1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2018 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{} 1988-2018 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) 1988-2018 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 The original port to the OpenRISC 1000 is believed to be due to
550 Alessandro Forin and Per Bothner. More recent ports have been the work
551 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
555 @chapter A Sample @value{GDBN} Session
557 You can use this manual at your leisure to read all about @value{GDBN}.
558 However, a handful of commands are enough to get started using the
559 debugger. This chapter illustrates those commands.
562 In this sample session, we emphasize user input like this: @b{input},
563 to make it easier to pick out from the surrounding output.
566 @c FIXME: this example may not be appropriate for some configs, where
567 @c FIXME...primary interest is in remote use.
569 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
570 processor) exhibits the following bug: sometimes, when we change its
571 quote strings from the default, the commands used to capture one macro
572 definition within another stop working. In the following short @code{m4}
573 session, we define a macro @code{foo} which expands to @code{0000}; we
574 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
575 same thing. However, when we change the open quote string to
576 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
577 procedure fails to define a new synonym @code{baz}:
586 @b{define(bar,defn(`foo'))}
590 @b{changequote(<QUOTE>,<UNQUOTE>)}
592 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
595 m4: End of input: 0: fatal error: EOF in string
599 Let us use @value{GDBN} to try to see what is going on.
602 $ @b{@value{GDBP} m4}
603 @c FIXME: this falsifies the exact text played out, to permit smallbook
604 @c FIXME... format to come out better.
605 @value{GDBN} is free software and you are welcome to distribute copies
606 of it under certain conditions; type "show copying" to see
608 There is absolutely no warranty for @value{GDBN}; type "show warranty"
611 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
616 @value{GDBN} reads only enough symbol data to know where to find the
617 rest when needed; as a result, the first prompt comes up very quickly.
618 We now tell @value{GDBN} to use a narrower display width than usual, so
619 that examples fit in this manual.
622 (@value{GDBP}) @b{set width 70}
626 We need to see how the @code{m4} built-in @code{changequote} works.
627 Having looked at the source, we know the relevant subroutine is
628 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
629 @code{break} command.
632 (@value{GDBP}) @b{break m4_changequote}
633 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
637 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
638 control; as long as control does not reach the @code{m4_changequote}
639 subroutine, the program runs as usual:
642 (@value{GDBP}) @b{run}
643 Starting program: /work/Editorial/gdb/gnu/m4/m4
651 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
652 suspends execution of @code{m4}, displaying information about the
653 context where it stops.
656 @b{changequote(<QUOTE>,<UNQUOTE>)}
658 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
660 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
664 Now we use the command @code{n} (@code{next}) to advance execution to
665 the next line of the current function.
669 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
674 @code{set_quotes} looks like a promising subroutine. We can go into it
675 by using the command @code{s} (@code{step}) instead of @code{next}.
676 @code{step} goes to the next line to be executed in @emph{any}
677 subroutine, so it steps into @code{set_quotes}.
681 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
683 530 if (lquote != def_lquote)
687 The display that shows the subroutine where @code{m4} is now
688 suspended (and its arguments) is called a stack frame display. It
689 shows a summary of the stack. We can use the @code{backtrace}
690 command (which can also be spelled @code{bt}), to see where we are
691 in the stack as a whole: the @code{backtrace} command displays a
692 stack frame for each active subroutine.
695 (@value{GDBP}) @b{bt}
696 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
698 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
700 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
701 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
703 #4 0x79dc in expand_input () at macro.c:40
704 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
708 We step through a few more lines to see what happens. The first two
709 times, we can use @samp{s}; the next two times we use @code{n} to avoid
710 falling into the @code{xstrdup} subroutine.
714 0x3b5c 532 if (rquote != def_rquote)
716 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
717 def_lquote : xstrdup(lq);
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
726 The last line displayed looks a little odd; we can examine the variables
727 @code{lquote} and @code{rquote} to see if they are in fact the new left
728 and right quotes we specified. We use the command @code{p}
729 (@code{print}) to see their values.
732 (@value{GDBP}) @b{p lquote}
733 $1 = 0x35d40 "<QUOTE>"
734 (@value{GDBP}) @b{p rquote}
735 $2 = 0x35d50 "<UNQUOTE>"
739 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
740 To look at some context, we can display ten lines of source
741 surrounding the current line with the @code{l} (@code{list}) command.
747 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
749 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
752 538 len_lquote = strlen(rquote);
753 539 len_rquote = strlen(lquote);
760 Let us step past the two lines that set @code{len_lquote} and
761 @code{len_rquote}, and then examine the values of those variables.
765 539 len_rquote = strlen(lquote);
768 (@value{GDBP}) @b{p len_lquote}
770 (@value{GDBP}) @b{p len_rquote}
775 That certainly looks wrong, assuming @code{len_lquote} and
776 @code{len_rquote} are meant to be the lengths of @code{lquote} and
777 @code{rquote} respectively. We can set them to better values using
778 the @code{p} command, since it can print the value of
779 any expression---and that expression can include subroutine calls and
783 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
785 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
790 Is that enough to fix the problem of using the new quotes with the
791 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
792 executing with the @code{c} (@code{continue}) command, and then try the
793 example that caused trouble initially:
799 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
806 Success! The new quotes now work just as well as the default ones. The
807 problem seems to have been just the two typos defining the wrong
808 lengths. We allow @code{m4} exit by giving it an EOF as input:
812 Program exited normally.
816 The message @samp{Program exited normally.} is from @value{GDBN}; it
817 indicates @code{m4} has finished executing. We can end our @value{GDBN}
818 session with the @value{GDBN} @code{quit} command.
821 (@value{GDBP}) @b{quit}
825 @chapter Getting In and Out of @value{GDBN}
827 This chapter discusses how to start @value{GDBN}, and how to get out of it.
831 type @samp{@value{GDBP}} to start @value{GDBN}.
833 type @kbd{quit} or @kbd{Ctrl-d} to exit.
837 * Invoking GDB:: How to start @value{GDBN}
838 * Quitting GDB:: How to quit @value{GDBN}
839 * Shell Commands:: How to use shell commands inside @value{GDBN}
840 * Logging Output:: How to log @value{GDBN}'s output to a file
844 @section Invoking @value{GDBN}
846 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
847 @value{GDBN} reads commands from the terminal until you tell it to exit.
849 You can also run @code{@value{GDBP}} with a variety of arguments and options,
850 to specify more of your debugging environment at the outset.
852 The command-line options described here are designed
853 to cover a variety of situations; in some environments, some of these
854 options may effectively be unavailable.
856 The most usual way to start @value{GDBN} is with one argument,
857 specifying an executable program:
860 @value{GDBP} @var{program}
864 You can also start with both an executable program and a core file
868 @value{GDBP} @var{program} @var{core}
871 You can, instead, specify a process ID as a second argument, if you want
872 to debug a running process:
875 @value{GDBP} @var{program} 1234
879 would attach @value{GDBN} to process @code{1234} (unless you also have a file
880 named @file{1234}; @value{GDBN} does check for a core file first).
882 Taking advantage of the second command-line argument requires a fairly
883 complete operating system; when you use @value{GDBN} as a remote
884 debugger attached to a bare board, there may not be any notion of
885 ``process'', and there is often no way to get a core dump. @value{GDBN}
886 will warn you if it is unable to attach or to read core dumps.
888 You can optionally have @code{@value{GDBP}} pass any arguments after the
889 executable file to the inferior using @code{--args}. This option stops
892 @value{GDBP} --args gcc -O2 -c foo.c
894 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
895 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
897 You can run @code{@value{GDBP}} without printing the front material, which describes
898 @value{GDBN}'s non-warranty, by specifying @code{--silent}
899 (or @code{-q}/@code{--quiet}):
902 @value{GDBP} --silent
906 You can further control how @value{GDBN} starts up by using command-line
907 options. @value{GDBN} itself can remind you of the options available.
917 to display all available options and briefly describe their use
918 (@samp{@value{GDBP} -h} is a shorter equivalent).
920 All options and command line arguments you give are processed
921 in sequential order. The order makes a difference when the
922 @samp{-x} option is used.
926 * File Options:: Choosing files
927 * Mode Options:: Choosing modes
928 * Startup:: What @value{GDBN} does during startup
932 @subsection Choosing Files
934 When @value{GDBN} starts, it reads any arguments other than options as
935 specifying an executable file and core file (or process ID). This is
936 the same as if the arguments were specified by the @samp{-se} and
937 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
938 first argument that does not have an associated option flag as
939 equivalent to the @samp{-se} option followed by that argument; and the
940 second argument that does not have an associated option flag, if any, as
941 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
942 If the second argument begins with a decimal digit, @value{GDBN} will
943 first attempt to attach to it as a process, and if that fails, attempt
944 to open it as a corefile. If you have a corefile whose name begins with
945 a digit, you can prevent @value{GDBN} from treating it as a pid by
946 prefixing it with @file{./}, e.g.@: @file{./12345}.
948 If @value{GDBN} has not been configured to included core file support,
949 such as for most embedded targets, then it will complain about a second
950 argument and ignore it.
952 Many options have both long and short forms; both are shown in the
953 following list. @value{GDBN} also recognizes the long forms if you truncate
954 them, so long as enough of the option is present to be unambiguous.
955 (If you prefer, you can flag option arguments with @samp{--} rather
956 than @samp{-}, though we illustrate the more usual convention.)
958 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
959 @c way, both those who look for -foo and --foo in the index, will find
963 @item -symbols @var{file}
965 @cindex @code{--symbols}
967 Read symbol table from file @var{file}.
969 @item -exec @var{file}
971 @cindex @code{--exec}
973 Use file @var{file} as the executable file to execute when appropriate,
974 and for examining pure data in conjunction with a core dump.
978 Read symbol table from file @var{file} and use it as the executable
981 @item -core @var{file}
983 @cindex @code{--core}
985 Use file @var{file} as a core dump to examine.
987 @item -pid @var{number}
988 @itemx -p @var{number}
991 Connect to process ID @var{number}, as with the @code{attach} command.
993 @item -command @var{file}
995 @cindex @code{--command}
997 Execute commands from file @var{file}. The contents of this file is
998 evaluated exactly as the @code{source} command would.
999 @xref{Command Files,, Command files}.
1001 @item -eval-command @var{command}
1002 @itemx -ex @var{command}
1003 @cindex @code{--eval-command}
1005 Execute a single @value{GDBN} command.
1007 This option may be used multiple times to call multiple commands. It may
1008 also be interleaved with @samp{-command} as required.
1011 @value{GDBP} -ex 'target sim' -ex 'load' \
1012 -x setbreakpoints -ex 'run' a.out
1015 @item -init-command @var{file}
1016 @itemx -ix @var{file}
1017 @cindex @code{--init-command}
1019 Execute commands from file @var{file} before loading the inferior (but
1020 after loading gdbinit files).
1023 @item -init-eval-command @var{command}
1024 @itemx -iex @var{command}
1025 @cindex @code{--init-eval-command}
1027 Execute a single @value{GDBN} command before loading the inferior (but
1028 after loading gdbinit files).
1031 @item -directory @var{directory}
1032 @itemx -d @var{directory}
1033 @cindex @code{--directory}
1035 Add @var{directory} to the path to search for source and script files.
1039 @cindex @code{--readnow}
1041 Read each symbol file's entire symbol table immediately, rather than
1042 the default, which is to read it incrementally as it is needed.
1043 This makes startup slower, but makes future operations faster.
1046 @anchor{--readnever}
1047 @cindex @code{--readnever}, command-line option
1048 Do not read each symbol file's symbolic debug information. This makes
1049 startup faster but at the expense of not being able to perform
1050 symbolic debugging. DWARF unwind information is also not read,
1051 meaning backtraces may become incomplete or inaccurate. One use of
1052 this is when a user simply wants to do the following sequence: attach,
1053 dump core, detach. Loading the debugging information in this case is
1054 an unnecessary cause of delay.
1058 @subsection Choosing Modes
1060 You can run @value{GDBN} in various alternative modes---for example, in
1061 batch mode or quiet mode.
1069 Do not execute commands found in any initialization file.
1070 There are three init files, loaded in the following order:
1073 @item @file{system.gdbinit}
1074 This is the system-wide init file.
1075 Its location is specified with the @code{--with-system-gdbinit}
1076 configure option (@pxref{System-wide configuration}).
1077 It is loaded first when @value{GDBN} starts, before command line options
1078 have been processed.
1079 @item @file{~/.gdbinit}
1080 This is the init file in your home directory.
1081 It is loaded next, after @file{system.gdbinit}, and before
1082 command options have been processed.
1083 @item @file{./.gdbinit}
1084 This is the init file in the current directory.
1085 It is loaded last, after command line options other than @code{-x} and
1086 @code{-ex} have been processed. Command line options @code{-x} and
1087 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1090 For further documentation on startup processing, @xref{Startup}.
1091 For documentation on how to write command files,
1092 @xref{Command Files,,Command Files}.
1097 Do not execute commands found in @file{~/.gdbinit}, the init file
1098 in your home directory.
1104 @cindex @code{--quiet}
1105 @cindex @code{--silent}
1107 ``Quiet''. Do not print the introductory and copyright messages. These
1108 messages are also suppressed in batch mode.
1111 @cindex @code{--batch}
1112 Run in batch mode. Exit with status @code{0} after processing all the
1113 command files specified with @samp{-x} (and all commands from
1114 initialization files, if not inhibited with @samp{-n}). Exit with
1115 nonzero status if an error occurs in executing the @value{GDBN} commands
1116 in the command files. Batch mode also disables pagination, sets unlimited
1117 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1118 off} were in effect (@pxref{Messages/Warnings}).
1120 Batch mode may be useful for running @value{GDBN} as a filter, for
1121 example to download and run a program on another computer; in order to
1122 make this more useful, the message
1125 Program exited normally.
1129 (which is ordinarily issued whenever a program running under
1130 @value{GDBN} control terminates) is not issued when running in batch
1134 @cindex @code{--batch-silent}
1135 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1136 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1137 unaffected). This is much quieter than @samp{-silent} and would be useless
1138 for an interactive session.
1140 This is particularly useful when using targets that give @samp{Loading section}
1141 messages, for example.
1143 Note that targets that give their output via @value{GDBN}, as opposed to
1144 writing directly to @code{stdout}, will also be made silent.
1146 @item -return-child-result
1147 @cindex @code{--return-child-result}
1148 The return code from @value{GDBN} will be the return code from the child
1149 process (the process being debugged), with the following exceptions:
1153 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1154 internal error. In this case the exit code is the same as it would have been
1155 without @samp{-return-child-result}.
1157 The user quits with an explicit value. E.g., @samp{quit 1}.
1159 The child process never runs, or is not allowed to terminate, in which case
1160 the exit code will be -1.
1163 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1164 when @value{GDBN} is being used as a remote program loader or simulator
1169 @cindex @code{--nowindows}
1171 ``No windows''. If @value{GDBN} comes with a graphical user interface
1172 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1173 interface. If no GUI is available, this option has no effect.
1177 @cindex @code{--windows}
1179 If @value{GDBN} includes a GUI, then this option requires it to be
1182 @item -cd @var{directory}
1184 Run @value{GDBN} using @var{directory} as its working directory,
1185 instead of the current directory.
1187 @item -data-directory @var{directory}
1188 @itemx -D @var{directory}
1189 @cindex @code{--data-directory}
1191 Run @value{GDBN} using @var{directory} as its data directory.
1192 The data directory is where @value{GDBN} searches for its
1193 auxiliary files. @xref{Data Files}.
1197 @cindex @code{--fullname}
1199 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1200 subprocess. It tells @value{GDBN} to output the full file name and line
1201 number in a standard, recognizable fashion each time a stack frame is
1202 displayed (which includes each time your program stops). This
1203 recognizable format looks like two @samp{\032} characters, followed by
1204 the file name, line number and character position separated by colons,
1205 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1206 @samp{\032} characters as a signal to display the source code for the
1209 @item -annotate @var{level}
1210 @cindex @code{--annotate}
1211 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1212 effect is identical to using @samp{set annotate @var{level}}
1213 (@pxref{Annotations}). The annotation @var{level} controls how much
1214 information @value{GDBN} prints together with its prompt, values of
1215 expressions, source lines, and other types of output. Level 0 is the
1216 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1217 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1218 that control @value{GDBN}, and level 2 has been deprecated.
1220 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1224 @cindex @code{--args}
1225 Change interpretation of command line so that arguments following the
1226 executable file are passed as command line arguments to the inferior.
1227 This option stops option processing.
1229 @item -baud @var{bps}
1231 @cindex @code{--baud}
1233 Set the line speed (baud rate or bits per second) of any serial
1234 interface used by @value{GDBN} for remote debugging.
1236 @item -l @var{timeout}
1238 Set the timeout (in seconds) of any communication used by @value{GDBN}
1239 for remote debugging.
1241 @item -tty @var{device}
1242 @itemx -t @var{device}
1243 @cindex @code{--tty}
1245 Run using @var{device} for your program's standard input and output.
1246 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1248 @c resolve the situation of these eventually
1250 @cindex @code{--tui}
1251 Activate the @dfn{Text User Interface} when starting. The Text User
1252 Interface manages several text windows on the terminal, showing
1253 source, assembly, registers and @value{GDBN} command outputs
1254 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1255 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1256 Using @value{GDBN} under @sc{gnu} Emacs}).
1258 @item -interpreter @var{interp}
1259 @cindex @code{--interpreter}
1260 Use the interpreter @var{interp} for interface with the controlling
1261 program or device. This option is meant to be set by programs which
1262 communicate with @value{GDBN} using it as a back end.
1263 @xref{Interpreters, , Command Interpreters}.
1265 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1266 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1267 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1268 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1269 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1270 @sc{gdb/mi} interfaces are no longer supported.
1273 @cindex @code{--write}
1274 Open the executable and core files for both reading and writing. This
1275 is equivalent to the @samp{set write on} command inside @value{GDBN}
1279 @cindex @code{--statistics}
1280 This option causes @value{GDBN} to print statistics about time and
1281 memory usage after it completes each command and returns to the prompt.
1284 @cindex @code{--version}
1285 This option causes @value{GDBN} to print its version number and
1286 no-warranty blurb, and exit.
1288 @item -configuration
1289 @cindex @code{--configuration}
1290 This option causes @value{GDBN} to print details about its build-time
1291 configuration parameters, and then exit. These details can be
1292 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1297 @subsection What @value{GDBN} Does During Startup
1298 @cindex @value{GDBN} startup
1300 Here's the description of what @value{GDBN} does during session startup:
1304 Sets up the command interpreter as specified by the command line
1305 (@pxref{Mode Options, interpreter}).
1309 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1310 used when building @value{GDBN}; @pxref{System-wide configuration,
1311 ,System-wide configuration and settings}) and executes all the commands in
1314 @anchor{Home Directory Init File}
1316 Reads the init file (if any) in your home directory@footnote{On
1317 DOS/Windows systems, the home directory is the one pointed to by the
1318 @code{HOME} environment variable.} and executes all the commands in
1321 @anchor{Option -init-eval-command}
1323 Executes commands and command files specified by the @samp{-iex} and
1324 @samp{-ix} options in their specified order. Usually you should use the
1325 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1326 settings before @value{GDBN} init files get executed and before inferior
1330 Processes command line options and operands.
1332 @anchor{Init File in the Current Directory during Startup}
1334 Reads and executes the commands from init file (if any) in the current
1335 working directory as long as @samp{set auto-load local-gdbinit} is set to
1336 @samp{on} (@pxref{Init File in the Current Directory}).
1337 This is only done if the current directory is
1338 different from your home directory. Thus, you can have more than one
1339 init file, one generic in your home directory, and another, specific
1340 to the program you are debugging, in the directory where you invoke
1344 If the command line specified a program to debug, or a process to
1345 attach to, or a core file, @value{GDBN} loads any auto-loaded
1346 scripts provided for the program or for its loaded shared libraries.
1347 @xref{Auto-loading}.
1349 If you wish to disable the auto-loading during startup,
1350 you must do something like the following:
1353 $ gdb -iex "set auto-load python-scripts off" myprogram
1356 Option @samp{-ex} does not work because the auto-loading is then turned
1360 Executes commands and command files specified by the @samp{-ex} and
1361 @samp{-x} options in their specified order. @xref{Command Files}, for
1362 more details about @value{GDBN} command files.
1365 Reads the command history recorded in the @dfn{history file}.
1366 @xref{Command History}, for more details about the command history and the
1367 files where @value{GDBN} records it.
1370 Init files use the same syntax as @dfn{command files} (@pxref{Command
1371 Files}) and are processed by @value{GDBN} in the same way. The init
1372 file in your home directory can set options (such as @samp{set
1373 complaints}) that affect subsequent processing of command line options
1374 and operands. Init files are not executed if you use the @samp{-nx}
1375 option (@pxref{Mode Options, ,Choosing Modes}).
1377 To display the list of init files loaded by gdb at startup, you
1378 can use @kbd{gdb --help}.
1380 @cindex init file name
1381 @cindex @file{.gdbinit}
1382 @cindex @file{gdb.ini}
1383 The @value{GDBN} init files are normally called @file{.gdbinit}.
1384 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1385 the limitations of file names imposed by DOS filesystems. The Windows
1386 port of @value{GDBN} uses the standard name, but if it finds a
1387 @file{gdb.ini} file in your home directory, it warns you about that
1388 and suggests to rename the file to the standard name.
1392 @section Quitting @value{GDBN}
1393 @cindex exiting @value{GDBN}
1394 @cindex leaving @value{GDBN}
1397 @kindex quit @r{[}@var{expression}@r{]}
1398 @kindex q @r{(@code{quit})}
1399 @item quit @r{[}@var{expression}@r{]}
1401 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1402 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1403 do not supply @var{expression}, @value{GDBN} will terminate normally;
1404 otherwise it will terminate using the result of @var{expression} as the
1409 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1410 terminates the action of any @value{GDBN} command that is in progress and
1411 returns to @value{GDBN} command level. It is safe to type the interrupt
1412 character at any time because @value{GDBN} does not allow it to take effect
1413 until a time when it is safe.
1415 If you have been using @value{GDBN} to control an attached process or
1416 device, you can release it with the @code{detach} command
1417 (@pxref{Attach, ,Debugging an Already-running Process}).
1419 @node Shell Commands
1420 @section Shell Commands
1422 If you need to execute occasional shell commands during your
1423 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1424 just use the @code{shell} command.
1429 @cindex shell escape
1430 @item shell @var{command-string}
1431 @itemx !@var{command-string}
1432 Invoke a standard shell to execute @var{command-string}.
1433 Note that no space is needed between @code{!} and @var{command-string}.
1434 If it exists, the environment variable @code{SHELL} determines which
1435 shell to run. Otherwise @value{GDBN} uses the default shell
1436 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1439 The utility @code{make} is often needed in development environments.
1440 You do not have to use the @code{shell} command for this purpose in
1445 @cindex calling make
1446 @item make @var{make-args}
1447 Execute the @code{make} program with the specified
1448 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1451 @node Logging Output
1452 @section Logging Output
1453 @cindex logging @value{GDBN} output
1454 @cindex save @value{GDBN} output to a file
1456 You may want to save the output of @value{GDBN} commands to a file.
1457 There are several commands to control @value{GDBN}'s logging.
1461 @item set logging on
1463 @item set logging off
1465 @cindex logging file name
1466 @item set logging file @var{file}
1467 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1468 @item set logging overwrite [on|off]
1469 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1470 you want @code{set logging on} to overwrite the logfile instead.
1471 @item set logging redirect [on|off]
1472 By default, @value{GDBN} output will go to both the terminal and the logfile.
1473 Set @code{redirect} if you want output to go only to the log file.
1474 @kindex show logging
1476 Show the current values of the logging settings.
1480 @chapter @value{GDBN} Commands
1482 You can abbreviate a @value{GDBN} command to the first few letters of the command
1483 name, if that abbreviation is unambiguous; and you can repeat certain
1484 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1485 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1486 show you the alternatives available, if there is more than one possibility).
1489 * Command Syntax:: How to give commands to @value{GDBN}
1490 * Completion:: Command completion
1491 * Help:: How to ask @value{GDBN} for help
1494 @node Command Syntax
1495 @section Command Syntax
1497 A @value{GDBN} command is a single line of input. There is no limit on
1498 how long it can be. It starts with a command name, which is followed by
1499 arguments whose meaning depends on the command name. For example, the
1500 command @code{step} accepts an argument which is the number of times to
1501 step, as in @samp{step 5}. You can also use the @code{step} command
1502 with no arguments. Some commands do not allow any arguments.
1504 @cindex abbreviation
1505 @value{GDBN} command names may always be truncated if that abbreviation is
1506 unambiguous. Other possible command abbreviations are listed in the
1507 documentation for individual commands. In some cases, even ambiguous
1508 abbreviations are allowed; for example, @code{s} is specially defined as
1509 equivalent to @code{step} even though there are other commands whose
1510 names start with @code{s}. You can test abbreviations by using them as
1511 arguments to the @code{help} command.
1513 @cindex repeating commands
1514 @kindex RET @r{(repeat last command)}
1515 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1516 repeat the previous command. Certain commands (for example, @code{run})
1517 will not repeat this way; these are commands whose unintentional
1518 repetition might cause trouble and which you are unlikely to want to
1519 repeat. User-defined commands can disable this feature; see
1520 @ref{Define, dont-repeat}.
1522 The @code{list} and @code{x} commands, when you repeat them with
1523 @key{RET}, construct new arguments rather than repeating
1524 exactly as typed. This permits easy scanning of source or memory.
1526 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1527 output, in a way similar to the common utility @code{more}
1528 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1529 @key{RET} too many in this situation, @value{GDBN} disables command
1530 repetition after any command that generates this sort of display.
1532 @kindex # @r{(a comment)}
1534 Any text from a @kbd{#} to the end of the line is a comment; it does
1535 nothing. This is useful mainly in command files (@pxref{Command
1536 Files,,Command Files}).
1538 @cindex repeating command sequences
1539 @kindex Ctrl-o @r{(operate-and-get-next)}
1540 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1541 commands. This command accepts the current line, like @key{RET}, and
1542 then fetches the next line relative to the current line from the history
1546 @section Command Completion
1549 @cindex word completion
1550 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1551 only one possibility; it can also show you what the valid possibilities
1552 are for the next word in a command, at any time. This works for @value{GDBN}
1553 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1555 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1556 of a word. If there is only one possibility, @value{GDBN} fills in the
1557 word, and waits for you to finish the command (or press @key{RET} to
1558 enter it). For example, if you type
1560 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1561 @c complete accuracy in these examples; space introduced for clarity.
1562 @c If texinfo enhancements make it unnecessary, it would be nice to
1563 @c replace " @key" by "@key" in the following...
1565 (@value{GDBP}) info bre @key{TAB}
1569 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1570 the only @code{info} subcommand beginning with @samp{bre}:
1573 (@value{GDBP}) info breakpoints
1577 You can either press @key{RET} at this point, to run the @code{info
1578 breakpoints} command, or backspace and enter something else, if
1579 @samp{breakpoints} does not look like the command you expected. (If you
1580 were sure you wanted @code{info breakpoints} in the first place, you
1581 might as well just type @key{RET} immediately after @samp{info bre},
1582 to exploit command abbreviations rather than command completion).
1584 If there is more than one possibility for the next word when you press
1585 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1586 characters and try again, or just press @key{TAB} a second time;
1587 @value{GDBN} displays all the possible completions for that word. For
1588 example, you might want to set a breakpoint on a subroutine whose name
1589 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1590 just sounds the bell. Typing @key{TAB} again displays all the
1591 function names in your program that begin with those characters, for
1595 (@value{GDBP}) b make_ @key{TAB}
1596 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1597 make_a_section_from_file make_environ
1598 make_abs_section make_function_type
1599 make_blockvector make_pointer_type
1600 make_cleanup make_reference_type
1601 make_command make_symbol_completion_list
1602 (@value{GDBP}) b make_
1606 After displaying the available possibilities, @value{GDBN} copies your
1607 partial input (@samp{b make_} in the example) so you can finish the
1610 If you just want to see the list of alternatives in the first place, you
1611 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1612 means @kbd{@key{META} ?}. You can type this either by holding down a
1613 key designated as the @key{META} shift on your keyboard (if there is
1614 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1616 If the number of possible completions is large, @value{GDBN} will
1617 print as much of the list as it has collected, as well as a message
1618 indicating that the list may be truncated.
1621 (@value{GDBP}) b m@key{TAB}@key{TAB}
1623 <... the rest of the possible completions ...>
1624 *** List may be truncated, max-completions reached. ***
1629 This behavior can be controlled with the following commands:
1632 @kindex set max-completions
1633 @item set max-completions @var{limit}
1634 @itemx set max-completions unlimited
1635 Set the maximum number of completion candidates. @value{GDBN} will
1636 stop looking for more completions once it collects this many candidates.
1637 This is useful when completing on things like function names as collecting
1638 all the possible candidates can be time consuming.
1639 The default value is 200. A value of zero disables tab-completion.
1640 Note that setting either no limit or a very large limit can make
1642 @kindex show max-completions
1643 @item show max-completions
1644 Show the maximum number of candidates that @value{GDBN} will collect and show
1648 @cindex quotes in commands
1649 @cindex completion of quoted strings
1650 Sometimes the string you need, while logically a ``word'', may contain
1651 parentheses or other characters that @value{GDBN} normally excludes from
1652 its notion of a word. To permit word completion to work in this
1653 situation, you may enclose words in @code{'} (single quote marks) in
1654 @value{GDBN} commands.
1656 A likely situation where you might need this is in typing an
1657 expression that involves a C@t{++} symbol name with template
1658 parameters. This is because when completing expressions, GDB treats
1659 the @samp{<} character as word delimiter, assuming that it's the
1660 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1663 For example, when you want to call a C@t{++} template function
1664 interactively using the @code{print} or @code{call} commands, you may
1665 need to distinguish whether you mean the version of @code{name} that
1666 was specialized for @code{int}, @code{name<int>()}, or the version
1667 that was specialized for @code{float}, @code{name<float>()}. To use
1668 the word-completion facilities in this situation, type a single quote
1669 @code{'} at the beginning of the function name. This alerts
1670 @value{GDBN} that it may need to consider more information than usual
1671 when you press @key{TAB} or @kbd{M-?} to request word completion:
1674 (@value{GDBP}) p 'func< @kbd{M-?}
1675 func<int>() func<float>()
1676 (@value{GDBP}) p 'func<
1679 When setting breakpoints however (@pxref{Specify Location}), you don't
1680 usually need to type a quote before the function name, because
1681 @value{GDBN} understands that you want to set a breakpoint on a
1685 (@value{GDBP}) b func< @kbd{M-?}
1686 func<int>() func<float>()
1687 (@value{GDBP}) b func<
1690 This is true even in the case of typing the name of C@t{++} overloaded
1691 functions (multiple definitions of the same function, distinguished by
1692 argument type). For example, when you want to set a breakpoint you
1693 don't need to distinguish whether you mean the version of @code{name}
1694 that takes an @code{int} parameter, @code{name(int)}, or the version
1695 that takes a @code{float} parameter, @code{name(float)}.
1698 (@value{GDBP}) b bubble( @kbd{M-?}
1699 bubble(int) bubble(double)
1700 (@value{GDBP}) b bubble(dou @kbd{M-?}
1704 See @ref{quoting names} for a description of other scenarios that
1707 For more information about overloaded functions, see @ref{C Plus Plus
1708 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1709 overload-resolution off} to disable overload resolution;
1710 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1712 @cindex completion of structure field names
1713 @cindex structure field name completion
1714 @cindex completion of union field names
1715 @cindex union field name completion
1716 When completing in an expression which looks up a field in a
1717 structure, @value{GDBN} also tries@footnote{The completer can be
1718 confused by certain kinds of invalid expressions. Also, it only
1719 examines the static type of the expression, not the dynamic type.} to
1720 limit completions to the field names available in the type of the
1724 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1725 magic to_fputs to_rewind
1726 to_data to_isatty to_write
1727 to_delete to_put to_write_async_safe
1732 This is because the @code{gdb_stdout} is a variable of the type
1733 @code{struct ui_file} that is defined in @value{GDBN} sources as
1740 ui_file_flush_ftype *to_flush;
1741 ui_file_write_ftype *to_write;
1742 ui_file_write_async_safe_ftype *to_write_async_safe;
1743 ui_file_fputs_ftype *to_fputs;
1744 ui_file_read_ftype *to_read;
1745 ui_file_delete_ftype *to_delete;
1746 ui_file_isatty_ftype *to_isatty;
1747 ui_file_rewind_ftype *to_rewind;
1748 ui_file_put_ftype *to_put;
1755 @section Getting Help
1756 @cindex online documentation
1759 You can always ask @value{GDBN} itself for information on its commands,
1760 using the command @code{help}.
1763 @kindex h @r{(@code{help})}
1766 You can use @code{help} (abbreviated @code{h}) with no arguments to
1767 display a short list of named classes of commands:
1771 List of classes of commands:
1773 aliases -- Aliases of other commands
1774 breakpoints -- Making program stop at certain points
1775 data -- Examining data
1776 files -- Specifying and examining files
1777 internals -- Maintenance commands
1778 obscure -- Obscure features
1779 running -- Running the program
1780 stack -- Examining the stack
1781 status -- Status inquiries
1782 support -- Support facilities
1783 tracepoints -- Tracing of program execution without
1784 stopping the program
1785 user-defined -- User-defined commands
1787 Type "help" followed by a class name for a list of
1788 commands in that class.
1789 Type "help" followed by command name for full
1791 Command name abbreviations are allowed if unambiguous.
1794 @c the above line break eliminates huge line overfull...
1796 @item help @var{class}
1797 Using one of the general help classes as an argument, you can get a
1798 list of the individual commands in that class. For example, here is the
1799 help display for the class @code{status}:
1802 (@value{GDBP}) help status
1807 @c Line break in "show" line falsifies real output, but needed
1808 @c to fit in smallbook page size.
1809 info -- Generic command for showing things
1810 about the program being debugged
1811 show -- Generic command for showing things
1814 Type "help" followed by command name for full
1816 Command name abbreviations are allowed if unambiguous.
1820 @item help @var{command}
1821 With a command name as @code{help} argument, @value{GDBN} displays a
1822 short paragraph on how to use that command.
1825 @item apropos @var{args}
1826 The @code{apropos} command searches through all of the @value{GDBN}
1827 commands, and their documentation, for the regular expression specified in
1828 @var{args}. It prints out all matches found. For example:
1839 alias -- Define a new command that is an alias of an existing command
1840 aliases -- Aliases of other commands
1841 d -- Delete some breakpoints or auto-display expressions
1842 del -- Delete some breakpoints or auto-display expressions
1843 delete -- Delete some breakpoints or auto-display expressions
1848 @item complete @var{args}
1849 The @code{complete @var{args}} command lists all the possible completions
1850 for the beginning of a command. Use @var{args} to specify the beginning of the
1851 command you want completed. For example:
1857 @noindent results in:
1868 @noindent This is intended for use by @sc{gnu} Emacs.
1871 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1872 and @code{show} to inquire about the state of your program, or the state
1873 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1874 manual introduces each of them in the appropriate context. The listings
1875 under @code{info} and under @code{show} in the Command, Variable, and
1876 Function Index point to all the sub-commands. @xref{Command and Variable
1882 @kindex i @r{(@code{info})}
1884 This command (abbreviated @code{i}) is for describing the state of your
1885 program. For example, you can show the arguments passed to a function
1886 with @code{info args}, list the registers currently in use with @code{info
1887 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1888 You can get a complete list of the @code{info} sub-commands with
1889 @w{@code{help info}}.
1893 You can assign the result of an expression to an environment variable with
1894 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1895 @code{set prompt $}.
1899 In contrast to @code{info}, @code{show} is for describing the state of
1900 @value{GDBN} itself.
1901 You can change most of the things you can @code{show}, by using the
1902 related command @code{set}; for example, you can control what number
1903 system is used for displays with @code{set radix}, or simply inquire
1904 which is currently in use with @code{show radix}.
1907 To display all the settable parameters and their current
1908 values, you can use @code{show} with no arguments; you may also use
1909 @code{info set}. Both commands produce the same display.
1910 @c FIXME: "info set" violates the rule that "info" is for state of
1911 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1912 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1916 Here are several miscellaneous @code{show} subcommands, all of which are
1917 exceptional in lacking corresponding @code{set} commands:
1920 @kindex show version
1921 @cindex @value{GDBN} version number
1923 Show what version of @value{GDBN} is running. You should include this
1924 information in @value{GDBN} bug-reports. If multiple versions of
1925 @value{GDBN} are in use at your site, you may need to determine which
1926 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1927 commands are introduced, and old ones may wither away. Also, many
1928 system vendors ship variant versions of @value{GDBN}, and there are
1929 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1930 The version number is the same as the one announced when you start
1933 @kindex show copying
1934 @kindex info copying
1935 @cindex display @value{GDBN} copyright
1938 Display information about permission for copying @value{GDBN}.
1940 @kindex show warranty
1941 @kindex info warranty
1943 @itemx info warranty
1944 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1945 if your version of @value{GDBN} comes with one.
1947 @kindex show configuration
1948 @item show configuration
1949 Display detailed information about the way @value{GDBN} was configured
1950 when it was built. This displays the optional arguments passed to the
1951 @file{configure} script and also configuration parameters detected
1952 automatically by @command{configure}. When reporting a @value{GDBN}
1953 bug (@pxref{GDB Bugs}), it is important to include this information in
1959 @chapter Running Programs Under @value{GDBN}
1961 When you run a program under @value{GDBN}, you must first generate
1962 debugging information when you compile it.
1964 You may start @value{GDBN} with its arguments, if any, in an environment
1965 of your choice. If you are doing native debugging, you may redirect
1966 your program's input and output, debug an already running process, or
1967 kill a child process.
1970 * Compilation:: Compiling for debugging
1971 * Starting:: Starting your program
1972 * Arguments:: Your program's arguments
1973 * Environment:: Your program's environment
1975 * Working Directory:: Your program's working directory
1976 * Input/Output:: Your program's input and output
1977 * Attach:: Debugging an already-running process
1978 * Kill Process:: Killing the child process
1980 * Inferiors and Programs:: Debugging multiple inferiors and programs
1981 * Threads:: Debugging programs with multiple threads
1982 * Forks:: Debugging forks
1983 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1987 @section Compiling for Debugging
1989 In order to debug a program effectively, you need to generate
1990 debugging information when you compile it. This debugging information
1991 is stored in the object file; it describes the data type of each
1992 variable or function and the correspondence between source line numbers
1993 and addresses in the executable code.
1995 To request debugging information, specify the @samp{-g} option when you run
1998 Programs that are to be shipped to your customers are compiled with
1999 optimizations, using the @samp{-O} compiler option. However, some
2000 compilers are unable to handle the @samp{-g} and @samp{-O} options
2001 together. Using those compilers, you cannot generate optimized
2002 executables containing debugging information.
2004 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2005 without @samp{-O}, making it possible to debug optimized code. We
2006 recommend that you @emph{always} use @samp{-g} whenever you compile a
2007 program. You may think your program is correct, but there is no sense
2008 in pushing your luck. For more information, see @ref{Optimized Code}.
2010 Older versions of the @sc{gnu} C compiler permitted a variant option
2011 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2012 format; if your @sc{gnu} C compiler has this option, do not use it.
2014 @value{GDBN} knows about preprocessor macros and can show you their
2015 expansion (@pxref{Macros}). Most compilers do not include information
2016 about preprocessor macros in the debugging information if you specify
2017 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2018 the @sc{gnu} C compiler, provides macro information if you are using
2019 the DWARF debugging format, and specify the option @option{-g3}.
2021 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2022 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2023 information on @value{NGCC} options affecting debug information.
2025 You will have the best debugging experience if you use the latest
2026 version of the DWARF debugging format that your compiler supports.
2027 DWARF is currently the most expressive and best supported debugging
2028 format in @value{GDBN}.
2032 @section Starting your Program
2038 @kindex r @r{(@code{run})}
2041 Use the @code{run} command to start your program under @value{GDBN}.
2042 You must first specify the program name with an argument to
2043 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2044 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2045 command (@pxref{Files, ,Commands to Specify Files}).
2049 If you are running your program in an execution environment that
2050 supports processes, @code{run} creates an inferior process and makes
2051 that process run your program. In some environments without processes,
2052 @code{run} jumps to the start of your program. Other targets,
2053 like @samp{remote}, are always running. If you get an error
2054 message like this one:
2057 The "remote" target does not support "run".
2058 Try "help target" or "continue".
2062 then use @code{continue} to run your program. You may need @code{load}
2063 first (@pxref{load}).
2065 The execution of a program is affected by certain information it
2066 receives from its superior. @value{GDBN} provides ways to specify this
2067 information, which you must do @emph{before} starting your program. (You
2068 can change it after starting your program, but such changes only affect
2069 your program the next time you start it.) This information may be
2070 divided into four categories:
2073 @item The @emph{arguments.}
2074 Specify the arguments to give your program as the arguments of the
2075 @code{run} command. If a shell is available on your target, the shell
2076 is used to pass the arguments, so that you may use normal conventions
2077 (such as wildcard expansion or variable substitution) in describing
2079 In Unix systems, you can control which shell is used with the
2080 @code{SHELL} environment variable. If you do not define @code{SHELL},
2081 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2082 use of any shell with the @code{set startup-with-shell} command (see
2085 @item The @emph{environment.}
2086 Your program normally inherits its environment from @value{GDBN}, but you can
2087 use the @value{GDBN} commands @code{set environment} and @code{unset
2088 environment} to change parts of the environment that affect
2089 your program. @xref{Environment, ,Your Program's Environment}.
2091 @item The @emph{working directory.}
2092 You can set your program's working directory with the command
2093 @kbd{set cwd}. If you do not set any working directory with this
2094 command, your program will inherit @value{GDBN}'s working directory if
2095 native debugging, or the remote server's working directory if remote
2096 debugging. @xref{Working Directory, ,Your Program's Working
2099 @item The @emph{standard input and output.}
2100 Your program normally uses the same device for standard input and
2101 standard output as @value{GDBN} is using. You can redirect input and output
2102 in the @code{run} command line, or you can use the @code{tty} command to
2103 set a different device for your program.
2104 @xref{Input/Output, ,Your Program's Input and Output}.
2107 @emph{Warning:} While input and output redirection work, you cannot use
2108 pipes to pass the output of the program you are debugging to another
2109 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2113 When you issue the @code{run} command, your program begins to execute
2114 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2115 of how to arrange for your program to stop. Once your program has
2116 stopped, you may call functions in your program, using the @code{print}
2117 or @code{call} commands. @xref{Data, ,Examining Data}.
2119 If the modification time of your symbol file has changed since the last
2120 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2121 table, and reads it again. When it does this, @value{GDBN} tries to retain
2122 your current breakpoints.
2127 @cindex run to main procedure
2128 The name of the main procedure can vary from language to language.
2129 With C or C@t{++}, the main procedure name is always @code{main}, but
2130 other languages such as Ada do not require a specific name for their
2131 main procedure. The debugger provides a convenient way to start the
2132 execution of the program and to stop at the beginning of the main
2133 procedure, depending on the language used.
2135 The @samp{start} command does the equivalent of setting a temporary
2136 breakpoint at the beginning of the main procedure and then invoking
2137 the @samp{run} command.
2139 @cindex elaboration phase
2140 Some programs contain an @dfn{elaboration} phase where some startup code is
2141 executed before the main procedure is called. This depends on the
2142 languages used to write your program. In C@t{++}, for instance,
2143 constructors for static and global objects are executed before
2144 @code{main} is called. It is therefore possible that the debugger stops
2145 before reaching the main procedure. However, the temporary breakpoint
2146 will remain to halt execution.
2148 Specify the arguments to give to your program as arguments to the
2149 @samp{start} command. These arguments will be given verbatim to the
2150 underlying @samp{run} command. Note that the same arguments will be
2151 reused if no argument is provided during subsequent calls to
2152 @samp{start} or @samp{run}.
2154 It is sometimes necessary to debug the program during elaboration. In
2155 these cases, using the @code{start} command would stop the execution
2156 of your program too late, as the program would have already completed
2157 the elaboration phase. Under these circumstances, either insert
2158 breakpoints in your elaboration code before running your program or
2159 use the @code{starti} command.
2163 @cindex run to first instruction
2164 The @samp{starti} command does the equivalent of setting a temporary
2165 breakpoint at the first instruction of a program's execution and then
2166 invoking the @samp{run} command. For programs containing an
2167 elaboration phase, the @code{starti} command will stop execution at
2168 the start of the elaboration phase.
2170 @anchor{set exec-wrapper}
2171 @kindex set exec-wrapper
2172 @item set exec-wrapper @var{wrapper}
2173 @itemx show exec-wrapper
2174 @itemx unset exec-wrapper
2175 When @samp{exec-wrapper} is set, the specified wrapper is used to
2176 launch programs for debugging. @value{GDBN} starts your program
2177 with a shell command of the form @kbd{exec @var{wrapper}
2178 @var{program}}. Quoting is added to @var{program} and its
2179 arguments, but not to @var{wrapper}, so you should add quotes if
2180 appropriate for your shell. The wrapper runs until it executes
2181 your program, and then @value{GDBN} takes control.
2183 You can use any program that eventually calls @code{execve} with
2184 its arguments as a wrapper. Several standard Unix utilities do
2185 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2186 with @code{exec "$@@"} will also work.
2188 For example, you can use @code{env} to pass an environment variable to
2189 the debugged program, without setting the variable in your shell's
2193 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2197 This command is available when debugging locally on most targets, excluding
2198 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2200 @kindex set startup-with-shell
2201 @anchor{set startup-with-shell}
2202 @item set startup-with-shell
2203 @itemx set startup-with-shell on
2204 @itemx set startup-with-shell off
2205 @itemx show startup-with-shell
2206 On Unix systems, by default, if a shell is available on your target,
2207 @value{GDBN}) uses it to start your program. Arguments of the
2208 @code{run} command are passed to the shell, which does variable
2209 substitution, expands wildcard characters and performs redirection of
2210 I/O. In some circumstances, it may be useful to disable such use of a
2211 shell, for example, when debugging the shell itself or diagnosing
2212 startup failures such as:
2216 Starting program: ./a.out
2217 During startup program terminated with signal SIGSEGV, Segmentation fault.
2221 which indicates the shell or the wrapper specified with
2222 @samp{exec-wrapper} crashed, not your program. Most often, this is
2223 caused by something odd in your shell's non-interactive mode
2224 initialization file---such as @file{.cshrc} for C-shell,
2225 $@file{.zshenv} for the Z shell, or the file specified in the
2226 @samp{BASH_ENV} environment variable for BASH.
2228 @anchor{set auto-connect-native-target}
2229 @kindex set auto-connect-native-target
2230 @item set auto-connect-native-target
2231 @itemx set auto-connect-native-target on
2232 @itemx set auto-connect-native-target off
2233 @itemx show auto-connect-native-target
2235 By default, if not connected to any target yet (e.g., with
2236 @code{target remote}), the @code{run} command starts your program as a
2237 native process under @value{GDBN}, on your local machine. If you're
2238 sure you don't want to debug programs on your local machine, you can
2239 tell @value{GDBN} to not connect to the native target automatically
2240 with the @code{set auto-connect-native-target off} command.
2242 If @code{on}, which is the default, and if @value{GDBN} is not
2243 connected to a target already, the @code{run} command automaticaly
2244 connects to the native target, if one is available.
2246 If @code{off}, and if @value{GDBN} is not connected to a target
2247 already, the @code{run} command fails with an error:
2251 Don't know how to run. Try "help target".
2254 If @value{GDBN} is already connected to a target, @value{GDBN} always
2255 uses it with the @code{run} command.
2257 In any case, you can explicitly connect to the native target with the
2258 @code{target native} command. For example,
2261 (@value{GDBP}) set auto-connect-native-target off
2263 Don't know how to run. Try "help target".
2264 (@value{GDBP}) target native
2266 Starting program: ./a.out
2267 [Inferior 1 (process 10421) exited normally]
2270 In case you connected explicitly to the @code{native} target,
2271 @value{GDBN} remains connected even if all inferiors exit, ready for
2272 the next @code{run} command. Use the @code{disconnect} command to
2275 Examples of other commands that likewise respect the
2276 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2277 proc}, @code{info os}.
2279 @kindex set disable-randomization
2280 @item set disable-randomization
2281 @itemx set disable-randomization on
2282 This option (enabled by default in @value{GDBN}) will turn off the native
2283 randomization of the virtual address space of the started program. This option
2284 is useful for multiple debugging sessions to make the execution better
2285 reproducible and memory addresses reusable across debugging sessions.
2287 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2288 On @sc{gnu}/Linux you can get the same behavior using
2291 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2294 @item set disable-randomization off
2295 Leave the behavior of the started executable unchanged. Some bugs rear their
2296 ugly heads only when the program is loaded at certain addresses. If your bug
2297 disappears when you run the program under @value{GDBN}, that might be because
2298 @value{GDBN} by default disables the address randomization on platforms, such
2299 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2300 disable-randomization off} to try to reproduce such elusive bugs.
2302 On targets where it is available, virtual address space randomization
2303 protects the programs against certain kinds of security attacks. In these
2304 cases the attacker needs to know the exact location of a concrete executable
2305 code. Randomizing its location makes it impossible to inject jumps misusing
2306 a code at its expected addresses.
2308 Prelinking shared libraries provides a startup performance advantage but it
2309 makes addresses in these libraries predictable for privileged processes by
2310 having just unprivileged access at the target system. Reading the shared
2311 library binary gives enough information for assembling the malicious code
2312 misusing it. Still even a prelinked shared library can get loaded at a new
2313 random address just requiring the regular relocation process during the
2314 startup. Shared libraries not already prelinked are always loaded at
2315 a randomly chosen address.
2317 Position independent executables (PIE) contain position independent code
2318 similar to the shared libraries and therefore such executables get loaded at
2319 a randomly chosen address upon startup. PIE executables always load even
2320 already prelinked shared libraries at a random address. You can build such
2321 executable using @command{gcc -fPIE -pie}.
2323 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2324 (as long as the randomization is enabled).
2326 @item show disable-randomization
2327 Show the current setting of the explicit disable of the native randomization of
2328 the virtual address space of the started program.
2333 @section Your Program's Arguments
2335 @cindex arguments (to your program)
2336 The arguments to your program can be specified by the arguments of the
2338 They are passed to a shell, which expands wildcard characters and
2339 performs redirection of I/O, and thence to your program. Your
2340 @code{SHELL} environment variable (if it exists) specifies what shell
2341 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2342 the default shell (@file{/bin/sh} on Unix).
2344 On non-Unix systems, the program is usually invoked directly by
2345 @value{GDBN}, which emulates I/O redirection via the appropriate system
2346 calls, and the wildcard characters are expanded by the startup code of
2347 the program, not by the shell.
2349 @code{run} with no arguments uses the same arguments used by the previous
2350 @code{run}, or those set by the @code{set args} command.
2355 Specify the arguments to be used the next time your program is run. If
2356 @code{set args} has no arguments, @code{run} executes your program
2357 with no arguments. Once you have run your program with arguments,
2358 using @code{set args} before the next @code{run} is the only way to run
2359 it again without arguments.
2363 Show the arguments to give your program when it is started.
2367 @section Your Program's Environment
2369 @cindex environment (of your program)
2370 The @dfn{environment} consists of a set of environment variables and
2371 their values. Environment variables conventionally record such things as
2372 your user name, your home directory, your terminal type, and your search
2373 path for programs to run. Usually you set up environment variables with
2374 the shell and they are inherited by all the other programs you run. When
2375 debugging, it can be useful to try running your program with a modified
2376 environment without having to start @value{GDBN} over again.
2380 @item path @var{directory}
2381 Add @var{directory} to the front of the @code{PATH} environment variable
2382 (the search path for executables) that will be passed to your program.
2383 The value of @code{PATH} used by @value{GDBN} does not change.
2384 You may specify several directory names, separated by whitespace or by a
2385 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2386 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2387 is moved to the front, so it is searched sooner.
2389 You can use the string @samp{$cwd} to refer to whatever is the current
2390 working directory at the time @value{GDBN} searches the path. If you
2391 use @samp{.} instead, it refers to the directory where you executed the
2392 @code{path} command. @value{GDBN} replaces @samp{.} in the
2393 @var{directory} argument (with the current path) before adding
2394 @var{directory} to the search path.
2395 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2396 @c document that, since repeating it would be a no-op.
2400 Display the list of search paths for executables (the @code{PATH}
2401 environment variable).
2403 @kindex show environment
2404 @item show environment @r{[}@var{varname}@r{]}
2405 Print the value of environment variable @var{varname} to be given to
2406 your program when it starts. If you do not supply @var{varname},
2407 print the names and values of all environment variables to be given to
2408 your program. You can abbreviate @code{environment} as @code{env}.
2410 @kindex set environment
2411 @anchor{set environment}
2412 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2413 Set environment variable @var{varname} to @var{value}. The value
2414 changes for your program (and the shell @value{GDBN} uses to launch
2415 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2416 values of environment variables are just strings, and any
2417 interpretation is supplied by your program itself. The @var{value}
2418 parameter is optional; if it is eliminated, the variable is set to a
2420 @c "any string" here does not include leading, trailing
2421 @c blanks. Gnu asks: does anyone care?
2423 For example, this command:
2430 tells the debugged program, when subsequently run, that its user is named
2431 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2432 are not actually required.)
2434 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2435 which also inherits the environment set with @code{set environment}.
2436 If necessary, you can avoid that by using the @samp{env} program as a
2437 wrapper instead of using @code{set environment}. @xref{set
2438 exec-wrapper}, for an example doing just that.
2440 Environment variables that are set by the user are also transmitted to
2441 @command{gdbserver} to be used when starting the remote inferior.
2442 @pxref{QEnvironmentHexEncoded}.
2444 @kindex unset environment
2445 @anchor{unset environment}
2446 @item unset environment @var{varname}
2447 Remove variable @var{varname} from the environment to be passed to your
2448 program. This is different from @samp{set env @var{varname} =};
2449 @code{unset environment} removes the variable from the environment,
2450 rather than assigning it an empty value.
2452 Environment variables that are unset by the user are also unset on
2453 @command{gdbserver} when starting the remote inferior.
2454 @pxref{QEnvironmentUnset}.
2457 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2458 the shell indicated by your @code{SHELL} environment variable if it
2459 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2460 names a shell that runs an initialization file when started
2461 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2462 for the Z shell, or the file specified in the @samp{BASH_ENV}
2463 environment variable for BASH---any variables you set in that file
2464 affect your program. You may wish to move setting of environment
2465 variables to files that are only run when you sign on, such as
2466 @file{.login} or @file{.profile}.
2468 @node Working Directory
2469 @section Your Program's Working Directory
2471 @cindex working directory (of your program)
2472 Each time you start your program with @code{run}, the inferior will be
2473 initialized with the current working directory specified by the
2474 @kbd{set cwd} command. If no directory has been specified by this
2475 command, then the inferior will inherit @value{GDBN}'s current working
2476 directory as its working directory if native debugging, or it will
2477 inherit the remote server's current working directory if remote
2482 @cindex change inferior's working directory
2483 @anchor{set cwd command}
2484 @item set cwd @r{[}@var{directory}@r{]}
2485 Set the inferior's working directory to @var{directory}, which will be
2486 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2487 argument has been specified, the command clears the setting and resets
2488 it to an empty state. This setting has no effect on @value{GDBN}'s
2489 working directory, and it only takes effect the next time you start
2490 the inferior. The @file{~} in @var{directory} is a short for the
2491 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2492 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2493 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2496 You can also change @value{GDBN}'s current working directory by using
2497 the @code{cd} command.
2501 @cindex show inferior's working directory
2503 Show the inferior's working directory. If no directory has been
2504 specified by @kbd{set cwd}, then the default inferior's working
2505 directory is the same as @value{GDBN}'s working directory.
2508 @cindex change @value{GDBN}'s working directory
2510 @item cd @r{[}@var{directory}@r{]}
2511 Set the @value{GDBN} working directory to @var{directory}. If not
2512 given, @var{directory} uses @file{'~'}.
2514 The @value{GDBN} working directory serves as a default for the
2515 commands that specify files for @value{GDBN} to operate on.
2516 @xref{Files, ,Commands to Specify Files}.
2517 @xref{set cwd command}.
2521 Print the @value{GDBN} working directory.
2524 It is generally impossible to find the current working directory of
2525 the process being debugged (since a program can change its directory
2526 during its run). If you work on a system where @value{GDBN} supports
2527 the @code{info proc} command (@pxref{Process Information}), you can
2528 use the @code{info proc} command to find out the
2529 current working directory of the debuggee.
2532 @section Your Program's Input and Output
2537 By default, the program you run under @value{GDBN} does input and output to
2538 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2539 to its own terminal modes to interact with you, but it records the terminal
2540 modes your program was using and switches back to them when you continue
2541 running your program.
2544 @kindex info terminal
2546 Displays information recorded by @value{GDBN} about the terminal modes your
2550 You can redirect your program's input and/or output using shell
2551 redirection with the @code{run} command. For example,
2558 starts your program, diverting its output to the file @file{outfile}.
2561 @cindex controlling terminal
2562 Another way to specify where your program should do input and output is
2563 with the @code{tty} command. This command accepts a file name as
2564 argument, and causes this file to be the default for future @code{run}
2565 commands. It also resets the controlling terminal for the child
2566 process, for future @code{run} commands. For example,
2573 directs that processes started with subsequent @code{run} commands
2574 default to do input and output on the terminal @file{/dev/ttyb} and have
2575 that as their controlling terminal.
2577 An explicit redirection in @code{run} overrides the @code{tty} command's
2578 effect on the input/output device, but not its effect on the controlling
2581 When you use the @code{tty} command or redirect input in the @code{run}
2582 command, only the input @emph{for your program} is affected. The input
2583 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2584 for @code{set inferior-tty}.
2586 @cindex inferior tty
2587 @cindex set inferior controlling terminal
2588 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2589 display the name of the terminal that will be used for future runs of your
2593 @item set inferior-tty [ @var{tty} ]
2594 @kindex set inferior-tty
2595 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2596 restores the default behavior, which is to use the same terminal as
2599 @item show inferior-tty
2600 @kindex show inferior-tty
2601 Show the current tty for the program being debugged.
2605 @section Debugging an Already-running Process
2610 @item attach @var{process-id}
2611 This command attaches to a running process---one that was started
2612 outside @value{GDBN}. (@code{info files} shows your active
2613 targets.) The command takes as argument a process ID. The usual way to
2614 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2615 or with the @samp{jobs -l} shell command.
2617 @code{attach} does not repeat if you press @key{RET} a second time after
2618 executing the command.
2621 To use @code{attach}, your program must be running in an environment
2622 which supports processes; for example, @code{attach} does not work for
2623 programs on bare-board targets that lack an operating system. You must
2624 also have permission to send the process a signal.
2626 When you use @code{attach}, the debugger finds the program running in
2627 the process first by looking in the current working directory, then (if
2628 the program is not found) by using the source file search path
2629 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2630 the @code{file} command to load the program. @xref{Files, ,Commands to
2633 The first thing @value{GDBN} does after arranging to debug the specified
2634 process is to stop it. You can examine and modify an attached process
2635 with all the @value{GDBN} commands that are ordinarily available when
2636 you start processes with @code{run}. You can insert breakpoints; you
2637 can step and continue; you can modify storage. If you would rather the
2638 process continue running, you may use the @code{continue} command after
2639 attaching @value{GDBN} to the process.
2644 When you have finished debugging the attached process, you can use the
2645 @code{detach} command to release it from @value{GDBN} control. Detaching
2646 the process continues its execution. After the @code{detach} command,
2647 that process and @value{GDBN} become completely independent once more, and you
2648 are ready to @code{attach} another process or start one with @code{run}.
2649 @code{detach} does not repeat if you press @key{RET} again after
2650 executing the command.
2653 If you exit @value{GDBN} while you have an attached process, you detach
2654 that process. If you use the @code{run} command, you kill that process.
2655 By default, @value{GDBN} asks for confirmation if you try to do either of these
2656 things; you can control whether or not you need to confirm by using the
2657 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2661 @section Killing the Child Process
2666 Kill the child process in which your program is running under @value{GDBN}.
2669 This command is useful if you wish to debug a core dump instead of a
2670 running process. @value{GDBN} ignores any core dump file while your program
2673 On some operating systems, a program cannot be executed outside @value{GDBN}
2674 while you have breakpoints set on it inside @value{GDBN}. You can use the
2675 @code{kill} command in this situation to permit running your program
2676 outside the debugger.
2678 The @code{kill} command is also useful if you wish to recompile and
2679 relink your program, since on many systems it is impossible to modify an
2680 executable file while it is running in a process. In this case, when you
2681 next type @code{run}, @value{GDBN} notices that the file has changed, and
2682 reads the symbol table again (while trying to preserve your current
2683 breakpoint settings).
2685 @node Inferiors and Programs
2686 @section Debugging Multiple Inferiors and Programs
2688 @value{GDBN} lets you run and debug multiple programs in a single
2689 session. In addition, @value{GDBN} on some systems may let you run
2690 several programs simultaneously (otherwise you have to exit from one
2691 before starting another). In the most general case, you can have
2692 multiple threads of execution in each of multiple processes, launched
2693 from multiple executables.
2696 @value{GDBN} represents the state of each program execution with an
2697 object called an @dfn{inferior}. An inferior typically corresponds to
2698 a process, but is more general and applies also to targets that do not
2699 have processes. Inferiors may be created before a process runs, and
2700 may be retained after a process exits. Inferiors have unique
2701 identifiers that are different from process ids. Usually each
2702 inferior will also have its own distinct address space, although some
2703 embedded targets may have several inferiors running in different parts
2704 of a single address space. Each inferior may in turn have multiple
2705 threads running in it.
2707 To find out what inferiors exist at any moment, use @w{@code{info
2711 @kindex info inferiors [ @var{id}@dots{} ]
2712 @item info inferiors
2713 Print a list of all inferiors currently being managed by @value{GDBN}.
2714 By default all inferiors are printed, but the argument @var{id}@dots{}
2715 -- a space separated list of inferior numbers -- can be used to limit
2716 the display to just the requested inferiors.
2718 @value{GDBN} displays for each inferior (in this order):
2722 the inferior number assigned by @value{GDBN}
2725 the target system's inferior identifier
2728 the name of the executable the inferior is running.
2733 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2734 indicates the current inferior.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info inferiors
2742 Num Description Executable
2743 2 process 2307 hello
2744 * 1 process 3401 goodbye
2747 To switch focus between inferiors, use the @code{inferior} command:
2750 @kindex inferior @var{infno}
2751 @item inferior @var{infno}
2752 Make inferior number @var{infno} the current inferior. The argument
2753 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2754 in the first field of the @samp{info inferiors} display.
2757 @vindex $_inferior@r{, convenience variable}
2758 The debugger convenience variable @samp{$_inferior} contains the
2759 number of the current inferior. You may find this useful in writing
2760 breakpoint conditional expressions, command scripts, and so forth.
2761 @xref{Convenience Vars,, Convenience Variables}, for general
2762 information on convenience variables.
2764 You can get multiple executables into a debugging session via the
2765 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2766 systems @value{GDBN} can add inferiors to the debug session
2767 automatically by following calls to @code{fork} and @code{exec}. To
2768 remove inferiors from the debugging session use the
2769 @w{@code{remove-inferiors}} command.
2772 @kindex add-inferior
2773 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2774 Adds @var{n} inferiors to be run using @var{executable} as the
2775 executable; @var{n} defaults to 1. If no executable is specified,
2776 the inferiors begins empty, with no program. You can still assign or
2777 change the program assigned to the inferior at any time by using the
2778 @code{file} command with the executable name as its argument.
2780 @kindex clone-inferior
2781 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2782 Adds @var{n} inferiors ready to execute the same program as inferior
2783 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2784 number of the current inferior. This is a convenient command when you
2785 want to run another instance of the inferior you are debugging.
2788 (@value{GDBP}) info inferiors
2789 Num Description Executable
2790 * 1 process 29964 helloworld
2791 (@value{GDBP}) clone-inferior
2794 (@value{GDBP}) info inferiors
2795 Num Description Executable
2797 * 1 process 29964 helloworld
2800 You can now simply switch focus to inferior 2 and run it.
2802 @kindex remove-inferiors
2803 @item remove-inferiors @var{infno}@dots{}
2804 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2805 possible to remove an inferior that is running with this command. For
2806 those, use the @code{kill} or @code{detach} command first.
2810 To quit debugging one of the running inferiors that is not the current
2811 inferior, you can either detach from it by using the @w{@code{detach
2812 inferior}} command (allowing it to run independently), or kill it
2813 using the @w{@code{kill inferiors}} command:
2816 @kindex detach inferiors @var{infno}@dots{}
2817 @item detach inferior @var{infno}@dots{}
2818 Detach from the inferior or inferiors identified by @value{GDBN}
2819 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2820 still stays on the list of inferiors shown by @code{info inferiors},
2821 but its Description will show @samp{<null>}.
2823 @kindex kill inferiors @var{infno}@dots{}
2824 @item kill inferiors @var{infno}@dots{}
2825 Kill the inferior or inferiors identified by @value{GDBN} inferior
2826 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2827 stays on the list of inferiors shown by @code{info inferiors}, but its
2828 Description will show @samp{<null>}.
2831 After the successful completion of a command such as @code{detach},
2832 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2833 a normal process exit, the inferior is still valid and listed with
2834 @code{info inferiors}, ready to be restarted.
2837 To be notified when inferiors are started or exit under @value{GDBN}'s
2838 control use @w{@code{set print inferior-events}}:
2841 @kindex set print inferior-events
2842 @cindex print messages on inferior start and exit
2843 @item set print inferior-events
2844 @itemx set print inferior-events on
2845 @itemx set print inferior-events off
2846 The @code{set print inferior-events} command allows you to enable or
2847 disable printing of messages when @value{GDBN} notices that new
2848 inferiors have started or that inferiors have exited or have been
2849 detached. By default, these messages will not be printed.
2851 @kindex show print inferior-events
2852 @item show print inferior-events
2853 Show whether messages will be printed when @value{GDBN} detects that
2854 inferiors have started, exited or have been detached.
2857 Many commands will work the same with multiple programs as with a
2858 single program: e.g., @code{print myglobal} will simply display the
2859 value of @code{myglobal} in the current inferior.
2862 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2863 get more info about the relationship of inferiors, programs, address
2864 spaces in a debug session. You can do that with the @w{@code{maint
2865 info program-spaces}} command.
2868 @kindex maint info program-spaces
2869 @item maint info program-spaces
2870 Print a list of all program spaces currently being managed by
2873 @value{GDBN} displays for each program space (in this order):
2877 the program space number assigned by @value{GDBN}
2880 the name of the executable loaded into the program space, with e.g.,
2881 the @code{file} command.
2886 An asterisk @samp{*} preceding the @value{GDBN} program space number
2887 indicates the current program space.
2889 In addition, below each program space line, @value{GDBN} prints extra
2890 information that isn't suitable to display in tabular form. For
2891 example, the list of inferiors bound to the program space.
2894 (@value{GDBP}) maint info program-spaces
2898 Bound inferiors: ID 1 (process 21561)
2901 Here we can see that no inferior is running the program @code{hello},
2902 while @code{process 21561} is running the program @code{goodbye}. On
2903 some targets, it is possible that multiple inferiors are bound to the
2904 same program space. The most common example is that of debugging both
2905 the parent and child processes of a @code{vfork} call. For example,
2908 (@value{GDBP}) maint info program-spaces
2911 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2914 Here, both inferior 2 and inferior 1 are running in the same program
2915 space as a result of inferior 1 having executed a @code{vfork} call.
2919 @section Debugging Programs with Multiple Threads
2921 @cindex threads of execution
2922 @cindex multiple threads
2923 @cindex switching threads
2924 In some operating systems, such as GNU/Linux and Solaris, a single program
2925 may have more than one @dfn{thread} of execution. The precise semantics
2926 of threads differ from one operating system to another, but in general
2927 the threads of a single program are akin to multiple processes---except
2928 that they share one address space (that is, they can all examine and
2929 modify the same variables). On the other hand, each thread has its own
2930 registers and execution stack, and perhaps private memory.
2932 @value{GDBN} provides these facilities for debugging multi-thread
2936 @item automatic notification of new threads
2937 @item @samp{thread @var{thread-id}}, a command to switch among threads
2938 @item @samp{info threads}, a command to inquire about existing threads
2939 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2940 a command to apply a command to a list of threads
2941 @item thread-specific breakpoints
2942 @item @samp{set print thread-events}, which controls printing of
2943 messages on thread start and exit.
2944 @item @samp{set libthread-db-search-path @var{path}}, which lets
2945 the user specify which @code{libthread_db} to use if the default choice
2946 isn't compatible with the program.
2949 @cindex focus of debugging
2950 @cindex current thread
2951 The @value{GDBN} thread debugging facility allows you to observe all
2952 threads while your program runs---but whenever @value{GDBN} takes
2953 control, one thread in particular is always the focus of debugging.
2954 This thread is called the @dfn{current thread}. Debugging commands show
2955 program information from the perspective of the current thread.
2957 @cindex @code{New} @var{systag} message
2958 @cindex thread identifier (system)
2959 @c FIXME-implementors!! It would be more helpful if the [New...] message
2960 @c included GDB's numeric thread handle, so you could just go to that
2961 @c thread without first checking `info threads'.
2962 Whenever @value{GDBN} detects a new thread in your program, it displays
2963 the target system's identification for the thread with a message in the
2964 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2965 whose form varies depending on the particular system. For example, on
2966 @sc{gnu}/Linux, you might see
2969 [New Thread 0x41e02940 (LWP 25582)]
2973 when @value{GDBN} notices a new thread. In contrast, on other systems,
2974 the @var{systag} is simply something like @samp{process 368}, with no
2977 @c FIXME!! (1) Does the [New...] message appear even for the very first
2978 @c thread of a program, or does it only appear for the
2979 @c second---i.e.@: when it becomes obvious we have a multithread
2981 @c (2) *Is* there necessarily a first thread always? Or do some
2982 @c multithread systems permit starting a program with multiple
2983 @c threads ab initio?
2985 @anchor{thread numbers}
2986 @cindex thread number, per inferior
2987 @cindex thread identifier (GDB)
2988 For debugging purposes, @value{GDBN} associates its own thread number
2989 ---always a single integer---with each thread of an inferior. This
2990 number is unique between all threads of an inferior, but not unique
2991 between threads of different inferiors.
2993 @cindex qualified thread ID
2994 You can refer to a given thread in an inferior using the qualified
2995 @var{inferior-num}.@var{thread-num} syntax, also known as
2996 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2997 number and @var{thread-num} being the thread number of the given
2998 inferior. For example, thread @code{2.3} refers to thread number 3 of
2999 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3000 then @value{GDBN} infers you're referring to a thread of the current
3003 Until you create a second inferior, @value{GDBN} does not show the
3004 @var{inferior-num} part of thread IDs, even though you can always use
3005 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3006 of inferior 1, the initial inferior.
3008 @anchor{thread ID lists}
3009 @cindex thread ID lists
3010 Some commands accept a space-separated @dfn{thread ID list} as
3011 argument. A list element can be:
3015 A thread ID as shown in the first field of the @samp{info threads}
3016 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3020 A range of thread numbers, again with or without an inferior
3021 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3022 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3025 All threads of an inferior, specified with a star wildcard, with or
3026 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3027 @samp{1.*}) or @code{*}. The former refers to all threads of the
3028 given inferior, and the latter form without an inferior qualifier
3029 refers to all threads of the current inferior.
3033 For example, if the current inferior is 1, and inferior 7 has one
3034 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3035 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3036 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3037 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3041 @anchor{global thread numbers}
3042 @cindex global thread number
3043 @cindex global thread identifier (GDB)
3044 In addition to a @emph{per-inferior} number, each thread is also
3045 assigned a unique @emph{global} number, also known as @dfn{global
3046 thread ID}, a single integer. Unlike the thread number component of
3047 the thread ID, no two threads have the same global ID, even when
3048 you're debugging multiple inferiors.
3050 From @value{GDBN}'s perspective, a process always has at least one
3051 thread. In other words, @value{GDBN} assigns a thread number to the
3052 program's ``main thread'' even if the program is not multi-threaded.
3054 @vindex $_thread@r{, convenience variable}
3055 @vindex $_gthread@r{, convenience variable}
3056 The debugger convenience variables @samp{$_thread} and
3057 @samp{$_gthread} contain, respectively, the per-inferior thread number
3058 and the global thread number of the current thread. You may find this
3059 useful in writing breakpoint conditional expressions, command scripts,
3060 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3061 general information on convenience variables.
3063 If @value{GDBN} detects the program is multi-threaded, it augments the
3064 usual message about stopping at a breakpoint with the ID and name of
3065 the thread that hit the breakpoint.
3068 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3071 Likewise when the program receives a signal:
3074 Thread 1 "main" received signal SIGINT, Interrupt.
3078 @kindex info threads
3079 @item info threads @r{[}@var{thread-id-list}@r{]}
3081 Display information about one or more threads. With no arguments
3082 displays information about all threads. You can specify the list of
3083 threads that you want to display using the thread ID list syntax
3084 (@pxref{thread ID lists}).
3086 @value{GDBN} displays for each thread (in this order):
3090 the per-inferior thread number assigned by @value{GDBN}
3093 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3094 option was specified
3097 the target system's thread identifier (@var{systag})
3100 the thread's name, if one is known. A thread can either be named by
3101 the user (see @code{thread name}, below), or, in some cases, by the
3105 the current stack frame summary for that thread
3109 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3110 indicates the current thread.
3114 @c end table here to get a little more width for example
3117 (@value{GDBP}) info threads
3119 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3120 2 process 35 thread 23 0x34e5 in sigpause ()
3121 3 process 35 thread 27 0x34e5 in sigpause ()
3125 If you're debugging multiple inferiors, @value{GDBN} displays thread
3126 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3127 Otherwise, only @var{thread-num} is shown.
3129 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3130 indicating each thread's global thread ID:
3133 (@value{GDBP}) info threads
3134 Id GId Target Id Frame
3135 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3136 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3137 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3138 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3141 On Solaris, you can display more information about user threads with a
3142 Solaris-specific command:
3145 @item maint info sol-threads
3146 @kindex maint info sol-threads
3147 @cindex thread info (Solaris)
3148 Display info on Solaris user threads.
3152 @kindex thread @var{thread-id}
3153 @item thread @var{thread-id}
3154 Make thread ID @var{thread-id} the current thread. The command
3155 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3156 the first field of the @samp{info threads} display, with or without an
3157 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3159 @value{GDBN} responds by displaying the system identifier of the
3160 thread you selected, and its current stack frame summary:
3163 (@value{GDBP}) thread 2
3164 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3165 #0 some_function (ignore=0x0) at example.c:8
3166 8 printf ("hello\n");
3170 As with the @samp{[New @dots{}]} message, the form of the text after
3171 @samp{Switching to} depends on your system's conventions for identifying
3174 @kindex thread apply
3175 @cindex apply command to several threads
3176 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3177 The @code{thread apply} command allows you to apply the named
3178 @var{command} to one or more threads. Specify the threads that you
3179 want affected using the thread ID list syntax (@pxref{thread ID
3180 lists}), or specify @code{all} to apply to all threads. To apply a
3181 command to all threads in descending order, type @kbd{thread apply all
3182 @var{command}}. To apply a command to all threads in ascending order,
3183 type @kbd{thread apply all -ascending @var{command}}.
3187 @cindex name a thread
3188 @item thread name [@var{name}]
3189 This command assigns a name to the current thread. If no argument is
3190 given, any existing user-specified name is removed. The thread name
3191 appears in the @samp{info threads} display.
3193 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3194 determine the name of the thread as given by the OS. On these
3195 systems, a name specified with @samp{thread name} will override the
3196 system-give name, and removing the user-specified name will cause
3197 @value{GDBN} to once again display the system-specified name.
3200 @cindex search for a thread
3201 @item thread find [@var{regexp}]
3202 Search for and display thread ids whose name or @var{systag}
3203 matches the supplied regular expression.
3205 As well as being the complement to the @samp{thread name} command,
3206 this command also allows you to identify a thread by its target
3207 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3211 (@value{GDBN}) thread find 26688
3212 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3213 (@value{GDBN}) info thread 4
3215 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3218 @kindex set print thread-events
3219 @cindex print messages on thread start and exit
3220 @item set print thread-events
3221 @itemx set print thread-events on
3222 @itemx set print thread-events off
3223 The @code{set print thread-events} command allows you to enable or
3224 disable printing of messages when @value{GDBN} notices that new threads have
3225 started or that threads have exited. By default, these messages will
3226 be printed if detection of these events is supported by the target.
3227 Note that these messages cannot be disabled on all targets.
3229 @kindex show print thread-events
3230 @item show print thread-events
3231 Show whether messages will be printed when @value{GDBN} detects that threads
3232 have started and exited.
3235 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3236 more information about how @value{GDBN} behaves when you stop and start
3237 programs with multiple threads.
3239 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3240 watchpoints in programs with multiple threads.
3242 @anchor{set libthread-db-search-path}
3244 @kindex set libthread-db-search-path
3245 @cindex search path for @code{libthread_db}
3246 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3247 If this variable is set, @var{path} is a colon-separated list of
3248 directories @value{GDBN} will use to search for @code{libthread_db}.
3249 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3250 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3251 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3254 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3255 @code{libthread_db} library to obtain information about threads in the
3256 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3257 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3258 specific thread debugging library loading is enabled
3259 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3261 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3262 refers to the default system directories that are
3263 normally searched for loading shared libraries. The @samp{$sdir} entry
3264 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3265 (@pxref{libthread_db.so.1 file}).
3267 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3268 refers to the directory from which @code{libpthread}
3269 was loaded in the inferior process.
3271 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3272 @value{GDBN} attempts to initialize it with the current inferior process.
3273 If this initialization fails (which could happen because of a version
3274 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3275 will unload @code{libthread_db}, and continue with the next directory.
3276 If none of @code{libthread_db} libraries initialize successfully,
3277 @value{GDBN} will issue a warning and thread debugging will be disabled.
3279 Setting @code{libthread-db-search-path} is currently implemented
3280 only on some platforms.
3282 @kindex show libthread-db-search-path
3283 @item show libthread-db-search-path
3284 Display current libthread_db search path.
3286 @kindex set debug libthread-db
3287 @kindex show debug libthread-db
3288 @cindex debugging @code{libthread_db}
3289 @item set debug libthread-db
3290 @itemx show debug libthread-db
3291 Turns on or off display of @code{libthread_db}-related events.
3292 Use @code{1} to enable, @code{0} to disable.
3296 @section Debugging Forks
3298 @cindex fork, debugging programs which call
3299 @cindex multiple processes
3300 @cindex processes, multiple
3301 On most systems, @value{GDBN} has no special support for debugging
3302 programs which create additional processes using the @code{fork}
3303 function. When a program forks, @value{GDBN} will continue to debug the
3304 parent process and the child process will run unimpeded. If you have
3305 set a breakpoint in any code which the child then executes, the child
3306 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3307 will cause it to terminate.
3309 However, if you want to debug the child process there is a workaround
3310 which isn't too painful. Put a call to @code{sleep} in the code which
3311 the child process executes after the fork. It may be useful to sleep
3312 only if a certain environment variable is set, or a certain file exists,
3313 so that the delay need not occur when you don't want to run @value{GDBN}
3314 on the child. While the child is sleeping, use the @code{ps} program to
3315 get its process ID. Then tell @value{GDBN} (a new invocation of
3316 @value{GDBN} if you are also debugging the parent process) to attach to
3317 the child process (@pxref{Attach}). From that point on you can debug
3318 the child process just like any other process which you attached to.
3320 On some systems, @value{GDBN} provides support for debugging programs
3321 that create additional processes using the @code{fork} or @code{vfork}
3322 functions. On @sc{gnu}/Linux platforms, this feature is supported
3323 with kernel version 2.5.46 and later.
3325 The fork debugging commands are supported in native mode and when
3326 connected to @code{gdbserver} in either @code{target remote} mode or
3327 @code{target extended-remote} mode.
3329 By default, when a program forks, @value{GDBN} will continue to debug
3330 the parent process and the child process will run unimpeded.
3332 If you want to follow the child process instead of the parent process,
3333 use the command @w{@code{set follow-fork-mode}}.
3336 @kindex set follow-fork-mode
3337 @item set follow-fork-mode @var{mode}
3338 Set the debugger response to a program call of @code{fork} or
3339 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3340 process. The @var{mode} argument can be:
3344 The original process is debugged after a fork. The child process runs
3345 unimpeded. This is the default.
3348 The new process is debugged after a fork. The parent process runs
3353 @kindex show follow-fork-mode
3354 @item show follow-fork-mode
3355 Display the current debugger response to a @code{fork} or @code{vfork} call.
3358 @cindex debugging multiple processes
3359 On Linux, if you want to debug both the parent and child processes, use the
3360 command @w{@code{set detach-on-fork}}.
3363 @kindex set detach-on-fork
3364 @item set detach-on-fork @var{mode}
3365 Tells gdb whether to detach one of the processes after a fork, or
3366 retain debugger control over them both.
3370 The child process (or parent process, depending on the value of
3371 @code{follow-fork-mode}) will be detached and allowed to run
3372 independently. This is the default.
3375 Both processes will be held under the control of @value{GDBN}.
3376 One process (child or parent, depending on the value of
3377 @code{follow-fork-mode}) is debugged as usual, while the other
3382 @kindex show detach-on-fork
3383 @item show detach-on-fork
3384 Show whether detach-on-fork mode is on/off.
3387 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3388 will retain control of all forked processes (including nested forks).
3389 You can list the forked processes under the control of @value{GDBN} by
3390 using the @w{@code{info inferiors}} command, and switch from one fork
3391 to another by using the @code{inferior} command (@pxref{Inferiors and
3392 Programs, ,Debugging Multiple Inferiors and Programs}).
3394 To quit debugging one of the forked processes, you can either detach
3395 from it by using the @w{@code{detach inferiors}} command (allowing it
3396 to run independently), or kill it using the @w{@code{kill inferiors}}
3397 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3400 If you ask to debug a child process and a @code{vfork} is followed by an
3401 @code{exec}, @value{GDBN} executes the new target up to the first
3402 breakpoint in the new target. If you have a breakpoint set on
3403 @code{main} in your original program, the breakpoint will also be set on
3404 the child process's @code{main}.
3406 On some systems, when a child process is spawned by @code{vfork}, you
3407 cannot debug the child or parent until an @code{exec} call completes.
3409 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3410 call executes, the new target restarts. To restart the parent
3411 process, use the @code{file} command with the parent executable name
3412 as its argument. By default, after an @code{exec} call executes,
3413 @value{GDBN} discards the symbols of the previous executable image.
3414 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3418 @kindex set follow-exec-mode
3419 @item set follow-exec-mode @var{mode}
3421 Set debugger response to a program call of @code{exec}. An
3422 @code{exec} call replaces the program image of a process.
3424 @code{follow-exec-mode} can be:
3428 @value{GDBN} creates a new inferior and rebinds the process to this
3429 new inferior. The program the process was running before the
3430 @code{exec} call can be restarted afterwards by restarting the
3436 (@value{GDBP}) info inferiors
3438 Id Description Executable
3441 process 12020 is executing new program: prog2
3442 Program exited normally.
3443 (@value{GDBP}) info inferiors
3444 Id Description Executable
3450 @value{GDBN} keeps the process bound to the same inferior. The new
3451 executable image replaces the previous executable loaded in the
3452 inferior. Restarting the inferior after the @code{exec} call, with
3453 e.g., the @code{run} command, restarts the executable the process was
3454 running after the @code{exec} call. This is the default mode.
3459 (@value{GDBP}) info inferiors
3460 Id Description Executable
3463 process 12020 is executing new program: prog2
3464 Program exited normally.
3465 (@value{GDBP}) info inferiors
3466 Id Description Executable
3473 @code{follow-exec-mode} is supported in native mode and
3474 @code{target extended-remote} mode.
3476 You can use the @code{catch} command to make @value{GDBN} stop whenever
3477 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3478 Catchpoints, ,Setting Catchpoints}.
3480 @node Checkpoint/Restart
3481 @section Setting a @emph{Bookmark} to Return to Later
3486 @cindex snapshot of a process
3487 @cindex rewind program state
3489 On certain operating systems@footnote{Currently, only
3490 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3491 program's state, called a @dfn{checkpoint}, and come back to it
3494 Returning to a checkpoint effectively undoes everything that has
3495 happened in the program since the @code{checkpoint} was saved. This
3496 includes changes in memory, registers, and even (within some limits)
3497 system state. Effectively, it is like going back in time to the
3498 moment when the checkpoint was saved.
3500 Thus, if you're stepping thru a program and you think you're
3501 getting close to the point where things go wrong, you can save
3502 a checkpoint. Then, if you accidentally go too far and miss
3503 the critical statement, instead of having to restart your program
3504 from the beginning, you can just go back to the checkpoint and
3505 start again from there.
3507 This can be especially useful if it takes a lot of time or
3508 steps to reach the point where you think the bug occurs.
3510 To use the @code{checkpoint}/@code{restart} method of debugging:
3515 Save a snapshot of the debugged program's current execution state.
3516 The @code{checkpoint} command takes no arguments, but each checkpoint
3517 is assigned a small integer id, similar to a breakpoint id.
3519 @kindex info checkpoints
3520 @item info checkpoints
3521 List the checkpoints that have been saved in the current debugging
3522 session. For each checkpoint, the following information will be
3529 @item Source line, or label
3532 @kindex restart @var{checkpoint-id}
3533 @item restart @var{checkpoint-id}
3534 Restore the program state that was saved as checkpoint number
3535 @var{checkpoint-id}. All program variables, registers, stack frames
3536 etc.@: will be returned to the values that they had when the checkpoint
3537 was saved. In essence, gdb will ``wind back the clock'' to the point
3538 in time when the checkpoint was saved.
3540 Note that breakpoints, @value{GDBN} variables, command history etc.
3541 are not affected by restoring a checkpoint. In general, a checkpoint
3542 only restores things that reside in the program being debugged, not in
3545 @kindex delete checkpoint @var{checkpoint-id}
3546 @item delete checkpoint @var{checkpoint-id}
3547 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3551 Returning to a previously saved checkpoint will restore the user state
3552 of the program being debugged, plus a significant subset of the system
3553 (OS) state, including file pointers. It won't ``un-write'' data from
3554 a file, but it will rewind the file pointer to the previous location,
3555 so that the previously written data can be overwritten. For files
3556 opened in read mode, the pointer will also be restored so that the
3557 previously read data can be read again.
3559 Of course, characters that have been sent to a printer (or other
3560 external device) cannot be ``snatched back'', and characters received
3561 from eg.@: a serial device can be removed from internal program buffers,
3562 but they cannot be ``pushed back'' into the serial pipeline, ready to
3563 be received again. Similarly, the actual contents of files that have
3564 been changed cannot be restored (at this time).
3566 However, within those constraints, you actually can ``rewind'' your
3567 program to a previously saved point in time, and begin debugging it
3568 again --- and you can change the course of events so as to debug a
3569 different execution path this time.
3571 @cindex checkpoints and process id
3572 Finally, there is one bit of internal program state that will be
3573 different when you return to a checkpoint --- the program's process
3574 id. Each checkpoint will have a unique process id (or @var{pid}),
3575 and each will be different from the program's original @var{pid}.
3576 If your program has saved a local copy of its process id, this could
3577 potentially pose a problem.
3579 @subsection A Non-obvious Benefit of Using Checkpoints
3581 On some systems such as @sc{gnu}/Linux, address space randomization
3582 is performed on new processes for security reasons. This makes it
3583 difficult or impossible to set a breakpoint, or watchpoint, on an
3584 absolute address if you have to restart the program, since the
3585 absolute location of a symbol will change from one execution to the
3588 A checkpoint, however, is an @emph{identical} copy of a process.
3589 Therefore if you create a checkpoint at (eg.@:) the start of main,
3590 and simply return to that checkpoint instead of restarting the
3591 process, you can avoid the effects of address randomization and
3592 your symbols will all stay in the same place.
3595 @chapter Stopping and Continuing
3597 The principal purposes of using a debugger are so that you can stop your
3598 program before it terminates; or so that, if your program runs into
3599 trouble, you can investigate and find out why.
3601 Inside @value{GDBN}, your program may stop for any of several reasons,
3602 such as a signal, a breakpoint, or reaching a new line after a
3603 @value{GDBN} command such as @code{step}. You may then examine and
3604 change variables, set new breakpoints or remove old ones, and then
3605 continue execution. Usually, the messages shown by @value{GDBN} provide
3606 ample explanation of the status of your program---but you can also
3607 explicitly request this information at any time.
3610 @kindex info program
3612 Display information about the status of your program: whether it is
3613 running or not, what process it is, and why it stopped.
3617 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3618 * Continuing and Stepping:: Resuming execution
3619 * Skipping Over Functions and Files::
3620 Skipping over functions and files
3622 * Thread Stops:: Stopping and starting multi-thread programs
3626 @section Breakpoints, Watchpoints, and Catchpoints
3629 A @dfn{breakpoint} makes your program stop whenever a certain point in
3630 the program is reached. For each breakpoint, you can add conditions to
3631 control in finer detail whether your program stops. You can set
3632 breakpoints with the @code{break} command and its variants (@pxref{Set
3633 Breaks, ,Setting Breakpoints}), to specify the place where your program
3634 should stop by line number, function name or exact address in the
3637 On some systems, you can set breakpoints in shared libraries before
3638 the executable is run.
3641 @cindex data breakpoints
3642 @cindex memory tracing
3643 @cindex breakpoint on memory address
3644 @cindex breakpoint on variable modification
3645 A @dfn{watchpoint} is a special breakpoint that stops your program
3646 when the value of an expression changes. The expression may be a value
3647 of a variable, or it could involve values of one or more variables
3648 combined by operators, such as @samp{a + b}. This is sometimes called
3649 @dfn{data breakpoints}. You must use a different command to set
3650 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3651 from that, you can manage a watchpoint like any other breakpoint: you
3652 enable, disable, and delete both breakpoints and watchpoints using the
3655 You can arrange to have values from your program displayed automatically
3656 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3660 @cindex breakpoint on events
3661 A @dfn{catchpoint} is another special breakpoint that stops your program
3662 when a certain kind of event occurs, such as the throwing of a C@t{++}
3663 exception or the loading of a library. As with watchpoints, you use a
3664 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3665 Catchpoints}), but aside from that, you can manage a catchpoint like any
3666 other breakpoint. (To stop when your program receives a signal, use the
3667 @code{handle} command; see @ref{Signals, ,Signals}.)
3669 @cindex breakpoint numbers
3670 @cindex numbers for breakpoints
3671 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3672 catchpoint when you create it; these numbers are successive integers
3673 starting with one. In many of the commands for controlling various
3674 features of breakpoints you use the breakpoint number to say which
3675 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3676 @dfn{disabled}; if disabled, it has no effect on your program until you
3679 @cindex breakpoint ranges
3680 @cindex breakpoint lists
3681 @cindex ranges of breakpoints
3682 @cindex lists of breakpoints
3683 Some @value{GDBN} commands accept a space-separated list of breakpoints
3684 on which to operate. A list element can be either a single breakpoint number,
3685 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3686 When a breakpoint list is given to a command, all breakpoints in that list
3690 * Set Breaks:: Setting breakpoints
3691 * Set Watchpoints:: Setting watchpoints
3692 * Set Catchpoints:: Setting catchpoints
3693 * Delete Breaks:: Deleting breakpoints
3694 * Disabling:: Disabling breakpoints
3695 * Conditions:: Break conditions
3696 * Break Commands:: Breakpoint command lists
3697 * Dynamic Printf:: Dynamic printf
3698 * Save Breakpoints:: How to save breakpoints in a file
3699 * Static Probe Points:: Listing static probe points
3700 * Error in Breakpoints:: ``Cannot insert breakpoints''
3701 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3705 @subsection Setting Breakpoints
3707 @c FIXME LMB what does GDB do if no code on line of breakpt?
3708 @c consider in particular declaration with/without initialization.
3710 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3713 @kindex b @r{(@code{break})}
3714 @vindex $bpnum@r{, convenience variable}
3715 @cindex latest breakpoint
3716 Breakpoints are set with the @code{break} command (abbreviated
3717 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3718 number of the breakpoint you've set most recently; see @ref{Convenience
3719 Vars,, Convenience Variables}, for a discussion of what you can do with
3720 convenience variables.
3723 @item break @var{location}
3724 Set a breakpoint at the given @var{location}, which can specify a
3725 function name, a line number, or an address of an instruction.
3726 (@xref{Specify Location}, for a list of all the possible ways to
3727 specify a @var{location}.) The breakpoint will stop your program just
3728 before it executes any of the code in the specified @var{location}.
3730 When using source languages that permit overloading of symbols, such as
3731 C@t{++}, a function name may refer to more than one possible place to break.
3732 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3735 It is also possible to insert a breakpoint that will stop the program
3736 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3737 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3740 When called without any arguments, @code{break} sets a breakpoint at
3741 the next instruction to be executed in the selected stack frame
3742 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3743 innermost, this makes your program stop as soon as control
3744 returns to that frame. This is similar to the effect of a
3745 @code{finish} command in the frame inside the selected frame---except
3746 that @code{finish} does not leave an active breakpoint. If you use
3747 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3748 the next time it reaches the current location; this may be useful
3751 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3752 least one instruction has been executed. If it did not do this, you
3753 would be unable to proceed past a breakpoint without first disabling the
3754 breakpoint. This rule applies whether or not the breakpoint already
3755 existed when your program stopped.
3757 @item break @dots{} if @var{cond}
3758 Set a breakpoint with condition @var{cond}; evaluate the expression
3759 @var{cond} each time the breakpoint is reached, and stop only if the
3760 value is nonzero---that is, if @var{cond} evaluates as true.
3761 @samp{@dots{}} stands for one of the possible arguments described
3762 above (or no argument) specifying where to break. @xref{Conditions,
3763 ,Break Conditions}, for more information on breakpoint conditions.
3766 @item tbreak @var{args}
3767 Set a breakpoint enabled only for one stop. The @var{args} are the
3768 same as for the @code{break} command, and the breakpoint is set in the same
3769 way, but the breakpoint is automatically deleted after the first time your
3770 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3773 @cindex hardware breakpoints
3774 @item hbreak @var{args}
3775 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3776 @code{break} command and the breakpoint is set in the same way, but the
3777 breakpoint requires hardware support and some target hardware may not
3778 have this support. The main purpose of this is EPROM/ROM code
3779 debugging, so you can set a breakpoint at an instruction without
3780 changing the instruction. This can be used with the new trap-generation
3781 provided by SPARClite DSU and most x86-based targets. These targets
3782 will generate traps when a program accesses some data or instruction
3783 address that is assigned to the debug registers. However the hardware
3784 breakpoint registers can take a limited number of breakpoints. For
3785 example, on the DSU, only two data breakpoints can be set at a time, and
3786 @value{GDBN} will reject this command if more than two are used. Delete
3787 or disable unused hardware breakpoints before setting new ones
3788 (@pxref{Disabling, ,Disabling Breakpoints}).
3789 @xref{Conditions, ,Break Conditions}.
3790 For remote targets, you can restrict the number of hardware
3791 breakpoints @value{GDBN} will use, see @ref{set remote
3792 hardware-breakpoint-limit}.
3795 @item thbreak @var{args}
3796 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3797 are the same as for the @code{hbreak} command and the breakpoint is set in
3798 the same way. However, like the @code{tbreak} command,
3799 the breakpoint is automatically deleted after the
3800 first time your program stops there. Also, like the @code{hbreak}
3801 command, the breakpoint requires hardware support and some target hardware
3802 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3803 See also @ref{Conditions, ,Break Conditions}.
3806 @cindex regular expression
3807 @cindex breakpoints at functions matching a regexp
3808 @cindex set breakpoints in many functions
3809 @item rbreak @var{regex}
3810 Set breakpoints on all functions matching the regular expression
3811 @var{regex}. This command sets an unconditional breakpoint on all
3812 matches, printing a list of all breakpoints it set. Once these
3813 breakpoints are set, they are treated just like the breakpoints set with
3814 the @code{break} command. You can delete them, disable them, or make
3815 them conditional the same way as any other breakpoint.
3817 The syntax of the regular expression is the standard one used with tools
3818 like @file{grep}. Note that this is different from the syntax used by
3819 shells, so for instance @code{foo*} matches all functions that include
3820 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3821 @code{.*} leading and trailing the regular expression you supply, so to
3822 match only functions that begin with @code{foo}, use @code{^foo}.
3824 @cindex non-member C@t{++} functions, set breakpoint in
3825 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3826 breakpoints on overloaded functions that are not members of any special
3829 @cindex set breakpoints on all functions
3830 The @code{rbreak} command can be used to set breakpoints in
3831 @strong{all} the functions in a program, like this:
3834 (@value{GDBP}) rbreak .
3837 @item rbreak @var{file}:@var{regex}
3838 If @code{rbreak} is called with a filename qualification, it limits
3839 the search for functions matching the given regular expression to the
3840 specified @var{file}. This can be used, for example, to set breakpoints on
3841 every function in a given file:
3844 (@value{GDBP}) rbreak file.c:.
3847 The colon separating the filename qualifier from the regex may
3848 optionally be surrounded by spaces.
3850 @kindex info breakpoints
3851 @cindex @code{$_} and @code{info breakpoints}
3852 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3853 @itemx info break @r{[}@var{list}@dots{}@r{]}
3854 Print a table of all breakpoints, watchpoints, and catchpoints set and
3855 not deleted. Optional argument @var{n} means print information only
3856 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3857 For each breakpoint, following columns are printed:
3860 @item Breakpoint Numbers
3862 Breakpoint, watchpoint, or catchpoint.
3864 Whether the breakpoint is marked to be disabled or deleted when hit.
3865 @item Enabled or Disabled
3866 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3867 that are not enabled.
3869 Where the breakpoint is in your program, as a memory address. For a
3870 pending breakpoint whose address is not yet known, this field will
3871 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3872 library that has the symbol or line referred by breakpoint is loaded.
3873 See below for details. A breakpoint with several locations will
3874 have @samp{<MULTIPLE>} in this field---see below for details.
3876 Where the breakpoint is in the source for your program, as a file and
3877 line number. For a pending breakpoint, the original string passed to
3878 the breakpoint command will be listed as it cannot be resolved until
3879 the appropriate shared library is loaded in the future.
3883 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3884 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3885 @value{GDBN} on the host's side. If it is ``target'', then the condition
3886 is evaluated by the target. The @code{info break} command shows
3887 the condition on the line following the affected breakpoint, together with
3888 its condition evaluation mode in between parentheses.
3890 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3891 allowed to have a condition specified for it. The condition is not parsed for
3892 validity until a shared library is loaded that allows the pending
3893 breakpoint to resolve to a valid location.
3896 @code{info break} with a breakpoint
3897 number @var{n} as argument lists only that breakpoint. The
3898 convenience variable @code{$_} and the default examining-address for
3899 the @code{x} command are set to the address of the last breakpoint
3900 listed (@pxref{Memory, ,Examining Memory}).
3903 @code{info break} displays a count of the number of times the breakpoint
3904 has been hit. This is especially useful in conjunction with the
3905 @code{ignore} command. You can ignore a large number of breakpoint
3906 hits, look at the breakpoint info to see how many times the breakpoint
3907 was hit, and then run again, ignoring one less than that number. This
3908 will get you quickly to the last hit of that breakpoint.
3911 For a breakpoints with an enable count (xref) greater than 1,
3912 @code{info break} also displays that count.
3916 @value{GDBN} allows you to set any number of breakpoints at the same place in
3917 your program. There is nothing silly or meaningless about this. When
3918 the breakpoints are conditional, this is even useful
3919 (@pxref{Conditions, ,Break Conditions}).
3921 @cindex multiple locations, breakpoints
3922 @cindex breakpoints, multiple locations
3923 It is possible that a breakpoint corresponds to several locations
3924 in your program. Examples of this situation are:
3928 Multiple functions in the program may have the same name.
3931 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3932 instances of the function body, used in different cases.
3935 For a C@t{++} template function, a given line in the function can
3936 correspond to any number of instantiations.
3939 For an inlined function, a given source line can correspond to
3940 several places where that function is inlined.
3943 In all those cases, @value{GDBN} will insert a breakpoint at all
3944 the relevant locations.
3946 A breakpoint with multiple locations is displayed in the breakpoint
3947 table using several rows---one header row, followed by one row for
3948 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3949 address column. The rows for individual locations contain the actual
3950 addresses for locations, and show the functions to which those
3951 locations belong. The number column for a location is of the form
3952 @var{breakpoint-number}.@var{location-number}.
3957 Num Type Disp Enb Address What
3958 1 breakpoint keep y <MULTIPLE>
3960 breakpoint already hit 1 time
3961 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3962 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3965 You cannot delete the individual locations from a breakpoint. However,
3966 each location can be individually enabled or disabled by passing
3967 @var{breakpoint-number}.@var{location-number} as argument to the
3968 @code{enable} and @code{disable} commands. It's also possible to
3969 @code{enable} and @code{disable} a range of @var{location-number}
3970 locations using a @var{breakpoint-number} and two @var{location-number}s,
3971 in increasing order, separated by a hyphen, like
3972 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
3973 in which case @value{GDBN} acts on all the locations in the range (inclusive).
3974 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
3975 all of the locations that belong to that breakpoint.
3977 @cindex pending breakpoints
3978 It's quite common to have a breakpoint inside a shared library.
3979 Shared libraries can be loaded and unloaded explicitly,
3980 and possibly repeatedly, as the program is executed. To support
3981 this use case, @value{GDBN} updates breakpoint locations whenever
3982 any shared library is loaded or unloaded. Typically, you would
3983 set a breakpoint in a shared library at the beginning of your
3984 debugging session, when the library is not loaded, and when the
3985 symbols from the library are not available. When you try to set
3986 breakpoint, @value{GDBN} will ask you if you want to set
3987 a so called @dfn{pending breakpoint}---breakpoint whose address
3988 is not yet resolved.
3990 After the program is run, whenever a new shared library is loaded,
3991 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3992 shared library contains the symbol or line referred to by some
3993 pending breakpoint, that breakpoint is resolved and becomes an
3994 ordinary breakpoint. When a library is unloaded, all breakpoints
3995 that refer to its symbols or source lines become pending again.
3997 This logic works for breakpoints with multiple locations, too. For
3998 example, if you have a breakpoint in a C@t{++} template function, and
3999 a newly loaded shared library has an instantiation of that template,
4000 a new location is added to the list of locations for the breakpoint.
4002 Except for having unresolved address, pending breakpoints do not
4003 differ from regular breakpoints. You can set conditions or commands,
4004 enable and disable them and perform other breakpoint operations.
4006 @value{GDBN} provides some additional commands for controlling what
4007 happens when the @samp{break} command cannot resolve breakpoint
4008 address specification to an address:
4010 @kindex set breakpoint pending
4011 @kindex show breakpoint pending
4013 @item set breakpoint pending auto
4014 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4015 location, it queries you whether a pending breakpoint should be created.
4017 @item set breakpoint pending on
4018 This indicates that an unrecognized breakpoint location should automatically
4019 result in a pending breakpoint being created.
4021 @item set breakpoint pending off
4022 This indicates that pending breakpoints are not to be created. Any
4023 unrecognized breakpoint location results in an error. This setting does
4024 not affect any pending breakpoints previously created.
4026 @item show breakpoint pending
4027 Show the current behavior setting for creating pending breakpoints.
4030 The settings above only affect the @code{break} command and its
4031 variants. Once breakpoint is set, it will be automatically updated
4032 as shared libraries are loaded and unloaded.
4034 @cindex automatic hardware breakpoints
4035 For some targets, @value{GDBN} can automatically decide if hardware or
4036 software breakpoints should be used, depending on whether the
4037 breakpoint address is read-only or read-write. This applies to
4038 breakpoints set with the @code{break} command as well as to internal
4039 breakpoints set by commands like @code{next} and @code{finish}. For
4040 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4043 You can control this automatic behaviour with the following commands:
4045 @kindex set breakpoint auto-hw
4046 @kindex show breakpoint auto-hw
4048 @item set breakpoint auto-hw on
4049 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4050 will try to use the target memory map to decide if software or hardware
4051 breakpoint must be used.
4053 @item set breakpoint auto-hw off
4054 This indicates @value{GDBN} should not automatically select breakpoint
4055 type. If the target provides a memory map, @value{GDBN} will warn when
4056 trying to set software breakpoint at a read-only address.
4059 @value{GDBN} normally implements breakpoints by replacing the program code
4060 at the breakpoint address with a special instruction, which, when
4061 executed, given control to the debugger. By default, the program
4062 code is so modified only when the program is resumed. As soon as
4063 the program stops, @value{GDBN} restores the original instructions. This
4064 behaviour guards against leaving breakpoints inserted in the
4065 target should gdb abrubptly disconnect. However, with slow remote
4066 targets, inserting and removing breakpoint can reduce the performance.
4067 This behavior can be controlled with the following commands::
4069 @kindex set breakpoint always-inserted
4070 @kindex show breakpoint always-inserted
4072 @item set breakpoint always-inserted off
4073 All breakpoints, including newly added by the user, are inserted in
4074 the target only when the target is resumed. All breakpoints are
4075 removed from the target when it stops. This is the default mode.
4077 @item set breakpoint always-inserted on
4078 Causes all breakpoints to be inserted in the target at all times. If
4079 the user adds a new breakpoint, or changes an existing breakpoint, the
4080 breakpoints in the target are updated immediately. A breakpoint is
4081 removed from the target only when breakpoint itself is deleted.
4084 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4085 when a breakpoint breaks. If the condition is true, then the process being
4086 debugged stops, otherwise the process is resumed.
4088 If the target supports evaluating conditions on its end, @value{GDBN} may
4089 download the breakpoint, together with its conditions, to it.
4091 This feature can be controlled via the following commands:
4093 @kindex set breakpoint condition-evaluation
4094 @kindex show breakpoint condition-evaluation
4096 @item set breakpoint condition-evaluation host
4097 This option commands @value{GDBN} to evaluate the breakpoint
4098 conditions on the host's side. Unconditional breakpoints are sent to
4099 the target which in turn receives the triggers and reports them back to GDB
4100 for condition evaluation. This is the standard evaluation mode.
4102 @item set breakpoint condition-evaluation target
4103 This option commands @value{GDBN} to download breakpoint conditions
4104 to the target at the moment of their insertion. The target
4105 is responsible for evaluating the conditional expression and reporting
4106 breakpoint stop events back to @value{GDBN} whenever the condition
4107 is true. Due to limitations of target-side evaluation, some conditions
4108 cannot be evaluated there, e.g., conditions that depend on local data
4109 that is only known to the host. Examples include
4110 conditional expressions involving convenience variables, complex types
4111 that cannot be handled by the agent expression parser and expressions
4112 that are too long to be sent over to the target, specially when the
4113 target is a remote system. In these cases, the conditions will be
4114 evaluated by @value{GDBN}.
4116 @item set breakpoint condition-evaluation auto
4117 This is the default mode. If the target supports evaluating breakpoint
4118 conditions on its end, @value{GDBN} will download breakpoint conditions to
4119 the target (limitations mentioned previously apply). If the target does
4120 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4121 to evaluating all these conditions on the host's side.
4125 @cindex negative breakpoint numbers
4126 @cindex internal @value{GDBN} breakpoints
4127 @value{GDBN} itself sometimes sets breakpoints in your program for
4128 special purposes, such as proper handling of @code{longjmp} (in C
4129 programs). These internal breakpoints are assigned negative numbers,
4130 starting with @code{-1}; @samp{info breakpoints} does not display them.
4131 You can see these breakpoints with the @value{GDBN} maintenance command
4132 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4135 @node Set Watchpoints
4136 @subsection Setting Watchpoints
4138 @cindex setting watchpoints
4139 You can use a watchpoint to stop execution whenever the value of an
4140 expression changes, without having to predict a particular place where
4141 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4142 The expression may be as simple as the value of a single variable, or
4143 as complex as many variables combined by operators. Examples include:
4147 A reference to the value of a single variable.
4150 An address cast to an appropriate data type. For example,
4151 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4152 address (assuming an @code{int} occupies 4 bytes).
4155 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4156 expression can use any operators valid in the program's native
4157 language (@pxref{Languages}).
4160 You can set a watchpoint on an expression even if the expression can
4161 not be evaluated yet. For instance, you can set a watchpoint on
4162 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4163 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4164 the expression produces a valid value. If the expression becomes
4165 valid in some other way than changing a variable (e.g.@: if the memory
4166 pointed to by @samp{*global_ptr} becomes readable as the result of a
4167 @code{malloc} call), @value{GDBN} may not stop until the next time
4168 the expression changes.
4170 @cindex software watchpoints
4171 @cindex hardware watchpoints
4172 Depending on your system, watchpoints may be implemented in software or
4173 hardware. @value{GDBN} does software watchpointing by single-stepping your
4174 program and testing the variable's value each time, which is hundreds of
4175 times slower than normal execution. (But this may still be worth it, to
4176 catch errors where you have no clue what part of your program is the
4179 On some systems, such as most PowerPC or x86-based targets,
4180 @value{GDBN} includes support for hardware watchpoints, which do not
4181 slow down the running of your program.
4185 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4186 Set a watchpoint for an expression. @value{GDBN} will break when the
4187 expression @var{expr} is written into by the program and its value
4188 changes. The simplest (and the most popular) use of this command is
4189 to watch the value of a single variable:
4192 (@value{GDBP}) watch foo
4195 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4196 argument, @value{GDBN} breaks only when the thread identified by
4197 @var{thread-id} changes the value of @var{expr}. If any other threads
4198 change the value of @var{expr}, @value{GDBN} will not break. Note
4199 that watchpoints restricted to a single thread in this way only work
4200 with Hardware Watchpoints.
4202 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4203 (see below). The @code{-location} argument tells @value{GDBN} to
4204 instead watch the memory referred to by @var{expr}. In this case,
4205 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4206 and watch the memory at that address. The type of the result is used
4207 to determine the size of the watched memory. If the expression's
4208 result does not have an address, then @value{GDBN} will print an
4211 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4212 of masked watchpoints, if the current architecture supports this
4213 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4214 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4215 to an address to watch. The mask specifies that some bits of an address
4216 (the bits which are reset in the mask) should be ignored when matching
4217 the address accessed by the inferior against the watchpoint address.
4218 Thus, a masked watchpoint watches many addresses simultaneously---those
4219 addresses whose unmasked bits are identical to the unmasked bits in the
4220 watchpoint address. The @code{mask} argument implies @code{-location}.
4224 (@value{GDBP}) watch foo mask 0xffff00ff
4225 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4229 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4230 Set a watchpoint that will break when the value of @var{expr} is read
4234 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4235 Set a watchpoint that will break when @var{expr} is either read from
4236 or written into by the program.
4238 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4239 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4240 This command prints a list of watchpoints, using the same format as
4241 @code{info break} (@pxref{Set Breaks}).
4244 If you watch for a change in a numerically entered address you need to
4245 dereference it, as the address itself is just a constant number which will
4246 never change. @value{GDBN} refuses to create a watchpoint that watches
4247 a never-changing value:
4250 (@value{GDBP}) watch 0x600850
4251 Cannot watch constant value 0x600850.
4252 (@value{GDBP}) watch *(int *) 0x600850
4253 Watchpoint 1: *(int *) 6293584
4256 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4257 watchpoints execute very quickly, and the debugger reports a change in
4258 value at the exact instruction where the change occurs. If @value{GDBN}
4259 cannot set a hardware watchpoint, it sets a software watchpoint, which
4260 executes more slowly and reports the change in value at the next
4261 @emph{statement}, not the instruction, after the change occurs.
4263 @cindex use only software watchpoints
4264 You can force @value{GDBN} to use only software watchpoints with the
4265 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4266 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4267 the underlying system supports them. (Note that hardware-assisted
4268 watchpoints that were set @emph{before} setting
4269 @code{can-use-hw-watchpoints} to zero will still use the hardware
4270 mechanism of watching expression values.)
4273 @item set can-use-hw-watchpoints
4274 @kindex set can-use-hw-watchpoints
4275 Set whether or not to use hardware watchpoints.
4277 @item show can-use-hw-watchpoints
4278 @kindex show can-use-hw-watchpoints
4279 Show the current mode of using hardware watchpoints.
4282 For remote targets, you can restrict the number of hardware
4283 watchpoints @value{GDBN} will use, see @ref{set remote
4284 hardware-breakpoint-limit}.
4286 When you issue the @code{watch} command, @value{GDBN} reports
4289 Hardware watchpoint @var{num}: @var{expr}
4293 if it was able to set a hardware watchpoint.
4295 Currently, the @code{awatch} and @code{rwatch} commands can only set
4296 hardware watchpoints, because accesses to data that don't change the
4297 value of the watched expression cannot be detected without examining
4298 every instruction as it is being executed, and @value{GDBN} does not do
4299 that currently. If @value{GDBN} finds that it is unable to set a
4300 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4301 will print a message like this:
4304 Expression cannot be implemented with read/access watchpoint.
4307 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4308 data type of the watched expression is wider than what a hardware
4309 watchpoint on the target machine can handle. For example, some systems
4310 can only watch regions that are up to 4 bytes wide; on such systems you
4311 cannot set hardware watchpoints for an expression that yields a
4312 double-precision floating-point number (which is typically 8 bytes
4313 wide). As a work-around, it might be possible to break the large region
4314 into a series of smaller ones and watch them with separate watchpoints.
4316 If you set too many hardware watchpoints, @value{GDBN} might be unable
4317 to insert all of them when you resume the execution of your program.
4318 Since the precise number of active watchpoints is unknown until such
4319 time as the program is about to be resumed, @value{GDBN} might not be
4320 able to warn you about this when you set the watchpoints, and the
4321 warning will be printed only when the program is resumed:
4324 Hardware watchpoint @var{num}: Could not insert watchpoint
4328 If this happens, delete or disable some of the watchpoints.
4330 Watching complex expressions that reference many variables can also
4331 exhaust the resources available for hardware-assisted watchpoints.
4332 That's because @value{GDBN} needs to watch every variable in the
4333 expression with separately allocated resources.
4335 If you call a function interactively using @code{print} or @code{call},
4336 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4337 kind of breakpoint or the call completes.
4339 @value{GDBN} automatically deletes watchpoints that watch local
4340 (automatic) variables, or expressions that involve such variables, when
4341 they go out of scope, that is, when the execution leaves the block in
4342 which these variables were defined. In particular, when the program
4343 being debugged terminates, @emph{all} local variables go out of scope,
4344 and so only watchpoints that watch global variables remain set. If you
4345 rerun the program, you will need to set all such watchpoints again. One
4346 way of doing that would be to set a code breakpoint at the entry to the
4347 @code{main} function and when it breaks, set all the watchpoints.
4349 @cindex watchpoints and threads
4350 @cindex threads and watchpoints
4351 In multi-threaded programs, watchpoints will detect changes to the
4352 watched expression from every thread.
4355 @emph{Warning:} In multi-threaded programs, software watchpoints
4356 have only limited usefulness. If @value{GDBN} creates a software
4357 watchpoint, it can only watch the value of an expression @emph{in a
4358 single thread}. If you are confident that the expression can only
4359 change due to the current thread's activity (and if you are also
4360 confident that no other thread can become current), then you can use
4361 software watchpoints as usual. However, @value{GDBN} may not notice
4362 when a non-current thread's activity changes the expression. (Hardware
4363 watchpoints, in contrast, watch an expression in all threads.)
4366 @xref{set remote hardware-watchpoint-limit}.
4368 @node Set Catchpoints
4369 @subsection Setting Catchpoints
4370 @cindex catchpoints, setting
4371 @cindex exception handlers
4372 @cindex event handling
4374 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4375 kinds of program events, such as C@t{++} exceptions or the loading of a
4376 shared library. Use the @code{catch} command to set a catchpoint.
4380 @item catch @var{event}
4381 Stop when @var{event} occurs. The @var{event} can be any of the following:
4384 @item throw @r{[}@var{regexp}@r{]}
4385 @itemx rethrow @r{[}@var{regexp}@r{]}
4386 @itemx catch @r{[}@var{regexp}@r{]}
4388 @kindex catch rethrow
4390 @cindex stop on C@t{++} exceptions
4391 The throwing, re-throwing, or catching of a C@t{++} exception.
4393 If @var{regexp} is given, then only exceptions whose type matches the
4394 regular expression will be caught.
4396 @vindex $_exception@r{, convenience variable}
4397 The convenience variable @code{$_exception} is available at an
4398 exception-related catchpoint, on some systems. This holds the
4399 exception being thrown.
4401 There are currently some limitations to C@t{++} exception handling in
4406 The support for these commands is system-dependent. Currently, only
4407 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4411 The regular expression feature and the @code{$_exception} convenience
4412 variable rely on the presence of some SDT probes in @code{libstdc++}.
4413 If these probes are not present, then these features cannot be used.
4414 These probes were first available in the GCC 4.8 release, but whether
4415 or not they are available in your GCC also depends on how it was
4419 The @code{$_exception} convenience variable is only valid at the
4420 instruction at which an exception-related catchpoint is set.
4423 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4424 location in the system library which implements runtime exception
4425 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4426 (@pxref{Selection}) to get to your code.
4429 If you call a function interactively, @value{GDBN} normally returns
4430 control to you when the function has finished executing. If the call
4431 raises an exception, however, the call may bypass the mechanism that
4432 returns control to you and cause your program either to abort or to
4433 simply continue running until it hits a breakpoint, catches a signal
4434 that @value{GDBN} is listening for, or exits. This is the case even if
4435 you set a catchpoint for the exception; catchpoints on exceptions are
4436 disabled within interactive calls. @xref{Calling}, for information on
4437 controlling this with @code{set unwind-on-terminating-exception}.
4440 You cannot raise an exception interactively.
4443 You cannot install an exception handler interactively.
4447 @kindex catch exception
4448 @cindex Ada exception catching
4449 @cindex catch Ada exceptions
4450 An Ada exception being raised. If an exception name is specified
4451 at the end of the command (eg @code{catch exception Program_Error}),
4452 the debugger will stop only when this specific exception is raised.
4453 Otherwise, the debugger stops execution when any Ada exception is raised.
4455 When inserting an exception catchpoint on a user-defined exception whose
4456 name is identical to one of the exceptions defined by the language, the
4457 fully qualified name must be used as the exception name. Otherwise,
4458 @value{GDBN} will assume that it should stop on the pre-defined exception
4459 rather than the user-defined one. For instance, assuming an exception
4460 called @code{Constraint_Error} is defined in package @code{Pck}, then
4461 the command to use to catch such exceptions is @kbd{catch exception
4462 Pck.Constraint_Error}.
4465 @kindex catch handlers
4466 @cindex Ada exception handlers catching
4467 @cindex catch Ada exceptions when handled
4468 An Ada exception being handled. If an exception name is
4469 specified at the end of the command
4470 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4471 only when this specific exception is handled.
4472 Otherwise, the debugger stops execution when any Ada exception is handled.
4474 When inserting a handlers catchpoint on a user-defined
4475 exception whose name is identical to one of the exceptions
4476 defined by the language, the fully qualified name must be used
4477 as the exception name. Otherwise, @value{GDBN} will assume that it
4478 should stop on the pre-defined exception rather than the
4479 user-defined one. For instance, assuming an exception called
4480 @code{Constraint_Error} is defined in package @code{Pck}, then the
4481 command to use to catch such exceptions handling is
4482 @kbd{catch handlers Pck.Constraint_Error}.
4484 @item exception unhandled
4485 @kindex catch exception unhandled
4486 An exception that was raised but is not handled by the program.
4489 @kindex catch assert
4490 A failed Ada assertion.
4494 @cindex break on fork/exec
4495 A call to @code{exec}.
4498 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4499 @kindex catch syscall
4500 @cindex break on a system call.
4501 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4502 syscall is a mechanism for application programs to request a service
4503 from the operating system (OS) or one of the OS system services.
4504 @value{GDBN} can catch some or all of the syscalls issued by the
4505 debuggee, and show the related information for each syscall. If no
4506 argument is specified, calls to and returns from all system calls
4509 @var{name} can be any system call name that is valid for the
4510 underlying OS. Just what syscalls are valid depends on the OS. On
4511 GNU and Unix systems, you can find the full list of valid syscall
4512 names on @file{/usr/include/asm/unistd.h}.
4514 @c For MS-Windows, the syscall names and the corresponding numbers
4515 @c can be found, e.g., on this URL:
4516 @c http://www.metasploit.com/users/opcode/syscalls.html
4517 @c but we don't support Windows syscalls yet.
4519 Normally, @value{GDBN} knows in advance which syscalls are valid for
4520 each OS, so you can use the @value{GDBN} command-line completion
4521 facilities (@pxref{Completion,, command completion}) to list the
4524 You may also specify the system call numerically. A syscall's
4525 number is the value passed to the OS's syscall dispatcher to
4526 identify the requested service. When you specify the syscall by its
4527 name, @value{GDBN} uses its database of syscalls to convert the name
4528 into the corresponding numeric code, but using the number directly
4529 may be useful if @value{GDBN}'s database does not have the complete
4530 list of syscalls on your system (e.g., because @value{GDBN} lags
4531 behind the OS upgrades).
4533 You may specify a group of related syscalls to be caught at once using
4534 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4535 instance, on some platforms @value{GDBN} allows you to catch all
4536 network related syscalls, by passing the argument @code{group:network}
4537 to @code{catch syscall}. Note that not all syscall groups are
4538 available in every system. You can use the command completion
4539 facilities (@pxref{Completion,, command completion}) to list the
4540 syscall groups available on your environment.
4542 The example below illustrates how this command works if you don't provide
4546 (@value{GDBP}) catch syscall
4547 Catchpoint 1 (syscall)
4549 Starting program: /tmp/catch-syscall
4551 Catchpoint 1 (call to syscall 'close'), \
4552 0xffffe424 in __kernel_vsyscall ()
4556 Catchpoint 1 (returned from syscall 'close'), \
4557 0xffffe424 in __kernel_vsyscall ()
4561 Here is an example of catching a system call by name:
4564 (@value{GDBP}) catch syscall chroot
4565 Catchpoint 1 (syscall 'chroot' [61])
4567 Starting program: /tmp/catch-syscall
4569 Catchpoint 1 (call to syscall 'chroot'), \
4570 0xffffe424 in __kernel_vsyscall ()
4574 Catchpoint 1 (returned from syscall 'chroot'), \
4575 0xffffe424 in __kernel_vsyscall ()
4579 An example of specifying a system call numerically. In the case
4580 below, the syscall number has a corresponding entry in the XML
4581 file, so @value{GDBN} finds its name and prints it:
4584 (@value{GDBP}) catch syscall 252
4585 Catchpoint 1 (syscall(s) 'exit_group')
4587 Starting program: /tmp/catch-syscall
4589 Catchpoint 1 (call to syscall 'exit_group'), \
4590 0xffffe424 in __kernel_vsyscall ()
4594 Program exited normally.
4598 Here is an example of catching a syscall group:
4601 (@value{GDBP}) catch syscall group:process
4602 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4603 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4604 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4606 Starting program: /tmp/catch-syscall
4608 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4609 from /lib64/ld-linux-x86-64.so.2
4615 However, there can be situations when there is no corresponding name
4616 in XML file for that syscall number. In this case, @value{GDBN} prints
4617 a warning message saying that it was not able to find the syscall name,
4618 but the catchpoint will be set anyway. See the example below:
4621 (@value{GDBP}) catch syscall 764
4622 warning: The number '764' does not represent a known syscall.
4623 Catchpoint 2 (syscall 764)
4627 If you configure @value{GDBN} using the @samp{--without-expat} option,
4628 it will not be able to display syscall names. Also, if your
4629 architecture does not have an XML file describing its system calls,
4630 you will not be able to see the syscall names. It is important to
4631 notice that these two features are used for accessing the syscall
4632 name database. In either case, you will see a warning like this:
4635 (@value{GDBP}) catch syscall
4636 warning: Could not open "syscalls/i386-linux.xml"
4637 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4638 GDB will not be able to display syscall names.
4639 Catchpoint 1 (syscall)
4643 Of course, the file name will change depending on your architecture and system.
4645 Still using the example above, you can also try to catch a syscall by its
4646 number. In this case, you would see something like:
4649 (@value{GDBP}) catch syscall 252
4650 Catchpoint 1 (syscall(s) 252)
4653 Again, in this case @value{GDBN} would not be able to display syscall's names.
4657 A call to @code{fork}.
4661 A call to @code{vfork}.
4663 @item load @r{[}regexp@r{]}
4664 @itemx unload @r{[}regexp@r{]}
4666 @kindex catch unload
4667 The loading or unloading of a shared library. If @var{regexp} is
4668 given, then the catchpoint will stop only if the regular expression
4669 matches one of the affected libraries.
4671 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4672 @kindex catch signal
4673 The delivery of a signal.
4675 With no arguments, this catchpoint will catch any signal that is not
4676 used internally by @value{GDBN}, specifically, all signals except
4677 @samp{SIGTRAP} and @samp{SIGINT}.
4679 With the argument @samp{all}, all signals, including those used by
4680 @value{GDBN}, will be caught. This argument cannot be used with other
4683 Otherwise, the arguments are a list of signal names as given to
4684 @code{handle} (@pxref{Signals}). Only signals specified in this list
4687 One reason that @code{catch signal} can be more useful than
4688 @code{handle} is that you can attach commands and conditions to the
4691 When a signal is caught by a catchpoint, the signal's @code{stop} and
4692 @code{print} settings, as specified by @code{handle}, are ignored.
4693 However, whether the signal is still delivered to the inferior depends
4694 on the @code{pass} setting; this can be changed in the catchpoint's
4699 @item tcatch @var{event}
4701 Set a catchpoint that is enabled only for one stop. The catchpoint is
4702 automatically deleted after the first time the event is caught.
4706 Use the @code{info break} command to list the current catchpoints.
4710 @subsection Deleting Breakpoints
4712 @cindex clearing breakpoints, watchpoints, catchpoints
4713 @cindex deleting breakpoints, watchpoints, catchpoints
4714 It is often necessary to eliminate a breakpoint, watchpoint, or
4715 catchpoint once it has done its job and you no longer want your program
4716 to stop there. This is called @dfn{deleting} the breakpoint. A
4717 breakpoint that has been deleted no longer exists; it is forgotten.
4719 With the @code{clear} command you can delete breakpoints according to
4720 where they are in your program. With the @code{delete} command you can
4721 delete individual breakpoints, watchpoints, or catchpoints by specifying
4722 their breakpoint numbers.
4724 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4725 automatically ignores breakpoints on the first instruction to be executed
4726 when you continue execution without changing the execution address.
4731 Delete any breakpoints at the next instruction to be executed in the
4732 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4733 the innermost frame is selected, this is a good way to delete a
4734 breakpoint where your program just stopped.
4736 @item clear @var{location}
4737 Delete any breakpoints set at the specified @var{location}.
4738 @xref{Specify Location}, for the various forms of @var{location}; the
4739 most useful ones are listed below:
4742 @item clear @var{function}
4743 @itemx clear @var{filename}:@var{function}
4744 Delete any breakpoints set at entry to the named @var{function}.
4746 @item clear @var{linenum}
4747 @itemx clear @var{filename}:@var{linenum}
4748 Delete any breakpoints set at or within the code of the specified
4749 @var{linenum} of the specified @var{filename}.
4752 @cindex delete breakpoints
4754 @kindex d @r{(@code{delete})}
4755 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4756 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4757 list specified as argument. If no argument is specified, delete all
4758 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4759 confirm off}). You can abbreviate this command as @code{d}.
4763 @subsection Disabling Breakpoints
4765 @cindex enable/disable a breakpoint
4766 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4767 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4768 it had been deleted, but remembers the information on the breakpoint so
4769 that you can @dfn{enable} it again later.
4771 You disable and enable breakpoints, watchpoints, and catchpoints with
4772 the @code{enable} and @code{disable} commands, optionally specifying
4773 one or more breakpoint numbers as arguments. Use @code{info break} to
4774 print a list of all breakpoints, watchpoints, and catchpoints if you
4775 do not know which numbers to use.
4777 Disabling and enabling a breakpoint that has multiple locations
4778 affects all of its locations.
4780 A breakpoint, watchpoint, or catchpoint can have any of several
4781 different states of enablement:
4785 Enabled. The breakpoint stops your program. A breakpoint set
4786 with the @code{break} command starts out in this state.
4788 Disabled. The breakpoint has no effect on your program.
4790 Enabled once. The breakpoint stops your program, but then becomes
4793 Enabled for a count. The breakpoint stops your program for the next
4794 N times, then becomes disabled.
4796 Enabled for deletion. The breakpoint stops your program, but
4797 immediately after it does so it is deleted permanently. A breakpoint
4798 set with the @code{tbreak} command starts out in this state.
4801 You can use the following commands to enable or disable breakpoints,
4802 watchpoints, and catchpoints:
4806 @kindex dis @r{(@code{disable})}
4807 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4808 Disable the specified breakpoints---or all breakpoints, if none are
4809 listed. A disabled breakpoint has no effect but is not forgotten. All
4810 options such as ignore-counts, conditions and commands are remembered in
4811 case the breakpoint is enabled again later. You may abbreviate
4812 @code{disable} as @code{dis}.
4815 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4816 Enable the specified breakpoints (or all defined breakpoints). They
4817 become effective once again in stopping your program.
4819 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4820 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4821 of these breakpoints immediately after stopping your program.
4823 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4824 Enable the specified breakpoints temporarily. @value{GDBN} records
4825 @var{count} with each of the specified breakpoints, and decrements a
4826 breakpoint's count when it is hit. When any count reaches 0,
4827 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4828 count (@pxref{Conditions, ,Break Conditions}), that will be
4829 decremented to 0 before @var{count} is affected.
4831 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4832 Enable the specified breakpoints to work once, then die. @value{GDBN}
4833 deletes any of these breakpoints as soon as your program stops there.
4834 Breakpoints set by the @code{tbreak} command start out in this state.
4837 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4838 @c confusing: tbreak is also initially enabled.
4839 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4840 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4841 subsequently, they become disabled or enabled only when you use one of
4842 the commands above. (The command @code{until} can set and delete a
4843 breakpoint of its own, but it does not change the state of your other
4844 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4848 @subsection Break Conditions
4849 @cindex conditional breakpoints
4850 @cindex breakpoint conditions
4852 @c FIXME what is scope of break condition expr? Context where wanted?
4853 @c in particular for a watchpoint?
4854 The simplest sort of breakpoint breaks every time your program reaches a
4855 specified place. You can also specify a @dfn{condition} for a
4856 breakpoint. A condition is just a Boolean expression in your
4857 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4858 a condition evaluates the expression each time your program reaches it,
4859 and your program stops only if the condition is @emph{true}.
4861 This is the converse of using assertions for program validation; in that
4862 situation, you want to stop when the assertion is violated---that is,
4863 when the condition is false. In C, if you want to test an assertion expressed
4864 by the condition @var{assert}, you should set the condition
4865 @samp{! @var{assert}} on the appropriate breakpoint.
4867 Conditions are also accepted for watchpoints; you may not need them,
4868 since a watchpoint is inspecting the value of an expression anyhow---but
4869 it might be simpler, say, to just set a watchpoint on a variable name,
4870 and specify a condition that tests whether the new value is an interesting
4873 Break conditions can have side effects, and may even call functions in
4874 your program. This can be useful, for example, to activate functions
4875 that log program progress, or to use your own print functions to
4876 format special data structures. The effects are completely predictable
4877 unless there is another enabled breakpoint at the same address. (In
4878 that case, @value{GDBN} might see the other breakpoint first and stop your
4879 program without checking the condition of this one.) Note that
4880 breakpoint commands are usually more convenient and flexible than break
4882 purpose of performing side effects when a breakpoint is reached
4883 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4885 Breakpoint conditions can also be evaluated on the target's side if
4886 the target supports it. Instead of evaluating the conditions locally,
4887 @value{GDBN} encodes the expression into an agent expression
4888 (@pxref{Agent Expressions}) suitable for execution on the target,
4889 independently of @value{GDBN}. Global variables become raw memory
4890 locations, locals become stack accesses, and so forth.
4892 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4893 when its condition evaluates to true. This mechanism may provide faster
4894 response times depending on the performance characteristics of the target
4895 since it does not need to keep @value{GDBN} informed about
4896 every breakpoint trigger, even those with false conditions.
4898 Break conditions can be specified when a breakpoint is set, by using
4899 @samp{if} in the arguments to the @code{break} command. @xref{Set
4900 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4901 with the @code{condition} command.
4903 You can also use the @code{if} keyword with the @code{watch} command.
4904 The @code{catch} command does not recognize the @code{if} keyword;
4905 @code{condition} is the only way to impose a further condition on a
4910 @item condition @var{bnum} @var{expression}
4911 Specify @var{expression} as the break condition for breakpoint,
4912 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4913 breakpoint @var{bnum} stops your program only if the value of
4914 @var{expression} is true (nonzero, in C). When you use
4915 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4916 syntactic correctness, and to determine whether symbols in it have
4917 referents in the context of your breakpoint. If @var{expression} uses
4918 symbols not referenced in the context of the breakpoint, @value{GDBN}
4919 prints an error message:
4922 No symbol "foo" in current context.
4927 not actually evaluate @var{expression} at the time the @code{condition}
4928 command (or a command that sets a breakpoint with a condition, like
4929 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4931 @item condition @var{bnum}
4932 Remove the condition from breakpoint number @var{bnum}. It becomes
4933 an ordinary unconditional breakpoint.
4936 @cindex ignore count (of breakpoint)
4937 A special case of a breakpoint condition is to stop only when the
4938 breakpoint has been reached a certain number of times. This is so
4939 useful that there is a special way to do it, using the @dfn{ignore
4940 count} of the breakpoint. Every breakpoint has an ignore count, which
4941 is an integer. Most of the time, the ignore count is zero, and
4942 therefore has no effect. But if your program reaches a breakpoint whose
4943 ignore count is positive, then instead of stopping, it just decrements
4944 the ignore count by one and continues. As a result, if the ignore count
4945 value is @var{n}, the breakpoint does not stop the next @var{n} times
4946 your program reaches it.
4950 @item ignore @var{bnum} @var{count}
4951 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4952 The next @var{count} times the breakpoint is reached, your program's
4953 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4956 To make the breakpoint stop the next time it is reached, specify
4959 When you use @code{continue} to resume execution of your program from a
4960 breakpoint, you can specify an ignore count directly as an argument to
4961 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4962 Stepping,,Continuing and Stepping}.
4964 If a breakpoint has a positive ignore count and a condition, the
4965 condition is not checked. Once the ignore count reaches zero,
4966 @value{GDBN} resumes checking the condition.
4968 You could achieve the effect of the ignore count with a condition such
4969 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4970 is decremented each time. @xref{Convenience Vars, ,Convenience
4974 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4977 @node Break Commands
4978 @subsection Breakpoint Command Lists
4980 @cindex breakpoint commands
4981 You can give any breakpoint (or watchpoint or catchpoint) a series of
4982 commands to execute when your program stops due to that breakpoint. For
4983 example, you might want to print the values of certain expressions, or
4984 enable other breakpoints.
4988 @kindex end@r{ (breakpoint commands)}
4989 @item commands @r{[}@var{list}@dots{}@r{]}
4990 @itemx @dots{} @var{command-list} @dots{}
4992 Specify a list of commands for the given breakpoints. The commands
4993 themselves appear on the following lines. Type a line containing just
4994 @code{end} to terminate the commands.
4996 To remove all commands from a breakpoint, type @code{commands} and
4997 follow it immediately with @code{end}; that is, give no commands.
4999 With no argument, @code{commands} refers to the last breakpoint,
5000 watchpoint, or catchpoint set (not to the breakpoint most recently
5001 encountered). If the most recent breakpoints were set with a single
5002 command, then the @code{commands} will apply to all the breakpoints
5003 set by that command. This applies to breakpoints set by
5004 @code{rbreak}, and also applies when a single @code{break} command
5005 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5009 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5010 disabled within a @var{command-list}.
5012 You can use breakpoint commands to start your program up again. Simply
5013 use the @code{continue} command, or @code{step}, or any other command
5014 that resumes execution.
5016 Any other commands in the command list, after a command that resumes
5017 execution, are ignored. This is because any time you resume execution
5018 (even with a simple @code{next} or @code{step}), you may encounter
5019 another breakpoint---which could have its own command list, leading to
5020 ambiguities about which list to execute.
5023 If the first command you specify in a command list is @code{silent}, the
5024 usual message about stopping at a breakpoint is not printed. This may
5025 be desirable for breakpoints that are to print a specific message and
5026 then continue. If none of the remaining commands print anything, you
5027 see no sign that the breakpoint was reached. @code{silent} is
5028 meaningful only at the beginning of a breakpoint command list.
5030 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5031 print precisely controlled output, and are often useful in silent
5032 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5034 For example, here is how you could use breakpoint commands to print the
5035 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5041 printf "x is %d\n",x
5046 One application for breakpoint commands is to compensate for one bug so
5047 you can test for another. Put a breakpoint just after the erroneous line
5048 of code, give it a condition to detect the case in which something
5049 erroneous has been done, and give it commands to assign correct values
5050 to any variables that need them. End with the @code{continue} command
5051 so that your program does not stop, and start with the @code{silent}
5052 command so that no output is produced. Here is an example:
5063 @node Dynamic Printf
5064 @subsection Dynamic Printf
5066 @cindex dynamic printf
5068 The dynamic printf command @code{dprintf} combines a breakpoint with
5069 formatted printing of your program's data to give you the effect of
5070 inserting @code{printf} calls into your program on-the-fly, without
5071 having to recompile it.
5073 In its most basic form, the output goes to the GDB console. However,
5074 you can set the variable @code{dprintf-style} for alternate handling.
5075 For instance, you can ask to format the output by calling your
5076 program's @code{printf} function. This has the advantage that the
5077 characters go to the program's output device, so they can recorded in
5078 redirects to files and so forth.
5080 If you are doing remote debugging with a stub or agent, you can also
5081 ask to have the printf handled by the remote agent. In addition to
5082 ensuring that the output goes to the remote program's device along
5083 with any other output the program might produce, you can also ask that
5084 the dprintf remain active even after disconnecting from the remote
5085 target. Using the stub/agent is also more efficient, as it can do
5086 everything without needing to communicate with @value{GDBN}.
5090 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5091 Whenever execution reaches @var{location}, print the values of one or
5092 more @var{expressions} under the control of the string @var{template}.
5093 To print several values, separate them with commas.
5095 @item set dprintf-style @var{style}
5096 Set the dprintf output to be handled in one of several different
5097 styles enumerated below. A change of style affects all existing
5098 dynamic printfs immediately. (If you need individual control over the
5099 print commands, simply define normal breakpoints with
5100 explicitly-supplied command lists.)
5104 @kindex dprintf-style gdb
5105 Handle the output using the @value{GDBN} @code{printf} command.
5108 @kindex dprintf-style call
5109 Handle the output by calling a function in your program (normally
5113 @kindex dprintf-style agent
5114 Have the remote debugging agent (such as @code{gdbserver}) handle
5115 the output itself. This style is only available for agents that
5116 support running commands on the target.
5119 @item set dprintf-function @var{function}
5120 Set the function to call if the dprintf style is @code{call}. By
5121 default its value is @code{printf}. You may set it to any expression.
5122 that @value{GDBN} can evaluate to a function, as per the @code{call}
5125 @item set dprintf-channel @var{channel}
5126 Set a ``channel'' for dprintf. If set to a non-empty value,
5127 @value{GDBN} will evaluate it as an expression and pass the result as
5128 a first argument to the @code{dprintf-function}, in the manner of
5129 @code{fprintf} and similar functions. Otherwise, the dprintf format
5130 string will be the first argument, in the manner of @code{printf}.
5132 As an example, if you wanted @code{dprintf} output to go to a logfile
5133 that is a standard I/O stream assigned to the variable @code{mylog},
5134 you could do the following:
5137 (gdb) set dprintf-style call
5138 (gdb) set dprintf-function fprintf
5139 (gdb) set dprintf-channel mylog
5140 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5141 Dprintf 1 at 0x123456: file main.c, line 25.
5143 1 dprintf keep y 0x00123456 in main at main.c:25
5144 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5149 Note that the @code{info break} displays the dynamic printf commands
5150 as normal breakpoint commands; you can thus easily see the effect of
5151 the variable settings.
5153 @item set disconnected-dprintf on
5154 @itemx set disconnected-dprintf off
5155 @kindex set disconnected-dprintf
5156 Choose whether @code{dprintf} commands should continue to run if
5157 @value{GDBN} has disconnected from the target. This only applies
5158 if the @code{dprintf-style} is @code{agent}.
5160 @item show disconnected-dprintf off
5161 @kindex show disconnected-dprintf
5162 Show the current choice for disconnected @code{dprintf}.
5166 @value{GDBN} does not check the validity of function and channel,
5167 relying on you to supply values that are meaningful for the contexts
5168 in which they are being used. For instance, the function and channel
5169 may be the values of local variables, but if that is the case, then
5170 all enabled dynamic prints must be at locations within the scope of
5171 those locals. If evaluation fails, @value{GDBN} will report an error.
5173 @node Save Breakpoints
5174 @subsection How to save breakpoints to a file
5176 To save breakpoint definitions to a file use the @w{@code{save
5177 breakpoints}} command.
5180 @kindex save breakpoints
5181 @cindex save breakpoints to a file for future sessions
5182 @item save breakpoints [@var{filename}]
5183 This command saves all current breakpoint definitions together with
5184 their commands and ignore counts, into a file @file{@var{filename}}
5185 suitable for use in a later debugging session. This includes all
5186 types of breakpoints (breakpoints, watchpoints, catchpoints,
5187 tracepoints). To read the saved breakpoint definitions, use the
5188 @code{source} command (@pxref{Command Files}). Note that watchpoints
5189 with expressions involving local variables may fail to be recreated
5190 because it may not be possible to access the context where the
5191 watchpoint is valid anymore. Because the saved breakpoint definitions
5192 are simply a sequence of @value{GDBN} commands that recreate the
5193 breakpoints, you can edit the file in your favorite editing program,
5194 and remove the breakpoint definitions you're not interested in, or
5195 that can no longer be recreated.
5198 @node Static Probe Points
5199 @subsection Static Probe Points
5201 @cindex static probe point, SystemTap
5202 @cindex static probe point, DTrace
5203 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5204 for Statically Defined Tracing, and the probes are designed to have a tiny
5205 runtime code and data footprint, and no dynamic relocations.
5207 Currently, the following types of probes are supported on
5208 ELF-compatible systems:
5212 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5213 @acronym{SDT} probes@footnote{See
5214 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5215 for more information on how to add @code{SystemTap} @acronym{SDT}
5216 probes in your applications.}. @code{SystemTap} probes are usable
5217 from assembly, C and C@t{++} languages@footnote{See
5218 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5219 for a good reference on how the @acronym{SDT} probes are implemented.}.
5221 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5222 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5226 @cindex semaphores on static probe points
5227 Some @code{SystemTap} probes have an associated semaphore variable;
5228 for instance, this happens automatically if you defined your probe
5229 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5230 @value{GDBN} will automatically enable it when you specify a
5231 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5232 breakpoint at a probe's location by some other method (e.g.,
5233 @code{break file:line}), then @value{GDBN} will not automatically set
5234 the semaphore. @code{DTrace} probes do not support semaphores.
5236 You can examine the available static static probes using @code{info
5237 probes}, with optional arguments:
5241 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5242 If given, @var{type} is either @code{stap} for listing
5243 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5244 probes. If omitted all probes are listed regardless of their types.
5246 If given, @var{provider} is a regular expression used to match against provider
5247 names when selecting which probes to list. If omitted, probes by all
5248 probes from all providers are listed.
5250 If given, @var{name} is a regular expression to match against probe names
5251 when selecting which probes to list. If omitted, probe names are not
5252 considered when deciding whether to display them.
5254 If given, @var{objfile} is a regular expression used to select which
5255 object files (executable or shared libraries) to examine. If not
5256 given, all object files are considered.
5258 @item info probes all
5259 List the available static probes, from all types.
5262 @cindex enabling and disabling probes
5263 Some probe points can be enabled and/or disabled. The effect of
5264 enabling or disabling a probe depends on the type of probe being
5265 handled. Some @code{DTrace} probes can be enabled or
5266 disabled, but @code{SystemTap} probes cannot be disabled.
5268 You can enable (or disable) one or more probes using the following
5269 commands, with optional arguments:
5272 @kindex enable probes
5273 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5274 If given, @var{provider} is a regular expression used to match against
5275 provider names when selecting which probes to enable. If omitted,
5276 all probes from all providers are enabled.
5278 If given, @var{name} is a regular expression to match against probe
5279 names when selecting which probes to enable. If omitted, probe names
5280 are not considered when deciding whether to enable them.
5282 If given, @var{objfile} is a regular expression used to select which
5283 object files (executable or shared libraries) to examine. If not
5284 given, all object files are considered.
5286 @kindex disable probes
5287 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5288 See the @code{enable probes} command above for a description of the
5289 optional arguments accepted by this command.
5292 @vindex $_probe_arg@r{, convenience variable}
5293 A probe may specify up to twelve arguments. These are available at the
5294 point at which the probe is defined---that is, when the current PC is
5295 at the probe's location. The arguments are available using the
5296 convenience variables (@pxref{Convenience Vars})
5297 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5298 probes each probe argument is an integer of the appropriate size;
5299 types are not preserved. In @code{DTrace} probes types are preserved
5300 provided that they are recognized as such by @value{GDBN}; otherwise
5301 the value of the probe argument will be a long integer. The
5302 convenience variable @code{$_probe_argc} holds the number of arguments
5303 at the current probe point.
5305 These variables are always available, but attempts to access them at
5306 any location other than a probe point will cause @value{GDBN} to give
5310 @c @ifclear BARETARGET
5311 @node Error in Breakpoints
5312 @subsection ``Cannot insert breakpoints''
5314 If you request too many active hardware-assisted breakpoints and
5315 watchpoints, you will see this error message:
5317 @c FIXME: the precise wording of this message may change; the relevant
5318 @c source change is not committed yet (Sep 3, 1999).
5320 Stopped; cannot insert breakpoints.
5321 You may have requested too many hardware breakpoints and watchpoints.
5325 This message is printed when you attempt to resume the program, since
5326 only then @value{GDBN} knows exactly how many hardware breakpoints and
5327 watchpoints it needs to insert.
5329 When this message is printed, you need to disable or remove some of the
5330 hardware-assisted breakpoints and watchpoints, and then continue.
5332 @node Breakpoint-related Warnings
5333 @subsection ``Breakpoint address adjusted...''
5334 @cindex breakpoint address adjusted
5336 Some processor architectures place constraints on the addresses at
5337 which breakpoints may be placed. For architectures thus constrained,
5338 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5339 with the constraints dictated by the architecture.
5341 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5342 a VLIW architecture in which a number of RISC-like instructions may be
5343 bundled together for parallel execution. The FR-V architecture
5344 constrains the location of a breakpoint instruction within such a
5345 bundle to the instruction with the lowest address. @value{GDBN}
5346 honors this constraint by adjusting a breakpoint's address to the
5347 first in the bundle.
5349 It is not uncommon for optimized code to have bundles which contain
5350 instructions from different source statements, thus it may happen that
5351 a breakpoint's address will be adjusted from one source statement to
5352 another. Since this adjustment may significantly alter @value{GDBN}'s
5353 breakpoint related behavior from what the user expects, a warning is
5354 printed when the breakpoint is first set and also when the breakpoint
5357 A warning like the one below is printed when setting a breakpoint
5358 that's been subject to address adjustment:
5361 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5364 Such warnings are printed both for user settable and @value{GDBN}'s
5365 internal breakpoints. If you see one of these warnings, you should
5366 verify that a breakpoint set at the adjusted address will have the
5367 desired affect. If not, the breakpoint in question may be removed and
5368 other breakpoints may be set which will have the desired behavior.
5369 E.g., it may be sufficient to place the breakpoint at a later
5370 instruction. A conditional breakpoint may also be useful in some
5371 cases to prevent the breakpoint from triggering too often.
5373 @value{GDBN} will also issue a warning when stopping at one of these
5374 adjusted breakpoints:
5377 warning: Breakpoint 1 address previously adjusted from 0x00010414
5381 When this warning is encountered, it may be too late to take remedial
5382 action except in cases where the breakpoint is hit earlier or more
5383 frequently than expected.
5385 @node Continuing and Stepping
5386 @section Continuing and Stepping
5390 @cindex resuming execution
5391 @dfn{Continuing} means resuming program execution until your program
5392 completes normally. In contrast, @dfn{stepping} means executing just
5393 one more ``step'' of your program, where ``step'' may mean either one
5394 line of source code, or one machine instruction (depending on what
5395 particular command you use). Either when continuing or when stepping,
5396 your program may stop even sooner, due to a breakpoint or a signal. (If
5397 it stops due to a signal, you may want to use @code{handle}, or use
5398 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5399 or you may step into the signal's handler (@pxref{stepping and signal
5404 @kindex c @r{(@code{continue})}
5405 @kindex fg @r{(resume foreground execution)}
5406 @item continue @r{[}@var{ignore-count}@r{]}
5407 @itemx c @r{[}@var{ignore-count}@r{]}
5408 @itemx fg @r{[}@var{ignore-count}@r{]}
5409 Resume program execution, at the address where your program last stopped;
5410 any breakpoints set at that address are bypassed. The optional argument
5411 @var{ignore-count} allows you to specify a further number of times to
5412 ignore a breakpoint at this location; its effect is like that of
5413 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5415 The argument @var{ignore-count} is meaningful only when your program
5416 stopped due to a breakpoint. At other times, the argument to
5417 @code{continue} is ignored.
5419 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5420 debugged program is deemed to be the foreground program) are provided
5421 purely for convenience, and have exactly the same behavior as
5425 To resume execution at a different place, you can use @code{return}
5426 (@pxref{Returning, ,Returning from a Function}) to go back to the
5427 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5428 Different Address}) to go to an arbitrary location in your program.
5430 A typical technique for using stepping is to set a breakpoint
5431 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5432 beginning of the function or the section of your program where a problem
5433 is believed to lie, run your program until it stops at that breakpoint,
5434 and then step through the suspect area, examining the variables that are
5435 interesting, until you see the problem happen.
5439 @kindex s @r{(@code{step})}
5441 Continue running your program until control reaches a different source
5442 line, then stop it and return control to @value{GDBN}. This command is
5443 abbreviated @code{s}.
5446 @c "without debugging information" is imprecise; actually "without line
5447 @c numbers in the debugging information". (gcc -g1 has debugging info but
5448 @c not line numbers). But it seems complex to try to make that
5449 @c distinction here.
5450 @emph{Warning:} If you use the @code{step} command while control is
5451 within a function that was compiled without debugging information,
5452 execution proceeds until control reaches a function that does have
5453 debugging information. Likewise, it will not step into a function which
5454 is compiled without debugging information. To step through functions
5455 without debugging information, use the @code{stepi} command, described
5459 The @code{step} command only stops at the first instruction of a source
5460 line. This prevents the multiple stops that could otherwise occur in
5461 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5462 to stop if a function that has debugging information is called within
5463 the line. In other words, @code{step} @emph{steps inside} any functions
5464 called within the line.
5466 Also, the @code{step} command only enters a function if there is line
5467 number information for the function. Otherwise it acts like the
5468 @code{next} command. This avoids problems when using @code{cc -gl}
5469 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5470 was any debugging information about the routine.
5472 @item step @var{count}
5473 Continue running as in @code{step}, but do so @var{count} times. If a
5474 breakpoint is reached, or a signal not related to stepping occurs before
5475 @var{count} steps, stepping stops right away.
5478 @kindex n @r{(@code{next})}
5479 @item next @r{[}@var{count}@r{]}
5480 Continue to the next source line in the current (innermost) stack frame.
5481 This is similar to @code{step}, but function calls that appear within
5482 the line of code are executed without stopping. Execution stops when
5483 control reaches a different line of code at the original stack level
5484 that was executing when you gave the @code{next} command. This command
5485 is abbreviated @code{n}.
5487 An argument @var{count} is a repeat count, as for @code{step}.
5490 @c FIX ME!! Do we delete this, or is there a way it fits in with
5491 @c the following paragraph? --- Vctoria
5493 @c @code{next} within a function that lacks debugging information acts like
5494 @c @code{step}, but any function calls appearing within the code of the
5495 @c function are executed without stopping.
5497 The @code{next} command only stops at the first instruction of a
5498 source line. This prevents multiple stops that could otherwise occur in
5499 @code{switch} statements, @code{for} loops, etc.
5501 @kindex set step-mode
5503 @cindex functions without line info, and stepping
5504 @cindex stepping into functions with no line info
5505 @itemx set step-mode on
5506 The @code{set step-mode on} command causes the @code{step} command to
5507 stop at the first instruction of a function which contains no debug line
5508 information rather than stepping over it.
5510 This is useful in cases where you may be interested in inspecting the
5511 machine instructions of a function which has no symbolic info and do not
5512 want @value{GDBN} to automatically skip over this function.
5514 @item set step-mode off
5515 Causes the @code{step} command to step over any functions which contains no
5516 debug information. This is the default.
5518 @item show step-mode
5519 Show whether @value{GDBN} will stop in or step over functions without
5520 source line debug information.
5523 @kindex fin @r{(@code{finish})}
5525 Continue running until just after function in the selected stack frame
5526 returns. Print the returned value (if any). This command can be
5527 abbreviated as @code{fin}.
5529 Contrast this with the @code{return} command (@pxref{Returning,
5530 ,Returning from a Function}).
5533 @kindex u @r{(@code{until})}
5534 @cindex run until specified location
5537 Continue running until a source line past the current line, in the
5538 current stack frame, is reached. This command is used to avoid single
5539 stepping through a loop more than once. It is like the @code{next}
5540 command, except that when @code{until} encounters a jump, it
5541 automatically continues execution until the program counter is greater
5542 than the address of the jump.
5544 This means that when you reach the end of a loop after single stepping
5545 though it, @code{until} makes your program continue execution until it
5546 exits the loop. In contrast, a @code{next} command at the end of a loop
5547 simply steps back to the beginning of the loop, which forces you to step
5548 through the next iteration.
5550 @code{until} always stops your program if it attempts to exit the current
5553 @code{until} may produce somewhat counterintuitive results if the order
5554 of machine code does not match the order of the source lines. For
5555 example, in the following excerpt from a debugging session, the @code{f}
5556 (@code{frame}) command shows that execution is stopped at line
5557 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5561 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5563 (@value{GDBP}) until
5564 195 for ( ; argc > 0; NEXTARG) @{
5567 This happened because, for execution efficiency, the compiler had
5568 generated code for the loop closure test at the end, rather than the
5569 start, of the loop---even though the test in a C @code{for}-loop is
5570 written before the body of the loop. The @code{until} command appeared
5571 to step back to the beginning of the loop when it advanced to this
5572 expression; however, it has not really gone to an earlier
5573 statement---not in terms of the actual machine code.
5575 @code{until} with no argument works by means of single
5576 instruction stepping, and hence is slower than @code{until} with an
5579 @item until @var{location}
5580 @itemx u @var{location}
5581 Continue running your program until either the specified @var{location} is
5582 reached, or the current stack frame returns. The location is any of
5583 the forms described in @ref{Specify Location}.
5584 This form of the command uses temporary breakpoints, and
5585 hence is quicker than @code{until} without an argument. The specified
5586 location is actually reached only if it is in the current frame. This
5587 implies that @code{until} can be used to skip over recursive function
5588 invocations. For instance in the code below, if the current location is
5589 line @code{96}, issuing @code{until 99} will execute the program up to
5590 line @code{99} in the same invocation of factorial, i.e., after the inner
5591 invocations have returned.
5594 94 int factorial (int value)
5596 96 if (value > 1) @{
5597 97 value *= factorial (value - 1);
5604 @kindex advance @var{location}
5605 @item advance @var{location}
5606 Continue running the program up to the given @var{location}. An argument is
5607 required, which should be of one of the forms described in
5608 @ref{Specify Location}.
5609 Execution will also stop upon exit from the current stack
5610 frame. This command is similar to @code{until}, but @code{advance} will
5611 not skip over recursive function calls, and the target location doesn't
5612 have to be in the same frame as the current one.
5616 @kindex si @r{(@code{stepi})}
5618 @itemx stepi @var{arg}
5620 Execute one machine instruction, then stop and return to the debugger.
5622 It is often useful to do @samp{display/i $pc} when stepping by machine
5623 instructions. This makes @value{GDBN} automatically display the next
5624 instruction to be executed, each time your program stops. @xref{Auto
5625 Display,, Automatic Display}.
5627 An argument is a repeat count, as in @code{step}.
5631 @kindex ni @r{(@code{nexti})}
5633 @itemx nexti @var{arg}
5635 Execute one machine instruction, but if it is a function call,
5636 proceed until the function returns.
5638 An argument is a repeat count, as in @code{next}.
5642 @anchor{range stepping}
5643 @cindex range stepping
5644 @cindex target-assisted range stepping
5645 By default, and if available, @value{GDBN} makes use of
5646 target-assisted @dfn{range stepping}. In other words, whenever you
5647 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5648 tells the target to step the corresponding range of instruction
5649 addresses instead of issuing multiple single-steps. This speeds up
5650 line stepping, particularly for remote targets. Ideally, there should
5651 be no reason you would want to turn range stepping off. However, it's
5652 possible that a bug in the debug info, a bug in the remote stub (for
5653 remote targets), or even a bug in @value{GDBN} could make line
5654 stepping behave incorrectly when target-assisted range stepping is
5655 enabled. You can use the following command to turn off range stepping
5659 @kindex set range-stepping
5660 @kindex show range-stepping
5661 @item set range-stepping
5662 @itemx show range-stepping
5663 Control whether range stepping is enabled.
5665 If @code{on}, and the target supports it, @value{GDBN} tells the
5666 target to step a range of addresses itself, instead of issuing
5667 multiple single-steps. If @code{off}, @value{GDBN} always issues
5668 single-steps, even if range stepping is supported by the target. The
5669 default is @code{on}.
5673 @node Skipping Over Functions and Files
5674 @section Skipping Over Functions and Files
5675 @cindex skipping over functions and files
5677 The program you are debugging may contain some functions which are
5678 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5679 skip a function, all functions in a file or a particular function in
5680 a particular file when stepping.
5682 For example, consider the following C function:
5693 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5694 are not interested in stepping through @code{boring}. If you run @code{step}
5695 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5696 step over both @code{foo} and @code{boring}!
5698 One solution is to @code{step} into @code{boring} and use the @code{finish}
5699 command to immediately exit it. But this can become tedious if @code{boring}
5700 is called from many places.
5702 A more flexible solution is to execute @kbd{skip boring}. This instructs
5703 @value{GDBN} never to step into @code{boring}. Now when you execute
5704 @code{step} at line 103, you'll step over @code{boring} and directly into
5707 Functions may be skipped by providing either a function name, linespec
5708 (@pxref{Specify Location}), regular expression that matches the function's
5709 name, file name or a @code{glob}-style pattern that matches the file name.
5711 On Posix systems the form of the regular expression is
5712 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5713 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5714 expression is whatever is provided by the @code{regcomp} function of
5715 the underlying system.
5716 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5717 description of @code{glob}-style patterns.
5721 @item skip @r{[}@var{options}@r{]}
5722 The basic form of the @code{skip} command takes zero or more options
5723 that specify what to skip.
5724 The @var{options} argument is any useful combination of the following:
5727 @item -file @var{file}
5728 @itemx -fi @var{file}
5729 Functions in @var{file} will be skipped over when stepping.
5731 @item -gfile @var{file-glob-pattern}
5732 @itemx -gfi @var{file-glob-pattern}
5733 @cindex skipping over files via glob-style patterns
5734 Functions in files matching @var{file-glob-pattern} will be skipped
5738 (gdb) skip -gfi utils/*.c
5741 @item -function @var{linespec}
5742 @itemx -fu @var{linespec}
5743 Functions named by @var{linespec} or the function containing the line
5744 named by @var{linespec} will be skipped over when stepping.
5745 @xref{Specify Location}.
5747 @item -rfunction @var{regexp}
5748 @itemx -rfu @var{regexp}
5749 @cindex skipping over functions via regular expressions
5750 Functions whose name matches @var{regexp} will be skipped over when stepping.
5752 This form is useful for complex function names.
5753 For example, there is generally no need to step into C@t{++} @code{std::string}
5754 constructors or destructors. Plus with C@t{++} templates it can be hard to
5755 write out the full name of the function, and often it doesn't matter what
5756 the template arguments are. Specifying the function to be skipped as a
5757 regular expression makes this easier.
5760 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5763 If you want to skip every templated C@t{++} constructor and destructor
5764 in the @code{std} namespace you can do:
5767 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5771 If no options are specified, the function you're currently debugging
5774 @kindex skip function
5775 @item skip function @r{[}@var{linespec}@r{]}
5776 After running this command, the function named by @var{linespec} or the
5777 function containing the line named by @var{linespec} will be skipped over when
5778 stepping. @xref{Specify Location}.
5780 If you do not specify @var{linespec}, the function you're currently debugging
5783 (If you have a function called @code{file} that you want to skip, use
5784 @kbd{skip function file}.)
5787 @item skip file @r{[}@var{filename}@r{]}
5788 After running this command, any function whose source lives in @var{filename}
5789 will be skipped over when stepping.
5792 (gdb) skip file boring.c
5793 File boring.c will be skipped when stepping.
5796 If you do not specify @var{filename}, functions whose source lives in the file
5797 you're currently debugging will be skipped.
5800 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5801 These are the commands for managing your list of skips:
5805 @item info skip @r{[}@var{range}@r{]}
5806 Print details about the specified skip(s). If @var{range} is not specified,
5807 print a table with details about all functions and files marked for skipping.
5808 @code{info skip} prints the following information about each skip:
5812 A number identifying this skip.
5813 @item Enabled or Disabled
5814 Enabled skips are marked with @samp{y}.
5815 Disabled skips are marked with @samp{n}.
5817 If the file name is a @samp{glob} pattern this is @samp{y}.
5818 Otherwise it is @samp{n}.
5820 The name or @samp{glob} pattern of the file to be skipped.
5821 If no file is specified this is @samp{<none>}.
5823 If the function name is a @samp{regular expression} this is @samp{y}.
5824 Otherwise it is @samp{n}.
5826 The name or regular expression of the function to skip.
5827 If no function is specified this is @samp{<none>}.
5831 @item skip delete @r{[}@var{range}@r{]}
5832 Delete the specified skip(s). If @var{range} is not specified, delete all
5836 @item skip enable @r{[}@var{range}@r{]}
5837 Enable the specified skip(s). If @var{range} is not specified, enable all
5840 @kindex skip disable
5841 @item skip disable @r{[}@var{range}@r{]}
5842 Disable the specified skip(s). If @var{range} is not specified, disable all
5851 A signal is an asynchronous event that can happen in a program. The
5852 operating system defines the possible kinds of signals, and gives each
5853 kind a name and a number. For example, in Unix @code{SIGINT} is the
5854 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5855 @code{SIGSEGV} is the signal a program gets from referencing a place in
5856 memory far away from all the areas in use; @code{SIGALRM} occurs when
5857 the alarm clock timer goes off (which happens only if your program has
5858 requested an alarm).
5860 @cindex fatal signals
5861 Some signals, including @code{SIGALRM}, are a normal part of the
5862 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5863 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5864 program has not specified in advance some other way to handle the signal.
5865 @code{SIGINT} does not indicate an error in your program, but it is normally
5866 fatal so it can carry out the purpose of the interrupt: to kill the program.
5868 @value{GDBN} has the ability to detect any occurrence of a signal in your
5869 program. You can tell @value{GDBN} in advance what to do for each kind of
5872 @cindex handling signals
5873 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5874 @code{SIGALRM} be silently passed to your program
5875 (so as not to interfere with their role in the program's functioning)
5876 but to stop your program immediately whenever an error signal happens.
5877 You can change these settings with the @code{handle} command.
5880 @kindex info signals
5884 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5885 handle each one. You can use this to see the signal numbers of all
5886 the defined types of signals.
5888 @item info signals @var{sig}
5889 Similar, but print information only about the specified signal number.
5891 @code{info handle} is an alias for @code{info signals}.
5893 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5894 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5895 for details about this command.
5898 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5899 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5900 can be the number of a signal or its name (with or without the
5901 @samp{SIG} at the beginning); a list of signal numbers of the form
5902 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5903 known signals. Optional arguments @var{keywords}, described below,
5904 say what change to make.
5908 The keywords allowed by the @code{handle} command can be abbreviated.
5909 Their full names are:
5913 @value{GDBN} should not stop your program when this signal happens. It may
5914 still print a message telling you that the signal has come in.
5917 @value{GDBN} should stop your program when this signal happens. This implies
5918 the @code{print} keyword as well.
5921 @value{GDBN} should print a message when this signal happens.
5924 @value{GDBN} should not mention the occurrence of the signal at all. This
5925 implies the @code{nostop} keyword as well.
5929 @value{GDBN} should allow your program to see this signal; your program
5930 can handle the signal, or else it may terminate if the signal is fatal
5931 and not handled. @code{pass} and @code{noignore} are synonyms.
5935 @value{GDBN} should not allow your program to see this signal.
5936 @code{nopass} and @code{ignore} are synonyms.
5940 When a signal stops your program, the signal is not visible to the
5942 continue. Your program sees the signal then, if @code{pass} is in
5943 effect for the signal in question @emph{at that time}. In other words,
5944 after @value{GDBN} reports a signal, you can use the @code{handle}
5945 command with @code{pass} or @code{nopass} to control whether your
5946 program sees that signal when you continue.
5948 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5949 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5950 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5953 You can also use the @code{signal} command to prevent your program from
5954 seeing a signal, or cause it to see a signal it normally would not see,
5955 or to give it any signal at any time. For example, if your program stopped
5956 due to some sort of memory reference error, you might store correct
5957 values into the erroneous variables and continue, hoping to see more
5958 execution; but your program would probably terminate immediately as
5959 a result of the fatal signal once it saw the signal. To prevent this,
5960 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5963 @cindex stepping and signal handlers
5964 @anchor{stepping and signal handlers}
5966 @value{GDBN} optimizes for stepping the mainline code. If a signal
5967 that has @code{handle nostop} and @code{handle pass} set arrives while
5968 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5969 in progress, @value{GDBN} lets the signal handler run and then resumes
5970 stepping the mainline code once the signal handler returns. In other
5971 words, @value{GDBN} steps over the signal handler. This prevents
5972 signals that you've specified as not interesting (with @code{handle
5973 nostop}) from changing the focus of debugging unexpectedly. Note that
5974 the signal handler itself may still hit a breakpoint, stop for another
5975 signal that has @code{handle stop} in effect, or for any other event
5976 that normally results in stopping the stepping command sooner. Also
5977 note that @value{GDBN} still informs you that the program received a
5978 signal if @code{handle print} is set.
5980 @anchor{stepping into signal handlers}
5982 If you set @code{handle pass} for a signal, and your program sets up a
5983 handler for it, then issuing a stepping command, such as @code{step}
5984 or @code{stepi}, when your program is stopped due to the signal will
5985 step @emph{into} the signal handler (if the target supports that).
5987 Likewise, if you use the @code{queue-signal} command to queue a signal
5988 to be delivered to the current thread when execution of the thread
5989 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5990 stepping command will step into the signal handler.
5992 Here's an example, using @code{stepi} to step to the first instruction
5993 of @code{SIGUSR1}'s handler:
5996 (@value{GDBP}) handle SIGUSR1
5997 Signal Stop Print Pass to program Description
5998 SIGUSR1 Yes Yes Yes User defined signal 1
6002 Program received signal SIGUSR1, User defined signal 1.
6003 main () sigusr1.c:28
6006 sigusr1_handler () at sigusr1.c:9
6010 The same, but using @code{queue-signal} instead of waiting for the
6011 program to receive the signal first:
6016 (@value{GDBP}) queue-signal SIGUSR1
6018 sigusr1_handler () at sigusr1.c:9
6023 @cindex extra signal information
6024 @anchor{extra signal information}
6026 On some targets, @value{GDBN} can inspect extra signal information
6027 associated with the intercepted signal, before it is actually
6028 delivered to the program being debugged. This information is exported
6029 by the convenience variable @code{$_siginfo}, and consists of data
6030 that is passed by the kernel to the signal handler at the time of the
6031 receipt of a signal. The data type of the information itself is
6032 target dependent. You can see the data type using the @code{ptype
6033 $_siginfo} command. On Unix systems, it typically corresponds to the
6034 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6037 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6038 referenced address that raised a segmentation fault.
6042 (@value{GDBP}) continue
6043 Program received signal SIGSEGV, Segmentation fault.
6044 0x0000000000400766 in main ()
6046 (@value{GDBP}) ptype $_siginfo
6053 struct @{...@} _kill;
6054 struct @{...@} _timer;
6056 struct @{...@} _sigchld;
6057 struct @{...@} _sigfault;
6058 struct @{...@} _sigpoll;
6061 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6065 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6066 $1 = (void *) 0x7ffff7ff7000
6070 Depending on target support, @code{$_siginfo} may also be writable.
6072 @cindex Intel MPX boundary violations
6073 @cindex boundary violations, Intel MPX
6074 On some targets, a @code{SIGSEGV} can be caused by a boundary
6075 violation, i.e., accessing an address outside of the allowed range.
6076 In those cases @value{GDBN} may displays additional information,
6077 depending on how @value{GDBN} has been told to handle the signal.
6078 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6079 kind: "Upper" or "Lower", the memory address accessed and the
6080 bounds, while with @code{handle nostop SIGSEGV} no additional
6081 information is displayed.
6083 The usual output of a segfault is:
6085 Program received signal SIGSEGV, Segmentation fault
6086 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6087 68 value = *(p + len);
6090 While a bound violation is presented as:
6092 Program received signal SIGSEGV, Segmentation fault
6093 Upper bound violation while accessing address 0x7fffffffc3b3
6094 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6095 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6096 68 value = *(p + len);
6100 @section Stopping and Starting Multi-thread Programs
6102 @cindex stopped threads
6103 @cindex threads, stopped
6105 @cindex continuing threads
6106 @cindex threads, continuing
6108 @value{GDBN} supports debugging programs with multiple threads
6109 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6110 are two modes of controlling execution of your program within the
6111 debugger. In the default mode, referred to as @dfn{all-stop mode},
6112 when any thread in your program stops (for example, at a breakpoint
6113 or while being stepped), all other threads in the program are also stopped by
6114 @value{GDBN}. On some targets, @value{GDBN} also supports
6115 @dfn{non-stop mode}, in which other threads can continue to run freely while
6116 you examine the stopped thread in the debugger.
6119 * All-Stop Mode:: All threads stop when GDB takes control
6120 * Non-Stop Mode:: Other threads continue to execute
6121 * Background Execution:: Running your program asynchronously
6122 * Thread-Specific Breakpoints:: Controlling breakpoints
6123 * Interrupted System Calls:: GDB may interfere with system calls
6124 * Observer Mode:: GDB does not alter program behavior
6128 @subsection All-Stop Mode
6130 @cindex all-stop mode
6132 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6133 @emph{all} threads of execution stop, not just the current thread. This
6134 allows you to examine the overall state of the program, including
6135 switching between threads, without worrying that things may change
6138 Conversely, whenever you restart the program, @emph{all} threads start
6139 executing. @emph{This is true even when single-stepping} with commands
6140 like @code{step} or @code{next}.
6142 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6143 Since thread scheduling is up to your debugging target's operating
6144 system (not controlled by @value{GDBN}), other threads may
6145 execute more than one statement while the current thread completes a
6146 single step. Moreover, in general other threads stop in the middle of a
6147 statement, rather than at a clean statement boundary, when the program
6150 You might even find your program stopped in another thread after
6151 continuing or even single-stepping. This happens whenever some other
6152 thread runs into a breakpoint, a signal, or an exception before the
6153 first thread completes whatever you requested.
6155 @cindex automatic thread selection
6156 @cindex switching threads automatically
6157 @cindex threads, automatic switching
6158 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6159 signal, it automatically selects the thread where that breakpoint or
6160 signal happened. @value{GDBN} alerts you to the context switch with a
6161 message such as @samp{[Switching to Thread @var{n}]} to identify the
6164 On some OSes, you can modify @value{GDBN}'s default behavior by
6165 locking the OS scheduler to allow only a single thread to run.
6168 @item set scheduler-locking @var{mode}
6169 @cindex scheduler locking mode
6170 @cindex lock scheduler
6171 Set the scheduler locking mode. It applies to normal execution,
6172 record mode, and replay mode. If it is @code{off}, then there is no
6173 locking and any thread may run at any time. If @code{on}, then only
6174 the current thread may run when the inferior is resumed. The
6175 @code{step} mode optimizes for single-stepping; it prevents other
6176 threads from preempting the current thread while you are stepping, so
6177 that the focus of debugging does not change unexpectedly. Other
6178 threads never get a chance to run when you step, and they are
6179 completely free to run when you use commands like @samp{continue},
6180 @samp{until}, or @samp{finish}. However, unless another thread hits a
6181 breakpoint during its timeslice, @value{GDBN} does not change the
6182 current thread away from the thread that you are debugging. The
6183 @code{replay} mode behaves like @code{off} in record mode and like
6184 @code{on} in replay mode.
6186 @item show scheduler-locking
6187 Display the current scheduler locking mode.
6190 @cindex resume threads of multiple processes simultaneously
6191 By default, when you issue one of the execution commands such as
6192 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6193 threads of the current inferior to run. For example, if @value{GDBN}
6194 is attached to two inferiors, each with two threads, the
6195 @code{continue} command resumes only the two threads of the current
6196 inferior. This is useful, for example, when you debug a program that
6197 forks and you want to hold the parent stopped (so that, for instance,
6198 it doesn't run to exit), while you debug the child. In other
6199 situations, you may not be interested in inspecting the current state
6200 of any of the processes @value{GDBN} is attached to, and you may want
6201 to resume them all until some breakpoint is hit. In the latter case,
6202 you can instruct @value{GDBN} to allow all threads of all the
6203 inferiors to run with the @w{@code{set schedule-multiple}} command.
6206 @kindex set schedule-multiple
6207 @item set schedule-multiple
6208 Set the mode for allowing threads of multiple processes to be resumed
6209 when an execution command is issued. When @code{on}, all threads of
6210 all processes are allowed to run. When @code{off}, only the threads
6211 of the current process are resumed. The default is @code{off}. The
6212 @code{scheduler-locking} mode takes precedence when set to @code{on},
6213 or while you are stepping and set to @code{step}.
6215 @item show schedule-multiple
6216 Display the current mode for resuming the execution of threads of
6221 @subsection Non-Stop Mode
6223 @cindex non-stop mode
6225 @c This section is really only a place-holder, and needs to be expanded
6226 @c with more details.
6228 For some multi-threaded targets, @value{GDBN} supports an optional
6229 mode of operation in which you can examine stopped program threads in
6230 the debugger while other threads continue to execute freely. This
6231 minimizes intrusion when debugging live systems, such as programs
6232 where some threads have real-time constraints or must continue to
6233 respond to external events. This is referred to as @dfn{non-stop} mode.
6235 In non-stop mode, when a thread stops to report a debugging event,
6236 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6237 threads as well, in contrast to the all-stop mode behavior. Additionally,
6238 execution commands such as @code{continue} and @code{step} apply by default
6239 only to the current thread in non-stop mode, rather than all threads as
6240 in all-stop mode. This allows you to control threads explicitly in
6241 ways that are not possible in all-stop mode --- for example, stepping
6242 one thread while allowing others to run freely, stepping
6243 one thread while holding all others stopped, or stepping several threads
6244 independently and simultaneously.
6246 To enter non-stop mode, use this sequence of commands before you run
6247 or attach to your program:
6250 # If using the CLI, pagination breaks non-stop.
6253 # Finally, turn it on!
6257 You can use these commands to manipulate the non-stop mode setting:
6260 @kindex set non-stop
6261 @item set non-stop on
6262 Enable selection of non-stop mode.
6263 @item set non-stop off
6264 Disable selection of non-stop mode.
6265 @kindex show non-stop
6267 Show the current non-stop enablement setting.
6270 Note these commands only reflect whether non-stop mode is enabled,
6271 not whether the currently-executing program is being run in non-stop mode.
6272 In particular, the @code{set non-stop} preference is only consulted when
6273 @value{GDBN} starts or connects to the target program, and it is generally
6274 not possible to switch modes once debugging has started. Furthermore,
6275 since not all targets support non-stop mode, even when you have enabled
6276 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6279 In non-stop mode, all execution commands apply only to the current thread
6280 by default. That is, @code{continue} only continues one thread.
6281 To continue all threads, issue @code{continue -a} or @code{c -a}.
6283 You can use @value{GDBN}'s background execution commands
6284 (@pxref{Background Execution}) to run some threads in the background
6285 while you continue to examine or step others from @value{GDBN}.
6286 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6287 always executed asynchronously in non-stop mode.
6289 Suspending execution is done with the @code{interrupt} command when
6290 running in the background, or @kbd{Ctrl-c} during foreground execution.
6291 In all-stop mode, this stops the whole process;
6292 but in non-stop mode the interrupt applies only to the current thread.
6293 To stop the whole program, use @code{interrupt -a}.
6295 Other execution commands do not currently support the @code{-a} option.
6297 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6298 that thread current, as it does in all-stop mode. This is because the
6299 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6300 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6301 changed to a different thread just as you entered a command to operate on the
6302 previously current thread.
6304 @node Background Execution
6305 @subsection Background Execution
6307 @cindex foreground execution
6308 @cindex background execution
6309 @cindex asynchronous execution
6310 @cindex execution, foreground, background and asynchronous
6312 @value{GDBN}'s execution commands have two variants: the normal
6313 foreground (synchronous) behavior, and a background
6314 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6315 the program to report that some thread has stopped before prompting for
6316 another command. In background execution, @value{GDBN} immediately gives
6317 a command prompt so that you can issue other commands while your program runs.
6319 If the target doesn't support async mode, @value{GDBN} issues an error
6320 message if you attempt to use the background execution commands.
6322 To specify background execution, add a @code{&} to the command. For example,
6323 the background form of the @code{continue} command is @code{continue&}, or
6324 just @code{c&}. The execution commands that accept background execution
6330 @xref{Starting, , Starting your Program}.
6334 @xref{Attach, , Debugging an Already-running Process}.
6338 @xref{Continuing and Stepping, step}.
6342 @xref{Continuing and Stepping, stepi}.
6346 @xref{Continuing and Stepping, next}.
6350 @xref{Continuing and Stepping, nexti}.
6354 @xref{Continuing and Stepping, continue}.
6358 @xref{Continuing and Stepping, finish}.
6362 @xref{Continuing and Stepping, until}.
6366 Background execution is especially useful in conjunction with non-stop
6367 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6368 However, you can also use these commands in the normal all-stop mode with
6369 the restriction that you cannot issue another execution command until the
6370 previous one finishes. Examples of commands that are valid in all-stop
6371 mode while the program is running include @code{help} and @code{info break}.
6373 You can interrupt your program while it is running in the background by
6374 using the @code{interrupt} command.
6381 Suspend execution of the running program. In all-stop mode,
6382 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6383 only the current thread. To stop the whole program in non-stop mode,
6384 use @code{interrupt -a}.
6387 @node Thread-Specific Breakpoints
6388 @subsection Thread-Specific Breakpoints
6390 When your program has multiple threads (@pxref{Threads,, Debugging
6391 Programs with Multiple Threads}), you can choose whether to set
6392 breakpoints on all threads, or on a particular thread.
6395 @cindex breakpoints and threads
6396 @cindex thread breakpoints
6397 @kindex break @dots{} thread @var{thread-id}
6398 @item break @var{location} thread @var{thread-id}
6399 @itemx break @var{location} thread @var{thread-id} if @dots{}
6400 @var{location} specifies source lines; there are several ways of
6401 writing them (@pxref{Specify Location}), but the effect is always to
6402 specify some source line.
6404 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6405 to specify that you only want @value{GDBN} to stop the program when a
6406 particular thread reaches this breakpoint. The @var{thread-id} specifier
6407 is one of the thread identifiers assigned by @value{GDBN}, shown
6408 in the first column of the @samp{info threads} display.
6410 If you do not specify @samp{thread @var{thread-id}} when you set a
6411 breakpoint, the breakpoint applies to @emph{all} threads of your
6414 You can use the @code{thread} qualifier on conditional breakpoints as
6415 well; in this case, place @samp{thread @var{thread-id}} before or
6416 after the breakpoint condition, like this:
6419 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6424 Thread-specific breakpoints are automatically deleted when
6425 @value{GDBN} detects the corresponding thread is no longer in the
6426 thread list. For example:
6430 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6433 There are several ways for a thread to disappear, such as a regular
6434 thread exit, but also when you detach from the process with the
6435 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6436 Process}), or if @value{GDBN} loses the remote connection
6437 (@pxref{Remote Debugging}), etc. Note that with some targets,
6438 @value{GDBN} is only able to detect a thread has exited when the user
6439 explictly asks for the thread list with the @code{info threads}
6442 @node Interrupted System Calls
6443 @subsection Interrupted System Calls
6445 @cindex thread breakpoints and system calls
6446 @cindex system calls and thread breakpoints
6447 @cindex premature return from system calls
6448 There is an unfortunate side effect when using @value{GDBN} to debug
6449 multi-threaded programs. If one thread stops for a
6450 breakpoint, or for some other reason, and another thread is blocked in a
6451 system call, then the system call may return prematurely. This is a
6452 consequence of the interaction between multiple threads and the signals
6453 that @value{GDBN} uses to implement breakpoints and other events that
6456 To handle this problem, your program should check the return value of
6457 each system call and react appropriately. This is good programming
6460 For example, do not write code like this:
6466 The call to @code{sleep} will return early if a different thread stops
6467 at a breakpoint or for some other reason.
6469 Instead, write this:
6474 unslept = sleep (unslept);
6477 A system call is allowed to return early, so the system is still
6478 conforming to its specification. But @value{GDBN} does cause your
6479 multi-threaded program to behave differently than it would without
6482 Also, @value{GDBN} uses internal breakpoints in the thread library to
6483 monitor certain events such as thread creation and thread destruction.
6484 When such an event happens, a system call in another thread may return
6485 prematurely, even though your program does not appear to stop.
6488 @subsection Observer Mode
6490 If you want to build on non-stop mode and observe program behavior
6491 without any chance of disruption by @value{GDBN}, you can set
6492 variables to disable all of the debugger's attempts to modify state,
6493 whether by writing memory, inserting breakpoints, etc. These operate
6494 at a low level, intercepting operations from all commands.
6496 When all of these are set to @code{off}, then @value{GDBN} is said to
6497 be @dfn{observer mode}. As a convenience, the variable
6498 @code{observer} can be set to disable these, plus enable non-stop
6501 Note that @value{GDBN} will not prevent you from making nonsensical
6502 combinations of these settings. For instance, if you have enabled
6503 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6504 then breakpoints that work by writing trap instructions into the code
6505 stream will still not be able to be placed.
6510 @item set observer on
6511 @itemx set observer off
6512 When set to @code{on}, this disables all the permission variables
6513 below (except for @code{insert-fast-tracepoints}), plus enables
6514 non-stop debugging. Setting this to @code{off} switches back to
6515 normal debugging, though remaining in non-stop mode.
6518 Show whether observer mode is on or off.
6520 @kindex may-write-registers
6521 @item set may-write-registers on
6522 @itemx set may-write-registers off
6523 This controls whether @value{GDBN} will attempt to alter the values of
6524 registers, such as with assignment expressions in @code{print}, or the
6525 @code{jump} command. It defaults to @code{on}.
6527 @item show may-write-registers
6528 Show the current permission to write registers.
6530 @kindex may-write-memory
6531 @item set may-write-memory on
6532 @itemx set may-write-memory off
6533 This controls whether @value{GDBN} will attempt to alter the contents
6534 of memory, such as with assignment expressions in @code{print}. It
6535 defaults to @code{on}.
6537 @item show may-write-memory
6538 Show the current permission to write memory.
6540 @kindex may-insert-breakpoints
6541 @item set may-insert-breakpoints on
6542 @itemx set may-insert-breakpoints off
6543 This controls whether @value{GDBN} will attempt to insert breakpoints.
6544 This affects all breakpoints, including internal breakpoints defined
6545 by @value{GDBN}. It defaults to @code{on}.
6547 @item show may-insert-breakpoints
6548 Show the current permission to insert breakpoints.
6550 @kindex may-insert-tracepoints
6551 @item set may-insert-tracepoints on
6552 @itemx set may-insert-tracepoints off
6553 This controls whether @value{GDBN} will attempt to insert (regular)
6554 tracepoints at the beginning of a tracing experiment. It affects only
6555 non-fast tracepoints, fast tracepoints being under the control of
6556 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6558 @item show may-insert-tracepoints
6559 Show the current permission to insert tracepoints.
6561 @kindex may-insert-fast-tracepoints
6562 @item set may-insert-fast-tracepoints on
6563 @itemx set may-insert-fast-tracepoints off
6564 This controls whether @value{GDBN} will attempt to insert fast
6565 tracepoints at the beginning of a tracing experiment. It affects only
6566 fast tracepoints, regular (non-fast) tracepoints being under the
6567 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6569 @item show may-insert-fast-tracepoints
6570 Show the current permission to insert fast tracepoints.
6572 @kindex may-interrupt
6573 @item set may-interrupt on
6574 @itemx set may-interrupt off
6575 This controls whether @value{GDBN} will attempt to interrupt or stop
6576 program execution. When this variable is @code{off}, the
6577 @code{interrupt} command will have no effect, nor will
6578 @kbd{Ctrl-c}. It defaults to @code{on}.
6580 @item show may-interrupt
6581 Show the current permission to interrupt or stop the program.
6585 @node Reverse Execution
6586 @chapter Running programs backward
6587 @cindex reverse execution
6588 @cindex running programs backward
6590 When you are debugging a program, it is not unusual to realize that
6591 you have gone too far, and some event of interest has already happened.
6592 If the target environment supports it, @value{GDBN} can allow you to
6593 ``rewind'' the program by running it backward.
6595 A target environment that supports reverse execution should be able
6596 to ``undo'' the changes in machine state that have taken place as the
6597 program was executing normally. Variables, registers etc.@: should
6598 revert to their previous values. Obviously this requires a great
6599 deal of sophistication on the part of the target environment; not
6600 all target environments can support reverse execution.
6602 When a program is executed in reverse, the instructions that
6603 have most recently been executed are ``un-executed'', in reverse
6604 order. The program counter runs backward, following the previous
6605 thread of execution in reverse. As each instruction is ``un-executed'',
6606 the values of memory and/or registers that were changed by that
6607 instruction are reverted to their previous states. After executing
6608 a piece of source code in reverse, all side effects of that code
6609 should be ``undone'', and all variables should be returned to their
6610 prior values@footnote{
6611 Note that some side effects are easier to undo than others. For instance,
6612 memory and registers are relatively easy, but device I/O is hard. Some
6613 targets may be able undo things like device I/O, and some may not.
6615 The contract between @value{GDBN} and the reverse executing target
6616 requires only that the target do something reasonable when
6617 @value{GDBN} tells it to execute backwards, and then report the
6618 results back to @value{GDBN}. Whatever the target reports back to
6619 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6620 assumes that the memory and registers that the target reports are in a
6621 consistant state, but @value{GDBN} accepts whatever it is given.
6624 If you are debugging in a target environment that supports
6625 reverse execution, @value{GDBN} provides the following commands.
6628 @kindex reverse-continue
6629 @kindex rc @r{(@code{reverse-continue})}
6630 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6631 @itemx rc @r{[}@var{ignore-count}@r{]}
6632 Beginning at the point where your program last stopped, start executing
6633 in reverse. Reverse execution will stop for breakpoints and synchronous
6634 exceptions (signals), just like normal execution. Behavior of
6635 asynchronous signals depends on the target environment.
6637 @kindex reverse-step
6638 @kindex rs @r{(@code{step})}
6639 @item reverse-step @r{[}@var{count}@r{]}
6640 Run the program backward until control reaches the start of a
6641 different source line; then stop it, and return control to @value{GDBN}.
6643 Like the @code{step} command, @code{reverse-step} will only stop
6644 at the beginning of a source line. It ``un-executes'' the previously
6645 executed source line. If the previous source line included calls to
6646 debuggable functions, @code{reverse-step} will step (backward) into
6647 the called function, stopping at the beginning of the @emph{last}
6648 statement in the called function (typically a return statement).
6650 Also, as with the @code{step} command, if non-debuggable functions are
6651 called, @code{reverse-step} will run thru them backward without stopping.
6653 @kindex reverse-stepi
6654 @kindex rsi @r{(@code{reverse-stepi})}
6655 @item reverse-stepi @r{[}@var{count}@r{]}
6656 Reverse-execute one machine instruction. Note that the instruction
6657 to be reverse-executed is @emph{not} the one pointed to by the program
6658 counter, but the instruction executed prior to that one. For instance,
6659 if the last instruction was a jump, @code{reverse-stepi} will take you
6660 back from the destination of the jump to the jump instruction itself.
6662 @kindex reverse-next
6663 @kindex rn @r{(@code{reverse-next})}
6664 @item reverse-next @r{[}@var{count}@r{]}
6665 Run backward to the beginning of the previous line executed in
6666 the current (innermost) stack frame. If the line contains function
6667 calls, they will be ``un-executed'' without stopping. Starting from
6668 the first line of a function, @code{reverse-next} will take you back
6669 to the caller of that function, @emph{before} the function was called,
6670 just as the normal @code{next} command would take you from the last
6671 line of a function back to its return to its caller
6672 @footnote{Unless the code is too heavily optimized.}.
6674 @kindex reverse-nexti
6675 @kindex rni @r{(@code{reverse-nexti})}
6676 @item reverse-nexti @r{[}@var{count}@r{]}
6677 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6678 in reverse, except that called functions are ``un-executed'' atomically.
6679 That is, if the previously executed instruction was a return from
6680 another function, @code{reverse-nexti} will continue to execute
6681 in reverse until the call to that function (from the current stack
6684 @kindex reverse-finish
6685 @item reverse-finish
6686 Just as the @code{finish} command takes you to the point where the
6687 current function returns, @code{reverse-finish} takes you to the point
6688 where it was called. Instead of ending up at the end of the current
6689 function invocation, you end up at the beginning.
6691 @kindex set exec-direction
6692 @item set exec-direction
6693 Set the direction of target execution.
6694 @item set exec-direction reverse
6695 @cindex execute forward or backward in time
6696 @value{GDBN} will perform all execution commands in reverse, until the
6697 exec-direction mode is changed to ``forward''. Affected commands include
6698 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6699 command cannot be used in reverse mode.
6700 @item set exec-direction forward
6701 @value{GDBN} will perform all execution commands in the normal fashion.
6702 This is the default.
6706 @node Process Record and Replay
6707 @chapter Recording Inferior's Execution and Replaying It
6708 @cindex process record and replay
6709 @cindex recording inferior's execution and replaying it
6711 On some platforms, @value{GDBN} provides a special @dfn{process record
6712 and replay} target that can record a log of the process execution, and
6713 replay it later with both forward and reverse execution commands.
6716 When this target is in use, if the execution log includes the record
6717 for the next instruction, @value{GDBN} will debug in @dfn{replay
6718 mode}. In the replay mode, the inferior does not really execute code
6719 instructions. Instead, all the events that normally happen during
6720 code execution are taken from the execution log. While code is not
6721 really executed in replay mode, the values of registers (including the
6722 program counter register) and the memory of the inferior are still
6723 changed as they normally would. Their contents are taken from the
6727 If the record for the next instruction is not in the execution log,
6728 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6729 inferior executes normally, and @value{GDBN} records the execution log
6732 The process record and replay target supports reverse execution
6733 (@pxref{Reverse Execution}), even if the platform on which the
6734 inferior runs does not. However, the reverse execution is limited in
6735 this case by the range of the instructions recorded in the execution
6736 log. In other words, reverse execution on platforms that don't
6737 support it directly can only be done in the replay mode.
6739 When debugging in the reverse direction, @value{GDBN} will work in
6740 replay mode as long as the execution log includes the record for the
6741 previous instruction; otherwise, it will work in record mode, if the
6742 platform supports reverse execution, or stop if not.
6744 For architecture environments that support process record and replay,
6745 @value{GDBN} provides the following commands:
6748 @kindex target record
6749 @kindex target record-full
6750 @kindex target record-btrace
6753 @kindex record btrace
6754 @kindex record btrace bts
6755 @kindex record btrace pt
6761 @kindex rec btrace bts
6762 @kindex rec btrace pt
6765 @item record @var{method}
6766 This command starts the process record and replay target. The
6767 recording method can be specified as parameter. Without a parameter
6768 the command uses the @code{full} recording method. The following
6769 recording methods are available:
6773 Full record/replay recording using @value{GDBN}'s software record and
6774 replay implementation. This method allows replaying and reverse
6777 @item btrace @var{format}
6778 Hardware-supported instruction recording. This method does not record
6779 data. Further, the data is collected in a ring buffer so old data will
6780 be overwritten when the buffer is full. It allows limited reverse
6781 execution. Variables and registers are not available during reverse
6782 execution. In remote debugging, recording continues on disconnect.
6783 Recorded data can be inspected after reconnecting. The recording may
6784 be stopped using @code{record stop}.
6786 The recording format can be specified as parameter. Without a parameter
6787 the command chooses the recording format. The following recording
6788 formats are available:
6792 @cindex branch trace store
6793 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6794 this format, the processor stores a from/to record for each executed
6795 branch in the btrace ring buffer.
6798 @cindex Intel Processor Trace
6799 Use the @dfn{Intel Processor Trace} recording format. In this
6800 format, the processor stores the execution trace in a compressed form
6801 that is afterwards decoded by @value{GDBN}.
6803 The trace can be recorded with very low overhead. The compressed
6804 trace format also allows small trace buffers to already contain a big
6805 number of instructions compared to @acronym{BTS}.
6807 Decoding the recorded execution trace, on the other hand, is more
6808 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6809 increased number of instructions to process. You should increase the
6810 buffer-size with care.
6813 Not all recording formats may be available on all processors.
6816 The process record and replay target can only debug a process that is
6817 already running. Therefore, you need first to start the process with
6818 the @kbd{run} or @kbd{start} commands, and then start the recording
6819 with the @kbd{record @var{method}} command.
6821 @cindex displaced stepping, and process record and replay
6822 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6823 will be automatically disabled when process record and replay target
6824 is started. That's because the process record and replay target
6825 doesn't support displaced stepping.
6827 @cindex non-stop mode, and process record and replay
6828 @cindex asynchronous execution, and process record and replay
6829 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6830 the asynchronous execution mode (@pxref{Background Execution}), not
6831 all recording methods are available. The @code{full} recording method
6832 does not support these two modes.
6837 Stop the process record and replay target. When process record and
6838 replay target stops, the entire execution log will be deleted and the
6839 inferior will either be terminated, or will remain in its final state.
6841 When you stop the process record and replay target in record mode (at
6842 the end of the execution log), the inferior will be stopped at the
6843 next instruction that would have been recorded. In other words, if
6844 you record for a while and then stop recording, the inferior process
6845 will be left in the same state as if the recording never happened.
6847 On the other hand, if the process record and replay target is stopped
6848 while in replay mode (that is, not at the end of the execution log,
6849 but at some earlier point), the inferior process will become ``live''
6850 at that earlier state, and it will then be possible to continue the
6851 usual ``live'' debugging of the process from that state.
6853 When the inferior process exits, or @value{GDBN} detaches from it,
6854 process record and replay target will automatically stop itself.
6858 Go to a specific location in the execution log. There are several
6859 ways to specify the location to go to:
6862 @item record goto begin
6863 @itemx record goto start
6864 Go to the beginning of the execution log.
6866 @item record goto end
6867 Go to the end of the execution log.
6869 @item record goto @var{n}
6870 Go to instruction number @var{n} in the execution log.
6874 @item record save @var{filename}
6875 Save the execution log to a file @file{@var{filename}}.
6876 Default filename is @file{gdb_record.@var{process_id}}, where
6877 @var{process_id} is the process ID of the inferior.
6879 This command may not be available for all recording methods.
6881 @kindex record restore
6882 @item record restore @var{filename}
6883 Restore the execution log from a file @file{@var{filename}}.
6884 File must have been created with @code{record save}.
6886 @kindex set record full
6887 @item set record full insn-number-max @var{limit}
6888 @itemx set record full insn-number-max unlimited
6889 Set the limit of instructions to be recorded for the @code{full}
6890 recording method. Default value is 200000.
6892 If @var{limit} is a positive number, then @value{GDBN} will start
6893 deleting instructions from the log once the number of the record
6894 instructions becomes greater than @var{limit}. For every new recorded
6895 instruction, @value{GDBN} will delete the earliest recorded
6896 instruction to keep the number of recorded instructions at the limit.
6897 (Since deleting recorded instructions loses information, @value{GDBN}
6898 lets you control what happens when the limit is reached, by means of
6899 the @code{stop-at-limit} option, described below.)
6901 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6902 delete recorded instructions from the execution log. The number of
6903 recorded instructions is limited only by the available memory.
6905 @kindex show record full
6906 @item show record full insn-number-max
6907 Show the limit of instructions to be recorded with the @code{full}
6910 @item set record full stop-at-limit
6911 Control the behavior of the @code{full} recording method when the
6912 number of recorded instructions reaches the limit. If ON (the
6913 default), @value{GDBN} will stop when the limit is reached for the
6914 first time and ask you whether you want to stop the inferior or
6915 continue running it and recording the execution log. If you decide
6916 to continue recording, each new recorded instruction will cause the
6917 oldest one to be deleted.
6919 If this option is OFF, @value{GDBN} will automatically delete the
6920 oldest record to make room for each new one, without asking.
6922 @item show record full stop-at-limit
6923 Show the current setting of @code{stop-at-limit}.
6925 @item set record full memory-query
6926 Control the behavior when @value{GDBN} is unable to record memory
6927 changes caused by an instruction for the @code{full} recording method.
6928 If ON, @value{GDBN} will query whether to stop the inferior in that
6931 If this option is OFF (the default), @value{GDBN} will automatically
6932 ignore the effect of such instructions on memory. Later, when
6933 @value{GDBN} replays this execution log, it will mark the log of this
6934 instruction as not accessible, and it will not affect the replay
6937 @item show record full memory-query
6938 Show the current setting of @code{memory-query}.
6940 @kindex set record btrace
6941 The @code{btrace} record target does not trace data. As a
6942 convenience, when replaying, @value{GDBN} reads read-only memory off
6943 the live program directly, assuming that the addresses of the
6944 read-only areas don't change. This for example makes it possible to
6945 disassemble code while replaying, but not to print variables.
6946 In some cases, being able to inspect variables might be useful.
6947 You can use the following command for that:
6949 @item set record btrace replay-memory-access
6950 Control the behavior of the @code{btrace} recording method when
6951 accessing memory during replay. If @code{read-only} (the default),
6952 @value{GDBN} will only allow accesses to read-only memory.
6953 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6954 and to read-write memory. Beware that the accessed memory corresponds
6955 to the live target and not necessarily to the current replay
6958 @item set record btrace cpu @var{identifier}
6959 Set the processor to be used for enabling workarounds for processor
6960 errata when decoding the trace.
6962 Processor errata are defects in processor operation, caused by its
6963 design or manufacture. They can cause a trace not to match the
6964 specification. This, in turn, may cause trace decode to fail.
6965 @value{GDBN} can detect erroneous trace packets and correct them, thus
6966 avoiding the decoding failures. These corrections are known as
6967 @dfn{errata workarounds}, and are enabled based on the processor on
6968 which the trace was recorded.
6970 By default, @value{GDBN} attempts to detect the processor
6971 automatically, and apply the necessary workarounds for it. However,
6972 you may need to specify the processor if @value{GDBN} does not yet
6973 support it. This command allows you to do that, and also allows to
6974 disable the workarounds.
6976 The argument @var{identifier} identifies the @sc{cpu} and is of the
6977 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
6978 there are two special identifiers, @code{none} and @code{auto}
6981 The following vendor identifiers and corresponding processor
6982 identifiers are currently supported:
6984 @multitable @columnfractions .1 .9
6987 @tab @var{family}/@var{model}[/@var{stepping}]
6991 On GNU/Linux systems, the processor @var{family}, @var{model}, and
6992 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
6994 If @var{identifier} is @code{auto}, enable errata workarounds for the
6995 processor on which the trace was recorded. If @var{identifier} is
6996 @code{none}, errata workarounds are disabled.
6998 For example, when using an old @value{GDBN} on a new system, decode
6999 may fail because @value{GDBN} does not support the new processor. It
7000 often suffices to specify an older processor that @value{GDBN}
7005 Active record target: record-btrace
7006 Recording format: Intel Processor Trace.
7008 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7009 (gdb) set record btrace cpu intel:6/158
7011 Active record target: record-btrace
7012 Recording format: Intel Processor Trace.
7014 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7017 @kindex show record btrace
7018 @item show record btrace replay-memory-access
7019 Show the current setting of @code{replay-memory-access}.
7021 @item show record btrace cpu
7022 Show the processor to be used for enabling trace decode errata
7025 @kindex set record btrace bts
7026 @item set record btrace bts buffer-size @var{size}
7027 @itemx set record btrace bts buffer-size unlimited
7028 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7029 format. Default is 64KB.
7031 If @var{size} is a positive number, then @value{GDBN} will try to
7032 allocate a buffer of at least @var{size} bytes for each new thread
7033 that uses the btrace recording method and the @acronym{BTS} format.
7034 The actually obtained buffer size may differ from the requested
7035 @var{size}. Use the @code{info record} command to see the actual
7036 buffer size for each thread that uses the btrace recording method and
7037 the @acronym{BTS} format.
7039 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7040 allocate a buffer of 4MB.
7042 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7043 also need longer to process the branch trace data before it can be used.
7045 @item show record btrace bts buffer-size @var{size}
7046 Show the current setting of the requested ring buffer size for branch
7047 tracing in @acronym{BTS} format.
7049 @kindex set record btrace pt
7050 @item set record btrace pt buffer-size @var{size}
7051 @itemx set record btrace pt buffer-size unlimited
7052 Set the requested ring buffer size for branch tracing in Intel
7053 Processor Trace format. Default is 16KB.
7055 If @var{size} is a positive number, then @value{GDBN} will try to
7056 allocate a buffer of at least @var{size} bytes for each new thread
7057 that uses the btrace recording method and the Intel Processor Trace
7058 format. The actually obtained buffer size may differ from the
7059 requested @var{size}. Use the @code{info record} command to see the
7060 actual buffer size for each thread.
7062 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7063 allocate a buffer of 4MB.
7065 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7066 also need longer to process the branch trace data before it can be used.
7068 @item show record btrace pt buffer-size @var{size}
7069 Show the current setting of the requested ring buffer size for branch
7070 tracing in Intel Processor Trace format.
7074 Show various statistics about the recording depending on the recording
7079 For the @code{full} recording method, it shows the state of process
7080 record and its in-memory execution log buffer, including:
7084 Whether in record mode or replay mode.
7086 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7088 Highest recorded instruction number.
7090 Current instruction about to be replayed (if in replay mode).
7092 Number of instructions contained in the execution log.
7094 Maximum number of instructions that may be contained in the execution log.
7098 For the @code{btrace} recording method, it shows:
7104 Number of instructions that have been recorded.
7106 Number of blocks of sequential control-flow formed by the recorded
7109 Whether in record mode or replay mode.
7112 For the @code{bts} recording format, it also shows:
7115 Size of the perf ring buffer.
7118 For the @code{pt} recording format, it also shows:
7121 Size of the perf ring buffer.
7125 @kindex record delete
7128 When record target runs in replay mode (``in the past''), delete the
7129 subsequent execution log and begin to record a new execution log starting
7130 from the current address. This means you will abandon the previously
7131 recorded ``future'' and begin recording a new ``future''.
7133 @kindex record instruction-history
7134 @kindex rec instruction-history
7135 @item record instruction-history
7136 Disassembles instructions from the recorded execution log. By
7137 default, ten instructions are disassembled. This can be changed using
7138 the @code{set record instruction-history-size} command. Instructions
7139 are printed in execution order.
7141 It can also print mixed source+disassembly if you specify the the
7142 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7143 as well as in symbolic form by specifying the @code{/r} modifier.
7145 The current position marker is printed for the instruction at the
7146 current program counter value. This instruction can appear multiple
7147 times in the trace and the current position marker will be printed
7148 every time. To omit the current position marker, specify the
7151 To better align the printed instructions when the trace contains
7152 instructions from more than one function, the function name may be
7153 omitted by specifying the @code{/f} modifier.
7155 Speculatively executed instructions are prefixed with @samp{?}. This
7156 feature is not available for all recording formats.
7158 There are several ways to specify what part of the execution log to
7162 @item record instruction-history @var{insn}
7163 Disassembles ten instructions starting from instruction number
7166 @item record instruction-history @var{insn}, +/-@var{n}
7167 Disassembles @var{n} instructions around instruction number
7168 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7169 @var{n} instructions after instruction number @var{insn}. If
7170 @var{n} is preceded with @code{-}, disassembles @var{n}
7171 instructions before instruction number @var{insn}.
7173 @item record instruction-history
7174 Disassembles ten more instructions after the last disassembly.
7176 @item record instruction-history -
7177 Disassembles ten more instructions before the last disassembly.
7179 @item record instruction-history @var{begin}, @var{end}
7180 Disassembles instructions beginning with instruction number
7181 @var{begin} until instruction number @var{end}. The instruction
7182 number @var{end} is included.
7185 This command may not be available for all recording methods.
7188 @item set record instruction-history-size @var{size}
7189 @itemx set record instruction-history-size unlimited
7190 Define how many instructions to disassemble in the @code{record
7191 instruction-history} command. The default value is 10.
7192 A @var{size} of @code{unlimited} means unlimited instructions.
7195 @item show record instruction-history-size
7196 Show how many instructions to disassemble in the @code{record
7197 instruction-history} command.
7199 @kindex record function-call-history
7200 @kindex rec function-call-history
7201 @item record function-call-history
7202 Prints the execution history at function granularity. It prints one
7203 line for each sequence of instructions that belong to the same
7204 function giving the name of that function, the source lines
7205 for this instruction sequence (if the @code{/l} modifier is
7206 specified), and the instructions numbers that form the sequence (if
7207 the @code{/i} modifier is specified). The function names are indented
7208 to reflect the call stack depth if the @code{/c} modifier is
7209 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7213 (@value{GDBP}) @b{list 1, 10}
7224 (@value{GDBP}) @b{record function-call-history /ilc}
7225 1 bar inst 1,4 at foo.c:6,8
7226 2 foo inst 5,10 at foo.c:2,3
7227 3 bar inst 11,13 at foo.c:9,10
7230 By default, ten lines are printed. This can be changed using the
7231 @code{set record function-call-history-size} command. Functions are
7232 printed in execution order. There are several ways to specify what
7236 @item record function-call-history @var{func}
7237 Prints ten functions starting from function number @var{func}.
7239 @item record function-call-history @var{func}, +/-@var{n}
7240 Prints @var{n} functions around function number @var{func}. If
7241 @var{n} is preceded with @code{+}, prints @var{n} functions after
7242 function number @var{func}. If @var{n} is preceded with @code{-},
7243 prints @var{n} functions before function number @var{func}.
7245 @item record function-call-history
7246 Prints ten more functions after the last ten-line print.
7248 @item record function-call-history -
7249 Prints ten more functions before the last ten-line print.
7251 @item record function-call-history @var{begin}, @var{end}
7252 Prints functions beginning with function number @var{begin} until
7253 function number @var{end}. The function number @var{end} is included.
7256 This command may not be available for all recording methods.
7258 @item set record function-call-history-size @var{size}
7259 @itemx set record function-call-history-size unlimited
7260 Define how many lines to print in the
7261 @code{record function-call-history} command. The default value is 10.
7262 A size of @code{unlimited} means unlimited lines.
7264 @item show record function-call-history-size
7265 Show how many lines to print in the
7266 @code{record function-call-history} command.
7271 @chapter Examining the Stack
7273 When your program has stopped, the first thing you need to know is where it
7274 stopped and how it got there.
7277 Each time your program performs a function call, information about the call
7279 That information includes the location of the call in your program,
7280 the arguments of the call,
7281 and the local variables of the function being called.
7282 The information is saved in a block of data called a @dfn{stack frame}.
7283 The stack frames are allocated in a region of memory called the @dfn{call
7286 When your program stops, the @value{GDBN} commands for examining the
7287 stack allow you to see all of this information.
7289 @cindex selected frame
7290 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7291 @value{GDBN} commands refer implicitly to the selected frame. In
7292 particular, whenever you ask @value{GDBN} for the value of a variable in
7293 your program, the value is found in the selected frame. There are
7294 special @value{GDBN} commands to select whichever frame you are
7295 interested in. @xref{Selection, ,Selecting a Frame}.
7297 When your program stops, @value{GDBN} automatically selects the
7298 currently executing frame and describes it briefly, similar to the
7299 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7302 * Frames:: Stack frames
7303 * Backtrace:: Backtraces
7304 * Selection:: Selecting a frame
7305 * Frame Info:: Information on a frame
7306 * Frame Filter Management:: Managing frame filters
7311 @section Stack Frames
7313 @cindex frame, definition
7315 The call stack is divided up into contiguous pieces called @dfn{stack
7316 frames}, or @dfn{frames} for short; each frame is the data associated
7317 with one call to one function. The frame contains the arguments given
7318 to the function, the function's local variables, and the address at
7319 which the function is executing.
7321 @cindex initial frame
7322 @cindex outermost frame
7323 @cindex innermost frame
7324 When your program is started, the stack has only one frame, that of the
7325 function @code{main}. This is called the @dfn{initial} frame or the
7326 @dfn{outermost} frame. Each time a function is called, a new frame is
7327 made. Each time a function returns, the frame for that function invocation
7328 is eliminated. If a function is recursive, there can be many frames for
7329 the same function. The frame for the function in which execution is
7330 actually occurring is called the @dfn{innermost} frame. This is the most
7331 recently created of all the stack frames that still exist.
7333 @cindex frame pointer
7334 Inside your program, stack frames are identified by their addresses. A
7335 stack frame consists of many bytes, each of which has its own address; each
7336 kind of computer has a convention for choosing one byte whose
7337 address serves as the address of the frame. Usually this address is kept
7338 in a register called the @dfn{frame pointer register}
7339 (@pxref{Registers, $fp}) while execution is going on in that frame.
7341 @cindex frame number
7342 @value{GDBN} assigns numbers to all existing stack frames, starting with
7343 zero for the innermost frame, one for the frame that called it,
7344 and so on upward. These numbers do not really exist in your program;
7345 they are assigned by @value{GDBN} to give you a way of designating stack
7346 frames in @value{GDBN} commands.
7348 @c The -fomit-frame-pointer below perennially causes hbox overflow
7349 @c underflow problems.
7350 @cindex frameless execution
7351 Some compilers provide a way to compile functions so that they operate
7352 without stack frames. (For example, the @value{NGCC} option
7354 @samp{-fomit-frame-pointer}
7356 generates functions without a frame.)
7357 This is occasionally done with heavily used library functions to save
7358 the frame setup time. @value{GDBN} has limited facilities for dealing
7359 with these function invocations. If the innermost function invocation
7360 has no stack frame, @value{GDBN} nevertheless regards it as though
7361 it had a separate frame, which is numbered zero as usual, allowing
7362 correct tracing of the function call chain. However, @value{GDBN} has
7363 no provision for frameless functions elsewhere in the stack.
7369 @cindex call stack traces
7370 A backtrace is a summary of how your program got where it is. It shows one
7371 line per frame, for many frames, starting with the currently executing
7372 frame (frame zero), followed by its caller (frame one), and on up the
7375 @anchor{backtrace-command}
7377 @kindex bt @r{(@code{backtrace})}
7378 To print a backtrace of the entire stack, use the @code{backtrace}
7379 command, or its alias @code{bt}. This command will print one line per
7380 frame for frames in the stack. By default, all stack frames are
7381 printed. You can stop the backtrace at any time by typing the system
7382 interrupt character, normally @kbd{Ctrl-c}.
7385 @item backtrace [@var{args}@dots{}]
7386 @itemx bt [@var{args}@dots{}]
7387 Print the backtrace of the entire stack. The optional @var{args} can
7388 be one of the following:
7393 Print only the innermost @var{n} frames, where @var{n} is a positive
7398 Print only the outermost @var{n} frames, where @var{n} is a positive
7402 Print the values of the local variables also. This can be combined
7403 with a number to limit the number of frames shown.
7406 Do not run Python frame filters on this backtrace. @xref{Frame
7407 Filter API}, for more information. Additionally use @ref{disable
7408 frame-filter all} to turn off all frame filters. This is only
7409 relevant when @value{GDBN} has been configured with @code{Python}
7413 A Python frame filter might decide to ``elide'' some frames. Normally
7414 such elided frames are still printed, but they are indented relative
7415 to the filtered frames that cause them to be elided. The @code{hide}
7416 option causes elided frames to not be printed at all.
7422 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7423 are additional aliases for @code{backtrace}.
7425 @cindex multiple threads, backtrace
7426 In a multi-threaded program, @value{GDBN} by default shows the
7427 backtrace only for the current thread. To display the backtrace for
7428 several or all of the threads, use the command @code{thread apply}
7429 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7430 apply all backtrace}, @value{GDBN} will display the backtrace for all
7431 the threads; this is handy when you debug a core dump of a
7432 multi-threaded program.
7434 Each line in the backtrace shows the frame number and the function name.
7435 The program counter value is also shown---unless you use @code{set
7436 print address off}. The backtrace also shows the source file name and
7437 line number, as well as the arguments to the function. The program
7438 counter value is omitted if it is at the beginning of the code for that
7441 Here is an example of a backtrace. It was made with the command
7442 @samp{bt 3}, so it shows the innermost three frames.
7446 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7448 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7449 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7451 (More stack frames follow...)
7456 The display for frame zero does not begin with a program counter
7457 value, indicating that your program has stopped at the beginning of the
7458 code for line @code{993} of @code{builtin.c}.
7461 The value of parameter @code{data} in frame 1 has been replaced by
7462 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7463 only if it is a scalar (integer, pointer, enumeration, etc). See command
7464 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7465 on how to configure the way function parameter values are printed.
7467 @cindex optimized out, in backtrace
7468 @cindex function call arguments, optimized out
7469 If your program was compiled with optimizations, some compilers will
7470 optimize away arguments passed to functions if those arguments are
7471 never used after the call. Such optimizations generate code that
7472 passes arguments through registers, but doesn't store those arguments
7473 in the stack frame. @value{GDBN} has no way of displaying such
7474 arguments in stack frames other than the innermost one. Here's what
7475 such a backtrace might look like:
7479 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7481 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7482 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7484 (More stack frames follow...)
7489 The values of arguments that were not saved in their stack frames are
7490 shown as @samp{<optimized out>}.
7492 If you need to display the values of such optimized-out arguments,
7493 either deduce that from other variables whose values depend on the one
7494 you are interested in, or recompile without optimizations.
7496 @cindex backtrace beyond @code{main} function
7497 @cindex program entry point
7498 @cindex startup code, and backtrace
7499 Most programs have a standard user entry point---a place where system
7500 libraries and startup code transition into user code. For C this is
7501 @code{main}@footnote{
7502 Note that embedded programs (the so-called ``free-standing''
7503 environment) are not required to have a @code{main} function as the
7504 entry point. They could even have multiple entry points.}.
7505 When @value{GDBN} finds the entry function in a backtrace
7506 it will terminate the backtrace, to avoid tracing into highly
7507 system-specific (and generally uninteresting) code.
7509 If you need to examine the startup code, or limit the number of levels
7510 in a backtrace, you can change this behavior:
7513 @item set backtrace past-main
7514 @itemx set backtrace past-main on
7515 @kindex set backtrace
7516 Backtraces will continue past the user entry point.
7518 @item set backtrace past-main off
7519 Backtraces will stop when they encounter the user entry point. This is the
7522 @item show backtrace past-main
7523 @kindex show backtrace
7524 Display the current user entry point backtrace policy.
7526 @item set backtrace past-entry
7527 @itemx set backtrace past-entry on
7528 Backtraces will continue past the internal entry point of an application.
7529 This entry point is encoded by the linker when the application is built,
7530 and is likely before the user entry point @code{main} (or equivalent) is called.
7532 @item set backtrace past-entry off
7533 Backtraces will stop when they encounter the internal entry point of an
7534 application. This is the default.
7536 @item show backtrace past-entry
7537 Display the current internal entry point backtrace policy.
7539 @item set backtrace limit @var{n}
7540 @itemx set backtrace limit 0
7541 @itemx set backtrace limit unlimited
7542 @cindex backtrace limit
7543 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7544 or zero means unlimited levels.
7546 @item show backtrace limit
7547 Display the current limit on backtrace levels.
7550 You can control how file names are displayed.
7553 @item set filename-display
7554 @itemx set filename-display relative
7555 @cindex filename-display
7556 Display file names relative to the compilation directory. This is the default.
7558 @item set filename-display basename
7559 Display only basename of a filename.
7561 @item set filename-display absolute
7562 Display an absolute filename.
7564 @item show filename-display
7565 Show the current way to display filenames.
7569 @section Selecting a Frame
7571 Most commands for examining the stack and other data in your program work on
7572 whichever stack frame is selected at the moment. Here are the commands for
7573 selecting a stack frame; all of them finish by printing a brief description
7574 of the stack frame just selected.
7577 @kindex frame@r{, selecting}
7578 @kindex f @r{(@code{frame})}
7581 Select frame number @var{n}. Recall that frame zero is the innermost
7582 (currently executing) frame, frame one is the frame that called the
7583 innermost one, and so on. The highest-numbered frame is the one for
7586 @item frame @var{stack-addr} [ @var{pc-addr} ]
7587 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7588 Select the frame at address @var{stack-addr}. This is useful mainly if the
7589 chaining of stack frames has been damaged by a bug, making it
7590 impossible for @value{GDBN} to assign numbers properly to all frames. In
7591 addition, this can be useful when your program has multiple stacks and
7592 switches between them. The optional @var{pc-addr} can also be given to
7593 specify the value of PC for the stack frame.
7597 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7598 numbers @var{n}, this advances toward the outermost frame, to higher
7599 frame numbers, to frames that have existed longer.
7602 @kindex do @r{(@code{down})}
7604 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7605 positive numbers @var{n}, this advances toward the innermost frame, to
7606 lower frame numbers, to frames that were created more recently.
7607 You may abbreviate @code{down} as @code{do}.
7610 All of these commands end by printing two lines of output describing the
7611 frame. The first line shows the frame number, the function name, the
7612 arguments, and the source file and line number of execution in that
7613 frame. The second line shows the text of that source line.
7621 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7623 10 read_input_file (argv[i]);
7627 After such a printout, the @code{list} command with no arguments
7628 prints ten lines centered on the point of execution in the frame.
7629 You can also edit the program at the point of execution with your favorite
7630 editing program by typing @code{edit}.
7631 @xref{List, ,Printing Source Lines},
7635 @kindex select-frame
7637 The @code{select-frame} command is a variant of @code{frame} that does
7638 not display the new frame after selecting it. This command is
7639 intended primarily for use in @value{GDBN} command scripts, where the
7640 output might be unnecessary and distracting.
7642 @kindex down-silently
7644 @item up-silently @var{n}
7645 @itemx down-silently @var{n}
7646 These two commands are variants of @code{up} and @code{down},
7647 respectively; they differ in that they do their work silently, without
7648 causing display of the new frame. They are intended primarily for use
7649 in @value{GDBN} command scripts, where the output might be unnecessary and
7654 @section Information About a Frame
7656 There are several other commands to print information about the selected
7662 When used without any argument, this command does not change which
7663 frame is selected, but prints a brief description of the currently
7664 selected stack frame. It can be abbreviated @code{f}. With an
7665 argument, this command is used to select a stack frame.
7666 @xref{Selection, ,Selecting a Frame}.
7669 @kindex info f @r{(@code{info frame})}
7672 This command prints a verbose description of the selected stack frame,
7677 the address of the frame
7679 the address of the next frame down (called by this frame)
7681 the address of the next frame up (caller of this frame)
7683 the language in which the source code corresponding to this frame is written
7685 the address of the frame's arguments
7687 the address of the frame's local variables
7689 the program counter saved in it (the address of execution in the caller frame)
7691 which registers were saved in the frame
7694 @noindent The verbose description is useful when
7695 something has gone wrong that has made the stack format fail to fit
7696 the usual conventions.
7698 @item info frame @var{addr}
7699 @itemx info f @var{addr}
7700 Print a verbose description of the frame at address @var{addr}, without
7701 selecting that frame. The selected frame remains unchanged by this
7702 command. This requires the same kind of address (more than one for some
7703 architectures) that you specify in the @code{frame} command.
7704 @xref{Selection, ,Selecting a Frame}.
7708 Print the arguments of the selected frame, each on a separate line.
7712 Print the local variables of the selected frame, each on a separate
7713 line. These are all variables (declared either static or automatic)
7714 accessible at the point of execution of the selected frame.
7718 @node Frame Filter Management
7719 @section Management of Frame Filters.
7720 @cindex managing frame filters
7722 Frame filters are Python based utilities to manage and decorate the
7723 output of frames. @xref{Frame Filter API}, for further information.
7725 Managing frame filters is performed by several commands available
7726 within @value{GDBN}, detailed here.
7729 @kindex info frame-filter
7730 @item info frame-filter
7731 Print a list of installed frame filters from all dictionaries, showing
7732 their name, priority and enabled status.
7734 @kindex disable frame-filter
7735 @anchor{disable frame-filter all}
7736 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7737 Disable a frame filter in the dictionary matching
7738 @var{filter-dictionary} and @var{filter-name}. The
7739 @var{filter-dictionary} may be @code{all}, @code{global},
7740 @code{progspace}, or the name of the object file where the frame filter
7741 dictionary resides. When @code{all} is specified, all frame filters
7742 across all dictionaries are disabled. The @var{filter-name} is the name
7743 of the frame filter and is used when @code{all} is not the option for
7744 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7745 may be enabled again later.
7747 @kindex enable frame-filter
7748 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7749 Enable a frame filter in the dictionary matching
7750 @var{filter-dictionary} and @var{filter-name}. The
7751 @var{filter-dictionary} may be @code{all}, @code{global},
7752 @code{progspace} or the name of the object file where the frame filter
7753 dictionary resides. When @code{all} is specified, all frame filters across
7754 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7755 filter and is used when @code{all} is not the option for
7756 @var{filter-dictionary}.
7761 (gdb) info frame-filter
7763 global frame-filters:
7764 Priority Enabled Name
7765 1000 No PrimaryFunctionFilter
7768 progspace /build/test frame-filters:
7769 Priority Enabled Name
7770 100 Yes ProgspaceFilter
7772 objfile /build/test frame-filters:
7773 Priority Enabled Name
7774 999 Yes BuildProgra Filter
7776 (gdb) disable frame-filter /build/test BuildProgramFilter
7777 (gdb) info frame-filter
7779 global frame-filters:
7780 Priority Enabled Name
7781 1000 No PrimaryFunctionFilter
7784 progspace /build/test frame-filters:
7785 Priority Enabled Name
7786 100 Yes ProgspaceFilter
7788 objfile /build/test frame-filters:
7789 Priority Enabled Name
7790 999 No BuildProgramFilter
7792 (gdb) enable frame-filter global PrimaryFunctionFilter
7793 (gdb) info frame-filter
7795 global frame-filters:
7796 Priority Enabled Name
7797 1000 Yes PrimaryFunctionFilter
7800 progspace /build/test frame-filters:
7801 Priority Enabled Name
7802 100 Yes ProgspaceFilter
7804 objfile /build/test frame-filters:
7805 Priority Enabled Name
7806 999 No BuildProgramFilter
7809 @kindex set frame-filter priority
7810 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7811 Set the @var{priority} of a frame filter in the dictionary matching
7812 @var{filter-dictionary}, and the frame filter name matching
7813 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7814 @code{progspace} or the name of the object file where the frame filter
7815 dictionary resides. The @var{priority} is an integer.
7817 @kindex show frame-filter priority
7818 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7819 Show the @var{priority} of a frame filter in the dictionary matching
7820 @var{filter-dictionary}, and the frame filter name matching
7821 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7822 @code{progspace} or the name of the object file where the frame filter
7828 (gdb) info frame-filter
7830 global frame-filters:
7831 Priority Enabled Name
7832 1000 Yes PrimaryFunctionFilter
7835 progspace /build/test frame-filters:
7836 Priority Enabled Name
7837 100 Yes ProgspaceFilter
7839 objfile /build/test frame-filters:
7840 Priority Enabled Name
7841 999 No BuildProgramFilter
7843 (gdb) set frame-filter priority global Reverse 50
7844 (gdb) info frame-filter
7846 global frame-filters:
7847 Priority Enabled Name
7848 1000 Yes PrimaryFunctionFilter
7851 progspace /build/test frame-filters:
7852 Priority Enabled Name
7853 100 Yes ProgspaceFilter
7855 objfile /build/test frame-filters:
7856 Priority Enabled Name
7857 999 No BuildProgramFilter
7862 @chapter Examining Source Files
7864 @value{GDBN} can print parts of your program's source, since the debugging
7865 information recorded in the program tells @value{GDBN} what source files were
7866 used to build it. When your program stops, @value{GDBN} spontaneously prints
7867 the line where it stopped. Likewise, when you select a stack frame
7868 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7869 execution in that frame has stopped. You can print other portions of
7870 source files by explicit command.
7872 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7873 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7874 @value{GDBN} under @sc{gnu} Emacs}.
7877 * List:: Printing source lines
7878 * Specify Location:: How to specify code locations
7879 * Edit:: Editing source files
7880 * Search:: Searching source files
7881 * Source Path:: Specifying source directories
7882 * Machine Code:: Source and machine code
7886 @section Printing Source Lines
7889 @kindex l @r{(@code{list})}
7890 To print lines from a source file, use the @code{list} command
7891 (abbreviated @code{l}). By default, ten lines are printed.
7892 There are several ways to specify what part of the file you want to
7893 print; see @ref{Specify Location}, for the full list.
7895 Here are the forms of the @code{list} command most commonly used:
7898 @item list @var{linenum}
7899 Print lines centered around line number @var{linenum} in the
7900 current source file.
7902 @item list @var{function}
7903 Print lines centered around the beginning of function
7907 Print more lines. If the last lines printed were printed with a
7908 @code{list} command, this prints lines following the last lines
7909 printed; however, if the last line printed was a solitary line printed
7910 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7911 Stack}), this prints lines centered around that line.
7914 Print lines just before the lines last printed.
7917 @cindex @code{list}, how many lines to display
7918 By default, @value{GDBN} prints ten source lines with any of these forms of
7919 the @code{list} command. You can change this using @code{set listsize}:
7922 @kindex set listsize
7923 @item set listsize @var{count}
7924 @itemx set listsize unlimited
7925 Make the @code{list} command display @var{count} source lines (unless
7926 the @code{list} argument explicitly specifies some other number).
7927 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7929 @kindex show listsize
7931 Display the number of lines that @code{list} prints.
7934 Repeating a @code{list} command with @key{RET} discards the argument,
7935 so it is equivalent to typing just @code{list}. This is more useful
7936 than listing the same lines again. An exception is made for an
7937 argument of @samp{-}; that argument is preserved in repetition so that
7938 each repetition moves up in the source file.
7940 In general, the @code{list} command expects you to supply zero, one or two
7941 @dfn{locations}. Locations specify source lines; there are several ways
7942 of writing them (@pxref{Specify Location}), but the effect is always
7943 to specify some source line.
7945 Here is a complete description of the possible arguments for @code{list}:
7948 @item list @var{location}
7949 Print lines centered around the line specified by @var{location}.
7951 @item list @var{first},@var{last}
7952 Print lines from @var{first} to @var{last}. Both arguments are
7953 locations. When a @code{list} command has two locations, and the
7954 source file of the second location is omitted, this refers to
7955 the same source file as the first location.
7957 @item list ,@var{last}
7958 Print lines ending with @var{last}.
7960 @item list @var{first},
7961 Print lines starting with @var{first}.
7964 Print lines just after the lines last printed.
7967 Print lines just before the lines last printed.
7970 As described in the preceding table.
7973 @node Specify Location
7974 @section Specifying a Location
7975 @cindex specifying location
7977 @cindex source location
7980 * Linespec Locations:: Linespec locations
7981 * Explicit Locations:: Explicit locations
7982 * Address Locations:: Address locations
7985 Several @value{GDBN} commands accept arguments that specify a location
7986 of your program's code. Since @value{GDBN} is a source-level
7987 debugger, a location usually specifies some line in the source code.
7988 Locations may be specified using three different formats:
7989 linespec locations, explicit locations, or address locations.
7991 @node Linespec Locations
7992 @subsection Linespec Locations
7993 @cindex linespec locations
7995 A @dfn{linespec} is a colon-separated list of source location parameters such
7996 as file name, function name, etc. Here are all the different ways of
7997 specifying a linespec:
8001 Specifies the line number @var{linenum} of the current source file.
8004 @itemx +@var{offset}
8005 Specifies the line @var{offset} lines before or after the @dfn{current
8006 line}. For the @code{list} command, the current line is the last one
8007 printed; for the breakpoint commands, this is the line at which
8008 execution stopped in the currently selected @dfn{stack frame}
8009 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8010 used as the second of the two linespecs in a @code{list} command,
8011 this specifies the line @var{offset} lines up or down from the first
8014 @item @var{filename}:@var{linenum}
8015 Specifies the line @var{linenum} in the source file @var{filename}.
8016 If @var{filename} is a relative file name, then it will match any
8017 source file name with the same trailing components. For example, if
8018 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8019 name of @file{/build/trunk/gcc/expr.c}, but not
8020 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8022 @item @var{function}
8023 Specifies the line that begins the body of the function @var{function}.
8024 For example, in C, this is the line with the open brace.
8026 By default, in C@t{++} and Ada, @var{function} is interpreted as
8027 specifying all functions named @var{function} in all scopes. For
8028 C@t{++}, this means in all namespaces and classes. For Ada, this
8029 means in all packages.
8031 For example, assuming a program with C@t{++} symbols named
8032 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8033 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8035 Commands that accept a linespec let you override this with the
8036 @code{-qualified} option. For example, @w{@kbd{break -qualified
8037 func}} sets a breakpoint on a free-function named @code{func} ignoring
8038 any C@t{++} class methods and namespace functions called @code{func}.
8040 @xref{Explicit Locations}.
8042 @item @var{function}:@var{label}
8043 Specifies the line where @var{label} appears in @var{function}.
8045 @item @var{filename}:@var{function}
8046 Specifies the line that begins the body of the function @var{function}
8047 in the file @var{filename}. You only need the file name with a
8048 function name to avoid ambiguity when there are identically named
8049 functions in different source files.
8052 Specifies the line at which the label named @var{label} appears
8053 in the function corresponding to the currently selected stack frame.
8054 If there is no current selected stack frame (for instance, if the inferior
8055 is not running), then @value{GDBN} will not search for a label.
8057 @cindex breakpoint at static probe point
8058 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8059 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8060 applications to embed static probes. @xref{Static Probe Points}, for more
8061 information on finding and using static probes. This form of linespec
8062 specifies the location of such a static probe.
8064 If @var{objfile} is given, only probes coming from that shared library
8065 or executable matching @var{objfile} as a regular expression are considered.
8066 If @var{provider} is given, then only probes from that provider are considered.
8067 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8068 each one of those probes.
8071 @node Explicit Locations
8072 @subsection Explicit Locations
8073 @cindex explicit locations
8075 @dfn{Explicit locations} allow the user to directly specify the source
8076 location's parameters using option-value pairs.
8078 Explicit locations are useful when several functions, labels, or
8079 file names have the same name (base name for files) in the program's
8080 sources. In these cases, explicit locations point to the source
8081 line you meant more accurately and unambiguously. Also, using
8082 explicit locations might be faster in large programs.
8084 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8085 defined in the file named @file{foo} or the label @code{bar} in a function
8086 named @code{foo}. @value{GDBN} must search either the file system or
8087 the symbol table to know.
8089 The list of valid explicit location options is summarized in the
8093 @item -source @var{filename}
8094 The value specifies the source file name. To differentiate between
8095 files with the same base name, prepend as many directories as is necessary
8096 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8097 @value{GDBN} will use the first file it finds with the given base
8098 name. This option requires the use of either @code{-function} or @code{-line}.
8100 @item -function @var{function}
8101 The value specifies the name of a function. Operations
8102 on function locations unmodified by other options (such as @code{-label}
8103 or @code{-line}) refer to the line that begins the body of the function.
8104 In C, for example, this is the line with the open brace.
8106 By default, in C@t{++} and Ada, @var{function} is interpreted as
8107 specifying all functions named @var{function} in all scopes. For
8108 C@t{++}, this means in all namespaces and classes. For Ada, this
8109 means in all packages.
8111 For example, assuming a program with C@t{++} symbols named
8112 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8113 -function func}} and @w{@kbd{break -function B::func}} set a
8114 breakpoint on both symbols.
8116 You can use the @kbd{-qualified} flag to override this (see below).
8120 This flag makes @value{GDBN} interpret a function name specified with
8121 @kbd{-function} as a complete fully-qualified name.
8123 For example, assuming a C@t{++} program with symbols named
8124 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8125 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8127 (Note: the @kbd{-qualified} option can precede a linespec as well
8128 (@pxref{Linespec Locations}), so the particular example above could be
8129 simplified as @w{@kbd{break -qualified B::func}}.)
8131 @item -label @var{label}
8132 The value specifies the name of a label. When the function
8133 name is not specified, the label is searched in the function of the currently
8134 selected stack frame.
8136 @item -line @var{number}
8137 The value specifies a line offset for the location. The offset may either
8138 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8139 the command. When specified without any other options, the line offset is
8140 relative to the current line.
8143 Explicit location options may be abbreviated by omitting any non-unique
8144 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8146 @node Address Locations
8147 @subsection Address Locations
8148 @cindex address locations
8150 @dfn{Address locations} indicate a specific program address. They have
8151 the generalized form *@var{address}.
8153 For line-oriented commands, such as @code{list} and @code{edit}, this
8154 specifies a source line that contains @var{address}. For @code{break} and
8155 other breakpoint-oriented commands, this can be used to set breakpoints in
8156 parts of your program which do not have debugging information or
8159 Here @var{address} may be any expression valid in the current working
8160 language (@pxref{Languages, working language}) that specifies a code
8161 address. In addition, as a convenience, @value{GDBN} extends the
8162 semantics of expressions used in locations to cover several situations
8163 that frequently occur during debugging. Here are the various forms
8167 @item @var{expression}
8168 Any expression valid in the current working language.
8170 @item @var{funcaddr}
8171 An address of a function or procedure derived from its name. In C,
8172 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8173 simply the function's name @var{function} (and actually a special case
8174 of a valid expression). In Pascal and Modula-2, this is
8175 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8176 (although the Pascal form also works).
8178 This form specifies the address of the function's first instruction,
8179 before the stack frame and arguments have been set up.
8181 @item '@var{filename}':@var{funcaddr}
8182 Like @var{funcaddr} above, but also specifies the name of the source
8183 file explicitly. This is useful if the name of the function does not
8184 specify the function unambiguously, e.g., if there are several
8185 functions with identical names in different source files.
8189 @section Editing Source Files
8190 @cindex editing source files
8193 @kindex e @r{(@code{edit})}
8194 To edit the lines in a source file, use the @code{edit} command.
8195 The editing program of your choice
8196 is invoked with the current line set to
8197 the active line in the program.
8198 Alternatively, there are several ways to specify what part of the file you
8199 want to print if you want to see other parts of the program:
8202 @item edit @var{location}
8203 Edit the source file specified by @code{location}. Editing starts at
8204 that @var{location}, e.g., at the specified source line of the
8205 specified file. @xref{Specify Location}, for all the possible forms
8206 of the @var{location} argument; here are the forms of the @code{edit}
8207 command most commonly used:
8210 @item edit @var{number}
8211 Edit the current source file with @var{number} as the active line number.
8213 @item edit @var{function}
8214 Edit the file containing @var{function} at the beginning of its definition.
8219 @subsection Choosing your Editor
8220 You can customize @value{GDBN} to use any editor you want
8222 The only restriction is that your editor (say @code{ex}), recognizes the
8223 following command-line syntax:
8225 ex +@var{number} file
8227 The optional numeric value +@var{number} specifies the number of the line in
8228 the file where to start editing.}.
8229 By default, it is @file{@value{EDITOR}}, but you can change this
8230 by setting the environment variable @code{EDITOR} before using
8231 @value{GDBN}. For example, to configure @value{GDBN} to use the
8232 @code{vi} editor, you could use these commands with the @code{sh} shell:
8238 or in the @code{csh} shell,
8240 setenv EDITOR /usr/bin/vi
8245 @section Searching Source Files
8246 @cindex searching source files
8248 There are two commands for searching through the current source file for a
8253 @kindex forward-search
8254 @kindex fo @r{(@code{forward-search})}
8255 @item forward-search @var{regexp}
8256 @itemx search @var{regexp}
8257 The command @samp{forward-search @var{regexp}} checks each line,
8258 starting with the one following the last line listed, for a match for
8259 @var{regexp}. It lists the line that is found. You can use the
8260 synonym @samp{search @var{regexp}} or abbreviate the command name as
8263 @kindex reverse-search
8264 @item reverse-search @var{regexp}
8265 The command @samp{reverse-search @var{regexp}} checks each line, starting
8266 with the one before the last line listed and going backward, for a match
8267 for @var{regexp}. It lists the line that is found. You can abbreviate
8268 this command as @code{rev}.
8272 @section Specifying Source Directories
8275 @cindex directories for source files
8276 Executable programs sometimes do not record the directories of the source
8277 files from which they were compiled, just the names. Even when they do,
8278 the directories could be moved between the compilation and your debugging
8279 session. @value{GDBN} has a list of directories to search for source files;
8280 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8281 it tries all the directories in the list, in the order they are present
8282 in the list, until it finds a file with the desired name.
8284 For example, suppose an executable references the file
8285 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8286 @file{/mnt/cross}. The file is first looked up literally; if this
8287 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8288 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8289 message is printed. @value{GDBN} does not look up the parts of the
8290 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8291 Likewise, the subdirectories of the source path are not searched: if
8292 the source path is @file{/mnt/cross}, and the binary refers to
8293 @file{foo.c}, @value{GDBN} would not find it under
8294 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8296 Plain file names, relative file names with leading directories, file
8297 names containing dots, etc.@: are all treated as described above; for
8298 instance, if the source path is @file{/mnt/cross}, and the source file
8299 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8300 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8301 that---@file{/mnt/cross/foo.c}.
8303 Note that the executable search path is @emph{not} used to locate the
8306 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8307 any information it has cached about where source files are found and where
8308 each line is in the file.
8312 When you start @value{GDBN}, its source path includes only @samp{cdir}
8313 and @samp{cwd}, in that order.
8314 To add other directories, use the @code{directory} command.
8316 The search path is used to find both program source files and @value{GDBN}
8317 script files (read using the @samp{-command} option and @samp{source} command).
8319 In addition to the source path, @value{GDBN} provides a set of commands
8320 that manage a list of source path substitution rules. A @dfn{substitution
8321 rule} specifies how to rewrite source directories stored in the program's
8322 debug information in case the sources were moved to a different
8323 directory between compilation and debugging. A rule is made of
8324 two strings, the first specifying what needs to be rewritten in
8325 the path, and the second specifying how it should be rewritten.
8326 In @ref{set substitute-path}, we name these two parts @var{from} and
8327 @var{to} respectively. @value{GDBN} does a simple string replacement
8328 of @var{from} with @var{to} at the start of the directory part of the
8329 source file name, and uses that result instead of the original file
8330 name to look up the sources.
8332 Using the previous example, suppose the @file{foo-1.0} tree has been
8333 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8334 @value{GDBN} to replace @file{/usr/src} in all source path names with
8335 @file{/mnt/cross}. The first lookup will then be
8336 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8337 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8338 substitution rule, use the @code{set substitute-path} command
8339 (@pxref{set substitute-path}).
8341 To avoid unexpected substitution results, a rule is applied only if the
8342 @var{from} part of the directory name ends at a directory separator.
8343 For instance, a rule substituting @file{/usr/source} into
8344 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8345 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8346 is applied only at the beginning of the directory name, this rule will
8347 not be applied to @file{/root/usr/source/baz.c} either.
8349 In many cases, you can achieve the same result using the @code{directory}
8350 command. However, @code{set substitute-path} can be more efficient in
8351 the case where the sources are organized in a complex tree with multiple
8352 subdirectories. With the @code{directory} command, you need to add each
8353 subdirectory of your project. If you moved the entire tree while
8354 preserving its internal organization, then @code{set substitute-path}
8355 allows you to direct the debugger to all the sources with one single
8358 @code{set substitute-path} is also more than just a shortcut command.
8359 The source path is only used if the file at the original location no
8360 longer exists. On the other hand, @code{set substitute-path} modifies
8361 the debugger behavior to look at the rewritten location instead. So, if
8362 for any reason a source file that is not relevant to your executable is
8363 located at the original location, a substitution rule is the only
8364 method available to point @value{GDBN} at the new location.
8366 @cindex @samp{--with-relocated-sources}
8367 @cindex default source path substitution
8368 You can configure a default source path substitution rule by
8369 configuring @value{GDBN} with the
8370 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8371 should be the name of a directory under @value{GDBN}'s configured
8372 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8373 directory names in debug information under @var{dir} will be adjusted
8374 automatically if the installed @value{GDBN} is moved to a new
8375 location. This is useful if @value{GDBN}, libraries or executables
8376 with debug information and corresponding source code are being moved
8380 @item directory @var{dirname} @dots{}
8381 @item dir @var{dirname} @dots{}
8382 Add directory @var{dirname} to the front of the source path. Several
8383 directory names may be given to this command, separated by @samp{:}
8384 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8385 part of absolute file names) or
8386 whitespace. You may specify a directory that is already in the source
8387 path; this moves it forward, so @value{GDBN} searches it sooner.
8391 @vindex $cdir@r{, convenience variable}
8392 @vindex $cwd@r{, convenience variable}
8393 @cindex compilation directory
8394 @cindex current directory
8395 @cindex working directory
8396 @cindex directory, current
8397 @cindex directory, compilation
8398 You can use the string @samp{$cdir} to refer to the compilation
8399 directory (if one is recorded), and @samp{$cwd} to refer to the current
8400 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8401 tracks the current working directory as it changes during your @value{GDBN}
8402 session, while the latter is immediately expanded to the current
8403 directory at the time you add an entry to the source path.
8406 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8408 @c RET-repeat for @code{directory} is explicitly disabled, but since
8409 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8411 @item set directories @var{path-list}
8412 @kindex set directories
8413 Set the source path to @var{path-list}.
8414 @samp{$cdir:$cwd} are added if missing.
8416 @item show directories
8417 @kindex show directories
8418 Print the source path: show which directories it contains.
8420 @anchor{set substitute-path}
8421 @item set substitute-path @var{from} @var{to}
8422 @kindex set substitute-path
8423 Define a source path substitution rule, and add it at the end of the
8424 current list of existing substitution rules. If a rule with the same
8425 @var{from} was already defined, then the old rule is also deleted.
8427 For example, if the file @file{/foo/bar/baz.c} was moved to
8428 @file{/mnt/cross/baz.c}, then the command
8431 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8435 will tell @value{GDBN} to replace @samp{/foo/bar} with
8436 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8437 @file{baz.c} even though it was moved.
8439 In the case when more than one substitution rule have been defined,
8440 the rules are evaluated one by one in the order where they have been
8441 defined. The first one matching, if any, is selected to perform
8444 For instance, if we had entered the following commands:
8447 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8448 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8452 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8453 @file{/mnt/include/defs.h} by using the first rule. However, it would
8454 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8455 @file{/mnt/src/lib/foo.c}.
8458 @item unset substitute-path [path]
8459 @kindex unset substitute-path
8460 If a path is specified, search the current list of substitution rules
8461 for a rule that would rewrite that path. Delete that rule if found.
8462 A warning is emitted by the debugger if no rule could be found.
8464 If no path is specified, then all substitution rules are deleted.
8466 @item show substitute-path [path]
8467 @kindex show substitute-path
8468 If a path is specified, then print the source path substitution rule
8469 which would rewrite that path, if any.
8471 If no path is specified, then print all existing source path substitution
8476 If your source path is cluttered with directories that are no longer of
8477 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8478 versions of source. You can correct the situation as follows:
8482 Use @code{directory} with no argument to reset the source path to its default value.
8485 Use @code{directory} with suitable arguments to reinstall the
8486 directories you want in the source path. You can add all the
8487 directories in one command.
8491 @section Source and Machine Code
8492 @cindex source line and its code address
8494 You can use the command @code{info line} to map source lines to program
8495 addresses (and vice versa), and the command @code{disassemble} to display
8496 a range of addresses as machine instructions. You can use the command
8497 @code{set disassemble-next-line} to set whether to disassemble next
8498 source line when execution stops. When run under @sc{gnu} Emacs
8499 mode, the @code{info line} command causes the arrow to point to the
8500 line specified. Also, @code{info line} prints addresses in symbolic form as
8506 @itemx info line @var{location}
8507 Print the starting and ending addresses of the compiled code for
8508 source line @var{location}. You can specify source lines in any of
8509 the ways documented in @ref{Specify Location}. With no @var{location}
8510 information about the current source line is printed.
8513 For example, we can use @code{info line} to discover the location of
8514 the object code for the first line of function
8515 @code{m4_changequote}:
8518 (@value{GDBP}) info line m4_changequote
8519 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8520 ends at 0x6350 <m4_changequote+4>.
8524 @cindex code address and its source line
8525 We can also inquire (using @code{*@var{addr}} as the form for
8526 @var{location}) what source line covers a particular address:
8528 (@value{GDBP}) info line *0x63ff
8529 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8530 ends at 0x6404 <m4_changequote+184>.
8533 @cindex @code{$_} and @code{info line}
8534 @cindex @code{x} command, default address
8535 @kindex x@r{(examine), and} info line
8536 After @code{info line}, the default address for the @code{x} command
8537 is changed to the starting address of the line, so that @samp{x/i} is
8538 sufficient to begin examining the machine code (@pxref{Memory,
8539 ,Examining Memory}). Also, this address is saved as the value of the
8540 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8543 @cindex info line, repeated calls
8544 After @code{info line}, using @code{info line} again without
8545 specifying a location will display information about the next source
8550 @cindex assembly instructions
8551 @cindex instructions, assembly
8552 @cindex machine instructions
8553 @cindex listing machine instructions
8555 @itemx disassemble /m
8556 @itemx disassemble /s
8557 @itemx disassemble /r
8558 This specialized command dumps a range of memory as machine
8559 instructions. It can also print mixed source+disassembly by specifying
8560 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8561 as well as in symbolic form by specifying the @code{/r} modifier.
8562 The default memory range is the function surrounding the
8563 program counter of the selected frame. A single argument to this
8564 command is a program counter value; @value{GDBN} dumps the function
8565 surrounding this value. When two arguments are given, they should
8566 be separated by a comma, possibly surrounded by whitespace. The
8567 arguments specify a range of addresses to dump, in one of two forms:
8570 @item @var{start},@var{end}
8571 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8572 @item @var{start},+@var{length}
8573 the addresses from @var{start} (inclusive) to
8574 @code{@var{start}+@var{length}} (exclusive).
8578 When 2 arguments are specified, the name of the function is also
8579 printed (since there could be several functions in the given range).
8581 The argument(s) can be any expression yielding a numeric value, such as
8582 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8584 If the range of memory being disassembled contains current program counter,
8585 the instruction at that location is shown with a @code{=>} marker.
8588 The following example shows the disassembly of a range of addresses of
8589 HP PA-RISC 2.0 code:
8592 (@value{GDBP}) disas 0x32c4, 0x32e4
8593 Dump of assembler code from 0x32c4 to 0x32e4:
8594 0x32c4 <main+204>: addil 0,dp
8595 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8596 0x32cc <main+212>: ldil 0x3000,r31
8597 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8598 0x32d4 <main+220>: ldo 0(r31),rp
8599 0x32d8 <main+224>: addil -0x800,dp
8600 0x32dc <main+228>: ldo 0x588(r1),r26
8601 0x32e0 <main+232>: ldil 0x3000,r31
8602 End of assembler dump.
8605 Here is an example showing mixed source+assembly for Intel x86
8606 with @code{/m} or @code{/s}, when the program is stopped just after
8607 function prologue in a non-optimized function with no inline code.
8610 (@value{GDBP}) disas /m main
8611 Dump of assembler code for function main:
8613 0x08048330 <+0>: push %ebp
8614 0x08048331 <+1>: mov %esp,%ebp
8615 0x08048333 <+3>: sub $0x8,%esp
8616 0x08048336 <+6>: and $0xfffffff0,%esp
8617 0x08048339 <+9>: sub $0x10,%esp
8619 6 printf ("Hello.\n");
8620 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8621 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8625 0x08048348 <+24>: mov $0x0,%eax
8626 0x0804834d <+29>: leave
8627 0x0804834e <+30>: ret
8629 End of assembler dump.
8632 The @code{/m} option is deprecated as its output is not useful when
8633 there is either inlined code or re-ordered code.
8634 The @code{/s} option is the preferred choice.
8635 Here is an example for AMD x86-64 showing the difference between
8636 @code{/m} output and @code{/s} output.
8637 This example has one inline function defined in a header file,
8638 and the code is compiled with @samp{-O2} optimization.
8639 Note how the @code{/m} output is missing the disassembly of
8640 several instructions that are present in the @code{/s} output.
8670 (@value{GDBP}) disas /m main
8671 Dump of assembler code for function main:
8675 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8676 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8680 0x000000000040041d <+29>: xor %eax,%eax
8681 0x000000000040041f <+31>: retq
8682 0x0000000000400420 <+32>: add %eax,%eax
8683 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8685 End of assembler dump.
8686 (@value{GDBP}) disas /s main
8687 Dump of assembler code for function main:
8691 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8695 0x0000000000400406 <+6>: test %eax,%eax
8696 0x0000000000400408 <+8>: js 0x400420 <main+32>
8701 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8702 0x000000000040040d <+13>: test %eax,%eax
8703 0x000000000040040f <+15>: mov $0x1,%eax
8704 0x0000000000400414 <+20>: cmovne %edx,%eax
8708 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8712 0x000000000040041d <+29>: xor %eax,%eax
8713 0x000000000040041f <+31>: retq
8717 0x0000000000400420 <+32>: add %eax,%eax
8718 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8719 End of assembler dump.
8722 Here is another example showing raw instructions in hex for AMD x86-64,
8725 (gdb) disas /r 0x400281,+10
8726 Dump of assembler code from 0x400281 to 0x40028b:
8727 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8728 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8729 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8730 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8731 End of assembler dump.
8734 Addresses cannot be specified as a location (@pxref{Specify Location}).
8735 So, for example, if you want to disassemble function @code{bar}
8736 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8737 and not @samp{disassemble foo.c:bar}.
8739 Some architectures have more than one commonly-used set of instruction
8740 mnemonics or other syntax.
8742 For programs that were dynamically linked and use shared libraries,
8743 instructions that call functions or branch to locations in the shared
8744 libraries might show a seemingly bogus location---it's actually a
8745 location of the relocation table. On some architectures, @value{GDBN}
8746 might be able to resolve these to actual function names.
8749 @kindex set disassembler-options
8750 @cindex disassembler options
8751 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8752 This command controls the passing of target specific information to
8753 the disassembler. For a list of valid options, please refer to the
8754 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8755 manual and/or the output of @kbd{objdump --help}
8756 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8757 The default value is the empty string.
8759 If it is necessary to specify more than one disassembler option, then
8760 multiple options can be placed together into a comma separated list.
8761 Currently this command is only supported on targets ARM, PowerPC
8764 @kindex show disassembler-options
8765 @item show disassembler-options
8766 Show the current setting of the disassembler options.
8770 @kindex set disassembly-flavor
8771 @cindex Intel disassembly flavor
8772 @cindex AT&T disassembly flavor
8773 @item set disassembly-flavor @var{instruction-set}
8774 Select the instruction set to use when disassembling the
8775 program via the @code{disassemble} or @code{x/i} commands.
8777 Currently this command is only defined for the Intel x86 family. You
8778 can set @var{instruction-set} to either @code{intel} or @code{att}.
8779 The default is @code{att}, the AT&T flavor used by default by Unix
8780 assemblers for x86-based targets.
8782 @kindex show disassembly-flavor
8783 @item show disassembly-flavor
8784 Show the current setting of the disassembly flavor.
8788 @kindex set disassemble-next-line
8789 @kindex show disassemble-next-line
8790 @item set disassemble-next-line
8791 @itemx show disassemble-next-line
8792 Control whether or not @value{GDBN} will disassemble the next source
8793 line or instruction when execution stops. If ON, @value{GDBN} will
8794 display disassembly of the next source line when execution of the
8795 program being debugged stops. This is @emph{in addition} to
8796 displaying the source line itself, which @value{GDBN} always does if
8797 possible. If the next source line cannot be displayed for some reason
8798 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8799 info in the debug info), @value{GDBN} will display disassembly of the
8800 next @emph{instruction} instead of showing the next source line. If
8801 AUTO, @value{GDBN} will display disassembly of next instruction only
8802 if the source line cannot be displayed. This setting causes
8803 @value{GDBN} to display some feedback when you step through a function
8804 with no line info or whose source file is unavailable. The default is
8805 OFF, which means never display the disassembly of the next line or
8811 @chapter Examining Data
8813 @cindex printing data
8814 @cindex examining data
8817 The usual way to examine data in your program is with the @code{print}
8818 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8819 evaluates and prints the value of an expression of the language your
8820 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8821 Different Languages}). It may also print the expression using a
8822 Python-based pretty-printer (@pxref{Pretty Printing}).
8825 @item print @var{expr}
8826 @itemx print /@var{f} @var{expr}
8827 @var{expr} is an expression (in the source language). By default the
8828 value of @var{expr} is printed in a format appropriate to its data type;
8829 you can choose a different format by specifying @samp{/@var{f}}, where
8830 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8834 @itemx print /@var{f}
8835 @cindex reprint the last value
8836 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8837 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8838 conveniently inspect the same value in an alternative format.
8841 A more low-level way of examining data is with the @code{x} command.
8842 It examines data in memory at a specified address and prints it in a
8843 specified format. @xref{Memory, ,Examining Memory}.
8845 If you are interested in information about types, or about how the
8846 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8847 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8850 @cindex exploring hierarchical data structures
8852 Another way of examining values of expressions and type information is
8853 through the Python extension command @code{explore} (available only if
8854 the @value{GDBN} build is configured with @code{--with-python}). It
8855 offers an interactive way to start at the highest level (or, the most
8856 abstract level) of the data type of an expression (or, the data type
8857 itself) and explore all the way down to leaf scalar values/fields
8858 embedded in the higher level data types.
8861 @item explore @var{arg}
8862 @var{arg} is either an expression (in the source language), or a type
8863 visible in the current context of the program being debugged.
8866 The working of the @code{explore} command can be illustrated with an
8867 example. If a data type @code{struct ComplexStruct} is defined in your
8877 struct ComplexStruct
8879 struct SimpleStruct *ss_p;
8885 followed by variable declarations as
8888 struct SimpleStruct ss = @{ 10, 1.11 @};
8889 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8893 then, the value of the variable @code{cs} can be explored using the
8894 @code{explore} command as follows.
8898 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8899 the following fields:
8901 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8902 arr = <Enter 1 to explore this field of type `int [10]'>
8904 Enter the field number of choice:
8908 Since the fields of @code{cs} are not scalar values, you are being
8909 prompted to chose the field you want to explore. Let's say you choose
8910 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8911 pointer, you will be asked if it is pointing to a single value. From
8912 the declaration of @code{cs} above, it is indeed pointing to a single
8913 value, hence you enter @code{y}. If you enter @code{n}, then you will
8914 be asked if it were pointing to an array of values, in which case this
8915 field will be explored as if it were an array.
8918 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8919 Continue exploring it as a pointer to a single value [y/n]: y
8920 The value of `*(cs.ss_p)' is a struct/class of type `struct
8921 SimpleStruct' with the following fields:
8923 i = 10 .. (Value of type `int')
8924 d = 1.1100000000000001 .. (Value of type `double')
8926 Press enter to return to parent value:
8930 If the field @code{arr} of @code{cs} was chosen for exploration by
8931 entering @code{1} earlier, then since it is as array, you will be
8932 prompted to enter the index of the element in the array that you want
8936 `cs.arr' is an array of `int'.
8937 Enter the index of the element you want to explore in `cs.arr': 5
8939 `(cs.arr)[5]' is a scalar value of type `int'.
8943 Press enter to return to parent value:
8946 In general, at any stage of exploration, you can go deeper towards the
8947 leaf values by responding to the prompts appropriately, or hit the
8948 return key to return to the enclosing data structure (the @i{higher}
8949 level data structure).
8951 Similar to exploring values, you can use the @code{explore} command to
8952 explore types. Instead of specifying a value (which is typically a
8953 variable name or an expression valid in the current context of the
8954 program being debugged), you specify a type name. If you consider the
8955 same example as above, your can explore the type
8956 @code{struct ComplexStruct} by passing the argument
8957 @code{struct ComplexStruct} to the @code{explore} command.
8960 (gdb) explore struct ComplexStruct
8964 By responding to the prompts appropriately in the subsequent interactive
8965 session, you can explore the type @code{struct ComplexStruct} in a
8966 manner similar to how the value @code{cs} was explored in the above
8969 The @code{explore} command also has two sub-commands,
8970 @code{explore value} and @code{explore type}. The former sub-command is
8971 a way to explicitly specify that value exploration of the argument is
8972 being invoked, while the latter is a way to explicitly specify that type
8973 exploration of the argument is being invoked.
8976 @item explore value @var{expr}
8977 @cindex explore value
8978 This sub-command of @code{explore} explores the value of the
8979 expression @var{expr} (if @var{expr} is an expression valid in the
8980 current context of the program being debugged). The behavior of this
8981 command is identical to that of the behavior of the @code{explore}
8982 command being passed the argument @var{expr}.
8984 @item explore type @var{arg}
8985 @cindex explore type
8986 This sub-command of @code{explore} explores the type of @var{arg} (if
8987 @var{arg} is a type visible in the current context of program being
8988 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8989 is an expression valid in the current context of the program being
8990 debugged). If @var{arg} is a type, then the behavior of this command is
8991 identical to that of the @code{explore} command being passed the
8992 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8993 this command will be identical to that of the @code{explore} command
8994 being passed the type of @var{arg} as the argument.
8998 * Expressions:: Expressions
8999 * Ambiguous Expressions:: Ambiguous Expressions
9000 * Variables:: Program variables
9001 * Arrays:: Artificial arrays
9002 * Output Formats:: Output formats
9003 * Memory:: Examining memory
9004 * Auto Display:: Automatic display
9005 * Print Settings:: Print settings
9006 * Pretty Printing:: Python pretty printing
9007 * Value History:: Value history
9008 * Convenience Vars:: Convenience variables
9009 * Convenience Funs:: Convenience functions
9010 * Registers:: Registers
9011 * Floating Point Hardware:: Floating point hardware
9012 * Vector Unit:: Vector Unit
9013 * OS Information:: Auxiliary data provided by operating system
9014 * Memory Region Attributes:: Memory region attributes
9015 * Dump/Restore Files:: Copy between memory and a file
9016 * Core File Generation:: Cause a program dump its core
9017 * Character Sets:: Debugging programs that use a different
9018 character set than GDB does
9019 * Caching Target Data:: Data caching for targets
9020 * Searching Memory:: Searching memory for a sequence of bytes
9021 * Value Sizes:: Managing memory allocated for values
9025 @section Expressions
9028 @code{print} and many other @value{GDBN} commands accept an expression and
9029 compute its value. Any kind of constant, variable or operator defined
9030 by the programming language you are using is valid in an expression in
9031 @value{GDBN}. This includes conditional expressions, function calls,
9032 casts, and string constants. It also includes preprocessor macros, if
9033 you compiled your program to include this information; see
9036 @cindex arrays in expressions
9037 @value{GDBN} supports array constants in expressions input by
9038 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9039 you can use the command @code{print @{1, 2, 3@}} to create an array
9040 of three integers. If you pass an array to a function or assign it
9041 to a program variable, @value{GDBN} copies the array to memory that
9042 is @code{malloc}ed in the target program.
9044 Because C is so widespread, most of the expressions shown in examples in
9045 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9046 Languages}, for information on how to use expressions in other
9049 In this section, we discuss operators that you can use in @value{GDBN}
9050 expressions regardless of your programming language.
9052 @cindex casts, in expressions
9053 Casts are supported in all languages, not just in C, because it is so
9054 useful to cast a number into a pointer in order to examine a structure
9055 at that address in memory.
9056 @c FIXME: casts supported---Mod2 true?
9058 @value{GDBN} supports these operators, in addition to those common
9059 to programming languages:
9063 @samp{@@} is a binary operator for treating parts of memory as arrays.
9064 @xref{Arrays, ,Artificial Arrays}, for more information.
9067 @samp{::} allows you to specify a variable in terms of the file or
9068 function where it is defined. @xref{Variables, ,Program Variables}.
9070 @cindex @{@var{type}@}
9071 @cindex type casting memory
9072 @cindex memory, viewing as typed object
9073 @cindex casts, to view memory
9074 @item @{@var{type}@} @var{addr}
9075 Refers to an object of type @var{type} stored at address @var{addr} in
9076 memory. The address @var{addr} may be any expression whose value is
9077 an integer or pointer (but parentheses are required around binary
9078 operators, just as in a cast). This construct is allowed regardless
9079 of what kind of data is normally supposed to reside at @var{addr}.
9082 @node Ambiguous Expressions
9083 @section Ambiguous Expressions
9084 @cindex ambiguous expressions
9086 Expressions can sometimes contain some ambiguous elements. For instance,
9087 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9088 a single function name to be defined several times, for application in
9089 different contexts. This is called @dfn{overloading}. Another example
9090 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9091 templates and is typically instantiated several times, resulting in
9092 the same function name being defined in different contexts.
9094 In some cases and depending on the language, it is possible to adjust
9095 the expression to remove the ambiguity. For instance in C@t{++}, you
9096 can specify the signature of the function you want to break on, as in
9097 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9098 qualified name of your function often makes the expression unambiguous
9101 When an ambiguity that needs to be resolved is detected, the debugger
9102 has the capability to display a menu of numbered choices for each
9103 possibility, and then waits for the selection with the prompt @samp{>}.
9104 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9105 aborts the current command. If the command in which the expression was
9106 used allows more than one choice to be selected, the next option in the
9107 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9110 For example, the following session excerpt shows an attempt to set a
9111 breakpoint at the overloaded symbol @code{String::after}.
9112 We choose three particular definitions of that function name:
9114 @c FIXME! This is likely to change to show arg type lists, at least
9117 (@value{GDBP}) b String::after
9120 [2] file:String.cc; line number:867
9121 [3] file:String.cc; line number:860
9122 [4] file:String.cc; line number:875
9123 [5] file:String.cc; line number:853
9124 [6] file:String.cc; line number:846
9125 [7] file:String.cc; line number:735
9127 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9128 Breakpoint 2 at 0xb344: file String.cc, line 875.
9129 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9130 Multiple breakpoints were set.
9131 Use the "delete" command to delete unwanted
9138 @kindex set multiple-symbols
9139 @item set multiple-symbols @var{mode}
9140 @cindex multiple-symbols menu
9142 This option allows you to adjust the debugger behavior when an expression
9145 By default, @var{mode} is set to @code{all}. If the command with which
9146 the expression is used allows more than one choice, then @value{GDBN}
9147 automatically selects all possible choices. For instance, inserting
9148 a breakpoint on a function using an ambiguous name results in a breakpoint
9149 inserted on each possible match. However, if a unique choice must be made,
9150 then @value{GDBN} uses the menu to help you disambiguate the expression.
9151 For instance, printing the address of an overloaded function will result
9152 in the use of the menu.
9154 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9155 when an ambiguity is detected.
9157 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9158 an error due to the ambiguity and the command is aborted.
9160 @kindex show multiple-symbols
9161 @item show multiple-symbols
9162 Show the current value of the @code{multiple-symbols} setting.
9166 @section Program Variables
9168 The most common kind of expression to use is the name of a variable
9171 Variables in expressions are understood in the selected stack frame
9172 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9176 global (or file-static)
9183 visible according to the scope rules of the
9184 programming language from the point of execution in that frame
9187 @noindent This means that in the function
9202 you can examine and use the variable @code{a} whenever your program is
9203 executing within the function @code{foo}, but you can only use or
9204 examine the variable @code{b} while your program is executing inside
9205 the block where @code{b} is declared.
9207 @cindex variable name conflict
9208 There is an exception: you can refer to a variable or function whose
9209 scope is a single source file even if the current execution point is not
9210 in this file. But it is possible to have more than one such variable or
9211 function with the same name (in different source files). If that
9212 happens, referring to that name has unpredictable effects. If you wish,
9213 you can specify a static variable in a particular function or file by
9214 using the colon-colon (@code{::}) notation:
9216 @cindex colon-colon, context for variables/functions
9218 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9219 @cindex @code{::}, context for variables/functions
9222 @var{file}::@var{variable}
9223 @var{function}::@var{variable}
9227 Here @var{file} or @var{function} is the name of the context for the
9228 static @var{variable}. In the case of file names, you can use quotes to
9229 make sure @value{GDBN} parses the file name as a single word---for example,
9230 to print a global value of @code{x} defined in @file{f2.c}:
9233 (@value{GDBP}) p 'f2.c'::x
9236 The @code{::} notation is normally used for referring to
9237 static variables, since you typically disambiguate uses of local variables
9238 in functions by selecting the appropriate frame and using the
9239 simple name of the variable. However, you may also use this notation
9240 to refer to local variables in frames enclosing the selected frame:
9249 process (a); /* Stop here */
9260 For example, if there is a breakpoint at the commented line,
9261 here is what you might see
9262 when the program stops after executing the call @code{bar(0)}:
9267 (@value{GDBP}) p bar::a
9270 #2 0x080483d0 in foo (a=5) at foobar.c:12
9273 (@value{GDBP}) p bar::a
9277 @cindex C@t{++} scope resolution
9278 These uses of @samp{::} are very rarely in conflict with the very
9279 similar use of the same notation in C@t{++}. When they are in
9280 conflict, the C@t{++} meaning takes precedence; however, this can be
9281 overridden by quoting the file or function name with single quotes.
9283 For example, suppose the program is stopped in a method of a class
9284 that has a field named @code{includefile}, and there is also an
9285 include file named @file{includefile} that defines a variable,
9289 (@value{GDBP}) p includefile
9291 (@value{GDBP}) p includefile::some_global
9292 A syntax error in expression, near `'.
9293 (@value{GDBP}) p 'includefile'::some_global
9297 @cindex wrong values
9298 @cindex variable values, wrong
9299 @cindex function entry/exit, wrong values of variables
9300 @cindex optimized code, wrong values of variables
9302 @emph{Warning:} Occasionally, a local variable may appear to have the
9303 wrong value at certain points in a function---just after entry to a new
9304 scope, and just before exit.
9306 You may see this problem when you are stepping by machine instructions.
9307 This is because, on most machines, it takes more than one instruction to
9308 set up a stack frame (including local variable definitions); if you are
9309 stepping by machine instructions, variables may appear to have the wrong
9310 values until the stack frame is completely built. On exit, it usually
9311 also takes more than one machine instruction to destroy a stack frame;
9312 after you begin stepping through that group of instructions, local
9313 variable definitions may be gone.
9315 This may also happen when the compiler does significant optimizations.
9316 To be sure of always seeing accurate values, turn off all optimization
9319 @cindex ``No symbol "foo" in current context''
9320 Another possible effect of compiler optimizations is to optimize
9321 unused variables out of existence, or assign variables to registers (as
9322 opposed to memory addresses). Depending on the support for such cases
9323 offered by the debug info format used by the compiler, @value{GDBN}
9324 might not be able to display values for such local variables. If that
9325 happens, @value{GDBN} will print a message like this:
9328 No symbol "foo" in current context.
9331 To solve such problems, either recompile without optimizations, or use a
9332 different debug info format, if the compiler supports several such
9333 formats. @xref{Compilation}, for more information on choosing compiler
9334 options. @xref{C, ,C and C@t{++}}, for more information about debug
9335 info formats that are best suited to C@t{++} programs.
9337 If you ask to print an object whose contents are unknown to
9338 @value{GDBN}, e.g., because its data type is not completely specified
9339 by the debug information, @value{GDBN} will say @samp{<incomplete
9340 type>}. @xref{Symbols, incomplete type}, for more about this.
9342 @cindex no debug info variables
9343 If you try to examine or use the value of a (global) variable for
9344 which @value{GDBN} has no type information, e.g., because the program
9345 includes no debug information, @value{GDBN} displays an error message.
9346 @xref{Symbols, unknown type}, for more about unknown types. If you
9347 cast the variable to its declared type, @value{GDBN} gets the
9348 variable's value using the cast-to type as the variable's type. For
9349 example, in a C program:
9352 (@value{GDBP}) p var
9353 'var' has unknown type; cast it to its declared type
9354 (@value{GDBP}) p (float) var
9358 If you append @kbd{@@entry} string to a function parameter name you get its
9359 value at the time the function got called. If the value is not available an
9360 error message is printed. Entry values are available only with some compilers.
9361 Entry values are normally also printed at the function parameter list according
9362 to @ref{set print entry-values}.
9365 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9371 (gdb) print i@@entry
9375 Strings are identified as arrays of @code{char} values without specified
9376 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9377 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9378 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9379 defines literal string type @code{"char"} as @code{char} without a sign.
9384 signed char var1[] = "A";
9387 You get during debugging
9392 $2 = @{65 'A', 0 '\0'@}
9396 @section Artificial Arrays
9398 @cindex artificial array
9400 @kindex @@@r{, referencing memory as an array}
9401 It is often useful to print out several successive objects of the
9402 same type in memory; a section of an array, or an array of
9403 dynamically determined size for which only a pointer exists in the
9406 You can do this by referring to a contiguous span of memory as an
9407 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9408 operand of @samp{@@} should be the first element of the desired array
9409 and be an individual object. The right operand should be the desired length
9410 of the array. The result is an array value whose elements are all of
9411 the type of the left argument. The first element is actually the left
9412 argument; the second element comes from bytes of memory immediately
9413 following those that hold the first element, and so on. Here is an
9414 example. If a program says
9417 int *array = (int *) malloc (len * sizeof (int));
9421 you can print the contents of @code{array} with
9427 The left operand of @samp{@@} must reside in memory. Array values made
9428 with @samp{@@} in this way behave just like other arrays in terms of
9429 subscripting, and are coerced to pointers when used in expressions.
9430 Artificial arrays most often appear in expressions via the value history
9431 (@pxref{Value History, ,Value History}), after printing one out.
9433 Another way to create an artificial array is to use a cast.
9434 This re-interprets a value as if it were an array.
9435 The value need not be in memory:
9437 (@value{GDBP}) p/x (short[2])0x12345678
9438 $1 = @{0x1234, 0x5678@}
9441 As a convenience, if you leave the array length out (as in
9442 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9443 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9445 (@value{GDBP}) p/x (short[])0x12345678
9446 $2 = @{0x1234, 0x5678@}
9449 Sometimes the artificial array mechanism is not quite enough; in
9450 moderately complex data structures, the elements of interest may not
9451 actually be adjacent---for example, if you are interested in the values
9452 of pointers in an array. One useful work-around in this situation is
9453 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9454 Variables}) as a counter in an expression that prints the first
9455 interesting value, and then repeat that expression via @key{RET}. For
9456 instance, suppose you have an array @code{dtab} of pointers to
9457 structures, and you are interested in the values of a field @code{fv}
9458 in each structure. Here is an example of what you might type:
9468 @node Output Formats
9469 @section Output Formats
9471 @cindex formatted output
9472 @cindex output formats
9473 By default, @value{GDBN} prints a value according to its data type. Sometimes
9474 this is not what you want. For example, you might want to print a number
9475 in hex, or a pointer in decimal. Or you might want to view data in memory
9476 at a certain address as a character string or as an instruction. To do
9477 these things, specify an @dfn{output format} when you print a value.
9479 The simplest use of output formats is to say how to print a value
9480 already computed. This is done by starting the arguments of the
9481 @code{print} command with a slash and a format letter. The format
9482 letters supported are:
9486 Regard the bits of the value as an integer, and print the integer in
9490 Print as integer in signed decimal.
9493 Print as integer in unsigned decimal.
9496 Print as integer in octal.
9499 Print as integer in binary. The letter @samp{t} stands for ``two''.
9500 @footnote{@samp{b} cannot be used because these format letters are also
9501 used with the @code{x} command, where @samp{b} stands for ``byte'';
9502 see @ref{Memory,,Examining Memory}.}
9505 @cindex unknown address, locating
9506 @cindex locate address
9507 Print as an address, both absolute in hexadecimal and as an offset from
9508 the nearest preceding symbol. You can use this format used to discover
9509 where (in what function) an unknown address is located:
9512 (@value{GDBP}) p/a 0x54320
9513 $3 = 0x54320 <_initialize_vx+396>
9517 The command @code{info symbol 0x54320} yields similar results.
9518 @xref{Symbols, info symbol}.
9521 Regard as an integer and print it as a character constant. This
9522 prints both the numerical value and its character representation. The
9523 character representation is replaced with the octal escape @samp{\nnn}
9524 for characters outside the 7-bit @sc{ascii} range.
9526 Without this format, @value{GDBN} displays @code{char},
9527 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9528 constants. Single-byte members of vectors are displayed as integer
9532 Regard the bits of the value as a floating point number and print
9533 using typical floating point syntax.
9536 @cindex printing strings
9537 @cindex printing byte arrays
9538 Regard as a string, if possible. With this format, pointers to single-byte
9539 data are displayed as null-terminated strings and arrays of single-byte data
9540 are displayed as fixed-length strings. Other values are displayed in their
9543 Without this format, @value{GDBN} displays pointers to and arrays of
9544 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9545 strings. Single-byte members of a vector are displayed as an integer
9549 Like @samp{x} formatting, the value is treated as an integer and
9550 printed as hexadecimal, but leading zeros are printed to pad the value
9551 to the size of the integer type.
9554 @cindex raw printing
9555 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9556 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9557 Printing}). This typically results in a higher-level display of the
9558 value's contents. The @samp{r} format bypasses any Python
9559 pretty-printer which might exist.
9562 For example, to print the program counter in hex (@pxref{Registers}), type
9569 Note that no space is required before the slash; this is because command
9570 names in @value{GDBN} cannot contain a slash.
9572 To reprint the last value in the value history with a different format,
9573 you can use the @code{print} command with just a format and no
9574 expression. For example, @samp{p/x} reprints the last value in hex.
9577 @section Examining Memory
9579 You can use the command @code{x} (for ``examine'') to examine memory in
9580 any of several formats, independently of your program's data types.
9582 @cindex examining memory
9584 @kindex x @r{(examine memory)}
9585 @item x/@var{nfu} @var{addr}
9588 Use the @code{x} command to examine memory.
9591 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9592 much memory to display and how to format it; @var{addr} is an
9593 expression giving the address where you want to start displaying memory.
9594 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9595 Several commands set convenient defaults for @var{addr}.
9598 @item @var{n}, the repeat count
9599 The repeat count is a decimal integer; the default is 1. It specifies
9600 how much memory (counting by units @var{u}) to display. If a negative
9601 number is specified, memory is examined backward from @var{addr}.
9602 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9605 @item @var{f}, the display format
9606 The display format is one of the formats used by @code{print}
9607 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9608 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9609 The default is @samp{x} (hexadecimal) initially. The default changes
9610 each time you use either @code{x} or @code{print}.
9612 @item @var{u}, the unit size
9613 The unit size is any of
9619 Halfwords (two bytes).
9621 Words (four bytes). This is the initial default.
9623 Giant words (eight bytes).
9626 Each time you specify a unit size with @code{x}, that size becomes the
9627 default unit the next time you use @code{x}. For the @samp{i} format,
9628 the unit size is ignored and is normally not written. For the @samp{s} format,
9629 the unit size defaults to @samp{b}, unless it is explicitly given.
9630 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9631 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9632 Note that the results depend on the programming language of the
9633 current compilation unit. If the language is C, the @samp{s}
9634 modifier will use the UTF-16 encoding while @samp{w} will use
9635 UTF-32. The encoding is set by the programming language and cannot
9638 @item @var{addr}, starting display address
9639 @var{addr} is the address where you want @value{GDBN} to begin displaying
9640 memory. The expression need not have a pointer value (though it may);
9641 it is always interpreted as an integer address of a byte of memory.
9642 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9643 @var{addr} is usually just after the last address examined---but several
9644 other commands also set the default address: @code{info breakpoints} (to
9645 the address of the last breakpoint listed), @code{info line} (to the
9646 starting address of a line), and @code{print} (if you use it to display
9647 a value from memory).
9650 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9651 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9652 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9653 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9654 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9656 You can also specify a negative repeat count to examine memory backward
9657 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9658 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9660 Since the letters indicating unit sizes are all distinct from the
9661 letters specifying output formats, you do not have to remember whether
9662 unit size or format comes first; either order works. The output
9663 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9664 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9666 Even though the unit size @var{u} is ignored for the formats @samp{s}
9667 and @samp{i}, you might still want to use a count @var{n}; for example,
9668 @samp{3i} specifies that you want to see three machine instructions,
9669 including any operands. For convenience, especially when used with
9670 the @code{display} command, the @samp{i} format also prints branch delay
9671 slot instructions, if any, beyond the count specified, which immediately
9672 follow the last instruction that is within the count. The command
9673 @code{disassemble} gives an alternative way of inspecting machine
9674 instructions; see @ref{Machine Code,,Source and Machine Code}.
9676 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9677 the command displays null-terminated strings or instructions before the given
9678 address as many as the absolute value of the given number. For the @samp{i}
9679 format, we use line number information in the debug info to accurately locate
9680 instruction boundaries while disassembling backward. If line info is not
9681 available, the command stops examining memory with an error message.
9683 All the defaults for the arguments to @code{x} are designed to make it
9684 easy to continue scanning memory with minimal specifications each time
9685 you use @code{x}. For example, after you have inspected three machine
9686 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9687 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9688 the repeat count @var{n} is used again; the other arguments default as
9689 for successive uses of @code{x}.
9691 When examining machine instructions, the instruction at current program
9692 counter is shown with a @code{=>} marker. For example:
9695 (@value{GDBP}) x/5i $pc-6
9696 0x804837f <main+11>: mov %esp,%ebp
9697 0x8048381 <main+13>: push %ecx
9698 0x8048382 <main+14>: sub $0x4,%esp
9699 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9700 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9703 @cindex @code{$_}, @code{$__}, and value history
9704 The addresses and contents printed by the @code{x} command are not saved
9705 in the value history because there is often too much of them and they
9706 would get in the way. Instead, @value{GDBN} makes these values available for
9707 subsequent use in expressions as values of the convenience variables
9708 @code{$_} and @code{$__}. After an @code{x} command, the last address
9709 examined is available for use in expressions in the convenience variable
9710 @code{$_}. The contents of that address, as examined, are available in
9711 the convenience variable @code{$__}.
9713 If the @code{x} command has a repeat count, the address and contents saved
9714 are from the last memory unit printed; this is not the same as the last
9715 address printed if several units were printed on the last line of output.
9717 @anchor{addressable memory unit}
9718 @cindex addressable memory unit
9719 Most targets have an addressable memory unit size of 8 bits. This means
9720 that to each memory address are associated 8 bits of data. Some
9721 targets, however, have other addressable memory unit sizes.
9722 Within @value{GDBN} and this document, the term
9723 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9724 when explicitly referring to a chunk of data of that size. The word
9725 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9726 the addressable memory unit size of the target. For most systems,
9727 addressable memory unit is a synonym of byte.
9729 @cindex remote memory comparison
9730 @cindex target memory comparison
9731 @cindex verify remote memory image
9732 @cindex verify target memory image
9733 When you are debugging a program running on a remote target machine
9734 (@pxref{Remote Debugging}), you may wish to verify the program's image
9735 in the remote machine's memory against the executable file you
9736 downloaded to the target. Or, on any target, you may want to check
9737 whether the program has corrupted its own read-only sections. The
9738 @code{compare-sections} command is provided for such situations.
9741 @kindex compare-sections
9742 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9743 Compare the data of a loadable section @var{section-name} in the
9744 executable file of the program being debugged with the same section in
9745 the target machine's memory, and report any mismatches. With no
9746 arguments, compares all loadable sections. With an argument of
9747 @code{-r}, compares all loadable read-only sections.
9749 Note: for remote targets, this command can be accelerated if the
9750 target supports computing the CRC checksum of a block of memory
9751 (@pxref{qCRC packet}).
9755 @section Automatic Display
9756 @cindex automatic display
9757 @cindex display of expressions
9759 If you find that you want to print the value of an expression frequently
9760 (to see how it changes), you might want to add it to the @dfn{automatic
9761 display list} so that @value{GDBN} prints its value each time your program stops.
9762 Each expression added to the list is given a number to identify it;
9763 to remove an expression from the list, you specify that number.
9764 The automatic display looks like this:
9768 3: bar[5] = (struct hack *) 0x3804
9772 This display shows item numbers, expressions and their current values. As with
9773 displays you request manually using @code{x} or @code{print}, you can
9774 specify the output format you prefer; in fact, @code{display} decides
9775 whether to use @code{print} or @code{x} depending your format
9776 specification---it uses @code{x} if you specify either the @samp{i}
9777 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9781 @item display @var{expr}
9782 Add the expression @var{expr} to the list of expressions to display
9783 each time your program stops. @xref{Expressions, ,Expressions}.
9785 @code{display} does not repeat if you press @key{RET} again after using it.
9787 @item display/@var{fmt} @var{expr}
9788 For @var{fmt} specifying only a display format and not a size or
9789 count, add the expression @var{expr} to the auto-display list but
9790 arrange to display it each time in the specified format @var{fmt}.
9791 @xref{Output Formats,,Output Formats}.
9793 @item display/@var{fmt} @var{addr}
9794 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9795 number of units, add the expression @var{addr} as a memory address to
9796 be examined each time your program stops. Examining means in effect
9797 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9800 For example, @samp{display/i $pc} can be helpful, to see the machine
9801 instruction about to be executed each time execution stops (@samp{$pc}
9802 is a common name for the program counter; @pxref{Registers, ,Registers}).
9805 @kindex delete display
9807 @item undisplay @var{dnums}@dots{}
9808 @itemx delete display @var{dnums}@dots{}
9809 Remove items from the list of expressions to display. Specify the
9810 numbers of the displays that you want affected with the command
9811 argument @var{dnums}. It can be a single display number, one of the
9812 numbers shown in the first field of the @samp{info display} display;
9813 or it could be a range of display numbers, as in @code{2-4}.
9815 @code{undisplay} does not repeat if you press @key{RET} after using it.
9816 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9818 @kindex disable display
9819 @item disable display @var{dnums}@dots{}
9820 Disable the display of item numbers @var{dnums}. A disabled display
9821 item is not printed automatically, but is not forgotten. It may be
9822 enabled again later. Specify the numbers of the displays that you
9823 want affected with the command argument @var{dnums}. It can be a
9824 single display number, one of the numbers shown in the first field of
9825 the @samp{info display} display; or it could be a range of display
9826 numbers, as in @code{2-4}.
9828 @kindex enable display
9829 @item enable display @var{dnums}@dots{}
9830 Enable display of item numbers @var{dnums}. It becomes effective once
9831 again in auto display of its expression, until you specify otherwise.
9832 Specify the numbers of the displays that you want affected with the
9833 command argument @var{dnums}. It can be a single display number, one
9834 of the numbers shown in the first field of the @samp{info display}
9835 display; or it could be a range of display numbers, as in @code{2-4}.
9838 Display the current values of the expressions on the list, just as is
9839 done when your program stops.
9841 @kindex info display
9843 Print the list of expressions previously set up to display
9844 automatically, each one with its item number, but without showing the
9845 values. This includes disabled expressions, which are marked as such.
9846 It also includes expressions which would not be displayed right now
9847 because they refer to automatic variables not currently available.
9850 @cindex display disabled out of scope
9851 If a display expression refers to local variables, then it does not make
9852 sense outside the lexical context for which it was set up. Such an
9853 expression is disabled when execution enters a context where one of its
9854 variables is not defined. For example, if you give the command
9855 @code{display last_char} while inside a function with an argument
9856 @code{last_char}, @value{GDBN} displays this argument while your program
9857 continues to stop inside that function. When it stops elsewhere---where
9858 there is no variable @code{last_char}---the display is disabled
9859 automatically. The next time your program stops where @code{last_char}
9860 is meaningful, you can enable the display expression once again.
9862 @node Print Settings
9863 @section Print Settings
9865 @cindex format options
9866 @cindex print settings
9867 @value{GDBN} provides the following ways to control how arrays, structures,
9868 and symbols are printed.
9871 These settings are useful for debugging programs in any language:
9875 @item set print address
9876 @itemx set print address on
9877 @cindex print/don't print memory addresses
9878 @value{GDBN} prints memory addresses showing the location of stack
9879 traces, structure values, pointer values, breakpoints, and so forth,
9880 even when it also displays the contents of those addresses. The default
9881 is @code{on}. For example, this is what a stack frame display looks like with
9882 @code{set print address on}:
9887 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9889 530 if (lquote != def_lquote)
9893 @item set print address off
9894 Do not print addresses when displaying their contents. For example,
9895 this is the same stack frame displayed with @code{set print address off}:
9899 (@value{GDBP}) set print addr off
9901 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9902 530 if (lquote != def_lquote)
9906 You can use @samp{set print address off} to eliminate all machine
9907 dependent displays from the @value{GDBN} interface. For example, with
9908 @code{print address off}, you should get the same text for backtraces on
9909 all machines---whether or not they involve pointer arguments.
9912 @item show print address
9913 Show whether or not addresses are to be printed.
9916 When @value{GDBN} prints a symbolic address, it normally prints the
9917 closest earlier symbol plus an offset. If that symbol does not uniquely
9918 identify the address (for example, it is a name whose scope is a single
9919 source file), you may need to clarify. One way to do this is with
9920 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9921 you can set @value{GDBN} to print the source file and line number when
9922 it prints a symbolic address:
9925 @item set print symbol-filename on
9926 @cindex source file and line of a symbol
9927 @cindex symbol, source file and line
9928 Tell @value{GDBN} to print the source file name and line number of a
9929 symbol in the symbolic form of an address.
9931 @item set print symbol-filename off
9932 Do not print source file name and line number of a symbol. This is the
9935 @item show print symbol-filename
9936 Show whether or not @value{GDBN} will print the source file name and
9937 line number of a symbol in the symbolic form of an address.
9940 Another situation where it is helpful to show symbol filenames and line
9941 numbers is when disassembling code; @value{GDBN} shows you the line
9942 number and source file that corresponds to each instruction.
9944 Also, you may wish to see the symbolic form only if the address being
9945 printed is reasonably close to the closest earlier symbol:
9948 @item set print max-symbolic-offset @var{max-offset}
9949 @itemx set print max-symbolic-offset unlimited
9950 @cindex maximum value for offset of closest symbol
9951 Tell @value{GDBN} to only display the symbolic form of an address if the
9952 offset between the closest earlier symbol and the address is less than
9953 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9954 to always print the symbolic form of an address if any symbol precedes
9955 it. Zero is equivalent to @code{unlimited}.
9957 @item show print max-symbolic-offset
9958 Ask how large the maximum offset is that @value{GDBN} prints in a
9962 @cindex wild pointer, interpreting
9963 @cindex pointer, finding referent
9964 If you have a pointer and you are not sure where it points, try
9965 @samp{set print symbol-filename on}. Then you can determine the name
9966 and source file location of the variable where it points, using
9967 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9968 For example, here @value{GDBN} shows that a variable @code{ptt} points
9969 at another variable @code{t}, defined in @file{hi2.c}:
9972 (@value{GDBP}) set print symbol-filename on
9973 (@value{GDBP}) p/a ptt
9974 $4 = 0xe008 <t in hi2.c>
9978 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9979 does not show the symbol name and filename of the referent, even with
9980 the appropriate @code{set print} options turned on.
9983 You can also enable @samp{/a}-like formatting all the time using
9984 @samp{set print symbol on}:
9987 @item set print symbol on
9988 Tell @value{GDBN} to print the symbol corresponding to an address, if
9991 @item set print symbol off
9992 Tell @value{GDBN} not to print the symbol corresponding to an
9993 address. In this mode, @value{GDBN} will still print the symbol
9994 corresponding to pointers to functions. This is the default.
9996 @item show print symbol
9997 Show whether @value{GDBN} will display the symbol corresponding to an
10001 Other settings control how different kinds of objects are printed:
10004 @item set print array
10005 @itemx set print array on
10006 @cindex pretty print arrays
10007 Pretty print arrays. This format is more convenient to read,
10008 but uses more space. The default is off.
10010 @item set print array off
10011 Return to compressed format for arrays.
10013 @item show print array
10014 Show whether compressed or pretty format is selected for displaying
10017 @cindex print array indexes
10018 @item set print array-indexes
10019 @itemx set print array-indexes on
10020 Print the index of each element when displaying arrays. May be more
10021 convenient to locate a given element in the array or quickly find the
10022 index of a given element in that printed array. The default is off.
10024 @item set print array-indexes off
10025 Stop printing element indexes when displaying arrays.
10027 @item show print array-indexes
10028 Show whether the index of each element is printed when displaying
10031 @item set print elements @var{number-of-elements}
10032 @itemx set print elements unlimited
10033 @cindex number of array elements to print
10034 @cindex limit on number of printed array elements
10035 Set a limit on how many elements of an array @value{GDBN} will print.
10036 If @value{GDBN} is printing a large array, it stops printing after it has
10037 printed the number of elements set by the @code{set print elements} command.
10038 This limit also applies to the display of strings.
10039 When @value{GDBN} starts, this limit is set to 200.
10040 Setting @var{number-of-elements} to @code{unlimited} or zero means
10041 that the number of elements to print is unlimited.
10043 @item show print elements
10044 Display the number of elements of a large array that @value{GDBN} will print.
10045 If the number is 0, then the printing is unlimited.
10047 @item set print frame-arguments @var{value}
10048 @kindex set print frame-arguments
10049 @cindex printing frame argument values
10050 @cindex print all frame argument values
10051 @cindex print frame argument values for scalars only
10052 @cindex do not print frame argument values
10053 This command allows to control how the values of arguments are printed
10054 when the debugger prints a frame (@pxref{Frames}). The possible
10059 The values of all arguments are printed.
10062 Print the value of an argument only if it is a scalar. The value of more
10063 complex arguments such as arrays, structures, unions, etc, is replaced
10064 by @code{@dots{}}. This is the default. Here is an example where
10065 only scalar arguments are shown:
10068 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10073 None of the argument values are printed. Instead, the value of each argument
10074 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10077 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10082 By default, only scalar arguments are printed. This command can be used
10083 to configure the debugger to print the value of all arguments, regardless
10084 of their type. However, it is often advantageous to not print the value
10085 of more complex parameters. For instance, it reduces the amount of
10086 information printed in each frame, making the backtrace more readable.
10087 Also, it improves performance when displaying Ada frames, because
10088 the computation of large arguments can sometimes be CPU-intensive,
10089 especially in large applications. Setting @code{print frame-arguments}
10090 to @code{scalars} (the default) or @code{none} avoids this computation,
10091 thus speeding up the display of each Ada frame.
10093 @item show print frame-arguments
10094 Show how the value of arguments should be displayed when printing a frame.
10096 @item set print raw frame-arguments on
10097 Print frame arguments in raw, non pretty-printed, form.
10099 @item set print raw frame-arguments off
10100 Print frame arguments in pretty-printed form, if there is a pretty-printer
10101 for the value (@pxref{Pretty Printing}),
10102 otherwise print the value in raw form.
10103 This is the default.
10105 @item show print raw frame-arguments
10106 Show whether to print frame arguments in raw form.
10108 @anchor{set print entry-values}
10109 @item set print entry-values @var{value}
10110 @kindex set print entry-values
10111 Set printing of frame argument values at function entry. In some cases
10112 @value{GDBN} can determine the value of function argument which was passed by
10113 the function caller, even if the value was modified inside the called function
10114 and therefore is different. With optimized code, the current value could be
10115 unavailable, but the entry value may still be known.
10117 The default value is @code{default} (see below for its description). Older
10118 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10119 this feature will behave in the @code{default} setting the same way as with the
10122 This functionality is currently supported only by DWARF 2 debugging format and
10123 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10124 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10127 The @var{value} parameter can be one of the following:
10131 Print only actual parameter values, never print values from function entry
10135 #0 different (val=6)
10136 #0 lost (val=<optimized out>)
10138 #0 invalid (val=<optimized out>)
10142 Print only parameter values from function entry point. The actual parameter
10143 values are never printed.
10145 #0 equal (val@@entry=5)
10146 #0 different (val@@entry=5)
10147 #0 lost (val@@entry=5)
10148 #0 born (val@@entry=<optimized out>)
10149 #0 invalid (val@@entry=<optimized out>)
10153 Print only parameter values from function entry point. If value from function
10154 entry point is not known while the actual value is known, print the actual
10155 value for such parameter.
10157 #0 equal (val@@entry=5)
10158 #0 different (val@@entry=5)
10159 #0 lost (val@@entry=5)
10161 #0 invalid (val@@entry=<optimized out>)
10165 Print actual parameter values. If actual parameter value is not known while
10166 value from function entry point is known, print the entry point value for such
10170 #0 different (val=6)
10171 #0 lost (val@@entry=5)
10173 #0 invalid (val=<optimized out>)
10177 Always print both the actual parameter value and its value from function entry
10178 point, even if values of one or both are not available due to compiler
10181 #0 equal (val=5, val@@entry=5)
10182 #0 different (val=6, val@@entry=5)
10183 #0 lost (val=<optimized out>, val@@entry=5)
10184 #0 born (val=10, val@@entry=<optimized out>)
10185 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10189 Print the actual parameter value if it is known and also its value from
10190 function entry point if it is known. If neither is known, print for the actual
10191 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10192 values are known and identical, print the shortened
10193 @code{param=param@@entry=VALUE} notation.
10195 #0 equal (val=val@@entry=5)
10196 #0 different (val=6, val@@entry=5)
10197 #0 lost (val@@entry=5)
10199 #0 invalid (val=<optimized out>)
10203 Always print the actual parameter value. Print also its value from function
10204 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10205 if both values are known and identical, print the shortened
10206 @code{param=param@@entry=VALUE} notation.
10208 #0 equal (val=val@@entry=5)
10209 #0 different (val=6, val@@entry=5)
10210 #0 lost (val=<optimized out>, val@@entry=5)
10212 #0 invalid (val=<optimized out>)
10216 For analysis messages on possible failures of frame argument values at function
10217 entry resolution see @ref{set debug entry-values}.
10219 @item show print entry-values
10220 Show the method being used for printing of frame argument values at function
10223 @item set print repeats @var{number-of-repeats}
10224 @itemx set print repeats unlimited
10225 @cindex repeated array elements
10226 Set the threshold for suppressing display of repeated array
10227 elements. When the number of consecutive identical elements of an
10228 array exceeds the threshold, @value{GDBN} prints the string
10229 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10230 identical repetitions, instead of displaying the identical elements
10231 themselves. Setting the threshold to @code{unlimited} or zero will
10232 cause all elements to be individually printed. The default threshold
10235 @item show print repeats
10236 Display the current threshold for printing repeated identical
10239 @item set print null-stop
10240 @cindex @sc{null} elements in arrays
10241 Cause @value{GDBN} to stop printing the characters of an array when the first
10242 @sc{null} is encountered. This is useful when large arrays actually
10243 contain only short strings.
10244 The default is off.
10246 @item show print null-stop
10247 Show whether @value{GDBN} stops printing an array on the first
10248 @sc{null} character.
10250 @item set print pretty on
10251 @cindex print structures in indented form
10252 @cindex indentation in structure display
10253 Cause @value{GDBN} to print structures in an indented format with one member
10254 per line, like this:
10269 @item set print pretty off
10270 Cause @value{GDBN} to print structures in a compact format, like this:
10274 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10275 meat = 0x54 "Pork"@}
10280 This is the default format.
10282 @item show print pretty
10283 Show which format @value{GDBN} is using to print structures.
10285 @item set print sevenbit-strings on
10286 @cindex eight-bit characters in strings
10287 @cindex octal escapes in strings
10288 Print using only seven-bit characters; if this option is set,
10289 @value{GDBN} displays any eight-bit characters (in strings or
10290 character values) using the notation @code{\}@var{nnn}. This setting is
10291 best if you are working in English (@sc{ascii}) and you use the
10292 high-order bit of characters as a marker or ``meta'' bit.
10294 @item set print sevenbit-strings off
10295 Print full eight-bit characters. This allows the use of more
10296 international character sets, and is the default.
10298 @item show print sevenbit-strings
10299 Show whether or not @value{GDBN} is printing only seven-bit characters.
10301 @item set print union on
10302 @cindex unions in structures, printing
10303 Tell @value{GDBN} to print unions which are contained in structures
10304 and other unions. This is the default setting.
10306 @item set print union off
10307 Tell @value{GDBN} not to print unions which are contained in
10308 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10311 @item show print union
10312 Ask @value{GDBN} whether or not it will print unions which are contained in
10313 structures and other unions.
10315 For example, given the declarations
10318 typedef enum @{Tree, Bug@} Species;
10319 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10320 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10331 struct thing foo = @{Tree, @{Acorn@}@};
10335 with @code{set print union on} in effect @samp{p foo} would print
10338 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10342 and with @code{set print union off} in effect it would print
10345 $1 = @{it = Tree, form = @{...@}@}
10349 @code{set print union} affects programs written in C-like languages
10355 These settings are of interest when debugging C@t{++} programs:
10358 @cindex demangling C@t{++} names
10359 @item set print demangle
10360 @itemx set print demangle on
10361 Print C@t{++} names in their source form rather than in the encoded
10362 (``mangled'') form passed to the assembler and linker for type-safe
10363 linkage. The default is on.
10365 @item show print demangle
10366 Show whether C@t{++} names are printed in mangled or demangled form.
10368 @item set print asm-demangle
10369 @itemx set print asm-demangle on
10370 Print C@t{++} names in their source form rather than their mangled form, even
10371 in assembler code printouts such as instruction disassemblies.
10372 The default is off.
10374 @item show print asm-demangle
10375 Show whether C@t{++} names in assembly listings are printed in mangled
10378 @cindex C@t{++} symbol decoding style
10379 @cindex symbol decoding style, C@t{++}
10380 @kindex set demangle-style
10381 @item set demangle-style @var{style}
10382 Choose among several encoding schemes used by different compilers to
10383 represent C@t{++} names. The choices for @var{style} are currently:
10387 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10388 This is the default.
10391 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10394 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10397 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10400 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10401 @strong{Warning:} this setting alone is not sufficient to allow
10402 debugging @code{cfront}-generated executables. @value{GDBN} would
10403 require further enhancement to permit that.
10406 If you omit @var{style}, you will see a list of possible formats.
10408 @item show demangle-style
10409 Display the encoding style currently in use for decoding C@t{++} symbols.
10411 @item set print object
10412 @itemx set print object on
10413 @cindex derived type of an object, printing
10414 @cindex display derived types
10415 When displaying a pointer to an object, identify the @emph{actual}
10416 (derived) type of the object rather than the @emph{declared} type, using
10417 the virtual function table. Note that the virtual function table is
10418 required---this feature can only work for objects that have run-time
10419 type identification; a single virtual method in the object's declared
10420 type is sufficient. Note that this setting is also taken into account when
10421 working with variable objects via MI (@pxref{GDB/MI}).
10423 @item set print object off
10424 Display only the declared type of objects, without reference to the
10425 virtual function table. This is the default setting.
10427 @item show print object
10428 Show whether actual, or declared, object types are displayed.
10430 @item set print static-members
10431 @itemx set print static-members on
10432 @cindex static members of C@t{++} objects
10433 Print static members when displaying a C@t{++} object. The default is on.
10435 @item set print static-members off
10436 Do not print static members when displaying a C@t{++} object.
10438 @item show print static-members
10439 Show whether C@t{++} static members are printed or not.
10441 @item set print pascal_static-members
10442 @itemx set print pascal_static-members on
10443 @cindex static members of Pascal objects
10444 @cindex Pascal objects, static members display
10445 Print static members when displaying a Pascal object. The default is on.
10447 @item set print pascal_static-members off
10448 Do not print static members when displaying a Pascal object.
10450 @item show print pascal_static-members
10451 Show whether Pascal static members are printed or not.
10453 @c These don't work with HP ANSI C++ yet.
10454 @item set print vtbl
10455 @itemx set print vtbl on
10456 @cindex pretty print C@t{++} virtual function tables
10457 @cindex virtual functions (C@t{++}) display
10458 @cindex VTBL display
10459 Pretty print C@t{++} virtual function tables. The default is off.
10460 (The @code{vtbl} commands do not work on programs compiled with the HP
10461 ANSI C@t{++} compiler (@code{aCC}).)
10463 @item set print vtbl off
10464 Do not pretty print C@t{++} virtual function tables.
10466 @item show print vtbl
10467 Show whether C@t{++} virtual function tables are pretty printed, or not.
10470 @node Pretty Printing
10471 @section Pretty Printing
10473 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10474 Python code. It greatly simplifies the display of complex objects. This
10475 mechanism works for both MI and the CLI.
10478 * Pretty-Printer Introduction:: Introduction to pretty-printers
10479 * Pretty-Printer Example:: An example pretty-printer
10480 * Pretty-Printer Commands:: Pretty-printer commands
10483 @node Pretty-Printer Introduction
10484 @subsection Pretty-Printer Introduction
10486 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10487 registered for the value. If there is then @value{GDBN} invokes the
10488 pretty-printer to print the value. Otherwise the value is printed normally.
10490 Pretty-printers are normally named. This makes them easy to manage.
10491 The @samp{info pretty-printer} command will list all the installed
10492 pretty-printers with their names.
10493 If a pretty-printer can handle multiple data types, then its
10494 @dfn{subprinters} are the printers for the individual data types.
10495 Each such subprinter has its own name.
10496 The format of the name is @var{printer-name};@var{subprinter-name}.
10498 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10499 Typically they are automatically loaded and registered when the corresponding
10500 debug information is loaded, thus making them available without having to
10501 do anything special.
10503 There are three places where a pretty-printer can be registered.
10507 Pretty-printers registered globally are available when debugging
10511 Pretty-printers registered with a program space are available only
10512 when debugging that program.
10513 @xref{Progspaces In Python}, for more details on program spaces in Python.
10516 Pretty-printers registered with an objfile are loaded and unloaded
10517 with the corresponding objfile (e.g., shared library).
10518 @xref{Objfiles In Python}, for more details on objfiles in Python.
10521 @xref{Selecting Pretty-Printers}, for further information on how
10522 pretty-printers are selected,
10524 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10527 @node Pretty-Printer Example
10528 @subsection Pretty-Printer Example
10530 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10533 (@value{GDBP}) print s
10535 static npos = 4294967295,
10537 <std::allocator<char>> = @{
10538 <__gnu_cxx::new_allocator<char>> = @{
10539 <No data fields>@}, <No data fields>
10541 members of std::basic_string<char, std::char_traits<char>,
10542 std::allocator<char> >::_Alloc_hider:
10543 _M_p = 0x804a014 "abcd"
10548 With a pretty-printer for @code{std::string} only the contents are printed:
10551 (@value{GDBP}) print s
10555 @node Pretty-Printer Commands
10556 @subsection Pretty-Printer Commands
10557 @cindex pretty-printer commands
10560 @kindex info pretty-printer
10561 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10562 Print the list of installed pretty-printers.
10563 This includes disabled pretty-printers, which are marked as such.
10565 @var{object-regexp} is a regular expression matching the objects
10566 whose pretty-printers to list.
10567 Objects can be @code{global}, the program space's file
10568 (@pxref{Progspaces In Python}),
10569 and the object files within that program space (@pxref{Objfiles In Python}).
10570 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10571 looks up a printer from these three objects.
10573 @var{name-regexp} is a regular expression matching the name of the printers
10576 @kindex disable pretty-printer
10577 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10578 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10579 A disabled pretty-printer is not forgotten, it may be enabled again later.
10581 @kindex enable pretty-printer
10582 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10583 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10588 Suppose we have three pretty-printers installed: one from library1.so
10589 named @code{foo} that prints objects of type @code{foo}, and
10590 another from library2.so named @code{bar} that prints two types of objects,
10591 @code{bar1} and @code{bar2}.
10594 (gdb) info pretty-printer
10601 (gdb) info pretty-printer library2
10606 (gdb) disable pretty-printer library1
10608 2 of 3 printers enabled
10609 (gdb) info pretty-printer
10616 (gdb) disable pretty-printer library2 bar:bar1
10618 1 of 3 printers enabled
10619 (gdb) info pretty-printer library2
10626 (gdb) disable pretty-printer library2 bar
10628 0 of 3 printers enabled
10629 (gdb) info pretty-printer library2
10638 Note that for @code{bar} the entire printer can be disabled,
10639 as can each individual subprinter.
10641 @node Value History
10642 @section Value History
10644 @cindex value history
10645 @cindex history of values printed by @value{GDBN}
10646 Values printed by the @code{print} command are saved in the @value{GDBN}
10647 @dfn{value history}. This allows you to refer to them in other expressions.
10648 Values are kept until the symbol table is re-read or discarded
10649 (for example with the @code{file} or @code{symbol-file} commands).
10650 When the symbol table changes, the value history is discarded,
10651 since the values may contain pointers back to the types defined in the
10656 @cindex history number
10657 The values printed are given @dfn{history numbers} by which you can
10658 refer to them. These are successive integers starting with one.
10659 @code{print} shows you the history number assigned to a value by
10660 printing @samp{$@var{num} = } before the value; here @var{num} is the
10663 To refer to any previous value, use @samp{$} followed by the value's
10664 history number. The way @code{print} labels its output is designed to
10665 remind you of this. Just @code{$} refers to the most recent value in
10666 the history, and @code{$$} refers to the value before that.
10667 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10668 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10669 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10671 For example, suppose you have just printed a pointer to a structure and
10672 want to see the contents of the structure. It suffices to type
10678 If you have a chain of structures where the component @code{next} points
10679 to the next one, you can print the contents of the next one with this:
10686 You can print successive links in the chain by repeating this
10687 command---which you can do by just typing @key{RET}.
10689 Note that the history records values, not expressions. If the value of
10690 @code{x} is 4 and you type these commands:
10698 then the value recorded in the value history by the @code{print} command
10699 remains 4 even though the value of @code{x} has changed.
10702 @kindex show values
10704 Print the last ten values in the value history, with their item numbers.
10705 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10706 values} does not change the history.
10708 @item show values @var{n}
10709 Print ten history values centered on history item number @var{n}.
10711 @item show values +
10712 Print ten history values just after the values last printed. If no more
10713 values are available, @code{show values +} produces no display.
10716 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10717 same effect as @samp{show values +}.
10719 @node Convenience Vars
10720 @section Convenience Variables
10722 @cindex convenience variables
10723 @cindex user-defined variables
10724 @value{GDBN} provides @dfn{convenience variables} that you can use within
10725 @value{GDBN} to hold on to a value and refer to it later. These variables
10726 exist entirely within @value{GDBN}; they are not part of your program, and
10727 setting a convenience variable has no direct effect on further execution
10728 of your program. That is why you can use them freely.
10730 Convenience variables are prefixed with @samp{$}. Any name preceded by
10731 @samp{$} can be used for a convenience variable, unless it is one of
10732 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10733 (Value history references, in contrast, are @emph{numbers} preceded
10734 by @samp{$}. @xref{Value History, ,Value History}.)
10736 You can save a value in a convenience variable with an assignment
10737 expression, just as you would set a variable in your program.
10741 set $foo = *object_ptr
10745 would save in @code{$foo} the value contained in the object pointed to by
10748 Using a convenience variable for the first time creates it, but its
10749 value is @code{void} until you assign a new value. You can alter the
10750 value with another assignment at any time.
10752 Convenience variables have no fixed types. You can assign a convenience
10753 variable any type of value, including structures and arrays, even if
10754 that variable already has a value of a different type. The convenience
10755 variable, when used as an expression, has the type of its current value.
10758 @kindex show convenience
10759 @cindex show all user variables and functions
10760 @item show convenience
10761 Print a list of convenience variables used so far, and their values,
10762 as well as a list of the convenience functions.
10763 Abbreviated @code{show conv}.
10765 @kindex init-if-undefined
10766 @cindex convenience variables, initializing
10767 @item init-if-undefined $@var{variable} = @var{expression}
10768 Set a convenience variable if it has not already been set. This is useful
10769 for user-defined commands that keep some state. It is similar, in concept,
10770 to using local static variables with initializers in C (except that
10771 convenience variables are global). It can also be used to allow users to
10772 override default values used in a command script.
10774 If the variable is already defined then the expression is not evaluated so
10775 any side-effects do not occur.
10778 One of the ways to use a convenience variable is as a counter to be
10779 incremented or a pointer to be advanced. For example, to print
10780 a field from successive elements of an array of structures:
10784 print bar[$i++]->contents
10788 Repeat that command by typing @key{RET}.
10790 Some convenience variables are created automatically by @value{GDBN} and given
10791 values likely to be useful.
10794 @vindex $_@r{, convenience variable}
10796 The variable @code{$_} is automatically set by the @code{x} command to
10797 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10798 commands which provide a default address for @code{x} to examine also
10799 set @code{$_} to that address; these commands include @code{info line}
10800 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10801 except when set by the @code{x} command, in which case it is a pointer
10802 to the type of @code{$__}.
10804 @vindex $__@r{, convenience variable}
10806 The variable @code{$__} is automatically set by the @code{x} command
10807 to the value found in the last address examined. Its type is chosen
10808 to match the format in which the data was printed.
10811 @vindex $_exitcode@r{, convenience variable}
10812 When the program being debugged terminates normally, @value{GDBN}
10813 automatically sets this variable to the exit code of the program, and
10814 resets @code{$_exitsignal} to @code{void}.
10817 @vindex $_exitsignal@r{, convenience variable}
10818 When the program being debugged dies due to an uncaught signal,
10819 @value{GDBN} automatically sets this variable to that signal's number,
10820 and resets @code{$_exitcode} to @code{void}.
10822 To distinguish between whether the program being debugged has exited
10823 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10824 @code{$_exitsignal} is not @code{void}), the convenience function
10825 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10826 Functions}). For example, considering the following source code:
10829 #include <signal.h>
10832 main (int argc, char *argv[])
10839 A valid way of telling whether the program being debugged has exited
10840 or signalled would be:
10843 (@value{GDBP}) define has_exited_or_signalled
10844 Type commands for definition of ``has_exited_or_signalled''.
10845 End with a line saying just ``end''.
10846 >if $_isvoid ($_exitsignal)
10847 >echo The program has exited\n
10849 >echo The program has signalled\n
10855 Program terminated with signal SIGALRM, Alarm clock.
10856 The program no longer exists.
10857 (@value{GDBP}) has_exited_or_signalled
10858 The program has signalled
10861 As can be seen, @value{GDBN} correctly informs that the program being
10862 debugged has signalled, since it calls @code{raise} and raises a
10863 @code{SIGALRM} signal. If the program being debugged had not called
10864 @code{raise}, then @value{GDBN} would report a normal exit:
10867 (@value{GDBP}) has_exited_or_signalled
10868 The program has exited
10872 The variable @code{$_exception} is set to the exception object being
10873 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10876 @itemx $_probe_arg0@dots{}$_probe_arg11
10877 Arguments to a static probe. @xref{Static Probe Points}.
10880 @vindex $_sdata@r{, inspect, convenience variable}
10881 The variable @code{$_sdata} contains extra collected static tracepoint
10882 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10883 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10884 if extra static tracepoint data has not been collected.
10887 @vindex $_siginfo@r{, convenience variable}
10888 The variable @code{$_siginfo} contains extra signal information
10889 (@pxref{extra signal information}). Note that @code{$_siginfo}
10890 could be empty, if the application has not yet received any signals.
10891 For example, it will be empty before you execute the @code{run} command.
10894 @vindex $_tlb@r{, convenience variable}
10895 The variable @code{$_tlb} is automatically set when debugging
10896 applications running on MS-Windows in native mode or connected to
10897 gdbserver that supports the @code{qGetTIBAddr} request.
10898 @xref{General Query Packets}.
10899 This variable contains the address of the thread information block.
10902 The number of the current inferior. @xref{Inferiors and
10903 Programs, ,Debugging Multiple Inferiors and Programs}.
10906 The thread number of the current thread. @xref{thread numbers}.
10909 The global number of the current thread. @xref{global thread numbers}.
10913 @node Convenience Funs
10914 @section Convenience Functions
10916 @cindex convenience functions
10917 @value{GDBN} also supplies some @dfn{convenience functions}. These
10918 have a syntax similar to convenience variables. A convenience
10919 function can be used in an expression just like an ordinary function;
10920 however, a convenience function is implemented internally to
10923 These functions do not require @value{GDBN} to be configured with
10924 @code{Python} support, which means that they are always available.
10928 @item $_isvoid (@var{expr})
10929 @findex $_isvoid@r{, convenience function}
10930 Return one if the expression @var{expr} is @code{void}. Otherwise it
10933 A @code{void} expression is an expression where the type of the result
10934 is @code{void}. For example, you can examine a convenience variable
10935 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10939 (@value{GDBP}) print $_exitcode
10941 (@value{GDBP}) print $_isvoid ($_exitcode)
10944 Starting program: ./a.out
10945 [Inferior 1 (process 29572) exited normally]
10946 (@value{GDBP}) print $_exitcode
10948 (@value{GDBP}) print $_isvoid ($_exitcode)
10952 In the example above, we used @code{$_isvoid} to check whether
10953 @code{$_exitcode} is @code{void} before and after the execution of the
10954 program being debugged. Before the execution there is no exit code to
10955 be examined, therefore @code{$_exitcode} is @code{void}. After the
10956 execution the program being debugged returned zero, therefore
10957 @code{$_exitcode} is zero, which means that it is not @code{void}
10960 The @code{void} expression can also be a call of a function from the
10961 program being debugged. For example, given the following function:
10970 The result of calling it inside @value{GDBN} is @code{void}:
10973 (@value{GDBP}) print foo ()
10975 (@value{GDBP}) print $_isvoid (foo ())
10977 (@value{GDBP}) set $v = foo ()
10978 (@value{GDBP}) print $v
10980 (@value{GDBP}) print $_isvoid ($v)
10986 These functions require @value{GDBN} to be configured with
10987 @code{Python} support.
10991 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10992 @findex $_memeq@r{, convenience function}
10993 Returns one if the @var{length} bytes at the addresses given by
10994 @var{buf1} and @var{buf2} are equal.
10995 Otherwise it returns zero.
10997 @item $_regex(@var{str}, @var{regex})
10998 @findex $_regex@r{, convenience function}
10999 Returns one if the string @var{str} matches the regular expression
11000 @var{regex}. Otherwise it returns zero.
11001 The syntax of the regular expression is that specified by @code{Python}'s
11002 regular expression support.
11004 @item $_streq(@var{str1}, @var{str2})
11005 @findex $_streq@r{, convenience function}
11006 Returns one if the strings @var{str1} and @var{str2} are equal.
11007 Otherwise it returns zero.
11009 @item $_strlen(@var{str})
11010 @findex $_strlen@r{, convenience function}
11011 Returns the length of string @var{str}.
11013 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11014 @findex $_caller_is@r{, convenience function}
11015 Returns one if the calling function's name is equal to @var{name}.
11016 Otherwise it returns zero.
11018 If the optional argument @var{number_of_frames} is provided,
11019 it is the number of frames up in the stack to look.
11027 at testsuite/gdb.python/py-caller-is.c:21
11028 #1 0x00000000004005a0 in middle_func ()
11029 at testsuite/gdb.python/py-caller-is.c:27
11030 #2 0x00000000004005ab in top_func ()
11031 at testsuite/gdb.python/py-caller-is.c:33
11032 #3 0x00000000004005b6 in main ()
11033 at testsuite/gdb.python/py-caller-is.c:39
11034 (gdb) print $_caller_is ("middle_func")
11036 (gdb) print $_caller_is ("top_func", 2)
11040 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11041 @findex $_caller_matches@r{, convenience function}
11042 Returns one if the calling function's name matches the regular expression
11043 @var{regexp}. Otherwise it returns zero.
11045 If the optional argument @var{number_of_frames} is provided,
11046 it is the number of frames up in the stack to look.
11049 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11050 @findex $_any_caller_is@r{, convenience function}
11051 Returns one if any calling function's name is equal to @var{name}.
11052 Otherwise it returns zero.
11054 If the optional argument @var{number_of_frames} is provided,
11055 it is the number of frames up in the stack to look.
11058 This function differs from @code{$_caller_is} in that this function
11059 checks all stack frames from the immediate caller to the frame specified
11060 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11061 frame specified by @var{number_of_frames}.
11063 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11064 @findex $_any_caller_matches@r{, convenience function}
11065 Returns one if any calling function's name matches the regular expression
11066 @var{regexp}. Otherwise it returns zero.
11068 If the optional argument @var{number_of_frames} is provided,
11069 it is the number of frames up in the stack to look.
11072 This function differs from @code{$_caller_matches} in that this function
11073 checks all stack frames from the immediate caller to the frame specified
11074 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11075 frame specified by @var{number_of_frames}.
11077 @item $_as_string(@var{value})
11078 @findex $_as_string@r{, convenience function}
11079 Return the string representation of @var{value}.
11081 This function is useful to obtain the textual label (enumerator) of an
11082 enumeration value. For example, assuming the variable @var{node} is of
11083 an enumerated type:
11086 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11087 Visiting node of type NODE_INTEGER
11092 @value{GDBN} provides the ability to list and get help on
11093 convenience functions.
11096 @item help function
11097 @kindex help function
11098 @cindex show all convenience functions
11099 Print a list of all convenience functions.
11106 You can refer to machine register contents, in expressions, as variables
11107 with names starting with @samp{$}. The names of registers are different
11108 for each machine; use @code{info registers} to see the names used on
11112 @kindex info registers
11113 @item info registers
11114 Print the names and values of all registers except floating-point
11115 and vector registers (in the selected stack frame).
11117 @kindex info all-registers
11118 @cindex floating point registers
11119 @item info all-registers
11120 Print the names and values of all registers, including floating-point
11121 and vector registers (in the selected stack frame).
11123 @item info registers @var{reggroup} @dots{}
11124 Print the name and value of the registers in each of the specified
11125 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11126 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11128 @item info registers @var{regname} @dots{}
11129 Print the @dfn{relativized} value of each specified register @var{regname}.
11130 As discussed in detail below, register values are normally relative to
11131 the selected stack frame. The @var{regname} may be any register name valid on
11132 the machine you are using, with or without the initial @samp{$}.
11135 @anchor{standard registers}
11136 @cindex stack pointer register
11137 @cindex program counter register
11138 @cindex process status register
11139 @cindex frame pointer register
11140 @cindex standard registers
11141 @value{GDBN} has four ``standard'' register names that are available (in
11142 expressions) on most machines---whenever they do not conflict with an
11143 architecture's canonical mnemonics for registers. The register names
11144 @code{$pc} and @code{$sp} are used for the program counter register and
11145 the stack pointer. @code{$fp} is used for a register that contains a
11146 pointer to the current stack frame, and @code{$ps} is used for a
11147 register that contains the processor status. For example,
11148 you could print the program counter in hex with
11155 or print the instruction to be executed next with
11162 or add four to the stack pointer@footnote{This is a way of removing
11163 one word from the stack, on machines where stacks grow downward in
11164 memory (most machines, nowadays). This assumes that the innermost
11165 stack frame is selected; setting @code{$sp} is not allowed when other
11166 stack frames are selected. To pop entire frames off the stack,
11167 regardless of machine architecture, use @code{return};
11168 see @ref{Returning, ,Returning from a Function}.} with
11174 Whenever possible, these four standard register names are available on
11175 your machine even though the machine has different canonical mnemonics,
11176 so long as there is no conflict. The @code{info registers} command
11177 shows the canonical names. For example, on the SPARC, @code{info
11178 registers} displays the processor status register as @code{$psr} but you
11179 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11180 is an alias for the @sc{eflags} register.
11182 @value{GDBN} always considers the contents of an ordinary register as an
11183 integer when the register is examined in this way. Some machines have
11184 special registers which can hold nothing but floating point; these
11185 registers are considered to have floating point values. There is no way
11186 to refer to the contents of an ordinary register as floating point value
11187 (although you can @emph{print} it as a floating point value with
11188 @samp{print/f $@var{regname}}).
11190 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11191 means that the data format in which the register contents are saved by
11192 the operating system is not the same one that your program normally
11193 sees. For example, the registers of the 68881 floating point
11194 coprocessor are always saved in ``extended'' (raw) format, but all C
11195 programs expect to work with ``double'' (virtual) format. In such
11196 cases, @value{GDBN} normally works with the virtual format only (the format
11197 that makes sense for your program), but the @code{info registers} command
11198 prints the data in both formats.
11200 @cindex SSE registers (x86)
11201 @cindex MMX registers (x86)
11202 Some machines have special registers whose contents can be interpreted
11203 in several different ways. For example, modern x86-based machines
11204 have SSE and MMX registers that can hold several values packed
11205 together in several different formats. @value{GDBN} refers to such
11206 registers in @code{struct} notation:
11209 (@value{GDBP}) print $xmm1
11211 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11212 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11213 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11214 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11215 v4_int32 = @{0, 20657912, 11, 13@},
11216 v2_int64 = @{88725056443645952, 55834574859@},
11217 uint128 = 0x0000000d0000000b013b36f800000000
11222 To set values of such registers, you need to tell @value{GDBN} which
11223 view of the register you wish to change, as if you were assigning
11224 value to a @code{struct} member:
11227 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11230 Normally, register values are relative to the selected stack frame
11231 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11232 value that the register would contain if all stack frames farther in
11233 were exited and their saved registers restored. In order to see the
11234 true contents of hardware registers, you must select the innermost
11235 frame (with @samp{frame 0}).
11237 @cindex caller-saved registers
11238 @cindex call-clobbered registers
11239 @cindex volatile registers
11240 @cindex <not saved> values
11241 Usually ABIs reserve some registers as not needed to be saved by the
11242 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11243 registers). It may therefore not be possible for @value{GDBN} to know
11244 the value a register had before the call (in other words, in the outer
11245 frame), if the register value has since been changed by the callee.
11246 @value{GDBN} tries to deduce where the inner frame saved
11247 (``callee-saved'') registers, from the debug info, unwind info, or the
11248 machine code generated by your compiler. If some register is not
11249 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11250 its own knowledge of the ABI, or because the debug/unwind info
11251 explicitly says the register's value is undefined), @value{GDBN}
11252 displays @w{@samp{<not saved>}} as the register's value. With targets
11253 that @value{GDBN} has no knowledge of the register saving convention,
11254 if a register was not saved by the callee, then its value and location
11255 in the outer frame are assumed to be the same of the inner frame.
11256 This is usually harmless, because if the register is call-clobbered,
11257 the caller either does not care what is in the register after the
11258 call, or has code to restore the value that it does care about. Note,
11259 however, that if you change such a register in the outer frame, you
11260 may also be affecting the inner frame. Also, the more ``outer'' the
11261 frame is you're looking at, the more likely a call-clobbered
11262 register's value is to be wrong, in the sense that it doesn't actually
11263 represent the value the register had just before the call.
11265 @node Floating Point Hardware
11266 @section Floating Point Hardware
11267 @cindex floating point
11269 Depending on the configuration, @value{GDBN} may be able to give
11270 you more information about the status of the floating point hardware.
11275 Display hardware-dependent information about the floating
11276 point unit. The exact contents and layout vary depending on the
11277 floating point chip. Currently, @samp{info float} is supported on
11278 the ARM and x86 machines.
11282 @section Vector Unit
11283 @cindex vector unit
11285 Depending on the configuration, @value{GDBN} may be able to give you
11286 more information about the status of the vector unit.
11289 @kindex info vector
11291 Display information about the vector unit. The exact contents and
11292 layout vary depending on the hardware.
11295 @node OS Information
11296 @section Operating System Auxiliary Information
11297 @cindex OS information
11299 @value{GDBN} provides interfaces to useful OS facilities that can help
11300 you debug your program.
11302 @cindex auxiliary vector
11303 @cindex vector, auxiliary
11304 Some operating systems supply an @dfn{auxiliary vector} to programs at
11305 startup. This is akin to the arguments and environment that you
11306 specify for a program, but contains a system-dependent variety of
11307 binary values that tell system libraries important details about the
11308 hardware, operating system, and process. Each value's purpose is
11309 identified by an integer tag; the meanings are well-known but system-specific.
11310 Depending on the configuration and operating system facilities,
11311 @value{GDBN} may be able to show you this information. For remote
11312 targets, this functionality may further depend on the remote stub's
11313 support of the @samp{qXfer:auxv:read} packet, see
11314 @ref{qXfer auxiliary vector read}.
11319 Display the auxiliary vector of the inferior, which can be either a
11320 live process or a core dump file. @value{GDBN} prints each tag value
11321 numerically, and also shows names and text descriptions for recognized
11322 tags. Some values in the vector are numbers, some bit masks, and some
11323 pointers to strings or other data. @value{GDBN} displays each value in the
11324 most appropriate form for a recognized tag, and in hexadecimal for
11325 an unrecognized tag.
11328 On some targets, @value{GDBN} can access operating system-specific
11329 information and show it to you. The types of information available
11330 will differ depending on the type of operating system running on the
11331 target. The mechanism used to fetch the data is described in
11332 @ref{Operating System Information}. For remote targets, this
11333 functionality depends on the remote stub's support of the
11334 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11338 @item info os @var{infotype}
11340 Display OS information of the requested type.
11342 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11344 @anchor{linux info os infotypes}
11346 @kindex info os cpus
11348 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11349 the available fields from /proc/cpuinfo. For each supported architecture
11350 different fields are available. Two common entries are processor which gives
11351 CPU number and bogomips; a system constant that is calculated during
11352 kernel initialization.
11354 @kindex info os files
11356 Display the list of open file descriptors on the target. For each
11357 file descriptor, @value{GDBN} prints the identifier of the process
11358 owning the descriptor, the command of the owning process, the value
11359 of the descriptor, and the target of the descriptor.
11361 @kindex info os modules
11363 Display the list of all loaded kernel modules on the target. For each
11364 module, @value{GDBN} prints the module name, the size of the module in
11365 bytes, the number of times the module is used, the dependencies of the
11366 module, the status of the module, and the address of the loaded module
11369 @kindex info os msg
11371 Display the list of all System V message queues on the target. For each
11372 message queue, @value{GDBN} prints the message queue key, the message
11373 queue identifier, the access permissions, the current number of bytes
11374 on the queue, the current number of messages on the queue, the processes
11375 that last sent and received a message on the queue, the user and group
11376 of the owner and creator of the message queue, the times at which a
11377 message was last sent and received on the queue, and the time at which
11378 the message queue was last changed.
11380 @kindex info os processes
11382 Display the list of processes on the target. For each process,
11383 @value{GDBN} prints the process identifier, the name of the user, the
11384 command corresponding to the process, and the list of processor cores
11385 that the process is currently running on. (To understand what these
11386 properties mean, for this and the following info types, please consult
11387 the general @sc{gnu}/Linux documentation.)
11389 @kindex info os procgroups
11391 Display the list of process groups on the target. For each process,
11392 @value{GDBN} prints the identifier of the process group that it belongs
11393 to, the command corresponding to the process group leader, the process
11394 identifier, and the command line of the process. The list is sorted
11395 first by the process group identifier, then by the process identifier,
11396 so that processes belonging to the same process group are grouped together
11397 and the process group leader is listed first.
11399 @kindex info os semaphores
11401 Display the list of all System V semaphore sets on the target. For each
11402 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11403 set identifier, the access permissions, the number of semaphores in the
11404 set, the user and group of the owner and creator of the semaphore set,
11405 and the times at which the semaphore set was operated upon and changed.
11407 @kindex info os shm
11409 Display the list of all System V shared-memory regions on the target.
11410 For each shared-memory region, @value{GDBN} prints the region key,
11411 the shared-memory identifier, the access permissions, the size of the
11412 region, the process that created the region, the process that last
11413 attached to or detached from the region, the current number of live
11414 attaches to the region, and the times at which the region was last
11415 attached to, detach from, and changed.
11417 @kindex info os sockets
11419 Display the list of Internet-domain sockets on the target. For each
11420 socket, @value{GDBN} prints the address and port of the local and
11421 remote endpoints, the current state of the connection, the creator of
11422 the socket, the IP address family of the socket, and the type of the
11425 @kindex info os threads
11427 Display the list of threads running on the target. For each thread,
11428 @value{GDBN} prints the identifier of the process that the thread
11429 belongs to, the command of the process, the thread identifier, and the
11430 processor core that it is currently running on. The main thread of a
11431 process is not listed.
11435 If @var{infotype} is omitted, then list the possible values for
11436 @var{infotype} and the kind of OS information available for each
11437 @var{infotype}. If the target does not return a list of possible
11438 types, this command will report an error.
11441 @node Memory Region Attributes
11442 @section Memory Region Attributes
11443 @cindex memory region attributes
11445 @dfn{Memory region attributes} allow you to describe special handling
11446 required by regions of your target's memory. @value{GDBN} uses
11447 attributes to determine whether to allow certain types of memory
11448 accesses; whether to use specific width accesses; and whether to cache
11449 target memory. By default the description of memory regions is
11450 fetched from the target (if the current target supports this), but the
11451 user can override the fetched regions.
11453 Defined memory regions can be individually enabled and disabled. When a
11454 memory region is disabled, @value{GDBN} uses the default attributes when
11455 accessing memory in that region. Similarly, if no memory regions have
11456 been defined, @value{GDBN} uses the default attributes when accessing
11459 When a memory region is defined, it is given a number to identify it;
11460 to enable, disable, or remove a memory region, you specify that number.
11464 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11465 Define a memory region bounded by @var{lower} and @var{upper} with
11466 attributes @var{attributes}@dots{}, and add it to the list of regions
11467 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11468 case: it is treated as the target's maximum memory address.
11469 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11472 Discard any user changes to the memory regions and use target-supplied
11473 regions, if available, or no regions if the target does not support.
11476 @item delete mem @var{nums}@dots{}
11477 Remove memory regions @var{nums}@dots{} from the list of regions
11478 monitored by @value{GDBN}.
11480 @kindex disable mem
11481 @item disable mem @var{nums}@dots{}
11482 Disable monitoring of memory regions @var{nums}@dots{}.
11483 A disabled memory region is not forgotten.
11484 It may be enabled again later.
11487 @item enable mem @var{nums}@dots{}
11488 Enable monitoring of memory regions @var{nums}@dots{}.
11492 Print a table of all defined memory regions, with the following columns
11496 @item Memory Region Number
11497 @item Enabled or Disabled.
11498 Enabled memory regions are marked with @samp{y}.
11499 Disabled memory regions are marked with @samp{n}.
11502 The address defining the inclusive lower bound of the memory region.
11505 The address defining the exclusive upper bound of the memory region.
11508 The list of attributes set for this memory region.
11513 @subsection Attributes
11515 @subsubsection Memory Access Mode
11516 The access mode attributes set whether @value{GDBN} may make read or
11517 write accesses to a memory region.
11519 While these attributes prevent @value{GDBN} from performing invalid
11520 memory accesses, they do nothing to prevent the target system, I/O DMA,
11521 etc.@: from accessing memory.
11525 Memory is read only.
11527 Memory is write only.
11529 Memory is read/write. This is the default.
11532 @subsubsection Memory Access Size
11533 The access size attribute tells @value{GDBN} to use specific sized
11534 accesses in the memory region. Often memory mapped device registers
11535 require specific sized accesses. If no access size attribute is
11536 specified, @value{GDBN} may use accesses of any size.
11540 Use 8 bit memory accesses.
11542 Use 16 bit memory accesses.
11544 Use 32 bit memory accesses.
11546 Use 64 bit memory accesses.
11549 @c @subsubsection Hardware/Software Breakpoints
11550 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11551 @c will use hardware or software breakpoints for the internal breakpoints
11552 @c used by the step, next, finish, until, etc. commands.
11556 @c Always use hardware breakpoints
11557 @c @item swbreak (default)
11560 @subsubsection Data Cache
11561 The data cache attributes set whether @value{GDBN} will cache target
11562 memory. While this generally improves performance by reducing debug
11563 protocol overhead, it can lead to incorrect results because @value{GDBN}
11564 does not know about volatile variables or memory mapped device
11569 Enable @value{GDBN} to cache target memory.
11571 Disable @value{GDBN} from caching target memory. This is the default.
11574 @subsection Memory Access Checking
11575 @value{GDBN} can be instructed to refuse accesses to memory that is
11576 not explicitly described. This can be useful if accessing such
11577 regions has undesired effects for a specific target, or to provide
11578 better error checking. The following commands control this behaviour.
11581 @kindex set mem inaccessible-by-default
11582 @item set mem inaccessible-by-default [on|off]
11583 If @code{on} is specified, make @value{GDBN} treat memory not
11584 explicitly described by the memory ranges as non-existent and refuse accesses
11585 to such memory. The checks are only performed if there's at least one
11586 memory range defined. If @code{off} is specified, make @value{GDBN}
11587 treat the memory not explicitly described by the memory ranges as RAM.
11588 The default value is @code{on}.
11589 @kindex show mem inaccessible-by-default
11590 @item show mem inaccessible-by-default
11591 Show the current handling of accesses to unknown memory.
11595 @c @subsubsection Memory Write Verification
11596 @c The memory write verification attributes set whether @value{GDBN}
11597 @c will re-reads data after each write to verify the write was successful.
11601 @c @item noverify (default)
11604 @node Dump/Restore Files
11605 @section Copy Between Memory and a File
11606 @cindex dump/restore files
11607 @cindex append data to a file
11608 @cindex dump data to a file
11609 @cindex restore data from a file
11611 You can use the commands @code{dump}, @code{append}, and
11612 @code{restore} to copy data between target memory and a file. The
11613 @code{dump} and @code{append} commands write data to a file, and the
11614 @code{restore} command reads data from a file back into the inferior's
11615 memory. Files may be in binary, Motorola S-record, Intel hex,
11616 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11617 append to binary files, and cannot read from Verilog Hex files.
11622 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11623 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11624 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11625 or the value of @var{expr}, to @var{filename} in the given format.
11627 The @var{format} parameter may be any one of:
11634 Motorola S-record format.
11636 Tektronix Hex format.
11638 Verilog Hex format.
11641 @value{GDBN} uses the same definitions of these formats as the
11642 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11643 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11647 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11648 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11649 Append the contents of memory from @var{start_addr} to @var{end_addr},
11650 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11651 (@value{GDBN} can only append data to files in raw binary form.)
11654 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11655 Restore the contents of file @var{filename} into memory. The
11656 @code{restore} command can automatically recognize any known @sc{bfd}
11657 file format, except for raw binary. To restore a raw binary file you
11658 must specify the optional keyword @code{binary} after the filename.
11660 If @var{bias} is non-zero, its value will be added to the addresses
11661 contained in the file. Binary files always start at address zero, so
11662 they will be restored at address @var{bias}. Other bfd files have
11663 a built-in location; they will be restored at offset @var{bias}
11664 from that location.
11666 If @var{start} and/or @var{end} are non-zero, then only data between
11667 file offset @var{start} and file offset @var{end} will be restored.
11668 These offsets are relative to the addresses in the file, before
11669 the @var{bias} argument is applied.
11673 @node Core File Generation
11674 @section How to Produce a Core File from Your Program
11675 @cindex dump core from inferior
11677 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11678 image of a running process and its process status (register values
11679 etc.). Its primary use is post-mortem debugging of a program that
11680 crashed while it ran outside a debugger. A program that crashes
11681 automatically produces a core file, unless this feature is disabled by
11682 the user. @xref{Files}, for information on invoking @value{GDBN} in
11683 the post-mortem debugging mode.
11685 Occasionally, you may wish to produce a core file of the program you
11686 are debugging in order to preserve a snapshot of its state.
11687 @value{GDBN} has a special command for that.
11691 @kindex generate-core-file
11692 @item generate-core-file [@var{file}]
11693 @itemx gcore [@var{file}]
11694 Produce a core dump of the inferior process. The optional argument
11695 @var{file} specifies the file name where to put the core dump. If not
11696 specified, the file name defaults to @file{core.@var{pid}}, where
11697 @var{pid} is the inferior process ID.
11699 Note that this command is implemented only for some systems (as of
11700 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11702 On @sc{gnu}/Linux, this command can take into account the value of the
11703 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11704 dump (@pxref{set use-coredump-filter}), and by default honors the
11705 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11706 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11708 @kindex set use-coredump-filter
11709 @anchor{set use-coredump-filter}
11710 @item set use-coredump-filter on
11711 @itemx set use-coredump-filter off
11712 Enable or disable the use of the file
11713 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11714 files. This file is used by the Linux kernel to decide what types of
11715 memory mappings will be dumped or ignored when generating a core dump
11716 file. @var{pid} is the process ID of a currently running process.
11718 To make use of this feature, you have to write in the
11719 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11720 which is a bit mask representing the memory mapping types. If a bit
11721 is set in the bit mask, then the memory mappings of the corresponding
11722 types will be dumped; otherwise, they will be ignored. This
11723 configuration is inherited by child processes. For more information
11724 about the bits that can be set in the
11725 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11726 manpage of @code{core(5)}.
11728 By default, this option is @code{on}. If this option is turned
11729 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11730 and instead uses the same default value as the Linux kernel in order
11731 to decide which pages will be dumped in the core dump file. This
11732 value is currently @code{0x33}, which means that bits @code{0}
11733 (anonymous private mappings), @code{1} (anonymous shared mappings),
11734 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11735 This will cause these memory mappings to be dumped automatically.
11737 @kindex set dump-excluded-mappings
11738 @anchor{set dump-excluded-mappings}
11739 @item set dump-excluded-mappings on
11740 @itemx set dump-excluded-mappings off
11741 If @code{on} is specified, @value{GDBN} will dump memory mappings
11742 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11743 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11745 The default value is @code{off}.
11748 @node Character Sets
11749 @section Character Sets
11750 @cindex character sets
11752 @cindex translating between character sets
11753 @cindex host character set
11754 @cindex target character set
11756 If the program you are debugging uses a different character set to
11757 represent characters and strings than the one @value{GDBN} uses itself,
11758 @value{GDBN} can automatically translate between the character sets for
11759 you. The character set @value{GDBN} uses we call the @dfn{host
11760 character set}; the one the inferior program uses we call the
11761 @dfn{target character set}.
11763 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11764 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11765 remote protocol (@pxref{Remote Debugging}) to debug a program
11766 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11767 then the host character set is Latin-1, and the target character set is
11768 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11769 target-charset EBCDIC-US}, then @value{GDBN} translates between
11770 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11771 character and string literals in expressions.
11773 @value{GDBN} has no way to automatically recognize which character set
11774 the inferior program uses; you must tell it, using the @code{set
11775 target-charset} command, described below.
11777 Here are the commands for controlling @value{GDBN}'s character set
11781 @item set target-charset @var{charset}
11782 @kindex set target-charset
11783 Set the current target character set to @var{charset}. To display the
11784 list of supported target character sets, type
11785 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11787 @item set host-charset @var{charset}
11788 @kindex set host-charset
11789 Set the current host character set to @var{charset}.
11791 By default, @value{GDBN} uses a host character set appropriate to the
11792 system it is running on; you can override that default using the
11793 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11794 automatically determine the appropriate host character set. In this
11795 case, @value{GDBN} uses @samp{UTF-8}.
11797 @value{GDBN} can only use certain character sets as its host character
11798 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11799 @value{GDBN} will list the host character sets it supports.
11801 @item set charset @var{charset}
11802 @kindex set charset
11803 Set the current host and target character sets to @var{charset}. As
11804 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11805 @value{GDBN} will list the names of the character sets that can be used
11806 for both host and target.
11809 @kindex show charset
11810 Show the names of the current host and target character sets.
11812 @item show host-charset
11813 @kindex show host-charset
11814 Show the name of the current host character set.
11816 @item show target-charset
11817 @kindex show target-charset
11818 Show the name of the current target character set.
11820 @item set target-wide-charset @var{charset}
11821 @kindex set target-wide-charset
11822 Set the current target's wide character set to @var{charset}. This is
11823 the character set used by the target's @code{wchar_t} type. To
11824 display the list of supported wide character sets, type
11825 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11827 @item show target-wide-charset
11828 @kindex show target-wide-charset
11829 Show the name of the current target's wide character set.
11832 Here is an example of @value{GDBN}'s character set support in action.
11833 Assume that the following source code has been placed in the file
11834 @file{charset-test.c}:
11840 = @{72, 101, 108, 108, 111, 44, 32, 119,
11841 111, 114, 108, 100, 33, 10, 0@};
11842 char ibm1047_hello[]
11843 = @{200, 133, 147, 147, 150, 107, 64, 166,
11844 150, 153, 147, 132, 90, 37, 0@};
11848 printf ("Hello, world!\n");
11852 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11853 containing the string @samp{Hello, world!} followed by a newline,
11854 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11856 We compile the program, and invoke the debugger on it:
11859 $ gcc -g charset-test.c -o charset-test
11860 $ gdb -nw charset-test
11861 GNU gdb 2001-12-19-cvs
11862 Copyright 2001 Free Software Foundation, Inc.
11867 We can use the @code{show charset} command to see what character sets
11868 @value{GDBN} is currently using to interpret and display characters and
11872 (@value{GDBP}) show charset
11873 The current host and target character set is `ISO-8859-1'.
11877 For the sake of printing this manual, let's use @sc{ascii} as our
11878 initial character set:
11880 (@value{GDBP}) set charset ASCII
11881 (@value{GDBP}) show charset
11882 The current host and target character set is `ASCII'.
11886 Let's assume that @sc{ascii} is indeed the correct character set for our
11887 host system --- in other words, let's assume that if @value{GDBN} prints
11888 characters using the @sc{ascii} character set, our terminal will display
11889 them properly. Since our current target character set is also
11890 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11893 (@value{GDBP}) print ascii_hello
11894 $1 = 0x401698 "Hello, world!\n"
11895 (@value{GDBP}) print ascii_hello[0]
11900 @value{GDBN} uses the target character set for character and string
11901 literals you use in expressions:
11904 (@value{GDBP}) print '+'
11909 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11912 @value{GDBN} relies on the user to tell it which character set the
11913 target program uses. If we print @code{ibm1047_hello} while our target
11914 character set is still @sc{ascii}, we get jibberish:
11917 (@value{GDBP}) print ibm1047_hello
11918 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11919 (@value{GDBP}) print ibm1047_hello[0]
11924 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11925 @value{GDBN} tells us the character sets it supports:
11928 (@value{GDBP}) set target-charset
11929 ASCII EBCDIC-US IBM1047 ISO-8859-1
11930 (@value{GDBP}) set target-charset
11933 We can select @sc{ibm1047} as our target character set, and examine the
11934 program's strings again. Now the @sc{ascii} string is wrong, but
11935 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11936 target character set, @sc{ibm1047}, to the host character set,
11937 @sc{ascii}, and they display correctly:
11940 (@value{GDBP}) set target-charset IBM1047
11941 (@value{GDBP}) show charset
11942 The current host character set is `ASCII'.
11943 The current target character set is `IBM1047'.
11944 (@value{GDBP}) print ascii_hello
11945 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11946 (@value{GDBP}) print ascii_hello[0]
11948 (@value{GDBP}) print ibm1047_hello
11949 $8 = 0x4016a8 "Hello, world!\n"
11950 (@value{GDBP}) print ibm1047_hello[0]
11955 As above, @value{GDBN} uses the target character set for character and
11956 string literals you use in expressions:
11959 (@value{GDBP}) print '+'
11964 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11967 @node Caching Target Data
11968 @section Caching Data of Targets
11969 @cindex caching data of targets
11971 @value{GDBN} caches data exchanged between the debugger and a target.
11972 Each cache is associated with the address space of the inferior.
11973 @xref{Inferiors and Programs}, about inferior and address space.
11974 Such caching generally improves performance in remote debugging
11975 (@pxref{Remote Debugging}), because it reduces the overhead of the
11976 remote protocol by bundling memory reads and writes into large chunks.
11977 Unfortunately, simply caching everything would lead to incorrect results,
11978 since @value{GDBN} does not necessarily know anything about volatile
11979 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11980 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11982 Therefore, by default, @value{GDBN} only caches data
11983 known to be on the stack@footnote{In non-stop mode, it is moderately
11984 rare for a running thread to modify the stack of a stopped thread
11985 in a way that would interfere with a backtrace, and caching of
11986 stack reads provides a significant speed up of remote backtraces.} or
11987 in the code segment.
11988 Other regions of memory can be explicitly marked as
11989 cacheable; @pxref{Memory Region Attributes}.
11992 @kindex set remotecache
11993 @item set remotecache on
11994 @itemx set remotecache off
11995 This option no longer does anything; it exists for compatibility
11998 @kindex show remotecache
11999 @item show remotecache
12000 Show the current state of the obsolete remotecache flag.
12002 @kindex set stack-cache
12003 @item set stack-cache on
12004 @itemx set stack-cache off
12005 Enable or disable caching of stack accesses. When @code{on}, use
12006 caching. By default, this option is @code{on}.
12008 @kindex show stack-cache
12009 @item show stack-cache
12010 Show the current state of data caching for memory accesses.
12012 @kindex set code-cache
12013 @item set code-cache on
12014 @itemx set code-cache off
12015 Enable or disable caching of code segment accesses. When @code{on},
12016 use caching. By default, this option is @code{on}. This improves
12017 performance of disassembly in remote debugging.
12019 @kindex show code-cache
12020 @item show code-cache
12021 Show the current state of target memory cache for code segment
12024 @kindex info dcache
12025 @item info dcache @r{[}line@r{]}
12026 Print the information about the performance of data cache of the
12027 current inferior's address space. The information displayed
12028 includes the dcache width and depth, and for each cache line, its
12029 number, address, and how many times it was referenced. This
12030 command is useful for debugging the data cache operation.
12032 If a line number is specified, the contents of that line will be
12035 @item set dcache size @var{size}
12036 @cindex dcache size
12037 @kindex set dcache size
12038 Set maximum number of entries in dcache (dcache depth above).
12040 @item set dcache line-size @var{line-size}
12041 @cindex dcache line-size
12042 @kindex set dcache line-size
12043 Set number of bytes each dcache entry caches (dcache width above).
12044 Must be a power of 2.
12046 @item show dcache size
12047 @kindex show dcache size
12048 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12050 @item show dcache line-size
12051 @kindex show dcache line-size
12052 Show default size of dcache lines.
12056 @node Searching Memory
12057 @section Search Memory
12058 @cindex searching memory
12060 Memory can be searched for a particular sequence of bytes with the
12061 @code{find} command.
12065 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12066 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12067 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12068 etc. The search begins at address @var{start_addr} and continues for either
12069 @var{len} bytes or through to @var{end_addr} inclusive.
12072 @var{s} and @var{n} are optional parameters.
12073 They may be specified in either order, apart or together.
12076 @item @var{s}, search query size
12077 The size of each search query value.
12083 halfwords (two bytes)
12087 giant words (eight bytes)
12090 All values are interpreted in the current language.
12091 This means, for example, that if the current source language is C/C@t{++}
12092 then searching for the string ``hello'' includes the trailing '\0'.
12093 The null terminator can be removed from searching by using casts,
12094 e.g.: @samp{@{char[5]@}"hello"}.
12096 If the value size is not specified, it is taken from the
12097 value's type in the current language.
12098 This is useful when one wants to specify the search
12099 pattern as a mixture of types.
12100 Note that this means, for example, that in the case of C-like languages
12101 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12102 which is typically four bytes.
12104 @item @var{n}, maximum number of finds
12105 The maximum number of matches to print. The default is to print all finds.
12108 You can use strings as search values. Quote them with double-quotes
12110 The string value is copied into the search pattern byte by byte,
12111 regardless of the endianness of the target and the size specification.
12113 The address of each match found is printed as well as a count of the
12114 number of matches found.
12116 The address of the last value found is stored in convenience variable
12118 A count of the number of matches is stored in @samp{$numfound}.
12120 For example, if stopped at the @code{printf} in this function:
12126 static char hello[] = "hello-hello";
12127 static struct @{ char c; short s; int i; @}
12128 __attribute__ ((packed)) mixed
12129 = @{ 'c', 0x1234, 0x87654321 @};
12130 printf ("%s\n", hello);
12135 you get during debugging:
12138 (gdb) find &hello[0], +sizeof(hello), "hello"
12139 0x804956d <hello.1620+6>
12141 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12142 0x8049567 <hello.1620>
12143 0x804956d <hello.1620+6>
12145 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12146 0x8049567 <hello.1620>
12147 0x804956d <hello.1620+6>
12149 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12150 0x8049567 <hello.1620>
12152 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12153 0x8049560 <mixed.1625>
12155 (gdb) print $numfound
12158 $2 = (void *) 0x8049560
12162 @section Value Sizes
12164 Whenever @value{GDBN} prints a value memory will be allocated within
12165 @value{GDBN} to hold the contents of the value. It is possible in
12166 some languages with dynamic typing systems, that an invalid program
12167 may indicate a value that is incorrectly large, this in turn may cause
12168 @value{GDBN} to try and allocate an overly large ammount of memory.
12171 @kindex set max-value-size
12172 @item set max-value-size @var{bytes}
12173 @itemx set max-value-size unlimited
12174 Set the maximum size of memory that @value{GDBN} will allocate for the
12175 contents of a value to @var{bytes}, trying to display a value that
12176 requires more memory than that will result in an error.
12178 Setting this variable does not effect values that have already been
12179 allocated within @value{GDBN}, only future allocations.
12181 There's a minimum size that @code{max-value-size} can be set to in
12182 order that @value{GDBN} can still operate correctly, this minimum is
12183 currently 16 bytes.
12185 The limit applies to the results of some subexpressions as well as to
12186 complete expressions. For example, an expression denoting a simple
12187 integer component, such as @code{x.y.z}, may fail if the size of
12188 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12189 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12190 @var{A} is an array variable with non-constant size, will generally
12191 succeed regardless of the bounds on @var{A}, as long as the component
12192 size is less than @var{bytes}.
12194 The default value of @code{max-value-size} is currently 64k.
12196 @kindex show max-value-size
12197 @item show max-value-size
12198 Show the maximum size of memory, in bytes, that @value{GDBN} will
12199 allocate for the contents of a value.
12202 @node Optimized Code
12203 @chapter Debugging Optimized Code
12204 @cindex optimized code, debugging
12205 @cindex debugging optimized code
12207 Almost all compilers support optimization. With optimization
12208 disabled, the compiler generates assembly code that corresponds
12209 directly to your source code, in a simplistic way. As the compiler
12210 applies more powerful optimizations, the generated assembly code
12211 diverges from your original source code. With help from debugging
12212 information generated by the compiler, @value{GDBN} can map from
12213 the running program back to constructs from your original source.
12215 @value{GDBN} is more accurate with optimization disabled. If you
12216 can recompile without optimization, it is easier to follow the
12217 progress of your program during debugging. But, there are many cases
12218 where you may need to debug an optimized version.
12220 When you debug a program compiled with @samp{-g -O}, remember that the
12221 optimizer has rearranged your code; the debugger shows you what is
12222 really there. Do not be too surprised when the execution path does not
12223 exactly match your source file! An extreme example: if you define a
12224 variable, but never use it, @value{GDBN} never sees that
12225 variable---because the compiler optimizes it out of existence.
12227 Some things do not work as well with @samp{-g -O} as with just
12228 @samp{-g}, particularly on machines with instruction scheduling. If in
12229 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12230 please report it to us as a bug (including a test case!).
12231 @xref{Variables}, for more information about debugging optimized code.
12234 * Inline Functions:: How @value{GDBN} presents inlining
12235 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12238 @node Inline Functions
12239 @section Inline Functions
12240 @cindex inline functions, debugging
12242 @dfn{Inlining} is an optimization that inserts a copy of the function
12243 body directly at each call site, instead of jumping to a shared
12244 routine. @value{GDBN} displays inlined functions just like
12245 non-inlined functions. They appear in backtraces. You can view their
12246 arguments and local variables, step into them with @code{step}, skip
12247 them with @code{next}, and escape from them with @code{finish}.
12248 You can check whether a function was inlined by using the
12249 @code{info frame} command.
12251 For @value{GDBN} to support inlined functions, the compiler must
12252 record information about inlining in the debug information ---
12253 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12254 other compilers do also. @value{GDBN} only supports inlined functions
12255 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12256 do not emit two required attributes (@samp{DW_AT_call_file} and
12257 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12258 function calls with earlier versions of @value{NGCC}. It instead
12259 displays the arguments and local variables of inlined functions as
12260 local variables in the caller.
12262 The body of an inlined function is directly included at its call site;
12263 unlike a non-inlined function, there are no instructions devoted to
12264 the call. @value{GDBN} still pretends that the call site and the
12265 start of the inlined function are different instructions. Stepping to
12266 the call site shows the call site, and then stepping again shows
12267 the first line of the inlined function, even though no additional
12268 instructions are executed.
12270 This makes source-level debugging much clearer; you can see both the
12271 context of the call and then the effect of the call. Only stepping by
12272 a single instruction using @code{stepi} or @code{nexti} does not do
12273 this; single instruction steps always show the inlined body.
12275 There are some ways that @value{GDBN} does not pretend that inlined
12276 function calls are the same as normal calls:
12280 Setting breakpoints at the call site of an inlined function may not
12281 work, because the call site does not contain any code. @value{GDBN}
12282 may incorrectly move the breakpoint to the next line of the enclosing
12283 function, after the call. This limitation will be removed in a future
12284 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12285 or inside the inlined function instead.
12288 @value{GDBN} cannot locate the return value of inlined calls after
12289 using the @code{finish} command. This is a limitation of compiler-generated
12290 debugging information; after @code{finish}, you can step to the next line
12291 and print a variable where your program stored the return value.
12295 @node Tail Call Frames
12296 @section Tail Call Frames
12297 @cindex tail call frames, debugging
12299 Function @code{B} can call function @code{C} in its very last statement. In
12300 unoptimized compilation the call of @code{C} is immediately followed by return
12301 instruction at the end of @code{B} code. Optimizing compiler may replace the
12302 call and return in function @code{B} into one jump to function @code{C}
12303 instead. Such use of a jump instruction is called @dfn{tail call}.
12305 During execution of function @code{C}, there will be no indication in the
12306 function call stack frames that it was tail-called from @code{B}. If function
12307 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12308 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12309 some cases @value{GDBN} can determine that @code{C} was tail-called from
12310 @code{B}, and it will then create fictitious call frame for that, with the
12311 return address set up as if @code{B} called @code{C} normally.
12313 This functionality is currently supported only by DWARF 2 debugging format and
12314 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12315 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12318 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12319 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12323 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12325 Stack level 1, frame at 0x7fffffffda30:
12326 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12327 tail call frame, caller of frame at 0x7fffffffda30
12328 source language c++.
12329 Arglist at unknown address.
12330 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12333 The detection of all the possible code path executions can find them ambiguous.
12334 There is no execution history stored (possible @ref{Reverse Execution} is never
12335 used for this purpose) and the last known caller could have reached the known
12336 callee by multiple different jump sequences. In such case @value{GDBN} still
12337 tries to show at least all the unambiguous top tail callers and all the
12338 unambiguous bottom tail calees, if any.
12341 @anchor{set debug entry-values}
12342 @item set debug entry-values
12343 @kindex set debug entry-values
12344 When set to on, enables printing of analysis messages for both frame argument
12345 values at function entry and tail calls. It will show all the possible valid
12346 tail calls code paths it has considered. It will also print the intersection
12347 of them with the final unambiguous (possibly partial or even empty) code path
12350 @item show debug entry-values
12351 @kindex show debug entry-values
12352 Show the current state of analysis messages printing for both frame argument
12353 values at function entry and tail calls.
12356 The analysis messages for tail calls can for example show why the virtual tail
12357 call frame for function @code{c} has not been recognized (due to the indirect
12358 reference by variable @code{x}):
12361 static void __attribute__((noinline, noclone)) c (void);
12362 void (*x) (void) = c;
12363 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12364 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12365 int main (void) @{ x (); return 0; @}
12367 Breakpoint 1, DW_OP_entry_value resolving cannot find
12368 DW_TAG_call_site 0x40039a in main
12370 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12373 #1 0x000000000040039a in main () at t.c:5
12376 Another possibility is an ambiguous virtual tail call frames resolution:
12380 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12381 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12382 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12383 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12384 static void __attribute__((noinline, noclone)) b (void)
12385 @{ if (i) c (); else e (); @}
12386 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12387 int main (void) @{ a (); return 0; @}
12389 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12390 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12391 tailcall: reduced: 0x4004d2(a) |
12394 #1 0x00000000004004d2 in a () at t.c:8
12395 #2 0x0000000000400395 in main () at t.c:9
12398 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12399 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12401 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12402 @ifset HAVE_MAKEINFO_CLICK
12403 @set ARROW @click{}
12404 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12405 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12407 @ifclear HAVE_MAKEINFO_CLICK
12409 @set CALLSEQ1B @value{CALLSEQ1A}
12410 @set CALLSEQ2B @value{CALLSEQ2A}
12413 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12414 The code can have possible execution paths @value{CALLSEQ1B} or
12415 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12417 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12418 has found. It then finds another possible calling sequcen - that one is
12419 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12420 printed as the @code{reduced:} calling sequence. That one could have many
12421 futher @code{compare:} and @code{reduced:} statements as long as there remain
12422 any non-ambiguous sequence entries.
12424 For the frame of function @code{b} in both cases there are different possible
12425 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12426 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12427 therefore this one is displayed to the user while the ambiguous frames are
12430 There can be also reasons why printing of frame argument values at function
12435 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12436 static void __attribute__((noinline, noclone)) a (int i);
12437 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12438 static void __attribute__((noinline, noclone)) a (int i)
12439 @{ if (i) b (i - 1); else c (0); @}
12440 int main (void) @{ a (5); return 0; @}
12443 #0 c (i=i@@entry=0) at t.c:2
12444 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12445 function "a" at 0x400420 can call itself via tail calls
12446 i=<optimized out>) at t.c:6
12447 #2 0x000000000040036e in main () at t.c:7
12450 @value{GDBN} cannot find out from the inferior state if and how many times did
12451 function @code{a} call itself (via function @code{b}) as these calls would be
12452 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12453 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12454 prints @code{<optimized out>} instead.
12457 @chapter C Preprocessor Macros
12459 Some languages, such as C and C@t{++}, provide a way to define and invoke
12460 ``preprocessor macros'' which expand into strings of tokens.
12461 @value{GDBN} can evaluate expressions containing macro invocations, show
12462 the result of macro expansion, and show a macro's definition, including
12463 where it was defined.
12465 You may need to compile your program specially to provide @value{GDBN}
12466 with information about preprocessor macros. Most compilers do not
12467 include macros in their debugging information, even when you compile
12468 with the @option{-g} flag. @xref{Compilation}.
12470 A program may define a macro at one point, remove that definition later,
12471 and then provide a different definition after that. Thus, at different
12472 points in the program, a macro may have different definitions, or have
12473 no definition at all. If there is a current stack frame, @value{GDBN}
12474 uses the macros in scope at that frame's source code line. Otherwise,
12475 @value{GDBN} uses the macros in scope at the current listing location;
12478 Whenever @value{GDBN} evaluates an expression, it always expands any
12479 macro invocations present in the expression. @value{GDBN} also provides
12480 the following commands for working with macros explicitly.
12484 @kindex macro expand
12485 @cindex macro expansion, showing the results of preprocessor
12486 @cindex preprocessor macro expansion, showing the results of
12487 @cindex expanding preprocessor macros
12488 @item macro expand @var{expression}
12489 @itemx macro exp @var{expression}
12490 Show the results of expanding all preprocessor macro invocations in
12491 @var{expression}. Since @value{GDBN} simply expands macros, but does
12492 not parse the result, @var{expression} need not be a valid expression;
12493 it can be any string of tokens.
12496 @item macro expand-once @var{expression}
12497 @itemx macro exp1 @var{expression}
12498 @cindex expand macro once
12499 @i{(This command is not yet implemented.)} Show the results of
12500 expanding those preprocessor macro invocations that appear explicitly in
12501 @var{expression}. Macro invocations appearing in that expansion are
12502 left unchanged. This command allows you to see the effect of a
12503 particular macro more clearly, without being confused by further
12504 expansions. Since @value{GDBN} simply expands macros, but does not
12505 parse the result, @var{expression} need not be a valid expression; it
12506 can be any string of tokens.
12509 @cindex macro definition, showing
12510 @cindex definition of a macro, showing
12511 @cindex macros, from debug info
12512 @item info macro [-a|-all] [--] @var{macro}
12513 Show the current definition or all definitions of the named @var{macro},
12514 and describe the source location or compiler command-line where that
12515 definition was established. The optional double dash is to signify the end of
12516 argument processing and the beginning of @var{macro} for non C-like macros where
12517 the macro may begin with a hyphen.
12519 @kindex info macros
12520 @item info macros @var{location}
12521 Show all macro definitions that are in effect at the location specified
12522 by @var{location}, and describe the source location or compiler
12523 command-line where those definitions were established.
12525 @kindex macro define
12526 @cindex user-defined macros
12527 @cindex defining macros interactively
12528 @cindex macros, user-defined
12529 @item macro define @var{macro} @var{replacement-list}
12530 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12531 Introduce a definition for a preprocessor macro named @var{macro},
12532 invocations of which are replaced by the tokens given in
12533 @var{replacement-list}. The first form of this command defines an
12534 ``object-like'' macro, which takes no arguments; the second form
12535 defines a ``function-like'' macro, which takes the arguments given in
12538 A definition introduced by this command is in scope in every
12539 expression evaluated in @value{GDBN}, until it is removed with the
12540 @code{macro undef} command, described below. The definition overrides
12541 all definitions for @var{macro} present in the program being debugged,
12542 as well as any previous user-supplied definition.
12544 @kindex macro undef
12545 @item macro undef @var{macro}
12546 Remove any user-supplied definition for the macro named @var{macro}.
12547 This command only affects definitions provided with the @code{macro
12548 define} command, described above; it cannot remove definitions present
12549 in the program being debugged.
12553 List all the macros defined using the @code{macro define} command.
12556 @cindex macros, example of debugging with
12557 Here is a transcript showing the above commands in action. First, we
12558 show our source files:
12563 #include "sample.h"
12566 #define ADD(x) (M + x)
12571 printf ("Hello, world!\n");
12573 printf ("We're so creative.\n");
12575 printf ("Goodbye, world!\n");
12582 Now, we compile the program using the @sc{gnu} C compiler,
12583 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12584 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12585 and @option{-gdwarf-4}; we recommend always choosing the most recent
12586 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12587 includes information about preprocessor macros in the debugging
12591 $ gcc -gdwarf-2 -g3 sample.c -o sample
12595 Now, we start @value{GDBN} on our sample program:
12599 GNU gdb 2002-05-06-cvs
12600 Copyright 2002 Free Software Foundation, Inc.
12601 GDB is free software, @dots{}
12605 We can expand macros and examine their definitions, even when the
12606 program is not running. @value{GDBN} uses the current listing position
12607 to decide which macro definitions are in scope:
12610 (@value{GDBP}) list main
12613 5 #define ADD(x) (M + x)
12618 10 printf ("Hello, world!\n");
12620 12 printf ("We're so creative.\n");
12621 (@value{GDBP}) info macro ADD
12622 Defined at /home/jimb/gdb/macros/play/sample.c:5
12623 #define ADD(x) (M + x)
12624 (@value{GDBP}) info macro Q
12625 Defined at /home/jimb/gdb/macros/play/sample.h:1
12626 included at /home/jimb/gdb/macros/play/sample.c:2
12628 (@value{GDBP}) macro expand ADD(1)
12629 expands to: (42 + 1)
12630 (@value{GDBP}) macro expand-once ADD(1)
12631 expands to: once (M + 1)
12635 In the example above, note that @code{macro expand-once} expands only
12636 the macro invocation explicit in the original text --- the invocation of
12637 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12638 which was introduced by @code{ADD}.
12640 Once the program is running, @value{GDBN} uses the macro definitions in
12641 force at the source line of the current stack frame:
12644 (@value{GDBP}) break main
12645 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12647 Starting program: /home/jimb/gdb/macros/play/sample
12649 Breakpoint 1, main () at sample.c:10
12650 10 printf ("Hello, world!\n");
12654 At line 10, the definition of the macro @code{N} at line 9 is in force:
12657 (@value{GDBP}) info macro N
12658 Defined at /home/jimb/gdb/macros/play/sample.c:9
12660 (@value{GDBP}) macro expand N Q M
12661 expands to: 28 < 42
12662 (@value{GDBP}) print N Q M
12667 As we step over directives that remove @code{N}'s definition, and then
12668 give it a new definition, @value{GDBN} finds the definition (or lack
12669 thereof) in force at each point:
12672 (@value{GDBP}) next
12674 12 printf ("We're so creative.\n");
12675 (@value{GDBP}) info macro N
12676 The symbol `N' has no definition as a C/C++ preprocessor macro
12677 at /home/jimb/gdb/macros/play/sample.c:12
12678 (@value{GDBP}) next
12680 14 printf ("Goodbye, world!\n");
12681 (@value{GDBP}) info macro N
12682 Defined at /home/jimb/gdb/macros/play/sample.c:13
12684 (@value{GDBP}) macro expand N Q M
12685 expands to: 1729 < 42
12686 (@value{GDBP}) print N Q M
12691 In addition to source files, macros can be defined on the compilation command
12692 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12693 such a way, @value{GDBN} displays the location of their definition as line zero
12694 of the source file submitted to the compiler.
12697 (@value{GDBP}) info macro __STDC__
12698 Defined at /home/jimb/gdb/macros/play/sample.c:0
12705 @chapter Tracepoints
12706 @c This chapter is based on the documentation written by Michael
12707 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12709 @cindex tracepoints
12710 In some applications, it is not feasible for the debugger to interrupt
12711 the program's execution long enough for the developer to learn
12712 anything helpful about its behavior. If the program's correctness
12713 depends on its real-time behavior, delays introduced by a debugger
12714 might cause the program to change its behavior drastically, or perhaps
12715 fail, even when the code itself is correct. It is useful to be able
12716 to observe the program's behavior without interrupting it.
12718 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12719 specify locations in the program, called @dfn{tracepoints}, and
12720 arbitrary expressions to evaluate when those tracepoints are reached.
12721 Later, using the @code{tfind} command, you can examine the values
12722 those expressions had when the program hit the tracepoints. The
12723 expressions may also denote objects in memory---structures or arrays,
12724 for example---whose values @value{GDBN} should record; while visiting
12725 a particular tracepoint, you may inspect those objects as if they were
12726 in memory at that moment. However, because @value{GDBN} records these
12727 values without interacting with you, it can do so quickly and
12728 unobtrusively, hopefully not disturbing the program's behavior.
12730 The tracepoint facility is currently available only for remote
12731 targets. @xref{Targets}. In addition, your remote target must know
12732 how to collect trace data. This functionality is implemented in the
12733 remote stub; however, none of the stubs distributed with @value{GDBN}
12734 support tracepoints as of this writing. The format of the remote
12735 packets used to implement tracepoints are described in @ref{Tracepoint
12738 It is also possible to get trace data from a file, in a manner reminiscent
12739 of corefiles; you specify the filename, and use @code{tfind} to search
12740 through the file. @xref{Trace Files}, for more details.
12742 This chapter describes the tracepoint commands and features.
12745 * Set Tracepoints::
12746 * Analyze Collected Data::
12747 * Tracepoint Variables::
12751 @node Set Tracepoints
12752 @section Commands to Set Tracepoints
12754 Before running such a @dfn{trace experiment}, an arbitrary number of
12755 tracepoints can be set. A tracepoint is actually a special type of
12756 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12757 standard breakpoint commands. For instance, as with breakpoints,
12758 tracepoint numbers are successive integers starting from one, and many
12759 of the commands associated with tracepoints take the tracepoint number
12760 as their argument, to identify which tracepoint to work on.
12762 For each tracepoint, you can specify, in advance, some arbitrary set
12763 of data that you want the target to collect in the trace buffer when
12764 it hits that tracepoint. The collected data can include registers,
12765 local variables, or global data. Later, you can use @value{GDBN}
12766 commands to examine the values these data had at the time the
12767 tracepoint was hit.
12769 Tracepoints do not support every breakpoint feature. Ignore counts on
12770 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12771 commands when they are hit. Tracepoints may not be thread-specific
12774 @cindex fast tracepoints
12775 Some targets may support @dfn{fast tracepoints}, which are inserted in
12776 a different way (such as with a jump instead of a trap), that is
12777 faster but possibly restricted in where they may be installed.
12779 @cindex static tracepoints
12780 @cindex markers, static tracepoints
12781 @cindex probing markers, static tracepoints
12782 Regular and fast tracepoints are dynamic tracing facilities, meaning
12783 that they can be used to insert tracepoints at (almost) any location
12784 in the target. Some targets may also support controlling @dfn{static
12785 tracepoints} from @value{GDBN}. With static tracing, a set of
12786 instrumentation points, also known as @dfn{markers}, are embedded in
12787 the target program, and can be activated or deactivated by name or
12788 address. These are usually placed at locations which facilitate
12789 investigating what the target is actually doing. @value{GDBN}'s
12790 support for static tracing includes being able to list instrumentation
12791 points, and attach them with @value{GDBN} defined high level
12792 tracepoints that expose the whole range of convenience of
12793 @value{GDBN}'s tracepoints support. Namely, support for collecting
12794 registers values and values of global or local (to the instrumentation
12795 point) variables; tracepoint conditions and trace state variables.
12796 The act of installing a @value{GDBN} static tracepoint on an
12797 instrumentation point, or marker, is referred to as @dfn{probing} a
12798 static tracepoint marker.
12800 @code{gdbserver} supports tracepoints on some target systems.
12801 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12803 This section describes commands to set tracepoints and associated
12804 conditions and actions.
12807 * Create and Delete Tracepoints::
12808 * Enable and Disable Tracepoints::
12809 * Tracepoint Passcounts::
12810 * Tracepoint Conditions::
12811 * Trace State Variables::
12812 * Tracepoint Actions::
12813 * Listing Tracepoints::
12814 * Listing Static Tracepoint Markers::
12815 * Starting and Stopping Trace Experiments::
12816 * Tracepoint Restrictions::
12819 @node Create and Delete Tracepoints
12820 @subsection Create and Delete Tracepoints
12823 @cindex set tracepoint
12825 @item trace @var{location}
12826 The @code{trace} command is very similar to the @code{break} command.
12827 Its argument @var{location} can be any valid location.
12828 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12829 which is a point in the target program where the debugger will briefly stop,
12830 collect some data, and then allow the program to continue. Setting a tracepoint
12831 or changing its actions takes effect immediately if the remote stub
12832 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12834 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12835 these changes don't take effect until the next @code{tstart}
12836 command, and once a trace experiment is running, further changes will
12837 not have any effect until the next trace experiment starts. In addition,
12838 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12839 address is not yet resolved. (This is similar to pending breakpoints.)
12840 Pending tracepoints are not downloaded to the target and not installed
12841 until they are resolved. The resolution of pending tracepoints requires
12842 @value{GDBN} support---when debugging with the remote target, and
12843 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12844 tracing}), pending tracepoints can not be resolved (and downloaded to
12845 the remote stub) while @value{GDBN} is disconnected.
12847 Here are some examples of using the @code{trace} command:
12850 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12852 (@value{GDBP}) @b{trace +2} // 2 lines forward
12854 (@value{GDBP}) @b{trace my_function} // first source line of function
12856 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12858 (@value{GDBP}) @b{trace *0x2117c4} // an address
12862 You can abbreviate @code{trace} as @code{tr}.
12864 @item trace @var{location} if @var{cond}
12865 Set a tracepoint with condition @var{cond}; evaluate the expression
12866 @var{cond} each time the tracepoint is reached, and collect data only
12867 if the value is nonzero---that is, if @var{cond} evaluates as true.
12868 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12869 information on tracepoint conditions.
12871 @item ftrace @var{location} [ if @var{cond} ]
12872 @cindex set fast tracepoint
12873 @cindex fast tracepoints, setting
12875 The @code{ftrace} command sets a fast tracepoint. For targets that
12876 support them, fast tracepoints will use a more efficient but possibly
12877 less general technique to trigger data collection, such as a jump
12878 instruction instead of a trap, or some sort of hardware support. It
12879 may not be possible to create a fast tracepoint at the desired
12880 location, in which case the command will exit with an explanatory
12883 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12886 On 32-bit x86-architecture systems, fast tracepoints normally need to
12887 be placed at an instruction that is 5 bytes or longer, but can be
12888 placed at 4-byte instructions if the low 64K of memory of the target
12889 program is available to install trampolines. Some Unix-type systems,
12890 such as @sc{gnu}/Linux, exclude low addresses from the program's
12891 address space; but for instance with the Linux kernel it is possible
12892 to let @value{GDBN} use this area by doing a @command{sysctl} command
12893 to set the @code{mmap_min_addr} kernel parameter, as in
12896 sudo sysctl -w vm.mmap_min_addr=32768
12900 which sets the low address to 32K, which leaves plenty of room for
12901 trampolines. The minimum address should be set to a page boundary.
12903 @item strace @var{location} [ if @var{cond} ]
12904 @cindex set static tracepoint
12905 @cindex static tracepoints, setting
12906 @cindex probe static tracepoint marker
12908 The @code{strace} command sets a static tracepoint. For targets that
12909 support it, setting a static tracepoint probes a static
12910 instrumentation point, or marker, found at @var{location}. It may not
12911 be possible to set a static tracepoint at the desired location, in
12912 which case the command will exit with an explanatory message.
12914 @value{GDBN} handles arguments to @code{strace} exactly as for
12915 @code{trace}, with the addition that the user can also specify
12916 @code{-m @var{marker}} as @var{location}. This probes the marker
12917 identified by the @var{marker} string identifier. This identifier
12918 depends on the static tracepoint backend library your program is
12919 using. You can find all the marker identifiers in the @samp{ID} field
12920 of the @code{info static-tracepoint-markers} command output.
12921 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12922 Markers}. For example, in the following small program using the UST
12928 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12933 the marker id is composed of joining the first two arguments to the
12934 @code{trace_mark} call with a slash, which translates to:
12937 (@value{GDBP}) info static-tracepoint-markers
12938 Cnt Enb ID Address What
12939 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12945 so you may probe the marker above with:
12948 (@value{GDBP}) strace -m ust/bar33
12951 Static tracepoints accept an extra collect action --- @code{collect
12952 $_sdata}. This collects arbitrary user data passed in the probe point
12953 call to the tracing library. In the UST example above, you'll see
12954 that the third argument to @code{trace_mark} is a printf-like format
12955 string. The user data is then the result of running that formating
12956 string against the following arguments. Note that @code{info
12957 static-tracepoint-markers} command output lists that format string in
12958 the @samp{Data:} field.
12960 You can inspect this data when analyzing the trace buffer, by printing
12961 the $_sdata variable like any other variable available to
12962 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12965 @cindex last tracepoint number
12966 @cindex recent tracepoint number
12967 @cindex tracepoint number
12968 The convenience variable @code{$tpnum} records the tracepoint number
12969 of the most recently set tracepoint.
12971 @kindex delete tracepoint
12972 @cindex tracepoint deletion
12973 @item delete tracepoint @r{[}@var{num}@r{]}
12974 Permanently delete one or more tracepoints. With no argument, the
12975 default is to delete all tracepoints. Note that the regular
12976 @code{delete} command can remove tracepoints also.
12981 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12983 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12987 You can abbreviate this command as @code{del tr}.
12990 @node Enable and Disable Tracepoints
12991 @subsection Enable and Disable Tracepoints
12993 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12996 @kindex disable tracepoint
12997 @item disable tracepoint @r{[}@var{num}@r{]}
12998 Disable tracepoint @var{num}, or all tracepoints if no argument
12999 @var{num} is given. A disabled tracepoint will have no effect during
13000 a trace experiment, but it is not forgotten. You can re-enable
13001 a disabled tracepoint using the @code{enable tracepoint} command.
13002 If the command is issued during a trace experiment and the debug target
13003 has support for disabling tracepoints during a trace experiment, then the
13004 change will be effective immediately. Otherwise, it will be applied to the
13005 next trace experiment.
13007 @kindex enable tracepoint
13008 @item enable tracepoint @r{[}@var{num}@r{]}
13009 Enable tracepoint @var{num}, or all tracepoints. If this command is
13010 issued during a trace experiment and the debug target supports enabling
13011 tracepoints during a trace experiment, then the enabled tracepoints will
13012 become effective immediately. Otherwise, they will become effective the
13013 next time a trace experiment is run.
13016 @node Tracepoint Passcounts
13017 @subsection Tracepoint Passcounts
13021 @cindex tracepoint pass count
13022 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13023 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13024 automatically stop a trace experiment. If a tracepoint's passcount is
13025 @var{n}, then the trace experiment will be automatically stopped on
13026 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13027 @var{num} is not specified, the @code{passcount} command sets the
13028 passcount of the most recently defined tracepoint. If no passcount is
13029 given, the trace experiment will run until stopped explicitly by the
13035 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13036 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13038 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13039 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13040 (@value{GDBP}) @b{trace foo}
13041 (@value{GDBP}) @b{pass 3}
13042 (@value{GDBP}) @b{trace bar}
13043 (@value{GDBP}) @b{pass 2}
13044 (@value{GDBP}) @b{trace baz}
13045 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13046 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13047 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13048 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13052 @node Tracepoint Conditions
13053 @subsection Tracepoint Conditions
13054 @cindex conditional tracepoints
13055 @cindex tracepoint conditions
13057 The simplest sort of tracepoint collects data every time your program
13058 reaches a specified place. You can also specify a @dfn{condition} for
13059 a tracepoint. A condition is just a Boolean expression in your
13060 programming language (@pxref{Expressions, ,Expressions}). A
13061 tracepoint with a condition evaluates the expression each time your
13062 program reaches it, and data collection happens only if the condition
13065 Tracepoint conditions can be specified when a tracepoint is set, by
13066 using @samp{if} in the arguments to the @code{trace} command.
13067 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13068 also be set or changed at any time with the @code{condition} command,
13069 just as with breakpoints.
13071 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13072 the conditional expression itself. Instead, @value{GDBN} encodes the
13073 expression into an agent expression (@pxref{Agent Expressions})
13074 suitable for execution on the target, independently of @value{GDBN}.
13075 Global variables become raw memory locations, locals become stack
13076 accesses, and so forth.
13078 For instance, suppose you have a function that is usually called
13079 frequently, but should not be called after an error has occurred. You
13080 could use the following tracepoint command to collect data about calls
13081 of that function that happen while the error code is propagating
13082 through the program; an unconditional tracepoint could end up
13083 collecting thousands of useless trace frames that you would have to
13087 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13090 @node Trace State Variables
13091 @subsection Trace State Variables
13092 @cindex trace state variables
13094 A @dfn{trace state variable} is a special type of variable that is
13095 created and managed by target-side code. The syntax is the same as
13096 that for GDB's convenience variables (a string prefixed with ``$''),
13097 but they are stored on the target. They must be created explicitly,
13098 using a @code{tvariable} command. They are always 64-bit signed
13101 Trace state variables are remembered by @value{GDBN}, and downloaded
13102 to the target along with tracepoint information when the trace
13103 experiment starts. There are no intrinsic limits on the number of
13104 trace state variables, beyond memory limitations of the target.
13106 @cindex convenience variables, and trace state variables
13107 Although trace state variables are managed by the target, you can use
13108 them in print commands and expressions as if they were convenience
13109 variables; @value{GDBN} will get the current value from the target
13110 while the trace experiment is running. Trace state variables share
13111 the same namespace as other ``$'' variables, which means that you
13112 cannot have trace state variables with names like @code{$23} or
13113 @code{$pc}, nor can you have a trace state variable and a convenience
13114 variable with the same name.
13118 @item tvariable $@var{name} [ = @var{expression} ]
13120 The @code{tvariable} command creates a new trace state variable named
13121 @code{$@var{name}}, and optionally gives it an initial value of
13122 @var{expression}. The @var{expression} is evaluated when this command is
13123 entered; the result will be converted to an integer if possible,
13124 otherwise @value{GDBN} will report an error. A subsequent
13125 @code{tvariable} command specifying the same name does not create a
13126 variable, but instead assigns the supplied initial value to the
13127 existing variable of that name, overwriting any previous initial
13128 value. The default initial value is 0.
13130 @item info tvariables
13131 @kindex info tvariables
13132 List all the trace state variables along with their initial values.
13133 Their current values may also be displayed, if the trace experiment is
13136 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13137 @kindex delete tvariable
13138 Delete the given trace state variables, or all of them if no arguments
13143 @node Tracepoint Actions
13144 @subsection Tracepoint Action Lists
13148 @cindex tracepoint actions
13149 @item actions @r{[}@var{num}@r{]}
13150 This command will prompt for a list of actions to be taken when the
13151 tracepoint is hit. If the tracepoint number @var{num} is not
13152 specified, this command sets the actions for the one that was most
13153 recently defined (so that you can define a tracepoint and then say
13154 @code{actions} without bothering about its number). You specify the
13155 actions themselves on the following lines, one action at a time, and
13156 terminate the actions list with a line containing just @code{end}. So
13157 far, the only defined actions are @code{collect}, @code{teval}, and
13158 @code{while-stepping}.
13160 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13161 Commands, ,Breakpoint Command Lists}), except that only the defined
13162 actions are allowed; any other @value{GDBN} command is rejected.
13164 @cindex remove actions from a tracepoint
13165 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13166 and follow it immediately with @samp{end}.
13169 (@value{GDBP}) @b{collect @var{data}} // collect some data
13171 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13173 (@value{GDBP}) @b{end} // signals the end of actions.
13176 In the following example, the action list begins with @code{collect}
13177 commands indicating the things to be collected when the tracepoint is
13178 hit. Then, in order to single-step and collect additional data
13179 following the tracepoint, a @code{while-stepping} command is used,
13180 followed by the list of things to be collected after each step in a
13181 sequence of single steps. The @code{while-stepping} command is
13182 terminated by its own separate @code{end} command. Lastly, the action
13183 list is terminated by an @code{end} command.
13186 (@value{GDBP}) @b{trace foo}
13187 (@value{GDBP}) @b{actions}
13188 Enter actions for tracepoint 1, one per line:
13191 > while-stepping 12
13192 > collect $pc, arr[i]
13197 @kindex collect @r{(tracepoints)}
13198 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13199 Collect values of the given expressions when the tracepoint is hit.
13200 This command accepts a comma-separated list of any valid expressions.
13201 In addition to global, static, or local variables, the following
13202 special arguments are supported:
13206 Collect all registers.
13209 Collect all function arguments.
13212 Collect all local variables.
13215 Collect the return address. This is helpful if you want to see more
13218 @emph{Note:} The return address location can not always be reliably
13219 determined up front, and the wrong address / registers may end up
13220 collected instead. On some architectures the reliability is higher
13221 for tracepoints at function entry, while on others it's the opposite.
13222 When this happens, backtracing will stop because the return address is
13223 found unavailable (unless another collect rule happened to match it).
13226 Collects the number of arguments from the static probe at which the
13227 tracepoint is located.
13228 @xref{Static Probe Points}.
13230 @item $_probe_arg@var{n}
13231 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13232 from the static probe at which the tracepoint is located.
13233 @xref{Static Probe Points}.
13236 @vindex $_sdata@r{, collect}
13237 Collect static tracepoint marker specific data. Only available for
13238 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13239 Lists}. On the UST static tracepoints library backend, an
13240 instrumentation point resembles a @code{printf} function call. The
13241 tracing library is able to collect user specified data formatted to a
13242 character string using the format provided by the programmer that
13243 instrumented the program. Other backends have similar mechanisms.
13244 Here's an example of a UST marker call:
13247 const char master_name[] = "$your_name";
13248 trace_mark(channel1, marker1, "hello %s", master_name)
13251 In this case, collecting @code{$_sdata} collects the string
13252 @samp{hello $yourname}. When analyzing the trace buffer, you can
13253 inspect @samp{$_sdata} like any other variable available to
13257 You can give several consecutive @code{collect} commands, each one
13258 with a single argument, or one @code{collect} command with several
13259 arguments separated by commas; the effect is the same.
13261 The optional @var{mods} changes the usual handling of the arguments.
13262 @code{s} requests that pointers to chars be handled as strings, in
13263 particular collecting the contents of the memory being pointed at, up
13264 to the first zero. The upper bound is by default the value of the
13265 @code{print elements} variable; if @code{s} is followed by a decimal
13266 number, that is the upper bound instead. So for instance
13267 @samp{collect/s25 mystr} collects as many as 25 characters at
13270 The command @code{info scope} (@pxref{Symbols, info scope}) is
13271 particularly useful for figuring out what data to collect.
13273 @kindex teval @r{(tracepoints)}
13274 @item teval @var{expr1}, @var{expr2}, @dots{}
13275 Evaluate the given expressions when the tracepoint is hit. This
13276 command accepts a comma-separated list of expressions. The results
13277 are discarded, so this is mainly useful for assigning values to trace
13278 state variables (@pxref{Trace State Variables}) without adding those
13279 values to the trace buffer, as would be the case if the @code{collect}
13282 @kindex while-stepping @r{(tracepoints)}
13283 @item while-stepping @var{n}
13284 Perform @var{n} single-step instruction traces after the tracepoint,
13285 collecting new data after each step. The @code{while-stepping}
13286 command is followed by the list of what to collect while stepping
13287 (followed by its own @code{end} command):
13290 > while-stepping 12
13291 > collect $regs, myglobal
13297 Note that @code{$pc} is not automatically collected by
13298 @code{while-stepping}; you need to explicitly collect that register if
13299 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13302 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13303 @kindex set default-collect
13304 @cindex default collection action
13305 This variable is a list of expressions to collect at each tracepoint
13306 hit. It is effectively an additional @code{collect} action prepended
13307 to every tracepoint action list. The expressions are parsed
13308 individually for each tracepoint, so for instance a variable named
13309 @code{xyz} may be interpreted as a global for one tracepoint, and a
13310 local for another, as appropriate to the tracepoint's location.
13312 @item show default-collect
13313 @kindex show default-collect
13314 Show the list of expressions that are collected by default at each
13319 @node Listing Tracepoints
13320 @subsection Listing Tracepoints
13323 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13324 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13325 @cindex information about tracepoints
13326 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13327 Display information about the tracepoint @var{num}. If you don't
13328 specify a tracepoint number, displays information about all the
13329 tracepoints defined so far. The format is similar to that used for
13330 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13331 command, simply restricting itself to tracepoints.
13333 A tracepoint's listing may include additional information specific to
13338 its passcount as given by the @code{passcount @var{n}} command
13341 the state about installed on target of each location
13345 (@value{GDBP}) @b{info trace}
13346 Num Type Disp Enb Address What
13347 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13349 collect globfoo, $regs
13354 2 tracepoint keep y <MULTIPLE>
13356 2.1 y 0x0804859c in func4 at change-loc.h:35
13357 installed on target
13358 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13359 installed on target
13360 2.3 y <PENDING> set_tracepoint
13361 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13362 not installed on target
13367 This command can be abbreviated @code{info tp}.
13370 @node Listing Static Tracepoint Markers
13371 @subsection Listing Static Tracepoint Markers
13374 @kindex info static-tracepoint-markers
13375 @cindex information about static tracepoint markers
13376 @item info static-tracepoint-markers
13377 Display information about all static tracepoint markers defined in the
13380 For each marker, the following columns are printed:
13384 An incrementing counter, output to help readability. This is not a
13387 The marker ID, as reported by the target.
13388 @item Enabled or Disabled
13389 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13390 that are not enabled.
13392 Where the marker is in your program, as a memory address.
13394 Where the marker is in the source for your program, as a file and line
13395 number. If the debug information included in the program does not
13396 allow @value{GDBN} to locate the source of the marker, this column
13397 will be left blank.
13401 In addition, the following information may be printed for each marker:
13405 User data passed to the tracing library by the marker call. In the
13406 UST backend, this is the format string passed as argument to the
13408 @item Static tracepoints probing the marker
13409 The list of static tracepoints attached to the marker.
13413 (@value{GDBP}) info static-tracepoint-markers
13414 Cnt ID Enb Address What
13415 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13416 Data: number1 %d number2 %d
13417 Probed by static tracepoints: #2
13418 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13424 @node Starting and Stopping Trace Experiments
13425 @subsection Starting and Stopping Trace Experiments
13428 @kindex tstart [ @var{notes} ]
13429 @cindex start a new trace experiment
13430 @cindex collected data discarded
13432 This command starts the trace experiment, and begins collecting data.
13433 It has the side effect of discarding all the data collected in the
13434 trace buffer during the previous trace experiment. If any arguments
13435 are supplied, they are taken as a note and stored with the trace
13436 experiment's state. The notes may be arbitrary text, and are
13437 especially useful with disconnected tracing in a multi-user context;
13438 the notes can explain what the trace is doing, supply user contact
13439 information, and so forth.
13441 @kindex tstop [ @var{notes} ]
13442 @cindex stop a running trace experiment
13444 This command stops the trace experiment. If any arguments are
13445 supplied, they are recorded with the experiment as a note. This is
13446 useful if you are stopping a trace started by someone else, for
13447 instance if the trace is interfering with the system's behavior and
13448 needs to be stopped quickly.
13450 @strong{Note}: a trace experiment and data collection may stop
13451 automatically if any tracepoint's passcount is reached
13452 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13455 @cindex status of trace data collection
13456 @cindex trace experiment, status of
13458 This command displays the status of the current trace data
13462 Here is an example of the commands we described so far:
13465 (@value{GDBP}) @b{trace gdb_c_test}
13466 (@value{GDBP}) @b{actions}
13467 Enter actions for tracepoint #1, one per line.
13468 > collect $regs,$locals,$args
13469 > while-stepping 11
13473 (@value{GDBP}) @b{tstart}
13474 [time passes @dots{}]
13475 (@value{GDBP}) @b{tstop}
13478 @anchor{disconnected tracing}
13479 @cindex disconnected tracing
13480 You can choose to continue running the trace experiment even if
13481 @value{GDBN} disconnects from the target, voluntarily or
13482 involuntarily. For commands such as @code{detach}, the debugger will
13483 ask what you want to do with the trace. But for unexpected
13484 terminations (@value{GDBN} crash, network outage), it would be
13485 unfortunate to lose hard-won trace data, so the variable
13486 @code{disconnected-tracing} lets you decide whether the trace should
13487 continue running without @value{GDBN}.
13490 @item set disconnected-tracing on
13491 @itemx set disconnected-tracing off
13492 @kindex set disconnected-tracing
13493 Choose whether a tracing run should continue to run if @value{GDBN}
13494 has disconnected from the target. Note that @code{detach} or
13495 @code{quit} will ask you directly what to do about a running trace no
13496 matter what this variable's setting, so the variable is mainly useful
13497 for handling unexpected situations, such as loss of the network.
13499 @item show disconnected-tracing
13500 @kindex show disconnected-tracing
13501 Show the current choice for disconnected tracing.
13505 When you reconnect to the target, the trace experiment may or may not
13506 still be running; it might have filled the trace buffer in the
13507 meantime, or stopped for one of the other reasons. If it is running,
13508 it will continue after reconnection.
13510 Upon reconnection, the target will upload information about the
13511 tracepoints in effect. @value{GDBN} will then compare that
13512 information to the set of tracepoints currently defined, and attempt
13513 to match them up, allowing for the possibility that the numbers may
13514 have changed due to creation and deletion in the meantime. If one of
13515 the target's tracepoints does not match any in @value{GDBN}, the
13516 debugger will create a new tracepoint, so that you have a number with
13517 which to specify that tracepoint. This matching-up process is
13518 necessarily heuristic, and it may result in useless tracepoints being
13519 created; you may simply delete them if they are of no use.
13521 @cindex circular trace buffer
13522 If your target agent supports a @dfn{circular trace buffer}, then you
13523 can run a trace experiment indefinitely without filling the trace
13524 buffer; when space runs out, the agent deletes already-collected trace
13525 frames, oldest first, until there is enough room to continue
13526 collecting. This is especially useful if your tracepoints are being
13527 hit too often, and your trace gets terminated prematurely because the
13528 buffer is full. To ask for a circular trace buffer, simply set
13529 @samp{circular-trace-buffer} to on. You can set this at any time,
13530 including during tracing; if the agent can do it, it will change
13531 buffer handling on the fly, otherwise it will not take effect until
13535 @item set circular-trace-buffer on
13536 @itemx set circular-trace-buffer off
13537 @kindex set circular-trace-buffer
13538 Choose whether a tracing run should use a linear or circular buffer
13539 for trace data. A linear buffer will not lose any trace data, but may
13540 fill up prematurely, while a circular buffer will discard old trace
13541 data, but it will have always room for the latest tracepoint hits.
13543 @item show circular-trace-buffer
13544 @kindex show circular-trace-buffer
13545 Show the current choice for the trace buffer. Note that this may not
13546 match the agent's current buffer handling, nor is it guaranteed to
13547 match the setting that might have been in effect during a past run,
13548 for instance if you are looking at frames from a trace file.
13553 @item set trace-buffer-size @var{n}
13554 @itemx set trace-buffer-size unlimited
13555 @kindex set trace-buffer-size
13556 Request that the target use a trace buffer of @var{n} bytes. Not all
13557 targets will honor the request; they may have a compiled-in size for
13558 the trace buffer, or some other limitation. Set to a value of
13559 @code{unlimited} or @code{-1} to let the target use whatever size it
13560 likes. This is also the default.
13562 @item show trace-buffer-size
13563 @kindex show trace-buffer-size
13564 Show the current requested size for the trace buffer. Note that this
13565 will only match the actual size if the target supports size-setting,
13566 and was able to handle the requested size. For instance, if the
13567 target can only change buffer size between runs, this variable will
13568 not reflect the change until the next run starts. Use @code{tstatus}
13569 to get a report of the actual buffer size.
13573 @item set trace-user @var{text}
13574 @kindex set trace-user
13576 @item show trace-user
13577 @kindex show trace-user
13579 @item set trace-notes @var{text}
13580 @kindex set trace-notes
13581 Set the trace run's notes.
13583 @item show trace-notes
13584 @kindex show trace-notes
13585 Show the trace run's notes.
13587 @item set trace-stop-notes @var{text}
13588 @kindex set trace-stop-notes
13589 Set the trace run's stop notes. The handling of the note is as for
13590 @code{tstop} arguments; the set command is convenient way to fix a
13591 stop note that is mistaken or incomplete.
13593 @item show trace-stop-notes
13594 @kindex show trace-stop-notes
13595 Show the trace run's stop notes.
13599 @node Tracepoint Restrictions
13600 @subsection Tracepoint Restrictions
13602 @cindex tracepoint restrictions
13603 There are a number of restrictions on the use of tracepoints. As
13604 described above, tracepoint data gathering occurs on the target
13605 without interaction from @value{GDBN}. Thus the full capabilities of
13606 the debugger are not available during data gathering, and then at data
13607 examination time, you will be limited by only having what was
13608 collected. The following items describe some common problems, but it
13609 is not exhaustive, and you may run into additional difficulties not
13615 Tracepoint expressions are intended to gather objects (lvalues). Thus
13616 the full flexibility of GDB's expression evaluator is not available.
13617 You cannot call functions, cast objects to aggregate types, access
13618 convenience variables or modify values (except by assignment to trace
13619 state variables). Some language features may implicitly call
13620 functions (for instance Objective-C fields with accessors), and therefore
13621 cannot be collected either.
13624 Collection of local variables, either individually or in bulk with
13625 @code{$locals} or @code{$args}, during @code{while-stepping} may
13626 behave erratically. The stepping action may enter a new scope (for
13627 instance by stepping into a function), or the location of the variable
13628 may change (for instance it is loaded into a register). The
13629 tracepoint data recorded uses the location information for the
13630 variables that is correct for the tracepoint location. When the
13631 tracepoint is created, it is not possible, in general, to determine
13632 where the steps of a @code{while-stepping} sequence will advance the
13633 program---particularly if a conditional branch is stepped.
13636 Collection of an incompletely-initialized or partially-destroyed object
13637 may result in something that @value{GDBN} cannot display, or displays
13638 in a misleading way.
13641 When @value{GDBN} displays a pointer to character it automatically
13642 dereferences the pointer to also display characters of the string
13643 being pointed to. However, collecting the pointer during tracing does
13644 not automatically collect the string. You need to explicitly
13645 dereference the pointer and provide size information if you want to
13646 collect not only the pointer, but the memory pointed to. For example,
13647 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13651 It is not possible to collect a complete stack backtrace at a
13652 tracepoint. Instead, you may collect the registers and a few hundred
13653 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13654 (adjust to use the name of the actual stack pointer register on your
13655 target architecture, and the amount of stack you wish to capture).
13656 Then the @code{backtrace} command will show a partial backtrace when
13657 using a trace frame. The number of stack frames that can be examined
13658 depends on the sizes of the frames in the collected stack. Note that
13659 if you ask for a block so large that it goes past the bottom of the
13660 stack, the target agent may report an error trying to read from an
13664 If you do not collect registers at a tracepoint, @value{GDBN} can
13665 infer that the value of @code{$pc} must be the same as the address of
13666 the tracepoint and use that when you are looking at a trace frame
13667 for that tracepoint. However, this cannot work if the tracepoint has
13668 multiple locations (for instance if it was set in a function that was
13669 inlined), or if it has a @code{while-stepping} loop. In those cases
13670 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13675 @node Analyze Collected Data
13676 @section Using the Collected Data
13678 After the tracepoint experiment ends, you use @value{GDBN} commands
13679 for examining the trace data. The basic idea is that each tracepoint
13680 collects a trace @dfn{snapshot} every time it is hit and another
13681 snapshot every time it single-steps. All these snapshots are
13682 consecutively numbered from zero and go into a buffer, and you can
13683 examine them later. The way you examine them is to @dfn{focus} on a
13684 specific trace snapshot. When the remote stub is focused on a trace
13685 snapshot, it will respond to all @value{GDBN} requests for memory and
13686 registers by reading from the buffer which belongs to that snapshot,
13687 rather than from @emph{real} memory or registers of the program being
13688 debugged. This means that @strong{all} @value{GDBN} commands
13689 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13690 behave as if we were currently debugging the program state as it was
13691 when the tracepoint occurred. Any requests for data that are not in
13692 the buffer will fail.
13695 * tfind:: How to select a trace snapshot
13696 * tdump:: How to display all data for a snapshot
13697 * save tracepoints:: How to save tracepoints for a future run
13701 @subsection @code{tfind @var{n}}
13704 @cindex select trace snapshot
13705 @cindex find trace snapshot
13706 The basic command for selecting a trace snapshot from the buffer is
13707 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13708 counting from zero. If no argument @var{n} is given, the next
13709 snapshot is selected.
13711 Here are the various forms of using the @code{tfind} command.
13715 Find the first snapshot in the buffer. This is a synonym for
13716 @code{tfind 0} (since 0 is the number of the first snapshot).
13719 Stop debugging trace snapshots, resume @emph{live} debugging.
13722 Same as @samp{tfind none}.
13725 No argument means find the next trace snapshot or find the first
13726 one if no trace snapshot is selected.
13729 Find the previous trace snapshot before the current one. This permits
13730 retracing earlier steps.
13732 @item tfind tracepoint @var{num}
13733 Find the next snapshot associated with tracepoint @var{num}. Search
13734 proceeds forward from the last examined trace snapshot. If no
13735 argument @var{num} is given, it means find the next snapshot collected
13736 for the same tracepoint as the current snapshot.
13738 @item tfind pc @var{addr}
13739 Find the next snapshot associated with the value @var{addr} of the
13740 program counter. Search proceeds forward from the last examined trace
13741 snapshot. If no argument @var{addr} is given, it means find the next
13742 snapshot with the same value of PC as the current snapshot.
13744 @item tfind outside @var{addr1}, @var{addr2}
13745 Find the next snapshot whose PC is outside the given range of
13746 addresses (exclusive).
13748 @item tfind range @var{addr1}, @var{addr2}
13749 Find the next snapshot whose PC is between @var{addr1} and
13750 @var{addr2} (inclusive).
13752 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13753 Find the next snapshot associated with the source line @var{n}. If
13754 the optional argument @var{file} is given, refer to line @var{n} in
13755 that source file. Search proceeds forward from the last examined
13756 trace snapshot. If no argument @var{n} is given, it means find the
13757 next line other than the one currently being examined; thus saying
13758 @code{tfind line} repeatedly can appear to have the same effect as
13759 stepping from line to line in a @emph{live} debugging session.
13762 The default arguments for the @code{tfind} commands are specifically
13763 designed to make it easy to scan through the trace buffer. For
13764 instance, @code{tfind} with no argument selects the next trace
13765 snapshot, and @code{tfind -} with no argument selects the previous
13766 trace snapshot. So, by giving one @code{tfind} command, and then
13767 simply hitting @key{RET} repeatedly you can examine all the trace
13768 snapshots in order. Or, by saying @code{tfind -} and then hitting
13769 @key{RET} repeatedly you can examine the snapshots in reverse order.
13770 The @code{tfind line} command with no argument selects the snapshot
13771 for the next source line executed. The @code{tfind pc} command with
13772 no argument selects the next snapshot with the same program counter
13773 (PC) as the current frame. The @code{tfind tracepoint} command with
13774 no argument selects the next trace snapshot collected by the same
13775 tracepoint as the current one.
13777 In addition to letting you scan through the trace buffer manually,
13778 these commands make it easy to construct @value{GDBN} scripts that
13779 scan through the trace buffer and print out whatever collected data
13780 you are interested in. Thus, if we want to examine the PC, FP, and SP
13781 registers from each trace frame in the buffer, we can say this:
13784 (@value{GDBP}) @b{tfind start}
13785 (@value{GDBP}) @b{while ($trace_frame != -1)}
13786 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13787 $trace_frame, $pc, $sp, $fp
13791 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13792 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13793 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13794 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13795 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13796 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13797 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13798 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13799 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13800 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13801 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13804 Or, if we want to examine the variable @code{X} at each source line in
13808 (@value{GDBP}) @b{tfind start}
13809 (@value{GDBP}) @b{while ($trace_frame != -1)}
13810 > printf "Frame %d, X == %d\n", $trace_frame, X
13820 @subsection @code{tdump}
13822 @cindex dump all data collected at tracepoint
13823 @cindex tracepoint data, display
13825 This command takes no arguments. It prints all the data collected at
13826 the current trace snapshot.
13829 (@value{GDBP}) @b{trace 444}
13830 (@value{GDBP}) @b{actions}
13831 Enter actions for tracepoint #2, one per line:
13832 > collect $regs, $locals, $args, gdb_long_test
13835 (@value{GDBP}) @b{tstart}
13837 (@value{GDBP}) @b{tfind line 444}
13838 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13840 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13842 (@value{GDBP}) @b{tdump}
13843 Data collected at tracepoint 2, trace frame 1:
13844 d0 0xc4aa0085 -995491707
13848 d4 0x71aea3d 119204413
13851 d7 0x380035 3670069
13852 a0 0x19e24a 1696330
13853 a1 0x3000668 50333288
13855 a3 0x322000 3284992
13856 a4 0x3000698 50333336
13857 a5 0x1ad3cc 1758156
13858 fp 0x30bf3c 0x30bf3c
13859 sp 0x30bf34 0x30bf34
13861 pc 0x20b2c8 0x20b2c8
13865 p = 0x20e5b4 "gdb-test"
13872 gdb_long_test = 17 '\021'
13877 @code{tdump} works by scanning the tracepoint's current collection
13878 actions and printing the value of each expression listed. So
13879 @code{tdump} can fail, if after a run, you change the tracepoint's
13880 actions to mention variables that were not collected during the run.
13882 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13883 uses the collected value of @code{$pc} to distinguish between trace
13884 frames that were collected at the tracepoint hit, and frames that were
13885 collected while stepping. This allows it to correctly choose whether
13886 to display the basic list of collections, or the collections from the
13887 body of the while-stepping loop. However, if @code{$pc} was not collected,
13888 then @code{tdump} will always attempt to dump using the basic collection
13889 list, and may fail if a while-stepping frame does not include all the
13890 same data that is collected at the tracepoint hit.
13891 @c This is getting pretty arcane, example would be good.
13893 @node save tracepoints
13894 @subsection @code{save tracepoints @var{filename}}
13895 @kindex save tracepoints
13896 @kindex save-tracepoints
13897 @cindex save tracepoints for future sessions
13899 This command saves all current tracepoint definitions together with
13900 their actions and passcounts, into a file @file{@var{filename}}
13901 suitable for use in a later debugging session. To read the saved
13902 tracepoint definitions, use the @code{source} command (@pxref{Command
13903 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13904 alias for @w{@code{save tracepoints}}
13906 @node Tracepoint Variables
13907 @section Convenience Variables for Tracepoints
13908 @cindex tracepoint variables
13909 @cindex convenience variables for tracepoints
13912 @vindex $trace_frame
13913 @item (int) $trace_frame
13914 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13915 snapshot is selected.
13917 @vindex $tracepoint
13918 @item (int) $tracepoint
13919 The tracepoint for the current trace snapshot.
13921 @vindex $trace_line
13922 @item (int) $trace_line
13923 The line number for the current trace snapshot.
13925 @vindex $trace_file
13926 @item (char []) $trace_file
13927 The source file for the current trace snapshot.
13929 @vindex $trace_func
13930 @item (char []) $trace_func
13931 The name of the function containing @code{$tracepoint}.
13934 Note: @code{$trace_file} is not suitable for use in @code{printf},
13935 use @code{output} instead.
13937 Here's a simple example of using these convenience variables for
13938 stepping through all the trace snapshots and printing some of their
13939 data. Note that these are not the same as trace state variables,
13940 which are managed by the target.
13943 (@value{GDBP}) @b{tfind start}
13945 (@value{GDBP}) @b{while $trace_frame != -1}
13946 > output $trace_file
13947 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13953 @section Using Trace Files
13954 @cindex trace files
13956 In some situations, the target running a trace experiment may no
13957 longer be available; perhaps it crashed, or the hardware was needed
13958 for a different activity. To handle these cases, you can arrange to
13959 dump the trace data into a file, and later use that file as a source
13960 of trace data, via the @code{target tfile} command.
13965 @item tsave [ -r ] @var{filename}
13966 @itemx tsave [-ctf] @var{dirname}
13967 Save the trace data to @var{filename}. By default, this command
13968 assumes that @var{filename} refers to the host filesystem, so if
13969 necessary @value{GDBN} will copy raw trace data up from the target and
13970 then save it. If the target supports it, you can also supply the
13971 optional argument @code{-r} (``remote'') to direct the target to save
13972 the data directly into @var{filename} in its own filesystem, which may be
13973 more efficient if the trace buffer is very large. (Note, however, that
13974 @code{target tfile} can only read from files accessible to the host.)
13975 By default, this command will save trace frame in tfile format.
13976 You can supply the optional argument @code{-ctf} to save data in CTF
13977 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13978 that can be shared by multiple debugging and tracing tools. Please go to
13979 @indicateurl{http://www.efficios.com/ctf} to get more information.
13981 @kindex target tfile
13985 @item target tfile @var{filename}
13986 @itemx target ctf @var{dirname}
13987 Use the file named @var{filename} or directory named @var{dirname} as
13988 a source of trace data. Commands that examine data work as they do with
13989 a live target, but it is not possible to run any new trace experiments.
13990 @code{tstatus} will report the state of the trace run at the moment
13991 the data was saved, as well as the current trace frame you are examining.
13992 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13996 (@value{GDBP}) target ctf ctf.ctf
13997 (@value{GDBP}) tfind
13998 Found trace frame 0, tracepoint 2
13999 39 ++a; /* set tracepoint 1 here */
14000 (@value{GDBP}) tdump
14001 Data collected at tracepoint 2, trace frame 0:
14005 c = @{"123", "456", "789", "123", "456", "789"@}
14006 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14014 @chapter Debugging Programs That Use Overlays
14017 If your program is too large to fit completely in your target system's
14018 memory, you can sometimes use @dfn{overlays} to work around this
14019 problem. @value{GDBN} provides some support for debugging programs that
14023 * How Overlays Work:: A general explanation of overlays.
14024 * Overlay Commands:: Managing overlays in @value{GDBN}.
14025 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14026 mapped by asking the inferior.
14027 * Overlay Sample Program:: A sample program using overlays.
14030 @node How Overlays Work
14031 @section How Overlays Work
14032 @cindex mapped overlays
14033 @cindex unmapped overlays
14034 @cindex load address, overlay's
14035 @cindex mapped address
14036 @cindex overlay area
14038 Suppose you have a computer whose instruction address space is only 64
14039 kilobytes long, but which has much more memory which can be accessed by
14040 other means: special instructions, segment registers, or memory
14041 management hardware, for example. Suppose further that you want to
14042 adapt a program which is larger than 64 kilobytes to run on this system.
14044 One solution is to identify modules of your program which are relatively
14045 independent, and need not call each other directly; call these modules
14046 @dfn{overlays}. Separate the overlays from the main program, and place
14047 their machine code in the larger memory. Place your main program in
14048 instruction memory, but leave at least enough space there to hold the
14049 largest overlay as well.
14051 Now, to call a function located in an overlay, you must first copy that
14052 overlay's machine code from the large memory into the space set aside
14053 for it in the instruction memory, and then jump to its entry point
14056 @c NB: In the below the mapped area's size is greater or equal to the
14057 @c size of all overlays. This is intentional to remind the developer
14058 @c that overlays don't necessarily need to be the same size.
14062 Data Instruction Larger
14063 Address Space Address Space Address Space
14064 +-----------+ +-----------+ +-----------+
14066 +-----------+ +-----------+ +-----------+<-- overlay 1
14067 | program | | main | .----| overlay 1 | load address
14068 | variables | | program | | +-----------+
14069 | and heap | | | | | |
14070 +-----------+ | | | +-----------+<-- overlay 2
14071 | | +-----------+ | | | load address
14072 +-----------+ | | | .-| overlay 2 |
14074 mapped --->+-----------+ | | +-----------+
14075 address | | | | | |
14076 | overlay | <-' | | |
14077 | area | <---' +-----------+<-- overlay 3
14078 | | <---. | | load address
14079 +-----------+ `--| overlay 3 |
14086 @anchor{A code overlay}A code overlay
14090 The diagram (@pxref{A code overlay}) shows a system with separate data
14091 and instruction address spaces. To map an overlay, the program copies
14092 its code from the larger address space to the instruction address space.
14093 Since the overlays shown here all use the same mapped address, only one
14094 may be mapped at a time. For a system with a single address space for
14095 data and instructions, the diagram would be similar, except that the
14096 program variables and heap would share an address space with the main
14097 program and the overlay area.
14099 An overlay loaded into instruction memory and ready for use is called a
14100 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14101 instruction memory. An overlay not present (or only partially present)
14102 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14103 is its address in the larger memory. The mapped address is also called
14104 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14105 called the @dfn{load memory address}, or @dfn{LMA}.
14107 Unfortunately, overlays are not a completely transparent way to adapt a
14108 program to limited instruction memory. They introduce a new set of
14109 global constraints you must keep in mind as you design your program:
14114 Before calling or returning to a function in an overlay, your program
14115 must make sure that overlay is actually mapped. Otherwise, the call or
14116 return will transfer control to the right address, but in the wrong
14117 overlay, and your program will probably crash.
14120 If the process of mapping an overlay is expensive on your system, you
14121 will need to choose your overlays carefully to minimize their effect on
14122 your program's performance.
14125 The executable file you load onto your system must contain each
14126 overlay's instructions, appearing at the overlay's load address, not its
14127 mapped address. However, each overlay's instructions must be relocated
14128 and its symbols defined as if the overlay were at its mapped address.
14129 You can use GNU linker scripts to specify different load and relocation
14130 addresses for pieces of your program; see @ref{Overlay Description,,,
14131 ld.info, Using ld: the GNU linker}.
14134 The procedure for loading executable files onto your system must be able
14135 to load their contents into the larger address space as well as the
14136 instruction and data spaces.
14140 The overlay system described above is rather simple, and could be
14141 improved in many ways:
14146 If your system has suitable bank switch registers or memory management
14147 hardware, you could use those facilities to make an overlay's load area
14148 contents simply appear at their mapped address in instruction space.
14149 This would probably be faster than copying the overlay to its mapped
14150 area in the usual way.
14153 If your overlays are small enough, you could set aside more than one
14154 overlay area, and have more than one overlay mapped at a time.
14157 You can use overlays to manage data, as well as instructions. In
14158 general, data overlays are even less transparent to your design than
14159 code overlays: whereas code overlays only require care when you call or
14160 return to functions, data overlays require care every time you access
14161 the data. Also, if you change the contents of a data overlay, you
14162 must copy its contents back out to its load address before you can copy a
14163 different data overlay into the same mapped area.
14168 @node Overlay Commands
14169 @section Overlay Commands
14171 To use @value{GDBN}'s overlay support, each overlay in your program must
14172 correspond to a separate section of the executable file. The section's
14173 virtual memory address and load memory address must be the overlay's
14174 mapped and load addresses. Identifying overlays with sections allows
14175 @value{GDBN} to determine the appropriate address of a function or
14176 variable, depending on whether the overlay is mapped or not.
14178 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14179 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14184 Disable @value{GDBN}'s overlay support. When overlay support is
14185 disabled, @value{GDBN} assumes that all functions and variables are
14186 always present at their mapped addresses. By default, @value{GDBN}'s
14187 overlay support is disabled.
14189 @item overlay manual
14190 @cindex manual overlay debugging
14191 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14192 relies on you to tell it which overlays are mapped, and which are not,
14193 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14194 commands described below.
14196 @item overlay map-overlay @var{overlay}
14197 @itemx overlay map @var{overlay}
14198 @cindex map an overlay
14199 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14200 be the name of the object file section containing the overlay. When an
14201 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14202 functions and variables at their mapped addresses. @value{GDBN} assumes
14203 that any other overlays whose mapped ranges overlap that of
14204 @var{overlay} are now unmapped.
14206 @item overlay unmap-overlay @var{overlay}
14207 @itemx overlay unmap @var{overlay}
14208 @cindex unmap an overlay
14209 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14210 must be the name of the object file section containing the overlay.
14211 When an overlay is unmapped, @value{GDBN} assumes it can find the
14212 overlay's functions and variables at their load addresses.
14215 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14216 consults a data structure the overlay manager maintains in the inferior
14217 to see which overlays are mapped. For details, see @ref{Automatic
14218 Overlay Debugging}.
14220 @item overlay load-target
14221 @itemx overlay load
14222 @cindex reloading the overlay table
14223 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14224 re-reads the table @value{GDBN} automatically each time the inferior
14225 stops, so this command should only be necessary if you have changed the
14226 overlay mapping yourself using @value{GDBN}. This command is only
14227 useful when using automatic overlay debugging.
14229 @item overlay list-overlays
14230 @itemx overlay list
14231 @cindex listing mapped overlays
14232 Display a list of the overlays currently mapped, along with their mapped
14233 addresses, load addresses, and sizes.
14237 Normally, when @value{GDBN} prints a code address, it includes the name
14238 of the function the address falls in:
14241 (@value{GDBP}) print main
14242 $3 = @{int ()@} 0x11a0 <main>
14245 When overlay debugging is enabled, @value{GDBN} recognizes code in
14246 unmapped overlays, and prints the names of unmapped functions with
14247 asterisks around them. For example, if @code{foo} is a function in an
14248 unmapped overlay, @value{GDBN} prints it this way:
14251 (@value{GDBP}) overlay list
14252 No sections are mapped.
14253 (@value{GDBP}) print foo
14254 $5 = @{int (int)@} 0x100000 <*foo*>
14257 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14261 (@value{GDBP}) overlay list
14262 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14263 mapped at 0x1016 - 0x104a
14264 (@value{GDBP}) print foo
14265 $6 = @{int (int)@} 0x1016 <foo>
14268 When overlay debugging is enabled, @value{GDBN} can find the correct
14269 address for functions and variables in an overlay, whether or not the
14270 overlay is mapped. This allows most @value{GDBN} commands, like
14271 @code{break} and @code{disassemble}, to work normally, even on unmapped
14272 code. However, @value{GDBN}'s breakpoint support has some limitations:
14276 @cindex breakpoints in overlays
14277 @cindex overlays, setting breakpoints in
14278 You can set breakpoints in functions in unmapped overlays, as long as
14279 @value{GDBN} can write to the overlay at its load address.
14281 @value{GDBN} can not set hardware or simulator-based breakpoints in
14282 unmapped overlays. However, if you set a breakpoint at the end of your
14283 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14284 you are using manual overlay management), @value{GDBN} will re-set its
14285 breakpoints properly.
14289 @node Automatic Overlay Debugging
14290 @section Automatic Overlay Debugging
14291 @cindex automatic overlay debugging
14293 @value{GDBN} can automatically track which overlays are mapped and which
14294 are not, given some simple co-operation from the overlay manager in the
14295 inferior. If you enable automatic overlay debugging with the
14296 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14297 looks in the inferior's memory for certain variables describing the
14298 current state of the overlays.
14300 Here are the variables your overlay manager must define to support
14301 @value{GDBN}'s automatic overlay debugging:
14305 @item @code{_ovly_table}:
14306 This variable must be an array of the following structures:
14311 /* The overlay's mapped address. */
14314 /* The size of the overlay, in bytes. */
14315 unsigned long size;
14317 /* The overlay's load address. */
14320 /* Non-zero if the overlay is currently mapped;
14322 unsigned long mapped;
14326 @item @code{_novlys}:
14327 This variable must be a four-byte signed integer, holding the total
14328 number of elements in @code{_ovly_table}.
14332 To decide whether a particular overlay is mapped or not, @value{GDBN}
14333 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14334 @code{lma} members equal the VMA and LMA of the overlay's section in the
14335 executable file. When @value{GDBN} finds a matching entry, it consults
14336 the entry's @code{mapped} member to determine whether the overlay is
14339 In addition, your overlay manager may define a function called
14340 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14341 will silently set a breakpoint there. If the overlay manager then
14342 calls this function whenever it has changed the overlay table, this
14343 will enable @value{GDBN} to accurately keep track of which overlays
14344 are in program memory, and update any breakpoints that may be set
14345 in overlays. This will allow breakpoints to work even if the
14346 overlays are kept in ROM or other non-writable memory while they
14347 are not being executed.
14349 @node Overlay Sample Program
14350 @section Overlay Sample Program
14351 @cindex overlay example program
14353 When linking a program which uses overlays, you must place the overlays
14354 at their load addresses, while relocating them to run at their mapped
14355 addresses. To do this, you must write a linker script (@pxref{Overlay
14356 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14357 since linker scripts are specific to a particular host system, target
14358 architecture, and target memory layout, this manual cannot provide
14359 portable sample code demonstrating @value{GDBN}'s overlay support.
14361 However, the @value{GDBN} source distribution does contain an overlaid
14362 program, with linker scripts for a few systems, as part of its test
14363 suite. The program consists of the following files from
14364 @file{gdb/testsuite/gdb.base}:
14368 The main program file.
14370 A simple overlay manager, used by @file{overlays.c}.
14375 Overlay modules, loaded and used by @file{overlays.c}.
14378 Linker scripts for linking the test program on the @code{d10v-elf}
14379 and @code{m32r-elf} targets.
14382 You can build the test program using the @code{d10v-elf} GCC
14383 cross-compiler like this:
14386 $ d10v-elf-gcc -g -c overlays.c
14387 $ d10v-elf-gcc -g -c ovlymgr.c
14388 $ d10v-elf-gcc -g -c foo.c
14389 $ d10v-elf-gcc -g -c bar.c
14390 $ d10v-elf-gcc -g -c baz.c
14391 $ d10v-elf-gcc -g -c grbx.c
14392 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14393 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14396 The build process is identical for any other architecture, except that
14397 you must substitute the appropriate compiler and linker script for the
14398 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14402 @chapter Using @value{GDBN} with Different Languages
14405 Although programming languages generally have common aspects, they are
14406 rarely expressed in the same manner. For instance, in ANSI C,
14407 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14408 Modula-2, it is accomplished by @code{p^}. Values can also be
14409 represented (and displayed) differently. Hex numbers in C appear as
14410 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14412 @cindex working language
14413 Language-specific information is built into @value{GDBN} for some languages,
14414 allowing you to express operations like the above in your program's
14415 native language, and allowing @value{GDBN} to output values in a manner
14416 consistent with the syntax of your program's native language. The
14417 language you use to build expressions is called the @dfn{working
14421 * Setting:: Switching between source languages
14422 * Show:: Displaying the language
14423 * Checks:: Type and range checks
14424 * Supported Languages:: Supported languages
14425 * Unsupported Languages:: Unsupported languages
14429 @section Switching Between Source Languages
14431 There are two ways to control the working language---either have @value{GDBN}
14432 set it automatically, or select it manually yourself. You can use the
14433 @code{set language} command for either purpose. On startup, @value{GDBN}
14434 defaults to setting the language automatically. The working language is
14435 used to determine how expressions you type are interpreted, how values
14438 In addition to the working language, every source file that
14439 @value{GDBN} knows about has its own working language. For some object
14440 file formats, the compiler might indicate which language a particular
14441 source file is in. However, most of the time @value{GDBN} infers the
14442 language from the name of the file. The language of a source file
14443 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14444 show each frame appropriately for its own language. There is no way to
14445 set the language of a source file from within @value{GDBN}, but you can
14446 set the language associated with a filename extension. @xref{Show, ,
14447 Displaying the Language}.
14449 This is most commonly a problem when you use a program, such
14450 as @code{cfront} or @code{f2c}, that generates C but is written in
14451 another language. In that case, make the
14452 program use @code{#line} directives in its C output; that way
14453 @value{GDBN} will know the correct language of the source code of the original
14454 program, and will display that source code, not the generated C code.
14457 * Filenames:: Filename extensions and languages.
14458 * Manually:: Setting the working language manually
14459 * Automatically:: Having @value{GDBN} infer the source language
14463 @subsection List of Filename Extensions and Languages
14465 If a source file name ends in one of the following extensions, then
14466 @value{GDBN} infers that its language is the one indicated.
14484 C@t{++} source file
14490 Objective-C source file
14494 Fortran source file
14497 Modula-2 source file
14501 Assembler source file. This actually behaves almost like C, but
14502 @value{GDBN} does not skip over function prologues when stepping.
14505 In addition, you may set the language associated with a filename
14506 extension. @xref{Show, , Displaying the Language}.
14509 @subsection Setting the Working Language
14511 If you allow @value{GDBN} to set the language automatically,
14512 expressions are interpreted the same way in your debugging session and
14515 @kindex set language
14516 If you wish, you may set the language manually. To do this, issue the
14517 command @samp{set language @var{lang}}, where @var{lang} is the name of
14518 a language, such as
14519 @code{c} or @code{modula-2}.
14520 For a list of the supported languages, type @samp{set language}.
14522 Setting the language manually prevents @value{GDBN} from updating the working
14523 language automatically. This can lead to confusion if you try
14524 to debug a program when the working language is not the same as the
14525 source language, when an expression is acceptable to both
14526 languages---but means different things. For instance, if the current
14527 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14535 might not have the effect you intended. In C, this means to add
14536 @code{b} and @code{c} and place the result in @code{a}. The result
14537 printed would be the value of @code{a}. In Modula-2, this means to compare
14538 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14540 @node Automatically
14541 @subsection Having @value{GDBN} Infer the Source Language
14543 To have @value{GDBN} set the working language automatically, use
14544 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14545 then infers the working language. That is, when your program stops in a
14546 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14547 working language to the language recorded for the function in that
14548 frame. If the language for a frame is unknown (that is, if the function
14549 or block corresponding to the frame was defined in a source file that
14550 does not have a recognized extension), the current working language is
14551 not changed, and @value{GDBN} issues a warning.
14553 This may not seem necessary for most programs, which are written
14554 entirely in one source language. However, program modules and libraries
14555 written in one source language can be used by a main program written in
14556 a different source language. Using @samp{set language auto} in this
14557 case frees you from having to set the working language manually.
14560 @section Displaying the Language
14562 The following commands help you find out which language is the
14563 working language, and also what language source files were written in.
14566 @item show language
14567 @anchor{show language}
14568 @kindex show language
14569 Display the current working language. This is the
14570 language you can use with commands such as @code{print} to
14571 build and compute expressions that may involve variables in your program.
14574 @kindex info frame@r{, show the source language}
14575 Display the source language for this frame. This language becomes the
14576 working language if you use an identifier from this frame.
14577 @xref{Frame Info, ,Information about a Frame}, to identify the other
14578 information listed here.
14581 @kindex info source@r{, show the source language}
14582 Display the source language of this source file.
14583 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14584 information listed here.
14587 In unusual circumstances, you may have source files with extensions
14588 not in the standard list. You can then set the extension associated
14589 with a language explicitly:
14592 @item set extension-language @var{ext} @var{language}
14593 @kindex set extension-language
14594 Tell @value{GDBN} that source files with extension @var{ext} are to be
14595 assumed as written in the source language @var{language}.
14597 @item info extensions
14598 @kindex info extensions
14599 List all the filename extensions and the associated languages.
14603 @section Type and Range Checking
14605 Some languages are designed to guard you against making seemingly common
14606 errors through a series of compile- and run-time checks. These include
14607 checking the type of arguments to functions and operators and making
14608 sure mathematical overflows are caught at run time. Checks such as
14609 these help to ensure a program's correctness once it has been compiled
14610 by eliminating type mismatches and providing active checks for range
14611 errors when your program is running.
14613 By default @value{GDBN} checks for these errors according to the
14614 rules of the current source language. Although @value{GDBN} does not check
14615 the statements in your program, it can check expressions entered directly
14616 into @value{GDBN} for evaluation via the @code{print} command, for example.
14619 * Type Checking:: An overview of type checking
14620 * Range Checking:: An overview of range checking
14623 @cindex type checking
14624 @cindex checks, type
14625 @node Type Checking
14626 @subsection An Overview of Type Checking
14628 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14629 arguments to operators and functions have to be of the correct type,
14630 otherwise an error occurs. These checks prevent type mismatch
14631 errors from ever causing any run-time problems. For example,
14634 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14636 (@value{GDBP}) print obj.my_method (0)
14639 (@value{GDBP}) print obj.my_method (0x1234)
14640 Cannot resolve method klass::my_method to any overloaded instance
14643 The second example fails because in C@t{++} the integer constant
14644 @samp{0x1234} is not type-compatible with the pointer parameter type.
14646 For the expressions you use in @value{GDBN} commands, you can tell
14647 @value{GDBN} to not enforce strict type checking or
14648 to treat any mismatches as errors and abandon the expression;
14649 When type checking is disabled, @value{GDBN} successfully evaluates
14650 expressions like the second example above.
14652 Even if type checking is off, there may be other reasons
14653 related to type that prevent @value{GDBN} from evaluating an expression.
14654 For instance, @value{GDBN} does not know how to add an @code{int} and
14655 a @code{struct foo}. These particular type errors have nothing to do
14656 with the language in use and usually arise from expressions which make
14657 little sense to evaluate anyway.
14659 @value{GDBN} provides some additional commands for controlling type checking:
14661 @kindex set check type
14662 @kindex show check type
14664 @item set check type on
14665 @itemx set check type off
14666 Set strict type checking on or off. If any type mismatches occur in
14667 evaluating an expression while type checking is on, @value{GDBN} prints a
14668 message and aborts evaluation of the expression.
14670 @item show check type
14671 Show the current setting of type checking and whether @value{GDBN}
14672 is enforcing strict type checking rules.
14675 @cindex range checking
14676 @cindex checks, range
14677 @node Range Checking
14678 @subsection An Overview of Range Checking
14680 In some languages (such as Modula-2), it is an error to exceed the
14681 bounds of a type; this is enforced with run-time checks. Such range
14682 checking is meant to ensure program correctness by making sure
14683 computations do not overflow, or indices on an array element access do
14684 not exceed the bounds of the array.
14686 For expressions you use in @value{GDBN} commands, you can tell
14687 @value{GDBN} to treat range errors in one of three ways: ignore them,
14688 always treat them as errors and abandon the expression, or issue
14689 warnings but evaluate the expression anyway.
14691 A range error can result from numerical overflow, from exceeding an
14692 array index bound, or when you type a constant that is not a member
14693 of any type. Some languages, however, do not treat overflows as an
14694 error. In many implementations of C, mathematical overflow causes the
14695 result to ``wrap around'' to lower values---for example, if @var{m} is
14696 the largest integer value, and @var{s} is the smallest, then
14699 @var{m} + 1 @result{} @var{s}
14702 This, too, is specific to individual languages, and in some cases
14703 specific to individual compilers or machines. @xref{Supported Languages, ,
14704 Supported Languages}, for further details on specific languages.
14706 @value{GDBN} provides some additional commands for controlling the range checker:
14708 @kindex set check range
14709 @kindex show check range
14711 @item set check range auto
14712 Set range checking on or off based on the current working language.
14713 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14716 @item set check range on
14717 @itemx set check range off
14718 Set range checking on or off, overriding the default setting for the
14719 current working language. A warning is issued if the setting does not
14720 match the language default. If a range error occurs and range checking is on,
14721 then a message is printed and evaluation of the expression is aborted.
14723 @item set check range warn
14724 Output messages when the @value{GDBN} range checker detects a range error,
14725 but attempt to evaluate the expression anyway. Evaluating the
14726 expression may still be impossible for other reasons, such as accessing
14727 memory that the process does not own (a typical example from many Unix
14731 Show the current setting of the range checker, and whether or not it is
14732 being set automatically by @value{GDBN}.
14735 @node Supported Languages
14736 @section Supported Languages
14738 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14739 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14740 @c This is false ...
14741 Some @value{GDBN} features may be used in expressions regardless of the
14742 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14743 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14744 ,Expressions}) can be used with the constructs of any supported
14747 The following sections detail to what degree each source language is
14748 supported by @value{GDBN}. These sections are not meant to be language
14749 tutorials or references, but serve only as a reference guide to what the
14750 @value{GDBN} expression parser accepts, and what input and output
14751 formats should look like for different languages. There are many good
14752 books written on each of these languages; please look to these for a
14753 language reference or tutorial.
14756 * C:: C and C@t{++}
14759 * Objective-C:: Objective-C
14760 * OpenCL C:: OpenCL C
14761 * Fortran:: Fortran
14764 * Modula-2:: Modula-2
14769 @subsection C and C@t{++}
14771 @cindex C and C@t{++}
14772 @cindex expressions in C or C@t{++}
14774 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14775 to both languages. Whenever this is the case, we discuss those languages
14779 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14780 @cindex @sc{gnu} C@t{++}
14781 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14782 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14783 effectively, you must compile your C@t{++} programs with a supported
14784 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14785 compiler (@code{aCC}).
14788 * C Operators:: C and C@t{++} operators
14789 * C Constants:: C and C@t{++} constants
14790 * C Plus Plus Expressions:: C@t{++} expressions
14791 * C Defaults:: Default settings for C and C@t{++}
14792 * C Checks:: C and C@t{++} type and range checks
14793 * Debugging C:: @value{GDBN} and C
14794 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14795 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14799 @subsubsection C and C@t{++} Operators
14801 @cindex C and C@t{++} operators
14803 Operators must be defined on values of specific types. For instance,
14804 @code{+} is defined on numbers, but not on structures. Operators are
14805 often defined on groups of types.
14807 For the purposes of C and C@t{++}, the following definitions hold:
14812 @emph{Integral types} include @code{int} with any of its storage-class
14813 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14816 @emph{Floating-point types} include @code{float}, @code{double}, and
14817 @code{long double} (if supported by the target platform).
14820 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14823 @emph{Scalar types} include all of the above.
14828 The following operators are supported. They are listed here
14829 in order of increasing precedence:
14833 The comma or sequencing operator. Expressions in a comma-separated list
14834 are evaluated from left to right, with the result of the entire
14835 expression being the last expression evaluated.
14838 Assignment. The value of an assignment expression is the value
14839 assigned. Defined on scalar types.
14842 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14843 and translated to @w{@code{@var{a} = @var{a op b}}}.
14844 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14845 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14846 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14849 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14850 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14851 should be of an integral type.
14854 Logical @sc{or}. Defined on integral types.
14857 Logical @sc{and}. Defined on integral types.
14860 Bitwise @sc{or}. Defined on integral types.
14863 Bitwise exclusive-@sc{or}. Defined on integral types.
14866 Bitwise @sc{and}. Defined on integral types.
14869 Equality and inequality. Defined on scalar types. The value of these
14870 expressions is 0 for false and non-zero for true.
14872 @item <@r{, }>@r{, }<=@r{, }>=
14873 Less than, greater than, less than or equal, greater than or equal.
14874 Defined on scalar types. The value of these expressions is 0 for false
14875 and non-zero for true.
14878 left shift, and right shift. Defined on integral types.
14881 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14884 Addition and subtraction. Defined on integral types, floating-point types and
14887 @item *@r{, }/@r{, }%
14888 Multiplication, division, and modulus. Multiplication and division are
14889 defined on integral and floating-point types. Modulus is defined on
14893 Increment and decrement. When appearing before a variable, the
14894 operation is performed before the variable is used in an expression;
14895 when appearing after it, the variable's value is used before the
14896 operation takes place.
14899 Pointer dereferencing. Defined on pointer types. Same precedence as
14903 Address operator. Defined on variables. Same precedence as @code{++}.
14905 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14906 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14907 to examine the address
14908 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14912 Negative. Defined on integral and floating-point types. Same
14913 precedence as @code{++}.
14916 Logical negation. Defined on integral types. Same precedence as
14920 Bitwise complement operator. Defined on integral types. Same precedence as
14925 Structure member, and pointer-to-structure member. For convenience,
14926 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14927 pointer based on the stored type information.
14928 Defined on @code{struct} and @code{union} data.
14931 Dereferences of pointers to members.
14934 Array indexing. @code{@var{a}[@var{i}]} is defined as
14935 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14938 Function parameter list. Same precedence as @code{->}.
14941 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14942 and @code{class} types.
14945 Doubled colons also represent the @value{GDBN} scope operator
14946 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14950 If an operator is redefined in the user code, @value{GDBN} usually
14951 attempts to invoke the redefined version instead of using the operator's
14952 predefined meaning.
14955 @subsubsection C and C@t{++} Constants
14957 @cindex C and C@t{++} constants
14959 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14964 Integer constants are a sequence of digits. Octal constants are
14965 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14966 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14967 @samp{l}, specifying that the constant should be treated as a
14971 Floating point constants are a sequence of digits, followed by a decimal
14972 point, followed by a sequence of digits, and optionally followed by an
14973 exponent. An exponent is of the form:
14974 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14975 sequence of digits. The @samp{+} is optional for positive exponents.
14976 A floating-point constant may also end with a letter @samp{f} or
14977 @samp{F}, specifying that the constant should be treated as being of
14978 the @code{float} (as opposed to the default @code{double}) type; or with
14979 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14983 Enumerated constants consist of enumerated identifiers, or their
14984 integral equivalents.
14987 Character constants are a single character surrounded by single quotes
14988 (@code{'}), or a number---the ordinal value of the corresponding character
14989 (usually its @sc{ascii} value). Within quotes, the single character may
14990 be represented by a letter or by @dfn{escape sequences}, which are of
14991 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14992 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14993 @samp{@var{x}} is a predefined special character---for example,
14994 @samp{\n} for newline.
14996 Wide character constants can be written by prefixing a character
14997 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14998 form of @samp{x}. The target wide character set is used when
14999 computing the value of this constant (@pxref{Character Sets}).
15002 String constants are a sequence of character constants surrounded by
15003 double quotes (@code{"}). Any valid character constant (as described
15004 above) may appear. Double quotes within the string must be preceded by
15005 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15008 Wide string constants can be written by prefixing a string constant
15009 with @samp{L}, as in C. The target wide character set is used when
15010 computing the value of this constant (@pxref{Character Sets}).
15013 Pointer constants are an integral value. You can also write pointers
15014 to constants using the C operator @samp{&}.
15017 Array constants are comma-separated lists surrounded by braces @samp{@{}
15018 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15019 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15020 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15023 @node C Plus Plus Expressions
15024 @subsubsection C@t{++} Expressions
15026 @cindex expressions in C@t{++}
15027 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15029 @cindex debugging C@t{++} programs
15030 @cindex C@t{++} compilers
15031 @cindex debug formats and C@t{++}
15032 @cindex @value{NGCC} and C@t{++}
15034 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15035 the proper compiler and the proper debug format. Currently,
15036 @value{GDBN} works best when debugging C@t{++} code that is compiled
15037 with the most recent version of @value{NGCC} possible. The DWARF
15038 debugging format is preferred; @value{NGCC} defaults to this on most
15039 popular platforms. Other compilers and/or debug formats are likely to
15040 work badly or not at all when using @value{GDBN} to debug C@t{++}
15041 code. @xref{Compilation}.
15046 @cindex member functions
15048 Member function calls are allowed; you can use expressions like
15051 count = aml->GetOriginal(x, y)
15054 @vindex this@r{, inside C@t{++} member functions}
15055 @cindex namespace in C@t{++}
15057 While a member function is active (in the selected stack frame), your
15058 expressions have the same namespace available as the member function;
15059 that is, @value{GDBN} allows implicit references to the class instance
15060 pointer @code{this} following the same rules as C@t{++}. @code{using}
15061 declarations in the current scope are also respected by @value{GDBN}.
15063 @cindex call overloaded functions
15064 @cindex overloaded functions, calling
15065 @cindex type conversions in C@t{++}
15067 You can call overloaded functions; @value{GDBN} resolves the function
15068 call to the right definition, with some restrictions. @value{GDBN} does not
15069 perform overload resolution involving user-defined type conversions,
15070 calls to constructors, or instantiations of templates that do not exist
15071 in the program. It also cannot handle ellipsis argument lists or
15074 It does perform integral conversions and promotions, floating-point
15075 promotions, arithmetic conversions, pointer conversions, conversions of
15076 class objects to base classes, and standard conversions such as those of
15077 functions or arrays to pointers; it requires an exact match on the
15078 number of function arguments.
15080 Overload resolution is always performed, unless you have specified
15081 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15082 ,@value{GDBN} Features for C@t{++}}.
15084 You must specify @code{set overload-resolution off} in order to use an
15085 explicit function signature to call an overloaded function, as in
15087 p 'foo(char,int)'('x', 13)
15090 The @value{GDBN} command-completion facility can simplify this;
15091 see @ref{Completion, ,Command Completion}.
15093 @cindex reference declarations
15095 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15096 references; you can use them in expressions just as you do in C@t{++}
15097 source---they are automatically dereferenced.
15099 In the parameter list shown when @value{GDBN} displays a frame, the values of
15100 reference variables are not displayed (unlike other variables); this
15101 avoids clutter, since references are often used for large structures.
15102 The @emph{address} of a reference variable is always shown, unless
15103 you have specified @samp{set print address off}.
15106 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15107 expressions can use it just as expressions in your program do. Since
15108 one scope may be defined in another, you can use @code{::} repeatedly if
15109 necessary, for example in an expression like
15110 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15111 resolving name scope by reference to source files, in both C and C@t{++}
15112 debugging (@pxref{Variables, ,Program Variables}).
15115 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15120 @subsubsection C and C@t{++} Defaults
15122 @cindex C and C@t{++} defaults
15124 If you allow @value{GDBN} to set range checking automatically, it
15125 defaults to @code{off} whenever the working language changes to
15126 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15127 selects the working language.
15129 If you allow @value{GDBN} to set the language automatically, it
15130 recognizes source files whose names end with @file{.c}, @file{.C}, or
15131 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15132 these files, it sets the working language to C or C@t{++}.
15133 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15134 for further details.
15137 @subsubsection C and C@t{++} Type and Range Checks
15139 @cindex C and C@t{++} checks
15141 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15142 checking is used. However, if you turn type checking off, @value{GDBN}
15143 will allow certain non-standard conversions, such as promoting integer
15144 constants to pointers.
15146 Range checking, if turned on, is done on mathematical operations. Array
15147 indices are not checked, since they are often used to index a pointer
15148 that is not itself an array.
15151 @subsubsection @value{GDBN} and C
15153 The @code{set print union} and @code{show print union} commands apply to
15154 the @code{union} type. When set to @samp{on}, any @code{union} that is
15155 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15156 appears as @samp{@{...@}}.
15158 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15159 with pointers and a memory allocation function. @xref{Expressions,
15162 @node Debugging C Plus Plus
15163 @subsubsection @value{GDBN} Features for C@t{++}
15165 @cindex commands for C@t{++}
15167 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15168 designed specifically for use with C@t{++}. Here is a summary:
15171 @cindex break in overloaded functions
15172 @item @r{breakpoint menus}
15173 When you want a breakpoint in a function whose name is overloaded,
15174 @value{GDBN} has the capability to display a menu of possible breakpoint
15175 locations to help you specify which function definition you want.
15176 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15178 @cindex overloading in C@t{++}
15179 @item rbreak @var{regex}
15180 Setting breakpoints using regular expressions is helpful for setting
15181 breakpoints on overloaded functions that are not members of any special
15183 @xref{Set Breaks, ,Setting Breakpoints}.
15185 @cindex C@t{++} exception handling
15187 @itemx catch rethrow
15189 Debug C@t{++} exception handling using these commands. @xref{Set
15190 Catchpoints, , Setting Catchpoints}.
15192 @cindex inheritance
15193 @item ptype @var{typename}
15194 Print inheritance relationships as well as other information for type
15196 @xref{Symbols, ,Examining the Symbol Table}.
15198 @item info vtbl @var{expression}.
15199 The @code{info vtbl} command can be used to display the virtual
15200 method tables of the object computed by @var{expression}. This shows
15201 one entry per virtual table; there may be multiple virtual tables when
15202 multiple inheritance is in use.
15204 @cindex C@t{++} demangling
15205 @item demangle @var{name}
15206 Demangle @var{name}.
15207 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15209 @cindex C@t{++} symbol display
15210 @item set print demangle
15211 @itemx show print demangle
15212 @itemx set print asm-demangle
15213 @itemx show print asm-demangle
15214 Control whether C@t{++} symbols display in their source form, both when
15215 displaying code as C@t{++} source and when displaying disassemblies.
15216 @xref{Print Settings, ,Print Settings}.
15218 @item set print object
15219 @itemx show print object
15220 Choose whether to print derived (actual) or declared types of objects.
15221 @xref{Print Settings, ,Print Settings}.
15223 @item set print vtbl
15224 @itemx show print vtbl
15225 Control the format for printing virtual function tables.
15226 @xref{Print Settings, ,Print Settings}.
15227 (The @code{vtbl} commands do not work on programs compiled with the HP
15228 ANSI C@t{++} compiler (@code{aCC}).)
15230 @kindex set overload-resolution
15231 @cindex overloaded functions, overload resolution
15232 @item set overload-resolution on
15233 Enable overload resolution for C@t{++} expression evaluation. The default
15234 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15235 and searches for a function whose signature matches the argument types,
15236 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15237 Expressions, ,C@t{++} Expressions}, for details).
15238 If it cannot find a match, it emits a message.
15240 @item set overload-resolution off
15241 Disable overload resolution for C@t{++} expression evaluation. For
15242 overloaded functions that are not class member functions, @value{GDBN}
15243 chooses the first function of the specified name that it finds in the
15244 symbol table, whether or not its arguments are of the correct type. For
15245 overloaded functions that are class member functions, @value{GDBN}
15246 searches for a function whose signature @emph{exactly} matches the
15249 @kindex show overload-resolution
15250 @item show overload-resolution
15251 Show the current setting of overload resolution.
15253 @item @r{Overloaded symbol names}
15254 You can specify a particular definition of an overloaded symbol, using
15255 the same notation that is used to declare such symbols in C@t{++}: type
15256 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15257 also use the @value{GDBN} command-line word completion facilities to list the
15258 available choices, or to finish the type list for you.
15259 @xref{Completion,, Command Completion}, for details on how to do this.
15261 @item @r{Breakpoints in functions with ABI tags}
15263 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15264 correspond to changes in the ABI of a type, function, or variable that
15265 would not otherwise be reflected in a mangled name. See
15266 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15269 The ABI tags are visible in C@t{++} demangled names. For example, a
15270 function that returns a std::string:
15273 std::string function(int);
15277 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15278 tag, and @value{GDBN} displays the symbol like this:
15281 function[abi:cxx11](int)
15284 You can set a breakpoint on such functions simply as if they had no
15288 (gdb) b function(int)
15289 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15290 (gdb) info breakpoints
15291 Num Type Disp Enb Address What
15292 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15296 On the rare occasion you need to disambiguate between different ABI
15297 tags, you can do so by simply including the ABI tag in the function
15301 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15305 @node Decimal Floating Point
15306 @subsubsection Decimal Floating Point format
15307 @cindex decimal floating point format
15309 @value{GDBN} can examine, set and perform computations with numbers in
15310 decimal floating point format, which in the C language correspond to the
15311 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15312 specified by the extension to support decimal floating-point arithmetic.
15314 There are two encodings in use, depending on the architecture: BID (Binary
15315 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15316 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15319 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15320 to manipulate decimal floating point numbers, it is not possible to convert
15321 (using a cast, for example) integers wider than 32-bit to decimal float.
15323 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15324 point computations, error checking in decimal float operations ignores
15325 underflow, overflow and divide by zero exceptions.
15327 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15328 to inspect @code{_Decimal128} values stored in floating point registers.
15329 See @ref{PowerPC,,PowerPC} for more details.
15335 @value{GDBN} can be used to debug programs written in D and compiled with
15336 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15337 specific feature --- dynamic arrays.
15342 @cindex Go (programming language)
15343 @value{GDBN} can be used to debug programs written in Go and compiled with
15344 @file{gccgo} or @file{6g} compilers.
15346 Here is a summary of the Go-specific features and restrictions:
15349 @cindex current Go package
15350 @item The current Go package
15351 The name of the current package does not need to be specified when
15352 specifying global variables and functions.
15354 For example, given the program:
15358 var myglob = "Shall we?"
15364 When stopped inside @code{main} either of these work:
15368 (gdb) p main.myglob
15371 @cindex builtin Go types
15372 @item Builtin Go types
15373 The @code{string} type is recognized by @value{GDBN} and is printed
15376 @cindex builtin Go functions
15377 @item Builtin Go functions
15378 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15379 function and handles it internally.
15381 @cindex restrictions on Go expressions
15382 @item Restrictions on Go expressions
15383 All Go operators are supported except @code{&^}.
15384 The Go @code{_} ``blank identifier'' is not supported.
15385 Automatic dereferencing of pointers is not supported.
15389 @subsection Objective-C
15391 @cindex Objective-C
15392 This section provides information about some commands and command
15393 options that are useful for debugging Objective-C code. See also
15394 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15395 few more commands specific to Objective-C support.
15398 * Method Names in Commands::
15399 * The Print Command with Objective-C::
15402 @node Method Names in Commands
15403 @subsubsection Method Names in Commands
15405 The following commands have been extended to accept Objective-C method
15406 names as line specifications:
15408 @kindex clear@r{, and Objective-C}
15409 @kindex break@r{, and Objective-C}
15410 @kindex info line@r{, and Objective-C}
15411 @kindex jump@r{, and Objective-C}
15412 @kindex list@r{, and Objective-C}
15416 @item @code{info line}
15421 A fully qualified Objective-C method name is specified as
15424 -[@var{Class} @var{methodName}]
15427 where the minus sign is used to indicate an instance method and a
15428 plus sign (not shown) is used to indicate a class method. The class
15429 name @var{Class} and method name @var{methodName} are enclosed in
15430 brackets, similar to the way messages are specified in Objective-C
15431 source code. For example, to set a breakpoint at the @code{create}
15432 instance method of class @code{Fruit} in the program currently being
15436 break -[Fruit create]
15439 To list ten program lines around the @code{initialize} class method,
15443 list +[NSText initialize]
15446 In the current version of @value{GDBN}, the plus or minus sign is
15447 required. In future versions of @value{GDBN}, the plus or minus
15448 sign will be optional, but you can use it to narrow the search. It
15449 is also possible to specify just a method name:
15455 You must specify the complete method name, including any colons. If
15456 your program's source files contain more than one @code{create} method,
15457 you'll be presented with a numbered list of classes that implement that
15458 method. Indicate your choice by number, or type @samp{0} to exit if
15461 As another example, to clear a breakpoint established at the
15462 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15465 clear -[NSWindow makeKeyAndOrderFront:]
15468 @node The Print Command with Objective-C
15469 @subsubsection The Print Command With Objective-C
15470 @cindex Objective-C, print objects
15471 @kindex print-object
15472 @kindex po @r{(@code{print-object})}
15474 The print command has also been extended to accept methods. For example:
15477 print -[@var{object} hash]
15480 @cindex print an Objective-C object description
15481 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15483 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15484 and print the result. Also, an additional command has been added,
15485 @code{print-object} or @code{po} for short, which is meant to print
15486 the description of an object. However, this command may only work
15487 with certain Objective-C libraries that have a particular hook
15488 function, @code{_NSPrintForDebugger}, defined.
15491 @subsection OpenCL C
15494 This section provides information about @value{GDBN}s OpenCL C support.
15497 * OpenCL C Datatypes::
15498 * OpenCL C Expressions::
15499 * OpenCL C Operators::
15502 @node OpenCL C Datatypes
15503 @subsubsection OpenCL C Datatypes
15505 @cindex OpenCL C Datatypes
15506 @value{GDBN} supports the builtin scalar and vector datatypes specified
15507 by OpenCL 1.1. In addition the half- and double-precision floating point
15508 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15509 extensions are also known to @value{GDBN}.
15511 @node OpenCL C Expressions
15512 @subsubsection OpenCL C Expressions
15514 @cindex OpenCL C Expressions
15515 @value{GDBN} supports accesses to vector components including the access as
15516 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15517 supported by @value{GDBN} can be used as well.
15519 @node OpenCL C Operators
15520 @subsubsection OpenCL C Operators
15522 @cindex OpenCL C Operators
15523 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15527 @subsection Fortran
15528 @cindex Fortran-specific support in @value{GDBN}
15530 @value{GDBN} can be used to debug programs written in Fortran, but it
15531 currently supports only the features of Fortran 77 language.
15533 @cindex trailing underscore, in Fortran symbols
15534 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15535 among them) append an underscore to the names of variables and
15536 functions. When you debug programs compiled by those compilers, you
15537 will need to refer to variables and functions with a trailing
15541 * Fortran Operators:: Fortran operators and expressions
15542 * Fortran Defaults:: Default settings for Fortran
15543 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15546 @node Fortran Operators
15547 @subsubsection Fortran Operators and Expressions
15549 @cindex Fortran operators and expressions
15551 Operators must be defined on values of specific types. For instance,
15552 @code{+} is defined on numbers, but not on characters or other non-
15553 arithmetic types. Operators are often defined on groups of types.
15557 The exponentiation operator. It raises the first operand to the power
15561 The range operator. Normally used in the form of array(low:high) to
15562 represent a section of array.
15565 The access component operator. Normally used to access elements in derived
15566 types. Also suitable for unions. As unions aren't part of regular Fortran,
15567 this can only happen when accessing a register that uses a gdbarch-defined
15571 @node Fortran Defaults
15572 @subsubsection Fortran Defaults
15574 @cindex Fortran Defaults
15576 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15577 default uses case-insensitive matches for Fortran symbols. You can
15578 change that with the @samp{set case-insensitive} command, see
15579 @ref{Symbols}, for the details.
15581 @node Special Fortran Commands
15582 @subsubsection Special Fortran Commands
15584 @cindex Special Fortran commands
15586 @value{GDBN} has some commands to support Fortran-specific features,
15587 such as displaying common blocks.
15590 @cindex @code{COMMON} blocks, Fortran
15591 @kindex info common
15592 @item info common @r{[}@var{common-name}@r{]}
15593 This command prints the values contained in the Fortran @code{COMMON}
15594 block whose name is @var{common-name}. With no argument, the names of
15595 all @code{COMMON} blocks visible at the current program location are
15602 @cindex Pascal support in @value{GDBN}, limitations
15603 Debugging Pascal programs which use sets, subranges, file variables, or
15604 nested functions does not currently work. @value{GDBN} does not support
15605 entering expressions, printing values, or similar features using Pascal
15608 The Pascal-specific command @code{set print pascal_static-members}
15609 controls whether static members of Pascal objects are displayed.
15610 @xref{Print Settings, pascal_static-members}.
15615 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15616 Programming Language}. Type- and value-printing, and expression
15617 parsing, are reasonably complete. However, there are a few
15618 peculiarities and holes to be aware of.
15622 Linespecs (@pxref{Specify Location}) are never relative to the current
15623 crate. Instead, they act as if there were a global namespace of
15624 crates, somewhat similar to the way @code{extern crate} behaves.
15626 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15627 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15628 to set a breakpoint in a function named @samp{f} in a crate named
15631 As a consequence of this approach, linespecs also cannot refer to
15632 items using @samp{self::} or @samp{super::}.
15635 Because @value{GDBN} implements Rust name-lookup semantics in
15636 expressions, it will sometimes prepend the current crate to a name.
15637 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15638 @samp{K}, then @code{print ::x::y} will try to find the symbol
15641 However, since it is useful to be able to refer to other crates when
15642 debugging, @value{GDBN} provides the @code{extern} extension to
15643 circumvent this. To use the extension, just put @code{extern} before
15644 a path expression to refer to the otherwise unavailable ``global''
15647 In the above example, if you wanted to refer to the symbol @samp{y} in
15648 the crate @samp{x}, you would use @code{print extern x::y}.
15651 The Rust expression evaluator does not support ``statement-like''
15652 expressions such as @code{if} or @code{match}, or lambda expressions.
15655 Tuple expressions are not implemented.
15658 The Rust expression evaluator does not currently implement the
15659 @code{Drop} trait. Objects that may be created by the evaluator will
15660 never be destroyed.
15663 @value{GDBN} does not implement type inference for generics. In order
15664 to call generic functions or otherwise refer to generic items, you
15665 will have to specify the type parameters manually.
15668 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15669 cases this does not cause any problems. However, in an expression
15670 context, completing a generic function name will give syntactically
15671 invalid results. This happens because Rust requires the @samp{::}
15672 operator between the function name and its generic arguments. For
15673 example, @value{GDBN} might provide a completion like
15674 @code{crate::f<u32>}, where the parser would require
15675 @code{crate::f::<u32>}.
15678 As of this writing, the Rust compiler (version 1.8) has a few holes in
15679 the debugging information it generates. These holes prevent certain
15680 features from being implemented by @value{GDBN}:
15684 Method calls cannot be made via traits.
15687 Operator overloading is not implemented.
15690 When debugging in a monomorphized function, you cannot use the generic
15694 The type @code{Self} is not available.
15697 @code{use} statements are not available, so some names may not be
15698 available in the crate.
15703 @subsection Modula-2
15705 @cindex Modula-2, @value{GDBN} support
15707 The extensions made to @value{GDBN} to support Modula-2 only support
15708 output from the @sc{gnu} Modula-2 compiler (which is currently being
15709 developed). Other Modula-2 compilers are not currently supported, and
15710 attempting to debug executables produced by them is most likely
15711 to give an error as @value{GDBN} reads in the executable's symbol
15714 @cindex expressions in Modula-2
15716 * M2 Operators:: Built-in operators
15717 * Built-In Func/Proc:: Built-in functions and procedures
15718 * M2 Constants:: Modula-2 constants
15719 * M2 Types:: Modula-2 types
15720 * M2 Defaults:: Default settings for Modula-2
15721 * Deviations:: Deviations from standard Modula-2
15722 * M2 Checks:: Modula-2 type and range checks
15723 * M2 Scope:: The scope operators @code{::} and @code{.}
15724 * GDB/M2:: @value{GDBN} and Modula-2
15728 @subsubsection Operators
15729 @cindex Modula-2 operators
15731 Operators must be defined on values of specific types. For instance,
15732 @code{+} is defined on numbers, but not on structures. Operators are
15733 often defined on groups of types. For the purposes of Modula-2, the
15734 following definitions hold:
15739 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15743 @emph{Character types} consist of @code{CHAR} and its subranges.
15746 @emph{Floating-point types} consist of @code{REAL}.
15749 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15753 @emph{Scalar types} consist of all of the above.
15756 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15759 @emph{Boolean types} consist of @code{BOOLEAN}.
15763 The following operators are supported, and appear in order of
15764 increasing precedence:
15768 Function argument or array index separator.
15771 Assignment. The value of @var{var} @code{:=} @var{value} is
15775 Less than, greater than on integral, floating-point, or enumerated
15779 Less than or equal to, greater than or equal to
15780 on integral, floating-point and enumerated types, or set inclusion on
15781 set types. Same precedence as @code{<}.
15783 @item =@r{, }<>@r{, }#
15784 Equality and two ways of expressing inequality, valid on scalar types.
15785 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15786 available for inequality, since @code{#} conflicts with the script
15790 Set membership. Defined on set types and the types of their members.
15791 Same precedence as @code{<}.
15794 Boolean disjunction. Defined on boolean types.
15797 Boolean conjunction. Defined on boolean types.
15800 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15803 Addition and subtraction on integral and floating-point types, or union
15804 and difference on set types.
15807 Multiplication on integral and floating-point types, or set intersection
15811 Division on floating-point types, or symmetric set difference on set
15812 types. Same precedence as @code{*}.
15815 Integer division and remainder. Defined on integral types. Same
15816 precedence as @code{*}.
15819 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15822 Pointer dereferencing. Defined on pointer types.
15825 Boolean negation. Defined on boolean types. Same precedence as
15829 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15830 precedence as @code{^}.
15833 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15836 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15840 @value{GDBN} and Modula-2 scope operators.
15844 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15845 treats the use of the operator @code{IN}, or the use of operators
15846 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15847 @code{<=}, and @code{>=} on sets as an error.
15851 @node Built-In Func/Proc
15852 @subsubsection Built-in Functions and Procedures
15853 @cindex Modula-2 built-ins
15855 Modula-2 also makes available several built-in procedures and functions.
15856 In describing these, the following metavariables are used:
15861 represents an @code{ARRAY} variable.
15864 represents a @code{CHAR} constant or variable.
15867 represents a variable or constant of integral type.
15870 represents an identifier that belongs to a set. Generally used in the
15871 same function with the metavariable @var{s}. The type of @var{s} should
15872 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15875 represents a variable or constant of integral or floating-point type.
15878 represents a variable or constant of floating-point type.
15884 represents a variable.
15887 represents a variable or constant of one of many types. See the
15888 explanation of the function for details.
15891 All Modula-2 built-in procedures also return a result, described below.
15895 Returns the absolute value of @var{n}.
15898 If @var{c} is a lower case letter, it returns its upper case
15899 equivalent, otherwise it returns its argument.
15902 Returns the character whose ordinal value is @var{i}.
15905 Decrements the value in the variable @var{v} by one. Returns the new value.
15907 @item DEC(@var{v},@var{i})
15908 Decrements the value in the variable @var{v} by @var{i}. Returns the
15911 @item EXCL(@var{m},@var{s})
15912 Removes the element @var{m} from the set @var{s}. Returns the new
15915 @item FLOAT(@var{i})
15916 Returns the floating point equivalent of the integer @var{i}.
15918 @item HIGH(@var{a})
15919 Returns the index of the last member of @var{a}.
15922 Increments the value in the variable @var{v} by one. Returns the new value.
15924 @item INC(@var{v},@var{i})
15925 Increments the value in the variable @var{v} by @var{i}. Returns the
15928 @item INCL(@var{m},@var{s})
15929 Adds the element @var{m} to the set @var{s} if it is not already
15930 there. Returns the new set.
15933 Returns the maximum value of the type @var{t}.
15936 Returns the minimum value of the type @var{t}.
15939 Returns boolean TRUE if @var{i} is an odd number.
15942 Returns the ordinal value of its argument. For example, the ordinal
15943 value of a character is its @sc{ascii} value (on machines supporting
15944 the @sc{ascii} character set). The argument @var{x} must be of an
15945 ordered type, which include integral, character and enumerated types.
15947 @item SIZE(@var{x})
15948 Returns the size of its argument. The argument @var{x} can be a
15949 variable or a type.
15951 @item TRUNC(@var{r})
15952 Returns the integral part of @var{r}.
15954 @item TSIZE(@var{x})
15955 Returns the size of its argument. The argument @var{x} can be a
15956 variable or a type.
15958 @item VAL(@var{t},@var{i})
15959 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15963 @emph{Warning:} Sets and their operations are not yet supported, so
15964 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15968 @cindex Modula-2 constants
15970 @subsubsection Constants
15972 @value{GDBN} allows you to express the constants of Modula-2 in the following
15978 Integer constants are simply a sequence of digits. When used in an
15979 expression, a constant is interpreted to be type-compatible with the
15980 rest of the expression. Hexadecimal integers are specified by a
15981 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15984 Floating point constants appear as a sequence of digits, followed by a
15985 decimal point and another sequence of digits. An optional exponent can
15986 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15987 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15988 digits of the floating point constant must be valid decimal (base 10)
15992 Character constants consist of a single character enclosed by a pair of
15993 like quotes, either single (@code{'}) or double (@code{"}). They may
15994 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15995 followed by a @samp{C}.
15998 String constants consist of a sequence of characters enclosed by a
15999 pair of like quotes, either single (@code{'}) or double (@code{"}).
16000 Escape sequences in the style of C are also allowed. @xref{C
16001 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16005 Enumerated constants consist of an enumerated identifier.
16008 Boolean constants consist of the identifiers @code{TRUE} and
16012 Pointer constants consist of integral values only.
16015 Set constants are not yet supported.
16019 @subsubsection Modula-2 Types
16020 @cindex Modula-2 types
16022 Currently @value{GDBN} can print the following data types in Modula-2
16023 syntax: array types, record types, set types, pointer types, procedure
16024 types, enumerated types, subrange types and base types. You can also
16025 print the contents of variables declared using these type.
16026 This section gives a number of simple source code examples together with
16027 sample @value{GDBN} sessions.
16029 The first example contains the following section of code:
16038 and you can request @value{GDBN} to interrogate the type and value of
16039 @code{r} and @code{s}.
16042 (@value{GDBP}) print s
16044 (@value{GDBP}) ptype s
16046 (@value{GDBP}) print r
16048 (@value{GDBP}) ptype r
16053 Likewise if your source code declares @code{s} as:
16057 s: SET ['A'..'Z'] ;
16061 then you may query the type of @code{s} by:
16064 (@value{GDBP}) ptype s
16065 type = SET ['A'..'Z']
16069 Note that at present you cannot interactively manipulate set
16070 expressions using the debugger.
16072 The following example shows how you might declare an array in Modula-2
16073 and how you can interact with @value{GDBN} to print its type and contents:
16077 s: ARRAY [-10..10] OF CHAR ;
16081 (@value{GDBP}) ptype s
16082 ARRAY [-10..10] OF CHAR
16085 Note that the array handling is not yet complete and although the type
16086 is printed correctly, expression handling still assumes that all
16087 arrays have a lower bound of zero and not @code{-10} as in the example
16090 Here are some more type related Modula-2 examples:
16094 colour = (blue, red, yellow, green) ;
16095 t = [blue..yellow] ;
16103 The @value{GDBN} interaction shows how you can query the data type
16104 and value of a variable.
16107 (@value{GDBP}) print s
16109 (@value{GDBP}) ptype t
16110 type = [blue..yellow]
16114 In this example a Modula-2 array is declared and its contents
16115 displayed. Observe that the contents are written in the same way as
16116 their @code{C} counterparts.
16120 s: ARRAY [1..5] OF CARDINAL ;
16126 (@value{GDBP}) print s
16127 $1 = @{1, 0, 0, 0, 0@}
16128 (@value{GDBP}) ptype s
16129 type = ARRAY [1..5] OF CARDINAL
16132 The Modula-2 language interface to @value{GDBN} also understands
16133 pointer types as shown in this example:
16137 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16144 and you can request that @value{GDBN} describes the type of @code{s}.
16147 (@value{GDBP}) ptype s
16148 type = POINTER TO ARRAY [1..5] OF CARDINAL
16151 @value{GDBN} handles compound types as we can see in this example.
16152 Here we combine array types, record types, pointer types and subrange
16163 myarray = ARRAY myrange OF CARDINAL ;
16164 myrange = [-2..2] ;
16166 s: POINTER TO ARRAY myrange OF foo ;
16170 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16174 (@value{GDBP}) ptype s
16175 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16178 f3 : ARRAY [-2..2] OF CARDINAL;
16183 @subsubsection Modula-2 Defaults
16184 @cindex Modula-2 defaults
16186 If type and range checking are set automatically by @value{GDBN}, they
16187 both default to @code{on} whenever the working language changes to
16188 Modula-2. This happens regardless of whether you or @value{GDBN}
16189 selected the working language.
16191 If you allow @value{GDBN} to set the language automatically, then entering
16192 code compiled from a file whose name ends with @file{.mod} sets the
16193 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16194 Infer the Source Language}, for further details.
16197 @subsubsection Deviations from Standard Modula-2
16198 @cindex Modula-2, deviations from
16200 A few changes have been made to make Modula-2 programs easier to debug.
16201 This is done primarily via loosening its type strictness:
16205 Unlike in standard Modula-2, pointer constants can be formed by
16206 integers. This allows you to modify pointer variables during
16207 debugging. (In standard Modula-2, the actual address contained in a
16208 pointer variable is hidden from you; it can only be modified
16209 through direct assignment to another pointer variable or expression that
16210 returned a pointer.)
16213 C escape sequences can be used in strings and characters to represent
16214 non-printable characters. @value{GDBN} prints out strings with these
16215 escape sequences embedded. Single non-printable characters are
16216 printed using the @samp{CHR(@var{nnn})} format.
16219 The assignment operator (@code{:=}) returns the value of its right-hand
16223 All built-in procedures both modify @emph{and} return their argument.
16227 @subsubsection Modula-2 Type and Range Checks
16228 @cindex Modula-2 checks
16231 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16234 @c FIXME remove warning when type/range checks added
16236 @value{GDBN} considers two Modula-2 variables type equivalent if:
16240 They are of types that have been declared equivalent via a @code{TYPE
16241 @var{t1} = @var{t2}} statement
16244 They have been declared on the same line. (Note: This is true of the
16245 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16248 As long as type checking is enabled, any attempt to combine variables
16249 whose types are not equivalent is an error.
16251 Range checking is done on all mathematical operations, assignment, array
16252 index bounds, and all built-in functions and procedures.
16255 @subsubsection The Scope Operators @code{::} and @code{.}
16257 @cindex @code{.}, Modula-2 scope operator
16258 @cindex colon, doubled as scope operator
16260 @vindex colon-colon@r{, in Modula-2}
16261 @c Info cannot handle :: but TeX can.
16264 @vindex ::@r{, in Modula-2}
16267 There are a few subtle differences between the Modula-2 scope operator
16268 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16273 @var{module} . @var{id}
16274 @var{scope} :: @var{id}
16278 where @var{scope} is the name of a module or a procedure,
16279 @var{module} the name of a module, and @var{id} is any declared
16280 identifier within your program, except another module.
16282 Using the @code{::} operator makes @value{GDBN} search the scope
16283 specified by @var{scope} for the identifier @var{id}. If it is not
16284 found in the specified scope, then @value{GDBN} searches all scopes
16285 enclosing the one specified by @var{scope}.
16287 Using the @code{.} operator makes @value{GDBN} search the current scope for
16288 the identifier specified by @var{id} that was imported from the
16289 definition module specified by @var{module}. With this operator, it is
16290 an error if the identifier @var{id} was not imported from definition
16291 module @var{module}, or if @var{id} is not an identifier in
16295 @subsubsection @value{GDBN} and Modula-2
16297 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16298 Five subcommands of @code{set print} and @code{show print} apply
16299 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16300 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16301 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16302 analogue in Modula-2.
16304 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16305 with any language, is not useful with Modula-2. Its
16306 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16307 created in Modula-2 as they can in C or C@t{++}. However, because an
16308 address can be specified by an integral constant, the construct
16309 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16311 @cindex @code{#} in Modula-2
16312 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16313 interpreted as the beginning of a comment. Use @code{<>} instead.
16319 The extensions made to @value{GDBN} for Ada only support
16320 output from the @sc{gnu} Ada (GNAT) compiler.
16321 Other Ada compilers are not currently supported, and
16322 attempting to debug executables produced by them is most likely
16326 @cindex expressions in Ada
16328 * Ada Mode Intro:: General remarks on the Ada syntax
16329 and semantics supported by Ada mode
16331 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16332 * Additions to Ada:: Extensions of the Ada expression syntax.
16333 * Overloading support for Ada:: Support for expressions involving overloaded
16335 * Stopping Before Main Program:: Debugging the program during elaboration.
16336 * Ada Exceptions:: Ada Exceptions
16337 * Ada Tasks:: Listing and setting breakpoints in tasks.
16338 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16339 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16341 * Ada Settings:: New settable GDB parameters for Ada.
16342 * Ada Glitches:: Known peculiarities of Ada mode.
16345 @node Ada Mode Intro
16346 @subsubsection Introduction
16347 @cindex Ada mode, general
16349 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16350 syntax, with some extensions.
16351 The philosophy behind the design of this subset is
16355 That @value{GDBN} should provide basic literals and access to operations for
16356 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16357 leaving more sophisticated computations to subprograms written into the
16358 program (which therefore may be called from @value{GDBN}).
16361 That type safety and strict adherence to Ada language restrictions
16362 are not particularly important to the @value{GDBN} user.
16365 That brevity is important to the @value{GDBN} user.
16368 Thus, for brevity, the debugger acts as if all names declared in
16369 user-written packages are directly visible, even if they are not visible
16370 according to Ada rules, thus making it unnecessary to fully qualify most
16371 names with their packages, regardless of context. Where this causes
16372 ambiguity, @value{GDBN} asks the user's intent.
16374 The debugger will start in Ada mode if it detects an Ada main program.
16375 As for other languages, it will enter Ada mode when stopped in a program that
16376 was translated from an Ada source file.
16378 While in Ada mode, you may use `@t{--}' for comments. This is useful
16379 mostly for documenting command files. The standard @value{GDBN} comment
16380 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16381 middle (to allow based literals).
16383 @node Omissions from Ada
16384 @subsubsection Omissions from Ada
16385 @cindex Ada, omissions from
16387 Here are the notable omissions from the subset:
16391 Only a subset of the attributes are supported:
16395 @t{'First}, @t{'Last}, and @t{'Length}
16396 on array objects (not on types and subtypes).
16399 @t{'Min} and @t{'Max}.
16402 @t{'Pos} and @t{'Val}.
16408 @t{'Range} on array objects (not subtypes), but only as the right
16409 operand of the membership (@code{in}) operator.
16412 @t{'Access}, @t{'Unchecked_Access}, and
16413 @t{'Unrestricted_Access} (a GNAT extension).
16421 @code{Characters.Latin_1} are not available and
16422 concatenation is not implemented. Thus, escape characters in strings are
16423 not currently available.
16426 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16427 equality of representations. They will generally work correctly
16428 for strings and arrays whose elements have integer or enumeration types.
16429 They may not work correctly for arrays whose element
16430 types have user-defined equality, for arrays of real values
16431 (in particular, IEEE-conformant floating point, because of negative
16432 zeroes and NaNs), and for arrays whose elements contain unused bits with
16433 indeterminate values.
16436 The other component-by-component array operations (@code{and}, @code{or},
16437 @code{xor}, @code{not}, and relational tests other than equality)
16438 are not implemented.
16441 @cindex array aggregates (Ada)
16442 @cindex record aggregates (Ada)
16443 @cindex aggregates (Ada)
16444 There is limited support for array and record aggregates. They are
16445 permitted only on the right sides of assignments, as in these examples:
16448 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16449 (@value{GDBP}) set An_Array := (1, others => 0)
16450 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16451 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16452 (@value{GDBP}) set A_Record := (1, "Peter", True);
16453 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16457 discriminant's value by assigning an aggregate has an
16458 undefined effect if that discriminant is used within the record.
16459 However, you can first modify discriminants by directly assigning to
16460 them (which normally would not be allowed in Ada), and then performing an
16461 aggregate assignment. For example, given a variable @code{A_Rec}
16462 declared to have a type such as:
16465 type Rec (Len : Small_Integer := 0) is record
16467 Vals : IntArray (1 .. Len);
16471 you can assign a value with a different size of @code{Vals} with two
16475 (@value{GDBP}) set A_Rec.Len := 4
16476 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16479 As this example also illustrates, @value{GDBN} is very loose about the usual
16480 rules concerning aggregates. You may leave out some of the
16481 components of an array or record aggregate (such as the @code{Len}
16482 component in the assignment to @code{A_Rec} above); they will retain their
16483 original values upon assignment. You may freely use dynamic values as
16484 indices in component associations. You may even use overlapping or
16485 redundant component associations, although which component values are
16486 assigned in such cases is not defined.
16489 Calls to dispatching subprograms are not implemented.
16492 The overloading algorithm is much more limited (i.e., less selective)
16493 than that of real Ada. It makes only limited use of the context in
16494 which a subexpression appears to resolve its meaning, and it is much
16495 looser in its rules for allowing type matches. As a result, some
16496 function calls will be ambiguous, and the user will be asked to choose
16497 the proper resolution.
16500 The @code{new} operator is not implemented.
16503 Entry calls are not implemented.
16506 Aside from printing, arithmetic operations on the native VAX floating-point
16507 formats are not supported.
16510 It is not possible to slice a packed array.
16513 The names @code{True} and @code{False}, when not part of a qualified name,
16514 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16516 Should your program
16517 redefine these names in a package or procedure (at best a dubious practice),
16518 you will have to use fully qualified names to access their new definitions.
16521 @node Additions to Ada
16522 @subsubsection Additions to Ada
16523 @cindex Ada, deviations from
16525 As it does for other languages, @value{GDBN} makes certain generic
16526 extensions to Ada (@pxref{Expressions}):
16530 If the expression @var{E} is a variable residing in memory (typically
16531 a local variable or array element) and @var{N} is a positive integer,
16532 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16533 @var{N}-1 adjacent variables following it in memory as an array. In
16534 Ada, this operator is generally not necessary, since its prime use is
16535 in displaying parts of an array, and slicing will usually do this in
16536 Ada. However, there are occasional uses when debugging programs in
16537 which certain debugging information has been optimized away.
16540 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16541 appears in function or file @var{B}.'' When @var{B} is a file name,
16542 you must typically surround it in single quotes.
16545 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16546 @var{type} that appears at address @var{addr}.''
16549 A name starting with @samp{$} is a convenience variable
16550 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16553 In addition, @value{GDBN} provides a few other shortcuts and outright
16554 additions specific to Ada:
16558 The assignment statement is allowed as an expression, returning
16559 its right-hand operand as its value. Thus, you may enter
16562 (@value{GDBP}) set x := y + 3
16563 (@value{GDBP}) print A(tmp := y + 1)
16567 The semicolon is allowed as an ``operator,'' returning as its value
16568 the value of its right-hand operand.
16569 This allows, for example,
16570 complex conditional breaks:
16573 (@value{GDBP}) break f
16574 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16578 Rather than use catenation and symbolic character names to introduce special
16579 characters into strings, one may instead use a special bracket notation,
16580 which is also used to print strings. A sequence of characters of the form
16581 @samp{["@var{XX}"]} within a string or character literal denotes the
16582 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16583 sequence of characters @samp{["""]} also denotes a single quotation mark
16584 in strings. For example,
16586 "One line.["0a"]Next line.["0a"]"
16589 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16593 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16594 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16598 (@value{GDBP}) print 'max(x, y)
16602 When printing arrays, @value{GDBN} uses positional notation when the
16603 array has a lower bound of 1, and uses a modified named notation otherwise.
16604 For example, a one-dimensional array of three integers with a lower bound
16605 of 3 might print as
16612 That is, in contrast to valid Ada, only the first component has a @code{=>}
16616 You may abbreviate attributes in expressions with any unique,
16617 multi-character subsequence of
16618 their names (an exact match gets preference).
16619 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16620 in place of @t{a'length}.
16623 @cindex quoting Ada internal identifiers
16624 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16625 to lower case. The GNAT compiler uses upper-case characters for
16626 some of its internal identifiers, which are normally of no interest to users.
16627 For the rare occasions when you actually have to look at them,
16628 enclose them in angle brackets to avoid the lower-case mapping.
16631 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16635 Printing an object of class-wide type or dereferencing an
16636 access-to-class-wide value will display all the components of the object's
16637 specific type (as indicated by its run-time tag). Likewise, component
16638 selection on such a value will operate on the specific type of the
16643 @node Overloading support for Ada
16644 @subsubsection Overloading support for Ada
16645 @cindex overloading, Ada
16647 The debugger supports limited overloading. Given a subprogram call in which
16648 the function symbol has multiple definitions, it will use the number of
16649 actual parameters and some information about their types to attempt to narrow
16650 the set of definitions. It also makes very limited use of context, preferring
16651 procedures to functions in the context of the @code{call} command, and
16652 functions to procedures elsewhere.
16654 If, after narrowing, the set of matching definitions still contains more than
16655 one definition, @value{GDBN} will display a menu to query which one it should
16659 (@value{GDBP}) print f(1)
16660 Multiple matches for f
16662 [1] foo.f (integer) return boolean at foo.adb:23
16663 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16667 In this case, just select one menu entry either to cancel expression evaluation
16668 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16669 instance (type the corresponding number and press @key{RET}).
16671 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16676 @kindex set ada print-signatures
16677 @item set ada print-signatures
16678 Control whether parameter types and return types are displayed in overloads
16679 selection menus. It is @code{on} by default.
16680 @xref{Overloading support for Ada}.
16682 @kindex show ada print-signatures
16683 @item show ada print-signatures
16684 Show the current setting for displaying parameter types and return types in
16685 overloads selection menu.
16686 @xref{Overloading support for Ada}.
16690 @node Stopping Before Main Program
16691 @subsubsection Stopping at the Very Beginning
16693 @cindex breakpointing Ada elaboration code
16694 It is sometimes necessary to debug the program during elaboration, and
16695 before reaching the main procedure.
16696 As defined in the Ada Reference
16697 Manual, the elaboration code is invoked from a procedure called
16698 @code{adainit}. To run your program up to the beginning of
16699 elaboration, simply use the following two commands:
16700 @code{tbreak adainit} and @code{run}.
16702 @node Ada Exceptions
16703 @subsubsection Ada Exceptions
16705 A command is provided to list all Ada exceptions:
16708 @kindex info exceptions
16709 @item info exceptions
16710 @itemx info exceptions @var{regexp}
16711 The @code{info exceptions} command allows you to list all Ada exceptions
16712 defined within the program being debugged, as well as their addresses.
16713 With a regular expression, @var{regexp}, as argument, only those exceptions
16714 whose names match @var{regexp} are listed.
16717 Below is a small example, showing how the command can be used, first
16718 without argument, and next with a regular expression passed as an
16722 (@value{GDBP}) info exceptions
16723 All defined Ada exceptions:
16724 constraint_error: 0x613da0
16725 program_error: 0x613d20
16726 storage_error: 0x613ce0
16727 tasking_error: 0x613ca0
16728 const.aint_global_e: 0x613b00
16729 (@value{GDBP}) info exceptions const.aint
16730 All Ada exceptions matching regular expression "const.aint":
16731 constraint_error: 0x613da0
16732 const.aint_global_e: 0x613b00
16735 It is also possible to ask @value{GDBN} to stop your program's execution
16736 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16739 @subsubsection Extensions for Ada Tasks
16740 @cindex Ada, tasking
16742 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16743 @value{GDBN} provides the following task-related commands:
16748 This command shows a list of current Ada tasks, as in the following example:
16755 (@value{GDBP}) info tasks
16756 ID TID P-ID Pri State Name
16757 1 8088000 0 15 Child Activation Wait main_task
16758 2 80a4000 1 15 Accept Statement b
16759 3 809a800 1 15 Child Activation Wait a
16760 * 4 80ae800 3 15 Runnable c
16765 In this listing, the asterisk before the last task indicates it to be the
16766 task currently being inspected.
16770 Represents @value{GDBN}'s internal task number.
16776 The parent's task ID (@value{GDBN}'s internal task number).
16779 The base priority of the task.
16782 Current state of the task.
16786 The task has been created but has not been activated. It cannot be
16790 The task is not blocked for any reason known to Ada. (It may be waiting
16791 for a mutex, though.) It is conceptually "executing" in normal mode.
16794 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16795 that were waiting on terminate alternatives have been awakened and have
16796 terminated themselves.
16798 @item Child Activation Wait
16799 The task is waiting for created tasks to complete activation.
16801 @item Accept Statement
16802 The task is waiting on an accept or selective wait statement.
16804 @item Waiting on entry call
16805 The task is waiting on an entry call.
16807 @item Async Select Wait
16808 The task is waiting to start the abortable part of an asynchronous
16812 The task is waiting on a select statement with only a delay
16815 @item Child Termination Wait
16816 The task is sleeping having completed a master within itself, and is
16817 waiting for the tasks dependent on that master to become terminated or
16818 waiting on a terminate Phase.
16820 @item Wait Child in Term Alt
16821 The task is sleeping waiting for tasks on terminate alternatives to
16822 finish terminating.
16824 @item Accepting RV with @var{taskno}
16825 The task is accepting a rendez-vous with the task @var{taskno}.
16829 Name of the task in the program.
16833 @kindex info task @var{taskno}
16834 @item info task @var{taskno}
16835 This command shows detailled informations on the specified task, as in
16836 the following example:
16841 (@value{GDBP}) info tasks
16842 ID TID P-ID Pri State Name
16843 1 8077880 0 15 Child Activation Wait main_task
16844 * 2 807c468 1 15 Runnable task_1
16845 (@value{GDBP}) info task 2
16846 Ada Task: 0x807c468
16849 Parent: 1 (main_task)
16855 @kindex task@r{ (Ada)}
16856 @cindex current Ada task ID
16857 This command prints the ID of the current task.
16863 (@value{GDBP}) info tasks
16864 ID TID P-ID Pri State Name
16865 1 8077870 0 15 Child Activation Wait main_task
16866 * 2 807c458 1 15 Runnable t
16867 (@value{GDBP}) task
16868 [Current task is 2]
16871 @item task @var{taskno}
16872 @cindex Ada task switching
16873 This command is like the @code{thread @var{thread-id}}
16874 command (@pxref{Threads}). It switches the context of debugging
16875 from the current task to the given task.
16881 (@value{GDBP}) info tasks
16882 ID TID P-ID Pri State Name
16883 1 8077870 0 15 Child Activation Wait main_task
16884 * 2 807c458 1 15 Runnable t
16885 (@value{GDBP}) task 1
16886 [Switching to task 1]
16887 #0 0x8067726 in pthread_cond_wait ()
16889 #0 0x8067726 in pthread_cond_wait ()
16890 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16891 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16892 #3 0x806153e in system.tasking.stages.activate_tasks ()
16893 #4 0x804aacc in un () at un.adb:5
16896 @item break @var{location} task @var{taskno}
16897 @itemx break @var{location} task @var{taskno} if @dots{}
16898 @cindex breakpoints and tasks, in Ada
16899 @cindex task breakpoints, in Ada
16900 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16901 These commands are like the @code{break @dots{} thread @dots{}}
16902 command (@pxref{Thread Stops}). The
16903 @var{location} argument specifies source lines, as described
16904 in @ref{Specify Location}.
16906 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16907 to specify that you only want @value{GDBN} to stop the program when a
16908 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16909 numeric task identifiers assigned by @value{GDBN}, shown in the first
16910 column of the @samp{info tasks} display.
16912 If you do not specify @samp{task @var{taskno}} when you set a
16913 breakpoint, the breakpoint applies to @emph{all} tasks of your
16916 You can use the @code{task} qualifier on conditional breakpoints as
16917 well; in this case, place @samp{task @var{taskno}} before the
16918 breakpoint condition (before the @code{if}).
16926 (@value{GDBP}) info tasks
16927 ID TID P-ID Pri State Name
16928 1 140022020 0 15 Child Activation Wait main_task
16929 2 140045060 1 15 Accept/Select Wait t2
16930 3 140044840 1 15 Runnable t1
16931 * 4 140056040 1 15 Runnable t3
16932 (@value{GDBP}) b 15 task 2
16933 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16934 (@value{GDBP}) cont
16939 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16941 (@value{GDBP}) info tasks
16942 ID TID P-ID Pri State Name
16943 1 140022020 0 15 Child Activation Wait main_task
16944 * 2 140045060 1 15 Runnable t2
16945 3 140044840 1 15 Runnable t1
16946 4 140056040 1 15 Delay Sleep t3
16950 @node Ada Tasks and Core Files
16951 @subsubsection Tasking Support when Debugging Core Files
16952 @cindex Ada tasking and core file debugging
16954 When inspecting a core file, as opposed to debugging a live program,
16955 tasking support may be limited or even unavailable, depending on
16956 the platform being used.
16957 For instance, on x86-linux, the list of tasks is available, but task
16958 switching is not supported.
16960 On certain platforms, the debugger needs to perform some
16961 memory writes in order to provide Ada tasking support. When inspecting
16962 a core file, this means that the core file must be opened with read-write
16963 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16964 Under these circumstances, you should make a backup copy of the core
16965 file before inspecting it with @value{GDBN}.
16967 @node Ravenscar Profile
16968 @subsubsection Tasking Support when using the Ravenscar Profile
16969 @cindex Ravenscar Profile
16971 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16972 specifically designed for systems with safety-critical real-time
16976 @kindex set ravenscar task-switching on
16977 @cindex task switching with program using Ravenscar Profile
16978 @item set ravenscar task-switching on
16979 Allows task switching when debugging a program that uses the Ravenscar
16980 Profile. This is the default.
16982 @kindex set ravenscar task-switching off
16983 @item set ravenscar task-switching off
16984 Turn off task switching when debugging a program that uses the Ravenscar
16985 Profile. This is mostly intended to disable the code that adds support
16986 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16987 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16988 To be effective, this command should be run before the program is started.
16990 @kindex show ravenscar task-switching
16991 @item show ravenscar task-switching
16992 Show whether it is possible to switch from task to task in a program
16993 using the Ravenscar Profile.
16998 @subsubsection Ada Settings
16999 @cindex Ada settings
17002 @kindex set varsize-limit
17003 @item set varsize-limit @var{size}
17004 Prevent @value{GDBN} from attempting to evaluate objects whose size
17005 is above the given limit (@var{size}) when those sizes are computed
17006 from run-time quantities. This is typically the case when the object
17007 has a variable size, such as an array whose bounds are not known at
17008 compile time for example. Setting @var{size} to @code{unlimited}
17009 removes the size limitation. By default, the limit is about 65KB.
17011 The purpose of having such a limit is to prevent @value{GDBN} from
17012 trying to grab enormous chunks of virtual memory when asked to evaluate
17013 a quantity whose bounds have been corrupted or have not yet been fully
17014 initialized. The limit applies to the results of some subexpressions
17015 as well as to complete expressions. For example, an expression denoting
17016 a simple integer component, such as @code{x.y.z}, may fail if the size of
17017 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17018 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17019 @code{A} is an array variable with non-constant size, will generally
17020 succeed regardless of the bounds on @code{A}, as long as the component
17021 size is less than @var{size}.
17023 @kindex show varsize-limit
17024 @item show varsize-limit
17025 Show the limit on types whose size is determined by run-time quantities.
17029 @subsubsection Known Peculiarities of Ada Mode
17030 @cindex Ada, problems
17032 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17033 we know of several problems with and limitations of Ada mode in
17035 some of which will be fixed with planned future releases of the debugger
17036 and the GNU Ada compiler.
17040 Static constants that the compiler chooses not to materialize as objects in
17041 storage are invisible to the debugger.
17044 Named parameter associations in function argument lists are ignored (the
17045 argument lists are treated as positional).
17048 Many useful library packages are currently invisible to the debugger.
17051 Fixed-point arithmetic, conversions, input, and output is carried out using
17052 floating-point arithmetic, and may give results that only approximate those on
17056 The GNAT compiler never generates the prefix @code{Standard} for any of
17057 the standard symbols defined by the Ada language. @value{GDBN} knows about
17058 this: it will strip the prefix from names when you use it, and will never
17059 look for a name you have so qualified among local symbols, nor match against
17060 symbols in other packages or subprograms. If you have
17061 defined entities anywhere in your program other than parameters and
17062 local variables whose simple names match names in @code{Standard},
17063 GNAT's lack of qualification here can cause confusion. When this happens,
17064 you can usually resolve the confusion
17065 by qualifying the problematic names with package
17066 @code{Standard} explicitly.
17069 Older versions of the compiler sometimes generate erroneous debugging
17070 information, resulting in the debugger incorrectly printing the value
17071 of affected entities. In some cases, the debugger is able to work
17072 around an issue automatically. In other cases, the debugger is able
17073 to work around the issue, but the work-around has to be specifically
17076 @kindex set ada trust-PAD-over-XVS
17077 @kindex show ada trust-PAD-over-XVS
17080 @item set ada trust-PAD-over-XVS on
17081 Configure GDB to strictly follow the GNAT encoding when computing the
17082 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17083 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17084 a complete description of the encoding used by the GNAT compiler).
17085 This is the default.
17087 @item set ada trust-PAD-over-XVS off
17088 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17089 sometimes prints the wrong value for certain entities, changing @code{ada
17090 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17091 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17092 @code{off}, but this incurs a slight performance penalty, so it is
17093 recommended to leave this setting to @code{on} unless necessary.
17097 @cindex GNAT descriptive types
17098 @cindex GNAT encoding
17099 Internally, the debugger also relies on the compiler following a number
17100 of conventions known as the @samp{GNAT Encoding}, all documented in
17101 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17102 how the debugging information should be generated for certain types.
17103 In particular, this convention makes use of @dfn{descriptive types},
17104 which are artificial types generated purely to help the debugger.
17106 These encodings were defined at a time when the debugging information
17107 format used was not powerful enough to describe some of the more complex
17108 types available in Ada. Since DWARF allows us to express nearly all
17109 Ada features, the long-term goal is to slowly replace these descriptive
17110 types by their pure DWARF equivalent. To facilitate that transition,
17111 a new maintenance option is available to force the debugger to ignore
17112 those descriptive types. It allows the user to quickly evaluate how
17113 well @value{GDBN} works without them.
17117 @kindex maint ada set ignore-descriptive-types
17118 @item maintenance ada set ignore-descriptive-types [on|off]
17119 Control whether the debugger should ignore descriptive types.
17120 The default is not to ignore descriptives types (@code{off}).
17122 @kindex maint ada show ignore-descriptive-types
17123 @item maintenance ada show ignore-descriptive-types
17124 Show if descriptive types are ignored by @value{GDBN}.
17128 @node Unsupported Languages
17129 @section Unsupported Languages
17131 @cindex unsupported languages
17132 @cindex minimal language
17133 In addition to the other fully-supported programming languages,
17134 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17135 It does not represent a real programming language, but provides a set
17136 of capabilities close to what the C or assembly languages provide.
17137 This should allow most simple operations to be performed while debugging
17138 an application that uses a language currently not supported by @value{GDBN}.
17140 If the language is set to @code{auto}, @value{GDBN} will automatically
17141 select this language if the current frame corresponds to an unsupported
17145 @chapter Examining the Symbol Table
17147 The commands described in this chapter allow you to inquire about the
17148 symbols (names of variables, functions and types) defined in your
17149 program. This information is inherent in the text of your program and
17150 does not change as your program executes. @value{GDBN} finds it in your
17151 program's symbol table, in the file indicated when you started @value{GDBN}
17152 (@pxref{File Options, ,Choosing Files}), or by one of the
17153 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17155 @cindex symbol names
17156 @cindex names of symbols
17157 @cindex quoting names
17158 @anchor{quoting names}
17159 Occasionally, you may need to refer to symbols that contain unusual
17160 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17161 most frequent case is in referring to static variables in other
17162 source files (@pxref{Variables,,Program Variables}). File names
17163 are recorded in object files as debugging symbols, but @value{GDBN} would
17164 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17165 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17166 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17173 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17176 @cindex case-insensitive symbol names
17177 @cindex case sensitivity in symbol names
17178 @kindex set case-sensitive
17179 @item set case-sensitive on
17180 @itemx set case-sensitive off
17181 @itemx set case-sensitive auto
17182 Normally, when @value{GDBN} looks up symbols, it matches their names
17183 with case sensitivity determined by the current source language.
17184 Occasionally, you may wish to control that. The command @code{set
17185 case-sensitive} lets you do that by specifying @code{on} for
17186 case-sensitive matches or @code{off} for case-insensitive ones. If
17187 you specify @code{auto}, case sensitivity is reset to the default
17188 suitable for the source language. The default is case-sensitive
17189 matches for all languages except for Fortran, for which the default is
17190 case-insensitive matches.
17192 @kindex show case-sensitive
17193 @item show case-sensitive
17194 This command shows the current setting of case sensitivity for symbols
17197 @kindex set print type methods
17198 @item set print type methods
17199 @itemx set print type methods on
17200 @itemx set print type methods off
17201 Normally, when @value{GDBN} prints a class, it displays any methods
17202 declared in that class. You can control this behavior either by
17203 passing the appropriate flag to @code{ptype}, or using @command{set
17204 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17205 display the methods; this is the default. Specifying @code{off} will
17206 cause @value{GDBN} to omit the methods.
17208 @kindex show print type methods
17209 @item show print type methods
17210 This command shows the current setting of method display when printing
17213 @kindex set print type nested-type-limit
17214 @item set print type nested-type-limit @var{limit}
17215 @itemx set print type nested-type-limit unlimited
17216 Set the limit of displayed nested types that the type printer will
17217 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17218 nested definitions. By default, the type printer will not show any nested
17219 types defined in classes.
17221 @kindex show print type nested-type-limit
17222 @item show print type nested-type-limit
17223 This command shows the current display limit of nested types when
17226 @kindex set print type typedefs
17227 @item set print type typedefs
17228 @itemx set print type typedefs on
17229 @itemx set print type typedefs off
17231 Normally, when @value{GDBN} prints a class, it displays any typedefs
17232 defined in that class. You can control this behavior either by
17233 passing the appropriate flag to @code{ptype}, or using @command{set
17234 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17235 display the typedef definitions; this is the default. Specifying
17236 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17237 Note that this controls whether the typedef definition itself is
17238 printed, not whether typedef names are substituted when printing other
17241 @kindex show print type typedefs
17242 @item show print type typedefs
17243 This command shows the current setting of typedef display when
17246 @kindex info address
17247 @cindex address of a symbol
17248 @item info address @var{symbol}
17249 Describe where the data for @var{symbol} is stored. For a register
17250 variable, this says which register it is kept in. For a non-register
17251 local variable, this prints the stack-frame offset at which the variable
17254 Note the contrast with @samp{print &@var{symbol}}, which does not work
17255 at all for a register variable, and for a stack local variable prints
17256 the exact address of the current instantiation of the variable.
17258 @kindex info symbol
17259 @cindex symbol from address
17260 @cindex closest symbol and offset for an address
17261 @item info symbol @var{addr}
17262 Print the name of a symbol which is stored at the address @var{addr}.
17263 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17264 nearest symbol and an offset from it:
17267 (@value{GDBP}) info symbol 0x54320
17268 _initialize_vx + 396 in section .text
17272 This is the opposite of the @code{info address} command. You can use
17273 it to find out the name of a variable or a function given its address.
17275 For dynamically linked executables, the name of executable or shared
17276 library containing the symbol is also printed:
17279 (@value{GDBP}) info symbol 0x400225
17280 _start + 5 in section .text of /tmp/a.out
17281 (@value{GDBP}) info symbol 0x2aaaac2811cf
17282 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17287 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17288 Demangle @var{name}.
17289 If @var{language} is provided it is the name of the language to demangle
17290 @var{name} in. Otherwise @var{name} is demangled in the current language.
17292 The @samp{--} option specifies the end of options,
17293 and is useful when @var{name} begins with a dash.
17295 The parameter @code{demangle-style} specifies how to interpret the kind
17296 of mangling used. @xref{Print Settings}.
17299 @item whatis[/@var{flags}] [@var{arg}]
17300 Print the data type of @var{arg}, which can be either an expression
17301 or a name of a data type. With no argument, print the data type of
17302 @code{$}, the last value in the value history.
17304 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17305 is not actually evaluated, and any side-effecting operations (such as
17306 assignments or function calls) inside it do not take place.
17308 If @var{arg} is a variable or an expression, @code{whatis} prints its
17309 literal type as it is used in the source code. If the type was
17310 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17311 the data type underlying the @code{typedef}. If the type of the
17312 variable or the expression is a compound data type, such as
17313 @code{struct} or @code{class}, @code{whatis} never prints their
17314 fields or methods. It just prints the @code{struct}/@code{class}
17315 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17316 such a compound data type, use @code{ptype}.
17318 If @var{arg} is a type name that was defined using @code{typedef},
17319 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17320 Unrolling means that @code{whatis} will show the underlying type used
17321 in the @code{typedef} declaration of @var{arg}. However, if that
17322 underlying type is also a @code{typedef}, @code{whatis} will not
17325 For C code, the type names may also have the form @samp{class
17326 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17327 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17329 @var{flags} can be used to modify how the type is displayed.
17330 Available flags are:
17334 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17335 parameters and typedefs defined in a class when printing the class'
17336 members. The @code{/r} flag disables this.
17339 Do not print methods defined in the class.
17342 Print methods defined in the class. This is the default, but the flag
17343 exists in case you change the default with @command{set print type methods}.
17346 Do not print typedefs defined in the class. Note that this controls
17347 whether the typedef definition itself is printed, not whether typedef
17348 names are substituted when printing other types.
17351 Print typedefs defined in the class. This is the default, but the flag
17352 exists in case you change the default with @command{set print type typedefs}.
17355 Print the offsets and sizes of fields in a struct, similar to what the
17356 @command{pahole} tool does. This option implies the @code{/tm} flags.
17358 For example, given the following declarations:
17394 Issuing a @kbd{ptype /o struct tuv} command would print:
17397 (@value{GDBP}) ptype /o struct tuv
17398 /* offset | size */ type = struct tuv @{
17399 /* 0 | 4 */ int a1;
17400 /* XXX 4-byte hole */
17401 /* 8 | 8 */ char *a2;
17402 /* 16 | 4 */ int a3;
17404 /* total size (bytes): 24 */
17408 Notice the format of the first column of comments. There, you can
17409 find two parts separated by the @samp{|} character: the @emph{offset},
17410 which indicates where the field is located inside the struct, in
17411 bytes, and the @emph{size} of the field. Another interesting line is
17412 the marker of a @emph{hole} in the struct, indicating that it may be
17413 possible to pack the struct and make it use less space by reorganizing
17416 It is also possible to print offsets inside an union:
17419 (@value{GDBP}) ptype /o union qwe
17420 /* offset | size */ type = union qwe @{
17421 /* 24 */ struct tuv @{
17422 /* 0 | 4 */ int a1;
17423 /* XXX 4-byte hole */
17424 /* 8 | 8 */ char *a2;
17425 /* 16 | 4 */ int a3;
17427 /* total size (bytes): 24 */
17429 /* 40 */ struct xyz @{
17430 /* 0 | 4 */ int f1;
17431 /* 4 | 1 */ char f2;
17432 /* XXX 3-byte hole */
17433 /* 8 | 8 */ void *f3;
17434 /* 16 | 24 */ struct tuv @{
17435 /* 16 | 4 */ int a1;
17436 /* XXX 4-byte hole */
17437 /* 24 | 8 */ char *a2;
17438 /* 32 | 4 */ int a3;
17440 /* total size (bytes): 24 */
17443 /* total size (bytes): 40 */
17446 /* total size (bytes): 40 */
17450 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17451 same space (because we are dealing with an union), the offset is not
17452 printed for them. However, you can still examine the offset of each
17453 of these structures' fields.
17455 Another useful scenario is printing the offsets of a struct containing
17459 (@value{GDBP}) ptype /o struct tyu
17460 /* offset | size */ type = struct tyu @{
17461 /* 0:31 | 4 */ int a1 : 1;
17462 /* 0:28 | 4 */ int a2 : 3;
17463 /* 0: 5 | 4 */ int a3 : 23;
17464 /* 3: 3 | 1 */ signed char a4 : 2;
17465 /* XXX 3-bit hole */
17466 /* XXX 4-byte hole */
17467 /* 8 | 8 */ int64_t a5;
17468 /* 16:27 | 4 */ int a6 : 5;
17469 /* 16:56 | 8 */ int64_t a7 : 3;
17471 /* total size (bytes): 24 */
17475 Note how the offset information is now extended to also include how
17476 many bits are left to be used in each bitfield.
17480 @item ptype[/@var{flags}] [@var{arg}]
17481 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17482 detailed description of the type, instead of just the name of the type.
17483 @xref{Expressions, ,Expressions}.
17485 Contrary to @code{whatis}, @code{ptype} always unrolls any
17486 @code{typedef}s in its argument declaration, whether the argument is
17487 a variable, expression, or a data type. This means that @code{ptype}
17488 of a variable or an expression will not print literally its type as
17489 present in the source code---use @code{whatis} for that. @code{typedef}s at
17490 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17491 fields, methods and inner @code{class typedef}s of @code{struct}s,
17492 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17494 For example, for this variable declaration:
17497 typedef double real_t;
17498 struct complex @{ real_t real; double imag; @};
17499 typedef struct complex complex_t;
17501 real_t *real_pointer_var;
17505 the two commands give this output:
17509 (@value{GDBP}) whatis var
17511 (@value{GDBP}) ptype var
17512 type = struct complex @{
17516 (@value{GDBP}) whatis complex_t
17517 type = struct complex
17518 (@value{GDBP}) whatis struct complex
17519 type = struct complex
17520 (@value{GDBP}) ptype struct complex
17521 type = struct complex @{
17525 (@value{GDBP}) whatis real_pointer_var
17527 (@value{GDBP}) ptype real_pointer_var
17533 As with @code{whatis}, using @code{ptype} without an argument refers to
17534 the type of @code{$}, the last value in the value history.
17536 @cindex incomplete type
17537 Sometimes, programs use opaque data types or incomplete specifications
17538 of complex data structure. If the debug information included in the
17539 program does not allow @value{GDBN} to display a full declaration of
17540 the data type, it will say @samp{<incomplete type>}. For example,
17541 given these declarations:
17545 struct foo *fooptr;
17549 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17552 (@value{GDBP}) ptype foo
17553 $1 = <incomplete type>
17557 ``Incomplete type'' is C terminology for data types that are not
17558 completely specified.
17560 @cindex unknown type
17561 Othertimes, information about a variable's type is completely absent
17562 from the debug information included in the program. This most often
17563 happens when the program or library where the variable is defined
17564 includes no debug information at all. @value{GDBN} knows the variable
17565 exists from inspecting the linker/loader symbol table (e.g., the ELF
17566 dynamic symbol table), but such symbols do not contain type
17567 information. Inspecting the type of a (global) variable for which
17568 @value{GDBN} has no type information shows:
17571 (@value{GDBP}) ptype var
17572 type = <data variable, no debug info>
17575 @xref{Variables, no debug info variables}, for how to print the values
17579 @item info types @var{regexp}
17581 Print a brief description of all types whose names match the regular
17582 expression @var{regexp} (or all types in your program, if you supply
17583 no argument). Each complete typename is matched as though it were a
17584 complete line; thus, @samp{i type value} gives information on all
17585 types in your program whose names include the string @code{value}, but
17586 @samp{i type ^value$} gives information only on types whose complete
17587 name is @code{value}.
17589 This command differs from @code{ptype} in two ways: first, like
17590 @code{whatis}, it does not print a detailed description; second, it
17591 lists all source files and line numbers where a type is defined.
17593 @kindex info type-printers
17594 @item info type-printers
17595 Versions of @value{GDBN} that ship with Python scripting enabled may
17596 have ``type printers'' available. When using @command{ptype} or
17597 @command{whatis}, these printers are consulted when the name of a type
17598 is needed. @xref{Type Printing API}, for more information on writing
17601 @code{info type-printers} displays all the available type printers.
17603 @kindex enable type-printer
17604 @kindex disable type-printer
17605 @item enable type-printer @var{name}@dots{}
17606 @item disable type-printer @var{name}@dots{}
17607 These commands can be used to enable or disable type printers.
17610 @cindex local variables
17611 @item info scope @var{location}
17612 List all the variables local to a particular scope. This command
17613 accepts a @var{location} argument---a function name, a source line, or
17614 an address preceded by a @samp{*}, and prints all the variables local
17615 to the scope defined by that location. (@xref{Specify Location}, for
17616 details about supported forms of @var{location}.) For example:
17619 (@value{GDBP}) @b{info scope command_line_handler}
17620 Scope for command_line_handler:
17621 Symbol rl is an argument at stack/frame offset 8, length 4.
17622 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17623 Symbol linelength is in static storage at address 0x150a1c, length 4.
17624 Symbol p is a local variable in register $esi, length 4.
17625 Symbol p1 is a local variable in register $ebx, length 4.
17626 Symbol nline is a local variable in register $edx, length 4.
17627 Symbol repeat is a local variable at frame offset -8, length 4.
17631 This command is especially useful for determining what data to collect
17632 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17635 @kindex info source
17637 Show information about the current source file---that is, the source file for
17638 the function containing the current point of execution:
17641 the name of the source file, and the directory containing it,
17643 the directory it was compiled in,
17645 its length, in lines,
17647 which programming language it is written in,
17649 if the debug information provides it, the program that compiled the file
17650 (which may include, e.g., the compiler version and command line arguments),
17652 whether the executable includes debugging information for that file, and
17653 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17655 whether the debugging information includes information about
17656 preprocessor macros.
17660 @kindex info sources
17662 Print the names of all source files in your program for which there is
17663 debugging information, organized into two lists: files whose symbols
17664 have already been read, and files whose symbols will be read when needed.
17666 @kindex info functions
17667 @item info functions
17668 Print the names and data types of all defined functions.
17669 Similarly to @samp{info types}, this command groups its output by source
17670 files and annotates each function definition with its source line
17673 @item info functions @var{regexp}
17674 Like @samp{info functions}, but only print the names and data types of
17675 functions whose names contain a match for regular expression
17676 @var{regexp}. Thus, @samp{info fun step} finds all functions whose
17677 names include @code{step}; @samp{info fun ^step} finds those whose names
17678 start with @code{step}. If a function name contains characters that
17679 conflict with the regular expression language (e.g.@:
17680 @samp{operator*()}), they may be quoted with a backslash.
17682 @kindex info variables
17683 @item info variables
17684 Print the names and data types of all variables that are defined
17685 outside of functions (i.e.@: excluding local variables).
17686 The printed variables are grouped by source files and annotated with
17687 their respective source line numbers.
17689 @item info variables @var{regexp}
17690 Like @kbd{info variables}, but only print the names and data types of
17691 non-local variables whose names contain a match for regular expression
17694 @kindex info classes
17695 @cindex Objective-C, classes and selectors
17697 @itemx info classes @var{regexp}
17698 Display all Objective-C classes in your program, or
17699 (with the @var{regexp} argument) all those matching a particular regular
17702 @kindex info selectors
17703 @item info selectors
17704 @itemx info selectors @var{regexp}
17705 Display all Objective-C selectors in your program, or
17706 (with the @var{regexp} argument) all those matching a particular regular
17710 This was never implemented.
17711 @kindex info methods
17713 @itemx info methods @var{regexp}
17714 The @code{info methods} command permits the user to examine all defined
17715 methods within C@t{++} program, or (with the @var{regexp} argument) a
17716 specific set of methods found in the various C@t{++} classes. Many
17717 C@t{++} classes provide a large number of methods. Thus, the output
17718 from the @code{ptype} command can be overwhelming and hard to use. The
17719 @code{info-methods} command filters the methods, printing only those
17720 which match the regular-expression @var{regexp}.
17723 @cindex opaque data types
17724 @kindex set opaque-type-resolution
17725 @item set opaque-type-resolution on
17726 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17727 declared as a pointer to a @code{struct}, @code{class}, or
17728 @code{union}---for example, @code{struct MyType *}---that is used in one
17729 source file although the full declaration of @code{struct MyType} is in
17730 another source file. The default is on.
17732 A change in the setting of this subcommand will not take effect until
17733 the next time symbols for a file are loaded.
17735 @item set opaque-type-resolution off
17736 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17737 is printed as follows:
17739 @{<no data fields>@}
17742 @kindex show opaque-type-resolution
17743 @item show opaque-type-resolution
17744 Show whether opaque types are resolved or not.
17746 @kindex set print symbol-loading
17747 @cindex print messages when symbols are loaded
17748 @item set print symbol-loading
17749 @itemx set print symbol-loading full
17750 @itemx set print symbol-loading brief
17751 @itemx set print symbol-loading off
17752 The @code{set print symbol-loading} command allows you to control the
17753 printing of messages when @value{GDBN} loads symbol information.
17754 By default a message is printed for the executable and one for each
17755 shared library, and normally this is what you want. However, when
17756 debugging apps with large numbers of shared libraries these messages
17758 When set to @code{brief} a message is printed for each executable,
17759 and when @value{GDBN} loads a collection of shared libraries at once
17760 it will only print one message regardless of the number of shared
17761 libraries. When set to @code{off} no messages are printed.
17763 @kindex show print symbol-loading
17764 @item show print symbol-loading
17765 Show whether messages will be printed when a @value{GDBN} command
17766 entered from the keyboard causes symbol information to be loaded.
17768 @kindex maint print symbols
17769 @cindex symbol dump
17770 @kindex maint print psymbols
17771 @cindex partial symbol dump
17772 @kindex maint print msymbols
17773 @cindex minimal symbol dump
17774 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17775 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17776 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17777 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17778 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17779 Write a dump of debugging symbol data into the file @var{filename} or
17780 the terminal if @var{filename} is unspecified.
17781 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17783 If @code{-pc @var{address}} is specified, only dump symbols for the file
17784 with code at that address. Note that @var{address} may be a symbol like
17786 If @code{-source @var{source}} is specified, only dump symbols for that
17789 These commands are used to debug the @value{GDBN} symbol-reading code.
17790 These commands do not modify internal @value{GDBN} state, therefore
17791 @samp{maint print symbols} will only print symbols for already expanded symbol
17793 You can use the command @code{info sources} to find out which files these are.
17794 If you use @samp{maint print psymbols} instead, the dump shows information
17795 about symbols that @value{GDBN} only knows partially---that is, symbols
17796 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17797 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17800 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17801 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17803 @kindex maint info symtabs
17804 @kindex maint info psymtabs
17805 @cindex listing @value{GDBN}'s internal symbol tables
17806 @cindex symbol tables, listing @value{GDBN}'s internal
17807 @cindex full symbol tables, listing @value{GDBN}'s internal
17808 @cindex partial symbol tables, listing @value{GDBN}'s internal
17809 @item maint info symtabs @r{[} @var{regexp} @r{]}
17810 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17812 List the @code{struct symtab} or @code{struct partial_symtab}
17813 structures whose names match @var{regexp}. If @var{regexp} is not
17814 given, list them all. The output includes expressions which you can
17815 copy into a @value{GDBN} debugging this one to examine a particular
17816 structure in more detail. For example:
17819 (@value{GDBP}) maint info psymtabs dwarf2read
17820 @{ objfile /home/gnu/build/gdb/gdb
17821 ((struct objfile *) 0x82e69d0)
17822 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17823 ((struct partial_symtab *) 0x8474b10)
17826 text addresses 0x814d3c8 -- 0x8158074
17827 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17828 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17829 dependencies (none)
17832 (@value{GDBP}) maint info symtabs
17836 We see that there is one partial symbol table whose filename contains
17837 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17838 and we see that @value{GDBN} has not read in any symtabs yet at all.
17839 If we set a breakpoint on a function, that will cause @value{GDBN} to
17840 read the symtab for the compilation unit containing that function:
17843 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17844 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17846 (@value{GDBP}) maint info symtabs
17847 @{ objfile /home/gnu/build/gdb/gdb
17848 ((struct objfile *) 0x82e69d0)
17849 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17850 ((struct symtab *) 0x86c1f38)
17853 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17854 linetable ((struct linetable *) 0x8370fa0)
17855 debugformat DWARF 2
17861 @kindex maint info line-table
17862 @cindex listing @value{GDBN}'s internal line tables
17863 @cindex line tables, listing @value{GDBN}'s internal
17864 @item maint info line-table @r{[} @var{regexp} @r{]}
17866 List the @code{struct linetable} from all @code{struct symtab}
17867 instances whose name matches @var{regexp}. If @var{regexp} is not
17868 given, list the @code{struct linetable} from all @code{struct symtab}.
17870 @kindex maint set symbol-cache-size
17871 @cindex symbol cache size
17872 @item maint set symbol-cache-size @var{size}
17873 Set the size of the symbol cache to @var{size}.
17874 The default size is intended to be good enough for debugging
17875 most applications. This option exists to allow for experimenting
17876 with different sizes.
17878 @kindex maint show symbol-cache-size
17879 @item maint show symbol-cache-size
17880 Show the size of the symbol cache.
17882 @kindex maint print symbol-cache
17883 @cindex symbol cache, printing its contents
17884 @item maint print symbol-cache
17885 Print the contents of the symbol cache.
17886 This is useful when debugging symbol cache issues.
17888 @kindex maint print symbol-cache-statistics
17889 @cindex symbol cache, printing usage statistics
17890 @item maint print symbol-cache-statistics
17891 Print symbol cache usage statistics.
17892 This helps determine how well the cache is being utilized.
17894 @kindex maint flush-symbol-cache
17895 @cindex symbol cache, flushing
17896 @item maint flush-symbol-cache
17897 Flush the contents of the symbol cache, all entries are removed.
17898 This command is useful when debugging the symbol cache.
17899 It is also useful when collecting performance data.
17904 @chapter Altering Execution
17906 Once you think you have found an error in your program, you might want to
17907 find out for certain whether correcting the apparent error would lead to
17908 correct results in the rest of the run. You can find the answer by
17909 experiment, using the @value{GDBN} features for altering execution of the
17912 For example, you can store new values into variables or memory
17913 locations, give your program a signal, restart it at a different
17914 address, or even return prematurely from a function.
17917 * Assignment:: Assignment to variables
17918 * Jumping:: Continuing at a different address
17919 * Signaling:: Giving your program a signal
17920 * Returning:: Returning from a function
17921 * Calling:: Calling your program's functions
17922 * Patching:: Patching your program
17923 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17927 @section Assignment to Variables
17930 @cindex setting variables
17931 To alter the value of a variable, evaluate an assignment expression.
17932 @xref{Expressions, ,Expressions}. For example,
17939 stores the value 4 into the variable @code{x}, and then prints the
17940 value of the assignment expression (which is 4).
17941 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17942 information on operators in supported languages.
17944 @kindex set variable
17945 @cindex variables, setting
17946 If you are not interested in seeing the value of the assignment, use the
17947 @code{set} command instead of the @code{print} command. @code{set} is
17948 really the same as @code{print} except that the expression's value is
17949 not printed and is not put in the value history (@pxref{Value History,
17950 ,Value History}). The expression is evaluated only for its effects.
17952 If the beginning of the argument string of the @code{set} command
17953 appears identical to a @code{set} subcommand, use the @code{set
17954 variable} command instead of just @code{set}. This command is identical
17955 to @code{set} except for its lack of subcommands. For example, if your
17956 program has a variable @code{width}, you get an error if you try to set
17957 a new value with just @samp{set width=13}, because @value{GDBN} has the
17958 command @code{set width}:
17961 (@value{GDBP}) whatis width
17963 (@value{GDBP}) p width
17965 (@value{GDBP}) set width=47
17966 Invalid syntax in expression.
17970 The invalid expression, of course, is @samp{=47}. In
17971 order to actually set the program's variable @code{width}, use
17974 (@value{GDBP}) set var width=47
17977 Because the @code{set} command has many subcommands that can conflict
17978 with the names of program variables, it is a good idea to use the
17979 @code{set variable} command instead of just @code{set}. For example, if
17980 your program has a variable @code{g}, you run into problems if you try
17981 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17982 the command @code{set gnutarget}, abbreviated @code{set g}:
17986 (@value{GDBP}) whatis g
17990 (@value{GDBP}) set g=4
17994 The program being debugged has been started already.
17995 Start it from the beginning? (y or n) y
17996 Starting program: /home/smith/cc_progs/a.out
17997 "/home/smith/cc_progs/a.out": can't open to read symbols:
17998 Invalid bfd target.
17999 (@value{GDBP}) show g
18000 The current BFD target is "=4".
18005 The program variable @code{g} did not change, and you silently set the
18006 @code{gnutarget} to an invalid value. In order to set the variable
18010 (@value{GDBP}) set var g=4
18013 @value{GDBN} allows more implicit conversions in assignments than C; you can
18014 freely store an integer value into a pointer variable or vice versa,
18015 and you can convert any structure to any other structure that is the
18016 same length or shorter.
18017 @comment FIXME: how do structs align/pad in these conversions?
18018 @comment /doc@cygnus.com 18dec1990
18020 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18021 construct to generate a value of specified type at a specified address
18022 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18023 to memory location @code{0x83040} as an integer (which implies a certain size
18024 and representation in memory), and
18027 set @{int@}0x83040 = 4
18031 stores the value 4 into that memory location.
18034 @section Continuing at a Different Address
18036 Ordinarily, when you continue your program, you do so at the place where
18037 it stopped, with the @code{continue} command. You can instead continue at
18038 an address of your own choosing, with the following commands:
18042 @kindex j @r{(@code{jump})}
18043 @item jump @var{location}
18044 @itemx j @var{location}
18045 Resume execution at @var{location}. Execution stops again immediately
18046 if there is a breakpoint there. @xref{Specify Location}, for a description
18047 of the different forms of @var{location}. It is common
18048 practice to use the @code{tbreak} command in conjunction with
18049 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18051 The @code{jump} command does not change the current stack frame, or
18052 the stack pointer, or the contents of any memory location or any
18053 register other than the program counter. If @var{location} is in
18054 a different function from the one currently executing, the results may
18055 be bizarre if the two functions expect different patterns of arguments or
18056 of local variables. For this reason, the @code{jump} command requests
18057 confirmation if the specified line is not in the function currently
18058 executing. However, even bizarre results are predictable if you are
18059 well acquainted with the machine-language code of your program.
18062 On many systems, you can get much the same effect as the @code{jump}
18063 command by storing a new value into the register @code{$pc}. The
18064 difference is that this does not start your program running; it only
18065 changes the address of where it @emph{will} run when you continue. For
18073 makes the next @code{continue} command or stepping command execute at
18074 address @code{0x485}, rather than at the address where your program stopped.
18075 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18077 The most common occasion to use the @code{jump} command is to back
18078 up---perhaps with more breakpoints set---over a portion of a program
18079 that has already executed, in order to examine its execution in more
18084 @section Giving your Program a Signal
18085 @cindex deliver a signal to a program
18089 @item signal @var{signal}
18090 Resume execution where your program is stopped, but immediately give it the
18091 signal @var{signal}. The @var{signal} can be the name or the number of a
18092 signal. For example, on many systems @code{signal 2} and @code{signal
18093 SIGINT} are both ways of sending an interrupt signal.
18095 Alternatively, if @var{signal} is zero, continue execution without
18096 giving a signal. This is useful when your program stopped on account of
18097 a signal and would ordinarily see the signal when resumed with the
18098 @code{continue} command; @samp{signal 0} causes it to resume without a
18101 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18102 delivered to the currently selected thread, not the thread that last
18103 reported a stop. This includes the situation where a thread was
18104 stopped due to a signal. So if you want to continue execution
18105 suppressing the signal that stopped a thread, you should select that
18106 same thread before issuing the @samp{signal 0} command. If you issue
18107 the @samp{signal 0} command with another thread as the selected one,
18108 @value{GDBN} detects that and asks for confirmation.
18110 Invoking the @code{signal} command is not the same as invoking the
18111 @code{kill} utility from the shell. Sending a signal with @code{kill}
18112 causes @value{GDBN} to decide what to do with the signal depending on
18113 the signal handling tables (@pxref{Signals}). The @code{signal} command
18114 passes the signal directly to your program.
18116 @code{signal} does not repeat when you press @key{RET} a second time
18117 after executing the command.
18119 @kindex queue-signal
18120 @item queue-signal @var{signal}
18121 Queue @var{signal} to be delivered immediately to the current thread
18122 when execution of the thread resumes. The @var{signal} can be the name or
18123 the number of a signal. For example, on many systems @code{signal 2} and
18124 @code{signal SIGINT} are both ways of sending an interrupt signal.
18125 The handling of the signal must be set to pass the signal to the program,
18126 otherwise @value{GDBN} will report an error.
18127 You can control the handling of signals from @value{GDBN} with the
18128 @code{handle} command (@pxref{Signals}).
18130 Alternatively, if @var{signal} is zero, any currently queued signal
18131 for the current thread is discarded and when execution resumes no signal
18132 will be delivered. This is useful when your program stopped on account
18133 of a signal and would ordinarily see the signal when resumed with the
18134 @code{continue} command.
18136 This command differs from the @code{signal} command in that the signal
18137 is just queued, execution is not resumed. And @code{queue-signal} cannot
18138 be used to pass a signal whose handling state has been set to @code{nopass}
18143 @xref{stepping into signal handlers}, for information on how stepping
18144 commands behave when the thread has a signal queued.
18147 @section Returning from a Function
18150 @cindex returning from a function
18153 @itemx return @var{expression}
18154 You can cancel execution of a function call with the @code{return}
18155 command. If you give an
18156 @var{expression} argument, its value is used as the function's return
18160 When you use @code{return}, @value{GDBN} discards the selected stack frame
18161 (and all frames within it). You can think of this as making the
18162 discarded frame return prematurely. If you wish to specify a value to
18163 be returned, give that value as the argument to @code{return}.
18165 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18166 Frame}), and any other frames inside of it, leaving its caller as the
18167 innermost remaining frame. That frame becomes selected. The
18168 specified value is stored in the registers used for returning values
18171 The @code{return} command does not resume execution; it leaves the
18172 program stopped in the state that would exist if the function had just
18173 returned. In contrast, the @code{finish} command (@pxref{Continuing
18174 and Stepping, ,Continuing and Stepping}) resumes execution until the
18175 selected stack frame returns naturally.
18177 @value{GDBN} needs to know how the @var{expression} argument should be set for
18178 the inferior. The concrete registers assignment depends on the OS ABI and the
18179 type being returned by the selected stack frame. For example it is common for
18180 OS ABI to return floating point values in FPU registers while integer values in
18181 CPU registers. Still some ABIs return even floating point values in CPU
18182 registers. Larger integer widths (such as @code{long long int}) also have
18183 specific placement rules. @value{GDBN} already knows the OS ABI from its
18184 current target so it needs to find out also the type being returned to make the
18185 assignment into the right register(s).
18187 Normally, the selected stack frame has debug info. @value{GDBN} will always
18188 use the debug info instead of the implicit type of @var{expression} when the
18189 debug info is available. For example, if you type @kbd{return -1}, and the
18190 function in the current stack frame is declared to return a @code{long long
18191 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18192 into a @code{long long int}:
18195 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18197 (@value{GDBP}) return -1
18198 Make func return now? (y or n) y
18199 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18200 43 printf ("result=%lld\n", func ());
18204 However, if the selected stack frame does not have a debug info, e.g., if the
18205 function was compiled without debug info, @value{GDBN} has to find out the type
18206 to return from user. Specifying a different type by mistake may set the value
18207 in different inferior registers than the caller code expects. For example,
18208 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18209 of a @code{long long int} result for a debug info less function (on 32-bit
18210 architectures). Therefore the user is required to specify the return type by
18211 an appropriate cast explicitly:
18214 Breakpoint 2, 0x0040050b in func ()
18215 (@value{GDBP}) return -1
18216 Return value type not available for selected stack frame.
18217 Please use an explicit cast of the value to return.
18218 (@value{GDBP}) return (long long int) -1
18219 Make selected stack frame return now? (y or n) y
18220 #0 0x00400526 in main ()
18225 @section Calling Program Functions
18228 @cindex calling functions
18229 @cindex inferior functions, calling
18230 @item print @var{expr}
18231 Evaluate the expression @var{expr} and display the resulting value.
18232 The expression may include calls to functions in the program being
18236 @item call @var{expr}
18237 Evaluate the expression @var{expr} without displaying @code{void}
18240 You can use this variant of the @code{print} command if you want to
18241 execute a function from your program that does not return anything
18242 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18243 with @code{void} returned values that @value{GDBN} will otherwise
18244 print. If the result is not void, it is printed and saved in the
18248 It is possible for the function you call via the @code{print} or
18249 @code{call} command to generate a signal (e.g., if there's a bug in
18250 the function, or if you passed it incorrect arguments). What happens
18251 in that case is controlled by the @code{set unwindonsignal} command.
18253 Similarly, with a C@t{++} program it is possible for the function you
18254 call via the @code{print} or @code{call} command to generate an
18255 exception that is not handled due to the constraints of the dummy
18256 frame. In this case, any exception that is raised in the frame, but has
18257 an out-of-frame exception handler will not be found. GDB builds a
18258 dummy-frame for the inferior function call, and the unwinder cannot
18259 seek for exception handlers outside of this dummy-frame. What happens
18260 in that case is controlled by the
18261 @code{set unwind-on-terminating-exception} command.
18264 @item set unwindonsignal
18265 @kindex set unwindonsignal
18266 @cindex unwind stack in called functions
18267 @cindex call dummy stack unwinding
18268 Set unwinding of the stack if a signal is received while in a function
18269 that @value{GDBN} called in the program being debugged. If set to on,
18270 @value{GDBN} unwinds the stack it created for the call and restores
18271 the context to what it was before the call. If set to off (the
18272 default), @value{GDBN} stops in the frame where the signal was
18275 @item show unwindonsignal
18276 @kindex show unwindonsignal
18277 Show the current setting of stack unwinding in the functions called by
18280 @item set unwind-on-terminating-exception
18281 @kindex set unwind-on-terminating-exception
18282 @cindex unwind stack in called functions with unhandled exceptions
18283 @cindex call dummy stack unwinding on unhandled exception.
18284 Set unwinding of the stack if a C@t{++} exception is raised, but left
18285 unhandled while in a function that @value{GDBN} called in the program being
18286 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18287 it created for the call and restores the context to what it was before
18288 the call. If set to off, @value{GDBN} the exception is delivered to
18289 the default C@t{++} exception handler and the inferior terminated.
18291 @item show unwind-on-terminating-exception
18292 @kindex show unwind-on-terminating-exception
18293 Show the current setting of stack unwinding in the functions called by
18298 @subsection Calling functions with no debug info
18300 @cindex no debug info functions
18301 Sometimes, a function you wish to call is missing debug information.
18302 In such case, @value{GDBN} does not know the type of the function,
18303 including the types of the function's parameters. To avoid calling
18304 the inferior function incorrectly, which could result in the called
18305 function functioning erroneously and even crash, @value{GDBN} refuses
18306 to call the function unless you tell it the type of the function.
18308 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18309 to do that. The simplest is to cast the call to the function's
18310 declared return type. For example:
18313 (@value{GDBP}) p getenv ("PATH")
18314 'getenv' has unknown return type; cast the call to its declared return type
18315 (@value{GDBP}) p (char *) getenv ("PATH")
18316 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18319 Casting the return type of a no-debug function is equivalent to
18320 casting the function to a pointer to a prototyped function that has a
18321 prototype that matches the types of the passed-in arguments, and
18322 calling that. I.e., the call above is equivalent to:
18325 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18329 and given this prototyped C or C++ function with float parameters:
18332 float multiply (float v1, float v2) @{ return v1 * v2; @}
18336 these calls are equivalent:
18339 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18340 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18343 If the function you wish to call is declared as unprototyped (i.e.@:
18344 old K&R style), you must use the cast-to-function-pointer syntax, so
18345 that @value{GDBN} knows that it needs to apply default argument
18346 promotions (promote float arguments to double). @xref{ABI, float
18347 promotion}. For example, given this unprototyped C function with
18348 float parameters, and no debug info:
18352 multiply_noproto (v1, v2)
18360 you call it like this:
18363 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18367 @section Patching Programs
18369 @cindex patching binaries
18370 @cindex writing into executables
18371 @cindex writing into corefiles
18373 By default, @value{GDBN} opens the file containing your program's
18374 executable code (or the corefile) read-only. This prevents accidental
18375 alterations to machine code; but it also prevents you from intentionally
18376 patching your program's binary.
18378 If you'd like to be able to patch the binary, you can specify that
18379 explicitly with the @code{set write} command. For example, you might
18380 want to turn on internal debugging flags, or even to make emergency
18386 @itemx set write off
18387 If you specify @samp{set write on}, @value{GDBN} opens executable and
18388 core files for both reading and writing; if you specify @kbd{set write
18389 off} (the default), @value{GDBN} opens them read-only.
18391 If you have already loaded a file, you must load it again (using the
18392 @code{exec-file} or @code{core-file} command) after changing @code{set
18393 write}, for your new setting to take effect.
18397 Display whether executable files and core files are opened for writing
18398 as well as reading.
18401 @node Compiling and Injecting Code
18402 @section Compiling and injecting code in @value{GDBN}
18403 @cindex injecting code
18404 @cindex writing into executables
18405 @cindex compiling code
18407 @value{GDBN} supports on-demand compilation and code injection into
18408 programs running under @value{GDBN}. GCC 5.0 or higher built with
18409 @file{libcc1.so} must be installed for this functionality to be enabled.
18410 This functionality is implemented with the following commands.
18413 @kindex compile code
18414 @item compile code @var{source-code}
18415 @itemx compile code -raw @var{--} @var{source-code}
18416 Compile @var{source-code} with the compiler language found as the current
18417 language in @value{GDBN} (@pxref{Languages}). If compilation and
18418 injection is not supported with the current language specified in
18419 @value{GDBN}, or the compiler does not support this feature, an error
18420 message will be printed. If @var{source-code} compiles and links
18421 successfully, @value{GDBN} will load the object-code emitted,
18422 and execute it within the context of the currently selected inferior.
18423 It is important to note that the compiled code is executed immediately.
18424 After execution, the compiled code is removed from @value{GDBN} and any
18425 new types or variables you have defined will be deleted.
18427 The command allows you to specify @var{source-code} in two ways.
18428 The simplest method is to provide a single line of code to the command.
18432 compile code printf ("hello world\n");
18435 If you specify options on the command line as well as source code, they
18436 may conflict. The @samp{--} delimiter can be used to separate options
18437 from actual source code. E.g.:
18440 compile code -r -- printf ("hello world\n");
18443 Alternatively you can enter source code as multiple lines of text. To
18444 enter this mode, invoke the @samp{compile code} command without any text
18445 following the command. This will start the multiple-line editor and
18446 allow you to type as many lines of source code as required. When you
18447 have completed typing, enter @samp{end} on its own line to exit the
18452 >printf ("hello\n");
18453 >printf ("world\n");
18457 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18458 provided @var{source-code} in a callable scope. In this case, you must
18459 specify the entry point of the code by defining a function named
18460 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18461 inferior. Using @samp{-raw} option may be needed for example when
18462 @var{source-code} requires @samp{#include} lines which may conflict with
18463 inferior symbols otherwise.
18465 @kindex compile file
18466 @item compile file @var{filename}
18467 @itemx compile file -raw @var{filename}
18468 Like @code{compile code}, but take the source code from @var{filename}.
18471 compile file /home/user/example.c
18476 @item compile print @var{expr}
18477 @itemx compile print /@var{f} @var{expr}
18478 Compile and execute @var{expr} with the compiler language found as the
18479 current language in @value{GDBN} (@pxref{Languages}). By default the
18480 value of @var{expr} is printed in a format appropriate to its data type;
18481 you can choose a different format by specifying @samp{/@var{f}}, where
18482 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18485 @item compile print
18486 @itemx compile print /@var{f}
18487 @cindex reprint the last value
18488 Alternatively you can enter the expression (source code producing it) as
18489 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18490 command without any text following the command. This will start the
18491 multiple-line editor.
18495 The process of compiling and injecting the code can be inspected using:
18498 @anchor{set debug compile}
18499 @item set debug compile
18500 @cindex compile command debugging info
18501 Turns on or off display of @value{GDBN} process of compiling and
18502 injecting the code. The default is off.
18504 @item show debug compile
18505 Displays the current state of displaying @value{GDBN} process of
18506 compiling and injecting the code.
18509 @subsection Compilation options for the @code{compile} command
18511 @value{GDBN} needs to specify the right compilation options for the code
18512 to be injected, in part to make its ABI compatible with the inferior
18513 and in part to make the injected code compatible with @value{GDBN}'s
18517 The options used, in increasing precedence:
18520 @item target architecture and OS options (@code{gdbarch})
18521 These options depend on target processor type and target operating
18522 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18523 (@code{-m64}) compilation option.
18525 @item compilation options recorded in the target
18526 @value{NGCC} (since version 4.7) stores the options used for compilation
18527 into @code{DW_AT_producer} part of DWARF debugging information according
18528 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18529 explicitly specify @code{-g} during inferior compilation otherwise
18530 @value{NGCC} produces no DWARF. This feature is only relevant for
18531 platforms where @code{-g} produces DWARF by default, otherwise one may
18532 try to enforce DWARF by using @code{-gdwarf-4}.
18534 @item compilation options set by @code{set compile-args}
18538 You can override compilation options using the following command:
18541 @item set compile-args
18542 @cindex compile command options override
18543 Set compilation options used for compiling and injecting code with the
18544 @code{compile} commands. These options override any conflicting ones
18545 from the target architecture and/or options stored during inferior
18548 @item show compile-args
18549 Displays the current state of compilation options override.
18550 This does not show all the options actually used during compilation,
18551 use @ref{set debug compile} for that.
18554 @subsection Caveats when using the @code{compile} command
18556 There are a few caveats to keep in mind when using the @code{compile}
18557 command. As the caveats are different per language, the table below
18558 highlights specific issues on a per language basis.
18561 @item C code examples and caveats
18562 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18563 attempt to compile the source code with a @samp{C} compiler. The source
18564 code provided to the @code{compile} command will have much the same
18565 access to variables and types as it normally would if it were part of
18566 the program currently being debugged in @value{GDBN}.
18568 Below is a sample program that forms the basis of the examples that
18569 follow. This program has been compiled and loaded into @value{GDBN},
18570 much like any other normal debugging session.
18573 void function1 (void)
18576 printf ("function 1\n");
18579 void function2 (void)
18594 For the purposes of the examples in this section, the program above has
18595 been compiled, loaded into @value{GDBN}, stopped at the function
18596 @code{main}, and @value{GDBN} is awaiting input from the user.
18598 To access variables and types for any program in @value{GDBN}, the
18599 program must be compiled and packaged with debug information. The
18600 @code{compile} command is not an exception to this rule. Without debug
18601 information, you can still use the @code{compile} command, but you will
18602 be very limited in what variables and types you can access.
18604 So with that in mind, the example above has been compiled with debug
18605 information enabled. The @code{compile} command will have access to
18606 all variables and types (except those that may have been optimized
18607 out). Currently, as @value{GDBN} has stopped the program in the
18608 @code{main} function, the @code{compile} command would have access to
18609 the variable @code{k}. You could invoke the @code{compile} command
18610 and type some source code to set the value of @code{k}. You can also
18611 read it, or do anything with that variable you would normally do in
18612 @code{C}. Be aware that changes to inferior variables in the
18613 @code{compile} command are persistent. In the following example:
18616 compile code k = 3;
18620 the variable @code{k} is now 3. It will retain that value until
18621 something else in the example program changes it, or another
18622 @code{compile} command changes it.
18624 Normal scope and access rules apply to source code compiled and
18625 injected by the @code{compile} command. In the example, the variables
18626 @code{j} and @code{k} are not accessible yet, because the program is
18627 currently stopped in the @code{main} function, where these variables
18628 are not in scope. Therefore, the following command
18631 compile code j = 3;
18635 will result in a compilation error message.
18637 Once the program is continued, execution will bring these variables in
18638 scope, and they will become accessible; then the code you specify via
18639 the @code{compile} command will be able to access them.
18641 You can create variables and types with the @code{compile} command as
18642 part of your source code. Variables and types that are created as part
18643 of the @code{compile} command are not visible to the rest of the program for
18644 the duration of its run. This example is valid:
18647 compile code int ff = 5; printf ("ff is %d\n", ff);
18650 However, if you were to type the following into @value{GDBN} after that
18651 command has completed:
18654 compile code printf ("ff is %d\n'', ff);
18658 a compiler error would be raised as the variable @code{ff} no longer
18659 exists. Object code generated and injected by the @code{compile}
18660 command is removed when its execution ends. Caution is advised
18661 when assigning to program variables values of variables created by the
18662 code submitted to the @code{compile} command. This example is valid:
18665 compile code int ff = 5; k = ff;
18668 The value of the variable @code{ff} is assigned to @code{k}. The variable
18669 @code{k} does not require the existence of @code{ff} to maintain the value
18670 it has been assigned. However, pointers require particular care in
18671 assignment. If the source code compiled with the @code{compile} command
18672 changed the address of a pointer in the example program, perhaps to a
18673 variable created in the @code{compile} command, that pointer would point
18674 to an invalid location when the command exits. The following example
18675 would likely cause issues with your debugged program:
18678 compile code int ff = 5; p = &ff;
18681 In this example, @code{p} would point to @code{ff} when the
18682 @code{compile} command is executing the source code provided to it.
18683 However, as variables in the (example) program persist with their
18684 assigned values, the variable @code{p} would point to an invalid
18685 location when the command exists. A general rule should be followed
18686 in that you should either assign @code{NULL} to any assigned pointers,
18687 or restore a valid location to the pointer before the command exits.
18689 Similar caution must be exercised with any structs, unions, and typedefs
18690 defined in @code{compile} command. Types defined in the @code{compile}
18691 command will no longer be available in the next @code{compile} command.
18692 Therefore, if you cast a variable to a type defined in the
18693 @code{compile} command, care must be taken to ensure that any future
18694 need to resolve the type can be achieved.
18697 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18698 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18699 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18700 Compilation failed.
18701 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18705 Variables that have been optimized away by the compiler are not
18706 accessible to the code submitted to the @code{compile} command.
18707 Access to those variables will generate a compiler error which @value{GDBN}
18708 will print to the console.
18711 @subsection Compiler search for the @code{compile} command
18713 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18714 which may not be obvious for remote targets of different architecture
18715 than where @value{GDBN} is running. Environment variable @code{PATH} on
18716 @value{GDBN} host is searched for @value{NGCC} binary matching the
18717 target architecture and operating system. This search can be overriden
18718 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18719 taken from shell that executed @value{GDBN}, it is not the value set by
18720 @value{GDBN} command @code{set environment}). @xref{Environment}.
18723 Specifically @code{PATH} is searched for binaries matching regular expression
18724 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18725 debugged. @var{arch} is processor name --- multiarch is supported, so for
18726 example both @code{i386} and @code{x86_64} targets look for pattern
18727 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18728 for pattern @code{s390x?}. @var{os} is currently supported only for
18729 pattern @code{linux(-gnu)?}.
18731 On Posix hosts the compiler driver @value{GDBN} needs to find also
18732 shared library @file{libcc1.so} from the compiler. It is searched in
18733 default shared library search path (overridable with usual environment
18734 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18735 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18736 according to the installation of the found compiler --- as possibly
18737 specified by the @code{set compile-gcc} command.
18740 @item set compile-gcc
18741 @cindex compile command driver filename override
18742 Set compilation command used for compiling and injecting code with the
18743 @code{compile} commands. If this option is not set (it is set to
18744 an empty string), the search described above will occur --- that is the
18747 @item show compile-gcc
18748 Displays the current compile command @value{NGCC} driver filename.
18749 If set, it is the main command @command{gcc}, found usually for example
18750 under name @file{x86_64-linux-gnu-gcc}.
18754 @chapter @value{GDBN} Files
18756 @value{GDBN} needs to know the file name of the program to be debugged,
18757 both in order to read its symbol table and in order to start your
18758 program. To debug a core dump of a previous run, you must also tell
18759 @value{GDBN} the name of the core dump file.
18762 * Files:: Commands to specify files
18763 * File Caching:: Information about @value{GDBN}'s file caching
18764 * Separate Debug Files:: Debugging information in separate files
18765 * MiniDebugInfo:: Debugging information in a special section
18766 * Index Files:: Index files speed up GDB
18767 * Symbol Errors:: Errors reading symbol files
18768 * Data Files:: GDB data files
18772 @section Commands to Specify Files
18774 @cindex symbol table
18775 @cindex core dump file
18777 You may want to specify executable and core dump file names. The usual
18778 way to do this is at start-up time, using the arguments to
18779 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18780 Out of @value{GDBN}}).
18782 Occasionally it is necessary to change to a different file during a
18783 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18784 specify a file you want to use. Or you are debugging a remote target
18785 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18786 Program}). In these situations the @value{GDBN} commands to specify
18787 new files are useful.
18790 @cindex executable file
18792 @item file @var{filename}
18793 Use @var{filename} as the program to be debugged. It is read for its
18794 symbols and for the contents of pure memory. It is also the program
18795 executed when you use the @code{run} command. If you do not specify a
18796 directory and the file is not found in the @value{GDBN} working directory,
18797 @value{GDBN} uses the environment variable @code{PATH} as a list of
18798 directories to search, just as the shell does when looking for a program
18799 to run. You can change the value of this variable, for both @value{GDBN}
18800 and your program, using the @code{path} command.
18802 @cindex unlinked object files
18803 @cindex patching object files
18804 You can load unlinked object @file{.o} files into @value{GDBN} using
18805 the @code{file} command. You will not be able to ``run'' an object
18806 file, but you can disassemble functions and inspect variables. Also,
18807 if the underlying BFD functionality supports it, you could use
18808 @kbd{gdb -write} to patch object files using this technique. Note
18809 that @value{GDBN} can neither interpret nor modify relocations in this
18810 case, so branches and some initialized variables will appear to go to
18811 the wrong place. But this feature is still handy from time to time.
18814 @code{file} with no argument makes @value{GDBN} discard any information it
18815 has on both executable file and the symbol table.
18818 @item exec-file @r{[} @var{filename} @r{]}
18819 Specify that the program to be run (but not the symbol table) is found
18820 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18821 if necessary to locate your program. Omitting @var{filename} means to
18822 discard information on the executable file.
18824 @kindex symbol-file
18825 @item symbol-file @r{[} @var{filename} @r{]}
18826 Read symbol table information from file @var{filename}. @code{PATH} is
18827 searched when necessary. Use the @code{file} command to get both symbol
18828 table and program to run from the same file.
18830 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18831 program's symbol table.
18833 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18834 some breakpoints and auto-display expressions. This is because they may
18835 contain pointers to the internal data recording symbols and data types,
18836 which are part of the old symbol table data being discarded inside
18839 @code{symbol-file} does not repeat if you press @key{RET} again after
18842 When @value{GDBN} is configured for a particular environment, it
18843 understands debugging information in whatever format is the standard
18844 generated for that environment; you may use either a @sc{gnu} compiler, or
18845 other compilers that adhere to the local conventions.
18846 Best results are usually obtained from @sc{gnu} compilers; for example,
18847 using @code{@value{NGCC}} you can generate debugging information for
18850 For most kinds of object files, with the exception of old SVR3 systems
18851 using COFF, the @code{symbol-file} command does not normally read the
18852 symbol table in full right away. Instead, it scans the symbol table
18853 quickly to find which source files and which symbols are present. The
18854 details are read later, one source file at a time, as they are needed.
18856 The purpose of this two-stage reading strategy is to make @value{GDBN}
18857 start up faster. For the most part, it is invisible except for
18858 occasional pauses while the symbol table details for a particular source
18859 file are being read. (The @code{set verbose} command can turn these
18860 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18861 Warnings and Messages}.)
18863 We have not implemented the two-stage strategy for COFF yet. When the
18864 symbol table is stored in COFF format, @code{symbol-file} reads the
18865 symbol table data in full right away. Note that ``stabs-in-COFF''
18866 still does the two-stage strategy, since the debug info is actually
18870 @cindex reading symbols immediately
18871 @cindex symbols, reading immediately
18872 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18873 @itemx file @r{[} -readnow @r{]} @var{filename}
18874 You can override the @value{GDBN} two-stage strategy for reading symbol
18875 tables by using the @samp{-readnow} option with any of the commands that
18876 load symbol table information, if you want to be sure @value{GDBN} has the
18877 entire symbol table available.
18879 @cindex @code{-readnever}, option for symbol-file command
18880 @cindex never read symbols
18881 @cindex symbols, never read
18882 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18883 @itemx file @r{[} -readnever @r{]} @var{filename}
18884 You can instruct @value{GDBN} to never read the symbolic information
18885 contained in @var{filename} by using the @samp{-readnever} option.
18886 @xref{--readnever}.
18888 @c FIXME: for now no mention of directories, since this seems to be in
18889 @c flux. 13mar1992 status is that in theory GDB would look either in
18890 @c current dir or in same dir as myprog; but issues like competing
18891 @c GDB's, or clutter in system dirs, mean that in practice right now
18892 @c only current dir is used. FFish says maybe a special GDB hierarchy
18893 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18897 @item core-file @r{[}@var{filename}@r{]}
18899 Specify the whereabouts of a core dump file to be used as the ``contents
18900 of memory''. Traditionally, core files contain only some parts of the
18901 address space of the process that generated them; @value{GDBN} can access the
18902 executable file itself for other parts.
18904 @code{core-file} with no argument specifies that no core file is
18907 Note that the core file is ignored when your program is actually running
18908 under @value{GDBN}. So, if you have been running your program and you
18909 wish to debug a core file instead, you must kill the subprocess in which
18910 the program is running. To do this, use the @code{kill} command
18911 (@pxref{Kill Process, ,Killing the Child Process}).
18913 @kindex add-symbol-file
18914 @cindex dynamic linking
18915 @item add-symbol-file @var{filename} @var{address}
18916 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18917 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18918 The @code{add-symbol-file} command reads additional symbol table
18919 information from the file @var{filename}. You would use this command
18920 when @var{filename} has been dynamically loaded (by some other means)
18921 into the program that is running. The @var{address} should give the memory
18922 address at which the file has been loaded; @value{GDBN} cannot figure
18923 this out for itself. You can additionally specify an arbitrary number
18924 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18925 section name and base address for that section. You can specify any
18926 @var{address} as an expression.
18928 The symbol table of the file @var{filename} is added to the symbol table
18929 originally read with the @code{symbol-file} command. You can use the
18930 @code{add-symbol-file} command any number of times; the new symbol data
18931 thus read is kept in addition to the old.
18933 Changes can be reverted using the command @code{remove-symbol-file}.
18935 @cindex relocatable object files, reading symbols from
18936 @cindex object files, relocatable, reading symbols from
18937 @cindex reading symbols from relocatable object files
18938 @cindex symbols, reading from relocatable object files
18939 @cindex @file{.o} files, reading symbols from
18940 Although @var{filename} is typically a shared library file, an
18941 executable file, or some other object file which has been fully
18942 relocated for loading into a process, you can also load symbolic
18943 information from relocatable @file{.o} files, as long as:
18947 the file's symbolic information refers only to linker symbols defined in
18948 that file, not to symbols defined by other object files,
18950 every section the file's symbolic information refers to has actually
18951 been loaded into the inferior, as it appears in the file, and
18953 you can determine the address at which every section was loaded, and
18954 provide these to the @code{add-symbol-file} command.
18958 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18959 relocatable files into an already running program; such systems
18960 typically make the requirements above easy to meet. However, it's
18961 important to recognize that many native systems use complex link
18962 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18963 assembly, for example) that make the requirements difficult to meet. In
18964 general, one cannot assume that using @code{add-symbol-file} to read a
18965 relocatable object file's symbolic information will have the same effect
18966 as linking the relocatable object file into the program in the normal
18969 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18971 @kindex remove-symbol-file
18972 @item remove-symbol-file @var{filename}
18973 @item remove-symbol-file -a @var{address}
18974 Remove a symbol file added via the @code{add-symbol-file} command. The
18975 file to remove can be identified by its @var{filename} or by an @var{address}
18976 that lies within the boundaries of this symbol file in memory. Example:
18979 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18980 add symbol table from file "/home/user/gdb/mylib.so" at
18981 .text_addr = 0x7ffff7ff9480
18983 Reading symbols from /home/user/gdb/mylib.so...done.
18984 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18985 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18990 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18992 @kindex add-symbol-file-from-memory
18993 @cindex @code{syscall DSO}
18994 @cindex load symbols from memory
18995 @item add-symbol-file-from-memory @var{address}
18996 Load symbols from the given @var{address} in a dynamically loaded
18997 object file whose image is mapped directly into the inferior's memory.
18998 For example, the Linux kernel maps a @code{syscall DSO} into each
18999 process's address space; this DSO provides kernel-specific code for
19000 some system calls. The argument can be any expression whose
19001 evaluation yields the address of the file's shared object file header.
19002 For this command to work, you must have used @code{symbol-file} or
19003 @code{exec-file} commands in advance.
19006 @item section @var{section} @var{addr}
19007 The @code{section} command changes the base address of the named
19008 @var{section} of the exec file to @var{addr}. This can be used if the
19009 exec file does not contain section addresses, (such as in the
19010 @code{a.out} format), or when the addresses specified in the file
19011 itself are wrong. Each section must be changed separately. The
19012 @code{info files} command, described below, lists all the sections and
19016 @kindex info target
19019 @code{info files} and @code{info target} are synonymous; both print the
19020 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19021 including the names of the executable and core dump files currently in
19022 use by @value{GDBN}, and the files from which symbols were loaded. The
19023 command @code{help target} lists all possible targets rather than
19026 @kindex maint info sections
19027 @item maint info sections
19028 Another command that can give you extra information about program sections
19029 is @code{maint info sections}. In addition to the section information
19030 displayed by @code{info files}, this command displays the flags and file
19031 offset of each section in the executable and core dump files. In addition,
19032 @code{maint info sections} provides the following command options (which
19033 may be arbitrarily combined):
19037 Display sections for all loaded object files, including shared libraries.
19038 @item @var{sections}
19039 Display info only for named @var{sections}.
19040 @item @var{section-flags}
19041 Display info only for sections for which @var{section-flags} are true.
19042 The section flags that @value{GDBN} currently knows about are:
19045 Section will have space allocated in the process when loaded.
19046 Set for all sections except those containing debug information.
19048 Section will be loaded from the file into the child process memory.
19049 Set for pre-initialized code and data, clear for @code{.bss} sections.
19051 Section needs to be relocated before loading.
19053 Section cannot be modified by the child process.
19055 Section contains executable code only.
19057 Section contains data only (no executable code).
19059 Section will reside in ROM.
19061 Section contains data for constructor/destructor lists.
19063 Section is not empty.
19065 An instruction to the linker to not output the section.
19066 @item COFF_SHARED_LIBRARY
19067 A notification to the linker that the section contains
19068 COFF shared library information.
19070 Section contains common symbols.
19073 @kindex set trust-readonly-sections
19074 @cindex read-only sections
19075 @item set trust-readonly-sections on
19076 Tell @value{GDBN} that readonly sections in your object file
19077 really are read-only (i.e.@: that their contents will not change).
19078 In that case, @value{GDBN} can fetch values from these sections
19079 out of the object file, rather than from the target program.
19080 For some targets (notably embedded ones), this can be a significant
19081 enhancement to debugging performance.
19083 The default is off.
19085 @item set trust-readonly-sections off
19086 Tell @value{GDBN} not to trust readonly sections. This means that
19087 the contents of the section might change while the program is running,
19088 and must therefore be fetched from the target when needed.
19090 @item show trust-readonly-sections
19091 Show the current setting of trusting readonly sections.
19094 All file-specifying commands allow both absolute and relative file names
19095 as arguments. @value{GDBN} always converts the file name to an absolute file
19096 name and remembers it that way.
19098 @cindex shared libraries
19099 @anchor{Shared Libraries}
19100 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19101 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19102 DSBT (TIC6X) shared libraries.
19104 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19105 shared libraries. @xref{Expat}.
19107 @value{GDBN} automatically loads symbol definitions from shared libraries
19108 when you use the @code{run} command, or when you examine a core file.
19109 (Before you issue the @code{run} command, @value{GDBN} does not understand
19110 references to a function in a shared library, however---unless you are
19111 debugging a core file).
19113 @c FIXME: some @value{GDBN} release may permit some refs to undef
19114 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19115 @c FIXME...lib; check this from time to time when updating manual
19117 There are times, however, when you may wish to not automatically load
19118 symbol definitions from shared libraries, such as when they are
19119 particularly large or there are many of them.
19121 To control the automatic loading of shared library symbols, use the
19125 @kindex set auto-solib-add
19126 @item set auto-solib-add @var{mode}
19127 If @var{mode} is @code{on}, symbols from all shared object libraries
19128 will be loaded automatically when the inferior begins execution, you
19129 attach to an independently started inferior, or when the dynamic linker
19130 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19131 is @code{off}, symbols must be loaded manually, using the
19132 @code{sharedlibrary} command. The default value is @code{on}.
19134 @cindex memory used for symbol tables
19135 If your program uses lots of shared libraries with debug info that
19136 takes large amounts of memory, you can decrease the @value{GDBN}
19137 memory footprint by preventing it from automatically loading the
19138 symbols from shared libraries. To that end, type @kbd{set
19139 auto-solib-add off} before running the inferior, then load each
19140 library whose debug symbols you do need with @kbd{sharedlibrary
19141 @var{regexp}}, where @var{regexp} is a regular expression that matches
19142 the libraries whose symbols you want to be loaded.
19144 @kindex show auto-solib-add
19145 @item show auto-solib-add
19146 Display the current autoloading mode.
19149 @cindex load shared library
19150 To explicitly load shared library symbols, use the @code{sharedlibrary}
19154 @kindex info sharedlibrary
19156 @item info share @var{regex}
19157 @itemx info sharedlibrary @var{regex}
19158 Print the names of the shared libraries which are currently loaded
19159 that match @var{regex}. If @var{regex} is omitted then print
19160 all shared libraries that are loaded.
19163 @item info dll @var{regex}
19164 This is an alias of @code{info sharedlibrary}.
19166 @kindex sharedlibrary
19168 @item sharedlibrary @var{regex}
19169 @itemx share @var{regex}
19170 Load shared object library symbols for files matching a
19171 Unix regular expression.
19172 As with files loaded automatically, it only loads shared libraries
19173 required by your program for a core file or after typing @code{run}. If
19174 @var{regex} is omitted all shared libraries required by your program are
19177 @item nosharedlibrary
19178 @kindex nosharedlibrary
19179 @cindex unload symbols from shared libraries
19180 Unload all shared object library symbols. This discards all symbols
19181 that have been loaded from all shared libraries. Symbols from shared
19182 libraries that were loaded by explicit user requests are not
19186 Sometimes you may wish that @value{GDBN} stops and gives you control
19187 when any of shared library events happen. The best way to do this is
19188 to use @code{catch load} and @code{catch unload} (@pxref{Set
19191 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19192 command for this. This command exists for historical reasons. It is
19193 less useful than setting a catchpoint, because it does not allow for
19194 conditions or commands as a catchpoint does.
19197 @item set stop-on-solib-events
19198 @kindex set stop-on-solib-events
19199 This command controls whether @value{GDBN} should give you control
19200 when the dynamic linker notifies it about some shared library event.
19201 The most common event of interest is loading or unloading of a new
19204 @item show stop-on-solib-events
19205 @kindex show stop-on-solib-events
19206 Show whether @value{GDBN} stops and gives you control when shared
19207 library events happen.
19210 Shared libraries are also supported in many cross or remote debugging
19211 configurations. @value{GDBN} needs to have access to the target's libraries;
19212 this can be accomplished either by providing copies of the libraries
19213 on the host system, or by asking @value{GDBN} to automatically retrieve the
19214 libraries from the target. If copies of the target libraries are
19215 provided, they need to be the same as the target libraries, although the
19216 copies on the target can be stripped as long as the copies on the host are
19219 @cindex where to look for shared libraries
19220 For remote debugging, you need to tell @value{GDBN} where the target
19221 libraries are, so that it can load the correct copies---otherwise, it
19222 may try to load the host's libraries. @value{GDBN} has two variables
19223 to specify the search directories for target libraries.
19226 @cindex prefix for executable and shared library file names
19227 @cindex system root, alternate
19228 @kindex set solib-absolute-prefix
19229 @kindex set sysroot
19230 @item set sysroot @var{path}
19231 Use @var{path} as the system root for the program being debugged. Any
19232 absolute shared library paths will be prefixed with @var{path}; many
19233 runtime loaders store the absolute paths to the shared library in the
19234 target program's memory. When starting processes remotely, and when
19235 attaching to already-running processes (local or remote), their
19236 executable filenames will be prefixed with @var{path} if reported to
19237 @value{GDBN} as absolute by the operating system. If you use
19238 @code{set sysroot} to find executables and shared libraries, they need
19239 to be laid out in the same way that they are on the target, with
19240 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19243 If @var{path} starts with the sequence @file{target:} and the target
19244 system is remote then @value{GDBN} will retrieve the target binaries
19245 from the remote system. This is only supported when using a remote
19246 target that supports the @code{remote get} command (@pxref{File
19247 Transfer,,Sending files to a remote system}). The part of @var{path}
19248 following the initial @file{target:} (if present) is used as system
19249 root prefix on the remote file system. If @var{path} starts with the
19250 sequence @file{remote:} this is converted to the sequence
19251 @file{target:} by @code{set sysroot}@footnote{Historically the
19252 functionality to retrieve binaries from the remote system was
19253 provided by prefixing @var{path} with @file{remote:}}. If you want
19254 to specify a local system root using a directory that happens to be
19255 named @file{target:} or @file{remote:}, you need to use some
19256 equivalent variant of the name like @file{./target:}.
19258 For targets with an MS-DOS based filesystem, such as MS-Windows and
19259 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19260 absolute file name with @var{path}. But first, on Unix hosts,
19261 @value{GDBN} converts all backslash directory separators into forward
19262 slashes, because the backslash is not a directory separator on Unix:
19265 c:\foo\bar.dll @result{} c:/foo/bar.dll
19268 Then, @value{GDBN} attempts prefixing the target file name with
19269 @var{path}, and looks for the resulting file name in the host file
19273 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19276 If that does not find the binary, @value{GDBN} tries removing
19277 the @samp{:} character from the drive spec, both for convenience, and,
19278 for the case of the host file system not supporting file names with
19282 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19285 This makes it possible to have a system root that mirrors a target
19286 with more than one drive. E.g., you may want to setup your local
19287 copies of the target system shared libraries like so (note @samp{c} vs
19291 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19292 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19293 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19297 and point the system root at @file{/path/to/sysroot}, so that
19298 @value{GDBN} can find the correct copies of both
19299 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19301 If that still does not find the binary, @value{GDBN} tries
19302 removing the whole drive spec from the target file name:
19305 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19308 This last lookup makes it possible to not care about the drive name,
19309 if you don't want or need to.
19311 The @code{set solib-absolute-prefix} command is an alias for @code{set
19314 @cindex default system root
19315 @cindex @samp{--with-sysroot}
19316 You can set the default system root by using the configure-time
19317 @samp{--with-sysroot} option. If the system root is inside
19318 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19319 @samp{--exec-prefix}), then the default system root will be updated
19320 automatically if the installed @value{GDBN} is moved to a new
19323 @kindex show sysroot
19325 Display the current executable and shared library prefix.
19327 @kindex set solib-search-path
19328 @item set solib-search-path @var{path}
19329 If this variable is set, @var{path} is a colon-separated list of
19330 directories to search for shared libraries. @samp{solib-search-path}
19331 is used after @samp{sysroot} fails to locate the library, or if the
19332 path to the library is relative instead of absolute. If you want to
19333 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19334 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19335 finding your host's libraries. @samp{sysroot} is preferred; setting
19336 it to a nonexistent directory may interfere with automatic loading
19337 of shared library symbols.
19339 @kindex show solib-search-path
19340 @item show solib-search-path
19341 Display the current shared library search path.
19343 @cindex DOS file-name semantics of file names.
19344 @kindex set target-file-system-kind (unix|dos-based|auto)
19345 @kindex show target-file-system-kind
19346 @item set target-file-system-kind @var{kind}
19347 Set assumed file system kind for target reported file names.
19349 Shared library file names as reported by the target system may not
19350 make sense as is on the system @value{GDBN} is running on. For
19351 example, when remote debugging a target that has MS-DOS based file
19352 system semantics, from a Unix host, the target may be reporting to
19353 @value{GDBN} a list of loaded shared libraries with file names such as
19354 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19355 drive letters, so the @samp{c:\} prefix is not normally understood as
19356 indicating an absolute file name, and neither is the backslash
19357 normally considered a directory separator character. In that case,
19358 the native file system would interpret this whole absolute file name
19359 as a relative file name with no directory components. This would make
19360 it impossible to point @value{GDBN} at a copy of the remote target's
19361 shared libraries on the host using @code{set sysroot}, and impractical
19362 with @code{set solib-search-path}. Setting
19363 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19364 to interpret such file names similarly to how the target would, and to
19365 map them to file names valid on @value{GDBN}'s native file system
19366 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19367 to one of the supported file system kinds. In that case, @value{GDBN}
19368 tries to determine the appropriate file system variant based on the
19369 current target's operating system (@pxref{ABI, ,Configuring the
19370 Current ABI}). The supported file system settings are:
19374 Instruct @value{GDBN} to assume the target file system is of Unix
19375 kind. Only file names starting the forward slash (@samp{/}) character
19376 are considered absolute, and the directory separator character is also
19380 Instruct @value{GDBN} to assume the target file system is DOS based.
19381 File names starting with either a forward slash, or a drive letter
19382 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19383 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19384 considered directory separators.
19387 Instruct @value{GDBN} to use the file system kind associated with the
19388 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19389 This is the default.
19393 @cindex file name canonicalization
19394 @cindex base name differences
19395 When processing file names provided by the user, @value{GDBN}
19396 frequently needs to compare them to the file names recorded in the
19397 program's debug info. Normally, @value{GDBN} compares just the
19398 @dfn{base names} of the files as strings, which is reasonably fast
19399 even for very large programs. (The base name of a file is the last
19400 portion of its name, after stripping all the leading directories.)
19401 This shortcut in comparison is based upon the assumption that files
19402 cannot have more than one base name. This is usually true, but
19403 references to files that use symlinks or similar filesystem
19404 facilities violate that assumption. If your program records files
19405 using such facilities, or if you provide file names to @value{GDBN}
19406 using symlinks etc., you can set @code{basenames-may-differ} to
19407 @code{true} to instruct @value{GDBN} to completely canonicalize each
19408 pair of file names it needs to compare. This will make file-name
19409 comparisons accurate, but at a price of a significant slowdown.
19412 @item set basenames-may-differ
19413 @kindex set basenames-may-differ
19414 Set whether a source file may have multiple base names.
19416 @item show basenames-may-differ
19417 @kindex show basenames-may-differ
19418 Show whether a source file may have multiple base names.
19422 @section File Caching
19423 @cindex caching of opened files
19424 @cindex caching of bfd objects
19426 To speed up file loading, and reduce memory usage, @value{GDBN} will
19427 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19428 BFD, bfd, The Binary File Descriptor Library}. The following commands
19429 allow visibility and control of the caching behavior.
19432 @kindex maint info bfds
19433 @item maint info bfds
19434 This prints information about each @code{bfd} object that is known to
19437 @kindex maint set bfd-sharing
19438 @kindex maint show bfd-sharing
19439 @kindex bfd caching
19440 @item maint set bfd-sharing
19441 @item maint show bfd-sharing
19442 Control whether @code{bfd} objects can be shared. When sharing is
19443 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19444 than reopening the same file. Turning sharing off does not cause
19445 already shared @code{bfd} objects to be unshared, but all future files
19446 that are opened will create a new @code{bfd} object. Similarly,
19447 re-enabling sharing does not cause multiple existing @code{bfd}
19448 objects to be collapsed into a single shared @code{bfd} object.
19450 @kindex set debug bfd-cache @var{level}
19451 @kindex bfd caching
19452 @item set debug bfd-cache @var{level}
19453 Turns on debugging of the bfd cache, setting the level to @var{level}.
19455 @kindex show debug bfd-cache
19456 @kindex bfd caching
19457 @item show debug bfd-cache
19458 Show the current debugging level of the bfd cache.
19461 @node Separate Debug Files
19462 @section Debugging Information in Separate Files
19463 @cindex separate debugging information files
19464 @cindex debugging information in separate files
19465 @cindex @file{.debug} subdirectories
19466 @cindex debugging information directory, global
19467 @cindex global debugging information directories
19468 @cindex build ID, and separate debugging files
19469 @cindex @file{.build-id} directory
19471 @value{GDBN} allows you to put a program's debugging information in a
19472 file separate from the executable itself, in a way that allows
19473 @value{GDBN} to find and load the debugging information automatically.
19474 Since debugging information can be very large---sometimes larger
19475 than the executable code itself---some systems distribute debugging
19476 information for their executables in separate files, which users can
19477 install only when they need to debug a problem.
19479 @value{GDBN} supports two ways of specifying the separate debug info
19484 The executable contains a @dfn{debug link} that specifies the name of
19485 the separate debug info file. The separate debug file's name is
19486 usually @file{@var{executable}.debug}, where @var{executable} is the
19487 name of the corresponding executable file without leading directories
19488 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19489 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19490 checksum for the debug file, which @value{GDBN} uses to validate that
19491 the executable and the debug file came from the same build.
19494 The executable contains a @dfn{build ID}, a unique bit string that is
19495 also present in the corresponding debug info file. (This is supported
19496 only on some operating systems, when using the ELF or PE file formats
19497 for binary files and the @sc{gnu} Binutils.) For more details about
19498 this feature, see the description of the @option{--build-id}
19499 command-line option in @ref{Options, , Command Line Options, ld.info,
19500 The GNU Linker}. The debug info file's name is not specified
19501 explicitly by the build ID, but can be computed from the build ID, see
19505 Depending on the way the debug info file is specified, @value{GDBN}
19506 uses two different methods of looking for the debug file:
19510 For the ``debug link'' method, @value{GDBN} looks up the named file in
19511 the directory of the executable file, then in a subdirectory of that
19512 directory named @file{.debug}, and finally under each one of the global debug
19513 directories, in a subdirectory whose name is identical to the leading
19514 directories of the executable's absolute file name.
19517 For the ``build ID'' method, @value{GDBN} looks in the
19518 @file{.build-id} subdirectory of each one of the global debug directories for
19519 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19520 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19521 are the rest of the bit string. (Real build ID strings are 32 or more
19522 hex characters, not 10.)
19525 So, for example, suppose you ask @value{GDBN} to debug
19526 @file{/usr/bin/ls}, which has a debug link that specifies the
19527 file @file{ls.debug}, and a build ID whose value in hex is
19528 @code{abcdef1234}. If the list of the global debug directories includes
19529 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19530 debug information files, in the indicated order:
19534 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19536 @file{/usr/bin/ls.debug}
19538 @file{/usr/bin/.debug/ls.debug}
19540 @file{/usr/lib/debug/usr/bin/ls.debug}.
19543 @anchor{debug-file-directory}
19544 Global debugging info directories default to what is set by @value{GDBN}
19545 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19546 you can also set the global debugging info directories, and view the list
19547 @value{GDBN} is currently using.
19551 @kindex set debug-file-directory
19552 @item set debug-file-directory @var{directories}
19553 Set the directories which @value{GDBN} searches for separate debugging
19554 information files to @var{directory}. Multiple path components can be set
19555 concatenating them by a path separator.
19557 @kindex show debug-file-directory
19558 @item show debug-file-directory
19559 Show the directories @value{GDBN} searches for separate debugging
19564 @cindex @code{.gnu_debuglink} sections
19565 @cindex debug link sections
19566 A debug link is a special section of the executable file named
19567 @code{.gnu_debuglink}. The section must contain:
19571 A filename, with any leading directory components removed, followed by
19574 zero to three bytes of padding, as needed to reach the next four-byte
19575 boundary within the section, and
19577 a four-byte CRC checksum, stored in the same endianness used for the
19578 executable file itself. The checksum is computed on the debugging
19579 information file's full contents by the function given below, passing
19580 zero as the @var{crc} argument.
19583 Any executable file format can carry a debug link, as long as it can
19584 contain a section named @code{.gnu_debuglink} with the contents
19587 @cindex @code{.note.gnu.build-id} sections
19588 @cindex build ID sections
19589 The build ID is a special section in the executable file (and in other
19590 ELF binary files that @value{GDBN} may consider). This section is
19591 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19592 It contains unique identification for the built files---the ID remains
19593 the same across multiple builds of the same build tree. The default
19594 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19595 content for the build ID string. The same section with an identical
19596 value is present in the original built binary with symbols, in its
19597 stripped variant, and in the separate debugging information file.
19599 The debugging information file itself should be an ordinary
19600 executable, containing a full set of linker symbols, sections, and
19601 debugging information. The sections of the debugging information file
19602 should have the same names, addresses, and sizes as the original file,
19603 but they need not contain any data---much like a @code{.bss} section
19604 in an ordinary executable.
19606 The @sc{gnu} binary utilities (Binutils) package includes the
19607 @samp{objcopy} utility that can produce
19608 the separated executable / debugging information file pairs using the
19609 following commands:
19612 @kbd{objcopy --only-keep-debug foo foo.debug}
19617 These commands remove the debugging
19618 information from the executable file @file{foo} and place it in the file
19619 @file{foo.debug}. You can use the first, second or both methods to link the
19624 The debug link method needs the following additional command to also leave
19625 behind a debug link in @file{foo}:
19628 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19631 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19632 a version of the @code{strip} command such that the command @kbd{strip foo -f
19633 foo.debug} has the same functionality as the two @code{objcopy} commands and
19634 the @code{ln -s} command above, together.
19637 Build ID gets embedded into the main executable using @code{ld --build-id} or
19638 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19639 compatibility fixes for debug files separation are present in @sc{gnu} binary
19640 utilities (Binutils) package since version 2.18.
19645 @cindex CRC algorithm definition
19646 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19647 IEEE 802.3 using the polynomial:
19649 @c TexInfo requires naked braces for multi-digit exponents for Tex
19650 @c output, but this causes HTML output to barf. HTML has to be set using
19651 @c raw commands. So we end up having to specify this equation in 2
19656 <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>
19657 + <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
19663 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19664 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19668 The function is computed byte at a time, taking the least
19669 significant bit of each byte first. The initial pattern
19670 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19671 the final result is inverted to ensure trailing zeros also affect the
19674 @emph{Note:} This is the same CRC polynomial as used in handling the
19675 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19676 However in the case of the Remote Serial Protocol, the CRC is computed
19677 @emph{most} significant bit first, and the result is not inverted, so
19678 trailing zeros have no effect on the CRC value.
19680 To complete the description, we show below the code of the function
19681 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19682 initially supplied @code{crc} argument means that an initial call to
19683 this function passing in zero will start computing the CRC using
19686 @kindex gnu_debuglink_crc32
19689 gnu_debuglink_crc32 (unsigned long crc,
19690 unsigned char *buf, size_t len)
19692 static const unsigned long crc32_table[256] =
19694 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19695 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19696 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19697 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19698 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19699 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19700 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19701 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19702 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19703 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19704 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19705 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19706 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19707 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19708 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19709 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19710 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19711 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19712 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19713 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19714 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19715 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19716 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19717 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19718 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19719 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19720 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19721 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19722 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19723 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19724 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19725 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19726 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19727 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19728 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19729 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19730 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19731 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19732 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19733 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19734 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19735 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19736 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19737 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19738 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19739 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19740 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19741 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19742 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19743 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19744 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19747 unsigned char *end;
19749 crc = ~crc & 0xffffffff;
19750 for (end = buf + len; buf < end; ++buf)
19751 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19752 return ~crc & 0xffffffff;
19757 This computation does not apply to the ``build ID'' method.
19759 @node MiniDebugInfo
19760 @section Debugging information in a special section
19761 @cindex separate debug sections
19762 @cindex @samp{.gnu_debugdata} section
19764 Some systems ship pre-built executables and libraries that have a
19765 special @samp{.gnu_debugdata} section. This feature is called
19766 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19767 is used to supply extra symbols for backtraces.
19769 The intent of this section is to provide extra minimal debugging
19770 information for use in simple backtraces. It is not intended to be a
19771 replacement for full separate debugging information (@pxref{Separate
19772 Debug Files}). The example below shows the intended use; however,
19773 @value{GDBN} does not currently put restrictions on what sort of
19774 debugging information might be included in the section.
19776 @value{GDBN} has support for this extension. If the section exists,
19777 then it is used provided that no other source of debugging information
19778 can be found, and that @value{GDBN} was configured with LZMA support.
19780 This section can be easily created using @command{objcopy} and other
19781 standard utilities:
19784 # Extract the dynamic symbols from the main binary, there is no need
19785 # to also have these in the normal symbol table.
19786 nm -D @var{binary} --format=posix --defined-only \
19787 | awk '@{ print $1 @}' | sort > dynsyms
19789 # Extract all the text (i.e. function) symbols from the debuginfo.
19790 # (Note that we actually also accept "D" symbols, for the benefit
19791 # of platforms like PowerPC64 that use function descriptors.)
19792 nm @var{binary} --format=posix --defined-only \
19793 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19796 # Keep all the function symbols not already in the dynamic symbol
19798 comm -13 dynsyms funcsyms > keep_symbols
19800 # Separate full debug info into debug binary.
19801 objcopy --only-keep-debug @var{binary} debug
19803 # Copy the full debuginfo, keeping only a minimal set of symbols and
19804 # removing some unnecessary sections.
19805 objcopy -S --remove-section .gdb_index --remove-section .comment \
19806 --keep-symbols=keep_symbols debug mini_debuginfo
19808 # Drop the full debug info from the original binary.
19809 strip --strip-all -R .comment @var{binary}
19811 # Inject the compressed data into the .gnu_debugdata section of the
19814 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19818 @section Index Files Speed Up @value{GDBN}
19819 @cindex index files
19820 @cindex @samp{.gdb_index} section
19822 When @value{GDBN} finds a symbol file, it scans the symbols in the
19823 file in order to construct an internal symbol table. This lets most
19824 @value{GDBN} operations work quickly---at the cost of a delay early
19825 on. For large programs, this delay can be quite lengthy, so
19826 @value{GDBN} provides a way to build an index, which speeds up
19829 For convenience, @value{GDBN} comes with a program,
19830 @command{gdb-add-index}, which can be used to add the index to a
19831 symbol file. It takes the symbol file as its only argument:
19834 $ gdb-add-index symfile
19837 @xref{gdb-add-index}.
19839 It is also possible to do the work manually. Here is what
19840 @command{gdb-add-index} does behind the curtains.
19842 The index is stored as a section in the symbol file. @value{GDBN} can
19843 write the index to a file, then you can put it into the symbol file
19844 using @command{objcopy}.
19846 To create an index file, use the @code{save gdb-index} command:
19849 @item save gdb-index [-dwarf-5] @var{directory}
19850 @kindex save gdb-index
19851 Create index files for all symbol files currently known by
19852 @value{GDBN}. For each known @var{symbol-file}, this command by
19853 default creates it produces a single file
19854 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19855 the @option{-dwarf-5} option, it produces 2 files:
19856 @file{@var{symbol-file}.debug_names} and
19857 @file{@var{symbol-file}.debug_str}. The files are created in the
19858 given @var{directory}.
19861 Once you have created an index file you can merge it into your symbol
19862 file, here named @file{symfile}, using @command{objcopy}:
19865 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19866 --set-section-flags .gdb_index=readonly symfile symfile
19869 Or for @code{-dwarf-5}:
19872 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19873 $ cat symfile.debug_str >>symfile.debug_str.new
19874 $ objcopy --add-section .debug_names=symfile.gdb-index \
19875 --set-section-flags .debug_names=readonly \
19876 --update-section .debug_str=symfile.debug_str.new symfile symfile
19879 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19880 sections that have been deprecated. Usually they are deprecated because
19881 they are missing a new feature or have performance issues.
19882 To tell @value{GDBN} to use a deprecated index section anyway
19883 specify @code{set use-deprecated-index-sections on}.
19884 The default is @code{off}.
19885 This can speed up startup, but may result in some functionality being lost.
19886 @xref{Index Section Format}.
19888 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19889 must be done before gdb reads the file. The following will not work:
19892 $ gdb -ex "set use-deprecated-index-sections on" <program>
19895 Instead you must do, for example,
19898 $ gdb -iex "set use-deprecated-index-sections on" <program>
19901 There are currently some limitation on indices. They only work when
19902 for DWARF debugging information, not stabs. And, they do not
19903 currently work for programs using Ada.
19905 @node Symbol Errors
19906 @section Errors Reading Symbol Files
19908 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19909 such as symbol types it does not recognize, or known bugs in compiler
19910 output. By default, @value{GDBN} does not notify you of such problems, since
19911 they are relatively common and primarily of interest to people
19912 debugging compilers. If you are interested in seeing information
19913 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19914 only one message about each such type of problem, no matter how many
19915 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19916 to see how many times the problems occur, with the @code{set
19917 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19920 The messages currently printed, and their meanings, include:
19923 @item inner block not inside outer block in @var{symbol}
19925 The symbol information shows where symbol scopes begin and end
19926 (such as at the start of a function or a block of statements). This
19927 error indicates that an inner scope block is not fully contained
19928 in its outer scope blocks.
19930 @value{GDBN} circumvents the problem by treating the inner block as if it had
19931 the same scope as the outer block. In the error message, @var{symbol}
19932 may be shown as ``@code{(don't know)}'' if the outer block is not a
19935 @item block at @var{address} out of order
19937 The symbol information for symbol scope blocks should occur in
19938 order of increasing addresses. This error indicates that it does not
19941 @value{GDBN} does not circumvent this problem, and has trouble
19942 locating symbols in the source file whose symbols it is reading. (You
19943 can often determine what source file is affected by specifying
19944 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19947 @item bad block start address patched
19949 The symbol information for a symbol scope block has a start address
19950 smaller than the address of the preceding source line. This is known
19951 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19953 @value{GDBN} circumvents the problem by treating the symbol scope block as
19954 starting on the previous source line.
19956 @item bad string table offset in symbol @var{n}
19959 Symbol number @var{n} contains a pointer into the string table which is
19960 larger than the size of the string table.
19962 @value{GDBN} circumvents the problem by considering the symbol to have the
19963 name @code{foo}, which may cause other problems if many symbols end up
19966 @item unknown symbol type @code{0x@var{nn}}
19968 The symbol information contains new data types that @value{GDBN} does
19969 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19970 uncomprehended information, in hexadecimal.
19972 @value{GDBN} circumvents the error by ignoring this symbol information.
19973 This usually allows you to debug your program, though certain symbols
19974 are not accessible. If you encounter such a problem and feel like
19975 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19976 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19977 and examine @code{*bufp} to see the symbol.
19979 @item stub type has NULL name
19981 @value{GDBN} could not find the full definition for a struct or class.
19983 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19984 The symbol information for a C@t{++} member function is missing some
19985 information that recent versions of the compiler should have output for
19988 @item info mismatch between compiler and debugger
19990 @value{GDBN} could not parse a type specification output by the compiler.
19995 @section GDB Data Files
19997 @cindex prefix for data files
19998 @value{GDBN} will sometimes read an auxiliary data file. These files
19999 are kept in a directory known as the @dfn{data directory}.
20001 You can set the data directory's name, and view the name @value{GDBN}
20002 is currently using.
20005 @kindex set data-directory
20006 @item set data-directory @var{directory}
20007 Set the directory which @value{GDBN} searches for auxiliary data files
20008 to @var{directory}.
20010 @kindex show data-directory
20011 @item show data-directory
20012 Show the directory @value{GDBN} searches for auxiliary data files.
20015 @cindex default data directory
20016 @cindex @samp{--with-gdb-datadir}
20017 You can set the default data directory by using the configure-time
20018 @samp{--with-gdb-datadir} option. If the data directory is inside
20019 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20020 @samp{--exec-prefix}), then the default data directory will be updated
20021 automatically if the installed @value{GDBN} is moved to a new
20024 The data directory may also be specified with the
20025 @code{--data-directory} command line option.
20026 @xref{Mode Options}.
20029 @chapter Specifying a Debugging Target
20031 @cindex debugging target
20032 A @dfn{target} is the execution environment occupied by your program.
20034 Often, @value{GDBN} runs in the same host environment as your program;
20035 in that case, the debugging target is specified as a side effect when
20036 you use the @code{file} or @code{core} commands. When you need more
20037 flexibility---for example, running @value{GDBN} on a physically separate
20038 host, or controlling a standalone system over a serial port or a
20039 realtime system over a TCP/IP connection---you can use the @code{target}
20040 command to specify one of the target types configured for @value{GDBN}
20041 (@pxref{Target Commands, ,Commands for Managing Targets}).
20043 @cindex target architecture
20044 It is possible to build @value{GDBN} for several different @dfn{target
20045 architectures}. When @value{GDBN} is built like that, you can choose
20046 one of the available architectures with the @kbd{set architecture}
20050 @kindex set architecture
20051 @kindex show architecture
20052 @item set architecture @var{arch}
20053 This command sets the current target architecture to @var{arch}. The
20054 value of @var{arch} can be @code{"auto"}, in addition to one of the
20055 supported architectures.
20057 @item show architecture
20058 Show the current target architecture.
20060 @item set processor
20062 @kindex set processor
20063 @kindex show processor
20064 These are alias commands for, respectively, @code{set architecture}
20065 and @code{show architecture}.
20069 * Active Targets:: Active targets
20070 * Target Commands:: Commands for managing targets
20071 * Byte Order:: Choosing target byte order
20074 @node Active Targets
20075 @section Active Targets
20077 @cindex stacking targets
20078 @cindex active targets
20079 @cindex multiple targets
20081 There are multiple classes of targets such as: processes, executable files or
20082 recording sessions. Core files belong to the process class, making core file
20083 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20084 on multiple active targets, one in each class. This allows you to (for
20085 example) start a process and inspect its activity, while still having access to
20086 the executable file after the process finishes. Or if you start process
20087 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20088 presented a virtual layer of the recording target, while the process target
20089 remains stopped at the chronologically last point of the process execution.
20091 Use the @code{core-file} and @code{exec-file} commands to select a new core
20092 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20093 specify as a target a process that is already running, use the @code{attach}
20094 command (@pxref{Attach, ,Debugging an Already-running Process}).
20096 @node Target Commands
20097 @section Commands for Managing Targets
20100 @item target @var{type} @var{parameters}
20101 Connects the @value{GDBN} host environment to a target machine or
20102 process. A target is typically a protocol for talking to debugging
20103 facilities. You use the argument @var{type} to specify the type or
20104 protocol of the target machine.
20106 Further @var{parameters} are interpreted by the target protocol, but
20107 typically include things like device names or host names to connect
20108 with, process numbers, and baud rates.
20110 The @code{target} command does not repeat if you press @key{RET} again
20111 after executing the command.
20113 @kindex help target
20115 Displays the names of all targets available. To display targets
20116 currently selected, use either @code{info target} or @code{info files}
20117 (@pxref{Files, ,Commands to Specify Files}).
20119 @item help target @var{name}
20120 Describe a particular target, including any parameters necessary to
20123 @kindex set gnutarget
20124 @item set gnutarget @var{args}
20125 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20126 knows whether it is reading an @dfn{executable},
20127 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20128 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20129 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20132 @emph{Warning:} To specify a file format with @code{set gnutarget},
20133 you must know the actual BFD name.
20137 @xref{Files, , Commands to Specify Files}.
20139 @kindex show gnutarget
20140 @item show gnutarget
20141 Use the @code{show gnutarget} command to display what file format
20142 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20143 @value{GDBN} will determine the file format for each file automatically,
20144 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20147 @cindex common targets
20148 Here are some common targets (available, or not, depending on the GDB
20153 @item target exec @var{program}
20154 @cindex executable file target
20155 An executable file. @samp{target exec @var{program}} is the same as
20156 @samp{exec-file @var{program}}.
20158 @item target core @var{filename}
20159 @cindex core dump file target
20160 A core dump file. @samp{target core @var{filename}} is the same as
20161 @samp{core-file @var{filename}}.
20163 @item target remote @var{medium}
20164 @cindex remote target
20165 A remote system connected to @value{GDBN} via a serial line or network
20166 connection. This command tells @value{GDBN} to use its own remote
20167 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20169 For example, if you have a board connected to @file{/dev/ttya} on the
20170 machine running @value{GDBN}, you could say:
20173 target remote /dev/ttya
20176 @code{target remote} supports the @code{load} command. This is only
20177 useful if you have some other way of getting the stub to the target
20178 system, and you can put it somewhere in memory where it won't get
20179 clobbered by the download.
20181 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20182 @cindex built-in simulator target
20183 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20191 works; however, you cannot assume that a specific memory map, device
20192 drivers, or even basic I/O is available, although some simulators do
20193 provide these. For info about any processor-specific simulator details,
20194 see the appropriate section in @ref{Embedded Processors, ,Embedded
20197 @item target native
20198 @cindex native target
20199 Setup for local/native process debugging. Useful to make the
20200 @code{run} command spawn native processes (likewise @code{attach},
20201 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20202 (@pxref{set auto-connect-native-target}).
20206 Different targets are available on different configurations of @value{GDBN};
20207 your configuration may have more or fewer targets.
20209 Many remote targets require you to download the executable's code once
20210 you've successfully established a connection. You may wish to control
20211 various aspects of this process.
20216 @kindex set hash@r{, for remote monitors}
20217 @cindex hash mark while downloading
20218 This command controls whether a hash mark @samp{#} is displayed while
20219 downloading a file to the remote monitor. If on, a hash mark is
20220 displayed after each S-record is successfully downloaded to the
20224 @kindex show hash@r{, for remote monitors}
20225 Show the current status of displaying the hash mark.
20227 @item set debug monitor
20228 @kindex set debug monitor
20229 @cindex display remote monitor communications
20230 Enable or disable display of communications messages between
20231 @value{GDBN} and the remote monitor.
20233 @item show debug monitor
20234 @kindex show debug monitor
20235 Show the current status of displaying communications between
20236 @value{GDBN} and the remote monitor.
20241 @kindex load @var{filename} @var{offset}
20242 @item load @var{filename} @var{offset}
20244 Depending on what remote debugging facilities are configured into
20245 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20246 is meant to make @var{filename} (an executable) available for debugging
20247 on the remote system---by downloading, or dynamic linking, for example.
20248 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20249 the @code{add-symbol-file} command.
20251 If your @value{GDBN} does not have a @code{load} command, attempting to
20252 execute it gets the error message ``@code{You can't do that when your
20253 target is @dots{}}''
20255 The file is loaded at whatever address is specified in the executable.
20256 For some object file formats, you can specify the load address when you
20257 link the program; for other formats, like a.out, the object file format
20258 specifies a fixed address.
20259 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20261 It is also possible to tell @value{GDBN} to load the executable file at a
20262 specific offset described by the optional argument @var{offset}. When
20263 @var{offset} is provided, @var{filename} must also be provided.
20265 Depending on the remote side capabilities, @value{GDBN} may be able to
20266 load programs into flash memory.
20268 @code{load} does not repeat if you press @key{RET} again after using it.
20273 @kindex flash-erase
20275 @anchor{flash-erase}
20277 Erases all known flash memory regions on the target.
20282 @section Choosing Target Byte Order
20284 @cindex choosing target byte order
20285 @cindex target byte order
20287 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20288 offer the ability to run either big-endian or little-endian byte
20289 orders. Usually the executable or symbol will include a bit to
20290 designate the endian-ness, and you will not need to worry about
20291 which to use. However, you may still find it useful to adjust
20292 @value{GDBN}'s idea of processor endian-ness manually.
20296 @item set endian big
20297 Instruct @value{GDBN} to assume the target is big-endian.
20299 @item set endian little
20300 Instruct @value{GDBN} to assume the target is little-endian.
20302 @item set endian auto
20303 Instruct @value{GDBN} to use the byte order associated with the
20307 Display @value{GDBN}'s current idea of the target byte order.
20311 Note that these commands merely adjust interpretation of symbolic
20312 data on the host, and that they have absolutely no effect on the
20316 @node Remote Debugging
20317 @chapter Debugging Remote Programs
20318 @cindex remote debugging
20320 If you are trying to debug a program running on a machine that cannot run
20321 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20322 For example, you might use remote debugging on an operating system kernel,
20323 or on a small system which does not have a general purpose operating system
20324 powerful enough to run a full-featured debugger.
20326 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20327 to make this work with particular debugging targets. In addition,
20328 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20329 but not specific to any particular target system) which you can use if you
20330 write the remote stubs---the code that runs on the remote system to
20331 communicate with @value{GDBN}.
20333 Other remote targets may be available in your
20334 configuration of @value{GDBN}; use @code{help target} to list them.
20337 * Connecting:: Connecting to a remote target
20338 * File Transfer:: Sending files to a remote system
20339 * Server:: Using the gdbserver program
20340 * Remote Configuration:: Remote configuration
20341 * Remote Stub:: Implementing a remote stub
20345 @section Connecting to a Remote Target
20346 @cindex remote debugging, connecting
20347 @cindex @code{gdbserver}, connecting
20348 @cindex remote debugging, types of connections
20349 @cindex @code{gdbserver}, types of connections
20350 @cindex @code{gdbserver}, @code{target remote} mode
20351 @cindex @code{gdbserver}, @code{target extended-remote} mode
20353 This section describes how to connect to a remote target, including the
20354 types of connections and their differences, how to set up executable and
20355 symbol files on the host and target, and the commands used for
20356 connecting to and disconnecting from the remote target.
20358 @subsection Types of Remote Connections
20360 @value{GDBN} supports two types of remote connections, @code{target remote}
20361 mode and @code{target extended-remote} mode. Note that many remote targets
20362 support only @code{target remote} mode. There are several major
20363 differences between the two types of connections, enumerated here:
20367 @cindex remote debugging, detach and program exit
20368 @item Result of detach or program exit
20369 @strong{With target remote mode:} When the debugged program exits or you
20370 detach from it, @value{GDBN} disconnects from the target. When using
20371 @code{gdbserver}, @code{gdbserver} will exit.
20373 @strong{With target extended-remote mode:} When the debugged program exits or
20374 you detach from it, @value{GDBN} remains connected to the target, even
20375 though no program is running. You can rerun the program, attach to a
20376 running program, or use @code{monitor} commands specific to the target.
20378 When using @code{gdbserver} in this case, it does not exit unless it was
20379 invoked using the @option{--once} option. If the @option{--once} option
20380 was not used, you can ask @code{gdbserver} to exit using the
20381 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20383 @item Specifying the program to debug
20384 For both connection types you use the @code{file} command to specify the
20385 program on the host system. If you are using @code{gdbserver} there are
20386 some differences in how to specify the location of the program on the
20389 @strong{With target remote mode:} You must either specify the program to debug
20390 on the @code{gdbserver} command line or use the @option{--attach} option
20391 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20393 @cindex @option{--multi}, @code{gdbserver} option
20394 @strong{With target extended-remote mode:} You may specify the program to debug
20395 on the @code{gdbserver} command line, or you can load the program or attach
20396 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20398 @anchor{--multi Option in Types of Remote Connnections}
20399 You can start @code{gdbserver} without supplying an initial command to run
20400 or process ID to attach. To do this, use the @option{--multi} command line
20401 option. Then you can connect using @code{target extended-remote} and start
20402 the program you want to debug (see below for details on using the
20403 @code{run} command in this scenario). Note that the conditions under which
20404 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20405 (@code{target remote} or @code{target extended-remote}). The
20406 @option{--multi} option to @code{gdbserver} has no influence on that.
20408 @item The @code{run} command
20409 @strong{With target remote mode:} The @code{run} command is not
20410 supported. Once a connection has been established, you can use all
20411 the usual @value{GDBN} commands to examine and change data. The
20412 remote program is already running, so you can use commands like
20413 @kbd{step} and @kbd{continue}.
20415 @strong{With target extended-remote mode:} The @code{run} command is
20416 supported. The @code{run} command uses the value set by
20417 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20418 the program to run. Command line arguments are supported, except for
20419 wildcard expansion and I/O redirection (@pxref{Arguments}).
20421 If you specify the program to debug on the command line, then the
20422 @code{run} command is not required to start execution, and you can
20423 resume using commands like @kbd{step} and @kbd{continue} as with
20424 @code{target remote} mode.
20426 @anchor{Attaching in Types of Remote Connections}
20428 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20429 not supported. To attach to a running program using @code{gdbserver}, you
20430 must use the @option{--attach} option (@pxref{Running gdbserver}).
20432 @strong{With target extended-remote mode:} To attach to a running program,
20433 you may use the @code{attach} command after the connection has been
20434 established. If you are using @code{gdbserver}, you may also invoke
20435 @code{gdbserver} using the @option{--attach} option
20436 (@pxref{Running gdbserver}).
20440 @anchor{Host and target files}
20441 @subsection Host and Target Files
20442 @cindex remote debugging, symbol files
20443 @cindex symbol files, remote debugging
20445 @value{GDBN}, running on the host, needs access to symbol and debugging
20446 information for your program running on the target. This requires
20447 access to an unstripped copy of your program, and possibly any associated
20448 symbol files. Note that this section applies equally to both @code{target
20449 remote} mode and @code{target extended-remote} mode.
20451 Some remote targets (@pxref{qXfer executable filename read}, and
20452 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20453 the same connection used to communicate with @value{GDBN}. With such a
20454 target, if the remote program is unstripped, the only command you need is
20455 @code{target remote} (or @code{target extended-remote}).
20457 If the remote program is stripped, or the target does not support remote
20458 program file access, start up @value{GDBN} using the name of the local
20459 unstripped copy of your program as the first argument, or use the
20460 @code{file} command. Use @code{set sysroot} to specify the location (on
20461 the host) of target libraries (unless your @value{GDBN} was compiled with
20462 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20463 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20466 The symbol file and target libraries must exactly match the executable
20467 and libraries on the target, with one exception: the files on the host
20468 system should not be stripped, even if the files on the target system
20469 are. Mismatched or missing files will lead to confusing results
20470 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20471 files may also prevent @code{gdbserver} from debugging multi-threaded
20474 @subsection Remote Connection Commands
20475 @cindex remote connection commands
20476 @value{GDBN} can communicate with the target over a serial line, or
20477 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20478 each case, @value{GDBN} uses the same protocol for debugging your
20479 program; only the medium carrying the debugging packets varies. The
20480 @code{target remote} and @code{target extended-remote} commands
20481 establish a connection to the target. Both commands accept the same
20482 arguments, which indicate the medium to use:
20486 @item target remote @var{serial-device}
20487 @itemx target extended-remote @var{serial-device}
20488 @cindex serial line, @code{target remote}
20489 Use @var{serial-device} to communicate with the target. For example,
20490 to use a serial line connected to the device named @file{/dev/ttyb}:
20493 target remote /dev/ttyb
20496 If you're using a serial line, you may want to give @value{GDBN} the
20497 @samp{--baud} option, or use the @code{set serial baud} command
20498 (@pxref{Remote Configuration, set serial baud}) before the
20499 @code{target} command.
20501 @item target remote @code{@var{host}:@var{port}}
20502 @itemx target remote @code{tcp:@var{host}:@var{port}}
20503 @itemx target extended-remote @code{@var{host}:@var{port}}
20504 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20505 @cindex @acronym{TCP} port, @code{target remote}
20506 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20507 The @var{host} may be either a host name or a numeric @acronym{IP}
20508 address; @var{port} must be a decimal number. The @var{host} could be
20509 the target machine itself, if it is directly connected to the net, or
20510 it might be a terminal server which in turn has a serial line to the
20513 For example, to connect to port 2828 on a terminal server named
20517 target remote manyfarms:2828
20520 If your remote target is actually running on the same machine as your
20521 debugger session (e.g.@: a simulator for your target running on the
20522 same host), you can omit the hostname. For example, to connect to
20523 port 1234 on your local machine:
20526 target remote :1234
20530 Note that the colon is still required here.
20532 @item target remote @code{udp:@var{host}:@var{port}}
20533 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20534 @cindex @acronym{UDP} port, @code{target remote}
20535 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20536 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20539 target remote udp:manyfarms:2828
20542 When using a @acronym{UDP} connection for remote debugging, you should
20543 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20544 can silently drop packets on busy or unreliable networks, which will
20545 cause havoc with your debugging session.
20547 @item target remote | @var{command}
20548 @itemx target extended-remote | @var{command}
20549 @cindex pipe, @code{target remote} to
20550 Run @var{command} in the background and communicate with it using a
20551 pipe. The @var{command} is a shell command, to be parsed and expanded
20552 by the system's command shell, @code{/bin/sh}; it should expect remote
20553 protocol packets on its standard input, and send replies on its
20554 standard output. You could use this to run a stand-alone simulator
20555 that speaks the remote debugging protocol, to make net connections
20556 using programs like @code{ssh}, or for other similar tricks.
20558 If @var{command} closes its standard output (perhaps by exiting),
20559 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20560 program has already exited, this will have no effect.)
20564 @cindex interrupting remote programs
20565 @cindex remote programs, interrupting
20566 Whenever @value{GDBN} is waiting for the remote program, if you type the
20567 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20568 program. This may or may not succeed, depending in part on the hardware
20569 and the serial drivers the remote system uses. If you type the
20570 interrupt character once again, @value{GDBN} displays this prompt:
20573 Interrupted while waiting for the program.
20574 Give up (and stop debugging it)? (y or n)
20577 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20578 the remote debugging session. (If you decide you want to try again later,
20579 you can use @kbd{target remote} again to connect once more.) If you type
20580 @kbd{n}, @value{GDBN} goes back to waiting.
20582 In @code{target extended-remote} mode, typing @kbd{n} will leave
20583 @value{GDBN} connected to the target.
20586 @kindex detach (remote)
20588 When you have finished debugging the remote program, you can use the
20589 @code{detach} command to release it from @value{GDBN} control.
20590 Detaching from the target normally resumes its execution, but the results
20591 will depend on your particular remote stub. After the @code{detach}
20592 command in @code{target remote} mode, @value{GDBN} is free to connect to
20593 another target. In @code{target extended-remote} mode, @value{GDBN} is
20594 still connected to the target.
20598 The @code{disconnect} command closes the connection to the target, and
20599 the target is generally not resumed. It will wait for @value{GDBN}
20600 (this instance or another one) to connect and continue debugging. After
20601 the @code{disconnect} command, @value{GDBN} is again free to connect to
20604 @cindex send command to remote monitor
20605 @cindex extend @value{GDBN} for remote targets
20606 @cindex add new commands for external monitor
20608 @item monitor @var{cmd}
20609 This command allows you to send arbitrary commands directly to the
20610 remote monitor. Since @value{GDBN} doesn't care about the commands it
20611 sends like this, this command is the way to extend @value{GDBN}---you
20612 can add new commands that only the external monitor will understand
20616 @node File Transfer
20617 @section Sending files to a remote system
20618 @cindex remote target, file transfer
20619 @cindex file transfer
20620 @cindex sending files to remote systems
20622 Some remote targets offer the ability to transfer files over the same
20623 connection used to communicate with @value{GDBN}. This is convenient
20624 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20625 running @code{gdbserver} over a network interface. For other targets,
20626 e.g.@: embedded devices with only a single serial port, this may be
20627 the only way to upload or download files.
20629 Not all remote targets support these commands.
20633 @item remote put @var{hostfile} @var{targetfile}
20634 Copy file @var{hostfile} from the host system (the machine running
20635 @value{GDBN}) to @var{targetfile} on the target system.
20638 @item remote get @var{targetfile} @var{hostfile}
20639 Copy file @var{targetfile} from the target system to @var{hostfile}
20640 on the host system.
20642 @kindex remote delete
20643 @item remote delete @var{targetfile}
20644 Delete @var{targetfile} from the target system.
20649 @section Using the @code{gdbserver} Program
20652 @cindex remote connection without stubs
20653 @code{gdbserver} is a control program for Unix-like systems, which
20654 allows you to connect your program with a remote @value{GDBN} via
20655 @code{target remote} or @code{target extended-remote}---but without
20656 linking in the usual debugging stub.
20658 @code{gdbserver} is not a complete replacement for the debugging stubs,
20659 because it requires essentially the same operating-system facilities
20660 that @value{GDBN} itself does. In fact, a system that can run
20661 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20662 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20663 because it is a much smaller program than @value{GDBN} itself. It is
20664 also easier to port than all of @value{GDBN}, so you may be able to get
20665 started more quickly on a new system by using @code{gdbserver}.
20666 Finally, if you develop code for real-time systems, you may find that
20667 the tradeoffs involved in real-time operation make it more convenient to
20668 do as much development work as possible on another system, for example
20669 by cross-compiling. You can use @code{gdbserver} to make a similar
20670 choice for debugging.
20672 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20673 or a TCP connection, using the standard @value{GDBN} remote serial
20677 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20678 Do not run @code{gdbserver} connected to any public network; a
20679 @value{GDBN} connection to @code{gdbserver} provides access to the
20680 target system with the same privileges as the user running
20684 @anchor{Running gdbserver}
20685 @subsection Running @code{gdbserver}
20686 @cindex arguments, to @code{gdbserver}
20687 @cindex @code{gdbserver}, command-line arguments
20689 Run @code{gdbserver} on the target system. You need a copy of the
20690 program you want to debug, including any libraries it requires.
20691 @code{gdbserver} does not need your program's symbol table, so you can
20692 strip the program if necessary to save space. @value{GDBN} on the host
20693 system does all the symbol handling.
20695 To use the server, you must tell it how to communicate with @value{GDBN};
20696 the name of your program; and the arguments for your program. The usual
20700 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20703 @var{comm} is either a device name (to use a serial line), or a TCP
20704 hostname and portnumber, or @code{-} or @code{stdio} to use
20705 stdin/stdout of @code{gdbserver}.
20706 For example, to debug Emacs with the argument
20707 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20711 target> gdbserver /dev/com1 emacs foo.txt
20714 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20717 To use a TCP connection instead of a serial line:
20720 target> gdbserver host:2345 emacs foo.txt
20723 The only difference from the previous example is the first argument,
20724 specifying that you are communicating with the host @value{GDBN} via
20725 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20726 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20727 (Currently, the @samp{host} part is ignored.) You can choose any number
20728 you want for the port number as long as it does not conflict with any
20729 TCP ports already in use on the target system (for example, @code{23} is
20730 reserved for @code{telnet}).@footnote{If you choose a port number that
20731 conflicts with another service, @code{gdbserver} prints an error message
20732 and exits.} You must use the same port number with the host @value{GDBN}
20733 @code{target remote} command.
20735 The @code{stdio} connection is useful when starting @code{gdbserver}
20739 (gdb) target remote | ssh -T hostname gdbserver - hello
20742 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20743 and we don't want escape-character handling. Ssh does this by default when
20744 a command is provided, the flag is provided to make it explicit.
20745 You could elide it if you want to.
20747 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20748 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20749 display through a pipe connected to gdbserver.
20750 Both @code{stdout} and @code{stderr} use the same pipe.
20752 @anchor{Attaching to a program}
20753 @subsubsection Attaching to a Running Program
20754 @cindex attach to a program, @code{gdbserver}
20755 @cindex @option{--attach}, @code{gdbserver} option
20757 On some targets, @code{gdbserver} can also attach to running programs.
20758 This is accomplished via the @code{--attach} argument. The syntax is:
20761 target> gdbserver --attach @var{comm} @var{pid}
20764 @var{pid} is the process ID of a currently running process. It isn't
20765 necessary to point @code{gdbserver} at a binary for the running process.
20767 In @code{target extended-remote} mode, you can also attach using the
20768 @value{GDBN} attach command
20769 (@pxref{Attaching in Types of Remote Connections}).
20772 You can debug processes by name instead of process ID if your target has the
20773 @code{pidof} utility:
20776 target> gdbserver --attach @var{comm} `pidof @var{program}`
20779 In case more than one copy of @var{program} is running, or @var{program}
20780 has multiple threads, most versions of @code{pidof} support the
20781 @code{-s} option to only return the first process ID.
20783 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20785 This section applies only when @code{gdbserver} is run to listen on a TCP
20788 @code{gdbserver} normally terminates after all of its debugged processes have
20789 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20790 extended-remote}, @code{gdbserver} stays running even with no processes left.
20791 @value{GDBN} normally terminates the spawned debugged process on its exit,
20792 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20793 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20794 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20795 stays running even in the @kbd{target remote} mode.
20797 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20798 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20799 completeness, at most one @value{GDBN} can be connected at a time.
20801 @cindex @option{--once}, @code{gdbserver} option
20802 By default, @code{gdbserver} keeps the listening TCP port open, so that
20803 subsequent connections are possible. However, if you start @code{gdbserver}
20804 with the @option{--once} option, it will stop listening for any further
20805 connection attempts after connecting to the first @value{GDBN} session. This
20806 means no further connections to @code{gdbserver} will be possible after the
20807 first one. It also means @code{gdbserver} will terminate after the first
20808 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20809 connections and even in the @kbd{target extended-remote} mode. The
20810 @option{--once} option allows reusing the same port number for connecting to
20811 multiple instances of @code{gdbserver} running on the same host, since each
20812 instance closes its port after the first connection.
20814 @anchor{Other Command-Line Arguments for gdbserver}
20815 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20817 You can use the @option{--multi} option to start @code{gdbserver} without
20818 specifying a program to debug or a process to attach to. Then you can
20819 attach in @code{target extended-remote} mode and run or attach to a
20820 program. For more information,
20821 @pxref{--multi Option in Types of Remote Connnections}.
20823 @cindex @option{--debug}, @code{gdbserver} option
20824 The @option{--debug} option tells @code{gdbserver} to display extra
20825 status information about the debugging process.
20826 @cindex @option{--remote-debug}, @code{gdbserver} option
20827 The @option{--remote-debug} option tells @code{gdbserver} to display
20828 remote protocol debug output. These options are intended for
20829 @code{gdbserver} development and for bug reports to the developers.
20831 @cindex @option{--debug-format}, @code{gdbserver} option
20832 The @option{--debug-format=option1[,option2,...]} option tells
20833 @code{gdbserver} to include additional information in each output.
20834 Possible options are:
20838 Turn off all extra information in debugging output.
20840 Turn on all extra information in debugging output.
20842 Include a timestamp in each line of debugging output.
20845 Options are processed in order. Thus, for example, if @option{none}
20846 appears last then no additional information is added to debugging output.
20848 @cindex @option{--wrapper}, @code{gdbserver} option
20849 The @option{--wrapper} option specifies a wrapper to launch programs
20850 for debugging. The option should be followed by the name of the
20851 wrapper, then any command-line arguments to pass to the wrapper, then
20852 @kbd{--} indicating the end of the wrapper arguments.
20854 @code{gdbserver} runs the specified wrapper program with a combined
20855 command line including the wrapper arguments, then the name of the
20856 program to debug, then any arguments to the program. The wrapper
20857 runs until it executes your program, and then @value{GDBN} gains control.
20859 You can use any program that eventually calls @code{execve} with
20860 its arguments as a wrapper. Several standard Unix utilities do
20861 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20862 with @code{exec "$@@"} will also work.
20864 For example, you can use @code{env} to pass an environment variable to
20865 the debugged program, without setting the variable in @code{gdbserver}'s
20869 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20872 @cindex @option{--selftest}
20873 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20876 $ gdbserver --selftest
20877 Ran 2 unit tests, 0 failed
20880 These tests are disabled in release.
20881 @subsection Connecting to @code{gdbserver}
20883 The basic procedure for connecting to the remote target is:
20887 Run @value{GDBN} on the host system.
20890 Make sure you have the necessary symbol files
20891 (@pxref{Host and target files}).
20892 Load symbols for your application using the @code{file} command before you
20893 connect. Use @code{set sysroot} to locate target libraries (unless your
20894 @value{GDBN} was compiled with the correct sysroot using
20895 @code{--with-sysroot}).
20898 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20899 For TCP connections, you must start up @code{gdbserver} prior to using
20900 the @code{target} command. Otherwise you may get an error whose
20901 text depends on the host system, but which usually looks something like
20902 @samp{Connection refused}. Don't use the @code{load}
20903 command in @value{GDBN} when using @code{target remote} mode, since the
20904 program is already on the target.
20908 @anchor{Monitor Commands for gdbserver}
20909 @subsection Monitor Commands for @code{gdbserver}
20910 @cindex monitor commands, for @code{gdbserver}
20912 During a @value{GDBN} session using @code{gdbserver}, you can use the
20913 @code{monitor} command to send special requests to @code{gdbserver}.
20914 Here are the available commands.
20918 List the available monitor commands.
20920 @item monitor set debug 0
20921 @itemx monitor set debug 1
20922 Disable or enable general debugging messages.
20924 @item monitor set remote-debug 0
20925 @itemx monitor set remote-debug 1
20926 Disable or enable specific debugging messages associated with the remote
20927 protocol (@pxref{Remote Protocol}).
20929 @item monitor set debug-format option1@r{[},option2,...@r{]}
20930 Specify additional text to add to debugging messages.
20931 Possible options are:
20935 Turn off all extra information in debugging output.
20937 Turn on all extra information in debugging output.
20939 Include a timestamp in each line of debugging output.
20942 Options are processed in order. Thus, for example, if @option{none}
20943 appears last then no additional information is added to debugging output.
20945 @item monitor set libthread-db-search-path [PATH]
20946 @cindex gdbserver, search path for @code{libthread_db}
20947 When this command is issued, @var{path} is a colon-separated list of
20948 directories to search for @code{libthread_db} (@pxref{Threads,,set
20949 libthread-db-search-path}). If you omit @var{path},
20950 @samp{libthread-db-search-path} will be reset to its default value.
20952 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20953 not supported in @code{gdbserver}.
20956 Tell gdbserver to exit immediately. This command should be followed by
20957 @code{disconnect} to close the debugging session. @code{gdbserver} will
20958 detach from any attached processes and kill any processes it created.
20959 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20960 of a multi-process mode debug session.
20964 @subsection Tracepoints support in @code{gdbserver}
20965 @cindex tracepoints support in @code{gdbserver}
20967 On some targets, @code{gdbserver} supports tracepoints, fast
20968 tracepoints and static tracepoints.
20970 For fast or static tracepoints to work, a special library called the
20971 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20972 This library is built and distributed as an integral part of
20973 @code{gdbserver}. In addition, support for static tracepoints
20974 requires building the in-process agent library with static tracepoints
20975 support. At present, the UST (LTTng Userspace Tracer,
20976 @url{http://lttng.org/ust}) tracing engine is supported. This support
20977 is automatically available if UST development headers are found in the
20978 standard include path when @code{gdbserver} is built, or if
20979 @code{gdbserver} was explicitly configured using @option{--with-ust}
20980 to point at such headers. You can explicitly disable the support
20981 using @option{--with-ust=no}.
20983 There are several ways to load the in-process agent in your program:
20986 @item Specifying it as dependency at link time
20988 You can link your program dynamically with the in-process agent
20989 library. On most systems, this is accomplished by adding
20990 @code{-linproctrace} to the link command.
20992 @item Using the system's preloading mechanisms
20994 You can force loading the in-process agent at startup time by using
20995 your system's support for preloading shared libraries. Many Unixes
20996 support the concept of preloading user defined libraries. In most
20997 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20998 in the environment. See also the description of @code{gdbserver}'s
20999 @option{--wrapper} command line option.
21001 @item Using @value{GDBN} to force loading the agent at run time
21003 On some systems, you can force the inferior to load a shared library,
21004 by calling a dynamic loader function in the inferior that takes care
21005 of dynamically looking up and loading a shared library. On most Unix
21006 systems, the function is @code{dlopen}. You'll use the @code{call}
21007 command for that. For example:
21010 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21013 Note that on most Unix systems, for the @code{dlopen} function to be
21014 available, the program needs to be linked with @code{-ldl}.
21017 On systems that have a userspace dynamic loader, like most Unix
21018 systems, when you connect to @code{gdbserver} using @code{target
21019 remote}, you'll find that the program is stopped at the dynamic
21020 loader's entry point, and no shared library has been loaded in the
21021 program's address space yet, including the in-process agent. In that
21022 case, before being able to use any of the fast or static tracepoints
21023 features, you need to let the loader run and load the shared
21024 libraries. The simplest way to do that is to run the program to the
21025 main procedure. E.g., if debugging a C or C@t{++} program, start
21026 @code{gdbserver} like so:
21029 $ gdbserver :9999 myprogram
21032 Start GDB and connect to @code{gdbserver} like so, and run to main:
21036 (@value{GDBP}) target remote myhost:9999
21037 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21038 (@value{GDBP}) b main
21039 (@value{GDBP}) continue
21042 The in-process tracing agent library should now be loaded into the
21043 process; you can confirm it with the @code{info sharedlibrary}
21044 command, which will list @file{libinproctrace.so} as loaded in the
21045 process. You are now ready to install fast tracepoints, list static
21046 tracepoint markers, probe static tracepoints markers, and start
21049 @node Remote Configuration
21050 @section Remote Configuration
21053 @kindex show remote
21054 This section documents the configuration options available when
21055 debugging remote programs. For the options related to the File I/O
21056 extensions of the remote protocol, see @ref{system,
21057 system-call-allowed}.
21060 @item set remoteaddresssize @var{bits}
21061 @cindex address size for remote targets
21062 @cindex bits in remote address
21063 Set the maximum size of address in a memory packet to the specified
21064 number of bits. @value{GDBN} will mask off the address bits above
21065 that number, when it passes addresses to the remote target. The
21066 default value is the number of bits in the target's address.
21068 @item show remoteaddresssize
21069 Show the current value of remote address size in bits.
21071 @item set serial baud @var{n}
21072 @cindex baud rate for remote targets
21073 Set the baud rate for the remote serial I/O to @var{n} baud. The
21074 value is used to set the speed of the serial port used for debugging
21077 @item show serial baud
21078 Show the current speed of the remote connection.
21080 @item set serial parity @var{parity}
21081 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21082 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21084 @item show serial parity
21085 Show the current parity of the serial port.
21087 @item set remotebreak
21088 @cindex interrupt remote programs
21089 @cindex BREAK signal instead of Ctrl-C
21090 @anchor{set remotebreak}
21091 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21092 when you type @kbd{Ctrl-c} to interrupt the program running
21093 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21094 character instead. The default is off, since most remote systems
21095 expect to see @samp{Ctrl-C} as the interrupt signal.
21097 @item show remotebreak
21098 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21099 interrupt the remote program.
21101 @item set remoteflow on
21102 @itemx set remoteflow off
21103 @kindex set remoteflow
21104 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21105 on the serial port used to communicate to the remote target.
21107 @item show remoteflow
21108 @kindex show remoteflow
21109 Show the current setting of hardware flow control.
21111 @item set remotelogbase @var{base}
21112 Set the base (a.k.a.@: radix) of logging serial protocol
21113 communications to @var{base}. Supported values of @var{base} are:
21114 @code{ascii}, @code{octal}, and @code{hex}. The default is
21117 @item show remotelogbase
21118 Show the current setting of the radix for logging remote serial
21121 @item set remotelogfile @var{file}
21122 @cindex record serial communications on file
21123 Record remote serial communications on the named @var{file}. The
21124 default is not to record at all.
21126 @item show remotelogfile.
21127 Show the current setting of the file name on which to record the
21128 serial communications.
21130 @item set remotetimeout @var{num}
21131 @cindex timeout for serial communications
21132 @cindex remote timeout
21133 Set the timeout limit to wait for the remote target to respond to
21134 @var{num} seconds. The default is 2 seconds.
21136 @item show remotetimeout
21137 Show the current number of seconds to wait for the remote target
21140 @cindex limit hardware breakpoints and watchpoints
21141 @cindex remote target, limit break- and watchpoints
21142 @anchor{set remote hardware-watchpoint-limit}
21143 @anchor{set remote hardware-breakpoint-limit}
21144 @item set remote hardware-watchpoint-limit @var{limit}
21145 @itemx set remote hardware-breakpoint-limit @var{limit}
21146 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
21147 watchpoints. A limit of -1, the default, is treated as unlimited.
21149 @cindex limit hardware watchpoints length
21150 @cindex remote target, limit watchpoints length
21151 @anchor{set remote hardware-watchpoint-length-limit}
21152 @item set remote hardware-watchpoint-length-limit @var{limit}
21153 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
21154 a remote hardware watchpoint. A limit of -1, the default, is treated
21157 @item show remote hardware-watchpoint-length-limit
21158 Show the current limit (in bytes) of the maximum length of
21159 a remote hardware watchpoint.
21161 @item set remote exec-file @var{filename}
21162 @itemx show remote exec-file
21163 @anchor{set remote exec-file}
21164 @cindex executable file, for remote target
21165 Select the file used for @code{run} with @code{target
21166 extended-remote}. This should be set to a filename valid on the
21167 target system. If it is not set, the target will use a default
21168 filename (e.g.@: the last program run).
21170 @item set remote interrupt-sequence
21171 @cindex interrupt remote programs
21172 @cindex select Ctrl-C, BREAK or BREAK-g
21173 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21174 @samp{BREAK-g} as the
21175 sequence to the remote target in order to interrupt the execution.
21176 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21177 is high level of serial line for some certain time.
21178 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21179 It is @code{BREAK} signal followed by character @code{g}.
21181 @item show interrupt-sequence
21182 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21183 is sent by @value{GDBN} to interrupt the remote program.
21184 @code{BREAK-g} is BREAK signal followed by @code{g} and
21185 also known as Magic SysRq g.
21187 @item set remote interrupt-on-connect
21188 @cindex send interrupt-sequence on start
21189 Specify whether interrupt-sequence is sent to remote target when
21190 @value{GDBN} connects to it. This is mostly needed when you debug
21191 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21192 which is known as Magic SysRq g in order to connect @value{GDBN}.
21194 @item show interrupt-on-connect
21195 Show whether interrupt-sequence is sent
21196 to remote target when @value{GDBN} connects to it.
21200 @item set tcp auto-retry on
21201 @cindex auto-retry, for remote TCP target
21202 Enable auto-retry for remote TCP connections. This is useful if the remote
21203 debugging agent is launched in parallel with @value{GDBN}; there is a race
21204 condition because the agent may not become ready to accept the connection
21205 before @value{GDBN} attempts to connect. When auto-retry is
21206 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21207 to establish the connection using the timeout specified by
21208 @code{set tcp connect-timeout}.
21210 @item set tcp auto-retry off
21211 Do not auto-retry failed TCP connections.
21213 @item show tcp auto-retry
21214 Show the current auto-retry setting.
21216 @item set tcp connect-timeout @var{seconds}
21217 @itemx set tcp connect-timeout unlimited
21218 @cindex connection timeout, for remote TCP target
21219 @cindex timeout, for remote target connection
21220 Set the timeout for establishing a TCP connection to the remote target to
21221 @var{seconds}. The timeout affects both polling to retry failed connections
21222 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21223 that are merely slow to complete, and represents an approximate cumulative
21224 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21225 @value{GDBN} will keep attempting to establish a connection forever,
21226 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21228 @item show tcp connect-timeout
21229 Show the current connection timeout setting.
21232 @cindex remote packets, enabling and disabling
21233 The @value{GDBN} remote protocol autodetects the packets supported by
21234 your debugging stub. If you need to override the autodetection, you
21235 can use these commands to enable or disable individual packets. Each
21236 packet can be set to @samp{on} (the remote target supports this
21237 packet), @samp{off} (the remote target does not support this packet),
21238 or @samp{auto} (detect remote target support for this packet). They
21239 all default to @samp{auto}. For more information about each packet,
21240 see @ref{Remote Protocol}.
21242 During normal use, you should not have to use any of these commands.
21243 If you do, that may be a bug in your remote debugging stub, or a bug
21244 in @value{GDBN}. You may want to report the problem to the
21245 @value{GDBN} developers.
21247 For each packet @var{name}, the command to enable or disable the
21248 packet is @code{set remote @var{name}-packet}. The available settings
21251 @multitable @columnfractions 0.28 0.32 0.25
21254 @tab Related Features
21256 @item @code{fetch-register}
21258 @tab @code{info registers}
21260 @item @code{set-register}
21264 @item @code{binary-download}
21266 @tab @code{load}, @code{set}
21268 @item @code{read-aux-vector}
21269 @tab @code{qXfer:auxv:read}
21270 @tab @code{info auxv}
21272 @item @code{symbol-lookup}
21273 @tab @code{qSymbol}
21274 @tab Detecting multiple threads
21276 @item @code{attach}
21277 @tab @code{vAttach}
21280 @item @code{verbose-resume}
21282 @tab Stepping or resuming multiple threads
21288 @item @code{software-breakpoint}
21292 @item @code{hardware-breakpoint}
21296 @item @code{write-watchpoint}
21300 @item @code{read-watchpoint}
21304 @item @code{access-watchpoint}
21308 @item @code{pid-to-exec-file}
21309 @tab @code{qXfer:exec-file:read}
21310 @tab @code{attach}, @code{run}
21312 @item @code{target-features}
21313 @tab @code{qXfer:features:read}
21314 @tab @code{set architecture}
21316 @item @code{library-info}
21317 @tab @code{qXfer:libraries:read}
21318 @tab @code{info sharedlibrary}
21320 @item @code{memory-map}
21321 @tab @code{qXfer:memory-map:read}
21322 @tab @code{info mem}
21324 @item @code{read-sdata-object}
21325 @tab @code{qXfer:sdata:read}
21326 @tab @code{print $_sdata}
21328 @item @code{read-spu-object}
21329 @tab @code{qXfer:spu:read}
21330 @tab @code{info spu}
21332 @item @code{write-spu-object}
21333 @tab @code{qXfer:spu:write}
21334 @tab @code{info spu}
21336 @item @code{read-siginfo-object}
21337 @tab @code{qXfer:siginfo:read}
21338 @tab @code{print $_siginfo}
21340 @item @code{write-siginfo-object}
21341 @tab @code{qXfer:siginfo:write}
21342 @tab @code{set $_siginfo}
21344 @item @code{threads}
21345 @tab @code{qXfer:threads:read}
21346 @tab @code{info threads}
21348 @item @code{get-thread-local-@*storage-address}
21349 @tab @code{qGetTLSAddr}
21350 @tab Displaying @code{__thread} variables
21352 @item @code{get-thread-information-block-address}
21353 @tab @code{qGetTIBAddr}
21354 @tab Display MS-Windows Thread Information Block.
21356 @item @code{search-memory}
21357 @tab @code{qSearch:memory}
21360 @item @code{supported-packets}
21361 @tab @code{qSupported}
21362 @tab Remote communications parameters
21364 @item @code{catch-syscalls}
21365 @tab @code{QCatchSyscalls}
21366 @tab @code{catch syscall}
21368 @item @code{pass-signals}
21369 @tab @code{QPassSignals}
21370 @tab @code{handle @var{signal}}
21372 @item @code{program-signals}
21373 @tab @code{QProgramSignals}
21374 @tab @code{handle @var{signal}}
21376 @item @code{hostio-close-packet}
21377 @tab @code{vFile:close}
21378 @tab @code{remote get}, @code{remote put}
21380 @item @code{hostio-open-packet}
21381 @tab @code{vFile:open}
21382 @tab @code{remote get}, @code{remote put}
21384 @item @code{hostio-pread-packet}
21385 @tab @code{vFile:pread}
21386 @tab @code{remote get}, @code{remote put}
21388 @item @code{hostio-pwrite-packet}
21389 @tab @code{vFile:pwrite}
21390 @tab @code{remote get}, @code{remote put}
21392 @item @code{hostio-unlink-packet}
21393 @tab @code{vFile:unlink}
21394 @tab @code{remote delete}
21396 @item @code{hostio-readlink-packet}
21397 @tab @code{vFile:readlink}
21400 @item @code{hostio-fstat-packet}
21401 @tab @code{vFile:fstat}
21404 @item @code{hostio-setfs-packet}
21405 @tab @code{vFile:setfs}
21408 @item @code{noack-packet}
21409 @tab @code{QStartNoAckMode}
21410 @tab Packet acknowledgment
21412 @item @code{osdata}
21413 @tab @code{qXfer:osdata:read}
21414 @tab @code{info os}
21416 @item @code{query-attached}
21417 @tab @code{qAttached}
21418 @tab Querying remote process attach state.
21420 @item @code{trace-buffer-size}
21421 @tab @code{QTBuffer:size}
21422 @tab @code{set trace-buffer-size}
21424 @item @code{trace-status}
21425 @tab @code{qTStatus}
21426 @tab @code{tstatus}
21428 @item @code{traceframe-info}
21429 @tab @code{qXfer:traceframe-info:read}
21430 @tab Traceframe info
21432 @item @code{install-in-trace}
21433 @tab @code{InstallInTrace}
21434 @tab Install tracepoint in tracing
21436 @item @code{disable-randomization}
21437 @tab @code{QDisableRandomization}
21438 @tab @code{set disable-randomization}
21440 @item @code{startup-with-shell}
21441 @tab @code{QStartupWithShell}
21442 @tab @code{set startup-with-shell}
21444 @item @code{environment-hex-encoded}
21445 @tab @code{QEnvironmentHexEncoded}
21446 @tab @code{set environment}
21448 @item @code{environment-unset}
21449 @tab @code{QEnvironmentUnset}
21450 @tab @code{unset environment}
21452 @item @code{environment-reset}
21453 @tab @code{QEnvironmentReset}
21454 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21456 @item @code{set-working-dir}
21457 @tab @code{QSetWorkingDir}
21458 @tab @code{set cwd}
21460 @item @code{conditional-breakpoints-packet}
21461 @tab @code{Z0 and Z1}
21462 @tab @code{Support for target-side breakpoint condition evaluation}
21464 @item @code{multiprocess-extensions}
21465 @tab @code{multiprocess extensions}
21466 @tab Debug multiple processes and remote process PID awareness
21468 @item @code{swbreak-feature}
21469 @tab @code{swbreak stop reason}
21472 @item @code{hwbreak-feature}
21473 @tab @code{hwbreak stop reason}
21476 @item @code{fork-event-feature}
21477 @tab @code{fork stop reason}
21480 @item @code{vfork-event-feature}
21481 @tab @code{vfork stop reason}
21484 @item @code{exec-event-feature}
21485 @tab @code{exec stop reason}
21488 @item @code{thread-events}
21489 @tab @code{QThreadEvents}
21490 @tab Tracking thread lifetime.
21492 @item @code{no-resumed-stop-reply}
21493 @tab @code{no resumed thread left stop reply}
21494 @tab Tracking thread lifetime.
21499 @section Implementing a Remote Stub
21501 @cindex debugging stub, example
21502 @cindex remote stub, example
21503 @cindex stub example, remote debugging
21504 The stub files provided with @value{GDBN} implement the target side of the
21505 communication protocol, and the @value{GDBN} side is implemented in the
21506 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21507 these subroutines to communicate, and ignore the details. (If you're
21508 implementing your own stub file, you can still ignore the details: start
21509 with one of the existing stub files. @file{sparc-stub.c} is the best
21510 organized, and therefore the easiest to read.)
21512 @cindex remote serial debugging, overview
21513 To debug a program running on another machine (the debugging
21514 @dfn{target} machine), you must first arrange for all the usual
21515 prerequisites for the program to run by itself. For example, for a C
21520 A startup routine to set up the C runtime environment; these usually
21521 have a name like @file{crt0}. The startup routine may be supplied by
21522 your hardware supplier, or you may have to write your own.
21525 A C subroutine library to support your program's
21526 subroutine calls, notably managing input and output.
21529 A way of getting your program to the other machine---for example, a
21530 download program. These are often supplied by the hardware
21531 manufacturer, but you may have to write your own from hardware
21535 The next step is to arrange for your program to use a serial port to
21536 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21537 machine). In general terms, the scheme looks like this:
21541 @value{GDBN} already understands how to use this protocol; when everything
21542 else is set up, you can simply use the @samp{target remote} command
21543 (@pxref{Targets,,Specifying a Debugging Target}).
21545 @item On the target,
21546 you must link with your program a few special-purpose subroutines that
21547 implement the @value{GDBN} remote serial protocol. The file containing these
21548 subroutines is called a @dfn{debugging stub}.
21550 On certain remote targets, you can use an auxiliary program
21551 @code{gdbserver} instead of linking a stub into your program.
21552 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21555 The debugging stub is specific to the architecture of the remote
21556 machine; for example, use @file{sparc-stub.c} to debug programs on
21559 @cindex remote serial stub list
21560 These working remote stubs are distributed with @value{GDBN}:
21565 @cindex @file{i386-stub.c}
21568 For Intel 386 and compatible architectures.
21571 @cindex @file{m68k-stub.c}
21572 @cindex Motorola 680x0
21574 For Motorola 680x0 architectures.
21577 @cindex @file{sh-stub.c}
21580 For Renesas SH architectures.
21583 @cindex @file{sparc-stub.c}
21585 For @sc{sparc} architectures.
21587 @item sparcl-stub.c
21588 @cindex @file{sparcl-stub.c}
21591 For Fujitsu @sc{sparclite} architectures.
21595 The @file{README} file in the @value{GDBN} distribution may list other
21596 recently added stubs.
21599 * Stub Contents:: What the stub can do for you
21600 * Bootstrapping:: What you must do for the stub
21601 * Debug Session:: Putting it all together
21604 @node Stub Contents
21605 @subsection What the Stub Can Do for You
21607 @cindex remote serial stub
21608 The debugging stub for your architecture supplies these three
21612 @item set_debug_traps
21613 @findex set_debug_traps
21614 @cindex remote serial stub, initialization
21615 This routine arranges for @code{handle_exception} to run when your
21616 program stops. You must call this subroutine explicitly in your
21617 program's startup code.
21619 @item handle_exception
21620 @findex handle_exception
21621 @cindex remote serial stub, main routine
21622 This is the central workhorse, but your program never calls it
21623 explicitly---the setup code arranges for @code{handle_exception} to
21624 run when a trap is triggered.
21626 @code{handle_exception} takes control when your program stops during
21627 execution (for example, on a breakpoint), and mediates communications
21628 with @value{GDBN} on the host machine. This is where the communications
21629 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21630 representative on the target machine. It begins by sending summary
21631 information on the state of your program, then continues to execute,
21632 retrieving and transmitting any information @value{GDBN} needs, until you
21633 execute a @value{GDBN} command that makes your program resume; at that point,
21634 @code{handle_exception} returns control to your own code on the target
21638 @cindex @code{breakpoint} subroutine, remote
21639 Use this auxiliary subroutine to make your program contain a
21640 breakpoint. Depending on the particular situation, this may be the only
21641 way for @value{GDBN} to get control. For instance, if your target
21642 machine has some sort of interrupt button, you won't need to call this;
21643 pressing the interrupt button transfers control to
21644 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21645 simply receiving characters on the serial port may also trigger a trap;
21646 again, in that situation, you don't need to call @code{breakpoint} from
21647 your own program---simply running @samp{target remote} from the host
21648 @value{GDBN} session gets control.
21650 Call @code{breakpoint} if none of these is true, or if you simply want
21651 to make certain your program stops at a predetermined point for the
21652 start of your debugging session.
21655 @node Bootstrapping
21656 @subsection What You Must Do for the Stub
21658 @cindex remote stub, support routines
21659 The debugging stubs that come with @value{GDBN} are set up for a particular
21660 chip architecture, but they have no information about the rest of your
21661 debugging target machine.
21663 First of all you need to tell the stub how to communicate with the
21667 @item int getDebugChar()
21668 @findex getDebugChar
21669 Write this subroutine to read a single character from the serial port.
21670 It may be identical to @code{getchar} for your target system; a
21671 different name is used to allow you to distinguish the two if you wish.
21673 @item void putDebugChar(int)
21674 @findex putDebugChar
21675 Write this subroutine to write a single character to the serial port.
21676 It may be identical to @code{putchar} for your target system; a
21677 different name is used to allow you to distinguish the two if you wish.
21680 @cindex control C, and remote debugging
21681 @cindex interrupting remote targets
21682 If you want @value{GDBN} to be able to stop your program while it is
21683 running, you need to use an interrupt-driven serial driver, and arrange
21684 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21685 character). That is the character which @value{GDBN} uses to tell the
21686 remote system to stop.
21688 Getting the debugging target to return the proper status to @value{GDBN}
21689 probably requires changes to the standard stub; one quick and dirty way
21690 is to just execute a breakpoint instruction (the ``dirty'' part is that
21691 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21693 Other routines you need to supply are:
21696 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21697 @findex exceptionHandler
21698 Write this function to install @var{exception_address} in the exception
21699 handling tables. You need to do this because the stub does not have any
21700 way of knowing what the exception handling tables on your target system
21701 are like (for example, the processor's table might be in @sc{rom},
21702 containing entries which point to a table in @sc{ram}).
21703 The @var{exception_number} specifies the exception which should be changed;
21704 its meaning is architecture-dependent (for example, different numbers
21705 might represent divide by zero, misaligned access, etc). When this
21706 exception occurs, control should be transferred directly to
21707 @var{exception_address}, and the processor state (stack, registers,
21708 and so on) should be just as it is when a processor exception occurs. So if
21709 you want to use a jump instruction to reach @var{exception_address}, it
21710 should be a simple jump, not a jump to subroutine.
21712 For the 386, @var{exception_address} should be installed as an interrupt
21713 gate so that interrupts are masked while the handler runs. The gate
21714 should be at privilege level 0 (the most privileged level). The
21715 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21716 help from @code{exceptionHandler}.
21718 @item void flush_i_cache()
21719 @findex flush_i_cache
21720 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21721 instruction cache, if any, on your target machine. If there is no
21722 instruction cache, this subroutine may be a no-op.
21724 On target machines that have instruction caches, @value{GDBN} requires this
21725 function to make certain that the state of your program is stable.
21729 You must also make sure this library routine is available:
21732 @item void *memset(void *, int, int)
21734 This is the standard library function @code{memset} that sets an area of
21735 memory to a known value. If you have one of the free versions of
21736 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21737 either obtain it from your hardware manufacturer, or write your own.
21740 If you do not use the GNU C compiler, you may need other standard
21741 library subroutines as well; this varies from one stub to another,
21742 but in general the stubs are likely to use any of the common library
21743 subroutines which @code{@value{NGCC}} generates as inline code.
21746 @node Debug Session
21747 @subsection Putting it All Together
21749 @cindex remote serial debugging summary
21750 In summary, when your program is ready to debug, you must follow these
21755 Make sure you have defined the supporting low-level routines
21756 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21758 @code{getDebugChar}, @code{putDebugChar},
21759 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21763 Insert these lines in your program's startup code, before the main
21764 procedure is called:
21771 On some machines, when a breakpoint trap is raised, the hardware
21772 automatically makes the PC point to the instruction after the
21773 breakpoint. If your machine doesn't do that, you may need to adjust
21774 @code{handle_exception} to arrange for it to return to the instruction
21775 after the breakpoint on this first invocation, so that your program
21776 doesn't keep hitting the initial breakpoint instead of making
21780 For the 680x0 stub only, you need to provide a variable called
21781 @code{exceptionHook}. Normally you just use:
21784 void (*exceptionHook)() = 0;
21788 but if before calling @code{set_debug_traps}, you set it to point to a
21789 function in your program, that function is called when
21790 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21791 error). The function indicated by @code{exceptionHook} is called with
21792 one parameter: an @code{int} which is the exception number.
21795 Compile and link together: your program, the @value{GDBN} debugging stub for
21796 your target architecture, and the supporting subroutines.
21799 Make sure you have a serial connection between your target machine and
21800 the @value{GDBN} host, and identify the serial port on the host.
21803 @c The "remote" target now provides a `load' command, so we should
21804 @c document that. FIXME.
21805 Download your program to your target machine (or get it there by
21806 whatever means the manufacturer provides), and start it.
21809 Start @value{GDBN} on the host, and connect to the target
21810 (@pxref{Connecting,,Connecting to a Remote Target}).
21814 @node Configurations
21815 @chapter Configuration-Specific Information
21817 While nearly all @value{GDBN} commands are available for all native and
21818 cross versions of the debugger, there are some exceptions. This chapter
21819 describes things that are only available in certain configurations.
21821 There are three major categories of configurations: native
21822 configurations, where the host and target are the same, embedded
21823 operating system configurations, which are usually the same for several
21824 different processor architectures, and bare embedded processors, which
21825 are quite different from each other.
21830 * Embedded Processors::
21837 This section describes details specific to particular native
21841 * BSD libkvm Interface:: Debugging BSD kernel memory images
21842 * Process Information:: Process information
21843 * DJGPP Native:: Features specific to the DJGPP port
21844 * Cygwin Native:: Features specific to the Cygwin port
21845 * Hurd Native:: Features specific to @sc{gnu} Hurd
21846 * Darwin:: Features specific to Darwin
21849 @node BSD libkvm Interface
21850 @subsection BSD libkvm Interface
21853 @cindex kernel memory image
21854 @cindex kernel crash dump
21856 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21857 interface that provides a uniform interface for accessing kernel virtual
21858 memory images, including live systems and crash dumps. @value{GDBN}
21859 uses this interface to allow you to debug live kernels and kernel crash
21860 dumps on many native BSD configurations. This is implemented as a
21861 special @code{kvm} debugging target. For debugging a live system, load
21862 the currently running kernel into @value{GDBN} and connect to the
21866 (@value{GDBP}) @b{target kvm}
21869 For debugging crash dumps, provide the file name of the crash dump as an
21873 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21876 Once connected to the @code{kvm} target, the following commands are
21882 Set current context from the @dfn{Process Control Block} (PCB) address.
21885 Set current context from proc address. This command isn't available on
21886 modern FreeBSD systems.
21889 @node Process Information
21890 @subsection Process Information
21892 @cindex examine process image
21893 @cindex process info via @file{/proc}
21895 Some operating systems provide interfaces to fetch additional
21896 information about running processes beyond memory and per-thread
21897 register state. If @value{GDBN} is configured for an operating system
21898 with a supported interface, the command @code{info proc} is available
21899 to report information about the process running your program, or about
21900 any process running on your system.
21902 One supported interface is a facility called @samp{/proc} that can be
21903 used to examine the image of a running process using file-system
21904 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
21907 On FreeBSD systems, system control nodes are used to query process
21910 In addition, some systems may provide additional process information
21911 in core files. Note that a core file may include a subset of the
21912 information available from a live process. Process information is
21913 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
21920 @itemx info proc @var{process-id}
21921 Summarize available information about any running process. If a
21922 process ID is specified by @var{process-id}, display information about
21923 that process; otherwise display information about the program being
21924 debugged. The summary includes the debugged process ID, the command
21925 line used to invoke it, its current working directory, and its
21926 executable file's absolute file name.
21928 On some systems, @var{process-id} can be of the form
21929 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21930 within a process. If the optional @var{pid} part is missing, it means
21931 a thread from the process being debugged (the leading @samp{/} still
21932 needs to be present, or else @value{GDBN} will interpret the number as
21933 a process ID rather than a thread ID).
21935 @item info proc cmdline
21936 @cindex info proc cmdline
21937 Show the original command line of the process. This command is
21938 supported on @sc{gnu}/Linux and FreeBSD.
21940 @item info proc cwd
21941 @cindex info proc cwd
21942 Show the current working directory of the process. This command is
21943 supported on @sc{gnu}/Linux and FreeBSD.
21945 @item info proc exe
21946 @cindex info proc exe
21947 Show the name of executable of the process. This command is supported
21948 on @sc{gnu}/Linux and FreeBSD.
21950 @item info proc mappings
21951 @cindex memory address space mappings
21952 Report the memory address space ranges accessible in the program. On
21953 Solaris and FreeBSD systems, each memory range includes information on
21954 whether the process has read, write, or execute access rights to each
21955 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
21956 includes the object file which is mapped to that range.
21958 @item info proc stat
21959 @itemx info proc status
21960 @cindex process detailed status information
21961 Show additional process-related information, including the user ID and
21962 group ID; virtual memory usage; the signals that are pending, blocked,
21963 and ignored; its TTY; its consumption of system and user time; its
21964 stack size; its @samp{nice} value; etc. These commands are supported
21965 on @sc{gnu}/Linux and FreeBSD.
21967 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
21968 information (type @kbd{man 5 proc} from your shell prompt).
21970 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
21973 @item info proc all
21974 Show all the information about the process described under all of the
21975 above @code{info proc} subcommands.
21978 @comment These sub-options of 'info proc' were not included when
21979 @comment procfs.c was re-written. Keep their descriptions around
21980 @comment against the day when someone finds the time to put them back in.
21981 @kindex info proc times
21982 @item info proc times
21983 Starting time, user CPU time, and system CPU time for your program and
21986 @kindex info proc id
21988 Report on the process IDs related to your program: its own process ID,
21989 the ID of its parent, the process group ID, and the session ID.
21992 @item set procfs-trace
21993 @kindex set procfs-trace
21994 @cindex @code{procfs} API calls
21995 This command enables and disables tracing of @code{procfs} API calls.
21997 @item show procfs-trace
21998 @kindex show procfs-trace
21999 Show the current state of @code{procfs} API call tracing.
22001 @item set procfs-file @var{file}
22002 @kindex set procfs-file
22003 Tell @value{GDBN} to write @code{procfs} API trace to the named
22004 @var{file}. @value{GDBN} appends the trace info to the previous
22005 contents of the file. The default is to display the trace on the
22008 @item show procfs-file
22009 @kindex show procfs-file
22010 Show the file to which @code{procfs} API trace is written.
22012 @item proc-trace-entry
22013 @itemx proc-trace-exit
22014 @itemx proc-untrace-entry
22015 @itemx proc-untrace-exit
22016 @kindex proc-trace-entry
22017 @kindex proc-trace-exit
22018 @kindex proc-untrace-entry
22019 @kindex proc-untrace-exit
22020 These commands enable and disable tracing of entries into and exits
22021 from the @code{syscall} interface.
22024 @kindex info pidlist
22025 @cindex process list, QNX Neutrino
22026 For QNX Neutrino only, this command displays the list of all the
22027 processes and all the threads within each process.
22030 @kindex info meminfo
22031 @cindex mapinfo list, QNX Neutrino
22032 For QNX Neutrino only, this command displays the list of all mapinfos.
22036 @subsection Features for Debugging @sc{djgpp} Programs
22037 @cindex @sc{djgpp} debugging
22038 @cindex native @sc{djgpp} debugging
22039 @cindex MS-DOS-specific commands
22042 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22043 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22044 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22045 top of real-mode DOS systems and their emulations.
22047 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22048 defines a few commands specific to the @sc{djgpp} port. This
22049 subsection describes those commands.
22054 This is a prefix of @sc{djgpp}-specific commands which print
22055 information about the target system and important OS structures.
22058 @cindex MS-DOS system info
22059 @cindex free memory information (MS-DOS)
22060 @item info dos sysinfo
22061 This command displays assorted information about the underlying
22062 platform: the CPU type and features, the OS version and flavor, the
22063 DPMI version, and the available conventional and DPMI memory.
22068 @cindex segment descriptor tables
22069 @cindex descriptor tables display
22071 @itemx info dos ldt
22072 @itemx info dos idt
22073 These 3 commands display entries from, respectively, Global, Local,
22074 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22075 tables are data structures which store a descriptor for each segment
22076 that is currently in use. The segment's selector is an index into a
22077 descriptor table; the table entry for that index holds the
22078 descriptor's base address and limit, and its attributes and access
22081 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22082 segment (used for both data and the stack), and a DOS segment (which
22083 allows access to DOS/BIOS data structures and absolute addresses in
22084 conventional memory). However, the DPMI host will usually define
22085 additional segments in order to support the DPMI environment.
22087 @cindex garbled pointers
22088 These commands allow to display entries from the descriptor tables.
22089 Without an argument, all entries from the specified table are
22090 displayed. An argument, which should be an integer expression, means
22091 display a single entry whose index is given by the argument. For
22092 example, here's a convenient way to display information about the
22093 debugged program's data segment:
22096 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22097 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22101 This comes in handy when you want to see whether a pointer is outside
22102 the data segment's limit (i.e.@: @dfn{garbled}).
22104 @cindex page tables display (MS-DOS)
22106 @itemx info dos pte
22107 These two commands display entries from, respectively, the Page
22108 Directory and the Page Tables. Page Directories and Page Tables are
22109 data structures which control how virtual memory addresses are mapped
22110 into physical addresses. A Page Table includes an entry for every
22111 page of memory that is mapped into the program's address space; there
22112 may be several Page Tables, each one holding up to 4096 entries. A
22113 Page Directory has up to 4096 entries, one each for every Page Table
22114 that is currently in use.
22116 Without an argument, @kbd{info dos pde} displays the entire Page
22117 Directory, and @kbd{info dos pte} displays all the entries in all of
22118 the Page Tables. An argument, an integer expression, given to the
22119 @kbd{info dos pde} command means display only that entry from the Page
22120 Directory table. An argument given to the @kbd{info dos pte} command
22121 means display entries from a single Page Table, the one pointed to by
22122 the specified entry in the Page Directory.
22124 @cindex direct memory access (DMA) on MS-DOS
22125 These commands are useful when your program uses @dfn{DMA} (Direct
22126 Memory Access), which needs physical addresses to program the DMA
22129 These commands are supported only with some DPMI servers.
22131 @cindex physical address from linear address
22132 @item info dos address-pte @var{addr}
22133 This command displays the Page Table entry for a specified linear
22134 address. The argument @var{addr} is a linear address which should
22135 already have the appropriate segment's base address added to it,
22136 because this command accepts addresses which may belong to @emph{any}
22137 segment. For example, here's how to display the Page Table entry for
22138 the page where a variable @code{i} is stored:
22141 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22142 @exdent @code{Page Table entry for address 0x11a00d30:}
22143 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22147 This says that @code{i} is stored at offset @code{0xd30} from the page
22148 whose physical base address is @code{0x02698000}, and shows all the
22149 attributes of that page.
22151 Note that you must cast the addresses of variables to a @code{char *},
22152 since otherwise the value of @code{__djgpp_base_address}, the base
22153 address of all variables and functions in a @sc{djgpp} program, will
22154 be added using the rules of C pointer arithmetics: if @code{i} is
22155 declared an @code{int}, @value{GDBN} will add 4 times the value of
22156 @code{__djgpp_base_address} to the address of @code{i}.
22158 Here's another example, it displays the Page Table entry for the
22162 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22163 @exdent @code{Page Table entry for address 0x29110:}
22164 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22168 (The @code{+ 3} offset is because the transfer buffer's address is the
22169 3rd member of the @code{_go32_info_block} structure.) The output
22170 clearly shows that this DPMI server maps the addresses in conventional
22171 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22172 linear (@code{0x29110}) addresses are identical.
22174 This command is supported only with some DPMI servers.
22177 @cindex DOS serial data link, remote debugging
22178 In addition to native debugging, the DJGPP port supports remote
22179 debugging via a serial data link. The following commands are specific
22180 to remote serial debugging in the DJGPP port of @value{GDBN}.
22183 @kindex set com1base
22184 @kindex set com1irq
22185 @kindex set com2base
22186 @kindex set com2irq
22187 @kindex set com3base
22188 @kindex set com3irq
22189 @kindex set com4base
22190 @kindex set com4irq
22191 @item set com1base @var{addr}
22192 This command sets the base I/O port address of the @file{COM1} serial
22195 @item set com1irq @var{irq}
22196 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22197 for the @file{COM1} serial port.
22199 There are similar commands @samp{set com2base}, @samp{set com3irq},
22200 etc.@: for setting the port address and the @code{IRQ} lines for the
22203 @kindex show com1base
22204 @kindex show com1irq
22205 @kindex show com2base
22206 @kindex show com2irq
22207 @kindex show com3base
22208 @kindex show com3irq
22209 @kindex show com4base
22210 @kindex show com4irq
22211 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22212 display the current settings of the base address and the @code{IRQ}
22213 lines used by the COM ports.
22216 @kindex info serial
22217 @cindex DOS serial port status
22218 This command prints the status of the 4 DOS serial ports. For each
22219 port, it prints whether it's active or not, its I/O base address and
22220 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22221 counts of various errors encountered so far.
22225 @node Cygwin Native
22226 @subsection Features for Debugging MS Windows PE Executables
22227 @cindex MS Windows debugging
22228 @cindex native Cygwin debugging
22229 @cindex Cygwin-specific commands
22231 @value{GDBN} supports native debugging of MS Windows programs, including
22232 DLLs with and without symbolic debugging information.
22234 @cindex Ctrl-BREAK, MS-Windows
22235 @cindex interrupt debuggee on MS-Windows
22236 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22237 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22238 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22239 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22240 sequence, which can be used to interrupt the debuggee even if it
22243 There are various additional Cygwin-specific commands, described in
22244 this section. Working with DLLs that have no debugging symbols is
22245 described in @ref{Non-debug DLL Symbols}.
22250 This is a prefix of MS Windows-specific commands which print
22251 information about the target system and important OS structures.
22253 @item info w32 selector
22254 This command displays information returned by
22255 the Win32 API @code{GetThreadSelectorEntry} function.
22256 It takes an optional argument that is evaluated to
22257 a long value to give the information about this given selector.
22258 Without argument, this command displays information
22259 about the six segment registers.
22261 @item info w32 thread-information-block
22262 This command displays thread specific information stored in the
22263 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22264 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22266 @kindex signal-event
22267 @item signal-event @var{id}
22268 This command signals an event with user-provided @var{id}. Used to resume
22269 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22271 To use it, create or edit the following keys in
22272 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22273 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22274 (for x86_64 versions):
22278 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22279 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22280 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22282 The first @code{%ld} will be replaced by the process ID of the
22283 crashing process, the second @code{%ld} will be replaced by the ID of
22284 the event that blocks the crashing process, waiting for @value{GDBN}
22288 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22289 make the system run debugger specified by the Debugger key
22290 automatically, @code{0} will cause a dialog box with ``OK'' and
22291 ``Cancel'' buttons to appear, which allows the user to either
22292 terminate the crashing process (OK) or debug it (Cancel).
22295 @kindex set cygwin-exceptions
22296 @cindex debugging the Cygwin DLL
22297 @cindex Cygwin DLL, debugging
22298 @item set cygwin-exceptions @var{mode}
22299 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22300 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22301 @value{GDBN} will delay recognition of exceptions, and may ignore some
22302 exceptions which seem to be caused by internal Cygwin DLL
22303 ``bookkeeping''. This option is meant primarily for debugging the
22304 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22305 @value{GDBN} users with false @code{SIGSEGV} signals.
22307 @kindex show cygwin-exceptions
22308 @item show cygwin-exceptions
22309 Displays whether @value{GDBN} will break on exceptions that happen
22310 inside the Cygwin DLL itself.
22312 @kindex set new-console
22313 @item set new-console @var{mode}
22314 If @var{mode} is @code{on} the debuggee will
22315 be started in a new console on next start.
22316 If @var{mode} is @code{off}, the debuggee will
22317 be started in the same console as the debugger.
22319 @kindex show new-console
22320 @item show new-console
22321 Displays whether a new console is used
22322 when the debuggee is started.
22324 @kindex set new-group
22325 @item set new-group @var{mode}
22326 This boolean value controls whether the debuggee should
22327 start a new group or stay in the same group as the debugger.
22328 This affects the way the Windows OS handles
22331 @kindex show new-group
22332 @item show new-group
22333 Displays current value of new-group boolean.
22335 @kindex set debugevents
22336 @item set debugevents
22337 This boolean value adds debug output concerning kernel events related
22338 to the debuggee seen by the debugger. This includes events that
22339 signal thread and process creation and exit, DLL loading and
22340 unloading, console interrupts, and debugging messages produced by the
22341 Windows @code{OutputDebugString} API call.
22343 @kindex set debugexec
22344 @item set debugexec
22345 This boolean value adds debug output concerning execute events
22346 (such as resume thread) seen by the debugger.
22348 @kindex set debugexceptions
22349 @item set debugexceptions
22350 This boolean value adds debug output concerning exceptions in the
22351 debuggee seen by the debugger.
22353 @kindex set debugmemory
22354 @item set debugmemory
22355 This boolean value adds debug output concerning debuggee memory reads
22356 and writes by the debugger.
22360 This boolean values specifies whether the debuggee is called
22361 via a shell or directly (default value is on).
22365 Displays if the debuggee will be started with a shell.
22370 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22373 @node Non-debug DLL Symbols
22374 @subsubsection Support for DLLs without Debugging Symbols
22375 @cindex DLLs with no debugging symbols
22376 @cindex Minimal symbols and DLLs
22378 Very often on windows, some of the DLLs that your program relies on do
22379 not include symbolic debugging information (for example,
22380 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22381 symbols in a DLL, it relies on the minimal amount of symbolic
22382 information contained in the DLL's export table. This section
22383 describes working with such symbols, known internally to @value{GDBN} as
22384 ``minimal symbols''.
22386 Note that before the debugged program has started execution, no DLLs
22387 will have been loaded. The easiest way around this problem is simply to
22388 start the program --- either by setting a breakpoint or letting the
22389 program run once to completion.
22391 @subsubsection DLL Name Prefixes
22393 In keeping with the naming conventions used by the Microsoft debugging
22394 tools, DLL export symbols are made available with a prefix based on the
22395 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22396 also entered into the symbol table, so @code{CreateFileA} is often
22397 sufficient. In some cases there will be name clashes within a program
22398 (particularly if the executable itself includes full debugging symbols)
22399 necessitating the use of the fully qualified name when referring to the
22400 contents of the DLL. Use single-quotes around the name to avoid the
22401 exclamation mark (``!'') being interpreted as a language operator.
22403 Note that the internal name of the DLL may be all upper-case, even
22404 though the file name of the DLL is lower-case, or vice-versa. Since
22405 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22406 some confusion. If in doubt, try the @code{info functions} and
22407 @code{info variables} commands or even @code{maint print msymbols}
22408 (@pxref{Symbols}). Here's an example:
22411 (@value{GDBP}) info function CreateFileA
22412 All functions matching regular expression "CreateFileA":
22414 Non-debugging symbols:
22415 0x77e885f4 CreateFileA
22416 0x77e885f4 KERNEL32!CreateFileA
22420 (@value{GDBP}) info function !
22421 All functions matching regular expression "!":
22423 Non-debugging symbols:
22424 0x6100114c cygwin1!__assert
22425 0x61004034 cygwin1!_dll_crt0@@0
22426 0x61004240 cygwin1!dll_crt0(per_process *)
22430 @subsubsection Working with Minimal Symbols
22432 Symbols extracted from a DLL's export table do not contain very much
22433 type information. All that @value{GDBN} can do is guess whether a symbol
22434 refers to a function or variable depending on the linker section that
22435 contains the symbol. Also note that the actual contents of the memory
22436 contained in a DLL are not available unless the program is running. This
22437 means that you cannot examine the contents of a variable or disassemble
22438 a function within a DLL without a running program.
22440 Variables are generally treated as pointers and dereferenced
22441 automatically. For this reason, it is often necessary to prefix a
22442 variable name with the address-of operator (``&'') and provide explicit
22443 type information in the command. Here's an example of the type of
22447 (@value{GDBP}) print 'cygwin1!__argv'
22448 'cygwin1!__argv' has unknown type; cast it to its declared type
22452 (@value{GDBP}) x 'cygwin1!__argv'
22453 'cygwin1!__argv' has unknown type; cast it to its declared type
22456 And two possible solutions:
22459 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22460 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22464 (@value{GDBP}) x/2x &'cygwin1!__argv'
22465 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22466 (@value{GDBP}) x/x 0x10021608
22467 0x10021608: 0x0022fd98
22468 (@value{GDBP}) x/s 0x0022fd98
22469 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22472 Setting a break point within a DLL is possible even before the program
22473 starts execution. However, under these circumstances, @value{GDBN} can't
22474 examine the initial instructions of the function in order to skip the
22475 function's frame set-up code. You can work around this by using ``*&''
22476 to set the breakpoint at a raw memory address:
22479 (@value{GDBP}) break *&'python22!PyOS_Readline'
22480 Breakpoint 1 at 0x1e04eff0
22483 The author of these extensions is not entirely convinced that setting a
22484 break point within a shared DLL like @file{kernel32.dll} is completely
22488 @subsection Commands Specific to @sc{gnu} Hurd Systems
22489 @cindex @sc{gnu} Hurd debugging
22491 This subsection describes @value{GDBN} commands specific to the
22492 @sc{gnu} Hurd native debugging.
22497 @kindex set signals@r{, Hurd command}
22498 @kindex set sigs@r{, Hurd command}
22499 This command toggles the state of inferior signal interception by
22500 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22501 affected by this command. @code{sigs} is a shorthand alias for
22506 @kindex show signals@r{, Hurd command}
22507 @kindex show sigs@r{, Hurd command}
22508 Show the current state of intercepting inferior's signals.
22510 @item set signal-thread
22511 @itemx set sigthread
22512 @kindex set signal-thread
22513 @kindex set sigthread
22514 This command tells @value{GDBN} which thread is the @code{libc} signal
22515 thread. That thread is run when a signal is delivered to a running
22516 process. @code{set sigthread} is the shorthand alias of @code{set
22519 @item show signal-thread
22520 @itemx show sigthread
22521 @kindex show signal-thread
22522 @kindex show sigthread
22523 These two commands show which thread will run when the inferior is
22524 delivered a signal.
22527 @kindex set stopped@r{, Hurd command}
22528 This commands tells @value{GDBN} that the inferior process is stopped,
22529 as with the @code{SIGSTOP} signal. The stopped process can be
22530 continued by delivering a signal to it.
22533 @kindex show stopped@r{, Hurd command}
22534 This command shows whether @value{GDBN} thinks the debuggee is
22537 @item set exceptions
22538 @kindex set exceptions@r{, Hurd command}
22539 Use this command to turn off trapping of exceptions in the inferior.
22540 When exception trapping is off, neither breakpoints nor
22541 single-stepping will work. To restore the default, set exception
22544 @item show exceptions
22545 @kindex show exceptions@r{, Hurd command}
22546 Show the current state of trapping exceptions in the inferior.
22548 @item set task pause
22549 @kindex set task@r{, Hurd commands}
22550 @cindex task attributes (@sc{gnu} Hurd)
22551 @cindex pause current task (@sc{gnu} Hurd)
22552 This command toggles task suspension when @value{GDBN} has control.
22553 Setting it to on takes effect immediately, and the task is suspended
22554 whenever @value{GDBN} gets control. Setting it to off will take
22555 effect the next time the inferior is continued. If this option is set
22556 to off, you can use @code{set thread default pause on} or @code{set
22557 thread pause on} (see below) to pause individual threads.
22559 @item show task pause
22560 @kindex show task@r{, Hurd commands}
22561 Show the current state of task suspension.
22563 @item set task detach-suspend-count
22564 @cindex task suspend count
22565 @cindex detach from task, @sc{gnu} Hurd
22566 This command sets the suspend count the task will be left with when
22567 @value{GDBN} detaches from it.
22569 @item show task detach-suspend-count
22570 Show the suspend count the task will be left with when detaching.
22572 @item set task exception-port
22573 @itemx set task excp
22574 @cindex task exception port, @sc{gnu} Hurd
22575 This command sets the task exception port to which @value{GDBN} will
22576 forward exceptions. The argument should be the value of the @dfn{send
22577 rights} of the task. @code{set task excp} is a shorthand alias.
22579 @item set noninvasive
22580 @cindex noninvasive task options
22581 This command switches @value{GDBN} to a mode that is the least
22582 invasive as far as interfering with the inferior is concerned. This
22583 is the same as using @code{set task pause}, @code{set exceptions}, and
22584 @code{set signals} to values opposite to the defaults.
22586 @item info send-rights
22587 @itemx info receive-rights
22588 @itemx info port-rights
22589 @itemx info port-sets
22590 @itemx info dead-names
22593 @cindex send rights, @sc{gnu} Hurd
22594 @cindex receive rights, @sc{gnu} Hurd
22595 @cindex port rights, @sc{gnu} Hurd
22596 @cindex port sets, @sc{gnu} Hurd
22597 @cindex dead names, @sc{gnu} Hurd
22598 These commands display information about, respectively, send rights,
22599 receive rights, port rights, port sets, and dead names of a task.
22600 There are also shorthand aliases: @code{info ports} for @code{info
22601 port-rights} and @code{info psets} for @code{info port-sets}.
22603 @item set thread pause
22604 @kindex set thread@r{, Hurd command}
22605 @cindex thread properties, @sc{gnu} Hurd
22606 @cindex pause current thread (@sc{gnu} Hurd)
22607 This command toggles current thread suspension when @value{GDBN} has
22608 control. Setting it to on takes effect immediately, and the current
22609 thread is suspended whenever @value{GDBN} gets control. Setting it to
22610 off will take effect the next time the inferior is continued.
22611 Normally, this command has no effect, since when @value{GDBN} has
22612 control, the whole task is suspended. However, if you used @code{set
22613 task pause off} (see above), this command comes in handy to suspend
22614 only the current thread.
22616 @item show thread pause
22617 @kindex show thread@r{, Hurd command}
22618 This command shows the state of current thread suspension.
22620 @item set thread run
22621 This command sets whether the current thread is allowed to run.
22623 @item show thread run
22624 Show whether the current thread is allowed to run.
22626 @item set thread detach-suspend-count
22627 @cindex thread suspend count, @sc{gnu} Hurd
22628 @cindex detach from thread, @sc{gnu} Hurd
22629 This command sets the suspend count @value{GDBN} will leave on a
22630 thread when detaching. This number is relative to the suspend count
22631 found by @value{GDBN} when it notices the thread; use @code{set thread
22632 takeover-suspend-count} to force it to an absolute value.
22634 @item show thread detach-suspend-count
22635 Show the suspend count @value{GDBN} will leave on the thread when
22638 @item set thread exception-port
22639 @itemx set thread excp
22640 Set the thread exception port to which to forward exceptions. This
22641 overrides the port set by @code{set task exception-port} (see above).
22642 @code{set thread excp} is the shorthand alias.
22644 @item set thread takeover-suspend-count
22645 Normally, @value{GDBN}'s thread suspend counts are relative to the
22646 value @value{GDBN} finds when it notices each thread. This command
22647 changes the suspend counts to be absolute instead.
22649 @item set thread default
22650 @itemx show thread default
22651 @cindex thread default settings, @sc{gnu} Hurd
22652 Each of the above @code{set thread} commands has a @code{set thread
22653 default} counterpart (e.g., @code{set thread default pause}, @code{set
22654 thread default exception-port}, etc.). The @code{thread default}
22655 variety of commands sets the default thread properties for all
22656 threads; you can then change the properties of individual threads with
22657 the non-default commands.
22664 @value{GDBN} provides the following commands specific to the Darwin target:
22667 @item set debug darwin @var{num}
22668 @kindex set debug darwin
22669 When set to a non zero value, enables debugging messages specific to
22670 the Darwin support. Higher values produce more verbose output.
22672 @item show debug darwin
22673 @kindex show debug darwin
22674 Show the current state of Darwin messages.
22676 @item set debug mach-o @var{num}
22677 @kindex set debug mach-o
22678 When set to a non zero value, enables debugging messages while
22679 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22680 file format used on Darwin for object and executable files.) Higher
22681 values produce more verbose output. This is a command to diagnose
22682 problems internal to @value{GDBN} and should not be needed in normal
22685 @item show debug mach-o
22686 @kindex show debug mach-o
22687 Show the current state of Mach-O file messages.
22689 @item set mach-exceptions on
22690 @itemx set mach-exceptions off
22691 @kindex set mach-exceptions
22692 On Darwin, faults are first reported as a Mach exception and are then
22693 mapped to a Posix signal. Use this command to turn on trapping of
22694 Mach exceptions in the inferior. This might be sometimes useful to
22695 better understand the cause of a fault. The default is off.
22697 @item show mach-exceptions
22698 @kindex show mach-exceptions
22699 Show the current state of exceptions trapping.
22704 @section Embedded Operating Systems
22706 This section describes configurations involving the debugging of
22707 embedded operating systems that are available for several different
22710 @value{GDBN} includes the ability to debug programs running on
22711 various real-time operating systems.
22713 @node Embedded Processors
22714 @section Embedded Processors
22716 This section goes into details specific to particular embedded
22719 @cindex send command to simulator
22720 Whenever a specific embedded processor has a simulator, @value{GDBN}
22721 allows to send an arbitrary command to the simulator.
22724 @item sim @var{command}
22725 @kindex sim@r{, a command}
22726 Send an arbitrary @var{command} string to the simulator. Consult the
22727 documentation for the specific simulator in use for information about
22728 acceptable commands.
22733 * ARC:: Synopsys ARC
22735 * M68K:: Motorola M68K
22736 * MicroBlaze:: Xilinx MicroBlaze
22737 * MIPS Embedded:: MIPS Embedded
22738 * OpenRISC 1000:: OpenRISC 1000 (or1k)
22739 * PowerPC Embedded:: PowerPC Embedded
22742 * Super-H:: Renesas Super-H
22746 @subsection Synopsys ARC
22747 @cindex Synopsys ARC
22748 @cindex ARC specific commands
22754 @value{GDBN} provides the following ARC-specific commands:
22757 @item set debug arc
22758 @kindex set debug arc
22759 Control the level of ARC specific debug messages. Use 0 for no messages (the
22760 default), 1 for debug messages, and 2 for even more debug messages.
22762 @item show debug arc
22763 @kindex show debug arc
22764 Show the level of ARC specific debugging in operation.
22766 @item maint print arc arc-instruction @var{address}
22767 @kindex maint print arc arc-instruction
22768 Print internal disassembler information about instruction at a given address.
22775 @value{GDBN} provides the following ARM-specific commands:
22778 @item set arm disassembler
22780 This commands selects from a list of disassembly styles. The
22781 @code{"std"} style is the standard style.
22783 @item show arm disassembler
22785 Show the current disassembly style.
22787 @item set arm apcs32
22788 @cindex ARM 32-bit mode
22789 This command toggles ARM operation mode between 32-bit and 26-bit.
22791 @item show arm apcs32
22792 Display the current usage of the ARM 32-bit mode.
22794 @item set arm fpu @var{fputype}
22795 This command sets the ARM floating-point unit (FPU) type. The
22796 argument @var{fputype} can be one of these:
22800 Determine the FPU type by querying the OS ABI.
22802 Software FPU, with mixed-endian doubles on little-endian ARM
22805 GCC-compiled FPA co-processor.
22807 Software FPU with pure-endian doubles.
22813 Show the current type of the FPU.
22816 This command forces @value{GDBN} to use the specified ABI.
22819 Show the currently used ABI.
22821 @item set arm fallback-mode (arm|thumb|auto)
22822 @value{GDBN} uses the symbol table, when available, to determine
22823 whether instructions are ARM or Thumb. This command controls
22824 @value{GDBN}'s default behavior when the symbol table is not
22825 available. The default is @samp{auto}, which causes @value{GDBN} to
22826 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22829 @item show arm fallback-mode
22830 Show the current fallback instruction mode.
22832 @item set arm force-mode (arm|thumb|auto)
22833 This command overrides use of the symbol table to determine whether
22834 instructions are ARM or Thumb. The default is @samp{auto}, which
22835 causes @value{GDBN} to use the symbol table and then the setting
22836 of @samp{set arm fallback-mode}.
22838 @item show arm force-mode
22839 Show the current forced instruction mode.
22841 @item set debug arm
22842 Toggle whether to display ARM-specific debugging messages from the ARM
22843 target support subsystem.
22845 @item show debug arm
22846 Show whether ARM-specific debugging messages are enabled.
22850 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22851 The @value{GDBN} ARM simulator accepts the following optional arguments.
22854 @item --swi-support=@var{type}
22855 Tell the simulator which SWI interfaces to support. The argument
22856 @var{type} may be a comma separated list of the following values.
22857 The default value is @code{all}.
22872 The Motorola m68k configuration includes ColdFire support.
22875 @subsection MicroBlaze
22876 @cindex Xilinx MicroBlaze
22877 @cindex XMD, Xilinx Microprocessor Debugger
22879 The MicroBlaze is a soft-core processor supported on various Xilinx
22880 FPGAs, such as Spartan or Virtex series. Boards with these processors
22881 usually have JTAG ports which connect to a host system running the Xilinx
22882 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22883 This host system is used to download the configuration bitstream to
22884 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22885 communicates with the target board using the JTAG interface and
22886 presents a @code{gdbserver} interface to the board. By default
22887 @code{xmd} uses port @code{1234}. (While it is possible to change
22888 this default port, it requires the use of undocumented @code{xmd}
22889 commands. Contact Xilinx support if you need to do this.)
22891 Use these GDB commands to connect to the MicroBlaze target processor.
22894 @item target remote :1234
22895 Use this command to connect to the target if you are running @value{GDBN}
22896 on the same system as @code{xmd}.
22898 @item target remote @var{xmd-host}:1234
22899 Use this command to connect to the target if it is connected to @code{xmd}
22900 running on a different system named @var{xmd-host}.
22903 Use this command to download a program to the MicroBlaze target.
22905 @item set debug microblaze @var{n}
22906 Enable MicroBlaze-specific debugging messages if non-zero.
22908 @item show debug microblaze @var{n}
22909 Show MicroBlaze-specific debugging level.
22912 @node MIPS Embedded
22913 @subsection @acronym{MIPS} Embedded
22916 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22919 @item set mipsfpu double
22920 @itemx set mipsfpu single
22921 @itemx set mipsfpu none
22922 @itemx set mipsfpu auto
22923 @itemx show mipsfpu
22924 @kindex set mipsfpu
22925 @kindex show mipsfpu
22926 @cindex @acronym{MIPS} remote floating point
22927 @cindex floating point, @acronym{MIPS} remote
22928 If your target board does not support the @acronym{MIPS} floating point
22929 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22930 need this, you may wish to put the command in your @value{GDBN} init
22931 file). This tells @value{GDBN} how to find the return value of
22932 functions which return floating point values. It also allows
22933 @value{GDBN} to avoid saving the floating point registers when calling
22934 functions on the board. If you are using a floating point coprocessor
22935 with only single precision floating point support, as on the @sc{r4650}
22936 processor, use the command @samp{set mipsfpu single}. The default
22937 double precision floating point coprocessor may be selected using
22938 @samp{set mipsfpu double}.
22940 In previous versions the only choices were double precision or no
22941 floating point, so @samp{set mipsfpu on} will select double precision
22942 and @samp{set mipsfpu off} will select no floating point.
22944 As usual, you can inquire about the @code{mipsfpu} variable with
22945 @samp{show mipsfpu}.
22948 @node OpenRISC 1000
22949 @subsection OpenRISC 1000
22950 @cindex OpenRISC 1000
22953 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
22954 mainly provided as a soft-core which can run on Xilinx, Altera and other
22957 @value{GDBN} for OpenRISC supports the below commands when connecting to
22965 Runs the builtin CPU simulator which can run very basic
22966 programs but does not support most hardware functions like MMU.
22967 For more complex use cases the user is advised to run an external
22968 target, and connect using @samp{target remote}.
22970 Example: @code{target sim}
22972 @item set debug or1k
22973 Toggle whether to display OpenRISC-specific debugging messages from the
22974 OpenRISC target support subsystem.
22976 @item show debug or1k
22977 Show whether OpenRISC-specific debugging messages are enabled.
22980 @node PowerPC Embedded
22981 @subsection PowerPC Embedded
22983 @cindex DVC register
22984 @value{GDBN} supports using the DVC (Data Value Compare) register to
22985 implement in hardware simple hardware watchpoint conditions of the form:
22988 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22989 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22992 The DVC register will be automatically used when @value{GDBN} detects
22993 such pattern in a condition expression, and the created watchpoint uses one
22994 debug register (either the @code{exact-watchpoints} option is on and the
22995 variable is scalar, or the variable has a length of one byte). This feature
22996 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22999 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23000 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23001 in which case watchpoints using only one debug register are created when
23002 watching variables of scalar types.
23004 You can create an artificial array to watch an arbitrary memory
23005 region using one of the following commands (@pxref{Expressions}):
23008 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23009 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23012 PowerPC embedded processors support masked watchpoints. See the discussion
23013 about the @code{mask} argument in @ref{Set Watchpoints}.
23015 @cindex ranged breakpoint
23016 PowerPC embedded processors support hardware accelerated
23017 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23018 the inferior whenever it executes an instruction at any address within
23019 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23020 use the @code{break-range} command.
23022 @value{GDBN} provides the following PowerPC-specific commands:
23025 @kindex break-range
23026 @item break-range @var{start-location}, @var{end-location}
23027 Set a breakpoint for an address range given by
23028 @var{start-location} and @var{end-location}, which can specify a function name,
23029 a line number, an offset of lines from the current line or from the start
23030 location, or an address of an instruction (see @ref{Specify Location},
23031 for a list of all the possible ways to specify a @var{location}.)
23032 The breakpoint will stop execution of the inferior whenever it
23033 executes an instruction at any address within the specified range,
23034 (including @var{start-location} and @var{end-location}.)
23036 @kindex set powerpc
23037 @item set powerpc soft-float
23038 @itemx show powerpc soft-float
23039 Force @value{GDBN} to use (or not use) a software floating point calling
23040 convention. By default, @value{GDBN} selects the calling convention based
23041 on the selected architecture and the provided executable file.
23043 @item set powerpc vector-abi
23044 @itemx show powerpc vector-abi
23045 Force @value{GDBN} to use the specified calling convention for vector
23046 arguments and return values. The valid options are @samp{auto};
23047 @samp{generic}, to avoid vector registers even if they are present;
23048 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23049 registers. By default, @value{GDBN} selects the calling convention
23050 based on the selected architecture and the provided executable file.
23052 @item set powerpc exact-watchpoints
23053 @itemx show powerpc exact-watchpoints
23054 Allow @value{GDBN} to use only one debug register when watching a variable
23055 of scalar type, thus assuming that the variable is accessed through the
23056 address of its first byte.
23061 @subsection Atmel AVR
23064 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23065 following AVR-specific commands:
23068 @item info io_registers
23069 @kindex info io_registers@r{, AVR}
23070 @cindex I/O registers (Atmel AVR)
23071 This command displays information about the AVR I/O registers. For
23072 each register, @value{GDBN} prints its number and value.
23079 When configured for debugging CRIS, @value{GDBN} provides the
23080 following CRIS-specific commands:
23083 @item set cris-version @var{ver}
23084 @cindex CRIS version
23085 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23086 The CRIS version affects register names and sizes. This command is useful in
23087 case autodetection of the CRIS version fails.
23089 @item show cris-version
23090 Show the current CRIS version.
23092 @item set cris-dwarf2-cfi
23093 @cindex DWARF-2 CFI and CRIS
23094 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23095 Change to @samp{off} when using @code{gcc-cris} whose version is below
23098 @item show cris-dwarf2-cfi
23099 Show the current state of using DWARF-2 CFI.
23101 @item set cris-mode @var{mode}
23103 Set the current CRIS mode to @var{mode}. It should only be changed when
23104 debugging in guru mode, in which case it should be set to
23105 @samp{guru} (the default is @samp{normal}).
23107 @item show cris-mode
23108 Show the current CRIS mode.
23112 @subsection Renesas Super-H
23115 For the Renesas Super-H processor, @value{GDBN} provides these
23119 @item set sh calling-convention @var{convention}
23120 @kindex set sh calling-convention
23121 Set the calling-convention used when calling functions from @value{GDBN}.
23122 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23123 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23124 convention. If the DWARF-2 information of the called function specifies
23125 that the function follows the Renesas calling convention, the function
23126 is called using the Renesas calling convention. If the calling convention
23127 is set to @samp{renesas}, the Renesas calling convention is always used,
23128 regardless of the DWARF-2 information. This can be used to override the
23129 default of @samp{gcc} if debug information is missing, or the compiler
23130 does not emit the DWARF-2 calling convention entry for a function.
23132 @item show sh calling-convention
23133 @kindex show sh calling-convention
23134 Show the current calling convention setting.
23139 @node Architectures
23140 @section Architectures
23142 This section describes characteristics of architectures that affect
23143 all uses of @value{GDBN} with the architecture, both native and cross.
23150 * HPPA:: HP PA architecture
23151 * SPU:: Cell Broadband Engine SPU architecture
23158 @subsection AArch64
23159 @cindex AArch64 support
23161 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23162 following special commands:
23165 @item set debug aarch64
23166 @kindex set debug aarch64
23167 This command determines whether AArch64 architecture-specific debugging
23168 messages are to be displayed.
23170 @item show debug aarch64
23171 Show whether AArch64 debugging messages are displayed.
23176 @subsection x86 Architecture-specific Issues
23179 @item set struct-convention @var{mode}
23180 @kindex set struct-convention
23181 @cindex struct return convention
23182 @cindex struct/union returned in registers
23183 Set the convention used by the inferior to return @code{struct}s and
23184 @code{union}s from functions to @var{mode}. Possible values of
23185 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23186 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23187 are returned on the stack, while @code{"reg"} means that a
23188 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23189 be returned in a register.
23191 @item show struct-convention
23192 @kindex show struct-convention
23193 Show the current setting of the convention to return @code{struct}s
23198 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23199 @cindex Intel Memory Protection Extensions (MPX).
23201 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23202 @footnote{The register named with capital letters represent the architecture
23203 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23204 which are the lower bound and upper bound. Bounds are effective addresses or
23205 memory locations. The upper bounds are architecturally represented in 1's
23206 complement form. A bound having lower bound = 0, and upper bound = 0
23207 (1's complement of all bits set) will allow access to the entire address space.
23209 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23210 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23211 display the upper bound performing the complement of one operation on the
23212 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23213 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23214 can also be noted that the upper bounds are inclusive.
23216 As an example, assume that the register BND0 holds bounds for a pointer having
23217 access allowed for the range between 0x32 and 0x71. The values present on
23218 bnd0raw and bnd registers are presented as follows:
23221 bnd0raw = @{0x32, 0xffffffff8e@}
23222 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23225 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23226 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23227 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23228 Python, the display includes the memory size, in bits, accessible to
23231 Bounds can also be stored in bounds tables, which are stored in
23232 application memory. These tables store bounds for pointers by specifying
23233 the bounds pointer's value along with its bounds. Evaluating and changing
23234 bounds located in bound tables is therefore interesting while investigating
23235 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23238 @item show mpx bound @var{pointer}
23239 @kindex show mpx bound
23240 Display bounds of the given @var{pointer}.
23242 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23243 @kindex set mpx bound
23244 Set the bounds of a pointer in the bound table.
23245 This command takes three parameters: @var{pointer} is the pointers
23246 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23247 for lower and upper bounds respectively.
23250 When you call an inferior function on an Intel MPX enabled program,
23251 GDB sets the inferior's bound registers to the init (disabled) state
23252 before calling the function. As a consequence, bounds checks for the
23253 pointer arguments passed to the function will always pass.
23255 This is necessary because when you call an inferior function, the
23256 program is usually in the middle of the execution of other function.
23257 Since at that point bound registers are in an arbitrary state, not
23258 clearing them would lead to random bound violations in the called
23261 You can still examine the influence of the bound registers on the
23262 execution of the called function by stopping the execution of the
23263 called function at its prologue, setting bound registers, and
23264 continuing the execution. For example:
23268 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23269 $ print upper (a, b, c, d, 1)
23270 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23272 @{lbound = 0x0, ubound = ffffffff@} : size -1
23275 At this last step the value of bnd0 can be changed for investigation of bound
23276 violations caused along the execution of the call. In order to know how to
23277 set the bound registers or bound table for the call consult the ABI.
23282 See the following section.
23285 @subsection @acronym{MIPS}
23287 @cindex stack on Alpha
23288 @cindex stack on @acronym{MIPS}
23289 @cindex Alpha stack
23290 @cindex @acronym{MIPS} stack
23291 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23292 sometimes requires @value{GDBN} to search backward in the object code to
23293 find the beginning of a function.
23295 @cindex response time, @acronym{MIPS} debugging
23296 To improve response time (especially for embedded applications, where
23297 @value{GDBN} may be restricted to a slow serial line for this search)
23298 you may want to limit the size of this search, using one of these
23302 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23303 @item set heuristic-fence-post @var{limit}
23304 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23305 search for the beginning of a function. A value of @var{0} (the
23306 default) means there is no limit. However, except for @var{0}, the
23307 larger the limit the more bytes @code{heuristic-fence-post} must search
23308 and therefore the longer it takes to run. You should only need to use
23309 this command when debugging a stripped executable.
23311 @item show heuristic-fence-post
23312 Display the current limit.
23316 These commands are available @emph{only} when @value{GDBN} is configured
23317 for debugging programs on Alpha or @acronym{MIPS} processors.
23319 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23323 @item set mips abi @var{arg}
23324 @kindex set mips abi
23325 @cindex set ABI for @acronym{MIPS}
23326 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23327 values of @var{arg} are:
23331 The default ABI associated with the current binary (this is the
23341 @item show mips abi
23342 @kindex show mips abi
23343 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23345 @item set mips compression @var{arg}
23346 @kindex set mips compression
23347 @cindex code compression, @acronym{MIPS}
23348 Tell @value{GDBN} which @acronym{MIPS} compressed
23349 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23350 inferior. @value{GDBN} uses this for code disassembly and other
23351 internal interpretation purposes. This setting is only referred to
23352 when no executable has been associated with the debugging session or
23353 the executable does not provide information about the encoding it uses.
23354 Otherwise this setting is automatically updated from information
23355 provided by the executable.
23357 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23358 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23359 executables containing @acronym{MIPS16} code frequently are not
23360 identified as such.
23362 This setting is ``sticky''; that is, it retains its value across
23363 debugging sessions until reset either explicitly with this command or
23364 implicitly from an executable.
23366 The compiler and/or assembler typically add symbol table annotations to
23367 identify functions compiled for the @acronym{MIPS16} or
23368 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23369 are present, @value{GDBN} uses them in preference to the global
23370 compressed @acronym{ISA} encoding setting.
23372 @item show mips compression
23373 @kindex show mips compression
23374 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23375 @value{GDBN} to debug the inferior.
23378 @itemx show mipsfpu
23379 @xref{MIPS Embedded, set mipsfpu}.
23381 @item set mips mask-address @var{arg}
23382 @kindex set mips mask-address
23383 @cindex @acronym{MIPS} addresses, masking
23384 This command determines whether the most-significant 32 bits of 64-bit
23385 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23386 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23387 setting, which lets @value{GDBN} determine the correct value.
23389 @item show mips mask-address
23390 @kindex show mips mask-address
23391 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23394 @item set remote-mips64-transfers-32bit-regs
23395 @kindex set remote-mips64-transfers-32bit-regs
23396 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23397 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23398 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23399 and 64 bits for other registers, set this option to @samp{on}.
23401 @item show remote-mips64-transfers-32bit-regs
23402 @kindex show remote-mips64-transfers-32bit-regs
23403 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23405 @item set debug mips
23406 @kindex set debug mips
23407 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23408 target code in @value{GDBN}.
23410 @item show debug mips
23411 @kindex show debug mips
23412 Show the current setting of @acronym{MIPS} debugging messages.
23418 @cindex HPPA support
23420 When @value{GDBN} is debugging the HP PA architecture, it provides the
23421 following special commands:
23424 @item set debug hppa
23425 @kindex set debug hppa
23426 This command determines whether HPPA architecture-specific debugging
23427 messages are to be displayed.
23429 @item show debug hppa
23430 Show whether HPPA debugging messages are displayed.
23432 @item maint print unwind @var{address}
23433 @kindex maint print unwind@r{, HPPA}
23434 This command displays the contents of the unwind table entry at the
23435 given @var{address}.
23441 @subsection Cell Broadband Engine SPU architecture
23442 @cindex Cell Broadband Engine
23445 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23446 it provides the following special commands:
23449 @item info spu event
23451 Display SPU event facility status. Shows current event mask
23452 and pending event status.
23454 @item info spu signal
23455 Display SPU signal notification facility status. Shows pending
23456 signal-control word and signal notification mode of both signal
23457 notification channels.
23459 @item info spu mailbox
23460 Display SPU mailbox facility status. Shows all pending entries,
23461 in order of processing, in each of the SPU Write Outbound,
23462 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23465 Display MFC DMA status. Shows all pending commands in the MFC
23466 DMA queue. For each entry, opcode, tag, class IDs, effective
23467 and local store addresses and transfer size are shown.
23469 @item info spu proxydma
23470 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23471 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23472 and local store addresses and transfer size are shown.
23476 When @value{GDBN} is debugging a combined PowerPC/SPU application
23477 on the Cell Broadband Engine, it provides in addition the following
23481 @item set spu stop-on-load @var{arg}
23483 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23484 will give control to the user when a new SPE thread enters its @code{main}
23485 function. The default is @code{off}.
23487 @item show spu stop-on-load
23489 Show whether to stop for new SPE threads.
23491 @item set spu auto-flush-cache @var{arg}
23492 Set whether to automatically flush the software-managed cache. When set to
23493 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23494 cache to be flushed whenever SPE execution stops. This provides a consistent
23495 view of PowerPC memory that is accessed via the cache. If an application
23496 does not use the software-managed cache, this option has no effect.
23498 @item show spu auto-flush-cache
23499 Show whether to automatically flush the software-managed cache.
23504 @subsection PowerPC
23505 @cindex PowerPC architecture
23507 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23508 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23509 numbers stored in the floating point registers. These values must be stored
23510 in two consecutive registers, always starting at an even register like
23511 @code{f0} or @code{f2}.
23513 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23514 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23515 @code{f2} and @code{f3} for @code{$dl1} and so on.
23517 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23518 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23521 @subsection Nios II
23522 @cindex Nios II architecture
23524 When @value{GDBN} is debugging the Nios II architecture,
23525 it provides the following special commands:
23529 @item set debug nios2
23530 @kindex set debug nios2
23531 This command turns on and off debugging messages for the Nios II
23532 target code in @value{GDBN}.
23534 @item show debug nios2
23535 @kindex show debug nios2
23536 Show the current setting of Nios II debugging messages.
23540 @subsection Sparc64
23541 @cindex Sparc64 support
23542 @cindex Application Data Integrity
23543 @subsubsection ADI Support
23545 The M7 processor supports an Application Data Integrity (ADI) feature that
23546 detects invalid data accesses. When software allocates memory and enables
23547 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23548 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23549 the 4-bit version in every cacheline of that data. Hardware saves the latter
23550 in spare bits in the cache and memory hierarchy. On each load and store,
23551 the processor compares the upper 4 VA (virtual address) bits to the
23552 cacheline's version. If there is a mismatch, the processor generates a
23553 version mismatch trap which can be either precise or disrupting. The trap
23554 is an error condition which the kernel delivers to the process as a SIGSEGV
23557 Note that only 64-bit applications can use ADI and need to be built with
23560 Values of the ADI version tags, which are in granularity of a
23561 cacheline (64 bytes), can be viewed or modified.
23565 @kindex adi examine
23566 @item adi (examine | x) [ / @var{n} ] @var{addr}
23568 The @code{adi examine} command displays the value of one ADI version tag per
23571 @var{n} is a decimal integer specifying the number in bytes; the default
23572 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23573 block size, to display.
23575 @var{addr} is the address in user address space where you want @value{GDBN}
23576 to begin displaying the ADI version tags.
23578 Below is an example of displaying ADI versions of variable "shmaddr".
23581 (@value{GDBP}) adi x/100 shmaddr
23582 0xfff800010002c000: 0 0
23586 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23588 The @code{adi assign} command is used to assign new ADI version tag
23591 @var{n} is a decimal integer specifying the number in bytes;
23592 the default is 1. It specifies how much ADI version information, at the
23593 ratio of 1:ADI block size, to modify.
23595 @var{addr} is the address in user address space where you want @value{GDBN}
23596 to begin modifying the ADI version tags.
23598 @var{tag} is the new ADI version tag.
23600 For example, do the following to modify then verify ADI versions of
23601 variable "shmaddr":
23604 (@value{GDBP}) adi a/100 shmaddr = 7
23605 (@value{GDBP}) adi x/100 shmaddr
23606 0xfff800010002c000: 7 7
23611 @node Controlling GDB
23612 @chapter Controlling @value{GDBN}
23614 You can alter the way @value{GDBN} interacts with you by using the
23615 @code{set} command. For commands controlling how @value{GDBN} displays
23616 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23621 * Editing:: Command editing
23622 * Command History:: Command history
23623 * Screen Size:: Screen size
23624 * Numbers:: Numbers
23625 * ABI:: Configuring the current ABI
23626 * Auto-loading:: Automatically loading associated files
23627 * Messages/Warnings:: Optional warnings and messages
23628 * Debugging Output:: Optional messages about internal happenings
23629 * Other Misc Settings:: Other Miscellaneous Settings
23637 @value{GDBN} indicates its readiness to read a command by printing a string
23638 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23639 can change the prompt string with the @code{set prompt} command. For
23640 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23641 the prompt in one of the @value{GDBN} sessions so that you can always tell
23642 which one you are talking to.
23644 @emph{Note:} @code{set prompt} does not add a space for you after the
23645 prompt you set. This allows you to set a prompt which ends in a space
23646 or a prompt that does not.
23650 @item set prompt @var{newprompt}
23651 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23653 @kindex show prompt
23655 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23658 Versions of @value{GDBN} that ship with Python scripting enabled have
23659 prompt extensions. The commands for interacting with these extensions
23663 @kindex set extended-prompt
23664 @item set extended-prompt @var{prompt}
23665 Set an extended prompt that allows for substitutions.
23666 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23667 substitution. Any escape sequences specified as part of the prompt
23668 string are replaced with the corresponding strings each time the prompt
23674 set extended-prompt Current working directory: \w (gdb)
23677 Note that when an extended-prompt is set, it takes control of the
23678 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23680 @kindex show extended-prompt
23681 @item show extended-prompt
23682 Prints the extended prompt. Any escape sequences specified as part of
23683 the prompt string with @code{set extended-prompt}, are replaced with the
23684 corresponding strings each time the prompt is displayed.
23688 @section Command Editing
23690 @cindex command line editing
23692 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23693 @sc{gnu} library provides consistent behavior for programs which provide a
23694 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23695 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23696 substitution, and a storage and recall of command history across
23697 debugging sessions.
23699 You may control the behavior of command line editing in @value{GDBN} with the
23700 command @code{set}.
23703 @kindex set editing
23706 @itemx set editing on
23707 Enable command line editing (enabled by default).
23709 @item set editing off
23710 Disable command line editing.
23712 @kindex show editing
23714 Show whether command line editing is enabled.
23717 @ifset SYSTEM_READLINE
23718 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23720 @ifclear SYSTEM_READLINE
23721 @xref{Command Line Editing},
23723 for more details about the Readline
23724 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23725 encouraged to read that chapter.
23727 @node Command History
23728 @section Command History
23729 @cindex command history
23731 @value{GDBN} can keep track of the commands you type during your
23732 debugging sessions, so that you can be certain of precisely what
23733 happened. Use these commands to manage the @value{GDBN} command
23736 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23737 package, to provide the history facility.
23738 @ifset SYSTEM_READLINE
23739 @xref{Using History Interactively, , , history, GNU History Library},
23741 @ifclear SYSTEM_READLINE
23742 @xref{Using History Interactively},
23744 for the detailed description of the History library.
23746 To issue a command to @value{GDBN} without affecting certain aspects of
23747 the state which is seen by users, prefix it with @samp{server }
23748 (@pxref{Server Prefix}). This
23749 means that this command will not affect the command history, nor will it
23750 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23751 pressed on a line by itself.
23753 @cindex @code{server}, command prefix
23754 The server prefix does not affect the recording of values into the value
23755 history; to print a value without recording it into the value history,
23756 use the @code{output} command instead of the @code{print} command.
23758 Here is the description of @value{GDBN} commands related to command
23762 @cindex history substitution
23763 @cindex history file
23764 @kindex set history filename
23765 @cindex @env{GDBHISTFILE}, environment variable
23766 @item set history filename @var{fname}
23767 Set the name of the @value{GDBN} command history file to @var{fname}.
23768 This is the file where @value{GDBN} reads an initial command history
23769 list, and where it writes the command history from this session when it
23770 exits. You can access this list through history expansion or through
23771 the history command editing characters listed below. This file defaults
23772 to the value of the environment variable @code{GDBHISTFILE}, or to
23773 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23776 @cindex save command history
23777 @kindex set history save
23778 @item set history save
23779 @itemx set history save on
23780 Record command history in a file, whose name may be specified with the
23781 @code{set history filename} command. By default, this option is disabled.
23783 @item set history save off
23784 Stop recording command history in a file.
23786 @cindex history size
23787 @kindex set history size
23788 @cindex @env{GDBHISTSIZE}, environment variable
23789 @item set history size @var{size}
23790 @itemx set history size unlimited
23791 Set the number of commands which @value{GDBN} keeps in its history list.
23792 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23793 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23794 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23795 either a negative number or the empty string, then the number of commands
23796 @value{GDBN} keeps in the history list is unlimited.
23798 @cindex remove duplicate history
23799 @kindex set history remove-duplicates
23800 @item set history remove-duplicates @var{count}
23801 @itemx set history remove-duplicates unlimited
23802 Control the removal of duplicate history entries in the command history list.
23803 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23804 history entries and remove the first entry that is a duplicate of the current
23805 entry being added to the command history list. If @var{count} is
23806 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23807 removal of duplicate history entries is disabled.
23809 Only history entries added during the current session are considered for
23810 removal. This option is set to 0 by default.
23814 History expansion assigns special meaning to the character @kbd{!}.
23815 @ifset SYSTEM_READLINE
23816 @xref{Event Designators, , , history, GNU History Library},
23818 @ifclear SYSTEM_READLINE
23819 @xref{Event Designators},
23823 @cindex history expansion, turn on/off
23824 Since @kbd{!} is also the logical not operator in C, history expansion
23825 is off by default. If you decide to enable history expansion with the
23826 @code{set history expansion on} command, you may sometimes need to
23827 follow @kbd{!} (when it is used as logical not, in an expression) with
23828 a space or a tab to prevent it from being expanded. The readline
23829 history facilities do not attempt substitution on the strings
23830 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23832 The commands to control history expansion are:
23835 @item set history expansion on
23836 @itemx set history expansion
23837 @kindex set history expansion
23838 Enable history expansion. History expansion is off by default.
23840 @item set history expansion off
23841 Disable history expansion.
23844 @kindex show history
23846 @itemx show history filename
23847 @itemx show history save
23848 @itemx show history size
23849 @itemx show history expansion
23850 These commands display the state of the @value{GDBN} history parameters.
23851 @code{show history} by itself displays all four states.
23856 @kindex show commands
23857 @cindex show last commands
23858 @cindex display command history
23859 @item show commands
23860 Display the last ten commands in the command history.
23862 @item show commands @var{n}
23863 Print ten commands centered on command number @var{n}.
23865 @item show commands +
23866 Print ten commands just after the commands last printed.
23870 @section Screen Size
23871 @cindex size of screen
23872 @cindex screen size
23875 @cindex pauses in output
23877 Certain commands to @value{GDBN} may produce large amounts of
23878 information output to the screen. To help you read all of it,
23879 @value{GDBN} pauses and asks you for input at the end of each page of
23880 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23881 to discard the remaining output. Also, the screen width setting
23882 determines when to wrap lines of output. Depending on what is being
23883 printed, @value{GDBN} tries to break the line at a readable place,
23884 rather than simply letting it overflow onto the following line.
23886 Normally @value{GDBN} knows the size of the screen from the terminal
23887 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23888 together with the value of the @code{TERM} environment variable and the
23889 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23890 you can override it with the @code{set height} and @code{set
23897 @kindex show height
23898 @item set height @var{lpp}
23899 @itemx set height unlimited
23901 @itemx set width @var{cpl}
23902 @itemx set width unlimited
23904 These @code{set} commands specify a screen height of @var{lpp} lines and
23905 a screen width of @var{cpl} characters. The associated @code{show}
23906 commands display the current settings.
23908 If you specify a height of either @code{unlimited} or zero lines,
23909 @value{GDBN} does not pause during output no matter how long the
23910 output is. This is useful if output is to a file or to an editor
23913 Likewise, you can specify @samp{set width unlimited} or @samp{set
23914 width 0} to prevent @value{GDBN} from wrapping its output.
23916 @item set pagination on
23917 @itemx set pagination off
23918 @kindex set pagination
23919 Turn the output pagination on or off; the default is on. Turning
23920 pagination off is the alternative to @code{set height unlimited}. Note that
23921 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23922 Options, -batch}) also automatically disables pagination.
23924 @item show pagination
23925 @kindex show pagination
23926 Show the current pagination mode.
23931 @cindex number representation
23932 @cindex entering numbers
23934 You can always enter numbers in octal, decimal, or hexadecimal in
23935 @value{GDBN} by the usual conventions: octal numbers begin with
23936 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23937 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23938 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23939 10; likewise, the default display for numbers---when no particular
23940 format is specified---is base 10. You can change the default base for
23941 both input and output with the commands described below.
23944 @kindex set input-radix
23945 @item set input-radix @var{base}
23946 Set the default base for numeric input. Supported choices
23947 for @var{base} are decimal 8, 10, or 16. The base must itself be
23948 specified either unambiguously or using the current input radix; for
23952 set input-radix 012
23953 set input-radix 10.
23954 set input-radix 0xa
23958 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23959 leaves the input radix unchanged, no matter what it was, since
23960 @samp{10}, being without any leading or trailing signs of its base, is
23961 interpreted in the current radix. Thus, if the current radix is 16,
23962 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23965 @kindex set output-radix
23966 @item set output-radix @var{base}
23967 Set the default base for numeric display. Supported choices
23968 for @var{base} are decimal 8, 10, or 16. The base must itself be
23969 specified either unambiguously or using the current input radix.
23971 @kindex show input-radix
23972 @item show input-radix
23973 Display the current default base for numeric input.
23975 @kindex show output-radix
23976 @item show output-radix
23977 Display the current default base for numeric display.
23979 @item set radix @r{[}@var{base}@r{]}
23983 These commands set and show the default base for both input and output
23984 of numbers. @code{set radix} sets the radix of input and output to
23985 the same base; without an argument, it resets the radix back to its
23986 default value of 10.
23991 @section Configuring the Current ABI
23993 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23994 application automatically. However, sometimes you need to override its
23995 conclusions. Use these commands to manage @value{GDBN}'s view of the
24001 @cindex Newlib OS ABI and its influence on the longjmp handling
24003 One @value{GDBN} configuration can debug binaries for multiple operating
24004 system targets, either via remote debugging or native emulation.
24005 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24006 but you can override its conclusion using the @code{set osabi} command.
24007 One example where this is useful is in debugging of binaries which use
24008 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24009 not have the same identifying marks that the standard C library for your
24012 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24013 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24014 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24015 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24019 Show the OS ABI currently in use.
24022 With no argument, show the list of registered available OS ABI's.
24024 @item set osabi @var{abi}
24025 Set the current OS ABI to @var{abi}.
24028 @cindex float promotion
24030 Generally, the way that an argument of type @code{float} is passed to a
24031 function depends on whether the function is prototyped. For a prototyped
24032 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24033 according to the architecture's convention for @code{float}. For unprototyped
24034 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24035 @code{double} and then passed.
24037 Unfortunately, some forms of debug information do not reliably indicate whether
24038 a function is prototyped. If @value{GDBN} calls a function that is not marked
24039 as prototyped, it consults @kbd{set coerce-float-to-double}.
24042 @kindex set coerce-float-to-double
24043 @item set coerce-float-to-double
24044 @itemx set coerce-float-to-double on
24045 Arguments of type @code{float} will be promoted to @code{double} when passed
24046 to an unprototyped function. This is the default setting.
24048 @item set coerce-float-to-double off
24049 Arguments of type @code{float} will be passed directly to unprototyped
24052 @kindex show coerce-float-to-double
24053 @item show coerce-float-to-double
24054 Show the current setting of promoting @code{float} to @code{double}.
24058 @kindex show cp-abi
24059 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24060 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24061 used to build your application. @value{GDBN} only fully supports
24062 programs with a single C@t{++} ABI; if your program contains code using
24063 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24064 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24065 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24066 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24067 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24068 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24073 Show the C@t{++} ABI currently in use.
24076 With no argument, show the list of supported C@t{++} ABI's.
24078 @item set cp-abi @var{abi}
24079 @itemx set cp-abi auto
24080 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24084 @section Automatically loading associated files
24085 @cindex auto-loading
24087 @value{GDBN} sometimes reads files with commands and settings automatically,
24088 without being explicitly told so by the user. We call this feature
24089 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24090 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24091 results or introduce security risks (e.g., if the file comes from untrusted
24095 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24096 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24098 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24099 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24102 There are various kinds of files @value{GDBN} can automatically load.
24103 In addition to these files, @value{GDBN} supports auto-loading code written
24104 in various extension languages. @xref{Auto-loading extensions}.
24106 Note that loading of these associated files (including the local @file{.gdbinit}
24107 file) requires accordingly configured @code{auto-load safe-path}
24108 (@pxref{Auto-loading safe path}).
24110 For these reasons, @value{GDBN} includes commands and options to let you
24111 control when to auto-load files and which files should be auto-loaded.
24114 @anchor{set auto-load off}
24115 @kindex set auto-load off
24116 @item set auto-load off
24117 Globally disable loading of all auto-loaded files.
24118 You may want to use this command with the @samp{-iex} option
24119 (@pxref{Option -init-eval-command}) such as:
24121 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24124 Be aware that system init file (@pxref{System-wide configuration})
24125 and init files from your home directory (@pxref{Home Directory Init File})
24126 still get read (as they come from generally trusted directories).
24127 To prevent @value{GDBN} from auto-loading even those init files, use the
24128 @option{-nx} option (@pxref{Mode Options}), in addition to
24129 @code{set auto-load no}.
24131 @anchor{show auto-load}
24132 @kindex show auto-load
24133 @item show auto-load
24134 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24138 (gdb) show auto-load
24139 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24140 libthread-db: Auto-loading of inferior specific libthread_db is on.
24141 local-gdbinit: Auto-loading of .gdbinit script from current directory
24143 python-scripts: Auto-loading of Python scripts is on.
24144 safe-path: List of directories from which it is safe to auto-load files
24145 is $debugdir:$datadir/auto-load.
24146 scripts-directory: List of directories from which to load auto-loaded scripts
24147 is $debugdir:$datadir/auto-load.
24150 @anchor{info auto-load}
24151 @kindex info auto-load
24152 @item info auto-load
24153 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24157 (gdb) info auto-load
24160 Yes /home/user/gdb/gdb-gdb.gdb
24161 libthread-db: No auto-loaded libthread-db.
24162 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24166 Yes /home/user/gdb/gdb-gdb.py
24170 These are @value{GDBN} control commands for the auto-loading:
24172 @multitable @columnfractions .5 .5
24173 @item @xref{set auto-load off}.
24174 @tab Disable auto-loading globally.
24175 @item @xref{show auto-load}.
24176 @tab Show setting of all kinds of files.
24177 @item @xref{info auto-load}.
24178 @tab Show state of all kinds of files.
24179 @item @xref{set auto-load gdb-scripts}.
24180 @tab Control for @value{GDBN} command scripts.
24181 @item @xref{show auto-load gdb-scripts}.
24182 @tab Show setting of @value{GDBN} command scripts.
24183 @item @xref{info auto-load gdb-scripts}.
24184 @tab Show state of @value{GDBN} command scripts.
24185 @item @xref{set auto-load python-scripts}.
24186 @tab Control for @value{GDBN} Python scripts.
24187 @item @xref{show auto-load python-scripts}.
24188 @tab Show setting of @value{GDBN} Python scripts.
24189 @item @xref{info auto-load python-scripts}.
24190 @tab Show state of @value{GDBN} Python scripts.
24191 @item @xref{set auto-load guile-scripts}.
24192 @tab Control for @value{GDBN} Guile scripts.
24193 @item @xref{show auto-load guile-scripts}.
24194 @tab Show setting of @value{GDBN} Guile scripts.
24195 @item @xref{info auto-load guile-scripts}.
24196 @tab Show state of @value{GDBN} Guile scripts.
24197 @item @xref{set auto-load scripts-directory}.
24198 @tab Control for @value{GDBN} auto-loaded scripts location.
24199 @item @xref{show auto-load scripts-directory}.
24200 @tab Show @value{GDBN} auto-loaded scripts location.
24201 @item @xref{add-auto-load-scripts-directory}.
24202 @tab Add directory for auto-loaded scripts location list.
24203 @item @xref{set auto-load local-gdbinit}.
24204 @tab Control for init file in the current directory.
24205 @item @xref{show auto-load local-gdbinit}.
24206 @tab Show setting of init file in the current directory.
24207 @item @xref{info auto-load local-gdbinit}.
24208 @tab Show state of init file in the current directory.
24209 @item @xref{set auto-load libthread-db}.
24210 @tab Control for thread debugging library.
24211 @item @xref{show auto-load libthread-db}.
24212 @tab Show setting of thread debugging library.
24213 @item @xref{info auto-load libthread-db}.
24214 @tab Show state of thread debugging library.
24215 @item @xref{set auto-load safe-path}.
24216 @tab Control directories trusted for automatic loading.
24217 @item @xref{show auto-load safe-path}.
24218 @tab Show directories trusted for automatic loading.
24219 @item @xref{add-auto-load-safe-path}.
24220 @tab Add directory trusted for automatic loading.
24223 @node Init File in the Current Directory
24224 @subsection Automatically loading init file in the current directory
24225 @cindex auto-loading init file in the current directory
24227 By default, @value{GDBN} reads and executes the canned sequences of commands
24228 from init file (if any) in the current working directory,
24229 see @ref{Init File in the Current Directory during Startup}.
24231 Note that loading of this local @file{.gdbinit} file also requires accordingly
24232 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24235 @anchor{set auto-load local-gdbinit}
24236 @kindex set auto-load local-gdbinit
24237 @item set auto-load local-gdbinit [on|off]
24238 Enable or disable the auto-loading of canned sequences of commands
24239 (@pxref{Sequences}) found in init file in the current directory.
24241 @anchor{show auto-load local-gdbinit}
24242 @kindex show auto-load local-gdbinit
24243 @item show auto-load local-gdbinit
24244 Show whether auto-loading of canned sequences of commands from init file in the
24245 current directory is enabled or disabled.
24247 @anchor{info auto-load local-gdbinit}
24248 @kindex info auto-load local-gdbinit
24249 @item info auto-load local-gdbinit
24250 Print whether canned sequences of commands from init file in the
24251 current directory have been auto-loaded.
24254 @node libthread_db.so.1 file
24255 @subsection Automatically loading thread debugging library
24256 @cindex auto-loading libthread_db.so.1
24258 This feature is currently present only on @sc{gnu}/Linux native hosts.
24260 @value{GDBN} reads in some cases thread debugging library from places specific
24261 to the inferior (@pxref{set libthread-db-search-path}).
24263 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24264 without checking this @samp{set auto-load libthread-db} switch as system
24265 libraries have to be trusted in general. In all other cases of
24266 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24267 auto-load libthread-db} is enabled before trying to open such thread debugging
24270 Note that loading of this debugging library also requires accordingly configured
24271 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24274 @anchor{set auto-load libthread-db}
24275 @kindex set auto-load libthread-db
24276 @item set auto-load libthread-db [on|off]
24277 Enable or disable the auto-loading of inferior specific thread debugging library.
24279 @anchor{show auto-load libthread-db}
24280 @kindex show auto-load libthread-db
24281 @item show auto-load libthread-db
24282 Show whether auto-loading of inferior specific thread debugging library is
24283 enabled or disabled.
24285 @anchor{info auto-load libthread-db}
24286 @kindex info auto-load libthread-db
24287 @item info auto-load libthread-db
24288 Print the list of all loaded inferior specific thread debugging libraries and
24289 for each such library print list of inferior @var{pid}s using it.
24292 @node Auto-loading safe path
24293 @subsection Security restriction for auto-loading
24294 @cindex auto-loading safe-path
24296 As the files of inferior can come from untrusted source (such as submitted by
24297 an application user) @value{GDBN} does not always load any files automatically.
24298 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24299 directories trusted for loading files not explicitly requested by user.
24300 Each directory can also be a shell wildcard pattern.
24302 If the path is not set properly you will see a warning and the file will not
24307 Reading symbols from /home/user/gdb/gdb...done.
24308 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24309 declined by your `auto-load safe-path' set
24310 to "$debugdir:$datadir/auto-load".
24311 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24312 declined by your `auto-load safe-path' set
24313 to "$debugdir:$datadir/auto-load".
24317 To instruct @value{GDBN} to go ahead and use the init files anyway,
24318 invoke @value{GDBN} like this:
24321 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24324 The list of trusted directories is controlled by the following commands:
24327 @anchor{set auto-load safe-path}
24328 @kindex set auto-load safe-path
24329 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24330 Set the list of directories (and their subdirectories) trusted for automatic
24331 loading and execution of scripts. You can also enter a specific trusted file.
24332 Each directory can also be a shell wildcard pattern; wildcards do not match
24333 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24334 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24335 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24336 its default value as specified during @value{GDBN} compilation.
24338 The list of directories uses path separator (@samp{:} on GNU and Unix
24339 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24340 to the @env{PATH} environment variable.
24342 @anchor{show auto-load safe-path}
24343 @kindex show auto-load safe-path
24344 @item show auto-load safe-path
24345 Show the list of directories trusted for automatic loading and execution of
24348 @anchor{add-auto-load-safe-path}
24349 @kindex add-auto-load-safe-path
24350 @item add-auto-load-safe-path
24351 Add an entry (or list of entries) to the list of directories trusted for
24352 automatic loading and execution of scripts. Multiple entries may be delimited
24353 by the host platform path separator in use.
24356 This variable defaults to what @code{--with-auto-load-dir} has been configured
24357 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24358 substitution applies the same as for @ref{set auto-load scripts-directory}.
24359 The default @code{set auto-load safe-path} value can be also overriden by
24360 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24362 Setting this variable to @file{/} disables this security protection,
24363 corresponding @value{GDBN} configuration option is
24364 @option{--without-auto-load-safe-path}.
24365 This variable is supposed to be set to the system directories writable by the
24366 system superuser only. Users can add their source directories in init files in
24367 their home directories (@pxref{Home Directory Init File}). See also deprecated
24368 init file in the current directory
24369 (@pxref{Init File in the Current Directory during Startup}).
24371 To force @value{GDBN} to load the files it declined to load in the previous
24372 example, you could use one of the following ways:
24375 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24376 Specify this trusted directory (or a file) as additional component of the list.
24377 You have to specify also any existing directories displayed by
24378 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24380 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24381 Specify this directory as in the previous case but just for a single
24382 @value{GDBN} session.
24384 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24385 Disable auto-loading safety for a single @value{GDBN} session.
24386 This assumes all the files you debug during this @value{GDBN} session will come
24387 from trusted sources.
24389 @item @kbd{./configure --without-auto-load-safe-path}
24390 During compilation of @value{GDBN} you may disable any auto-loading safety.
24391 This assumes all the files you will ever debug with this @value{GDBN} come from
24395 On the other hand you can also explicitly forbid automatic files loading which
24396 also suppresses any such warning messages:
24399 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24400 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24402 @item @file{~/.gdbinit}: @samp{set auto-load no}
24403 Disable auto-loading globally for the user
24404 (@pxref{Home Directory Init File}). While it is improbable, you could also
24405 use system init file instead (@pxref{System-wide configuration}).
24408 This setting applies to the file names as entered by user. If no entry matches
24409 @value{GDBN} tries as a last resort to also resolve all the file names into
24410 their canonical form (typically resolving symbolic links) and compare the
24411 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24412 own before starting the comparison so a canonical form of directories is
24413 recommended to be entered.
24415 @node Auto-loading verbose mode
24416 @subsection Displaying files tried for auto-load
24417 @cindex auto-loading verbose mode
24419 For better visibility of all the file locations where you can place scripts to
24420 be auto-loaded with inferior --- or to protect yourself against accidental
24421 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24422 all the files attempted to be loaded. Both existing and non-existing files may
24425 For example the list of directories from which it is safe to auto-load files
24426 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24427 may not be too obvious while setting it up.
24430 (gdb) set debug auto-load on
24431 (gdb) file ~/src/t/true
24432 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24433 for objfile "/tmp/true".
24434 auto-load: Updating directories of "/usr:/opt".
24435 auto-load: Using directory "/usr".
24436 auto-load: Using directory "/opt".
24437 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24438 by your `auto-load safe-path' set to "/usr:/opt".
24442 @anchor{set debug auto-load}
24443 @kindex set debug auto-load
24444 @item set debug auto-load [on|off]
24445 Set whether to print the filenames attempted to be auto-loaded.
24447 @anchor{show debug auto-load}
24448 @kindex show debug auto-load
24449 @item show debug auto-load
24450 Show whether printing of the filenames attempted to be auto-loaded is turned
24454 @node Messages/Warnings
24455 @section Optional Warnings and Messages
24457 @cindex verbose operation
24458 @cindex optional warnings
24459 By default, @value{GDBN} is silent about its inner workings. If you are
24460 running on a slow machine, you may want to use the @code{set verbose}
24461 command. This makes @value{GDBN} tell you when it does a lengthy
24462 internal operation, so you will not think it has crashed.
24464 Currently, the messages controlled by @code{set verbose} are those
24465 which announce that the symbol table for a source file is being read;
24466 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24469 @kindex set verbose
24470 @item set verbose on
24471 Enables @value{GDBN} output of certain informational messages.
24473 @item set verbose off
24474 Disables @value{GDBN} output of certain informational messages.
24476 @kindex show verbose
24478 Displays whether @code{set verbose} is on or off.
24481 By default, if @value{GDBN} encounters bugs in the symbol table of an
24482 object file, it is silent; but if you are debugging a compiler, you may
24483 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24488 @kindex set complaints
24489 @item set complaints @var{limit}
24490 Permits @value{GDBN} to output @var{limit} complaints about each type of
24491 unusual symbols before becoming silent about the problem. Set
24492 @var{limit} to zero to suppress all complaints; set it to a large number
24493 to prevent complaints from being suppressed.
24495 @kindex show complaints
24496 @item show complaints
24497 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24501 @anchor{confirmation requests}
24502 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24503 lot of stupid questions to confirm certain commands. For example, if
24504 you try to run a program which is already running:
24508 The program being debugged has been started already.
24509 Start it from the beginning? (y or n)
24512 If you are willing to unflinchingly face the consequences of your own
24513 commands, you can disable this ``feature'':
24517 @kindex set confirm
24519 @cindex confirmation
24520 @cindex stupid questions
24521 @item set confirm off
24522 Disables confirmation requests. Note that running @value{GDBN} with
24523 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24524 automatically disables confirmation requests.
24526 @item set confirm on
24527 Enables confirmation requests (the default).
24529 @kindex show confirm
24531 Displays state of confirmation requests.
24535 @cindex command tracing
24536 If you need to debug user-defined commands or sourced files you may find it
24537 useful to enable @dfn{command tracing}. In this mode each command will be
24538 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24539 quantity denoting the call depth of each command.
24542 @kindex set trace-commands
24543 @cindex command scripts, debugging
24544 @item set trace-commands on
24545 Enable command tracing.
24546 @item set trace-commands off
24547 Disable command tracing.
24548 @item show trace-commands
24549 Display the current state of command tracing.
24552 @node Debugging Output
24553 @section Optional Messages about Internal Happenings
24554 @cindex optional debugging messages
24556 @value{GDBN} has commands that enable optional debugging messages from
24557 various @value{GDBN} subsystems; normally these commands are of
24558 interest to @value{GDBN} maintainers, or when reporting a bug. This
24559 section documents those commands.
24562 @kindex set exec-done-display
24563 @item set exec-done-display
24564 Turns on or off the notification of asynchronous commands'
24565 completion. When on, @value{GDBN} will print a message when an
24566 asynchronous command finishes its execution. The default is off.
24567 @kindex show exec-done-display
24568 @item show exec-done-display
24569 Displays the current setting of asynchronous command completion
24572 @cindex ARM AArch64
24573 @item set debug aarch64
24574 Turns on or off display of debugging messages related to ARM AArch64.
24575 The default is off.
24577 @item show debug aarch64
24578 Displays the current state of displaying debugging messages related to
24580 @cindex gdbarch debugging info
24581 @cindex architecture debugging info
24582 @item set debug arch
24583 Turns on or off display of gdbarch debugging info. The default is off
24584 @item show debug arch
24585 Displays the current state of displaying gdbarch debugging info.
24586 @item set debug aix-solib
24587 @cindex AIX shared library debugging
24588 Control display of debugging messages from the AIX shared library
24589 support module. The default is off.
24590 @item show debug aix-thread
24591 Show the current state of displaying AIX shared library debugging messages.
24592 @item set debug aix-thread
24593 @cindex AIX threads
24594 Display debugging messages about inner workings of the AIX thread
24596 @item show debug aix-thread
24597 Show the current state of AIX thread debugging info display.
24598 @item set debug check-physname
24600 Check the results of the ``physname'' computation. When reading DWARF
24601 debugging information for C@t{++}, @value{GDBN} attempts to compute
24602 each entity's name. @value{GDBN} can do this computation in two
24603 different ways, depending on exactly what information is present.
24604 When enabled, this setting causes @value{GDBN} to compute the names
24605 both ways and display any discrepancies.
24606 @item show debug check-physname
24607 Show the current state of ``physname'' checking.
24608 @item set debug coff-pe-read
24609 @cindex COFF/PE exported symbols
24610 Control display of debugging messages related to reading of COFF/PE
24611 exported symbols. The default is off.
24612 @item show debug coff-pe-read
24613 Displays the current state of displaying debugging messages related to
24614 reading of COFF/PE exported symbols.
24615 @item set debug dwarf-die
24617 Dump DWARF DIEs after they are read in.
24618 The value is the number of nesting levels to print.
24619 A value of zero turns off the display.
24620 @item show debug dwarf-die
24621 Show the current state of DWARF DIE debugging.
24622 @item set debug dwarf-line
24623 @cindex DWARF Line Tables
24624 Turns on or off display of debugging messages related to reading
24625 DWARF line tables. The default is 0 (off).
24626 A value of 1 provides basic information.
24627 A value greater than 1 provides more verbose information.
24628 @item show debug dwarf-line
24629 Show the current state of DWARF line table debugging.
24630 @item set debug dwarf-read
24631 @cindex DWARF Reading
24632 Turns on or off display of debugging messages related to reading
24633 DWARF debug info. The default is 0 (off).
24634 A value of 1 provides basic information.
24635 A value greater than 1 provides more verbose information.
24636 @item show debug dwarf-read
24637 Show the current state of DWARF reader debugging.
24638 @item set debug displaced
24639 @cindex displaced stepping debugging info
24640 Turns on or off display of @value{GDBN} debugging info for the
24641 displaced stepping support. The default is off.
24642 @item show debug displaced
24643 Displays the current state of displaying @value{GDBN} debugging info
24644 related to displaced stepping.
24645 @item set debug event
24646 @cindex event debugging info
24647 Turns on or off display of @value{GDBN} event debugging info. The
24649 @item show debug event
24650 Displays the current state of displaying @value{GDBN} event debugging
24652 @item set debug expression
24653 @cindex expression debugging info
24654 Turns on or off display of debugging info about @value{GDBN}
24655 expression parsing. The default is off.
24656 @item show debug expression
24657 Displays the current state of displaying debugging info about
24658 @value{GDBN} expression parsing.
24659 @item set debug fbsd-lwp
24660 @cindex FreeBSD LWP debug messages
24661 Turns on or off debugging messages from the FreeBSD LWP debug support.
24662 @item show debug fbsd-lwp
24663 Show the current state of FreeBSD LWP debugging messages.
24664 @item set debug fbsd-nat
24665 @cindex FreeBSD native target debug messages
24666 Turns on or off debugging messages from the FreeBSD native target.
24667 @item show debug fbsd-nat
24668 Show the current state of FreeBSD native target debugging messages.
24669 @item set debug frame
24670 @cindex frame debugging info
24671 Turns on or off display of @value{GDBN} frame debugging info. The
24673 @item show debug frame
24674 Displays the current state of displaying @value{GDBN} frame debugging
24676 @item set debug gnu-nat
24677 @cindex @sc{gnu}/Hurd debug messages
24678 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24679 @item show debug gnu-nat
24680 Show the current state of @sc{gnu}/Hurd debugging messages.
24681 @item set debug infrun
24682 @cindex inferior debugging info
24683 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24684 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24685 for implementing operations such as single-stepping the inferior.
24686 @item show debug infrun
24687 Displays the current state of @value{GDBN} inferior debugging.
24688 @item set debug jit
24689 @cindex just-in-time compilation, debugging messages
24690 Turn on or off debugging messages from JIT debug support.
24691 @item show debug jit
24692 Displays the current state of @value{GDBN} JIT debugging.
24693 @item set debug lin-lwp
24694 @cindex @sc{gnu}/Linux LWP debug messages
24695 @cindex Linux lightweight processes
24696 Turn on or off debugging messages from the Linux LWP debug support.
24697 @item show debug lin-lwp
24698 Show the current state of Linux LWP debugging messages.
24699 @item set debug linux-namespaces
24700 @cindex @sc{gnu}/Linux namespaces debug messages
24701 Turn on or off debugging messages from the Linux namespaces debug support.
24702 @item show debug linux-namespaces
24703 Show the current state of Linux namespaces debugging messages.
24704 @item set debug mach-o
24705 @cindex Mach-O symbols processing
24706 Control display of debugging messages related to Mach-O symbols
24707 processing. The default is off.
24708 @item show debug mach-o
24709 Displays the current state of displaying debugging messages related to
24710 reading of COFF/PE exported symbols.
24711 @item set debug notification
24712 @cindex remote async notification debugging info
24713 Turn on or off debugging messages about remote async notification.
24714 The default is off.
24715 @item show debug notification
24716 Displays the current state of remote async notification debugging messages.
24717 @item set debug observer
24718 @cindex observer debugging info
24719 Turns on or off display of @value{GDBN} observer debugging. This
24720 includes info such as the notification of observable events.
24721 @item show debug observer
24722 Displays the current state of observer debugging.
24723 @item set debug overload
24724 @cindex C@t{++} overload debugging info
24725 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24726 info. This includes info such as ranking of functions, etc. The default
24728 @item show debug overload
24729 Displays the current state of displaying @value{GDBN} C@t{++} overload
24731 @cindex expression parser, debugging info
24732 @cindex debug expression parser
24733 @item set debug parser
24734 Turns on or off the display of expression parser debugging output.
24735 Internally, this sets the @code{yydebug} variable in the expression
24736 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24737 details. The default is off.
24738 @item show debug parser
24739 Show the current state of expression parser debugging.
24740 @cindex packets, reporting on stdout
24741 @cindex serial connections, debugging
24742 @cindex debug remote protocol
24743 @cindex remote protocol debugging
24744 @cindex display remote packets
24745 @item set debug remote
24746 Turns on or off display of reports on all packets sent back and forth across
24747 the serial line to the remote machine. The info is printed on the
24748 @value{GDBN} standard output stream. The default is off.
24749 @item show debug remote
24750 Displays the state of display of remote packets.
24752 @item set debug separate-debug-file
24753 Turns on or off display of debug output about separate debug file search.
24754 @item show debug separate-debug-file
24755 Displays the state of separate debug file search debug output.
24757 @item set debug serial
24758 Turns on or off display of @value{GDBN} serial debugging info. The
24760 @item show debug serial
24761 Displays the current state of displaying @value{GDBN} serial debugging
24763 @item set debug solib-frv
24764 @cindex FR-V shared-library debugging
24765 Turn on or off debugging messages for FR-V shared-library code.
24766 @item show debug solib-frv
24767 Display the current state of FR-V shared-library code debugging
24769 @item set debug symbol-lookup
24770 @cindex symbol lookup
24771 Turns on or off display of debugging messages related to symbol lookup.
24772 The default is 0 (off).
24773 A value of 1 provides basic information.
24774 A value greater than 1 provides more verbose information.
24775 @item show debug symbol-lookup
24776 Show the current state of symbol lookup debugging messages.
24777 @item set debug symfile
24778 @cindex symbol file functions
24779 Turns on or off display of debugging messages related to symbol file functions.
24780 The default is off. @xref{Files}.
24781 @item show debug symfile
24782 Show the current state of symbol file debugging messages.
24783 @item set debug symtab-create
24784 @cindex symbol table creation
24785 Turns on or off display of debugging messages related to symbol table creation.
24786 The default is 0 (off).
24787 A value of 1 provides basic information.
24788 A value greater than 1 provides more verbose information.
24789 @item show debug symtab-create
24790 Show the current state of symbol table creation debugging.
24791 @item set debug target
24792 @cindex target debugging info
24793 Turns on or off display of @value{GDBN} target debugging info. This info
24794 includes what is going on at the target level of GDB, as it happens. The
24795 default is 0. Set it to 1 to track events, and to 2 to also track the
24796 value of large memory transfers.
24797 @item show debug target
24798 Displays the current state of displaying @value{GDBN} target debugging
24800 @item set debug timestamp
24801 @cindex timestampping debugging info
24802 Turns on or off display of timestamps with @value{GDBN} debugging info.
24803 When enabled, seconds and microseconds are displayed before each debugging
24805 @item show debug timestamp
24806 Displays the current state of displaying timestamps with @value{GDBN}
24808 @item set debug varobj
24809 @cindex variable object debugging info
24810 Turns on or off display of @value{GDBN} variable object debugging
24811 info. The default is off.
24812 @item show debug varobj
24813 Displays the current state of displaying @value{GDBN} variable object
24815 @item set debug xml
24816 @cindex XML parser debugging
24817 Turn on or off debugging messages for built-in XML parsers.
24818 @item show debug xml
24819 Displays the current state of XML debugging messages.
24822 @node Other Misc Settings
24823 @section Other Miscellaneous Settings
24824 @cindex miscellaneous settings
24827 @kindex set interactive-mode
24828 @item set interactive-mode
24829 If @code{on}, forces @value{GDBN} to assume that GDB was started
24830 in a terminal. In practice, this means that @value{GDBN} should wait
24831 for the user to answer queries generated by commands entered at
24832 the command prompt. If @code{off}, forces @value{GDBN} to operate
24833 in the opposite mode, and it uses the default answers to all queries.
24834 If @code{auto} (the default), @value{GDBN} tries to determine whether
24835 its standard input is a terminal, and works in interactive-mode if it
24836 is, non-interactively otherwise.
24838 In the vast majority of cases, the debugger should be able to guess
24839 correctly which mode should be used. But this setting can be useful
24840 in certain specific cases, such as running a MinGW @value{GDBN}
24841 inside a cygwin window.
24843 @kindex show interactive-mode
24844 @item show interactive-mode
24845 Displays whether the debugger is operating in interactive mode or not.
24848 @node Extending GDB
24849 @chapter Extending @value{GDBN}
24850 @cindex extending GDB
24852 @value{GDBN} provides several mechanisms for extension.
24853 @value{GDBN} also provides the ability to automatically load
24854 extensions when it reads a file for debugging. This allows the
24855 user to automatically customize @value{GDBN} for the program
24859 * Sequences:: Canned Sequences of @value{GDBN} Commands
24860 * Python:: Extending @value{GDBN} using Python
24861 * Guile:: Extending @value{GDBN} using Guile
24862 * Auto-loading extensions:: Automatically loading extensions
24863 * Multiple Extension Languages:: Working with multiple extension languages
24864 * Aliases:: Creating new spellings of existing commands
24867 To facilitate the use of extension languages, @value{GDBN} is capable
24868 of evaluating the contents of a file. When doing so, @value{GDBN}
24869 can recognize which extension language is being used by looking at
24870 the filename extension. Files with an unrecognized filename extension
24871 are always treated as a @value{GDBN} Command Files.
24872 @xref{Command Files,, Command files}.
24874 You can control how @value{GDBN} evaluates these files with the following
24878 @kindex set script-extension
24879 @kindex show script-extension
24880 @item set script-extension off
24881 All scripts are always evaluated as @value{GDBN} Command Files.
24883 @item set script-extension soft
24884 The debugger determines the scripting language based on filename
24885 extension. If this scripting language is supported, @value{GDBN}
24886 evaluates the script using that language. Otherwise, it evaluates
24887 the file as a @value{GDBN} Command File.
24889 @item set script-extension strict
24890 The debugger determines the scripting language based on filename
24891 extension, and evaluates the script using that language. If the
24892 language is not supported, then the evaluation fails.
24894 @item show script-extension
24895 Display the current value of the @code{script-extension} option.
24900 @section Canned Sequences of Commands
24902 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24903 Command Lists}), @value{GDBN} provides two ways to store sequences of
24904 commands for execution as a unit: user-defined commands and command
24908 * Define:: How to define your own commands
24909 * Hooks:: Hooks for user-defined commands
24910 * Command Files:: How to write scripts of commands to be stored in a file
24911 * Output:: Commands for controlled output
24912 * Auto-loading sequences:: Controlling auto-loaded command files
24916 @subsection User-defined Commands
24918 @cindex user-defined command
24919 @cindex arguments, to user-defined commands
24920 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24921 which you assign a new name as a command. This is done with the
24922 @code{define} command. User commands may accept an unlimited number of arguments
24923 separated by whitespace. Arguments are accessed within the user command
24924 via @code{$arg0@dots{}$argN}. A trivial example:
24928 print $arg0 + $arg1 + $arg2
24933 To execute the command use:
24940 This defines the command @code{adder}, which prints the sum of
24941 its three arguments. Note the arguments are text substitutions, so they may
24942 reference variables, use complex expressions, or even perform inferior
24945 @cindex argument count in user-defined commands
24946 @cindex how many arguments (user-defined commands)
24947 In addition, @code{$argc} may be used to find out how many arguments have
24953 print $arg0 + $arg1
24956 print $arg0 + $arg1 + $arg2
24961 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24962 to process a variable number of arguments:
24969 eval "set $sum = $sum + $arg%d", $i
24979 @item define @var{commandname}
24980 Define a command named @var{commandname}. If there is already a command
24981 by that name, you are asked to confirm that you want to redefine it.
24982 The argument @var{commandname} may be a bare command name consisting of letters,
24983 numbers, dashes, and underscores. It may also start with any predefined
24984 prefix command. For example, @samp{define target my-target} creates
24985 a user-defined @samp{target my-target} command.
24987 The definition of the command is made up of other @value{GDBN} command lines,
24988 which are given following the @code{define} command. The end of these
24989 commands is marked by a line containing @code{end}.
24992 @kindex end@r{ (user-defined commands)}
24993 @item document @var{commandname}
24994 Document the user-defined command @var{commandname}, so that it can be
24995 accessed by @code{help}. The command @var{commandname} must already be
24996 defined. This command reads lines of documentation just as @code{define}
24997 reads the lines of the command definition, ending with @code{end}.
24998 After the @code{document} command is finished, @code{help} on command
24999 @var{commandname} displays the documentation you have written.
25001 You may use the @code{document} command again to change the
25002 documentation of a command. Redefining the command with @code{define}
25003 does not change the documentation.
25005 @kindex dont-repeat
25006 @cindex don't repeat command
25008 Used inside a user-defined command, this tells @value{GDBN} that this
25009 command should not be repeated when the user hits @key{RET}
25010 (@pxref{Command Syntax, repeat last command}).
25012 @kindex help user-defined
25013 @item help user-defined
25014 List all user-defined commands and all python commands defined in class
25015 COMAND_USER. The first line of the documentation or docstring is
25020 @itemx show user @var{commandname}
25021 Display the @value{GDBN} commands used to define @var{commandname} (but
25022 not its documentation). If no @var{commandname} is given, display the
25023 definitions for all user-defined commands.
25024 This does not work for user-defined python commands.
25026 @cindex infinite recursion in user-defined commands
25027 @kindex show max-user-call-depth
25028 @kindex set max-user-call-depth
25029 @item show max-user-call-depth
25030 @itemx set max-user-call-depth
25031 The value of @code{max-user-call-depth} controls how many recursion
25032 levels are allowed in user-defined commands before @value{GDBN} suspects an
25033 infinite recursion and aborts the command.
25034 This does not apply to user-defined python commands.
25037 In addition to the above commands, user-defined commands frequently
25038 use control flow commands, described in @ref{Command Files}.
25040 When user-defined commands are executed, the
25041 commands of the definition are not printed. An error in any command
25042 stops execution of the user-defined command.
25044 If used interactively, commands that would ask for confirmation proceed
25045 without asking when used inside a user-defined command. Many @value{GDBN}
25046 commands that normally print messages to say what they are doing omit the
25047 messages when used in a user-defined command.
25050 @subsection User-defined Command Hooks
25051 @cindex command hooks
25052 @cindex hooks, for commands
25053 @cindex hooks, pre-command
25056 You may define @dfn{hooks}, which are a special kind of user-defined
25057 command. Whenever you run the command @samp{foo}, if the user-defined
25058 command @samp{hook-foo} exists, it is executed (with no arguments)
25059 before that command.
25061 @cindex hooks, post-command
25063 A hook may also be defined which is run after the command you executed.
25064 Whenever you run the command @samp{foo}, if the user-defined command
25065 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25066 that command. Post-execution hooks may exist simultaneously with
25067 pre-execution hooks, for the same command.
25069 It is valid for a hook to call the command which it hooks. If this
25070 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25072 @c It would be nice if hookpost could be passed a parameter indicating
25073 @c if the command it hooks executed properly or not. FIXME!
25075 @kindex stop@r{, a pseudo-command}
25076 In addition, a pseudo-command, @samp{stop} exists. Defining
25077 (@samp{hook-stop}) makes the associated commands execute every time
25078 execution stops in your program: before breakpoint commands are run,
25079 displays are printed, or the stack frame is printed.
25081 For example, to ignore @code{SIGALRM} signals while
25082 single-stepping, but treat them normally during normal execution,
25087 handle SIGALRM nopass
25091 handle SIGALRM pass
25094 define hook-continue
25095 handle SIGALRM pass
25099 As a further example, to hook at the beginning and end of the @code{echo}
25100 command, and to add extra text to the beginning and end of the message,
25108 define hookpost-echo
25112 (@value{GDBP}) echo Hello World
25113 <<<---Hello World--->>>
25118 You can define a hook for any single-word command in @value{GDBN}, but
25119 not for command aliases; you should define a hook for the basic command
25120 name, e.g.@: @code{backtrace} rather than @code{bt}.
25121 @c FIXME! So how does Joe User discover whether a command is an alias
25123 You can hook a multi-word command by adding @code{hook-} or
25124 @code{hookpost-} to the last word of the command, e.g.@:
25125 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25127 If an error occurs during the execution of your hook, execution of
25128 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25129 (before the command that you actually typed had a chance to run).
25131 If you try to define a hook which does not match any known command, you
25132 get a warning from the @code{define} command.
25134 @node Command Files
25135 @subsection Command Files
25137 @cindex command files
25138 @cindex scripting commands
25139 A command file for @value{GDBN} is a text file made of lines that are
25140 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25141 also be included. An empty line in a command file does nothing; it
25142 does not mean to repeat the last command, as it would from the
25145 You can request the execution of a command file with the @code{source}
25146 command. Note that the @code{source} command is also used to evaluate
25147 scripts that are not Command Files. The exact behavior can be configured
25148 using the @code{script-extension} setting.
25149 @xref{Extending GDB,, Extending GDB}.
25153 @cindex execute commands from a file
25154 @item source [-s] [-v] @var{filename}
25155 Execute the command file @var{filename}.
25158 The lines in a command file are generally executed sequentially,
25159 unless the order of execution is changed by one of the
25160 @emph{flow-control commands} described below. The commands are not
25161 printed as they are executed. An error in any command terminates
25162 execution of the command file and control is returned to the console.
25164 @value{GDBN} first searches for @var{filename} in the current directory.
25165 If the file is not found there, and @var{filename} does not specify a
25166 directory, then @value{GDBN} also looks for the file on the source search path
25167 (specified with the @samp{directory} command);
25168 except that @file{$cdir} is not searched because the compilation directory
25169 is not relevant to scripts.
25171 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25172 on the search path even if @var{filename} specifies a directory.
25173 The search is done by appending @var{filename} to each element of the
25174 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25175 and the search path contains @file{/home/user} then @value{GDBN} will
25176 look for the script @file{/home/user/mylib/myscript}.
25177 The search is also done if @var{filename} is an absolute path.
25178 For example, if @var{filename} is @file{/tmp/myscript} and
25179 the search path contains @file{/home/user} then @value{GDBN} will
25180 look for the script @file{/home/user/tmp/myscript}.
25181 For DOS-like systems, if @var{filename} contains a drive specification,
25182 it is stripped before concatenation. For example, if @var{filename} is
25183 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25184 will look for the script @file{c:/tmp/myscript}.
25186 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25187 each command as it is executed. The option must be given before
25188 @var{filename}, and is interpreted as part of the filename anywhere else.
25190 Commands that would ask for confirmation if used interactively proceed
25191 without asking when used in a command file. Many @value{GDBN} commands that
25192 normally print messages to say what they are doing omit the messages
25193 when called from command files.
25195 @value{GDBN} also accepts command input from standard input. In this
25196 mode, normal output goes to standard output and error output goes to
25197 standard error. Errors in a command file supplied on standard input do
25198 not terminate execution of the command file---execution continues with
25202 gdb < cmds > log 2>&1
25205 (The syntax above will vary depending on the shell used.) This example
25206 will execute commands from the file @file{cmds}. All output and errors
25207 would be directed to @file{log}.
25209 Since commands stored on command files tend to be more general than
25210 commands typed interactively, they frequently need to deal with
25211 complicated situations, such as different or unexpected values of
25212 variables and symbols, changes in how the program being debugged is
25213 built, etc. @value{GDBN} provides a set of flow-control commands to
25214 deal with these complexities. Using these commands, you can write
25215 complex scripts that loop over data structures, execute commands
25216 conditionally, etc.
25223 This command allows to include in your script conditionally executed
25224 commands. The @code{if} command takes a single argument, which is an
25225 expression to evaluate. It is followed by a series of commands that
25226 are executed only if the expression is true (its value is nonzero).
25227 There can then optionally be an @code{else} line, followed by a series
25228 of commands that are only executed if the expression was false. The
25229 end of the list is marked by a line containing @code{end}.
25233 This command allows to write loops. Its syntax is similar to
25234 @code{if}: the command takes a single argument, which is an expression
25235 to evaluate, and must be followed by the commands to execute, one per
25236 line, terminated by an @code{end}. These commands are called the
25237 @dfn{body} of the loop. The commands in the body of @code{while} are
25238 executed repeatedly as long as the expression evaluates to true.
25242 This command exits the @code{while} loop in whose body it is included.
25243 Execution of the script continues after that @code{while}s @code{end}
25246 @kindex loop_continue
25247 @item loop_continue
25248 This command skips the execution of the rest of the body of commands
25249 in the @code{while} loop in whose body it is included. Execution
25250 branches to the beginning of the @code{while} loop, where it evaluates
25251 the controlling expression.
25253 @kindex end@r{ (if/else/while commands)}
25255 Terminate the block of commands that are the body of @code{if},
25256 @code{else}, or @code{while} flow-control commands.
25261 @subsection Commands for Controlled Output
25263 During the execution of a command file or a user-defined command, normal
25264 @value{GDBN} output is suppressed; the only output that appears is what is
25265 explicitly printed by the commands in the definition. This section
25266 describes three commands useful for generating exactly the output you
25271 @item echo @var{text}
25272 @c I do not consider backslash-space a standard C escape sequence
25273 @c because it is not in ANSI.
25274 Print @var{text}. Nonprinting characters can be included in
25275 @var{text} using C escape sequences, such as @samp{\n} to print a
25276 newline. @strong{No newline is printed unless you specify one.}
25277 In addition to the standard C escape sequences, a backslash followed
25278 by a space stands for a space. This is useful for displaying a
25279 string with spaces at the beginning or the end, since leading and
25280 trailing spaces are otherwise trimmed from all arguments.
25281 To print @samp{@w{ }and foo =@w{ }}, use the command
25282 @samp{echo \@w{ }and foo = \@w{ }}.
25284 A backslash at the end of @var{text} can be used, as in C, to continue
25285 the command onto subsequent lines. For example,
25288 echo This is some text\n\
25289 which is continued\n\
25290 onto several lines.\n
25293 produces the same output as
25296 echo This is some text\n
25297 echo which is continued\n
25298 echo onto several lines.\n
25302 @item output @var{expression}
25303 Print the value of @var{expression} and nothing but that value: no
25304 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25305 value history either. @xref{Expressions, ,Expressions}, for more information
25308 @item output/@var{fmt} @var{expression}
25309 Print the value of @var{expression} in format @var{fmt}. You can use
25310 the same formats as for @code{print}. @xref{Output Formats,,Output
25311 Formats}, for more information.
25314 @item printf @var{template}, @var{expressions}@dots{}
25315 Print the values of one or more @var{expressions} under the control of
25316 the string @var{template}. To print several values, make
25317 @var{expressions} be a comma-separated list of individual expressions,
25318 which may be either numbers or pointers. Their values are printed as
25319 specified by @var{template}, exactly as a C program would do by
25320 executing the code below:
25323 printf (@var{template}, @var{expressions}@dots{});
25326 As in @code{C} @code{printf}, ordinary characters in @var{template}
25327 are printed verbatim, while @dfn{conversion specification} introduced
25328 by the @samp{%} character cause subsequent @var{expressions} to be
25329 evaluated, their values converted and formatted according to type and
25330 style information encoded in the conversion specifications, and then
25333 For example, you can print two values in hex like this:
25336 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25339 @code{printf} supports all the standard @code{C} conversion
25340 specifications, including the flags and modifiers between the @samp{%}
25341 character and the conversion letter, with the following exceptions:
25345 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25348 The modifier @samp{*} is not supported for specifying precision or
25352 The @samp{'} flag (for separation of digits into groups according to
25353 @code{LC_NUMERIC'}) is not supported.
25356 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25360 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25363 The conversion letters @samp{a} and @samp{A} are not supported.
25367 Note that the @samp{ll} type modifier is supported only if the
25368 underlying @code{C} implementation used to build @value{GDBN} supports
25369 the @code{long long int} type, and the @samp{L} type modifier is
25370 supported only if @code{long double} type is available.
25372 As in @code{C}, @code{printf} supports simple backslash-escape
25373 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25374 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25375 single character. Octal and hexadecimal escape sequences are not
25378 Additionally, @code{printf} supports conversion specifications for DFP
25379 (@dfn{Decimal Floating Point}) types using the following length modifiers
25380 together with a floating point specifier.
25385 @samp{H} for printing @code{Decimal32} types.
25388 @samp{D} for printing @code{Decimal64} types.
25391 @samp{DD} for printing @code{Decimal128} types.
25394 If the underlying @code{C} implementation used to build @value{GDBN} has
25395 support for the three length modifiers for DFP types, other modifiers
25396 such as width and precision will also be available for @value{GDBN} to use.
25398 In case there is no such @code{C} support, no additional modifiers will be
25399 available and the value will be printed in the standard way.
25401 Here's an example of printing DFP types using the above conversion letters:
25403 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25408 @item eval @var{template}, @var{expressions}@dots{}
25409 Convert the values of one or more @var{expressions} under the control of
25410 the string @var{template} to a command line, and call it.
25414 @node Auto-loading sequences
25415 @subsection Controlling auto-loading native @value{GDBN} scripts
25416 @cindex native script auto-loading
25418 When a new object file is read (for example, due to the @code{file}
25419 command, or because the inferior has loaded a shared library),
25420 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25421 @xref{Auto-loading extensions}.
25423 Auto-loading can be enabled or disabled,
25424 and the list of auto-loaded scripts can be printed.
25427 @anchor{set auto-load gdb-scripts}
25428 @kindex set auto-load gdb-scripts
25429 @item set auto-load gdb-scripts [on|off]
25430 Enable or disable the auto-loading of canned sequences of commands scripts.
25432 @anchor{show auto-load gdb-scripts}
25433 @kindex show auto-load gdb-scripts
25434 @item show auto-load gdb-scripts
25435 Show whether auto-loading of canned sequences of commands scripts is enabled or
25438 @anchor{info auto-load gdb-scripts}
25439 @kindex info auto-load gdb-scripts
25440 @cindex print list of auto-loaded canned sequences of commands scripts
25441 @item info auto-load gdb-scripts [@var{regexp}]
25442 Print the list of all canned sequences of commands scripts that @value{GDBN}
25446 If @var{regexp} is supplied only canned sequences of commands scripts with
25447 matching names are printed.
25449 @c Python docs live in a separate file.
25450 @include python.texi
25452 @c Guile docs live in a separate file.
25453 @include guile.texi
25455 @node Auto-loading extensions
25456 @section Auto-loading extensions
25457 @cindex auto-loading extensions
25459 @value{GDBN} provides two mechanisms for automatically loading extensions
25460 when a new object file is read (for example, due to the @code{file}
25461 command, or because the inferior has loaded a shared library):
25462 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25463 section of modern file formats like ELF.
25466 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25467 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25468 * Which flavor to choose?::
25471 The auto-loading feature is useful for supplying application-specific
25472 debugging commands and features.
25474 Auto-loading can be enabled or disabled,
25475 and the list of auto-loaded scripts can be printed.
25476 See the @samp{auto-loading} section of each extension language
25477 for more information.
25478 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25479 For Python files see @ref{Python Auto-loading}.
25481 Note that loading of this script file also requires accordingly configured
25482 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25484 @node objfile-gdbdotext file
25485 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25486 @cindex @file{@var{objfile}-gdb.gdb}
25487 @cindex @file{@var{objfile}-gdb.py}
25488 @cindex @file{@var{objfile}-gdb.scm}
25490 When a new object file is read, @value{GDBN} looks for a file named
25491 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25492 where @var{objfile} is the object file's name and
25493 where @var{ext} is the file extension for the extension language:
25496 @item @file{@var{objfile}-gdb.gdb}
25497 GDB's own command language
25498 @item @file{@var{objfile}-gdb.py}
25500 @item @file{@var{objfile}-gdb.scm}
25504 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25505 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25506 components, and appending the @file{-gdb.@var{ext}} suffix.
25507 If this file exists and is readable, @value{GDBN} will evaluate it as a
25508 script in the specified extension language.
25510 If this file does not exist, then @value{GDBN} will look for
25511 @var{script-name} file in all of the directories as specified below.
25513 Note that loading of these files requires an accordingly configured
25514 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25516 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25517 scripts normally according to its @file{.exe} filename. But if no scripts are
25518 found @value{GDBN} also tries script filenames matching the object file without
25519 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25520 is attempted on any platform. This makes the script filenames compatible
25521 between Unix and MS-Windows hosts.
25524 @anchor{set auto-load scripts-directory}
25525 @kindex set auto-load scripts-directory
25526 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25527 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25528 may be delimited by the host platform path separator in use
25529 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25531 Each entry here needs to be covered also by the security setting
25532 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25534 @anchor{with-auto-load-dir}
25535 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25536 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25537 configuration option @option{--with-auto-load-dir}.
25539 Any reference to @file{$debugdir} will get replaced by
25540 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25541 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25542 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25543 @file{$datadir} must be placed as a directory component --- either alone or
25544 delimited by @file{/} or @file{\} directory separators, depending on the host
25547 The list of directories uses path separator (@samp{:} on GNU and Unix
25548 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25549 to the @env{PATH} environment variable.
25551 @anchor{show auto-load scripts-directory}
25552 @kindex show auto-load scripts-directory
25553 @item show auto-load scripts-directory
25554 Show @value{GDBN} auto-loaded scripts location.
25556 @anchor{add-auto-load-scripts-directory}
25557 @kindex add-auto-load-scripts-directory
25558 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25559 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25560 Multiple entries may be delimited by the host platform path separator in use.
25563 @value{GDBN} does not track which files it has already auto-loaded this way.
25564 @value{GDBN} will load the associated script every time the corresponding
25565 @var{objfile} is opened.
25566 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25567 is evaluated more than once.
25569 @node dotdebug_gdb_scripts section
25570 @subsection The @code{.debug_gdb_scripts} section
25571 @cindex @code{.debug_gdb_scripts} section
25573 For systems using file formats like ELF and COFF,
25574 when @value{GDBN} loads a new object file
25575 it will look for a special section named @code{.debug_gdb_scripts}.
25576 If this section exists, its contents is a list of null-terminated entries
25577 specifying scripts to load. Each entry begins with a non-null prefix byte that
25578 specifies the kind of entry, typically the extension language and whether the
25579 script is in a file or inlined in @code{.debug_gdb_scripts}.
25581 The following entries are supported:
25584 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25585 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25586 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25587 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25590 @subsubsection Script File Entries
25592 If the entry specifies a file, @value{GDBN} will look for the file first
25593 in the current directory and then along the source search path
25594 (@pxref{Source Path, ,Specifying Source Directories}),
25595 except that @file{$cdir} is not searched, since the compilation
25596 directory is not relevant to scripts.
25598 File entries can be placed in section @code{.debug_gdb_scripts} with,
25599 for example, this GCC macro for Python scripts.
25602 /* Note: The "MS" section flags are to remove duplicates. */
25603 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25605 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25606 .byte 1 /* Python */\n\
25607 .asciz \"" script_name "\"\n\
25613 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25614 Then one can reference the macro in a header or source file like this:
25617 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25620 The script name may include directories if desired.
25622 Note that loading of this script file also requires accordingly configured
25623 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25625 If the macro invocation is put in a header, any application or library
25626 using this header will get a reference to the specified script,
25627 and with the use of @code{"MS"} attributes on the section, the linker
25628 will remove duplicates.
25630 @subsubsection Script Text Entries
25632 Script text entries allow to put the executable script in the entry
25633 itself instead of loading it from a file.
25634 The first line of the entry, everything after the prefix byte and up to
25635 the first newline (@code{0xa}) character, is the script name, and must not
25636 contain any kind of space character, e.g., spaces or tabs.
25637 The rest of the entry, up to the trailing null byte, is the script to
25638 execute in the specified language. The name needs to be unique among
25639 all script names, as @value{GDBN} executes each script only once based
25642 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25646 #include "symcat.h"
25647 #include "gdb/section-scripts.h"
25649 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25650 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25651 ".ascii \"gdb.inlined-script\\n\"\n"
25652 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25653 ".ascii \" def __init__ (self):\\n\"\n"
25654 ".ascii \" super (test_cmd, self).__init__ ("
25655 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25656 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25657 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25658 ".ascii \"test_cmd ()\\n\"\n"
25664 Loading of inlined scripts requires a properly configured
25665 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25666 The path to specify in @code{auto-load safe-path} is the path of the file
25667 containing the @code{.debug_gdb_scripts} section.
25669 @node Which flavor to choose?
25670 @subsection Which flavor to choose?
25672 Given the multiple ways of auto-loading extensions, it might not always
25673 be clear which one to choose. This section provides some guidance.
25676 Benefits of the @file{-gdb.@var{ext}} way:
25680 Can be used with file formats that don't support multiple sections.
25683 Ease of finding scripts for public libraries.
25685 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25686 in the source search path.
25687 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25688 isn't a source directory in which to find the script.
25691 Doesn't require source code additions.
25695 Benefits of the @code{.debug_gdb_scripts} way:
25699 Works with static linking.
25701 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25702 trigger their loading. When an application is statically linked the only
25703 objfile available is the executable, and it is cumbersome to attach all the
25704 scripts from all the input libraries to the executable's
25705 @file{-gdb.@var{ext}} script.
25708 Works with classes that are entirely inlined.
25710 Some classes can be entirely inlined, and thus there may not be an associated
25711 shared library to attach a @file{-gdb.@var{ext}} script to.
25714 Scripts needn't be copied out of the source tree.
25716 In some circumstances, apps can be built out of large collections of internal
25717 libraries, and the build infrastructure necessary to install the
25718 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25719 cumbersome. It may be easier to specify the scripts in the
25720 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25721 top of the source tree to the source search path.
25724 @node Multiple Extension Languages
25725 @section Multiple Extension Languages
25727 The Guile and Python extension languages do not share any state,
25728 and generally do not interfere with each other.
25729 There are some things to be aware of, however.
25731 @subsection Python comes first
25733 Python was @value{GDBN}'s first extension language, and to avoid breaking
25734 existing behaviour Python comes first. This is generally solved by the
25735 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25736 extension languages, and when it makes a call to an extension language,
25737 (say to pretty-print a value), it tries each in turn until an extension
25738 language indicates it has performed the request (e.g., has returned the
25739 pretty-printed form of a value).
25740 This extends to errors while performing such requests: If an error happens
25741 while, for example, trying to pretty-print an object then the error is
25742 reported and any following extension languages are not tried.
25745 @section Creating new spellings of existing commands
25746 @cindex aliases for commands
25748 It is often useful to define alternate spellings of existing commands.
25749 For example, if a new @value{GDBN} command defined in Python has
25750 a long name to type, it is handy to have an abbreviated version of it
25751 that involves less typing.
25753 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25754 of the @samp{step} command even though it is otherwise an ambiguous
25755 abbreviation of other commands like @samp{set} and @samp{show}.
25757 Aliases are also used to provide shortened or more common versions
25758 of multi-word commands. For example, @value{GDBN} provides the
25759 @samp{tty} alias of the @samp{set inferior-tty} command.
25761 You can define a new alias with the @samp{alias} command.
25766 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25770 @var{ALIAS} specifies the name of the new alias.
25771 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25774 @var{COMMAND} specifies the name of an existing command
25775 that is being aliased.
25777 The @samp{-a} option specifies that the new alias is an abbreviation
25778 of the command. Abbreviations are not shown in command
25779 lists displayed by the @samp{help} command.
25781 The @samp{--} option specifies the end of options,
25782 and is useful when @var{ALIAS} begins with a dash.
25784 Here is a simple example showing how to make an abbreviation
25785 of a command so that there is less to type.
25786 Suppose you were tired of typing @samp{disas}, the current
25787 shortest unambiguous abbreviation of the @samp{disassemble} command
25788 and you wanted an even shorter version named @samp{di}.
25789 The following will accomplish this.
25792 (gdb) alias -a di = disas
25795 Note that aliases are different from user-defined commands.
25796 With a user-defined command, you also need to write documentation
25797 for it with the @samp{document} command.
25798 An alias automatically picks up the documentation of the existing command.
25800 Here is an example where we make @samp{elms} an abbreviation of
25801 @samp{elements} in the @samp{set print elements} command.
25802 This is to show that you can make an abbreviation of any part
25806 (gdb) alias -a set print elms = set print elements
25807 (gdb) alias -a show print elms = show print elements
25808 (gdb) set p elms 20
25810 Limit on string chars or array elements to print is 200.
25813 Note that if you are defining an alias of a @samp{set} command,
25814 and you want to have an alias for the corresponding @samp{show}
25815 command, then you need to define the latter separately.
25817 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25818 @var{ALIAS}, just as they are normally.
25821 (gdb) alias -a set pr elms = set p ele
25824 Finally, here is an example showing the creation of a one word
25825 alias for a more complex command.
25826 This creates alias @samp{spe} of the command @samp{set print elements}.
25829 (gdb) alias spe = set print elements
25834 @chapter Command Interpreters
25835 @cindex command interpreters
25837 @value{GDBN} supports multiple command interpreters, and some command
25838 infrastructure to allow users or user interface writers to switch
25839 between interpreters or run commands in other interpreters.
25841 @value{GDBN} currently supports two command interpreters, the console
25842 interpreter (sometimes called the command-line interpreter or @sc{cli})
25843 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25844 describes both of these interfaces in great detail.
25846 By default, @value{GDBN} will start with the console interpreter.
25847 However, the user may choose to start @value{GDBN} with another
25848 interpreter by specifying the @option{-i} or @option{--interpreter}
25849 startup options. Defined interpreters include:
25853 @cindex console interpreter
25854 The traditional console or command-line interpreter. This is the most often
25855 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25856 @value{GDBN} will use this interpreter.
25859 @cindex mi interpreter
25860 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25861 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25862 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25866 @cindex mi2 interpreter
25867 The current @sc{gdb/mi} interface.
25870 @cindex mi1 interpreter
25871 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25875 @cindex invoke another interpreter
25877 @kindex interpreter-exec
25878 You may execute commands in any interpreter from the current
25879 interpreter using the appropriate command. If you are running the
25880 console interpreter, simply use the @code{interpreter-exec} command:
25883 interpreter-exec mi "-data-list-register-names"
25886 @sc{gdb/mi} has a similar command, although it is only available in versions of
25887 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25889 Note that @code{interpreter-exec} only changes the interpreter for the
25890 duration of the specified command. It does not change the interpreter
25893 @cindex start a new independent interpreter
25895 Although you may only choose a single interpreter at startup, it is
25896 possible to run an independent interpreter on a specified input/output
25897 device (usually a tty).
25899 For example, consider a debugger GUI or IDE that wants to provide a
25900 @value{GDBN} console view. It may do so by embedding a terminal
25901 emulator widget in its GUI, starting @value{GDBN} in the traditional
25902 command-line mode with stdin/stdout/stderr redirected to that
25903 terminal, and then creating an MI interpreter running on a specified
25904 input/output device. The console interpreter created by @value{GDBN}
25905 at startup handles commands the user types in the terminal widget,
25906 while the GUI controls and synchronizes state with @value{GDBN} using
25907 the separate MI interpreter.
25909 To start a new secondary @dfn{user interface} running MI, use the
25910 @code{new-ui} command:
25913 @cindex new user interface
25915 new-ui @var{interpreter} @var{tty}
25918 The @var{interpreter} parameter specifies the interpreter to run.
25919 This accepts the same values as the @code{interpreter-exec} command.
25920 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25921 @var{tty} parameter specifies the name of the bidirectional file the
25922 interpreter uses for input/output, usually the name of a
25923 pseudoterminal slave on Unix systems. For example:
25926 (@value{GDBP}) new-ui mi /dev/pts/9
25930 runs an MI interpreter on @file{/dev/pts/9}.
25933 @chapter @value{GDBN} Text User Interface
25935 @cindex Text User Interface
25938 * TUI Overview:: TUI overview
25939 * TUI Keys:: TUI key bindings
25940 * TUI Single Key Mode:: TUI single key mode
25941 * TUI Commands:: TUI-specific commands
25942 * TUI Configuration:: TUI configuration variables
25945 The @value{GDBN} Text User Interface (TUI) is a terminal
25946 interface which uses the @code{curses} library to show the source
25947 file, the assembly output, the program registers and @value{GDBN}
25948 commands in separate text windows. The TUI mode is supported only
25949 on platforms where a suitable version of the @code{curses} library
25952 The TUI mode is enabled by default when you invoke @value{GDBN} as
25953 @samp{@value{GDBP} -tui}.
25954 You can also switch in and out of TUI mode while @value{GDBN} runs by
25955 using various TUI commands and key bindings, such as @command{tui
25956 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25957 @ref{TUI Keys, ,TUI Key Bindings}.
25960 @section TUI Overview
25962 In TUI mode, @value{GDBN} can display several text windows:
25966 This window is the @value{GDBN} command window with the @value{GDBN}
25967 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25968 managed using readline.
25971 The source window shows the source file of the program. The current
25972 line and active breakpoints are displayed in this window.
25975 The assembly window shows the disassembly output of the program.
25978 This window shows the processor registers. Registers are highlighted
25979 when their values change.
25982 The source and assembly windows show the current program position
25983 by highlighting the current line and marking it with a @samp{>} marker.
25984 Breakpoints are indicated with two markers. The first marker
25985 indicates the breakpoint type:
25989 Breakpoint which was hit at least once.
25992 Breakpoint which was never hit.
25995 Hardware breakpoint which was hit at least once.
25998 Hardware breakpoint which was never hit.
26001 The second marker indicates whether the breakpoint is enabled or not:
26005 Breakpoint is enabled.
26008 Breakpoint is disabled.
26011 The source, assembly and register windows are updated when the current
26012 thread changes, when the frame changes, or when the program counter
26015 These windows are not all visible at the same time. The command
26016 window is always visible. The others can be arranged in several
26027 source and assembly,
26030 source and registers, or
26033 assembly and registers.
26036 A status line above the command window shows the following information:
26040 Indicates the current @value{GDBN} target.
26041 (@pxref{Targets, ,Specifying a Debugging Target}).
26044 Gives the current process or thread number.
26045 When no process is being debugged, this field is set to @code{No process}.
26048 Gives the current function name for the selected frame.
26049 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26050 When there is no symbol corresponding to the current program counter,
26051 the string @code{??} is displayed.
26054 Indicates the current line number for the selected frame.
26055 When the current line number is not known, the string @code{??} is displayed.
26058 Indicates the current program counter address.
26062 @section TUI Key Bindings
26063 @cindex TUI key bindings
26065 The TUI installs several key bindings in the readline keymaps
26066 @ifset SYSTEM_READLINE
26067 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26069 @ifclear SYSTEM_READLINE
26070 (@pxref{Command Line Editing}).
26072 The following key bindings are installed for both TUI mode and the
26073 @value{GDBN} standard mode.
26082 Enter or leave the TUI mode. When leaving the TUI mode,
26083 the curses window management stops and @value{GDBN} operates using
26084 its standard mode, writing on the terminal directly. When reentering
26085 the TUI mode, control is given back to the curses windows.
26086 The screen is then refreshed.
26090 Use a TUI layout with only one window. The layout will
26091 either be @samp{source} or @samp{assembly}. When the TUI mode
26092 is not active, it will switch to the TUI mode.
26094 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26098 Use a TUI layout with at least two windows. When the current
26099 layout already has two windows, the next layout with two windows is used.
26100 When a new layout is chosen, one window will always be common to the
26101 previous layout and the new one.
26103 Think of it as the Emacs @kbd{C-x 2} binding.
26107 Change the active window. The TUI associates several key bindings
26108 (like scrolling and arrow keys) with the active window. This command
26109 gives the focus to the next TUI window.
26111 Think of it as the Emacs @kbd{C-x o} binding.
26115 Switch in and out of the TUI SingleKey mode that binds single
26116 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26119 The following key bindings only work in the TUI mode:
26124 Scroll the active window one page up.
26128 Scroll the active window one page down.
26132 Scroll the active window one line up.
26136 Scroll the active window one line down.
26140 Scroll the active window one column left.
26144 Scroll the active window one column right.
26148 Refresh the screen.
26151 Because the arrow keys scroll the active window in the TUI mode, they
26152 are not available for their normal use by readline unless the command
26153 window has the focus. When another window is active, you must use
26154 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26155 and @kbd{C-f} to control the command window.
26157 @node TUI Single Key Mode
26158 @section TUI Single Key Mode
26159 @cindex TUI single key mode
26161 The TUI also provides a @dfn{SingleKey} mode, which binds several
26162 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26163 switch into this mode, where the following key bindings are used:
26166 @kindex c @r{(SingleKey TUI key)}
26170 @kindex d @r{(SingleKey TUI key)}
26174 @kindex f @r{(SingleKey TUI key)}
26178 @kindex n @r{(SingleKey TUI key)}
26182 @kindex o @r{(SingleKey TUI key)}
26184 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26186 @kindex q @r{(SingleKey TUI key)}
26188 exit the SingleKey mode.
26190 @kindex r @r{(SingleKey TUI key)}
26194 @kindex s @r{(SingleKey TUI key)}
26198 @kindex i @r{(SingleKey TUI key)}
26200 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26202 @kindex u @r{(SingleKey TUI key)}
26206 @kindex v @r{(SingleKey TUI key)}
26210 @kindex w @r{(SingleKey TUI key)}
26215 Other keys temporarily switch to the @value{GDBN} command prompt.
26216 The key that was pressed is inserted in the editing buffer so that
26217 it is possible to type most @value{GDBN} commands without interaction
26218 with the TUI SingleKey mode. Once the command is entered the TUI
26219 SingleKey mode is restored. The only way to permanently leave
26220 this mode is by typing @kbd{q} or @kbd{C-x s}.
26224 @section TUI-specific Commands
26225 @cindex TUI commands
26227 The TUI has specific commands to control the text windows.
26228 These commands are always available, even when @value{GDBN} is not in
26229 the TUI mode. When @value{GDBN} is in the standard mode, most
26230 of these commands will automatically switch to the TUI mode.
26232 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26233 terminal, or @value{GDBN} has been started with the machine interface
26234 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26235 these commands will fail with an error, because it would not be
26236 possible or desirable to enable curses window management.
26241 Activate TUI mode. The last active TUI window layout will be used if
26242 TUI mode has prevsiouly been used in the current debugging session,
26243 otherwise a default layout is used.
26246 @kindex tui disable
26247 Disable TUI mode, returning to the console interpreter.
26251 List and give the size of all displayed windows.
26253 @item layout @var{name}
26255 Changes which TUI windows are displayed. In each layout the command
26256 window is always displayed, the @var{name} parameter controls which
26257 additional windows are displayed, and can be any of the following:
26261 Display the next layout.
26264 Display the previous layout.
26267 Display the source and command windows.
26270 Display the assembly and command windows.
26273 Display the source, assembly, and command windows.
26276 When in @code{src} layout display the register, source, and command
26277 windows. When in @code{asm} or @code{split} layout display the
26278 register, assembler, and command windows.
26281 @item focus @var{name}
26283 Changes which TUI window is currently active for scrolling. The
26284 @var{name} parameter can be any of the following:
26288 Make the next window active for scrolling.
26291 Make the previous window active for scrolling.
26294 Make the source window active for scrolling.
26297 Make the assembly window active for scrolling.
26300 Make the register window active for scrolling.
26303 Make the command window active for scrolling.
26308 Refresh the screen. This is similar to typing @kbd{C-L}.
26310 @item tui reg @var{group}
26312 Changes the register group displayed in the tui register window to
26313 @var{group}. If the register window is not currently displayed this
26314 command will cause the register window to be displayed. The list of
26315 register groups, as well as their order is target specific. The
26316 following groups are available on most targets:
26319 Repeatedly selecting this group will cause the display to cycle
26320 through all of the available register groups.
26323 Repeatedly selecting this group will cause the display to cycle
26324 through all of the available register groups in the reverse order to
26328 Display the general registers.
26330 Display the floating point registers.
26332 Display the system registers.
26334 Display the vector registers.
26336 Display all registers.
26341 Update the source window and the current execution point.
26343 @item winheight @var{name} +@var{count}
26344 @itemx winheight @var{name} -@var{count}
26346 Change the height of the window @var{name} by @var{count}
26347 lines. Positive counts increase the height, while negative counts
26348 decrease it. The @var{name} parameter can be one of @code{src} (the
26349 source window), @code{cmd} (the command window), @code{asm} (the
26350 disassembly window), or @code{regs} (the register display window).
26352 @item tabset @var{nchars}
26354 Set the width of tab stops to be @var{nchars} characters. This
26355 setting affects the display of TAB characters in the source and
26359 @node TUI Configuration
26360 @section TUI Configuration Variables
26361 @cindex TUI configuration variables
26363 Several configuration variables control the appearance of TUI windows.
26366 @item set tui border-kind @var{kind}
26367 @kindex set tui border-kind
26368 Select the border appearance for the source, assembly and register windows.
26369 The possible values are the following:
26372 Use a space character to draw the border.
26375 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26378 Use the Alternate Character Set to draw the border. The border is
26379 drawn using character line graphics if the terminal supports them.
26382 @item set tui border-mode @var{mode}
26383 @kindex set tui border-mode
26384 @itemx set tui active-border-mode @var{mode}
26385 @kindex set tui active-border-mode
26386 Select the display attributes for the borders of the inactive windows
26387 or the active window. The @var{mode} can be one of the following:
26390 Use normal attributes to display the border.
26396 Use reverse video mode.
26399 Use half bright mode.
26401 @item half-standout
26402 Use half bright and standout mode.
26405 Use extra bright or bold mode.
26407 @item bold-standout
26408 Use extra bright or bold and standout mode.
26413 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26416 @cindex @sc{gnu} Emacs
26417 A special interface allows you to use @sc{gnu} Emacs to view (and
26418 edit) the source files for the program you are debugging with
26421 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26422 executable file you want to debug as an argument. This command starts
26423 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26424 created Emacs buffer.
26425 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26427 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26432 All ``terminal'' input and output goes through an Emacs buffer, called
26435 This applies both to @value{GDBN} commands and their output, and to the input
26436 and output done by the program you are debugging.
26438 This is useful because it means that you can copy the text of previous
26439 commands and input them again; you can even use parts of the output
26442 All the facilities of Emacs' Shell mode are available for interacting
26443 with your program. In particular, you can send signals the usual
26444 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26448 @value{GDBN} displays source code through Emacs.
26450 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26451 source file for that frame and puts an arrow (@samp{=>}) at the
26452 left margin of the current line. Emacs uses a separate buffer for
26453 source display, and splits the screen to show both your @value{GDBN} session
26456 Explicit @value{GDBN} @code{list} or search commands still produce output as
26457 usual, but you probably have no reason to use them from Emacs.
26460 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26461 a graphical mode, enabled by default, which provides further buffers
26462 that can control the execution and describe the state of your program.
26463 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26465 If you specify an absolute file name when prompted for the @kbd{M-x
26466 gdb} argument, then Emacs sets your current working directory to where
26467 your program resides. If you only specify the file name, then Emacs
26468 sets your current working directory to the directory associated
26469 with the previous buffer. In this case, @value{GDBN} may find your
26470 program by searching your environment's @code{PATH} variable, but on
26471 some operating systems it might not find the source. So, although the
26472 @value{GDBN} input and output session proceeds normally, the auxiliary
26473 buffer does not display the current source and line of execution.
26475 The initial working directory of @value{GDBN} is printed on the top
26476 line of the GUD buffer and this serves as a default for the commands
26477 that specify files for @value{GDBN} to operate on. @xref{Files,
26478 ,Commands to Specify Files}.
26480 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26481 need to call @value{GDBN} by a different name (for example, if you
26482 keep several configurations around, with different names) you can
26483 customize the Emacs variable @code{gud-gdb-command-name} to run the
26486 In the GUD buffer, you can use these special Emacs commands in
26487 addition to the standard Shell mode commands:
26491 Describe the features of Emacs' GUD Mode.
26494 Execute to another source line, like the @value{GDBN} @code{step} command; also
26495 update the display window to show the current file and location.
26498 Execute to next source line in this function, skipping all function
26499 calls, like the @value{GDBN} @code{next} command. Then update the display window
26500 to show the current file and location.
26503 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26504 display window accordingly.
26507 Execute until exit from the selected stack frame, like the @value{GDBN}
26508 @code{finish} command.
26511 Continue execution of your program, like the @value{GDBN} @code{continue}
26515 Go up the number of frames indicated by the numeric argument
26516 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26517 like the @value{GDBN} @code{up} command.
26520 Go down the number of frames indicated by the numeric argument, like the
26521 @value{GDBN} @code{down} command.
26524 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26525 tells @value{GDBN} to set a breakpoint on the source line point is on.
26527 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26528 separate frame which shows a backtrace when the GUD buffer is current.
26529 Move point to any frame in the stack and type @key{RET} to make it
26530 become the current frame and display the associated source in the
26531 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26532 selected frame become the current one. In graphical mode, the
26533 speedbar displays watch expressions.
26535 If you accidentally delete the source-display buffer, an easy way to get
26536 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26537 request a frame display; when you run under Emacs, this recreates
26538 the source buffer if necessary to show you the context of the current
26541 The source files displayed in Emacs are in ordinary Emacs buffers
26542 which are visiting the source files in the usual way. You can edit
26543 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26544 communicates with Emacs in terms of line numbers. If you add or
26545 delete lines from the text, the line numbers that @value{GDBN} knows cease
26546 to correspond properly with the code.
26548 A more detailed description of Emacs' interaction with @value{GDBN} is
26549 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26553 @chapter The @sc{gdb/mi} Interface
26555 @unnumberedsec Function and Purpose
26557 @cindex @sc{gdb/mi}, its purpose
26558 @sc{gdb/mi} is a line based machine oriented text interface to
26559 @value{GDBN} and is activated by specifying using the
26560 @option{--interpreter} command line option (@pxref{Mode Options}). It
26561 is specifically intended to support the development of systems which
26562 use the debugger as just one small component of a larger system.
26564 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26565 in the form of a reference manual.
26567 Note that @sc{gdb/mi} is still under construction, so some of the
26568 features described below are incomplete and subject to change
26569 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26571 @unnumberedsec Notation and Terminology
26573 @cindex notational conventions, for @sc{gdb/mi}
26574 This chapter uses the following notation:
26578 @code{|} separates two alternatives.
26581 @code{[ @var{something} ]} indicates that @var{something} is optional:
26582 it may or may not be given.
26585 @code{( @var{group} )*} means that @var{group} inside the parentheses
26586 may repeat zero or more times.
26589 @code{( @var{group} )+} means that @var{group} inside the parentheses
26590 may repeat one or more times.
26593 @code{"@var{string}"} means a literal @var{string}.
26597 @heading Dependencies
26601 * GDB/MI General Design::
26602 * GDB/MI Command Syntax::
26603 * GDB/MI Compatibility with CLI::
26604 * GDB/MI Development and Front Ends::
26605 * GDB/MI Output Records::
26606 * GDB/MI Simple Examples::
26607 * GDB/MI Command Description Format::
26608 * GDB/MI Breakpoint Commands::
26609 * GDB/MI Catchpoint Commands::
26610 * GDB/MI Program Context::
26611 * GDB/MI Thread Commands::
26612 * GDB/MI Ada Tasking Commands::
26613 * GDB/MI Program Execution::
26614 * GDB/MI Stack Manipulation::
26615 * GDB/MI Variable Objects::
26616 * GDB/MI Data Manipulation::
26617 * GDB/MI Tracepoint Commands::
26618 * GDB/MI Symbol Query::
26619 * GDB/MI File Commands::
26621 * GDB/MI Kod Commands::
26622 * GDB/MI Memory Overlay Commands::
26623 * GDB/MI Signal Handling Commands::
26625 * GDB/MI Target Manipulation::
26626 * GDB/MI File Transfer Commands::
26627 * GDB/MI Ada Exceptions Commands::
26628 * GDB/MI Support Commands::
26629 * GDB/MI Miscellaneous Commands::
26632 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26633 @node GDB/MI General Design
26634 @section @sc{gdb/mi} General Design
26635 @cindex GDB/MI General Design
26637 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26638 parts---commands sent to @value{GDBN}, responses to those commands
26639 and notifications. Each command results in exactly one response,
26640 indicating either successful completion of the command, or an error.
26641 For the commands that do not resume the target, the response contains the
26642 requested information. For the commands that resume the target, the
26643 response only indicates whether the target was successfully resumed.
26644 Notifications is the mechanism for reporting changes in the state of the
26645 target, or in @value{GDBN} state, that cannot conveniently be associated with
26646 a command and reported as part of that command response.
26648 The important examples of notifications are:
26652 Exec notifications. These are used to report changes in
26653 target state---when a target is resumed, or stopped. It would not
26654 be feasible to include this information in response of resuming
26655 commands, because one resume commands can result in multiple events in
26656 different threads. Also, quite some time may pass before any event
26657 happens in the target, while a frontend needs to know whether the resuming
26658 command itself was successfully executed.
26661 Console output, and status notifications. Console output
26662 notifications are used to report output of CLI commands, as well as
26663 diagnostics for other commands. Status notifications are used to
26664 report the progress of a long-running operation. Naturally, including
26665 this information in command response would mean no output is produced
26666 until the command is finished, which is undesirable.
26669 General notifications. Commands may have various side effects on
26670 the @value{GDBN} or target state beyond their official purpose. For example,
26671 a command may change the selected thread. Although such changes can
26672 be included in command response, using notification allows for more
26673 orthogonal frontend design.
26677 There's no guarantee that whenever an MI command reports an error,
26678 @value{GDBN} or the target are in any specific state, and especially,
26679 the state is not reverted to the state before the MI command was
26680 processed. Therefore, whenever an MI command results in an error,
26681 we recommend that the frontend refreshes all the information shown in
26682 the user interface.
26686 * Context management::
26687 * Asynchronous and non-stop modes::
26691 @node Context management
26692 @subsection Context management
26694 @subsubsection Threads and Frames
26696 In most cases when @value{GDBN} accesses the target, this access is
26697 done in context of a specific thread and frame (@pxref{Frames}).
26698 Often, even when accessing global data, the target requires that a thread
26699 be specified. The CLI interface maintains the selected thread and frame,
26700 and supplies them to target on each command. This is convenient,
26701 because a command line user would not want to specify that information
26702 explicitly on each command, and because user interacts with
26703 @value{GDBN} via a single terminal, so no confusion is possible as
26704 to what thread and frame are the current ones.
26706 In the case of MI, the concept of selected thread and frame is less
26707 useful. First, a frontend can easily remember this information
26708 itself. Second, a graphical frontend can have more than one window,
26709 each one used for debugging a different thread, and the frontend might
26710 want to access additional threads for internal purposes. This
26711 increases the risk that by relying on implicitly selected thread, the
26712 frontend may be operating on a wrong one. Therefore, each MI command
26713 should explicitly specify which thread and frame to operate on. To
26714 make it possible, each MI command accepts the @samp{--thread} and
26715 @samp{--frame} options, the value to each is @value{GDBN} global
26716 identifier for thread and frame to operate on.
26718 Usually, each top-level window in a frontend allows the user to select
26719 a thread and a frame, and remembers the user selection for further
26720 operations. However, in some cases @value{GDBN} may suggest that the
26721 current thread or frame be changed. For example, when stopping on a
26722 breakpoint it is reasonable to switch to the thread where breakpoint is
26723 hit. For another example, if the user issues the CLI @samp{thread} or
26724 @samp{frame} commands via the frontend, it is desirable to change the
26725 frontend's selection to the one specified by user. @value{GDBN}
26726 communicates the suggestion to change current thread and frame using the
26727 @samp{=thread-selected} notification.
26729 Note that historically, MI shares the selected thread with CLI, so
26730 frontends used the @code{-thread-select} to execute commands in the
26731 right context. However, getting this to work right is cumbersome. The
26732 simplest way is for frontend to emit @code{-thread-select} command
26733 before every command. This doubles the number of commands that need
26734 to be sent. The alternative approach is to suppress @code{-thread-select}
26735 if the selected thread in @value{GDBN} is supposed to be identical to the
26736 thread the frontend wants to operate on. However, getting this
26737 optimization right can be tricky. In particular, if the frontend
26738 sends several commands to @value{GDBN}, and one of the commands changes the
26739 selected thread, then the behaviour of subsequent commands will
26740 change. So, a frontend should either wait for response from such
26741 problematic commands, or explicitly add @code{-thread-select} for
26742 all subsequent commands. No frontend is known to do this exactly
26743 right, so it is suggested to just always pass the @samp{--thread} and
26744 @samp{--frame} options.
26746 @subsubsection Language
26748 The execution of several commands depends on which language is selected.
26749 By default, the current language (@pxref{show language}) is used.
26750 But for commands known to be language-sensitive, it is recommended
26751 to use the @samp{--language} option. This option takes one argument,
26752 which is the name of the language to use while executing the command.
26756 -data-evaluate-expression --language c "sizeof (void*)"
26761 The valid language names are the same names accepted by the
26762 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26763 @samp{local} or @samp{unknown}.
26765 @node Asynchronous and non-stop modes
26766 @subsection Asynchronous command execution and non-stop mode
26768 On some targets, @value{GDBN} is capable of processing MI commands
26769 even while the target is running. This is called @dfn{asynchronous
26770 command execution} (@pxref{Background Execution}). The frontend may
26771 specify a preferrence for asynchronous execution using the
26772 @code{-gdb-set mi-async 1} command, which should be emitted before
26773 either running the executable or attaching to the target. After the
26774 frontend has started the executable or attached to the target, it can
26775 find if asynchronous execution is enabled using the
26776 @code{-list-target-features} command.
26779 @item -gdb-set mi-async on
26780 @item -gdb-set mi-async off
26781 Set whether MI is in asynchronous mode.
26783 When @code{off}, which is the default, MI execution commands (e.g.,
26784 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26785 for the program to stop before processing further commands.
26787 When @code{on}, MI execution commands are background execution
26788 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26789 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26790 MI commands even while the target is running.
26792 @item -gdb-show mi-async
26793 Show whether MI asynchronous mode is enabled.
26796 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26797 @code{target-async} instead of @code{mi-async}, and it had the effect
26798 of both putting MI in asynchronous mode and making CLI background
26799 commands possible. CLI background commands are now always possible
26800 ``out of the box'' if the target supports them. The old spelling is
26801 kept as a deprecated alias for backwards compatibility.
26803 Even if @value{GDBN} can accept a command while target is running,
26804 many commands that access the target do not work when the target is
26805 running. Therefore, asynchronous command execution is most useful
26806 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26807 it is possible to examine the state of one thread, while other threads
26810 When a given thread is running, MI commands that try to access the
26811 target in the context of that thread may not work, or may work only on
26812 some targets. In particular, commands that try to operate on thread's
26813 stack will not work, on any target. Commands that read memory, or
26814 modify breakpoints, may work or not work, depending on the target. Note
26815 that even commands that operate on global state, such as @code{print},
26816 @code{set}, and breakpoint commands, still access the target in the
26817 context of a specific thread, so frontend should try to find a
26818 stopped thread and perform the operation on that thread (using the
26819 @samp{--thread} option).
26821 Which commands will work in the context of a running thread is
26822 highly target dependent. However, the two commands
26823 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26824 to find the state of a thread, will always work.
26826 @node Thread groups
26827 @subsection Thread groups
26828 @value{GDBN} may be used to debug several processes at the same time.
26829 On some platfroms, @value{GDBN} may support debugging of several
26830 hardware systems, each one having several cores with several different
26831 processes running on each core. This section describes the MI
26832 mechanism to support such debugging scenarios.
26834 The key observation is that regardless of the structure of the
26835 target, MI can have a global list of threads, because most commands that
26836 accept the @samp{--thread} option do not need to know what process that
26837 thread belongs to. Therefore, it is not necessary to introduce
26838 neither additional @samp{--process} option, nor an notion of the
26839 current process in the MI interface. The only strictly new feature
26840 that is required is the ability to find how the threads are grouped
26843 To allow the user to discover such grouping, and to support arbitrary
26844 hierarchy of machines/cores/processes, MI introduces the concept of a
26845 @dfn{thread group}. Thread group is a collection of threads and other
26846 thread groups. A thread group always has a string identifier, a type,
26847 and may have additional attributes specific to the type. A new
26848 command, @code{-list-thread-groups}, returns the list of top-level
26849 thread groups, which correspond to processes that @value{GDBN} is
26850 debugging at the moment. By passing an identifier of a thread group
26851 to the @code{-list-thread-groups} command, it is possible to obtain
26852 the members of specific thread group.
26854 To allow the user to easily discover processes, and other objects, he
26855 wishes to debug, a concept of @dfn{available thread group} is
26856 introduced. Available thread group is an thread group that
26857 @value{GDBN} is not debugging, but that can be attached to, using the
26858 @code{-target-attach} command. The list of available top-level thread
26859 groups can be obtained using @samp{-list-thread-groups --available}.
26860 In general, the content of a thread group may be only retrieved only
26861 after attaching to that thread group.
26863 Thread groups are related to inferiors (@pxref{Inferiors and
26864 Programs}). Each inferior corresponds to a thread group of a special
26865 type @samp{process}, and some additional operations are permitted on
26866 such thread groups.
26868 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26869 @node GDB/MI Command Syntax
26870 @section @sc{gdb/mi} Command Syntax
26873 * GDB/MI Input Syntax::
26874 * GDB/MI Output Syntax::
26877 @node GDB/MI Input Syntax
26878 @subsection @sc{gdb/mi} Input Syntax
26880 @cindex input syntax for @sc{gdb/mi}
26881 @cindex @sc{gdb/mi}, input syntax
26883 @item @var{command} @expansion{}
26884 @code{@var{cli-command} | @var{mi-command}}
26886 @item @var{cli-command} @expansion{}
26887 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26888 @var{cli-command} is any existing @value{GDBN} CLI command.
26890 @item @var{mi-command} @expansion{}
26891 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26892 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26894 @item @var{token} @expansion{}
26895 "any sequence of digits"
26897 @item @var{option} @expansion{}
26898 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26900 @item @var{parameter} @expansion{}
26901 @code{@var{non-blank-sequence} | @var{c-string}}
26903 @item @var{operation} @expansion{}
26904 @emph{any of the operations described in this chapter}
26906 @item @var{non-blank-sequence} @expansion{}
26907 @emph{anything, provided it doesn't contain special characters such as
26908 "-", @var{nl}, """ and of course " "}
26910 @item @var{c-string} @expansion{}
26911 @code{""" @var{seven-bit-iso-c-string-content} """}
26913 @item @var{nl} @expansion{}
26922 The CLI commands are still handled by the @sc{mi} interpreter; their
26923 output is described below.
26926 The @code{@var{token}}, when present, is passed back when the command
26930 Some @sc{mi} commands accept optional arguments as part of the parameter
26931 list. Each option is identified by a leading @samp{-} (dash) and may be
26932 followed by an optional argument parameter. Options occur first in the
26933 parameter list and can be delimited from normal parameters using
26934 @samp{--} (this is useful when some parameters begin with a dash).
26941 We want easy access to the existing CLI syntax (for debugging).
26944 We want it to be easy to spot a @sc{mi} operation.
26947 @node GDB/MI Output Syntax
26948 @subsection @sc{gdb/mi} Output Syntax
26950 @cindex output syntax of @sc{gdb/mi}
26951 @cindex @sc{gdb/mi}, output syntax
26952 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26953 followed, optionally, by a single result record. This result record
26954 is for the most recent command. The sequence of output records is
26955 terminated by @samp{(gdb)}.
26957 If an input command was prefixed with a @code{@var{token}} then the
26958 corresponding output for that command will also be prefixed by that same
26962 @item @var{output} @expansion{}
26963 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26965 @item @var{result-record} @expansion{}
26966 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26968 @item @var{out-of-band-record} @expansion{}
26969 @code{@var{async-record} | @var{stream-record}}
26971 @item @var{async-record} @expansion{}
26972 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26974 @item @var{exec-async-output} @expansion{}
26975 @code{[ @var{token} ] "*" @var{async-output nl}}
26977 @item @var{status-async-output} @expansion{}
26978 @code{[ @var{token} ] "+" @var{async-output nl}}
26980 @item @var{notify-async-output} @expansion{}
26981 @code{[ @var{token} ] "=" @var{async-output nl}}
26983 @item @var{async-output} @expansion{}
26984 @code{@var{async-class} ( "," @var{result} )*}
26986 @item @var{result-class} @expansion{}
26987 @code{"done" | "running" | "connected" | "error" | "exit"}
26989 @item @var{async-class} @expansion{}
26990 @code{"stopped" | @var{others}} (where @var{others} will be added
26991 depending on the needs---this is still in development).
26993 @item @var{result} @expansion{}
26994 @code{ @var{variable} "=" @var{value}}
26996 @item @var{variable} @expansion{}
26997 @code{ @var{string} }
26999 @item @var{value} @expansion{}
27000 @code{ @var{const} | @var{tuple} | @var{list} }
27002 @item @var{const} @expansion{}
27003 @code{@var{c-string}}
27005 @item @var{tuple} @expansion{}
27006 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27008 @item @var{list} @expansion{}
27009 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27010 @var{result} ( "," @var{result} )* "]" }
27012 @item @var{stream-record} @expansion{}
27013 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27015 @item @var{console-stream-output} @expansion{}
27016 @code{"~" @var{c-string nl}}
27018 @item @var{target-stream-output} @expansion{}
27019 @code{"@@" @var{c-string nl}}
27021 @item @var{log-stream-output} @expansion{}
27022 @code{"&" @var{c-string nl}}
27024 @item @var{nl} @expansion{}
27027 @item @var{token} @expansion{}
27028 @emph{any sequence of digits}.
27036 All output sequences end in a single line containing a period.
27039 The @code{@var{token}} is from the corresponding request. Note that
27040 for all async output, while the token is allowed by the grammar and
27041 may be output by future versions of @value{GDBN} for select async
27042 output messages, it is generally omitted. Frontends should treat
27043 all async output as reporting general changes in the state of the
27044 target and there should be no need to associate async output to any
27048 @cindex status output in @sc{gdb/mi}
27049 @var{status-async-output} contains on-going status information about the
27050 progress of a slow operation. It can be discarded. All status output is
27051 prefixed by @samp{+}.
27054 @cindex async output in @sc{gdb/mi}
27055 @var{exec-async-output} contains asynchronous state change on the target
27056 (stopped, started, disappeared). All async output is prefixed by
27060 @cindex notify output in @sc{gdb/mi}
27061 @var{notify-async-output} contains supplementary information that the
27062 client should handle (e.g., a new breakpoint information). All notify
27063 output is prefixed by @samp{=}.
27066 @cindex console output in @sc{gdb/mi}
27067 @var{console-stream-output} is output that should be displayed as is in the
27068 console. It is the textual response to a CLI command. All the console
27069 output is prefixed by @samp{~}.
27072 @cindex target output in @sc{gdb/mi}
27073 @var{target-stream-output} is the output produced by the target program.
27074 All the target output is prefixed by @samp{@@}.
27077 @cindex log output in @sc{gdb/mi}
27078 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27079 instance messages that should be displayed as part of an error log. All
27080 the log output is prefixed by @samp{&}.
27083 @cindex list output in @sc{gdb/mi}
27084 New @sc{gdb/mi} commands should only output @var{lists} containing
27090 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27091 details about the various output records.
27093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27094 @node GDB/MI Compatibility with CLI
27095 @section @sc{gdb/mi} Compatibility with CLI
27097 @cindex compatibility, @sc{gdb/mi} and CLI
27098 @cindex @sc{gdb/mi}, compatibility with CLI
27100 For the developers convenience CLI commands can be entered directly,
27101 but there may be some unexpected behaviour. For example, commands
27102 that query the user will behave as if the user replied yes, breakpoint
27103 command lists are not executed and some CLI commands, such as
27104 @code{if}, @code{when} and @code{define}, prompt for further input with
27105 @samp{>}, which is not valid MI output.
27107 This feature may be removed at some stage in the future and it is
27108 recommended that front ends use the @code{-interpreter-exec} command
27109 (@pxref{-interpreter-exec}).
27111 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27112 @node GDB/MI Development and Front Ends
27113 @section @sc{gdb/mi} Development and Front Ends
27114 @cindex @sc{gdb/mi} development
27116 The application which takes the MI output and presents the state of the
27117 program being debugged to the user is called a @dfn{front end}.
27119 Although @sc{gdb/mi} is still incomplete, it is currently being used
27120 by a variety of front ends to @value{GDBN}. This makes it difficult
27121 to introduce new functionality without breaking existing usage. This
27122 section tries to minimize the problems by describing how the protocol
27125 Some changes in MI need not break a carefully designed front end, and
27126 for these the MI version will remain unchanged. The following is a
27127 list of changes that may occur within one level, so front ends should
27128 parse MI output in a way that can handle them:
27132 New MI commands may be added.
27135 New fields may be added to the output of any MI command.
27138 The range of values for fields with specified values, e.g.,
27139 @code{in_scope} (@pxref{-var-update}) may be extended.
27141 @c The format of field's content e.g type prefix, may change so parse it
27142 @c at your own risk. Yes, in general?
27144 @c The order of fields may change? Shouldn't really matter but it might
27145 @c resolve inconsistencies.
27148 If the changes are likely to break front ends, the MI version level
27149 will be increased by one. This will allow the front end to parse the
27150 output according to the MI version. Apart from mi0, new versions of
27151 @value{GDBN} will not support old versions of MI and it will be the
27152 responsibility of the front end to work with the new one.
27154 @c Starting with mi3, add a new command -mi-version that prints the MI
27157 The best way to avoid unexpected changes in MI that might break your front
27158 end is to make your project known to @value{GDBN} developers and
27159 follow development on @email{gdb@@sourceware.org} and
27160 @email{gdb-patches@@sourceware.org}.
27161 @cindex mailing lists
27163 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27164 @node GDB/MI Output Records
27165 @section @sc{gdb/mi} Output Records
27168 * GDB/MI Result Records::
27169 * GDB/MI Stream Records::
27170 * GDB/MI Async Records::
27171 * GDB/MI Breakpoint Information::
27172 * GDB/MI Frame Information::
27173 * GDB/MI Thread Information::
27174 * GDB/MI Ada Exception Information::
27177 @node GDB/MI Result Records
27178 @subsection @sc{gdb/mi} Result Records
27180 @cindex result records in @sc{gdb/mi}
27181 @cindex @sc{gdb/mi}, result records
27182 In addition to a number of out-of-band notifications, the response to a
27183 @sc{gdb/mi} command includes one of the following result indications:
27187 @item "^done" [ "," @var{results} ]
27188 The synchronous operation was successful, @code{@var{results}} are the return
27193 This result record is equivalent to @samp{^done}. Historically, it
27194 was output instead of @samp{^done} if the command has resumed the
27195 target. This behaviour is maintained for backward compatibility, but
27196 all frontends should treat @samp{^done} and @samp{^running}
27197 identically and rely on the @samp{*running} output record to determine
27198 which threads are resumed.
27202 @value{GDBN} has connected to a remote target.
27204 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27206 The operation failed. The @code{msg=@var{c-string}} variable contains
27207 the corresponding error message.
27209 If present, the @code{code=@var{c-string}} variable provides an error
27210 code on which consumers can rely on to detect the corresponding
27211 error condition. At present, only one error code is defined:
27214 @item "undefined-command"
27215 Indicates that the command causing the error does not exist.
27220 @value{GDBN} has terminated.
27224 @node GDB/MI Stream Records
27225 @subsection @sc{gdb/mi} Stream Records
27227 @cindex @sc{gdb/mi}, stream records
27228 @cindex stream records in @sc{gdb/mi}
27229 @value{GDBN} internally maintains a number of output streams: the console, the
27230 target, and the log. The output intended for each of these streams is
27231 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27233 Each stream record begins with a unique @dfn{prefix character} which
27234 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27235 Syntax}). In addition to the prefix, each stream record contains a
27236 @code{@var{string-output}}. This is either raw text (with an implicit new
27237 line) or a quoted C string (which does not contain an implicit newline).
27240 @item "~" @var{string-output}
27241 The console output stream contains text that should be displayed in the
27242 CLI console window. It contains the textual responses to CLI commands.
27244 @item "@@" @var{string-output}
27245 The target output stream contains any textual output from the running
27246 target. This is only present when GDB's event loop is truly
27247 asynchronous, which is currently only the case for remote targets.
27249 @item "&" @var{string-output}
27250 The log stream contains debugging messages being produced by @value{GDBN}'s
27254 @node GDB/MI Async Records
27255 @subsection @sc{gdb/mi} Async Records
27257 @cindex async records in @sc{gdb/mi}
27258 @cindex @sc{gdb/mi}, async records
27259 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27260 additional changes that have occurred. Those changes can either be a
27261 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27262 target activity (e.g., target stopped).
27264 The following is the list of possible async records:
27268 @item *running,thread-id="@var{thread}"
27269 The target is now running. The @var{thread} field can be the global
27270 thread ID of the the thread that is now running, and it can be
27271 @samp{all} if all threads are running. The frontend should assume
27272 that no interaction with a running thread is possible after this
27273 notification is produced. The frontend should not assume that this
27274 notification is output only once for any command. @value{GDBN} may
27275 emit this notification several times, either for different threads,
27276 because it cannot resume all threads together, or even for a single
27277 thread, if the thread must be stepped though some code before letting
27280 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27281 The target has stopped. The @var{reason} field can have one of the
27285 @item breakpoint-hit
27286 A breakpoint was reached.
27287 @item watchpoint-trigger
27288 A watchpoint was triggered.
27289 @item read-watchpoint-trigger
27290 A read watchpoint was triggered.
27291 @item access-watchpoint-trigger
27292 An access watchpoint was triggered.
27293 @item function-finished
27294 An -exec-finish or similar CLI command was accomplished.
27295 @item location-reached
27296 An -exec-until or similar CLI command was accomplished.
27297 @item watchpoint-scope
27298 A watchpoint has gone out of scope.
27299 @item end-stepping-range
27300 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27301 similar CLI command was accomplished.
27302 @item exited-signalled
27303 The inferior exited because of a signal.
27305 The inferior exited.
27306 @item exited-normally
27307 The inferior exited normally.
27308 @item signal-received
27309 A signal was received by the inferior.
27311 The inferior has stopped due to a library being loaded or unloaded.
27312 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27313 set or when a @code{catch load} or @code{catch unload} catchpoint is
27314 in use (@pxref{Set Catchpoints}).
27316 The inferior has forked. This is reported when @code{catch fork}
27317 (@pxref{Set Catchpoints}) has been used.
27319 The inferior has vforked. This is reported in when @code{catch vfork}
27320 (@pxref{Set Catchpoints}) has been used.
27321 @item syscall-entry
27322 The inferior entered a system call. This is reported when @code{catch
27323 syscall} (@pxref{Set Catchpoints}) has been used.
27324 @item syscall-return
27325 The inferior returned from a system call. This is reported when
27326 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27328 The inferior called @code{exec}. This is reported when @code{catch exec}
27329 (@pxref{Set Catchpoints}) has been used.
27332 The @var{id} field identifies the global thread ID of the thread
27333 that directly caused the stop -- for example by hitting a breakpoint.
27334 Depending on whether all-stop
27335 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27336 stop all threads, or only the thread that directly triggered the stop.
27337 If all threads are stopped, the @var{stopped} field will have the
27338 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27339 field will be a list of thread identifiers. Presently, this list will
27340 always include a single thread, but frontend should be prepared to see
27341 several threads in the list. The @var{core} field reports the
27342 processor core on which the stop event has happened. This field may be absent
27343 if such information is not available.
27345 @item =thread-group-added,id="@var{id}"
27346 @itemx =thread-group-removed,id="@var{id}"
27347 A thread group was either added or removed. The @var{id} field
27348 contains the @value{GDBN} identifier of the thread group. When a thread
27349 group is added, it generally might not be associated with a running
27350 process. When a thread group is removed, its id becomes invalid and
27351 cannot be used in any way.
27353 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27354 A thread group became associated with a running program,
27355 either because the program was just started or the thread group
27356 was attached to a program. The @var{id} field contains the
27357 @value{GDBN} identifier of the thread group. The @var{pid} field
27358 contains process identifier, specific to the operating system.
27360 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27361 A thread group is no longer associated with a running program,
27362 either because the program has exited, or because it was detached
27363 from. The @var{id} field contains the @value{GDBN} identifier of the
27364 thread group. The @var{code} field is the exit code of the inferior; it exists
27365 only when the inferior exited with some code.
27367 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27368 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27369 A thread either was created, or has exited. The @var{id} field
27370 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27371 field identifies the thread group this thread belongs to.
27373 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27374 Informs that the selected thread or frame were changed. This notification
27375 is not emitted as result of the @code{-thread-select} or
27376 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27377 that is not documented to change the selected thread and frame actually
27378 changes them. In particular, invoking, directly or indirectly
27379 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27380 will generate this notification. Changing the thread or frame from another
27381 user interface (see @ref{Interpreters}) will also generate this notification.
27383 The @var{frame} field is only present if the newly selected thread is
27384 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27386 We suggest that in response to this notification, front ends
27387 highlight the selected thread and cause subsequent commands to apply to
27390 @item =library-loaded,...
27391 Reports that a new library file was loaded by the program. This
27392 notification has 5 fields---@var{id}, @var{target-name},
27393 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27394 opaque identifier of the library. For remote debugging case,
27395 @var{target-name} and @var{host-name} fields give the name of the
27396 library file on the target, and on the host respectively. For native
27397 debugging, both those fields have the same value. The
27398 @var{symbols-loaded} field is emitted only for backward compatibility
27399 and should not be relied on to convey any useful information. The
27400 @var{thread-group} field, if present, specifies the id of the thread
27401 group in whose context the library was loaded. If the field is
27402 absent, it means the library was loaded in the context of all present
27403 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27406 @item =library-unloaded,...
27407 Reports that a library was unloaded by the program. This notification
27408 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27409 the same meaning as for the @code{=library-loaded} notification.
27410 The @var{thread-group} field, if present, specifies the id of the
27411 thread group in whose context the library was unloaded. If the field is
27412 absent, it means the library was unloaded in the context of all present
27415 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27416 @itemx =traceframe-changed,end
27417 Reports that the trace frame was changed and its new number is
27418 @var{tfnum}. The number of the tracepoint associated with this trace
27419 frame is @var{tpnum}.
27421 @item =tsv-created,name=@var{name},initial=@var{initial}
27422 Reports that the new trace state variable @var{name} is created with
27423 initial value @var{initial}.
27425 @item =tsv-deleted,name=@var{name}
27426 @itemx =tsv-deleted
27427 Reports that the trace state variable @var{name} is deleted or all
27428 trace state variables are deleted.
27430 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27431 Reports that the trace state variable @var{name} is modified with
27432 the initial value @var{initial}. The current value @var{current} of
27433 trace state variable is optional and is reported if the current
27434 value of trace state variable is known.
27436 @item =breakpoint-created,bkpt=@{...@}
27437 @itemx =breakpoint-modified,bkpt=@{...@}
27438 @itemx =breakpoint-deleted,id=@var{number}
27439 Reports that a breakpoint was created, modified, or deleted,
27440 respectively. Only user-visible breakpoints are reported to the MI
27443 The @var{bkpt} argument is of the same form as returned by the various
27444 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27445 @var{number} is the ordinal number of the breakpoint.
27447 Note that if a breakpoint is emitted in the result record of a
27448 command, then it will not also be emitted in an async record.
27450 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27451 @itemx =record-stopped,thread-group="@var{id}"
27452 Execution log recording was either started or stopped on an
27453 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27454 group corresponding to the affected inferior.
27456 The @var{method} field indicates the method used to record execution. If the
27457 method in use supports multiple recording formats, @var{format} will be present
27458 and contain the currently used format. @xref{Process Record and Replay},
27459 for existing method and format values.
27461 @item =cmd-param-changed,param=@var{param},value=@var{value}
27462 Reports that a parameter of the command @code{set @var{param}} is
27463 changed to @var{value}. In the multi-word @code{set} command,
27464 the @var{param} is the whole parameter list to @code{set} command.
27465 For example, In command @code{set check type on}, @var{param}
27466 is @code{check type} and @var{value} is @code{on}.
27468 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27469 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27470 written in an inferior. The @var{id} is the identifier of the
27471 thread group corresponding to the affected inferior. The optional
27472 @code{type="code"} part is reported if the memory written to holds
27476 @node GDB/MI Breakpoint Information
27477 @subsection @sc{gdb/mi} Breakpoint Information
27479 When @value{GDBN} reports information about a breakpoint, a
27480 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27485 The breakpoint number. For a breakpoint that represents one location
27486 of a multi-location breakpoint, this will be a dotted pair, like
27490 The type of the breakpoint. For ordinary breakpoints this will be
27491 @samp{breakpoint}, but many values are possible.
27494 If the type of the breakpoint is @samp{catchpoint}, then this
27495 indicates the exact type of catchpoint.
27498 This is the breakpoint disposition---either @samp{del}, meaning that
27499 the breakpoint will be deleted at the next stop, or @samp{keep},
27500 meaning that the breakpoint will not be deleted.
27503 This indicates whether the breakpoint is enabled, in which case the
27504 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27505 Note that this is not the same as the field @code{enable}.
27508 The address of the breakpoint. This may be a hexidecimal number,
27509 giving the address; or the string @samp{<PENDING>}, for a pending
27510 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27511 multiple locations. This field will not be present if no address can
27512 be determined. For example, a watchpoint does not have an address.
27515 If known, the function in which the breakpoint appears.
27516 If not known, this field is not present.
27519 The name of the source file which contains this function, if known.
27520 If not known, this field is not present.
27523 The full file name of the source file which contains this function, if
27524 known. If not known, this field is not present.
27527 The line number at which this breakpoint appears, if known.
27528 If not known, this field is not present.
27531 If the source file is not known, this field may be provided. If
27532 provided, this holds the address of the breakpoint, possibly followed
27536 If this breakpoint is pending, this field is present and holds the
27537 text used to set the breakpoint, as entered by the user.
27540 Where this breakpoint's condition is evaluated, either @samp{host} or
27544 If this is a thread-specific breakpoint, then this identifies the
27545 thread in which the breakpoint can trigger.
27548 If this breakpoint is restricted to a particular Ada task, then this
27549 field will hold the task identifier.
27552 If the breakpoint is conditional, this is the condition expression.
27555 The ignore count of the breakpoint.
27558 The enable count of the breakpoint.
27560 @item traceframe-usage
27563 @item static-tracepoint-marker-string-id
27564 For a static tracepoint, the name of the static tracepoint marker.
27567 For a masked watchpoint, this is the mask.
27570 A tracepoint's pass count.
27572 @item original-location
27573 The location of the breakpoint as originally specified by the user.
27574 This field is optional.
27577 The number of times the breakpoint has been hit.
27580 This field is only given for tracepoints. This is either @samp{y},
27581 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27585 Some extra data, the exact contents of which are type-dependent.
27589 For example, here is what the output of @code{-break-insert}
27590 (@pxref{GDB/MI Breakpoint Commands}) might be:
27593 -> -break-insert main
27594 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27595 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27596 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27601 @node GDB/MI Frame Information
27602 @subsection @sc{gdb/mi} Frame Information
27604 Response from many MI commands includes an information about stack
27605 frame. This information is a tuple that may have the following
27610 The level of the stack frame. The innermost frame has the level of
27611 zero. This field is always present.
27614 The name of the function corresponding to the frame. This field may
27615 be absent if @value{GDBN} is unable to determine the function name.
27618 The code address for the frame. This field is always present.
27621 The name of the source files that correspond to the frame's code
27622 address. This field may be absent.
27625 The source line corresponding to the frames' code address. This field
27629 The name of the binary file (either executable or shared library) the
27630 corresponds to the frame's code address. This field may be absent.
27634 @node GDB/MI Thread Information
27635 @subsection @sc{gdb/mi} Thread Information
27637 Whenever @value{GDBN} has to report an information about a thread, it
27638 uses a tuple with the following fields. The fields are always present unless
27643 The global numeric id assigned to the thread by @value{GDBN}.
27646 The target-specific string identifying the thread.
27649 Additional information about the thread provided by the target.
27650 It is supposed to be human-readable and not interpreted by the
27651 frontend. This field is optional.
27654 The name of the thread. If the user specified a name using the
27655 @code{thread name} command, then this name is given. Otherwise, if
27656 @value{GDBN} can extract the thread name from the target, then that
27657 name is given. If @value{GDBN} cannot find the thread name, then this
27661 The execution state of the thread, either @samp{stopped} or @samp{running},
27662 depending on whether the thread is presently running.
27665 The stack frame currently executing in the thread. This field is only present
27666 if the thread is stopped. Its format is documented in
27667 @ref{GDB/MI Frame Information}.
27670 The value of this field is an integer number of the processor core the
27671 thread was last seen on. This field is optional.
27674 @node GDB/MI Ada Exception Information
27675 @subsection @sc{gdb/mi} Ada Exception Information
27677 Whenever a @code{*stopped} record is emitted because the program
27678 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27679 @value{GDBN} provides the name of the exception that was raised via
27680 the @code{exception-name} field. Also, for exceptions that were raised
27681 with an exception message, @value{GDBN} provides that message via
27682 the @code{exception-message} field.
27684 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27685 @node GDB/MI Simple Examples
27686 @section Simple Examples of @sc{gdb/mi} Interaction
27687 @cindex @sc{gdb/mi}, simple examples
27689 This subsection presents several simple examples of interaction using
27690 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27691 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27692 the output received from @sc{gdb/mi}.
27694 Note the line breaks shown in the examples are here only for
27695 readability, they don't appear in the real output.
27697 @subheading Setting a Breakpoint
27699 Setting a breakpoint generates synchronous output which contains detailed
27700 information of the breakpoint.
27703 -> -break-insert main
27704 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27705 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27706 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27711 @subheading Program Execution
27713 Program execution generates asynchronous records and MI gives the
27714 reason that execution stopped.
27720 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27721 frame=@{addr="0x08048564",func="main",
27722 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27723 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27728 <- *stopped,reason="exited-normally"
27732 @subheading Quitting @value{GDBN}
27734 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27742 Please note that @samp{^exit} is printed immediately, but it might
27743 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27744 performs necessary cleanups, including killing programs being debugged
27745 or disconnecting from debug hardware, so the frontend should wait till
27746 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27747 fails to exit in reasonable time.
27749 @subheading A Bad Command
27751 Here's what happens if you pass a non-existent command:
27755 <- ^error,msg="Undefined MI command: rubbish"
27760 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27761 @node GDB/MI Command Description Format
27762 @section @sc{gdb/mi} Command Description Format
27764 The remaining sections describe blocks of commands. Each block of
27765 commands is laid out in a fashion similar to this section.
27767 @subheading Motivation
27769 The motivation for this collection of commands.
27771 @subheading Introduction
27773 A brief introduction to this collection of commands as a whole.
27775 @subheading Commands
27777 For each command in the block, the following is described:
27779 @subsubheading Synopsis
27782 -command @var{args}@dots{}
27785 @subsubheading Result
27787 @subsubheading @value{GDBN} Command
27789 The corresponding @value{GDBN} CLI command(s), if any.
27791 @subsubheading Example
27793 Example(s) formatted for readability. Some of the described commands have
27794 not been implemented yet and these are labeled N.A.@: (not available).
27797 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27798 @node GDB/MI Breakpoint Commands
27799 @section @sc{gdb/mi} Breakpoint Commands
27801 @cindex breakpoint commands for @sc{gdb/mi}
27802 @cindex @sc{gdb/mi}, breakpoint commands
27803 This section documents @sc{gdb/mi} commands for manipulating
27806 @subheading The @code{-break-after} Command
27807 @findex -break-after
27809 @subsubheading Synopsis
27812 -break-after @var{number} @var{count}
27815 The breakpoint number @var{number} is not in effect until it has been
27816 hit @var{count} times. To see how this is reflected in the output of
27817 the @samp{-break-list} command, see the description of the
27818 @samp{-break-list} command below.
27820 @subsubheading @value{GDBN} Command
27822 The corresponding @value{GDBN} command is @samp{ignore}.
27824 @subsubheading Example
27829 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27830 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27831 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27839 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27840 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27841 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27842 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27843 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27844 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27845 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27846 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27847 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27848 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27853 @subheading The @code{-break-catch} Command
27854 @findex -break-catch
27857 @subheading The @code{-break-commands} Command
27858 @findex -break-commands
27860 @subsubheading Synopsis
27863 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27866 Specifies the CLI commands that should be executed when breakpoint
27867 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27868 are the commands. If no command is specified, any previously-set
27869 commands are cleared. @xref{Break Commands}. Typical use of this
27870 functionality is tracing a program, that is, printing of values of
27871 some variables whenever breakpoint is hit and then continuing.
27873 @subsubheading @value{GDBN} Command
27875 The corresponding @value{GDBN} command is @samp{commands}.
27877 @subsubheading Example
27882 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27883 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27884 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27887 -break-commands 1 "print v" "continue"
27892 @subheading The @code{-break-condition} Command
27893 @findex -break-condition
27895 @subsubheading Synopsis
27898 -break-condition @var{number} @var{expr}
27901 Breakpoint @var{number} will stop the program only if the condition in
27902 @var{expr} is true. The condition becomes part of the
27903 @samp{-break-list} output (see the description of the @samp{-break-list}
27906 @subsubheading @value{GDBN} Command
27908 The corresponding @value{GDBN} command is @samp{condition}.
27910 @subsubheading Example
27914 -break-condition 1 1
27918 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27919 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27920 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27921 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27922 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27923 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27924 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27925 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27926 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27927 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27931 @subheading The @code{-break-delete} Command
27932 @findex -break-delete
27934 @subsubheading Synopsis
27937 -break-delete ( @var{breakpoint} )+
27940 Delete the breakpoint(s) whose number(s) are specified in the argument
27941 list. This is obviously reflected in the breakpoint list.
27943 @subsubheading @value{GDBN} Command
27945 The corresponding @value{GDBN} command is @samp{delete}.
27947 @subsubheading Example
27955 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27956 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27957 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27958 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27959 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27960 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27961 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27966 @subheading The @code{-break-disable} Command
27967 @findex -break-disable
27969 @subsubheading Synopsis
27972 -break-disable ( @var{breakpoint} )+
27975 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27976 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27978 @subsubheading @value{GDBN} Command
27980 The corresponding @value{GDBN} command is @samp{disable}.
27982 @subsubheading Example
27990 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27991 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27992 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27993 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27994 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27995 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27996 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27997 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27998 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27999 line="5",thread-groups=["i1"],times="0"@}]@}
28003 @subheading The @code{-break-enable} Command
28004 @findex -break-enable
28006 @subsubheading Synopsis
28009 -break-enable ( @var{breakpoint} )+
28012 Enable (previously disabled) @var{breakpoint}(s).
28014 @subsubheading @value{GDBN} Command
28016 The corresponding @value{GDBN} command is @samp{enable}.
28018 @subsubheading Example
28026 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28027 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28028 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28029 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28030 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28031 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28032 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28033 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28034 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28035 line="5",thread-groups=["i1"],times="0"@}]@}
28039 @subheading The @code{-break-info} Command
28040 @findex -break-info
28042 @subsubheading Synopsis
28045 -break-info @var{breakpoint}
28049 Get information about a single breakpoint.
28051 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28052 Information}, for details on the format of each breakpoint in the
28055 @subsubheading @value{GDBN} Command
28057 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28059 @subsubheading Example
28062 @subheading The @code{-break-insert} Command
28063 @findex -break-insert
28064 @anchor{-break-insert}
28066 @subsubheading Synopsis
28069 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28070 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28071 [ -p @var{thread-id} ] [ @var{location} ]
28075 If specified, @var{location}, can be one of:
28078 @item linespec location
28079 A linespec location. @xref{Linespec Locations}.
28081 @item explicit location
28082 An explicit location. @sc{gdb/mi} explicit locations are
28083 analogous to the CLI's explicit locations using the option names
28084 listed below. @xref{Explicit Locations}.
28087 @item --source @var{filename}
28088 The source file name of the location. This option requires the use
28089 of either @samp{--function} or @samp{--line}.
28091 @item --function @var{function}
28092 The name of a function or method.
28094 @item --label @var{label}
28095 The name of a label.
28097 @item --line @var{lineoffset}
28098 An absolute or relative line offset from the start of the location.
28101 @item address location
28102 An address location, *@var{address}. @xref{Address Locations}.
28106 The possible optional parameters of this command are:
28110 Insert a temporary breakpoint.
28112 Insert a hardware breakpoint.
28114 If @var{location} cannot be parsed (for example if it
28115 refers to unknown files or functions), create a pending
28116 breakpoint. Without this flag, @value{GDBN} will report
28117 an error, and won't create a breakpoint, if @var{location}
28120 Create a disabled breakpoint.
28122 Create a tracepoint. @xref{Tracepoints}. When this parameter
28123 is used together with @samp{-h}, a fast tracepoint is created.
28124 @item -c @var{condition}
28125 Make the breakpoint conditional on @var{condition}.
28126 @item -i @var{ignore-count}
28127 Initialize the @var{ignore-count}.
28128 @item -p @var{thread-id}
28129 Restrict the breakpoint to the thread with the specified global
28133 @subsubheading Result
28135 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28136 resulting breakpoint.
28138 Note: this format is open to change.
28139 @c An out-of-band breakpoint instead of part of the result?
28141 @subsubheading @value{GDBN} Command
28143 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28144 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28146 @subsubheading Example
28151 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28152 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28155 -break-insert -t foo
28156 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28157 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28161 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28162 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28163 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28164 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28165 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28166 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28167 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28168 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28169 addr="0x0001072c", func="main",file="recursive2.c",
28170 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28172 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28173 addr="0x00010774",func="foo",file="recursive2.c",
28174 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28177 @c -break-insert -r foo.*
28178 @c ~int foo(int, int);
28179 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28180 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28185 @subheading The @code{-dprintf-insert} Command
28186 @findex -dprintf-insert
28188 @subsubheading Synopsis
28191 -dprintf-insert [ -t ] [ -f ] [ -d ]
28192 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28193 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28198 If supplied, @var{location} may be specified the same way as for
28199 the @code{-break-insert} command. @xref{-break-insert}.
28201 The possible optional parameters of this command are:
28205 Insert a temporary breakpoint.
28207 If @var{location} cannot be parsed (for example, if it
28208 refers to unknown files or functions), create a pending
28209 breakpoint. Without this flag, @value{GDBN} will report
28210 an error, and won't create a breakpoint, if @var{location}
28213 Create a disabled breakpoint.
28214 @item -c @var{condition}
28215 Make the breakpoint conditional on @var{condition}.
28216 @item -i @var{ignore-count}
28217 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28218 to @var{ignore-count}.
28219 @item -p @var{thread-id}
28220 Restrict the breakpoint to the thread with the specified global
28224 @subsubheading Result
28226 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28227 resulting breakpoint.
28229 @c An out-of-band breakpoint instead of part of the result?
28231 @subsubheading @value{GDBN} Command
28233 The corresponding @value{GDBN} command is @samp{dprintf}.
28235 @subsubheading Example
28239 4-dprintf-insert foo "At foo entry\n"
28240 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28241 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28242 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28243 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28244 original-location="foo"@}
28246 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28247 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28248 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28249 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28250 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28251 original-location="mi-dprintf.c:26"@}
28255 @subheading The @code{-break-list} Command
28256 @findex -break-list
28258 @subsubheading Synopsis
28264 Displays the list of inserted breakpoints, showing the following fields:
28268 number of the breakpoint
28270 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28272 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28275 is the breakpoint enabled or no: @samp{y} or @samp{n}
28277 memory location at which the breakpoint is set
28279 logical location of the breakpoint, expressed by function name, file
28281 @item Thread-groups
28282 list of thread groups to which this breakpoint applies
28284 number of times the breakpoint has been hit
28287 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28288 @code{body} field is an empty list.
28290 @subsubheading @value{GDBN} Command
28292 The corresponding @value{GDBN} command is @samp{info break}.
28294 @subsubheading Example
28299 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28300 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28301 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28302 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28303 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28304 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28305 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28306 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28307 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28309 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28310 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28311 line="13",thread-groups=["i1"],times="0"@}]@}
28315 Here's an example of the result when there are no breakpoints:
28320 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28321 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28322 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28323 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28324 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28325 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28326 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28331 @subheading The @code{-break-passcount} Command
28332 @findex -break-passcount
28334 @subsubheading Synopsis
28337 -break-passcount @var{tracepoint-number} @var{passcount}
28340 Set the passcount for tracepoint @var{tracepoint-number} to
28341 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28342 is not a tracepoint, error is emitted. This corresponds to CLI
28343 command @samp{passcount}.
28345 @subheading The @code{-break-watch} Command
28346 @findex -break-watch
28348 @subsubheading Synopsis
28351 -break-watch [ -a | -r ]
28354 Create a watchpoint. With the @samp{-a} option it will create an
28355 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28356 read from or on a write to the memory location. With the @samp{-r}
28357 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28358 trigger only when the memory location is accessed for reading. Without
28359 either of the options, the watchpoint created is a regular watchpoint,
28360 i.e., it will trigger when the memory location is accessed for writing.
28361 @xref{Set Watchpoints, , Setting Watchpoints}.
28363 Note that @samp{-break-list} will report a single list of watchpoints and
28364 breakpoints inserted.
28366 @subsubheading @value{GDBN} Command
28368 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28371 @subsubheading Example
28373 Setting a watchpoint on a variable in the @code{main} function:
28378 ^done,wpt=@{number="2",exp="x"@}
28383 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28384 value=@{old="-268439212",new="55"@},
28385 frame=@{func="main",args=[],file="recursive2.c",
28386 fullname="/home/foo/bar/recursive2.c",line="5"@}
28390 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28391 the program execution twice: first for the variable changing value, then
28392 for the watchpoint going out of scope.
28397 ^done,wpt=@{number="5",exp="C"@}
28402 *stopped,reason="watchpoint-trigger",
28403 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28404 frame=@{func="callee4",args=[],
28405 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28406 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28411 *stopped,reason="watchpoint-scope",wpnum="5",
28412 frame=@{func="callee3",args=[@{name="strarg",
28413 value="0x11940 \"A string argument.\""@}],
28414 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28415 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28419 Listing breakpoints and watchpoints, at different points in the program
28420 execution. Note that once the watchpoint goes out of scope, it is
28426 ^done,wpt=@{number="2",exp="C"@}
28429 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28430 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28431 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28432 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28433 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28434 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28435 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28436 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28437 addr="0x00010734",func="callee4",
28438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28439 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28441 bkpt=@{number="2",type="watchpoint",disp="keep",
28442 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28447 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28448 value=@{old="-276895068",new="3"@},
28449 frame=@{func="callee4",args=[],
28450 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28451 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28454 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28455 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28456 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28457 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28458 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28459 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28460 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28461 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28462 addr="0x00010734",func="callee4",
28463 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28464 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28466 bkpt=@{number="2",type="watchpoint",disp="keep",
28467 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28471 ^done,reason="watchpoint-scope",wpnum="2",
28472 frame=@{func="callee3",args=[@{name="strarg",
28473 value="0x11940 \"A string argument.\""@}],
28474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28475 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28478 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28479 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28480 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28481 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28482 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28483 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28484 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28485 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28486 addr="0x00010734",func="callee4",
28487 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28488 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28489 thread-groups=["i1"],times="1"@}]@}
28494 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28495 @node GDB/MI Catchpoint Commands
28496 @section @sc{gdb/mi} Catchpoint Commands
28498 This section documents @sc{gdb/mi} commands for manipulating
28502 * Shared Library GDB/MI Catchpoint Commands::
28503 * Ada Exception GDB/MI Catchpoint Commands::
28506 @node Shared Library GDB/MI Catchpoint Commands
28507 @subsection Shared Library @sc{gdb/mi} Catchpoints
28509 @subheading The @code{-catch-load} Command
28510 @findex -catch-load
28512 @subsubheading Synopsis
28515 -catch-load [ -t ] [ -d ] @var{regexp}
28518 Add a catchpoint for library load events. If the @samp{-t} option is used,
28519 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28520 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28521 in a disabled state. The @samp{regexp} argument is a regular
28522 expression used to match the name of the loaded library.
28525 @subsubheading @value{GDBN} Command
28527 The corresponding @value{GDBN} command is @samp{catch load}.
28529 @subsubheading Example
28532 -catch-load -t foo.so
28533 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28534 what="load of library matching foo.so",catch-type="load",times="0"@}
28539 @subheading The @code{-catch-unload} Command
28540 @findex -catch-unload
28542 @subsubheading Synopsis
28545 -catch-unload [ -t ] [ -d ] @var{regexp}
28548 Add a catchpoint for library unload events. If the @samp{-t} option is
28549 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28550 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28551 created in a disabled state. The @samp{regexp} argument is a regular
28552 expression used to match the name of the unloaded library.
28554 @subsubheading @value{GDBN} Command
28556 The corresponding @value{GDBN} command is @samp{catch unload}.
28558 @subsubheading Example
28561 -catch-unload -d bar.so
28562 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28563 what="load of library matching bar.so",catch-type="unload",times="0"@}
28567 @node Ada Exception GDB/MI Catchpoint Commands
28568 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28570 The following @sc{gdb/mi} commands can be used to create catchpoints
28571 that stop the execution when Ada exceptions are being raised.
28573 @subheading The @code{-catch-assert} Command
28574 @findex -catch-assert
28576 @subsubheading Synopsis
28579 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28582 Add a catchpoint for failed Ada assertions.
28584 The possible optional parameters for this command are:
28587 @item -c @var{condition}
28588 Make the catchpoint conditional on @var{condition}.
28590 Create a disabled catchpoint.
28592 Create a temporary catchpoint.
28595 @subsubheading @value{GDBN} Command
28597 The corresponding @value{GDBN} command is @samp{catch assert}.
28599 @subsubheading Example
28603 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28604 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28605 thread-groups=["i1"],times="0",
28606 original-location="__gnat_debug_raise_assert_failure"@}
28610 @subheading The @code{-catch-exception} Command
28611 @findex -catch-exception
28613 @subsubheading Synopsis
28616 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28620 Add a catchpoint stopping when Ada exceptions are raised.
28621 By default, the command stops the program when any Ada exception
28622 gets raised. But it is also possible, by using some of the
28623 optional parameters described below, to create more selective
28626 The possible optional parameters for this command are:
28629 @item -c @var{condition}
28630 Make the catchpoint conditional on @var{condition}.
28632 Create a disabled catchpoint.
28633 @item -e @var{exception-name}
28634 Only stop when @var{exception-name} is raised. This option cannot
28635 be used combined with @samp{-u}.
28637 Create a temporary catchpoint.
28639 Stop only when an unhandled exception gets raised. This option
28640 cannot be used combined with @samp{-e}.
28643 @subsubheading @value{GDBN} Command
28645 The corresponding @value{GDBN} commands are @samp{catch exception}
28646 and @samp{catch exception unhandled}.
28648 @subsubheading Example
28651 -catch-exception -e Program_Error
28652 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28653 enabled="y",addr="0x0000000000404874",
28654 what="`Program_Error' Ada exception", thread-groups=["i1"],
28655 times="0",original-location="__gnat_debug_raise_exception"@}
28659 @subheading The @code{-catch-handlers} Command
28660 @findex -catch-handlers
28662 @subsubheading Synopsis
28665 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28669 Add a catchpoint stopping when Ada exceptions are handled.
28670 By default, the command stops the program when any Ada exception
28671 gets handled. But it is also possible, by using some of the
28672 optional parameters described below, to create more selective
28675 The possible optional parameters for this command are:
28678 @item -c @var{condition}
28679 Make the catchpoint conditional on @var{condition}.
28681 Create a disabled catchpoint.
28682 @item -e @var{exception-name}
28683 Only stop when @var{exception-name} is handled.
28685 Create a temporary catchpoint.
28688 @subsubheading @value{GDBN} Command
28690 The corresponding @value{GDBN} command is @samp{catch handlers}.
28692 @subsubheading Example
28695 -catch-handlers -e Constraint_Error
28696 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28697 enabled="y",addr="0x0000000000402f68",
28698 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
28699 times="0",original-location="__gnat_begin_handler"@}
28703 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28704 @node GDB/MI Program Context
28705 @section @sc{gdb/mi} Program Context
28707 @subheading The @code{-exec-arguments} Command
28708 @findex -exec-arguments
28711 @subsubheading Synopsis
28714 -exec-arguments @var{args}
28717 Set the inferior program arguments, to be used in the next
28720 @subsubheading @value{GDBN} Command
28722 The corresponding @value{GDBN} command is @samp{set args}.
28724 @subsubheading Example
28728 -exec-arguments -v word
28735 @subheading The @code{-exec-show-arguments} Command
28736 @findex -exec-show-arguments
28738 @subsubheading Synopsis
28741 -exec-show-arguments
28744 Print the arguments of the program.
28746 @subsubheading @value{GDBN} Command
28748 The corresponding @value{GDBN} command is @samp{show args}.
28750 @subsubheading Example
28755 @subheading The @code{-environment-cd} Command
28756 @findex -environment-cd
28758 @subsubheading Synopsis
28761 -environment-cd @var{pathdir}
28764 Set @value{GDBN}'s working directory.
28766 @subsubheading @value{GDBN} Command
28768 The corresponding @value{GDBN} command is @samp{cd}.
28770 @subsubheading Example
28774 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28780 @subheading The @code{-environment-directory} Command
28781 @findex -environment-directory
28783 @subsubheading Synopsis
28786 -environment-directory [ -r ] [ @var{pathdir} ]+
28789 Add directories @var{pathdir} to beginning of search path for source files.
28790 If the @samp{-r} option is used, the search path is reset to the default
28791 search path. If directories @var{pathdir} are supplied in addition to the
28792 @samp{-r} option, the search path is first reset and then addition
28794 Multiple directories may be specified, separated by blanks. Specifying
28795 multiple directories in a single command
28796 results in the directories added to the beginning of the
28797 search path in the same order they were presented in the command.
28798 If blanks are needed as
28799 part of a directory name, double-quotes should be used around
28800 the name. In the command output, the path will show up separated
28801 by the system directory-separator character. The directory-separator
28802 character must not be used
28803 in any directory name.
28804 If no directories are specified, the current search path is displayed.
28806 @subsubheading @value{GDBN} Command
28808 The corresponding @value{GDBN} command is @samp{dir}.
28810 @subsubheading Example
28814 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28815 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28817 -environment-directory ""
28818 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28820 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28821 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28823 -environment-directory -r
28824 ^done,source-path="$cdir:$cwd"
28829 @subheading The @code{-environment-path} Command
28830 @findex -environment-path
28832 @subsubheading Synopsis
28835 -environment-path [ -r ] [ @var{pathdir} ]+
28838 Add directories @var{pathdir} to beginning of search path for object files.
28839 If the @samp{-r} option is used, the search path is reset to the original
28840 search path that existed at gdb start-up. If directories @var{pathdir} are
28841 supplied in addition to the
28842 @samp{-r} option, the search path is first reset and then addition
28844 Multiple directories may be specified, separated by blanks. Specifying
28845 multiple directories in a single command
28846 results in the directories added to the beginning of the
28847 search path in the same order they were presented in the command.
28848 If blanks are needed as
28849 part of a directory name, double-quotes should be used around
28850 the name. In the command output, the path will show up separated
28851 by the system directory-separator character. The directory-separator
28852 character must not be used
28853 in any directory name.
28854 If no directories are specified, the current path is displayed.
28857 @subsubheading @value{GDBN} Command
28859 The corresponding @value{GDBN} command is @samp{path}.
28861 @subsubheading Example
28866 ^done,path="/usr/bin"
28868 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28869 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28871 -environment-path -r /usr/local/bin
28872 ^done,path="/usr/local/bin:/usr/bin"
28877 @subheading The @code{-environment-pwd} Command
28878 @findex -environment-pwd
28880 @subsubheading Synopsis
28886 Show the current working directory.
28888 @subsubheading @value{GDBN} Command
28890 The corresponding @value{GDBN} command is @samp{pwd}.
28892 @subsubheading Example
28897 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28901 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28902 @node GDB/MI Thread Commands
28903 @section @sc{gdb/mi} Thread Commands
28906 @subheading The @code{-thread-info} Command
28907 @findex -thread-info
28909 @subsubheading Synopsis
28912 -thread-info [ @var{thread-id} ]
28915 Reports information about either a specific thread, if the
28916 @var{thread-id} parameter is present, or about all threads.
28917 @var{thread-id} is the thread's global thread ID. When printing
28918 information about all threads, also reports the global ID of the
28921 @subsubheading @value{GDBN} Command
28923 The @samp{info thread} command prints the same information
28926 @subsubheading Result
28928 The result contains the following attributes:
28932 A list of threads. The format of the elements of the list is described in
28933 @ref{GDB/MI Thread Information}.
28935 @item current-thread-id
28936 The global id of the currently selected thread. This field is omitted if there
28937 is no selected thread (for example, when the selected inferior is not running,
28938 and therefore has no threads) or if a @var{thread-id} argument was passed to
28943 @subsubheading Example
28948 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28949 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28950 args=[]@},state="running"@},
28951 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28952 frame=@{level="0",addr="0x0804891f",func="foo",
28953 args=[@{name="i",value="10"@}],
28954 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28955 state="running"@}],
28956 current-thread-id="1"
28960 @subheading The @code{-thread-list-ids} Command
28961 @findex -thread-list-ids
28963 @subsubheading Synopsis
28969 Produces a list of the currently known global @value{GDBN} thread ids.
28970 At the end of the list it also prints the total number of such
28973 This command is retained for historical reasons, the
28974 @code{-thread-info} command should be used instead.
28976 @subsubheading @value{GDBN} Command
28978 Part of @samp{info threads} supplies the same information.
28980 @subsubheading Example
28985 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28986 current-thread-id="1",number-of-threads="3"
28991 @subheading The @code{-thread-select} Command
28992 @findex -thread-select
28994 @subsubheading Synopsis
28997 -thread-select @var{thread-id}
29000 Make thread with global thread number @var{thread-id} the current
29001 thread. It prints the number of the new current thread, and the
29002 topmost frame for that thread.
29004 This command is deprecated in favor of explicitly using the
29005 @samp{--thread} option to each command.
29007 @subsubheading @value{GDBN} Command
29009 The corresponding @value{GDBN} command is @samp{thread}.
29011 @subsubheading Example
29018 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29019 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29023 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29024 number-of-threads="3"
29027 ^done,new-thread-id="3",
29028 frame=@{level="0",func="vprintf",
29029 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29030 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29035 @node GDB/MI Ada Tasking Commands
29036 @section @sc{gdb/mi} Ada Tasking Commands
29038 @subheading The @code{-ada-task-info} Command
29039 @findex -ada-task-info
29041 @subsubheading Synopsis
29044 -ada-task-info [ @var{task-id} ]
29047 Reports information about either a specific Ada task, if the
29048 @var{task-id} parameter is present, or about all Ada tasks.
29050 @subsubheading @value{GDBN} Command
29052 The @samp{info tasks} command prints the same information
29053 about all Ada tasks (@pxref{Ada Tasks}).
29055 @subsubheading Result
29057 The result is a table of Ada tasks. The following columns are
29058 defined for each Ada task:
29062 This field exists only for the current thread. It has the value @samp{*}.
29065 The identifier that @value{GDBN} uses to refer to the Ada task.
29068 The identifier that the target uses to refer to the Ada task.
29071 The global thread identifier of the thread corresponding to the Ada
29074 This field should always exist, as Ada tasks are always implemented
29075 on top of a thread. But if @value{GDBN} cannot find this corresponding
29076 thread for any reason, the field is omitted.
29079 This field exists only when the task was created by another task.
29080 In this case, it provides the ID of the parent task.
29083 The base priority of the task.
29086 The current state of the task. For a detailed description of the
29087 possible states, see @ref{Ada Tasks}.
29090 The name of the task.
29094 @subsubheading Example
29098 ^done,tasks=@{nr_rows="3",nr_cols="8",
29099 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29100 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29101 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29102 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29103 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29104 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29105 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29106 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29107 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29108 state="Child Termination Wait",name="main_task"@}]@}
29112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29113 @node GDB/MI Program Execution
29114 @section @sc{gdb/mi} Program Execution
29116 These are the asynchronous commands which generate the out-of-band
29117 record @samp{*stopped}. Currently @value{GDBN} only really executes
29118 asynchronously with remote targets and this interaction is mimicked in
29121 @subheading The @code{-exec-continue} Command
29122 @findex -exec-continue
29124 @subsubheading Synopsis
29127 -exec-continue [--reverse] [--all|--thread-group N]
29130 Resumes the execution of the inferior program, which will continue
29131 to execute until it reaches a debugger stop event. If the
29132 @samp{--reverse} option is specified, execution resumes in reverse until
29133 it reaches a stop event. Stop events may include
29136 breakpoints or watchpoints
29138 signals or exceptions
29140 the end of the process (or its beginning under @samp{--reverse})
29142 the end or beginning of a replay log if one is being used.
29144 In all-stop mode (@pxref{All-Stop
29145 Mode}), may resume only one thread, or all threads, depending on the
29146 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29147 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29148 ignored in all-stop mode. If the @samp{--thread-group} options is
29149 specified, then all threads in that thread group are resumed.
29151 @subsubheading @value{GDBN} Command
29153 The corresponding @value{GDBN} corresponding is @samp{continue}.
29155 @subsubheading Example
29162 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29163 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29169 @subheading The @code{-exec-finish} Command
29170 @findex -exec-finish
29172 @subsubheading Synopsis
29175 -exec-finish [--reverse]
29178 Resumes the execution of the inferior program until the current
29179 function is exited. Displays the results returned by the function.
29180 If the @samp{--reverse} option is specified, resumes the reverse
29181 execution of the inferior program until the point where current
29182 function was called.
29184 @subsubheading @value{GDBN} Command
29186 The corresponding @value{GDBN} command is @samp{finish}.
29188 @subsubheading Example
29190 Function returning @code{void}.
29197 *stopped,reason="function-finished",frame=@{func="main",args=[],
29198 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29202 Function returning other than @code{void}. The name of the internal
29203 @value{GDBN} variable storing the result is printed, together with the
29210 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29211 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29212 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29213 gdb-result-var="$1",return-value="0"
29218 @subheading The @code{-exec-interrupt} Command
29219 @findex -exec-interrupt
29221 @subsubheading Synopsis
29224 -exec-interrupt [--all|--thread-group N]
29227 Interrupts the background execution of the target. Note how the token
29228 associated with the stop message is the one for the execution command
29229 that has been interrupted. The token for the interrupt itself only
29230 appears in the @samp{^done} output. If the user is trying to
29231 interrupt a non-running program, an error message will be printed.
29233 Note that when asynchronous execution is enabled, this command is
29234 asynchronous just like other execution commands. That is, first the
29235 @samp{^done} response will be printed, and the target stop will be
29236 reported after that using the @samp{*stopped} notification.
29238 In non-stop mode, only the context thread is interrupted by default.
29239 All threads (in all inferiors) will be interrupted if the
29240 @samp{--all} option is specified. If the @samp{--thread-group}
29241 option is specified, all threads in that group will be interrupted.
29243 @subsubheading @value{GDBN} Command
29245 The corresponding @value{GDBN} command is @samp{interrupt}.
29247 @subsubheading Example
29258 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29259 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29260 fullname="/home/foo/bar/try.c",line="13"@}
29265 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29269 @subheading The @code{-exec-jump} Command
29272 @subsubheading Synopsis
29275 -exec-jump @var{location}
29278 Resumes execution of the inferior program at the location specified by
29279 parameter. @xref{Specify Location}, for a description of the
29280 different forms of @var{location}.
29282 @subsubheading @value{GDBN} Command
29284 The corresponding @value{GDBN} command is @samp{jump}.
29286 @subsubheading Example
29289 -exec-jump foo.c:10
29290 *running,thread-id="all"
29295 @subheading The @code{-exec-next} Command
29298 @subsubheading Synopsis
29301 -exec-next [--reverse]
29304 Resumes execution of the inferior program, stopping when the beginning
29305 of the next source line is reached.
29307 If the @samp{--reverse} option is specified, resumes reverse execution
29308 of the inferior program, stopping at the beginning of the previous
29309 source line. If you issue this command on the first line of a
29310 function, it will take you back to the caller of that function, to the
29311 source line where the function was called.
29314 @subsubheading @value{GDBN} Command
29316 The corresponding @value{GDBN} command is @samp{next}.
29318 @subsubheading Example
29324 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29329 @subheading The @code{-exec-next-instruction} Command
29330 @findex -exec-next-instruction
29332 @subsubheading Synopsis
29335 -exec-next-instruction [--reverse]
29338 Executes one machine instruction. If the instruction is a function
29339 call, continues until the function returns. If the program stops at an
29340 instruction in the middle of a source line, the address will be
29343 If the @samp{--reverse} option is specified, resumes reverse execution
29344 of the inferior program, stopping at the previous instruction. If the
29345 previously executed instruction was a return from another function,
29346 it will continue to execute in reverse until the call to that function
29347 (from the current stack frame) is reached.
29349 @subsubheading @value{GDBN} Command
29351 The corresponding @value{GDBN} command is @samp{nexti}.
29353 @subsubheading Example
29357 -exec-next-instruction
29361 *stopped,reason="end-stepping-range",
29362 addr="0x000100d4",line="5",file="hello.c"
29367 @subheading The @code{-exec-return} Command
29368 @findex -exec-return
29370 @subsubheading Synopsis
29376 Makes current function return immediately. Doesn't execute the inferior.
29377 Displays the new current frame.
29379 @subsubheading @value{GDBN} Command
29381 The corresponding @value{GDBN} command is @samp{return}.
29383 @subsubheading Example
29387 200-break-insert callee4
29388 200^done,bkpt=@{number="1",addr="0x00010734",
29389 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29394 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29395 frame=@{func="callee4",args=[],
29396 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29397 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29403 111^done,frame=@{level="0",func="callee3",
29404 args=[@{name="strarg",
29405 value="0x11940 \"A string argument.\""@}],
29406 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29407 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29412 @subheading The @code{-exec-run} Command
29415 @subsubheading Synopsis
29418 -exec-run [ --all | --thread-group N ] [ --start ]
29421 Starts execution of the inferior from the beginning. The inferior
29422 executes until either a breakpoint is encountered or the program
29423 exits. In the latter case the output will include an exit code, if
29424 the program has exited exceptionally.
29426 When neither the @samp{--all} nor the @samp{--thread-group} option
29427 is specified, the current inferior is started. If the
29428 @samp{--thread-group} option is specified, it should refer to a thread
29429 group of type @samp{process}, and that thread group will be started.
29430 If the @samp{--all} option is specified, then all inferiors will be started.
29432 Using the @samp{--start} option instructs the debugger to stop
29433 the execution at the start of the inferior's main subprogram,
29434 following the same behavior as the @code{start} command
29435 (@pxref{Starting}).
29437 @subsubheading @value{GDBN} Command
29439 The corresponding @value{GDBN} command is @samp{run}.
29441 @subsubheading Examples
29446 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29451 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29452 frame=@{func="main",args=[],file="recursive2.c",
29453 fullname="/home/foo/bar/recursive2.c",line="4"@}
29458 Program exited normally:
29466 *stopped,reason="exited-normally"
29471 Program exited exceptionally:
29479 *stopped,reason="exited",exit-code="01"
29483 Another way the program can terminate is if it receives a signal such as
29484 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29488 *stopped,reason="exited-signalled",signal-name="SIGINT",
29489 signal-meaning="Interrupt"
29493 @c @subheading -exec-signal
29496 @subheading The @code{-exec-step} Command
29499 @subsubheading Synopsis
29502 -exec-step [--reverse]
29505 Resumes execution of the inferior program, stopping when the beginning
29506 of the next source line is reached, if the next source line is not a
29507 function call. If it is, stop at the first instruction of the called
29508 function. If the @samp{--reverse} option is specified, resumes reverse
29509 execution of the inferior program, stopping at the beginning of the
29510 previously executed source line.
29512 @subsubheading @value{GDBN} Command
29514 The corresponding @value{GDBN} command is @samp{step}.
29516 @subsubheading Example
29518 Stepping into a function:
29524 *stopped,reason="end-stepping-range",
29525 frame=@{func="foo",args=[@{name="a",value="10"@},
29526 @{name="b",value="0"@}],file="recursive2.c",
29527 fullname="/home/foo/bar/recursive2.c",line="11"@}
29537 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29542 @subheading The @code{-exec-step-instruction} Command
29543 @findex -exec-step-instruction
29545 @subsubheading Synopsis
29548 -exec-step-instruction [--reverse]
29551 Resumes the inferior which executes one machine instruction. If the
29552 @samp{--reverse} option is specified, resumes reverse execution of the
29553 inferior program, stopping at the previously executed instruction.
29554 The output, once @value{GDBN} has stopped, will vary depending on
29555 whether we have stopped in the middle of a source line or not. In the
29556 former case, the address at which the program stopped will be printed
29559 @subsubheading @value{GDBN} Command
29561 The corresponding @value{GDBN} command is @samp{stepi}.
29563 @subsubheading Example
29567 -exec-step-instruction
29571 *stopped,reason="end-stepping-range",
29572 frame=@{func="foo",args=[],file="try.c",
29573 fullname="/home/foo/bar/try.c",line="10"@}
29575 -exec-step-instruction
29579 *stopped,reason="end-stepping-range",
29580 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29581 fullname="/home/foo/bar/try.c",line="10"@}
29586 @subheading The @code{-exec-until} Command
29587 @findex -exec-until
29589 @subsubheading Synopsis
29592 -exec-until [ @var{location} ]
29595 Executes the inferior until the @var{location} specified in the
29596 argument is reached. If there is no argument, the inferior executes
29597 until a source line greater than the current one is reached. The
29598 reason for stopping in this case will be @samp{location-reached}.
29600 @subsubheading @value{GDBN} Command
29602 The corresponding @value{GDBN} command is @samp{until}.
29604 @subsubheading Example
29608 -exec-until recursive2.c:6
29612 *stopped,reason="location-reached",frame=@{func="main",args=[],
29613 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29618 @subheading -file-clear
29619 Is this going away????
29622 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29623 @node GDB/MI Stack Manipulation
29624 @section @sc{gdb/mi} Stack Manipulation Commands
29626 @subheading The @code{-enable-frame-filters} Command
29627 @findex -enable-frame-filters
29630 -enable-frame-filters
29633 @value{GDBN} allows Python-based frame filters to affect the output of
29634 the MI commands relating to stack traces. As there is no way to
29635 implement this in a fully backward-compatible way, a front end must
29636 request that this functionality be enabled.
29638 Once enabled, this feature cannot be disabled.
29640 Note that if Python support has not been compiled into @value{GDBN},
29641 this command will still succeed (and do nothing).
29643 @subheading The @code{-stack-info-frame} Command
29644 @findex -stack-info-frame
29646 @subsubheading Synopsis
29652 Get info on the selected frame.
29654 @subsubheading @value{GDBN} Command
29656 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29657 (without arguments).
29659 @subsubheading Example
29664 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29665 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29666 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29670 @subheading The @code{-stack-info-depth} Command
29671 @findex -stack-info-depth
29673 @subsubheading Synopsis
29676 -stack-info-depth [ @var{max-depth} ]
29679 Return the depth of the stack. If the integer argument @var{max-depth}
29680 is specified, do not count beyond @var{max-depth} frames.
29682 @subsubheading @value{GDBN} Command
29684 There's no equivalent @value{GDBN} command.
29686 @subsubheading Example
29688 For a stack with frame levels 0 through 11:
29695 -stack-info-depth 4
29698 -stack-info-depth 12
29701 -stack-info-depth 11
29704 -stack-info-depth 13
29709 @anchor{-stack-list-arguments}
29710 @subheading The @code{-stack-list-arguments} Command
29711 @findex -stack-list-arguments
29713 @subsubheading Synopsis
29716 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29717 [ @var{low-frame} @var{high-frame} ]
29720 Display a list of the arguments for the frames between @var{low-frame}
29721 and @var{high-frame} (inclusive). If @var{low-frame} and
29722 @var{high-frame} are not provided, list the arguments for the whole
29723 call stack. If the two arguments are equal, show the single frame
29724 at the corresponding level. It is an error if @var{low-frame} is
29725 larger than the actual number of frames. On the other hand,
29726 @var{high-frame} may be larger than the actual number of frames, in
29727 which case only existing frames will be returned.
29729 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29730 the variables; if it is 1 or @code{--all-values}, print also their
29731 values; and if it is 2 or @code{--simple-values}, print the name,
29732 type and value for simple data types, and the name and type for arrays,
29733 structures and unions. If the option @code{--no-frame-filters} is
29734 supplied, then Python frame filters will not be executed.
29736 If the @code{--skip-unavailable} option is specified, arguments that
29737 are not available are not listed. Partially available arguments
29738 are still displayed, however.
29740 Use of this command to obtain arguments in a single frame is
29741 deprecated in favor of the @samp{-stack-list-variables} command.
29743 @subsubheading @value{GDBN} Command
29745 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29746 @samp{gdb_get_args} command which partially overlaps with the
29747 functionality of @samp{-stack-list-arguments}.
29749 @subsubheading Example
29756 frame=@{level="0",addr="0x00010734",func="callee4",
29757 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29758 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29759 frame=@{level="1",addr="0x0001076c",func="callee3",
29760 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29761 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29762 frame=@{level="2",addr="0x0001078c",func="callee2",
29763 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29764 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29765 frame=@{level="3",addr="0x000107b4",func="callee1",
29766 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29767 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29768 frame=@{level="4",addr="0x000107e0",func="main",
29769 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29770 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29772 -stack-list-arguments 0
29775 frame=@{level="0",args=[]@},
29776 frame=@{level="1",args=[name="strarg"]@},
29777 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29778 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29779 frame=@{level="4",args=[]@}]
29781 -stack-list-arguments 1
29784 frame=@{level="0",args=[]@},
29786 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29787 frame=@{level="2",args=[
29788 @{name="intarg",value="2"@},
29789 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29790 @{frame=@{level="3",args=[
29791 @{name="intarg",value="2"@},
29792 @{name="strarg",value="0x11940 \"A string argument.\""@},
29793 @{name="fltarg",value="3.5"@}]@},
29794 frame=@{level="4",args=[]@}]
29796 -stack-list-arguments 0 2 2
29797 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29799 -stack-list-arguments 1 2 2
29800 ^done,stack-args=[frame=@{level="2",
29801 args=[@{name="intarg",value="2"@},
29802 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29806 @c @subheading -stack-list-exception-handlers
29809 @anchor{-stack-list-frames}
29810 @subheading The @code{-stack-list-frames} Command
29811 @findex -stack-list-frames
29813 @subsubheading Synopsis
29816 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29819 List the frames currently on the stack. For each frame it displays the
29824 The frame number, 0 being the topmost frame, i.e., the innermost function.
29826 The @code{$pc} value for that frame.
29830 File name of the source file where the function lives.
29831 @item @var{fullname}
29832 The full file name of the source file where the function lives.
29834 Line number corresponding to the @code{$pc}.
29836 The shared library where this function is defined. This is only given
29837 if the frame's function is not known.
29840 If invoked without arguments, this command prints a backtrace for the
29841 whole stack. If given two integer arguments, it shows the frames whose
29842 levels are between the two arguments (inclusive). If the two arguments
29843 are equal, it shows the single frame at the corresponding level. It is
29844 an error if @var{low-frame} is larger than the actual number of
29845 frames. On the other hand, @var{high-frame} may be larger than the
29846 actual number of frames, in which case only existing frames will be
29847 returned. If the option @code{--no-frame-filters} is supplied, then
29848 Python frame filters will not be executed.
29850 @subsubheading @value{GDBN} Command
29852 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29854 @subsubheading Example
29856 Full stack backtrace:
29862 [frame=@{level="0",addr="0x0001076c",func="foo",
29863 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29864 frame=@{level="1",addr="0x000107a4",func="foo",
29865 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29866 frame=@{level="2",addr="0x000107a4",func="foo",
29867 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29868 frame=@{level="3",addr="0x000107a4",func="foo",
29869 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29870 frame=@{level="4",addr="0x000107a4",func="foo",
29871 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29872 frame=@{level="5",addr="0x000107a4",func="foo",
29873 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29874 frame=@{level="6",addr="0x000107a4",func="foo",
29875 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29876 frame=@{level="7",addr="0x000107a4",func="foo",
29877 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29878 frame=@{level="8",addr="0x000107a4",func="foo",
29879 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29880 frame=@{level="9",addr="0x000107a4",func="foo",
29881 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29882 frame=@{level="10",addr="0x000107a4",func="foo",
29883 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29884 frame=@{level="11",addr="0x00010738",func="main",
29885 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29889 Show frames between @var{low_frame} and @var{high_frame}:
29893 -stack-list-frames 3 5
29895 [frame=@{level="3",addr="0x000107a4",func="foo",
29896 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29897 frame=@{level="4",addr="0x000107a4",func="foo",
29898 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29899 frame=@{level="5",addr="0x000107a4",func="foo",
29900 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29904 Show a single frame:
29908 -stack-list-frames 3 3
29910 [frame=@{level="3",addr="0x000107a4",func="foo",
29911 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29916 @subheading The @code{-stack-list-locals} Command
29917 @findex -stack-list-locals
29918 @anchor{-stack-list-locals}
29920 @subsubheading Synopsis
29923 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29926 Display the local variable names for the selected frame. If
29927 @var{print-values} is 0 or @code{--no-values}, print only the names of
29928 the variables; if it is 1 or @code{--all-values}, print also their
29929 values; and if it is 2 or @code{--simple-values}, print the name,
29930 type and value for simple data types, and the name and type for arrays,
29931 structures and unions. In this last case, a frontend can immediately
29932 display the value of simple data types and create variable objects for
29933 other data types when the user wishes to explore their values in
29934 more detail. If the option @code{--no-frame-filters} is supplied, then
29935 Python frame filters will not be executed.
29937 If the @code{--skip-unavailable} option is specified, local variables
29938 that are not available are not listed. Partially available local
29939 variables are still displayed, however.
29941 This command is deprecated in favor of the
29942 @samp{-stack-list-variables} command.
29944 @subsubheading @value{GDBN} Command
29946 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29948 @subsubheading Example
29952 -stack-list-locals 0
29953 ^done,locals=[name="A",name="B",name="C"]
29955 -stack-list-locals --all-values
29956 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29957 @{name="C",value="@{1, 2, 3@}"@}]
29958 -stack-list-locals --simple-values
29959 ^done,locals=[@{name="A",type="int",value="1"@},
29960 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29964 @anchor{-stack-list-variables}
29965 @subheading The @code{-stack-list-variables} Command
29966 @findex -stack-list-variables
29968 @subsubheading Synopsis
29971 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29974 Display the names of local variables and function arguments for the selected frame. If
29975 @var{print-values} is 0 or @code{--no-values}, print only the names of
29976 the variables; if it is 1 or @code{--all-values}, print also their
29977 values; and if it is 2 or @code{--simple-values}, print the name,
29978 type and value for simple data types, and the name and type for arrays,
29979 structures and unions. If the option @code{--no-frame-filters} is
29980 supplied, then Python frame filters will not be executed.
29982 If the @code{--skip-unavailable} option is specified, local variables
29983 and arguments that are not available are not listed. Partially
29984 available arguments and local variables are still displayed, however.
29986 @subsubheading Example
29990 -stack-list-variables --thread 1 --frame 0 --all-values
29991 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29996 @subheading The @code{-stack-select-frame} Command
29997 @findex -stack-select-frame
29999 @subsubheading Synopsis
30002 -stack-select-frame @var{framenum}
30005 Change the selected frame. Select a different frame @var{framenum} on
30008 This command in deprecated in favor of passing the @samp{--frame}
30009 option to every command.
30011 @subsubheading @value{GDBN} Command
30013 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30014 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30016 @subsubheading Example
30020 -stack-select-frame 2
30025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30026 @node GDB/MI Variable Objects
30027 @section @sc{gdb/mi} Variable Objects
30031 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30033 For the implementation of a variable debugger window (locals, watched
30034 expressions, etc.), we are proposing the adaptation of the existing code
30035 used by @code{Insight}.
30037 The two main reasons for that are:
30041 It has been proven in practice (it is already on its second generation).
30044 It will shorten development time (needless to say how important it is
30048 The original interface was designed to be used by Tcl code, so it was
30049 slightly changed so it could be used through @sc{gdb/mi}. This section
30050 describes the @sc{gdb/mi} operations that will be available and gives some
30051 hints about their use.
30053 @emph{Note}: In addition to the set of operations described here, we
30054 expect the @sc{gui} implementation of a variable window to require, at
30055 least, the following operations:
30058 @item @code{-gdb-show} @code{output-radix}
30059 @item @code{-stack-list-arguments}
30060 @item @code{-stack-list-locals}
30061 @item @code{-stack-select-frame}
30066 @subheading Introduction to Variable Objects
30068 @cindex variable objects in @sc{gdb/mi}
30070 Variable objects are "object-oriented" MI interface for examining and
30071 changing values of expressions. Unlike some other MI interfaces that
30072 work with expressions, variable objects are specifically designed for
30073 simple and efficient presentation in the frontend. A variable object
30074 is identified by string name. When a variable object is created, the
30075 frontend specifies the expression for that variable object. The
30076 expression can be a simple variable, or it can be an arbitrary complex
30077 expression, and can even involve CPU registers. After creating a
30078 variable object, the frontend can invoke other variable object
30079 operations---for example to obtain or change the value of a variable
30080 object, or to change display format.
30082 Variable objects have hierarchical tree structure. Any variable object
30083 that corresponds to a composite type, such as structure in C, has
30084 a number of child variable objects, for example corresponding to each
30085 element of a structure. A child variable object can itself have
30086 children, recursively. Recursion ends when we reach
30087 leaf variable objects, which always have built-in types. Child variable
30088 objects are created only by explicit request, so if a frontend
30089 is not interested in the children of a particular variable object, no
30090 child will be created.
30092 For a leaf variable object it is possible to obtain its value as a
30093 string, or set the value from a string. String value can be also
30094 obtained for a non-leaf variable object, but it's generally a string
30095 that only indicates the type of the object, and does not list its
30096 contents. Assignment to a non-leaf variable object is not allowed.
30098 A frontend does not need to read the values of all variable objects each time
30099 the program stops. Instead, MI provides an update command that lists all
30100 variable objects whose values has changed since the last update
30101 operation. This considerably reduces the amount of data that must
30102 be transferred to the frontend. As noted above, children variable
30103 objects are created on demand, and only leaf variable objects have a
30104 real value. As result, gdb will read target memory only for leaf
30105 variables that frontend has created.
30107 The automatic update is not always desirable. For example, a frontend
30108 might want to keep a value of some expression for future reference,
30109 and never update it. For another example, fetching memory is
30110 relatively slow for embedded targets, so a frontend might want
30111 to disable automatic update for the variables that are either not
30112 visible on the screen, or ``closed''. This is possible using so
30113 called ``frozen variable objects''. Such variable objects are never
30114 implicitly updated.
30116 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30117 fixed variable object, the expression is parsed when the variable
30118 object is created, including associating identifiers to specific
30119 variables. The meaning of expression never changes. For a floating
30120 variable object the values of variables whose names appear in the
30121 expressions are re-evaluated every time in the context of the current
30122 frame. Consider this example:
30127 struct work_state state;
30134 If a fixed variable object for the @code{state} variable is created in
30135 this function, and we enter the recursive call, the variable
30136 object will report the value of @code{state} in the top-level
30137 @code{do_work} invocation. On the other hand, a floating variable
30138 object will report the value of @code{state} in the current frame.
30140 If an expression specified when creating a fixed variable object
30141 refers to a local variable, the variable object becomes bound to the
30142 thread and frame in which the variable object is created. When such
30143 variable object is updated, @value{GDBN} makes sure that the
30144 thread/frame combination the variable object is bound to still exists,
30145 and re-evaluates the variable object in context of that thread/frame.
30147 The following is the complete set of @sc{gdb/mi} operations defined to
30148 access this functionality:
30150 @multitable @columnfractions .4 .6
30151 @item @strong{Operation}
30152 @tab @strong{Description}
30154 @item @code{-enable-pretty-printing}
30155 @tab enable Python-based pretty-printing
30156 @item @code{-var-create}
30157 @tab create a variable object
30158 @item @code{-var-delete}
30159 @tab delete the variable object and/or its children
30160 @item @code{-var-set-format}
30161 @tab set the display format of this variable
30162 @item @code{-var-show-format}
30163 @tab show the display format of this variable
30164 @item @code{-var-info-num-children}
30165 @tab tells how many children this object has
30166 @item @code{-var-list-children}
30167 @tab return a list of the object's children
30168 @item @code{-var-info-type}
30169 @tab show the type of this variable object
30170 @item @code{-var-info-expression}
30171 @tab print parent-relative expression that this variable object represents
30172 @item @code{-var-info-path-expression}
30173 @tab print full expression that this variable object represents
30174 @item @code{-var-show-attributes}
30175 @tab is this variable editable? does it exist here?
30176 @item @code{-var-evaluate-expression}
30177 @tab get the value of this variable
30178 @item @code{-var-assign}
30179 @tab set the value of this variable
30180 @item @code{-var-update}
30181 @tab update the variable and its children
30182 @item @code{-var-set-frozen}
30183 @tab set frozeness attribute
30184 @item @code{-var-set-update-range}
30185 @tab set range of children to display on update
30188 In the next subsection we describe each operation in detail and suggest
30189 how it can be used.
30191 @subheading Description And Use of Operations on Variable Objects
30193 @subheading The @code{-enable-pretty-printing} Command
30194 @findex -enable-pretty-printing
30197 -enable-pretty-printing
30200 @value{GDBN} allows Python-based visualizers to affect the output of the
30201 MI variable object commands. However, because there was no way to
30202 implement this in a fully backward-compatible way, a front end must
30203 request that this functionality be enabled.
30205 Once enabled, this feature cannot be disabled.
30207 Note that if Python support has not been compiled into @value{GDBN},
30208 this command will still succeed (and do nothing).
30210 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30211 may work differently in future versions of @value{GDBN}.
30213 @subheading The @code{-var-create} Command
30214 @findex -var-create
30216 @subsubheading Synopsis
30219 -var-create @{@var{name} | "-"@}
30220 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30223 This operation creates a variable object, which allows the monitoring of
30224 a variable, the result of an expression, a memory cell or a CPU
30227 The @var{name} parameter is the string by which the object can be
30228 referenced. It must be unique. If @samp{-} is specified, the varobj
30229 system will generate a string ``varNNNNNN'' automatically. It will be
30230 unique provided that one does not specify @var{name} of that format.
30231 The command fails if a duplicate name is found.
30233 The frame under which the expression should be evaluated can be
30234 specified by @var{frame-addr}. A @samp{*} indicates that the current
30235 frame should be used. A @samp{@@} indicates that a floating variable
30236 object must be created.
30238 @var{expression} is any expression valid on the current language set (must not
30239 begin with a @samp{*}), or one of the following:
30243 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30246 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30249 @samp{$@var{regname}} --- a CPU register name
30252 @cindex dynamic varobj
30253 A varobj's contents may be provided by a Python-based pretty-printer. In this
30254 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30255 have slightly different semantics in some cases. If the
30256 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30257 will never create a dynamic varobj. This ensures backward
30258 compatibility for existing clients.
30260 @subsubheading Result
30262 This operation returns attributes of the newly-created varobj. These
30267 The name of the varobj.
30270 The number of children of the varobj. This number is not necessarily
30271 reliable for a dynamic varobj. Instead, you must examine the
30272 @samp{has_more} attribute.
30275 The varobj's scalar value. For a varobj whose type is some sort of
30276 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30277 will not be interesting.
30280 The varobj's type. This is a string representation of the type, as
30281 would be printed by the @value{GDBN} CLI. If @samp{print object}
30282 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30283 @emph{actual} (derived) type of the object is shown rather than the
30284 @emph{declared} one.
30287 If a variable object is bound to a specific thread, then this is the
30288 thread's global identifier.
30291 For a dynamic varobj, this indicates whether there appear to be any
30292 children available. For a non-dynamic varobj, this will be 0.
30295 This attribute will be present and have the value @samp{1} if the
30296 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30297 then this attribute will not be present.
30300 A dynamic varobj can supply a display hint to the front end. The
30301 value comes directly from the Python pretty-printer object's
30302 @code{display_hint} method. @xref{Pretty Printing API}.
30305 Typical output will look like this:
30308 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30309 has_more="@var{has_more}"
30313 @subheading The @code{-var-delete} Command
30314 @findex -var-delete
30316 @subsubheading Synopsis
30319 -var-delete [ -c ] @var{name}
30322 Deletes a previously created variable object and all of its children.
30323 With the @samp{-c} option, just deletes the children.
30325 Returns an error if the object @var{name} is not found.
30328 @subheading The @code{-var-set-format} Command
30329 @findex -var-set-format
30331 @subsubheading Synopsis
30334 -var-set-format @var{name} @var{format-spec}
30337 Sets the output format for the value of the object @var{name} to be
30340 @anchor{-var-set-format}
30341 The syntax for the @var{format-spec} is as follows:
30344 @var{format-spec} @expansion{}
30345 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30348 The natural format is the default format choosen automatically
30349 based on the variable type (like decimal for an @code{int}, hex
30350 for pointers, etc.).
30352 The zero-hexadecimal format has a representation similar to hexadecimal
30353 but with padding zeroes to the left of the value. For example, a 32-bit
30354 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30355 zero-hexadecimal format.
30357 For a variable with children, the format is set only on the
30358 variable itself, and the children are not affected.
30360 @subheading The @code{-var-show-format} Command
30361 @findex -var-show-format
30363 @subsubheading Synopsis
30366 -var-show-format @var{name}
30369 Returns the format used to display the value of the object @var{name}.
30372 @var{format} @expansion{}
30377 @subheading The @code{-var-info-num-children} Command
30378 @findex -var-info-num-children
30380 @subsubheading Synopsis
30383 -var-info-num-children @var{name}
30386 Returns the number of children of a variable object @var{name}:
30392 Note that this number is not completely reliable for a dynamic varobj.
30393 It will return the current number of children, but more children may
30397 @subheading The @code{-var-list-children} Command
30398 @findex -var-list-children
30400 @subsubheading Synopsis
30403 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30405 @anchor{-var-list-children}
30407 Return a list of the children of the specified variable object and
30408 create variable objects for them, if they do not already exist. With
30409 a single argument or if @var{print-values} has a value of 0 or
30410 @code{--no-values}, print only the names of the variables; if
30411 @var{print-values} is 1 or @code{--all-values}, also print their
30412 values; and if it is 2 or @code{--simple-values} print the name and
30413 value for simple data types and just the name for arrays, structures
30416 @var{from} and @var{to}, if specified, indicate the range of children
30417 to report. If @var{from} or @var{to} is less than zero, the range is
30418 reset and all children will be reported. Otherwise, children starting
30419 at @var{from} (zero-based) and up to and excluding @var{to} will be
30422 If a child range is requested, it will only affect the current call to
30423 @code{-var-list-children}, but not future calls to @code{-var-update}.
30424 For this, you must instead use @code{-var-set-update-range}. The
30425 intent of this approach is to enable a front end to implement any
30426 update approach it likes; for example, scrolling a view may cause the
30427 front end to request more children with @code{-var-list-children}, and
30428 then the front end could call @code{-var-set-update-range} with a
30429 different range to ensure that future updates are restricted to just
30432 For each child the following results are returned:
30437 Name of the variable object created for this child.
30440 The expression to be shown to the user by the front end to designate this child.
30441 For example this may be the name of a structure member.
30443 For a dynamic varobj, this value cannot be used to form an
30444 expression. There is no way to do this at all with a dynamic varobj.
30446 For C/C@t{++} structures there are several pseudo children returned to
30447 designate access qualifiers. For these pseudo children @var{exp} is
30448 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30449 type and value are not present.
30451 A dynamic varobj will not report the access qualifying
30452 pseudo-children, regardless of the language. This information is not
30453 available at all with a dynamic varobj.
30456 Number of children this child has. For a dynamic varobj, this will be
30460 The type of the child. If @samp{print object}
30461 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30462 @emph{actual} (derived) type of the object is shown rather than the
30463 @emph{declared} one.
30466 If values were requested, this is the value.
30469 If this variable object is associated with a thread, this is the
30470 thread's global thread id. Otherwise this result is not present.
30473 If the variable object is frozen, this variable will be present with a value of 1.
30476 A dynamic varobj can supply a display hint to the front end. The
30477 value comes directly from the Python pretty-printer object's
30478 @code{display_hint} method. @xref{Pretty Printing API}.
30481 This attribute will be present and have the value @samp{1} if the
30482 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30483 then this attribute will not be present.
30487 The result may have its own attributes:
30491 A dynamic varobj can supply a display hint to the front end. The
30492 value comes directly from the Python pretty-printer object's
30493 @code{display_hint} method. @xref{Pretty Printing API}.
30496 This is an integer attribute which is nonzero if there are children
30497 remaining after the end of the selected range.
30500 @subsubheading Example
30504 -var-list-children n
30505 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30506 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30508 -var-list-children --all-values n
30509 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30510 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30514 @subheading The @code{-var-info-type} Command
30515 @findex -var-info-type
30517 @subsubheading Synopsis
30520 -var-info-type @var{name}
30523 Returns the type of the specified variable @var{name}. The type is
30524 returned as a string in the same format as it is output by the
30528 type=@var{typename}
30532 @subheading The @code{-var-info-expression} Command
30533 @findex -var-info-expression
30535 @subsubheading Synopsis
30538 -var-info-expression @var{name}
30541 Returns a string that is suitable for presenting this
30542 variable object in user interface. The string is generally
30543 not valid expression in the current language, and cannot be evaluated.
30545 For example, if @code{a} is an array, and variable object
30546 @code{A} was created for @code{a}, then we'll get this output:
30549 (gdb) -var-info-expression A.1
30550 ^done,lang="C",exp="1"
30554 Here, the value of @code{lang} is the language name, which can be
30555 found in @ref{Supported Languages}.
30557 Note that the output of the @code{-var-list-children} command also
30558 includes those expressions, so the @code{-var-info-expression} command
30561 @subheading The @code{-var-info-path-expression} Command
30562 @findex -var-info-path-expression
30564 @subsubheading Synopsis
30567 -var-info-path-expression @var{name}
30570 Returns an expression that can be evaluated in the current
30571 context and will yield the same value that a variable object has.
30572 Compare this with the @code{-var-info-expression} command, which
30573 result can be used only for UI presentation. Typical use of
30574 the @code{-var-info-path-expression} command is creating a
30575 watchpoint from a variable object.
30577 This command is currently not valid for children of a dynamic varobj,
30578 and will give an error when invoked on one.
30580 For example, suppose @code{C} is a C@t{++} class, derived from class
30581 @code{Base}, and that the @code{Base} class has a member called
30582 @code{m_size}. Assume a variable @code{c} is has the type of
30583 @code{C} and a variable object @code{C} was created for variable
30584 @code{c}. Then, we'll get this output:
30586 (gdb) -var-info-path-expression C.Base.public.m_size
30587 ^done,path_expr=((Base)c).m_size)
30590 @subheading The @code{-var-show-attributes} Command
30591 @findex -var-show-attributes
30593 @subsubheading Synopsis
30596 -var-show-attributes @var{name}
30599 List attributes of the specified variable object @var{name}:
30602 status=@var{attr} [ ( ,@var{attr} )* ]
30606 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30608 @subheading The @code{-var-evaluate-expression} Command
30609 @findex -var-evaluate-expression
30611 @subsubheading Synopsis
30614 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30617 Evaluates the expression that is represented by the specified variable
30618 object and returns its value as a string. The format of the string
30619 can be specified with the @samp{-f} option. The possible values of
30620 this option are the same as for @code{-var-set-format}
30621 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30622 the current display format will be used. The current display format
30623 can be changed using the @code{-var-set-format} command.
30629 Note that one must invoke @code{-var-list-children} for a variable
30630 before the value of a child variable can be evaluated.
30632 @subheading The @code{-var-assign} Command
30633 @findex -var-assign
30635 @subsubheading Synopsis
30638 -var-assign @var{name} @var{expression}
30641 Assigns the value of @var{expression} to the variable object specified
30642 by @var{name}. The object must be @samp{editable}. If the variable's
30643 value is altered by the assign, the variable will show up in any
30644 subsequent @code{-var-update} list.
30646 @subsubheading Example
30654 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30658 @subheading The @code{-var-update} Command
30659 @findex -var-update
30661 @subsubheading Synopsis
30664 -var-update [@var{print-values}] @{@var{name} | "*"@}
30667 Reevaluate the expressions corresponding to the variable object
30668 @var{name} and all its direct and indirect children, and return the
30669 list of variable objects whose values have changed; @var{name} must
30670 be a root variable object. Here, ``changed'' means that the result of
30671 @code{-var-evaluate-expression} before and after the
30672 @code{-var-update} is different. If @samp{*} is used as the variable
30673 object names, all existing variable objects are updated, except
30674 for frozen ones (@pxref{-var-set-frozen}). The option
30675 @var{print-values} determines whether both names and values, or just
30676 names are printed. The possible values of this option are the same
30677 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30678 recommended to use the @samp{--all-values} option, to reduce the
30679 number of MI commands needed on each program stop.
30681 With the @samp{*} parameter, if a variable object is bound to a
30682 currently running thread, it will not be updated, without any
30685 If @code{-var-set-update-range} was previously used on a varobj, then
30686 only the selected range of children will be reported.
30688 @code{-var-update} reports all the changed varobjs in a tuple named
30691 Each item in the change list is itself a tuple holding:
30695 The name of the varobj.
30698 If values were requested for this update, then this field will be
30699 present and will hold the value of the varobj.
30702 @anchor{-var-update}
30703 This field is a string which may take one of three values:
30707 The variable object's current value is valid.
30710 The variable object does not currently hold a valid value but it may
30711 hold one in the future if its associated expression comes back into
30715 The variable object no longer holds a valid value.
30716 This can occur when the executable file being debugged has changed,
30717 either through recompilation or by using the @value{GDBN} @code{file}
30718 command. The front end should normally choose to delete these variable
30722 In the future new values may be added to this list so the front should
30723 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30726 This is only present if the varobj is still valid. If the type
30727 changed, then this will be the string @samp{true}; otherwise it will
30730 When a varobj's type changes, its children are also likely to have
30731 become incorrect. Therefore, the varobj's children are automatically
30732 deleted when this attribute is @samp{true}. Also, the varobj's update
30733 range, when set using the @code{-var-set-update-range} command, is
30737 If the varobj's type changed, then this field will be present and will
30740 @item new_num_children
30741 For a dynamic varobj, if the number of children changed, or if the
30742 type changed, this will be the new number of children.
30744 The @samp{numchild} field in other varobj responses is generally not
30745 valid for a dynamic varobj -- it will show the number of children that
30746 @value{GDBN} knows about, but because dynamic varobjs lazily
30747 instantiate their children, this will not reflect the number of
30748 children which may be available.
30750 The @samp{new_num_children} attribute only reports changes to the
30751 number of children known by @value{GDBN}. This is the only way to
30752 detect whether an update has removed children (which necessarily can
30753 only happen at the end of the update range).
30756 The display hint, if any.
30759 This is an integer value, which will be 1 if there are more children
30760 available outside the varobj's update range.
30763 This attribute will be present and have the value @samp{1} if the
30764 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30765 then this attribute will not be present.
30768 If new children were added to a dynamic varobj within the selected
30769 update range (as set by @code{-var-set-update-range}), then they will
30770 be listed in this attribute.
30773 @subsubheading Example
30780 -var-update --all-values var1
30781 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30782 type_changed="false"@}]
30786 @subheading The @code{-var-set-frozen} Command
30787 @findex -var-set-frozen
30788 @anchor{-var-set-frozen}
30790 @subsubheading Synopsis
30793 -var-set-frozen @var{name} @var{flag}
30796 Set the frozenness flag on the variable object @var{name}. The
30797 @var{flag} parameter should be either @samp{1} to make the variable
30798 frozen or @samp{0} to make it unfrozen. If a variable object is
30799 frozen, then neither itself, nor any of its children, are
30800 implicitly updated by @code{-var-update} of
30801 a parent variable or by @code{-var-update *}. Only
30802 @code{-var-update} of the variable itself will update its value and
30803 values of its children. After a variable object is unfrozen, it is
30804 implicitly updated by all subsequent @code{-var-update} operations.
30805 Unfreezing a variable does not update it, only subsequent
30806 @code{-var-update} does.
30808 @subsubheading Example
30812 -var-set-frozen V 1
30817 @subheading The @code{-var-set-update-range} command
30818 @findex -var-set-update-range
30819 @anchor{-var-set-update-range}
30821 @subsubheading Synopsis
30824 -var-set-update-range @var{name} @var{from} @var{to}
30827 Set the range of children to be returned by future invocations of
30828 @code{-var-update}.
30830 @var{from} and @var{to} indicate the range of children to report. If
30831 @var{from} or @var{to} is less than zero, the range is reset and all
30832 children will be reported. Otherwise, children starting at @var{from}
30833 (zero-based) and up to and excluding @var{to} will be reported.
30835 @subsubheading Example
30839 -var-set-update-range V 1 2
30843 @subheading The @code{-var-set-visualizer} command
30844 @findex -var-set-visualizer
30845 @anchor{-var-set-visualizer}
30847 @subsubheading Synopsis
30850 -var-set-visualizer @var{name} @var{visualizer}
30853 Set a visualizer for the variable object @var{name}.
30855 @var{visualizer} is the visualizer to use. The special value
30856 @samp{None} means to disable any visualizer in use.
30858 If not @samp{None}, @var{visualizer} must be a Python expression.
30859 This expression must evaluate to a callable object which accepts a
30860 single argument. @value{GDBN} will call this object with the value of
30861 the varobj @var{name} as an argument (this is done so that the same
30862 Python pretty-printing code can be used for both the CLI and MI).
30863 When called, this object must return an object which conforms to the
30864 pretty-printing interface (@pxref{Pretty Printing API}).
30866 The pre-defined function @code{gdb.default_visualizer} may be used to
30867 select a visualizer by following the built-in process
30868 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30869 a varobj is created, and so ordinarily is not needed.
30871 This feature is only available if Python support is enabled. The MI
30872 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30873 can be used to check this.
30875 @subsubheading Example
30877 Resetting the visualizer:
30881 -var-set-visualizer V None
30885 Reselecting the default (type-based) visualizer:
30889 -var-set-visualizer V gdb.default_visualizer
30893 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30894 can be used to instantiate this class for a varobj:
30898 -var-set-visualizer V "lambda val: SomeClass()"
30902 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30903 @node GDB/MI Data Manipulation
30904 @section @sc{gdb/mi} Data Manipulation
30906 @cindex data manipulation, in @sc{gdb/mi}
30907 @cindex @sc{gdb/mi}, data manipulation
30908 This section describes the @sc{gdb/mi} commands that manipulate data:
30909 examine memory and registers, evaluate expressions, etc.
30911 For details about what an addressable memory unit is,
30912 @pxref{addressable memory unit}.
30914 @c REMOVED FROM THE INTERFACE.
30915 @c @subheading -data-assign
30916 @c Change the value of a program variable. Plenty of side effects.
30917 @c @subsubheading GDB Command
30919 @c @subsubheading Example
30922 @subheading The @code{-data-disassemble} Command
30923 @findex -data-disassemble
30925 @subsubheading Synopsis
30929 [ -s @var{start-addr} -e @var{end-addr} ]
30930 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30938 @item @var{start-addr}
30939 is the beginning address (or @code{$pc})
30940 @item @var{end-addr}
30942 @item @var{filename}
30943 is the name of the file to disassemble
30944 @item @var{linenum}
30945 is the line number to disassemble around
30947 is the number of disassembly lines to be produced. If it is -1,
30948 the whole function will be disassembled, in case no @var{end-addr} is
30949 specified. If @var{end-addr} is specified as a non-zero value, and
30950 @var{lines} is lower than the number of disassembly lines between
30951 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30952 displayed; if @var{lines} is higher than the number of lines between
30953 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30958 @item 0 disassembly only
30959 @item 1 mixed source and disassembly (deprecated)
30960 @item 2 disassembly with raw opcodes
30961 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30962 @item 4 mixed source and disassembly
30963 @item 5 mixed source and disassembly with raw opcodes
30966 Modes 1 and 3 are deprecated. The output is ``source centric''
30967 which hasn't proved useful in practice.
30968 @xref{Machine Code}, for a discussion of the difference between
30969 @code{/m} and @code{/s} output of the @code{disassemble} command.
30972 @subsubheading Result
30974 The result of the @code{-data-disassemble} command will be a list named
30975 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30976 used with the @code{-data-disassemble} command.
30978 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30983 The address at which this instruction was disassembled.
30986 The name of the function this instruction is within.
30989 The decimal offset in bytes from the start of @samp{func-name}.
30992 The text disassembly for this @samp{address}.
30995 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30996 bytes for the @samp{inst} field.
31000 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31001 @samp{src_and_asm_line}, each of which has the following fields:
31005 The line number within @samp{file}.
31008 The file name from the compilation unit. This might be an absolute
31009 file name or a relative file name depending on the compile command
31013 Absolute file name of @samp{file}. It is converted to a canonical form
31014 using the source file search path
31015 (@pxref{Source Path, ,Specifying Source Directories})
31016 and after resolving all the symbolic links.
31018 If the source file is not found this field will contain the path as
31019 present in the debug information.
31021 @item line_asm_insn
31022 This is a list of tuples containing the disassembly for @samp{line} in
31023 @samp{file}. The fields of each tuple are the same as for
31024 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31025 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31030 Note that whatever included in the @samp{inst} field, is not
31031 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31034 @subsubheading @value{GDBN} Command
31036 The corresponding @value{GDBN} command is @samp{disassemble}.
31038 @subsubheading Example
31040 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31044 -data-disassemble -s $pc -e "$pc + 20" -- 0
31047 @{address="0x000107c0",func-name="main",offset="4",
31048 inst="mov 2, %o0"@},
31049 @{address="0x000107c4",func-name="main",offset="8",
31050 inst="sethi %hi(0x11800), %o2"@},
31051 @{address="0x000107c8",func-name="main",offset="12",
31052 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31053 @{address="0x000107cc",func-name="main",offset="16",
31054 inst="sethi %hi(0x11800), %o2"@},
31055 @{address="0x000107d0",func-name="main",offset="20",
31056 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31060 Disassemble the whole @code{main} function. Line 32 is part of
31064 -data-disassemble -f basics.c -l 32 -- 0
31066 @{address="0x000107bc",func-name="main",offset="0",
31067 inst="save %sp, -112, %sp"@},
31068 @{address="0x000107c0",func-name="main",offset="4",
31069 inst="mov 2, %o0"@},
31070 @{address="0x000107c4",func-name="main",offset="8",
31071 inst="sethi %hi(0x11800), %o2"@},
31073 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31074 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31078 Disassemble 3 instructions from the start of @code{main}:
31082 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31084 @{address="0x000107bc",func-name="main",offset="0",
31085 inst="save %sp, -112, %sp"@},
31086 @{address="0x000107c0",func-name="main",offset="4",
31087 inst="mov 2, %o0"@},
31088 @{address="0x000107c4",func-name="main",offset="8",
31089 inst="sethi %hi(0x11800), %o2"@}]
31093 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31097 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31099 src_and_asm_line=@{line="31",
31100 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31101 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31102 line_asm_insn=[@{address="0x000107bc",
31103 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31104 src_and_asm_line=@{line="32",
31105 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31106 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31107 line_asm_insn=[@{address="0x000107c0",
31108 func-name="main",offset="4",inst="mov 2, %o0"@},
31109 @{address="0x000107c4",func-name="main",offset="8",
31110 inst="sethi %hi(0x11800), %o2"@}]@}]
31115 @subheading The @code{-data-evaluate-expression} Command
31116 @findex -data-evaluate-expression
31118 @subsubheading Synopsis
31121 -data-evaluate-expression @var{expr}
31124 Evaluate @var{expr} as an expression. The expression could contain an
31125 inferior function call. The function call will execute synchronously.
31126 If the expression contains spaces, it must be enclosed in double quotes.
31128 @subsubheading @value{GDBN} Command
31130 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31131 @samp{call}. In @code{gdbtk} only, there's a corresponding
31132 @samp{gdb_eval} command.
31134 @subsubheading Example
31136 In the following example, the numbers that precede the commands are the
31137 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31138 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31142 211-data-evaluate-expression A
31145 311-data-evaluate-expression &A
31146 311^done,value="0xefffeb7c"
31148 411-data-evaluate-expression A+3
31151 511-data-evaluate-expression "A + 3"
31157 @subheading The @code{-data-list-changed-registers} Command
31158 @findex -data-list-changed-registers
31160 @subsubheading Synopsis
31163 -data-list-changed-registers
31166 Display a list of the registers that have changed.
31168 @subsubheading @value{GDBN} Command
31170 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31171 has the corresponding command @samp{gdb_changed_register_list}.
31173 @subsubheading Example
31175 On a PPC MBX board:
31183 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31184 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31187 -data-list-changed-registers
31188 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31189 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31190 "24","25","26","27","28","30","31","64","65","66","67","69"]
31195 @subheading The @code{-data-list-register-names} Command
31196 @findex -data-list-register-names
31198 @subsubheading Synopsis
31201 -data-list-register-names [ ( @var{regno} )+ ]
31204 Show a list of register names for the current target. If no arguments
31205 are given, it shows a list of the names of all the registers. If
31206 integer numbers are given as arguments, it will print a list of the
31207 names of the registers corresponding to the arguments. To ensure
31208 consistency between a register name and its number, the output list may
31209 include empty register names.
31211 @subsubheading @value{GDBN} Command
31213 @value{GDBN} does not have a command which corresponds to
31214 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31215 corresponding command @samp{gdb_regnames}.
31217 @subsubheading Example
31219 For the PPC MBX board:
31222 -data-list-register-names
31223 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31224 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31225 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31226 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31227 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31228 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31229 "", "pc","ps","cr","lr","ctr","xer"]
31231 -data-list-register-names 1 2 3
31232 ^done,register-names=["r1","r2","r3"]
31236 @subheading The @code{-data-list-register-values} Command
31237 @findex -data-list-register-values
31239 @subsubheading Synopsis
31242 -data-list-register-values
31243 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31246 Display the registers' contents. The format according to which the
31247 registers' contents are to be returned is given by @var{fmt}, followed
31248 by an optional list of numbers specifying the registers to display. A
31249 missing list of numbers indicates that the contents of all the
31250 registers must be returned. The @code{--skip-unavailable} option
31251 indicates that only the available registers are to be returned.
31253 Allowed formats for @var{fmt} are:
31270 @subsubheading @value{GDBN} Command
31272 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31273 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31275 @subsubheading Example
31277 For a PPC MBX board (note: line breaks are for readability only, they
31278 don't appear in the actual output):
31282 -data-list-register-values r 64 65
31283 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31284 @{number="65",value="0x00029002"@}]
31286 -data-list-register-values x
31287 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31288 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31289 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31290 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31291 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31292 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31293 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31294 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31295 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31296 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31297 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31298 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31299 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31300 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31301 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31302 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31303 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31304 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31305 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31306 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31307 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31308 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31309 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31310 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31311 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31312 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31313 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31314 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31315 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31316 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31317 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31318 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31319 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31320 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31321 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31322 @{number="69",value="0x20002b03"@}]
31327 @subheading The @code{-data-read-memory} Command
31328 @findex -data-read-memory
31330 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31332 @subsubheading Synopsis
31335 -data-read-memory [ -o @var{byte-offset} ]
31336 @var{address} @var{word-format} @var{word-size}
31337 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31344 @item @var{address}
31345 An expression specifying the address of the first memory word to be
31346 read. Complex expressions containing embedded white space should be
31347 quoted using the C convention.
31349 @item @var{word-format}
31350 The format to be used to print the memory words. The notation is the
31351 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31354 @item @var{word-size}
31355 The size of each memory word in bytes.
31357 @item @var{nr-rows}
31358 The number of rows in the output table.
31360 @item @var{nr-cols}
31361 The number of columns in the output table.
31364 If present, indicates that each row should include an @sc{ascii} dump. The
31365 value of @var{aschar} is used as a padding character when a byte is not a
31366 member of the printable @sc{ascii} character set (printable @sc{ascii}
31367 characters are those whose code is between 32 and 126, inclusively).
31369 @item @var{byte-offset}
31370 An offset to add to the @var{address} before fetching memory.
31373 This command displays memory contents as a table of @var{nr-rows} by
31374 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31375 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31376 (returned as @samp{total-bytes}). Should less than the requested number
31377 of bytes be returned by the target, the missing words are identified
31378 using @samp{N/A}. The number of bytes read from the target is returned
31379 in @samp{nr-bytes} and the starting address used to read memory in
31382 The address of the next/previous row or page is available in
31383 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31386 @subsubheading @value{GDBN} Command
31388 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31389 @samp{gdb_get_mem} memory read command.
31391 @subsubheading Example
31393 Read six bytes of memory starting at @code{bytes+6} but then offset by
31394 @code{-6} bytes. Format as three rows of two columns. One byte per
31395 word. Display each word in hex.
31399 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31400 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31401 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31402 prev-page="0x0000138a",memory=[
31403 @{addr="0x00001390",data=["0x00","0x01"]@},
31404 @{addr="0x00001392",data=["0x02","0x03"]@},
31405 @{addr="0x00001394",data=["0x04","0x05"]@}]
31409 Read two bytes of memory starting at address @code{shorts + 64} and
31410 display as a single word formatted in decimal.
31414 5-data-read-memory shorts+64 d 2 1 1
31415 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31416 next-row="0x00001512",prev-row="0x0000150e",
31417 next-page="0x00001512",prev-page="0x0000150e",memory=[
31418 @{addr="0x00001510",data=["128"]@}]
31422 Read thirty two bytes of memory starting at @code{bytes+16} and format
31423 as eight rows of four columns. Include a string encoding with @samp{x}
31424 used as the non-printable character.
31428 4-data-read-memory bytes+16 x 1 8 4 x
31429 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31430 next-row="0x000013c0",prev-row="0x0000139c",
31431 next-page="0x000013c0",prev-page="0x00001380",memory=[
31432 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31433 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31434 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31435 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31436 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31437 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31438 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31439 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31443 @subheading The @code{-data-read-memory-bytes} Command
31444 @findex -data-read-memory-bytes
31446 @subsubheading Synopsis
31449 -data-read-memory-bytes [ -o @var{offset} ]
31450 @var{address} @var{count}
31457 @item @var{address}
31458 An expression specifying the address of the first addressable memory unit
31459 to be read. Complex expressions containing embedded white space should be
31460 quoted using the C convention.
31463 The number of addressable memory units to read. This should be an integer
31467 The offset relative to @var{address} at which to start reading. This
31468 should be an integer literal. This option is provided so that a frontend
31469 is not required to first evaluate address and then perform address
31470 arithmetics itself.
31474 This command attempts to read all accessible memory regions in the
31475 specified range. First, all regions marked as unreadable in the memory
31476 map (if one is defined) will be skipped. @xref{Memory Region
31477 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31478 regions. For each one, if reading full region results in an errors,
31479 @value{GDBN} will try to read a subset of the region.
31481 In general, every single memory unit in the region may be readable or not,
31482 and the only way to read every readable unit is to try a read at
31483 every address, which is not practical. Therefore, @value{GDBN} will
31484 attempt to read all accessible memory units at either beginning or the end
31485 of the region, using a binary division scheme. This heuristic works
31486 well for reading accross a memory map boundary. Note that if a region
31487 has a readable range that is neither at the beginning or the end,
31488 @value{GDBN} will not read it.
31490 The result record (@pxref{GDB/MI Result Records}) that is output of
31491 the command includes a field named @samp{memory} whose content is a
31492 list of tuples. Each tuple represent a successfully read memory block
31493 and has the following fields:
31497 The start address of the memory block, as hexadecimal literal.
31500 The end address of the memory block, as hexadecimal literal.
31503 The offset of the memory block, as hexadecimal literal, relative to
31504 the start address passed to @code{-data-read-memory-bytes}.
31507 The contents of the memory block, in hex.
31513 @subsubheading @value{GDBN} Command
31515 The corresponding @value{GDBN} command is @samp{x}.
31517 @subsubheading Example
31521 -data-read-memory-bytes &a 10
31522 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31524 contents="01000000020000000300"@}]
31529 @subheading The @code{-data-write-memory-bytes} Command
31530 @findex -data-write-memory-bytes
31532 @subsubheading Synopsis
31535 -data-write-memory-bytes @var{address} @var{contents}
31536 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31543 @item @var{address}
31544 An expression specifying the address of the first addressable memory unit
31545 to be written. Complex expressions containing embedded white space should
31546 be quoted using the C convention.
31548 @item @var{contents}
31549 The hex-encoded data to write. It is an error if @var{contents} does
31550 not represent an integral number of addressable memory units.
31553 Optional argument indicating the number of addressable memory units to be
31554 written. If @var{count} is greater than @var{contents}' length,
31555 @value{GDBN} will repeatedly write @var{contents} until it fills
31556 @var{count} memory units.
31560 @subsubheading @value{GDBN} Command
31562 There's no corresponding @value{GDBN} command.
31564 @subsubheading Example
31568 -data-write-memory-bytes &a "aabbccdd"
31575 -data-write-memory-bytes &a "aabbccdd" 16e
31580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31581 @node GDB/MI Tracepoint Commands
31582 @section @sc{gdb/mi} Tracepoint Commands
31584 The commands defined in this section implement MI support for
31585 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31587 @subheading The @code{-trace-find} Command
31588 @findex -trace-find
31590 @subsubheading Synopsis
31593 -trace-find @var{mode} [@var{parameters}@dots{}]
31596 Find a trace frame using criteria defined by @var{mode} and
31597 @var{parameters}. The following table lists permissible
31598 modes and their parameters. For details of operation, see @ref{tfind}.
31603 No parameters are required. Stops examining trace frames.
31606 An integer is required as parameter. Selects tracepoint frame with
31609 @item tracepoint-number
31610 An integer is required as parameter. Finds next
31611 trace frame that corresponds to tracepoint with the specified number.
31614 An address is required as parameter. Finds
31615 next trace frame that corresponds to any tracepoint at the specified
31618 @item pc-inside-range
31619 Two addresses are required as parameters. Finds next trace
31620 frame that corresponds to a tracepoint at an address inside the
31621 specified range. Both bounds are considered to be inside the range.
31623 @item pc-outside-range
31624 Two addresses are required as parameters. Finds
31625 next trace frame that corresponds to a tracepoint at an address outside
31626 the specified range. Both bounds are considered to be inside the range.
31629 Line specification is required as parameter. @xref{Specify Location}.
31630 Finds next trace frame that corresponds to a tracepoint at
31631 the specified location.
31635 If @samp{none} was passed as @var{mode}, the response does not
31636 have fields. Otherwise, the response may have the following fields:
31640 This field has either @samp{0} or @samp{1} as the value, depending
31641 on whether a matching tracepoint was found.
31644 The index of the found traceframe. This field is present iff
31645 the @samp{found} field has value of @samp{1}.
31648 The index of the found tracepoint. This field is present iff
31649 the @samp{found} field has value of @samp{1}.
31652 The information about the frame corresponding to the found trace
31653 frame. This field is present only if a trace frame was found.
31654 @xref{GDB/MI Frame Information}, for description of this field.
31658 @subsubheading @value{GDBN} Command
31660 The corresponding @value{GDBN} command is @samp{tfind}.
31662 @subheading -trace-define-variable
31663 @findex -trace-define-variable
31665 @subsubheading Synopsis
31668 -trace-define-variable @var{name} [ @var{value} ]
31671 Create trace variable @var{name} if it does not exist. If
31672 @var{value} is specified, sets the initial value of the specified
31673 trace variable to that value. Note that the @var{name} should start
31674 with the @samp{$} character.
31676 @subsubheading @value{GDBN} Command
31678 The corresponding @value{GDBN} command is @samp{tvariable}.
31680 @subheading The @code{-trace-frame-collected} Command
31681 @findex -trace-frame-collected
31683 @subsubheading Synopsis
31686 -trace-frame-collected
31687 [--var-print-values @var{var_pval}]
31688 [--comp-print-values @var{comp_pval}]
31689 [--registers-format @var{regformat}]
31690 [--memory-contents]
31693 This command returns the set of collected objects, register names,
31694 trace state variable names, memory ranges and computed expressions
31695 that have been collected at a particular trace frame. The optional
31696 parameters to the command affect the output format in different ways.
31697 See the output description table below for more details.
31699 The reported names can be used in the normal manner to create
31700 varobjs and inspect the objects themselves. The items returned by
31701 this command are categorized so that it is clear which is a variable,
31702 which is a register, which is a trace state variable, which is a
31703 memory range and which is a computed expression.
31705 For instance, if the actions were
31707 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31708 collect *(int*)0xaf02bef0@@40
31712 the object collected in its entirety would be @code{myVar}. The
31713 object @code{myArray} would be partially collected, because only the
31714 element at index @code{myIndex} would be collected. The remaining
31715 objects would be computed expressions.
31717 An example output would be:
31721 -trace-frame-collected
31723 explicit-variables=[@{name="myVar",value="1"@}],
31724 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31725 @{name="myObj.field",value="0"@},
31726 @{name="myPtr->field",value="1"@},
31727 @{name="myCount + 2",value="3"@},
31728 @{name="$tvar1 + 1",value="43970027"@}],
31729 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31730 @{number="1",value="0x0"@},
31731 @{number="2",value="0x4"@},
31733 @{number="125",value="0x0"@}],
31734 tvars=[@{name="$tvar1",current="43970026"@}],
31735 memory=[@{address="0x0000000000602264",length="4"@},
31736 @{address="0x0000000000615bc0",length="4"@}]
31743 @item explicit-variables
31744 The set of objects that have been collected in their entirety (as
31745 opposed to collecting just a few elements of an array or a few struct
31746 members). For each object, its name and value are printed.
31747 The @code{--var-print-values} option affects how or whether the value
31748 field is output. If @var{var_pval} is 0, then print only the names;
31749 if it is 1, print also their values; and if it is 2, print the name,
31750 type and value for simple data types, and the name and type for
31751 arrays, structures and unions.
31753 @item computed-expressions
31754 The set of computed expressions that have been collected at the
31755 current trace frame. The @code{--comp-print-values} option affects
31756 this set like the @code{--var-print-values} option affects the
31757 @code{explicit-variables} set. See above.
31760 The registers that have been collected at the current trace frame.
31761 For each register collected, the name and current value are returned.
31762 The value is formatted according to the @code{--registers-format}
31763 option. See the @command{-data-list-register-values} command for a
31764 list of the allowed formats. The default is @samp{x}.
31767 The trace state variables that have been collected at the current
31768 trace frame. For each trace state variable collected, the name and
31769 current value are returned.
31772 The set of memory ranges that have been collected at the current trace
31773 frame. Its content is a list of tuples. Each tuple represents a
31774 collected memory range and has the following fields:
31778 The start address of the memory range, as hexadecimal literal.
31781 The length of the memory range, as decimal literal.
31784 The contents of the memory block, in hex. This field is only present
31785 if the @code{--memory-contents} option is specified.
31791 @subsubheading @value{GDBN} Command
31793 There is no corresponding @value{GDBN} command.
31795 @subsubheading Example
31797 @subheading -trace-list-variables
31798 @findex -trace-list-variables
31800 @subsubheading Synopsis
31803 -trace-list-variables
31806 Return a table of all defined trace variables. Each element of the
31807 table has the following fields:
31811 The name of the trace variable. This field is always present.
31814 The initial value. This is a 64-bit signed integer. This
31815 field is always present.
31818 The value the trace variable has at the moment. This is a 64-bit
31819 signed integer. This field is absent iff current value is
31820 not defined, for example if the trace was never run, or is
31825 @subsubheading @value{GDBN} Command
31827 The corresponding @value{GDBN} command is @samp{tvariables}.
31829 @subsubheading Example
31833 -trace-list-variables
31834 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31835 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31836 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31837 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31838 body=[variable=@{name="$trace_timestamp",initial="0"@}
31839 variable=@{name="$foo",initial="10",current="15"@}]@}
31843 @subheading -trace-save
31844 @findex -trace-save
31846 @subsubheading Synopsis
31849 -trace-save [ -r ] [ -ctf ] @var{filename}
31852 Saves the collected trace data to @var{filename}. Without the
31853 @samp{-r} option, the data is downloaded from the target and saved
31854 in a local file. With the @samp{-r} option the target is asked
31855 to perform the save.
31857 By default, this command will save the trace in the tfile format. You can
31858 supply the optional @samp{-ctf} argument to save it the CTF format. See
31859 @ref{Trace Files} for more information about CTF.
31861 @subsubheading @value{GDBN} Command
31863 The corresponding @value{GDBN} command is @samp{tsave}.
31866 @subheading -trace-start
31867 @findex -trace-start
31869 @subsubheading Synopsis
31875 Starts a tracing experiment. The result of this command does not
31878 @subsubheading @value{GDBN} Command
31880 The corresponding @value{GDBN} command is @samp{tstart}.
31882 @subheading -trace-status
31883 @findex -trace-status
31885 @subsubheading Synopsis
31891 Obtains the status of a tracing experiment. The result may include
31892 the following fields:
31897 May have a value of either @samp{0}, when no tracing operations are
31898 supported, @samp{1}, when all tracing operations are supported, or
31899 @samp{file} when examining trace file. In the latter case, examining
31900 of trace frame is possible but new tracing experiement cannot be
31901 started. This field is always present.
31904 May have a value of either @samp{0} or @samp{1} depending on whether
31905 tracing experiement is in progress on target. This field is present
31906 if @samp{supported} field is not @samp{0}.
31909 Report the reason why the tracing was stopped last time. This field
31910 may be absent iff tracing was never stopped on target yet. The
31911 value of @samp{request} means the tracing was stopped as result of
31912 the @code{-trace-stop} command. The value of @samp{overflow} means
31913 the tracing buffer is full. The value of @samp{disconnection} means
31914 tracing was automatically stopped when @value{GDBN} has disconnected.
31915 The value of @samp{passcount} means tracing was stopped when a
31916 tracepoint was passed a maximal number of times for that tracepoint.
31917 This field is present if @samp{supported} field is not @samp{0}.
31919 @item stopping-tracepoint
31920 The number of tracepoint whose passcount as exceeded. This field is
31921 present iff the @samp{stop-reason} field has the value of
31925 @itemx frames-created
31926 The @samp{frames} field is a count of the total number of trace frames
31927 in the trace buffer, while @samp{frames-created} is the total created
31928 during the run, including ones that were discarded, such as when a
31929 circular trace buffer filled up. Both fields are optional.
31933 These fields tell the current size of the tracing buffer and the
31934 remaining space. These fields are optional.
31937 The value of the circular trace buffer flag. @code{1} means that the
31938 trace buffer is circular and old trace frames will be discarded if
31939 necessary to make room, @code{0} means that the trace buffer is linear
31943 The value of the disconnected tracing flag. @code{1} means that
31944 tracing will continue after @value{GDBN} disconnects, @code{0} means
31945 that the trace run will stop.
31948 The filename of the trace file being examined. This field is
31949 optional, and only present when examining a trace file.
31953 @subsubheading @value{GDBN} Command
31955 The corresponding @value{GDBN} command is @samp{tstatus}.
31957 @subheading -trace-stop
31958 @findex -trace-stop
31960 @subsubheading Synopsis
31966 Stops a tracing experiment. The result of this command has the same
31967 fields as @code{-trace-status}, except that the @samp{supported} and
31968 @samp{running} fields are not output.
31970 @subsubheading @value{GDBN} Command
31972 The corresponding @value{GDBN} command is @samp{tstop}.
31975 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31976 @node GDB/MI Symbol Query
31977 @section @sc{gdb/mi} Symbol Query Commands
31981 @subheading The @code{-symbol-info-address} Command
31982 @findex -symbol-info-address
31984 @subsubheading Synopsis
31987 -symbol-info-address @var{symbol}
31990 Describe where @var{symbol} is stored.
31992 @subsubheading @value{GDBN} Command
31994 The corresponding @value{GDBN} command is @samp{info address}.
31996 @subsubheading Example
32000 @subheading The @code{-symbol-info-file} Command
32001 @findex -symbol-info-file
32003 @subsubheading Synopsis
32009 Show the file for the symbol.
32011 @subsubheading @value{GDBN} Command
32013 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32014 @samp{gdb_find_file}.
32016 @subsubheading Example
32020 @subheading The @code{-symbol-info-function} Command
32021 @findex -symbol-info-function
32023 @subsubheading Synopsis
32026 -symbol-info-function
32029 Show which function the symbol lives in.
32031 @subsubheading @value{GDBN} Command
32033 @samp{gdb_get_function} in @code{gdbtk}.
32035 @subsubheading Example
32039 @subheading The @code{-symbol-info-line} Command
32040 @findex -symbol-info-line
32042 @subsubheading Synopsis
32048 Show the core addresses of the code for a source line.
32050 @subsubheading @value{GDBN} Command
32052 The corresponding @value{GDBN} command is @samp{info line}.
32053 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32055 @subsubheading Example
32059 @subheading The @code{-symbol-info-symbol} Command
32060 @findex -symbol-info-symbol
32062 @subsubheading Synopsis
32065 -symbol-info-symbol @var{addr}
32068 Describe what symbol is at location @var{addr}.
32070 @subsubheading @value{GDBN} Command
32072 The corresponding @value{GDBN} command is @samp{info symbol}.
32074 @subsubheading Example
32078 @subheading The @code{-symbol-list-functions} Command
32079 @findex -symbol-list-functions
32081 @subsubheading Synopsis
32084 -symbol-list-functions
32087 List the functions in the executable.
32089 @subsubheading @value{GDBN} Command
32091 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32092 @samp{gdb_search} in @code{gdbtk}.
32094 @subsubheading Example
32099 @subheading The @code{-symbol-list-lines} Command
32100 @findex -symbol-list-lines
32102 @subsubheading Synopsis
32105 -symbol-list-lines @var{filename}
32108 Print the list of lines that contain code and their associated program
32109 addresses for the given source filename. The entries are sorted in
32110 ascending PC order.
32112 @subsubheading @value{GDBN} Command
32114 There is no corresponding @value{GDBN} command.
32116 @subsubheading Example
32119 -symbol-list-lines basics.c
32120 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32126 @subheading The @code{-symbol-list-types} Command
32127 @findex -symbol-list-types
32129 @subsubheading Synopsis
32135 List all the type names.
32137 @subsubheading @value{GDBN} Command
32139 The corresponding commands are @samp{info types} in @value{GDBN},
32140 @samp{gdb_search} in @code{gdbtk}.
32142 @subsubheading Example
32146 @subheading The @code{-symbol-list-variables} Command
32147 @findex -symbol-list-variables
32149 @subsubheading Synopsis
32152 -symbol-list-variables
32155 List all the global and static variable names.
32157 @subsubheading @value{GDBN} Command
32159 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32161 @subsubheading Example
32165 @subheading The @code{-symbol-locate} Command
32166 @findex -symbol-locate
32168 @subsubheading Synopsis
32174 @subsubheading @value{GDBN} Command
32176 @samp{gdb_loc} in @code{gdbtk}.
32178 @subsubheading Example
32182 @subheading The @code{-symbol-type} Command
32183 @findex -symbol-type
32185 @subsubheading Synopsis
32188 -symbol-type @var{variable}
32191 Show type of @var{variable}.
32193 @subsubheading @value{GDBN} Command
32195 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32196 @samp{gdb_obj_variable}.
32198 @subsubheading Example
32203 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32204 @node GDB/MI File Commands
32205 @section @sc{gdb/mi} File Commands
32207 This section describes the GDB/MI commands to specify executable file names
32208 and to read in and obtain symbol table information.
32210 @subheading The @code{-file-exec-and-symbols} Command
32211 @findex -file-exec-and-symbols
32213 @subsubheading Synopsis
32216 -file-exec-and-symbols @var{file}
32219 Specify the executable file to be debugged. This file is the one from
32220 which the symbol table is also read. If no file is specified, the
32221 command clears the executable and symbol information. If breakpoints
32222 are set when using this command with no arguments, @value{GDBN} will produce
32223 error messages. Otherwise, no output is produced, except a completion
32226 @subsubheading @value{GDBN} Command
32228 The corresponding @value{GDBN} command is @samp{file}.
32230 @subsubheading Example
32234 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32240 @subheading The @code{-file-exec-file} Command
32241 @findex -file-exec-file
32243 @subsubheading Synopsis
32246 -file-exec-file @var{file}
32249 Specify the executable file to be debugged. Unlike
32250 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32251 from this file. If used without argument, @value{GDBN} clears the information
32252 about the executable file. No output is produced, except a completion
32255 @subsubheading @value{GDBN} Command
32257 The corresponding @value{GDBN} command is @samp{exec-file}.
32259 @subsubheading Example
32263 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32270 @subheading The @code{-file-list-exec-sections} Command
32271 @findex -file-list-exec-sections
32273 @subsubheading Synopsis
32276 -file-list-exec-sections
32279 List the sections of the current executable file.
32281 @subsubheading @value{GDBN} Command
32283 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32284 information as this command. @code{gdbtk} has a corresponding command
32285 @samp{gdb_load_info}.
32287 @subsubheading Example
32292 @subheading The @code{-file-list-exec-source-file} Command
32293 @findex -file-list-exec-source-file
32295 @subsubheading Synopsis
32298 -file-list-exec-source-file
32301 List the line number, the current source file, and the absolute path
32302 to the current source file for the current executable. The macro
32303 information field has a value of @samp{1} or @samp{0} depending on
32304 whether or not the file includes preprocessor macro information.
32306 @subsubheading @value{GDBN} Command
32308 The @value{GDBN} equivalent is @samp{info source}
32310 @subsubheading Example
32314 123-file-list-exec-source-file
32315 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32320 @subheading The @code{-file-list-exec-source-files} Command
32321 @findex -file-list-exec-source-files
32323 @subsubheading Synopsis
32326 -file-list-exec-source-files
32329 List the source files for the current executable.
32331 It will always output both the filename and fullname (absolute file
32332 name) of a source file.
32334 @subsubheading @value{GDBN} Command
32336 The @value{GDBN} equivalent is @samp{info sources}.
32337 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32339 @subsubheading Example
32342 -file-list-exec-source-files
32344 @{file=foo.c,fullname=/home/foo.c@},
32345 @{file=/home/bar.c,fullname=/home/bar.c@},
32346 @{file=gdb_could_not_find_fullpath.c@}]
32350 @subheading The @code{-file-list-shared-libraries} Command
32351 @findex -file-list-shared-libraries
32353 @subsubheading Synopsis
32356 -file-list-shared-libraries [ @var{regexp} ]
32359 List the shared libraries in the program.
32360 With a regular expression @var{regexp}, only those libraries whose
32361 names match @var{regexp} are listed.
32363 @subsubheading @value{GDBN} Command
32365 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32366 have a similar meaning to the @code{=library-loaded} notification.
32367 The @code{ranges} field specifies the multiple segments belonging to this
32368 library. Each range has the following fields:
32372 The address defining the inclusive lower bound of the segment.
32374 The address defining the exclusive upper bound of the segment.
32377 @subsubheading Example
32380 -file-list-exec-source-files
32381 ^done,shared-libraries=[
32382 @{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"@}]@},
32383 @{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"@}]@}]
32389 @subheading The @code{-file-list-symbol-files} Command
32390 @findex -file-list-symbol-files
32392 @subsubheading Synopsis
32395 -file-list-symbol-files
32400 @subsubheading @value{GDBN} Command
32402 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32404 @subsubheading Example
32409 @subheading The @code{-file-symbol-file} Command
32410 @findex -file-symbol-file
32412 @subsubheading Synopsis
32415 -file-symbol-file @var{file}
32418 Read symbol table info from the specified @var{file} argument. When
32419 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32420 produced, except for a completion notification.
32422 @subsubheading @value{GDBN} Command
32424 The corresponding @value{GDBN} command is @samp{symbol-file}.
32426 @subsubheading Example
32430 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32436 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32437 @node GDB/MI Memory Overlay Commands
32438 @section @sc{gdb/mi} Memory Overlay Commands
32440 The memory overlay commands are not implemented.
32442 @c @subheading -overlay-auto
32444 @c @subheading -overlay-list-mapping-state
32446 @c @subheading -overlay-list-overlays
32448 @c @subheading -overlay-map
32450 @c @subheading -overlay-off
32452 @c @subheading -overlay-on
32454 @c @subheading -overlay-unmap
32456 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32457 @node GDB/MI Signal Handling Commands
32458 @section @sc{gdb/mi} Signal Handling Commands
32460 Signal handling commands are not implemented.
32462 @c @subheading -signal-handle
32464 @c @subheading -signal-list-handle-actions
32466 @c @subheading -signal-list-signal-types
32470 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32471 @node GDB/MI Target Manipulation
32472 @section @sc{gdb/mi} Target Manipulation Commands
32475 @subheading The @code{-target-attach} Command
32476 @findex -target-attach
32478 @subsubheading Synopsis
32481 -target-attach @var{pid} | @var{gid} | @var{file}
32484 Attach to a process @var{pid} or a file @var{file} outside of
32485 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32486 group, the id previously returned by
32487 @samp{-list-thread-groups --available} must be used.
32489 @subsubheading @value{GDBN} Command
32491 The corresponding @value{GDBN} command is @samp{attach}.
32493 @subsubheading Example
32497 =thread-created,id="1"
32498 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32504 @subheading The @code{-target-compare-sections} Command
32505 @findex -target-compare-sections
32507 @subsubheading Synopsis
32510 -target-compare-sections [ @var{section} ]
32513 Compare data of section @var{section} on target to the exec file.
32514 Without the argument, all sections are compared.
32516 @subsubheading @value{GDBN} Command
32518 The @value{GDBN} equivalent is @samp{compare-sections}.
32520 @subsubheading Example
32525 @subheading The @code{-target-detach} Command
32526 @findex -target-detach
32528 @subsubheading Synopsis
32531 -target-detach [ @var{pid} | @var{gid} ]
32534 Detach from the remote target which normally resumes its execution.
32535 If either @var{pid} or @var{gid} is specified, detaches from either
32536 the specified process, or specified thread group. There's no output.
32538 @subsubheading @value{GDBN} Command
32540 The corresponding @value{GDBN} command is @samp{detach}.
32542 @subsubheading Example
32552 @subheading The @code{-target-disconnect} Command
32553 @findex -target-disconnect
32555 @subsubheading Synopsis
32561 Disconnect from the remote target. There's no output and the target is
32562 generally not resumed.
32564 @subsubheading @value{GDBN} Command
32566 The corresponding @value{GDBN} command is @samp{disconnect}.
32568 @subsubheading Example
32578 @subheading The @code{-target-download} Command
32579 @findex -target-download
32581 @subsubheading Synopsis
32587 Loads the executable onto the remote target.
32588 It prints out an update message every half second, which includes the fields:
32592 The name of the section.
32594 The size of what has been sent so far for that section.
32596 The size of the section.
32598 The total size of what was sent so far (the current and the previous sections).
32600 The size of the overall executable to download.
32604 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32605 @sc{gdb/mi} Output Syntax}).
32607 In addition, it prints the name and size of the sections, as they are
32608 downloaded. These messages include the following fields:
32612 The name of the section.
32614 The size of the section.
32616 The size of the overall executable to download.
32620 At the end, a summary is printed.
32622 @subsubheading @value{GDBN} Command
32624 The corresponding @value{GDBN} command is @samp{load}.
32626 @subsubheading Example
32628 Note: each status message appears on a single line. Here the messages
32629 have been broken down so that they can fit onto a page.
32634 +download,@{section=".text",section-size="6668",total-size="9880"@}
32635 +download,@{section=".text",section-sent="512",section-size="6668",
32636 total-sent="512",total-size="9880"@}
32637 +download,@{section=".text",section-sent="1024",section-size="6668",
32638 total-sent="1024",total-size="9880"@}
32639 +download,@{section=".text",section-sent="1536",section-size="6668",
32640 total-sent="1536",total-size="9880"@}
32641 +download,@{section=".text",section-sent="2048",section-size="6668",
32642 total-sent="2048",total-size="9880"@}
32643 +download,@{section=".text",section-sent="2560",section-size="6668",
32644 total-sent="2560",total-size="9880"@}
32645 +download,@{section=".text",section-sent="3072",section-size="6668",
32646 total-sent="3072",total-size="9880"@}
32647 +download,@{section=".text",section-sent="3584",section-size="6668",
32648 total-sent="3584",total-size="9880"@}
32649 +download,@{section=".text",section-sent="4096",section-size="6668",
32650 total-sent="4096",total-size="9880"@}
32651 +download,@{section=".text",section-sent="4608",section-size="6668",
32652 total-sent="4608",total-size="9880"@}
32653 +download,@{section=".text",section-sent="5120",section-size="6668",
32654 total-sent="5120",total-size="9880"@}
32655 +download,@{section=".text",section-sent="5632",section-size="6668",
32656 total-sent="5632",total-size="9880"@}
32657 +download,@{section=".text",section-sent="6144",section-size="6668",
32658 total-sent="6144",total-size="9880"@}
32659 +download,@{section=".text",section-sent="6656",section-size="6668",
32660 total-sent="6656",total-size="9880"@}
32661 +download,@{section=".init",section-size="28",total-size="9880"@}
32662 +download,@{section=".fini",section-size="28",total-size="9880"@}
32663 +download,@{section=".data",section-size="3156",total-size="9880"@}
32664 +download,@{section=".data",section-sent="512",section-size="3156",
32665 total-sent="7236",total-size="9880"@}
32666 +download,@{section=".data",section-sent="1024",section-size="3156",
32667 total-sent="7748",total-size="9880"@}
32668 +download,@{section=".data",section-sent="1536",section-size="3156",
32669 total-sent="8260",total-size="9880"@}
32670 +download,@{section=".data",section-sent="2048",section-size="3156",
32671 total-sent="8772",total-size="9880"@}
32672 +download,@{section=".data",section-sent="2560",section-size="3156",
32673 total-sent="9284",total-size="9880"@}
32674 +download,@{section=".data",section-sent="3072",section-size="3156",
32675 total-sent="9796",total-size="9880"@}
32676 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32683 @subheading The @code{-target-exec-status} Command
32684 @findex -target-exec-status
32686 @subsubheading Synopsis
32689 -target-exec-status
32692 Provide information on the state of the target (whether it is running or
32693 not, for instance).
32695 @subsubheading @value{GDBN} Command
32697 There's no equivalent @value{GDBN} command.
32699 @subsubheading Example
32703 @subheading The @code{-target-list-available-targets} Command
32704 @findex -target-list-available-targets
32706 @subsubheading Synopsis
32709 -target-list-available-targets
32712 List the possible targets to connect to.
32714 @subsubheading @value{GDBN} Command
32716 The corresponding @value{GDBN} command is @samp{help target}.
32718 @subsubheading Example
32722 @subheading The @code{-target-list-current-targets} Command
32723 @findex -target-list-current-targets
32725 @subsubheading Synopsis
32728 -target-list-current-targets
32731 Describe the current target.
32733 @subsubheading @value{GDBN} Command
32735 The corresponding information is printed by @samp{info file} (among
32738 @subsubheading Example
32742 @subheading The @code{-target-list-parameters} Command
32743 @findex -target-list-parameters
32745 @subsubheading Synopsis
32748 -target-list-parameters
32754 @subsubheading @value{GDBN} Command
32758 @subsubheading Example
32761 @subheading The @code{-target-flash-erase} Command
32762 @findex -target-flash-erase
32764 @subsubheading Synopsis
32767 -target-flash-erase
32770 Erases all known flash memory regions on the target.
32772 The corresponding @value{GDBN} command is @samp{flash-erase}.
32774 The output is a list of flash regions that have been erased, with starting
32775 addresses and memory region sizes.
32779 -target-flash-erase
32780 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32784 @subheading The @code{-target-select} Command
32785 @findex -target-select
32787 @subsubheading Synopsis
32790 -target-select @var{type} @var{parameters @dots{}}
32793 Connect @value{GDBN} to the remote target. This command takes two args:
32797 The type of target, for instance @samp{remote}, etc.
32798 @item @var{parameters}
32799 Device names, host names and the like. @xref{Target Commands, ,
32800 Commands for Managing Targets}, for more details.
32803 The output is a connection notification, followed by the address at
32804 which the target program is, in the following form:
32807 ^connected,addr="@var{address}",func="@var{function name}",
32808 args=[@var{arg list}]
32811 @subsubheading @value{GDBN} Command
32813 The corresponding @value{GDBN} command is @samp{target}.
32815 @subsubheading Example
32819 -target-select remote /dev/ttya
32820 ^connected,addr="0xfe00a300",func="??",args=[]
32824 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32825 @node GDB/MI File Transfer Commands
32826 @section @sc{gdb/mi} File Transfer Commands
32829 @subheading The @code{-target-file-put} Command
32830 @findex -target-file-put
32832 @subsubheading Synopsis
32835 -target-file-put @var{hostfile} @var{targetfile}
32838 Copy file @var{hostfile} from the host system (the machine running
32839 @value{GDBN}) to @var{targetfile} on the target system.
32841 @subsubheading @value{GDBN} Command
32843 The corresponding @value{GDBN} command is @samp{remote put}.
32845 @subsubheading Example
32849 -target-file-put localfile remotefile
32855 @subheading The @code{-target-file-get} Command
32856 @findex -target-file-get
32858 @subsubheading Synopsis
32861 -target-file-get @var{targetfile} @var{hostfile}
32864 Copy file @var{targetfile} from the target system to @var{hostfile}
32865 on the host system.
32867 @subsubheading @value{GDBN} Command
32869 The corresponding @value{GDBN} command is @samp{remote get}.
32871 @subsubheading Example
32875 -target-file-get remotefile localfile
32881 @subheading The @code{-target-file-delete} Command
32882 @findex -target-file-delete
32884 @subsubheading Synopsis
32887 -target-file-delete @var{targetfile}
32890 Delete @var{targetfile} from the target system.
32892 @subsubheading @value{GDBN} Command
32894 The corresponding @value{GDBN} command is @samp{remote delete}.
32896 @subsubheading Example
32900 -target-file-delete remotefile
32906 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32907 @node GDB/MI Ada Exceptions Commands
32908 @section Ada Exceptions @sc{gdb/mi} Commands
32910 @subheading The @code{-info-ada-exceptions} Command
32911 @findex -info-ada-exceptions
32913 @subsubheading Synopsis
32916 -info-ada-exceptions [ @var{regexp}]
32919 List all Ada exceptions defined within the program being debugged.
32920 With a regular expression @var{regexp}, only those exceptions whose
32921 names match @var{regexp} are listed.
32923 @subsubheading @value{GDBN} Command
32925 The corresponding @value{GDBN} command is @samp{info exceptions}.
32927 @subsubheading Result
32929 The result is a table of Ada exceptions. The following columns are
32930 defined for each exception:
32934 The name of the exception.
32937 The address of the exception.
32941 @subsubheading Example
32944 -info-ada-exceptions aint
32945 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32946 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32947 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32948 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32949 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32952 @subheading Catching Ada Exceptions
32954 The commands describing how to ask @value{GDBN} to stop when a program
32955 raises an exception are described at @ref{Ada Exception GDB/MI
32956 Catchpoint Commands}.
32959 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32960 @node GDB/MI Support Commands
32961 @section @sc{gdb/mi} Support Commands
32963 Since new commands and features get regularly added to @sc{gdb/mi},
32964 some commands are available to help front-ends query the debugger
32965 about support for these capabilities. Similarly, it is also possible
32966 to query @value{GDBN} about target support of certain features.
32968 @subheading The @code{-info-gdb-mi-command} Command
32969 @cindex @code{-info-gdb-mi-command}
32970 @findex -info-gdb-mi-command
32972 @subsubheading Synopsis
32975 -info-gdb-mi-command @var{cmd_name}
32978 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32980 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32981 is technically not part of the command name (@pxref{GDB/MI Input
32982 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32983 for ease of use, this command also accepts the form with the leading
32986 @subsubheading @value{GDBN} Command
32988 There is no corresponding @value{GDBN} command.
32990 @subsubheading Result
32992 The result is a tuple. There is currently only one field:
32996 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32997 @code{"false"} otherwise.
33001 @subsubheading Example
33003 Here is an example where the @sc{gdb/mi} command does not exist:
33006 -info-gdb-mi-command unsupported-command
33007 ^done,command=@{exists="false"@}
33011 And here is an example where the @sc{gdb/mi} command is known
33015 -info-gdb-mi-command symbol-list-lines
33016 ^done,command=@{exists="true"@}
33019 @subheading The @code{-list-features} Command
33020 @findex -list-features
33021 @cindex supported @sc{gdb/mi} features, list
33023 Returns a list of particular features of the MI protocol that
33024 this version of gdb implements. A feature can be a command,
33025 or a new field in an output of some command, or even an
33026 important bugfix. While a frontend can sometimes detect presence
33027 of a feature at runtime, it is easier to perform detection at debugger
33030 The command returns a list of strings, with each string naming an
33031 available feature. Each returned string is just a name, it does not
33032 have any internal structure. The list of possible feature names
33038 (gdb) -list-features
33039 ^done,result=["feature1","feature2"]
33042 The current list of features is:
33045 @item frozen-varobjs
33046 Indicates support for the @code{-var-set-frozen} command, as well
33047 as possible presense of the @code{frozen} field in the output
33048 of @code{-varobj-create}.
33049 @item pending-breakpoints
33050 Indicates support for the @option{-f} option to the @code{-break-insert}
33053 Indicates Python scripting support, Python-based
33054 pretty-printing commands, and possible presence of the
33055 @samp{display_hint} field in the output of @code{-var-list-children}
33057 Indicates support for the @code{-thread-info} command.
33058 @item data-read-memory-bytes
33059 Indicates support for the @code{-data-read-memory-bytes} and the
33060 @code{-data-write-memory-bytes} commands.
33061 @item breakpoint-notifications
33062 Indicates that changes to breakpoints and breakpoints created via the
33063 CLI will be announced via async records.
33064 @item ada-task-info
33065 Indicates support for the @code{-ada-task-info} command.
33066 @item language-option
33067 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33068 option (@pxref{Context management}).
33069 @item info-gdb-mi-command
33070 Indicates support for the @code{-info-gdb-mi-command} command.
33071 @item undefined-command-error-code
33072 Indicates support for the "undefined-command" error code in error result
33073 records, produced when trying to execute an undefined @sc{gdb/mi} command
33074 (@pxref{GDB/MI Result Records}).
33075 @item exec-run-start-option
33076 Indicates that the @code{-exec-run} command supports the @option{--start}
33077 option (@pxref{GDB/MI Program Execution}).
33080 @subheading The @code{-list-target-features} Command
33081 @findex -list-target-features
33083 Returns a list of particular features that are supported by the
33084 target. Those features affect the permitted MI commands, but
33085 unlike the features reported by the @code{-list-features} command, the
33086 features depend on which target GDB is using at the moment. Whenever
33087 a target can change, due to commands such as @code{-target-select},
33088 @code{-target-attach} or @code{-exec-run}, the list of target features
33089 may change, and the frontend should obtain it again.
33093 (gdb) -list-target-features
33094 ^done,result=["async"]
33097 The current list of features is:
33101 Indicates that the target is capable of asynchronous command
33102 execution, which means that @value{GDBN} will accept further commands
33103 while the target is running.
33106 Indicates that the target is capable of reverse execution.
33107 @xref{Reverse Execution}, for more information.
33111 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33112 @node GDB/MI Miscellaneous Commands
33113 @section Miscellaneous @sc{gdb/mi} Commands
33115 @c @subheading -gdb-complete
33117 @subheading The @code{-gdb-exit} Command
33120 @subsubheading Synopsis
33126 Exit @value{GDBN} immediately.
33128 @subsubheading @value{GDBN} Command
33130 Approximately corresponds to @samp{quit}.
33132 @subsubheading Example
33142 @subheading The @code{-exec-abort} Command
33143 @findex -exec-abort
33145 @subsubheading Synopsis
33151 Kill the inferior running program.
33153 @subsubheading @value{GDBN} Command
33155 The corresponding @value{GDBN} command is @samp{kill}.
33157 @subsubheading Example
33162 @subheading The @code{-gdb-set} Command
33165 @subsubheading Synopsis
33171 Set an internal @value{GDBN} variable.
33172 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33174 @subsubheading @value{GDBN} Command
33176 The corresponding @value{GDBN} command is @samp{set}.
33178 @subsubheading Example
33188 @subheading The @code{-gdb-show} Command
33191 @subsubheading Synopsis
33197 Show the current value of a @value{GDBN} variable.
33199 @subsubheading @value{GDBN} Command
33201 The corresponding @value{GDBN} command is @samp{show}.
33203 @subsubheading Example
33212 @c @subheading -gdb-source
33215 @subheading The @code{-gdb-version} Command
33216 @findex -gdb-version
33218 @subsubheading Synopsis
33224 Show version information for @value{GDBN}. Used mostly in testing.
33226 @subsubheading @value{GDBN} Command
33228 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33229 default shows this information when you start an interactive session.
33231 @subsubheading Example
33233 @c This example modifies the actual output from GDB to avoid overfull
33239 ~Copyright 2000 Free Software Foundation, Inc.
33240 ~GDB is free software, covered by the GNU General Public License, and
33241 ~you are welcome to change it and/or distribute copies of it under
33242 ~ certain conditions.
33243 ~Type "show copying" to see the conditions.
33244 ~There is absolutely no warranty for GDB. Type "show warranty" for
33246 ~This GDB was configured as
33247 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33252 @subheading The @code{-list-thread-groups} Command
33253 @findex -list-thread-groups
33255 @subheading Synopsis
33258 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33261 Lists thread groups (@pxref{Thread groups}). When a single thread
33262 group is passed as the argument, lists the children of that group.
33263 When several thread group are passed, lists information about those
33264 thread groups. Without any parameters, lists information about all
33265 top-level thread groups.
33267 Normally, thread groups that are being debugged are reported.
33268 With the @samp{--available} option, @value{GDBN} reports thread groups
33269 available on the target.
33271 The output of this command may have either a @samp{threads} result or
33272 a @samp{groups} result. The @samp{thread} result has a list of tuples
33273 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33274 Information}). The @samp{groups} result has a list of tuples as value,
33275 each tuple describing a thread group. If top-level groups are
33276 requested (that is, no parameter is passed), or when several groups
33277 are passed, the output always has a @samp{groups} result. The format
33278 of the @samp{group} result is described below.
33280 To reduce the number of roundtrips it's possible to list thread groups
33281 together with their children, by passing the @samp{--recurse} option
33282 and the recursion depth. Presently, only recursion depth of 1 is
33283 permitted. If this option is present, then every reported thread group
33284 will also include its children, either as @samp{group} or
33285 @samp{threads} field.
33287 In general, any combination of option and parameters is permitted, with
33288 the following caveats:
33292 When a single thread group is passed, the output will typically
33293 be the @samp{threads} result. Because threads may not contain
33294 anything, the @samp{recurse} option will be ignored.
33297 When the @samp{--available} option is passed, limited information may
33298 be available. In particular, the list of threads of a process might
33299 be inaccessible. Further, specifying specific thread groups might
33300 not give any performance advantage over listing all thread groups.
33301 The frontend should assume that @samp{-list-thread-groups --available}
33302 is always an expensive operation and cache the results.
33306 The @samp{groups} result is a list of tuples, where each tuple may
33307 have the following fields:
33311 Identifier of the thread group. This field is always present.
33312 The identifier is an opaque string; frontends should not try to
33313 convert it to an integer, even though it might look like one.
33316 The type of the thread group. At present, only @samp{process} is a
33320 The target-specific process identifier. This field is only present
33321 for thread groups of type @samp{process} and only if the process exists.
33324 The exit code of this group's last exited thread, formatted in octal.
33325 This field is only present for thread groups of type @samp{process} and
33326 only if the process is not running.
33329 The number of children this thread group has. This field may be
33330 absent for an available thread group.
33333 This field has a list of tuples as value, each tuple describing a
33334 thread. It may be present if the @samp{--recurse} option is
33335 specified, and it's actually possible to obtain the threads.
33338 This field is a list of integers, each identifying a core that one
33339 thread of the group is running on. This field may be absent if
33340 such information is not available.
33343 The name of the executable file that corresponds to this thread group.
33344 The field is only present for thread groups of type @samp{process},
33345 and only if there is a corresponding executable file.
33349 @subheading Example
33353 -list-thread-groups
33354 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33355 -list-thread-groups 17
33356 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33357 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33358 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33359 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33360 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33361 -list-thread-groups --available
33362 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33363 -list-thread-groups --available --recurse 1
33364 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33365 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33366 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33367 -list-thread-groups --available --recurse 1 17 18
33368 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33369 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33370 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33373 @subheading The @code{-info-os} Command
33376 @subsubheading Synopsis
33379 -info-os [ @var{type} ]
33382 If no argument is supplied, the command returns a table of available
33383 operating-system-specific information types. If one of these types is
33384 supplied as an argument @var{type}, then the command returns a table
33385 of data of that type.
33387 The types of information available depend on the target operating
33390 @subsubheading @value{GDBN} Command
33392 The corresponding @value{GDBN} command is @samp{info os}.
33394 @subsubheading Example
33396 When run on a @sc{gnu}/Linux system, the output will look something
33402 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33403 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33404 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33405 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33406 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33408 item=@{col0="files",col1="Listing of all file descriptors",
33409 col2="File descriptors"@},
33410 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33411 col2="Kernel modules"@},
33412 item=@{col0="msg",col1="Listing of all message queues",
33413 col2="Message queues"@},
33414 item=@{col0="processes",col1="Listing of all processes",
33415 col2="Processes"@},
33416 item=@{col0="procgroups",col1="Listing of all process groups",
33417 col2="Process groups"@},
33418 item=@{col0="semaphores",col1="Listing of all semaphores",
33419 col2="Semaphores"@},
33420 item=@{col0="shm",col1="Listing of all shared-memory regions",
33421 col2="Shared-memory regions"@},
33422 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33424 item=@{col0="threads",col1="Listing of all threads",
33428 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33429 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33430 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33431 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33432 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33433 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33434 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33435 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33437 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33438 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33442 (Note that the MI output here includes a @code{"Title"} column that
33443 does not appear in command-line @code{info os}; this column is useful
33444 for MI clients that want to enumerate the types of data, such as in a
33445 popup menu, but is needless clutter on the command line, and
33446 @code{info os} omits it.)
33448 @subheading The @code{-add-inferior} Command
33449 @findex -add-inferior
33451 @subheading Synopsis
33457 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33458 inferior is not associated with any executable. Such association may
33459 be established with the @samp{-file-exec-and-symbols} command
33460 (@pxref{GDB/MI File Commands}). The command response has a single
33461 field, @samp{inferior}, whose value is the identifier of the
33462 thread group corresponding to the new inferior.
33464 @subheading Example
33469 ^done,inferior="i3"
33472 @subheading The @code{-interpreter-exec} Command
33473 @findex -interpreter-exec
33475 @subheading Synopsis
33478 -interpreter-exec @var{interpreter} @var{command}
33480 @anchor{-interpreter-exec}
33482 Execute the specified @var{command} in the given @var{interpreter}.
33484 @subheading @value{GDBN} Command
33486 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33488 @subheading Example
33492 -interpreter-exec console "break main"
33493 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33494 &"During symbol reading, bad structure-type format.\n"
33495 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33500 @subheading The @code{-inferior-tty-set} Command
33501 @findex -inferior-tty-set
33503 @subheading Synopsis
33506 -inferior-tty-set /dev/pts/1
33509 Set terminal for future runs of the program being debugged.
33511 @subheading @value{GDBN} Command
33513 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33515 @subheading Example
33519 -inferior-tty-set /dev/pts/1
33524 @subheading The @code{-inferior-tty-show} Command
33525 @findex -inferior-tty-show
33527 @subheading Synopsis
33533 Show terminal for future runs of program being debugged.
33535 @subheading @value{GDBN} Command
33537 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33539 @subheading Example
33543 -inferior-tty-set /dev/pts/1
33547 ^done,inferior_tty_terminal="/dev/pts/1"
33551 @subheading The @code{-enable-timings} Command
33552 @findex -enable-timings
33554 @subheading Synopsis
33557 -enable-timings [yes | no]
33560 Toggle the printing of the wallclock, user and system times for an MI
33561 command as a field in its output. This command is to help frontend
33562 developers optimize the performance of their code. No argument is
33563 equivalent to @samp{yes}.
33565 @subheading @value{GDBN} Command
33569 @subheading Example
33577 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33578 addr="0x080484ed",func="main",file="myprog.c",
33579 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33581 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33589 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33590 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33591 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33592 fullname="/home/nickrob/myprog.c",line="73"@}
33597 @chapter @value{GDBN} Annotations
33599 This chapter describes annotations in @value{GDBN}. Annotations were
33600 designed to interface @value{GDBN} to graphical user interfaces or other
33601 similar programs which want to interact with @value{GDBN} at a
33602 relatively high level.
33604 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33608 This is Edition @value{EDITION}, @value{DATE}.
33612 * Annotations Overview:: What annotations are; the general syntax.
33613 * Server Prefix:: Issuing a command without affecting user state.
33614 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33615 * Errors:: Annotations for error messages.
33616 * Invalidation:: Some annotations describe things now invalid.
33617 * Annotations for Running::
33618 Whether the program is running, how it stopped, etc.
33619 * Source Annotations:: Annotations describing source code.
33622 @node Annotations Overview
33623 @section What is an Annotation?
33624 @cindex annotations
33626 Annotations start with a newline character, two @samp{control-z}
33627 characters, and the name of the annotation. If there is no additional
33628 information associated with this annotation, the name of the annotation
33629 is followed immediately by a newline. If there is additional
33630 information, the name of the annotation is followed by a space, the
33631 additional information, and a newline. The additional information
33632 cannot contain newline characters.
33634 Any output not beginning with a newline and two @samp{control-z}
33635 characters denotes literal output from @value{GDBN}. Currently there is
33636 no need for @value{GDBN} to output a newline followed by two
33637 @samp{control-z} characters, but if there was such a need, the
33638 annotations could be extended with an @samp{escape} annotation which
33639 means those three characters as output.
33641 The annotation @var{level}, which is specified using the
33642 @option{--annotate} command line option (@pxref{Mode Options}), controls
33643 how much information @value{GDBN} prints together with its prompt,
33644 values of expressions, source lines, and other types of output. Level 0
33645 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33646 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33647 for programs that control @value{GDBN}, and level 2 annotations have
33648 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33649 Interface, annotate, GDB's Obsolete Annotations}).
33652 @kindex set annotate
33653 @item set annotate @var{level}
33654 The @value{GDBN} command @code{set annotate} sets the level of
33655 annotations to the specified @var{level}.
33657 @item show annotate
33658 @kindex show annotate
33659 Show the current annotation level.
33662 This chapter describes level 3 annotations.
33664 A simple example of starting up @value{GDBN} with annotations is:
33667 $ @kbd{gdb --annotate=3}
33669 Copyright 2003 Free Software Foundation, Inc.
33670 GDB is free software, covered by the GNU General Public License,
33671 and you are welcome to change it and/or distribute copies of it
33672 under certain conditions.
33673 Type "show copying" to see the conditions.
33674 There is absolutely no warranty for GDB. Type "show warranty"
33676 This GDB was configured as "i386-pc-linux-gnu"
33687 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33688 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33689 denotes a @samp{control-z} character) are annotations; the rest is
33690 output from @value{GDBN}.
33692 @node Server Prefix
33693 @section The Server Prefix
33694 @cindex server prefix
33696 If you prefix a command with @samp{server } then it will not affect
33697 the command history, nor will it affect @value{GDBN}'s notion of which
33698 command to repeat if @key{RET} is pressed on a line by itself. This
33699 means that commands can be run behind a user's back by a front-end in
33700 a transparent manner.
33702 The @code{server } prefix does not affect the recording of values into
33703 the value history; to print a value without recording it into the
33704 value history, use the @code{output} command instead of the
33705 @code{print} command.
33707 Using this prefix also disables confirmation requests
33708 (@pxref{confirmation requests}).
33711 @section Annotation for @value{GDBN} Input
33713 @cindex annotations for prompts
33714 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33715 to know when to send output, when the output from a given command is
33718 Different kinds of input each have a different @dfn{input type}. Each
33719 input type has three annotations: a @code{pre-} annotation, which
33720 denotes the beginning of any prompt which is being output, a plain
33721 annotation, which denotes the end of the prompt, and then a @code{post-}
33722 annotation which denotes the end of any echo which may (or may not) be
33723 associated with the input. For example, the @code{prompt} input type
33724 features the following annotations:
33732 The input types are
33735 @findex pre-prompt annotation
33736 @findex prompt annotation
33737 @findex post-prompt annotation
33739 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33741 @findex pre-commands annotation
33742 @findex commands annotation
33743 @findex post-commands annotation
33745 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33746 command. The annotations are repeated for each command which is input.
33748 @findex pre-overload-choice annotation
33749 @findex overload-choice annotation
33750 @findex post-overload-choice annotation
33751 @item overload-choice
33752 When @value{GDBN} wants the user to select between various overloaded functions.
33754 @findex pre-query annotation
33755 @findex query annotation
33756 @findex post-query annotation
33758 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33760 @findex pre-prompt-for-continue annotation
33761 @findex prompt-for-continue annotation
33762 @findex post-prompt-for-continue annotation
33763 @item prompt-for-continue
33764 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33765 expect this to work well; instead use @code{set height 0} to disable
33766 prompting. This is because the counting of lines is buggy in the
33767 presence of annotations.
33772 @cindex annotations for errors, warnings and interrupts
33774 @findex quit annotation
33779 This annotation occurs right before @value{GDBN} responds to an interrupt.
33781 @findex error annotation
33786 This annotation occurs right before @value{GDBN} responds to an error.
33788 Quit and error annotations indicate that any annotations which @value{GDBN} was
33789 in the middle of may end abruptly. For example, if a
33790 @code{value-history-begin} annotation is followed by a @code{error}, one
33791 cannot expect to receive the matching @code{value-history-end}. One
33792 cannot expect not to receive it either, however; an error annotation
33793 does not necessarily mean that @value{GDBN} is immediately returning all the way
33796 @findex error-begin annotation
33797 A quit or error annotation may be preceded by
33803 Any output between that and the quit or error annotation is the error
33806 Warning messages are not yet annotated.
33807 @c If we want to change that, need to fix warning(), type_error(),
33808 @c range_error(), and possibly other places.
33811 @section Invalidation Notices
33813 @cindex annotations for invalidation messages
33814 The following annotations say that certain pieces of state may have
33818 @findex frames-invalid annotation
33819 @item ^Z^Zframes-invalid
33821 The frames (for example, output from the @code{backtrace} command) may
33824 @findex breakpoints-invalid annotation
33825 @item ^Z^Zbreakpoints-invalid
33827 The breakpoints may have changed. For example, the user just added or
33828 deleted a breakpoint.
33831 @node Annotations for Running
33832 @section Running the Program
33833 @cindex annotations for running programs
33835 @findex starting annotation
33836 @findex stopping annotation
33837 When the program starts executing due to a @value{GDBN} command such as
33838 @code{step} or @code{continue},
33844 is output. When the program stops,
33850 is output. Before the @code{stopped} annotation, a variety of
33851 annotations describe how the program stopped.
33854 @findex exited annotation
33855 @item ^Z^Zexited @var{exit-status}
33856 The program exited, and @var{exit-status} is the exit status (zero for
33857 successful exit, otherwise nonzero).
33859 @findex signalled annotation
33860 @findex signal-name annotation
33861 @findex signal-name-end annotation
33862 @findex signal-string annotation
33863 @findex signal-string-end annotation
33864 @item ^Z^Zsignalled
33865 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33866 annotation continues:
33872 ^Z^Zsignal-name-end
33876 ^Z^Zsignal-string-end
33881 where @var{name} is the name of the signal, such as @code{SIGILL} or
33882 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33883 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33884 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33885 user's benefit and have no particular format.
33887 @findex signal annotation
33889 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33890 just saying that the program received the signal, not that it was
33891 terminated with it.
33893 @findex breakpoint annotation
33894 @item ^Z^Zbreakpoint @var{number}
33895 The program hit breakpoint number @var{number}.
33897 @findex watchpoint annotation
33898 @item ^Z^Zwatchpoint @var{number}
33899 The program hit watchpoint number @var{number}.
33902 @node Source Annotations
33903 @section Displaying Source
33904 @cindex annotations for source display
33906 @findex source annotation
33907 The following annotation is used instead of displaying source code:
33910 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33913 where @var{filename} is an absolute file name indicating which source
33914 file, @var{line} is the line number within that file (where 1 is the
33915 first line in the file), @var{character} is the character position
33916 within the file (where 0 is the first character in the file) (for most
33917 debug formats this will necessarily point to the beginning of a line),
33918 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33919 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33920 @var{addr} is the address in the target program associated with the
33921 source which is being displayed. The @var{addr} is in the form @samp{0x}
33922 followed by one or more lowercase hex digits (note that this does not
33923 depend on the language).
33925 @node JIT Interface
33926 @chapter JIT Compilation Interface
33927 @cindex just-in-time compilation
33928 @cindex JIT compilation interface
33930 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33931 interface. A JIT compiler is a program or library that generates native
33932 executable code at runtime and executes it, usually in order to achieve good
33933 performance while maintaining platform independence.
33935 Programs that use JIT compilation are normally difficult to debug because
33936 portions of their code are generated at runtime, instead of being loaded from
33937 object files, which is where @value{GDBN} normally finds the program's symbols
33938 and debug information. In order to debug programs that use JIT compilation,
33939 @value{GDBN} has an interface that allows the program to register in-memory
33940 symbol files with @value{GDBN} at runtime.
33942 If you are using @value{GDBN} to debug a program that uses this interface, then
33943 it should work transparently so long as you have not stripped the binary. If
33944 you are developing a JIT compiler, then the interface is documented in the rest
33945 of this chapter. At this time, the only known client of this interface is the
33948 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33949 JIT compiler communicates with @value{GDBN} by writing data into a global
33950 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33951 attaches, it reads a linked list of symbol files from the global variable to
33952 find existing code, and puts a breakpoint in the function so that it can find
33953 out about additional code.
33956 * Declarations:: Relevant C struct declarations
33957 * Registering Code:: Steps to register code
33958 * Unregistering Code:: Steps to unregister code
33959 * Custom Debug Info:: Emit debug information in a custom format
33963 @section JIT Declarations
33965 These are the relevant struct declarations that a C program should include to
33966 implement the interface:
33976 struct jit_code_entry
33978 struct jit_code_entry *next_entry;
33979 struct jit_code_entry *prev_entry;
33980 const char *symfile_addr;
33981 uint64_t symfile_size;
33984 struct jit_descriptor
33987 /* This type should be jit_actions_t, but we use uint32_t
33988 to be explicit about the bitwidth. */
33989 uint32_t action_flag;
33990 struct jit_code_entry *relevant_entry;
33991 struct jit_code_entry *first_entry;
33994 /* GDB puts a breakpoint in this function. */
33995 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33997 /* Make sure to specify the version statically, because the
33998 debugger may check the version before we can set it. */
33999 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34002 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34003 modifications to this global data properly, which can easily be done by putting
34004 a global mutex around modifications to these structures.
34006 @node Registering Code
34007 @section Registering Code
34009 To register code with @value{GDBN}, the JIT should follow this protocol:
34013 Generate an object file in memory with symbols and other desired debug
34014 information. The file must include the virtual addresses of the sections.
34017 Create a code entry for the file, which gives the start and size of the symbol
34021 Add it to the linked list in the JIT descriptor.
34024 Point the relevant_entry field of the descriptor at the entry.
34027 Set @code{action_flag} to @code{JIT_REGISTER} and call
34028 @code{__jit_debug_register_code}.
34031 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34032 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34033 new code. However, the linked list must still be maintained in order to allow
34034 @value{GDBN} to attach to a running process and still find the symbol files.
34036 @node Unregistering Code
34037 @section Unregistering Code
34039 If code is freed, then the JIT should use the following protocol:
34043 Remove the code entry corresponding to the code from the linked list.
34046 Point the @code{relevant_entry} field of the descriptor at the code entry.
34049 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34050 @code{__jit_debug_register_code}.
34053 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34054 and the JIT will leak the memory used for the associated symbol files.
34056 @node Custom Debug Info
34057 @section Custom Debug Info
34058 @cindex custom JIT debug info
34059 @cindex JIT debug info reader
34061 Generating debug information in platform-native file formats (like ELF
34062 or COFF) may be an overkill for JIT compilers; especially if all the
34063 debug info is used for is displaying a meaningful backtrace. The
34064 issue can be resolved by having the JIT writers decide on a debug info
34065 format and also provide a reader that parses the debug info generated
34066 by the JIT compiler. This section gives a brief overview on writing
34067 such a parser. More specific details can be found in the source file
34068 @file{gdb/jit-reader.in}, which is also installed as a header at
34069 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34071 The reader is implemented as a shared object (so this functionality is
34072 not available on platforms which don't allow loading shared objects at
34073 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34074 @code{jit-reader-unload} are provided, to be used to load and unload
34075 the readers from a preconfigured directory. Once loaded, the shared
34076 object is used the parse the debug information emitted by the JIT
34080 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34081 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34084 @node Using JIT Debug Info Readers
34085 @subsection Using JIT Debug Info Readers
34086 @kindex jit-reader-load
34087 @kindex jit-reader-unload
34089 Readers can be loaded and unloaded using the @code{jit-reader-load}
34090 and @code{jit-reader-unload} commands.
34093 @item jit-reader-load @var{reader}
34094 Load the JIT reader named @var{reader}, which is a shared
34095 object specified as either an absolute or a relative file name. In
34096 the latter case, @value{GDBN} will try to load the reader from a
34097 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34098 system (here @var{libdir} is the system library directory, often
34099 @file{/usr/local/lib}).
34101 Only one reader can be active at a time; trying to load a second
34102 reader when one is already loaded will result in @value{GDBN}
34103 reporting an error. A new JIT reader can be loaded by first unloading
34104 the current one using @code{jit-reader-unload} and then invoking
34105 @code{jit-reader-load}.
34107 @item jit-reader-unload
34108 Unload the currently loaded JIT reader.
34112 @node Writing JIT Debug Info Readers
34113 @subsection Writing JIT Debug Info Readers
34114 @cindex writing JIT debug info readers
34116 As mentioned, a reader is essentially a shared object conforming to a
34117 certain ABI. This ABI is described in @file{jit-reader.h}.
34119 @file{jit-reader.h} defines the structures, macros and functions
34120 required to write a reader. It is installed (along with
34121 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34122 the system include directory.
34124 Readers need to be released under a GPL compatible license. A reader
34125 can be declared as released under such a license by placing the macro
34126 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34128 The entry point for readers is the symbol @code{gdb_init_reader},
34129 which is expected to be a function with the prototype
34131 @findex gdb_init_reader
34133 extern struct gdb_reader_funcs *gdb_init_reader (void);
34136 @cindex @code{struct gdb_reader_funcs}
34138 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34139 functions. These functions are executed to read the debug info
34140 generated by the JIT compiler (@code{read}), to unwind stack frames
34141 (@code{unwind}) and to create canonical frame IDs
34142 (@code{get_Frame_id}). It also has a callback that is called when the
34143 reader is being unloaded (@code{destroy}). The struct looks like this
34146 struct gdb_reader_funcs
34148 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34149 int reader_version;
34151 /* For use by the reader. */
34154 gdb_read_debug_info *read;
34155 gdb_unwind_frame *unwind;
34156 gdb_get_frame_id *get_frame_id;
34157 gdb_destroy_reader *destroy;
34161 @cindex @code{struct gdb_symbol_callbacks}
34162 @cindex @code{struct gdb_unwind_callbacks}
34164 The callbacks are provided with another set of callbacks by
34165 @value{GDBN} to do their job. For @code{read}, these callbacks are
34166 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34167 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34168 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34169 files and new symbol tables inside those object files. @code{struct
34170 gdb_unwind_callbacks} has callbacks to read registers off the current
34171 frame and to write out the values of the registers in the previous
34172 frame. Both have a callback (@code{target_read}) to read bytes off the
34173 target's address space.
34175 @node In-Process Agent
34176 @chapter In-Process Agent
34177 @cindex debugging agent
34178 The traditional debugging model is conceptually low-speed, but works fine,
34179 because most bugs can be reproduced in debugging-mode execution. However,
34180 as multi-core or many-core processors are becoming mainstream, and
34181 multi-threaded programs become more and more popular, there should be more
34182 and more bugs that only manifest themselves at normal-mode execution, for
34183 example, thread races, because debugger's interference with the program's
34184 timing may conceal the bugs. On the other hand, in some applications,
34185 it is not feasible for the debugger to interrupt the program's execution
34186 long enough for the developer to learn anything helpful about its behavior.
34187 If the program's correctness depends on its real-time behavior, delays
34188 introduced by a debugger might cause the program to fail, even when the
34189 code itself is correct. It is useful to be able to observe the program's
34190 behavior without interrupting it.
34192 Therefore, traditional debugging model is too intrusive to reproduce
34193 some bugs. In order to reduce the interference with the program, we can
34194 reduce the number of operations performed by debugger. The
34195 @dfn{In-Process Agent}, a shared library, is running within the same
34196 process with inferior, and is able to perform some debugging operations
34197 itself. As a result, debugger is only involved when necessary, and
34198 performance of debugging can be improved accordingly. Note that
34199 interference with program can be reduced but can't be removed completely,
34200 because the in-process agent will still stop or slow down the program.
34202 The in-process agent can interpret and execute Agent Expressions
34203 (@pxref{Agent Expressions}) during performing debugging operations. The
34204 agent expressions can be used for different purposes, such as collecting
34205 data in tracepoints, and condition evaluation in breakpoints.
34207 @anchor{Control Agent}
34208 You can control whether the in-process agent is used as an aid for
34209 debugging with the following commands:
34212 @kindex set agent on
34214 Causes the in-process agent to perform some operations on behalf of the
34215 debugger. Just which operations requested by the user will be done
34216 by the in-process agent depends on the its capabilities. For example,
34217 if you request to evaluate breakpoint conditions in the in-process agent,
34218 and the in-process agent has such capability as well, then breakpoint
34219 conditions will be evaluated in the in-process agent.
34221 @kindex set agent off
34222 @item set agent off
34223 Disables execution of debugging operations by the in-process agent. All
34224 of the operations will be performed by @value{GDBN}.
34228 Display the current setting of execution of debugging operations by
34229 the in-process agent.
34233 * In-Process Agent Protocol::
34236 @node In-Process Agent Protocol
34237 @section In-Process Agent Protocol
34238 @cindex in-process agent protocol
34240 The in-process agent is able to communicate with both @value{GDBN} and
34241 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34242 used for communications between @value{GDBN} or GDBserver and the IPA.
34243 In general, @value{GDBN} or GDBserver sends commands
34244 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34245 in-process agent replies back with the return result of the command, or
34246 some other information. The data sent to in-process agent is composed
34247 of primitive data types, such as 4-byte or 8-byte type, and composite
34248 types, which are called objects (@pxref{IPA Protocol Objects}).
34251 * IPA Protocol Objects::
34252 * IPA Protocol Commands::
34255 @node IPA Protocol Objects
34256 @subsection IPA Protocol Objects
34257 @cindex ipa protocol objects
34259 The commands sent to and results received from agent may contain some
34260 complex data types called @dfn{objects}.
34262 The in-process agent is running on the same machine with @value{GDBN}
34263 or GDBserver, so it doesn't have to handle as much differences between
34264 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34265 However, there are still some differences of two ends in two processes:
34269 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34270 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34272 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34273 GDBserver is compiled with one, and in-process agent is compiled with
34277 Here are the IPA Protocol Objects:
34281 agent expression object. It represents an agent expression
34282 (@pxref{Agent Expressions}).
34283 @anchor{agent expression object}
34285 tracepoint action object. It represents a tracepoint action
34286 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34287 memory, static trace data and to evaluate expression.
34288 @anchor{tracepoint action object}
34290 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34291 @anchor{tracepoint object}
34295 The following table describes important attributes of each IPA protocol
34298 @multitable @columnfractions .30 .20 .50
34299 @headitem Name @tab Size @tab Description
34300 @item @emph{agent expression object} @tab @tab
34301 @item length @tab 4 @tab length of bytes code
34302 @item byte code @tab @var{length} @tab contents of byte code
34303 @item @emph{tracepoint action for collecting memory} @tab @tab
34304 @item 'M' @tab 1 @tab type of tracepoint action
34305 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34306 address of the lowest byte to collect, otherwise @var{addr} is the offset
34307 of @var{basereg} for memory collecting.
34308 @item len @tab 8 @tab length of memory for collecting
34309 @item basereg @tab 4 @tab the register number containing the starting
34310 memory address for collecting.
34311 @item @emph{tracepoint action for collecting registers} @tab @tab
34312 @item 'R' @tab 1 @tab type of tracepoint action
34313 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34314 @item 'L' @tab 1 @tab type of tracepoint action
34315 @item @emph{tracepoint action for expression evaluation} @tab @tab
34316 @item 'X' @tab 1 @tab type of tracepoint action
34317 @item agent expression @tab length of @tab @ref{agent expression object}
34318 @item @emph{tracepoint object} @tab @tab
34319 @item number @tab 4 @tab number of tracepoint
34320 @item address @tab 8 @tab address of tracepoint inserted on
34321 @item type @tab 4 @tab type of tracepoint
34322 @item enabled @tab 1 @tab enable or disable of tracepoint
34323 @item step_count @tab 8 @tab step
34324 @item pass_count @tab 8 @tab pass
34325 @item numactions @tab 4 @tab number of tracepoint actions
34326 @item hit count @tab 8 @tab hit count
34327 @item trace frame usage @tab 8 @tab trace frame usage
34328 @item compiled_cond @tab 8 @tab compiled condition
34329 @item orig_size @tab 8 @tab orig size
34330 @item condition @tab 4 if condition is NULL otherwise length of
34331 @ref{agent expression object}
34332 @tab zero if condition is NULL, otherwise is
34333 @ref{agent expression object}
34334 @item actions @tab variable
34335 @tab numactions number of @ref{tracepoint action object}
34338 @node IPA Protocol Commands
34339 @subsection IPA Protocol Commands
34340 @cindex ipa protocol commands
34342 The spaces in each command are delimiters to ease reading this commands
34343 specification. They don't exist in real commands.
34347 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34348 Installs a new fast tracepoint described by @var{tracepoint_object}
34349 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34350 head of @dfn{jumppad}, which is used to jump to data collection routine
34355 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34356 @var{target_address} is address of tracepoint in the inferior.
34357 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34358 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34359 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34360 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34367 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34368 is about to kill inferiors.
34376 @item probe_marker_at:@var{address}
34377 Asks in-process agent to probe the marker at @var{address}.
34384 @item unprobe_marker_at:@var{address}
34385 Asks in-process agent to unprobe the marker at @var{address}.
34389 @chapter Reporting Bugs in @value{GDBN}
34390 @cindex bugs in @value{GDBN}
34391 @cindex reporting bugs in @value{GDBN}
34393 Your bug reports play an essential role in making @value{GDBN} reliable.
34395 Reporting a bug may help you by bringing a solution to your problem, or it
34396 may not. But in any case the principal function of a bug report is to help
34397 the entire community by making the next version of @value{GDBN} work better. Bug
34398 reports are your contribution to the maintenance of @value{GDBN}.
34400 In order for a bug report to serve its purpose, you must include the
34401 information that enables us to fix the bug.
34404 * Bug Criteria:: Have you found a bug?
34405 * Bug Reporting:: How to report bugs
34409 @section Have You Found a Bug?
34410 @cindex bug criteria
34412 If you are not sure whether you have found a bug, here are some guidelines:
34415 @cindex fatal signal
34416 @cindex debugger crash
34417 @cindex crash of debugger
34419 If the debugger gets a fatal signal, for any input whatever, that is a
34420 @value{GDBN} bug. Reliable debuggers never crash.
34422 @cindex error on valid input
34424 If @value{GDBN} produces an error message for valid input, that is a
34425 bug. (Note that if you're cross debugging, the problem may also be
34426 somewhere in the connection to the target.)
34428 @cindex invalid input
34430 If @value{GDBN} does not produce an error message for invalid input,
34431 that is a bug. However, you should note that your idea of
34432 ``invalid input'' might be our idea of ``an extension'' or ``support
34433 for traditional practice''.
34436 If you are an experienced user of debugging tools, your suggestions
34437 for improvement of @value{GDBN} are welcome in any case.
34440 @node Bug Reporting
34441 @section How to Report Bugs
34442 @cindex bug reports
34443 @cindex @value{GDBN} bugs, reporting
34445 A number of companies and individuals offer support for @sc{gnu} products.
34446 If you obtained @value{GDBN} from a support organization, we recommend you
34447 contact that organization first.
34449 You can find contact information for many support companies and
34450 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34452 @c should add a web page ref...
34455 @ifset BUGURL_DEFAULT
34456 In any event, we also recommend that you submit bug reports for
34457 @value{GDBN}. The preferred method is to submit them directly using
34458 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34459 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34462 @strong{Do not send bug reports to @samp{info-gdb}, or to
34463 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34464 not want to receive bug reports. Those that do have arranged to receive
34467 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34468 serves as a repeater. The mailing list and the newsgroup carry exactly
34469 the same messages. Often people think of posting bug reports to the
34470 newsgroup instead of mailing them. This appears to work, but it has one
34471 problem which can be crucial: a newsgroup posting often lacks a mail
34472 path back to the sender. Thus, if we need to ask for more information,
34473 we may be unable to reach you. For this reason, it is better to send
34474 bug reports to the mailing list.
34476 @ifclear BUGURL_DEFAULT
34477 In any event, we also recommend that you submit bug reports for
34478 @value{GDBN} to @value{BUGURL}.
34482 The fundamental principle of reporting bugs usefully is this:
34483 @strong{report all the facts}. If you are not sure whether to state a
34484 fact or leave it out, state it!
34486 Often people omit facts because they think they know what causes the
34487 problem and assume that some details do not matter. Thus, you might
34488 assume that the name of the variable you use in an example does not matter.
34489 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34490 stray memory reference which happens to fetch from the location where that
34491 name is stored in memory; perhaps, if the name were different, the contents
34492 of that location would fool the debugger into doing the right thing despite
34493 the bug. Play it safe and give a specific, complete example. That is the
34494 easiest thing for you to do, and the most helpful.
34496 Keep in mind that the purpose of a bug report is to enable us to fix the
34497 bug. It may be that the bug has been reported previously, but neither
34498 you nor we can know that unless your bug report is complete and
34501 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34502 bell?'' Those bug reports are useless, and we urge everyone to
34503 @emph{refuse to respond to them} except to chide the sender to report
34506 To enable us to fix the bug, you should include all these things:
34510 The version of @value{GDBN}. @value{GDBN} announces it if you start
34511 with no arguments; you can also print it at any time using @code{show
34514 Without this, we will not know whether there is any point in looking for
34515 the bug in the current version of @value{GDBN}.
34518 The type of machine you are using, and the operating system name and
34522 The details of the @value{GDBN} build-time configuration.
34523 @value{GDBN} shows these details if you invoke it with the
34524 @option{--configuration} command-line option, or if you type
34525 @code{show configuration} at @value{GDBN}'s prompt.
34528 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34529 ``@value{GCC}--2.8.1''.
34532 What compiler (and its version) was used to compile the program you are
34533 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34534 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34535 to get this information; for other compilers, see the documentation for
34539 The command arguments you gave the compiler to compile your example and
34540 observe the bug. For example, did you use @samp{-O}? To guarantee
34541 you will not omit something important, list them all. A copy of the
34542 Makefile (or the output from make) is sufficient.
34544 If we were to try to guess the arguments, we would probably guess wrong
34545 and then we might not encounter the bug.
34548 A complete input script, and all necessary source files, that will
34552 A description of what behavior you observe that you believe is
34553 incorrect. For example, ``It gets a fatal signal.''
34555 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34556 will certainly notice it. But if the bug is incorrect output, we might
34557 not notice unless it is glaringly wrong. You might as well not give us
34558 a chance to make a mistake.
34560 Even if the problem you experience is a fatal signal, you should still
34561 say so explicitly. Suppose something strange is going on, such as, your
34562 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34563 the C library on your system. (This has happened!) Your copy might
34564 crash and ours would not. If you told us to expect a crash, then when
34565 ours fails to crash, we would know that the bug was not happening for
34566 us. If you had not told us to expect a crash, then we would not be able
34567 to draw any conclusion from our observations.
34570 @cindex recording a session script
34571 To collect all this information, you can use a session recording program
34572 such as @command{script}, which is available on many Unix systems.
34573 Just run your @value{GDBN} session inside @command{script} and then
34574 include the @file{typescript} file with your bug report.
34576 Another way to record a @value{GDBN} session is to run @value{GDBN}
34577 inside Emacs and then save the entire buffer to a file.
34580 If you wish to suggest changes to the @value{GDBN} source, send us context
34581 diffs. If you even discuss something in the @value{GDBN} source, refer to
34582 it by context, not by line number.
34584 The line numbers in our development sources will not match those in your
34585 sources. Your line numbers would convey no useful information to us.
34589 Here are some things that are not necessary:
34593 A description of the envelope of the bug.
34595 Often people who encounter a bug spend a lot of time investigating
34596 which changes to the input file will make the bug go away and which
34597 changes will not affect it.
34599 This is often time consuming and not very useful, because the way we
34600 will find the bug is by running a single example under the debugger
34601 with breakpoints, not by pure deduction from a series of examples.
34602 We recommend that you save your time for something else.
34604 Of course, if you can find a simpler example to report @emph{instead}
34605 of the original one, that is a convenience for us. Errors in the
34606 output will be easier to spot, running under the debugger will take
34607 less time, and so on.
34609 However, simplification is not vital; if you do not want to do this,
34610 report the bug anyway and send us the entire test case you used.
34613 A patch for the bug.
34615 A patch for the bug does help us if it is a good one. But do not omit
34616 the necessary information, such as the test case, on the assumption that
34617 a patch is all we need. We might see problems with your patch and decide
34618 to fix the problem another way, or we might not understand it at all.
34620 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34621 construct an example that will make the program follow a certain path
34622 through the code. If you do not send us the example, we will not be able
34623 to construct one, so we will not be able to verify that the bug is fixed.
34625 And if we cannot understand what bug you are trying to fix, or why your
34626 patch should be an improvement, we will not install it. A test case will
34627 help us to understand.
34630 A guess about what the bug is or what it depends on.
34632 Such guesses are usually wrong. Even we cannot guess right about such
34633 things without first using the debugger to find the facts.
34636 @c The readline documentation is distributed with the readline code
34637 @c and consists of the two following files:
34640 @c Use -I with makeinfo to point to the appropriate directory,
34641 @c environment var TEXINPUTS with TeX.
34642 @ifclear SYSTEM_READLINE
34643 @include rluser.texi
34644 @include hsuser.texi
34648 @appendix In Memoriam
34650 The @value{GDBN} project mourns the loss of the following long-time
34655 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34656 to Free Software in general. Outside of @value{GDBN}, he was known in
34657 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34659 @item Michael Snyder
34660 Michael was one of the Global Maintainers of the @value{GDBN} project,
34661 with contributions recorded as early as 1996, until 2011. In addition
34662 to his day to day participation, he was a large driving force behind
34663 adding Reverse Debugging to @value{GDBN}.
34666 Beyond their technical contributions to the project, they were also
34667 enjoyable members of the Free Software Community. We will miss them.
34669 @node Formatting Documentation
34670 @appendix Formatting Documentation
34672 @cindex @value{GDBN} reference card
34673 @cindex reference card
34674 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34675 for printing with PostScript or Ghostscript, in the @file{gdb}
34676 subdirectory of the main source directory@footnote{In
34677 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34678 release.}. If you can use PostScript or Ghostscript with your printer,
34679 you can print the reference card immediately with @file{refcard.ps}.
34681 The release also includes the source for the reference card. You
34682 can format it, using @TeX{}, by typing:
34688 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34689 mode on US ``letter'' size paper;
34690 that is, on a sheet 11 inches wide by 8.5 inches
34691 high. You will need to specify this form of printing as an option to
34692 your @sc{dvi} output program.
34694 @cindex documentation
34696 All the documentation for @value{GDBN} comes as part of the machine-readable
34697 distribution. The documentation is written in Texinfo format, which is
34698 a documentation system that uses a single source file to produce both
34699 on-line information and a printed manual. You can use one of the Info
34700 formatting commands to create the on-line version of the documentation
34701 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34703 @value{GDBN} includes an already formatted copy of the on-line Info
34704 version of this manual in the @file{gdb} subdirectory. The main Info
34705 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34706 subordinate files matching @samp{gdb.info*} in the same directory. If
34707 necessary, you can print out these files, or read them with any editor;
34708 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34709 Emacs or the standalone @code{info} program, available as part of the
34710 @sc{gnu} Texinfo distribution.
34712 If you want to format these Info files yourself, you need one of the
34713 Info formatting programs, such as @code{texinfo-format-buffer} or
34716 If you have @code{makeinfo} installed, and are in the top level
34717 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34718 version @value{GDBVN}), you can make the Info file by typing:
34725 If you want to typeset and print copies of this manual, you need @TeX{},
34726 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34727 Texinfo definitions file.
34729 @TeX{} is a typesetting program; it does not print files directly, but
34730 produces output files called @sc{dvi} files. To print a typeset
34731 document, you need a program to print @sc{dvi} files. If your system
34732 has @TeX{} installed, chances are it has such a program. The precise
34733 command to use depends on your system; @kbd{lpr -d} is common; another
34734 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34735 require a file name without any extension or a @samp{.dvi} extension.
34737 @TeX{} also requires a macro definitions file called
34738 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34739 written in Texinfo format. On its own, @TeX{} cannot either read or
34740 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34741 and is located in the @file{gdb-@var{version-number}/texinfo}
34744 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34745 typeset and print this manual. First switch to the @file{gdb}
34746 subdirectory of the main source directory (for example, to
34747 @file{gdb-@value{GDBVN}/gdb}) and type:
34753 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34755 @node Installing GDB
34756 @appendix Installing @value{GDBN}
34757 @cindex installation
34760 * Requirements:: Requirements for building @value{GDBN}
34761 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34762 * Separate Objdir:: Compiling @value{GDBN} in another directory
34763 * Config Names:: Specifying names for hosts and targets
34764 * Configure Options:: Summary of options for configure
34765 * System-wide configuration:: Having a system-wide init file
34769 @section Requirements for Building @value{GDBN}
34770 @cindex building @value{GDBN}, requirements for
34772 Building @value{GDBN} requires various tools and packages to be available.
34773 Other packages will be used only if they are found.
34775 @heading Tools/Packages Necessary for Building @value{GDBN}
34777 @item ISO C90 compiler
34778 @value{GDBN} is written in ISO C90. It should be buildable with any
34779 working C90 compiler, e.g.@: GCC.
34783 @heading Tools/Packages Optional for Building @value{GDBN}
34787 @value{GDBN} can use the Expat XML parsing library. This library may be
34788 included with your operating system distribution; if it is not, you
34789 can get the latest version from @url{http://expat.sourceforge.net}.
34790 The @file{configure} script will search for this library in several
34791 standard locations; if it is installed in an unusual path, you can
34792 use the @option{--with-libexpat-prefix} option to specify its location.
34798 Remote protocol memory maps (@pxref{Memory Map Format})
34800 Target descriptions (@pxref{Target Descriptions})
34802 Remote shared library lists (@xref{Library List Format},
34803 or alternatively @pxref{Library List Format for SVR4 Targets})
34805 MS-Windows shared libraries (@pxref{Shared Libraries})
34807 Traceframe info (@pxref{Traceframe Info Format})
34809 Branch trace (@pxref{Branch Trace Format},
34810 @pxref{Branch Trace Configuration Format})
34815 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34816 library. This library may be included with your operating system
34817 distribution; if it is not, you can get the latest version from
34818 @url{http://www.mpfr.org}. The @file{configure} script will search
34819 for this library in several standard locations; if it is installed
34820 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34821 option to specify its location.
34823 GNU MPFR is used to emulate target floating-point arithmetic during
34824 expression evaluation when the target uses different floating-point
34825 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34826 will fall back to using host floating-point arithmetic.
34829 @cindex compressed debug sections
34830 @value{GDBN} will use the @samp{zlib} library, if available, to read
34831 compressed debug sections. Some linkers, such as GNU gold, are capable
34832 of producing binaries with compressed debug sections. If @value{GDBN}
34833 is compiled with @samp{zlib}, it will be able to read the debug
34834 information in such binaries.
34836 The @samp{zlib} library is likely included with your operating system
34837 distribution; if it is not, you can get the latest version from
34838 @url{http://zlib.net}.
34841 @value{GDBN}'s features related to character sets (@pxref{Character
34842 Sets}) require a functioning @code{iconv} implementation. If you are
34843 on a GNU system, then this is provided by the GNU C Library. Some
34844 other systems also provide a working @code{iconv}.
34846 If @value{GDBN} is using the @code{iconv} program which is installed
34847 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34848 This is done with @option{--with-iconv-bin} which specifies the
34849 directory that contains the @code{iconv} program.
34851 On systems without @code{iconv}, you can install GNU Libiconv. If you
34852 have previously installed Libiconv, you can use the
34853 @option{--with-libiconv-prefix} option to configure.
34855 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34856 arrange to build Libiconv if a directory named @file{libiconv} appears
34857 in the top-most source directory. If Libiconv is built this way, and
34858 if the operating system does not provide a suitable @code{iconv}
34859 implementation, then the just-built library will automatically be used
34860 by @value{GDBN}. One easy way to set this up is to download GNU
34861 Libiconv, unpack it, and then rename the directory holding the
34862 Libiconv source code to @samp{libiconv}.
34865 @node Running Configure
34866 @section Invoking the @value{GDBN} @file{configure} Script
34867 @cindex configuring @value{GDBN}
34868 @value{GDBN} comes with a @file{configure} script that automates the process
34869 of preparing @value{GDBN} for installation; you can then use @code{make} to
34870 build the @code{gdb} program.
34872 @c irrelevant in info file; it's as current as the code it lives with.
34873 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34874 look at the @file{README} file in the sources; we may have improved the
34875 installation procedures since publishing this manual.}
34878 The @value{GDBN} distribution includes all the source code you need for
34879 @value{GDBN} in a single directory, whose name is usually composed by
34880 appending the version number to @samp{gdb}.
34882 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34883 @file{gdb-@value{GDBVN}} directory. That directory contains:
34886 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34887 script for configuring @value{GDBN} and all its supporting libraries
34889 @item gdb-@value{GDBVN}/gdb
34890 the source specific to @value{GDBN} itself
34892 @item gdb-@value{GDBVN}/bfd
34893 source for the Binary File Descriptor library
34895 @item gdb-@value{GDBVN}/include
34896 @sc{gnu} include files
34898 @item gdb-@value{GDBVN}/libiberty
34899 source for the @samp{-liberty} free software library
34901 @item gdb-@value{GDBVN}/opcodes
34902 source for the library of opcode tables and disassemblers
34904 @item gdb-@value{GDBVN}/readline
34905 source for the @sc{gnu} command-line interface
34907 @item gdb-@value{GDBVN}/glob
34908 source for the @sc{gnu} filename pattern-matching subroutine
34910 @item gdb-@value{GDBVN}/mmalloc
34911 source for the @sc{gnu} memory-mapped malloc package
34914 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34915 from the @file{gdb-@var{version-number}} source directory, which in
34916 this example is the @file{gdb-@value{GDBVN}} directory.
34918 First switch to the @file{gdb-@var{version-number}} source directory
34919 if you are not already in it; then run @file{configure}. Pass the
34920 identifier for the platform on which @value{GDBN} will run as an
34926 cd gdb-@value{GDBVN}
34927 ./configure @var{host}
34932 where @var{host} is an identifier such as @samp{sun4} or
34933 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34934 (You can often leave off @var{host}; @file{configure} tries to guess the
34935 correct value by examining your system.)
34937 Running @samp{configure @var{host}} and then running @code{make} builds the
34938 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34939 libraries, then @code{gdb} itself. The configured source files, and the
34940 binaries, are left in the corresponding source directories.
34943 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34944 system does not recognize this automatically when you run a different
34945 shell, you may need to run @code{sh} on it explicitly:
34948 sh configure @var{host}
34951 If you run @file{configure} from a directory that contains source
34952 directories for multiple libraries or programs, such as the
34953 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34955 creates configuration files for every directory level underneath (unless
34956 you tell it not to, with the @samp{--norecursion} option).
34958 You should run the @file{configure} script from the top directory in the
34959 source tree, the @file{gdb-@var{version-number}} directory. If you run
34960 @file{configure} from one of the subdirectories, you will configure only
34961 that subdirectory. That is usually not what you want. In particular,
34962 if you run the first @file{configure} from the @file{gdb} subdirectory
34963 of the @file{gdb-@var{version-number}} directory, you will omit the
34964 configuration of @file{bfd}, @file{readline}, and other sibling
34965 directories of the @file{gdb} subdirectory. This leads to build errors
34966 about missing include files such as @file{bfd/bfd.h}.
34968 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34969 However, you should make sure that the shell on your path (named by
34970 the @samp{SHELL} environment variable) is publicly readable. Remember
34971 that @value{GDBN} uses the shell to start your program---some systems refuse to
34972 let @value{GDBN} debug child processes whose programs are not readable.
34974 @node Separate Objdir
34975 @section Compiling @value{GDBN} in Another Directory
34977 If you want to run @value{GDBN} versions for several host or target machines,
34978 you need a different @code{gdb} compiled for each combination of
34979 host and target. @file{configure} is designed to make this easy by
34980 allowing you to generate each configuration in a separate subdirectory,
34981 rather than in the source directory. If your @code{make} program
34982 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34983 @code{make} in each of these directories builds the @code{gdb}
34984 program specified there.
34986 To build @code{gdb} in a separate directory, run @file{configure}
34987 with the @samp{--srcdir} option to specify where to find the source.
34988 (You also need to specify a path to find @file{configure}
34989 itself from your working directory. If the path to @file{configure}
34990 would be the same as the argument to @samp{--srcdir}, you can leave out
34991 the @samp{--srcdir} option; it is assumed.)
34993 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34994 separate directory for a Sun 4 like this:
34998 cd gdb-@value{GDBVN}
35001 ../gdb-@value{GDBVN}/configure sun4
35006 When @file{configure} builds a configuration using a remote source
35007 directory, it creates a tree for the binaries with the same structure
35008 (and using the same names) as the tree under the source directory. In
35009 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35010 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35011 @file{gdb-sun4/gdb}.
35013 Make sure that your path to the @file{configure} script has just one
35014 instance of @file{gdb} in it. If your path to @file{configure} looks
35015 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35016 one subdirectory of @value{GDBN}, not the whole package. This leads to
35017 build errors about missing include files such as @file{bfd/bfd.h}.
35019 One popular reason to build several @value{GDBN} configurations in separate
35020 directories is to configure @value{GDBN} for cross-compiling (where
35021 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35022 programs that run on another machine---the @dfn{target}).
35023 You specify a cross-debugging target by
35024 giving the @samp{--target=@var{target}} option to @file{configure}.
35026 When you run @code{make} to build a program or library, you must run
35027 it in a configured directory---whatever directory you were in when you
35028 called @file{configure} (or one of its subdirectories).
35030 The @code{Makefile} that @file{configure} generates in each source
35031 directory also runs recursively. If you type @code{make} in a source
35032 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35033 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35034 will build all the required libraries, and then build GDB.
35036 When you have multiple hosts or targets configured in separate
35037 directories, you can run @code{make} on them in parallel (for example,
35038 if they are NFS-mounted on each of the hosts); they will not interfere
35042 @section Specifying Names for Hosts and Targets
35044 The specifications used for hosts and targets in the @file{configure}
35045 script are based on a three-part naming scheme, but some short predefined
35046 aliases are also supported. The full naming scheme encodes three pieces
35047 of information in the following pattern:
35050 @var{architecture}-@var{vendor}-@var{os}
35053 For example, you can use the alias @code{sun4} as a @var{host} argument,
35054 or as the value for @var{target} in a @code{--target=@var{target}}
35055 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35057 The @file{configure} script accompanying @value{GDBN} does not provide
35058 any query facility to list all supported host and target names or
35059 aliases. @file{configure} calls the Bourne shell script
35060 @code{config.sub} to map abbreviations to full names; you can read the
35061 script, if you wish, or you can use it to test your guesses on
35062 abbreviations---for example:
35065 % sh config.sub i386-linux
35067 % sh config.sub alpha-linux
35068 alpha-unknown-linux-gnu
35069 % sh config.sub hp9k700
35071 % sh config.sub sun4
35072 sparc-sun-sunos4.1.1
35073 % sh config.sub sun3
35074 m68k-sun-sunos4.1.1
35075 % sh config.sub i986v
35076 Invalid configuration `i986v': machine `i986v' not recognized
35080 @code{config.sub} is also distributed in the @value{GDBN} source
35081 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35083 @node Configure Options
35084 @section @file{configure} Options
35086 Here is a summary of the @file{configure} options and arguments that
35087 are most often useful for building @value{GDBN}. @file{configure} also has
35088 several other options not listed here. @inforef{What Configure
35089 Does,,configure.info}, for a full explanation of @file{configure}.
35092 configure @r{[}--help@r{]}
35093 @r{[}--prefix=@var{dir}@r{]}
35094 @r{[}--exec-prefix=@var{dir}@r{]}
35095 @r{[}--srcdir=@var{dirname}@r{]}
35096 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35097 @r{[}--target=@var{target}@r{]}
35102 You may introduce options with a single @samp{-} rather than
35103 @samp{--} if you prefer; but you may abbreviate option names if you use
35108 Display a quick summary of how to invoke @file{configure}.
35110 @item --prefix=@var{dir}
35111 Configure the source to install programs and files under directory
35114 @item --exec-prefix=@var{dir}
35115 Configure the source to install programs under directory
35118 @c avoid splitting the warning from the explanation:
35120 @item --srcdir=@var{dirname}
35121 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35122 @code{make} that implements the @code{VPATH} feature.}@*
35123 Use this option to make configurations in directories separate from the
35124 @value{GDBN} source directories. Among other things, you can use this to
35125 build (or maintain) several configurations simultaneously, in separate
35126 directories. @file{configure} writes configuration-specific files in
35127 the current directory, but arranges for them to use the source in the
35128 directory @var{dirname}. @file{configure} creates directories under
35129 the working directory in parallel to the source directories below
35132 @item --norecursion
35133 Configure only the directory level where @file{configure} is executed; do not
35134 propagate configuration to subdirectories.
35136 @item --target=@var{target}
35137 Configure @value{GDBN} for cross-debugging programs running on the specified
35138 @var{target}. Without this option, @value{GDBN} is configured to debug
35139 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35141 There is no convenient way to generate a list of all available targets.
35143 @item @var{host} @dots{}
35144 Configure @value{GDBN} to run on the specified @var{host}.
35146 There is no convenient way to generate a list of all available hosts.
35149 There are many other options available as well, but they are generally
35150 needed for special purposes only.
35152 @node System-wide configuration
35153 @section System-wide configuration and settings
35154 @cindex system-wide init file
35156 @value{GDBN} can be configured to have a system-wide init file;
35157 this file will be read and executed at startup (@pxref{Startup, , What
35158 @value{GDBN} does during startup}).
35160 Here is the corresponding configure option:
35163 @item --with-system-gdbinit=@var{file}
35164 Specify that the default location of the system-wide init file is
35168 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35169 it may be subject to relocation. Two possible cases:
35173 If the default location of this init file contains @file{$prefix},
35174 it will be subject to relocation. Suppose that the configure options
35175 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35176 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35177 init file is looked for as @file{$install/etc/gdbinit} instead of
35178 @file{$prefix/etc/gdbinit}.
35181 By contrast, if the default location does not contain the prefix,
35182 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35183 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35184 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35185 wherever @value{GDBN} is installed.
35188 If the configured location of the system-wide init file (as given by the
35189 @option{--with-system-gdbinit} option at configure time) is in the
35190 data-directory (as specified by @option{--with-gdb-datadir} at configure
35191 time) or in one of its subdirectories, then @value{GDBN} will look for the
35192 system-wide init file in the directory specified by the
35193 @option{--data-directory} command-line option.
35194 Note that the system-wide init file is only read once, during @value{GDBN}
35195 initialization. If the data-directory is changed after @value{GDBN} has
35196 started with the @code{set data-directory} command, the file will not be
35200 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
35203 @node System-wide Configuration Scripts
35204 @subsection Installed System-wide Configuration Scripts
35205 @cindex system-wide configuration scripts
35207 The @file{system-gdbinit} directory, located inside the data-directory
35208 (as specified by @option{--with-gdb-datadir} at configure time) contains
35209 a number of scripts which can be used as system-wide init files. To
35210 automatically source those scripts at startup, @value{GDBN} should be
35211 configured with @option{--with-system-gdbinit}. Otherwise, any user
35212 should be able to source them by hand as needed.
35214 The following scripts are currently available:
35217 @item @file{elinos.py}
35219 @cindex ELinOS system-wide configuration script
35220 This script is useful when debugging a program on an ELinOS target.
35221 It takes advantage of the environment variables defined in a standard
35222 ELinOS environment in order to determine the location of the system
35223 shared libraries, and then sets the @samp{solib-absolute-prefix}
35224 and @samp{solib-search-path} variables appropriately.
35226 @item @file{wrs-linux.py}
35227 @pindex wrs-linux.py
35228 @cindex Wind River Linux system-wide configuration script
35229 This script is useful when debugging a program on a target running
35230 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
35231 the host-side sysroot used by the target system.
35235 @node Maintenance Commands
35236 @appendix Maintenance Commands
35237 @cindex maintenance commands
35238 @cindex internal commands
35240 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35241 includes a number of commands intended for @value{GDBN} developers,
35242 that are not documented elsewhere in this manual. These commands are
35243 provided here for reference. (For commands that turn on debugging
35244 messages, see @ref{Debugging Output}.)
35247 @kindex maint agent
35248 @kindex maint agent-eval
35249 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35250 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35251 Translate the given @var{expression} into remote agent bytecodes.
35252 This command is useful for debugging the Agent Expression mechanism
35253 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35254 expression useful for data collection, such as by tracepoints, while
35255 @samp{maint agent-eval} produces an expression that evaluates directly
35256 to a result. For instance, a collection expression for @code{globa +
35257 globb} will include bytecodes to record four bytes of memory at each
35258 of the addresses of @code{globa} and @code{globb}, while discarding
35259 the result of the addition, while an evaluation expression will do the
35260 addition and return the sum.
35261 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35262 If not, generate remote agent bytecode for current frame PC address.
35264 @kindex maint agent-printf
35265 @item maint agent-printf @var{format},@var{expr},...
35266 Translate the given format string and list of argument expressions
35267 into remote agent bytecodes and display them as a disassembled list.
35268 This command is useful for debugging the agent version of dynamic
35269 printf (@pxref{Dynamic Printf}).
35271 @kindex maint info breakpoints
35272 @item @anchor{maint info breakpoints}maint info breakpoints
35273 Using the same format as @samp{info breakpoints}, display both the
35274 breakpoints you've set explicitly, and those @value{GDBN} is using for
35275 internal purposes. Internal breakpoints are shown with negative
35276 breakpoint numbers. The type column identifies what kind of breakpoint
35281 Normal, explicitly set breakpoint.
35284 Normal, explicitly set watchpoint.
35287 Internal breakpoint, used to handle correctly stepping through
35288 @code{longjmp} calls.
35290 @item longjmp resume
35291 Internal breakpoint at the target of a @code{longjmp}.
35294 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35297 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35300 Shared library events.
35304 @kindex maint info btrace
35305 @item maint info btrace
35306 Pint information about raw branch tracing data.
35308 @kindex maint btrace packet-history
35309 @item maint btrace packet-history
35310 Print the raw branch trace packets that are used to compute the
35311 execution history for the @samp{record btrace} command. Both the
35312 information and the format in which it is printed depend on the btrace
35317 For the BTS recording format, print a list of blocks of sequential
35318 code. For each block, the following information is printed:
35322 Newer blocks have higher numbers. The oldest block has number zero.
35323 @item Lowest @samp{PC}
35324 @item Highest @samp{PC}
35328 For the Intel Processor Trace recording format, print a list of
35329 Intel Processor Trace packets. For each packet, the following
35330 information is printed:
35333 @item Packet number
35334 Newer packets have higher numbers. The oldest packet has number zero.
35336 The packet's offset in the trace stream.
35337 @item Packet opcode and payload
35341 @kindex maint btrace clear-packet-history
35342 @item maint btrace clear-packet-history
35343 Discards the cached packet history printed by the @samp{maint btrace
35344 packet-history} command. The history will be computed again when
35347 @kindex maint btrace clear
35348 @item maint btrace clear
35349 Discard the branch trace data. The data will be fetched anew and the
35350 branch trace will be recomputed when needed.
35352 This implicitly truncates the branch trace to a single branch trace
35353 buffer. When updating branch trace incrementally, the branch trace
35354 available to @value{GDBN} may be bigger than a single branch trace
35357 @kindex maint set btrace pt skip-pad
35358 @item maint set btrace pt skip-pad
35359 @kindex maint show btrace pt skip-pad
35360 @item maint show btrace pt skip-pad
35361 Control whether @value{GDBN} will skip PAD packets when computing the
35364 @kindex set displaced-stepping
35365 @kindex show displaced-stepping
35366 @cindex displaced stepping support
35367 @cindex out-of-line single-stepping
35368 @item set displaced-stepping
35369 @itemx show displaced-stepping
35370 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35371 if the target supports it. Displaced stepping is a way to single-step
35372 over breakpoints without removing them from the inferior, by executing
35373 an out-of-line copy of the instruction that was originally at the
35374 breakpoint location. It is also known as out-of-line single-stepping.
35377 @item set displaced-stepping on
35378 If the target architecture supports it, @value{GDBN} will use
35379 displaced stepping to step over breakpoints.
35381 @item set displaced-stepping off
35382 @value{GDBN} will not use displaced stepping to step over breakpoints,
35383 even if such is supported by the target architecture.
35385 @cindex non-stop mode, and @samp{set displaced-stepping}
35386 @item set displaced-stepping auto
35387 This is the default mode. @value{GDBN} will use displaced stepping
35388 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35389 architecture supports displaced stepping.
35392 @kindex maint check-psymtabs
35393 @item maint check-psymtabs
35394 Check the consistency of currently expanded psymtabs versus symtabs.
35395 Use this to check, for example, whether a symbol is in one but not the other.
35397 @kindex maint check-symtabs
35398 @item maint check-symtabs
35399 Check the consistency of currently expanded symtabs.
35401 @kindex maint expand-symtabs
35402 @item maint expand-symtabs [@var{regexp}]
35403 Expand symbol tables.
35404 If @var{regexp} is specified, only expand symbol tables for file
35405 names matching @var{regexp}.
35407 @kindex maint set catch-demangler-crashes
35408 @kindex maint show catch-demangler-crashes
35409 @cindex demangler crashes
35410 @item maint set catch-demangler-crashes [on|off]
35411 @itemx maint show catch-demangler-crashes
35412 Control whether @value{GDBN} should attempt to catch crashes in the
35413 symbol name demangler. The default is to attempt to catch crashes.
35414 If enabled, the first time a crash is caught, a core file is created,
35415 the offending symbol is displayed and the user is presented with the
35416 option to terminate the current session.
35418 @kindex maint cplus first_component
35419 @item maint cplus first_component @var{name}
35420 Print the first C@t{++} class/namespace component of @var{name}.
35422 @kindex maint cplus namespace
35423 @item maint cplus namespace
35424 Print the list of possible C@t{++} namespaces.
35426 @kindex maint deprecate
35427 @kindex maint undeprecate
35428 @cindex deprecated commands
35429 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35430 @itemx maint undeprecate @var{command}
35431 Deprecate or undeprecate the named @var{command}. Deprecated commands
35432 cause @value{GDBN} to issue a warning when you use them. The optional
35433 argument @var{replacement} says which newer command should be used in
35434 favor of the deprecated one; if it is given, @value{GDBN} will mention
35435 the replacement as part of the warning.
35437 @kindex maint dump-me
35438 @item maint dump-me
35439 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35440 Cause a fatal signal in the debugger and force it to dump its core.
35441 This is supported only on systems which support aborting a program
35442 with the @code{SIGQUIT} signal.
35444 @kindex maint internal-error
35445 @kindex maint internal-warning
35446 @kindex maint demangler-warning
35447 @cindex demangler crashes
35448 @item maint internal-error @r{[}@var{message-text}@r{]}
35449 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35450 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35452 Cause @value{GDBN} to call the internal function @code{internal_error},
35453 @code{internal_warning} or @code{demangler_warning} and hence behave
35454 as though an internal problem has been detected. In addition to
35455 reporting the internal problem, these functions give the user the
35456 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35457 and @code{internal_warning}) create a core file of the current
35458 @value{GDBN} session.
35460 These commands take an optional parameter @var{message-text} that is
35461 used as the text of the error or warning message.
35463 Here's an example of using @code{internal-error}:
35466 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35467 @dots{}/maint.c:121: internal-error: testing, 1, 2
35468 A problem internal to GDB has been detected. Further
35469 debugging may prove unreliable.
35470 Quit this debugging session? (y or n) @kbd{n}
35471 Create a core file? (y or n) @kbd{n}
35475 @cindex @value{GDBN} internal error
35476 @cindex internal errors, control of @value{GDBN} behavior
35477 @cindex demangler crashes
35479 @kindex maint set internal-error
35480 @kindex maint show internal-error
35481 @kindex maint set internal-warning
35482 @kindex maint show internal-warning
35483 @kindex maint set demangler-warning
35484 @kindex maint show demangler-warning
35485 @item maint set internal-error @var{action} [ask|yes|no]
35486 @itemx maint show internal-error @var{action}
35487 @itemx maint set internal-warning @var{action} [ask|yes|no]
35488 @itemx maint show internal-warning @var{action}
35489 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35490 @itemx maint show demangler-warning @var{action}
35491 When @value{GDBN} reports an internal problem (error or warning) it
35492 gives the user the opportunity to both quit @value{GDBN} and create a
35493 core file of the current @value{GDBN} session. These commands let you
35494 override the default behaviour for each particular @var{action},
35495 described in the table below.
35499 You can specify that @value{GDBN} should always (yes) or never (no)
35500 quit. The default is to ask the user what to do.
35503 You can specify that @value{GDBN} should always (yes) or never (no)
35504 create a core file. The default is to ask the user what to do. Note
35505 that there is no @code{corefile} option for @code{demangler-warning}:
35506 demangler warnings always create a core file and this cannot be
35510 @kindex maint packet
35511 @item maint packet @var{text}
35512 If @value{GDBN} is talking to an inferior via the serial protocol,
35513 then this command sends the string @var{text} to the inferior, and
35514 displays the response packet. @value{GDBN} supplies the initial
35515 @samp{$} character, the terminating @samp{#} character, and the
35518 @kindex maint print architecture
35519 @item maint print architecture @r{[}@var{file}@r{]}
35520 Print the entire architecture configuration. The optional argument
35521 @var{file} names the file where the output goes.
35523 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35524 @item maint print c-tdesc
35525 Print the target description (@pxref{Target Descriptions}) as
35526 a C source file. By default, the target description is for the current
35527 target, but if the optional argument @var{file} is provided, that file
35528 is used to produce the description. The @var{file} should be an XML
35529 document, of the form described in @ref{Target Description Format}.
35530 The created source file is built into @value{GDBN} when @value{GDBN} is
35531 built again. This command is used by developers after they add or
35532 modify XML target descriptions.
35534 @kindex maint check xml-descriptions
35535 @item maint check xml-descriptions @var{dir}
35536 Check that the target descriptions dynamically created by @value{GDBN}
35537 equal the descriptions created from XML files found in @var{dir}.
35539 @kindex maint print dummy-frames
35540 @item maint print dummy-frames
35541 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35544 (@value{GDBP}) @kbd{b add}
35546 (@value{GDBP}) @kbd{print add(2,3)}
35547 Breakpoint 2, add (a=2, b=3) at @dots{}
35549 The program being debugged stopped while in a function called from GDB.
35551 (@value{GDBP}) @kbd{maint print dummy-frames}
35552 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35556 Takes an optional file parameter.
35558 @kindex maint print registers
35559 @kindex maint print raw-registers
35560 @kindex maint print cooked-registers
35561 @kindex maint print register-groups
35562 @kindex maint print remote-registers
35563 @item maint print registers @r{[}@var{file}@r{]}
35564 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35565 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35566 @itemx maint print register-groups @r{[}@var{file}@r{]}
35567 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35568 Print @value{GDBN}'s internal register data structures.
35570 The command @code{maint print raw-registers} includes the contents of
35571 the raw register cache; the command @code{maint print
35572 cooked-registers} includes the (cooked) value of all registers,
35573 including registers which aren't available on the target nor visible
35574 to user; the command @code{maint print register-groups} includes the
35575 groups that each register is a member of; and the command @code{maint
35576 print remote-registers} includes the remote target's register numbers
35577 and offsets in the `G' packets.
35579 These commands take an optional parameter, a file name to which to
35580 write the information.
35582 @kindex maint print reggroups
35583 @item maint print reggroups @r{[}@var{file}@r{]}
35584 Print @value{GDBN}'s internal register group data structures. The
35585 optional argument @var{file} tells to what file to write the
35588 The register groups info looks like this:
35591 (@value{GDBP}) @kbd{maint print reggroups}
35604 This command forces @value{GDBN} to flush its internal register cache.
35606 @kindex maint print objfiles
35607 @cindex info for known object files
35608 @item maint print objfiles @r{[}@var{regexp}@r{]}
35609 Print a dump of all known object files.
35610 If @var{regexp} is specified, only print object files whose names
35611 match @var{regexp}. For each object file, this command prints its name,
35612 address in memory, and all of its psymtabs and symtabs.
35614 @kindex maint print user-registers
35615 @cindex user registers
35616 @item maint print user-registers
35617 List all currently available @dfn{user registers}. User registers
35618 typically provide alternate names for actual hardware registers. They
35619 include the four ``standard'' registers @code{$fp}, @code{$pc},
35620 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35621 registers can be used in expressions in the same way as the canonical
35622 register names, but only the latter are listed by the @code{info
35623 registers} and @code{maint print registers} commands.
35625 @kindex maint print section-scripts
35626 @cindex info for known .debug_gdb_scripts-loaded scripts
35627 @item maint print section-scripts [@var{regexp}]
35628 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35629 If @var{regexp} is specified, only print scripts loaded by object files
35630 matching @var{regexp}.
35631 For each script, this command prints its name as specified in the objfile,
35632 and the full path if known.
35633 @xref{dotdebug_gdb_scripts section}.
35635 @kindex maint print statistics
35636 @cindex bcache statistics
35637 @item maint print statistics
35638 This command prints, for each object file in the program, various data
35639 about that object file followed by the byte cache (@dfn{bcache})
35640 statistics for the object file. The objfile data includes the number
35641 of minimal, partial, full, and stabs symbols, the number of types
35642 defined by the objfile, the number of as yet unexpanded psym tables,
35643 the number of line tables and string tables, and the amount of memory
35644 used by the various tables. The bcache statistics include the counts,
35645 sizes, and counts of duplicates of all and unique objects, max,
35646 average, and median entry size, total memory used and its overhead and
35647 savings, and various measures of the hash table size and chain
35650 @kindex maint print target-stack
35651 @cindex target stack description
35652 @item maint print target-stack
35653 A @dfn{target} is an interface between the debugger and a particular
35654 kind of file or process. Targets can be stacked in @dfn{strata},
35655 so that more than one target can potentially respond to a request.
35656 In particular, memory accesses will walk down the stack of targets
35657 until they find a target that is interested in handling that particular
35660 This command prints a short description of each layer that was pushed on
35661 the @dfn{target stack}, starting from the top layer down to the bottom one.
35663 @kindex maint print type
35664 @cindex type chain of a data type
35665 @item maint print type @var{expr}
35666 Print the type chain for a type specified by @var{expr}. The argument
35667 can be either a type name or a symbol. If it is a symbol, the type of
35668 that symbol is described. The type chain produced by this command is
35669 a recursive definition of the data type as stored in @value{GDBN}'s
35670 data structures, including its flags and contained types.
35672 @kindex maint selftest
35674 @item maint selftest @r{[}@var{filter}@r{]}
35675 Run any self tests that were compiled in to @value{GDBN}. This will
35676 print a message showing how many tests were run, and how many failed.
35677 If a @var{filter} is passed, only the tests with @var{filter} in their
35680 @kindex "maint info selftests"
35682 @item maint info selftests
35683 List the selftests compiled in to @value{GDBN}.
35685 @kindex maint set dwarf always-disassemble
35686 @kindex maint show dwarf always-disassemble
35687 @item maint set dwarf always-disassemble
35688 @item maint show dwarf always-disassemble
35689 Control the behavior of @code{info address} when using DWARF debugging
35692 The default is @code{off}, which means that @value{GDBN} should try to
35693 describe a variable's location in an easily readable format. When
35694 @code{on}, @value{GDBN} will instead display the DWARF location
35695 expression in an assembly-like format. Note that some locations are
35696 too complex for @value{GDBN} to describe simply; in this case you will
35697 always see the disassembly form.
35699 Here is an example of the resulting disassembly:
35702 (gdb) info addr argc
35703 Symbol "argc" is a complex DWARF expression:
35707 For more information on these expressions, see
35708 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35710 @kindex maint set dwarf max-cache-age
35711 @kindex maint show dwarf max-cache-age
35712 @item maint set dwarf max-cache-age
35713 @itemx maint show dwarf max-cache-age
35714 Control the DWARF compilation unit cache.
35716 @cindex DWARF compilation units cache
35717 In object files with inter-compilation-unit references, such as those
35718 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35719 reader needs to frequently refer to previously read compilation units.
35720 This setting controls how long a compilation unit will remain in the
35721 cache if it is not referenced. A higher limit means that cached
35722 compilation units will be stored in memory longer, and more total
35723 memory will be used. Setting it to zero disables caching, which will
35724 slow down @value{GDBN} startup, but reduce memory consumption.
35726 @kindex maint set profile
35727 @kindex maint show profile
35728 @cindex profiling GDB
35729 @item maint set profile
35730 @itemx maint show profile
35731 Control profiling of @value{GDBN}.
35733 Profiling will be disabled until you use the @samp{maint set profile}
35734 command to enable it. When you enable profiling, the system will begin
35735 collecting timing and execution count data; when you disable profiling or
35736 exit @value{GDBN}, the results will be written to a log file. Remember that
35737 if you use profiling, @value{GDBN} will overwrite the profiling log file
35738 (often called @file{gmon.out}). If you have a record of important profiling
35739 data in a @file{gmon.out} file, be sure to move it to a safe location.
35741 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35742 compiled with the @samp{-pg} compiler option.
35744 @kindex maint set show-debug-regs
35745 @kindex maint show show-debug-regs
35746 @cindex hardware debug registers
35747 @item maint set show-debug-regs
35748 @itemx maint show show-debug-regs
35749 Control whether to show variables that mirror the hardware debug
35750 registers. Use @code{on} to enable, @code{off} to disable. If
35751 enabled, the debug registers values are shown when @value{GDBN} inserts or
35752 removes a hardware breakpoint or watchpoint, and when the inferior
35753 triggers a hardware-assisted breakpoint or watchpoint.
35755 @kindex maint set show-all-tib
35756 @kindex maint show show-all-tib
35757 @item maint set show-all-tib
35758 @itemx maint show show-all-tib
35759 Control whether to show all non zero areas within a 1k block starting
35760 at thread local base, when using the @samp{info w32 thread-information-block}
35763 @kindex maint set target-async
35764 @kindex maint show target-async
35765 @item maint set target-async
35766 @itemx maint show target-async
35767 This controls whether @value{GDBN} targets operate in synchronous or
35768 asynchronous mode (@pxref{Background Execution}). Normally the
35769 default is asynchronous, if it is available; but this can be changed
35770 to more easily debug problems occurring only in synchronous mode.
35772 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35773 @kindex maint show target-non-stop
35774 @item maint set target-non-stop
35775 @itemx maint show target-non-stop
35777 This controls whether @value{GDBN} targets always operate in non-stop
35778 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35779 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35780 if supported by the target.
35783 @item maint set target-non-stop auto
35784 This is the default mode. @value{GDBN} controls the target in
35785 non-stop mode if the target supports it.
35787 @item maint set target-non-stop on
35788 @value{GDBN} controls the target in non-stop mode even if the target
35789 does not indicate support.
35791 @item maint set target-non-stop off
35792 @value{GDBN} does not control the target in non-stop mode even if the
35793 target supports it.
35796 @kindex maint set per-command
35797 @kindex maint show per-command
35798 @item maint set per-command
35799 @itemx maint show per-command
35800 @cindex resources used by commands
35802 @value{GDBN} can display the resources used by each command.
35803 This is useful in debugging performance problems.
35806 @item maint set per-command space [on|off]
35807 @itemx maint show per-command space
35808 Enable or disable the printing of the memory used by GDB for each command.
35809 If enabled, @value{GDBN} will display how much memory each command
35810 took, following the command's own output.
35811 This can also be requested by invoking @value{GDBN} with the
35812 @option{--statistics} command-line switch (@pxref{Mode Options}).
35814 @item maint set per-command time [on|off]
35815 @itemx maint show per-command time
35816 Enable or disable the printing of the execution time of @value{GDBN}
35818 If enabled, @value{GDBN} will display how much time it
35819 took to execute each command, following the command's own output.
35820 Both CPU time and wallclock time are printed.
35821 Printing both is useful when trying to determine whether the cost is
35822 CPU or, e.g., disk/network latency.
35823 Note that the CPU time printed is for @value{GDBN} only, it does not include
35824 the execution time of the inferior because there's no mechanism currently
35825 to compute how much time was spent by @value{GDBN} and how much time was
35826 spent by the program been debugged.
35827 This can also be requested by invoking @value{GDBN} with the
35828 @option{--statistics} command-line switch (@pxref{Mode Options}).
35830 @item maint set per-command symtab [on|off]
35831 @itemx maint show per-command symtab
35832 Enable or disable the printing of basic symbol table statistics
35834 If enabled, @value{GDBN} will display the following information:
35838 number of symbol tables
35840 number of primary symbol tables
35842 number of blocks in the blockvector
35846 @kindex maint space
35847 @cindex memory used by commands
35848 @item maint space @var{value}
35849 An alias for @code{maint set per-command space}.
35850 A non-zero value enables it, zero disables it.
35853 @cindex time of command execution
35854 @item maint time @var{value}
35855 An alias for @code{maint set per-command time}.
35856 A non-zero value enables it, zero disables it.
35858 @kindex maint translate-address
35859 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35860 Find the symbol stored at the location specified by the address
35861 @var{addr} and an optional section name @var{section}. If found,
35862 @value{GDBN} prints the name of the closest symbol and an offset from
35863 the symbol's location to the specified address. This is similar to
35864 the @code{info address} command (@pxref{Symbols}), except that this
35865 command also allows to find symbols in other sections.
35867 If section was not specified, the section in which the symbol was found
35868 is also printed. For dynamically linked executables, the name of
35869 executable or shared library containing the symbol is printed as well.
35873 The following command is useful for non-interactive invocations of
35874 @value{GDBN}, such as in the test suite.
35877 @item set watchdog @var{nsec}
35878 @kindex set watchdog
35879 @cindex watchdog timer
35880 @cindex timeout for commands
35881 Set the maximum number of seconds @value{GDBN} will wait for the
35882 target operation to finish. If this time expires, @value{GDBN}
35883 reports and error and the command is aborted.
35885 @item show watchdog
35886 Show the current setting of the target wait timeout.
35889 @node Remote Protocol
35890 @appendix @value{GDBN} Remote Serial Protocol
35895 * Stop Reply Packets::
35896 * General Query Packets::
35897 * Architecture-Specific Protocol Details::
35898 * Tracepoint Packets::
35899 * Host I/O Packets::
35901 * Notification Packets::
35902 * Remote Non-Stop::
35903 * Packet Acknowledgment::
35905 * File-I/O Remote Protocol Extension::
35906 * Library List Format::
35907 * Library List Format for SVR4 Targets::
35908 * Memory Map Format::
35909 * Thread List Format::
35910 * Traceframe Info Format::
35911 * Branch Trace Format::
35912 * Branch Trace Configuration Format::
35918 There may be occasions when you need to know something about the
35919 protocol---for example, if there is only one serial port to your target
35920 machine, you might want your program to do something special if it
35921 recognizes a packet meant for @value{GDBN}.
35923 In the examples below, @samp{->} and @samp{<-} are used to indicate
35924 transmitted and received data, respectively.
35926 @cindex protocol, @value{GDBN} remote serial
35927 @cindex serial protocol, @value{GDBN} remote
35928 @cindex remote serial protocol
35929 All @value{GDBN} commands and responses (other than acknowledgments
35930 and notifications, see @ref{Notification Packets}) are sent as a
35931 @var{packet}. A @var{packet} is introduced with the character
35932 @samp{$}, the actual @var{packet-data}, and the terminating character
35933 @samp{#} followed by a two-digit @var{checksum}:
35936 @code{$}@var{packet-data}@code{#}@var{checksum}
35940 @cindex checksum, for @value{GDBN} remote
35942 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35943 characters between the leading @samp{$} and the trailing @samp{#} (an
35944 eight bit unsigned checksum).
35946 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35947 specification also included an optional two-digit @var{sequence-id}:
35950 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35953 @cindex sequence-id, for @value{GDBN} remote
35955 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35956 has never output @var{sequence-id}s. Stubs that handle packets added
35957 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35959 When either the host or the target machine receives a packet, the first
35960 response expected is an acknowledgment: either @samp{+} (to indicate
35961 the package was received correctly) or @samp{-} (to request
35965 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35970 The @samp{+}/@samp{-} acknowledgments can be disabled
35971 once a connection is established.
35972 @xref{Packet Acknowledgment}, for details.
35974 The host (@value{GDBN}) sends @var{command}s, and the target (the
35975 debugging stub incorporated in your program) sends a @var{response}. In
35976 the case of step and continue @var{command}s, the response is only sent
35977 when the operation has completed, and the target has again stopped all
35978 threads in all attached processes. This is the default all-stop mode
35979 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35980 execution mode; see @ref{Remote Non-Stop}, for details.
35982 @var{packet-data} consists of a sequence of characters with the
35983 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35986 @cindex remote protocol, field separator
35987 Fields within the packet should be separated using @samp{,} @samp{;} or
35988 @samp{:}. Except where otherwise noted all numbers are represented in
35989 @sc{hex} with leading zeros suppressed.
35991 Implementors should note that prior to @value{GDBN} 5.0, the character
35992 @samp{:} could not appear as the third character in a packet (as it
35993 would potentially conflict with the @var{sequence-id}).
35995 @cindex remote protocol, binary data
35996 @anchor{Binary Data}
35997 Binary data in most packets is encoded either as two hexadecimal
35998 digits per byte of binary data. This allowed the traditional remote
35999 protocol to work over connections which were only seven-bit clean.
36000 Some packets designed more recently assume an eight-bit clean
36001 connection, and use a more efficient encoding to send and receive
36004 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
36005 as an escape character. Any escaped byte is transmitted as the escape
36006 character followed by the original character XORed with @code{0x20}.
36007 For example, the byte @code{0x7d} would be transmitted as the two
36008 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
36009 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
36010 @samp{@}}) must always be escaped. Responses sent by the stub
36011 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
36012 is not interpreted as the start of a run-length encoded sequence
36015 Response @var{data} can be run-length encoded to save space.
36016 Run-length encoding replaces runs of identical characters with one
36017 instance of the repeated character, followed by a @samp{*} and a
36018 repeat count. The repeat count is itself sent encoded, to avoid
36019 binary characters in @var{data}: a value of @var{n} is sent as
36020 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
36021 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
36022 code 32) for a repeat count of 3. (This is because run-length
36023 encoding starts to win for counts 3 or more.) Thus, for example,
36024 @samp{0* } is a run-length encoding of ``0000'': the space character
36025 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
36028 The printable characters @samp{#} and @samp{$} or with a numeric value
36029 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
36030 seven repeats (@samp{$}) can be expanded using a repeat count of only
36031 five (@samp{"}). For example, @samp{00000000} can be encoded as
36034 The error response returned for some packets includes a two character
36035 error number. That number is not well defined.
36037 @cindex empty response, for unsupported packets
36038 For any @var{command} not supported by the stub, an empty response
36039 (@samp{$#00}) should be returned. That way it is possible to extend the
36040 protocol. A newer @value{GDBN} can tell if a packet is supported based
36043 At a minimum, a stub is required to support the @samp{g} and @samp{G}
36044 commands for register access, and the @samp{m} and @samp{M} commands
36045 for memory access. Stubs that only control single-threaded targets
36046 can implement run control with the @samp{c} (continue), and @samp{s}
36047 (step) commands. Stubs that support multi-threading targets should
36048 support the @samp{vCont} command. All other commands are optional.
36053 The following table provides a complete list of all currently defined
36054 @var{command}s and their corresponding response @var{data}.
36055 @xref{File-I/O Remote Protocol Extension}, for details about the File
36056 I/O extension of the remote protocol.
36058 Each packet's description has a template showing the packet's overall
36059 syntax, followed by an explanation of the packet's meaning. We
36060 include spaces in some of the templates for clarity; these are not
36061 part of the packet's syntax. No @value{GDBN} packet uses spaces to
36062 separate its components. For example, a template like @samp{foo
36063 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
36064 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
36065 @var{baz}. @value{GDBN} does not transmit a space character between the
36066 @samp{foo} and the @var{bar}, or between the @var{bar} and the
36069 @cindex @var{thread-id}, in remote protocol
36070 @anchor{thread-id syntax}
36071 Several packets and replies include a @var{thread-id} field to identify
36072 a thread. Normally these are positive numbers with a target-specific
36073 interpretation, formatted as big-endian hex strings. A @var{thread-id}
36074 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
36077 In addition, the remote protocol supports a multiprocess feature in
36078 which the @var{thread-id} syntax is extended to optionally include both
36079 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36080 The @var{pid} (process) and @var{tid} (thread) components each have the
36081 format described above: a positive number with target-specific
36082 interpretation formatted as a big-endian hex string, literal @samp{-1}
36083 to indicate all processes or threads (respectively), or @samp{0} to
36084 indicate an arbitrary process or thread. Specifying just a process, as
36085 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36086 error to specify all processes but a specific thread, such as
36087 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36088 for those packets and replies explicitly documented to include a process
36089 ID, rather than a @var{thread-id}.
36091 The multiprocess @var{thread-id} syntax extensions are only used if both
36092 @value{GDBN} and the stub report support for the @samp{multiprocess}
36093 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36096 Note that all packet forms beginning with an upper- or lower-case
36097 letter, other than those described here, are reserved for future use.
36099 Here are the packet descriptions.
36104 @cindex @samp{!} packet
36105 @anchor{extended mode}
36106 Enable extended mode. In extended mode, the remote server is made
36107 persistent. The @samp{R} packet is used to restart the program being
36113 The remote target both supports and has enabled extended mode.
36117 @cindex @samp{?} packet
36119 Indicate the reason the target halted. The reply is the same as for
36120 step and continue. This packet has a special interpretation when the
36121 target is in non-stop mode; see @ref{Remote Non-Stop}.
36124 @xref{Stop Reply Packets}, for the reply specifications.
36126 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36127 @cindex @samp{A} packet
36128 Initialized @code{argv[]} array passed into program. @var{arglen}
36129 specifies the number of bytes in the hex encoded byte stream
36130 @var{arg}. See @code{gdbserver} for more details.
36135 The arguments were set.
36141 @cindex @samp{b} packet
36142 (Don't use this packet; its behavior is not well-defined.)
36143 Change the serial line speed to @var{baud}.
36145 JTC: @emph{When does the transport layer state change? When it's
36146 received, or after the ACK is transmitted. In either case, there are
36147 problems if the command or the acknowledgment packet is dropped.}
36149 Stan: @emph{If people really wanted to add something like this, and get
36150 it working for the first time, they ought to modify ser-unix.c to send
36151 some kind of out-of-band message to a specially-setup stub and have the
36152 switch happen "in between" packets, so that from remote protocol's point
36153 of view, nothing actually happened.}
36155 @item B @var{addr},@var{mode}
36156 @cindex @samp{B} packet
36157 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36158 breakpoint at @var{addr}.
36160 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36161 (@pxref{insert breakpoint or watchpoint packet}).
36163 @cindex @samp{bc} packet
36166 Backward continue. Execute the target system in reverse. No parameter.
36167 @xref{Reverse Execution}, for more information.
36170 @xref{Stop Reply Packets}, for the reply specifications.
36172 @cindex @samp{bs} packet
36175 Backward single step. Execute one instruction in reverse. No parameter.
36176 @xref{Reverse Execution}, for more information.
36179 @xref{Stop Reply Packets}, for the reply specifications.
36181 @item c @r{[}@var{addr}@r{]}
36182 @cindex @samp{c} packet
36183 Continue at @var{addr}, which is the address to resume. If @var{addr}
36184 is omitted, resume at current address.
36186 This packet is deprecated for multi-threading support. @xref{vCont
36190 @xref{Stop Reply Packets}, for the reply specifications.
36192 @item C @var{sig}@r{[};@var{addr}@r{]}
36193 @cindex @samp{C} packet
36194 Continue with signal @var{sig} (hex signal number). If
36195 @samp{;@var{addr}} is omitted, resume at same address.
36197 This packet is deprecated for multi-threading support. @xref{vCont
36201 @xref{Stop Reply Packets}, for the reply specifications.
36204 @cindex @samp{d} packet
36207 Don't use this packet; instead, define a general set packet
36208 (@pxref{General Query Packets}).
36212 @cindex @samp{D} packet
36213 The first form of the packet is used to detach @value{GDBN} from the
36214 remote system. It is sent to the remote target
36215 before @value{GDBN} disconnects via the @code{detach} command.
36217 The second form, including a process ID, is used when multiprocess
36218 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36219 detach only a specific process. The @var{pid} is specified as a
36220 big-endian hex string.
36230 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36231 @cindex @samp{F} packet
36232 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36233 This is part of the File-I/O protocol extension. @xref{File-I/O
36234 Remote Protocol Extension}, for the specification.
36237 @anchor{read registers packet}
36238 @cindex @samp{g} packet
36239 Read general registers.
36243 @item @var{XX@dots{}}
36244 Each byte of register data is described by two hex digits. The bytes
36245 with the register are transmitted in target byte order. The size of
36246 each register and their position within the @samp{g} packet are
36247 determined by the @value{GDBN} internal gdbarch functions
36248 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
36250 When reading registers from a trace frame (@pxref{Analyze Collected
36251 Data,,Using the Collected Data}), the stub may also return a string of
36252 literal @samp{x}'s in place of the register data digits, to indicate
36253 that the corresponding register has not been collected, thus its value
36254 is unavailable. For example, for an architecture with 4 registers of
36255 4 bytes each, the following reply indicates to @value{GDBN} that
36256 registers 0 and 2 have not been collected, while registers 1 and 3
36257 have been collected, and both have zero value:
36261 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36268 @item G @var{XX@dots{}}
36269 @cindex @samp{G} packet
36270 Write general registers. @xref{read registers packet}, for a
36271 description of the @var{XX@dots{}} data.
36281 @item H @var{op} @var{thread-id}
36282 @cindex @samp{H} packet
36283 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36284 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
36285 should be @samp{c} for step and continue operations (note that this
36286 is deprecated, supporting the @samp{vCont} command is a better
36287 option), and @samp{g} for other operations. The thread designator
36288 @var{thread-id} has the format and interpretation described in
36289 @ref{thread-id syntax}.
36300 @c 'H': How restrictive (or permissive) is the thread model. If a
36301 @c thread is selected and stopped, are other threads allowed
36302 @c to continue to execute? As I mentioned above, I think the
36303 @c semantics of each command when a thread is selected must be
36304 @c described. For example:
36306 @c 'g': If the stub supports threads and a specific thread is
36307 @c selected, returns the register block from that thread;
36308 @c otherwise returns current registers.
36310 @c 'G' If the stub supports threads and a specific thread is
36311 @c selected, sets the registers of the register block of
36312 @c that thread; otherwise sets current registers.
36314 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36315 @anchor{cycle step packet}
36316 @cindex @samp{i} packet
36317 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36318 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36319 step starting at that address.
36322 @cindex @samp{I} packet
36323 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36327 @cindex @samp{k} packet
36330 The exact effect of this packet is not specified.
36332 For a bare-metal target, it may power cycle or reset the target
36333 system. For that reason, the @samp{k} packet has no reply.
36335 For a single-process target, it may kill that process if possible.
36337 A multiple-process target may choose to kill just one process, or all
36338 that are under @value{GDBN}'s control. For more precise control, use
36339 the vKill packet (@pxref{vKill packet}).
36341 If the target system immediately closes the connection in response to
36342 @samp{k}, @value{GDBN} does not consider the lack of packet
36343 acknowledgment to be an error, and assumes the kill was successful.
36345 If connected using @kbd{target extended-remote}, and the target does
36346 not close the connection in response to a kill request, @value{GDBN}
36347 probes the target state as if a new connection was opened
36348 (@pxref{? packet}).
36350 @item m @var{addr},@var{length}
36351 @cindex @samp{m} packet
36352 Read @var{length} addressable memory units starting at address @var{addr}
36353 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36354 any particular boundary.
36356 The stub need not use any particular size or alignment when gathering
36357 data from memory for the response; even if @var{addr} is word-aligned
36358 and @var{length} is a multiple of the word size, the stub is free to
36359 use byte accesses, or not. For this reason, this packet may not be
36360 suitable for accessing memory-mapped I/O devices.
36361 @cindex alignment of remote memory accesses
36362 @cindex size of remote memory accesses
36363 @cindex memory, alignment and size of remote accesses
36367 @item @var{XX@dots{}}
36368 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36369 The reply may contain fewer addressable memory units than requested if the
36370 server was able to read only part of the region of memory.
36375 @item M @var{addr},@var{length}:@var{XX@dots{}}
36376 @cindex @samp{M} packet
36377 Write @var{length} addressable memory units starting at address @var{addr}
36378 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36379 byte is transmitted as a two-digit hexadecimal number.
36386 for an error (this includes the case where only part of the data was
36391 @cindex @samp{p} packet
36392 Read the value of register @var{n}; @var{n} is in hex.
36393 @xref{read registers packet}, for a description of how the returned
36394 register value is encoded.
36398 @item @var{XX@dots{}}
36399 the register's value
36403 Indicating an unrecognized @var{query}.
36406 @item P @var{n@dots{}}=@var{r@dots{}}
36407 @anchor{write register packet}
36408 @cindex @samp{P} packet
36409 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36410 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36411 digits for each byte in the register (target byte order).
36421 @item q @var{name} @var{params}@dots{}
36422 @itemx Q @var{name} @var{params}@dots{}
36423 @cindex @samp{q} packet
36424 @cindex @samp{Q} packet
36425 General query (@samp{q}) and set (@samp{Q}). These packets are
36426 described fully in @ref{General Query Packets}.
36429 @cindex @samp{r} packet
36430 Reset the entire system.
36432 Don't use this packet; use the @samp{R} packet instead.
36435 @cindex @samp{R} packet
36436 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36437 This packet is only available in extended mode (@pxref{extended mode}).
36439 The @samp{R} packet has no reply.
36441 @item s @r{[}@var{addr}@r{]}
36442 @cindex @samp{s} packet
36443 Single step, resuming at @var{addr}. If
36444 @var{addr} is omitted, resume at same address.
36446 This packet is deprecated for multi-threading support. @xref{vCont
36450 @xref{Stop Reply Packets}, for the reply specifications.
36452 @item S @var{sig}@r{[};@var{addr}@r{]}
36453 @anchor{step with signal packet}
36454 @cindex @samp{S} packet
36455 Step with signal. This is analogous to the @samp{C} packet, but
36456 requests a single-step, rather than a normal resumption of execution.
36458 This packet is deprecated for multi-threading support. @xref{vCont
36462 @xref{Stop Reply Packets}, for the reply specifications.
36464 @item t @var{addr}:@var{PP},@var{MM}
36465 @cindex @samp{t} packet
36466 Search backwards starting at address @var{addr} for a match with pattern
36467 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36468 There must be at least 3 digits in @var{addr}.
36470 @item T @var{thread-id}
36471 @cindex @samp{T} packet
36472 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36477 thread is still alive
36483 Packets starting with @samp{v} are identified by a multi-letter name,
36484 up to the first @samp{;} or @samp{?} (or the end of the packet).
36486 @item vAttach;@var{pid}
36487 @cindex @samp{vAttach} packet
36488 Attach to a new process with the specified process ID @var{pid}.
36489 The process ID is a
36490 hexadecimal integer identifying the process. In all-stop mode, all
36491 threads in the attached process are stopped; in non-stop mode, it may be
36492 attached without being stopped if that is supported by the target.
36494 @c In non-stop mode, on a successful vAttach, the stub should set the
36495 @c current thread to a thread of the newly-attached process. After
36496 @c attaching, GDB queries for the attached process's thread ID with qC.
36497 @c Also note that, from a user perspective, whether or not the
36498 @c target is stopped on attach in non-stop mode depends on whether you
36499 @c use the foreground or background version of the attach command, not
36500 @c on what vAttach does; GDB does the right thing with respect to either
36501 @c stopping or restarting threads.
36503 This packet is only available in extended mode (@pxref{extended mode}).
36509 @item @r{Any stop packet}
36510 for success in all-stop mode (@pxref{Stop Reply Packets})
36512 for success in non-stop mode (@pxref{Remote Non-Stop})
36515 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36516 @cindex @samp{vCont} packet
36517 @anchor{vCont packet}
36518 Resume the inferior, specifying different actions for each thread.
36520 For each inferior thread, the leftmost action with a matching
36521 @var{thread-id} is applied. Threads that don't match any action
36522 remain in their current state. Thread IDs are specified using the
36523 syntax described in @ref{thread-id syntax}. If multiprocess
36524 extensions (@pxref{multiprocess extensions}) are supported, actions
36525 can be specified to match all threads in a process by using the
36526 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36527 @var{thread-id} matches all threads. Specifying no actions is an
36530 Currently supported actions are:
36536 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36540 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36543 @item r @var{start},@var{end}
36544 Step once, and then keep stepping as long as the thread stops at
36545 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36546 The remote stub reports a stop reply when either the thread goes out
36547 of the range or is stopped due to an unrelated reason, such as hitting
36548 a breakpoint. @xref{range stepping}.
36550 If the range is empty (@var{start} == @var{end}), then the action
36551 becomes equivalent to the @samp{s} action. In other words,
36552 single-step once, and report the stop (even if the stepped instruction
36553 jumps to @var{start}).
36555 (A stop reply may be sent at any point even if the PC is still within
36556 the stepping range; for example, it is valid to implement this packet
36557 in a degenerate way as a single instruction step operation.)
36561 The optional argument @var{addr} normally associated with the
36562 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36563 not supported in @samp{vCont}.
36565 The @samp{t} action is only relevant in non-stop mode
36566 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36567 A stop reply should be generated for any affected thread not already stopped.
36568 When a thread is stopped by means of a @samp{t} action,
36569 the corresponding stop reply should indicate that the thread has stopped with
36570 signal @samp{0}, regardless of whether the target uses some other signal
36571 as an implementation detail.
36573 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36574 @samp{r} actions for threads that are already running. Conversely,
36575 the server must ignore @samp{t} actions for threads that are already
36578 @emph{Note:} In non-stop mode, a thread is considered running until
36579 @value{GDBN} acknowleges an asynchronous stop notification for it with
36580 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36582 The stub must support @samp{vCont} if it reports support for
36583 multiprocess extensions (@pxref{multiprocess extensions}).
36586 @xref{Stop Reply Packets}, for the reply specifications.
36589 @cindex @samp{vCont?} packet
36590 Request a list of actions supported by the @samp{vCont} packet.
36594 @item vCont@r{[};@var{action}@dots{}@r{]}
36595 The @samp{vCont} packet is supported. Each @var{action} is a supported
36596 command in the @samp{vCont} packet.
36598 The @samp{vCont} packet is not supported.
36601 @anchor{vCtrlC packet}
36603 @cindex @samp{vCtrlC} packet
36604 Interrupt remote target as if a control-C was pressed on the remote
36605 terminal. This is the equivalent to reacting to the @code{^C}
36606 (@samp{\003}, the control-C character) character in all-stop mode
36607 while the target is running, except this works in non-stop mode.
36608 @xref{interrupting remote targets}, for more info on the all-stop
36619 @item vFile:@var{operation}:@var{parameter}@dots{}
36620 @cindex @samp{vFile} packet
36621 Perform a file operation on the target system. For details,
36622 see @ref{Host I/O Packets}.
36624 @item vFlashErase:@var{addr},@var{length}
36625 @cindex @samp{vFlashErase} packet
36626 Direct the stub to erase @var{length} bytes of flash starting at
36627 @var{addr}. The region may enclose any number of flash blocks, but
36628 its start and end must fall on block boundaries, as indicated by the
36629 flash block size appearing in the memory map (@pxref{Memory Map
36630 Format}). @value{GDBN} groups flash memory programming operations
36631 together, and sends a @samp{vFlashDone} request after each group; the
36632 stub is allowed to delay erase operation until the @samp{vFlashDone}
36633 packet is received.
36643 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36644 @cindex @samp{vFlashWrite} packet
36645 Direct the stub to write data to flash address @var{addr}. The data
36646 is passed in binary form using the same encoding as for the @samp{X}
36647 packet (@pxref{Binary Data}). The memory ranges specified by
36648 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36649 not overlap, and must appear in order of increasing addresses
36650 (although @samp{vFlashErase} packets for higher addresses may already
36651 have been received; the ordering is guaranteed only between
36652 @samp{vFlashWrite} packets). If a packet writes to an address that was
36653 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36654 target-specific method, the results are unpredictable.
36662 for vFlashWrite addressing non-flash memory
36668 @cindex @samp{vFlashDone} packet
36669 Indicate to the stub that flash programming operation is finished.
36670 The stub is permitted to delay or batch the effects of a group of
36671 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36672 @samp{vFlashDone} packet is received. The contents of the affected
36673 regions of flash memory are unpredictable until the @samp{vFlashDone}
36674 request is completed.
36676 @item vKill;@var{pid}
36677 @cindex @samp{vKill} packet
36678 @anchor{vKill packet}
36679 Kill the process with the specified process ID @var{pid}, which is a
36680 hexadecimal integer identifying the process. This packet is used in
36681 preference to @samp{k} when multiprocess protocol extensions are
36682 supported; see @ref{multiprocess extensions}.
36692 @item vMustReplyEmpty
36693 @cindex @samp{vMustReplyEmpty} packet
36694 The correct reply to an unknown @samp{v} packet is to return the empty
36695 string, however, some older versions of @command{gdbserver} would
36696 incorrectly return @samp{OK} for unknown @samp{v} packets.
36698 The @samp{vMustReplyEmpty} is used as a feature test to check how
36699 @command{gdbserver} handles unknown packets, it is important that this
36700 packet be handled in the same way as other unknown @samp{v} packets.
36701 If this packet is handled differently to other unknown @samp{v}
36702 packets then it is possile that @value{GDBN} may run into problems in
36703 other areas, specifically around use of @samp{vFile:setfs:}.
36705 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36706 @cindex @samp{vRun} packet
36707 Run the program @var{filename}, passing it each @var{argument} on its
36708 command line. The file and arguments are hex-encoded strings. If
36709 @var{filename} is an empty string, the stub may use a default program
36710 (e.g.@: the last program run). The program is created in the stopped
36713 @c FIXME: What about non-stop mode?
36715 This packet is only available in extended mode (@pxref{extended mode}).
36721 @item @r{Any stop packet}
36722 for success (@pxref{Stop Reply Packets})
36726 @cindex @samp{vStopped} packet
36727 @xref{Notification Packets}.
36729 @item X @var{addr},@var{length}:@var{XX@dots{}}
36731 @cindex @samp{X} packet
36732 Write data to memory, where the data is transmitted in binary.
36733 Memory is specified by its address @var{addr} and number of addressable memory
36734 units @var{length} (@pxref{addressable memory unit});
36735 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36745 @item z @var{type},@var{addr},@var{kind}
36746 @itemx Z @var{type},@var{addr},@var{kind}
36747 @anchor{insert breakpoint or watchpoint packet}
36748 @cindex @samp{z} packet
36749 @cindex @samp{Z} packets
36750 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36751 watchpoint starting at address @var{address} of kind @var{kind}.
36753 Each breakpoint and watchpoint packet @var{type} is documented
36756 @emph{Implementation notes: A remote target shall return an empty string
36757 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36758 remote target shall support either both or neither of a given
36759 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36760 avoid potential problems with duplicate packets, the operations should
36761 be implemented in an idempotent way.}
36763 @item z0,@var{addr},@var{kind}
36764 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36765 @cindex @samp{z0} packet
36766 @cindex @samp{Z0} packet
36767 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36768 @var{addr} of type @var{kind}.
36770 A software breakpoint is implemented by replacing the instruction at
36771 @var{addr} with a software breakpoint or trap instruction. The
36772 @var{kind} is target-specific and typically indicates the size of the
36773 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36774 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36775 architectures have additional meanings for @var{kind}
36776 (@pxref{Architecture-Specific Protocol Details}); if no
36777 architecture-specific value is being used, it should be @samp{0}.
36778 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36779 conditional expressions in bytecode form that should be evaluated on
36780 the target's side. These are the conditions that should be taken into
36781 consideration when deciding if the breakpoint trigger should be
36782 reported back to @value{GDBN}.
36784 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36785 for how to best report a software breakpoint event to @value{GDBN}.
36787 The @var{cond_list} parameter is comprised of a series of expressions,
36788 concatenated without separators. Each expression has the following form:
36792 @item X @var{len},@var{expr}
36793 @var{len} is the length of the bytecode expression and @var{expr} is the
36794 actual conditional expression in bytecode form.
36798 The optional @var{cmd_list} parameter introduces commands that may be
36799 run on the target, rather than being reported back to @value{GDBN}.
36800 The parameter starts with a numeric flag @var{persist}; if the flag is
36801 nonzero, then the breakpoint may remain active and the commands
36802 continue to be run even when @value{GDBN} disconnects from the target.
36803 Following this flag is a series of expressions concatenated with no
36804 separators. Each expression has the following form:
36808 @item X @var{len},@var{expr}
36809 @var{len} is the length of the bytecode expression and @var{expr} is the
36810 actual commands expression in bytecode form.
36814 @emph{Implementation note: It is possible for a target to copy or move
36815 code that contains software breakpoints (e.g., when implementing
36816 overlays). The behavior of this packet, in the presence of such a
36817 target, is not defined.}
36829 @item z1,@var{addr},@var{kind}
36830 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36831 @cindex @samp{z1} packet
36832 @cindex @samp{Z1} packet
36833 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36834 address @var{addr}.
36836 A hardware breakpoint is implemented using a mechanism that is not
36837 dependent on being able to modify the target's memory. The
36838 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36839 same meaning as in @samp{Z0} packets.
36841 @emph{Implementation note: A hardware breakpoint is not affected by code
36854 @item z2,@var{addr},@var{kind}
36855 @itemx Z2,@var{addr},@var{kind}
36856 @cindex @samp{z2} packet
36857 @cindex @samp{Z2} packet
36858 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36859 The number of bytes to watch is specified by @var{kind}.
36871 @item z3,@var{addr},@var{kind}
36872 @itemx Z3,@var{addr},@var{kind}
36873 @cindex @samp{z3} packet
36874 @cindex @samp{Z3} packet
36875 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36876 The number of bytes to watch is specified by @var{kind}.
36888 @item z4,@var{addr},@var{kind}
36889 @itemx Z4,@var{addr},@var{kind}
36890 @cindex @samp{z4} packet
36891 @cindex @samp{Z4} packet
36892 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36893 The number of bytes to watch is specified by @var{kind}.
36907 @node Stop Reply Packets
36908 @section Stop Reply Packets
36909 @cindex stop reply packets
36911 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36912 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36913 receive any of the below as a reply. Except for @samp{?}
36914 and @samp{vStopped}, that reply is only returned
36915 when the target halts. In the below the exact meaning of @dfn{signal
36916 number} is defined by the header @file{include/gdb/signals.h} in the
36917 @value{GDBN} source code.
36919 In non-stop mode, the server will simply reply @samp{OK} to commands
36920 such as @samp{vCont}; any stop will be the subject of a future
36921 notification. @xref{Remote Non-Stop}.
36923 As in the description of request packets, we include spaces in the
36924 reply templates for clarity; these are not part of the reply packet's
36925 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36931 The program received signal number @var{AA} (a two-digit hexadecimal
36932 number). This is equivalent to a @samp{T} response with no
36933 @var{n}:@var{r} pairs.
36935 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36936 @cindex @samp{T} packet reply
36937 The program received signal number @var{AA} (a two-digit hexadecimal
36938 number). This is equivalent to an @samp{S} response, except that the
36939 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36940 and other information directly in the stop reply packet, reducing
36941 round-trip latency. Single-step and breakpoint traps are reported
36942 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36946 If @var{n} is a hexadecimal number, it is a register number, and the
36947 corresponding @var{r} gives that register's value. The data @var{r} is a
36948 series of bytes in target byte order, with each byte given by a
36949 two-digit hex number.
36952 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36953 the stopped thread, as specified in @ref{thread-id syntax}.
36956 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36957 the core on which the stop event was detected.
36960 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36961 specific event that stopped the target. The currently defined stop
36962 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36963 signal. At most one stop reason should be present.
36966 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36967 and go on to the next; this allows us to extend the protocol in the
36971 The currently defined stop reasons are:
36977 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36980 @item syscall_entry
36981 @itemx syscall_return
36982 The packet indicates a syscall entry or return, and @var{r} is the
36983 syscall number, in hex.
36985 @cindex shared library events, remote reply
36987 The packet indicates that the loaded libraries have changed.
36988 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36989 list of loaded libraries. The @var{r} part is ignored.
36991 @cindex replay log events, remote reply
36993 The packet indicates that the target cannot continue replaying
36994 logged execution events, because it has reached the end (or the
36995 beginning when executing backward) of the log. The value of @var{r}
36996 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36997 for more information.
37000 @anchor{swbreak stop reason}
37001 The packet indicates a software breakpoint instruction was executed,
37002 irrespective of whether it was @value{GDBN} that planted the
37003 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
37004 part must be left empty.
37006 On some architectures, such as x86, at the architecture level, when a
37007 breakpoint instruction executes the program counter points at the
37008 breakpoint address plus an offset. On such targets, the stub is
37009 responsible for adjusting the PC to point back at the breakpoint
37012 This packet should not be sent by default; older @value{GDBN} versions
37013 did not support it. @value{GDBN} requests it, by supplying an
37014 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37015 remote stub must also supply the appropriate @samp{qSupported} feature
37016 indicating support.
37018 This packet is required for correct non-stop mode operation.
37021 The packet indicates the target stopped for a hardware breakpoint.
37022 The @var{r} part must be left empty.
37024 The same remarks about @samp{qSupported} and non-stop mode above
37027 @cindex fork events, remote reply
37029 The packet indicates that @code{fork} was called, and @var{r}
37030 is the thread ID of the new child process. Refer to
37031 @ref{thread-id syntax} for the format of the @var{thread-id}
37032 field. This packet is only applicable to targets that support
37035 This packet should not be sent by default; older @value{GDBN} versions
37036 did not support it. @value{GDBN} requests it, by supplying an
37037 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37038 remote stub must also supply the appropriate @samp{qSupported} feature
37039 indicating support.
37041 @cindex vfork events, remote reply
37043 The packet indicates that @code{vfork} was called, and @var{r}
37044 is the thread ID of the new child process. Refer to
37045 @ref{thread-id syntax} for the format of the @var{thread-id}
37046 field. This packet is only applicable to targets that support
37049 This packet should not be sent by default; older @value{GDBN} versions
37050 did not support it. @value{GDBN} requests it, by supplying an
37051 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37052 remote stub must also supply the appropriate @samp{qSupported} feature
37053 indicating support.
37055 @cindex vforkdone events, remote reply
37057 The packet indicates that a child process created by a vfork
37058 has either called @code{exec} or terminated, so that the
37059 address spaces of the parent and child process are no longer
37060 shared. The @var{r} part is ignored. This packet is only
37061 applicable to targets that support vforkdone events.
37063 This packet should not be sent by default; older @value{GDBN} versions
37064 did not support it. @value{GDBN} requests it, by supplying an
37065 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37066 remote stub must also supply the appropriate @samp{qSupported} feature
37067 indicating support.
37069 @cindex exec events, remote reply
37071 The packet indicates that @code{execve} was called, and @var{r}
37072 is the absolute pathname of the file that was executed, in hex.
37073 This packet is only applicable to targets that support exec events.
37075 This packet should not be sent by default; older @value{GDBN} versions
37076 did not support it. @value{GDBN} requests it, by supplying an
37077 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37078 remote stub must also supply the appropriate @samp{qSupported} feature
37079 indicating support.
37081 @cindex thread create event, remote reply
37082 @anchor{thread create event}
37084 The packet indicates that the thread was just created. The new thread
37085 is stopped until @value{GDBN} sets it running with a resumption packet
37086 (@pxref{vCont packet}). This packet should not be sent by default;
37087 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
37088 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
37089 @var{r} part is ignored.
37094 @itemx W @var{AA} ; process:@var{pid}
37095 The process exited, and @var{AA} is the exit status. This is only
37096 applicable to certain targets.
37098 The second form of the response, including the process ID of the
37099 exited process, can be used only when @value{GDBN} has reported
37100 support for multiprocess protocol extensions; see @ref{multiprocess
37101 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37105 @itemx X @var{AA} ; process:@var{pid}
37106 The process terminated with signal @var{AA}.
37108 The second form of the response, including the process ID of the
37109 terminated process, can be used only when @value{GDBN} has reported
37110 support for multiprocess protocol extensions; see @ref{multiprocess
37111 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37114 @anchor{thread exit event}
37115 @cindex thread exit event, remote reply
37116 @item w @var{AA} ; @var{tid}
37118 The thread exited, and @var{AA} is the exit status. This response
37119 should not be sent by default; @value{GDBN} requests it with the
37120 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
37121 @var{AA} is formatted as a big-endian hex string.
37124 There are no resumed threads left in the target. In other words, even
37125 though the process is alive, the last resumed thread has exited. For
37126 example, say the target process has two threads: thread 1 and thread
37127 2. The client leaves thread 1 stopped, and resumes thread 2, which
37128 subsequently exits. At this point, even though the process is still
37129 alive, and thus no @samp{W} stop reply is sent, no thread is actually
37130 executing either. The @samp{N} stop reply thus informs the client
37131 that it can stop waiting for stop replies. This packet should not be
37132 sent by default; older @value{GDBN} versions did not support it.
37133 @value{GDBN} requests it, by supplying an appropriate
37134 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
37135 also supply the appropriate @samp{qSupported} feature indicating
37138 @item O @var{XX}@dots{}
37139 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
37140 written as the program's console output. This can happen at any time
37141 while the program is running and the debugger should continue to wait
37142 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
37144 @item F @var{call-id},@var{parameter}@dots{}
37145 @var{call-id} is the identifier which says which host system call should
37146 be called. This is just the name of the function. Translation into the
37147 correct system call is only applicable as it's defined in @value{GDBN}.
37148 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
37151 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
37152 this very system call.
37154 The target replies with this packet when it expects @value{GDBN} to
37155 call a host system call on behalf of the target. @value{GDBN} replies
37156 with an appropriate @samp{F} packet and keeps up waiting for the next
37157 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
37158 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
37159 Protocol Extension}, for more details.
37163 @node General Query Packets
37164 @section General Query Packets
37165 @cindex remote query requests
37167 Packets starting with @samp{q} are @dfn{general query packets};
37168 packets starting with @samp{Q} are @dfn{general set packets}. General
37169 query and set packets are a semi-unified form for retrieving and
37170 sending information to and from the stub.
37172 The initial letter of a query or set packet is followed by a name
37173 indicating what sort of thing the packet applies to. For example,
37174 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
37175 definitions with the stub. These packet names follow some
37180 The name must not contain commas, colons or semicolons.
37182 Most @value{GDBN} query and set packets have a leading upper case
37185 The names of custom vendor packets should use a company prefix, in
37186 lower case, followed by a period. For example, packets designed at
37187 the Acme Corporation might begin with @samp{qacme.foo} (for querying
37188 foos) or @samp{Qacme.bar} (for setting bars).
37191 The name of a query or set packet should be separated from any
37192 parameters by a @samp{:}; the parameters themselves should be
37193 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
37194 full packet name, and check for a separator or the end of the packet,
37195 in case two packet names share a common prefix. New packets should not begin
37196 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
37197 packets predate these conventions, and have arguments without any terminator
37198 for the packet name; we suspect they are in widespread use in places that
37199 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
37200 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
37203 Like the descriptions of the other packets, each description here
37204 has a template showing the packet's overall syntax, followed by an
37205 explanation of the packet's meaning. We include spaces in some of the
37206 templates for clarity; these are not part of the packet's syntax. No
37207 @value{GDBN} packet uses spaces to separate its components.
37209 Here are the currently defined query and set packets:
37215 Turn on or off the agent as a helper to perform some debugging operations
37216 delegated from @value{GDBN} (@pxref{Control Agent}).
37218 @item QAllow:@var{op}:@var{val}@dots{}
37219 @cindex @samp{QAllow} packet
37220 Specify which operations @value{GDBN} expects to request of the
37221 target, as a semicolon-separated list of operation name and value
37222 pairs. Possible values for @var{op} include @samp{WriteReg},
37223 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
37224 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
37225 indicating that @value{GDBN} will not request the operation, or 1,
37226 indicating that it may. (The target can then use this to set up its
37227 own internals optimally, for instance if the debugger never expects to
37228 insert breakpoints, it may not need to install its own trap handler.)
37231 @cindex current thread, remote request
37232 @cindex @samp{qC} packet
37233 Return the current thread ID.
37237 @item QC @var{thread-id}
37238 Where @var{thread-id} is a thread ID as documented in
37239 @ref{thread-id syntax}.
37240 @item @r{(anything else)}
37241 Any other reply implies the old thread ID.
37244 @item qCRC:@var{addr},@var{length}
37245 @cindex CRC of memory block, remote request
37246 @cindex @samp{qCRC} packet
37247 @anchor{qCRC packet}
37248 Compute the CRC checksum of a block of memory using CRC-32 defined in
37249 IEEE 802.3. The CRC is computed byte at a time, taking the most
37250 significant bit of each byte first. The initial pattern code
37251 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
37253 @emph{Note:} This is the same CRC used in validating separate debug
37254 files (@pxref{Separate Debug Files, , Debugging Information in Separate
37255 Files}). However the algorithm is slightly different. When validating
37256 separate debug files, the CRC is computed taking the @emph{least}
37257 significant bit of each byte first, and the final result is inverted to
37258 detect trailing zeros.
37263 An error (such as memory fault)
37264 @item C @var{crc32}
37265 The specified memory region's checksum is @var{crc32}.
37268 @item QDisableRandomization:@var{value}
37269 @cindex disable address space randomization, remote request
37270 @cindex @samp{QDisableRandomization} packet
37271 Some target operating systems will randomize the virtual address space
37272 of the inferior process as a security feature, but provide a feature
37273 to disable such randomization, e.g.@: to allow for a more deterministic
37274 debugging experience. On such systems, this packet with a @var{value}
37275 of 1 directs the target to disable address space randomization for
37276 processes subsequently started via @samp{vRun} packets, while a packet
37277 with a @var{value} of 0 tells the target to enable address space
37280 This packet is only available in extended mode (@pxref{extended mode}).
37285 The request succeeded.
37288 An error occurred. The error number @var{nn} is given as hex digits.
37291 An empty reply indicates that @samp{QDisableRandomization} is not supported
37295 This packet is not probed by default; the remote stub must request it,
37296 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37297 This should only be done on targets that actually support disabling
37298 address space randomization.
37300 @item QStartupWithShell:@var{value}
37301 @cindex startup with shell, remote request
37302 @cindex @samp{QStartupWithShell} packet
37303 On UNIX-like targets, it is possible to start the inferior using a
37304 shell program. This is the default behavior on both @value{GDBN} and
37305 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
37306 used to inform @command{gdbserver} whether it should start the
37307 inferior using a shell or not.
37309 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
37310 to start the inferior. If @var{value} is @samp{1},
37311 @command{gdbserver} will use a shell to start the inferior. All other
37312 values are considered an error.
37314 This packet is only available in extended mode (@pxref{extended
37320 The request succeeded.
37323 An error occurred. The error number @var{nn} is given as hex digits.
37326 This packet is not probed by default; the remote stub must request it,
37327 by supplying an appropriate @samp{qSupported} response
37328 (@pxref{qSupported}). This should only be done on targets that
37329 actually support starting the inferior using a shell.
37331 Use of this packet is controlled by the @code{set startup-with-shell}
37332 command; @pxref{set startup-with-shell}.
37334 @item QEnvironmentHexEncoded:@var{hex-value}
37335 @anchor{QEnvironmentHexEncoded}
37336 @cindex set environment variable, remote request
37337 @cindex @samp{QEnvironmentHexEncoded} packet
37338 On UNIX-like targets, it is possible to set environment variables that
37339 will be passed to the inferior during the startup process. This
37340 packet is used to inform @command{gdbserver} of an environment
37341 variable that has been defined by the user on @value{GDBN} (@pxref{set
37344 The packet is composed by @var{hex-value}, an hex encoded
37345 representation of the @var{name=value} format representing an
37346 environment variable. The name of the environment variable is
37347 represented by @var{name}, and the value to be assigned to the
37348 environment variable is represented by @var{value}. If the variable
37349 has no value (i.e., the value is @code{null}), then @var{value} will
37352 This packet is only available in extended mode (@pxref{extended
37358 The request succeeded.
37361 This packet is not probed by default; the remote stub must request it,
37362 by supplying an appropriate @samp{qSupported} response
37363 (@pxref{qSupported}). This should only be done on targets that
37364 actually support passing environment variables to the starting
37367 This packet is related to the @code{set environment} command;
37368 @pxref{set environment}.
37370 @item QEnvironmentUnset:@var{hex-value}
37371 @anchor{QEnvironmentUnset}
37372 @cindex unset environment variable, remote request
37373 @cindex @samp{QEnvironmentUnset} packet
37374 On UNIX-like targets, it is possible to unset environment variables
37375 before starting the inferior in the remote target. This packet is
37376 used to inform @command{gdbserver} of an environment variable that has
37377 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37379 The packet is composed by @var{hex-value}, an hex encoded
37380 representation of the name of the environment variable to be unset.
37382 This packet is only available in extended mode (@pxref{extended
37388 The request succeeded.
37391 This packet is not probed by default; the remote stub must request it,
37392 by supplying an appropriate @samp{qSupported} response
37393 (@pxref{qSupported}). This should only be done on targets that
37394 actually support passing environment variables to the starting
37397 This packet is related to the @code{unset environment} command;
37398 @pxref{unset environment}.
37400 @item QEnvironmentReset
37401 @anchor{QEnvironmentReset}
37402 @cindex reset environment, remote request
37403 @cindex @samp{QEnvironmentReset} packet
37404 On UNIX-like targets, this packet is used to reset the state of
37405 environment variables in the remote target before starting the
37406 inferior. In this context, reset means unsetting all environment
37407 variables that were previously set by the user (i.e., were not
37408 initially present in the environment). It is sent to
37409 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37410 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37411 (@pxref{QEnvironmentUnset}) packets.
37413 This packet is only available in extended mode (@pxref{extended
37419 The request succeeded.
37422 This packet is not probed by default; the remote stub must request it,
37423 by supplying an appropriate @samp{qSupported} response
37424 (@pxref{qSupported}). This should only be done on targets that
37425 actually support passing environment variables to the starting
37428 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37429 @anchor{QSetWorkingDir packet}
37430 @cindex set working directory, remote request
37431 @cindex @samp{QSetWorkingDir} packet
37432 This packet is used to inform the remote server of the intended
37433 current working directory for programs that are going to be executed.
37435 The packet is composed by @var{directory}, an hex encoded
37436 representation of the directory that the remote inferior will use as
37437 its current working directory. If @var{directory} is an empty string,
37438 the remote server should reset the inferior's current working
37439 directory to its original, empty value.
37441 This packet is only available in extended mode (@pxref{extended
37447 The request succeeded.
37451 @itemx qsThreadInfo
37452 @cindex list active threads, remote request
37453 @cindex @samp{qfThreadInfo} packet
37454 @cindex @samp{qsThreadInfo} packet
37455 Obtain a list of all active thread IDs from the target (OS). Since there
37456 may be too many active threads to fit into one reply packet, this query
37457 works iteratively: it may require more than one query/reply sequence to
37458 obtain the entire list of threads. The first query of the sequence will
37459 be the @samp{qfThreadInfo} query; subsequent queries in the
37460 sequence will be the @samp{qsThreadInfo} query.
37462 NOTE: This packet replaces the @samp{qL} query (see below).
37466 @item m @var{thread-id}
37468 @item m @var{thread-id},@var{thread-id}@dots{}
37469 a comma-separated list of thread IDs
37471 (lower case letter @samp{L}) denotes end of list.
37474 In response to each query, the target will reply with a list of one or
37475 more thread IDs, separated by commas.
37476 @value{GDBN} will respond to each reply with a request for more thread
37477 ids (using the @samp{qs} form of the query), until the target responds
37478 with @samp{l} (lower-case ell, for @dfn{last}).
37479 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37482 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37483 initial connection with the remote target, and the very first thread ID
37484 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37485 message. Therefore, the stub should ensure that the first thread ID in
37486 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37488 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37489 @cindex get thread-local storage address, remote request
37490 @cindex @samp{qGetTLSAddr} packet
37491 Fetch the address associated with thread local storage specified
37492 by @var{thread-id}, @var{offset}, and @var{lm}.
37494 @var{thread-id} is the thread ID associated with the
37495 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37497 @var{offset} is the (big endian, hex encoded) offset associated with the
37498 thread local variable. (This offset is obtained from the debug
37499 information associated with the variable.)
37501 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37502 load module associated with the thread local storage. For example,
37503 a @sc{gnu}/Linux system will pass the link map address of the shared
37504 object associated with the thread local storage under consideration.
37505 Other operating environments may choose to represent the load module
37506 differently, so the precise meaning of this parameter will vary.
37510 @item @var{XX}@dots{}
37511 Hex encoded (big endian) bytes representing the address of the thread
37512 local storage requested.
37515 An error occurred. The error number @var{nn} is given as hex digits.
37518 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37521 @item qGetTIBAddr:@var{thread-id}
37522 @cindex get thread information block address
37523 @cindex @samp{qGetTIBAddr} packet
37524 Fetch address of the Windows OS specific Thread Information Block.
37526 @var{thread-id} is the thread ID associated with the thread.
37530 @item @var{XX}@dots{}
37531 Hex encoded (big endian) bytes representing the linear address of the
37532 thread information block.
37535 An error occured. This means that either the thread was not found, or the
37536 address could not be retrieved.
37539 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37542 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37543 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37544 digit) is one to indicate the first query and zero to indicate a
37545 subsequent query; @var{threadcount} (two hex digits) is the maximum
37546 number of threads the response packet can contain; and @var{nextthread}
37547 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37548 returned in the response as @var{argthread}.
37550 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37554 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37555 Where: @var{count} (two hex digits) is the number of threads being
37556 returned; @var{done} (one hex digit) is zero to indicate more threads
37557 and one indicates no further threads; @var{argthreadid} (eight hex
37558 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37559 is a sequence of thread IDs, @var{threadid} (eight hex
37560 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37564 @cindex section offsets, remote request
37565 @cindex @samp{qOffsets} packet
37566 Get section offsets that the target used when relocating the downloaded
37571 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37572 Relocate the @code{Text} section by @var{xxx} from its original address.
37573 Relocate the @code{Data} section by @var{yyy} from its original address.
37574 If the object file format provides segment information (e.g.@: @sc{elf}
37575 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37576 segments by the supplied offsets.
37578 @emph{Note: while a @code{Bss} offset may be included in the response,
37579 @value{GDBN} ignores this and instead applies the @code{Data} offset
37580 to the @code{Bss} section.}
37582 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37583 Relocate the first segment of the object file, which conventionally
37584 contains program code, to a starting address of @var{xxx}. If
37585 @samp{DataSeg} is specified, relocate the second segment, which
37586 conventionally contains modifiable data, to a starting address of
37587 @var{yyy}. @value{GDBN} will report an error if the object file
37588 does not contain segment information, or does not contain at least
37589 as many segments as mentioned in the reply. Extra segments are
37590 kept at fixed offsets relative to the last relocated segment.
37593 @item qP @var{mode} @var{thread-id}
37594 @cindex thread information, remote request
37595 @cindex @samp{qP} packet
37596 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37597 encoded 32 bit mode; @var{thread-id} is a thread ID
37598 (@pxref{thread-id syntax}).
37600 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37603 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37607 @cindex non-stop mode, remote request
37608 @cindex @samp{QNonStop} packet
37610 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37611 @xref{Remote Non-Stop}, for more information.
37616 The request succeeded.
37619 An error occurred. The error number @var{nn} is given as hex digits.
37622 An empty reply indicates that @samp{QNonStop} is not supported by
37626 This packet is not probed by default; the remote stub must request it,
37627 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37628 Use of this packet is controlled by the @code{set non-stop} command;
37629 @pxref{Non-Stop Mode}.
37631 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37632 @itemx QCatchSyscalls:0
37633 @cindex catch syscalls from inferior, remote request
37634 @cindex @samp{QCatchSyscalls} packet
37635 @anchor{QCatchSyscalls}
37636 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37637 catching syscalls from the inferior process.
37639 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37640 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37641 is listed, every system call should be reported.
37643 Note that if a syscall not in the list is reported, @value{GDBN} will
37644 still filter the event according to its own list from all corresponding
37645 @code{catch syscall} commands. However, it is more efficient to only
37646 report the requested syscalls.
37648 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37649 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37651 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37652 kept for the new process too. On targets where exec may affect syscall
37653 numbers, for example with exec between 32 and 64-bit processes, the
37654 client should send a new packet with the new syscall list.
37659 The request succeeded.
37662 An error occurred. @var{nn} are hex digits.
37665 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37669 Use of this packet is controlled by the @code{set remote catch-syscalls}
37670 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37671 This packet is not probed by default; the remote stub must request it,
37672 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37674 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37675 @cindex pass signals to inferior, remote request
37676 @cindex @samp{QPassSignals} packet
37677 @anchor{QPassSignals}
37678 Each listed @var{signal} should be passed directly to the inferior process.
37679 Signals are numbered identically to continue packets and stop replies
37680 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37681 strictly greater than the previous item. These signals do not need to stop
37682 the inferior, or be reported to @value{GDBN}. All other signals should be
37683 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37684 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37685 new list. This packet improves performance when using @samp{handle
37686 @var{signal} nostop noprint pass}.
37691 The request succeeded.
37694 An error occurred. The error number @var{nn} is given as hex digits.
37697 An empty reply indicates that @samp{QPassSignals} is not supported by
37701 Use of this packet is controlled by the @code{set remote pass-signals}
37702 command (@pxref{Remote Configuration, set remote pass-signals}).
37703 This packet is not probed by default; the remote stub must request it,
37704 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37706 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37707 @cindex signals the inferior may see, remote request
37708 @cindex @samp{QProgramSignals} packet
37709 @anchor{QProgramSignals}
37710 Each listed @var{signal} may be delivered to the inferior process.
37711 Others should be silently discarded.
37713 In some cases, the remote stub may need to decide whether to deliver a
37714 signal to the program or not without @value{GDBN} involvement. One
37715 example of that is while detaching --- the program's threads may have
37716 stopped for signals that haven't yet had a chance of being reported to
37717 @value{GDBN}, and so the remote stub can use the signal list specified
37718 by this packet to know whether to deliver or ignore those pending
37721 This does not influence whether to deliver a signal as requested by a
37722 resumption packet (@pxref{vCont packet}).
37724 Signals are numbered identically to continue packets and stop replies
37725 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37726 strictly greater than the previous item. Multiple
37727 @samp{QProgramSignals} packets do not combine; any earlier
37728 @samp{QProgramSignals} list is completely replaced by the new list.
37733 The request succeeded.
37736 An error occurred. The error number @var{nn} is given as hex digits.
37739 An empty reply indicates that @samp{QProgramSignals} is not supported
37743 Use of this packet is controlled by the @code{set remote program-signals}
37744 command (@pxref{Remote Configuration, set remote program-signals}).
37745 This packet is not probed by default; the remote stub must request it,
37746 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37748 @anchor{QThreadEvents}
37749 @item QThreadEvents:1
37750 @itemx QThreadEvents:0
37751 @cindex thread create/exit events, remote request
37752 @cindex @samp{QThreadEvents} packet
37754 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37755 reporting of thread create and exit events. @xref{thread create
37756 event}, for the reply specifications. For example, this is used in
37757 non-stop mode when @value{GDBN} stops a set of threads and
37758 synchronously waits for the their corresponding stop replies. Without
37759 exit events, if one of the threads exits, @value{GDBN} would hang
37760 forever not knowing that it should no longer expect a stop for that
37761 same thread. @value{GDBN} does not enable this feature unless the
37762 stub reports that it supports it by including @samp{QThreadEvents+} in
37763 its @samp{qSupported} reply.
37768 The request succeeded.
37771 An error occurred. The error number @var{nn} is given as hex digits.
37774 An empty reply indicates that @samp{QThreadEvents} is not supported by
37778 Use of this packet is controlled by the @code{set remote thread-events}
37779 command (@pxref{Remote Configuration, set remote thread-events}).
37781 @item qRcmd,@var{command}
37782 @cindex execute remote command, remote request
37783 @cindex @samp{qRcmd} packet
37784 @var{command} (hex encoded) is passed to the local interpreter for
37785 execution. Invalid commands should be reported using the output
37786 string. Before the final result packet, the target may also respond
37787 with a number of intermediate @samp{O@var{output}} console output
37788 packets. @emph{Implementors should note that providing access to a
37789 stubs's interpreter may have security implications}.
37794 A command response with no output.
37796 A command response with the hex encoded output string @var{OUTPUT}.
37798 Indicate a badly formed request.
37800 An empty reply indicates that @samp{qRcmd} is not recognized.
37803 (Note that the @code{qRcmd} packet's name is separated from the
37804 command by a @samp{,}, not a @samp{:}, contrary to the naming
37805 conventions above. Please don't use this packet as a model for new
37808 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37809 @cindex searching memory, in remote debugging
37811 @cindex @samp{qSearch:memory} packet
37813 @cindex @samp{qSearch memory} packet
37814 @anchor{qSearch memory}
37815 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37816 Both @var{address} and @var{length} are encoded in hex;
37817 @var{search-pattern} is a sequence of bytes, also hex encoded.
37822 The pattern was not found.
37824 The pattern was found at @var{address}.
37826 A badly formed request or an error was encountered while searching memory.
37828 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37831 @item QStartNoAckMode
37832 @cindex @samp{QStartNoAckMode} packet
37833 @anchor{QStartNoAckMode}
37834 Request that the remote stub disable the normal @samp{+}/@samp{-}
37835 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37840 The stub has switched to no-acknowledgment mode.
37841 @value{GDBN} acknowledges this reponse,
37842 but neither the stub nor @value{GDBN} shall send or expect further
37843 @samp{+}/@samp{-} acknowledgments in the current connection.
37845 An empty reply indicates that the stub does not support no-acknowledgment mode.
37848 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37849 @cindex supported packets, remote query
37850 @cindex features of the remote protocol
37851 @cindex @samp{qSupported} packet
37852 @anchor{qSupported}
37853 Tell the remote stub about features supported by @value{GDBN}, and
37854 query the stub for features it supports. This packet allows
37855 @value{GDBN} and the remote stub to take advantage of each others'
37856 features. @samp{qSupported} also consolidates multiple feature probes
37857 at startup, to improve @value{GDBN} performance---a single larger
37858 packet performs better than multiple smaller probe packets on
37859 high-latency links. Some features may enable behavior which must not
37860 be on by default, e.g.@: because it would confuse older clients or
37861 stubs. Other features may describe packets which could be
37862 automatically probed for, but are not. These features must be
37863 reported before @value{GDBN} will use them. This ``default
37864 unsupported'' behavior is not appropriate for all packets, but it
37865 helps to keep the initial connection time under control with new
37866 versions of @value{GDBN} which support increasing numbers of packets.
37870 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37871 The stub supports or does not support each returned @var{stubfeature},
37872 depending on the form of each @var{stubfeature} (see below for the
37875 An empty reply indicates that @samp{qSupported} is not recognized,
37876 or that no features needed to be reported to @value{GDBN}.
37879 The allowed forms for each feature (either a @var{gdbfeature} in the
37880 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37884 @item @var{name}=@var{value}
37885 The remote protocol feature @var{name} is supported, and associated
37886 with the specified @var{value}. The format of @var{value} depends
37887 on the feature, but it must not include a semicolon.
37889 The remote protocol feature @var{name} is supported, and does not
37890 need an associated value.
37892 The remote protocol feature @var{name} is not supported.
37894 The remote protocol feature @var{name} may be supported, and
37895 @value{GDBN} should auto-detect support in some other way when it is
37896 needed. This form will not be used for @var{gdbfeature} notifications,
37897 but may be used for @var{stubfeature} responses.
37900 Whenever the stub receives a @samp{qSupported} request, the
37901 supplied set of @value{GDBN} features should override any previous
37902 request. This allows @value{GDBN} to put the stub in a known
37903 state, even if the stub had previously been communicating with
37904 a different version of @value{GDBN}.
37906 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37911 This feature indicates whether @value{GDBN} supports multiprocess
37912 extensions to the remote protocol. @value{GDBN} does not use such
37913 extensions unless the stub also reports that it supports them by
37914 including @samp{multiprocess+} in its @samp{qSupported} reply.
37915 @xref{multiprocess extensions}, for details.
37918 This feature indicates that @value{GDBN} supports the XML target
37919 description. If the stub sees @samp{xmlRegisters=} with target
37920 specific strings separated by a comma, it will report register
37924 This feature indicates whether @value{GDBN} supports the
37925 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37926 instruction reply packet}).
37929 This feature indicates whether @value{GDBN} supports the swbreak stop
37930 reason in stop replies. @xref{swbreak stop reason}, for details.
37933 This feature indicates whether @value{GDBN} supports the hwbreak stop
37934 reason in stop replies. @xref{swbreak stop reason}, for details.
37937 This feature indicates whether @value{GDBN} supports fork event
37938 extensions to the remote protocol. @value{GDBN} does not use such
37939 extensions unless the stub also reports that it supports them by
37940 including @samp{fork-events+} in its @samp{qSupported} reply.
37943 This feature indicates whether @value{GDBN} supports vfork event
37944 extensions to the remote protocol. @value{GDBN} does not use such
37945 extensions unless the stub also reports that it supports them by
37946 including @samp{vfork-events+} in its @samp{qSupported} reply.
37949 This feature indicates whether @value{GDBN} supports exec event
37950 extensions to the remote protocol. @value{GDBN} does not use such
37951 extensions unless the stub also reports that it supports them by
37952 including @samp{exec-events+} in its @samp{qSupported} reply.
37954 @item vContSupported
37955 This feature indicates whether @value{GDBN} wants to know the
37956 supported actions in the reply to @samp{vCont?} packet.
37959 Stubs should ignore any unknown values for
37960 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37961 packet supports receiving packets of unlimited length (earlier
37962 versions of @value{GDBN} may reject overly long responses). Additional values
37963 for @var{gdbfeature} may be defined in the future to let the stub take
37964 advantage of new features in @value{GDBN}, e.g.@: incompatible
37965 improvements in the remote protocol---the @samp{multiprocess} feature is
37966 an example of such a feature. The stub's reply should be independent
37967 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37968 describes all the features it supports, and then the stub replies with
37969 all the features it supports.
37971 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37972 responses, as long as each response uses one of the standard forms.
37974 Some features are flags. A stub which supports a flag feature
37975 should respond with a @samp{+} form response. Other features
37976 require values, and the stub should respond with an @samp{=}
37979 Each feature has a default value, which @value{GDBN} will use if
37980 @samp{qSupported} is not available or if the feature is not mentioned
37981 in the @samp{qSupported} response. The default values are fixed; a
37982 stub is free to omit any feature responses that match the defaults.
37984 Not all features can be probed, but for those which can, the probing
37985 mechanism is useful: in some cases, a stub's internal
37986 architecture may not allow the protocol layer to know some information
37987 about the underlying target in advance. This is especially common in
37988 stubs which may be configured for multiple targets.
37990 These are the currently defined stub features and their properties:
37992 @multitable @columnfractions 0.35 0.2 0.12 0.2
37993 @c NOTE: The first row should be @headitem, but we do not yet require
37994 @c a new enough version of Texinfo (4.7) to use @headitem.
37996 @tab Value Required
38000 @item @samp{PacketSize}
38005 @item @samp{qXfer:auxv:read}
38010 @item @samp{qXfer:btrace:read}
38015 @item @samp{qXfer:btrace-conf:read}
38020 @item @samp{qXfer:exec-file:read}
38025 @item @samp{qXfer:features:read}
38030 @item @samp{qXfer:libraries:read}
38035 @item @samp{qXfer:libraries-svr4:read}
38040 @item @samp{augmented-libraries-svr4-read}
38045 @item @samp{qXfer:memory-map:read}
38050 @item @samp{qXfer:sdata:read}
38055 @item @samp{qXfer:spu:read}
38060 @item @samp{qXfer:spu:write}
38065 @item @samp{qXfer:siginfo:read}
38070 @item @samp{qXfer:siginfo:write}
38075 @item @samp{qXfer:threads:read}
38080 @item @samp{qXfer:traceframe-info:read}
38085 @item @samp{qXfer:uib:read}
38090 @item @samp{qXfer:fdpic:read}
38095 @item @samp{Qbtrace:off}
38100 @item @samp{Qbtrace:bts}
38105 @item @samp{Qbtrace:pt}
38110 @item @samp{Qbtrace-conf:bts:size}
38115 @item @samp{Qbtrace-conf:pt:size}
38120 @item @samp{QNonStop}
38125 @item @samp{QCatchSyscalls}
38130 @item @samp{QPassSignals}
38135 @item @samp{QStartNoAckMode}
38140 @item @samp{multiprocess}
38145 @item @samp{ConditionalBreakpoints}
38150 @item @samp{ConditionalTracepoints}
38155 @item @samp{ReverseContinue}
38160 @item @samp{ReverseStep}
38165 @item @samp{TracepointSource}
38170 @item @samp{QAgent}
38175 @item @samp{QAllow}
38180 @item @samp{QDisableRandomization}
38185 @item @samp{EnableDisableTracepoints}
38190 @item @samp{QTBuffer:size}
38195 @item @samp{tracenz}
38200 @item @samp{BreakpointCommands}
38205 @item @samp{swbreak}
38210 @item @samp{hwbreak}
38215 @item @samp{fork-events}
38220 @item @samp{vfork-events}
38225 @item @samp{exec-events}
38230 @item @samp{QThreadEvents}
38235 @item @samp{no-resumed}
38242 These are the currently defined stub features, in more detail:
38245 @cindex packet size, remote protocol
38246 @item PacketSize=@var{bytes}
38247 The remote stub can accept packets up to at least @var{bytes} in
38248 length. @value{GDBN} will send packets up to this size for bulk
38249 transfers, and will never send larger packets. This is a limit on the
38250 data characters in the packet, including the frame and checksum.
38251 There is no trailing NUL byte in a remote protocol packet; if the stub
38252 stores packets in a NUL-terminated format, it should allow an extra
38253 byte in its buffer for the NUL. If this stub feature is not supported,
38254 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38256 @item qXfer:auxv:read
38257 The remote stub understands the @samp{qXfer:auxv:read} packet
38258 (@pxref{qXfer auxiliary vector read}).
38260 @item qXfer:btrace:read
38261 The remote stub understands the @samp{qXfer:btrace:read}
38262 packet (@pxref{qXfer btrace read}).
38264 @item qXfer:btrace-conf:read
38265 The remote stub understands the @samp{qXfer:btrace-conf:read}
38266 packet (@pxref{qXfer btrace-conf read}).
38268 @item qXfer:exec-file:read
38269 The remote stub understands the @samp{qXfer:exec-file:read} packet
38270 (@pxref{qXfer executable filename read}).
38272 @item qXfer:features:read
38273 The remote stub understands the @samp{qXfer:features:read} packet
38274 (@pxref{qXfer target description read}).
38276 @item qXfer:libraries:read
38277 The remote stub understands the @samp{qXfer:libraries:read} packet
38278 (@pxref{qXfer library list read}).
38280 @item qXfer:libraries-svr4:read
38281 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38282 (@pxref{qXfer svr4 library list read}).
38284 @item augmented-libraries-svr4-read
38285 The remote stub understands the augmented form of the
38286 @samp{qXfer:libraries-svr4:read} packet
38287 (@pxref{qXfer svr4 library list read}).
38289 @item qXfer:memory-map:read
38290 The remote stub understands the @samp{qXfer:memory-map:read} packet
38291 (@pxref{qXfer memory map read}).
38293 @item qXfer:sdata:read
38294 The remote stub understands the @samp{qXfer:sdata:read} packet
38295 (@pxref{qXfer sdata read}).
38297 @item qXfer:spu:read
38298 The remote stub understands the @samp{qXfer:spu:read} packet
38299 (@pxref{qXfer spu read}).
38301 @item qXfer:spu:write
38302 The remote stub understands the @samp{qXfer:spu:write} packet
38303 (@pxref{qXfer spu write}).
38305 @item qXfer:siginfo:read
38306 The remote stub understands the @samp{qXfer:siginfo:read} packet
38307 (@pxref{qXfer siginfo read}).
38309 @item qXfer:siginfo:write
38310 The remote stub understands the @samp{qXfer:siginfo:write} packet
38311 (@pxref{qXfer siginfo write}).
38313 @item qXfer:threads:read
38314 The remote stub understands the @samp{qXfer:threads:read} packet
38315 (@pxref{qXfer threads read}).
38317 @item qXfer:traceframe-info:read
38318 The remote stub understands the @samp{qXfer:traceframe-info:read}
38319 packet (@pxref{qXfer traceframe info read}).
38321 @item qXfer:uib:read
38322 The remote stub understands the @samp{qXfer:uib:read}
38323 packet (@pxref{qXfer unwind info block}).
38325 @item qXfer:fdpic:read
38326 The remote stub understands the @samp{qXfer:fdpic:read}
38327 packet (@pxref{qXfer fdpic loadmap read}).
38330 The remote stub understands the @samp{QNonStop} packet
38331 (@pxref{QNonStop}).
38333 @item QCatchSyscalls
38334 The remote stub understands the @samp{QCatchSyscalls} packet
38335 (@pxref{QCatchSyscalls}).
38338 The remote stub understands the @samp{QPassSignals} packet
38339 (@pxref{QPassSignals}).
38341 @item QStartNoAckMode
38342 The remote stub understands the @samp{QStartNoAckMode} packet and
38343 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38346 @anchor{multiprocess extensions}
38347 @cindex multiprocess extensions, in remote protocol
38348 The remote stub understands the multiprocess extensions to the remote
38349 protocol syntax. The multiprocess extensions affect the syntax of
38350 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38351 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38352 replies. Note that reporting this feature indicates support for the
38353 syntactic extensions only, not that the stub necessarily supports
38354 debugging of more than one process at a time. The stub must not use
38355 multiprocess extensions in packet replies unless @value{GDBN} has also
38356 indicated it supports them in its @samp{qSupported} request.
38358 @item qXfer:osdata:read
38359 The remote stub understands the @samp{qXfer:osdata:read} packet
38360 ((@pxref{qXfer osdata read}).
38362 @item ConditionalBreakpoints
38363 The target accepts and implements evaluation of conditional expressions
38364 defined for breakpoints. The target will only report breakpoint triggers
38365 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38367 @item ConditionalTracepoints
38368 The remote stub accepts and implements conditional expressions defined
38369 for tracepoints (@pxref{Tracepoint Conditions}).
38371 @item ReverseContinue
38372 The remote stub accepts and implements the reverse continue packet
38376 The remote stub accepts and implements the reverse step packet
38379 @item TracepointSource
38380 The remote stub understands the @samp{QTDPsrc} packet that supplies
38381 the source form of tracepoint definitions.
38384 The remote stub understands the @samp{QAgent} packet.
38387 The remote stub understands the @samp{QAllow} packet.
38389 @item QDisableRandomization
38390 The remote stub understands the @samp{QDisableRandomization} packet.
38392 @item StaticTracepoint
38393 @cindex static tracepoints, in remote protocol
38394 The remote stub supports static tracepoints.
38396 @item InstallInTrace
38397 @anchor{install tracepoint in tracing}
38398 The remote stub supports installing tracepoint in tracing.
38400 @item EnableDisableTracepoints
38401 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38402 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38403 to be enabled and disabled while a trace experiment is running.
38405 @item QTBuffer:size
38406 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38407 packet that allows to change the size of the trace buffer.
38410 @cindex string tracing, in remote protocol
38411 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38412 See @ref{Bytecode Descriptions} for details about the bytecode.
38414 @item BreakpointCommands
38415 @cindex breakpoint commands, in remote protocol
38416 The remote stub supports running a breakpoint's command list itself,
38417 rather than reporting the hit to @value{GDBN}.
38420 The remote stub understands the @samp{Qbtrace:off} packet.
38423 The remote stub understands the @samp{Qbtrace:bts} packet.
38426 The remote stub understands the @samp{Qbtrace:pt} packet.
38428 @item Qbtrace-conf:bts:size
38429 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38431 @item Qbtrace-conf:pt:size
38432 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38435 The remote stub reports the @samp{swbreak} stop reason for memory
38439 The remote stub reports the @samp{hwbreak} stop reason for hardware
38443 The remote stub reports the @samp{fork} stop reason for fork events.
38446 The remote stub reports the @samp{vfork} stop reason for vfork events
38447 and vforkdone events.
38450 The remote stub reports the @samp{exec} stop reason for exec events.
38452 @item vContSupported
38453 The remote stub reports the supported actions in the reply to
38454 @samp{vCont?} packet.
38456 @item QThreadEvents
38457 The remote stub understands the @samp{QThreadEvents} packet.
38460 The remote stub reports the @samp{N} stop reply.
38465 @cindex symbol lookup, remote request
38466 @cindex @samp{qSymbol} packet
38467 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38468 requests. Accept requests from the target for the values of symbols.
38473 The target does not need to look up any (more) symbols.
38474 @item qSymbol:@var{sym_name}
38475 The target requests the value of symbol @var{sym_name} (hex encoded).
38476 @value{GDBN} may provide the value by using the
38477 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38481 @item qSymbol:@var{sym_value}:@var{sym_name}
38482 Set the value of @var{sym_name} to @var{sym_value}.
38484 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38485 target has previously requested.
38487 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38488 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38494 The target does not need to look up any (more) symbols.
38495 @item qSymbol:@var{sym_name}
38496 The target requests the value of a new symbol @var{sym_name} (hex
38497 encoded). @value{GDBN} will continue to supply the values of symbols
38498 (if available), until the target ceases to request them.
38503 @itemx QTDisconnected
38510 @itemx qTMinFTPILen
38512 @xref{Tracepoint Packets}.
38514 @item qThreadExtraInfo,@var{thread-id}
38515 @cindex thread attributes info, remote request
38516 @cindex @samp{qThreadExtraInfo} packet
38517 Obtain from the target OS a printable string description of thread
38518 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38519 for the forms of @var{thread-id}. This
38520 string may contain anything that the target OS thinks is interesting
38521 for @value{GDBN} to tell the user about the thread. The string is
38522 displayed in @value{GDBN}'s @code{info threads} display. Some
38523 examples of possible thread extra info strings are @samp{Runnable}, or
38524 @samp{Blocked on Mutex}.
38528 @item @var{XX}@dots{}
38529 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38530 comprising the printable string containing the extra information about
38531 the thread's attributes.
38534 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38535 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38536 conventions above. Please don't use this packet as a model for new
38555 @xref{Tracepoint Packets}.
38557 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38558 @cindex read special object, remote request
38559 @cindex @samp{qXfer} packet
38560 @anchor{qXfer read}
38561 Read uninterpreted bytes from the target's special data area
38562 identified by the keyword @var{object}. Request @var{length} bytes
38563 starting at @var{offset} bytes into the data. The content and
38564 encoding of @var{annex} is specific to @var{object}; it can supply
38565 additional details about what data to access.
38570 Data @var{data} (@pxref{Binary Data}) has been read from the
38571 target. There may be more data at a higher address (although
38572 it is permitted to return @samp{m} even for the last valid
38573 block of data, as long as at least one byte of data was read).
38574 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38578 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38579 There is no more data to be read. It is possible for @var{data} to
38580 have fewer bytes than the @var{length} in the request.
38583 The @var{offset} in the request is at the end of the data.
38584 There is no more data to be read.
38587 The request was malformed, or @var{annex} was invalid.
38590 The offset was invalid, or there was an error encountered reading the data.
38591 The @var{nn} part is a hex-encoded @code{errno} value.
38594 An empty reply indicates the @var{object} string was not recognized by
38595 the stub, or that the object does not support reading.
38598 Here are the specific requests of this form defined so far. All the
38599 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38600 formats, listed above.
38603 @item qXfer:auxv:read::@var{offset},@var{length}
38604 @anchor{qXfer auxiliary vector read}
38605 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38606 auxiliary vector}. Note @var{annex} must be empty.
38608 This packet is not probed by default; the remote stub must request it,
38609 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38611 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38612 @anchor{qXfer btrace read}
38614 Return a description of the current branch trace.
38615 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38616 packet may have one of the following values:
38620 Returns all available branch trace.
38623 Returns all available branch trace if the branch trace changed since
38624 the last read request.
38627 Returns the new branch trace since the last read request. Adds a new
38628 block to the end of the trace that begins at zero and ends at the source
38629 location of the first branch in the trace buffer. This extra block is
38630 used to stitch traces together.
38632 If the trace buffer overflowed, returns an error indicating the overflow.
38635 This packet is not probed by default; the remote stub must request it
38636 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38638 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38639 @anchor{qXfer btrace-conf read}
38641 Return a description of the current branch trace configuration.
38642 @xref{Branch Trace Configuration Format}.
38644 This packet is not probed by default; the remote stub must request it
38645 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38647 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38648 @anchor{qXfer executable filename read}
38649 Return the full absolute name of the file that was executed to create
38650 a process running on the remote system. The annex specifies the
38651 numeric process ID of the process to query, encoded as a hexadecimal
38652 number. If the annex part is empty the remote stub should return the
38653 filename corresponding to the currently executing process.
38655 This packet is not probed by default; the remote stub must request it,
38656 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38658 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38659 @anchor{qXfer target description read}
38660 Access the @dfn{target description}. @xref{Target Descriptions}. The
38661 annex specifies which XML document to access. The main description is
38662 always loaded from the @samp{target.xml} annex.
38664 This packet is not probed by default; the remote stub must request it,
38665 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38667 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38668 @anchor{qXfer library list read}
38669 Access the target's list of loaded libraries. @xref{Library List Format}.
38670 The annex part of the generic @samp{qXfer} packet must be empty
38671 (@pxref{qXfer read}).
38673 Targets which maintain a list of libraries in the program's memory do
38674 not need to implement this packet; it is designed for platforms where
38675 the operating system manages the list of loaded libraries.
38677 This packet is not probed by default; the remote stub must request it,
38678 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38680 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38681 @anchor{qXfer svr4 library list read}
38682 Access the target's list of loaded libraries when the target is an SVR4
38683 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38684 of the generic @samp{qXfer} packet must be empty unless the remote
38685 stub indicated it supports the augmented form of this packet
38686 by supplying an appropriate @samp{qSupported} response
38687 (@pxref{qXfer read}, @ref{qSupported}).
38689 This packet is optional for better performance on SVR4 targets.
38690 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38692 This packet is not probed by default; the remote stub must request it,
38693 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38695 If the remote stub indicates it supports the augmented form of this
38696 packet then the annex part of the generic @samp{qXfer} packet may
38697 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38698 arguments. The currently supported arguments are:
38701 @item start=@var{address}
38702 A hexadecimal number specifying the address of the @samp{struct
38703 link_map} to start reading the library list from. If unset or zero
38704 then the first @samp{struct link_map} in the library list will be
38705 chosen as the starting point.
38707 @item prev=@var{address}
38708 A hexadecimal number specifying the address of the @samp{struct
38709 link_map} immediately preceding the @samp{struct link_map}
38710 specified by the @samp{start} argument. If unset or zero then
38711 the remote stub will expect that no @samp{struct link_map}
38712 exists prior to the starting point.
38716 Arguments that are not understood by the remote stub will be silently
38719 @item qXfer:memory-map:read::@var{offset},@var{length}
38720 @anchor{qXfer memory map read}
38721 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38722 annex part of the generic @samp{qXfer} packet must be empty
38723 (@pxref{qXfer read}).
38725 This packet is not probed by default; the remote stub must request it,
38726 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38728 @item qXfer:sdata:read::@var{offset},@var{length}
38729 @anchor{qXfer sdata read}
38731 Read contents of the extra collected static tracepoint marker
38732 information. The annex part of the generic @samp{qXfer} packet must
38733 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38736 This packet is not probed by default; the remote stub must request it,
38737 by supplying an appropriate @samp{qSupported} response
38738 (@pxref{qSupported}).
38740 @item qXfer:siginfo:read::@var{offset},@var{length}
38741 @anchor{qXfer siginfo read}
38742 Read contents of the extra signal information on the target
38743 system. The annex part of the generic @samp{qXfer} packet must be
38744 empty (@pxref{qXfer read}).
38746 This packet is not probed by default; the remote stub must request it,
38747 by supplying an appropriate @samp{qSupported} response
38748 (@pxref{qSupported}).
38750 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38751 @anchor{qXfer spu read}
38752 Read contents of an @code{spufs} file on the target system. The
38753 annex specifies which file to read; it must be of the form
38754 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38755 in the target process, and @var{name} identifes the @code{spufs} file
38756 in that context to be accessed.
38758 This packet is not probed by default; the remote stub must request it,
38759 by supplying an appropriate @samp{qSupported} response
38760 (@pxref{qSupported}).
38762 @item qXfer:threads:read::@var{offset},@var{length}
38763 @anchor{qXfer threads read}
38764 Access the list of threads on target. @xref{Thread List Format}. The
38765 annex part of the generic @samp{qXfer} packet must be empty
38766 (@pxref{qXfer read}).
38768 This packet is not probed by default; the remote stub must request it,
38769 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38771 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38772 @anchor{qXfer traceframe info read}
38774 Return a description of the current traceframe's contents.
38775 @xref{Traceframe Info Format}. The annex part of the generic
38776 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38778 This packet is not probed by default; the remote stub must request it,
38779 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38781 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38782 @anchor{qXfer unwind info block}
38784 Return the unwind information block for @var{pc}. This packet is used
38785 on OpenVMS/ia64 to ask the kernel unwind information.
38787 This packet is not probed by default.
38789 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38790 @anchor{qXfer fdpic loadmap read}
38791 Read contents of @code{loadmap}s on the target system. The
38792 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38793 executable @code{loadmap} or interpreter @code{loadmap} to read.
38795 This packet is not probed by default; the remote stub must request it,
38796 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38798 @item qXfer:osdata:read::@var{offset},@var{length}
38799 @anchor{qXfer osdata read}
38800 Access the target's @dfn{operating system information}.
38801 @xref{Operating System Information}.
38805 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38806 @cindex write data into object, remote request
38807 @anchor{qXfer write}
38808 Write uninterpreted bytes into the target's special data area
38809 identified by the keyword @var{object}, starting at @var{offset} bytes
38810 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38811 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38812 is specific to @var{object}; it can supply additional details about what data
38818 @var{nn} (hex encoded) is the number of bytes written.
38819 This may be fewer bytes than supplied in the request.
38822 The request was malformed, or @var{annex} was invalid.
38825 The offset was invalid, or there was an error encountered writing the data.
38826 The @var{nn} part is a hex-encoded @code{errno} value.
38829 An empty reply indicates the @var{object} string was not
38830 recognized by the stub, or that the object does not support writing.
38833 Here are the specific requests of this form defined so far. All the
38834 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38835 formats, listed above.
38838 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38839 @anchor{qXfer siginfo write}
38840 Write @var{data} to the extra signal information on the target system.
38841 The annex part of the generic @samp{qXfer} packet must be
38842 empty (@pxref{qXfer write}).
38844 This packet is not probed by default; the remote stub must request it,
38845 by supplying an appropriate @samp{qSupported} response
38846 (@pxref{qSupported}).
38848 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38849 @anchor{qXfer spu write}
38850 Write @var{data} to an @code{spufs} file on the target system. The
38851 annex specifies which file to write; it must be of the form
38852 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38853 in the target process, and @var{name} identifes the @code{spufs} file
38854 in that context to be accessed.
38856 This packet is not probed by default; the remote stub must request it,
38857 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38860 @item qXfer:@var{object}:@var{operation}:@dots{}
38861 Requests of this form may be added in the future. When a stub does
38862 not recognize the @var{object} keyword, or its support for
38863 @var{object} does not recognize the @var{operation} keyword, the stub
38864 must respond with an empty packet.
38866 @item qAttached:@var{pid}
38867 @cindex query attached, remote request
38868 @cindex @samp{qAttached} packet
38869 Return an indication of whether the remote server attached to an
38870 existing process or created a new process. When the multiprocess
38871 protocol extensions are supported (@pxref{multiprocess extensions}),
38872 @var{pid} is an integer in hexadecimal format identifying the target
38873 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38874 the query packet will be simplified as @samp{qAttached}.
38876 This query is used, for example, to know whether the remote process
38877 should be detached or killed when a @value{GDBN} session is ended with
38878 the @code{quit} command.
38883 The remote server attached to an existing process.
38885 The remote server created a new process.
38887 A badly formed request or an error was encountered.
38891 Enable branch tracing for the current thread using Branch Trace Store.
38896 Branch tracing has been enabled.
38898 A badly formed request or an error was encountered.
38902 Enable branch tracing for the current thread using Intel Processor Trace.
38907 Branch tracing has been enabled.
38909 A badly formed request or an error was encountered.
38913 Disable branch tracing for the current thread.
38918 Branch tracing has been disabled.
38920 A badly formed request or an error was encountered.
38923 @item Qbtrace-conf:bts:size=@var{value}
38924 Set the requested ring buffer size for new threads that use the
38925 btrace recording method in bts format.
38930 The ring buffer size has been set.
38932 A badly formed request or an error was encountered.
38935 @item Qbtrace-conf:pt:size=@var{value}
38936 Set the requested ring buffer size for new threads that use the
38937 btrace recording method in pt format.
38942 The ring buffer size has been set.
38944 A badly formed request or an error was encountered.
38949 @node Architecture-Specific Protocol Details
38950 @section Architecture-Specific Protocol Details
38952 This section describes how the remote protocol is applied to specific
38953 target architectures. Also see @ref{Standard Target Features}, for
38954 details of XML target descriptions for each architecture.
38957 * ARM-Specific Protocol Details::
38958 * MIPS-Specific Protocol Details::
38961 @node ARM-Specific Protocol Details
38962 @subsection @acronym{ARM}-specific Protocol Details
38965 * ARM Breakpoint Kinds::
38968 @node ARM Breakpoint Kinds
38969 @subsubsection @acronym{ARM} Breakpoint Kinds
38970 @cindex breakpoint kinds, @acronym{ARM}
38972 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38977 16-bit Thumb mode breakpoint.
38980 32-bit Thumb mode (Thumb-2) breakpoint.
38983 32-bit @acronym{ARM} mode breakpoint.
38987 @node MIPS-Specific Protocol Details
38988 @subsection @acronym{MIPS}-specific Protocol Details
38991 * MIPS Register packet Format::
38992 * MIPS Breakpoint Kinds::
38995 @node MIPS Register packet Format
38996 @subsubsection @acronym{MIPS} Register Packet Format
38997 @cindex register packet format, @acronym{MIPS}
38999 The following @code{g}/@code{G} packets have previously been defined.
39000 In the below, some thirty-two bit registers are transferred as
39001 sixty-four bits. Those registers should be zero/sign extended (which?)
39002 to fill the space allocated. Register bytes are transferred in target
39003 byte order. The two nibbles within a register byte are transferred
39004 most-significant -- least-significant.
39009 All registers are transferred as thirty-two bit quantities in the order:
39010 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39011 registers; fsr; fir; fp.
39014 All registers are transferred as sixty-four bit quantities (including
39015 thirty-two bit registers such as @code{sr}). The ordering is the same
39020 @node MIPS Breakpoint Kinds
39021 @subsubsection @acronym{MIPS} Breakpoint Kinds
39022 @cindex breakpoint kinds, @acronym{MIPS}
39024 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39029 16-bit @acronym{MIPS16} mode breakpoint.
39032 16-bit @acronym{microMIPS} mode breakpoint.
39035 32-bit standard @acronym{MIPS} mode breakpoint.
39038 32-bit @acronym{microMIPS} mode breakpoint.
39042 @node Tracepoint Packets
39043 @section Tracepoint Packets
39044 @cindex tracepoint packets
39045 @cindex packets, tracepoint
39047 Here we describe the packets @value{GDBN} uses to implement
39048 tracepoints (@pxref{Tracepoints}).
39052 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39053 @cindex @samp{QTDP} packet
39054 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39055 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39056 the tracepoint is disabled. The @var{step} gives the tracepoint's step
39057 count, and @var{pass} gives its pass count. If an @samp{F} is present,
39058 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39059 the number of bytes that the target should copy elsewhere to make room
39060 for the tracepoint. If an @samp{X} is present, it introduces a
39061 tracepoint condition, which consists of a hexadecimal length, followed
39062 by a comma and hex-encoded bytes, in a manner similar to action
39063 encodings as described below. If the trailing @samp{-} is present,
39064 further @samp{QTDP} packets will follow to specify this tracepoint's
39070 The packet was understood and carried out.
39072 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39074 The packet was not recognized.
39077 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39078 Define actions to be taken when a tracepoint is hit. The @var{n} and
39079 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39080 this tracepoint. This packet may only be sent immediately after
39081 another @samp{QTDP} packet that ended with a @samp{-}. If the
39082 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39083 specifying more actions for this tracepoint.
39085 In the series of action packets for a given tracepoint, at most one
39086 can have an @samp{S} before its first @var{action}. If such a packet
39087 is sent, it and the following packets define ``while-stepping''
39088 actions. Any prior packets define ordinary actions --- that is, those
39089 taken when the tracepoint is first hit. If no action packet has an
39090 @samp{S}, then all the packets in the series specify ordinary
39091 tracepoint actions.
39093 The @samp{@var{action}@dots{}} portion of the packet is a series of
39094 actions, concatenated without separators. Each action has one of the
39100 Collect the registers whose bits are set in @var{mask},
39101 a hexadecimal number whose @var{i}'th bit is set if register number
39102 @var{i} should be collected. (The least significant bit is numbered
39103 zero.) Note that @var{mask} may be any number of digits long; it may
39104 not fit in a 32-bit word.
39106 @item M @var{basereg},@var{offset},@var{len}
39107 Collect @var{len} bytes of memory starting at the address in register
39108 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39109 @samp{-1}, then the range has a fixed address: @var{offset} is the
39110 address of the lowest byte to collect. The @var{basereg},
39111 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39112 values (the @samp{-1} value for @var{basereg} is a special case).
39114 @item X @var{len},@var{expr}
39115 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39116 it directs. The agent expression @var{expr} is as described in
39117 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39118 two-digit hex number in the packet; @var{len} is the number of bytes
39119 in the expression (and thus one-half the number of hex digits in the
39124 Any number of actions may be packed together in a single @samp{QTDP}
39125 packet, as long as the packet does not exceed the maximum packet
39126 length (400 bytes, for many stubs). There may be only one @samp{R}
39127 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39128 actions. Any registers referred to by @samp{M} and @samp{X} actions
39129 must be collected by a preceding @samp{R} action. (The
39130 ``while-stepping'' actions are treated as if they were attached to a
39131 separate tracepoint, as far as these restrictions are concerned.)
39136 The packet was understood and carried out.
39138 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39140 The packet was not recognized.
39143 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39144 @cindex @samp{QTDPsrc} packet
39145 Specify a source string of tracepoint @var{n} at address @var{addr}.
39146 This is useful to get accurate reproduction of the tracepoints
39147 originally downloaded at the beginning of the trace run. The @var{type}
39148 is the name of the tracepoint part, such as @samp{cond} for the
39149 tracepoint's conditional expression (see below for a list of types), while
39150 @var{bytes} is the string, encoded in hexadecimal.
39152 @var{start} is the offset of the @var{bytes} within the overall source
39153 string, while @var{slen} is the total length of the source string.
39154 This is intended for handling source strings that are longer than will
39155 fit in a single packet.
39156 @c Add detailed example when this info is moved into a dedicated
39157 @c tracepoint descriptions section.
39159 The available string types are @samp{at} for the location,
39160 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39161 @value{GDBN} sends a separate packet for each command in the action
39162 list, in the same order in which the commands are stored in the list.
39164 The target does not need to do anything with source strings except
39165 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39168 Although this packet is optional, and @value{GDBN} will only send it
39169 if the target replies with @samp{TracepointSource} @xref{General
39170 Query Packets}, it makes both disconnected tracing and trace files
39171 much easier to use. Otherwise the user must be careful that the
39172 tracepoints in effect while looking at trace frames are identical to
39173 the ones in effect during the trace run; even a small discrepancy
39174 could cause @samp{tdump} not to work, or a particular trace frame not
39177 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
39178 @cindex define trace state variable, remote request
39179 @cindex @samp{QTDV} packet
39180 Create a new trace state variable, number @var{n}, with an initial
39181 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39182 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39183 the option of not using this packet for initial values of zero; the
39184 target should simply create the trace state variables as they are
39185 mentioned in expressions. The value @var{builtin} should be 1 (one)
39186 if the trace state variable is builtin and 0 (zero) if it is not builtin.
39187 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
39188 @samp{qTsV} packet had it set. The contents of @var{name} is the
39189 hex-encoded name (without the leading @samp{$}) of the trace state
39192 @item QTFrame:@var{n}
39193 @cindex @samp{QTFrame} packet
39194 Select the @var{n}'th tracepoint frame from the buffer, and use the
39195 register and memory contents recorded there to answer subsequent
39196 request packets from @value{GDBN}.
39198 A successful reply from the stub indicates that the stub has found the
39199 requested frame. The response is a series of parts, concatenated
39200 without separators, describing the frame we selected. Each part has
39201 one of the following forms:
39205 The selected frame is number @var{n} in the trace frame buffer;
39206 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39207 was no frame matching the criteria in the request packet.
39210 The selected trace frame records a hit of tracepoint number @var{t};
39211 @var{t} is a hexadecimal number.
39215 @item QTFrame:pc:@var{addr}
39216 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39217 currently selected frame whose PC is @var{addr};
39218 @var{addr} is a hexadecimal number.
39220 @item QTFrame:tdp:@var{t}
39221 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39222 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39223 is a hexadecimal number.
39225 @item QTFrame:range:@var{start}:@var{end}
39226 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39227 currently selected frame whose PC is between @var{start} (inclusive)
39228 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39231 @item QTFrame:outside:@var{start}:@var{end}
39232 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39233 frame @emph{outside} the given range of addresses (exclusive).
39236 @cindex @samp{qTMinFTPILen} packet
39237 This packet requests the minimum length of instruction at which a fast
39238 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39239 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39240 it depends on the target system being able to create trampolines in
39241 the first 64K of memory, which might or might not be possible for that
39242 system. So the reply to this packet will be 4 if it is able to
39249 The minimum instruction length is currently unknown.
39251 The minimum instruction length is @var{length}, where @var{length}
39252 is a hexadecimal number greater or equal to 1. A reply
39253 of 1 means that a fast tracepoint may be placed on any instruction
39254 regardless of size.
39256 An error has occurred.
39258 An empty reply indicates that the request is not supported by the stub.
39262 @cindex @samp{QTStart} packet
39263 Begin the tracepoint experiment. Begin collecting data from
39264 tracepoint hits in the trace frame buffer. This packet supports the
39265 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39266 instruction reply packet}).
39269 @cindex @samp{QTStop} packet
39270 End the tracepoint experiment. Stop collecting trace frames.
39272 @item QTEnable:@var{n}:@var{addr}
39274 @cindex @samp{QTEnable} packet
39275 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39276 experiment. If the tracepoint was previously disabled, then collection
39277 of data from it will resume.
39279 @item QTDisable:@var{n}:@var{addr}
39281 @cindex @samp{QTDisable} packet
39282 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39283 experiment. No more data will be collected from the tracepoint unless
39284 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39287 @cindex @samp{QTinit} packet
39288 Clear the table of tracepoints, and empty the trace frame buffer.
39290 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39291 @cindex @samp{QTro} packet
39292 Establish the given ranges of memory as ``transparent''. The stub
39293 will answer requests for these ranges from memory's current contents,
39294 if they were not collected as part of the tracepoint hit.
39296 @value{GDBN} uses this to mark read-only regions of memory, like those
39297 containing program code. Since these areas never change, they should
39298 still have the same contents they did when the tracepoint was hit, so
39299 there's no reason for the stub to refuse to provide their contents.
39301 @item QTDisconnected:@var{value}
39302 @cindex @samp{QTDisconnected} packet
39303 Set the choice to what to do with the tracing run when @value{GDBN}
39304 disconnects from the target. A @var{value} of 1 directs the target to
39305 continue the tracing run, while 0 tells the target to stop tracing if
39306 @value{GDBN} is no longer in the picture.
39309 @cindex @samp{qTStatus} packet
39310 Ask the stub if there is a trace experiment running right now.
39312 The reply has the form:
39316 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39317 @var{running} is a single digit @code{1} if the trace is presently
39318 running, or @code{0} if not. It is followed by semicolon-separated
39319 optional fields that an agent may use to report additional status.
39323 If the trace is not running, the agent may report any of several
39324 explanations as one of the optional fields:
39329 No trace has been run yet.
39331 @item tstop[:@var{text}]:0
39332 The trace was stopped by a user-originated stop command. The optional
39333 @var{text} field is a user-supplied string supplied as part of the
39334 stop command (for instance, an explanation of why the trace was
39335 stopped manually). It is hex-encoded.
39338 The trace stopped because the trace buffer filled up.
39340 @item tdisconnected:0
39341 The trace stopped because @value{GDBN} disconnected from the target.
39343 @item tpasscount:@var{tpnum}
39344 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39346 @item terror:@var{text}:@var{tpnum}
39347 The trace stopped because tracepoint @var{tpnum} had an error. The
39348 string @var{text} is available to describe the nature of the error
39349 (for instance, a divide by zero in the condition expression); it
39353 The trace stopped for some other reason.
39357 Additional optional fields supply statistical and other information.
39358 Although not required, they are extremely useful for users monitoring
39359 the progress of a trace run. If a trace has stopped, and these
39360 numbers are reported, they must reflect the state of the just-stopped
39365 @item tframes:@var{n}
39366 The number of trace frames in the buffer.
39368 @item tcreated:@var{n}
39369 The total number of trace frames created during the run. This may
39370 be larger than the trace frame count, if the buffer is circular.
39372 @item tsize:@var{n}
39373 The total size of the trace buffer, in bytes.
39375 @item tfree:@var{n}
39376 The number of bytes still unused in the buffer.
39378 @item circular:@var{n}
39379 The value of the circular trace buffer flag. @code{1} means that the
39380 trace buffer is circular and old trace frames will be discarded if
39381 necessary to make room, @code{0} means that the trace buffer is linear
39384 @item disconn:@var{n}
39385 The value of the disconnected tracing flag. @code{1} means that
39386 tracing will continue after @value{GDBN} disconnects, @code{0} means
39387 that the trace run will stop.
39391 @item qTP:@var{tp}:@var{addr}
39392 @cindex tracepoint status, remote request
39393 @cindex @samp{qTP} packet
39394 Ask the stub for the current state of tracepoint number @var{tp} at
39395 address @var{addr}.
39399 @item V@var{hits}:@var{usage}
39400 The tracepoint has been hit @var{hits} times so far during the trace
39401 run, and accounts for @var{usage} in the trace buffer. Note that
39402 @code{while-stepping} steps are not counted as separate hits, but the
39403 steps' space consumption is added into the usage number.
39407 @item qTV:@var{var}
39408 @cindex trace state variable value, remote request
39409 @cindex @samp{qTV} packet
39410 Ask the stub for the value of the trace state variable number @var{var}.
39415 The value of the variable is @var{value}. This will be the current
39416 value of the variable if the user is examining a running target, or a
39417 saved value if the variable was collected in the trace frame that the
39418 user is looking at. Note that multiple requests may result in
39419 different reply values, such as when requesting values while the
39420 program is running.
39423 The value of the variable is unknown. This would occur, for example,
39424 if the user is examining a trace frame in which the requested variable
39429 @cindex @samp{qTfP} packet
39431 @cindex @samp{qTsP} packet
39432 These packets request data about tracepoints that are being used by
39433 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39434 of data, and multiple @code{qTsP} to get additional pieces. Replies
39435 to these packets generally take the form of the @code{QTDP} packets
39436 that define tracepoints. (FIXME add detailed syntax)
39439 @cindex @samp{qTfV} packet
39441 @cindex @samp{qTsV} packet
39442 These packets request data about trace state variables that are on the
39443 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39444 and multiple @code{qTsV} to get additional variables. Replies to
39445 these packets follow the syntax of the @code{QTDV} packets that define
39446 trace state variables.
39452 @cindex @samp{qTfSTM} packet
39453 @cindex @samp{qTsSTM} packet
39454 These packets request data about static tracepoint markers that exist
39455 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39456 first piece of data, and multiple @code{qTsSTM} to get additional
39457 pieces. Replies to these packets take the following form:
39461 @item m @var{address}:@var{id}:@var{extra}
39463 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39464 a comma-separated list of markers
39466 (lower case letter @samp{L}) denotes end of list.
39468 An error occurred. The error number @var{nn} is given as hex digits.
39470 An empty reply indicates that the request is not supported by the
39474 The @var{address} is encoded in hex;
39475 @var{id} and @var{extra} are strings encoded in hex.
39477 In response to each query, the target will reply with a list of one or
39478 more markers, separated by commas. @value{GDBN} will respond to each
39479 reply with a request for more markers (using the @samp{qs} form of the
39480 query), until the target responds with @samp{l} (lower-case ell, for
39483 @item qTSTMat:@var{address}
39485 @cindex @samp{qTSTMat} packet
39486 This packets requests data about static tracepoint markers in the
39487 target program at @var{address}. Replies to this packet follow the
39488 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39489 tracepoint markers.
39491 @item QTSave:@var{filename}
39492 @cindex @samp{QTSave} packet
39493 This packet directs the target to save trace data to the file name
39494 @var{filename} in the target's filesystem. The @var{filename} is encoded
39495 as a hex string; the interpretation of the file name (relative vs
39496 absolute, wild cards, etc) is up to the target.
39498 @item qTBuffer:@var{offset},@var{len}
39499 @cindex @samp{qTBuffer} packet
39500 Return up to @var{len} bytes of the current contents of trace buffer,
39501 starting at @var{offset}. The trace buffer is treated as if it were
39502 a contiguous collection of traceframes, as per the trace file format.
39503 The reply consists as many hex-encoded bytes as the target can deliver
39504 in a packet; it is not an error to return fewer than were asked for.
39505 A reply consisting of just @code{l} indicates that no bytes are
39508 @item QTBuffer:circular:@var{value}
39509 This packet directs the target to use a circular trace buffer if
39510 @var{value} is 1, or a linear buffer if the value is 0.
39512 @item QTBuffer:size:@var{size}
39513 @anchor{QTBuffer-size}
39514 @cindex @samp{QTBuffer size} packet
39515 This packet directs the target to make the trace buffer be of size
39516 @var{size} if possible. A value of @code{-1} tells the target to
39517 use whatever size it prefers.
39519 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39520 @cindex @samp{QTNotes} packet
39521 This packet adds optional textual notes to the trace run. Allowable
39522 types include @code{user}, @code{notes}, and @code{tstop}, the
39523 @var{text} fields are arbitrary strings, hex-encoded.
39527 @subsection Relocate instruction reply packet
39528 When installing fast tracepoints in memory, the target may need to
39529 relocate the instruction currently at the tracepoint address to a
39530 different address in memory. For most instructions, a simple copy is
39531 enough, but, for example, call instructions that implicitly push the
39532 return address on the stack, and relative branches or other
39533 PC-relative instructions require offset adjustment, so that the effect
39534 of executing the instruction at a different address is the same as if
39535 it had executed in the original location.
39537 In response to several of the tracepoint packets, the target may also
39538 respond with a number of intermediate @samp{qRelocInsn} request
39539 packets before the final result packet, to have @value{GDBN} handle
39540 this relocation operation. If a packet supports this mechanism, its
39541 documentation will explicitly say so. See for example the above
39542 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39543 format of the request is:
39546 @item qRelocInsn:@var{from};@var{to}
39548 This requests @value{GDBN} to copy instruction at address @var{from}
39549 to address @var{to}, possibly adjusted so that executing the
39550 instruction at @var{to} has the same effect as executing it at
39551 @var{from}. @value{GDBN} writes the adjusted instruction to target
39552 memory starting at @var{to}.
39557 @item qRelocInsn:@var{adjusted_size}
39558 Informs the stub the relocation is complete. The @var{adjusted_size} is
39559 the length in bytes of resulting relocated instruction sequence.
39561 A badly formed request was detected, or an error was encountered while
39562 relocating the instruction.
39565 @node Host I/O Packets
39566 @section Host I/O Packets
39567 @cindex Host I/O, remote protocol
39568 @cindex file transfer, remote protocol
39570 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39571 operations on the far side of a remote link. For example, Host I/O is
39572 used to upload and download files to a remote target with its own
39573 filesystem. Host I/O uses the same constant values and data structure
39574 layout as the target-initiated File-I/O protocol. However, the
39575 Host I/O packets are structured differently. The target-initiated
39576 protocol relies on target memory to store parameters and buffers.
39577 Host I/O requests are initiated by @value{GDBN}, and the
39578 target's memory is not involved. @xref{File-I/O Remote Protocol
39579 Extension}, for more details on the target-initiated protocol.
39581 The Host I/O request packets all encode a single operation along with
39582 its arguments. They have this format:
39586 @item vFile:@var{operation}: @var{parameter}@dots{}
39587 @var{operation} is the name of the particular request; the target
39588 should compare the entire packet name up to the second colon when checking
39589 for a supported operation. The format of @var{parameter} depends on
39590 the operation. Numbers are always passed in hexadecimal. Negative
39591 numbers have an explicit minus sign (i.e.@: two's complement is not
39592 used). Strings (e.g.@: filenames) are encoded as a series of
39593 hexadecimal bytes. The last argument to a system call may be a
39594 buffer of escaped binary data (@pxref{Binary Data}).
39598 The valid responses to Host I/O packets are:
39602 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39603 @var{result} is the integer value returned by this operation, usually
39604 non-negative for success and -1 for errors. If an error has occured,
39605 @var{errno} will be included in the result specifying a
39606 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39607 operations which return data, @var{attachment} supplies the data as a
39608 binary buffer. Binary buffers in response packets are escaped in the
39609 normal way (@pxref{Binary Data}). See the individual packet
39610 documentation for the interpretation of @var{result} and
39614 An empty response indicates that this operation is not recognized.
39618 These are the supported Host I/O operations:
39621 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39622 Open a file at @var{filename} and return a file descriptor for it, or
39623 return -1 if an error occurs. The @var{filename} is a string,
39624 @var{flags} is an integer indicating a mask of open flags
39625 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39626 of mode bits to use if the file is created (@pxref{mode_t Values}).
39627 @xref{open}, for details of the open flags and mode values.
39629 @item vFile:close: @var{fd}
39630 Close the open file corresponding to @var{fd} and return 0, or
39631 -1 if an error occurs.
39633 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39634 Read data from the open file corresponding to @var{fd}. Up to
39635 @var{count} bytes will be read from the file, starting at @var{offset}
39636 relative to the start of the file. The target may read fewer bytes;
39637 common reasons include packet size limits and an end-of-file
39638 condition. The number of bytes read is returned. Zero should only be
39639 returned for a successful read at the end of the file, or if
39640 @var{count} was zero.
39642 The data read should be returned as a binary attachment on success.
39643 If zero bytes were read, the response should include an empty binary
39644 attachment (i.e.@: a trailing semicolon). The return value is the
39645 number of target bytes read; the binary attachment may be longer if
39646 some characters were escaped.
39648 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39649 Write @var{data} (a binary buffer) to the open file corresponding
39650 to @var{fd}. Start the write at @var{offset} from the start of the
39651 file. Unlike many @code{write} system calls, there is no
39652 separate @var{count} argument; the length of @var{data} in the
39653 packet is used. @samp{vFile:write} returns the number of bytes written,
39654 which may be shorter than the length of @var{data}, or -1 if an
39657 @item vFile:fstat: @var{fd}
39658 Get information about the open file corresponding to @var{fd}.
39659 On success the information is returned as a binary attachment
39660 and the return value is the size of this attachment in bytes.
39661 If an error occurs the return value is -1. The format of the
39662 returned binary attachment is as described in @ref{struct stat}.
39664 @item vFile:unlink: @var{filename}
39665 Delete the file at @var{filename} on the target. Return 0,
39666 or -1 if an error occurs. The @var{filename} is a string.
39668 @item vFile:readlink: @var{filename}
39669 Read value of symbolic link @var{filename} on the target. Return
39670 the number of bytes read, or -1 if an error occurs.
39672 The data read should be returned as a binary attachment on success.
39673 If zero bytes were read, the response should include an empty binary
39674 attachment (i.e.@: a trailing semicolon). The return value is the
39675 number of target bytes read; the binary attachment may be longer if
39676 some characters were escaped.
39678 @item vFile:setfs: @var{pid}
39679 Select the filesystem on which @code{vFile} operations with
39680 @var{filename} arguments will operate. This is required for
39681 @value{GDBN} to be able to access files on remote targets where
39682 the remote stub does not share a common filesystem with the
39685 If @var{pid} is nonzero, select the filesystem as seen by process
39686 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39687 the remote stub. Return 0 on success, or -1 if an error occurs.
39688 If @code{vFile:setfs:} indicates success, the selected filesystem
39689 remains selected until the next successful @code{vFile:setfs:}
39695 @section Interrupts
39696 @cindex interrupts (remote protocol)
39697 @anchor{interrupting remote targets}
39699 In all-stop mode, when a program on the remote target is running,
39700 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39701 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39702 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39704 The precise meaning of @code{BREAK} is defined by the transport
39705 mechanism and may, in fact, be undefined. @value{GDBN} does not
39706 currently define a @code{BREAK} mechanism for any of the network
39707 interfaces except for TCP, in which case @value{GDBN} sends the
39708 @code{telnet} BREAK sequence.
39710 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39711 transport mechanisms. It is represented by sending the single byte
39712 @code{0x03} without any of the usual packet overhead described in
39713 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39714 transmitted as part of a packet, it is considered to be packet data
39715 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39716 (@pxref{X packet}), used for binary downloads, may include an unescaped
39717 @code{0x03} as part of its packet.
39719 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39720 When Linux kernel receives this sequence from serial port,
39721 it stops execution and connects to gdb.
39723 In non-stop mode, because packet resumptions are asynchronous
39724 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39725 command to the remote stub, even when the target is running. For that
39726 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39727 packet}) with the usual packet framing instead of the single byte
39730 Stubs are not required to recognize these interrupt mechanisms and the
39731 precise meaning associated with receipt of the interrupt is
39732 implementation defined. If the target supports debugging of multiple
39733 threads and/or processes, it should attempt to interrupt all
39734 currently-executing threads and processes.
39735 If the stub is successful at interrupting the
39736 running program, it should send one of the stop
39737 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39738 of successfully stopping the program in all-stop mode, and a stop reply
39739 for each stopped thread in non-stop mode.
39740 Interrupts received while the
39741 program is stopped are queued and the program will be interrupted when
39742 it is resumed next time.
39744 @node Notification Packets
39745 @section Notification Packets
39746 @cindex notification packets
39747 @cindex packets, notification
39749 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39750 packets that require no acknowledgment. Both the GDB and the stub
39751 may send notifications (although the only notifications defined at
39752 present are sent by the stub). Notifications carry information
39753 without incurring the round-trip latency of an acknowledgment, and so
39754 are useful for low-impact communications where occasional packet loss
39757 A notification packet has the form @samp{% @var{data} #
39758 @var{checksum}}, where @var{data} is the content of the notification,
39759 and @var{checksum} is a checksum of @var{data}, computed and formatted
39760 as for ordinary @value{GDBN} packets. A notification's @var{data}
39761 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39762 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39763 to acknowledge the notification's receipt or to report its corruption.
39765 Every notification's @var{data} begins with a name, which contains no
39766 colon characters, followed by a colon character.
39768 Recipients should silently ignore corrupted notifications and
39769 notifications they do not understand. Recipients should restart
39770 timeout periods on receipt of a well-formed notification, whether or
39771 not they understand it.
39773 Senders should only send the notifications described here when this
39774 protocol description specifies that they are permitted. In the
39775 future, we may extend the protocol to permit existing notifications in
39776 new contexts; this rule helps older senders avoid confusing newer
39779 (Older versions of @value{GDBN} ignore bytes received until they see
39780 the @samp{$} byte that begins an ordinary packet, so new stubs may
39781 transmit notifications without fear of confusing older clients. There
39782 are no notifications defined for @value{GDBN} to send at the moment, but we
39783 assume that most older stubs would ignore them, as well.)
39785 Each notification is comprised of three parts:
39787 @item @var{name}:@var{event}
39788 The notification packet is sent by the side that initiates the
39789 exchange (currently, only the stub does that), with @var{event}
39790 carrying the specific information about the notification, and
39791 @var{name} specifying the name of the notification.
39793 The acknowledge sent by the other side, usually @value{GDBN}, to
39794 acknowledge the exchange and request the event.
39797 The purpose of an asynchronous notification mechanism is to report to
39798 @value{GDBN} that something interesting happened in the remote stub.
39800 The remote stub may send notification @var{name}:@var{event}
39801 at any time, but @value{GDBN} acknowledges the notification when
39802 appropriate. The notification event is pending before @value{GDBN}
39803 acknowledges. Only one notification at a time may be pending; if
39804 additional events occur before @value{GDBN} has acknowledged the
39805 previous notification, they must be queued by the stub for later
39806 synchronous transmission in response to @var{ack} packets from
39807 @value{GDBN}. Because the notification mechanism is unreliable,
39808 the stub is permitted to resend a notification if it believes
39809 @value{GDBN} may not have received it.
39811 Specifically, notifications may appear when @value{GDBN} is not
39812 otherwise reading input from the stub, or when @value{GDBN} is
39813 expecting to read a normal synchronous response or a
39814 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39815 Notification packets are distinct from any other communication from
39816 the stub so there is no ambiguity.
39818 After receiving a notification, @value{GDBN} shall acknowledge it by
39819 sending a @var{ack} packet as a regular, synchronous request to the
39820 stub. Such acknowledgment is not required to happen immediately, as
39821 @value{GDBN} is permitted to send other, unrelated packets to the
39822 stub first, which the stub should process normally.
39824 Upon receiving a @var{ack} packet, if the stub has other queued
39825 events to report to @value{GDBN}, it shall respond by sending a
39826 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39827 packet to solicit further responses; again, it is permitted to send
39828 other, unrelated packets as well which the stub should process
39831 If the stub receives a @var{ack} packet and there are no additional
39832 @var{event} to report, the stub shall return an @samp{OK} response.
39833 At this point, @value{GDBN} has finished processing a notification
39834 and the stub has completed sending any queued events. @value{GDBN}
39835 won't accept any new notifications until the final @samp{OK} is
39836 received . If further notification events occur, the stub shall send
39837 a new notification, @value{GDBN} shall accept the notification, and
39838 the process shall be repeated.
39840 The process of asynchronous notification can be illustrated by the
39843 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39846 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39848 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39853 The following notifications are defined:
39854 @multitable @columnfractions 0.12 0.12 0.38 0.38
39863 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39864 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39865 for information on how these notifications are acknowledged by
39867 @tab Report an asynchronous stop event in non-stop mode.
39871 @node Remote Non-Stop
39872 @section Remote Protocol Support for Non-Stop Mode
39874 @value{GDBN}'s remote protocol supports non-stop debugging of
39875 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39876 supports non-stop mode, it should report that to @value{GDBN} by including
39877 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39879 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39880 establishing a new connection with the stub. Entering non-stop mode
39881 does not alter the state of any currently-running threads, but targets
39882 must stop all threads in any already-attached processes when entering
39883 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39884 probe the target state after a mode change.
39886 In non-stop mode, when an attached process encounters an event that
39887 would otherwise be reported with a stop reply, it uses the
39888 asynchronous notification mechanism (@pxref{Notification Packets}) to
39889 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39890 in all processes are stopped when a stop reply is sent, in non-stop
39891 mode only the thread reporting the stop event is stopped. That is,
39892 when reporting a @samp{S} or @samp{T} response to indicate completion
39893 of a step operation, hitting a breakpoint, or a fault, only the
39894 affected thread is stopped; any other still-running threads continue
39895 to run. When reporting a @samp{W} or @samp{X} response, all running
39896 threads belonging to other attached processes continue to run.
39898 In non-stop mode, the target shall respond to the @samp{?} packet as
39899 follows. First, any incomplete stop reply notification/@samp{vStopped}
39900 sequence in progress is abandoned. The target must begin a new
39901 sequence reporting stop events for all stopped threads, whether or not
39902 it has previously reported those events to @value{GDBN}. The first
39903 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39904 subsequent stop replies are sent as responses to @samp{vStopped} packets
39905 using the mechanism described above. The target must not send
39906 asynchronous stop reply notifications until the sequence is complete.
39907 If all threads are running when the target receives the @samp{?} packet,
39908 or if the target is not attached to any process, it shall respond
39911 If the stub supports non-stop mode, it should also support the
39912 @samp{swbreak} stop reason if software breakpoints are supported, and
39913 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39914 (@pxref{swbreak stop reason}). This is because given the asynchronous
39915 nature of non-stop mode, between the time a thread hits a breakpoint
39916 and the time the event is finally processed by @value{GDBN}, the
39917 breakpoint may have already been removed from the target. Due to
39918 this, @value{GDBN} needs to be able to tell whether a trap stop was
39919 caused by a delayed breakpoint event, which should be ignored, as
39920 opposed to a random trap signal, which should be reported to the user.
39921 Note the @samp{swbreak} feature implies that the target is responsible
39922 for adjusting the PC when a software breakpoint triggers, if
39923 necessary, such as on the x86 architecture.
39925 @node Packet Acknowledgment
39926 @section Packet Acknowledgment
39928 @cindex acknowledgment, for @value{GDBN} remote
39929 @cindex packet acknowledgment, for @value{GDBN} remote
39930 By default, when either the host or the target machine receives a packet,
39931 the first response expected is an acknowledgment: either @samp{+} (to indicate
39932 the package was received correctly) or @samp{-} (to request retransmission).
39933 This mechanism allows the @value{GDBN} remote protocol to operate over
39934 unreliable transport mechanisms, such as a serial line.
39936 In cases where the transport mechanism is itself reliable (such as a pipe or
39937 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39938 It may be desirable to disable them in that case to reduce communication
39939 overhead, or for other reasons. This can be accomplished by means of the
39940 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39942 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39943 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39944 and response format still includes the normal checksum, as described in
39945 @ref{Overview}, but the checksum may be ignored by the receiver.
39947 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39948 no-acknowledgment mode, it should report that to @value{GDBN}
39949 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39950 @pxref{qSupported}.
39951 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39952 disabled via the @code{set remote noack-packet off} command
39953 (@pxref{Remote Configuration}),
39954 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39955 Only then may the stub actually turn off packet acknowledgments.
39956 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39957 response, which can be safely ignored by the stub.
39959 Note that @code{set remote noack-packet} command only affects negotiation
39960 between @value{GDBN} and the stub when subsequent connections are made;
39961 it does not affect the protocol acknowledgment state for any current
39963 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39964 new connection is established,
39965 there is also no protocol request to re-enable the acknowledgments
39966 for the current connection, once disabled.
39971 Example sequence of a target being re-started. Notice how the restart
39972 does not get any direct output:
39977 @emph{target restarts}
39980 <- @code{T001:1234123412341234}
39984 Example sequence of a target being stepped by a single instruction:
39987 -> @code{G1445@dots{}}
39992 <- @code{T001:1234123412341234}
39996 <- @code{1455@dots{}}
40000 @node File-I/O Remote Protocol Extension
40001 @section File-I/O Remote Protocol Extension
40002 @cindex File-I/O remote protocol extension
40005 * File-I/O Overview::
40006 * Protocol Basics::
40007 * The F Request Packet::
40008 * The F Reply Packet::
40009 * The Ctrl-C Message::
40011 * List of Supported Calls::
40012 * Protocol-specific Representation of Datatypes::
40014 * File-I/O Examples::
40017 @node File-I/O Overview
40018 @subsection File-I/O Overview
40019 @cindex file-i/o overview
40021 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40022 target to use the host's file system and console I/O to perform various
40023 system calls. System calls on the target system are translated into a
40024 remote protocol packet to the host system, which then performs the needed
40025 actions and returns a response packet to the target system.
40026 This simulates file system operations even on targets that lack file systems.
40028 The protocol is defined to be independent of both the host and target systems.
40029 It uses its own internal representation of datatypes and values. Both
40030 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40031 translating the system-dependent value representations into the internal
40032 protocol representations when data is transmitted.
40034 The communication is synchronous. A system call is possible only when
40035 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40036 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40037 the target is stopped to allow deterministic access to the target's
40038 memory. Therefore File-I/O is not interruptible by target signals. On
40039 the other hand, it is possible to interrupt File-I/O by a user interrupt
40040 (@samp{Ctrl-C}) within @value{GDBN}.
40042 The target's request to perform a host system call does not finish
40043 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40044 after finishing the system call, the target returns to continuing the
40045 previous activity (continue, step). No additional continue or step
40046 request from @value{GDBN} is required.
40049 (@value{GDBP}) continue
40050 <- target requests 'system call X'
40051 target is stopped, @value{GDBN} executes system call
40052 -> @value{GDBN} returns result
40053 ... target continues, @value{GDBN} returns to wait for the target
40054 <- target hits breakpoint and sends a Txx packet
40057 The protocol only supports I/O on the console and to regular files on
40058 the host file system. Character or block special devices, pipes,
40059 named pipes, sockets or any other communication method on the host
40060 system are not supported by this protocol.
40062 File I/O is not supported in non-stop mode.
40064 @node Protocol Basics
40065 @subsection Protocol Basics
40066 @cindex protocol basics, file-i/o
40068 The File-I/O protocol uses the @code{F} packet as the request as well
40069 as reply packet. Since a File-I/O system call can only occur when
40070 @value{GDBN} is waiting for a response from the continuing or stepping target,
40071 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40072 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40073 This @code{F} packet contains all information needed to allow @value{GDBN}
40074 to call the appropriate host system call:
40078 A unique identifier for the requested system call.
40081 All parameters to the system call. Pointers are given as addresses
40082 in the target memory address space. Pointers to strings are given as
40083 pointer/length pair. Numerical values are given as they are.
40084 Numerical control flags are given in a protocol-specific representation.
40088 At this point, @value{GDBN} has to perform the following actions.
40092 If the parameters include pointer values to data needed as input to a
40093 system call, @value{GDBN} requests this data from the target with a
40094 standard @code{m} packet request. This additional communication has to be
40095 expected by the target implementation and is handled as any other @code{m}
40099 @value{GDBN} translates all value from protocol representation to host
40100 representation as needed. Datatypes are coerced into the host types.
40103 @value{GDBN} calls the system call.
40106 It then coerces datatypes back to protocol representation.
40109 If the system call is expected to return data in buffer space specified
40110 by pointer parameters to the call, the data is transmitted to the
40111 target using a @code{M} or @code{X} packet. This packet has to be expected
40112 by the target implementation and is handled as any other @code{M} or @code{X}
40117 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40118 necessary information for the target to continue. This at least contains
40125 @code{errno}, if has been changed by the system call.
40132 After having done the needed type and value coercion, the target continues
40133 the latest continue or step action.
40135 @node The F Request Packet
40136 @subsection The @code{F} Request Packet
40137 @cindex file-i/o request packet
40138 @cindex @code{F} request packet
40140 The @code{F} request packet has the following format:
40143 @item F@var{call-id},@var{parameter@dots{}}
40145 @var{call-id} is the identifier to indicate the host system call to be called.
40146 This is just the name of the function.
40148 @var{parameter@dots{}} are the parameters to the system call.
40149 Parameters are hexadecimal integer values, either the actual values in case
40150 of scalar datatypes, pointers to target buffer space in case of compound
40151 datatypes and unspecified memory areas, or pointer/length pairs in case
40152 of string parameters. These are appended to the @var{call-id} as a
40153 comma-delimited list. All values are transmitted in ASCII
40154 string representation, pointer/length pairs separated by a slash.
40160 @node The F Reply Packet
40161 @subsection The @code{F} Reply Packet
40162 @cindex file-i/o reply packet
40163 @cindex @code{F} reply packet
40165 The @code{F} reply packet has the following format:
40169 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40171 @var{retcode} is the return code of the system call as hexadecimal value.
40173 @var{errno} is the @code{errno} set by the call, in protocol-specific
40175 This parameter can be omitted if the call was successful.
40177 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40178 case, @var{errno} must be sent as well, even if the call was successful.
40179 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40186 or, if the call was interrupted before the host call has been performed:
40193 assuming 4 is the protocol-specific representation of @code{EINTR}.
40198 @node The Ctrl-C Message
40199 @subsection The @samp{Ctrl-C} Message
40200 @cindex ctrl-c message, in file-i/o protocol
40202 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40203 reply packet (@pxref{The F Reply Packet}),
40204 the target should behave as if it had
40205 gotten a break message. The meaning for the target is ``system call
40206 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40207 (as with a break message) and return to @value{GDBN} with a @code{T02}
40210 It's important for the target to know in which
40211 state the system call was interrupted. There are two possible cases:
40215 The system call hasn't been performed on the host yet.
40218 The system call on the host has been finished.
40222 These two states can be distinguished by the target by the value of the
40223 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40224 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40225 on POSIX systems. In any other case, the target may presume that the
40226 system call has been finished --- successfully or not --- and should behave
40227 as if the break message arrived right after the system call.
40229 @value{GDBN} must behave reliably. If the system call has not been called
40230 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40231 @code{errno} in the packet. If the system call on the host has been finished
40232 before the user requests a break, the full action must be finished by
40233 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40234 The @code{F} packet may only be sent when either nothing has happened
40235 or the full action has been completed.
40238 @subsection Console I/O
40239 @cindex console i/o as part of file-i/o
40241 By default and if not explicitly closed by the target system, the file
40242 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40243 on the @value{GDBN} console is handled as any other file output operation
40244 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40245 by @value{GDBN} so that after the target read request from file descriptor
40246 0 all following typing is buffered until either one of the following
40251 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40253 system call is treated as finished.
40256 The user presses @key{RET}. This is treated as end of input with a trailing
40260 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40261 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40265 If the user has typed more characters than fit in the buffer given to
40266 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40267 either another @code{read(0, @dots{})} is requested by the target, or debugging
40268 is stopped at the user's request.
40271 @node List of Supported Calls
40272 @subsection List of Supported Calls
40273 @cindex list of supported file-i/o calls
40290 @unnumberedsubsubsec open
40291 @cindex open, file-i/o system call
40296 int open(const char *pathname, int flags);
40297 int open(const char *pathname, int flags, mode_t mode);
40301 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40304 @var{flags} is the bitwise @code{OR} of the following values:
40308 If the file does not exist it will be created. The host
40309 rules apply as far as file ownership and time stamps
40313 When used with @code{O_CREAT}, if the file already exists it is
40314 an error and open() fails.
40317 If the file already exists and the open mode allows
40318 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40319 truncated to zero length.
40322 The file is opened in append mode.
40325 The file is opened for reading only.
40328 The file is opened for writing only.
40331 The file is opened for reading and writing.
40335 Other bits are silently ignored.
40339 @var{mode} is the bitwise @code{OR} of the following values:
40343 User has read permission.
40346 User has write permission.
40349 Group has read permission.
40352 Group has write permission.
40355 Others have read permission.
40358 Others have write permission.
40362 Other bits are silently ignored.
40365 @item Return value:
40366 @code{open} returns the new file descriptor or -1 if an error
40373 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40376 @var{pathname} refers to a directory.
40379 The requested access is not allowed.
40382 @var{pathname} was too long.
40385 A directory component in @var{pathname} does not exist.
40388 @var{pathname} refers to a device, pipe, named pipe or socket.
40391 @var{pathname} refers to a file on a read-only filesystem and
40392 write access was requested.
40395 @var{pathname} is an invalid pointer value.
40398 No space on device to create the file.
40401 The process already has the maximum number of files open.
40404 The limit on the total number of files open on the system
40408 The call was interrupted by the user.
40414 @unnumberedsubsubsec close
40415 @cindex close, file-i/o system call
40424 @samp{Fclose,@var{fd}}
40426 @item Return value:
40427 @code{close} returns zero on success, or -1 if an error occurred.
40433 @var{fd} isn't a valid open file descriptor.
40436 The call was interrupted by the user.
40442 @unnumberedsubsubsec read
40443 @cindex read, file-i/o system call
40448 int read(int fd, void *buf, unsigned int count);
40452 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40454 @item Return value:
40455 On success, the number of bytes read is returned.
40456 Zero indicates end of file. If count is zero, read
40457 returns zero as well. On error, -1 is returned.
40463 @var{fd} is not a valid file descriptor or is not open for
40467 @var{bufptr} is an invalid pointer value.
40470 The call was interrupted by the user.
40476 @unnumberedsubsubsec write
40477 @cindex write, file-i/o system call
40482 int write(int fd, const void *buf, unsigned int count);
40486 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40488 @item Return value:
40489 On success, the number of bytes written are returned.
40490 Zero indicates nothing was written. On error, -1
40497 @var{fd} is not a valid file descriptor or is not open for
40501 @var{bufptr} is an invalid pointer value.
40504 An attempt was made to write a file that exceeds the
40505 host-specific maximum file size allowed.
40508 No space on device to write the data.
40511 The call was interrupted by the user.
40517 @unnumberedsubsubsec lseek
40518 @cindex lseek, file-i/o system call
40523 long lseek (int fd, long offset, int flag);
40527 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40529 @var{flag} is one of:
40533 The offset is set to @var{offset} bytes.
40536 The offset is set to its current location plus @var{offset}
40540 The offset is set to the size of the file plus @var{offset}
40544 @item Return value:
40545 On success, the resulting unsigned offset in bytes from
40546 the beginning of the file is returned. Otherwise, a
40547 value of -1 is returned.
40553 @var{fd} is not a valid open file descriptor.
40556 @var{fd} is associated with the @value{GDBN} console.
40559 @var{flag} is not a proper value.
40562 The call was interrupted by the user.
40568 @unnumberedsubsubsec rename
40569 @cindex rename, file-i/o system call
40574 int rename(const char *oldpath, const char *newpath);
40578 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40580 @item Return value:
40581 On success, zero is returned. On error, -1 is returned.
40587 @var{newpath} is an existing directory, but @var{oldpath} is not a
40591 @var{newpath} is a non-empty directory.
40594 @var{oldpath} or @var{newpath} is a directory that is in use by some
40598 An attempt was made to make a directory a subdirectory
40602 A component used as a directory in @var{oldpath} or new
40603 path is not a directory. Or @var{oldpath} is a directory
40604 and @var{newpath} exists but is not a directory.
40607 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40610 No access to the file or the path of the file.
40614 @var{oldpath} or @var{newpath} was too long.
40617 A directory component in @var{oldpath} or @var{newpath} does not exist.
40620 The file is on a read-only filesystem.
40623 The device containing the file has no room for the new
40627 The call was interrupted by the user.
40633 @unnumberedsubsubsec unlink
40634 @cindex unlink, file-i/o system call
40639 int unlink(const char *pathname);
40643 @samp{Funlink,@var{pathnameptr}/@var{len}}
40645 @item Return value:
40646 On success, zero is returned. On error, -1 is returned.
40652 No access to the file or the path of the file.
40655 The system does not allow unlinking of directories.
40658 The file @var{pathname} cannot be unlinked because it's
40659 being used by another process.
40662 @var{pathnameptr} is an invalid pointer value.
40665 @var{pathname} was too long.
40668 A directory component in @var{pathname} does not exist.
40671 A component of the path is not a directory.
40674 The file is on a read-only filesystem.
40677 The call was interrupted by the user.
40683 @unnumberedsubsubsec stat/fstat
40684 @cindex fstat, file-i/o system call
40685 @cindex stat, file-i/o system call
40690 int stat(const char *pathname, struct stat *buf);
40691 int fstat(int fd, struct stat *buf);
40695 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40696 @samp{Ffstat,@var{fd},@var{bufptr}}
40698 @item Return value:
40699 On success, zero is returned. On error, -1 is returned.
40705 @var{fd} is not a valid open file.
40708 A directory component in @var{pathname} does not exist or the
40709 path is an empty string.
40712 A component of the path is not a directory.
40715 @var{pathnameptr} is an invalid pointer value.
40718 No access to the file or the path of the file.
40721 @var{pathname} was too long.
40724 The call was interrupted by the user.
40730 @unnumberedsubsubsec gettimeofday
40731 @cindex gettimeofday, file-i/o system call
40736 int gettimeofday(struct timeval *tv, void *tz);
40740 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40742 @item Return value:
40743 On success, 0 is returned, -1 otherwise.
40749 @var{tz} is a non-NULL pointer.
40752 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40758 @unnumberedsubsubsec isatty
40759 @cindex isatty, file-i/o system call
40764 int isatty(int fd);
40768 @samp{Fisatty,@var{fd}}
40770 @item Return value:
40771 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40777 The call was interrupted by the user.
40782 Note that the @code{isatty} call is treated as a special case: it returns
40783 1 to the target if the file descriptor is attached
40784 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40785 would require implementing @code{ioctl} and would be more complex than
40790 @unnumberedsubsubsec system
40791 @cindex system, file-i/o system call
40796 int system(const char *command);
40800 @samp{Fsystem,@var{commandptr}/@var{len}}
40802 @item Return value:
40803 If @var{len} is zero, the return value indicates whether a shell is
40804 available. A zero return value indicates a shell is not available.
40805 For non-zero @var{len}, the value returned is -1 on error and the
40806 return status of the command otherwise. Only the exit status of the
40807 command is returned, which is extracted from the host's @code{system}
40808 return value by calling @code{WEXITSTATUS(retval)}. In case
40809 @file{/bin/sh} could not be executed, 127 is returned.
40815 The call was interrupted by the user.
40820 @value{GDBN} takes over the full task of calling the necessary host calls
40821 to perform the @code{system} call. The return value of @code{system} on
40822 the host is simplified before it's returned
40823 to the target. Any termination signal information from the child process
40824 is discarded, and the return value consists
40825 entirely of the exit status of the called command.
40827 Due to security concerns, the @code{system} call is by default refused
40828 by @value{GDBN}. The user has to allow this call explicitly with the
40829 @code{set remote system-call-allowed 1} command.
40832 @item set remote system-call-allowed
40833 @kindex set remote system-call-allowed
40834 Control whether to allow the @code{system} calls in the File I/O
40835 protocol for the remote target. The default is zero (disabled).
40837 @item show remote system-call-allowed
40838 @kindex show remote system-call-allowed
40839 Show whether the @code{system} calls are allowed in the File I/O
40843 @node Protocol-specific Representation of Datatypes
40844 @subsection Protocol-specific Representation of Datatypes
40845 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40848 * Integral Datatypes::
40850 * Memory Transfer::
40855 @node Integral Datatypes
40856 @unnumberedsubsubsec Integral Datatypes
40857 @cindex integral datatypes, in file-i/o protocol
40859 The integral datatypes used in the system calls are @code{int},
40860 @code{unsigned int}, @code{long}, @code{unsigned long},
40861 @code{mode_t}, and @code{time_t}.
40863 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40864 implemented as 32 bit values in this protocol.
40866 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40868 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40869 in @file{limits.h}) to allow range checking on host and target.
40871 @code{time_t} datatypes are defined as seconds since the Epoch.
40873 All integral datatypes transferred as part of a memory read or write of a
40874 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40877 @node Pointer Values
40878 @unnumberedsubsubsec Pointer Values
40879 @cindex pointer values, in file-i/o protocol
40881 Pointers to target data are transmitted as they are. An exception
40882 is made for pointers to buffers for which the length isn't
40883 transmitted as part of the function call, namely strings. Strings
40884 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40891 which is a pointer to data of length 18 bytes at position 0x1aaf.
40892 The length is defined as the full string length in bytes, including
40893 the trailing null byte. For example, the string @code{"hello world"}
40894 at address 0x123456 is transmitted as
40900 @node Memory Transfer
40901 @unnumberedsubsubsec Memory Transfer
40902 @cindex memory transfer, in file-i/o protocol
40904 Structured data which is transferred using a memory read or write (for
40905 example, a @code{struct stat}) is expected to be in a protocol-specific format
40906 with all scalar multibyte datatypes being big endian. Translation to
40907 this representation needs to be done both by the target before the @code{F}
40908 packet is sent, and by @value{GDBN} before
40909 it transfers memory to the target. Transferred pointers to structured
40910 data should point to the already-coerced data at any time.
40914 @unnumberedsubsubsec struct stat
40915 @cindex struct stat, in file-i/o protocol
40917 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40918 is defined as follows:
40922 unsigned int st_dev; /* device */
40923 unsigned int st_ino; /* inode */
40924 mode_t st_mode; /* protection */
40925 unsigned int st_nlink; /* number of hard links */
40926 unsigned int st_uid; /* user ID of owner */
40927 unsigned int st_gid; /* group ID of owner */
40928 unsigned int st_rdev; /* device type (if inode device) */
40929 unsigned long st_size; /* total size, in bytes */
40930 unsigned long st_blksize; /* blocksize for filesystem I/O */
40931 unsigned long st_blocks; /* number of blocks allocated */
40932 time_t st_atime; /* time of last access */
40933 time_t st_mtime; /* time of last modification */
40934 time_t st_ctime; /* time of last change */
40938 The integral datatypes conform to the definitions given in the
40939 appropriate section (see @ref{Integral Datatypes}, for details) so this
40940 structure is of size 64 bytes.
40942 The values of several fields have a restricted meaning and/or
40948 A value of 0 represents a file, 1 the console.
40951 No valid meaning for the target. Transmitted unchanged.
40954 Valid mode bits are described in @ref{Constants}. Any other
40955 bits have currently no meaning for the target.
40960 No valid meaning for the target. Transmitted unchanged.
40965 These values have a host and file system dependent
40966 accuracy. Especially on Windows hosts, the file system may not
40967 support exact timing values.
40970 The target gets a @code{struct stat} of the above representation and is
40971 responsible for coercing it to the target representation before
40974 Note that due to size differences between the host, target, and protocol
40975 representations of @code{struct stat} members, these members could eventually
40976 get truncated on the target.
40978 @node struct timeval
40979 @unnumberedsubsubsec struct timeval
40980 @cindex struct timeval, in file-i/o protocol
40982 The buffer of type @code{struct timeval} used by the File-I/O protocol
40983 is defined as follows:
40987 time_t tv_sec; /* second */
40988 long tv_usec; /* microsecond */
40992 The integral datatypes conform to the definitions given in the
40993 appropriate section (see @ref{Integral Datatypes}, for details) so this
40994 structure is of size 8 bytes.
40997 @subsection Constants
40998 @cindex constants, in file-i/o protocol
41000 The following values are used for the constants inside of the
41001 protocol. @value{GDBN} and target are responsible for translating these
41002 values before and after the call as needed.
41013 @unnumberedsubsubsec Open Flags
41014 @cindex open flags, in file-i/o protocol
41016 All values are given in hexadecimal representation.
41028 @node mode_t Values
41029 @unnumberedsubsubsec mode_t Values
41030 @cindex mode_t values, in file-i/o protocol
41032 All values are given in octal representation.
41049 @unnumberedsubsubsec Errno Values
41050 @cindex errno values, in file-i/o protocol
41052 All values are given in decimal representation.
41077 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41078 any error value not in the list of supported error numbers.
41081 @unnumberedsubsubsec Lseek Flags
41082 @cindex lseek flags, in file-i/o protocol
41091 @unnumberedsubsubsec Limits
41092 @cindex limits, in file-i/o protocol
41094 All values are given in decimal representation.
41097 INT_MIN -2147483648
41099 UINT_MAX 4294967295
41100 LONG_MIN -9223372036854775808
41101 LONG_MAX 9223372036854775807
41102 ULONG_MAX 18446744073709551615
41105 @node File-I/O Examples
41106 @subsection File-I/O Examples
41107 @cindex file-i/o examples
41109 Example sequence of a write call, file descriptor 3, buffer is at target
41110 address 0x1234, 6 bytes should be written:
41113 <- @code{Fwrite,3,1234,6}
41114 @emph{request memory read from target}
41117 @emph{return "6 bytes written"}
41121 Example sequence of a read call, file descriptor 3, buffer is at target
41122 address 0x1234, 6 bytes should be read:
41125 <- @code{Fread,3,1234,6}
41126 @emph{request memory write to target}
41127 -> @code{X1234,6:XXXXXX}
41128 @emph{return "6 bytes read"}
41132 Example sequence of a read call, call fails on the host due to invalid
41133 file descriptor (@code{EBADF}):
41136 <- @code{Fread,3,1234,6}
41140 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41144 <- @code{Fread,3,1234,6}
41149 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41153 <- @code{Fread,3,1234,6}
41154 -> @code{X1234,6:XXXXXX}
41158 @node Library List Format
41159 @section Library List Format
41160 @cindex library list format, remote protocol
41162 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41163 same process as your application to manage libraries. In this case,
41164 @value{GDBN} can use the loader's symbol table and normal memory
41165 operations to maintain a list of shared libraries. On other
41166 platforms, the operating system manages loaded libraries.
41167 @value{GDBN} can not retrieve the list of currently loaded libraries
41168 through memory operations, so it uses the @samp{qXfer:libraries:read}
41169 packet (@pxref{qXfer library list read}) instead. The remote stub
41170 queries the target's operating system and reports which libraries
41173 The @samp{qXfer:libraries:read} packet returns an XML document which
41174 lists loaded libraries and their offsets. Each library has an
41175 associated name and one or more segment or section base addresses,
41176 which report where the library was loaded in memory.
41178 For the common case of libraries that are fully linked binaries, the
41179 library should have a list of segments. If the target supports
41180 dynamic linking of a relocatable object file, its library XML element
41181 should instead include a list of allocated sections. The segment or
41182 section bases are start addresses, not relocation offsets; they do not
41183 depend on the library's link-time base addresses.
41185 @value{GDBN} must be linked with the Expat library to support XML
41186 library lists. @xref{Expat}.
41188 A simple memory map, with one loaded library relocated by a single
41189 offset, looks like this:
41193 <library name="/lib/libc.so.6">
41194 <segment address="0x10000000"/>
41199 Another simple memory map, with one loaded library with three
41200 allocated sections (.text, .data, .bss), looks like this:
41204 <library name="sharedlib.o">
41205 <section address="0x10000000"/>
41206 <section address="0x20000000"/>
41207 <section address="0x30000000"/>
41212 The format of a library list is described by this DTD:
41215 <!-- library-list: Root element with versioning -->
41216 <!ELEMENT library-list (library)*>
41217 <!ATTLIST library-list version CDATA #FIXED "1.0">
41218 <!ELEMENT library (segment*, section*)>
41219 <!ATTLIST library name CDATA #REQUIRED>
41220 <!ELEMENT segment EMPTY>
41221 <!ATTLIST segment address CDATA #REQUIRED>
41222 <!ELEMENT section EMPTY>
41223 <!ATTLIST section address CDATA #REQUIRED>
41226 In addition, segments and section descriptors cannot be mixed within a
41227 single library element, and you must supply at least one segment or
41228 section for each library.
41230 @node Library List Format for SVR4 Targets
41231 @section Library List Format for SVR4 Targets
41232 @cindex library list format, remote protocol
41234 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41235 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41236 shared libraries. Still a special library list provided by this packet is
41237 more efficient for the @value{GDBN} remote protocol.
41239 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41240 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41241 target, the following parameters are reported:
41245 @code{name}, the absolute file name from the @code{l_name} field of
41246 @code{struct link_map}.
41248 @code{lm} with address of @code{struct link_map} used for TLS
41249 (Thread Local Storage) access.
41251 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41252 @code{struct link_map}. For prelinked libraries this is not an absolute
41253 memory address. It is a displacement of absolute memory address against
41254 address the file was prelinked to during the library load.
41256 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41259 Additionally the single @code{main-lm} attribute specifies address of
41260 @code{struct link_map} used for the main executable. This parameter is used
41261 for TLS access and its presence is optional.
41263 @value{GDBN} must be linked with the Expat library to support XML
41264 SVR4 library lists. @xref{Expat}.
41266 A simple memory map, with two loaded libraries (which do not use prelink),
41270 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41271 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41273 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41275 </library-list-svr>
41278 The format of an SVR4 library list is described by this DTD:
41281 <!-- library-list-svr4: Root element with versioning -->
41282 <!ELEMENT library-list-svr4 (library)*>
41283 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41284 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41285 <!ELEMENT library EMPTY>
41286 <!ATTLIST library name CDATA #REQUIRED>
41287 <!ATTLIST library lm CDATA #REQUIRED>
41288 <!ATTLIST library l_addr CDATA #REQUIRED>
41289 <!ATTLIST library l_ld CDATA #REQUIRED>
41292 @node Memory Map Format
41293 @section Memory Map Format
41294 @cindex memory map format
41296 To be able to write into flash memory, @value{GDBN} needs to obtain a
41297 memory map from the target. This section describes the format of the
41300 The memory map is obtained using the @samp{qXfer:memory-map:read}
41301 (@pxref{qXfer memory map read}) packet and is an XML document that
41302 lists memory regions.
41304 @value{GDBN} must be linked with the Expat library to support XML
41305 memory maps. @xref{Expat}.
41307 The top-level structure of the document is shown below:
41310 <?xml version="1.0"?>
41311 <!DOCTYPE memory-map
41312 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41313 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41319 Each region can be either:
41324 A region of RAM starting at @var{addr} and extending for @var{length}
41328 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41333 A region of read-only memory:
41336 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41341 A region of flash memory, with erasure blocks @var{blocksize}
41345 <memory type="flash" start="@var{addr}" length="@var{length}">
41346 <property name="blocksize">@var{blocksize}</property>
41352 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41353 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41354 packets to write to addresses in such ranges.
41356 The formal DTD for memory map format is given below:
41359 <!-- ................................................... -->
41360 <!-- Memory Map XML DTD ................................ -->
41361 <!-- File: memory-map.dtd .............................. -->
41362 <!-- .................................... .............. -->
41363 <!-- memory-map.dtd -->
41364 <!-- memory-map: Root element with versioning -->
41365 <!ELEMENT memory-map (memory)*>
41366 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41367 <!ELEMENT memory (property)*>
41368 <!-- memory: Specifies a memory region,
41369 and its type, or device. -->
41370 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41371 start CDATA #REQUIRED
41372 length CDATA #REQUIRED>
41373 <!-- property: Generic attribute tag -->
41374 <!ELEMENT property (#PCDATA | property)*>
41375 <!ATTLIST property name (blocksize) #REQUIRED>
41378 @node Thread List Format
41379 @section Thread List Format
41380 @cindex thread list format
41382 To efficiently update the list of threads and their attributes,
41383 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41384 (@pxref{qXfer threads read}) and obtains the XML document with
41385 the following structure:
41388 <?xml version="1.0"?>
41390 <thread id="id" core="0" name="name">
41391 ... description ...
41396 Each @samp{thread} element must have the @samp{id} attribute that
41397 identifies the thread (@pxref{thread-id syntax}). The
41398 @samp{core} attribute, if present, specifies which processor core
41399 the thread was last executing on. The @samp{name} attribute, if
41400 present, specifies the human-readable name of the thread. The content
41401 of the of @samp{thread} element is interpreted as human-readable
41402 auxiliary information. The @samp{handle} attribute, if present,
41403 is a hex encoded representation of the thread handle.
41406 @node Traceframe Info Format
41407 @section Traceframe Info Format
41408 @cindex traceframe info format
41410 To be able to know which objects in the inferior can be examined when
41411 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41412 memory ranges, registers and trace state variables that have been
41413 collected in a traceframe.
41415 This list is obtained using the @samp{qXfer:traceframe-info:read}
41416 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41418 @value{GDBN} must be linked with the Expat library to support XML
41419 traceframe info discovery. @xref{Expat}.
41421 The top-level structure of the document is shown below:
41424 <?xml version="1.0"?>
41425 <!DOCTYPE traceframe-info
41426 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41427 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41433 Each traceframe block can be either:
41438 A region of collected memory starting at @var{addr} and extending for
41439 @var{length} bytes from there:
41442 <memory start="@var{addr}" length="@var{length}"/>
41446 A block indicating trace state variable numbered @var{number} has been
41450 <tvar id="@var{number}"/>
41455 The formal DTD for the traceframe info format is given below:
41458 <!ELEMENT traceframe-info (memory | tvar)* >
41459 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41461 <!ELEMENT memory EMPTY>
41462 <!ATTLIST memory start CDATA #REQUIRED
41463 length CDATA #REQUIRED>
41465 <!ATTLIST tvar id CDATA #REQUIRED>
41468 @node Branch Trace Format
41469 @section Branch Trace Format
41470 @cindex branch trace format
41472 In order to display the branch trace of an inferior thread,
41473 @value{GDBN} needs to obtain the list of branches. This list is
41474 represented as list of sequential code blocks that are connected via
41475 branches. The code in each block has been executed sequentially.
41477 This list is obtained using the @samp{qXfer:btrace:read}
41478 (@pxref{qXfer btrace read}) packet and is an XML document.
41480 @value{GDBN} must be linked with the Expat library to support XML
41481 traceframe info discovery. @xref{Expat}.
41483 The top-level structure of the document is shown below:
41486 <?xml version="1.0"?>
41488 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41489 "http://sourceware.org/gdb/gdb-btrace.dtd">
41498 A block of sequentially executed instructions starting at @var{begin}
41499 and ending at @var{end}:
41502 <block begin="@var{begin}" end="@var{end}"/>
41507 The formal DTD for the branch trace format is given below:
41510 <!ELEMENT btrace (block* | pt) >
41511 <!ATTLIST btrace version CDATA #FIXED "1.0">
41513 <!ELEMENT block EMPTY>
41514 <!ATTLIST block begin CDATA #REQUIRED
41515 end CDATA #REQUIRED>
41517 <!ELEMENT pt (pt-config?, raw?)>
41519 <!ELEMENT pt-config (cpu?)>
41521 <!ELEMENT cpu EMPTY>
41522 <!ATTLIST cpu vendor CDATA #REQUIRED
41523 family CDATA #REQUIRED
41524 model CDATA #REQUIRED
41525 stepping CDATA #REQUIRED>
41527 <!ELEMENT raw (#PCDATA)>
41530 @node Branch Trace Configuration Format
41531 @section Branch Trace Configuration Format
41532 @cindex branch trace configuration format
41534 For each inferior thread, @value{GDBN} can obtain the branch trace
41535 configuration using the @samp{qXfer:btrace-conf:read}
41536 (@pxref{qXfer btrace-conf read}) packet.
41538 The configuration describes the branch trace format and configuration
41539 settings for that format. The following information is described:
41543 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41546 The size of the @acronym{BTS} ring buffer in bytes.
41549 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41553 The size of the @acronym{Intel PT} ring buffer in bytes.
41557 @value{GDBN} must be linked with the Expat library to support XML
41558 branch trace configuration discovery. @xref{Expat}.
41560 The formal DTD for the branch trace configuration format is given below:
41563 <!ELEMENT btrace-conf (bts?, pt?)>
41564 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41566 <!ELEMENT bts EMPTY>
41567 <!ATTLIST bts size CDATA #IMPLIED>
41569 <!ELEMENT pt EMPTY>
41570 <!ATTLIST pt size CDATA #IMPLIED>
41573 @include agentexpr.texi
41575 @node Target Descriptions
41576 @appendix Target Descriptions
41577 @cindex target descriptions
41579 One of the challenges of using @value{GDBN} to debug embedded systems
41580 is that there are so many minor variants of each processor
41581 architecture in use. It is common practice for vendors to start with
41582 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41583 and then make changes to adapt it to a particular market niche. Some
41584 architectures have hundreds of variants, available from dozens of
41585 vendors. This leads to a number of problems:
41589 With so many different customized processors, it is difficult for
41590 the @value{GDBN} maintainers to keep up with the changes.
41592 Since individual variants may have short lifetimes or limited
41593 audiences, it may not be worthwhile to carry information about every
41594 variant in the @value{GDBN} source tree.
41596 When @value{GDBN} does support the architecture of the embedded system
41597 at hand, the task of finding the correct architecture name to give the
41598 @command{set architecture} command can be error-prone.
41601 To address these problems, the @value{GDBN} remote protocol allows a
41602 target system to not only identify itself to @value{GDBN}, but to
41603 actually describe its own features. This lets @value{GDBN} support
41604 processor variants it has never seen before --- to the extent that the
41605 descriptions are accurate, and that @value{GDBN} understands them.
41607 @value{GDBN} must be linked with the Expat library to support XML
41608 target descriptions. @xref{Expat}.
41611 * Retrieving Descriptions:: How descriptions are fetched from a target.
41612 * Target Description Format:: The contents of a target description.
41613 * Predefined Target Types:: Standard types available for target
41615 * Enum Target Types:: How to define enum target types.
41616 * Standard Target Features:: Features @value{GDBN} knows about.
41619 @node Retrieving Descriptions
41620 @section Retrieving Descriptions
41622 Target descriptions can be read from the target automatically, or
41623 specified by the user manually. The default behavior is to read the
41624 description from the target. @value{GDBN} retrieves it via the remote
41625 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41626 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41627 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41628 XML document, of the form described in @ref{Target Description
41631 Alternatively, you can specify a file to read for the target description.
41632 If a file is set, the target will not be queried. The commands to
41633 specify a file are:
41636 @cindex set tdesc filename
41637 @item set tdesc filename @var{path}
41638 Read the target description from @var{path}.
41640 @cindex unset tdesc filename
41641 @item unset tdesc filename
41642 Do not read the XML target description from a file. @value{GDBN}
41643 will use the description supplied by the current target.
41645 @cindex show tdesc filename
41646 @item show tdesc filename
41647 Show the filename to read for a target description, if any.
41651 @node Target Description Format
41652 @section Target Description Format
41653 @cindex target descriptions, XML format
41655 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41656 document which complies with the Document Type Definition provided in
41657 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41658 means you can use generally available tools like @command{xmllint} to
41659 check that your feature descriptions are well-formed and valid.
41660 However, to help people unfamiliar with XML write descriptions for
41661 their targets, we also describe the grammar here.
41663 Target descriptions can identify the architecture of the remote target
41664 and (for some architectures) provide information about custom register
41665 sets. They can also identify the OS ABI of the remote target.
41666 @value{GDBN} can use this information to autoconfigure for your
41667 target, or to warn you if you connect to an unsupported target.
41669 Here is a simple target description:
41672 <target version="1.0">
41673 <architecture>i386:x86-64</architecture>
41678 This minimal description only says that the target uses
41679 the x86-64 architecture.
41681 A target description has the following overall form, with [ ] marking
41682 optional elements and @dots{} marking repeatable elements. The elements
41683 are explained further below.
41686 <?xml version="1.0"?>
41687 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41688 <target version="1.0">
41689 @r{[}@var{architecture}@r{]}
41690 @r{[}@var{osabi}@r{]}
41691 @r{[}@var{compatible}@r{]}
41692 @r{[}@var{feature}@dots{}@r{]}
41697 The description is generally insensitive to whitespace and line
41698 breaks, under the usual common-sense rules. The XML version
41699 declaration and document type declaration can generally be omitted
41700 (@value{GDBN} does not require them), but specifying them may be
41701 useful for XML validation tools. The @samp{version} attribute for
41702 @samp{<target>} may also be omitted, but we recommend
41703 including it; if future versions of @value{GDBN} use an incompatible
41704 revision of @file{gdb-target.dtd}, they will detect and report
41705 the version mismatch.
41707 @subsection Inclusion
41708 @cindex target descriptions, inclusion
41711 @cindex <xi:include>
41714 It can sometimes be valuable to split a target description up into
41715 several different annexes, either for organizational purposes, or to
41716 share files between different possible target descriptions. You can
41717 divide a description into multiple files by replacing any element of
41718 the target description with an inclusion directive of the form:
41721 <xi:include href="@var{document}"/>
41725 When @value{GDBN} encounters an element of this form, it will retrieve
41726 the named XML @var{document}, and replace the inclusion directive with
41727 the contents of that document. If the current description was read
41728 using @samp{qXfer}, then so will be the included document;
41729 @var{document} will be interpreted as the name of an annex. If the
41730 current description was read from a file, @value{GDBN} will look for
41731 @var{document} as a file in the same directory where it found the
41732 original description.
41734 @subsection Architecture
41735 @cindex <architecture>
41737 An @samp{<architecture>} element has this form:
41740 <architecture>@var{arch}</architecture>
41743 @var{arch} is one of the architectures from the set accepted by
41744 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41747 @cindex @code{<osabi>}
41749 This optional field was introduced in @value{GDBN} version 7.0.
41750 Previous versions of @value{GDBN} ignore it.
41752 An @samp{<osabi>} element has this form:
41755 <osabi>@var{abi-name}</osabi>
41758 @var{abi-name} is an OS ABI name from the same selection accepted by
41759 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41761 @subsection Compatible Architecture
41762 @cindex @code{<compatible>}
41764 This optional field was introduced in @value{GDBN} version 7.0.
41765 Previous versions of @value{GDBN} ignore it.
41767 A @samp{<compatible>} element has this form:
41770 <compatible>@var{arch}</compatible>
41773 @var{arch} is one of the architectures from the set accepted by
41774 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41776 A @samp{<compatible>} element is used to specify that the target
41777 is able to run binaries in some other than the main target architecture
41778 given by the @samp{<architecture>} element. For example, on the
41779 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41780 or @code{powerpc:common64}, but the system is able to run binaries
41781 in the @code{spu} architecture as well. The way to describe this
41782 capability with @samp{<compatible>} is as follows:
41785 <architecture>powerpc:common</architecture>
41786 <compatible>spu</compatible>
41789 @subsection Features
41792 Each @samp{<feature>} describes some logical portion of the target
41793 system. Features are currently used to describe available CPU
41794 registers and the types of their contents. A @samp{<feature>} element
41798 <feature name="@var{name}">
41799 @r{[}@var{type}@dots{}@r{]}
41805 Each feature's name should be unique within the description. The name
41806 of a feature does not matter unless @value{GDBN} has some special
41807 knowledge of the contents of that feature; if it does, the feature
41808 should have its standard name. @xref{Standard Target Features}.
41812 Any register's value is a collection of bits which @value{GDBN} must
41813 interpret. The default interpretation is a two's complement integer,
41814 but other types can be requested by name in the register description.
41815 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41816 Target Types}), and the description can define additional composite
41819 Each type element must have an @samp{id} attribute, which gives
41820 a unique (within the containing @samp{<feature>}) name to the type.
41821 Types must be defined before they are used.
41824 Some targets offer vector registers, which can be treated as arrays
41825 of scalar elements. These types are written as @samp{<vector>} elements,
41826 specifying the array element type, @var{type}, and the number of elements,
41830 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41834 If a register's value is usefully viewed in multiple ways, define it
41835 with a union type containing the useful representations. The
41836 @samp{<union>} element contains one or more @samp{<field>} elements,
41837 each of which has a @var{name} and a @var{type}:
41840 <union id="@var{id}">
41841 <field name="@var{name}" type="@var{type}"/>
41848 If a register's value is composed from several separate values, define
41849 it with either a structure type or a flags type.
41850 A flags type may only contain bitfields.
41851 A structure type may either contain only bitfields or contain no bitfields.
41852 If the value contains only bitfields, its total size in bytes must be
41855 Non-bitfield values have a @var{name} and @var{type}.
41858 <struct id="@var{id}">
41859 <field name="@var{name}" type="@var{type}"/>
41864 Both @var{name} and @var{type} values are required.
41865 No implicit padding is added.
41867 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41870 <struct id="@var{id}" size="@var{size}">
41871 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41877 <flags id="@var{id}" size="@var{size}">
41878 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41883 The @var{name} value is required.
41884 Bitfield values may be named with the empty string, @samp{""},
41885 in which case the field is ``filler'' and its value is not printed.
41886 Not all bits need to be specified, so ``filler'' fields are optional.
41888 The @var{start} and @var{end} values are required, and @var{type}
41890 The field's @var{start} must be less than or equal to its @var{end},
41891 and zero represents the least significant bit.
41893 The default value of @var{type} is @code{bool} for single bit fields,
41894 and an unsigned integer otherwise.
41896 Which to choose? Structures or flags?
41898 Registers defined with @samp{flags} have these advantages over
41899 defining them with @samp{struct}:
41903 Arithmetic may be performed on them as if they were integers.
41905 They are printed in a more readable fashion.
41908 Registers defined with @samp{struct} have one advantage over
41909 defining them with @samp{flags}:
41913 One can fetch individual fields like in @samp{C}.
41916 (gdb) print $my_struct_reg.field3
41922 @subsection Registers
41925 Each register is represented as an element with this form:
41928 <reg name="@var{name}"
41929 bitsize="@var{size}"
41930 @r{[}regnum="@var{num}"@r{]}
41931 @r{[}save-restore="@var{save-restore}"@r{]}
41932 @r{[}type="@var{type}"@r{]}
41933 @r{[}group="@var{group}"@r{]}/>
41937 The components are as follows:
41942 The register's name; it must be unique within the target description.
41945 The register's size, in bits.
41948 The register's number. If omitted, a register's number is one greater
41949 than that of the previous register (either in the current feature or in
41950 a preceding feature); the first register in the target description
41951 defaults to zero. This register number is used to read or write
41952 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41953 packets, and registers appear in the @code{g} and @code{G} packets
41954 in order of increasing register number.
41957 Whether the register should be preserved across inferior function
41958 calls; this must be either @code{yes} or @code{no}. The default is
41959 @code{yes}, which is appropriate for most registers except for
41960 some system control registers; this is not related to the target's
41964 The type of the register. It may be a predefined type, a type
41965 defined in the current feature, or one of the special types @code{int}
41966 and @code{float}. @code{int} is an integer type of the correct size
41967 for @var{bitsize}, and @code{float} is a floating point type (in the
41968 architecture's normal floating point format) of the correct size for
41969 @var{bitsize}. The default is @code{int}.
41972 The register group to which this register belongs. It can be one of the
41973 standard register groups @code{general}, @code{float}, @code{vector} or an
41974 arbitrary string. Group names should be limited to alphanumeric characters.
41975 If a group name is made up of multiple words the words may be separated by
41976 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
41977 @var{group} is specified, @value{GDBN} will not display the register in
41978 @code{info registers}.
41982 @node Predefined Target Types
41983 @section Predefined Target Types
41984 @cindex target descriptions, predefined types
41986 Type definitions in the self-description can build up composite types
41987 from basic building blocks, but can not define fundamental types. Instead,
41988 standard identifiers are provided by @value{GDBN} for the fundamental
41989 types. The currently supported types are:
41994 Boolean type, occupying a single bit.
42001 Signed integer types holding the specified number of bits.
42008 Unsigned integer types holding the specified number of bits.
42012 Pointers to unspecified code and data. The program counter and
42013 any dedicated return address register may be marked as code
42014 pointers; printing a code pointer converts it into a symbolic
42015 address. The stack pointer and any dedicated address registers
42016 may be marked as data pointers.
42019 Single precision IEEE floating point.
42022 Double precision IEEE floating point.
42025 The 12-byte extended precision format used by ARM FPA registers.
42028 The 10-byte extended precision format used by x87 registers.
42031 32bit @sc{eflags} register used by x86.
42034 32bit @sc{mxcsr} register used by x86.
42038 @node Enum Target Types
42039 @section Enum Target Types
42040 @cindex target descriptions, enum types
42042 Enum target types are useful in @samp{struct} and @samp{flags}
42043 register descriptions. @xref{Target Description Format}.
42045 Enum types have a name, size and a list of name/value pairs.
42048 <enum id="@var{id}" size="@var{size}">
42049 <evalue name="@var{name}" value="@var{value}"/>
42054 Enums must be defined before they are used.
42057 <enum id="levels_type" size="4">
42058 <evalue name="low" value="0"/>
42059 <evalue name="high" value="1"/>
42061 <flags id="flags_type" size="4">
42062 <field name="X" start="0"/>
42063 <field name="LEVEL" start="1" end="1" type="levels_type"/>
42065 <reg name="flags" bitsize="32" type="flags_type"/>
42068 Given that description, a value of 3 for the @samp{flags} register
42069 would be printed as:
42072 (gdb) info register flags
42073 flags 0x3 [ X LEVEL=high ]
42076 @node Standard Target Features
42077 @section Standard Target Features
42078 @cindex target descriptions, standard features
42080 A target description must contain either no registers or all the
42081 target's registers. If the description contains no registers, then
42082 @value{GDBN} will assume a default register layout, selected based on
42083 the architecture. If the description contains any registers, the
42084 default layout will not be used; the standard registers must be
42085 described in the target description, in such a way that @value{GDBN}
42086 can recognize them.
42088 This is accomplished by giving specific names to feature elements
42089 which contain standard registers. @value{GDBN} will look for features
42090 with those names and verify that they contain the expected registers;
42091 if any known feature is missing required registers, or if any required
42092 feature is missing, @value{GDBN} will reject the target
42093 description. You can add additional registers to any of the
42094 standard features --- @value{GDBN} will display them just as if
42095 they were added to an unrecognized feature.
42097 This section lists the known features and their expected contents.
42098 Sample XML documents for these features are included in the
42099 @value{GDBN} source tree, in the directory @file{gdb/features}.
42101 Names recognized by @value{GDBN} should include the name of the
42102 company or organization which selected the name, and the overall
42103 architecture to which the feature applies; so e.g.@: the feature
42104 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42106 The names of registers are not case sensitive for the purpose
42107 of recognizing standard features, but @value{GDBN} will only display
42108 registers using the capitalization used in the description.
42111 * AArch64 Features::
42115 * MicroBlaze Features::
42119 * Nios II Features::
42120 * OpenRISC 1000 Features::
42121 * PowerPC Features::
42122 * S/390 and System z Features::
42128 @node AArch64 Features
42129 @subsection AArch64 Features
42130 @cindex target descriptions, AArch64 features
42132 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42133 targets. It should contain registers @samp{x0} through @samp{x30},
42134 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42136 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42137 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42140 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
42141 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
42142 through @samp{p15}, @samp{ffr} and @samp{vg}.
42145 @subsection ARC Features
42146 @cindex target descriptions, ARC Features
42148 ARC processors are highly configurable, so even core registers and their number
42149 are not completely predetermined. In addition flags and PC registers which are
42150 important to @value{GDBN} are not ``core'' registers in ARC. It is required
42151 that one of the core registers features is present.
42152 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
42154 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
42155 targets with a normal register file. It should contain registers @samp{r0}
42156 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42157 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
42158 and any of extension core registers @samp{r32} through @samp{r59/acch}.
42159 @samp{ilink} and extension core registers are not available to read/write, when
42160 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
42162 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
42163 ARC HS targets with a reduced register file. It should contain registers
42164 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
42165 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
42166 This feature may contain register @samp{ilink} and any of extension core
42167 registers @samp{r32} through @samp{r59/acch}.
42169 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
42170 targets with a normal register file. It should contain registers @samp{r0}
42171 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42172 @samp{lp_count} and @samp{pcl}. This feature may contain registers
42173 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
42174 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
42175 registers are not available when debugging GNU/Linux applications. The only
42176 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
42177 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
42178 ARC v2, but @samp{ilink2} is optional on ARCompact.
42180 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
42181 targets. It should contain registers @samp{pc} and @samp{status32}.
42184 @subsection ARM Features
42185 @cindex target descriptions, ARM features
42187 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42189 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42190 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42192 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42193 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42194 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42197 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42198 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42200 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42201 it should contain at least registers @samp{wR0} through @samp{wR15} and
42202 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42203 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42205 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42206 should contain at least registers @samp{d0} through @samp{d15}. If
42207 they are present, @samp{d16} through @samp{d31} should also be included.
42208 @value{GDBN} will synthesize the single-precision registers from
42209 halves of the double-precision registers.
42211 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42212 need to contain registers; it instructs @value{GDBN} to display the
42213 VFP double-precision registers as vectors and to synthesize the
42214 quad-precision registers from pairs of double-precision registers.
42215 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42216 be present and include 32 double-precision registers.
42218 @node i386 Features
42219 @subsection i386 Features
42220 @cindex target descriptions, i386 features
42222 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42223 targets. It should describe the following registers:
42227 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42229 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42231 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42232 @samp{fs}, @samp{gs}
42234 @samp{st0} through @samp{st7}
42236 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42237 @samp{foseg}, @samp{fooff} and @samp{fop}
42240 The register sets may be different, depending on the target.
42242 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42243 describe registers:
42247 @samp{xmm0} through @samp{xmm7} for i386
42249 @samp{xmm0} through @samp{xmm15} for amd64
42254 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42255 @samp{org.gnu.gdb.i386.sse} feature. It should
42256 describe the upper 128 bits of @sc{ymm} registers:
42260 @samp{ymm0h} through @samp{ymm7h} for i386
42262 @samp{ymm0h} through @samp{ymm15h} for amd64
42265 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
42266 Memory Protection Extension (MPX). It should describe the following registers:
42270 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
42272 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
42275 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42276 describe a single register, @samp{orig_eax}.
42278 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
42279 describe two system registers: @samp{fs_base} and @samp{gs_base}.
42281 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
42282 @samp{org.gnu.gdb.i386.avx} feature. It should
42283 describe additional @sc{xmm} registers:
42287 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
42290 It should describe the upper 128 bits of additional @sc{ymm} registers:
42294 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
42298 describe the upper 256 bits of @sc{zmm} registers:
42302 @samp{zmm0h} through @samp{zmm7h} for i386.
42304 @samp{zmm0h} through @samp{zmm15h} for amd64.
42308 describe the additional @sc{zmm} registers:
42312 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
42315 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
42316 describe a single register, @samp{pkru}. It is a 32-bit register
42317 valid for i386 and amd64.
42319 @node MicroBlaze Features
42320 @subsection MicroBlaze Features
42321 @cindex target descriptions, MicroBlaze features
42323 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
42324 targets. It should contain registers @samp{r0} through @samp{r31},
42325 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
42326 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
42327 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
42329 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
42330 If present, it should contain registers @samp{rshr} and @samp{rslr}
42332 @node MIPS Features
42333 @subsection @acronym{MIPS} Features
42334 @cindex target descriptions, @acronym{MIPS} features
42336 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42337 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42338 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42341 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42342 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42343 registers. They may be 32-bit or 64-bit depending on the target.
42345 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42346 it may be optional in a future version of @value{GDBN}. It should
42347 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42348 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42350 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42351 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42352 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42353 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42355 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42356 contain a single register, @samp{restart}, which is used by the
42357 Linux kernel to control restartable syscalls.
42359 @node M68K Features
42360 @subsection M68K Features
42361 @cindex target descriptions, M68K features
42364 @item @samp{org.gnu.gdb.m68k.core}
42365 @itemx @samp{org.gnu.gdb.coldfire.core}
42366 @itemx @samp{org.gnu.gdb.fido.core}
42367 One of those features must be always present.
42368 The feature that is present determines which flavor of m68k is
42369 used. The feature that is present should contain registers
42370 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42371 @samp{sp}, @samp{ps} and @samp{pc}.
42373 @item @samp{org.gnu.gdb.coldfire.fp}
42374 This feature is optional. If present, it should contain registers
42375 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42379 @node NDS32 Features
42380 @subsection NDS32 Features
42381 @cindex target descriptions, NDS32 features
42383 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42384 targets. It should contain at least registers @samp{r0} through
42385 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42388 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42389 it should contain 64-bit double-precision floating-point registers
42390 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42391 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42393 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42394 registers are overlapped with the thirty-two 32-bit single-precision
42395 floating-point registers. The 32-bit single-precision registers, if
42396 not being listed explicitly, will be synthesized from halves of the
42397 overlapping 64-bit double-precision registers. Listing 32-bit
42398 single-precision registers explicitly is deprecated, and the
42399 support to it could be totally removed some day.
42401 @node Nios II Features
42402 @subsection Nios II Features
42403 @cindex target descriptions, Nios II features
42405 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42406 targets. It should contain the 32 core registers (@samp{zero},
42407 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42408 @samp{pc}, and the 16 control registers (@samp{status} through
42411 @node OpenRISC 1000 Features
42412 @subsection Openrisc 1000 Features
42413 @cindex target descriptions, OpenRISC 1000 features
42415 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42416 targets. It should contain the 32 general purpose registers (@samp{r0}
42417 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42419 @node PowerPC Features
42420 @subsection PowerPC Features
42421 @cindex target descriptions, PowerPC features
42423 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42424 targets. It should contain registers @samp{r0} through @samp{r31},
42425 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42426 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42428 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42429 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42431 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42432 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42435 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42436 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42437 will combine these registers with the floating point registers
42438 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42439 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42440 through @samp{vs63}, the set of vector registers for POWER7.
42442 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42443 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42444 @samp{spefscr}. SPE targets should provide 32-bit registers in
42445 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42446 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42447 these to present registers @samp{ev0} through @samp{ev31} to the
42450 @node S/390 and System z Features
42451 @subsection S/390 and System z Features
42452 @cindex target descriptions, S/390 features
42453 @cindex target descriptions, System z features
42455 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42456 System z targets. It should contain the PSW and the 16 general
42457 registers. In particular, System z targets should provide the 64-bit
42458 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42459 S/390 targets should provide the 32-bit versions of these registers.
42460 A System z target that runs in 31-bit addressing mode should provide
42461 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42462 register's upper halves @samp{r0h} through @samp{r15h}, and their
42463 lower halves @samp{r0l} through @samp{r15l}.
42465 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42466 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42469 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42470 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42472 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42473 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42474 targets and 32-bit otherwise. In addition, the feature may contain
42475 the @samp{last_break} register, whose width depends on the addressing
42476 mode, as well as the @samp{system_call} register, which is always
42479 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42480 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42481 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42483 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42484 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42485 combined by @value{GDBN} with the floating point registers @samp{f0}
42486 through @samp{f15} to present the 128-bit wide vector registers
42487 @samp{v0} through @samp{v15}. In addition, this feature should
42488 contain the 128-bit wide vector registers @samp{v16} through
42491 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42492 the 64-bit wide guarded-storage-control registers @samp{gsd},
42493 @samp{gssm}, and @samp{gsepla}.
42495 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42496 the 64-bit wide guarded-storage broadcast control registers
42497 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42499 @node Sparc Features
42500 @subsection Sparc Features
42501 @cindex target descriptions, sparc32 features
42502 @cindex target descriptions, sparc64 features
42503 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42504 targets. It should describe the following registers:
42508 @samp{g0} through @samp{g7}
42510 @samp{o0} through @samp{o7}
42512 @samp{l0} through @samp{l7}
42514 @samp{i0} through @samp{i7}
42517 They may be 32-bit or 64-bit depending on the target.
42519 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42520 targets. It should describe the following registers:
42524 @samp{f0} through @samp{f31}
42526 @samp{f32} through @samp{f62} for sparc64
42529 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42530 targets. It should describe the following registers:
42534 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42535 @samp{fsr}, and @samp{csr} for sparc32
42537 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42541 @node TIC6x Features
42542 @subsection TMS320C6x Features
42543 @cindex target descriptions, TIC6x features
42544 @cindex target descriptions, TMS320C6x features
42545 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42546 targets. It should contain registers @samp{A0} through @samp{A15},
42547 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42549 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42550 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42551 through @samp{B31}.
42553 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42554 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42556 @node Operating System Information
42557 @appendix Operating System Information
42558 @cindex operating system information
42564 Users of @value{GDBN} often wish to obtain information about the state of
42565 the operating system running on the target---for example the list of
42566 processes, or the list of open files. This section describes the
42567 mechanism that makes it possible. This mechanism is similar to the
42568 target features mechanism (@pxref{Target Descriptions}), but focuses
42569 on a different aspect of target.
42571 Operating system information is retrived from the target via the
42572 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42573 read}). The object name in the request should be @samp{osdata}, and
42574 the @var{annex} identifies the data to be fetched.
42577 @appendixsection Process list
42578 @cindex operating system information, process list
42580 When requesting the process list, the @var{annex} field in the
42581 @samp{qXfer} request should be @samp{processes}. The returned data is
42582 an XML document. The formal syntax of this document is defined in
42583 @file{gdb/features/osdata.dtd}.
42585 An example document is:
42588 <?xml version="1.0"?>
42589 <!DOCTYPE target SYSTEM "osdata.dtd">
42590 <osdata type="processes">
42592 <column name="pid">1</column>
42593 <column name="user">root</column>
42594 <column name="command">/sbin/init</column>
42595 <column name="cores">1,2,3</column>
42600 Each item should include a column whose name is @samp{pid}. The value
42601 of that column should identify the process on the target. The
42602 @samp{user} and @samp{command} columns are optional, and will be
42603 displayed by @value{GDBN}. The @samp{cores} column, if present,
42604 should contain a comma-separated list of cores that this process
42605 is running on. Target may provide additional columns,
42606 which @value{GDBN} currently ignores.
42608 @node Trace File Format
42609 @appendix Trace File Format
42610 @cindex trace file format
42612 The trace file comes in three parts: a header, a textual description
42613 section, and a trace frame section with binary data.
42615 The header has the form @code{\x7fTRACE0\n}. The first byte is
42616 @code{0x7f} so as to indicate that the file contains binary data,
42617 while the @code{0} is a version number that may have different values
42620 The description section consists of multiple lines of @sc{ascii} text
42621 separated by newline characters (@code{0xa}). The lines may include a
42622 variety of optional descriptive or context-setting information, such
42623 as tracepoint definitions or register set size. @value{GDBN} will
42624 ignore any line that it does not recognize. An empty line marks the end
42629 Specifies the size of a register block in bytes. This is equal to the
42630 size of a @code{g} packet payload in the remote protocol. @var{size}
42631 is an ascii decimal number. There should be only one such line in
42632 a single trace file.
42634 @item status @var{status}
42635 Trace status. @var{status} has the same format as a @code{qTStatus}
42636 remote packet reply. There should be only one such line in a single trace
42639 @item tp @var{payload}
42640 Tracepoint definition. The @var{payload} has the same format as
42641 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42642 may take multiple lines of definition, corresponding to the multiple
42645 @item tsv @var{payload}
42646 Trace state variable definition. The @var{payload} has the same format as
42647 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42648 may take multiple lines of definition, corresponding to the multiple
42651 @item tdesc @var{payload}
42652 Target description in XML format. The @var{payload} is a single line of
42653 the XML file. All such lines should be concatenated together to get
42654 the original XML file. This file is in the same format as @code{qXfer}
42655 @code{features} payload, and corresponds to the main @code{target.xml}
42656 file. Includes are not allowed.
42660 The trace frame section consists of a number of consecutive frames.
42661 Each frame begins with a two-byte tracepoint number, followed by a
42662 four-byte size giving the amount of data in the frame. The data in
42663 the frame consists of a number of blocks, each introduced by a
42664 character indicating its type (at least register, memory, and trace
42665 state variable). The data in this section is raw binary, not a
42666 hexadecimal or other encoding; its endianness matches the target's
42669 @c FIXME bi-arch may require endianness/arch info in description section
42672 @item R @var{bytes}
42673 Register block. The number and ordering of bytes matches that of a
42674 @code{g} packet in the remote protocol. Note that these are the
42675 actual bytes, in target order, not a hexadecimal encoding.
42677 @item M @var{address} @var{length} @var{bytes}...
42678 Memory block. This is a contiguous block of memory, at the 8-byte
42679 address @var{address}, with a 2-byte length @var{length}, followed by
42680 @var{length} bytes.
42682 @item V @var{number} @var{value}
42683 Trace state variable block. This records the 8-byte signed value
42684 @var{value} of trace state variable numbered @var{number}.
42688 Future enhancements of the trace file format may include additional types
42691 @node Index Section Format
42692 @appendix @code{.gdb_index} section format
42693 @cindex .gdb_index section format
42694 @cindex index section format
42696 This section documents the index section that is created by @code{save
42697 gdb-index} (@pxref{Index Files}). The index section is
42698 DWARF-specific; some knowledge of DWARF is assumed in this
42701 The mapped index file format is designed to be directly
42702 @code{mmap}able on any architecture. In most cases, a datum is
42703 represented using a little-endian 32-bit integer value, called an
42704 @code{offset_type}. Big endian machines must byte-swap the values
42705 before using them. Exceptions to this rule are noted. The data is
42706 laid out such that alignment is always respected.
42708 A mapped index consists of several areas, laid out in order.
42712 The file header. This is a sequence of values, of @code{offset_type}
42713 unless otherwise noted:
42717 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42718 Version 4 uses a different hashing function from versions 5 and 6.
42719 Version 6 includes symbols for inlined functions, whereas versions 4
42720 and 5 do not. Version 7 adds attributes to the CU indices in the
42721 symbol table. Version 8 specifies that symbols from DWARF type units
42722 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42723 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42725 @value{GDBN} will only read version 4, 5, or 6 indices
42726 by specifying @code{set use-deprecated-index-sections on}.
42727 GDB has a workaround for potentially broken version 7 indices so it is
42728 currently not flagged as deprecated.
42731 The offset, from the start of the file, of the CU list.
42734 The offset, from the start of the file, of the types CU list. Note
42735 that this area can be empty, in which case this offset will be equal
42736 to the next offset.
42739 The offset, from the start of the file, of the address area.
42742 The offset, from the start of the file, of the symbol table.
42745 The offset, from the start of the file, of the constant pool.
42749 The CU list. This is a sequence of pairs of 64-bit little-endian
42750 values, sorted by the CU offset. The first element in each pair is
42751 the offset of a CU in the @code{.debug_info} section. The second
42752 element in each pair is the length of that CU. References to a CU
42753 elsewhere in the map are done using a CU index, which is just the
42754 0-based index into this table. Note that if there are type CUs, then
42755 conceptually CUs and type CUs form a single list for the purposes of
42759 The types CU list. This is a sequence of triplets of 64-bit
42760 little-endian values. In a triplet, the first value is the CU offset,
42761 the second value is the type offset in the CU, and the third value is
42762 the type signature. The types CU list is not sorted.
42765 The address area. The address area consists of a sequence of address
42766 entries. Each address entry has three elements:
42770 The low address. This is a 64-bit little-endian value.
42773 The high address. This is a 64-bit little-endian value. Like
42774 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42777 The CU index. This is an @code{offset_type} value.
42781 The symbol table. This is an open-addressed hash table. The size of
42782 the hash table is always a power of 2.
42784 Each slot in the hash table consists of a pair of @code{offset_type}
42785 values. The first value is the offset of the symbol's name in the
42786 constant pool. The second value is the offset of the CU vector in the
42789 If both values are 0, then this slot in the hash table is empty. This
42790 is ok because while 0 is a valid constant pool index, it cannot be a
42791 valid index for both a string and a CU vector.
42793 The hash value for a table entry is computed by applying an
42794 iterative hash function to the symbol's name. Starting with an
42795 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42796 the string is incorporated into the hash using the formula depending on the
42801 The formula is @code{r = r * 67 + c - 113}.
42803 @item Versions 5 to 7
42804 The formula is @code{r = r * 67 + tolower (c) - 113}.
42807 The terminating @samp{\0} is not incorporated into the hash.
42809 The step size used in the hash table is computed via
42810 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42811 value, and @samp{size} is the size of the hash table. The step size
42812 is used to find the next candidate slot when handling a hash
42815 The names of C@t{++} symbols in the hash table are canonicalized. We
42816 don't currently have a simple description of the canonicalization
42817 algorithm; if you intend to create new index sections, you must read
42821 The constant pool. This is simply a bunch of bytes. It is organized
42822 so that alignment is correct: CU vectors are stored first, followed by
42825 A CU vector in the constant pool is a sequence of @code{offset_type}
42826 values. The first value is the number of CU indices in the vector.
42827 Each subsequent value is the index and symbol attributes of a CU in
42828 the CU list. This element in the hash table is used to indicate which
42829 CUs define the symbol and how the symbol is used.
42830 See below for the format of each CU index+attributes entry.
42832 A string in the constant pool is zero-terminated.
42835 Attributes were added to CU index values in @code{.gdb_index} version 7.
42836 If a symbol has multiple uses within a CU then there is one
42837 CU index+attributes value for each use.
42839 The format of each CU index+attributes entry is as follows
42845 This is the index of the CU in the CU list.
42847 These bits are reserved for future purposes and must be zero.
42849 The kind of the symbol in the CU.
42853 This value is reserved and should not be used.
42854 By reserving zero the full @code{offset_type} value is backwards compatible
42855 with previous versions of the index.
42857 The symbol is a type.
42859 The symbol is a variable or an enum value.
42861 The symbol is a function.
42863 Any other kind of symbol.
42865 These values are reserved.
42869 This bit is zero if the value is global and one if it is static.
42871 The determination of whether a symbol is global or static is complicated.
42872 The authorative reference is the file @file{dwarf2read.c} in
42873 @value{GDBN} sources.
42877 This pseudo-code describes the computation of a symbol's kind and
42878 global/static attributes in the index.
42881 is_external = get_attribute (die, DW_AT_external);
42882 language = get_attribute (cu_die, DW_AT_language);
42885 case DW_TAG_typedef:
42886 case DW_TAG_base_type:
42887 case DW_TAG_subrange_type:
42891 case DW_TAG_enumerator:
42893 is_static = language != CPLUS;
42895 case DW_TAG_subprogram:
42897 is_static = ! (is_external || language == ADA);
42899 case DW_TAG_constant:
42901 is_static = ! is_external;
42903 case DW_TAG_variable:
42905 is_static = ! is_external;
42907 case DW_TAG_namespace:
42911 case DW_TAG_class_type:
42912 case DW_TAG_interface_type:
42913 case DW_TAG_structure_type:
42914 case DW_TAG_union_type:
42915 case DW_TAG_enumeration_type:
42917 is_static = language != CPLUS;
42925 @appendix Manual pages
42929 * gdb man:: The GNU Debugger man page
42930 * gdbserver man:: Remote Server for the GNU Debugger man page
42931 * gcore man:: Generate a core file of a running program
42932 * gdbinit man:: gdbinit scripts
42933 * gdb-add-index man:: Add index files to speed up GDB
42939 @c man title gdb The GNU Debugger
42941 @c man begin SYNOPSIS gdb
42942 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42943 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42944 [@option{-b}@w{ }@var{bps}]
42945 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42946 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42947 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42948 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42949 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42952 @c man begin DESCRIPTION gdb
42953 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42954 going on ``inside'' another program while it executes -- or what another
42955 program was doing at the moment it crashed.
42957 @value{GDBN} can do four main kinds of things (plus other things in support of
42958 these) to help you catch bugs in the act:
42962 Start your program, specifying anything that might affect its behavior.
42965 Make your program stop on specified conditions.
42968 Examine what has happened, when your program has stopped.
42971 Change things in your program, so you can experiment with correcting the
42972 effects of one bug and go on to learn about another.
42975 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42978 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42979 commands from the terminal until you tell it to exit with the @value{GDBN}
42980 command @code{quit}. You can get online help from @value{GDBN} itself
42981 by using the command @code{help}.
42983 You can run @code{gdb} with no arguments or options; but the most
42984 usual way to start @value{GDBN} is with one argument or two, specifying an
42985 executable program as the argument:
42991 You can also start with both an executable program and a core file specified:
42997 You can, instead, specify a process ID as a second argument, if you want
42998 to debug a running process:
43006 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43007 named @file{1234}; @value{GDBN} does check for a core file first).
43008 With option @option{-p} you can omit the @var{program} filename.
43010 Here are some of the most frequently needed @value{GDBN} commands:
43012 @c pod2man highlights the right hand side of the @item lines.
43014 @item break [@var{file}:]@var{function}
43015 Set a breakpoint at @var{function} (in @var{file}).
43017 @item run [@var{arglist}]
43018 Start your program (with @var{arglist}, if specified).
43021 Backtrace: display the program stack.
43023 @item print @var{expr}
43024 Display the value of an expression.
43027 Continue running your program (after stopping, e.g. at a breakpoint).
43030 Execute next program line (after stopping); step @emph{over} any
43031 function calls in the line.
43033 @item edit [@var{file}:]@var{function}
43034 look at the program line where it is presently stopped.
43036 @item list [@var{file}:]@var{function}
43037 type the text of the program in the vicinity of where it is presently stopped.
43040 Execute next program line (after stopping); step @emph{into} any
43041 function calls in the line.
43043 @item help [@var{name}]
43044 Show information about @value{GDBN} command @var{name}, or general information
43045 about using @value{GDBN}.
43048 Exit from @value{GDBN}.
43052 For full details on @value{GDBN},
43053 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43054 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43055 as the @code{gdb} entry in the @code{info} program.
43059 @c man begin OPTIONS gdb
43060 Any arguments other than options specify an executable
43061 file and core file (or process ID); that is, the first argument
43062 encountered with no
43063 associated option flag is equivalent to a @option{-se} option, and the second,
43064 if any, is equivalent to a @option{-c} option if it's the name of a file.
43066 both long and short forms; both are shown here. The long forms are also
43067 recognized if you truncate them, so long as enough of the option is
43068 present to be unambiguous. (If you prefer, you can flag option
43069 arguments with @option{+} rather than @option{-}, though we illustrate the
43070 more usual convention.)
43072 All the options and command line arguments you give are processed
43073 in sequential order. The order makes a difference when the @option{-x}
43079 List all options, with brief explanations.
43081 @item -symbols=@var{file}
43082 @itemx -s @var{file}
43083 Read symbol table from file @var{file}.
43086 Enable writing into executable and core files.
43088 @item -exec=@var{file}
43089 @itemx -e @var{file}
43090 Use file @var{file} as the executable file to execute when
43091 appropriate, and for examining pure data in conjunction with a core
43094 @item -se=@var{file}
43095 Read symbol table from file @var{file} and use it as the executable
43098 @item -core=@var{file}
43099 @itemx -c @var{file}
43100 Use file @var{file} as a core dump to examine.
43102 @item -command=@var{file}
43103 @itemx -x @var{file}
43104 Execute @value{GDBN} commands from file @var{file}.
43106 @item -ex @var{command}
43107 Execute given @value{GDBN} @var{command}.
43109 @item -directory=@var{directory}
43110 @itemx -d @var{directory}
43111 Add @var{directory} to the path to search for source files.
43114 Do not execute commands from @file{~/.gdbinit}.
43118 Do not execute commands from any @file{.gdbinit} initialization files.
43122 ``Quiet''. Do not print the introductory and copyright messages. These
43123 messages are also suppressed in batch mode.
43126 Run in batch mode. Exit with status @code{0} after processing all the command
43127 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43128 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43129 commands in the command files.
43131 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43132 download and run a program on another computer; in order to make this
43133 more useful, the message
43136 Program exited normally.
43140 (which is ordinarily issued whenever a program running under @value{GDBN} control
43141 terminates) is not issued when running in batch mode.
43143 @item -cd=@var{directory}
43144 Run @value{GDBN} using @var{directory} as its working directory,
43145 instead of the current directory.
43149 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43150 @value{GDBN} to output the full file name and line number in a standard,
43151 recognizable fashion each time a stack frame is displayed (which
43152 includes each time the program stops). This recognizable format looks
43153 like two @samp{\032} characters, followed by the file name, line number
43154 and character position separated by colons, and a newline. The
43155 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43156 characters as a signal to display the source code for the frame.
43159 Set the line speed (baud rate or bits per second) of any serial
43160 interface used by @value{GDBN} for remote debugging.
43162 @item -tty=@var{device}
43163 Run using @var{device} for your program's standard input and output.
43167 @c man begin SEEALSO gdb
43169 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43170 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43171 documentation are properly installed at your site, the command
43178 should give you access to the complete manual.
43180 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43181 Richard M. Stallman and Roland H. Pesch, July 1991.
43185 @node gdbserver man
43186 @heading gdbserver man
43188 @c man title gdbserver Remote Server for the GNU Debugger
43190 @c man begin SYNOPSIS gdbserver
43191 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43193 gdbserver --attach @var{comm} @var{pid}
43195 gdbserver --multi @var{comm}
43199 @c man begin DESCRIPTION gdbserver
43200 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43201 than the one which is running the program being debugged.
43204 @subheading Usage (server (target) side)
43207 Usage (server (target) side):
43210 First, you need to have a copy of the program you want to debug put onto
43211 the target system. The program can be stripped to save space if needed, as
43212 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43213 the @value{GDBN} running on the host system.
43215 To use the server, you log on to the target system, and run the @command{gdbserver}
43216 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43217 your program, and (c) its arguments. The general syntax is:
43220 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43223 For example, using a serial port, you might say:
43227 @c @file would wrap it as F</dev/com1>.
43228 target> gdbserver /dev/com1 emacs foo.txt
43231 target> gdbserver @file{/dev/com1} emacs foo.txt
43235 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43236 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43237 waits patiently for the host @value{GDBN} to communicate with it.
43239 To use a TCP connection, you could say:
43242 target> gdbserver host:2345 emacs foo.txt
43245 This says pretty much the same thing as the last example, except that we are
43246 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43247 that we are expecting to see a TCP connection from @code{host} to local TCP port
43248 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43249 want for the port number as long as it does not conflict with any existing TCP
43250 ports on the target system. This same port number must be used in the host
43251 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43252 you chose a port number that conflicts with another service, @command{gdbserver} will
43253 print an error message and exit.
43255 @command{gdbserver} can also attach to running programs.
43256 This is accomplished via the @option{--attach} argument. The syntax is:
43259 target> gdbserver --attach @var{comm} @var{pid}
43262 @var{pid} is the process ID of a currently running process. It isn't
43263 necessary to point @command{gdbserver} at a binary for the running process.
43265 To start @code{gdbserver} without supplying an initial command to run
43266 or process ID to attach, use the @option{--multi} command line option.
43267 In such case you should connect using @kbd{target extended-remote} to start
43268 the program you want to debug.
43271 target> gdbserver --multi @var{comm}
43275 @subheading Usage (host side)
43281 You need an unstripped copy of the target program on your host system, since
43282 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43283 would, with the target program as the first argument. (You may need to use the
43284 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43285 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43286 new command you need to know about is @code{target remote}
43287 (or @code{target extended-remote}). Its argument is either
43288 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43289 descriptor. For example:
43293 @c @file would wrap it as F</dev/ttyb>.
43294 (gdb) target remote /dev/ttyb
43297 (gdb) target remote @file{/dev/ttyb}
43302 communicates with the server via serial line @file{/dev/ttyb}, and:
43305 (gdb) target remote the-target:2345
43309 communicates via a TCP connection to port 2345 on host `the-target', where
43310 you previously started up @command{gdbserver} with the same port number. Note that for
43311 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43312 command, otherwise you may get an error that looks something like
43313 `Connection refused'.
43315 @command{gdbserver} can also debug multiple inferiors at once,
43318 the @value{GDBN} manual in node @code{Inferiors and Programs}
43319 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43322 @ref{Inferiors and Programs}.
43324 In such case use the @code{extended-remote} @value{GDBN} command variant:
43327 (gdb) target extended-remote the-target:2345
43330 The @command{gdbserver} option @option{--multi} may or may not be used in such
43334 @c man begin OPTIONS gdbserver
43335 There are three different modes for invoking @command{gdbserver}:
43340 Debug a specific program specified by its program name:
43343 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43346 The @var{comm} parameter specifies how should the server communicate
43347 with @value{GDBN}; it is either a device name (to use a serial line),
43348 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43349 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43350 debug in @var{prog}. Any remaining arguments will be passed to the
43351 program verbatim. When the program exits, @value{GDBN} will close the
43352 connection, and @code{gdbserver} will exit.
43355 Debug a specific program by specifying the process ID of a running
43359 gdbserver --attach @var{comm} @var{pid}
43362 The @var{comm} parameter is as described above. Supply the process ID
43363 of a running program in @var{pid}; @value{GDBN} will do everything
43364 else. Like with the previous mode, when the process @var{pid} exits,
43365 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43368 Multi-process mode -- debug more than one program/process:
43371 gdbserver --multi @var{comm}
43374 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43375 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43376 close the connection when a process being debugged exits, so you can
43377 debug several processes in the same session.
43380 In each of the modes you may specify these options:
43385 List all options, with brief explanations.
43388 This option causes @command{gdbserver} to print its version number and exit.
43391 @command{gdbserver} will attach to a running program. The syntax is:
43394 target> gdbserver --attach @var{comm} @var{pid}
43397 @var{pid} is the process ID of a currently running process. It isn't
43398 necessary to point @command{gdbserver} at a binary for the running process.
43401 To start @code{gdbserver} without supplying an initial command to run
43402 or process ID to attach, use this command line option.
43403 Then you can connect using @kbd{target extended-remote} and start
43404 the program you want to debug. The syntax is:
43407 target> gdbserver --multi @var{comm}
43411 Instruct @code{gdbserver} to display extra status information about the debugging
43413 This option is intended for @code{gdbserver} development and for bug reports to
43416 @item --remote-debug
43417 Instruct @code{gdbserver} to display remote protocol debug output.
43418 This option is intended for @code{gdbserver} development and for bug reports to
43421 @item --debug-format=option1@r{[},option2,...@r{]}
43422 Instruct @code{gdbserver} to include extra information in each line
43423 of debugging output.
43424 @xref{Other Command-Line Arguments for gdbserver}.
43427 Specify a wrapper to launch programs
43428 for debugging. The option should be followed by the name of the
43429 wrapper, then any command-line arguments to pass to the wrapper, then
43430 @kbd{--} indicating the end of the wrapper arguments.
43433 By default, @command{gdbserver} keeps the listening TCP port open, so that
43434 additional connections are possible. However, if you start @code{gdbserver}
43435 with the @option{--once} option, it will stop listening for any further
43436 connection attempts after connecting to the first @value{GDBN} session.
43438 @c --disable-packet is not documented for users.
43440 @c --disable-randomization and --no-disable-randomization are superseded by
43441 @c QDisableRandomization.
43446 @c man begin SEEALSO gdbserver
43448 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43449 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43450 documentation are properly installed at your site, the command
43456 should give you access to the complete manual.
43458 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43459 Richard M. Stallman and Roland H. Pesch, July 1991.
43466 @c man title gcore Generate a core file of a running program
43469 @c man begin SYNOPSIS gcore
43470 gcore [-a] [-o @var{filename}] @var{pid}
43474 @c man begin DESCRIPTION gcore
43475 Generate a core dump of a running program with process ID @var{pid}.
43476 Produced file is equivalent to a kernel produced core file as if the process
43477 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43478 limit). Unlike after a crash, after @command{gcore} the program remains
43479 running without any change.
43482 @c man begin OPTIONS gcore
43485 Dump all memory mappings. The actual effect of this option depends on
43486 the Operating System. On @sc{gnu}/Linux, it will disable
43487 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43488 enable @code{dump-excluded-mappings} (@pxref{set
43489 dump-excluded-mappings}).
43491 @item -o @var{filename}
43492 The optional argument
43493 @var{filename} specifies the file name where to put the core dump.
43494 If not specified, the file name defaults to @file{core.@var{pid}},
43495 where @var{pid} is the running program process ID.
43499 @c man begin SEEALSO gcore
43501 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43502 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43503 documentation are properly installed at your site, the command
43510 should give you access to the complete manual.
43512 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43513 Richard M. Stallman and Roland H. Pesch, July 1991.
43520 @c man title gdbinit GDB initialization scripts
43523 @c man begin SYNOPSIS gdbinit
43524 @ifset SYSTEM_GDBINIT
43525 @value{SYSTEM_GDBINIT}
43534 @c man begin DESCRIPTION gdbinit
43535 These files contain @value{GDBN} commands to automatically execute during
43536 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43539 the @value{GDBN} manual in node @code{Sequences}
43540 -- shell command @code{info -f gdb -n Sequences}.
43546 Please read more in
43548 the @value{GDBN} manual in node @code{Startup}
43549 -- shell command @code{info -f gdb -n Startup}.
43556 @ifset SYSTEM_GDBINIT
43557 @item @value{SYSTEM_GDBINIT}
43559 @ifclear SYSTEM_GDBINIT
43560 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43562 System-wide initialization file. It is executed unless user specified
43563 @value{GDBN} option @code{-nx} or @code{-n}.
43566 the @value{GDBN} manual in node @code{System-wide configuration}
43567 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43570 @ref{System-wide configuration}.
43574 User initialization file. It is executed unless user specified
43575 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43578 Initialization file for current directory. It may need to be enabled with
43579 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43582 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43583 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43586 @ref{Init File in the Current Directory}.
43591 @c man begin SEEALSO gdbinit
43593 gdb(1), @code{info -f gdb -n Startup}
43595 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43596 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43597 documentation are properly installed at your site, the command
43603 should give you access to the complete manual.
43605 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43606 Richard M. Stallman and Roland H. Pesch, July 1991.
43610 @node gdb-add-index man
43611 @heading gdb-add-index
43612 @pindex gdb-add-index
43613 @anchor{gdb-add-index}
43615 @c man title gdb-add-index Add index files to speed up GDB
43617 @c man begin SYNOPSIS gdb-add-index
43618 gdb-add-index @var{filename}
43621 @c man begin DESCRIPTION gdb-add-index
43622 When @value{GDBN} finds a symbol file, it scans the symbols in the
43623 file in order to construct an internal symbol table. This lets most
43624 @value{GDBN} operations work quickly--at the cost of a delay early on.
43625 For large programs, this delay can be quite lengthy, so @value{GDBN}
43626 provides a way to build an index, which speeds up startup.
43628 To determine whether a file contains such an index, use the command
43629 @kbd{readelf -S filename}: the index is stored in a section named
43630 @code{.gdb_index}. The index file can only be produced on systems
43631 which use ELF binaries and DWARF debug information (i.e., sections
43632 named @code{.debug_*}).
43634 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
43635 in the @env{PATH} environment variable. If you want to use different
43636 versions of these programs, you can specify them through the
43637 @env{GDB} and @env{OBJDUMP} environment variables.
43641 the @value{GDBN} manual in node @code{Index Files}
43642 -- shell command @kbd{info -f gdb -n "Index Files"}.
43649 @c man begin SEEALSO gdb-add-index
43651 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43652 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43653 documentation are properly installed at your site, the command
43659 should give you access to the complete manual.
43661 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43662 Richard M. Stallman and Roland H. Pesch, July 1991.
43668 @node GNU Free Documentation License
43669 @appendix GNU Free Documentation License
43672 @node Concept Index
43673 @unnumbered Concept Index
43677 @node Command and Variable Index
43678 @unnumbered Command, Variable, and Function Index
43683 % I think something like @@colophon should be in texinfo. In the
43685 \long\def\colophon{\hbox to0pt{}\vfill
43686 \centerline{The body of this manual is set in}
43687 \centerline{\fontname\tenrm,}
43688 \centerline{with headings in {\bf\fontname\tenbf}}
43689 \centerline{and examples in {\tt\fontname\tentt}.}
43690 \centerline{{\it\fontname\tenit\/},}
43691 \centerline{{\bf\fontname\tenbf}, and}
43692 \centerline{{\sl\fontname\tensl\/}}
43693 \centerline{are used for emphasis.}\vfill}
43695 % Blame: doc@@cygnus.com, 1991.