symbols. The default is off.
23959 @item show debug coff-pe-read
23960 Displays the current state of displaying debugging messages related to
23961 reading of COFF/PE exported symbols.
23962 @item set debug dwarf-die
23964 Dump DWARF DIEs after they are read in.
23965 The value is the number of nesting levels to print.
23966 A value of zero turns off the display.
23967 @item show debug dwarf-die
23968 Show the current state of DWARF DIE debugging.
23969 @item set debug dwarf-line
23970 @cindex DWARF Line Tables
23971 Turns on or off display of debugging messages related to reading
23972 DWARF line tables. The default is 0 (off).
23973 A value of 1 provides basic information.
23974 A value greater than 1 provides more verbose information.
23975 @item show debug dwarf-line
23976 Show the current state of DWARF line table debugging.
23977 @item set debug dwarf-read
23978 @cindex DWARF Reading
23979 Turns on or off display of debugging messages related to reading
23980 DWARF debug info. The default is 0 (off).
23981 A value of 1 provides basic information.
23982 A value greater than 1 provides more verbose information.
23983 @item show debug dwarf-read
23984 Show the current state of DWARF reader debugging.
23985 @item set debug displaced
23986 @cindex displaced stepping debugging info
23987 Turns on or off display of @value{GDBN} debugging info for the
23988 displaced stepping support. The default is off.
23989 @item show debug displaced
23990 Displays the current state of displaying @value{GDBN} debugging info
23991 related to displaced stepping.
23992 @item set debug event
23993 @cindex event debugging info
23994 Turns on or off display of @value{GDBN} event debugging info. The
23996 @item show debug event
23997 Displays the current state of displaying @value{GDBN} event debugging
23999 @item set debug expression
24000 @cindex expression debugging info
24001 Turns on or off display of debugging info about @value{GDBN}
24002 expression parsing. The default is off.
24003 @item show debug expression
24004 Displays the current state of displaying debugging info about
24005 @value{GDBN} expression parsing.
24006 @item set debug fbsd-lwp
24007 @cindex FreeBSD LWP debug messages
24008 Turns on or off debugging messages from the FreeBSD LWP debug support.
24009 @item show debug fbsd-lwp
24010 Show the current state of FreeBSD LWP debugging messages.
24011 @item set debug frame
24012 @cindex frame debugging info
24013 Turns on or off display of @value{GDBN} frame debugging info. The
24015 @item show debug frame
24016 Displays the current state of displaying @value{GDBN} frame debugging
24018 @item set debug gnu-nat
24019 @cindex @sc{gnu}/Hurd debug messages
24020 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24021 @item show debug gnu-nat
24022 Show the current state of @sc{gnu}/Hurd debugging messages.
24023 @item set debug infrun
24024 @cindex inferior debugging info
24025 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24026 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24027 for implementing operations such as single-stepping the inferior.
24028 @item show debug infrun
24029 Displays the current state of @value{GDBN} inferior debugging.
24030 @item set debug jit
24031 @cindex just-in-time compilation, debugging messages
24032 Turn on or off debugging messages from JIT debug support.
24033 @item show debug jit
24034 Displays the current state of @value{GDBN} JIT debugging.
24035 @item set debug lin-lwp
24036 @cindex @sc{gnu}/Linux LWP debug messages
24037 @cindex Linux lightweight processes
24038 Turn on or off debugging messages from the Linux LWP debug support.
24039 @item show debug lin-lwp
24040 Show the current state of Linux LWP debugging messages.
24041 @item set debug linux-namespaces
24042 @cindex @sc{gnu}/Linux namespaces debug messages
24043 Turn on or off debugging messages from the Linux namespaces debug support.
24044 @item show debug linux-namespaces
24045 Show the current state of Linux namespaces debugging messages.
24046 @item set debug mach-o
24047 @cindex Mach-O symbols processing
24048 Control display of debugging messages related to Mach-O symbols
24049 processing. The default is off.
24050 @item show debug mach-o
24051 Displays the current state of displaying debugging messages related to
24052 reading of COFF/PE exported symbols.
24053 @item set debug notification
24054 @cindex remote async notification debugging info
24055 Turn on or off debugging messages about remote async notification.
24056 The default is off.
24057 @item show debug notification
24058 Displays the current state of remote async notification debugging messages.
24059 @item set debug observer
24060 @cindex observer debugging info
24061 Turns on or off display of @value{GDBN} observer debugging. This
24062 includes info such as the notification of observable events.
24063 @item show debug observer
24064 Displays the current state of observer debugging.
24065 @item set debug overload
24066 @cindex C@t{++} overload debugging info
24067 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24068 info. This includes info such as ranking of functions, etc. The default
24070 @item show debug overload
24071 Displays the current state of displaying @value{GDBN} C@t{++} overload
24073 @cindex expression parser, debugging info
24074 @cindex debug expression parser
24075 @item set debug parser
24076 Turns on or off the display of expression parser debugging output.
24077 Internally, this sets the @code{yydebug} variable in the expression
24078 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24079 details. The default is off.
24080 @item show debug parser
24081 Show the current state of expression parser debugging.
24082 @cindex packets, reporting on stdout
24083 @cindex serial connections, debugging
24084 @cindex debug remote protocol
24085 @cindex remote protocol debugging
24086 @cindex display remote packets
24087 @item set debug remote
24088 Turns on or off display of reports on all packets sent back and forth across
24089 the serial line to the remote machine. The info is printed on the
24090 @value{GDBN} standard output stream. The default is off.
24091 @item show debug remote
24092 Displays the state of display of remote packets.
24094 @item set debug separate-debug-file
24095 Turns on or off display of debug output about separate debug file search.
24096 @item show debug separate-debug-file
24097 Displays the state of separate debug file search debug output.
24099 @item set debug serial
24100 Turns on or off display of @value{GDBN} serial debugging info. The
24102 @item show debug serial
24103 Displays the current state of displaying @value{GDBN} serial debugging
24105 @item set debug solib-frv
24106 @cindex FR-V shared-library debugging
24107 Turn on or off debugging messages for FR-V shared-library code.
24108 @item show debug solib-frv
24109 Display the current state of FR-V shared-library code debugging
24111 @item set debug symbol-lookup
24112 @cindex symbol lookup
24113 Turns on or off display of debugging messages related to symbol lookup.
24114 The default is 0 (off).
24115 A value of 1 provides basic information.
24116 A value greater than 1 provides more verbose information.
24117 @item show debug symbol-lookup
24118 Show the current state of symbol lookup debugging messages.
24119 @item set debug symfile
24120 @cindex symbol file functions
24121 Turns on or off display of debugging messages related to symbol file functions.
24122 The default is off. @xref{Files}.
24123 @item show debug symfile
24124 Show the current state of symbol file debugging messages.
24125 @item set debug symtab-create
24126 @cindex symbol table creation
24127 Turns on or off display of debugging messages related to symbol table creation.
24128 The default is 0 (off).
24129 A value of 1 provides basic information.
24130 A value greater than 1 provides more verbose information.
24131 @item show debug symtab-create
24132 Show the current state of symbol table creation debugging.
24133 @item set debug target
24134 @cindex target debugging info
24135 Turns on or off display of @value{GDBN} target debugging info. This info
24136 includes what is going on at the target level of GDB, as it happens. The
24137 default is 0. Set it to 1 to track events, and to 2 to also track the
24138 value of large memory transfers.
24139 @item show debug target
24140 Displays the current state of displaying @value{GDBN} target debugging
24142 @item set debug timestamp
24143 @cindex timestampping debugging info
24144 Turns on or off display of timestamps with @value{GDBN} debugging info.
24145 When enabled, seconds and microseconds are displayed before each debugging
24147 @item show debug timestamp
24148 Displays the current state of displaying timestamps with @value{GDBN}
24150 @item set debug varobj
24151 @cindex variable object debugging info
24152 Turns on or off display of @value{GDBN} variable object debugging
24153 info. The default is off.
24154 @item show debug varobj
24155 Displays the current state of displaying @value{GDBN} variable object
24157 @item set debug xml
24158 @cindex XML parser debugging
24159 Turn on or off debugging messages for built-in XML parsers.
24160 @item show debug xml
24161 Displays the current state of XML debugging messages.
24164 @node Other Misc Settings
24165 @section Other Miscellaneous Settings
24166 @cindex miscellaneous settings
24169 @kindex set interactive-mode
24170 @item set interactive-mode
24171 If @code{on}, forces @value{GDBN} to assume that GDB was started
24172 in a terminal. In practice, this means that @value{GDBN} should wait
24173 for the user to answer queries generated by commands entered at
24174 the command prompt. If @code{off}, forces @value{GDBN} to operate
24175 in the opposite mode, and it uses the default answers to all queries.
24176 If @code{auto} (the default), @value{GDBN} tries to determine whether
24177 its standard input is a terminal, and works in interactive-mode if it
24178 is, non-interactively otherwise.
24180 In the vast majority of cases, the debugger should be able to guess
24181 correctly which mode should be used. But this setting can be useful
24182 in certain specific cases, such as running a MinGW @value{GDBN}
24183 inside a cygwin window.
24185 @kindex show interactive-mode
24186 @item show interactive-mode
24187 Displays whether the debugger is operating in interactive mode or not.
24190 @node Extending GDB
24191 @chapter Extending @value{GDBN}
24192 @cindex extending GDB
24194 @value{GDBN} provides several mechanisms for extension.
24195 @value{GDBN} also provides the ability to automatically load
24196 extensions when it reads a file for debugging. This allows the
24197 user to automatically customize @value{GDBN} for the program
24201 * Sequences:: Canned Sequences of @value{GDBN} Commands
24202 * Python:: Extending @value{GDBN} using Python
24203 * Guile:: Extending @value{GDBN} using Guile
24204 * Auto-loading extensions:: Automatically loading extensions
24205 * Multiple Extension Languages:: Working with multiple extension languages
24206 * Aliases:: Creating new spellings of existing commands
24209 To facilitate the use of extension languages, @value{GDBN} is capable
24210 of evaluating the contents of a file. When doing so, @value{GDBN}
24211 can recognize which extension language is being used by looking at
24212 the filename extension. Files with an unrecognized filename extension
24213 are always treated as a @value{GDBN} Command Files.
24214 @xref{Command Files,, Command files}.
24216 You can control how @value{GDBN} evaluates these files with the following
24220 @kindex set script-extension
24221 @kindex show script-extension
24222 @item set script-extension off
24223 All scripts are always evaluated as @value{GDBN} Command Files.
24225 @item set script-extension soft
24226 The debugger determines the scripting language based on filename
24227 extension. If this scripting language is supported, @value{GDBN}
24228 evaluates the script using that language. Otherwise, it evaluates
24229 the file as a @value{GDBN} Command File.
24231 @item set script-extension strict
24232 The debugger determines the scripting language based on filename
24233 extension, and evaluates the script using that language. If the
24234 language is not supported, then the evaluation fails.
24236 @item show script-extension
24237 Display the current value of the @code{script-extension} option.
24242 @section Canned Sequences of Commands
24244 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24245 Command Lists}), @value{GDBN} provides two ways to store sequences of
24246 commands for execution as a unit: user-defined commands and command
24250 * Define:: How to define your own commands
24251 * Hooks:: Hooks for user-defined commands
24252 * Command Files:: How to write scripts of commands to be stored in a file
24253 * Output:: Commands for controlled output
24254 * Auto-loading sequences:: Controlling auto-loaded command files
24258 @subsection User-defined Commands
24260 @cindex user-defined command
24261 @cindex arguments, to user-defined commands
24262 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24263 which you assign a new name as a command. This is done with the
24264 @code{define} command. User commands may accept an unlimited number of arguments
24265 separated by whitespace. Arguments are accessed within the user command
24266 via @code{$arg0@dots{}$argN}. A trivial example:
24270 print $arg0 + $arg1 + $arg2
24275 To execute the command use:
24282 This defines the command @code{adder}, which prints the sum of
24283 its three arguments. Note the arguments are text substitutions, so they may
24284 reference variables, use complex expressions, or even perform inferior
24287 @cindex argument count in user-defined commands
24288 @cindex how many arguments (user-defined commands)
24289 In addition, @code{$argc} may be used to find out how many arguments have
24295 print $arg0 + $arg1
24298 print $arg0 + $arg1 + $arg2
24303 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24304 to process a variable number of arguments:
24311 eval "set $sum = $sum + $arg%d", $i
24321 @item define @var{commandname}
24322 Define a command named @var{commandname}. If there is already a command
24323 by that name, you are asked to confirm that you want to redefine it.
24324 The argument @var{commandname} may be a bare command name consisting of letters,
24325 numbers, dashes, and underscores. It may also start with any predefined
24326 prefix command. For example, @samp{define target my-target} creates
24327 a user-defined @samp{target my-target} command.
24329 The definition of the command is made up of other @value{GDBN} command lines,
24330 which are given following the @code{define} command. The end of these
24331 commands is marked by a line containing @code{end}.
24334 @kindex end@r{ (user-defined commands)}
24335 @item document @var{commandname}
24336 Document the user-defined command @var{commandname}, so that it can be
24337 accessed by @code{help}. The command @var{commandname} must already be
24338 defined. This command reads lines of documentation just as @code{define}
24339 reads the lines of the command definition, ending with @code{end}.
24340 After the @code{document} command is finished, @code{help} on command
24341 @var{commandname} displays the documentation you have written.
24343 You may use the @code{document} command again to change the
24344 documentation of a command. Redefining the command with @code{define}
24345 does not change the documentation.
24347 @kindex dont-repeat
24348 @cindex don't repeat command
24350 Used inside a user-defined command, this tells @value{GDBN} that this
24351 command should not be repeated when the user hits @key{RET}
24352 (@pxref{Command Syntax, repeat last command}).
24354 @kindex help user-defined
24355 @item help user-defined
24356 List all user-defined commands and all python commands defined in class
24357 COMAND_USER. The first line of the documentation or docstring is
24362 @itemx show user @var{commandname}
24363 Display the @value{GDBN} commands used to define @var{commandname} (but
24364 not its documentation). If no @var{commandname} is given, display the
24365 definitions for all user-defined commands.
24366 This does not work for user-defined python commands.
24368 @cindex infinite recursion in user-defined commands
24369 @kindex show max-user-call-depth
24370 @kindex set max-user-call-depth
24371 @item show max-user-call-depth
24372 @itemx set max-user-call-depth
24373 The value of @code{max-user-call-depth} controls how many recursion
24374 levels are allowed in user-defined commands before @value{GDBN} suspects an
24375 infinite recursion and aborts the command.
24376 This does not apply to user-defined python commands.
24379 In addition to the above commands, user-defined commands frequently
24380 use control flow commands, described in @ref{Command Files}.
24382 When user-defined commands are executed, the
24383 commands of the definition are not printed. An error in any command
24384 stops execution of the user-defined command.
24386 If used interactively, commands that would ask for confirmation proceed
24387 without asking when used inside a user-defined command. Many @value{GDBN}
24388 commands that normally print messages to say what they are doing omit the
24389 messages when used in a user-defined command.
24392 @subsection User-defined Command Hooks
24393 @cindex command hooks
24394 @cindex hooks, for commands
24395 @cindex hooks, pre-command
24398 You may define @dfn{hooks}, which are a special kind of user-defined
24399 command. Whenever you run the command @samp{foo}, if the user-defined
24400 command @samp{hook-foo} exists, it is executed (with no arguments)
24401 before that command.
24403 @cindex hooks, post-command
24405 A hook may also be defined which is run after the command you executed.
24406 Whenever you run the command @samp{foo}, if the user-defined command
24407 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24408 that command. Post-execution hooks may exist simultaneously with
24409 pre-execution hooks, for the same command.
24411 It is valid for a hook to call the command which it hooks. If this
24412 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24414 @c It would be nice if hookpost could be passed a parameter indicating
24415 @c if the command it hooks executed properly or not. FIXME!
24417 @kindex stop@r{, a pseudo-command}
24418 In addition, a pseudo-command, @samp{stop} exists. Defining
24419 (@samp{hook-stop}) makes the associated commands execute every time
24420 execution stops in your program: before breakpoint commands are run,
24421 displays are printed, or the stack frame is printed.
24423 For example, to ignore @code{SIGALRM} signals while
24424 single-stepping, but treat them normally during normal execution,
24429 handle SIGALRM nopass
24433 handle SIGALRM pass
24436 define hook-continue
24437 handle SIGALRM pass
24441 As a further example, to hook at the beginning and end of the @code{echo}
24442 command, and to add extra text to the beginning and end of the message,
24450 define hookpost-echo
24454 (@value{GDBP}) echo Hello World
24455 <<<---Hello World--->>>
24460 You can define a hook for any single-word command in @value{GDBN}, but
24461 not for command aliases; you should define a hook for the basic command
24462 name, e.g.@: @code{backtrace} rather than @code{bt}.
24463 @c FIXME! So how does Joe User discover whether a command is an alias
24465 You can hook a multi-word command by adding @code{hook-} or
24466 @code{hookpost-} to the last word of the command, e.g.@:
24467 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24469 If an error occurs during the execution of your hook, execution of
24470 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24471 (before the command that you actually typed had a chance to run).
24473 If you try to define a hook which does not match any known command, you
24474 get a warning from the @code{define} command.
24476 @node Command Files
24477 @subsection Command Files
24479 @cindex command files
24480 @cindex scripting commands
24481 A command file for @value{GDBN} is a text file made of lines that are
24482 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24483 also be included. An empty line in a command file does nothing; it
24484 does not mean to repeat the last command, as it would from the
24487 You can request the execution of a command file with the @code{source}
24488 command. Note that the @code{source} command is also used to evaluate
24489 scripts that are not Command Files. The exact behavior can be configured
24490 using the @code{script-extension} setting.
24491 @xref{Extending GDB,, Extending GDB}.
24495 @cindex execute commands from a file
24496 @item source [-s] [-v] @var{filename}
24497 Execute the command file @var{filename}.
24500 The lines in a command file are generally executed sequentially,
24501 unless the order of execution is changed by one of the
24502 @emph{flow-control commands} described below. The commands are not
24503 printed as they are executed. An error in any command terminates
24504 execution of the command file and control is returned to the console.
24506 @value{GDBN} first searches for @var{filename} in the current directory.
24507 If the file is not found there, and @var{filename} does not specify a
24508 directory, then @value{GDBN} also looks for the file on the source search path
24509 (specified with the @samp{directory} command);
24510 except that @file{$cdir} is not searched because the compilation directory
24511 is not relevant to scripts.
24513 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24514 on the search path even if @var{filename} specifies a directory.
24515 The search is done by appending @var{filename} to each element of the
24516 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24517 and the search path contains @file{/home/user} then @value{GDBN} will
24518 look for the script @file{/home/user/mylib/myscript}.
24519 The search is also done if @var{filename} is an absolute path.
24520 For example, if @var{filename} is @file{/tmp/myscript} and
24521 the search path contains @file{/home/user} then @value{GDBN} will
24522 look for the script @file{/home/user/tmp/myscript}.
24523 For DOS-like systems, if @var{filename} contains a drive specification,
24524 it is stripped before concatenation. For example, if @var{filename} is
24525 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24526 will look for the script @file{c:/tmp/myscript}.
24528 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24529 each command as it is executed. The option must be given before
24530 @var{filename}, and is interpreted as part of the filename anywhere else.
24532 Commands that would ask for confirmation if used interactively proceed
24533 without asking when used in a command file. Many @value{GDBN} commands that
24534 normally print messages to say what they are doing omit the messages
24535 when called from command files.
24537 @value{GDBN} also accepts command input from standard input. In this
24538 mode, normal output goes to standard output and error output goes to
24539 standard error. Errors in a command file supplied on standard input do
24540 not terminate execution of the command file---execution continues with
24544 gdb < cmds > log 2>&1
24547 (The syntax above will vary depending on the shell used.) This example
24548 will execute commands from the file @file{cmds}. All output and errors
24549 would be directed to @file{log}.
24551 Since commands stored on command files tend to be more general than
24552 commands typed interactively, they frequently need to deal with
24553 complicated situations, such as different or unexpected values of
24554 variables and symbols, changes in how the program being debugged is
24555 built, etc. @value{GDBN} provides a set of flow-control commands to
24556 deal with these complexities. Using these commands, you can write
24557 complex scripts that loop over data structures, execute commands
24558 conditionally, etc.
24565 This command allows to include in your script conditionally executed
24566 commands. The @code{if} command takes a single argument, which is an
24567 expression to evaluate. It is followed by a series of commands that
24568 are executed only if the expression is true (its value is nonzero).
24569 There can then optionally be an @code{else} line, followed by a series
24570 of commands that are only executed if the expression was false. The
24571 end of the list is marked by a line containing @code{end}.
24575 This command allows to write loops. Its syntax is similar to
24576 @code{if}: the command takes a single argument, which is an expression
24577 to evaluate, and must be followed by the commands to execute, one per
24578 line, terminated by an @code{end}. These commands are called the
24579 @dfn{body} of the loop. The commands in the body of @code{while} are
24580 executed repeatedly as long as the expression evaluates to true.
24584 This command exits the @code{while} loop in whose body it is included.
24585 Execution of the script continues after that @code{while}s @code{end}
24588 @kindex loop_continue
24589 @item loop_continue
24590 This command skips the execution of the rest of the body of commands
24591 in the @code{while} loop in whose body it is included. Execution
24592 branches to the beginning of the @code{while} loop, where it evaluates
24593 the controlling expression.
24595 @kindex end@r{ (if/else/while commands)}
24597 Terminate the block of commands that are the body of @code{if},
24598 @code{else}, or @code{while} flow-control commands.
24603 @subsection Commands for Controlled Output
24605 During the execution of a command file or a user-defined command, normal
24606 @value{GDBN} output is suppressed; the only output that appears is what is
24607 explicitly printed by the commands in the definition. This section
24608 describes three commands useful for generating exactly the output you
24613 @item echo @var{text}
24614 @c I do not consider backslash-space a standard C escape sequence
24615 @c because it is not in ANSI.
24616 Print @var{text}. Nonprinting characters can be included in
24617 @var{text} using C escape sequences, such as @samp{\n} to print a
24618 newline. @strong{No newline is printed unless you specify one.}
24619 In addition to the standard C escape sequences, a backslash followed
24620 by a space stands for a space. This is useful for displaying a
24621 string with spaces at the beginning or the end, since leading and
24622 trailing spaces are otherwise trimmed from all arguments.
24623 To print @samp{@w{ }and foo =@w{ }}, use the command
24624 @samp{echo \@w{ }and foo = \@w{ }}.
24626 A backslash at the end of @var{text} can be used, as in C, to continue
24627 the command onto subsequent lines. For example,
24630 echo This is some text\n\
24631 which is continued\n\
24632 onto several lines.\n
24635 produces the same output as
24638 echo This is some text\n
24639 echo which is continued\n
24640 echo onto several lines.\n
24644 @item output @var{expression}
24645 Print the value of @var{expression} and nothing but that value: no
24646 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24647 value history either. @xref{Expressions, ,Expressions}, for more information
24650 @item output/@var{fmt} @var{expression}
24651 Print the value of @var{expression} in format @var{fmt}. You can use
24652 the same formats as for @code{print}. @xref{Output Formats,,Output
24653 Formats}, for more information.
24656 @item printf @var{template}, @var{expressions}@dots{}
24657 Print the values of one or more @var{expressions} under the control of
24658 the string @var{template}. To print several values, make
24659 @var{expressions} be a comma-separated list of individual expressions,
24660 which may be either numbers or pointers. Their values are printed as
24661 specified by @var{template}, exactly as a C program would do by
24662 executing the code below:
24665 printf (@var{template}, @var{expressions}@dots{});
24668 As in @code{C} @code{printf}, ordinary characters in @var{template}
24669 are printed verbatim, while @dfn{conversion specification} introduced
24670 by the @samp{%} character cause subsequent @var{expressions} to be
24671 evaluated, their values converted and formatted according to type and
24672 style information encoded in the conversion specifications, and then
24675 For example, you can print two values in hex like this:
24678 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24681 @code{printf} supports all the standard @code{C} conversion
24682 specifications, including the flags and modifiers between the @samp{%}
24683 character and the conversion letter, with the following exceptions:
24687 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24690 The modifier @samp{*} is not supported for specifying precision or
24694 The @samp{'} flag (for separation of digits into groups according to
24695 @code{LC_NUMERIC'}) is not supported.
24698 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24702 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24705 The conversion letters @samp{a} and @samp{A} are not supported.
24709 Note that the @samp{ll} type modifier is supported only if the
24710 underlying @code{C} implementation used to build @value{GDBN} supports
24711 the @code{long long int} type, and the @samp{L} type modifier is
24712 supported only if @code{long double} type is available.
24714 As in @code{C}, @code{printf} supports simple backslash-escape
24715 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24716 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24717 single character. Octal and hexadecimal escape sequences are not
24720 Additionally, @code{printf} supports conversion specifications for DFP
24721 (@dfn{Decimal Floating Point}) types using the following length modifiers
24722 together with a floating point specifier.
24727 @samp{H} for printing @code{Decimal32} types.
24730 @samp{D} for printing @code{Decimal64} types.
24733 @samp{DD} for printing @code{Decimal128} types.
24736 If the underlying @code{C} implementation used to build @value{GDBN} has
24737 support for the three length modifiers for DFP types, other modifiers
24738 such as width and precision will also be available for @value{GDBN} to use.
24740 In case there is no such @code{C} support, no additional modifiers will be
24741 available and the value will be printed in the standard way.
24743 Here's an example of printing DFP types using the above conversion letters:
24745 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24750 @item eval @var{template}, @var{expressions}@dots{}
24751 Convert the values of one or more @var{expressions} under the control of
24752 the string @var{template} to a command line, and call it.
24756 @node Auto-loading sequences
24757 @subsection Controlling auto-loading native @value{GDBN} scripts
24758 @cindex native script auto-loading
24760 When a new object file is read (for example, due to the @code{file}
24761 command, or because the inferior has loaded a shared library),
24762 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24763 @xref{Auto-loading extensions}.
24765 Auto-loading can be enabled or disabled,
24766 and the list of auto-loaded scripts can be printed.
24769 @anchor{set auto-load gdb-scripts}
24770 @kindex set auto-load gdb-scripts
24771 @item set auto-load gdb-scripts [on|off]
24772 Enable or disable the auto-loading of canned sequences of commands scripts.
24774 @anchor{show auto-load gdb-scripts}
24775 @kindex show auto-load gdb-scripts
24776 @item show auto-load gdb-scripts
24777 Show whether auto-loading of canned sequences of commands scripts is enabled or
24780 @anchor{info auto-load gdb-scripts}
24781 @kindex info auto-load gdb-scripts
24782 @cindex print list of auto-loaded canned sequences of commands scripts
24783 @item info auto-load gdb-scripts [@var{regexp}]
24784 Print the list of all canned sequences of commands scripts that @value{GDBN}
24788 If @var{regexp} is supplied only canned sequences of commands scripts with
24789 matching names are printed.
24791 @c Python docs live in a separate file.
24792 @include python.texi
24794 @c Guile docs live in a separate file.
24795 @include guile.texi
24797 @node Auto-loading extensions
24798 @section Auto-loading extensions
24799 @cindex auto-loading extensions
24801 @value{GDBN} provides two mechanisms for automatically loading extensions
24802 when a new object file is read (for example, due to the @code{file}
24803 command, or because the inferior has loaded a shared library):
24804 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24805 section of modern file formats like ELF.
24808 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24809 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24810 * Which flavor to choose?::
24813 The auto-loading feature is useful for supplying application-specific
24814 debugging commands and features.
24816 Auto-loading can be enabled or disabled,
24817 and the list of auto-loaded scripts can be printed.
24818 See the @samp{auto-loading} section of each extension language
24819 for more information.
24820 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24821 For Python files see @ref{Python Auto-loading}.
24823 Note that loading of this script file also requires accordingly configured
24824 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24826 @node objfile-gdbdotext file
24827 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24828 @cindex @file{@var{objfile}-gdb.gdb}
24829 @cindex @file{@var{objfile}-gdb.py}
24830 @cindex @file{@var{objfile}-gdb.scm}
24832 When a new object file is read, @value{GDBN} looks for a file named
24833 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24834 where @var{objfile} is the object file's name and
24835 where @var{ext} is the file extension for the extension language:
24838 @item @file{@var{objfile}-gdb.gdb}
24839 GDB's own command language
24840 @item @file{@var{objfile}-gdb.py}
24842 @item @file{@var{objfile}-gdb.scm}
24846 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24847 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24848 components, and appending the @file{-gdb.@var{ext}} suffix.
24849 If this file exists and is readable, @value{GDBN} will evaluate it as a
24850 script in the specified extension language.
24852 If this file does not exist, then @value{GDBN} will look for
24853 @var{script-name} file in all of the directories as specified below.
24855 Note that loading of these files requires an accordingly configured
24856 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24858 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24859 scripts normally according to its @file{.exe} filename. But if no scripts are
24860 found @value{GDBN} also tries script filenames matching the object file without
24861 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24862 is attempted on any platform. This makes the script filenames compatible
24863 between Unix and MS-Windows hosts.
24866 @anchor{set auto-load scripts-directory}
24867 @kindex set auto-load scripts-directory
24868 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24869 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24870 may be delimited by the host platform path separator in use
24871 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24873 Each entry here needs to be covered also by the security setting
24874 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24876 @anchor{with-auto-load-dir}
24877 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24878 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24879 configuration option @option{--with-auto-load-dir}.
24881 Any reference to @file{$debugdir} will get replaced by
24882 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24883 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24884 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24885 @file{$datadir} must be placed as a directory component --- either alone or
24886 delimited by @file{/} or @file{\} directory separators, depending on the host
24889 The list of directories uses path separator (@samp{:} on GNU and Unix
24890 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24891 to the @env{PATH} environment variable.
24893 @anchor{show auto-load scripts-directory}
24894 @kindex show auto-load scripts-directory
24895 @item show auto-load scripts-directory
24896 Show @value{GDBN} auto-loaded scripts location.
24898 @anchor{add-auto-load-scripts-directory}
24899 @kindex add-auto-load-scripts-directory
24900 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24901 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24902 Multiple entries may be delimited by the host platform path separator in use.
24905 @value{GDBN} does not track which files it has already auto-loaded this way.
24906 @value{GDBN} will load the associated script every time the corresponding
24907 @var{objfile} is opened.
24908 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24909 is evaluated more than once.
24911 @node dotdebug_gdb_scripts section
24912 @subsection The @code{.debug_gdb_scripts} section
24913 @cindex @code{.debug_gdb_scripts} section
24915 For systems using file formats like ELF and COFF,
24916 when @value{GDBN} loads a new object file
24917 it will look for a special section named @code{.debug_gdb_scripts}.
24918 If this section exists, its contents is a list of null-terminated entries
24919 specifying scripts to load. Each entry begins with a non-null prefix byte that
24920 specifies the kind of entry, typically the extension language and whether the
24921 script is in a file or inlined in @code{.debug_gdb_scripts}.
24923 The following entries are supported:
24926 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24927 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24928 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24929 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24932 @subsubsection Script File Entries
24934 If the entry specifies a file, @value{GDBN} will look for the file first
24935 in the current directory and then along the source search path
24936 (@pxref{Source Path, ,Specifying Source Directories}),
24937 except that @file{$cdir} is not searched, since the compilation
24938 directory is not relevant to scripts.
24940 File entries can be placed in section @code{.debug_gdb_scripts} with,
24941 for example, this GCC macro for Python scripts.
24944 /* Note: The "MS" section flags are to remove duplicates. */
24945 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24947 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24948 .byte 1 /* Python */\n\
24949 .asciz \"" script_name "\"\n\
24955 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24956 Then one can reference the macro in a header or source file like this:
24959 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24962 The script name may include directories if desired.
24964 Note that loading of this script file also requires accordingly configured
24965 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24967 If the macro invocation is put in a header, any application or library
24968 using this header will get a reference to the specified script,
24969 and with the use of @code{"MS"} attributes on the section, the linker
24970 will remove duplicates.
24972 @subsubsection Script Text Entries
24974 Script text entries allow to put the executable script in the entry
24975 itself instead of loading it from a file.
24976 The first line of the entry, everything after the prefix byte and up to
24977 the first newline (@code{0xa}) character, is the script name, and must not
24978 contain any kind of space character, e.g., spaces or tabs.
24979 The rest of the entry, up to the trailing null byte, is the script to
24980 execute in the specified language. The name needs to be unique among
24981 all script names, as @value{GDBN} executes each script only once based
24984 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24988 #include "symcat.h"
24989 #include "gdb/section-scripts.h"
24991 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24992 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24993 ".ascii \"gdb.inlined-script\\n\"\n"
24994 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24995 ".ascii \" def __init__ (self):\\n\"\n"
24996 ".ascii \" super (test_cmd, self).__init__ ("
24997 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24998 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24999 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25000 ".ascii \"test_cmd ()\\n\"\n"
25006 Loading of inlined scripts requires a properly configured
25007 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25008 The path to specify in @code{auto-load safe-path} is the path of the file
25009 containing the @code{.debug_gdb_scripts} section.
25011 @node Which flavor to choose?
25012 @subsection Which flavor to choose?
25014 Given the multiple ways of auto-loading extensions, it might not always
25015 be clear which one to choose. This section provides some guidance.
25018 Benefits of the @file{-gdb.@var{ext}} way:
25022 Can be used with file formats that don't support multiple sections.
25025 Ease of finding scripts for public libraries.
25027 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25028 in the source search path.
25029 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25030 isn't a source directory in which to find the script.
25033 Doesn't require source code additions.
25037 Benefits of the @code{.debug_gdb_scripts} way:
25041 Works with static linking.
25043 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25044 trigger their loading. When an application is statically linked the only
25045 objfile available is the executable, and it is cumbersome to attach all the
25046 scripts from all the input libraries to the executable's
25047 @file{-gdb.@var{ext}} script.
25050 Works with classes that are entirely inlined.
25052 Some classes can be entirely inlined, and thus there may not be an associated
25053 shared library to attach a @file{-gdb.@var{ext}} script to.
25056 Scripts needn't be copied out of the source tree.
25058 In some circumstances, apps can be built out of large collections of internal
25059 libraries, and the build infrastructure necessary to install the
25060 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25061 cumbersome. It may be easier to specify the scripts in the
25062 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25063 top of the source tree to the source search path.
25066 @node Multiple Extension Languages
25067 @section Multiple Extension Languages
25069 The Guile and Python extension languages do not share any state,
25070 and generally do not interfere with each other.
25071 There are some things to be aware of, however.
25073 @subsection Python comes first
25075 Python was @value{GDBN}'s first extension language, and to avoid breaking
25076 existing behaviour Python comes first. This is generally solved by the
25077 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25078 extension languages, and when it makes a call to an extension language,
25079 (say to pretty-print a value), it tries each in turn until an extension
25080 language indicates it has performed the request (e.g., has returned the
25081 pretty-printed form of a value).
25082 This extends to errors while performing such requests: If an error happens
25083 while, for example, trying to pretty-print an object then the error is
25084 reported and any following extension languages are not tried.
25087 @section Creating new spellings of existing commands
25088 @cindex aliases for commands
25090 It is often useful to define alternate spellings of existing commands.
25091 For example, if a new @value{GDBN} command defined in Python has
25092 a long name to type, it is handy to have an abbreviated version of it
25093 that involves less typing.
25095 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25096 of the @samp{step} command even though it is otherwise an ambiguous
25097 abbreviation of other commands like @samp{set} and @samp{show}.
25099 Aliases are also used to provide shortened or more common versions
25100 of multi-word commands. For example, @value{GDBN} provides the
25101 @samp{tty} alias of the @samp{set inferior-tty} command.
25103 You can define a new alias with the @samp{alias} command.
25108 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25112 @var{ALIAS} specifies the name of the new alias.
25113 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25116 @var{COMMAND} specifies the name of an existing command
25117 that is being aliased.
25119 The @samp{-a} option specifies that the new alias is an abbreviation
25120 of the command. Abbreviations are not shown in command
25121 lists displayed by the @samp{help} command.
25123 The @samp{--} option specifies the end of options,
25124 and is useful when @var{ALIAS} begins with a dash.
25126 Here is a simple example showing how to make an abbreviation
25127 of a command so that there is less to type.
25128 Suppose you were tired of typing @samp{disas}, the current
25129 shortest unambiguous abbreviation of the @samp{disassemble} command
25130 and you wanted an even shorter version named @samp{di}.
25131 The following will accomplish this.
25134 (gdb) alias -a di = disas
25137 Note that aliases are different from user-defined commands.
25138 With a user-defined command, you also need to write documentation
25139 for it with the @samp{document} command.
25140 An alias automatically picks up the documentation of the existing command.
25142 Here is an example where we make @samp{elms} an abbreviation of
25143 @samp{elements} in the @samp{set print elements} command.
25144 This is to show that you can make an abbreviation of any part
25148 (gdb) alias -a set print elms = set print elements
25149 (gdb) alias -a show print elms = show print elements
25150 (gdb) set p elms 20
25152 Limit on string chars or array elements to print is 200.
25155 Note that if you are defining an alias of a @samp{set} command,
25156 and you want to have an alias for the corresponding @samp{show}
25157 command, then you need to define the latter separately.
25159 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25160 @var{ALIAS}, just as they are normally.
25163 (gdb) alias -a set pr elms = set p ele
25166 Finally, here is an example showing the creation of a one word
25167 alias for a more complex command.
25168 This creates alias @samp{spe} of the command @samp{set print elements}.
25171 (gdb) alias spe = set print elements
25176 @chapter Command Interpreters
25177 @cindex command interpreters
25179 @value{GDBN} supports multiple command interpreters, and some command
25180 infrastructure to allow users or user interface writers to switch
25181 between interpreters or run commands in other interpreters.
25183 @value{GDBN} currently supports two command interpreters, the console
25184 interpreter (sometimes called the command-line interpreter or @sc{cli})
25185 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25186 describes both of these interfaces in great detail.
25188 By default, @value{GDBN} will start with the console interpreter.
25189 However, the user may choose to start @value{GDBN} with another
25190 interpreter by specifying the @option{-i} or @option{--interpreter}
25191 startup options. Defined interpreters include:
25195 @cindex console interpreter
25196 The traditional console or command-line interpreter. This is the most often
25197 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25198 @value{GDBN} will use this interpreter.
25201 @cindex mi interpreter
25202 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25203 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25204 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25208 @cindex mi2 interpreter
25209 The current @sc{gdb/mi} interface.
25212 @cindex mi1 interpreter
25213 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25217 @cindex invoke another interpreter
25219 @kindex interpreter-exec
25220 You may execute commands in any interpreter from the current
25221 interpreter using the appropriate command. If you are running the
25222 console interpreter, simply use the @code{interpreter-exec} command:
25225 interpreter-exec mi "-data-list-register-names"
25228 @sc{gdb/mi} has a similar command, although it is only available in versions of
25229 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25231 Note that @code{interpreter-exec} only changes the interpreter for the
25232 duration of the specified command. It does not change the interpreter
25235 @cindex start a new independent interpreter
25237 Although you may only choose a single interpreter at startup, it is
25238 possible to run an independent interpreter on a specified input/output
25239 device (usually a tty).
25241 For example, consider a debugger GUI or IDE that wants to provide a
25242 @value{GDBN} console view. It may do so by embedding a terminal
25243 emulator widget in its GUI, starting @value{GDBN} in the traditional
25244 command-line mode with stdin/stdout/stderr redirected to that
25245 terminal, and then creating an MI interpreter running on a specified
25246 input/output device. The console interpreter created by @value{GDBN}
25247 at startup handles commands the user types in the terminal widget,
25248 while the GUI controls and synchronizes state with @value{GDBN} using
25249 the separate MI interpreter.
25251 To start a new secondary @dfn{user interface} running MI, use the
25252 @code{new-ui} command:
25255 @cindex new user interface
25257 new-ui @var{interpreter} @var{tty}
25260 The @var{interpreter} parameter specifies the interpreter to run.
25261 This accepts the same values as the @code{interpreter-exec} command.
25262 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25263 @var{tty} parameter specifies the name of the bidirectional file the
25264 interpreter uses for input/output, usually the name of a
25265 pseudoterminal slave on Unix systems. For example:
25268 (@value{GDBP}) new-ui mi /dev/pts/9
25272 runs an MI interpreter on @file{/dev/pts/9}.
25275 @chapter @value{GDBN} Text User Interface
25277 @cindex Text User Interface
25280 * TUI Overview:: TUI overview
25281 * TUI Keys:: TUI key bindings
25282 * TUI Single Key Mode:: TUI single key mode
25283 * TUI Commands:: TUI-specific commands
25284 * TUI Configuration:: TUI configuration variables
25287 The @value{GDBN} Text User Interface (TUI) is a terminal
25288 interface which uses the @code{curses} library to show the source
25289 file, the assembly output, the program registers and @value{GDBN}
25290 commands in separate text windows. The TUI mode is supported only
25291 on platforms where a suitable version of the @code{curses} library
25294 The TUI mode is enabled by default when you invoke @value{GDBN} as
25295 @samp{@value{GDBP} -tui}.
25296 You can also switch in and out of TUI mode while @value{GDBN} runs by
25297 using various TUI commands and key bindings, such as @command{tui
25298 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25299 @ref{TUI Keys, ,TUI Key Bindings}.
25302 @section TUI Overview
25304 In TUI mode, @value{GDBN} can display several text windows:
25308 This window is the @value{GDBN} command window with the @value{GDBN}
25309 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25310 managed using readline.
25313 The source window shows the source file of the program. The current
25314 line and active breakpoints are displayed in this window.
25317 The assembly window shows the disassembly output of the program.
25320 This window shows the processor registers. Registers are highlighted
25321 when their values change.
25324 The source and assembly windows show the current program position
25325 by highlighting the current line and marking it with a @samp{>} marker.
25326 Breakpoints are indicated with two markers. The first marker
25327 indicates the breakpoint type:
25331 Breakpoint which was hit at least once.
25334 Breakpoint which was never hit.
25337 Hardware breakpoint which was hit at least once.
25340 Hardware breakpoint which was never hit.
25343 The second marker indicates whether the breakpoint is enabled or not:
25347 Breakpoint is enabled.
25350 Breakpoint is disabled.
25353 The source, assembly and register windows are updated when the current
25354 thread changes, when the frame changes, or when the program counter
25357 These windows are not all visible at the same time. The command
25358 window is always visible. The others can be arranged in several
25369 source and assembly,
25372 source and registers, or
25375 assembly and registers.
25378 A status line above the command window shows the following information:
25382 Indicates the current @value{GDBN} target.
25383 (@pxref{Targets, ,Specifying a Debugging Target}).
25386 Gives the current process or thread number.
25387 When no process is being debugged, this field is set to @code{No process}.
25390 Gives the current function name for the selected frame.
25391 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25392 When there is no symbol corresponding to the current program counter,
25393 the string @code{??} is displayed.
25396 Indicates the current line number for the selected frame.
25397 When the current line number is not known, the string @code{??} is displayed.
25400 Indicates the current program counter address.
25404 @section TUI Key Bindings
25405 @cindex TUI key bindings
25407 The TUI installs several key bindings in the readline keymaps
25408 @ifset SYSTEM_READLINE
25409 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25411 @ifclear SYSTEM_READLINE
25412 (@pxref{Command Line Editing}).
25414 The following key bindings are installed for both TUI mode and the
25415 @value{GDBN} standard mode.
25424 Enter or leave the TUI mode. When leaving the TUI mode,
25425 the curses window management stops and @value{GDBN} operates using
25426 its standard mode, writing on the terminal directly. When reentering
25427 the TUI mode, control is given back to the curses windows.
25428 The screen is then refreshed.
25432 Use a TUI layout with only one window. The layout will
25433 either be @samp{source} or @samp{assembly}. When the TUI mode
25434 is not active, it will switch to the TUI mode.
25436 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25440 Use a TUI layout with at least two windows. When the current
25441 layout already has two windows, the next layout with two windows is used.
25442 When a new layout is chosen, one window will always be common to the
25443 previous layout and the new one.
25445 Think of it as the Emacs @kbd{C-x 2} binding.
25449 Change the active window. The TUI associates several key bindings
25450 (like scrolling and arrow keys) with the active window. This command
25451 gives the focus to the next TUI window.
25453 Think of it as the Emacs @kbd{C-x o} binding.
25457 Switch in and out of the TUI SingleKey mode that binds single
25458 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25461 The following key bindings only work in the TUI mode:
25466 Scroll the active window one page up.
25470 Scroll the active window one page down.
25474 Scroll the active window one line up.
25478 Scroll the active window one line down.
25482 Scroll the active window one column left.
25486 Scroll the active window one column right.
25490 Refresh the screen.
25493 Because the arrow keys scroll the active window in the TUI mode, they
25494 are not available for their normal use by readline unless the command
25495 window has the focus. When another window is active, you must use
25496 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25497 and @kbd{C-f} to control the command window.
25499 @node TUI Single Key Mode
25500 @section TUI Single Key Mode
25501 @cindex TUI single key mode
25503 The TUI also provides a @dfn{SingleKey} mode, which binds several
25504 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25505 switch into this mode, where the following key bindings are used:
25508 @kindex c @r{(SingleKey TUI key)}
25512 @kindex d @r{(SingleKey TUI key)}
25516 @kindex f @r{(SingleKey TUI key)}
25520 @kindex n @r{(SingleKey TUI key)}
25524 @kindex o @r{(SingleKey TUI key)}
25526 nexti. The shortcut letter @samp{o} stands for ``step Over''.
25528 @kindex q @r{(SingleKey TUI key)}
25530 exit the SingleKey mode.
25532 @kindex r @r{(SingleKey TUI key)}
25536 @kindex s @r{(SingleKey TUI key)}
25540 @kindex i @r{(SingleKey TUI key)}
25542 stepi. The shortcut letter @samp{i} stands for ``step Into''.
25544 @kindex u @r{(SingleKey TUI key)}
25548 @kindex v @r{(SingleKey TUI key)}
25552 @kindex w @r{(SingleKey TUI key)}
25557 Other keys temporarily switch to the @value{GDBN} command prompt.
25558 The key that was pressed is inserted in the editing buffer so that
25559 it is possible to type most @value{GDBN} commands without interaction
25560 with the TUI SingleKey mode. Once the command is entered the TUI
25561 SingleKey mode is restored. The only way to permanently leave
25562 this mode is by typing @kbd{q} or @kbd{C-x s}.
25566 @section TUI-specific Commands
25567 @cindex TUI commands
25569 The TUI has specific commands to control the text windows.
25570 These commands are always available, even when @value{GDBN} is not in
25571 the TUI mode. When @value{GDBN} is in the standard mode, most
25572 of these commands will automatically switch to the TUI mode.
25574 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25575 terminal, or @value{GDBN} has been started with the machine interface
25576 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25577 these commands will fail with an error, because it would not be
25578 possible or desirable to enable curses window management.
25583 Activate TUI mode. The last active TUI window layout will be used if
25584 TUI mode has prevsiouly been used in the current debugging session,
25585 otherwise a default layout is used.
25588 @kindex tui disable
25589 Disable TUI mode, returning to the console interpreter.
25593 List and give the size of all displayed windows.
25595 @item layout @var{name}
25597 Changes which TUI windows are displayed. In each layout the command
25598 window is always displayed, the @var{name} parameter controls which
25599 additional windows are displayed, and can be any of the following:
25603 Display the next layout.
25606 Display the previous layout.
25609 Display the source and command windows.
25612 Display the assembly and command windows.
25615 Display the source, assembly, and command windows.
25618 When in @code{src} layout display the register, source, and command
25619 windows. When in @code{asm} or @code{split} layout display the
25620 register, assembler, and command windows.
25623 @item focus @var{name}
25625 Changes which TUI window is currently active for scrolling. The
25626 @var{name} parameter can be any of the following:
25630 Make the next window active for scrolling.
25633 Make the previous window active for scrolling.
25636 Make the source window active for scrolling.
25639 Make the assembly window active for scrolling.
25642 Make the register window active for scrolling.
25645 Make the command window active for scrolling.
25650 Refresh the screen. This is similar to typing @kbd{C-L}.
25652 @item tui reg @var{group}
25654 Changes the register group displayed in the tui register window to
25655 @var{group}. If the register window is not currently displayed this
25656 command will cause the register window to be displayed. The list of
25657 register groups, as well as their order is target specific. The
25658 following groups are available on most targets:
25661 Repeatedly selecting this group will cause the display to cycle
25662 through all of the available register groups.
25665 Repeatedly selecting this group will cause the display to cycle
25666 through all of the available register groups in the reverse order to
25670 Display the general registers.
25672 Display the floating point registers.
25674 Display the system registers.
25676 Display the vector registers.
25678 Display all registers.
25683 Update the source window and the current execution point.
25685 @item winheight @var{name} +@var{count}
25686 @itemx winheight @var{name} -@var{count}
25688 Change the height of the window @var{name} by @var{count}
25689 lines. Positive counts increase the height, while negative counts
25690 decrease it. The @var{name} parameter can be one of @code{src} (the
25691 source window), @code{cmd} (the command window), @code{asm} (the
25692 disassembly window), or @code{regs} (the register display window).
25694 @item tabset @var{nchars}
25696 Set the width of tab stops to be @var{nchars} characters. This
25697 setting affects the display of TAB characters in the source and
25701 @node TUI Configuration
25702 @section TUI Configuration Variables
25703 @cindex TUI configuration variables
25705 Several configuration variables control the appearance of TUI windows.
25708 @item set tui border-kind @var{kind}
25709 @kindex set tui border-kind
25710 Select the border appearance for the source, assembly and register windows.
25711 The possible values are the following:
25714 Use a space character to draw the border.
25717 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25720 Use the Alternate Character Set to draw the border. The border is
25721 drawn using character line graphics if the terminal supports them.
25724 @item set tui border-mode @var{mode}
25725 @kindex set tui border-mode
25726 @itemx set tui active-border-mode @var{mode}
25727 @kindex set tui active-border-mode
25728 Select the display attributes for the borders of the inactive windows
25729 or the active window. The @var{mode} can be one of the following:
25732 Use normal attributes to display the border.
25738 Use reverse video mode.
25741 Use half bright mode.
25743 @item half-standout
25744 Use half bright and standout mode.
25747 Use extra bright or bold mode.
25749 @item bold-standout
25750 Use extra bright or bold and standout mode.
25755 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25758 @cindex @sc{gnu} Emacs
25759 A special interface allows you to use @sc{gnu} Emacs to view (and
25760 edit) the source files for the program you are debugging with
25763 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25764 executable file you want to debug as an argument. This command starts
25765 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25766 created Emacs buffer.
25767 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25769 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25774 All ``terminal'' input and output goes through an Emacs buffer, called
25777 This applies both to @value{GDBN} commands and their output, and to the input
25778 and output done by the program you are debugging.
25780 This is useful because it means that you can copy the text of previous
25781 commands and input them again; you can even use parts of the output
25784 All the facilities of Emacs' Shell mode are available for interacting
25785 with your program. In particular, you can send signals the usual
25786 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25790 @value{GDBN} displays source code through Emacs.
25792 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25793 source file for that frame and puts an arrow (@samp{=>}) at the
25794 left margin of the current line. Emacs uses a separate buffer for
25795 source display, and splits the screen to show both your @value{GDBN} session
25798 Explicit @value{GDBN} @code{list} or search commands still produce output as
25799 usual, but you probably have no reason to use them from Emacs.
25802 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25803 a graphical mode, enabled by default, which provides further buffers
25804 that can control the execution and describe the state of your program.
25805 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25807 If you specify an absolute file name when prompted for the @kbd{M-x
25808 gdb} argument, then Emacs sets your current working directory to where
25809 your program resides. If you only specify the file name, then Emacs
25810 sets your current working directory to the directory associated
25811 with the previous buffer. In this case, @value{GDBN} may find your
25812 program by searching your environment's @code{PATH} variable, but on
25813 some operating systems it might not find the source. So, although the
25814 @value{GDBN} input and output session proceeds normally, the auxiliary
25815 buffer does not display the current source and line of execution.
25817 The initial working directory of @value{GDBN} is printed on the top
25818 line of the GUD buffer and this serves as a default for the commands
25819 that specify files for @value{GDBN} to operate on. @xref{Files,
25820 ,Commands to Specify Files}.
25822 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25823 need to call @value{GDBN} by a different name (for example, if you
25824 keep several configurations around, with different names) you can
25825 customize the Emacs variable @code{gud-gdb-command-name} to run the
25828 In the GUD buffer, you can use these special Emacs commands in
25829 addition to the standard Shell mode commands:
25833 Describe the features of Emacs' GUD Mode.
25836 Execute to another source line, like the @value{GDBN} @code{step} command; also
25837 update the display window to show the current file and location.
25840 Execute to next source line in this function, skipping all function
25841 calls, like the @value{GDBN} @code{next} command. Then update the display window
25842 to show the current file and location.
25845 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25846 display window accordingly.
25849 Execute until exit from the selected stack frame, like the @value{GDBN}
25850 @code{finish} command.
25853 Continue execution of your program, like the @value{GDBN} @code{continue}
25857 Go up the number of frames indicated by the numeric argument
25858 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25859 like the @value{GDBN} @code{up} command.
25862 Go down the number of frames indicated by the numeric argument, like the
25863 @value{GDBN} @code{down} command.
25866 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25867 tells @value{GDBN} to set a breakpoint on the source line point is on.
25869 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25870 separate frame which shows a backtrace when the GUD buffer is current.
25871 Move point to any frame in the stack and type @key{RET} to make it
25872 become the current frame and display the associated source in the
25873 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25874 selected frame become the current one. In graphical mode, the
25875 speedbar displays watch expressions.
25877 If you accidentally delete the source-display buffer, an easy way to get
25878 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25879 request a frame display; when you run under Emacs, this recreates
25880 the source buffer if necessary to show you the context of the current
25883 The source files displayed in Emacs are in ordinary Emacs buffers
25884 which are visiting the source files in the usual way. You can edit
25885 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25886 communicates with Emacs in terms of line numbers. If you add or
25887 delete lines from the text, the line numbers that @value{GDBN} knows cease
25888 to correspond properly with the code.
25890 A more detailed description of Emacs' interaction with @value{GDBN} is
25891 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25895 @chapter The @sc{gdb/mi} Interface
25897 @unnumberedsec Function and Purpose
25899 @cindex @sc{gdb/mi}, its purpose
25900 @sc{gdb/mi} is a line based machine oriented text interface to
25901 @value{GDBN} and is activated by specifying using the
25902 @option{--interpreter} command line option (@pxref{Mode Options}). It
25903 is specifically intended to support the development of systems which
25904 use the debugger as just one small component of a larger system.
25906 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25907 in the form of a reference manual.
25909 Note that @sc{gdb/mi} is still under construction, so some of the
25910 features described below are incomplete and subject to change
25911 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25913 @unnumberedsec Notation and Terminology
25915 @cindex notational conventions, for @sc{gdb/mi}
25916 This chapter uses the following notation:
25920 @code{|} separates two alternatives.
25923 @code{[ @var{something} ]} indicates that @var{something} is optional:
25924 it may or may not be given.
25927 @code{( @var{group} )*} means that @var{group} inside the parentheses
25928 may repeat zero or more times.
25931 @code{( @var{group} )+} means that @var{group} inside the parentheses
25932 may repeat one or more times.
25935 @code{"@var{string}"} means a literal @var{string}.
25939 @heading Dependencies
25943 * GDB/MI General Design::
25944 * GDB/MI Command Syntax::
25945 * GDB/MI Compatibility with CLI::
25946 * GDB/MI Development and Front Ends::
25947 * GDB/MI Output Records::
25948 * GDB/MI Simple Examples::
25949 * GDB/MI Command Description Format::
25950 * GDB/MI Breakpoint Commands::
25951 * GDB/MI Catchpoint Commands::
25952 * GDB/MI Program Context::
25953 * GDB/MI Thread Commands::
25954 * GDB/MI Ada Tasking Commands::
25955 * GDB/MI Program Execution::
25956 * GDB/MI Stack Manipulation::
25957 * GDB/MI Variable Objects::
25958 * GDB/MI Data Manipulation::
25959 * GDB/MI Tracepoint Commands::
25960 * GDB/MI Symbol Query::
25961 * GDB/MI File Commands::
25963 * GDB/MI Kod Commands::
25964 * GDB/MI Memory Overlay Commands::
25965 * GDB/MI Signal Handling Commands::
25967 * GDB/MI Target Manipulation::
25968 * GDB/MI File Transfer Commands::
25969 * GDB/MI Ada Exceptions Commands::
25970 * GDB/MI Support Commands::
25971 * GDB/MI Miscellaneous Commands::
25974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25975 @node GDB/MI General Design
25976 @section @sc{gdb/mi} General Design
25977 @cindex GDB/MI General Design
25979 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25980 parts---commands sent to @value{GDBN}, responses to those commands
25981 and notifications. Each command results in exactly one response,
25982 indicating either successful completion of the command, or an error.
25983 For the commands that do not resume the target, the response contains the
25984 requested information. For the commands that resume the target, the
25985 response only indicates whether the target was successfully resumed.
25986 Notifications is the mechanism for reporting changes in the state of the
25987 target, or in @value{GDBN} state, that cannot conveniently be associated with
25988 a command and reported as part of that command response.
25990 The important examples of notifications are:
25994 Exec notifications. These are used to report changes in
25995 target state---when a target is resumed, or stopped. It would not
25996 be feasible to include this information in response of resuming
25997 commands, because one resume commands can result in multiple events in
25998 different threads. Also, quite some time may pass before any event
25999 happens in the target, while a frontend needs to know whether the resuming
26000 command itself was successfully executed.
26003 Console output, and status notifications. Console output
26004 notifications are used to report output of CLI commands, as well as
26005 diagnostics for other commands. Status notifications are used to
26006 report the progress of a long-running operation. Naturally, including
26007 this information in command response would mean no output is produced
26008 until the command is finished, which is undesirable.
26011 General notifications. Commands may have various side effects on
26012 the @value{GDBN} or target state beyond their official purpose. For example,
26013 a command may change the selected thread. Although such changes can
26014 be included in command response, using notification allows for more
26015 orthogonal frontend design.
26019 There's no guarantee that whenever an MI command reports an error,
26020 @value{GDBN} or the target are in any specific state, and especially,
26021 the state is not reverted to the state before the MI command was
26022 processed. Therefore, whenever an MI command results in an error,
26023 we recommend that the frontend refreshes all the information shown in
26024 the user interface.
26028 * Context management::
26029 * Asynchronous and non-stop modes::
26033 @node Context management
26034 @subsection Context management
26036 @subsubsection Threads and Frames
26038 In most cases when @value{GDBN} accesses the target, this access is
26039 done in context of a specific thread and frame (@pxref{Frames}).
26040 Often, even when accessing global data, the target requires that a thread
26041 be specified. The CLI interface maintains the selected thread and frame,
26042 and supplies them to target on each command. This is convenient,
26043 because a command line user would not want to specify that information
26044 explicitly on each command, and because user interacts with
26045 @value{GDBN} via a single terminal, so no confusion is possible as
26046 to what thread and frame are the current ones.
26048 In the case of MI, the concept of selected thread and frame is less
26049 useful. First, a frontend can easily remember this information
26050 itself. Second, a graphical frontend can have more than one window,
26051 each one used for debugging a different thread, and the frontend might
26052 want to access additional threads for internal purposes. This
26053 increases the risk that by relying on implicitly selected thread, the
26054 frontend may be operating on a wrong one. Therefore, each MI command
26055 should explicitly specify which thread and frame to operate on. To
26056 make it possible, each MI command accepts the @samp{--thread} and
26057 @samp{--frame} options, the value to each is @value{GDBN} global
26058 identifier for thread and frame to operate on.
26060 Usually, each top-level window in a frontend allows the user to select
26061 a thread and a frame, and remembers the user selection for further
26062 operations. However, in some cases @value{GDBN} may suggest that the
26063 current thread or frame be changed. For example, when stopping on a
26064 breakpoint it is reasonable to switch to the thread where breakpoint is
26065 hit. For another example, if the user issues the CLI @samp{thread} or
26066 @samp{frame} commands via the frontend, it is desirable to change the
26067 frontend's selection to the one specified by user. @value{GDBN}
26068 communicates the suggestion to change current thread and frame using the
26069 @samp{=thread-selected} notification.
26071 Note that historically, MI shares the selected thread with CLI, so
26072 frontends used the @code{-thread-select} to execute commands in the
26073 right context. However, getting this to work right is cumbersome. The
26074 simplest way is for frontend to emit @code{-thread-select} command
26075 before every command. This doubles the number of commands that need
26076 to be sent. The alternative approach is to suppress @code{-thread-select}
26077 if the selected thread in @value{GDBN} is supposed to be identical to the
26078 thread the frontend wants to operate on. However, getting this
26079 optimization right can be tricky. In particular, if the frontend
26080 sends several commands to @value{GDBN}, and one of the commands changes the
26081 selected thread, then the behaviour of subsequent commands will
26082 change. So, a frontend should either wait for response from such
26083 problematic commands, or explicitly add @code{-thread-select} for
26084 all subsequent commands. No frontend is known to do this exactly
26085 right, so it is suggested to just always pass the @samp{--thread} and
26086 @samp{--frame} options.
26088 @subsubsection Language
26090 The execution of several commands depends on which language is selected.
26091 By default, the current language (@pxref{show language}) is used.
26092 But for commands known to be language-sensitive, it is recommended
26093 to use the @samp{--language} option. This option takes one argument,
26094 which is the name of the language to use while executing the command.
26098 -data-evaluate-expression --language c "sizeof (void*)"
26103 The valid language names are the same names accepted by the
26104 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26105 @samp{local} or @samp{unknown}.
26107 @node Asynchronous and non-stop modes
26108 @subsection Asynchronous command execution and non-stop mode
26110 On some targets, @value{GDBN} is capable of processing MI commands
26111 even while the target is running. This is called @dfn{asynchronous
26112 command execution} (@pxref{Background Execution}). The frontend may
26113 specify a preferrence for asynchronous execution using the
26114 @code{-gdb-set mi-async 1} command, which should be emitted before
26115 either running the executable or attaching to the target. After the
26116 frontend has started the executable or attached to the target, it can
26117 find if asynchronous execution is enabled using the
26118 @code{-list-target-features} command.
26121 @item -gdb-set mi-async on
26122 @item -gdb-set mi-async off
26123 Set whether MI is in asynchronous mode.
26125 When @code{off}, which is the default, MI execution commands (e.g.,
26126 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26127 for the program to stop before processing further commands.
26129 When @code{on}, MI execution commands are background execution
26130 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26131 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26132 MI commands even while the target is running.
26134 @item -gdb-show mi-async
26135 Show whether MI asynchronous mode is enabled.
26138 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26139 @code{target-async} instead of @code{mi-async}, and it had the effect
26140 of both putting MI in asynchronous mode and making CLI background
26141 commands possible. CLI background commands are now always possible
26142 ``out of the box'' if the target supports them. The old spelling is
26143 kept as a deprecated alias for backwards compatibility.
26145 Even if @value{GDBN} can accept a command while target is running,
26146 many commands that access the target do not work when the target is
26147 running. Therefore, asynchronous command execution is most useful
26148 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26149 it is possible to examine the state of one thread, while other threads
26152 When a given thread is running, MI commands that try to access the
26153 target in the context of that thread may not work, or may work only on
26154 some targets. In particular, commands that try to operate on thread's
26155 stack will not work, on any target. Commands that read memory, or
26156 modify breakpoints, may work or not work, depending on the target. Note
26157 that even commands that operate on global state, such as @code{print},
26158 @code{set}, and breakpoint commands, still access the target in the
26159 context of a specific thread, so frontend should try to find a
26160 stopped thread and perform the operation on that thread (using the
26161 @samp{--thread} option).
26163 Which commands will work in the context of a running thread is
26164 highly target dependent. However, the two commands
26165 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26166 to find the state of a thread, will always work.
26168 @node Thread groups
26169 @subsection Thread groups
26170 @value{GDBN} may be used to debug several processes at the same time.
26171 On some platfroms, @value{GDBN} may support debugging of several
26172 hardware systems, each one having several cores with several different
26173 processes running on each core. This section describes the MI
26174 mechanism to support such debugging scenarios.
26176 The key observation is that regardless of the structure of the
26177 target, MI can have a global list of threads, because most commands that
26178 accept the @samp{--thread} option do not need to know what process that
26179 thread belongs to. Therefore, it is not necessary to introduce
26180 neither additional @samp{--process} option, nor an notion of the
26181 current process in the MI interface. The only strictly new feature
26182 that is required is the ability to find how the threads are grouped
26185 To allow the user to discover such grouping, and to support arbitrary
26186 hierarchy of machines/cores/processes, MI introduces the concept of a
26187 @dfn{thread group}. Thread group is a collection of threads and other
26188 thread groups. A thread group always has a string identifier, a type,
26189 and may have additional attributes specific to the type. A new
26190 command, @code{-list-thread-groups}, returns the list of top-level
26191 thread groups, which correspond to processes that @value{GDBN} is
26192 debugging at the moment. By passing an identifier of a thread group
26193 to the @code{-list-thread-groups} command, it is possible to obtain
26194 the members of specific thread group.
26196 To allow the user to easily discover processes, and other objects, he
26197 wishes to debug, a concept of @dfn{available thread group} is
26198 introduced. Available thread group is an thread group that
26199 @value{GDBN} is not debugging, but that can be attached to, using the
26200 @code{-target-attach} command. The list of available top-level thread
26201 groups can be obtained using @samp{-list-thread-groups --available}.
26202 In general, the content of a thread group may be only retrieved only
26203 after attaching to that thread group.
26205 Thread groups are related to inferiors (@pxref{Inferiors and
26206 Programs}). Each inferior corresponds to a thread group of a special
26207 type @samp{process}, and some additional operations are permitted on
26208 such thread groups.
26210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26211 @node GDB/MI Command Syntax
26212 @section @sc{gdb/mi} Command Syntax
26215 * GDB/MI Input Syntax::
26216 * GDB/MI Output Syntax::
26219 @node GDB/MI Input Syntax
26220 @subsection @sc{gdb/mi} Input Syntax
26222 @cindex input syntax for @sc{gdb/mi}
26223 @cindex @sc{gdb/mi}, input syntax
26225 @item @var{command} @expansion{}
26226 @code{@var{cli-command} | @var{mi-command}}
26228 @item @var{cli-command} @expansion{}
26229 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26230 @var{cli-command} is any existing @value{GDBN} CLI command.
26232 @item @var{mi-command} @expansion{}
26233 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26234 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26236 @item @var{token} @expansion{}
26237 "any sequence of digits"
26239 @item @var{option} @expansion{}
26240 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26242 @item @var{parameter} @expansion{}
26243 @code{@var{non-blank-sequence} | @var{c-string}}
26245 @item @var{operation} @expansion{}
26246 @emph{any of the operations described in this chapter}
26248 @item @var{non-blank-sequence} @expansion{}
26249 @emph{anything, provided it doesn't contain special characters such as
26250 "-", @var{nl}, """ and of course " "}
26252 @item @var{c-string} @expansion{}
26253 @code{""" @var{seven-bit-iso-c-string-content} """}
26255 @item @var{nl} @expansion{}
26264 The CLI commands are still handled by the @sc{mi} interpreter; their
26265 output is described below.
26268 The @code{@var{token}}, when present, is passed back when the command
26272 Some @sc{mi} commands accept optional arguments as part of the parameter
26273 list. Each option is identified by a leading @samp{-} (dash) and may be
26274 followed by an optional argument parameter. Options occur first in the
26275 parameter list and can be delimited from normal parameters using
26276 @samp{--} (this is useful when some parameters begin with a dash).
26283 We want easy access to the existing CLI syntax (for debugging).
26286 We want it to be easy to spot a @sc{mi} operation.
26289 @node GDB/MI Output Syntax
26290 @subsection @sc{gdb/mi} Output Syntax
26292 @cindex output syntax of @sc{gdb/mi}
26293 @cindex @sc{gdb/mi}, output syntax
26294 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26295 followed, optionally, by a single result record. This result record
26296 is for the most recent command. The sequence of output records is
26297 terminated by @samp{(gdb)}.
26299 If an input command was prefixed with a @code{@var{token}} then the
26300 corresponding output for that command will also be prefixed by that same
26304 @item @var{output} @expansion{}
26305 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26307 @item @var{result-record} @expansion{}
26308 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26310 @item @var{out-of-band-record} @expansion{}
26311 @code{@var{async-record} | @var{stream-record}}
26313 @item @var{async-record} @expansion{}
26314 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26316 @item @var{exec-async-output} @expansion{}
26317 @code{[ @var{token} ] "*" @var{async-output nl}}
26319 @item @var{status-async-output} @expansion{}
26320 @code{[ @var{token} ] "+" @var{async-output nl}}
26322 @item @var{notify-async-output} @expansion{}
26323 @code{[ @var{token} ] "=" @var{async-output nl}}
26325 @item @var{async-output} @expansion{}
26326 @code{@var{async-class} ( "," @var{result} )*}
26328 @item @var{result-class} @expansion{}
26329 @code{"done" | "running" | "connected" | "error" | "exit"}
26331 @item @var{async-class} @expansion{}
26332 @code{"stopped" | @var{others}} (where @var{others} will be added
26333 depending on the needs---this is still in development).
26335 @item @var{result} @expansion{}
26336 @code{ @var{variable} "=" @var{value}}
26338 @item @var{variable} @expansion{}
26339 @code{ @var{string} }
26341 @item @var{value} @expansion{}
26342 @code{ @var{const} | @var{tuple} | @var{list} }
26344 @item @var{const} @expansion{}
26345 @code{@var{c-string}}
26347 @item @var{tuple} @expansion{}
26348 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26350 @item @var{list} @expansion{}
26351 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26352 @var{result} ( "," @var{result} )* "]" }
26354 @item @var{stream-record} @expansion{}
26355 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26357 @item @var{console-stream-output} @expansion{}
26358 @code{"~" @var{c-string nl}}
26360 @item @var{target-stream-output} @expansion{}
26361 @code{"@@" @var{c-string nl}}
26363 @item @var{log-stream-output} @expansion{}
26364 @code{"&" @var{c-string nl}}
26366 @item @var{nl} @expansion{}
26369 @item @var{token} @expansion{}
26370 @emph{any sequence of digits}.
26378 All output sequences end in a single line containing a period.
26381 The @code{@var{token}} is from the corresponding request. Note that
26382 for all async output, while the token is allowed by the grammar and
26383 may be output by future versions of @value{GDBN} for select async
26384 output messages, it is generally omitted. Frontends should treat
26385 all async output as reporting general changes in the state of the
26386 target and there should be no need to associate async output to any
26390 @cindex status output in @sc{gdb/mi}
26391 @var{status-async-output} contains on-going status information about the
26392 progress of a slow operation. It can be discarded. All status output is
26393 prefixed by @samp{+}.
26396 @cindex async output in @sc{gdb/mi}
26397 @var{exec-async-output} contains asynchronous state change on the target
26398 (stopped, started, disappeared). All async output is prefixed by
26402 @cindex notify output in @sc{gdb/mi}
26403 @var{notify-async-output} contains supplementary information that the
26404 client should handle (e.g., a new breakpoint information). All notify
26405 output is prefixed by @samp{=}.
26408 @cindex console output in @sc{gdb/mi}
26409 @var{console-stream-output} is output that should be displayed as is in the
26410 console. It is the textual response to a CLI command. All the console
26411 output is prefixed by @samp{~}.
26414 @cindex target output in @sc{gdb/mi}
26415 @var{target-stream-output} is the output produced by the target program.
26416 All the target output is prefixed by @samp{@@}.
26419 @cindex log output in @sc{gdb/mi}
26420 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26421 instance messages that should be displayed as part of an error log. All
26422 the log output is prefixed by @samp{&}.
26425 @cindex list output in @sc{gdb/mi}
26426 New @sc{gdb/mi} commands should only output @var{lists} containing
26432 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26433 details about the various output records.
26435 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26436 @node GDB/MI Compatibility with CLI
26437 @section @sc{gdb/mi} Compatibility with CLI
26439 @cindex compatibility, @sc{gdb/mi} and CLI
26440 @cindex @sc{gdb/mi}, compatibility with CLI
26442 For the developers convenience CLI commands can be entered directly,
26443 but there may be some unexpected behaviour. For example, commands
26444 that query the user will behave as if the user replied yes, breakpoint
26445 command lists are not executed and some CLI commands, such as
26446 @code{if}, @code{when} and @code{define}, prompt for further input with
26447 @samp{>}, which is not valid MI output.
26449 This feature may be removed at some stage in the future and it is
26450 recommended that front ends use the @code{-interpreter-exec} command
26451 (@pxref{-interpreter-exec}).
26453 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26454 @node GDB/MI Development and Front Ends
26455 @section @sc{gdb/mi} Development and Front Ends
26456 @cindex @sc{gdb/mi} development
26458 The application which takes the MI output and presents the state of the
26459 program being debugged to the user is called a @dfn{front end}.
26461 Although @sc{gdb/mi} is still incomplete, it is currently being used
26462 by a variety of front ends to @value{GDBN}. This makes it difficult
26463 to introduce new functionality without breaking existing usage. This
26464 section tries to minimize the problems by describing how the protocol
26467 Some changes in MI need not break a carefully designed front end, and
26468 for these the MI version will remain unchanged. The following is a
26469 list of changes that may occur within one level, so front ends should
26470 parse MI output in a way that can handle them:
26474 New MI commands may be added.
26477 New fields may be added to the output of any MI command.
26480 The range of values for fields with specified values, e.g.,
26481 @code{in_scope} (@pxref{-var-update}) may be extended.
26483 @c The format of field's content e.g type prefix, may change so parse it
26484 @c at your own risk. Yes, in general?
26486 @c The order of fields may change? Shouldn't really matter but it might
26487 @c resolve inconsistencies.
26490 If the changes are likely to break front ends, the MI version level
26491 will be increased by one. This will allow the front end to parse the
26492 output according to the MI version. Apart from mi0, new versions of
26493 @value{GDBN} will not support old versions of MI and it will be the
26494 responsibility of the front end to work with the new one.
26496 @c Starting with mi3, add a new command -mi-version that prints the MI
26499 The best way to avoid unexpected changes in MI that might break your front
26500 end is to make your project known to @value{GDBN} developers and
26501 follow development on @email{gdb@@sourceware.org} and
26502 @email{gdb-patches@@sourceware.org}.
26503 @cindex mailing lists
26505 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26506 @node GDB/MI Output Records
26507 @section @sc{gdb/mi} Output Records
26510 * GDB/MI Result Records::
26511 * GDB/MI Stream Records::
26512 * GDB/MI Async Records::
26513 * GDB/MI Breakpoint Information::
26514 * GDB/MI Frame Information::
26515 * GDB/MI Thread Information::
26516 * GDB/MI Ada Exception Information::
26519 @node GDB/MI Result Records
26520 @subsection @sc{gdb/mi} Result Records
26522 @cindex result records in @sc{gdb/mi}
26523 @cindex @sc{gdb/mi}, result records
26524 In addition to a number of out-of-band notifications, the response to a
26525 @sc{gdb/mi} command includes one of the following result indications:
26529 @item "^done" [ "," @var{results} ]
26530 The synchronous operation was successful, @code{@var{results}} are the return
26535 This result record is equivalent to @samp{^done}. Historically, it
26536 was output instead of @samp{^done} if the command has resumed the
26537 target. This behaviour is maintained for backward compatibility, but
26538 all frontends should treat @samp{^done} and @samp{^running}
26539 identically and rely on the @samp{*running} output record to determine
26540 which threads are resumed.
26544 @value{GDBN} has connected to a remote target.
26546 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26548 The operation failed. The @code{msg=@var{c-string}} variable contains
26549 the corresponding error message.
26551 If present, the @code{code=@var{c-string}} variable provides an error
26552 code on which consumers can rely on to detect the corresponding
26553 error condition. At present, only one error code is defined:
26556 @item "undefined-command"
26557 Indicates that the command causing the error does not exist.
26562 @value{GDBN} has terminated.
26566 @node GDB/MI Stream Records
26567 @subsection @sc{gdb/mi} Stream Records
26569 @cindex @sc{gdb/mi}, stream records
26570 @cindex stream records in @sc{gdb/mi}
26571 @value{GDBN} internally maintains a number of output streams: the console, the
26572 target, and the log. The output intended for each of these streams is
26573 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26575 Each stream record begins with a unique @dfn{prefix character} which
26576 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26577 Syntax}). In addition to the prefix, each stream record contains a
26578 @code{@var{string-output}}. This is either raw text (with an implicit new
26579 line) or a quoted C string (which does not contain an implicit newline).
26582 @item "~" @var{string-output}
26583 The console output stream contains text that should be displayed in the
26584 CLI console window. It contains the textual responses to CLI commands.
26586 @item "@@" @var{string-output}
26587 The target output stream contains any textual output from the running
26588 target. This is only present when GDB's event loop is truly
26589 asynchronous, which is currently only the case for remote targets.
26591 @item "&" @var{string-output}
26592 The log stream contains debugging messages being produced by @value{GDBN}'s
26596 @node GDB/MI Async Records
26597 @subsection @sc{gdb/mi} Async Records
26599 @cindex async records in @sc{gdb/mi}
26600 @cindex @sc{gdb/mi}, async records
26601 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26602 additional changes that have occurred. Those changes can either be a
26603 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26604 target activity (e.g., target stopped).
26606 The following is the list of possible async records:
26610 @item *running,thread-id="@var{thread}"
26611 The target is now running. The @var{thread} field can be the global
26612 thread ID of the the thread that is now running, and it can be
26613 @samp{all} if all threads are running. The frontend should assume
26614 that no interaction with a running thread is possible after this
26615 notification is produced. The frontend should not assume that this
26616 notification is output only once for any command. @value{GDBN} may
26617 emit this notification several times, either for different threads,
26618 because it cannot resume all threads together, or even for a single
26619 thread, if the thread must be stepped though some code before letting
26622 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26623 The target has stopped. The @var{reason} field can have one of the
26627 @item breakpoint-hit
26628 A breakpoint was reached.
26629 @item watchpoint-trigger
26630 A watchpoint was triggered.
26631 @item read-watchpoint-trigger
26632 A read watchpoint was triggered.
26633 @item access-watchpoint-trigger
26634 An access watchpoint was triggered.
26635 @item function-finished
26636 An -exec-finish or similar CLI command was accomplished.
26637 @item location-reached
26638 An -exec-until or similar CLI command was accomplished.
26639 @item watchpoint-scope
26640 A watchpoint has gone out of scope.
26641 @item end-stepping-range
26642 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26643 similar CLI command was accomplished.
26644 @item exited-signalled
26645 The inferior exited because of a signal.
26647 The inferior exited.
26648 @item exited-normally
26649 The inferior exited normally.
26650 @item signal-received
26651 A signal was received by the inferior.
26653 The inferior has stopped due to a library being loaded or unloaded.
26654 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26655 set or when a @code{catch load} or @code{catch unload} catchpoint is
26656 in use (@pxref{Set Catchpoints}).
26658 The inferior has forked. This is reported when @code{catch fork}
26659 (@pxref{Set Catchpoints}) has been used.
26661 The inferior has vforked. This is reported in when @code{catch vfork}
26662 (@pxref{Set Catchpoints}) has been used.
26663 @item syscall-entry
26664 The inferior entered a system call. This is reported when @code{catch
26665 syscall} (@pxref{Set Catchpoints}) has been used.
26666 @item syscall-return
26667 The inferior returned from a system call. This is reported when
26668 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26670 The inferior called @code{exec}. This is reported when @code{catch exec}
26671 (@pxref{Set Catchpoints}) has been used.
26674 The @var{id} field identifies the global thread ID of the thread
26675 that directly caused the stop -- for example by hitting a breakpoint.
26676 Depending on whether all-stop
26677 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26678 stop all threads, or only the thread that directly triggered the stop.
26679 If all threads are stopped, the @var{stopped} field will have the
26680 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26681 field will be a list of thread identifiers. Presently, this list will
26682 always include a single thread, but frontend should be prepared to see
26683 several threads in the list. The @var{core} field reports the
26684 processor core on which the stop event has happened. This field may be absent
26685 if such information is not available.
26687 @item =thread-group-added,id="@var{id}"
26688 @itemx =thread-group-removed,id="@var{id}"
26689 A thread group was either added or removed. The @var{id} field
26690 contains the @value{GDBN} identifier of the thread group. When a thread
26691 group is added, it generally might not be associated with a running
26692 process. When a thread group is removed, its id becomes invalid and
26693 cannot be used in any way.
26695 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26696 A thread group became associated with a running program,
26697 either because the program was just started or the thread group
26698 was attached to a program. The @var{id} field contains the
26699 @value{GDBN} identifier of the thread group. The @var{pid} field
26700 contains process identifier, specific to the operating system.
26702 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26703 A thread group is no longer associated with a running program,
26704 either because the program has exited, or because it was detached
26705 from. The @var{id} field contains the @value{GDBN} identifier of the
26706 thread group. The @var{code} field is the exit code of the inferior; it exists
26707 only when the inferior exited with some code.
26709 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26710 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26711 A thread either was created, or has exited. The @var{id} field
26712 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26713 field identifies the thread group this thread belongs to.
26715 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26716 Informs that the selected thread or frame were changed. This notification
26717 is not emitted as result of the @code{-thread-select} or
26718 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26719 that is not documented to change the selected thread and frame actually
26720 changes them. In particular, invoking, directly or indirectly
26721 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26722 will generate this notification. Changing the thread or frame from another
26723 user interface (see @ref{Interpreters}) will also generate this notification.
26725 The @var{frame} field is only present if the newly selected thread is
26726 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
26728 We suggest that in response to this notification, front ends
26729 highlight the selected thread and cause subsequent commands to apply to
26732 @item =library-loaded,...
26733 Reports that a new library file was loaded by the program. This
26734 notification has 5 fields---@var{id}, @var{target-name},
26735 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
26736 opaque identifier of the library. For remote debugging case,
26737 @var{target-name} and @var{host-name} fields give the name of the
26738 library file on the target, and on the host respectively. For native
26739 debugging, both those fields have the same value. The
26740 @var{symbols-loaded} field is emitted only for backward compatibility
26741 and should not be relied on to convey any useful information. The
26742 @var{thread-group} field, if present, specifies the id of the thread
26743 group in whose context the library was loaded. If the field is
26744 absent, it means the library was loaded in the context of all present
26745 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
26748 @item =library-unloaded,...
26749 Reports that a library was unloaded by the program. This notification
26750 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26751 the same meaning as for the @code{=library-loaded} notification.
26752 The @var{thread-group} field, if present, specifies the id of the
26753 thread group in whose context the library was unloaded. If the field is
26754 absent, it means the library was unloaded in the context of all present
26757 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26758 @itemx =traceframe-changed,end
26759 Reports that the trace frame was changed and its new number is
26760 @var{tfnum}. The number of the tracepoint associated with this trace
26761 frame is @var{tpnum}.
26763 @item =tsv-created,name=@var{name},initial=@var{initial}
26764 Reports that the new trace state variable @var{name} is created with
26765 initial value @var{initial}.
26767 @item =tsv-deleted,name=@var{name}
26768 @itemx =tsv-deleted
26769 Reports that the trace state variable @var{name} is deleted or all
26770 trace state variables are deleted.
26772 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26773 Reports that the trace state variable @var{name} is modified with
26774 the initial value @var{initial}. The current value @var{current} of
26775 trace state variable is optional and is reported if the current
26776 value of trace state variable is known.
26778 @item =breakpoint-created,bkpt=@{...@}
26779 @itemx =breakpoint-modified,bkpt=@{...@}
26780 @itemx =breakpoint-deleted,id=@var{number}
26781 Reports that a breakpoint was created, modified, or deleted,
26782 respectively. Only user-visible breakpoints are reported to the MI
26785 The @var{bkpt} argument is of the same form as returned by the various
26786 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26787 @var{number} is the ordinal number of the breakpoint.
26789 Note that if a breakpoint is emitted in the result record of a
26790 command, then it will not also be emitted in an async record.
26792 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26793 @itemx =record-stopped,thread-group="@var{id}"
26794 Execution log recording was either started or stopped on an
26795 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26796 group corresponding to the affected inferior.
26798 The @var{method} field indicates the method used to record execution. If the
26799 method in use supports multiple recording formats, @var{format} will be present
26800 and contain the currently used format. @xref{Process Record and Replay},
26801 for existing method and format values.
26803 @item =cmd-param-changed,param=@var{param},value=@var{value}
26804 Reports that a parameter of the command @code{set @var{param}} is
26805 changed to @var{value}. In the multi-word @code{set} command,
26806 the @var{param} is the whole parameter list to @code{set} command.
26807 For example, In command @code{set check type on}, @var{param}
26808 is @code{check type} and @var{value} is @code{on}.
26810 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26811 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26812 written in an inferior. The @var{id} is the identifier of the
26813 thread group corresponding to the affected inferior. The optional
26814 @code{type="code"} part is reported if the memory written to holds
26818 @node GDB/MI Breakpoint Information
26819 @subsection @sc{gdb/mi} Breakpoint Information
26821 When @value{GDBN} reports information about a breakpoint, a
26822 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26827 The breakpoint number. For a breakpoint that represents one location
26828 of a multi-location breakpoint, this will be a dotted pair, like
26832 The type of the breakpoint. For ordinary breakpoints this will be
26833 @samp{breakpoint}, but many values are possible.
26836 If the type of the breakpoint is @samp{catchpoint}, then this
26837 indicates the exact type of catchpoint.
26840 This is the breakpoint disposition---either @samp{del}, meaning that
26841 the breakpoint will be deleted at the next stop, or @samp{keep},
26842 meaning that the breakpoint will not be deleted.
26845 This indicates whether the breakpoint is enabled, in which case the
26846 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26847 Note that this is not the same as the field @code{enable}.
26850 The address of the breakpoint. This may be a hexidecimal number,
26851 giving the address; or the string @samp{<PENDING>}, for a pending
26852 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26853 multiple locations. This field will not be present if no address can
26854 be determined. For example, a watchpoint does not have an address.
26857 If known, the function in which the breakpoint appears.
26858 If not known, this field is not present.
26861 The name of the source file which contains this function, if known.
26862 If not known, this field is not present.
26865 The full file name of the source file which contains this function, if
26866 known. If not known, this field is not present.
26869 The line number at which this breakpoint appears, if known.
26870 If not known, this field is not present.
26873 If the source file is not known, this field may be provided. If
26874 provided, this holds the address of the breakpoint, possibly followed
26878 If this breakpoint is pending, this field is present and holds the
26879 text used to set the breakpoint, as entered by the user.
26882 Where this breakpoint's condition is evaluated, either @samp{host} or
26886 If this is a thread-specific breakpoint, then this identifies the
26887 thread in which the breakpoint can trigger.
26890 If this breakpoint is restricted to a particular Ada task, then this
26891 field will hold the task identifier.
26894 If the breakpoint is conditional, this is the condition expression.
26897 The ignore count of the breakpoint.
26900 The enable count of the breakpoint.
26902 @item traceframe-usage
26905 @item static-tracepoint-marker-string-id
26906 For a static tracepoint, the name of the static tracepoint marker.
26909 For a masked watchpoint, this is the mask.
26912 A tracepoint's pass count.
26914 @item original-location
26915 The location of the breakpoint as originally specified by the user.
26916 This field is optional.
26919 The number of times the breakpoint has been hit.
26922 This field is only given for tracepoints. This is either @samp{y},
26923 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26927 Some extra data, the exact contents of which are type-dependent.
26931 For example, here is what the output of @code{-break-insert}
26932 (@pxref{GDB/MI Breakpoint Commands}) might be:
26935 -> -break-insert main
26936 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26937 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26938 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26943 @node GDB/MI Frame Information
26944 @subsection @sc{gdb/mi} Frame Information
26946 Response from many MI commands includes an information about stack
26947 frame. This information is a tuple that may have the following
26952 The level of the stack frame. The innermost frame has the level of
26953 zero. This field is always present.
26956 The name of the function corresponding to the frame. This field may
26957 be absent if @value{GDBN} is unable to determine the function name.
26960 The code address for the frame. This field is always present.
26963 The name of the source files that correspond to the frame's code
26964 address. This field may be absent.
26967 The source line corresponding to the frames' code address. This field
26971 The name of the binary file (either executable or shared library) the
26972 corresponds to the frame's code address. This field may be absent.
26976 @node GDB/MI Thread Information
26977 @subsection @sc{gdb/mi} Thread Information
26979 Whenever @value{GDBN} has to report an information about a thread, it
26980 uses a tuple with the following fields. The fields are always present unless
26985 The global numeric id assigned to the thread by @value{GDBN}.
26988 The target-specific string identifying the thread.
26991 Additional information about the thread provided by the target.
26992 It is supposed to be human-readable and not interpreted by the
26993 frontend. This field is optional.
26996 The name of the thread. If the user specified a name using the
26997 @code{thread name} command, then this name is given. Otherwise, if
26998 @value{GDBN} can extract the thread name from the target, then that
26999 name is given. If @value{GDBN} cannot find the thread name, then this
27003 The execution state of the thread, either @samp{stopped} or @samp{running},
27004 depending on whether the thread is presently running.
27007 The stack frame currently executing in the thread. This field is only present
27008 if the thread is stopped. Its format is documented in
27009 @ref{GDB/MI Frame Information}.
27012 The value of this field is an integer number of the processor core the
27013 thread was last seen on. This field is optional.
27016 @node GDB/MI Ada Exception Information
27017 @subsection @sc{gdb/mi} Ada Exception Information
27019 Whenever a @code{*stopped} record is emitted because the program
27020 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27021 @value{GDBN} provides the name of the exception that was raised via
27022 the @code{exception-name} field.
27024 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27025 @node GDB/MI Simple Examples
27026 @section Simple Examples of @sc{gdb/mi} Interaction
27027 @cindex @sc{gdb/mi}, simple examples
27029 This subsection presents several simple examples of interaction using
27030 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27031 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27032 the output received from @sc{gdb/mi}.
27034 Note the line breaks shown in the examples are here only for
27035 readability, they don't appear in the real output.
27037 @subheading Setting a Breakpoint
27039 Setting a breakpoint generates synchronous output which contains detailed
27040 information of the breakpoint.
27043 -> -break-insert main
27044 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27045 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27046 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27051 @subheading Program Execution
27053 Program execution generates asynchronous records and MI gives the
27054 reason that execution stopped.
27060 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27061 frame=@{addr="0x08048564",func="main",
27062 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27063 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27068 <- *stopped,reason="exited-normally"
27072 @subheading Quitting @value{GDBN}
27074 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27082 Please note that @samp{^exit} is printed immediately, but it might
27083 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27084 performs necessary cleanups, including killing programs being debugged
27085 or disconnecting from debug hardware, so the frontend should wait till
27086 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27087 fails to exit in reasonable time.
27089 @subheading A Bad Command
27091 Here's what happens if you pass a non-existent command:
27095 <- ^error,msg="Undefined MI command: rubbish"
27100 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27101 @node GDB/MI Command Description Format
27102 @section @sc{gdb/mi} Command Description Format
27104 The remaining sections describe blocks of commands. Each block of
27105 commands is laid out in a fashion similar to this section.
27107 @subheading Motivation
27109 The motivation for this collection of commands.
27111 @subheading Introduction
27113 A brief introduction to this collection of commands as a whole.
27115 @subheading Commands
27117 For each command in the block, the following is described:
27119 @subsubheading Synopsis
27122 -command @var{args}@dots{}
27125 @subsubheading Result
27127 @subsubheading @value{GDBN} Command
27129 The corresponding @value{GDBN} CLI command(s), if any.
27131 @subsubheading Example
27133 Example(s) formatted for readability. Some of the described commands have
27134 not been implemented yet and these are labeled N.A.@: (not available).
27137 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27138 @node GDB/MI Breakpoint Commands
27139 @section @sc{gdb/mi} Breakpoint Commands
27141 @cindex breakpoint commands for @sc{gdb/mi}
27142 @cindex @sc{gdb/mi}, breakpoint commands
27143 This section documents @sc{gdb/mi} commands for manipulating
27146 @subheading The @code{-break-after} Command
27147 @findex -break-after
27149 @subsubheading Synopsis
27152 -break-after @var{number} @var{count}
27155 The breakpoint number @var{number} is not in effect until it has been
27156 hit @var{count} times. To see how this is reflected in the output of
27157 the @samp{-break-list} command, see the description of the
27158 @samp{-break-list} command below.
27160 @subsubheading @value{GDBN} Command
27162 The corresponding @value{GDBN} command is @samp{ignore}.
27164 @subsubheading Example
27169 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27170 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27171 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27179 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27180 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27181 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27182 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27183 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27184 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27185 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27186 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27187 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27188 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27193 @subheading The @code{-break-catch} Command
27194 @findex -break-catch
27197 @subheading The @code{-break-commands} Command
27198 @findex -break-commands
27200 @subsubheading Synopsis
27203 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27206 Specifies the CLI commands that should be executed when breakpoint
27207 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27208 are the commands. If no command is specified, any previously-set
27209 commands are cleared. @xref{Break Commands}. Typical use of this
27210 functionality is tracing a program, that is, printing of values of
27211 some variables whenever breakpoint is hit and then continuing.
27213 @subsubheading @value{GDBN} Command
27215 The corresponding @value{GDBN} command is @samp{commands}.
27217 @subsubheading Example
27222 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27223 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27224 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27227 -break-commands 1 "print v" "continue"
27232 @subheading The @code{-break-condition} Command
27233 @findex -break-condition
27235 @subsubheading Synopsis
27238 -break-condition @var{number} @var{expr}
27241 Breakpoint @var{number} will stop the program only if the condition in
27242 @var{expr} is true. The condition becomes part of the
27243 @samp{-break-list} output (see the description of the @samp{-break-list}
27246 @subsubheading @value{GDBN} Command
27248 The corresponding @value{GDBN} command is @samp{condition}.
27250 @subsubheading Example
27254 -break-condition 1 1
27258 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27259 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27260 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27261 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27262 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27263 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27264 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27265 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27266 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27267 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27271 @subheading The @code{-break-delete} Command
27272 @findex -break-delete
27274 @subsubheading Synopsis
27277 -break-delete ( @var{breakpoint} )+
27280 Delete the breakpoint(s) whose number(s) are specified in the argument
27281 list. This is obviously reflected in the breakpoint list.
27283 @subsubheading @value{GDBN} Command
27285 The corresponding @value{GDBN} command is @samp{delete}.
27287 @subsubheading Example
27295 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27296 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27297 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27298 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27299 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27300 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27301 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27306 @subheading The @code{-break-disable} Command
27307 @findex -break-disable
27309 @subsubheading Synopsis
27312 -break-disable ( @var{breakpoint} )+
27315 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27316 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27318 @subsubheading @value{GDBN} Command
27320 The corresponding @value{GDBN} command is @samp{disable}.
27322 @subsubheading Example
27330 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27331 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27332 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27333 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27334 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27335 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27336 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27337 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27338 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27339 line="5",thread-groups=["i1"],times="0"@}]@}
27343 @subheading The @code{-break-enable} Command
27344 @findex -break-enable
27346 @subsubheading Synopsis
27349 -break-enable ( @var{breakpoint} )+
27352 Enable (previously disabled) @var{breakpoint}(s).
27354 @subsubheading @value{GDBN} Command
27356 The corresponding @value{GDBN} command is @samp{enable}.
27358 @subsubheading Example
27366 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27367 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27368 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27369 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27370 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27371 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27372 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27373 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27374 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27375 line="5",thread-groups=["i1"],times="0"@}]@}
27379 @subheading The @code{-break-info} Command
27380 @findex -break-info
27382 @subsubheading Synopsis
27385 -break-info @var{breakpoint}
27389 Get information about a single breakpoint.
27391 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27392 Information}, for details on the format of each breakpoint in the
27395 @subsubheading @value{GDBN} Command
27397 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27399 @subsubheading Example
27402 @subheading The @code{-break-insert} Command
27403 @findex -break-insert
27404 @anchor{-break-insert}
27406 @subsubheading Synopsis
27409 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27410 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27411 [ -p @var{thread-id} ] [ @var{location} ]
27415 If specified, @var{location}, can be one of:
27418 @item linespec location
27419 A linespec location. @xref{Linespec Locations}.
27421 @item explicit location
27422 An explicit location. @sc{gdb/mi} explicit locations are
27423 analogous to the CLI's explicit locations using the option names
27424 listed below. @xref{Explicit Locations}.
27427 @item --source @var{filename}
27428 The source file name of the location. This option requires the use
27429 of either @samp{--function} or @samp{--line}.
27431 @item --function @var{function}
27432 The name of a function or method.
27434 @item --label @var{label}
27435 The name of a label.
27437 @item --line @var{lineoffset}
27438 An absolute or relative line offset from the start of the location.
27441 @item address location
27442 An address location, *@var{address}. @xref{Address Locations}.
27446 The possible optional parameters of this command are:
27450 Insert a temporary breakpoint.
27452 Insert a hardware breakpoint.
27454 If @var{location} cannot be parsed (for example if it
27455 refers to unknown files or functions), create a pending
27456 breakpoint. Without this flag, @value{GDBN} will report
27457 an error, and won't create a breakpoint, if @var{location}
27460 Create a disabled breakpoint.
27462 Create a tracepoint. @xref{Tracepoints}. When this parameter
27463 is used together with @samp{-h}, a fast tracepoint is created.
27464 @item -c @var{condition}
27465 Make the breakpoint conditional on @var{condition}.
27466 @item -i @var{ignore-count}
27467 Initialize the @var{ignore-count}.
27468 @item -p @var{thread-id}
27469 Restrict the breakpoint to the thread with the specified global
27473 @subsubheading Result
27475 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27476 resulting breakpoint.
27478 Note: this format is open to change.
27479 @c An out-of-band breakpoint instead of part of the result?
27481 @subsubheading @value{GDBN} Command
27483 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27484 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27486 @subsubheading Example
27491 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27492 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27495 -break-insert -t foo
27496 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27497 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27501 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27502 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27503 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27504 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27505 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27506 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27507 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27508 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27509 addr="0x0001072c", func="main",file="recursive2.c",
27510 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27512 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27513 addr="0x00010774",func="foo",file="recursive2.c",
27514 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27517 @c -break-insert -r foo.*
27518 @c ~int foo(int, int);
27519 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27520 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27525 @subheading The @code{-dprintf-insert} Command
27526 @findex -dprintf-insert
27528 @subsubheading Synopsis
27531 -dprintf-insert [ -t ] [ -f ] [ -d ]
27532 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27533 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27538 If supplied, @var{location} may be specified the same way as for
27539 the @code{-break-insert} command. @xref{-break-insert}.
27541 The possible optional parameters of this command are:
27545 Insert a temporary breakpoint.
27547 If @var{location} cannot be parsed (for example, if it
27548 refers to unknown files or functions), create a pending
27549 breakpoint. Without this flag, @value{GDBN} will report
27550 an error, and won't create a breakpoint, if @var{location}
27553 Create a disabled breakpoint.
27554 @item -c @var{condition}
27555 Make the breakpoint conditional on @var{condition}.
27556 @item -i @var{ignore-count}
27557 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27558 to @var{ignore-count}.
27559 @item -p @var{thread-id}
27560 Restrict the breakpoint to the thread with the specified global
27564 @subsubheading Result
27566 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27567 resulting breakpoint.
27569 @c An out-of-band breakpoint instead of part of the result?
27571 @subsubheading @value{GDBN} Command
27573 The corresponding @value{GDBN} command is @samp{dprintf}.
27575 @subsubheading Example
27579 4-dprintf-insert foo "At foo entry\n"
27580 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27581 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27582 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27583 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27584 original-location="foo"@}
27586 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27587 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27588 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27589 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27590 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27591 original-location="mi-dprintf.c:26"@}
27595 @subheading The @code{-break-list} Command
27596 @findex -break-list
27598 @subsubheading Synopsis
27604 Displays the list of inserted breakpoints, showing the following fields:
27608 number of the breakpoint
27610 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27612 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27615 is the breakpoint enabled or no: @samp{y} or @samp{n}
27617 memory location at which the breakpoint is set
27619 logical location of the breakpoint, expressed by function name, file
27621 @item Thread-groups
27622 list of thread groups to which this breakpoint applies
27624 number of times the breakpoint has been hit
27627 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27628 @code{body} field is an empty list.
27630 @subsubheading @value{GDBN} Command
27632 The corresponding @value{GDBN} command is @samp{info break}.
27634 @subsubheading Example
27639 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27640 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27641 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27642 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27643 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27644 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27645 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27646 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27647 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27649 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27650 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27651 line="13",thread-groups=["i1"],times="0"@}]@}
27655 Here's an example of the result when there are no breakpoints:
27660 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27661 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27662 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27663 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27664 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27665 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27666 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27671 @subheading The @code{-break-passcount} Command
27672 @findex -break-passcount
27674 @subsubheading Synopsis
27677 -break-passcount @var{tracepoint-number} @var{passcount}
27680 Set the passcount for tracepoint @var{tracepoint-number} to
27681 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27682 is not a tracepoint, error is emitted. This corresponds to CLI
27683 command @samp{passcount}.
27685 @subheading The @code{-break-watch} Command
27686 @findex -break-watch
27688 @subsubheading Synopsis
27691 -break-watch [ -a | -r ]
27694 Create a watchpoint. With the @samp{-a} option it will create an
27695 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27696 read from or on a write to the memory location. With the @samp{-r}
27697 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27698 trigger only when the memory location is accessed for reading. Without
27699 either of the options, the watchpoint created is a regular watchpoint,
27700 i.e., it will trigger when the memory location is accessed for writing.
27701 @xref{Set Watchpoints, , Setting Watchpoints}.
27703 Note that @samp{-break-list} will report a single list of watchpoints and
27704 breakpoints inserted.
27706 @subsubheading @value{GDBN} Command
27708 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27711 @subsubheading Example
27713 Setting a watchpoint on a variable in the @code{main} function:
27718 ^done,wpt=@{number="2",exp="x"@}
27723 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27724 value=@{old="-268439212",new="55"@},
27725 frame=@{func="main",args=[],file="recursive2.c",
27726 fullname="/home/foo/bar/recursive2.c",line="5"@}
27730 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27731 the program execution twice: first for the variable changing value, then
27732 for the watchpoint going out of scope.
27737 ^done,wpt=@{number="5",exp="C"@}
27742 *stopped,reason="watchpoint-trigger",
27743 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27744 frame=@{func="callee4",args=[],
27745 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27746 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27751 *stopped,reason="watchpoint-scope",wpnum="5",
27752 frame=@{func="callee3",args=[@{name="strarg",
27753 value="0x11940 \"A string argument.\""@}],
27754 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27755 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27759 Listing breakpoints and watchpoints, at different points in the program
27760 execution. Note that once the watchpoint goes out of scope, it is
27766 ^done,wpt=@{number="2",exp="C"@}
27769 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27770 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27771 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27772 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27773 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27774 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27775 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27776 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27777 addr="0x00010734",func="callee4",
27778 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27779 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27781 bkpt=@{number="2",type="watchpoint",disp="keep",
27782 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27787 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27788 value=@{old="-276895068",new="3"@},
27789 frame=@{func="callee4",args=[],
27790 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27791 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27794 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27795 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27796 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27797 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27798 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27799 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27800 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27801 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27802 addr="0x00010734",func="callee4",
27803 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27804 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27806 bkpt=@{number="2",type="watchpoint",disp="keep",
27807 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27811 ^done,reason="watchpoint-scope",wpnum="2",
27812 frame=@{func="callee3",args=[@{name="strarg",
27813 value="0x11940 \"A string argument.\""@}],
27814 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27815 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27818 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27819 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27820 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27821 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27822 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27823 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27824 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27825 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27826 addr="0x00010734",func="callee4",
27827 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27828 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27829 thread-groups=["i1"],times="1"@}]@}
27834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27835 @node GDB/MI Catchpoint Commands
27836 @section @sc{gdb/mi} Catchpoint Commands
27838 This section documents @sc{gdb/mi} commands for manipulating
27842 * Shared Library GDB/MI Catchpoint Commands::
27843 * Ada Exception GDB/MI Catchpoint Commands::
27846 @node Shared Library GDB/MI Catchpoint Commands
27847 @subsection Shared Library @sc{gdb/mi} Catchpoints
27849 @subheading The @code{-catch-load} Command
27850 @findex -catch-load
27852 @subsubheading Synopsis
27855 -catch-load [ -t ] [ -d ] @var{regexp}
27858 Add a catchpoint for library load events. If the @samp{-t} option is used,
27859 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27860 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27861 in a disabled state. The @samp{regexp} argument is a regular
27862 expression used to match the name of the loaded library.
27865 @subsubheading @value{GDBN} Command
27867 The corresponding @value{GDBN} command is @samp{catch load}.
27869 @subsubheading Example
27872 -catch-load -t foo.so
27873 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27874 what="load of library matching foo.so",catch-type="load",times="0"@}
27879 @subheading The @code{-catch-unload} Command
27880 @findex -catch-unload
27882 @subsubheading Synopsis
27885 -catch-unload [ -t ] [ -d ] @var{regexp}
27888 Add a catchpoint for library unload events. If the @samp{-t} option is
27889 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27890 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27891 created in a disabled state. The @samp{regexp} argument is a regular
27892 expression used to match the name of the unloaded library.
27894 @subsubheading @value{GDBN} Command
27896 The corresponding @value{GDBN} command is @samp{catch unload}.
27898 @subsubheading Example
27901 -catch-unload -d bar.so
27902 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27903 what="load of library matching bar.so",catch-type="unload",times="0"@}
27907 @node Ada Exception GDB/MI Catchpoint Commands
27908 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27910 The following @sc{gdb/mi} commands can be used to create catchpoints
27911 that stop the execution when Ada exceptions are being raised.
27913 @subheading The @code{-catch-assert} Command
27914 @findex -catch-assert
27916 @subsubheading Synopsis
27919 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27922 Add a catchpoint for failed Ada assertions.
27924 The possible optional parameters for this command are:
27927 @item -c @var{condition}
27928 Make the catchpoint conditional on @var{condition}.
27930 Create a disabled catchpoint.
27932 Create a temporary catchpoint.
27935 @subsubheading @value{GDBN} Command
27937 The corresponding @value{GDBN} command is @samp{catch assert}.
27939 @subsubheading Example
27943 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27944 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27945 thread-groups=["i1"],times="0",
27946 original-location="__gnat_debug_raise_assert_failure"@}
27950 @subheading The @code{-catch-exception} Command
27951 @findex -catch-exception
27953 @subsubheading Synopsis
27956 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27960 Add a catchpoint stopping when Ada exceptions are raised.
27961 By default, the command stops the program when any Ada exception
27962 gets raised. But it is also possible, by using some of the
27963 optional parameters described below, to create more selective
27966 The possible optional parameters for this command are:
27969 @item -c @var{condition}
27970 Make the catchpoint conditional on @var{condition}.
27972 Create a disabled catchpoint.
27973 @item -e @var{exception-name}
27974 Only stop when @var{exception-name} is raised. This option cannot
27975 be used combined with @samp{-u}.
27977 Create a temporary catchpoint.
27979 Stop only when an unhandled exception gets raised. This option
27980 cannot be used combined with @samp{-e}.
27983 @subsubheading @value{GDBN} Command
27985 The corresponding @value{GDBN} commands are @samp{catch exception}
27986 and @samp{catch exception unhandled}.
27988 @subsubheading Example
27991 -catch-exception -e Program_Error
27992 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27993 enabled="y",addr="0x0000000000404874",
27994 what="`Program_Error' Ada exception", thread-groups=["i1"],
27995 times="0",original-location="__gnat_debug_raise_exception"@}
27999 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28000 @node GDB/MI Program Context
28001 @section @sc{gdb/mi} Program Context
28003 @subheading The @code{-exec-arguments} Command
28004 @findex -exec-arguments
28007 @subsubheading Synopsis
28010 -exec-arguments @var{args}
28013 Set the inferior program arguments, to be used in the next
28016 @subsubheading @value{GDBN} Command
28018 The corresponding @value{GDBN} command is @samp{set args}.
28020 @subsubheading Example
28024 -exec-arguments -v word
28031 @subheading The @code{-exec-show-arguments} Command
28032 @findex -exec-show-arguments
28034 @subsubheading Synopsis
28037 -exec-show-arguments
28040 Print the arguments of the program.
28042 @subsubheading @value{GDBN} Command
28044 The corresponding @value{GDBN} command is @samp{show args}.
28046 @subsubheading Example
28051 @subheading The @code{-environment-cd} Command
28052 @findex -environment-cd
28054 @subsubheading Synopsis
28057 -environment-cd @var{pathdir}
28060 Set @value{GDBN}'s working directory.
28062 @subsubheading @value{GDBN} Command
28064 The corresponding @value{GDBN} command is @samp{cd}.
28066 @subsubheading Example
28070 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28076 @subheading The @code{-environment-directory} Command
28077 @findex -environment-directory
28079 @subsubheading Synopsis
28082 -environment-directory [ -r ] [ @var{pathdir} ]+
28085 Add directories @var{pathdir} to beginning of search path for source files.
28086 If the @samp{-r} option is used, the search path is reset to the default
28087 search path. If directories @var{pathdir} are supplied in addition to the
28088 @samp{-r} option, the search path is first reset and then addition
28090 Multiple directories may be specified, separated by blanks. Specifying
28091 multiple directories in a single command
28092 results in the directories added to the beginning of the
28093 search path in the same order they were presented in the command.
28094 If blanks are needed as
28095 part of a directory name, double-quotes should be used around
28096 the name. In the command output, the path will show up separated
28097 by the system directory-separator character. The directory-separator
28098 character must not be used
28099 in any directory name.
28100 If no directories are specified, the current search path is displayed.
28102 @subsubheading @value{GDBN} Command
28104 The corresponding @value{GDBN} command is @samp{dir}.
28106 @subsubheading Example
28110 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28111 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28113 -environment-directory ""
28114 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28116 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28117 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28119 -environment-directory -r
28120 ^done,source-path="$cdir:$cwd"
28125 @subheading The @code{-environment-path} Command
28126 @findex -environment-path
28128 @subsubheading Synopsis
28131 -environment-path [ -r ] [ @var{pathdir} ]+
28134 Add directories @var{pathdir} to beginning of search path for object files.
28135 If the @samp{-r} option is used, the search path is reset to the original
28136 search path that existed at gdb start-up. If directories @var{pathdir} are
28137 supplied in addition to the
28138 @samp{-r} option, the search path is first reset and then addition
28140 Multiple directories may be specified, separated by blanks. Specifying
28141 multiple directories in a single command
28142 results in the directories added to the beginning of the
28143 search path in the same order they were presented in the command.
28144 If blanks are needed as
28145 part of a directory name, double-quotes should be used around
28146 the name. In the command output, the path will show up separated
28147 by the system directory-separator character. The directory-separator
28148 character must not be used
28149 in any directory name.
28150 If no directories are specified, the current path is displayed.
28153 @subsubheading @value{GDBN} Command
28155 The corresponding @value{GDBN} command is @samp{path}.
28157 @subsubheading Example
28162 ^done,path="/usr/bin"
28164 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28165 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28167 -environment-path -r /usr/local/bin
28168 ^done,path="/usr/local/bin:/usr/bin"
28173 @subheading The @code{-environment-pwd} Command
28174 @findex -environment-pwd
28176 @subsubheading Synopsis
28182 Show the current working directory.
28184 @subsubheading @value{GDBN} Command
28186 The corresponding @value{GDBN} command is @samp{pwd}.
28188 @subsubheading Example
28193 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28197 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28198 @node GDB/MI Thread Commands
28199 @section @sc{gdb/mi} Thread Commands
28202 @subheading The @code{-thread-info} Command
28203 @findex -thread-info
28205 @subsubheading Synopsis
28208 -thread-info [ @var{thread-id} ]
28211 Reports information about either a specific thread, if the
28212 @var{thread-id} parameter is present, or about all threads.
28213 @var{thread-id} is the thread's global thread ID. When printing
28214 information about all threads, also reports the global ID of the
28217 @subsubheading @value{GDBN} Command
28219 The @samp{info thread} command prints the same information
28222 @subsubheading Result
28224 The result contains the following attributes:
28228 A list of threads. The format of the elements of the list is described in
28229 @ref{GDB/MI Thread Information}.
28231 @item current-thread-id
28232 The global id of the currently selected thread. This field is omitted if there
28233 is no selected thread (for example, when the selected inferior is not running,
28234 and therefore has no threads) or if a @var{thread-id} argument was passed to
28239 @subsubheading Example
28244 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28245 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28246 args=[]@},state="running"@},
28247 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28248 frame=@{level="0",addr="0x0804891f",func="foo",
28249 args=[@{name="i",value="10"@}],
28250 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28251 state="running"@}],
28252 current-thread-id="1"
28256 @subheading The @code{-thread-list-ids} Command
28257 @findex -thread-list-ids
28259 @subsubheading Synopsis
28265 Produces a list of the currently known global @value{GDBN} thread ids.
28266 At the end of the list it also prints the total number of such
28269 This command is retained for historical reasons, the
28270 @code{-thread-info} command should be used instead.
28272 @subsubheading @value{GDBN} Command
28274 Part of @samp{info threads} supplies the same information.
28276 @subsubheading Example
28281 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28282 current-thread-id="1",number-of-threads="3"
28287 @subheading The @code{-thread-select} Command
28288 @findex -thread-select
28290 @subsubheading Synopsis
28293 -thread-select @var{thread-id}
28296 Make thread with global thread number @var{thread-id} the current
28297 thread. It prints the number of the new current thread, and the
28298 topmost frame for that thread.
28300 This command is deprecated in favor of explicitly using the
28301 @samp{--thread} option to each command.
28303 @subsubheading @value{GDBN} Command
28305 The corresponding @value{GDBN} command is @samp{thread}.
28307 @subsubheading Example
28314 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28315 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28319 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28320 number-of-threads="3"
28323 ^done,new-thread-id="3",
28324 frame=@{level="0",func="vprintf",
28325 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28326 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28331 @node GDB/MI Ada Tasking Commands
28332 @section @sc{gdb/mi} Ada Tasking Commands
28334 @subheading The @code{-ada-task-info} Command
28335 @findex -ada-task-info
28337 @subsubheading Synopsis
28340 -ada-task-info [ @var{task-id} ]
28343 Reports information about either a specific Ada task, if the
28344 @var{task-id} parameter is present, or about all Ada tasks.
28346 @subsubheading @value{GDBN} Command
28348 The @samp{info tasks} command prints the same information
28349 about all Ada tasks (@pxref{Ada Tasks}).
28351 @subsubheading Result
28353 The result is a table of Ada tasks. The following columns are
28354 defined for each Ada task:
28358 This field exists only for the current thread. It has the value @samp{*}.
28361 The identifier that @value{GDBN} uses to refer to the Ada task.
28364 The identifier that the target uses to refer to the Ada task.
28367 The global thread identifier of the thread corresponding to the Ada
28370 This field should always exist, as Ada tasks are always implemented
28371 on top of a thread. But if @value{GDBN} cannot find this corresponding
28372 thread for any reason, the field is omitted.
28375 This field exists only when the task was created by another task.
28376 In this case, it provides the ID of the parent task.
28379 The base priority of the task.
28382 The current state of the task. For a detailed description of the
28383 possible states, see @ref{Ada Tasks}.
28386 The name of the task.
28390 @subsubheading Example
28394 ^done,tasks=@{nr_rows="3",nr_cols="8",
28395 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28396 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28397 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28398 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28399 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28400 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28401 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28402 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28403 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28404 state="Child Termination Wait",name="main_task"@}]@}
28408 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28409 @node GDB/MI Program Execution
28410 @section @sc{gdb/mi} Program Execution
28412 These are the asynchronous commands which generate the out-of-band
28413 record @samp{*stopped}. Currently @value{GDBN} only really executes
28414 asynchronously with remote targets and this interaction is mimicked in
28417 @subheading The @code{-exec-continue} Command
28418 @findex -exec-continue
28420 @subsubheading Synopsis
28423 -exec-continue [--reverse] [--all|--thread-group N]
28426 Resumes the execution of the inferior program, which will continue
28427 to execute until it reaches a debugger stop event. If the
28428 @samp{--reverse} option is specified, execution resumes in reverse until
28429 it reaches a stop event. Stop events may include
28432 breakpoints or watchpoints
28434 signals or exceptions
28436 the end of the process (or its beginning under @samp{--reverse})
28438 the end or beginning of a replay log if one is being used.
28440 In all-stop mode (@pxref{All-Stop
28441 Mode}), may resume only one thread, or all threads, depending on the
28442 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28443 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28444 ignored in all-stop mode. If the @samp{--thread-group} options is
28445 specified, then all threads in that thread group are resumed.
28447 @subsubheading @value{GDBN} Command
28449 The corresponding @value{GDBN} corresponding is @samp{continue}.
28451 @subsubheading Example
28458 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28459 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28465 @subheading The @code{-exec-finish} Command
28466 @findex -exec-finish
28468 @subsubheading Synopsis
28471 -exec-finish [--reverse]
28474 Resumes the execution of the inferior program until the current
28475 function is exited. Displays the results returned by the function.
28476 If the @samp{--reverse} option is specified, resumes the reverse
28477 execution of the inferior program until the point where current
28478 function was called.
28480 @subsubheading @value{GDBN} Command
28482 The corresponding @value{GDBN} command is @samp{finish}.
28484 @subsubheading Example
28486 Function returning @code{void}.
28493 *stopped,reason="function-finished",frame=@{func="main",args=[],
28494 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28498 Function returning other than @code{void}. The name of the internal
28499 @value{GDBN} variable storing the result is printed, together with the
28506 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28507 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28509 gdb-result-var="$1",return-value="0"
28514 @subheading The @code{-exec-interrupt} Command
28515 @findex -exec-interrupt
28517 @subsubheading Synopsis
28520 -exec-interrupt [--all|--thread-group N]
28523 Interrupts the background execution of the target. Note how the token
28524 associated with the stop message is the one for the execution command
28525 that has been interrupted. The token for the interrupt itself only
28526 appears in the @samp{^done} output. If the user is trying to
28527 interrupt a non-running program, an error message will be printed.
28529 Note that when asynchronous execution is enabled, this command is
28530 asynchronous just like other execution commands. That is, first the
28531 @samp{^done} response will be printed, and the target stop will be
28532 reported after that using the @samp{*stopped} notification.
28534 In non-stop mode, only the context thread is interrupted by default.
28535 All threads (in all inferiors) will be interrupted if the
28536 @samp{--all} option is specified. If the @samp{--thread-group}
28537 option is specified, all threads in that group will be interrupted.
28539 @subsubheading @value{GDBN} Command
28541 The corresponding @value{GDBN} command is @samp{interrupt}.
28543 @subsubheading Example
28554 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28555 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28556 fullname="/home/foo/bar/try.c",line="13"@}
28561 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28565 @subheading The @code{-exec-jump} Command
28568 @subsubheading Synopsis
28571 -exec-jump @var{location}
28574 Resumes execution of the inferior program at the location specified by
28575 parameter. @xref{Specify Location}, for a description of the
28576 different forms of @var{location}.
28578 @subsubheading @value{GDBN} Command
28580 The corresponding @value{GDBN} command is @samp{jump}.
28582 @subsubheading Example
28585 -exec-jump foo.c:10
28586 *running,thread-id="all"
28591 @subheading The @code{-exec-next} Command
28594 @subsubheading Synopsis
28597 -exec-next [--reverse]
28600 Resumes execution of the inferior program, stopping when the beginning
28601 of the next source line is reached.
28603 If the @samp{--reverse} option is specified, resumes reverse execution
28604 of the inferior program, stopping at the beginning of the previous
28605 source line. If you issue this command on the first line of a
28606 function, it will take you back to the caller of that function, to the
28607 source line where the function was called.
28610 @subsubheading @value{GDBN} Command
28612 The corresponding @value{GDBN} command is @samp{next}.
28614 @subsubheading Example
28620 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28625 @subheading The @code{-exec-next-instruction} Command
28626 @findex -exec-next-instruction
28628 @subsubheading Synopsis
28631 -exec-next-instruction [--reverse]
28634 Executes one machine instruction. If the instruction is a function
28635 call, continues until the function returns. If the program stops at an
28636 instruction in the middle of a source line, the address will be
28639 If the @samp{--reverse} option is specified, resumes reverse execution
28640 of the inferior program, stopping at the previous instruction. If the
28641 previously executed instruction was a return from another function,
28642 it will continue to execute in reverse until the call to that function
28643 (from the current stack frame) is reached.
28645 @subsubheading @value{GDBN} Command
28647 The corresponding @value{GDBN} command is @samp{nexti}.
28649 @subsubheading Example
28653 -exec-next-instruction
28657 *stopped,reason="end-stepping-range",
28658 addr="0x000100d4",line="5",file="hello.c"
28663 @subheading The @code{-exec-return} Command
28664 @findex -exec-return
28666 @subsubheading Synopsis
28672 Makes current function return immediately. Doesn't execute the inferior.
28673 Displays the new current frame.
28675 @subsubheading @value{GDBN} Command
28677 The corresponding @value{GDBN} command is @samp{return}.
28679 @subsubheading Example
28683 200-break-insert callee4
28684 200^done,bkpt=@{number="1",addr="0x00010734",
28685 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28690 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28691 frame=@{func="callee4",args=[],
28692 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28693 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28699 111^done,frame=@{level="0",func="callee3",
28700 args=[@{name="strarg",
28701 value="0x11940 \"A string argument.\""@}],
28702 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28703 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28708 @subheading The @code{-exec-run} Command
28711 @subsubheading Synopsis
28714 -exec-run [ --all | --thread-group N ] [ --start ]
28717 Starts execution of the inferior from the beginning. The inferior
28718 executes until either a breakpoint is encountered or the program
28719 exits. In the latter case the output will include an exit code, if
28720 the program has exited exceptionally.
28722 When neither the @samp{--all} nor the @samp{--thread-group} option
28723 is specified, the current inferior is started. If the
28724 @samp{--thread-group} option is specified, it should refer to a thread
28725 group of type @samp{process}, and that thread group will be started.
28726 If the @samp{--all} option is specified, then all inferiors will be started.
28728 Using the @samp{--start} option instructs the debugger to stop
28729 the execution at the start of the inferior's main subprogram,
28730 following the same behavior as the @code{start} command
28731 (@pxref{Starting}).
28733 @subsubheading @value{GDBN} Command
28735 The corresponding @value{GDBN} command is @samp{run}.
28737 @subsubheading Examples
28742 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28747 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28748 frame=@{func="main",args=[],file="recursive2.c",
28749 fullname="/home/foo/bar/recursive2.c",line="4"@}
28754 Program exited normally:
28762 *stopped,reason="exited-normally"
28767 Program exited exceptionally:
28775 *stopped,reason="exited",exit-code="01"
28779 Another way the program can terminate is if it receives a signal such as
28780 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28784 *stopped,reason="exited-signalled",signal-name="SIGINT",
28785 signal-meaning="Interrupt"
28789 @c @subheading -exec-signal
28792 @subheading The @code{-exec-step} Command
28795 @subsubheading Synopsis
28798 -exec-step [--reverse]
28801 Resumes execution of the inferior program, stopping when the beginning
28802 of the next source line is reached, if the next source line is not a
28803 function call. If it is, stop at the first instruction of the called
28804 function. If the @samp{--reverse} option is specified, resumes reverse
28805 execution of the inferior program, stopping at the beginning of the
28806 previously executed source line.
28808 @subsubheading @value{GDBN} Command
28810 The corresponding @value{GDBN} command is @samp{step}.
28812 @subsubheading Example
28814 Stepping into a function:
28820 *stopped,reason="end-stepping-range",
28821 frame=@{func="foo",args=[@{name="a",value="10"@},
28822 @{name="b",value="0"@}],file="recursive2.c",
28823 fullname="/home/foo/bar/recursive2.c",line="11"@}
28833 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28838 @subheading The @code{-exec-step-instruction} Command
28839 @findex -exec-step-instruction
28841 @subsubheading Synopsis
28844 -exec-step-instruction [--reverse]
28847 Resumes the inferior which executes one machine instruction. If the
28848 @samp{--reverse} option is specified, resumes reverse execution of the
28849 inferior program, stopping at the previously executed instruction.
28850 The output, once @value{GDBN} has stopped, will vary depending on
28851 whether we have stopped in the middle of a source line or not. In the
28852 former case, the address at which the program stopped will be printed
28855 @subsubheading @value{GDBN} Command
28857 The corresponding @value{GDBN} command is @samp{stepi}.
28859 @subsubheading Example
28863 -exec-step-instruction
28867 *stopped,reason="end-stepping-range",
28868 frame=@{func="foo",args=[],file="try.c",
28869 fullname="/home/foo/bar/try.c",line="10"@}
28871 -exec-step-instruction
28875 *stopped,reason="end-stepping-range",
28876 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28877 fullname="/home/foo/bar/try.c",line="10"@}
28882 @subheading The @code{-exec-until} Command
28883 @findex -exec-until
28885 @subsubheading Synopsis
28888 -exec-until [ @var{location} ]
28891 Executes the inferior until the @var{location} specified in the
28892 argument is reached. If there is no argument, the inferior executes
28893 until a source line greater than the current one is reached. The
28894 reason for stopping in this case will be @samp{location-reached}.
28896 @subsubheading @value{GDBN} Command
28898 The corresponding @value{GDBN} command is @samp{until}.
28900 @subsubheading Example
28904 -exec-until recursive2.c:6
28908 *stopped,reason="location-reached",frame=@{func="main",args=[],
28909 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28914 @subheading -file-clear
28915 Is this going away????
28918 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28919 @node GDB/MI Stack Manipulation
28920 @section @sc{gdb/mi} Stack Manipulation Commands
28922 @subheading The @code{-enable-frame-filters} Command
28923 @findex -enable-frame-filters
28926 -enable-frame-filters
28929 @value{GDBN} allows Python-based frame filters to affect the output of
28930 the MI commands relating to stack traces. As there is no way to
28931 implement this in a fully backward-compatible way, a front end must
28932 request that this functionality be enabled.
28934 Once enabled, this feature cannot be disabled.
28936 Note that if Python support has not been compiled into @value{GDBN},
28937 this command will still succeed (and do nothing).
28939 @subheading The @code{-stack-info-frame} Command
28940 @findex -stack-info-frame
28942 @subsubheading Synopsis
28948 Get info on the selected frame.
28950 @subsubheading @value{GDBN} Command
28952 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28953 (without arguments).
28955 @subsubheading Example
28960 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28961 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28962 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28966 @subheading The @code{-stack-info-depth} Command
28967 @findex -stack-info-depth
28969 @subsubheading Synopsis
28972 -stack-info-depth [ @var{max-depth} ]
28975 Return the depth of the stack. If the integer argument @var{max-depth}
28976 is specified, do not count beyond @var{max-depth} frames.
28978 @subsubheading @value{GDBN} Command
28980 There's no equivalent @value{GDBN} command.
28982 @subsubheading Example
28984 For a stack with frame levels 0 through 11:
28991 -stack-info-depth 4
28994 -stack-info-depth 12
28997 -stack-info-depth 11
29000 -stack-info-depth 13
29005 @anchor{-stack-list-arguments}
29006 @subheading The @code{-stack-list-arguments} Command
29007 @findex -stack-list-arguments
29009 @subsubheading Synopsis
29012 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29013 [ @var{low-frame} @var{high-frame} ]
29016 Display a list of the arguments for the frames between @var{low-frame}
29017 and @var{high-frame} (inclusive). If @var{low-frame} and
29018 @var{high-frame} are not provided, list the arguments for the whole
29019 call stack. If the two arguments are equal, show the single frame
29020 at the corresponding level. It is an error if @var{low-frame} is
29021 larger than the actual number of frames. On the other hand,
29022 @var{high-frame} may be larger than the actual number of frames, in
29023 which case only existing frames will be returned.
29025 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29026 the variables; if it is 1 or @code{--all-values}, print also their
29027 values; and if it is 2 or @code{--simple-values}, print the name,
29028 type and value for simple data types, and the name and type for arrays,
29029 structures and unions. If the option @code{--no-frame-filters} is
29030 supplied, then Python frame filters will not be executed.
29032 If the @code{--skip-unavailable} option is specified, arguments that
29033 are not available are not listed. Partially available arguments
29034 are still displayed, however.
29036 Use of this command to obtain arguments in a single frame is
29037 deprecated in favor of the @samp{-stack-list-variables} command.
29039 @subsubheading @value{GDBN} Command
29041 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29042 @samp{gdb_get_args} command which partially overlaps with the
29043 functionality of @samp{-stack-list-arguments}.
29045 @subsubheading Example
29052 frame=@{level="0",addr="0x00010734",func="callee4",
29053 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29054 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29055 frame=@{level="1",addr="0x0001076c",func="callee3",
29056 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29057 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29058 frame=@{level="2",addr="0x0001078c",func="callee2",
29059 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29060 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29061 frame=@{level="3",addr="0x000107b4",func="callee1",
29062 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29063 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29064 frame=@{level="4",addr="0x000107e0",func="main",
29065 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29066 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29068 -stack-list-arguments 0
29071 frame=@{level="0",args=[]@},
29072 frame=@{level="1",args=[name="strarg"]@},
29073 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29074 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29075 frame=@{level="4",args=[]@}]
29077 -stack-list-arguments 1
29080 frame=@{level="0",args=[]@},
29082 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29083 frame=@{level="2",args=[
29084 @{name="intarg",value="2"@},
29085 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29086 @{frame=@{level="3",args=[
29087 @{name="intarg",value="2"@},
29088 @{name="strarg",value="0x11940 \"A string argument.\""@},
29089 @{name="fltarg",value="3.5"@}]@},
29090 frame=@{level="4",args=[]@}]
29092 -stack-list-arguments 0 2 2
29093 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29095 -stack-list-arguments 1 2 2
29096 ^done,stack-args=[frame=@{level="2",
29097 args=[@{name="intarg",value="2"@},
29098 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29102 @c @subheading -stack-list-exception-handlers
29105 @anchor{-stack-list-frames}
29106 @subheading The @code{-stack-list-frames} Command
29107 @findex -stack-list-frames
29109 @subsubheading Synopsis
29112 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29115 List the frames currently on the stack. For each frame it displays the
29120 The frame number, 0 being the topmost frame, i.e., the innermost function.
29122 The @code{$pc} value for that frame.
29126 File name of the source file where the function lives.
29127 @item @var{fullname}
29128 The full file name of the source file where the function lives.
29130 Line number corresponding to the @code{$pc}.
29132 The shared library where this function is defined. This is only given
29133 if the frame's function is not known.
29136 If invoked without arguments, this command prints a backtrace for the
29137 whole stack. If given two integer arguments, it shows the frames whose
29138 levels are between the two arguments (inclusive). If the two arguments
29139 are equal, it shows the single frame at the corresponding level. It is
29140 an error if @var{low-frame} is larger than the actual number of
29141 frames. On the other hand, @var{high-frame} may be larger than the
29142 actual number of frames, in which case only existing frames will be
29143 returned. If the option @code{--no-frame-filters} is supplied, then
29144 Python frame filters will not be executed.
29146 @subsubheading @value{GDBN} Command
29148 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29150 @subsubheading Example
29152 Full stack backtrace:
29158 [frame=@{level="0",addr="0x0001076c",func="foo",
29159 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29160 frame=@{level="1",addr="0x000107a4",func="foo",
29161 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29162 frame=@{level="2",addr="0x000107a4",func="foo",
29163 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29164 frame=@{level="3",addr="0x000107a4",func="foo",
29165 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29166 frame=@{level="4",addr="0x000107a4",func="foo",
29167 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29168 frame=@{level="5",addr="0x000107a4",func="foo",
29169 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29170 frame=@{level="6",addr="0x000107a4",func="foo",
29171 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29172 frame=@{level="7",addr="0x000107a4",func="foo",
29173 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29174 frame=@{level="8",addr="0x000107a4",func="foo",
29175 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29176 frame=@{level="9",addr="0x000107a4",func="foo",
29177 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29178 frame=@{level="10",addr="0x000107a4",func="foo",
29179 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29180 frame=@{level="11",addr="0x00010738",func="main",
29181 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29185 Show frames between @var{low_frame} and @var{high_frame}:
29189 -stack-list-frames 3 5
29191 [frame=@{level="3",addr="0x000107a4",func="foo",
29192 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29193 frame=@{level="4",addr="0x000107a4",func="foo",
29194 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29195 frame=@{level="5",addr="0x000107a4",func="foo",
29196 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29200 Show a single frame:
29204 -stack-list-frames 3 3
29206 [frame=@{level="3",addr="0x000107a4",func="foo",
29207 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29212 @subheading The @code{-stack-list-locals} Command
29213 @findex -stack-list-locals
29214 @anchor{-stack-list-locals}
29216 @subsubheading Synopsis
29219 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29222 Display the local variable names for the selected frame. If
29223 @var{print-values} is 0 or @code{--no-values}, print only the names of
29224 the variables; if it is 1 or @code{--all-values}, print also their
29225 values; and if it is 2 or @code{--simple-values}, print the name,
29226 type and value for simple data types, and the name and type for arrays,
29227 structures and unions. In this last case, a frontend can immediately
29228 display the value of simple data types and create variable objects for
29229 other data types when the user wishes to explore their values in
29230 more detail. If the option @code{--no-frame-filters} is supplied, then
29231 Python frame filters will not be executed.
29233 If the @code{--skip-unavailable} option is specified, local variables
29234 that are not available are not listed. Partially available local
29235 variables are still displayed, however.
29237 This command is deprecated in favor of the
29238 @samp{-stack-list-variables} command.
29240 @subsubheading @value{GDBN} Command
29242 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29244 @subsubheading Example
29248 -stack-list-locals 0
29249 ^done,locals=[name="A",name="B",name="C"]
29251 -stack-list-locals --all-values
29252 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29253 @{name="C",value="@{1, 2, 3@}"@}]
29254 -stack-list-locals --simple-values
29255 ^done,locals=[@{name="A",type="int",value="1"@},
29256 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29260 @anchor{-stack-list-variables}
29261 @subheading The @code{-stack-list-variables} Command
29262 @findex -stack-list-variables
29264 @subsubheading Synopsis
29267 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29270 Display the names of local variables and function arguments for the selected frame. If
29271 @var{print-values} is 0 or @code{--no-values}, print only the names of
29272 the variables; if it is 1 or @code{--all-values}, print also their
29273 values; and if it is 2 or @code{--simple-values}, print the name,
29274 type and value for simple data types, and the name and type for arrays,
29275 structures and unions. If the option @code{--no-frame-filters} is
29276 supplied, then Python frame filters will not be executed.
29278 If the @code{--skip-unavailable} option is specified, local variables
29279 and arguments that are not available are not listed. Partially
29280 available arguments and local variables are still displayed, however.
29282 @subsubheading Example
29286 -stack-list-variables --thread 1 --frame 0 --all-values
29287 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29292 @subheading The @code{-stack-select-frame} Command
29293 @findex -stack-select-frame
29295 @subsubheading Synopsis
29298 -stack-select-frame @var{framenum}
29301 Change the selected frame. Select a different frame @var{framenum} on
29304 This command in deprecated in favor of passing the @samp{--frame}
29305 option to every command.
29307 @subsubheading @value{GDBN} Command
29309 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29310 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29312 @subsubheading Example
29316 -stack-select-frame 2
29321 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29322 @node GDB/MI Variable Objects
29323 @section @sc{gdb/mi} Variable Objects
29327 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29329 For the implementation of a variable debugger window (locals, watched
29330 expressions, etc.), we are proposing the adaptation of the existing code
29331 used by @code{Insight}.
29333 The two main reasons for that are:
29337 It has been proven in practice (it is already on its second generation).
29340 It will shorten development time (needless to say how important it is
29344 The original interface was designed to be used by Tcl code, so it was
29345 slightly changed so it could be used through @sc{gdb/mi}. This section
29346 describes the @sc{gdb/mi} operations that will be available and gives some
29347 hints about their use.
29349 @emph{Note}: In addition to the set of operations described here, we
29350 expect the @sc{gui} implementation of a variable window to require, at
29351 least, the following operations:
29354 @item @code{-gdb-show} @code{output-radix}
29355 @item @code{-stack-list-arguments}
29356 @item @code{-stack-list-locals}
29357 @item @code{-stack-select-frame}
29362 @subheading Introduction to Variable Objects
29364 @cindex variable objects in @sc{gdb/mi}
29366 Variable objects are "object-oriented" MI interface for examining and
29367 changing values of expressions. Unlike some other MI interfaces that
29368 work with expressions, variable objects are specifically designed for
29369 simple and efficient presentation in the frontend. A variable object
29370 is identified by string name. When a variable object is created, the
29371 frontend specifies the expression for that variable object. The
29372 expression can be a simple variable, or it can be an arbitrary complex
29373 expression, and can even involve CPU registers. After creating a
29374 variable object, the frontend can invoke other variable object
29375 operations---for example to obtain or change the value of a variable
29376 object, or to change display format.
29378 Variable objects have hierarchical tree structure. Any variable object
29379 that corresponds to a composite type, such as structure in C, has
29380 a number of child variable objects, for example corresponding to each
29381 element of a structure. A child variable object can itself have
29382 children, recursively. Recursion ends when we reach
29383 leaf variable objects, which always have built-in types. Child variable
29384 objects are created only by explicit request, so if a frontend
29385 is not interested in the children of a particular variable object, no
29386 child will be created.
29388 For a leaf variable object it is possible to obtain its value as a
29389 string, or set the value from a string. String value can be also
29390 obtained for a non-leaf variable object, but it's generally a string
29391 that only indicates the type of the object, and does not list its
29392 contents. Assignment to a non-leaf variable object is not allowed.
29394 A frontend does not need to read the values of all variable objects each time
29395 the program stops. Instead, MI provides an update command that lists all
29396 variable objects whose values has changed since the last update
29397 operation. This considerably reduces the amount of data that must
29398 be transferred to the frontend. As noted above, children variable
29399 objects are created on demand, and only leaf variable objects have a
29400 real value. As result, gdb will read target memory only for leaf
29401 variables that frontend has created.
29403 The automatic update is not always desirable. For example, a frontend
29404 might want to keep a value of some expression for future reference,
29405 and never update it. For another example, fetching memory is
29406 relatively slow for embedded targets, so a frontend might want
29407 to disable automatic update for the variables that are either not
29408 visible on the screen, or ``closed''. This is possible using so
29409 called ``frozen variable objects''. Such variable objects are never
29410 implicitly updated.
29412 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29413 fixed variable object, the expression is parsed when the variable
29414 object is created, including associating identifiers to specific
29415 variables. The meaning of expression never changes. For a floating
29416 variable object the values of variables whose names appear in the
29417 expressions are re-evaluated every time in the context of the current
29418 frame. Consider this example:
29423 struct work_state state;
29430 If a fixed variable object for the @code{state} variable is created in
29431 this function, and we enter the recursive call, the variable
29432 object will report the value of @code{state} in the top-level
29433 @code{do_work} invocation. On the other hand, a floating variable
29434 object will report the value of @code{state} in the current frame.
29436 If an expression specified when creating a fixed variable object
29437 refers to a local variable, the variable object becomes bound to the
29438 thread and frame in which the variable object is created. When such
29439 variable object is updated, @value{GDBN} makes sure that the
29440 thread/frame combination the variable object is bound to still exists,
29441 and re-evaluates the variable object in context of that thread/frame.
29443 The following is the complete set of @sc{gdb/mi} operations defined to
29444 access this functionality:
29446 @multitable @columnfractions .4 .6
29447 @item @strong{Operation}
29448 @tab @strong{Description}
29450 @item @code{-enable-pretty-printing}
29451 @tab enable Python-based pretty-printing
29452 @item @code{-var-create}
29453 @tab create a variable object
29454 @item @code{-var-delete}
29455 @tab delete the variable object and/or its children
29456 @item @code{-var-set-format}
29457 @tab set the display format of this variable
29458 @item @code{-var-show-format}
29459 @tab show the display format of this variable
29460 @item @code{-var-info-num-children}
29461 @tab tells how many children this object has
29462 @item @code{-var-list-children}
29463 @tab return a list of the object's children
29464 @item @code{-var-info-type}
29465 @tab show the type of this variable object
29466 @item @code{-var-info-expression}
29467 @tab print parent-relative expression that this variable object represents
29468 @item @code{-var-info-path-expression}
29469 @tab print full expression that this variable object represents
29470 @item @code{-var-show-attributes}
29471 @tab is this variable editable? does it exist here?
29472 @item @code{-var-evaluate-expression}
29473 @tab get the value of this variable
29474 @item @code{-var-assign}
29475 @tab set the value of this variable
29476 @item @code{-var-update}
29477 @tab update the variable and its children
29478 @item @code{-var-set-frozen}
29479 @tab set frozeness attribute
29480 @item @code{-var-set-update-range}
29481 @tab set range of children to display on update
29484 In the next subsection we describe each operation in detail and suggest
29485 how it can be used.
29487 @subheading Description And Use of Operations on Variable Objects
29489 @subheading The @code{-enable-pretty-printing} Command
29490 @findex -enable-pretty-printing
29493 -enable-pretty-printing
29496 @value{GDBN} allows Python-based visualizers to affect the output of the
29497 MI variable object commands. However, because there was no way to
29498 implement this in a fully backward-compatible way, a front end must
29499 request that this functionality be enabled.
29501 Once enabled, this feature cannot be disabled.
29503 Note that if Python support has not been compiled into @value{GDBN},
29504 this command will still succeed (and do nothing).
29506 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29507 may work differently in future versions of @value{GDBN}.
29509 @subheading The @code{-var-create} Command
29510 @findex -var-create
29512 @subsubheading Synopsis
29515 -var-create @{@var{name} | "-"@}
29516 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29519 This operation creates a variable object, which allows the monitoring of
29520 a variable, the result of an expression, a memory cell or a CPU
29523 The @var{name} parameter is the string by which the object can be
29524 referenced. It must be unique. If @samp{-} is specified, the varobj
29525 system will generate a string ``varNNNNNN'' automatically. It will be
29526 unique provided that one does not specify @var{name} of that format.
29527 The command fails if a duplicate name is found.
29529 The frame under which the expression should be evaluated can be
29530 specified by @var{frame-addr}. A @samp{*} indicates that the current
29531 frame should be used. A @samp{@@} indicates that a floating variable
29532 object must be created.
29534 @var{expression} is any expression valid on the current language set (must not
29535 begin with a @samp{*}), or one of the following:
29539 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29542 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29545 @samp{$@var{regname}} --- a CPU register name
29548 @cindex dynamic varobj
29549 A varobj's contents may be provided by a Python-based pretty-printer. In this
29550 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29551 have slightly different semantics in some cases. If the
29552 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29553 will never create a dynamic varobj. This ensures backward
29554 compatibility for existing clients.
29556 @subsubheading Result
29558 This operation returns attributes of the newly-created varobj. These
29563 The name of the varobj.
29566 The number of children of the varobj. This number is not necessarily
29567 reliable for a dynamic varobj. Instead, you must examine the
29568 @samp{has_more} attribute.
29571 The varobj's scalar value. For a varobj whose type is some sort of
29572 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29573 will not be interesting.
29576 The varobj's type. This is a string representation of the type, as
29577 would be printed by the @value{GDBN} CLI. If @samp{print object}
29578 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29579 @emph{actual} (derived) type of the object is shown rather than the
29580 @emph{declared} one.
29583 If a variable object is bound to a specific thread, then this is the
29584 thread's global identifier.
29587 For a dynamic varobj, this indicates whether there appear to be any
29588 children available. For a non-dynamic varobj, this will be 0.
29591 This attribute will be present and have the value @samp{1} if the
29592 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29593 then this attribute will not be present.
29596 A dynamic varobj can supply a display hint to the front end. The
29597 value comes directly from the Python pretty-printer object's
29598 @code{display_hint} method. @xref{Pretty Printing API}.
29601 Typical output will look like this:
29604 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29605 has_more="@var{has_more}"
29609 @subheading The @code{-var-delete} Command
29610 @findex -var-delete
29612 @subsubheading Synopsis
29615 -var-delete [ -c ] @var{name}
29618 Deletes a previously created variable object and all of its children.
29619 With the @samp{-c} option, just deletes the children.
29621 Returns an error if the object @var{name} is not found.
29624 @subheading The @code{-var-set-format} Command
29625 @findex -var-set-format
29627 @subsubheading Synopsis
29630 -var-set-format @var{name} @var{format-spec}
29633 Sets the output format for the value of the object @var{name} to be
29636 @anchor{-var-set-format}
29637 The syntax for the @var{format-spec} is as follows:
29640 @var{format-spec} @expansion{}
29641 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29644 The natural format is the default format choosen automatically
29645 based on the variable type (like decimal for an @code{int}, hex
29646 for pointers, etc.).
29648 The zero-hexadecimal format has a representation similar to hexadecimal
29649 but with padding zeroes to the left of the value. For example, a 32-bit
29650 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29651 zero-hexadecimal format.
29653 For a variable with children, the format is set only on the
29654 variable itself, and the children are not affected.
29656 @subheading The @code{-var-show-format} Command
29657 @findex -var-show-format
29659 @subsubheading Synopsis
29662 -var-show-format @var{name}
29665 Returns the format used to display the value of the object @var{name}.
29668 @var{format} @expansion{}
29673 @subheading The @code{-var-info-num-children} Command
29674 @findex -var-info-num-children
29676 @subsubheading Synopsis
29679 -var-info-num-children @var{name}
29682 Returns the number of children of a variable object @var{name}:
29688 Note that this number is not completely reliable for a dynamic varobj.
29689 It will return the current number of children, but more children may
29693 @subheading The @code{-var-list-children} Command
29694 @findex -var-list-children
29696 @subsubheading Synopsis
29699 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29701 @anchor{-var-list-children}
29703 Return a list of the children of the specified variable object and
29704 create variable objects for them, if they do not already exist. With
29705 a single argument or if @var{print-values} has a value of 0 or
29706 @code{--no-values}, print only the names of the variables; if
29707 @var{print-values} is 1 or @code{--all-values}, also print their
29708 values; and if it is 2 or @code{--simple-values} print the name and
29709 value for simple data types and just the name for arrays, structures
29712 @var{from} and @var{to}, if specified, indicate the range of children
29713 to report. If @var{from} or @var{to} is less than zero, the range is
29714 reset and all children will be reported. Otherwise, children starting
29715 at @var{from} (zero-based) and up to and excluding @var{to} will be
29718 If a child range is requested, it will only affect the current call to
29719 @code{-var-list-children}, but not future calls to @code{-var-update}.
29720 For this, you must instead use @code{-var-set-update-range}. The
29721 intent of this approach is to enable a front end to implement any
29722 update approach it likes; for example, scrolling a view may cause the
29723 front end to request more children with @code{-var-list-children}, and
29724 then the front end could call @code{-var-set-update-range} with a
29725 different range to ensure that future updates are restricted to just
29728 For each child the following results are returned:
29733 Name of the variable object created for this child.
29736 The expression to be shown to the user by the front end to designate this child.
29737 For example this may be the name of a structure member.
29739 For a dynamic varobj, this value cannot be used to form an
29740 expression. There is no way to do this at all with a dynamic varobj.
29742 For C/C@t{++} structures there are several pseudo children returned to
29743 designate access qualifiers. For these pseudo children @var{exp} is
29744 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29745 type and value are not present.
29747 A dynamic varobj will not report the access qualifying
29748 pseudo-children, regardless of the language. This information is not
29749 available at all with a dynamic varobj.
29752 Number of children this child has. For a dynamic varobj, this will be
29756 The type of the child. If @samp{print object}
29757 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29758 @emph{actual} (derived) type of the object is shown rather than the
29759 @emph{declared} one.
29762 If values were requested, this is the value.
29765 If this variable object is associated with a thread, this is the
29766 thread's global thread id. Otherwise this result is not present.
29769 If the variable object is frozen, this variable will be present with a value of 1.
29772 A dynamic varobj can supply a display hint to the front end. The
29773 value comes directly from the Python pretty-printer object's
29774 @code{display_hint} method. @xref{Pretty Printing API}.
29777 This attribute will be present and have the value @samp{1} if the
29778 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29779 then this attribute will not be present.
29783 The result may have its own attributes:
29787 A dynamic varobj can supply a display hint to the front end. The
29788 value comes directly from the Python pretty-printer object's
29789 @code{display_hint} method. @xref{Pretty Printing API}.
29792 This is an integer attribute which is nonzero if there are children
29793 remaining after the end of the selected range.
29796 @subsubheading Example
29800 -var-list-children n
29801 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29802 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29804 -var-list-children --all-values n
29805 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29806 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29810 @subheading The @code{-var-info-type} Command
29811 @findex -var-info-type
29813 @subsubheading Synopsis
29816 -var-info-type @var{name}
29819 Returns the type of the specified variable @var{name}. The type is
29820 returned as a string in the same format as it is output by the
29824 type=@var{typename}
29828 @subheading The @code{-var-info-expression} Command
29829 @findex -var-info-expression
29831 @subsubheading Synopsis
29834 -var-info-expression @var{name}
29837 Returns a string that is suitable for presenting this
29838 variable object in user interface. The string is generally
29839 not valid expression in the current language, and cannot be evaluated.
29841 For example, if @code{a} is an array, and variable object
29842 @code{A} was created for @code{a}, then we'll get this output:
29845 (gdb) -var-info-expression A.1
29846 ^done,lang="C",exp="1"
29850 Here, the value of @code{lang} is the language name, which can be
29851 found in @ref{Supported Languages}.
29853 Note that the output of the @code{-var-list-children} command also
29854 includes those expressions, so the @code{-var-info-expression} command
29857 @subheading The @code{-var-info-path-expression} Command
29858 @findex -var-info-path-expression
29860 @subsubheading Synopsis
29863 -var-info-path-expression @var{name}
29866 Returns an expression that can be evaluated in the current
29867 context and will yield the same value that a variable object has.
29868 Compare this with the @code{-var-info-expression} command, which
29869 result can be used only for UI presentation. Typical use of
29870 the @code{-var-info-path-expression} command is creating a
29871 watchpoint from a variable object.
29873 This command is currently not valid for children of a dynamic varobj,
29874 and will give an error when invoked on one.
29876 For example, suppose @code{C} is a C@t{++} class, derived from class
29877 @code{Base}, and that the @code{Base} class has a member called
29878 @code{m_size}. Assume a variable @code{c} is has the type of
29879 @code{C} and a variable object @code{C} was created for variable
29880 @code{c}. Then, we'll get this output:
29882 (gdb) -var-info-path-expression C.Base.public.m_size
29883 ^done,path_expr=((Base)c).m_size)
29886 @subheading The @code{-var-show-attributes} Command
29887 @findex -var-show-attributes
29889 @subsubheading Synopsis
29892 -var-show-attributes @var{name}
29895 List attributes of the specified variable object @var{name}:
29898 status=@var{attr} [ ( ,@var{attr} )* ]
29902 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29904 @subheading The @code{-var-evaluate-expression} Command
29905 @findex -var-evaluate-expression
29907 @subsubheading Synopsis
29910 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29913 Evaluates the expression that is represented by the specified variable
29914 object and returns its value as a string. The format of the string
29915 can be specified with the @samp{-f} option. The possible values of
29916 this option are the same as for @code{-var-set-format}
29917 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29918 the current display format will be used. The current display format
29919 can be changed using the @code{-var-set-format} command.
29925 Note that one must invoke @code{-var-list-children} for a variable
29926 before the value of a child variable can be evaluated.
29928 @subheading The @code{-var-assign} Command
29929 @findex -var-assign
29931 @subsubheading Synopsis
29934 -var-assign @var{name} @var{expression}
29937 Assigns the value of @var{expression} to the variable object specified
29938 by @var{name}. The object must be @samp{editable}. If the variable's
29939 value is altered by the assign, the variable will show up in any
29940 subsequent @code{-var-update} list.
29942 @subsubheading Example
29950 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29954 @subheading The @code{-var-update} Command
29955 @findex -var-update
29957 @subsubheading Synopsis
29960 -var-update [@var{print-values}] @{@var{name} | "*"@}
29963 Reevaluate the expressions corresponding to the variable object
29964 @var{name} and all its direct and indirect children, and return the
29965 list of variable objects whose values have changed; @var{name} must
29966 be a root variable object. Here, ``changed'' means that the result of
29967 @code{-var-evaluate-expression} before and after the
29968 @code{-var-update} is different. If @samp{*} is used as the variable
29969 object names, all existing variable objects are updated, except
29970 for frozen ones (@pxref{-var-set-frozen}). The option
29971 @var{print-values} determines whether both names and values, or just
29972 names are printed. The possible values of this option are the same
29973 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29974 recommended to use the @samp{--all-values} option, to reduce the
29975 number of MI commands needed on each program stop.
29977 With the @samp{*} parameter, if a variable object is bound to a
29978 currently running thread, it will not be updated, without any
29981 If @code{-var-set-update-range} was previously used on a varobj, then
29982 only the selected range of children will be reported.
29984 @code{-var-update} reports all the changed varobjs in a tuple named
29987 Each item in the change list is itself a tuple holding:
29991 The name of the varobj.
29994 If values were requested for this update, then this field will be
29995 present and will hold the value of the varobj.
29998 @anchor{-var-update}
29999 This field is a string which may take one of three values:
30003 The variable object's current value is valid.
30006 The variable object does not currently hold a valid value but it may
30007 hold one in the future if its associated expression comes back into
30011 The variable object no longer holds a valid value.
30012 This can occur when the executable file being debugged has changed,
30013 either through recompilation or by using the @value{GDBN} @code{file}
30014 command. The front end should normally choose to delete these variable
30018 In the future new values may be added to this list so the front should
30019 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30022 This is only present if the varobj is still valid. If the type
30023 changed, then this will be the string @samp{true}; otherwise it will
30026 When a varobj's type changes, its children are also likely to have
30027 become incorrect. Therefore, the varobj's children are automatically
30028 deleted when this attribute is @samp{true}. Also, the varobj's update
30029 range, when set using the @code{-var-set-update-range} command, is
30033 If the varobj's type changed, then this field will be present and will
30036 @item new_num_children
30037 For a dynamic varobj, if the number of children changed, or if the
30038 type changed, this will be the new number of children.
30040 The @samp{numchild} field in other varobj responses is generally not
30041 valid for a dynamic varobj -- it will show the number of children that
30042 @value{GDBN} knows about, but because dynamic varobjs lazily
30043 instantiate their children, this will not reflect the number of
30044 children which may be available.
30046 The @samp{new_num_children} attribute only reports changes to the
30047 number of children known by @value{GDBN}. This is the only way to
30048 detect whether an update has removed children (which necessarily can
30049 only happen at the end of the update range).
30052 The display hint, if any.
30055 This is an integer value, which will be 1 if there are more children
30056 available outside the varobj's update range.
30059 This attribute will be present and have the value @samp{1} if the
30060 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30061 then this attribute will not be present.
30064 If new children were added to a dynamic varobj within the selected
30065 update range (as set by @code{-var-set-update-range}), then they will
30066 be listed in this attribute.
30069 @subsubheading Example
30076 -var-update --all-values var1
30077 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30078 type_changed="false"@}]
30082 @subheading The @code{-var-set-frozen} Command
30083 @findex -var-set-frozen
30084 @anchor{-var-set-frozen}
30086 @subsubheading Synopsis
30089 -var-set-frozen @var{name} @var{flag}
30092 Set the frozenness flag on the variable object @var{name}. The
30093 @var{flag} parameter should be either @samp{1} to make the variable
30094 frozen or @samp{0} to make it unfrozen. If a variable object is
30095 frozen, then neither itself, nor any of its children, are
30096 implicitly updated by @code{-var-update} of
30097 a parent variable or by @code{-var-update *}. Only
30098 @code{-var-update} of the variable itself will update its value and
30099 values of its children. After a variable object is unfrozen, it is
30100 implicitly updated by all subsequent @code{-var-update} operations.
30101 Unfreezing a variable does not update it, only subsequent
30102 @code{-var-update} does.
30104 @subsubheading Example
30108 -var-set-frozen V 1
30113 @subheading The @code{-var-set-update-range} command
30114 @findex -var-set-update-range
30115 @anchor{-var-set-update-range}
30117 @subsubheading Synopsis
30120 -var-set-update-range @var{name} @var{from} @var{to}
30123 Set the range of children to be returned by future invocations of
30124 @code{-var-update}.
30126 @var{from} and @var{to} indicate the range of children to report. If
30127 @var{from} or @var{to} is less than zero, the range is reset and all
30128 children will be reported. Otherwise, children starting at @var{from}
30129 (zero-based) and up to and excluding @var{to} will be reported.
30131 @subsubheading Example
30135 -var-set-update-range V 1 2
30139 @subheading The @code{-var-set-visualizer} command
30140 @findex -var-set-visualizer
30141 @anchor{-var-set-visualizer}
30143 @subsubheading Synopsis
30146 -var-set-visualizer @var{name} @var{visualizer}
30149 Set a visualizer for the variable object @var{name}.
30151 @var{visualizer} is the visualizer to use. The special value
30152 @samp{None} means to disable any visualizer in use.
30154 If not @samp{None}, @var{visualizer} must be a Python expression.
30155 This expression must evaluate to a callable object which accepts a
30156 single argument. @value{GDBN} will call this object with the value of
30157 the varobj @var{name} as an argument (this is done so that the same
30158 Python pretty-printing code can be used for both the CLI and MI).
30159 When called, this object must return an object which conforms to the
30160 pretty-printing interface (@pxref{Pretty Printing API}).
30162 The pre-defined function @code{gdb.default_visualizer} may be used to
30163 select a visualizer by following the built-in process
30164 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30165 a varobj is created, and so ordinarily is not needed.
30167 This feature is only available if Python support is enabled. The MI
30168 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30169 can be used to check this.
30171 @subsubheading Example
30173 Resetting the visualizer:
30177 -var-set-visualizer V None
30181 Reselecting the default (type-based) visualizer:
30185 -var-set-visualizer V gdb.default_visualizer
30189 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30190 can be used to instantiate this class for a varobj:
30194 -var-set-visualizer V "lambda val: SomeClass()"
30198 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30199 @node GDB/MI Data Manipulation
30200 @section @sc{gdb/mi} Data Manipulation
30202 @cindex data manipulation, in @sc{gdb/mi}
30203 @cindex @sc{gdb/mi}, data manipulation
30204 This section describes the @sc{gdb/mi} commands that manipulate data:
30205 examine memory and registers, evaluate expressions, etc.
30207 For details about what an addressable memory unit is,
30208 @pxref{addressable memory unit}.
30210 @c REMOVED FROM THE INTERFACE.
30211 @c @subheading -data-assign
30212 @c Change the value of a program variable. Plenty of side effects.
30213 @c @subsubheading GDB Command
30215 @c @subsubheading Example
30218 @subheading The @code{-data-disassemble} Command
30219 @findex -data-disassemble
30221 @subsubheading Synopsis
30225 [ -s @var{start-addr} -e @var{end-addr} ]
30226 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30234 @item @var{start-addr}
30235 is the beginning address (or @code{$pc})
30236 @item @var{end-addr}
30238 @item @var{filename}
30239 is the name of the file to disassemble
30240 @item @var{linenum}
30241 is the line number to disassemble around
30243 is the number of disassembly lines to be produced. If it is -1,
30244 the whole function will be disassembled, in case no @var{end-addr} is
30245 specified. If @var{end-addr} is specified as a non-zero value, and
30246 @var{lines} is lower than the number of disassembly lines between
30247 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30248 displayed; if @var{lines} is higher than the number of lines between
30249 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30254 @item 0 disassembly only
30255 @item 1 mixed source and disassembly (deprecated)
30256 @item 2 disassembly with raw opcodes
30257 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30258 @item 4 mixed source and disassembly
30259 @item 5 mixed source and disassembly with raw opcodes
30262 Modes 1 and 3 are deprecated. The output is ``source centric''
30263 which hasn't proved useful in practice.
30264 @xref{Machine Code}, for a discussion of the difference between
30265 @code{/m} and @code{/s} output of the @code{disassemble} command.
30268 @subsubheading Result
30270 The result of the @code{-data-disassemble} command will be a list named
30271 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30272 used with the @code{-data-disassemble} command.
30274 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30279 The address at which this instruction was disassembled.
30282 The name of the function this instruction is within.
30285 The decimal offset in bytes from the start of @samp{func-name}.
30288 The text disassembly for this @samp{address}.
30291 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30292 bytes for the @samp{inst} field.
30296 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30297 @samp{src_and_asm_line}, each of which has the following fields:
30301 The line number within @samp{file}.
30304 The file name from the compilation unit. This might be an absolute
30305 file name or a relative file name depending on the compile command
30309 Absolute file name of @samp{file}. It is converted to a canonical form
30310 using the source file search path
30311 (@pxref{Source Path, ,Specifying Source Directories})
30312 and after resolving all the symbolic links.
30314 If the source file is not found this field will contain the path as
30315 present in the debug information.
30317 @item line_asm_insn
30318 This is a list of tuples containing the disassembly for @samp{line} in
30319 @samp{file}. The fields of each tuple are the same as for
30320 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30321 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30326 Note that whatever included in the @samp{inst} field, is not
30327 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30330 @subsubheading @value{GDBN} Command
30332 The corresponding @value{GDBN} command is @samp{disassemble}.
30334 @subsubheading Example
30336 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30340 -data-disassemble -s $pc -e "$pc + 20" -- 0
30343 @{address="0x000107c0",func-name="main",offset="4",
30344 inst="mov 2, %o0"@},
30345 @{address="0x000107c4",func-name="main",offset="8",
30346 inst="sethi %hi(0x11800), %o2"@},
30347 @{address="0x000107c8",func-name="main",offset="12",
30348 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30349 @{address="0x000107cc",func-name="main",offset="16",
30350 inst="sethi %hi(0x11800), %o2"@},
30351 @{address="0x000107d0",func-name="main",offset="20",
30352 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30356 Disassemble the whole @code{main} function. Line 32 is part of
30360 -data-disassemble -f basics.c -l 32 -- 0
30362 @{address="0x000107bc",func-name="main",offset="0",
30363 inst="save %sp, -112, %sp"@},
30364 @{address="0x000107c0",func-name="main",offset="4",
30365 inst="mov 2, %o0"@},
30366 @{address="0x000107c4",func-name="main",offset="8",
30367 inst="sethi %hi(0x11800), %o2"@},
30369 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30370 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30374 Disassemble 3 instructions from the start of @code{main}:
30378 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30380 @{address="0x000107bc",func-name="main",offset="0",
30381 inst="save %sp, -112, %sp"@},
30382 @{address="0x000107c0",func-name="main",offset="4",
30383 inst="mov 2, %o0"@},
30384 @{address="0x000107c4",func-name="main",offset="8",
30385 inst="sethi %hi(0x11800), %o2"@}]
30389 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30393 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30395 src_and_asm_line=@{line="31",
30396 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30397 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30398 line_asm_insn=[@{address="0x000107bc",
30399 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30400 src_and_asm_line=@{line="32",
30401 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30402 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30403 line_asm_insn=[@{address="0x000107c0",
30404 func-name="main",offset="4",inst="mov 2, %o0"@},
30405 @{address="0x000107c4",func-name="main",offset="8",
30406 inst="sethi %hi(0x11800), %o2"@}]@}]
30411 @subheading The @code{-data-evaluate-expression} Command
30412 @findex -data-evaluate-expression
30414 @subsubheading Synopsis
30417 -data-evaluate-expression @var{expr}
30420 Evaluate @var{expr} as an expression. The expression could contain an
30421 inferior function call. The function call will execute synchronously.
30422 If the expression contains spaces, it must be enclosed in double quotes.
30424 @subsubheading @value{GDBN} Command
30426 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30427 @samp{call}. In @code{gdbtk} only, there's a corresponding
30428 @samp{gdb_eval} command.
30430 @subsubheading Example
30432 In the following example, the numbers that precede the commands are the
30433 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30434 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30438 211-data-evaluate-expression A
30441 311-data-evaluate-expression &A
30442 311^done,value="0xefffeb7c"
30444 411-data-evaluate-expression A+3
30447 511-data-evaluate-expression "A + 3"
30453 @subheading The @code{-data-list-changed-registers} Command
30454 @findex -data-list-changed-registers
30456 @subsubheading Synopsis
30459 -data-list-changed-registers
30462 Display a list of the registers that have changed.
30464 @subsubheading @value{GDBN} Command
30466 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30467 has the corresponding command @samp{gdb_changed_register_list}.
30469 @subsubheading Example
30471 On a PPC MBX board:
30479 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30480 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30483 -data-list-changed-registers
30484 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30485 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30486 "24","25","26","27","28","30","31","64","65","66","67","69"]
30491 @subheading The @code{-data-list-register-names} Command
30492 @findex -data-list-register-names
30494 @subsubheading Synopsis
30497 -data-list-register-names [ ( @var{regno} )+ ]
30500 Show a list of register names for the current target. If no arguments
30501 are given, it shows a list of the names of all the registers. If
30502 integer numbers are given as arguments, it will print a list of the
30503 names of the registers corresponding to the arguments. To ensure
30504 consistency between a register name and its number, the output list may
30505 include empty register names.
30507 @subsubheading @value{GDBN} Command
30509 @value{GDBN} does not have a command which corresponds to
30510 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30511 corresponding command @samp{gdb_regnames}.
30513 @subsubheading Example
30515 For the PPC MBX board:
30518 -data-list-register-names
30519 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30520 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30521 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30522 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30523 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30524 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30525 "", "pc","ps","cr","lr","ctr","xer"]
30527 -data-list-register-names 1 2 3
30528 ^done,register-names=["r1","r2","r3"]
30532 @subheading The @code{-data-list-register-values} Command
30533 @findex -data-list-register-values
30535 @subsubheading Synopsis
30538 -data-list-register-values
30539 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30542 Display the registers' contents. The format according to which the
30543 registers' contents are to be returned is given by @var{fmt}, followed
30544 by an optional list of numbers specifying the registers to display. A
30545 missing list of numbers indicates that the contents of all the
30546 registers must be returned. The @code{--skip-unavailable} option
30547 indicates that only the available registers are to be returned.
30549 Allowed formats for @var{fmt} are:
30566 @subsubheading @value{GDBN} Command
30568 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30569 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30571 @subsubheading Example
30573 For a PPC MBX board (note: line breaks are for readability only, they
30574 don't appear in the actual output):
30578 -data-list-register-values r 64 65
30579 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30580 @{number="65",value="0x00029002"@}]
30582 -data-list-register-values x
30583 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30584 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30585 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30586 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30587 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30588 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30589 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30590 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30591 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30592 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30593 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30594 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30595 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30596 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30597 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30598 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30599 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30600 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30601 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30602 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30603 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30604 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30605 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30606 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30607 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30608 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30609 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30610 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30611 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30612 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30613 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30614 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30615 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30616 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30617 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30618 @{number="69",value="0x20002b03"@}]
30623 @subheading The @code{-data-read-memory} Command
30624 @findex -data-read-memory
30626 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30628 @subsubheading Synopsis
30631 -data-read-memory [ -o @var{byte-offset} ]
30632 @var{address} @var{word-format} @var{word-size}
30633 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30640 @item @var{address}
30641 An expression specifying the address of the first memory word to be
30642 read. Complex expressions containing embedded white space should be
30643 quoted using the C convention.
30645 @item @var{word-format}
30646 The format to be used to print the memory words. The notation is the
30647 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30650 @item @var{word-size}
30651 The size of each memory word in bytes.
30653 @item @var{nr-rows}
30654 The number of rows in the output table.
30656 @item @var{nr-cols}
30657 The number of columns in the output table.
30660 If present, indicates that each row should include an @sc{ascii} dump. The
30661 value of @var{aschar} is used as a padding character when a byte is not a
30662 member of the printable @sc{ascii} character set (printable @sc{ascii}
30663 characters are those whose code is between 32 and 126, inclusively).
30665 @item @var{byte-offset}
30666 An offset to add to the @var{address} before fetching memory.
30669 This command displays memory contents as a table of @var{nr-rows} by
30670 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30671 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30672 (returned as @samp{total-bytes}). Should less than the requested number
30673 of bytes be returned by the target, the missing words are identified
30674 using @samp{N/A}. The number of bytes read from the target is returned
30675 in @samp{nr-bytes} and the starting address used to read memory in
30678 The address of the next/previous row or page is available in
30679 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30682 @subsubheading @value{GDBN} Command
30684 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30685 @samp{gdb_get_mem} memory read command.
30687 @subsubheading Example
30689 Read six bytes of memory starting at @code{bytes+6} but then offset by
30690 @code{-6} bytes. Format as three rows of two columns. One byte per
30691 word. Display each word in hex.
30695 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30696 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30697 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30698 prev-page="0x0000138a",memory=[
30699 @{addr="0x00001390",data=["0x00","0x01"]@},
30700 @{addr="0x00001392",data=["0x02","0x03"]@},
30701 @{addr="0x00001394",data=["0x04","0x05"]@}]
30705 Read two bytes of memory starting at address @code{shorts + 64} and
30706 display as a single word formatted in decimal.
30710 5-data-read-memory shorts+64 d 2 1 1
30711 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30712 next-row="0x00001512",prev-row="0x0000150e",
30713 next-page="0x00001512",prev-page="0x0000150e",memory=[
30714 @{addr="0x00001510",data=["128"]@}]
30718 Read thirty two bytes of memory starting at @code{bytes+16} and format
30719 as eight rows of four columns. Include a string encoding with @samp{x}
30720 used as the non-printable character.
30724 4-data-read-memory bytes+16 x 1 8 4 x
30725 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30726 next-row="0x000013c0",prev-row="0x0000139c",
30727 next-page="0x000013c0",prev-page="0x00001380",memory=[
30728 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30729 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30730 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30731 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30732 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30733 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30734 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30735 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30739 @subheading The @code{-data-read-memory-bytes} Command
30740 @findex -data-read-memory-bytes
30742 @subsubheading Synopsis
30745 -data-read-memory-bytes [ -o @var{offset} ]
30746 @var{address} @var{count}
30753 @item @var{address}
30754 An expression specifying the address of the first addressable memory unit
30755 to be read. Complex expressions containing embedded white space should be
30756 quoted using the C convention.
30759 The number of addressable memory units to read. This should be an integer
30763 The offset relative to @var{address} at which to start reading. This
30764 should be an integer literal. This option is provided so that a frontend
30765 is not required to first evaluate address and then perform address
30766 arithmetics itself.
30770 This command attempts to read all accessible memory regions in the
30771 specified range. First, all regions marked as unreadable in the memory
30772 map (if one is defined) will be skipped. @xref{Memory Region
30773 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30774 regions. For each one, if reading full region results in an errors,
30775 @value{GDBN} will try to read a subset of the region.
30777 In general, every single memory unit in the region may be readable or not,
30778 and the only way to read every readable unit is to try a read at
30779 every address, which is not practical. Therefore, @value{GDBN} will
30780 attempt to read all accessible memory units at either beginning or the end
30781 of the region, using a binary division scheme. This heuristic works
30782 well for reading accross a memory map boundary. Note that if a region
30783 has a readable range that is neither at the beginning or the end,
30784 @value{GDBN} will not read it.
30786 The result record (@pxref{GDB/MI Result Records}) that is output of
30787 the command includes a field named @samp{memory} whose content is a
30788 list of tuples. Each tuple represent a successfully read memory block
30789 and has the following fields:
30793 The start address of the memory block, as hexadecimal literal.
30796 The end address of the memory block, as hexadecimal literal.
30799 The offset of the memory block, as hexadecimal literal, relative to
30800 the start address passed to @code{-data-read-memory-bytes}.
30803 The contents of the memory block, in hex.
30809 @subsubheading @value{GDBN} Command
30811 The corresponding @value{GDBN} command is @samp{x}.
30813 @subsubheading Example
30817 -data-read-memory-bytes &a 10
30818 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30820 contents="01000000020000000300"@}]
30825 @subheading The @code{-data-write-memory-bytes} Command
30826 @findex -data-write-memory-bytes
30828 @subsubheading Synopsis
30831 -data-write-memory-bytes @var{address} @var{contents}
30832 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30839 @item @var{address}
30840 An expression specifying the address of the first addressable memory unit
30841 to be written. Complex expressions containing embedded white space should
30842 be quoted using the C convention.
30844 @item @var{contents}
30845 The hex-encoded data to write. It is an error if @var{contents} does
30846 not represent an integral number of addressable memory units.
30849 Optional argument indicating the number of addressable memory units to be
30850 written. If @var{count} is greater than @var{contents}' length,
30851 @value{GDBN} will repeatedly write @var{contents} until it fills
30852 @var{count} memory units.
30856 @subsubheading @value{GDBN} Command
30858 There's no corresponding @value{GDBN} command.
30860 @subsubheading Example
30864 -data-write-memory-bytes &a "aabbccdd"
30871 -data-write-memory-bytes &a "aabbccdd" 16e
30876 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30877 @node GDB/MI Tracepoint Commands
30878 @section @sc{gdb/mi} Tracepoint Commands
30880 The commands defined in this section implement MI support for
30881 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30883 @subheading The @code{-trace-find} Command
30884 @findex -trace-find
30886 @subsubheading Synopsis
30889 -trace-find @var{mode} [@var{parameters}@dots{}]
30892 Find a trace frame using criteria defined by @var{mode} and
30893 @var{parameters}. The following table lists permissible
30894 modes and their parameters. For details of operation, see @ref{tfind}.
30899 No parameters are required. Stops examining trace frames.
30902 An integer is required as parameter. Selects tracepoint frame with
30905 @item tracepoint-number
30906 An integer is required as parameter. Finds next
30907 trace frame that corresponds to tracepoint with the specified number.
30910 An address is required as parameter. Finds
30911 next trace frame that corresponds to any tracepoint at the specified
30914 @item pc-inside-range
30915 Two addresses are required as parameters. Finds next trace
30916 frame that corresponds to a tracepoint at an address inside the
30917 specified range. Both bounds are considered to be inside the range.
30919 @item pc-outside-range
30920 Two addresses are required as parameters. Finds
30921 next trace frame that corresponds to a tracepoint at an address outside
30922 the specified range. Both bounds are considered to be inside the range.
30925 Line specification is required as parameter. @xref{Specify Location}.
30926 Finds next trace frame that corresponds to a tracepoint at
30927 the specified location.
30931 If @samp{none} was passed as @var{mode}, the response does not
30932 have fields. Otherwise, the response may have the following fields:
30936 This field has either @samp{0} or @samp{1} as the value, depending
30937 on whether a matching tracepoint was found.
30940 The index of the found traceframe. This field is present iff
30941 the @samp{found} field has value of @samp{1}.
30944 The index of the found tracepoint. This field is present iff
30945 the @samp{found} field has value of @samp{1}.
30948 The information about the frame corresponding to the found trace
30949 frame. This field is present only if a trace frame was found.
30950 @xref{GDB/MI Frame Information}, for description of this field.
30954 @subsubheading @value{GDBN} Command
30956 The corresponding @value{GDBN} command is @samp{tfind}.
30958 @subheading -trace-define-variable
30959 @findex -trace-define-variable
30961 @subsubheading Synopsis
30964 -trace-define-variable @var{name} [ @var{value} ]
30967 Create trace variable @var{name} if it does not exist. If
30968 @var{value} is specified, sets the initial value of the specified
30969 trace variable to that value. Note that the @var{name} should start
30970 with the @samp{$} character.
30972 @subsubheading @value{GDBN} Command
30974 The corresponding @value{GDBN} command is @samp{tvariable}.
30976 @subheading The @code{-trace-frame-collected} Command
30977 @findex -trace-frame-collected
30979 @subsubheading Synopsis
30982 -trace-frame-collected
30983 [--var-print-values @var{var_pval}]
30984 [--comp-print-values @var{comp_pval}]
30985 [--registers-format @var{regformat}]
30986 [--memory-contents]
30989 This command returns the set of collected objects, register names,
30990 trace state variable names, memory ranges and computed expressions
30991 that have been collected at a particular trace frame. The optional
30992 parameters to the command affect the output format in different ways.
30993 See the output description table below for more details.
30995 The reported names can be used in the normal manner to create
30996 varobjs and inspect the objects themselves. The items returned by
30997 this command are categorized so that it is clear which is a variable,
30998 which is a register, which is a trace state variable, which is a
30999 memory range and which is a computed expression.
31001 For instance, if the actions were
31003 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31004 collect *(int*)0xaf02bef0@@40
31008 the object collected in its entirety would be @code{myVar}. The
31009 object @code{myArray} would be partially collected, because only the
31010 element at index @code{myIndex} would be collected. The remaining
31011 objects would be computed expressions.
31013 An example output would be:
31017 -trace-frame-collected
31019 explicit-variables=[@{name="myVar",value="1"@}],
31020 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31021 @{name="myObj.field",value="0"@},
31022 @{name="myPtr->field",value="1"@},
31023 @{name="myCount + 2",value="3"@},
31024 @{name="$tvar1 + 1",value="43970027"@}],
31025 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31026 @{number="1",value="0x0"@},
31027 @{number="2",value="0x4"@},
31029 @{number="125",value="0x0"@}],
31030 tvars=[@{name="$tvar1",current="43970026"@}],
31031 memory=[@{address="0x0000000000602264",length="4"@},
31032 @{address="0x0000000000615bc0",length="4"@}]
31039 @item explicit-variables
31040 The set of objects that have been collected in their entirety (as
31041 opposed to collecting just a few elements of an array or a few struct
31042 members). For each object, its name and value are printed.
31043 The @code{--var-print-values} option affects how or whether the value
31044 field is output. If @var{var_pval} is 0, then print only the names;
31045 if it is 1, print also their values; and if it is 2, print the name,
31046 type and value for simple data types, and the name and type for
31047 arrays, structures and unions.
31049 @item computed-expressions
31050 The set of computed expressions that have been collected at the
31051 current trace frame. The @code{--comp-print-values} option affects
31052 this set like the @code{--var-print-values} option affects the
31053 @code{explicit-variables} set. See above.
31056 The registers that have been collected at the current trace frame.
31057 For each register collected, the name and current value are returned.
31058 The value is formatted according to the @code{--registers-format}
31059 option. See the @command{-data-list-register-values} command for a
31060 list of the allowed formats. The default is @samp{x}.
31063 The trace state variables that have been collected at the current
31064 trace frame. For each trace state variable collected, the name and
31065 current value are returned.
31068 The set of memory ranges that have been collected at the current trace
31069 frame. Its content is a list of tuples. Each tuple represents a
31070 collected memory range and has the following fields:
31074 The start address of the memory range, as hexadecimal literal.
31077 The length of the memory range, as decimal literal.
31080 The contents of the memory block, in hex. This field is only present
31081 if the @code{--memory-contents} option is specified.
31087 @subsubheading @value{GDBN} Command
31089 There is no corresponding @value{GDBN} command.
31091 @subsubheading Example
31093 @subheading -trace-list-variables
31094 @findex -trace-list-variables
31096 @subsubheading Synopsis
31099 -trace-list-variables
31102 Return a table of all defined trace variables. Each element of the
31103 table has the following fields:
31107 The name of the trace variable. This field is always present.
31110 The initial value. This is a 64-bit signed integer. This
31111 field is always present.
31114 The value the trace variable has at the moment. This is a 64-bit
31115 signed integer. This field is absent iff current value is
31116 not defined, for example if the trace was never run, or is
31121 @subsubheading @value{GDBN} Command
31123 The corresponding @value{GDBN} command is @samp{tvariables}.
31125 @subsubheading Example
31129 -trace-list-variables
31130 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31131 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31132 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31133 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31134 body=[variable=@{name="$trace_timestamp",initial="0"@}
31135 variable=@{name="$foo",initial="10",current="15"@}]@}
31139 @subheading -trace-save
31140 @findex -trace-save
31142 @subsubheading Synopsis
31145 -trace-save [ -r ] [ -ctf ] @var{filename}
31148 Saves the collected trace data to @var{filename}. Without the
31149 @samp{-r} option, the data is downloaded from the target and saved
31150 in a local file. With the @samp{-r} option the target is asked
31151 to perform the save.
31153 By default, this command will save the trace in the tfile format. You can
31154 supply the optional @samp{-ctf} argument to save it the CTF format. See
31155 @ref{Trace Files} for more information about CTF.
31157 @subsubheading @value{GDBN} Command
31159 The corresponding @value{GDBN} command is @samp{tsave}.
31162 @subheading -trace-start
31163 @findex -trace-start
31165 @subsubheading Synopsis
31171 Starts a tracing experiment. The result of this command does not
31174 @subsubheading @value{GDBN} Command
31176 The corresponding @value{GDBN} command is @samp{tstart}.
31178 @subheading -trace-status
31179 @findex -trace-status
31181 @subsubheading Synopsis
31187 Obtains the status of a tracing experiment. The result may include
31188 the following fields:
31193 May have a value of either @samp{0}, when no tracing operations are
31194 supported, @samp{1}, when all tracing operations are supported, or
31195 @samp{file} when examining trace file. In the latter case, examining
31196 of trace frame is possible but new tracing experiement cannot be
31197 started. This field is always present.
31200 May have a value of either @samp{0} or @samp{1} depending on whether
31201 tracing experiement is in progress on target. This field is present
31202 if @samp{supported} field is not @samp{0}.
31205 Report the reason why the tracing was stopped last time. This field
31206 may be absent iff tracing was never stopped on target yet. The
31207 value of @samp{request} means the tracing was stopped as result of
31208 the @code{-trace-stop} command. The value of @samp{overflow} means
31209 the tracing buffer is full. The value of @samp{disconnection} means
31210 tracing was automatically stopped when @value{GDBN} has disconnected.
31211 The value of @samp{passcount} means tracing was stopped when a
31212 tracepoint was passed a maximal number of times for that tracepoint.
31213 This field is present if @samp{supported} field is not @samp{0}.
31215 @item stopping-tracepoint
31216 The number of tracepoint whose passcount as exceeded. This field is
31217 present iff the @samp{stop-reason} field has the value of
31221 @itemx frames-created
31222 The @samp{frames} field is a count of the total number of trace frames
31223 in the trace buffer, while @samp{frames-created} is the total created
31224 during the run, including ones that were discarded, such as when a
31225 circular trace buffer filled up. Both fields are optional.
31229 These fields tell the current size of the tracing buffer and the
31230 remaining space. These fields are optional.
31233 The value of the circular trace buffer flag. @code{1} means that the
31234 trace buffer is circular and old trace frames will be discarded if
31235 necessary to make room, @code{0} means that the trace buffer is linear
31239 The value of the disconnected tracing flag. @code{1} means that
31240 tracing will continue after @value{GDBN} disconnects, @code{0} means
31241 that the trace run will stop.
31244 The filename of the trace file being examined. This field is
31245 optional, and only present when examining a trace file.
31249 @subsubheading @value{GDBN} Command
31251 The corresponding @value{GDBN} command is @samp{tstatus}.
31253 @subheading -trace-stop
31254 @findex -trace-stop
31256 @subsubheading Synopsis
31262 Stops a tracing experiment. The result of this command has the same
31263 fields as @code{-trace-status}, except that the @samp{supported} and
31264 @samp{running} fields are not output.
31266 @subsubheading @value{GDBN} Command
31268 The corresponding @value{GDBN} command is @samp{tstop}.
31271 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31272 @node GDB/MI Symbol Query
31273 @section @sc{gdb/mi} Symbol Query Commands
31277 @subheading The @code{-symbol-info-address} Command
31278 @findex -symbol-info-address
31280 @subsubheading Synopsis
31283 -symbol-info-address @var{symbol}
31286 Describe where @var{symbol} is stored.
31288 @subsubheading @value{GDBN} Command
31290 The corresponding @value{GDBN} command is @samp{info address}.
31292 @subsubheading Example
31296 @subheading The @code{-symbol-info-file} Command
31297 @findex -symbol-info-file
31299 @subsubheading Synopsis
31305 Show the file for the symbol.
31307 @subsubheading @value{GDBN} Command
31309 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31310 @samp{gdb_find_file}.
31312 @subsubheading Example
31316 @subheading The @code{-symbol-info-function} Command
31317 @findex -symbol-info-function
31319 @subsubheading Synopsis
31322 -symbol-info-function
31325 Show which function the symbol lives in.
31327 @subsubheading @value{GDBN} Command
31329 @samp{gdb_get_function} in @code{gdbtk}.
31331 @subsubheading Example
31335 @subheading The @code{-symbol-info-line} Command
31336 @findex -symbol-info-line
31338 @subsubheading Synopsis
31344 Show the core addresses of the code for a source line.
31346 @subsubheading @value{GDBN} Command
31348 The corresponding @value{GDBN} command is @samp{info line}.
31349 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31351 @subsubheading Example
31355 @subheading The @code{-symbol-info-symbol} Command
31356 @findex -symbol-info-symbol
31358 @subsubheading Synopsis
31361 -symbol-info-symbol @var{addr}
31364 Describe what symbol is at location @var{addr}.
31366 @subsubheading @value{GDBN} Command
31368 The corresponding @value{GDBN} command is @samp{info symbol}.
31370 @subsubheading Example
31374 @subheading The @code{-symbol-list-functions} Command
31375 @findex -symbol-list-functions
31377 @subsubheading Synopsis
31380 -symbol-list-functions
31383 List the functions in the executable.
31385 @subsubheading @value{GDBN} Command
31387 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31388 @samp{gdb_search} in @code{gdbtk}.
31390 @subsubheading Example
31395 @subheading The @code{-symbol-list-lines} Command
31396 @findex -symbol-list-lines
31398 @subsubheading Synopsis
31401 -symbol-list-lines @var{filename}
31404 Print the list of lines that contain code and their associated program
31405 addresses for the given source filename. The entries are sorted in
31406 ascending PC order.
31408 @subsubheading @value{GDBN} Command
31410 There is no corresponding @value{GDBN} command.
31412 @subsubheading Example
31415 -symbol-list-lines basics.c
31416 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31422 @subheading The @code{-symbol-list-types} Command
31423 @findex -symbol-list-types
31425 @subsubheading Synopsis
31431 List all the type names.
31433 @subsubheading @value{GDBN} Command
31435 The corresponding commands are @samp{info types} in @value{GDBN},
31436 @samp{gdb_search} in @code{gdbtk}.
31438 @subsubheading Example
31442 @subheading The @code{-symbol-list-variables} Command
31443 @findex -symbol-list-variables
31445 @subsubheading Synopsis
31448 -symbol-list-variables
31451 List all the global and static variable names.
31453 @subsubheading @value{GDBN} Command
31455 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31457 @subsubheading Example
31461 @subheading The @code{-symbol-locate} Command
31462 @findex -symbol-locate
31464 @subsubheading Synopsis
31470 @subsubheading @value{GDBN} Command
31472 @samp{gdb_loc} in @code{gdbtk}.
31474 @subsubheading Example
31478 @subheading The @code{-symbol-type} Command
31479 @findex -symbol-type
31481 @subsubheading Synopsis
31484 -symbol-type @var{variable}
31487 Show type of @var{variable}.
31489 @subsubheading @value{GDBN} Command
31491 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31492 @samp{gdb_obj_variable}.
31494 @subsubheading Example
31499 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31500 @node GDB/MI File Commands
31501 @section @sc{gdb/mi} File Commands
31503 This section describes the GDB/MI commands to specify executable file names
31504 and to read in and obtain symbol table information.
31506 @subheading The @code{-file-exec-and-symbols} Command
31507 @findex -file-exec-and-symbols
31509 @subsubheading Synopsis
31512 -file-exec-and-symbols @var{file}
31515 Specify the executable file to be debugged. This file is the one from
31516 which the symbol table is also read. If no file is specified, the
31517 command clears the executable and symbol information. If breakpoints
31518 are set when using this command with no arguments, @value{GDBN} will produce
31519 error messages. Otherwise, no output is produced, except a completion
31522 @subsubheading @value{GDBN} Command
31524 The corresponding @value{GDBN} command is @samp{file}.
31526 @subsubheading Example
31530 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31536 @subheading The @code{-file-exec-file} Command
31537 @findex -file-exec-file
31539 @subsubheading Synopsis
31542 -file-exec-file @var{file}
31545 Specify the executable file to be debugged. Unlike
31546 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31547 from this file. If used without argument, @value{GDBN} clears the information
31548 about the executable file. No output is produced, except a completion
31551 @subsubheading @value{GDBN} Command
31553 The corresponding @value{GDBN} command is @samp{exec-file}.
31555 @subsubheading Example
31559 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31566 @subheading The @code{-file-list-exec-sections} Command
31567 @findex -file-list-exec-sections
31569 @subsubheading Synopsis
31572 -file-list-exec-sections
31575 List the sections of the current executable file.
31577 @subsubheading @value{GDBN} Command
31579 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31580 information as this command. @code{gdbtk} has a corresponding command
31581 @samp{gdb_load_info}.
31583 @subsubheading Example
31588 @subheading The @code{-file-list-exec-source-file} Command
31589 @findex -file-list-exec-source-file
31591 @subsubheading Synopsis
31594 -file-list-exec-source-file
31597 List the line number, the current source file, and the absolute path
31598 to the current source file for the current executable. The macro
31599 information field has a value of @samp{1} or @samp{0} depending on
31600 whether or not the file includes preprocessor macro information.
31602 @subsubheading @value{GDBN} Command
31604 The @value{GDBN} equivalent is @samp{info source}
31606 @subsubheading Example
31610 123-file-list-exec-source-file
31611 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31616 @subheading The @code{-file-list-exec-source-files} Command
31617 @findex -file-list-exec-source-files
31619 @subsubheading Synopsis
31622 -file-list-exec-source-files
31625 List the source files for the current executable.
31627 It will always output both the filename and fullname (absolute file
31628 name) of a source file.
31630 @subsubheading @value{GDBN} Command
31632 The @value{GDBN} equivalent is @samp{info sources}.
31633 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31635 @subsubheading Example
31638 -file-list-exec-source-files
31640 @{file=foo.c,fullname=/home/foo.c@},
31641 @{file=/home/bar.c,fullname=/home/bar.c@},
31642 @{file=gdb_could_not_find_fullpath.c@}]
31646 @subheading The @code{-file-list-shared-libraries} Command
31647 @findex -file-list-shared-libraries
31649 @subsubheading Synopsis
31652 -file-list-shared-libraries [ @var{regexp} ]
31655 List the shared libraries in the program.
31656 With a regular expression @var{regexp}, only those libraries whose
31657 names match @var{regexp} are listed.
31659 @subsubheading @value{GDBN} Command
31661 The corresponding @value{GDBN} command is @samp{info shared}. The fields
31662 have a similar meaning to the @code{=library-loaded} notification.
31663 The @code{ranges} field specifies the multiple segments belonging to this
31664 library. Each range has the following fields:
31668 The address defining the inclusive lower bound of the segment.
31670 The address defining the exclusive upper bound of the segment.
31673 @subsubheading Example
31676 -file-list-exec-source-files
31677 ^done,shared-libraries=[
31678 @{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"@}]@},
31679 @{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"@}]@}]
31685 @subheading The @code{-file-list-symbol-files} Command
31686 @findex -file-list-symbol-files
31688 @subsubheading Synopsis
31691 -file-list-symbol-files
31696 @subsubheading @value{GDBN} Command
31698 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31700 @subsubheading Example
31705 @subheading The @code{-file-symbol-file} Command
31706 @findex -file-symbol-file
31708 @subsubheading Synopsis
31711 -file-symbol-file @var{file}
31714 Read symbol table info from the specified @var{file} argument. When
31715 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31716 produced, except for a completion notification.
31718 @subsubheading @value{GDBN} Command
31720 The corresponding @value{GDBN} command is @samp{symbol-file}.
31722 @subsubheading Example
31726 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31732 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31733 @node GDB/MI Memory Overlay Commands
31734 @section @sc{gdb/mi} Memory Overlay Commands
31736 The memory overlay commands are not implemented.
31738 @c @subheading -overlay-auto
31740 @c @subheading -overlay-list-mapping-state
31742 @c @subheading -overlay-list-overlays
31744 @c @subheading -overlay-map
31746 @c @subheading -overlay-off
31748 @c @subheading -overlay-on
31750 @c @subheading -overlay-unmap
31752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31753 @node GDB/MI Signal Handling Commands
31754 @section @sc{gdb/mi} Signal Handling Commands
31756 Signal handling commands are not implemented.
31758 @c @subheading -signal-handle
31760 @c @subheading -signal-list-handle-actions
31762 @c @subheading -signal-list-signal-types
31766 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31767 @node GDB/MI Target Manipulation
31768 @section @sc{gdb/mi} Target Manipulation Commands
31771 @subheading The @code{-target-attach} Command
31772 @findex -target-attach
31774 @subsubheading Synopsis
31777 -target-attach @var{pid} | @var{gid} | @var{file}
31780 Attach to a process @var{pid} or a file @var{file} outside of
31781 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31782 group, the id previously returned by
31783 @samp{-list-thread-groups --available} must be used.
31785 @subsubheading @value{GDBN} Command
31787 The corresponding @value{GDBN} command is @samp{attach}.
31789 @subsubheading Example
31793 =thread-created,id="1"
31794 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31800 @subheading The @code{-target-compare-sections} Command
31801 @findex -target-compare-sections
31803 @subsubheading Synopsis
31806 -target-compare-sections [ @var{section} ]
31809 Compare data of section @var{section} on target to the exec file.
31810 Without the argument, all sections are compared.
31812 @subsubheading @value{GDBN} Command
31814 The @value{GDBN} equivalent is @samp{compare-sections}.
31816 @subsubheading Example
31821 @subheading The @code{-target-detach} Command
31822 @findex -target-detach
31824 @subsubheading Synopsis
31827 -target-detach [ @var{pid} | @var{gid} ]
31830 Detach from the remote target which normally resumes its execution.
31831 If either @var{pid} or @var{gid} is specified, detaches from either
31832 the specified process, or specified thread group. There's no output.
31834 @subsubheading @value{GDBN} Command
31836 The corresponding @value{GDBN} command is @samp{detach}.
31838 @subsubheading Example
31848 @subheading The @code{-target-disconnect} Command
31849 @findex -target-disconnect
31851 @subsubheading Synopsis
31857 Disconnect from the remote target. There's no output and the target is
31858 generally not resumed.
31860 @subsubheading @value{GDBN} Command
31862 The corresponding @value{GDBN} command is @samp{disconnect}.
31864 @subsubheading Example
31874 @subheading The @code{-target-download} Command
31875 @findex -target-download
31877 @subsubheading Synopsis
31883 Loads the executable onto the remote target.
31884 It prints out an update message every half second, which includes the fields:
31888 The name of the section.
31890 The size of what has been sent so far for that section.
31892 The size of the section.
31894 The total size of what was sent so far (the current and the previous sections).
31896 The size of the overall executable to download.
31900 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31901 @sc{gdb/mi} Output Syntax}).
31903 In addition, it prints the name and size of the sections, as they are
31904 downloaded. These messages include the following fields:
31908 The name of the section.
31910 The size of the section.
31912 The size of the overall executable to download.
31916 At the end, a summary is printed.
31918 @subsubheading @value{GDBN} Command
31920 The corresponding @value{GDBN} command is @samp{load}.
31922 @subsubheading Example
31924 Note: each status message appears on a single line. Here the messages
31925 have been broken down so that they can fit onto a page.
31930 +download,@{section=".text",section-size="6668",total-size="9880"@}
31931 +download,@{section=".text",section-sent="512",section-size="6668",
31932 total-sent="512",total-size="9880"@}
31933 +download,@{section=".text",section-sent="1024",section-size="6668",
31934 total-sent="1024",total-size="9880"@}
31935 +download,@{section=".text",section-sent="1536",section-size="6668",
31936 total-sent="1536",total-size="9880"@}
31937 +download,@{section=".text",section-sent="2048",section-size="6668",
31938 total-sent="2048",total-size="9880"@}
31939 +download,@{section=".text",section-sent="2560",section-size="6668",
31940 total-sent="2560",total-size="9880"@}
31941 +download,@{section=".text",section-sent="3072",section-size="6668",
31942 total-sent="3072",total-size="9880"@}
31943 +download,@{section=".text",section-sent="3584",section-size="6668",
31944 total-sent="3584",total-size="9880"@}
31945 +download,@{section=".text",section-sent="4096",section-size="6668",
31946 total-sent="4096",total-size="9880"@}
31947 +download,@{section=".text",section-sent="4608",section-size="6668",
31948 total-sent="4608",total-size="9880"@}
31949 +download,@{section=".text",section-sent="5120",section-size="6668",
31950 total-sent="5120",total-size="9880"@}
31951 +download,@{section=".text",section-sent="5632",section-size="6668",
31952 total-sent="5632",total-size="9880"@}
31953 +download,@{section=".text",section-sent="6144",section-size="6668",
31954 total-sent="6144",total-size="9880"@}
31955 +download,@{section=".text",section-sent="6656",section-size="6668",
31956 total-sent="6656",total-size="9880"@}
31957 +download,@{section=".init",section-size="28",total-size="9880"@}
31958 +download,@{section=".fini",section-size="28",total-size="9880"@}
31959 +download,@{section=".data",section-size="3156",total-size="9880"@}
31960 +download,@{section=".data",section-sent="512",section-size="3156",
31961 total-sent="7236",total-size="9880"@}
31962 +download,@{section=".data",section-sent="1024",section-size="3156",
31963 total-sent="7748",total-size="9880"@}
31964 +download,@{section=".data",section-sent="1536",section-size="3156",
31965 total-sent="8260",total-size="9880"@}
31966 +download,@{section=".data",section-sent="2048",section-size="3156",
31967 total-sent="8772",total-size="9880"@}
31968 +download,@{section=".data",section-sent="2560",section-size="3156",
31969 total-sent="9284",total-size="9880"@}
31970 +download,@{section=".data",section-sent="3072",section-size="3156",
31971 total-sent="9796",total-size="9880"@}
31972 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31979 @subheading The @code{-target-exec-status} Command
31980 @findex -target-exec-status
31982 @subsubheading Synopsis
31985 -target-exec-status
31988 Provide information on the state of the target (whether it is running or
31989 not, for instance).
31991 @subsubheading @value{GDBN} Command
31993 There's no equivalent @value{GDBN} command.
31995 @subsubheading Example
31999 @subheading The @code{-target-list-available-targets} Command
32000 @findex -target-list-available-targets
32002 @subsubheading Synopsis
32005 -target-list-available-targets
32008 List the possible targets to connect to.
32010 @subsubheading @value{GDBN} Command
32012 The corresponding @value{GDBN} command is @samp{help target}.
32014 @subsubheading Example
32018 @subheading The @code{-target-list-current-targets} Command
32019 @findex -target-list-current-targets
32021 @subsubheading Synopsis
32024 -target-list-current-targets
32027 Describe the current target.
32029 @subsubheading @value{GDBN} Command
32031 The corresponding information is printed by @samp{info file} (among
32034 @subsubheading Example
32038 @subheading The @code{-target-list-parameters} Command
32039 @findex -target-list-parameters
32041 @subsubheading Synopsis
32044 -target-list-parameters
32050 @subsubheading @value{GDBN} Command
32054 @subsubheading Example
32057 @subheading The @code{-target-flash-erase} Command
32058 @findex -target-flash-erase
32060 @subsubheading Synopsis
32063 -target-flash-erase
32066 Erases all known flash memory regions on the target.
32068 The corresponding @value{GDBN} command is @samp{flash-erase}.
32070 The output is a list of flash regions that have been erased, with starting
32071 addresses and memory region sizes.
32075 -target-flash-erase
32076 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32080 @subheading The @code{-target-select} Command
32081 @findex -target-select
32083 @subsubheading Synopsis
32086 -target-select @var{type} @var{parameters @dots{}}
32089 Connect @value{GDBN} to the remote target. This command takes two args:
32093 The type of target, for instance @samp{remote}, etc.
32094 @item @var{parameters}
32095 Device names, host names and the like. @xref{Target Commands, ,
32096 Commands for Managing Targets}, for more details.
32099 The output is a connection notification, followed by the address at
32100 which the target program is, in the following form:
32103 ^connected,addr="@var{address}",func="@var{function name}",
32104 args=[@var{arg list}]
32107 @subsubheading @value{GDBN} Command
32109 The corresponding @value{GDBN} command is @samp{target}.
32111 @subsubheading Example
32115 -target-select remote /dev/ttya
32116 ^connected,addr="0xfe00a300",func="??",args=[]
32120 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32121 @node GDB/MI File Transfer Commands
32122 @section @sc{gdb/mi} File Transfer Commands
32125 @subheading The @code{-target-file-put} Command
32126 @findex -target-file-put
32128 @subsubheading Synopsis
32131 -target-file-put @var{hostfile} @var{targetfile}
32134 Copy file @var{hostfile} from the host system (the machine running
32135 @value{GDBN}) to @var{targetfile} on the target system.
32137 @subsubheading @value{GDBN} Command
32139 The corresponding @value{GDBN} command is @samp{remote put}.
32141 @subsubheading Example
32145 -target-file-put localfile remotefile
32151 @subheading The @code{-target-file-get} Command
32152 @findex -target-file-get
32154 @subsubheading Synopsis
32157 -target-file-get @var{targetfile} @var{hostfile}
32160 Copy file @var{targetfile} from the target system to @var{hostfile}
32161 on the host system.
32163 @subsubheading @value{GDBN} Command
32165 The corresponding @value{GDBN} command is @samp{remote get}.
32167 @subsubheading Example
32171 -target-file-get remotefile localfile
32177 @subheading The @code{-target-file-delete} Command
32178 @findex -target-file-delete
32180 @subsubheading Synopsis
32183 -target-file-delete @var{targetfile}
32186 Delete @var{targetfile} from the target system.
32188 @subsubheading @value{GDBN} Command
32190 The corresponding @value{GDBN} command is @samp{remote delete}.
32192 @subsubheading Example
32196 -target-file-delete remotefile
32202 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32203 @node GDB/MI Ada Exceptions Commands
32204 @section Ada Exceptions @sc{gdb/mi} Commands
32206 @subheading The @code{-info-ada-exceptions} Command
32207 @findex -info-ada-exceptions
32209 @subsubheading Synopsis
32212 -info-ada-exceptions [ @var{regexp}]
32215 List all Ada exceptions defined within the program being debugged.
32216 With a regular expression @var{regexp}, only those exceptions whose
32217 names match @var{regexp} are listed.
32219 @subsubheading @value{GDBN} Command
32221 The corresponding @value{GDBN} command is @samp{info exceptions}.
32223 @subsubheading Result
32225 The result is a table of Ada exceptions. The following columns are
32226 defined for each exception:
32230 The name of the exception.
32233 The address of the exception.
32237 @subsubheading Example
32240 -info-ada-exceptions aint
32241 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32242 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32243 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32244 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32245 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32248 @subheading Catching Ada Exceptions
32250 The commands describing how to ask @value{GDBN} to stop when a program
32251 raises an exception are described at @ref{Ada Exception GDB/MI
32252 Catchpoint Commands}.
32255 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32256 @node GDB/MI Support Commands
32257 @section @sc{gdb/mi} Support Commands
32259 Since new commands and features get regularly added to @sc{gdb/mi},
32260 some commands are available to help front-ends query the debugger
32261 about support for these capabilities. Similarly, it is also possible
32262 to query @value{GDBN} about target support of certain features.
32264 @subheading The @code{-info-gdb-mi-command} Command
32265 @cindex @code{-info-gdb-mi-command}
32266 @findex -info-gdb-mi-command
32268 @subsubheading Synopsis
32271 -info-gdb-mi-command @var{cmd_name}
32274 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32276 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32277 is technically not part of the command name (@pxref{GDB/MI Input
32278 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32279 for ease of use, this command also accepts the form with the leading
32282 @subsubheading @value{GDBN} Command
32284 There is no corresponding @value{GDBN} command.
32286 @subsubheading Result
32288 The result is a tuple. There is currently only one field:
32292 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32293 @code{"false"} otherwise.
32297 @subsubheading Example
32299 Here is an example where the @sc{gdb/mi} command does not exist:
32302 -info-gdb-mi-command unsupported-command
32303 ^done,command=@{exists="false"@}
32307 And here is an example where the @sc{gdb/mi} command is known
32311 -info-gdb-mi-command symbol-list-lines
32312 ^done,command=@{exists="true"@}
32315 @subheading The @code{-list-features} Command
32316 @findex -list-features
32317 @cindex supported @sc{gdb/mi} features, list
32319 Returns a list of particular features of the MI protocol that
32320 this version of gdb implements. A feature can be a command,
32321 or a new field in an output of some command, or even an
32322 important bugfix. While a frontend can sometimes detect presence
32323 of a feature at runtime, it is easier to perform detection at debugger
32326 The command returns a list of strings, with each string naming an
32327 available feature. Each returned string is just a name, it does not
32328 have any internal structure. The list of possible feature names
32334 (gdb) -list-features
32335 ^done,result=["feature1","feature2"]
32338 The current list of features is:
32341 @item frozen-varobjs
32342 Indicates support for the @code{-var-set-frozen} command, as well
32343 as possible presense of the @code{frozen} field in the output
32344 of @code{-varobj-create}.
32345 @item pending-breakpoints
32346 Indicates support for the @option{-f} option to the @code{-break-insert}
32349 Indicates Python scripting support, Python-based
32350 pretty-printing commands, and possible presence of the
32351 @samp{display_hint} field in the output of @code{-var-list-children}
32353 Indicates support for the @code{-thread-info} command.
32354 @item data-read-memory-bytes
32355 Indicates support for the @code{-data-read-memory-bytes} and the
32356 @code{-data-write-memory-bytes} commands.
32357 @item breakpoint-notifications
32358 Indicates that changes to breakpoints and breakpoints created via the
32359 CLI will be announced via async records.
32360 @item ada-task-info
32361 Indicates support for the @code{-ada-task-info} command.
32362 @item language-option
32363 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32364 option (@pxref{Context management}).
32365 @item info-gdb-mi-command
32366 Indicates support for the @code{-info-gdb-mi-command} command.
32367 @item undefined-command-error-code
32368 Indicates support for the "undefined-command" error code in error result
32369 records, produced when trying to execute an undefined @sc{gdb/mi} command
32370 (@pxref{GDB/MI Result Records}).
32371 @item exec-run-start-option
32372 Indicates that the @code{-exec-run} command supports the @option{--start}
32373 option (@pxref{GDB/MI Program Execution}).
32376 @subheading The @code{-list-target-features} Command
32377 @findex -list-target-features
32379 Returns a list of particular features that are supported by the
32380 target. Those features affect the permitted MI commands, but
32381 unlike the features reported by the @code{-list-features} command, the
32382 features depend on which target GDB is using at the moment. Whenever
32383 a target can change, due to commands such as @code{-target-select},
32384 @code{-target-attach} or @code{-exec-run}, the list of target features
32385 may change, and the frontend should obtain it again.
32389 (gdb) -list-target-features
32390 ^done,result=["async"]
32393 The current list of features is:
32397 Indicates that the target is capable of asynchronous command
32398 execution, which means that @value{GDBN} will accept further commands
32399 while the target is running.
32402 Indicates that the target is capable of reverse execution.
32403 @xref{Reverse Execution}, for more information.
32407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32408 @node GDB/MI Miscellaneous Commands
32409 @section Miscellaneous @sc{gdb/mi} Commands
32411 @c @subheading -gdb-complete
32413 @subheading The @code{-gdb-exit} Command
32416 @subsubheading Synopsis
32422 Exit @value{GDBN} immediately.
32424 @subsubheading @value{GDBN} Command
32426 Approximately corresponds to @samp{quit}.
32428 @subsubheading Example
32438 @subheading The @code{-exec-abort} Command
32439 @findex -exec-abort
32441 @subsubheading Synopsis
32447 Kill the inferior running program.
32449 @subsubheading @value{GDBN} Command
32451 The corresponding @value{GDBN} command is @samp{kill}.
32453 @subsubheading Example
32458 @subheading The @code{-gdb-set} Command
32461 @subsubheading Synopsis
32467 Set an internal @value{GDBN} variable.
32468 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32470 @subsubheading @value{GDBN} Command
32472 The corresponding @value{GDBN} command is @samp{set}.
32474 @subsubheading Example
32484 @subheading The @code{-gdb-show} Command
32487 @subsubheading Synopsis
32493 Show the current value of a @value{GDBN} variable.
32495 @subsubheading @value{GDBN} Command
32497 The corresponding @value{GDBN} command is @samp{show}.
32499 @subsubheading Example
32508 @c @subheading -gdb-source
32511 @subheading The @code{-gdb-version} Command
32512 @findex -gdb-version
32514 @subsubheading Synopsis
32520 Show version information for @value{GDBN}. Used mostly in testing.
32522 @subsubheading @value{GDBN} Command
32524 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32525 default shows this information when you start an interactive session.
32527 @subsubheading Example
32529 @c This example modifies the actual output from GDB to avoid overfull
32535 ~Copyright 2000 Free Software Foundation, Inc.
32536 ~GDB is free software, covered by the GNU General Public License, and
32537 ~you are welcome to change it and/or distribute copies of it under
32538 ~ certain conditions.
32539 ~Type "show copying" to see the conditions.
32540 ~There is absolutely no warranty for GDB. Type "show warranty" for
32542 ~This GDB was configured as
32543 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32548 @subheading The @code{-list-thread-groups} Command
32549 @findex -list-thread-groups
32551 @subheading Synopsis
32554 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32557 Lists thread groups (@pxref{Thread groups}). When a single thread
32558 group is passed as the argument, lists the children of that group.
32559 When several thread group are passed, lists information about those
32560 thread groups. Without any parameters, lists information about all
32561 top-level thread groups.
32563 Normally, thread groups that are being debugged are reported.
32564 With the @samp{--available} option, @value{GDBN} reports thread groups
32565 available on the target.
32567 The output of this command may have either a @samp{threads} result or
32568 a @samp{groups} result. The @samp{thread} result has a list of tuples
32569 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32570 Information}). The @samp{groups} result has a list of tuples as value,
32571 each tuple describing a thread group. If top-level groups are
32572 requested (that is, no parameter is passed), or when several groups
32573 are passed, the output always has a @samp{groups} result. The format
32574 of the @samp{group} result is described below.
32576 To reduce the number of roundtrips it's possible to list thread groups
32577 together with their children, by passing the @samp{--recurse} option
32578 and the recursion depth. Presently, only recursion depth of 1 is
32579 permitted. If this option is present, then every reported thread group
32580 will also include its children, either as @samp{group} or
32581 @samp{threads} field.
32583 In general, any combination of option and parameters is permitted, with
32584 the following caveats:
32588 When a single thread group is passed, the output will typically
32589 be the @samp{threads} result. Because threads may not contain
32590 anything, the @samp{recurse} option will be ignored.
32593 When the @samp{--available} option is passed, limited information may
32594 be available. In particular, the list of threads of a process might
32595 be inaccessible. Further, specifying specific thread groups might
32596 not give any performance advantage over listing all thread groups.
32597 The frontend should assume that @samp{-list-thread-groups --available}
32598 is always an expensive operation and cache the results.
32602 The @samp{groups} result is a list of tuples, where each tuple may
32603 have the following fields:
32607 Identifier of the thread group. This field is always present.
32608 The identifier is an opaque string; frontends should not try to
32609 convert it to an integer, even though it might look like one.
32612 The type of the thread group. At present, only @samp{process} is a
32616 The target-specific process identifier. This field is only present
32617 for thread groups of type @samp{process} and only if the process exists.
32620 The exit code of this group's last exited thread, formatted in octal.
32621 This field is only present for thread groups of type @samp{process} and
32622 only if the process is not running.
32625 The number of children this thread group has. This field may be
32626 absent for an available thread group.
32629 This field has a list of tuples as value, each tuple describing a
32630 thread. It may be present if the @samp{--recurse} option is
32631 specified, and it's actually possible to obtain the threads.
32634 This field is a list of integers, each identifying a core that one
32635 thread of the group is running on. This field may be absent if
32636 such information is not available.
32639 The name of the executable file that corresponds to this thread group.
32640 The field is only present for thread groups of type @samp{process},
32641 and only if there is a corresponding executable file.
32645 @subheading Example
32649 -list-thread-groups
32650 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32651 -list-thread-groups 17
32652 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32653 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32654 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32655 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32656 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32657 -list-thread-groups --available
32658 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32659 -list-thread-groups --available --recurse 1
32660 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32661 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32662 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32663 -list-thread-groups --available --recurse 1 17 18
32664 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32665 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32666 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32669 @subheading The @code{-info-os} Command
32672 @subsubheading Synopsis
32675 -info-os [ @var{type} ]
32678 If no argument is supplied, the command returns a table of available
32679 operating-system-specific information types. If one of these types is
32680 supplied as an argument @var{type}, then the command returns a table
32681 of data of that type.
32683 The types of information available depend on the target operating
32686 @subsubheading @value{GDBN} Command
32688 The corresponding @value{GDBN} command is @samp{info os}.
32690 @subsubheading Example
32692 When run on a @sc{gnu}/Linux system, the output will look something
32698 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32699 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32700 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32701 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32702 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32704 item=@{col0="files",col1="Listing of all file descriptors",
32705 col2="File descriptors"@},
32706 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32707 col2="Kernel modules"@},
32708 item=@{col0="msg",col1="Listing of all message queues",
32709 col2="Message queues"@},
32710 item=@{col0="processes",col1="Listing of all processes",
32711 col2="Processes"@},
32712 item=@{col0="procgroups",col1="Listing of all process groups",
32713 col2="Process groups"@},
32714 item=@{col0="semaphores",col1="Listing of all semaphores",
32715 col2="Semaphores"@},
32716 item=@{col0="shm",col1="Listing of all shared-memory regions",
32717 col2="Shared-memory regions"@},
32718 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32720 item=@{col0="threads",col1="Listing of all threads",
32724 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32725 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32726 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32727 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32728 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32729 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32730 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32731 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32733 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32734 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32738 (Note that the MI output here includes a @code{"Title"} column that
32739 does not appear in command-line @code{info os}; this column is useful
32740 for MI clients that want to enumerate the types of data, such as in a
32741 popup menu, but is needless clutter on the command line, and
32742 @code{info os} omits it.)
32744 @subheading The @code{-add-inferior} Command
32745 @findex -add-inferior
32747 @subheading Synopsis
32753 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32754 inferior is not associated with any executable. Such association may
32755 be established with the @samp{-file-exec-and-symbols} command
32756 (@pxref{GDB/MI File Commands}). The command response has a single
32757 field, @samp{inferior}, whose value is the identifier of the
32758 thread group corresponding to the new inferior.
32760 @subheading Example
32765 ^done,inferior="i3"
32768 @subheading The @code{-interpreter-exec} Command
32769 @findex -interpreter-exec
32771 @subheading Synopsis
32774 -interpreter-exec @var{interpreter} @var{command}
32776 @anchor{-interpreter-exec}
32778 Execute the specified @var{command} in the given @var{interpreter}.
32780 @subheading @value{GDBN} Command
32782 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32784 @subheading Example
32788 -interpreter-exec console "break main"
32789 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32790 &"During symbol reading, bad structure-type format.\n"
32791 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32796 @subheading The @code{-inferior-tty-set} Command
32797 @findex -inferior-tty-set
32799 @subheading Synopsis
32802 -inferior-tty-set /dev/pts/1
32805 Set terminal for future runs of the program being debugged.
32807 @subheading @value{GDBN} Command
32809 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32811 @subheading Example
32815 -inferior-tty-set /dev/pts/1
32820 @subheading The @code{-inferior-tty-show} Command
32821 @findex -inferior-tty-show
32823 @subheading Synopsis
32829 Show terminal for future runs of program being debugged.
32831 @subheading @value{GDBN} Command
32833 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32835 @subheading Example
32839 -inferior-tty-set /dev/pts/1
32843 ^done,inferior_tty_terminal="/dev/pts/1"
32847 @subheading The @code{-enable-timings} Command
32848 @findex -enable-timings
32850 @subheading Synopsis
32853 -enable-timings [yes | no]
32856 Toggle the printing of the wallclock, user and system times for an MI
32857 command as a field in its output. This command is to help frontend
32858 developers optimize the performance of their code. No argument is
32859 equivalent to @samp{yes}.
32861 @subheading @value{GDBN} Command
32865 @subheading Example
32873 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32874 addr="0x080484ed",func="main",file="myprog.c",
32875 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32877 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32885 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32886 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32887 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32888 fullname="/home/nickrob/myprog.c",line="73"@}
32893 @chapter @value{GDBN} Annotations
32895 This chapter describes annotations in @value{GDBN}. Annotations were
32896 designed to interface @value{GDBN} to graphical user interfaces or other
32897 similar programs which want to interact with @value{GDBN} at a
32898 relatively high level.
32900 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32904 This is Edition @value{EDITION}, @value{DATE}.
32908 * Annotations Overview:: What annotations are; the general syntax.
32909 * Server Prefix:: Issuing a command without affecting user state.
32910 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32911 * Errors:: Annotations for error messages.
32912 * Invalidation:: Some annotations describe things now invalid.
32913 * Annotations for Running::
32914 Whether the program is running, how it stopped, etc.
32915 * Source Annotations:: Annotations describing source code.
32918 @node Annotations Overview
32919 @section What is an Annotation?
32920 @cindex annotations
32922 Annotations start with a newline character, two @samp{control-z}
32923 characters, and the name of the annotation. If there is no additional
32924 information associated with this annotation, the name of the annotation
32925 is followed immediately by a newline. If there is additional
32926 information, the name of the annotation is followed by a space, the
32927 additional information, and a newline. The additional information
32928 cannot contain newline characters.
32930 Any output not beginning with a newline and two @samp{control-z}
32931 characters denotes literal output from @value{GDBN}. Currently there is
32932 no need for @value{GDBN} to output a newline followed by two
32933 @samp{control-z} characters, but if there was such a need, the
32934 annotations could be extended with an @samp{escape} annotation which
32935 means those three characters as output.
32937 The annotation @var{level}, which is specified using the
32938 @option{--annotate} command line option (@pxref{Mode Options}), controls
32939 how much information @value{GDBN} prints together with its prompt,
32940 values of expressions, source lines, and other types of output. Level 0
32941 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32942 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32943 for programs that control @value{GDBN}, and level 2 annotations have
32944 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32945 Interface, annotate, GDB's Obsolete Annotations}).
32948 @kindex set annotate
32949 @item set annotate @var{level}
32950 The @value{GDBN} command @code{set annotate} sets the level of
32951 annotations to the specified @var{level}.
32953 @item show annotate
32954 @kindex show annotate
32955 Show the current annotation level.
32958 This chapter describes level 3 annotations.
32960 A simple example of starting up @value{GDBN} with annotations is:
32963 $ @kbd{gdb --annotate=3}
32965 Copyright 2003 Free Software Foundation, Inc.
32966 GDB is free software, covered by the GNU General Public License,
32967 and you are welcome to change it and/or distribute copies of it
32968 under certain conditions.
32969 Type "show copying" to see the conditions.
32970 There is absolutely no warranty for GDB. Type "show warranty"
32972 This GDB was configured as "i386-pc-linux-gnu"
32983 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32984 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32985 denotes a @samp{control-z} character) are annotations; the rest is
32986 output from @value{GDBN}.
32988 @node Server Prefix
32989 @section The Server Prefix
32990 @cindex server prefix
32992 If you prefix a command with @samp{server } then it will not affect
32993 the command history, nor will it affect @value{GDBN}'s notion of which
32994 command to repeat if @key{RET} is pressed on a line by itself. This
32995 means that commands can be run behind a user's back by a front-end in
32996 a transparent manner.
32998 The @code{server } prefix does not affect the recording of values into
32999 the value history; to print a value without recording it into the
33000 value history, use the @code{output} command instead of the
33001 @code{print} command.
33003 Using this prefix also disables confirmation requests
33004 (@pxref{confirmation requests}).
33007 @section Annotation for @value{GDBN} Input
33009 @cindex annotations for prompts
33010 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33011 to know when to send output, when the output from a given command is
33014 Different kinds of input each have a different @dfn{input type}. Each
33015 input type has three annotations: a @code{pre-} annotation, which
33016 denotes the beginning of any prompt which is being output, a plain
33017 annotation, which denotes the end of the prompt, and then a @code{post-}
33018 annotation which denotes the end of any echo which may (or may not) be
33019 associated with the input. For example, the @code{prompt} input type
33020 features the following annotations:
33028 The input types are
33031 @findex pre-prompt annotation
33032 @findex prompt annotation
33033 @findex post-prompt annotation
33035 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33037 @findex pre-commands annotation
33038 @findex commands annotation
33039 @findex post-commands annotation
33041 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33042 command. The annotations are repeated for each command which is input.
33044 @findex pre-overload-choice annotation
33045 @findex overload-choice annotation
33046 @findex post-overload-choice annotation
33047 @item overload-choice
33048 When @value{GDBN} wants the user to select between various overloaded functions.
33050 @findex pre-query annotation
33051 @findex query annotation
33052 @findex post-query annotation
33054 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33056 @findex pre-prompt-for-continue annotation
33057 @findex prompt-for-continue annotation
33058 @findex post-prompt-for-continue annotation
33059 @item prompt-for-continue
33060 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33061 expect this to work well; instead use @code{set height 0} to disable
33062 prompting. This is because the counting of lines is buggy in the
33063 presence of annotations.
33068 @cindex annotations for errors, warnings and interrupts
33070 @findex quit annotation
33075 This annotation occurs right before @value{GDBN} responds to an interrupt.
33077 @findex error annotation
33082 This annotation occurs right before @value{GDBN} responds to an error.
33084 Quit and error annotations indicate that any annotations which @value{GDBN} was
33085 in the middle of may end abruptly. For example, if a
33086 @code{value-history-begin} annotation is followed by a @code{error}, one
33087 cannot expect to receive the matching @code{value-history-end}. One
33088 cannot expect not to receive it either, however; an error annotation
33089 does not necessarily mean that @value{GDBN} is immediately returning all the way
33092 @findex error-begin annotation
33093 A quit or error annotation may be preceded by
33099 Any output between that and the quit or error annotation is the error
33102 Warning messages are not yet annotated.
33103 @c If we want to change that, need to fix warning(), type_error(),
33104 @c range_error(), and possibly other places.
33107 @section Invalidation Notices
33109 @cindex annotations for invalidation messages
33110 The following annotations say that certain pieces of state may have
33114 @findex frames-invalid annotation
33115 @item ^Z^Zframes-invalid
33117 The frames (for example, output from the @code{backtrace} command) may
33120 @findex breakpoints-invalid annotation
33121 @item ^Z^Zbreakpoints-invalid
33123 The breakpoints may have changed. For example, the user just added or
33124 deleted a breakpoint.
33127 @node Annotations for Running
33128 @section Running the Program
33129 @cindex annotations for running programs
33131 @findex starting annotation
33132 @findex stopping annotation
33133 When the program starts executing due to a @value{GDBN} command such as
33134 @code{step} or @code{continue},
33140 is output. When the program stops,
33146 is output. Before the @code{stopped} annotation, a variety of
33147 annotations describe how the program stopped.
33150 @findex exited annotation
33151 @item ^Z^Zexited @var{exit-status}
33152 The program exited, and @var{exit-status} is the exit status (zero for
33153 successful exit, otherwise nonzero).
33155 @findex signalled annotation
33156 @findex signal-name annotation
33157 @findex signal-name-end annotation
33158 @findex signal-string annotation
33159 @findex signal-string-end annotation
33160 @item ^Z^Zsignalled
33161 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33162 annotation continues:
33168 ^Z^Zsignal-name-end
33172 ^Z^Zsignal-string-end
33177 where @var{name} is the name of the signal, such as @code{SIGILL} or
33178 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33179 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33180 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33181 user's benefit and have no particular format.
33183 @findex signal annotation
33185 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33186 just saying that the program received the signal, not that it was
33187 terminated with it.
33189 @findex breakpoint annotation
33190 @item ^Z^Zbreakpoint @var{number}
33191 The program hit breakpoint number @var{number}.
33193 @findex watchpoint annotation
33194 @item ^Z^Zwatchpoint @var{number}
33195 The program hit watchpoint number @var{number}.
33198 @node Source Annotations
33199 @section Displaying Source
33200 @cindex annotations for source display
33202 @findex source annotation
33203 The following annotation is used instead of displaying source code:
33206 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33209 where @var{filename} is an absolute file name indicating which source
33210 file, @var{line} is the line number within that file (where 1 is the
33211 first line in the file), @var{character} is the character position
33212 within the file (where 0 is the first character in the file) (for most
33213 debug formats this will necessarily point to the beginning of a line),
33214 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33215 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33216 @var{addr} is the address in the target program associated with the
33217 source which is being displayed. The @var{addr} is in the form @samp{0x}
33218 followed by one or more lowercase hex digits (note that this does not
33219 depend on the language).
33221 @node JIT Interface
33222 @chapter JIT Compilation Interface
33223 @cindex just-in-time compilation
33224 @cindex JIT compilation interface
33226 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33227 interface. A JIT compiler is a program or library that generates native
33228 executable code at runtime and executes it, usually in order to achieve good
33229 performance while maintaining platform independence.
33231 Programs that use JIT compilation are normally difficult to debug because
33232 portions of their code are generated at runtime, instead of being loaded from
33233 object files, which is where @value{GDBN} normally finds the program's symbols
33234 and debug information. In order to debug programs that use JIT compilation,
33235 @value{GDBN} has an interface that allows the program to register in-memory
33236 symbol files with @value{GDBN} at runtime.
33238 If you are using @value{GDBN} to debug a program that uses this interface, then
33239 it should work transparently so long as you have not stripped the binary. If
33240 you are developing a JIT compiler, then the interface is documented in the rest
33241 of this chapter. At this time, the only known client of this interface is the
33244 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33245 JIT compiler communicates with @value{GDBN} by writing data into a global
33246 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33247 attaches, it reads a linked list of symbol files from the global variable to
33248 find existing code, and puts a breakpoint in the function so that it can find
33249 out about additional code.
33252 * Declarations:: Relevant C struct declarations
33253 * Registering Code:: Steps to register code
33254 * Unregistering Code:: Steps to unregister code
33255 * Custom Debug Info:: Emit debug information in a custom format
33259 @section JIT Declarations
33261 These are the relevant struct declarations that a C program should include to
33262 implement the interface:
33272 struct jit_code_entry
33274 struct jit_code_entry *next_entry;
33275 struct jit_code_entry *prev_entry;
33276 const char *symfile_addr;
33277 uint64_t symfile_size;
33280 struct jit_descriptor
33283 /* This type should be jit_actions_t, but we use uint32_t
33284 to be explicit about the bitwidth. */
33285 uint32_t action_flag;
33286 struct jit_code_entry *relevant_entry;
33287 struct jit_code_entry *first_entry;
33290 /* GDB puts a breakpoint in this function. */
33291 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33293 /* Make sure to specify the version statically, because the
33294 debugger may check the version before we can set it. */
33295 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33298 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33299 modifications to this global data properly, which can easily be done by putting
33300 a global mutex around modifications to these structures.
33302 @node Registering Code
33303 @section Registering Code
33305 To register code with @value{GDBN}, the JIT should follow this protocol:
33309 Generate an object file in memory with symbols and other desired debug
33310 information. The file must include the virtual addresses of the sections.
33313 Create a code entry for the file, which gives the start and size of the symbol
33317 Add it to the linked list in the JIT descriptor.
33320 Point the relevant_entry field of the descriptor at the entry.
33323 Set @code{action_flag} to @code{JIT_REGISTER} and call
33324 @code{__jit_debug_register_code}.
33327 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33328 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33329 new code. However, the linked list must still be maintained in order to allow
33330 @value{GDBN} to attach to a running process and still find the symbol files.
33332 @node Unregistering Code
33333 @section Unregistering Code
33335 If code is freed, then the JIT should use the following protocol:
33339 Remove the code entry corresponding to the code from the linked list.
33342 Point the @code{relevant_entry} field of the descriptor at the code entry.
33345 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33346 @code{__jit_debug_register_code}.
33349 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33350 and the JIT will leak the memory used for the associated symbol files.
33352 @node Custom Debug Info
33353 @section Custom Debug Info
33354 @cindex custom JIT debug info
33355 @cindex JIT debug info reader
33357 Generating debug information in platform-native file formats (like ELF
33358 or COFF) may be an overkill for JIT compilers; especially if all the
33359 debug info is used for is displaying a meaningful backtrace. The
33360 issue can be resolved by having the JIT writers decide on a debug info
33361 format and also provide a reader that parses the debug info generated
33362 by the JIT compiler. This section gives a brief overview on writing
33363 such a parser. More specific details can be found in the source file
33364 @file{gdb/jit-reader.in}, which is also installed as a header at
33365 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33367 The reader is implemented as a shared object (so this functionality is
33368 not available on platforms which don't allow loading shared objects at
33369 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33370 @code{jit-reader-unload} are provided, to be used to load and unload
33371 the readers from a preconfigured directory. Once loaded, the shared
33372 object is used the parse the debug information emitted by the JIT
33376 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33377 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33380 @node Using JIT Debug Info Readers
33381 @subsection Using JIT Debug Info Readers
33382 @kindex jit-reader-load
33383 @kindex jit-reader-unload
33385 Readers can be loaded and unloaded using the @code{jit-reader-load}
33386 and @code{jit-reader-unload} commands.
33389 @item jit-reader-load @var{reader}
33390 Load the JIT reader named @var{reader}, which is a shared
33391 object specified as either an absolute or a relative file name. In
33392 the latter case, @value{GDBN} will try to load the reader from a
33393 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33394 system (here @var{libdir} is the system library directory, often
33395 @file{/usr/local/lib}).
33397 Only one reader can be active at a time; trying to load a second
33398 reader when one is already loaded will result in @value{GDBN}
33399 reporting an error. A new JIT reader can be loaded by first unloading
33400 the current one using @code{jit-reader-unload} and then invoking
33401 @code{jit-reader-load}.
33403 @item jit-reader-unload
33404 Unload the currently loaded JIT reader.
33408 @node Writing JIT Debug Info Readers
33409 @subsection Writing JIT Debug Info Readers
33410 @cindex writing JIT debug info readers
33412 As mentioned, a reader is essentially a shared object conforming to a
33413 certain ABI. This ABI is described in @file{jit-reader.h}.
33415 @file{jit-reader.h} defines the structures, macros and functions
33416 required to write a reader. It is installed (along with
33417 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33418 the system include directory.
33420 Readers need to be released under a GPL compatible license. A reader
33421 can be declared as released under such a license by placing the macro
33422 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33424 The entry point for readers is the symbol @code{gdb_init_reader},
33425 which is expected to be a function with the prototype
33427 @findex gdb_init_reader
33429 extern struct gdb_reader_funcs *gdb_init_reader (void);
33432 @cindex @code{struct gdb_reader_funcs}
33434 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33435 functions. These functions are executed to read the debug info
33436 generated by the JIT compiler (@code{read}), to unwind stack frames
33437 (@code{unwind}) and to create canonical frame IDs
33438 (@code{get_Frame_id}). It also has a callback that is called when the
33439 reader is being unloaded (@code{destroy}). The struct looks like this
33442 struct gdb_reader_funcs
33444 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33445 int reader_version;
33447 /* For use by the reader. */
33450 gdb_read_debug_info *read;
33451 gdb_unwind_frame *unwind;
33452 gdb_get_frame_id *get_frame_id;
33453 gdb_destroy_reader *destroy;
33457 @cindex @code{struct gdb_symbol_callbacks}
33458 @cindex @code{struct gdb_unwind_callbacks}
33460 The callbacks are provided with another set of callbacks by
33461 @value{GDBN} to do their job. For @code{read}, these callbacks are
33462 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33463 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33464 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33465 files and new symbol tables inside those object files. @code{struct
33466 gdb_unwind_callbacks} has callbacks to read registers off the current
33467 frame and to write out the values of the registers in the previous
33468 frame. Both have a callback (@code{target_read}) to read bytes off the
33469 target's address space.
33471 @node In-Process Agent
33472 @chapter In-Process Agent
33473 @cindex debugging agent
33474 The traditional debugging model is conceptually low-speed, but works fine,
33475 because most bugs can be reproduced in debugging-mode execution. However,
33476 as multi-core or many-core processors are becoming mainstream, and
33477 multi-threaded programs become more and more popular, there should be more
33478 and more bugs that only manifest themselves at normal-mode execution, for
33479 example, thread races, because debugger's interference with the program's
33480 timing may conceal the bugs. On the other hand, in some applications,
33481 it is not feasible for the debugger to interrupt the program's execution
33482 long enough for the developer to learn anything helpful about its behavior.
33483 If the program's correctness depends on its real-time behavior, delays
33484 introduced by a debugger might cause the program to fail, even when the
33485 code itself is correct. It is useful to be able to observe the program's
33486 behavior without interrupting it.
33488 Therefore, traditional debugging model is too intrusive to reproduce
33489 some bugs. In order to reduce the interference with the program, we can
33490 reduce the number of operations performed by debugger. The
33491 @dfn{In-Process Agent}, a shared library, is running within the same
33492 process with inferior, and is able to perform some debugging operations
33493 itself. As a result, debugger is only involved when necessary, and
33494 performance of debugging can be improved accordingly. Note that
33495 interference with program can be reduced but can't be removed completely,
33496 because the in-process agent will still stop or slow down the program.
33498 The in-process agent can interpret and execute Agent Expressions
33499 (@pxref{Agent Expressions}) during performing debugging operations. The
33500 agent expressions can be used for different purposes, such as collecting
33501 data in tracepoints, and condition evaluation in breakpoints.
33503 @anchor{Control Agent}
33504 You can control whether the in-process agent is used as an aid for
33505 debugging with the following commands:
33508 @kindex set agent on
33510 Causes the in-process agent to perform some operations on behalf of the
33511 debugger. Just which operations requested by the user will be done
33512 by the in-process agent depends on the its capabilities. For example,
33513 if you request to evaluate breakpoint conditions in the in-process agent,
33514 and the in-process agent has such capability as well, then breakpoint
33515 conditions will be evaluated in the in-process agent.
33517 @kindex set agent off
33518 @item set agent off
33519 Disables execution of debugging operations by the in-process agent. All
33520 of the operations will be performed by @value{GDBN}.
33524 Display the current setting of execution of debugging operations by
33525 the in-process agent.
33529 * In-Process Agent Protocol::
33532 @node In-Process Agent Protocol
33533 @section In-Process Agent Protocol
33534 @cindex in-process agent protocol
33536 The in-process agent is able to communicate with both @value{GDBN} and
33537 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33538 used for communications between @value{GDBN} or GDBserver and the IPA.
33539 In general, @value{GDBN} or GDBserver sends commands
33540 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33541 in-process agent replies back with the return result of the command, or
33542 some other information. The data sent to in-process agent is composed
33543 of primitive data types, such as 4-byte or 8-byte type, and composite
33544 types, which are called objects (@pxref{IPA Protocol Objects}).
33547 * IPA Protocol Objects::
33548 * IPA Protocol Commands::
33551 @node IPA Protocol Objects
33552 @subsection IPA Protocol Objects
33553 @cindex ipa protocol objects
33555 The commands sent to and results received from agent may contain some
33556 complex data types called @dfn{objects}.
33558 The in-process agent is running on the same machine with @value{GDBN}
33559 or GDBserver, so it doesn't have to handle as much differences between
33560 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33561 However, there are still some differences of two ends in two processes:
33565 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33566 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33568 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33569 GDBserver is compiled with one, and in-process agent is compiled with
33573 Here are the IPA Protocol Objects:
33577 agent expression object. It represents an agent expression
33578 (@pxref{Agent Expressions}).
33579 @anchor{agent expression object}
33581 tracepoint action object. It represents a tracepoint action
33582 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33583 memory, static trace data and to evaluate expression.
33584 @anchor{tracepoint action object}
33586 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33587 @anchor{tracepoint object}
33591 The following table describes important attributes of each IPA protocol
33594 @multitable @columnfractions .30 .20 .50
33595 @headitem Name @tab Size @tab Description
33596 @item @emph{agent expression object} @tab @tab
33597 @item length @tab 4 @tab length of bytes code
33598 @item byte code @tab @var{length} @tab contents of byte code
33599 @item @emph{tracepoint action for collecting memory} @tab @tab
33600 @item 'M' @tab 1 @tab type of tracepoint action
33601 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33602 address of the lowest byte to collect, otherwise @var{addr} is the offset
33603 of @var{basereg} for memory collecting.
33604 @item len @tab 8 @tab length of memory for collecting
33605 @item basereg @tab 4 @tab the register number containing the starting
33606 memory address for collecting.
33607 @item @emph{tracepoint action for collecting registers} @tab @tab
33608 @item 'R' @tab 1 @tab type of tracepoint action
33609 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33610 @item 'L' @tab 1 @tab type of tracepoint action
33611 @item @emph{tracepoint action for expression evaluation} @tab @tab
33612 @item 'X' @tab 1 @tab type of tracepoint action
33613 @item agent expression @tab length of @tab @ref{agent expression object}
33614 @item @emph{tracepoint object} @tab @tab
33615 @item number @tab 4 @tab number of tracepoint
33616 @item address @tab 8 @tab address of tracepoint inserted on
33617 @item type @tab 4 @tab type of tracepoint
33618 @item enabled @tab 1 @tab enable or disable of tracepoint
33619 @item step_count @tab 8 @tab step
33620 @item pass_count @tab 8 @tab pass
33621 @item numactions @tab 4 @tab number of tracepoint actions
33622 @item hit count @tab 8 @tab hit count
33623 @item trace frame usage @tab 8 @tab trace frame usage
33624 @item compiled_cond @tab 8 @tab compiled condition
33625 @item orig_size @tab 8 @tab orig size
33626 @item condition @tab 4 if condition is NULL otherwise length of
33627 @ref{agent expression object}
33628 @tab zero if condition is NULL, otherwise is
33629 @ref{agent expression object}
33630 @item actions @tab variable
33631 @tab numactions number of @ref{tracepoint action object}
33634 @node IPA Protocol Commands
33635 @subsection IPA Protocol Commands
33636 @cindex ipa protocol commands
33638 The spaces in each command are delimiters to ease reading this commands
33639 specification. They don't exist in real commands.
33643 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33644 Installs a new fast tracepoint described by @var{tracepoint_object}
33645 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33646 head of @dfn{jumppad}, which is used to jump to data collection routine
33651 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33652 @var{target_address} is address of tracepoint in the inferior.
33653 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33654 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33655 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33656 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33663 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33664 is about to kill inferiors.
33672 @item probe_marker_at:@var{address}
33673 Asks in-process agent to probe the marker at @var{address}.
33680 @item unprobe_marker_at:@var{address}
33681 Asks in-process agent to unprobe the marker at @var{address}.
33685 @chapter Reporting Bugs in @value{GDBN}
33686 @cindex bugs in @value{GDBN}
33687 @cindex reporting bugs in @value{GDBN}
33689 Your bug reports play an essential role in making @value{GDBN} reliable.
33691 Reporting a bug may help you by bringing a solution to your problem, or it
33692 may not. But in any case the principal function of a bug report is to help
33693 the entire community by making the next version of @value{GDBN} work better. Bug
33694 reports are your contribution to the maintenance of @value{GDBN}.
33696 In order for a bug report to serve its purpose, you must include the
33697 information that enables us to fix the bug.
33700 * Bug Criteria:: Have you found a bug?
33701 * Bug Reporting:: How to report bugs
33705 @section Have You Found a Bug?
33706 @cindex bug criteria
33708 If you are not sure whether you have found a bug, here are some guidelines:
33711 @cindex fatal signal
33712 @cindex debugger crash
33713 @cindex crash of debugger
33715 If the debugger gets a fatal signal, for any input whatever, that is a
33716 @value{GDBN} bug. Reliable debuggers never crash.
33718 @cindex error on valid input
33720 If @value{GDBN} produces an error message for valid input, that is a
33721 bug. (Note that if you're cross debugging, the problem may also be
33722 somewhere in the connection to the target.)
33724 @cindex invalid input
33726 If @value{GDBN} does not produce an error message for invalid input,
33727 that is a bug. However, you should note that your idea of
33728 ``invalid input'' might be our idea of ``an extension'' or ``support
33729 for traditional practice''.
33732 If you are an experienced user of debugging tools, your suggestions
33733 for improvement of @value{GDBN} are welcome in any case.
33736 @node Bug Reporting
33737 @section How to Report Bugs
33738 @cindex bug reports
33739 @cindex @value{GDBN} bugs, reporting
33741 A number of companies and individuals offer support for @sc{gnu} products.
33742 If you obtained @value{GDBN} from a support organization, we recommend you
33743 contact that organization first.
33745 You can find contact information for many support companies and
33746 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33748 @c should add a web page ref...
33751 @ifset BUGURL_DEFAULT
33752 In any event, we also recommend that you submit bug reports for
33753 @value{GDBN}. The preferred method is to submit them directly using
33754 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33755 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33758 @strong{Do not send bug reports to @samp{info-gdb}, or to
33759 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33760 not want to receive bug reports. Those that do have arranged to receive
33763 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33764 serves as a repeater. The mailing list and the newsgroup carry exactly
33765 the same messages. Often people think of posting bug reports to the
33766 newsgroup instead of mailing them. This appears to work, but it has one
33767 problem which can be crucial: a newsgroup posting often lacks a mail
33768 path back to the sender. Thus, if we need to ask for more information,
33769 we may be unable to reach you. For this reason, it is better to send
33770 bug reports to the mailing list.
33772 @ifclear BUGURL_DEFAULT
33773 In any event, we also recommend that you submit bug reports for
33774 @value{GDBN} to @value{BUGURL}.
33778 The fundamental principle of reporting bugs usefully is this:
33779 @strong{report all the facts}. If you are not sure whether to state a
33780 fact or leave it out, state it!
33782 Often people omit facts because they think they know what causes the
33783 problem and assume that some details do not matter. Thus, you might
33784 assume that the name of the variable you use in an example does not matter.
33785 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33786 stray memory reference which happens to fetch from the location where that
33787 name is stored in memory; perhaps, if the name were different, the contents
33788 of that location would fool the debugger into doing the right thing despite
33789 the bug. Play it safe and give a specific, complete example. That is the
33790 easiest thing for you to do, and the most helpful.
33792 Keep in mind that the purpose of a bug report is to enable us to fix the
33793 bug. It may be that the bug has been reported previously, but neither
33794 you nor we can know that unless your bug report is complete and
33797 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33798 bell?'' Those bug reports are useless, and we urge everyone to
33799 @emph{refuse to respond to them} except to chide the sender to report
33802 To enable us to fix the bug, you should include all these things:
33806 The version of @value{GDBN}. @value{GDBN} announces it if you start
33807 with no arguments; you can also print it at any time using @code{show
33810 Without this, we will not know whether there is any point in looking for
33811 the bug in the current version of @value{GDBN}.
33814 The type of machine you are using, and the operating system name and
33818 The details of the @value{GDBN} build-time configuration.
33819 @value{GDBN} shows these details if you invoke it with the
33820 @option{--configuration} command-line option, or if you type
33821 @code{show configuration} at @value{GDBN}'s prompt.
33824 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33825 ``@value{GCC}--2.8.1''.
33828 What compiler (and its version) was used to compile the program you are
33829 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33830 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33831 to get this information; for other compilers, see the documentation for
33835 The command arguments you gave the compiler to compile your example and
33836 observe the bug. For example, did you use @samp{-O}? To guarantee
33837 you will not omit something important, list them all. A copy of the
33838 Makefile (or the output from make) is sufficient.
33840 If we were to try to guess the arguments, we would probably guess wrong
33841 and then we might not encounter the bug.
33844 A complete input script, and all necessary source files, that will
33848 A description of what behavior you observe that you believe is
33849 incorrect. For example, ``It gets a fatal signal.''
33851 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33852 will certainly notice it. But if the bug is incorrect output, we might
33853 not notice unless it is glaringly wrong. You might as well not give us
33854 a chance to make a mistake.
33856 Even if the problem you experience is a fatal signal, you should still
33857 say so explicitly. Suppose something strange is going on, such as, your
33858 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33859 the C library on your system. (This has happened!) Your copy might
33860 crash and ours would not. If you told us to expect a crash, then when
33861 ours fails to crash, we would know that the bug was not happening for
33862 us. If you had not told us to expect a crash, then we would not be able
33863 to draw any conclusion from our observations.
33866 @cindex recording a session script
33867 To collect all this information, you can use a session recording program
33868 such as @command{script}, which is available on many Unix systems.
33869 Just run your @value{GDBN} session inside @command{script} and then
33870 include the @file{typescript} file with your bug report.
33872 Another way to record a @value{GDBN} session is to run @value{GDBN}
33873 inside Emacs and then save the entire buffer to a file.
33876 If you wish to suggest changes to the @value{GDBN} source, send us context
33877 diffs. If you even discuss something in the @value{GDBN} source, refer to
33878 it by context, not by line number.
33880 The line numbers in our development sources will not match those in your
33881 sources. Your line numbers would convey no useful information to us.
33885 Here are some things that are not necessary:
33889 A description of the envelope of the bug.
33891 Often people who encounter a bug spend a lot of time investigating
33892 which changes to the input file will make the bug go away and which
33893 changes will not affect it.
33895 This is often time consuming and not very useful, because the way we
33896 will find the bug is by running a single example under the debugger
33897 with breakpoints, not by pure deduction from a series of examples.
33898 We recommend that you save your time for something else.
33900 Of course, if you can find a simpler example to report @emph{instead}
33901 of the original one, that is a convenience for us. Errors in the
33902 output will be easier to spot, running under the debugger will take
33903 less time, and so on.
33905 However, simplification is not vital; if you do not want to do this,
33906 report the bug anyway and send us the entire test case you used.
33909 A patch for the bug.
33911 A patch for the bug does help us if it is a good one. But do not omit
33912 the necessary information, such as the test case, on the assumption that
33913 a patch is all we need. We might see problems with your patch and decide
33914 to fix the problem another way, or we might not understand it at all.
33916 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33917 construct an example that will make the program follow a certain path
33918 through the code. If you do not send us the example, we will not be able
33919 to construct one, so we will not be able to verify that the bug is fixed.
33921 And if we cannot understand what bug you are trying to fix, or why your
33922 patch should be an improvement, we will not install it. A test case will
33923 help us to understand.
33926 A guess about what the bug is or what it depends on.
33928 Such guesses are usually wrong. Even we cannot guess right about such
33929 things without first using the debugger to find the facts.
33932 @c The readline documentation is distributed with the readline code
33933 @c and consists of the two following files:
33936 @c Use -I with makeinfo to point to the appropriate directory,
33937 @c environment var TEXINPUTS with TeX.
33938 @ifclear SYSTEM_READLINE
33939 @include rluser.texi
33940 @include hsuser.texi
33944 @appendix In Memoriam
33946 The @value{GDBN} project mourns the loss of the following long-time
33951 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33952 to Free Software in general. Outside of @value{GDBN}, he was known in
33953 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33955 @item Michael Snyder
33956 Michael was one of the Global Maintainers of the @value{GDBN} project,
33957 with contributions recorded as early as 1996, until 2011. In addition
33958 to his day to day participation, he was a large driving force behind
33959 adding Reverse Debugging to @value{GDBN}.
33962 Beyond their technical contributions to the project, they were also
33963 enjoyable members of the Free Software Community. We will miss them.
33965 @node Formatting Documentation
33966 @appendix Formatting Documentation
33968 @cindex @value{GDBN} reference card
33969 @cindex reference card
33970 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33971 for printing with PostScript or Ghostscript, in the @file{gdb}
33972 subdirectory of the main source directory@footnote{In
33973 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33974 release.}. If you can use PostScript or Ghostscript with your printer,
33975 you can print the reference card immediately with @file{refcard.ps}.
33977 The release also includes the source for the reference card. You
33978 can format it, using @TeX{}, by typing:
33984 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33985 mode on US ``letter'' size paper;
33986 that is, on a sheet 11 inches wide by 8.5 inches
33987 high. You will need to specify this form of printing as an option to
33988 your @sc{dvi} output program.
33990 @cindex documentation
33992 All the documentation for @value{GDBN} comes as part of the machine-readable
33993 distribution. The documentation is written in Texinfo format, which is
33994 a documentation system that uses a single source file to produce both
33995 on-line information and a printed manual. You can use one of the Info
33996 formatting commands to create the on-line version of the documentation
33997 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33999 @value{GDBN} includes an already formatted copy of the on-line Info
34000 version of this manual in the @file{gdb} subdirectory. The main Info
34001 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34002 subordinate files matching @samp{gdb.info*} in the same directory. If
34003 necessary, you can print out these files, or read them with any editor;
34004 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34005 Emacs or the standalone @code{info} program, available as part of the
34006 @sc{gnu} Texinfo distribution.
34008 If you want to format these Info files yourself, you need one of the
34009 Info formatting programs, such as @code{texinfo-format-buffer} or
34012 If you have @code{makeinfo} installed, and are in the top level
34013 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34014 version @value{GDBVN}), you can make the Info file by typing:
34021 If you want to typeset and print copies of this manual, you need @TeX{},
34022 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34023 Texinfo definitions file.
34025 @TeX{} is a typesetting program; it does not print files directly, but
34026 produces output files called @sc{dvi} files. To print a typeset
34027 document, you need a program to print @sc{dvi} files. If your system
34028 has @TeX{} installed, chances are it has such a program. The precise
34029 command to use depends on your system; @kbd{lpr -d} is common; another
34030 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34031 require a file name without any extension or a @samp{.dvi} extension.
34033 @TeX{} also requires a macro definitions file called
34034 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34035 written in Texinfo format. On its own, @TeX{} cannot either read or
34036 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34037 and is located in the @file{gdb-@var{version-number}/texinfo}
34040 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34041 typeset and print this manual. First switch to the @file{gdb}
34042 subdirectory of the main source directory (for example, to
34043 @file{gdb-@value{GDBVN}/gdb}) and type:
34049 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34051 @node Installing GDB
34052 @appendix Installing @value{GDBN}
34053 @cindex installation
34056 * Requirements:: Requirements for building @value{GDBN}
34057 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34058 * Separate Objdir:: Compiling @value{GDBN} in another directory
34059 * Config Names:: Specifying names for hosts and targets
34060 * Configure Options:: Summary of options for configure
34061 * System-wide configuration:: Having a system-wide init file
34065 @section Requirements for Building @value{GDBN}
34066 @cindex building @value{GDBN}, requirements for
34068 Building @value{GDBN} requires various tools and packages to be available.
34069 Other packages will be used only if they are found.
34071 @heading Tools/Packages Necessary for Building @value{GDBN}
34073 @item ISO C90 compiler
34074 @value{GDBN} is written in ISO C90. It should be buildable with any
34075 working C90 compiler, e.g.@: GCC.
34079 @heading Tools/Packages Optional for Building @value{GDBN}
34083 @value{GDBN} can use the Expat XML parsing library. This library may be
34084 included with your operating system distribution; if it is not, you
34085 can get the latest version from @url{http://expat.sourceforge.net}.
34086 The @file{configure} script will search for this library in several
34087 standard locations; if it is installed in an unusual path, you can
34088 use the @option{--with-libexpat-prefix} option to specify its location.
34094 Remote protocol memory maps (@pxref{Memory Map Format})
34096 Target descriptions (@pxref{Target Descriptions})
34098 Remote shared library lists (@xref{Library List Format},
34099 or alternatively @pxref{Library List Format for SVR4 Targets})
34101 MS-Windows shared libraries (@pxref{Shared Libraries})
34103 Traceframe info (@pxref{Traceframe Info Format})
34105 Branch trace (@pxref{Branch Trace Format},
34106 @pxref{Branch Trace Configuration Format})
34110 @cindex compressed debug sections
34111 @value{GDBN} will use the @samp{zlib} library, if available, to read
34112 compressed debug sections. Some linkers, such as GNU gold, are capable
34113 of producing binaries with compressed debug sections. If @value{GDBN}
34114 is compiled with @samp{zlib}, it will be able to read the debug
34115 information in such binaries.
34117 The @samp{zlib} library is likely included with your operating system
34118 distribution; if it is not, you can get the latest version from
34119 @url{http://zlib.net}.
34122 @value{GDBN}'s features related to character sets (@pxref{Character
34123 Sets}) require a functioning @code{iconv} implementation. If you are
34124 on a GNU system, then this is provided by the GNU C Library. Some
34125 other systems also provide a working @code{iconv}.
34127 If @value{GDBN} is using the @code{iconv} program which is installed
34128 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34129 This is done with @option{--with-iconv-bin} which specifies the
34130 directory that contains the @code{iconv} program.
34132 On systems without @code{iconv}, you can install GNU Libiconv. If you
34133 have previously installed Libiconv, you can use the
34134 @option{--with-libiconv-prefix} option to configure.
34136 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34137 arrange to build Libiconv if a directory named @file{libiconv} appears
34138 in the top-most source directory. If Libiconv is built this way, and
34139 if the operating system does not provide a suitable @code{iconv}
34140 implementation, then the just-built library will automatically be used
34141 by @value{GDBN}. One easy way to set this up is to download GNU
34142 Libiconv, unpack it, and then rename the directory holding the
34143 Libiconv source code to @samp{libiconv}.
34146 @node Running Configure
34147 @section Invoking the @value{GDBN} @file{configure} Script
34148 @cindex configuring @value{GDBN}
34149 @value{GDBN} comes with a @file{configure} script that automates the process
34150 of preparing @value{GDBN} for installation; you can then use @code{make} to
34151 build the @code{gdb} program.
34153 @c irrelevant in info file; it's as current as the code it lives with.
34154 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34155 look at the @file{README} file in the sources; we may have improved the
34156 installation procedures since publishing this manual.}
34159 The @value{GDBN} distribution includes all the source code you need for
34160 @value{GDBN} in a single directory, whose name is usually composed by
34161 appending the version number to @samp{gdb}.
34163 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34164 @file{gdb-@value{GDBVN}} directory. That directory contains:
34167 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34168 script for configuring @value{GDBN} and all its supporting libraries
34170 @item gdb-@value{GDBVN}/gdb
34171 the source specific to @value{GDBN} itself
34173 @item gdb-@value{GDBVN}/bfd
34174 source for the Binary File Descriptor library
34176 @item gdb-@value{GDBVN}/include
34177 @sc{gnu} include files
34179 @item gdb-@value{GDBVN}/libiberty
34180 source for the @samp{-liberty} free software library
34182 @item gdb-@value{GDBVN}/opcodes
34183 source for the library of opcode tables and disassemblers
34185 @item gdb-@value{GDBVN}/readline
34186 source for the @sc{gnu} command-line interface
34188 @item gdb-@value{GDBVN}/glob
34189 source for the @sc{gnu} filename pattern-matching subroutine
34191 @item gdb-@value{GDBVN}/mmalloc
34192 source for the @sc{gnu} memory-mapped malloc package
34195 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34196 from the @file{gdb-@var{version-number}} source directory, which in
34197 this example is the @file{gdb-@value{GDBVN}} directory.
34199 First switch to the @file{gdb-@var{version-number}} source directory
34200 if you are not already in it; then run @file{configure}. Pass the
34201 identifier for the platform on which @value{GDBN} will run as an
34207 cd gdb-@value{GDBVN}
34208 ./configure @var{host}
34213 where @var{host} is an identifier such as @samp{sun4} or
34214 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34215 (You can often leave off @var{host}; @file{configure} tries to guess the
34216 correct value by examining your system.)
34218 Running @samp{configure @var{host}} and then running @code{make} builds the
34219 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34220 libraries, then @code{gdb} itself. The configured source files, and the
34221 binaries, are left in the corresponding source directories.
34224 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34225 system does not recognize this automatically when you run a different
34226 shell, you may need to run @code{sh} on it explicitly:
34229 sh configure @var{host}
34232 If you run @file{configure} from a directory that contains source
34233 directories for multiple libraries or programs, such as the
34234 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34236 creates configuration files for every directory level underneath (unless
34237 you tell it not to, with the @samp{--norecursion} option).
34239 You should run the @file{configure} script from the top directory in the
34240 source tree, the @file{gdb-@var{version-number}} directory. If you run
34241 @file{configure} from one of the subdirectories, you will configure only
34242 that subdirectory. That is usually not what you want. In particular,
34243 if you run the first @file{configure} from the @file{gdb} subdirectory
34244 of the @file{gdb-@var{version-number}} directory, you will omit the
34245 configuration of @file{bfd}, @file{readline}, and other sibling
34246 directories of the @file{gdb} subdirectory. This leads to build errors
34247 about missing include files such as @file{bfd/bfd.h}.
34249 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34250 However, you should make sure that the shell on your path (named by
34251 the @samp{SHELL} environment variable) is publicly readable. Remember
34252 that @value{GDBN} uses the shell to start your program---some systems refuse to
34253 let @value{GDBN} debug child processes whose programs are not readable.
34255 @node Separate Objdir
34256 @section Compiling @value{GDBN} in Another Directory
34258 If you want to run @value{GDBN} versions for several host or target machines,
34259 you need a different @code{gdb} compiled for each combination of
34260 host and target. @file{configure} is designed to make this easy by
34261 allowing you to generate each configuration in a separate subdirectory,
34262 rather than in the source directory. If your @code{make} program
34263 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34264 @code{make} in each of these directories builds the @code{gdb}
34265 program specified there.
34267 To build @code{gdb} in a separate directory, run @file{configure}
34268 with the @samp{--srcdir} option to specify where to find the source.
34269 (You also need to specify a path to find @file{configure}
34270 itself from your working directory. If the path to @file{configure}
34271 would be the same as the argument to @samp{--srcdir}, you can leave out
34272 the @samp{--srcdir} option; it is assumed.)
34274 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34275 separate directory for a Sun 4 like this:
34279 cd gdb-@value{GDBVN}
34282 ../gdb-@value{GDBVN}/configure sun4
34287 When @file{configure} builds a configuration using a remote source
34288 directory, it creates a tree for the binaries with the same structure
34289 (and using the same names) as the tree under the source directory. In
34290 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34291 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34292 @file{gdb-sun4/gdb}.
34294 Make sure that your path to the @file{configure} script has just one
34295 instance of @file{gdb} in it. If your path to @file{configure} looks
34296 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34297 one subdirectory of @value{GDBN}, not the whole package. This leads to
34298 build errors about missing include files such as @file{bfd/bfd.h}.
34300 One popular reason to build several @value{GDBN} configurations in separate
34301 directories is to configure @value{GDBN} for cross-compiling (where
34302 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34303 programs that run on another machine---the @dfn{target}).
34304 You specify a cross-debugging target by
34305 giving the @samp{--target=@var{target}} option to @file{configure}.
34307 When you run @code{make} to build a program or library, you must run
34308 it in a configured directory---whatever directory you were in when you
34309 called @file{configure} (or one of its subdirectories).
34311 The @code{Makefile} that @file{configure} generates in each source
34312 directory also runs recursively. If you type @code{make} in a source
34313 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34314 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34315 will build all the required libraries, and then build GDB.
34317 When you have multiple hosts or targets configured in separate
34318 directories, you can run @code{make} on them in parallel (for example,
34319 if they are NFS-mounted on each of the hosts); they will not interfere
34323 @section Specifying Names for Hosts and Targets
34325 The specifications used for hosts and targets in the @file{configure}
34326 script are based on a three-part naming scheme, but some short predefined
34327 aliases are also supported. The full naming scheme encodes three pieces
34328 of information in the following pattern:
34331 @var{architecture}-@var{vendor}-@var{os}
34334 For example, you can use the alias @code{sun4} as a @var{host} argument,
34335 or as the value for @var{target} in a @code{--target=@var{target}}
34336 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34338 The @file{configure} script accompanying @value{GDBN} does not provide
34339 any query facility to list all supported host and target names or
34340 aliases. @file{configure} calls the Bourne shell script
34341 @code{config.sub} to map abbreviations to full names; you can read the
34342 script, if you wish, or you can use it to test your guesses on
34343 abbreviations---for example:
34346 % sh config.sub i386-linux
34348 % sh config.sub alpha-linux
34349 alpha-unknown-linux-gnu
34350 % sh config.sub hp9k700
34352 % sh config.sub sun4
34353 sparc-sun-sunos4.1.1
34354 % sh config.sub sun3
34355 m68k-sun-sunos4.1.1
34356 % sh config.sub i986v
34357 Invalid configuration `i986v': machine `i986v' not recognized
34361 @code{config.sub} is also distributed in the @value{GDBN} source
34362 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34364 @node Configure Options
34365 @section @file{configure} Options
34367 Here is a summary of the @file{configure} options and arguments that
34368 are most often useful for building @value{GDBN}. @file{configure} also has
34369 several other options not listed here. @inforef{What Configure
34370 Does,,configure.info}, for a full explanation of @file{configure}.
34373 configure @r{[}--help@r{]}
34374 @r{[}--prefix=@var{dir}@r{]}
34375 @r{[}--exec-prefix=@var{dir}@r{]}
34376 @r{[}--srcdir=@var{dirname}@r{]}
34377 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34378 @r{[}--target=@var{target}@r{]}
34383 You may introduce options with a single @samp{-} rather than
34384 @samp{--} if you prefer; but you may abbreviate option names if you use
34389 Display a quick summary of how to invoke @file{configure}.
34391 @item --prefix=@var{dir}
34392 Configure the source to install programs and files under directory
34395 @item --exec-prefix=@var{dir}
34396 Configure the source to install programs under directory
34399 @c avoid splitting the warning from the explanation:
34401 @item --srcdir=@var{dirname}
34402 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34403 @code{make} that implements the @code{VPATH} feature.}@*
34404 Use this option to make configurations in directories separate from the
34405 @value{GDBN} source directories. Among other things, you can use this to
34406 build (or maintain) several configurations simultaneously, in separate
34407 directories. @file{configure} writes configuration-specific files in
34408 the current directory, but arranges for them to use the source in the
34409 directory @var{dirname}. @file{configure} creates directories under
34410 the working directory in parallel to the source directories below
34413 @item --norecursion
34414 Configure only the directory level where @file{configure} is executed; do not
34415 propagate configuration to subdirectories.
34417 @item --target=@var{target}
34418 Configure @value{GDBN} for cross-debugging programs running on the specified
34419 @var{target}. Without this option, @value{GDBN} is configured to debug
34420 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34422 There is no convenient way to generate a list of all available targets.
34424 @item @var{host} @dots{}
34425 Configure @value{GDBN} to run on the specified @var{host}.
34427 There is no convenient way to generate a list of all available hosts.
34430 There are many other options available as well, but they are generally
34431 needed for special purposes only.
34433 @node System-wide configuration
34434 @section System-wide configuration and settings
34435 @cindex system-wide init file
34437 @value{GDBN} can be configured to have a system-wide init file;
34438 this file will be read and executed at startup (@pxref{Startup, , What
34439 @value{GDBN} does during startup}).
34441 Here is the corresponding configure option:
34444 @item --with-system-gdbinit=@var{file}
34445 Specify that the default location of the system-wide init file is
34449 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34450 it may be subject to relocation. Two possible cases:
34454 If the default location of this init file contains @file{$prefix},
34455 it will be subject to relocation. Suppose that the configure options
34456 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34457 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34458 init file is looked for as @file{$install/etc/gdbinit} instead of
34459 @file{$prefix/etc/gdbinit}.
34462 By contrast, if the default location does not contain the prefix,
34463 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34464 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34465 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34466 wherever @value{GDBN} is installed.
34469 If the configured location of the system-wide init file (as given by the
34470 @option{--with-system-gdbinit} option at configure time) is in the
34471 data-directory (as specified by @option{--with-gdb-datadir} at configure
34472 time) or in one of its subdirectories, then @value{GDBN} will look for the
34473 system-wide init file in the directory specified by the
34474 @option{--data-directory} command-line option.
34475 Note that the system-wide init file is only read once, during @value{GDBN}
34476 initialization. If the data-directory is changed after @value{GDBN} has
34477 started with the @code{set data-directory} command, the file will not be
34481 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34484 @node System-wide Configuration Scripts
34485 @subsection Installed System-wide Configuration Scripts
34486 @cindex system-wide configuration scripts
34488 The @file{system-gdbinit} directory, located inside the data-directory
34489 (as specified by @option{--with-gdb-datadir} at configure time) contains
34490 a number of scripts which can be used as system-wide init files. To
34491 automatically source those scripts at startup, @value{GDBN} should be
34492 configured with @option{--with-system-gdbinit}. Otherwise, any user
34493 should be able to source them by hand as needed.
34495 The following scripts are currently available:
34498 @item @file{elinos.py}
34500 @cindex ELinOS system-wide configuration script
34501 This script is useful when debugging a program on an ELinOS target.
34502 It takes advantage of the environment variables defined in a standard
34503 ELinOS environment in order to determine the location of the system
34504 shared libraries, and then sets the @samp{solib-absolute-prefix}
34505 and @samp{solib-search-path} variables appropriately.
34507 @item @file{wrs-linux.py}
34508 @pindex wrs-linux.py
34509 @cindex Wind River Linux system-wide configuration script
34510 This script is useful when debugging a program on a target running
34511 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34512 the host-side sysroot used by the target system.
34516 @node Maintenance Commands
34517 @appendix Maintenance Commands
34518 @cindex maintenance commands
34519 @cindex internal commands
34521 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34522 includes a number of commands intended for @value{GDBN} developers,
34523 that are not documented elsewhere in this manual. These commands are
34524 provided here for reference. (For commands that turn on debugging
34525 messages, see @ref{Debugging Output}.)
34528 @kindex maint agent
34529 @kindex maint agent-eval
34530 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34531 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34532 Translate the given @var{expression} into remote agent bytecodes.
34533 This command is useful for debugging the Agent Expression mechanism
34534 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34535 expression useful for data collection, such as by tracepoints, while
34536 @samp{maint agent-eval} produces an expression that evaluates directly
34537 to a result. For instance, a collection expression for @code{globa +
34538 globb} will include bytecodes to record four bytes of memory at each
34539 of the addresses of @code{globa} and @code{globb}, while discarding
34540 the result of the addition, while an evaluation expression will do the
34541 addition and return the sum.
34542 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34543 If not, generate remote agent bytecode for current frame PC address.
34545 @kindex maint agent-printf
34546 @item maint agent-printf @var{format},@var{expr},...
34547 Translate the given format string and list of argument expressions
34548 into remote agent bytecodes and display them as a disassembled list.
34549 This command is useful for debugging the agent version of dynamic
34550 printf (@pxref{Dynamic Printf}).
34552 @kindex maint info breakpoints
34553 @item @anchor{maint info breakpoints}maint info breakpoints
34554 Using the same format as @samp{info breakpoints}, display both the
34555 breakpoints you've set explicitly, and those @value{GDBN} is using for
34556 internal purposes. Internal breakpoints are shown with negative
34557 breakpoint numbers. The type column identifies what kind of breakpoint
34562 Normal, explicitly set breakpoint.
34565 Normal, explicitly set watchpoint.
34568 Internal breakpoint, used to handle correctly stepping through
34569 @code{longjmp} calls.
34571 @item longjmp resume
34572 Internal breakpoint at the target of a @code{longjmp}.
34575 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34578 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34581 Shared library events.
34585 @kindex maint info btrace
34586 @item maint info btrace
34587 Pint information about raw branch tracing data.
34589 @kindex maint btrace packet-history
34590 @item maint btrace packet-history
34591 Print the raw branch trace packets that are used to compute the
34592 execution history for the @samp{record btrace} command. Both the
34593 information and the format in which it is printed depend on the btrace
34598 For the BTS recording format, print a list of blocks of sequential
34599 code. For each block, the following information is printed:
34603 Newer blocks have higher numbers. The oldest block has number zero.
34604 @item Lowest @samp{PC}
34605 @item Highest @samp{PC}
34609 For the Intel Processor Trace recording format, print a list of
34610 Intel Processor Trace packets. For each packet, the following
34611 information is printed:
34614 @item Packet number
34615 Newer packets have higher numbers. The oldest packet has number zero.
34617 The packet's offset in the trace stream.
34618 @item Packet opcode and payload
34622 @kindex maint btrace clear-packet-history
34623 @item maint btrace clear-packet-history
34624 Discards the cached packet history printed by the @samp{maint btrace
34625 packet-history} command. The history will be computed again when
34628 @kindex maint btrace clear
34629 @item maint btrace clear
34630 Discard the branch trace data. The data will be fetched anew and the
34631 branch trace will be recomputed when needed.
34633 This implicitly truncates the branch trace to a single branch trace
34634 buffer. When updating branch trace incrementally, the branch trace
34635 available to @value{GDBN} may be bigger than a single branch trace
34638 @kindex maint set btrace pt skip-pad
34639 @item maint set btrace pt skip-pad
34640 @kindex maint show btrace pt skip-pad
34641 @item maint show btrace pt skip-pad
34642 Control whether @value{GDBN} will skip PAD packets when computing the
34645 @kindex set displaced-stepping
34646 @kindex show displaced-stepping
34647 @cindex displaced stepping support
34648 @cindex out-of-line single-stepping
34649 @item set displaced-stepping
34650 @itemx show displaced-stepping
34651 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34652 if the target supports it. Displaced stepping is a way to single-step
34653 over breakpoints without removing them from the inferior, by executing
34654 an out-of-line copy of the instruction that was originally at the
34655 breakpoint location. It is also known as out-of-line single-stepping.
34658 @item set displaced-stepping on
34659 If the target architecture supports it, @value{GDBN} will use
34660 displaced stepping to step over breakpoints.
34662 @item set displaced-stepping off
34663 @value{GDBN} will not use displaced stepping to step over breakpoints,
34664 even if such is supported by the target architecture.
34666 @cindex non-stop mode, and @samp{set displaced-stepping}
34667 @item set displaced-stepping auto
34668 This is the default mode. @value{GDBN} will use displaced stepping
34669 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34670 architecture supports displaced stepping.
34673 @kindex maint check-psymtabs
34674 @item maint check-psymtabs
34675 Check the consistency of currently expanded psymtabs versus symtabs.
34676 Use this to check, for example, whether a symbol is in one but not the other.
34678 @kindex maint check-symtabs
34679 @item maint check-symtabs
34680 Check the consistency of currently expanded symtabs.
34682 @kindex maint expand-symtabs
34683 @item maint expand-symtabs [@var{regexp}]
34684 Expand symbol tables.
34685 If @var{regexp} is specified, only expand symbol tables for file
34686 names matching @var{regexp}.
34688 @kindex maint set catch-demangler-crashes
34689 @kindex maint show catch-demangler-crashes
34690 @cindex demangler crashes
34691 @item maint set catch-demangler-crashes [on|off]
34692 @itemx maint show catch-demangler-crashes
34693 Control whether @value{GDBN} should attempt to catch crashes in the
34694 symbol name demangler. The default is to attempt to catch crashes.
34695 If enabled, the first time a crash is caught, a core file is created,
34696 the offending symbol is displayed and the user is presented with the
34697 option to terminate the current session.
34699 @kindex maint cplus first_component
34700 @item maint cplus first_component @var{name}
34701 Print the first C@t{++} class/namespace component of @var{name}.
34703 @kindex maint cplus namespace
34704 @item maint cplus namespace
34705 Print the list of possible C@t{++} namespaces.
34707 @kindex maint deprecate
34708 @kindex maint undeprecate
34709 @cindex deprecated commands
34710 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34711 @itemx maint undeprecate @var{command}
34712 Deprecate or undeprecate the named @var{command}. Deprecated commands
34713 cause @value{GDBN} to issue a warning when you use them. The optional
34714 argument @var{replacement} says which newer command should be used in
34715 favor of the deprecated one; if it is given, @value{GDBN} will mention
34716 the replacement as part of the warning.
34718 @kindex maint dump-me
34719 @item maint dump-me
34720 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34721 Cause a fatal signal in the debugger and force it to dump its core.
34722 This is supported only on systems which support aborting a program
34723 with the @code{SIGQUIT} signal.
34725 @kindex maint internal-error
34726 @kindex maint internal-warning
34727 @kindex maint demangler-warning
34728 @cindex demangler crashes
34729 @item maint internal-error @r{[}@var{message-text}@r{]}
34730 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34731 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34733 Cause @value{GDBN} to call the internal function @code{internal_error},
34734 @code{internal_warning} or @code{demangler_warning} and hence behave
34735 as though an internal problem has been detected. In addition to
34736 reporting the internal problem, these functions give the user the
34737 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34738 and @code{internal_warning}) create a core file of the current
34739 @value{GDBN} session.
34741 These commands take an optional parameter @var{message-text} that is
34742 used as the text of the error or warning message.
34744 Here's an example of using @code{internal-error}:
34747 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34748 @dots{}/maint.c:121: internal-error: testing, 1, 2
34749 A problem internal to GDB has been detected. Further
34750 debugging may prove unreliable.
34751 Quit this debugging session? (y or n) @kbd{n}
34752 Create a core file? (y or n) @kbd{n}
34756 @cindex @value{GDBN} internal error
34757 @cindex internal errors, control of @value{GDBN} behavior
34758 @cindex demangler crashes
34760 @kindex maint set internal-error
34761 @kindex maint show internal-error
34762 @kindex maint set internal-warning
34763 @kindex maint show internal-warning
34764 @kindex maint set demangler-warning
34765 @kindex maint show demangler-warning
34766 @item maint set internal-error @var{action} [ask|yes|no]
34767 @itemx maint show internal-error @var{action}
34768 @itemx maint set internal-warning @var{action} [ask|yes|no]
34769 @itemx maint show internal-warning @var{action}
34770 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34771 @itemx maint show demangler-warning @var{action}
34772 When @value{GDBN} reports an internal problem (error or warning) it
34773 gives the user the opportunity to both quit @value{GDBN} and create a
34774 core file of the current @value{GDBN} session. These commands let you
34775 override the default behaviour for each particular @var{action},
34776 described in the table below.
34780 You can specify that @value{GDBN} should always (yes) or never (no)
34781 quit. The default is to ask the user what to do.
34784 You can specify that @value{GDBN} should always (yes) or never (no)
34785 create a core file. The default is to ask the user what to do. Note
34786 that there is no @code{corefile} option for @code{demangler-warning}:
34787 demangler warnings always create a core file and this cannot be
34791 @kindex maint packet
34792 @item maint packet @var{text}
34793 If @value{GDBN} is talking to an inferior via the serial protocol,
34794 then this command sends the string @var{text} to the inferior, and
34795 displays the response packet. @value{GDBN} supplies the initial
34796 @samp{$} character, the terminating @samp{#} character, and the
34799 @kindex maint print architecture
34800 @item maint print architecture @r{[}@var{file}@r{]}
34801 Print the entire architecture configuration. The optional argument
34802 @var{file} names the file where the output goes.
34804 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
34805 @item maint print c-tdesc
34806 Print the target description (@pxref{Target Descriptions}) as
34807 a C source file. By default, the target description is for the current
34808 target, but if the optional argument @var{file} is provided, that file
34809 is used to produce the description. The @var{file} should be an XML
34810 document, of the form described in @ref{Target Description Format}.
34811 The created source file is built into @value{GDBN} when @value{GDBN} is
34812 built again. This command is used by developers after they add or
34813 modify XML target descriptions.
34815 @kindex maint check xml-descriptions
34816 @item maint check xml-descriptions @var{dir}
34817 Check that the target descriptions dynamically created by @value{GDBN}
34818 equal the descriptions created from XML files found in @var{dir}.
34820 @kindex maint print dummy-frames
34821 @item maint print dummy-frames
34822 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34825 (@value{GDBP}) @kbd{b add}
34827 (@value{GDBP}) @kbd{print add(2,3)}
34828 Breakpoint 2, add (a=2, b=3) at @dots{}
34830 The program being debugged stopped while in a function called from GDB.
34832 (@value{GDBP}) @kbd{maint print dummy-frames}
34833 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34837 Takes an optional file parameter.
34839 @kindex maint print registers
34840 @kindex maint print raw-registers
34841 @kindex maint print cooked-registers
34842 @kindex maint print register-groups
34843 @kindex maint print remote-registers
34844 @item maint print registers @r{[}@var{file}@r{]}
34845 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34846 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34847 @itemx maint print register-groups @r{[}@var{file}@r{]}
34848 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34849 Print @value{GDBN}'s internal register data structures.
34851 The command @code{maint print raw-registers} includes the contents of
34852 the raw register cache; the command @code{maint print
34853 cooked-registers} includes the (cooked) value of all registers,
34854 including registers which aren't available on the target nor visible
34855 to user; the command @code{maint print register-groups} includes the
34856 groups that each register is a member of; and the command @code{maint
34857 print remote-registers} includes the remote target's register numbers
34858 and offsets in the `G' packets.
34860 These commands take an optional parameter, a file name to which to
34861 write the information.
34863 @kindex maint print reggroups
34864 @item maint print reggroups @r{[}@var{file}@r{]}
34865 Print @value{GDBN}'s internal register group data structures. The
34866 optional argument @var{file} tells to what file to write the
34869 The register groups info looks like this:
34872 (@value{GDBP}) @kbd{maint print reggroups}
34885 This command forces @value{GDBN} to flush its internal register cache.
34887 @kindex maint print objfiles
34888 @cindex info for known object files
34889 @item maint print objfiles @r{[}@var{regexp}@r{]}
34890 Print a dump of all known object files.
34891 If @var{regexp} is specified, only print object files whose names
34892 match @var{regexp}. For each object file, this command prints its name,
34893 address in memory, and all of its psymtabs and symtabs.
34895 @kindex maint print user-registers
34896 @cindex user registers
34897 @item maint print user-registers
34898 List all currently available @dfn{user registers}. User registers
34899 typically provide alternate names for actual hardware registers. They
34900 include the four ``standard'' registers @code{$fp}, @code{$pc},
34901 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34902 registers can be used in expressions in the same way as the canonical
34903 register names, but only the latter are listed by the @code{info
34904 registers} and @code{maint print registers} commands.
34906 @kindex maint print section-scripts
34907 @cindex info for known .debug_gdb_scripts-loaded scripts
34908 @item maint print section-scripts [@var{regexp}]
34909 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34910 If @var{regexp} is specified, only print scripts loaded by object files
34911 matching @var{regexp}.
34912 For each script, this command prints its name as specified in the objfile,
34913 and the full path if known.
34914 @xref{dotdebug_gdb_scripts section}.
34916 @kindex maint print statistics
34917 @cindex bcache statistics
34918 @item maint print statistics
34919 This command prints, for each object file in the program, various data
34920 about that object file followed by the byte cache (@dfn{bcache})
34921 statistics for the object file. The objfile data includes the number
34922 of minimal, partial, full, and stabs symbols, the number of types
34923 defined by the objfile, the number of as yet unexpanded psym tables,
34924 the number of line tables and string tables, and the amount of memory
34925 used by the various tables. The bcache statistics include the counts,
34926 sizes, and counts of duplicates of all and unique objects, max,
34927 average, and median entry size, total memory used and its overhead and
34928 savings, and various measures of the hash table size and chain
34931 @kindex maint print target-stack
34932 @cindex target stack description
34933 @item maint print target-stack
34934 A @dfn{target} is an interface between the debugger and a particular
34935 kind of file or process. Targets can be stacked in @dfn{strata},
34936 so that more than one target can potentially respond to a request.
34937 In particular, memory accesses will walk down the stack of targets
34938 until they find a target that is interested in handling that particular
34941 This command prints a short description of each layer that was pushed on
34942 the @dfn{target stack}, starting from the top layer down to the bottom one.
34944 @kindex maint print type
34945 @cindex type chain of a data type
34946 @item maint print type @var{expr}
34947 Print the type chain for a type specified by @var{expr}. The argument
34948 can be either a type name or a symbol. If it is a symbol, the type of
34949 that symbol is described. The type chain produced by this command is
34950 a recursive definition of the data type as stored in @value{GDBN}'s
34951 data structures, including its flags and contained types.
34953 @kindex maint selftest
34955 Run any self tests that were compiled in to @value{GDBN}. This will
34956 print a message showing how many tests were run, and how many failed.
34958 @kindex maint set dwarf always-disassemble
34959 @kindex maint show dwarf always-disassemble
34960 @item maint set dwarf always-disassemble
34961 @item maint show dwarf always-disassemble
34962 Control the behavior of @code{info address} when using DWARF debugging
34965 The default is @code{off}, which means that @value{GDBN} should try to
34966 describe a variable's location in an easily readable format. When
34967 @code{on}, @value{GDBN} will instead display the DWARF location
34968 expression in an assembly-like format. Note that some locations are
34969 too complex for @value{GDBN} to describe simply; in this case you will
34970 always see the disassembly form.
34972 Here is an example of the resulting disassembly:
34975 (gdb) info addr argc
34976 Symbol "argc" is a complex DWARF expression:
34980 For more information on these expressions, see
34981 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34983 @kindex maint set dwarf max-cache-age
34984 @kindex maint show dwarf max-cache-age
34985 @item maint set dwarf max-cache-age
34986 @itemx maint show dwarf max-cache-age
34987 Control the DWARF compilation unit cache.
34989 @cindex DWARF compilation units cache
34990 In object files with inter-compilation-unit references, such as those
34991 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34992 reader needs to frequently refer to previously read compilation units.
34993 This setting controls how long a compilation unit will remain in the
34994 cache if it is not referenced. A higher limit means that cached
34995 compilation units will be stored in memory longer, and more total
34996 memory will be used. Setting it to zero disables caching, which will
34997 slow down @value{GDBN} startup, but reduce memory consumption.
34999 @kindex maint set profile
35000 @kindex maint show profile
35001 @cindex profiling GDB
35002 @item maint set profile
35003 @itemx maint show profile
35004 Control profiling of @value{GDBN}.
35006 Profiling will be disabled until you use the @samp{maint set profile}
35007 command to enable it. When you enable profiling, the system will begin
35008 collecting timing and execution count data; when you disable profiling or
35009 exit @value{GDBN}, the results will be written to a log file. Remember that
35010 if you use profiling, @value{GDBN} will overwrite the profiling log file
35011 (often called @file{gmon.out}). If you have a record of important profiling
35012 data in a @file{gmon.out} file, be sure to move it to a safe location.
35014 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35015 compiled with the @samp{-pg} compiler option.
35017 @kindex maint set show-debug-regs
35018 @kindex maint show show-debug-regs
35019 @cindex hardware debug registers
35020 @item maint set show-debug-regs
35021 @itemx maint show show-debug-regs
35022 Control whether to show variables that mirror the hardware debug
35023 registers. Use @code{on} to enable, @code{off} to disable. If
35024 enabled, the debug registers values are shown when @value{GDBN} inserts or
35025 removes a hardware breakpoint or watchpoint, and when the inferior
35026 triggers a hardware-assisted breakpoint or watchpoint.
35028 @kindex maint set show-all-tib
35029 @kindex maint show show-all-tib
35030 @item maint set show-all-tib
35031 @itemx maint show show-all-tib
35032 Control whether to show all non zero areas within a 1k block starting
35033 at thread local base, when using the @samp{info w32 thread-information-block}
35036 @kindex maint set target-async
35037 @kindex maint show target-async
35038 @item maint set target-async
35039 @itemx maint show target-async
35040 This controls whether @value{GDBN} targets operate in synchronous or
35041 asynchronous mode (@pxref{Background Execution}). Normally the
35042 default is asynchronous, if it is available; but this can be changed
35043 to more easily debug problems occurring only in synchronous mode.
35045 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35046 @kindex maint show target-non-stop
35047 @item maint set target-non-stop
35048 @itemx maint show target-non-stop
35050 This controls whether @value{GDBN} targets always operate in non-stop
35051 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35052 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35053 if supported by the target.
35056 @item maint set target-non-stop auto
35057 This is the default mode. @value{GDBN} controls the target in
35058 non-stop mode if the target supports it.
35060 @item maint set target-non-stop on
35061 @value{GDBN} controls the target in non-stop mode even if the target
35062 does not indicate support.
35064 @item maint set target-non-stop off
35065 @value{GDBN} does not control the target in non-stop mode even if the
35066 target supports it.
35069 @kindex maint set per-command
35070 @kindex maint show per-command
35071 @item maint set per-command
35072 @itemx maint show per-command
35073 @cindex resources used by commands
35075 @value{GDBN} can display the resources used by each command.
35076 This is useful in debugging performance problems.
35079 @item maint set per-command space [on|off]
35080 @itemx maint show per-command space
35081 Enable or disable the printing of the memory used by GDB for each command.
35082 If enabled, @value{GDBN} will display how much memory each command
35083 took, following the command's own output.
35084 This can also be requested by invoking @value{GDBN} with the
35085 @option{--statistics} command-line switch (@pxref{Mode Options}).
35087 @item maint set per-command time [on|off]
35088 @itemx maint show per-command time
35089 Enable or disable the printing of the execution time of @value{GDBN}
35091 If enabled, @value{GDBN} will display how much time it
35092 took to execute each command, following the command's own output.
35093 Both CPU time and wallclock time are printed.
35094 Printing both is useful when trying to determine whether the cost is
35095 CPU or, e.g., disk/network latency.
35096 Note that the CPU time printed is for @value{GDBN} only, it does not include
35097 the execution time of the inferior because there's no mechanism currently
35098 to compute how much time was spent by @value{GDBN} and how much time was
35099 spent by the program been debugged.
35100 This can also be requested by invoking @value{GDBN} with the
35101 @option{--statistics} command-line switch (@pxref{Mode Options}).
35103 @item maint set per-command symtab [on|off]
35104 @itemx maint show per-command symtab
35105 Enable or disable the printing of basic symbol table statistics
35107 If enabled, @value{GDBN} will display the following information:
35111 number of symbol tables
35113 number of primary symbol tables
35115 number of blocks in the blockvector
35119 @kindex maint space
35120 @cindex memory used by commands
35121 @item maint space @var{value}
35122 An alias for @code{maint set per-command space}.
35123 A non-zero value enables it, zero disables it.
35126 @cindex time of command execution
35127 @item maint time @var{value}
35128 An alias for @code{maint set per-command time}.
35129 A non-zero value enables it, zero disables it.
35131 @kindex maint translate-address
35132 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35133 Find the symbol stored at the location specified by the address
35134 @var{addr} and an optional section name @var{section}. If found,
35135 @value{GDBN} prints the name of the closest symbol and an offset from
35136 the symbol's location to the specified address. This is similar to
35137 the @code{info address} command (@pxref{Symbols}), except that this
35138 command also allows to find symbols in other sections.
35140 If section was not specified, the section in which the symbol was found
35141 is also printed. For dynamically linked executables, the name of
35142 executable or shared library containing the symbol is printed as well.
35146 The following command is useful for non-interactive invocations of
35147 @value{GDBN}, such as in the test suite.
35150 @item set watchdog @var{nsec}
35151 @kindex set watchdog
35152 @cindex watchdog timer
35153 @cindex timeout for commands
35154 Set the maximum number of seconds @value{GDBN} will wait for the
35155 target operation to finish. If this time expires, @value{GDBN}
35156 reports and error and the command is aborted.
35158 @item show watchdog
35159 Show the current setting of the target wait timeout.
35162 @node Remote Protocol
35163 @appendix @value{GDBN} Remote Serial Protocol
35168 * Stop Reply Packets::
35169 * General Query Packets::
35170 * Architecture-Specific Protocol Details::
35171 * Tracepoint Packets::
35172 * Host I/O Packets::
35174 * Notification Packets::
35175 * Remote Non-Stop::
35176 * Packet Acknowledgment::
35178 * File-I/O Remote Protocol Extension::
35179 * Library List Format::
35180 * Library List Format for SVR4 Targets::
35181 * Memory Map Format::
35182 * Thread List Format::
35183 * Traceframe Info Format::
35184 * Branch Trace Format::
35185 * Branch Trace Configuration Format::
35191 There may be occasions when you need to know something about the
35192 protocol---for example, if there is only one serial port to your target
35193 machine, you might want your program to do something special if it
35194 recognizes a packet meant for @value{GDBN}.
35196 In the examples below, @samp{->} and @samp{<-} are used to indicate
35197 transmitted and received data, respectively.
35199 @cindex protocol, @value{GDBN} remote serial
35200 @cindex serial protocol, @value{GDBN} remote
35201 @cindex remote serial protocol
35202 All @value{GDBN} commands and responses (other than acknowledgments
35203 and notifications, see @ref{Notification Packets}) are sent as a
35204 @var{packet}. A @var{packet} is introduced with the character
35205 @samp{$}, the actual @var{packet-data}, and the terminating character
35206 @samp{#} followed by a two-digit @var{checksum}:
35209 @code{$}@var{packet-data}@code{#}@var{checksum}
35213 @cindex checksum, for @value{GDBN} remote
35215 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35216 characters between the leading @samp{$} and the trailing @samp{#} (an
35217 eight bit unsigned checksum).
35219 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35220 specification also included an optional two-digit @var{sequence-id}:
35223 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35226 @cindex sequence-id, for @value{GDBN} remote
35228 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35229 has never output @var{sequence-id}s. Stubs that handle packets added
35230 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35232 When either the host or the target machine receives a packet, the first
35233 response expected is an acknowledgment: either @samp{+} (to indicate
35234 the package was received correctly) or @samp{-} (to request
35238 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35243 The @samp{+}/@samp{-} acknowledgments can be disabled
35244 once a connection is established.
35245 @xref{Packet Acknowledgment}, for details.
35247 The host (@value{GDBN}) sends @var{command}s, and the target (the
35248 debugging stub incorporated in your program) sends a @var{response}. In
35249 the case of step and continue @var{command}s, the response is only sent
35250 when the operation has completed, and the target has again stopped all
35251 threads in all attached processes. This is the default all-stop mode
35252 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35253 execution mode; see @ref{Remote Non-Stop}, for details.
35255 @var{packet-data} consists of a sequence of characters with the
35256 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35259 @cindex remote protocol, field separator
35260 Fields within the packet should be separated using @samp{,} @samp{;} or
35261 @samp{:}. Except where otherwise noted all numbers are represented in
35262 @sc{hex} with leading zeros suppressed.
35264 Implementors should note that prior to @value{GDBN} 5.0, the character
35265 @samp{:} could not appear as the third character in a packet (as it
35266 would potentially conflict with the @var{sequence-id}).
35268 @cindex remote protocol, binary data
35269 @anchor{Binary Data}
35270 Binary data in most packets is encoded either as two hexadecimal
35271 digits per byte of binary data. This allowed the traditional remote
35272 protocol to work over connections which were only seven-bit clean.
35273 Some packets designed more recently assume an eight-bit clean
35274 connection, and use a more efficient encoding to send and receive
35277 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35278 as an escape character. Any escaped byte is transmitted as the escape
35279 character followed by the original character XORed with @code{0x20}.
35280 For example, the byte @code{0x7d} would be transmitted as the two
35281 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35282 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35283 @samp{@}}) must always be escaped. Responses sent by the stub
35284 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35285 is not interpreted as the start of a run-length encoded sequence
35288 Response @var{data} can be run-length encoded to save space.
35289 Run-length encoding replaces runs of identical characters with one
35290 instance of the repeated character, followed by a @samp{*} and a
35291 repeat count. The repeat count is itself sent encoded, to avoid
35292 binary characters in @var{data}: a value of @var{n} is sent as
35293 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35294 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35295 code 32) for a repeat count of 3. (This is because run-length
35296 encoding starts to win for counts 3 or more.) Thus, for example,
35297 @samp{0* } is a run-length encoding of ``0000'': the space character
35298 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35301 The printable characters @samp{#} and @samp{$} or with a numeric value
35302 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35303 seven repeats (@samp{$}) can be expanded using a repeat count of only
35304 five (@samp{"}). For example, @samp{00000000} can be encoded as
35307 The error response returned for some packets includes a two character
35308 error number. That number is not well defined.
35310 @cindex empty response, for unsupported packets
35311 For any @var{command} not supported by the stub, an empty response
35312 (@samp{$#00}) should be returned. That way it is possible to extend the
35313 protocol. A newer @value{GDBN} can tell if a packet is supported based
35316 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35317 commands for register access, and the @samp{m} and @samp{M} commands
35318 for memory access. Stubs that only control single-threaded targets
35319 can implement run control with the @samp{c} (continue), and @samp{s}
35320 (step) commands. Stubs that support multi-threading targets should
35321 support the @samp{vCont} command. All other commands are optional.
35326 The following table provides a complete list of all currently defined
35327 @var{command}s and their corresponding response @var{data}.
35328 @xref{File-I/O Remote Protocol Extension}, for details about the File
35329 I/O extension of the remote protocol.
35331 Each packet's description has a template showing the packet's overall
35332 syntax, followed by an explanation of the packet's meaning. We
35333 include spaces in some of the templates for clarity; these are not
35334 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35335 separate its components. For example, a template like @samp{foo
35336 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35337 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35338 @var{baz}. @value{GDBN} does not transmit a space character between the
35339 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35342 @cindex @var{thread-id}, in remote protocol
35343 @anchor{thread-id syntax}
35344 Several packets and replies include a @var{thread-id} field to identify
35345 a thread. Normally these are positive numbers with a target-specific
35346 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35347 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35350 In addition, the remote protocol supports a multiprocess feature in
35351 which the @var{thread-id} syntax is extended to optionally include both
35352 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35353 The @var{pid} (process) and @var{tid} (thread) components each have the
35354 format described above: a positive number with target-specific
35355 interpretation formatted as a big-endian hex string, literal @samp{-1}
35356 to indicate all processes or threads (respectively), or @samp{0} to
35357 indicate an arbitrary process or thread. Specifying just a process, as
35358 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35359 error to specify all processes but a specific thread, such as
35360 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35361 for those packets and replies explicitly documented to include a process
35362 ID, rather than a @var{thread-id}.
35364 The multiprocess @var{thread-id} syntax extensions are only used if both
35365 @value{GDBN} and the stub report support for the @samp{multiprocess}
35366 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35369 Note that all packet forms beginning with an upper- or lower-case
35370 letter, other than those described here, are reserved for future use.
35372 Here are the packet descriptions.
35377 @cindex @samp{!} packet
35378 @anchor{extended mode}
35379 Enable extended mode. In extended mode, the remote server is made
35380 persistent. The @samp{R} packet is used to restart the program being
35386 The remote target both supports and has enabled extended mode.
35390 @cindex @samp{?} packet
35392 Indicate the reason the target halted. The reply is the same as for
35393 step and continue. This packet has a special interpretation when the
35394 target is in non-stop mode; see @ref{Remote Non-Stop}.
35397 @xref{Stop Reply Packets}, for the reply specifications.
35399 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35400 @cindex @samp{A} packet
35401 Initialized @code{argv[]} array passed into program. @var{arglen}
35402 specifies the number of bytes in the hex encoded byte stream
35403 @var{arg}. See @code{gdbserver} for more details.
35408 The arguments were set.
35414 @cindex @samp{b} packet
35415 (Don't use this packet; its behavior is not well-defined.)
35416 Change the serial line speed to @var{baud}.
35418 JTC: @emph{When does the transport layer state change? When it's
35419 received, or after the ACK is transmitted. In either case, there are
35420 problems if the command or the acknowledgment packet is dropped.}
35422 Stan: @emph{If people really wanted to add something like this, and get
35423 it working for the first time, they ought to modify ser-unix.c to send
35424 some kind of out-of-band message to a specially-setup stub and have the
35425 switch happen "in between" packets, so that from remote protocol's point
35426 of view, nothing actually happened.}
35428 @item B @var{addr},@var{mode}
35429 @cindex @samp{B} packet
35430 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35431 breakpoint at @var{addr}.
35433 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35434 (@pxref{insert breakpoint or watchpoint packet}).
35436 @cindex @samp{bc} packet
35439 Backward continue. Execute the target system in reverse. No parameter.
35440 @xref{Reverse Execution}, for more information.
35443 @xref{Stop Reply Packets}, for the reply specifications.
35445 @cindex @samp{bs} packet
35448 Backward single step. Execute one instruction in reverse. No parameter.
35449 @xref{Reverse Execution}, for more information.
35452 @xref{Stop Reply Packets}, for the reply specifications.
35454 @item c @r{[}@var{addr}@r{]}
35455 @cindex @samp{c} packet
35456 Continue at @var{addr}, which is the address to resume. If @var{addr}
35457 is omitted, resume at current address.
35459 This packet is deprecated for multi-threading support. @xref{vCont
35463 @xref{Stop Reply Packets}, for the reply specifications.
35465 @item C @var{sig}@r{[};@var{addr}@r{]}
35466 @cindex @samp{C} packet
35467 Continue with signal @var{sig} (hex signal number). If
35468 @samp{;@var{addr}} is omitted, resume at same address.
35470 This packet is deprecated for multi-threading support. @xref{vCont
35474 @xref{Stop Reply Packets}, for the reply specifications.
35477 @cindex @samp{d} packet
35480 Don't use this packet; instead, define a general set packet
35481 (@pxref{General Query Packets}).
35485 @cindex @samp{D} packet
35486 The first form of the packet is used to detach @value{GDBN} from the
35487 remote system. It is sent to the remote target
35488 before @value{GDBN} disconnects via the @code{detach} command.
35490 The second form, including a process ID, is used when multiprocess
35491 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35492 detach only a specific process. The @var{pid} is specified as a
35493 big-endian hex string.
35503 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35504 @cindex @samp{F} packet
35505 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35506 This is part of the File-I/O protocol extension. @xref{File-I/O
35507 Remote Protocol Extension}, for the specification.
35510 @anchor{read registers packet}
35511 @cindex @samp{g} packet
35512 Read general registers.
35516 @item @var{XX@dots{}}
35517 Each byte of register data is described by two hex digits. The bytes
35518 with the register are transmitted in target byte order. The size of
35519 each register and their position within the @samp{g} packet are
35520 determined by the @value{GDBN} internal gdbarch functions
35521 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35523 When reading registers from a trace frame (@pxref{Analyze Collected
35524 Data,,Using the Collected Data}), the stub may also return a string of
35525 literal @samp{x}'s in place of the register data digits, to indicate
35526 that the corresponding register has not been collected, thus its value
35527 is unavailable. For example, for an architecture with 4 registers of
35528 4 bytes each, the following reply indicates to @value{GDBN} that
35529 registers 0 and 2 have not been collected, while registers 1 and 3
35530 have been collected, and both have zero value:
35534 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35541 @item G @var{XX@dots{}}
35542 @cindex @samp{G} packet
35543 Write general registers. @xref{read registers packet}, for a
35544 description of the @var{XX@dots{}} data.
35554 @item H @var{op} @var{thread-id}
35555 @cindex @samp{H} packet
35556 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35557 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35558 should be @samp{c} for step and continue operations (note that this
35559 is deprecated, supporting the @samp{vCont} command is a better
35560 option), and @samp{g} for other operations. The thread designator
35561 @var{thread-id} has the format and interpretation described in
35562 @ref{thread-id syntax}.
35573 @c 'H': How restrictive (or permissive) is the thread model. If a
35574 @c thread is selected and stopped, are other threads allowed
35575 @c to continue to execute? As I mentioned above, I think the
35576 @c semantics of each command when a thread is selected must be
35577 @c described. For example:
35579 @c 'g': If the stub supports threads and a specific thread is
35580 @c selected, returns the register block from that thread;
35581 @c otherwise returns current registers.
35583 @c 'G' If the stub supports threads and a specific thread is
35584 @c selected, sets the registers of the register block of
35585 @c that thread; otherwise sets current registers.
35587 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35588 @anchor{cycle step packet}
35589 @cindex @samp{i} packet
35590 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35591 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35592 step starting at that address.
35595 @cindex @samp{I} packet
35596 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35600 @cindex @samp{k} packet
35603 The exact effect of this packet is not specified.
35605 For a bare-metal target, it may power cycle or reset the target
35606 system. For that reason, the @samp{k} packet has no reply.
35608 For a single-process target, it may kill that process if possible.
35610 A multiple-process target may choose to kill just one process, or all
35611 that are under @value{GDBN}'s control. For more precise control, use
35612 the vKill packet (@pxref{vKill packet}).
35614 If the target system immediately closes the connection in response to
35615 @samp{k}, @value{GDBN} does not consider the lack of packet
35616 acknowledgment to be an error, and assumes the kill was successful.
35618 If connected using @kbd{target extended-remote}, and the target does
35619 not close the connection in response to a kill request, @value{GDBN}
35620 probes the target state as if a new connection was opened
35621 (@pxref{? packet}).
35623 @item m @var{addr},@var{length}
35624 @cindex @samp{m} packet
35625 Read @var{length} addressable memory units starting at address @var{addr}
35626 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35627 any particular boundary.
35629 The stub need not use any particular size or alignment when gathering
35630 data from memory for the response; even if @var{addr} is word-aligned
35631 and @var{length} is a multiple of the word size, the stub is free to
35632 use byte accesses, or not. For this reason, this packet may not be
35633 suitable for accessing memory-mapped I/O devices.
35634 @cindex alignment of remote memory accesses
35635 @cindex size of remote memory accesses
35636 @cindex memory, alignment and size of remote accesses
35640 @item @var{XX@dots{}}
35641 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35642 The reply may contain fewer addressable memory units than requested if the
35643 server was able to read only part of the region of memory.
35648 @item M @var{addr},@var{length}:@var{XX@dots{}}
35649 @cindex @samp{M} packet
35650 Write @var{length} addressable memory units starting at address @var{addr}
35651 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35652 byte is transmitted as a two-digit hexadecimal number.
35659 for an error (this includes the case where only part of the data was
35664 @cindex @samp{p} packet
35665 Read the value of register @var{n}; @var{n} is in hex.
35666 @xref{read registers packet}, for a description of how the returned
35667 register value is encoded.
35671 @item @var{XX@dots{}}
35672 the register's value
35676 Indicating an unrecognized @var{query}.
35679 @item P @var{n@dots{}}=@var{r@dots{}}
35680 @anchor{write register packet}
35681 @cindex @samp{P} packet
35682 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35683 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35684 digits for each byte in the register (target byte order).
35694 @item q @var{name} @var{params}@dots{}
35695 @itemx Q @var{name} @var{params}@dots{}
35696 @cindex @samp{q} packet
35697 @cindex @samp{Q} packet
35698 General query (@samp{q}) and set (@samp{Q}). These packets are
35699 described fully in @ref{General Query Packets}.
35702 @cindex @samp{r} packet
35703 Reset the entire system.
35705 Don't use this packet; use the @samp{R} packet instead.
35708 @cindex @samp{R} packet
35709 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35710 This packet is only available in extended mode (@pxref{extended mode}).
35712 The @samp{R} packet has no reply.
35714 @item s @r{[}@var{addr}@r{]}
35715 @cindex @samp{s} packet
35716 Single step, resuming at @var{addr}. If
35717 @var{addr} is omitted, resume at same address.
35719 This packet is deprecated for multi-threading support. @xref{vCont
35723 @xref{Stop Reply Packets}, for the reply specifications.
35725 @item S @var{sig}@r{[};@var{addr}@r{]}
35726 @anchor{step with signal packet}
35727 @cindex @samp{S} packet
35728 Step with signal. This is analogous to the @samp{C} packet, but
35729 requests a single-step, rather than a normal resumption of execution.
35731 This packet is deprecated for multi-threading support. @xref{vCont
35735 @xref{Stop Reply Packets}, for the reply specifications.
35737 @item t @var{addr}:@var{PP},@var{MM}
35738 @cindex @samp{t} packet
35739 Search backwards starting at address @var{addr} for a match with pattern
35740 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35741 There must be at least 3 digits in @var{addr}.
35743 @item T @var{thread-id}
35744 @cindex @samp{T} packet
35745 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35750 thread is still alive
35756 Packets starting with @samp{v} are identified by a multi-letter name,
35757 up to the first @samp{;} or @samp{?} (or the end of the packet).
35759 @item vAttach;@var{pid}
35760 @cindex @samp{vAttach} packet
35761 Attach to a new process with the specified process ID @var{pid}.
35762 The process ID is a
35763 hexadecimal integer identifying the process. In all-stop mode, all
35764 threads in the attached process are stopped; in non-stop mode, it may be
35765 attached without being stopped if that is supported by the target.
35767 @c In non-stop mode, on a successful vAttach, the stub should set the
35768 @c current thread to a thread of the newly-attached process. After
35769 @c attaching, GDB queries for the attached process's thread ID with qC.
35770 @c Also note that, from a user perspective, whether or not the
35771 @c target is stopped on attach in non-stop mode depends on whether you
35772 @c use the foreground or background version of the attach command, not
35773 @c on what vAttach does; GDB does the right thing with respect to either
35774 @c stopping or restarting threads.
35776 This packet is only available in extended mode (@pxref{extended mode}).
35782 @item @r{Any stop packet}
35783 for success in all-stop mode (@pxref{Stop Reply Packets})
35785 for success in non-stop mode (@pxref{Remote Non-Stop})
35788 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35789 @cindex @samp{vCont} packet
35790 @anchor{vCont packet}
35791 Resume the inferior, specifying different actions for each thread.
35793 For each inferior thread, the leftmost action with a matching
35794 @var{thread-id} is applied. Threads that don't match any action
35795 remain in their current state. Thread IDs are specified using the
35796 syntax described in @ref{thread-id syntax}. If multiprocess
35797 extensions (@pxref{multiprocess extensions}) are supported, actions
35798 can be specified to match all threads in a process by using the
35799 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
35800 @var{thread-id} matches all threads. Specifying no actions is an
35803 Currently supported actions are:
35809 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35813 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35816 @item r @var{start},@var{end}
35817 Step once, and then keep stepping as long as the thread stops at
35818 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35819 The remote stub reports a stop reply when either the thread goes out
35820 of the range or is stopped due to an unrelated reason, such as hitting
35821 a breakpoint. @xref{range stepping}.
35823 If the range is empty (@var{start} == @var{end}), then the action
35824 becomes equivalent to the @samp{s} action. In other words,
35825 single-step once, and report the stop (even if the stepped instruction
35826 jumps to @var{start}).
35828 (A stop reply may be sent at any point even if the PC is still within
35829 the stepping range; for example, it is valid to implement this packet
35830 in a degenerate way as a single instruction step operation.)
35834 The optional argument @var{addr} normally associated with the
35835 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35836 not supported in @samp{vCont}.
35838 The @samp{t} action is only relevant in non-stop mode
35839 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35840 A stop reply should be generated for any affected thread not already stopped.
35841 When a thread is stopped by means of a @samp{t} action,
35842 the corresponding stop reply should indicate that the thread has stopped with
35843 signal @samp{0}, regardless of whether the target uses some other signal
35844 as an implementation detail.
35846 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
35847 @samp{r} actions for threads that are already running. Conversely,
35848 the server must ignore @samp{t} actions for threads that are already
35851 @emph{Note:} In non-stop mode, a thread is considered running until
35852 @value{GDBN} acknowleges an asynchronous stop notification for it with
35853 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
35855 The stub must support @samp{vCont} if it reports support for
35856 multiprocess extensions (@pxref{multiprocess extensions}).
35859 @xref{Stop Reply Packets}, for the reply specifications.
35862 @cindex @samp{vCont?} packet
35863 Request a list of actions supported by the @samp{vCont} packet.
35867 @item vCont@r{[};@var{action}@dots{}@r{]}
35868 The @samp{vCont} packet is supported. Each @var{action} is a supported
35869 command in the @samp{vCont} packet.
35871 The @samp{vCont} packet is not supported.
35874 @anchor{vCtrlC packet}
35876 @cindex @samp{vCtrlC} packet
35877 Interrupt remote target as if a control-C was pressed on the remote
35878 terminal. This is the equivalent to reacting to the @code{^C}
35879 (@samp{\003}, the control-C character) character in all-stop mode
35880 while the target is running, except this works in non-stop mode.
35881 @xref{interrupting remote targets}, for more info on the all-stop
35892 @item vFile:@var{operation}:@var{parameter}@dots{}
35893 @cindex @samp{vFile} packet
35894 Perform a file operation on the target system. For details,
35895 see @ref{Host I/O Packets}.
35897 @item vFlashErase:@var{addr},@var{length}
35898 @cindex @samp{vFlashErase} packet
35899 Direct the stub to erase @var{length} bytes of flash starting at
35900 @var{addr}. The region may enclose any number of flash blocks, but
35901 its start and end must fall on block boundaries, as indicated by the
35902 flash block size appearing in the memory map (@pxref{Memory Map
35903 Format}). @value{GDBN} groups flash memory programming operations
35904 together, and sends a @samp{vFlashDone} request after each group; the
35905 stub is allowed to delay erase operation until the @samp{vFlashDone}
35906 packet is received.
35916 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35917 @cindex @samp{vFlashWrite} packet
35918 Direct the stub to write data to flash address @var{addr}. The data
35919 is passed in binary form using the same encoding as for the @samp{X}
35920 packet (@pxref{Binary Data}). The memory ranges specified by
35921 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35922 not overlap, and must appear in order of increasing addresses
35923 (although @samp{vFlashErase} packets for higher addresses may already
35924 have been received; the ordering is guaranteed only between
35925 @samp{vFlashWrite} packets). If a packet writes to an address that was
35926 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35927 target-specific method, the results are unpredictable.
35935 for vFlashWrite addressing non-flash memory
35941 @cindex @samp{vFlashDone} packet
35942 Indicate to the stub that flash programming operation is finished.
35943 The stub is permitted to delay or batch the effects of a group of
35944 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35945 @samp{vFlashDone} packet is received. The contents of the affected
35946 regions of flash memory are unpredictable until the @samp{vFlashDone}
35947 request is completed.
35949 @item vKill;@var{pid}
35950 @cindex @samp{vKill} packet
35951 @anchor{vKill packet}
35952 Kill the process with the specified process ID @var{pid}, which is a
35953 hexadecimal integer identifying the process. This packet is used in
35954 preference to @samp{k} when multiprocess protocol extensions are
35955 supported; see @ref{multiprocess extensions}.
35965 @item vMustReplyEmpty
35966 @cindex @samp{vMustReplyEmpty} packet
35967 The correct reply to an unknown @samp{v} packet is to return the empty
35968 string, however, some older versions of @command{gdbserver} would
35969 incorrectly return @samp{OK} for unknown @samp{v} packets.
35971 The @samp{vMustReplyEmpty} is used as a feature test to check how
35972 @command{gdbserver} handles unknown packets, it is important that this
35973 packet be handled in the same way as other unknown @samp{v} packets.
35974 If this packet is handled differently to other unknown @samp{v}
35975 packets then it is possile that @value{GDBN} may run into problems in
35976 other areas, specifically around use of @samp{vFile:setfs:}.
35978 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35979 @cindex @samp{vRun} packet
35980 Run the program @var{filename}, passing it each @var{argument} on its
35981 command line. The file and arguments are hex-encoded strings. If
35982 @var{filename} is an empty string, the stub may use a default program
35983 (e.g.@: the last program run). The program is created in the stopped
35986 @c FIXME: What about non-stop mode?
35988 This packet is only available in extended mode (@pxref{extended mode}).
35994 @item @r{Any stop packet}
35995 for success (@pxref{Stop Reply Packets})
35999 @cindex @samp{vStopped} packet
36000 @xref{Notification Packets}.
36002 @item X @var{addr},@var{length}:@var{XX@dots{}}
36004 @cindex @samp{X} packet
36005 Write data to memory, where the data is transmitted in binary.
36006 Memory is specified by its address @var{addr} and number of addressable memory
36007 units @var{length} (@pxref{addressable memory unit});
36008 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36018 @item z @var{type},@var{addr},@var{kind}
36019 @itemx Z @var{type},@var{addr},@var{kind}
36020 @anchor{insert breakpoint or watchpoint packet}
36021 @cindex @samp{z} packet
36022 @cindex @samp{Z} packets
36023 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36024 watchpoint starting at address @var{address} of kind @var{kind}.
36026 Each breakpoint and watchpoint packet @var{type} is documented
36029 @emph{Implementation notes: A remote target shall return an empty string
36030 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36031 remote target shall support either both or neither of a given
36032 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36033 avoid potential problems with duplicate packets, the operations should
36034 be implemented in an idempotent way.}
36036 @item z0,@var{addr},@var{kind}
36037 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36038 @cindex @samp{z0} packet
36039 @cindex @samp{Z0} packet
36040 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36041 @var{addr} of type @var{kind}.
36043 A software breakpoint is implemented by replacing the instruction at
36044 @var{addr} with a software breakpoint or trap instruction. The
36045 @var{kind} is target-specific and typically indicates the size of the
36046 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36047 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36048 architectures have additional meanings for @var{kind}
36049 (@pxref{Architecture-Specific Protocol Details}); if no
36050 architecture-specific value is being used, it should be @samp{0}.
36051 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36052 conditional expressions in bytecode form that should be evaluated on
36053 the target's side. These are the conditions that should be taken into
36054 consideration when deciding if the breakpoint trigger should be
36055 reported back to @value{GDBN}.
36057 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36058 for how to best report a software breakpoint event to @value{GDBN}.
36060 The @var{cond_list} parameter is comprised of a series of expressions,
36061 concatenated without separators. Each expression has the following form:
36065 @item X @var{len},@var{expr}
36066 @var{len} is the length of the bytecode expression and @var{expr} is the
36067 actual conditional expression in bytecode form.
36071 The optional @var{cmd_list} parameter introduces commands that may be
36072 run on the target, rather than being reported back to @value{GDBN}.
36073 The parameter starts with a numeric flag @var{persist}; if the flag is
36074 nonzero, then the breakpoint may remain active and the commands
36075 continue to be run even when @value{GDBN} disconnects from the target.
36076 Following this flag is a series of expressions concatenated with no
36077 separators. Each expression has the following form:
36081 @item X @var{len},@var{expr}
36082 @var{len} is the length of the bytecode expression and @var{expr} is the
36083 actual commands expression in bytecode form.
36087 @emph{Implementation note: It is possible for a target to copy or move
36088 code that contains software breakpoints (e.g., when implementing
36089 overlays). The behavior of this packet, in the presence of such a
36090 target, is not defined.}
36102 @item z1,@var{addr},@var{kind}
36103 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36104 @cindex @samp{z1} packet
36105 @cindex @samp{Z1} packet
36106 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36107 address @var{addr}.
36109 A hardware breakpoint is implemented using a mechanism that is not
36110 dependent on being able to modify the target's memory. The
36111 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36112 same meaning as in @samp{Z0} packets.
36114 @emph{Implementation note: A hardware breakpoint is not affected by code
36127 @item z2,@var{addr},@var{kind}
36128 @itemx Z2,@var{addr},@var{kind}
36129 @cindex @samp{z2} packet
36130 @cindex @samp{Z2} packet
36131 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36132 The number of bytes to watch is specified by @var{kind}.
36144 @item z3,@var{addr},@var{kind}
36145 @itemx Z3,@var{addr},@var{kind}
36146 @cindex @samp{z3} packet
36147 @cindex @samp{Z3} packet
36148 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36149 The number of bytes to watch is specified by @var{kind}.
36161 @item z4,@var{addr},@var{kind}
36162 @itemx Z4,@var{addr},@var{kind}
36163 @cindex @samp{z4} packet
36164 @cindex @samp{Z4} packet
36165 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36166 The number of bytes to watch is specified by @var{kind}.
36180 @node Stop Reply Packets
36181 @section Stop Reply Packets
36182 @cindex stop reply packets
36184 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36185 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36186 receive any of the below as a reply. Except for @samp{?}
36187 and @samp{vStopped}, that reply is only returned
36188 when the target halts. In the below the exact meaning of @dfn{signal
36189 number} is defined by the header @file{include/gdb/signals.h} in the
36190 @value{GDBN} source code.
36192 In non-stop mode, the server will simply reply @samp{OK} to commands
36193 such as @samp{vCont}; any stop will be the subject of a future
36194 notification. @xref{Remote Non-Stop}.
36196 As in the description of request packets, we include spaces in the
36197 reply templates for clarity; these are not part of the reply packet's
36198 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36204 The program received signal number @var{AA} (a two-digit hexadecimal
36205 number). This is equivalent to a @samp{T} response with no
36206 @var{n}:@var{r} pairs.
36208 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36209 @cindex @samp{T} packet reply
36210 The program received signal number @var{AA} (a two-digit hexadecimal
36211 number). This is equivalent to an @samp{S} response, except that the
36212 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36213 and other information directly in the stop reply packet, reducing
36214 round-trip latency. Single-step and breakpoint traps are reported
36215 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36219 If @var{n} is a hexadecimal number, it is a register number, and the
36220 corresponding @var{r} gives that register's value. The data @var{r} is a
36221 series of bytes in target byte order, with each byte given by a
36222 two-digit hex number.
36225 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36226 the stopped thread, as specified in @ref{thread-id syntax}.
36229 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36230 the core on which the stop event was detected.
36233 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36234 specific event that stopped the target. The currently defined stop
36235 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36236 signal. At most one stop reason should be present.
36239 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36240 and go on to the next; this allows us to extend the protocol in the
36244 The currently defined stop reasons are:
36250 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36253 @item syscall_entry
36254 @itemx syscall_return
36255 The packet indicates a syscall entry or return, and @var{r} is the
36256 syscall number, in hex.
36258 @cindex shared library events, remote reply
36260 The packet indicates that the loaded libraries have changed.
36261 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36262 list of loaded libraries. The @var{r} part is ignored.
36264 @cindex replay log events, remote reply
36266 The packet indicates that the target cannot continue replaying
36267 logged execution events, because it has reached the end (or the
36268 beginning when executing backward) of the log. The value of @var{r}
36269 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36270 for more information.
36273 @anchor{swbreak stop reason}
36274 The packet indicates a software breakpoint instruction was executed,
36275 irrespective of whether it was @value{GDBN} that planted the
36276 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36277 part must be left empty.
36279 On some architectures, such as x86, at the architecture level, when a
36280 breakpoint instruction executes the program counter points at the
36281 breakpoint address plus an offset. On such targets, the stub is
36282 responsible for adjusting the PC to point back at the breakpoint
36285 This packet should not be sent by default; older @value{GDBN} versions
36286 did not support it. @value{GDBN} requests it, by supplying an
36287 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36288 remote stub must also supply the appropriate @samp{qSupported} feature
36289 indicating support.
36291 This packet is required for correct non-stop mode operation.
36294 The packet indicates the target stopped for a hardware breakpoint.
36295 The @var{r} part must be left empty.
36297 The same remarks about @samp{qSupported} and non-stop mode above
36300 @cindex fork events, remote reply
36302 The packet indicates that @code{fork} was called, and @var{r}
36303 is the thread ID of the new child process. Refer to
36304 @ref{thread-id syntax} for the format of the @var{thread-id}
36305 field. This packet is only applicable to targets that support
36308 This packet should not be sent by default; older @value{GDBN} versions
36309 did not support it. @value{GDBN} requests it, by supplying an
36310 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36311 remote stub must also supply the appropriate @samp{qSupported} feature
36312 indicating support.
36314 @cindex vfork events, remote reply
36316 The packet indicates that @code{vfork} was called, and @var{r}
36317 is the thread ID of the new child process. Refer to
36318 @ref{thread-id syntax} for the format of the @var{thread-id}
36319 field. This packet is only applicable to targets that support
36322 This packet should not be sent by default; older @value{GDBN} versions
36323 did not support it. @value{GDBN} requests it, by supplying an
36324 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36325 remote stub must also supply the appropriate @samp{qSupported} feature
36326 indicating support.
36328 @cindex vforkdone events, remote reply
36330 The packet indicates that a child process created by a vfork
36331 has either called @code{exec} or terminated, so that the
36332 address spaces of the parent and child process are no longer
36333 shared. The @var{r} part is ignored. This packet is only
36334 applicable to targets that support vforkdone events.
36336 This packet should not be sent by default; older @value{GDBN} versions
36337 did not support it. @value{GDBN} requests it, by supplying an
36338 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36339 remote stub must also supply the appropriate @samp{qSupported} feature
36340 indicating support.
36342 @cindex exec events, remote reply
36344 The packet indicates that @code{execve} was called, and @var{r}
36345 is the absolute pathname of the file that was executed, in hex.
36346 This packet is only applicable to targets that support exec events.
36348 This packet should not be sent by default; older @value{GDBN} versions
36349 did not support it. @value{GDBN} requests it, by supplying an
36350 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36351 remote stub must also supply the appropriate @samp{qSupported} feature
36352 indicating support.
36354 @cindex thread create event, remote reply
36355 @anchor{thread create event}
36357 The packet indicates that the thread was just created. The new thread
36358 is stopped until @value{GDBN} sets it running with a resumption packet
36359 (@pxref{vCont packet}). This packet should not be sent by default;
36360 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36361 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36362 @var{r} part is ignored.
36367 @itemx W @var{AA} ; process:@var{pid}
36368 The process exited, and @var{AA} is the exit status. This is only
36369 applicable to certain targets.
36371 The second form of the response, including the process ID of the
36372 exited process, can be used only when @value{GDBN} has reported
36373 support for multiprocess protocol extensions; see @ref{multiprocess
36374 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36378 @itemx X @var{AA} ; process:@var{pid}
36379 The process terminated with signal @var{AA}.
36381 The second form of the response, including the process ID of the
36382 terminated process, can be used only when @value{GDBN} has reported
36383 support for multiprocess protocol extensions; see @ref{multiprocess
36384 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36387 @anchor{thread exit event}
36388 @cindex thread exit event, remote reply
36389 @item w @var{AA} ; @var{tid}
36391 The thread exited, and @var{AA} is the exit status. This response
36392 should not be sent by default; @value{GDBN} requests it with the
36393 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36394 @var{AA} is formatted as a big-endian hex string.
36397 There are no resumed threads left in the target. In other words, even
36398 though the process is alive, the last resumed thread has exited. For
36399 example, say the target process has two threads: thread 1 and thread
36400 2. The client leaves thread 1 stopped, and resumes thread 2, which
36401 subsequently exits. At this point, even though the process is still
36402 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36403 executing either. The @samp{N} stop reply thus informs the client
36404 that it can stop waiting for stop replies. This packet should not be
36405 sent by default; older @value{GDBN} versions did not support it.
36406 @value{GDBN} requests it, by supplying an appropriate
36407 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36408 also supply the appropriate @samp{qSupported} feature indicating
36411 @item O @var{XX}@dots{}
36412 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36413 written as the program's console output. This can happen at any time
36414 while the program is running and the debugger should continue to wait
36415 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36417 @item F @var{call-id},@var{parameter}@dots{}
36418 @var{call-id} is the identifier which says which host system call should
36419 be called. This is just the name of the function. Translation into the
36420 correct system call is only applicable as it's defined in @value{GDBN}.
36421 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36424 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36425 this very system call.
36427 The target replies with this packet when it expects @value{GDBN} to
36428 call a host system call on behalf of the target. @value{GDBN} replies
36429 with an appropriate @samp{F} packet and keeps up waiting for the next
36430 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36431 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36432 Protocol Extension}, for more details.
36436 @node General Query Packets
36437 @section General Query Packets
36438 @cindex remote query requests
36440 Packets starting with @samp{q} are @dfn{general query packets};
36441 packets starting with @samp{Q} are @dfn{general set packets}. General
36442 query and set packets are a semi-unified form for retrieving and
36443 sending information to and from the stub.
36445 The initial letter of a query or set packet is followed by a name
36446 indicating what sort of thing the packet applies to. For example,
36447 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36448 definitions with the stub. These packet names follow some
36453 The name must not contain commas, colons or semicolons.
36455 Most @value{GDBN} query and set packets have a leading upper case
36458 The names of custom vendor packets should use a company prefix, in
36459 lower case, followed by a period. For example, packets designed at
36460 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36461 foos) or @samp{Qacme.bar} (for setting bars).
36464 The name of a query or set packet should be separated from any
36465 parameters by a @samp{:}; the parameters themselves should be
36466 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36467 full packet name, and check for a separator or the end of the packet,
36468 in case two packet names share a common prefix. New packets should not begin
36469 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36470 packets predate these conventions, and have arguments without any terminator
36471 for the packet name; we suspect they are in widespread use in places that
36472 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36473 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36476 Like the descriptions of the other packets, each description here
36477 has a template showing the packet's overall syntax, followed by an
36478 explanation of the packet's meaning. We include spaces in some of the
36479 templates for clarity; these are not part of the packet's syntax. No
36480 @value{GDBN} packet uses spaces to separate its components.
36482 Here are the currently defined query and set packets:
36488 Turn on or off the agent as a helper to perform some debugging operations
36489 delegated from @value{GDBN} (@pxref{Control Agent}).
36491 @item QAllow:@var{op}:@var{val}@dots{}
36492 @cindex @samp{QAllow} packet
36493 Specify which operations @value{GDBN} expects to request of the
36494 target, as a semicolon-separated list of operation name and value
36495 pairs. Possible values for @var{op} include @samp{WriteReg},
36496 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36497 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36498 indicating that @value{GDBN} will not request the operation, or 1,
36499 indicating that it may. (The target can then use this to set up its
36500 own internals optimally, for instance if the debugger never expects to
36501 insert breakpoints, it may not need to install its own trap handler.)
36504 @cindex current thread, remote request
36505 @cindex @samp{qC} packet
36506 Return the current thread ID.
36510 @item QC @var{thread-id}
36511 Where @var{thread-id} is a thread ID as documented in
36512 @ref{thread-id syntax}.
36513 @item @r{(anything else)}
36514 Any other reply implies the old thread ID.
36517 @item qCRC:@var{addr},@var{length}
36518 @cindex CRC of memory block, remote request
36519 @cindex @samp{qCRC} packet
36520 @anchor{qCRC packet}
36521 Compute the CRC checksum of a block of memory using CRC-32 defined in
36522 IEEE 802.3. The CRC is computed byte at a time, taking the most
36523 significant bit of each byte first. The initial pattern code
36524 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36526 @emph{Note:} This is the same CRC used in validating separate debug
36527 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36528 Files}). However the algorithm is slightly different. When validating
36529 separate debug files, the CRC is computed taking the @emph{least}
36530 significant bit of each byte first, and the final result is inverted to
36531 detect trailing zeros.
36536 An error (such as memory fault)
36537 @item C @var{crc32}
36538 The specified memory region's checksum is @var{crc32}.
36541 @item QDisableRandomization:@var{value}
36542 @cindex disable address space randomization, remote request
36543 @cindex @samp{QDisableRandomization} packet
36544 Some target operating systems will randomize the virtual address space
36545 of the inferior process as a security feature, but provide a feature
36546 to disable such randomization, e.g.@: to allow for a more deterministic
36547 debugging experience. On such systems, this packet with a @var{value}
36548 of 1 directs the target to disable address space randomization for
36549 processes subsequently started via @samp{vRun} packets, while a packet
36550 with a @var{value} of 0 tells the target to enable address space
36553 This packet is only available in extended mode (@pxref{extended mode}).
36558 The request succeeded.
36561 An error occurred. The error number @var{nn} is given as hex digits.
36564 An empty reply indicates that @samp{QDisableRandomization} is not supported
36568 This packet is not probed by default; the remote stub must request it,
36569 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36570 This should only be done on targets that actually support disabling
36571 address space randomization.
36573 @item QStartupWithShell:@var{value}
36574 @cindex startup with shell, remote request
36575 @cindex @samp{QStartupWithShell} packet
36576 On UNIX-like targets, it is possible to start the inferior using a
36577 shell program. This is the default behavior on both @value{GDBN} and
36578 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
36579 used to inform @command{gdbserver} whether it should start the
36580 inferior using a shell or not.
36582 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
36583 to start the inferior. If @var{value} is @samp{1},
36584 @command{gdbserver} will use a shell to start the inferior. All other
36585 values are considered an error.
36587 This packet is only available in extended mode (@pxref{extended
36593 The request succeeded.
36596 An error occurred. The error number @var{nn} is given as hex digits.
36599 This packet is not probed by default; the remote stub must request it,
36600 by supplying an appropriate @samp{qSupported} response
36601 (@pxref{qSupported}). This should only be done on targets that
36602 actually support starting the inferior using a shell.
36604 Use of this packet is controlled by the @code{set startup-with-shell}
36605 command; @pxref{set startup-with-shell}.
36608 @itemx qsThreadInfo
36609 @cindex list active threads, remote request
36610 @cindex @samp{qfThreadInfo} packet
36611 @cindex @samp{qsThreadInfo} packet
36612 Obtain a list of all active thread IDs from the target (OS). Since there
36613 may be too many active threads to fit into one reply packet, this query
36614 works iteratively: it may require more than one query/reply sequence to
36615 obtain the entire list of threads. The first query of the sequence will
36616 be the @samp{qfThreadInfo} query; subsequent queries in the
36617 sequence will be the @samp{qsThreadInfo} query.
36619 NOTE: This packet replaces the @samp{qL} query (see below).
36623 @item m @var{thread-id}
36625 @item m @var{thread-id},@var{thread-id}@dots{}
36626 a comma-separated list of thread IDs
36628 (lower case letter @samp{L}) denotes end of list.
36631 In response to each query, the target will reply with a list of one or
36632 more thread IDs, separated by commas.
36633 @value{GDBN} will respond to each reply with a request for more thread
36634 ids (using the @samp{qs} form of the query), until the target responds
36635 with @samp{l} (lower-case ell, for @dfn{last}).
36636 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36639 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36640 initial connection with the remote target, and the very first thread ID
36641 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36642 message. Therefore, the stub should ensure that the first thread ID in
36643 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36645 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36646 @cindex get thread-local storage address, remote request
36647 @cindex @samp{qGetTLSAddr} packet
36648 Fetch the address associated with thread local storage specified
36649 by @var{thread-id}, @var{offset}, and @var{lm}.
36651 @var{thread-id} is the thread ID associated with the
36652 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36654 @var{offset} is the (big endian, hex encoded) offset associated with the
36655 thread local variable. (This offset is obtained from the debug
36656 information associated with the variable.)
36658 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36659 load module associated with the thread local storage. For example,
36660 a @sc{gnu}/Linux system will pass the link map address of the shared
36661 object associated with the thread local storage under consideration.
36662 Other operating environments may choose to represent the load module
36663 differently, so the precise meaning of this parameter will vary.
36667 @item @var{XX}@dots{}
36668 Hex encoded (big endian) bytes representing the address of the thread
36669 local storage requested.
36672 An error occurred. The error number @var{nn} is given as hex digits.
36675 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36678 @item qGetTIBAddr:@var{thread-id}
36679 @cindex get thread information block address
36680 @cindex @samp{qGetTIBAddr} packet
36681 Fetch address of the Windows OS specific Thread Information Block.
36683 @var{thread-id} is the thread ID associated with the thread.
36687 @item @var{XX}@dots{}
36688 Hex encoded (big endian) bytes representing the linear address of the
36689 thread information block.
36692 An error occured. This means that either the thread was not found, or the
36693 address could not be retrieved.
36696 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36699 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36700 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36701 digit) is one to indicate the first query and zero to indicate a
36702 subsequent query; @var{threadcount} (two hex digits) is the maximum
36703 number of threads the response packet can contain; and @var{nextthread}
36704 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36705 returned in the response as @var{argthread}.
36707 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36711 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36712 Where: @var{count} (two hex digits) is the number of threads being
36713 returned; @var{done} (one hex digit) is zero to indicate more threads
36714 and one indicates no further threads; @var{argthreadid} (eight hex
36715 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36716 is a sequence of thread IDs, @var{threadid} (eight hex
36717 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36721 @cindex section offsets, remote request
36722 @cindex @samp{qOffsets} packet
36723 Get section offsets that the target used when relocating the downloaded
36728 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36729 Relocate the @code{Text} section by @var{xxx} from its original address.
36730 Relocate the @code{Data} section by @var{yyy} from its original address.
36731 If the object file format provides segment information (e.g.@: @sc{elf}
36732 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36733 segments by the supplied offsets.
36735 @emph{Note: while a @code{Bss} offset may be included in the response,
36736 @value{GDBN} ignores this and instead applies the @code{Data} offset
36737 to the @code{Bss} section.}
36739 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36740 Relocate the first segment of the object file, which conventionally
36741 contains program code, to a starting address of @var{xxx}. If
36742 @samp{DataSeg} is specified, relocate the second segment, which
36743 conventionally contains modifiable data, to a starting address of
36744 @var{yyy}. @value{GDBN} will report an error if the object file
36745 does not contain segment information, or does not contain at least
36746 as many segments as mentioned in the reply. Extra segments are
36747 kept at fixed offsets relative to the last relocated segment.
36750 @item qP @var{mode} @var{thread-id}
36751 @cindex thread information, remote request
36752 @cindex @samp{qP} packet
36753 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36754 encoded 32 bit mode; @var{thread-id} is a thread ID
36755 (@pxref{thread-id syntax}).
36757 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36760 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36764 @cindex non-stop mode, remote request
36765 @cindex @samp{QNonStop} packet
36767 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36768 @xref{Remote Non-Stop}, for more information.
36773 The request succeeded.
36776 An error occurred. The error number @var{nn} is given as hex digits.
36779 An empty reply indicates that @samp{QNonStop} is not supported by
36783 This packet is not probed by default; the remote stub must request it,
36784 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36785 Use of this packet is controlled by the @code{set non-stop} command;
36786 @pxref{Non-Stop Mode}.
36788 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36789 @itemx QCatchSyscalls:0
36790 @cindex catch syscalls from inferior, remote request
36791 @cindex @samp{QCatchSyscalls} packet
36792 @anchor{QCatchSyscalls}
36793 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36794 catching syscalls from the inferior process.
36796 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36797 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36798 is listed, every system call should be reported.
36800 Note that if a syscall not in the list is reported, @value{GDBN} will
36801 still filter the event according to its own list from all corresponding
36802 @code{catch syscall} commands. However, it is more efficient to only
36803 report the requested syscalls.
36805 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36806 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36808 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36809 kept for the new process too. On targets where exec may affect syscall
36810 numbers, for example with exec between 32 and 64-bit processes, the
36811 client should send a new packet with the new syscall list.
36816 The request succeeded.
36819 An error occurred. @var{nn} are hex digits.
36822 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36826 Use of this packet is controlled by the @code{set remote catch-syscalls}
36827 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36828 This packet is not probed by default; the remote stub must request it,
36829 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36831 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36832 @cindex pass signals to inferior, remote request
36833 @cindex @samp{QPassSignals} packet
36834 @anchor{QPassSignals}
36835 Each listed @var{signal} should be passed directly to the inferior process.
36836 Signals are numbered identically to continue packets and stop replies
36837 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36838 strictly greater than the previous item. These signals do not need to stop
36839 the inferior, or be reported to @value{GDBN}. All other signals should be
36840 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36841 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36842 new list. This packet improves performance when using @samp{handle
36843 @var{signal} nostop noprint pass}.
36848 The request succeeded.
36851 An error occurred. The error number @var{nn} is given as hex digits.
36854 An empty reply indicates that @samp{QPassSignals} is not supported by
36858 Use of this packet is controlled by the @code{set remote pass-signals}
36859 command (@pxref{Remote Configuration, set remote pass-signals}).
36860 This packet is not probed by default; the remote stub must request it,
36861 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36863 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36864 @cindex signals the inferior may see, remote request
36865 @cindex @samp{QProgramSignals} packet
36866 @anchor{QProgramSignals}
36867 Each listed @var{signal} may be delivered to the inferior process.
36868 Others should be silently discarded.
36870 In some cases, the remote stub may need to decide whether to deliver a
36871 signal to the program or not without @value{GDBN} involvement. One
36872 example of that is while detaching --- the program's threads may have
36873 stopped for signals that haven't yet had a chance of being reported to
36874 @value{GDBN}, and so the remote stub can use the signal list specified
36875 by this packet to know whether to deliver or ignore those pending
36878 This does not influence whether to deliver a signal as requested by a
36879 resumption packet (@pxref{vCont packet}).
36881 Signals are numbered identically to continue packets and stop replies
36882 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36883 strictly greater than the previous item. Multiple
36884 @samp{QProgramSignals} packets do not combine; any earlier
36885 @samp{QProgramSignals} list is completely replaced by the new list.
36890 The request succeeded.
36893 An error occurred. The error number @var{nn} is given as hex digits.
36896 An empty reply indicates that @samp{QProgramSignals} is not supported
36900 Use of this packet is controlled by the @code{set remote program-signals}
36901 command (@pxref{Remote Configuration, set remote program-signals}).
36902 This packet is not probed by default; the remote stub must request it,
36903 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36905 @anchor{QThreadEvents}
36906 @item QThreadEvents:1
36907 @itemx QThreadEvents:0
36908 @cindex thread create/exit events, remote request
36909 @cindex @samp{QThreadEvents} packet
36911 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36912 reporting of thread create and exit events. @xref{thread create
36913 event}, for the reply specifications. For example, this is used in
36914 non-stop mode when @value{GDBN} stops a set of threads and
36915 synchronously waits for the their corresponding stop replies. Without
36916 exit events, if one of the threads exits, @value{GDBN} would hang
36917 forever not knowing that it should no longer expect a stop for that
36918 same thread. @value{GDBN} does not enable this feature unless the
36919 stub reports that it supports it by including @samp{QThreadEvents+} in
36920 its @samp{qSupported} reply.
36925 The request succeeded.
36928 An error occurred. The error number @var{nn} is given as hex digits.
36931 An empty reply indicates that @samp{QThreadEvents} is not supported by
36935 Use of this packet is controlled by the @code{set remote thread-events}
36936 command (@pxref{Remote Configuration, set remote thread-events}).
36938 @item qRcmd,@var{command}
36939 @cindex execute remote command, remote request
36940 @cindex @samp{qRcmd} packet
36941 @var{command} (hex encoded) is passed to the local interpreter for
36942 execution. Invalid commands should be reported using the output
36943 string. Before the final result packet, the target may also respond
36944 with a number of intermediate @samp{O@var{output}} console output
36945 packets. @emph{Implementors should note that providing access to a
36946 stubs's interpreter may have security implications}.
36951 A command response with no output.
36953 A command response with the hex encoded output string @var{OUTPUT}.
36955 Indicate a badly formed request.
36957 An empty reply indicates that @samp{qRcmd} is not recognized.
36960 (Note that the @code{qRcmd} packet's name is separated from the
36961 command by a @samp{,}, not a @samp{:}, contrary to the naming
36962 conventions above. Please don't use this packet as a model for new
36965 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36966 @cindex searching memory, in remote debugging
36968 @cindex @samp{qSearch:memory} packet
36970 @cindex @samp{qSearch memory} packet
36971 @anchor{qSearch memory}
36972 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36973 Both @var{address} and @var{length} are encoded in hex;
36974 @var{search-pattern} is a sequence of bytes, also hex encoded.
36979 The pattern was not found.
36981 The pattern was found at @var{address}.
36983 A badly formed request or an error was encountered while searching memory.
36985 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36988 @item QStartNoAckMode
36989 @cindex @samp{QStartNoAckMode} packet
36990 @anchor{QStartNoAckMode}
36991 Request that the remote stub disable the normal @samp{+}/@samp{-}
36992 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36997 The stub has switched to no-acknowledgment mode.
36998 @value{GDBN} acknowledges this reponse,
36999 but neither the stub nor @value{GDBN} shall send or expect further
37000 @samp{+}/@samp{-} acknowledgments in the current connection.
37002 An empty reply indicates that the stub does not support no-acknowledgment mode.
37005 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37006 @cindex supported packets, remote query
37007 @cindex features of the remote protocol
37008 @cindex @samp{qSupported} packet
37009 @anchor{qSupported}
37010 Tell the remote stub about features supported by @value{GDBN}, and
37011 query the stub for features it supports. This packet allows
37012 @value{GDBN} and the remote stub to take advantage of each others'
37013 features. @samp{qSupported} also consolidates multiple feature probes
37014 at startup, to improve @value{GDBN} performance---a single larger
37015 packet performs better than multiple smaller probe packets on
37016 high-latency links. Some features may enable behavior which must not
37017 be on by default, e.g.@: because it would confuse older clients or
37018 stubs. Other features may describe packets which could be
37019 automatically probed for, but are not. These features must be
37020 reported before @value{GDBN} will use them. This ``default
37021 unsupported'' behavior is not appropriate for all packets, but it
37022 helps to keep the initial connection time under control with new
37023 versions of @value{GDBN} which support increasing numbers of packets.
37027 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37028 The stub supports or does not support each returned @var{stubfeature},
37029 depending on the form of each @var{stubfeature} (see below for the
37032 An empty reply indicates that @samp{qSupported} is not recognized,
37033 or that no features needed to be reported to @value{GDBN}.
37036 The allowed forms for each feature (either a @var{gdbfeature} in the
37037 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37041 @item @var{name}=@var{value}
37042 The remote protocol feature @var{name} is supported, and associated
37043 with the specified @var{value}. The format of @var{value} depends
37044 on the feature, but it must not include a semicolon.
37046 The remote protocol feature @var{name} is supported, and does not
37047 need an associated value.
37049 The remote protocol feature @var{name} is not supported.
37051 The remote protocol feature @var{name} may be supported, and
37052 @value{GDBN} should auto-detect support in some other way when it is
37053 needed. This form will not be used for @var{gdbfeature} notifications,
37054 but may be used for @var{stubfeature} responses.
37057 Whenever the stub receives a @samp{qSupported} request, the
37058 supplied set of @value{GDBN} features should override any previous
37059 request. This allows @value{GDBN} to put the stub in a known
37060 state, even if the stub had previously been communicating with
37061 a different version of @value{GDBN}.
37063 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37068 This feature indicates whether @value{GDBN} supports multiprocess
37069 extensions to the remote protocol. @value{GDBN} does not use such
37070 extensions unless the stub also reports that it supports them by
37071 including @samp{multiprocess+} in its @samp{qSupported} reply.
37072 @xref{multiprocess extensions}, for details.
37075 This feature indicates that @value{GDBN} supports the XML target
37076 description. If the stub sees @samp{xmlRegisters=} with target
37077 specific strings separated by a comma, it will report register
37081 This feature indicates whether @value{GDBN} supports the
37082 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37083 instruction reply packet}).
37086 This feature indicates whether @value{GDBN} supports the swbreak stop
37087 reason in stop replies. @xref{swbreak stop reason}, for details.
37090 This feature indicates whether @value{GDBN} supports the hwbreak stop
37091 reason in stop replies. @xref{swbreak stop reason}, for details.
37094 This feature indicates whether @value{GDBN} supports fork event
37095 extensions to the remote protocol. @value{GDBN} does not use such
37096 extensions unless the stub also reports that it supports them by
37097 including @samp{fork-events+} in its @samp{qSupported} reply.
37100 This feature indicates whether @value{GDBN} supports vfork event
37101 extensions to the remote protocol. @value{GDBN} does not use such
37102 extensions unless the stub also reports that it supports them by
37103 including @samp{vfork-events+} in its @samp{qSupported} reply.
37106 This feature indicates whether @value{GDBN} supports exec event
37107 extensions to the remote protocol. @value{GDBN} does not use such
37108 extensions unless the stub also reports that it supports them by
37109 including @samp{exec-events+} in its @samp{qSupported} reply.
37111 @item vContSupported
37112 This feature indicates whether @value{GDBN} wants to know the
37113 supported actions in the reply to @samp{vCont?} packet.
37116 Stubs should ignore any unknown values for
37117 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37118 packet supports receiving packets of unlimited length (earlier
37119 versions of @value{GDBN} may reject overly long responses). Additional values
37120 for @var{gdbfeature} may be defined in the future to let the stub take
37121 advantage of new features in @value{GDBN}, e.g.@: incompatible
37122 improvements in the remote protocol---the @samp{multiprocess} feature is
37123 an example of such a feature. The stub's reply should be independent
37124 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37125 describes all the features it supports, and then the stub replies with
37126 all the features it supports.
37128 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37129 responses, as long as each response uses one of the standard forms.
37131 Some features are flags. A stub which supports a flag feature
37132 should respond with a @samp{+} form response. Other features
37133 require values, and the stub should respond with an @samp{=}
37136 Each feature has a default value, which @value{GDBN} will use if
37137 @samp{qSupported} is not available or if the feature is not mentioned
37138 in the @samp{qSupported} response. The default values are fixed; a
37139 stub is free to omit any feature responses that match the defaults.
37141 Not all features can be probed, but for those which can, the probing
37142 mechanism is useful: in some cases, a stub's internal
37143 architecture may not allow the protocol layer to know some information
37144 about the underlying target in advance. This is especially common in
37145 stubs which may be configured for multiple targets.
37147 These are the currently defined stub features and their properties:
37149 @multitable @columnfractions 0.35 0.2 0.12 0.2
37150 @c NOTE: The first row should be @headitem, but we do not yet require
37151 @c a new enough version of Texinfo (4.7) to use @headitem.
37153 @tab Value Required
37157 @item @samp{PacketSize}
37162 @item @samp{qXfer:auxv:read}
37167 @item @samp{qXfer:btrace:read}
37172 @item @samp{qXfer:btrace-conf:read}
37177 @item @samp{qXfer:exec-file:read}
37182 @item @samp{qXfer:features:read}
37187 @item @samp{qXfer:libraries:read}
37192 @item @samp{qXfer:libraries-svr4:read}
37197 @item @samp{augmented-libraries-svr4-read}
37202 @item @samp{qXfer:memory-map:read}
37207 @item @samp{qXfer:sdata:read}
37212 @item @samp{qXfer:spu:read}
37217 @item @samp{qXfer:spu:write}
37222 @item @samp{qXfer:siginfo:read}
37227 @item @samp{qXfer:siginfo:write}
37232 @item @samp{qXfer:threads:read}
37237 @item @samp{qXfer:traceframe-info:read}
37242 @item @samp{qXfer:uib:read}
37247 @item @samp{qXfer:fdpic:read}
37252 @item @samp{Qbtrace:off}
37257 @item @samp{Qbtrace:bts}
37262 @item @samp{Qbtrace:pt}
37267 @item @samp{Qbtrace-conf:bts:size}
37272 @item @samp{Qbtrace-conf:pt:size}
37277 @item @samp{QNonStop}
37282 @item @samp{QCatchSyscalls}
37287 @item @samp{QPassSignals}
37292 @item @samp{QStartNoAckMode}
37297 @item @samp{multiprocess}
37302 @item @samp{ConditionalBreakpoints}
37307 @item @samp{ConditionalTracepoints}
37312 @item @samp{ReverseContinue}
37317 @item @samp{ReverseStep}
37322 @item @samp{TracepointSource}
37327 @item @samp{QAgent}
37332 @item @samp{QAllow}
37337 @item @samp{QDisableRandomization}
37342 @item @samp{EnableDisableTracepoints}
37347 @item @samp{QTBuffer:size}
37352 @item @samp{tracenz}
37357 @item @samp{BreakpointCommands}
37362 @item @samp{swbreak}
37367 @item @samp{hwbreak}
37372 @item @samp{fork-events}
37377 @item @samp{vfork-events}
37382 @item @samp{exec-events}
37387 @item @samp{QThreadEvents}
37392 @item @samp{no-resumed}
37399 These are the currently defined stub features, in more detail:
37402 @cindex packet size, remote protocol
37403 @item PacketSize=@var{bytes}
37404 The remote stub can accept packets up to at least @var{bytes} in
37405 length. @value{GDBN} will send packets up to this size for bulk
37406 transfers, and will never send larger packets. This is a limit on the
37407 data characters in the packet, including the frame and checksum.
37408 There is no trailing NUL byte in a remote protocol packet; if the stub
37409 stores packets in a NUL-terminated format, it should allow an extra
37410 byte in its buffer for the NUL. If this stub feature is not supported,
37411 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37413 @item qXfer:auxv:read
37414 The remote stub understands the @samp{qXfer:auxv:read} packet
37415 (@pxref{qXfer auxiliary vector read}).
37417 @item qXfer:btrace:read
37418 The remote stub understands the @samp{qXfer:btrace:read}
37419 packet (@pxref{qXfer btrace read}).
37421 @item qXfer:btrace-conf:read
37422 The remote stub understands the @samp{qXfer:btrace-conf:read}
37423 packet (@pxref{qXfer btrace-conf read}).
37425 @item qXfer:exec-file:read
37426 The remote stub understands the @samp{qXfer:exec-file:read} packet
37427 (@pxref{qXfer executable filename read}).
37429 @item qXfer:features:read
37430 The remote stub understands the @samp{qXfer:features:read} packet
37431 (@pxref{qXfer target description read}).
37433 @item qXfer:libraries:read
37434 The remote stub understands the @samp{qXfer:libraries:read} packet
37435 (@pxref{qXfer library list read}).
37437 @item qXfer:libraries-svr4:read
37438 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37439 (@pxref{qXfer svr4 library list read}).
37441 @item augmented-libraries-svr4-read
37442 The remote stub understands the augmented form of the
37443 @samp{qXfer:libraries-svr4:read} packet
37444 (@pxref{qXfer svr4 library list read}).
37446 @item qXfer:memory-map:read
37447 The remote stub understands the @samp{qXfer:memory-map:read} packet
37448 (@pxref{qXfer memory map read}).
37450 @item qXfer:sdata:read
37451 The remote stub understands the @samp{qXfer:sdata:read} packet
37452 (@pxref{qXfer sdata read}).
37454 @item qXfer:spu:read
37455 The remote stub understands the @samp{qXfer:spu:read} packet
37456 (@pxref{qXfer spu read}).
37458 @item qXfer:spu:write
37459 The remote stub understands the @samp{qXfer:spu:write} packet
37460 (@pxref{qXfer spu write}).
37462 @item qXfer:siginfo:read
37463 The remote stub understands the @samp{qXfer:siginfo:read} packet
37464 (@pxref{qXfer siginfo read}).
37466 @item qXfer:siginfo:write
37467 The remote stub understands the @samp{qXfer:siginfo:write} packet
37468 (@pxref{qXfer siginfo write}).
37470 @item qXfer:threads:read
37471 The remote stub understands the @samp{qXfer:threads:read} packet
37472 (@pxref{qXfer threads read}).
37474 @item qXfer:traceframe-info:read
37475 The remote stub understands the @samp{qXfer:traceframe-info:read}
37476 packet (@pxref{qXfer traceframe info read}).
37478 @item qXfer:uib:read
37479 The remote stub understands the @samp{qXfer:uib:read}
37480 packet (@pxref{qXfer unwind info block}).
37482 @item qXfer:fdpic:read
37483 The remote stub understands the @samp{qXfer:fdpic:read}
37484 packet (@pxref{qXfer fdpic loadmap read}).
37487 The remote stub understands the @samp{QNonStop} packet
37488 (@pxref{QNonStop}).
37490 @item QCatchSyscalls
37491 The remote stub understands the @samp{QCatchSyscalls} packet
37492 (@pxref{QCatchSyscalls}).
37495 The remote stub understands the @samp{QPassSignals} packet
37496 (@pxref{QPassSignals}).
37498 @item QStartNoAckMode
37499 The remote stub understands the @samp{QStartNoAckMode} packet and
37500 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37503 @anchor{multiprocess extensions}
37504 @cindex multiprocess extensions, in remote protocol
37505 The remote stub understands the multiprocess extensions to the remote
37506 protocol syntax. The multiprocess extensions affect the syntax of
37507 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37508 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37509 replies. Note that reporting this feature indicates support for the
37510 syntactic extensions only, not that the stub necessarily supports
37511 debugging of more than one process at a time. The stub must not use
37512 multiprocess extensions in packet replies unless @value{GDBN} has also
37513 indicated it supports them in its @samp{qSupported} request.
37515 @item qXfer:osdata:read
37516 The remote stub understands the @samp{qXfer:osdata:read} packet
37517 ((@pxref{qXfer osdata read}).
37519 @item ConditionalBreakpoints
37520 The target accepts and implements evaluation of conditional expressions
37521 defined for breakpoints. The target will only report breakpoint triggers
37522 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37524 @item ConditionalTracepoints
37525 The remote stub accepts and implements conditional expressions defined
37526 for tracepoints (@pxref{Tracepoint Conditions}).
37528 @item ReverseContinue
37529 The remote stub accepts and implements the reverse continue packet
37533 The remote stub accepts and implements the reverse step packet
37536 @item TracepointSource
37537 The remote stub understands the @samp{QTDPsrc} packet that supplies
37538 the source form of tracepoint definitions.
37541 The remote stub understands the @samp{QAgent} packet.
37544 The remote stub understands the @samp{QAllow} packet.
37546 @item QDisableRandomization
37547 The remote stub understands the @samp{QDisableRandomization} packet.
37549 @item StaticTracepoint
37550 @cindex static tracepoints, in remote protocol
37551 The remote stub supports static tracepoints.
37553 @item InstallInTrace
37554 @anchor{install tracepoint in tracing}
37555 The remote stub supports installing tracepoint in tracing.
37557 @item EnableDisableTracepoints
37558 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37559 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37560 to be enabled and disabled while a trace experiment is running.
37562 @item QTBuffer:size
37563 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37564 packet that allows to change the size of the trace buffer.
37567 @cindex string tracing, in remote protocol
37568 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37569 See @ref{Bytecode Descriptions} for details about the bytecode.
37571 @item BreakpointCommands
37572 @cindex breakpoint commands, in remote protocol
37573 The remote stub supports running a breakpoint's command list itself,
37574 rather than reporting the hit to @value{GDBN}.
37577 The remote stub understands the @samp{Qbtrace:off} packet.
37580 The remote stub understands the @samp{Qbtrace:bts} packet.
37583 The remote stub understands the @samp{Qbtrace:pt} packet.
37585 @item Qbtrace-conf:bts:size
37586 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37588 @item Qbtrace-conf:pt:size
37589 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37592 The remote stub reports the @samp{swbreak} stop reason for memory
37596 The remote stub reports the @samp{hwbreak} stop reason for hardware
37600 The remote stub reports the @samp{fork} stop reason for fork events.
37603 The remote stub reports the @samp{vfork} stop reason for vfork events
37604 and vforkdone events.
37607 The remote stub reports the @samp{exec} stop reason for exec events.
37609 @item vContSupported
37610 The remote stub reports the supported actions in the reply to
37611 @samp{vCont?} packet.
37613 @item QThreadEvents
37614 The remote stub understands the @samp{QThreadEvents} packet.
37617 The remote stub reports the @samp{N} stop reply.
37622 @cindex symbol lookup, remote request
37623 @cindex @samp{qSymbol} packet
37624 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37625 requests. Accept requests from the target for the values of symbols.
37630 The target does not need to look up any (more) symbols.
37631 @item qSymbol:@var{sym_name}
37632 The target requests the value of symbol @var{sym_name} (hex encoded).
37633 @value{GDBN} may provide the value by using the
37634 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37638 @item qSymbol:@var{sym_value}:@var{sym_name}
37639 Set the value of @var{sym_name} to @var{sym_value}.
37641 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37642 target has previously requested.
37644 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37645 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37651 The target does not need to look up any (more) symbols.
37652 @item qSymbol:@var{sym_name}
37653 The target requests the value of a new symbol @var{sym_name} (hex
37654 encoded). @value{GDBN} will continue to supply the values of symbols
37655 (if available), until the target ceases to request them.
37660 @itemx QTDisconnected
37667 @itemx qTMinFTPILen
37669 @xref{Tracepoint Packets}.
37671 @item qThreadExtraInfo,@var{thread-id}
37672 @cindex thread attributes info, remote request
37673 @cindex @samp{qThreadExtraInfo} packet
37674 Obtain from the target OS a printable string description of thread
37675 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37676 for the forms of @var{thread-id}. This
37677 string may contain anything that the target OS thinks is interesting
37678 for @value{GDBN} to tell the user about the thread. The string is
37679 displayed in @value{GDBN}'s @code{info threads} display. Some
37680 examples of possible thread extra info strings are @samp{Runnable}, or
37681 @samp{Blocked on Mutex}.
37685 @item @var{XX}@dots{}
37686 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37687 comprising the printable string containing the extra information about
37688 the thread's attributes.
37691 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37692 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37693 conventions above. Please don't use this packet as a model for new
37712 @xref{Tracepoint Packets}.
37714 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37715 @cindex read special object, remote request
37716 @cindex @samp{qXfer} packet
37717 @anchor{qXfer read}
37718 Read uninterpreted bytes from the target's special data area
37719 identified by the keyword @var{object}. Request @var{length} bytes
37720 starting at @var{offset} bytes into the data. The content and
37721 encoding of @var{annex} is specific to @var{object}; it can supply
37722 additional details about what data to access.
37727 Data @var{data} (@pxref{Binary Data}) has been read from the
37728 target. There may be more data at a higher address (although
37729 it is permitted to return @samp{m} even for the last valid
37730 block of data, as long as at least one byte of data was read).
37731 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37735 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37736 There is no more data to be read. It is possible for @var{data} to
37737 have fewer bytes than the @var{length} in the request.
37740 The @var{offset} in the request is at the end of the data.
37741 There is no more data to be read.
37744 The request was malformed, or @var{annex} was invalid.
37747 The offset was invalid, or there was an error encountered reading the data.
37748 The @var{nn} part is a hex-encoded @code{errno} value.
37751 An empty reply indicates the @var{object} string was not recognized by
37752 the stub, or that the object does not support reading.
37755 Here are the specific requests of this form defined so far. All the
37756 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37757 formats, listed above.
37760 @item qXfer:auxv:read::@var{offset},@var{length}
37761 @anchor{qXfer auxiliary vector read}
37762 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37763 auxiliary vector}. Note @var{annex} must be empty.
37765 This packet is not probed by default; the remote stub must request it,
37766 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37768 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37769 @anchor{qXfer btrace read}
37771 Return a description of the current branch trace.
37772 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37773 packet may have one of the following values:
37777 Returns all available branch trace.
37780 Returns all available branch trace if the branch trace changed since
37781 the last read request.
37784 Returns the new branch trace since the last read request. Adds a new
37785 block to the end of the trace that begins at zero and ends at the source
37786 location of the first branch in the trace buffer. This extra block is
37787 used to stitch traces together.
37789 If the trace buffer overflowed, returns an error indicating the overflow.
37792 This packet is not probed by default; the remote stub must request it
37793 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37795 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37796 @anchor{qXfer btrace-conf read}
37798 Return a description of the current branch trace configuration.
37799 @xref{Branch Trace Configuration Format}.
37801 This packet is not probed by default; the remote stub must request it
37802 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37804 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37805 @anchor{qXfer executable filename read}
37806 Return the full absolute name of the file that was executed to create
37807 a process running on the remote system. The annex specifies the
37808 numeric process ID of the process to query, encoded as a hexadecimal
37809 number. If the annex part is empty the remote stub should return the
37810 filename corresponding to the currently executing process.
37812 This packet is not probed by default; the remote stub must request it,
37813 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37815 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37816 @anchor{qXfer target description read}
37817 Access the @dfn{target description}. @xref{Target Descriptions}. The
37818 annex specifies which XML document to access. The main description is
37819 always loaded from the @samp{target.xml} annex.
37821 This packet is not probed by default; the remote stub must request it,
37822 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37824 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37825 @anchor{qXfer library list read}
37826 Access the target's list of loaded libraries. @xref{Library List Format}.
37827 The annex part of the generic @samp{qXfer} packet must be empty
37828 (@pxref{qXfer read}).
37830 Targets which maintain a list of libraries in the program's memory do
37831 not need to implement this packet; it is designed for platforms where
37832 the operating system manages the list of loaded libraries.
37834 This packet is not probed by default; the remote stub must request it,
37835 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37837 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37838 @anchor{qXfer svr4 library list read}
37839 Access the target's list of loaded libraries when the target is an SVR4
37840 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37841 of the generic @samp{qXfer} packet must be empty unless the remote
37842 stub indicated it supports the augmented form of this packet
37843 by supplying an appropriate @samp{qSupported} response
37844 (@pxref{qXfer read}, @ref{qSupported}).
37846 This packet is optional for better performance on SVR4 targets.
37847 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37849 This packet is not probed by default; the remote stub must request it,
37850 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37852 If the remote stub indicates it supports the augmented form of this
37853 packet then the annex part of the generic @samp{qXfer} packet may
37854 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37855 arguments. The currently supported arguments are:
37858 @item start=@var{address}
37859 A hexadecimal number specifying the address of the @samp{struct
37860 link_map} to start reading the library list from. If unset or zero
37861 then the first @samp{struct link_map} in the library list will be
37862 chosen as the starting point.
37864 @item prev=@var{address}
37865 A hexadecimal number specifying the address of the @samp{struct
37866 link_map} immediately preceding the @samp{struct link_map}
37867 specified by the @samp{start} argument. If unset or zero then
37868 the remote stub will expect that no @samp{struct link_map}
37869 exists prior to the starting point.
37873 Arguments that are not understood by the remote stub will be silently
37876 @item qXfer:memory-map:read::@var{offset},@var{length}
37877 @anchor{qXfer memory map read}
37878 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37879 annex part of the generic @samp{qXfer} packet must be empty
37880 (@pxref{qXfer read}).
37882 This packet is not probed by default; the remote stub must request it,
37883 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37885 @item qXfer:sdata:read::@var{offset},@var{length}
37886 @anchor{qXfer sdata read}
37888 Read contents of the extra collected static tracepoint marker
37889 information. The annex part of the generic @samp{qXfer} packet must
37890 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37893 This packet is not probed by default; the remote stub must request it,
37894 by supplying an appropriate @samp{qSupported} response
37895 (@pxref{qSupported}).
37897 @item qXfer:siginfo:read::@var{offset},@var{length}
37898 @anchor{qXfer siginfo read}
37899 Read contents of the extra signal information on the target
37900 system. The annex part of the generic @samp{qXfer} packet must be
37901 empty (@pxref{qXfer read}).
37903 This packet is not probed by default; the remote stub must request it,
37904 by supplying an appropriate @samp{qSupported} response
37905 (@pxref{qSupported}).
37907 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37908 @anchor{qXfer spu read}
37909 Read contents of an @code{spufs} file on the target system. The
37910 annex specifies which file to read; it must be of the form
37911 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37912 in the target process, and @var{name} identifes the @code{spufs} file
37913 in that context to be accessed.
37915 This packet is not probed by default; the remote stub must request it,
37916 by supplying an appropriate @samp{qSupported} response
37917 (@pxref{qSupported}).
37919 @item qXfer:threads:read::@var{offset},@var{length}
37920 @anchor{qXfer threads read}
37921 Access the list of threads on target. @xref{Thread List Format}. The
37922 annex part of the generic @samp{qXfer} packet must be empty
37923 (@pxref{qXfer read}).
37925 This packet is not probed by default; the remote stub must request it,
37926 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37928 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37929 @anchor{qXfer traceframe info read}
37931 Return a description of the current traceframe's contents.
37932 @xref{Traceframe Info Format}. The annex part of the generic
37933 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37935 This packet is not probed by default; the remote stub must request it,
37936 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37938 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37939 @anchor{qXfer unwind info block}
37941 Return the unwind information block for @var{pc}. This packet is used
37942 on OpenVMS/ia64 to ask the kernel unwind information.
37944 This packet is not probed by default.
37946 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37947 @anchor{qXfer fdpic loadmap read}
37948 Read contents of @code{loadmap}s on the target system. The
37949 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37950 executable @code{loadmap} or interpreter @code{loadmap} to read.
37952 This packet is not probed by default; the remote stub must request it,
37953 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37955 @item qXfer:osdata:read::@var{offset},@var{length}
37956 @anchor{qXfer osdata read}
37957 Access the target's @dfn{operating system information}.
37958 @xref{Operating System Information}.
37962 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37963 @cindex write data into object, remote request
37964 @anchor{qXfer write}
37965 Write uninterpreted bytes into the target's special data area
37966 identified by the keyword @var{object}, starting at @var{offset} bytes
37967 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37968 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37969 is specific to @var{object}; it can supply additional details about what data
37975 @var{nn} (hex encoded) is the number of bytes written.
37976 This may be fewer bytes than supplied in the request.
37979 The request was malformed, or @var{annex} was invalid.
37982 The offset was invalid, or there was an error encountered writing the data.
37983 The @var{nn} part is a hex-encoded @code{errno} value.
37986 An empty reply indicates the @var{object} string was not
37987 recognized by the stub, or that the object does not support writing.
37990 Here are the specific requests of this form defined so far. All the
37991 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37992 formats, listed above.
37995 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37996 @anchor{qXfer siginfo write}
37997 Write @var{data} to the extra signal information on the target system.
37998 The annex part of the generic @samp{qXfer} packet must be
37999 empty (@pxref{qXfer write}).
38001 This packet is not probed by default; the remote stub must request it,
38002 by supplying an appropriate @samp{qSupported} response
38003 (@pxref{qSupported}).
38005 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38006 @anchor{qXfer spu write}
38007 Write @var{data} to an @code{spufs} file on the target system. The
38008 annex specifies which file to write; it must be of the form
38009 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38010 in the target process, and @var{name} identifes the @code{spufs} file
38011 in that context to be accessed.
38013 This packet is not probed by default; the remote stub must request it,
38014 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38017 @item qXfer:@var{object}:@var{operation}:@dots{}
38018 Requests of this form may be added in the future. When a stub does
38019 not recognize the @var{object} keyword, or its support for
38020 @var{object} does not recognize the @var{operation} keyword, the stub
38021 must respond with an empty packet.
38023 @item qAttached:@var{pid}
38024 @cindex query attached, remote request
38025 @cindex @samp{qAttached} packet
38026 Return an indication of whether the remote server attached to an
38027 existing process or created a new process. When the multiprocess
38028 protocol extensions are supported (@pxref{multiprocess extensions}),
38029 @var{pid} is an integer in hexadecimal format identifying the target
38030 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38031 the query packet will be simplified as @samp{qAttached}.
38033 This query is used, for example, to know whether the remote process
38034 should be detached or killed when a @value{GDBN} session is ended with
38035 the @code{quit} command.
38040 The remote server attached to an existing process.
38042 The remote server created a new process.
38044 A badly formed request or an error was encountered.
38048 Enable branch tracing for the current thread using Branch Trace Store.
38053 Branch tracing has been enabled.
38055 A badly formed request or an error was encountered.
38059 Enable branch tracing for the current thread using Intel Processor Trace.
38064 Branch tracing has been enabled.
38066 A badly formed request or an error was encountered.
38070 Disable branch tracing for the current thread.
38075 Branch tracing has been disabled.
38077 A badly formed request or an error was encountered.
38080 @item Qbtrace-conf:bts:size=@var{value}
38081 Set the requested ring buffer size for new threads that use the
38082 btrace recording method in bts format.
38087 The ring buffer size has been set.
38089 A badly formed request or an error was encountered.
38092 @item Qbtrace-conf:pt:size=@var{value}
38093 Set the requested ring buffer size for new threads that use the
38094 btrace recording method in pt format.
38099 The ring buffer size has been set.
38101 A badly formed request or an error was encountered.
38106 @node Architecture-Specific Protocol Details
38107 @section Architecture-Specific Protocol Details
38109 This section describes how the remote protocol is applied to specific
38110 target architectures. Also see @ref{Standard Target Features}, for
38111 details of XML target descriptions for each architecture.
38114 * ARM-Specific Protocol Details::
38115 * MIPS-Specific Protocol Details::
38118 @node ARM-Specific Protocol Details
38119 @subsection @acronym{ARM}-specific Protocol Details
38122 * ARM Breakpoint Kinds::
38125 @node ARM Breakpoint Kinds
38126 @subsubsection @acronym{ARM} Breakpoint Kinds
38127 @cindex breakpoint kinds, @acronym{ARM}
38129 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38134 16-bit Thumb mode breakpoint.
38137 32-bit Thumb mode (Thumb-2) breakpoint.
38140 32-bit @acronym{ARM} mode breakpoint.
38144 @node MIPS-Specific Protocol Details
38145 @subsection @acronym{MIPS}-specific Protocol Details
38148 * MIPS Register packet Format::
38149 * MIPS Breakpoint Kinds::
38152 @node MIPS Register packet Format
38153 @subsubsection @acronym{MIPS} Register Packet Format
38154 @cindex register packet format, @acronym{MIPS}
38156 The following @code{g}/@code{G} packets have previously been defined.
38157 In the below, some thirty-two bit registers are transferred as
38158 sixty-four bits. Those registers should be zero/sign extended (which?)
38159 to fill the space allocated. Register bytes are transferred in target
38160 byte order. The two nibbles within a register byte are transferred
38161 most-significant -- least-significant.
38166 All registers are transferred as thirty-two bit quantities in the order:
38167 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38168 registers; fsr; fir; fp.
38171 All registers are transferred as sixty-four bit quantities (including
38172 thirty-two bit registers such as @code{sr}). The ordering is the same
38177 @node MIPS Breakpoint Kinds
38178 @subsubsection @acronym{MIPS} Breakpoint Kinds
38179 @cindex breakpoint kinds, @acronym{MIPS}
38181 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38186 16-bit @acronym{MIPS16} mode breakpoint.
38189 16-bit @acronym{microMIPS} mode breakpoint.
38192 32-bit standard @acronym{MIPS} mode breakpoint.
38195 32-bit @acronym{microMIPS} mode breakpoint.
38199 @node Tracepoint Packets
38200 @section Tracepoint Packets
38201 @cindex tracepoint packets
38202 @cindex packets, tracepoint
38204 Here we describe the packets @value{GDBN} uses to implement
38205 tracepoints (@pxref{Tracepoints}).
38209 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38210 @cindex @samp{QTDP} packet
38211 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38212 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38213 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38214 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38215 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38216 the number of bytes that the target should copy elsewhere to make room
38217 for the tracepoint. If an @samp{X} is present, it introduces a
38218 tracepoint condition, which consists of a hexadecimal length, followed
38219 by a comma and hex-encoded bytes, in a manner similar to action
38220 encodings as described below. If the trailing @samp{-} is present,
38221 further @samp{QTDP} packets will follow to specify this tracepoint's
38227 The packet was understood and carried out.
38229 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38231 The packet was not recognized.
38234 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38235 Define actions to be taken when a tracepoint is hit. The @var{n} and
38236 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38237 this tracepoint. This packet may only be sent immediately after
38238 another @samp{QTDP} packet that ended with a @samp{-}. If the
38239 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38240 specifying more actions for this tracepoint.
38242 In the series of action packets for a given tracepoint, at most one
38243 can have an @samp{S} before its first @var{action}. If such a packet
38244 is sent, it and the following packets define ``while-stepping''
38245 actions. Any prior packets define ordinary actions --- that is, those
38246 taken when the tracepoint is first hit. If no action packet has an
38247 @samp{S}, then all the packets in the series specify ordinary
38248 tracepoint actions.
38250 The @samp{@var{action}@dots{}} portion of the packet is a series of
38251 actions, concatenated without separators. Each action has one of the
38257 Collect the registers whose bits are set in @var{mask},
38258 a hexadecimal number whose @var{i}'th bit is set if register number
38259 @var{i} should be collected. (The least significant bit is numbered
38260 zero.) Note that @var{mask} may be any number of digits long; it may
38261 not fit in a 32-bit word.
38263 @item M @var{basereg},@var{offset},@var{len}
38264 Collect @var{len} bytes of memory starting at the address in register
38265 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38266 @samp{-1}, then the range has a fixed address: @var{offset} is the
38267 address of the lowest byte to collect. The @var{basereg},
38268 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38269 values (the @samp{-1} value for @var{basereg} is a special case).
38271 @item X @var{len},@var{expr}
38272 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38273 it directs. The agent expression @var{expr} is as described in
38274 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38275 two-digit hex number in the packet; @var{len} is the number of bytes
38276 in the expression (and thus one-half the number of hex digits in the
38281 Any number of actions may be packed together in a single @samp{QTDP}
38282 packet, as long as the packet does not exceed the maximum packet
38283 length (400 bytes, for many stubs). There may be only one @samp{R}
38284 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38285 actions. Any registers referred to by @samp{M} and @samp{X} actions
38286 must be collected by a preceding @samp{R} action. (The
38287 ``while-stepping'' actions are treated as if they were attached to a
38288 separate tracepoint, as far as these restrictions are concerned.)
38293 The packet was understood and carried out.
38295 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38297 The packet was not recognized.
38300 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38301 @cindex @samp{QTDPsrc} packet
38302 Specify a source string of tracepoint @var{n} at address @var{addr}.
38303 This is useful to get accurate reproduction of the tracepoints
38304 originally downloaded at the beginning of the trace run. The @var{type}
38305 is the name of the tracepoint part, such as @samp{cond} for the
38306 tracepoint's conditional expression (see below for a list of types), while
38307 @var{bytes} is the string, encoded in hexadecimal.
38309 @var{start} is the offset of the @var{bytes} within the overall source
38310 string, while @var{slen} is the total length of the source string.
38311 This is intended for handling source strings that are longer than will
38312 fit in a single packet.
38313 @c Add detailed example when this info is moved into a dedicated
38314 @c tracepoint descriptions section.
38316 The available string types are @samp{at} for the location,
38317 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38318 @value{GDBN} sends a separate packet for each command in the action
38319 list, in the same order in which the commands are stored in the list.
38321 The target does not need to do anything with source strings except
38322 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38325 Although this packet is optional, and @value{GDBN} will only send it
38326 if the target replies with @samp{TracepointSource} @xref{General
38327 Query Packets}, it makes both disconnected tracing and trace files
38328 much easier to use. Otherwise the user must be careful that the
38329 tracepoints in effect while looking at trace frames are identical to
38330 the ones in effect during the trace run; even a small discrepancy
38331 could cause @samp{tdump} not to work, or a particular trace frame not
38334 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38335 @cindex define trace state variable, remote request
38336 @cindex @samp{QTDV} packet
38337 Create a new trace state variable, number @var{n}, with an initial
38338 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38339 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38340 the option of not using this packet for initial values of zero; the
38341 target should simply create the trace state variables as they are
38342 mentioned in expressions. The value @var{builtin} should be 1 (one)
38343 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38344 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38345 @samp{qTsV} packet had it set. The contents of @var{name} is the
38346 hex-encoded name (without the leading @samp{$}) of the trace state
38349 @item QTFrame:@var{n}
38350 @cindex @samp{QTFrame} packet
38351 Select the @var{n}'th tracepoint frame from the buffer, and use the
38352 register and memory contents recorded there to answer subsequent
38353 request packets from @value{GDBN}.
38355 A successful reply from the stub indicates that the stub has found the
38356 requested frame. The response is a series of parts, concatenated
38357 without separators, describing the frame we selected. Each part has
38358 one of the following forms:
38362 The selected frame is number @var{n} in the trace frame buffer;
38363 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38364 was no frame matching the criteria in the request packet.
38367 The selected trace frame records a hit of tracepoint number @var{t};
38368 @var{t} is a hexadecimal number.
38372 @item QTFrame:pc:@var{addr}
38373 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38374 currently selected frame whose PC is @var{addr};
38375 @var{addr} is a hexadecimal number.
38377 @item QTFrame:tdp:@var{t}
38378 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38379 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38380 is a hexadecimal number.
38382 @item QTFrame:range:@var{start}:@var{end}
38383 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38384 currently selected frame whose PC is between @var{start} (inclusive)
38385 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38388 @item QTFrame:outside:@var{start}:@var{end}
38389 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38390 frame @emph{outside} the given range of addresses (exclusive).
38393 @cindex @samp{qTMinFTPILen} packet
38394 This packet requests the minimum length of instruction at which a fast
38395 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38396 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38397 it depends on the target system being able to create trampolines in
38398 the first 64K of memory, which might or might not be possible for that
38399 system. So the reply to this packet will be 4 if it is able to
38406 The minimum instruction length is currently unknown.
38408 The minimum instruction length is @var{length}, where @var{length}
38409 is a hexadecimal number greater or equal to 1. A reply
38410 of 1 means that a fast tracepoint may be placed on any instruction
38411 regardless of size.
38413 An error has occurred.
38415 An empty reply indicates that the request is not supported by the stub.
38419 @cindex @samp{QTStart} packet
38420 Begin the tracepoint experiment. Begin collecting data from
38421 tracepoint hits in the trace frame buffer. This packet supports the
38422 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38423 instruction reply packet}).
38426 @cindex @samp{QTStop} packet
38427 End the tracepoint experiment. Stop collecting trace frames.
38429 @item QTEnable:@var{n}:@var{addr}
38431 @cindex @samp{QTEnable} packet
38432 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38433 experiment. If the tracepoint was previously disabled, then collection
38434 of data from it will resume.
38436 @item QTDisable:@var{n}:@var{addr}
38438 @cindex @samp{QTDisable} packet
38439 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38440 experiment. No more data will be collected from the tracepoint unless
38441 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38444 @cindex @samp{QTinit} packet
38445 Clear the table of tracepoints, and empty the trace frame buffer.
38447 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38448 @cindex @samp{QTro} packet
38449 Establish the given ranges of memory as ``transparent''. The stub
38450 will answer requests for these ranges from memory's current contents,
38451 if they were not collected as part of the tracepoint hit.
38453 @value{GDBN} uses this to mark read-only regions of memory, like those
38454 containing program code. Since these areas never change, they should
38455 still have the same contents they did when the tracepoint was hit, so
38456 there's no reason for the stub to refuse to provide their contents.
38458 @item QTDisconnected:@var{value}
38459 @cindex @samp{QTDisconnected} packet
38460 Set the choice to what to do with the tracing run when @value{GDBN}
38461 disconnects from the target. A @var{value} of 1 directs the target to
38462 continue the tracing run, while 0 tells the target to stop tracing if
38463 @value{GDBN} is no longer in the picture.
38466 @cindex @samp{qTStatus} packet
38467 Ask the stub if there is a trace experiment running right now.
38469 The reply has the form:
38473 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38474 @var{running} is a single digit @code{1} if the trace is presently
38475 running, or @code{0} if not. It is followed by semicolon-separated
38476 optional fields that an agent may use to report additional status.
38480 If the trace is not running, the agent may report any of several
38481 explanations as one of the optional fields:
38486 No trace has been run yet.
38488 @item tstop[:@var{text}]:0
38489 The trace was stopped by a user-originated stop command. The optional
38490 @var{text} field is a user-supplied string supplied as part of the
38491 stop command (for instance, an explanation of why the trace was
38492 stopped manually). It is hex-encoded.
38495 The trace stopped because the trace buffer filled up.
38497 @item tdisconnected:0
38498 The trace stopped because @value{GDBN} disconnected from the target.
38500 @item tpasscount:@var{tpnum}
38501 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38503 @item terror:@var{text}:@var{tpnum}
38504 The trace stopped because tracepoint @var{tpnum} had an error. The
38505 string @var{text} is available to describe the nature of the error
38506 (for instance, a divide by zero in the condition expression); it
38510 The trace stopped for some other reason.
38514 Additional optional fields supply statistical and other information.
38515 Although not required, they are extremely useful for users monitoring
38516 the progress of a trace run. If a trace has stopped, and these
38517 numbers are reported, they must reflect the state of the just-stopped
38522 @item tframes:@var{n}
38523 The number of trace frames in the buffer.
38525 @item tcreated:@var{n}
38526 The total number of trace frames created during the run. This may
38527 be larger than the trace frame count, if the buffer is circular.
38529 @item tsize:@var{n}
38530 The total size of the trace buffer, in bytes.
38532 @item tfree:@var{n}
38533 The number of bytes still unused in the buffer.
38535 @item circular:@var{n}
38536 The value of the circular trace buffer flag. @code{1} means that the
38537 trace buffer is circular and old trace frames will be discarded if
38538 necessary to make room, @code{0} means that the trace buffer is linear
38541 @item disconn:@var{n}
38542 The value of the disconnected tracing flag. @code{1} means that
38543 tracing will continue after @value{GDBN} disconnects, @code{0} means
38544 that the trace run will stop.
38548 @item qTP:@var{tp}:@var{addr}
38549 @cindex tracepoint status, remote request
38550 @cindex @samp{qTP} packet
38551 Ask the stub for the current state of tracepoint number @var{tp} at
38552 address @var{addr}.
38556 @item V@var{hits}:@var{usage}
38557 The tracepoint has been hit @var{hits} times so far during the trace
38558 run, and accounts for @var{usage} in the trace buffer. Note that
38559 @code{while-stepping} steps are not counted as separate hits, but the
38560 steps' space consumption is added into the usage number.
38564 @item qTV:@var{var}
38565 @cindex trace state variable value, remote request
38566 @cindex @samp{qTV} packet
38567 Ask the stub for the value of the trace state variable number @var{var}.
38572 The value of the variable is @var{value}. This will be the current
38573 value of the variable if the user is examining a running target, or a
38574 saved value if the variable was collected in the trace frame that the
38575 user is looking at. Note that multiple requests may result in
38576 different reply values, such as when requesting values while the
38577 program is running.
38580 The value of the variable is unknown. This would occur, for example,
38581 if the user is examining a trace frame in which the requested variable
38586 @cindex @samp{qTfP} packet
38588 @cindex @samp{qTsP} packet
38589 These packets request data about tracepoints that are being used by
38590 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38591 of data, and multiple @code{qTsP} to get additional pieces. Replies
38592 to these packets generally take the form of the @code{QTDP} packets
38593 that define tracepoints. (FIXME add detailed syntax)
38596 @cindex @samp{qTfV} packet
38598 @cindex @samp{qTsV} packet
38599 These packets request data about trace state variables that are on the
38600 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38601 and multiple @code{qTsV} to get additional variables. Replies to
38602 these packets follow the syntax of the @code{QTDV} packets that define
38603 trace state variables.
38609 @cindex @samp{qTfSTM} packet
38610 @cindex @samp{qTsSTM} packet
38611 These packets request data about static tracepoint markers that exist
38612 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38613 first piece of data, and multiple @code{qTsSTM} to get additional
38614 pieces. Replies to these packets take the following form:
38618 @item m @var{address}:@var{id}:@var{extra}
38620 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38621 a comma-separated list of markers
38623 (lower case letter @samp{L}) denotes end of list.
38625 An error occurred. The error number @var{nn} is given as hex digits.
38627 An empty reply indicates that the request is not supported by the
38631 The @var{address} is encoded in hex;
38632 @var{id} and @var{extra} are strings encoded in hex.
38634 In response to each query, the target will reply with a list of one or
38635 more markers, separated by commas. @value{GDBN} will respond to each
38636 reply with a request for more markers (using the @samp{qs} form of the
38637 query), until the target responds with @samp{l} (lower-case ell, for
38640 @item qTSTMat:@var{address}
38642 @cindex @samp{qTSTMat} packet
38643 This packets requests data about static tracepoint markers in the
38644 target program at @var{address}. Replies to this packet follow the
38645 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38646 tracepoint markers.
38648 @item QTSave:@var{filename}
38649 @cindex @samp{QTSave} packet
38650 This packet directs the target to save trace data to the file name
38651 @var{filename} in the target's filesystem. The @var{filename} is encoded
38652 as a hex string; the interpretation of the file name (relative vs
38653 absolute, wild cards, etc) is up to the target.
38655 @item qTBuffer:@var{offset},@var{len}
38656 @cindex @samp{qTBuffer} packet
38657 Return up to @var{len} bytes of the current contents of trace buffer,
38658 starting at @var{offset}. The trace buffer is treated as if it were
38659 a contiguous collection of traceframes, as per the trace file format.
38660 The reply consists as many hex-encoded bytes as the target can deliver
38661 in a packet; it is not an error to return fewer than were asked for.
38662 A reply consisting of just @code{l} indicates that no bytes are
38665 @item QTBuffer:circular:@var{value}
38666 This packet directs the target to use a circular trace buffer if
38667 @var{value} is 1, or a linear buffer if the value is 0.
38669 @item QTBuffer:size:@var{size}
38670 @anchor{QTBuffer-size}
38671 @cindex @samp{QTBuffer size} packet
38672 This packet directs the target to make the trace buffer be of size
38673 @var{size} if possible. A value of @code{-1} tells the target to
38674 use whatever size it prefers.
38676 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38677 @cindex @samp{QTNotes} packet
38678 This packet adds optional textual notes to the trace run. Allowable
38679 types include @code{user}, @code{notes}, and @code{tstop}, the
38680 @var{text} fields are arbitrary strings, hex-encoded.
38684 @subsection Relocate instruction reply packet
38685 When installing fast tracepoints in memory, the target may need to
38686 relocate the instruction currently at the tracepoint address to a
38687 different address in memory. For most instructions, a simple copy is
38688 enough, but, for example, call instructions that implicitly push the
38689 return address on the stack, and relative branches or other
38690 PC-relative instructions require offset adjustment, so that the effect
38691 of executing the instruction at a different address is the same as if
38692 it had executed in the original location.
38694 In response to several of the tracepoint packets, the target may also
38695 respond with a number of intermediate @samp{qRelocInsn} request
38696 packets before the final result packet, to have @value{GDBN} handle
38697 this relocation operation. If a packet supports this mechanism, its
38698 documentation will explicitly say so. See for example the above
38699 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38700 format of the request is:
38703 @item qRelocInsn:@var{from};@var{to}
38705 This requests @value{GDBN} to copy instruction at address @var{from}
38706 to address @var{to}, possibly adjusted so that executing the
38707 instruction at @var{to} has the same effect as executing it at
38708 @var{from}. @value{GDBN} writes the adjusted instruction to target
38709 memory starting at @var{to}.
38714 @item qRelocInsn:@var{adjusted_size}
38715 Informs the stub the relocation is complete. The @var{adjusted_size} is
38716 the length in bytes of resulting relocated instruction sequence.
38718 A badly formed request was detected, or an error was encountered while
38719 relocating the instruction.
38722 @node Host I/O Packets
38723 @section Host I/O Packets
38724 @cindex Host I/O, remote protocol
38725 @cindex file transfer, remote protocol
38727 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38728 operations on the far side of a remote link. For example, Host I/O is
38729 used to upload and download files to a remote target with its own
38730 filesystem. Host I/O uses the same constant values and data structure
38731 layout as the target-initiated File-I/O protocol. However, the
38732 Host I/O packets are structured differently. The target-initiated
38733 protocol relies on target memory to store parameters and buffers.
38734 Host I/O requests are initiated by @value{GDBN}, and the
38735 target's memory is not involved. @xref{File-I/O Remote Protocol
38736 Extension}, for more details on the target-initiated protocol.
38738 The Host I/O request packets all encode a single operation along with
38739 its arguments. They have this format:
38743 @item vFile:@var{operation}: @var{parameter}@dots{}
38744 @var{operation} is the name of the particular request; the target
38745 should compare the entire packet name up to the second colon when checking
38746 for a supported operation. The format of @var{parameter} depends on
38747 the operation. Numbers are always passed in hexadecimal. Negative
38748 numbers have an explicit minus sign (i.e.@: two's complement is not
38749 used). Strings (e.g.@: filenames) are encoded as a series of
38750 hexadecimal bytes. The last argument to a system call may be a
38751 buffer of escaped binary data (@pxref{Binary Data}).
38755 The valid responses to Host I/O packets are:
38759 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38760 @var{result} is the integer value returned by this operation, usually
38761 non-negative for success and -1 for errors. If an error has occured,
38762 @var{errno} will be included in the result specifying a
38763 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38764 operations which return data, @var{attachment} supplies the data as a
38765 binary buffer. Binary buffers in response packets are escaped in the
38766 normal way (@pxref{Binary Data}). See the individual packet
38767 documentation for the interpretation of @var{result} and
38771 An empty response indicates that this operation is not recognized.
38775 These are the supported Host I/O operations:
38778 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38779 Open a file at @var{filename} and return a file descriptor for it, or
38780 return -1 if an error occurs. The @var{filename} is a string,
38781 @var{flags} is an integer indicating a mask of open flags
38782 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38783 of mode bits to use if the file is created (@pxref{mode_t Values}).
38784 @xref{open}, for details of the open flags and mode values.
38786 @item vFile:close: @var{fd}
38787 Close the open file corresponding to @var{fd} and return 0, or
38788 -1 if an error occurs.
38790 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38791 Read data from the open file corresponding to @var{fd}. Up to
38792 @var{count} bytes will be read from the file, starting at @var{offset}
38793 relative to the start of the file. The target may read fewer bytes;
38794 common reasons include packet size limits and an end-of-file
38795 condition. The number of bytes read is returned. Zero should only be
38796 returned for a successful read at the end of the file, or if
38797 @var{count} was zero.
38799 The data read should be returned as a binary attachment on success.
38800 If zero bytes were read, the response should include an empty binary
38801 attachment (i.e.@: a trailing semicolon). The return value is the
38802 number of target bytes read; the binary attachment may be longer if
38803 some characters were escaped.
38805 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38806 Write @var{data} (a binary buffer) to the open file corresponding
38807 to @var{fd}. Start the write at @var{offset} from the start of the
38808 file. Unlike many @code{write} system calls, there is no
38809 separate @var{count} argument; the length of @var{data} in the
38810 packet is used. @samp{vFile:write} returns the number of bytes written,
38811 which may be shorter than the length of @var{data}, or -1 if an
38814 @item vFile:fstat: @var{fd}
38815 Get information about the open file corresponding to @var{fd}.
38816 On success the information is returned as a binary attachment
38817 and the return value is the size of this attachment in bytes.
38818 If an error occurs the return value is -1. The format of the
38819 returned binary attachment is as described in @ref{struct stat}.
38821 @item vFile:unlink: @var{filename}
38822 Delete the file at @var{filename} on the target. Return 0,
38823 or -1 if an error occurs. The @var{filename} is a string.
38825 @item vFile:readlink: @var{filename}
38826 Read value of symbolic link @var{filename} on the target. Return
38827 the number of bytes read, or -1 if an error occurs.
38829 The data read should be returned as a binary attachment on success.
38830 If zero bytes were read, the response should include an empty binary
38831 attachment (i.e.@: a trailing semicolon). The return value is the
38832 number of target bytes read; the binary attachment may be longer if
38833 some characters were escaped.
38835 @item vFile:setfs: @var{pid}
38836 Select the filesystem on which @code{vFile} operations with
38837 @var{filename} arguments will operate. This is required for
38838 @value{GDBN} to be able to access files on remote targets where
38839 the remote stub does not share a common filesystem with the
38842 If @var{pid} is nonzero, select the filesystem as seen by process
38843 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38844 the remote stub. Return 0 on success, or -1 if an error occurs.
38845 If @code{vFile:setfs:} indicates success, the selected filesystem
38846 remains selected until the next successful @code{vFile:setfs:}
38852 @section Interrupts
38853 @cindex interrupts (remote protocol)
38854 @anchor{interrupting remote targets}
38856 In all-stop mode, when a program on the remote target is running,
38857 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38858 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38859 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38861 The precise meaning of @code{BREAK} is defined by the transport
38862 mechanism and may, in fact, be undefined. @value{GDBN} does not
38863 currently define a @code{BREAK} mechanism for any of the network
38864 interfaces except for TCP, in which case @value{GDBN} sends the
38865 @code{telnet} BREAK sequence.
38867 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38868 transport mechanisms. It is represented by sending the single byte
38869 @code{0x03} without any of the usual packet overhead described in
38870 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38871 transmitted as part of a packet, it is considered to be packet data
38872 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38873 (@pxref{X packet}), used for binary downloads, may include an unescaped
38874 @code{0x03} as part of its packet.
38876 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38877 When Linux kernel receives this sequence from serial port,
38878 it stops execution and connects to gdb.
38880 In non-stop mode, because packet resumptions are asynchronous
38881 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38882 command to the remote stub, even when the target is running. For that
38883 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38884 packet}) with the usual packet framing instead of the single byte
38887 Stubs are not required to recognize these interrupt mechanisms and the
38888 precise meaning associated with receipt of the interrupt is
38889 implementation defined. If the target supports debugging of multiple
38890 threads and/or processes, it should attempt to interrupt all
38891 currently-executing threads and processes.
38892 If the stub is successful at interrupting the
38893 running program, it should send one of the stop
38894 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38895 of successfully stopping the program in all-stop mode, and a stop reply
38896 for each stopped thread in non-stop mode.
38897 Interrupts received while the
38898 program is stopped are queued and the program will be interrupted when
38899 it is resumed next time.
38901 @node Notification Packets
38902 @section Notification Packets
38903 @cindex notification packets
38904 @cindex packets, notification
38906 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38907 packets that require no acknowledgment. Both the GDB and the stub
38908 may send notifications (although the only notifications defined at
38909 present are sent by the stub). Notifications carry information
38910 without incurring the round-trip latency of an acknowledgment, and so
38911 are useful for low-impact communications where occasional packet loss
38914 A notification packet has the form @samp{% @var{data} #
38915 @var{checksum}}, where @var{data} is the content of the notification,
38916 and @var{checksum} is a checksum of @var{data}, computed and formatted
38917 as for ordinary @value{GDBN} packets. A notification's @var{data}
38918 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38919 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38920 to acknowledge the notification's receipt or to report its corruption.
38922 Every notification's @var{data} begins with a name, which contains no
38923 colon characters, followed by a colon character.
38925 Recipients should silently ignore corrupted notifications and
38926 notifications they do not understand. Recipients should restart
38927 timeout periods on receipt of a well-formed notification, whether or
38928 not they understand it.
38930 Senders should only send the notifications described here when this
38931 protocol description specifies that they are permitted. In the
38932 future, we may extend the protocol to permit existing notifications in
38933 new contexts; this rule helps older senders avoid confusing newer
38936 (Older versions of @value{GDBN} ignore bytes received until they see
38937 the @samp{$} byte that begins an ordinary packet, so new stubs may
38938 transmit notifications without fear of confusing older clients. There
38939 are no notifications defined for @value{GDBN} to send at the moment, but we
38940 assume that most older stubs would ignore them, as well.)
38942 Each notification is comprised of three parts:
38944 @item @var{name}:@var{event}
38945 The notification packet is sent by the side that initiates the
38946 exchange (currently, only the stub does that), with @var{event}
38947 carrying the specific information about the notification, and
38948 @var{name} specifying the name of the notification.
38950 The acknowledge sent by the other side, usually @value{GDBN}, to
38951 acknowledge the exchange and request the event.
38954 The purpose of an asynchronous notification mechanism is to report to
38955 @value{GDBN} that something interesting happened in the remote stub.
38957 The remote stub may send notification @var{name}:@var{event}
38958 at any time, but @value{GDBN} acknowledges the notification when
38959 appropriate. The notification event is pending before @value{GDBN}
38960 acknowledges. Only one notification at a time may be pending; if
38961 additional events occur before @value{GDBN} has acknowledged the
38962 previous notification, they must be queued by the stub for later
38963 synchronous transmission in response to @var{ack} packets from
38964 @value{GDBN}. Because the notification mechanism is unreliable,
38965 the stub is permitted to resend a notification if it believes
38966 @value{GDBN} may not have received it.
38968 Specifically, notifications may appear when @value{GDBN} is not
38969 otherwise reading input from the stub, or when @value{GDBN} is
38970 expecting to read a normal synchronous response or a
38971 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38972 Notification packets are distinct from any other communication from
38973 the stub so there is no ambiguity.
38975 After receiving a notification, @value{GDBN} shall acknowledge it by
38976 sending a @var{ack} packet as a regular, synchronous request to the
38977 stub. Such acknowledgment is not required to happen immediately, as
38978 @value{GDBN} is permitted to send other, unrelated packets to the
38979 stub first, which the stub should process normally.
38981 Upon receiving a @var{ack} packet, if the stub has other queued
38982 events to report to @value{GDBN}, it shall respond by sending a
38983 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38984 packet to solicit further responses; again, it is permitted to send
38985 other, unrelated packets as well which the stub should process
38988 If the stub receives a @var{ack} packet and there are no additional
38989 @var{event} to report, the stub shall return an @samp{OK} response.
38990 At this point, @value{GDBN} has finished processing a notification
38991 and the stub has completed sending any queued events. @value{GDBN}
38992 won't accept any new notifications until the final @samp{OK} is
38993 received . If further notification events occur, the stub shall send
38994 a new notification, @value{GDBN} shall accept the notification, and
38995 the process shall be repeated.
38997 The process of asynchronous notification can be illustrated by the
39000 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39003 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39005 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39010 The following notifications are defined:
39011 @multitable @columnfractions 0.12 0.12 0.38 0.38
39020 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39021 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39022 for information on how these notifications are acknowledged by
39024 @tab Report an asynchronous stop event in non-stop mode.
39028 @node Remote Non-Stop
39029 @section Remote Protocol Support for Non-Stop Mode
39031 @value{GDBN}'s remote protocol supports non-stop debugging of
39032 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39033 supports non-stop mode, it should report that to @value{GDBN} by including
39034 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39036 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39037 establishing a new connection with the stub. Entering non-stop mode
39038 does not alter the state of any currently-running threads, but targets
39039 must stop all threads in any already-attached processes when entering
39040 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39041 probe the target state after a mode change.
39043 In non-stop mode, when an attached process encounters an event that
39044 would otherwise be reported with a stop reply, it uses the
39045 asynchronous notification mechanism (@pxref{Notification Packets}) to
39046 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39047 in all processes are stopped when a stop reply is sent, in non-stop
39048 mode only the thread reporting the stop event is stopped. That is,
39049 when reporting a @samp{S} or @samp{T} response to indicate completion
39050 of a step operation, hitting a breakpoint, or a fault, only the
39051 affected thread is stopped; any other still-running threads continue
39052 to run. When reporting a @samp{W} or @samp{X} response, all running
39053 threads belonging to other attached processes continue to run.
39055 In non-stop mode, the target shall respond to the @samp{?} packet as
39056 follows. First, any incomplete stop reply notification/@samp{vStopped}
39057 sequence in progress is abandoned. The target must begin a new
39058 sequence reporting stop events for all stopped threads, whether or not
39059 it has previously reported those events to @value{GDBN}. The first
39060 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39061 subsequent stop replies are sent as responses to @samp{vStopped} packets
39062 using the mechanism described above. The target must not send
39063 asynchronous stop reply notifications until the sequence is complete.
39064 If all threads are running when the target receives the @samp{?} packet,
39065 or if the target is not attached to any process, it shall respond
39068 If the stub supports non-stop mode, it should also support the
39069 @samp{swbreak} stop reason if software breakpoints are supported, and
39070 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39071 (@pxref{swbreak stop reason}). This is because given the asynchronous
39072 nature of non-stop mode, between the time a thread hits a breakpoint
39073 and the time the event is finally processed by @value{GDBN}, the
39074 breakpoint may have already been removed from the target. Due to
39075 this, @value{GDBN} needs to be able to tell whether a trap stop was
39076 caused by a delayed breakpoint event, which should be ignored, as
39077 opposed to a random trap signal, which should be reported to the user.
39078 Note the @samp{swbreak} feature implies that the target is responsible
39079 for adjusting the PC when a software breakpoint triggers, if
39080 necessary, such as on the x86 architecture.
39082 @node Packet Acknowledgment
39083 @section Packet Acknowledgment
39085 @cindex acknowledgment, for @value{GDBN} remote
39086 @cindex packet acknowledgment, for @value{GDBN} remote
39087 By default, when either the host or the target machine receives a packet,
39088 the first response expected is an acknowledgment: either @samp{+} (to indicate
39089 the package was received correctly) or @samp{-} (to request retransmission).
39090 This mechanism allows the @value{GDBN} remote protocol to operate over
39091 unreliable transport mechanisms, such as a serial line.
39093 In cases where the transport mechanism is itself reliable (such as a pipe or
39094 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39095 It may be desirable to disable them in that case to reduce communication
39096 overhead, or for other reasons. This can be accomplished by means of the
39097 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39099 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39100 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39101 and response format still includes the normal checksum, as described in
39102 @ref{Overview}, but the checksum may be ignored by the receiver.
39104 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39105 no-acknowledgment mode, it should report that to @value{GDBN}
39106 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39107 @pxref{qSupported}.
39108 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39109 disabled via the @code{set remote noack-packet off} command
39110 (@pxref{Remote Configuration}),
39111 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39112 Only then may the stub actually turn off packet acknowledgments.
39113 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39114 response, which can be safely ignored by the stub.
39116 Note that @code{set remote noack-packet} command only affects negotiation
39117 between @value{GDBN} and the stub when subsequent connections are made;
39118 it does not affect the protocol acknowledgment state for any current
39120 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39121 new connection is established,
39122 there is also no protocol request to re-enable the acknowledgments
39123 for the current connection, once disabled.
39128 Example sequence of a target being re-started. Notice how the restart
39129 does not get any direct output:
39134 @emph{target restarts}
39137 <- @code{T001:1234123412341234}
39141 Example sequence of a target being stepped by a single instruction:
39144 -> @code{G1445@dots{}}
39149 <- @code{T001:1234123412341234}
39153 <- @code{1455@dots{}}
39157 @node File-I/O Remote Protocol Extension
39158 @section File-I/O Remote Protocol Extension
39159 @cindex File-I/O remote protocol extension
39162 * File-I/O Overview::
39163 * Protocol Basics::
39164 * The F Request Packet::
39165 * The F Reply Packet::
39166 * The Ctrl-C Message::
39168 * List of Supported Calls::
39169 * Protocol-specific Representation of Datatypes::
39171 * File-I/O Examples::
39174 @node File-I/O Overview
39175 @subsection File-I/O Overview
39176 @cindex file-i/o overview
39178 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39179 target to use the host's file system and console I/O to perform various
39180 system calls. System calls on the target system are translated into a
39181 remote protocol packet to the host system, which then performs the needed
39182 actions and returns a response packet to the target system.
39183 This simulates file system operations even on targets that lack file systems.
39185 The protocol is defined to be independent of both the host and target systems.
39186 It uses its own internal representation of datatypes and values. Both
39187 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39188 translating the system-dependent value representations into the internal
39189 protocol representations when data is transmitted.
39191 The communication is synchronous. A system call is possible only when
39192 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39193 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39194 the target is stopped to allow deterministic access to the target's
39195 memory. Therefore File-I/O is not interruptible by target signals. On
39196 the other hand, it is possible to interrupt File-I/O by a user interrupt
39197 (@samp{Ctrl-C}) within @value{GDBN}.
39199 The target's request to perform a host system call does not finish
39200 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39201 after finishing the system call, the target returns to continuing the
39202 previous activity (continue, step). No additional continue or step
39203 request from @value{GDBN} is required.
39206 (@value{GDBP}) continue
39207 <- target requests 'system call X'
39208 target is stopped, @value{GDBN} executes system call
39209 -> @value{GDBN} returns result
39210 ... target continues, @value{GDBN} returns to wait for the target
39211 <- target hits breakpoint and sends a Txx packet
39214 The protocol only supports I/O on the console and to regular files on
39215 the host file system. Character or block special devices, pipes,
39216 named pipes, sockets or any other communication method on the host
39217 system are not supported by this protocol.
39219 File I/O is not supported in non-stop mode.
39221 @node Protocol Basics
39222 @subsection Protocol Basics
39223 @cindex protocol basics, file-i/o
39225 The File-I/O protocol uses the @code{F} packet as the request as well
39226 as reply packet. Since a File-I/O system call can only occur when
39227 @value{GDBN} is waiting for a response from the continuing or stepping target,
39228 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39229 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39230 This @code{F} packet contains all information needed to allow @value{GDBN}
39231 to call the appropriate host system call:
39235 A unique identifier for the requested system call.
39238 All parameters to the system call. Pointers are given as addresses
39239 in the target memory address space. Pointers to strings are given as
39240 pointer/length pair. Numerical values are given as they are.
39241 Numerical control flags are given in a protocol-specific representation.
39245 At this point, @value{GDBN} has to perform the following actions.
39249 If the parameters include pointer values to data needed as input to a
39250 system call, @value{GDBN} requests this data from the target with a
39251 standard @code{m} packet request. This additional communication has to be
39252 expected by the target implementation and is handled as any other @code{m}
39256 @value{GDBN} translates all value from protocol representation to host
39257 representation as needed. Datatypes are coerced into the host types.
39260 @value{GDBN} calls the system call.
39263 It then coerces datatypes back to protocol representation.
39266 If the system call is expected to return data in buffer space specified
39267 by pointer parameters to the call, the data is transmitted to the
39268 target using a @code{M} or @code{X} packet. This packet has to be expected
39269 by the target implementation and is handled as any other @code{M} or @code{X}
39274 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39275 necessary information for the target to continue. This at least contains
39282 @code{errno}, if has been changed by the system call.
39289 After having done the needed type and value coercion, the target continues
39290 the latest continue or step action.
39292 @node The F Request Packet
39293 @subsection The @code{F} Request Packet
39294 @cindex file-i/o request packet
39295 @cindex @code{F} request packet
39297 The @code{F} request packet has the following format:
39300 @item F@var{call-id},@var{parameter@dots{}}
39302 @var{call-id} is the identifier to indicate the host system call to be called.
39303 This is just the name of the function.
39305 @var{parameter@dots{}} are the parameters to the system call.
39306 Parameters are hexadecimal integer values, either the actual values in case
39307 of scalar datatypes, pointers to target buffer space in case of compound
39308 datatypes and unspecified memory areas, or pointer/length pairs in case
39309 of string parameters. These are appended to the @var{call-id} as a
39310 comma-delimited list. All values are transmitted in ASCII
39311 string representation, pointer/length pairs separated by a slash.
39317 @node The F Reply Packet
39318 @subsection The @code{F} Reply Packet
39319 @cindex file-i/o reply packet
39320 @cindex @code{F} reply packet
39322 The @code{F} reply packet has the following format:
39326 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39328 @var{retcode} is the return code of the system call as hexadecimal value.
39330 @var{errno} is the @code{errno} set by the call, in protocol-specific
39332 This parameter can be omitted if the call was successful.
39334 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39335 case, @var{errno} must be sent as well, even if the call was successful.
39336 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39343 or, if the call was interrupted before the host call has been performed:
39350 assuming 4 is the protocol-specific representation of @code{EINTR}.
39355 @node The Ctrl-C Message
39356 @subsection The @samp{Ctrl-C} Message
39357 @cindex ctrl-c message, in file-i/o protocol
39359 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39360 reply packet (@pxref{The F Reply Packet}),
39361 the target should behave as if it had
39362 gotten a break message. The meaning for the target is ``system call
39363 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39364 (as with a break message) and return to @value{GDBN} with a @code{T02}
39367 It's important for the target to know in which
39368 state the system call was interrupted. There are two possible cases:
39372 The system call hasn't been performed on the host yet.
39375 The system call on the host has been finished.
39379 These two states can be distinguished by the target by the value of the
39380 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39381 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39382 on POSIX systems. In any other case, the target may presume that the
39383 system call has been finished --- successfully or not --- and should behave
39384 as if the break message arrived right after the system call.
39386 @value{GDBN} must behave reliably. If the system call has not been called
39387 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39388 @code{errno} in the packet. If the system call on the host has been finished
39389 before the user requests a break, the full action must be finished by
39390 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39391 The @code{F} packet may only be sent when either nothing has happened
39392 or the full action has been completed.
39395 @subsection Console I/O
39396 @cindex console i/o as part of file-i/o
39398 By default and if not explicitly closed by the target system, the file
39399 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39400 on the @value{GDBN} console is handled as any other file output operation
39401 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39402 by @value{GDBN} so that after the target read request from file descriptor
39403 0 all following typing is buffered until either one of the following
39408 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39410 system call is treated as finished.
39413 The user presses @key{RET}. This is treated as end of input with a trailing
39417 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39418 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39422 If the user has typed more characters than fit in the buffer given to
39423 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39424 either another @code{read(0, @dots{})} is requested by the target, or debugging
39425 is stopped at the user's request.
39428 @node List of Supported Calls
39429 @subsection List of Supported Calls
39430 @cindex list of supported file-i/o calls
39447 @unnumberedsubsubsec open
39448 @cindex open, file-i/o system call
39453 int open(const char *pathname, int flags);
39454 int open(const char *pathname, int flags, mode_t mode);
39458 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39461 @var{flags} is the bitwise @code{OR} of the following values:
39465 If the file does not exist it will be created. The host
39466 rules apply as far as file ownership and time stamps
39470 When used with @code{O_CREAT}, if the file already exists it is
39471 an error and open() fails.
39474 If the file already exists and the open mode allows
39475 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39476 truncated to zero length.
39479 The file is opened in append mode.
39482 The file is opened for reading only.
39485 The file is opened for writing only.
39488 The file is opened for reading and writing.
39492 Other bits are silently ignored.
39496 @var{mode} is the bitwise @code{OR} of the following values:
39500 User has read permission.
39503 User has write permission.
39506 Group has read permission.
39509 Group has write permission.
39512 Others have read permission.
39515 Others have write permission.
39519 Other bits are silently ignored.
39522 @item Return value:
39523 @code{open} returns the new file descriptor or -1 if an error
39530 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39533 @var{pathname} refers to a directory.
39536 The requested access is not allowed.
39539 @var{pathname} was too long.
39542 A directory component in @var{pathname} does not exist.
39545 @var{pathname} refers to a device, pipe, named pipe or socket.
39548 @var{pathname} refers to a file on a read-only filesystem and
39549 write access was requested.
39552 @var{pathname} is an invalid pointer value.
39555 No space on device to create the file.
39558 The process already has the maximum number of files open.
39561 The limit on the total number of files open on the system
39565 The call was interrupted by the user.
39571 @unnumberedsubsubsec close
39572 @cindex close, file-i/o system call
39581 @samp{Fclose,@var{fd}}
39583 @item Return value:
39584 @code{close} returns zero on success, or -1 if an error occurred.
39590 @var{fd} isn't a valid open file descriptor.
39593 The call was interrupted by the user.
39599 @unnumberedsubsubsec read
39600 @cindex read, file-i/o system call
39605 int read(int fd, void *buf, unsigned int count);
39609 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39611 @item Return value:
39612 On success, the number of bytes read is returned.
39613 Zero indicates end of file. If count is zero, read
39614 returns zero as well. On error, -1 is returned.
39620 @var{fd} is not a valid file descriptor or is not open for
39624 @var{bufptr} is an invalid pointer value.
39627 The call was interrupted by the user.
39633 @unnumberedsubsubsec write
39634 @cindex write, file-i/o system call
39639 int write(int fd, const void *buf, unsigned int count);
39643 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39645 @item Return value:
39646 On success, the number of bytes written are returned.
39647 Zero indicates nothing was written. On error, -1
39654 @var{fd} is not a valid file descriptor or is not open for
39658 @var{bufptr} is an invalid pointer value.
39661 An attempt was made to write a file that exceeds the
39662 host-specific maximum file size allowed.
39665 No space on device to write the data.
39668 The call was interrupted by the user.
39674 @unnumberedsubsubsec lseek
39675 @cindex lseek, file-i/o system call
39680 long lseek (int fd, long offset, int flag);
39684 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39686 @var{flag} is one of:
39690 The offset is set to @var{offset} bytes.
39693 The offset is set to its current location plus @var{offset}
39697 The offset is set to the size of the file plus @var{offset}
39701 @item Return value:
39702 On success, the resulting unsigned offset in bytes from
39703 the beginning of the file is returned. Otherwise, a
39704 value of -1 is returned.
39710 @var{fd} is not a valid open file descriptor.
39713 @var{fd} is associated with the @value{GDBN} console.
39716 @var{flag} is not a proper value.
39719 The call was interrupted by the user.
39725 @unnumberedsubsubsec rename
39726 @cindex rename, file-i/o system call
39731 int rename(const char *oldpath, const char *newpath);
39735 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39737 @item Return value:
39738 On success, zero is returned. On error, -1 is returned.
39744 @var{newpath} is an existing directory, but @var{oldpath} is not a
39748 @var{newpath} is a non-empty directory.
39751 @var{oldpath} or @var{newpath} is a directory that is in use by some
39755 An attempt was made to make a directory a subdirectory
39759 A component used as a directory in @var{oldpath} or new
39760 path is not a directory. Or @var{oldpath} is a directory
39761 and @var{newpath} exists but is not a directory.
39764 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39767 No access to the file or the path of the file.
39771 @var{oldpath} or @var{newpath} was too long.
39774 A directory component in @var{oldpath} or @var{newpath} does not exist.
39777 The file is on a read-only filesystem.
39780 The device containing the file has no room for the new
39784 The call was interrupted by the user.
39790 @unnumberedsubsubsec unlink
39791 @cindex unlink, file-i/o system call
39796 int unlink(const char *pathname);
39800 @samp{Funlink,@var{pathnameptr}/@var{len}}
39802 @item Return value:
39803 On success, zero is returned. On error, -1 is returned.
39809 No access to the file or the path of the file.
39812 The system does not allow unlinking of directories.
39815 The file @var{pathname} cannot be unlinked because it's
39816 being used by another process.
39819 @var{pathnameptr} is an invalid pointer value.
39822 @var{pathname} was too long.
39825 A directory component in @var{pathname} does not exist.
39828 A component of the path is not a directory.
39831 The file is on a read-only filesystem.
39834 The call was interrupted by the user.
39840 @unnumberedsubsubsec stat/fstat
39841 @cindex fstat, file-i/o system call
39842 @cindex stat, file-i/o system call
39847 int stat(const char *pathname, struct stat *buf);
39848 int fstat(int fd, struct stat *buf);
39852 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39853 @samp{Ffstat,@var{fd},@var{bufptr}}
39855 @item Return value:
39856 On success, zero is returned. On error, -1 is returned.
39862 @var{fd} is not a valid open file.
39865 A directory component in @var{pathname} does not exist or the
39866 path is an empty string.
39869 A component of the path is not a directory.
39872 @var{pathnameptr} is an invalid pointer value.
39875 No access to the file or the path of the file.
39878 @var{pathname} was too long.
39881 The call was interrupted by the user.
39887 @unnumberedsubsubsec gettimeofday
39888 @cindex gettimeofday, file-i/o system call
39893 int gettimeofday(struct timeval *tv, void *tz);
39897 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39899 @item Return value:
39900 On success, 0 is returned, -1 otherwise.
39906 @var{tz} is a non-NULL pointer.
39909 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39915 @unnumberedsubsubsec isatty
39916 @cindex isatty, file-i/o system call
39921 int isatty(int fd);
39925 @samp{Fisatty,@var{fd}}
39927 @item Return value:
39928 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39934 The call was interrupted by the user.
39939 Note that the @code{isatty} call is treated as a special case: it returns
39940 1 to the target if the file descriptor is attached
39941 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39942 would require implementing @code{ioctl} and would be more complex than
39947 @unnumberedsubsubsec system
39948 @cindex system, file-i/o system call
39953 int system(const char *command);
39957 @samp{Fsystem,@var{commandptr}/@var{len}}
39959 @item Return value:
39960 If @var{len} is zero, the return value indicates whether a shell is
39961 available. A zero return value indicates a shell is not available.
39962 For non-zero @var{len}, the value returned is -1 on error and the
39963 return status of the command otherwise. Only the exit status of the
39964 command is returned, which is extracted from the host's @code{system}
39965 return value by calling @code{WEXITSTATUS(retval)}. In case
39966 @file{/bin/sh} could not be executed, 127 is returned.
39972 The call was interrupted by the user.
39977 @value{GDBN} takes over the full task of calling the necessary host calls
39978 to perform the @code{system} call. The return value of @code{system} on
39979 the host is simplified before it's returned
39980 to the target. Any termination signal information from the child process
39981 is discarded, and the return value consists
39982 entirely of the exit status of the called command.
39984 Due to security concerns, the @code{system} call is by default refused
39985 by @value{GDBN}. The user has to allow this call explicitly with the
39986 @code{set remote system-call-allowed 1} command.
39989 @item set remote system-call-allowed
39990 @kindex set remote system-call-allowed
39991 Control whether to allow the @code{system} calls in the File I/O
39992 protocol for the remote target. The default is zero (disabled).
39994 @item show remote system-call-allowed
39995 @kindex show remote system-call-allowed
39996 Show whether the @code{system} calls are allowed in the File I/O
40000 @node Protocol-specific Representation of Datatypes
40001 @subsection Protocol-specific Representation of Datatypes
40002 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40005 * Integral Datatypes::
40007 * Memory Transfer::
40012 @node Integral Datatypes
40013 @unnumberedsubsubsec Integral Datatypes
40014 @cindex integral datatypes, in file-i/o protocol
40016 The integral datatypes used in the system calls are @code{int},
40017 @code{unsigned int}, @code{long}, @code{unsigned long},
40018 @code{mode_t}, and @code{time_t}.
40020 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40021 implemented as 32 bit values in this protocol.
40023 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40025 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40026 in @file{limits.h}) to allow range checking on host and target.
40028 @code{time_t} datatypes are defined as seconds since the Epoch.
40030 All integral datatypes transferred as part of a memory read or write of a
40031 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40034 @node Pointer Values
40035 @unnumberedsubsubsec Pointer Values
40036 @cindex pointer values, in file-i/o protocol
40038 Pointers to target data are transmitted as they are. An exception
40039 is made for pointers to buffers for which the length isn't
40040 transmitted as part of the function call, namely strings. Strings
40041 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40048 which is a pointer to data of length 18 bytes at position 0x1aaf.
40049 The length is defined as the full string length in bytes, including
40050 the trailing null byte. For example, the string @code{"hello world"}
40051 at address 0x123456 is transmitted as
40057 @node Memory Transfer
40058 @unnumberedsubsubsec Memory Transfer
40059 @cindex memory transfer, in file-i/o protocol
40061 Structured data which is transferred using a memory read or write (for
40062 example, a @code{struct stat}) is expected to be in a protocol-specific format
40063 with all scalar multibyte datatypes being big endian. Translation to
40064 this representation needs to be done both by the target before the @code{F}
40065 packet is sent, and by @value{GDBN} before
40066 it transfers memory to the target. Transferred pointers to structured
40067 data should point to the already-coerced data at any time.
40071 @unnumberedsubsubsec struct stat
40072 @cindex struct stat, in file-i/o protocol
40074 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40075 is defined as follows:
40079 unsigned int st_dev; /* device */
40080 unsigned int st_ino; /* inode */
40081 mode_t st_mode; /* protection */
40082 unsigned int st_nlink; /* number of hard links */
40083 unsigned int st_uid; /* user ID of owner */
40084 unsigned int st_gid; /* group ID of owner */
40085 unsigned int st_rdev; /* device type (if inode device) */
40086 unsigned long st_size; /* total size, in bytes */
40087 unsigned long st_blksize; /* blocksize for filesystem I/O */
40088 unsigned long st_blocks; /* number of blocks allocated */
40089 time_t st_atime; /* time of last access */
40090 time_t st_mtime; /* time of last modification */
40091 time_t st_ctime; /* time of last change */
40095 The integral datatypes conform to the definitions given in the
40096 appropriate section (see @ref{Integral Datatypes}, for details) so this
40097 structure is of size 64 bytes.
40099 The values of several fields have a restricted meaning and/or
40105 A value of 0 represents a file, 1 the console.
40108 No valid meaning for the target. Transmitted unchanged.
40111 Valid mode bits are described in @ref{Constants}. Any other
40112 bits have currently no meaning for the target.
40117 No valid meaning for the target. Transmitted unchanged.
40122 These values have a host and file system dependent
40123 accuracy. Especially on Windows hosts, the file system may not
40124 support exact timing values.
40127 The target gets a @code{struct stat} of the above representation and is
40128 responsible for coercing it to the target representation before
40131 Note that due to size differences between the host, target, and protocol
40132 representations of @code{struct stat} members, these members could eventually
40133 get truncated on the target.
40135 @node struct timeval
40136 @unnumberedsubsubsec struct timeval
40137 @cindex struct timeval, in file-i/o protocol
40139 The buffer of type @code{struct timeval} used by the File-I/O protocol
40140 is defined as follows:
40144 time_t tv_sec; /* second */
40145 long tv_usec; /* microsecond */
40149 The integral datatypes conform to the definitions given in the
40150 appropriate section (see @ref{Integral Datatypes}, for details) so this
40151 structure is of size 8 bytes.
40154 @subsection Constants
40155 @cindex constants, in file-i/o protocol
40157 The following values are used for the constants inside of the
40158 protocol. @value{GDBN} and target are responsible for translating these
40159 values before and after the call as needed.
40170 @unnumberedsubsubsec Open Flags
40171 @cindex open flags, in file-i/o protocol
40173 All values are given in hexadecimal representation.
40185 @node mode_t Values
40186 @unnumberedsubsubsec mode_t Values
40187 @cindex mode_t values, in file-i/o protocol
40189 All values are given in octal representation.
40206 @unnumberedsubsubsec Errno Values
40207 @cindex errno values, in file-i/o protocol
40209 All values are given in decimal representation.
40234 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40235 any error value not in the list of supported error numbers.
40238 @unnumberedsubsubsec Lseek Flags
40239 @cindex lseek flags, in file-i/o protocol
40248 @unnumberedsubsubsec Limits
40249 @cindex limits, in file-i/o protocol
40251 All values are given in decimal representation.
40254 INT_MIN -2147483648
40256 UINT_MAX 4294967295
40257 LONG_MIN -9223372036854775808
40258 LONG_MAX 9223372036854775807
40259 ULONG_MAX 18446744073709551615
40262 @node File-I/O Examples
40263 @subsection File-I/O Examples
40264 @cindex file-i/o examples
40266 Example sequence of a write call, file descriptor 3, buffer is at target
40267 address 0x1234, 6 bytes should be written:
40270 <- @code{Fwrite,3,1234,6}
40271 @emph{request memory read from target}
40274 @emph{return "6 bytes written"}
40278 Example sequence of a read call, file descriptor 3, buffer is at target
40279 address 0x1234, 6 bytes should be read:
40282 <- @code{Fread,3,1234,6}
40283 @emph{request memory write to target}
40284 -> @code{X1234,6:XXXXXX}
40285 @emph{return "6 bytes read"}
40289 Example sequence of a read call, call fails on the host due to invalid
40290 file descriptor (@code{EBADF}):
40293 <- @code{Fread,3,1234,6}
40297 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40301 <- @code{Fread,3,1234,6}
40306 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40310 <- @code{Fread,3,1234,6}
40311 -> @code{X1234,6:XXXXXX}
40315 @node Library List Format
40316 @section Library List Format
40317 @cindex library list format, remote protocol
40319 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40320 same process as your application to manage libraries. In this case,
40321 @value{GDBN} can use the loader's symbol table and normal memory
40322 operations to maintain a list of shared libraries. On other
40323 platforms, the operating system manages loaded libraries.
40324 @value{GDBN} can not retrieve the list of currently loaded libraries
40325 through memory operations, so it uses the @samp{qXfer:libraries:read}
40326 packet (@pxref{qXfer library list read}) instead. The remote stub
40327 queries the target's operating system and reports which libraries
40330 The @samp{qXfer:libraries:read} packet returns an XML document which
40331 lists loaded libraries and their offsets. Each library has an
40332 associated name and one or more segment or section base addresses,
40333 which report where the library was loaded in memory.
40335 For the common case of libraries that are fully linked binaries, the
40336 library should have a list of segments. If the target supports
40337 dynamic linking of a relocatable object file, its library XML element
40338 should instead include a list of allocated sections. The segment or
40339 section bases are start addresses, not relocation offsets; they do not
40340 depend on the library's link-time base addresses.
40342 @value{GDBN} must be linked with the Expat library to support XML
40343 library lists. @xref{Expat}.
40345 A simple memory map, with one loaded library relocated by a single
40346 offset, looks like this:
40350 <library name="/lib/libc.so.6">
40351 <segment address="0x10000000"/>
40356 Another simple memory map, with one loaded library with three
40357 allocated sections (.text, .data, .bss), looks like this:
40361 <library name="sharedlib.o">
40362 <section address="0x10000000"/>
40363 <section address="0x20000000"/>
40364 <section address="0x30000000"/>
40369 The format of a library list is described by this DTD:
40372 <!-- library-list: Root element with versioning -->
40373 <!ELEMENT library-list (library)*>
40374 <!ATTLIST library-list version CDATA #FIXED "1.0">
40375 <!ELEMENT library (segment*, section*)>
40376 <!ATTLIST library name CDATA #REQUIRED>
40377 <!ELEMENT segment EMPTY>
40378 <!ATTLIST segment address CDATA #REQUIRED>
40379 <!ELEMENT section EMPTY>
40380 <!ATTLIST section address CDATA #REQUIRED>
40383 In addition, segments and section descriptors cannot be mixed within a
40384 single library element, and you must supply at least one segment or
40385 section for each library.
40387 @node Library List Format for SVR4 Targets
40388 @section Library List Format for SVR4 Targets
40389 @cindex library list format, remote protocol
40391 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40392 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40393 shared libraries. Still a special library list provided by this packet is
40394 more efficient for the @value{GDBN} remote protocol.
40396 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40397 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40398 target, the following parameters are reported:
40402 @code{name}, the absolute file name from the @code{l_name} field of
40403 @code{struct link_map}.
40405 @code{lm} with address of @code{struct link_map} used for TLS
40406 (Thread Local Storage) access.
40408 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40409 @code{struct link_map}. For prelinked libraries this is not an absolute
40410 memory address. It is a displacement of absolute memory address against
40411 address the file was prelinked to during the library load.
40413 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40416 Additionally the single @code{main-lm} attribute specifies address of
40417 @code{struct link_map} used for the main executable. This parameter is used
40418 for TLS access and its presence is optional.
40420 @value{GDBN} must be linked with the Expat library to support XML
40421 SVR4 library lists. @xref{Expat}.
40423 A simple memory map, with two loaded libraries (which do not use prelink),
40427 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40428 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40430 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40432 </library-list-svr>
40435 The format of an SVR4 library list is described by this DTD:
40438 <!-- library-list-svr4: Root element with versioning -->
40439 <!ELEMENT library-list-svr4 (library)*>
40440 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40441 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40442 <!ELEMENT library EMPTY>
40443 <!ATTLIST library name CDATA #REQUIRED>
40444 <!ATTLIST library lm CDATA #REQUIRED>
40445 <!ATTLIST library l_addr CDATA #REQUIRED>
40446 <!ATTLIST library l_ld CDATA #REQUIRED>
40449 @node Memory Map Format
40450 @section Memory Map Format
40451 @cindex memory map format
40453 To be able to write into flash memory, @value{GDBN} needs to obtain a
40454 memory map from the target. This section describes the format of the
40457 The memory map is obtained using the @samp{qXfer:memory-map:read}
40458 (@pxref{qXfer memory map read}) packet and is an XML document that
40459 lists memory regions.
40461 @value{GDBN} must be linked with the Expat library to support XML
40462 memory maps. @xref{Expat}.
40464 The top-level structure of the document is shown below:
40467 <?xml version="1.0"?>
40468 <!DOCTYPE memory-map
40469 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40470 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40476 Each region can be either:
40481 A region of RAM starting at @var{addr} and extending for @var{length}
40485 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40490 A region of read-only memory:
40493 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40498 A region of flash memory, with erasure blocks @var{blocksize}
40502 <memory type="flash" start="@var{addr}" length="@var{length}">
40503 <property name="blocksize">@var{blocksize}</property>
40509 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40510 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40511 packets to write to addresses in such ranges.
40513 The formal DTD for memory map format is given below:
40516 <!-- ................................................... -->
40517 <!-- Memory Map XML DTD ................................ -->
40518 <!-- File: memory-map.dtd .............................. -->
40519 <!-- .................................... .............. -->
40520 <!-- memory-map.dtd -->
40521 <!-- memory-map: Root element with versioning -->
40522 <!ELEMENT memory-map (memory | property)>
40523 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40524 <!ELEMENT memory (property)>
40525 <!-- memory: Specifies a memory region,
40526 and its type, or device. -->
40527 <!ATTLIST memory type CDATA #REQUIRED
40528 start CDATA #REQUIRED
40529 length CDATA #REQUIRED
40530 device CDATA #IMPLIED>
40531 <!-- property: Generic attribute tag -->
40532 <!ELEMENT property (#PCDATA | property)*>
40533 <!ATTLIST property name CDATA #REQUIRED>
40536 @node Thread List Format
40537 @section Thread List Format
40538 @cindex thread list format
40540 To efficiently update the list of threads and their attributes,
40541 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40542 (@pxref{qXfer threads read}) and obtains the XML document with
40543 the following structure:
40546 <?xml version="1.0"?>
40548 <thread id="id" core="0" name="name">
40549 ... description ...
40554 Each @samp{thread} element must have the @samp{id} attribute that
40555 identifies the thread (@pxref{thread-id syntax}). The
40556 @samp{core} attribute, if present, specifies which processor core
40557 the thread was last executing on. The @samp{name} attribute, if
40558 present, specifies the human-readable name of the thread. The content
40559 of the of @samp{thread} element is interpreted as human-readable
40560 auxiliary information.
40562 @node Traceframe Info Format
40563 @section Traceframe Info Format
40564 @cindex traceframe info format
40566 To be able to know which objects in the inferior can be examined when
40567 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40568 memory ranges, registers and trace state variables that have been
40569 collected in a traceframe.
40571 This list is obtained using the @samp{qXfer:traceframe-info:read}
40572 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40574 @value{GDBN} must be linked with the Expat library to support XML
40575 traceframe info discovery. @xref{Expat}.
40577 The top-level structure of the document is shown below:
40580 <?xml version="1.0"?>
40581 <!DOCTYPE traceframe-info
40582 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40583 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40589 Each traceframe block can be either:
40594 A region of collected memory starting at @var{addr} and extending for
40595 @var{length} bytes from there:
40598 <memory start="@var{addr}" length="@var{length}"/>
40602 A block indicating trace state variable numbered @var{number} has been
40606 <tvar id="@var{number}"/>
40611 The formal DTD for the traceframe info format is given below:
40614 <!ELEMENT traceframe-info (memory | tvar)* >
40615 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40617 <!ELEMENT memory EMPTY>
40618 <!ATTLIST memory start CDATA #REQUIRED
40619 length CDATA #REQUIRED>
40621 <!ATTLIST tvar id CDATA #REQUIRED>
40624 @node Branch Trace Format
40625 @section Branch Trace Format
40626 @cindex branch trace format
40628 In order to display the branch trace of an inferior thread,
40629 @value{GDBN} needs to obtain the list of branches. This list is
40630 represented as list of sequential code blocks that are connected via
40631 branches. The code in each block has been executed sequentially.
40633 This list is obtained using the @samp{qXfer:btrace:read}
40634 (@pxref{qXfer btrace read}) packet and is an XML document.
40636 @value{GDBN} must be linked with the Expat library to support XML
40637 traceframe info discovery. @xref{Expat}.
40639 The top-level structure of the document is shown below:
40642 <?xml version="1.0"?>
40644 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40645 "http://sourceware.org/gdb/gdb-btrace.dtd">
40654 A block of sequentially executed instructions starting at @var{begin}
40655 and ending at @var{end}:
40658 <block begin="@var{begin}" end="@var{end}"/>
40663 The formal DTD for the branch trace format is given below:
40666 <!ELEMENT btrace (block* | pt) >
40667 <!ATTLIST btrace version CDATA #FIXED "1.0">
40669 <!ELEMENT block EMPTY>
40670 <!ATTLIST block begin CDATA #REQUIRED
40671 end CDATA #REQUIRED>
40673 <!ELEMENT pt (pt-config?, raw?)>
40675 <!ELEMENT pt-config (cpu?)>
40677 <!ELEMENT cpu EMPTY>
40678 <!ATTLIST cpu vendor CDATA #REQUIRED
40679 family CDATA #REQUIRED
40680 model CDATA #REQUIRED
40681 stepping CDATA #REQUIRED>
40683 <!ELEMENT raw (#PCDATA)>
40686 @node Branch Trace Configuration Format
40687 @section Branch Trace Configuration Format
40688 @cindex branch trace configuration format
40690 For each inferior thread, @value{GDBN} can obtain the branch trace
40691 configuration using the @samp{qXfer:btrace-conf:read}
40692 (@pxref{qXfer btrace-conf read}) packet.
40694 The configuration describes the branch trace format and configuration
40695 settings for that format. The following information is described:
40699 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40702 The size of the @acronym{BTS} ring buffer in bytes.
40705 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40709 The size of the @acronym{Intel PT} ring buffer in bytes.
40713 @value{GDBN} must be linked with the Expat library to support XML
40714 branch trace configuration discovery. @xref{Expat}.
40716 The formal DTD for the branch trace configuration format is given below:
40719 <!ELEMENT btrace-conf (bts?, pt?)>
40720 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40722 <!ELEMENT bts EMPTY>
40723 <!ATTLIST bts size CDATA #IMPLIED>
40725 <!ELEMENT pt EMPTY>
40726 <!ATTLIST pt size CDATA #IMPLIED>
40729 @include agentexpr.texi
40731 @node Target Descriptions
40732 @appendix Target Descriptions
40733 @cindex target descriptions
40735 One of the challenges of using @value{GDBN} to debug embedded systems
40736 is that there are so many minor variants of each processor
40737 architecture in use. It is common practice for vendors to start with
40738 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40739 and then make changes to adapt it to a particular market niche. Some
40740 architectures have hundreds of variants, available from dozens of
40741 vendors. This leads to a number of problems:
40745 With so many different customized processors, it is difficult for
40746 the @value{GDBN} maintainers to keep up with the changes.
40748 Since individual variants may have short lifetimes or limited
40749 audiences, it may not be worthwhile to carry information about every
40750 variant in the @value{GDBN} source tree.
40752 When @value{GDBN} does support the architecture of the embedded system
40753 at hand, the task of finding the correct architecture name to give the
40754 @command{set architecture} command can be error-prone.
40757 To address these problems, the @value{GDBN} remote protocol allows a
40758 target system to not only identify itself to @value{GDBN}, but to
40759 actually describe its own features. This lets @value{GDBN} support
40760 processor variants it has never seen before --- to the extent that the
40761 descriptions are accurate, and that @value{GDBN} understands them.
40763 @value{GDBN} must be linked with the Expat library to support XML
40764 target descriptions. @xref{Expat}.
40767 * Retrieving Descriptions:: How descriptions are fetched from a target.
40768 * Target Description Format:: The contents of a target description.
40769 * Predefined Target Types:: Standard types available for target
40771 * Enum Target Types:: How to define enum target types.
40772 * Standard Target Features:: Features @value{GDBN} knows about.
40775 @node Retrieving Descriptions
40776 @section Retrieving Descriptions
40778 Target descriptions can be read from the target automatically, or
40779 specified by the user manually. The default behavior is to read the
40780 description from the target. @value{GDBN} retrieves it via the remote
40781 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40782 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40783 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40784 XML document, of the form described in @ref{Target Description
40787 Alternatively, you can specify a file to read for the target description.
40788 If a file is set, the target will not be queried. The commands to
40789 specify a file are:
40792 @cindex set tdesc filename
40793 @item set tdesc filename @var{path}
40794 Read the target description from @var{path}.
40796 @cindex unset tdesc filename
40797 @item unset tdesc filename
40798 Do not read the XML target description from a file. @value{GDBN}
40799 will use the description supplied by the current target.
40801 @cindex show tdesc filename
40802 @item show tdesc filename
40803 Show the filename to read for a target description, if any.
40807 @node Target Description Format
40808 @section Target Description Format
40809 @cindex target descriptions, XML format
40811 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40812 document which complies with the Document Type Definition provided in
40813 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40814 means you can use generally available tools like @command{xmllint} to
40815 check that your feature descriptions are well-formed and valid.
40816 However, to help people unfamiliar with XML write descriptions for
40817 their targets, we also describe the grammar here.
40819 Target descriptions can identify the architecture of the remote target
40820 and (for some architectures) provide information about custom register
40821 sets. They can also identify the OS ABI of the remote target.
40822 @value{GDBN} can use this information to autoconfigure for your
40823 target, or to warn you if you connect to an unsupported target.
40825 Here is a simple target description:
40828 <target version="1.0">
40829 <architecture>i386:x86-64</architecture>
40834 This minimal description only says that the target uses
40835 the x86-64 architecture.
40837 A target description has the following overall form, with [ ] marking
40838 optional elements and @dots{} marking repeatable elements. The elements
40839 are explained further below.
40842 <?xml version="1.0"?>
40843 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40844 <target version="1.0">
40845 @r{[}@var{architecture}@r{]}
40846 @r{[}@var{osabi}@r{]}
40847 @r{[}@var{compatible}@r{]}
40848 @r{[}@var{feature}@dots{}@r{]}
40853 The description is generally insensitive to whitespace and line
40854 breaks, under the usual common-sense rules. The XML version
40855 declaration and document type declaration can generally be omitted
40856 (@value{GDBN} does not require them), but specifying them may be
40857 useful for XML validation tools. The @samp{version} attribute for
40858 @samp{<target>} may also be omitted, but we recommend
40859 including it; if future versions of @value{GDBN} use an incompatible
40860 revision of @file{gdb-target.dtd}, they will detect and report
40861 the version mismatch.
40863 @subsection Inclusion
40864 @cindex target descriptions, inclusion
40867 @cindex <xi:include>
40870 It can sometimes be valuable to split a target description up into
40871 several different annexes, either for organizational purposes, or to
40872 share files between different possible target descriptions. You can
40873 divide a description into multiple files by replacing any element of
40874 the target description with an inclusion directive of the form:
40877 <xi:include href="@var{document}"/>
40881 When @value{GDBN} encounters an element of this form, it will retrieve
40882 the named XML @var{document}, and replace the inclusion directive with
40883 the contents of that document. If the current description was read
40884 using @samp{qXfer}, then so will be the included document;
40885 @var{document} will be interpreted as the name of an annex. If the
40886 current description was read from a file, @value{GDBN} will look for
40887 @var{document} as a file in the same directory where it found the
40888 original description.
40890 @subsection Architecture
40891 @cindex <architecture>
40893 An @samp{<architecture>} element has this form:
40896 <architecture>@var{arch}</architecture>
40899 @var{arch} is one of the architectures from the set accepted by
40900 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40903 @cindex @code{<osabi>}
40905 This optional field was introduced in @value{GDBN} version 7.0.
40906 Previous versions of @value{GDBN} ignore it.
40908 An @samp{<osabi>} element has this form:
40911 <osabi>@var{abi-name}</osabi>
40914 @var{abi-name} is an OS ABI name from the same selection accepted by
40915 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40917 @subsection Compatible Architecture
40918 @cindex @code{<compatible>}
40920 This optional field was introduced in @value{GDBN} version 7.0.
40921 Previous versions of @value{GDBN} ignore it.
40923 A @samp{<compatible>} element has this form:
40926 <compatible>@var{arch}</compatible>
40929 @var{arch} is one of the architectures from the set accepted by
40930 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40932 A @samp{<compatible>} element is used to specify that the target
40933 is able to run binaries in some other than the main target architecture
40934 given by the @samp{<architecture>} element. For example, on the
40935 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40936 or @code{powerpc:common64}, but the system is able to run binaries
40937 in the @code{spu} architecture as well. The way to describe this
40938 capability with @samp{<compatible>} is as follows:
40941 <architecture>powerpc:common</architecture>
40942 <compatible>spu</compatible>
40945 @subsection Features
40948 Each @samp{<feature>} describes some logical portion of the target
40949 system. Features are currently used to describe available CPU
40950 registers and the types of their contents. A @samp{<feature>} element
40954 <feature name="@var{name}">
40955 @r{[}@var{type}@dots{}@r{]}
40961 Each feature's name should be unique within the description. The name
40962 of a feature does not matter unless @value{GDBN} has some special
40963 knowledge of the contents of that feature; if it does, the feature
40964 should have its standard name. @xref{Standard Target Features}.
40968 Any register's value is a collection of bits which @value{GDBN} must
40969 interpret. The default interpretation is a two's complement integer,
40970 but other types can be requested by name in the register description.
40971 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40972 Target Types}), and the description can define additional composite
40975 Each type element must have an @samp{id} attribute, which gives
40976 a unique (within the containing @samp{<feature>}) name to the type.
40977 Types must be defined before they are used.
40980 Some targets offer vector registers, which can be treated as arrays
40981 of scalar elements. These types are written as @samp{<vector>} elements,
40982 specifying the array element type, @var{type}, and the number of elements,
40986 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40990 If a register's value is usefully viewed in multiple ways, define it
40991 with a union type containing the useful representations. The
40992 @samp{<union>} element contains one or more @samp{<field>} elements,
40993 each of which has a @var{name} and a @var{type}:
40996 <union id="@var{id}">
40997 <field name="@var{name}" type="@var{type}"/>
41004 If a register's value is composed from several separate values, define
41005 it with either a structure type or a flags type.
41006 A flags type may only contain bitfields.
41007 A structure type may either contain only bitfields or contain no bitfields.
41008 If the value contains only bitfields, its total size in bytes must be
41011 Non-bitfield values have a @var{name} and @var{type}.
41014 <struct id="@var{id}">
41015 <field name="@var{name}" type="@var{type}"/>
41020 Both @var{name} and @var{type} values are required.
41021 No implicit padding is added.
41023 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41026 <struct id="@var{id}" size="@var{size}">
41027 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41033 <flags id="@var{id}" size="@var{size}">
41034 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41039 The @var{name} value is required.
41040 Bitfield values may be named with the empty string, @samp{""},
41041 in which case the field is ``filler'' and its value is not printed.
41042 Not all bits need to be specified, so ``filler'' fields are optional.
41044 The @var{start} and @var{end} values are required, and @var{type}
41046 The field's @var{start} must be less than or equal to its @var{end},
41047 and zero represents the least significant bit.
41049 The default value of @var{type} is @code{bool} for single bit fields,
41050 and an unsigned integer otherwise.
41052 Which to choose? Structures or flags?
41054 Registers defined with @samp{flags} have these advantages over
41055 defining them with @samp{struct}:
41059 Arithmetic may be performed on them as if they were integers.
41061 They are printed in a more readable fashion.
41064 Registers defined with @samp{struct} have one advantage over
41065 defining them with @samp{flags}:
41069 One can fetch individual fields like in @samp{C}.
41072 (gdb) print $my_struct_reg.field3
41078 @subsection Registers
41081 Each register is represented as an element with this form:
41084 <reg name="@var{name}"
41085 bitsize="@var{size}"
41086 @r{[}regnum="@var{num}"@r{]}
41087 @r{[}save-restore="@var{save-restore}"@r{]}
41088 @r{[}type="@var{type}"@r{]}
41089 @r{[}group="@var{group}"@r{]}/>
41093 The components are as follows:
41098 The register's name; it must be unique within the target description.
41101 The register's size, in bits.
41104 The register's number. If omitted, a register's number is one greater
41105 than that of the previous register (either in the current feature or in
41106 a preceding feature); the first register in the target description
41107 defaults to zero. This register number is used to read or write
41108 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41109 packets, and registers appear in the @code{g} and @code{G} packets
41110 in order of increasing register number.
41113 Whether the register should be preserved across inferior function
41114 calls; this must be either @code{yes} or @code{no}. The default is
41115 @code{yes}, which is appropriate for most registers except for
41116 some system control registers; this is not related to the target's
41120 The type of the register. It may be a predefined type, a type
41121 defined in the current feature, or one of the special types @code{int}
41122 and @code{float}. @code{int} is an integer type of the correct size
41123 for @var{bitsize}, and @code{float} is a floating point type (in the
41124 architecture's normal floating point format) of the correct size for
41125 @var{bitsize}. The default is @code{int}.
41128 The register group to which this register belongs. It must
41129 be either @code{general}, @code{float}, or @code{vector}. If no
41130 @var{group} is specified, @value{GDBN} will not display the register
41131 in @code{info registers}.
41135 @node Predefined Target Types
41136 @section Predefined Target Types
41137 @cindex target descriptions, predefined types
41139 Type definitions in the self-description can build up composite types
41140 from basic building blocks, but can not define fundamental types. Instead,
41141 standard identifiers are provided by @value{GDBN} for the fundamental
41142 types. The currently supported types are:
41147 Boolean type, occupying a single bit.
41154 Signed integer types holding the specified number of bits.
41161 Unsigned integer types holding the specified number of bits.
41165 Pointers to unspecified code and data. The program counter and
41166 any dedicated return address register may be marked as code
41167 pointers; printing a code pointer converts it into a symbolic
41168 address. The stack pointer and any dedicated address registers
41169 may be marked as data pointers.
41172 Single precision IEEE floating point.
41175 Double precision IEEE floating point.
41178 The 12-byte extended precision format used by ARM FPA registers.
41181 The 10-byte extended precision format used by x87 registers.
41184 32bit @sc{eflags} register used by x86.
41187 32bit @sc{mxcsr} register used by x86.
41191 @node Enum Target Types
41192 @section Enum Target Types
41193 @cindex target descriptions, enum types
41195 Enum target types are useful in @samp{struct} and @samp{flags}
41196 register descriptions. @xref{Target Description Format}.
41198 Enum types have a name, size and a list of name/value pairs.
41201 <enum id="@var{id}" size="@var{size}">
41202 <evalue name="@var{name}" value="@var{value}"/>
41207 Enums must be defined before they are used.
41210 <enum id="levels_type" size="4">
41211 <evalue name="low" value="0"/>
41212 <evalue name="high" value="1"/>
41214 <flags id="flags_type" size="4">
41215 <field name="X" start="0"/>
41216 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41218 <reg name="flags" bitsize="32" type="flags_type"/>
41221 Given that description, a value of 3 for the @samp{flags} register
41222 would be printed as:
41225 (gdb) info register flags
41226 flags 0x3 [ X LEVEL=high ]
41229 @node Standard Target Features
41230 @section Standard Target Features
41231 @cindex target descriptions, standard features
41233 A target description must contain either no registers or all the
41234 target's registers. If the description contains no registers, then
41235 @value{GDBN} will assume a default register layout, selected based on
41236 the architecture. If the description contains any registers, the
41237 default layout will not be used; the standard registers must be
41238 described in the target description, in such a way that @value{GDBN}
41239 can recognize them.
41241 This is accomplished by giving specific names to feature elements
41242 which contain standard registers. @value{GDBN} will look for features
41243 with those names and verify that they contain the expected registers;
41244 if any known feature is missing required registers, or if any required
41245 feature is missing, @value{GDBN} will reject the target
41246 description. You can add additional registers to any of the
41247 standard features --- @value{GDBN} will display them just as if
41248 they were added to an unrecognized feature.
41250 This section lists the known features and their expected contents.
41251 Sample XML documents for these features are included in the
41252 @value{GDBN} source tree, in the directory @file{gdb/features}.
41254 Names recognized by @value{GDBN} should include the name of the
41255 company or organization which selected the name, and the overall
41256 architecture to which the feature applies; so e.g.@: the feature
41257 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41259 The names of registers are not case sensitive for the purpose
41260 of recognizing standard features, but @value{GDBN} will only display
41261 registers using the capitalization used in the description.
41264 * AArch64 Features::
41268 * MicroBlaze Features::
41272 * Nios II Features::
41273 * PowerPC Features::
41274 * S/390 and System z Features::
41280 @node AArch64 Features
41281 @subsection AArch64 Features
41282 @cindex target descriptions, AArch64 features
41284 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41285 targets. It should contain registers @samp{x0} through @samp{x30},
41286 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41288 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41289 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41293 @subsection ARC Features
41294 @cindex target descriptions, ARC Features
41296 ARC processors are highly configurable, so even core registers and their number
41297 are not completely predetermined. In addition flags and PC registers which are
41298 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41299 that one of the core registers features is present.
41300 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41302 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41303 targets with a normal register file. It should contain registers @samp{r0}
41304 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41305 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41306 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41307 @samp{ilink} and extension core registers are not available to read/write, when
41308 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41310 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41311 ARC HS targets with a reduced register file. It should contain registers
41312 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41313 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41314 This feature may contain register @samp{ilink} and any of extension core
41315 registers @samp{r32} through @samp{r59/acch}.
41317 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41318 targets with a normal register file. It should contain registers @samp{r0}
41319 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41320 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41321 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41322 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41323 registers are not available when debugging GNU/Linux applications. The only
41324 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41325 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41326 ARC v2, but @samp{ilink2} is optional on ARCompact.
41328 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41329 targets. It should contain registers @samp{pc} and @samp{status32}.
41332 @subsection ARM Features
41333 @cindex target descriptions, ARM features
41335 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41337 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41338 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41340 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41341 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41342 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41345 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41346 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41348 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41349 it should contain at least registers @samp{wR0} through @samp{wR15} and
41350 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41351 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41353 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41354 should contain at least registers @samp{d0} through @samp{d15}. If
41355 they are present, @samp{d16} through @samp{d31} should also be included.
41356 @value{GDBN} will synthesize the single-precision registers from
41357 halves of the double-precision registers.
41359 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41360 need to contain registers; it instructs @value{GDBN} to display the
41361 VFP double-precision registers as vectors and to synthesize the
41362 quad-precision registers from pairs of double-precision registers.
41363 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41364 be present and include 32 double-precision registers.
41366 @node i386 Features
41367 @subsection i386 Features
41368 @cindex target descriptions, i386 features
41370 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41371 targets. It should describe the following registers:
41375 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41377 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41379 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41380 @samp{fs}, @samp{gs}
41382 @samp{st0} through @samp{st7}
41384 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41385 @samp{foseg}, @samp{fooff} and @samp{fop}
41388 The register sets may be different, depending on the target.
41390 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41391 describe registers:
41395 @samp{xmm0} through @samp{xmm7} for i386
41397 @samp{xmm0} through @samp{xmm15} for amd64
41402 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41403 @samp{org.gnu.gdb.i386.sse} feature. It should
41404 describe the upper 128 bits of @sc{ymm} registers:
41408 @samp{ymm0h} through @samp{ymm7h} for i386
41410 @samp{ymm0h} through @samp{ymm15h} for amd64
41413 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41414 Memory Protection Extension (MPX). It should describe the following registers:
41418 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41420 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41423 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41424 describe a single register, @samp{orig_eax}.
41426 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41427 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41429 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41430 @samp{org.gnu.gdb.i386.avx} feature. It should
41431 describe additional @sc{xmm} registers:
41435 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41438 It should describe the upper 128 bits of additional @sc{ymm} registers:
41442 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41446 describe the upper 256 bits of @sc{zmm} registers:
41450 @samp{zmm0h} through @samp{zmm7h} for i386.
41452 @samp{zmm0h} through @samp{zmm15h} for amd64.
41456 describe the additional @sc{zmm} registers:
41460 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41463 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
41464 describe a single register, @samp{pkru}. It is a 32-bit register
41465 valid for i386 and amd64.
41467 @node MicroBlaze Features
41468 @subsection MicroBlaze Features
41469 @cindex target descriptions, MicroBlaze features
41471 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41472 targets. It should contain registers @samp{r0} through @samp{r31},
41473 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41474 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41475 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41477 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41478 If present, it should contain registers @samp{rshr} and @samp{rslr}
41480 @node MIPS Features
41481 @subsection @acronym{MIPS} Features
41482 @cindex target descriptions, @acronym{MIPS} features
41484 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41485 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41486 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41489 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41490 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41491 registers. They may be 32-bit or 64-bit depending on the target.
41493 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41494 it may be optional in a future version of @value{GDBN}. It should
41495 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41496 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41498 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41499 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41500 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41501 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41503 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41504 contain a single register, @samp{restart}, which is used by the
41505 Linux kernel to control restartable syscalls.
41507 @node M68K Features
41508 @subsection M68K Features
41509 @cindex target descriptions, M68K features
41512 @item @samp{org.gnu.gdb.m68k.core}
41513 @itemx @samp{org.gnu.gdb.coldfire.core}
41514 @itemx @samp{org.gnu.gdb.fido.core}
41515 One of those features must be always present.
41516 The feature that is present determines which flavor of m68k is
41517 used. The feature that is present should contain registers
41518 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41519 @samp{sp}, @samp{ps} and @samp{pc}.
41521 @item @samp{org.gnu.gdb.coldfire.fp}
41522 This feature is optional. If present, it should contain registers
41523 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41527 @node NDS32 Features
41528 @subsection NDS32 Features
41529 @cindex target descriptions, NDS32 features
41531 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41532 targets. It should contain at least registers @samp{r0} through
41533 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41536 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41537 it should contain 64-bit double-precision floating-point registers
41538 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41539 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41541 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41542 registers are overlapped with the thirty-two 32-bit single-precision
41543 floating-point registers. The 32-bit single-precision registers, if
41544 not being listed explicitly, will be synthesized from halves of the
41545 overlapping 64-bit double-precision registers. Listing 32-bit
41546 single-precision registers explicitly is deprecated, and the
41547 support to it could be totally removed some day.
41549 @node Nios II Features
41550 @subsection Nios II Features
41551 @cindex target descriptions, Nios II features
41553 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41554 targets. It should contain the 32 core registers (@samp{zero},
41555 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41556 @samp{pc}, and the 16 control registers (@samp{status} through
41559 @node PowerPC Features
41560 @subsection PowerPC Features
41561 @cindex target descriptions, PowerPC features
41563 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41564 targets. It should contain registers @samp{r0} through @samp{r31},
41565 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41566 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41568 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41569 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41571 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41572 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41575 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41576 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41577 will combine these registers with the floating point registers
41578 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41579 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41580 through @samp{vs63}, the set of vector registers for POWER7.
41582 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41583 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41584 @samp{spefscr}. SPE targets should provide 32-bit registers in
41585 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41586 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41587 these to present registers @samp{ev0} through @samp{ev31} to the
41590 @node S/390 and System z Features
41591 @subsection S/390 and System z Features
41592 @cindex target descriptions, S/390 features
41593 @cindex target descriptions, System z features
41595 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41596 System z targets. It should contain the PSW and the 16 general
41597 registers. In particular, System z targets should provide the 64-bit
41598 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41599 S/390 targets should provide the 32-bit versions of these registers.
41600 A System z target that runs in 31-bit addressing mode should provide
41601 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41602 register's upper halves @samp{r0h} through @samp{r15h}, and their
41603 lower halves @samp{r0l} through @samp{r15l}.
41605 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41606 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41609 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41610 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41612 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41613 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41614 targets and 32-bit otherwise. In addition, the feature may contain
41615 the @samp{last_break} register, whose width depends on the addressing
41616 mode, as well as the @samp{system_call} register, which is always
41619 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41620 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41621 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41623 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41624 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41625 combined by @value{GDBN} with the floating point registers @samp{f0}
41626 through @samp{f15} to present the 128-bit wide vector registers
41627 @samp{v0} through @samp{v15}. In addition, this feature should
41628 contain the 128-bit wide vector registers @samp{v16} through
41631 @node Sparc Features
41632 @subsection Sparc Features
41633 @cindex target descriptions, sparc32 features
41634 @cindex target descriptions, sparc64 features
41635 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
41636 targets. It should describe the following registers:
41640 @samp{g0} through @samp{g7}
41642 @samp{o0} through @samp{o7}
41644 @samp{l0} through @samp{l7}
41646 @samp{i0} through @samp{i7}
41649 They may be 32-bit or 64-bit depending on the target.
41651 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
41652 targets. It should describe the following registers:
41656 @samp{f0} through @samp{f31}
41658 @samp{f32} through @samp{f62} for sparc64
41661 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
41662 targets. It should describe the following registers:
41666 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
41667 @samp{fsr}, and @samp{csr} for sparc32
41669 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
41673 @node TIC6x Features
41674 @subsection TMS320C6x Features
41675 @cindex target descriptions, TIC6x features
41676 @cindex target descriptions, TMS320C6x features
41677 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41678 targets. It should contain registers @samp{A0} through @samp{A15},
41679 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41681 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41682 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41683 through @samp{B31}.
41685 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41686 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41688 @node Operating System Information
41689 @appendix Operating System Information
41690 @cindex operating system information
41696 Users of @value{GDBN} often wish to obtain information about the state of
41697 the operating system running on the target---for example the list of
41698 processes, or the list of open files. This section describes the
41699 mechanism that makes it possible. This mechanism is similar to the
41700 target features mechanism (@pxref{Target Descriptions}), but focuses
41701 on a different aspect of target.
41703 Operating system information is retrived from the target via the
41704 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41705 read}). The object name in the request should be @samp{osdata}, and
41706 the @var{annex} identifies the data to be fetched.
41709 @appendixsection Process list
41710 @cindex operating system information, process list
41712 When requesting the process list, the @var{annex} field in the
41713 @samp{qXfer} request should be @samp{processes}. The returned data is
41714 an XML document. The formal syntax of this document is defined in
41715 @file{gdb/features/osdata.dtd}.
41717 An example document is:
41720 <?xml version="1.0"?>
41721 <!DOCTYPE target SYSTEM "osdata.dtd">
41722 <osdata type="processes">
41724 <column name="pid">1</column>
41725 <column name="user">root</column>
41726 <column name="command">/sbin/init</column>
41727 <column name="cores">1,2,3</column>
41732 Each item should include a column whose name is @samp{pid}. The value
41733 of that column should identify the process on the target. The
41734 @samp{user} and @samp{command} columns are optional, and will be
41735 displayed by @value{GDBN}. The @samp{cores} column, if present,
41736 should contain a comma-separated list of cores that this process
41737 is running on. Target may provide additional columns,
41738 which @value{GDBN} currently ignores.
41740 @node Trace File Format
41741 @appendix Trace File Format
41742 @cindex trace file format
41744 The trace file comes in three parts: a header, a textual description
41745 section, and a trace frame section with binary data.
41747 The header has the form @code{\x7fTRACE0\n}. The first byte is
41748 @code{0x7f} so as to indicate that the file contains binary data,
41749 while the @code{0} is a version number that may have different values
41752 The description section consists of multiple lines of @sc{ascii} text
41753 separated by newline characters (@code{0xa}). The lines may include a
41754 variety of optional descriptive or context-setting information, such
41755 as tracepoint definitions or register set size. @value{GDBN} will
41756 ignore any line that it does not recognize. An empty line marks the end
41761 Specifies the size of a register block in bytes. This is equal to the
41762 size of a @code{g} packet payload in the remote protocol. @var{size}
41763 is an ascii decimal number. There should be only one such line in
41764 a single trace file.
41766 @item status @var{status}
41767 Trace status. @var{status} has the same format as a @code{qTStatus}
41768 remote packet reply. There should be only one such line in a single trace
41771 @item tp @var{payload}
41772 Tracepoint definition. The @var{payload} has the same format as
41773 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41774 may take multiple lines of definition, corresponding to the multiple
41777 @item tsv @var{payload}
41778 Trace state variable definition. The @var{payload} has the same format as
41779 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41780 may take multiple lines of definition, corresponding to the multiple
41783 @item tdesc @var{payload}
41784 Target description in XML format. The @var{payload} is a single line of
41785 the XML file. All such lines should be concatenated together to get
41786 the original XML file. This file is in the same format as @code{qXfer}
41787 @code{features} payload, and corresponds to the main @code{target.xml}
41788 file. Includes are not allowed.
41792 The trace frame section consists of a number of consecutive frames.
41793 Each frame begins with a two-byte tracepoint number, followed by a
41794 four-byte size giving the amount of data in the frame. The data in
41795 the frame consists of a number of blocks, each introduced by a
41796 character indicating its type (at least register, memory, and trace
41797 state variable). The data in this section is raw binary, not a
41798 hexadecimal or other encoding; its endianness matches the target's
41801 @c FIXME bi-arch may require endianness/arch info in description section
41804 @item R @var{bytes}
41805 Register block. The number and ordering of bytes matches that of a
41806 @code{g} packet in the remote protocol. Note that these are the
41807 actual bytes, in target order, not a hexadecimal encoding.
41809 @item M @var{address} @var{length} @var{bytes}...
41810 Memory block. This is a contiguous block of memory, at the 8-byte
41811 address @var{address}, with a 2-byte length @var{length}, followed by
41812 @var{length} bytes.
41814 @item V @var{number} @var{value}
41815 Trace state variable block. This records the 8-byte signed value
41816 @var{value} of trace state variable numbered @var{number}.
41820 Future enhancements of the trace file format may include additional types
41823 @node Index Section Format
41824 @appendix @code{.gdb_index} section format
41825 @cindex .gdb_index section format
41826 @cindex index section format
41828 This section documents the index section that is created by @code{save
41829 gdb-index} (@pxref{Index Files}). The index section is
41830 DWARF-specific; some knowledge of DWARF is assumed in this
41833 The mapped index file format is designed to be directly
41834 @code{mmap}able on any architecture. In most cases, a datum is
41835 represented using a little-endian 32-bit integer value, called an
41836 @code{offset_type}. Big endian machines must byte-swap the values
41837 before using them. Exceptions to this rule are noted. The data is
41838 laid out such that alignment is always respected.
41840 A mapped index consists of several areas, laid out in order.
41844 The file header. This is a sequence of values, of @code{offset_type}
41845 unless otherwise noted:
41849 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41850 Version 4 uses a different hashing function from versions 5 and 6.
41851 Version 6 includes symbols for inlined functions, whereas versions 4
41852 and 5 do not. Version 7 adds attributes to the CU indices in the
41853 symbol table. Version 8 specifies that symbols from DWARF type units
41854 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41855 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41857 @value{GDBN} will only read version 4, 5, or 6 indices
41858 by specifying @code{set use-deprecated-index-sections on}.
41859 GDB has a workaround for potentially broken version 7 indices so it is
41860 currently not flagged as deprecated.
41863 The offset, from the start of the file, of the CU list.
41866 The offset, from the start of the file, of the types CU list. Note
41867 that this area can be empty, in which case this offset will be equal
41868 to the next offset.
41871 The offset, from the start of the file, of the address area.
41874 The offset, from the start of the file, of the symbol table.
41877 The offset, from the start of the file, of the constant pool.
41881 The CU list. This is a sequence of pairs of 64-bit little-endian
41882 values, sorted by the CU offset. The first element in each pair is
41883 the offset of a CU in the @code{.debug_info} section. The second
41884 element in each pair is the length of that CU. References to a CU
41885 elsewhere in the map are done using a CU index, which is just the
41886 0-based index into this table. Note that if there are type CUs, then
41887 conceptually CUs and type CUs form a single list for the purposes of
41891 The types CU list. This is a sequence of triplets of 64-bit
41892 little-endian values. In a triplet, the first value is the CU offset,
41893 the second value is the type offset in the CU, and the third value is
41894 the type signature. The types CU list is not sorted.
41897 The address area. The address area consists of a sequence of address
41898 entries. Each address entry has three elements:
41902 The low address. This is a 64-bit little-endian value.
41905 The high address. This is a 64-bit little-endian value. Like
41906 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41909 The CU index. This is an @code{offset_type} value.
41913 The symbol table. This is an open-addressed hash table. The size of
41914 the hash table is always a power of 2.
41916 Each slot in the hash table consists of a pair of @code{offset_type}
41917 values. The first value is the offset of the symbol's name in the
41918 constant pool. The second value is the offset of the CU vector in the
41921 If both values are 0, then this slot in the hash table is empty. This
41922 is ok because while 0 is a valid constant pool index, it cannot be a
41923 valid index for both a string and a CU vector.
41925 The hash value for a table entry is computed by applying an
41926 iterative hash function to the symbol's name. Starting with an
41927 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41928 the string is incorporated into the hash using the formula depending on the
41933 The formula is @code{r = r * 67 + c - 113}.
41935 @item Versions 5 to 7
41936 The formula is @code{r = r * 67 + tolower (c) - 113}.
41939 The terminating @samp{\0} is not incorporated into the hash.
41941 The step size used in the hash table is computed via
41942 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41943 value, and @samp{size} is the size of the hash table. The step size
41944 is used to find the next candidate slot when handling a hash
41947 The names of C@t{++} symbols in the hash table are canonicalized. We
41948 don't currently have a simple description of the canonicalization
41949 algorithm; if you intend to create new index sections, you must read
41953 The constant pool. This is simply a bunch of bytes. It is organized
41954 so that alignment is correct: CU vectors are stored first, followed by
41957 A CU vector in the constant pool is a sequence of @code{offset_type}
41958 values. The first value is the number of CU indices in the vector.
41959 Each subsequent value is the index and symbol attributes of a CU in
41960 the CU list. This element in the hash table is used to indicate which
41961 CUs define the symbol and how the symbol is used.
41962 See below for the format of each CU index+attributes entry.
41964 A string in the constant pool is zero-terminated.
41967 Attributes were added to CU index values in @code{.gdb_index} version 7.
41968 If a symbol has multiple uses within a CU then there is one
41969 CU index+attributes value for each use.
41971 The format of each CU index+attributes entry is as follows
41977 This is the index of the CU in the CU list.
41979 These bits are reserved for future purposes and must be zero.
41981 The kind of the symbol in the CU.
41985 This value is reserved and should not be used.
41986 By reserving zero the full @code{offset_type} value is backwards compatible
41987 with previous versions of the index.
41989 The symbol is a type.
41991 The symbol is a variable or an enum value.
41993 The symbol is a function.
41995 Any other kind of symbol.
41997 These values are reserved.
42001 This bit is zero if the value is global and one if it is static.
42003 The determination of whether a symbol is global or static is complicated.
42004 The authorative reference is the file @file{dwarf2read.c} in
42005 @value{GDBN} sources.
42009 This pseudo-code describes the computation of a symbol's kind and
42010 global/static attributes in the index.
42013 is_external = get_attribute (die, DW_AT_external);
42014 language = get_attribute (cu_die, DW_AT_language);
42017 case DW_TAG_typedef:
42018 case DW_TAG_base_type:
42019 case DW_TAG_subrange_type:
42023 case DW_TAG_enumerator:
42025 is_static = language != CPLUS;
42027 case DW_TAG_subprogram:
42029 is_static = ! (is_external || language == ADA);
42031 case DW_TAG_constant:
42033 is_static = ! is_external;
42035 case DW_TAG_variable:
42037 is_static = ! is_external;
42039 case DW_TAG_namespace:
42043 case DW_TAG_class_type:
42044 case DW_TAG_interface_type:
42045 case DW_TAG_structure_type:
42046 case DW_TAG_union_type:
42047 case DW_TAG_enumeration_type:
42049 is_static = language != CPLUS;
42057 @appendix Manual pages
42061 * gdb man:: The GNU Debugger man page
42062 * gdbserver man:: Remote Server for the GNU Debugger man page
42063 * gcore man:: Generate a core file of a running program
42064 * gdbinit man:: gdbinit scripts
42070 @c man title gdb The GNU Debugger
42072 @c man begin SYNOPSIS gdb
42073 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42074 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42075 [@option{-b}@w{ }@var{bps}]
42076 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42077 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42078 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42079 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42080 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42083 @c man begin DESCRIPTION gdb
42084 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42085 going on ``inside'' another program while it executes -- or what another
42086 program was doing at the moment it crashed.
42088 @value{GDBN} can do four main kinds of things (plus other things in support of
42089 these) to help you catch bugs in the act:
42093 Start your program, specifying anything that might affect its behavior.
42096 Make your program stop on specified conditions.
42099 Examine what has happened, when your program has stopped.
42102 Change things in your program, so you can experiment with correcting the
42103 effects of one bug and go on to learn about another.
42106 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42109 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42110 commands from the terminal until you tell it to exit with the @value{GDBN}
42111 command @code{quit}. You can get online help from @value{GDBN} itself
42112 by using the command @code{help}.
42114 You can run @code{gdb} with no arguments or options; but the most
42115 usual way to start @value{GDBN} is with one argument or two, specifying an
42116 executable program as the argument:
42122 You can also start with both an executable program and a core file specified:
42128 You can, instead, specify a process ID as a second argument, if you want
42129 to debug a running process:
42137 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42138 named @file{1234}; @value{GDBN} does check for a core file first).
42139 With option @option{-p} you can omit the @var{program} filename.
42141 Here are some of the most frequently needed @value{GDBN} commands:
42143 @c pod2man highlights the right hand side of the @item lines.
42145 @item break [@var{file}:]@var{function}
42146 Set a breakpoint at @var{function} (in @var{file}).
42148 @item run [@var{arglist}]
42149 Start your program (with @var{arglist}, if specified).
42152 Backtrace: display the program stack.
42154 @item print @var{expr}
42155 Display the value of an expression.
42158 Continue running your program (after stopping, e.g. at a breakpoint).
42161 Execute next program line (after stopping); step @emph{over} any
42162 function calls in the line.
42164 @item edit [@var{file}:]@var{function}
42165 look at the program line where it is presently stopped.
42167 @item list [@var{file}:]@var{function}
42168 type the text of the program in the vicinity of where it is presently stopped.
42171 Execute next program line (after stopping); step @emph{into} any
42172 function calls in the line.
42174 @item help [@var{name}]
42175 Show information about @value{GDBN} command @var{name}, or general information
42176 about using @value{GDBN}.
42179 Exit from @value{GDBN}.
42183 For full details on @value{GDBN},
42184 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42185 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42186 as the @code{gdb} entry in the @code{info} program.
42190 @c man begin OPTIONS gdb
42191 Any arguments other than options specify an executable
42192 file and core file (or process ID); that is, the first argument
42193 encountered with no
42194 associated option flag is equivalent to a @option{-se} option, and the second,
42195 if any, is equivalent to a @option{-c} option if it's the name of a file.
42197 both long and short forms; both are shown here. The long forms are also
42198 recognized if you truncate them, so long as enough of the option is
42199 present to be unambiguous. (If you prefer, you can flag option
42200 arguments with @option{+} rather than @option{-}, though we illustrate the
42201 more usual convention.)
42203 All the options and command line arguments you give are processed
42204 in sequential order. The order makes a difference when the @option{-x}
42210 List all options, with brief explanations.
42212 @item -symbols=@var{file}
42213 @itemx -s @var{file}
42214 Read symbol table from file @var{file}.
42217 Enable writing into executable and core files.
42219 @item -exec=@var{file}
42220 @itemx -e @var{file}
42221 Use file @var{file} as the executable file to execute when
42222 appropriate, and for examining pure data in conjunction with a core
42225 @item -se=@var{file}
42226 Read symbol table from file @var{file} and use it as the executable
42229 @item -core=@var{file}
42230 @itemx -c @var{file}
42231 Use file @var{file} as a core dump to examine.
42233 @item -command=@var{file}
42234 @itemx -x @var{file}
42235 Execute @value{GDBN} commands from file @var{file}.
42237 @item -ex @var{command}
42238 Execute given @value{GDBN} @var{command}.
42240 @item -directory=@var{directory}
42241 @itemx -d @var{directory}
42242 Add @var{directory} to the path to search for source files.
42245 Do not execute commands from @file{~/.gdbinit}.
42249 Do not execute commands from any @file{.gdbinit} initialization files.
42253 ``Quiet''. Do not print the introductory and copyright messages. These
42254 messages are also suppressed in batch mode.
42257 Run in batch mode. Exit with status @code{0} after processing all the command
42258 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42259 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42260 commands in the command files.
42262 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42263 download and run a program on another computer; in order to make this
42264 more useful, the message
42267 Program exited normally.
42271 (which is ordinarily issued whenever a program running under @value{GDBN} control
42272 terminates) is not issued when running in batch mode.
42274 @item -cd=@var{directory}
42275 Run @value{GDBN} using @var{directory} as its working directory,
42276 instead of the current directory.
42280 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42281 @value{GDBN} to output the full file name and line number in a standard,
42282 recognizable fashion each time a stack frame is displayed (which
42283 includes each time the program stops). This recognizable format looks
42284 like two @samp{\032} characters, followed by the file name, line number
42285 and character position separated by colons, and a newline. The
42286 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42287 characters as a signal to display the source code for the frame.
42290 Set the line speed (baud rate or bits per second) of any serial
42291 interface used by @value{GDBN} for remote debugging.
42293 @item -tty=@var{device}
42294 Run using @var{device} for your program's standard input and output.
42298 @c man begin SEEALSO gdb
42300 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42301 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42302 documentation are properly installed at your site, the command
42309 should give you access to the complete manual.
42311 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42312 Richard M. Stallman and Roland H. Pesch, July 1991.
42316 @node gdbserver man
42317 @heading gdbserver man
42319 @c man title gdbserver Remote Server for the GNU Debugger
42321 @c man begin SYNOPSIS gdbserver
42322 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42324 gdbserver --attach @var{comm} @var{pid}
42326 gdbserver --multi @var{comm}
42330 @c man begin DESCRIPTION gdbserver
42331 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42332 than the one which is running the program being debugged.
42335 @subheading Usage (server (target) side)
42338 Usage (server (target) side):
42341 First, you need to have a copy of the program you want to debug put onto
42342 the target system. The program can be stripped to save space if needed, as
42343 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42344 the @value{GDBN} running on the host system.
42346 To use the server, you log on to the target system, and run the @command{gdbserver}
42347 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42348 your program, and (c) its arguments. The general syntax is:
42351 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42354 For example, using a serial port, you might say:
42358 @c @file would wrap it as F</dev/com1>.
42359 target> gdbserver /dev/com1 emacs foo.txt
42362 target> gdbserver @file{/dev/com1} emacs foo.txt
42366 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42367 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42368 waits patiently for the host @value{GDBN} to communicate with it.
42370 To use a TCP connection, you could say:
42373 target> gdbserver host:2345 emacs foo.txt
42376 This says pretty much the same thing as the last example, except that we are
42377 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42378 that we are expecting to see a TCP connection from @code{host} to local TCP port
42379 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42380 want for the port number as long as it does not conflict with any existing TCP
42381 ports on the target system. This same port number must be used in the host
42382 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42383 you chose a port number that conflicts with another service, @command{gdbserver} will
42384 print an error message and exit.
42386 @command{gdbserver} can also attach to running programs.
42387 This is accomplished via the @option{--attach} argument. The syntax is:
42390 target> gdbserver --attach @var{comm} @var{pid}
42393 @var{pid} is the process ID of a currently running process. It isn't
42394 necessary to point @command{gdbserver} at a binary for the running process.
42396 To start @code{gdbserver} without supplying an initial command to run
42397 or process ID to attach, use the @option{--multi} command line option.
42398 In such case you should connect using @kbd{target extended-remote} to start
42399 the program you want to debug.
42402 target> gdbserver --multi @var{comm}
42406 @subheading Usage (host side)
42412 You need an unstripped copy of the target program on your host system, since
42413 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42414 would, with the target program as the first argument. (You may need to use the
42415 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42416 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42417 new command you need to know about is @code{target remote}
42418 (or @code{target extended-remote}). Its argument is either
42419 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42420 descriptor. For example:
42424 @c @file would wrap it as F</dev/ttyb>.
42425 (gdb) target remote /dev/ttyb
42428 (gdb) target remote @file{/dev/ttyb}
42433 communicates with the server via serial line @file{/dev/ttyb}, and:
42436 (gdb) target remote the-target:2345
42440 communicates via a TCP connection to port 2345 on host `the-target', where
42441 you previously started up @command{gdbserver} with the same port number. Note that for
42442 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42443 command, otherwise you may get an error that looks something like
42444 `Connection refused'.
42446 @command{gdbserver} can also debug multiple inferiors at once,
42449 the @value{GDBN} manual in node @code{Inferiors and Programs}
42450 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42453 @ref{Inferiors and Programs}.
42455 In such case use the @code{extended-remote} @value{GDBN} command variant:
42458 (gdb) target extended-remote the-target:2345
42461 The @command{gdbserver} option @option{--multi} may or may not be used in such
42465 @c man begin OPTIONS gdbserver
42466 There are three different modes for invoking @command{gdbserver}:
42471 Debug a specific program specified by its program name:
42474 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42477 The @var{comm} parameter specifies how should the server communicate
42478 with @value{GDBN}; it is either a device name (to use a serial line),
42479 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42480 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42481 debug in @var{prog}. Any remaining arguments will be passed to the
42482 program verbatim. When the program exits, @value{GDBN} will close the
42483 connection, and @code{gdbserver} will exit.
42486 Debug a specific program by specifying the process ID of a running
42490 gdbserver --attach @var{comm} @var{pid}
42493 The @var{comm} parameter is as described above. Supply the process ID
42494 of a running program in @var{pid}; @value{GDBN} will do everything
42495 else. Like with the previous mode, when the process @var{pid} exits,
42496 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42499 Multi-process mode -- debug more than one program/process:
42502 gdbserver --multi @var{comm}
42505 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42506 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42507 close the connection when a process being debugged exits, so you can
42508 debug several processes in the same session.
42511 In each of the modes you may specify these options:
42516 List all options, with brief explanations.
42519 This option causes @command{gdbserver} to print its version number and exit.
42522 @command{gdbserver} will attach to a running program. The syntax is:
42525 target> gdbserver --attach @var{comm} @var{pid}
42528 @var{pid} is the process ID of a currently running process. It isn't
42529 necessary to point @command{gdbserver} at a binary for the running process.
42532 To start @code{gdbserver} without supplying an initial command to run
42533 or process ID to attach, use this command line option.
42534 Then you can connect using @kbd{target extended-remote} and start
42535 the program you want to debug. The syntax is:
42538 target> gdbserver --multi @var{comm}
42542 Instruct @code{gdbserver} to display extra status information about the debugging
42544 This option is intended for @code{gdbserver} development and for bug reports to
42547 @item --remote-debug
42548 Instruct @code{gdbserver} to display remote protocol debug output.
42549 This option is intended for @code{gdbserver} development and for bug reports to
42552 @item --debug-format=option1@r{[},option2,...@r{]}
42553 Instruct @code{gdbserver} to include extra information in each line
42554 of debugging output.
42555 @xref{Other Command-Line Arguments for gdbserver}.
42558 Specify a wrapper to launch programs
42559 for debugging. The option should be followed by the name of the
42560 wrapper, then any command-line arguments to pass to the wrapper, then
42561 @kbd{--} indicating the end of the wrapper arguments.
42564 By default, @command{gdbserver} keeps the listening TCP port open, so that
42565 additional connections are possible. However, if you start @code{gdbserver}
42566 with the @option{--once} option, it will stop listening for any further
42567 connection attempts after connecting to the first @value{GDBN} session.
42569 @c --disable-packet is not documented for users.
42571 @c --disable-randomization and --no-disable-randomization are superseded by
42572 @c QDisableRandomization.
42577 @c man begin SEEALSO gdbserver
42579 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42580 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42581 documentation are properly installed at your site, the command
42587 should give you access to the complete manual.
42589 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42590 Richard M. Stallman and Roland H. Pesch, July 1991.
42597 @c man title gcore Generate a core file of a running program
42600 @c man begin SYNOPSIS gcore
42601 gcore [-o @var{filename}] @var{pid}
42605 @c man begin DESCRIPTION gcore
42606 Generate a core dump of a running program with process ID @var{pid}.
42607 Produced file is equivalent to a kernel produced core file as if the process
42608 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42609 limit). Unlike after a crash, after @command{gcore} the program remains
42610 running without any change.
42613 @c man begin OPTIONS gcore
42615 @item -o @var{filename}
42616 The optional argument
42617 @var{filename} specifies the file name where to put the core dump.
42618 If not specified, the file name defaults to @file{core.@var{pid}},
42619 where @var{pid} is the running program process ID.
42623 @c man begin SEEALSO gcore
42625 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42626 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42627 documentation are properly installed at your site, the command
42634 should give you access to the complete manual.
42636 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42637 Richard M. Stallman and Roland H. Pesch, July 1991.
42644 @c man title gdbinit GDB initialization scripts
42647 @c man begin SYNOPSIS gdbinit
42648 @ifset SYSTEM_GDBINIT
42649 @value{SYSTEM_GDBINIT}
42658 @c man begin DESCRIPTION gdbinit
42659 These files contain @value{GDBN} commands to automatically execute during
42660 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42663 the @value{GDBN} manual in node @code{Sequences}
42664 -- shell command @code{info -f gdb -n Sequences}.
42670 Please read more in
42672 the @value{GDBN} manual in node @code{Startup}
42673 -- shell command @code{info -f gdb -n Startup}.
42680 @ifset SYSTEM_GDBINIT
42681 @item @value{SYSTEM_GDBINIT}
42683 @ifclear SYSTEM_GDBINIT
42684 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42686 System-wide initialization file. It is executed unless user specified
42687 @value{GDBN} option @code{-nx} or @code{-n}.
42690 the @value{GDBN} manual in node @code{System-wide configuration}
42691 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42694 @ref{System-wide configuration}.
42698 User initialization file. It is executed unless user specified
42699 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42702 Initialization file for current directory. It may need to be enabled with
42703 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42706 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42707 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42710 @ref{Init File in the Current Directory}.
42715 @c man begin SEEALSO gdbinit
42717 gdb(1), @code{info -f gdb -n Startup}
42719 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42720 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42721 documentation are properly installed at your site, the command
42727 should give you access to the complete manual.
42729 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42730 Richard M. Stallman and Roland H. Pesch, July 1991.
42736 @node GNU Free Documentation License
42737 @appendix GNU Free Documentation License
42740 @node Concept Index
42741 @unnumbered Concept Index
42745 @node Command and Variable Index
42746 @unnumbered Command, Variable, and Function Index
42751 % I think something like @@colophon should be in texinfo. In the
42753 \long\def\colophon{\hbox to0pt{}\vfill
42754 \centerline{The body of this manual is set in}
42755 \centerline{\fontname\tenrm,}
42756 \centerline{with headings in {\bf\fontname\tenbf}}
42757 \centerline{and examples in {\tt\fontname\tentt}.}
42758 \centerline{{\it\fontname\tenit\/},}
42759 \centerline{{\bf\fontname\tenbf}, and}
42760 \centerline{{\sl\fontname\tensl\/}}
42761 \centerline{are used for emphasis.}\vfill}
42763 % Blame: doc@@cygnus.com, 1991.