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 @cindex @code{&}, background execution of commands
6323 To specify background execution, add a @code{&} to the command. For example,
6324 the background form of the @code{continue} command is @code{continue&}, or
6325 just @code{c&}. The execution commands that accept background execution
6331 @xref{Starting, , Starting your Program}.
6335 @xref{Attach, , Debugging an Already-running Process}.
6339 @xref{Continuing and Stepping, step}.
6343 @xref{Continuing and Stepping, stepi}.
6347 @xref{Continuing and Stepping, next}.
6351 @xref{Continuing and Stepping, nexti}.
6355 @xref{Continuing and Stepping, continue}.
6359 @xref{Continuing and Stepping, finish}.
6363 @xref{Continuing and Stepping, until}.
6367 Background execution is especially useful in conjunction with non-stop
6368 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6369 However, you can also use these commands in the normal all-stop mode with
6370 the restriction that you cannot issue another execution command until the
6371 previous one finishes. Examples of commands that are valid in all-stop
6372 mode while the program is running include @code{help} and @code{info break}.
6374 You can interrupt your program while it is running in the background by
6375 using the @code{interrupt} command.
6382 Suspend execution of the running program. In all-stop mode,
6383 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6384 only the current thread. To stop the whole program in non-stop mode,
6385 use @code{interrupt -a}.
6388 @node Thread-Specific Breakpoints
6389 @subsection Thread-Specific Breakpoints
6391 When your program has multiple threads (@pxref{Threads,, Debugging
6392 Programs with Multiple Threads}), you can choose whether to set
6393 breakpoints on all threads, or on a particular thread.
6396 @cindex breakpoints and threads
6397 @cindex thread breakpoints
6398 @kindex break @dots{} thread @var{thread-id}
6399 @item break @var{location} thread @var{thread-id}
6400 @itemx break @var{location} thread @var{thread-id} if @dots{}
6401 @var{location} specifies source lines; there are several ways of
6402 writing them (@pxref{Specify Location}), but the effect is always to
6403 specify some source line.
6405 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6406 to specify that you only want @value{GDBN} to stop the program when a
6407 particular thread reaches this breakpoint. The @var{thread-id} specifier
6408 is one of the thread identifiers assigned by @value{GDBN}, shown
6409 in the first column of the @samp{info threads} display.
6411 If you do not specify @samp{thread @var{thread-id}} when you set a
6412 breakpoint, the breakpoint applies to @emph{all} threads of your
6415 You can use the @code{thread} qualifier on conditional breakpoints as
6416 well; in this case, place @samp{thread @var{thread-id}} before or
6417 after the breakpoint condition, like this:
6420 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6425 Thread-specific breakpoints are automatically deleted when
6426 @value{GDBN} detects the corresponding thread is no longer in the
6427 thread list. For example:
6431 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6434 There are several ways for a thread to disappear, such as a regular
6435 thread exit, but also when you detach from the process with the
6436 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6437 Process}), or if @value{GDBN} loses the remote connection
6438 (@pxref{Remote Debugging}), etc. Note that with some targets,
6439 @value{GDBN} is only able to detect a thread has exited when the user
6440 explictly asks for the thread list with the @code{info threads}
6443 @node Interrupted System Calls
6444 @subsection Interrupted System Calls
6446 @cindex thread breakpoints and system calls
6447 @cindex system calls and thread breakpoints
6448 @cindex premature return from system calls
6449 There is an unfortunate side effect when using @value{GDBN} to debug
6450 multi-threaded programs. If one thread stops for a
6451 breakpoint, or for some other reason, and another thread is blocked in a
6452 system call, then the system call may return prematurely. This is a
6453 consequence of the interaction between multiple threads and the signals
6454 that @value{GDBN} uses to implement breakpoints and other events that
6457 To handle this problem, your program should check the return value of
6458 each system call and react appropriately. This is good programming
6461 For example, do not write code like this:
6467 The call to @code{sleep} will return early if a different thread stops
6468 at a breakpoint or for some other reason.
6470 Instead, write this:
6475 unslept = sleep (unslept);
6478 A system call is allowed to return early, so the system is still
6479 conforming to its specification. But @value{GDBN} does cause your
6480 multi-threaded program to behave differently than it would without
6483 Also, @value{GDBN} uses internal breakpoints in the thread library to
6484 monitor certain events such as thread creation and thread destruction.
6485 When such an event happens, a system call in another thread may return
6486 prematurely, even though your program does not appear to stop.
6489 @subsection Observer Mode
6491 If you want to build on non-stop mode and observe program behavior
6492 without any chance of disruption by @value{GDBN}, you can set
6493 variables to disable all of the debugger's attempts to modify state,
6494 whether by writing memory, inserting breakpoints, etc. These operate
6495 at a low level, intercepting operations from all commands.
6497 When all of these are set to @code{off}, then @value{GDBN} is said to
6498 be @dfn{observer mode}. As a convenience, the variable
6499 @code{observer} can be set to disable these, plus enable non-stop
6502 Note that @value{GDBN} will not prevent you from making nonsensical
6503 combinations of these settings. For instance, if you have enabled
6504 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6505 then breakpoints that work by writing trap instructions into the code
6506 stream will still not be able to be placed.
6511 @item set observer on
6512 @itemx set observer off
6513 When set to @code{on}, this disables all the permission variables
6514 below (except for @code{insert-fast-tracepoints}), plus enables
6515 non-stop debugging. Setting this to @code{off} switches back to
6516 normal debugging, though remaining in non-stop mode.
6519 Show whether observer mode is on or off.
6521 @kindex may-write-registers
6522 @item set may-write-registers on
6523 @itemx set may-write-registers off
6524 This controls whether @value{GDBN} will attempt to alter the values of
6525 registers, such as with assignment expressions in @code{print}, or the
6526 @code{jump} command. It defaults to @code{on}.
6528 @item show may-write-registers
6529 Show the current permission to write registers.
6531 @kindex may-write-memory
6532 @item set may-write-memory on
6533 @itemx set may-write-memory off
6534 This controls whether @value{GDBN} will attempt to alter the contents
6535 of memory, such as with assignment expressions in @code{print}. It
6536 defaults to @code{on}.
6538 @item show may-write-memory
6539 Show the current permission to write memory.
6541 @kindex may-insert-breakpoints
6542 @item set may-insert-breakpoints on
6543 @itemx set may-insert-breakpoints off
6544 This controls whether @value{GDBN} will attempt to insert breakpoints.
6545 This affects all breakpoints, including internal breakpoints defined
6546 by @value{GDBN}. It defaults to @code{on}.
6548 @item show may-insert-breakpoints
6549 Show the current permission to insert breakpoints.
6551 @kindex may-insert-tracepoints
6552 @item set may-insert-tracepoints on
6553 @itemx set may-insert-tracepoints off
6554 This controls whether @value{GDBN} will attempt to insert (regular)
6555 tracepoints at the beginning of a tracing experiment. It affects only
6556 non-fast tracepoints, fast tracepoints being under the control of
6557 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6559 @item show may-insert-tracepoints
6560 Show the current permission to insert tracepoints.
6562 @kindex may-insert-fast-tracepoints
6563 @item set may-insert-fast-tracepoints on
6564 @itemx set may-insert-fast-tracepoints off
6565 This controls whether @value{GDBN} will attempt to insert fast
6566 tracepoints at the beginning of a tracing experiment. It affects only
6567 fast tracepoints, regular (non-fast) tracepoints being under the
6568 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6570 @item show may-insert-fast-tracepoints
6571 Show the current permission to insert fast tracepoints.
6573 @kindex may-interrupt
6574 @item set may-interrupt on
6575 @itemx set may-interrupt off
6576 This controls whether @value{GDBN} will attempt to interrupt or stop
6577 program execution. When this variable is @code{off}, the
6578 @code{interrupt} command will have no effect, nor will
6579 @kbd{Ctrl-c}. It defaults to @code{on}.
6581 @item show may-interrupt
6582 Show the current permission to interrupt or stop the program.
6586 @node Reverse Execution
6587 @chapter Running programs backward
6588 @cindex reverse execution
6589 @cindex running programs backward
6591 When you are debugging a program, it is not unusual to realize that
6592 you have gone too far, and some event of interest has already happened.
6593 If the target environment supports it, @value{GDBN} can allow you to
6594 ``rewind'' the program by running it backward.
6596 A target environment that supports reverse execution should be able
6597 to ``undo'' the changes in machine state that have taken place as the
6598 program was executing normally. Variables, registers etc.@: should
6599 revert to their previous values. Obviously this requires a great
6600 deal of sophistication on the part of the target environment; not
6601 all target environments can support reverse execution.
6603 When a program is executed in reverse, the instructions that
6604 have most recently been executed are ``un-executed'', in reverse
6605 order. The program counter runs backward, following the previous
6606 thread of execution in reverse. As each instruction is ``un-executed'',
6607 the values of memory and/or registers that were changed by that
6608 instruction are reverted to their previous states. After executing
6609 a piece of source code in reverse, all side effects of that code
6610 should be ``undone'', and all variables should be returned to their
6611 prior values@footnote{
6612 Note that some side effects are easier to undo than others. For instance,
6613 memory and registers are relatively easy, but device I/O is hard. Some
6614 targets may be able undo things like device I/O, and some may not.
6616 The contract between @value{GDBN} and the reverse executing target
6617 requires only that the target do something reasonable when
6618 @value{GDBN} tells it to execute backwards, and then report the
6619 results back to @value{GDBN}. Whatever the target reports back to
6620 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6621 assumes that the memory and registers that the target reports are in a
6622 consistant state, but @value{GDBN} accepts whatever it is given.
6625 If you are debugging in a target environment that supports
6626 reverse execution, @value{GDBN} provides the following commands.
6629 @kindex reverse-continue
6630 @kindex rc @r{(@code{reverse-continue})}
6631 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6632 @itemx rc @r{[}@var{ignore-count}@r{]}
6633 Beginning at the point where your program last stopped, start executing
6634 in reverse. Reverse execution will stop for breakpoints and synchronous
6635 exceptions (signals), just like normal execution. Behavior of
6636 asynchronous signals depends on the target environment.
6638 @kindex reverse-step
6639 @kindex rs @r{(@code{step})}
6640 @item reverse-step @r{[}@var{count}@r{]}
6641 Run the program backward until control reaches the start of a
6642 different source line; then stop it, and return control to @value{GDBN}.
6644 Like the @code{step} command, @code{reverse-step} will only stop
6645 at the beginning of a source line. It ``un-executes'' the previously
6646 executed source line. If the previous source line included calls to
6647 debuggable functions, @code{reverse-step} will step (backward) into
6648 the called function, stopping at the beginning of the @emph{last}
6649 statement in the called function (typically a return statement).
6651 Also, as with the @code{step} command, if non-debuggable functions are
6652 called, @code{reverse-step} will run thru them backward without stopping.
6654 @kindex reverse-stepi
6655 @kindex rsi @r{(@code{reverse-stepi})}
6656 @item reverse-stepi @r{[}@var{count}@r{]}
6657 Reverse-execute one machine instruction. Note that the instruction
6658 to be reverse-executed is @emph{not} the one pointed to by the program
6659 counter, but the instruction executed prior to that one. For instance,
6660 if the last instruction was a jump, @code{reverse-stepi} will take you
6661 back from the destination of the jump to the jump instruction itself.
6663 @kindex reverse-next
6664 @kindex rn @r{(@code{reverse-next})}
6665 @item reverse-next @r{[}@var{count}@r{]}
6666 Run backward to the beginning of the previous line executed in
6667 the current (innermost) stack frame. If the line contains function
6668 calls, they will be ``un-executed'' without stopping. Starting from
6669 the first line of a function, @code{reverse-next} will take you back
6670 to the caller of that function, @emph{before} the function was called,
6671 just as the normal @code{next} command would take you from the last
6672 line of a function back to its return to its caller
6673 @footnote{Unless the code is too heavily optimized.}.
6675 @kindex reverse-nexti
6676 @kindex rni @r{(@code{reverse-nexti})}
6677 @item reverse-nexti @r{[}@var{count}@r{]}
6678 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6679 in reverse, except that called functions are ``un-executed'' atomically.
6680 That is, if the previously executed instruction was a return from
6681 another function, @code{reverse-nexti} will continue to execute
6682 in reverse until the call to that function (from the current stack
6685 @kindex reverse-finish
6686 @item reverse-finish
6687 Just as the @code{finish} command takes you to the point where the
6688 current function returns, @code{reverse-finish} takes you to the point
6689 where it was called. Instead of ending up at the end of the current
6690 function invocation, you end up at the beginning.
6692 @kindex set exec-direction
6693 @item set exec-direction
6694 Set the direction of target execution.
6695 @item set exec-direction reverse
6696 @cindex execute forward or backward in time
6697 @value{GDBN} will perform all execution commands in reverse, until the
6698 exec-direction mode is changed to ``forward''. Affected commands include
6699 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6700 command cannot be used in reverse mode.
6701 @item set exec-direction forward
6702 @value{GDBN} will perform all execution commands in the normal fashion.
6703 This is the default.
6707 @node Process Record and Replay
6708 @chapter Recording Inferior's Execution and Replaying It
6709 @cindex process record and replay
6710 @cindex recording inferior's execution and replaying it
6712 On some platforms, @value{GDBN} provides a special @dfn{process record
6713 and replay} target that can record a log of the process execution, and
6714 replay it later with both forward and reverse execution commands.
6717 When this target is in use, if the execution log includes the record
6718 for the next instruction, @value{GDBN} will debug in @dfn{replay
6719 mode}. In the replay mode, the inferior does not really execute code
6720 instructions. Instead, all the events that normally happen during
6721 code execution are taken from the execution log. While code is not
6722 really executed in replay mode, the values of registers (including the
6723 program counter register) and the memory of the inferior are still
6724 changed as they normally would. Their contents are taken from the
6728 If the record for the next instruction is not in the execution log,
6729 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6730 inferior executes normally, and @value{GDBN} records the execution log
6733 The process record and replay target supports reverse execution
6734 (@pxref{Reverse Execution}), even if the platform on which the
6735 inferior runs does not. However, the reverse execution is limited in
6736 this case by the range of the instructions recorded in the execution
6737 log. In other words, reverse execution on platforms that don't
6738 support it directly can only be done in the replay mode.
6740 When debugging in the reverse direction, @value{GDBN} will work in
6741 replay mode as long as the execution log includes the record for the
6742 previous instruction; otherwise, it will work in record mode, if the
6743 platform supports reverse execution, or stop if not.
6745 For architecture environments that support process record and replay,
6746 @value{GDBN} provides the following commands:
6749 @kindex target record
6750 @kindex target record-full
6751 @kindex target record-btrace
6754 @kindex record btrace
6755 @kindex record btrace bts
6756 @kindex record btrace pt
6762 @kindex rec btrace bts
6763 @kindex rec btrace pt
6766 @item record @var{method}
6767 This command starts the process record and replay target. The
6768 recording method can be specified as parameter. Without a parameter
6769 the command uses the @code{full} recording method. The following
6770 recording methods are available:
6774 Full record/replay recording using @value{GDBN}'s software record and
6775 replay implementation. This method allows replaying and reverse
6778 @item btrace @var{format}
6779 Hardware-supported instruction recording. This method does not record
6780 data. Further, the data is collected in a ring buffer so old data will
6781 be overwritten when the buffer is full. It allows limited reverse
6782 execution. Variables and registers are not available during reverse
6783 execution. In remote debugging, recording continues on disconnect.
6784 Recorded data can be inspected after reconnecting. The recording may
6785 be stopped using @code{record stop}.
6787 The recording format can be specified as parameter. Without a parameter
6788 the command chooses the recording format. The following recording
6789 formats are available:
6793 @cindex branch trace store
6794 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6795 this format, the processor stores a from/to record for each executed
6796 branch in the btrace ring buffer.
6799 @cindex Intel Processor Trace
6800 Use the @dfn{Intel Processor Trace} recording format. In this
6801 format, the processor stores the execution trace in a compressed form
6802 that is afterwards decoded by @value{GDBN}.
6804 The trace can be recorded with very low overhead. The compressed
6805 trace format also allows small trace buffers to already contain a big
6806 number of instructions compared to @acronym{BTS}.
6808 Decoding the recorded execution trace, on the other hand, is more
6809 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6810 increased number of instructions to process. You should increase the
6811 buffer-size with care.
6814 Not all recording formats may be available on all processors.
6817 The process record and replay target can only debug a process that is
6818 already running. Therefore, you need first to start the process with
6819 the @kbd{run} or @kbd{start} commands, and then start the recording
6820 with the @kbd{record @var{method}} command.
6822 @cindex displaced stepping, and process record and replay
6823 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6824 will be automatically disabled when process record and replay target
6825 is started. That's because the process record and replay target
6826 doesn't support displaced stepping.
6828 @cindex non-stop mode, and process record and replay
6829 @cindex asynchronous execution, and process record and replay
6830 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6831 the asynchronous execution mode (@pxref{Background Execution}), not
6832 all recording methods are available. The @code{full} recording method
6833 does not support these two modes.
6838 Stop the process record and replay target. When process record and
6839 replay target stops, the entire execution log will be deleted and the
6840 inferior will either be terminated, or will remain in its final state.
6842 When you stop the process record and replay target in record mode (at
6843 the end of the execution log), the inferior will be stopped at the
6844 next instruction that would have been recorded. In other words, if
6845 you record for a while and then stop recording, the inferior process
6846 will be left in the same state as if the recording never happened.
6848 On the other hand, if the process record and replay target is stopped
6849 while in replay mode (that is, not at the end of the execution log,
6850 but at some earlier point), the inferior process will become ``live''
6851 at that earlier state, and it will then be possible to continue the
6852 usual ``live'' debugging of the process from that state.
6854 When the inferior process exits, or @value{GDBN} detaches from it,
6855 process record and replay target will automatically stop itself.
6859 Go to a specific location in the execution log. There are several
6860 ways to specify the location to go to:
6863 @item record goto begin
6864 @itemx record goto start
6865 Go to the beginning of the execution log.
6867 @item record goto end
6868 Go to the end of the execution log.
6870 @item record goto @var{n}
6871 Go to instruction number @var{n} in the execution log.
6875 @item record save @var{filename}
6876 Save the execution log to a file @file{@var{filename}}.
6877 Default filename is @file{gdb_record.@var{process_id}}, where
6878 @var{process_id} is the process ID of the inferior.
6880 This command may not be available for all recording methods.
6882 @kindex record restore
6883 @item record restore @var{filename}
6884 Restore the execution log from a file @file{@var{filename}}.
6885 File must have been created with @code{record save}.
6887 @kindex set record full
6888 @item set record full insn-number-max @var{limit}
6889 @itemx set record full insn-number-max unlimited
6890 Set the limit of instructions to be recorded for the @code{full}
6891 recording method. Default value is 200000.
6893 If @var{limit} is a positive number, then @value{GDBN} will start
6894 deleting instructions from the log once the number of the record
6895 instructions becomes greater than @var{limit}. For every new recorded
6896 instruction, @value{GDBN} will delete the earliest recorded
6897 instruction to keep the number of recorded instructions at the limit.
6898 (Since deleting recorded instructions loses information, @value{GDBN}
6899 lets you control what happens when the limit is reached, by means of
6900 the @code{stop-at-limit} option, described below.)
6902 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6903 delete recorded instructions from the execution log. The number of
6904 recorded instructions is limited only by the available memory.
6906 @kindex show record full
6907 @item show record full insn-number-max
6908 Show the limit of instructions to be recorded with the @code{full}
6911 @item set record full stop-at-limit
6912 Control the behavior of the @code{full} recording method when the
6913 number of recorded instructions reaches the limit. If ON (the
6914 default), @value{GDBN} will stop when the limit is reached for the
6915 first time and ask you whether you want to stop the inferior or
6916 continue running it and recording the execution log. If you decide
6917 to continue recording, each new recorded instruction will cause the
6918 oldest one to be deleted.
6920 If this option is OFF, @value{GDBN} will automatically delete the
6921 oldest record to make room for each new one, without asking.
6923 @item show record full stop-at-limit
6924 Show the current setting of @code{stop-at-limit}.
6926 @item set record full memory-query
6927 Control the behavior when @value{GDBN} is unable to record memory
6928 changes caused by an instruction for the @code{full} recording method.
6929 If ON, @value{GDBN} will query whether to stop the inferior in that
6932 If this option is OFF (the default), @value{GDBN} will automatically
6933 ignore the effect of such instructions on memory. Later, when
6934 @value{GDBN} replays this execution log, it will mark the log of this
6935 instruction as not accessible, and it will not affect the replay
6938 @item show record full memory-query
6939 Show the current setting of @code{memory-query}.
6941 @kindex set record btrace
6942 The @code{btrace} record target does not trace data. As a
6943 convenience, when replaying, @value{GDBN} reads read-only memory off
6944 the live program directly, assuming that the addresses of the
6945 read-only areas don't change. This for example makes it possible to
6946 disassemble code while replaying, but not to print variables.
6947 In some cases, being able to inspect variables might be useful.
6948 You can use the following command for that:
6950 @item set record btrace replay-memory-access
6951 Control the behavior of the @code{btrace} recording method when
6952 accessing memory during replay. If @code{read-only} (the default),
6953 @value{GDBN} will only allow accesses to read-only memory.
6954 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6955 and to read-write memory. Beware that the accessed memory corresponds
6956 to the live target and not necessarily to the current replay
6959 @item set record btrace cpu @var{identifier}
6960 Set the processor to be used for enabling workarounds for processor
6961 errata when decoding the trace.
6963 Processor errata are defects in processor operation, caused by its
6964 design or manufacture. They can cause a trace not to match the
6965 specification. This, in turn, may cause trace decode to fail.
6966 @value{GDBN} can detect erroneous trace packets and correct them, thus
6967 avoiding the decoding failures. These corrections are known as
6968 @dfn{errata workarounds}, and are enabled based on the processor on
6969 which the trace was recorded.
6971 By default, @value{GDBN} attempts to detect the processor
6972 automatically, and apply the necessary workarounds for it. However,
6973 you may need to specify the processor if @value{GDBN} does not yet
6974 support it. This command allows you to do that, and also allows to
6975 disable the workarounds.
6977 The argument @var{identifier} identifies the @sc{cpu} and is of the
6978 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
6979 there are two special identifiers, @code{none} and @code{auto}
6982 The following vendor identifiers and corresponding processor
6983 identifiers are currently supported:
6985 @multitable @columnfractions .1 .9
6988 @tab @var{family}/@var{model}[/@var{stepping}]
6992 On GNU/Linux systems, the processor @var{family}, @var{model}, and
6993 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
6995 If @var{identifier} is @code{auto}, enable errata workarounds for the
6996 processor on which the trace was recorded. If @var{identifier} is
6997 @code{none}, errata workarounds are disabled.
6999 For example, when using an old @value{GDBN} on a new system, decode
7000 may fail because @value{GDBN} does not support the new processor. It
7001 often suffices to specify an older processor that @value{GDBN}
7006 Active record target: record-btrace
7007 Recording format: Intel Processor Trace.
7009 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7010 (gdb) set record btrace cpu intel:6/158
7012 Active record target: record-btrace
7013 Recording format: Intel Processor Trace.
7015 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7018 @kindex show record btrace
7019 @item show record btrace replay-memory-access
7020 Show the current setting of @code{replay-memory-access}.
7022 @item show record btrace cpu
7023 Show the processor to be used for enabling trace decode errata
7026 @kindex set record btrace bts
7027 @item set record btrace bts buffer-size @var{size}
7028 @itemx set record btrace bts buffer-size unlimited
7029 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7030 format. Default is 64KB.
7032 If @var{size} is a positive number, then @value{GDBN} will try to
7033 allocate a buffer of at least @var{size} bytes for each new thread
7034 that uses the btrace recording method and the @acronym{BTS} format.
7035 The actually obtained buffer size may differ from the requested
7036 @var{size}. Use the @code{info record} command to see the actual
7037 buffer size for each thread that uses the btrace recording method and
7038 the @acronym{BTS} format.
7040 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7041 allocate a buffer of 4MB.
7043 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7044 also need longer to process the branch trace data before it can be used.
7046 @item show record btrace bts buffer-size @var{size}
7047 Show the current setting of the requested ring buffer size for branch
7048 tracing in @acronym{BTS} format.
7050 @kindex set record btrace pt
7051 @item set record btrace pt buffer-size @var{size}
7052 @itemx set record btrace pt buffer-size unlimited
7053 Set the requested ring buffer size for branch tracing in Intel
7054 Processor Trace format. Default is 16KB.
7056 If @var{size} is a positive number, then @value{GDBN} will try to
7057 allocate a buffer of at least @var{size} bytes for each new thread
7058 that uses the btrace recording method and the Intel Processor Trace
7059 format. The actually obtained buffer size may differ from the
7060 requested @var{size}. Use the @code{info record} command to see the
7061 actual buffer size for each thread.
7063 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7064 allocate a buffer of 4MB.
7066 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7067 also need longer to process the branch trace data before it can be used.
7069 @item show record btrace pt buffer-size @var{size}
7070 Show the current setting of the requested ring buffer size for branch
7071 tracing in Intel Processor Trace format.
7075 Show various statistics about the recording depending on the recording
7080 For the @code{full} recording method, it shows the state of process
7081 record and its in-memory execution log buffer, including:
7085 Whether in record mode or replay mode.
7087 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7089 Highest recorded instruction number.
7091 Current instruction about to be replayed (if in replay mode).
7093 Number of instructions contained in the execution log.
7095 Maximum number of instructions that may be contained in the execution log.
7099 For the @code{btrace} recording method, it shows:
7105 Number of instructions that have been recorded.
7107 Number of blocks of sequential control-flow formed by the recorded
7110 Whether in record mode or replay mode.
7113 For the @code{bts} recording format, it also shows:
7116 Size of the perf ring buffer.
7119 For the @code{pt} recording format, it also shows:
7122 Size of the perf ring buffer.
7126 @kindex record delete
7129 When record target runs in replay mode (``in the past''), delete the
7130 subsequent execution log and begin to record a new execution log starting
7131 from the current address. This means you will abandon the previously
7132 recorded ``future'' and begin recording a new ``future''.
7134 @kindex record instruction-history
7135 @kindex rec instruction-history
7136 @item record instruction-history
7137 Disassembles instructions from the recorded execution log. By
7138 default, ten instructions are disassembled. This can be changed using
7139 the @code{set record instruction-history-size} command. Instructions
7140 are printed in execution order.
7142 It can also print mixed source+disassembly if you specify the the
7143 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7144 as well as in symbolic form by specifying the @code{/r} modifier.
7146 The current position marker is printed for the instruction at the
7147 current program counter value. This instruction can appear multiple
7148 times in the trace and the current position marker will be printed
7149 every time. To omit the current position marker, specify the
7152 To better align the printed instructions when the trace contains
7153 instructions from more than one function, the function name may be
7154 omitted by specifying the @code{/f} modifier.
7156 Speculatively executed instructions are prefixed with @samp{?}. This
7157 feature is not available for all recording formats.
7159 There are several ways to specify what part of the execution log to
7163 @item record instruction-history @var{insn}
7164 Disassembles ten instructions starting from instruction number
7167 @item record instruction-history @var{insn}, +/-@var{n}
7168 Disassembles @var{n} instructions around instruction number
7169 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7170 @var{n} instructions after instruction number @var{insn}. If
7171 @var{n} is preceded with @code{-}, disassembles @var{n}
7172 instructions before instruction number @var{insn}.
7174 @item record instruction-history
7175 Disassembles ten more instructions after the last disassembly.
7177 @item record instruction-history -
7178 Disassembles ten more instructions before the last disassembly.
7180 @item record instruction-history @var{begin}, @var{end}
7181 Disassembles instructions beginning with instruction number
7182 @var{begin} until instruction number @var{end}. The instruction
7183 number @var{end} is included.
7186 This command may not be available for all recording methods.
7189 @item set record instruction-history-size @var{size}
7190 @itemx set record instruction-history-size unlimited
7191 Define how many instructions to disassemble in the @code{record
7192 instruction-history} command. The default value is 10.
7193 A @var{size} of @code{unlimited} means unlimited instructions.
7196 @item show record instruction-history-size
7197 Show how many instructions to disassemble in the @code{record
7198 instruction-history} command.
7200 @kindex record function-call-history
7201 @kindex rec function-call-history
7202 @item record function-call-history
7203 Prints the execution history at function granularity. It prints one
7204 line for each sequence of instructions that belong to the same
7205 function giving the name of that function, the source lines
7206 for this instruction sequence (if the @code{/l} modifier is
7207 specified), and the instructions numbers that form the sequence (if
7208 the @code{/i} modifier is specified). The function names are indented
7209 to reflect the call stack depth if the @code{/c} modifier is
7210 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7214 (@value{GDBP}) @b{list 1, 10}
7225 (@value{GDBP}) @b{record function-call-history /ilc}
7226 1 bar inst 1,4 at foo.c:6,8
7227 2 foo inst 5,10 at foo.c:2,3
7228 3 bar inst 11,13 at foo.c:9,10
7231 By default, ten lines are printed. This can be changed using the
7232 @code{set record function-call-history-size} command. Functions are
7233 printed in execution order. There are several ways to specify what
7237 @item record function-call-history @var{func}
7238 Prints ten functions starting from function number @var{func}.
7240 @item record function-call-history @var{func}, +/-@var{n}
7241 Prints @var{n} functions around function number @var{func}. If
7242 @var{n} is preceded with @code{+}, prints @var{n} functions after
7243 function number @var{func}. If @var{n} is preceded with @code{-},
7244 prints @var{n} functions before function number @var{func}.
7246 @item record function-call-history
7247 Prints ten more functions after the last ten-line print.
7249 @item record function-call-history -
7250 Prints ten more functions before the last ten-line print.
7252 @item record function-call-history @var{begin}, @var{end}
7253 Prints functions beginning with function number @var{begin} until
7254 function number @var{end}. The function number @var{end} is included.
7257 This command may not be available for all recording methods.
7259 @item set record function-call-history-size @var{size}
7260 @itemx set record function-call-history-size unlimited
7261 Define how many lines to print in the
7262 @code{record function-call-history} command. The default value is 10.
7263 A size of @code{unlimited} means unlimited lines.
7265 @item show record function-call-history-size
7266 Show how many lines to print in the
7267 @code{record function-call-history} command.
7272 @chapter Examining the Stack
7274 When your program has stopped, the first thing you need to know is where it
7275 stopped and how it got there.
7278 Each time your program performs a function call, information about the call
7280 That information includes the location of the call in your program,
7281 the arguments of the call,
7282 and the local variables of the function being called.
7283 The information is saved in a block of data called a @dfn{stack frame}.
7284 The stack frames are allocated in a region of memory called the @dfn{call
7287 When your program stops, the @value{GDBN} commands for examining the
7288 stack allow you to see all of this information.
7290 @cindex selected frame
7291 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7292 @value{GDBN} commands refer implicitly to the selected frame. In
7293 particular, whenever you ask @value{GDBN} for the value of a variable in
7294 your program, the value is found in the selected frame. There are
7295 special @value{GDBN} commands to select whichever frame you are
7296 interested in. @xref{Selection, ,Selecting a Frame}.
7298 When your program stops, @value{GDBN} automatically selects the
7299 currently executing frame and describes it briefly, similar to the
7300 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7303 * Frames:: Stack frames
7304 * Backtrace:: Backtraces
7305 * Selection:: Selecting a frame
7306 * Frame Info:: Information on a frame
7307 * Frame Filter Management:: Managing frame filters
7312 @section Stack Frames
7314 @cindex frame, definition
7316 The call stack is divided up into contiguous pieces called @dfn{stack
7317 frames}, or @dfn{frames} for short; each frame is the data associated
7318 with one call to one function. The frame contains the arguments given
7319 to the function, the function's local variables, and the address at
7320 which the function is executing.
7322 @cindex initial frame
7323 @cindex outermost frame
7324 @cindex innermost frame
7325 When your program is started, the stack has only one frame, that of the
7326 function @code{main}. This is called the @dfn{initial} frame or the
7327 @dfn{outermost} frame. Each time a function is called, a new frame is
7328 made. Each time a function returns, the frame for that function invocation
7329 is eliminated. If a function is recursive, there can be many frames for
7330 the same function. The frame for the function in which execution is
7331 actually occurring is called the @dfn{innermost} frame. This is the most
7332 recently created of all the stack frames that still exist.
7334 @cindex frame pointer
7335 Inside your program, stack frames are identified by their addresses. A
7336 stack frame consists of many bytes, each of which has its own address; each
7337 kind of computer has a convention for choosing one byte whose
7338 address serves as the address of the frame. Usually this address is kept
7339 in a register called the @dfn{frame pointer register}
7340 (@pxref{Registers, $fp}) while execution is going on in that frame.
7342 @cindex frame number
7343 @value{GDBN} assigns numbers to all existing stack frames, starting with
7344 zero for the innermost frame, one for the frame that called it,
7345 and so on upward. These numbers do not really exist in your program;
7346 they are assigned by @value{GDBN} to give you a way of designating stack
7347 frames in @value{GDBN} commands.
7349 @c The -fomit-frame-pointer below perennially causes hbox overflow
7350 @c underflow problems.
7351 @cindex frameless execution
7352 Some compilers provide a way to compile functions so that they operate
7353 without stack frames. (For example, the @value{NGCC} option
7355 @samp{-fomit-frame-pointer}
7357 generates functions without a frame.)
7358 This is occasionally done with heavily used library functions to save
7359 the frame setup time. @value{GDBN} has limited facilities for dealing
7360 with these function invocations. If the innermost function invocation
7361 has no stack frame, @value{GDBN} nevertheless regards it as though
7362 it had a separate frame, which is numbered zero as usual, allowing
7363 correct tracing of the function call chain. However, @value{GDBN} has
7364 no provision for frameless functions elsewhere in the stack.
7370 @cindex call stack traces
7371 A backtrace is a summary of how your program got where it is. It shows one
7372 line per frame, for many frames, starting with the currently executing
7373 frame (frame zero), followed by its caller (frame one), and on up the
7376 @anchor{backtrace-command}
7378 @kindex bt @r{(@code{backtrace})}
7379 To print a backtrace of the entire stack, use the @code{backtrace}
7380 command, or its alias @code{bt}. This command will print one line per
7381 frame for frames in the stack. By default, all stack frames are
7382 printed. You can stop the backtrace at any time by typing the system
7383 interrupt character, normally @kbd{Ctrl-c}.
7386 @item backtrace [@var{args}@dots{}]
7387 @itemx bt [@var{args}@dots{}]
7388 Print the backtrace of the entire stack. The optional @var{args} can
7389 be one of the following:
7394 Print only the innermost @var{n} frames, where @var{n} is a positive
7399 Print only the outermost @var{n} frames, where @var{n} is a positive
7403 Print the values of the local variables also. This can be combined
7404 with a number to limit the number of frames shown.
7407 Do not run Python frame filters on this backtrace. @xref{Frame
7408 Filter API}, for more information. Additionally use @ref{disable
7409 frame-filter all} to turn off all frame filters. This is only
7410 relevant when @value{GDBN} has been configured with @code{Python}
7414 A Python frame filter might decide to ``elide'' some frames. Normally
7415 such elided frames are still printed, but they are indented relative
7416 to the filtered frames that cause them to be elided. The @code{hide}
7417 option causes elided frames to not be printed at all.
7423 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7424 are additional aliases for @code{backtrace}.
7426 @cindex multiple threads, backtrace
7427 In a multi-threaded program, @value{GDBN} by default shows the
7428 backtrace only for the current thread. To display the backtrace for
7429 several or all of the threads, use the command @code{thread apply}
7430 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7431 apply all backtrace}, @value{GDBN} will display the backtrace for all
7432 the threads; this is handy when you debug a core dump of a
7433 multi-threaded program.
7435 Each line in the backtrace shows the frame number and the function name.
7436 The program counter value is also shown---unless you use @code{set
7437 print address off}. The backtrace also shows the source file name and
7438 line number, as well as the arguments to the function. The program
7439 counter value is omitted if it is at the beginning of the code for that
7442 Here is an example of a backtrace. It was made with the command
7443 @samp{bt 3}, so it shows the innermost three frames.
7447 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7449 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7450 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7452 (More stack frames follow...)
7457 The display for frame zero does not begin with a program counter
7458 value, indicating that your program has stopped at the beginning of the
7459 code for line @code{993} of @code{builtin.c}.
7462 The value of parameter @code{data} in frame 1 has been replaced by
7463 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7464 only if it is a scalar (integer, pointer, enumeration, etc). See command
7465 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7466 on how to configure the way function parameter values are printed.
7468 @cindex optimized out, in backtrace
7469 @cindex function call arguments, optimized out
7470 If your program was compiled with optimizations, some compilers will
7471 optimize away arguments passed to functions if those arguments are
7472 never used after the call. Such optimizations generate code that
7473 passes arguments through registers, but doesn't store those arguments
7474 in the stack frame. @value{GDBN} has no way of displaying such
7475 arguments in stack frames other than the innermost one. Here's what
7476 such a backtrace might look like:
7480 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7482 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7483 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7485 (More stack frames follow...)
7490 The values of arguments that were not saved in their stack frames are
7491 shown as @samp{<optimized out>}.
7493 If you need to display the values of such optimized-out arguments,
7494 either deduce that from other variables whose values depend on the one
7495 you are interested in, or recompile without optimizations.
7497 @cindex backtrace beyond @code{main} function
7498 @cindex program entry point
7499 @cindex startup code, and backtrace
7500 Most programs have a standard user entry point---a place where system
7501 libraries and startup code transition into user code. For C this is
7502 @code{main}@footnote{
7503 Note that embedded programs (the so-called ``free-standing''
7504 environment) are not required to have a @code{main} function as the
7505 entry point. They could even have multiple entry points.}.
7506 When @value{GDBN} finds the entry function in a backtrace
7507 it will terminate the backtrace, to avoid tracing into highly
7508 system-specific (and generally uninteresting) code.
7510 If you need to examine the startup code, or limit the number of levels
7511 in a backtrace, you can change this behavior:
7514 @item set backtrace past-main
7515 @itemx set backtrace past-main on
7516 @kindex set backtrace
7517 Backtraces will continue past the user entry point.
7519 @item set backtrace past-main off
7520 Backtraces will stop when they encounter the user entry point. This is the
7523 @item show backtrace past-main
7524 @kindex show backtrace
7525 Display the current user entry point backtrace policy.
7527 @item set backtrace past-entry
7528 @itemx set backtrace past-entry on
7529 Backtraces will continue past the internal entry point of an application.
7530 This entry point is encoded by the linker when the application is built,
7531 and is likely before the user entry point @code{main} (or equivalent) is called.
7533 @item set backtrace past-entry off
7534 Backtraces will stop when they encounter the internal entry point of an
7535 application. This is the default.
7537 @item show backtrace past-entry
7538 Display the current internal entry point backtrace policy.
7540 @item set backtrace limit @var{n}
7541 @itemx set backtrace limit 0
7542 @itemx set backtrace limit unlimited
7543 @cindex backtrace limit
7544 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7545 or zero means unlimited levels.
7547 @item show backtrace limit
7548 Display the current limit on backtrace levels.
7551 You can control how file names are displayed.
7554 @item set filename-display
7555 @itemx set filename-display relative
7556 @cindex filename-display
7557 Display file names relative to the compilation directory. This is the default.
7559 @item set filename-display basename
7560 Display only basename of a filename.
7562 @item set filename-display absolute
7563 Display an absolute filename.
7565 @item show filename-display
7566 Show the current way to display filenames.
7570 @section Selecting a Frame
7572 Most commands for examining the stack and other data in your program work on
7573 whichever stack frame is selected at the moment. Here are the commands for
7574 selecting a stack frame; all of them finish by printing a brief description
7575 of the stack frame just selected.
7578 @kindex frame@r{, selecting}
7579 @kindex f @r{(@code{frame})}
7582 Select frame number @var{n}. Recall that frame zero is the innermost
7583 (currently executing) frame, frame one is the frame that called the
7584 innermost one, and so on. The highest-numbered frame is the one for
7587 @item frame @var{stack-addr} [ @var{pc-addr} ]
7588 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7589 Select the frame at address @var{stack-addr}. This is useful mainly if the
7590 chaining of stack frames has been damaged by a bug, making it
7591 impossible for @value{GDBN} to assign numbers properly to all frames. In
7592 addition, this can be useful when your program has multiple stacks and
7593 switches between them. The optional @var{pc-addr} can also be given to
7594 specify the value of PC for the stack frame.
7598 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7599 numbers @var{n}, this advances toward the outermost frame, to higher
7600 frame numbers, to frames that have existed longer.
7603 @kindex do @r{(@code{down})}
7605 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7606 positive numbers @var{n}, this advances toward the innermost frame, to
7607 lower frame numbers, to frames that were created more recently.
7608 You may abbreviate @code{down} as @code{do}.
7611 All of these commands end by printing two lines of output describing the
7612 frame. The first line shows the frame number, the function name, the
7613 arguments, and the source file and line number of execution in that
7614 frame. The second line shows the text of that source line.
7622 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7624 10 read_input_file (argv[i]);
7628 After such a printout, the @code{list} command with no arguments
7629 prints ten lines centered on the point of execution in the frame.
7630 You can also edit the program at the point of execution with your favorite
7631 editing program by typing @code{edit}.
7632 @xref{List, ,Printing Source Lines},
7636 @kindex select-frame
7638 The @code{select-frame} command is a variant of @code{frame} that does
7639 not display the new frame after selecting it. This command is
7640 intended primarily for use in @value{GDBN} command scripts, where the
7641 output might be unnecessary and distracting.
7643 @kindex down-silently
7645 @item up-silently @var{n}
7646 @itemx down-silently @var{n}
7647 These two commands are variants of @code{up} and @code{down},
7648 respectively; they differ in that they do their work silently, without
7649 causing display of the new frame. They are intended primarily for use
7650 in @value{GDBN} command scripts, where the output might be unnecessary and
7655 @section Information About a Frame
7657 There are several other commands to print information about the selected
7663 When used without any argument, this command does not change which
7664 frame is selected, but prints a brief description of the currently
7665 selected stack frame. It can be abbreviated @code{f}. With an
7666 argument, this command is used to select a stack frame.
7667 @xref{Selection, ,Selecting a Frame}.
7670 @kindex info f @r{(@code{info frame})}
7673 This command prints a verbose description of the selected stack frame,
7678 the address of the frame
7680 the address of the next frame down (called by this frame)
7682 the address of the next frame up (caller of this frame)
7684 the language in which the source code corresponding to this frame is written
7686 the address of the frame's arguments
7688 the address of the frame's local variables
7690 the program counter saved in it (the address of execution in the caller frame)
7692 which registers were saved in the frame
7695 @noindent The verbose description is useful when
7696 something has gone wrong that has made the stack format fail to fit
7697 the usual conventions.
7699 @item info frame @var{addr}
7700 @itemx info f @var{addr}
7701 Print a verbose description of the frame at address @var{addr}, without
7702 selecting that frame. The selected frame remains unchanged by this
7703 command. This requires the same kind of address (more than one for some
7704 architectures) that you specify in the @code{frame} command.
7705 @xref{Selection, ,Selecting a Frame}.
7709 Print the arguments of the selected frame, each on a separate line.
7713 Print the local variables of the selected frame, each on a separate
7714 line. These are all variables (declared either static or automatic)
7715 accessible at the point of execution of the selected frame.
7719 @node Frame Filter Management
7720 @section Management of Frame Filters.
7721 @cindex managing frame filters
7723 Frame filters are Python based utilities to manage and decorate the
7724 output of frames. @xref{Frame Filter API}, for further information.
7726 Managing frame filters is performed by several commands available
7727 within @value{GDBN}, detailed here.
7730 @kindex info frame-filter
7731 @item info frame-filter
7732 Print a list of installed frame filters from all dictionaries, showing
7733 their name, priority and enabled status.
7735 @kindex disable frame-filter
7736 @anchor{disable frame-filter all}
7737 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7738 Disable a frame filter in the dictionary matching
7739 @var{filter-dictionary} and @var{filter-name}. The
7740 @var{filter-dictionary} may be @code{all}, @code{global},
7741 @code{progspace}, or the name of the object file where the frame filter
7742 dictionary resides. When @code{all} is specified, all frame filters
7743 across all dictionaries are disabled. The @var{filter-name} is the name
7744 of the frame filter and is used when @code{all} is not the option for
7745 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7746 may be enabled again later.
7748 @kindex enable frame-filter
7749 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7750 Enable a frame filter in the dictionary matching
7751 @var{filter-dictionary} and @var{filter-name}. The
7752 @var{filter-dictionary} may be @code{all}, @code{global},
7753 @code{progspace} or the name of the object file where the frame filter
7754 dictionary resides. When @code{all} is specified, all frame filters across
7755 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7756 filter and is used when @code{all} is not the option for
7757 @var{filter-dictionary}.
7762 (gdb) info frame-filter
7764 global frame-filters:
7765 Priority Enabled Name
7766 1000 No PrimaryFunctionFilter
7769 progspace /build/test frame-filters:
7770 Priority Enabled Name
7771 100 Yes ProgspaceFilter
7773 objfile /build/test frame-filters:
7774 Priority Enabled Name
7775 999 Yes BuildProgra Filter
7777 (gdb) disable frame-filter /build/test BuildProgramFilter
7778 (gdb) info frame-filter
7780 global frame-filters:
7781 Priority Enabled Name
7782 1000 No PrimaryFunctionFilter
7785 progspace /build/test frame-filters:
7786 Priority Enabled Name
7787 100 Yes ProgspaceFilter
7789 objfile /build/test frame-filters:
7790 Priority Enabled Name
7791 999 No BuildProgramFilter
7793 (gdb) enable frame-filter global PrimaryFunctionFilter
7794 (gdb) info frame-filter
7796 global frame-filters:
7797 Priority Enabled Name
7798 1000 Yes PrimaryFunctionFilter
7801 progspace /build/test frame-filters:
7802 Priority Enabled Name
7803 100 Yes ProgspaceFilter
7805 objfile /build/test frame-filters:
7806 Priority Enabled Name
7807 999 No BuildProgramFilter
7810 @kindex set frame-filter priority
7811 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7812 Set the @var{priority} of a frame filter in the dictionary matching
7813 @var{filter-dictionary}, and the frame filter name matching
7814 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7815 @code{progspace} or the name of the object file where the frame filter
7816 dictionary resides. The @var{priority} is an integer.
7818 @kindex show frame-filter priority
7819 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7820 Show the @var{priority} of a frame filter in the dictionary matching
7821 @var{filter-dictionary}, and the frame filter name matching
7822 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7823 @code{progspace} or the name of the object file where the frame filter
7829 (gdb) info frame-filter
7831 global frame-filters:
7832 Priority Enabled Name
7833 1000 Yes PrimaryFunctionFilter
7836 progspace /build/test frame-filters:
7837 Priority Enabled Name
7838 100 Yes ProgspaceFilter
7840 objfile /build/test frame-filters:
7841 Priority Enabled Name
7842 999 No BuildProgramFilter
7844 (gdb) set frame-filter priority global Reverse 50
7845 (gdb) info frame-filter
7847 global frame-filters:
7848 Priority Enabled Name
7849 1000 Yes PrimaryFunctionFilter
7852 progspace /build/test frame-filters:
7853 Priority Enabled Name
7854 100 Yes ProgspaceFilter
7856 objfile /build/test frame-filters:
7857 Priority Enabled Name
7858 999 No BuildProgramFilter
7863 @chapter Examining Source Files
7865 @value{GDBN} can print parts of your program's source, since the debugging
7866 information recorded in the program tells @value{GDBN} what source files were
7867 used to build it. When your program stops, @value{GDBN} spontaneously prints
7868 the line where it stopped. Likewise, when you select a stack frame
7869 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7870 execution in that frame has stopped. You can print other portions of
7871 source files by explicit command.
7873 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7874 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7875 @value{GDBN} under @sc{gnu} Emacs}.
7878 * List:: Printing source lines
7879 * Specify Location:: How to specify code locations
7880 * Edit:: Editing source files
7881 * Search:: Searching source files
7882 * Source Path:: Specifying source directories
7883 * Machine Code:: Source and machine code
7887 @section Printing Source Lines
7890 @kindex l @r{(@code{list})}
7891 To print lines from a source file, use the @code{list} command
7892 (abbreviated @code{l}). By default, ten lines are printed.
7893 There are several ways to specify what part of the file you want to
7894 print; see @ref{Specify Location}, for the full list.
7896 Here are the forms of the @code{list} command most commonly used:
7899 @item list @var{linenum}
7900 Print lines centered around line number @var{linenum} in the
7901 current source file.
7903 @item list @var{function}
7904 Print lines centered around the beginning of function
7908 Print more lines. If the last lines printed were printed with a
7909 @code{list} command, this prints lines following the last lines
7910 printed; however, if the last line printed was a solitary line printed
7911 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7912 Stack}), this prints lines centered around that line.
7915 Print lines just before the lines last printed.
7918 @cindex @code{list}, how many lines to display
7919 By default, @value{GDBN} prints ten source lines with any of these forms of
7920 the @code{list} command. You can change this using @code{set listsize}:
7923 @kindex set listsize
7924 @item set listsize @var{count}
7925 @itemx set listsize unlimited
7926 Make the @code{list} command display @var{count} source lines (unless
7927 the @code{list} argument explicitly specifies some other number).
7928 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7930 @kindex show listsize
7932 Display the number of lines that @code{list} prints.
7935 Repeating a @code{list} command with @key{RET} discards the argument,
7936 so it is equivalent to typing just @code{list}. This is more useful
7937 than listing the same lines again. An exception is made for an
7938 argument of @samp{-}; that argument is preserved in repetition so that
7939 each repetition moves up in the source file.
7941 In general, the @code{list} command expects you to supply zero, one or two
7942 @dfn{locations}. Locations specify source lines; there are several ways
7943 of writing them (@pxref{Specify Location}), but the effect is always
7944 to specify some source line.
7946 Here is a complete description of the possible arguments for @code{list}:
7949 @item list @var{location}
7950 Print lines centered around the line specified by @var{location}.
7952 @item list @var{first},@var{last}
7953 Print lines from @var{first} to @var{last}. Both arguments are
7954 locations. When a @code{list} command has two locations, and the
7955 source file of the second location is omitted, this refers to
7956 the same source file as the first location.
7958 @item list ,@var{last}
7959 Print lines ending with @var{last}.
7961 @item list @var{first},
7962 Print lines starting with @var{first}.
7965 Print lines just after the lines last printed.
7968 Print lines just before the lines last printed.
7971 As described in the preceding table.
7974 @node Specify Location
7975 @section Specifying a Location
7976 @cindex specifying location
7978 @cindex source location
7981 * Linespec Locations:: Linespec locations
7982 * Explicit Locations:: Explicit locations
7983 * Address Locations:: Address locations
7986 Several @value{GDBN} commands accept arguments that specify a location
7987 of your program's code. Since @value{GDBN} is a source-level
7988 debugger, a location usually specifies some line in the source code.
7989 Locations may be specified using three different formats:
7990 linespec locations, explicit locations, or address locations.
7992 @node Linespec Locations
7993 @subsection Linespec Locations
7994 @cindex linespec locations
7996 A @dfn{linespec} is a colon-separated list of source location parameters such
7997 as file name, function name, etc. Here are all the different ways of
7998 specifying a linespec:
8002 Specifies the line number @var{linenum} of the current source file.
8005 @itemx +@var{offset}
8006 Specifies the line @var{offset} lines before or after the @dfn{current
8007 line}. For the @code{list} command, the current line is the last one
8008 printed; for the breakpoint commands, this is the line at which
8009 execution stopped in the currently selected @dfn{stack frame}
8010 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8011 used as the second of the two linespecs in a @code{list} command,
8012 this specifies the line @var{offset} lines up or down from the first
8015 @item @var{filename}:@var{linenum}
8016 Specifies the line @var{linenum} in the source file @var{filename}.
8017 If @var{filename} is a relative file name, then it will match any
8018 source file name with the same trailing components. For example, if
8019 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8020 name of @file{/build/trunk/gcc/expr.c}, but not
8021 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8023 @item @var{function}
8024 Specifies the line that begins the body of the function @var{function}.
8025 For example, in C, this is the line with the open brace.
8027 By default, in C@t{++} and Ada, @var{function} is interpreted as
8028 specifying all functions named @var{function} in all scopes. For
8029 C@t{++}, this means in all namespaces and classes. For Ada, this
8030 means in all packages.
8032 For example, assuming a program with C@t{++} symbols named
8033 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8034 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8036 Commands that accept a linespec let you override this with the
8037 @code{-qualified} option. For example, @w{@kbd{break -qualified
8038 func}} sets a breakpoint on a free-function named @code{func} ignoring
8039 any C@t{++} class methods and namespace functions called @code{func}.
8041 @xref{Explicit Locations}.
8043 @item @var{function}:@var{label}
8044 Specifies the line where @var{label} appears in @var{function}.
8046 @item @var{filename}:@var{function}
8047 Specifies the line that begins the body of the function @var{function}
8048 in the file @var{filename}. You only need the file name with a
8049 function name to avoid ambiguity when there are identically named
8050 functions in different source files.
8053 Specifies the line at which the label named @var{label} appears
8054 in the function corresponding to the currently selected stack frame.
8055 If there is no current selected stack frame (for instance, if the inferior
8056 is not running), then @value{GDBN} will not search for a label.
8058 @cindex breakpoint at static probe point
8059 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8060 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8061 applications to embed static probes. @xref{Static Probe Points}, for more
8062 information on finding and using static probes. This form of linespec
8063 specifies the location of such a static probe.
8065 If @var{objfile} is given, only probes coming from that shared library
8066 or executable matching @var{objfile} as a regular expression are considered.
8067 If @var{provider} is given, then only probes from that provider are considered.
8068 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8069 each one of those probes.
8072 @node Explicit Locations
8073 @subsection Explicit Locations
8074 @cindex explicit locations
8076 @dfn{Explicit locations} allow the user to directly specify the source
8077 location's parameters using option-value pairs.
8079 Explicit locations are useful when several functions, labels, or
8080 file names have the same name (base name for files) in the program's
8081 sources. In these cases, explicit locations point to the source
8082 line you meant more accurately and unambiguously. Also, using
8083 explicit locations might be faster in large programs.
8085 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8086 defined in the file named @file{foo} or the label @code{bar} in a function
8087 named @code{foo}. @value{GDBN} must search either the file system or
8088 the symbol table to know.
8090 The list of valid explicit location options is summarized in the
8094 @item -source @var{filename}
8095 The value specifies the source file name. To differentiate between
8096 files with the same base name, prepend as many directories as is necessary
8097 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8098 @value{GDBN} will use the first file it finds with the given base
8099 name. This option requires the use of either @code{-function} or @code{-line}.
8101 @item -function @var{function}
8102 The value specifies the name of a function. Operations
8103 on function locations unmodified by other options (such as @code{-label}
8104 or @code{-line}) refer to the line that begins the body of the function.
8105 In C, for example, this is the line with the open brace.
8107 By default, in C@t{++} and Ada, @var{function} is interpreted as
8108 specifying all functions named @var{function} in all scopes. For
8109 C@t{++}, this means in all namespaces and classes. For Ada, this
8110 means in all packages.
8112 For example, assuming a program with C@t{++} symbols named
8113 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8114 -function func}} and @w{@kbd{break -function B::func}} set a
8115 breakpoint on both symbols.
8117 You can use the @kbd{-qualified} flag to override this (see below).
8121 This flag makes @value{GDBN} interpret a function name specified with
8122 @kbd{-function} as a complete fully-qualified name.
8124 For example, assuming a C@t{++} program with symbols named
8125 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8126 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8128 (Note: the @kbd{-qualified} option can precede a linespec as well
8129 (@pxref{Linespec Locations}), so the particular example above could be
8130 simplified as @w{@kbd{break -qualified B::func}}.)
8132 @item -label @var{label}
8133 The value specifies the name of a label. When the function
8134 name is not specified, the label is searched in the function of the currently
8135 selected stack frame.
8137 @item -line @var{number}
8138 The value specifies a line offset for the location. The offset may either
8139 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8140 the command. When specified without any other options, the line offset is
8141 relative to the current line.
8144 Explicit location options may be abbreviated by omitting any non-unique
8145 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8147 @node Address Locations
8148 @subsection Address Locations
8149 @cindex address locations
8151 @dfn{Address locations} indicate a specific program address. They have
8152 the generalized form *@var{address}.
8154 For line-oriented commands, such as @code{list} and @code{edit}, this
8155 specifies a source line that contains @var{address}. For @code{break} and
8156 other breakpoint-oriented commands, this can be used to set breakpoints in
8157 parts of your program which do not have debugging information or
8160 Here @var{address} may be any expression valid in the current working
8161 language (@pxref{Languages, working language}) that specifies a code
8162 address. In addition, as a convenience, @value{GDBN} extends the
8163 semantics of expressions used in locations to cover several situations
8164 that frequently occur during debugging. Here are the various forms
8168 @item @var{expression}
8169 Any expression valid in the current working language.
8171 @item @var{funcaddr}
8172 An address of a function or procedure derived from its name. In C,
8173 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8174 simply the function's name @var{function} (and actually a special case
8175 of a valid expression). In Pascal and Modula-2, this is
8176 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8177 (although the Pascal form also works).
8179 This form specifies the address of the function's first instruction,
8180 before the stack frame and arguments have been set up.
8182 @item '@var{filename}':@var{funcaddr}
8183 Like @var{funcaddr} above, but also specifies the name of the source
8184 file explicitly. This is useful if the name of the function does not
8185 specify the function unambiguously, e.g., if there are several
8186 functions with identical names in different source files.
8190 @section Editing Source Files
8191 @cindex editing source files
8194 @kindex e @r{(@code{edit})}
8195 To edit the lines in a source file, use the @code{edit} command.
8196 The editing program of your choice
8197 is invoked with the current line set to
8198 the active line in the program.
8199 Alternatively, there are several ways to specify what part of the file you
8200 want to print if you want to see other parts of the program:
8203 @item edit @var{location}
8204 Edit the source file specified by @code{location}. Editing starts at
8205 that @var{location}, e.g., at the specified source line of the
8206 specified file. @xref{Specify Location}, for all the possible forms
8207 of the @var{location} argument; here are the forms of the @code{edit}
8208 command most commonly used:
8211 @item edit @var{number}
8212 Edit the current source file with @var{number} as the active line number.
8214 @item edit @var{function}
8215 Edit the file containing @var{function} at the beginning of its definition.
8220 @subsection Choosing your Editor
8221 You can customize @value{GDBN} to use any editor you want
8223 The only restriction is that your editor (say @code{ex}), recognizes the
8224 following command-line syntax:
8226 ex +@var{number} file
8228 The optional numeric value +@var{number} specifies the number of the line in
8229 the file where to start editing.}.
8230 By default, it is @file{@value{EDITOR}}, but you can change this
8231 by setting the environment variable @code{EDITOR} before using
8232 @value{GDBN}. For example, to configure @value{GDBN} to use the
8233 @code{vi} editor, you could use these commands with the @code{sh} shell:
8239 or in the @code{csh} shell,
8241 setenv EDITOR /usr/bin/vi
8246 @section Searching Source Files
8247 @cindex searching source files
8249 There are two commands for searching through the current source file for a
8254 @kindex forward-search
8255 @kindex fo @r{(@code{forward-search})}
8256 @item forward-search @var{regexp}
8257 @itemx search @var{regexp}
8258 The command @samp{forward-search @var{regexp}} checks each line,
8259 starting with the one following the last line listed, for a match for
8260 @var{regexp}. It lists the line that is found. You can use the
8261 synonym @samp{search @var{regexp}} or abbreviate the command name as
8264 @kindex reverse-search
8265 @item reverse-search @var{regexp}
8266 The command @samp{reverse-search @var{regexp}} checks each line, starting
8267 with the one before the last line listed and going backward, for a match
8268 for @var{regexp}. It lists the line that is found. You can abbreviate
8269 this command as @code{rev}.
8273 @section Specifying Source Directories
8276 @cindex directories for source files
8277 Executable programs sometimes do not record the directories of the source
8278 files from which they were compiled, just the names. Even when they do,
8279 the directories could be moved between the compilation and your debugging
8280 session. @value{GDBN} has a list of directories to search for source files;
8281 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8282 it tries all the directories in the list, in the order they are present
8283 in the list, until it finds a file with the desired name.
8285 For example, suppose an executable references the file
8286 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8287 @file{/mnt/cross}. The file is first looked up literally; if this
8288 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8289 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8290 message is printed. @value{GDBN} does not look up the parts of the
8291 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8292 Likewise, the subdirectories of the source path are not searched: if
8293 the source path is @file{/mnt/cross}, and the binary refers to
8294 @file{foo.c}, @value{GDBN} would not find it under
8295 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8297 Plain file names, relative file names with leading directories, file
8298 names containing dots, etc.@: are all treated as described above; for
8299 instance, if the source path is @file{/mnt/cross}, and the source file
8300 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8301 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8302 that---@file{/mnt/cross/foo.c}.
8304 Note that the executable search path is @emph{not} used to locate the
8307 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8308 any information it has cached about where source files are found and where
8309 each line is in the file.
8313 When you start @value{GDBN}, its source path includes only @samp{cdir}
8314 and @samp{cwd}, in that order.
8315 To add other directories, use the @code{directory} command.
8317 The search path is used to find both program source files and @value{GDBN}
8318 script files (read using the @samp{-command} option and @samp{source} command).
8320 In addition to the source path, @value{GDBN} provides a set of commands
8321 that manage a list of source path substitution rules. A @dfn{substitution
8322 rule} specifies how to rewrite source directories stored in the program's
8323 debug information in case the sources were moved to a different
8324 directory between compilation and debugging. A rule is made of
8325 two strings, the first specifying what needs to be rewritten in
8326 the path, and the second specifying how it should be rewritten.
8327 In @ref{set substitute-path}, we name these two parts @var{from} and
8328 @var{to} respectively. @value{GDBN} does a simple string replacement
8329 of @var{from} with @var{to} at the start of the directory part of the
8330 source file name, and uses that result instead of the original file
8331 name to look up the sources.
8333 Using the previous example, suppose the @file{foo-1.0} tree has been
8334 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8335 @value{GDBN} to replace @file{/usr/src} in all source path names with
8336 @file{/mnt/cross}. The first lookup will then be
8337 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8338 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8339 substitution rule, use the @code{set substitute-path} command
8340 (@pxref{set substitute-path}).
8342 To avoid unexpected substitution results, a rule is applied only if the
8343 @var{from} part of the directory name ends at a directory separator.
8344 For instance, a rule substituting @file{/usr/source} into
8345 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8346 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8347 is applied only at the beginning of the directory name, this rule will
8348 not be applied to @file{/root/usr/source/baz.c} either.
8350 In many cases, you can achieve the same result using the @code{directory}
8351 command. However, @code{set substitute-path} can be more efficient in
8352 the case where the sources are organized in a complex tree with multiple
8353 subdirectories. With the @code{directory} command, you need to add each
8354 subdirectory of your project. If you moved the entire tree while
8355 preserving its internal organization, then @code{set substitute-path}
8356 allows you to direct the debugger to all the sources with one single
8359 @code{set substitute-path} is also more than just a shortcut command.
8360 The source path is only used if the file at the original location no
8361 longer exists. On the other hand, @code{set substitute-path} modifies
8362 the debugger behavior to look at the rewritten location instead. So, if
8363 for any reason a source file that is not relevant to your executable is
8364 located at the original location, a substitution rule is the only
8365 method available to point @value{GDBN} at the new location.
8367 @cindex @samp{--with-relocated-sources}
8368 @cindex default source path substitution
8369 You can configure a default source path substitution rule by
8370 configuring @value{GDBN} with the
8371 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8372 should be the name of a directory under @value{GDBN}'s configured
8373 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8374 directory names in debug information under @var{dir} will be adjusted
8375 automatically if the installed @value{GDBN} is moved to a new
8376 location. This is useful if @value{GDBN}, libraries or executables
8377 with debug information and corresponding source code are being moved
8381 @item directory @var{dirname} @dots{}
8382 @item dir @var{dirname} @dots{}
8383 Add directory @var{dirname} to the front of the source path. Several
8384 directory names may be given to this command, separated by @samp{:}
8385 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8386 part of absolute file names) or
8387 whitespace. You may specify a directory that is already in the source
8388 path; this moves it forward, so @value{GDBN} searches it sooner.
8392 @vindex $cdir@r{, convenience variable}
8393 @vindex $cwd@r{, convenience variable}
8394 @cindex compilation directory
8395 @cindex current directory
8396 @cindex working directory
8397 @cindex directory, current
8398 @cindex directory, compilation
8399 You can use the string @samp{$cdir} to refer to the compilation
8400 directory (if one is recorded), and @samp{$cwd} to refer to the current
8401 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8402 tracks the current working directory as it changes during your @value{GDBN}
8403 session, while the latter is immediately expanded to the current
8404 directory at the time you add an entry to the source path.
8407 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8409 @c RET-repeat for @code{directory} is explicitly disabled, but since
8410 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8412 @item set directories @var{path-list}
8413 @kindex set directories
8414 Set the source path to @var{path-list}.
8415 @samp{$cdir:$cwd} are added if missing.
8417 @item show directories
8418 @kindex show directories
8419 Print the source path: show which directories it contains.
8421 @anchor{set substitute-path}
8422 @item set substitute-path @var{from} @var{to}
8423 @kindex set substitute-path
8424 Define a source path substitution rule, and add it at the end of the
8425 current list of existing substitution rules. If a rule with the same
8426 @var{from} was already defined, then the old rule is also deleted.
8428 For example, if the file @file{/foo/bar/baz.c} was moved to
8429 @file{/mnt/cross/baz.c}, then the command
8432 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8436 will tell @value{GDBN} to replace @samp{/foo/bar} with
8437 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8438 @file{baz.c} even though it was moved.
8440 In the case when more than one substitution rule have been defined,
8441 the rules are evaluated one by one in the order where they have been
8442 defined. The first one matching, if any, is selected to perform
8445 For instance, if we had entered the following commands:
8448 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8449 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8453 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8454 @file{/mnt/include/defs.h} by using the first rule. However, it would
8455 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8456 @file{/mnt/src/lib/foo.c}.
8459 @item unset substitute-path [path]
8460 @kindex unset substitute-path
8461 If a path is specified, search the current list of substitution rules
8462 for a rule that would rewrite that path. Delete that rule if found.
8463 A warning is emitted by the debugger if no rule could be found.
8465 If no path is specified, then all substitution rules are deleted.
8467 @item show substitute-path [path]
8468 @kindex show substitute-path
8469 If a path is specified, then print the source path substitution rule
8470 which would rewrite that path, if any.
8472 If no path is specified, then print all existing source path substitution
8477 If your source path is cluttered with directories that are no longer of
8478 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8479 versions of source. You can correct the situation as follows:
8483 Use @code{directory} with no argument to reset the source path to its default value.
8486 Use @code{directory} with suitable arguments to reinstall the
8487 directories you want in the source path. You can add all the
8488 directories in one command.
8492 @section Source and Machine Code
8493 @cindex source line and its code address
8495 You can use the command @code{info line} to map source lines to program
8496 addresses (and vice versa), and the command @code{disassemble} to display
8497 a range of addresses as machine instructions. You can use the command
8498 @code{set disassemble-next-line} to set whether to disassemble next
8499 source line when execution stops. When run under @sc{gnu} Emacs
8500 mode, the @code{info line} command causes the arrow to point to the
8501 line specified. Also, @code{info line} prints addresses in symbolic form as
8507 @itemx info line @var{location}
8508 Print the starting and ending addresses of the compiled code for
8509 source line @var{location}. You can specify source lines in any of
8510 the ways documented in @ref{Specify Location}. With no @var{location}
8511 information about the current source line is printed.
8514 For example, we can use @code{info line} to discover the location of
8515 the object code for the first line of function
8516 @code{m4_changequote}:
8519 (@value{GDBP}) info line m4_changequote
8520 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8521 ends at 0x6350 <m4_changequote+4>.
8525 @cindex code address and its source line
8526 We can also inquire (using @code{*@var{addr}} as the form for
8527 @var{location}) what source line covers a particular address:
8529 (@value{GDBP}) info line *0x63ff
8530 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8531 ends at 0x6404 <m4_changequote+184>.
8534 @cindex @code{$_} and @code{info line}
8535 @cindex @code{x} command, default address
8536 @kindex x@r{(examine), and} info line
8537 After @code{info line}, the default address for the @code{x} command
8538 is changed to the starting address of the line, so that @samp{x/i} is
8539 sufficient to begin examining the machine code (@pxref{Memory,
8540 ,Examining Memory}). Also, this address is saved as the value of the
8541 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8544 @cindex info line, repeated calls
8545 After @code{info line}, using @code{info line} again without
8546 specifying a location will display information about the next source
8551 @cindex assembly instructions
8552 @cindex instructions, assembly
8553 @cindex machine instructions
8554 @cindex listing machine instructions
8556 @itemx disassemble /m
8557 @itemx disassemble /s
8558 @itemx disassemble /r
8559 This specialized command dumps a range of memory as machine
8560 instructions. It can also print mixed source+disassembly by specifying
8561 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8562 as well as in symbolic form by specifying the @code{/r} modifier.
8563 The default memory range is the function surrounding the
8564 program counter of the selected frame. A single argument to this
8565 command is a program counter value; @value{GDBN} dumps the function
8566 surrounding this value. When two arguments are given, they should
8567 be separated by a comma, possibly surrounded by whitespace. The
8568 arguments specify a range of addresses to dump, in one of two forms:
8571 @item @var{start},@var{end}
8572 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8573 @item @var{start},+@var{length}
8574 the addresses from @var{start} (inclusive) to
8575 @code{@var{start}+@var{length}} (exclusive).
8579 When 2 arguments are specified, the name of the function is also
8580 printed (since there could be several functions in the given range).
8582 The argument(s) can be any expression yielding a numeric value, such as
8583 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8585 If the range of memory being disassembled contains current program counter,
8586 the instruction at that location is shown with a @code{=>} marker.
8589 The following example shows the disassembly of a range of addresses of
8590 HP PA-RISC 2.0 code:
8593 (@value{GDBP}) disas 0x32c4, 0x32e4
8594 Dump of assembler code from 0x32c4 to 0x32e4:
8595 0x32c4 <main+204>: addil 0,dp
8596 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8597 0x32cc <main+212>: ldil 0x3000,r31
8598 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8599 0x32d4 <main+220>: ldo 0(r31),rp
8600 0x32d8 <main+224>: addil -0x800,dp
8601 0x32dc <main+228>: ldo 0x588(r1),r26
8602 0x32e0 <main+232>: ldil 0x3000,r31
8603 End of assembler dump.
8606 Here is an example showing mixed source+assembly for Intel x86
8607 with @code{/m} or @code{/s}, when the program is stopped just after
8608 function prologue in a non-optimized function with no inline code.
8611 (@value{GDBP}) disas /m main
8612 Dump of assembler code for function main:
8614 0x08048330 <+0>: push %ebp
8615 0x08048331 <+1>: mov %esp,%ebp
8616 0x08048333 <+3>: sub $0x8,%esp
8617 0x08048336 <+6>: and $0xfffffff0,%esp
8618 0x08048339 <+9>: sub $0x10,%esp
8620 6 printf ("Hello.\n");
8621 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8622 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8626 0x08048348 <+24>: mov $0x0,%eax
8627 0x0804834d <+29>: leave
8628 0x0804834e <+30>: ret
8630 End of assembler dump.
8633 The @code{/m} option is deprecated as its output is not useful when
8634 there is either inlined code or re-ordered code.
8635 The @code{/s} option is the preferred choice.
8636 Here is an example for AMD x86-64 showing the difference between
8637 @code{/m} output and @code{/s} output.
8638 This example has one inline function defined in a header file,
8639 and the code is compiled with @samp{-O2} optimization.
8640 Note how the @code{/m} output is missing the disassembly of
8641 several instructions that are present in the @code{/s} output.
8671 (@value{GDBP}) disas /m main
8672 Dump of assembler code for function main:
8676 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8677 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8681 0x000000000040041d <+29>: xor %eax,%eax
8682 0x000000000040041f <+31>: retq
8683 0x0000000000400420 <+32>: add %eax,%eax
8684 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8686 End of assembler dump.
8687 (@value{GDBP}) disas /s main
8688 Dump of assembler code for function main:
8692 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8696 0x0000000000400406 <+6>: test %eax,%eax
8697 0x0000000000400408 <+8>: js 0x400420 <main+32>
8702 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8703 0x000000000040040d <+13>: test %eax,%eax
8704 0x000000000040040f <+15>: mov $0x1,%eax
8705 0x0000000000400414 <+20>: cmovne %edx,%eax
8709 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8713 0x000000000040041d <+29>: xor %eax,%eax
8714 0x000000000040041f <+31>: retq
8718 0x0000000000400420 <+32>: add %eax,%eax
8719 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8720 End of assembler dump.
8723 Here is another example showing raw instructions in hex for AMD x86-64,
8726 (gdb) disas /r 0x400281,+10
8727 Dump of assembler code from 0x400281 to 0x40028b:
8728 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8729 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8730 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8731 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8732 End of assembler dump.
8735 Addresses cannot be specified as a location (@pxref{Specify Location}).
8736 So, for example, if you want to disassemble function @code{bar}
8737 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8738 and not @samp{disassemble foo.c:bar}.
8740 Some architectures have more than one commonly-used set of instruction
8741 mnemonics or other syntax.
8743 For programs that were dynamically linked and use shared libraries,
8744 instructions that call functions or branch to locations in the shared
8745 libraries might show a seemingly bogus location---it's actually a
8746 location of the relocation table. On some architectures, @value{GDBN}
8747 might be able to resolve these to actual function names.
8750 @kindex set disassembler-options
8751 @cindex disassembler options
8752 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8753 This command controls the passing of target specific information to
8754 the disassembler. For a list of valid options, please refer to the
8755 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8756 manual and/or the output of @kbd{objdump --help}
8757 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8758 The default value is the empty string.
8760 If it is necessary to specify more than one disassembler option, then
8761 multiple options can be placed together into a comma separated list.
8762 Currently this command is only supported on targets ARM, MIPS, PowerPC
8765 @kindex show disassembler-options
8766 @item show disassembler-options
8767 Show the current setting of the disassembler options.
8771 @kindex set disassembly-flavor
8772 @cindex Intel disassembly flavor
8773 @cindex AT&T disassembly flavor
8774 @item set disassembly-flavor @var{instruction-set}
8775 Select the instruction set to use when disassembling the
8776 program via the @code{disassemble} or @code{x/i} commands.
8778 Currently this command is only defined for the Intel x86 family. You
8779 can set @var{instruction-set} to either @code{intel} or @code{att}.
8780 The default is @code{att}, the AT&T flavor used by default by Unix
8781 assemblers for x86-based targets.
8783 @kindex show disassembly-flavor
8784 @item show disassembly-flavor
8785 Show the current setting of the disassembly flavor.
8789 @kindex set disassemble-next-line
8790 @kindex show disassemble-next-line
8791 @item set disassemble-next-line
8792 @itemx show disassemble-next-line
8793 Control whether or not @value{GDBN} will disassemble the next source
8794 line or instruction when execution stops. If ON, @value{GDBN} will
8795 display disassembly of the next source line when execution of the
8796 program being debugged stops. This is @emph{in addition} to
8797 displaying the source line itself, which @value{GDBN} always does if
8798 possible. If the next source line cannot be displayed for some reason
8799 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8800 info in the debug info), @value{GDBN} will display disassembly of the
8801 next @emph{instruction} instead of showing the next source line. If
8802 AUTO, @value{GDBN} will display disassembly of next instruction only
8803 if the source line cannot be displayed. This setting causes
8804 @value{GDBN} to display some feedback when you step through a function
8805 with no line info or whose source file is unavailable. The default is
8806 OFF, which means never display the disassembly of the next line or
8812 @chapter Examining Data
8814 @cindex printing data
8815 @cindex examining data
8818 The usual way to examine data in your program is with the @code{print}
8819 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8820 evaluates and prints the value of an expression of the language your
8821 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8822 Different Languages}). It may also print the expression using a
8823 Python-based pretty-printer (@pxref{Pretty Printing}).
8826 @item print @var{expr}
8827 @itemx print /@var{f} @var{expr}
8828 @var{expr} is an expression (in the source language). By default the
8829 value of @var{expr} is printed in a format appropriate to its data type;
8830 you can choose a different format by specifying @samp{/@var{f}}, where
8831 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8835 @itemx print /@var{f}
8836 @cindex reprint the last value
8837 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8838 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8839 conveniently inspect the same value in an alternative format.
8842 A more low-level way of examining data is with the @code{x} command.
8843 It examines data in memory at a specified address and prints it in a
8844 specified format. @xref{Memory, ,Examining Memory}.
8846 If you are interested in information about types, or about how the
8847 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8848 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8851 @cindex exploring hierarchical data structures
8853 Another way of examining values of expressions and type information is
8854 through the Python extension command @code{explore} (available only if
8855 the @value{GDBN} build is configured with @code{--with-python}). It
8856 offers an interactive way to start at the highest level (or, the most
8857 abstract level) of the data type of an expression (or, the data type
8858 itself) and explore all the way down to leaf scalar values/fields
8859 embedded in the higher level data types.
8862 @item explore @var{arg}
8863 @var{arg} is either an expression (in the source language), or a type
8864 visible in the current context of the program being debugged.
8867 The working of the @code{explore} command can be illustrated with an
8868 example. If a data type @code{struct ComplexStruct} is defined in your
8878 struct ComplexStruct
8880 struct SimpleStruct *ss_p;
8886 followed by variable declarations as
8889 struct SimpleStruct ss = @{ 10, 1.11 @};
8890 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8894 then, the value of the variable @code{cs} can be explored using the
8895 @code{explore} command as follows.
8899 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8900 the following fields:
8902 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8903 arr = <Enter 1 to explore this field of type `int [10]'>
8905 Enter the field number of choice:
8909 Since the fields of @code{cs} are not scalar values, you are being
8910 prompted to chose the field you want to explore. Let's say you choose
8911 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8912 pointer, you will be asked if it is pointing to a single value. From
8913 the declaration of @code{cs} above, it is indeed pointing to a single
8914 value, hence you enter @code{y}. If you enter @code{n}, then you will
8915 be asked if it were pointing to an array of values, in which case this
8916 field will be explored as if it were an array.
8919 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8920 Continue exploring it as a pointer to a single value [y/n]: y
8921 The value of `*(cs.ss_p)' is a struct/class of type `struct
8922 SimpleStruct' with the following fields:
8924 i = 10 .. (Value of type `int')
8925 d = 1.1100000000000001 .. (Value of type `double')
8927 Press enter to return to parent value:
8931 If the field @code{arr} of @code{cs} was chosen for exploration by
8932 entering @code{1} earlier, then since it is as array, you will be
8933 prompted to enter the index of the element in the array that you want
8937 `cs.arr' is an array of `int'.
8938 Enter the index of the element you want to explore in `cs.arr': 5
8940 `(cs.arr)[5]' is a scalar value of type `int'.
8944 Press enter to return to parent value:
8947 In general, at any stage of exploration, you can go deeper towards the
8948 leaf values by responding to the prompts appropriately, or hit the
8949 return key to return to the enclosing data structure (the @i{higher}
8950 level data structure).
8952 Similar to exploring values, you can use the @code{explore} command to
8953 explore types. Instead of specifying a value (which is typically a
8954 variable name or an expression valid in the current context of the
8955 program being debugged), you specify a type name. If you consider the
8956 same example as above, your can explore the type
8957 @code{struct ComplexStruct} by passing the argument
8958 @code{struct ComplexStruct} to the @code{explore} command.
8961 (gdb) explore struct ComplexStruct
8965 By responding to the prompts appropriately in the subsequent interactive
8966 session, you can explore the type @code{struct ComplexStruct} in a
8967 manner similar to how the value @code{cs} was explored in the above
8970 The @code{explore} command also has two sub-commands,
8971 @code{explore value} and @code{explore type}. The former sub-command is
8972 a way to explicitly specify that value exploration of the argument is
8973 being invoked, while the latter is a way to explicitly specify that type
8974 exploration of the argument is being invoked.
8977 @item explore value @var{expr}
8978 @cindex explore value
8979 This sub-command of @code{explore} explores the value of the
8980 expression @var{expr} (if @var{expr} is an expression valid in the
8981 current context of the program being debugged). The behavior of this
8982 command is identical to that of the behavior of the @code{explore}
8983 command being passed the argument @var{expr}.
8985 @item explore type @var{arg}
8986 @cindex explore type
8987 This sub-command of @code{explore} explores the type of @var{arg} (if
8988 @var{arg} is a type visible in the current context of program being
8989 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8990 is an expression valid in the current context of the program being
8991 debugged). If @var{arg} is a type, then the behavior of this command is
8992 identical to that of the @code{explore} command being passed the
8993 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8994 this command will be identical to that of the @code{explore} command
8995 being passed the type of @var{arg} as the argument.
8999 * Expressions:: Expressions
9000 * Ambiguous Expressions:: Ambiguous Expressions
9001 * Variables:: Program variables
9002 * Arrays:: Artificial arrays
9003 * Output Formats:: Output formats
9004 * Memory:: Examining memory
9005 * Auto Display:: Automatic display
9006 * Print Settings:: Print settings
9007 * Pretty Printing:: Python pretty printing
9008 * Value History:: Value history
9009 * Convenience Vars:: Convenience variables
9010 * Convenience Funs:: Convenience functions
9011 * Registers:: Registers
9012 * Floating Point Hardware:: Floating point hardware
9013 * Vector Unit:: Vector Unit
9014 * OS Information:: Auxiliary data provided by operating system
9015 * Memory Region Attributes:: Memory region attributes
9016 * Dump/Restore Files:: Copy between memory and a file
9017 * Core File Generation:: Cause a program dump its core
9018 * Character Sets:: Debugging programs that use a different
9019 character set than GDB does
9020 * Caching Target Data:: Data caching for targets
9021 * Searching Memory:: Searching memory for a sequence of bytes
9022 * Value Sizes:: Managing memory allocated for values
9026 @section Expressions
9029 @code{print} and many other @value{GDBN} commands accept an expression and
9030 compute its value. Any kind of constant, variable or operator defined
9031 by the programming language you are using is valid in an expression in
9032 @value{GDBN}. This includes conditional expressions, function calls,
9033 casts, and string constants. It also includes preprocessor macros, if
9034 you compiled your program to include this information; see
9037 @cindex arrays in expressions
9038 @value{GDBN} supports array constants in expressions input by
9039 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9040 you can use the command @code{print @{1, 2, 3@}} to create an array
9041 of three integers. If you pass an array to a function or assign it
9042 to a program variable, @value{GDBN} copies the array to memory that
9043 is @code{malloc}ed in the target program.
9045 Because C is so widespread, most of the expressions shown in examples in
9046 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9047 Languages}, for information on how to use expressions in other
9050 In this section, we discuss operators that you can use in @value{GDBN}
9051 expressions regardless of your programming language.
9053 @cindex casts, in expressions
9054 Casts are supported in all languages, not just in C, because it is so
9055 useful to cast a number into a pointer in order to examine a structure
9056 at that address in memory.
9057 @c FIXME: casts supported---Mod2 true?
9059 @value{GDBN} supports these operators, in addition to those common
9060 to programming languages:
9064 @samp{@@} is a binary operator for treating parts of memory as arrays.
9065 @xref{Arrays, ,Artificial Arrays}, for more information.
9068 @samp{::} allows you to specify a variable in terms of the file or
9069 function where it is defined. @xref{Variables, ,Program Variables}.
9071 @cindex @{@var{type}@}
9072 @cindex type casting memory
9073 @cindex memory, viewing as typed object
9074 @cindex casts, to view memory
9075 @item @{@var{type}@} @var{addr}
9076 Refers to an object of type @var{type} stored at address @var{addr} in
9077 memory. The address @var{addr} may be any expression whose value is
9078 an integer or pointer (but parentheses are required around binary
9079 operators, just as in a cast). This construct is allowed regardless
9080 of what kind of data is normally supposed to reside at @var{addr}.
9083 @node Ambiguous Expressions
9084 @section Ambiguous Expressions
9085 @cindex ambiguous expressions
9087 Expressions can sometimes contain some ambiguous elements. For instance,
9088 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9089 a single function name to be defined several times, for application in
9090 different contexts. This is called @dfn{overloading}. Another example
9091 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9092 templates and is typically instantiated several times, resulting in
9093 the same function name being defined in different contexts.
9095 In some cases and depending on the language, it is possible to adjust
9096 the expression to remove the ambiguity. For instance in C@t{++}, you
9097 can specify the signature of the function you want to break on, as in
9098 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9099 qualified name of your function often makes the expression unambiguous
9102 When an ambiguity that needs to be resolved is detected, the debugger
9103 has the capability to display a menu of numbered choices for each
9104 possibility, and then waits for the selection with the prompt @samp{>}.
9105 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9106 aborts the current command. If the command in which the expression was
9107 used allows more than one choice to be selected, the next option in the
9108 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9111 For example, the following session excerpt shows an attempt to set a
9112 breakpoint at the overloaded symbol @code{String::after}.
9113 We choose three particular definitions of that function name:
9115 @c FIXME! This is likely to change to show arg type lists, at least
9118 (@value{GDBP}) b String::after
9121 [2] file:String.cc; line number:867
9122 [3] file:String.cc; line number:860
9123 [4] file:String.cc; line number:875
9124 [5] file:String.cc; line number:853
9125 [6] file:String.cc; line number:846
9126 [7] file:String.cc; line number:735
9128 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9129 Breakpoint 2 at 0xb344: file String.cc, line 875.
9130 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9131 Multiple breakpoints were set.
9132 Use the "delete" command to delete unwanted
9139 @kindex set multiple-symbols
9140 @item set multiple-symbols @var{mode}
9141 @cindex multiple-symbols menu
9143 This option allows you to adjust the debugger behavior when an expression
9146 By default, @var{mode} is set to @code{all}. If the command with which
9147 the expression is used allows more than one choice, then @value{GDBN}
9148 automatically selects all possible choices. For instance, inserting
9149 a breakpoint on a function using an ambiguous name results in a breakpoint
9150 inserted on each possible match. However, if a unique choice must be made,
9151 then @value{GDBN} uses the menu to help you disambiguate the expression.
9152 For instance, printing the address of an overloaded function will result
9153 in the use of the menu.
9155 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9156 when an ambiguity is detected.
9158 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9159 an error due to the ambiguity and the command is aborted.
9161 @kindex show multiple-symbols
9162 @item show multiple-symbols
9163 Show the current value of the @code{multiple-symbols} setting.
9167 @section Program Variables
9169 The most common kind of expression to use is the name of a variable
9172 Variables in expressions are understood in the selected stack frame
9173 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9177 global (or file-static)
9184 visible according to the scope rules of the
9185 programming language from the point of execution in that frame
9188 @noindent This means that in the function
9203 you can examine and use the variable @code{a} whenever your program is
9204 executing within the function @code{foo}, but you can only use or
9205 examine the variable @code{b} while your program is executing inside
9206 the block where @code{b} is declared.
9208 @cindex variable name conflict
9209 There is an exception: you can refer to a variable or function whose
9210 scope is a single source file even if the current execution point is not
9211 in this file. But it is possible to have more than one such variable or
9212 function with the same name (in different source files). If that
9213 happens, referring to that name has unpredictable effects. If you wish,
9214 you can specify a static variable in a particular function or file by
9215 using the colon-colon (@code{::}) notation:
9217 @cindex colon-colon, context for variables/functions
9219 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9220 @cindex @code{::}, context for variables/functions
9223 @var{file}::@var{variable}
9224 @var{function}::@var{variable}
9228 Here @var{file} or @var{function} is the name of the context for the
9229 static @var{variable}. In the case of file names, you can use quotes to
9230 make sure @value{GDBN} parses the file name as a single word---for example,
9231 to print a global value of @code{x} defined in @file{f2.c}:
9234 (@value{GDBP}) p 'f2.c'::x
9237 The @code{::} notation is normally used for referring to
9238 static variables, since you typically disambiguate uses of local variables
9239 in functions by selecting the appropriate frame and using the
9240 simple name of the variable. However, you may also use this notation
9241 to refer to local variables in frames enclosing the selected frame:
9250 process (a); /* Stop here */
9261 For example, if there is a breakpoint at the commented line,
9262 here is what you might see
9263 when the program stops after executing the call @code{bar(0)}:
9268 (@value{GDBP}) p bar::a
9271 #2 0x080483d0 in foo (a=5) at foobar.c:12
9274 (@value{GDBP}) p bar::a
9278 @cindex C@t{++} scope resolution
9279 These uses of @samp{::} are very rarely in conflict with the very
9280 similar use of the same notation in C@t{++}. When they are in
9281 conflict, the C@t{++} meaning takes precedence; however, this can be
9282 overridden by quoting the file or function name with single quotes.
9284 For example, suppose the program is stopped in a method of a class
9285 that has a field named @code{includefile}, and there is also an
9286 include file named @file{includefile} that defines a variable,
9290 (@value{GDBP}) p includefile
9292 (@value{GDBP}) p includefile::some_global
9293 A syntax error in expression, near `'.
9294 (@value{GDBP}) p 'includefile'::some_global
9298 @cindex wrong values
9299 @cindex variable values, wrong
9300 @cindex function entry/exit, wrong values of variables
9301 @cindex optimized code, wrong values of variables
9303 @emph{Warning:} Occasionally, a local variable may appear to have the
9304 wrong value at certain points in a function---just after entry to a new
9305 scope, and just before exit.
9307 You may see this problem when you are stepping by machine instructions.
9308 This is because, on most machines, it takes more than one instruction to
9309 set up a stack frame (including local variable definitions); if you are
9310 stepping by machine instructions, variables may appear to have the wrong
9311 values until the stack frame is completely built. On exit, it usually
9312 also takes more than one machine instruction to destroy a stack frame;
9313 after you begin stepping through that group of instructions, local
9314 variable definitions may be gone.
9316 This may also happen when the compiler does significant optimizations.
9317 To be sure of always seeing accurate values, turn off all optimization
9320 @cindex ``No symbol "foo" in current context''
9321 Another possible effect of compiler optimizations is to optimize
9322 unused variables out of existence, or assign variables to registers (as
9323 opposed to memory addresses). Depending on the support for such cases
9324 offered by the debug info format used by the compiler, @value{GDBN}
9325 might not be able to display values for such local variables. If that
9326 happens, @value{GDBN} will print a message like this:
9329 No symbol "foo" in current context.
9332 To solve such problems, either recompile without optimizations, or use a
9333 different debug info format, if the compiler supports several such
9334 formats. @xref{Compilation}, for more information on choosing compiler
9335 options. @xref{C, ,C and C@t{++}}, for more information about debug
9336 info formats that are best suited to C@t{++} programs.
9338 If you ask to print an object whose contents are unknown to
9339 @value{GDBN}, e.g., because its data type is not completely specified
9340 by the debug information, @value{GDBN} will say @samp{<incomplete
9341 type>}. @xref{Symbols, incomplete type}, for more about this.
9343 @cindex no debug info variables
9344 If you try to examine or use the value of a (global) variable for
9345 which @value{GDBN} has no type information, e.g., because the program
9346 includes no debug information, @value{GDBN} displays an error message.
9347 @xref{Symbols, unknown type}, for more about unknown types. If you
9348 cast the variable to its declared type, @value{GDBN} gets the
9349 variable's value using the cast-to type as the variable's type. For
9350 example, in a C program:
9353 (@value{GDBP}) p var
9354 'var' has unknown type; cast it to its declared type
9355 (@value{GDBP}) p (float) var
9359 If you append @kbd{@@entry} string to a function parameter name you get its
9360 value at the time the function got called. If the value is not available an
9361 error message is printed. Entry values are available only with some compilers.
9362 Entry values are normally also printed at the function parameter list according
9363 to @ref{set print entry-values}.
9366 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9372 (gdb) print i@@entry
9376 Strings are identified as arrays of @code{char} values without specified
9377 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9378 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9379 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9380 defines literal string type @code{"char"} as @code{char} without a sign.
9385 signed char var1[] = "A";
9388 You get during debugging
9393 $2 = @{65 'A', 0 '\0'@}
9397 @section Artificial Arrays
9399 @cindex artificial array
9401 @kindex @@@r{, referencing memory as an array}
9402 It is often useful to print out several successive objects of the
9403 same type in memory; a section of an array, or an array of
9404 dynamically determined size for which only a pointer exists in the
9407 You can do this by referring to a contiguous span of memory as an
9408 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9409 operand of @samp{@@} should be the first element of the desired array
9410 and be an individual object. The right operand should be the desired length
9411 of the array. The result is an array value whose elements are all of
9412 the type of the left argument. The first element is actually the left
9413 argument; the second element comes from bytes of memory immediately
9414 following those that hold the first element, and so on. Here is an
9415 example. If a program says
9418 int *array = (int *) malloc (len * sizeof (int));
9422 you can print the contents of @code{array} with
9428 The left operand of @samp{@@} must reside in memory. Array values made
9429 with @samp{@@} in this way behave just like other arrays in terms of
9430 subscripting, and are coerced to pointers when used in expressions.
9431 Artificial arrays most often appear in expressions via the value history
9432 (@pxref{Value History, ,Value History}), after printing one out.
9434 Another way to create an artificial array is to use a cast.
9435 This re-interprets a value as if it were an array.
9436 The value need not be in memory:
9438 (@value{GDBP}) p/x (short[2])0x12345678
9439 $1 = @{0x1234, 0x5678@}
9442 As a convenience, if you leave the array length out (as in
9443 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9444 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9446 (@value{GDBP}) p/x (short[])0x12345678
9447 $2 = @{0x1234, 0x5678@}
9450 Sometimes the artificial array mechanism is not quite enough; in
9451 moderately complex data structures, the elements of interest may not
9452 actually be adjacent---for example, if you are interested in the values
9453 of pointers in an array. One useful work-around in this situation is
9454 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9455 Variables}) as a counter in an expression that prints the first
9456 interesting value, and then repeat that expression via @key{RET}. For
9457 instance, suppose you have an array @code{dtab} of pointers to
9458 structures, and you are interested in the values of a field @code{fv}
9459 in each structure. Here is an example of what you might type:
9469 @node Output Formats
9470 @section Output Formats
9472 @cindex formatted output
9473 @cindex output formats
9474 By default, @value{GDBN} prints a value according to its data type. Sometimes
9475 this is not what you want. For example, you might want to print a number
9476 in hex, or a pointer in decimal. Or you might want to view data in memory
9477 at a certain address as a character string or as an instruction. To do
9478 these things, specify an @dfn{output format} when you print a value.
9480 The simplest use of output formats is to say how to print a value
9481 already computed. This is done by starting the arguments of the
9482 @code{print} command with a slash and a format letter. The format
9483 letters supported are:
9487 Regard the bits of the value as an integer, and print the integer in
9491 Print as integer in signed decimal.
9494 Print as integer in unsigned decimal.
9497 Print as integer in octal.
9500 Print as integer in binary. The letter @samp{t} stands for ``two''.
9501 @footnote{@samp{b} cannot be used because these format letters are also
9502 used with the @code{x} command, where @samp{b} stands for ``byte'';
9503 see @ref{Memory,,Examining Memory}.}
9506 @cindex unknown address, locating
9507 @cindex locate address
9508 Print as an address, both absolute in hexadecimal and as an offset from
9509 the nearest preceding symbol. You can use this format used to discover
9510 where (in what function) an unknown address is located:
9513 (@value{GDBP}) p/a 0x54320
9514 $3 = 0x54320 <_initialize_vx+396>
9518 The command @code{info symbol 0x54320} yields similar results.
9519 @xref{Symbols, info symbol}.
9522 Regard as an integer and print it as a character constant. This
9523 prints both the numerical value and its character representation. The
9524 character representation is replaced with the octal escape @samp{\nnn}
9525 for characters outside the 7-bit @sc{ascii} range.
9527 Without this format, @value{GDBN} displays @code{char},
9528 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9529 constants. Single-byte members of vectors are displayed as integer
9533 Regard the bits of the value as a floating point number and print
9534 using typical floating point syntax.
9537 @cindex printing strings
9538 @cindex printing byte arrays
9539 Regard as a string, if possible. With this format, pointers to single-byte
9540 data are displayed as null-terminated strings and arrays of single-byte data
9541 are displayed as fixed-length strings. Other values are displayed in their
9544 Without this format, @value{GDBN} displays pointers to and arrays of
9545 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9546 strings. Single-byte members of a vector are displayed as an integer
9550 Like @samp{x} formatting, the value is treated as an integer and
9551 printed as hexadecimal, but leading zeros are printed to pad the value
9552 to the size of the integer type.
9555 @cindex raw printing
9556 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9557 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9558 Printing}). This typically results in a higher-level display of the
9559 value's contents. The @samp{r} format bypasses any Python
9560 pretty-printer which might exist.
9563 For example, to print the program counter in hex (@pxref{Registers}), type
9570 Note that no space is required before the slash; this is because command
9571 names in @value{GDBN} cannot contain a slash.
9573 To reprint the last value in the value history with a different format,
9574 you can use the @code{print} command with just a format and no
9575 expression. For example, @samp{p/x} reprints the last value in hex.
9578 @section Examining Memory
9580 You can use the command @code{x} (for ``examine'') to examine memory in
9581 any of several formats, independently of your program's data types.
9583 @cindex examining memory
9585 @kindex x @r{(examine memory)}
9586 @item x/@var{nfu} @var{addr}
9589 Use the @code{x} command to examine memory.
9592 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9593 much memory to display and how to format it; @var{addr} is an
9594 expression giving the address where you want to start displaying memory.
9595 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9596 Several commands set convenient defaults for @var{addr}.
9599 @item @var{n}, the repeat count
9600 The repeat count is a decimal integer; the default is 1. It specifies
9601 how much memory (counting by units @var{u}) to display. If a negative
9602 number is specified, memory is examined backward from @var{addr}.
9603 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9606 @item @var{f}, the display format
9607 The display format is one of the formats used by @code{print}
9608 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9609 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9610 The default is @samp{x} (hexadecimal) initially. The default changes
9611 each time you use either @code{x} or @code{print}.
9613 @item @var{u}, the unit size
9614 The unit size is any of
9620 Halfwords (two bytes).
9622 Words (four bytes). This is the initial default.
9624 Giant words (eight bytes).
9627 Each time you specify a unit size with @code{x}, that size becomes the
9628 default unit the next time you use @code{x}. For the @samp{i} format,
9629 the unit size is ignored and is normally not written. For the @samp{s} format,
9630 the unit size defaults to @samp{b}, unless it is explicitly given.
9631 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9632 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9633 Note that the results depend on the programming language of the
9634 current compilation unit. If the language is C, the @samp{s}
9635 modifier will use the UTF-16 encoding while @samp{w} will use
9636 UTF-32. The encoding is set by the programming language and cannot
9639 @item @var{addr}, starting display address
9640 @var{addr} is the address where you want @value{GDBN} to begin displaying
9641 memory. The expression need not have a pointer value (though it may);
9642 it is always interpreted as an integer address of a byte of memory.
9643 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9644 @var{addr} is usually just after the last address examined---but several
9645 other commands also set the default address: @code{info breakpoints} (to
9646 the address of the last breakpoint listed), @code{info line} (to the
9647 starting address of a line), and @code{print} (if you use it to display
9648 a value from memory).
9651 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9652 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9653 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9654 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9655 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9657 You can also specify a negative repeat count to examine memory backward
9658 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9659 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9661 Since the letters indicating unit sizes are all distinct from the
9662 letters specifying output formats, you do not have to remember whether
9663 unit size or format comes first; either order works. The output
9664 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9665 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9667 Even though the unit size @var{u} is ignored for the formats @samp{s}
9668 and @samp{i}, you might still want to use a count @var{n}; for example,
9669 @samp{3i} specifies that you want to see three machine instructions,
9670 including any operands. For convenience, especially when used with
9671 the @code{display} command, the @samp{i} format also prints branch delay
9672 slot instructions, if any, beyond the count specified, which immediately
9673 follow the last instruction that is within the count. The command
9674 @code{disassemble} gives an alternative way of inspecting machine
9675 instructions; see @ref{Machine Code,,Source and Machine Code}.
9677 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9678 the command displays null-terminated strings or instructions before the given
9679 address as many as the absolute value of the given number. For the @samp{i}
9680 format, we use line number information in the debug info to accurately locate
9681 instruction boundaries while disassembling backward. If line info is not
9682 available, the command stops examining memory with an error message.
9684 All the defaults for the arguments to @code{x} are designed to make it
9685 easy to continue scanning memory with minimal specifications each time
9686 you use @code{x}. For example, after you have inspected three machine
9687 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9688 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9689 the repeat count @var{n} is used again; the other arguments default as
9690 for successive uses of @code{x}.
9692 When examining machine instructions, the instruction at current program
9693 counter is shown with a @code{=>} marker. For example:
9696 (@value{GDBP}) x/5i $pc-6
9697 0x804837f <main+11>: mov %esp,%ebp
9698 0x8048381 <main+13>: push %ecx
9699 0x8048382 <main+14>: sub $0x4,%esp
9700 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9701 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9704 @cindex @code{$_}, @code{$__}, and value history
9705 The addresses and contents printed by the @code{x} command are not saved
9706 in the value history because there is often too much of them and they
9707 would get in the way. Instead, @value{GDBN} makes these values available for
9708 subsequent use in expressions as values of the convenience variables
9709 @code{$_} and @code{$__}. After an @code{x} command, the last address
9710 examined is available for use in expressions in the convenience variable
9711 @code{$_}. The contents of that address, as examined, are available in
9712 the convenience variable @code{$__}.
9714 If the @code{x} command has a repeat count, the address and contents saved
9715 are from the last memory unit printed; this is not the same as the last
9716 address printed if several units were printed on the last line of output.
9718 @anchor{addressable memory unit}
9719 @cindex addressable memory unit
9720 Most targets have an addressable memory unit size of 8 bits. This means
9721 that to each memory address are associated 8 bits of data. Some
9722 targets, however, have other addressable memory unit sizes.
9723 Within @value{GDBN} and this document, the term
9724 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9725 when explicitly referring to a chunk of data of that size. The word
9726 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9727 the addressable memory unit size of the target. For most systems,
9728 addressable memory unit is a synonym of byte.
9730 @cindex remote memory comparison
9731 @cindex target memory comparison
9732 @cindex verify remote memory image
9733 @cindex verify target memory image
9734 When you are debugging a program running on a remote target machine
9735 (@pxref{Remote Debugging}), you may wish to verify the program's image
9736 in the remote machine's memory against the executable file you
9737 downloaded to the target. Or, on any target, you may want to check
9738 whether the program has corrupted its own read-only sections. The
9739 @code{compare-sections} command is provided for such situations.
9742 @kindex compare-sections
9743 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9744 Compare the data of a loadable section @var{section-name} in the
9745 executable file of the program being debugged with the same section in
9746 the target machine's memory, and report any mismatches. With no
9747 arguments, compares all loadable sections. With an argument of
9748 @code{-r}, compares all loadable read-only sections.
9750 Note: for remote targets, this command can be accelerated if the
9751 target supports computing the CRC checksum of a block of memory
9752 (@pxref{qCRC packet}).
9756 @section Automatic Display
9757 @cindex automatic display
9758 @cindex display of expressions
9760 If you find that you want to print the value of an expression frequently
9761 (to see how it changes), you might want to add it to the @dfn{automatic
9762 display list} so that @value{GDBN} prints its value each time your program stops.
9763 Each expression added to the list is given a number to identify it;
9764 to remove an expression from the list, you specify that number.
9765 The automatic display looks like this:
9769 3: bar[5] = (struct hack *) 0x3804
9773 This display shows item numbers, expressions and their current values. As with
9774 displays you request manually using @code{x} or @code{print}, you can
9775 specify the output format you prefer; in fact, @code{display} decides
9776 whether to use @code{print} or @code{x} depending your format
9777 specification---it uses @code{x} if you specify either the @samp{i}
9778 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9782 @item display @var{expr}
9783 Add the expression @var{expr} to the list of expressions to display
9784 each time your program stops. @xref{Expressions, ,Expressions}.
9786 @code{display} does not repeat if you press @key{RET} again after using it.
9788 @item display/@var{fmt} @var{expr}
9789 For @var{fmt} specifying only a display format and not a size or
9790 count, add the expression @var{expr} to the auto-display list but
9791 arrange to display it each time in the specified format @var{fmt}.
9792 @xref{Output Formats,,Output Formats}.
9794 @item display/@var{fmt} @var{addr}
9795 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9796 number of units, add the expression @var{addr} as a memory address to
9797 be examined each time your program stops. Examining means in effect
9798 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9801 For example, @samp{display/i $pc} can be helpful, to see the machine
9802 instruction about to be executed each time execution stops (@samp{$pc}
9803 is a common name for the program counter; @pxref{Registers, ,Registers}).
9806 @kindex delete display
9808 @item undisplay @var{dnums}@dots{}
9809 @itemx delete display @var{dnums}@dots{}
9810 Remove items from the list of expressions to display. Specify the
9811 numbers of the displays that you want affected with the command
9812 argument @var{dnums}. It can be a single display number, one of the
9813 numbers shown in the first field of the @samp{info display} display;
9814 or it could be a range of display numbers, as in @code{2-4}.
9816 @code{undisplay} does not repeat if you press @key{RET} after using it.
9817 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9819 @kindex disable display
9820 @item disable display @var{dnums}@dots{}
9821 Disable the display of item numbers @var{dnums}. A disabled display
9822 item is not printed automatically, but is not forgotten. It may be
9823 enabled again later. Specify the numbers of the displays that you
9824 want affected with the command argument @var{dnums}. It can be a
9825 single display number, one of the numbers shown in the first field of
9826 the @samp{info display} display; or it could be a range of display
9827 numbers, as in @code{2-4}.
9829 @kindex enable display
9830 @item enable display @var{dnums}@dots{}
9831 Enable display of item numbers @var{dnums}. It becomes effective once
9832 again in auto display of its expression, until you specify otherwise.
9833 Specify the numbers of the displays that you want affected with the
9834 command argument @var{dnums}. It can be a single display number, one
9835 of the numbers shown in the first field of the @samp{info display}
9836 display; or it could be a range of display numbers, as in @code{2-4}.
9839 Display the current values of the expressions on the list, just as is
9840 done when your program stops.
9842 @kindex info display
9844 Print the list of expressions previously set up to display
9845 automatically, each one with its item number, but without showing the
9846 values. This includes disabled expressions, which are marked as such.
9847 It also includes expressions which would not be displayed right now
9848 because they refer to automatic variables not currently available.
9851 @cindex display disabled out of scope
9852 If a display expression refers to local variables, then it does not make
9853 sense outside the lexical context for which it was set up. Such an
9854 expression is disabled when execution enters a context where one of its
9855 variables is not defined. For example, if you give the command
9856 @code{display last_char} while inside a function with an argument
9857 @code{last_char}, @value{GDBN} displays this argument while your program
9858 continues to stop inside that function. When it stops elsewhere---where
9859 there is no variable @code{last_char}---the display is disabled
9860 automatically. The next time your program stops where @code{last_char}
9861 is meaningful, you can enable the display expression once again.
9863 @node Print Settings
9864 @section Print Settings
9866 @cindex format options
9867 @cindex print settings
9868 @value{GDBN} provides the following ways to control how arrays, structures,
9869 and symbols are printed.
9872 These settings are useful for debugging programs in any language:
9876 @item set print address
9877 @itemx set print address on
9878 @cindex print/don't print memory addresses
9879 @value{GDBN} prints memory addresses showing the location of stack
9880 traces, structure values, pointer values, breakpoints, and so forth,
9881 even when it also displays the contents of those addresses. The default
9882 is @code{on}. For example, this is what a stack frame display looks like with
9883 @code{set print address on}:
9888 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9890 530 if (lquote != def_lquote)
9894 @item set print address off
9895 Do not print addresses when displaying their contents. For example,
9896 this is the same stack frame displayed with @code{set print address off}:
9900 (@value{GDBP}) set print addr off
9902 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9903 530 if (lquote != def_lquote)
9907 You can use @samp{set print address off} to eliminate all machine
9908 dependent displays from the @value{GDBN} interface. For example, with
9909 @code{print address off}, you should get the same text for backtraces on
9910 all machines---whether or not they involve pointer arguments.
9913 @item show print address
9914 Show whether or not addresses are to be printed.
9917 When @value{GDBN} prints a symbolic address, it normally prints the
9918 closest earlier symbol plus an offset. If that symbol does not uniquely
9919 identify the address (for example, it is a name whose scope is a single
9920 source file), you may need to clarify. One way to do this is with
9921 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9922 you can set @value{GDBN} to print the source file and line number when
9923 it prints a symbolic address:
9926 @item set print symbol-filename on
9927 @cindex source file and line of a symbol
9928 @cindex symbol, source file and line
9929 Tell @value{GDBN} to print the source file name and line number of a
9930 symbol in the symbolic form of an address.
9932 @item set print symbol-filename off
9933 Do not print source file name and line number of a symbol. This is the
9936 @item show print symbol-filename
9937 Show whether or not @value{GDBN} will print the source file name and
9938 line number of a symbol in the symbolic form of an address.
9941 Another situation where it is helpful to show symbol filenames and line
9942 numbers is when disassembling code; @value{GDBN} shows you the line
9943 number and source file that corresponds to each instruction.
9945 Also, you may wish to see the symbolic form only if the address being
9946 printed is reasonably close to the closest earlier symbol:
9949 @item set print max-symbolic-offset @var{max-offset}
9950 @itemx set print max-symbolic-offset unlimited
9951 @cindex maximum value for offset of closest symbol
9952 Tell @value{GDBN} to only display the symbolic form of an address if the
9953 offset between the closest earlier symbol and the address is less than
9954 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9955 to always print the symbolic form of an address if any symbol precedes
9956 it. Zero is equivalent to @code{unlimited}.
9958 @item show print max-symbolic-offset
9959 Ask how large the maximum offset is that @value{GDBN} prints in a
9963 @cindex wild pointer, interpreting
9964 @cindex pointer, finding referent
9965 If you have a pointer and you are not sure where it points, try
9966 @samp{set print symbol-filename on}. Then you can determine the name
9967 and source file location of the variable where it points, using
9968 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9969 For example, here @value{GDBN} shows that a variable @code{ptt} points
9970 at another variable @code{t}, defined in @file{hi2.c}:
9973 (@value{GDBP}) set print symbol-filename on
9974 (@value{GDBP}) p/a ptt
9975 $4 = 0xe008 <t in hi2.c>
9979 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9980 does not show the symbol name and filename of the referent, even with
9981 the appropriate @code{set print} options turned on.
9984 You can also enable @samp{/a}-like formatting all the time using
9985 @samp{set print symbol on}:
9988 @item set print symbol on
9989 Tell @value{GDBN} to print the symbol corresponding to an address, if
9992 @item set print symbol off
9993 Tell @value{GDBN} not to print the symbol corresponding to an
9994 address. In this mode, @value{GDBN} will still print the symbol
9995 corresponding to pointers to functions. This is the default.
9997 @item show print symbol
9998 Show whether @value{GDBN} will display the symbol corresponding to an
10002 Other settings control how different kinds of objects are printed:
10005 @item set print array
10006 @itemx set print array on
10007 @cindex pretty print arrays
10008 Pretty print arrays. This format is more convenient to read,
10009 but uses more space. The default is off.
10011 @item set print array off
10012 Return to compressed format for arrays.
10014 @item show print array
10015 Show whether compressed or pretty format is selected for displaying
10018 @cindex print array indexes
10019 @item set print array-indexes
10020 @itemx set print array-indexes on
10021 Print the index of each element when displaying arrays. May be more
10022 convenient to locate a given element in the array or quickly find the
10023 index of a given element in that printed array. The default is off.
10025 @item set print array-indexes off
10026 Stop printing element indexes when displaying arrays.
10028 @item show print array-indexes
10029 Show whether the index of each element is printed when displaying
10032 @item set print elements @var{number-of-elements}
10033 @itemx set print elements unlimited
10034 @cindex number of array elements to print
10035 @cindex limit on number of printed array elements
10036 Set a limit on how many elements of an array @value{GDBN} will print.
10037 If @value{GDBN} is printing a large array, it stops printing after it has
10038 printed the number of elements set by the @code{set print elements} command.
10039 This limit also applies to the display of strings.
10040 When @value{GDBN} starts, this limit is set to 200.
10041 Setting @var{number-of-elements} to @code{unlimited} or zero means
10042 that the number of elements to print is unlimited.
10044 @item show print elements
10045 Display the number of elements of a large array that @value{GDBN} will print.
10046 If the number is 0, then the printing is unlimited.
10048 @item set print frame-arguments @var{value}
10049 @kindex set print frame-arguments
10050 @cindex printing frame argument values
10051 @cindex print all frame argument values
10052 @cindex print frame argument values for scalars only
10053 @cindex do not print frame argument values
10054 This command allows to control how the values of arguments are printed
10055 when the debugger prints a frame (@pxref{Frames}). The possible
10060 The values of all arguments are printed.
10063 Print the value of an argument only if it is a scalar. The value of more
10064 complex arguments such as arrays, structures, unions, etc, is replaced
10065 by @code{@dots{}}. This is the default. Here is an example where
10066 only scalar arguments are shown:
10069 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10074 None of the argument values are printed. Instead, the value of each argument
10075 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10078 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10083 By default, only scalar arguments are printed. This command can be used
10084 to configure the debugger to print the value of all arguments, regardless
10085 of their type. However, it is often advantageous to not print the value
10086 of more complex parameters. For instance, it reduces the amount of
10087 information printed in each frame, making the backtrace more readable.
10088 Also, it improves performance when displaying Ada frames, because
10089 the computation of large arguments can sometimes be CPU-intensive,
10090 especially in large applications. Setting @code{print frame-arguments}
10091 to @code{scalars} (the default) or @code{none} avoids this computation,
10092 thus speeding up the display of each Ada frame.
10094 @item show print frame-arguments
10095 Show how the value of arguments should be displayed when printing a frame.
10097 @item set print raw frame-arguments on
10098 Print frame arguments in raw, non pretty-printed, form.
10100 @item set print raw frame-arguments off
10101 Print frame arguments in pretty-printed form, if there is a pretty-printer
10102 for the value (@pxref{Pretty Printing}),
10103 otherwise print the value in raw form.
10104 This is the default.
10106 @item show print raw frame-arguments
10107 Show whether to print frame arguments in raw form.
10109 @anchor{set print entry-values}
10110 @item set print entry-values @var{value}
10111 @kindex set print entry-values
10112 Set printing of frame argument values at function entry. In some cases
10113 @value{GDBN} can determine the value of function argument which was passed by
10114 the function caller, even if the value was modified inside the called function
10115 and therefore is different. With optimized code, the current value could be
10116 unavailable, but the entry value may still be known.
10118 The default value is @code{default} (see below for its description). Older
10119 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10120 this feature will behave in the @code{default} setting the same way as with the
10123 This functionality is currently supported only by DWARF 2 debugging format and
10124 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10125 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10128 The @var{value} parameter can be one of the following:
10132 Print only actual parameter values, never print values from function entry
10136 #0 different (val=6)
10137 #0 lost (val=<optimized out>)
10139 #0 invalid (val=<optimized out>)
10143 Print only parameter values from function entry point. The actual parameter
10144 values are never printed.
10146 #0 equal (val@@entry=5)
10147 #0 different (val@@entry=5)
10148 #0 lost (val@@entry=5)
10149 #0 born (val@@entry=<optimized out>)
10150 #0 invalid (val@@entry=<optimized out>)
10154 Print only parameter values from function entry point. If value from function
10155 entry point is not known while the actual value is known, print the actual
10156 value for such parameter.
10158 #0 equal (val@@entry=5)
10159 #0 different (val@@entry=5)
10160 #0 lost (val@@entry=5)
10162 #0 invalid (val@@entry=<optimized out>)
10166 Print actual parameter values. If actual parameter value is not known while
10167 value from function entry point is known, print the entry point value for such
10171 #0 different (val=6)
10172 #0 lost (val@@entry=5)
10174 #0 invalid (val=<optimized out>)
10178 Always print both the actual parameter value and its value from function entry
10179 point, even if values of one or both are not available due to compiler
10182 #0 equal (val=5, val@@entry=5)
10183 #0 different (val=6, val@@entry=5)
10184 #0 lost (val=<optimized out>, val@@entry=5)
10185 #0 born (val=10, val@@entry=<optimized out>)
10186 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10190 Print the actual parameter value if it is known and also its value from
10191 function entry point if it is known. If neither is known, print for the actual
10192 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10193 values are known and identical, print the shortened
10194 @code{param=param@@entry=VALUE} notation.
10196 #0 equal (val=val@@entry=5)
10197 #0 different (val=6, val@@entry=5)
10198 #0 lost (val@@entry=5)
10200 #0 invalid (val=<optimized out>)
10204 Always print the actual parameter value. Print also its value from function
10205 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10206 if both values are known and identical, print the shortened
10207 @code{param=param@@entry=VALUE} notation.
10209 #0 equal (val=val@@entry=5)
10210 #0 different (val=6, val@@entry=5)
10211 #0 lost (val=<optimized out>, val@@entry=5)
10213 #0 invalid (val=<optimized out>)
10217 For analysis messages on possible failures of frame argument values at function
10218 entry resolution see @ref{set debug entry-values}.
10220 @item show print entry-values
10221 Show the method being used for printing of frame argument values at function
10224 @item set print repeats @var{number-of-repeats}
10225 @itemx set print repeats unlimited
10226 @cindex repeated array elements
10227 Set the threshold for suppressing display of repeated array
10228 elements. When the number of consecutive identical elements of an
10229 array exceeds the threshold, @value{GDBN} prints the string
10230 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10231 identical repetitions, instead of displaying the identical elements
10232 themselves. Setting the threshold to @code{unlimited} or zero will
10233 cause all elements to be individually printed. The default threshold
10236 @item show print repeats
10237 Display the current threshold for printing repeated identical
10240 @item set print null-stop
10241 @cindex @sc{null} elements in arrays
10242 Cause @value{GDBN} to stop printing the characters of an array when the first
10243 @sc{null} is encountered. This is useful when large arrays actually
10244 contain only short strings.
10245 The default is off.
10247 @item show print null-stop
10248 Show whether @value{GDBN} stops printing an array on the first
10249 @sc{null} character.
10251 @item set print pretty on
10252 @cindex print structures in indented form
10253 @cindex indentation in structure display
10254 Cause @value{GDBN} to print structures in an indented format with one member
10255 per line, like this:
10270 @item set print pretty off
10271 Cause @value{GDBN} to print structures in a compact format, like this:
10275 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10276 meat = 0x54 "Pork"@}
10281 This is the default format.
10283 @item show print pretty
10284 Show which format @value{GDBN} is using to print structures.
10286 @item set print sevenbit-strings on
10287 @cindex eight-bit characters in strings
10288 @cindex octal escapes in strings
10289 Print using only seven-bit characters; if this option is set,
10290 @value{GDBN} displays any eight-bit characters (in strings or
10291 character values) using the notation @code{\}@var{nnn}. This setting is
10292 best if you are working in English (@sc{ascii}) and you use the
10293 high-order bit of characters as a marker or ``meta'' bit.
10295 @item set print sevenbit-strings off
10296 Print full eight-bit characters. This allows the use of more
10297 international character sets, and is the default.
10299 @item show print sevenbit-strings
10300 Show whether or not @value{GDBN} is printing only seven-bit characters.
10302 @item set print union on
10303 @cindex unions in structures, printing
10304 Tell @value{GDBN} to print unions which are contained in structures
10305 and other unions. This is the default setting.
10307 @item set print union off
10308 Tell @value{GDBN} not to print unions which are contained in
10309 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10312 @item show print union
10313 Ask @value{GDBN} whether or not it will print unions which are contained in
10314 structures and other unions.
10316 For example, given the declarations
10319 typedef enum @{Tree, Bug@} Species;
10320 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10321 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10332 struct thing foo = @{Tree, @{Acorn@}@};
10336 with @code{set print union on} in effect @samp{p foo} would print
10339 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10343 and with @code{set print union off} in effect it would print
10346 $1 = @{it = Tree, form = @{...@}@}
10350 @code{set print union} affects programs written in C-like languages
10356 These settings are of interest when debugging C@t{++} programs:
10359 @cindex demangling C@t{++} names
10360 @item set print demangle
10361 @itemx set print demangle on
10362 Print C@t{++} names in their source form rather than in the encoded
10363 (``mangled'') form passed to the assembler and linker for type-safe
10364 linkage. The default is on.
10366 @item show print demangle
10367 Show whether C@t{++} names are printed in mangled or demangled form.
10369 @item set print asm-demangle
10370 @itemx set print asm-demangle on
10371 Print C@t{++} names in their source form rather than their mangled form, even
10372 in assembler code printouts such as instruction disassemblies.
10373 The default is off.
10375 @item show print asm-demangle
10376 Show whether C@t{++} names in assembly listings are printed in mangled
10379 @cindex C@t{++} symbol decoding style
10380 @cindex symbol decoding style, C@t{++}
10381 @kindex set demangle-style
10382 @item set demangle-style @var{style}
10383 Choose among several encoding schemes used by different compilers to
10384 represent C@t{++} names. The choices for @var{style} are currently:
10388 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10389 This is the default.
10392 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10395 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10398 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10401 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10402 @strong{Warning:} this setting alone is not sufficient to allow
10403 debugging @code{cfront}-generated executables. @value{GDBN} would
10404 require further enhancement to permit that.
10407 If you omit @var{style}, you will see a list of possible formats.
10409 @item show demangle-style
10410 Display the encoding style currently in use for decoding C@t{++} symbols.
10412 @item set print object
10413 @itemx set print object on
10414 @cindex derived type of an object, printing
10415 @cindex display derived types
10416 When displaying a pointer to an object, identify the @emph{actual}
10417 (derived) type of the object rather than the @emph{declared} type, using
10418 the virtual function table. Note that the virtual function table is
10419 required---this feature can only work for objects that have run-time
10420 type identification; a single virtual method in the object's declared
10421 type is sufficient. Note that this setting is also taken into account when
10422 working with variable objects via MI (@pxref{GDB/MI}).
10424 @item set print object off
10425 Display only the declared type of objects, without reference to the
10426 virtual function table. This is the default setting.
10428 @item show print object
10429 Show whether actual, or declared, object types are displayed.
10431 @item set print static-members
10432 @itemx set print static-members on
10433 @cindex static members of C@t{++} objects
10434 Print static members when displaying a C@t{++} object. The default is on.
10436 @item set print static-members off
10437 Do not print static members when displaying a C@t{++} object.
10439 @item show print static-members
10440 Show whether C@t{++} static members are printed or not.
10442 @item set print pascal_static-members
10443 @itemx set print pascal_static-members on
10444 @cindex static members of Pascal objects
10445 @cindex Pascal objects, static members display
10446 Print static members when displaying a Pascal object. The default is on.
10448 @item set print pascal_static-members off
10449 Do not print static members when displaying a Pascal object.
10451 @item show print pascal_static-members
10452 Show whether Pascal static members are printed or not.
10454 @c These don't work with HP ANSI C++ yet.
10455 @item set print vtbl
10456 @itemx set print vtbl on
10457 @cindex pretty print C@t{++} virtual function tables
10458 @cindex virtual functions (C@t{++}) display
10459 @cindex VTBL display
10460 Pretty print C@t{++} virtual function tables. The default is off.
10461 (The @code{vtbl} commands do not work on programs compiled with the HP
10462 ANSI C@t{++} compiler (@code{aCC}).)
10464 @item set print vtbl off
10465 Do not pretty print C@t{++} virtual function tables.
10467 @item show print vtbl
10468 Show whether C@t{++} virtual function tables are pretty printed, or not.
10471 @node Pretty Printing
10472 @section Pretty Printing
10474 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10475 Python code. It greatly simplifies the display of complex objects. This
10476 mechanism works for both MI and the CLI.
10479 * Pretty-Printer Introduction:: Introduction to pretty-printers
10480 * Pretty-Printer Example:: An example pretty-printer
10481 * Pretty-Printer Commands:: Pretty-printer commands
10484 @node Pretty-Printer Introduction
10485 @subsection Pretty-Printer Introduction
10487 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10488 registered for the value. If there is then @value{GDBN} invokes the
10489 pretty-printer to print the value. Otherwise the value is printed normally.
10491 Pretty-printers are normally named. This makes them easy to manage.
10492 The @samp{info pretty-printer} command will list all the installed
10493 pretty-printers with their names.
10494 If a pretty-printer can handle multiple data types, then its
10495 @dfn{subprinters} are the printers for the individual data types.
10496 Each such subprinter has its own name.
10497 The format of the name is @var{printer-name};@var{subprinter-name}.
10499 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10500 Typically they are automatically loaded and registered when the corresponding
10501 debug information is loaded, thus making them available without having to
10502 do anything special.
10504 There are three places where a pretty-printer can be registered.
10508 Pretty-printers registered globally are available when debugging
10512 Pretty-printers registered with a program space are available only
10513 when debugging that program.
10514 @xref{Progspaces In Python}, for more details on program spaces in Python.
10517 Pretty-printers registered with an objfile are loaded and unloaded
10518 with the corresponding objfile (e.g., shared library).
10519 @xref{Objfiles In Python}, for more details on objfiles in Python.
10522 @xref{Selecting Pretty-Printers}, for further information on how
10523 pretty-printers are selected,
10525 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10528 @node Pretty-Printer Example
10529 @subsection Pretty-Printer Example
10531 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10534 (@value{GDBP}) print s
10536 static npos = 4294967295,
10538 <std::allocator<char>> = @{
10539 <__gnu_cxx::new_allocator<char>> = @{
10540 <No data fields>@}, <No data fields>
10542 members of std::basic_string<char, std::char_traits<char>,
10543 std::allocator<char> >::_Alloc_hider:
10544 _M_p = 0x804a014 "abcd"
10549 With a pretty-printer for @code{std::string} only the contents are printed:
10552 (@value{GDBP}) print s
10556 @node Pretty-Printer Commands
10557 @subsection Pretty-Printer Commands
10558 @cindex pretty-printer commands
10561 @kindex info pretty-printer
10562 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10563 Print the list of installed pretty-printers.
10564 This includes disabled pretty-printers, which are marked as such.
10566 @var{object-regexp} is a regular expression matching the objects
10567 whose pretty-printers to list.
10568 Objects can be @code{global}, the program space's file
10569 (@pxref{Progspaces In Python}),
10570 and the object files within that program space (@pxref{Objfiles In Python}).
10571 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10572 looks up a printer from these three objects.
10574 @var{name-regexp} is a regular expression matching the name of the printers
10577 @kindex disable pretty-printer
10578 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10579 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10580 A disabled pretty-printer is not forgotten, it may be enabled again later.
10582 @kindex enable pretty-printer
10583 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10584 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10589 Suppose we have three pretty-printers installed: one from library1.so
10590 named @code{foo} that prints objects of type @code{foo}, and
10591 another from library2.so named @code{bar} that prints two types of objects,
10592 @code{bar1} and @code{bar2}.
10595 (gdb) info pretty-printer
10602 (gdb) info pretty-printer library2
10607 (gdb) disable pretty-printer library1
10609 2 of 3 printers enabled
10610 (gdb) info pretty-printer
10617 (gdb) disable pretty-printer library2 bar:bar1
10619 1 of 3 printers enabled
10620 (gdb) info pretty-printer library2
10627 (gdb) disable pretty-printer library2 bar
10629 0 of 3 printers enabled
10630 (gdb) info pretty-printer library2
10639 Note that for @code{bar} the entire printer can be disabled,
10640 as can each individual subprinter.
10642 @node Value History
10643 @section Value History
10645 @cindex value history
10646 @cindex history of values printed by @value{GDBN}
10647 Values printed by the @code{print} command are saved in the @value{GDBN}
10648 @dfn{value history}. This allows you to refer to them in other expressions.
10649 Values are kept until the symbol table is re-read or discarded
10650 (for example with the @code{file} or @code{symbol-file} commands).
10651 When the symbol table changes, the value history is discarded,
10652 since the values may contain pointers back to the types defined in the
10657 @cindex history number
10658 The values printed are given @dfn{history numbers} by which you can
10659 refer to them. These are successive integers starting with one.
10660 @code{print} shows you the history number assigned to a value by
10661 printing @samp{$@var{num} = } before the value; here @var{num} is the
10664 To refer to any previous value, use @samp{$} followed by the value's
10665 history number. The way @code{print} labels its output is designed to
10666 remind you of this. Just @code{$} refers to the most recent value in
10667 the history, and @code{$$} refers to the value before that.
10668 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10669 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10670 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10672 For example, suppose you have just printed a pointer to a structure and
10673 want to see the contents of the structure. It suffices to type
10679 If you have a chain of structures where the component @code{next} points
10680 to the next one, you can print the contents of the next one with this:
10687 You can print successive links in the chain by repeating this
10688 command---which you can do by just typing @key{RET}.
10690 Note that the history records values, not expressions. If the value of
10691 @code{x} is 4 and you type these commands:
10699 then the value recorded in the value history by the @code{print} command
10700 remains 4 even though the value of @code{x} has changed.
10703 @kindex show values
10705 Print the last ten values in the value history, with their item numbers.
10706 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10707 values} does not change the history.
10709 @item show values @var{n}
10710 Print ten history values centered on history item number @var{n}.
10712 @item show values +
10713 Print ten history values just after the values last printed. If no more
10714 values are available, @code{show values +} produces no display.
10717 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10718 same effect as @samp{show values +}.
10720 @node Convenience Vars
10721 @section Convenience Variables
10723 @cindex convenience variables
10724 @cindex user-defined variables
10725 @value{GDBN} provides @dfn{convenience variables} that you can use within
10726 @value{GDBN} to hold on to a value and refer to it later. These variables
10727 exist entirely within @value{GDBN}; they are not part of your program, and
10728 setting a convenience variable has no direct effect on further execution
10729 of your program. That is why you can use them freely.
10731 Convenience variables are prefixed with @samp{$}. Any name preceded by
10732 @samp{$} can be used for a convenience variable, unless it is one of
10733 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10734 (Value history references, in contrast, are @emph{numbers} preceded
10735 by @samp{$}. @xref{Value History, ,Value History}.)
10737 You can save a value in a convenience variable with an assignment
10738 expression, just as you would set a variable in your program.
10742 set $foo = *object_ptr
10746 would save in @code{$foo} the value contained in the object pointed to by
10749 Using a convenience variable for the first time creates it, but its
10750 value is @code{void} until you assign a new value. You can alter the
10751 value with another assignment at any time.
10753 Convenience variables have no fixed types. You can assign a convenience
10754 variable any type of value, including structures and arrays, even if
10755 that variable already has a value of a different type. The convenience
10756 variable, when used as an expression, has the type of its current value.
10759 @kindex show convenience
10760 @cindex show all user variables and functions
10761 @item show convenience
10762 Print a list of convenience variables used so far, and their values,
10763 as well as a list of the convenience functions.
10764 Abbreviated @code{show conv}.
10766 @kindex init-if-undefined
10767 @cindex convenience variables, initializing
10768 @item init-if-undefined $@var{variable} = @var{expression}
10769 Set a convenience variable if it has not already been set. This is useful
10770 for user-defined commands that keep some state. It is similar, in concept,
10771 to using local static variables with initializers in C (except that
10772 convenience variables are global). It can also be used to allow users to
10773 override default values used in a command script.
10775 If the variable is already defined then the expression is not evaluated so
10776 any side-effects do not occur.
10779 One of the ways to use a convenience variable is as a counter to be
10780 incremented or a pointer to be advanced. For example, to print
10781 a field from successive elements of an array of structures:
10785 print bar[$i++]->contents
10789 Repeat that command by typing @key{RET}.
10791 Some convenience variables are created automatically by @value{GDBN} and given
10792 values likely to be useful.
10795 @vindex $_@r{, convenience variable}
10797 The variable @code{$_} is automatically set by the @code{x} command to
10798 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10799 commands which provide a default address for @code{x} to examine also
10800 set @code{$_} to that address; these commands include @code{info line}
10801 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10802 except when set by the @code{x} command, in which case it is a pointer
10803 to the type of @code{$__}.
10805 @vindex $__@r{, convenience variable}
10807 The variable @code{$__} is automatically set by the @code{x} command
10808 to the value found in the last address examined. Its type is chosen
10809 to match the format in which the data was printed.
10812 @vindex $_exitcode@r{, convenience variable}
10813 When the program being debugged terminates normally, @value{GDBN}
10814 automatically sets this variable to the exit code of the program, and
10815 resets @code{$_exitsignal} to @code{void}.
10818 @vindex $_exitsignal@r{, convenience variable}
10819 When the program being debugged dies due to an uncaught signal,
10820 @value{GDBN} automatically sets this variable to that signal's number,
10821 and resets @code{$_exitcode} to @code{void}.
10823 To distinguish between whether the program being debugged has exited
10824 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10825 @code{$_exitsignal} is not @code{void}), the convenience function
10826 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10827 Functions}). For example, considering the following source code:
10830 #include <signal.h>
10833 main (int argc, char *argv[])
10840 A valid way of telling whether the program being debugged has exited
10841 or signalled would be:
10844 (@value{GDBP}) define has_exited_or_signalled
10845 Type commands for definition of ``has_exited_or_signalled''.
10846 End with a line saying just ``end''.
10847 >if $_isvoid ($_exitsignal)
10848 >echo The program has exited\n
10850 >echo The program has signalled\n
10856 Program terminated with signal SIGALRM, Alarm clock.
10857 The program no longer exists.
10858 (@value{GDBP}) has_exited_or_signalled
10859 The program has signalled
10862 As can be seen, @value{GDBN} correctly informs that the program being
10863 debugged has signalled, since it calls @code{raise} and raises a
10864 @code{SIGALRM} signal. If the program being debugged had not called
10865 @code{raise}, then @value{GDBN} would report a normal exit:
10868 (@value{GDBP}) has_exited_or_signalled
10869 The program has exited
10873 The variable @code{$_exception} is set to the exception object being
10874 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10877 @itemx $_probe_arg0@dots{}$_probe_arg11
10878 Arguments to a static probe. @xref{Static Probe Points}.
10881 @vindex $_sdata@r{, inspect, convenience variable}
10882 The variable @code{$_sdata} contains extra collected static tracepoint
10883 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10884 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10885 if extra static tracepoint data has not been collected.
10888 @vindex $_siginfo@r{, convenience variable}
10889 The variable @code{$_siginfo} contains extra signal information
10890 (@pxref{extra signal information}). Note that @code{$_siginfo}
10891 could be empty, if the application has not yet received any signals.
10892 For example, it will be empty before you execute the @code{run} command.
10895 @vindex $_tlb@r{, convenience variable}
10896 The variable @code{$_tlb} is automatically set when debugging
10897 applications running on MS-Windows in native mode or connected to
10898 gdbserver that supports the @code{qGetTIBAddr} request.
10899 @xref{General Query Packets}.
10900 This variable contains the address of the thread information block.
10903 The number of the current inferior. @xref{Inferiors and
10904 Programs, ,Debugging Multiple Inferiors and Programs}.
10907 The thread number of the current thread. @xref{thread numbers}.
10910 The global number of the current thread. @xref{global thread numbers}.
10914 @node Convenience Funs
10915 @section Convenience Functions
10917 @cindex convenience functions
10918 @value{GDBN} also supplies some @dfn{convenience functions}. These
10919 have a syntax similar to convenience variables. A convenience
10920 function can be used in an expression just like an ordinary function;
10921 however, a convenience function is implemented internally to
10924 These functions do not require @value{GDBN} to be configured with
10925 @code{Python} support, which means that they are always available.
10929 @item $_isvoid (@var{expr})
10930 @findex $_isvoid@r{, convenience function}
10931 Return one if the expression @var{expr} is @code{void}. Otherwise it
10934 A @code{void} expression is an expression where the type of the result
10935 is @code{void}. For example, you can examine a convenience variable
10936 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10940 (@value{GDBP}) print $_exitcode
10942 (@value{GDBP}) print $_isvoid ($_exitcode)
10945 Starting program: ./a.out
10946 [Inferior 1 (process 29572) exited normally]
10947 (@value{GDBP}) print $_exitcode
10949 (@value{GDBP}) print $_isvoid ($_exitcode)
10953 In the example above, we used @code{$_isvoid} to check whether
10954 @code{$_exitcode} is @code{void} before and after the execution of the
10955 program being debugged. Before the execution there is no exit code to
10956 be examined, therefore @code{$_exitcode} is @code{void}. After the
10957 execution the program being debugged returned zero, therefore
10958 @code{$_exitcode} is zero, which means that it is not @code{void}
10961 The @code{void} expression can also be a call of a function from the
10962 program being debugged. For example, given the following function:
10971 The result of calling it inside @value{GDBN} is @code{void}:
10974 (@value{GDBP}) print foo ()
10976 (@value{GDBP}) print $_isvoid (foo ())
10978 (@value{GDBP}) set $v = foo ()
10979 (@value{GDBP}) print $v
10981 (@value{GDBP}) print $_isvoid ($v)
10987 These functions require @value{GDBN} to be configured with
10988 @code{Python} support.
10992 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10993 @findex $_memeq@r{, convenience function}
10994 Returns one if the @var{length} bytes at the addresses given by
10995 @var{buf1} and @var{buf2} are equal.
10996 Otherwise it returns zero.
10998 @item $_regex(@var{str}, @var{regex})
10999 @findex $_regex@r{, convenience function}
11000 Returns one if the string @var{str} matches the regular expression
11001 @var{regex}. Otherwise it returns zero.
11002 The syntax of the regular expression is that specified by @code{Python}'s
11003 regular expression support.
11005 @item $_streq(@var{str1}, @var{str2})
11006 @findex $_streq@r{, convenience function}
11007 Returns one if the strings @var{str1} and @var{str2} are equal.
11008 Otherwise it returns zero.
11010 @item $_strlen(@var{str})
11011 @findex $_strlen@r{, convenience function}
11012 Returns the length of string @var{str}.
11014 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11015 @findex $_caller_is@r{, convenience function}
11016 Returns one if the calling function's name is equal to @var{name}.
11017 Otherwise it returns zero.
11019 If the optional argument @var{number_of_frames} is provided,
11020 it is the number of frames up in the stack to look.
11028 at testsuite/gdb.python/py-caller-is.c:21
11029 #1 0x00000000004005a0 in middle_func ()
11030 at testsuite/gdb.python/py-caller-is.c:27
11031 #2 0x00000000004005ab in top_func ()
11032 at testsuite/gdb.python/py-caller-is.c:33
11033 #3 0x00000000004005b6 in main ()
11034 at testsuite/gdb.python/py-caller-is.c:39
11035 (gdb) print $_caller_is ("middle_func")
11037 (gdb) print $_caller_is ("top_func", 2)
11041 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11042 @findex $_caller_matches@r{, convenience function}
11043 Returns one if the calling function's name matches the regular expression
11044 @var{regexp}. Otherwise it returns zero.
11046 If the optional argument @var{number_of_frames} is provided,
11047 it is the number of frames up in the stack to look.
11050 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11051 @findex $_any_caller_is@r{, convenience function}
11052 Returns one if any calling function's name is equal to @var{name}.
11053 Otherwise it returns zero.
11055 If the optional argument @var{number_of_frames} is provided,
11056 it is the number of frames up in the stack to look.
11059 This function differs from @code{$_caller_is} in that this function
11060 checks all stack frames from the immediate caller to the frame specified
11061 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11062 frame specified by @var{number_of_frames}.
11064 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11065 @findex $_any_caller_matches@r{, convenience function}
11066 Returns one if any calling function's name matches the regular expression
11067 @var{regexp}. Otherwise it returns zero.
11069 If the optional argument @var{number_of_frames} is provided,
11070 it is the number of frames up in the stack to look.
11073 This function differs from @code{$_caller_matches} in that this function
11074 checks all stack frames from the immediate caller to the frame specified
11075 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11076 frame specified by @var{number_of_frames}.
11078 @item $_as_string(@var{value})
11079 @findex $_as_string@r{, convenience function}
11080 Return the string representation of @var{value}.
11082 This function is useful to obtain the textual label (enumerator) of an
11083 enumeration value. For example, assuming the variable @var{node} is of
11084 an enumerated type:
11087 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11088 Visiting node of type NODE_INTEGER
11093 @value{GDBN} provides the ability to list and get help on
11094 convenience functions.
11097 @item help function
11098 @kindex help function
11099 @cindex show all convenience functions
11100 Print a list of all convenience functions.
11107 You can refer to machine register contents, in expressions, as variables
11108 with names starting with @samp{$}. The names of registers are different
11109 for each machine; use @code{info registers} to see the names used on
11113 @kindex info registers
11114 @item info registers
11115 Print the names and values of all registers except floating-point
11116 and vector registers (in the selected stack frame).
11118 @kindex info all-registers
11119 @cindex floating point registers
11120 @item info all-registers
11121 Print the names and values of all registers, including floating-point
11122 and vector registers (in the selected stack frame).
11124 @item info registers @var{reggroup} @dots{}
11125 Print the name and value of the registers in each of the specified
11126 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11127 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11129 @item info registers @var{regname} @dots{}
11130 Print the @dfn{relativized} value of each specified register @var{regname}.
11131 As discussed in detail below, register values are normally relative to
11132 the selected stack frame. The @var{regname} may be any register name valid on
11133 the machine you are using, with or without the initial @samp{$}.
11136 @anchor{standard registers}
11137 @cindex stack pointer register
11138 @cindex program counter register
11139 @cindex process status register
11140 @cindex frame pointer register
11141 @cindex standard registers
11142 @value{GDBN} has four ``standard'' register names that are available (in
11143 expressions) on most machines---whenever they do not conflict with an
11144 architecture's canonical mnemonics for registers. The register names
11145 @code{$pc} and @code{$sp} are used for the program counter register and
11146 the stack pointer. @code{$fp} is used for a register that contains a
11147 pointer to the current stack frame, and @code{$ps} is used for a
11148 register that contains the processor status. For example,
11149 you could print the program counter in hex with
11156 or print the instruction to be executed next with
11163 or add four to the stack pointer@footnote{This is a way of removing
11164 one word from the stack, on machines where stacks grow downward in
11165 memory (most machines, nowadays). This assumes that the innermost
11166 stack frame is selected; setting @code{$sp} is not allowed when other
11167 stack frames are selected. To pop entire frames off the stack,
11168 regardless of machine architecture, use @code{return};
11169 see @ref{Returning, ,Returning from a Function}.} with
11175 Whenever possible, these four standard register names are available on
11176 your machine even though the machine has different canonical mnemonics,
11177 so long as there is no conflict. The @code{info registers} command
11178 shows the canonical names. For example, on the SPARC, @code{info
11179 registers} displays the processor status register as @code{$psr} but you
11180 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11181 is an alias for the @sc{eflags} register.
11183 @value{GDBN} always considers the contents of an ordinary register as an
11184 integer when the register is examined in this way. Some machines have
11185 special registers which can hold nothing but floating point; these
11186 registers are considered to have floating point values. There is no way
11187 to refer to the contents of an ordinary register as floating point value
11188 (although you can @emph{print} it as a floating point value with
11189 @samp{print/f $@var{regname}}).
11191 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11192 means that the data format in which the register contents are saved by
11193 the operating system is not the same one that your program normally
11194 sees. For example, the registers of the 68881 floating point
11195 coprocessor are always saved in ``extended'' (raw) format, but all C
11196 programs expect to work with ``double'' (virtual) format. In such
11197 cases, @value{GDBN} normally works with the virtual format only (the format
11198 that makes sense for your program), but the @code{info registers} command
11199 prints the data in both formats.
11201 @cindex SSE registers (x86)
11202 @cindex MMX registers (x86)
11203 Some machines have special registers whose contents can be interpreted
11204 in several different ways. For example, modern x86-based machines
11205 have SSE and MMX registers that can hold several values packed
11206 together in several different formats. @value{GDBN} refers to such
11207 registers in @code{struct} notation:
11210 (@value{GDBP}) print $xmm1
11212 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11213 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11214 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11215 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11216 v4_int32 = @{0, 20657912, 11, 13@},
11217 v2_int64 = @{88725056443645952, 55834574859@},
11218 uint128 = 0x0000000d0000000b013b36f800000000
11223 To set values of such registers, you need to tell @value{GDBN} which
11224 view of the register you wish to change, as if you were assigning
11225 value to a @code{struct} member:
11228 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11231 Normally, register values are relative to the selected stack frame
11232 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11233 value that the register would contain if all stack frames farther in
11234 were exited and their saved registers restored. In order to see the
11235 true contents of hardware registers, you must select the innermost
11236 frame (with @samp{frame 0}).
11238 @cindex caller-saved registers
11239 @cindex call-clobbered registers
11240 @cindex volatile registers
11241 @cindex <not saved> values
11242 Usually ABIs reserve some registers as not needed to be saved by the
11243 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11244 registers). It may therefore not be possible for @value{GDBN} to know
11245 the value a register had before the call (in other words, in the outer
11246 frame), if the register value has since been changed by the callee.
11247 @value{GDBN} tries to deduce where the inner frame saved
11248 (``callee-saved'') registers, from the debug info, unwind info, or the
11249 machine code generated by your compiler. If some register is not
11250 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11251 its own knowledge of the ABI, or because the debug/unwind info
11252 explicitly says the register's value is undefined), @value{GDBN}
11253 displays @w{@samp{<not saved>}} as the register's value. With targets
11254 that @value{GDBN} has no knowledge of the register saving convention,
11255 if a register was not saved by the callee, then its value and location
11256 in the outer frame are assumed to be the same of the inner frame.
11257 This is usually harmless, because if the register is call-clobbered,
11258 the caller either does not care what is in the register after the
11259 call, or has code to restore the value that it does care about. Note,
11260 however, that if you change such a register in the outer frame, you
11261 may also be affecting the inner frame. Also, the more ``outer'' the
11262 frame is you're looking at, the more likely a call-clobbered
11263 register's value is to be wrong, in the sense that it doesn't actually
11264 represent the value the register had just before the call.
11266 @node Floating Point Hardware
11267 @section Floating Point Hardware
11268 @cindex floating point
11270 Depending on the configuration, @value{GDBN} may be able to give
11271 you more information about the status of the floating point hardware.
11276 Display hardware-dependent information about the floating
11277 point unit. The exact contents and layout vary depending on the
11278 floating point chip. Currently, @samp{info float} is supported on
11279 the ARM and x86 machines.
11283 @section Vector Unit
11284 @cindex vector unit
11286 Depending on the configuration, @value{GDBN} may be able to give you
11287 more information about the status of the vector unit.
11290 @kindex info vector
11292 Display information about the vector unit. The exact contents and
11293 layout vary depending on the hardware.
11296 @node OS Information
11297 @section Operating System Auxiliary Information
11298 @cindex OS information
11300 @value{GDBN} provides interfaces to useful OS facilities that can help
11301 you debug your program.
11303 @cindex auxiliary vector
11304 @cindex vector, auxiliary
11305 Some operating systems supply an @dfn{auxiliary vector} to programs at
11306 startup. This is akin to the arguments and environment that you
11307 specify for a program, but contains a system-dependent variety of
11308 binary values that tell system libraries important details about the
11309 hardware, operating system, and process. Each value's purpose is
11310 identified by an integer tag; the meanings are well-known but system-specific.
11311 Depending on the configuration and operating system facilities,
11312 @value{GDBN} may be able to show you this information. For remote
11313 targets, this functionality may further depend on the remote stub's
11314 support of the @samp{qXfer:auxv:read} packet, see
11315 @ref{qXfer auxiliary vector read}.
11320 Display the auxiliary vector of the inferior, which can be either a
11321 live process or a core dump file. @value{GDBN} prints each tag value
11322 numerically, and also shows names and text descriptions for recognized
11323 tags. Some values in the vector are numbers, some bit masks, and some
11324 pointers to strings or other data. @value{GDBN} displays each value in the
11325 most appropriate form for a recognized tag, and in hexadecimal for
11326 an unrecognized tag.
11329 On some targets, @value{GDBN} can access operating system-specific
11330 information and show it to you. The types of information available
11331 will differ depending on the type of operating system running on the
11332 target. The mechanism used to fetch the data is described in
11333 @ref{Operating System Information}. For remote targets, this
11334 functionality depends on the remote stub's support of the
11335 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11339 @item info os @var{infotype}
11341 Display OS information of the requested type.
11343 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11345 @anchor{linux info os infotypes}
11347 @kindex info os cpus
11349 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11350 the available fields from /proc/cpuinfo. For each supported architecture
11351 different fields are available. Two common entries are processor which gives
11352 CPU number and bogomips; a system constant that is calculated during
11353 kernel initialization.
11355 @kindex info os files
11357 Display the list of open file descriptors on the target. For each
11358 file descriptor, @value{GDBN} prints the identifier of the process
11359 owning the descriptor, the command of the owning process, the value
11360 of the descriptor, and the target of the descriptor.
11362 @kindex info os modules
11364 Display the list of all loaded kernel modules on the target. For each
11365 module, @value{GDBN} prints the module name, the size of the module in
11366 bytes, the number of times the module is used, the dependencies of the
11367 module, the status of the module, and the address of the loaded module
11370 @kindex info os msg
11372 Display the list of all System V message queues on the target. For each
11373 message queue, @value{GDBN} prints the message queue key, the message
11374 queue identifier, the access permissions, the current number of bytes
11375 on the queue, the current number of messages on the queue, the processes
11376 that last sent and received a message on the queue, the user and group
11377 of the owner and creator of the message queue, the times at which a
11378 message was last sent and received on the queue, and the time at which
11379 the message queue was last changed.
11381 @kindex info os processes
11383 Display the list of processes on the target. For each process,
11384 @value{GDBN} prints the process identifier, the name of the user, the
11385 command corresponding to the process, and the list of processor cores
11386 that the process is currently running on. (To understand what these
11387 properties mean, for this and the following info types, please consult
11388 the general @sc{gnu}/Linux documentation.)
11390 @kindex info os procgroups
11392 Display the list of process groups on the target. For each process,
11393 @value{GDBN} prints the identifier of the process group that it belongs
11394 to, the command corresponding to the process group leader, the process
11395 identifier, and the command line of the process. The list is sorted
11396 first by the process group identifier, then by the process identifier,
11397 so that processes belonging to the same process group are grouped together
11398 and the process group leader is listed first.
11400 @kindex info os semaphores
11402 Display the list of all System V semaphore sets on the target. For each
11403 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11404 set identifier, the access permissions, the number of semaphores in the
11405 set, the user and group of the owner and creator of the semaphore set,
11406 and the times at which the semaphore set was operated upon and changed.
11408 @kindex info os shm
11410 Display the list of all System V shared-memory regions on the target.
11411 For each shared-memory region, @value{GDBN} prints the region key,
11412 the shared-memory identifier, the access permissions, the size of the
11413 region, the process that created the region, the process that last
11414 attached to or detached from the region, the current number of live
11415 attaches to the region, and the times at which the region was last
11416 attached to, detach from, and changed.
11418 @kindex info os sockets
11420 Display the list of Internet-domain sockets on the target. For each
11421 socket, @value{GDBN} prints the address and port of the local and
11422 remote endpoints, the current state of the connection, the creator of
11423 the socket, the IP address family of the socket, and the type of the
11426 @kindex info os threads
11428 Display the list of threads running on the target. For each thread,
11429 @value{GDBN} prints the identifier of the process that the thread
11430 belongs to, the command of the process, the thread identifier, and the
11431 processor core that it is currently running on. The main thread of a
11432 process is not listed.
11436 If @var{infotype} is omitted, then list the possible values for
11437 @var{infotype} and the kind of OS information available for each
11438 @var{infotype}. If the target does not return a list of possible
11439 types, this command will report an error.
11442 @node Memory Region Attributes
11443 @section Memory Region Attributes
11444 @cindex memory region attributes
11446 @dfn{Memory region attributes} allow you to describe special handling
11447 required by regions of your target's memory. @value{GDBN} uses
11448 attributes to determine whether to allow certain types of memory
11449 accesses; whether to use specific width accesses; and whether to cache
11450 target memory. By default the description of memory regions is
11451 fetched from the target (if the current target supports this), but the
11452 user can override the fetched regions.
11454 Defined memory regions can be individually enabled and disabled. When a
11455 memory region is disabled, @value{GDBN} uses the default attributes when
11456 accessing memory in that region. Similarly, if no memory regions have
11457 been defined, @value{GDBN} uses the default attributes when accessing
11460 When a memory region is defined, it is given a number to identify it;
11461 to enable, disable, or remove a memory region, you specify that number.
11465 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11466 Define a memory region bounded by @var{lower} and @var{upper} with
11467 attributes @var{attributes}@dots{}, and add it to the list of regions
11468 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11469 case: it is treated as the target's maximum memory address.
11470 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11473 Discard any user changes to the memory regions and use target-supplied
11474 regions, if available, or no regions if the target does not support.
11477 @item delete mem @var{nums}@dots{}
11478 Remove memory regions @var{nums}@dots{} from the list of regions
11479 monitored by @value{GDBN}.
11481 @kindex disable mem
11482 @item disable mem @var{nums}@dots{}
11483 Disable monitoring of memory regions @var{nums}@dots{}.
11484 A disabled memory region is not forgotten.
11485 It may be enabled again later.
11488 @item enable mem @var{nums}@dots{}
11489 Enable monitoring of memory regions @var{nums}@dots{}.
11493 Print a table of all defined memory regions, with the following columns
11497 @item Memory Region Number
11498 @item Enabled or Disabled.
11499 Enabled memory regions are marked with @samp{y}.
11500 Disabled memory regions are marked with @samp{n}.
11503 The address defining the inclusive lower bound of the memory region.
11506 The address defining the exclusive upper bound of the memory region.
11509 The list of attributes set for this memory region.
11514 @subsection Attributes
11516 @subsubsection Memory Access Mode
11517 The access mode attributes set whether @value{GDBN} may make read or
11518 write accesses to a memory region.
11520 While these attributes prevent @value{GDBN} from performing invalid
11521 memory accesses, they do nothing to prevent the target system, I/O DMA,
11522 etc.@: from accessing memory.
11526 Memory is read only.
11528 Memory is write only.
11530 Memory is read/write. This is the default.
11533 @subsubsection Memory Access Size
11534 The access size attribute tells @value{GDBN} to use specific sized
11535 accesses in the memory region. Often memory mapped device registers
11536 require specific sized accesses. If no access size attribute is
11537 specified, @value{GDBN} may use accesses of any size.
11541 Use 8 bit memory accesses.
11543 Use 16 bit memory accesses.
11545 Use 32 bit memory accesses.
11547 Use 64 bit memory accesses.
11550 @c @subsubsection Hardware/Software Breakpoints
11551 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11552 @c will use hardware or software breakpoints for the internal breakpoints
11553 @c used by the step, next, finish, until, etc. commands.
11557 @c Always use hardware breakpoints
11558 @c @item swbreak (default)
11561 @subsubsection Data Cache
11562 The data cache attributes set whether @value{GDBN} will cache target
11563 memory. While this generally improves performance by reducing debug
11564 protocol overhead, it can lead to incorrect results because @value{GDBN}
11565 does not know about volatile variables or memory mapped device
11570 Enable @value{GDBN} to cache target memory.
11572 Disable @value{GDBN} from caching target memory. This is the default.
11575 @subsection Memory Access Checking
11576 @value{GDBN} can be instructed to refuse accesses to memory that is
11577 not explicitly described. This can be useful if accessing such
11578 regions has undesired effects for a specific target, or to provide
11579 better error checking. The following commands control this behaviour.
11582 @kindex set mem inaccessible-by-default
11583 @item set mem inaccessible-by-default [on|off]
11584 If @code{on} is specified, make @value{GDBN} treat memory not
11585 explicitly described by the memory ranges as non-existent and refuse accesses
11586 to such memory. The checks are only performed if there's at least one
11587 memory range defined. If @code{off} is specified, make @value{GDBN}
11588 treat the memory not explicitly described by the memory ranges as RAM.
11589 The default value is @code{on}.
11590 @kindex show mem inaccessible-by-default
11591 @item show mem inaccessible-by-default
11592 Show the current handling of accesses to unknown memory.
11596 @c @subsubsection Memory Write Verification
11597 @c The memory write verification attributes set whether @value{GDBN}
11598 @c will re-reads data after each write to verify the write was successful.
11602 @c @item noverify (default)
11605 @node Dump/Restore Files
11606 @section Copy Between Memory and a File
11607 @cindex dump/restore files
11608 @cindex append data to a file
11609 @cindex dump data to a file
11610 @cindex restore data from a file
11612 You can use the commands @code{dump}, @code{append}, and
11613 @code{restore} to copy data between target memory and a file. The
11614 @code{dump} and @code{append} commands write data to a file, and the
11615 @code{restore} command reads data from a file back into the inferior's
11616 memory. Files may be in binary, Motorola S-record, Intel hex,
11617 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11618 append to binary files, and cannot read from Verilog Hex files.
11623 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11624 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11625 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11626 or the value of @var{expr}, to @var{filename} in the given format.
11628 The @var{format} parameter may be any one of:
11635 Motorola S-record format.
11637 Tektronix Hex format.
11639 Verilog Hex format.
11642 @value{GDBN} uses the same definitions of these formats as the
11643 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11644 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11648 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11649 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11650 Append the contents of memory from @var{start_addr} to @var{end_addr},
11651 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11652 (@value{GDBN} can only append data to files in raw binary form.)
11655 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11656 Restore the contents of file @var{filename} into memory. The
11657 @code{restore} command can automatically recognize any known @sc{bfd}
11658 file format, except for raw binary. To restore a raw binary file you
11659 must specify the optional keyword @code{binary} after the filename.
11661 If @var{bias} is non-zero, its value will be added to the addresses
11662 contained in the file. Binary files always start at address zero, so
11663 they will be restored at address @var{bias}. Other bfd files have
11664 a built-in location; they will be restored at offset @var{bias}
11665 from that location.
11667 If @var{start} and/or @var{end} are non-zero, then only data between
11668 file offset @var{start} and file offset @var{end} will be restored.
11669 These offsets are relative to the addresses in the file, before
11670 the @var{bias} argument is applied.
11674 @node Core File Generation
11675 @section How to Produce a Core File from Your Program
11676 @cindex dump core from inferior
11678 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11679 image of a running process and its process status (register values
11680 etc.). Its primary use is post-mortem debugging of a program that
11681 crashed while it ran outside a debugger. A program that crashes
11682 automatically produces a core file, unless this feature is disabled by
11683 the user. @xref{Files}, for information on invoking @value{GDBN} in
11684 the post-mortem debugging mode.
11686 Occasionally, you may wish to produce a core file of the program you
11687 are debugging in order to preserve a snapshot of its state.
11688 @value{GDBN} has a special command for that.
11692 @kindex generate-core-file
11693 @item generate-core-file [@var{file}]
11694 @itemx gcore [@var{file}]
11695 Produce a core dump of the inferior process. The optional argument
11696 @var{file} specifies the file name where to put the core dump. If not
11697 specified, the file name defaults to @file{core.@var{pid}}, where
11698 @var{pid} is the inferior process ID.
11700 Note that this command is implemented only for some systems (as of
11701 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11703 On @sc{gnu}/Linux, this command can take into account the value of the
11704 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11705 dump (@pxref{set use-coredump-filter}), and by default honors the
11706 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11707 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11709 @kindex set use-coredump-filter
11710 @anchor{set use-coredump-filter}
11711 @item set use-coredump-filter on
11712 @itemx set use-coredump-filter off
11713 Enable or disable the use of the file
11714 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11715 files. This file is used by the Linux kernel to decide what types of
11716 memory mappings will be dumped or ignored when generating a core dump
11717 file. @var{pid} is the process ID of a currently running process.
11719 To make use of this feature, you have to write in the
11720 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11721 which is a bit mask representing the memory mapping types. If a bit
11722 is set in the bit mask, then the memory mappings of the corresponding
11723 types will be dumped; otherwise, they will be ignored. This
11724 configuration is inherited by child processes. For more information
11725 about the bits that can be set in the
11726 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11727 manpage of @code{core(5)}.
11729 By default, this option is @code{on}. If this option is turned
11730 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11731 and instead uses the same default value as the Linux kernel in order
11732 to decide which pages will be dumped in the core dump file. This
11733 value is currently @code{0x33}, which means that bits @code{0}
11734 (anonymous private mappings), @code{1} (anonymous shared mappings),
11735 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11736 This will cause these memory mappings to be dumped automatically.
11738 @kindex set dump-excluded-mappings
11739 @anchor{set dump-excluded-mappings}
11740 @item set dump-excluded-mappings on
11741 @itemx set dump-excluded-mappings off
11742 If @code{on} is specified, @value{GDBN} will dump memory mappings
11743 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11744 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11746 The default value is @code{off}.
11749 @node Character Sets
11750 @section Character Sets
11751 @cindex character sets
11753 @cindex translating between character sets
11754 @cindex host character set
11755 @cindex target character set
11757 If the program you are debugging uses a different character set to
11758 represent characters and strings than the one @value{GDBN} uses itself,
11759 @value{GDBN} can automatically translate between the character sets for
11760 you. The character set @value{GDBN} uses we call the @dfn{host
11761 character set}; the one the inferior program uses we call the
11762 @dfn{target character set}.
11764 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11765 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11766 remote protocol (@pxref{Remote Debugging}) to debug a program
11767 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11768 then the host character set is Latin-1, and the target character set is
11769 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11770 target-charset EBCDIC-US}, then @value{GDBN} translates between
11771 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11772 character and string literals in expressions.
11774 @value{GDBN} has no way to automatically recognize which character set
11775 the inferior program uses; you must tell it, using the @code{set
11776 target-charset} command, described below.
11778 Here are the commands for controlling @value{GDBN}'s character set
11782 @item set target-charset @var{charset}
11783 @kindex set target-charset
11784 Set the current target character set to @var{charset}. To display the
11785 list of supported target character sets, type
11786 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11788 @item set host-charset @var{charset}
11789 @kindex set host-charset
11790 Set the current host character set to @var{charset}.
11792 By default, @value{GDBN} uses a host character set appropriate to the
11793 system it is running on; you can override that default using the
11794 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11795 automatically determine the appropriate host character set. In this
11796 case, @value{GDBN} uses @samp{UTF-8}.
11798 @value{GDBN} can only use certain character sets as its host character
11799 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11800 @value{GDBN} will list the host character sets it supports.
11802 @item set charset @var{charset}
11803 @kindex set charset
11804 Set the current host and target character sets to @var{charset}. As
11805 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11806 @value{GDBN} will list the names of the character sets that can be used
11807 for both host and target.
11810 @kindex show charset
11811 Show the names of the current host and target character sets.
11813 @item show host-charset
11814 @kindex show host-charset
11815 Show the name of the current host character set.
11817 @item show target-charset
11818 @kindex show target-charset
11819 Show the name of the current target character set.
11821 @item set target-wide-charset @var{charset}
11822 @kindex set target-wide-charset
11823 Set the current target's wide character set to @var{charset}. This is
11824 the character set used by the target's @code{wchar_t} type. To
11825 display the list of supported wide character sets, type
11826 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11828 @item show target-wide-charset
11829 @kindex show target-wide-charset
11830 Show the name of the current target's wide character set.
11833 Here is an example of @value{GDBN}'s character set support in action.
11834 Assume that the following source code has been placed in the file
11835 @file{charset-test.c}:
11841 = @{72, 101, 108, 108, 111, 44, 32, 119,
11842 111, 114, 108, 100, 33, 10, 0@};
11843 char ibm1047_hello[]
11844 = @{200, 133, 147, 147, 150, 107, 64, 166,
11845 150, 153, 147, 132, 90, 37, 0@};
11849 printf ("Hello, world!\n");
11853 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11854 containing the string @samp{Hello, world!} followed by a newline,
11855 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11857 We compile the program, and invoke the debugger on it:
11860 $ gcc -g charset-test.c -o charset-test
11861 $ gdb -nw charset-test
11862 GNU gdb 2001-12-19-cvs
11863 Copyright 2001 Free Software Foundation, Inc.
11868 We can use the @code{show charset} command to see what character sets
11869 @value{GDBN} is currently using to interpret and display characters and
11873 (@value{GDBP}) show charset
11874 The current host and target character set is `ISO-8859-1'.
11878 For the sake of printing this manual, let's use @sc{ascii} as our
11879 initial character set:
11881 (@value{GDBP}) set charset ASCII
11882 (@value{GDBP}) show charset
11883 The current host and target character set is `ASCII'.
11887 Let's assume that @sc{ascii} is indeed the correct character set for our
11888 host system --- in other words, let's assume that if @value{GDBN} prints
11889 characters using the @sc{ascii} character set, our terminal will display
11890 them properly. Since our current target character set is also
11891 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11894 (@value{GDBP}) print ascii_hello
11895 $1 = 0x401698 "Hello, world!\n"
11896 (@value{GDBP}) print ascii_hello[0]
11901 @value{GDBN} uses the target character set for character and string
11902 literals you use in expressions:
11905 (@value{GDBP}) print '+'
11910 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11913 @value{GDBN} relies on the user to tell it which character set the
11914 target program uses. If we print @code{ibm1047_hello} while our target
11915 character set is still @sc{ascii}, we get jibberish:
11918 (@value{GDBP}) print ibm1047_hello
11919 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11920 (@value{GDBP}) print ibm1047_hello[0]
11925 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11926 @value{GDBN} tells us the character sets it supports:
11929 (@value{GDBP}) set target-charset
11930 ASCII EBCDIC-US IBM1047 ISO-8859-1
11931 (@value{GDBP}) set target-charset
11934 We can select @sc{ibm1047} as our target character set, and examine the
11935 program's strings again. Now the @sc{ascii} string is wrong, but
11936 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11937 target character set, @sc{ibm1047}, to the host character set,
11938 @sc{ascii}, and they display correctly:
11941 (@value{GDBP}) set target-charset IBM1047
11942 (@value{GDBP}) show charset
11943 The current host character set is `ASCII'.
11944 The current target character set is `IBM1047'.
11945 (@value{GDBP}) print ascii_hello
11946 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11947 (@value{GDBP}) print ascii_hello[0]
11949 (@value{GDBP}) print ibm1047_hello
11950 $8 = 0x4016a8 "Hello, world!\n"
11951 (@value{GDBP}) print ibm1047_hello[0]
11956 As above, @value{GDBN} uses the target character set for character and
11957 string literals you use in expressions:
11960 (@value{GDBP}) print '+'
11965 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11968 @node Caching Target Data
11969 @section Caching Data of Targets
11970 @cindex caching data of targets
11972 @value{GDBN} caches data exchanged between the debugger and a target.
11973 Each cache is associated with the address space of the inferior.
11974 @xref{Inferiors and Programs}, about inferior and address space.
11975 Such caching generally improves performance in remote debugging
11976 (@pxref{Remote Debugging}), because it reduces the overhead of the
11977 remote protocol by bundling memory reads and writes into large chunks.
11978 Unfortunately, simply caching everything would lead to incorrect results,
11979 since @value{GDBN} does not necessarily know anything about volatile
11980 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11981 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11983 Therefore, by default, @value{GDBN} only caches data
11984 known to be on the stack@footnote{In non-stop mode, it is moderately
11985 rare for a running thread to modify the stack of a stopped thread
11986 in a way that would interfere with a backtrace, and caching of
11987 stack reads provides a significant speed up of remote backtraces.} or
11988 in the code segment.
11989 Other regions of memory can be explicitly marked as
11990 cacheable; @pxref{Memory Region Attributes}.
11993 @kindex set remotecache
11994 @item set remotecache on
11995 @itemx set remotecache off
11996 This option no longer does anything; it exists for compatibility
11999 @kindex show remotecache
12000 @item show remotecache
12001 Show the current state of the obsolete remotecache flag.
12003 @kindex set stack-cache
12004 @item set stack-cache on
12005 @itemx set stack-cache off
12006 Enable or disable caching of stack accesses. When @code{on}, use
12007 caching. By default, this option is @code{on}.
12009 @kindex show stack-cache
12010 @item show stack-cache
12011 Show the current state of data caching for memory accesses.
12013 @kindex set code-cache
12014 @item set code-cache on
12015 @itemx set code-cache off
12016 Enable or disable caching of code segment accesses. When @code{on},
12017 use caching. By default, this option is @code{on}. This improves
12018 performance of disassembly in remote debugging.
12020 @kindex show code-cache
12021 @item show code-cache
12022 Show the current state of target memory cache for code segment
12025 @kindex info dcache
12026 @item info dcache @r{[}line@r{]}
12027 Print the information about the performance of data cache of the
12028 current inferior's address space. The information displayed
12029 includes the dcache width and depth, and for each cache line, its
12030 number, address, and how many times it was referenced. This
12031 command is useful for debugging the data cache operation.
12033 If a line number is specified, the contents of that line will be
12036 @item set dcache size @var{size}
12037 @cindex dcache size
12038 @kindex set dcache size
12039 Set maximum number of entries in dcache (dcache depth above).
12041 @item set dcache line-size @var{line-size}
12042 @cindex dcache line-size
12043 @kindex set dcache line-size
12044 Set number of bytes each dcache entry caches (dcache width above).
12045 Must be a power of 2.
12047 @item show dcache size
12048 @kindex show dcache size
12049 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12051 @item show dcache line-size
12052 @kindex show dcache line-size
12053 Show default size of dcache lines.
12057 @node Searching Memory
12058 @section Search Memory
12059 @cindex searching memory
12061 Memory can be searched for a particular sequence of bytes with the
12062 @code{find} command.
12066 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12067 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12068 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12069 etc. The search begins at address @var{start_addr} and continues for either
12070 @var{len} bytes or through to @var{end_addr} inclusive.
12073 @var{s} and @var{n} are optional parameters.
12074 They may be specified in either order, apart or together.
12077 @item @var{s}, search query size
12078 The size of each search query value.
12084 halfwords (two bytes)
12088 giant words (eight bytes)
12091 All values are interpreted in the current language.
12092 This means, for example, that if the current source language is C/C@t{++}
12093 then searching for the string ``hello'' includes the trailing '\0'.
12094 The null terminator can be removed from searching by using casts,
12095 e.g.: @samp{@{char[5]@}"hello"}.
12097 If the value size is not specified, it is taken from the
12098 value's type in the current language.
12099 This is useful when one wants to specify the search
12100 pattern as a mixture of types.
12101 Note that this means, for example, that in the case of C-like languages
12102 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12103 which is typically four bytes.
12105 @item @var{n}, maximum number of finds
12106 The maximum number of matches to print. The default is to print all finds.
12109 You can use strings as search values. Quote them with double-quotes
12111 The string value is copied into the search pattern byte by byte,
12112 regardless of the endianness of the target and the size specification.
12114 The address of each match found is printed as well as a count of the
12115 number of matches found.
12117 The address of the last value found is stored in convenience variable
12119 A count of the number of matches is stored in @samp{$numfound}.
12121 For example, if stopped at the @code{printf} in this function:
12127 static char hello[] = "hello-hello";
12128 static struct @{ char c; short s; int i; @}
12129 __attribute__ ((packed)) mixed
12130 = @{ 'c', 0x1234, 0x87654321 @};
12131 printf ("%s\n", hello);
12136 you get during debugging:
12139 (gdb) find &hello[0], +sizeof(hello), "hello"
12140 0x804956d <hello.1620+6>
12142 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12143 0x8049567 <hello.1620>
12144 0x804956d <hello.1620+6>
12146 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12147 0x8049567 <hello.1620>
12148 0x804956d <hello.1620+6>
12150 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12151 0x8049567 <hello.1620>
12153 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12154 0x8049560 <mixed.1625>
12156 (gdb) print $numfound
12159 $2 = (void *) 0x8049560
12163 @section Value Sizes
12165 Whenever @value{GDBN} prints a value memory will be allocated within
12166 @value{GDBN} to hold the contents of the value. It is possible in
12167 some languages with dynamic typing systems, that an invalid program
12168 may indicate a value that is incorrectly large, this in turn may cause
12169 @value{GDBN} to try and allocate an overly large ammount of memory.
12172 @kindex set max-value-size
12173 @item set max-value-size @var{bytes}
12174 @itemx set max-value-size unlimited
12175 Set the maximum size of memory that @value{GDBN} will allocate for the
12176 contents of a value to @var{bytes}, trying to display a value that
12177 requires more memory than that will result in an error.
12179 Setting this variable does not effect values that have already been
12180 allocated within @value{GDBN}, only future allocations.
12182 There's a minimum size that @code{max-value-size} can be set to in
12183 order that @value{GDBN} can still operate correctly, this minimum is
12184 currently 16 bytes.
12186 The limit applies to the results of some subexpressions as well as to
12187 complete expressions. For example, an expression denoting a simple
12188 integer component, such as @code{x.y.z}, may fail if the size of
12189 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12190 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12191 @var{A} is an array variable with non-constant size, will generally
12192 succeed regardless of the bounds on @var{A}, as long as the component
12193 size is less than @var{bytes}.
12195 The default value of @code{max-value-size} is currently 64k.
12197 @kindex show max-value-size
12198 @item show max-value-size
12199 Show the maximum size of memory, in bytes, that @value{GDBN} will
12200 allocate for the contents of a value.
12203 @node Optimized Code
12204 @chapter Debugging Optimized Code
12205 @cindex optimized code, debugging
12206 @cindex debugging optimized code
12208 Almost all compilers support optimization. With optimization
12209 disabled, the compiler generates assembly code that corresponds
12210 directly to your source code, in a simplistic way. As the compiler
12211 applies more powerful optimizations, the generated assembly code
12212 diverges from your original source code. With help from debugging
12213 information generated by the compiler, @value{GDBN} can map from
12214 the running program back to constructs from your original source.
12216 @value{GDBN} is more accurate with optimization disabled. If you
12217 can recompile without optimization, it is easier to follow the
12218 progress of your program during debugging. But, there are many cases
12219 where you may need to debug an optimized version.
12221 When you debug a program compiled with @samp{-g -O}, remember that the
12222 optimizer has rearranged your code; the debugger shows you what is
12223 really there. Do not be too surprised when the execution path does not
12224 exactly match your source file! An extreme example: if you define a
12225 variable, but never use it, @value{GDBN} never sees that
12226 variable---because the compiler optimizes it out of existence.
12228 Some things do not work as well with @samp{-g -O} as with just
12229 @samp{-g}, particularly on machines with instruction scheduling. If in
12230 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12231 please report it to us as a bug (including a test case!).
12232 @xref{Variables}, for more information about debugging optimized code.
12235 * Inline Functions:: How @value{GDBN} presents inlining
12236 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12239 @node Inline Functions
12240 @section Inline Functions
12241 @cindex inline functions, debugging
12243 @dfn{Inlining} is an optimization that inserts a copy of the function
12244 body directly at each call site, instead of jumping to a shared
12245 routine. @value{GDBN} displays inlined functions just like
12246 non-inlined functions. They appear in backtraces. You can view their
12247 arguments and local variables, step into them with @code{step}, skip
12248 them with @code{next}, and escape from them with @code{finish}.
12249 You can check whether a function was inlined by using the
12250 @code{info frame} command.
12252 For @value{GDBN} to support inlined functions, the compiler must
12253 record information about inlining in the debug information ---
12254 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12255 other compilers do also. @value{GDBN} only supports inlined functions
12256 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12257 do not emit two required attributes (@samp{DW_AT_call_file} and
12258 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12259 function calls with earlier versions of @value{NGCC}. It instead
12260 displays the arguments and local variables of inlined functions as
12261 local variables in the caller.
12263 The body of an inlined function is directly included at its call site;
12264 unlike a non-inlined function, there are no instructions devoted to
12265 the call. @value{GDBN} still pretends that the call site and the
12266 start of the inlined function are different instructions. Stepping to
12267 the call site shows the call site, and then stepping again shows
12268 the first line of the inlined function, even though no additional
12269 instructions are executed.
12271 This makes source-level debugging much clearer; you can see both the
12272 context of the call and then the effect of the call. Only stepping by
12273 a single instruction using @code{stepi} or @code{nexti} does not do
12274 this; single instruction steps always show the inlined body.
12276 There are some ways that @value{GDBN} does not pretend that inlined
12277 function calls are the same as normal calls:
12281 Setting breakpoints at the call site of an inlined function may not
12282 work, because the call site does not contain any code. @value{GDBN}
12283 may incorrectly move the breakpoint to the next line of the enclosing
12284 function, after the call. This limitation will be removed in a future
12285 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12286 or inside the inlined function instead.
12289 @value{GDBN} cannot locate the return value of inlined calls after
12290 using the @code{finish} command. This is a limitation of compiler-generated
12291 debugging information; after @code{finish}, you can step to the next line
12292 and print a variable where your program stored the return value.
12296 @node Tail Call Frames
12297 @section Tail Call Frames
12298 @cindex tail call frames, debugging
12300 Function @code{B} can call function @code{C} in its very last statement. In
12301 unoptimized compilation the call of @code{C} is immediately followed by return
12302 instruction at the end of @code{B} code. Optimizing compiler may replace the
12303 call and return in function @code{B} into one jump to function @code{C}
12304 instead. Such use of a jump instruction is called @dfn{tail call}.
12306 During execution of function @code{C}, there will be no indication in the
12307 function call stack frames that it was tail-called from @code{B}. If function
12308 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12309 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12310 some cases @value{GDBN} can determine that @code{C} was tail-called from
12311 @code{B}, and it will then create fictitious call frame for that, with the
12312 return address set up as if @code{B} called @code{C} normally.
12314 This functionality is currently supported only by DWARF 2 debugging format and
12315 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12316 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12319 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12320 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12324 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12326 Stack level 1, frame at 0x7fffffffda30:
12327 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12328 tail call frame, caller of frame at 0x7fffffffda30
12329 source language c++.
12330 Arglist at unknown address.
12331 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12334 The detection of all the possible code path executions can find them ambiguous.
12335 There is no execution history stored (possible @ref{Reverse Execution} is never
12336 used for this purpose) and the last known caller could have reached the known
12337 callee by multiple different jump sequences. In such case @value{GDBN} still
12338 tries to show at least all the unambiguous top tail callers and all the
12339 unambiguous bottom tail calees, if any.
12342 @anchor{set debug entry-values}
12343 @item set debug entry-values
12344 @kindex set debug entry-values
12345 When set to on, enables printing of analysis messages for both frame argument
12346 values at function entry and tail calls. It will show all the possible valid
12347 tail calls code paths it has considered. It will also print the intersection
12348 of them with the final unambiguous (possibly partial or even empty) code path
12351 @item show debug entry-values
12352 @kindex show debug entry-values
12353 Show the current state of analysis messages printing for both frame argument
12354 values at function entry and tail calls.
12357 The analysis messages for tail calls can for example show why the virtual tail
12358 call frame for function @code{c} has not been recognized (due to the indirect
12359 reference by variable @code{x}):
12362 static void __attribute__((noinline, noclone)) c (void);
12363 void (*x) (void) = c;
12364 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12365 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12366 int main (void) @{ x (); return 0; @}
12368 Breakpoint 1, DW_OP_entry_value resolving cannot find
12369 DW_TAG_call_site 0x40039a in main
12371 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12374 #1 0x000000000040039a in main () at t.c:5
12377 Another possibility is an ambiguous virtual tail call frames resolution:
12381 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12382 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12383 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12384 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12385 static void __attribute__((noinline, noclone)) b (void)
12386 @{ if (i) c (); else e (); @}
12387 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12388 int main (void) @{ a (); return 0; @}
12390 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12391 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12392 tailcall: reduced: 0x4004d2(a) |
12395 #1 0x00000000004004d2 in a () at t.c:8
12396 #2 0x0000000000400395 in main () at t.c:9
12399 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12400 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12402 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12403 @ifset HAVE_MAKEINFO_CLICK
12404 @set ARROW @click{}
12405 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12406 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12408 @ifclear HAVE_MAKEINFO_CLICK
12410 @set CALLSEQ1B @value{CALLSEQ1A}
12411 @set CALLSEQ2B @value{CALLSEQ2A}
12414 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12415 The code can have possible execution paths @value{CALLSEQ1B} or
12416 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12418 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12419 has found. It then finds another possible calling sequcen - that one is
12420 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12421 printed as the @code{reduced:} calling sequence. That one could have many
12422 futher @code{compare:} and @code{reduced:} statements as long as there remain
12423 any non-ambiguous sequence entries.
12425 For the frame of function @code{b} in both cases there are different possible
12426 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12427 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12428 therefore this one is displayed to the user while the ambiguous frames are
12431 There can be also reasons why printing of frame argument values at function
12436 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12437 static void __attribute__((noinline, noclone)) a (int i);
12438 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12439 static void __attribute__((noinline, noclone)) a (int i)
12440 @{ if (i) b (i - 1); else c (0); @}
12441 int main (void) @{ a (5); return 0; @}
12444 #0 c (i=i@@entry=0) at t.c:2
12445 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12446 function "a" at 0x400420 can call itself via tail calls
12447 i=<optimized out>) at t.c:6
12448 #2 0x000000000040036e in main () at t.c:7
12451 @value{GDBN} cannot find out from the inferior state if and how many times did
12452 function @code{a} call itself (via function @code{b}) as these calls would be
12453 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12454 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12455 prints @code{<optimized out>} instead.
12458 @chapter C Preprocessor Macros
12460 Some languages, such as C and C@t{++}, provide a way to define and invoke
12461 ``preprocessor macros'' which expand into strings of tokens.
12462 @value{GDBN} can evaluate expressions containing macro invocations, show
12463 the result of macro expansion, and show a macro's definition, including
12464 where it was defined.
12466 You may need to compile your program specially to provide @value{GDBN}
12467 with information about preprocessor macros. Most compilers do not
12468 include macros in their debugging information, even when you compile
12469 with the @option{-g} flag. @xref{Compilation}.
12471 A program may define a macro at one point, remove that definition later,
12472 and then provide a different definition after that. Thus, at different
12473 points in the program, a macro may have different definitions, or have
12474 no definition at all. If there is a current stack frame, @value{GDBN}
12475 uses the macros in scope at that frame's source code line. Otherwise,
12476 @value{GDBN} uses the macros in scope at the current listing location;
12479 Whenever @value{GDBN} evaluates an expression, it always expands any
12480 macro invocations present in the expression. @value{GDBN} also provides
12481 the following commands for working with macros explicitly.
12485 @kindex macro expand
12486 @cindex macro expansion, showing the results of preprocessor
12487 @cindex preprocessor macro expansion, showing the results of
12488 @cindex expanding preprocessor macros
12489 @item macro expand @var{expression}
12490 @itemx macro exp @var{expression}
12491 Show the results of expanding all preprocessor macro invocations in
12492 @var{expression}. Since @value{GDBN} simply expands macros, but does
12493 not parse the result, @var{expression} need not be a valid expression;
12494 it can be any string of tokens.
12497 @item macro expand-once @var{expression}
12498 @itemx macro exp1 @var{expression}
12499 @cindex expand macro once
12500 @i{(This command is not yet implemented.)} Show the results of
12501 expanding those preprocessor macro invocations that appear explicitly in
12502 @var{expression}. Macro invocations appearing in that expansion are
12503 left unchanged. This command allows you to see the effect of a
12504 particular macro more clearly, without being confused by further
12505 expansions. Since @value{GDBN} simply expands macros, but does not
12506 parse the result, @var{expression} need not be a valid expression; it
12507 can be any string of tokens.
12510 @cindex macro definition, showing
12511 @cindex definition of a macro, showing
12512 @cindex macros, from debug info
12513 @item info macro [-a|-all] [--] @var{macro}
12514 Show the current definition or all definitions of the named @var{macro},
12515 and describe the source location or compiler command-line where that
12516 definition was established. The optional double dash is to signify the end of
12517 argument processing and the beginning of @var{macro} for non C-like macros where
12518 the macro may begin with a hyphen.
12520 @kindex info macros
12521 @item info macros @var{location}
12522 Show all macro definitions that are in effect at the location specified
12523 by @var{location}, and describe the source location or compiler
12524 command-line where those definitions were established.
12526 @kindex macro define
12527 @cindex user-defined macros
12528 @cindex defining macros interactively
12529 @cindex macros, user-defined
12530 @item macro define @var{macro} @var{replacement-list}
12531 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12532 Introduce a definition for a preprocessor macro named @var{macro},
12533 invocations of which are replaced by the tokens given in
12534 @var{replacement-list}. The first form of this command defines an
12535 ``object-like'' macro, which takes no arguments; the second form
12536 defines a ``function-like'' macro, which takes the arguments given in
12539 A definition introduced by this command is in scope in every
12540 expression evaluated in @value{GDBN}, until it is removed with the
12541 @code{macro undef} command, described below. The definition overrides
12542 all definitions for @var{macro} present in the program being debugged,
12543 as well as any previous user-supplied definition.
12545 @kindex macro undef
12546 @item macro undef @var{macro}
12547 Remove any user-supplied definition for the macro named @var{macro}.
12548 This command only affects definitions provided with the @code{macro
12549 define} command, described above; it cannot remove definitions present
12550 in the program being debugged.
12554 List all the macros defined using the @code{macro define} command.
12557 @cindex macros, example of debugging with
12558 Here is a transcript showing the above commands in action. First, we
12559 show our source files:
12564 #include "sample.h"
12567 #define ADD(x) (M + x)
12572 printf ("Hello, world!\n");
12574 printf ("We're so creative.\n");
12576 printf ("Goodbye, world!\n");
12583 Now, we compile the program using the @sc{gnu} C compiler,
12584 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12585 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12586 and @option{-gdwarf-4}; we recommend always choosing the most recent
12587 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12588 includes information about preprocessor macros in the debugging
12592 $ gcc -gdwarf-2 -g3 sample.c -o sample
12596 Now, we start @value{GDBN} on our sample program:
12600 GNU gdb 2002-05-06-cvs
12601 Copyright 2002 Free Software Foundation, Inc.
12602 GDB is free software, @dots{}
12606 We can expand macros and examine their definitions, even when the
12607 program is not running. @value{GDBN} uses the current listing position
12608 to decide which macro definitions are in scope:
12611 (@value{GDBP}) list main
12614 5 #define ADD(x) (M + x)
12619 10 printf ("Hello, world!\n");
12621 12 printf ("We're so creative.\n");
12622 (@value{GDBP}) info macro ADD
12623 Defined at /home/jimb/gdb/macros/play/sample.c:5
12624 #define ADD(x) (M + x)
12625 (@value{GDBP}) info macro Q
12626 Defined at /home/jimb/gdb/macros/play/sample.h:1
12627 included at /home/jimb/gdb/macros/play/sample.c:2
12629 (@value{GDBP}) macro expand ADD(1)
12630 expands to: (42 + 1)
12631 (@value{GDBP}) macro expand-once ADD(1)
12632 expands to: once (M + 1)
12636 In the example above, note that @code{macro expand-once} expands only
12637 the macro invocation explicit in the original text --- the invocation of
12638 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12639 which was introduced by @code{ADD}.
12641 Once the program is running, @value{GDBN} uses the macro definitions in
12642 force at the source line of the current stack frame:
12645 (@value{GDBP}) break main
12646 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12648 Starting program: /home/jimb/gdb/macros/play/sample
12650 Breakpoint 1, main () at sample.c:10
12651 10 printf ("Hello, world!\n");
12655 At line 10, the definition of the macro @code{N} at line 9 is in force:
12658 (@value{GDBP}) info macro N
12659 Defined at /home/jimb/gdb/macros/play/sample.c:9
12661 (@value{GDBP}) macro expand N Q M
12662 expands to: 28 < 42
12663 (@value{GDBP}) print N Q M
12668 As we step over directives that remove @code{N}'s definition, and then
12669 give it a new definition, @value{GDBN} finds the definition (or lack
12670 thereof) in force at each point:
12673 (@value{GDBP}) next
12675 12 printf ("We're so creative.\n");
12676 (@value{GDBP}) info macro N
12677 The symbol `N' has no definition as a C/C++ preprocessor macro
12678 at /home/jimb/gdb/macros/play/sample.c:12
12679 (@value{GDBP}) next
12681 14 printf ("Goodbye, world!\n");
12682 (@value{GDBP}) info macro N
12683 Defined at /home/jimb/gdb/macros/play/sample.c:13
12685 (@value{GDBP}) macro expand N Q M
12686 expands to: 1729 < 42
12687 (@value{GDBP}) print N Q M
12692 In addition to source files, macros can be defined on the compilation command
12693 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12694 such a way, @value{GDBN} displays the location of their definition as line zero
12695 of the source file submitted to the compiler.
12698 (@value{GDBP}) info macro __STDC__
12699 Defined at /home/jimb/gdb/macros/play/sample.c:0
12706 @chapter Tracepoints
12707 @c This chapter is based on the documentation written by Michael
12708 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12710 @cindex tracepoints
12711 In some applications, it is not feasible for the debugger to interrupt
12712 the program's execution long enough for the developer to learn
12713 anything helpful about its behavior. If the program's correctness
12714 depends on its real-time behavior, delays introduced by a debugger
12715 might cause the program to change its behavior drastically, or perhaps
12716 fail, even when the code itself is correct. It is useful to be able
12717 to observe the program's behavior without interrupting it.
12719 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12720 specify locations in the program, called @dfn{tracepoints}, and
12721 arbitrary expressions to evaluate when those tracepoints are reached.
12722 Later, using the @code{tfind} command, you can examine the values
12723 those expressions had when the program hit the tracepoints. The
12724 expressions may also denote objects in memory---structures or arrays,
12725 for example---whose values @value{GDBN} should record; while visiting
12726 a particular tracepoint, you may inspect those objects as if they were
12727 in memory at that moment. However, because @value{GDBN} records these
12728 values without interacting with you, it can do so quickly and
12729 unobtrusively, hopefully not disturbing the program's behavior.
12731 The tracepoint facility is currently available only for remote
12732 targets. @xref{Targets}. In addition, your remote target must know
12733 how to collect trace data. This functionality is implemented in the
12734 remote stub; however, none of the stubs distributed with @value{GDBN}
12735 support tracepoints as of this writing. The format of the remote
12736 packets used to implement tracepoints are described in @ref{Tracepoint
12739 It is also possible to get trace data from a file, in a manner reminiscent
12740 of corefiles; you specify the filename, and use @code{tfind} to search
12741 through the file. @xref{Trace Files}, for more details.
12743 This chapter describes the tracepoint commands and features.
12746 * Set Tracepoints::
12747 * Analyze Collected Data::
12748 * Tracepoint Variables::
12752 @node Set Tracepoints
12753 @section Commands to Set Tracepoints
12755 Before running such a @dfn{trace experiment}, an arbitrary number of
12756 tracepoints can be set. A tracepoint is actually a special type of
12757 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12758 standard breakpoint commands. For instance, as with breakpoints,
12759 tracepoint numbers are successive integers starting from one, and many
12760 of the commands associated with tracepoints take the tracepoint number
12761 as their argument, to identify which tracepoint to work on.
12763 For each tracepoint, you can specify, in advance, some arbitrary set
12764 of data that you want the target to collect in the trace buffer when
12765 it hits that tracepoint. The collected data can include registers,
12766 local variables, or global data. Later, you can use @value{GDBN}
12767 commands to examine the values these data had at the time the
12768 tracepoint was hit.
12770 Tracepoints do not support every breakpoint feature. Ignore counts on
12771 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12772 commands when they are hit. Tracepoints may not be thread-specific
12775 @cindex fast tracepoints
12776 Some targets may support @dfn{fast tracepoints}, which are inserted in
12777 a different way (such as with a jump instead of a trap), that is
12778 faster but possibly restricted in where they may be installed.
12780 @cindex static tracepoints
12781 @cindex markers, static tracepoints
12782 @cindex probing markers, static tracepoints
12783 Regular and fast tracepoints are dynamic tracing facilities, meaning
12784 that they can be used to insert tracepoints at (almost) any location
12785 in the target. Some targets may also support controlling @dfn{static
12786 tracepoints} from @value{GDBN}. With static tracing, a set of
12787 instrumentation points, also known as @dfn{markers}, are embedded in
12788 the target program, and can be activated or deactivated by name or
12789 address. These are usually placed at locations which facilitate
12790 investigating what the target is actually doing. @value{GDBN}'s
12791 support for static tracing includes being able to list instrumentation
12792 points, and attach them with @value{GDBN} defined high level
12793 tracepoints that expose the whole range of convenience of
12794 @value{GDBN}'s tracepoints support. Namely, support for collecting
12795 registers values and values of global or local (to the instrumentation
12796 point) variables; tracepoint conditions and trace state variables.
12797 The act of installing a @value{GDBN} static tracepoint on an
12798 instrumentation point, or marker, is referred to as @dfn{probing} a
12799 static tracepoint marker.
12801 @code{gdbserver} supports tracepoints on some target systems.
12802 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12804 This section describes commands to set tracepoints and associated
12805 conditions and actions.
12808 * Create and Delete Tracepoints::
12809 * Enable and Disable Tracepoints::
12810 * Tracepoint Passcounts::
12811 * Tracepoint Conditions::
12812 * Trace State Variables::
12813 * Tracepoint Actions::
12814 * Listing Tracepoints::
12815 * Listing Static Tracepoint Markers::
12816 * Starting and Stopping Trace Experiments::
12817 * Tracepoint Restrictions::
12820 @node Create and Delete Tracepoints
12821 @subsection Create and Delete Tracepoints
12824 @cindex set tracepoint
12826 @item trace @var{location}
12827 The @code{trace} command is very similar to the @code{break} command.
12828 Its argument @var{location} can be any valid location.
12829 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12830 which is a point in the target program where the debugger will briefly stop,
12831 collect some data, and then allow the program to continue. Setting a tracepoint
12832 or changing its actions takes effect immediately if the remote stub
12833 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12835 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12836 these changes don't take effect until the next @code{tstart}
12837 command, and once a trace experiment is running, further changes will
12838 not have any effect until the next trace experiment starts. In addition,
12839 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12840 address is not yet resolved. (This is similar to pending breakpoints.)
12841 Pending tracepoints are not downloaded to the target and not installed
12842 until they are resolved. The resolution of pending tracepoints requires
12843 @value{GDBN} support---when debugging with the remote target, and
12844 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12845 tracing}), pending tracepoints can not be resolved (and downloaded to
12846 the remote stub) while @value{GDBN} is disconnected.
12848 Here are some examples of using the @code{trace} command:
12851 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12853 (@value{GDBP}) @b{trace +2} // 2 lines forward
12855 (@value{GDBP}) @b{trace my_function} // first source line of function
12857 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12859 (@value{GDBP}) @b{trace *0x2117c4} // an address
12863 You can abbreviate @code{trace} as @code{tr}.
12865 @item trace @var{location} if @var{cond}
12866 Set a tracepoint with condition @var{cond}; evaluate the expression
12867 @var{cond} each time the tracepoint is reached, and collect data only
12868 if the value is nonzero---that is, if @var{cond} evaluates as true.
12869 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12870 information on tracepoint conditions.
12872 @item ftrace @var{location} [ if @var{cond} ]
12873 @cindex set fast tracepoint
12874 @cindex fast tracepoints, setting
12876 The @code{ftrace} command sets a fast tracepoint. For targets that
12877 support them, fast tracepoints will use a more efficient but possibly
12878 less general technique to trigger data collection, such as a jump
12879 instruction instead of a trap, or some sort of hardware support. It
12880 may not be possible to create a fast tracepoint at the desired
12881 location, in which case the command will exit with an explanatory
12884 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12887 On 32-bit x86-architecture systems, fast tracepoints normally need to
12888 be placed at an instruction that is 5 bytes or longer, but can be
12889 placed at 4-byte instructions if the low 64K of memory of the target
12890 program is available to install trampolines. Some Unix-type systems,
12891 such as @sc{gnu}/Linux, exclude low addresses from the program's
12892 address space; but for instance with the Linux kernel it is possible
12893 to let @value{GDBN} use this area by doing a @command{sysctl} command
12894 to set the @code{mmap_min_addr} kernel parameter, as in
12897 sudo sysctl -w vm.mmap_min_addr=32768
12901 which sets the low address to 32K, which leaves plenty of room for
12902 trampolines. The minimum address should be set to a page boundary.
12904 @item strace @var{location} [ if @var{cond} ]
12905 @cindex set static tracepoint
12906 @cindex static tracepoints, setting
12907 @cindex probe static tracepoint marker
12909 The @code{strace} command sets a static tracepoint. For targets that
12910 support it, setting a static tracepoint probes a static
12911 instrumentation point, or marker, found at @var{location}. It may not
12912 be possible to set a static tracepoint at the desired location, in
12913 which case the command will exit with an explanatory message.
12915 @value{GDBN} handles arguments to @code{strace} exactly as for
12916 @code{trace}, with the addition that the user can also specify
12917 @code{-m @var{marker}} as @var{location}. This probes the marker
12918 identified by the @var{marker} string identifier. This identifier
12919 depends on the static tracepoint backend library your program is
12920 using. You can find all the marker identifiers in the @samp{ID} field
12921 of the @code{info static-tracepoint-markers} command output.
12922 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12923 Markers}. For example, in the following small program using the UST
12929 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12934 the marker id is composed of joining the first two arguments to the
12935 @code{trace_mark} call with a slash, which translates to:
12938 (@value{GDBP}) info static-tracepoint-markers
12939 Cnt Enb ID Address What
12940 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12946 so you may probe the marker above with:
12949 (@value{GDBP}) strace -m ust/bar33
12952 Static tracepoints accept an extra collect action --- @code{collect
12953 $_sdata}. This collects arbitrary user data passed in the probe point
12954 call to the tracing library. In the UST example above, you'll see
12955 that the third argument to @code{trace_mark} is a printf-like format
12956 string. The user data is then the result of running that formating
12957 string against the following arguments. Note that @code{info
12958 static-tracepoint-markers} command output lists that format string in
12959 the @samp{Data:} field.
12961 You can inspect this data when analyzing the trace buffer, by printing
12962 the $_sdata variable like any other variable available to
12963 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12966 @cindex last tracepoint number
12967 @cindex recent tracepoint number
12968 @cindex tracepoint number
12969 The convenience variable @code{$tpnum} records the tracepoint number
12970 of the most recently set tracepoint.
12972 @kindex delete tracepoint
12973 @cindex tracepoint deletion
12974 @item delete tracepoint @r{[}@var{num}@r{]}
12975 Permanently delete one or more tracepoints. With no argument, the
12976 default is to delete all tracepoints. Note that the regular
12977 @code{delete} command can remove tracepoints also.
12982 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12984 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12988 You can abbreviate this command as @code{del tr}.
12991 @node Enable and Disable Tracepoints
12992 @subsection Enable and Disable Tracepoints
12994 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12997 @kindex disable tracepoint
12998 @item disable tracepoint @r{[}@var{num}@r{]}
12999 Disable tracepoint @var{num}, or all tracepoints if no argument
13000 @var{num} is given. A disabled tracepoint will have no effect during
13001 a trace experiment, but it is not forgotten. You can re-enable
13002 a disabled tracepoint using the @code{enable tracepoint} command.
13003 If the command is issued during a trace experiment and the debug target
13004 has support for disabling tracepoints during a trace experiment, then the
13005 change will be effective immediately. Otherwise, it will be applied to the
13006 next trace experiment.
13008 @kindex enable tracepoint
13009 @item enable tracepoint @r{[}@var{num}@r{]}
13010 Enable tracepoint @var{num}, or all tracepoints. If this command is
13011 issued during a trace experiment and the debug target supports enabling
13012 tracepoints during a trace experiment, then the enabled tracepoints will
13013 become effective immediately. Otherwise, they will become effective the
13014 next time a trace experiment is run.
13017 @node Tracepoint Passcounts
13018 @subsection Tracepoint Passcounts
13022 @cindex tracepoint pass count
13023 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13024 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13025 automatically stop a trace experiment. If a tracepoint's passcount is
13026 @var{n}, then the trace experiment will be automatically stopped on
13027 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13028 @var{num} is not specified, the @code{passcount} command sets the
13029 passcount of the most recently defined tracepoint. If no passcount is
13030 given, the trace experiment will run until stopped explicitly by the
13036 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13037 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13039 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13040 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13041 (@value{GDBP}) @b{trace foo}
13042 (@value{GDBP}) @b{pass 3}
13043 (@value{GDBP}) @b{trace bar}
13044 (@value{GDBP}) @b{pass 2}
13045 (@value{GDBP}) @b{trace baz}
13046 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13047 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13048 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13049 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13053 @node Tracepoint Conditions
13054 @subsection Tracepoint Conditions
13055 @cindex conditional tracepoints
13056 @cindex tracepoint conditions
13058 The simplest sort of tracepoint collects data every time your program
13059 reaches a specified place. You can also specify a @dfn{condition} for
13060 a tracepoint. A condition is just a Boolean expression in your
13061 programming language (@pxref{Expressions, ,Expressions}). A
13062 tracepoint with a condition evaluates the expression each time your
13063 program reaches it, and data collection happens only if the condition
13066 Tracepoint conditions can be specified when a tracepoint is set, by
13067 using @samp{if} in the arguments to the @code{trace} command.
13068 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13069 also be set or changed at any time with the @code{condition} command,
13070 just as with breakpoints.
13072 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13073 the conditional expression itself. Instead, @value{GDBN} encodes the
13074 expression into an agent expression (@pxref{Agent Expressions})
13075 suitable for execution on the target, independently of @value{GDBN}.
13076 Global variables become raw memory locations, locals become stack
13077 accesses, and so forth.
13079 For instance, suppose you have a function that is usually called
13080 frequently, but should not be called after an error has occurred. You
13081 could use the following tracepoint command to collect data about calls
13082 of that function that happen while the error code is propagating
13083 through the program; an unconditional tracepoint could end up
13084 collecting thousands of useless trace frames that you would have to
13088 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13091 @node Trace State Variables
13092 @subsection Trace State Variables
13093 @cindex trace state variables
13095 A @dfn{trace state variable} is a special type of variable that is
13096 created and managed by target-side code. The syntax is the same as
13097 that for GDB's convenience variables (a string prefixed with ``$''),
13098 but they are stored on the target. They must be created explicitly,
13099 using a @code{tvariable} command. They are always 64-bit signed
13102 Trace state variables are remembered by @value{GDBN}, and downloaded
13103 to the target along with tracepoint information when the trace
13104 experiment starts. There are no intrinsic limits on the number of
13105 trace state variables, beyond memory limitations of the target.
13107 @cindex convenience variables, and trace state variables
13108 Although trace state variables are managed by the target, you can use
13109 them in print commands and expressions as if they were convenience
13110 variables; @value{GDBN} will get the current value from the target
13111 while the trace experiment is running. Trace state variables share
13112 the same namespace as other ``$'' variables, which means that you
13113 cannot have trace state variables with names like @code{$23} or
13114 @code{$pc}, nor can you have a trace state variable and a convenience
13115 variable with the same name.
13119 @item tvariable $@var{name} [ = @var{expression} ]
13121 The @code{tvariable} command creates a new trace state variable named
13122 @code{$@var{name}}, and optionally gives it an initial value of
13123 @var{expression}. The @var{expression} is evaluated when this command is
13124 entered; the result will be converted to an integer if possible,
13125 otherwise @value{GDBN} will report an error. A subsequent
13126 @code{tvariable} command specifying the same name does not create a
13127 variable, but instead assigns the supplied initial value to the
13128 existing variable of that name, overwriting any previous initial
13129 value. The default initial value is 0.
13131 @item info tvariables
13132 @kindex info tvariables
13133 List all the trace state variables along with their initial values.
13134 Their current values may also be displayed, if the trace experiment is
13137 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13138 @kindex delete tvariable
13139 Delete the given trace state variables, or all of them if no arguments
13144 @node Tracepoint Actions
13145 @subsection Tracepoint Action Lists
13149 @cindex tracepoint actions
13150 @item actions @r{[}@var{num}@r{]}
13151 This command will prompt for a list of actions to be taken when the
13152 tracepoint is hit. If the tracepoint number @var{num} is not
13153 specified, this command sets the actions for the one that was most
13154 recently defined (so that you can define a tracepoint and then say
13155 @code{actions} without bothering about its number). You specify the
13156 actions themselves on the following lines, one action at a time, and
13157 terminate the actions list with a line containing just @code{end}. So
13158 far, the only defined actions are @code{collect}, @code{teval}, and
13159 @code{while-stepping}.
13161 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13162 Commands, ,Breakpoint Command Lists}), except that only the defined
13163 actions are allowed; any other @value{GDBN} command is rejected.
13165 @cindex remove actions from a tracepoint
13166 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13167 and follow it immediately with @samp{end}.
13170 (@value{GDBP}) @b{collect @var{data}} // collect some data
13172 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13174 (@value{GDBP}) @b{end} // signals the end of actions.
13177 In the following example, the action list begins with @code{collect}
13178 commands indicating the things to be collected when the tracepoint is
13179 hit. Then, in order to single-step and collect additional data
13180 following the tracepoint, a @code{while-stepping} command is used,
13181 followed by the list of things to be collected after each step in a
13182 sequence of single steps. The @code{while-stepping} command is
13183 terminated by its own separate @code{end} command. Lastly, the action
13184 list is terminated by an @code{end} command.
13187 (@value{GDBP}) @b{trace foo}
13188 (@value{GDBP}) @b{actions}
13189 Enter actions for tracepoint 1, one per line:
13192 > while-stepping 12
13193 > collect $pc, arr[i]
13198 @kindex collect @r{(tracepoints)}
13199 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13200 Collect values of the given expressions when the tracepoint is hit.
13201 This command accepts a comma-separated list of any valid expressions.
13202 In addition to global, static, or local variables, the following
13203 special arguments are supported:
13207 Collect all registers.
13210 Collect all function arguments.
13213 Collect all local variables.
13216 Collect the return address. This is helpful if you want to see more
13219 @emph{Note:} The return address location can not always be reliably
13220 determined up front, and the wrong address / registers may end up
13221 collected instead. On some architectures the reliability is higher
13222 for tracepoints at function entry, while on others it's the opposite.
13223 When this happens, backtracing will stop because the return address is
13224 found unavailable (unless another collect rule happened to match it).
13227 Collects the number of arguments from the static probe at which the
13228 tracepoint is located.
13229 @xref{Static Probe Points}.
13231 @item $_probe_arg@var{n}
13232 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13233 from the static probe at which the tracepoint is located.
13234 @xref{Static Probe Points}.
13237 @vindex $_sdata@r{, collect}
13238 Collect static tracepoint marker specific data. Only available for
13239 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13240 Lists}. On the UST static tracepoints library backend, an
13241 instrumentation point resembles a @code{printf} function call. The
13242 tracing library is able to collect user specified data formatted to a
13243 character string using the format provided by the programmer that
13244 instrumented the program. Other backends have similar mechanisms.
13245 Here's an example of a UST marker call:
13248 const char master_name[] = "$your_name";
13249 trace_mark(channel1, marker1, "hello %s", master_name)
13252 In this case, collecting @code{$_sdata} collects the string
13253 @samp{hello $yourname}. When analyzing the trace buffer, you can
13254 inspect @samp{$_sdata} like any other variable available to
13258 You can give several consecutive @code{collect} commands, each one
13259 with a single argument, or one @code{collect} command with several
13260 arguments separated by commas; the effect is the same.
13262 The optional @var{mods} changes the usual handling of the arguments.
13263 @code{s} requests that pointers to chars be handled as strings, in
13264 particular collecting the contents of the memory being pointed at, up
13265 to the first zero. The upper bound is by default the value of the
13266 @code{print elements} variable; if @code{s} is followed by a decimal
13267 number, that is the upper bound instead. So for instance
13268 @samp{collect/s25 mystr} collects as many as 25 characters at
13271 The command @code{info scope} (@pxref{Symbols, info scope}) is
13272 particularly useful for figuring out what data to collect.
13274 @kindex teval @r{(tracepoints)}
13275 @item teval @var{expr1}, @var{expr2}, @dots{}
13276 Evaluate the given expressions when the tracepoint is hit. This
13277 command accepts a comma-separated list of expressions. The results
13278 are discarded, so this is mainly useful for assigning values to trace
13279 state variables (@pxref{Trace State Variables}) without adding those
13280 values to the trace buffer, as would be the case if the @code{collect}
13283 @kindex while-stepping @r{(tracepoints)}
13284 @item while-stepping @var{n}
13285 Perform @var{n} single-step instruction traces after the tracepoint,
13286 collecting new data after each step. The @code{while-stepping}
13287 command is followed by the list of what to collect while stepping
13288 (followed by its own @code{end} command):
13291 > while-stepping 12
13292 > collect $regs, myglobal
13298 Note that @code{$pc} is not automatically collected by
13299 @code{while-stepping}; you need to explicitly collect that register if
13300 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13303 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13304 @kindex set default-collect
13305 @cindex default collection action
13306 This variable is a list of expressions to collect at each tracepoint
13307 hit. It is effectively an additional @code{collect} action prepended
13308 to every tracepoint action list. The expressions are parsed
13309 individually for each tracepoint, so for instance a variable named
13310 @code{xyz} may be interpreted as a global for one tracepoint, and a
13311 local for another, as appropriate to the tracepoint's location.
13313 @item show default-collect
13314 @kindex show default-collect
13315 Show the list of expressions that are collected by default at each
13320 @node Listing Tracepoints
13321 @subsection Listing Tracepoints
13324 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13325 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13326 @cindex information about tracepoints
13327 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13328 Display information about the tracepoint @var{num}. If you don't
13329 specify a tracepoint number, displays information about all the
13330 tracepoints defined so far. The format is similar to that used for
13331 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13332 command, simply restricting itself to tracepoints.
13334 A tracepoint's listing may include additional information specific to
13339 its passcount as given by the @code{passcount @var{n}} command
13342 the state about installed on target of each location
13346 (@value{GDBP}) @b{info trace}
13347 Num Type Disp Enb Address What
13348 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13350 collect globfoo, $regs
13355 2 tracepoint keep y <MULTIPLE>
13357 2.1 y 0x0804859c in func4 at change-loc.h:35
13358 installed on target
13359 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13360 installed on target
13361 2.3 y <PENDING> set_tracepoint
13362 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13363 not installed on target
13368 This command can be abbreviated @code{info tp}.
13371 @node Listing Static Tracepoint Markers
13372 @subsection Listing Static Tracepoint Markers
13375 @kindex info static-tracepoint-markers
13376 @cindex information about static tracepoint markers
13377 @item info static-tracepoint-markers
13378 Display information about all static tracepoint markers defined in the
13381 For each marker, the following columns are printed:
13385 An incrementing counter, output to help readability. This is not a
13388 The marker ID, as reported by the target.
13389 @item Enabled or Disabled
13390 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13391 that are not enabled.
13393 Where the marker is in your program, as a memory address.
13395 Where the marker is in the source for your program, as a file and line
13396 number. If the debug information included in the program does not
13397 allow @value{GDBN} to locate the source of the marker, this column
13398 will be left blank.
13402 In addition, the following information may be printed for each marker:
13406 User data passed to the tracing library by the marker call. In the
13407 UST backend, this is the format string passed as argument to the
13409 @item Static tracepoints probing the marker
13410 The list of static tracepoints attached to the marker.
13414 (@value{GDBP}) info static-tracepoint-markers
13415 Cnt ID Enb Address What
13416 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13417 Data: number1 %d number2 %d
13418 Probed by static tracepoints: #2
13419 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13425 @node Starting and Stopping Trace Experiments
13426 @subsection Starting and Stopping Trace Experiments
13429 @kindex tstart [ @var{notes} ]
13430 @cindex start a new trace experiment
13431 @cindex collected data discarded
13433 This command starts the trace experiment, and begins collecting data.
13434 It has the side effect of discarding all the data collected in the
13435 trace buffer during the previous trace experiment. If any arguments
13436 are supplied, they are taken as a note and stored with the trace
13437 experiment's state. The notes may be arbitrary text, and are
13438 especially useful with disconnected tracing in a multi-user context;
13439 the notes can explain what the trace is doing, supply user contact
13440 information, and so forth.
13442 @kindex tstop [ @var{notes} ]
13443 @cindex stop a running trace experiment
13445 This command stops the trace experiment. If any arguments are
13446 supplied, they are recorded with the experiment as a note. This is
13447 useful if you are stopping a trace started by someone else, for
13448 instance if the trace is interfering with the system's behavior and
13449 needs to be stopped quickly.
13451 @strong{Note}: a trace experiment and data collection may stop
13452 automatically if any tracepoint's passcount is reached
13453 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13456 @cindex status of trace data collection
13457 @cindex trace experiment, status of
13459 This command displays the status of the current trace data
13463 Here is an example of the commands we described so far:
13466 (@value{GDBP}) @b{trace gdb_c_test}
13467 (@value{GDBP}) @b{actions}
13468 Enter actions for tracepoint #1, one per line.
13469 > collect $regs,$locals,$args
13470 > while-stepping 11
13474 (@value{GDBP}) @b{tstart}
13475 [time passes @dots{}]
13476 (@value{GDBP}) @b{tstop}
13479 @anchor{disconnected tracing}
13480 @cindex disconnected tracing
13481 You can choose to continue running the trace experiment even if
13482 @value{GDBN} disconnects from the target, voluntarily or
13483 involuntarily. For commands such as @code{detach}, the debugger will
13484 ask what you want to do with the trace. But for unexpected
13485 terminations (@value{GDBN} crash, network outage), it would be
13486 unfortunate to lose hard-won trace data, so the variable
13487 @code{disconnected-tracing} lets you decide whether the trace should
13488 continue running without @value{GDBN}.
13491 @item set disconnected-tracing on
13492 @itemx set disconnected-tracing off
13493 @kindex set disconnected-tracing
13494 Choose whether a tracing run should continue to run if @value{GDBN}
13495 has disconnected from the target. Note that @code{detach} or
13496 @code{quit} will ask you directly what to do about a running trace no
13497 matter what this variable's setting, so the variable is mainly useful
13498 for handling unexpected situations, such as loss of the network.
13500 @item show disconnected-tracing
13501 @kindex show disconnected-tracing
13502 Show the current choice for disconnected tracing.
13506 When you reconnect to the target, the trace experiment may or may not
13507 still be running; it might have filled the trace buffer in the
13508 meantime, or stopped for one of the other reasons. If it is running,
13509 it will continue after reconnection.
13511 Upon reconnection, the target will upload information about the
13512 tracepoints in effect. @value{GDBN} will then compare that
13513 information to the set of tracepoints currently defined, and attempt
13514 to match them up, allowing for the possibility that the numbers may
13515 have changed due to creation and deletion in the meantime. If one of
13516 the target's tracepoints does not match any in @value{GDBN}, the
13517 debugger will create a new tracepoint, so that you have a number with
13518 which to specify that tracepoint. This matching-up process is
13519 necessarily heuristic, and it may result in useless tracepoints being
13520 created; you may simply delete them if they are of no use.
13522 @cindex circular trace buffer
13523 If your target agent supports a @dfn{circular trace buffer}, then you
13524 can run a trace experiment indefinitely without filling the trace
13525 buffer; when space runs out, the agent deletes already-collected trace
13526 frames, oldest first, until there is enough room to continue
13527 collecting. This is especially useful if your tracepoints are being
13528 hit too often, and your trace gets terminated prematurely because the
13529 buffer is full. To ask for a circular trace buffer, simply set
13530 @samp{circular-trace-buffer} to on. You can set this at any time,
13531 including during tracing; if the agent can do it, it will change
13532 buffer handling on the fly, otherwise it will not take effect until
13536 @item set circular-trace-buffer on
13537 @itemx set circular-trace-buffer off
13538 @kindex set circular-trace-buffer
13539 Choose whether a tracing run should use a linear or circular buffer
13540 for trace data. A linear buffer will not lose any trace data, but may
13541 fill up prematurely, while a circular buffer will discard old trace
13542 data, but it will have always room for the latest tracepoint hits.
13544 @item show circular-trace-buffer
13545 @kindex show circular-trace-buffer
13546 Show the current choice for the trace buffer. Note that this may not
13547 match the agent's current buffer handling, nor is it guaranteed to
13548 match the setting that might have been in effect during a past run,
13549 for instance if you are looking at frames from a trace file.
13554 @item set trace-buffer-size @var{n}
13555 @itemx set trace-buffer-size unlimited
13556 @kindex set trace-buffer-size
13557 Request that the target use a trace buffer of @var{n} bytes. Not all
13558 targets will honor the request; they may have a compiled-in size for
13559 the trace buffer, or some other limitation. Set to a value of
13560 @code{unlimited} or @code{-1} to let the target use whatever size it
13561 likes. This is also the default.
13563 @item show trace-buffer-size
13564 @kindex show trace-buffer-size
13565 Show the current requested size for the trace buffer. Note that this
13566 will only match the actual size if the target supports size-setting,
13567 and was able to handle the requested size. For instance, if the
13568 target can only change buffer size between runs, this variable will
13569 not reflect the change until the next run starts. Use @code{tstatus}
13570 to get a report of the actual buffer size.
13574 @item set trace-user @var{text}
13575 @kindex set trace-user
13577 @item show trace-user
13578 @kindex show trace-user
13580 @item set trace-notes @var{text}
13581 @kindex set trace-notes
13582 Set the trace run's notes.
13584 @item show trace-notes
13585 @kindex show trace-notes
13586 Show the trace run's notes.
13588 @item set trace-stop-notes @var{text}
13589 @kindex set trace-stop-notes
13590 Set the trace run's stop notes. The handling of the note is as for
13591 @code{tstop} arguments; the set command is convenient way to fix a
13592 stop note that is mistaken or incomplete.
13594 @item show trace-stop-notes
13595 @kindex show trace-stop-notes
13596 Show the trace run's stop notes.
13600 @node Tracepoint Restrictions
13601 @subsection Tracepoint Restrictions
13603 @cindex tracepoint restrictions
13604 There are a number of restrictions on the use of tracepoints. As
13605 described above, tracepoint data gathering occurs on the target
13606 without interaction from @value{GDBN}. Thus the full capabilities of
13607 the debugger are not available during data gathering, and then at data
13608 examination time, you will be limited by only having what was
13609 collected. The following items describe some common problems, but it
13610 is not exhaustive, and you may run into additional difficulties not
13616 Tracepoint expressions are intended to gather objects (lvalues). Thus
13617 the full flexibility of GDB's expression evaluator is not available.
13618 You cannot call functions, cast objects to aggregate types, access
13619 convenience variables or modify values (except by assignment to trace
13620 state variables). Some language features may implicitly call
13621 functions (for instance Objective-C fields with accessors), and therefore
13622 cannot be collected either.
13625 Collection of local variables, either individually or in bulk with
13626 @code{$locals} or @code{$args}, during @code{while-stepping} may
13627 behave erratically. The stepping action may enter a new scope (for
13628 instance by stepping into a function), or the location of the variable
13629 may change (for instance it is loaded into a register). The
13630 tracepoint data recorded uses the location information for the
13631 variables that is correct for the tracepoint location. When the
13632 tracepoint is created, it is not possible, in general, to determine
13633 where the steps of a @code{while-stepping} sequence will advance the
13634 program---particularly if a conditional branch is stepped.
13637 Collection of an incompletely-initialized or partially-destroyed object
13638 may result in something that @value{GDBN} cannot display, or displays
13639 in a misleading way.
13642 When @value{GDBN} displays a pointer to character it automatically
13643 dereferences the pointer to also display characters of the string
13644 being pointed to. However, collecting the pointer during tracing does
13645 not automatically collect the string. You need to explicitly
13646 dereference the pointer and provide size information if you want to
13647 collect not only the pointer, but the memory pointed to. For example,
13648 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13652 It is not possible to collect a complete stack backtrace at a
13653 tracepoint. Instead, you may collect the registers and a few hundred
13654 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13655 (adjust to use the name of the actual stack pointer register on your
13656 target architecture, and the amount of stack you wish to capture).
13657 Then the @code{backtrace} command will show a partial backtrace when
13658 using a trace frame. The number of stack frames that can be examined
13659 depends on the sizes of the frames in the collected stack. Note that
13660 if you ask for a block so large that it goes past the bottom of the
13661 stack, the target agent may report an error trying to read from an
13665 If you do not collect registers at a tracepoint, @value{GDBN} can
13666 infer that the value of @code{$pc} must be the same as the address of
13667 the tracepoint and use that when you are looking at a trace frame
13668 for that tracepoint. However, this cannot work if the tracepoint has
13669 multiple locations (for instance if it was set in a function that was
13670 inlined), or if it has a @code{while-stepping} loop. In those cases
13671 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13676 @node Analyze Collected Data
13677 @section Using the Collected Data
13679 After the tracepoint experiment ends, you use @value{GDBN} commands
13680 for examining the trace data. The basic idea is that each tracepoint
13681 collects a trace @dfn{snapshot} every time it is hit and another
13682 snapshot every time it single-steps. All these snapshots are
13683 consecutively numbered from zero and go into a buffer, and you can
13684 examine them later. The way you examine them is to @dfn{focus} on a
13685 specific trace snapshot. When the remote stub is focused on a trace
13686 snapshot, it will respond to all @value{GDBN} requests for memory and
13687 registers by reading from the buffer which belongs to that snapshot,
13688 rather than from @emph{real} memory or registers of the program being
13689 debugged. This means that @strong{all} @value{GDBN} commands
13690 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13691 behave as if we were currently debugging the program state as it was
13692 when the tracepoint occurred. Any requests for data that are not in
13693 the buffer will fail.
13696 * tfind:: How to select a trace snapshot
13697 * tdump:: How to display all data for a snapshot
13698 * save tracepoints:: How to save tracepoints for a future run
13702 @subsection @code{tfind @var{n}}
13705 @cindex select trace snapshot
13706 @cindex find trace snapshot
13707 The basic command for selecting a trace snapshot from the buffer is
13708 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13709 counting from zero. If no argument @var{n} is given, the next
13710 snapshot is selected.
13712 Here are the various forms of using the @code{tfind} command.
13716 Find the first snapshot in the buffer. This is a synonym for
13717 @code{tfind 0} (since 0 is the number of the first snapshot).
13720 Stop debugging trace snapshots, resume @emph{live} debugging.
13723 Same as @samp{tfind none}.
13726 No argument means find the next trace snapshot or find the first
13727 one if no trace snapshot is selected.
13730 Find the previous trace snapshot before the current one. This permits
13731 retracing earlier steps.
13733 @item tfind tracepoint @var{num}
13734 Find the next snapshot associated with tracepoint @var{num}. Search
13735 proceeds forward from the last examined trace snapshot. If no
13736 argument @var{num} is given, it means find the next snapshot collected
13737 for the same tracepoint as the current snapshot.
13739 @item tfind pc @var{addr}
13740 Find the next snapshot associated with the value @var{addr} of the
13741 program counter. Search proceeds forward from the last examined trace
13742 snapshot. If no argument @var{addr} is given, it means find the next
13743 snapshot with the same value of PC as the current snapshot.
13745 @item tfind outside @var{addr1}, @var{addr2}
13746 Find the next snapshot whose PC is outside the given range of
13747 addresses (exclusive).
13749 @item tfind range @var{addr1}, @var{addr2}
13750 Find the next snapshot whose PC is between @var{addr1} and
13751 @var{addr2} (inclusive).
13753 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13754 Find the next snapshot associated with the source line @var{n}. If
13755 the optional argument @var{file} is given, refer to line @var{n} in
13756 that source file. Search proceeds forward from the last examined
13757 trace snapshot. If no argument @var{n} is given, it means find the
13758 next line other than the one currently being examined; thus saying
13759 @code{tfind line} repeatedly can appear to have the same effect as
13760 stepping from line to line in a @emph{live} debugging session.
13763 The default arguments for the @code{tfind} commands are specifically
13764 designed to make it easy to scan through the trace buffer. For
13765 instance, @code{tfind} with no argument selects the next trace
13766 snapshot, and @code{tfind -} with no argument selects the previous
13767 trace snapshot. So, by giving one @code{tfind} command, and then
13768 simply hitting @key{RET} repeatedly you can examine all the trace
13769 snapshots in order. Or, by saying @code{tfind -} and then hitting
13770 @key{RET} repeatedly you can examine the snapshots in reverse order.
13771 The @code{tfind line} command with no argument selects the snapshot
13772 for the next source line executed. The @code{tfind pc} command with
13773 no argument selects the next snapshot with the same program counter
13774 (PC) as the current frame. The @code{tfind tracepoint} command with
13775 no argument selects the next trace snapshot collected by the same
13776 tracepoint as the current one.
13778 In addition to letting you scan through the trace buffer manually,
13779 these commands make it easy to construct @value{GDBN} scripts that
13780 scan through the trace buffer and print out whatever collected data
13781 you are interested in. Thus, if we want to examine the PC, FP, and SP
13782 registers from each trace frame in the buffer, we can say this:
13785 (@value{GDBP}) @b{tfind start}
13786 (@value{GDBP}) @b{while ($trace_frame != -1)}
13787 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13788 $trace_frame, $pc, $sp, $fp
13792 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13793 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13794 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13795 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13796 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13797 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13798 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13799 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13800 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13801 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13802 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13805 Or, if we want to examine the variable @code{X} at each source line in
13809 (@value{GDBP}) @b{tfind start}
13810 (@value{GDBP}) @b{while ($trace_frame != -1)}
13811 > printf "Frame %d, X == %d\n", $trace_frame, X
13821 @subsection @code{tdump}
13823 @cindex dump all data collected at tracepoint
13824 @cindex tracepoint data, display
13826 This command takes no arguments. It prints all the data collected at
13827 the current trace snapshot.
13830 (@value{GDBP}) @b{trace 444}
13831 (@value{GDBP}) @b{actions}
13832 Enter actions for tracepoint #2, one per line:
13833 > collect $regs, $locals, $args, gdb_long_test
13836 (@value{GDBP}) @b{tstart}
13838 (@value{GDBP}) @b{tfind line 444}
13839 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13841 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13843 (@value{GDBP}) @b{tdump}
13844 Data collected at tracepoint 2, trace frame 1:
13845 d0 0xc4aa0085 -995491707
13849 d4 0x71aea3d 119204413
13852 d7 0x380035 3670069
13853 a0 0x19e24a 1696330
13854 a1 0x3000668 50333288
13856 a3 0x322000 3284992
13857 a4 0x3000698 50333336
13858 a5 0x1ad3cc 1758156
13859 fp 0x30bf3c 0x30bf3c
13860 sp 0x30bf34 0x30bf34
13862 pc 0x20b2c8 0x20b2c8
13866 p = 0x20e5b4 "gdb-test"
13873 gdb_long_test = 17 '\021'
13878 @code{tdump} works by scanning the tracepoint's current collection
13879 actions and printing the value of each expression listed. So
13880 @code{tdump} can fail, if after a run, you change the tracepoint's
13881 actions to mention variables that were not collected during the run.
13883 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13884 uses the collected value of @code{$pc} to distinguish between trace
13885 frames that were collected at the tracepoint hit, and frames that were
13886 collected while stepping. This allows it to correctly choose whether
13887 to display the basic list of collections, or the collections from the
13888 body of the while-stepping loop. However, if @code{$pc} was not collected,
13889 then @code{tdump} will always attempt to dump using the basic collection
13890 list, and may fail if a while-stepping frame does not include all the
13891 same data that is collected at the tracepoint hit.
13892 @c This is getting pretty arcane, example would be good.
13894 @node save tracepoints
13895 @subsection @code{save tracepoints @var{filename}}
13896 @kindex save tracepoints
13897 @kindex save-tracepoints
13898 @cindex save tracepoints for future sessions
13900 This command saves all current tracepoint definitions together with
13901 their actions and passcounts, into a file @file{@var{filename}}
13902 suitable for use in a later debugging session. To read the saved
13903 tracepoint definitions, use the @code{source} command (@pxref{Command
13904 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13905 alias for @w{@code{save tracepoints}}
13907 @node Tracepoint Variables
13908 @section Convenience Variables for Tracepoints
13909 @cindex tracepoint variables
13910 @cindex convenience variables for tracepoints
13913 @vindex $trace_frame
13914 @item (int) $trace_frame
13915 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13916 snapshot is selected.
13918 @vindex $tracepoint
13919 @item (int) $tracepoint
13920 The tracepoint for the current trace snapshot.
13922 @vindex $trace_line
13923 @item (int) $trace_line
13924 The line number for the current trace snapshot.
13926 @vindex $trace_file
13927 @item (char []) $trace_file
13928 The source file for the current trace snapshot.
13930 @vindex $trace_func
13931 @item (char []) $trace_func
13932 The name of the function containing @code{$tracepoint}.
13935 Note: @code{$trace_file} is not suitable for use in @code{printf},
13936 use @code{output} instead.
13938 Here's a simple example of using these convenience variables for
13939 stepping through all the trace snapshots and printing some of their
13940 data. Note that these are not the same as trace state variables,
13941 which are managed by the target.
13944 (@value{GDBP}) @b{tfind start}
13946 (@value{GDBP}) @b{while $trace_frame != -1}
13947 > output $trace_file
13948 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13954 @section Using Trace Files
13955 @cindex trace files
13957 In some situations, the target running a trace experiment may no
13958 longer be available; perhaps it crashed, or the hardware was needed
13959 for a different activity. To handle these cases, you can arrange to
13960 dump the trace data into a file, and later use that file as a source
13961 of trace data, via the @code{target tfile} command.
13966 @item tsave [ -r ] @var{filename}
13967 @itemx tsave [-ctf] @var{dirname}
13968 Save the trace data to @var{filename}. By default, this command
13969 assumes that @var{filename} refers to the host filesystem, so if
13970 necessary @value{GDBN} will copy raw trace data up from the target and
13971 then save it. If the target supports it, you can also supply the
13972 optional argument @code{-r} (``remote'') to direct the target to save
13973 the data directly into @var{filename} in its own filesystem, which may be
13974 more efficient if the trace buffer is very large. (Note, however, that
13975 @code{target tfile} can only read from files accessible to the host.)
13976 By default, this command will save trace frame in tfile format.
13977 You can supply the optional argument @code{-ctf} to save data in CTF
13978 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13979 that can be shared by multiple debugging and tracing tools. Please go to
13980 @indicateurl{http://www.efficios.com/ctf} to get more information.
13982 @kindex target tfile
13986 @item target tfile @var{filename}
13987 @itemx target ctf @var{dirname}
13988 Use the file named @var{filename} or directory named @var{dirname} as
13989 a source of trace data. Commands that examine data work as they do with
13990 a live target, but it is not possible to run any new trace experiments.
13991 @code{tstatus} will report the state of the trace run at the moment
13992 the data was saved, as well as the current trace frame you are examining.
13993 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13997 (@value{GDBP}) target ctf ctf.ctf
13998 (@value{GDBP}) tfind
13999 Found trace frame 0, tracepoint 2
14000 39 ++a; /* set tracepoint 1 here */
14001 (@value{GDBP}) tdump
14002 Data collected at tracepoint 2, trace frame 0:
14006 c = @{"123", "456", "789", "123", "456", "789"@}
14007 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14015 @chapter Debugging Programs That Use Overlays
14018 If your program is too large to fit completely in your target system's
14019 memory, you can sometimes use @dfn{overlays} to work around this
14020 problem. @value{GDBN} provides some support for debugging programs that
14024 * How Overlays Work:: A general explanation of overlays.
14025 * Overlay Commands:: Managing overlays in @value{GDBN}.
14026 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14027 mapped by asking the inferior.
14028 * Overlay Sample Program:: A sample program using overlays.
14031 @node How Overlays Work
14032 @section How Overlays Work
14033 @cindex mapped overlays
14034 @cindex unmapped overlays
14035 @cindex load address, overlay's
14036 @cindex mapped address
14037 @cindex overlay area
14039 Suppose you have a computer whose instruction address space is only 64
14040 kilobytes long, but which has much more memory which can be accessed by
14041 other means: special instructions, segment registers, or memory
14042 management hardware, for example. Suppose further that you want to
14043 adapt a program which is larger than 64 kilobytes to run on this system.
14045 One solution is to identify modules of your program which are relatively
14046 independent, and need not call each other directly; call these modules
14047 @dfn{overlays}. Separate the overlays from the main program, and place
14048 their machine code in the larger memory. Place your main program in
14049 instruction memory, but leave at least enough space there to hold the
14050 largest overlay as well.
14052 Now, to call a function located in an overlay, you must first copy that
14053 overlay's machine code from the large memory into the space set aside
14054 for it in the instruction memory, and then jump to its entry point
14057 @c NB: In the below the mapped area's size is greater or equal to the
14058 @c size of all overlays. This is intentional to remind the developer
14059 @c that overlays don't necessarily need to be the same size.
14063 Data Instruction Larger
14064 Address Space Address Space Address Space
14065 +-----------+ +-----------+ +-----------+
14067 +-----------+ +-----------+ +-----------+<-- overlay 1
14068 | program | | main | .----| overlay 1 | load address
14069 | variables | | program | | +-----------+
14070 | and heap | | | | | |
14071 +-----------+ | | | +-----------+<-- overlay 2
14072 | | +-----------+ | | | load address
14073 +-----------+ | | | .-| overlay 2 |
14075 mapped --->+-----------+ | | +-----------+
14076 address | | | | | |
14077 | overlay | <-' | | |
14078 | area | <---' +-----------+<-- overlay 3
14079 | | <---. | | load address
14080 +-----------+ `--| overlay 3 |
14087 @anchor{A code overlay}A code overlay
14091 The diagram (@pxref{A code overlay}) shows a system with separate data
14092 and instruction address spaces. To map an overlay, the program copies
14093 its code from the larger address space to the instruction address space.
14094 Since the overlays shown here all use the same mapped address, only one
14095 may be mapped at a time. For a system with a single address space for
14096 data and instructions, the diagram would be similar, except that the
14097 program variables and heap would share an address space with the main
14098 program and the overlay area.
14100 An overlay loaded into instruction memory and ready for use is called a
14101 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14102 instruction memory. An overlay not present (or only partially present)
14103 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14104 is its address in the larger memory. The mapped address is also called
14105 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14106 called the @dfn{load memory address}, or @dfn{LMA}.
14108 Unfortunately, overlays are not a completely transparent way to adapt a
14109 program to limited instruction memory. They introduce a new set of
14110 global constraints you must keep in mind as you design your program:
14115 Before calling or returning to a function in an overlay, your program
14116 must make sure that overlay is actually mapped. Otherwise, the call or
14117 return will transfer control to the right address, but in the wrong
14118 overlay, and your program will probably crash.
14121 If the process of mapping an overlay is expensive on your system, you
14122 will need to choose your overlays carefully to minimize their effect on
14123 your program's performance.
14126 The executable file you load onto your system must contain each
14127 overlay's instructions, appearing at the overlay's load address, not its
14128 mapped address. However, each overlay's instructions must be relocated
14129 and its symbols defined as if the overlay were at its mapped address.
14130 You can use GNU linker scripts to specify different load and relocation
14131 addresses for pieces of your program; see @ref{Overlay Description,,,
14132 ld.info, Using ld: the GNU linker}.
14135 The procedure for loading executable files onto your system must be able
14136 to load their contents into the larger address space as well as the
14137 instruction and data spaces.
14141 The overlay system described above is rather simple, and could be
14142 improved in many ways:
14147 If your system has suitable bank switch registers or memory management
14148 hardware, you could use those facilities to make an overlay's load area
14149 contents simply appear at their mapped address in instruction space.
14150 This would probably be faster than copying the overlay to its mapped
14151 area in the usual way.
14154 If your overlays are small enough, you could set aside more than one
14155 overlay area, and have more than one overlay mapped at a time.
14158 You can use overlays to manage data, as well as instructions. In
14159 general, data overlays are even less transparent to your design than
14160 code overlays: whereas code overlays only require care when you call or
14161 return to functions, data overlays require care every time you access
14162 the data. Also, if you change the contents of a data overlay, you
14163 must copy its contents back out to its load address before you can copy a
14164 different data overlay into the same mapped area.
14169 @node Overlay Commands
14170 @section Overlay Commands
14172 To use @value{GDBN}'s overlay support, each overlay in your program must
14173 correspond to a separate section of the executable file. The section's
14174 virtual memory address and load memory address must be the overlay's
14175 mapped and load addresses. Identifying overlays with sections allows
14176 @value{GDBN} to determine the appropriate address of a function or
14177 variable, depending on whether the overlay is mapped or not.
14179 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14180 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14185 Disable @value{GDBN}'s overlay support. When overlay support is
14186 disabled, @value{GDBN} assumes that all functions and variables are
14187 always present at their mapped addresses. By default, @value{GDBN}'s
14188 overlay support is disabled.
14190 @item overlay manual
14191 @cindex manual overlay debugging
14192 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14193 relies on you to tell it which overlays are mapped, and which are not,
14194 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14195 commands described below.
14197 @item overlay map-overlay @var{overlay}
14198 @itemx overlay map @var{overlay}
14199 @cindex map an overlay
14200 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14201 be the name of the object file section containing the overlay. When an
14202 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14203 functions and variables at their mapped addresses. @value{GDBN} assumes
14204 that any other overlays whose mapped ranges overlap that of
14205 @var{overlay} are now unmapped.
14207 @item overlay unmap-overlay @var{overlay}
14208 @itemx overlay unmap @var{overlay}
14209 @cindex unmap an overlay
14210 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14211 must be the name of the object file section containing the overlay.
14212 When an overlay is unmapped, @value{GDBN} assumes it can find the
14213 overlay's functions and variables at their load addresses.
14216 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14217 consults a data structure the overlay manager maintains in the inferior
14218 to see which overlays are mapped. For details, see @ref{Automatic
14219 Overlay Debugging}.
14221 @item overlay load-target
14222 @itemx overlay load
14223 @cindex reloading the overlay table
14224 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14225 re-reads the table @value{GDBN} automatically each time the inferior
14226 stops, so this command should only be necessary if you have changed the
14227 overlay mapping yourself using @value{GDBN}. This command is only
14228 useful when using automatic overlay debugging.
14230 @item overlay list-overlays
14231 @itemx overlay list
14232 @cindex listing mapped overlays
14233 Display a list of the overlays currently mapped, along with their mapped
14234 addresses, load addresses, and sizes.
14238 Normally, when @value{GDBN} prints a code address, it includes the name
14239 of the function the address falls in:
14242 (@value{GDBP}) print main
14243 $3 = @{int ()@} 0x11a0 <main>
14246 When overlay debugging is enabled, @value{GDBN} recognizes code in
14247 unmapped overlays, and prints the names of unmapped functions with
14248 asterisks around them. For example, if @code{foo} is a function in an
14249 unmapped overlay, @value{GDBN} prints it this way:
14252 (@value{GDBP}) overlay list
14253 No sections are mapped.
14254 (@value{GDBP}) print foo
14255 $5 = @{int (int)@} 0x100000 <*foo*>
14258 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14262 (@value{GDBP}) overlay list
14263 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14264 mapped at 0x1016 - 0x104a
14265 (@value{GDBP}) print foo
14266 $6 = @{int (int)@} 0x1016 <foo>
14269 When overlay debugging is enabled, @value{GDBN} can find the correct
14270 address for functions and variables in an overlay, whether or not the
14271 overlay is mapped. This allows most @value{GDBN} commands, like
14272 @code{break} and @code{disassemble}, to work normally, even on unmapped
14273 code. However, @value{GDBN}'s breakpoint support has some limitations:
14277 @cindex breakpoints in overlays
14278 @cindex overlays, setting breakpoints in
14279 You can set breakpoints in functions in unmapped overlays, as long as
14280 @value{GDBN} can write to the overlay at its load address.
14282 @value{GDBN} can not set hardware or simulator-based breakpoints in
14283 unmapped overlays. However, if you set a breakpoint at the end of your
14284 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14285 you are using manual overlay management), @value{GDBN} will re-set its
14286 breakpoints properly.
14290 @node Automatic Overlay Debugging
14291 @section Automatic Overlay Debugging
14292 @cindex automatic overlay debugging
14294 @value{GDBN} can automatically track which overlays are mapped and which
14295 are not, given some simple co-operation from the overlay manager in the
14296 inferior. If you enable automatic overlay debugging with the
14297 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14298 looks in the inferior's memory for certain variables describing the
14299 current state of the overlays.
14301 Here are the variables your overlay manager must define to support
14302 @value{GDBN}'s automatic overlay debugging:
14306 @item @code{_ovly_table}:
14307 This variable must be an array of the following structures:
14312 /* The overlay's mapped address. */
14315 /* The size of the overlay, in bytes. */
14316 unsigned long size;
14318 /* The overlay's load address. */
14321 /* Non-zero if the overlay is currently mapped;
14323 unsigned long mapped;
14327 @item @code{_novlys}:
14328 This variable must be a four-byte signed integer, holding the total
14329 number of elements in @code{_ovly_table}.
14333 To decide whether a particular overlay is mapped or not, @value{GDBN}
14334 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14335 @code{lma} members equal the VMA and LMA of the overlay's section in the
14336 executable file. When @value{GDBN} finds a matching entry, it consults
14337 the entry's @code{mapped} member to determine whether the overlay is
14340 In addition, your overlay manager may define a function called
14341 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14342 will silently set a breakpoint there. If the overlay manager then
14343 calls this function whenever it has changed the overlay table, this
14344 will enable @value{GDBN} to accurately keep track of which overlays
14345 are in program memory, and update any breakpoints that may be set
14346 in overlays. This will allow breakpoints to work even if the
14347 overlays are kept in ROM or other non-writable memory while they
14348 are not being executed.
14350 @node Overlay Sample Program
14351 @section Overlay Sample Program
14352 @cindex overlay example program
14354 When linking a program which uses overlays, you must place the overlays
14355 at their load addresses, while relocating them to run at their mapped
14356 addresses. To do this, you must write a linker script (@pxref{Overlay
14357 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14358 since linker scripts are specific to a particular host system, target
14359 architecture, and target memory layout, this manual cannot provide
14360 portable sample code demonstrating @value{GDBN}'s overlay support.
14362 However, the @value{GDBN} source distribution does contain an overlaid
14363 program, with linker scripts for a few systems, as part of its test
14364 suite. The program consists of the following files from
14365 @file{gdb/testsuite/gdb.base}:
14369 The main program file.
14371 A simple overlay manager, used by @file{overlays.c}.
14376 Overlay modules, loaded and used by @file{overlays.c}.
14379 Linker scripts for linking the test program on the @code{d10v-elf}
14380 and @code{m32r-elf} targets.
14383 You can build the test program using the @code{d10v-elf} GCC
14384 cross-compiler like this:
14387 $ d10v-elf-gcc -g -c overlays.c
14388 $ d10v-elf-gcc -g -c ovlymgr.c
14389 $ d10v-elf-gcc -g -c foo.c
14390 $ d10v-elf-gcc -g -c bar.c
14391 $ d10v-elf-gcc -g -c baz.c
14392 $ d10v-elf-gcc -g -c grbx.c
14393 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14394 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14397 The build process is identical for any other architecture, except that
14398 you must substitute the appropriate compiler and linker script for the
14399 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14403 @chapter Using @value{GDBN} with Different Languages
14406 Although programming languages generally have common aspects, they are
14407 rarely expressed in the same manner. For instance, in ANSI C,
14408 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14409 Modula-2, it is accomplished by @code{p^}. Values can also be
14410 represented (and displayed) differently. Hex numbers in C appear as
14411 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14413 @cindex working language
14414 Language-specific information is built into @value{GDBN} for some languages,
14415 allowing you to express operations like the above in your program's
14416 native language, and allowing @value{GDBN} to output values in a manner
14417 consistent with the syntax of your program's native language. The
14418 language you use to build expressions is called the @dfn{working
14422 * Setting:: Switching between source languages
14423 * Show:: Displaying the language
14424 * Checks:: Type and range checks
14425 * Supported Languages:: Supported languages
14426 * Unsupported Languages:: Unsupported languages
14430 @section Switching Between Source Languages
14432 There are two ways to control the working language---either have @value{GDBN}
14433 set it automatically, or select it manually yourself. You can use the
14434 @code{set language} command for either purpose. On startup, @value{GDBN}
14435 defaults to setting the language automatically. The working language is
14436 used to determine how expressions you type are interpreted, how values
14439 In addition to the working language, every source file that
14440 @value{GDBN} knows about has its own working language. For some object
14441 file formats, the compiler might indicate which language a particular
14442 source file is in. However, most of the time @value{GDBN} infers the
14443 language from the name of the file. The language of a source file
14444 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14445 show each frame appropriately for its own language. There is no way to
14446 set the language of a source file from within @value{GDBN}, but you can
14447 set the language associated with a filename extension. @xref{Show, ,
14448 Displaying the Language}.
14450 This is most commonly a problem when you use a program, such
14451 as @code{cfront} or @code{f2c}, that generates C but is written in
14452 another language. In that case, make the
14453 program use @code{#line} directives in its C output; that way
14454 @value{GDBN} will know the correct language of the source code of the original
14455 program, and will display that source code, not the generated C code.
14458 * Filenames:: Filename extensions and languages.
14459 * Manually:: Setting the working language manually
14460 * Automatically:: Having @value{GDBN} infer the source language
14464 @subsection List of Filename Extensions and Languages
14466 If a source file name ends in one of the following extensions, then
14467 @value{GDBN} infers that its language is the one indicated.
14485 C@t{++} source file
14491 Objective-C source file
14495 Fortran source file
14498 Modula-2 source file
14502 Assembler source file. This actually behaves almost like C, but
14503 @value{GDBN} does not skip over function prologues when stepping.
14506 In addition, you may set the language associated with a filename
14507 extension. @xref{Show, , Displaying the Language}.
14510 @subsection Setting the Working Language
14512 If you allow @value{GDBN} to set the language automatically,
14513 expressions are interpreted the same way in your debugging session and
14516 @kindex set language
14517 If you wish, you may set the language manually. To do this, issue the
14518 command @samp{set language @var{lang}}, where @var{lang} is the name of
14519 a language, such as
14520 @code{c} or @code{modula-2}.
14521 For a list of the supported languages, type @samp{set language}.
14523 Setting the language manually prevents @value{GDBN} from updating the working
14524 language automatically. This can lead to confusion if you try
14525 to debug a program when the working language is not the same as the
14526 source language, when an expression is acceptable to both
14527 languages---but means different things. For instance, if the current
14528 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14536 might not have the effect you intended. In C, this means to add
14537 @code{b} and @code{c} and place the result in @code{a}. The result
14538 printed would be the value of @code{a}. In Modula-2, this means to compare
14539 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14541 @node Automatically
14542 @subsection Having @value{GDBN} Infer the Source Language
14544 To have @value{GDBN} set the working language automatically, use
14545 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14546 then infers the working language. That is, when your program stops in a
14547 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14548 working language to the language recorded for the function in that
14549 frame. If the language for a frame is unknown (that is, if the function
14550 or block corresponding to the frame was defined in a source file that
14551 does not have a recognized extension), the current working language is
14552 not changed, and @value{GDBN} issues a warning.
14554 This may not seem necessary for most programs, which are written
14555 entirely in one source language. However, program modules and libraries
14556 written in one source language can be used by a main program written in
14557 a different source language. Using @samp{set language auto} in this
14558 case frees you from having to set the working language manually.
14561 @section Displaying the Language
14563 The following commands help you find out which language is the
14564 working language, and also what language source files were written in.
14567 @item show language
14568 @anchor{show language}
14569 @kindex show language
14570 Display the current working language. This is the
14571 language you can use with commands such as @code{print} to
14572 build and compute expressions that may involve variables in your program.
14575 @kindex info frame@r{, show the source language}
14576 Display the source language for this frame. This language becomes the
14577 working language if you use an identifier from this frame.
14578 @xref{Frame Info, ,Information about a Frame}, to identify the other
14579 information listed here.
14582 @kindex info source@r{, show the source language}
14583 Display the source language of this source file.
14584 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14585 information listed here.
14588 In unusual circumstances, you may have source files with extensions
14589 not in the standard list. You can then set the extension associated
14590 with a language explicitly:
14593 @item set extension-language @var{ext} @var{language}
14594 @kindex set extension-language
14595 Tell @value{GDBN} that source files with extension @var{ext} are to be
14596 assumed as written in the source language @var{language}.
14598 @item info extensions
14599 @kindex info extensions
14600 List all the filename extensions and the associated languages.
14604 @section Type and Range Checking
14606 Some languages are designed to guard you against making seemingly common
14607 errors through a series of compile- and run-time checks. These include
14608 checking the type of arguments to functions and operators and making
14609 sure mathematical overflows are caught at run time. Checks such as
14610 these help to ensure a program's correctness once it has been compiled
14611 by eliminating type mismatches and providing active checks for range
14612 errors when your program is running.
14614 By default @value{GDBN} checks for these errors according to the
14615 rules of the current source language. Although @value{GDBN} does not check
14616 the statements in your program, it can check expressions entered directly
14617 into @value{GDBN} for evaluation via the @code{print} command, for example.
14620 * Type Checking:: An overview of type checking
14621 * Range Checking:: An overview of range checking
14624 @cindex type checking
14625 @cindex checks, type
14626 @node Type Checking
14627 @subsection An Overview of Type Checking
14629 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14630 arguments to operators and functions have to be of the correct type,
14631 otherwise an error occurs. These checks prevent type mismatch
14632 errors from ever causing any run-time problems. For example,
14635 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14637 (@value{GDBP}) print obj.my_method (0)
14640 (@value{GDBP}) print obj.my_method (0x1234)
14641 Cannot resolve method klass::my_method to any overloaded instance
14644 The second example fails because in C@t{++} the integer constant
14645 @samp{0x1234} is not type-compatible with the pointer parameter type.
14647 For the expressions you use in @value{GDBN} commands, you can tell
14648 @value{GDBN} to not enforce strict type checking or
14649 to treat any mismatches as errors and abandon the expression;
14650 When type checking is disabled, @value{GDBN} successfully evaluates
14651 expressions like the second example above.
14653 Even if type checking is off, there may be other reasons
14654 related to type that prevent @value{GDBN} from evaluating an expression.
14655 For instance, @value{GDBN} does not know how to add an @code{int} and
14656 a @code{struct foo}. These particular type errors have nothing to do
14657 with the language in use and usually arise from expressions which make
14658 little sense to evaluate anyway.
14660 @value{GDBN} provides some additional commands for controlling type checking:
14662 @kindex set check type
14663 @kindex show check type
14665 @item set check type on
14666 @itemx set check type off
14667 Set strict type checking on or off. If any type mismatches occur in
14668 evaluating an expression while type checking is on, @value{GDBN} prints a
14669 message and aborts evaluation of the expression.
14671 @item show check type
14672 Show the current setting of type checking and whether @value{GDBN}
14673 is enforcing strict type checking rules.
14676 @cindex range checking
14677 @cindex checks, range
14678 @node Range Checking
14679 @subsection An Overview of Range Checking
14681 In some languages (such as Modula-2), it is an error to exceed the
14682 bounds of a type; this is enforced with run-time checks. Such range
14683 checking is meant to ensure program correctness by making sure
14684 computations do not overflow, or indices on an array element access do
14685 not exceed the bounds of the array.
14687 For expressions you use in @value{GDBN} commands, you can tell
14688 @value{GDBN} to treat range errors in one of three ways: ignore them,
14689 always treat them as errors and abandon the expression, or issue
14690 warnings but evaluate the expression anyway.
14692 A range error can result from numerical overflow, from exceeding an
14693 array index bound, or when you type a constant that is not a member
14694 of any type. Some languages, however, do not treat overflows as an
14695 error. In many implementations of C, mathematical overflow causes the
14696 result to ``wrap around'' to lower values---for example, if @var{m} is
14697 the largest integer value, and @var{s} is the smallest, then
14700 @var{m} + 1 @result{} @var{s}
14703 This, too, is specific to individual languages, and in some cases
14704 specific to individual compilers or machines. @xref{Supported Languages, ,
14705 Supported Languages}, for further details on specific languages.
14707 @value{GDBN} provides some additional commands for controlling the range checker:
14709 @kindex set check range
14710 @kindex show check range
14712 @item set check range auto
14713 Set range checking on or off based on the current working language.
14714 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14717 @item set check range on
14718 @itemx set check range off
14719 Set range checking on or off, overriding the default setting for the
14720 current working language. A warning is issued if the setting does not
14721 match the language default. If a range error occurs and range checking is on,
14722 then a message is printed and evaluation of the expression is aborted.
14724 @item set check range warn
14725 Output messages when the @value{GDBN} range checker detects a range error,
14726 but attempt to evaluate the expression anyway. Evaluating the
14727 expression may still be impossible for other reasons, such as accessing
14728 memory that the process does not own (a typical example from many Unix
14732 Show the current setting of the range checker, and whether or not it is
14733 being set automatically by @value{GDBN}.
14736 @node Supported Languages
14737 @section Supported Languages
14739 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14740 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14741 @c This is false ...
14742 Some @value{GDBN} features may be used in expressions regardless of the
14743 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14744 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14745 ,Expressions}) can be used with the constructs of any supported
14748 The following sections detail to what degree each source language is
14749 supported by @value{GDBN}. These sections are not meant to be language
14750 tutorials or references, but serve only as a reference guide to what the
14751 @value{GDBN} expression parser accepts, and what input and output
14752 formats should look like for different languages. There are many good
14753 books written on each of these languages; please look to these for a
14754 language reference or tutorial.
14757 * C:: C and C@t{++}
14760 * Objective-C:: Objective-C
14761 * OpenCL C:: OpenCL C
14762 * Fortran:: Fortran
14765 * Modula-2:: Modula-2
14770 @subsection C and C@t{++}
14772 @cindex C and C@t{++}
14773 @cindex expressions in C or C@t{++}
14775 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14776 to both languages. Whenever this is the case, we discuss those languages
14780 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14781 @cindex @sc{gnu} C@t{++}
14782 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14783 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14784 effectively, you must compile your C@t{++} programs with a supported
14785 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14786 compiler (@code{aCC}).
14789 * C Operators:: C and C@t{++} operators
14790 * C Constants:: C and C@t{++} constants
14791 * C Plus Plus Expressions:: C@t{++} expressions
14792 * C Defaults:: Default settings for C and C@t{++}
14793 * C Checks:: C and C@t{++} type and range checks
14794 * Debugging C:: @value{GDBN} and C
14795 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14796 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14800 @subsubsection C and C@t{++} Operators
14802 @cindex C and C@t{++} operators
14804 Operators must be defined on values of specific types. For instance,
14805 @code{+} is defined on numbers, but not on structures. Operators are
14806 often defined on groups of types.
14808 For the purposes of C and C@t{++}, the following definitions hold:
14813 @emph{Integral types} include @code{int} with any of its storage-class
14814 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14817 @emph{Floating-point types} include @code{float}, @code{double}, and
14818 @code{long double} (if supported by the target platform).
14821 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14824 @emph{Scalar types} include all of the above.
14829 The following operators are supported. They are listed here
14830 in order of increasing precedence:
14834 The comma or sequencing operator. Expressions in a comma-separated list
14835 are evaluated from left to right, with the result of the entire
14836 expression being the last expression evaluated.
14839 Assignment. The value of an assignment expression is the value
14840 assigned. Defined on scalar types.
14843 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14844 and translated to @w{@code{@var{a} = @var{a op b}}}.
14845 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14846 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14847 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14850 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14851 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14852 should be of an integral type.
14855 Logical @sc{or}. Defined on integral types.
14858 Logical @sc{and}. Defined on integral types.
14861 Bitwise @sc{or}. Defined on integral types.
14864 Bitwise exclusive-@sc{or}. Defined on integral types.
14867 Bitwise @sc{and}. Defined on integral types.
14870 Equality and inequality. Defined on scalar types. The value of these
14871 expressions is 0 for false and non-zero for true.
14873 @item <@r{, }>@r{, }<=@r{, }>=
14874 Less than, greater than, less than or equal, greater than or equal.
14875 Defined on scalar types. The value of these expressions is 0 for false
14876 and non-zero for true.
14879 left shift, and right shift. Defined on integral types.
14882 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14885 Addition and subtraction. Defined on integral types, floating-point types and
14888 @item *@r{, }/@r{, }%
14889 Multiplication, division, and modulus. Multiplication and division are
14890 defined on integral and floating-point types. Modulus is defined on
14894 Increment and decrement. When appearing before a variable, the
14895 operation is performed before the variable is used in an expression;
14896 when appearing after it, the variable's value is used before the
14897 operation takes place.
14900 Pointer dereferencing. Defined on pointer types. Same precedence as
14904 Address operator. Defined on variables. Same precedence as @code{++}.
14906 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14907 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14908 to examine the address
14909 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14913 Negative. Defined on integral and floating-point types. Same
14914 precedence as @code{++}.
14917 Logical negation. Defined on integral types. Same precedence as
14921 Bitwise complement operator. Defined on integral types. Same precedence as
14926 Structure member, and pointer-to-structure member. For convenience,
14927 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14928 pointer based on the stored type information.
14929 Defined on @code{struct} and @code{union} data.
14932 Dereferences of pointers to members.
14935 Array indexing. @code{@var{a}[@var{i}]} is defined as
14936 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14939 Function parameter list. Same precedence as @code{->}.
14942 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14943 and @code{class} types.
14946 Doubled colons also represent the @value{GDBN} scope operator
14947 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14951 If an operator is redefined in the user code, @value{GDBN} usually
14952 attempts to invoke the redefined version instead of using the operator's
14953 predefined meaning.
14956 @subsubsection C and C@t{++} Constants
14958 @cindex C and C@t{++} constants
14960 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14965 Integer constants are a sequence of digits. Octal constants are
14966 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14967 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14968 @samp{l}, specifying that the constant should be treated as a
14972 Floating point constants are a sequence of digits, followed by a decimal
14973 point, followed by a sequence of digits, and optionally followed by an
14974 exponent. An exponent is of the form:
14975 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14976 sequence of digits. The @samp{+} is optional for positive exponents.
14977 A floating-point constant may also end with a letter @samp{f} or
14978 @samp{F}, specifying that the constant should be treated as being of
14979 the @code{float} (as opposed to the default @code{double}) type; or with
14980 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14984 Enumerated constants consist of enumerated identifiers, or their
14985 integral equivalents.
14988 Character constants are a single character surrounded by single quotes
14989 (@code{'}), or a number---the ordinal value of the corresponding character
14990 (usually its @sc{ascii} value). Within quotes, the single character may
14991 be represented by a letter or by @dfn{escape sequences}, which are of
14992 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14993 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14994 @samp{@var{x}} is a predefined special character---for example,
14995 @samp{\n} for newline.
14997 Wide character constants can be written by prefixing a character
14998 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14999 form of @samp{x}. The target wide character set is used when
15000 computing the value of this constant (@pxref{Character Sets}).
15003 String constants are a sequence of character constants surrounded by
15004 double quotes (@code{"}). Any valid character constant (as described
15005 above) may appear. Double quotes within the string must be preceded by
15006 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15009 Wide string constants can be written by prefixing a string constant
15010 with @samp{L}, as in C. The target wide character set is used when
15011 computing the value of this constant (@pxref{Character Sets}).
15014 Pointer constants are an integral value. You can also write pointers
15015 to constants using the C operator @samp{&}.
15018 Array constants are comma-separated lists surrounded by braces @samp{@{}
15019 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15020 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15021 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15024 @node C Plus Plus Expressions
15025 @subsubsection C@t{++} Expressions
15027 @cindex expressions in C@t{++}
15028 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15030 @cindex debugging C@t{++} programs
15031 @cindex C@t{++} compilers
15032 @cindex debug formats and C@t{++}
15033 @cindex @value{NGCC} and C@t{++}
15035 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15036 the proper compiler and the proper debug format. Currently,
15037 @value{GDBN} works best when debugging C@t{++} code that is compiled
15038 with the most recent version of @value{NGCC} possible. The DWARF
15039 debugging format is preferred; @value{NGCC} defaults to this on most
15040 popular platforms. Other compilers and/or debug formats are likely to
15041 work badly or not at all when using @value{GDBN} to debug C@t{++}
15042 code. @xref{Compilation}.
15047 @cindex member functions
15049 Member function calls are allowed; you can use expressions like
15052 count = aml->GetOriginal(x, y)
15055 @vindex this@r{, inside C@t{++} member functions}
15056 @cindex namespace in C@t{++}
15058 While a member function is active (in the selected stack frame), your
15059 expressions have the same namespace available as the member function;
15060 that is, @value{GDBN} allows implicit references to the class instance
15061 pointer @code{this} following the same rules as C@t{++}. @code{using}
15062 declarations in the current scope are also respected by @value{GDBN}.
15064 @cindex call overloaded functions
15065 @cindex overloaded functions, calling
15066 @cindex type conversions in C@t{++}
15068 You can call overloaded functions; @value{GDBN} resolves the function
15069 call to the right definition, with some restrictions. @value{GDBN} does not
15070 perform overload resolution involving user-defined type conversions,
15071 calls to constructors, or instantiations of templates that do not exist
15072 in the program. It also cannot handle ellipsis argument lists or
15075 It does perform integral conversions and promotions, floating-point
15076 promotions, arithmetic conversions, pointer conversions, conversions of
15077 class objects to base classes, and standard conversions such as those of
15078 functions or arrays to pointers; it requires an exact match on the
15079 number of function arguments.
15081 Overload resolution is always performed, unless you have specified
15082 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15083 ,@value{GDBN} Features for C@t{++}}.
15085 You must specify @code{set overload-resolution off} in order to use an
15086 explicit function signature to call an overloaded function, as in
15088 p 'foo(char,int)'('x', 13)
15091 The @value{GDBN} command-completion facility can simplify this;
15092 see @ref{Completion, ,Command Completion}.
15094 @cindex reference declarations
15096 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15097 references; you can use them in expressions just as you do in C@t{++}
15098 source---they are automatically dereferenced.
15100 In the parameter list shown when @value{GDBN} displays a frame, the values of
15101 reference variables are not displayed (unlike other variables); this
15102 avoids clutter, since references are often used for large structures.
15103 The @emph{address} of a reference variable is always shown, unless
15104 you have specified @samp{set print address off}.
15107 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15108 expressions can use it just as expressions in your program do. Since
15109 one scope may be defined in another, you can use @code{::} repeatedly if
15110 necessary, for example in an expression like
15111 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15112 resolving name scope by reference to source files, in both C and C@t{++}
15113 debugging (@pxref{Variables, ,Program Variables}).
15116 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15121 @subsubsection C and C@t{++} Defaults
15123 @cindex C and C@t{++} defaults
15125 If you allow @value{GDBN} to set range checking automatically, it
15126 defaults to @code{off} whenever the working language changes to
15127 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15128 selects the working language.
15130 If you allow @value{GDBN} to set the language automatically, it
15131 recognizes source files whose names end with @file{.c}, @file{.C}, or
15132 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15133 these files, it sets the working language to C or C@t{++}.
15134 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15135 for further details.
15138 @subsubsection C and C@t{++} Type and Range Checks
15140 @cindex C and C@t{++} checks
15142 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15143 checking is used. However, if you turn type checking off, @value{GDBN}
15144 will allow certain non-standard conversions, such as promoting integer
15145 constants to pointers.
15147 Range checking, if turned on, is done on mathematical operations. Array
15148 indices are not checked, since they are often used to index a pointer
15149 that is not itself an array.
15152 @subsubsection @value{GDBN} and C
15154 The @code{set print union} and @code{show print union} commands apply to
15155 the @code{union} type. When set to @samp{on}, any @code{union} that is
15156 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15157 appears as @samp{@{...@}}.
15159 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15160 with pointers and a memory allocation function. @xref{Expressions,
15163 @node Debugging C Plus Plus
15164 @subsubsection @value{GDBN} Features for C@t{++}
15166 @cindex commands for C@t{++}
15168 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15169 designed specifically for use with C@t{++}. Here is a summary:
15172 @cindex break in overloaded functions
15173 @item @r{breakpoint menus}
15174 When you want a breakpoint in a function whose name is overloaded,
15175 @value{GDBN} has the capability to display a menu of possible breakpoint
15176 locations to help you specify which function definition you want.
15177 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15179 @cindex overloading in C@t{++}
15180 @item rbreak @var{regex}
15181 Setting breakpoints using regular expressions is helpful for setting
15182 breakpoints on overloaded functions that are not members of any special
15184 @xref{Set Breaks, ,Setting Breakpoints}.
15186 @cindex C@t{++} exception handling
15188 @itemx catch rethrow
15190 Debug C@t{++} exception handling using these commands. @xref{Set
15191 Catchpoints, , Setting Catchpoints}.
15193 @cindex inheritance
15194 @item ptype @var{typename}
15195 Print inheritance relationships as well as other information for type
15197 @xref{Symbols, ,Examining the Symbol Table}.
15199 @item info vtbl @var{expression}.
15200 The @code{info vtbl} command can be used to display the virtual
15201 method tables of the object computed by @var{expression}. This shows
15202 one entry per virtual table; there may be multiple virtual tables when
15203 multiple inheritance is in use.
15205 @cindex C@t{++} demangling
15206 @item demangle @var{name}
15207 Demangle @var{name}.
15208 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15210 @cindex C@t{++} symbol display
15211 @item set print demangle
15212 @itemx show print demangle
15213 @itemx set print asm-demangle
15214 @itemx show print asm-demangle
15215 Control whether C@t{++} symbols display in their source form, both when
15216 displaying code as C@t{++} source and when displaying disassemblies.
15217 @xref{Print Settings, ,Print Settings}.
15219 @item set print object
15220 @itemx show print object
15221 Choose whether to print derived (actual) or declared types of objects.
15222 @xref{Print Settings, ,Print Settings}.
15224 @item set print vtbl
15225 @itemx show print vtbl
15226 Control the format for printing virtual function tables.
15227 @xref{Print Settings, ,Print Settings}.
15228 (The @code{vtbl} commands do not work on programs compiled with the HP
15229 ANSI C@t{++} compiler (@code{aCC}).)
15231 @kindex set overload-resolution
15232 @cindex overloaded functions, overload resolution
15233 @item set overload-resolution on
15234 Enable overload resolution for C@t{++} expression evaluation. The default
15235 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15236 and searches for a function whose signature matches the argument types,
15237 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15238 Expressions, ,C@t{++} Expressions}, for details).
15239 If it cannot find a match, it emits a message.
15241 @item set overload-resolution off
15242 Disable overload resolution for C@t{++} expression evaluation. For
15243 overloaded functions that are not class member functions, @value{GDBN}
15244 chooses the first function of the specified name that it finds in the
15245 symbol table, whether or not its arguments are of the correct type. For
15246 overloaded functions that are class member functions, @value{GDBN}
15247 searches for a function whose signature @emph{exactly} matches the
15250 @kindex show overload-resolution
15251 @item show overload-resolution
15252 Show the current setting of overload resolution.
15254 @item @r{Overloaded symbol names}
15255 You can specify a particular definition of an overloaded symbol, using
15256 the same notation that is used to declare such symbols in C@t{++}: type
15257 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15258 also use the @value{GDBN} command-line word completion facilities to list the
15259 available choices, or to finish the type list for you.
15260 @xref{Completion,, Command Completion}, for details on how to do this.
15262 @item @r{Breakpoints in functions with ABI tags}
15264 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15265 correspond to changes in the ABI of a type, function, or variable that
15266 would not otherwise be reflected in a mangled name. See
15267 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15270 The ABI tags are visible in C@t{++} demangled names. For example, a
15271 function that returns a std::string:
15274 std::string function(int);
15278 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15279 tag, and @value{GDBN} displays the symbol like this:
15282 function[abi:cxx11](int)
15285 You can set a breakpoint on such functions simply as if they had no
15289 (gdb) b function(int)
15290 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15291 (gdb) info breakpoints
15292 Num Type Disp Enb Address What
15293 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15297 On the rare occasion you need to disambiguate between different ABI
15298 tags, you can do so by simply including the ABI tag in the function
15302 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15306 @node Decimal Floating Point
15307 @subsubsection Decimal Floating Point format
15308 @cindex decimal floating point format
15310 @value{GDBN} can examine, set and perform computations with numbers in
15311 decimal floating point format, which in the C language correspond to the
15312 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15313 specified by the extension to support decimal floating-point arithmetic.
15315 There are two encodings in use, depending on the architecture: BID (Binary
15316 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15317 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15320 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15321 to manipulate decimal floating point numbers, it is not possible to convert
15322 (using a cast, for example) integers wider than 32-bit to decimal float.
15324 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15325 point computations, error checking in decimal float operations ignores
15326 underflow, overflow and divide by zero exceptions.
15328 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15329 to inspect @code{_Decimal128} values stored in floating point registers.
15330 See @ref{PowerPC,,PowerPC} for more details.
15336 @value{GDBN} can be used to debug programs written in D and compiled with
15337 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15338 specific feature --- dynamic arrays.
15343 @cindex Go (programming language)
15344 @value{GDBN} can be used to debug programs written in Go and compiled with
15345 @file{gccgo} or @file{6g} compilers.
15347 Here is a summary of the Go-specific features and restrictions:
15350 @cindex current Go package
15351 @item The current Go package
15352 The name of the current package does not need to be specified when
15353 specifying global variables and functions.
15355 For example, given the program:
15359 var myglob = "Shall we?"
15365 When stopped inside @code{main} either of these work:
15369 (gdb) p main.myglob
15372 @cindex builtin Go types
15373 @item Builtin Go types
15374 The @code{string} type is recognized by @value{GDBN} and is printed
15377 @cindex builtin Go functions
15378 @item Builtin Go functions
15379 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15380 function and handles it internally.
15382 @cindex restrictions on Go expressions
15383 @item Restrictions on Go expressions
15384 All Go operators are supported except @code{&^}.
15385 The Go @code{_} ``blank identifier'' is not supported.
15386 Automatic dereferencing of pointers is not supported.
15390 @subsection Objective-C
15392 @cindex Objective-C
15393 This section provides information about some commands and command
15394 options that are useful for debugging Objective-C code. See also
15395 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15396 few more commands specific to Objective-C support.
15399 * Method Names in Commands::
15400 * The Print Command with Objective-C::
15403 @node Method Names in Commands
15404 @subsubsection Method Names in Commands
15406 The following commands have been extended to accept Objective-C method
15407 names as line specifications:
15409 @kindex clear@r{, and Objective-C}
15410 @kindex break@r{, and Objective-C}
15411 @kindex info line@r{, and Objective-C}
15412 @kindex jump@r{, and Objective-C}
15413 @kindex list@r{, and Objective-C}
15417 @item @code{info line}
15422 A fully qualified Objective-C method name is specified as
15425 -[@var{Class} @var{methodName}]
15428 where the minus sign is used to indicate an instance method and a
15429 plus sign (not shown) is used to indicate a class method. The class
15430 name @var{Class} and method name @var{methodName} are enclosed in
15431 brackets, similar to the way messages are specified in Objective-C
15432 source code. For example, to set a breakpoint at the @code{create}
15433 instance method of class @code{Fruit} in the program currently being
15437 break -[Fruit create]
15440 To list ten program lines around the @code{initialize} class method,
15444 list +[NSText initialize]
15447 In the current version of @value{GDBN}, the plus or minus sign is
15448 required. In future versions of @value{GDBN}, the plus or minus
15449 sign will be optional, but you can use it to narrow the search. It
15450 is also possible to specify just a method name:
15456 You must specify the complete method name, including any colons. If
15457 your program's source files contain more than one @code{create} method,
15458 you'll be presented with a numbered list of classes that implement that
15459 method. Indicate your choice by number, or type @samp{0} to exit if
15462 As another example, to clear a breakpoint established at the
15463 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15466 clear -[NSWindow makeKeyAndOrderFront:]
15469 @node The Print Command with Objective-C
15470 @subsubsection The Print Command With Objective-C
15471 @cindex Objective-C, print objects
15472 @kindex print-object
15473 @kindex po @r{(@code{print-object})}
15475 The print command has also been extended to accept methods. For example:
15478 print -[@var{object} hash]
15481 @cindex print an Objective-C object description
15482 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15484 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15485 and print the result. Also, an additional command has been added,
15486 @code{print-object} or @code{po} for short, which is meant to print
15487 the description of an object. However, this command may only work
15488 with certain Objective-C libraries that have a particular hook
15489 function, @code{_NSPrintForDebugger}, defined.
15492 @subsection OpenCL C
15495 This section provides information about @value{GDBN}s OpenCL C support.
15498 * OpenCL C Datatypes::
15499 * OpenCL C Expressions::
15500 * OpenCL C Operators::
15503 @node OpenCL C Datatypes
15504 @subsubsection OpenCL C Datatypes
15506 @cindex OpenCL C Datatypes
15507 @value{GDBN} supports the builtin scalar and vector datatypes specified
15508 by OpenCL 1.1. In addition the half- and double-precision floating point
15509 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15510 extensions are also known to @value{GDBN}.
15512 @node OpenCL C Expressions
15513 @subsubsection OpenCL C Expressions
15515 @cindex OpenCL C Expressions
15516 @value{GDBN} supports accesses to vector components including the access as
15517 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15518 supported by @value{GDBN} can be used as well.
15520 @node OpenCL C Operators
15521 @subsubsection OpenCL C Operators
15523 @cindex OpenCL C Operators
15524 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15528 @subsection Fortran
15529 @cindex Fortran-specific support in @value{GDBN}
15531 @value{GDBN} can be used to debug programs written in Fortran, but it
15532 currently supports only the features of Fortran 77 language.
15534 @cindex trailing underscore, in Fortran symbols
15535 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15536 among them) append an underscore to the names of variables and
15537 functions. When you debug programs compiled by those compilers, you
15538 will need to refer to variables and functions with a trailing
15542 * Fortran Operators:: Fortran operators and expressions
15543 * Fortran Defaults:: Default settings for Fortran
15544 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15547 @node Fortran Operators
15548 @subsubsection Fortran Operators and Expressions
15550 @cindex Fortran operators and expressions
15552 Operators must be defined on values of specific types. For instance,
15553 @code{+} is defined on numbers, but not on characters or other non-
15554 arithmetic types. Operators are often defined on groups of types.
15558 The exponentiation operator. It raises the first operand to the power
15562 The range operator. Normally used in the form of array(low:high) to
15563 represent a section of array.
15566 The access component operator. Normally used to access elements in derived
15567 types. Also suitable for unions. As unions aren't part of regular Fortran,
15568 this can only happen when accessing a register that uses a gdbarch-defined
15572 @node Fortran Defaults
15573 @subsubsection Fortran Defaults
15575 @cindex Fortran Defaults
15577 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15578 default uses case-insensitive matches for Fortran symbols. You can
15579 change that with the @samp{set case-insensitive} command, see
15580 @ref{Symbols}, for the details.
15582 @node Special Fortran Commands
15583 @subsubsection Special Fortran Commands
15585 @cindex Special Fortran commands
15587 @value{GDBN} has some commands to support Fortran-specific features,
15588 such as displaying common blocks.
15591 @cindex @code{COMMON} blocks, Fortran
15592 @kindex info common
15593 @item info common @r{[}@var{common-name}@r{]}
15594 This command prints the values contained in the Fortran @code{COMMON}
15595 block whose name is @var{common-name}. With no argument, the names of
15596 all @code{COMMON} blocks visible at the current program location are
15603 @cindex Pascal support in @value{GDBN}, limitations
15604 Debugging Pascal programs which use sets, subranges, file variables, or
15605 nested functions does not currently work. @value{GDBN} does not support
15606 entering expressions, printing values, or similar features using Pascal
15609 The Pascal-specific command @code{set print pascal_static-members}
15610 controls whether static members of Pascal objects are displayed.
15611 @xref{Print Settings, pascal_static-members}.
15616 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15617 Programming Language}. Type- and value-printing, and expression
15618 parsing, are reasonably complete. However, there are a few
15619 peculiarities and holes to be aware of.
15623 Linespecs (@pxref{Specify Location}) are never relative to the current
15624 crate. Instead, they act as if there were a global namespace of
15625 crates, somewhat similar to the way @code{extern crate} behaves.
15627 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15628 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15629 to set a breakpoint in a function named @samp{f} in a crate named
15632 As a consequence of this approach, linespecs also cannot refer to
15633 items using @samp{self::} or @samp{super::}.
15636 Because @value{GDBN} implements Rust name-lookup semantics in
15637 expressions, it will sometimes prepend the current crate to a name.
15638 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15639 @samp{K}, then @code{print ::x::y} will try to find the symbol
15642 However, since it is useful to be able to refer to other crates when
15643 debugging, @value{GDBN} provides the @code{extern} extension to
15644 circumvent this. To use the extension, just put @code{extern} before
15645 a path expression to refer to the otherwise unavailable ``global''
15648 In the above example, if you wanted to refer to the symbol @samp{y} in
15649 the crate @samp{x}, you would use @code{print extern x::y}.
15652 The Rust expression evaluator does not support ``statement-like''
15653 expressions such as @code{if} or @code{match}, or lambda expressions.
15656 Tuple expressions are not implemented.
15659 The Rust expression evaluator does not currently implement the
15660 @code{Drop} trait. Objects that may be created by the evaluator will
15661 never be destroyed.
15664 @value{GDBN} does not implement type inference for generics. In order
15665 to call generic functions or otherwise refer to generic items, you
15666 will have to specify the type parameters manually.
15669 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15670 cases this does not cause any problems. However, in an expression
15671 context, completing a generic function name will give syntactically
15672 invalid results. This happens because Rust requires the @samp{::}
15673 operator between the function name and its generic arguments. For
15674 example, @value{GDBN} might provide a completion like
15675 @code{crate::f<u32>}, where the parser would require
15676 @code{crate::f::<u32>}.
15679 As of this writing, the Rust compiler (version 1.8) has a few holes in
15680 the debugging information it generates. These holes prevent certain
15681 features from being implemented by @value{GDBN}:
15685 Method calls cannot be made via traits.
15688 Operator overloading is not implemented.
15691 When debugging in a monomorphized function, you cannot use the generic
15695 The type @code{Self} is not available.
15698 @code{use} statements are not available, so some names may not be
15699 available in the crate.
15704 @subsection Modula-2
15706 @cindex Modula-2, @value{GDBN} support
15708 The extensions made to @value{GDBN} to support Modula-2 only support
15709 output from the @sc{gnu} Modula-2 compiler (which is currently being
15710 developed). Other Modula-2 compilers are not currently supported, and
15711 attempting to debug executables produced by them is most likely
15712 to give an error as @value{GDBN} reads in the executable's symbol
15715 @cindex expressions in Modula-2
15717 * M2 Operators:: Built-in operators
15718 * Built-In Func/Proc:: Built-in functions and procedures
15719 * M2 Constants:: Modula-2 constants
15720 * M2 Types:: Modula-2 types
15721 * M2 Defaults:: Default settings for Modula-2
15722 * Deviations:: Deviations from standard Modula-2
15723 * M2 Checks:: Modula-2 type and range checks
15724 * M2 Scope:: The scope operators @code{::} and @code{.}
15725 * GDB/M2:: @value{GDBN} and Modula-2
15729 @subsubsection Operators
15730 @cindex Modula-2 operators
15732 Operators must be defined on values of specific types. For instance,
15733 @code{+} is defined on numbers, but not on structures. Operators are
15734 often defined on groups of types. For the purposes of Modula-2, the
15735 following definitions hold:
15740 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15744 @emph{Character types} consist of @code{CHAR} and its subranges.
15747 @emph{Floating-point types} consist of @code{REAL}.
15750 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15754 @emph{Scalar types} consist of all of the above.
15757 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15760 @emph{Boolean types} consist of @code{BOOLEAN}.
15764 The following operators are supported, and appear in order of
15765 increasing precedence:
15769 Function argument or array index separator.
15772 Assignment. The value of @var{var} @code{:=} @var{value} is
15776 Less than, greater than on integral, floating-point, or enumerated
15780 Less than or equal to, greater than or equal to
15781 on integral, floating-point and enumerated types, or set inclusion on
15782 set types. Same precedence as @code{<}.
15784 @item =@r{, }<>@r{, }#
15785 Equality and two ways of expressing inequality, valid on scalar types.
15786 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15787 available for inequality, since @code{#} conflicts with the script
15791 Set membership. Defined on set types and the types of their members.
15792 Same precedence as @code{<}.
15795 Boolean disjunction. Defined on boolean types.
15798 Boolean conjunction. Defined on boolean types.
15801 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15804 Addition and subtraction on integral and floating-point types, or union
15805 and difference on set types.
15808 Multiplication on integral and floating-point types, or set intersection
15812 Division on floating-point types, or symmetric set difference on set
15813 types. Same precedence as @code{*}.
15816 Integer division and remainder. Defined on integral types. Same
15817 precedence as @code{*}.
15820 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15823 Pointer dereferencing. Defined on pointer types.
15826 Boolean negation. Defined on boolean types. Same precedence as
15830 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15831 precedence as @code{^}.
15834 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15837 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15841 @value{GDBN} and Modula-2 scope operators.
15845 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15846 treats the use of the operator @code{IN}, or the use of operators
15847 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15848 @code{<=}, and @code{>=} on sets as an error.
15852 @node Built-In Func/Proc
15853 @subsubsection Built-in Functions and Procedures
15854 @cindex Modula-2 built-ins
15856 Modula-2 also makes available several built-in procedures and functions.
15857 In describing these, the following metavariables are used:
15862 represents an @code{ARRAY} variable.
15865 represents a @code{CHAR} constant or variable.
15868 represents a variable or constant of integral type.
15871 represents an identifier that belongs to a set. Generally used in the
15872 same function with the metavariable @var{s}. The type of @var{s} should
15873 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15876 represents a variable or constant of integral or floating-point type.
15879 represents a variable or constant of floating-point type.
15885 represents a variable.
15888 represents a variable or constant of one of many types. See the
15889 explanation of the function for details.
15892 All Modula-2 built-in procedures also return a result, described below.
15896 Returns the absolute value of @var{n}.
15899 If @var{c} is a lower case letter, it returns its upper case
15900 equivalent, otherwise it returns its argument.
15903 Returns the character whose ordinal value is @var{i}.
15906 Decrements the value in the variable @var{v} by one. Returns the new value.
15908 @item DEC(@var{v},@var{i})
15909 Decrements the value in the variable @var{v} by @var{i}. Returns the
15912 @item EXCL(@var{m},@var{s})
15913 Removes the element @var{m} from the set @var{s}. Returns the new
15916 @item FLOAT(@var{i})
15917 Returns the floating point equivalent of the integer @var{i}.
15919 @item HIGH(@var{a})
15920 Returns the index of the last member of @var{a}.
15923 Increments the value in the variable @var{v} by one. Returns the new value.
15925 @item INC(@var{v},@var{i})
15926 Increments the value in the variable @var{v} by @var{i}. Returns the
15929 @item INCL(@var{m},@var{s})
15930 Adds the element @var{m} to the set @var{s} if it is not already
15931 there. Returns the new set.
15934 Returns the maximum value of the type @var{t}.
15937 Returns the minimum value of the type @var{t}.
15940 Returns boolean TRUE if @var{i} is an odd number.
15943 Returns the ordinal value of its argument. For example, the ordinal
15944 value of a character is its @sc{ascii} value (on machines supporting
15945 the @sc{ascii} character set). The argument @var{x} must be of an
15946 ordered type, which include integral, character and enumerated types.
15948 @item SIZE(@var{x})
15949 Returns the size of its argument. The argument @var{x} can be a
15950 variable or a type.
15952 @item TRUNC(@var{r})
15953 Returns the integral part of @var{r}.
15955 @item TSIZE(@var{x})
15956 Returns the size of its argument. The argument @var{x} can be a
15957 variable or a type.
15959 @item VAL(@var{t},@var{i})
15960 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15964 @emph{Warning:} Sets and their operations are not yet supported, so
15965 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15969 @cindex Modula-2 constants
15971 @subsubsection Constants
15973 @value{GDBN} allows you to express the constants of Modula-2 in the following
15979 Integer constants are simply a sequence of digits. When used in an
15980 expression, a constant is interpreted to be type-compatible with the
15981 rest of the expression. Hexadecimal integers are specified by a
15982 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15985 Floating point constants appear as a sequence of digits, followed by a
15986 decimal point and another sequence of digits. An optional exponent can
15987 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15988 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15989 digits of the floating point constant must be valid decimal (base 10)
15993 Character constants consist of a single character enclosed by a pair of
15994 like quotes, either single (@code{'}) or double (@code{"}). They may
15995 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15996 followed by a @samp{C}.
15999 String constants consist of a sequence of characters enclosed by a
16000 pair of like quotes, either single (@code{'}) or double (@code{"}).
16001 Escape sequences in the style of C are also allowed. @xref{C
16002 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16006 Enumerated constants consist of an enumerated identifier.
16009 Boolean constants consist of the identifiers @code{TRUE} and
16013 Pointer constants consist of integral values only.
16016 Set constants are not yet supported.
16020 @subsubsection Modula-2 Types
16021 @cindex Modula-2 types
16023 Currently @value{GDBN} can print the following data types in Modula-2
16024 syntax: array types, record types, set types, pointer types, procedure
16025 types, enumerated types, subrange types and base types. You can also
16026 print the contents of variables declared using these type.
16027 This section gives a number of simple source code examples together with
16028 sample @value{GDBN} sessions.
16030 The first example contains the following section of code:
16039 and you can request @value{GDBN} to interrogate the type and value of
16040 @code{r} and @code{s}.
16043 (@value{GDBP}) print s
16045 (@value{GDBP}) ptype s
16047 (@value{GDBP}) print r
16049 (@value{GDBP}) ptype r
16054 Likewise if your source code declares @code{s} as:
16058 s: SET ['A'..'Z'] ;
16062 then you may query the type of @code{s} by:
16065 (@value{GDBP}) ptype s
16066 type = SET ['A'..'Z']
16070 Note that at present you cannot interactively manipulate set
16071 expressions using the debugger.
16073 The following example shows how you might declare an array in Modula-2
16074 and how you can interact with @value{GDBN} to print its type and contents:
16078 s: ARRAY [-10..10] OF CHAR ;
16082 (@value{GDBP}) ptype s
16083 ARRAY [-10..10] OF CHAR
16086 Note that the array handling is not yet complete and although the type
16087 is printed correctly, expression handling still assumes that all
16088 arrays have a lower bound of zero and not @code{-10} as in the example
16091 Here are some more type related Modula-2 examples:
16095 colour = (blue, red, yellow, green) ;
16096 t = [blue..yellow] ;
16104 The @value{GDBN} interaction shows how you can query the data type
16105 and value of a variable.
16108 (@value{GDBP}) print s
16110 (@value{GDBP}) ptype t
16111 type = [blue..yellow]
16115 In this example a Modula-2 array is declared and its contents
16116 displayed. Observe that the contents are written in the same way as
16117 their @code{C} counterparts.
16121 s: ARRAY [1..5] OF CARDINAL ;
16127 (@value{GDBP}) print s
16128 $1 = @{1, 0, 0, 0, 0@}
16129 (@value{GDBP}) ptype s
16130 type = ARRAY [1..5] OF CARDINAL
16133 The Modula-2 language interface to @value{GDBN} also understands
16134 pointer types as shown in this example:
16138 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16145 and you can request that @value{GDBN} describes the type of @code{s}.
16148 (@value{GDBP}) ptype s
16149 type = POINTER TO ARRAY [1..5] OF CARDINAL
16152 @value{GDBN} handles compound types as we can see in this example.
16153 Here we combine array types, record types, pointer types and subrange
16164 myarray = ARRAY myrange OF CARDINAL ;
16165 myrange = [-2..2] ;
16167 s: POINTER TO ARRAY myrange OF foo ;
16171 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16175 (@value{GDBP}) ptype s
16176 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16179 f3 : ARRAY [-2..2] OF CARDINAL;
16184 @subsubsection Modula-2 Defaults
16185 @cindex Modula-2 defaults
16187 If type and range checking are set automatically by @value{GDBN}, they
16188 both default to @code{on} whenever the working language changes to
16189 Modula-2. This happens regardless of whether you or @value{GDBN}
16190 selected the working language.
16192 If you allow @value{GDBN} to set the language automatically, then entering
16193 code compiled from a file whose name ends with @file{.mod} sets the
16194 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16195 Infer the Source Language}, for further details.
16198 @subsubsection Deviations from Standard Modula-2
16199 @cindex Modula-2, deviations from
16201 A few changes have been made to make Modula-2 programs easier to debug.
16202 This is done primarily via loosening its type strictness:
16206 Unlike in standard Modula-2, pointer constants can be formed by
16207 integers. This allows you to modify pointer variables during
16208 debugging. (In standard Modula-2, the actual address contained in a
16209 pointer variable is hidden from you; it can only be modified
16210 through direct assignment to another pointer variable or expression that
16211 returned a pointer.)
16214 C escape sequences can be used in strings and characters to represent
16215 non-printable characters. @value{GDBN} prints out strings with these
16216 escape sequences embedded. Single non-printable characters are
16217 printed using the @samp{CHR(@var{nnn})} format.
16220 The assignment operator (@code{:=}) returns the value of its right-hand
16224 All built-in procedures both modify @emph{and} return their argument.
16228 @subsubsection Modula-2 Type and Range Checks
16229 @cindex Modula-2 checks
16232 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16235 @c FIXME remove warning when type/range checks added
16237 @value{GDBN} considers two Modula-2 variables type equivalent if:
16241 They are of types that have been declared equivalent via a @code{TYPE
16242 @var{t1} = @var{t2}} statement
16245 They have been declared on the same line. (Note: This is true of the
16246 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16249 As long as type checking is enabled, any attempt to combine variables
16250 whose types are not equivalent is an error.
16252 Range checking is done on all mathematical operations, assignment, array
16253 index bounds, and all built-in functions and procedures.
16256 @subsubsection The Scope Operators @code{::} and @code{.}
16258 @cindex @code{.}, Modula-2 scope operator
16259 @cindex colon, doubled as scope operator
16261 @vindex colon-colon@r{, in Modula-2}
16262 @c Info cannot handle :: but TeX can.
16265 @vindex ::@r{, in Modula-2}
16268 There are a few subtle differences between the Modula-2 scope operator
16269 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16274 @var{module} . @var{id}
16275 @var{scope} :: @var{id}
16279 where @var{scope} is the name of a module or a procedure,
16280 @var{module} the name of a module, and @var{id} is any declared
16281 identifier within your program, except another module.
16283 Using the @code{::} operator makes @value{GDBN} search the scope
16284 specified by @var{scope} for the identifier @var{id}. If it is not
16285 found in the specified scope, then @value{GDBN} searches all scopes
16286 enclosing the one specified by @var{scope}.
16288 Using the @code{.} operator makes @value{GDBN} search the current scope for
16289 the identifier specified by @var{id} that was imported from the
16290 definition module specified by @var{module}. With this operator, it is
16291 an error if the identifier @var{id} was not imported from definition
16292 module @var{module}, or if @var{id} is not an identifier in
16296 @subsubsection @value{GDBN} and Modula-2
16298 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16299 Five subcommands of @code{set print} and @code{show print} apply
16300 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16301 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16302 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16303 analogue in Modula-2.
16305 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16306 with any language, is not useful with Modula-2. Its
16307 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16308 created in Modula-2 as they can in C or C@t{++}. However, because an
16309 address can be specified by an integral constant, the construct
16310 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16312 @cindex @code{#} in Modula-2
16313 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16314 interpreted as the beginning of a comment. Use @code{<>} instead.
16320 The extensions made to @value{GDBN} for Ada only support
16321 output from the @sc{gnu} Ada (GNAT) compiler.
16322 Other Ada compilers are not currently supported, and
16323 attempting to debug executables produced by them is most likely
16327 @cindex expressions in Ada
16329 * Ada Mode Intro:: General remarks on the Ada syntax
16330 and semantics supported by Ada mode
16332 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16333 * Additions to Ada:: Extensions of the Ada expression syntax.
16334 * Overloading support for Ada:: Support for expressions involving overloaded
16336 * Stopping Before Main Program:: Debugging the program during elaboration.
16337 * Ada Exceptions:: Ada Exceptions
16338 * Ada Tasks:: Listing and setting breakpoints in tasks.
16339 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16340 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16342 * Ada Settings:: New settable GDB parameters for Ada.
16343 * Ada Glitches:: Known peculiarities of Ada mode.
16346 @node Ada Mode Intro
16347 @subsubsection Introduction
16348 @cindex Ada mode, general
16350 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16351 syntax, with some extensions.
16352 The philosophy behind the design of this subset is
16356 That @value{GDBN} should provide basic literals and access to operations for
16357 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16358 leaving more sophisticated computations to subprograms written into the
16359 program (which therefore may be called from @value{GDBN}).
16362 That type safety and strict adherence to Ada language restrictions
16363 are not particularly important to the @value{GDBN} user.
16366 That brevity is important to the @value{GDBN} user.
16369 Thus, for brevity, the debugger acts as if all names declared in
16370 user-written packages are directly visible, even if they are not visible
16371 according to Ada rules, thus making it unnecessary to fully qualify most
16372 names with their packages, regardless of context. Where this causes
16373 ambiguity, @value{GDBN} asks the user's intent.
16375 The debugger will start in Ada mode if it detects an Ada main program.
16376 As for other languages, it will enter Ada mode when stopped in a program that
16377 was translated from an Ada source file.
16379 While in Ada mode, you may use `@t{--}' for comments. This is useful
16380 mostly for documenting command files. The standard @value{GDBN} comment
16381 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16382 middle (to allow based literals).
16384 @node Omissions from Ada
16385 @subsubsection Omissions from Ada
16386 @cindex Ada, omissions from
16388 Here are the notable omissions from the subset:
16392 Only a subset of the attributes are supported:
16396 @t{'First}, @t{'Last}, and @t{'Length}
16397 on array objects (not on types and subtypes).
16400 @t{'Min} and @t{'Max}.
16403 @t{'Pos} and @t{'Val}.
16409 @t{'Range} on array objects (not subtypes), but only as the right
16410 operand of the membership (@code{in}) operator.
16413 @t{'Access}, @t{'Unchecked_Access}, and
16414 @t{'Unrestricted_Access} (a GNAT extension).
16422 @code{Characters.Latin_1} are not available and
16423 concatenation is not implemented. Thus, escape characters in strings are
16424 not currently available.
16427 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16428 equality of representations. They will generally work correctly
16429 for strings and arrays whose elements have integer or enumeration types.
16430 They may not work correctly for arrays whose element
16431 types have user-defined equality, for arrays of real values
16432 (in particular, IEEE-conformant floating point, because of negative
16433 zeroes and NaNs), and for arrays whose elements contain unused bits with
16434 indeterminate values.
16437 The other component-by-component array operations (@code{and}, @code{or},
16438 @code{xor}, @code{not}, and relational tests other than equality)
16439 are not implemented.
16442 @cindex array aggregates (Ada)
16443 @cindex record aggregates (Ada)
16444 @cindex aggregates (Ada)
16445 There is limited support for array and record aggregates. They are
16446 permitted only on the right sides of assignments, as in these examples:
16449 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16450 (@value{GDBP}) set An_Array := (1, others => 0)
16451 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16452 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16453 (@value{GDBP}) set A_Record := (1, "Peter", True);
16454 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16458 discriminant's value by assigning an aggregate has an
16459 undefined effect if that discriminant is used within the record.
16460 However, you can first modify discriminants by directly assigning to
16461 them (which normally would not be allowed in Ada), and then performing an
16462 aggregate assignment. For example, given a variable @code{A_Rec}
16463 declared to have a type such as:
16466 type Rec (Len : Small_Integer := 0) is record
16468 Vals : IntArray (1 .. Len);
16472 you can assign a value with a different size of @code{Vals} with two
16476 (@value{GDBP}) set A_Rec.Len := 4
16477 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16480 As this example also illustrates, @value{GDBN} is very loose about the usual
16481 rules concerning aggregates. You may leave out some of the
16482 components of an array or record aggregate (such as the @code{Len}
16483 component in the assignment to @code{A_Rec} above); they will retain their
16484 original values upon assignment. You may freely use dynamic values as
16485 indices in component associations. You may even use overlapping or
16486 redundant component associations, although which component values are
16487 assigned in such cases is not defined.
16490 Calls to dispatching subprograms are not implemented.
16493 The overloading algorithm is much more limited (i.e., less selective)
16494 than that of real Ada. It makes only limited use of the context in
16495 which a subexpression appears to resolve its meaning, and it is much
16496 looser in its rules for allowing type matches. As a result, some
16497 function calls will be ambiguous, and the user will be asked to choose
16498 the proper resolution.
16501 The @code{new} operator is not implemented.
16504 Entry calls are not implemented.
16507 Aside from printing, arithmetic operations on the native VAX floating-point
16508 formats are not supported.
16511 It is not possible to slice a packed array.
16514 The names @code{True} and @code{False}, when not part of a qualified name,
16515 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16517 Should your program
16518 redefine these names in a package or procedure (at best a dubious practice),
16519 you will have to use fully qualified names to access their new definitions.
16522 @node Additions to Ada
16523 @subsubsection Additions to Ada
16524 @cindex Ada, deviations from
16526 As it does for other languages, @value{GDBN} makes certain generic
16527 extensions to Ada (@pxref{Expressions}):
16531 If the expression @var{E} is a variable residing in memory (typically
16532 a local variable or array element) and @var{N} is a positive integer,
16533 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16534 @var{N}-1 adjacent variables following it in memory as an array. In
16535 Ada, this operator is generally not necessary, since its prime use is
16536 in displaying parts of an array, and slicing will usually do this in
16537 Ada. However, there are occasional uses when debugging programs in
16538 which certain debugging information has been optimized away.
16541 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16542 appears in function or file @var{B}.'' When @var{B} is a file name,
16543 you must typically surround it in single quotes.
16546 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16547 @var{type} that appears at address @var{addr}.''
16550 A name starting with @samp{$} is a convenience variable
16551 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16554 In addition, @value{GDBN} provides a few other shortcuts and outright
16555 additions specific to Ada:
16559 The assignment statement is allowed as an expression, returning
16560 its right-hand operand as its value. Thus, you may enter
16563 (@value{GDBP}) set x := y + 3
16564 (@value{GDBP}) print A(tmp := y + 1)
16568 The semicolon is allowed as an ``operator,'' returning as its value
16569 the value of its right-hand operand.
16570 This allows, for example,
16571 complex conditional breaks:
16574 (@value{GDBP}) break f
16575 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16579 Rather than use catenation and symbolic character names to introduce special
16580 characters into strings, one may instead use a special bracket notation,
16581 which is also used to print strings. A sequence of characters of the form
16582 @samp{["@var{XX}"]} within a string or character literal denotes the
16583 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16584 sequence of characters @samp{["""]} also denotes a single quotation mark
16585 in strings. For example,
16587 "One line.["0a"]Next line.["0a"]"
16590 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16594 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16595 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16599 (@value{GDBP}) print 'max(x, y)
16603 When printing arrays, @value{GDBN} uses positional notation when the
16604 array has a lower bound of 1, and uses a modified named notation otherwise.
16605 For example, a one-dimensional array of three integers with a lower bound
16606 of 3 might print as
16613 That is, in contrast to valid Ada, only the first component has a @code{=>}
16617 You may abbreviate attributes in expressions with any unique,
16618 multi-character subsequence of
16619 their names (an exact match gets preference).
16620 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16621 in place of @t{a'length}.
16624 @cindex quoting Ada internal identifiers
16625 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16626 to lower case. The GNAT compiler uses upper-case characters for
16627 some of its internal identifiers, which are normally of no interest to users.
16628 For the rare occasions when you actually have to look at them,
16629 enclose them in angle brackets to avoid the lower-case mapping.
16632 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16636 Printing an object of class-wide type or dereferencing an
16637 access-to-class-wide value will display all the components of the object's
16638 specific type (as indicated by its run-time tag). Likewise, component
16639 selection on such a value will operate on the specific type of the
16644 @node Overloading support for Ada
16645 @subsubsection Overloading support for Ada
16646 @cindex overloading, Ada
16648 The debugger supports limited overloading. Given a subprogram call in which
16649 the function symbol has multiple definitions, it will use the number of
16650 actual parameters and some information about their types to attempt to narrow
16651 the set of definitions. It also makes very limited use of context, preferring
16652 procedures to functions in the context of the @code{call} command, and
16653 functions to procedures elsewhere.
16655 If, after narrowing, the set of matching definitions still contains more than
16656 one definition, @value{GDBN} will display a menu to query which one it should
16660 (@value{GDBP}) print f(1)
16661 Multiple matches for f
16663 [1] foo.f (integer) return boolean at foo.adb:23
16664 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16668 In this case, just select one menu entry either to cancel expression evaluation
16669 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16670 instance (type the corresponding number and press @key{RET}).
16672 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16677 @kindex set ada print-signatures
16678 @item set ada print-signatures
16679 Control whether parameter types and return types are displayed in overloads
16680 selection menus. It is @code{on} by default.
16681 @xref{Overloading support for Ada}.
16683 @kindex show ada print-signatures
16684 @item show ada print-signatures
16685 Show the current setting for displaying parameter types and return types in
16686 overloads selection menu.
16687 @xref{Overloading support for Ada}.
16691 @node Stopping Before Main Program
16692 @subsubsection Stopping at the Very Beginning
16694 @cindex breakpointing Ada elaboration code
16695 It is sometimes necessary to debug the program during elaboration, and
16696 before reaching the main procedure.
16697 As defined in the Ada Reference
16698 Manual, the elaboration code is invoked from a procedure called
16699 @code{adainit}. To run your program up to the beginning of
16700 elaboration, simply use the following two commands:
16701 @code{tbreak adainit} and @code{run}.
16703 @node Ada Exceptions
16704 @subsubsection Ada Exceptions
16706 A command is provided to list all Ada exceptions:
16709 @kindex info exceptions
16710 @item info exceptions
16711 @itemx info exceptions @var{regexp}
16712 The @code{info exceptions} command allows you to list all Ada exceptions
16713 defined within the program being debugged, as well as their addresses.
16714 With a regular expression, @var{regexp}, as argument, only those exceptions
16715 whose names match @var{regexp} are listed.
16718 Below is a small example, showing how the command can be used, first
16719 without argument, and next with a regular expression passed as an
16723 (@value{GDBP}) info exceptions
16724 All defined Ada exceptions:
16725 constraint_error: 0x613da0
16726 program_error: 0x613d20
16727 storage_error: 0x613ce0
16728 tasking_error: 0x613ca0
16729 const.aint_global_e: 0x613b00
16730 (@value{GDBP}) info exceptions const.aint
16731 All Ada exceptions matching regular expression "const.aint":
16732 constraint_error: 0x613da0
16733 const.aint_global_e: 0x613b00
16736 It is also possible to ask @value{GDBN} to stop your program's execution
16737 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16740 @subsubsection Extensions for Ada Tasks
16741 @cindex Ada, tasking
16743 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16744 @value{GDBN} provides the following task-related commands:
16749 This command shows a list of current Ada tasks, as in the following example:
16756 (@value{GDBP}) info tasks
16757 ID TID P-ID Pri State Name
16758 1 8088000 0 15 Child Activation Wait main_task
16759 2 80a4000 1 15 Accept Statement b
16760 3 809a800 1 15 Child Activation Wait a
16761 * 4 80ae800 3 15 Runnable c
16766 In this listing, the asterisk before the last task indicates it to be the
16767 task currently being inspected.
16771 Represents @value{GDBN}'s internal task number.
16777 The parent's task ID (@value{GDBN}'s internal task number).
16780 The base priority of the task.
16783 Current state of the task.
16787 The task has been created but has not been activated. It cannot be
16791 The task is not blocked for any reason known to Ada. (It may be waiting
16792 for a mutex, though.) It is conceptually "executing" in normal mode.
16795 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16796 that were waiting on terminate alternatives have been awakened and have
16797 terminated themselves.
16799 @item Child Activation Wait
16800 The task is waiting for created tasks to complete activation.
16802 @item Accept Statement
16803 The task is waiting on an accept or selective wait statement.
16805 @item Waiting on entry call
16806 The task is waiting on an entry call.
16808 @item Async Select Wait
16809 The task is waiting to start the abortable part of an asynchronous
16813 The task is waiting on a select statement with only a delay
16816 @item Child Termination Wait
16817 The task is sleeping having completed a master within itself, and is
16818 waiting for the tasks dependent on that master to become terminated or
16819 waiting on a terminate Phase.
16821 @item Wait Child in Term Alt
16822 The task is sleeping waiting for tasks on terminate alternatives to
16823 finish terminating.
16825 @item Accepting RV with @var{taskno}
16826 The task is accepting a rendez-vous with the task @var{taskno}.
16830 Name of the task in the program.
16834 @kindex info task @var{taskno}
16835 @item info task @var{taskno}
16836 This command shows detailled informations on the specified task, as in
16837 the following example:
16842 (@value{GDBP}) info tasks
16843 ID TID P-ID Pri State Name
16844 1 8077880 0 15 Child Activation Wait main_task
16845 * 2 807c468 1 15 Runnable task_1
16846 (@value{GDBP}) info task 2
16847 Ada Task: 0x807c468
16850 Parent: 1 (main_task)
16856 @kindex task@r{ (Ada)}
16857 @cindex current Ada task ID
16858 This command prints the ID of the current task.
16864 (@value{GDBP}) info tasks
16865 ID TID P-ID Pri State Name
16866 1 8077870 0 15 Child Activation Wait main_task
16867 * 2 807c458 1 15 Runnable t
16868 (@value{GDBP}) task
16869 [Current task is 2]
16872 @item task @var{taskno}
16873 @cindex Ada task switching
16874 This command is like the @code{thread @var{thread-id}}
16875 command (@pxref{Threads}). It switches the context of debugging
16876 from the current task to the given task.
16882 (@value{GDBP}) info tasks
16883 ID TID P-ID Pri State Name
16884 1 8077870 0 15 Child Activation Wait main_task
16885 * 2 807c458 1 15 Runnable t
16886 (@value{GDBP}) task 1
16887 [Switching to task 1]
16888 #0 0x8067726 in pthread_cond_wait ()
16890 #0 0x8067726 in pthread_cond_wait ()
16891 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16892 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16893 #3 0x806153e in system.tasking.stages.activate_tasks ()
16894 #4 0x804aacc in un () at un.adb:5
16897 @item break @var{location} task @var{taskno}
16898 @itemx break @var{location} task @var{taskno} if @dots{}
16899 @cindex breakpoints and tasks, in Ada
16900 @cindex task breakpoints, in Ada
16901 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16902 These commands are like the @code{break @dots{} thread @dots{}}
16903 command (@pxref{Thread Stops}). The
16904 @var{location} argument specifies source lines, as described
16905 in @ref{Specify Location}.
16907 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16908 to specify that you only want @value{GDBN} to stop the program when a
16909 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16910 numeric task identifiers assigned by @value{GDBN}, shown in the first
16911 column of the @samp{info tasks} display.
16913 If you do not specify @samp{task @var{taskno}} when you set a
16914 breakpoint, the breakpoint applies to @emph{all} tasks of your
16917 You can use the @code{task} qualifier on conditional breakpoints as
16918 well; in this case, place @samp{task @var{taskno}} before the
16919 breakpoint condition (before the @code{if}).
16927 (@value{GDBP}) info tasks
16928 ID TID P-ID Pri State Name
16929 1 140022020 0 15 Child Activation Wait main_task
16930 2 140045060 1 15 Accept/Select Wait t2
16931 3 140044840 1 15 Runnable t1
16932 * 4 140056040 1 15 Runnable t3
16933 (@value{GDBP}) b 15 task 2
16934 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16935 (@value{GDBP}) cont
16940 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16942 (@value{GDBP}) info tasks
16943 ID TID P-ID Pri State Name
16944 1 140022020 0 15 Child Activation Wait main_task
16945 * 2 140045060 1 15 Runnable t2
16946 3 140044840 1 15 Runnable t1
16947 4 140056040 1 15 Delay Sleep t3
16951 @node Ada Tasks and Core Files
16952 @subsubsection Tasking Support when Debugging Core Files
16953 @cindex Ada tasking and core file debugging
16955 When inspecting a core file, as opposed to debugging a live program,
16956 tasking support may be limited or even unavailable, depending on
16957 the platform being used.
16958 For instance, on x86-linux, the list of tasks is available, but task
16959 switching is not supported.
16961 On certain platforms, the debugger needs to perform some
16962 memory writes in order to provide Ada tasking support. When inspecting
16963 a core file, this means that the core file must be opened with read-write
16964 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16965 Under these circumstances, you should make a backup copy of the core
16966 file before inspecting it with @value{GDBN}.
16968 @node Ravenscar Profile
16969 @subsubsection Tasking Support when using the Ravenscar Profile
16970 @cindex Ravenscar Profile
16972 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16973 specifically designed for systems with safety-critical real-time
16977 @kindex set ravenscar task-switching on
16978 @cindex task switching with program using Ravenscar Profile
16979 @item set ravenscar task-switching on
16980 Allows task switching when debugging a program that uses the Ravenscar
16981 Profile. This is the default.
16983 @kindex set ravenscar task-switching off
16984 @item set ravenscar task-switching off
16985 Turn off task switching when debugging a program that uses the Ravenscar
16986 Profile. This is mostly intended to disable the code that adds support
16987 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16988 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16989 To be effective, this command should be run before the program is started.
16991 @kindex show ravenscar task-switching
16992 @item show ravenscar task-switching
16993 Show whether it is possible to switch from task to task in a program
16994 using the Ravenscar Profile.
16999 @subsubsection Ada Settings
17000 @cindex Ada settings
17003 @kindex set varsize-limit
17004 @item set varsize-limit @var{size}
17005 Prevent @value{GDBN} from attempting to evaluate objects whose size
17006 is above the given limit (@var{size}) when those sizes are computed
17007 from run-time quantities. This is typically the case when the object
17008 has a variable size, such as an array whose bounds are not known at
17009 compile time for example. Setting @var{size} to @code{unlimited}
17010 removes the size limitation. By default, the limit is about 65KB.
17012 The purpose of having such a limit is to prevent @value{GDBN} from
17013 trying to grab enormous chunks of virtual memory when asked to evaluate
17014 a quantity whose bounds have been corrupted or have not yet been fully
17015 initialized. The limit applies to the results of some subexpressions
17016 as well as to complete expressions. For example, an expression denoting
17017 a simple integer component, such as @code{x.y.z}, may fail if the size of
17018 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17019 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17020 @code{A} is an array variable with non-constant size, will generally
17021 succeed regardless of the bounds on @code{A}, as long as the component
17022 size is less than @var{size}.
17024 @kindex show varsize-limit
17025 @item show varsize-limit
17026 Show the limit on types whose size is determined by run-time quantities.
17030 @subsubsection Known Peculiarities of Ada Mode
17031 @cindex Ada, problems
17033 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17034 we know of several problems with and limitations of Ada mode in
17036 some of which will be fixed with planned future releases of the debugger
17037 and the GNU Ada compiler.
17041 Static constants that the compiler chooses not to materialize as objects in
17042 storage are invisible to the debugger.
17045 Named parameter associations in function argument lists are ignored (the
17046 argument lists are treated as positional).
17049 Many useful library packages are currently invisible to the debugger.
17052 Fixed-point arithmetic, conversions, input, and output is carried out using
17053 floating-point arithmetic, and may give results that only approximate those on
17057 The GNAT compiler never generates the prefix @code{Standard} for any of
17058 the standard symbols defined by the Ada language. @value{GDBN} knows about
17059 this: it will strip the prefix from names when you use it, and will never
17060 look for a name you have so qualified among local symbols, nor match against
17061 symbols in other packages or subprograms. If you have
17062 defined entities anywhere in your program other than parameters and
17063 local variables whose simple names match names in @code{Standard},
17064 GNAT's lack of qualification here can cause confusion. When this happens,
17065 you can usually resolve the confusion
17066 by qualifying the problematic names with package
17067 @code{Standard} explicitly.
17070 Older versions of the compiler sometimes generate erroneous debugging
17071 information, resulting in the debugger incorrectly printing the value
17072 of affected entities. In some cases, the debugger is able to work
17073 around an issue automatically. In other cases, the debugger is able
17074 to work around the issue, but the work-around has to be specifically
17077 @kindex set ada trust-PAD-over-XVS
17078 @kindex show ada trust-PAD-over-XVS
17081 @item set ada trust-PAD-over-XVS on
17082 Configure GDB to strictly follow the GNAT encoding when computing the
17083 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17084 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17085 a complete description of the encoding used by the GNAT compiler).
17086 This is the default.
17088 @item set ada trust-PAD-over-XVS off
17089 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17090 sometimes prints the wrong value for certain entities, changing @code{ada
17091 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17092 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17093 @code{off}, but this incurs a slight performance penalty, so it is
17094 recommended to leave this setting to @code{on} unless necessary.
17098 @cindex GNAT descriptive types
17099 @cindex GNAT encoding
17100 Internally, the debugger also relies on the compiler following a number
17101 of conventions known as the @samp{GNAT Encoding}, all documented in
17102 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17103 how the debugging information should be generated for certain types.
17104 In particular, this convention makes use of @dfn{descriptive types},
17105 which are artificial types generated purely to help the debugger.
17107 These encodings were defined at a time when the debugging information
17108 format used was not powerful enough to describe some of the more complex
17109 types available in Ada. Since DWARF allows us to express nearly all
17110 Ada features, the long-term goal is to slowly replace these descriptive
17111 types by their pure DWARF equivalent. To facilitate that transition,
17112 a new maintenance option is available to force the debugger to ignore
17113 those descriptive types. It allows the user to quickly evaluate how
17114 well @value{GDBN} works without them.
17118 @kindex maint ada set ignore-descriptive-types
17119 @item maintenance ada set ignore-descriptive-types [on|off]
17120 Control whether the debugger should ignore descriptive types.
17121 The default is not to ignore descriptives types (@code{off}).
17123 @kindex maint ada show ignore-descriptive-types
17124 @item maintenance ada show ignore-descriptive-types
17125 Show if descriptive types are ignored by @value{GDBN}.
17129 @node Unsupported Languages
17130 @section Unsupported Languages
17132 @cindex unsupported languages
17133 @cindex minimal language
17134 In addition to the other fully-supported programming languages,
17135 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17136 It does not represent a real programming language, but provides a set
17137 of capabilities close to what the C or assembly languages provide.
17138 This should allow most simple operations to be performed while debugging
17139 an application that uses a language currently not supported by @value{GDBN}.
17141 If the language is set to @code{auto}, @value{GDBN} will automatically
17142 select this language if the current frame corresponds to an unsupported
17146 @chapter Examining the Symbol Table
17148 The commands described in this chapter allow you to inquire about the
17149 symbols (names of variables, functions and types) defined in your
17150 program. This information is inherent in the text of your program and
17151 does not change as your program executes. @value{GDBN} finds it in your
17152 program's symbol table, in the file indicated when you started @value{GDBN}
17153 (@pxref{File Options, ,Choosing Files}), or by one of the
17154 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17156 @cindex symbol names
17157 @cindex names of symbols
17158 @cindex quoting names
17159 @anchor{quoting names}
17160 Occasionally, you may need to refer to symbols that contain unusual
17161 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17162 most frequent case is in referring to static variables in other
17163 source files (@pxref{Variables,,Program Variables}). File names
17164 are recorded in object files as debugging symbols, but @value{GDBN} would
17165 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17166 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17167 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17174 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17177 @cindex case-insensitive symbol names
17178 @cindex case sensitivity in symbol names
17179 @kindex set case-sensitive
17180 @item set case-sensitive on
17181 @itemx set case-sensitive off
17182 @itemx set case-sensitive auto
17183 Normally, when @value{GDBN} looks up symbols, it matches their names
17184 with case sensitivity determined by the current source language.
17185 Occasionally, you may wish to control that. The command @code{set
17186 case-sensitive} lets you do that by specifying @code{on} for
17187 case-sensitive matches or @code{off} for case-insensitive ones. If
17188 you specify @code{auto}, case sensitivity is reset to the default
17189 suitable for the source language. The default is case-sensitive
17190 matches for all languages except for Fortran, for which the default is
17191 case-insensitive matches.
17193 @kindex show case-sensitive
17194 @item show case-sensitive
17195 This command shows the current setting of case sensitivity for symbols
17198 @kindex set print type methods
17199 @item set print type methods
17200 @itemx set print type methods on
17201 @itemx set print type methods off
17202 Normally, when @value{GDBN} prints a class, it displays any methods
17203 declared in that class. You can control this behavior either by
17204 passing the appropriate flag to @code{ptype}, or using @command{set
17205 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17206 display the methods; this is the default. Specifying @code{off} will
17207 cause @value{GDBN} to omit the methods.
17209 @kindex show print type methods
17210 @item show print type methods
17211 This command shows the current setting of method display when printing
17214 @kindex set print type nested-type-limit
17215 @item set print type nested-type-limit @var{limit}
17216 @itemx set print type nested-type-limit unlimited
17217 Set the limit of displayed nested types that the type printer will
17218 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17219 nested definitions. By default, the type printer will not show any nested
17220 types defined in classes.
17222 @kindex show print type nested-type-limit
17223 @item show print type nested-type-limit
17224 This command shows the current display limit of nested types when
17227 @kindex set print type typedefs
17228 @item set print type typedefs
17229 @itemx set print type typedefs on
17230 @itemx set print type typedefs off
17232 Normally, when @value{GDBN} prints a class, it displays any typedefs
17233 defined in that class. You can control this behavior either by
17234 passing the appropriate flag to @code{ptype}, or using @command{set
17235 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17236 display the typedef definitions; this is the default. Specifying
17237 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17238 Note that this controls whether the typedef definition itself is
17239 printed, not whether typedef names are substituted when printing other
17242 @kindex show print type typedefs
17243 @item show print type typedefs
17244 This command shows the current setting of typedef display when
17247 @kindex info address
17248 @cindex address of a symbol
17249 @item info address @var{symbol}
17250 Describe where the data for @var{symbol} is stored. For a register
17251 variable, this says which register it is kept in. For a non-register
17252 local variable, this prints the stack-frame offset at which the variable
17255 Note the contrast with @samp{print &@var{symbol}}, which does not work
17256 at all for a register variable, and for a stack local variable prints
17257 the exact address of the current instantiation of the variable.
17259 @kindex info symbol
17260 @cindex symbol from address
17261 @cindex closest symbol and offset for an address
17262 @item info symbol @var{addr}
17263 Print the name of a symbol which is stored at the address @var{addr}.
17264 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17265 nearest symbol and an offset from it:
17268 (@value{GDBP}) info symbol 0x54320
17269 _initialize_vx + 396 in section .text
17273 This is the opposite of the @code{info address} command. You can use
17274 it to find out the name of a variable or a function given its address.
17276 For dynamically linked executables, the name of executable or shared
17277 library containing the symbol is also printed:
17280 (@value{GDBP}) info symbol 0x400225
17281 _start + 5 in section .text of /tmp/a.out
17282 (@value{GDBP}) info symbol 0x2aaaac2811cf
17283 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17288 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17289 Demangle @var{name}.
17290 If @var{language} is provided it is the name of the language to demangle
17291 @var{name} in. Otherwise @var{name} is demangled in the current language.
17293 The @samp{--} option specifies the end of options,
17294 and is useful when @var{name} begins with a dash.
17296 The parameter @code{demangle-style} specifies how to interpret the kind
17297 of mangling used. @xref{Print Settings}.
17300 @item whatis[/@var{flags}] [@var{arg}]
17301 Print the data type of @var{arg}, which can be either an expression
17302 or a name of a data type. With no argument, print the data type of
17303 @code{$}, the last value in the value history.
17305 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17306 is not actually evaluated, and any side-effecting operations (such as
17307 assignments or function calls) inside it do not take place.
17309 If @var{arg} is a variable or an expression, @code{whatis} prints its
17310 literal type as it is used in the source code. If the type was
17311 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17312 the data type underlying the @code{typedef}. If the type of the
17313 variable or the expression is a compound data type, such as
17314 @code{struct} or @code{class}, @code{whatis} never prints their
17315 fields or methods. It just prints the @code{struct}/@code{class}
17316 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17317 such a compound data type, use @code{ptype}.
17319 If @var{arg} is a type name that was defined using @code{typedef},
17320 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17321 Unrolling means that @code{whatis} will show the underlying type used
17322 in the @code{typedef} declaration of @var{arg}. However, if that
17323 underlying type is also a @code{typedef}, @code{whatis} will not
17326 For C code, the type names may also have the form @samp{class
17327 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17328 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17330 @var{flags} can be used to modify how the type is displayed.
17331 Available flags are:
17335 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17336 parameters and typedefs defined in a class when printing the class'
17337 members. The @code{/r} flag disables this.
17340 Do not print methods defined in the class.
17343 Print methods defined in the class. This is the default, but the flag
17344 exists in case you change the default with @command{set print type methods}.
17347 Do not print typedefs defined in the class. Note that this controls
17348 whether the typedef definition itself is printed, not whether typedef
17349 names are substituted when printing other types.
17352 Print typedefs defined in the class. This is the default, but the flag
17353 exists in case you change the default with @command{set print type typedefs}.
17356 Print the offsets and sizes of fields in a struct, similar to what the
17357 @command{pahole} tool does. This option implies the @code{/tm} flags.
17359 For example, given the following declarations:
17395 Issuing a @kbd{ptype /o struct tuv} command would print:
17398 (@value{GDBP}) ptype /o struct tuv
17399 /* offset | size */ type = struct tuv @{
17400 /* 0 | 4 */ int a1;
17401 /* XXX 4-byte hole */
17402 /* 8 | 8 */ char *a2;
17403 /* 16 | 4 */ int a3;
17405 /* total size (bytes): 24 */
17409 Notice the format of the first column of comments. There, you can
17410 find two parts separated by the @samp{|} character: the @emph{offset},
17411 which indicates where the field is located inside the struct, in
17412 bytes, and the @emph{size} of the field. Another interesting line is
17413 the marker of a @emph{hole} in the struct, indicating that it may be
17414 possible to pack the struct and make it use less space by reorganizing
17417 It is also possible to print offsets inside an union:
17420 (@value{GDBP}) ptype /o union qwe
17421 /* offset | size */ type = union qwe @{
17422 /* 24 */ struct tuv @{
17423 /* 0 | 4 */ int a1;
17424 /* XXX 4-byte hole */
17425 /* 8 | 8 */ char *a2;
17426 /* 16 | 4 */ int a3;
17428 /* total size (bytes): 24 */
17430 /* 40 */ struct xyz @{
17431 /* 0 | 4 */ int f1;
17432 /* 4 | 1 */ char f2;
17433 /* XXX 3-byte hole */
17434 /* 8 | 8 */ void *f3;
17435 /* 16 | 24 */ struct tuv @{
17436 /* 16 | 4 */ int a1;
17437 /* XXX 4-byte hole */
17438 /* 24 | 8 */ char *a2;
17439 /* 32 | 4 */ int a3;
17441 /* total size (bytes): 24 */
17444 /* total size (bytes): 40 */
17447 /* total size (bytes): 40 */
17451 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17452 same space (because we are dealing with an union), the offset is not
17453 printed for them. However, you can still examine the offset of each
17454 of these structures' fields.
17456 Another useful scenario is printing the offsets of a struct containing
17460 (@value{GDBP}) ptype /o struct tyu
17461 /* offset | size */ type = struct tyu @{
17462 /* 0:31 | 4 */ int a1 : 1;
17463 /* 0:28 | 4 */ int a2 : 3;
17464 /* 0: 5 | 4 */ int a3 : 23;
17465 /* 3: 3 | 1 */ signed char a4 : 2;
17466 /* XXX 3-bit hole */
17467 /* XXX 4-byte hole */
17468 /* 8 | 8 */ int64_t a5;
17469 /* 16:27 | 4 */ int a6 : 5;
17470 /* 16:56 | 8 */ int64_t a7 : 3;
17472 /* total size (bytes): 24 */
17476 Note how the offset information is now extended to also include how
17477 many bits are left to be used in each bitfield.
17481 @item ptype[/@var{flags}] [@var{arg}]
17482 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17483 detailed description of the type, instead of just the name of the type.
17484 @xref{Expressions, ,Expressions}.
17486 Contrary to @code{whatis}, @code{ptype} always unrolls any
17487 @code{typedef}s in its argument declaration, whether the argument is
17488 a variable, expression, or a data type. This means that @code{ptype}
17489 of a variable or an expression will not print literally its type as
17490 present in the source code---use @code{whatis} for that. @code{typedef}s at
17491 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17492 fields, methods and inner @code{class typedef}s of @code{struct}s,
17493 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17495 For example, for this variable declaration:
17498 typedef double real_t;
17499 struct complex @{ real_t real; double imag; @};
17500 typedef struct complex complex_t;
17502 real_t *real_pointer_var;
17506 the two commands give this output:
17510 (@value{GDBP}) whatis var
17512 (@value{GDBP}) ptype var
17513 type = struct complex @{
17517 (@value{GDBP}) whatis complex_t
17518 type = struct complex
17519 (@value{GDBP}) whatis struct complex
17520 type = struct complex
17521 (@value{GDBP}) ptype struct complex
17522 type = struct complex @{
17526 (@value{GDBP}) whatis real_pointer_var
17528 (@value{GDBP}) ptype real_pointer_var
17534 As with @code{whatis}, using @code{ptype} without an argument refers to
17535 the type of @code{$}, the last value in the value history.
17537 @cindex incomplete type
17538 Sometimes, programs use opaque data types or incomplete specifications
17539 of complex data structure. If the debug information included in the
17540 program does not allow @value{GDBN} to display a full declaration of
17541 the data type, it will say @samp{<incomplete type>}. For example,
17542 given these declarations:
17546 struct foo *fooptr;
17550 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17553 (@value{GDBP}) ptype foo
17554 $1 = <incomplete type>
17558 ``Incomplete type'' is C terminology for data types that are not
17559 completely specified.
17561 @cindex unknown type
17562 Othertimes, information about a variable's type is completely absent
17563 from the debug information included in the program. This most often
17564 happens when the program or library where the variable is defined
17565 includes no debug information at all. @value{GDBN} knows the variable
17566 exists from inspecting the linker/loader symbol table (e.g., the ELF
17567 dynamic symbol table), but such symbols do not contain type
17568 information. Inspecting the type of a (global) variable for which
17569 @value{GDBN} has no type information shows:
17572 (@value{GDBP}) ptype var
17573 type = <data variable, no debug info>
17576 @xref{Variables, no debug info variables}, for how to print the values
17580 @item info types @var{regexp}
17582 Print a brief description of all types whose names match the regular
17583 expression @var{regexp} (or all types in your program, if you supply
17584 no argument). Each complete typename is matched as though it were a
17585 complete line; thus, @samp{i type value} gives information on all
17586 types in your program whose names include the string @code{value}, but
17587 @samp{i type ^value$} gives information only on types whose complete
17588 name is @code{value}.
17590 This command differs from @code{ptype} in two ways: first, like
17591 @code{whatis}, it does not print a detailed description; second, it
17592 lists all source files and line numbers where a type is defined.
17594 @kindex info type-printers
17595 @item info type-printers
17596 Versions of @value{GDBN} that ship with Python scripting enabled may
17597 have ``type printers'' available. When using @command{ptype} or
17598 @command{whatis}, these printers are consulted when the name of a type
17599 is needed. @xref{Type Printing API}, for more information on writing
17602 @code{info type-printers} displays all the available type printers.
17604 @kindex enable type-printer
17605 @kindex disable type-printer
17606 @item enable type-printer @var{name}@dots{}
17607 @item disable type-printer @var{name}@dots{}
17608 These commands can be used to enable or disable type printers.
17611 @cindex local variables
17612 @item info scope @var{location}
17613 List all the variables local to a particular scope. This command
17614 accepts a @var{location} argument---a function name, a source line, or
17615 an address preceded by a @samp{*}, and prints all the variables local
17616 to the scope defined by that location. (@xref{Specify Location}, for
17617 details about supported forms of @var{location}.) For example:
17620 (@value{GDBP}) @b{info scope command_line_handler}
17621 Scope for command_line_handler:
17622 Symbol rl is an argument at stack/frame offset 8, length 4.
17623 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17624 Symbol linelength is in static storage at address 0x150a1c, length 4.
17625 Symbol p is a local variable in register $esi, length 4.
17626 Symbol p1 is a local variable in register $ebx, length 4.
17627 Symbol nline is a local variable in register $edx, length 4.
17628 Symbol repeat is a local variable at frame offset -8, length 4.
17632 This command is especially useful for determining what data to collect
17633 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17636 @kindex info source
17638 Show information about the current source file---that is, the source file for
17639 the function containing the current point of execution:
17642 the name of the source file, and the directory containing it,
17644 the directory it was compiled in,
17646 its length, in lines,
17648 which programming language it is written in,
17650 if the debug information provides it, the program that compiled the file
17651 (which may include, e.g., the compiler version and command line arguments),
17653 whether the executable includes debugging information for that file, and
17654 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17656 whether the debugging information includes information about
17657 preprocessor macros.
17661 @kindex info sources
17663 Print the names of all source files in your program for which there is
17664 debugging information, organized into two lists: files whose symbols
17665 have already been read, and files whose symbols will be read when needed.
17667 @kindex info functions
17668 @item info functions
17669 Print the names and data types of all defined functions.
17670 Similarly to @samp{info types}, this command groups its output by source
17671 files and annotates each function definition with its source line
17674 @item info functions @var{regexp}
17675 Like @samp{info functions}, but only print the names and data types of
17676 functions whose names contain a match for regular expression
17677 @var{regexp}. Thus, @samp{info fun step} finds all functions whose
17678 names include @code{step}; @samp{info fun ^step} finds those whose names
17679 start with @code{step}. If a function name contains characters that
17680 conflict with the regular expression language (e.g.@:
17681 @samp{operator*()}), they may be quoted with a backslash.
17683 @kindex info variables
17684 @item info variables
17685 Print the names and data types of all variables that are defined
17686 outside of functions (i.e.@: excluding local variables).
17687 The printed variables are grouped by source files and annotated with
17688 their respective source line numbers.
17690 @item info variables @var{regexp}
17691 Like @kbd{info variables}, but only print the names and data types of
17692 non-local variables whose names contain a match for regular expression
17695 @kindex info classes
17696 @cindex Objective-C, classes and selectors
17698 @itemx info classes @var{regexp}
17699 Display all Objective-C classes in your program, or
17700 (with the @var{regexp} argument) all those matching a particular regular
17703 @kindex info selectors
17704 @item info selectors
17705 @itemx info selectors @var{regexp}
17706 Display all Objective-C selectors in your program, or
17707 (with the @var{regexp} argument) all those matching a particular regular
17711 This was never implemented.
17712 @kindex info methods
17714 @itemx info methods @var{regexp}
17715 The @code{info methods} command permits the user to examine all defined
17716 methods within C@t{++} program, or (with the @var{regexp} argument) a
17717 specific set of methods found in the various C@t{++} classes. Many
17718 C@t{++} classes provide a large number of methods. Thus, the output
17719 from the @code{ptype} command can be overwhelming and hard to use. The
17720 @code{info-methods} command filters the methods, printing only those
17721 which match the regular-expression @var{regexp}.
17724 @cindex opaque data types
17725 @kindex set opaque-type-resolution
17726 @item set opaque-type-resolution on
17727 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17728 declared as a pointer to a @code{struct}, @code{class}, or
17729 @code{union}---for example, @code{struct MyType *}---that is used in one
17730 source file although the full declaration of @code{struct MyType} is in
17731 another source file. The default is on.
17733 A change in the setting of this subcommand will not take effect until
17734 the next time symbols for a file are loaded.
17736 @item set opaque-type-resolution off
17737 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17738 is printed as follows:
17740 @{<no data fields>@}
17743 @kindex show opaque-type-resolution
17744 @item show opaque-type-resolution
17745 Show whether opaque types are resolved or not.
17747 @kindex set print symbol-loading
17748 @cindex print messages when symbols are loaded
17749 @item set print symbol-loading
17750 @itemx set print symbol-loading full
17751 @itemx set print symbol-loading brief
17752 @itemx set print symbol-loading off
17753 The @code{set print symbol-loading} command allows you to control the
17754 printing of messages when @value{GDBN} loads symbol information.
17755 By default a message is printed for the executable and one for each
17756 shared library, and normally this is what you want. However, when
17757 debugging apps with large numbers of shared libraries these messages
17759 When set to @code{brief} a message is printed for each executable,
17760 and when @value{GDBN} loads a collection of shared libraries at once
17761 it will only print one message regardless of the number of shared
17762 libraries. When set to @code{off} no messages are printed.
17764 @kindex show print symbol-loading
17765 @item show print symbol-loading
17766 Show whether messages will be printed when a @value{GDBN} command
17767 entered from the keyboard causes symbol information to be loaded.
17769 @kindex maint print symbols
17770 @cindex symbol dump
17771 @kindex maint print psymbols
17772 @cindex partial symbol dump
17773 @kindex maint print msymbols
17774 @cindex minimal symbol dump
17775 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17776 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17777 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17778 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17779 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17780 Write a dump of debugging symbol data into the file @var{filename} or
17781 the terminal if @var{filename} is unspecified.
17782 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17784 If @code{-pc @var{address}} is specified, only dump symbols for the file
17785 with code at that address. Note that @var{address} may be a symbol like
17787 If @code{-source @var{source}} is specified, only dump symbols for that
17790 These commands are used to debug the @value{GDBN} symbol-reading code.
17791 These commands do not modify internal @value{GDBN} state, therefore
17792 @samp{maint print symbols} will only print symbols for already expanded symbol
17794 You can use the command @code{info sources} to find out which files these are.
17795 If you use @samp{maint print psymbols} instead, the dump shows information
17796 about symbols that @value{GDBN} only knows partially---that is, symbols
17797 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17798 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17801 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17802 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17804 @kindex maint info symtabs
17805 @kindex maint info psymtabs
17806 @cindex listing @value{GDBN}'s internal symbol tables
17807 @cindex symbol tables, listing @value{GDBN}'s internal
17808 @cindex full symbol tables, listing @value{GDBN}'s internal
17809 @cindex partial symbol tables, listing @value{GDBN}'s internal
17810 @item maint info symtabs @r{[} @var{regexp} @r{]}
17811 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17813 List the @code{struct symtab} or @code{struct partial_symtab}
17814 structures whose names match @var{regexp}. If @var{regexp} is not
17815 given, list them all. The output includes expressions which you can
17816 copy into a @value{GDBN} debugging this one to examine a particular
17817 structure in more detail. For example:
17820 (@value{GDBP}) maint info psymtabs dwarf2read
17821 @{ objfile /home/gnu/build/gdb/gdb
17822 ((struct objfile *) 0x82e69d0)
17823 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17824 ((struct partial_symtab *) 0x8474b10)
17827 text addresses 0x814d3c8 -- 0x8158074
17828 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17829 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17830 dependencies (none)
17833 (@value{GDBP}) maint info symtabs
17837 We see that there is one partial symbol table whose filename contains
17838 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17839 and we see that @value{GDBN} has not read in any symtabs yet at all.
17840 If we set a breakpoint on a function, that will cause @value{GDBN} to
17841 read the symtab for the compilation unit containing that function:
17844 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17845 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17847 (@value{GDBP}) maint info symtabs
17848 @{ objfile /home/gnu/build/gdb/gdb
17849 ((struct objfile *) 0x82e69d0)
17850 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17851 ((struct symtab *) 0x86c1f38)
17854 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17855 linetable ((struct linetable *) 0x8370fa0)
17856 debugformat DWARF 2
17862 @kindex maint info line-table
17863 @cindex listing @value{GDBN}'s internal line tables
17864 @cindex line tables, listing @value{GDBN}'s internal
17865 @item maint info line-table @r{[} @var{regexp} @r{]}
17867 List the @code{struct linetable} from all @code{struct symtab}
17868 instances whose name matches @var{regexp}. If @var{regexp} is not
17869 given, list the @code{struct linetable} from all @code{struct symtab}.
17871 @kindex maint set symbol-cache-size
17872 @cindex symbol cache size
17873 @item maint set symbol-cache-size @var{size}
17874 Set the size of the symbol cache to @var{size}.
17875 The default size is intended to be good enough for debugging
17876 most applications. This option exists to allow for experimenting
17877 with different sizes.
17879 @kindex maint show symbol-cache-size
17880 @item maint show symbol-cache-size
17881 Show the size of the symbol cache.
17883 @kindex maint print symbol-cache
17884 @cindex symbol cache, printing its contents
17885 @item maint print symbol-cache
17886 Print the contents of the symbol cache.
17887 This is useful when debugging symbol cache issues.
17889 @kindex maint print symbol-cache-statistics
17890 @cindex symbol cache, printing usage statistics
17891 @item maint print symbol-cache-statistics
17892 Print symbol cache usage statistics.
17893 This helps determine how well the cache is being utilized.
17895 @kindex maint flush-symbol-cache
17896 @cindex symbol cache, flushing
17897 @item maint flush-symbol-cache
17898 Flush the contents of the symbol cache, all entries are removed.
17899 This command is useful when debugging the symbol cache.
17900 It is also useful when collecting performance data.
17905 @chapter Altering Execution
17907 Once you think you have found an error in your program, you might want to
17908 find out for certain whether correcting the apparent error would lead to
17909 correct results in the rest of the run. You can find the answer by
17910 experiment, using the @value{GDBN} features for altering execution of the
17913 For example, you can store new values into variables or memory
17914 locations, give your program a signal, restart it at a different
17915 address, or even return prematurely from a function.
17918 * Assignment:: Assignment to variables
17919 * Jumping:: Continuing at a different address
17920 * Signaling:: Giving your program a signal
17921 * Returning:: Returning from a function
17922 * Calling:: Calling your program's functions
17923 * Patching:: Patching your program
17924 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17928 @section Assignment to Variables
17931 @cindex setting variables
17932 To alter the value of a variable, evaluate an assignment expression.
17933 @xref{Expressions, ,Expressions}. For example,
17940 stores the value 4 into the variable @code{x}, and then prints the
17941 value of the assignment expression (which is 4).
17942 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17943 information on operators in supported languages.
17945 @kindex set variable
17946 @cindex variables, setting
17947 If you are not interested in seeing the value of the assignment, use the
17948 @code{set} command instead of the @code{print} command. @code{set} is
17949 really the same as @code{print} except that the expression's value is
17950 not printed and is not put in the value history (@pxref{Value History,
17951 ,Value History}). The expression is evaluated only for its effects.
17953 If the beginning of the argument string of the @code{set} command
17954 appears identical to a @code{set} subcommand, use the @code{set
17955 variable} command instead of just @code{set}. This command is identical
17956 to @code{set} except for its lack of subcommands. For example, if your
17957 program has a variable @code{width}, you get an error if you try to set
17958 a new value with just @samp{set width=13}, because @value{GDBN} has the
17959 command @code{set width}:
17962 (@value{GDBP}) whatis width
17964 (@value{GDBP}) p width
17966 (@value{GDBP}) set width=47
17967 Invalid syntax in expression.
17971 The invalid expression, of course, is @samp{=47}. In
17972 order to actually set the program's variable @code{width}, use
17975 (@value{GDBP}) set var width=47
17978 Because the @code{set} command has many subcommands that can conflict
17979 with the names of program variables, it is a good idea to use the
17980 @code{set variable} command instead of just @code{set}. For example, if
17981 your program has a variable @code{g}, you run into problems if you try
17982 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17983 the command @code{set gnutarget}, abbreviated @code{set g}:
17987 (@value{GDBP}) whatis g
17991 (@value{GDBP}) set g=4
17995 The program being debugged has been started already.
17996 Start it from the beginning? (y or n) y
17997 Starting program: /home/smith/cc_progs/a.out
17998 "/home/smith/cc_progs/a.out": can't open to read symbols:
17999 Invalid bfd target.
18000 (@value{GDBP}) show g
18001 The current BFD target is "=4".
18006 The program variable @code{g} did not change, and you silently set the
18007 @code{gnutarget} to an invalid value. In order to set the variable
18011 (@value{GDBP}) set var g=4
18014 @value{GDBN} allows more implicit conversions in assignments than C; you can
18015 freely store an integer value into a pointer variable or vice versa,
18016 and you can convert any structure to any other structure that is the
18017 same length or shorter.
18018 @comment FIXME: how do structs align/pad in these conversions?
18019 @comment /doc@cygnus.com 18dec1990
18021 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18022 construct to generate a value of specified type at a specified address
18023 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18024 to memory location @code{0x83040} as an integer (which implies a certain size
18025 and representation in memory), and
18028 set @{int@}0x83040 = 4
18032 stores the value 4 into that memory location.
18035 @section Continuing at a Different Address
18037 Ordinarily, when you continue your program, you do so at the place where
18038 it stopped, with the @code{continue} command. You can instead continue at
18039 an address of your own choosing, with the following commands:
18043 @kindex j @r{(@code{jump})}
18044 @item jump @var{location}
18045 @itemx j @var{location}
18046 Resume execution at @var{location}. Execution stops again immediately
18047 if there is a breakpoint there. @xref{Specify Location}, for a description
18048 of the different forms of @var{location}. It is common
18049 practice to use the @code{tbreak} command in conjunction with
18050 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18052 The @code{jump} command does not change the current stack frame, or
18053 the stack pointer, or the contents of any memory location or any
18054 register other than the program counter. If @var{location} is in
18055 a different function from the one currently executing, the results may
18056 be bizarre if the two functions expect different patterns of arguments or
18057 of local variables. For this reason, the @code{jump} command requests
18058 confirmation if the specified line is not in the function currently
18059 executing. However, even bizarre results are predictable if you are
18060 well acquainted with the machine-language code of your program.
18063 On many systems, you can get much the same effect as the @code{jump}
18064 command by storing a new value into the register @code{$pc}. The
18065 difference is that this does not start your program running; it only
18066 changes the address of where it @emph{will} run when you continue. For
18074 makes the next @code{continue} command or stepping command execute at
18075 address @code{0x485}, rather than at the address where your program stopped.
18076 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18078 The most common occasion to use the @code{jump} command is to back
18079 up---perhaps with more breakpoints set---over a portion of a program
18080 that has already executed, in order to examine its execution in more
18085 @section Giving your Program a Signal
18086 @cindex deliver a signal to a program
18090 @item signal @var{signal}
18091 Resume execution where your program is stopped, but immediately give it the
18092 signal @var{signal}. The @var{signal} can be the name or the number of a
18093 signal. For example, on many systems @code{signal 2} and @code{signal
18094 SIGINT} are both ways of sending an interrupt signal.
18096 Alternatively, if @var{signal} is zero, continue execution without
18097 giving a signal. This is useful when your program stopped on account of
18098 a signal and would ordinarily see the signal when resumed with the
18099 @code{continue} command; @samp{signal 0} causes it to resume without a
18102 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18103 delivered to the currently selected thread, not the thread that last
18104 reported a stop. This includes the situation where a thread was
18105 stopped due to a signal. So if you want to continue execution
18106 suppressing the signal that stopped a thread, you should select that
18107 same thread before issuing the @samp{signal 0} command. If you issue
18108 the @samp{signal 0} command with another thread as the selected one,
18109 @value{GDBN} detects that and asks for confirmation.
18111 Invoking the @code{signal} command is not the same as invoking the
18112 @code{kill} utility from the shell. Sending a signal with @code{kill}
18113 causes @value{GDBN} to decide what to do with the signal depending on
18114 the signal handling tables (@pxref{Signals}). The @code{signal} command
18115 passes the signal directly to your program.
18117 @code{signal} does not repeat when you press @key{RET} a second time
18118 after executing the command.
18120 @kindex queue-signal
18121 @item queue-signal @var{signal}
18122 Queue @var{signal} to be delivered immediately to the current thread
18123 when execution of the thread resumes. The @var{signal} can be the name or
18124 the number of a signal. For example, on many systems @code{signal 2} and
18125 @code{signal SIGINT} are both ways of sending an interrupt signal.
18126 The handling of the signal must be set to pass the signal to the program,
18127 otherwise @value{GDBN} will report an error.
18128 You can control the handling of signals from @value{GDBN} with the
18129 @code{handle} command (@pxref{Signals}).
18131 Alternatively, if @var{signal} is zero, any currently queued signal
18132 for the current thread is discarded and when execution resumes no signal
18133 will be delivered. This is useful when your program stopped on account
18134 of a signal and would ordinarily see the signal when resumed with the
18135 @code{continue} command.
18137 This command differs from the @code{signal} command in that the signal
18138 is just queued, execution is not resumed. And @code{queue-signal} cannot
18139 be used to pass a signal whose handling state has been set to @code{nopass}
18144 @xref{stepping into signal handlers}, for information on how stepping
18145 commands behave when the thread has a signal queued.
18148 @section Returning from a Function
18151 @cindex returning from a function
18154 @itemx return @var{expression}
18155 You can cancel execution of a function call with the @code{return}
18156 command. If you give an
18157 @var{expression} argument, its value is used as the function's return
18161 When you use @code{return}, @value{GDBN} discards the selected stack frame
18162 (and all frames within it). You can think of this as making the
18163 discarded frame return prematurely. If you wish to specify a value to
18164 be returned, give that value as the argument to @code{return}.
18166 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18167 Frame}), and any other frames inside of it, leaving its caller as the
18168 innermost remaining frame. That frame becomes selected. The
18169 specified value is stored in the registers used for returning values
18172 The @code{return} command does not resume execution; it leaves the
18173 program stopped in the state that would exist if the function had just
18174 returned. In contrast, the @code{finish} command (@pxref{Continuing
18175 and Stepping, ,Continuing and Stepping}) resumes execution until the
18176 selected stack frame returns naturally.
18178 @value{GDBN} needs to know how the @var{expression} argument should be set for
18179 the inferior. The concrete registers assignment depends on the OS ABI and the
18180 type being returned by the selected stack frame. For example it is common for
18181 OS ABI to return floating point values in FPU registers while integer values in
18182 CPU registers. Still some ABIs return even floating point values in CPU
18183 registers. Larger integer widths (such as @code{long long int}) also have
18184 specific placement rules. @value{GDBN} already knows the OS ABI from its
18185 current target so it needs to find out also the type being returned to make the
18186 assignment into the right register(s).
18188 Normally, the selected stack frame has debug info. @value{GDBN} will always
18189 use the debug info instead of the implicit type of @var{expression} when the
18190 debug info is available. For example, if you type @kbd{return -1}, and the
18191 function in the current stack frame is declared to return a @code{long long
18192 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18193 into a @code{long long int}:
18196 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18198 (@value{GDBP}) return -1
18199 Make func return now? (y or n) y
18200 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18201 43 printf ("result=%lld\n", func ());
18205 However, if the selected stack frame does not have a debug info, e.g., if the
18206 function was compiled without debug info, @value{GDBN} has to find out the type
18207 to return from user. Specifying a different type by mistake may set the value
18208 in different inferior registers than the caller code expects. For example,
18209 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18210 of a @code{long long int} result for a debug info less function (on 32-bit
18211 architectures). Therefore the user is required to specify the return type by
18212 an appropriate cast explicitly:
18215 Breakpoint 2, 0x0040050b in func ()
18216 (@value{GDBP}) return -1
18217 Return value type not available for selected stack frame.
18218 Please use an explicit cast of the value to return.
18219 (@value{GDBP}) return (long long int) -1
18220 Make selected stack frame return now? (y or n) y
18221 #0 0x00400526 in main ()
18226 @section Calling Program Functions
18229 @cindex calling functions
18230 @cindex inferior functions, calling
18231 @item print @var{expr}
18232 Evaluate the expression @var{expr} and display the resulting value.
18233 The expression may include calls to functions in the program being
18237 @item call @var{expr}
18238 Evaluate the expression @var{expr} without displaying @code{void}
18241 You can use this variant of the @code{print} command if you want to
18242 execute a function from your program that does not return anything
18243 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18244 with @code{void} returned values that @value{GDBN} will otherwise
18245 print. If the result is not void, it is printed and saved in the
18249 It is possible for the function you call via the @code{print} or
18250 @code{call} command to generate a signal (e.g., if there's a bug in
18251 the function, or if you passed it incorrect arguments). What happens
18252 in that case is controlled by the @code{set unwindonsignal} command.
18254 Similarly, with a C@t{++} program it is possible for the function you
18255 call via the @code{print} or @code{call} command to generate an
18256 exception that is not handled due to the constraints of the dummy
18257 frame. In this case, any exception that is raised in the frame, but has
18258 an out-of-frame exception handler will not be found. GDB builds a
18259 dummy-frame for the inferior function call, and the unwinder cannot
18260 seek for exception handlers outside of this dummy-frame. What happens
18261 in that case is controlled by the
18262 @code{set unwind-on-terminating-exception} command.
18265 @item set unwindonsignal
18266 @kindex set unwindonsignal
18267 @cindex unwind stack in called functions
18268 @cindex call dummy stack unwinding
18269 Set unwinding of the stack if a signal is received while in a function
18270 that @value{GDBN} called in the program being debugged. If set to on,
18271 @value{GDBN} unwinds the stack it created for the call and restores
18272 the context to what it was before the call. If set to off (the
18273 default), @value{GDBN} stops in the frame where the signal was
18276 @item show unwindonsignal
18277 @kindex show unwindonsignal
18278 Show the current setting of stack unwinding in the functions called by
18281 @item set unwind-on-terminating-exception
18282 @kindex set unwind-on-terminating-exception
18283 @cindex unwind stack in called functions with unhandled exceptions
18284 @cindex call dummy stack unwinding on unhandled exception.
18285 Set unwinding of the stack if a C@t{++} exception is raised, but left
18286 unhandled while in a function that @value{GDBN} called in the program being
18287 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18288 it created for the call and restores the context to what it was before
18289 the call. If set to off, @value{GDBN} the exception is delivered to
18290 the default C@t{++} exception handler and the inferior terminated.
18292 @item show unwind-on-terminating-exception
18293 @kindex show unwind-on-terminating-exception
18294 Show the current setting of stack unwinding in the functions called by
18299 @subsection Calling functions with no debug info
18301 @cindex no debug info functions
18302 Sometimes, a function you wish to call is missing debug information.
18303 In such case, @value{GDBN} does not know the type of the function,
18304 including the types of the function's parameters. To avoid calling
18305 the inferior function incorrectly, which could result in the called
18306 function functioning erroneously and even crash, @value{GDBN} refuses
18307 to call the function unless you tell it the type of the function.
18309 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18310 to do that. The simplest is to cast the call to the function's
18311 declared return type. For example:
18314 (@value{GDBP}) p getenv ("PATH")
18315 'getenv' has unknown return type; cast the call to its declared return type
18316 (@value{GDBP}) p (char *) getenv ("PATH")
18317 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18320 Casting the return type of a no-debug function is equivalent to
18321 casting the function to a pointer to a prototyped function that has a
18322 prototype that matches the types of the passed-in arguments, and
18323 calling that. I.e., the call above is equivalent to:
18326 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18330 and given this prototyped C or C++ function with float parameters:
18333 float multiply (float v1, float v2) @{ return v1 * v2; @}
18337 these calls are equivalent:
18340 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18341 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18344 If the function you wish to call is declared as unprototyped (i.e.@:
18345 old K&R style), you must use the cast-to-function-pointer syntax, so
18346 that @value{GDBN} knows that it needs to apply default argument
18347 promotions (promote float arguments to double). @xref{ABI, float
18348 promotion}. For example, given this unprototyped C function with
18349 float parameters, and no debug info:
18353 multiply_noproto (v1, v2)
18361 you call it like this:
18364 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18368 @section Patching Programs
18370 @cindex patching binaries
18371 @cindex writing into executables
18372 @cindex writing into corefiles
18374 By default, @value{GDBN} opens the file containing your program's
18375 executable code (or the corefile) read-only. This prevents accidental
18376 alterations to machine code; but it also prevents you from intentionally
18377 patching your program's binary.
18379 If you'd like to be able to patch the binary, you can specify that
18380 explicitly with the @code{set write} command. For example, you might
18381 want to turn on internal debugging flags, or even to make emergency
18387 @itemx set write off
18388 If you specify @samp{set write on}, @value{GDBN} opens executable and
18389 core files for both reading and writing; if you specify @kbd{set write
18390 off} (the default), @value{GDBN} opens them read-only.
18392 If you have already loaded a file, you must load it again (using the
18393 @code{exec-file} or @code{core-file} command) after changing @code{set
18394 write}, for your new setting to take effect.
18398 Display whether executable files and core files are opened for writing
18399 as well as reading.
18402 @node Compiling and Injecting Code
18403 @section Compiling and injecting code in @value{GDBN}
18404 @cindex injecting code
18405 @cindex writing into executables
18406 @cindex compiling code
18408 @value{GDBN} supports on-demand compilation and code injection into
18409 programs running under @value{GDBN}. GCC 5.0 or higher built with
18410 @file{libcc1.so} must be installed for this functionality to be enabled.
18411 This functionality is implemented with the following commands.
18414 @kindex compile code
18415 @item compile code @var{source-code}
18416 @itemx compile code -raw @var{--} @var{source-code}
18417 Compile @var{source-code} with the compiler language found as the current
18418 language in @value{GDBN} (@pxref{Languages}). If compilation and
18419 injection is not supported with the current language specified in
18420 @value{GDBN}, or the compiler does not support this feature, an error
18421 message will be printed. If @var{source-code} compiles and links
18422 successfully, @value{GDBN} will load the object-code emitted,
18423 and execute it within the context of the currently selected inferior.
18424 It is important to note that the compiled code is executed immediately.
18425 After execution, the compiled code is removed from @value{GDBN} and any
18426 new types or variables you have defined will be deleted.
18428 The command allows you to specify @var{source-code} in two ways.
18429 The simplest method is to provide a single line of code to the command.
18433 compile code printf ("hello world\n");
18436 If you specify options on the command line as well as source code, they
18437 may conflict. The @samp{--} delimiter can be used to separate options
18438 from actual source code. E.g.:
18441 compile code -r -- printf ("hello world\n");
18444 Alternatively you can enter source code as multiple lines of text. To
18445 enter this mode, invoke the @samp{compile code} command without any text
18446 following the command. This will start the multiple-line editor and
18447 allow you to type as many lines of source code as required. When you
18448 have completed typing, enter @samp{end} on its own line to exit the
18453 >printf ("hello\n");
18454 >printf ("world\n");
18458 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18459 provided @var{source-code} in a callable scope. In this case, you must
18460 specify the entry point of the code by defining a function named
18461 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18462 inferior. Using @samp{-raw} option may be needed for example when
18463 @var{source-code} requires @samp{#include} lines which may conflict with
18464 inferior symbols otherwise.
18466 @kindex compile file
18467 @item compile file @var{filename}
18468 @itemx compile file -raw @var{filename}
18469 Like @code{compile code}, but take the source code from @var{filename}.
18472 compile file /home/user/example.c
18477 @item compile print @var{expr}
18478 @itemx compile print /@var{f} @var{expr}
18479 Compile and execute @var{expr} with the compiler language found as the
18480 current language in @value{GDBN} (@pxref{Languages}). By default the
18481 value of @var{expr} is printed in a format appropriate to its data type;
18482 you can choose a different format by specifying @samp{/@var{f}}, where
18483 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18486 @item compile print
18487 @itemx compile print /@var{f}
18488 @cindex reprint the last value
18489 Alternatively you can enter the expression (source code producing it) as
18490 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18491 command without any text following the command. This will start the
18492 multiple-line editor.
18496 The process of compiling and injecting the code can be inspected using:
18499 @anchor{set debug compile}
18500 @item set debug compile
18501 @cindex compile command debugging info
18502 Turns on or off display of @value{GDBN} process of compiling and
18503 injecting the code. The default is off.
18505 @item show debug compile
18506 Displays the current state of displaying @value{GDBN} process of
18507 compiling and injecting the code.
18510 @subsection Compilation options for the @code{compile} command
18512 @value{GDBN} needs to specify the right compilation options for the code
18513 to be injected, in part to make its ABI compatible with the inferior
18514 and in part to make the injected code compatible with @value{GDBN}'s
18518 The options used, in increasing precedence:
18521 @item target architecture and OS options (@code{gdbarch})
18522 These options depend on target processor type and target operating
18523 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18524 (@code{-m64}) compilation option.
18526 @item compilation options recorded in the target
18527 @value{NGCC} (since version 4.7) stores the options used for compilation
18528 into @code{DW_AT_producer} part of DWARF debugging information according
18529 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18530 explicitly specify @code{-g} during inferior compilation otherwise
18531 @value{NGCC} produces no DWARF. This feature is only relevant for
18532 platforms where @code{-g} produces DWARF by default, otherwise one may
18533 try to enforce DWARF by using @code{-gdwarf-4}.
18535 @item compilation options set by @code{set compile-args}
18539 You can override compilation options using the following command:
18542 @item set compile-args
18543 @cindex compile command options override
18544 Set compilation options used for compiling and injecting code with the
18545 @code{compile} commands. These options override any conflicting ones
18546 from the target architecture and/or options stored during inferior
18549 @item show compile-args
18550 Displays the current state of compilation options override.
18551 This does not show all the options actually used during compilation,
18552 use @ref{set debug compile} for that.
18555 @subsection Caveats when using the @code{compile} command
18557 There are a few caveats to keep in mind when using the @code{compile}
18558 command. As the caveats are different per language, the table below
18559 highlights specific issues on a per language basis.
18562 @item C code examples and caveats
18563 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18564 attempt to compile the source code with a @samp{C} compiler. The source
18565 code provided to the @code{compile} command will have much the same
18566 access to variables and types as it normally would if it were part of
18567 the program currently being debugged in @value{GDBN}.
18569 Below is a sample program that forms the basis of the examples that
18570 follow. This program has been compiled and loaded into @value{GDBN},
18571 much like any other normal debugging session.
18574 void function1 (void)
18577 printf ("function 1\n");
18580 void function2 (void)
18595 For the purposes of the examples in this section, the program above has
18596 been compiled, loaded into @value{GDBN}, stopped at the function
18597 @code{main}, and @value{GDBN} is awaiting input from the user.
18599 To access variables and types for any program in @value{GDBN}, the
18600 program must be compiled and packaged with debug information. The
18601 @code{compile} command is not an exception to this rule. Without debug
18602 information, you can still use the @code{compile} command, but you will
18603 be very limited in what variables and types you can access.
18605 So with that in mind, the example above has been compiled with debug
18606 information enabled. The @code{compile} command will have access to
18607 all variables and types (except those that may have been optimized
18608 out). Currently, as @value{GDBN} has stopped the program in the
18609 @code{main} function, the @code{compile} command would have access to
18610 the variable @code{k}. You could invoke the @code{compile} command
18611 and type some source code to set the value of @code{k}. You can also
18612 read it, or do anything with that variable you would normally do in
18613 @code{C}. Be aware that changes to inferior variables in the
18614 @code{compile} command are persistent. In the following example:
18617 compile code k = 3;
18621 the variable @code{k} is now 3. It will retain that value until
18622 something else in the example program changes it, or another
18623 @code{compile} command changes it.
18625 Normal scope and access rules apply to source code compiled and
18626 injected by the @code{compile} command. In the example, the variables
18627 @code{j} and @code{k} are not accessible yet, because the program is
18628 currently stopped in the @code{main} function, where these variables
18629 are not in scope. Therefore, the following command
18632 compile code j = 3;
18636 will result in a compilation error message.
18638 Once the program is continued, execution will bring these variables in
18639 scope, and they will become accessible; then the code you specify via
18640 the @code{compile} command will be able to access them.
18642 You can create variables and types with the @code{compile} command as
18643 part of your source code. Variables and types that are created as part
18644 of the @code{compile} command are not visible to the rest of the program for
18645 the duration of its run. This example is valid:
18648 compile code int ff = 5; printf ("ff is %d\n", ff);
18651 However, if you were to type the following into @value{GDBN} after that
18652 command has completed:
18655 compile code printf ("ff is %d\n'', ff);
18659 a compiler error would be raised as the variable @code{ff} no longer
18660 exists. Object code generated and injected by the @code{compile}
18661 command is removed when its execution ends. Caution is advised
18662 when assigning to program variables values of variables created by the
18663 code submitted to the @code{compile} command. This example is valid:
18666 compile code int ff = 5; k = ff;
18669 The value of the variable @code{ff} is assigned to @code{k}. The variable
18670 @code{k} does not require the existence of @code{ff} to maintain the value
18671 it has been assigned. However, pointers require particular care in
18672 assignment. If the source code compiled with the @code{compile} command
18673 changed the address of a pointer in the example program, perhaps to a
18674 variable created in the @code{compile} command, that pointer would point
18675 to an invalid location when the command exits. The following example
18676 would likely cause issues with your debugged program:
18679 compile code int ff = 5; p = &ff;
18682 In this example, @code{p} would point to @code{ff} when the
18683 @code{compile} command is executing the source code provided to it.
18684 However, as variables in the (example) program persist with their
18685 assigned values, the variable @code{p} would point to an invalid
18686 location when the command exists. A general rule should be followed
18687 in that you should either assign @code{NULL} to any assigned pointers,
18688 or restore a valid location to the pointer before the command exits.
18690 Similar caution must be exercised with any structs, unions, and typedefs
18691 defined in @code{compile} command. Types defined in the @code{compile}
18692 command will no longer be available in the next @code{compile} command.
18693 Therefore, if you cast a variable to a type defined in the
18694 @code{compile} command, care must be taken to ensure that any future
18695 need to resolve the type can be achieved.
18698 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18699 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18700 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18701 Compilation failed.
18702 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18706 Variables that have been optimized away by the compiler are not
18707 accessible to the code submitted to the @code{compile} command.
18708 Access to those variables will generate a compiler error which @value{GDBN}
18709 will print to the console.
18712 @subsection Compiler search for the @code{compile} command
18714 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18715 which may not be obvious for remote targets of different architecture
18716 than where @value{GDBN} is running. Environment variable @code{PATH} on
18717 @value{GDBN} host is searched for @value{NGCC} binary matching the
18718 target architecture and operating system. This search can be overriden
18719 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18720 taken from shell that executed @value{GDBN}, it is not the value set by
18721 @value{GDBN} command @code{set environment}). @xref{Environment}.
18724 Specifically @code{PATH} is searched for binaries matching regular expression
18725 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18726 debugged. @var{arch} is processor name --- multiarch is supported, so for
18727 example both @code{i386} and @code{x86_64} targets look for pattern
18728 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18729 for pattern @code{s390x?}. @var{os} is currently supported only for
18730 pattern @code{linux(-gnu)?}.
18732 On Posix hosts the compiler driver @value{GDBN} needs to find also
18733 shared library @file{libcc1.so} from the compiler. It is searched in
18734 default shared library search path (overridable with usual environment
18735 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18736 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18737 according to the installation of the found compiler --- as possibly
18738 specified by the @code{set compile-gcc} command.
18741 @item set compile-gcc
18742 @cindex compile command driver filename override
18743 Set compilation command used for compiling and injecting code with the
18744 @code{compile} commands. If this option is not set (it is set to
18745 an empty string), the search described above will occur --- that is the
18748 @item show compile-gcc
18749 Displays the current compile command @value{NGCC} driver filename.
18750 If set, it is the main command @command{gcc}, found usually for example
18751 under name @file{x86_64-linux-gnu-gcc}.
18755 @chapter @value{GDBN} Files
18757 @value{GDBN} needs to know the file name of the program to be debugged,
18758 both in order to read its symbol table and in order to start your
18759 program. To debug a core dump of a previous run, you must also tell
18760 @value{GDBN} the name of the core dump file.
18763 * Files:: Commands to specify files
18764 * File Caching:: Information about @value{GDBN}'s file caching
18765 * Separate Debug Files:: Debugging information in separate files
18766 * MiniDebugInfo:: Debugging information in a special section
18767 * Index Files:: Index files speed up GDB
18768 * Symbol Errors:: Errors reading symbol files
18769 * Data Files:: GDB data files
18773 @section Commands to Specify Files
18775 @cindex symbol table
18776 @cindex core dump file
18778 You may want to specify executable and core dump file names. The usual
18779 way to do this is at start-up time, using the arguments to
18780 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18781 Out of @value{GDBN}}).
18783 Occasionally it is necessary to change to a different file during a
18784 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18785 specify a file you want to use. Or you are debugging a remote target
18786 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18787 Program}). In these situations the @value{GDBN} commands to specify
18788 new files are useful.
18791 @cindex executable file
18793 @item file @var{filename}
18794 Use @var{filename} as the program to be debugged. It is read for its
18795 symbols and for the contents of pure memory. It is also the program
18796 executed when you use the @code{run} command. If you do not specify a
18797 directory and the file is not found in the @value{GDBN} working directory,
18798 @value{GDBN} uses the environment variable @code{PATH} as a list of
18799 directories to search, just as the shell does when looking for a program
18800 to run. You can change the value of this variable, for both @value{GDBN}
18801 and your program, using the @code{path} command.
18803 @cindex unlinked object files
18804 @cindex patching object files
18805 You can load unlinked object @file{.o} files into @value{GDBN} using
18806 the @code{file} command. You will not be able to ``run'' an object
18807 file, but you can disassemble functions and inspect variables. Also,
18808 if the underlying BFD functionality supports it, you could use
18809 @kbd{gdb -write} to patch object files using this technique. Note
18810 that @value{GDBN} can neither interpret nor modify relocations in this
18811 case, so branches and some initialized variables will appear to go to
18812 the wrong place. But this feature is still handy from time to time.
18815 @code{file} with no argument makes @value{GDBN} discard any information it
18816 has on both executable file and the symbol table.
18819 @item exec-file @r{[} @var{filename} @r{]}
18820 Specify that the program to be run (but not the symbol table) is found
18821 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18822 if necessary to locate your program. Omitting @var{filename} means to
18823 discard information on the executable file.
18825 @kindex symbol-file
18826 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
18827 Read symbol table information from file @var{filename}. @code{PATH} is
18828 searched when necessary. Use the @code{file} command to get both symbol
18829 table and program to run from the same file.
18831 If an optional @var{offset} is specified, it is added to the start
18832 address of each section in the symbol file. This is useful if the
18833 program is relocated at runtime, such as the Linux kernel with kASLR
18836 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18837 program's symbol table.
18839 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18840 some breakpoints and auto-display expressions. This is because they may
18841 contain pointers to the internal data recording symbols and data types,
18842 which are part of the old symbol table data being discarded inside
18845 @code{symbol-file} does not repeat if you press @key{RET} again after
18848 When @value{GDBN} is configured for a particular environment, it
18849 understands debugging information in whatever format is the standard
18850 generated for that environment; you may use either a @sc{gnu} compiler, or
18851 other compilers that adhere to the local conventions.
18852 Best results are usually obtained from @sc{gnu} compilers; for example,
18853 using @code{@value{NGCC}} you can generate debugging information for
18856 For most kinds of object files, with the exception of old SVR3 systems
18857 using COFF, the @code{symbol-file} command does not normally read the
18858 symbol table in full right away. Instead, it scans the symbol table
18859 quickly to find which source files and which symbols are present. The
18860 details are read later, one source file at a time, as they are needed.
18862 The purpose of this two-stage reading strategy is to make @value{GDBN}
18863 start up faster. For the most part, it is invisible except for
18864 occasional pauses while the symbol table details for a particular source
18865 file are being read. (The @code{set verbose} command can turn these
18866 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18867 Warnings and Messages}.)
18869 We have not implemented the two-stage strategy for COFF yet. When the
18870 symbol table is stored in COFF format, @code{symbol-file} reads the
18871 symbol table data in full right away. Note that ``stabs-in-COFF''
18872 still does the two-stage strategy, since the debug info is actually
18876 @cindex reading symbols immediately
18877 @cindex symbols, reading immediately
18878 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18879 @itemx file @r{[} -readnow @r{]} @var{filename}
18880 You can override the @value{GDBN} two-stage strategy for reading symbol
18881 tables by using the @samp{-readnow} option with any of the commands that
18882 load symbol table information, if you want to be sure @value{GDBN} has the
18883 entire symbol table available.
18885 @cindex @code{-readnever}, option for symbol-file command
18886 @cindex never read symbols
18887 @cindex symbols, never read
18888 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18889 @itemx file @r{[} -readnever @r{]} @var{filename}
18890 You can instruct @value{GDBN} to never read the symbolic information
18891 contained in @var{filename} by using the @samp{-readnever} option.
18892 @xref{--readnever}.
18894 @c FIXME: for now no mention of directories, since this seems to be in
18895 @c flux. 13mar1992 status is that in theory GDB would look either in
18896 @c current dir or in same dir as myprog; but issues like competing
18897 @c GDB's, or clutter in system dirs, mean that in practice right now
18898 @c only current dir is used. FFish says maybe a special GDB hierarchy
18899 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18903 @item core-file @r{[}@var{filename}@r{]}
18905 Specify the whereabouts of a core dump file to be used as the ``contents
18906 of memory''. Traditionally, core files contain only some parts of the
18907 address space of the process that generated them; @value{GDBN} can access the
18908 executable file itself for other parts.
18910 @code{core-file} with no argument specifies that no core file is
18913 Note that the core file is ignored when your program is actually running
18914 under @value{GDBN}. So, if you have been running your program and you
18915 wish to debug a core file instead, you must kill the subprocess in which
18916 the program is running. To do this, use the @code{kill} command
18917 (@pxref{Kill Process, ,Killing the Child Process}).
18919 @kindex add-symbol-file
18920 @cindex dynamic linking
18921 @item add-symbol-file @var{filename} @r{[} -readnow @r{|} -readnever @r{]} @r{[} -o @var{offset} @r{]} @r{[} @var{textaddress} @r{]} @r{[} -s @var{section} @var{address} @dots{} @r{]}
18922 The @code{add-symbol-file} command reads additional symbol table
18923 information from the file @var{filename}. You would use this command
18924 when @var{filename} has been dynamically loaded (by some other means)
18925 into the program that is running. The @var{textaddress} parameter gives
18926 the memory address at which the file's text section has been loaded.
18927 You can additionally specify the base address of other sections using
18928 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
18929 If a section is omitted, @value{GDBN} will use its default addresses
18930 as found in @var{filename}. Any @var{address} or @var{textaddress}
18931 can be given as an expression.
18933 If an optional @var{offset} is specified, it is added to the start
18934 address of each section, except those for which the address was
18935 specified explicitly.
18937 The symbol table of the file @var{filename} is added to the symbol table
18938 originally read with the @code{symbol-file} command. You can use the
18939 @code{add-symbol-file} command any number of times; the new symbol data
18940 thus read is kept in addition to the old.
18942 Changes can be reverted using the command @code{remove-symbol-file}.
18944 @cindex relocatable object files, reading symbols from
18945 @cindex object files, relocatable, reading symbols from
18946 @cindex reading symbols from relocatable object files
18947 @cindex symbols, reading from relocatable object files
18948 @cindex @file{.o} files, reading symbols from
18949 Although @var{filename} is typically a shared library file, an
18950 executable file, or some other object file which has been fully
18951 relocated for loading into a process, you can also load symbolic
18952 information from relocatable @file{.o} files, as long as:
18956 the file's symbolic information refers only to linker symbols defined in
18957 that file, not to symbols defined by other object files,
18959 every section the file's symbolic information refers to has actually
18960 been loaded into the inferior, as it appears in the file, and
18962 you can determine the address at which every section was loaded, and
18963 provide these to the @code{add-symbol-file} command.
18967 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18968 relocatable files into an already running program; such systems
18969 typically make the requirements above easy to meet. However, it's
18970 important to recognize that many native systems use complex link
18971 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18972 assembly, for example) that make the requirements difficult to meet. In
18973 general, one cannot assume that using @code{add-symbol-file} to read a
18974 relocatable object file's symbolic information will have the same effect
18975 as linking the relocatable object file into the program in the normal
18978 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18980 @kindex remove-symbol-file
18981 @item remove-symbol-file @var{filename}
18982 @item remove-symbol-file -a @var{address}
18983 Remove a symbol file added via the @code{add-symbol-file} command. The
18984 file to remove can be identified by its @var{filename} or by an @var{address}
18985 that lies within the boundaries of this symbol file in memory. Example:
18988 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18989 add symbol table from file "/home/user/gdb/mylib.so" at
18990 .text_addr = 0x7ffff7ff9480
18992 Reading symbols from /home/user/gdb/mylib.so...done.
18993 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18994 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18999 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19001 @kindex add-symbol-file-from-memory
19002 @cindex @code{syscall DSO}
19003 @cindex load symbols from memory
19004 @item add-symbol-file-from-memory @var{address}
19005 Load symbols from the given @var{address} in a dynamically loaded
19006 object file whose image is mapped directly into the inferior's memory.
19007 For example, the Linux kernel maps a @code{syscall DSO} into each
19008 process's address space; this DSO provides kernel-specific code for
19009 some system calls. The argument can be any expression whose
19010 evaluation yields the address of the file's shared object file header.
19011 For this command to work, you must have used @code{symbol-file} or
19012 @code{exec-file} commands in advance.
19015 @item section @var{section} @var{addr}
19016 The @code{section} command changes the base address of the named
19017 @var{section} of the exec file to @var{addr}. This can be used if the
19018 exec file does not contain section addresses, (such as in the
19019 @code{a.out} format), or when the addresses specified in the file
19020 itself are wrong. Each section must be changed separately. The
19021 @code{info files} command, described below, lists all the sections and
19025 @kindex info target
19028 @code{info files} and @code{info target} are synonymous; both print the
19029 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19030 including the names of the executable and core dump files currently in
19031 use by @value{GDBN}, and the files from which symbols were loaded. The
19032 command @code{help target} lists all possible targets rather than
19035 @kindex maint info sections
19036 @item maint info sections
19037 Another command that can give you extra information about program sections
19038 is @code{maint info sections}. In addition to the section information
19039 displayed by @code{info files}, this command displays the flags and file
19040 offset of each section in the executable and core dump files. In addition,
19041 @code{maint info sections} provides the following command options (which
19042 may be arbitrarily combined):
19046 Display sections for all loaded object files, including shared libraries.
19047 @item @var{sections}
19048 Display info only for named @var{sections}.
19049 @item @var{section-flags}
19050 Display info only for sections for which @var{section-flags} are true.
19051 The section flags that @value{GDBN} currently knows about are:
19054 Section will have space allocated in the process when loaded.
19055 Set for all sections except those containing debug information.
19057 Section will be loaded from the file into the child process memory.
19058 Set for pre-initialized code and data, clear for @code{.bss} sections.
19060 Section needs to be relocated before loading.
19062 Section cannot be modified by the child process.
19064 Section contains executable code only.
19066 Section contains data only (no executable code).
19068 Section will reside in ROM.
19070 Section contains data for constructor/destructor lists.
19072 Section is not empty.
19074 An instruction to the linker to not output the section.
19075 @item COFF_SHARED_LIBRARY
19076 A notification to the linker that the section contains
19077 COFF shared library information.
19079 Section contains common symbols.
19082 @kindex set trust-readonly-sections
19083 @cindex read-only sections
19084 @item set trust-readonly-sections on
19085 Tell @value{GDBN} that readonly sections in your object file
19086 really are read-only (i.e.@: that their contents will not change).
19087 In that case, @value{GDBN} can fetch values from these sections
19088 out of the object file, rather than from the target program.
19089 For some targets (notably embedded ones), this can be a significant
19090 enhancement to debugging performance.
19092 The default is off.
19094 @item set trust-readonly-sections off
19095 Tell @value{GDBN} not to trust readonly sections. This means that
19096 the contents of the section might change while the program is running,
19097 and must therefore be fetched from the target when needed.
19099 @item show trust-readonly-sections
19100 Show the current setting of trusting readonly sections.
19103 All file-specifying commands allow both absolute and relative file names
19104 as arguments. @value{GDBN} always converts the file name to an absolute file
19105 name and remembers it that way.
19107 @cindex shared libraries
19108 @anchor{Shared Libraries}
19109 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19110 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19111 DSBT (TIC6X) shared libraries.
19113 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19114 shared libraries. @xref{Expat}.
19116 @value{GDBN} automatically loads symbol definitions from shared libraries
19117 when you use the @code{run} command, or when you examine a core file.
19118 (Before you issue the @code{run} command, @value{GDBN} does not understand
19119 references to a function in a shared library, however---unless you are
19120 debugging a core file).
19122 @c FIXME: some @value{GDBN} release may permit some refs to undef
19123 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19124 @c FIXME...lib; check this from time to time when updating manual
19126 There are times, however, when you may wish to not automatically load
19127 symbol definitions from shared libraries, such as when they are
19128 particularly large or there are many of them.
19130 To control the automatic loading of shared library symbols, use the
19134 @kindex set auto-solib-add
19135 @item set auto-solib-add @var{mode}
19136 If @var{mode} is @code{on}, symbols from all shared object libraries
19137 will be loaded automatically when the inferior begins execution, you
19138 attach to an independently started inferior, or when the dynamic linker
19139 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19140 is @code{off}, symbols must be loaded manually, using the
19141 @code{sharedlibrary} command. The default value is @code{on}.
19143 @cindex memory used for symbol tables
19144 If your program uses lots of shared libraries with debug info that
19145 takes large amounts of memory, you can decrease the @value{GDBN}
19146 memory footprint by preventing it from automatically loading the
19147 symbols from shared libraries. To that end, type @kbd{set
19148 auto-solib-add off} before running the inferior, then load each
19149 library whose debug symbols you do need with @kbd{sharedlibrary
19150 @var{regexp}}, where @var{regexp} is a regular expression that matches
19151 the libraries whose symbols you want to be loaded.
19153 @kindex show auto-solib-add
19154 @item show auto-solib-add
19155 Display the current autoloading mode.
19158 @cindex load shared library
19159 To explicitly load shared library symbols, use the @code{sharedlibrary}
19163 @kindex info sharedlibrary
19165 @item info share @var{regex}
19166 @itemx info sharedlibrary @var{regex}
19167 Print the names of the shared libraries which are currently loaded
19168 that match @var{regex}. If @var{regex} is omitted then print
19169 all shared libraries that are loaded.
19172 @item info dll @var{regex}
19173 This is an alias of @code{info sharedlibrary}.
19175 @kindex sharedlibrary
19177 @item sharedlibrary @var{regex}
19178 @itemx share @var{regex}
19179 Load shared object library symbols for files matching a
19180 Unix regular expression.
19181 As with files loaded automatically, it only loads shared libraries
19182 required by your program for a core file or after typing @code{run}. If
19183 @var{regex} is omitted all shared libraries required by your program are
19186 @item nosharedlibrary
19187 @kindex nosharedlibrary
19188 @cindex unload symbols from shared libraries
19189 Unload all shared object library symbols. This discards all symbols
19190 that have been loaded from all shared libraries. Symbols from shared
19191 libraries that were loaded by explicit user requests are not
19195 Sometimes you may wish that @value{GDBN} stops and gives you control
19196 when any of shared library events happen. The best way to do this is
19197 to use @code{catch load} and @code{catch unload} (@pxref{Set
19200 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19201 command for this. This command exists for historical reasons. It is
19202 less useful than setting a catchpoint, because it does not allow for
19203 conditions or commands as a catchpoint does.
19206 @item set stop-on-solib-events
19207 @kindex set stop-on-solib-events
19208 This command controls whether @value{GDBN} should give you control
19209 when the dynamic linker notifies it about some shared library event.
19210 The most common event of interest is loading or unloading of a new
19213 @item show stop-on-solib-events
19214 @kindex show stop-on-solib-events
19215 Show whether @value{GDBN} stops and gives you control when shared
19216 library events happen.
19219 Shared libraries are also supported in many cross or remote debugging
19220 configurations. @value{GDBN} needs to have access to the target's libraries;
19221 this can be accomplished either by providing copies of the libraries
19222 on the host system, or by asking @value{GDBN} to automatically retrieve the
19223 libraries from the target. If copies of the target libraries are
19224 provided, they need to be the same as the target libraries, although the
19225 copies on the target can be stripped as long as the copies on the host are
19228 @cindex where to look for shared libraries
19229 For remote debugging, you need to tell @value{GDBN} where the target
19230 libraries are, so that it can load the correct copies---otherwise, it
19231 may try to load the host's libraries. @value{GDBN} has two variables
19232 to specify the search directories for target libraries.
19235 @cindex prefix for executable and shared library file names
19236 @cindex system root, alternate
19237 @kindex set solib-absolute-prefix
19238 @kindex set sysroot
19239 @item set sysroot @var{path}
19240 Use @var{path} as the system root for the program being debugged. Any
19241 absolute shared library paths will be prefixed with @var{path}; many
19242 runtime loaders store the absolute paths to the shared library in the
19243 target program's memory. When starting processes remotely, and when
19244 attaching to already-running processes (local or remote), their
19245 executable filenames will be prefixed with @var{path} if reported to
19246 @value{GDBN} as absolute by the operating system. If you use
19247 @code{set sysroot} to find executables and shared libraries, they need
19248 to be laid out in the same way that they are on the target, with
19249 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19252 If @var{path} starts with the sequence @file{target:} and the target
19253 system is remote then @value{GDBN} will retrieve the target binaries
19254 from the remote system. This is only supported when using a remote
19255 target that supports the @code{remote get} command (@pxref{File
19256 Transfer,,Sending files to a remote system}). The part of @var{path}
19257 following the initial @file{target:} (if present) is used as system
19258 root prefix on the remote file system. If @var{path} starts with the
19259 sequence @file{remote:} this is converted to the sequence
19260 @file{target:} by @code{set sysroot}@footnote{Historically the
19261 functionality to retrieve binaries from the remote system was
19262 provided by prefixing @var{path} with @file{remote:}}. If you want
19263 to specify a local system root using a directory that happens to be
19264 named @file{target:} or @file{remote:}, you need to use some
19265 equivalent variant of the name like @file{./target:}.
19267 For targets with an MS-DOS based filesystem, such as MS-Windows and
19268 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19269 absolute file name with @var{path}. But first, on Unix hosts,
19270 @value{GDBN} converts all backslash directory separators into forward
19271 slashes, because the backslash is not a directory separator on Unix:
19274 c:\foo\bar.dll @result{} c:/foo/bar.dll
19277 Then, @value{GDBN} attempts prefixing the target file name with
19278 @var{path}, and looks for the resulting file name in the host file
19282 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19285 If that does not find the binary, @value{GDBN} tries removing
19286 the @samp{:} character from the drive spec, both for convenience, and,
19287 for the case of the host file system not supporting file names with
19291 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19294 This makes it possible to have a system root that mirrors a target
19295 with more than one drive. E.g., you may want to setup your local
19296 copies of the target system shared libraries like so (note @samp{c} vs
19300 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19301 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19302 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19306 and point the system root at @file{/path/to/sysroot}, so that
19307 @value{GDBN} can find the correct copies of both
19308 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19310 If that still does not find the binary, @value{GDBN} tries
19311 removing the whole drive spec from the target file name:
19314 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19317 This last lookup makes it possible to not care about the drive name,
19318 if you don't want or need to.
19320 The @code{set solib-absolute-prefix} command is an alias for @code{set
19323 @cindex default system root
19324 @cindex @samp{--with-sysroot}
19325 You can set the default system root by using the configure-time
19326 @samp{--with-sysroot} option. If the system root is inside
19327 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19328 @samp{--exec-prefix}), then the default system root will be updated
19329 automatically if the installed @value{GDBN} is moved to a new
19332 @kindex show sysroot
19334 Display the current executable and shared library prefix.
19336 @kindex set solib-search-path
19337 @item set solib-search-path @var{path}
19338 If this variable is set, @var{path} is a colon-separated list of
19339 directories to search for shared libraries. @samp{solib-search-path}
19340 is used after @samp{sysroot} fails to locate the library, or if the
19341 path to the library is relative instead of absolute. If you want to
19342 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19343 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19344 finding your host's libraries. @samp{sysroot} is preferred; setting
19345 it to a nonexistent directory may interfere with automatic loading
19346 of shared library symbols.
19348 @kindex show solib-search-path
19349 @item show solib-search-path
19350 Display the current shared library search path.
19352 @cindex DOS file-name semantics of file names.
19353 @kindex set target-file-system-kind (unix|dos-based|auto)
19354 @kindex show target-file-system-kind
19355 @item set target-file-system-kind @var{kind}
19356 Set assumed file system kind for target reported file names.
19358 Shared library file names as reported by the target system may not
19359 make sense as is on the system @value{GDBN} is running on. For
19360 example, when remote debugging a target that has MS-DOS based file
19361 system semantics, from a Unix host, the target may be reporting to
19362 @value{GDBN} a list of loaded shared libraries with file names such as
19363 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19364 drive letters, so the @samp{c:\} prefix is not normally understood as
19365 indicating an absolute file name, and neither is the backslash
19366 normally considered a directory separator character. In that case,
19367 the native file system would interpret this whole absolute file name
19368 as a relative file name with no directory components. This would make
19369 it impossible to point @value{GDBN} at a copy of the remote target's
19370 shared libraries on the host using @code{set sysroot}, and impractical
19371 with @code{set solib-search-path}. Setting
19372 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19373 to interpret such file names similarly to how the target would, and to
19374 map them to file names valid on @value{GDBN}'s native file system
19375 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19376 to one of the supported file system kinds. In that case, @value{GDBN}
19377 tries to determine the appropriate file system variant based on the
19378 current target's operating system (@pxref{ABI, ,Configuring the
19379 Current ABI}). The supported file system settings are:
19383 Instruct @value{GDBN} to assume the target file system is of Unix
19384 kind. Only file names starting the forward slash (@samp{/}) character
19385 are considered absolute, and the directory separator character is also
19389 Instruct @value{GDBN} to assume the target file system is DOS based.
19390 File names starting with either a forward slash, or a drive letter
19391 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19392 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19393 considered directory separators.
19396 Instruct @value{GDBN} to use the file system kind associated with the
19397 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19398 This is the default.
19402 @cindex file name canonicalization
19403 @cindex base name differences
19404 When processing file names provided by the user, @value{GDBN}
19405 frequently needs to compare them to the file names recorded in the
19406 program's debug info. Normally, @value{GDBN} compares just the
19407 @dfn{base names} of the files as strings, which is reasonably fast
19408 even for very large programs. (The base name of a file is the last
19409 portion of its name, after stripping all the leading directories.)
19410 This shortcut in comparison is based upon the assumption that files
19411 cannot have more than one base name. This is usually true, but
19412 references to files that use symlinks or similar filesystem
19413 facilities violate that assumption. If your program records files
19414 using such facilities, or if you provide file names to @value{GDBN}
19415 using symlinks etc., you can set @code{basenames-may-differ} to
19416 @code{true} to instruct @value{GDBN} to completely canonicalize each
19417 pair of file names it needs to compare. This will make file-name
19418 comparisons accurate, but at a price of a significant slowdown.
19421 @item set basenames-may-differ
19422 @kindex set basenames-may-differ
19423 Set whether a source file may have multiple base names.
19425 @item show basenames-may-differ
19426 @kindex show basenames-may-differ
19427 Show whether a source file may have multiple base names.
19431 @section File Caching
19432 @cindex caching of opened files
19433 @cindex caching of bfd objects
19435 To speed up file loading, and reduce memory usage, @value{GDBN} will
19436 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19437 BFD, bfd, The Binary File Descriptor Library}. The following commands
19438 allow visibility and control of the caching behavior.
19441 @kindex maint info bfds
19442 @item maint info bfds
19443 This prints information about each @code{bfd} object that is known to
19446 @kindex maint set bfd-sharing
19447 @kindex maint show bfd-sharing
19448 @kindex bfd caching
19449 @item maint set bfd-sharing
19450 @item maint show bfd-sharing
19451 Control whether @code{bfd} objects can be shared. When sharing is
19452 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19453 than reopening the same file. Turning sharing off does not cause
19454 already shared @code{bfd} objects to be unshared, but all future files
19455 that are opened will create a new @code{bfd} object. Similarly,
19456 re-enabling sharing does not cause multiple existing @code{bfd}
19457 objects to be collapsed into a single shared @code{bfd} object.
19459 @kindex set debug bfd-cache @var{level}
19460 @kindex bfd caching
19461 @item set debug bfd-cache @var{level}
19462 Turns on debugging of the bfd cache, setting the level to @var{level}.
19464 @kindex show debug bfd-cache
19465 @kindex bfd caching
19466 @item show debug bfd-cache
19467 Show the current debugging level of the bfd cache.
19470 @node Separate Debug Files
19471 @section Debugging Information in Separate Files
19472 @cindex separate debugging information files
19473 @cindex debugging information in separate files
19474 @cindex @file{.debug} subdirectories
19475 @cindex debugging information directory, global
19476 @cindex global debugging information directories
19477 @cindex build ID, and separate debugging files
19478 @cindex @file{.build-id} directory
19480 @value{GDBN} allows you to put a program's debugging information in a
19481 file separate from the executable itself, in a way that allows
19482 @value{GDBN} to find and load the debugging information automatically.
19483 Since debugging information can be very large---sometimes larger
19484 than the executable code itself---some systems distribute debugging
19485 information for their executables in separate files, which users can
19486 install only when they need to debug a problem.
19488 @value{GDBN} supports two ways of specifying the separate debug info
19493 The executable contains a @dfn{debug link} that specifies the name of
19494 the separate debug info file. The separate debug file's name is
19495 usually @file{@var{executable}.debug}, where @var{executable} is the
19496 name of the corresponding executable file without leading directories
19497 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19498 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19499 checksum for the debug file, which @value{GDBN} uses to validate that
19500 the executable and the debug file came from the same build.
19503 The executable contains a @dfn{build ID}, a unique bit string that is
19504 also present in the corresponding debug info file. (This is supported
19505 only on some operating systems, when using the ELF or PE file formats
19506 for binary files and the @sc{gnu} Binutils.) For more details about
19507 this feature, see the description of the @option{--build-id}
19508 command-line option in @ref{Options, , Command Line Options, ld.info,
19509 The GNU Linker}. The debug info file's name is not specified
19510 explicitly by the build ID, but can be computed from the build ID, see
19514 Depending on the way the debug info file is specified, @value{GDBN}
19515 uses two different methods of looking for the debug file:
19519 For the ``debug link'' method, @value{GDBN} looks up the named file in
19520 the directory of the executable file, then in a subdirectory of that
19521 directory named @file{.debug}, and finally under each one of the global debug
19522 directories, in a subdirectory whose name is identical to the leading
19523 directories of the executable's absolute file name.
19526 For the ``build ID'' method, @value{GDBN} looks in the
19527 @file{.build-id} subdirectory of each one of the global debug directories for
19528 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19529 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19530 are the rest of the bit string. (Real build ID strings are 32 or more
19531 hex characters, not 10.)
19534 So, for example, suppose you ask @value{GDBN} to debug
19535 @file{/usr/bin/ls}, which has a debug link that specifies the
19536 file @file{ls.debug}, and a build ID whose value in hex is
19537 @code{abcdef1234}. If the list of the global debug directories includes
19538 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19539 debug information files, in the indicated order:
19543 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19545 @file{/usr/bin/ls.debug}
19547 @file{/usr/bin/.debug/ls.debug}
19549 @file{/usr/lib/debug/usr/bin/ls.debug}.
19552 @anchor{debug-file-directory}
19553 Global debugging info directories default to what is set by @value{GDBN}
19554 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19555 you can also set the global debugging info directories, and view the list
19556 @value{GDBN} is currently using.
19560 @kindex set debug-file-directory
19561 @item set debug-file-directory @var{directories}
19562 Set the directories which @value{GDBN} searches for separate debugging
19563 information files to @var{directory}. Multiple path components can be set
19564 concatenating them by a path separator.
19566 @kindex show debug-file-directory
19567 @item show debug-file-directory
19568 Show the directories @value{GDBN} searches for separate debugging
19573 @cindex @code{.gnu_debuglink} sections
19574 @cindex debug link sections
19575 A debug link is a special section of the executable file named
19576 @code{.gnu_debuglink}. The section must contain:
19580 A filename, with any leading directory components removed, followed by
19583 zero to three bytes of padding, as needed to reach the next four-byte
19584 boundary within the section, and
19586 a four-byte CRC checksum, stored in the same endianness used for the
19587 executable file itself. The checksum is computed on the debugging
19588 information file's full contents by the function given below, passing
19589 zero as the @var{crc} argument.
19592 Any executable file format can carry a debug link, as long as it can
19593 contain a section named @code{.gnu_debuglink} with the contents
19596 @cindex @code{.note.gnu.build-id} sections
19597 @cindex build ID sections
19598 The build ID is a special section in the executable file (and in other
19599 ELF binary files that @value{GDBN} may consider). This section is
19600 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19601 It contains unique identification for the built files---the ID remains
19602 the same across multiple builds of the same build tree. The default
19603 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19604 content for the build ID string. The same section with an identical
19605 value is present in the original built binary with symbols, in its
19606 stripped variant, and in the separate debugging information file.
19608 The debugging information file itself should be an ordinary
19609 executable, containing a full set of linker symbols, sections, and
19610 debugging information. The sections of the debugging information file
19611 should have the same names, addresses, and sizes as the original file,
19612 but they need not contain any data---much like a @code{.bss} section
19613 in an ordinary executable.
19615 The @sc{gnu} binary utilities (Binutils) package includes the
19616 @samp{objcopy} utility that can produce
19617 the separated executable / debugging information file pairs using the
19618 following commands:
19621 @kbd{objcopy --only-keep-debug foo foo.debug}
19626 These commands remove the debugging
19627 information from the executable file @file{foo} and place it in the file
19628 @file{foo.debug}. You can use the first, second or both methods to link the
19633 The debug link method needs the following additional command to also leave
19634 behind a debug link in @file{foo}:
19637 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19640 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19641 a version of the @code{strip} command such that the command @kbd{strip foo -f
19642 foo.debug} has the same functionality as the two @code{objcopy} commands and
19643 the @code{ln -s} command above, together.
19646 Build ID gets embedded into the main executable using @code{ld --build-id} or
19647 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19648 compatibility fixes for debug files separation are present in @sc{gnu} binary
19649 utilities (Binutils) package since version 2.18.
19654 @cindex CRC algorithm definition
19655 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19656 IEEE 802.3 using the polynomial:
19658 @c TexInfo requires naked braces for multi-digit exponents for Tex
19659 @c output, but this causes HTML output to barf. HTML has to be set using
19660 @c raw commands. So we end up having to specify this equation in 2
19665 <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>
19666 + <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
19672 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19673 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19677 The function is computed byte at a time, taking the least
19678 significant bit of each byte first. The initial pattern
19679 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19680 the final result is inverted to ensure trailing zeros also affect the
19683 @emph{Note:} This is the same CRC polynomial as used in handling the
19684 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19685 However in the case of the Remote Serial Protocol, the CRC is computed
19686 @emph{most} significant bit first, and the result is not inverted, so
19687 trailing zeros have no effect on the CRC value.
19689 To complete the description, we show below the code of the function
19690 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19691 initially supplied @code{crc} argument means that an initial call to
19692 this function passing in zero will start computing the CRC using
19695 @kindex gnu_debuglink_crc32
19698 gnu_debuglink_crc32 (unsigned long crc,
19699 unsigned char *buf, size_t len)
19701 static const unsigned long crc32_table[256] =
19703 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19704 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19705 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19706 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19707 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19708 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19709 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19710 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19711 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19712 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19713 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19714 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19715 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19716 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19717 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19718 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19719 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19720 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19721 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19722 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19723 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19724 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19725 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19726 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19727 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19728 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19729 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19730 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19731 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19732 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19733 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19734 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19735 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19736 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19737 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19738 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19739 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19740 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19741 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19742 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19743 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19744 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19745 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19746 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19747 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19748 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19749 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19750 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19751 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19752 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19753 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19756 unsigned char *end;
19758 crc = ~crc & 0xffffffff;
19759 for (end = buf + len; buf < end; ++buf)
19760 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19761 return ~crc & 0xffffffff;
19766 This computation does not apply to the ``build ID'' method.
19768 @node MiniDebugInfo
19769 @section Debugging information in a special section
19770 @cindex separate debug sections
19771 @cindex @samp{.gnu_debugdata} section
19773 Some systems ship pre-built executables and libraries that have a
19774 special @samp{.gnu_debugdata} section. This feature is called
19775 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19776 is used to supply extra symbols for backtraces.
19778 The intent of this section is to provide extra minimal debugging
19779 information for use in simple backtraces. It is not intended to be a
19780 replacement for full separate debugging information (@pxref{Separate
19781 Debug Files}). The example below shows the intended use; however,
19782 @value{GDBN} does not currently put restrictions on what sort of
19783 debugging information might be included in the section.
19785 @value{GDBN} has support for this extension. If the section exists,
19786 then it is used provided that no other source of debugging information
19787 can be found, and that @value{GDBN} was configured with LZMA support.
19789 This section can be easily created using @command{objcopy} and other
19790 standard utilities:
19793 # Extract the dynamic symbols from the main binary, there is no need
19794 # to also have these in the normal symbol table.
19795 nm -D @var{binary} --format=posix --defined-only \
19796 | awk '@{ print $1 @}' | sort > dynsyms
19798 # Extract all the text (i.e. function) symbols from the debuginfo.
19799 # (Note that we actually also accept "D" symbols, for the benefit
19800 # of platforms like PowerPC64 that use function descriptors.)
19801 nm @var{binary} --format=posix --defined-only \
19802 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19805 # Keep all the function symbols not already in the dynamic symbol
19807 comm -13 dynsyms funcsyms > keep_symbols
19809 # Separate full debug info into debug binary.
19810 objcopy --only-keep-debug @var{binary} debug
19812 # Copy the full debuginfo, keeping only a minimal set of symbols and
19813 # removing some unnecessary sections.
19814 objcopy -S --remove-section .gdb_index --remove-section .comment \
19815 --keep-symbols=keep_symbols debug mini_debuginfo
19817 # Drop the full debug info from the original binary.
19818 strip --strip-all -R .comment @var{binary}
19820 # Inject the compressed data into the .gnu_debugdata section of the
19823 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19827 @section Index Files Speed Up @value{GDBN}
19828 @cindex index files
19829 @cindex @samp{.gdb_index} section
19831 When @value{GDBN} finds a symbol file, it scans the symbols in the
19832 file in order to construct an internal symbol table. This lets most
19833 @value{GDBN} operations work quickly---at the cost of a delay early
19834 on. For large programs, this delay can be quite lengthy, so
19835 @value{GDBN} provides a way to build an index, which speeds up
19838 For convenience, @value{GDBN} comes with a program,
19839 @command{gdb-add-index}, which can be used to add the index to a
19840 symbol file. It takes the symbol file as its only argument:
19843 $ gdb-add-index symfile
19846 @xref{gdb-add-index}.
19848 It is also possible to do the work manually. Here is what
19849 @command{gdb-add-index} does behind the curtains.
19851 The index is stored as a section in the symbol file. @value{GDBN} can
19852 write the index to a file, then you can put it into the symbol file
19853 using @command{objcopy}.
19855 To create an index file, use the @code{save gdb-index} command:
19858 @item save gdb-index [-dwarf-5] @var{directory}
19859 @kindex save gdb-index
19860 Create index files for all symbol files currently known by
19861 @value{GDBN}. For each known @var{symbol-file}, this command by
19862 default creates it produces a single file
19863 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19864 the @option{-dwarf-5} option, it produces 2 files:
19865 @file{@var{symbol-file}.debug_names} and
19866 @file{@var{symbol-file}.debug_str}. The files are created in the
19867 given @var{directory}.
19870 Once you have created an index file you can merge it into your symbol
19871 file, here named @file{symfile}, using @command{objcopy}:
19874 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19875 --set-section-flags .gdb_index=readonly symfile symfile
19878 Or for @code{-dwarf-5}:
19881 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19882 $ cat symfile.debug_str >>symfile.debug_str.new
19883 $ objcopy --add-section .debug_names=symfile.gdb-index \
19884 --set-section-flags .debug_names=readonly \
19885 --update-section .debug_str=symfile.debug_str.new symfile symfile
19888 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19889 sections that have been deprecated. Usually they are deprecated because
19890 they are missing a new feature or have performance issues.
19891 To tell @value{GDBN} to use a deprecated index section anyway
19892 specify @code{set use-deprecated-index-sections on}.
19893 The default is @code{off}.
19894 This can speed up startup, but may result in some functionality being lost.
19895 @xref{Index Section Format}.
19897 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19898 must be done before gdb reads the file. The following will not work:
19901 $ gdb -ex "set use-deprecated-index-sections on" <program>
19904 Instead you must do, for example,
19907 $ gdb -iex "set use-deprecated-index-sections on" <program>
19910 There are currently some limitation on indices. They only work when
19911 for DWARF debugging information, not stabs. And, they do not
19912 currently work for programs using Ada.
19914 @node Symbol Errors
19915 @section Errors Reading Symbol Files
19917 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19918 such as symbol types it does not recognize, or known bugs in compiler
19919 output. By default, @value{GDBN} does not notify you of such problems, since
19920 they are relatively common and primarily of interest to people
19921 debugging compilers. If you are interested in seeing information
19922 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19923 only one message about each such type of problem, no matter how many
19924 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19925 to see how many times the problems occur, with the @code{set
19926 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19929 The messages currently printed, and their meanings, include:
19932 @item inner block not inside outer block in @var{symbol}
19934 The symbol information shows where symbol scopes begin and end
19935 (such as at the start of a function or a block of statements). This
19936 error indicates that an inner scope block is not fully contained
19937 in its outer scope blocks.
19939 @value{GDBN} circumvents the problem by treating the inner block as if it had
19940 the same scope as the outer block. In the error message, @var{symbol}
19941 may be shown as ``@code{(don't know)}'' if the outer block is not a
19944 @item block at @var{address} out of order
19946 The symbol information for symbol scope blocks should occur in
19947 order of increasing addresses. This error indicates that it does not
19950 @value{GDBN} does not circumvent this problem, and has trouble
19951 locating symbols in the source file whose symbols it is reading. (You
19952 can often determine what source file is affected by specifying
19953 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19956 @item bad block start address patched
19958 The symbol information for a symbol scope block has a start address
19959 smaller than the address of the preceding source line. This is known
19960 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19962 @value{GDBN} circumvents the problem by treating the symbol scope block as
19963 starting on the previous source line.
19965 @item bad string table offset in symbol @var{n}
19968 Symbol number @var{n} contains a pointer into the string table which is
19969 larger than the size of the string table.
19971 @value{GDBN} circumvents the problem by considering the symbol to have the
19972 name @code{foo}, which may cause other problems if many symbols end up
19975 @item unknown symbol type @code{0x@var{nn}}
19977 The symbol information contains new data types that @value{GDBN} does
19978 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19979 uncomprehended information, in hexadecimal.
19981 @value{GDBN} circumvents the error by ignoring this symbol information.
19982 This usually allows you to debug your program, though certain symbols
19983 are not accessible. If you encounter such a problem and feel like
19984 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19985 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19986 and examine @code{*bufp} to see the symbol.
19988 @item stub type has NULL name
19990 @value{GDBN} could not find the full definition for a struct or class.
19992 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19993 The symbol information for a C@t{++} member function is missing some
19994 information that recent versions of the compiler should have output for
19997 @item info mismatch between compiler and debugger
19999 @value{GDBN} could not parse a type specification output by the compiler.
20004 @section GDB Data Files
20006 @cindex prefix for data files
20007 @value{GDBN} will sometimes read an auxiliary data file. These files
20008 are kept in a directory known as the @dfn{data directory}.
20010 You can set the data directory's name, and view the name @value{GDBN}
20011 is currently using.
20014 @kindex set data-directory
20015 @item set data-directory @var{directory}
20016 Set the directory which @value{GDBN} searches for auxiliary data files
20017 to @var{directory}.
20019 @kindex show data-directory
20020 @item show data-directory
20021 Show the directory @value{GDBN} searches for auxiliary data files.
20024 @cindex default data directory
20025 @cindex @samp{--with-gdb-datadir}
20026 You can set the default data directory by using the configure-time
20027 @samp{--with-gdb-datadir} option. If the data directory is inside
20028 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20029 @samp{--exec-prefix}), then the default data directory will be updated
20030 automatically if the installed @value{GDBN} is moved to a new
20033 The data directory may also be specified with the
20034 @code{--data-directory} command line option.
20035 @xref{Mode Options}.
20038 @chapter Specifying a Debugging Target
20040 @cindex debugging target
20041 A @dfn{target} is the execution environment occupied by your program.
20043 Often, @value{GDBN} runs in the same host environment as your program;
20044 in that case, the debugging target is specified as a side effect when
20045 you use the @code{file} or @code{core} commands. When you need more
20046 flexibility---for example, running @value{GDBN} on a physically separate
20047 host, or controlling a standalone system over a serial port or a
20048 realtime system over a TCP/IP connection---you can use the @code{target}
20049 command to specify one of the target types configured for @value{GDBN}
20050 (@pxref{Target Commands, ,Commands for Managing Targets}).
20052 @cindex target architecture
20053 It is possible to build @value{GDBN} for several different @dfn{target
20054 architectures}. When @value{GDBN} is built like that, you can choose
20055 one of the available architectures with the @kbd{set architecture}
20059 @kindex set architecture
20060 @kindex show architecture
20061 @item set architecture @var{arch}
20062 This command sets the current target architecture to @var{arch}. The
20063 value of @var{arch} can be @code{"auto"}, in addition to one of the
20064 supported architectures.
20066 @item show architecture
20067 Show the current target architecture.
20069 @item set processor
20071 @kindex set processor
20072 @kindex show processor
20073 These are alias commands for, respectively, @code{set architecture}
20074 and @code{show architecture}.
20078 * Active Targets:: Active targets
20079 * Target Commands:: Commands for managing targets
20080 * Byte Order:: Choosing target byte order
20083 @node Active Targets
20084 @section Active Targets
20086 @cindex stacking targets
20087 @cindex active targets
20088 @cindex multiple targets
20090 There are multiple classes of targets such as: processes, executable files or
20091 recording sessions. Core files belong to the process class, making core file
20092 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20093 on multiple active targets, one in each class. This allows you to (for
20094 example) start a process and inspect its activity, while still having access to
20095 the executable file after the process finishes. Or if you start process
20096 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20097 presented a virtual layer of the recording target, while the process target
20098 remains stopped at the chronologically last point of the process execution.
20100 Use the @code{core-file} and @code{exec-file} commands to select a new core
20101 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20102 specify as a target a process that is already running, use the @code{attach}
20103 command (@pxref{Attach, ,Debugging an Already-running Process}).
20105 @node Target Commands
20106 @section Commands for Managing Targets
20109 @item target @var{type} @var{parameters}
20110 Connects the @value{GDBN} host environment to a target machine or
20111 process. A target is typically a protocol for talking to debugging
20112 facilities. You use the argument @var{type} to specify the type or
20113 protocol of the target machine.
20115 Further @var{parameters} are interpreted by the target protocol, but
20116 typically include things like device names or host names to connect
20117 with, process numbers, and baud rates.
20119 The @code{target} command does not repeat if you press @key{RET} again
20120 after executing the command.
20122 @kindex help target
20124 Displays the names of all targets available. To display targets
20125 currently selected, use either @code{info target} or @code{info files}
20126 (@pxref{Files, ,Commands to Specify Files}).
20128 @item help target @var{name}
20129 Describe a particular target, including any parameters necessary to
20132 @kindex set gnutarget
20133 @item set gnutarget @var{args}
20134 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20135 knows whether it is reading an @dfn{executable},
20136 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20137 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20138 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20141 @emph{Warning:} To specify a file format with @code{set gnutarget},
20142 you must know the actual BFD name.
20146 @xref{Files, , Commands to Specify Files}.
20148 @kindex show gnutarget
20149 @item show gnutarget
20150 Use the @code{show gnutarget} command to display what file format
20151 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20152 @value{GDBN} will determine the file format for each file automatically,
20153 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20156 @cindex common targets
20157 Here are some common targets (available, or not, depending on the GDB
20162 @item target exec @var{program}
20163 @cindex executable file target
20164 An executable file. @samp{target exec @var{program}} is the same as
20165 @samp{exec-file @var{program}}.
20167 @item target core @var{filename}
20168 @cindex core dump file target
20169 A core dump file. @samp{target core @var{filename}} is the same as
20170 @samp{core-file @var{filename}}.
20172 @item target remote @var{medium}
20173 @cindex remote target
20174 A remote system connected to @value{GDBN} via a serial line or network
20175 connection. This command tells @value{GDBN} to use its own remote
20176 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20178 For example, if you have a board connected to @file{/dev/ttya} on the
20179 machine running @value{GDBN}, you could say:
20182 target remote /dev/ttya
20185 @code{target remote} supports the @code{load} command. This is only
20186 useful if you have some other way of getting the stub to the target
20187 system, and you can put it somewhere in memory where it won't get
20188 clobbered by the download.
20190 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20191 @cindex built-in simulator target
20192 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20200 works; however, you cannot assume that a specific memory map, device
20201 drivers, or even basic I/O is available, although some simulators do
20202 provide these. For info about any processor-specific simulator details,
20203 see the appropriate section in @ref{Embedded Processors, ,Embedded
20206 @item target native
20207 @cindex native target
20208 Setup for local/native process debugging. Useful to make the
20209 @code{run} command spawn native processes (likewise @code{attach},
20210 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20211 (@pxref{set auto-connect-native-target}).
20215 Different targets are available on different configurations of @value{GDBN};
20216 your configuration may have more or fewer targets.
20218 Many remote targets require you to download the executable's code once
20219 you've successfully established a connection. You may wish to control
20220 various aspects of this process.
20225 @kindex set hash@r{, for remote monitors}
20226 @cindex hash mark while downloading
20227 This command controls whether a hash mark @samp{#} is displayed while
20228 downloading a file to the remote monitor. If on, a hash mark is
20229 displayed after each S-record is successfully downloaded to the
20233 @kindex show hash@r{, for remote monitors}
20234 Show the current status of displaying the hash mark.
20236 @item set debug monitor
20237 @kindex set debug monitor
20238 @cindex display remote monitor communications
20239 Enable or disable display of communications messages between
20240 @value{GDBN} and the remote monitor.
20242 @item show debug monitor
20243 @kindex show debug monitor
20244 Show the current status of displaying communications between
20245 @value{GDBN} and the remote monitor.
20250 @kindex load @var{filename} @var{offset}
20251 @item load @var{filename} @var{offset}
20253 Depending on what remote debugging facilities are configured into
20254 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20255 is meant to make @var{filename} (an executable) available for debugging
20256 on the remote system---by downloading, or dynamic linking, for example.
20257 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20258 the @code{add-symbol-file} command.
20260 If your @value{GDBN} does not have a @code{load} command, attempting to
20261 execute it gets the error message ``@code{You can't do that when your
20262 target is @dots{}}''
20264 The file is loaded at whatever address is specified in the executable.
20265 For some object file formats, you can specify the load address when you
20266 link the program; for other formats, like a.out, the object file format
20267 specifies a fixed address.
20268 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20270 It is also possible to tell @value{GDBN} to load the executable file at a
20271 specific offset described by the optional argument @var{offset}. When
20272 @var{offset} is provided, @var{filename} must also be provided.
20274 Depending on the remote side capabilities, @value{GDBN} may be able to
20275 load programs into flash memory.
20277 @code{load} does not repeat if you press @key{RET} again after using it.
20282 @kindex flash-erase
20284 @anchor{flash-erase}
20286 Erases all known flash memory regions on the target.
20291 @section Choosing Target Byte Order
20293 @cindex choosing target byte order
20294 @cindex target byte order
20296 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20297 offer the ability to run either big-endian or little-endian byte
20298 orders. Usually the executable or symbol will include a bit to
20299 designate the endian-ness, and you will not need to worry about
20300 which to use. However, you may still find it useful to adjust
20301 @value{GDBN}'s idea of processor endian-ness manually.
20305 @item set endian big
20306 Instruct @value{GDBN} to assume the target is big-endian.
20308 @item set endian little
20309 Instruct @value{GDBN} to assume the target is little-endian.
20311 @item set endian auto
20312 Instruct @value{GDBN} to use the byte order associated with the
20316 Display @value{GDBN}'s current idea of the target byte order.
20320 If the @code{set endian auto} mode is in effect and no executable has
20321 been selected, then the endianness used is the last one chosen either
20322 by one of the @code{set endian big} and @code{set endian little}
20323 commands or by inferring from the last executable used. If no
20324 endianness has been previously chosen, then the default for this mode
20325 is inferred from the target @value{GDBN} has been built for, and is
20326 @code{little} if the name of the target CPU has an @code{el} suffix
20327 and @code{big} otherwise.
20329 Note that these commands merely adjust interpretation of symbolic
20330 data on the host, and that they have absolutely no effect on the
20334 @node Remote Debugging
20335 @chapter Debugging Remote Programs
20336 @cindex remote debugging
20338 If you are trying to debug a program running on a machine that cannot run
20339 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20340 For example, you might use remote debugging on an operating system kernel,
20341 or on a small system which does not have a general purpose operating system
20342 powerful enough to run a full-featured debugger.
20344 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20345 to make this work with particular debugging targets. In addition,
20346 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20347 but not specific to any particular target system) which you can use if you
20348 write the remote stubs---the code that runs on the remote system to
20349 communicate with @value{GDBN}.
20351 Other remote targets may be available in your
20352 configuration of @value{GDBN}; use @code{help target} to list them.
20355 * Connecting:: Connecting to a remote target
20356 * File Transfer:: Sending files to a remote system
20357 * Server:: Using the gdbserver program
20358 * Remote Configuration:: Remote configuration
20359 * Remote Stub:: Implementing a remote stub
20363 @section Connecting to a Remote Target
20364 @cindex remote debugging, connecting
20365 @cindex @code{gdbserver}, connecting
20366 @cindex remote debugging, types of connections
20367 @cindex @code{gdbserver}, types of connections
20368 @cindex @code{gdbserver}, @code{target remote} mode
20369 @cindex @code{gdbserver}, @code{target extended-remote} mode
20371 This section describes how to connect to a remote target, including the
20372 types of connections and their differences, how to set up executable and
20373 symbol files on the host and target, and the commands used for
20374 connecting to and disconnecting from the remote target.
20376 @subsection Types of Remote Connections
20378 @value{GDBN} supports two types of remote connections, @code{target remote}
20379 mode and @code{target extended-remote} mode. Note that many remote targets
20380 support only @code{target remote} mode. There are several major
20381 differences between the two types of connections, enumerated here:
20385 @cindex remote debugging, detach and program exit
20386 @item Result of detach or program exit
20387 @strong{With target remote mode:} When the debugged program exits or you
20388 detach from it, @value{GDBN} disconnects from the target. When using
20389 @code{gdbserver}, @code{gdbserver} will exit.
20391 @strong{With target extended-remote mode:} When the debugged program exits or
20392 you detach from it, @value{GDBN} remains connected to the target, even
20393 though no program is running. You can rerun the program, attach to a
20394 running program, or use @code{monitor} commands specific to the target.
20396 When using @code{gdbserver} in this case, it does not exit unless it was
20397 invoked using the @option{--once} option. If the @option{--once} option
20398 was not used, you can ask @code{gdbserver} to exit using the
20399 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20401 @item Specifying the program to debug
20402 For both connection types you use the @code{file} command to specify the
20403 program on the host system. If you are using @code{gdbserver} there are
20404 some differences in how to specify the location of the program on the
20407 @strong{With target remote mode:} You must either specify the program to debug
20408 on the @code{gdbserver} command line or use the @option{--attach} option
20409 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20411 @cindex @option{--multi}, @code{gdbserver} option
20412 @strong{With target extended-remote mode:} You may specify the program to debug
20413 on the @code{gdbserver} command line, or you can load the program or attach
20414 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20416 @anchor{--multi Option in Types of Remote Connnections}
20417 You can start @code{gdbserver} without supplying an initial command to run
20418 or process ID to attach. To do this, use the @option{--multi} command line
20419 option. Then you can connect using @code{target extended-remote} and start
20420 the program you want to debug (see below for details on using the
20421 @code{run} command in this scenario). Note that the conditions under which
20422 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20423 (@code{target remote} or @code{target extended-remote}). The
20424 @option{--multi} option to @code{gdbserver} has no influence on that.
20426 @item The @code{run} command
20427 @strong{With target remote mode:} The @code{run} command is not
20428 supported. Once a connection has been established, you can use all
20429 the usual @value{GDBN} commands to examine and change data. The
20430 remote program is already running, so you can use commands like
20431 @kbd{step} and @kbd{continue}.
20433 @strong{With target extended-remote mode:} The @code{run} command is
20434 supported. The @code{run} command uses the value set by
20435 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20436 the program to run. Command line arguments are supported, except for
20437 wildcard expansion and I/O redirection (@pxref{Arguments}).
20439 If you specify the program to debug on the command line, then the
20440 @code{run} command is not required to start execution, and you can
20441 resume using commands like @kbd{step} and @kbd{continue} as with
20442 @code{target remote} mode.
20444 @anchor{Attaching in Types of Remote Connections}
20446 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20447 not supported. To attach to a running program using @code{gdbserver}, you
20448 must use the @option{--attach} option (@pxref{Running gdbserver}).
20450 @strong{With target extended-remote mode:} To attach to a running program,
20451 you may use the @code{attach} command after the connection has been
20452 established. If you are using @code{gdbserver}, you may also invoke
20453 @code{gdbserver} using the @option{--attach} option
20454 (@pxref{Running gdbserver}).
20458 @anchor{Host and target files}
20459 @subsection Host and Target Files
20460 @cindex remote debugging, symbol files
20461 @cindex symbol files, remote debugging
20463 @value{GDBN}, running on the host, needs access to symbol and debugging
20464 information for your program running on the target. This requires
20465 access to an unstripped copy of your program, and possibly any associated
20466 symbol files. Note that this section applies equally to both @code{target
20467 remote} mode and @code{target extended-remote} mode.
20469 Some remote targets (@pxref{qXfer executable filename read}, and
20470 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20471 the same connection used to communicate with @value{GDBN}. With such a
20472 target, if the remote program is unstripped, the only command you need is
20473 @code{target remote} (or @code{target extended-remote}).
20475 If the remote program is stripped, or the target does not support remote
20476 program file access, start up @value{GDBN} using the name of the local
20477 unstripped copy of your program as the first argument, or use the
20478 @code{file} command. Use @code{set sysroot} to specify the location (on
20479 the host) of target libraries (unless your @value{GDBN} was compiled with
20480 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20481 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20484 The symbol file and target libraries must exactly match the executable
20485 and libraries on the target, with one exception: the files on the host
20486 system should not be stripped, even if the files on the target system
20487 are. Mismatched or missing files will lead to confusing results
20488 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20489 files may also prevent @code{gdbserver} from debugging multi-threaded
20492 @subsection Remote Connection Commands
20493 @cindex remote connection commands
20494 @value{GDBN} can communicate with the target over a serial line, or
20495 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20496 each case, @value{GDBN} uses the same protocol for debugging your
20497 program; only the medium carrying the debugging packets varies. The
20498 @code{target remote} and @code{target extended-remote} commands
20499 establish a connection to the target. Both commands accept the same
20500 arguments, which indicate the medium to use:
20504 @item target remote @var{serial-device}
20505 @itemx target extended-remote @var{serial-device}
20506 @cindex serial line, @code{target remote}
20507 Use @var{serial-device} to communicate with the target. For example,
20508 to use a serial line connected to the device named @file{/dev/ttyb}:
20511 target remote /dev/ttyb
20514 If you're using a serial line, you may want to give @value{GDBN} the
20515 @samp{--baud} option, or use the @code{set serial baud} command
20516 (@pxref{Remote Configuration, set serial baud}) before the
20517 @code{target} command.
20519 @item target remote @code{@var{host}:@var{port}}
20520 @itemx target remote @code{tcp:@var{host}:@var{port}}
20521 @itemx target extended-remote @code{@var{host}:@var{port}}
20522 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20523 @cindex @acronym{TCP} port, @code{target remote}
20524 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20525 The @var{host} may be either a host name or a numeric @acronym{IP}
20526 address; @var{port} must be a decimal number. The @var{host} could be
20527 the target machine itself, if it is directly connected to the net, or
20528 it might be a terminal server which in turn has a serial line to the
20531 For example, to connect to port 2828 on a terminal server named
20535 target remote manyfarms:2828
20538 If your remote target is actually running on the same machine as your
20539 debugger session (e.g.@: a simulator for your target running on the
20540 same host), you can omit the hostname. For example, to connect to
20541 port 1234 on your local machine:
20544 target remote :1234
20548 Note that the colon is still required here.
20550 @item target remote @code{udp:@var{host}:@var{port}}
20551 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20552 @cindex @acronym{UDP} port, @code{target remote}
20553 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20554 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20557 target remote udp:manyfarms:2828
20560 When using a @acronym{UDP} connection for remote debugging, you should
20561 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20562 can silently drop packets on busy or unreliable networks, which will
20563 cause havoc with your debugging session.
20565 @item target remote | @var{command}
20566 @itemx target extended-remote | @var{command}
20567 @cindex pipe, @code{target remote} to
20568 Run @var{command} in the background and communicate with it using a
20569 pipe. The @var{command} is a shell command, to be parsed and expanded
20570 by the system's command shell, @code{/bin/sh}; it should expect remote
20571 protocol packets on its standard input, and send replies on its
20572 standard output. You could use this to run a stand-alone simulator
20573 that speaks the remote debugging protocol, to make net connections
20574 using programs like @code{ssh}, or for other similar tricks.
20576 If @var{command} closes its standard output (perhaps by exiting),
20577 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20578 program has already exited, this will have no effect.)
20582 @cindex interrupting remote programs
20583 @cindex remote programs, interrupting
20584 Whenever @value{GDBN} is waiting for the remote program, if you type the
20585 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20586 program. This may or may not succeed, depending in part on the hardware
20587 and the serial drivers the remote system uses. If you type the
20588 interrupt character once again, @value{GDBN} displays this prompt:
20591 Interrupted while waiting for the program.
20592 Give up (and stop debugging it)? (y or n)
20595 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20596 the remote debugging session. (If you decide you want to try again later,
20597 you can use @kbd{target remote} again to connect once more.) If you type
20598 @kbd{n}, @value{GDBN} goes back to waiting.
20600 In @code{target extended-remote} mode, typing @kbd{n} will leave
20601 @value{GDBN} connected to the target.
20604 @kindex detach (remote)
20606 When you have finished debugging the remote program, you can use the
20607 @code{detach} command to release it from @value{GDBN} control.
20608 Detaching from the target normally resumes its execution, but the results
20609 will depend on your particular remote stub. After the @code{detach}
20610 command in @code{target remote} mode, @value{GDBN} is free to connect to
20611 another target. In @code{target extended-remote} mode, @value{GDBN} is
20612 still connected to the target.
20616 The @code{disconnect} command closes the connection to the target, and
20617 the target is generally not resumed. It will wait for @value{GDBN}
20618 (this instance or another one) to connect and continue debugging. After
20619 the @code{disconnect} command, @value{GDBN} is again free to connect to
20622 @cindex send command to remote monitor
20623 @cindex extend @value{GDBN} for remote targets
20624 @cindex add new commands for external monitor
20626 @item monitor @var{cmd}
20627 This command allows you to send arbitrary commands directly to the
20628 remote monitor. Since @value{GDBN} doesn't care about the commands it
20629 sends like this, this command is the way to extend @value{GDBN}---you
20630 can add new commands that only the external monitor will understand
20634 @node File Transfer
20635 @section Sending files to a remote system
20636 @cindex remote target, file transfer
20637 @cindex file transfer
20638 @cindex sending files to remote systems
20640 Some remote targets offer the ability to transfer files over the same
20641 connection used to communicate with @value{GDBN}. This is convenient
20642 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20643 running @code{gdbserver} over a network interface. For other targets,
20644 e.g.@: embedded devices with only a single serial port, this may be
20645 the only way to upload or download files.
20647 Not all remote targets support these commands.
20651 @item remote put @var{hostfile} @var{targetfile}
20652 Copy file @var{hostfile} from the host system (the machine running
20653 @value{GDBN}) to @var{targetfile} on the target system.
20656 @item remote get @var{targetfile} @var{hostfile}
20657 Copy file @var{targetfile} from the target system to @var{hostfile}
20658 on the host system.
20660 @kindex remote delete
20661 @item remote delete @var{targetfile}
20662 Delete @var{targetfile} from the target system.
20667 @section Using the @code{gdbserver} Program
20670 @cindex remote connection without stubs
20671 @code{gdbserver} is a control program for Unix-like systems, which
20672 allows you to connect your program with a remote @value{GDBN} via
20673 @code{target remote} or @code{target extended-remote}---but without
20674 linking in the usual debugging stub.
20676 @code{gdbserver} is not a complete replacement for the debugging stubs,
20677 because it requires essentially the same operating-system facilities
20678 that @value{GDBN} itself does. In fact, a system that can run
20679 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20680 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20681 because it is a much smaller program than @value{GDBN} itself. It is
20682 also easier to port than all of @value{GDBN}, so you may be able to get
20683 started more quickly on a new system by using @code{gdbserver}.
20684 Finally, if you develop code for real-time systems, you may find that
20685 the tradeoffs involved in real-time operation make it more convenient to
20686 do as much development work as possible on another system, for example
20687 by cross-compiling. You can use @code{gdbserver} to make a similar
20688 choice for debugging.
20690 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20691 or a TCP connection, using the standard @value{GDBN} remote serial
20695 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20696 Do not run @code{gdbserver} connected to any public network; a
20697 @value{GDBN} connection to @code{gdbserver} provides access to the
20698 target system with the same privileges as the user running
20702 @anchor{Running gdbserver}
20703 @subsection Running @code{gdbserver}
20704 @cindex arguments, to @code{gdbserver}
20705 @cindex @code{gdbserver}, command-line arguments
20707 Run @code{gdbserver} on the target system. You need a copy of the
20708 program you want to debug, including any libraries it requires.
20709 @code{gdbserver} does not need your program's symbol table, so you can
20710 strip the program if necessary to save space. @value{GDBN} on the host
20711 system does all the symbol handling.
20713 To use the server, you must tell it how to communicate with @value{GDBN};
20714 the name of your program; and the arguments for your program. The usual
20718 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20721 @var{comm} is either a device name (to use a serial line), or a TCP
20722 hostname and portnumber, or @code{-} or @code{stdio} to use
20723 stdin/stdout of @code{gdbserver}.
20724 For example, to debug Emacs with the argument
20725 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20729 target> gdbserver /dev/com1 emacs foo.txt
20732 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20735 To use a TCP connection instead of a serial line:
20738 target> gdbserver host:2345 emacs foo.txt
20741 The only difference from the previous example is the first argument,
20742 specifying that you are communicating with the host @value{GDBN} via
20743 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20744 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20745 (Currently, the @samp{host} part is ignored.) You can choose any number
20746 you want for the port number as long as it does not conflict with any
20747 TCP ports already in use on the target system (for example, @code{23} is
20748 reserved for @code{telnet}).@footnote{If you choose a port number that
20749 conflicts with another service, @code{gdbserver} prints an error message
20750 and exits.} You must use the same port number with the host @value{GDBN}
20751 @code{target remote} command.
20753 The @code{stdio} connection is useful when starting @code{gdbserver}
20757 (gdb) target remote | ssh -T hostname gdbserver - hello
20760 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20761 and we don't want escape-character handling. Ssh does this by default when
20762 a command is provided, the flag is provided to make it explicit.
20763 You could elide it if you want to.
20765 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20766 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20767 display through a pipe connected to gdbserver.
20768 Both @code{stdout} and @code{stderr} use the same pipe.
20770 @anchor{Attaching to a program}
20771 @subsubsection Attaching to a Running Program
20772 @cindex attach to a program, @code{gdbserver}
20773 @cindex @option{--attach}, @code{gdbserver} option
20775 On some targets, @code{gdbserver} can also attach to running programs.
20776 This is accomplished via the @code{--attach} argument. The syntax is:
20779 target> gdbserver --attach @var{comm} @var{pid}
20782 @var{pid} is the process ID of a currently running process. It isn't
20783 necessary to point @code{gdbserver} at a binary for the running process.
20785 In @code{target extended-remote} mode, you can also attach using the
20786 @value{GDBN} attach command
20787 (@pxref{Attaching in Types of Remote Connections}).
20790 You can debug processes by name instead of process ID if your target has the
20791 @code{pidof} utility:
20794 target> gdbserver --attach @var{comm} `pidof @var{program}`
20797 In case more than one copy of @var{program} is running, or @var{program}
20798 has multiple threads, most versions of @code{pidof} support the
20799 @code{-s} option to only return the first process ID.
20801 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20803 This section applies only when @code{gdbserver} is run to listen on a TCP
20806 @code{gdbserver} normally terminates after all of its debugged processes have
20807 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20808 extended-remote}, @code{gdbserver} stays running even with no processes left.
20809 @value{GDBN} normally terminates the spawned debugged process on its exit,
20810 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20811 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20812 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20813 stays running even in the @kbd{target remote} mode.
20815 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20816 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20817 completeness, at most one @value{GDBN} can be connected at a time.
20819 @cindex @option{--once}, @code{gdbserver} option
20820 By default, @code{gdbserver} keeps the listening TCP port open, so that
20821 subsequent connections are possible. However, if you start @code{gdbserver}
20822 with the @option{--once} option, it will stop listening for any further
20823 connection attempts after connecting to the first @value{GDBN} session. This
20824 means no further connections to @code{gdbserver} will be possible after the
20825 first one. It also means @code{gdbserver} will terminate after the first
20826 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20827 connections and even in the @kbd{target extended-remote} mode. The
20828 @option{--once} option allows reusing the same port number for connecting to
20829 multiple instances of @code{gdbserver} running on the same host, since each
20830 instance closes its port after the first connection.
20832 @anchor{Other Command-Line Arguments for gdbserver}
20833 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20835 You can use the @option{--multi} option to start @code{gdbserver} without
20836 specifying a program to debug or a process to attach to. Then you can
20837 attach in @code{target extended-remote} mode and run or attach to a
20838 program. For more information,
20839 @pxref{--multi Option in Types of Remote Connnections}.
20841 @cindex @option{--debug}, @code{gdbserver} option
20842 The @option{--debug} option tells @code{gdbserver} to display extra
20843 status information about the debugging process.
20844 @cindex @option{--remote-debug}, @code{gdbserver} option
20845 The @option{--remote-debug} option tells @code{gdbserver} to display
20846 remote protocol debug output. These options are intended for
20847 @code{gdbserver} development and for bug reports to the developers.
20849 @cindex @option{--debug-format}, @code{gdbserver} option
20850 The @option{--debug-format=option1[,option2,...]} option tells
20851 @code{gdbserver} to include additional information in each output.
20852 Possible options are:
20856 Turn off all extra information in debugging output.
20858 Turn on all extra information in debugging output.
20860 Include a timestamp in each line of debugging output.
20863 Options are processed in order. Thus, for example, if @option{none}
20864 appears last then no additional information is added to debugging output.
20866 @cindex @option{--wrapper}, @code{gdbserver} option
20867 The @option{--wrapper} option specifies a wrapper to launch programs
20868 for debugging. The option should be followed by the name of the
20869 wrapper, then any command-line arguments to pass to the wrapper, then
20870 @kbd{--} indicating the end of the wrapper arguments.
20872 @code{gdbserver} runs the specified wrapper program with a combined
20873 command line including the wrapper arguments, then the name of the
20874 program to debug, then any arguments to the program. The wrapper
20875 runs until it executes your program, and then @value{GDBN} gains control.
20877 You can use any program that eventually calls @code{execve} with
20878 its arguments as a wrapper. Several standard Unix utilities do
20879 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20880 with @code{exec "$@@"} will also work.
20882 For example, you can use @code{env} to pass an environment variable to
20883 the debugged program, without setting the variable in @code{gdbserver}'s
20887 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20890 @cindex @option{--selftest}
20891 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20894 $ gdbserver --selftest
20895 Ran 2 unit tests, 0 failed
20898 These tests are disabled in release.
20899 @subsection Connecting to @code{gdbserver}
20901 The basic procedure for connecting to the remote target is:
20905 Run @value{GDBN} on the host system.
20908 Make sure you have the necessary symbol files
20909 (@pxref{Host and target files}).
20910 Load symbols for your application using the @code{file} command before you
20911 connect. Use @code{set sysroot} to locate target libraries (unless your
20912 @value{GDBN} was compiled with the correct sysroot using
20913 @code{--with-sysroot}).
20916 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20917 For TCP connections, you must start up @code{gdbserver} prior to using
20918 the @code{target} command. Otherwise you may get an error whose
20919 text depends on the host system, but which usually looks something like
20920 @samp{Connection refused}. Don't use the @code{load}
20921 command in @value{GDBN} when using @code{target remote} mode, since the
20922 program is already on the target.
20926 @anchor{Monitor Commands for gdbserver}
20927 @subsection Monitor Commands for @code{gdbserver}
20928 @cindex monitor commands, for @code{gdbserver}
20930 During a @value{GDBN} session using @code{gdbserver}, you can use the
20931 @code{monitor} command to send special requests to @code{gdbserver}.
20932 Here are the available commands.
20936 List the available monitor commands.
20938 @item monitor set debug 0
20939 @itemx monitor set debug 1
20940 Disable or enable general debugging messages.
20942 @item monitor set remote-debug 0
20943 @itemx monitor set remote-debug 1
20944 Disable or enable specific debugging messages associated with the remote
20945 protocol (@pxref{Remote Protocol}).
20947 @item monitor set debug-format option1@r{[},option2,...@r{]}
20948 Specify additional text to add to debugging messages.
20949 Possible options are:
20953 Turn off all extra information in debugging output.
20955 Turn on all extra information in debugging output.
20957 Include a timestamp in each line of debugging output.
20960 Options are processed in order. Thus, for example, if @option{none}
20961 appears last then no additional information is added to debugging output.
20963 @item monitor set libthread-db-search-path [PATH]
20964 @cindex gdbserver, search path for @code{libthread_db}
20965 When this command is issued, @var{path} is a colon-separated list of
20966 directories to search for @code{libthread_db} (@pxref{Threads,,set
20967 libthread-db-search-path}). If you omit @var{path},
20968 @samp{libthread-db-search-path} will be reset to its default value.
20970 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20971 not supported in @code{gdbserver}.
20974 Tell gdbserver to exit immediately. This command should be followed by
20975 @code{disconnect} to close the debugging session. @code{gdbserver} will
20976 detach from any attached processes and kill any processes it created.
20977 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20978 of a multi-process mode debug session.
20982 @subsection Tracepoints support in @code{gdbserver}
20983 @cindex tracepoints support in @code{gdbserver}
20985 On some targets, @code{gdbserver} supports tracepoints, fast
20986 tracepoints and static tracepoints.
20988 For fast or static tracepoints to work, a special library called the
20989 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20990 This library is built and distributed as an integral part of
20991 @code{gdbserver}. In addition, support for static tracepoints
20992 requires building the in-process agent library with static tracepoints
20993 support. At present, the UST (LTTng Userspace Tracer,
20994 @url{http://lttng.org/ust}) tracing engine is supported. This support
20995 is automatically available if UST development headers are found in the
20996 standard include path when @code{gdbserver} is built, or if
20997 @code{gdbserver} was explicitly configured using @option{--with-ust}
20998 to point at such headers. You can explicitly disable the support
20999 using @option{--with-ust=no}.
21001 There are several ways to load the in-process agent in your program:
21004 @item Specifying it as dependency at link time
21006 You can link your program dynamically with the in-process agent
21007 library. On most systems, this is accomplished by adding
21008 @code{-linproctrace} to the link command.
21010 @item Using the system's preloading mechanisms
21012 You can force loading the in-process agent at startup time by using
21013 your system's support for preloading shared libraries. Many Unixes
21014 support the concept of preloading user defined libraries. In most
21015 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21016 in the environment. See also the description of @code{gdbserver}'s
21017 @option{--wrapper} command line option.
21019 @item Using @value{GDBN} to force loading the agent at run time
21021 On some systems, you can force the inferior to load a shared library,
21022 by calling a dynamic loader function in the inferior that takes care
21023 of dynamically looking up and loading a shared library. On most Unix
21024 systems, the function is @code{dlopen}. You'll use the @code{call}
21025 command for that. For example:
21028 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21031 Note that on most Unix systems, for the @code{dlopen} function to be
21032 available, the program needs to be linked with @code{-ldl}.
21035 On systems that have a userspace dynamic loader, like most Unix
21036 systems, when you connect to @code{gdbserver} using @code{target
21037 remote}, you'll find that the program is stopped at the dynamic
21038 loader's entry point, and no shared library has been loaded in the
21039 program's address space yet, including the in-process agent. In that
21040 case, before being able to use any of the fast or static tracepoints
21041 features, you need to let the loader run and load the shared
21042 libraries. The simplest way to do that is to run the program to the
21043 main procedure. E.g., if debugging a C or C@t{++} program, start
21044 @code{gdbserver} like so:
21047 $ gdbserver :9999 myprogram
21050 Start GDB and connect to @code{gdbserver} like so, and run to main:
21054 (@value{GDBP}) target remote myhost:9999
21055 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21056 (@value{GDBP}) b main
21057 (@value{GDBP}) continue
21060 The in-process tracing agent library should now be loaded into the
21061 process; you can confirm it with the @code{info sharedlibrary}
21062 command, which will list @file{libinproctrace.so} as loaded in the
21063 process. You are now ready to install fast tracepoints, list static
21064 tracepoint markers, probe static tracepoints markers, and start
21067 @node Remote Configuration
21068 @section Remote Configuration
21071 @kindex show remote
21072 This section documents the configuration options available when
21073 debugging remote programs. For the options related to the File I/O
21074 extensions of the remote protocol, see @ref{system,
21075 system-call-allowed}.
21078 @item set remoteaddresssize @var{bits}
21079 @cindex address size for remote targets
21080 @cindex bits in remote address
21081 Set the maximum size of address in a memory packet to the specified
21082 number of bits. @value{GDBN} will mask off the address bits above
21083 that number, when it passes addresses to the remote target. The
21084 default value is the number of bits in the target's address.
21086 @item show remoteaddresssize
21087 Show the current value of remote address size in bits.
21089 @item set serial baud @var{n}
21090 @cindex baud rate for remote targets
21091 Set the baud rate for the remote serial I/O to @var{n} baud. The
21092 value is used to set the speed of the serial port used for debugging
21095 @item show serial baud
21096 Show the current speed of the remote connection.
21098 @item set serial parity @var{parity}
21099 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21100 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21102 @item show serial parity
21103 Show the current parity of the serial port.
21105 @item set remotebreak
21106 @cindex interrupt remote programs
21107 @cindex BREAK signal instead of Ctrl-C
21108 @anchor{set remotebreak}
21109 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21110 when you type @kbd{Ctrl-c} to interrupt the program running
21111 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21112 character instead. The default is off, since most remote systems
21113 expect to see @samp{Ctrl-C} as the interrupt signal.
21115 @item show remotebreak
21116 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21117 interrupt the remote program.
21119 @item set remoteflow on
21120 @itemx set remoteflow off
21121 @kindex set remoteflow
21122 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21123 on the serial port used to communicate to the remote target.
21125 @item show remoteflow
21126 @kindex show remoteflow
21127 Show the current setting of hardware flow control.
21129 @item set remotelogbase @var{base}
21130 Set the base (a.k.a.@: radix) of logging serial protocol
21131 communications to @var{base}. Supported values of @var{base} are:
21132 @code{ascii}, @code{octal}, and @code{hex}. The default is
21135 @item show remotelogbase
21136 Show the current setting of the radix for logging remote serial
21139 @item set remotelogfile @var{file}
21140 @cindex record serial communications on file
21141 Record remote serial communications on the named @var{file}. The
21142 default is not to record at all.
21144 @item show remotelogfile.
21145 Show the current setting of the file name on which to record the
21146 serial communications.
21148 @item set remotetimeout @var{num}
21149 @cindex timeout for serial communications
21150 @cindex remote timeout
21151 Set the timeout limit to wait for the remote target to respond to
21152 @var{num} seconds. The default is 2 seconds.
21154 @item show remotetimeout
21155 Show the current number of seconds to wait for the remote target
21158 @cindex limit hardware breakpoints and watchpoints
21159 @cindex remote target, limit break- and watchpoints
21160 @anchor{set remote hardware-watchpoint-limit}
21161 @anchor{set remote hardware-breakpoint-limit}
21162 @item set remote hardware-watchpoint-limit @var{limit}
21163 @itemx set remote hardware-breakpoint-limit @var{limit}
21164 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21165 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21166 watchpoints or breakpoints, and @code{unlimited} for unlimited
21167 watchpoints or breakpoints.
21169 @item show remote hardware-watchpoint-limit
21170 @itemx show remote hardware-breakpoint-limit
21171 Show the current limit for the number of hardware watchpoints or
21172 breakpoints that @value{GDBN} can use.
21174 @cindex limit hardware watchpoints length
21175 @cindex remote target, limit watchpoints length
21176 @anchor{set remote hardware-watchpoint-length-limit}
21177 @item set remote hardware-watchpoint-length-limit @var{limit}
21178 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21179 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21180 hardware watchpoints and @code{unlimited} allows watchpoints of any
21183 @item show remote hardware-watchpoint-length-limit
21184 Show the current limit (in bytes) of the maximum length of
21185 a remote hardware watchpoint.
21187 @item set remote exec-file @var{filename}
21188 @itemx show remote exec-file
21189 @anchor{set remote exec-file}
21190 @cindex executable file, for remote target
21191 Select the file used for @code{run} with @code{target
21192 extended-remote}. This should be set to a filename valid on the
21193 target system. If it is not set, the target will use a default
21194 filename (e.g.@: the last program run).
21196 @item set remote interrupt-sequence
21197 @cindex interrupt remote programs
21198 @cindex select Ctrl-C, BREAK or BREAK-g
21199 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21200 @samp{BREAK-g} as the
21201 sequence to the remote target in order to interrupt the execution.
21202 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21203 is high level of serial line for some certain time.
21204 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21205 It is @code{BREAK} signal followed by character @code{g}.
21207 @item show interrupt-sequence
21208 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21209 is sent by @value{GDBN} to interrupt the remote program.
21210 @code{BREAK-g} is BREAK signal followed by @code{g} and
21211 also known as Magic SysRq g.
21213 @item set remote interrupt-on-connect
21214 @cindex send interrupt-sequence on start
21215 Specify whether interrupt-sequence is sent to remote target when
21216 @value{GDBN} connects to it. This is mostly needed when you debug
21217 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21218 which is known as Magic SysRq g in order to connect @value{GDBN}.
21220 @item show interrupt-on-connect
21221 Show whether interrupt-sequence is sent
21222 to remote target when @value{GDBN} connects to it.
21226 @item set tcp auto-retry on
21227 @cindex auto-retry, for remote TCP target
21228 Enable auto-retry for remote TCP connections. This is useful if the remote
21229 debugging agent is launched in parallel with @value{GDBN}; there is a race
21230 condition because the agent may not become ready to accept the connection
21231 before @value{GDBN} attempts to connect. When auto-retry is
21232 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21233 to establish the connection using the timeout specified by
21234 @code{set tcp connect-timeout}.
21236 @item set tcp auto-retry off
21237 Do not auto-retry failed TCP connections.
21239 @item show tcp auto-retry
21240 Show the current auto-retry setting.
21242 @item set tcp connect-timeout @var{seconds}
21243 @itemx set tcp connect-timeout unlimited
21244 @cindex connection timeout, for remote TCP target
21245 @cindex timeout, for remote target connection
21246 Set the timeout for establishing a TCP connection to the remote target to
21247 @var{seconds}. The timeout affects both polling to retry failed connections
21248 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21249 that are merely slow to complete, and represents an approximate cumulative
21250 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21251 @value{GDBN} will keep attempting to establish a connection forever,
21252 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21254 @item show tcp connect-timeout
21255 Show the current connection timeout setting.
21258 @cindex remote packets, enabling and disabling
21259 The @value{GDBN} remote protocol autodetects the packets supported by
21260 your debugging stub. If you need to override the autodetection, you
21261 can use these commands to enable or disable individual packets. Each
21262 packet can be set to @samp{on} (the remote target supports this
21263 packet), @samp{off} (the remote target does not support this packet),
21264 or @samp{auto} (detect remote target support for this packet). They
21265 all default to @samp{auto}. For more information about each packet,
21266 see @ref{Remote Protocol}.
21268 During normal use, you should not have to use any of these commands.
21269 If you do, that may be a bug in your remote debugging stub, or a bug
21270 in @value{GDBN}. You may want to report the problem to the
21271 @value{GDBN} developers.
21273 For each packet @var{name}, the command to enable or disable the
21274 packet is @code{set remote @var{name}-packet}. The available settings
21277 @multitable @columnfractions 0.28 0.32 0.25
21280 @tab Related Features
21282 @item @code{fetch-register}
21284 @tab @code{info registers}
21286 @item @code{set-register}
21290 @item @code{binary-download}
21292 @tab @code{load}, @code{set}
21294 @item @code{read-aux-vector}
21295 @tab @code{qXfer:auxv:read}
21296 @tab @code{info auxv}
21298 @item @code{symbol-lookup}
21299 @tab @code{qSymbol}
21300 @tab Detecting multiple threads
21302 @item @code{attach}
21303 @tab @code{vAttach}
21306 @item @code{verbose-resume}
21308 @tab Stepping or resuming multiple threads
21314 @item @code{software-breakpoint}
21318 @item @code{hardware-breakpoint}
21322 @item @code{write-watchpoint}
21326 @item @code{read-watchpoint}
21330 @item @code{access-watchpoint}
21334 @item @code{pid-to-exec-file}
21335 @tab @code{qXfer:exec-file:read}
21336 @tab @code{attach}, @code{run}
21338 @item @code{target-features}
21339 @tab @code{qXfer:features:read}
21340 @tab @code{set architecture}
21342 @item @code{library-info}
21343 @tab @code{qXfer:libraries:read}
21344 @tab @code{info sharedlibrary}
21346 @item @code{memory-map}
21347 @tab @code{qXfer:memory-map:read}
21348 @tab @code{info mem}
21350 @item @code{read-sdata-object}
21351 @tab @code{qXfer:sdata:read}
21352 @tab @code{print $_sdata}
21354 @item @code{read-spu-object}
21355 @tab @code{qXfer:spu:read}
21356 @tab @code{info spu}
21358 @item @code{write-spu-object}
21359 @tab @code{qXfer:spu:write}
21360 @tab @code{info spu}
21362 @item @code{read-siginfo-object}
21363 @tab @code{qXfer:siginfo:read}
21364 @tab @code{print $_siginfo}
21366 @item @code{write-siginfo-object}
21367 @tab @code{qXfer:siginfo:write}
21368 @tab @code{set $_siginfo}
21370 @item @code{threads}
21371 @tab @code{qXfer:threads:read}
21372 @tab @code{info threads}
21374 @item @code{get-thread-local-@*storage-address}
21375 @tab @code{qGetTLSAddr}
21376 @tab Displaying @code{__thread} variables
21378 @item @code{get-thread-information-block-address}
21379 @tab @code{qGetTIBAddr}
21380 @tab Display MS-Windows Thread Information Block.
21382 @item @code{search-memory}
21383 @tab @code{qSearch:memory}
21386 @item @code{supported-packets}
21387 @tab @code{qSupported}
21388 @tab Remote communications parameters
21390 @item @code{catch-syscalls}
21391 @tab @code{QCatchSyscalls}
21392 @tab @code{catch syscall}
21394 @item @code{pass-signals}
21395 @tab @code{QPassSignals}
21396 @tab @code{handle @var{signal}}
21398 @item @code{program-signals}
21399 @tab @code{QProgramSignals}
21400 @tab @code{handle @var{signal}}
21402 @item @code{hostio-close-packet}
21403 @tab @code{vFile:close}
21404 @tab @code{remote get}, @code{remote put}
21406 @item @code{hostio-open-packet}
21407 @tab @code{vFile:open}
21408 @tab @code{remote get}, @code{remote put}
21410 @item @code{hostio-pread-packet}
21411 @tab @code{vFile:pread}
21412 @tab @code{remote get}, @code{remote put}
21414 @item @code{hostio-pwrite-packet}
21415 @tab @code{vFile:pwrite}
21416 @tab @code{remote get}, @code{remote put}
21418 @item @code{hostio-unlink-packet}
21419 @tab @code{vFile:unlink}
21420 @tab @code{remote delete}
21422 @item @code{hostio-readlink-packet}
21423 @tab @code{vFile:readlink}
21426 @item @code{hostio-fstat-packet}
21427 @tab @code{vFile:fstat}
21430 @item @code{hostio-setfs-packet}
21431 @tab @code{vFile:setfs}
21434 @item @code{noack-packet}
21435 @tab @code{QStartNoAckMode}
21436 @tab Packet acknowledgment
21438 @item @code{osdata}
21439 @tab @code{qXfer:osdata:read}
21440 @tab @code{info os}
21442 @item @code{query-attached}
21443 @tab @code{qAttached}
21444 @tab Querying remote process attach state.
21446 @item @code{trace-buffer-size}
21447 @tab @code{QTBuffer:size}
21448 @tab @code{set trace-buffer-size}
21450 @item @code{trace-status}
21451 @tab @code{qTStatus}
21452 @tab @code{tstatus}
21454 @item @code{traceframe-info}
21455 @tab @code{qXfer:traceframe-info:read}
21456 @tab Traceframe info
21458 @item @code{install-in-trace}
21459 @tab @code{InstallInTrace}
21460 @tab Install tracepoint in tracing
21462 @item @code{disable-randomization}
21463 @tab @code{QDisableRandomization}
21464 @tab @code{set disable-randomization}
21466 @item @code{startup-with-shell}
21467 @tab @code{QStartupWithShell}
21468 @tab @code{set startup-with-shell}
21470 @item @code{environment-hex-encoded}
21471 @tab @code{QEnvironmentHexEncoded}
21472 @tab @code{set environment}
21474 @item @code{environment-unset}
21475 @tab @code{QEnvironmentUnset}
21476 @tab @code{unset environment}
21478 @item @code{environment-reset}
21479 @tab @code{QEnvironmentReset}
21480 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21482 @item @code{set-working-dir}
21483 @tab @code{QSetWorkingDir}
21484 @tab @code{set cwd}
21486 @item @code{conditional-breakpoints-packet}
21487 @tab @code{Z0 and Z1}
21488 @tab @code{Support for target-side breakpoint condition evaluation}
21490 @item @code{multiprocess-extensions}
21491 @tab @code{multiprocess extensions}
21492 @tab Debug multiple processes and remote process PID awareness
21494 @item @code{swbreak-feature}
21495 @tab @code{swbreak stop reason}
21498 @item @code{hwbreak-feature}
21499 @tab @code{hwbreak stop reason}
21502 @item @code{fork-event-feature}
21503 @tab @code{fork stop reason}
21506 @item @code{vfork-event-feature}
21507 @tab @code{vfork stop reason}
21510 @item @code{exec-event-feature}
21511 @tab @code{exec stop reason}
21514 @item @code{thread-events}
21515 @tab @code{QThreadEvents}
21516 @tab Tracking thread lifetime.
21518 @item @code{no-resumed-stop-reply}
21519 @tab @code{no resumed thread left stop reply}
21520 @tab Tracking thread lifetime.
21525 @section Implementing a Remote Stub
21527 @cindex debugging stub, example
21528 @cindex remote stub, example
21529 @cindex stub example, remote debugging
21530 The stub files provided with @value{GDBN} implement the target side of the
21531 communication protocol, and the @value{GDBN} side is implemented in the
21532 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21533 these subroutines to communicate, and ignore the details. (If you're
21534 implementing your own stub file, you can still ignore the details: start
21535 with one of the existing stub files. @file{sparc-stub.c} is the best
21536 organized, and therefore the easiest to read.)
21538 @cindex remote serial debugging, overview
21539 To debug a program running on another machine (the debugging
21540 @dfn{target} machine), you must first arrange for all the usual
21541 prerequisites for the program to run by itself. For example, for a C
21546 A startup routine to set up the C runtime environment; these usually
21547 have a name like @file{crt0}. The startup routine may be supplied by
21548 your hardware supplier, or you may have to write your own.
21551 A C subroutine library to support your program's
21552 subroutine calls, notably managing input and output.
21555 A way of getting your program to the other machine---for example, a
21556 download program. These are often supplied by the hardware
21557 manufacturer, but you may have to write your own from hardware
21561 The next step is to arrange for your program to use a serial port to
21562 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21563 machine). In general terms, the scheme looks like this:
21567 @value{GDBN} already understands how to use this protocol; when everything
21568 else is set up, you can simply use the @samp{target remote} command
21569 (@pxref{Targets,,Specifying a Debugging Target}).
21571 @item On the target,
21572 you must link with your program a few special-purpose subroutines that
21573 implement the @value{GDBN} remote serial protocol. The file containing these
21574 subroutines is called a @dfn{debugging stub}.
21576 On certain remote targets, you can use an auxiliary program
21577 @code{gdbserver} instead of linking a stub into your program.
21578 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21581 The debugging stub is specific to the architecture of the remote
21582 machine; for example, use @file{sparc-stub.c} to debug programs on
21585 @cindex remote serial stub list
21586 These working remote stubs are distributed with @value{GDBN}:
21591 @cindex @file{i386-stub.c}
21594 For Intel 386 and compatible architectures.
21597 @cindex @file{m68k-stub.c}
21598 @cindex Motorola 680x0
21600 For Motorola 680x0 architectures.
21603 @cindex @file{sh-stub.c}
21606 For Renesas SH architectures.
21609 @cindex @file{sparc-stub.c}
21611 For @sc{sparc} architectures.
21613 @item sparcl-stub.c
21614 @cindex @file{sparcl-stub.c}
21617 For Fujitsu @sc{sparclite} architectures.
21621 The @file{README} file in the @value{GDBN} distribution may list other
21622 recently added stubs.
21625 * Stub Contents:: What the stub can do for you
21626 * Bootstrapping:: What you must do for the stub
21627 * Debug Session:: Putting it all together
21630 @node Stub Contents
21631 @subsection What the Stub Can Do for You
21633 @cindex remote serial stub
21634 The debugging stub for your architecture supplies these three
21638 @item set_debug_traps
21639 @findex set_debug_traps
21640 @cindex remote serial stub, initialization
21641 This routine arranges for @code{handle_exception} to run when your
21642 program stops. You must call this subroutine explicitly in your
21643 program's startup code.
21645 @item handle_exception
21646 @findex handle_exception
21647 @cindex remote serial stub, main routine
21648 This is the central workhorse, but your program never calls it
21649 explicitly---the setup code arranges for @code{handle_exception} to
21650 run when a trap is triggered.
21652 @code{handle_exception} takes control when your program stops during
21653 execution (for example, on a breakpoint), and mediates communications
21654 with @value{GDBN} on the host machine. This is where the communications
21655 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21656 representative on the target machine. It begins by sending summary
21657 information on the state of your program, then continues to execute,
21658 retrieving and transmitting any information @value{GDBN} needs, until you
21659 execute a @value{GDBN} command that makes your program resume; at that point,
21660 @code{handle_exception} returns control to your own code on the target
21664 @cindex @code{breakpoint} subroutine, remote
21665 Use this auxiliary subroutine to make your program contain a
21666 breakpoint. Depending on the particular situation, this may be the only
21667 way for @value{GDBN} to get control. For instance, if your target
21668 machine has some sort of interrupt button, you won't need to call this;
21669 pressing the interrupt button transfers control to
21670 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21671 simply receiving characters on the serial port may also trigger a trap;
21672 again, in that situation, you don't need to call @code{breakpoint} from
21673 your own program---simply running @samp{target remote} from the host
21674 @value{GDBN} session gets control.
21676 Call @code{breakpoint} if none of these is true, or if you simply want
21677 to make certain your program stops at a predetermined point for the
21678 start of your debugging session.
21681 @node Bootstrapping
21682 @subsection What You Must Do for the Stub
21684 @cindex remote stub, support routines
21685 The debugging stubs that come with @value{GDBN} are set up for a particular
21686 chip architecture, but they have no information about the rest of your
21687 debugging target machine.
21689 First of all you need to tell the stub how to communicate with the
21693 @item int getDebugChar()
21694 @findex getDebugChar
21695 Write this subroutine to read a single character from the serial port.
21696 It may be identical to @code{getchar} for your target system; a
21697 different name is used to allow you to distinguish the two if you wish.
21699 @item void putDebugChar(int)
21700 @findex putDebugChar
21701 Write this subroutine to write a single character to the serial port.
21702 It may be identical to @code{putchar} for your target system; a
21703 different name is used to allow you to distinguish the two if you wish.
21706 @cindex control C, and remote debugging
21707 @cindex interrupting remote targets
21708 If you want @value{GDBN} to be able to stop your program while it is
21709 running, you need to use an interrupt-driven serial driver, and arrange
21710 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21711 character). That is the character which @value{GDBN} uses to tell the
21712 remote system to stop.
21714 Getting the debugging target to return the proper status to @value{GDBN}
21715 probably requires changes to the standard stub; one quick and dirty way
21716 is to just execute a breakpoint instruction (the ``dirty'' part is that
21717 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21719 Other routines you need to supply are:
21722 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21723 @findex exceptionHandler
21724 Write this function to install @var{exception_address} in the exception
21725 handling tables. You need to do this because the stub does not have any
21726 way of knowing what the exception handling tables on your target system
21727 are like (for example, the processor's table might be in @sc{rom},
21728 containing entries which point to a table in @sc{ram}).
21729 The @var{exception_number} specifies the exception which should be changed;
21730 its meaning is architecture-dependent (for example, different numbers
21731 might represent divide by zero, misaligned access, etc). When this
21732 exception occurs, control should be transferred directly to
21733 @var{exception_address}, and the processor state (stack, registers,
21734 and so on) should be just as it is when a processor exception occurs. So if
21735 you want to use a jump instruction to reach @var{exception_address}, it
21736 should be a simple jump, not a jump to subroutine.
21738 For the 386, @var{exception_address} should be installed as an interrupt
21739 gate so that interrupts are masked while the handler runs. The gate
21740 should be at privilege level 0 (the most privileged level). The
21741 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21742 help from @code{exceptionHandler}.
21744 @item void flush_i_cache()
21745 @findex flush_i_cache
21746 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21747 instruction cache, if any, on your target machine. If there is no
21748 instruction cache, this subroutine may be a no-op.
21750 On target machines that have instruction caches, @value{GDBN} requires this
21751 function to make certain that the state of your program is stable.
21755 You must also make sure this library routine is available:
21758 @item void *memset(void *, int, int)
21760 This is the standard library function @code{memset} that sets an area of
21761 memory to a known value. If you have one of the free versions of
21762 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21763 either obtain it from your hardware manufacturer, or write your own.
21766 If you do not use the GNU C compiler, you may need other standard
21767 library subroutines as well; this varies from one stub to another,
21768 but in general the stubs are likely to use any of the common library
21769 subroutines which @code{@value{NGCC}} generates as inline code.
21772 @node Debug Session
21773 @subsection Putting it All Together
21775 @cindex remote serial debugging summary
21776 In summary, when your program is ready to debug, you must follow these
21781 Make sure you have defined the supporting low-level routines
21782 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21784 @code{getDebugChar}, @code{putDebugChar},
21785 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21789 Insert these lines in your program's startup code, before the main
21790 procedure is called:
21797 On some machines, when a breakpoint trap is raised, the hardware
21798 automatically makes the PC point to the instruction after the
21799 breakpoint. If your machine doesn't do that, you may need to adjust
21800 @code{handle_exception} to arrange for it to return to the instruction
21801 after the breakpoint on this first invocation, so that your program
21802 doesn't keep hitting the initial breakpoint instead of making
21806 For the 680x0 stub only, you need to provide a variable called
21807 @code{exceptionHook}. Normally you just use:
21810 void (*exceptionHook)() = 0;
21814 but if before calling @code{set_debug_traps}, you set it to point to a
21815 function in your program, that function is called when
21816 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21817 error). The function indicated by @code{exceptionHook} is called with
21818 one parameter: an @code{int} which is the exception number.
21821 Compile and link together: your program, the @value{GDBN} debugging stub for
21822 your target architecture, and the supporting subroutines.
21825 Make sure you have a serial connection between your target machine and
21826 the @value{GDBN} host, and identify the serial port on the host.
21829 @c The "remote" target now provides a `load' command, so we should
21830 @c document that. FIXME.
21831 Download your program to your target machine (or get it there by
21832 whatever means the manufacturer provides), and start it.
21835 Start @value{GDBN} on the host, and connect to the target
21836 (@pxref{Connecting,,Connecting to a Remote Target}).
21840 @node Configurations
21841 @chapter Configuration-Specific Information
21843 While nearly all @value{GDBN} commands are available for all native and
21844 cross versions of the debugger, there are some exceptions. This chapter
21845 describes things that are only available in certain configurations.
21847 There are three major categories of configurations: native
21848 configurations, where the host and target are the same, embedded
21849 operating system configurations, which are usually the same for several
21850 different processor architectures, and bare embedded processors, which
21851 are quite different from each other.
21856 * Embedded Processors::
21863 This section describes details specific to particular native
21867 * BSD libkvm Interface:: Debugging BSD kernel memory images
21868 * Process Information:: Process information
21869 * DJGPP Native:: Features specific to the DJGPP port
21870 * Cygwin Native:: Features specific to the Cygwin port
21871 * Hurd Native:: Features specific to @sc{gnu} Hurd
21872 * Darwin:: Features specific to Darwin
21875 @node BSD libkvm Interface
21876 @subsection BSD libkvm Interface
21879 @cindex kernel memory image
21880 @cindex kernel crash dump
21882 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21883 interface that provides a uniform interface for accessing kernel virtual
21884 memory images, including live systems and crash dumps. @value{GDBN}
21885 uses this interface to allow you to debug live kernels and kernel crash
21886 dumps on many native BSD configurations. This is implemented as a
21887 special @code{kvm} debugging target. For debugging a live system, load
21888 the currently running kernel into @value{GDBN} and connect to the
21892 (@value{GDBP}) @b{target kvm}
21895 For debugging crash dumps, provide the file name of the crash dump as an
21899 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21902 Once connected to the @code{kvm} target, the following commands are
21908 Set current context from the @dfn{Process Control Block} (PCB) address.
21911 Set current context from proc address. This command isn't available on
21912 modern FreeBSD systems.
21915 @node Process Information
21916 @subsection Process Information
21918 @cindex examine process image
21919 @cindex process info via @file{/proc}
21921 Some operating systems provide interfaces to fetch additional
21922 information about running processes beyond memory and per-thread
21923 register state. If @value{GDBN} is configured for an operating system
21924 with a supported interface, the command @code{info proc} is available
21925 to report information about the process running your program, or about
21926 any process running on your system.
21928 One supported interface is a facility called @samp{/proc} that can be
21929 used to examine the image of a running process using file-system
21930 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
21933 On FreeBSD systems, system control nodes are used to query process
21936 In addition, some systems may provide additional process information
21937 in core files. Note that a core file may include a subset of the
21938 information available from a live process. Process information is
21939 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
21946 @itemx info proc @var{process-id}
21947 Summarize available information about any running process. If a
21948 process ID is specified by @var{process-id}, display information about
21949 that process; otherwise display information about the program being
21950 debugged. The summary includes the debugged process ID, the command
21951 line used to invoke it, its current working directory, and its
21952 executable file's absolute file name.
21954 On some systems, @var{process-id} can be of the form
21955 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21956 within a process. If the optional @var{pid} part is missing, it means
21957 a thread from the process being debugged (the leading @samp{/} still
21958 needs to be present, or else @value{GDBN} will interpret the number as
21959 a process ID rather than a thread ID).
21961 @item info proc cmdline
21962 @cindex info proc cmdline
21963 Show the original command line of the process. This command is
21964 supported on @sc{gnu}/Linux and FreeBSD.
21966 @item info proc cwd
21967 @cindex info proc cwd
21968 Show the current working directory of the process. This command is
21969 supported on @sc{gnu}/Linux and FreeBSD.
21971 @item info proc exe
21972 @cindex info proc exe
21973 Show the name of executable of the process. This command is supported
21974 on @sc{gnu}/Linux and FreeBSD.
21976 @item info proc mappings
21977 @cindex memory address space mappings
21978 Report the memory address space ranges accessible in the program. On
21979 Solaris and FreeBSD systems, each memory range includes information on
21980 whether the process has read, write, or execute access rights to each
21981 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
21982 includes the object file which is mapped to that range.
21984 @item info proc stat
21985 @itemx info proc status
21986 @cindex process detailed status information
21987 Show additional process-related information, including the user ID and
21988 group ID; virtual memory usage; the signals that are pending, blocked,
21989 and ignored; its TTY; its consumption of system and user time; its
21990 stack size; its @samp{nice} value; etc. These commands are supported
21991 on @sc{gnu}/Linux and FreeBSD.
21993 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
21994 information (type @kbd{man 5 proc} from your shell prompt).
21996 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
21999 @item info proc all
22000 Show all the information about the process described under all of the
22001 above @code{info proc} subcommands.
22004 @comment These sub-options of 'info proc' were not included when
22005 @comment procfs.c was re-written. Keep their descriptions around
22006 @comment against the day when someone finds the time to put them back in.
22007 @kindex info proc times
22008 @item info proc times
22009 Starting time, user CPU time, and system CPU time for your program and
22012 @kindex info proc id
22014 Report on the process IDs related to your program: its own process ID,
22015 the ID of its parent, the process group ID, and the session ID.
22018 @item set procfs-trace
22019 @kindex set procfs-trace
22020 @cindex @code{procfs} API calls
22021 This command enables and disables tracing of @code{procfs} API calls.
22023 @item show procfs-trace
22024 @kindex show procfs-trace
22025 Show the current state of @code{procfs} API call tracing.
22027 @item set procfs-file @var{file}
22028 @kindex set procfs-file
22029 Tell @value{GDBN} to write @code{procfs} API trace to the named
22030 @var{file}. @value{GDBN} appends the trace info to the previous
22031 contents of the file. The default is to display the trace on the
22034 @item show procfs-file
22035 @kindex show procfs-file
22036 Show the file to which @code{procfs} API trace is written.
22038 @item proc-trace-entry
22039 @itemx proc-trace-exit
22040 @itemx proc-untrace-entry
22041 @itemx proc-untrace-exit
22042 @kindex proc-trace-entry
22043 @kindex proc-trace-exit
22044 @kindex proc-untrace-entry
22045 @kindex proc-untrace-exit
22046 These commands enable and disable tracing of entries into and exits
22047 from the @code{syscall} interface.
22050 @kindex info pidlist
22051 @cindex process list, QNX Neutrino
22052 For QNX Neutrino only, this command displays the list of all the
22053 processes and all the threads within each process.
22056 @kindex info meminfo
22057 @cindex mapinfo list, QNX Neutrino
22058 For QNX Neutrino only, this command displays the list of all mapinfos.
22062 @subsection Features for Debugging @sc{djgpp} Programs
22063 @cindex @sc{djgpp} debugging
22064 @cindex native @sc{djgpp} debugging
22065 @cindex MS-DOS-specific commands
22068 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22069 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22070 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22071 top of real-mode DOS systems and their emulations.
22073 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22074 defines a few commands specific to the @sc{djgpp} port. This
22075 subsection describes those commands.
22080 This is a prefix of @sc{djgpp}-specific commands which print
22081 information about the target system and important OS structures.
22084 @cindex MS-DOS system info
22085 @cindex free memory information (MS-DOS)
22086 @item info dos sysinfo
22087 This command displays assorted information about the underlying
22088 platform: the CPU type and features, the OS version and flavor, the
22089 DPMI version, and the available conventional and DPMI memory.
22094 @cindex segment descriptor tables
22095 @cindex descriptor tables display
22097 @itemx info dos ldt
22098 @itemx info dos idt
22099 These 3 commands display entries from, respectively, Global, Local,
22100 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22101 tables are data structures which store a descriptor for each segment
22102 that is currently in use. The segment's selector is an index into a
22103 descriptor table; the table entry for that index holds the
22104 descriptor's base address and limit, and its attributes and access
22107 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22108 segment (used for both data and the stack), and a DOS segment (which
22109 allows access to DOS/BIOS data structures and absolute addresses in
22110 conventional memory). However, the DPMI host will usually define
22111 additional segments in order to support the DPMI environment.
22113 @cindex garbled pointers
22114 These commands allow to display entries from the descriptor tables.
22115 Without an argument, all entries from the specified table are
22116 displayed. An argument, which should be an integer expression, means
22117 display a single entry whose index is given by the argument. For
22118 example, here's a convenient way to display information about the
22119 debugged program's data segment:
22122 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22123 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22127 This comes in handy when you want to see whether a pointer is outside
22128 the data segment's limit (i.e.@: @dfn{garbled}).
22130 @cindex page tables display (MS-DOS)
22132 @itemx info dos pte
22133 These two commands display entries from, respectively, the Page
22134 Directory and the Page Tables. Page Directories and Page Tables are
22135 data structures which control how virtual memory addresses are mapped
22136 into physical addresses. A Page Table includes an entry for every
22137 page of memory that is mapped into the program's address space; there
22138 may be several Page Tables, each one holding up to 4096 entries. A
22139 Page Directory has up to 4096 entries, one each for every Page Table
22140 that is currently in use.
22142 Without an argument, @kbd{info dos pde} displays the entire Page
22143 Directory, and @kbd{info dos pte} displays all the entries in all of
22144 the Page Tables. An argument, an integer expression, given to the
22145 @kbd{info dos pde} command means display only that entry from the Page
22146 Directory table. An argument given to the @kbd{info dos pte} command
22147 means display entries from a single Page Table, the one pointed to by
22148 the specified entry in the Page Directory.
22150 @cindex direct memory access (DMA) on MS-DOS
22151 These commands are useful when your program uses @dfn{DMA} (Direct
22152 Memory Access), which needs physical addresses to program the DMA
22155 These commands are supported only with some DPMI servers.
22157 @cindex physical address from linear address
22158 @item info dos address-pte @var{addr}
22159 This command displays the Page Table entry for a specified linear
22160 address. The argument @var{addr} is a linear address which should
22161 already have the appropriate segment's base address added to it,
22162 because this command accepts addresses which may belong to @emph{any}
22163 segment. For example, here's how to display the Page Table entry for
22164 the page where a variable @code{i} is stored:
22167 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22168 @exdent @code{Page Table entry for address 0x11a00d30:}
22169 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22173 This says that @code{i} is stored at offset @code{0xd30} from the page
22174 whose physical base address is @code{0x02698000}, and shows all the
22175 attributes of that page.
22177 Note that you must cast the addresses of variables to a @code{char *},
22178 since otherwise the value of @code{__djgpp_base_address}, the base
22179 address of all variables and functions in a @sc{djgpp} program, will
22180 be added using the rules of C pointer arithmetics: if @code{i} is
22181 declared an @code{int}, @value{GDBN} will add 4 times the value of
22182 @code{__djgpp_base_address} to the address of @code{i}.
22184 Here's another example, it displays the Page Table entry for the
22188 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22189 @exdent @code{Page Table entry for address 0x29110:}
22190 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22194 (The @code{+ 3} offset is because the transfer buffer's address is the
22195 3rd member of the @code{_go32_info_block} structure.) The output
22196 clearly shows that this DPMI server maps the addresses in conventional
22197 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22198 linear (@code{0x29110}) addresses are identical.
22200 This command is supported only with some DPMI servers.
22203 @cindex DOS serial data link, remote debugging
22204 In addition to native debugging, the DJGPP port supports remote
22205 debugging via a serial data link. The following commands are specific
22206 to remote serial debugging in the DJGPP port of @value{GDBN}.
22209 @kindex set com1base
22210 @kindex set com1irq
22211 @kindex set com2base
22212 @kindex set com2irq
22213 @kindex set com3base
22214 @kindex set com3irq
22215 @kindex set com4base
22216 @kindex set com4irq
22217 @item set com1base @var{addr}
22218 This command sets the base I/O port address of the @file{COM1} serial
22221 @item set com1irq @var{irq}
22222 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22223 for the @file{COM1} serial port.
22225 There are similar commands @samp{set com2base}, @samp{set com3irq},
22226 etc.@: for setting the port address and the @code{IRQ} lines for the
22229 @kindex show com1base
22230 @kindex show com1irq
22231 @kindex show com2base
22232 @kindex show com2irq
22233 @kindex show com3base
22234 @kindex show com3irq
22235 @kindex show com4base
22236 @kindex show com4irq
22237 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22238 display the current settings of the base address and the @code{IRQ}
22239 lines used by the COM ports.
22242 @kindex info serial
22243 @cindex DOS serial port status
22244 This command prints the status of the 4 DOS serial ports. For each
22245 port, it prints whether it's active or not, its I/O base address and
22246 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22247 counts of various errors encountered so far.
22251 @node Cygwin Native
22252 @subsection Features for Debugging MS Windows PE Executables
22253 @cindex MS Windows debugging
22254 @cindex native Cygwin debugging
22255 @cindex Cygwin-specific commands
22257 @value{GDBN} supports native debugging of MS Windows programs, including
22258 DLLs with and without symbolic debugging information.
22260 @cindex Ctrl-BREAK, MS-Windows
22261 @cindex interrupt debuggee on MS-Windows
22262 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22263 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22264 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22265 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22266 sequence, which can be used to interrupt the debuggee even if it
22269 There are various additional Cygwin-specific commands, described in
22270 this section. Working with DLLs that have no debugging symbols is
22271 described in @ref{Non-debug DLL Symbols}.
22276 This is a prefix of MS Windows-specific commands which print
22277 information about the target system and important OS structures.
22279 @item info w32 selector
22280 This command displays information returned by
22281 the Win32 API @code{GetThreadSelectorEntry} function.
22282 It takes an optional argument that is evaluated to
22283 a long value to give the information about this given selector.
22284 Without argument, this command displays information
22285 about the six segment registers.
22287 @item info w32 thread-information-block
22288 This command displays thread specific information stored in the
22289 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22290 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22292 @kindex signal-event
22293 @item signal-event @var{id}
22294 This command signals an event with user-provided @var{id}. Used to resume
22295 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22297 To use it, create or edit the following keys in
22298 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22299 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22300 (for x86_64 versions):
22304 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22305 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22306 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22308 The first @code{%ld} will be replaced by the process ID of the
22309 crashing process, the second @code{%ld} will be replaced by the ID of
22310 the event that blocks the crashing process, waiting for @value{GDBN}
22314 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22315 make the system run debugger specified by the Debugger key
22316 automatically, @code{0} will cause a dialog box with ``OK'' and
22317 ``Cancel'' buttons to appear, which allows the user to either
22318 terminate the crashing process (OK) or debug it (Cancel).
22321 @kindex set cygwin-exceptions
22322 @cindex debugging the Cygwin DLL
22323 @cindex Cygwin DLL, debugging
22324 @item set cygwin-exceptions @var{mode}
22325 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22326 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22327 @value{GDBN} will delay recognition of exceptions, and may ignore some
22328 exceptions which seem to be caused by internal Cygwin DLL
22329 ``bookkeeping''. This option is meant primarily for debugging the
22330 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22331 @value{GDBN} users with false @code{SIGSEGV} signals.
22333 @kindex show cygwin-exceptions
22334 @item show cygwin-exceptions
22335 Displays whether @value{GDBN} will break on exceptions that happen
22336 inside the Cygwin DLL itself.
22338 @kindex set new-console
22339 @item set new-console @var{mode}
22340 If @var{mode} is @code{on} the debuggee will
22341 be started in a new console on next start.
22342 If @var{mode} is @code{off}, the debuggee will
22343 be started in the same console as the debugger.
22345 @kindex show new-console
22346 @item show new-console
22347 Displays whether a new console is used
22348 when the debuggee is started.
22350 @kindex set new-group
22351 @item set new-group @var{mode}
22352 This boolean value controls whether the debuggee should
22353 start a new group or stay in the same group as the debugger.
22354 This affects the way the Windows OS handles
22357 @kindex show new-group
22358 @item show new-group
22359 Displays current value of new-group boolean.
22361 @kindex set debugevents
22362 @item set debugevents
22363 This boolean value adds debug output concerning kernel events related
22364 to the debuggee seen by the debugger. This includes events that
22365 signal thread and process creation and exit, DLL loading and
22366 unloading, console interrupts, and debugging messages produced by the
22367 Windows @code{OutputDebugString} API call.
22369 @kindex set debugexec
22370 @item set debugexec
22371 This boolean value adds debug output concerning execute events
22372 (such as resume thread) seen by the debugger.
22374 @kindex set debugexceptions
22375 @item set debugexceptions
22376 This boolean value adds debug output concerning exceptions in the
22377 debuggee seen by the debugger.
22379 @kindex set debugmemory
22380 @item set debugmemory
22381 This boolean value adds debug output concerning debuggee memory reads
22382 and writes by the debugger.
22386 This boolean values specifies whether the debuggee is called
22387 via a shell or directly (default value is on).
22391 Displays if the debuggee will be started with a shell.
22396 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22399 @node Non-debug DLL Symbols
22400 @subsubsection Support for DLLs without Debugging Symbols
22401 @cindex DLLs with no debugging symbols
22402 @cindex Minimal symbols and DLLs
22404 Very often on windows, some of the DLLs that your program relies on do
22405 not include symbolic debugging information (for example,
22406 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22407 symbols in a DLL, it relies on the minimal amount of symbolic
22408 information contained in the DLL's export table. This section
22409 describes working with such symbols, known internally to @value{GDBN} as
22410 ``minimal symbols''.
22412 Note that before the debugged program has started execution, no DLLs
22413 will have been loaded. The easiest way around this problem is simply to
22414 start the program --- either by setting a breakpoint or letting the
22415 program run once to completion.
22417 @subsubsection DLL Name Prefixes
22419 In keeping with the naming conventions used by the Microsoft debugging
22420 tools, DLL export symbols are made available with a prefix based on the
22421 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22422 also entered into the symbol table, so @code{CreateFileA} is often
22423 sufficient. In some cases there will be name clashes within a program
22424 (particularly if the executable itself includes full debugging symbols)
22425 necessitating the use of the fully qualified name when referring to the
22426 contents of the DLL. Use single-quotes around the name to avoid the
22427 exclamation mark (``!'') being interpreted as a language operator.
22429 Note that the internal name of the DLL may be all upper-case, even
22430 though the file name of the DLL is lower-case, or vice-versa. Since
22431 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22432 some confusion. If in doubt, try the @code{info functions} and
22433 @code{info variables} commands or even @code{maint print msymbols}
22434 (@pxref{Symbols}). Here's an example:
22437 (@value{GDBP}) info function CreateFileA
22438 All functions matching regular expression "CreateFileA":
22440 Non-debugging symbols:
22441 0x77e885f4 CreateFileA
22442 0x77e885f4 KERNEL32!CreateFileA
22446 (@value{GDBP}) info function !
22447 All functions matching regular expression "!":
22449 Non-debugging symbols:
22450 0x6100114c cygwin1!__assert
22451 0x61004034 cygwin1!_dll_crt0@@0
22452 0x61004240 cygwin1!dll_crt0(per_process *)
22456 @subsubsection Working with Minimal Symbols
22458 Symbols extracted from a DLL's export table do not contain very much
22459 type information. All that @value{GDBN} can do is guess whether a symbol
22460 refers to a function or variable depending on the linker section that
22461 contains the symbol. Also note that the actual contents of the memory
22462 contained in a DLL are not available unless the program is running. This
22463 means that you cannot examine the contents of a variable or disassemble
22464 a function within a DLL without a running program.
22466 Variables are generally treated as pointers and dereferenced
22467 automatically. For this reason, it is often necessary to prefix a
22468 variable name with the address-of operator (``&'') and provide explicit
22469 type information in the command. Here's an example of the type of
22473 (@value{GDBP}) print 'cygwin1!__argv'
22474 'cygwin1!__argv' has unknown type; cast it to its declared type
22478 (@value{GDBP}) x 'cygwin1!__argv'
22479 'cygwin1!__argv' has unknown type; cast it to its declared type
22482 And two possible solutions:
22485 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22486 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22490 (@value{GDBP}) x/2x &'cygwin1!__argv'
22491 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22492 (@value{GDBP}) x/x 0x10021608
22493 0x10021608: 0x0022fd98
22494 (@value{GDBP}) x/s 0x0022fd98
22495 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22498 Setting a break point within a DLL is possible even before the program
22499 starts execution. However, under these circumstances, @value{GDBN} can't
22500 examine the initial instructions of the function in order to skip the
22501 function's frame set-up code. You can work around this by using ``*&''
22502 to set the breakpoint at a raw memory address:
22505 (@value{GDBP}) break *&'python22!PyOS_Readline'
22506 Breakpoint 1 at 0x1e04eff0
22509 The author of these extensions is not entirely convinced that setting a
22510 break point within a shared DLL like @file{kernel32.dll} is completely
22514 @subsection Commands Specific to @sc{gnu} Hurd Systems
22515 @cindex @sc{gnu} Hurd debugging
22517 This subsection describes @value{GDBN} commands specific to the
22518 @sc{gnu} Hurd native debugging.
22523 @kindex set signals@r{, Hurd command}
22524 @kindex set sigs@r{, Hurd command}
22525 This command toggles the state of inferior signal interception by
22526 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22527 affected by this command. @code{sigs} is a shorthand alias for
22532 @kindex show signals@r{, Hurd command}
22533 @kindex show sigs@r{, Hurd command}
22534 Show the current state of intercepting inferior's signals.
22536 @item set signal-thread
22537 @itemx set sigthread
22538 @kindex set signal-thread
22539 @kindex set sigthread
22540 This command tells @value{GDBN} which thread is the @code{libc} signal
22541 thread. That thread is run when a signal is delivered to a running
22542 process. @code{set sigthread} is the shorthand alias of @code{set
22545 @item show signal-thread
22546 @itemx show sigthread
22547 @kindex show signal-thread
22548 @kindex show sigthread
22549 These two commands show which thread will run when the inferior is
22550 delivered a signal.
22553 @kindex set stopped@r{, Hurd command}
22554 This commands tells @value{GDBN} that the inferior process is stopped,
22555 as with the @code{SIGSTOP} signal. The stopped process can be
22556 continued by delivering a signal to it.
22559 @kindex show stopped@r{, Hurd command}
22560 This command shows whether @value{GDBN} thinks the debuggee is
22563 @item set exceptions
22564 @kindex set exceptions@r{, Hurd command}
22565 Use this command to turn off trapping of exceptions in the inferior.
22566 When exception trapping is off, neither breakpoints nor
22567 single-stepping will work. To restore the default, set exception
22570 @item show exceptions
22571 @kindex show exceptions@r{, Hurd command}
22572 Show the current state of trapping exceptions in the inferior.
22574 @item set task pause
22575 @kindex set task@r{, Hurd commands}
22576 @cindex task attributes (@sc{gnu} Hurd)
22577 @cindex pause current task (@sc{gnu} Hurd)
22578 This command toggles task suspension when @value{GDBN} has control.
22579 Setting it to on takes effect immediately, and the task is suspended
22580 whenever @value{GDBN} gets control. Setting it to off will take
22581 effect the next time the inferior is continued. If this option is set
22582 to off, you can use @code{set thread default pause on} or @code{set
22583 thread pause on} (see below) to pause individual threads.
22585 @item show task pause
22586 @kindex show task@r{, Hurd commands}
22587 Show the current state of task suspension.
22589 @item set task detach-suspend-count
22590 @cindex task suspend count
22591 @cindex detach from task, @sc{gnu} Hurd
22592 This command sets the suspend count the task will be left with when
22593 @value{GDBN} detaches from it.
22595 @item show task detach-suspend-count
22596 Show the suspend count the task will be left with when detaching.
22598 @item set task exception-port
22599 @itemx set task excp
22600 @cindex task exception port, @sc{gnu} Hurd
22601 This command sets the task exception port to which @value{GDBN} will
22602 forward exceptions. The argument should be the value of the @dfn{send
22603 rights} of the task. @code{set task excp} is a shorthand alias.
22605 @item set noninvasive
22606 @cindex noninvasive task options
22607 This command switches @value{GDBN} to a mode that is the least
22608 invasive as far as interfering with the inferior is concerned. This
22609 is the same as using @code{set task pause}, @code{set exceptions}, and
22610 @code{set signals} to values opposite to the defaults.
22612 @item info send-rights
22613 @itemx info receive-rights
22614 @itemx info port-rights
22615 @itemx info port-sets
22616 @itemx info dead-names
22619 @cindex send rights, @sc{gnu} Hurd
22620 @cindex receive rights, @sc{gnu} Hurd
22621 @cindex port rights, @sc{gnu} Hurd
22622 @cindex port sets, @sc{gnu} Hurd
22623 @cindex dead names, @sc{gnu} Hurd
22624 These commands display information about, respectively, send rights,
22625 receive rights, port rights, port sets, and dead names of a task.
22626 There are also shorthand aliases: @code{info ports} for @code{info
22627 port-rights} and @code{info psets} for @code{info port-sets}.
22629 @item set thread pause
22630 @kindex set thread@r{, Hurd command}
22631 @cindex thread properties, @sc{gnu} Hurd
22632 @cindex pause current thread (@sc{gnu} Hurd)
22633 This command toggles current thread suspension when @value{GDBN} has
22634 control. Setting it to on takes effect immediately, and the current
22635 thread is suspended whenever @value{GDBN} gets control. Setting it to
22636 off will take effect the next time the inferior is continued.
22637 Normally, this command has no effect, since when @value{GDBN} has
22638 control, the whole task is suspended. However, if you used @code{set
22639 task pause off} (see above), this command comes in handy to suspend
22640 only the current thread.
22642 @item show thread pause
22643 @kindex show thread@r{, Hurd command}
22644 This command shows the state of current thread suspension.
22646 @item set thread run
22647 This command sets whether the current thread is allowed to run.
22649 @item show thread run
22650 Show whether the current thread is allowed to run.
22652 @item set thread detach-suspend-count
22653 @cindex thread suspend count, @sc{gnu} Hurd
22654 @cindex detach from thread, @sc{gnu} Hurd
22655 This command sets the suspend count @value{GDBN} will leave on a
22656 thread when detaching. This number is relative to the suspend count
22657 found by @value{GDBN} when it notices the thread; use @code{set thread
22658 takeover-suspend-count} to force it to an absolute value.
22660 @item show thread detach-suspend-count
22661 Show the suspend count @value{GDBN} will leave on the thread when
22664 @item set thread exception-port
22665 @itemx set thread excp
22666 Set the thread exception port to which to forward exceptions. This
22667 overrides the port set by @code{set task exception-port} (see above).
22668 @code{set thread excp} is the shorthand alias.
22670 @item set thread takeover-suspend-count
22671 Normally, @value{GDBN}'s thread suspend counts are relative to the
22672 value @value{GDBN} finds when it notices each thread. This command
22673 changes the suspend counts to be absolute instead.
22675 @item set thread default
22676 @itemx show thread default
22677 @cindex thread default settings, @sc{gnu} Hurd
22678 Each of the above @code{set thread} commands has a @code{set thread
22679 default} counterpart (e.g., @code{set thread default pause}, @code{set
22680 thread default exception-port}, etc.). The @code{thread default}
22681 variety of commands sets the default thread properties for all
22682 threads; you can then change the properties of individual threads with
22683 the non-default commands.
22690 @value{GDBN} provides the following commands specific to the Darwin target:
22693 @item set debug darwin @var{num}
22694 @kindex set debug darwin
22695 When set to a non zero value, enables debugging messages specific to
22696 the Darwin support. Higher values produce more verbose output.
22698 @item show debug darwin
22699 @kindex show debug darwin
22700 Show the current state of Darwin messages.
22702 @item set debug mach-o @var{num}
22703 @kindex set debug mach-o
22704 When set to a non zero value, enables debugging messages while
22705 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22706 file format used on Darwin for object and executable files.) Higher
22707 values produce more verbose output. This is a command to diagnose
22708 problems internal to @value{GDBN} and should not be needed in normal
22711 @item show debug mach-o
22712 @kindex show debug mach-o
22713 Show the current state of Mach-O file messages.
22715 @item set mach-exceptions on
22716 @itemx set mach-exceptions off
22717 @kindex set mach-exceptions
22718 On Darwin, faults are first reported as a Mach exception and are then
22719 mapped to a Posix signal. Use this command to turn on trapping of
22720 Mach exceptions in the inferior. This might be sometimes useful to
22721 better understand the cause of a fault. The default is off.
22723 @item show mach-exceptions
22724 @kindex show mach-exceptions
22725 Show the current state of exceptions trapping.
22730 @section Embedded Operating Systems
22732 This section describes configurations involving the debugging of
22733 embedded operating systems that are available for several different
22736 @value{GDBN} includes the ability to debug programs running on
22737 various real-time operating systems.
22739 @node Embedded Processors
22740 @section Embedded Processors
22742 This section goes into details specific to particular embedded
22745 @cindex send command to simulator
22746 Whenever a specific embedded processor has a simulator, @value{GDBN}
22747 allows to send an arbitrary command to the simulator.
22750 @item sim @var{command}
22751 @kindex sim@r{, a command}
22752 Send an arbitrary @var{command} string to the simulator. Consult the
22753 documentation for the specific simulator in use for information about
22754 acceptable commands.
22759 * ARC:: Synopsys ARC
22761 * M68K:: Motorola M68K
22762 * MicroBlaze:: Xilinx MicroBlaze
22763 * MIPS Embedded:: MIPS Embedded
22764 * OpenRISC 1000:: OpenRISC 1000 (or1k)
22765 * PowerPC Embedded:: PowerPC Embedded
22768 * Super-H:: Renesas Super-H
22772 @subsection Synopsys ARC
22773 @cindex Synopsys ARC
22774 @cindex ARC specific commands
22780 @value{GDBN} provides the following ARC-specific commands:
22783 @item set debug arc
22784 @kindex set debug arc
22785 Control the level of ARC specific debug messages. Use 0 for no messages (the
22786 default), 1 for debug messages, and 2 for even more debug messages.
22788 @item show debug arc
22789 @kindex show debug arc
22790 Show the level of ARC specific debugging in operation.
22792 @item maint print arc arc-instruction @var{address}
22793 @kindex maint print arc arc-instruction
22794 Print internal disassembler information about instruction at a given address.
22801 @value{GDBN} provides the following ARM-specific commands:
22804 @item set arm disassembler
22806 This commands selects from a list of disassembly styles. The
22807 @code{"std"} style is the standard style.
22809 @item show arm disassembler
22811 Show the current disassembly style.
22813 @item set arm apcs32
22814 @cindex ARM 32-bit mode
22815 This command toggles ARM operation mode between 32-bit and 26-bit.
22817 @item show arm apcs32
22818 Display the current usage of the ARM 32-bit mode.
22820 @item set arm fpu @var{fputype}
22821 This command sets the ARM floating-point unit (FPU) type. The
22822 argument @var{fputype} can be one of these:
22826 Determine the FPU type by querying the OS ABI.
22828 Software FPU, with mixed-endian doubles on little-endian ARM
22831 GCC-compiled FPA co-processor.
22833 Software FPU with pure-endian doubles.
22839 Show the current type of the FPU.
22842 This command forces @value{GDBN} to use the specified ABI.
22845 Show the currently used ABI.
22847 @item set arm fallback-mode (arm|thumb|auto)
22848 @value{GDBN} uses the symbol table, when available, to determine
22849 whether instructions are ARM or Thumb. This command controls
22850 @value{GDBN}'s default behavior when the symbol table is not
22851 available. The default is @samp{auto}, which causes @value{GDBN} to
22852 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22855 @item show arm fallback-mode
22856 Show the current fallback instruction mode.
22858 @item set arm force-mode (arm|thumb|auto)
22859 This command overrides use of the symbol table to determine whether
22860 instructions are ARM or Thumb. The default is @samp{auto}, which
22861 causes @value{GDBN} to use the symbol table and then the setting
22862 of @samp{set arm fallback-mode}.
22864 @item show arm force-mode
22865 Show the current forced instruction mode.
22867 @item set debug arm
22868 Toggle whether to display ARM-specific debugging messages from the ARM
22869 target support subsystem.
22871 @item show debug arm
22872 Show whether ARM-specific debugging messages are enabled.
22876 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22877 The @value{GDBN} ARM simulator accepts the following optional arguments.
22880 @item --swi-support=@var{type}
22881 Tell the simulator which SWI interfaces to support. The argument
22882 @var{type} may be a comma separated list of the following values.
22883 The default value is @code{all}.
22898 The Motorola m68k configuration includes ColdFire support.
22901 @subsection MicroBlaze
22902 @cindex Xilinx MicroBlaze
22903 @cindex XMD, Xilinx Microprocessor Debugger
22905 The MicroBlaze is a soft-core processor supported on various Xilinx
22906 FPGAs, such as Spartan or Virtex series. Boards with these processors
22907 usually have JTAG ports which connect to a host system running the Xilinx
22908 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22909 This host system is used to download the configuration bitstream to
22910 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22911 communicates with the target board using the JTAG interface and
22912 presents a @code{gdbserver} interface to the board. By default
22913 @code{xmd} uses port @code{1234}. (While it is possible to change
22914 this default port, it requires the use of undocumented @code{xmd}
22915 commands. Contact Xilinx support if you need to do this.)
22917 Use these GDB commands to connect to the MicroBlaze target processor.
22920 @item target remote :1234
22921 Use this command to connect to the target if you are running @value{GDBN}
22922 on the same system as @code{xmd}.
22924 @item target remote @var{xmd-host}:1234
22925 Use this command to connect to the target if it is connected to @code{xmd}
22926 running on a different system named @var{xmd-host}.
22929 Use this command to download a program to the MicroBlaze target.
22931 @item set debug microblaze @var{n}
22932 Enable MicroBlaze-specific debugging messages if non-zero.
22934 @item show debug microblaze @var{n}
22935 Show MicroBlaze-specific debugging level.
22938 @node MIPS Embedded
22939 @subsection @acronym{MIPS} Embedded
22942 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22945 @item set mipsfpu double
22946 @itemx set mipsfpu single
22947 @itemx set mipsfpu none
22948 @itemx set mipsfpu auto
22949 @itemx show mipsfpu
22950 @kindex set mipsfpu
22951 @kindex show mipsfpu
22952 @cindex @acronym{MIPS} remote floating point
22953 @cindex floating point, @acronym{MIPS} remote
22954 If your target board does not support the @acronym{MIPS} floating point
22955 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22956 need this, you may wish to put the command in your @value{GDBN} init
22957 file). This tells @value{GDBN} how to find the return value of
22958 functions which return floating point values. It also allows
22959 @value{GDBN} to avoid saving the floating point registers when calling
22960 functions on the board. If you are using a floating point coprocessor
22961 with only single precision floating point support, as on the @sc{r4650}
22962 processor, use the command @samp{set mipsfpu single}. The default
22963 double precision floating point coprocessor may be selected using
22964 @samp{set mipsfpu double}.
22966 In previous versions the only choices were double precision or no
22967 floating point, so @samp{set mipsfpu on} will select double precision
22968 and @samp{set mipsfpu off} will select no floating point.
22970 As usual, you can inquire about the @code{mipsfpu} variable with
22971 @samp{show mipsfpu}.
22974 @node OpenRISC 1000
22975 @subsection OpenRISC 1000
22976 @cindex OpenRISC 1000
22979 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
22980 mainly provided as a soft-core which can run on Xilinx, Altera and other
22983 @value{GDBN} for OpenRISC supports the below commands when connecting to
22991 Runs the builtin CPU simulator which can run very basic
22992 programs but does not support most hardware functions like MMU.
22993 For more complex use cases the user is advised to run an external
22994 target, and connect using @samp{target remote}.
22996 Example: @code{target sim}
22998 @item set debug or1k
22999 Toggle whether to display OpenRISC-specific debugging messages from the
23000 OpenRISC target support subsystem.
23002 @item show debug or1k
23003 Show whether OpenRISC-specific debugging messages are enabled.
23006 @node PowerPC Embedded
23007 @subsection PowerPC Embedded
23009 @cindex DVC register
23010 @value{GDBN} supports using the DVC (Data Value Compare) register to
23011 implement in hardware simple hardware watchpoint conditions of the form:
23014 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23015 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23018 The DVC register will be automatically used when @value{GDBN} detects
23019 such pattern in a condition expression, and the created watchpoint uses one
23020 debug register (either the @code{exact-watchpoints} option is on and the
23021 variable is scalar, or the variable has a length of one byte). This feature
23022 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23025 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23026 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23027 in which case watchpoints using only one debug register are created when
23028 watching variables of scalar types.
23030 You can create an artificial array to watch an arbitrary memory
23031 region using one of the following commands (@pxref{Expressions}):
23034 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23035 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23038 PowerPC embedded processors support masked watchpoints. See the discussion
23039 about the @code{mask} argument in @ref{Set Watchpoints}.
23041 @cindex ranged breakpoint
23042 PowerPC embedded processors support hardware accelerated
23043 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23044 the inferior whenever it executes an instruction at any address within
23045 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23046 use the @code{break-range} command.
23048 @value{GDBN} provides the following PowerPC-specific commands:
23051 @kindex break-range
23052 @item break-range @var{start-location}, @var{end-location}
23053 Set a breakpoint for an address range given by
23054 @var{start-location} and @var{end-location}, which can specify a function name,
23055 a line number, an offset of lines from the current line or from the start
23056 location, or an address of an instruction (see @ref{Specify Location},
23057 for a list of all the possible ways to specify a @var{location}.)
23058 The breakpoint will stop execution of the inferior whenever it
23059 executes an instruction at any address within the specified range,
23060 (including @var{start-location} and @var{end-location}.)
23062 @kindex set powerpc
23063 @item set powerpc soft-float
23064 @itemx show powerpc soft-float
23065 Force @value{GDBN} to use (or not use) a software floating point calling
23066 convention. By default, @value{GDBN} selects the calling convention based
23067 on the selected architecture and the provided executable file.
23069 @item set powerpc vector-abi
23070 @itemx show powerpc vector-abi
23071 Force @value{GDBN} to use the specified calling convention for vector
23072 arguments and return values. The valid options are @samp{auto};
23073 @samp{generic}, to avoid vector registers even if they are present;
23074 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23075 registers. By default, @value{GDBN} selects the calling convention
23076 based on the selected architecture and the provided executable file.
23078 @item set powerpc exact-watchpoints
23079 @itemx show powerpc exact-watchpoints
23080 Allow @value{GDBN} to use only one debug register when watching a variable
23081 of scalar type, thus assuming that the variable is accessed through the
23082 address of its first byte.
23087 @subsection Atmel AVR
23090 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23091 following AVR-specific commands:
23094 @item info io_registers
23095 @kindex info io_registers@r{, AVR}
23096 @cindex I/O registers (Atmel AVR)
23097 This command displays information about the AVR I/O registers. For
23098 each register, @value{GDBN} prints its number and value.
23105 When configured for debugging CRIS, @value{GDBN} provides the
23106 following CRIS-specific commands:
23109 @item set cris-version @var{ver}
23110 @cindex CRIS version
23111 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23112 The CRIS version affects register names and sizes. This command is useful in
23113 case autodetection of the CRIS version fails.
23115 @item show cris-version
23116 Show the current CRIS version.
23118 @item set cris-dwarf2-cfi
23119 @cindex DWARF-2 CFI and CRIS
23120 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23121 Change to @samp{off} when using @code{gcc-cris} whose version is below
23124 @item show cris-dwarf2-cfi
23125 Show the current state of using DWARF-2 CFI.
23127 @item set cris-mode @var{mode}
23129 Set the current CRIS mode to @var{mode}. It should only be changed when
23130 debugging in guru mode, in which case it should be set to
23131 @samp{guru} (the default is @samp{normal}).
23133 @item show cris-mode
23134 Show the current CRIS mode.
23138 @subsection Renesas Super-H
23141 For the Renesas Super-H processor, @value{GDBN} provides these
23145 @item set sh calling-convention @var{convention}
23146 @kindex set sh calling-convention
23147 Set the calling-convention used when calling functions from @value{GDBN}.
23148 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23149 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23150 convention. If the DWARF-2 information of the called function specifies
23151 that the function follows the Renesas calling convention, the function
23152 is called using the Renesas calling convention. If the calling convention
23153 is set to @samp{renesas}, the Renesas calling convention is always used,
23154 regardless of the DWARF-2 information. This can be used to override the
23155 default of @samp{gcc} if debug information is missing, or the compiler
23156 does not emit the DWARF-2 calling convention entry for a function.
23158 @item show sh calling-convention
23159 @kindex show sh calling-convention
23160 Show the current calling convention setting.
23165 @node Architectures
23166 @section Architectures
23168 This section describes characteristics of architectures that affect
23169 all uses of @value{GDBN} with the architecture, both native and cross.
23176 * HPPA:: HP PA architecture
23177 * SPU:: Cell Broadband Engine SPU architecture
23184 @subsection AArch64
23185 @cindex AArch64 support
23187 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23188 following special commands:
23191 @item set debug aarch64
23192 @kindex set debug aarch64
23193 This command determines whether AArch64 architecture-specific debugging
23194 messages are to be displayed.
23196 @item show debug aarch64
23197 Show whether AArch64 debugging messages are displayed.
23202 @subsection x86 Architecture-specific Issues
23205 @item set struct-convention @var{mode}
23206 @kindex set struct-convention
23207 @cindex struct return convention
23208 @cindex struct/union returned in registers
23209 Set the convention used by the inferior to return @code{struct}s and
23210 @code{union}s from functions to @var{mode}. Possible values of
23211 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23212 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23213 are returned on the stack, while @code{"reg"} means that a
23214 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23215 be returned in a register.
23217 @item show struct-convention
23218 @kindex show struct-convention
23219 Show the current setting of the convention to return @code{struct}s
23224 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23225 @cindex Intel Memory Protection Extensions (MPX).
23227 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23228 @footnote{The register named with capital letters represent the architecture
23229 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23230 which are the lower bound and upper bound. Bounds are effective addresses or
23231 memory locations. The upper bounds are architecturally represented in 1's
23232 complement form. A bound having lower bound = 0, and upper bound = 0
23233 (1's complement of all bits set) will allow access to the entire address space.
23235 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23236 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23237 display the upper bound performing the complement of one operation on the
23238 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23239 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23240 can also be noted that the upper bounds are inclusive.
23242 As an example, assume that the register BND0 holds bounds for a pointer having
23243 access allowed for the range between 0x32 and 0x71. The values present on
23244 bnd0raw and bnd registers are presented as follows:
23247 bnd0raw = @{0x32, 0xffffffff8e@}
23248 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23251 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23252 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23253 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23254 Python, the display includes the memory size, in bits, accessible to
23257 Bounds can also be stored in bounds tables, which are stored in
23258 application memory. These tables store bounds for pointers by specifying
23259 the bounds pointer's value along with its bounds. Evaluating and changing
23260 bounds located in bound tables is therefore interesting while investigating
23261 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23264 @item show mpx bound @var{pointer}
23265 @kindex show mpx bound
23266 Display bounds of the given @var{pointer}.
23268 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23269 @kindex set mpx bound
23270 Set the bounds of a pointer in the bound table.
23271 This command takes three parameters: @var{pointer} is the pointers
23272 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23273 for lower and upper bounds respectively.
23276 When you call an inferior function on an Intel MPX enabled program,
23277 GDB sets the inferior's bound registers to the init (disabled) state
23278 before calling the function. As a consequence, bounds checks for the
23279 pointer arguments passed to the function will always pass.
23281 This is necessary because when you call an inferior function, the
23282 program is usually in the middle of the execution of other function.
23283 Since at that point bound registers are in an arbitrary state, not
23284 clearing them would lead to random bound violations in the called
23287 You can still examine the influence of the bound registers on the
23288 execution of the called function by stopping the execution of the
23289 called function at its prologue, setting bound registers, and
23290 continuing the execution. For example:
23294 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23295 $ print upper (a, b, c, d, 1)
23296 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23298 @{lbound = 0x0, ubound = ffffffff@} : size -1
23301 At this last step the value of bnd0 can be changed for investigation of bound
23302 violations caused along the execution of the call. In order to know how to
23303 set the bound registers or bound table for the call consult the ABI.
23308 See the following section.
23311 @subsection @acronym{MIPS}
23313 @cindex stack on Alpha
23314 @cindex stack on @acronym{MIPS}
23315 @cindex Alpha stack
23316 @cindex @acronym{MIPS} stack
23317 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23318 sometimes requires @value{GDBN} to search backward in the object code to
23319 find the beginning of a function.
23321 @cindex response time, @acronym{MIPS} debugging
23322 To improve response time (especially for embedded applications, where
23323 @value{GDBN} may be restricted to a slow serial line for this search)
23324 you may want to limit the size of this search, using one of these
23328 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23329 @item set heuristic-fence-post @var{limit}
23330 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23331 search for the beginning of a function. A value of @var{0} (the
23332 default) means there is no limit. However, except for @var{0}, the
23333 larger the limit the more bytes @code{heuristic-fence-post} must search
23334 and therefore the longer it takes to run. You should only need to use
23335 this command when debugging a stripped executable.
23337 @item show heuristic-fence-post
23338 Display the current limit.
23342 These commands are available @emph{only} when @value{GDBN} is configured
23343 for debugging programs on Alpha or @acronym{MIPS} processors.
23345 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23349 @item set mips abi @var{arg}
23350 @kindex set mips abi
23351 @cindex set ABI for @acronym{MIPS}
23352 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23353 values of @var{arg} are:
23357 The default ABI associated with the current binary (this is the
23367 @item show mips abi
23368 @kindex show mips abi
23369 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23371 @item set mips compression @var{arg}
23372 @kindex set mips compression
23373 @cindex code compression, @acronym{MIPS}
23374 Tell @value{GDBN} which @acronym{MIPS} compressed
23375 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23376 inferior. @value{GDBN} uses this for code disassembly and other
23377 internal interpretation purposes. This setting is only referred to
23378 when no executable has been associated with the debugging session or
23379 the executable does not provide information about the encoding it uses.
23380 Otherwise this setting is automatically updated from information
23381 provided by the executable.
23383 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23384 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23385 executables containing @acronym{MIPS16} code frequently are not
23386 identified as such.
23388 This setting is ``sticky''; that is, it retains its value across
23389 debugging sessions until reset either explicitly with this command or
23390 implicitly from an executable.
23392 The compiler and/or assembler typically add symbol table annotations to
23393 identify functions compiled for the @acronym{MIPS16} or
23394 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23395 are present, @value{GDBN} uses them in preference to the global
23396 compressed @acronym{ISA} encoding setting.
23398 @item show mips compression
23399 @kindex show mips compression
23400 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23401 @value{GDBN} to debug the inferior.
23404 @itemx show mipsfpu
23405 @xref{MIPS Embedded, set mipsfpu}.
23407 @item set mips mask-address @var{arg}
23408 @kindex set mips mask-address
23409 @cindex @acronym{MIPS} addresses, masking
23410 This command determines whether the most-significant 32 bits of 64-bit
23411 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23412 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23413 setting, which lets @value{GDBN} determine the correct value.
23415 @item show mips mask-address
23416 @kindex show mips mask-address
23417 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23420 @item set remote-mips64-transfers-32bit-regs
23421 @kindex set remote-mips64-transfers-32bit-regs
23422 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23423 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23424 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23425 and 64 bits for other registers, set this option to @samp{on}.
23427 @item show remote-mips64-transfers-32bit-regs
23428 @kindex show remote-mips64-transfers-32bit-regs
23429 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23431 @item set debug mips
23432 @kindex set debug mips
23433 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23434 target code in @value{GDBN}.
23436 @item show debug mips
23437 @kindex show debug mips
23438 Show the current setting of @acronym{MIPS} debugging messages.
23444 @cindex HPPA support
23446 When @value{GDBN} is debugging the HP PA architecture, it provides the
23447 following special commands:
23450 @item set debug hppa
23451 @kindex set debug hppa
23452 This command determines whether HPPA architecture-specific debugging
23453 messages are to be displayed.
23455 @item show debug hppa
23456 Show whether HPPA debugging messages are displayed.
23458 @item maint print unwind @var{address}
23459 @kindex maint print unwind@r{, HPPA}
23460 This command displays the contents of the unwind table entry at the
23461 given @var{address}.
23467 @subsection Cell Broadband Engine SPU architecture
23468 @cindex Cell Broadband Engine
23471 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23472 it provides the following special commands:
23475 @item info spu event
23477 Display SPU event facility status. Shows current event mask
23478 and pending event status.
23480 @item info spu signal
23481 Display SPU signal notification facility status. Shows pending
23482 signal-control word and signal notification mode of both signal
23483 notification channels.
23485 @item info spu mailbox
23486 Display SPU mailbox facility status. Shows all pending entries,
23487 in order of processing, in each of the SPU Write Outbound,
23488 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23491 Display MFC DMA status. Shows all pending commands in the MFC
23492 DMA queue. For each entry, opcode, tag, class IDs, effective
23493 and local store addresses and transfer size are shown.
23495 @item info spu proxydma
23496 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23497 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23498 and local store addresses and transfer size are shown.
23502 When @value{GDBN} is debugging a combined PowerPC/SPU application
23503 on the Cell Broadband Engine, it provides in addition the following
23507 @item set spu stop-on-load @var{arg}
23509 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23510 will give control to the user when a new SPE thread enters its @code{main}
23511 function. The default is @code{off}.
23513 @item show spu stop-on-load
23515 Show whether to stop for new SPE threads.
23517 @item set spu auto-flush-cache @var{arg}
23518 Set whether to automatically flush the software-managed cache. When set to
23519 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23520 cache to be flushed whenever SPE execution stops. This provides a consistent
23521 view of PowerPC memory that is accessed via the cache. If an application
23522 does not use the software-managed cache, this option has no effect.
23524 @item show spu auto-flush-cache
23525 Show whether to automatically flush the software-managed cache.
23530 @subsection PowerPC
23531 @cindex PowerPC architecture
23533 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23534 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23535 numbers stored in the floating point registers. These values must be stored
23536 in two consecutive registers, always starting at an even register like
23537 @code{f0} or @code{f2}.
23539 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23540 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23541 @code{f2} and @code{f3} for @code{$dl1} and so on.
23543 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23544 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23547 @subsection Nios II
23548 @cindex Nios II architecture
23550 When @value{GDBN} is debugging the Nios II architecture,
23551 it provides the following special commands:
23555 @item set debug nios2
23556 @kindex set debug nios2
23557 This command turns on and off debugging messages for the Nios II
23558 target code in @value{GDBN}.
23560 @item show debug nios2
23561 @kindex show debug nios2
23562 Show the current setting of Nios II debugging messages.
23566 @subsection Sparc64
23567 @cindex Sparc64 support
23568 @cindex Application Data Integrity
23569 @subsubsection ADI Support
23571 The M7 processor supports an Application Data Integrity (ADI) feature that
23572 detects invalid data accesses. When software allocates memory and enables
23573 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23574 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23575 the 4-bit version in every cacheline of that data. Hardware saves the latter
23576 in spare bits in the cache and memory hierarchy. On each load and store,
23577 the processor compares the upper 4 VA (virtual address) bits to the
23578 cacheline's version. If there is a mismatch, the processor generates a
23579 version mismatch trap which can be either precise or disrupting. The trap
23580 is an error condition which the kernel delivers to the process as a SIGSEGV
23583 Note that only 64-bit applications can use ADI and need to be built with
23586 Values of the ADI version tags, which are in granularity of a
23587 cacheline (64 bytes), can be viewed or modified.
23591 @kindex adi examine
23592 @item adi (examine | x) [ / @var{n} ] @var{addr}
23594 The @code{adi examine} command displays the value of one ADI version tag per
23597 @var{n} is a decimal integer specifying the number in bytes; the default
23598 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23599 block size, to display.
23601 @var{addr} is the address in user address space where you want @value{GDBN}
23602 to begin displaying the ADI version tags.
23604 Below is an example of displaying ADI versions of variable "shmaddr".
23607 (@value{GDBP}) adi x/100 shmaddr
23608 0xfff800010002c000: 0 0
23612 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23614 The @code{adi assign} command is used to assign new ADI version tag
23617 @var{n} is a decimal integer specifying the number in bytes;
23618 the default is 1. It specifies how much ADI version information, at the
23619 ratio of 1:ADI block size, to modify.
23621 @var{addr} is the address in user address space where you want @value{GDBN}
23622 to begin modifying the ADI version tags.
23624 @var{tag} is the new ADI version tag.
23626 For example, do the following to modify then verify ADI versions of
23627 variable "shmaddr":
23630 (@value{GDBP}) adi a/100 shmaddr = 7
23631 (@value{GDBP}) adi x/100 shmaddr
23632 0xfff800010002c000: 7 7
23637 @node Controlling GDB
23638 @chapter Controlling @value{GDBN}
23640 You can alter the way @value{GDBN} interacts with you by using the
23641 @code{set} command. For commands controlling how @value{GDBN} displays
23642 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23647 * Editing:: Command editing
23648 * Command History:: Command history
23649 * Screen Size:: Screen size
23650 * Numbers:: Numbers
23651 * ABI:: Configuring the current ABI
23652 * Auto-loading:: Automatically loading associated files
23653 * Messages/Warnings:: Optional warnings and messages
23654 * Debugging Output:: Optional messages about internal happenings
23655 * Other Misc Settings:: Other Miscellaneous Settings
23663 @value{GDBN} indicates its readiness to read a command by printing a string
23664 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23665 can change the prompt string with the @code{set prompt} command. For
23666 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23667 the prompt in one of the @value{GDBN} sessions so that you can always tell
23668 which one you are talking to.
23670 @emph{Note:} @code{set prompt} does not add a space for you after the
23671 prompt you set. This allows you to set a prompt which ends in a space
23672 or a prompt that does not.
23676 @item set prompt @var{newprompt}
23677 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23679 @kindex show prompt
23681 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23684 Versions of @value{GDBN} that ship with Python scripting enabled have
23685 prompt extensions. The commands for interacting with these extensions
23689 @kindex set extended-prompt
23690 @item set extended-prompt @var{prompt}
23691 Set an extended prompt that allows for substitutions.
23692 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23693 substitution. Any escape sequences specified as part of the prompt
23694 string are replaced with the corresponding strings each time the prompt
23700 set extended-prompt Current working directory: \w (gdb)
23703 Note that when an extended-prompt is set, it takes control of the
23704 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23706 @kindex show extended-prompt
23707 @item show extended-prompt
23708 Prints the extended prompt. Any escape sequences specified as part of
23709 the prompt string with @code{set extended-prompt}, are replaced with the
23710 corresponding strings each time the prompt is displayed.
23714 @section Command Editing
23716 @cindex command line editing
23718 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23719 @sc{gnu} library provides consistent behavior for programs which provide a
23720 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23721 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23722 substitution, and a storage and recall of command history across
23723 debugging sessions.
23725 You may control the behavior of command line editing in @value{GDBN} with the
23726 command @code{set}.
23729 @kindex set editing
23732 @itemx set editing on
23733 Enable command line editing (enabled by default).
23735 @item set editing off
23736 Disable command line editing.
23738 @kindex show editing
23740 Show whether command line editing is enabled.
23743 @ifset SYSTEM_READLINE
23744 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23746 @ifclear SYSTEM_READLINE
23747 @xref{Command Line Editing},
23749 for more details about the Readline
23750 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23751 encouraged to read that chapter.
23753 @node Command History
23754 @section Command History
23755 @cindex command history
23757 @value{GDBN} can keep track of the commands you type during your
23758 debugging sessions, so that you can be certain of precisely what
23759 happened. Use these commands to manage the @value{GDBN} command
23762 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23763 package, to provide the history facility.
23764 @ifset SYSTEM_READLINE
23765 @xref{Using History Interactively, , , history, GNU History Library},
23767 @ifclear SYSTEM_READLINE
23768 @xref{Using History Interactively},
23770 for the detailed description of the History library.
23772 To issue a command to @value{GDBN} without affecting certain aspects of
23773 the state which is seen by users, prefix it with @samp{server }
23774 (@pxref{Server Prefix}). This
23775 means that this command will not affect the command history, nor will it
23776 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23777 pressed on a line by itself.
23779 @cindex @code{server}, command prefix
23780 The server prefix does not affect the recording of values into the value
23781 history; to print a value without recording it into the value history,
23782 use the @code{output} command instead of the @code{print} command.
23784 Here is the description of @value{GDBN} commands related to command
23788 @cindex history substitution
23789 @cindex history file
23790 @kindex set history filename
23791 @cindex @env{GDBHISTFILE}, environment variable
23792 @item set history filename @var{fname}
23793 Set the name of the @value{GDBN} command history file to @var{fname}.
23794 This is the file where @value{GDBN} reads an initial command history
23795 list, and where it writes the command history from this session when it
23796 exits. You can access this list through history expansion or through
23797 the history command editing characters listed below. This file defaults
23798 to the value of the environment variable @code{GDBHISTFILE}, or to
23799 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23802 @cindex save command history
23803 @kindex set history save
23804 @item set history save
23805 @itemx set history save on
23806 Record command history in a file, whose name may be specified with the
23807 @code{set history filename} command. By default, this option is disabled.
23809 @item set history save off
23810 Stop recording command history in a file.
23812 @cindex history size
23813 @kindex set history size
23814 @cindex @env{GDBHISTSIZE}, environment variable
23815 @item set history size @var{size}
23816 @itemx set history size unlimited
23817 Set the number of commands which @value{GDBN} keeps in its history list.
23818 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23819 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23820 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23821 either a negative number or the empty string, then the number of commands
23822 @value{GDBN} keeps in the history list is unlimited.
23824 @cindex remove duplicate history
23825 @kindex set history remove-duplicates
23826 @item set history remove-duplicates @var{count}
23827 @itemx set history remove-duplicates unlimited
23828 Control the removal of duplicate history entries in the command history list.
23829 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23830 history entries and remove the first entry that is a duplicate of the current
23831 entry being added to the command history list. If @var{count} is
23832 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23833 removal of duplicate history entries is disabled.
23835 Only history entries added during the current session are considered for
23836 removal. This option is set to 0 by default.
23840 History expansion assigns special meaning to the character @kbd{!}.
23841 @ifset SYSTEM_READLINE
23842 @xref{Event Designators, , , history, GNU History Library},
23844 @ifclear SYSTEM_READLINE
23845 @xref{Event Designators},
23849 @cindex history expansion, turn on/off
23850 Since @kbd{!} is also the logical not operator in C, history expansion
23851 is off by default. If you decide to enable history expansion with the
23852 @code{set history expansion on} command, you may sometimes need to
23853 follow @kbd{!} (when it is used as logical not, in an expression) with
23854 a space or a tab to prevent it from being expanded. The readline
23855 history facilities do not attempt substitution on the strings
23856 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23858 The commands to control history expansion are:
23861 @item set history expansion on
23862 @itemx set history expansion
23863 @kindex set history expansion
23864 Enable history expansion. History expansion is off by default.
23866 @item set history expansion off
23867 Disable history expansion.
23870 @kindex show history
23872 @itemx show history filename
23873 @itemx show history save
23874 @itemx show history size
23875 @itemx show history expansion
23876 These commands display the state of the @value{GDBN} history parameters.
23877 @code{show history} by itself displays all four states.
23882 @kindex show commands
23883 @cindex show last commands
23884 @cindex display command history
23885 @item show commands
23886 Display the last ten commands in the command history.
23888 @item show commands @var{n}
23889 Print ten commands centered on command number @var{n}.
23891 @item show commands +
23892 Print ten commands just after the commands last printed.
23896 @section Screen Size
23897 @cindex size of screen
23898 @cindex screen size
23901 @cindex pauses in output
23903 Certain commands to @value{GDBN} may produce large amounts of
23904 information output to the screen. To help you read all of it,
23905 @value{GDBN} pauses and asks you for input at the end of each page of
23906 output. Type @key{RET} when you want to see one more page of output,
23907 @kbd{q} to discard the remaining output, or @kbd{c} to continue
23908 without paging for the rest of the current command. Also, the screen
23909 width setting determines when to wrap lines of output. Depending on
23910 what is being printed, @value{GDBN} tries to break the line at a
23911 readable place, rather than simply letting it overflow onto the
23914 Normally @value{GDBN} knows the size of the screen from the terminal
23915 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23916 together with the value of the @code{TERM} environment variable and the
23917 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23918 you can override it with the @code{set height} and @code{set
23925 @kindex show height
23926 @item set height @var{lpp}
23927 @itemx set height unlimited
23929 @itemx set width @var{cpl}
23930 @itemx set width unlimited
23932 These @code{set} commands specify a screen height of @var{lpp} lines and
23933 a screen width of @var{cpl} characters. The associated @code{show}
23934 commands display the current settings.
23936 If you specify a height of either @code{unlimited} or zero lines,
23937 @value{GDBN} does not pause during output no matter how long the
23938 output is. This is useful if output is to a file or to an editor
23941 Likewise, you can specify @samp{set width unlimited} or @samp{set
23942 width 0} to prevent @value{GDBN} from wrapping its output.
23944 @item set pagination on
23945 @itemx set pagination off
23946 @kindex set pagination
23947 Turn the output pagination on or off; the default is on. Turning
23948 pagination off is the alternative to @code{set height unlimited}. Note that
23949 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23950 Options, -batch}) also automatically disables pagination.
23952 @item show pagination
23953 @kindex show pagination
23954 Show the current pagination mode.
23959 @cindex number representation
23960 @cindex entering numbers
23962 You can always enter numbers in octal, decimal, or hexadecimal in
23963 @value{GDBN} by the usual conventions: octal numbers begin with
23964 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23965 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23966 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23967 10; likewise, the default display for numbers---when no particular
23968 format is specified---is base 10. You can change the default base for
23969 both input and output with the commands described below.
23972 @kindex set input-radix
23973 @item set input-radix @var{base}
23974 Set the default base for numeric input. Supported choices
23975 for @var{base} are decimal 8, 10, or 16. The base must itself be
23976 specified either unambiguously or using the current input radix; for
23980 set input-radix 012
23981 set input-radix 10.
23982 set input-radix 0xa
23986 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23987 leaves the input radix unchanged, no matter what it was, since
23988 @samp{10}, being without any leading or trailing signs of its base, is
23989 interpreted in the current radix. Thus, if the current radix is 16,
23990 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23993 @kindex set output-radix
23994 @item set output-radix @var{base}
23995 Set the default base for numeric display. Supported choices
23996 for @var{base} are decimal 8, 10, or 16. The base must itself be
23997 specified either unambiguously or using the current input radix.
23999 @kindex show input-radix
24000 @item show input-radix
24001 Display the current default base for numeric input.
24003 @kindex show output-radix
24004 @item show output-radix
24005 Display the current default base for numeric display.
24007 @item set radix @r{[}@var{base}@r{]}
24011 These commands set and show the default base for both input and output
24012 of numbers. @code{set radix} sets the radix of input and output to
24013 the same base; without an argument, it resets the radix back to its
24014 default value of 10.
24019 @section Configuring the Current ABI
24021 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24022 application automatically. However, sometimes you need to override its
24023 conclusions. Use these commands to manage @value{GDBN}'s view of the
24029 @cindex Newlib OS ABI and its influence on the longjmp handling
24031 One @value{GDBN} configuration can debug binaries for multiple operating
24032 system targets, either via remote debugging or native emulation.
24033 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24034 but you can override its conclusion using the @code{set osabi} command.
24035 One example where this is useful is in debugging of binaries which use
24036 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24037 not have the same identifying marks that the standard C library for your
24040 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24041 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24042 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24043 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24047 Show the OS ABI currently in use.
24050 With no argument, show the list of registered available OS ABI's.
24052 @item set osabi @var{abi}
24053 Set the current OS ABI to @var{abi}.
24056 @cindex float promotion
24058 Generally, the way that an argument of type @code{float} is passed to a
24059 function depends on whether the function is prototyped. For a prototyped
24060 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24061 according to the architecture's convention for @code{float}. For unprototyped
24062 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24063 @code{double} and then passed.
24065 Unfortunately, some forms of debug information do not reliably indicate whether
24066 a function is prototyped. If @value{GDBN} calls a function that is not marked
24067 as prototyped, it consults @kbd{set coerce-float-to-double}.
24070 @kindex set coerce-float-to-double
24071 @item set coerce-float-to-double
24072 @itemx set coerce-float-to-double on
24073 Arguments of type @code{float} will be promoted to @code{double} when passed
24074 to an unprototyped function. This is the default setting.
24076 @item set coerce-float-to-double off
24077 Arguments of type @code{float} will be passed directly to unprototyped
24080 @kindex show coerce-float-to-double
24081 @item show coerce-float-to-double
24082 Show the current setting of promoting @code{float} to @code{double}.
24086 @kindex show cp-abi
24087 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24088 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24089 used to build your application. @value{GDBN} only fully supports
24090 programs with a single C@t{++} ABI; if your program contains code using
24091 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24092 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24093 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24094 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24095 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24096 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24101 Show the C@t{++} ABI currently in use.
24104 With no argument, show the list of supported C@t{++} ABI's.
24106 @item set cp-abi @var{abi}
24107 @itemx set cp-abi auto
24108 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24112 @section Automatically loading associated files
24113 @cindex auto-loading
24115 @value{GDBN} sometimes reads files with commands and settings automatically,
24116 without being explicitly told so by the user. We call this feature
24117 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24118 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24119 results or introduce security risks (e.g., if the file comes from untrusted
24123 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24124 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24126 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24127 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24130 There are various kinds of files @value{GDBN} can automatically load.
24131 In addition to these files, @value{GDBN} supports auto-loading code written
24132 in various extension languages. @xref{Auto-loading extensions}.
24134 Note that loading of these associated files (including the local @file{.gdbinit}
24135 file) requires accordingly configured @code{auto-load safe-path}
24136 (@pxref{Auto-loading safe path}).
24138 For these reasons, @value{GDBN} includes commands and options to let you
24139 control when to auto-load files and which files should be auto-loaded.
24142 @anchor{set auto-load off}
24143 @kindex set auto-load off
24144 @item set auto-load off
24145 Globally disable loading of all auto-loaded files.
24146 You may want to use this command with the @samp{-iex} option
24147 (@pxref{Option -init-eval-command}) such as:
24149 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24152 Be aware that system init file (@pxref{System-wide configuration})
24153 and init files from your home directory (@pxref{Home Directory Init File})
24154 still get read (as they come from generally trusted directories).
24155 To prevent @value{GDBN} from auto-loading even those init files, use the
24156 @option{-nx} option (@pxref{Mode Options}), in addition to
24157 @code{set auto-load no}.
24159 @anchor{show auto-load}
24160 @kindex show auto-load
24161 @item show auto-load
24162 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24166 (gdb) show auto-load
24167 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24168 libthread-db: Auto-loading of inferior specific libthread_db is on.
24169 local-gdbinit: Auto-loading of .gdbinit script from current directory
24171 python-scripts: Auto-loading of Python scripts is on.
24172 safe-path: List of directories from which it is safe to auto-load files
24173 is $debugdir:$datadir/auto-load.
24174 scripts-directory: List of directories from which to load auto-loaded scripts
24175 is $debugdir:$datadir/auto-load.
24178 @anchor{info auto-load}
24179 @kindex info auto-load
24180 @item info auto-load
24181 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24185 (gdb) info auto-load
24188 Yes /home/user/gdb/gdb-gdb.gdb
24189 libthread-db: No auto-loaded libthread-db.
24190 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24194 Yes /home/user/gdb/gdb-gdb.py
24198 These are @value{GDBN} control commands for the auto-loading:
24200 @multitable @columnfractions .5 .5
24201 @item @xref{set auto-load off}.
24202 @tab Disable auto-loading globally.
24203 @item @xref{show auto-load}.
24204 @tab Show setting of all kinds of files.
24205 @item @xref{info auto-load}.
24206 @tab Show state of all kinds of files.
24207 @item @xref{set auto-load gdb-scripts}.
24208 @tab Control for @value{GDBN} command scripts.
24209 @item @xref{show auto-load gdb-scripts}.
24210 @tab Show setting of @value{GDBN} command scripts.
24211 @item @xref{info auto-load gdb-scripts}.
24212 @tab Show state of @value{GDBN} command scripts.
24213 @item @xref{set auto-load python-scripts}.
24214 @tab Control for @value{GDBN} Python scripts.
24215 @item @xref{show auto-load python-scripts}.
24216 @tab Show setting of @value{GDBN} Python scripts.
24217 @item @xref{info auto-load python-scripts}.
24218 @tab Show state of @value{GDBN} Python scripts.
24219 @item @xref{set auto-load guile-scripts}.
24220 @tab Control for @value{GDBN} Guile scripts.
24221 @item @xref{show auto-load guile-scripts}.
24222 @tab Show setting of @value{GDBN} Guile scripts.
24223 @item @xref{info auto-load guile-scripts}.
24224 @tab Show state of @value{GDBN} Guile scripts.
24225 @item @xref{set auto-load scripts-directory}.
24226 @tab Control for @value{GDBN} auto-loaded scripts location.
24227 @item @xref{show auto-load scripts-directory}.
24228 @tab Show @value{GDBN} auto-loaded scripts location.
24229 @item @xref{add-auto-load-scripts-directory}.
24230 @tab Add directory for auto-loaded scripts location list.
24231 @item @xref{set auto-load local-gdbinit}.
24232 @tab Control for init file in the current directory.
24233 @item @xref{show auto-load local-gdbinit}.
24234 @tab Show setting of init file in the current directory.
24235 @item @xref{info auto-load local-gdbinit}.
24236 @tab Show state of init file in the current directory.
24237 @item @xref{set auto-load libthread-db}.
24238 @tab Control for thread debugging library.
24239 @item @xref{show auto-load libthread-db}.
24240 @tab Show setting of thread debugging library.
24241 @item @xref{info auto-load libthread-db}.
24242 @tab Show state of thread debugging library.
24243 @item @xref{set auto-load safe-path}.
24244 @tab Control directories trusted for automatic loading.
24245 @item @xref{show auto-load safe-path}.
24246 @tab Show directories trusted for automatic loading.
24247 @item @xref{add-auto-load-safe-path}.
24248 @tab Add directory trusted for automatic loading.
24251 @node Init File in the Current Directory
24252 @subsection Automatically loading init file in the current directory
24253 @cindex auto-loading init file in the current directory
24255 By default, @value{GDBN} reads and executes the canned sequences of commands
24256 from init file (if any) in the current working directory,
24257 see @ref{Init File in the Current Directory during Startup}.
24259 Note that loading of this local @file{.gdbinit} file also requires accordingly
24260 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24263 @anchor{set auto-load local-gdbinit}
24264 @kindex set auto-load local-gdbinit
24265 @item set auto-load local-gdbinit [on|off]
24266 Enable or disable the auto-loading of canned sequences of commands
24267 (@pxref{Sequences}) found in init file in the current directory.
24269 @anchor{show auto-load local-gdbinit}
24270 @kindex show auto-load local-gdbinit
24271 @item show auto-load local-gdbinit
24272 Show whether auto-loading of canned sequences of commands from init file in the
24273 current directory is enabled or disabled.
24275 @anchor{info auto-load local-gdbinit}
24276 @kindex info auto-load local-gdbinit
24277 @item info auto-load local-gdbinit
24278 Print whether canned sequences of commands from init file in the
24279 current directory have been auto-loaded.
24282 @node libthread_db.so.1 file
24283 @subsection Automatically loading thread debugging library
24284 @cindex auto-loading libthread_db.so.1
24286 This feature is currently present only on @sc{gnu}/Linux native hosts.
24288 @value{GDBN} reads in some cases thread debugging library from places specific
24289 to the inferior (@pxref{set libthread-db-search-path}).
24291 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24292 without checking this @samp{set auto-load libthread-db} switch as system
24293 libraries have to be trusted in general. In all other cases of
24294 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24295 auto-load libthread-db} is enabled before trying to open such thread debugging
24298 Note that loading of this debugging library also requires accordingly configured
24299 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24302 @anchor{set auto-load libthread-db}
24303 @kindex set auto-load libthread-db
24304 @item set auto-load libthread-db [on|off]
24305 Enable or disable the auto-loading of inferior specific thread debugging library.
24307 @anchor{show auto-load libthread-db}
24308 @kindex show auto-load libthread-db
24309 @item show auto-load libthread-db
24310 Show whether auto-loading of inferior specific thread debugging library is
24311 enabled or disabled.
24313 @anchor{info auto-load libthread-db}
24314 @kindex info auto-load libthread-db
24315 @item info auto-load libthread-db
24316 Print the list of all loaded inferior specific thread debugging libraries and
24317 for each such library print list of inferior @var{pid}s using it.
24320 @node Auto-loading safe path
24321 @subsection Security restriction for auto-loading
24322 @cindex auto-loading safe-path
24324 As the files of inferior can come from untrusted source (such as submitted by
24325 an application user) @value{GDBN} does not always load any files automatically.
24326 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24327 directories trusted for loading files not explicitly requested by user.
24328 Each directory can also be a shell wildcard pattern.
24330 If the path is not set properly you will see a warning and the file will not
24335 Reading symbols from /home/user/gdb/gdb...done.
24336 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24337 declined by your `auto-load safe-path' set
24338 to "$debugdir:$datadir/auto-load".
24339 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24340 declined by your `auto-load safe-path' set
24341 to "$debugdir:$datadir/auto-load".
24345 To instruct @value{GDBN} to go ahead and use the init files anyway,
24346 invoke @value{GDBN} like this:
24349 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24352 The list of trusted directories is controlled by the following commands:
24355 @anchor{set auto-load safe-path}
24356 @kindex set auto-load safe-path
24357 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24358 Set the list of directories (and their subdirectories) trusted for automatic
24359 loading and execution of scripts. You can also enter a specific trusted file.
24360 Each directory can also be a shell wildcard pattern; wildcards do not match
24361 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24362 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24363 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24364 its default value as specified during @value{GDBN} compilation.
24366 The list of directories uses path separator (@samp{:} on GNU and Unix
24367 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24368 to the @env{PATH} environment variable.
24370 @anchor{show auto-load safe-path}
24371 @kindex show auto-load safe-path
24372 @item show auto-load safe-path
24373 Show the list of directories trusted for automatic loading and execution of
24376 @anchor{add-auto-load-safe-path}
24377 @kindex add-auto-load-safe-path
24378 @item add-auto-load-safe-path
24379 Add an entry (or list of entries) to the list of directories trusted for
24380 automatic loading and execution of scripts. Multiple entries may be delimited
24381 by the host platform path separator in use.
24384 This variable defaults to what @code{--with-auto-load-dir} has been configured
24385 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24386 substitution applies the same as for @ref{set auto-load scripts-directory}.
24387 The default @code{set auto-load safe-path} value can be also overriden by
24388 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24390 Setting this variable to @file{/} disables this security protection,
24391 corresponding @value{GDBN} configuration option is
24392 @option{--without-auto-load-safe-path}.
24393 This variable is supposed to be set to the system directories writable by the
24394 system superuser only. Users can add their source directories in init files in
24395 their home directories (@pxref{Home Directory Init File}). See also deprecated
24396 init file in the current directory
24397 (@pxref{Init File in the Current Directory during Startup}).
24399 To force @value{GDBN} to load the files it declined to load in the previous
24400 example, you could use one of the following ways:
24403 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24404 Specify this trusted directory (or a file) as additional component of the list.
24405 You have to specify also any existing directories displayed by
24406 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24408 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24409 Specify this directory as in the previous case but just for a single
24410 @value{GDBN} session.
24412 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24413 Disable auto-loading safety for a single @value{GDBN} session.
24414 This assumes all the files you debug during this @value{GDBN} session will come
24415 from trusted sources.
24417 @item @kbd{./configure --without-auto-load-safe-path}
24418 During compilation of @value{GDBN} you may disable any auto-loading safety.
24419 This assumes all the files you will ever debug with this @value{GDBN} come from
24423 On the other hand you can also explicitly forbid automatic files loading which
24424 also suppresses any such warning messages:
24427 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24428 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24430 @item @file{~/.gdbinit}: @samp{set auto-load no}
24431 Disable auto-loading globally for the user
24432 (@pxref{Home Directory Init File}). While it is improbable, you could also
24433 use system init file instead (@pxref{System-wide configuration}).
24436 This setting applies to the file names as entered by user. If no entry matches
24437 @value{GDBN} tries as a last resort to also resolve all the file names into
24438 their canonical form (typically resolving symbolic links) and compare the
24439 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24440 own before starting the comparison so a canonical form of directories is
24441 recommended to be entered.
24443 @node Auto-loading verbose mode
24444 @subsection Displaying files tried for auto-load
24445 @cindex auto-loading verbose mode
24447 For better visibility of all the file locations where you can place scripts to
24448 be auto-loaded with inferior --- or to protect yourself against accidental
24449 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24450 all the files attempted to be loaded. Both existing and non-existing files may
24453 For example the list of directories from which it is safe to auto-load files
24454 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24455 may not be too obvious while setting it up.
24458 (gdb) set debug auto-load on
24459 (gdb) file ~/src/t/true
24460 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24461 for objfile "/tmp/true".
24462 auto-load: Updating directories of "/usr:/opt".
24463 auto-load: Using directory "/usr".
24464 auto-load: Using directory "/opt".
24465 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24466 by your `auto-load safe-path' set to "/usr:/opt".
24470 @anchor{set debug auto-load}
24471 @kindex set debug auto-load
24472 @item set debug auto-load [on|off]
24473 Set whether to print the filenames attempted to be auto-loaded.
24475 @anchor{show debug auto-load}
24476 @kindex show debug auto-load
24477 @item show debug auto-load
24478 Show whether printing of the filenames attempted to be auto-loaded is turned
24482 @node Messages/Warnings
24483 @section Optional Warnings and Messages
24485 @cindex verbose operation
24486 @cindex optional warnings
24487 By default, @value{GDBN} is silent about its inner workings. If you are
24488 running on a slow machine, you may want to use the @code{set verbose}
24489 command. This makes @value{GDBN} tell you when it does a lengthy
24490 internal operation, so you will not think it has crashed.
24492 Currently, the messages controlled by @code{set verbose} are those
24493 which announce that the symbol table for a source file is being read;
24494 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24497 @kindex set verbose
24498 @item set verbose on
24499 Enables @value{GDBN} output of certain informational messages.
24501 @item set verbose off
24502 Disables @value{GDBN} output of certain informational messages.
24504 @kindex show verbose
24506 Displays whether @code{set verbose} is on or off.
24509 By default, if @value{GDBN} encounters bugs in the symbol table of an
24510 object file, it is silent; but if you are debugging a compiler, you may
24511 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24516 @kindex set complaints
24517 @item set complaints @var{limit}
24518 Permits @value{GDBN} to output @var{limit} complaints about each type of
24519 unusual symbols before becoming silent about the problem. Set
24520 @var{limit} to zero to suppress all complaints; set it to a large number
24521 to prevent complaints from being suppressed.
24523 @kindex show complaints
24524 @item show complaints
24525 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24529 @anchor{confirmation requests}
24530 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24531 lot of stupid questions to confirm certain commands. For example, if
24532 you try to run a program which is already running:
24536 The program being debugged has been started already.
24537 Start it from the beginning? (y or n)
24540 If you are willing to unflinchingly face the consequences of your own
24541 commands, you can disable this ``feature'':
24545 @kindex set confirm
24547 @cindex confirmation
24548 @cindex stupid questions
24549 @item set confirm off
24550 Disables confirmation requests. Note that running @value{GDBN} with
24551 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24552 automatically disables confirmation requests.
24554 @item set confirm on
24555 Enables confirmation requests (the default).
24557 @kindex show confirm
24559 Displays state of confirmation requests.
24563 @cindex command tracing
24564 If you need to debug user-defined commands or sourced files you may find it
24565 useful to enable @dfn{command tracing}. In this mode each command will be
24566 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24567 quantity denoting the call depth of each command.
24570 @kindex set trace-commands
24571 @cindex command scripts, debugging
24572 @item set trace-commands on
24573 Enable command tracing.
24574 @item set trace-commands off
24575 Disable command tracing.
24576 @item show trace-commands
24577 Display the current state of command tracing.
24580 @node Debugging Output
24581 @section Optional Messages about Internal Happenings
24582 @cindex optional debugging messages
24584 @value{GDBN} has commands that enable optional debugging messages from
24585 various @value{GDBN} subsystems; normally these commands are of
24586 interest to @value{GDBN} maintainers, or when reporting a bug. This
24587 section documents those commands.
24590 @kindex set exec-done-display
24591 @item set exec-done-display
24592 Turns on or off the notification of asynchronous commands'
24593 completion. When on, @value{GDBN} will print a message when an
24594 asynchronous command finishes its execution. The default is off.
24595 @kindex show exec-done-display
24596 @item show exec-done-display
24597 Displays the current setting of asynchronous command completion
24600 @cindex ARM AArch64
24601 @item set debug aarch64
24602 Turns on or off display of debugging messages related to ARM AArch64.
24603 The default is off.
24605 @item show debug aarch64
24606 Displays the current state of displaying debugging messages related to
24608 @cindex gdbarch debugging info
24609 @cindex architecture debugging info
24610 @item set debug arch
24611 Turns on or off display of gdbarch debugging info. The default is off
24612 @item show debug arch
24613 Displays the current state of displaying gdbarch debugging info.
24614 @item set debug aix-solib
24615 @cindex AIX shared library debugging
24616 Control display of debugging messages from the AIX shared library
24617 support module. The default is off.
24618 @item show debug aix-thread
24619 Show the current state of displaying AIX shared library debugging messages.
24620 @item set debug aix-thread
24621 @cindex AIX threads
24622 Display debugging messages about inner workings of the AIX thread
24624 @item show debug aix-thread
24625 Show the current state of AIX thread debugging info display.
24626 @item set debug check-physname
24628 Check the results of the ``physname'' computation. When reading DWARF
24629 debugging information for C@t{++}, @value{GDBN} attempts to compute
24630 each entity's name. @value{GDBN} can do this computation in two
24631 different ways, depending on exactly what information is present.
24632 When enabled, this setting causes @value{GDBN} to compute the names
24633 both ways and display any discrepancies.
24634 @item show debug check-physname
24635 Show the current state of ``physname'' checking.
24636 @item set debug coff-pe-read
24637 @cindex COFF/PE exported symbols
24638 Control display of debugging messages related to reading of COFF/PE
24639 exported symbols. The default is off.
24640 @item show debug coff-pe-read
24641 Displays the current state of displaying debugging messages related to
24642 reading of COFF/PE exported symbols.
24643 @item set debug dwarf-die
24645 Dump DWARF DIEs after they are read in.
24646 The value is the number of nesting levels to print.
24647 A value of zero turns off the display.
24648 @item show debug dwarf-die
24649 Show the current state of DWARF DIE debugging.
24650 @item set debug dwarf-line
24651 @cindex DWARF Line Tables
24652 Turns on or off display of debugging messages related to reading
24653 DWARF line tables. The default is 0 (off).
24654 A value of 1 provides basic information.
24655 A value greater than 1 provides more verbose information.
24656 @item show debug dwarf-line
24657 Show the current state of DWARF line table debugging.
24658 @item set debug dwarf-read
24659 @cindex DWARF Reading
24660 Turns on or off display of debugging messages related to reading
24661 DWARF debug info. The default is 0 (off).
24662 A value of 1 provides basic information.
24663 A value greater than 1 provides more verbose information.
24664 @item show debug dwarf-read
24665 Show the current state of DWARF reader debugging.
24666 @item set debug displaced
24667 @cindex displaced stepping debugging info
24668 Turns on or off display of @value{GDBN} debugging info for the
24669 displaced stepping support. The default is off.
24670 @item show debug displaced
24671 Displays the current state of displaying @value{GDBN} debugging info
24672 related to displaced stepping.
24673 @item set debug event
24674 @cindex event debugging info
24675 Turns on or off display of @value{GDBN} event debugging info. The
24677 @item show debug event
24678 Displays the current state of displaying @value{GDBN} event debugging
24680 @item set debug expression
24681 @cindex expression debugging info
24682 Turns on or off display of debugging info about @value{GDBN}
24683 expression parsing. The default is off.
24684 @item show debug expression
24685 Displays the current state of displaying debugging info about
24686 @value{GDBN} expression parsing.
24687 @item set debug fbsd-lwp
24688 @cindex FreeBSD LWP debug messages
24689 Turns on or off debugging messages from the FreeBSD LWP debug support.
24690 @item show debug fbsd-lwp
24691 Show the current state of FreeBSD LWP debugging messages.
24692 @item set debug fbsd-nat
24693 @cindex FreeBSD native target debug messages
24694 Turns on or off debugging messages from the FreeBSD native target.
24695 @item show debug fbsd-nat
24696 Show the current state of FreeBSD native target debugging messages.
24697 @item set debug frame
24698 @cindex frame debugging info
24699 Turns on or off display of @value{GDBN} frame debugging info. The
24701 @item show debug frame
24702 Displays the current state of displaying @value{GDBN} frame debugging
24704 @item set debug gnu-nat
24705 @cindex @sc{gnu}/Hurd debug messages
24706 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24707 @item show debug gnu-nat
24708 Show the current state of @sc{gnu}/Hurd debugging messages.
24709 @item set debug infrun
24710 @cindex inferior debugging info
24711 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24712 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24713 for implementing operations such as single-stepping the inferior.
24714 @item show debug infrun
24715 Displays the current state of @value{GDBN} inferior debugging.
24716 @item set debug jit
24717 @cindex just-in-time compilation, debugging messages
24718 Turn on or off debugging messages from JIT debug support.
24719 @item show debug jit
24720 Displays the current state of @value{GDBN} JIT debugging.
24721 @item set debug lin-lwp
24722 @cindex @sc{gnu}/Linux LWP debug messages
24723 @cindex Linux lightweight processes
24724 Turn on or off debugging messages from the Linux LWP debug support.
24725 @item show debug lin-lwp
24726 Show the current state of Linux LWP debugging messages.
24727 @item set debug linux-namespaces
24728 @cindex @sc{gnu}/Linux namespaces debug messages
24729 Turn on or off debugging messages from the Linux namespaces debug support.
24730 @item show debug linux-namespaces
24731 Show the current state of Linux namespaces debugging messages.
24732 @item set debug mach-o
24733 @cindex Mach-O symbols processing
24734 Control display of debugging messages related to Mach-O symbols
24735 processing. The default is off.
24736 @item show debug mach-o
24737 Displays the current state of displaying debugging messages related to
24738 reading of COFF/PE exported symbols.
24739 @item set debug notification
24740 @cindex remote async notification debugging info
24741 Turn on or off debugging messages about remote async notification.
24742 The default is off.
24743 @item show debug notification
24744 Displays the current state of remote async notification debugging messages.
24745 @item set debug observer
24746 @cindex observer debugging info
24747 Turns on or off display of @value{GDBN} observer debugging. This
24748 includes info such as the notification of observable events.
24749 @item show debug observer
24750 Displays the current state of observer debugging.
24751 @item set debug overload
24752 @cindex C@t{++} overload debugging info
24753 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24754 info. This includes info such as ranking of functions, etc. The default
24756 @item show debug overload
24757 Displays the current state of displaying @value{GDBN} C@t{++} overload
24759 @cindex expression parser, debugging info
24760 @cindex debug expression parser
24761 @item set debug parser
24762 Turns on or off the display of expression parser debugging output.
24763 Internally, this sets the @code{yydebug} variable in the expression
24764 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24765 details. The default is off.
24766 @item show debug parser
24767 Show the current state of expression parser debugging.
24768 @cindex packets, reporting on stdout
24769 @cindex serial connections, debugging
24770 @cindex debug remote protocol
24771 @cindex remote protocol debugging
24772 @cindex display remote packets
24773 @item set debug remote
24774 Turns on or off display of reports on all packets sent back and forth across
24775 the serial line to the remote machine. The info is printed on the
24776 @value{GDBN} standard output stream. The default is off.
24777 @item show debug remote
24778 Displays the state of display of remote packets.
24780 @item set debug separate-debug-file
24781 Turns on or off display of debug output about separate debug file search.
24782 @item show debug separate-debug-file
24783 Displays the state of separate debug file search debug output.
24785 @item set debug serial
24786 Turns on or off display of @value{GDBN} serial debugging info. The
24788 @item show debug serial
24789 Displays the current state of displaying @value{GDBN} serial debugging
24791 @item set debug solib-frv
24792 @cindex FR-V shared-library debugging
24793 Turn on or off debugging messages for FR-V shared-library code.
24794 @item show debug solib-frv
24795 Display the current state of FR-V shared-library code debugging
24797 @item set debug symbol-lookup
24798 @cindex symbol lookup
24799 Turns on or off display of debugging messages related to symbol lookup.
24800 The default is 0 (off).
24801 A value of 1 provides basic information.
24802 A value greater than 1 provides more verbose information.
24803 @item show debug symbol-lookup
24804 Show the current state of symbol lookup debugging messages.
24805 @item set debug symfile
24806 @cindex symbol file functions
24807 Turns on or off display of debugging messages related to symbol file functions.
24808 The default is off. @xref{Files}.
24809 @item show debug symfile
24810 Show the current state of symbol file debugging messages.
24811 @item set debug symtab-create
24812 @cindex symbol table creation
24813 Turns on or off display of debugging messages related to symbol table creation.
24814 The default is 0 (off).
24815 A value of 1 provides basic information.
24816 A value greater than 1 provides more verbose information.
24817 @item show debug symtab-create
24818 Show the current state of symbol table creation debugging.
24819 @item set debug target
24820 @cindex target debugging info
24821 Turns on or off display of @value{GDBN} target debugging info. This info
24822 includes what is going on at the target level of GDB, as it happens. The
24823 default is 0. Set it to 1 to track events, and to 2 to also track the
24824 value of large memory transfers.
24825 @item show debug target
24826 Displays the current state of displaying @value{GDBN} target debugging
24828 @item set debug timestamp
24829 @cindex timestampping debugging info
24830 Turns on or off display of timestamps with @value{GDBN} debugging info.
24831 When enabled, seconds and microseconds are displayed before each debugging
24833 @item show debug timestamp
24834 Displays the current state of displaying timestamps with @value{GDBN}
24836 @item set debug varobj
24837 @cindex variable object debugging info
24838 Turns on or off display of @value{GDBN} variable object debugging
24839 info. The default is off.
24840 @item show debug varobj
24841 Displays the current state of displaying @value{GDBN} variable object
24843 @item set debug xml
24844 @cindex XML parser debugging
24845 Turn on or off debugging messages for built-in XML parsers.
24846 @item show debug xml
24847 Displays the current state of XML debugging messages.
24850 @node Other Misc Settings
24851 @section Other Miscellaneous Settings
24852 @cindex miscellaneous settings
24855 @kindex set interactive-mode
24856 @item set interactive-mode
24857 If @code{on}, forces @value{GDBN} to assume that GDB was started
24858 in a terminal. In practice, this means that @value{GDBN} should wait
24859 for the user to answer queries generated by commands entered at
24860 the command prompt. If @code{off}, forces @value{GDBN} to operate
24861 in the opposite mode, and it uses the default answers to all queries.
24862 If @code{auto} (the default), @value{GDBN} tries to determine whether
24863 its standard input is a terminal, and works in interactive-mode if it
24864 is, non-interactively otherwise.
24866 In the vast majority of cases, the debugger should be able to guess
24867 correctly which mode should be used. But this setting can be useful
24868 in certain specific cases, such as running a MinGW @value{GDBN}
24869 inside a cygwin window.
24871 @kindex show interactive-mode
24872 @item show interactive-mode
24873 Displays whether the debugger is operating in interactive mode or not.
24876 @node Extending GDB
24877 @chapter Extending @value{GDBN}
24878 @cindex extending GDB
24880 @value{GDBN} provides several mechanisms for extension.
24881 @value{GDBN} also provides the ability to automatically load
24882 extensions when it reads a file for debugging. This allows the
24883 user to automatically customize @value{GDBN} for the program
24887 * Sequences:: Canned Sequences of @value{GDBN} Commands
24888 * Python:: Extending @value{GDBN} using Python
24889 * Guile:: Extending @value{GDBN} using Guile
24890 * Auto-loading extensions:: Automatically loading extensions
24891 * Multiple Extension Languages:: Working with multiple extension languages
24892 * Aliases:: Creating new spellings of existing commands
24895 To facilitate the use of extension languages, @value{GDBN} is capable
24896 of evaluating the contents of a file. When doing so, @value{GDBN}
24897 can recognize which extension language is being used by looking at
24898 the filename extension. Files with an unrecognized filename extension
24899 are always treated as a @value{GDBN} Command Files.
24900 @xref{Command Files,, Command files}.
24902 You can control how @value{GDBN} evaluates these files with the following
24906 @kindex set script-extension
24907 @kindex show script-extension
24908 @item set script-extension off
24909 All scripts are always evaluated as @value{GDBN} Command Files.
24911 @item set script-extension soft
24912 The debugger determines the scripting language based on filename
24913 extension. If this scripting language is supported, @value{GDBN}
24914 evaluates the script using that language. Otherwise, it evaluates
24915 the file as a @value{GDBN} Command File.
24917 @item set script-extension strict
24918 The debugger determines the scripting language based on filename
24919 extension, and evaluates the script using that language. If the
24920 language is not supported, then the evaluation fails.
24922 @item show script-extension
24923 Display the current value of the @code{script-extension} option.
24928 @section Canned Sequences of Commands
24930 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24931 Command Lists}), @value{GDBN} provides two ways to store sequences of
24932 commands for execution as a unit: user-defined commands and command
24936 * Define:: How to define your own commands
24937 * Hooks:: Hooks for user-defined commands
24938 * Command Files:: How to write scripts of commands to be stored in a file
24939 * Output:: Commands for controlled output
24940 * Auto-loading sequences:: Controlling auto-loaded command files
24944 @subsection User-defined Commands
24946 @cindex user-defined command
24947 @cindex arguments, to user-defined commands
24948 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24949 which you assign a new name as a command. This is done with the
24950 @code{define} command. User commands may accept an unlimited number of arguments
24951 separated by whitespace. Arguments are accessed within the user command
24952 via @code{$arg0@dots{}$argN}. A trivial example:
24956 print $arg0 + $arg1 + $arg2
24961 To execute the command use:
24968 This defines the command @code{adder}, which prints the sum of
24969 its three arguments. Note the arguments are text substitutions, so they may
24970 reference variables, use complex expressions, or even perform inferior
24973 @cindex argument count in user-defined commands
24974 @cindex how many arguments (user-defined commands)
24975 In addition, @code{$argc} may be used to find out how many arguments have
24981 print $arg0 + $arg1
24984 print $arg0 + $arg1 + $arg2
24989 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24990 to process a variable number of arguments:
24997 eval "set $sum = $sum + $arg%d", $i
25007 @item define @var{commandname}
25008 Define a command named @var{commandname}. If there is already a command
25009 by that name, you are asked to confirm that you want to redefine it.
25010 The argument @var{commandname} may be a bare command name consisting of letters,
25011 numbers, dashes, and underscores. It may also start with any predefined
25012 prefix command. For example, @samp{define target my-target} creates
25013 a user-defined @samp{target my-target} command.
25015 The definition of the command is made up of other @value{GDBN} command lines,
25016 which are given following the @code{define} command. The end of these
25017 commands is marked by a line containing @code{end}.
25020 @kindex end@r{ (user-defined commands)}
25021 @item document @var{commandname}
25022 Document the user-defined command @var{commandname}, so that it can be
25023 accessed by @code{help}. The command @var{commandname} must already be
25024 defined. This command reads lines of documentation just as @code{define}
25025 reads the lines of the command definition, ending with @code{end}.
25026 After the @code{document} command is finished, @code{help} on command
25027 @var{commandname} displays the documentation you have written.
25029 You may use the @code{document} command again to change the
25030 documentation of a command. Redefining the command with @code{define}
25031 does not change the documentation.
25033 @kindex dont-repeat
25034 @cindex don't repeat command
25036 Used inside a user-defined command, this tells @value{GDBN} that this
25037 command should not be repeated when the user hits @key{RET}
25038 (@pxref{Command Syntax, repeat last command}).
25040 @kindex help user-defined
25041 @item help user-defined
25042 List all user-defined commands and all python commands defined in class
25043 COMAND_USER. The first line of the documentation or docstring is
25048 @itemx show user @var{commandname}
25049 Display the @value{GDBN} commands used to define @var{commandname} (but
25050 not its documentation). If no @var{commandname} is given, display the
25051 definitions for all user-defined commands.
25052 This does not work for user-defined python commands.
25054 @cindex infinite recursion in user-defined commands
25055 @kindex show max-user-call-depth
25056 @kindex set max-user-call-depth
25057 @item show max-user-call-depth
25058 @itemx set max-user-call-depth
25059 The value of @code{max-user-call-depth} controls how many recursion
25060 levels are allowed in user-defined commands before @value{GDBN} suspects an
25061 infinite recursion and aborts the command.
25062 This does not apply to user-defined python commands.
25065 In addition to the above commands, user-defined commands frequently
25066 use control flow commands, described in @ref{Command Files}.
25068 When user-defined commands are executed, the
25069 commands of the definition are not printed. An error in any command
25070 stops execution of the user-defined command.
25072 If used interactively, commands that would ask for confirmation proceed
25073 without asking when used inside a user-defined command. Many @value{GDBN}
25074 commands that normally print messages to say what they are doing omit the
25075 messages when used in a user-defined command.
25078 @subsection User-defined Command Hooks
25079 @cindex command hooks
25080 @cindex hooks, for commands
25081 @cindex hooks, pre-command
25084 You may define @dfn{hooks}, which are a special kind of user-defined
25085 command. Whenever you run the command @samp{foo}, if the user-defined
25086 command @samp{hook-foo} exists, it is executed (with no arguments)
25087 before that command.
25089 @cindex hooks, post-command
25091 A hook may also be defined which is run after the command you executed.
25092 Whenever you run the command @samp{foo}, if the user-defined command
25093 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25094 that command. Post-execution hooks may exist simultaneously with
25095 pre-execution hooks, for the same command.
25097 It is valid for a hook to call the command which it hooks. If this
25098 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25100 @c It would be nice if hookpost could be passed a parameter indicating
25101 @c if the command it hooks executed properly or not. FIXME!
25103 @kindex stop@r{, a pseudo-command}
25104 In addition, a pseudo-command, @samp{stop} exists. Defining
25105 (@samp{hook-stop}) makes the associated commands execute every time
25106 execution stops in your program: before breakpoint commands are run,
25107 displays are printed, or the stack frame is printed.
25109 For example, to ignore @code{SIGALRM} signals while
25110 single-stepping, but treat them normally during normal execution,
25115 handle SIGALRM nopass
25119 handle SIGALRM pass
25122 define hook-continue
25123 handle SIGALRM pass
25127 As a further example, to hook at the beginning and end of the @code{echo}
25128 command, and to add extra text to the beginning and end of the message,
25136 define hookpost-echo
25140 (@value{GDBP}) echo Hello World
25141 <<<---Hello World--->>>
25146 You can define a hook for any single-word command in @value{GDBN}, but
25147 not for command aliases; you should define a hook for the basic command
25148 name, e.g.@: @code{backtrace} rather than @code{bt}.
25149 @c FIXME! So how does Joe User discover whether a command is an alias
25151 You can hook a multi-word command by adding @code{hook-} or
25152 @code{hookpost-} to the last word of the command, e.g.@:
25153 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25155 If an error occurs during the execution of your hook, execution of
25156 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25157 (before the command that you actually typed had a chance to run).
25159 If you try to define a hook which does not match any known command, you
25160 get a warning from the @code{define} command.
25162 @node Command Files
25163 @subsection Command Files
25165 @cindex command files
25166 @cindex scripting commands
25167 A command file for @value{GDBN} is a text file made of lines that are
25168 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25169 also be included. An empty line in a command file does nothing; it
25170 does not mean to repeat the last command, as it would from the
25173 You can request the execution of a command file with the @code{source}
25174 command. Note that the @code{source} command is also used to evaluate
25175 scripts that are not Command Files. The exact behavior can be configured
25176 using the @code{script-extension} setting.
25177 @xref{Extending GDB,, Extending GDB}.
25181 @cindex execute commands from a file
25182 @item source [-s] [-v] @var{filename}
25183 Execute the command file @var{filename}.
25186 The lines in a command file are generally executed sequentially,
25187 unless the order of execution is changed by one of the
25188 @emph{flow-control commands} described below. The commands are not
25189 printed as they are executed. An error in any command terminates
25190 execution of the command file and control is returned to the console.
25192 @value{GDBN} first searches for @var{filename} in the current directory.
25193 If the file is not found there, and @var{filename} does not specify a
25194 directory, then @value{GDBN} also looks for the file on the source search path
25195 (specified with the @samp{directory} command);
25196 except that @file{$cdir} is not searched because the compilation directory
25197 is not relevant to scripts.
25199 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25200 on the search path even if @var{filename} specifies a directory.
25201 The search is done by appending @var{filename} to each element of the
25202 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25203 and the search path contains @file{/home/user} then @value{GDBN} will
25204 look for the script @file{/home/user/mylib/myscript}.
25205 The search is also done if @var{filename} is an absolute path.
25206 For example, if @var{filename} is @file{/tmp/myscript} and
25207 the search path contains @file{/home/user} then @value{GDBN} will
25208 look for the script @file{/home/user/tmp/myscript}.
25209 For DOS-like systems, if @var{filename} contains a drive specification,
25210 it is stripped before concatenation. For example, if @var{filename} is
25211 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25212 will look for the script @file{c:/tmp/myscript}.
25214 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25215 each command as it is executed. The option must be given before
25216 @var{filename}, and is interpreted as part of the filename anywhere else.
25218 Commands that would ask for confirmation if used interactively proceed
25219 without asking when used in a command file. Many @value{GDBN} commands that
25220 normally print messages to say what they are doing omit the messages
25221 when called from command files.
25223 @value{GDBN} also accepts command input from standard input. In this
25224 mode, normal output goes to standard output and error output goes to
25225 standard error. Errors in a command file supplied on standard input do
25226 not terminate execution of the command file---execution continues with
25230 gdb < cmds > log 2>&1
25233 (The syntax above will vary depending on the shell used.) This example
25234 will execute commands from the file @file{cmds}. All output and errors
25235 would be directed to @file{log}.
25237 Since commands stored on command files tend to be more general than
25238 commands typed interactively, they frequently need to deal with
25239 complicated situations, such as different or unexpected values of
25240 variables and symbols, changes in how the program being debugged is
25241 built, etc. @value{GDBN} provides a set of flow-control commands to
25242 deal with these complexities. Using these commands, you can write
25243 complex scripts that loop over data structures, execute commands
25244 conditionally, etc.
25251 This command allows to include in your script conditionally executed
25252 commands. The @code{if} command takes a single argument, which is an
25253 expression to evaluate. It is followed by a series of commands that
25254 are executed only if the expression is true (its value is nonzero).
25255 There can then optionally be an @code{else} line, followed by a series
25256 of commands that are only executed if the expression was false. The
25257 end of the list is marked by a line containing @code{end}.
25261 This command allows to write loops. Its syntax is similar to
25262 @code{if}: the command takes a single argument, which is an expression
25263 to evaluate, and must be followed by the commands to execute, one per
25264 line, terminated by an @code{end}. These commands are called the
25265 @dfn{body} of the loop. The commands in the body of @code{while} are
25266 executed repeatedly as long as the expression evaluates to true.
25270 This command exits the @code{while} loop in whose body it is included.
25271 Execution of the script continues after that @code{while}s @code{end}
25274 @kindex loop_continue
25275 @item loop_continue
25276 This command skips the execution of the rest of the body of commands
25277 in the @code{while} loop in whose body it is included. Execution
25278 branches to the beginning of the @code{while} loop, where it evaluates
25279 the controlling expression.
25281 @kindex end@r{ (if/else/while commands)}
25283 Terminate the block of commands that are the body of @code{if},
25284 @code{else}, or @code{while} flow-control commands.
25289 @subsection Commands for Controlled Output
25291 During the execution of a command file or a user-defined command, normal
25292 @value{GDBN} output is suppressed; the only output that appears is what is
25293 explicitly printed by the commands in the definition. This section
25294 describes three commands useful for generating exactly the output you
25299 @item echo @var{text}
25300 @c I do not consider backslash-space a standard C escape sequence
25301 @c because it is not in ANSI.
25302 Print @var{text}. Nonprinting characters can be included in
25303 @var{text} using C escape sequences, such as @samp{\n} to print a
25304 newline. @strong{No newline is printed unless you specify one.}
25305 In addition to the standard C escape sequences, a backslash followed
25306 by a space stands for a space. This is useful for displaying a
25307 string with spaces at the beginning or the end, since leading and
25308 trailing spaces are otherwise trimmed from all arguments.
25309 To print @samp{@w{ }and foo =@w{ }}, use the command
25310 @samp{echo \@w{ }and foo = \@w{ }}.
25312 A backslash at the end of @var{text} can be used, as in C, to continue
25313 the command onto subsequent lines. For example,
25316 echo This is some text\n\
25317 which is continued\n\
25318 onto several lines.\n
25321 produces the same output as
25324 echo This is some text\n
25325 echo which is continued\n
25326 echo onto several lines.\n
25330 @item output @var{expression}
25331 Print the value of @var{expression} and nothing but that value: no
25332 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25333 value history either. @xref{Expressions, ,Expressions}, for more information
25336 @item output/@var{fmt} @var{expression}
25337 Print the value of @var{expression} in format @var{fmt}. You can use
25338 the same formats as for @code{print}. @xref{Output Formats,,Output
25339 Formats}, for more information.
25342 @item printf @var{template}, @var{expressions}@dots{}
25343 Print the values of one or more @var{expressions} under the control of
25344 the string @var{template}. To print several values, make
25345 @var{expressions} be a comma-separated list of individual expressions,
25346 which may be either numbers or pointers. Their values are printed as
25347 specified by @var{template}, exactly as a C program would do by
25348 executing the code below:
25351 printf (@var{template}, @var{expressions}@dots{});
25354 As in @code{C} @code{printf}, ordinary characters in @var{template}
25355 are printed verbatim, while @dfn{conversion specification} introduced
25356 by the @samp{%} character cause subsequent @var{expressions} to be
25357 evaluated, their values converted and formatted according to type and
25358 style information encoded in the conversion specifications, and then
25361 For example, you can print two values in hex like this:
25364 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25367 @code{printf} supports all the standard @code{C} conversion
25368 specifications, including the flags and modifiers between the @samp{%}
25369 character and the conversion letter, with the following exceptions:
25373 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25376 The modifier @samp{*} is not supported for specifying precision or
25380 The @samp{'} flag (for separation of digits into groups according to
25381 @code{LC_NUMERIC'}) is not supported.
25384 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25388 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25391 The conversion letters @samp{a} and @samp{A} are not supported.
25395 Note that the @samp{ll} type modifier is supported only if the
25396 underlying @code{C} implementation used to build @value{GDBN} supports
25397 the @code{long long int} type, and the @samp{L} type modifier is
25398 supported only if @code{long double} type is available.
25400 As in @code{C}, @code{printf} supports simple backslash-escape
25401 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25402 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25403 single character. Octal and hexadecimal escape sequences are not
25406 Additionally, @code{printf} supports conversion specifications for DFP
25407 (@dfn{Decimal Floating Point}) types using the following length modifiers
25408 together with a floating point specifier.
25413 @samp{H} for printing @code{Decimal32} types.
25416 @samp{D} for printing @code{Decimal64} types.
25419 @samp{DD} for printing @code{Decimal128} types.
25422 If the underlying @code{C} implementation used to build @value{GDBN} has
25423 support for the three length modifiers for DFP types, other modifiers
25424 such as width and precision will also be available for @value{GDBN} to use.
25426 In case there is no such @code{C} support, no additional modifiers will be
25427 available and the value will be printed in the standard way.
25429 Here's an example of printing DFP types using the above conversion letters:
25431 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25436 @item eval @var{template}, @var{expressions}@dots{}
25437 Convert the values of one or more @var{expressions} under the control of
25438 the string @var{template} to a command line, and call it.
25442 @node Auto-loading sequences
25443 @subsection Controlling auto-loading native @value{GDBN} scripts
25444 @cindex native script auto-loading
25446 When a new object file is read (for example, due to the @code{file}
25447 command, or because the inferior has loaded a shared library),
25448 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25449 @xref{Auto-loading extensions}.
25451 Auto-loading can be enabled or disabled,
25452 and the list of auto-loaded scripts can be printed.
25455 @anchor{set auto-load gdb-scripts}
25456 @kindex set auto-load gdb-scripts
25457 @item set auto-load gdb-scripts [on|off]
25458 Enable or disable the auto-loading of canned sequences of commands scripts.
25460 @anchor{show auto-load gdb-scripts}
25461 @kindex show auto-load gdb-scripts
25462 @item show auto-load gdb-scripts
25463 Show whether auto-loading of canned sequences of commands scripts is enabled or
25466 @anchor{info auto-load gdb-scripts}
25467 @kindex info auto-load gdb-scripts
25468 @cindex print list of auto-loaded canned sequences of commands scripts
25469 @item info auto-load gdb-scripts [@var{regexp}]
25470 Print the list of all canned sequences of commands scripts that @value{GDBN}
25474 If @var{regexp} is supplied only canned sequences of commands scripts with
25475 matching names are printed.
25477 @c Python docs live in a separate file.
25478 @include python.texi
25480 @c Guile docs live in a separate file.
25481 @include guile.texi
25483 @node Auto-loading extensions
25484 @section Auto-loading extensions
25485 @cindex auto-loading extensions
25487 @value{GDBN} provides two mechanisms for automatically loading extensions
25488 when a new object file is read (for example, due to the @code{file}
25489 command, or because the inferior has loaded a shared library):
25490 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25491 section of modern file formats like ELF.
25494 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25495 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25496 * Which flavor to choose?::
25499 The auto-loading feature is useful for supplying application-specific
25500 debugging commands and features.
25502 Auto-loading can be enabled or disabled,
25503 and the list of auto-loaded scripts can be printed.
25504 See the @samp{auto-loading} section of each extension language
25505 for more information.
25506 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25507 For Python files see @ref{Python Auto-loading}.
25509 Note that loading of this script file also requires accordingly configured
25510 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25512 @node objfile-gdbdotext file
25513 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25514 @cindex @file{@var{objfile}-gdb.gdb}
25515 @cindex @file{@var{objfile}-gdb.py}
25516 @cindex @file{@var{objfile}-gdb.scm}
25518 When a new object file is read, @value{GDBN} looks for a file named
25519 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25520 where @var{objfile} is the object file's name and
25521 where @var{ext} is the file extension for the extension language:
25524 @item @file{@var{objfile}-gdb.gdb}
25525 GDB's own command language
25526 @item @file{@var{objfile}-gdb.py}
25528 @item @file{@var{objfile}-gdb.scm}
25532 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25533 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25534 components, and appending the @file{-gdb.@var{ext}} suffix.
25535 If this file exists and is readable, @value{GDBN} will evaluate it as a
25536 script in the specified extension language.
25538 If this file does not exist, then @value{GDBN} will look for
25539 @var{script-name} file in all of the directories as specified below.
25541 Note that loading of these files requires an accordingly configured
25542 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25544 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25545 scripts normally according to its @file{.exe} filename. But if no scripts are
25546 found @value{GDBN} also tries script filenames matching the object file without
25547 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25548 is attempted on any platform. This makes the script filenames compatible
25549 between Unix and MS-Windows hosts.
25552 @anchor{set auto-load scripts-directory}
25553 @kindex set auto-load scripts-directory
25554 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25555 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25556 may be delimited by the host platform path separator in use
25557 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25559 Each entry here needs to be covered also by the security setting
25560 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25562 @anchor{with-auto-load-dir}
25563 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25564 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25565 configuration option @option{--with-auto-load-dir}.
25567 Any reference to @file{$debugdir} will get replaced by
25568 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25569 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25570 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25571 @file{$datadir} must be placed as a directory component --- either alone or
25572 delimited by @file{/} or @file{\} directory separators, depending on the host
25575 The list of directories uses path separator (@samp{:} on GNU and Unix
25576 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25577 to the @env{PATH} environment variable.
25579 @anchor{show auto-load scripts-directory}
25580 @kindex show auto-load scripts-directory
25581 @item show auto-load scripts-directory
25582 Show @value{GDBN} auto-loaded scripts location.
25584 @anchor{add-auto-load-scripts-directory}
25585 @kindex add-auto-load-scripts-directory
25586 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25587 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25588 Multiple entries may be delimited by the host platform path separator in use.
25591 @value{GDBN} does not track which files it has already auto-loaded this way.
25592 @value{GDBN} will load the associated script every time the corresponding
25593 @var{objfile} is opened.
25594 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25595 is evaluated more than once.
25597 @node dotdebug_gdb_scripts section
25598 @subsection The @code{.debug_gdb_scripts} section
25599 @cindex @code{.debug_gdb_scripts} section
25601 For systems using file formats like ELF and COFF,
25602 when @value{GDBN} loads a new object file
25603 it will look for a special section named @code{.debug_gdb_scripts}.
25604 If this section exists, its contents is a list of null-terminated entries
25605 specifying scripts to load. Each entry begins with a non-null prefix byte that
25606 specifies the kind of entry, typically the extension language and whether the
25607 script is in a file or inlined in @code{.debug_gdb_scripts}.
25609 The following entries are supported:
25612 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25613 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25614 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25615 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25618 @subsubsection Script File Entries
25620 If the entry specifies a file, @value{GDBN} will look for the file first
25621 in the current directory and then along the source search path
25622 (@pxref{Source Path, ,Specifying Source Directories}),
25623 except that @file{$cdir} is not searched, since the compilation
25624 directory is not relevant to scripts.
25626 File entries can be placed in section @code{.debug_gdb_scripts} with,
25627 for example, this GCC macro for Python scripts.
25630 /* Note: The "MS" section flags are to remove duplicates. */
25631 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25633 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25634 .byte 1 /* Python */\n\
25635 .asciz \"" script_name "\"\n\
25641 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25642 Then one can reference the macro in a header or source file like this:
25645 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25648 The script name may include directories if desired.
25650 Note that loading of this script file also requires accordingly configured
25651 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25653 If the macro invocation is put in a header, any application or library
25654 using this header will get a reference to the specified script,
25655 and with the use of @code{"MS"} attributes on the section, the linker
25656 will remove duplicates.
25658 @subsubsection Script Text Entries
25660 Script text entries allow to put the executable script in the entry
25661 itself instead of loading it from a file.
25662 The first line of the entry, everything after the prefix byte and up to
25663 the first newline (@code{0xa}) character, is the script name, and must not
25664 contain any kind of space character, e.g., spaces or tabs.
25665 The rest of the entry, up to the trailing null byte, is the script to
25666 execute in the specified language. The name needs to be unique among
25667 all script names, as @value{GDBN} executes each script only once based
25670 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25674 #include "symcat.h"
25675 #include "gdb/section-scripts.h"
25677 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25678 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25679 ".ascii \"gdb.inlined-script\\n\"\n"
25680 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25681 ".ascii \" def __init__ (self):\\n\"\n"
25682 ".ascii \" super (test_cmd, self).__init__ ("
25683 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25684 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25685 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25686 ".ascii \"test_cmd ()\\n\"\n"
25692 Loading of inlined scripts requires a properly configured
25693 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25694 The path to specify in @code{auto-load safe-path} is the path of the file
25695 containing the @code{.debug_gdb_scripts} section.
25697 @node Which flavor to choose?
25698 @subsection Which flavor to choose?
25700 Given the multiple ways of auto-loading extensions, it might not always
25701 be clear which one to choose. This section provides some guidance.
25704 Benefits of the @file{-gdb.@var{ext}} way:
25708 Can be used with file formats that don't support multiple sections.
25711 Ease of finding scripts for public libraries.
25713 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25714 in the source search path.
25715 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25716 isn't a source directory in which to find the script.
25719 Doesn't require source code additions.
25723 Benefits of the @code{.debug_gdb_scripts} way:
25727 Works with static linking.
25729 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25730 trigger their loading. When an application is statically linked the only
25731 objfile available is the executable, and it is cumbersome to attach all the
25732 scripts from all the input libraries to the executable's
25733 @file{-gdb.@var{ext}} script.
25736 Works with classes that are entirely inlined.
25738 Some classes can be entirely inlined, and thus there may not be an associated
25739 shared library to attach a @file{-gdb.@var{ext}} script to.
25742 Scripts needn't be copied out of the source tree.
25744 In some circumstances, apps can be built out of large collections of internal
25745 libraries, and the build infrastructure necessary to install the
25746 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25747 cumbersome. It may be easier to specify the scripts in the
25748 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25749 top of the source tree to the source search path.
25752 @node Multiple Extension Languages
25753 @section Multiple Extension Languages
25755 The Guile and Python extension languages do not share any state,
25756 and generally do not interfere with each other.
25757 There are some things to be aware of, however.
25759 @subsection Python comes first
25761 Python was @value{GDBN}'s first extension language, and to avoid breaking
25762 existing behaviour Python comes first. This is generally solved by the
25763 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25764 extension languages, and when it makes a call to an extension language,
25765 (say to pretty-print a value), it tries each in turn until an extension
25766 language indicates it has performed the request (e.g., has returned the
25767 pretty-printed form of a value).
25768 This extends to errors while performing such requests: If an error happens
25769 while, for example, trying to pretty-print an object then the error is
25770 reported and any following extension languages are not tried.
25773 @section Creating new spellings of existing commands
25774 @cindex aliases for commands
25776 It is often useful to define alternate spellings of existing commands.
25777 For example, if a new @value{GDBN} command defined in Python has
25778 a long name to type, it is handy to have an abbreviated version of it
25779 that involves less typing.
25781 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25782 of the @samp{step} command even though it is otherwise an ambiguous
25783 abbreviation of other commands like @samp{set} and @samp{show}.
25785 Aliases are also used to provide shortened or more common versions
25786 of multi-word commands. For example, @value{GDBN} provides the
25787 @samp{tty} alias of the @samp{set inferior-tty} command.
25789 You can define a new alias with the @samp{alias} command.
25794 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25798 @var{ALIAS} specifies the name of the new alias.
25799 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25802 @var{COMMAND} specifies the name of an existing command
25803 that is being aliased.
25805 The @samp{-a} option specifies that the new alias is an abbreviation
25806 of the command. Abbreviations are not shown in command
25807 lists displayed by the @samp{help} command.
25809 The @samp{--} option specifies the end of options,
25810 and is useful when @var{ALIAS} begins with a dash.
25812 Here is a simple example showing how to make an abbreviation
25813 of a command so that there is less to type.
25814 Suppose you were tired of typing @samp{disas}, the current
25815 shortest unambiguous abbreviation of the @samp{disassemble} command
25816 and you wanted an even shorter version named @samp{di}.
25817 The following will accomplish this.
25820 (gdb) alias -a di = disas
25823 Note that aliases are different from user-defined commands.
25824 With a user-defined command, you also need to write documentation
25825 for it with the @samp{document} command.
25826 An alias automatically picks up the documentation of the existing command.
25828 Here is an example where we make @samp{elms} an abbreviation of
25829 @samp{elements} in the @samp{set print elements} command.
25830 This is to show that you can make an abbreviation of any part
25834 (gdb) alias -a set print elms = set print elements
25835 (gdb) alias -a show print elms = show print elements
25836 (gdb) set p elms 20
25838 Limit on string chars or array elements to print is 200.
25841 Note that if you are defining an alias of a @samp{set} command,
25842 and you want to have an alias for the corresponding @samp{show}
25843 command, then you need to define the latter separately.
25845 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25846 @var{ALIAS}, just as they are normally.
25849 (gdb) alias -a set pr elms = set p ele
25852 Finally, here is an example showing the creation of a one word
25853 alias for a more complex command.
25854 This creates alias @samp{spe} of the command @samp{set print elements}.
25857 (gdb) alias spe = set print elements
25862 @chapter Command Interpreters
25863 @cindex command interpreters
25865 @value{GDBN} supports multiple command interpreters, and some command
25866 infrastructure to allow users or user interface writers to switch
25867 between interpreters or run commands in other interpreters.
25869 @value{GDBN} currently supports two command interpreters, the console
25870 interpreter (sometimes called the command-line interpreter or @sc{cli})
25871 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25872 describes both of these interfaces in great detail.
25874 By default, @value{GDBN} will start with the console interpreter.
25875 However, the user may choose to start @value{GDBN} with another
25876 interpreter by specifying the @option{-i} or @option{--interpreter}
25877 startup options. Defined interpreters include:
25881 @cindex console interpreter
25882 The traditional console or command-line interpreter. This is the most often
25883 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25884 @value{GDBN} will use this interpreter.
25887 @cindex mi interpreter
25888 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25889 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25890 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25894 @cindex mi2 interpreter
25895 The current @sc{gdb/mi} interface.
25898 @cindex mi1 interpreter
25899 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25903 @cindex invoke another interpreter
25905 @kindex interpreter-exec
25906 You may execute commands in any interpreter from the current
25907 interpreter using the appropriate command. If you are running the
25908 console interpreter, simply use the @code{interpreter-exec} command:
25911 interpreter-exec mi "-data-list-register-names"
25914 @sc{gdb/mi} has a similar command, although it is only available in versions of
25915 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25917 Note that @code{interpreter-exec} only changes the interpreter for the
25918 duration of the specified command. It does not change the interpreter
25921 @cindex start a new independent interpreter
25923 Although you may only choose a single interpreter at startup, it is
25924 possible to run an independent interpreter on a specified input/output
25925 device (usually a tty).
25927 For example, consider a debugger GUI or IDE that wants to provide a
25928 @value{GDBN} console view. It may do so by embedding a terminal
25929 emulator widget in its GUI, starting @value{GDBN} in the traditional
25930 command-line mode with stdin/stdout/stderr redirected to that
25931 terminal, and then creating an MI interpreter running on a specified
25932 input/output device. The console interpreter created by @value{GDBN}
25933 at startup handles commands the user types in the terminal widget,
25934 while the GUI controls and synchronizes state with @value{GDBN} using
25935 the separate MI interpreter.
25937 To start a new secondary @dfn{user interface} running MI, use the
25938 @code{new-ui} command:
25941 @cindex new user interface
25943 new-ui @var{interpreter} @var{tty}
25946 The @var{interpreter} parameter specifies the interpreter to run.
25947 This accepts the same values as the @code{interpreter-exec} command.
25948 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25949 @var{tty} parameter specifies the name of the bidirectional file the
25950 interpreter uses for input/output, usually the name of a
25951 pseudoterminal slave on Unix systems. For example:
25954 (@value{GDBP}) new-ui mi /dev/pts/9
25958 runs an MI interpreter on @file{/dev/pts/9}.
25961 @chapter @value{GDBN} Text User Interface
25963 @cindex Text User Interface
25966 * TUI Overview:: TUI overview
25967 * TUI Keys:: TUI key bindings
25968 * TUI Single Key Mode:: TUI single key mode
25969 * TUI Commands:: TUI-specific commands
25970 * TUI Configuration:: TUI configuration variables
25973 The @value{GDBN} Text User Interface (TUI) is a terminal
25974 interface which uses the @code{curses} library to show the source
25975 file, the assembly output, the program registers and @value{GDBN}
25976 commands in separate text windows. The TUI mode is supported only
25977 on platforms where a suitable version of the @code{curses} library
25980 The TUI mode is enabled by default when you invoke @value{GDBN} as
25981 @samp{@value{GDBP} -tui}.
25982 You can also switch in and out of TUI mode while @value{GDBN} runs by
25983 using various TUI commands and key bindings, such as @command{tui
25984 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25985 @ref{TUI Keys, ,TUI Key Bindings}.
25988 @section TUI Overview
25990 In TUI mode, @value{GDBN} can display several text windows:
25994 This window is the @value{GDBN} command window with the @value{GDBN}
25995 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25996 managed using readline.
25999 The source window shows the source file of the program. The current
26000 line and active breakpoints are displayed in this window.
26003 The assembly window shows the disassembly output of the program.
26006 This window shows the processor registers. Registers are highlighted
26007 when their values change.
26010 The source and assembly windows show the current program position
26011 by highlighting the current line and marking it with a @samp{>} marker.
26012 Breakpoints are indicated with two markers. The first marker
26013 indicates the breakpoint type:
26017 Breakpoint which was hit at least once.
26020 Breakpoint which was never hit.
26023 Hardware breakpoint which was hit at least once.
26026 Hardware breakpoint which was never hit.
26029 The second marker indicates whether the breakpoint is enabled or not:
26033 Breakpoint is enabled.
26036 Breakpoint is disabled.
26039 The source, assembly and register windows are updated when the current
26040 thread changes, when the frame changes, or when the program counter
26043 These windows are not all visible at the same time. The command
26044 window is always visible. The others can be arranged in several
26055 source and assembly,
26058 source and registers, or
26061 assembly and registers.
26064 A status line above the command window shows the following information:
26068 Indicates the current @value{GDBN} target.
26069 (@pxref{Targets, ,Specifying a Debugging Target}).
26072 Gives the current process or thread number.
26073 When no process is being debugged, this field is set to @code{No process}.
26076 Gives the current function name for the selected frame.
26077 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26078 When there is no symbol corresponding to the current program counter,
26079 the string @code{??} is displayed.
26082 Indicates the current line number for the selected frame.
26083 When the current line number is not known, the string @code{??} is displayed.
26086 Indicates the current program counter address.
26090 @section TUI Key Bindings
26091 @cindex TUI key bindings
26093 The TUI installs several key bindings in the readline keymaps
26094 @ifset SYSTEM_READLINE
26095 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26097 @ifclear SYSTEM_READLINE
26098 (@pxref{Command Line Editing}).
26100 The following key bindings are installed for both TUI mode and the
26101 @value{GDBN} standard mode.
26110 Enter or leave the TUI mode. When leaving the TUI mode,
26111 the curses window management stops and @value{GDBN} operates using
26112 its standard mode, writing on the terminal directly. When reentering
26113 the TUI mode, control is given back to the curses windows.
26114 The screen is then refreshed.
26118 Use a TUI layout with only one window. The layout will
26119 either be @samp{source} or @samp{assembly}. When the TUI mode
26120 is not active, it will switch to the TUI mode.
26122 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26126 Use a TUI layout with at least two windows. When the current
26127 layout already has two windows, the next layout with two windows is used.
26128 When a new layout is chosen, one window will always be common to the
26129 previous layout and the new one.
26131 Think of it as the Emacs @kbd{C-x 2} binding.
26135 Change the active window. The TUI associates several key bindings
26136 (like scrolling and arrow keys) with the active window. This command
26137 gives the focus to the next TUI window.
26139 Think of it as the Emacs @kbd{C-x o} binding.
26143 Switch in and out of the TUI SingleKey mode that binds single
26144 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26147 The following key bindings only work in the TUI mode:
26152 Scroll the active window one page up.
26156 Scroll the active window one page down.
26160 Scroll the active window one line up.
26164 Scroll the active window one line down.
26168 Scroll the active window one column left.
26172 Scroll the active window one column right.
26176 Refresh the screen.
26179 Because the arrow keys scroll the active window in the TUI mode, they
26180 are not available for their normal use by readline unless the command
26181 window has the focus. When another window is active, you must use
26182 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26183 and @kbd{C-f} to control the command window.
26185 @node TUI Single Key Mode
26186 @section TUI Single Key Mode
26187 @cindex TUI single key mode
26189 The TUI also provides a @dfn{SingleKey} mode, which binds several
26190 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26191 switch into this mode, where the following key bindings are used:
26194 @kindex c @r{(SingleKey TUI key)}
26198 @kindex d @r{(SingleKey TUI key)}
26202 @kindex f @r{(SingleKey TUI key)}
26206 @kindex n @r{(SingleKey TUI key)}
26210 @kindex o @r{(SingleKey TUI key)}
26212 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26214 @kindex q @r{(SingleKey TUI key)}
26216 exit the SingleKey mode.
26218 @kindex r @r{(SingleKey TUI key)}
26222 @kindex s @r{(SingleKey TUI key)}
26226 @kindex i @r{(SingleKey TUI key)}
26228 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26230 @kindex u @r{(SingleKey TUI key)}
26234 @kindex v @r{(SingleKey TUI key)}
26238 @kindex w @r{(SingleKey TUI key)}
26243 Other keys temporarily switch to the @value{GDBN} command prompt.
26244 The key that was pressed is inserted in the editing buffer so that
26245 it is possible to type most @value{GDBN} commands without interaction
26246 with the TUI SingleKey mode. Once the command is entered the TUI
26247 SingleKey mode is restored. The only way to permanently leave
26248 this mode is by typing @kbd{q} or @kbd{C-x s}.
26252 @section TUI-specific Commands
26253 @cindex TUI commands
26255 The TUI has specific commands to control the text windows.
26256 These commands are always available, even when @value{GDBN} is not in
26257 the TUI mode. When @value{GDBN} is in the standard mode, most
26258 of these commands will automatically switch to the TUI mode.
26260 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26261 terminal, or @value{GDBN} has been started with the machine interface
26262 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26263 these commands will fail with an error, because it would not be
26264 possible or desirable to enable curses window management.
26269 Activate TUI mode. The last active TUI window layout will be used if
26270 TUI mode has prevsiouly been used in the current debugging session,
26271 otherwise a default layout is used.
26274 @kindex tui disable
26275 Disable TUI mode, returning to the console interpreter.
26279 List and give the size of all displayed windows.
26281 @item layout @var{name}
26283 Changes which TUI windows are displayed. In each layout the command
26284 window is always displayed, the @var{name} parameter controls which
26285 additional windows are displayed, and can be any of the following:
26289 Display the next layout.
26292 Display the previous layout.
26295 Display the source and command windows.
26298 Display the assembly and command windows.
26301 Display the source, assembly, and command windows.
26304 When in @code{src} layout display the register, source, and command
26305 windows. When in @code{asm} or @code{split} layout display the
26306 register, assembler, and command windows.
26309 @item focus @var{name}
26311 Changes which TUI window is currently active for scrolling. The
26312 @var{name} parameter can be any of the following:
26316 Make the next window active for scrolling.
26319 Make the previous window active for scrolling.
26322 Make the source window active for scrolling.
26325 Make the assembly window active for scrolling.
26328 Make the register window active for scrolling.
26331 Make the command window active for scrolling.
26336 Refresh the screen. This is similar to typing @kbd{C-L}.
26338 @item tui reg @var{group}
26340 Changes the register group displayed in the tui register window to
26341 @var{group}. If the register window is not currently displayed this
26342 command will cause the register window to be displayed. The list of
26343 register groups, as well as their order is target specific. The
26344 following groups are available on most targets:
26347 Repeatedly selecting this group will cause the display to cycle
26348 through all of the available register groups.
26351 Repeatedly selecting this group will cause the display to cycle
26352 through all of the available register groups in the reverse order to
26356 Display the general registers.
26358 Display the floating point registers.
26360 Display the system registers.
26362 Display the vector registers.
26364 Display all registers.
26369 Update the source window and the current execution point.
26371 @item winheight @var{name} +@var{count}
26372 @itemx winheight @var{name} -@var{count}
26374 Change the height of the window @var{name} by @var{count}
26375 lines. Positive counts increase the height, while negative counts
26376 decrease it. The @var{name} parameter can be one of @code{src} (the
26377 source window), @code{cmd} (the command window), @code{asm} (the
26378 disassembly window), or @code{regs} (the register display window).
26380 @item tabset @var{nchars}
26382 Set the width of tab stops to be @var{nchars} characters. This
26383 setting affects the display of TAB characters in the source and
26387 @node TUI Configuration
26388 @section TUI Configuration Variables
26389 @cindex TUI configuration variables
26391 Several configuration variables control the appearance of TUI windows.
26394 @item set tui border-kind @var{kind}
26395 @kindex set tui border-kind
26396 Select the border appearance for the source, assembly and register windows.
26397 The possible values are the following:
26400 Use a space character to draw the border.
26403 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26406 Use the Alternate Character Set to draw the border. The border is
26407 drawn using character line graphics if the terminal supports them.
26410 @item set tui border-mode @var{mode}
26411 @kindex set tui border-mode
26412 @itemx set tui active-border-mode @var{mode}
26413 @kindex set tui active-border-mode
26414 Select the display attributes for the borders of the inactive windows
26415 or the active window. The @var{mode} can be one of the following:
26418 Use normal attributes to display the border.
26424 Use reverse video mode.
26427 Use half bright mode.
26429 @item half-standout
26430 Use half bright and standout mode.
26433 Use extra bright or bold mode.
26435 @item bold-standout
26436 Use extra bright or bold and standout mode.
26441 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26444 @cindex @sc{gnu} Emacs
26445 A special interface allows you to use @sc{gnu} Emacs to view (and
26446 edit) the source files for the program you are debugging with
26449 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26450 executable file you want to debug as an argument. This command starts
26451 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26452 created Emacs buffer.
26453 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26455 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26460 All ``terminal'' input and output goes through an Emacs buffer, called
26463 This applies both to @value{GDBN} commands and their output, and to the input
26464 and output done by the program you are debugging.
26466 This is useful because it means that you can copy the text of previous
26467 commands and input them again; you can even use parts of the output
26470 All the facilities of Emacs' Shell mode are available for interacting
26471 with your program. In particular, you can send signals the usual
26472 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26476 @value{GDBN} displays source code through Emacs.
26478 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26479 source file for that frame and puts an arrow (@samp{=>}) at the
26480 left margin of the current line. Emacs uses a separate buffer for
26481 source display, and splits the screen to show both your @value{GDBN} session
26484 Explicit @value{GDBN} @code{list} or search commands still produce output as
26485 usual, but you probably have no reason to use them from Emacs.
26488 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26489 a graphical mode, enabled by default, which provides further buffers
26490 that can control the execution and describe the state of your program.
26491 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26493 If you specify an absolute file name when prompted for the @kbd{M-x
26494 gdb} argument, then Emacs sets your current working directory to where
26495 your program resides. If you only specify the file name, then Emacs
26496 sets your current working directory to the directory associated
26497 with the previous buffer. In this case, @value{GDBN} may find your
26498 program by searching your environment's @code{PATH} variable, but on
26499 some operating systems it might not find the source. So, although the
26500 @value{GDBN} input and output session proceeds normally, the auxiliary
26501 buffer does not display the current source and line of execution.
26503 The initial working directory of @value{GDBN} is printed on the top
26504 line of the GUD buffer and this serves as a default for the commands
26505 that specify files for @value{GDBN} to operate on. @xref{Files,
26506 ,Commands to Specify Files}.
26508 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26509 need to call @value{GDBN} by a different name (for example, if you
26510 keep several configurations around, with different names) you can
26511 customize the Emacs variable @code{gud-gdb-command-name} to run the
26514 In the GUD buffer, you can use these special Emacs commands in
26515 addition to the standard Shell mode commands:
26519 Describe the features of Emacs' GUD Mode.
26522 Execute to another source line, like the @value{GDBN} @code{step} command; also
26523 update the display window to show the current file and location.
26526 Execute to next source line in this function, skipping all function
26527 calls, like the @value{GDBN} @code{next} command. Then update the display window
26528 to show the current file and location.
26531 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26532 display window accordingly.
26535 Execute until exit from the selected stack frame, like the @value{GDBN}
26536 @code{finish} command.
26539 Continue execution of your program, like the @value{GDBN} @code{continue}
26543 Go up the number of frames indicated by the numeric argument
26544 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26545 like the @value{GDBN} @code{up} command.
26548 Go down the number of frames indicated by the numeric argument, like the
26549 @value{GDBN} @code{down} command.
26552 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26553 tells @value{GDBN} to set a breakpoint on the source line point is on.
26555 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26556 separate frame which shows a backtrace when the GUD buffer is current.
26557 Move point to any frame in the stack and type @key{RET} to make it
26558 become the current frame and display the associated source in the
26559 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26560 selected frame become the current one. In graphical mode, the
26561 speedbar displays watch expressions.
26563 If you accidentally delete the source-display buffer, an easy way to get
26564 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26565 request a frame display; when you run under Emacs, this recreates
26566 the source buffer if necessary to show you the context of the current
26569 The source files displayed in Emacs are in ordinary Emacs buffers
26570 which are visiting the source files in the usual way. You can edit
26571 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26572 communicates with Emacs in terms of line numbers. If you add or
26573 delete lines from the text, the line numbers that @value{GDBN} knows cease
26574 to correspond properly with the code.
26576 A more detailed description of Emacs' interaction with @value{GDBN} is
26577 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26581 @chapter The @sc{gdb/mi} Interface
26583 @unnumberedsec Function and Purpose
26585 @cindex @sc{gdb/mi}, its purpose
26586 @sc{gdb/mi} is a line based machine oriented text interface to
26587 @value{GDBN} and is activated by specifying using the
26588 @option{--interpreter} command line option (@pxref{Mode Options}). It
26589 is specifically intended to support the development of systems which
26590 use the debugger as just one small component of a larger system.
26592 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26593 in the form of a reference manual.
26595 Note that @sc{gdb/mi} is still under construction, so some of the
26596 features described below are incomplete and subject to change
26597 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26599 @unnumberedsec Notation and Terminology
26601 @cindex notational conventions, for @sc{gdb/mi}
26602 This chapter uses the following notation:
26606 @code{|} separates two alternatives.
26609 @code{[ @var{something} ]} indicates that @var{something} is optional:
26610 it may or may not be given.
26613 @code{( @var{group} )*} means that @var{group} inside the parentheses
26614 may repeat zero or more times.
26617 @code{( @var{group} )+} means that @var{group} inside the parentheses
26618 may repeat one or more times.
26621 @code{"@var{string}"} means a literal @var{string}.
26625 @heading Dependencies
26629 * GDB/MI General Design::
26630 * GDB/MI Command Syntax::
26631 * GDB/MI Compatibility with CLI::
26632 * GDB/MI Development and Front Ends::
26633 * GDB/MI Output Records::
26634 * GDB/MI Simple Examples::
26635 * GDB/MI Command Description Format::
26636 * GDB/MI Breakpoint Commands::
26637 * GDB/MI Catchpoint Commands::
26638 * GDB/MI Program Context::
26639 * GDB/MI Thread Commands::
26640 * GDB/MI Ada Tasking Commands::
26641 * GDB/MI Program Execution::
26642 * GDB/MI Stack Manipulation::
26643 * GDB/MI Variable Objects::
26644 * GDB/MI Data Manipulation::
26645 * GDB/MI Tracepoint Commands::
26646 * GDB/MI Symbol Query::
26647 * GDB/MI File Commands::
26649 * GDB/MI Kod Commands::
26650 * GDB/MI Memory Overlay Commands::
26651 * GDB/MI Signal Handling Commands::
26653 * GDB/MI Target Manipulation::
26654 * GDB/MI File Transfer Commands::
26655 * GDB/MI Ada Exceptions Commands::
26656 * GDB/MI Support Commands::
26657 * GDB/MI Miscellaneous Commands::
26660 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26661 @node GDB/MI General Design
26662 @section @sc{gdb/mi} General Design
26663 @cindex GDB/MI General Design
26665 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26666 parts---commands sent to @value{GDBN}, responses to those commands
26667 and notifications. Each command results in exactly one response,
26668 indicating either successful completion of the command, or an error.
26669 For the commands that do not resume the target, the response contains the
26670 requested information. For the commands that resume the target, the
26671 response only indicates whether the target was successfully resumed.
26672 Notifications is the mechanism for reporting changes in the state of the
26673 target, or in @value{GDBN} state, that cannot conveniently be associated with
26674 a command and reported as part of that command response.
26676 The important examples of notifications are:
26680 Exec notifications. These are used to report changes in
26681 target state---when a target is resumed, or stopped. It would not
26682 be feasible to include this information in response of resuming
26683 commands, because one resume commands can result in multiple events in
26684 different threads. Also, quite some time may pass before any event
26685 happens in the target, while a frontend needs to know whether the resuming
26686 command itself was successfully executed.
26689 Console output, and status notifications. Console output
26690 notifications are used to report output of CLI commands, as well as
26691 diagnostics for other commands. Status notifications are used to
26692 report the progress of a long-running operation. Naturally, including
26693 this information in command response would mean no output is produced
26694 until the command is finished, which is undesirable.
26697 General notifications. Commands may have various side effects on
26698 the @value{GDBN} or target state beyond their official purpose. For example,
26699 a command may change the selected thread. Although such changes can
26700 be included in command response, using notification allows for more
26701 orthogonal frontend design.
26705 There's no guarantee that whenever an MI command reports an error,
26706 @value{GDBN} or the target are in any specific state, and especially,
26707 the state is not reverted to the state before the MI command was
26708 processed. Therefore, whenever an MI command results in an error,
26709 we recommend that the frontend refreshes all the information shown in
26710 the user interface.
26714 * Context management::
26715 * Asynchronous and non-stop modes::
26719 @node Context management
26720 @subsection Context management
26722 @subsubsection Threads and Frames
26724 In most cases when @value{GDBN} accesses the target, this access is
26725 done in context of a specific thread and frame (@pxref{Frames}).
26726 Often, even when accessing global data, the target requires that a thread
26727 be specified. The CLI interface maintains the selected thread and frame,
26728 and supplies them to target on each command. This is convenient,
26729 because a command line user would not want to specify that information
26730 explicitly on each command, and because user interacts with
26731 @value{GDBN} via a single terminal, so no confusion is possible as
26732 to what thread and frame are the current ones.
26734 In the case of MI, the concept of selected thread and frame is less
26735 useful. First, a frontend can easily remember this information
26736 itself. Second, a graphical frontend can have more than one window,
26737 each one used for debugging a different thread, and the frontend might
26738 want to access additional threads for internal purposes. This
26739 increases the risk that by relying on implicitly selected thread, the
26740 frontend may be operating on a wrong one. Therefore, each MI command
26741 should explicitly specify which thread and frame to operate on. To
26742 make it possible, each MI command accepts the @samp{--thread} and
26743 @samp{--frame} options, the value to each is @value{GDBN} global
26744 identifier for thread and frame to operate on.
26746 Usually, each top-level window in a frontend allows the user to select
26747 a thread and a frame, and remembers the user selection for further
26748 operations. However, in some cases @value{GDBN} may suggest that the
26749 current thread or frame be changed. For example, when stopping on a
26750 breakpoint it is reasonable to switch to the thread where breakpoint is
26751 hit. For another example, if the user issues the CLI @samp{thread} or
26752 @samp{frame} commands via the frontend, it is desirable to change the
26753 frontend's selection to the one specified by user. @value{GDBN}
26754 communicates the suggestion to change current thread and frame using the
26755 @samp{=thread-selected} notification.
26757 Note that historically, MI shares the selected thread with CLI, so
26758 frontends used the @code{-thread-select} to execute commands in the
26759 right context. However, getting this to work right is cumbersome. The
26760 simplest way is for frontend to emit @code{-thread-select} command
26761 before every command. This doubles the number of commands that need
26762 to be sent. The alternative approach is to suppress @code{-thread-select}
26763 if the selected thread in @value{GDBN} is supposed to be identical to the
26764 thread the frontend wants to operate on. However, getting this
26765 optimization right can be tricky. In particular, if the frontend
26766 sends several commands to @value{GDBN}, and one of the commands changes the
26767 selected thread, then the behaviour of subsequent commands will
26768 change. So, a frontend should either wait for response from such
26769 problematic commands, or explicitly add @code{-thread-select} for
26770 all subsequent commands. No frontend is known to do this exactly
26771 right, so it is suggested to just always pass the @samp{--thread} and
26772 @samp{--frame} options.
26774 @subsubsection Language
26776 The execution of several commands depends on which language is selected.
26777 By default, the current language (@pxref{show language}) is used.
26778 But for commands known to be language-sensitive, it is recommended
26779 to use the @samp{--language} option. This option takes one argument,
26780 which is the name of the language to use while executing the command.
26784 -data-evaluate-expression --language c "sizeof (void*)"
26789 The valid language names are the same names accepted by the
26790 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26791 @samp{local} or @samp{unknown}.
26793 @node Asynchronous and non-stop modes
26794 @subsection Asynchronous command execution and non-stop mode
26796 On some targets, @value{GDBN} is capable of processing MI commands
26797 even while the target is running. This is called @dfn{asynchronous
26798 command execution} (@pxref{Background Execution}). The frontend may
26799 specify a preferrence for asynchronous execution using the
26800 @code{-gdb-set mi-async 1} command, which should be emitted before
26801 either running the executable or attaching to the target. After the
26802 frontend has started the executable or attached to the target, it can
26803 find if asynchronous execution is enabled using the
26804 @code{-list-target-features} command.
26807 @item -gdb-set mi-async on
26808 @item -gdb-set mi-async off
26809 Set whether MI is in asynchronous mode.
26811 When @code{off}, which is the default, MI execution commands (e.g.,
26812 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26813 for the program to stop before processing further commands.
26815 When @code{on}, MI execution commands are background execution
26816 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26817 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26818 MI commands even while the target is running.
26820 @item -gdb-show mi-async
26821 Show whether MI asynchronous mode is enabled.
26824 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26825 @code{target-async} instead of @code{mi-async}, and it had the effect
26826 of both putting MI in asynchronous mode and making CLI background
26827 commands possible. CLI background commands are now always possible
26828 ``out of the box'' if the target supports them. The old spelling is
26829 kept as a deprecated alias for backwards compatibility.
26831 Even if @value{GDBN} can accept a command while target is running,
26832 many commands that access the target do not work when the target is
26833 running. Therefore, asynchronous command execution is most useful
26834 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26835 it is possible to examine the state of one thread, while other threads
26838 When a given thread is running, MI commands that try to access the
26839 target in the context of that thread may not work, or may work only on
26840 some targets. In particular, commands that try to operate on thread's
26841 stack will not work, on any target. Commands that read memory, or
26842 modify breakpoints, may work or not work, depending on the target. Note
26843 that even commands that operate on global state, such as @code{print},
26844 @code{set}, and breakpoint commands, still access the target in the
26845 context of a specific thread, so frontend should try to find a
26846 stopped thread and perform the operation on that thread (using the
26847 @samp{--thread} option).
26849 Which commands will work in the context of a running thread is
26850 highly target dependent. However, the two commands
26851 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26852 to find the state of a thread, will always work.
26854 @node Thread groups
26855 @subsection Thread groups
26856 @value{GDBN} may be used to debug several processes at the same time.
26857 On some platfroms, @value{GDBN} may support debugging of several
26858 hardware systems, each one having several cores with several different
26859 processes running on each core. This section describes the MI
26860 mechanism to support such debugging scenarios.
26862 The key observation is that regardless of the structure of the
26863 target, MI can have a global list of threads, because most commands that
26864 accept the @samp{--thread} option do not need to know what process that
26865 thread belongs to. Therefore, it is not necessary to introduce
26866 neither additional @samp{--process} option, nor an notion of the
26867 current process in the MI interface. The only strictly new feature
26868 that is required is the ability to find how the threads are grouped
26871 To allow the user to discover such grouping, and to support arbitrary
26872 hierarchy of machines/cores/processes, MI introduces the concept of a
26873 @dfn{thread group}. Thread group is a collection of threads and other
26874 thread groups. A thread group always has a string identifier, a type,
26875 and may have additional attributes specific to the type. A new
26876 command, @code{-list-thread-groups}, returns the list of top-level
26877 thread groups, which correspond to processes that @value{GDBN} is
26878 debugging at the moment. By passing an identifier of a thread group
26879 to the @code{-list-thread-groups} command, it is possible to obtain
26880 the members of specific thread group.
26882 To allow the user to easily discover processes, and other objects, he
26883 wishes to debug, a concept of @dfn{available thread group} is
26884 introduced. Available thread group is an thread group that
26885 @value{GDBN} is not debugging, but that can be attached to, using the
26886 @code{-target-attach} command. The list of available top-level thread
26887 groups can be obtained using @samp{-list-thread-groups --available}.
26888 In general, the content of a thread group may be only retrieved only
26889 after attaching to that thread group.
26891 Thread groups are related to inferiors (@pxref{Inferiors and
26892 Programs}). Each inferior corresponds to a thread group of a special
26893 type @samp{process}, and some additional operations are permitted on
26894 such thread groups.
26896 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26897 @node GDB/MI Command Syntax
26898 @section @sc{gdb/mi} Command Syntax
26901 * GDB/MI Input Syntax::
26902 * GDB/MI Output Syntax::
26905 @node GDB/MI Input Syntax
26906 @subsection @sc{gdb/mi} Input Syntax
26908 @cindex input syntax for @sc{gdb/mi}
26909 @cindex @sc{gdb/mi}, input syntax
26911 @item @var{command} @expansion{}
26912 @code{@var{cli-command} | @var{mi-command}}
26914 @item @var{cli-command} @expansion{}
26915 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26916 @var{cli-command} is any existing @value{GDBN} CLI command.
26918 @item @var{mi-command} @expansion{}
26919 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26920 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26922 @item @var{token} @expansion{}
26923 "any sequence of digits"
26925 @item @var{option} @expansion{}
26926 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26928 @item @var{parameter} @expansion{}
26929 @code{@var{non-blank-sequence} | @var{c-string}}
26931 @item @var{operation} @expansion{}
26932 @emph{any of the operations described in this chapter}
26934 @item @var{non-blank-sequence} @expansion{}
26935 @emph{anything, provided it doesn't contain special characters such as
26936 "-", @var{nl}, """ and of course " "}
26938 @item @var{c-string} @expansion{}
26939 @code{""" @var{seven-bit-iso-c-string-content} """}
26941 @item @var{nl} @expansion{}
26950 The CLI commands are still handled by the @sc{mi} interpreter; their
26951 output is described below.
26954 The @code{@var{token}}, when present, is passed back when the command
26958 Some @sc{mi} commands accept optional arguments as part of the parameter
26959 list. Each option is identified by a leading @samp{-} (dash) and may be
26960 followed by an optional argument parameter. Options occur first in the
26961 parameter list and can be delimited from normal parameters using
26962 @samp{--} (this is useful when some parameters begin with a dash).
26969 We want easy access to the existing CLI syntax (for debugging).
26972 We want it to be easy to spot a @sc{mi} operation.
26975 @node GDB/MI Output Syntax
26976 @subsection @sc{gdb/mi} Output Syntax
26978 @cindex output syntax of @sc{gdb/mi}
26979 @cindex @sc{gdb/mi}, output syntax
26980 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26981 followed, optionally, by a single result record. This result record
26982 is for the most recent command. The sequence of output records is
26983 terminated by @samp{(gdb)}.
26985 If an input command was prefixed with a @code{@var{token}} then the
26986 corresponding output for that command will also be prefixed by that same
26990 @item @var{output} @expansion{}
26991 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26993 @item @var{result-record} @expansion{}
26994 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26996 @item @var{out-of-band-record} @expansion{}
26997 @code{@var{async-record} | @var{stream-record}}
26999 @item @var{async-record} @expansion{}
27000 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27002 @item @var{exec-async-output} @expansion{}
27003 @code{[ @var{token} ] "*" @var{async-output nl}}
27005 @item @var{status-async-output} @expansion{}
27006 @code{[ @var{token} ] "+" @var{async-output nl}}
27008 @item @var{notify-async-output} @expansion{}
27009 @code{[ @var{token} ] "=" @var{async-output nl}}
27011 @item @var{async-output} @expansion{}
27012 @code{@var{async-class} ( "," @var{result} )*}
27014 @item @var{result-class} @expansion{}
27015 @code{"done" | "running" | "connected" | "error" | "exit"}
27017 @item @var{async-class} @expansion{}
27018 @code{"stopped" | @var{others}} (where @var{others} will be added
27019 depending on the needs---this is still in development).
27021 @item @var{result} @expansion{}
27022 @code{ @var{variable} "=" @var{value}}
27024 @item @var{variable} @expansion{}
27025 @code{ @var{string} }
27027 @item @var{value} @expansion{}
27028 @code{ @var{const} | @var{tuple} | @var{list} }
27030 @item @var{const} @expansion{}
27031 @code{@var{c-string}}
27033 @item @var{tuple} @expansion{}
27034 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27036 @item @var{list} @expansion{}
27037 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27038 @var{result} ( "," @var{result} )* "]" }
27040 @item @var{stream-record} @expansion{}
27041 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27043 @item @var{console-stream-output} @expansion{}
27044 @code{"~" @var{c-string nl}}
27046 @item @var{target-stream-output} @expansion{}
27047 @code{"@@" @var{c-string nl}}
27049 @item @var{log-stream-output} @expansion{}
27050 @code{"&" @var{c-string nl}}
27052 @item @var{nl} @expansion{}
27055 @item @var{token} @expansion{}
27056 @emph{any sequence of digits}.
27064 All output sequences end in a single line containing a period.
27067 The @code{@var{token}} is from the corresponding request. Note that
27068 for all async output, while the token is allowed by the grammar and
27069 may be output by future versions of @value{GDBN} for select async
27070 output messages, it is generally omitted. Frontends should treat
27071 all async output as reporting general changes in the state of the
27072 target and there should be no need to associate async output to any
27076 @cindex status output in @sc{gdb/mi}
27077 @var{status-async-output} contains on-going status information about the
27078 progress of a slow operation. It can be discarded. All status output is
27079 prefixed by @samp{+}.
27082 @cindex async output in @sc{gdb/mi}
27083 @var{exec-async-output} contains asynchronous state change on the target
27084 (stopped, started, disappeared). All async output is prefixed by
27088 @cindex notify output in @sc{gdb/mi}
27089 @var{notify-async-output} contains supplementary information that the
27090 client should handle (e.g., a new breakpoint information). All notify
27091 output is prefixed by @samp{=}.
27094 @cindex console output in @sc{gdb/mi}
27095 @var{console-stream-output} is output that should be displayed as is in the
27096 console. It is the textual response to a CLI command. All the console
27097 output is prefixed by @samp{~}.
27100 @cindex target output in @sc{gdb/mi}
27101 @var{target-stream-output} is the output produced by the target program.
27102 All the target output is prefixed by @samp{@@}.
27105 @cindex log output in @sc{gdb/mi}
27106 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27107 instance messages that should be displayed as part of an error log. All
27108 the log output is prefixed by @samp{&}.
27111 @cindex list output in @sc{gdb/mi}
27112 New @sc{gdb/mi} commands should only output @var{lists} containing
27118 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27119 details about the various output records.
27121 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27122 @node GDB/MI Compatibility with CLI
27123 @section @sc{gdb/mi} Compatibility with CLI
27125 @cindex compatibility, @sc{gdb/mi} and CLI
27126 @cindex @sc{gdb/mi}, compatibility with CLI
27128 For the developers convenience CLI commands can be entered directly,
27129 but there may be some unexpected behaviour. For example, commands
27130 that query the user will behave as if the user replied yes, breakpoint
27131 command lists are not executed and some CLI commands, such as
27132 @code{if}, @code{when} and @code{define}, prompt for further input with
27133 @samp{>}, which is not valid MI output.
27135 This feature may be removed at some stage in the future and it is
27136 recommended that front ends use the @code{-interpreter-exec} command
27137 (@pxref{-interpreter-exec}).
27139 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27140 @node GDB/MI Development and Front Ends
27141 @section @sc{gdb/mi} Development and Front Ends
27142 @cindex @sc{gdb/mi} development
27144 The application which takes the MI output and presents the state of the
27145 program being debugged to the user is called a @dfn{front end}.
27147 Although @sc{gdb/mi} is still incomplete, it is currently being used
27148 by a variety of front ends to @value{GDBN}. This makes it difficult
27149 to introduce new functionality without breaking existing usage. This
27150 section tries to minimize the problems by describing how the protocol
27153 Some changes in MI need not break a carefully designed front end, and
27154 for these the MI version will remain unchanged. The following is a
27155 list of changes that may occur within one level, so front ends should
27156 parse MI output in a way that can handle them:
27160 New MI commands may be added.
27163 New fields may be added to the output of any MI command.
27166 The range of values for fields with specified values, e.g.,
27167 @code{in_scope} (@pxref{-var-update}) may be extended.
27169 @c The format of field's content e.g type prefix, may change so parse it
27170 @c at your own risk. Yes, in general?
27172 @c The order of fields may change? Shouldn't really matter but it might
27173 @c resolve inconsistencies.
27176 If the changes are likely to break front ends, the MI version level
27177 will be increased by one. This will allow the front end to parse the
27178 output according to the MI version. Apart from mi0, new versions of
27179 @value{GDBN} will not support old versions of MI and it will be the
27180 responsibility of the front end to work with the new one.
27182 @c Starting with mi3, add a new command -mi-version that prints the MI
27185 The best way to avoid unexpected changes in MI that might break your front
27186 end is to make your project known to @value{GDBN} developers and
27187 follow development on @email{gdb@@sourceware.org} and
27188 @email{gdb-patches@@sourceware.org}.
27189 @cindex mailing lists
27191 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27192 @node GDB/MI Output Records
27193 @section @sc{gdb/mi} Output Records
27196 * GDB/MI Result Records::
27197 * GDB/MI Stream Records::
27198 * GDB/MI Async Records::
27199 * GDB/MI Breakpoint Information::
27200 * GDB/MI Frame Information::
27201 * GDB/MI Thread Information::
27202 * GDB/MI Ada Exception Information::
27205 @node GDB/MI Result Records
27206 @subsection @sc{gdb/mi} Result Records
27208 @cindex result records in @sc{gdb/mi}
27209 @cindex @sc{gdb/mi}, result records
27210 In addition to a number of out-of-band notifications, the response to a
27211 @sc{gdb/mi} command includes one of the following result indications:
27215 @item "^done" [ "," @var{results} ]
27216 The synchronous operation was successful, @code{@var{results}} are the return
27221 This result record is equivalent to @samp{^done}. Historically, it
27222 was output instead of @samp{^done} if the command has resumed the
27223 target. This behaviour is maintained for backward compatibility, but
27224 all frontends should treat @samp{^done} and @samp{^running}
27225 identically and rely on the @samp{*running} output record to determine
27226 which threads are resumed.
27230 @value{GDBN} has connected to a remote target.
27232 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27234 The operation failed. The @code{msg=@var{c-string}} variable contains
27235 the corresponding error message.
27237 If present, the @code{code=@var{c-string}} variable provides an error
27238 code on which consumers can rely on to detect the corresponding
27239 error condition. At present, only one error code is defined:
27242 @item "undefined-command"
27243 Indicates that the command causing the error does not exist.
27248 @value{GDBN} has terminated.
27252 @node GDB/MI Stream Records
27253 @subsection @sc{gdb/mi} Stream Records
27255 @cindex @sc{gdb/mi}, stream records
27256 @cindex stream records in @sc{gdb/mi}
27257 @value{GDBN} internally maintains a number of output streams: the console, the
27258 target, and the log. The output intended for each of these streams is
27259 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27261 Each stream record begins with a unique @dfn{prefix character} which
27262 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27263 Syntax}). In addition to the prefix, each stream record contains a
27264 @code{@var{string-output}}. This is either raw text (with an implicit new
27265 line) or a quoted C string (which does not contain an implicit newline).
27268 @item "~" @var{string-output}
27269 The console output stream contains text that should be displayed in the
27270 CLI console window. It contains the textual responses to CLI commands.
27272 @item "@@" @var{string-output}
27273 The target output stream contains any textual output from the running
27274 target. This is only present when GDB's event loop is truly
27275 asynchronous, which is currently only the case for remote targets.
27277 @item "&" @var{string-output}
27278 The log stream contains debugging messages being produced by @value{GDBN}'s
27282 @node GDB/MI Async Records
27283 @subsection @sc{gdb/mi} Async Records
27285 @cindex async records in @sc{gdb/mi}
27286 @cindex @sc{gdb/mi}, async records
27287 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27288 additional changes that have occurred. Those changes can either be a
27289 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27290 target activity (e.g., target stopped).
27292 The following is the list of possible async records:
27296 @item *running,thread-id="@var{thread}"
27297 The target is now running. The @var{thread} field can be the global
27298 thread ID of the the thread that is now running, and it can be
27299 @samp{all} if all threads are running. The frontend should assume
27300 that no interaction with a running thread is possible after this
27301 notification is produced. The frontend should not assume that this
27302 notification is output only once for any command. @value{GDBN} may
27303 emit this notification several times, either for different threads,
27304 because it cannot resume all threads together, or even for a single
27305 thread, if the thread must be stepped though some code before letting
27308 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27309 The target has stopped. The @var{reason} field can have one of the
27313 @item breakpoint-hit
27314 A breakpoint was reached.
27315 @item watchpoint-trigger
27316 A watchpoint was triggered.
27317 @item read-watchpoint-trigger
27318 A read watchpoint was triggered.
27319 @item access-watchpoint-trigger
27320 An access watchpoint was triggered.
27321 @item function-finished
27322 An -exec-finish or similar CLI command was accomplished.
27323 @item location-reached
27324 An -exec-until or similar CLI command was accomplished.
27325 @item watchpoint-scope
27326 A watchpoint has gone out of scope.
27327 @item end-stepping-range
27328 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27329 similar CLI command was accomplished.
27330 @item exited-signalled
27331 The inferior exited because of a signal.
27333 The inferior exited.
27334 @item exited-normally
27335 The inferior exited normally.
27336 @item signal-received
27337 A signal was received by the inferior.
27339 The inferior has stopped due to a library being loaded or unloaded.
27340 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27341 set or when a @code{catch load} or @code{catch unload} catchpoint is
27342 in use (@pxref{Set Catchpoints}).
27344 The inferior has forked. This is reported when @code{catch fork}
27345 (@pxref{Set Catchpoints}) has been used.
27347 The inferior has vforked. This is reported in when @code{catch vfork}
27348 (@pxref{Set Catchpoints}) has been used.
27349 @item syscall-entry
27350 The inferior entered a system call. This is reported when @code{catch
27351 syscall} (@pxref{Set Catchpoints}) has been used.
27352 @item syscall-return
27353 The inferior returned from a system call. This is reported when
27354 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27356 The inferior called @code{exec}. This is reported when @code{catch exec}
27357 (@pxref{Set Catchpoints}) has been used.
27360 The @var{id} field identifies the global thread ID of the thread
27361 that directly caused the stop -- for example by hitting a breakpoint.
27362 Depending on whether all-stop
27363 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27364 stop all threads, or only the thread that directly triggered the stop.
27365 If all threads are stopped, the @var{stopped} field will have the
27366 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27367 field will be a list of thread identifiers. Presently, this list will
27368 always include a single thread, but frontend should be prepared to see
27369 several threads in the list. The @var{core} field reports the
27370 processor core on which the stop event has happened. This field may be absent
27371 if such information is not available.
27373 @item =thread-group-added,id="@var{id}"
27374 @itemx =thread-group-removed,id="@var{id}"
27375 A thread group was either added or removed. The @var{id} field
27376 contains the @value{GDBN} identifier of the thread group. When a thread
27377 group is added, it generally might not be associated with a running
27378 process. When a thread group is removed, its id becomes invalid and
27379 cannot be used in any way.
27381 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27382 A thread group became associated with a running program,
27383 either because the program was just started or the thread group
27384 was attached to a program. The @var{id} field contains the
27385 @value{GDBN} identifier of the thread group. The @var{pid} field
27386 contains process identifier, specific to the operating system.
27388 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27389 A thread group is no longer associated with a running program,
27390 either because the program has exited, or because it was detached
27391 from. The @var{id} field contains the @value{GDBN} identifier of the
27392 thread group. The @var{code} field is the exit code of the inferior; it exists
27393 only when the inferior exited with some code.
27395 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27396 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27397 A thread either was created, or has exited. The @var{id} field
27398 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27399 field identifies the thread group this thread belongs to.
27401 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27402 Informs that the selected thread or frame were changed. This notification
27403 is not emitted as result of the @code{-thread-select} or
27404 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27405 that is not documented to change the selected thread and frame actually
27406 changes them. In particular, invoking, directly or indirectly
27407 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27408 will generate this notification. Changing the thread or frame from another
27409 user interface (see @ref{Interpreters}) will also generate this notification.
27411 The @var{frame} field is only present if the newly selected thread is
27412 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27414 We suggest that in response to this notification, front ends
27415 highlight the selected thread and cause subsequent commands to apply to
27418 @item =library-loaded,...
27419 Reports that a new library file was loaded by the program. This
27420 notification has 5 fields---@var{id}, @var{target-name},
27421 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27422 opaque identifier of the library. For remote debugging case,
27423 @var{target-name} and @var{host-name} fields give the name of the
27424 library file on the target, and on the host respectively. For native
27425 debugging, both those fields have the same value. The
27426 @var{symbols-loaded} field is emitted only for backward compatibility
27427 and should not be relied on to convey any useful information. The
27428 @var{thread-group} field, if present, specifies the id of the thread
27429 group in whose context the library was loaded. If the field is
27430 absent, it means the library was loaded in the context of all present
27431 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27434 @item =library-unloaded,...
27435 Reports that a library was unloaded by the program. This notification
27436 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27437 the same meaning as for the @code{=library-loaded} notification.
27438 The @var{thread-group} field, if present, specifies the id of the
27439 thread group in whose context the library was unloaded. If the field is
27440 absent, it means the library was unloaded in the context of all present
27443 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27444 @itemx =traceframe-changed,end
27445 Reports that the trace frame was changed and its new number is
27446 @var{tfnum}. The number of the tracepoint associated with this trace
27447 frame is @var{tpnum}.
27449 @item =tsv-created,name=@var{name},initial=@var{initial}
27450 Reports that the new trace state variable @var{name} is created with
27451 initial value @var{initial}.
27453 @item =tsv-deleted,name=@var{name}
27454 @itemx =tsv-deleted
27455 Reports that the trace state variable @var{name} is deleted or all
27456 trace state variables are deleted.
27458 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27459 Reports that the trace state variable @var{name} is modified with
27460 the initial value @var{initial}. The current value @var{current} of
27461 trace state variable is optional and is reported if the current
27462 value of trace state variable is known.
27464 @item =breakpoint-created,bkpt=@{...@}
27465 @itemx =breakpoint-modified,bkpt=@{...@}
27466 @itemx =breakpoint-deleted,id=@var{number}
27467 Reports that a breakpoint was created, modified, or deleted,
27468 respectively. Only user-visible breakpoints are reported to the MI
27471 The @var{bkpt} argument is of the same form as returned by the various
27472 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27473 @var{number} is the ordinal number of the breakpoint.
27475 Note that if a breakpoint is emitted in the result record of a
27476 command, then it will not also be emitted in an async record.
27478 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27479 @itemx =record-stopped,thread-group="@var{id}"
27480 Execution log recording was either started or stopped on an
27481 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27482 group corresponding to the affected inferior.
27484 The @var{method} field indicates the method used to record execution. If the
27485 method in use supports multiple recording formats, @var{format} will be present
27486 and contain the currently used format. @xref{Process Record and Replay},
27487 for existing method and format values.
27489 @item =cmd-param-changed,param=@var{param},value=@var{value}
27490 Reports that a parameter of the command @code{set @var{param}} is
27491 changed to @var{value}. In the multi-word @code{set} command,
27492 the @var{param} is the whole parameter list to @code{set} command.
27493 For example, In command @code{set check type on}, @var{param}
27494 is @code{check type} and @var{value} is @code{on}.
27496 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27497 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27498 written in an inferior. The @var{id} is the identifier of the
27499 thread group corresponding to the affected inferior. The optional
27500 @code{type="code"} part is reported if the memory written to holds
27504 @node GDB/MI Breakpoint Information
27505 @subsection @sc{gdb/mi} Breakpoint Information
27507 When @value{GDBN} reports information about a breakpoint, a
27508 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27513 The breakpoint number. For a breakpoint that represents one location
27514 of a multi-location breakpoint, this will be a dotted pair, like
27518 The type of the breakpoint. For ordinary breakpoints this will be
27519 @samp{breakpoint}, but many values are possible.
27522 If the type of the breakpoint is @samp{catchpoint}, then this
27523 indicates the exact type of catchpoint.
27526 This is the breakpoint disposition---either @samp{del}, meaning that
27527 the breakpoint will be deleted at the next stop, or @samp{keep},
27528 meaning that the breakpoint will not be deleted.
27531 This indicates whether the breakpoint is enabled, in which case the
27532 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27533 Note that this is not the same as the field @code{enable}.
27536 The address of the breakpoint. This may be a hexidecimal number,
27537 giving the address; or the string @samp{<PENDING>}, for a pending
27538 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27539 multiple locations. This field will not be present if no address can
27540 be determined. For example, a watchpoint does not have an address.
27543 If known, the function in which the breakpoint appears.
27544 If not known, this field is not present.
27547 The name of the source file which contains this function, if known.
27548 If not known, this field is not present.
27551 The full file name of the source file which contains this function, if
27552 known. If not known, this field is not present.
27555 The line number at which this breakpoint appears, if known.
27556 If not known, this field is not present.
27559 If the source file is not known, this field may be provided. If
27560 provided, this holds the address of the breakpoint, possibly followed
27564 If this breakpoint is pending, this field is present and holds the
27565 text used to set the breakpoint, as entered by the user.
27568 Where this breakpoint's condition is evaluated, either @samp{host} or
27572 If this is a thread-specific breakpoint, then this identifies the
27573 thread in which the breakpoint can trigger.
27576 If this breakpoint is restricted to a particular Ada task, then this
27577 field will hold the task identifier.
27580 If the breakpoint is conditional, this is the condition expression.
27583 The ignore count of the breakpoint.
27586 The enable count of the breakpoint.
27588 @item traceframe-usage
27591 @item static-tracepoint-marker-string-id
27592 For a static tracepoint, the name of the static tracepoint marker.
27595 For a masked watchpoint, this is the mask.
27598 A tracepoint's pass count.
27600 @item original-location
27601 The location of the breakpoint as originally specified by the user.
27602 This field is optional.
27605 The number of times the breakpoint has been hit.
27608 This field is only given for tracepoints. This is either @samp{y},
27609 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27613 Some extra data, the exact contents of which are type-dependent.
27617 For example, here is what the output of @code{-break-insert}
27618 (@pxref{GDB/MI Breakpoint Commands}) might be:
27621 -> -break-insert main
27622 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27623 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27624 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27629 @node GDB/MI Frame Information
27630 @subsection @sc{gdb/mi} Frame Information
27632 Response from many MI commands includes an information about stack
27633 frame. This information is a tuple that may have the following
27638 The level of the stack frame. The innermost frame has the level of
27639 zero. This field is always present.
27642 The name of the function corresponding to the frame. This field may
27643 be absent if @value{GDBN} is unable to determine the function name.
27646 The code address for the frame. This field is always present.
27649 The name of the source files that correspond to the frame's code
27650 address. This field may be absent.
27653 The source line corresponding to the frames' code address. This field
27657 The name of the binary file (either executable or shared library) the
27658 corresponds to the frame's code address. This field may be absent.
27662 @node GDB/MI Thread Information
27663 @subsection @sc{gdb/mi} Thread Information
27665 Whenever @value{GDBN} has to report an information about a thread, it
27666 uses a tuple with the following fields. The fields are always present unless
27671 The global numeric id assigned to the thread by @value{GDBN}.
27674 The target-specific string identifying the thread.
27677 Additional information about the thread provided by the target.
27678 It is supposed to be human-readable and not interpreted by the
27679 frontend. This field is optional.
27682 The name of the thread. If the user specified a name using the
27683 @code{thread name} command, then this name is given. Otherwise, if
27684 @value{GDBN} can extract the thread name from the target, then that
27685 name is given. If @value{GDBN} cannot find the thread name, then this
27689 The execution state of the thread, either @samp{stopped} or @samp{running},
27690 depending on whether the thread is presently running.
27693 The stack frame currently executing in the thread. This field is only present
27694 if the thread is stopped. Its format is documented in
27695 @ref{GDB/MI Frame Information}.
27698 The value of this field is an integer number of the processor core the
27699 thread was last seen on. This field is optional.
27702 @node GDB/MI Ada Exception Information
27703 @subsection @sc{gdb/mi} Ada Exception Information
27705 Whenever a @code{*stopped} record is emitted because the program
27706 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27707 @value{GDBN} provides the name of the exception that was raised via
27708 the @code{exception-name} field. Also, for exceptions that were raised
27709 with an exception message, @value{GDBN} provides that message via
27710 the @code{exception-message} field.
27712 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27713 @node GDB/MI Simple Examples
27714 @section Simple Examples of @sc{gdb/mi} Interaction
27715 @cindex @sc{gdb/mi}, simple examples
27717 This subsection presents several simple examples of interaction using
27718 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27719 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27720 the output received from @sc{gdb/mi}.
27722 Note the line breaks shown in the examples are here only for
27723 readability, they don't appear in the real output.
27725 @subheading Setting a Breakpoint
27727 Setting a breakpoint generates synchronous output which contains detailed
27728 information of the breakpoint.
27731 -> -break-insert main
27732 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27733 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27734 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27739 @subheading Program Execution
27741 Program execution generates asynchronous records and MI gives the
27742 reason that execution stopped.
27748 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27749 frame=@{addr="0x08048564",func="main",
27750 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27751 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27756 <- *stopped,reason="exited-normally"
27760 @subheading Quitting @value{GDBN}
27762 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27770 Please note that @samp{^exit} is printed immediately, but it might
27771 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27772 performs necessary cleanups, including killing programs being debugged
27773 or disconnecting from debug hardware, so the frontend should wait till
27774 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27775 fails to exit in reasonable time.
27777 @subheading A Bad Command
27779 Here's what happens if you pass a non-existent command:
27783 <- ^error,msg="Undefined MI command: rubbish"
27788 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27789 @node GDB/MI Command Description Format
27790 @section @sc{gdb/mi} Command Description Format
27792 The remaining sections describe blocks of commands. Each block of
27793 commands is laid out in a fashion similar to this section.
27795 @subheading Motivation
27797 The motivation for this collection of commands.
27799 @subheading Introduction
27801 A brief introduction to this collection of commands as a whole.
27803 @subheading Commands
27805 For each command in the block, the following is described:
27807 @subsubheading Synopsis
27810 -command @var{args}@dots{}
27813 @subsubheading Result
27815 @subsubheading @value{GDBN} Command
27817 The corresponding @value{GDBN} CLI command(s), if any.
27819 @subsubheading Example
27821 Example(s) formatted for readability. Some of the described commands have
27822 not been implemented yet and these are labeled N.A.@: (not available).
27825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27826 @node GDB/MI Breakpoint Commands
27827 @section @sc{gdb/mi} Breakpoint Commands
27829 @cindex breakpoint commands for @sc{gdb/mi}
27830 @cindex @sc{gdb/mi}, breakpoint commands
27831 This section documents @sc{gdb/mi} commands for manipulating
27834 @subheading The @code{-break-after} Command
27835 @findex -break-after
27837 @subsubheading Synopsis
27840 -break-after @var{number} @var{count}
27843 The breakpoint number @var{number} is not in effect until it has been
27844 hit @var{count} times. To see how this is reflected in the output of
27845 the @samp{-break-list} command, see the description of the
27846 @samp{-break-list} command below.
27848 @subsubheading @value{GDBN} Command
27850 The corresponding @value{GDBN} command is @samp{ignore}.
27852 @subsubheading Example
27857 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27858 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27859 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27867 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27868 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27869 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27870 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27871 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27872 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27873 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27874 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27875 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27876 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27881 @subheading The @code{-break-catch} Command
27882 @findex -break-catch
27885 @subheading The @code{-break-commands} Command
27886 @findex -break-commands
27888 @subsubheading Synopsis
27891 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27894 Specifies the CLI commands that should be executed when breakpoint
27895 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27896 are the commands. If no command is specified, any previously-set
27897 commands are cleared. @xref{Break Commands}. Typical use of this
27898 functionality is tracing a program, that is, printing of values of
27899 some variables whenever breakpoint is hit and then continuing.
27901 @subsubheading @value{GDBN} Command
27903 The corresponding @value{GDBN} command is @samp{commands}.
27905 @subsubheading Example
27910 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27911 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27912 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27915 -break-commands 1 "print v" "continue"
27920 @subheading The @code{-break-condition} Command
27921 @findex -break-condition
27923 @subsubheading Synopsis
27926 -break-condition @var{number} @var{expr}
27929 Breakpoint @var{number} will stop the program only if the condition in
27930 @var{expr} is true. The condition becomes part of the
27931 @samp{-break-list} output (see the description of the @samp{-break-list}
27934 @subsubheading @value{GDBN} Command
27936 The corresponding @value{GDBN} command is @samp{condition}.
27938 @subsubheading Example
27942 -break-condition 1 1
27946 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27947 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27948 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27949 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27950 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27951 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27952 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27953 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27954 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27955 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27959 @subheading The @code{-break-delete} Command
27960 @findex -break-delete
27962 @subsubheading Synopsis
27965 -break-delete ( @var{breakpoint} )+
27968 Delete the breakpoint(s) whose number(s) are specified in the argument
27969 list. This is obviously reflected in the breakpoint list.
27971 @subsubheading @value{GDBN} Command
27973 The corresponding @value{GDBN} command is @samp{delete}.
27975 @subsubheading Example
27983 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27984 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27985 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27986 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27987 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27988 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27989 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27994 @subheading The @code{-break-disable} Command
27995 @findex -break-disable
27997 @subsubheading Synopsis
28000 -break-disable ( @var{breakpoint} )+
28003 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28004 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28006 @subsubheading @value{GDBN} Command
28008 The corresponding @value{GDBN} command is @samp{disable}.
28010 @subsubheading Example
28018 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28019 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28020 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28021 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28022 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28023 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28024 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28025 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28026 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28027 line="5",thread-groups=["i1"],times="0"@}]@}
28031 @subheading The @code{-break-enable} Command
28032 @findex -break-enable
28034 @subsubheading Synopsis
28037 -break-enable ( @var{breakpoint} )+
28040 Enable (previously disabled) @var{breakpoint}(s).
28042 @subsubheading @value{GDBN} Command
28044 The corresponding @value{GDBN} command is @samp{enable}.
28046 @subsubheading Example
28054 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28055 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28056 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28057 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28058 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28059 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28060 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28061 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28062 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28063 line="5",thread-groups=["i1"],times="0"@}]@}
28067 @subheading The @code{-break-info} Command
28068 @findex -break-info
28070 @subsubheading Synopsis
28073 -break-info @var{breakpoint}
28077 Get information about a single breakpoint.
28079 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28080 Information}, for details on the format of each breakpoint in the
28083 @subsubheading @value{GDBN} Command
28085 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28087 @subsubheading Example
28090 @subheading The @code{-break-insert} Command
28091 @findex -break-insert
28092 @anchor{-break-insert}
28094 @subsubheading Synopsis
28097 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28098 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28099 [ -p @var{thread-id} ] [ @var{location} ]
28103 If specified, @var{location}, can be one of:
28106 @item linespec location
28107 A linespec location. @xref{Linespec Locations}.
28109 @item explicit location
28110 An explicit location. @sc{gdb/mi} explicit locations are
28111 analogous to the CLI's explicit locations using the option names
28112 listed below. @xref{Explicit Locations}.
28115 @item --source @var{filename}
28116 The source file name of the location. This option requires the use
28117 of either @samp{--function} or @samp{--line}.
28119 @item --function @var{function}
28120 The name of a function or method.
28122 @item --label @var{label}
28123 The name of a label.
28125 @item --line @var{lineoffset}
28126 An absolute or relative line offset from the start of the location.
28129 @item address location
28130 An address location, *@var{address}. @xref{Address Locations}.
28134 The possible optional parameters of this command are:
28138 Insert a temporary breakpoint.
28140 Insert a hardware breakpoint.
28142 If @var{location} cannot be parsed (for example if it
28143 refers to unknown files or functions), create a pending
28144 breakpoint. Without this flag, @value{GDBN} will report
28145 an error, and won't create a breakpoint, if @var{location}
28148 Create a disabled breakpoint.
28150 Create a tracepoint. @xref{Tracepoints}. When this parameter
28151 is used together with @samp{-h}, a fast tracepoint is created.
28152 @item -c @var{condition}
28153 Make the breakpoint conditional on @var{condition}.
28154 @item -i @var{ignore-count}
28155 Initialize the @var{ignore-count}.
28156 @item -p @var{thread-id}
28157 Restrict the breakpoint to the thread with the specified global
28161 @subsubheading Result
28163 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28164 resulting breakpoint.
28166 Note: this format is open to change.
28167 @c An out-of-band breakpoint instead of part of the result?
28169 @subsubheading @value{GDBN} Command
28171 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28172 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28174 @subsubheading Example
28179 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28180 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28183 -break-insert -t foo
28184 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28185 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28189 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28190 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28191 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28192 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28193 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28194 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28195 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28196 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28197 addr="0x0001072c", func="main",file="recursive2.c",
28198 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28200 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28201 addr="0x00010774",func="foo",file="recursive2.c",
28202 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28205 @c -break-insert -r foo.*
28206 @c ~int foo(int, int);
28207 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28208 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28213 @subheading The @code{-dprintf-insert} Command
28214 @findex -dprintf-insert
28216 @subsubheading Synopsis
28219 -dprintf-insert [ -t ] [ -f ] [ -d ]
28220 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28221 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28226 If supplied, @var{location} may be specified the same way as for
28227 the @code{-break-insert} command. @xref{-break-insert}.
28229 The possible optional parameters of this command are:
28233 Insert a temporary breakpoint.
28235 If @var{location} cannot be parsed (for example, if it
28236 refers to unknown files or functions), create a pending
28237 breakpoint. Without this flag, @value{GDBN} will report
28238 an error, and won't create a breakpoint, if @var{location}
28241 Create a disabled breakpoint.
28242 @item -c @var{condition}
28243 Make the breakpoint conditional on @var{condition}.
28244 @item -i @var{ignore-count}
28245 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28246 to @var{ignore-count}.
28247 @item -p @var{thread-id}
28248 Restrict the breakpoint to the thread with the specified global
28252 @subsubheading Result
28254 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28255 resulting breakpoint.
28257 @c An out-of-band breakpoint instead of part of the result?
28259 @subsubheading @value{GDBN} Command
28261 The corresponding @value{GDBN} command is @samp{dprintf}.
28263 @subsubheading Example
28267 4-dprintf-insert foo "At foo entry\n"
28268 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28269 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28270 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28271 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28272 original-location="foo"@}
28274 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28275 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28276 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28277 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28278 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28279 original-location="mi-dprintf.c:26"@}
28283 @subheading The @code{-break-list} Command
28284 @findex -break-list
28286 @subsubheading Synopsis
28292 Displays the list of inserted breakpoints, showing the following fields:
28296 number of the breakpoint
28298 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28300 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28303 is the breakpoint enabled or no: @samp{y} or @samp{n}
28305 memory location at which the breakpoint is set
28307 logical location of the breakpoint, expressed by function name, file
28309 @item Thread-groups
28310 list of thread groups to which this breakpoint applies
28312 number of times the breakpoint has been hit
28315 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28316 @code{body} field is an empty list.
28318 @subsubheading @value{GDBN} Command
28320 The corresponding @value{GDBN} command is @samp{info break}.
28322 @subsubheading Example
28327 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28328 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28329 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28330 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28331 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28332 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28333 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28334 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28335 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28337 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28338 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28339 line="13",thread-groups=["i1"],times="0"@}]@}
28343 Here's an example of the result when there are no breakpoints:
28348 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28349 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28350 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28351 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28352 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28353 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28354 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28359 @subheading The @code{-break-passcount} Command
28360 @findex -break-passcount
28362 @subsubheading Synopsis
28365 -break-passcount @var{tracepoint-number} @var{passcount}
28368 Set the passcount for tracepoint @var{tracepoint-number} to
28369 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28370 is not a tracepoint, error is emitted. This corresponds to CLI
28371 command @samp{passcount}.
28373 @subheading The @code{-break-watch} Command
28374 @findex -break-watch
28376 @subsubheading Synopsis
28379 -break-watch [ -a | -r ]
28382 Create a watchpoint. With the @samp{-a} option it will create an
28383 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28384 read from or on a write to the memory location. With the @samp{-r}
28385 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28386 trigger only when the memory location is accessed for reading. Without
28387 either of the options, the watchpoint created is a regular watchpoint,
28388 i.e., it will trigger when the memory location is accessed for writing.
28389 @xref{Set Watchpoints, , Setting Watchpoints}.
28391 Note that @samp{-break-list} will report a single list of watchpoints and
28392 breakpoints inserted.
28394 @subsubheading @value{GDBN} Command
28396 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28399 @subsubheading Example
28401 Setting a watchpoint on a variable in the @code{main} function:
28406 ^done,wpt=@{number="2",exp="x"@}
28411 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28412 value=@{old="-268439212",new="55"@},
28413 frame=@{func="main",args=[],file="recursive2.c",
28414 fullname="/home/foo/bar/recursive2.c",line="5"@}
28418 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28419 the program execution twice: first for the variable changing value, then
28420 for the watchpoint going out of scope.
28425 ^done,wpt=@{number="5",exp="C"@}
28430 *stopped,reason="watchpoint-trigger",
28431 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28432 frame=@{func="callee4",args=[],
28433 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28434 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28439 *stopped,reason="watchpoint-scope",wpnum="5",
28440 frame=@{func="callee3",args=[@{name="strarg",
28441 value="0x11940 \"A string argument.\""@}],
28442 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28443 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28447 Listing breakpoints and watchpoints, at different points in the program
28448 execution. Note that once the watchpoint goes out of scope, it is
28454 ^done,wpt=@{number="2",exp="C"@}
28457 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28458 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28459 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28460 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28461 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28462 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28463 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28464 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28465 addr="0x00010734",func="callee4",
28466 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28467 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28469 bkpt=@{number="2",type="watchpoint",disp="keep",
28470 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28475 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28476 value=@{old="-276895068",new="3"@},
28477 frame=@{func="callee4",args=[],
28478 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28479 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28482 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28483 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28484 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28485 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28486 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28487 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28488 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28489 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28490 addr="0x00010734",func="callee4",
28491 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28492 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28494 bkpt=@{number="2",type="watchpoint",disp="keep",
28495 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28499 ^done,reason="watchpoint-scope",wpnum="2",
28500 frame=@{func="callee3",args=[@{name="strarg",
28501 value="0x11940 \"A string argument.\""@}],
28502 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28503 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28506 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28507 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28508 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28509 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28510 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28511 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28512 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28513 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28514 addr="0x00010734",func="callee4",
28515 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28516 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28517 thread-groups=["i1"],times="1"@}]@}
28522 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28523 @node GDB/MI Catchpoint Commands
28524 @section @sc{gdb/mi} Catchpoint Commands
28526 This section documents @sc{gdb/mi} commands for manipulating
28530 * Shared Library GDB/MI Catchpoint Commands::
28531 * Ada Exception GDB/MI Catchpoint Commands::
28534 @node Shared Library GDB/MI Catchpoint Commands
28535 @subsection Shared Library @sc{gdb/mi} Catchpoints
28537 @subheading The @code{-catch-load} Command
28538 @findex -catch-load
28540 @subsubheading Synopsis
28543 -catch-load [ -t ] [ -d ] @var{regexp}
28546 Add a catchpoint for library load events. If the @samp{-t} option is used,
28547 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28548 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28549 in a disabled state. The @samp{regexp} argument is a regular
28550 expression used to match the name of the loaded library.
28553 @subsubheading @value{GDBN} Command
28555 The corresponding @value{GDBN} command is @samp{catch load}.
28557 @subsubheading Example
28560 -catch-load -t foo.so
28561 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28562 what="load of library matching foo.so",catch-type="load",times="0"@}
28567 @subheading The @code{-catch-unload} Command
28568 @findex -catch-unload
28570 @subsubheading Synopsis
28573 -catch-unload [ -t ] [ -d ] @var{regexp}
28576 Add a catchpoint for library unload events. If the @samp{-t} option is
28577 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28578 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28579 created in a disabled state. The @samp{regexp} argument is a regular
28580 expression used to match the name of the unloaded library.
28582 @subsubheading @value{GDBN} Command
28584 The corresponding @value{GDBN} command is @samp{catch unload}.
28586 @subsubheading Example
28589 -catch-unload -d bar.so
28590 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28591 what="load of library matching bar.so",catch-type="unload",times="0"@}
28595 @node Ada Exception GDB/MI Catchpoint Commands
28596 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28598 The following @sc{gdb/mi} commands can be used to create catchpoints
28599 that stop the execution when Ada exceptions are being raised.
28601 @subheading The @code{-catch-assert} Command
28602 @findex -catch-assert
28604 @subsubheading Synopsis
28607 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28610 Add a catchpoint for failed Ada assertions.
28612 The possible optional parameters for this command are:
28615 @item -c @var{condition}
28616 Make the catchpoint conditional on @var{condition}.
28618 Create a disabled catchpoint.
28620 Create a temporary catchpoint.
28623 @subsubheading @value{GDBN} Command
28625 The corresponding @value{GDBN} command is @samp{catch assert}.
28627 @subsubheading Example
28631 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28632 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28633 thread-groups=["i1"],times="0",
28634 original-location="__gnat_debug_raise_assert_failure"@}
28638 @subheading The @code{-catch-exception} Command
28639 @findex -catch-exception
28641 @subsubheading Synopsis
28644 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28648 Add a catchpoint stopping when Ada exceptions are raised.
28649 By default, the command stops the program when any Ada exception
28650 gets raised. But it is also possible, by using some of the
28651 optional parameters described below, to create more selective
28654 The possible optional parameters for this command are:
28657 @item -c @var{condition}
28658 Make the catchpoint conditional on @var{condition}.
28660 Create a disabled catchpoint.
28661 @item -e @var{exception-name}
28662 Only stop when @var{exception-name} is raised. This option cannot
28663 be used combined with @samp{-u}.
28665 Create a temporary catchpoint.
28667 Stop only when an unhandled exception gets raised. This option
28668 cannot be used combined with @samp{-e}.
28671 @subsubheading @value{GDBN} Command
28673 The corresponding @value{GDBN} commands are @samp{catch exception}
28674 and @samp{catch exception unhandled}.
28676 @subsubheading Example
28679 -catch-exception -e Program_Error
28680 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28681 enabled="y",addr="0x0000000000404874",
28682 what="`Program_Error' Ada exception", thread-groups=["i1"],
28683 times="0",original-location="__gnat_debug_raise_exception"@}
28687 @subheading The @code{-catch-handlers} Command
28688 @findex -catch-handlers
28690 @subsubheading Synopsis
28693 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28697 Add a catchpoint stopping when Ada exceptions are handled.
28698 By default, the command stops the program when any Ada exception
28699 gets handled. But it is also possible, by using some of the
28700 optional parameters described below, to create more selective
28703 The possible optional parameters for this command are:
28706 @item -c @var{condition}
28707 Make the catchpoint conditional on @var{condition}.
28709 Create a disabled catchpoint.
28710 @item -e @var{exception-name}
28711 Only stop when @var{exception-name} is handled.
28713 Create a temporary catchpoint.
28716 @subsubheading @value{GDBN} Command
28718 The corresponding @value{GDBN} command is @samp{catch handlers}.
28720 @subsubheading Example
28723 -catch-handlers -e Constraint_Error
28724 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28725 enabled="y",addr="0x0000000000402f68",
28726 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
28727 times="0",original-location="__gnat_begin_handler"@}
28731 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28732 @node GDB/MI Program Context
28733 @section @sc{gdb/mi} Program Context
28735 @subheading The @code{-exec-arguments} Command
28736 @findex -exec-arguments
28739 @subsubheading Synopsis
28742 -exec-arguments @var{args}
28745 Set the inferior program arguments, to be used in the next
28748 @subsubheading @value{GDBN} Command
28750 The corresponding @value{GDBN} command is @samp{set args}.
28752 @subsubheading Example
28756 -exec-arguments -v word
28763 @subheading The @code{-exec-show-arguments} Command
28764 @findex -exec-show-arguments
28766 @subsubheading Synopsis
28769 -exec-show-arguments
28772 Print the arguments of the program.
28774 @subsubheading @value{GDBN} Command
28776 The corresponding @value{GDBN} command is @samp{show args}.
28778 @subsubheading Example
28783 @subheading The @code{-environment-cd} Command
28784 @findex -environment-cd
28786 @subsubheading Synopsis
28789 -environment-cd @var{pathdir}
28792 Set @value{GDBN}'s working directory.
28794 @subsubheading @value{GDBN} Command
28796 The corresponding @value{GDBN} command is @samp{cd}.
28798 @subsubheading Example
28802 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28808 @subheading The @code{-environment-directory} Command
28809 @findex -environment-directory
28811 @subsubheading Synopsis
28814 -environment-directory [ -r ] [ @var{pathdir} ]+
28817 Add directories @var{pathdir} to beginning of search path for source files.
28818 If the @samp{-r} option is used, the search path is reset to the default
28819 search path. If directories @var{pathdir} are supplied in addition to the
28820 @samp{-r} option, the search path is first reset and then addition
28822 Multiple directories may be specified, separated by blanks. Specifying
28823 multiple directories in a single command
28824 results in the directories added to the beginning of the
28825 search path in the same order they were presented in the command.
28826 If blanks are needed as
28827 part of a directory name, double-quotes should be used around
28828 the name. In the command output, the path will show up separated
28829 by the system directory-separator character. The directory-separator
28830 character must not be used
28831 in any directory name.
28832 If no directories are specified, the current search path is displayed.
28834 @subsubheading @value{GDBN} Command
28836 The corresponding @value{GDBN} command is @samp{dir}.
28838 @subsubheading Example
28842 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28843 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28845 -environment-directory ""
28846 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28848 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28849 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28851 -environment-directory -r
28852 ^done,source-path="$cdir:$cwd"
28857 @subheading The @code{-environment-path} Command
28858 @findex -environment-path
28860 @subsubheading Synopsis
28863 -environment-path [ -r ] [ @var{pathdir} ]+
28866 Add directories @var{pathdir} to beginning of search path for object files.
28867 If the @samp{-r} option is used, the search path is reset to the original
28868 search path that existed at gdb start-up. If directories @var{pathdir} are
28869 supplied in addition to the
28870 @samp{-r} option, the search path is first reset and then addition
28872 Multiple directories may be specified, separated by blanks. Specifying
28873 multiple directories in a single command
28874 results in the directories added to the beginning of the
28875 search path in the same order they were presented in the command.
28876 If blanks are needed as
28877 part of a directory name, double-quotes should be used around
28878 the name. In the command output, the path will show up separated
28879 by the system directory-separator character. The directory-separator
28880 character must not be used
28881 in any directory name.
28882 If no directories are specified, the current path is displayed.
28885 @subsubheading @value{GDBN} Command
28887 The corresponding @value{GDBN} command is @samp{path}.
28889 @subsubheading Example
28894 ^done,path="/usr/bin"
28896 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28897 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28899 -environment-path -r /usr/local/bin
28900 ^done,path="/usr/local/bin:/usr/bin"
28905 @subheading The @code{-environment-pwd} Command
28906 @findex -environment-pwd
28908 @subsubheading Synopsis
28914 Show the current working directory.
28916 @subsubheading @value{GDBN} Command
28918 The corresponding @value{GDBN} command is @samp{pwd}.
28920 @subsubheading Example
28925 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28929 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28930 @node GDB/MI Thread Commands
28931 @section @sc{gdb/mi} Thread Commands
28934 @subheading The @code{-thread-info} Command
28935 @findex -thread-info
28937 @subsubheading Synopsis
28940 -thread-info [ @var{thread-id} ]
28943 Reports information about either a specific thread, if the
28944 @var{thread-id} parameter is present, or about all threads.
28945 @var{thread-id} is the thread's global thread ID. When printing
28946 information about all threads, also reports the global ID of the
28949 @subsubheading @value{GDBN} Command
28951 The @samp{info thread} command prints the same information
28954 @subsubheading Result
28956 The result contains the following attributes:
28960 A list of threads. The format of the elements of the list is described in
28961 @ref{GDB/MI Thread Information}.
28963 @item current-thread-id
28964 The global id of the currently selected thread. This field is omitted if there
28965 is no selected thread (for example, when the selected inferior is not running,
28966 and therefore has no threads) or if a @var{thread-id} argument was passed to
28971 @subsubheading Example
28976 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28977 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28978 args=[]@},state="running"@},
28979 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28980 frame=@{level="0",addr="0x0804891f",func="foo",
28981 args=[@{name="i",value="10"@}],
28982 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28983 state="running"@}],
28984 current-thread-id="1"
28988 @subheading The @code{-thread-list-ids} Command
28989 @findex -thread-list-ids
28991 @subsubheading Synopsis
28997 Produces a list of the currently known global @value{GDBN} thread ids.
28998 At the end of the list it also prints the total number of such
29001 This command is retained for historical reasons, the
29002 @code{-thread-info} command should be used instead.
29004 @subsubheading @value{GDBN} Command
29006 Part of @samp{info threads} supplies the same information.
29008 @subsubheading Example
29013 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29014 current-thread-id="1",number-of-threads="3"
29019 @subheading The @code{-thread-select} Command
29020 @findex -thread-select
29022 @subsubheading Synopsis
29025 -thread-select @var{thread-id}
29028 Make thread with global thread number @var{thread-id} the current
29029 thread. It prints the number of the new current thread, and the
29030 topmost frame for that thread.
29032 This command is deprecated in favor of explicitly using the
29033 @samp{--thread} option to each command.
29035 @subsubheading @value{GDBN} Command
29037 The corresponding @value{GDBN} command is @samp{thread}.
29039 @subsubheading Example
29046 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29047 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29051 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29052 number-of-threads="3"
29055 ^done,new-thread-id="3",
29056 frame=@{level="0",func="vprintf",
29057 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29058 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29062 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29063 @node GDB/MI Ada Tasking Commands
29064 @section @sc{gdb/mi} Ada Tasking Commands
29066 @subheading The @code{-ada-task-info} Command
29067 @findex -ada-task-info
29069 @subsubheading Synopsis
29072 -ada-task-info [ @var{task-id} ]
29075 Reports information about either a specific Ada task, if the
29076 @var{task-id} parameter is present, or about all Ada tasks.
29078 @subsubheading @value{GDBN} Command
29080 The @samp{info tasks} command prints the same information
29081 about all Ada tasks (@pxref{Ada Tasks}).
29083 @subsubheading Result
29085 The result is a table of Ada tasks. The following columns are
29086 defined for each Ada task:
29090 This field exists only for the current thread. It has the value @samp{*}.
29093 The identifier that @value{GDBN} uses to refer to the Ada task.
29096 The identifier that the target uses to refer to the Ada task.
29099 The global thread identifier of the thread corresponding to the Ada
29102 This field should always exist, as Ada tasks are always implemented
29103 on top of a thread. But if @value{GDBN} cannot find this corresponding
29104 thread for any reason, the field is omitted.
29107 This field exists only when the task was created by another task.
29108 In this case, it provides the ID of the parent task.
29111 The base priority of the task.
29114 The current state of the task. For a detailed description of the
29115 possible states, see @ref{Ada Tasks}.
29118 The name of the task.
29122 @subsubheading Example
29126 ^done,tasks=@{nr_rows="3",nr_cols="8",
29127 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29128 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29129 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29130 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29131 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29132 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29133 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29134 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29135 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29136 state="Child Termination Wait",name="main_task"@}]@}
29140 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29141 @node GDB/MI Program Execution
29142 @section @sc{gdb/mi} Program Execution
29144 These are the asynchronous commands which generate the out-of-band
29145 record @samp{*stopped}. Currently @value{GDBN} only really executes
29146 asynchronously with remote targets and this interaction is mimicked in
29149 @subheading The @code{-exec-continue} Command
29150 @findex -exec-continue
29152 @subsubheading Synopsis
29155 -exec-continue [--reverse] [--all|--thread-group N]
29158 Resumes the execution of the inferior program, which will continue
29159 to execute until it reaches a debugger stop event. If the
29160 @samp{--reverse} option is specified, execution resumes in reverse until
29161 it reaches a stop event. Stop events may include
29164 breakpoints or watchpoints
29166 signals or exceptions
29168 the end of the process (or its beginning under @samp{--reverse})
29170 the end or beginning of a replay log if one is being used.
29172 In all-stop mode (@pxref{All-Stop
29173 Mode}), may resume only one thread, or all threads, depending on the
29174 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29175 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29176 ignored in all-stop mode. If the @samp{--thread-group} options is
29177 specified, then all threads in that thread group are resumed.
29179 @subsubheading @value{GDBN} Command
29181 The corresponding @value{GDBN} corresponding is @samp{continue}.
29183 @subsubheading Example
29190 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29191 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29197 @subheading The @code{-exec-finish} Command
29198 @findex -exec-finish
29200 @subsubheading Synopsis
29203 -exec-finish [--reverse]
29206 Resumes the execution of the inferior program until the current
29207 function is exited. Displays the results returned by the function.
29208 If the @samp{--reverse} option is specified, resumes the reverse
29209 execution of the inferior program until the point where current
29210 function was called.
29212 @subsubheading @value{GDBN} Command
29214 The corresponding @value{GDBN} command is @samp{finish}.
29216 @subsubheading Example
29218 Function returning @code{void}.
29225 *stopped,reason="function-finished",frame=@{func="main",args=[],
29226 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29230 Function returning other than @code{void}. The name of the internal
29231 @value{GDBN} variable storing the result is printed, together with the
29238 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29239 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29240 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29241 gdb-result-var="$1",return-value="0"
29246 @subheading The @code{-exec-interrupt} Command
29247 @findex -exec-interrupt
29249 @subsubheading Synopsis
29252 -exec-interrupt [--all|--thread-group N]
29255 Interrupts the background execution of the target. Note how the token
29256 associated with the stop message is the one for the execution command
29257 that has been interrupted. The token for the interrupt itself only
29258 appears in the @samp{^done} output. If the user is trying to
29259 interrupt a non-running program, an error message will be printed.
29261 Note that when asynchronous execution is enabled, this command is
29262 asynchronous just like other execution commands. That is, first the
29263 @samp{^done} response will be printed, and the target stop will be
29264 reported after that using the @samp{*stopped} notification.
29266 In non-stop mode, only the context thread is interrupted by default.
29267 All threads (in all inferiors) will be interrupted if the
29268 @samp{--all} option is specified. If the @samp{--thread-group}
29269 option is specified, all threads in that group will be interrupted.
29271 @subsubheading @value{GDBN} Command
29273 The corresponding @value{GDBN} command is @samp{interrupt}.
29275 @subsubheading Example
29286 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29287 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29288 fullname="/home/foo/bar/try.c",line="13"@}
29293 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29297 @subheading The @code{-exec-jump} Command
29300 @subsubheading Synopsis
29303 -exec-jump @var{location}
29306 Resumes execution of the inferior program at the location specified by
29307 parameter. @xref{Specify Location}, for a description of the
29308 different forms of @var{location}.
29310 @subsubheading @value{GDBN} Command
29312 The corresponding @value{GDBN} command is @samp{jump}.
29314 @subsubheading Example
29317 -exec-jump foo.c:10
29318 *running,thread-id="all"
29323 @subheading The @code{-exec-next} Command
29326 @subsubheading Synopsis
29329 -exec-next [--reverse]
29332 Resumes execution of the inferior program, stopping when the beginning
29333 of the next source line is reached.
29335 If the @samp{--reverse} option is specified, resumes reverse execution
29336 of the inferior program, stopping at the beginning of the previous
29337 source line. If you issue this command on the first line of a
29338 function, it will take you back to the caller of that function, to the
29339 source line where the function was called.
29342 @subsubheading @value{GDBN} Command
29344 The corresponding @value{GDBN} command is @samp{next}.
29346 @subsubheading Example
29352 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29357 @subheading The @code{-exec-next-instruction} Command
29358 @findex -exec-next-instruction
29360 @subsubheading Synopsis
29363 -exec-next-instruction [--reverse]
29366 Executes one machine instruction. If the instruction is a function
29367 call, continues until the function returns. If the program stops at an
29368 instruction in the middle of a source line, the address will be
29371 If the @samp{--reverse} option is specified, resumes reverse execution
29372 of the inferior program, stopping at the previous instruction. If the
29373 previously executed instruction was a return from another function,
29374 it will continue to execute in reverse until the call to that function
29375 (from the current stack frame) is reached.
29377 @subsubheading @value{GDBN} Command
29379 The corresponding @value{GDBN} command is @samp{nexti}.
29381 @subsubheading Example
29385 -exec-next-instruction
29389 *stopped,reason="end-stepping-range",
29390 addr="0x000100d4",line="5",file="hello.c"
29395 @subheading The @code{-exec-return} Command
29396 @findex -exec-return
29398 @subsubheading Synopsis
29404 Makes current function return immediately. Doesn't execute the inferior.
29405 Displays the new current frame.
29407 @subsubheading @value{GDBN} Command
29409 The corresponding @value{GDBN} command is @samp{return}.
29411 @subsubheading Example
29415 200-break-insert callee4
29416 200^done,bkpt=@{number="1",addr="0x00010734",
29417 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29422 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29423 frame=@{func="callee4",args=[],
29424 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29425 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29431 111^done,frame=@{level="0",func="callee3",
29432 args=[@{name="strarg",
29433 value="0x11940 \"A string argument.\""@}],
29434 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29435 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29440 @subheading The @code{-exec-run} Command
29443 @subsubheading Synopsis
29446 -exec-run [ --all | --thread-group N ] [ --start ]
29449 Starts execution of the inferior from the beginning. The inferior
29450 executes until either a breakpoint is encountered or the program
29451 exits. In the latter case the output will include an exit code, if
29452 the program has exited exceptionally.
29454 When neither the @samp{--all} nor the @samp{--thread-group} option
29455 is specified, the current inferior is started. If the
29456 @samp{--thread-group} option is specified, it should refer to a thread
29457 group of type @samp{process}, and that thread group will be started.
29458 If the @samp{--all} option is specified, then all inferiors will be started.
29460 Using the @samp{--start} option instructs the debugger to stop
29461 the execution at the start of the inferior's main subprogram,
29462 following the same behavior as the @code{start} command
29463 (@pxref{Starting}).
29465 @subsubheading @value{GDBN} Command
29467 The corresponding @value{GDBN} command is @samp{run}.
29469 @subsubheading Examples
29474 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29479 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29480 frame=@{func="main",args=[],file="recursive2.c",
29481 fullname="/home/foo/bar/recursive2.c",line="4"@}
29486 Program exited normally:
29494 *stopped,reason="exited-normally"
29499 Program exited exceptionally:
29507 *stopped,reason="exited",exit-code="01"
29511 Another way the program can terminate is if it receives a signal such as
29512 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29516 *stopped,reason="exited-signalled",signal-name="SIGINT",
29517 signal-meaning="Interrupt"
29521 @c @subheading -exec-signal
29524 @subheading The @code{-exec-step} Command
29527 @subsubheading Synopsis
29530 -exec-step [--reverse]
29533 Resumes execution of the inferior program, stopping when the beginning
29534 of the next source line is reached, if the next source line is not a
29535 function call. If it is, stop at the first instruction of the called
29536 function. If the @samp{--reverse} option is specified, resumes reverse
29537 execution of the inferior program, stopping at the beginning of the
29538 previously executed source line.
29540 @subsubheading @value{GDBN} Command
29542 The corresponding @value{GDBN} command is @samp{step}.
29544 @subsubheading Example
29546 Stepping into a function:
29552 *stopped,reason="end-stepping-range",
29553 frame=@{func="foo",args=[@{name="a",value="10"@},
29554 @{name="b",value="0"@}],file="recursive2.c",
29555 fullname="/home/foo/bar/recursive2.c",line="11"@}
29565 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29570 @subheading The @code{-exec-step-instruction} Command
29571 @findex -exec-step-instruction
29573 @subsubheading Synopsis
29576 -exec-step-instruction [--reverse]
29579 Resumes the inferior which executes one machine instruction. If the
29580 @samp{--reverse} option is specified, resumes reverse execution of the
29581 inferior program, stopping at the previously executed instruction.
29582 The output, once @value{GDBN} has stopped, will vary depending on
29583 whether we have stopped in the middle of a source line or not. In the
29584 former case, the address at which the program stopped will be printed
29587 @subsubheading @value{GDBN} Command
29589 The corresponding @value{GDBN} command is @samp{stepi}.
29591 @subsubheading Example
29595 -exec-step-instruction
29599 *stopped,reason="end-stepping-range",
29600 frame=@{func="foo",args=[],file="try.c",
29601 fullname="/home/foo/bar/try.c",line="10"@}
29603 -exec-step-instruction
29607 *stopped,reason="end-stepping-range",
29608 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29609 fullname="/home/foo/bar/try.c",line="10"@}
29614 @subheading The @code{-exec-until} Command
29615 @findex -exec-until
29617 @subsubheading Synopsis
29620 -exec-until [ @var{location} ]
29623 Executes the inferior until the @var{location} specified in the
29624 argument is reached. If there is no argument, the inferior executes
29625 until a source line greater than the current one is reached. The
29626 reason for stopping in this case will be @samp{location-reached}.
29628 @subsubheading @value{GDBN} Command
29630 The corresponding @value{GDBN} command is @samp{until}.
29632 @subsubheading Example
29636 -exec-until recursive2.c:6
29640 *stopped,reason="location-reached",frame=@{func="main",args=[],
29641 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29646 @subheading -file-clear
29647 Is this going away????
29650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29651 @node GDB/MI Stack Manipulation
29652 @section @sc{gdb/mi} Stack Manipulation Commands
29654 @subheading The @code{-enable-frame-filters} Command
29655 @findex -enable-frame-filters
29658 -enable-frame-filters
29661 @value{GDBN} allows Python-based frame filters to affect the output of
29662 the MI commands relating to stack traces. As there is no way to
29663 implement this in a fully backward-compatible way, a front end must
29664 request that this functionality be enabled.
29666 Once enabled, this feature cannot be disabled.
29668 Note that if Python support has not been compiled into @value{GDBN},
29669 this command will still succeed (and do nothing).
29671 @subheading The @code{-stack-info-frame} Command
29672 @findex -stack-info-frame
29674 @subsubheading Synopsis
29680 Get info on the selected frame.
29682 @subsubheading @value{GDBN} Command
29684 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29685 (without arguments).
29687 @subsubheading Example
29692 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29693 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29694 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29698 @subheading The @code{-stack-info-depth} Command
29699 @findex -stack-info-depth
29701 @subsubheading Synopsis
29704 -stack-info-depth [ @var{max-depth} ]
29707 Return the depth of the stack. If the integer argument @var{max-depth}
29708 is specified, do not count beyond @var{max-depth} frames.
29710 @subsubheading @value{GDBN} Command
29712 There's no equivalent @value{GDBN} command.
29714 @subsubheading Example
29716 For a stack with frame levels 0 through 11:
29723 -stack-info-depth 4
29726 -stack-info-depth 12
29729 -stack-info-depth 11
29732 -stack-info-depth 13
29737 @anchor{-stack-list-arguments}
29738 @subheading The @code{-stack-list-arguments} Command
29739 @findex -stack-list-arguments
29741 @subsubheading Synopsis
29744 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29745 [ @var{low-frame} @var{high-frame} ]
29748 Display a list of the arguments for the frames between @var{low-frame}
29749 and @var{high-frame} (inclusive). If @var{low-frame} and
29750 @var{high-frame} are not provided, list the arguments for the whole
29751 call stack. If the two arguments are equal, show the single frame
29752 at the corresponding level. It is an error if @var{low-frame} is
29753 larger than the actual number of frames. On the other hand,
29754 @var{high-frame} may be larger than the actual number of frames, in
29755 which case only existing frames will be returned.
29757 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29758 the variables; if it is 1 or @code{--all-values}, print also their
29759 values; and if it is 2 or @code{--simple-values}, print the name,
29760 type and value for simple data types, and the name and type for arrays,
29761 structures and unions. If the option @code{--no-frame-filters} is
29762 supplied, then Python frame filters will not be executed.
29764 If the @code{--skip-unavailable} option is specified, arguments that
29765 are not available are not listed. Partially available arguments
29766 are still displayed, however.
29768 Use of this command to obtain arguments in a single frame is
29769 deprecated in favor of the @samp{-stack-list-variables} command.
29771 @subsubheading @value{GDBN} Command
29773 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29774 @samp{gdb_get_args} command which partially overlaps with the
29775 functionality of @samp{-stack-list-arguments}.
29777 @subsubheading Example
29784 frame=@{level="0",addr="0x00010734",func="callee4",
29785 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29786 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29787 frame=@{level="1",addr="0x0001076c",func="callee3",
29788 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29789 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29790 frame=@{level="2",addr="0x0001078c",func="callee2",
29791 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29792 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29793 frame=@{level="3",addr="0x000107b4",func="callee1",
29794 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29795 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29796 frame=@{level="4",addr="0x000107e0",func="main",
29797 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29798 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29800 -stack-list-arguments 0
29803 frame=@{level="0",args=[]@},
29804 frame=@{level="1",args=[name="strarg"]@},
29805 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29806 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29807 frame=@{level="4",args=[]@}]
29809 -stack-list-arguments 1
29812 frame=@{level="0",args=[]@},
29814 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29815 frame=@{level="2",args=[
29816 @{name="intarg",value="2"@},
29817 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29818 @{frame=@{level="3",args=[
29819 @{name="intarg",value="2"@},
29820 @{name="strarg",value="0x11940 \"A string argument.\""@},
29821 @{name="fltarg",value="3.5"@}]@},
29822 frame=@{level="4",args=[]@}]
29824 -stack-list-arguments 0 2 2
29825 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29827 -stack-list-arguments 1 2 2
29828 ^done,stack-args=[frame=@{level="2",
29829 args=[@{name="intarg",value="2"@},
29830 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29834 @c @subheading -stack-list-exception-handlers
29837 @anchor{-stack-list-frames}
29838 @subheading The @code{-stack-list-frames} Command
29839 @findex -stack-list-frames
29841 @subsubheading Synopsis
29844 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29847 List the frames currently on the stack. For each frame it displays the
29852 The frame number, 0 being the topmost frame, i.e., the innermost function.
29854 The @code{$pc} value for that frame.
29858 File name of the source file where the function lives.
29859 @item @var{fullname}
29860 The full file name of the source file where the function lives.
29862 Line number corresponding to the @code{$pc}.
29864 The shared library where this function is defined. This is only given
29865 if the frame's function is not known.
29868 If invoked without arguments, this command prints a backtrace for the
29869 whole stack. If given two integer arguments, it shows the frames whose
29870 levels are between the two arguments (inclusive). If the two arguments
29871 are equal, it shows the single frame at the corresponding level. It is
29872 an error if @var{low-frame} is larger than the actual number of
29873 frames. On the other hand, @var{high-frame} may be larger than the
29874 actual number of frames, in which case only existing frames will be
29875 returned. If the option @code{--no-frame-filters} is supplied, then
29876 Python frame filters will not be executed.
29878 @subsubheading @value{GDBN} Command
29880 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29882 @subsubheading Example
29884 Full stack backtrace:
29890 [frame=@{level="0",addr="0x0001076c",func="foo",
29891 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29892 frame=@{level="1",addr="0x000107a4",func="foo",
29893 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29894 frame=@{level="2",addr="0x000107a4",func="foo",
29895 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29896 frame=@{level="3",addr="0x000107a4",func="foo",
29897 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29898 frame=@{level="4",addr="0x000107a4",func="foo",
29899 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29900 frame=@{level="5",addr="0x000107a4",func="foo",
29901 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29902 frame=@{level="6",addr="0x000107a4",func="foo",
29903 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29904 frame=@{level="7",addr="0x000107a4",func="foo",
29905 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29906 frame=@{level="8",addr="0x000107a4",func="foo",
29907 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29908 frame=@{level="9",addr="0x000107a4",func="foo",
29909 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29910 frame=@{level="10",addr="0x000107a4",func="foo",
29911 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29912 frame=@{level="11",addr="0x00010738",func="main",
29913 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29917 Show frames between @var{low_frame} and @var{high_frame}:
29921 -stack-list-frames 3 5
29923 [frame=@{level="3",addr="0x000107a4",func="foo",
29924 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29925 frame=@{level="4",addr="0x000107a4",func="foo",
29926 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29927 frame=@{level="5",addr="0x000107a4",func="foo",
29928 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29932 Show a single frame:
29936 -stack-list-frames 3 3
29938 [frame=@{level="3",addr="0x000107a4",func="foo",
29939 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29944 @subheading The @code{-stack-list-locals} Command
29945 @findex -stack-list-locals
29946 @anchor{-stack-list-locals}
29948 @subsubheading Synopsis
29951 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29954 Display the local variable names for the selected frame. If
29955 @var{print-values} is 0 or @code{--no-values}, print only the names of
29956 the variables; if it is 1 or @code{--all-values}, print also their
29957 values; and if it is 2 or @code{--simple-values}, print the name,
29958 type and value for simple data types, and the name and type for arrays,
29959 structures and unions. In this last case, a frontend can immediately
29960 display the value of simple data types and create variable objects for
29961 other data types when the user wishes to explore their values in
29962 more detail. If the option @code{--no-frame-filters} is supplied, then
29963 Python frame filters will not be executed.
29965 If the @code{--skip-unavailable} option is specified, local variables
29966 that are not available are not listed. Partially available local
29967 variables are still displayed, however.
29969 This command is deprecated in favor of the
29970 @samp{-stack-list-variables} command.
29972 @subsubheading @value{GDBN} Command
29974 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29976 @subsubheading Example
29980 -stack-list-locals 0
29981 ^done,locals=[name="A",name="B",name="C"]
29983 -stack-list-locals --all-values
29984 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29985 @{name="C",value="@{1, 2, 3@}"@}]
29986 -stack-list-locals --simple-values
29987 ^done,locals=[@{name="A",type="int",value="1"@},
29988 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29992 @anchor{-stack-list-variables}
29993 @subheading The @code{-stack-list-variables} Command
29994 @findex -stack-list-variables
29996 @subsubheading Synopsis
29999 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30002 Display the names of local variables and function arguments for the selected frame. If
30003 @var{print-values} is 0 or @code{--no-values}, print only the names of
30004 the variables; if it is 1 or @code{--all-values}, print also their
30005 values; and if it is 2 or @code{--simple-values}, print the name,
30006 type and value for simple data types, and the name and type for arrays,
30007 structures and unions. If the option @code{--no-frame-filters} is
30008 supplied, then Python frame filters will not be executed.
30010 If the @code{--skip-unavailable} option is specified, local variables
30011 and arguments that are not available are not listed. Partially
30012 available arguments and local variables are still displayed, however.
30014 @subsubheading Example
30018 -stack-list-variables --thread 1 --frame 0 --all-values
30019 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30024 @subheading The @code{-stack-select-frame} Command
30025 @findex -stack-select-frame
30027 @subsubheading Synopsis
30030 -stack-select-frame @var{framenum}
30033 Change the selected frame. Select a different frame @var{framenum} on
30036 This command in deprecated in favor of passing the @samp{--frame}
30037 option to every command.
30039 @subsubheading @value{GDBN} Command
30041 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30042 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30044 @subsubheading Example
30048 -stack-select-frame 2
30053 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30054 @node GDB/MI Variable Objects
30055 @section @sc{gdb/mi} Variable Objects
30059 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30061 For the implementation of a variable debugger window (locals, watched
30062 expressions, etc.), we are proposing the adaptation of the existing code
30063 used by @code{Insight}.
30065 The two main reasons for that are:
30069 It has been proven in practice (it is already on its second generation).
30072 It will shorten development time (needless to say how important it is
30076 The original interface was designed to be used by Tcl code, so it was
30077 slightly changed so it could be used through @sc{gdb/mi}. This section
30078 describes the @sc{gdb/mi} operations that will be available and gives some
30079 hints about their use.
30081 @emph{Note}: In addition to the set of operations described here, we
30082 expect the @sc{gui} implementation of a variable window to require, at
30083 least, the following operations:
30086 @item @code{-gdb-show} @code{output-radix}
30087 @item @code{-stack-list-arguments}
30088 @item @code{-stack-list-locals}
30089 @item @code{-stack-select-frame}
30094 @subheading Introduction to Variable Objects
30096 @cindex variable objects in @sc{gdb/mi}
30098 Variable objects are "object-oriented" MI interface for examining and
30099 changing values of expressions. Unlike some other MI interfaces that
30100 work with expressions, variable objects are specifically designed for
30101 simple and efficient presentation in the frontend. A variable object
30102 is identified by string name. When a variable object is created, the
30103 frontend specifies the expression for that variable object. The
30104 expression can be a simple variable, or it can be an arbitrary complex
30105 expression, and can even involve CPU registers. After creating a
30106 variable object, the frontend can invoke other variable object
30107 operations---for example to obtain or change the value of a variable
30108 object, or to change display format.
30110 Variable objects have hierarchical tree structure. Any variable object
30111 that corresponds to a composite type, such as structure in C, has
30112 a number of child variable objects, for example corresponding to each
30113 element of a structure. A child variable object can itself have
30114 children, recursively. Recursion ends when we reach
30115 leaf variable objects, which always have built-in types. Child variable
30116 objects are created only by explicit request, so if a frontend
30117 is not interested in the children of a particular variable object, no
30118 child will be created.
30120 For a leaf variable object it is possible to obtain its value as a
30121 string, or set the value from a string. String value can be also
30122 obtained for a non-leaf variable object, but it's generally a string
30123 that only indicates the type of the object, and does not list its
30124 contents. Assignment to a non-leaf variable object is not allowed.
30126 A frontend does not need to read the values of all variable objects each time
30127 the program stops. Instead, MI provides an update command that lists all
30128 variable objects whose values has changed since the last update
30129 operation. This considerably reduces the amount of data that must
30130 be transferred to the frontend. As noted above, children variable
30131 objects are created on demand, and only leaf variable objects have a
30132 real value. As result, gdb will read target memory only for leaf
30133 variables that frontend has created.
30135 The automatic update is not always desirable. For example, a frontend
30136 might want to keep a value of some expression for future reference,
30137 and never update it. For another example, fetching memory is
30138 relatively slow for embedded targets, so a frontend might want
30139 to disable automatic update for the variables that are either not
30140 visible on the screen, or ``closed''. This is possible using so
30141 called ``frozen variable objects''. Such variable objects are never
30142 implicitly updated.
30144 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30145 fixed variable object, the expression is parsed when the variable
30146 object is created, including associating identifiers to specific
30147 variables. The meaning of expression never changes. For a floating
30148 variable object the values of variables whose names appear in the
30149 expressions are re-evaluated every time in the context of the current
30150 frame. Consider this example:
30155 struct work_state state;
30162 If a fixed variable object for the @code{state} variable is created in
30163 this function, and we enter the recursive call, the variable
30164 object will report the value of @code{state} in the top-level
30165 @code{do_work} invocation. On the other hand, a floating variable
30166 object will report the value of @code{state} in the current frame.
30168 If an expression specified when creating a fixed variable object
30169 refers to a local variable, the variable object becomes bound to the
30170 thread and frame in which the variable object is created. When such
30171 variable object is updated, @value{GDBN} makes sure that the
30172 thread/frame combination the variable object is bound to still exists,
30173 and re-evaluates the variable object in context of that thread/frame.
30175 The following is the complete set of @sc{gdb/mi} operations defined to
30176 access this functionality:
30178 @multitable @columnfractions .4 .6
30179 @item @strong{Operation}
30180 @tab @strong{Description}
30182 @item @code{-enable-pretty-printing}
30183 @tab enable Python-based pretty-printing
30184 @item @code{-var-create}
30185 @tab create a variable object
30186 @item @code{-var-delete}
30187 @tab delete the variable object and/or its children
30188 @item @code{-var-set-format}
30189 @tab set the display format of this variable
30190 @item @code{-var-show-format}
30191 @tab show the display format of this variable
30192 @item @code{-var-info-num-children}
30193 @tab tells how many children this object has
30194 @item @code{-var-list-children}
30195 @tab return a list of the object's children
30196 @item @code{-var-info-type}
30197 @tab show the type of this variable object
30198 @item @code{-var-info-expression}
30199 @tab print parent-relative expression that this variable object represents
30200 @item @code{-var-info-path-expression}
30201 @tab print full expression that this variable object represents
30202 @item @code{-var-show-attributes}
30203 @tab is this variable editable? does it exist here?
30204 @item @code{-var-evaluate-expression}
30205 @tab get the value of this variable
30206 @item @code{-var-assign}
30207 @tab set the value of this variable
30208 @item @code{-var-update}
30209 @tab update the variable and its children
30210 @item @code{-var-set-frozen}
30211 @tab set frozeness attribute
30212 @item @code{-var-set-update-range}
30213 @tab set range of children to display on update
30216 In the next subsection we describe each operation in detail and suggest
30217 how it can be used.
30219 @subheading Description And Use of Operations on Variable Objects
30221 @subheading The @code{-enable-pretty-printing} Command
30222 @findex -enable-pretty-printing
30225 -enable-pretty-printing
30228 @value{GDBN} allows Python-based visualizers to affect the output of the
30229 MI variable object commands. However, because there was no way to
30230 implement this in a fully backward-compatible way, a front end must
30231 request that this functionality be enabled.
30233 Once enabled, this feature cannot be disabled.
30235 Note that if Python support has not been compiled into @value{GDBN},
30236 this command will still succeed (and do nothing).
30238 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30239 may work differently in future versions of @value{GDBN}.
30241 @subheading The @code{-var-create} Command
30242 @findex -var-create
30244 @subsubheading Synopsis
30247 -var-create @{@var{name} | "-"@}
30248 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30251 This operation creates a variable object, which allows the monitoring of
30252 a variable, the result of an expression, a memory cell or a CPU
30255 The @var{name} parameter is the string by which the object can be
30256 referenced. It must be unique. If @samp{-} is specified, the varobj
30257 system will generate a string ``varNNNNNN'' automatically. It will be
30258 unique provided that one does not specify @var{name} of that format.
30259 The command fails if a duplicate name is found.
30261 The frame under which the expression should be evaluated can be
30262 specified by @var{frame-addr}. A @samp{*} indicates that the current
30263 frame should be used. A @samp{@@} indicates that a floating variable
30264 object must be created.
30266 @var{expression} is any expression valid on the current language set (must not
30267 begin with a @samp{*}), or one of the following:
30271 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30274 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30277 @samp{$@var{regname}} --- a CPU register name
30280 @cindex dynamic varobj
30281 A varobj's contents may be provided by a Python-based pretty-printer. In this
30282 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30283 have slightly different semantics in some cases. If the
30284 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30285 will never create a dynamic varobj. This ensures backward
30286 compatibility for existing clients.
30288 @subsubheading Result
30290 This operation returns attributes of the newly-created varobj. These
30295 The name of the varobj.
30298 The number of children of the varobj. This number is not necessarily
30299 reliable for a dynamic varobj. Instead, you must examine the
30300 @samp{has_more} attribute.
30303 The varobj's scalar value. For a varobj whose type is some sort of
30304 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30305 will not be interesting.
30308 The varobj's type. This is a string representation of the type, as
30309 would be printed by the @value{GDBN} CLI. If @samp{print object}
30310 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30311 @emph{actual} (derived) type of the object is shown rather than the
30312 @emph{declared} one.
30315 If a variable object is bound to a specific thread, then this is the
30316 thread's global identifier.
30319 For a dynamic varobj, this indicates whether there appear to be any
30320 children available. For a non-dynamic varobj, this will be 0.
30323 This attribute will be present and have the value @samp{1} if the
30324 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30325 then this attribute will not be present.
30328 A dynamic varobj can supply a display hint to the front end. The
30329 value comes directly from the Python pretty-printer object's
30330 @code{display_hint} method. @xref{Pretty Printing API}.
30333 Typical output will look like this:
30336 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30337 has_more="@var{has_more}"
30341 @subheading The @code{-var-delete} Command
30342 @findex -var-delete
30344 @subsubheading Synopsis
30347 -var-delete [ -c ] @var{name}
30350 Deletes a previously created variable object and all of its children.
30351 With the @samp{-c} option, just deletes the children.
30353 Returns an error if the object @var{name} is not found.
30356 @subheading The @code{-var-set-format} Command
30357 @findex -var-set-format
30359 @subsubheading Synopsis
30362 -var-set-format @var{name} @var{format-spec}
30365 Sets the output format for the value of the object @var{name} to be
30368 @anchor{-var-set-format}
30369 The syntax for the @var{format-spec} is as follows:
30372 @var{format-spec} @expansion{}
30373 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30376 The natural format is the default format choosen automatically
30377 based on the variable type (like decimal for an @code{int}, hex
30378 for pointers, etc.).
30380 The zero-hexadecimal format has a representation similar to hexadecimal
30381 but with padding zeroes to the left of the value. For example, a 32-bit
30382 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30383 zero-hexadecimal format.
30385 For a variable with children, the format is set only on the
30386 variable itself, and the children are not affected.
30388 @subheading The @code{-var-show-format} Command
30389 @findex -var-show-format
30391 @subsubheading Synopsis
30394 -var-show-format @var{name}
30397 Returns the format used to display the value of the object @var{name}.
30400 @var{format} @expansion{}
30405 @subheading The @code{-var-info-num-children} Command
30406 @findex -var-info-num-children
30408 @subsubheading Synopsis
30411 -var-info-num-children @var{name}
30414 Returns the number of children of a variable object @var{name}:
30420 Note that this number is not completely reliable for a dynamic varobj.
30421 It will return the current number of children, but more children may
30425 @subheading The @code{-var-list-children} Command
30426 @findex -var-list-children
30428 @subsubheading Synopsis
30431 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30433 @anchor{-var-list-children}
30435 Return a list of the children of the specified variable object and
30436 create variable objects for them, if they do not already exist. With
30437 a single argument or if @var{print-values} has a value of 0 or
30438 @code{--no-values}, print only the names of the variables; if
30439 @var{print-values} is 1 or @code{--all-values}, also print their
30440 values; and if it is 2 or @code{--simple-values} print the name and
30441 value for simple data types and just the name for arrays, structures
30444 @var{from} and @var{to}, if specified, indicate the range of children
30445 to report. If @var{from} or @var{to} is less than zero, the range is
30446 reset and all children will be reported. Otherwise, children starting
30447 at @var{from} (zero-based) and up to and excluding @var{to} will be
30450 If a child range is requested, it will only affect the current call to
30451 @code{-var-list-children}, but not future calls to @code{-var-update}.
30452 For this, you must instead use @code{-var-set-update-range}. The
30453 intent of this approach is to enable a front end to implement any
30454 update approach it likes; for example, scrolling a view may cause the
30455 front end to request more children with @code{-var-list-children}, and
30456 then the front end could call @code{-var-set-update-range} with a
30457 different range to ensure that future updates are restricted to just
30460 For each child the following results are returned:
30465 Name of the variable object created for this child.
30468 The expression to be shown to the user by the front end to designate this child.
30469 For example this may be the name of a structure member.
30471 For a dynamic varobj, this value cannot be used to form an
30472 expression. There is no way to do this at all with a dynamic varobj.
30474 For C/C@t{++} structures there are several pseudo children returned to
30475 designate access qualifiers. For these pseudo children @var{exp} is
30476 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30477 type and value are not present.
30479 A dynamic varobj will not report the access qualifying
30480 pseudo-children, regardless of the language. This information is not
30481 available at all with a dynamic varobj.
30484 Number of children this child has. For a dynamic varobj, this will be
30488 The type of the child. If @samp{print object}
30489 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30490 @emph{actual} (derived) type of the object is shown rather than the
30491 @emph{declared} one.
30494 If values were requested, this is the value.
30497 If this variable object is associated with a thread, this is the
30498 thread's global thread id. Otherwise this result is not present.
30501 If the variable object is frozen, this variable will be present with a value of 1.
30504 A dynamic varobj can supply a display hint to the front end. The
30505 value comes directly from the Python pretty-printer object's
30506 @code{display_hint} method. @xref{Pretty Printing API}.
30509 This attribute will be present and have the value @samp{1} if the
30510 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30511 then this attribute will not be present.
30515 The result may have its own attributes:
30519 A dynamic varobj can supply a display hint to the front end. The
30520 value comes directly from the Python pretty-printer object's
30521 @code{display_hint} method. @xref{Pretty Printing API}.
30524 This is an integer attribute which is nonzero if there are children
30525 remaining after the end of the selected range.
30528 @subsubheading Example
30532 -var-list-children n
30533 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30534 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30536 -var-list-children --all-values n
30537 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30538 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30542 @subheading The @code{-var-info-type} Command
30543 @findex -var-info-type
30545 @subsubheading Synopsis
30548 -var-info-type @var{name}
30551 Returns the type of the specified variable @var{name}. The type is
30552 returned as a string in the same format as it is output by the
30556 type=@var{typename}
30560 @subheading The @code{-var-info-expression} Command
30561 @findex -var-info-expression
30563 @subsubheading Synopsis
30566 -var-info-expression @var{name}
30569 Returns a string that is suitable for presenting this
30570 variable object in user interface. The string is generally
30571 not valid expression in the current language, and cannot be evaluated.
30573 For example, if @code{a} is an array, and variable object
30574 @code{A} was created for @code{a}, then we'll get this output:
30577 (gdb) -var-info-expression A.1
30578 ^done,lang="C",exp="1"
30582 Here, the value of @code{lang} is the language name, which can be
30583 found in @ref{Supported Languages}.
30585 Note that the output of the @code{-var-list-children} command also
30586 includes those expressions, so the @code{-var-info-expression} command
30589 @subheading The @code{-var-info-path-expression} Command
30590 @findex -var-info-path-expression
30592 @subsubheading Synopsis
30595 -var-info-path-expression @var{name}
30598 Returns an expression that can be evaluated in the current
30599 context and will yield the same value that a variable object has.
30600 Compare this with the @code{-var-info-expression} command, which
30601 result can be used only for UI presentation. Typical use of
30602 the @code{-var-info-path-expression} command is creating a
30603 watchpoint from a variable object.
30605 This command is currently not valid for children of a dynamic varobj,
30606 and will give an error when invoked on one.
30608 For example, suppose @code{C} is a C@t{++} class, derived from class
30609 @code{Base}, and that the @code{Base} class has a member called
30610 @code{m_size}. Assume a variable @code{c} is has the type of
30611 @code{C} and a variable object @code{C} was created for variable
30612 @code{c}. Then, we'll get this output:
30614 (gdb) -var-info-path-expression C.Base.public.m_size
30615 ^done,path_expr=((Base)c).m_size)
30618 @subheading The @code{-var-show-attributes} Command
30619 @findex -var-show-attributes
30621 @subsubheading Synopsis
30624 -var-show-attributes @var{name}
30627 List attributes of the specified variable object @var{name}:
30630 status=@var{attr} [ ( ,@var{attr} )* ]
30634 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30636 @subheading The @code{-var-evaluate-expression} Command
30637 @findex -var-evaluate-expression
30639 @subsubheading Synopsis
30642 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30645 Evaluates the expression that is represented by the specified variable
30646 object and returns its value as a string. The format of the string
30647 can be specified with the @samp{-f} option. The possible values of
30648 this option are the same as for @code{-var-set-format}
30649 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30650 the current display format will be used. The current display format
30651 can be changed using the @code{-var-set-format} command.
30657 Note that one must invoke @code{-var-list-children} for a variable
30658 before the value of a child variable can be evaluated.
30660 @subheading The @code{-var-assign} Command
30661 @findex -var-assign
30663 @subsubheading Synopsis
30666 -var-assign @var{name} @var{expression}
30669 Assigns the value of @var{expression} to the variable object specified
30670 by @var{name}. The object must be @samp{editable}. If the variable's
30671 value is altered by the assign, the variable will show up in any
30672 subsequent @code{-var-update} list.
30674 @subsubheading Example
30682 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30686 @subheading The @code{-var-update} Command
30687 @findex -var-update
30689 @subsubheading Synopsis
30692 -var-update [@var{print-values}] @{@var{name} | "*"@}
30695 Reevaluate the expressions corresponding to the variable object
30696 @var{name} and all its direct and indirect children, and return the
30697 list of variable objects whose values have changed; @var{name} must
30698 be a root variable object. Here, ``changed'' means that the result of
30699 @code{-var-evaluate-expression} before and after the
30700 @code{-var-update} is different. If @samp{*} is used as the variable
30701 object names, all existing variable objects are updated, except
30702 for frozen ones (@pxref{-var-set-frozen}). The option
30703 @var{print-values} determines whether both names and values, or just
30704 names are printed. The possible values of this option are the same
30705 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30706 recommended to use the @samp{--all-values} option, to reduce the
30707 number of MI commands needed on each program stop.
30709 With the @samp{*} parameter, if a variable object is bound to a
30710 currently running thread, it will not be updated, without any
30713 If @code{-var-set-update-range} was previously used on a varobj, then
30714 only the selected range of children will be reported.
30716 @code{-var-update} reports all the changed varobjs in a tuple named
30719 Each item in the change list is itself a tuple holding:
30723 The name of the varobj.
30726 If values were requested for this update, then this field will be
30727 present and will hold the value of the varobj.
30730 @anchor{-var-update}
30731 This field is a string which may take one of three values:
30735 The variable object's current value is valid.
30738 The variable object does not currently hold a valid value but it may
30739 hold one in the future if its associated expression comes back into
30743 The variable object no longer holds a valid value.
30744 This can occur when the executable file being debugged has changed,
30745 either through recompilation or by using the @value{GDBN} @code{file}
30746 command. The front end should normally choose to delete these variable
30750 In the future new values may be added to this list so the front should
30751 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30754 This is only present if the varobj is still valid. If the type
30755 changed, then this will be the string @samp{true}; otherwise it will
30758 When a varobj's type changes, its children are also likely to have
30759 become incorrect. Therefore, the varobj's children are automatically
30760 deleted when this attribute is @samp{true}. Also, the varobj's update
30761 range, when set using the @code{-var-set-update-range} command, is
30765 If the varobj's type changed, then this field will be present and will
30768 @item new_num_children
30769 For a dynamic varobj, if the number of children changed, or if the
30770 type changed, this will be the new number of children.
30772 The @samp{numchild} field in other varobj responses is generally not
30773 valid for a dynamic varobj -- it will show the number of children that
30774 @value{GDBN} knows about, but because dynamic varobjs lazily
30775 instantiate their children, this will not reflect the number of
30776 children which may be available.
30778 The @samp{new_num_children} attribute only reports changes to the
30779 number of children known by @value{GDBN}. This is the only way to
30780 detect whether an update has removed children (which necessarily can
30781 only happen at the end of the update range).
30784 The display hint, if any.
30787 This is an integer value, which will be 1 if there are more children
30788 available outside the varobj's update range.
30791 This attribute will be present and have the value @samp{1} if the
30792 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30793 then this attribute will not be present.
30796 If new children were added to a dynamic varobj within the selected
30797 update range (as set by @code{-var-set-update-range}), then they will
30798 be listed in this attribute.
30801 @subsubheading Example
30808 -var-update --all-values var1
30809 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30810 type_changed="false"@}]
30814 @subheading The @code{-var-set-frozen} Command
30815 @findex -var-set-frozen
30816 @anchor{-var-set-frozen}
30818 @subsubheading Synopsis
30821 -var-set-frozen @var{name} @var{flag}
30824 Set the frozenness flag on the variable object @var{name}. The
30825 @var{flag} parameter should be either @samp{1} to make the variable
30826 frozen or @samp{0} to make it unfrozen. If a variable object is
30827 frozen, then neither itself, nor any of its children, are
30828 implicitly updated by @code{-var-update} of
30829 a parent variable or by @code{-var-update *}. Only
30830 @code{-var-update} of the variable itself will update its value and
30831 values of its children. After a variable object is unfrozen, it is
30832 implicitly updated by all subsequent @code{-var-update} operations.
30833 Unfreezing a variable does not update it, only subsequent
30834 @code{-var-update} does.
30836 @subsubheading Example
30840 -var-set-frozen V 1
30845 @subheading The @code{-var-set-update-range} command
30846 @findex -var-set-update-range
30847 @anchor{-var-set-update-range}
30849 @subsubheading Synopsis
30852 -var-set-update-range @var{name} @var{from} @var{to}
30855 Set the range of children to be returned by future invocations of
30856 @code{-var-update}.
30858 @var{from} and @var{to} indicate the range of children to report. If
30859 @var{from} or @var{to} is less than zero, the range is reset and all
30860 children will be reported. Otherwise, children starting at @var{from}
30861 (zero-based) and up to and excluding @var{to} will be reported.
30863 @subsubheading Example
30867 -var-set-update-range V 1 2
30871 @subheading The @code{-var-set-visualizer} command
30872 @findex -var-set-visualizer
30873 @anchor{-var-set-visualizer}
30875 @subsubheading Synopsis
30878 -var-set-visualizer @var{name} @var{visualizer}
30881 Set a visualizer for the variable object @var{name}.
30883 @var{visualizer} is the visualizer to use. The special value
30884 @samp{None} means to disable any visualizer in use.
30886 If not @samp{None}, @var{visualizer} must be a Python expression.
30887 This expression must evaluate to a callable object which accepts a
30888 single argument. @value{GDBN} will call this object with the value of
30889 the varobj @var{name} as an argument (this is done so that the same
30890 Python pretty-printing code can be used for both the CLI and MI).
30891 When called, this object must return an object which conforms to the
30892 pretty-printing interface (@pxref{Pretty Printing API}).
30894 The pre-defined function @code{gdb.default_visualizer} may be used to
30895 select a visualizer by following the built-in process
30896 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30897 a varobj is created, and so ordinarily is not needed.
30899 This feature is only available if Python support is enabled. The MI
30900 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30901 can be used to check this.
30903 @subsubheading Example
30905 Resetting the visualizer:
30909 -var-set-visualizer V None
30913 Reselecting the default (type-based) visualizer:
30917 -var-set-visualizer V gdb.default_visualizer
30921 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30922 can be used to instantiate this class for a varobj:
30926 -var-set-visualizer V "lambda val: SomeClass()"
30930 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30931 @node GDB/MI Data Manipulation
30932 @section @sc{gdb/mi} Data Manipulation
30934 @cindex data manipulation, in @sc{gdb/mi}
30935 @cindex @sc{gdb/mi}, data manipulation
30936 This section describes the @sc{gdb/mi} commands that manipulate data:
30937 examine memory and registers, evaluate expressions, etc.
30939 For details about what an addressable memory unit is,
30940 @pxref{addressable memory unit}.
30942 @c REMOVED FROM THE INTERFACE.
30943 @c @subheading -data-assign
30944 @c Change the value of a program variable. Plenty of side effects.
30945 @c @subsubheading GDB Command
30947 @c @subsubheading Example
30950 @subheading The @code{-data-disassemble} Command
30951 @findex -data-disassemble
30953 @subsubheading Synopsis
30957 [ -s @var{start-addr} -e @var{end-addr} ]
30958 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30966 @item @var{start-addr}
30967 is the beginning address (or @code{$pc})
30968 @item @var{end-addr}
30970 @item @var{filename}
30971 is the name of the file to disassemble
30972 @item @var{linenum}
30973 is the line number to disassemble around
30975 is the number of disassembly lines to be produced. If it is -1,
30976 the whole function will be disassembled, in case no @var{end-addr} is
30977 specified. If @var{end-addr} is specified as a non-zero value, and
30978 @var{lines} is lower than the number of disassembly lines between
30979 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30980 displayed; if @var{lines} is higher than the number of lines between
30981 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30986 @item 0 disassembly only
30987 @item 1 mixed source and disassembly (deprecated)
30988 @item 2 disassembly with raw opcodes
30989 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30990 @item 4 mixed source and disassembly
30991 @item 5 mixed source and disassembly with raw opcodes
30994 Modes 1 and 3 are deprecated. The output is ``source centric''
30995 which hasn't proved useful in practice.
30996 @xref{Machine Code}, for a discussion of the difference between
30997 @code{/m} and @code{/s} output of the @code{disassemble} command.
31000 @subsubheading Result
31002 The result of the @code{-data-disassemble} command will be a list named
31003 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31004 used with the @code{-data-disassemble} command.
31006 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31011 The address at which this instruction was disassembled.
31014 The name of the function this instruction is within.
31017 The decimal offset in bytes from the start of @samp{func-name}.
31020 The text disassembly for this @samp{address}.
31023 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31024 bytes for the @samp{inst} field.
31028 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31029 @samp{src_and_asm_line}, each of which has the following fields:
31033 The line number within @samp{file}.
31036 The file name from the compilation unit. This might be an absolute
31037 file name or a relative file name depending on the compile command
31041 Absolute file name of @samp{file}. It is converted to a canonical form
31042 using the source file search path
31043 (@pxref{Source Path, ,Specifying Source Directories})
31044 and after resolving all the symbolic links.
31046 If the source file is not found this field will contain the path as
31047 present in the debug information.
31049 @item line_asm_insn
31050 This is a list of tuples containing the disassembly for @samp{line} in
31051 @samp{file}. The fields of each tuple are the same as for
31052 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31053 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31058 Note that whatever included in the @samp{inst} field, is not
31059 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31062 @subsubheading @value{GDBN} Command
31064 The corresponding @value{GDBN} command is @samp{disassemble}.
31066 @subsubheading Example
31068 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31072 -data-disassemble -s $pc -e "$pc + 20" -- 0
31075 @{address="0x000107c0",func-name="main",offset="4",
31076 inst="mov 2, %o0"@},
31077 @{address="0x000107c4",func-name="main",offset="8",
31078 inst="sethi %hi(0x11800), %o2"@},
31079 @{address="0x000107c8",func-name="main",offset="12",
31080 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31081 @{address="0x000107cc",func-name="main",offset="16",
31082 inst="sethi %hi(0x11800), %o2"@},
31083 @{address="0x000107d0",func-name="main",offset="20",
31084 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31088 Disassemble the whole @code{main} function. Line 32 is part of
31092 -data-disassemble -f basics.c -l 32 -- 0
31094 @{address="0x000107bc",func-name="main",offset="0",
31095 inst="save %sp, -112, %sp"@},
31096 @{address="0x000107c0",func-name="main",offset="4",
31097 inst="mov 2, %o0"@},
31098 @{address="0x000107c4",func-name="main",offset="8",
31099 inst="sethi %hi(0x11800), %o2"@},
31101 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31102 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31106 Disassemble 3 instructions from the start of @code{main}:
31110 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31112 @{address="0x000107bc",func-name="main",offset="0",
31113 inst="save %sp, -112, %sp"@},
31114 @{address="0x000107c0",func-name="main",offset="4",
31115 inst="mov 2, %o0"@},
31116 @{address="0x000107c4",func-name="main",offset="8",
31117 inst="sethi %hi(0x11800), %o2"@}]
31121 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31125 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31127 src_and_asm_line=@{line="31",
31128 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31129 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31130 line_asm_insn=[@{address="0x000107bc",
31131 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31132 src_and_asm_line=@{line="32",
31133 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31134 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31135 line_asm_insn=[@{address="0x000107c0",
31136 func-name="main",offset="4",inst="mov 2, %o0"@},
31137 @{address="0x000107c4",func-name="main",offset="8",
31138 inst="sethi %hi(0x11800), %o2"@}]@}]
31143 @subheading The @code{-data-evaluate-expression} Command
31144 @findex -data-evaluate-expression
31146 @subsubheading Synopsis
31149 -data-evaluate-expression @var{expr}
31152 Evaluate @var{expr} as an expression. The expression could contain an
31153 inferior function call. The function call will execute synchronously.
31154 If the expression contains spaces, it must be enclosed in double quotes.
31156 @subsubheading @value{GDBN} Command
31158 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31159 @samp{call}. In @code{gdbtk} only, there's a corresponding
31160 @samp{gdb_eval} command.
31162 @subsubheading Example
31164 In the following example, the numbers that precede the commands are the
31165 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31166 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31170 211-data-evaluate-expression A
31173 311-data-evaluate-expression &A
31174 311^done,value="0xefffeb7c"
31176 411-data-evaluate-expression A+3
31179 511-data-evaluate-expression "A + 3"
31185 @subheading The @code{-data-list-changed-registers} Command
31186 @findex -data-list-changed-registers
31188 @subsubheading Synopsis
31191 -data-list-changed-registers
31194 Display a list of the registers that have changed.
31196 @subsubheading @value{GDBN} Command
31198 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31199 has the corresponding command @samp{gdb_changed_register_list}.
31201 @subsubheading Example
31203 On a PPC MBX board:
31211 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31212 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31215 -data-list-changed-registers
31216 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31217 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31218 "24","25","26","27","28","30","31","64","65","66","67","69"]
31223 @subheading The @code{-data-list-register-names} Command
31224 @findex -data-list-register-names
31226 @subsubheading Synopsis
31229 -data-list-register-names [ ( @var{regno} )+ ]
31232 Show a list of register names for the current target. If no arguments
31233 are given, it shows a list of the names of all the registers. If
31234 integer numbers are given as arguments, it will print a list of the
31235 names of the registers corresponding to the arguments. To ensure
31236 consistency between a register name and its number, the output list may
31237 include empty register names.
31239 @subsubheading @value{GDBN} Command
31241 @value{GDBN} does not have a command which corresponds to
31242 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31243 corresponding command @samp{gdb_regnames}.
31245 @subsubheading Example
31247 For the PPC MBX board:
31250 -data-list-register-names
31251 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31252 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31253 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31254 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31255 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31256 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31257 "", "pc","ps","cr","lr","ctr","xer"]
31259 -data-list-register-names 1 2 3
31260 ^done,register-names=["r1","r2","r3"]
31264 @subheading The @code{-data-list-register-values} Command
31265 @findex -data-list-register-values
31267 @subsubheading Synopsis
31270 -data-list-register-values
31271 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31274 Display the registers' contents. The format according to which the
31275 registers' contents are to be returned is given by @var{fmt}, followed
31276 by an optional list of numbers specifying the registers to display. A
31277 missing list of numbers indicates that the contents of all the
31278 registers must be returned. The @code{--skip-unavailable} option
31279 indicates that only the available registers are to be returned.
31281 Allowed formats for @var{fmt} are:
31298 @subsubheading @value{GDBN} Command
31300 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31301 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31303 @subsubheading Example
31305 For a PPC MBX board (note: line breaks are for readability only, they
31306 don't appear in the actual output):
31310 -data-list-register-values r 64 65
31311 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31312 @{number="65",value="0x00029002"@}]
31314 -data-list-register-values x
31315 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31316 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31317 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31318 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31319 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31320 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31321 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31322 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31323 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31324 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31325 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31326 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31327 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31328 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31329 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31330 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31331 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31332 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31333 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31334 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31335 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31336 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31337 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31338 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31339 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31340 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31341 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31342 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31343 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31344 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31345 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31346 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31347 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31348 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31349 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31350 @{number="69",value="0x20002b03"@}]
31355 @subheading The @code{-data-read-memory} Command
31356 @findex -data-read-memory
31358 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31360 @subsubheading Synopsis
31363 -data-read-memory [ -o @var{byte-offset} ]
31364 @var{address} @var{word-format} @var{word-size}
31365 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31372 @item @var{address}
31373 An expression specifying the address of the first memory word to be
31374 read. Complex expressions containing embedded white space should be
31375 quoted using the C convention.
31377 @item @var{word-format}
31378 The format to be used to print the memory words. The notation is the
31379 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31382 @item @var{word-size}
31383 The size of each memory word in bytes.
31385 @item @var{nr-rows}
31386 The number of rows in the output table.
31388 @item @var{nr-cols}
31389 The number of columns in the output table.
31392 If present, indicates that each row should include an @sc{ascii} dump. The
31393 value of @var{aschar} is used as a padding character when a byte is not a
31394 member of the printable @sc{ascii} character set (printable @sc{ascii}
31395 characters are those whose code is between 32 and 126, inclusively).
31397 @item @var{byte-offset}
31398 An offset to add to the @var{address} before fetching memory.
31401 This command displays memory contents as a table of @var{nr-rows} by
31402 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31403 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31404 (returned as @samp{total-bytes}). Should less than the requested number
31405 of bytes be returned by the target, the missing words are identified
31406 using @samp{N/A}. The number of bytes read from the target is returned
31407 in @samp{nr-bytes} and the starting address used to read memory in
31410 The address of the next/previous row or page is available in
31411 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31414 @subsubheading @value{GDBN} Command
31416 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31417 @samp{gdb_get_mem} memory read command.
31419 @subsubheading Example
31421 Read six bytes of memory starting at @code{bytes+6} but then offset by
31422 @code{-6} bytes. Format as three rows of two columns. One byte per
31423 word. Display each word in hex.
31427 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31428 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31429 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31430 prev-page="0x0000138a",memory=[
31431 @{addr="0x00001390",data=["0x00","0x01"]@},
31432 @{addr="0x00001392",data=["0x02","0x03"]@},
31433 @{addr="0x00001394",data=["0x04","0x05"]@}]
31437 Read two bytes of memory starting at address @code{shorts + 64} and
31438 display as a single word formatted in decimal.
31442 5-data-read-memory shorts+64 d 2 1 1
31443 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31444 next-row="0x00001512",prev-row="0x0000150e",
31445 next-page="0x00001512",prev-page="0x0000150e",memory=[
31446 @{addr="0x00001510",data=["128"]@}]
31450 Read thirty two bytes of memory starting at @code{bytes+16} and format
31451 as eight rows of four columns. Include a string encoding with @samp{x}
31452 used as the non-printable character.
31456 4-data-read-memory bytes+16 x 1 8 4 x
31457 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31458 next-row="0x000013c0",prev-row="0x0000139c",
31459 next-page="0x000013c0",prev-page="0x00001380",memory=[
31460 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31461 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31462 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31463 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31464 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31465 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31466 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31467 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31471 @subheading The @code{-data-read-memory-bytes} Command
31472 @findex -data-read-memory-bytes
31474 @subsubheading Synopsis
31477 -data-read-memory-bytes [ -o @var{offset} ]
31478 @var{address} @var{count}
31485 @item @var{address}
31486 An expression specifying the address of the first addressable memory unit
31487 to be read. Complex expressions containing embedded white space should be
31488 quoted using the C convention.
31491 The number of addressable memory units to read. This should be an integer
31495 The offset relative to @var{address} at which to start reading. This
31496 should be an integer literal. This option is provided so that a frontend
31497 is not required to first evaluate address and then perform address
31498 arithmetics itself.
31502 This command attempts to read all accessible memory regions in the
31503 specified range. First, all regions marked as unreadable in the memory
31504 map (if one is defined) will be skipped. @xref{Memory Region
31505 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31506 regions. For each one, if reading full region results in an errors,
31507 @value{GDBN} will try to read a subset of the region.
31509 In general, every single memory unit in the region may be readable or not,
31510 and the only way to read every readable unit is to try a read at
31511 every address, which is not practical. Therefore, @value{GDBN} will
31512 attempt to read all accessible memory units at either beginning or the end
31513 of the region, using a binary division scheme. This heuristic works
31514 well for reading accross a memory map boundary. Note that if a region
31515 has a readable range that is neither at the beginning or the end,
31516 @value{GDBN} will not read it.
31518 The result record (@pxref{GDB/MI Result Records}) that is output of
31519 the command includes a field named @samp{memory} whose content is a
31520 list of tuples. Each tuple represent a successfully read memory block
31521 and has the following fields:
31525 The start address of the memory block, as hexadecimal literal.
31528 The end address of the memory block, as hexadecimal literal.
31531 The offset of the memory block, as hexadecimal literal, relative to
31532 the start address passed to @code{-data-read-memory-bytes}.
31535 The contents of the memory block, in hex.
31541 @subsubheading @value{GDBN} Command
31543 The corresponding @value{GDBN} command is @samp{x}.
31545 @subsubheading Example
31549 -data-read-memory-bytes &a 10
31550 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31552 contents="01000000020000000300"@}]
31557 @subheading The @code{-data-write-memory-bytes} Command
31558 @findex -data-write-memory-bytes
31560 @subsubheading Synopsis
31563 -data-write-memory-bytes @var{address} @var{contents}
31564 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31571 @item @var{address}
31572 An expression specifying the address of the first addressable memory unit
31573 to be written. Complex expressions containing embedded white space should
31574 be quoted using the C convention.
31576 @item @var{contents}
31577 The hex-encoded data to write. It is an error if @var{contents} does
31578 not represent an integral number of addressable memory units.
31581 Optional argument indicating the number of addressable memory units to be
31582 written. If @var{count} is greater than @var{contents}' length,
31583 @value{GDBN} will repeatedly write @var{contents} until it fills
31584 @var{count} memory units.
31588 @subsubheading @value{GDBN} Command
31590 There's no corresponding @value{GDBN} command.
31592 @subsubheading Example
31596 -data-write-memory-bytes &a "aabbccdd"
31603 -data-write-memory-bytes &a "aabbccdd" 16e
31608 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31609 @node GDB/MI Tracepoint Commands
31610 @section @sc{gdb/mi} Tracepoint Commands
31612 The commands defined in this section implement MI support for
31613 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31615 @subheading The @code{-trace-find} Command
31616 @findex -trace-find
31618 @subsubheading Synopsis
31621 -trace-find @var{mode} [@var{parameters}@dots{}]
31624 Find a trace frame using criteria defined by @var{mode} and
31625 @var{parameters}. The following table lists permissible
31626 modes and their parameters. For details of operation, see @ref{tfind}.
31631 No parameters are required. Stops examining trace frames.
31634 An integer is required as parameter. Selects tracepoint frame with
31637 @item tracepoint-number
31638 An integer is required as parameter. Finds next
31639 trace frame that corresponds to tracepoint with the specified number.
31642 An address is required as parameter. Finds
31643 next trace frame that corresponds to any tracepoint at the specified
31646 @item pc-inside-range
31647 Two addresses are required as parameters. Finds next trace
31648 frame that corresponds to a tracepoint at an address inside the
31649 specified range. Both bounds are considered to be inside the range.
31651 @item pc-outside-range
31652 Two addresses are required as parameters. Finds
31653 next trace frame that corresponds to a tracepoint at an address outside
31654 the specified range. Both bounds are considered to be inside the range.
31657 Line specification is required as parameter. @xref{Specify Location}.
31658 Finds next trace frame that corresponds to a tracepoint at
31659 the specified location.
31663 If @samp{none} was passed as @var{mode}, the response does not
31664 have fields. Otherwise, the response may have the following fields:
31668 This field has either @samp{0} or @samp{1} as the value, depending
31669 on whether a matching tracepoint was found.
31672 The index of the found traceframe. This field is present iff
31673 the @samp{found} field has value of @samp{1}.
31676 The index of the found tracepoint. This field is present iff
31677 the @samp{found} field has value of @samp{1}.
31680 The information about the frame corresponding to the found trace
31681 frame. This field is present only if a trace frame was found.
31682 @xref{GDB/MI Frame Information}, for description of this field.
31686 @subsubheading @value{GDBN} Command
31688 The corresponding @value{GDBN} command is @samp{tfind}.
31690 @subheading -trace-define-variable
31691 @findex -trace-define-variable
31693 @subsubheading Synopsis
31696 -trace-define-variable @var{name} [ @var{value} ]
31699 Create trace variable @var{name} if it does not exist. If
31700 @var{value} is specified, sets the initial value of the specified
31701 trace variable to that value. Note that the @var{name} should start
31702 with the @samp{$} character.
31704 @subsubheading @value{GDBN} Command
31706 The corresponding @value{GDBN} command is @samp{tvariable}.
31708 @subheading The @code{-trace-frame-collected} Command
31709 @findex -trace-frame-collected
31711 @subsubheading Synopsis
31714 -trace-frame-collected
31715 [--var-print-values @var{var_pval}]
31716 [--comp-print-values @var{comp_pval}]
31717 [--registers-format @var{regformat}]
31718 [--memory-contents]
31721 This command returns the set of collected objects, register names,
31722 trace state variable names, memory ranges and computed expressions
31723 that have been collected at a particular trace frame. The optional
31724 parameters to the command affect the output format in different ways.
31725 See the output description table below for more details.
31727 The reported names can be used in the normal manner to create
31728 varobjs and inspect the objects themselves. The items returned by
31729 this command are categorized so that it is clear which is a variable,
31730 which is a register, which is a trace state variable, which is a
31731 memory range and which is a computed expression.
31733 For instance, if the actions were
31735 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31736 collect *(int*)0xaf02bef0@@40
31740 the object collected in its entirety would be @code{myVar}. The
31741 object @code{myArray} would be partially collected, because only the
31742 element at index @code{myIndex} would be collected. The remaining
31743 objects would be computed expressions.
31745 An example output would be:
31749 -trace-frame-collected
31751 explicit-variables=[@{name="myVar",value="1"@}],
31752 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31753 @{name="myObj.field",value="0"@},
31754 @{name="myPtr->field",value="1"@},
31755 @{name="myCount + 2",value="3"@},
31756 @{name="$tvar1 + 1",value="43970027"@}],
31757 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31758 @{number="1",value="0x0"@},
31759 @{number="2",value="0x4"@},
31761 @{number="125",value="0x0"@}],
31762 tvars=[@{name="$tvar1",current="43970026"@}],
31763 memory=[@{address="0x0000000000602264",length="4"@},
31764 @{address="0x0000000000615bc0",length="4"@}]
31771 @item explicit-variables
31772 The set of objects that have been collected in their entirety (as
31773 opposed to collecting just a few elements of an array or a few struct
31774 members). For each object, its name and value are printed.
31775 The @code{--var-print-values} option affects how or whether the value
31776 field is output. If @var{var_pval} is 0, then print only the names;
31777 if it is 1, print also their values; and if it is 2, print the name,
31778 type and value for simple data types, and the name and type for
31779 arrays, structures and unions.
31781 @item computed-expressions
31782 The set of computed expressions that have been collected at the
31783 current trace frame. The @code{--comp-print-values} option affects
31784 this set like the @code{--var-print-values} option affects the
31785 @code{explicit-variables} set. See above.
31788 The registers that have been collected at the current trace frame.
31789 For each register collected, the name and current value are returned.
31790 The value is formatted according to the @code{--registers-format}
31791 option. See the @command{-data-list-register-values} command for a
31792 list of the allowed formats. The default is @samp{x}.
31795 The trace state variables that have been collected at the current
31796 trace frame. For each trace state variable collected, the name and
31797 current value are returned.
31800 The set of memory ranges that have been collected at the current trace
31801 frame. Its content is a list of tuples. Each tuple represents a
31802 collected memory range and has the following fields:
31806 The start address of the memory range, as hexadecimal literal.
31809 The length of the memory range, as decimal literal.
31812 The contents of the memory block, in hex. This field is only present
31813 if the @code{--memory-contents} option is specified.
31819 @subsubheading @value{GDBN} Command
31821 There is no corresponding @value{GDBN} command.
31823 @subsubheading Example
31825 @subheading -trace-list-variables
31826 @findex -trace-list-variables
31828 @subsubheading Synopsis
31831 -trace-list-variables
31834 Return a table of all defined trace variables. Each element of the
31835 table has the following fields:
31839 The name of the trace variable. This field is always present.
31842 The initial value. This is a 64-bit signed integer. This
31843 field is always present.
31846 The value the trace variable has at the moment. This is a 64-bit
31847 signed integer. This field is absent iff current value is
31848 not defined, for example if the trace was never run, or is
31853 @subsubheading @value{GDBN} Command
31855 The corresponding @value{GDBN} command is @samp{tvariables}.
31857 @subsubheading Example
31861 -trace-list-variables
31862 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31863 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31864 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31865 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31866 body=[variable=@{name="$trace_timestamp",initial="0"@}
31867 variable=@{name="$foo",initial="10",current="15"@}]@}
31871 @subheading -trace-save
31872 @findex -trace-save
31874 @subsubheading Synopsis
31877 -trace-save [ -r ] [ -ctf ] @var{filename}
31880 Saves the collected trace data to @var{filename}. Without the
31881 @samp{-r} option, the data is downloaded from the target and saved
31882 in a local file. With the @samp{-r} option the target is asked
31883 to perform the save.
31885 By default, this command will save the trace in the tfile format. You can
31886 supply the optional @samp{-ctf} argument to save it the CTF format. See
31887 @ref{Trace Files} for more information about CTF.
31889 @subsubheading @value{GDBN} Command
31891 The corresponding @value{GDBN} command is @samp{tsave}.
31894 @subheading -trace-start
31895 @findex -trace-start
31897 @subsubheading Synopsis
31903 Starts a tracing experiment. The result of this command does not
31906 @subsubheading @value{GDBN} Command
31908 The corresponding @value{GDBN} command is @samp{tstart}.
31910 @subheading -trace-status
31911 @findex -trace-status
31913 @subsubheading Synopsis
31919 Obtains the status of a tracing experiment. The result may include
31920 the following fields:
31925 May have a value of either @samp{0}, when no tracing operations are
31926 supported, @samp{1}, when all tracing operations are supported, or
31927 @samp{file} when examining trace file. In the latter case, examining
31928 of trace frame is possible but new tracing experiement cannot be
31929 started. This field is always present.
31932 May have a value of either @samp{0} or @samp{1} depending on whether
31933 tracing experiement is in progress on target. This field is present
31934 if @samp{supported} field is not @samp{0}.
31937 Report the reason why the tracing was stopped last time. This field
31938 may be absent iff tracing was never stopped on target yet. The
31939 value of @samp{request} means the tracing was stopped as result of
31940 the @code{-trace-stop} command. The value of @samp{overflow} means
31941 the tracing buffer is full. The value of @samp{disconnection} means
31942 tracing was automatically stopped when @value{GDBN} has disconnected.
31943 The value of @samp{passcount} means tracing was stopped when a
31944 tracepoint was passed a maximal number of times for that tracepoint.
31945 This field is present if @samp{supported} field is not @samp{0}.
31947 @item stopping-tracepoint
31948 The number of tracepoint whose passcount as exceeded. This field is
31949 present iff the @samp{stop-reason} field has the value of
31953 @itemx frames-created
31954 The @samp{frames} field is a count of the total number of trace frames
31955 in the trace buffer, while @samp{frames-created} is the total created
31956 during the run, including ones that were discarded, such as when a
31957 circular trace buffer filled up. Both fields are optional.
31961 These fields tell the current size of the tracing buffer and the
31962 remaining space. These fields are optional.
31965 The value of the circular trace buffer flag. @code{1} means that the
31966 trace buffer is circular and old trace frames will be discarded if
31967 necessary to make room, @code{0} means that the trace buffer is linear
31971 The value of the disconnected tracing flag. @code{1} means that
31972 tracing will continue after @value{GDBN} disconnects, @code{0} means
31973 that the trace run will stop.
31976 The filename of the trace file being examined. This field is
31977 optional, and only present when examining a trace file.
31981 @subsubheading @value{GDBN} Command
31983 The corresponding @value{GDBN} command is @samp{tstatus}.
31985 @subheading -trace-stop
31986 @findex -trace-stop
31988 @subsubheading Synopsis
31994 Stops a tracing experiment. The result of this command has the same
31995 fields as @code{-trace-status}, except that the @samp{supported} and
31996 @samp{running} fields are not output.
31998 @subsubheading @value{GDBN} Command
32000 The corresponding @value{GDBN} command is @samp{tstop}.
32003 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32004 @node GDB/MI Symbol Query
32005 @section @sc{gdb/mi} Symbol Query Commands
32009 @subheading The @code{-symbol-info-address} Command
32010 @findex -symbol-info-address
32012 @subsubheading Synopsis
32015 -symbol-info-address @var{symbol}
32018 Describe where @var{symbol} is stored.
32020 @subsubheading @value{GDBN} Command
32022 The corresponding @value{GDBN} command is @samp{info address}.
32024 @subsubheading Example
32028 @subheading The @code{-symbol-info-file} Command
32029 @findex -symbol-info-file
32031 @subsubheading Synopsis
32037 Show the file for the symbol.
32039 @subsubheading @value{GDBN} Command
32041 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32042 @samp{gdb_find_file}.
32044 @subsubheading Example
32048 @subheading The @code{-symbol-info-function} Command
32049 @findex -symbol-info-function
32051 @subsubheading Synopsis
32054 -symbol-info-function
32057 Show which function the symbol lives in.
32059 @subsubheading @value{GDBN} Command
32061 @samp{gdb_get_function} in @code{gdbtk}.
32063 @subsubheading Example
32067 @subheading The @code{-symbol-info-line} Command
32068 @findex -symbol-info-line
32070 @subsubheading Synopsis
32076 Show the core addresses of the code for a source line.
32078 @subsubheading @value{GDBN} Command
32080 The corresponding @value{GDBN} command is @samp{info line}.
32081 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32083 @subsubheading Example
32087 @subheading The @code{-symbol-info-symbol} Command
32088 @findex -symbol-info-symbol
32090 @subsubheading Synopsis
32093 -symbol-info-symbol @var{addr}
32096 Describe what symbol is at location @var{addr}.
32098 @subsubheading @value{GDBN} Command
32100 The corresponding @value{GDBN} command is @samp{info symbol}.
32102 @subsubheading Example
32106 @subheading The @code{-symbol-list-functions} Command
32107 @findex -symbol-list-functions
32109 @subsubheading Synopsis
32112 -symbol-list-functions
32115 List the functions in the executable.
32117 @subsubheading @value{GDBN} Command
32119 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32120 @samp{gdb_search} in @code{gdbtk}.
32122 @subsubheading Example
32127 @subheading The @code{-symbol-list-lines} Command
32128 @findex -symbol-list-lines
32130 @subsubheading Synopsis
32133 -symbol-list-lines @var{filename}
32136 Print the list of lines that contain code and their associated program
32137 addresses for the given source filename. The entries are sorted in
32138 ascending PC order.
32140 @subsubheading @value{GDBN} Command
32142 There is no corresponding @value{GDBN} command.
32144 @subsubheading Example
32147 -symbol-list-lines basics.c
32148 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32154 @subheading The @code{-symbol-list-types} Command
32155 @findex -symbol-list-types
32157 @subsubheading Synopsis
32163 List all the type names.
32165 @subsubheading @value{GDBN} Command
32167 The corresponding commands are @samp{info types} in @value{GDBN},
32168 @samp{gdb_search} in @code{gdbtk}.
32170 @subsubheading Example
32174 @subheading The @code{-symbol-list-variables} Command
32175 @findex -symbol-list-variables
32177 @subsubheading Synopsis
32180 -symbol-list-variables
32183 List all the global and static variable names.
32185 @subsubheading @value{GDBN} Command
32187 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32189 @subsubheading Example
32193 @subheading The @code{-symbol-locate} Command
32194 @findex -symbol-locate
32196 @subsubheading Synopsis
32202 @subsubheading @value{GDBN} Command
32204 @samp{gdb_loc} in @code{gdbtk}.
32206 @subsubheading Example
32210 @subheading The @code{-symbol-type} Command
32211 @findex -symbol-type
32213 @subsubheading Synopsis
32216 -symbol-type @var{variable}
32219 Show type of @var{variable}.
32221 @subsubheading @value{GDBN} Command
32223 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32224 @samp{gdb_obj_variable}.
32226 @subsubheading Example
32231 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32232 @node GDB/MI File Commands
32233 @section @sc{gdb/mi} File Commands
32235 This section describes the GDB/MI commands to specify executable file names
32236 and to read in and obtain symbol table information.
32238 @subheading The @code{-file-exec-and-symbols} Command
32239 @findex -file-exec-and-symbols
32241 @subsubheading Synopsis
32244 -file-exec-and-symbols @var{file}
32247 Specify the executable file to be debugged. This file is the one from
32248 which the symbol table is also read. If no file is specified, the
32249 command clears the executable and symbol information. If breakpoints
32250 are set when using this command with no arguments, @value{GDBN} will produce
32251 error messages. Otherwise, no output is produced, except a completion
32254 @subsubheading @value{GDBN} Command
32256 The corresponding @value{GDBN} command is @samp{file}.
32258 @subsubheading Example
32262 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32268 @subheading The @code{-file-exec-file} Command
32269 @findex -file-exec-file
32271 @subsubheading Synopsis
32274 -file-exec-file @var{file}
32277 Specify the executable file to be debugged. Unlike
32278 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32279 from this file. If used without argument, @value{GDBN} clears the information
32280 about the executable file. No output is produced, except a completion
32283 @subsubheading @value{GDBN} Command
32285 The corresponding @value{GDBN} command is @samp{exec-file}.
32287 @subsubheading Example
32291 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32298 @subheading The @code{-file-list-exec-sections} Command
32299 @findex -file-list-exec-sections
32301 @subsubheading Synopsis
32304 -file-list-exec-sections
32307 List the sections of the current executable file.
32309 @subsubheading @value{GDBN} Command
32311 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32312 information as this command. @code{gdbtk} has a corresponding command
32313 @samp{gdb_load_info}.
32315 @subsubheading Example
32320 @subheading The @code{-file-list-exec-source-file} Command
32321 @findex -file-list-exec-source-file
32323 @subsubheading Synopsis
32326 -file-list-exec-source-file
32329 List the line number, the current source file, and the absolute path
32330 to the current source file for the current executable. The macro
32331 information field has a value of @samp{1} or @samp{0} depending on
32332 whether or not the file includes preprocessor macro information.
32334 @subsubheading @value{GDBN} Command
32336 The @value{GDBN} equivalent is @samp{info source}
32338 @subsubheading Example
32342 123-file-list-exec-source-file
32343 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32348 @subheading The @code{-file-list-exec-source-files} Command
32349 @findex -file-list-exec-source-files
32351 @subsubheading Synopsis
32354 -file-list-exec-source-files
32357 List the source files for the current executable.
32359 It will always output both the filename and fullname (absolute file
32360 name) of a source file.
32362 @subsubheading @value{GDBN} Command
32364 The @value{GDBN} equivalent is @samp{info sources}.
32365 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32367 @subsubheading Example
32370 -file-list-exec-source-files
32372 @{file=foo.c,fullname=/home/foo.c@},
32373 @{file=/home/bar.c,fullname=/home/bar.c@},
32374 @{file=gdb_could_not_find_fullpath.c@}]
32378 @subheading The @code{-file-list-shared-libraries} Command
32379 @findex -file-list-shared-libraries
32381 @subsubheading Synopsis
32384 -file-list-shared-libraries [ @var{regexp} ]
32387 List the shared libraries in the program.
32388 With a regular expression @var{regexp}, only those libraries whose
32389 names match @var{regexp} are listed.
32391 @subsubheading @value{GDBN} Command
32393 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32394 have a similar meaning to the @code{=library-loaded} notification.
32395 The @code{ranges} field specifies the multiple segments belonging to this
32396 library. Each range has the following fields:
32400 The address defining the inclusive lower bound of the segment.
32402 The address defining the exclusive upper bound of the segment.
32405 @subsubheading Example
32408 -file-list-exec-source-files
32409 ^done,shared-libraries=[
32410 @{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"@}]@},
32411 @{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"@}]@}]
32417 @subheading The @code{-file-list-symbol-files} Command
32418 @findex -file-list-symbol-files
32420 @subsubheading Synopsis
32423 -file-list-symbol-files
32428 @subsubheading @value{GDBN} Command
32430 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32432 @subsubheading Example
32437 @subheading The @code{-file-symbol-file} Command
32438 @findex -file-symbol-file
32440 @subsubheading Synopsis
32443 -file-symbol-file @var{file}
32446 Read symbol table info from the specified @var{file} argument. When
32447 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32448 produced, except for a completion notification.
32450 @subsubheading @value{GDBN} Command
32452 The corresponding @value{GDBN} command is @samp{symbol-file}.
32454 @subsubheading Example
32458 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32464 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32465 @node GDB/MI Memory Overlay Commands
32466 @section @sc{gdb/mi} Memory Overlay Commands
32468 The memory overlay commands are not implemented.
32470 @c @subheading -overlay-auto
32472 @c @subheading -overlay-list-mapping-state
32474 @c @subheading -overlay-list-overlays
32476 @c @subheading -overlay-map
32478 @c @subheading -overlay-off
32480 @c @subheading -overlay-on
32482 @c @subheading -overlay-unmap
32484 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32485 @node GDB/MI Signal Handling Commands
32486 @section @sc{gdb/mi} Signal Handling Commands
32488 Signal handling commands are not implemented.
32490 @c @subheading -signal-handle
32492 @c @subheading -signal-list-handle-actions
32494 @c @subheading -signal-list-signal-types
32498 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32499 @node GDB/MI Target Manipulation
32500 @section @sc{gdb/mi} Target Manipulation Commands
32503 @subheading The @code{-target-attach} Command
32504 @findex -target-attach
32506 @subsubheading Synopsis
32509 -target-attach @var{pid} | @var{gid} | @var{file}
32512 Attach to a process @var{pid} or a file @var{file} outside of
32513 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32514 group, the id previously returned by
32515 @samp{-list-thread-groups --available} must be used.
32517 @subsubheading @value{GDBN} Command
32519 The corresponding @value{GDBN} command is @samp{attach}.
32521 @subsubheading Example
32525 =thread-created,id="1"
32526 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32532 @subheading The @code{-target-compare-sections} Command
32533 @findex -target-compare-sections
32535 @subsubheading Synopsis
32538 -target-compare-sections [ @var{section} ]
32541 Compare data of section @var{section} on target to the exec file.
32542 Without the argument, all sections are compared.
32544 @subsubheading @value{GDBN} Command
32546 The @value{GDBN} equivalent is @samp{compare-sections}.
32548 @subsubheading Example
32553 @subheading The @code{-target-detach} Command
32554 @findex -target-detach
32556 @subsubheading Synopsis
32559 -target-detach [ @var{pid} | @var{gid} ]
32562 Detach from the remote target which normally resumes its execution.
32563 If either @var{pid} or @var{gid} is specified, detaches from either
32564 the specified process, or specified thread group. There's no output.
32566 @subsubheading @value{GDBN} Command
32568 The corresponding @value{GDBN} command is @samp{detach}.
32570 @subsubheading Example
32580 @subheading The @code{-target-disconnect} Command
32581 @findex -target-disconnect
32583 @subsubheading Synopsis
32589 Disconnect from the remote target. There's no output and the target is
32590 generally not resumed.
32592 @subsubheading @value{GDBN} Command
32594 The corresponding @value{GDBN} command is @samp{disconnect}.
32596 @subsubheading Example
32606 @subheading The @code{-target-download} Command
32607 @findex -target-download
32609 @subsubheading Synopsis
32615 Loads the executable onto the remote target.
32616 It prints out an update message every half second, which includes the fields:
32620 The name of the section.
32622 The size of what has been sent so far for that section.
32624 The size of the section.
32626 The total size of what was sent so far (the current and the previous sections).
32628 The size of the overall executable to download.
32632 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32633 @sc{gdb/mi} Output Syntax}).
32635 In addition, it prints the name and size of the sections, as they are
32636 downloaded. These messages include the following fields:
32640 The name of the section.
32642 The size of the section.
32644 The size of the overall executable to download.
32648 At the end, a summary is printed.
32650 @subsubheading @value{GDBN} Command
32652 The corresponding @value{GDBN} command is @samp{load}.
32654 @subsubheading Example
32656 Note: each status message appears on a single line. Here the messages
32657 have been broken down so that they can fit onto a page.
32662 +download,@{section=".text",section-size="6668",total-size="9880"@}
32663 +download,@{section=".text",section-sent="512",section-size="6668",
32664 total-sent="512",total-size="9880"@}
32665 +download,@{section=".text",section-sent="1024",section-size="6668",
32666 total-sent="1024",total-size="9880"@}
32667 +download,@{section=".text",section-sent="1536",section-size="6668",
32668 total-sent="1536",total-size="9880"@}
32669 +download,@{section=".text",section-sent="2048",section-size="6668",
32670 total-sent="2048",total-size="9880"@}
32671 +download,@{section=".text",section-sent="2560",section-size="6668",
32672 total-sent="2560",total-size="9880"@}
32673 +download,@{section=".text",section-sent="3072",section-size="6668",
32674 total-sent="3072",total-size="9880"@}
32675 +download,@{section=".text",section-sent="3584",section-size="6668",
32676 total-sent="3584",total-size="9880"@}
32677 +download,@{section=".text",section-sent="4096",section-size="6668",
32678 total-sent="4096",total-size="9880"@}
32679 +download,@{section=".text",section-sent="4608",section-size="6668",
32680 total-sent="4608",total-size="9880"@}
32681 +download,@{section=".text",section-sent="5120",section-size="6668",
32682 total-sent="5120",total-size="9880"@}
32683 +download,@{section=".text",section-sent="5632",section-size="6668",
32684 total-sent="5632",total-size="9880"@}
32685 +download,@{section=".text",section-sent="6144",section-size="6668",
32686 total-sent="6144",total-size="9880"@}
32687 +download,@{section=".text",section-sent="6656",section-size="6668",
32688 total-sent="6656",total-size="9880"@}
32689 +download,@{section=".init",section-size="28",total-size="9880"@}
32690 +download,@{section=".fini",section-size="28",total-size="9880"@}
32691 +download,@{section=".data",section-size="3156",total-size="9880"@}
32692 +download,@{section=".data",section-sent="512",section-size="3156",
32693 total-sent="7236",total-size="9880"@}
32694 +download,@{section=".data",section-sent="1024",section-size="3156",
32695 total-sent="7748",total-size="9880"@}
32696 +download,@{section=".data",section-sent="1536",section-size="3156",
32697 total-sent="8260",total-size="9880"@}
32698 +download,@{section=".data",section-sent="2048",section-size="3156",
32699 total-sent="8772",total-size="9880"@}
32700 +download,@{section=".data",section-sent="2560",section-size="3156",
32701 total-sent="9284",total-size="9880"@}
32702 +download,@{section=".data",section-sent="3072",section-size="3156",
32703 total-sent="9796",total-size="9880"@}
32704 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32711 @subheading The @code{-target-exec-status} Command
32712 @findex -target-exec-status
32714 @subsubheading Synopsis
32717 -target-exec-status
32720 Provide information on the state of the target (whether it is running or
32721 not, for instance).
32723 @subsubheading @value{GDBN} Command
32725 There's no equivalent @value{GDBN} command.
32727 @subsubheading Example
32731 @subheading The @code{-target-list-available-targets} Command
32732 @findex -target-list-available-targets
32734 @subsubheading Synopsis
32737 -target-list-available-targets
32740 List the possible targets to connect to.
32742 @subsubheading @value{GDBN} Command
32744 The corresponding @value{GDBN} command is @samp{help target}.
32746 @subsubheading Example
32750 @subheading The @code{-target-list-current-targets} Command
32751 @findex -target-list-current-targets
32753 @subsubheading Synopsis
32756 -target-list-current-targets
32759 Describe the current target.
32761 @subsubheading @value{GDBN} Command
32763 The corresponding information is printed by @samp{info file} (among
32766 @subsubheading Example
32770 @subheading The @code{-target-list-parameters} Command
32771 @findex -target-list-parameters
32773 @subsubheading Synopsis
32776 -target-list-parameters
32782 @subsubheading @value{GDBN} Command
32786 @subsubheading Example
32789 @subheading The @code{-target-flash-erase} Command
32790 @findex -target-flash-erase
32792 @subsubheading Synopsis
32795 -target-flash-erase
32798 Erases all known flash memory regions on the target.
32800 The corresponding @value{GDBN} command is @samp{flash-erase}.
32802 The output is a list of flash regions that have been erased, with starting
32803 addresses and memory region sizes.
32807 -target-flash-erase
32808 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32812 @subheading The @code{-target-select} Command
32813 @findex -target-select
32815 @subsubheading Synopsis
32818 -target-select @var{type} @var{parameters @dots{}}
32821 Connect @value{GDBN} to the remote target. This command takes two args:
32825 The type of target, for instance @samp{remote}, etc.
32826 @item @var{parameters}
32827 Device names, host names and the like. @xref{Target Commands, ,
32828 Commands for Managing Targets}, for more details.
32831 The output is a connection notification, followed by the address at
32832 which the target program is, in the following form:
32835 ^connected,addr="@var{address}",func="@var{function name}",
32836 args=[@var{arg list}]
32839 @subsubheading @value{GDBN} Command
32841 The corresponding @value{GDBN} command is @samp{target}.
32843 @subsubheading Example
32847 -target-select remote /dev/ttya
32848 ^connected,addr="0xfe00a300",func="??",args=[]
32852 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32853 @node GDB/MI File Transfer Commands
32854 @section @sc{gdb/mi} File Transfer Commands
32857 @subheading The @code{-target-file-put} Command
32858 @findex -target-file-put
32860 @subsubheading Synopsis
32863 -target-file-put @var{hostfile} @var{targetfile}
32866 Copy file @var{hostfile} from the host system (the machine running
32867 @value{GDBN}) to @var{targetfile} on the target system.
32869 @subsubheading @value{GDBN} Command
32871 The corresponding @value{GDBN} command is @samp{remote put}.
32873 @subsubheading Example
32877 -target-file-put localfile remotefile
32883 @subheading The @code{-target-file-get} Command
32884 @findex -target-file-get
32886 @subsubheading Synopsis
32889 -target-file-get @var{targetfile} @var{hostfile}
32892 Copy file @var{targetfile} from the target system to @var{hostfile}
32893 on the host system.
32895 @subsubheading @value{GDBN} Command
32897 The corresponding @value{GDBN} command is @samp{remote get}.
32899 @subsubheading Example
32903 -target-file-get remotefile localfile
32909 @subheading The @code{-target-file-delete} Command
32910 @findex -target-file-delete
32912 @subsubheading Synopsis
32915 -target-file-delete @var{targetfile}
32918 Delete @var{targetfile} from the target system.
32920 @subsubheading @value{GDBN} Command
32922 The corresponding @value{GDBN} command is @samp{remote delete}.
32924 @subsubheading Example
32928 -target-file-delete remotefile
32934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32935 @node GDB/MI Ada Exceptions Commands
32936 @section Ada Exceptions @sc{gdb/mi} Commands
32938 @subheading The @code{-info-ada-exceptions} Command
32939 @findex -info-ada-exceptions
32941 @subsubheading Synopsis
32944 -info-ada-exceptions [ @var{regexp}]
32947 List all Ada exceptions defined within the program being debugged.
32948 With a regular expression @var{regexp}, only those exceptions whose
32949 names match @var{regexp} are listed.
32951 @subsubheading @value{GDBN} Command
32953 The corresponding @value{GDBN} command is @samp{info exceptions}.
32955 @subsubheading Result
32957 The result is a table of Ada exceptions. The following columns are
32958 defined for each exception:
32962 The name of the exception.
32965 The address of the exception.
32969 @subsubheading Example
32972 -info-ada-exceptions aint
32973 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32974 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32975 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32976 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32977 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32980 @subheading Catching Ada Exceptions
32982 The commands describing how to ask @value{GDBN} to stop when a program
32983 raises an exception are described at @ref{Ada Exception GDB/MI
32984 Catchpoint Commands}.
32987 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32988 @node GDB/MI Support Commands
32989 @section @sc{gdb/mi} Support Commands
32991 Since new commands and features get regularly added to @sc{gdb/mi},
32992 some commands are available to help front-ends query the debugger
32993 about support for these capabilities. Similarly, it is also possible
32994 to query @value{GDBN} about target support of certain features.
32996 @subheading The @code{-info-gdb-mi-command} Command
32997 @cindex @code{-info-gdb-mi-command}
32998 @findex -info-gdb-mi-command
33000 @subsubheading Synopsis
33003 -info-gdb-mi-command @var{cmd_name}
33006 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33008 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33009 is technically not part of the command name (@pxref{GDB/MI Input
33010 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33011 for ease of use, this command also accepts the form with the leading
33014 @subsubheading @value{GDBN} Command
33016 There is no corresponding @value{GDBN} command.
33018 @subsubheading Result
33020 The result is a tuple. There is currently only one field:
33024 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33025 @code{"false"} otherwise.
33029 @subsubheading Example
33031 Here is an example where the @sc{gdb/mi} command does not exist:
33034 -info-gdb-mi-command unsupported-command
33035 ^done,command=@{exists="false"@}
33039 And here is an example where the @sc{gdb/mi} command is known
33043 -info-gdb-mi-command symbol-list-lines
33044 ^done,command=@{exists="true"@}
33047 @subheading The @code{-list-features} Command
33048 @findex -list-features
33049 @cindex supported @sc{gdb/mi} features, list
33051 Returns a list of particular features of the MI protocol that
33052 this version of gdb implements. A feature can be a command,
33053 or a new field in an output of some command, or even an
33054 important bugfix. While a frontend can sometimes detect presence
33055 of a feature at runtime, it is easier to perform detection at debugger
33058 The command returns a list of strings, with each string naming an
33059 available feature. Each returned string is just a name, it does not
33060 have any internal structure. The list of possible feature names
33066 (gdb) -list-features
33067 ^done,result=["feature1","feature2"]
33070 The current list of features is:
33073 @item frozen-varobjs
33074 Indicates support for the @code{-var-set-frozen} command, as well
33075 as possible presense of the @code{frozen} field in the output
33076 of @code{-varobj-create}.
33077 @item pending-breakpoints
33078 Indicates support for the @option{-f} option to the @code{-break-insert}
33081 Indicates Python scripting support, Python-based
33082 pretty-printing commands, and possible presence of the
33083 @samp{display_hint} field in the output of @code{-var-list-children}
33085 Indicates support for the @code{-thread-info} command.
33086 @item data-read-memory-bytes
33087 Indicates support for the @code{-data-read-memory-bytes} and the
33088 @code{-data-write-memory-bytes} commands.
33089 @item breakpoint-notifications
33090 Indicates that changes to breakpoints and breakpoints created via the
33091 CLI will be announced via async records.
33092 @item ada-task-info
33093 Indicates support for the @code{-ada-task-info} command.
33094 @item language-option
33095 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33096 option (@pxref{Context management}).
33097 @item info-gdb-mi-command
33098 Indicates support for the @code{-info-gdb-mi-command} command.
33099 @item undefined-command-error-code
33100 Indicates support for the "undefined-command" error code in error result
33101 records, produced when trying to execute an undefined @sc{gdb/mi} command
33102 (@pxref{GDB/MI Result Records}).
33103 @item exec-run-start-option
33104 Indicates that the @code{-exec-run} command supports the @option{--start}
33105 option (@pxref{GDB/MI Program Execution}).
33108 @subheading The @code{-list-target-features} Command
33109 @findex -list-target-features
33111 Returns a list of particular features that are supported by the
33112 target. Those features affect the permitted MI commands, but
33113 unlike the features reported by the @code{-list-features} command, the
33114 features depend on which target GDB is using at the moment. Whenever
33115 a target can change, due to commands such as @code{-target-select},
33116 @code{-target-attach} or @code{-exec-run}, the list of target features
33117 may change, and the frontend should obtain it again.
33121 (gdb) -list-target-features
33122 ^done,result=["async"]
33125 The current list of features is:
33129 Indicates that the target is capable of asynchronous command
33130 execution, which means that @value{GDBN} will accept further commands
33131 while the target is running.
33134 Indicates that the target is capable of reverse execution.
33135 @xref{Reverse Execution}, for more information.
33139 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33140 @node GDB/MI Miscellaneous Commands
33141 @section Miscellaneous @sc{gdb/mi} Commands
33143 @c @subheading -gdb-complete
33145 @subheading The @code{-gdb-exit} Command
33148 @subsubheading Synopsis
33154 Exit @value{GDBN} immediately.
33156 @subsubheading @value{GDBN} Command
33158 Approximately corresponds to @samp{quit}.
33160 @subsubheading Example
33170 @subheading The @code{-exec-abort} Command
33171 @findex -exec-abort
33173 @subsubheading Synopsis
33179 Kill the inferior running program.
33181 @subsubheading @value{GDBN} Command
33183 The corresponding @value{GDBN} command is @samp{kill}.
33185 @subsubheading Example
33190 @subheading The @code{-gdb-set} Command
33193 @subsubheading Synopsis
33199 Set an internal @value{GDBN} variable.
33200 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33202 @subsubheading @value{GDBN} Command
33204 The corresponding @value{GDBN} command is @samp{set}.
33206 @subsubheading Example
33216 @subheading The @code{-gdb-show} Command
33219 @subsubheading Synopsis
33225 Show the current value of a @value{GDBN} variable.
33227 @subsubheading @value{GDBN} Command
33229 The corresponding @value{GDBN} command is @samp{show}.
33231 @subsubheading Example
33240 @c @subheading -gdb-source
33243 @subheading The @code{-gdb-version} Command
33244 @findex -gdb-version
33246 @subsubheading Synopsis
33252 Show version information for @value{GDBN}. Used mostly in testing.
33254 @subsubheading @value{GDBN} Command
33256 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33257 default shows this information when you start an interactive session.
33259 @subsubheading Example
33261 @c This example modifies the actual output from GDB to avoid overfull
33267 ~Copyright 2000 Free Software Foundation, Inc.
33268 ~GDB is free software, covered by the GNU General Public License, and
33269 ~you are welcome to change it and/or distribute copies of it under
33270 ~ certain conditions.
33271 ~Type "show copying" to see the conditions.
33272 ~There is absolutely no warranty for GDB. Type "show warranty" for
33274 ~This GDB was configured as
33275 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33280 @subheading The @code{-list-thread-groups} Command
33281 @findex -list-thread-groups
33283 @subheading Synopsis
33286 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33289 Lists thread groups (@pxref{Thread groups}). When a single thread
33290 group is passed as the argument, lists the children of that group.
33291 When several thread group are passed, lists information about those
33292 thread groups. Without any parameters, lists information about all
33293 top-level thread groups.
33295 Normally, thread groups that are being debugged are reported.
33296 With the @samp{--available} option, @value{GDBN} reports thread groups
33297 available on the target.
33299 The output of this command may have either a @samp{threads} result or
33300 a @samp{groups} result. The @samp{thread} result has a list of tuples
33301 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33302 Information}). The @samp{groups} result has a list of tuples as value,
33303 each tuple describing a thread group. If top-level groups are
33304 requested (that is, no parameter is passed), or when several groups
33305 are passed, the output always has a @samp{groups} result. The format
33306 of the @samp{group} result is described below.
33308 To reduce the number of roundtrips it's possible to list thread groups
33309 together with their children, by passing the @samp{--recurse} option
33310 and the recursion depth. Presently, only recursion depth of 1 is
33311 permitted. If this option is present, then every reported thread group
33312 will also include its children, either as @samp{group} or
33313 @samp{threads} field.
33315 In general, any combination of option and parameters is permitted, with
33316 the following caveats:
33320 When a single thread group is passed, the output will typically
33321 be the @samp{threads} result. Because threads may not contain
33322 anything, the @samp{recurse} option will be ignored.
33325 When the @samp{--available} option is passed, limited information may
33326 be available. In particular, the list of threads of a process might
33327 be inaccessible. Further, specifying specific thread groups might
33328 not give any performance advantage over listing all thread groups.
33329 The frontend should assume that @samp{-list-thread-groups --available}
33330 is always an expensive operation and cache the results.
33334 The @samp{groups} result is a list of tuples, where each tuple may
33335 have the following fields:
33339 Identifier of the thread group. This field is always present.
33340 The identifier is an opaque string; frontends should not try to
33341 convert it to an integer, even though it might look like one.
33344 The type of the thread group. At present, only @samp{process} is a
33348 The target-specific process identifier. This field is only present
33349 for thread groups of type @samp{process} and only if the process exists.
33352 The exit code of this group's last exited thread, formatted in octal.
33353 This field is only present for thread groups of type @samp{process} and
33354 only if the process is not running.
33357 The number of children this thread group has. This field may be
33358 absent for an available thread group.
33361 This field has a list of tuples as value, each tuple describing a
33362 thread. It may be present if the @samp{--recurse} option is
33363 specified, and it's actually possible to obtain the threads.
33366 This field is a list of integers, each identifying a core that one
33367 thread of the group is running on. This field may be absent if
33368 such information is not available.
33371 The name of the executable file that corresponds to this thread group.
33372 The field is only present for thread groups of type @samp{process},
33373 and only if there is a corresponding executable file.
33377 @subheading Example
33381 -list-thread-groups
33382 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33383 -list-thread-groups 17
33384 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33385 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33386 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33387 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33388 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33389 -list-thread-groups --available
33390 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33391 -list-thread-groups --available --recurse 1
33392 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33393 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33394 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33395 -list-thread-groups --available --recurse 1 17 18
33396 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33397 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33398 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33401 @subheading The @code{-info-os} Command
33404 @subsubheading Synopsis
33407 -info-os [ @var{type} ]
33410 If no argument is supplied, the command returns a table of available
33411 operating-system-specific information types. If one of these types is
33412 supplied as an argument @var{type}, then the command returns a table
33413 of data of that type.
33415 The types of information available depend on the target operating
33418 @subsubheading @value{GDBN} Command
33420 The corresponding @value{GDBN} command is @samp{info os}.
33422 @subsubheading Example
33424 When run on a @sc{gnu}/Linux system, the output will look something
33430 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33431 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33432 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33433 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33434 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33436 item=@{col0="files",col1="Listing of all file descriptors",
33437 col2="File descriptors"@},
33438 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33439 col2="Kernel modules"@},
33440 item=@{col0="msg",col1="Listing of all message queues",
33441 col2="Message queues"@},
33442 item=@{col0="processes",col1="Listing of all processes",
33443 col2="Processes"@},
33444 item=@{col0="procgroups",col1="Listing of all process groups",
33445 col2="Process groups"@},
33446 item=@{col0="semaphores",col1="Listing of all semaphores",
33447 col2="Semaphores"@},
33448 item=@{col0="shm",col1="Listing of all shared-memory regions",
33449 col2="Shared-memory regions"@},
33450 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33452 item=@{col0="threads",col1="Listing of all threads",
33456 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33457 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33458 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33459 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33460 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33461 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33462 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33463 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33465 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33466 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33470 (Note that the MI output here includes a @code{"Title"} column that
33471 does not appear in command-line @code{info os}; this column is useful
33472 for MI clients that want to enumerate the types of data, such as in a
33473 popup menu, but is needless clutter on the command line, and
33474 @code{info os} omits it.)
33476 @subheading The @code{-add-inferior} Command
33477 @findex -add-inferior
33479 @subheading Synopsis
33485 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33486 inferior is not associated with any executable. Such association may
33487 be established with the @samp{-file-exec-and-symbols} command
33488 (@pxref{GDB/MI File Commands}). The command response has a single
33489 field, @samp{inferior}, whose value is the identifier of the
33490 thread group corresponding to the new inferior.
33492 @subheading Example
33497 ^done,inferior="i3"
33500 @subheading The @code{-interpreter-exec} Command
33501 @findex -interpreter-exec
33503 @subheading Synopsis
33506 -interpreter-exec @var{interpreter} @var{command}
33508 @anchor{-interpreter-exec}
33510 Execute the specified @var{command} in the given @var{interpreter}.
33512 @subheading @value{GDBN} Command
33514 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33516 @subheading Example
33520 -interpreter-exec console "break main"
33521 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33522 &"During symbol reading, bad structure-type format.\n"
33523 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33528 @subheading The @code{-inferior-tty-set} Command
33529 @findex -inferior-tty-set
33531 @subheading Synopsis
33534 -inferior-tty-set /dev/pts/1
33537 Set terminal for future runs of the program being debugged.
33539 @subheading @value{GDBN} Command
33541 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33543 @subheading Example
33547 -inferior-tty-set /dev/pts/1
33552 @subheading The @code{-inferior-tty-show} Command
33553 @findex -inferior-tty-show
33555 @subheading Synopsis
33561 Show terminal for future runs of program being debugged.
33563 @subheading @value{GDBN} Command
33565 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33567 @subheading Example
33571 -inferior-tty-set /dev/pts/1
33575 ^done,inferior_tty_terminal="/dev/pts/1"
33579 @subheading The @code{-enable-timings} Command
33580 @findex -enable-timings
33582 @subheading Synopsis
33585 -enable-timings [yes | no]
33588 Toggle the printing of the wallclock, user and system times for an MI
33589 command as a field in its output. This command is to help frontend
33590 developers optimize the performance of their code. No argument is
33591 equivalent to @samp{yes}.
33593 @subheading @value{GDBN} Command
33597 @subheading Example
33605 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33606 addr="0x080484ed",func="main",file="myprog.c",
33607 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33609 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33617 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33618 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33619 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33620 fullname="/home/nickrob/myprog.c",line="73"@}
33625 @chapter @value{GDBN} Annotations
33627 This chapter describes annotations in @value{GDBN}. Annotations were
33628 designed to interface @value{GDBN} to graphical user interfaces or other
33629 similar programs which want to interact with @value{GDBN} at a
33630 relatively high level.
33632 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33636 This is Edition @value{EDITION}, @value{DATE}.
33640 * Annotations Overview:: What annotations are; the general syntax.
33641 * Server Prefix:: Issuing a command without affecting user state.
33642 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33643 * Errors:: Annotations for error messages.
33644 * Invalidation:: Some annotations describe things now invalid.
33645 * Annotations for Running::
33646 Whether the program is running, how it stopped, etc.
33647 * Source Annotations:: Annotations describing source code.
33650 @node Annotations Overview
33651 @section What is an Annotation?
33652 @cindex annotations
33654 Annotations start with a newline character, two @samp{control-z}
33655 characters, and the name of the annotation. If there is no additional
33656 information associated with this annotation, the name of the annotation
33657 is followed immediately by a newline. If there is additional
33658 information, the name of the annotation is followed by a space, the
33659 additional information, and a newline. The additional information
33660 cannot contain newline characters.
33662 Any output not beginning with a newline and two @samp{control-z}
33663 characters denotes literal output from @value{GDBN}. Currently there is
33664 no need for @value{GDBN} to output a newline followed by two
33665 @samp{control-z} characters, but if there was such a need, the
33666 annotations could be extended with an @samp{escape} annotation which
33667 means those three characters as output.
33669 The annotation @var{level}, which is specified using the
33670 @option{--annotate} command line option (@pxref{Mode Options}), controls
33671 how much information @value{GDBN} prints together with its prompt,
33672 values of expressions, source lines, and other types of output. Level 0
33673 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33674 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33675 for programs that control @value{GDBN}, and level 2 annotations have
33676 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33677 Interface, annotate, GDB's Obsolete Annotations}).
33680 @kindex set annotate
33681 @item set annotate @var{level}
33682 The @value{GDBN} command @code{set annotate} sets the level of
33683 annotations to the specified @var{level}.
33685 @item show annotate
33686 @kindex show annotate
33687 Show the current annotation level.
33690 This chapter describes level 3 annotations.
33692 A simple example of starting up @value{GDBN} with annotations is:
33695 $ @kbd{gdb --annotate=3}
33697 Copyright 2003 Free Software Foundation, Inc.
33698 GDB is free software, covered by the GNU General Public License,
33699 and you are welcome to change it and/or distribute copies of it
33700 under certain conditions.
33701 Type "show copying" to see the conditions.
33702 There is absolutely no warranty for GDB. Type "show warranty"
33704 This GDB was configured as "i386-pc-linux-gnu"
33715 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33716 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33717 denotes a @samp{control-z} character) are annotations; the rest is
33718 output from @value{GDBN}.
33720 @node Server Prefix
33721 @section The Server Prefix
33722 @cindex server prefix
33724 If you prefix a command with @samp{server } then it will not affect
33725 the command history, nor will it affect @value{GDBN}'s notion of which
33726 command to repeat if @key{RET} is pressed on a line by itself. This
33727 means that commands can be run behind a user's back by a front-end in
33728 a transparent manner.
33730 The @code{server } prefix does not affect the recording of values into
33731 the value history; to print a value without recording it into the
33732 value history, use the @code{output} command instead of the
33733 @code{print} command.
33735 Using this prefix also disables confirmation requests
33736 (@pxref{confirmation requests}).
33739 @section Annotation for @value{GDBN} Input
33741 @cindex annotations for prompts
33742 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33743 to know when to send output, when the output from a given command is
33746 Different kinds of input each have a different @dfn{input type}. Each
33747 input type has three annotations: a @code{pre-} annotation, which
33748 denotes the beginning of any prompt which is being output, a plain
33749 annotation, which denotes the end of the prompt, and then a @code{post-}
33750 annotation which denotes the end of any echo which may (or may not) be
33751 associated with the input. For example, the @code{prompt} input type
33752 features the following annotations:
33760 The input types are
33763 @findex pre-prompt annotation
33764 @findex prompt annotation
33765 @findex post-prompt annotation
33767 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33769 @findex pre-commands annotation
33770 @findex commands annotation
33771 @findex post-commands annotation
33773 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33774 command. The annotations are repeated for each command which is input.
33776 @findex pre-overload-choice annotation
33777 @findex overload-choice annotation
33778 @findex post-overload-choice annotation
33779 @item overload-choice
33780 When @value{GDBN} wants the user to select between various overloaded functions.
33782 @findex pre-query annotation
33783 @findex query annotation
33784 @findex post-query annotation
33786 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33788 @findex pre-prompt-for-continue annotation
33789 @findex prompt-for-continue annotation
33790 @findex post-prompt-for-continue annotation
33791 @item prompt-for-continue
33792 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33793 expect this to work well; instead use @code{set height 0} to disable
33794 prompting. This is because the counting of lines is buggy in the
33795 presence of annotations.
33800 @cindex annotations for errors, warnings and interrupts
33802 @findex quit annotation
33807 This annotation occurs right before @value{GDBN} responds to an interrupt.
33809 @findex error annotation
33814 This annotation occurs right before @value{GDBN} responds to an error.
33816 Quit and error annotations indicate that any annotations which @value{GDBN} was
33817 in the middle of may end abruptly. For example, if a
33818 @code{value-history-begin} annotation is followed by a @code{error}, one
33819 cannot expect to receive the matching @code{value-history-end}. One
33820 cannot expect not to receive it either, however; an error annotation
33821 does not necessarily mean that @value{GDBN} is immediately returning all the way
33824 @findex error-begin annotation
33825 A quit or error annotation may be preceded by
33831 Any output between that and the quit or error annotation is the error
33834 Warning messages are not yet annotated.
33835 @c If we want to change that, need to fix warning(), type_error(),
33836 @c range_error(), and possibly other places.
33839 @section Invalidation Notices
33841 @cindex annotations for invalidation messages
33842 The following annotations say that certain pieces of state may have
33846 @findex frames-invalid annotation
33847 @item ^Z^Zframes-invalid
33849 The frames (for example, output from the @code{backtrace} command) may
33852 @findex breakpoints-invalid annotation
33853 @item ^Z^Zbreakpoints-invalid
33855 The breakpoints may have changed. For example, the user just added or
33856 deleted a breakpoint.
33859 @node Annotations for Running
33860 @section Running the Program
33861 @cindex annotations for running programs
33863 @findex starting annotation
33864 @findex stopping annotation
33865 When the program starts executing due to a @value{GDBN} command such as
33866 @code{step} or @code{continue},
33872 is output. When the program stops,
33878 is output. Before the @code{stopped} annotation, a variety of
33879 annotations describe how the program stopped.
33882 @findex exited annotation
33883 @item ^Z^Zexited @var{exit-status}
33884 The program exited, and @var{exit-status} is the exit status (zero for
33885 successful exit, otherwise nonzero).
33887 @findex signalled annotation
33888 @findex signal-name annotation
33889 @findex signal-name-end annotation
33890 @findex signal-string annotation
33891 @findex signal-string-end annotation
33892 @item ^Z^Zsignalled
33893 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33894 annotation continues:
33900 ^Z^Zsignal-name-end
33904 ^Z^Zsignal-string-end
33909 where @var{name} is the name of the signal, such as @code{SIGILL} or
33910 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33911 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33912 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33913 user's benefit and have no particular format.
33915 @findex signal annotation
33917 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33918 just saying that the program received the signal, not that it was
33919 terminated with it.
33921 @findex breakpoint annotation
33922 @item ^Z^Zbreakpoint @var{number}
33923 The program hit breakpoint number @var{number}.
33925 @findex watchpoint annotation
33926 @item ^Z^Zwatchpoint @var{number}
33927 The program hit watchpoint number @var{number}.
33930 @node Source Annotations
33931 @section Displaying Source
33932 @cindex annotations for source display
33934 @findex source annotation
33935 The following annotation is used instead of displaying source code:
33938 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33941 where @var{filename} is an absolute file name indicating which source
33942 file, @var{line} is the line number within that file (where 1 is the
33943 first line in the file), @var{character} is the character position
33944 within the file (where 0 is the first character in the file) (for most
33945 debug formats this will necessarily point to the beginning of a line),
33946 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33947 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33948 @var{addr} is the address in the target program associated with the
33949 source which is being displayed. The @var{addr} is in the form @samp{0x}
33950 followed by one or more lowercase hex digits (note that this does not
33951 depend on the language).
33953 @node JIT Interface
33954 @chapter JIT Compilation Interface
33955 @cindex just-in-time compilation
33956 @cindex JIT compilation interface
33958 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33959 interface. A JIT compiler is a program or library that generates native
33960 executable code at runtime and executes it, usually in order to achieve good
33961 performance while maintaining platform independence.
33963 Programs that use JIT compilation are normally difficult to debug because
33964 portions of their code are generated at runtime, instead of being loaded from
33965 object files, which is where @value{GDBN} normally finds the program's symbols
33966 and debug information. In order to debug programs that use JIT compilation,
33967 @value{GDBN} has an interface that allows the program to register in-memory
33968 symbol files with @value{GDBN} at runtime.
33970 If you are using @value{GDBN} to debug a program that uses this interface, then
33971 it should work transparently so long as you have not stripped the binary. If
33972 you are developing a JIT compiler, then the interface is documented in the rest
33973 of this chapter. At this time, the only known client of this interface is the
33976 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33977 JIT compiler communicates with @value{GDBN} by writing data into a global
33978 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33979 attaches, it reads a linked list of symbol files from the global variable to
33980 find existing code, and puts a breakpoint in the function so that it can find
33981 out about additional code.
33984 * Declarations:: Relevant C struct declarations
33985 * Registering Code:: Steps to register code
33986 * Unregistering Code:: Steps to unregister code
33987 * Custom Debug Info:: Emit debug information in a custom format
33991 @section JIT Declarations
33993 These are the relevant struct declarations that a C program should include to
33994 implement the interface:
34004 struct jit_code_entry
34006 struct jit_code_entry *next_entry;
34007 struct jit_code_entry *prev_entry;
34008 const char *symfile_addr;
34009 uint64_t symfile_size;
34012 struct jit_descriptor
34015 /* This type should be jit_actions_t, but we use uint32_t
34016 to be explicit about the bitwidth. */
34017 uint32_t action_flag;
34018 struct jit_code_entry *relevant_entry;
34019 struct jit_code_entry *first_entry;
34022 /* GDB puts a breakpoint in this function. */
34023 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34025 /* Make sure to specify the version statically, because the
34026 debugger may check the version before we can set it. */
34027 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34030 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34031 modifications to this global data properly, which can easily be done by putting
34032 a global mutex around modifications to these structures.
34034 @node Registering Code
34035 @section Registering Code
34037 To register code with @value{GDBN}, the JIT should follow this protocol:
34041 Generate an object file in memory with symbols and other desired debug
34042 information. The file must include the virtual addresses of the sections.
34045 Create a code entry for the file, which gives the start and size of the symbol
34049 Add it to the linked list in the JIT descriptor.
34052 Point the relevant_entry field of the descriptor at the entry.
34055 Set @code{action_flag} to @code{JIT_REGISTER} and call
34056 @code{__jit_debug_register_code}.
34059 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34060 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34061 new code. However, the linked list must still be maintained in order to allow
34062 @value{GDBN} to attach to a running process and still find the symbol files.
34064 @node Unregistering Code
34065 @section Unregistering Code
34067 If code is freed, then the JIT should use the following protocol:
34071 Remove the code entry corresponding to the code from the linked list.
34074 Point the @code{relevant_entry} field of the descriptor at the code entry.
34077 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34078 @code{__jit_debug_register_code}.
34081 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34082 and the JIT will leak the memory used for the associated symbol files.
34084 @node Custom Debug Info
34085 @section Custom Debug Info
34086 @cindex custom JIT debug info
34087 @cindex JIT debug info reader
34089 Generating debug information in platform-native file formats (like ELF
34090 or COFF) may be an overkill for JIT compilers; especially if all the
34091 debug info is used for is displaying a meaningful backtrace. The
34092 issue can be resolved by having the JIT writers decide on a debug info
34093 format and also provide a reader that parses the debug info generated
34094 by the JIT compiler. This section gives a brief overview on writing
34095 such a parser. More specific details can be found in the source file
34096 @file{gdb/jit-reader.in}, which is also installed as a header at
34097 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34099 The reader is implemented as a shared object (so this functionality is
34100 not available on platforms which don't allow loading shared objects at
34101 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34102 @code{jit-reader-unload} are provided, to be used to load and unload
34103 the readers from a preconfigured directory. Once loaded, the shared
34104 object is used the parse the debug information emitted by the JIT
34108 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34109 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34112 @node Using JIT Debug Info Readers
34113 @subsection Using JIT Debug Info Readers
34114 @kindex jit-reader-load
34115 @kindex jit-reader-unload
34117 Readers can be loaded and unloaded using the @code{jit-reader-load}
34118 and @code{jit-reader-unload} commands.
34121 @item jit-reader-load @var{reader}
34122 Load the JIT reader named @var{reader}, which is a shared
34123 object specified as either an absolute or a relative file name. In
34124 the latter case, @value{GDBN} will try to load the reader from a
34125 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34126 system (here @var{libdir} is the system library directory, often
34127 @file{/usr/local/lib}).
34129 Only one reader can be active at a time; trying to load a second
34130 reader when one is already loaded will result in @value{GDBN}
34131 reporting an error. A new JIT reader can be loaded by first unloading
34132 the current one using @code{jit-reader-unload} and then invoking
34133 @code{jit-reader-load}.
34135 @item jit-reader-unload
34136 Unload the currently loaded JIT reader.
34140 @node Writing JIT Debug Info Readers
34141 @subsection Writing JIT Debug Info Readers
34142 @cindex writing JIT debug info readers
34144 As mentioned, a reader is essentially a shared object conforming to a
34145 certain ABI. This ABI is described in @file{jit-reader.h}.
34147 @file{jit-reader.h} defines the structures, macros and functions
34148 required to write a reader. It is installed (along with
34149 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34150 the system include directory.
34152 Readers need to be released under a GPL compatible license. A reader
34153 can be declared as released under such a license by placing the macro
34154 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34156 The entry point for readers is the symbol @code{gdb_init_reader},
34157 which is expected to be a function with the prototype
34159 @findex gdb_init_reader
34161 extern struct gdb_reader_funcs *gdb_init_reader (void);
34164 @cindex @code{struct gdb_reader_funcs}
34166 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34167 functions. These functions are executed to read the debug info
34168 generated by the JIT compiler (@code{read}), to unwind stack frames
34169 (@code{unwind}) and to create canonical frame IDs
34170 (@code{get_Frame_id}). It also has a callback that is called when the
34171 reader is being unloaded (@code{destroy}). The struct looks like this
34174 struct gdb_reader_funcs
34176 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34177 int reader_version;
34179 /* For use by the reader. */
34182 gdb_read_debug_info *read;
34183 gdb_unwind_frame *unwind;
34184 gdb_get_frame_id *get_frame_id;
34185 gdb_destroy_reader *destroy;
34189 @cindex @code{struct gdb_symbol_callbacks}
34190 @cindex @code{struct gdb_unwind_callbacks}
34192 The callbacks are provided with another set of callbacks by
34193 @value{GDBN} to do their job. For @code{read}, these callbacks are
34194 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34195 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34196 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34197 files and new symbol tables inside those object files. @code{struct
34198 gdb_unwind_callbacks} has callbacks to read registers off the current
34199 frame and to write out the values of the registers in the previous
34200 frame. Both have a callback (@code{target_read}) to read bytes off the
34201 target's address space.
34203 @node In-Process Agent
34204 @chapter In-Process Agent
34205 @cindex debugging agent
34206 The traditional debugging model is conceptually low-speed, but works fine,
34207 because most bugs can be reproduced in debugging-mode execution. However,
34208 as multi-core or many-core processors are becoming mainstream, and
34209 multi-threaded programs become more and more popular, there should be more
34210 and more bugs that only manifest themselves at normal-mode execution, for
34211 example, thread races, because debugger's interference with the program's
34212 timing may conceal the bugs. On the other hand, in some applications,
34213 it is not feasible for the debugger to interrupt the program's execution
34214 long enough for the developer to learn anything helpful about its behavior.
34215 If the program's correctness depends on its real-time behavior, delays
34216 introduced by a debugger might cause the program to fail, even when the
34217 code itself is correct. It is useful to be able to observe the program's
34218 behavior without interrupting it.
34220 Therefore, traditional debugging model is too intrusive to reproduce
34221 some bugs. In order to reduce the interference with the program, we can
34222 reduce the number of operations performed by debugger. The
34223 @dfn{In-Process Agent}, a shared library, is running within the same
34224 process with inferior, and is able to perform some debugging operations
34225 itself. As a result, debugger is only involved when necessary, and
34226 performance of debugging can be improved accordingly. Note that
34227 interference with program can be reduced but can't be removed completely,
34228 because the in-process agent will still stop or slow down the program.
34230 The in-process agent can interpret and execute Agent Expressions
34231 (@pxref{Agent Expressions}) during performing debugging operations. The
34232 agent expressions can be used for different purposes, such as collecting
34233 data in tracepoints, and condition evaluation in breakpoints.
34235 @anchor{Control Agent}
34236 You can control whether the in-process agent is used as an aid for
34237 debugging with the following commands:
34240 @kindex set agent on
34242 Causes the in-process agent to perform some operations on behalf of the
34243 debugger. Just which operations requested by the user will be done
34244 by the in-process agent depends on the its capabilities. For example,
34245 if you request to evaluate breakpoint conditions in the in-process agent,
34246 and the in-process agent has such capability as well, then breakpoint
34247 conditions will be evaluated in the in-process agent.
34249 @kindex set agent off
34250 @item set agent off
34251 Disables execution of debugging operations by the in-process agent. All
34252 of the operations will be performed by @value{GDBN}.
34256 Display the current setting of execution of debugging operations by
34257 the in-process agent.
34261 * In-Process Agent Protocol::
34264 @node In-Process Agent Protocol
34265 @section In-Process Agent Protocol
34266 @cindex in-process agent protocol
34268 The in-process agent is able to communicate with both @value{GDBN} and
34269 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34270 used for communications between @value{GDBN} or GDBserver and the IPA.
34271 In general, @value{GDBN} or GDBserver sends commands
34272 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34273 in-process agent replies back with the return result of the command, or
34274 some other information. The data sent to in-process agent is composed
34275 of primitive data types, such as 4-byte or 8-byte type, and composite
34276 types, which are called objects (@pxref{IPA Protocol Objects}).
34279 * IPA Protocol Objects::
34280 * IPA Protocol Commands::
34283 @node IPA Protocol Objects
34284 @subsection IPA Protocol Objects
34285 @cindex ipa protocol objects
34287 The commands sent to and results received from agent may contain some
34288 complex data types called @dfn{objects}.
34290 The in-process agent is running on the same machine with @value{GDBN}
34291 or GDBserver, so it doesn't have to handle as much differences between
34292 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34293 However, there are still some differences of two ends in two processes:
34297 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34298 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34300 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34301 GDBserver is compiled with one, and in-process agent is compiled with
34305 Here are the IPA Protocol Objects:
34309 agent expression object. It represents an agent expression
34310 (@pxref{Agent Expressions}).
34311 @anchor{agent expression object}
34313 tracepoint action object. It represents a tracepoint action
34314 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34315 memory, static trace data and to evaluate expression.
34316 @anchor{tracepoint action object}
34318 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34319 @anchor{tracepoint object}
34323 The following table describes important attributes of each IPA protocol
34326 @multitable @columnfractions .30 .20 .50
34327 @headitem Name @tab Size @tab Description
34328 @item @emph{agent expression object} @tab @tab
34329 @item length @tab 4 @tab length of bytes code
34330 @item byte code @tab @var{length} @tab contents of byte code
34331 @item @emph{tracepoint action for collecting memory} @tab @tab
34332 @item 'M' @tab 1 @tab type of tracepoint action
34333 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34334 address of the lowest byte to collect, otherwise @var{addr} is the offset
34335 of @var{basereg} for memory collecting.
34336 @item len @tab 8 @tab length of memory for collecting
34337 @item basereg @tab 4 @tab the register number containing the starting
34338 memory address for collecting.
34339 @item @emph{tracepoint action for collecting registers} @tab @tab
34340 @item 'R' @tab 1 @tab type of tracepoint action
34341 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34342 @item 'L' @tab 1 @tab type of tracepoint action
34343 @item @emph{tracepoint action for expression evaluation} @tab @tab
34344 @item 'X' @tab 1 @tab type of tracepoint action
34345 @item agent expression @tab length of @tab @ref{agent expression object}
34346 @item @emph{tracepoint object} @tab @tab
34347 @item number @tab 4 @tab number of tracepoint
34348 @item address @tab 8 @tab address of tracepoint inserted on
34349 @item type @tab 4 @tab type of tracepoint
34350 @item enabled @tab 1 @tab enable or disable of tracepoint
34351 @item step_count @tab 8 @tab step
34352 @item pass_count @tab 8 @tab pass
34353 @item numactions @tab 4 @tab number of tracepoint actions
34354 @item hit count @tab 8 @tab hit count
34355 @item trace frame usage @tab 8 @tab trace frame usage
34356 @item compiled_cond @tab 8 @tab compiled condition
34357 @item orig_size @tab 8 @tab orig size
34358 @item condition @tab 4 if condition is NULL otherwise length of
34359 @ref{agent expression object}
34360 @tab zero if condition is NULL, otherwise is
34361 @ref{agent expression object}
34362 @item actions @tab variable
34363 @tab numactions number of @ref{tracepoint action object}
34366 @node IPA Protocol Commands
34367 @subsection IPA Protocol Commands
34368 @cindex ipa protocol commands
34370 The spaces in each command are delimiters to ease reading this commands
34371 specification. They don't exist in real commands.
34375 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34376 Installs a new fast tracepoint described by @var{tracepoint_object}
34377 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34378 head of @dfn{jumppad}, which is used to jump to data collection routine
34383 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34384 @var{target_address} is address of tracepoint in the inferior.
34385 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34386 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34387 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34388 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34395 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34396 is about to kill inferiors.
34404 @item probe_marker_at:@var{address}
34405 Asks in-process agent to probe the marker at @var{address}.
34412 @item unprobe_marker_at:@var{address}
34413 Asks in-process agent to unprobe the marker at @var{address}.
34417 @chapter Reporting Bugs in @value{GDBN}
34418 @cindex bugs in @value{GDBN}
34419 @cindex reporting bugs in @value{GDBN}
34421 Your bug reports play an essential role in making @value{GDBN} reliable.
34423 Reporting a bug may help you by bringing a solution to your problem, or it
34424 may not. But in any case the principal function of a bug report is to help
34425 the entire community by making the next version of @value{GDBN} work better. Bug
34426 reports are your contribution to the maintenance of @value{GDBN}.
34428 In order for a bug report to serve its purpose, you must include the
34429 information that enables us to fix the bug.
34432 * Bug Criteria:: Have you found a bug?
34433 * Bug Reporting:: How to report bugs
34437 @section Have You Found a Bug?
34438 @cindex bug criteria
34440 If you are not sure whether you have found a bug, here are some guidelines:
34443 @cindex fatal signal
34444 @cindex debugger crash
34445 @cindex crash of debugger
34447 If the debugger gets a fatal signal, for any input whatever, that is a
34448 @value{GDBN} bug. Reliable debuggers never crash.
34450 @cindex error on valid input
34452 If @value{GDBN} produces an error message for valid input, that is a
34453 bug. (Note that if you're cross debugging, the problem may also be
34454 somewhere in the connection to the target.)
34456 @cindex invalid input
34458 If @value{GDBN} does not produce an error message for invalid input,
34459 that is a bug. However, you should note that your idea of
34460 ``invalid input'' might be our idea of ``an extension'' or ``support
34461 for traditional practice''.
34464 If you are an experienced user of debugging tools, your suggestions
34465 for improvement of @value{GDBN} are welcome in any case.
34468 @node Bug Reporting
34469 @section How to Report Bugs
34470 @cindex bug reports
34471 @cindex @value{GDBN} bugs, reporting
34473 A number of companies and individuals offer support for @sc{gnu} products.
34474 If you obtained @value{GDBN} from a support organization, we recommend you
34475 contact that organization first.
34477 You can find contact information for many support companies and
34478 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34480 @c should add a web page ref...
34483 @ifset BUGURL_DEFAULT
34484 In any event, we also recommend that you submit bug reports for
34485 @value{GDBN}. The preferred method is to submit them directly using
34486 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34487 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34490 @strong{Do not send bug reports to @samp{info-gdb}, or to
34491 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34492 not want to receive bug reports. Those that do have arranged to receive
34495 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34496 serves as a repeater. The mailing list and the newsgroup carry exactly
34497 the same messages. Often people think of posting bug reports to the
34498 newsgroup instead of mailing them. This appears to work, but it has one
34499 problem which can be crucial: a newsgroup posting often lacks a mail
34500 path back to the sender. Thus, if we need to ask for more information,
34501 we may be unable to reach you. For this reason, it is better to send
34502 bug reports to the mailing list.
34504 @ifclear BUGURL_DEFAULT
34505 In any event, we also recommend that you submit bug reports for
34506 @value{GDBN} to @value{BUGURL}.
34510 The fundamental principle of reporting bugs usefully is this:
34511 @strong{report all the facts}. If you are not sure whether to state a
34512 fact or leave it out, state it!
34514 Often people omit facts because they think they know what causes the
34515 problem and assume that some details do not matter. Thus, you might
34516 assume that the name of the variable you use in an example does not matter.
34517 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34518 stray memory reference which happens to fetch from the location where that
34519 name is stored in memory; perhaps, if the name were different, the contents
34520 of that location would fool the debugger into doing the right thing despite
34521 the bug. Play it safe and give a specific, complete example. That is the
34522 easiest thing for you to do, and the most helpful.
34524 Keep in mind that the purpose of a bug report is to enable us to fix the
34525 bug. It may be that the bug has been reported previously, but neither
34526 you nor we can know that unless your bug report is complete and
34529 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34530 bell?'' Those bug reports are useless, and we urge everyone to
34531 @emph{refuse to respond to them} except to chide the sender to report
34534 To enable us to fix the bug, you should include all these things:
34538 The version of @value{GDBN}. @value{GDBN} announces it if you start
34539 with no arguments; you can also print it at any time using @code{show
34542 Without this, we will not know whether there is any point in looking for
34543 the bug in the current version of @value{GDBN}.
34546 The type of machine you are using, and the operating system name and
34550 The details of the @value{GDBN} build-time configuration.
34551 @value{GDBN} shows these details if you invoke it with the
34552 @option{--configuration} command-line option, or if you type
34553 @code{show configuration} at @value{GDBN}'s prompt.
34556 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34557 ``@value{GCC}--2.8.1''.
34560 What compiler (and its version) was used to compile the program you are
34561 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34562 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34563 to get this information; for other compilers, see the documentation for
34567 The command arguments you gave the compiler to compile your example and
34568 observe the bug. For example, did you use @samp{-O}? To guarantee
34569 you will not omit something important, list them all. A copy of the
34570 Makefile (or the output from make) is sufficient.
34572 If we were to try to guess the arguments, we would probably guess wrong
34573 and then we might not encounter the bug.
34576 A complete input script, and all necessary source files, that will
34580 A description of what behavior you observe that you believe is
34581 incorrect. For example, ``It gets a fatal signal.''
34583 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34584 will certainly notice it. But if the bug is incorrect output, we might
34585 not notice unless it is glaringly wrong. You might as well not give us
34586 a chance to make a mistake.
34588 Even if the problem you experience is a fatal signal, you should still
34589 say so explicitly. Suppose something strange is going on, such as, your
34590 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34591 the C library on your system. (This has happened!) Your copy might
34592 crash and ours would not. If you told us to expect a crash, then when
34593 ours fails to crash, we would know that the bug was not happening for
34594 us. If you had not told us to expect a crash, then we would not be able
34595 to draw any conclusion from our observations.
34598 @cindex recording a session script
34599 To collect all this information, you can use a session recording program
34600 such as @command{script}, which is available on many Unix systems.
34601 Just run your @value{GDBN} session inside @command{script} and then
34602 include the @file{typescript} file with your bug report.
34604 Another way to record a @value{GDBN} session is to run @value{GDBN}
34605 inside Emacs and then save the entire buffer to a file.
34608 If you wish to suggest changes to the @value{GDBN} source, send us context
34609 diffs. If you even discuss something in the @value{GDBN} source, refer to
34610 it by context, not by line number.
34612 The line numbers in our development sources will not match those in your
34613 sources. Your line numbers would convey no useful information to us.
34617 Here are some things that are not necessary:
34621 A description of the envelope of the bug.
34623 Often people who encounter a bug spend a lot of time investigating
34624 which changes to the input file will make the bug go away and which
34625 changes will not affect it.
34627 This is often time consuming and not very useful, because the way we
34628 will find the bug is by running a single example under the debugger
34629 with breakpoints, not by pure deduction from a series of examples.
34630 We recommend that you save your time for something else.
34632 Of course, if you can find a simpler example to report @emph{instead}
34633 of the original one, that is a convenience for us. Errors in the
34634 output will be easier to spot, running under the debugger will take
34635 less time, and so on.
34637 However, simplification is not vital; if you do not want to do this,
34638 report the bug anyway and send us the entire test case you used.
34641 A patch for the bug.
34643 A patch for the bug does help us if it is a good one. But do not omit
34644 the necessary information, such as the test case, on the assumption that
34645 a patch is all we need. We might see problems with your patch and decide
34646 to fix the problem another way, or we might not understand it at all.
34648 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34649 construct an example that will make the program follow a certain path
34650 through the code. If you do not send us the example, we will not be able
34651 to construct one, so we will not be able to verify that the bug is fixed.
34653 And if we cannot understand what bug you are trying to fix, or why your
34654 patch should be an improvement, we will not install it. A test case will
34655 help us to understand.
34658 A guess about what the bug is or what it depends on.
34660 Such guesses are usually wrong. Even we cannot guess right about such
34661 things without first using the debugger to find the facts.
34664 @c The readline documentation is distributed with the readline code
34665 @c and consists of the two following files:
34668 @c Use -I with makeinfo to point to the appropriate directory,
34669 @c environment var TEXINPUTS with TeX.
34670 @ifclear SYSTEM_READLINE
34671 @include rluser.texi
34672 @include hsuser.texi
34676 @appendix In Memoriam
34678 The @value{GDBN} project mourns the loss of the following long-time
34683 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34684 to Free Software in general. Outside of @value{GDBN}, he was known in
34685 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34687 @item Michael Snyder
34688 Michael was one of the Global Maintainers of the @value{GDBN} project,
34689 with contributions recorded as early as 1996, until 2011. In addition
34690 to his day to day participation, he was a large driving force behind
34691 adding Reverse Debugging to @value{GDBN}.
34694 Beyond their technical contributions to the project, they were also
34695 enjoyable members of the Free Software Community. We will miss them.
34697 @node Formatting Documentation
34698 @appendix Formatting Documentation
34700 @cindex @value{GDBN} reference card
34701 @cindex reference card
34702 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34703 for printing with PostScript or Ghostscript, in the @file{gdb}
34704 subdirectory of the main source directory@footnote{In
34705 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34706 release.}. If you can use PostScript or Ghostscript with your printer,
34707 you can print the reference card immediately with @file{refcard.ps}.
34709 The release also includes the source for the reference card. You
34710 can format it, using @TeX{}, by typing:
34716 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34717 mode on US ``letter'' size paper;
34718 that is, on a sheet 11 inches wide by 8.5 inches
34719 high. You will need to specify this form of printing as an option to
34720 your @sc{dvi} output program.
34722 @cindex documentation
34724 All the documentation for @value{GDBN} comes as part of the machine-readable
34725 distribution. The documentation is written in Texinfo format, which is
34726 a documentation system that uses a single source file to produce both
34727 on-line information and a printed manual. You can use one of the Info
34728 formatting commands to create the on-line version of the documentation
34729 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34731 @value{GDBN} includes an already formatted copy of the on-line Info
34732 version of this manual in the @file{gdb} subdirectory. The main Info
34733 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34734 subordinate files matching @samp{gdb.info*} in the same directory. If
34735 necessary, you can print out these files, or read them with any editor;
34736 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34737 Emacs or the standalone @code{info} program, available as part of the
34738 @sc{gnu} Texinfo distribution.
34740 If you want to format these Info files yourself, you need one of the
34741 Info formatting programs, such as @code{texinfo-format-buffer} or
34744 If you have @code{makeinfo} installed, and are in the top level
34745 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34746 version @value{GDBVN}), you can make the Info file by typing:
34753 If you want to typeset and print copies of this manual, you need @TeX{},
34754 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34755 Texinfo definitions file.
34757 @TeX{} is a typesetting program; it does not print files directly, but
34758 produces output files called @sc{dvi} files. To print a typeset
34759 document, you need a program to print @sc{dvi} files. If your system
34760 has @TeX{} installed, chances are it has such a program. The precise
34761 command to use depends on your system; @kbd{lpr -d} is common; another
34762 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34763 require a file name without any extension or a @samp{.dvi} extension.
34765 @TeX{} also requires a macro definitions file called
34766 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34767 written in Texinfo format. On its own, @TeX{} cannot either read or
34768 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34769 and is located in the @file{gdb-@var{version-number}/texinfo}
34772 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34773 typeset and print this manual. First switch to the @file{gdb}
34774 subdirectory of the main source directory (for example, to
34775 @file{gdb-@value{GDBVN}/gdb}) and type:
34781 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34783 @node Installing GDB
34784 @appendix Installing @value{GDBN}
34785 @cindex installation
34788 * Requirements:: Requirements for building @value{GDBN}
34789 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34790 * Separate Objdir:: Compiling @value{GDBN} in another directory
34791 * Config Names:: Specifying names for hosts and targets
34792 * Configure Options:: Summary of options for configure
34793 * System-wide configuration:: Having a system-wide init file
34797 @section Requirements for Building @value{GDBN}
34798 @cindex building @value{GDBN}, requirements for
34800 Building @value{GDBN} requires various tools and packages to be available.
34801 Other packages will be used only if they are found.
34803 @heading Tools/Packages Necessary for Building @value{GDBN}
34805 @item ISO C90 compiler
34806 @value{GDBN} is written in ISO C90. It should be buildable with any
34807 working C90 compiler, e.g.@: GCC.
34811 @heading Tools/Packages Optional for Building @value{GDBN}
34815 @value{GDBN} can use the Expat XML parsing library. This library may be
34816 included with your operating system distribution; if it is not, you
34817 can get the latest version from @url{http://expat.sourceforge.net}.
34818 The @file{configure} script will search for this library in several
34819 standard locations; if it is installed in an unusual path, you can
34820 use the @option{--with-libexpat-prefix} option to specify its location.
34826 Remote protocol memory maps (@pxref{Memory Map Format})
34828 Target descriptions (@pxref{Target Descriptions})
34830 Remote shared library lists (@xref{Library List Format},
34831 or alternatively @pxref{Library List Format for SVR4 Targets})
34833 MS-Windows shared libraries (@pxref{Shared Libraries})
34835 Traceframe info (@pxref{Traceframe Info Format})
34837 Branch trace (@pxref{Branch Trace Format},
34838 @pxref{Branch Trace Configuration Format})
34843 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34844 library. This library may be included with your operating system
34845 distribution; if it is not, you can get the latest version from
34846 @url{http://www.mpfr.org}. The @file{configure} script will search
34847 for this library in several standard locations; if it is installed
34848 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34849 option to specify its location.
34851 GNU MPFR is used to emulate target floating-point arithmetic during
34852 expression evaluation when the target uses different floating-point
34853 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34854 will fall back to using host floating-point arithmetic.
34857 @cindex compressed debug sections
34858 @value{GDBN} will use the @samp{zlib} library, if available, to read
34859 compressed debug sections. Some linkers, such as GNU gold, are capable
34860 of producing binaries with compressed debug sections. If @value{GDBN}
34861 is compiled with @samp{zlib}, it will be able to read the debug
34862 information in such binaries.
34864 The @samp{zlib} library is likely included with your operating system
34865 distribution; if it is not, you can get the latest version from
34866 @url{http://zlib.net}.
34869 @value{GDBN}'s features related to character sets (@pxref{Character
34870 Sets}) require a functioning @code{iconv} implementation. If you are
34871 on a GNU system, then this is provided by the GNU C Library. Some
34872 other systems also provide a working @code{iconv}.
34874 If @value{GDBN} is using the @code{iconv} program which is installed
34875 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34876 This is done with @option{--with-iconv-bin} which specifies the
34877 directory that contains the @code{iconv} program.
34879 On systems without @code{iconv}, you can install GNU Libiconv. If you
34880 have previously installed Libiconv, you can use the
34881 @option{--with-libiconv-prefix} option to configure.
34883 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34884 arrange to build Libiconv if a directory named @file{libiconv} appears
34885 in the top-most source directory. If Libiconv is built this way, and
34886 if the operating system does not provide a suitable @code{iconv}
34887 implementation, then the just-built library will automatically be used
34888 by @value{GDBN}. One easy way to set this up is to download GNU
34889 Libiconv, unpack it, and then rename the directory holding the
34890 Libiconv source code to @samp{libiconv}.
34893 @node Running Configure
34894 @section Invoking the @value{GDBN} @file{configure} Script
34895 @cindex configuring @value{GDBN}
34896 @value{GDBN} comes with a @file{configure} script that automates the process
34897 of preparing @value{GDBN} for installation; you can then use @code{make} to
34898 build the @code{gdb} program.
34900 @c irrelevant in info file; it's as current as the code it lives with.
34901 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34902 look at the @file{README} file in the sources; we may have improved the
34903 installation procedures since publishing this manual.}
34906 The @value{GDBN} distribution includes all the source code you need for
34907 @value{GDBN} in a single directory, whose name is usually composed by
34908 appending the version number to @samp{gdb}.
34910 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34911 @file{gdb-@value{GDBVN}} directory. That directory contains:
34914 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34915 script for configuring @value{GDBN} and all its supporting libraries
34917 @item gdb-@value{GDBVN}/gdb
34918 the source specific to @value{GDBN} itself
34920 @item gdb-@value{GDBVN}/bfd
34921 source for the Binary File Descriptor library
34923 @item gdb-@value{GDBVN}/include
34924 @sc{gnu} include files
34926 @item gdb-@value{GDBVN}/libiberty
34927 source for the @samp{-liberty} free software library
34929 @item gdb-@value{GDBVN}/opcodes
34930 source for the library of opcode tables and disassemblers
34932 @item gdb-@value{GDBVN}/readline
34933 source for the @sc{gnu} command-line interface
34935 @item gdb-@value{GDBVN}/glob
34936 source for the @sc{gnu} filename pattern-matching subroutine
34938 @item gdb-@value{GDBVN}/mmalloc
34939 source for the @sc{gnu} memory-mapped malloc package
34942 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34943 from the @file{gdb-@var{version-number}} source directory, which in
34944 this example is the @file{gdb-@value{GDBVN}} directory.
34946 First switch to the @file{gdb-@var{version-number}} source directory
34947 if you are not already in it; then run @file{configure}. Pass the
34948 identifier for the platform on which @value{GDBN} will run as an
34954 cd gdb-@value{GDBVN}
34955 ./configure @var{host}
34960 where @var{host} is an identifier such as @samp{sun4} or
34961 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34962 (You can often leave off @var{host}; @file{configure} tries to guess the
34963 correct value by examining your system.)
34965 Running @samp{configure @var{host}} and then running @code{make} builds the
34966 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34967 libraries, then @code{gdb} itself. The configured source files, and the
34968 binaries, are left in the corresponding source directories.
34971 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34972 system does not recognize this automatically when you run a different
34973 shell, you may need to run @code{sh} on it explicitly:
34976 sh configure @var{host}
34979 If you run @file{configure} from a directory that contains source
34980 directories for multiple libraries or programs, such as the
34981 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34983 creates configuration files for every directory level underneath (unless
34984 you tell it not to, with the @samp{--norecursion} option).
34986 You should run the @file{configure} script from the top directory in the
34987 source tree, the @file{gdb-@var{version-number}} directory. If you run
34988 @file{configure} from one of the subdirectories, you will configure only
34989 that subdirectory. That is usually not what you want. In particular,
34990 if you run the first @file{configure} from the @file{gdb} subdirectory
34991 of the @file{gdb-@var{version-number}} directory, you will omit the
34992 configuration of @file{bfd}, @file{readline}, and other sibling
34993 directories of the @file{gdb} subdirectory. This leads to build errors
34994 about missing include files such as @file{bfd/bfd.h}.
34996 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34997 However, you should make sure that the shell on your path (named by
34998 the @samp{SHELL} environment variable) is publicly readable. Remember
34999 that @value{GDBN} uses the shell to start your program---some systems refuse to
35000 let @value{GDBN} debug child processes whose programs are not readable.
35002 @node Separate Objdir
35003 @section Compiling @value{GDBN} in Another Directory
35005 If you want to run @value{GDBN} versions for several host or target machines,
35006 you need a different @code{gdb} compiled for each combination of
35007 host and target. @file{configure} is designed to make this easy by
35008 allowing you to generate each configuration in a separate subdirectory,
35009 rather than in the source directory. If your @code{make} program
35010 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35011 @code{make} in each of these directories builds the @code{gdb}
35012 program specified there.
35014 To build @code{gdb} in a separate directory, run @file{configure}
35015 with the @samp{--srcdir} option to specify where to find the source.
35016 (You also need to specify a path to find @file{configure}
35017 itself from your working directory. If the path to @file{configure}
35018 would be the same as the argument to @samp{--srcdir}, you can leave out
35019 the @samp{--srcdir} option; it is assumed.)
35021 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35022 separate directory for a Sun 4 like this:
35026 cd gdb-@value{GDBVN}
35029 ../gdb-@value{GDBVN}/configure sun4
35034 When @file{configure} builds a configuration using a remote source
35035 directory, it creates a tree for the binaries with the same structure
35036 (and using the same names) as the tree under the source directory. In
35037 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35038 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35039 @file{gdb-sun4/gdb}.
35041 Make sure that your path to the @file{configure} script has just one
35042 instance of @file{gdb} in it. If your path to @file{configure} looks
35043 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35044 one subdirectory of @value{GDBN}, not the whole package. This leads to
35045 build errors about missing include files such as @file{bfd/bfd.h}.
35047 One popular reason to build several @value{GDBN} configurations in separate
35048 directories is to configure @value{GDBN} for cross-compiling (where
35049 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35050 programs that run on another machine---the @dfn{target}).
35051 You specify a cross-debugging target by
35052 giving the @samp{--target=@var{target}} option to @file{configure}.
35054 When you run @code{make} to build a program or library, you must run
35055 it in a configured directory---whatever directory you were in when you
35056 called @file{configure} (or one of its subdirectories).
35058 The @code{Makefile} that @file{configure} generates in each source
35059 directory also runs recursively. If you type @code{make} in a source
35060 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35061 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35062 will build all the required libraries, and then build GDB.
35064 When you have multiple hosts or targets configured in separate
35065 directories, you can run @code{make} on them in parallel (for example,
35066 if they are NFS-mounted on each of the hosts); they will not interfere
35070 @section Specifying Names for Hosts and Targets
35072 The specifications used for hosts and targets in the @file{configure}
35073 script are based on a three-part naming scheme, but some short predefined
35074 aliases are also supported. The full naming scheme encodes three pieces
35075 of information in the following pattern:
35078 @var{architecture}-@var{vendor}-@var{os}
35081 For example, you can use the alias @code{sun4} as a @var{host} argument,
35082 or as the value for @var{target} in a @code{--target=@var{target}}
35083 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35085 The @file{configure} script accompanying @value{GDBN} does not provide
35086 any query facility to list all supported host and target names or
35087 aliases. @file{configure} calls the Bourne shell script
35088 @code{config.sub} to map abbreviations to full names; you can read the
35089 script, if you wish, or you can use it to test your guesses on
35090 abbreviations---for example:
35093 % sh config.sub i386-linux
35095 % sh config.sub alpha-linux
35096 alpha-unknown-linux-gnu
35097 % sh config.sub hp9k700
35099 % sh config.sub sun4
35100 sparc-sun-sunos4.1.1
35101 % sh config.sub sun3
35102 m68k-sun-sunos4.1.1
35103 % sh config.sub i986v
35104 Invalid configuration `i986v': machine `i986v' not recognized
35108 @code{config.sub} is also distributed in the @value{GDBN} source
35109 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35111 @node Configure Options
35112 @section @file{configure} Options
35114 Here is a summary of the @file{configure} options and arguments that
35115 are most often useful for building @value{GDBN}. @file{configure} also has
35116 several other options not listed here. @inforef{What Configure
35117 Does,,configure.info}, for a full explanation of @file{configure}.
35120 configure @r{[}--help@r{]}
35121 @r{[}--prefix=@var{dir}@r{]}
35122 @r{[}--exec-prefix=@var{dir}@r{]}
35123 @r{[}--srcdir=@var{dirname}@r{]}
35124 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35125 @r{[}--target=@var{target}@r{]}
35130 You may introduce options with a single @samp{-} rather than
35131 @samp{--} if you prefer; but you may abbreviate option names if you use
35136 Display a quick summary of how to invoke @file{configure}.
35138 @item --prefix=@var{dir}
35139 Configure the source to install programs and files under directory
35142 @item --exec-prefix=@var{dir}
35143 Configure the source to install programs under directory
35146 @c avoid splitting the warning from the explanation:
35148 @item --srcdir=@var{dirname}
35149 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35150 @code{make} that implements the @code{VPATH} feature.}@*
35151 Use this option to make configurations in directories separate from the
35152 @value{GDBN} source directories. Among other things, you can use this to
35153 build (or maintain) several configurations simultaneously, in separate
35154 directories. @file{configure} writes configuration-specific files in
35155 the current directory, but arranges for them to use the source in the
35156 directory @var{dirname}. @file{configure} creates directories under
35157 the working directory in parallel to the source directories below
35160 @item --norecursion
35161 Configure only the directory level where @file{configure} is executed; do not
35162 propagate configuration to subdirectories.
35164 @item --target=@var{target}
35165 Configure @value{GDBN} for cross-debugging programs running on the specified
35166 @var{target}. Without this option, @value{GDBN} is configured to debug
35167 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35169 There is no convenient way to generate a list of all available targets.
35171 @item @var{host} @dots{}
35172 Configure @value{GDBN} to run on the specified @var{host}.
35174 There is no convenient way to generate a list of all available hosts.
35177 There are many other options available as well, but they are generally
35178 needed for special purposes only.
35180 @node System-wide configuration
35181 @section System-wide configuration and settings
35182 @cindex system-wide init file
35184 @value{GDBN} can be configured to have a system-wide init file;
35185 this file will be read and executed at startup (@pxref{Startup, , What
35186 @value{GDBN} does during startup}).
35188 Here is the corresponding configure option:
35191 @item --with-system-gdbinit=@var{file}
35192 Specify that the default location of the system-wide init file is
35196 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35197 it may be subject to relocation. Two possible cases:
35201 If the default location of this init file contains @file{$prefix},
35202 it will be subject to relocation. Suppose that the configure options
35203 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35204 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35205 init file is looked for as @file{$install/etc/gdbinit} instead of
35206 @file{$prefix/etc/gdbinit}.
35209 By contrast, if the default location does not contain the prefix,
35210 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35211 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35212 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35213 wherever @value{GDBN} is installed.
35216 If the configured location of the system-wide init file (as given by the
35217 @option{--with-system-gdbinit} option at configure time) is in the
35218 data-directory (as specified by @option{--with-gdb-datadir} at configure
35219 time) or in one of its subdirectories, then @value{GDBN} will look for the
35220 system-wide init file in the directory specified by the
35221 @option{--data-directory} command-line option.
35222 Note that the system-wide init file is only read once, during @value{GDBN}
35223 initialization. If the data-directory is changed after @value{GDBN} has
35224 started with the @code{set data-directory} command, the file will not be
35228 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
35231 @node System-wide Configuration Scripts
35232 @subsection Installed System-wide Configuration Scripts
35233 @cindex system-wide configuration scripts
35235 The @file{system-gdbinit} directory, located inside the data-directory
35236 (as specified by @option{--with-gdb-datadir} at configure time) contains
35237 a number of scripts which can be used as system-wide init files. To
35238 automatically source those scripts at startup, @value{GDBN} should be
35239 configured with @option{--with-system-gdbinit}. Otherwise, any user
35240 should be able to source them by hand as needed.
35242 The following scripts are currently available:
35245 @item @file{elinos.py}
35247 @cindex ELinOS system-wide configuration script
35248 This script is useful when debugging a program on an ELinOS target.
35249 It takes advantage of the environment variables defined in a standard
35250 ELinOS environment in order to determine the location of the system
35251 shared libraries, and then sets the @samp{solib-absolute-prefix}
35252 and @samp{solib-search-path} variables appropriately.
35254 @item @file{wrs-linux.py}
35255 @pindex wrs-linux.py
35256 @cindex Wind River Linux system-wide configuration script
35257 This script is useful when debugging a program on a target running
35258 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
35259 the host-side sysroot used by the target system.
35263 @node Maintenance Commands
35264 @appendix Maintenance Commands
35265 @cindex maintenance commands
35266 @cindex internal commands
35268 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35269 includes a number of commands intended for @value{GDBN} developers,
35270 that are not documented elsewhere in this manual. These commands are
35271 provided here for reference. (For commands that turn on debugging
35272 messages, see @ref{Debugging Output}.)
35275 @kindex maint agent
35276 @kindex maint agent-eval
35277 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35278 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35279 Translate the given @var{expression} into remote agent bytecodes.
35280 This command is useful for debugging the Agent Expression mechanism
35281 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35282 expression useful for data collection, such as by tracepoints, while
35283 @samp{maint agent-eval} produces an expression that evaluates directly
35284 to a result. For instance, a collection expression for @code{globa +
35285 globb} will include bytecodes to record four bytes of memory at each
35286 of the addresses of @code{globa} and @code{globb}, while discarding
35287 the result of the addition, while an evaluation expression will do the
35288 addition and return the sum.
35289 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35290 If not, generate remote agent bytecode for current frame PC address.
35292 @kindex maint agent-printf
35293 @item maint agent-printf @var{format},@var{expr},...
35294 Translate the given format string and list of argument expressions
35295 into remote agent bytecodes and display them as a disassembled list.
35296 This command is useful for debugging the agent version of dynamic
35297 printf (@pxref{Dynamic Printf}).
35299 @kindex maint info breakpoints
35300 @item @anchor{maint info breakpoints}maint info breakpoints
35301 Using the same format as @samp{info breakpoints}, display both the
35302 breakpoints you've set explicitly, and those @value{GDBN} is using for
35303 internal purposes. Internal breakpoints are shown with negative
35304 breakpoint numbers. The type column identifies what kind of breakpoint
35309 Normal, explicitly set breakpoint.
35312 Normal, explicitly set watchpoint.
35315 Internal breakpoint, used to handle correctly stepping through
35316 @code{longjmp} calls.
35318 @item longjmp resume
35319 Internal breakpoint at the target of a @code{longjmp}.
35322 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35325 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35328 Shared library events.
35332 @kindex maint info btrace
35333 @item maint info btrace
35334 Pint information about raw branch tracing data.
35336 @kindex maint btrace packet-history
35337 @item maint btrace packet-history
35338 Print the raw branch trace packets that are used to compute the
35339 execution history for the @samp{record btrace} command. Both the
35340 information and the format in which it is printed depend on the btrace
35345 For the BTS recording format, print a list of blocks of sequential
35346 code. For each block, the following information is printed:
35350 Newer blocks have higher numbers. The oldest block has number zero.
35351 @item Lowest @samp{PC}
35352 @item Highest @samp{PC}
35356 For the Intel Processor Trace recording format, print a list of
35357 Intel Processor Trace packets. For each packet, the following
35358 information is printed:
35361 @item Packet number
35362 Newer packets have higher numbers. The oldest packet has number zero.
35364 The packet's offset in the trace stream.
35365 @item Packet opcode and payload
35369 @kindex maint btrace clear-packet-history
35370 @item maint btrace clear-packet-history
35371 Discards the cached packet history printed by the @samp{maint btrace
35372 packet-history} command. The history will be computed again when
35375 @kindex maint btrace clear
35376 @item maint btrace clear
35377 Discard the branch trace data. The data will be fetched anew and the
35378 branch trace will be recomputed when needed.
35380 This implicitly truncates the branch trace to a single branch trace
35381 buffer. When updating branch trace incrementally, the branch trace
35382 available to @value{GDBN} may be bigger than a single branch trace
35385 @kindex maint set btrace pt skip-pad
35386 @item maint set btrace pt skip-pad
35387 @kindex maint show btrace pt skip-pad
35388 @item maint show btrace pt skip-pad
35389 Control whether @value{GDBN} will skip PAD packets when computing the
35392 @kindex set displaced-stepping
35393 @kindex show displaced-stepping
35394 @cindex displaced stepping support
35395 @cindex out-of-line single-stepping
35396 @item set displaced-stepping
35397 @itemx show displaced-stepping
35398 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35399 if the target supports it. Displaced stepping is a way to single-step
35400 over breakpoints without removing them from the inferior, by executing
35401 an out-of-line copy of the instruction that was originally at the
35402 breakpoint location. It is also known as out-of-line single-stepping.
35405 @item set displaced-stepping on
35406 If the target architecture supports it, @value{GDBN} will use
35407 displaced stepping to step over breakpoints.
35409 @item set displaced-stepping off
35410 @value{GDBN} will not use displaced stepping to step over breakpoints,
35411 even if such is supported by the target architecture.
35413 @cindex non-stop mode, and @samp{set displaced-stepping}
35414 @item set displaced-stepping auto
35415 This is the default mode. @value{GDBN} will use displaced stepping
35416 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35417 architecture supports displaced stepping.
35420 @kindex maint check-psymtabs
35421 @item maint check-psymtabs
35422 Check the consistency of currently expanded psymtabs versus symtabs.
35423 Use this to check, for example, whether a symbol is in one but not the other.
35425 @kindex maint check-symtabs
35426 @item maint check-symtabs
35427 Check the consistency of currently expanded symtabs.
35429 @kindex maint expand-symtabs
35430 @item maint expand-symtabs [@var{regexp}]
35431 Expand symbol tables.
35432 If @var{regexp} is specified, only expand symbol tables for file
35433 names matching @var{regexp}.
35435 @kindex maint set catch-demangler-crashes
35436 @kindex maint show catch-demangler-crashes
35437 @cindex demangler crashes
35438 @item maint set catch-demangler-crashes [on|off]
35439 @itemx maint show catch-demangler-crashes
35440 Control whether @value{GDBN} should attempt to catch crashes in the
35441 symbol name demangler. The default is to attempt to catch crashes.
35442 If enabled, the first time a crash is caught, a core file is created,
35443 the offending symbol is displayed and the user is presented with the
35444 option to terminate the current session.
35446 @kindex maint cplus first_component
35447 @item maint cplus first_component @var{name}
35448 Print the first C@t{++} class/namespace component of @var{name}.
35450 @kindex maint cplus namespace
35451 @item maint cplus namespace
35452 Print the list of possible C@t{++} namespaces.
35454 @kindex maint deprecate
35455 @kindex maint undeprecate
35456 @cindex deprecated commands
35457 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35458 @itemx maint undeprecate @var{command}
35459 Deprecate or undeprecate the named @var{command}. Deprecated commands
35460 cause @value{GDBN} to issue a warning when you use them. The optional
35461 argument @var{replacement} says which newer command should be used in
35462 favor of the deprecated one; if it is given, @value{GDBN} will mention
35463 the replacement as part of the warning.
35465 @kindex maint dump-me
35466 @item maint dump-me
35467 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35468 Cause a fatal signal in the debugger and force it to dump its core.
35469 This is supported only on systems which support aborting a program
35470 with the @code{SIGQUIT} signal.
35472 @kindex maint internal-error
35473 @kindex maint internal-warning
35474 @kindex maint demangler-warning
35475 @cindex demangler crashes
35476 @item maint internal-error @r{[}@var{message-text}@r{]}
35477 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35478 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35480 Cause @value{GDBN} to call the internal function @code{internal_error},
35481 @code{internal_warning} or @code{demangler_warning} and hence behave
35482 as though an internal problem has been detected. In addition to
35483 reporting the internal problem, these functions give the user the
35484 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35485 and @code{internal_warning}) create a core file of the current
35486 @value{GDBN} session.
35488 These commands take an optional parameter @var{message-text} that is
35489 used as the text of the error or warning message.
35491 Here's an example of using @code{internal-error}:
35494 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35495 @dots{}/maint.c:121: internal-error: testing, 1, 2
35496 A problem internal to GDB has been detected. Further
35497 debugging may prove unreliable.
35498 Quit this debugging session? (y or n) @kbd{n}
35499 Create a core file? (y or n) @kbd{n}
35503 @cindex @value{GDBN} internal error
35504 @cindex internal errors, control of @value{GDBN} behavior
35505 @cindex demangler crashes
35507 @kindex maint set internal-error
35508 @kindex maint show internal-error
35509 @kindex maint set internal-warning
35510 @kindex maint show internal-warning
35511 @kindex maint set demangler-warning
35512 @kindex maint show demangler-warning
35513 @item maint set internal-error @var{action} [ask|yes|no]
35514 @itemx maint show internal-error @var{action}
35515 @itemx maint set internal-warning @var{action} [ask|yes|no]
35516 @itemx maint show internal-warning @var{action}
35517 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35518 @itemx maint show demangler-warning @var{action}
35519 When @value{GDBN} reports an internal problem (error or warning) it
35520 gives the user the opportunity to both quit @value{GDBN} and create a
35521 core file of the current @value{GDBN} session. These commands let you
35522 override the default behaviour for each particular @var{action},
35523 described in the table below.
35527 You can specify that @value{GDBN} should always (yes) or never (no)
35528 quit. The default is to ask the user what to do.
35531 You can specify that @value{GDBN} should always (yes) or never (no)
35532 create a core file. The default is to ask the user what to do. Note
35533 that there is no @code{corefile} option for @code{demangler-warning}:
35534 demangler warnings always create a core file and this cannot be
35538 @kindex maint packet
35539 @item maint packet @var{text}
35540 If @value{GDBN} is talking to an inferior via the serial protocol,
35541 then this command sends the string @var{text} to the inferior, and
35542 displays the response packet. @value{GDBN} supplies the initial
35543 @samp{$} character, the terminating @samp{#} character, and the
35546 @kindex maint print architecture
35547 @item maint print architecture @r{[}@var{file}@r{]}
35548 Print the entire architecture configuration. The optional argument
35549 @var{file} names the file where the output goes.
35551 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35552 @item maint print c-tdesc
35553 Print the target description (@pxref{Target Descriptions}) as
35554 a C source file. By default, the target description is for the current
35555 target, but if the optional argument @var{file} is provided, that file
35556 is used to produce the description. The @var{file} should be an XML
35557 document, of the form described in @ref{Target Description Format}.
35558 The created source file is built into @value{GDBN} when @value{GDBN} is
35559 built again. This command is used by developers after they add or
35560 modify XML target descriptions.
35562 @kindex maint check xml-descriptions
35563 @item maint check xml-descriptions @var{dir}
35564 Check that the target descriptions dynamically created by @value{GDBN}
35565 equal the descriptions created from XML files found in @var{dir}.
35567 @anchor{maint check libthread-db}
35568 @kindex maint check libthread-db
35569 @item maint check libthread-db
35570 Run integrity checks on the current inferior's thread debugging
35571 library. This exercises all @code{libthread_db} functionality used by
35572 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
35573 @code{proc_service} functions provided by @value{GDBN} that
35574 @code{libthread_db} uses. Note that parts of the test may be skipped
35575 on some platforms when debugging core files.
35577 @kindex maint print dummy-frames
35578 @item maint print dummy-frames
35579 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35582 (@value{GDBP}) @kbd{b add}
35584 (@value{GDBP}) @kbd{print add(2,3)}
35585 Breakpoint 2, add (a=2, b=3) at @dots{}
35587 The program being debugged stopped while in a function called from GDB.
35589 (@value{GDBP}) @kbd{maint print dummy-frames}
35590 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35594 Takes an optional file parameter.
35596 @kindex maint print registers
35597 @kindex maint print raw-registers
35598 @kindex maint print cooked-registers
35599 @kindex maint print register-groups
35600 @kindex maint print remote-registers
35601 @item maint print registers @r{[}@var{file}@r{]}
35602 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35603 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35604 @itemx maint print register-groups @r{[}@var{file}@r{]}
35605 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35606 Print @value{GDBN}'s internal register data structures.
35608 The command @code{maint print raw-registers} includes the contents of
35609 the raw register cache; the command @code{maint print
35610 cooked-registers} includes the (cooked) value of all registers,
35611 including registers which aren't available on the target nor visible
35612 to user; the command @code{maint print register-groups} includes the
35613 groups that each register is a member of; and the command @code{maint
35614 print remote-registers} includes the remote target's register numbers
35615 and offsets in the `G' packets.
35617 These commands take an optional parameter, a file name to which to
35618 write the information.
35620 @kindex maint print reggroups
35621 @item maint print reggroups @r{[}@var{file}@r{]}
35622 Print @value{GDBN}'s internal register group data structures. The
35623 optional argument @var{file} tells to what file to write the
35626 The register groups info looks like this:
35629 (@value{GDBP}) @kbd{maint print reggroups}
35642 This command forces @value{GDBN} to flush its internal register cache.
35644 @kindex maint print objfiles
35645 @cindex info for known object files
35646 @item maint print objfiles @r{[}@var{regexp}@r{]}
35647 Print a dump of all known object files.
35648 If @var{regexp} is specified, only print object files whose names
35649 match @var{regexp}. For each object file, this command prints its name,
35650 address in memory, and all of its psymtabs and symtabs.
35652 @kindex maint print user-registers
35653 @cindex user registers
35654 @item maint print user-registers
35655 List all currently available @dfn{user registers}. User registers
35656 typically provide alternate names for actual hardware registers. They
35657 include the four ``standard'' registers @code{$fp}, @code{$pc},
35658 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35659 registers can be used in expressions in the same way as the canonical
35660 register names, but only the latter are listed by the @code{info
35661 registers} and @code{maint print registers} commands.
35663 @kindex maint print section-scripts
35664 @cindex info for known .debug_gdb_scripts-loaded scripts
35665 @item maint print section-scripts [@var{regexp}]
35666 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35667 If @var{regexp} is specified, only print scripts loaded by object files
35668 matching @var{regexp}.
35669 For each script, this command prints its name as specified in the objfile,
35670 and the full path if known.
35671 @xref{dotdebug_gdb_scripts section}.
35673 @kindex maint print statistics
35674 @cindex bcache statistics
35675 @item maint print statistics
35676 This command prints, for each object file in the program, various data
35677 about that object file followed by the byte cache (@dfn{bcache})
35678 statistics for the object file. The objfile data includes the number
35679 of minimal, partial, full, and stabs symbols, the number of types
35680 defined by the objfile, the number of as yet unexpanded psym tables,
35681 the number of line tables and string tables, and the amount of memory
35682 used by the various tables. The bcache statistics include the counts,
35683 sizes, and counts of duplicates of all and unique objects, max,
35684 average, and median entry size, total memory used and its overhead and
35685 savings, and various measures of the hash table size and chain
35688 @kindex maint print target-stack
35689 @cindex target stack description
35690 @item maint print target-stack
35691 A @dfn{target} is an interface between the debugger and a particular
35692 kind of file or process. Targets can be stacked in @dfn{strata},
35693 so that more than one target can potentially respond to a request.
35694 In particular, memory accesses will walk down the stack of targets
35695 until they find a target that is interested in handling that particular
35698 This command prints a short description of each layer that was pushed on
35699 the @dfn{target stack}, starting from the top layer down to the bottom one.
35701 @kindex maint print type
35702 @cindex type chain of a data type
35703 @item maint print type @var{expr}
35704 Print the type chain for a type specified by @var{expr}. The argument
35705 can be either a type name or a symbol. If it is a symbol, the type of
35706 that symbol is described. The type chain produced by this command is
35707 a recursive definition of the data type as stored in @value{GDBN}'s
35708 data structures, including its flags and contained types.
35710 @kindex maint selftest
35712 @item maint selftest @r{[}@var{filter}@r{]}
35713 Run any self tests that were compiled in to @value{GDBN}. This will
35714 print a message showing how many tests were run, and how many failed.
35715 If a @var{filter} is passed, only the tests with @var{filter} in their
35718 @kindex "maint info selftests"
35720 @item maint info selftests
35721 List the selftests compiled in to @value{GDBN}.
35723 @kindex maint set dwarf always-disassemble
35724 @kindex maint show dwarf always-disassemble
35725 @item maint set dwarf always-disassemble
35726 @item maint show dwarf always-disassemble
35727 Control the behavior of @code{info address} when using DWARF debugging
35730 The default is @code{off}, which means that @value{GDBN} should try to
35731 describe a variable's location in an easily readable format. When
35732 @code{on}, @value{GDBN} will instead display the DWARF location
35733 expression in an assembly-like format. Note that some locations are
35734 too complex for @value{GDBN} to describe simply; in this case you will
35735 always see the disassembly form.
35737 Here is an example of the resulting disassembly:
35740 (gdb) info addr argc
35741 Symbol "argc" is a complex DWARF expression:
35745 For more information on these expressions, see
35746 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35748 @kindex maint set dwarf max-cache-age
35749 @kindex maint show dwarf max-cache-age
35750 @item maint set dwarf max-cache-age
35751 @itemx maint show dwarf max-cache-age
35752 Control the DWARF compilation unit cache.
35754 @cindex DWARF compilation units cache
35755 In object files with inter-compilation-unit references, such as those
35756 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35757 reader needs to frequently refer to previously read compilation units.
35758 This setting controls how long a compilation unit will remain in the
35759 cache if it is not referenced. A higher limit means that cached
35760 compilation units will be stored in memory longer, and more total
35761 memory will be used. Setting it to zero disables caching, which will
35762 slow down @value{GDBN} startup, but reduce memory consumption.
35764 @kindex maint set profile
35765 @kindex maint show profile
35766 @cindex profiling GDB
35767 @item maint set profile
35768 @itemx maint show profile
35769 Control profiling of @value{GDBN}.
35771 Profiling will be disabled until you use the @samp{maint set profile}
35772 command to enable it. When you enable profiling, the system will begin
35773 collecting timing and execution count data; when you disable profiling or
35774 exit @value{GDBN}, the results will be written to a log file. Remember that
35775 if you use profiling, @value{GDBN} will overwrite the profiling log file
35776 (often called @file{gmon.out}). If you have a record of important profiling
35777 data in a @file{gmon.out} file, be sure to move it to a safe location.
35779 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35780 compiled with the @samp{-pg} compiler option.
35782 @kindex maint set show-debug-regs
35783 @kindex maint show show-debug-regs
35784 @cindex hardware debug registers
35785 @item maint set show-debug-regs
35786 @itemx maint show show-debug-regs
35787 Control whether to show variables that mirror the hardware debug
35788 registers. Use @code{on} to enable, @code{off} to disable. If
35789 enabled, the debug registers values are shown when @value{GDBN} inserts or
35790 removes a hardware breakpoint or watchpoint, and when the inferior
35791 triggers a hardware-assisted breakpoint or watchpoint.
35793 @kindex maint set show-all-tib
35794 @kindex maint show show-all-tib
35795 @item maint set show-all-tib
35796 @itemx maint show show-all-tib
35797 Control whether to show all non zero areas within a 1k block starting
35798 at thread local base, when using the @samp{info w32 thread-information-block}
35801 @kindex maint set target-async
35802 @kindex maint show target-async
35803 @item maint set target-async
35804 @itemx maint show target-async
35805 This controls whether @value{GDBN} targets operate in synchronous or
35806 asynchronous mode (@pxref{Background Execution}). Normally the
35807 default is asynchronous, if it is available; but this can be changed
35808 to more easily debug problems occurring only in synchronous mode.
35810 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35811 @kindex maint show target-non-stop
35812 @item maint set target-non-stop
35813 @itemx maint show target-non-stop
35815 This controls whether @value{GDBN} targets always operate in non-stop
35816 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35817 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35818 if supported by the target.
35821 @item maint set target-non-stop auto
35822 This is the default mode. @value{GDBN} controls the target in
35823 non-stop mode if the target supports it.
35825 @item maint set target-non-stop on
35826 @value{GDBN} controls the target in non-stop mode even if the target
35827 does not indicate support.
35829 @item maint set target-non-stop off
35830 @value{GDBN} does not control the target in non-stop mode even if the
35831 target supports it.
35834 @kindex maint set per-command
35835 @kindex maint show per-command
35836 @item maint set per-command
35837 @itemx maint show per-command
35838 @cindex resources used by commands
35840 @value{GDBN} can display the resources used by each command.
35841 This is useful in debugging performance problems.
35844 @item maint set per-command space [on|off]
35845 @itemx maint show per-command space
35846 Enable or disable the printing of the memory used by GDB for each command.
35847 If enabled, @value{GDBN} will display how much memory each command
35848 took, following the command's own output.
35849 This can also be requested by invoking @value{GDBN} with the
35850 @option{--statistics} command-line switch (@pxref{Mode Options}).
35852 @item maint set per-command time [on|off]
35853 @itemx maint show per-command time
35854 Enable or disable the printing of the execution time of @value{GDBN}
35856 If enabled, @value{GDBN} will display how much time it
35857 took to execute each command, following the command's own output.
35858 Both CPU time and wallclock time are printed.
35859 Printing both is useful when trying to determine whether the cost is
35860 CPU or, e.g., disk/network latency.
35861 Note that the CPU time printed is for @value{GDBN} only, it does not include
35862 the execution time of the inferior because there's no mechanism currently
35863 to compute how much time was spent by @value{GDBN} and how much time was
35864 spent by the program been debugged.
35865 This can also be requested by invoking @value{GDBN} with the
35866 @option{--statistics} command-line switch (@pxref{Mode Options}).
35868 @item maint set per-command symtab [on|off]
35869 @itemx maint show per-command symtab
35870 Enable or disable the printing of basic symbol table statistics
35872 If enabled, @value{GDBN} will display the following information:
35876 number of symbol tables
35878 number of primary symbol tables
35880 number of blocks in the blockvector
35884 @kindex maint set check-libthread-db
35885 @kindex maint show check-libthread-db
35886 @item maint set check-libthread-db [on|off]
35887 @itemx maint show check-libthread-db
35888 Control whether @value{GDBN} should run integrity checks on inferior
35889 specific thread debugging libraries as they are loaded. The default
35890 is not to perform such checks. If any check fails @value{GDBN} will
35891 unload the library and continue searching for a suitable candidate as
35892 described in @ref{set libthread-db-search-path}. For more information
35893 about the tests, see @ref{maint check libthread-db}.
35895 @kindex maint space
35896 @cindex memory used by commands
35897 @item maint space @var{value}
35898 An alias for @code{maint set per-command space}.
35899 A non-zero value enables it, zero disables it.
35902 @cindex time of command execution
35903 @item maint time @var{value}
35904 An alias for @code{maint set per-command time}.
35905 A non-zero value enables it, zero disables it.
35907 @kindex maint translate-address
35908 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35909 Find the symbol stored at the location specified by the address
35910 @var{addr} and an optional section name @var{section}. If found,
35911 @value{GDBN} prints the name of the closest symbol and an offset from
35912 the symbol's location to the specified address. This is similar to
35913 the @code{info address} command (@pxref{Symbols}), except that this
35914 command also allows to find symbols in other sections.
35916 If section was not specified, the section in which the symbol was found
35917 is also printed. For dynamically linked executables, the name of
35918 executable or shared library containing the symbol is printed as well.
35922 The following command is useful for non-interactive invocations of
35923 @value{GDBN}, such as in the test suite.
35926 @item set watchdog @var{nsec}
35927 @kindex set watchdog
35928 @cindex watchdog timer
35929 @cindex timeout for commands
35930 Set the maximum number of seconds @value{GDBN} will wait for the
35931 target operation to finish. If this time expires, @value{GDBN}
35932 reports and error and the command is aborted.
35934 @item show watchdog
35935 Show the current setting of the target wait timeout.
35938 @node Remote Protocol
35939 @appendix @value{GDBN} Remote Serial Protocol
35944 * Stop Reply Packets::
35945 * General Query Packets::
35946 * Architecture-Specific Protocol Details::
35947 * Tracepoint Packets::
35948 * Host I/O Packets::
35950 * Notification Packets::
35951 * Remote Non-Stop::
35952 * Packet Acknowledgment::
35954 * File-I/O Remote Protocol Extension::
35955 * Library List Format::
35956 * Library List Format for SVR4 Targets::
35957 * Memory Map Format::
35958 * Thread List Format::
35959 * Traceframe Info Format::
35960 * Branch Trace Format::
35961 * Branch Trace Configuration Format::
35967 There may be occasions when you need to know something about the
35968 protocol---for example, if there is only one serial port to your target
35969 machine, you might want your program to do something special if it
35970 recognizes a packet meant for @value{GDBN}.
35972 In the examples below, @samp{->} and @samp{<-} are used to indicate
35973 transmitted and received data, respectively.
35975 @cindex protocol, @value{GDBN} remote serial
35976 @cindex serial protocol, @value{GDBN} remote
35977 @cindex remote serial protocol
35978 All @value{GDBN} commands and responses (other than acknowledgments
35979 and notifications, see @ref{Notification Packets}) are sent as a
35980 @var{packet}. A @var{packet} is introduced with the character
35981 @samp{$}, the actual @var{packet-data}, and the terminating character
35982 @samp{#} followed by a two-digit @var{checksum}:
35985 @code{$}@var{packet-data}@code{#}@var{checksum}
35989 @cindex checksum, for @value{GDBN} remote
35991 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35992 characters between the leading @samp{$} and the trailing @samp{#} (an
35993 eight bit unsigned checksum).
35995 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35996 specification also included an optional two-digit @var{sequence-id}:
35999 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
36002 @cindex sequence-id, for @value{GDBN} remote
36004 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
36005 has never output @var{sequence-id}s. Stubs that handle packets added
36006 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
36008 When either the host or the target machine receives a packet, the first
36009 response expected is an acknowledgment: either @samp{+} (to indicate
36010 the package was received correctly) or @samp{-} (to request
36014 -> @code{$}@var{packet-data}@code{#}@var{checksum}
36019 The @samp{+}/@samp{-} acknowledgments can be disabled
36020 once a connection is established.
36021 @xref{Packet Acknowledgment}, for details.
36023 The host (@value{GDBN}) sends @var{command}s, and the target (the
36024 debugging stub incorporated in your program) sends a @var{response}. In
36025 the case of step and continue @var{command}s, the response is only sent
36026 when the operation has completed, and the target has again stopped all
36027 threads in all attached processes. This is the default all-stop mode
36028 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
36029 execution mode; see @ref{Remote Non-Stop}, for details.
36031 @var{packet-data} consists of a sequence of characters with the
36032 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
36035 @cindex remote protocol, field separator
36036 Fields within the packet should be separated using @samp{,} @samp{;} or
36037 @samp{:}. Except where otherwise noted all numbers are represented in
36038 @sc{hex} with leading zeros suppressed.
36040 Implementors should note that prior to @value{GDBN} 5.0, the character
36041 @samp{:} could not appear as the third character in a packet (as it
36042 would potentially conflict with the @var{sequence-id}).
36044 @cindex remote protocol, binary data
36045 @anchor{Binary Data}
36046 Binary data in most packets is encoded either as two hexadecimal
36047 digits per byte of binary data. This allowed the traditional remote
36048 protocol to work over connections which were only seven-bit clean.
36049 Some packets designed more recently assume an eight-bit clean
36050 connection, and use a more efficient encoding to send and receive
36053 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
36054 as an escape character. Any escaped byte is transmitted as the escape
36055 character followed by the original character XORed with @code{0x20}.
36056 For example, the byte @code{0x7d} would be transmitted as the two
36057 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
36058 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
36059 @samp{@}}) must always be escaped. Responses sent by the stub
36060 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
36061 is not interpreted as the start of a run-length encoded sequence
36064 Response @var{data} can be run-length encoded to save space.
36065 Run-length encoding replaces runs of identical characters with one
36066 instance of the repeated character, followed by a @samp{*} and a
36067 repeat count. The repeat count is itself sent encoded, to avoid
36068 binary characters in @var{data}: a value of @var{n} is sent as
36069 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
36070 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
36071 code 32) for a repeat count of 3. (This is because run-length
36072 encoding starts to win for counts 3 or more.) Thus, for example,
36073 @samp{0* } is a run-length encoding of ``0000'': the space character
36074 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
36077 The printable characters @samp{#} and @samp{$} or with a numeric value
36078 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
36079 seven repeats (@samp{$}) can be expanded using a repeat count of only
36080 five (@samp{"}). For example, @samp{00000000} can be encoded as
36083 The error response returned for some packets includes a two character
36084 error number. That number is not well defined.
36086 @cindex empty response, for unsupported packets
36087 For any @var{command} not supported by the stub, an empty response
36088 (@samp{$#00}) should be returned. That way it is possible to extend the
36089 protocol. A newer @value{GDBN} can tell if a packet is supported based
36092 At a minimum, a stub is required to support the @samp{g} and @samp{G}
36093 commands for register access, and the @samp{m} and @samp{M} commands
36094 for memory access. Stubs that only control single-threaded targets
36095 can implement run control with the @samp{c} (continue), and @samp{s}
36096 (step) commands. Stubs that support multi-threading targets should
36097 support the @samp{vCont} command. All other commands are optional.
36102 The following table provides a complete list of all currently defined
36103 @var{command}s and their corresponding response @var{data}.
36104 @xref{File-I/O Remote Protocol Extension}, for details about the File
36105 I/O extension of the remote protocol.
36107 Each packet's description has a template showing the packet's overall
36108 syntax, followed by an explanation of the packet's meaning. We
36109 include spaces in some of the templates for clarity; these are not
36110 part of the packet's syntax. No @value{GDBN} packet uses spaces to
36111 separate its components. For example, a template like @samp{foo
36112 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
36113 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
36114 @var{baz}. @value{GDBN} does not transmit a space character between the
36115 @samp{foo} and the @var{bar}, or between the @var{bar} and the
36118 @cindex @var{thread-id}, in remote protocol
36119 @anchor{thread-id syntax}
36120 Several packets and replies include a @var{thread-id} field to identify
36121 a thread. Normally these are positive numbers with a target-specific
36122 interpretation, formatted as big-endian hex strings. A @var{thread-id}
36123 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
36126 In addition, the remote protocol supports a multiprocess feature in
36127 which the @var{thread-id} syntax is extended to optionally include both
36128 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36129 The @var{pid} (process) and @var{tid} (thread) components each have the
36130 format described above: a positive number with target-specific
36131 interpretation formatted as a big-endian hex string, literal @samp{-1}
36132 to indicate all processes or threads (respectively), or @samp{0} to
36133 indicate an arbitrary process or thread. Specifying just a process, as
36134 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36135 error to specify all processes but a specific thread, such as
36136 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36137 for those packets and replies explicitly documented to include a process
36138 ID, rather than a @var{thread-id}.
36140 The multiprocess @var{thread-id} syntax extensions are only used if both
36141 @value{GDBN} and the stub report support for the @samp{multiprocess}
36142 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36145 Note that all packet forms beginning with an upper- or lower-case
36146 letter, other than those described here, are reserved for future use.
36148 Here are the packet descriptions.
36153 @cindex @samp{!} packet
36154 @anchor{extended mode}
36155 Enable extended mode. In extended mode, the remote server is made
36156 persistent. The @samp{R} packet is used to restart the program being
36162 The remote target both supports and has enabled extended mode.
36166 @cindex @samp{?} packet
36168 Indicate the reason the target halted. The reply is the same as for
36169 step and continue. This packet has a special interpretation when the
36170 target is in non-stop mode; see @ref{Remote Non-Stop}.
36173 @xref{Stop Reply Packets}, for the reply specifications.
36175 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36176 @cindex @samp{A} packet
36177 Initialized @code{argv[]} array passed into program. @var{arglen}
36178 specifies the number of bytes in the hex encoded byte stream
36179 @var{arg}. See @code{gdbserver} for more details.
36184 The arguments were set.
36190 @cindex @samp{b} packet
36191 (Don't use this packet; its behavior is not well-defined.)
36192 Change the serial line speed to @var{baud}.
36194 JTC: @emph{When does the transport layer state change? When it's
36195 received, or after the ACK is transmitted. In either case, there are
36196 problems if the command or the acknowledgment packet is dropped.}
36198 Stan: @emph{If people really wanted to add something like this, and get
36199 it working for the first time, they ought to modify ser-unix.c to send
36200 some kind of out-of-band message to a specially-setup stub and have the
36201 switch happen "in between" packets, so that from remote protocol's point
36202 of view, nothing actually happened.}
36204 @item B @var{addr},@var{mode}
36205 @cindex @samp{B} packet
36206 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36207 breakpoint at @var{addr}.
36209 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36210 (@pxref{insert breakpoint or watchpoint packet}).
36212 @cindex @samp{bc} packet
36215 Backward continue. Execute the target system in reverse. No parameter.
36216 @xref{Reverse Execution}, for more information.
36219 @xref{Stop Reply Packets}, for the reply specifications.
36221 @cindex @samp{bs} packet
36224 Backward single step. Execute one instruction in reverse. No parameter.
36225 @xref{Reverse Execution}, for more information.
36228 @xref{Stop Reply Packets}, for the reply specifications.
36230 @item c @r{[}@var{addr}@r{]}
36231 @cindex @samp{c} packet
36232 Continue at @var{addr}, which is the address to resume. If @var{addr}
36233 is omitted, resume at current address.
36235 This packet is deprecated for multi-threading support. @xref{vCont
36239 @xref{Stop Reply Packets}, for the reply specifications.
36241 @item C @var{sig}@r{[};@var{addr}@r{]}
36242 @cindex @samp{C} packet
36243 Continue with signal @var{sig} (hex signal number). If
36244 @samp{;@var{addr}} is omitted, resume at same address.
36246 This packet is deprecated for multi-threading support. @xref{vCont
36250 @xref{Stop Reply Packets}, for the reply specifications.
36253 @cindex @samp{d} packet
36256 Don't use this packet; instead, define a general set packet
36257 (@pxref{General Query Packets}).
36261 @cindex @samp{D} packet
36262 The first form of the packet is used to detach @value{GDBN} from the
36263 remote system. It is sent to the remote target
36264 before @value{GDBN} disconnects via the @code{detach} command.
36266 The second form, including a process ID, is used when multiprocess
36267 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36268 detach only a specific process. The @var{pid} is specified as a
36269 big-endian hex string.
36279 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36280 @cindex @samp{F} packet
36281 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36282 This is part of the File-I/O protocol extension. @xref{File-I/O
36283 Remote Protocol Extension}, for the specification.
36286 @anchor{read registers packet}
36287 @cindex @samp{g} packet
36288 Read general registers.
36292 @item @var{XX@dots{}}
36293 Each byte of register data is described by two hex digits. The bytes
36294 with the register are transmitted in target byte order. The size of
36295 each register and their position within the @samp{g} packet are
36296 determined by the @value{GDBN} internal gdbarch functions
36297 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
36299 When reading registers from a trace frame (@pxref{Analyze Collected
36300 Data,,Using the Collected Data}), the stub may also return a string of
36301 literal @samp{x}'s in place of the register data digits, to indicate
36302 that the corresponding register has not been collected, thus its value
36303 is unavailable. For example, for an architecture with 4 registers of
36304 4 bytes each, the following reply indicates to @value{GDBN} that
36305 registers 0 and 2 have not been collected, while registers 1 and 3
36306 have been collected, and both have zero value:
36310 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36317 @item G @var{XX@dots{}}
36318 @cindex @samp{G} packet
36319 Write general registers. @xref{read registers packet}, for a
36320 description of the @var{XX@dots{}} data.
36330 @item H @var{op} @var{thread-id}
36331 @cindex @samp{H} packet
36332 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36333 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
36334 should be @samp{c} for step and continue operations (note that this
36335 is deprecated, supporting the @samp{vCont} command is a better
36336 option), and @samp{g} for other operations. The thread designator
36337 @var{thread-id} has the format and interpretation described in
36338 @ref{thread-id syntax}.
36349 @c 'H': How restrictive (or permissive) is the thread model. If a
36350 @c thread is selected and stopped, are other threads allowed
36351 @c to continue to execute? As I mentioned above, I think the
36352 @c semantics of each command when a thread is selected must be
36353 @c described. For example:
36355 @c 'g': If the stub supports threads and a specific thread is
36356 @c selected, returns the register block from that thread;
36357 @c otherwise returns current registers.
36359 @c 'G' If the stub supports threads and a specific thread is
36360 @c selected, sets the registers of the register block of
36361 @c that thread; otherwise sets current registers.
36363 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36364 @anchor{cycle step packet}
36365 @cindex @samp{i} packet
36366 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36367 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36368 step starting at that address.
36371 @cindex @samp{I} packet
36372 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36376 @cindex @samp{k} packet
36379 The exact effect of this packet is not specified.
36381 For a bare-metal target, it may power cycle or reset the target
36382 system. For that reason, the @samp{k} packet has no reply.
36384 For a single-process target, it may kill that process if possible.
36386 A multiple-process target may choose to kill just one process, or all
36387 that are under @value{GDBN}'s control. For more precise control, use
36388 the vKill packet (@pxref{vKill packet}).
36390 If the target system immediately closes the connection in response to
36391 @samp{k}, @value{GDBN} does not consider the lack of packet
36392 acknowledgment to be an error, and assumes the kill was successful.
36394 If connected using @kbd{target extended-remote}, and the target does
36395 not close the connection in response to a kill request, @value{GDBN}
36396 probes the target state as if a new connection was opened
36397 (@pxref{? packet}).
36399 @item m @var{addr},@var{length}
36400 @cindex @samp{m} packet
36401 Read @var{length} addressable memory units starting at address @var{addr}
36402 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36403 any particular boundary.
36405 The stub need not use any particular size or alignment when gathering
36406 data from memory for the response; even if @var{addr} is word-aligned
36407 and @var{length} is a multiple of the word size, the stub is free to
36408 use byte accesses, or not. For this reason, this packet may not be
36409 suitable for accessing memory-mapped I/O devices.
36410 @cindex alignment of remote memory accesses
36411 @cindex size of remote memory accesses
36412 @cindex memory, alignment and size of remote accesses
36416 @item @var{XX@dots{}}
36417 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36418 The reply may contain fewer addressable memory units than requested if the
36419 server was able to read only part of the region of memory.
36424 @item M @var{addr},@var{length}:@var{XX@dots{}}
36425 @cindex @samp{M} packet
36426 Write @var{length} addressable memory units starting at address @var{addr}
36427 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36428 byte is transmitted as a two-digit hexadecimal number.
36435 for an error (this includes the case where only part of the data was
36440 @cindex @samp{p} packet
36441 Read the value of register @var{n}; @var{n} is in hex.
36442 @xref{read registers packet}, for a description of how the returned
36443 register value is encoded.
36447 @item @var{XX@dots{}}
36448 the register's value
36452 Indicating an unrecognized @var{query}.
36455 @item P @var{n@dots{}}=@var{r@dots{}}
36456 @anchor{write register packet}
36457 @cindex @samp{P} packet
36458 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36459 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36460 digits for each byte in the register (target byte order).
36470 @item q @var{name} @var{params}@dots{}
36471 @itemx Q @var{name} @var{params}@dots{}
36472 @cindex @samp{q} packet
36473 @cindex @samp{Q} packet
36474 General query (@samp{q}) and set (@samp{Q}). These packets are
36475 described fully in @ref{General Query Packets}.
36478 @cindex @samp{r} packet
36479 Reset the entire system.
36481 Don't use this packet; use the @samp{R} packet instead.
36484 @cindex @samp{R} packet
36485 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36486 This packet is only available in extended mode (@pxref{extended mode}).
36488 The @samp{R} packet has no reply.
36490 @item s @r{[}@var{addr}@r{]}
36491 @cindex @samp{s} packet
36492 Single step, resuming at @var{addr}. If
36493 @var{addr} is omitted, resume at same address.
36495 This packet is deprecated for multi-threading support. @xref{vCont
36499 @xref{Stop Reply Packets}, for the reply specifications.
36501 @item S @var{sig}@r{[};@var{addr}@r{]}
36502 @anchor{step with signal packet}
36503 @cindex @samp{S} packet
36504 Step with signal. This is analogous to the @samp{C} packet, but
36505 requests a single-step, rather than a normal resumption of execution.
36507 This packet is deprecated for multi-threading support. @xref{vCont
36511 @xref{Stop Reply Packets}, for the reply specifications.
36513 @item t @var{addr}:@var{PP},@var{MM}
36514 @cindex @samp{t} packet
36515 Search backwards starting at address @var{addr} for a match with pattern
36516 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36517 There must be at least 3 digits in @var{addr}.
36519 @item T @var{thread-id}
36520 @cindex @samp{T} packet
36521 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36526 thread is still alive
36532 Packets starting with @samp{v} are identified by a multi-letter name,
36533 up to the first @samp{;} or @samp{?} (or the end of the packet).
36535 @item vAttach;@var{pid}
36536 @cindex @samp{vAttach} packet
36537 Attach to a new process with the specified process ID @var{pid}.
36538 The process ID is a
36539 hexadecimal integer identifying the process. In all-stop mode, all
36540 threads in the attached process are stopped; in non-stop mode, it may be
36541 attached without being stopped if that is supported by the target.
36543 @c In non-stop mode, on a successful vAttach, the stub should set the
36544 @c current thread to a thread of the newly-attached process. After
36545 @c attaching, GDB queries for the attached process's thread ID with qC.
36546 @c Also note that, from a user perspective, whether or not the
36547 @c target is stopped on attach in non-stop mode depends on whether you
36548 @c use the foreground or background version of the attach command, not
36549 @c on what vAttach does; GDB does the right thing with respect to either
36550 @c stopping or restarting threads.
36552 This packet is only available in extended mode (@pxref{extended mode}).
36558 @item @r{Any stop packet}
36559 for success in all-stop mode (@pxref{Stop Reply Packets})
36561 for success in non-stop mode (@pxref{Remote Non-Stop})
36564 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36565 @cindex @samp{vCont} packet
36566 @anchor{vCont packet}
36567 Resume the inferior, specifying different actions for each thread.
36569 For each inferior thread, the leftmost action with a matching
36570 @var{thread-id} is applied. Threads that don't match any action
36571 remain in their current state. Thread IDs are specified using the
36572 syntax described in @ref{thread-id syntax}. If multiprocess
36573 extensions (@pxref{multiprocess extensions}) are supported, actions
36574 can be specified to match all threads in a process by using the
36575 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36576 @var{thread-id} matches all threads. Specifying no actions is an
36579 Currently supported actions are:
36585 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36589 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36592 @item r @var{start},@var{end}
36593 Step once, and then keep stepping as long as the thread stops at
36594 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36595 The remote stub reports a stop reply when either the thread goes out
36596 of the range or is stopped due to an unrelated reason, such as hitting
36597 a breakpoint. @xref{range stepping}.
36599 If the range is empty (@var{start} == @var{end}), then the action
36600 becomes equivalent to the @samp{s} action. In other words,
36601 single-step once, and report the stop (even if the stepped instruction
36602 jumps to @var{start}).
36604 (A stop reply may be sent at any point even if the PC is still within
36605 the stepping range; for example, it is valid to implement this packet
36606 in a degenerate way as a single instruction step operation.)
36610 The optional argument @var{addr} normally associated with the
36611 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36612 not supported in @samp{vCont}.
36614 The @samp{t} action is only relevant in non-stop mode
36615 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36616 A stop reply should be generated for any affected thread not already stopped.
36617 When a thread is stopped by means of a @samp{t} action,
36618 the corresponding stop reply should indicate that the thread has stopped with
36619 signal @samp{0}, regardless of whether the target uses some other signal
36620 as an implementation detail.
36622 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36623 @samp{r} actions for threads that are already running. Conversely,
36624 the server must ignore @samp{t} actions for threads that are already
36627 @emph{Note:} In non-stop mode, a thread is considered running until
36628 @value{GDBN} acknowleges an asynchronous stop notification for it with
36629 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36631 The stub must support @samp{vCont} if it reports support for
36632 multiprocess extensions (@pxref{multiprocess extensions}).
36635 @xref{Stop Reply Packets}, for the reply specifications.
36638 @cindex @samp{vCont?} packet
36639 Request a list of actions supported by the @samp{vCont} packet.
36643 @item vCont@r{[};@var{action}@dots{}@r{]}
36644 The @samp{vCont} packet is supported. Each @var{action} is a supported
36645 command in the @samp{vCont} packet.
36647 The @samp{vCont} packet is not supported.
36650 @anchor{vCtrlC packet}
36652 @cindex @samp{vCtrlC} packet
36653 Interrupt remote target as if a control-C was pressed on the remote
36654 terminal. This is the equivalent to reacting to the @code{^C}
36655 (@samp{\003}, the control-C character) character in all-stop mode
36656 while the target is running, except this works in non-stop mode.
36657 @xref{interrupting remote targets}, for more info on the all-stop
36668 @item vFile:@var{operation}:@var{parameter}@dots{}
36669 @cindex @samp{vFile} packet
36670 Perform a file operation on the target system. For details,
36671 see @ref{Host I/O Packets}.
36673 @item vFlashErase:@var{addr},@var{length}
36674 @cindex @samp{vFlashErase} packet
36675 Direct the stub to erase @var{length} bytes of flash starting at
36676 @var{addr}. The region may enclose any number of flash blocks, but
36677 its start and end must fall on block boundaries, as indicated by the
36678 flash block size appearing in the memory map (@pxref{Memory Map
36679 Format}). @value{GDBN} groups flash memory programming operations
36680 together, and sends a @samp{vFlashDone} request after each group; the
36681 stub is allowed to delay erase operation until the @samp{vFlashDone}
36682 packet is received.
36692 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36693 @cindex @samp{vFlashWrite} packet
36694 Direct the stub to write data to flash address @var{addr}. The data
36695 is passed in binary form using the same encoding as for the @samp{X}
36696 packet (@pxref{Binary Data}). The memory ranges specified by
36697 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36698 not overlap, and must appear in order of increasing addresses
36699 (although @samp{vFlashErase} packets for higher addresses may already
36700 have been received; the ordering is guaranteed only between
36701 @samp{vFlashWrite} packets). If a packet writes to an address that was
36702 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36703 target-specific method, the results are unpredictable.
36711 for vFlashWrite addressing non-flash memory
36717 @cindex @samp{vFlashDone} packet
36718 Indicate to the stub that flash programming operation is finished.
36719 The stub is permitted to delay or batch the effects of a group of
36720 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36721 @samp{vFlashDone} packet is received. The contents of the affected
36722 regions of flash memory are unpredictable until the @samp{vFlashDone}
36723 request is completed.
36725 @item vKill;@var{pid}
36726 @cindex @samp{vKill} packet
36727 @anchor{vKill packet}
36728 Kill the process with the specified process ID @var{pid}, which is a
36729 hexadecimal integer identifying the process. This packet is used in
36730 preference to @samp{k} when multiprocess protocol extensions are
36731 supported; see @ref{multiprocess extensions}.
36741 @item vMustReplyEmpty
36742 @cindex @samp{vMustReplyEmpty} packet
36743 The correct reply to an unknown @samp{v} packet is to return the empty
36744 string, however, some older versions of @command{gdbserver} would
36745 incorrectly return @samp{OK} for unknown @samp{v} packets.
36747 The @samp{vMustReplyEmpty} is used as a feature test to check how
36748 @command{gdbserver} handles unknown packets, it is important that this
36749 packet be handled in the same way as other unknown @samp{v} packets.
36750 If this packet is handled differently to other unknown @samp{v}
36751 packets then it is possile that @value{GDBN} may run into problems in
36752 other areas, specifically around use of @samp{vFile:setfs:}.
36754 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36755 @cindex @samp{vRun} packet
36756 Run the program @var{filename}, passing it each @var{argument} on its
36757 command line. The file and arguments are hex-encoded strings. If
36758 @var{filename} is an empty string, the stub may use a default program
36759 (e.g.@: the last program run). The program is created in the stopped
36762 @c FIXME: What about non-stop mode?
36764 This packet is only available in extended mode (@pxref{extended mode}).
36770 @item @r{Any stop packet}
36771 for success (@pxref{Stop Reply Packets})
36775 @cindex @samp{vStopped} packet
36776 @xref{Notification Packets}.
36778 @item X @var{addr},@var{length}:@var{XX@dots{}}
36780 @cindex @samp{X} packet
36781 Write data to memory, where the data is transmitted in binary.
36782 Memory is specified by its address @var{addr} and number of addressable memory
36783 units @var{length} (@pxref{addressable memory unit});
36784 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36794 @item z @var{type},@var{addr},@var{kind}
36795 @itemx Z @var{type},@var{addr},@var{kind}
36796 @anchor{insert breakpoint or watchpoint packet}
36797 @cindex @samp{z} packet
36798 @cindex @samp{Z} packets
36799 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36800 watchpoint starting at address @var{address} of kind @var{kind}.
36802 Each breakpoint and watchpoint packet @var{type} is documented
36805 @emph{Implementation notes: A remote target shall return an empty string
36806 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36807 remote target shall support either both or neither of a given
36808 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36809 avoid potential problems with duplicate packets, the operations should
36810 be implemented in an idempotent way.}
36812 @item z0,@var{addr},@var{kind}
36813 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36814 @cindex @samp{z0} packet
36815 @cindex @samp{Z0} packet
36816 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36817 @var{addr} of type @var{kind}.
36819 A software breakpoint is implemented by replacing the instruction at
36820 @var{addr} with a software breakpoint or trap instruction. The
36821 @var{kind} is target-specific and typically indicates the size of the
36822 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36823 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36824 architectures have additional meanings for @var{kind}
36825 (@pxref{Architecture-Specific Protocol Details}); if no
36826 architecture-specific value is being used, it should be @samp{0}.
36827 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36828 conditional expressions in bytecode form that should be evaluated on
36829 the target's side. These are the conditions that should be taken into
36830 consideration when deciding if the breakpoint trigger should be
36831 reported back to @value{GDBN}.
36833 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36834 for how to best report a software breakpoint event to @value{GDBN}.
36836 The @var{cond_list} parameter is comprised of a series of expressions,
36837 concatenated without separators. Each expression has the following form:
36841 @item X @var{len},@var{expr}
36842 @var{len} is the length of the bytecode expression and @var{expr} is the
36843 actual conditional expression in bytecode form.
36847 The optional @var{cmd_list} parameter introduces commands that may be
36848 run on the target, rather than being reported back to @value{GDBN}.
36849 The parameter starts with a numeric flag @var{persist}; if the flag is
36850 nonzero, then the breakpoint may remain active and the commands
36851 continue to be run even when @value{GDBN} disconnects from the target.
36852 Following this flag is a series of expressions concatenated with no
36853 separators. Each expression has the following form:
36857 @item X @var{len},@var{expr}
36858 @var{len} is the length of the bytecode expression and @var{expr} is the
36859 actual commands expression in bytecode form.
36863 @emph{Implementation note: It is possible for a target to copy or move
36864 code that contains software breakpoints (e.g., when implementing
36865 overlays). The behavior of this packet, in the presence of such a
36866 target, is not defined.}
36878 @item z1,@var{addr},@var{kind}
36879 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36880 @cindex @samp{z1} packet
36881 @cindex @samp{Z1} packet
36882 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36883 address @var{addr}.
36885 A hardware breakpoint is implemented using a mechanism that is not
36886 dependent on being able to modify the target's memory. The
36887 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36888 same meaning as in @samp{Z0} packets.
36890 @emph{Implementation note: A hardware breakpoint is not affected by code
36903 @item z2,@var{addr},@var{kind}
36904 @itemx Z2,@var{addr},@var{kind}
36905 @cindex @samp{z2} packet
36906 @cindex @samp{Z2} packet
36907 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36908 The number of bytes to watch is specified by @var{kind}.
36920 @item z3,@var{addr},@var{kind}
36921 @itemx Z3,@var{addr},@var{kind}
36922 @cindex @samp{z3} packet
36923 @cindex @samp{Z3} packet
36924 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36925 The number of bytes to watch is specified by @var{kind}.
36937 @item z4,@var{addr},@var{kind}
36938 @itemx Z4,@var{addr},@var{kind}
36939 @cindex @samp{z4} packet
36940 @cindex @samp{Z4} packet
36941 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36942 The number of bytes to watch is specified by @var{kind}.
36956 @node Stop Reply Packets
36957 @section Stop Reply Packets
36958 @cindex stop reply packets
36960 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36961 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36962 receive any of the below as a reply. Except for @samp{?}
36963 and @samp{vStopped}, that reply is only returned
36964 when the target halts. In the below the exact meaning of @dfn{signal
36965 number} is defined by the header @file{include/gdb/signals.h} in the
36966 @value{GDBN} source code.
36968 In non-stop mode, the server will simply reply @samp{OK} to commands
36969 such as @samp{vCont}; any stop will be the subject of a future
36970 notification. @xref{Remote Non-Stop}.
36972 As in the description of request packets, we include spaces in the
36973 reply templates for clarity; these are not part of the reply packet's
36974 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36980 The program received signal number @var{AA} (a two-digit hexadecimal
36981 number). This is equivalent to a @samp{T} response with no
36982 @var{n}:@var{r} pairs.
36984 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36985 @cindex @samp{T} packet reply
36986 The program received signal number @var{AA} (a two-digit hexadecimal
36987 number). This is equivalent to an @samp{S} response, except that the
36988 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36989 and other information directly in the stop reply packet, reducing
36990 round-trip latency. Single-step and breakpoint traps are reported
36991 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36995 If @var{n} is a hexadecimal number, it is a register number, and the
36996 corresponding @var{r} gives that register's value. The data @var{r} is a
36997 series of bytes in target byte order, with each byte given by a
36998 two-digit hex number.
37001 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
37002 the stopped thread, as specified in @ref{thread-id syntax}.
37005 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
37006 the core on which the stop event was detected.
37009 If @var{n} is a recognized @dfn{stop reason}, it describes a more
37010 specific event that stopped the target. The currently defined stop
37011 reasons are listed below. The @var{aa} should be @samp{05}, the trap
37012 signal. At most one stop reason should be present.
37015 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
37016 and go on to the next; this allows us to extend the protocol in the
37020 The currently defined stop reasons are:
37026 The packet indicates a watchpoint hit, and @var{r} is the data address, in
37029 @item syscall_entry
37030 @itemx syscall_return
37031 The packet indicates a syscall entry or return, and @var{r} is the
37032 syscall number, in hex.
37034 @cindex shared library events, remote reply
37036 The packet indicates that the loaded libraries have changed.
37037 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
37038 list of loaded libraries. The @var{r} part is ignored.
37040 @cindex replay log events, remote reply
37042 The packet indicates that the target cannot continue replaying
37043 logged execution events, because it has reached the end (or the
37044 beginning when executing backward) of the log. The value of @var{r}
37045 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
37046 for more information.
37049 @anchor{swbreak stop reason}
37050 The packet indicates a software breakpoint instruction was executed,
37051 irrespective of whether it was @value{GDBN} that planted the
37052 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
37053 part must be left empty.
37055 On some architectures, such as x86, at the architecture level, when a
37056 breakpoint instruction executes the program counter points at the
37057 breakpoint address plus an offset. On such targets, the stub is
37058 responsible for adjusting the PC to point back at the breakpoint
37061 This packet should not be sent by default; older @value{GDBN} versions
37062 did not support it. @value{GDBN} requests it, by supplying an
37063 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37064 remote stub must also supply the appropriate @samp{qSupported} feature
37065 indicating support.
37067 This packet is required for correct non-stop mode operation.
37070 The packet indicates the target stopped for a hardware breakpoint.
37071 The @var{r} part must be left empty.
37073 The same remarks about @samp{qSupported} and non-stop mode above
37076 @cindex fork events, remote reply
37078 The packet indicates that @code{fork} was called, and @var{r}
37079 is the thread ID of the new child process. Refer to
37080 @ref{thread-id syntax} for the format of the @var{thread-id}
37081 field. This packet is only applicable to targets that support
37084 This packet should not be sent by default; older @value{GDBN} versions
37085 did not support it. @value{GDBN} requests it, by supplying an
37086 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37087 remote stub must also supply the appropriate @samp{qSupported} feature
37088 indicating support.
37090 @cindex vfork events, remote reply
37092 The packet indicates that @code{vfork} was called, and @var{r}
37093 is the thread ID of the new child process. Refer to
37094 @ref{thread-id syntax} for the format of the @var{thread-id}
37095 field. This packet is only applicable to targets that support
37098 This packet should not be sent by default; older @value{GDBN} versions
37099 did not support it. @value{GDBN} requests it, by supplying an
37100 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37101 remote stub must also supply the appropriate @samp{qSupported} feature
37102 indicating support.
37104 @cindex vforkdone events, remote reply
37106 The packet indicates that a child process created by a vfork
37107 has either called @code{exec} or terminated, so that the
37108 address spaces of the parent and child process are no longer
37109 shared. The @var{r} part is ignored. This packet is only
37110 applicable to targets that support vforkdone events.
37112 This packet should not be sent by default; older @value{GDBN} versions
37113 did not support it. @value{GDBN} requests it, by supplying an
37114 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37115 remote stub must also supply the appropriate @samp{qSupported} feature
37116 indicating support.
37118 @cindex exec events, remote reply
37120 The packet indicates that @code{execve} was called, and @var{r}
37121 is the absolute pathname of the file that was executed, in hex.
37122 This packet is only applicable to targets that support exec events.
37124 This packet should not be sent by default; older @value{GDBN} versions
37125 did not support it. @value{GDBN} requests it, by supplying an
37126 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37127 remote stub must also supply the appropriate @samp{qSupported} feature
37128 indicating support.
37130 @cindex thread create event, remote reply
37131 @anchor{thread create event}
37133 The packet indicates that the thread was just created. The new thread
37134 is stopped until @value{GDBN} sets it running with a resumption packet
37135 (@pxref{vCont packet}). This packet should not be sent by default;
37136 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
37137 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
37138 @var{r} part is ignored.
37143 @itemx W @var{AA} ; process:@var{pid}
37144 The process exited, and @var{AA} is the exit status. This is only
37145 applicable to certain targets.
37147 The second form of the response, including the process ID of the
37148 exited process, can be used only when @value{GDBN} has reported
37149 support for multiprocess protocol extensions; see @ref{multiprocess
37150 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37154 @itemx X @var{AA} ; process:@var{pid}
37155 The process terminated with signal @var{AA}.
37157 The second form of the response, including the process ID of the
37158 terminated process, can be used only when @value{GDBN} has reported
37159 support for multiprocess protocol extensions; see @ref{multiprocess
37160 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37163 @anchor{thread exit event}
37164 @cindex thread exit event, remote reply
37165 @item w @var{AA} ; @var{tid}
37167 The thread exited, and @var{AA} is the exit status. This response
37168 should not be sent by default; @value{GDBN} requests it with the
37169 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
37170 @var{AA} is formatted as a big-endian hex string.
37173 There are no resumed threads left in the target. In other words, even
37174 though the process is alive, the last resumed thread has exited. For
37175 example, say the target process has two threads: thread 1 and thread
37176 2. The client leaves thread 1 stopped, and resumes thread 2, which
37177 subsequently exits. At this point, even though the process is still
37178 alive, and thus no @samp{W} stop reply is sent, no thread is actually
37179 executing either. The @samp{N} stop reply thus informs the client
37180 that it can stop waiting for stop replies. This packet should not be
37181 sent by default; older @value{GDBN} versions did not support it.
37182 @value{GDBN} requests it, by supplying an appropriate
37183 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
37184 also supply the appropriate @samp{qSupported} feature indicating
37187 @item O @var{XX}@dots{}
37188 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
37189 written as the program's console output. This can happen at any time
37190 while the program is running and the debugger should continue to wait
37191 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
37193 @item F @var{call-id},@var{parameter}@dots{}
37194 @var{call-id} is the identifier which says which host system call should
37195 be called. This is just the name of the function. Translation into the
37196 correct system call is only applicable as it's defined in @value{GDBN}.
37197 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
37200 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
37201 this very system call.
37203 The target replies with this packet when it expects @value{GDBN} to
37204 call a host system call on behalf of the target. @value{GDBN} replies
37205 with an appropriate @samp{F} packet and keeps up waiting for the next
37206 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
37207 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
37208 Protocol Extension}, for more details.
37212 @node General Query Packets
37213 @section General Query Packets
37214 @cindex remote query requests
37216 Packets starting with @samp{q} are @dfn{general query packets};
37217 packets starting with @samp{Q} are @dfn{general set packets}. General
37218 query and set packets are a semi-unified form for retrieving and
37219 sending information to and from the stub.
37221 The initial letter of a query or set packet is followed by a name
37222 indicating what sort of thing the packet applies to. For example,
37223 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
37224 definitions with the stub. These packet names follow some
37229 The name must not contain commas, colons or semicolons.
37231 Most @value{GDBN} query and set packets have a leading upper case
37234 The names of custom vendor packets should use a company prefix, in
37235 lower case, followed by a period. For example, packets designed at
37236 the Acme Corporation might begin with @samp{qacme.foo} (for querying
37237 foos) or @samp{Qacme.bar} (for setting bars).
37240 The name of a query or set packet should be separated from any
37241 parameters by a @samp{:}; the parameters themselves should be
37242 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
37243 full packet name, and check for a separator or the end of the packet,
37244 in case two packet names share a common prefix. New packets should not begin
37245 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
37246 packets predate these conventions, and have arguments without any terminator
37247 for the packet name; we suspect they are in widespread use in places that
37248 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
37249 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
37252 Like the descriptions of the other packets, each description here
37253 has a template showing the packet's overall syntax, followed by an
37254 explanation of the packet's meaning. We include spaces in some of the
37255 templates for clarity; these are not part of the packet's syntax. No
37256 @value{GDBN} packet uses spaces to separate its components.
37258 Here are the currently defined query and set packets:
37264 Turn on or off the agent as a helper to perform some debugging operations
37265 delegated from @value{GDBN} (@pxref{Control Agent}).
37267 @item QAllow:@var{op}:@var{val}@dots{}
37268 @cindex @samp{QAllow} packet
37269 Specify which operations @value{GDBN} expects to request of the
37270 target, as a semicolon-separated list of operation name and value
37271 pairs. Possible values for @var{op} include @samp{WriteReg},
37272 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
37273 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
37274 indicating that @value{GDBN} will not request the operation, or 1,
37275 indicating that it may. (The target can then use this to set up its
37276 own internals optimally, for instance if the debugger never expects to
37277 insert breakpoints, it may not need to install its own trap handler.)
37280 @cindex current thread, remote request
37281 @cindex @samp{qC} packet
37282 Return the current thread ID.
37286 @item QC @var{thread-id}
37287 Where @var{thread-id} is a thread ID as documented in
37288 @ref{thread-id syntax}.
37289 @item @r{(anything else)}
37290 Any other reply implies the old thread ID.
37293 @item qCRC:@var{addr},@var{length}
37294 @cindex CRC of memory block, remote request
37295 @cindex @samp{qCRC} packet
37296 @anchor{qCRC packet}
37297 Compute the CRC checksum of a block of memory using CRC-32 defined in
37298 IEEE 802.3. The CRC is computed byte at a time, taking the most
37299 significant bit of each byte first. The initial pattern code
37300 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
37302 @emph{Note:} This is the same CRC used in validating separate debug
37303 files (@pxref{Separate Debug Files, , Debugging Information in Separate
37304 Files}). However the algorithm is slightly different. When validating
37305 separate debug files, the CRC is computed taking the @emph{least}
37306 significant bit of each byte first, and the final result is inverted to
37307 detect trailing zeros.
37312 An error (such as memory fault)
37313 @item C @var{crc32}
37314 The specified memory region's checksum is @var{crc32}.
37317 @item QDisableRandomization:@var{value}
37318 @cindex disable address space randomization, remote request
37319 @cindex @samp{QDisableRandomization} packet
37320 Some target operating systems will randomize the virtual address space
37321 of the inferior process as a security feature, but provide a feature
37322 to disable such randomization, e.g.@: to allow for a more deterministic
37323 debugging experience. On such systems, this packet with a @var{value}
37324 of 1 directs the target to disable address space randomization for
37325 processes subsequently started via @samp{vRun} packets, while a packet
37326 with a @var{value} of 0 tells the target to enable address space
37329 This packet is only available in extended mode (@pxref{extended mode}).
37334 The request succeeded.
37337 An error occurred. The error number @var{nn} is given as hex digits.
37340 An empty reply indicates that @samp{QDisableRandomization} is not supported
37344 This packet is not probed by default; the remote stub must request it,
37345 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37346 This should only be done on targets that actually support disabling
37347 address space randomization.
37349 @item QStartupWithShell:@var{value}
37350 @cindex startup with shell, remote request
37351 @cindex @samp{QStartupWithShell} packet
37352 On UNIX-like targets, it is possible to start the inferior using a
37353 shell program. This is the default behavior on both @value{GDBN} and
37354 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
37355 used to inform @command{gdbserver} whether it should start the
37356 inferior using a shell or not.
37358 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
37359 to start the inferior. If @var{value} is @samp{1},
37360 @command{gdbserver} will use a shell to start the inferior. All other
37361 values are considered an error.
37363 This packet is only available in extended mode (@pxref{extended
37369 The request succeeded.
37372 An error occurred. The error number @var{nn} is given as hex digits.
37375 This packet is not probed by default; the remote stub must request it,
37376 by supplying an appropriate @samp{qSupported} response
37377 (@pxref{qSupported}). This should only be done on targets that
37378 actually support starting the inferior using a shell.
37380 Use of this packet is controlled by the @code{set startup-with-shell}
37381 command; @pxref{set startup-with-shell}.
37383 @item QEnvironmentHexEncoded:@var{hex-value}
37384 @anchor{QEnvironmentHexEncoded}
37385 @cindex set environment variable, remote request
37386 @cindex @samp{QEnvironmentHexEncoded} packet
37387 On UNIX-like targets, it is possible to set environment variables that
37388 will be passed to the inferior during the startup process. This
37389 packet is used to inform @command{gdbserver} of an environment
37390 variable that has been defined by the user on @value{GDBN} (@pxref{set
37393 The packet is composed by @var{hex-value}, an hex encoded
37394 representation of the @var{name=value} format representing an
37395 environment variable. The name of the environment variable is
37396 represented by @var{name}, and the value to be assigned to the
37397 environment variable is represented by @var{value}. If the variable
37398 has no value (i.e., the value is @code{null}), then @var{value} will
37401 This packet is only available in extended mode (@pxref{extended
37407 The request succeeded.
37410 This packet is not probed by default; the remote stub must request it,
37411 by supplying an appropriate @samp{qSupported} response
37412 (@pxref{qSupported}). This should only be done on targets that
37413 actually support passing environment variables to the starting
37416 This packet is related to the @code{set environment} command;
37417 @pxref{set environment}.
37419 @item QEnvironmentUnset:@var{hex-value}
37420 @anchor{QEnvironmentUnset}
37421 @cindex unset environment variable, remote request
37422 @cindex @samp{QEnvironmentUnset} packet
37423 On UNIX-like targets, it is possible to unset environment variables
37424 before starting the inferior in the remote target. This packet is
37425 used to inform @command{gdbserver} of an environment variable that has
37426 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37428 The packet is composed by @var{hex-value}, an hex encoded
37429 representation of the name of the environment variable to be unset.
37431 This packet is only available in extended mode (@pxref{extended
37437 The request succeeded.
37440 This packet is not probed by default; the remote stub must request it,
37441 by supplying an appropriate @samp{qSupported} response
37442 (@pxref{qSupported}). This should only be done on targets that
37443 actually support passing environment variables to the starting
37446 This packet is related to the @code{unset environment} command;
37447 @pxref{unset environment}.
37449 @item QEnvironmentReset
37450 @anchor{QEnvironmentReset}
37451 @cindex reset environment, remote request
37452 @cindex @samp{QEnvironmentReset} packet
37453 On UNIX-like targets, this packet is used to reset the state of
37454 environment variables in the remote target before starting the
37455 inferior. In this context, reset means unsetting all environment
37456 variables that were previously set by the user (i.e., were not
37457 initially present in the environment). It is sent to
37458 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37459 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37460 (@pxref{QEnvironmentUnset}) packets.
37462 This packet is only available in extended mode (@pxref{extended
37468 The request succeeded.
37471 This packet is not probed by default; the remote stub must request it,
37472 by supplying an appropriate @samp{qSupported} response
37473 (@pxref{qSupported}). This should only be done on targets that
37474 actually support passing environment variables to the starting
37477 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37478 @anchor{QSetWorkingDir packet}
37479 @cindex set working directory, remote request
37480 @cindex @samp{QSetWorkingDir} packet
37481 This packet is used to inform the remote server of the intended
37482 current working directory for programs that are going to be executed.
37484 The packet is composed by @var{directory}, an hex encoded
37485 representation of the directory that the remote inferior will use as
37486 its current working directory. If @var{directory} is an empty string,
37487 the remote server should reset the inferior's current working
37488 directory to its original, empty value.
37490 This packet is only available in extended mode (@pxref{extended
37496 The request succeeded.
37500 @itemx qsThreadInfo
37501 @cindex list active threads, remote request
37502 @cindex @samp{qfThreadInfo} packet
37503 @cindex @samp{qsThreadInfo} packet
37504 Obtain a list of all active thread IDs from the target (OS). Since there
37505 may be too many active threads to fit into one reply packet, this query
37506 works iteratively: it may require more than one query/reply sequence to
37507 obtain the entire list of threads. The first query of the sequence will
37508 be the @samp{qfThreadInfo} query; subsequent queries in the
37509 sequence will be the @samp{qsThreadInfo} query.
37511 NOTE: This packet replaces the @samp{qL} query (see below).
37515 @item m @var{thread-id}
37517 @item m @var{thread-id},@var{thread-id}@dots{}
37518 a comma-separated list of thread IDs
37520 (lower case letter @samp{L}) denotes end of list.
37523 In response to each query, the target will reply with a list of one or
37524 more thread IDs, separated by commas.
37525 @value{GDBN} will respond to each reply with a request for more thread
37526 ids (using the @samp{qs} form of the query), until the target responds
37527 with @samp{l} (lower-case ell, for @dfn{last}).
37528 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37531 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37532 initial connection with the remote target, and the very first thread ID
37533 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37534 message. Therefore, the stub should ensure that the first thread ID in
37535 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37537 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37538 @cindex get thread-local storage address, remote request
37539 @cindex @samp{qGetTLSAddr} packet
37540 Fetch the address associated with thread local storage specified
37541 by @var{thread-id}, @var{offset}, and @var{lm}.
37543 @var{thread-id} is the thread ID associated with the
37544 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37546 @var{offset} is the (big endian, hex encoded) offset associated with the
37547 thread local variable. (This offset is obtained from the debug
37548 information associated with the variable.)
37550 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37551 load module associated with the thread local storage. For example,
37552 a @sc{gnu}/Linux system will pass the link map address of the shared
37553 object associated with the thread local storage under consideration.
37554 Other operating environments may choose to represent the load module
37555 differently, so the precise meaning of this parameter will vary.
37559 @item @var{XX}@dots{}
37560 Hex encoded (big endian) bytes representing the address of the thread
37561 local storage requested.
37564 An error occurred. The error number @var{nn} is given as hex digits.
37567 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37570 @item qGetTIBAddr:@var{thread-id}
37571 @cindex get thread information block address
37572 @cindex @samp{qGetTIBAddr} packet
37573 Fetch address of the Windows OS specific Thread Information Block.
37575 @var{thread-id} is the thread ID associated with the thread.
37579 @item @var{XX}@dots{}
37580 Hex encoded (big endian) bytes representing the linear address of the
37581 thread information block.
37584 An error occured. This means that either the thread was not found, or the
37585 address could not be retrieved.
37588 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37591 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37592 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37593 digit) is one to indicate the first query and zero to indicate a
37594 subsequent query; @var{threadcount} (two hex digits) is the maximum
37595 number of threads the response packet can contain; and @var{nextthread}
37596 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37597 returned in the response as @var{argthread}.
37599 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37603 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37604 Where: @var{count} (two hex digits) is the number of threads being
37605 returned; @var{done} (one hex digit) is zero to indicate more threads
37606 and one indicates no further threads; @var{argthreadid} (eight hex
37607 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37608 is a sequence of thread IDs, @var{threadid} (eight hex
37609 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37613 @cindex section offsets, remote request
37614 @cindex @samp{qOffsets} packet
37615 Get section offsets that the target used when relocating the downloaded
37620 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37621 Relocate the @code{Text} section by @var{xxx} from its original address.
37622 Relocate the @code{Data} section by @var{yyy} from its original address.
37623 If the object file format provides segment information (e.g.@: @sc{elf}
37624 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37625 segments by the supplied offsets.
37627 @emph{Note: while a @code{Bss} offset may be included in the response,
37628 @value{GDBN} ignores this and instead applies the @code{Data} offset
37629 to the @code{Bss} section.}
37631 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37632 Relocate the first segment of the object file, which conventionally
37633 contains program code, to a starting address of @var{xxx}. If
37634 @samp{DataSeg} is specified, relocate the second segment, which
37635 conventionally contains modifiable data, to a starting address of
37636 @var{yyy}. @value{GDBN} will report an error if the object file
37637 does not contain segment information, or does not contain at least
37638 as many segments as mentioned in the reply. Extra segments are
37639 kept at fixed offsets relative to the last relocated segment.
37642 @item qP @var{mode} @var{thread-id}
37643 @cindex thread information, remote request
37644 @cindex @samp{qP} packet
37645 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37646 encoded 32 bit mode; @var{thread-id} is a thread ID
37647 (@pxref{thread-id syntax}).
37649 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37652 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37656 @cindex non-stop mode, remote request
37657 @cindex @samp{QNonStop} packet
37659 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37660 @xref{Remote Non-Stop}, for more information.
37665 The request succeeded.
37668 An error occurred. The error number @var{nn} is given as hex digits.
37671 An empty reply indicates that @samp{QNonStop} is not supported by
37675 This packet is not probed by default; the remote stub must request it,
37676 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37677 Use of this packet is controlled by the @code{set non-stop} command;
37678 @pxref{Non-Stop Mode}.
37680 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37681 @itemx QCatchSyscalls:0
37682 @cindex catch syscalls from inferior, remote request
37683 @cindex @samp{QCatchSyscalls} packet
37684 @anchor{QCatchSyscalls}
37685 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37686 catching syscalls from the inferior process.
37688 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37689 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37690 is listed, every system call should be reported.
37692 Note that if a syscall not in the list is reported, @value{GDBN} will
37693 still filter the event according to its own list from all corresponding
37694 @code{catch syscall} commands. However, it is more efficient to only
37695 report the requested syscalls.
37697 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37698 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37700 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37701 kept for the new process too. On targets where exec may affect syscall
37702 numbers, for example with exec between 32 and 64-bit processes, the
37703 client should send a new packet with the new syscall list.
37708 The request succeeded.
37711 An error occurred. @var{nn} are hex digits.
37714 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37718 Use of this packet is controlled by the @code{set remote catch-syscalls}
37719 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37720 This packet is not probed by default; the remote stub must request it,
37721 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37723 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37724 @cindex pass signals to inferior, remote request
37725 @cindex @samp{QPassSignals} packet
37726 @anchor{QPassSignals}
37727 Each listed @var{signal} should be passed directly to the inferior process.
37728 Signals are numbered identically to continue packets and stop replies
37729 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37730 strictly greater than the previous item. These signals do not need to stop
37731 the inferior, or be reported to @value{GDBN}. All other signals should be
37732 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37733 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37734 new list. This packet improves performance when using @samp{handle
37735 @var{signal} nostop noprint pass}.
37740 The request succeeded.
37743 An error occurred. The error number @var{nn} is given as hex digits.
37746 An empty reply indicates that @samp{QPassSignals} is not supported by
37750 Use of this packet is controlled by the @code{set remote pass-signals}
37751 command (@pxref{Remote Configuration, set remote pass-signals}).
37752 This packet is not probed by default; the remote stub must request it,
37753 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37755 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37756 @cindex signals the inferior may see, remote request
37757 @cindex @samp{QProgramSignals} packet
37758 @anchor{QProgramSignals}
37759 Each listed @var{signal} may be delivered to the inferior process.
37760 Others should be silently discarded.
37762 In some cases, the remote stub may need to decide whether to deliver a
37763 signal to the program or not without @value{GDBN} involvement. One
37764 example of that is while detaching --- the program's threads may have
37765 stopped for signals that haven't yet had a chance of being reported to
37766 @value{GDBN}, and so the remote stub can use the signal list specified
37767 by this packet to know whether to deliver or ignore those pending
37770 This does not influence whether to deliver a signal as requested by a
37771 resumption packet (@pxref{vCont packet}).
37773 Signals are numbered identically to continue packets and stop replies
37774 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37775 strictly greater than the previous item. Multiple
37776 @samp{QProgramSignals} packets do not combine; any earlier
37777 @samp{QProgramSignals} list is completely replaced by the new list.
37782 The request succeeded.
37785 An error occurred. The error number @var{nn} is given as hex digits.
37788 An empty reply indicates that @samp{QProgramSignals} is not supported
37792 Use of this packet is controlled by the @code{set remote program-signals}
37793 command (@pxref{Remote Configuration, set remote program-signals}).
37794 This packet is not probed by default; the remote stub must request it,
37795 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37797 @anchor{QThreadEvents}
37798 @item QThreadEvents:1
37799 @itemx QThreadEvents:0
37800 @cindex thread create/exit events, remote request
37801 @cindex @samp{QThreadEvents} packet
37803 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37804 reporting of thread create and exit events. @xref{thread create
37805 event}, for the reply specifications. For example, this is used in
37806 non-stop mode when @value{GDBN} stops a set of threads and
37807 synchronously waits for the their corresponding stop replies. Without
37808 exit events, if one of the threads exits, @value{GDBN} would hang
37809 forever not knowing that it should no longer expect a stop for that
37810 same thread. @value{GDBN} does not enable this feature unless the
37811 stub reports that it supports it by including @samp{QThreadEvents+} in
37812 its @samp{qSupported} reply.
37817 The request succeeded.
37820 An error occurred. The error number @var{nn} is given as hex digits.
37823 An empty reply indicates that @samp{QThreadEvents} is not supported by
37827 Use of this packet is controlled by the @code{set remote thread-events}
37828 command (@pxref{Remote Configuration, set remote thread-events}).
37830 @item qRcmd,@var{command}
37831 @cindex execute remote command, remote request
37832 @cindex @samp{qRcmd} packet
37833 @var{command} (hex encoded) is passed to the local interpreter for
37834 execution. Invalid commands should be reported using the output
37835 string. Before the final result packet, the target may also respond
37836 with a number of intermediate @samp{O@var{output}} console output
37837 packets. @emph{Implementors should note that providing access to a
37838 stubs's interpreter may have security implications}.
37843 A command response with no output.
37845 A command response with the hex encoded output string @var{OUTPUT}.
37847 Indicate a badly formed request.
37849 An empty reply indicates that @samp{qRcmd} is not recognized.
37852 (Note that the @code{qRcmd} packet's name is separated from the
37853 command by a @samp{,}, not a @samp{:}, contrary to the naming
37854 conventions above. Please don't use this packet as a model for new
37857 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37858 @cindex searching memory, in remote debugging
37860 @cindex @samp{qSearch:memory} packet
37862 @cindex @samp{qSearch memory} packet
37863 @anchor{qSearch memory}
37864 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37865 Both @var{address} and @var{length} are encoded in hex;
37866 @var{search-pattern} is a sequence of bytes, also hex encoded.
37871 The pattern was not found.
37873 The pattern was found at @var{address}.
37875 A badly formed request or an error was encountered while searching memory.
37877 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37880 @item QStartNoAckMode
37881 @cindex @samp{QStartNoAckMode} packet
37882 @anchor{QStartNoAckMode}
37883 Request that the remote stub disable the normal @samp{+}/@samp{-}
37884 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37889 The stub has switched to no-acknowledgment mode.
37890 @value{GDBN} acknowledges this reponse,
37891 but neither the stub nor @value{GDBN} shall send or expect further
37892 @samp{+}/@samp{-} acknowledgments in the current connection.
37894 An empty reply indicates that the stub does not support no-acknowledgment mode.
37897 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37898 @cindex supported packets, remote query
37899 @cindex features of the remote protocol
37900 @cindex @samp{qSupported} packet
37901 @anchor{qSupported}
37902 Tell the remote stub about features supported by @value{GDBN}, and
37903 query the stub for features it supports. This packet allows
37904 @value{GDBN} and the remote stub to take advantage of each others'
37905 features. @samp{qSupported} also consolidates multiple feature probes
37906 at startup, to improve @value{GDBN} performance---a single larger
37907 packet performs better than multiple smaller probe packets on
37908 high-latency links. Some features may enable behavior which must not
37909 be on by default, e.g.@: because it would confuse older clients or
37910 stubs. Other features may describe packets which could be
37911 automatically probed for, but are not. These features must be
37912 reported before @value{GDBN} will use them. This ``default
37913 unsupported'' behavior is not appropriate for all packets, but it
37914 helps to keep the initial connection time under control with new
37915 versions of @value{GDBN} which support increasing numbers of packets.
37919 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37920 The stub supports or does not support each returned @var{stubfeature},
37921 depending on the form of each @var{stubfeature} (see below for the
37924 An empty reply indicates that @samp{qSupported} is not recognized,
37925 or that no features needed to be reported to @value{GDBN}.
37928 The allowed forms for each feature (either a @var{gdbfeature} in the
37929 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37933 @item @var{name}=@var{value}
37934 The remote protocol feature @var{name} is supported, and associated
37935 with the specified @var{value}. The format of @var{value} depends
37936 on the feature, but it must not include a semicolon.
37938 The remote protocol feature @var{name} is supported, and does not
37939 need an associated value.
37941 The remote protocol feature @var{name} is not supported.
37943 The remote protocol feature @var{name} may be supported, and
37944 @value{GDBN} should auto-detect support in some other way when it is
37945 needed. This form will not be used for @var{gdbfeature} notifications,
37946 but may be used for @var{stubfeature} responses.
37949 Whenever the stub receives a @samp{qSupported} request, the
37950 supplied set of @value{GDBN} features should override any previous
37951 request. This allows @value{GDBN} to put the stub in a known
37952 state, even if the stub had previously been communicating with
37953 a different version of @value{GDBN}.
37955 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37960 This feature indicates whether @value{GDBN} supports multiprocess
37961 extensions to the remote protocol. @value{GDBN} does not use such
37962 extensions unless the stub also reports that it supports them by
37963 including @samp{multiprocess+} in its @samp{qSupported} reply.
37964 @xref{multiprocess extensions}, for details.
37967 This feature indicates that @value{GDBN} supports the XML target
37968 description. If the stub sees @samp{xmlRegisters=} with target
37969 specific strings separated by a comma, it will report register
37973 This feature indicates whether @value{GDBN} supports the
37974 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37975 instruction reply packet}).
37978 This feature indicates whether @value{GDBN} supports the swbreak stop
37979 reason in stop replies. @xref{swbreak stop reason}, for details.
37982 This feature indicates whether @value{GDBN} supports the hwbreak stop
37983 reason in stop replies. @xref{swbreak stop reason}, for details.
37986 This feature indicates whether @value{GDBN} supports fork event
37987 extensions to the remote protocol. @value{GDBN} does not use such
37988 extensions unless the stub also reports that it supports them by
37989 including @samp{fork-events+} in its @samp{qSupported} reply.
37992 This feature indicates whether @value{GDBN} supports vfork event
37993 extensions to the remote protocol. @value{GDBN} does not use such
37994 extensions unless the stub also reports that it supports them by
37995 including @samp{vfork-events+} in its @samp{qSupported} reply.
37998 This feature indicates whether @value{GDBN} supports exec event
37999 extensions to the remote protocol. @value{GDBN} does not use such
38000 extensions unless the stub also reports that it supports them by
38001 including @samp{exec-events+} in its @samp{qSupported} reply.
38003 @item vContSupported
38004 This feature indicates whether @value{GDBN} wants to know the
38005 supported actions in the reply to @samp{vCont?} packet.
38008 Stubs should ignore any unknown values for
38009 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38010 packet supports receiving packets of unlimited length (earlier
38011 versions of @value{GDBN} may reject overly long responses). Additional values
38012 for @var{gdbfeature} may be defined in the future to let the stub take
38013 advantage of new features in @value{GDBN}, e.g.@: incompatible
38014 improvements in the remote protocol---the @samp{multiprocess} feature is
38015 an example of such a feature. The stub's reply should be independent
38016 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38017 describes all the features it supports, and then the stub replies with
38018 all the features it supports.
38020 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38021 responses, as long as each response uses one of the standard forms.
38023 Some features are flags. A stub which supports a flag feature
38024 should respond with a @samp{+} form response. Other features
38025 require values, and the stub should respond with an @samp{=}
38028 Each feature has a default value, which @value{GDBN} will use if
38029 @samp{qSupported} is not available or if the feature is not mentioned
38030 in the @samp{qSupported} response. The default values are fixed; a
38031 stub is free to omit any feature responses that match the defaults.
38033 Not all features can be probed, but for those which can, the probing
38034 mechanism is useful: in some cases, a stub's internal
38035 architecture may not allow the protocol layer to know some information
38036 about the underlying target in advance. This is especially common in
38037 stubs which may be configured for multiple targets.
38039 These are the currently defined stub features and their properties:
38041 @multitable @columnfractions 0.35 0.2 0.12 0.2
38042 @c NOTE: The first row should be @headitem, but we do not yet require
38043 @c a new enough version of Texinfo (4.7) to use @headitem.
38045 @tab Value Required
38049 @item @samp{PacketSize}
38054 @item @samp{qXfer:auxv:read}
38059 @item @samp{qXfer:btrace:read}
38064 @item @samp{qXfer:btrace-conf:read}
38069 @item @samp{qXfer:exec-file:read}
38074 @item @samp{qXfer:features:read}
38079 @item @samp{qXfer:libraries:read}
38084 @item @samp{qXfer:libraries-svr4:read}
38089 @item @samp{augmented-libraries-svr4-read}
38094 @item @samp{qXfer:memory-map:read}
38099 @item @samp{qXfer:sdata:read}
38104 @item @samp{qXfer:spu:read}
38109 @item @samp{qXfer:spu:write}
38114 @item @samp{qXfer:siginfo:read}
38119 @item @samp{qXfer:siginfo:write}
38124 @item @samp{qXfer:threads:read}
38129 @item @samp{qXfer:traceframe-info:read}
38134 @item @samp{qXfer:uib:read}
38139 @item @samp{qXfer:fdpic:read}
38144 @item @samp{Qbtrace:off}
38149 @item @samp{Qbtrace:bts}
38154 @item @samp{Qbtrace:pt}
38159 @item @samp{Qbtrace-conf:bts:size}
38164 @item @samp{Qbtrace-conf:pt:size}
38169 @item @samp{QNonStop}
38174 @item @samp{QCatchSyscalls}
38179 @item @samp{QPassSignals}
38184 @item @samp{QStartNoAckMode}
38189 @item @samp{multiprocess}
38194 @item @samp{ConditionalBreakpoints}
38199 @item @samp{ConditionalTracepoints}
38204 @item @samp{ReverseContinue}
38209 @item @samp{ReverseStep}
38214 @item @samp{TracepointSource}
38219 @item @samp{QAgent}
38224 @item @samp{QAllow}
38229 @item @samp{QDisableRandomization}
38234 @item @samp{EnableDisableTracepoints}
38239 @item @samp{QTBuffer:size}
38244 @item @samp{tracenz}
38249 @item @samp{BreakpointCommands}
38254 @item @samp{swbreak}
38259 @item @samp{hwbreak}
38264 @item @samp{fork-events}
38269 @item @samp{vfork-events}
38274 @item @samp{exec-events}
38279 @item @samp{QThreadEvents}
38284 @item @samp{no-resumed}
38291 These are the currently defined stub features, in more detail:
38294 @cindex packet size, remote protocol
38295 @item PacketSize=@var{bytes}
38296 The remote stub can accept packets up to at least @var{bytes} in
38297 length. @value{GDBN} will send packets up to this size for bulk
38298 transfers, and will never send larger packets. This is a limit on the
38299 data characters in the packet, including the frame and checksum.
38300 There is no trailing NUL byte in a remote protocol packet; if the stub
38301 stores packets in a NUL-terminated format, it should allow an extra
38302 byte in its buffer for the NUL. If this stub feature is not supported,
38303 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38305 @item qXfer:auxv:read
38306 The remote stub understands the @samp{qXfer:auxv:read} packet
38307 (@pxref{qXfer auxiliary vector read}).
38309 @item qXfer:btrace:read
38310 The remote stub understands the @samp{qXfer:btrace:read}
38311 packet (@pxref{qXfer btrace read}).
38313 @item qXfer:btrace-conf:read
38314 The remote stub understands the @samp{qXfer:btrace-conf:read}
38315 packet (@pxref{qXfer btrace-conf read}).
38317 @item qXfer:exec-file:read
38318 The remote stub understands the @samp{qXfer:exec-file:read} packet
38319 (@pxref{qXfer executable filename read}).
38321 @item qXfer:features:read
38322 The remote stub understands the @samp{qXfer:features:read} packet
38323 (@pxref{qXfer target description read}).
38325 @item qXfer:libraries:read
38326 The remote stub understands the @samp{qXfer:libraries:read} packet
38327 (@pxref{qXfer library list read}).
38329 @item qXfer:libraries-svr4:read
38330 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38331 (@pxref{qXfer svr4 library list read}).
38333 @item augmented-libraries-svr4-read
38334 The remote stub understands the augmented form of the
38335 @samp{qXfer:libraries-svr4:read} packet
38336 (@pxref{qXfer svr4 library list read}).
38338 @item qXfer:memory-map:read
38339 The remote stub understands the @samp{qXfer:memory-map:read} packet
38340 (@pxref{qXfer memory map read}).
38342 @item qXfer:sdata:read
38343 The remote stub understands the @samp{qXfer:sdata:read} packet
38344 (@pxref{qXfer sdata read}).
38346 @item qXfer:spu:read
38347 The remote stub understands the @samp{qXfer:spu:read} packet
38348 (@pxref{qXfer spu read}).
38350 @item qXfer:spu:write
38351 The remote stub understands the @samp{qXfer:spu:write} packet
38352 (@pxref{qXfer spu write}).
38354 @item qXfer:siginfo:read
38355 The remote stub understands the @samp{qXfer:siginfo:read} packet
38356 (@pxref{qXfer siginfo read}).
38358 @item qXfer:siginfo:write
38359 The remote stub understands the @samp{qXfer:siginfo:write} packet
38360 (@pxref{qXfer siginfo write}).
38362 @item qXfer:threads:read
38363 The remote stub understands the @samp{qXfer:threads:read} packet
38364 (@pxref{qXfer threads read}).
38366 @item qXfer:traceframe-info:read
38367 The remote stub understands the @samp{qXfer:traceframe-info:read}
38368 packet (@pxref{qXfer traceframe info read}).
38370 @item qXfer:uib:read
38371 The remote stub understands the @samp{qXfer:uib:read}
38372 packet (@pxref{qXfer unwind info block}).
38374 @item qXfer:fdpic:read
38375 The remote stub understands the @samp{qXfer:fdpic:read}
38376 packet (@pxref{qXfer fdpic loadmap read}).
38379 The remote stub understands the @samp{QNonStop} packet
38380 (@pxref{QNonStop}).
38382 @item QCatchSyscalls
38383 The remote stub understands the @samp{QCatchSyscalls} packet
38384 (@pxref{QCatchSyscalls}).
38387 The remote stub understands the @samp{QPassSignals} packet
38388 (@pxref{QPassSignals}).
38390 @item QStartNoAckMode
38391 The remote stub understands the @samp{QStartNoAckMode} packet and
38392 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38395 @anchor{multiprocess extensions}
38396 @cindex multiprocess extensions, in remote protocol
38397 The remote stub understands the multiprocess extensions to the remote
38398 protocol syntax. The multiprocess extensions affect the syntax of
38399 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38400 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38401 replies. Note that reporting this feature indicates support for the
38402 syntactic extensions only, not that the stub necessarily supports
38403 debugging of more than one process at a time. The stub must not use
38404 multiprocess extensions in packet replies unless @value{GDBN} has also
38405 indicated it supports them in its @samp{qSupported} request.
38407 @item qXfer:osdata:read
38408 The remote stub understands the @samp{qXfer:osdata:read} packet
38409 ((@pxref{qXfer osdata read}).
38411 @item ConditionalBreakpoints
38412 The target accepts and implements evaluation of conditional expressions
38413 defined for breakpoints. The target will only report breakpoint triggers
38414 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38416 @item ConditionalTracepoints
38417 The remote stub accepts and implements conditional expressions defined
38418 for tracepoints (@pxref{Tracepoint Conditions}).
38420 @item ReverseContinue
38421 The remote stub accepts and implements the reverse continue packet
38425 The remote stub accepts and implements the reverse step packet
38428 @item TracepointSource
38429 The remote stub understands the @samp{QTDPsrc} packet that supplies
38430 the source form of tracepoint definitions.
38433 The remote stub understands the @samp{QAgent} packet.
38436 The remote stub understands the @samp{QAllow} packet.
38438 @item QDisableRandomization
38439 The remote stub understands the @samp{QDisableRandomization} packet.
38441 @item StaticTracepoint
38442 @cindex static tracepoints, in remote protocol
38443 The remote stub supports static tracepoints.
38445 @item InstallInTrace
38446 @anchor{install tracepoint in tracing}
38447 The remote stub supports installing tracepoint in tracing.
38449 @item EnableDisableTracepoints
38450 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38451 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38452 to be enabled and disabled while a trace experiment is running.
38454 @item QTBuffer:size
38455 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38456 packet that allows to change the size of the trace buffer.
38459 @cindex string tracing, in remote protocol
38460 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38461 See @ref{Bytecode Descriptions} for details about the bytecode.
38463 @item BreakpointCommands
38464 @cindex breakpoint commands, in remote protocol
38465 The remote stub supports running a breakpoint's command list itself,
38466 rather than reporting the hit to @value{GDBN}.
38469 The remote stub understands the @samp{Qbtrace:off} packet.
38472 The remote stub understands the @samp{Qbtrace:bts} packet.
38475 The remote stub understands the @samp{Qbtrace:pt} packet.
38477 @item Qbtrace-conf:bts:size
38478 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38480 @item Qbtrace-conf:pt:size
38481 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38484 The remote stub reports the @samp{swbreak} stop reason for memory
38488 The remote stub reports the @samp{hwbreak} stop reason for hardware
38492 The remote stub reports the @samp{fork} stop reason for fork events.
38495 The remote stub reports the @samp{vfork} stop reason for vfork events
38496 and vforkdone events.
38499 The remote stub reports the @samp{exec} stop reason for exec events.
38501 @item vContSupported
38502 The remote stub reports the supported actions in the reply to
38503 @samp{vCont?} packet.
38505 @item QThreadEvents
38506 The remote stub understands the @samp{QThreadEvents} packet.
38509 The remote stub reports the @samp{N} stop reply.
38514 @cindex symbol lookup, remote request
38515 @cindex @samp{qSymbol} packet
38516 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38517 requests. Accept requests from the target for the values of symbols.
38522 The target does not need to look up any (more) symbols.
38523 @item qSymbol:@var{sym_name}
38524 The target requests the value of symbol @var{sym_name} (hex encoded).
38525 @value{GDBN} may provide the value by using the
38526 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38530 @item qSymbol:@var{sym_value}:@var{sym_name}
38531 Set the value of @var{sym_name} to @var{sym_value}.
38533 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38534 target has previously requested.
38536 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38537 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38543 The target does not need to look up any (more) symbols.
38544 @item qSymbol:@var{sym_name}
38545 The target requests the value of a new symbol @var{sym_name} (hex
38546 encoded). @value{GDBN} will continue to supply the values of symbols
38547 (if available), until the target ceases to request them.
38552 @itemx QTDisconnected
38559 @itemx qTMinFTPILen
38561 @xref{Tracepoint Packets}.
38563 @item qThreadExtraInfo,@var{thread-id}
38564 @cindex thread attributes info, remote request
38565 @cindex @samp{qThreadExtraInfo} packet
38566 Obtain from the target OS a printable string description of thread
38567 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38568 for the forms of @var{thread-id}. This
38569 string may contain anything that the target OS thinks is interesting
38570 for @value{GDBN} to tell the user about the thread. The string is
38571 displayed in @value{GDBN}'s @code{info threads} display. Some
38572 examples of possible thread extra info strings are @samp{Runnable}, or
38573 @samp{Blocked on Mutex}.
38577 @item @var{XX}@dots{}
38578 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38579 comprising the printable string containing the extra information about
38580 the thread's attributes.
38583 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38584 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38585 conventions above. Please don't use this packet as a model for new
38604 @xref{Tracepoint Packets}.
38606 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38607 @cindex read special object, remote request
38608 @cindex @samp{qXfer} packet
38609 @anchor{qXfer read}
38610 Read uninterpreted bytes from the target's special data area
38611 identified by the keyword @var{object}. Request @var{length} bytes
38612 starting at @var{offset} bytes into the data. The content and
38613 encoding of @var{annex} is specific to @var{object}; it can supply
38614 additional details about what data to access.
38619 Data @var{data} (@pxref{Binary Data}) has been read from the
38620 target. There may be more data at a higher address (although
38621 it is permitted to return @samp{m} even for the last valid
38622 block of data, as long as at least one byte of data was read).
38623 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38627 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38628 There is no more data to be read. It is possible for @var{data} to
38629 have fewer bytes than the @var{length} in the request.
38632 The @var{offset} in the request is at the end of the data.
38633 There is no more data to be read.
38636 The request was malformed, or @var{annex} was invalid.
38639 The offset was invalid, or there was an error encountered reading the data.
38640 The @var{nn} part is a hex-encoded @code{errno} value.
38643 An empty reply indicates the @var{object} string was not recognized by
38644 the stub, or that the object does not support reading.
38647 Here are the specific requests of this form defined so far. All the
38648 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38649 formats, listed above.
38652 @item qXfer:auxv:read::@var{offset},@var{length}
38653 @anchor{qXfer auxiliary vector read}
38654 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38655 auxiliary vector}. Note @var{annex} must be empty.
38657 This packet is not probed by default; the remote stub must request it,
38658 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38660 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38661 @anchor{qXfer btrace read}
38663 Return a description of the current branch trace.
38664 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38665 packet may have one of the following values:
38669 Returns all available branch trace.
38672 Returns all available branch trace if the branch trace changed since
38673 the last read request.
38676 Returns the new branch trace since the last read request. Adds a new
38677 block to the end of the trace that begins at zero and ends at the source
38678 location of the first branch in the trace buffer. This extra block is
38679 used to stitch traces together.
38681 If the trace buffer overflowed, returns an error indicating the overflow.
38684 This packet is not probed by default; the remote stub must request it
38685 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38687 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38688 @anchor{qXfer btrace-conf read}
38690 Return a description of the current branch trace configuration.
38691 @xref{Branch Trace Configuration Format}.
38693 This packet is not probed by default; the remote stub must request it
38694 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38696 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38697 @anchor{qXfer executable filename read}
38698 Return the full absolute name of the file that was executed to create
38699 a process running on the remote system. The annex specifies the
38700 numeric process ID of the process to query, encoded as a hexadecimal
38701 number. If the annex part is empty the remote stub should return the
38702 filename corresponding to the currently executing process.
38704 This packet is not probed by default; the remote stub must request it,
38705 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38707 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38708 @anchor{qXfer target description read}
38709 Access the @dfn{target description}. @xref{Target Descriptions}. The
38710 annex specifies which XML document to access. The main description is
38711 always loaded from the @samp{target.xml} annex.
38713 This packet is not probed by default; the remote stub must request it,
38714 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38716 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38717 @anchor{qXfer library list read}
38718 Access the target's list of loaded libraries. @xref{Library List Format}.
38719 The annex part of the generic @samp{qXfer} packet must be empty
38720 (@pxref{qXfer read}).
38722 Targets which maintain a list of libraries in the program's memory do
38723 not need to implement this packet; it is designed for platforms where
38724 the operating system manages the list of loaded libraries.
38726 This packet is not probed by default; the remote stub must request it,
38727 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38729 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38730 @anchor{qXfer svr4 library list read}
38731 Access the target's list of loaded libraries when the target is an SVR4
38732 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38733 of the generic @samp{qXfer} packet must be empty unless the remote
38734 stub indicated it supports the augmented form of this packet
38735 by supplying an appropriate @samp{qSupported} response
38736 (@pxref{qXfer read}, @ref{qSupported}).
38738 This packet is optional for better performance on SVR4 targets.
38739 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38741 This packet is not probed by default; the remote stub must request it,
38742 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38744 If the remote stub indicates it supports the augmented form of this
38745 packet then the annex part of the generic @samp{qXfer} packet may
38746 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38747 arguments. The currently supported arguments are:
38750 @item start=@var{address}
38751 A hexadecimal number specifying the address of the @samp{struct
38752 link_map} to start reading the library list from. If unset or zero
38753 then the first @samp{struct link_map} in the library list will be
38754 chosen as the starting point.
38756 @item prev=@var{address}
38757 A hexadecimal number specifying the address of the @samp{struct
38758 link_map} immediately preceding the @samp{struct link_map}
38759 specified by the @samp{start} argument. If unset or zero then
38760 the remote stub will expect that no @samp{struct link_map}
38761 exists prior to the starting point.
38765 Arguments that are not understood by the remote stub will be silently
38768 @item qXfer:memory-map:read::@var{offset},@var{length}
38769 @anchor{qXfer memory map read}
38770 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38771 annex part of the generic @samp{qXfer} packet must be empty
38772 (@pxref{qXfer read}).
38774 This packet is not probed by default; the remote stub must request it,
38775 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38777 @item qXfer:sdata:read::@var{offset},@var{length}
38778 @anchor{qXfer sdata read}
38780 Read contents of the extra collected static tracepoint marker
38781 information. The annex part of the generic @samp{qXfer} packet must
38782 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38785 This packet is not probed by default; the remote stub must request it,
38786 by supplying an appropriate @samp{qSupported} response
38787 (@pxref{qSupported}).
38789 @item qXfer:siginfo:read::@var{offset},@var{length}
38790 @anchor{qXfer siginfo read}
38791 Read contents of the extra signal information on the target
38792 system. The annex part of the generic @samp{qXfer} packet must be
38793 empty (@pxref{qXfer read}).
38795 This packet is not probed by default; the remote stub must request it,
38796 by supplying an appropriate @samp{qSupported} response
38797 (@pxref{qSupported}).
38799 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38800 @anchor{qXfer spu read}
38801 Read contents of an @code{spufs} file on the target system. The
38802 annex specifies which file to read; it must be of the form
38803 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38804 in the target process, and @var{name} identifes the @code{spufs} file
38805 in that context to be accessed.
38807 This packet is not probed by default; the remote stub must request it,
38808 by supplying an appropriate @samp{qSupported} response
38809 (@pxref{qSupported}).
38811 @item qXfer:threads:read::@var{offset},@var{length}
38812 @anchor{qXfer threads read}
38813 Access the list of threads on target. @xref{Thread List Format}. The
38814 annex part of the generic @samp{qXfer} packet must be empty
38815 (@pxref{qXfer read}).
38817 This packet is not probed by default; the remote stub must request it,
38818 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38820 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38821 @anchor{qXfer traceframe info read}
38823 Return a description of the current traceframe's contents.
38824 @xref{Traceframe Info Format}. The annex part of the generic
38825 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38827 This packet is not probed by default; the remote stub must request it,
38828 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38830 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38831 @anchor{qXfer unwind info block}
38833 Return the unwind information block for @var{pc}. This packet is used
38834 on OpenVMS/ia64 to ask the kernel unwind information.
38836 This packet is not probed by default.
38838 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38839 @anchor{qXfer fdpic loadmap read}
38840 Read contents of @code{loadmap}s on the target system. The
38841 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38842 executable @code{loadmap} or interpreter @code{loadmap} to read.
38844 This packet is not probed by default; the remote stub must request it,
38845 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38847 @item qXfer:osdata:read::@var{offset},@var{length}
38848 @anchor{qXfer osdata read}
38849 Access the target's @dfn{operating system information}.
38850 @xref{Operating System Information}.
38854 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38855 @cindex write data into object, remote request
38856 @anchor{qXfer write}
38857 Write uninterpreted bytes into the target's special data area
38858 identified by the keyword @var{object}, starting at @var{offset} bytes
38859 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38860 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38861 is specific to @var{object}; it can supply additional details about what data
38867 @var{nn} (hex encoded) is the number of bytes written.
38868 This may be fewer bytes than supplied in the request.
38871 The request was malformed, or @var{annex} was invalid.
38874 The offset was invalid, or there was an error encountered writing the data.
38875 The @var{nn} part is a hex-encoded @code{errno} value.
38878 An empty reply indicates the @var{object} string was not
38879 recognized by the stub, or that the object does not support writing.
38882 Here are the specific requests of this form defined so far. All the
38883 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38884 formats, listed above.
38887 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38888 @anchor{qXfer siginfo write}
38889 Write @var{data} to the extra signal information on the target system.
38890 The annex part of the generic @samp{qXfer} packet must be
38891 empty (@pxref{qXfer write}).
38893 This packet is not probed by default; the remote stub must request it,
38894 by supplying an appropriate @samp{qSupported} response
38895 (@pxref{qSupported}).
38897 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38898 @anchor{qXfer spu write}
38899 Write @var{data} to an @code{spufs} file on the target system. The
38900 annex specifies which file to write; it must be of the form
38901 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38902 in the target process, and @var{name} identifes the @code{spufs} file
38903 in that context to be accessed.
38905 This packet is not probed by default; the remote stub must request it,
38906 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38909 @item qXfer:@var{object}:@var{operation}:@dots{}
38910 Requests of this form may be added in the future. When a stub does
38911 not recognize the @var{object} keyword, or its support for
38912 @var{object} does not recognize the @var{operation} keyword, the stub
38913 must respond with an empty packet.
38915 @item qAttached:@var{pid}
38916 @cindex query attached, remote request
38917 @cindex @samp{qAttached} packet
38918 Return an indication of whether the remote server attached to an
38919 existing process or created a new process. When the multiprocess
38920 protocol extensions are supported (@pxref{multiprocess extensions}),
38921 @var{pid} is an integer in hexadecimal format identifying the target
38922 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38923 the query packet will be simplified as @samp{qAttached}.
38925 This query is used, for example, to know whether the remote process
38926 should be detached or killed when a @value{GDBN} session is ended with
38927 the @code{quit} command.
38932 The remote server attached to an existing process.
38934 The remote server created a new process.
38936 A badly formed request or an error was encountered.
38940 Enable branch tracing for the current thread using Branch Trace Store.
38945 Branch tracing has been enabled.
38947 A badly formed request or an error was encountered.
38951 Enable branch tracing for the current thread using Intel Processor Trace.
38956 Branch tracing has been enabled.
38958 A badly formed request or an error was encountered.
38962 Disable branch tracing for the current thread.
38967 Branch tracing has been disabled.
38969 A badly formed request or an error was encountered.
38972 @item Qbtrace-conf:bts:size=@var{value}
38973 Set the requested ring buffer size for new threads that use the
38974 btrace recording method in bts format.
38979 The ring buffer size has been set.
38981 A badly formed request or an error was encountered.
38984 @item Qbtrace-conf:pt:size=@var{value}
38985 Set the requested ring buffer size for new threads that use the
38986 btrace recording method in pt format.
38991 The ring buffer size has been set.
38993 A badly formed request or an error was encountered.
38998 @node Architecture-Specific Protocol Details
38999 @section Architecture-Specific Protocol Details
39001 This section describes how the remote protocol is applied to specific
39002 target architectures. Also see @ref{Standard Target Features}, for
39003 details of XML target descriptions for each architecture.
39006 * ARM-Specific Protocol Details::
39007 * MIPS-Specific Protocol Details::
39010 @node ARM-Specific Protocol Details
39011 @subsection @acronym{ARM}-specific Protocol Details
39014 * ARM Breakpoint Kinds::
39017 @node ARM Breakpoint Kinds
39018 @subsubsection @acronym{ARM} Breakpoint Kinds
39019 @cindex breakpoint kinds, @acronym{ARM}
39021 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39026 16-bit Thumb mode breakpoint.
39029 32-bit Thumb mode (Thumb-2) breakpoint.
39032 32-bit @acronym{ARM} mode breakpoint.
39036 @node MIPS-Specific Protocol Details
39037 @subsection @acronym{MIPS}-specific Protocol Details
39040 * MIPS Register packet Format::
39041 * MIPS Breakpoint Kinds::
39044 @node MIPS Register packet Format
39045 @subsubsection @acronym{MIPS} Register Packet Format
39046 @cindex register packet format, @acronym{MIPS}
39048 The following @code{g}/@code{G} packets have previously been defined.
39049 In the below, some thirty-two bit registers are transferred as
39050 sixty-four bits. Those registers should be zero/sign extended (which?)
39051 to fill the space allocated. Register bytes are transferred in target
39052 byte order. The two nibbles within a register byte are transferred
39053 most-significant -- least-significant.
39058 All registers are transferred as thirty-two bit quantities in the order:
39059 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39060 registers; fsr; fir; fp.
39063 All registers are transferred as sixty-four bit quantities (including
39064 thirty-two bit registers such as @code{sr}). The ordering is the same
39069 @node MIPS Breakpoint Kinds
39070 @subsubsection @acronym{MIPS} Breakpoint Kinds
39071 @cindex breakpoint kinds, @acronym{MIPS}
39073 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39078 16-bit @acronym{MIPS16} mode breakpoint.
39081 16-bit @acronym{microMIPS} mode breakpoint.
39084 32-bit standard @acronym{MIPS} mode breakpoint.
39087 32-bit @acronym{microMIPS} mode breakpoint.
39091 @node Tracepoint Packets
39092 @section Tracepoint Packets
39093 @cindex tracepoint packets
39094 @cindex packets, tracepoint
39096 Here we describe the packets @value{GDBN} uses to implement
39097 tracepoints (@pxref{Tracepoints}).
39101 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39102 @cindex @samp{QTDP} packet
39103 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39104 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39105 the tracepoint is disabled. The @var{step} gives the tracepoint's step
39106 count, and @var{pass} gives its pass count. If an @samp{F} is present,
39107 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39108 the number of bytes that the target should copy elsewhere to make room
39109 for the tracepoint. If an @samp{X} is present, it introduces a
39110 tracepoint condition, which consists of a hexadecimal length, followed
39111 by a comma and hex-encoded bytes, in a manner similar to action
39112 encodings as described below. If the trailing @samp{-} is present,
39113 further @samp{QTDP} packets will follow to specify this tracepoint's
39119 The packet was understood and carried out.
39121 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39123 The packet was not recognized.
39126 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39127 Define actions to be taken when a tracepoint is hit. The @var{n} and
39128 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39129 this tracepoint. This packet may only be sent immediately after
39130 another @samp{QTDP} packet that ended with a @samp{-}. If the
39131 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39132 specifying more actions for this tracepoint.
39134 In the series of action packets for a given tracepoint, at most one
39135 can have an @samp{S} before its first @var{action}. If such a packet
39136 is sent, it and the following packets define ``while-stepping''
39137 actions. Any prior packets define ordinary actions --- that is, those
39138 taken when the tracepoint is first hit. If no action packet has an
39139 @samp{S}, then all the packets in the series specify ordinary
39140 tracepoint actions.
39142 The @samp{@var{action}@dots{}} portion of the packet is a series of
39143 actions, concatenated without separators. Each action has one of the
39149 Collect the registers whose bits are set in @var{mask},
39150 a hexadecimal number whose @var{i}'th bit is set if register number
39151 @var{i} should be collected. (The least significant bit is numbered
39152 zero.) Note that @var{mask} may be any number of digits long; it may
39153 not fit in a 32-bit word.
39155 @item M @var{basereg},@var{offset},@var{len}
39156 Collect @var{len} bytes of memory starting at the address in register
39157 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39158 @samp{-1}, then the range has a fixed address: @var{offset} is the
39159 address of the lowest byte to collect. The @var{basereg},
39160 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39161 values (the @samp{-1} value for @var{basereg} is a special case).
39163 @item X @var{len},@var{expr}
39164 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39165 it directs. The agent expression @var{expr} is as described in
39166 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39167 two-digit hex number in the packet; @var{len} is the number of bytes
39168 in the expression (and thus one-half the number of hex digits in the
39173 Any number of actions may be packed together in a single @samp{QTDP}
39174 packet, as long as the packet does not exceed the maximum packet
39175 length (400 bytes, for many stubs). There may be only one @samp{R}
39176 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39177 actions. Any registers referred to by @samp{M} and @samp{X} actions
39178 must be collected by a preceding @samp{R} action. (The
39179 ``while-stepping'' actions are treated as if they were attached to a
39180 separate tracepoint, as far as these restrictions are concerned.)
39185 The packet was understood and carried out.
39187 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39189 The packet was not recognized.
39192 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39193 @cindex @samp{QTDPsrc} packet
39194 Specify a source string of tracepoint @var{n} at address @var{addr}.
39195 This is useful to get accurate reproduction of the tracepoints
39196 originally downloaded at the beginning of the trace run. The @var{type}
39197 is the name of the tracepoint part, such as @samp{cond} for the
39198 tracepoint's conditional expression (see below for a list of types), while
39199 @var{bytes} is the string, encoded in hexadecimal.
39201 @var{start} is the offset of the @var{bytes} within the overall source
39202 string, while @var{slen} is the total length of the source string.
39203 This is intended for handling source strings that are longer than will
39204 fit in a single packet.
39205 @c Add detailed example when this info is moved into a dedicated
39206 @c tracepoint descriptions section.
39208 The available string types are @samp{at} for the location,
39209 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39210 @value{GDBN} sends a separate packet for each command in the action
39211 list, in the same order in which the commands are stored in the list.
39213 The target does not need to do anything with source strings except
39214 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39217 Although this packet is optional, and @value{GDBN} will only send it
39218 if the target replies with @samp{TracepointSource} @xref{General
39219 Query Packets}, it makes both disconnected tracing and trace files
39220 much easier to use. Otherwise the user must be careful that the
39221 tracepoints in effect while looking at trace frames are identical to
39222 the ones in effect during the trace run; even a small discrepancy
39223 could cause @samp{tdump} not to work, or a particular trace frame not
39226 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
39227 @cindex define trace state variable, remote request
39228 @cindex @samp{QTDV} packet
39229 Create a new trace state variable, number @var{n}, with an initial
39230 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39231 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39232 the option of not using this packet for initial values of zero; the
39233 target should simply create the trace state variables as they are
39234 mentioned in expressions. The value @var{builtin} should be 1 (one)
39235 if the trace state variable is builtin and 0 (zero) if it is not builtin.
39236 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
39237 @samp{qTsV} packet had it set. The contents of @var{name} is the
39238 hex-encoded name (without the leading @samp{$}) of the trace state
39241 @item QTFrame:@var{n}
39242 @cindex @samp{QTFrame} packet
39243 Select the @var{n}'th tracepoint frame from the buffer, and use the
39244 register and memory contents recorded there to answer subsequent
39245 request packets from @value{GDBN}.
39247 A successful reply from the stub indicates that the stub has found the
39248 requested frame. The response is a series of parts, concatenated
39249 without separators, describing the frame we selected. Each part has
39250 one of the following forms:
39254 The selected frame is number @var{n} in the trace frame buffer;
39255 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39256 was no frame matching the criteria in the request packet.
39259 The selected trace frame records a hit of tracepoint number @var{t};
39260 @var{t} is a hexadecimal number.
39264 @item QTFrame:pc:@var{addr}
39265 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39266 currently selected frame whose PC is @var{addr};
39267 @var{addr} is a hexadecimal number.
39269 @item QTFrame:tdp:@var{t}
39270 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39271 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39272 is a hexadecimal number.
39274 @item QTFrame:range:@var{start}:@var{end}
39275 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39276 currently selected frame whose PC is between @var{start} (inclusive)
39277 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39280 @item QTFrame:outside:@var{start}:@var{end}
39281 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39282 frame @emph{outside} the given range of addresses (exclusive).
39285 @cindex @samp{qTMinFTPILen} packet
39286 This packet requests the minimum length of instruction at which a fast
39287 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39288 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39289 it depends on the target system being able to create trampolines in
39290 the first 64K of memory, which might or might not be possible for that
39291 system. So the reply to this packet will be 4 if it is able to
39298 The minimum instruction length is currently unknown.
39300 The minimum instruction length is @var{length}, where @var{length}
39301 is a hexadecimal number greater or equal to 1. A reply
39302 of 1 means that a fast tracepoint may be placed on any instruction
39303 regardless of size.
39305 An error has occurred.
39307 An empty reply indicates that the request is not supported by the stub.
39311 @cindex @samp{QTStart} packet
39312 Begin the tracepoint experiment. Begin collecting data from
39313 tracepoint hits in the trace frame buffer. This packet supports the
39314 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39315 instruction reply packet}).
39318 @cindex @samp{QTStop} packet
39319 End the tracepoint experiment. Stop collecting trace frames.
39321 @item QTEnable:@var{n}:@var{addr}
39323 @cindex @samp{QTEnable} packet
39324 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39325 experiment. If the tracepoint was previously disabled, then collection
39326 of data from it will resume.
39328 @item QTDisable:@var{n}:@var{addr}
39330 @cindex @samp{QTDisable} packet
39331 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39332 experiment. No more data will be collected from the tracepoint unless
39333 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39336 @cindex @samp{QTinit} packet
39337 Clear the table of tracepoints, and empty the trace frame buffer.
39339 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39340 @cindex @samp{QTro} packet
39341 Establish the given ranges of memory as ``transparent''. The stub
39342 will answer requests for these ranges from memory's current contents,
39343 if they were not collected as part of the tracepoint hit.
39345 @value{GDBN} uses this to mark read-only regions of memory, like those
39346 containing program code. Since these areas never change, they should
39347 still have the same contents they did when the tracepoint was hit, so
39348 there's no reason for the stub to refuse to provide their contents.
39350 @item QTDisconnected:@var{value}
39351 @cindex @samp{QTDisconnected} packet
39352 Set the choice to what to do with the tracing run when @value{GDBN}
39353 disconnects from the target. A @var{value} of 1 directs the target to
39354 continue the tracing run, while 0 tells the target to stop tracing if
39355 @value{GDBN} is no longer in the picture.
39358 @cindex @samp{qTStatus} packet
39359 Ask the stub if there is a trace experiment running right now.
39361 The reply has the form:
39365 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39366 @var{running} is a single digit @code{1} if the trace is presently
39367 running, or @code{0} if not. It is followed by semicolon-separated
39368 optional fields that an agent may use to report additional status.
39372 If the trace is not running, the agent may report any of several
39373 explanations as one of the optional fields:
39378 No trace has been run yet.
39380 @item tstop[:@var{text}]:0
39381 The trace was stopped by a user-originated stop command. The optional
39382 @var{text} field is a user-supplied string supplied as part of the
39383 stop command (for instance, an explanation of why the trace was
39384 stopped manually). It is hex-encoded.
39387 The trace stopped because the trace buffer filled up.
39389 @item tdisconnected:0
39390 The trace stopped because @value{GDBN} disconnected from the target.
39392 @item tpasscount:@var{tpnum}
39393 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39395 @item terror:@var{text}:@var{tpnum}
39396 The trace stopped because tracepoint @var{tpnum} had an error. The
39397 string @var{text} is available to describe the nature of the error
39398 (for instance, a divide by zero in the condition expression); it
39402 The trace stopped for some other reason.
39406 Additional optional fields supply statistical and other information.
39407 Although not required, they are extremely useful for users monitoring
39408 the progress of a trace run. If a trace has stopped, and these
39409 numbers are reported, they must reflect the state of the just-stopped
39414 @item tframes:@var{n}
39415 The number of trace frames in the buffer.
39417 @item tcreated:@var{n}
39418 The total number of trace frames created during the run. This may
39419 be larger than the trace frame count, if the buffer is circular.
39421 @item tsize:@var{n}
39422 The total size of the trace buffer, in bytes.
39424 @item tfree:@var{n}
39425 The number of bytes still unused in the buffer.
39427 @item circular:@var{n}
39428 The value of the circular trace buffer flag. @code{1} means that the
39429 trace buffer is circular and old trace frames will be discarded if
39430 necessary to make room, @code{0} means that the trace buffer is linear
39433 @item disconn:@var{n}
39434 The value of the disconnected tracing flag. @code{1} means that
39435 tracing will continue after @value{GDBN} disconnects, @code{0} means
39436 that the trace run will stop.
39440 @item qTP:@var{tp}:@var{addr}
39441 @cindex tracepoint status, remote request
39442 @cindex @samp{qTP} packet
39443 Ask the stub for the current state of tracepoint number @var{tp} at
39444 address @var{addr}.
39448 @item V@var{hits}:@var{usage}
39449 The tracepoint has been hit @var{hits} times so far during the trace
39450 run, and accounts for @var{usage} in the trace buffer. Note that
39451 @code{while-stepping} steps are not counted as separate hits, but the
39452 steps' space consumption is added into the usage number.
39456 @item qTV:@var{var}
39457 @cindex trace state variable value, remote request
39458 @cindex @samp{qTV} packet
39459 Ask the stub for the value of the trace state variable number @var{var}.
39464 The value of the variable is @var{value}. This will be the current
39465 value of the variable if the user is examining a running target, or a
39466 saved value if the variable was collected in the trace frame that the
39467 user is looking at. Note that multiple requests may result in
39468 different reply values, such as when requesting values while the
39469 program is running.
39472 The value of the variable is unknown. This would occur, for example,
39473 if the user is examining a trace frame in which the requested variable
39478 @cindex @samp{qTfP} packet
39480 @cindex @samp{qTsP} packet
39481 These packets request data about tracepoints that are being used by
39482 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39483 of data, and multiple @code{qTsP} to get additional pieces. Replies
39484 to these packets generally take the form of the @code{QTDP} packets
39485 that define tracepoints. (FIXME add detailed syntax)
39488 @cindex @samp{qTfV} packet
39490 @cindex @samp{qTsV} packet
39491 These packets request data about trace state variables that are on the
39492 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39493 and multiple @code{qTsV} to get additional variables. Replies to
39494 these packets follow the syntax of the @code{QTDV} packets that define
39495 trace state variables.
39501 @cindex @samp{qTfSTM} packet
39502 @cindex @samp{qTsSTM} packet
39503 These packets request data about static tracepoint markers that exist
39504 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39505 first piece of data, and multiple @code{qTsSTM} to get additional
39506 pieces. Replies to these packets take the following form:
39510 @item m @var{address}:@var{id}:@var{extra}
39512 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39513 a comma-separated list of markers
39515 (lower case letter @samp{L}) denotes end of list.
39517 An error occurred. The error number @var{nn} is given as hex digits.
39519 An empty reply indicates that the request is not supported by the
39523 The @var{address} is encoded in hex;
39524 @var{id} and @var{extra} are strings encoded in hex.
39526 In response to each query, the target will reply with a list of one or
39527 more markers, separated by commas. @value{GDBN} will respond to each
39528 reply with a request for more markers (using the @samp{qs} form of the
39529 query), until the target responds with @samp{l} (lower-case ell, for
39532 @item qTSTMat:@var{address}
39534 @cindex @samp{qTSTMat} packet
39535 This packets requests data about static tracepoint markers in the
39536 target program at @var{address}. Replies to this packet follow the
39537 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39538 tracepoint markers.
39540 @item QTSave:@var{filename}
39541 @cindex @samp{QTSave} packet
39542 This packet directs the target to save trace data to the file name
39543 @var{filename} in the target's filesystem. The @var{filename} is encoded
39544 as a hex string; the interpretation of the file name (relative vs
39545 absolute, wild cards, etc) is up to the target.
39547 @item qTBuffer:@var{offset},@var{len}
39548 @cindex @samp{qTBuffer} packet
39549 Return up to @var{len} bytes of the current contents of trace buffer,
39550 starting at @var{offset}. The trace buffer is treated as if it were
39551 a contiguous collection of traceframes, as per the trace file format.
39552 The reply consists as many hex-encoded bytes as the target can deliver
39553 in a packet; it is not an error to return fewer than were asked for.
39554 A reply consisting of just @code{l} indicates that no bytes are
39557 @item QTBuffer:circular:@var{value}
39558 This packet directs the target to use a circular trace buffer if
39559 @var{value} is 1, or a linear buffer if the value is 0.
39561 @item QTBuffer:size:@var{size}
39562 @anchor{QTBuffer-size}
39563 @cindex @samp{QTBuffer size} packet
39564 This packet directs the target to make the trace buffer be of size
39565 @var{size} if possible. A value of @code{-1} tells the target to
39566 use whatever size it prefers.
39568 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39569 @cindex @samp{QTNotes} packet
39570 This packet adds optional textual notes to the trace run. Allowable
39571 types include @code{user}, @code{notes}, and @code{tstop}, the
39572 @var{text} fields are arbitrary strings, hex-encoded.
39576 @subsection Relocate instruction reply packet
39577 When installing fast tracepoints in memory, the target may need to
39578 relocate the instruction currently at the tracepoint address to a
39579 different address in memory. For most instructions, a simple copy is
39580 enough, but, for example, call instructions that implicitly push the
39581 return address on the stack, and relative branches or other
39582 PC-relative instructions require offset adjustment, so that the effect
39583 of executing the instruction at a different address is the same as if
39584 it had executed in the original location.
39586 In response to several of the tracepoint packets, the target may also
39587 respond with a number of intermediate @samp{qRelocInsn} request
39588 packets before the final result packet, to have @value{GDBN} handle
39589 this relocation operation. If a packet supports this mechanism, its
39590 documentation will explicitly say so. See for example the above
39591 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39592 format of the request is:
39595 @item qRelocInsn:@var{from};@var{to}
39597 This requests @value{GDBN} to copy instruction at address @var{from}
39598 to address @var{to}, possibly adjusted so that executing the
39599 instruction at @var{to} has the same effect as executing it at
39600 @var{from}. @value{GDBN} writes the adjusted instruction to target
39601 memory starting at @var{to}.
39606 @item qRelocInsn:@var{adjusted_size}
39607 Informs the stub the relocation is complete. The @var{adjusted_size} is
39608 the length in bytes of resulting relocated instruction sequence.
39610 A badly formed request was detected, or an error was encountered while
39611 relocating the instruction.
39614 @node Host I/O Packets
39615 @section Host I/O Packets
39616 @cindex Host I/O, remote protocol
39617 @cindex file transfer, remote protocol
39619 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39620 operations on the far side of a remote link. For example, Host I/O is
39621 used to upload and download files to a remote target with its own
39622 filesystem. Host I/O uses the same constant values and data structure
39623 layout as the target-initiated File-I/O protocol. However, the
39624 Host I/O packets are structured differently. The target-initiated
39625 protocol relies on target memory to store parameters and buffers.
39626 Host I/O requests are initiated by @value{GDBN}, and the
39627 target's memory is not involved. @xref{File-I/O Remote Protocol
39628 Extension}, for more details on the target-initiated protocol.
39630 The Host I/O request packets all encode a single operation along with
39631 its arguments. They have this format:
39635 @item vFile:@var{operation}: @var{parameter}@dots{}
39636 @var{operation} is the name of the particular request; the target
39637 should compare the entire packet name up to the second colon when checking
39638 for a supported operation. The format of @var{parameter} depends on
39639 the operation. Numbers are always passed in hexadecimal. Negative
39640 numbers have an explicit minus sign (i.e.@: two's complement is not
39641 used). Strings (e.g.@: filenames) are encoded as a series of
39642 hexadecimal bytes. The last argument to a system call may be a
39643 buffer of escaped binary data (@pxref{Binary Data}).
39647 The valid responses to Host I/O packets are:
39651 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39652 @var{result} is the integer value returned by this operation, usually
39653 non-negative for success and -1 for errors. If an error has occured,
39654 @var{errno} will be included in the result specifying a
39655 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39656 operations which return data, @var{attachment} supplies the data as a
39657 binary buffer. Binary buffers in response packets are escaped in the
39658 normal way (@pxref{Binary Data}). See the individual packet
39659 documentation for the interpretation of @var{result} and
39663 An empty response indicates that this operation is not recognized.
39667 These are the supported Host I/O operations:
39670 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39671 Open a file at @var{filename} and return a file descriptor for it, or
39672 return -1 if an error occurs. The @var{filename} is a string,
39673 @var{flags} is an integer indicating a mask of open flags
39674 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39675 of mode bits to use if the file is created (@pxref{mode_t Values}).
39676 @xref{open}, for details of the open flags and mode values.
39678 @item vFile:close: @var{fd}
39679 Close the open file corresponding to @var{fd} and return 0, or
39680 -1 if an error occurs.
39682 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39683 Read data from the open file corresponding to @var{fd}. Up to
39684 @var{count} bytes will be read from the file, starting at @var{offset}
39685 relative to the start of the file. The target may read fewer bytes;
39686 common reasons include packet size limits and an end-of-file
39687 condition. The number of bytes read is returned. Zero should only be
39688 returned for a successful read at the end of the file, or if
39689 @var{count} was zero.
39691 The data read should be returned as a binary attachment on success.
39692 If zero bytes were read, the response should include an empty binary
39693 attachment (i.e.@: a trailing semicolon). The return value is the
39694 number of target bytes read; the binary attachment may be longer if
39695 some characters were escaped.
39697 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39698 Write @var{data} (a binary buffer) to the open file corresponding
39699 to @var{fd}. Start the write at @var{offset} from the start of the
39700 file. Unlike many @code{write} system calls, there is no
39701 separate @var{count} argument; the length of @var{data} in the
39702 packet is used. @samp{vFile:write} returns the number of bytes written,
39703 which may be shorter than the length of @var{data}, or -1 if an
39706 @item vFile:fstat: @var{fd}
39707 Get information about the open file corresponding to @var{fd}.
39708 On success the information is returned as a binary attachment
39709 and the return value is the size of this attachment in bytes.
39710 If an error occurs the return value is -1. The format of the
39711 returned binary attachment is as described in @ref{struct stat}.
39713 @item vFile:unlink: @var{filename}
39714 Delete the file at @var{filename} on the target. Return 0,
39715 or -1 if an error occurs. The @var{filename} is a string.
39717 @item vFile:readlink: @var{filename}
39718 Read value of symbolic link @var{filename} on the target. Return
39719 the number of bytes read, or -1 if an error occurs.
39721 The data read should be returned as a binary attachment on success.
39722 If zero bytes were read, the response should include an empty binary
39723 attachment (i.e.@: a trailing semicolon). The return value is the
39724 number of target bytes read; the binary attachment may be longer if
39725 some characters were escaped.
39727 @item vFile:setfs: @var{pid}
39728 Select the filesystem on which @code{vFile} operations with
39729 @var{filename} arguments will operate. This is required for
39730 @value{GDBN} to be able to access files on remote targets where
39731 the remote stub does not share a common filesystem with the
39734 If @var{pid} is nonzero, select the filesystem as seen by process
39735 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39736 the remote stub. Return 0 on success, or -1 if an error occurs.
39737 If @code{vFile:setfs:} indicates success, the selected filesystem
39738 remains selected until the next successful @code{vFile:setfs:}
39744 @section Interrupts
39745 @cindex interrupts (remote protocol)
39746 @anchor{interrupting remote targets}
39748 In all-stop mode, when a program on the remote target is running,
39749 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39750 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39751 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39753 The precise meaning of @code{BREAK} is defined by the transport
39754 mechanism and may, in fact, be undefined. @value{GDBN} does not
39755 currently define a @code{BREAK} mechanism for any of the network
39756 interfaces except for TCP, in which case @value{GDBN} sends the
39757 @code{telnet} BREAK sequence.
39759 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39760 transport mechanisms. It is represented by sending the single byte
39761 @code{0x03} without any of the usual packet overhead described in
39762 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39763 transmitted as part of a packet, it is considered to be packet data
39764 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39765 (@pxref{X packet}), used for binary downloads, may include an unescaped
39766 @code{0x03} as part of its packet.
39768 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39769 When Linux kernel receives this sequence from serial port,
39770 it stops execution and connects to gdb.
39772 In non-stop mode, because packet resumptions are asynchronous
39773 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39774 command to the remote stub, even when the target is running. For that
39775 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39776 packet}) with the usual packet framing instead of the single byte
39779 Stubs are not required to recognize these interrupt mechanisms and the
39780 precise meaning associated with receipt of the interrupt is
39781 implementation defined. If the target supports debugging of multiple
39782 threads and/or processes, it should attempt to interrupt all
39783 currently-executing threads and processes.
39784 If the stub is successful at interrupting the
39785 running program, it should send one of the stop
39786 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39787 of successfully stopping the program in all-stop mode, and a stop reply
39788 for each stopped thread in non-stop mode.
39789 Interrupts received while the
39790 program is stopped are queued and the program will be interrupted when
39791 it is resumed next time.
39793 @node Notification Packets
39794 @section Notification Packets
39795 @cindex notification packets
39796 @cindex packets, notification
39798 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39799 packets that require no acknowledgment. Both the GDB and the stub
39800 may send notifications (although the only notifications defined at
39801 present are sent by the stub). Notifications carry information
39802 without incurring the round-trip latency of an acknowledgment, and so
39803 are useful for low-impact communications where occasional packet loss
39806 A notification packet has the form @samp{% @var{data} #
39807 @var{checksum}}, where @var{data} is the content of the notification,
39808 and @var{checksum} is a checksum of @var{data}, computed and formatted
39809 as for ordinary @value{GDBN} packets. A notification's @var{data}
39810 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39811 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39812 to acknowledge the notification's receipt or to report its corruption.
39814 Every notification's @var{data} begins with a name, which contains no
39815 colon characters, followed by a colon character.
39817 Recipients should silently ignore corrupted notifications and
39818 notifications they do not understand. Recipients should restart
39819 timeout periods on receipt of a well-formed notification, whether or
39820 not they understand it.
39822 Senders should only send the notifications described here when this
39823 protocol description specifies that they are permitted. In the
39824 future, we may extend the protocol to permit existing notifications in
39825 new contexts; this rule helps older senders avoid confusing newer
39828 (Older versions of @value{GDBN} ignore bytes received until they see
39829 the @samp{$} byte that begins an ordinary packet, so new stubs may
39830 transmit notifications without fear of confusing older clients. There
39831 are no notifications defined for @value{GDBN} to send at the moment, but we
39832 assume that most older stubs would ignore them, as well.)
39834 Each notification is comprised of three parts:
39836 @item @var{name}:@var{event}
39837 The notification packet is sent by the side that initiates the
39838 exchange (currently, only the stub does that), with @var{event}
39839 carrying the specific information about the notification, and
39840 @var{name} specifying the name of the notification.
39842 The acknowledge sent by the other side, usually @value{GDBN}, to
39843 acknowledge the exchange and request the event.
39846 The purpose of an asynchronous notification mechanism is to report to
39847 @value{GDBN} that something interesting happened in the remote stub.
39849 The remote stub may send notification @var{name}:@var{event}
39850 at any time, but @value{GDBN} acknowledges the notification when
39851 appropriate. The notification event is pending before @value{GDBN}
39852 acknowledges. Only one notification at a time may be pending; if
39853 additional events occur before @value{GDBN} has acknowledged the
39854 previous notification, they must be queued by the stub for later
39855 synchronous transmission in response to @var{ack} packets from
39856 @value{GDBN}. Because the notification mechanism is unreliable,
39857 the stub is permitted to resend a notification if it believes
39858 @value{GDBN} may not have received it.
39860 Specifically, notifications may appear when @value{GDBN} is not
39861 otherwise reading input from the stub, or when @value{GDBN} is
39862 expecting to read a normal synchronous response or a
39863 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39864 Notification packets are distinct from any other communication from
39865 the stub so there is no ambiguity.
39867 After receiving a notification, @value{GDBN} shall acknowledge it by
39868 sending a @var{ack} packet as a regular, synchronous request to the
39869 stub. Such acknowledgment is not required to happen immediately, as
39870 @value{GDBN} is permitted to send other, unrelated packets to the
39871 stub first, which the stub should process normally.
39873 Upon receiving a @var{ack} packet, if the stub has other queued
39874 events to report to @value{GDBN}, it shall respond by sending a
39875 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39876 packet to solicit further responses; again, it is permitted to send
39877 other, unrelated packets as well which the stub should process
39880 If the stub receives a @var{ack} packet and there are no additional
39881 @var{event} to report, the stub shall return an @samp{OK} response.
39882 At this point, @value{GDBN} has finished processing a notification
39883 and the stub has completed sending any queued events. @value{GDBN}
39884 won't accept any new notifications until the final @samp{OK} is
39885 received . If further notification events occur, the stub shall send
39886 a new notification, @value{GDBN} shall accept the notification, and
39887 the process shall be repeated.
39889 The process of asynchronous notification can be illustrated by the
39892 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39895 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39897 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39902 The following notifications are defined:
39903 @multitable @columnfractions 0.12 0.12 0.38 0.38
39912 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39913 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39914 for information on how these notifications are acknowledged by
39916 @tab Report an asynchronous stop event in non-stop mode.
39920 @node Remote Non-Stop
39921 @section Remote Protocol Support for Non-Stop Mode
39923 @value{GDBN}'s remote protocol supports non-stop debugging of
39924 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39925 supports non-stop mode, it should report that to @value{GDBN} by including
39926 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39928 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39929 establishing a new connection with the stub. Entering non-stop mode
39930 does not alter the state of any currently-running threads, but targets
39931 must stop all threads in any already-attached processes when entering
39932 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39933 probe the target state after a mode change.
39935 In non-stop mode, when an attached process encounters an event that
39936 would otherwise be reported with a stop reply, it uses the
39937 asynchronous notification mechanism (@pxref{Notification Packets}) to
39938 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39939 in all processes are stopped when a stop reply is sent, in non-stop
39940 mode only the thread reporting the stop event is stopped. That is,
39941 when reporting a @samp{S} or @samp{T} response to indicate completion
39942 of a step operation, hitting a breakpoint, or a fault, only the
39943 affected thread is stopped; any other still-running threads continue
39944 to run. When reporting a @samp{W} or @samp{X} response, all running
39945 threads belonging to other attached processes continue to run.
39947 In non-stop mode, the target shall respond to the @samp{?} packet as
39948 follows. First, any incomplete stop reply notification/@samp{vStopped}
39949 sequence in progress is abandoned. The target must begin a new
39950 sequence reporting stop events for all stopped threads, whether or not
39951 it has previously reported those events to @value{GDBN}. The first
39952 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39953 subsequent stop replies are sent as responses to @samp{vStopped} packets
39954 using the mechanism described above. The target must not send
39955 asynchronous stop reply notifications until the sequence is complete.
39956 If all threads are running when the target receives the @samp{?} packet,
39957 or if the target is not attached to any process, it shall respond
39960 If the stub supports non-stop mode, it should also support the
39961 @samp{swbreak} stop reason if software breakpoints are supported, and
39962 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39963 (@pxref{swbreak stop reason}). This is because given the asynchronous
39964 nature of non-stop mode, between the time a thread hits a breakpoint
39965 and the time the event is finally processed by @value{GDBN}, the
39966 breakpoint may have already been removed from the target. Due to
39967 this, @value{GDBN} needs to be able to tell whether a trap stop was
39968 caused by a delayed breakpoint event, which should be ignored, as
39969 opposed to a random trap signal, which should be reported to the user.
39970 Note the @samp{swbreak} feature implies that the target is responsible
39971 for adjusting the PC when a software breakpoint triggers, if
39972 necessary, such as on the x86 architecture.
39974 @node Packet Acknowledgment
39975 @section Packet Acknowledgment
39977 @cindex acknowledgment, for @value{GDBN} remote
39978 @cindex packet acknowledgment, for @value{GDBN} remote
39979 By default, when either the host or the target machine receives a packet,
39980 the first response expected is an acknowledgment: either @samp{+} (to indicate
39981 the package was received correctly) or @samp{-} (to request retransmission).
39982 This mechanism allows the @value{GDBN} remote protocol to operate over
39983 unreliable transport mechanisms, such as a serial line.
39985 In cases where the transport mechanism is itself reliable (such as a pipe or
39986 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39987 It may be desirable to disable them in that case to reduce communication
39988 overhead, or for other reasons. This can be accomplished by means of the
39989 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39991 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39992 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39993 and response format still includes the normal checksum, as described in
39994 @ref{Overview}, but the checksum may be ignored by the receiver.
39996 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39997 no-acknowledgment mode, it should report that to @value{GDBN}
39998 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39999 @pxref{qSupported}.
40000 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40001 disabled via the @code{set remote noack-packet off} command
40002 (@pxref{Remote Configuration}),
40003 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40004 Only then may the stub actually turn off packet acknowledgments.
40005 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40006 response, which can be safely ignored by the stub.
40008 Note that @code{set remote noack-packet} command only affects negotiation
40009 between @value{GDBN} and the stub when subsequent connections are made;
40010 it does not affect the protocol acknowledgment state for any current
40012 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40013 new connection is established,
40014 there is also no protocol request to re-enable the acknowledgments
40015 for the current connection, once disabled.
40020 Example sequence of a target being re-started. Notice how the restart
40021 does not get any direct output:
40026 @emph{target restarts}
40029 <- @code{T001:1234123412341234}
40033 Example sequence of a target being stepped by a single instruction:
40036 -> @code{G1445@dots{}}
40041 <- @code{T001:1234123412341234}
40045 <- @code{1455@dots{}}
40049 @node File-I/O Remote Protocol Extension
40050 @section File-I/O Remote Protocol Extension
40051 @cindex File-I/O remote protocol extension
40054 * File-I/O Overview::
40055 * Protocol Basics::
40056 * The F Request Packet::
40057 * The F Reply Packet::
40058 * The Ctrl-C Message::
40060 * List of Supported Calls::
40061 * Protocol-specific Representation of Datatypes::
40063 * File-I/O Examples::
40066 @node File-I/O Overview
40067 @subsection File-I/O Overview
40068 @cindex file-i/o overview
40070 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40071 target to use the host's file system and console I/O to perform various
40072 system calls. System calls on the target system are translated into a
40073 remote protocol packet to the host system, which then performs the needed
40074 actions and returns a response packet to the target system.
40075 This simulates file system operations even on targets that lack file systems.
40077 The protocol is defined to be independent of both the host and target systems.
40078 It uses its own internal representation of datatypes and values. Both
40079 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40080 translating the system-dependent value representations into the internal
40081 protocol representations when data is transmitted.
40083 The communication is synchronous. A system call is possible only when
40084 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40085 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40086 the target is stopped to allow deterministic access to the target's
40087 memory. Therefore File-I/O is not interruptible by target signals. On
40088 the other hand, it is possible to interrupt File-I/O by a user interrupt
40089 (@samp{Ctrl-C}) within @value{GDBN}.
40091 The target's request to perform a host system call does not finish
40092 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40093 after finishing the system call, the target returns to continuing the
40094 previous activity (continue, step). No additional continue or step
40095 request from @value{GDBN} is required.
40098 (@value{GDBP}) continue
40099 <- target requests 'system call X'
40100 target is stopped, @value{GDBN} executes system call
40101 -> @value{GDBN} returns result
40102 ... target continues, @value{GDBN} returns to wait for the target
40103 <- target hits breakpoint and sends a Txx packet
40106 The protocol only supports I/O on the console and to regular files on
40107 the host file system. Character or block special devices, pipes,
40108 named pipes, sockets or any other communication method on the host
40109 system are not supported by this protocol.
40111 File I/O is not supported in non-stop mode.
40113 @node Protocol Basics
40114 @subsection Protocol Basics
40115 @cindex protocol basics, file-i/o
40117 The File-I/O protocol uses the @code{F} packet as the request as well
40118 as reply packet. Since a File-I/O system call can only occur when
40119 @value{GDBN} is waiting for a response from the continuing or stepping target,
40120 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40121 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40122 This @code{F} packet contains all information needed to allow @value{GDBN}
40123 to call the appropriate host system call:
40127 A unique identifier for the requested system call.
40130 All parameters to the system call. Pointers are given as addresses
40131 in the target memory address space. Pointers to strings are given as
40132 pointer/length pair. Numerical values are given as they are.
40133 Numerical control flags are given in a protocol-specific representation.
40137 At this point, @value{GDBN} has to perform the following actions.
40141 If the parameters include pointer values to data needed as input to a
40142 system call, @value{GDBN} requests this data from the target with a
40143 standard @code{m} packet request. This additional communication has to be
40144 expected by the target implementation and is handled as any other @code{m}
40148 @value{GDBN} translates all value from protocol representation to host
40149 representation as needed. Datatypes are coerced into the host types.
40152 @value{GDBN} calls the system call.
40155 It then coerces datatypes back to protocol representation.
40158 If the system call is expected to return data in buffer space specified
40159 by pointer parameters to the call, the data is transmitted to the
40160 target using a @code{M} or @code{X} packet. This packet has to be expected
40161 by the target implementation and is handled as any other @code{M} or @code{X}
40166 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40167 necessary information for the target to continue. This at least contains
40174 @code{errno}, if has been changed by the system call.
40181 After having done the needed type and value coercion, the target continues
40182 the latest continue or step action.
40184 @node The F Request Packet
40185 @subsection The @code{F} Request Packet
40186 @cindex file-i/o request packet
40187 @cindex @code{F} request packet
40189 The @code{F} request packet has the following format:
40192 @item F@var{call-id},@var{parameter@dots{}}
40194 @var{call-id} is the identifier to indicate the host system call to be called.
40195 This is just the name of the function.
40197 @var{parameter@dots{}} are the parameters to the system call.
40198 Parameters are hexadecimal integer values, either the actual values in case
40199 of scalar datatypes, pointers to target buffer space in case of compound
40200 datatypes and unspecified memory areas, or pointer/length pairs in case
40201 of string parameters. These are appended to the @var{call-id} as a
40202 comma-delimited list. All values are transmitted in ASCII
40203 string representation, pointer/length pairs separated by a slash.
40209 @node The F Reply Packet
40210 @subsection The @code{F} Reply Packet
40211 @cindex file-i/o reply packet
40212 @cindex @code{F} reply packet
40214 The @code{F} reply packet has the following format:
40218 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40220 @var{retcode} is the return code of the system call as hexadecimal value.
40222 @var{errno} is the @code{errno} set by the call, in protocol-specific
40224 This parameter can be omitted if the call was successful.
40226 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40227 case, @var{errno} must be sent as well, even if the call was successful.
40228 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40235 or, if the call was interrupted before the host call has been performed:
40242 assuming 4 is the protocol-specific representation of @code{EINTR}.
40247 @node The Ctrl-C Message
40248 @subsection The @samp{Ctrl-C} Message
40249 @cindex ctrl-c message, in file-i/o protocol
40251 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40252 reply packet (@pxref{The F Reply Packet}),
40253 the target should behave as if it had
40254 gotten a break message. The meaning for the target is ``system call
40255 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40256 (as with a break message) and return to @value{GDBN} with a @code{T02}
40259 It's important for the target to know in which
40260 state the system call was interrupted. There are two possible cases:
40264 The system call hasn't been performed on the host yet.
40267 The system call on the host has been finished.
40271 These two states can be distinguished by the target by the value of the
40272 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40273 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40274 on POSIX systems. In any other case, the target may presume that the
40275 system call has been finished --- successfully or not --- and should behave
40276 as if the break message arrived right after the system call.
40278 @value{GDBN} must behave reliably. If the system call has not been called
40279 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40280 @code{errno} in the packet. If the system call on the host has been finished
40281 before the user requests a break, the full action must be finished by
40282 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40283 The @code{F} packet may only be sent when either nothing has happened
40284 or the full action has been completed.
40287 @subsection Console I/O
40288 @cindex console i/o as part of file-i/o
40290 By default and if not explicitly closed by the target system, the file
40291 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40292 on the @value{GDBN} console is handled as any other file output operation
40293 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40294 by @value{GDBN} so that after the target read request from file descriptor
40295 0 all following typing is buffered until either one of the following
40300 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40302 system call is treated as finished.
40305 The user presses @key{RET}. This is treated as end of input with a trailing
40309 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40310 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40314 If the user has typed more characters than fit in the buffer given to
40315 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40316 either another @code{read(0, @dots{})} is requested by the target, or debugging
40317 is stopped at the user's request.
40320 @node List of Supported Calls
40321 @subsection List of Supported Calls
40322 @cindex list of supported file-i/o calls
40339 @unnumberedsubsubsec open
40340 @cindex open, file-i/o system call
40345 int open(const char *pathname, int flags);
40346 int open(const char *pathname, int flags, mode_t mode);
40350 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40353 @var{flags} is the bitwise @code{OR} of the following values:
40357 If the file does not exist it will be created. The host
40358 rules apply as far as file ownership and time stamps
40362 When used with @code{O_CREAT}, if the file already exists it is
40363 an error and open() fails.
40366 If the file already exists and the open mode allows
40367 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40368 truncated to zero length.
40371 The file is opened in append mode.
40374 The file is opened for reading only.
40377 The file is opened for writing only.
40380 The file is opened for reading and writing.
40384 Other bits are silently ignored.
40388 @var{mode} is the bitwise @code{OR} of the following values:
40392 User has read permission.
40395 User has write permission.
40398 Group has read permission.
40401 Group has write permission.
40404 Others have read permission.
40407 Others have write permission.
40411 Other bits are silently ignored.
40414 @item Return value:
40415 @code{open} returns the new file descriptor or -1 if an error
40422 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40425 @var{pathname} refers to a directory.
40428 The requested access is not allowed.
40431 @var{pathname} was too long.
40434 A directory component in @var{pathname} does not exist.
40437 @var{pathname} refers to a device, pipe, named pipe or socket.
40440 @var{pathname} refers to a file on a read-only filesystem and
40441 write access was requested.
40444 @var{pathname} is an invalid pointer value.
40447 No space on device to create the file.
40450 The process already has the maximum number of files open.
40453 The limit on the total number of files open on the system
40457 The call was interrupted by the user.
40463 @unnumberedsubsubsec close
40464 @cindex close, file-i/o system call
40473 @samp{Fclose,@var{fd}}
40475 @item Return value:
40476 @code{close} returns zero on success, or -1 if an error occurred.
40482 @var{fd} isn't a valid open file descriptor.
40485 The call was interrupted by the user.
40491 @unnumberedsubsubsec read
40492 @cindex read, file-i/o system call
40497 int read(int fd, void *buf, unsigned int count);
40501 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40503 @item Return value:
40504 On success, the number of bytes read is returned.
40505 Zero indicates end of file. If count is zero, read
40506 returns zero as well. On error, -1 is returned.
40512 @var{fd} is not a valid file descriptor or is not open for
40516 @var{bufptr} is an invalid pointer value.
40519 The call was interrupted by the user.
40525 @unnumberedsubsubsec write
40526 @cindex write, file-i/o system call
40531 int write(int fd, const void *buf, unsigned int count);
40535 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40537 @item Return value:
40538 On success, the number of bytes written are returned.
40539 Zero indicates nothing was written. On error, -1
40546 @var{fd} is not a valid file descriptor or is not open for
40550 @var{bufptr} is an invalid pointer value.
40553 An attempt was made to write a file that exceeds the
40554 host-specific maximum file size allowed.
40557 No space on device to write the data.
40560 The call was interrupted by the user.
40566 @unnumberedsubsubsec lseek
40567 @cindex lseek, file-i/o system call
40572 long lseek (int fd, long offset, int flag);
40576 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40578 @var{flag} is one of:
40582 The offset is set to @var{offset} bytes.
40585 The offset is set to its current location plus @var{offset}
40589 The offset is set to the size of the file plus @var{offset}
40593 @item Return value:
40594 On success, the resulting unsigned offset in bytes from
40595 the beginning of the file is returned. Otherwise, a
40596 value of -1 is returned.
40602 @var{fd} is not a valid open file descriptor.
40605 @var{fd} is associated with the @value{GDBN} console.
40608 @var{flag} is not a proper value.
40611 The call was interrupted by the user.
40617 @unnumberedsubsubsec rename
40618 @cindex rename, file-i/o system call
40623 int rename(const char *oldpath, const char *newpath);
40627 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40629 @item Return value:
40630 On success, zero is returned. On error, -1 is returned.
40636 @var{newpath} is an existing directory, but @var{oldpath} is not a
40640 @var{newpath} is a non-empty directory.
40643 @var{oldpath} or @var{newpath} is a directory that is in use by some
40647 An attempt was made to make a directory a subdirectory
40651 A component used as a directory in @var{oldpath} or new
40652 path is not a directory. Or @var{oldpath} is a directory
40653 and @var{newpath} exists but is not a directory.
40656 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40659 No access to the file or the path of the file.
40663 @var{oldpath} or @var{newpath} was too long.
40666 A directory component in @var{oldpath} or @var{newpath} does not exist.
40669 The file is on a read-only filesystem.
40672 The device containing the file has no room for the new
40676 The call was interrupted by the user.
40682 @unnumberedsubsubsec unlink
40683 @cindex unlink, file-i/o system call
40688 int unlink(const char *pathname);
40692 @samp{Funlink,@var{pathnameptr}/@var{len}}
40694 @item Return value:
40695 On success, zero is returned. On error, -1 is returned.
40701 No access to the file or the path of the file.
40704 The system does not allow unlinking of directories.
40707 The file @var{pathname} cannot be unlinked because it's
40708 being used by another process.
40711 @var{pathnameptr} is an invalid pointer value.
40714 @var{pathname} was too long.
40717 A directory component in @var{pathname} does not exist.
40720 A component of the path is not a directory.
40723 The file is on a read-only filesystem.
40726 The call was interrupted by the user.
40732 @unnumberedsubsubsec stat/fstat
40733 @cindex fstat, file-i/o system call
40734 @cindex stat, file-i/o system call
40739 int stat(const char *pathname, struct stat *buf);
40740 int fstat(int fd, struct stat *buf);
40744 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40745 @samp{Ffstat,@var{fd},@var{bufptr}}
40747 @item Return value:
40748 On success, zero is returned. On error, -1 is returned.
40754 @var{fd} is not a valid open file.
40757 A directory component in @var{pathname} does not exist or the
40758 path is an empty string.
40761 A component of the path is not a directory.
40764 @var{pathnameptr} is an invalid pointer value.
40767 No access to the file or the path of the file.
40770 @var{pathname} was too long.
40773 The call was interrupted by the user.
40779 @unnumberedsubsubsec gettimeofday
40780 @cindex gettimeofday, file-i/o system call
40785 int gettimeofday(struct timeval *tv, void *tz);
40789 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40791 @item Return value:
40792 On success, 0 is returned, -1 otherwise.
40798 @var{tz} is a non-NULL pointer.
40801 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40807 @unnumberedsubsubsec isatty
40808 @cindex isatty, file-i/o system call
40813 int isatty(int fd);
40817 @samp{Fisatty,@var{fd}}
40819 @item Return value:
40820 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40826 The call was interrupted by the user.
40831 Note that the @code{isatty} call is treated as a special case: it returns
40832 1 to the target if the file descriptor is attached
40833 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40834 would require implementing @code{ioctl} and would be more complex than
40839 @unnumberedsubsubsec system
40840 @cindex system, file-i/o system call
40845 int system(const char *command);
40849 @samp{Fsystem,@var{commandptr}/@var{len}}
40851 @item Return value:
40852 If @var{len} is zero, the return value indicates whether a shell is
40853 available. A zero return value indicates a shell is not available.
40854 For non-zero @var{len}, the value returned is -1 on error and the
40855 return status of the command otherwise. Only the exit status of the
40856 command is returned, which is extracted from the host's @code{system}
40857 return value by calling @code{WEXITSTATUS(retval)}. In case
40858 @file{/bin/sh} could not be executed, 127 is returned.
40864 The call was interrupted by the user.
40869 @value{GDBN} takes over the full task of calling the necessary host calls
40870 to perform the @code{system} call. The return value of @code{system} on
40871 the host is simplified before it's returned
40872 to the target. Any termination signal information from the child process
40873 is discarded, and the return value consists
40874 entirely of the exit status of the called command.
40876 Due to security concerns, the @code{system} call is by default refused
40877 by @value{GDBN}. The user has to allow this call explicitly with the
40878 @code{set remote system-call-allowed 1} command.
40881 @item set remote system-call-allowed
40882 @kindex set remote system-call-allowed
40883 Control whether to allow the @code{system} calls in the File I/O
40884 protocol for the remote target. The default is zero (disabled).
40886 @item show remote system-call-allowed
40887 @kindex show remote system-call-allowed
40888 Show whether the @code{system} calls are allowed in the File I/O
40892 @node Protocol-specific Representation of Datatypes
40893 @subsection Protocol-specific Representation of Datatypes
40894 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40897 * Integral Datatypes::
40899 * Memory Transfer::
40904 @node Integral Datatypes
40905 @unnumberedsubsubsec Integral Datatypes
40906 @cindex integral datatypes, in file-i/o protocol
40908 The integral datatypes used in the system calls are @code{int},
40909 @code{unsigned int}, @code{long}, @code{unsigned long},
40910 @code{mode_t}, and @code{time_t}.
40912 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40913 implemented as 32 bit values in this protocol.
40915 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40917 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40918 in @file{limits.h}) to allow range checking on host and target.
40920 @code{time_t} datatypes are defined as seconds since the Epoch.
40922 All integral datatypes transferred as part of a memory read or write of a
40923 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40926 @node Pointer Values
40927 @unnumberedsubsubsec Pointer Values
40928 @cindex pointer values, in file-i/o protocol
40930 Pointers to target data are transmitted as they are. An exception
40931 is made for pointers to buffers for which the length isn't
40932 transmitted as part of the function call, namely strings. Strings
40933 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40940 which is a pointer to data of length 18 bytes at position 0x1aaf.
40941 The length is defined as the full string length in bytes, including
40942 the trailing null byte. For example, the string @code{"hello world"}
40943 at address 0x123456 is transmitted as
40949 @node Memory Transfer
40950 @unnumberedsubsubsec Memory Transfer
40951 @cindex memory transfer, in file-i/o protocol
40953 Structured data which is transferred using a memory read or write (for
40954 example, a @code{struct stat}) is expected to be in a protocol-specific format
40955 with all scalar multibyte datatypes being big endian. Translation to
40956 this representation needs to be done both by the target before the @code{F}
40957 packet is sent, and by @value{GDBN} before
40958 it transfers memory to the target. Transferred pointers to structured
40959 data should point to the already-coerced data at any time.
40963 @unnumberedsubsubsec struct stat
40964 @cindex struct stat, in file-i/o protocol
40966 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40967 is defined as follows:
40971 unsigned int st_dev; /* device */
40972 unsigned int st_ino; /* inode */
40973 mode_t st_mode; /* protection */
40974 unsigned int st_nlink; /* number of hard links */
40975 unsigned int st_uid; /* user ID of owner */
40976 unsigned int st_gid; /* group ID of owner */
40977 unsigned int st_rdev; /* device type (if inode device) */
40978 unsigned long st_size; /* total size, in bytes */
40979 unsigned long st_blksize; /* blocksize for filesystem I/O */
40980 unsigned long st_blocks; /* number of blocks allocated */
40981 time_t st_atime; /* time of last access */
40982 time_t st_mtime; /* time of last modification */
40983 time_t st_ctime; /* time of last change */
40987 The integral datatypes conform to the definitions given in the
40988 appropriate section (see @ref{Integral Datatypes}, for details) so this
40989 structure is of size 64 bytes.
40991 The values of several fields have a restricted meaning and/or
40997 A value of 0 represents a file, 1 the console.
41000 No valid meaning for the target. Transmitted unchanged.
41003 Valid mode bits are described in @ref{Constants}. Any other
41004 bits have currently no meaning for the target.
41009 No valid meaning for the target. Transmitted unchanged.
41014 These values have a host and file system dependent
41015 accuracy. Especially on Windows hosts, the file system may not
41016 support exact timing values.
41019 The target gets a @code{struct stat} of the above representation and is
41020 responsible for coercing it to the target representation before
41023 Note that due to size differences between the host, target, and protocol
41024 representations of @code{struct stat} members, these members could eventually
41025 get truncated on the target.
41027 @node struct timeval
41028 @unnumberedsubsubsec struct timeval
41029 @cindex struct timeval, in file-i/o protocol
41031 The buffer of type @code{struct timeval} used by the File-I/O protocol
41032 is defined as follows:
41036 time_t tv_sec; /* second */
41037 long tv_usec; /* microsecond */
41041 The integral datatypes conform to the definitions given in the
41042 appropriate section (see @ref{Integral Datatypes}, for details) so this
41043 structure is of size 8 bytes.
41046 @subsection Constants
41047 @cindex constants, in file-i/o protocol
41049 The following values are used for the constants inside of the
41050 protocol. @value{GDBN} and target are responsible for translating these
41051 values before and after the call as needed.
41062 @unnumberedsubsubsec Open Flags
41063 @cindex open flags, in file-i/o protocol
41065 All values are given in hexadecimal representation.
41077 @node mode_t Values
41078 @unnumberedsubsubsec mode_t Values
41079 @cindex mode_t values, in file-i/o protocol
41081 All values are given in octal representation.
41098 @unnumberedsubsubsec Errno Values
41099 @cindex errno values, in file-i/o protocol
41101 All values are given in decimal representation.
41126 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41127 any error value not in the list of supported error numbers.
41130 @unnumberedsubsubsec Lseek Flags
41131 @cindex lseek flags, in file-i/o protocol
41140 @unnumberedsubsubsec Limits
41141 @cindex limits, in file-i/o protocol
41143 All values are given in decimal representation.
41146 INT_MIN -2147483648
41148 UINT_MAX 4294967295
41149 LONG_MIN -9223372036854775808
41150 LONG_MAX 9223372036854775807
41151 ULONG_MAX 18446744073709551615
41154 @node File-I/O Examples
41155 @subsection File-I/O Examples
41156 @cindex file-i/o examples
41158 Example sequence of a write call, file descriptor 3, buffer is at target
41159 address 0x1234, 6 bytes should be written:
41162 <- @code{Fwrite,3,1234,6}
41163 @emph{request memory read from target}
41166 @emph{return "6 bytes written"}
41170 Example sequence of a read call, file descriptor 3, buffer is at target
41171 address 0x1234, 6 bytes should be read:
41174 <- @code{Fread,3,1234,6}
41175 @emph{request memory write to target}
41176 -> @code{X1234,6:XXXXXX}
41177 @emph{return "6 bytes read"}
41181 Example sequence of a read call, call fails on the host due to invalid
41182 file descriptor (@code{EBADF}):
41185 <- @code{Fread,3,1234,6}
41189 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41193 <- @code{Fread,3,1234,6}
41198 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41202 <- @code{Fread,3,1234,6}
41203 -> @code{X1234,6:XXXXXX}
41207 @node Library List Format
41208 @section Library List Format
41209 @cindex library list format, remote protocol
41211 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41212 same process as your application to manage libraries. In this case,
41213 @value{GDBN} can use the loader's symbol table and normal memory
41214 operations to maintain a list of shared libraries. On other
41215 platforms, the operating system manages loaded libraries.
41216 @value{GDBN} can not retrieve the list of currently loaded libraries
41217 through memory operations, so it uses the @samp{qXfer:libraries:read}
41218 packet (@pxref{qXfer library list read}) instead. The remote stub
41219 queries the target's operating system and reports which libraries
41222 The @samp{qXfer:libraries:read} packet returns an XML document which
41223 lists loaded libraries and their offsets. Each library has an
41224 associated name and one or more segment or section base addresses,
41225 which report where the library was loaded in memory.
41227 For the common case of libraries that are fully linked binaries, the
41228 library should have a list of segments. If the target supports
41229 dynamic linking of a relocatable object file, its library XML element
41230 should instead include a list of allocated sections. The segment or
41231 section bases are start addresses, not relocation offsets; they do not
41232 depend on the library's link-time base addresses.
41234 @value{GDBN} must be linked with the Expat library to support XML
41235 library lists. @xref{Expat}.
41237 A simple memory map, with one loaded library relocated by a single
41238 offset, looks like this:
41242 <library name="/lib/libc.so.6">
41243 <segment address="0x10000000"/>
41248 Another simple memory map, with one loaded library with three
41249 allocated sections (.text, .data, .bss), looks like this:
41253 <library name="sharedlib.o">
41254 <section address="0x10000000"/>
41255 <section address="0x20000000"/>
41256 <section address="0x30000000"/>
41261 The format of a library list is described by this DTD:
41264 <!-- library-list: Root element with versioning -->
41265 <!ELEMENT library-list (library)*>
41266 <!ATTLIST library-list version CDATA #FIXED "1.0">
41267 <!ELEMENT library (segment*, section*)>
41268 <!ATTLIST library name CDATA #REQUIRED>
41269 <!ELEMENT segment EMPTY>
41270 <!ATTLIST segment address CDATA #REQUIRED>
41271 <!ELEMENT section EMPTY>
41272 <!ATTLIST section address CDATA #REQUIRED>
41275 In addition, segments and section descriptors cannot be mixed within a
41276 single library element, and you must supply at least one segment or
41277 section for each library.
41279 @node Library List Format for SVR4 Targets
41280 @section Library List Format for SVR4 Targets
41281 @cindex library list format, remote protocol
41283 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41284 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41285 shared libraries. Still a special library list provided by this packet is
41286 more efficient for the @value{GDBN} remote protocol.
41288 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41289 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41290 target, the following parameters are reported:
41294 @code{name}, the absolute file name from the @code{l_name} field of
41295 @code{struct link_map}.
41297 @code{lm} with address of @code{struct link_map} used for TLS
41298 (Thread Local Storage) access.
41300 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41301 @code{struct link_map}. For prelinked libraries this is not an absolute
41302 memory address. It is a displacement of absolute memory address against
41303 address the file was prelinked to during the library load.
41305 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41308 Additionally the single @code{main-lm} attribute specifies address of
41309 @code{struct link_map} used for the main executable. This parameter is used
41310 for TLS access and its presence is optional.
41312 @value{GDBN} must be linked with the Expat library to support XML
41313 SVR4 library lists. @xref{Expat}.
41315 A simple memory map, with two loaded libraries (which do not use prelink),
41319 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41320 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41322 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41324 </library-list-svr>
41327 The format of an SVR4 library list is described by this DTD:
41330 <!-- library-list-svr4: Root element with versioning -->
41331 <!ELEMENT library-list-svr4 (library)*>
41332 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41333 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41334 <!ELEMENT library EMPTY>
41335 <!ATTLIST library name CDATA #REQUIRED>
41336 <!ATTLIST library lm CDATA #REQUIRED>
41337 <!ATTLIST library l_addr CDATA #REQUIRED>
41338 <!ATTLIST library l_ld CDATA #REQUIRED>
41341 @node Memory Map Format
41342 @section Memory Map Format
41343 @cindex memory map format
41345 To be able to write into flash memory, @value{GDBN} needs to obtain a
41346 memory map from the target. This section describes the format of the
41349 The memory map is obtained using the @samp{qXfer:memory-map:read}
41350 (@pxref{qXfer memory map read}) packet and is an XML document that
41351 lists memory regions.
41353 @value{GDBN} must be linked with the Expat library to support XML
41354 memory maps. @xref{Expat}.
41356 The top-level structure of the document is shown below:
41359 <?xml version="1.0"?>
41360 <!DOCTYPE memory-map
41361 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41362 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41368 Each region can be either:
41373 A region of RAM starting at @var{addr} and extending for @var{length}
41377 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41382 A region of read-only memory:
41385 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41390 A region of flash memory, with erasure blocks @var{blocksize}
41394 <memory type="flash" start="@var{addr}" length="@var{length}">
41395 <property name="blocksize">@var{blocksize}</property>
41401 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41402 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41403 packets to write to addresses in such ranges.
41405 The formal DTD for memory map format is given below:
41408 <!-- ................................................... -->
41409 <!-- Memory Map XML DTD ................................ -->
41410 <!-- File: memory-map.dtd .............................. -->
41411 <!-- .................................... .............. -->
41412 <!-- memory-map.dtd -->
41413 <!-- memory-map: Root element with versioning -->
41414 <!ELEMENT memory-map (memory)*>
41415 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41416 <!ELEMENT memory (property)*>
41417 <!-- memory: Specifies a memory region,
41418 and its type, or device. -->
41419 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41420 start CDATA #REQUIRED
41421 length CDATA #REQUIRED>
41422 <!-- property: Generic attribute tag -->
41423 <!ELEMENT property (#PCDATA | property)*>
41424 <!ATTLIST property name (blocksize) #REQUIRED>
41427 @node Thread List Format
41428 @section Thread List Format
41429 @cindex thread list format
41431 To efficiently update the list of threads and their attributes,
41432 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41433 (@pxref{qXfer threads read}) and obtains the XML document with
41434 the following structure:
41437 <?xml version="1.0"?>
41439 <thread id="id" core="0" name="name">
41440 ... description ...
41445 Each @samp{thread} element must have the @samp{id} attribute that
41446 identifies the thread (@pxref{thread-id syntax}). The
41447 @samp{core} attribute, if present, specifies which processor core
41448 the thread was last executing on. The @samp{name} attribute, if
41449 present, specifies the human-readable name of the thread. The content
41450 of the of @samp{thread} element is interpreted as human-readable
41451 auxiliary information. The @samp{handle} attribute, if present,
41452 is a hex encoded representation of the thread handle.
41455 @node Traceframe Info Format
41456 @section Traceframe Info Format
41457 @cindex traceframe info format
41459 To be able to know which objects in the inferior can be examined when
41460 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41461 memory ranges, registers and trace state variables that have been
41462 collected in a traceframe.
41464 This list is obtained using the @samp{qXfer:traceframe-info:read}
41465 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41467 @value{GDBN} must be linked with the Expat library to support XML
41468 traceframe info discovery. @xref{Expat}.
41470 The top-level structure of the document is shown below:
41473 <?xml version="1.0"?>
41474 <!DOCTYPE traceframe-info
41475 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41476 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41482 Each traceframe block can be either:
41487 A region of collected memory starting at @var{addr} and extending for
41488 @var{length} bytes from there:
41491 <memory start="@var{addr}" length="@var{length}"/>
41495 A block indicating trace state variable numbered @var{number} has been
41499 <tvar id="@var{number}"/>
41504 The formal DTD for the traceframe info format is given below:
41507 <!ELEMENT traceframe-info (memory | tvar)* >
41508 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41510 <!ELEMENT memory EMPTY>
41511 <!ATTLIST memory start CDATA #REQUIRED
41512 length CDATA #REQUIRED>
41514 <!ATTLIST tvar id CDATA #REQUIRED>
41517 @node Branch Trace Format
41518 @section Branch Trace Format
41519 @cindex branch trace format
41521 In order to display the branch trace of an inferior thread,
41522 @value{GDBN} needs to obtain the list of branches. This list is
41523 represented as list of sequential code blocks that are connected via
41524 branches. The code in each block has been executed sequentially.
41526 This list is obtained using the @samp{qXfer:btrace:read}
41527 (@pxref{qXfer btrace read}) packet and is an XML document.
41529 @value{GDBN} must be linked with the Expat library to support XML
41530 traceframe info discovery. @xref{Expat}.
41532 The top-level structure of the document is shown below:
41535 <?xml version="1.0"?>
41537 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41538 "http://sourceware.org/gdb/gdb-btrace.dtd">
41547 A block of sequentially executed instructions starting at @var{begin}
41548 and ending at @var{end}:
41551 <block begin="@var{begin}" end="@var{end}"/>
41556 The formal DTD for the branch trace format is given below:
41559 <!ELEMENT btrace (block* | pt) >
41560 <!ATTLIST btrace version CDATA #FIXED "1.0">
41562 <!ELEMENT block EMPTY>
41563 <!ATTLIST block begin CDATA #REQUIRED
41564 end CDATA #REQUIRED>
41566 <!ELEMENT pt (pt-config?, raw?)>
41568 <!ELEMENT pt-config (cpu?)>
41570 <!ELEMENT cpu EMPTY>
41571 <!ATTLIST cpu vendor CDATA #REQUIRED
41572 family CDATA #REQUIRED
41573 model CDATA #REQUIRED
41574 stepping CDATA #REQUIRED>
41576 <!ELEMENT raw (#PCDATA)>
41579 @node Branch Trace Configuration Format
41580 @section Branch Trace Configuration Format
41581 @cindex branch trace configuration format
41583 For each inferior thread, @value{GDBN} can obtain the branch trace
41584 configuration using the @samp{qXfer:btrace-conf:read}
41585 (@pxref{qXfer btrace-conf read}) packet.
41587 The configuration describes the branch trace format and configuration
41588 settings for that format. The following information is described:
41592 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41595 The size of the @acronym{BTS} ring buffer in bytes.
41598 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41602 The size of the @acronym{Intel PT} ring buffer in bytes.
41606 @value{GDBN} must be linked with the Expat library to support XML
41607 branch trace configuration discovery. @xref{Expat}.
41609 The formal DTD for the branch trace configuration format is given below:
41612 <!ELEMENT btrace-conf (bts?, pt?)>
41613 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41615 <!ELEMENT bts EMPTY>
41616 <!ATTLIST bts size CDATA #IMPLIED>
41618 <!ELEMENT pt EMPTY>
41619 <!ATTLIST pt size CDATA #IMPLIED>
41622 @include agentexpr.texi
41624 @node Target Descriptions
41625 @appendix Target Descriptions
41626 @cindex target descriptions
41628 One of the challenges of using @value{GDBN} to debug embedded systems
41629 is that there are so many minor variants of each processor
41630 architecture in use. It is common practice for vendors to start with
41631 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41632 and then make changes to adapt it to a particular market niche. Some
41633 architectures have hundreds of variants, available from dozens of
41634 vendors. This leads to a number of problems:
41638 With so many different customized processors, it is difficult for
41639 the @value{GDBN} maintainers to keep up with the changes.
41641 Since individual variants may have short lifetimes or limited
41642 audiences, it may not be worthwhile to carry information about every
41643 variant in the @value{GDBN} source tree.
41645 When @value{GDBN} does support the architecture of the embedded system
41646 at hand, the task of finding the correct architecture name to give the
41647 @command{set architecture} command can be error-prone.
41650 To address these problems, the @value{GDBN} remote protocol allows a
41651 target system to not only identify itself to @value{GDBN}, but to
41652 actually describe its own features. This lets @value{GDBN} support
41653 processor variants it has never seen before --- to the extent that the
41654 descriptions are accurate, and that @value{GDBN} understands them.
41656 @value{GDBN} must be linked with the Expat library to support XML
41657 target descriptions. @xref{Expat}.
41660 * Retrieving Descriptions:: How descriptions are fetched from a target.
41661 * Target Description Format:: The contents of a target description.
41662 * Predefined Target Types:: Standard types available for target
41664 * Enum Target Types:: How to define enum target types.
41665 * Standard Target Features:: Features @value{GDBN} knows about.
41668 @node Retrieving Descriptions
41669 @section Retrieving Descriptions
41671 Target descriptions can be read from the target automatically, or
41672 specified by the user manually. The default behavior is to read the
41673 description from the target. @value{GDBN} retrieves it via the remote
41674 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41675 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41676 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41677 XML document, of the form described in @ref{Target Description
41680 Alternatively, you can specify a file to read for the target description.
41681 If a file is set, the target will not be queried. The commands to
41682 specify a file are:
41685 @cindex set tdesc filename
41686 @item set tdesc filename @var{path}
41687 Read the target description from @var{path}.
41689 @cindex unset tdesc filename
41690 @item unset tdesc filename
41691 Do not read the XML target description from a file. @value{GDBN}
41692 will use the description supplied by the current target.
41694 @cindex show tdesc filename
41695 @item show tdesc filename
41696 Show the filename to read for a target description, if any.
41700 @node Target Description Format
41701 @section Target Description Format
41702 @cindex target descriptions, XML format
41704 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41705 document which complies with the Document Type Definition provided in
41706 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41707 means you can use generally available tools like @command{xmllint} to
41708 check that your feature descriptions are well-formed and valid.
41709 However, to help people unfamiliar with XML write descriptions for
41710 their targets, we also describe the grammar here.
41712 Target descriptions can identify the architecture of the remote target
41713 and (for some architectures) provide information about custom register
41714 sets. They can also identify the OS ABI of the remote target.
41715 @value{GDBN} can use this information to autoconfigure for your
41716 target, or to warn you if you connect to an unsupported target.
41718 Here is a simple target description:
41721 <target version="1.0">
41722 <architecture>i386:x86-64</architecture>
41727 This minimal description only says that the target uses
41728 the x86-64 architecture.
41730 A target description has the following overall form, with [ ] marking
41731 optional elements and @dots{} marking repeatable elements. The elements
41732 are explained further below.
41735 <?xml version="1.0"?>
41736 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41737 <target version="1.0">
41738 @r{[}@var{architecture}@r{]}
41739 @r{[}@var{osabi}@r{]}
41740 @r{[}@var{compatible}@r{]}
41741 @r{[}@var{feature}@dots{}@r{]}
41746 The description is generally insensitive to whitespace and line
41747 breaks, under the usual common-sense rules. The XML version
41748 declaration and document type declaration can generally be omitted
41749 (@value{GDBN} does not require them), but specifying them may be
41750 useful for XML validation tools. The @samp{version} attribute for
41751 @samp{<target>} may also be omitted, but we recommend
41752 including it; if future versions of @value{GDBN} use an incompatible
41753 revision of @file{gdb-target.dtd}, they will detect and report
41754 the version mismatch.
41756 @subsection Inclusion
41757 @cindex target descriptions, inclusion
41760 @cindex <xi:include>
41763 It can sometimes be valuable to split a target description up into
41764 several different annexes, either for organizational purposes, or to
41765 share files between different possible target descriptions. You can
41766 divide a description into multiple files by replacing any element of
41767 the target description with an inclusion directive of the form:
41770 <xi:include href="@var{document}"/>
41774 When @value{GDBN} encounters an element of this form, it will retrieve
41775 the named XML @var{document}, and replace the inclusion directive with
41776 the contents of that document. If the current description was read
41777 using @samp{qXfer}, then so will be the included document;
41778 @var{document} will be interpreted as the name of an annex. If the
41779 current description was read from a file, @value{GDBN} will look for
41780 @var{document} as a file in the same directory where it found the
41781 original description.
41783 @subsection Architecture
41784 @cindex <architecture>
41786 An @samp{<architecture>} element has this form:
41789 <architecture>@var{arch}</architecture>
41792 @var{arch} is one of the architectures from the set accepted by
41793 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41796 @cindex @code{<osabi>}
41798 This optional field was introduced in @value{GDBN} version 7.0.
41799 Previous versions of @value{GDBN} ignore it.
41801 An @samp{<osabi>} element has this form:
41804 <osabi>@var{abi-name}</osabi>
41807 @var{abi-name} is an OS ABI name from the same selection accepted by
41808 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41810 @subsection Compatible Architecture
41811 @cindex @code{<compatible>}
41813 This optional field was introduced in @value{GDBN} version 7.0.
41814 Previous versions of @value{GDBN} ignore it.
41816 A @samp{<compatible>} element has this form:
41819 <compatible>@var{arch}</compatible>
41822 @var{arch} is one of the architectures from the set accepted by
41823 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41825 A @samp{<compatible>} element is used to specify that the target
41826 is able to run binaries in some other than the main target architecture
41827 given by the @samp{<architecture>} element. For example, on the
41828 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41829 or @code{powerpc:common64}, but the system is able to run binaries
41830 in the @code{spu} architecture as well. The way to describe this
41831 capability with @samp{<compatible>} is as follows:
41834 <architecture>powerpc:common</architecture>
41835 <compatible>spu</compatible>
41838 @subsection Features
41841 Each @samp{<feature>} describes some logical portion of the target
41842 system. Features are currently used to describe available CPU
41843 registers and the types of their contents. A @samp{<feature>} element
41847 <feature name="@var{name}">
41848 @r{[}@var{type}@dots{}@r{]}
41854 Each feature's name should be unique within the description. The name
41855 of a feature does not matter unless @value{GDBN} has some special
41856 knowledge of the contents of that feature; if it does, the feature
41857 should have its standard name. @xref{Standard Target Features}.
41861 Any register's value is a collection of bits which @value{GDBN} must
41862 interpret. The default interpretation is a two's complement integer,
41863 but other types can be requested by name in the register description.
41864 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41865 Target Types}), and the description can define additional composite
41868 Each type element must have an @samp{id} attribute, which gives
41869 a unique (within the containing @samp{<feature>}) name to the type.
41870 Types must be defined before they are used.
41873 Some targets offer vector registers, which can be treated as arrays
41874 of scalar elements. These types are written as @samp{<vector>} elements,
41875 specifying the array element type, @var{type}, and the number of elements,
41879 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41883 If a register's value is usefully viewed in multiple ways, define it
41884 with a union type containing the useful representations. The
41885 @samp{<union>} element contains one or more @samp{<field>} elements,
41886 each of which has a @var{name} and a @var{type}:
41889 <union id="@var{id}">
41890 <field name="@var{name}" type="@var{type}"/>
41897 If a register's value is composed from several separate values, define
41898 it with either a structure type or a flags type.
41899 A flags type may only contain bitfields.
41900 A structure type may either contain only bitfields or contain no bitfields.
41901 If the value contains only bitfields, its total size in bytes must be
41904 Non-bitfield values have a @var{name} and @var{type}.
41907 <struct id="@var{id}">
41908 <field name="@var{name}" type="@var{type}"/>
41913 Both @var{name} and @var{type} values are required.
41914 No implicit padding is added.
41916 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41919 <struct id="@var{id}" size="@var{size}">
41920 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41926 <flags id="@var{id}" size="@var{size}">
41927 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41932 The @var{name} value is required.
41933 Bitfield values may be named with the empty string, @samp{""},
41934 in which case the field is ``filler'' and its value is not printed.
41935 Not all bits need to be specified, so ``filler'' fields are optional.
41937 The @var{start} and @var{end} values are required, and @var{type}
41939 The field's @var{start} must be less than or equal to its @var{end},
41940 and zero represents the least significant bit.
41942 The default value of @var{type} is @code{bool} for single bit fields,
41943 and an unsigned integer otherwise.
41945 Which to choose? Structures or flags?
41947 Registers defined with @samp{flags} have these advantages over
41948 defining them with @samp{struct}:
41952 Arithmetic may be performed on them as if they were integers.
41954 They are printed in a more readable fashion.
41957 Registers defined with @samp{struct} have one advantage over
41958 defining them with @samp{flags}:
41962 One can fetch individual fields like in @samp{C}.
41965 (gdb) print $my_struct_reg.field3
41971 @subsection Registers
41974 Each register is represented as an element with this form:
41977 <reg name="@var{name}"
41978 bitsize="@var{size}"
41979 @r{[}regnum="@var{num}"@r{]}
41980 @r{[}save-restore="@var{save-restore}"@r{]}
41981 @r{[}type="@var{type}"@r{]}
41982 @r{[}group="@var{group}"@r{]}/>
41986 The components are as follows:
41991 The register's name; it must be unique within the target description.
41994 The register's size, in bits.
41997 The register's number. If omitted, a register's number is one greater
41998 than that of the previous register (either in the current feature or in
41999 a preceding feature); the first register in the target description
42000 defaults to zero. This register number is used to read or write
42001 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42002 packets, and registers appear in the @code{g} and @code{G} packets
42003 in order of increasing register number.
42006 Whether the register should be preserved across inferior function
42007 calls; this must be either @code{yes} or @code{no}. The default is
42008 @code{yes}, which is appropriate for most registers except for
42009 some system control registers; this is not related to the target's
42013 The type of the register. It may be a predefined type, a type
42014 defined in the current feature, or one of the special types @code{int}
42015 and @code{float}. @code{int} is an integer type of the correct size
42016 for @var{bitsize}, and @code{float} is a floating point type (in the
42017 architecture's normal floating point format) of the correct size for
42018 @var{bitsize}. The default is @code{int}.
42021 The register group to which this register belongs. It can be one of the
42022 standard register groups @code{general}, @code{float}, @code{vector} or an
42023 arbitrary string. Group names should be limited to alphanumeric characters.
42024 If a group name is made up of multiple words the words may be separated by
42025 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
42026 @var{group} is specified, @value{GDBN} will not display the register in
42027 @code{info registers}.
42031 @node Predefined Target Types
42032 @section Predefined Target Types
42033 @cindex target descriptions, predefined types
42035 Type definitions in the self-description can build up composite types
42036 from basic building blocks, but can not define fundamental types. Instead,
42037 standard identifiers are provided by @value{GDBN} for the fundamental
42038 types. The currently supported types are:
42043 Boolean type, occupying a single bit.
42050 Signed integer types holding the specified number of bits.
42057 Unsigned integer types holding the specified number of bits.
42061 Pointers to unspecified code and data. The program counter and
42062 any dedicated return address register may be marked as code
42063 pointers; printing a code pointer converts it into a symbolic
42064 address. The stack pointer and any dedicated address registers
42065 may be marked as data pointers.
42068 Single precision IEEE floating point.
42071 Double precision IEEE floating point.
42074 The 12-byte extended precision format used by ARM FPA registers.
42077 The 10-byte extended precision format used by x87 registers.
42080 32bit @sc{eflags} register used by x86.
42083 32bit @sc{mxcsr} register used by x86.
42087 @node Enum Target Types
42088 @section Enum Target Types
42089 @cindex target descriptions, enum types
42091 Enum target types are useful in @samp{struct} and @samp{flags}
42092 register descriptions. @xref{Target Description Format}.
42094 Enum types have a name, size and a list of name/value pairs.
42097 <enum id="@var{id}" size="@var{size}">
42098 <evalue name="@var{name}" value="@var{value}"/>
42103 Enums must be defined before they are used.
42106 <enum id="levels_type" size="4">
42107 <evalue name="low" value="0"/>
42108 <evalue name="high" value="1"/>
42110 <flags id="flags_type" size="4">
42111 <field name="X" start="0"/>
42112 <field name="LEVEL" start="1" end="1" type="levels_type"/>
42114 <reg name="flags" bitsize="32" type="flags_type"/>
42117 Given that description, a value of 3 for the @samp{flags} register
42118 would be printed as:
42121 (gdb) info register flags
42122 flags 0x3 [ X LEVEL=high ]
42125 @node Standard Target Features
42126 @section Standard Target Features
42127 @cindex target descriptions, standard features
42129 A target description must contain either no registers or all the
42130 target's registers. If the description contains no registers, then
42131 @value{GDBN} will assume a default register layout, selected based on
42132 the architecture. If the description contains any registers, the
42133 default layout will not be used; the standard registers must be
42134 described in the target description, in such a way that @value{GDBN}
42135 can recognize them.
42137 This is accomplished by giving specific names to feature elements
42138 which contain standard registers. @value{GDBN} will look for features
42139 with those names and verify that they contain the expected registers;
42140 if any known feature is missing required registers, or if any required
42141 feature is missing, @value{GDBN} will reject the target
42142 description. You can add additional registers to any of the
42143 standard features --- @value{GDBN} will display them just as if
42144 they were added to an unrecognized feature.
42146 This section lists the known features and their expected contents.
42147 Sample XML documents for these features are included in the
42148 @value{GDBN} source tree, in the directory @file{gdb/features}.
42150 Names recognized by @value{GDBN} should include the name of the
42151 company or organization which selected the name, and the overall
42152 architecture to which the feature applies; so e.g.@: the feature
42153 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42155 The names of registers are not case sensitive for the purpose
42156 of recognizing standard features, but @value{GDBN} will only display
42157 registers using the capitalization used in the description.
42160 * AArch64 Features::
42164 * MicroBlaze Features::
42168 * Nios II Features::
42169 * OpenRISC 1000 Features::
42170 * PowerPC Features::
42171 * S/390 and System z Features::
42177 @node AArch64 Features
42178 @subsection AArch64 Features
42179 @cindex target descriptions, AArch64 features
42181 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42182 targets. It should contain registers @samp{x0} through @samp{x30},
42183 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42185 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42186 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42189 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
42190 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
42191 through @samp{p15}, @samp{ffr} and @samp{vg}.
42194 @subsection ARC Features
42195 @cindex target descriptions, ARC Features
42197 ARC processors are highly configurable, so even core registers and their number
42198 are not completely predetermined. In addition flags and PC registers which are
42199 important to @value{GDBN} are not ``core'' registers in ARC. It is required
42200 that one of the core registers features is present.
42201 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
42203 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
42204 targets with a normal register file. It should contain registers @samp{r0}
42205 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42206 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
42207 and any of extension core registers @samp{r32} through @samp{r59/acch}.
42208 @samp{ilink} and extension core registers are not available to read/write, when
42209 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
42211 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
42212 ARC HS targets with a reduced register file. It should contain registers
42213 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
42214 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
42215 This feature may contain register @samp{ilink} and any of extension core
42216 registers @samp{r32} through @samp{r59/acch}.
42218 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
42219 targets with a normal register file. It should contain registers @samp{r0}
42220 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42221 @samp{lp_count} and @samp{pcl}. This feature may contain registers
42222 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
42223 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
42224 registers are not available when debugging GNU/Linux applications. The only
42225 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
42226 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
42227 ARC v2, but @samp{ilink2} is optional on ARCompact.
42229 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
42230 targets. It should contain registers @samp{pc} and @samp{status32}.
42233 @subsection ARM Features
42234 @cindex target descriptions, ARM features
42236 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42238 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42239 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42241 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42242 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42243 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42246 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42247 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42249 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42250 it should contain at least registers @samp{wR0} through @samp{wR15} and
42251 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42252 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42254 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42255 should contain at least registers @samp{d0} through @samp{d15}. If
42256 they are present, @samp{d16} through @samp{d31} should also be included.
42257 @value{GDBN} will synthesize the single-precision registers from
42258 halves of the double-precision registers.
42260 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42261 need to contain registers; it instructs @value{GDBN} to display the
42262 VFP double-precision registers as vectors and to synthesize the
42263 quad-precision registers from pairs of double-precision registers.
42264 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42265 be present and include 32 double-precision registers.
42267 @node i386 Features
42268 @subsection i386 Features
42269 @cindex target descriptions, i386 features
42271 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42272 targets. It should describe the following registers:
42276 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42278 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42280 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42281 @samp{fs}, @samp{gs}
42283 @samp{st0} through @samp{st7}
42285 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42286 @samp{foseg}, @samp{fooff} and @samp{fop}
42289 The register sets may be different, depending on the target.
42291 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42292 describe registers:
42296 @samp{xmm0} through @samp{xmm7} for i386
42298 @samp{xmm0} through @samp{xmm15} for amd64
42303 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42304 @samp{org.gnu.gdb.i386.sse} feature. It should
42305 describe the upper 128 bits of @sc{ymm} registers:
42309 @samp{ymm0h} through @samp{ymm7h} for i386
42311 @samp{ymm0h} through @samp{ymm15h} for amd64
42314 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
42315 Memory Protection Extension (MPX). It should describe the following registers:
42319 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
42321 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
42324 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42325 describe a single register, @samp{orig_eax}.
42327 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
42328 describe two system registers: @samp{fs_base} and @samp{gs_base}.
42330 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
42331 @samp{org.gnu.gdb.i386.avx} feature. It should
42332 describe additional @sc{xmm} registers:
42336 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
42339 It should describe the upper 128 bits of additional @sc{ymm} registers:
42343 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
42347 describe the upper 256 bits of @sc{zmm} registers:
42351 @samp{zmm0h} through @samp{zmm7h} for i386.
42353 @samp{zmm0h} through @samp{zmm15h} for amd64.
42357 describe the additional @sc{zmm} registers:
42361 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
42364 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
42365 describe a single register, @samp{pkru}. It is a 32-bit register
42366 valid for i386 and amd64.
42368 @node MicroBlaze Features
42369 @subsection MicroBlaze Features
42370 @cindex target descriptions, MicroBlaze features
42372 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
42373 targets. It should contain registers @samp{r0} through @samp{r31},
42374 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
42375 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
42376 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
42378 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
42379 If present, it should contain registers @samp{rshr} and @samp{rslr}
42381 @node MIPS Features
42382 @subsection @acronym{MIPS} Features
42383 @cindex target descriptions, @acronym{MIPS} features
42385 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42386 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42387 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42390 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42391 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42392 registers. They may be 32-bit or 64-bit depending on the target.
42394 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42395 it may be optional in a future version of @value{GDBN}. It should
42396 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42397 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42399 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42400 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42401 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42402 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42404 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42405 contain a single register, @samp{restart}, which is used by the
42406 Linux kernel to control restartable syscalls.
42408 @node M68K Features
42409 @subsection M68K Features
42410 @cindex target descriptions, M68K features
42413 @item @samp{org.gnu.gdb.m68k.core}
42414 @itemx @samp{org.gnu.gdb.coldfire.core}
42415 @itemx @samp{org.gnu.gdb.fido.core}
42416 One of those features must be always present.
42417 The feature that is present determines which flavor of m68k is
42418 used. The feature that is present should contain registers
42419 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42420 @samp{sp}, @samp{ps} and @samp{pc}.
42422 @item @samp{org.gnu.gdb.coldfire.fp}
42423 This feature is optional. If present, it should contain registers
42424 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42428 @node NDS32 Features
42429 @subsection NDS32 Features
42430 @cindex target descriptions, NDS32 features
42432 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42433 targets. It should contain at least registers @samp{r0} through
42434 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42437 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42438 it should contain 64-bit double-precision floating-point registers
42439 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42440 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42442 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42443 registers are overlapped with the thirty-two 32-bit single-precision
42444 floating-point registers. The 32-bit single-precision registers, if
42445 not being listed explicitly, will be synthesized from halves of the
42446 overlapping 64-bit double-precision registers. Listing 32-bit
42447 single-precision registers explicitly is deprecated, and the
42448 support to it could be totally removed some day.
42450 @node Nios II Features
42451 @subsection Nios II Features
42452 @cindex target descriptions, Nios II features
42454 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42455 targets. It should contain the 32 core registers (@samp{zero},
42456 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42457 @samp{pc}, and the 16 control registers (@samp{status} through
42460 @node OpenRISC 1000 Features
42461 @subsection Openrisc 1000 Features
42462 @cindex target descriptions, OpenRISC 1000 features
42464 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42465 targets. It should contain the 32 general purpose registers (@samp{r0}
42466 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42468 @node PowerPC Features
42469 @subsection PowerPC Features
42470 @cindex target descriptions, PowerPC features
42472 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42473 targets. It should contain registers @samp{r0} through @samp{r31},
42474 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42475 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42477 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42478 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42480 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42481 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42484 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42485 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42486 will combine these registers with the floating point registers
42487 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42488 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42489 through @samp{vs63}, the set of vector registers for POWER7.
42491 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42492 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42493 @samp{spefscr}. SPE targets should provide 32-bit registers in
42494 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42495 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42496 these to present registers @samp{ev0} through @samp{ev31} to the
42499 @node S/390 and System z Features
42500 @subsection S/390 and System z Features
42501 @cindex target descriptions, S/390 features
42502 @cindex target descriptions, System z features
42504 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42505 System z targets. It should contain the PSW and the 16 general
42506 registers. In particular, System z targets should provide the 64-bit
42507 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42508 S/390 targets should provide the 32-bit versions of these registers.
42509 A System z target that runs in 31-bit addressing mode should provide
42510 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42511 register's upper halves @samp{r0h} through @samp{r15h}, and their
42512 lower halves @samp{r0l} through @samp{r15l}.
42514 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42515 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42518 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42519 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42521 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42522 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42523 targets and 32-bit otherwise. In addition, the feature may contain
42524 the @samp{last_break} register, whose width depends on the addressing
42525 mode, as well as the @samp{system_call} register, which is always
42528 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42529 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42530 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42532 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42533 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42534 combined by @value{GDBN} with the floating point registers @samp{f0}
42535 through @samp{f15} to present the 128-bit wide vector registers
42536 @samp{v0} through @samp{v15}. In addition, this feature should
42537 contain the 128-bit wide vector registers @samp{v16} through
42540 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42541 the 64-bit wide guarded-storage-control registers @samp{gsd},
42542 @samp{gssm}, and @samp{gsepla}.
42544 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42545 the 64-bit wide guarded-storage broadcast control registers
42546 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42548 @node Sparc Features
42549 @subsection Sparc Features
42550 @cindex target descriptions, sparc32 features
42551 @cindex target descriptions, sparc64 features
42552 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42553 targets. It should describe the following registers:
42557 @samp{g0} through @samp{g7}
42559 @samp{o0} through @samp{o7}
42561 @samp{l0} through @samp{l7}
42563 @samp{i0} through @samp{i7}
42566 They may be 32-bit or 64-bit depending on the target.
42568 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42569 targets. It should describe the following registers:
42573 @samp{f0} through @samp{f31}
42575 @samp{f32} through @samp{f62} for sparc64
42578 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42579 targets. It should describe the following registers:
42583 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42584 @samp{fsr}, and @samp{csr} for sparc32
42586 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42590 @node TIC6x Features
42591 @subsection TMS320C6x Features
42592 @cindex target descriptions, TIC6x features
42593 @cindex target descriptions, TMS320C6x features
42594 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42595 targets. It should contain registers @samp{A0} through @samp{A15},
42596 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42598 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42599 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42600 through @samp{B31}.
42602 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42603 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42605 @node Operating System Information
42606 @appendix Operating System Information
42607 @cindex operating system information
42613 Users of @value{GDBN} often wish to obtain information about the state of
42614 the operating system running on the target---for example the list of
42615 processes, or the list of open files. This section describes the
42616 mechanism that makes it possible. This mechanism is similar to the
42617 target features mechanism (@pxref{Target Descriptions}), but focuses
42618 on a different aspect of target.
42620 Operating system information is retrived from the target via the
42621 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42622 read}). The object name in the request should be @samp{osdata}, and
42623 the @var{annex} identifies the data to be fetched.
42626 @appendixsection Process list
42627 @cindex operating system information, process list
42629 When requesting the process list, the @var{annex} field in the
42630 @samp{qXfer} request should be @samp{processes}. The returned data is
42631 an XML document. The formal syntax of this document is defined in
42632 @file{gdb/features/osdata.dtd}.
42634 An example document is:
42637 <?xml version="1.0"?>
42638 <!DOCTYPE target SYSTEM "osdata.dtd">
42639 <osdata type="processes">
42641 <column name="pid">1</column>
42642 <column name="user">root</column>
42643 <column name="command">/sbin/init</column>
42644 <column name="cores">1,2,3</column>
42649 Each item should include a column whose name is @samp{pid}. The value
42650 of that column should identify the process on the target. The
42651 @samp{user} and @samp{command} columns are optional, and will be
42652 displayed by @value{GDBN}. The @samp{cores} column, if present,
42653 should contain a comma-separated list of cores that this process
42654 is running on. Target may provide additional columns,
42655 which @value{GDBN} currently ignores.
42657 @node Trace File Format
42658 @appendix Trace File Format
42659 @cindex trace file format
42661 The trace file comes in three parts: a header, a textual description
42662 section, and a trace frame section with binary data.
42664 The header has the form @code{\x7fTRACE0\n}. The first byte is
42665 @code{0x7f} so as to indicate that the file contains binary data,
42666 while the @code{0} is a version number that may have different values
42669 The description section consists of multiple lines of @sc{ascii} text
42670 separated by newline characters (@code{0xa}). The lines may include a
42671 variety of optional descriptive or context-setting information, such
42672 as tracepoint definitions or register set size. @value{GDBN} will
42673 ignore any line that it does not recognize. An empty line marks the end
42678 Specifies the size of a register block in bytes. This is equal to the
42679 size of a @code{g} packet payload in the remote protocol. @var{size}
42680 is an ascii decimal number. There should be only one such line in
42681 a single trace file.
42683 @item status @var{status}
42684 Trace status. @var{status} has the same format as a @code{qTStatus}
42685 remote packet reply. There should be only one such line in a single trace
42688 @item tp @var{payload}
42689 Tracepoint definition. The @var{payload} has the same format as
42690 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42691 may take multiple lines of definition, corresponding to the multiple
42694 @item tsv @var{payload}
42695 Trace state variable definition. The @var{payload} has the same format as
42696 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42697 may take multiple lines of definition, corresponding to the multiple
42700 @item tdesc @var{payload}
42701 Target description in XML format. The @var{payload} is a single line of
42702 the XML file. All such lines should be concatenated together to get
42703 the original XML file. This file is in the same format as @code{qXfer}
42704 @code{features} payload, and corresponds to the main @code{target.xml}
42705 file. Includes are not allowed.
42709 The trace frame section consists of a number of consecutive frames.
42710 Each frame begins with a two-byte tracepoint number, followed by a
42711 four-byte size giving the amount of data in the frame. The data in
42712 the frame consists of a number of blocks, each introduced by a
42713 character indicating its type (at least register, memory, and trace
42714 state variable). The data in this section is raw binary, not a
42715 hexadecimal or other encoding; its endianness matches the target's
42718 @c FIXME bi-arch may require endianness/arch info in description section
42721 @item R @var{bytes}
42722 Register block. The number and ordering of bytes matches that of a
42723 @code{g} packet in the remote protocol. Note that these are the
42724 actual bytes, in target order, not a hexadecimal encoding.
42726 @item M @var{address} @var{length} @var{bytes}...
42727 Memory block. This is a contiguous block of memory, at the 8-byte
42728 address @var{address}, with a 2-byte length @var{length}, followed by
42729 @var{length} bytes.
42731 @item V @var{number} @var{value}
42732 Trace state variable block. This records the 8-byte signed value
42733 @var{value} of trace state variable numbered @var{number}.
42737 Future enhancements of the trace file format may include additional types
42740 @node Index Section Format
42741 @appendix @code{.gdb_index} section format
42742 @cindex .gdb_index section format
42743 @cindex index section format
42745 This section documents the index section that is created by @code{save
42746 gdb-index} (@pxref{Index Files}). The index section is
42747 DWARF-specific; some knowledge of DWARF is assumed in this
42750 The mapped index file format is designed to be directly
42751 @code{mmap}able on any architecture. In most cases, a datum is
42752 represented using a little-endian 32-bit integer value, called an
42753 @code{offset_type}. Big endian machines must byte-swap the values
42754 before using them. Exceptions to this rule are noted. The data is
42755 laid out such that alignment is always respected.
42757 A mapped index consists of several areas, laid out in order.
42761 The file header. This is a sequence of values, of @code{offset_type}
42762 unless otherwise noted:
42766 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42767 Version 4 uses a different hashing function from versions 5 and 6.
42768 Version 6 includes symbols for inlined functions, whereas versions 4
42769 and 5 do not. Version 7 adds attributes to the CU indices in the
42770 symbol table. Version 8 specifies that symbols from DWARF type units
42771 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42772 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42774 @value{GDBN} will only read version 4, 5, or 6 indices
42775 by specifying @code{set use-deprecated-index-sections on}.
42776 GDB has a workaround for potentially broken version 7 indices so it is
42777 currently not flagged as deprecated.
42780 The offset, from the start of the file, of the CU list.
42783 The offset, from the start of the file, of the types CU list. Note
42784 that this area can be empty, in which case this offset will be equal
42785 to the next offset.
42788 The offset, from the start of the file, of the address area.
42791 The offset, from the start of the file, of the symbol table.
42794 The offset, from the start of the file, of the constant pool.
42798 The CU list. This is a sequence of pairs of 64-bit little-endian
42799 values, sorted by the CU offset. The first element in each pair is
42800 the offset of a CU in the @code{.debug_info} section. The second
42801 element in each pair is the length of that CU. References to a CU
42802 elsewhere in the map are done using a CU index, which is just the
42803 0-based index into this table. Note that if there are type CUs, then
42804 conceptually CUs and type CUs form a single list for the purposes of
42808 The types CU list. This is a sequence of triplets of 64-bit
42809 little-endian values. In a triplet, the first value is the CU offset,
42810 the second value is the type offset in the CU, and the third value is
42811 the type signature. The types CU list is not sorted.
42814 The address area. The address area consists of a sequence of address
42815 entries. Each address entry has three elements:
42819 The low address. This is a 64-bit little-endian value.
42822 The high address. This is a 64-bit little-endian value. Like
42823 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42826 The CU index. This is an @code{offset_type} value.
42830 The symbol table. This is an open-addressed hash table. The size of
42831 the hash table is always a power of 2.
42833 Each slot in the hash table consists of a pair of @code{offset_type}
42834 values. The first value is the offset of the symbol's name in the
42835 constant pool. The second value is the offset of the CU vector in the
42838 If both values are 0, then this slot in the hash table is empty. This
42839 is ok because while 0 is a valid constant pool index, it cannot be a
42840 valid index for both a string and a CU vector.
42842 The hash value for a table entry is computed by applying an
42843 iterative hash function to the symbol's name. Starting with an
42844 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42845 the string is incorporated into the hash using the formula depending on the
42850 The formula is @code{r = r * 67 + c - 113}.
42852 @item Versions 5 to 7
42853 The formula is @code{r = r * 67 + tolower (c) - 113}.
42856 The terminating @samp{\0} is not incorporated into the hash.
42858 The step size used in the hash table is computed via
42859 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42860 value, and @samp{size} is the size of the hash table. The step size
42861 is used to find the next candidate slot when handling a hash
42864 The names of C@t{++} symbols in the hash table are canonicalized. We
42865 don't currently have a simple description of the canonicalization
42866 algorithm; if you intend to create new index sections, you must read
42870 The constant pool. This is simply a bunch of bytes. It is organized
42871 so that alignment is correct: CU vectors are stored first, followed by
42874 A CU vector in the constant pool is a sequence of @code{offset_type}
42875 values. The first value is the number of CU indices in the vector.
42876 Each subsequent value is the index and symbol attributes of a CU in
42877 the CU list. This element in the hash table is used to indicate which
42878 CUs define the symbol and how the symbol is used.
42879 See below for the format of each CU index+attributes entry.
42881 A string in the constant pool is zero-terminated.
42884 Attributes were added to CU index values in @code{.gdb_index} version 7.
42885 If a symbol has multiple uses within a CU then there is one
42886 CU index+attributes value for each use.
42888 The format of each CU index+attributes entry is as follows
42894 This is the index of the CU in the CU list.
42896 These bits are reserved for future purposes and must be zero.
42898 The kind of the symbol in the CU.
42902 This value is reserved and should not be used.
42903 By reserving zero the full @code{offset_type} value is backwards compatible
42904 with previous versions of the index.
42906 The symbol is a type.
42908 The symbol is a variable or an enum value.
42910 The symbol is a function.
42912 Any other kind of symbol.
42914 These values are reserved.
42918 This bit is zero if the value is global and one if it is static.
42920 The determination of whether a symbol is global or static is complicated.
42921 The authorative reference is the file @file{dwarf2read.c} in
42922 @value{GDBN} sources.
42926 This pseudo-code describes the computation of a symbol's kind and
42927 global/static attributes in the index.
42930 is_external = get_attribute (die, DW_AT_external);
42931 language = get_attribute (cu_die, DW_AT_language);
42934 case DW_TAG_typedef:
42935 case DW_TAG_base_type:
42936 case DW_TAG_subrange_type:
42940 case DW_TAG_enumerator:
42942 is_static = language != CPLUS;
42944 case DW_TAG_subprogram:
42946 is_static = ! (is_external || language == ADA);
42948 case DW_TAG_constant:
42950 is_static = ! is_external;
42952 case DW_TAG_variable:
42954 is_static = ! is_external;
42956 case DW_TAG_namespace:
42960 case DW_TAG_class_type:
42961 case DW_TAG_interface_type:
42962 case DW_TAG_structure_type:
42963 case DW_TAG_union_type:
42964 case DW_TAG_enumeration_type:
42966 is_static = language != CPLUS;
42974 @appendix Manual pages
42978 * gdb man:: The GNU Debugger man page
42979 * gdbserver man:: Remote Server for the GNU Debugger man page
42980 * gcore man:: Generate a core file of a running program
42981 * gdbinit man:: gdbinit scripts
42982 * gdb-add-index man:: Add index files to speed up GDB
42988 @c man title gdb The GNU Debugger
42990 @c man begin SYNOPSIS gdb
42991 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42992 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42993 [@option{-b}@w{ }@var{bps}]
42994 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42995 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42996 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42997 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42998 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43001 @c man begin DESCRIPTION gdb
43002 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43003 going on ``inside'' another program while it executes -- or what another
43004 program was doing at the moment it crashed.
43006 @value{GDBN} can do four main kinds of things (plus other things in support of
43007 these) to help you catch bugs in the act:
43011 Start your program, specifying anything that might affect its behavior.
43014 Make your program stop on specified conditions.
43017 Examine what has happened, when your program has stopped.
43020 Change things in your program, so you can experiment with correcting the
43021 effects of one bug and go on to learn about another.
43024 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43027 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43028 commands from the terminal until you tell it to exit with the @value{GDBN}
43029 command @code{quit}. You can get online help from @value{GDBN} itself
43030 by using the command @code{help}.
43032 You can run @code{gdb} with no arguments or options; but the most
43033 usual way to start @value{GDBN} is with one argument or two, specifying an
43034 executable program as the argument:
43040 You can also start with both an executable program and a core file specified:
43046 You can, instead, specify a process ID as a second argument, if you want
43047 to debug a running process:
43055 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43056 named @file{1234}; @value{GDBN} does check for a core file first).
43057 With option @option{-p} you can omit the @var{program} filename.
43059 Here are some of the most frequently needed @value{GDBN} commands:
43061 @c pod2man highlights the right hand side of the @item lines.
43063 @item break [@var{file}:]@var{function}
43064 Set a breakpoint at @var{function} (in @var{file}).
43066 @item run [@var{arglist}]
43067 Start your program (with @var{arglist}, if specified).
43070 Backtrace: display the program stack.
43072 @item print @var{expr}
43073 Display the value of an expression.
43076 Continue running your program (after stopping, e.g. at a breakpoint).
43079 Execute next program line (after stopping); step @emph{over} any
43080 function calls in the line.
43082 @item edit [@var{file}:]@var{function}
43083 look at the program line where it is presently stopped.
43085 @item list [@var{file}:]@var{function}
43086 type the text of the program in the vicinity of where it is presently stopped.
43089 Execute next program line (after stopping); step @emph{into} any
43090 function calls in the line.
43092 @item help [@var{name}]
43093 Show information about @value{GDBN} command @var{name}, or general information
43094 about using @value{GDBN}.
43097 Exit from @value{GDBN}.
43101 For full details on @value{GDBN},
43102 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43103 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43104 as the @code{gdb} entry in the @code{info} program.
43108 @c man begin OPTIONS gdb
43109 Any arguments other than options specify an executable
43110 file and core file (or process ID); that is, the first argument
43111 encountered with no
43112 associated option flag is equivalent to a @option{-se} option, and the second,
43113 if any, is equivalent to a @option{-c} option if it's the name of a file.
43115 both long and short forms; both are shown here. The long forms are also
43116 recognized if you truncate them, so long as enough of the option is
43117 present to be unambiguous. (If you prefer, you can flag option
43118 arguments with @option{+} rather than @option{-}, though we illustrate the
43119 more usual convention.)
43121 All the options and command line arguments you give are processed
43122 in sequential order. The order makes a difference when the @option{-x}
43128 List all options, with brief explanations.
43130 @item -symbols=@var{file}
43131 @itemx -s @var{file}
43132 Read symbol table from file @var{file}.
43135 Enable writing into executable and core files.
43137 @item -exec=@var{file}
43138 @itemx -e @var{file}
43139 Use file @var{file} as the executable file to execute when
43140 appropriate, and for examining pure data in conjunction with a core
43143 @item -se=@var{file}
43144 Read symbol table from file @var{file} and use it as the executable
43147 @item -core=@var{file}
43148 @itemx -c @var{file}
43149 Use file @var{file} as a core dump to examine.
43151 @item -command=@var{file}
43152 @itemx -x @var{file}
43153 Execute @value{GDBN} commands from file @var{file}.
43155 @item -ex @var{command}
43156 Execute given @value{GDBN} @var{command}.
43158 @item -directory=@var{directory}
43159 @itemx -d @var{directory}
43160 Add @var{directory} to the path to search for source files.
43163 Do not execute commands from @file{~/.gdbinit}.
43167 Do not execute commands from any @file{.gdbinit} initialization files.
43171 ``Quiet''. Do not print the introductory and copyright messages. These
43172 messages are also suppressed in batch mode.
43175 Run in batch mode. Exit with status @code{0} after processing all the command
43176 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43177 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43178 commands in the command files.
43180 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43181 download and run a program on another computer; in order to make this
43182 more useful, the message
43185 Program exited normally.
43189 (which is ordinarily issued whenever a program running under @value{GDBN} control
43190 terminates) is not issued when running in batch mode.
43192 @item -cd=@var{directory}
43193 Run @value{GDBN} using @var{directory} as its working directory,
43194 instead of the current directory.
43198 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43199 @value{GDBN} to output the full file name and line number in a standard,
43200 recognizable fashion each time a stack frame is displayed (which
43201 includes each time the program stops). This recognizable format looks
43202 like two @samp{\032} characters, followed by the file name, line number
43203 and character position separated by colons, and a newline. The
43204 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43205 characters as a signal to display the source code for the frame.
43208 Set the line speed (baud rate or bits per second) of any serial
43209 interface used by @value{GDBN} for remote debugging.
43211 @item -tty=@var{device}
43212 Run using @var{device} for your program's standard input and output.
43216 @c man begin SEEALSO gdb
43218 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43219 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43220 documentation are properly installed at your site, the command
43227 should give you access to the complete manual.
43229 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43230 Richard M. Stallman and Roland H. Pesch, July 1991.
43234 @node gdbserver man
43235 @heading gdbserver man
43237 @c man title gdbserver Remote Server for the GNU Debugger
43239 @c man begin SYNOPSIS gdbserver
43240 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43242 gdbserver --attach @var{comm} @var{pid}
43244 gdbserver --multi @var{comm}
43248 @c man begin DESCRIPTION gdbserver
43249 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43250 than the one which is running the program being debugged.
43253 @subheading Usage (server (target) side)
43256 Usage (server (target) side):
43259 First, you need to have a copy of the program you want to debug put onto
43260 the target system. The program can be stripped to save space if needed, as
43261 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43262 the @value{GDBN} running on the host system.
43264 To use the server, you log on to the target system, and run the @command{gdbserver}
43265 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43266 your program, and (c) its arguments. The general syntax is:
43269 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43272 For example, using a serial port, you might say:
43276 @c @file would wrap it as F</dev/com1>.
43277 target> gdbserver /dev/com1 emacs foo.txt
43280 target> gdbserver @file{/dev/com1} emacs foo.txt
43284 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43285 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43286 waits patiently for the host @value{GDBN} to communicate with it.
43288 To use a TCP connection, you could say:
43291 target> gdbserver host:2345 emacs foo.txt
43294 This says pretty much the same thing as the last example, except that we are
43295 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43296 that we are expecting to see a TCP connection from @code{host} to local TCP port
43297 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43298 want for the port number as long as it does not conflict with any existing TCP
43299 ports on the target system. This same port number must be used in the host
43300 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43301 you chose a port number that conflicts with another service, @command{gdbserver} will
43302 print an error message and exit.
43304 @command{gdbserver} can also attach to running programs.
43305 This is accomplished via the @option{--attach} argument. The syntax is:
43308 target> gdbserver --attach @var{comm} @var{pid}
43311 @var{pid} is the process ID of a currently running process. It isn't
43312 necessary to point @command{gdbserver} at a binary for the running process.
43314 To start @code{gdbserver} without supplying an initial command to run
43315 or process ID to attach, use the @option{--multi} command line option.
43316 In such case you should connect using @kbd{target extended-remote} to start
43317 the program you want to debug.
43320 target> gdbserver --multi @var{comm}
43324 @subheading Usage (host side)
43330 You need an unstripped copy of the target program on your host system, since
43331 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43332 would, with the target program as the first argument. (You may need to use the
43333 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43334 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43335 new command you need to know about is @code{target remote}
43336 (or @code{target extended-remote}). Its argument is either
43337 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43338 descriptor. For example:
43342 @c @file would wrap it as F</dev/ttyb>.
43343 (gdb) target remote /dev/ttyb
43346 (gdb) target remote @file{/dev/ttyb}
43351 communicates with the server via serial line @file{/dev/ttyb}, and:
43354 (gdb) target remote the-target:2345
43358 communicates via a TCP connection to port 2345 on host `the-target', where
43359 you previously started up @command{gdbserver} with the same port number. Note that for
43360 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43361 command, otherwise you may get an error that looks something like
43362 `Connection refused'.
43364 @command{gdbserver} can also debug multiple inferiors at once,
43367 the @value{GDBN} manual in node @code{Inferiors and Programs}
43368 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43371 @ref{Inferiors and Programs}.
43373 In such case use the @code{extended-remote} @value{GDBN} command variant:
43376 (gdb) target extended-remote the-target:2345
43379 The @command{gdbserver} option @option{--multi} may or may not be used in such
43383 @c man begin OPTIONS gdbserver
43384 There are three different modes for invoking @command{gdbserver}:
43389 Debug a specific program specified by its program name:
43392 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43395 The @var{comm} parameter specifies how should the server communicate
43396 with @value{GDBN}; it is either a device name (to use a serial line),
43397 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43398 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43399 debug in @var{prog}. Any remaining arguments will be passed to the
43400 program verbatim. When the program exits, @value{GDBN} will close the
43401 connection, and @code{gdbserver} will exit.
43404 Debug a specific program by specifying the process ID of a running
43408 gdbserver --attach @var{comm} @var{pid}
43411 The @var{comm} parameter is as described above. Supply the process ID
43412 of a running program in @var{pid}; @value{GDBN} will do everything
43413 else. Like with the previous mode, when the process @var{pid} exits,
43414 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43417 Multi-process mode -- debug more than one program/process:
43420 gdbserver --multi @var{comm}
43423 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43424 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43425 close the connection when a process being debugged exits, so you can
43426 debug several processes in the same session.
43429 In each of the modes you may specify these options:
43434 List all options, with brief explanations.
43437 This option causes @command{gdbserver} to print its version number and exit.
43440 @command{gdbserver} will attach to a running program. The syntax is:
43443 target> gdbserver --attach @var{comm} @var{pid}
43446 @var{pid} is the process ID of a currently running process. It isn't
43447 necessary to point @command{gdbserver} at a binary for the running process.
43450 To start @code{gdbserver} without supplying an initial command to run
43451 or process ID to attach, use this command line option.
43452 Then you can connect using @kbd{target extended-remote} and start
43453 the program you want to debug. The syntax is:
43456 target> gdbserver --multi @var{comm}
43460 Instruct @code{gdbserver} to display extra status information about the debugging
43462 This option is intended for @code{gdbserver} development and for bug reports to
43465 @item --remote-debug
43466 Instruct @code{gdbserver} to display remote protocol debug output.
43467 This option is intended for @code{gdbserver} development and for bug reports to
43470 @item --debug-format=option1@r{[},option2,...@r{]}
43471 Instruct @code{gdbserver} to include extra information in each line
43472 of debugging output.
43473 @xref{Other Command-Line Arguments for gdbserver}.
43476 Specify a wrapper to launch programs
43477 for debugging. The option should be followed by the name of the
43478 wrapper, then any command-line arguments to pass to the wrapper, then
43479 @kbd{--} indicating the end of the wrapper arguments.
43482 By default, @command{gdbserver} keeps the listening TCP port open, so that
43483 additional connections are possible. However, if you start @code{gdbserver}
43484 with the @option{--once} option, it will stop listening for any further
43485 connection attempts after connecting to the first @value{GDBN} session.
43487 @c --disable-packet is not documented for users.
43489 @c --disable-randomization and --no-disable-randomization are superseded by
43490 @c QDisableRandomization.
43495 @c man begin SEEALSO gdbserver
43497 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43498 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43499 documentation are properly installed at your site, the command
43505 should give you access to the complete manual.
43507 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43508 Richard M. Stallman and Roland H. Pesch, July 1991.
43515 @c man title gcore Generate a core file of a running program
43518 @c man begin SYNOPSIS gcore
43519 gcore [-a] [-o @var{filename}] @var{pid}
43523 @c man begin DESCRIPTION gcore
43524 Generate a core dump of a running program with process ID @var{pid}.
43525 Produced file is equivalent to a kernel produced core file as if the process
43526 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43527 limit). Unlike after a crash, after @command{gcore} the program remains
43528 running without any change.
43531 @c man begin OPTIONS gcore
43534 Dump all memory mappings. The actual effect of this option depends on
43535 the Operating System. On @sc{gnu}/Linux, it will disable
43536 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43537 enable @code{dump-excluded-mappings} (@pxref{set
43538 dump-excluded-mappings}).
43540 @item -o @var{filename}
43541 The optional argument
43542 @var{filename} specifies the file name where to put the core dump.
43543 If not specified, the file name defaults to @file{core.@var{pid}},
43544 where @var{pid} is the running program process ID.
43548 @c man begin SEEALSO gcore
43550 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43551 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43552 documentation are properly installed at your site, the command
43559 should give you access to the complete manual.
43561 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43562 Richard M. Stallman and Roland H. Pesch, July 1991.
43569 @c man title gdbinit GDB initialization scripts
43572 @c man begin SYNOPSIS gdbinit
43573 @ifset SYSTEM_GDBINIT
43574 @value{SYSTEM_GDBINIT}
43583 @c man begin DESCRIPTION gdbinit
43584 These files contain @value{GDBN} commands to automatically execute during
43585 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43588 the @value{GDBN} manual in node @code{Sequences}
43589 -- shell command @code{info -f gdb -n Sequences}.
43595 Please read more in
43597 the @value{GDBN} manual in node @code{Startup}
43598 -- shell command @code{info -f gdb -n Startup}.
43605 @ifset SYSTEM_GDBINIT
43606 @item @value{SYSTEM_GDBINIT}
43608 @ifclear SYSTEM_GDBINIT
43609 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43611 System-wide initialization file. It is executed unless user specified
43612 @value{GDBN} option @code{-nx} or @code{-n}.
43615 the @value{GDBN} manual in node @code{System-wide configuration}
43616 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43619 @ref{System-wide configuration}.
43623 User initialization file. It is executed unless user specified
43624 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43627 Initialization file for current directory. It may need to be enabled with
43628 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43631 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43632 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43635 @ref{Init File in the Current Directory}.
43640 @c man begin SEEALSO gdbinit
43642 gdb(1), @code{info -f gdb -n Startup}
43644 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43645 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43646 documentation are properly installed at your site, the command
43652 should give you access to the complete manual.
43654 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43655 Richard M. Stallman and Roland H. Pesch, July 1991.
43659 @node gdb-add-index man
43660 @heading gdb-add-index
43661 @pindex gdb-add-index
43662 @anchor{gdb-add-index}
43664 @c man title gdb-add-index Add index files to speed up GDB
43666 @c man begin SYNOPSIS gdb-add-index
43667 gdb-add-index @var{filename}
43670 @c man begin DESCRIPTION gdb-add-index
43671 When @value{GDBN} finds a symbol file, it scans the symbols in the
43672 file in order to construct an internal symbol table. This lets most
43673 @value{GDBN} operations work quickly--at the cost of a delay early on.
43674 For large programs, this delay can be quite lengthy, so @value{GDBN}
43675 provides a way to build an index, which speeds up startup.
43677 To determine whether a file contains such an index, use the command
43678 @kbd{readelf -S filename}: the index is stored in a section named
43679 @code{.gdb_index}. The index file can only be produced on systems
43680 which use ELF binaries and DWARF debug information (i.e., sections
43681 named @code{.debug_*}).
43683 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
43684 in the @env{PATH} environment variable. If you want to use different
43685 versions of these programs, you can specify them through the
43686 @env{GDB} and @env{OBJDUMP} environment variables.
43690 the @value{GDBN} manual in node @code{Index Files}
43691 -- shell command @kbd{info -f gdb -n "Index Files"}.
43698 @c man begin SEEALSO gdb-add-index
43700 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43701 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43702 documentation are properly installed at your site, the command
43708 should give you access to the complete manual.
43710 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43711 Richard M. Stallman and Roland H. Pesch, July 1991.
43717 @node GNU Free Documentation License
43718 @appendix GNU Free Documentation License
43721 @node Concept Index
43722 @unnumbered Concept Index
43726 @node Command and Variable Index
43727 @unnumbered Command, Variable, and Function Index
43732 % I think something like @@colophon should be in texinfo. In the
43734 \long\def\colophon{\hbox to0pt{}\vfill
43735 \centerline{The body of this manual is set in}
43736 \centerline{\fontname\tenrm,}
43737 \centerline{with headings in {\bf\fontname\tenbf}}
43738 \centerline{and examples in {\tt\fontname\tentt}.}
43739 \centerline{{\it\fontname\tenit\/},}
43740 \centerline{{\bf\fontname\tenbf}, and}
43741 \centerline{{\sl\fontname\tensl\/}}
43742 \centerline{are used for emphasis.}\vfill}
43744 % Blame: doc@@cygnus.com, 1991.