1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2013 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.
51 @c man begin COPYRIGHT
52 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.3 or
56 any later version published by the Free Software Foundation; with the
57 Invariant Sections being ``Free Software'' and ``Free Software Needs
58 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
59 and with the Back-Cover Texts as in (a) below.
61 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
62 this GNU Manual. Buying copies from GNU Press supports the FSF in
63 developing GNU and promoting software freedom.''
68 This file documents the @sc{gnu} debugger @value{GDBN}.
70 This is the @value{EDITION} Edition, of @cite{Debugging with
71 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
72 @ifset VERSION_PACKAGE
73 @value{VERSION_PACKAGE}
75 Version @value{GDBVN}.
81 @title Debugging with @value{GDBN}
82 @subtitle The @sc{gnu} Source-Level Debugger
84 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
85 @ifset VERSION_PACKAGE
87 @subtitle @value{VERSION_PACKAGE}
89 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
93 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
94 \hfill {\it Debugging with @value{GDBN}}\par
95 \hfill \TeX{}info \texinfoversion\par
99 @vskip 0pt plus 1filll
100 Published by the Free Software Foundation @*
101 51 Franklin Street, Fifth Floor,
102 Boston, MA 02110-1301, USA@*
103 ISBN 978-0-9831592-3-0 @*
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2013 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Process Record and Replay:: Recording inferior's execution and replaying it
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Optimized Code:: Debugging optimized code
142 * Macros:: Preprocessor Macros
143 * Tracepoints:: Debugging remote targets non-intrusively
144 * Overlays:: Debugging programs that use overlays
146 * Languages:: Using @value{GDBN} with different languages
148 * Symbols:: Examining the symbol table
149 * Altering:: Altering execution
150 * GDB Files:: @value{GDBN} files
151 * Targets:: Specifying a debugging target
152 * Remote Debugging:: Debugging remote programs
153 * Configurations:: Configuration-specific information
154 * Controlling GDB:: Controlling @value{GDBN}
155 * Extending GDB:: Extending @value{GDBN}
156 * Interpreters:: Command Interpreters
157 * TUI:: @value{GDBN} Text User Interface
158 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
159 * GDB/MI:: @value{GDBN}'s Machine Interface.
160 * Annotations:: @value{GDBN}'s annotation interface.
161 * JIT Interface:: Using the JIT debugging interface.
162 * In-Process Agent:: In-Process Agent
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * In Memoriam:: In Memoriam
175 * Formatting Documentation:: How to format and print @value{GDBN} documentation
176 * Installing GDB:: Installing GDB
177 * Maintenance Commands:: Maintenance Commands
178 * Remote Protocol:: GDB Remote Serial Protocol
179 * Agent Expressions:: The GDB Agent Expression Mechanism
180 * Target Descriptions:: How targets can describe themselves to
182 * Operating System Information:: Getting additional information from
184 * Trace File Format:: GDB trace file format
185 * Index Section Format:: .gdb_index section format
186 * Man Pages:: Manual pages
187 * Copying:: GNU General Public License says
188 how you can copy and share GDB
189 * GNU Free Documentation License:: The license for this documentation
190 * Concept Index:: Index of @value{GDBN} concepts
191 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
192 functions, and Python data types
200 @unnumbered Summary of @value{GDBN}
202 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
203 going on ``inside'' another program while it executes---or what another
204 program was doing at the moment it crashed.
206 @value{GDBN} can do four main kinds of things (plus other things in support of
207 these) to help you catch bugs in the act:
211 Start your program, specifying anything that might affect its behavior.
214 Make your program stop on specified conditions.
217 Examine what has happened, when your program has stopped.
220 Change things in your program, so you can experiment with correcting the
221 effects of one bug and go on to learn about another.
224 You can use @value{GDBN} to debug programs written in C and C@t{++}.
225 For more information, see @ref{Supported Languages,,Supported Languages}.
226 For more information, see @ref{C,,C and C++}.
228 Support for D is partial. For information on D, see
232 Support for Modula-2 is partial. For information on Modula-2, see
233 @ref{Modula-2,,Modula-2}.
235 Support for OpenCL C is partial. For information on OpenCL C, see
236 @ref{OpenCL C,,OpenCL C}.
239 Debugging Pascal programs which use sets, subranges, file variables, or
240 nested functions does not currently work. @value{GDBN} does not support
241 entering expressions, printing values, or similar features using Pascal
245 @value{GDBN} can be used to debug programs written in Fortran, although
246 it may be necessary to refer to some variables with a trailing
249 @value{GDBN} can be used to debug programs written in Objective-C,
250 using either the Apple/NeXT or the GNU Objective-C runtime.
253 * Free Software:: Freely redistributable software
254 * Free Documentation:: Free Software Needs Free Documentation
255 * Contributors:: Contributors to GDB
259 @unnumberedsec Free Software
261 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
262 General Public License
263 (GPL). The GPL gives you the freedom to copy or adapt a licensed
264 program---but every person getting a copy also gets with it the
265 freedom to modify that copy (which means that they must get access to
266 the source code), and the freedom to distribute further copies.
267 Typical software companies use copyrights to limit your freedoms; the
268 Free Software Foundation uses the GPL to preserve these freedoms.
270 Fundamentally, the General Public License is a license which says that
271 you have these freedoms and that you cannot take these freedoms away
274 @node Free Documentation
275 @unnumberedsec Free Software Needs Free Documentation
277 The biggest deficiency in the free software community today is not in
278 the software---it is the lack of good free documentation that we can
279 include with the free software. Many of our most important
280 programs do not come with free reference manuals and free introductory
281 texts. Documentation is an essential part of any software package;
282 when an important free software package does not come with a free
283 manual and a free tutorial, that is a major gap. We have many such
286 Consider Perl, for instance. The tutorial manuals that people
287 normally use are non-free. How did this come about? Because the
288 authors of those manuals published them with restrictive terms---no
289 copying, no modification, source files not available---which exclude
290 them from the free software world.
292 That wasn't the first time this sort of thing happened, and it was far
293 from the last. Many times we have heard a GNU user eagerly describe a
294 manual that he is writing, his intended contribution to the community,
295 only to learn that he had ruined everything by signing a publication
296 contract to make it non-free.
298 Free documentation, like free software, is a matter of freedom, not
299 price. The problem with the non-free manual is not that publishers
300 charge a price for printed copies---that in itself is fine. (The Free
301 Software Foundation sells printed copies of manuals, too.) The
302 problem is the restrictions on the use of the manual. Free manuals
303 are available in source code form, and give you permission to copy and
304 modify. Non-free manuals do not allow this.
306 The criteria of freedom for a free manual are roughly the same as for
307 free software. Redistribution (including the normal kinds of
308 commercial redistribution) must be permitted, so that the manual can
309 accompany every copy of the program, both on-line and on paper.
311 Permission for modification of the technical content is crucial too.
312 When people modify the software, adding or changing features, if they
313 are conscientious they will change the manual too---so they can
314 provide accurate and clear documentation for the modified program. A
315 manual that leaves you no choice but to write a new manual to document
316 a changed version of the program is not really available to our
319 Some kinds of limits on the way modification is handled are
320 acceptable. For example, requirements to preserve the original
321 author's copyright notice, the distribution terms, or the list of
322 authors, are ok. It is also no problem to require modified versions
323 to include notice that they were modified. Even entire sections that
324 may not be deleted or changed are acceptable, as long as they deal
325 with nontechnical topics (like this one). These kinds of restrictions
326 are acceptable because they don't obstruct the community's normal use
329 However, it must be possible to modify all the @emph{technical}
330 content of the manual, and then distribute the result in all the usual
331 media, through all the usual channels. Otherwise, the restrictions
332 obstruct the use of the manual, it is not free, and we need another
333 manual to replace it.
335 Please spread the word about this issue. Our community continues to
336 lose manuals to proprietary publishing. If we spread the word that
337 free software needs free reference manuals and free tutorials, perhaps
338 the next person who wants to contribute by writing documentation will
339 realize, before it is too late, that only free manuals contribute to
340 the free software community.
342 If you are writing documentation, please insist on publishing it under
343 the GNU Free Documentation License or another free documentation
344 license. Remember that this decision requires your approval---you
345 don't have to let the publisher decide. Some commercial publishers
346 will use a free license if you insist, but they will not propose the
347 option; it is up to you to raise the issue and say firmly that this is
348 what you want. If the publisher you are dealing with refuses, please
349 try other publishers. If you're not sure whether a proposed license
350 is free, write to @email{licensing@@gnu.org}.
352 You can encourage commercial publishers to sell more free, copylefted
353 manuals and tutorials by buying them, and particularly by buying
354 copies from the publishers that paid for their writing or for major
355 improvements. Meanwhile, try to avoid buying non-free documentation
356 at all. Check the distribution terms of a manual before you buy it,
357 and insist that whoever seeks your business must respect your freedom.
358 Check the history of the book, and try to reward the publishers that
359 have paid or pay the authors to work on it.
361 The Free Software Foundation maintains a list of free documentation
362 published by other publishers, at
363 @url{http://www.fsf.org/doc/other-free-books.html}.
366 @unnumberedsec Contributors to @value{GDBN}
368 Richard Stallman was the original author of @value{GDBN}, and of many
369 other @sc{gnu} programs. Many others have contributed to its
370 development. This section attempts to credit major contributors. One
371 of the virtues of free software is that everyone is free to contribute
372 to it; with regret, we cannot actually acknowledge everyone here. The
373 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
374 blow-by-blow account.
376 Changes much prior to version 2.0 are lost in the mists of time.
379 @emph{Plea:} Additions to this section are particularly welcome. If you
380 or your friends (or enemies, to be evenhanded) have been unfairly
381 omitted from this list, we would like to add your names!
384 So that they may not regard their many labors as thankless, we
385 particularly thank those who shepherded @value{GDBN} through major
387 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
388 Jim Blandy (release 4.18);
389 Jason Molenda (release 4.17);
390 Stan Shebs (release 4.14);
391 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
392 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
393 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
394 Jim Kingdon (releases 3.5, 3.4, and 3.3);
395 and Randy Smith (releases 3.2, 3.1, and 3.0).
397 Richard Stallman, assisted at various times by Peter TerMaat, Chris
398 Hanson, and Richard Mlynarik, handled releases through 2.8.
400 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
401 in @value{GDBN}, with significant additional contributions from Per
402 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
403 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
404 much general update work leading to release 3.0).
406 @value{GDBN} uses the BFD subroutine library to examine multiple
407 object-file formats; BFD was a joint project of David V.
408 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
410 David Johnson wrote the original COFF support; Pace Willison did
411 the original support for encapsulated COFF.
413 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
415 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
416 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
418 Jean-Daniel Fekete contributed Sun 386i support.
419 Chris Hanson improved the HP9000 support.
420 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
421 David Johnson contributed Encore Umax support.
422 Jyrki Kuoppala contributed Altos 3068 support.
423 Jeff Law contributed HP PA and SOM support.
424 Keith Packard contributed NS32K support.
425 Doug Rabson contributed Acorn Risc Machine support.
426 Bob Rusk contributed Harris Nighthawk CX-UX support.
427 Chris Smith contributed Convex support (and Fortran debugging).
428 Jonathan Stone contributed Pyramid support.
429 Michael Tiemann contributed SPARC support.
430 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
431 Pace Willison contributed Intel 386 support.
432 Jay Vosburgh contributed Symmetry support.
433 Marko Mlinar contributed OpenRISC 1000 support.
435 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
437 Rich Schaefer and Peter Schauer helped with support of SunOS shared
440 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
441 about several machine instruction sets.
443 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
444 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
445 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
446 and RDI targets, respectively.
448 Brian Fox is the author of the readline libraries providing
449 command-line editing and command history.
451 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
452 Modula-2 support, and contributed the Languages chapter of this manual.
454 Fred Fish wrote most of the support for Unix System Vr4.
455 He also enhanced the command-completion support to cover C@t{++} overloaded
458 Hitachi America (now Renesas America), Ltd. sponsored the support for
459 H8/300, H8/500, and Super-H processors.
461 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
463 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
466 Toshiba sponsored the support for the TX39 Mips processor.
468 Matsushita sponsored the support for the MN10200 and MN10300 processors.
470 Fujitsu sponsored the support for SPARClite and FR30 processors.
472 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
475 Michael Snyder added support for tracepoints.
477 Stu Grossman wrote gdbserver.
479 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
480 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
482 The following people at the Hewlett-Packard Company contributed
483 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
484 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
485 compiler, and the Text User Interface (nee Terminal User Interface):
486 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
487 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
488 provided HP-specific information in this manual.
490 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
491 Robert Hoehne made significant contributions to the DJGPP port.
493 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
494 development since 1991. Cygnus engineers who have worked on @value{GDBN}
495 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
496 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
497 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
498 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
499 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
500 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
501 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
502 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
503 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
504 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
505 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
506 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
507 Zuhn have made contributions both large and small.
509 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
510 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
512 Jim Blandy added support for preprocessor macros, while working for Red
515 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
516 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
517 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
518 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
519 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
520 with the migration of old architectures to this new framework.
522 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
523 unwinder framework, this consisting of a fresh new design featuring
524 frame IDs, independent frame sniffers, and the sentinel frame. Mark
525 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
526 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
527 trad unwinders. The architecture-specific changes, each involving a
528 complete rewrite of the architecture's frame code, were carried out by
529 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
530 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
531 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
532 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
535 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
536 Tensilica, Inc.@: contributed support for Xtensa processors. Others
537 who have worked on the Xtensa port of @value{GDBN} in the past include
538 Steve Tjiang, John Newlin, and Scott Foehner.
540 Michael Eager and staff of Xilinx, Inc., contributed support for the
541 Xilinx MicroBlaze architecture.
544 @chapter A Sample @value{GDBN} Session
546 You can use this manual at your leisure to read all about @value{GDBN}.
547 However, a handful of commands are enough to get started using the
548 debugger. This chapter illustrates those commands.
551 In this sample session, we emphasize user input like this: @b{input},
552 to make it easier to pick out from the surrounding output.
555 @c FIXME: this example may not be appropriate for some configs, where
556 @c FIXME...primary interest is in remote use.
558 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
559 processor) exhibits the following bug: sometimes, when we change its
560 quote strings from the default, the commands used to capture one macro
561 definition within another stop working. In the following short @code{m4}
562 session, we define a macro @code{foo} which expands to @code{0000}; we
563 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
564 same thing. However, when we change the open quote string to
565 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
566 procedure fails to define a new synonym @code{baz}:
575 @b{define(bar,defn(`foo'))}
579 @b{changequote(<QUOTE>,<UNQUOTE>)}
581 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
584 m4: End of input: 0: fatal error: EOF in string
588 Let us use @value{GDBN} to try to see what is going on.
591 $ @b{@value{GDBP} m4}
592 @c FIXME: this falsifies the exact text played out, to permit smallbook
593 @c FIXME... format to come out better.
594 @value{GDBN} is free software and you are welcome to distribute copies
595 of it under certain conditions; type "show copying" to see
597 There is absolutely no warranty for @value{GDBN}; type "show warranty"
600 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
605 @value{GDBN} reads only enough symbol data to know where to find the
606 rest when needed; as a result, the first prompt comes up very quickly.
607 We now tell @value{GDBN} to use a narrower display width than usual, so
608 that examples fit in this manual.
611 (@value{GDBP}) @b{set width 70}
615 We need to see how the @code{m4} built-in @code{changequote} works.
616 Having looked at the source, we know the relevant subroutine is
617 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
618 @code{break} command.
621 (@value{GDBP}) @b{break m4_changequote}
622 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
626 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
627 control; as long as control does not reach the @code{m4_changequote}
628 subroutine, the program runs as usual:
631 (@value{GDBP}) @b{run}
632 Starting program: /work/Editorial/gdb/gnu/m4/m4
640 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
641 suspends execution of @code{m4}, displaying information about the
642 context where it stops.
645 @b{changequote(<QUOTE>,<UNQUOTE>)}
647 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
649 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
653 Now we use the command @code{n} (@code{next}) to advance execution to
654 the next line of the current function.
658 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
663 @code{set_quotes} looks like a promising subroutine. We can go into it
664 by using the command @code{s} (@code{step}) instead of @code{next}.
665 @code{step} goes to the next line to be executed in @emph{any}
666 subroutine, so it steps into @code{set_quotes}.
670 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
672 530 if (lquote != def_lquote)
676 The display that shows the subroutine where @code{m4} is now
677 suspended (and its arguments) is called a stack frame display. It
678 shows a summary of the stack. We can use the @code{backtrace}
679 command (which can also be spelled @code{bt}), to see where we are
680 in the stack as a whole: the @code{backtrace} command displays a
681 stack frame for each active subroutine.
684 (@value{GDBP}) @b{bt}
685 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
687 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
689 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
690 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
692 #4 0x79dc in expand_input () at macro.c:40
693 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
697 We step through a few more lines to see what happens. The first two
698 times, we can use @samp{s}; the next two times we use @code{n} to avoid
699 falling into the @code{xstrdup} subroutine.
703 0x3b5c 532 if (rquote != def_rquote)
705 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
706 def_lquote : xstrdup(lq);
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
715 The last line displayed looks a little odd; we can examine the variables
716 @code{lquote} and @code{rquote} to see if they are in fact the new left
717 and right quotes we specified. We use the command @code{p}
718 (@code{print}) to see their values.
721 (@value{GDBP}) @b{p lquote}
722 $1 = 0x35d40 "<QUOTE>"
723 (@value{GDBP}) @b{p rquote}
724 $2 = 0x35d50 "<UNQUOTE>"
728 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
729 To look at some context, we can display ten lines of source
730 surrounding the current line with the @code{l} (@code{list}) command.
736 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
738 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
741 538 len_lquote = strlen(rquote);
742 539 len_rquote = strlen(lquote);
749 Let us step past the two lines that set @code{len_lquote} and
750 @code{len_rquote}, and then examine the values of those variables.
754 539 len_rquote = strlen(lquote);
757 (@value{GDBP}) @b{p len_lquote}
759 (@value{GDBP}) @b{p len_rquote}
764 That certainly looks wrong, assuming @code{len_lquote} and
765 @code{len_rquote} are meant to be the lengths of @code{lquote} and
766 @code{rquote} respectively. We can set them to better values using
767 the @code{p} command, since it can print the value of
768 any expression---and that expression can include subroutine calls and
772 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
774 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
779 Is that enough to fix the problem of using the new quotes with the
780 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
781 executing with the @code{c} (@code{continue}) command, and then try the
782 example that caused trouble initially:
788 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
795 Success! The new quotes now work just as well as the default ones. The
796 problem seems to have been just the two typos defining the wrong
797 lengths. We allow @code{m4} exit by giving it an EOF as input:
801 Program exited normally.
805 The message @samp{Program exited normally.} is from @value{GDBN}; it
806 indicates @code{m4} has finished executing. We can end our @value{GDBN}
807 session with the @value{GDBN} @code{quit} command.
810 (@value{GDBP}) @b{quit}
814 @chapter Getting In and Out of @value{GDBN}
816 This chapter discusses how to start @value{GDBN}, and how to get out of it.
820 type @samp{@value{GDBP}} to start @value{GDBN}.
822 type @kbd{quit} or @kbd{Ctrl-d} to exit.
826 * Invoking GDB:: How to start @value{GDBN}
827 * Quitting GDB:: How to quit @value{GDBN}
828 * Shell Commands:: How to use shell commands inside @value{GDBN}
829 * Logging Output:: How to log @value{GDBN}'s output to a file
833 @section Invoking @value{GDBN}
835 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
836 @value{GDBN} reads commands from the terminal until you tell it to exit.
838 You can also run @code{@value{GDBP}} with a variety of arguments and options,
839 to specify more of your debugging environment at the outset.
841 The command-line options described here are designed
842 to cover a variety of situations; in some environments, some of these
843 options may effectively be unavailable.
845 The most usual way to start @value{GDBN} is with one argument,
846 specifying an executable program:
849 @value{GDBP} @var{program}
853 You can also start with both an executable program and a core file
857 @value{GDBP} @var{program} @var{core}
860 You can, instead, specify a process ID as a second argument, if you want
861 to debug a running process:
864 @value{GDBP} @var{program} 1234
868 would attach @value{GDBN} to process @code{1234} (unless you also have a file
869 named @file{1234}; @value{GDBN} does check for a core file first).
871 Taking advantage of the second command-line argument requires a fairly
872 complete operating system; when you use @value{GDBN} as a remote
873 debugger attached to a bare board, there may not be any notion of
874 ``process'', and there is often no way to get a core dump. @value{GDBN}
875 will warn you if it is unable to attach or to read core dumps.
877 You can optionally have @code{@value{GDBP}} pass any arguments after the
878 executable file to the inferior using @code{--args}. This option stops
881 @value{GDBP} --args gcc -O2 -c foo.c
883 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
884 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
886 You can run @code{@value{GDBP}} without printing the front material, which describes
887 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
894 You can further control how @value{GDBN} starts up by using command-line
895 options. @value{GDBN} itself can remind you of the options available.
905 to display all available options and briefly describe their use
906 (@samp{@value{GDBP} -h} is a shorter equivalent).
908 All options and command line arguments you give are processed
909 in sequential order. The order makes a difference when the
910 @samp{-x} option is used.
914 * File Options:: Choosing files
915 * Mode Options:: Choosing modes
916 * Startup:: What @value{GDBN} does during startup
920 @subsection Choosing Files
922 When @value{GDBN} starts, it reads any arguments other than options as
923 specifying an executable file and core file (or process ID). This is
924 the same as if the arguments were specified by the @samp{-se} and
925 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
926 first argument that does not have an associated option flag as
927 equivalent to the @samp{-se} option followed by that argument; and the
928 second argument that does not have an associated option flag, if any, as
929 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
930 If the second argument begins with a decimal digit, @value{GDBN} will
931 first attempt to attach to it as a process, and if that fails, attempt
932 to open it as a corefile. If you have a corefile whose name begins with
933 a digit, you can prevent @value{GDBN} from treating it as a pid by
934 prefixing it with @file{./}, e.g.@: @file{./12345}.
936 If @value{GDBN} has not been configured to included core file support,
937 such as for most embedded targets, then it will complain about a second
938 argument and ignore it.
940 Many options have both long and short forms; both are shown in the
941 following list. @value{GDBN} also recognizes the long forms if you truncate
942 them, so long as enough of the option is present to be unambiguous.
943 (If you prefer, you can flag option arguments with @samp{--} rather
944 than @samp{-}, though we illustrate the more usual convention.)
946 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
947 @c way, both those who look for -foo and --foo in the index, will find
951 @item -symbols @var{file}
953 @cindex @code{--symbols}
955 Read symbol table from file @var{file}.
957 @item -exec @var{file}
959 @cindex @code{--exec}
961 Use file @var{file} as the executable file to execute when appropriate,
962 and for examining pure data in conjunction with a core dump.
966 Read symbol table from file @var{file} and use it as the executable
969 @item -core @var{file}
971 @cindex @code{--core}
973 Use file @var{file} as a core dump to examine.
975 @item -pid @var{number}
976 @itemx -p @var{number}
979 Connect to process ID @var{number}, as with the @code{attach} command.
981 @item -command @var{file}
983 @cindex @code{--command}
985 Execute commands from file @var{file}. The contents of this file is
986 evaluated exactly as the @code{source} command would.
987 @xref{Command Files,, Command files}.
989 @item -eval-command @var{command}
990 @itemx -ex @var{command}
991 @cindex @code{--eval-command}
993 Execute a single @value{GDBN} command.
995 This option may be used multiple times to call multiple commands. It may
996 also be interleaved with @samp{-command} as required.
999 @value{GDBP} -ex 'target sim' -ex 'load' \
1000 -x setbreakpoints -ex 'run' a.out
1003 @item -init-command @var{file}
1004 @itemx -ix @var{file}
1005 @cindex @code{--init-command}
1007 Execute commands from file @var{file} before loading the inferior (but
1008 after loading gdbinit files).
1011 @item -init-eval-command @var{command}
1012 @itemx -iex @var{command}
1013 @cindex @code{--init-eval-command}
1015 Execute a single @value{GDBN} command before loading the inferior (but
1016 after loading gdbinit files).
1019 @item -directory @var{directory}
1020 @itemx -d @var{directory}
1021 @cindex @code{--directory}
1023 Add @var{directory} to the path to search for source and script files.
1027 @cindex @code{--readnow}
1029 Read each symbol file's entire symbol table immediately, rather than
1030 the default, which is to read it incrementally as it is needed.
1031 This makes startup slower, but makes future operations faster.
1036 @subsection Choosing Modes
1038 You can run @value{GDBN} in various alternative modes---for example, in
1039 batch mode or quiet mode.
1047 Do not execute commands found in any initialization file.
1048 There are three init files, loaded in the following order:
1051 @item @file{system.gdbinit}
1052 This is the system-wide init file.
1053 Its location is specified with the @code{--with-system-gdbinit}
1054 configure option (@pxref{System-wide configuration}).
1055 It is loaded first when @value{GDBN} starts, before command line options
1056 have been processed.
1057 @item @file{~/.gdbinit}
1058 This is the init file in your home directory.
1059 It is loaded next, after @file{system.gdbinit}, and before
1060 command options have been processed.
1061 @item @file{./.gdbinit}
1062 This is the init file in the current directory.
1063 It is loaded last, after command line options other than @code{-x} and
1064 @code{-ex} have been processed. Command line options @code{-x} and
1065 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1068 For further documentation on startup processing, @xref{Startup}.
1069 For documentation on how to write command files,
1070 @xref{Command Files,,Command Files}.
1075 Do not execute commands found in @file{~/.gdbinit}, the init file
1076 in your home directory.
1082 @cindex @code{--quiet}
1083 @cindex @code{--silent}
1085 ``Quiet''. Do not print the introductory and copyright messages. These
1086 messages are also suppressed in batch mode.
1089 @cindex @code{--batch}
1090 Run in batch mode. Exit with status @code{0} after processing all the
1091 command files specified with @samp{-x} (and all commands from
1092 initialization files, if not inhibited with @samp{-n}). Exit with
1093 nonzero status if an error occurs in executing the @value{GDBN} commands
1094 in the command files. Batch mode also disables pagination, sets unlimited
1095 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1096 off} were in effect (@pxref{Messages/Warnings}).
1098 Batch mode may be useful for running @value{GDBN} as a filter, for
1099 example to download and run a program on another computer; in order to
1100 make this more useful, the message
1103 Program exited normally.
1107 (which is ordinarily issued whenever a program running under
1108 @value{GDBN} control terminates) is not issued when running in batch
1112 @cindex @code{--batch-silent}
1113 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1114 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1115 unaffected). This is much quieter than @samp{-silent} and would be useless
1116 for an interactive session.
1118 This is particularly useful when using targets that give @samp{Loading section}
1119 messages, for example.
1121 Note that targets that give their output via @value{GDBN}, as opposed to
1122 writing directly to @code{stdout}, will also be made silent.
1124 @item -return-child-result
1125 @cindex @code{--return-child-result}
1126 The return code from @value{GDBN} will be the return code from the child
1127 process (the process being debugged), with the following exceptions:
1131 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1132 internal error. In this case the exit code is the same as it would have been
1133 without @samp{-return-child-result}.
1135 The user quits with an explicit value. E.g., @samp{quit 1}.
1137 The child process never runs, or is not allowed to terminate, in which case
1138 the exit code will be -1.
1141 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1142 when @value{GDBN} is being used as a remote program loader or simulator
1147 @cindex @code{--nowindows}
1149 ``No windows''. If @value{GDBN} comes with a graphical user interface
1150 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1151 interface. If no GUI is available, this option has no effect.
1155 @cindex @code{--windows}
1157 If @value{GDBN} includes a GUI, then this option requires it to be
1160 @item -cd @var{directory}
1162 Run @value{GDBN} using @var{directory} as its working directory,
1163 instead of the current directory.
1165 @item -data-directory @var{directory}
1166 @cindex @code{--data-directory}
1167 Run @value{GDBN} using @var{directory} as its data directory.
1168 The data directory is where @value{GDBN} searches for its
1169 auxiliary files. @xref{Data Files}.
1173 @cindex @code{--fullname}
1175 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1176 subprocess. It tells @value{GDBN} to output the full file name and line
1177 number in a standard, recognizable fashion each time a stack frame is
1178 displayed (which includes each time your program stops). This
1179 recognizable format looks like two @samp{\032} characters, followed by
1180 the file name, line number and character position separated by colons,
1181 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1182 @samp{\032} characters as a signal to display the source code for the
1185 @item -annotate @var{level}
1186 @cindex @code{--annotate}
1187 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1188 effect is identical to using @samp{set annotate @var{level}}
1189 (@pxref{Annotations}). The annotation @var{level} controls how much
1190 information @value{GDBN} prints together with its prompt, values of
1191 expressions, source lines, and other types of output. Level 0 is the
1192 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1193 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1194 that control @value{GDBN}, and level 2 has been deprecated.
1196 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1200 @cindex @code{--args}
1201 Change interpretation of command line so that arguments following the
1202 executable file are passed as command line arguments to the inferior.
1203 This option stops option processing.
1205 @item -baud @var{bps}
1207 @cindex @code{--baud}
1209 Set the line speed (baud rate or bits per second) of any serial
1210 interface used by @value{GDBN} for remote debugging.
1212 @item -l @var{timeout}
1214 Set the timeout (in seconds) of any communication used by @value{GDBN}
1215 for remote debugging.
1217 @item -tty @var{device}
1218 @itemx -t @var{device}
1219 @cindex @code{--tty}
1221 Run using @var{device} for your program's standard input and output.
1222 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1224 @c resolve the situation of these eventually
1226 @cindex @code{--tui}
1227 Activate the @dfn{Text User Interface} when starting. The Text User
1228 Interface manages several text windows on the terminal, showing
1229 source, assembly, registers and @value{GDBN} command outputs
1230 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1231 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1232 Using @value{GDBN} under @sc{gnu} Emacs}).
1235 @c @cindex @code{--xdb}
1236 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1237 @c For information, see the file @file{xdb_trans.html}, which is usually
1238 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1241 @item -interpreter @var{interp}
1242 @cindex @code{--interpreter}
1243 Use the interpreter @var{interp} for interface with the controlling
1244 program or device. This option is meant to be set by programs which
1245 communicate with @value{GDBN} using it as a back end.
1246 @xref{Interpreters, , Command Interpreters}.
1248 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1249 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1250 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1251 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1252 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1253 @sc{gdb/mi} interfaces are no longer supported.
1256 @cindex @code{--write}
1257 Open the executable and core files for both reading and writing. This
1258 is equivalent to the @samp{set write on} command inside @value{GDBN}
1262 @cindex @code{--statistics}
1263 This option causes @value{GDBN} to print statistics about time and
1264 memory usage after it completes each command and returns to the prompt.
1267 @cindex @code{--version}
1268 This option causes @value{GDBN} to print its version number and
1269 no-warranty blurb, and exit.
1274 @subsection What @value{GDBN} Does During Startup
1275 @cindex @value{GDBN} startup
1277 Here's the description of what @value{GDBN} does during session startup:
1281 Sets up the command interpreter as specified by the command line
1282 (@pxref{Mode Options, interpreter}).
1286 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1287 used when building @value{GDBN}; @pxref{System-wide configuration,
1288 ,System-wide configuration and settings}) and executes all the commands in
1291 @anchor{Home Directory Init File}
1293 Reads the init file (if any) in your home directory@footnote{On
1294 DOS/Windows systems, the home directory is the one pointed to by the
1295 @code{HOME} environment variable.} and executes all the commands in
1298 @anchor{Option -init-eval-command}
1300 Executes commands and command files specified by the @samp{-iex} and
1301 @samp{-ix} options in their specified order. Usually you should use the
1302 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1303 settings before @value{GDBN} init files get executed and before inferior
1307 Processes command line options and operands.
1309 @anchor{Init File in the Current Directory during Startup}
1311 Reads and executes the commands from init file (if any) in the current
1312 working directory as long as @samp{set auto-load local-gdbinit} is set to
1313 @samp{on} (@pxref{Init File in the Current Directory}).
1314 This is only done if the current directory is
1315 different from your home directory. Thus, you can have more than one
1316 init file, one generic in your home directory, and another, specific
1317 to the program you are debugging, in the directory where you invoke
1321 If the command line specified a program to debug, or a process to
1322 attach to, or a core file, @value{GDBN} loads any auto-loaded
1323 scripts provided for the program or for its loaded shared libraries.
1324 @xref{Auto-loading}.
1326 If you wish to disable the auto-loading during startup,
1327 you must do something like the following:
1330 $ gdb -iex "set auto-load python-scripts off" myprogram
1333 Option @samp{-ex} does not work because the auto-loading is then turned
1337 Executes commands and command files specified by the @samp{-ex} and
1338 @samp{-x} options in their specified order. @xref{Command Files}, for
1339 more details about @value{GDBN} command files.
1342 Reads the command history recorded in the @dfn{history file}.
1343 @xref{Command History}, for more details about the command history and the
1344 files where @value{GDBN} records it.
1347 Init files use the same syntax as @dfn{command files} (@pxref{Command
1348 Files}) and are processed by @value{GDBN} in the same way. The init
1349 file in your home directory can set options (such as @samp{set
1350 complaints}) that affect subsequent processing of command line options
1351 and operands. Init files are not executed if you use the @samp{-nx}
1352 option (@pxref{Mode Options, ,Choosing Modes}).
1354 To display the list of init files loaded by gdb at startup, you
1355 can use @kbd{gdb --help}.
1357 @cindex init file name
1358 @cindex @file{.gdbinit}
1359 @cindex @file{gdb.ini}
1360 The @value{GDBN} init files are normally called @file{.gdbinit}.
1361 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1362 the limitations of file names imposed by DOS filesystems. The Windows
1363 port of @value{GDBN} uses the standard name, but if it finds a
1364 @file{gdb.ini} file in your home directory, it warns you about that
1365 and suggests to rename the file to the standard name.
1369 @section Quitting @value{GDBN}
1370 @cindex exiting @value{GDBN}
1371 @cindex leaving @value{GDBN}
1374 @kindex quit @r{[}@var{expression}@r{]}
1375 @kindex q @r{(@code{quit})}
1376 @item quit @r{[}@var{expression}@r{]}
1378 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1379 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1380 do not supply @var{expression}, @value{GDBN} will terminate normally;
1381 otherwise it will terminate using the result of @var{expression} as the
1386 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1387 terminates the action of any @value{GDBN} command that is in progress and
1388 returns to @value{GDBN} command level. It is safe to type the interrupt
1389 character at any time because @value{GDBN} does not allow it to take effect
1390 until a time when it is safe.
1392 If you have been using @value{GDBN} to control an attached process or
1393 device, you can release it with the @code{detach} command
1394 (@pxref{Attach, ,Debugging an Already-running Process}).
1396 @node Shell Commands
1397 @section Shell Commands
1399 If you need to execute occasional shell commands during your
1400 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1401 just use the @code{shell} command.
1406 @cindex shell escape
1407 @item shell @var{command-string}
1408 @itemx !@var{command-string}
1409 Invoke a standard shell to execute @var{command-string}.
1410 Note that no space is needed between @code{!} and @var{command-string}.
1411 If it exists, the environment variable @code{SHELL} determines which
1412 shell to run. Otherwise @value{GDBN} uses the default shell
1413 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1416 The utility @code{make} is often needed in development environments.
1417 You do not have to use the @code{shell} command for this purpose in
1422 @cindex calling make
1423 @item make @var{make-args}
1424 Execute the @code{make} program with the specified
1425 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1428 @node Logging Output
1429 @section Logging Output
1430 @cindex logging @value{GDBN} output
1431 @cindex save @value{GDBN} output to a file
1433 You may want to save the output of @value{GDBN} commands to a file.
1434 There are several commands to control @value{GDBN}'s logging.
1438 @item set logging on
1440 @item set logging off
1442 @cindex logging file name
1443 @item set logging file @var{file}
1444 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1445 @item set logging overwrite [on|off]
1446 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1447 you want @code{set logging on} to overwrite the logfile instead.
1448 @item set logging redirect [on|off]
1449 By default, @value{GDBN} output will go to both the terminal and the logfile.
1450 Set @code{redirect} if you want output to go only to the log file.
1451 @kindex show logging
1453 Show the current values of the logging settings.
1457 @chapter @value{GDBN} Commands
1459 You can abbreviate a @value{GDBN} command to the first few letters of the command
1460 name, if that abbreviation is unambiguous; and you can repeat certain
1461 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1462 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1463 show you the alternatives available, if there is more than one possibility).
1466 * Command Syntax:: How to give commands to @value{GDBN}
1467 * Completion:: Command completion
1468 * Help:: How to ask @value{GDBN} for help
1471 @node Command Syntax
1472 @section Command Syntax
1474 A @value{GDBN} command is a single line of input. There is no limit on
1475 how long it can be. It starts with a command name, which is followed by
1476 arguments whose meaning depends on the command name. For example, the
1477 command @code{step} accepts an argument which is the number of times to
1478 step, as in @samp{step 5}. You can also use the @code{step} command
1479 with no arguments. Some commands do not allow any arguments.
1481 @cindex abbreviation
1482 @value{GDBN} command names may always be truncated if that abbreviation is
1483 unambiguous. Other possible command abbreviations are listed in the
1484 documentation for individual commands. In some cases, even ambiguous
1485 abbreviations are allowed; for example, @code{s} is specially defined as
1486 equivalent to @code{step} even though there are other commands whose
1487 names start with @code{s}. You can test abbreviations by using them as
1488 arguments to the @code{help} command.
1490 @cindex repeating commands
1491 @kindex RET @r{(repeat last command)}
1492 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1493 repeat the previous command. Certain commands (for example, @code{run})
1494 will not repeat this way; these are commands whose unintentional
1495 repetition might cause trouble and which you are unlikely to want to
1496 repeat. User-defined commands can disable this feature; see
1497 @ref{Define, dont-repeat}.
1499 The @code{list} and @code{x} commands, when you repeat them with
1500 @key{RET}, construct new arguments rather than repeating
1501 exactly as typed. This permits easy scanning of source or memory.
1503 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1504 output, in a way similar to the common utility @code{more}
1505 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1506 @key{RET} too many in this situation, @value{GDBN} disables command
1507 repetition after any command that generates this sort of display.
1509 @kindex # @r{(a comment)}
1511 Any text from a @kbd{#} to the end of the line is a comment; it does
1512 nothing. This is useful mainly in command files (@pxref{Command
1513 Files,,Command Files}).
1515 @cindex repeating command sequences
1516 @kindex Ctrl-o @r{(operate-and-get-next)}
1517 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1518 commands. This command accepts the current line, like @key{RET}, and
1519 then fetches the next line relative to the current line from the history
1523 @section Command Completion
1526 @cindex word completion
1527 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1528 only one possibility; it can also show you what the valid possibilities
1529 are for the next word in a command, at any time. This works for @value{GDBN}
1530 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1532 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1533 of a word. If there is only one possibility, @value{GDBN} fills in the
1534 word, and waits for you to finish the command (or press @key{RET} to
1535 enter it). For example, if you type
1537 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1538 @c complete accuracy in these examples; space introduced for clarity.
1539 @c If texinfo enhancements make it unnecessary, it would be nice to
1540 @c replace " @key" by "@key" in the following...
1542 (@value{GDBP}) info bre @key{TAB}
1546 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1547 the only @code{info} subcommand beginning with @samp{bre}:
1550 (@value{GDBP}) info breakpoints
1554 You can either press @key{RET} at this point, to run the @code{info
1555 breakpoints} command, or backspace and enter something else, if
1556 @samp{breakpoints} does not look like the command you expected. (If you
1557 were sure you wanted @code{info breakpoints} in the first place, you
1558 might as well just type @key{RET} immediately after @samp{info bre},
1559 to exploit command abbreviations rather than command completion).
1561 If there is more than one possibility for the next word when you press
1562 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1563 characters and try again, or just press @key{TAB} a second time;
1564 @value{GDBN} displays all the possible completions for that word. For
1565 example, you might want to set a breakpoint on a subroutine whose name
1566 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1567 just sounds the bell. Typing @key{TAB} again displays all the
1568 function names in your program that begin with those characters, for
1572 (@value{GDBP}) b make_ @key{TAB}
1573 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1574 make_a_section_from_file make_environ
1575 make_abs_section make_function_type
1576 make_blockvector make_pointer_type
1577 make_cleanup make_reference_type
1578 make_command make_symbol_completion_list
1579 (@value{GDBP}) b make_
1583 After displaying the available possibilities, @value{GDBN} copies your
1584 partial input (@samp{b make_} in the example) so you can finish the
1587 If you just want to see the list of alternatives in the first place, you
1588 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1589 means @kbd{@key{META} ?}. You can type this either by holding down a
1590 key designated as the @key{META} shift on your keyboard (if there is
1591 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1593 @cindex quotes in commands
1594 @cindex completion of quoted strings
1595 Sometimes the string you need, while logically a ``word'', may contain
1596 parentheses or other characters that @value{GDBN} normally excludes from
1597 its notion of a word. To permit word completion to work in this
1598 situation, you may enclose words in @code{'} (single quote marks) in
1599 @value{GDBN} commands.
1601 The most likely situation where you might need this is in typing the
1602 name of a C@t{++} function. This is because C@t{++} allows function
1603 overloading (multiple definitions of the same function, distinguished
1604 by argument type). For example, when you want to set a breakpoint you
1605 may need to distinguish whether you mean the version of @code{name}
1606 that takes an @code{int} parameter, @code{name(int)}, or the version
1607 that takes a @code{float} parameter, @code{name(float)}. To use the
1608 word-completion facilities in this situation, type a single quote
1609 @code{'} at the beginning of the function name. This alerts
1610 @value{GDBN} that it may need to consider more information than usual
1611 when you press @key{TAB} or @kbd{M-?} to request word completion:
1614 (@value{GDBP}) b 'bubble( @kbd{M-?}
1615 bubble(double,double) bubble(int,int)
1616 (@value{GDBP}) b 'bubble(
1619 In some cases, @value{GDBN} can tell that completing a name requires using
1620 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1621 completing as much as it can) if you do not type the quote in the first
1625 (@value{GDBP}) b bub @key{TAB}
1626 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1627 (@value{GDBP}) b 'bubble(
1631 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1632 you have not yet started typing the argument list when you ask for
1633 completion on an overloaded symbol.
1635 For more information about overloaded functions, see @ref{C Plus Plus
1636 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1637 overload-resolution off} to disable overload resolution;
1638 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1640 @cindex completion of structure field names
1641 @cindex structure field name completion
1642 @cindex completion of union field names
1643 @cindex union field name completion
1644 When completing in an expression which looks up a field in a
1645 structure, @value{GDBN} also tries@footnote{The completer can be
1646 confused by certain kinds of invalid expressions. Also, it only
1647 examines the static type of the expression, not the dynamic type.} to
1648 limit completions to the field names available in the type of the
1652 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1653 magic to_fputs to_rewind
1654 to_data to_isatty to_write
1655 to_delete to_put to_write_async_safe
1660 This is because the @code{gdb_stdout} is a variable of the type
1661 @code{struct ui_file} that is defined in @value{GDBN} sources as
1668 ui_file_flush_ftype *to_flush;
1669 ui_file_write_ftype *to_write;
1670 ui_file_write_async_safe_ftype *to_write_async_safe;
1671 ui_file_fputs_ftype *to_fputs;
1672 ui_file_read_ftype *to_read;
1673 ui_file_delete_ftype *to_delete;
1674 ui_file_isatty_ftype *to_isatty;
1675 ui_file_rewind_ftype *to_rewind;
1676 ui_file_put_ftype *to_put;
1683 @section Getting Help
1684 @cindex online documentation
1687 You can always ask @value{GDBN} itself for information on its commands,
1688 using the command @code{help}.
1691 @kindex h @r{(@code{help})}
1694 You can use @code{help} (abbreviated @code{h}) with no arguments to
1695 display a short list of named classes of commands:
1699 List of classes of commands:
1701 aliases -- Aliases of other commands
1702 breakpoints -- Making program stop at certain points
1703 data -- Examining data
1704 files -- Specifying and examining files
1705 internals -- Maintenance commands
1706 obscure -- Obscure features
1707 running -- Running the program
1708 stack -- Examining the stack
1709 status -- Status inquiries
1710 support -- Support facilities
1711 tracepoints -- Tracing of program execution without
1712 stopping the program
1713 user-defined -- User-defined commands
1715 Type "help" followed by a class name for a list of
1716 commands in that class.
1717 Type "help" followed by command name for full
1719 Command name abbreviations are allowed if unambiguous.
1722 @c the above line break eliminates huge line overfull...
1724 @item help @var{class}
1725 Using one of the general help classes as an argument, you can get a
1726 list of the individual commands in that class. For example, here is the
1727 help display for the class @code{status}:
1730 (@value{GDBP}) help status
1735 @c Line break in "show" line falsifies real output, but needed
1736 @c to fit in smallbook page size.
1737 info -- Generic command for showing things
1738 about the program being debugged
1739 show -- Generic command for showing things
1742 Type "help" followed by command name for full
1744 Command name abbreviations are allowed if unambiguous.
1748 @item help @var{command}
1749 With a command name as @code{help} argument, @value{GDBN} displays a
1750 short paragraph on how to use that command.
1753 @item apropos @var{args}
1754 The @code{apropos} command searches through all of the @value{GDBN}
1755 commands, and their documentation, for the regular expression specified in
1756 @var{args}. It prints out all matches found. For example:
1767 alias -- Define a new command that is an alias of an existing command
1768 aliases -- Aliases of other commands
1769 d -- Delete some breakpoints or auto-display expressions
1770 del -- Delete some breakpoints or auto-display expressions
1771 delete -- Delete some breakpoints or auto-display expressions
1776 @item complete @var{args}
1777 The @code{complete @var{args}} command lists all the possible completions
1778 for the beginning of a command. Use @var{args} to specify the beginning of the
1779 command you want completed. For example:
1785 @noindent results in:
1796 @noindent This is intended for use by @sc{gnu} Emacs.
1799 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1800 and @code{show} to inquire about the state of your program, or the state
1801 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1802 manual introduces each of them in the appropriate context. The listings
1803 under @code{info} and under @code{show} in the Command, Variable, and
1804 Function Index point to all the sub-commands. @xref{Command and Variable
1810 @kindex i @r{(@code{info})}
1812 This command (abbreviated @code{i}) is for describing the state of your
1813 program. For example, you can show the arguments passed to a function
1814 with @code{info args}, list the registers currently in use with @code{info
1815 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1816 You can get a complete list of the @code{info} sub-commands with
1817 @w{@code{help info}}.
1821 You can assign the result of an expression to an environment variable with
1822 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1823 @code{set prompt $}.
1827 In contrast to @code{info}, @code{show} is for describing the state of
1828 @value{GDBN} itself.
1829 You can change most of the things you can @code{show}, by using the
1830 related command @code{set}; for example, you can control what number
1831 system is used for displays with @code{set radix}, or simply inquire
1832 which is currently in use with @code{show radix}.
1835 To display all the settable parameters and their current
1836 values, you can use @code{show} with no arguments; you may also use
1837 @code{info set}. Both commands produce the same display.
1838 @c FIXME: "info set" violates the rule that "info" is for state of
1839 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1840 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1844 Here are three miscellaneous @code{show} subcommands, all of which are
1845 exceptional in lacking corresponding @code{set} commands:
1848 @kindex show version
1849 @cindex @value{GDBN} version number
1851 Show what version of @value{GDBN} is running. You should include this
1852 information in @value{GDBN} bug-reports. If multiple versions of
1853 @value{GDBN} are in use at your site, you may need to determine which
1854 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1855 commands are introduced, and old ones may wither away. Also, many
1856 system vendors ship variant versions of @value{GDBN}, and there are
1857 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1858 The version number is the same as the one announced when you start
1861 @kindex show copying
1862 @kindex info copying
1863 @cindex display @value{GDBN} copyright
1866 Display information about permission for copying @value{GDBN}.
1868 @kindex show warranty
1869 @kindex info warranty
1871 @itemx info warranty
1872 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1873 if your version of @value{GDBN} comes with one.
1878 @chapter Running Programs Under @value{GDBN}
1880 When you run a program under @value{GDBN}, you must first generate
1881 debugging information when you compile it.
1883 You may start @value{GDBN} with its arguments, if any, in an environment
1884 of your choice. If you are doing native debugging, you may redirect
1885 your program's input and output, debug an already running process, or
1886 kill a child process.
1889 * Compilation:: Compiling for debugging
1890 * Starting:: Starting your program
1891 * Arguments:: Your program's arguments
1892 * Environment:: Your program's environment
1894 * Working Directory:: Your program's working directory
1895 * Input/Output:: Your program's input and output
1896 * Attach:: Debugging an already-running process
1897 * Kill Process:: Killing the child process
1899 * Inferiors and Programs:: Debugging multiple inferiors and programs
1900 * Threads:: Debugging programs with multiple threads
1901 * Forks:: Debugging forks
1902 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1906 @section Compiling for Debugging
1908 In order to debug a program effectively, you need to generate
1909 debugging information when you compile it. This debugging information
1910 is stored in the object file; it describes the data type of each
1911 variable or function and the correspondence between source line numbers
1912 and addresses in the executable code.
1914 To request debugging information, specify the @samp{-g} option when you run
1917 Programs that are to be shipped to your customers are compiled with
1918 optimizations, using the @samp{-O} compiler option. However, some
1919 compilers are unable to handle the @samp{-g} and @samp{-O} options
1920 together. Using those compilers, you cannot generate optimized
1921 executables containing debugging information.
1923 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1924 without @samp{-O}, making it possible to debug optimized code. We
1925 recommend that you @emph{always} use @samp{-g} whenever you compile a
1926 program. You may think your program is correct, but there is no sense
1927 in pushing your luck. For more information, see @ref{Optimized Code}.
1929 Older versions of the @sc{gnu} C compiler permitted a variant option
1930 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1931 format; if your @sc{gnu} C compiler has this option, do not use it.
1933 @value{GDBN} knows about preprocessor macros and can show you their
1934 expansion (@pxref{Macros}). Most compilers do not include information
1935 about preprocessor macros in the debugging information if you specify
1936 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1937 the @sc{gnu} C compiler, provides macro information if you are using
1938 the DWARF debugging format, and specify the option @option{-g3}.
1940 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1941 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1942 information on @value{NGCC} options affecting debug information.
1944 You will have the best debugging experience if you use the latest
1945 version of the DWARF debugging format that your compiler supports.
1946 DWARF is currently the most expressive and best supported debugging
1947 format in @value{GDBN}.
1951 @section Starting your Program
1957 @kindex r @r{(@code{run})}
1960 Use the @code{run} command to start your program under @value{GDBN}.
1961 You must first specify the program name (except on VxWorks) with an
1962 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1963 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1964 (@pxref{Files, ,Commands to Specify Files}).
1968 If you are running your program in an execution environment that
1969 supports processes, @code{run} creates an inferior process and makes
1970 that process run your program. In some environments without processes,
1971 @code{run} jumps to the start of your program. Other targets,
1972 like @samp{remote}, are always running. If you get an error
1973 message like this one:
1976 The "remote" target does not support "run".
1977 Try "help target" or "continue".
1981 then use @code{continue} to run your program. You may need @code{load}
1982 first (@pxref{load}).
1984 The execution of a program is affected by certain information it
1985 receives from its superior. @value{GDBN} provides ways to specify this
1986 information, which you must do @emph{before} starting your program. (You
1987 can change it after starting your program, but such changes only affect
1988 your program the next time you start it.) This information may be
1989 divided into four categories:
1992 @item The @emph{arguments.}
1993 Specify the arguments to give your program as the arguments of the
1994 @code{run} command. If a shell is available on your target, the shell
1995 is used to pass the arguments, so that you may use normal conventions
1996 (such as wildcard expansion or variable substitution) in describing
1998 In Unix systems, you can control which shell is used with the
1999 @code{SHELL} environment variable.
2000 @xref{Arguments, ,Your Program's Arguments}.
2002 @item The @emph{environment.}
2003 Your program normally inherits its environment from @value{GDBN}, but you can
2004 use the @value{GDBN} commands @code{set environment} and @code{unset
2005 environment} to change parts of the environment that affect
2006 your program. @xref{Environment, ,Your Program's Environment}.
2008 @item The @emph{working directory.}
2009 Your program inherits its working directory from @value{GDBN}. You can set
2010 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2011 @xref{Working Directory, ,Your Program's Working Directory}.
2013 @item The @emph{standard input and output.}
2014 Your program normally uses the same device for standard input and
2015 standard output as @value{GDBN} is using. You can redirect input and output
2016 in the @code{run} command line, or you can use the @code{tty} command to
2017 set a different device for your program.
2018 @xref{Input/Output, ,Your Program's Input and Output}.
2021 @emph{Warning:} While input and output redirection work, you cannot use
2022 pipes to pass the output of the program you are debugging to another
2023 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2027 When you issue the @code{run} command, your program begins to execute
2028 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2029 of how to arrange for your program to stop. Once your program has
2030 stopped, you may call functions in your program, using the @code{print}
2031 or @code{call} commands. @xref{Data, ,Examining Data}.
2033 If the modification time of your symbol file has changed since the last
2034 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2035 table, and reads it again. When it does this, @value{GDBN} tries to retain
2036 your current breakpoints.
2041 @cindex run to main procedure
2042 The name of the main procedure can vary from language to language.
2043 With C or C@t{++}, the main procedure name is always @code{main}, but
2044 other languages such as Ada do not require a specific name for their
2045 main procedure. The debugger provides a convenient way to start the
2046 execution of the program and to stop at the beginning of the main
2047 procedure, depending on the language used.
2049 The @samp{start} command does the equivalent of setting a temporary
2050 breakpoint at the beginning of the main procedure and then invoking
2051 the @samp{run} command.
2053 @cindex elaboration phase
2054 Some programs contain an @dfn{elaboration} phase where some startup code is
2055 executed before the main procedure is called. This depends on the
2056 languages used to write your program. In C@t{++}, for instance,
2057 constructors for static and global objects are executed before
2058 @code{main} is called. It is therefore possible that the debugger stops
2059 before reaching the main procedure. However, the temporary breakpoint
2060 will remain to halt execution.
2062 Specify the arguments to give to your program as arguments to the
2063 @samp{start} command. These arguments will be given verbatim to the
2064 underlying @samp{run} command. Note that the same arguments will be
2065 reused if no argument is provided during subsequent calls to
2066 @samp{start} or @samp{run}.
2068 It is sometimes necessary to debug the program during elaboration. In
2069 these cases, using the @code{start} command would stop the execution of
2070 your program too late, as the program would have already completed the
2071 elaboration phase. Under these circumstances, insert breakpoints in your
2072 elaboration code before running your program.
2074 @kindex set exec-wrapper
2075 @item set exec-wrapper @var{wrapper}
2076 @itemx show exec-wrapper
2077 @itemx unset exec-wrapper
2078 When @samp{exec-wrapper} is set, the specified wrapper is used to
2079 launch programs for debugging. @value{GDBN} starts your program
2080 with a shell command of the form @kbd{exec @var{wrapper}
2081 @var{program}}. Quoting is added to @var{program} and its
2082 arguments, but not to @var{wrapper}, so you should add quotes if
2083 appropriate for your shell. The wrapper runs until it executes
2084 your program, and then @value{GDBN} takes control.
2086 You can use any program that eventually calls @code{execve} with
2087 its arguments as a wrapper. Several standard Unix utilities do
2088 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2089 with @code{exec "$@@"} will also work.
2091 For example, you can use @code{env} to pass an environment variable to
2092 the debugged program, without setting the variable in your shell's
2096 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2100 This command is available when debugging locally on most targets, excluding
2101 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2103 @kindex set disable-randomization
2104 @item set disable-randomization
2105 @itemx set disable-randomization on
2106 This option (enabled by default in @value{GDBN}) will turn off the native
2107 randomization of the virtual address space of the started program. This option
2108 is useful for multiple debugging sessions to make the execution better
2109 reproducible and memory addresses reusable across debugging sessions.
2111 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2112 On @sc{gnu}/Linux you can get the same behavior using
2115 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2118 @item set disable-randomization off
2119 Leave the behavior of the started executable unchanged. Some bugs rear their
2120 ugly heads only when the program is loaded at certain addresses. If your bug
2121 disappears when you run the program under @value{GDBN}, that might be because
2122 @value{GDBN} by default disables the address randomization on platforms, such
2123 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2124 disable-randomization off} to try to reproduce such elusive bugs.
2126 On targets where it is available, virtual address space randomization
2127 protects the programs against certain kinds of security attacks. In these
2128 cases the attacker needs to know the exact location of a concrete executable
2129 code. Randomizing its location makes it impossible to inject jumps misusing
2130 a code at its expected addresses.
2132 Prelinking shared libraries provides a startup performance advantage but it
2133 makes addresses in these libraries predictable for privileged processes by
2134 having just unprivileged access at the target system. Reading the shared
2135 library binary gives enough information for assembling the malicious code
2136 misusing it. Still even a prelinked shared library can get loaded at a new
2137 random address just requiring the regular relocation process during the
2138 startup. Shared libraries not already prelinked are always loaded at
2139 a randomly chosen address.
2141 Position independent executables (PIE) contain position independent code
2142 similar to the shared libraries and therefore such executables get loaded at
2143 a randomly chosen address upon startup. PIE executables always load even
2144 already prelinked shared libraries at a random address. You can build such
2145 executable using @command{gcc -fPIE -pie}.
2147 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2148 (as long as the randomization is enabled).
2150 @item show disable-randomization
2151 Show the current setting of the explicit disable of the native randomization of
2152 the virtual address space of the started program.
2157 @section Your Program's Arguments
2159 @cindex arguments (to your program)
2160 The arguments to your program can be specified by the arguments of the
2162 They are passed to a shell, which expands wildcard characters and
2163 performs redirection of I/O, and thence to your program. Your
2164 @code{SHELL} environment variable (if it exists) specifies what shell
2165 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2166 the default shell (@file{/bin/sh} on Unix).
2168 On non-Unix systems, the program is usually invoked directly by
2169 @value{GDBN}, which emulates I/O redirection via the appropriate system
2170 calls, and the wildcard characters are expanded by the startup code of
2171 the program, not by the shell.
2173 @code{run} with no arguments uses the same arguments used by the previous
2174 @code{run}, or those set by the @code{set args} command.
2179 Specify the arguments to be used the next time your program is run. If
2180 @code{set args} has no arguments, @code{run} executes your program
2181 with no arguments. Once you have run your program with arguments,
2182 using @code{set args} before the next @code{run} is the only way to run
2183 it again without arguments.
2187 Show the arguments to give your program when it is started.
2191 @section Your Program's Environment
2193 @cindex environment (of your program)
2194 The @dfn{environment} consists of a set of environment variables and
2195 their values. Environment variables conventionally record such things as
2196 your user name, your home directory, your terminal type, and your search
2197 path for programs to run. Usually you set up environment variables with
2198 the shell and they are inherited by all the other programs you run. When
2199 debugging, it can be useful to try running your program with a modified
2200 environment without having to start @value{GDBN} over again.
2204 @item path @var{directory}
2205 Add @var{directory} to the front of the @code{PATH} environment variable
2206 (the search path for executables) that will be passed to your program.
2207 The value of @code{PATH} used by @value{GDBN} does not change.
2208 You may specify several directory names, separated by whitespace or by a
2209 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2210 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2211 is moved to the front, so it is searched sooner.
2213 You can use the string @samp{$cwd} to refer to whatever is the current
2214 working directory at the time @value{GDBN} searches the path. If you
2215 use @samp{.} instead, it refers to the directory where you executed the
2216 @code{path} command. @value{GDBN} replaces @samp{.} in the
2217 @var{directory} argument (with the current path) before adding
2218 @var{directory} to the search path.
2219 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2220 @c document that, since repeating it would be a no-op.
2224 Display the list of search paths for executables (the @code{PATH}
2225 environment variable).
2227 @kindex show environment
2228 @item show environment @r{[}@var{varname}@r{]}
2229 Print the value of environment variable @var{varname} to be given to
2230 your program when it starts. If you do not supply @var{varname},
2231 print the names and values of all environment variables to be given to
2232 your program. You can abbreviate @code{environment} as @code{env}.
2234 @kindex set environment
2235 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2236 Set environment variable @var{varname} to @var{value}. The value
2237 changes for your program only, not for @value{GDBN} itself. @var{value} may
2238 be any string; the values of environment variables are just strings, and
2239 any interpretation is supplied by your program itself. The @var{value}
2240 parameter is optional; if it is eliminated, the variable is set to a
2242 @c "any string" here does not include leading, trailing
2243 @c blanks. Gnu asks: does anyone care?
2245 For example, this command:
2252 tells the debugged program, when subsequently run, that its user is named
2253 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2254 are not actually required.)
2256 @kindex unset environment
2257 @item unset environment @var{varname}
2258 Remove variable @var{varname} from the environment to be passed to your
2259 program. This is different from @samp{set env @var{varname} =};
2260 @code{unset environment} removes the variable from the environment,
2261 rather than assigning it an empty value.
2264 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2266 by your @code{SHELL} environment variable if it exists (or
2267 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2268 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2269 @file{.bashrc} for BASH---any variables you set in that file affect
2270 your program. You may wish to move setting of environment variables to
2271 files that are only run when you sign on, such as @file{.login} or
2274 @node Working Directory
2275 @section Your Program's Working Directory
2277 @cindex working directory (of your program)
2278 Each time you start your program with @code{run}, it inherits its
2279 working directory from the current working directory of @value{GDBN}.
2280 The @value{GDBN} working directory is initially whatever it inherited
2281 from its parent process (typically the shell), but you can specify a new
2282 working directory in @value{GDBN} with the @code{cd} command.
2284 The @value{GDBN} working directory also serves as a default for the commands
2285 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2290 @cindex change working directory
2291 @item cd @r{[}@var{directory}@r{]}
2292 Set the @value{GDBN} working directory to @var{directory}. If not
2293 given, @var{directory} uses @file{'~'}.
2297 Print the @value{GDBN} working directory.
2300 It is generally impossible to find the current working directory of
2301 the process being debugged (since a program can change its directory
2302 during its run). If you work on a system where @value{GDBN} is
2303 configured with the @file{/proc} support, you can use the @code{info
2304 proc} command (@pxref{SVR4 Process Information}) to find out the
2305 current working directory of the debuggee.
2308 @section Your Program's Input and Output
2313 By default, the program you run under @value{GDBN} does input and output to
2314 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2315 to its own terminal modes to interact with you, but it records the terminal
2316 modes your program was using and switches back to them when you continue
2317 running your program.
2320 @kindex info terminal
2322 Displays information recorded by @value{GDBN} about the terminal modes your
2326 You can redirect your program's input and/or output using shell
2327 redirection with the @code{run} command. For example,
2334 starts your program, diverting its output to the file @file{outfile}.
2337 @cindex controlling terminal
2338 Another way to specify where your program should do input and output is
2339 with the @code{tty} command. This command accepts a file name as
2340 argument, and causes this file to be the default for future @code{run}
2341 commands. It also resets the controlling terminal for the child
2342 process, for future @code{run} commands. For example,
2349 directs that processes started with subsequent @code{run} commands
2350 default to do input and output on the terminal @file{/dev/ttyb} and have
2351 that as their controlling terminal.
2353 An explicit redirection in @code{run} overrides the @code{tty} command's
2354 effect on the input/output device, but not its effect on the controlling
2357 When you use the @code{tty} command or redirect input in the @code{run}
2358 command, only the input @emph{for your program} is affected. The input
2359 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2360 for @code{set inferior-tty}.
2362 @cindex inferior tty
2363 @cindex set inferior controlling terminal
2364 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2365 display the name of the terminal that will be used for future runs of your
2369 @item set inferior-tty /dev/ttyb
2370 @kindex set inferior-tty
2371 Set the tty for the program being debugged to /dev/ttyb.
2373 @item show inferior-tty
2374 @kindex show inferior-tty
2375 Show the current tty for the program being debugged.
2379 @section Debugging an Already-running Process
2384 @item attach @var{process-id}
2385 This command attaches to a running process---one that was started
2386 outside @value{GDBN}. (@code{info files} shows your active
2387 targets.) The command takes as argument a process ID. The usual way to
2388 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2389 or with the @samp{jobs -l} shell command.
2391 @code{attach} does not repeat if you press @key{RET} a second time after
2392 executing the command.
2395 To use @code{attach}, your program must be running in an environment
2396 which supports processes; for example, @code{attach} does not work for
2397 programs on bare-board targets that lack an operating system. You must
2398 also have permission to send the process a signal.
2400 When you use @code{attach}, the debugger finds the program running in
2401 the process first by looking in the current working directory, then (if
2402 the program is not found) by using the source file search path
2403 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2404 the @code{file} command to load the program. @xref{Files, ,Commands to
2407 The first thing @value{GDBN} does after arranging to debug the specified
2408 process is to stop it. You can examine and modify an attached process
2409 with all the @value{GDBN} commands that are ordinarily available when
2410 you start processes with @code{run}. You can insert breakpoints; you
2411 can step and continue; you can modify storage. If you would rather the
2412 process continue running, you may use the @code{continue} command after
2413 attaching @value{GDBN} to the process.
2418 When you have finished debugging the attached process, you can use the
2419 @code{detach} command to release it from @value{GDBN} control. Detaching
2420 the process continues its execution. After the @code{detach} command,
2421 that process and @value{GDBN} become completely independent once more, and you
2422 are ready to @code{attach} another process or start one with @code{run}.
2423 @code{detach} does not repeat if you press @key{RET} again after
2424 executing the command.
2427 If you exit @value{GDBN} while you have an attached process, you detach
2428 that process. If you use the @code{run} command, you kill that process.
2429 By default, @value{GDBN} asks for confirmation if you try to do either of these
2430 things; you can control whether or not you need to confirm by using the
2431 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2435 @section Killing the Child Process
2440 Kill the child process in which your program is running under @value{GDBN}.
2443 This command is useful if you wish to debug a core dump instead of a
2444 running process. @value{GDBN} ignores any core dump file while your program
2447 On some operating systems, a program cannot be executed outside @value{GDBN}
2448 while you have breakpoints set on it inside @value{GDBN}. You can use the
2449 @code{kill} command in this situation to permit running your program
2450 outside the debugger.
2452 The @code{kill} command is also useful if you wish to recompile and
2453 relink your program, since on many systems it is impossible to modify an
2454 executable file while it is running in a process. In this case, when you
2455 next type @code{run}, @value{GDBN} notices that the file has changed, and
2456 reads the symbol table again (while trying to preserve your current
2457 breakpoint settings).
2459 @node Inferiors and Programs
2460 @section Debugging Multiple Inferiors and Programs
2462 @value{GDBN} lets you run and debug multiple programs in a single
2463 session. In addition, @value{GDBN} on some systems may let you run
2464 several programs simultaneously (otherwise you have to exit from one
2465 before starting another). In the most general case, you can have
2466 multiple threads of execution in each of multiple processes, launched
2467 from multiple executables.
2470 @value{GDBN} represents the state of each program execution with an
2471 object called an @dfn{inferior}. An inferior typically corresponds to
2472 a process, but is more general and applies also to targets that do not
2473 have processes. Inferiors may be created before a process runs, and
2474 may be retained after a process exits. Inferiors have unique
2475 identifiers that are different from process ids. Usually each
2476 inferior will also have its own distinct address space, although some
2477 embedded targets may have several inferiors running in different parts
2478 of a single address space. Each inferior may in turn have multiple
2479 threads running in it.
2481 To find out what inferiors exist at any moment, use @w{@code{info
2485 @kindex info inferiors
2486 @item info inferiors
2487 Print a list of all inferiors currently being managed by @value{GDBN}.
2489 @value{GDBN} displays for each inferior (in this order):
2493 the inferior number assigned by @value{GDBN}
2496 the target system's inferior identifier
2499 the name of the executable the inferior is running.
2504 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2505 indicates the current inferior.
2509 @c end table here to get a little more width for example
2512 (@value{GDBP}) info inferiors
2513 Num Description Executable
2514 2 process 2307 hello
2515 * 1 process 3401 goodbye
2518 To switch focus between inferiors, use the @code{inferior} command:
2521 @kindex inferior @var{infno}
2522 @item inferior @var{infno}
2523 Make inferior number @var{infno} the current inferior. The argument
2524 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2525 in the first field of the @samp{info inferiors} display.
2529 You can get multiple executables into a debugging session via the
2530 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2531 systems @value{GDBN} can add inferiors to the debug session
2532 automatically by following calls to @code{fork} and @code{exec}. To
2533 remove inferiors from the debugging session use the
2534 @w{@code{remove-inferiors}} command.
2537 @kindex add-inferior
2538 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2539 Adds @var{n} inferiors to be run using @var{executable} as the
2540 executable. @var{n} defaults to 1. If no executable is specified,
2541 the inferiors begins empty, with no program. You can still assign or
2542 change the program assigned to the inferior at any time by using the
2543 @code{file} command with the executable name as its argument.
2545 @kindex clone-inferior
2546 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2547 Adds @var{n} inferiors ready to execute the same program as inferior
2548 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2549 number of the current inferior. This is a convenient command when you
2550 want to run another instance of the inferior you are debugging.
2553 (@value{GDBP}) info inferiors
2554 Num Description Executable
2555 * 1 process 29964 helloworld
2556 (@value{GDBP}) clone-inferior
2559 (@value{GDBP}) info inferiors
2560 Num Description Executable
2562 * 1 process 29964 helloworld
2565 You can now simply switch focus to inferior 2 and run it.
2567 @kindex remove-inferiors
2568 @item remove-inferiors @var{infno}@dots{}
2569 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2570 possible to remove an inferior that is running with this command. For
2571 those, use the @code{kill} or @code{detach} command first.
2575 To quit debugging one of the running inferiors that is not the current
2576 inferior, you can either detach from it by using the @w{@code{detach
2577 inferior}} command (allowing it to run independently), or kill it
2578 using the @w{@code{kill inferiors}} command:
2581 @kindex detach inferiors @var{infno}@dots{}
2582 @item detach inferior @var{infno}@dots{}
2583 Detach from the inferior or inferiors identified by @value{GDBN}
2584 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2585 still stays on the list of inferiors shown by @code{info inferiors},
2586 but its Description will show @samp{<null>}.
2588 @kindex kill inferiors @var{infno}@dots{}
2589 @item kill inferiors @var{infno}@dots{}
2590 Kill the inferior or inferiors identified by @value{GDBN} inferior
2591 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2592 stays on the list of inferiors shown by @code{info inferiors}, but its
2593 Description will show @samp{<null>}.
2596 After the successful completion of a command such as @code{detach},
2597 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2598 a normal process exit, the inferior is still valid and listed with
2599 @code{info inferiors}, ready to be restarted.
2602 To be notified when inferiors are started or exit under @value{GDBN}'s
2603 control use @w{@code{set print inferior-events}}:
2606 @kindex set print inferior-events
2607 @cindex print messages on inferior start and exit
2608 @item set print inferior-events
2609 @itemx set print inferior-events on
2610 @itemx set print inferior-events off
2611 The @code{set print inferior-events} command allows you to enable or
2612 disable printing of messages when @value{GDBN} notices that new
2613 inferiors have started or that inferiors have exited or have been
2614 detached. By default, these messages will not be printed.
2616 @kindex show print inferior-events
2617 @item show print inferior-events
2618 Show whether messages will be printed when @value{GDBN} detects that
2619 inferiors have started, exited or have been detached.
2622 Many commands will work the same with multiple programs as with a
2623 single program: e.g., @code{print myglobal} will simply display the
2624 value of @code{myglobal} in the current inferior.
2627 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2628 get more info about the relationship of inferiors, programs, address
2629 spaces in a debug session. You can do that with the @w{@code{maint
2630 info program-spaces}} command.
2633 @kindex maint info program-spaces
2634 @item maint info program-spaces
2635 Print a list of all program spaces currently being managed by
2638 @value{GDBN} displays for each program space (in this order):
2642 the program space number assigned by @value{GDBN}
2645 the name of the executable loaded into the program space, with e.g.,
2646 the @code{file} command.
2651 An asterisk @samp{*} preceding the @value{GDBN} program space number
2652 indicates the current program space.
2654 In addition, below each program space line, @value{GDBN} prints extra
2655 information that isn't suitable to display in tabular form. For
2656 example, the list of inferiors bound to the program space.
2659 (@value{GDBP}) maint info program-spaces
2662 Bound inferiors: ID 1 (process 21561)
2666 Here we can see that no inferior is running the program @code{hello},
2667 while @code{process 21561} is running the program @code{goodbye}. On
2668 some targets, it is possible that multiple inferiors are bound to the
2669 same program space. The most common example is that of debugging both
2670 the parent and child processes of a @code{vfork} call. For example,
2673 (@value{GDBP}) maint info program-spaces
2676 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2679 Here, both inferior 2 and inferior 1 are running in the same program
2680 space as a result of inferior 1 having executed a @code{vfork} call.
2684 @section Debugging Programs with Multiple Threads
2686 @cindex threads of execution
2687 @cindex multiple threads
2688 @cindex switching threads
2689 In some operating systems, such as HP-UX and Solaris, a single program
2690 may have more than one @dfn{thread} of execution. The precise semantics
2691 of threads differ from one operating system to another, but in general
2692 the threads of a single program are akin to multiple processes---except
2693 that they share one address space (that is, they can all examine and
2694 modify the same variables). On the other hand, each thread has its own
2695 registers and execution stack, and perhaps private memory.
2697 @value{GDBN} provides these facilities for debugging multi-thread
2701 @item automatic notification of new threads
2702 @item @samp{thread @var{threadno}}, a command to switch among threads
2703 @item @samp{info threads}, a command to inquire about existing threads
2704 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2705 a command to apply a command to a list of threads
2706 @item thread-specific breakpoints
2707 @item @samp{set print thread-events}, which controls printing of
2708 messages on thread start and exit.
2709 @item @samp{set libthread-db-search-path @var{path}}, which lets
2710 the user specify which @code{libthread_db} to use if the default choice
2711 isn't compatible with the program.
2715 @emph{Warning:} These facilities are not yet available on every
2716 @value{GDBN} configuration where the operating system supports threads.
2717 If your @value{GDBN} does not support threads, these commands have no
2718 effect. For example, a system without thread support shows no output
2719 from @samp{info threads}, and always rejects the @code{thread} command,
2723 (@value{GDBP}) info threads
2724 (@value{GDBP}) thread 1
2725 Thread ID 1 not known. Use the "info threads" command to
2726 see the IDs of currently known threads.
2728 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2729 @c doesn't support threads"?
2732 @cindex focus of debugging
2733 @cindex current thread
2734 The @value{GDBN} thread debugging facility allows you to observe all
2735 threads while your program runs---but whenever @value{GDBN} takes
2736 control, one thread in particular is always the focus of debugging.
2737 This thread is called the @dfn{current thread}. Debugging commands show
2738 program information from the perspective of the current thread.
2740 @cindex @code{New} @var{systag} message
2741 @cindex thread identifier (system)
2742 @c FIXME-implementors!! It would be more helpful if the [New...] message
2743 @c included GDB's numeric thread handle, so you could just go to that
2744 @c thread without first checking `info threads'.
2745 Whenever @value{GDBN} detects a new thread in your program, it displays
2746 the target system's identification for the thread with a message in the
2747 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2748 whose form varies depending on the particular system. For example, on
2749 @sc{gnu}/Linux, you might see
2752 [New Thread 0x41e02940 (LWP 25582)]
2756 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2757 the @var{systag} is simply something like @samp{process 368}, with no
2760 @c FIXME!! (1) Does the [New...] message appear even for the very first
2761 @c thread of a program, or does it only appear for the
2762 @c second---i.e.@: when it becomes obvious we have a multithread
2764 @c (2) *Is* there necessarily a first thread always? Or do some
2765 @c multithread systems permit starting a program with multiple
2766 @c threads ab initio?
2768 @cindex thread number
2769 @cindex thread identifier (GDB)
2770 For debugging purposes, @value{GDBN} associates its own thread
2771 number---always a single integer---with each thread in your program.
2774 @kindex info threads
2775 @item info threads @r{[}@var{id}@dots{}@r{]}
2776 Display a summary of all threads currently in your program. Optional
2777 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2778 means to print information only about the specified thread or threads.
2779 @value{GDBN} displays for each thread (in this order):
2783 the thread number assigned by @value{GDBN}
2786 the target system's thread identifier (@var{systag})
2789 the thread's name, if one is known. A thread can either be named by
2790 the user (see @code{thread name}, below), or, in some cases, by the
2794 the current stack frame summary for that thread
2798 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2799 indicates the current thread.
2803 @c end table here to get a little more width for example
2806 (@value{GDBP}) info threads
2808 3 process 35 thread 27 0x34e5 in sigpause ()
2809 2 process 35 thread 23 0x34e5 in sigpause ()
2810 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2814 On Solaris, you can display more information about user threads with a
2815 Solaris-specific command:
2818 @item maint info sol-threads
2819 @kindex maint info sol-threads
2820 @cindex thread info (Solaris)
2821 Display info on Solaris user threads.
2825 @kindex thread @var{threadno}
2826 @item thread @var{threadno}
2827 Make thread number @var{threadno} the current thread. The command
2828 argument @var{threadno} is the internal @value{GDBN} thread number, as
2829 shown in the first field of the @samp{info threads} display.
2830 @value{GDBN} responds by displaying the system identifier of the thread
2831 you selected, and its current stack frame summary:
2834 (@value{GDBP}) thread 2
2835 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2836 #0 some_function (ignore=0x0) at example.c:8
2837 8 printf ("hello\n");
2841 As with the @samp{[New @dots{}]} message, the form of the text after
2842 @samp{Switching to} depends on your system's conventions for identifying
2845 @vindex $_thread@r{, convenience variable}
2846 The debugger convenience variable @samp{$_thread} contains the number
2847 of the current thread. You may find this useful in writing breakpoint
2848 conditional expressions, command scripts, and so forth. See
2849 @xref{Convenience Vars,, Convenience Variables}, for general
2850 information on convenience variables.
2852 @kindex thread apply
2853 @cindex apply command to several threads
2854 @item thread apply [@var{threadno} | all] @var{command}
2855 The @code{thread apply} command allows you to apply the named
2856 @var{command} to one or more threads. Specify the numbers of the
2857 threads that you want affected with the command argument
2858 @var{threadno}. It can be a single thread number, one of the numbers
2859 shown in the first field of the @samp{info threads} display; or it
2860 could be a range of thread numbers, as in @code{2-4}. To apply a
2861 command to all threads, type @kbd{thread apply all @var{command}}.
2864 @cindex name a thread
2865 @item thread name [@var{name}]
2866 This command assigns a name to the current thread. If no argument is
2867 given, any existing user-specified name is removed. The thread name
2868 appears in the @samp{info threads} display.
2870 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2871 determine the name of the thread as given by the OS. On these
2872 systems, a name specified with @samp{thread name} will override the
2873 system-give name, and removing the user-specified name will cause
2874 @value{GDBN} to once again display the system-specified name.
2877 @cindex search for a thread
2878 @item thread find [@var{regexp}]
2879 Search for and display thread ids whose name or @var{systag}
2880 matches the supplied regular expression.
2882 As well as being the complement to the @samp{thread name} command,
2883 this command also allows you to identify a thread by its target
2884 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2888 (@value{GDBN}) thread find 26688
2889 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2890 (@value{GDBN}) info thread 4
2892 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2895 @kindex set print thread-events
2896 @cindex print messages on thread start and exit
2897 @item set print thread-events
2898 @itemx set print thread-events on
2899 @itemx set print thread-events off
2900 The @code{set print thread-events} command allows you to enable or
2901 disable printing of messages when @value{GDBN} notices that new threads have
2902 started or that threads have exited. By default, these messages will
2903 be printed if detection of these events is supported by the target.
2904 Note that these messages cannot be disabled on all targets.
2906 @kindex show print thread-events
2907 @item show print thread-events
2908 Show whether messages will be printed when @value{GDBN} detects that threads
2909 have started and exited.
2912 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2913 more information about how @value{GDBN} behaves when you stop and start
2914 programs with multiple threads.
2916 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2917 watchpoints in programs with multiple threads.
2919 @anchor{set libthread-db-search-path}
2921 @kindex set libthread-db-search-path
2922 @cindex search path for @code{libthread_db}
2923 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2924 If this variable is set, @var{path} is a colon-separated list of
2925 directories @value{GDBN} will use to search for @code{libthread_db}.
2926 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2927 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2928 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2931 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2932 @code{libthread_db} library to obtain information about threads in the
2933 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2934 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2935 specific thread debugging library loading is enabled
2936 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2938 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2939 refers to the default system directories that are
2940 normally searched for loading shared libraries. The @samp{$sdir} entry
2941 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2942 (@pxref{libthread_db.so.1 file}).
2944 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2945 refers to the directory from which @code{libpthread}
2946 was loaded in the inferior process.
2948 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2949 @value{GDBN} attempts to initialize it with the current inferior process.
2950 If this initialization fails (which could happen because of a version
2951 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2952 will unload @code{libthread_db}, and continue with the next directory.
2953 If none of @code{libthread_db} libraries initialize successfully,
2954 @value{GDBN} will issue a warning and thread debugging will be disabled.
2956 Setting @code{libthread-db-search-path} is currently implemented
2957 only on some platforms.
2959 @kindex show libthread-db-search-path
2960 @item show libthread-db-search-path
2961 Display current libthread_db search path.
2963 @kindex set debug libthread-db
2964 @kindex show debug libthread-db
2965 @cindex debugging @code{libthread_db}
2966 @item set debug libthread-db
2967 @itemx show debug libthread-db
2968 Turns on or off display of @code{libthread_db}-related events.
2969 Use @code{1} to enable, @code{0} to disable.
2973 @section Debugging Forks
2975 @cindex fork, debugging programs which call
2976 @cindex multiple processes
2977 @cindex processes, multiple
2978 On most systems, @value{GDBN} has no special support for debugging
2979 programs which create additional processes using the @code{fork}
2980 function. When a program forks, @value{GDBN} will continue to debug the
2981 parent process and the child process will run unimpeded. If you have
2982 set a breakpoint in any code which the child then executes, the child
2983 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2984 will cause it to terminate.
2986 However, if you want to debug the child process there is a workaround
2987 which isn't too painful. Put a call to @code{sleep} in the code which
2988 the child process executes after the fork. It may be useful to sleep
2989 only if a certain environment variable is set, or a certain file exists,
2990 so that the delay need not occur when you don't want to run @value{GDBN}
2991 on the child. While the child is sleeping, use the @code{ps} program to
2992 get its process ID. Then tell @value{GDBN} (a new invocation of
2993 @value{GDBN} if you are also debugging the parent process) to attach to
2994 the child process (@pxref{Attach}). From that point on you can debug
2995 the child process just like any other process which you attached to.
2997 On some systems, @value{GDBN} provides support for debugging programs that
2998 create additional processes using the @code{fork} or @code{vfork} functions.
2999 Currently, the only platforms with this feature are HP-UX (11.x and later
3000 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3002 By default, when a program forks, @value{GDBN} will continue to debug
3003 the parent process and the child process will run unimpeded.
3005 If you want to follow the child process instead of the parent process,
3006 use the command @w{@code{set follow-fork-mode}}.
3009 @kindex set follow-fork-mode
3010 @item set follow-fork-mode @var{mode}
3011 Set the debugger response to a program call of @code{fork} or
3012 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3013 process. The @var{mode} argument can be:
3017 The original process is debugged after a fork. The child process runs
3018 unimpeded. This is the default.
3021 The new process is debugged after a fork. The parent process runs
3026 @kindex show follow-fork-mode
3027 @item show follow-fork-mode
3028 Display the current debugger response to a @code{fork} or @code{vfork} call.
3031 @cindex debugging multiple processes
3032 On Linux, if you want to debug both the parent and child processes, use the
3033 command @w{@code{set detach-on-fork}}.
3036 @kindex set detach-on-fork
3037 @item set detach-on-fork @var{mode}
3038 Tells gdb whether to detach one of the processes after a fork, or
3039 retain debugger control over them both.
3043 The child process (or parent process, depending on the value of
3044 @code{follow-fork-mode}) will be detached and allowed to run
3045 independently. This is the default.
3048 Both processes will be held under the control of @value{GDBN}.
3049 One process (child or parent, depending on the value of
3050 @code{follow-fork-mode}) is debugged as usual, while the other
3055 @kindex show detach-on-fork
3056 @item show detach-on-fork
3057 Show whether detach-on-fork mode is on/off.
3060 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3061 will retain control of all forked processes (including nested forks).
3062 You can list the forked processes under the control of @value{GDBN} by
3063 using the @w{@code{info inferiors}} command, and switch from one fork
3064 to another by using the @code{inferior} command (@pxref{Inferiors and
3065 Programs, ,Debugging Multiple Inferiors and Programs}).
3067 To quit debugging one of the forked processes, you can either detach
3068 from it by using the @w{@code{detach inferiors}} command (allowing it
3069 to run independently), or kill it using the @w{@code{kill inferiors}}
3070 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3073 If you ask to debug a child process and a @code{vfork} is followed by an
3074 @code{exec}, @value{GDBN} executes the new target up to the first
3075 breakpoint in the new target. If you have a breakpoint set on
3076 @code{main} in your original program, the breakpoint will also be set on
3077 the child process's @code{main}.
3079 On some systems, when a child process is spawned by @code{vfork}, you
3080 cannot debug the child or parent until an @code{exec} call completes.
3082 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3083 call executes, the new target restarts. To restart the parent
3084 process, use the @code{file} command with the parent executable name
3085 as its argument. By default, after an @code{exec} call executes,
3086 @value{GDBN} discards the symbols of the previous executable image.
3087 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3091 @kindex set follow-exec-mode
3092 @item set follow-exec-mode @var{mode}
3094 Set debugger response to a program call of @code{exec}. An
3095 @code{exec} call replaces the program image of a process.
3097 @code{follow-exec-mode} can be:
3101 @value{GDBN} creates a new inferior and rebinds the process to this
3102 new inferior. The program the process was running before the
3103 @code{exec} call can be restarted afterwards by restarting the
3109 (@value{GDBP}) info inferiors
3111 Id Description Executable
3114 process 12020 is executing new program: prog2
3115 Program exited normally.
3116 (@value{GDBP}) info inferiors
3117 Id Description Executable
3123 @value{GDBN} keeps the process bound to the same inferior. The new
3124 executable image replaces the previous executable loaded in the
3125 inferior. Restarting the inferior after the @code{exec} call, with
3126 e.g., the @code{run} command, restarts the executable the process was
3127 running after the @code{exec} call. This is the default mode.
3132 (@value{GDBP}) info inferiors
3133 Id Description Executable
3136 process 12020 is executing new program: prog2
3137 Program exited normally.
3138 (@value{GDBP}) info inferiors
3139 Id Description Executable
3146 You can use the @code{catch} command to make @value{GDBN} stop whenever
3147 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3148 Catchpoints, ,Setting Catchpoints}.
3150 @node Checkpoint/Restart
3151 @section Setting a @emph{Bookmark} to Return to Later
3156 @cindex snapshot of a process
3157 @cindex rewind program state
3159 On certain operating systems@footnote{Currently, only
3160 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3161 program's state, called a @dfn{checkpoint}, and come back to it
3164 Returning to a checkpoint effectively undoes everything that has
3165 happened in the program since the @code{checkpoint} was saved. This
3166 includes changes in memory, registers, and even (within some limits)
3167 system state. Effectively, it is like going back in time to the
3168 moment when the checkpoint was saved.
3170 Thus, if you're stepping thru a program and you think you're
3171 getting close to the point where things go wrong, you can save
3172 a checkpoint. Then, if you accidentally go too far and miss
3173 the critical statement, instead of having to restart your program
3174 from the beginning, you can just go back to the checkpoint and
3175 start again from there.
3177 This can be especially useful if it takes a lot of time or
3178 steps to reach the point where you think the bug occurs.
3180 To use the @code{checkpoint}/@code{restart} method of debugging:
3185 Save a snapshot of the debugged program's current execution state.
3186 The @code{checkpoint} command takes no arguments, but each checkpoint
3187 is assigned a small integer id, similar to a breakpoint id.
3189 @kindex info checkpoints
3190 @item info checkpoints
3191 List the checkpoints that have been saved in the current debugging
3192 session. For each checkpoint, the following information will be
3199 @item Source line, or label
3202 @kindex restart @var{checkpoint-id}
3203 @item restart @var{checkpoint-id}
3204 Restore the program state that was saved as checkpoint number
3205 @var{checkpoint-id}. All program variables, registers, stack frames
3206 etc.@: will be returned to the values that they had when the checkpoint
3207 was saved. In essence, gdb will ``wind back the clock'' to the point
3208 in time when the checkpoint was saved.
3210 Note that breakpoints, @value{GDBN} variables, command history etc.
3211 are not affected by restoring a checkpoint. In general, a checkpoint
3212 only restores things that reside in the program being debugged, not in
3215 @kindex delete checkpoint @var{checkpoint-id}
3216 @item delete checkpoint @var{checkpoint-id}
3217 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3221 Returning to a previously saved checkpoint will restore the user state
3222 of the program being debugged, plus a significant subset of the system
3223 (OS) state, including file pointers. It won't ``un-write'' data from
3224 a file, but it will rewind the file pointer to the previous location,
3225 so that the previously written data can be overwritten. For files
3226 opened in read mode, the pointer will also be restored so that the
3227 previously read data can be read again.
3229 Of course, characters that have been sent to a printer (or other
3230 external device) cannot be ``snatched back'', and characters received
3231 from eg.@: a serial device can be removed from internal program buffers,
3232 but they cannot be ``pushed back'' into the serial pipeline, ready to
3233 be received again. Similarly, the actual contents of files that have
3234 been changed cannot be restored (at this time).
3236 However, within those constraints, you actually can ``rewind'' your
3237 program to a previously saved point in time, and begin debugging it
3238 again --- and you can change the course of events so as to debug a
3239 different execution path this time.
3241 @cindex checkpoints and process id
3242 Finally, there is one bit of internal program state that will be
3243 different when you return to a checkpoint --- the program's process
3244 id. Each checkpoint will have a unique process id (or @var{pid}),
3245 and each will be different from the program's original @var{pid}.
3246 If your program has saved a local copy of its process id, this could
3247 potentially pose a problem.
3249 @subsection A Non-obvious Benefit of Using Checkpoints
3251 On some systems such as @sc{gnu}/Linux, address space randomization
3252 is performed on new processes for security reasons. This makes it
3253 difficult or impossible to set a breakpoint, or watchpoint, on an
3254 absolute address if you have to restart the program, since the
3255 absolute location of a symbol will change from one execution to the
3258 A checkpoint, however, is an @emph{identical} copy of a process.
3259 Therefore if you create a checkpoint at (eg.@:) the start of main,
3260 and simply return to that checkpoint instead of restarting the
3261 process, you can avoid the effects of address randomization and
3262 your symbols will all stay in the same place.
3265 @chapter Stopping and Continuing
3267 The principal purposes of using a debugger are so that you can stop your
3268 program before it terminates; or so that, if your program runs into
3269 trouble, you can investigate and find out why.
3271 Inside @value{GDBN}, your program may stop for any of several reasons,
3272 such as a signal, a breakpoint, or reaching a new line after a
3273 @value{GDBN} command such as @code{step}. You may then examine and
3274 change variables, set new breakpoints or remove old ones, and then
3275 continue execution. Usually, the messages shown by @value{GDBN} provide
3276 ample explanation of the status of your program---but you can also
3277 explicitly request this information at any time.
3280 @kindex info program
3282 Display information about the status of your program: whether it is
3283 running or not, what process it is, and why it stopped.
3287 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3288 * Continuing and Stepping:: Resuming execution
3289 * Skipping Over Functions and Files::
3290 Skipping over functions and files
3292 * Thread Stops:: Stopping and starting multi-thread programs
3296 @section Breakpoints, Watchpoints, and Catchpoints
3299 A @dfn{breakpoint} makes your program stop whenever a certain point in
3300 the program is reached. For each breakpoint, you can add conditions to
3301 control in finer detail whether your program stops. You can set
3302 breakpoints with the @code{break} command and its variants (@pxref{Set
3303 Breaks, ,Setting Breakpoints}), to specify the place where your program
3304 should stop by line number, function name or exact address in the
3307 On some systems, you can set breakpoints in shared libraries before
3308 the executable is run. There is a minor limitation on HP-UX systems:
3309 you must wait until the executable is run in order to set breakpoints
3310 in shared library routines that are not called directly by the program
3311 (for example, routines that are arguments in a @code{pthread_create}
3315 @cindex data breakpoints
3316 @cindex memory tracing
3317 @cindex breakpoint on memory address
3318 @cindex breakpoint on variable modification
3319 A @dfn{watchpoint} is a special breakpoint that stops your program
3320 when the value of an expression changes. The expression may be a value
3321 of a variable, or it could involve values of one or more variables
3322 combined by operators, such as @samp{a + b}. This is sometimes called
3323 @dfn{data breakpoints}. You must use a different command to set
3324 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3325 from that, you can manage a watchpoint like any other breakpoint: you
3326 enable, disable, and delete both breakpoints and watchpoints using the
3329 You can arrange to have values from your program displayed automatically
3330 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3334 @cindex breakpoint on events
3335 A @dfn{catchpoint} is another special breakpoint that stops your program
3336 when a certain kind of event occurs, such as the throwing of a C@t{++}
3337 exception or the loading of a library. As with watchpoints, you use a
3338 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3339 Catchpoints}), but aside from that, you can manage a catchpoint like any
3340 other breakpoint. (To stop when your program receives a signal, use the
3341 @code{handle} command; see @ref{Signals, ,Signals}.)
3343 @cindex breakpoint numbers
3344 @cindex numbers for breakpoints
3345 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3346 catchpoint when you create it; these numbers are successive integers
3347 starting with one. In many of the commands for controlling various
3348 features of breakpoints you use the breakpoint number to say which
3349 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3350 @dfn{disabled}; if disabled, it has no effect on your program until you
3353 @cindex breakpoint ranges
3354 @cindex ranges of breakpoints
3355 Some @value{GDBN} commands accept a range of breakpoints on which to
3356 operate. A breakpoint range is either a single breakpoint number, like
3357 @samp{5}, or two such numbers, in increasing order, separated by a
3358 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3359 all breakpoints in that range are operated on.
3362 * Set Breaks:: Setting breakpoints
3363 * Set Watchpoints:: Setting watchpoints
3364 * Set Catchpoints:: Setting catchpoints
3365 * Delete Breaks:: Deleting breakpoints
3366 * Disabling:: Disabling breakpoints
3367 * Conditions:: Break conditions
3368 * Break Commands:: Breakpoint command lists
3369 * Dynamic Printf:: Dynamic printf
3370 * Save Breakpoints:: How to save breakpoints in a file
3371 * Static Probe Points:: Listing static probe points
3372 * Error in Breakpoints:: ``Cannot insert breakpoints''
3373 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3377 @subsection Setting Breakpoints
3379 @c FIXME LMB what does GDB do if no code on line of breakpt?
3380 @c consider in particular declaration with/without initialization.
3382 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3385 @kindex b @r{(@code{break})}
3386 @vindex $bpnum@r{, convenience variable}
3387 @cindex latest breakpoint
3388 Breakpoints are set with the @code{break} command (abbreviated
3389 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3390 number of the breakpoint you've set most recently; see @ref{Convenience
3391 Vars,, Convenience Variables}, for a discussion of what you can do with
3392 convenience variables.
3395 @item break @var{location}
3396 Set a breakpoint at the given @var{location}, which can specify a
3397 function name, a line number, or an address of an instruction.
3398 (@xref{Specify Location}, for a list of all the possible ways to
3399 specify a @var{location}.) The breakpoint will stop your program just
3400 before it executes any of the code in the specified @var{location}.
3402 When using source languages that permit overloading of symbols, such as
3403 C@t{++}, a function name may refer to more than one possible place to break.
3404 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3407 It is also possible to insert a breakpoint that will stop the program
3408 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3409 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3412 When called without any arguments, @code{break} sets a breakpoint at
3413 the next instruction to be executed in the selected stack frame
3414 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3415 innermost, this makes your program stop as soon as control
3416 returns to that frame. This is similar to the effect of a
3417 @code{finish} command in the frame inside the selected frame---except
3418 that @code{finish} does not leave an active breakpoint. If you use
3419 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3420 the next time it reaches the current location; this may be useful
3423 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3424 least one instruction has been executed. If it did not do this, you
3425 would be unable to proceed past a breakpoint without first disabling the
3426 breakpoint. This rule applies whether or not the breakpoint already
3427 existed when your program stopped.
3429 @item break @dots{} if @var{cond}
3430 Set a breakpoint with condition @var{cond}; evaluate the expression
3431 @var{cond} each time the breakpoint is reached, and stop only if the
3432 value is nonzero---that is, if @var{cond} evaluates as true.
3433 @samp{@dots{}} stands for one of the possible arguments described
3434 above (or no argument) specifying where to break. @xref{Conditions,
3435 ,Break Conditions}, for more information on breakpoint conditions.
3438 @item tbreak @var{args}
3439 Set a breakpoint enabled only for one stop. @var{args} are the
3440 same as for the @code{break} command, and the breakpoint is set in the same
3441 way, but the breakpoint is automatically deleted after the first time your
3442 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3445 @cindex hardware breakpoints
3446 @item hbreak @var{args}
3447 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3448 @code{break} command and the breakpoint is set in the same way, but the
3449 breakpoint requires hardware support and some target hardware may not
3450 have this support. The main purpose of this is EPROM/ROM code
3451 debugging, so you can set a breakpoint at an instruction without
3452 changing the instruction. This can be used with the new trap-generation
3453 provided by SPARClite DSU and most x86-based targets. These targets
3454 will generate traps when a program accesses some data or instruction
3455 address that is assigned to the debug registers. However the hardware
3456 breakpoint registers can take a limited number of breakpoints. For
3457 example, on the DSU, only two data breakpoints can be set at a time, and
3458 @value{GDBN} will reject this command if more than two are used. Delete
3459 or disable unused hardware breakpoints before setting new ones
3460 (@pxref{Disabling, ,Disabling Breakpoints}).
3461 @xref{Conditions, ,Break Conditions}.
3462 For remote targets, you can restrict the number of hardware
3463 breakpoints @value{GDBN} will use, see @ref{set remote
3464 hardware-breakpoint-limit}.
3467 @item thbreak @var{args}
3468 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3469 are the same as for the @code{hbreak} command and the breakpoint is set in
3470 the same way. However, like the @code{tbreak} command,
3471 the breakpoint is automatically deleted after the
3472 first time your program stops there. Also, like the @code{hbreak}
3473 command, the breakpoint requires hardware support and some target hardware
3474 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3475 See also @ref{Conditions, ,Break Conditions}.
3478 @cindex regular expression
3479 @cindex breakpoints at functions matching a regexp
3480 @cindex set breakpoints in many functions
3481 @item rbreak @var{regex}
3482 Set breakpoints on all functions matching the regular expression
3483 @var{regex}. This command sets an unconditional breakpoint on all
3484 matches, printing a list of all breakpoints it set. Once these
3485 breakpoints are set, they are treated just like the breakpoints set with
3486 the @code{break} command. You can delete them, disable them, or make
3487 them conditional the same way as any other breakpoint.
3489 The syntax of the regular expression is the standard one used with tools
3490 like @file{grep}. Note that this is different from the syntax used by
3491 shells, so for instance @code{foo*} matches all functions that include
3492 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3493 @code{.*} leading and trailing the regular expression you supply, so to
3494 match only functions that begin with @code{foo}, use @code{^foo}.
3496 @cindex non-member C@t{++} functions, set breakpoint in
3497 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3498 breakpoints on overloaded functions that are not members of any special
3501 @cindex set breakpoints on all functions
3502 The @code{rbreak} command can be used to set breakpoints in
3503 @strong{all} the functions in a program, like this:
3506 (@value{GDBP}) rbreak .
3509 @item rbreak @var{file}:@var{regex}
3510 If @code{rbreak} is called with a filename qualification, it limits
3511 the search for functions matching the given regular expression to the
3512 specified @var{file}. This can be used, for example, to set breakpoints on
3513 every function in a given file:
3516 (@value{GDBP}) rbreak file.c:.
3519 The colon separating the filename qualifier from the regex may
3520 optionally be surrounded by spaces.
3522 @kindex info breakpoints
3523 @cindex @code{$_} and @code{info breakpoints}
3524 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3525 @itemx info break @r{[}@var{n}@dots{}@r{]}
3526 Print a table of all breakpoints, watchpoints, and catchpoints set and
3527 not deleted. Optional argument @var{n} means print information only
3528 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3529 For each breakpoint, following columns are printed:
3532 @item Breakpoint Numbers
3534 Breakpoint, watchpoint, or catchpoint.
3536 Whether the breakpoint is marked to be disabled or deleted when hit.
3537 @item Enabled or Disabled
3538 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3539 that are not enabled.
3541 Where the breakpoint is in your program, as a memory address. For a
3542 pending breakpoint whose address is not yet known, this field will
3543 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3544 library that has the symbol or line referred by breakpoint is loaded.
3545 See below for details. A breakpoint with several locations will
3546 have @samp{<MULTIPLE>} in this field---see below for details.
3548 Where the breakpoint is in the source for your program, as a file and
3549 line number. For a pending breakpoint, the original string passed to
3550 the breakpoint command will be listed as it cannot be resolved until
3551 the appropriate shared library is loaded in the future.
3555 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3556 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3557 @value{GDBN} on the host's side. If it is ``target'', then the condition
3558 is evaluated by the target. The @code{info break} command shows
3559 the condition on the line following the affected breakpoint, together with
3560 its condition evaluation mode in between parentheses.
3562 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3563 allowed to have a condition specified for it. The condition is not parsed for
3564 validity until a shared library is loaded that allows the pending
3565 breakpoint to resolve to a valid location.
3568 @code{info break} with a breakpoint
3569 number @var{n} as argument lists only that breakpoint. The
3570 convenience variable @code{$_} and the default examining-address for
3571 the @code{x} command are set to the address of the last breakpoint
3572 listed (@pxref{Memory, ,Examining Memory}).
3575 @code{info break} displays a count of the number of times the breakpoint
3576 has been hit. This is especially useful in conjunction with the
3577 @code{ignore} command. You can ignore a large number of breakpoint
3578 hits, look at the breakpoint info to see how many times the breakpoint
3579 was hit, and then run again, ignoring one less than that number. This
3580 will get you quickly to the last hit of that breakpoint.
3583 For a breakpoints with an enable count (xref) greater than 1,
3584 @code{info break} also displays that count.
3588 @value{GDBN} allows you to set any number of breakpoints at the same place in
3589 your program. There is nothing silly or meaningless about this. When
3590 the breakpoints are conditional, this is even useful
3591 (@pxref{Conditions, ,Break Conditions}).
3593 @cindex multiple locations, breakpoints
3594 @cindex breakpoints, multiple locations
3595 It is possible that a breakpoint corresponds to several locations
3596 in your program. Examples of this situation are:
3600 Multiple functions in the program may have the same name.
3603 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3604 instances of the function body, used in different cases.
3607 For a C@t{++} template function, a given line in the function can
3608 correspond to any number of instantiations.
3611 For an inlined function, a given source line can correspond to
3612 several places where that function is inlined.
3615 In all those cases, @value{GDBN} will insert a breakpoint at all
3616 the relevant locations.
3618 A breakpoint with multiple locations is displayed in the breakpoint
3619 table using several rows---one header row, followed by one row for
3620 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3621 address column. The rows for individual locations contain the actual
3622 addresses for locations, and show the functions to which those
3623 locations belong. The number column for a location is of the form
3624 @var{breakpoint-number}.@var{location-number}.
3629 Num Type Disp Enb Address What
3630 1 breakpoint keep y <MULTIPLE>
3632 breakpoint already hit 1 time
3633 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3634 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3637 Each location can be individually enabled or disabled by passing
3638 @var{breakpoint-number}.@var{location-number} as argument to the
3639 @code{enable} and @code{disable} commands. Note that you cannot
3640 delete the individual locations from the list, you can only delete the
3641 entire list of locations that belong to their parent breakpoint (with
3642 the @kbd{delete @var{num}} command, where @var{num} is the number of
3643 the parent breakpoint, 1 in the above example). Disabling or enabling
3644 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3645 that belong to that breakpoint.
3647 @cindex pending breakpoints
3648 It's quite common to have a breakpoint inside a shared library.
3649 Shared libraries can be loaded and unloaded explicitly,
3650 and possibly repeatedly, as the program is executed. To support
3651 this use case, @value{GDBN} updates breakpoint locations whenever
3652 any shared library is loaded or unloaded. Typically, you would
3653 set a breakpoint in a shared library at the beginning of your
3654 debugging session, when the library is not loaded, and when the
3655 symbols from the library are not available. When you try to set
3656 breakpoint, @value{GDBN} will ask you if you want to set
3657 a so called @dfn{pending breakpoint}---breakpoint whose address
3658 is not yet resolved.
3660 After the program is run, whenever a new shared library is loaded,
3661 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3662 shared library contains the symbol or line referred to by some
3663 pending breakpoint, that breakpoint is resolved and becomes an
3664 ordinary breakpoint. When a library is unloaded, all breakpoints
3665 that refer to its symbols or source lines become pending again.
3667 This logic works for breakpoints with multiple locations, too. For
3668 example, if you have a breakpoint in a C@t{++} template function, and
3669 a newly loaded shared library has an instantiation of that template,
3670 a new location is added to the list of locations for the breakpoint.
3672 Except for having unresolved address, pending breakpoints do not
3673 differ from regular breakpoints. You can set conditions or commands,
3674 enable and disable them and perform other breakpoint operations.
3676 @value{GDBN} provides some additional commands for controlling what
3677 happens when the @samp{break} command cannot resolve breakpoint
3678 address specification to an address:
3680 @kindex set breakpoint pending
3681 @kindex show breakpoint pending
3683 @item set breakpoint pending auto
3684 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3685 location, it queries you whether a pending breakpoint should be created.
3687 @item set breakpoint pending on
3688 This indicates that an unrecognized breakpoint location should automatically
3689 result in a pending breakpoint being created.
3691 @item set breakpoint pending off
3692 This indicates that pending breakpoints are not to be created. Any
3693 unrecognized breakpoint location results in an error. This setting does
3694 not affect any pending breakpoints previously created.
3696 @item show breakpoint pending
3697 Show the current behavior setting for creating pending breakpoints.
3700 The settings above only affect the @code{break} command and its
3701 variants. Once breakpoint is set, it will be automatically updated
3702 as shared libraries are loaded and unloaded.
3704 @cindex automatic hardware breakpoints
3705 For some targets, @value{GDBN} can automatically decide if hardware or
3706 software breakpoints should be used, depending on whether the
3707 breakpoint address is read-only or read-write. This applies to
3708 breakpoints set with the @code{break} command as well as to internal
3709 breakpoints set by commands like @code{next} and @code{finish}. For
3710 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3713 You can control this automatic behaviour with the following commands::
3715 @kindex set breakpoint auto-hw
3716 @kindex show breakpoint auto-hw
3718 @item set breakpoint auto-hw on
3719 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3720 will try to use the target memory map to decide if software or hardware
3721 breakpoint must be used.
3723 @item set breakpoint auto-hw off
3724 This indicates @value{GDBN} should not automatically select breakpoint
3725 type. If the target provides a memory map, @value{GDBN} will warn when
3726 trying to set software breakpoint at a read-only address.
3729 @value{GDBN} normally implements breakpoints by replacing the program code
3730 at the breakpoint address with a special instruction, which, when
3731 executed, given control to the debugger. By default, the program
3732 code is so modified only when the program is resumed. As soon as
3733 the program stops, @value{GDBN} restores the original instructions. This
3734 behaviour guards against leaving breakpoints inserted in the
3735 target should gdb abrubptly disconnect. However, with slow remote
3736 targets, inserting and removing breakpoint can reduce the performance.
3737 This behavior can be controlled with the following commands::
3739 @kindex set breakpoint always-inserted
3740 @kindex show breakpoint always-inserted
3742 @item set breakpoint always-inserted off
3743 All breakpoints, including newly added by the user, are inserted in
3744 the target only when the target is resumed. All breakpoints are
3745 removed from the target when it stops.
3747 @item set breakpoint always-inserted on
3748 Causes all breakpoints to be inserted in the target at all times. If
3749 the user adds a new breakpoint, or changes an existing breakpoint, the
3750 breakpoints in the target are updated immediately. A breakpoint is
3751 removed from the target only when breakpoint itself is removed.
3753 @cindex non-stop mode, and @code{breakpoint always-inserted}
3754 @item set breakpoint always-inserted auto
3755 This is the default mode. If @value{GDBN} is controlling the inferior
3756 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3757 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3758 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3759 @code{breakpoint always-inserted} mode is off.
3762 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3763 when a breakpoint breaks. If the condition is true, then the process being
3764 debugged stops, otherwise the process is resumed.
3766 If the target supports evaluating conditions on its end, @value{GDBN} may
3767 download the breakpoint, together with its conditions, to it.
3769 This feature can be controlled via the following commands:
3771 @kindex set breakpoint condition-evaluation
3772 @kindex show breakpoint condition-evaluation
3774 @item set breakpoint condition-evaluation host
3775 This option commands @value{GDBN} to evaluate the breakpoint
3776 conditions on the host's side. Unconditional breakpoints are sent to
3777 the target which in turn receives the triggers and reports them back to GDB
3778 for condition evaluation. This is the standard evaluation mode.
3780 @item set breakpoint condition-evaluation target
3781 This option commands @value{GDBN} to download breakpoint conditions
3782 to the target at the moment of their insertion. The target
3783 is responsible for evaluating the conditional expression and reporting
3784 breakpoint stop events back to @value{GDBN} whenever the condition
3785 is true. Due to limitations of target-side evaluation, some conditions
3786 cannot be evaluated there, e.g., conditions that depend on local data
3787 that is only known to the host. Examples include
3788 conditional expressions involving convenience variables, complex types
3789 that cannot be handled by the agent expression parser and expressions
3790 that are too long to be sent over to the target, specially when the
3791 target is a remote system. In these cases, the conditions will be
3792 evaluated by @value{GDBN}.
3794 @item set breakpoint condition-evaluation auto
3795 This is the default mode. If the target supports evaluating breakpoint
3796 conditions on its end, @value{GDBN} will download breakpoint conditions to
3797 the target (limitations mentioned previously apply). If the target does
3798 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3799 to evaluating all these conditions on the host's side.
3803 @cindex negative breakpoint numbers
3804 @cindex internal @value{GDBN} breakpoints
3805 @value{GDBN} itself sometimes sets breakpoints in your program for
3806 special purposes, such as proper handling of @code{longjmp} (in C
3807 programs). These internal breakpoints are assigned negative numbers,
3808 starting with @code{-1}; @samp{info breakpoints} does not display them.
3809 You can see these breakpoints with the @value{GDBN} maintenance command
3810 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3813 @node Set Watchpoints
3814 @subsection Setting Watchpoints
3816 @cindex setting watchpoints
3817 You can use a watchpoint to stop execution whenever the value of an
3818 expression changes, without having to predict a particular place where
3819 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3820 The expression may be as simple as the value of a single variable, or
3821 as complex as many variables combined by operators. Examples include:
3825 A reference to the value of a single variable.
3828 An address cast to an appropriate data type. For example,
3829 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3830 address (assuming an @code{int} occupies 4 bytes).
3833 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3834 expression can use any operators valid in the program's native
3835 language (@pxref{Languages}).
3838 You can set a watchpoint on an expression even if the expression can
3839 not be evaluated yet. For instance, you can set a watchpoint on
3840 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3841 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3842 the expression produces a valid value. If the expression becomes
3843 valid in some other way than changing a variable (e.g.@: if the memory
3844 pointed to by @samp{*global_ptr} becomes readable as the result of a
3845 @code{malloc} call), @value{GDBN} may not stop until the next time
3846 the expression changes.
3848 @cindex software watchpoints
3849 @cindex hardware watchpoints
3850 Depending on your system, watchpoints may be implemented in software or
3851 hardware. @value{GDBN} does software watchpointing by single-stepping your
3852 program and testing the variable's value each time, which is hundreds of
3853 times slower than normal execution. (But this may still be worth it, to
3854 catch errors where you have no clue what part of your program is the
3857 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3858 x86-based targets, @value{GDBN} includes support for hardware
3859 watchpoints, which do not slow down the running of your program.
3863 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3864 Set a watchpoint for an expression. @value{GDBN} will break when the
3865 expression @var{expr} is written into by the program and its value
3866 changes. The simplest (and the most popular) use of this command is
3867 to watch the value of a single variable:
3870 (@value{GDBP}) watch foo
3873 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3874 argument, @value{GDBN} breaks only when the thread identified by
3875 @var{threadnum} changes the value of @var{expr}. If any other threads
3876 change the value of @var{expr}, @value{GDBN} will not break. Note
3877 that watchpoints restricted to a single thread in this way only work
3878 with Hardware Watchpoints.
3880 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3881 (see below). The @code{-location} argument tells @value{GDBN} to
3882 instead watch the memory referred to by @var{expr}. In this case,
3883 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3884 and watch the memory at that address. The type of the result is used
3885 to determine the size of the watched memory. If the expression's
3886 result does not have an address, then @value{GDBN} will print an
3889 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3890 of masked watchpoints, if the current architecture supports this
3891 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3892 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3893 to an address to watch. The mask specifies that some bits of an address
3894 (the bits which are reset in the mask) should be ignored when matching
3895 the address accessed by the inferior against the watchpoint address.
3896 Thus, a masked watchpoint watches many addresses simultaneously---those
3897 addresses whose unmasked bits are identical to the unmasked bits in the
3898 watchpoint address. The @code{mask} argument implies @code{-location}.
3902 (@value{GDBP}) watch foo mask 0xffff00ff
3903 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3907 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3908 Set a watchpoint that will break when the value of @var{expr} is read
3912 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3913 Set a watchpoint that will break when @var{expr} is either read from
3914 or written into by the program.
3916 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3917 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3918 This command prints a list of watchpoints, using the same format as
3919 @code{info break} (@pxref{Set Breaks}).
3922 If you watch for a change in a numerically entered address you need to
3923 dereference it, as the address itself is just a constant number which will
3924 never change. @value{GDBN} refuses to create a watchpoint that watches
3925 a never-changing value:
3928 (@value{GDBP}) watch 0x600850
3929 Cannot watch constant value 0x600850.
3930 (@value{GDBP}) watch *(int *) 0x600850
3931 Watchpoint 1: *(int *) 6293584
3934 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3935 watchpoints execute very quickly, and the debugger reports a change in
3936 value at the exact instruction where the change occurs. If @value{GDBN}
3937 cannot set a hardware watchpoint, it sets a software watchpoint, which
3938 executes more slowly and reports the change in value at the next
3939 @emph{statement}, not the instruction, after the change occurs.
3941 @cindex use only software watchpoints
3942 You can force @value{GDBN} to use only software watchpoints with the
3943 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3944 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3945 the underlying system supports them. (Note that hardware-assisted
3946 watchpoints that were set @emph{before} setting
3947 @code{can-use-hw-watchpoints} to zero will still use the hardware
3948 mechanism of watching expression values.)
3951 @item set can-use-hw-watchpoints
3952 @kindex set can-use-hw-watchpoints
3953 Set whether or not to use hardware watchpoints.
3955 @item show can-use-hw-watchpoints
3956 @kindex show can-use-hw-watchpoints
3957 Show the current mode of using hardware watchpoints.
3960 For remote targets, you can restrict the number of hardware
3961 watchpoints @value{GDBN} will use, see @ref{set remote
3962 hardware-breakpoint-limit}.
3964 When you issue the @code{watch} command, @value{GDBN} reports
3967 Hardware watchpoint @var{num}: @var{expr}
3971 if it was able to set a hardware watchpoint.
3973 Currently, the @code{awatch} and @code{rwatch} commands can only set
3974 hardware watchpoints, because accesses to data that don't change the
3975 value of the watched expression cannot be detected without examining
3976 every instruction as it is being executed, and @value{GDBN} does not do
3977 that currently. If @value{GDBN} finds that it is unable to set a
3978 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3979 will print a message like this:
3982 Expression cannot be implemented with read/access watchpoint.
3985 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3986 data type of the watched expression is wider than what a hardware
3987 watchpoint on the target machine can handle. For example, some systems
3988 can only watch regions that are up to 4 bytes wide; on such systems you
3989 cannot set hardware watchpoints for an expression that yields a
3990 double-precision floating-point number (which is typically 8 bytes
3991 wide). As a work-around, it might be possible to break the large region
3992 into a series of smaller ones and watch them with separate watchpoints.
3994 If you set too many hardware watchpoints, @value{GDBN} might be unable
3995 to insert all of them when you resume the execution of your program.
3996 Since the precise number of active watchpoints is unknown until such
3997 time as the program is about to be resumed, @value{GDBN} might not be
3998 able to warn you about this when you set the watchpoints, and the
3999 warning will be printed only when the program is resumed:
4002 Hardware watchpoint @var{num}: Could not insert watchpoint
4006 If this happens, delete or disable some of the watchpoints.
4008 Watching complex expressions that reference many variables can also
4009 exhaust the resources available for hardware-assisted watchpoints.
4010 That's because @value{GDBN} needs to watch every variable in the
4011 expression with separately allocated resources.
4013 If you call a function interactively using @code{print} or @code{call},
4014 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4015 kind of breakpoint or the call completes.
4017 @value{GDBN} automatically deletes watchpoints that watch local
4018 (automatic) variables, or expressions that involve such variables, when
4019 they go out of scope, that is, when the execution leaves the block in
4020 which these variables were defined. In particular, when the program
4021 being debugged terminates, @emph{all} local variables go out of scope,
4022 and so only watchpoints that watch global variables remain set. If you
4023 rerun the program, you will need to set all such watchpoints again. One
4024 way of doing that would be to set a code breakpoint at the entry to the
4025 @code{main} function and when it breaks, set all the watchpoints.
4027 @cindex watchpoints and threads
4028 @cindex threads and watchpoints
4029 In multi-threaded programs, watchpoints will detect changes to the
4030 watched expression from every thread.
4033 @emph{Warning:} In multi-threaded programs, software watchpoints
4034 have only limited usefulness. If @value{GDBN} creates a software
4035 watchpoint, it can only watch the value of an expression @emph{in a
4036 single thread}. If you are confident that the expression can only
4037 change due to the current thread's activity (and if you are also
4038 confident that no other thread can become current), then you can use
4039 software watchpoints as usual. However, @value{GDBN} may not notice
4040 when a non-current thread's activity changes the expression. (Hardware
4041 watchpoints, in contrast, watch an expression in all threads.)
4044 @xref{set remote hardware-watchpoint-limit}.
4046 @node Set Catchpoints
4047 @subsection Setting Catchpoints
4048 @cindex catchpoints, setting
4049 @cindex exception handlers
4050 @cindex event handling
4052 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4053 kinds of program events, such as C@t{++} exceptions or the loading of a
4054 shared library. Use the @code{catch} command to set a catchpoint.
4058 @item catch @var{event}
4059 Stop when @var{event} occurs. @var{event} can be any of the following:
4062 @cindex stop on C@t{++} exceptions
4063 The throwing of a C@t{++} exception.
4066 The catching of a C@t{++} exception.
4069 @cindex Ada exception catching
4070 @cindex catch Ada exceptions
4071 An Ada exception being raised. If an exception name is specified
4072 at the end of the command (eg @code{catch exception Program_Error}),
4073 the debugger will stop only when this specific exception is raised.
4074 Otherwise, the debugger stops execution when any Ada exception is raised.
4076 When inserting an exception catchpoint on a user-defined exception whose
4077 name is identical to one of the exceptions defined by the language, the
4078 fully qualified name must be used as the exception name. Otherwise,
4079 @value{GDBN} will assume that it should stop on the pre-defined exception
4080 rather than the user-defined one. For instance, assuming an exception
4081 called @code{Constraint_Error} is defined in package @code{Pck}, then
4082 the command to use to catch such exceptions is @kbd{catch exception
4083 Pck.Constraint_Error}.
4085 @item exception unhandled
4086 An exception that was raised but is not handled by the program.
4089 A failed Ada assertion.
4092 @cindex break on fork/exec
4093 A call to @code{exec}. This is currently only available for HP-UX
4097 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4098 @cindex break on a system call.
4099 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4100 syscall is a mechanism for application programs to request a service
4101 from the operating system (OS) or one of the OS system services.
4102 @value{GDBN} can catch some or all of the syscalls issued by the
4103 debuggee, and show the related information for each syscall. If no
4104 argument is specified, calls to and returns from all system calls
4107 @var{name} can be any system call name that is valid for the
4108 underlying OS. Just what syscalls are valid depends on the OS. On
4109 GNU and Unix systems, you can find the full list of valid syscall
4110 names on @file{/usr/include/asm/unistd.h}.
4112 @c For MS-Windows, the syscall names and the corresponding numbers
4113 @c can be found, e.g., on this URL:
4114 @c http://www.metasploit.com/users/opcode/syscalls.html
4115 @c but we don't support Windows syscalls yet.
4117 Normally, @value{GDBN} knows in advance which syscalls are valid for
4118 each OS, so you can use the @value{GDBN} command-line completion
4119 facilities (@pxref{Completion,, command completion}) to list the
4122 You may also specify the system call numerically. A syscall's
4123 number is the value passed to the OS's syscall dispatcher to
4124 identify the requested service. When you specify the syscall by its
4125 name, @value{GDBN} uses its database of syscalls to convert the name
4126 into the corresponding numeric code, but using the number directly
4127 may be useful if @value{GDBN}'s database does not have the complete
4128 list of syscalls on your system (e.g., because @value{GDBN} lags
4129 behind the OS upgrades).
4131 The example below illustrates how this command works if you don't provide
4135 (@value{GDBP}) catch syscall
4136 Catchpoint 1 (syscall)
4138 Starting program: /tmp/catch-syscall
4140 Catchpoint 1 (call to syscall 'close'), \
4141 0xffffe424 in __kernel_vsyscall ()
4145 Catchpoint 1 (returned from syscall 'close'), \
4146 0xffffe424 in __kernel_vsyscall ()
4150 Here is an example of catching a system call by name:
4153 (@value{GDBP}) catch syscall chroot
4154 Catchpoint 1 (syscall 'chroot' [61])
4156 Starting program: /tmp/catch-syscall
4158 Catchpoint 1 (call to syscall 'chroot'), \
4159 0xffffe424 in __kernel_vsyscall ()
4163 Catchpoint 1 (returned from syscall 'chroot'), \
4164 0xffffe424 in __kernel_vsyscall ()
4168 An example of specifying a system call numerically. In the case
4169 below, the syscall number has a corresponding entry in the XML
4170 file, so @value{GDBN} finds its name and prints it:
4173 (@value{GDBP}) catch syscall 252
4174 Catchpoint 1 (syscall(s) 'exit_group')
4176 Starting program: /tmp/catch-syscall
4178 Catchpoint 1 (call to syscall 'exit_group'), \
4179 0xffffe424 in __kernel_vsyscall ()
4183 Program exited normally.
4187 However, there can be situations when there is no corresponding name
4188 in XML file for that syscall number. In this case, @value{GDBN} prints
4189 a warning message saying that it was not able to find the syscall name,
4190 but the catchpoint will be set anyway. See the example below:
4193 (@value{GDBP}) catch syscall 764
4194 warning: The number '764' does not represent a known syscall.
4195 Catchpoint 2 (syscall 764)
4199 If you configure @value{GDBN} using the @samp{--without-expat} option,
4200 it will not be able to display syscall names. Also, if your
4201 architecture does not have an XML file describing its system calls,
4202 you will not be able to see the syscall names. It is important to
4203 notice that these two features are used for accessing the syscall
4204 name database. In either case, you will see a warning like this:
4207 (@value{GDBP}) catch syscall
4208 warning: Could not open "syscalls/i386-linux.xml"
4209 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4210 GDB will not be able to display syscall names.
4211 Catchpoint 1 (syscall)
4215 Of course, the file name will change depending on your architecture and system.
4217 Still using the example above, you can also try to catch a syscall by its
4218 number. In this case, you would see something like:
4221 (@value{GDBP}) catch syscall 252
4222 Catchpoint 1 (syscall(s) 252)
4225 Again, in this case @value{GDBN} would not be able to display syscall's names.
4228 A call to @code{fork}. This is currently only available for HP-UX
4232 A call to @code{vfork}. This is currently only available for HP-UX
4235 @item load @r{[}regexp@r{]}
4236 @itemx unload @r{[}regexp@r{]}
4237 The loading or unloading of a shared library. If @var{regexp} is
4238 given, then the catchpoint will stop only if the regular expression
4239 matches one of the affected libraries.
4241 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4242 The delivery of a signal.
4244 With no arguments, this catchpoint will catch any signal that is not
4245 used internally by @value{GDBN}, specifically, all signals except
4246 @samp{SIGTRAP} and @samp{SIGINT}.
4248 With the argument @samp{all}, all signals, including those used by
4249 @value{GDBN}, will be caught. This argument cannot be used with other
4252 Otherwise, the arguments are a list of signal names as given to
4253 @code{handle} (@pxref{Signals}). Only signals specified in this list
4256 One reason that @code{catch signal} can be more useful than
4257 @code{handle} is that you can attach commands and conditions to the
4260 When a signal is caught by a catchpoint, the signal's @code{stop} and
4261 @code{print} settings, as specified by @code{handle}, are ignored.
4262 However, whether the signal is still delivered to the inferior depends
4263 on the @code{pass} setting; this can be changed in the catchpoint's
4268 @item tcatch @var{event}
4269 Set a catchpoint that is enabled only for one stop. The catchpoint is
4270 automatically deleted after the first time the event is caught.
4274 Use the @code{info break} command to list the current catchpoints.
4276 There are currently some limitations to C@t{++} exception handling
4277 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4281 If you call a function interactively, @value{GDBN} normally returns
4282 control to you when the function has finished executing. If the call
4283 raises an exception, however, the call may bypass the mechanism that
4284 returns control to you and cause your program either to abort or to
4285 simply continue running until it hits a breakpoint, catches a signal
4286 that @value{GDBN} is listening for, or exits. This is the case even if
4287 you set a catchpoint for the exception; catchpoints on exceptions are
4288 disabled within interactive calls.
4291 You cannot raise an exception interactively.
4294 You cannot install an exception handler interactively.
4297 @cindex raise exceptions
4298 Sometimes @code{catch} is not the best way to debug exception handling:
4299 if you need to know exactly where an exception is raised, it is better to
4300 stop @emph{before} the exception handler is called, since that way you
4301 can see the stack before any unwinding takes place. If you set a
4302 breakpoint in an exception handler instead, it may not be easy to find
4303 out where the exception was raised.
4305 To stop just before an exception handler is called, you need some
4306 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4307 raised by calling a library function named @code{__raise_exception}
4308 which has the following ANSI C interface:
4311 /* @var{addr} is where the exception identifier is stored.
4312 @var{id} is the exception identifier. */
4313 void __raise_exception (void **addr, void *id);
4317 To make the debugger catch all exceptions before any stack
4318 unwinding takes place, set a breakpoint on @code{__raise_exception}
4319 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4321 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4322 that depends on the value of @var{id}, you can stop your program when
4323 a specific exception is raised. You can use multiple conditional
4324 breakpoints to stop your program when any of a number of exceptions are
4329 @subsection Deleting Breakpoints
4331 @cindex clearing breakpoints, watchpoints, catchpoints
4332 @cindex deleting breakpoints, watchpoints, catchpoints
4333 It is often necessary to eliminate a breakpoint, watchpoint, or
4334 catchpoint once it has done its job and you no longer want your program
4335 to stop there. This is called @dfn{deleting} the breakpoint. A
4336 breakpoint that has been deleted no longer exists; it is forgotten.
4338 With the @code{clear} command you can delete breakpoints according to
4339 where they are in your program. With the @code{delete} command you can
4340 delete individual breakpoints, watchpoints, or catchpoints by specifying
4341 their breakpoint numbers.
4343 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4344 automatically ignores breakpoints on the first instruction to be executed
4345 when you continue execution without changing the execution address.
4350 Delete any breakpoints at the next instruction to be executed in the
4351 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4352 the innermost frame is selected, this is a good way to delete a
4353 breakpoint where your program just stopped.
4355 @item clear @var{location}
4356 Delete any breakpoints set at the specified @var{location}.
4357 @xref{Specify Location}, for the various forms of @var{location}; the
4358 most useful ones are listed below:
4361 @item clear @var{function}
4362 @itemx clear @var{filename}:@var{function}
4363 Delete any breakpoints set at entry to the named @var{function}.
4365 @item clear @var{linenum}
4366 @itemx clear @var{filename}:@var{linenum}
4367 Delete any breakpoints set at or within the code of the specified
4368 @var{linenum} of the specified @var{filename}.
4371 @cindex delete breakpoints
4373 @kindex d @r{(@code{delete})}
4374 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4375 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4376 ranges specified as arguments. If no argument is specified, delete all
4377 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4378 confirm off}). You can abbreviate this command as @code{d}.
4382 @subsection Disabling Breakpoints
4384 @cindex enable/disable a breakpoint
4385 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4386 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4387 it had been deleted, but remembers the information on the breakpoint so
4388 that you can @dfn{enable} it again later.
4390 You disable and enable breakpoints, watchpoints, and catchpoints with
4391 the @code{enable} and @code{disable} commands, optionally specifying
4392 one or more breakpoint numbers as arguments. Use @code{info break} to
4393 print a list of all breakpoints, watchpoints, and catchpoints if you
4394 do not know which numbers to use.
4396 Disabling and enabling a breakpoint that has multiple locations
4397 affects all of its locations.
4399 A breakpoint, watchpoint, or catchpoint can have any of several
4400 different states of enablement:
4404 Enabled. The breakpoint stops your program. A breakpoint set
4405 with the @code{break} command starts out in this state.
4407 Disabled. The breakpoint has no effect on your program.
4409 Enabled once. The breakpoint stops your program, but then becomes
4412 Enabled for a count. The breakpoint stops your program for the next
4413 N times, then becomes disabled.
4415 Enabled for deletion. The breakpoint stops your program, but
4416 immediately after it does so it is deleted permanently. A breakpoint
4417 set with the @code{tbreak} command starts out in this state.
4420 You can use the following commands to enable or disable breakpoints,
4421 watchpoints, and catchpoints:
4425 @kindex dis @r{(@code{disable})}
4426 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4427 Disable the specified breakpoints---or all breakpoints, if none are
4428 listed. A disabled breakpoint has no effect but is not forgotten. All
4429 options such as ignore-counts, conditions and commands are remembered in
4430 case the breakpoint is enabled again later. You may abbreviate
4431 @code{disable} as @code{dis}.
4434 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4435 Enable the specified breakpoints (or all defined breakpoints). They
4436 become effective once again in stopping your program.
4438 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4439 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4440 of these breakpoints immediately after stopping your program.
4442 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4443 Enable the specified breakpoints temporarily. @value{GDBN} records
4444 @var{count} with each of the specified breakpoints, and decrements a
4445 breakpoint's count when it is hit. When any count reaches 0,
4446 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4447 count (@pxref{Conditions, ,Break Conditions}), that will be
4448 decremented to 0 before @var{count} is affected.
4450 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4451 Enable the specified breakpoints to work once, then die. @value{GDBN}
4452 deletes any of these breakpoints as soon as your program stops there.
4453 Breakpoints set by the @code{tbreak} command start out in this state.
4456 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4457 @c confusing: tbreak is also initially enabled.
4458 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4459 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4460 subsequently, they become disabled or enabled only when you use one of
4461 the commands above. (The command @code{until} can set and delete a
4462 breakpoint of its own, but it does not change the state of your other
4463 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4467 @subsection Break Conditions
4468 @cindex conditional breakpoints
4469 @cindex breakpoint conditions
4471 @c FIXME what is scope of break condition expr? Context where wanted?
4472 @c in particular for a watchpoint?
4473 The simplest sort of breakpoint breaks every time your program reaches a
4474 specified place. You can also specify a @dfn{condition} for a
4475 breakpoint. A condition is just a Boolean expression in your
4476 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4477 a condition evaluates the expression each time your program reaches it,
4478 and your program stops only if the condition is @emph{true}.
4480 This is the converse of using assertions for program validation; in that
4481 situation, you want to stop when the assertion is violated---that is,
4482 when the condition is false. In C, if you want to test an assertion expressed
4483 by the condition @var{assert}, you should set the condition
4484 @samp{! @var{assert}} on the appropriate breakpoint.
4486 Conditions are also accepted for watchpoints; you may not need them,
4487 since a watchpoint is inspecting the value of an expression anyhow---but
4488 it might be simpler, say, to just set a watchpoint on a variable name,
4489 and specify a condition that tests whether the new value is an interesting
4492 Break conditions can have side effects, and may even call functions in
4493 your program. This can be useful, for example, to activate functions
4494 that log program progress, or to use your own print functions to
4495 format special data structures. The effects are completely predictable
4496 unless there is another enabled breakpoint at the same address. (In
4497 that case, @value{GDBN} might see the other breakpoint first and stop your
4498 program without checking the condition of this one.) Note that
4499 breakpoint commands are usually more convenient and flexible than break
4501 purpose of performing side effects when a breakpoint is reached
4502 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4504 Breakpoint conditions can also be evaluated on the target's side if
4505 the target supports it. Instead of evaluating the conditions locally,
4506 @value{GDBN} encodes the expression into an agent expression
4507 (@pxref{Agent Expressions}) suitable for execution on the target,
4508 independently of @value{GDBN}. Global variables become raw memory
4509 locations, locals become stack accesses, and so forth.
4511 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4512 when its condition evaluates to true. This mechanism may provide faster
4513 response times depending on the performance characteristics of the target
4514 since it does not need to keep @value{GDBN} informed about
4515 every breakpoint trigger, even those with false conditions.
4517 Break conditions can be specified when a breakpoint is set, by using
4518 @samp{if} in the arguments to the @code{break} command. @xref{Set
4519 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4520 with the @code{condition} command.
4522 You can also use the @code{if} keyword with the @code{watch} command.
4523 The @code{catch} command does not recognize the @code{if} keyword;
4524 @code{condition} is the only way to impose a further condition on a
4529 @item condition @var{bnum} @var{expression}
4530 Specify @var{expression} as the break condition for breakpoint,
4531 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4532 breakpoint @var{bnum} stops your program only if the value of
4533 @var{expression} is true (nonzero, in C). When you use
4534 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4535 syntactic correctness, and to determine whether symbols in it have
4536 referents in the context of your breakpoint. If @var{expression} uses
4537 symbols not referenced in the context of the breakpoint, @value{GDBN}
4538 prints an error message:
4541 No symbol "foo" in current context.
4546 not actually evaluate @var{expression} at the time the @code{condition}
4547 command (or a command that sets a breakpoint with a condition, like
4548 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4550 @item condition @var{bnum}
4551 Remove the condition from breakpoint number @var{bnum}. It becomes
4552 an ordinary unconditional breakpoint.
4555 @cindex ignore count (of breakpoint)
4556 A special case of a breakpoint condition is to stop only when the
4557 breakpoint has been reached a certain number of times. This is so
4558 useful that there is a special way to do it, using the @dfn{ignore
4559 count} of the breakpoint. Every breakpoint has an ignore count, which
4560 is an integer. Most of the time, the ignore count is zero, and
4561 therefore has no effect. But if your program reaches a breakpoint whose
4562 ignore count is positive, then instead of stopping, it just decrements
4563 the ignore count by one and continues. As a result, if the ignore count
4564 value is @var{n}, the breakpoint does not stop the next @var{n} times
4565 your program reaches it.
4569 @item ignore @var{bnum} @var{count}
4570 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4571 The next @var{count} times the breakpoint is reached, your program's
4572 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4575 To make the breakpoint stop the next time it is reached, specify
4578 When you use @code{continue} to resume execution of your program from a
4579 breakpoint, you can specify an ignore count directly as an argument to
4580 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4581 Stepping,,Continuing and Stepping}.
4583 If a breakpoint has a positive ignore count and a condition, the
4584 condition is not checked. Once the ignore count reaches zero,
4585 @value{GDBN} resumes checking the condition.
4587 You could achieve the effect of the ignore count with a condition such
4588 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4589 is decremented each time. @xref{Convenience Vars, ,Convenience
4593 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4596 @node Break Commands
4597 @subsection Breakpoint Command Lists
4599 @cindex breakpoint commands
4600 You can give any breakpoint (or watchpoint or catchpoint) a series of
4601 commands to execute when your program stops due to that breakpoint. For
4602 example, you might want to print the values of certain expressions, or
4603 enable other breakpoints.
4607 @kindex end@r{ (breakpoint commands)}
4608 @item commands @r{[}@var{range}@dots{}@r{]}
4609 @itemx @dots{} @var{command-list} @dots{}
4611 Specify a list of commands for the given breakpoints. The commands
4612 themselves appear on the following lines. Type a line containing just
4613 @code{end} to terminate the commands.
4615 To remove all commands from a breakpoint, type @code{commands} and
4616 follow it immediately with @code{end}; that is, give no commands.
4618 With no argument, @code{commands} refers to the last breakpoint,
4619 watchpoint, or catchpoint set (not to the breakpoint most recently
4620 encountered). If the most recent breakpoints were set with a single
4621 command, then the @code{commands} will apply to all the breakpoints
4622 set by that command. This applies to breakpoints set by
4623 @code{rbreak}, and also applies when a single @code{break} command
4624 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4628 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4629 disabled within a @var{command-list}.
4631 You can use breakpoint commands to start your program up again. Simply
4632 use the @code{continue} command, or @code{step}, or any other command
4633 that resumes execution.
4635 Any other commands in the command list, after a command that resumes
4636 execution, are ignored. This is because any time you resume execution
4637 (even with a simple @code{next} or @code{step}), you may encounter
4638 another breakpoint---which could have its own command list, leading to
4639 ambiguities about which list to execute.
4642 If the first command you specify in a command list is @code{silent}, the
4643 usual message about stopping at a breakpoint is not printed. This may
4644 be desirable for breakpoints that are to print a specific message and
4645 then continue. If none of the remaining commands print anything, you
4646 see no sign that the breakpoint was reached. @code{silent} is
4647 meaningful only at the beginning of a breakpoint command list.
4649 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4650 print precisely controlled output, and are often useful in silent
4651 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4653 For example, here is how you could use breakpoint commands to print the
4654 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4660 printf "x is %d\n",x
4665 One application for breakpoint commands is to compensate for one bug so
4666 you can test for another. Put a breakpoint just after the erroneous line
4667 of code, give it a condition to detect the case in which something
4668 erroneous has been done, and give it commands to assign correct values
4669 to any variables that need them. End with the @code{continue} command
4670 so that your program does not stop, and start with the @code{silent}
4671 command so that no output is produced. Here is an example:
4682 @node Dynamic Printf
4683 @subsection Dynamic Printf
4685 @cindex dynamic printf
4687 The dynamic printf command @code{dprintf} combines a breakpoint with
4688 formatted printing of your program's data to give you the effect of
4689 inserting @code{printf} calls into your program on-the-fly, without
4690 having to recompile it.
4692 In its most basic form, the output goes to the GDB console. However,
4693 you can set the variable @code{dprintf-style} for alternate handling.
4694 For instance, you can ask to format the output by calling your
4695 program's @code{printf} function. This has the advantage that the
4696 characters go to the program's output device, so they can recorded in
4697 redirects to files and so forth.
4699 If you are doing remote debugging with a stub or agent, you can also
4700 ask to have the printf handled by the remote agent. In addition to
4701 ensuring that the output goes to the remote program's device along
4702 with any other output the program might produce, you can also ask that
4703 the dprintf remain active even after disconnecting from the remote
4704 target. Using the stub/agent is also more efficient, as it can do
4705 everything without needing to communicate with @value{GDBN}.
4709 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4710 Whenever execution reaches @var{location}, print the values of one or
4711 more @var{expressions} under the control of the string @var{template}.
4712 To print several values, separate them with commas.
4714 @item set dprintf-style @var{style}
4715 Set the dprintf output to be handled in one of several different
4716 styles enumerated below. A change of style affects all existing
4717 dynamic printfs immediately. (If you need individual control over the
4718 print commands, simply define normal breakpoints with
4719 explicitly-supplied command lists.)
4722 @kindex dprintf-style gdb
4723 Handle the output using the @value{GDBN} @code{printf} command.
4726 @kindex dprintf-style call
4727 Handle the output by calling a function in your program (normally
4731 @kindex dprintf-style agent
4732 Have the remote debugging agent (such as @code{gdbserver}) handle
4733 the output itself. This style is only available for agents that
4734 support running commands on the target.
4736 @item set dprintf-function @var{function}
4737 Set the function to call if the dprintf style is @code{call}. By
4738 default its value is @code{printf}. You may set it to any expression.
4739 that @value{GDBN} can evaluate to a function, as per the @code{call}
4742 @item set dprintf-channel @var{channel}
4743 Set a ``channel'' for dprintf. If set to a non-empty value,
4744 @value{GDBN} will evaluate it as an expression and pass the result as
4745 a first argument to the @code{dprintf-function}, in the manner of
4746 @code{fprintf} and similar functions. Otherwise, the dprintf format
4747 string will be the first argument, in the manner of @code{printf}.
4749 As an example, if you wanted @code{dprintf} output to go to a logfile
4750 that is a standard I/O stream assigned to the variable @code{mylog},
4751 you could do the following:
4754 (gdb) set dprintf-style call
4755 (gdb) set dprintf-function fprintf
4756 (gdb) set dprintf-channel mylog
4757 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4758 Dprintf 1 at 0x123456: file main.c, line 25.
4760 1 dprintf keep y 0x00123456 in main at main.c:25
4761 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4766 Note that the @code{info break} displays the dynamic printf commands
4767 as normal breakpoint commands; you can thus easily see the effect of
4768 the variable settings.
4770 @item set disconnected-dprintf on
4771 @itemx set disconnected-dprintf off
4772 @kindex set disconnected-dprintf
4773 Choose whether @code{dprintf} commands should continue to run if
4774 @value{GDBN} has disconnected from the target. This only applies
4775 if the @code{dprintf-style} is @code{agent}.
4777 @item show disconnected-dprintf off
4778 @kindex show disconnected-dprintf
4779 Show the current choice for disconnected @code{dprintf}.
4783 @value{GDBN} does not check the validity of function and channel,
4784 relying on you to supply values that are meaningful for the contexts
4785 in which they are being used. For instance, the function and channel
4786 may be the values of local variables, but if that is the case, then
4787 all enabled dynamic prints must be at locations within the scope of
4788 those locals. If evaluation fails, @value{GDBN} will report an error.
4790 @node Save Breakpoints
4791 @subsection How to save breakpoints to a file
4793 To save breakpoint definitions to a file use the @w{@code{save
4794 breakpoints}} command.
4797 @kindex save breakpoints
4798 @cindex save breakpoints to a file for future sessions
4799 @item save breakpoints [@var{filename}]
4800 This command saves all current breakpoint definitions together with
4801 their commands and ignore counts, into a file @file{@var{filename}}
4802 suitable for use in a later debugging session. This includes all
4803 types of breakpoints (breakpoints, watchpoints, catchpoints,
4804 tracepoints). To read the saved breakpoint definitions, use the
4805 @code{source} command (@pxref{Command Files}). Note that watchpoints
4806 with expressions involving local variables may fail to be recreated
4807 because it may not be possible to access the context where the
4808 watchpoint is valid anymore. Because the saved breakpoint definitions
4809 are simply a sequence of @value{GDBN} commands that recreate the
4810 breakpoints, you can edit the file in your favorite editing program,
4811 and remove the breakpoint definitions you're not interested in, or
4812 that can no longer be recreated.
4815 @node Static Probe Points
4816 @subsection Static Probe Points
4818 @cindex static probe point, SystemTap
4819 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4820 for Statically Defined Tracing, and the probes are designed to have a tiny
4821 runtime code and data footprint, and no dynamic relocations. They are
4822 usable from assembly, C and C@t{++} languages. See
4823 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4824 for a good reference on how the @acronym{SDT} probes are implemented.
4826 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4827 @acronym{SDT} probes are supported on ELF-compatible systems. See
4828 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4829 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4830 in your applications.
4832 @cindex semaphores on static probe points
4833 Some probes have an associated semaphore variable; for instance, this
4834 happens automatically if you defined your probe using a DTrace-style
4835 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4836 automatically enable it when you specify a breakpoint using the
4837 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4838 location by some other method (e.g., @code{break file:line}), then
4839 @value{GDBN} will not automatically set the semaphore.
4841 You can examine the available static static probes using @code{info
4842 probes}, with optional arguments:
4846 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4847 If given, @var{provider} is a regular expression used to match against provider
4848 names when selecting which probes to list. If omitted, probes by all
4849 probes from all providers are listed.
4851 If given, @var{name} is a regular expression to match against probe names
4852 when selecting which probes to list. If omitted, probe names are not
4853 considered when deciding whether to display them.
4855 If given, @var{objfile} is a regular expression used to select which
4856 object files (executable or shared libraries) to examine. If not
4857 given, all object files are considered.
4859 @item info probes all
4860 List the available static probes, from all types.
4863 @vindex $_probe_arg@r{, convenience variable}
4864 A probe may specify up to twelve arguments. These are available at the
4865 point at which the probe is defined---that is, when the current PC is
4866 at the probe's location. The arguments are available using the
4867 convenience variables (@pxref{Convenience Vars})
4868 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4869 an integer of the appropriate size; types are not preserved. The
4870 convenience variable @code{$_probe_argc} holds the number of arguments
4871 at the current probe point.
4873 These variables are always available, but attempts to access them at
4874 any location other than a probe point will cause @value{GDBN} to give
4878 @c @ifclear BARETARGET
4879 @node Error in Breakpoints
4880 @subsection ``Cannot insert breakpoints''
4882 If you request too many active hardware-assisted breakpoints and
4883 watchpoints, you will see this error message:
4885 @c FIXME: the precise wording of this message may change; the relevant
4886 @c source change is not committed yet (Sep 3, 1999).
4888 Stopped; cannot insert breakpoints.
4889 You may have requested too many hardware breakpoints and watchpoints.
4893 This message is printed when you attempt to resume the program, since
4894 only then @value{GDBN} knows exactly how many hardware breakpoints and
4895 watchpoints it needs to insert.
4897 When this message is printed, you need to disable or remove some of the
4898 hardware-assisted breakpoints and watchpoints, and then continue.
4900 @node Breakpoint-related Warnings
4901 @subsection ``Breakpoint address adjusted...''
4902 @cindex breakpoint address adjusted
4904 Some processor architectures place constraints on the addresses at
4905 which breakpoints may be placed. For architectures thus constrained,
4906 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4907 with the constraints dictated by the architecture.
4909 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4910 a VLIW architecture in which a number of RISC-like instructions may be
4911 bundled together for parallel execution. The FR-V architecture
4912 constrains the location of a breakpoint instruction within such a
4913 bundle to the instruction with the lowest address. @value{GDBN}
4914 honors this constraint by adjusting a breakpoint's address to the
4915 first in the bundle.
4917 It is not uncommon for optimized code to have bundles which contain
4918 instructions from different source statements, thus it may happen that
4919 a breakpoint's address will be adjusted from one source statement to
4920 another. Since this adjustment may significantly alter @value{GDBN}'s
4921 breakpoint related behavior from what the user expects, a warning is
4922 printed when the breakpoint is first set and also when the breakpoint
4925 A warning like the one below is printed when setting a breakpoint
4926 that's been subject to address adjustment:
4929 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4932 Such warnings are printed both for user settable and @value{GDBN}'s
4933 internal breakpoints. If you see one of these warnings, you should
4934 verify that a breakpoint set at the adjusted address will have the
4935 desired affect. If not, the breakpoint in question may be removed and
4936 other breakpoints may be set which will have the desired behavior.
4937 E.g., it may be sufficient to place the breakpoint at a later
4938 instruction. A conditional breakpoint may also be useful in some
4939 cases to prevent the breakpoint from triggering too often.
4941 @value{GDBN} will also issue a warning when stopping at one of these
4942 adjusted breakpoints:
4945 warning: Breakpoint 1 address previously adjusted from 0x00010414
4949 When this warning is encountered, it may be too late to take remedial
4950 action except in cases where the breakpoint is hit earlier or more
4951 frequently than expected.
4953 @node Continuing and Stepping
4954 @section Continuing and Stepping
4958 @cindex resuming execution
4959 @dfn{Continuing} means resuming program execution until your program
4960 completes normally. In contrast, @dfn{stepping} means executing just
4961 one more ``step'' of your program, where ``step'' may mean either one
4962 line of source code, or one machine instruction (depending on what
4963 particular command you use). Either when continuing or when stepping,
4964 your program may stop even sooner, due to a breakpoint or a signal. (If
4965 it stops due to a signal, you may want to use @code{handle}, or use
4966 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4970 @kindex c @r{(@code{continue})}
4971 @kindex fg @r{(resume foreground execution)}
4972 @item continue @r{[}@var{ignore-count}@r{]}
4973 @itemx c @r{[}@var{ignore-count}@r{]}
4974 @itemx fg @r{[}@var{ignore-count}@r{]}
4975 Resume program execution, at the address where your program last stopped;
4976 any breakpoints set at that address are bypassed. The optional argument
4977 @var{ignore-count} allows you to specify a further number of times to
4978 ignore a breakpoint at this location; its effect is like that of
4979 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4981 The argument @var{ignore-count} is meaningful only when your program
4982 stopped due to a breakpoint. At other times, the argument to
4983 @code{continue} is ignored.
4985 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4986 debugged program is deemed to be the foreground program) are provided
4987 purely for convenience, and have exactly the same behavior as
4991 To resume execution at a different place, you can use @code{return}
4992 (@pxref{Returning, ,Returning from a Function}) to go back to the
4993 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4994 Different Address}) to go to an arbitrary location in your program.
4996 A typical technique for using stepping is to set a breakpoint
4997 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4998 beginning of the function or the section of your program where a problem
4999 is believed to lie, run your program until it stops at that breakpoint,
5000 and then step through the suspect area, examining the variables that are
5001 interesting, until you see the problem happen.
5005 @kindex s @r{(@code{step})}
5007 Continue running your program until control reaches a different source
5008 line, then stop it and return control to @value{GDBN}. This command is
5009 abbreviated @code{s}.
5012 @c "without debugging information" is imprecise; actually "without line
5013 @c numbers in the debugging information". (gcc -g1 has debugging info but
5014 @c not line numbers). But it seems complex to try to make that
5015 @c distinction here.
5016 @emph{Warning:} If you use the @code{step} command while control is
5017 within a function that was compiled without debugging information,
5018 execution proceeds until control reaches a function that does have
5019 debugging information. Likewise, it will not step into a function which
5020 is compiled without debugging information. To step through functions
5021 without debugging information, use the @code{stepi} command, described
5025 The @code{step} command only stops at the first instruction of a source
5026 line. This prevents the multiple stops that could otherwise occur in
5027 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5028 to stop if a function that has debugging information is called within
5029 the line. In other words, @code{step} @emph{steps inside} any functions
5030 called within the line.
5032 Also, the @code{step} command only enters a function if there is line
5033 number information for the function. Otherwise it acts like the
5034 @code{next} command. This avoids problems when using @code{cc -gl}
5035 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5036 was any debugging information about the routine.
5038 @item step @var{count}
5039 Continue running as in @code{step}, but do so @var{count} times. If a
5040 breakpoint is reached, or a signal not related to stepping occurs before
5041 @var{count} steps, stepping stops right away.
5044 @kindex n @r{(@code{next})}
5045 @item next @r{[}@var{count}@r{]}
5046 Continue to the next source line in the current (innermost) stack frame.
5047 This is similar to @code{step}, but function calls that appear within
5048 the line of code are executed without stopping. Execution stops when
5049 control reaches a different line of code at the original stack level
5050 that was executing when you gave the @code{next} command. This command
5051 is abbreviated @code{n}.
5053 An argument @var{count} is a repeat count, as for @code{step}.
5056 @c FIX ME!! Do we delete this, or is there a way it fits in with
5057 @c the following paragraph? --- Vctoria
5059 @c @code{next} within a function that lacks debugging information acts like
5060 @c @code{step}, but any function calls appearing within the code of the
5061 @c function are executed without stopping.
5063 The @code{next} command only stops at the first instruction of a
5064 source line. This prevents multiple stops that could otherwise occur in
5065 @code{switch} statements, @code{for} loops, etc.
5067 @kindex set step-mode
5069 @cindex functions without line info, and stepping
5070 @cindex stepping into functions with no line info
5071 @itemx set step-mode on
5072 The @code{set step-mode on} command causes the @code{step} command to
5073 stop at the first instruction of a function which contains no debug line
5074 information rather than stepping over it.
5076 This is useful in cases where you may be interested in inspecting the
5077 machine instructions of a function which has no symbolic info and do not
5078 want @value{GDBN} to automatically skip over this function.
5080 @item set step-mode off
5081 Causes the @code{step} command to step over any functions which contains no
5082 debug information. This is the default.
5084 @item show step-mode
5085 Show whether @value{GDBN} will stop in or step over functions without
5086 source line debug information.
5089 @kindex fin @r{(@code{finish})}
5091 Continue running until just after function in the selected stack frame
5092 returns. Print the returned value (if any). This command can be
5093 abbreviated as @code{fin}.
5095 Contrast this with the @code{return} command (@pxref{Returning,
5096 ,Returning from a Function}).
5099 @kindex u @r{(@code{until})}
5100 @cindex run until specified location
5103 Continue running until a source line past the current line, in the
5104 current stack frame, is reached. This command is used to avoid single
5105 stepping through a loop more than once. It is like the @code{next}
5106 command, except that when @code{until} encounters a jump, it
5107 automatically continues execution until the program counter is greater
5108 than the address of the jump.
5110 This means that when you reach the end of a loop after single stepping
5111 though it, @code{until} makes your program continue execution until it
5112 exits the loop. In contrast, a @code{next} command at the end of a loop
5113 simply steps back to the beginning of the loop, which forces you to step
5114 through the next iteration.
5116 @code{until} always stops your program if it attempts to exit the current
5119 @code{until} may produce somewhat counterintuitive results if the order
5120 of machine code does not match the order of the source lines. For
5121 example, in the following excerpt from a debugging session, the @code{f}
5122 (@code{frame}) command shows that execution is stopped at line
5123 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5127 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5129 (@value{GDBP}) until
5130 195 for ( ; argc > 0; NEXTARG) @{
5133 This happened because, for execution efficiency, the compiler had
5134 generated code for the loop closure test at the end, rather than the
5135 start, of the loop---even though the test in a C @code{for}-loop is
5136 written before the body of the loop. The @code{until} command appeared
5137 to step back to the beginning of the loop when it advanced to this
5138 expression; however, it has not really gone to an earlier
5139 statement---not in terms of the actual machine code.
5141 @code{until} with no argument works by means of single
5142 instruction stepping, and hence is slower than @code{until} with an
5145 @item until @var{location}
5146 @itemx u @var{location}
5147 Continue running your program until either the specified location is
5148 reached, or the current stack frame returns. @var{location} is any of
5149 the forms described in @ref{Specify Location}.
5150 This form of the command uses temporary breakpoints, and
5151 hence is quicker than @code{until} without an argument. The specified
5152 location is actually reached only if it is in the current frame. This
5153 implies that @code{until} can be used to skip over recursive function
5154 invocations. For instance in the code below, if the current location is
5155 line @code{96}, issuing @code{until 99} will execute the program up to
5156 line @code{99} in the same invocation of factorial, i.e., after the inner
5157 invocations have returned.
5160 94 int factorial (int value)
5162 96 if (value > 1) @{
5163 97 value *= factorial (value - 1);
5170 @kindex advance @var{location}
5171 @item advance @var{location}
5172 Continue running the program up to the given @var{location}. An argument is
5173 required, which should be of one of the forms described in
5174 @ref{Specify Location}.
5175 Execution will also stop upon exit from the current stack
5176 frame. This command is similar to @code{until}, but @code{advance} will
5177 not skip over recursive function calls, and the target location doesn't
5178 have to be in the same frame as the current one.
5182 @kindex si @r{(@code{stepi})}
5184 @itemx stepi @var{arg}
5186 Execute one machine instruction, then stop and return to the debugger.
5188 It is often useful to do @samp{display/i $pc} when stepping by machine
5189 instructions. This makes @value{GDBN} automatically display the next
5190 instruction to be executed, each time your program stops. @xref{Auto
5191 Display,, Automatic Display}.
5193 An argument is a repeat count, as in @code{step}.
5197 @kindex ni @r{(@code{nexti})}
5199 @itemx nexti @var{arg}
5201 Execute one machine instruction, but if it is a function call,
5202 proceed until the function returns.
5204 An argument is a repeat count, as in @code{next}.
5207 @node Skipping Over Functions and Files
5208 @section Skipping Over Functions and Files
5209 @cindex skipping over functions and files
5211 The program you are debugging may contain some functions which are
5212 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5213 skip a function or all functions in a file when stepping.
5215 For example, consider the following C function:
5226 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5227 are not interested in stepping through @code{boring}. If you run @code{step}
5228 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5229 step over both @code{foo} and @code{boring}!
5231 One solution is to @code{step} into @code{boring} and use the @code{finish}
5232 command to immediately exit it. But this can become tedious if @code{boring}
5233 is called from many places.
5235 A more flexible solution is to execute @kbd{skip boring}. This instructs
5236 @value{GDBN} never to step into @code{boring}. Now when you execute
5237 @code{step} at line 103, you'll step over @code{boring} and directly into
5240 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5241 example, @code{skip file boring.c}.
5244 @kindex skip function
5245 @item skip @r{[}@var{linespec}@r{]}
5246 @itemx skip function @r{[}@var{linespec}@r{]}
5247 After running this command, the function named by @var{linespec} or the
5248 function containing the line named by @var{linespec} will be skipped over when
5249 stepping. @xref{Specify Location}.
5251 If you do not specify @var{linespec}, the function you're currently debugging
5254 (If you have a function called @code{file} that you want to skip, use
5255 @kbd{skip function file}.)
5258 @item skip file @r{[}@var{filename}@r{]}
5259 After running this command, any function whose source lives in @var{filename}
5260 will be skipped over when stepping.
5262 If you do not specify @var{filename}, functions whose source lives in the file
5263 you're currently debugging will be skipped.
5266 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5267 These are the commands for managing your list of skips:
5271 @item info skip @r{[}@var{range}@r{]}
5272 Print details about the specified skip(s). If @var{range} is not specified,
5273 print a table with details about all functions and files marked for skipping.
5274 @code{info skip} prints the following information about each skip:
5278 A number identifying this skip.
5280 The type of this skip, either @samp{function} or @samp{file}.
5281 @item Enabled or Disabled
5282 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5284 For function skips, this column indicates the address in memory of the function
5285 being skipped. If you've set a function skip on a function which has not yet
5286 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5287 which has the function is loaded, @code{info skip} will show the function's
5290 For file skips, this field contains the filename being skipped. For functions
5291 skips, this field contains the function name and its line number in the file
5292 where it is defined.
5296 @item skip delete @r{[}@var{range}@r{]}
5297 Delete the specified skip(s). If @var{range} is not specified, delete all
5301 @item skip enable @r{[}@var{range}@r{]}
5302 Enable the specified skip(s). If @var{range} is not specified, enable all
5305 @kindex skip disable
5306 @item skip disable @r{[}@var{range}@r{]}
5307 Disable the specified skip(s). If @var{range} is not specified, disable all
5316 A signal is an asynchronous event that can happen in a program. The
5317 operating system defines the possible kinds of signals, and gives each
5318 kind a name and a number. For example, in Unix @code{SIGINT} is the
5319 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5320 @code{SIGSEGV} is the signal a program gets from referencing a place in
5321 memory far away from all the areas in use; @code{SIGALRM} occurs when
5322 the alarm clock timer goes off (which happens only if your program has
5323 requested an alarm).
5325 @cindex fatal signals
5326 Some signals, including @code{SIGALRM}, are a normal part of the
5327 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5328 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5329 program has not specified in advance some other way to handle the signal.
5330 @code{SIGINT} does not indicate an error in your program, but it is normally
5331 fatal so it can carry out the purpose of the interrupt: to kill the program.
5333 @value{GDBN} has the ability to detect any occurrence of a signal in your
5334 program. You can tell @value{GDBN} in advance what to do for each kind of
5337 @cindex handling signals
5338 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5339 @code{SIGALRM} be silently passed to your program
5340 (so as not to interfere with their role in the program's functioning)
5341 but to stop your program immediately whenever an error signal happens.
5342 You can change these settings with the @code{handle} command.
5345 @kindex info signals
5349 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5350 handle each one. You can use this to see the signal numbers of all
5351 the defined types of signals.
5353 @item info signals @var{sig}
5354 Similar, but print information only about the specified signal number.
5356 @code{info handle} is an alias for @code{info signals}.
5358 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5359 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5360 for details about this command.
5363 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5364 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5365 can be the number of a signal or its name (with or without the
5366 @samp{SIG} at the beginning); a list of signal numbers of the form
5367 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5368 known signals. Optional arguments @var{keywords}, described below,
5369 say what change to make.
5373 The keywords allowed by the @code{handle} command can be abbreviated.
5374 Their full names are:
5378 @value{GDBN} should not stop your program when this signal happens. It may
5379 still print a message telling you that the signal has come in.
5382 @value{GDBN} should stop your program when this signal happens. This implies
5383 the @code{print} keyword as well.
5386 @value{GDBN} should print a message when this signal happens.
5389 @value{GDBN} should not mention the occurrence of the signal at all. This
5390 implies the @code{nostop} keyword as well.
5394 @value{GDBN} should allow your program to see this signal; your program
5395 can handle the signal, or else it may terminate if the signal is fatal
5396 and not handled. @code{pass} and @code{noignore} are synonyms.
5400 @value{GDBN} should not allow your program to see this signal.
5401 @code{nopass} and @code{ignore} are synonyms.
5405 When a signal stops your program, the signal is not visible to the
5407 continue. Your program sees the signal then, if @code{pass} is in
5408 effect for the signal in question @emph{at that time}. In other words,
5409 after @value{GDBN} reports a signal, you can use the @code{handle}
5410 command with @code{pass} or @code{nopass} to control whether your
5411 program sees that signal when you continue.
5413 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5414 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5415 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5418 You can also use the @code{signal} command to prevent your program from
5419 seeing a signal, or cause it to see a signal it normally would not see,
5420 or to give it any signal at any time. For example, if your program stopped
5421 due to some sort of memory reference error, you might store correct
5422 values into the erroneous variables and continue, hoping to see more
5423 execution; but your program would probably terminate immediately as
5424 a result of the fatal signal once it saw the signal. To prevent this,
5425 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5428 @cindex extra signal information
5429 @anchor{extra signal information}
5431 On some targets, @value{GDBN} can inspect extra signal information
5432 associated with the intercepted signal, before it is actually
5433 delivered to the program being debugged. This information is exported
5434 by the convenience variable @code{$_siginfo}, and consists of data
5435 that is passed by the kernel to the signal handler at the time of the
5436 receipt of a signal. The data type of the information itself is
5437 target dependent. You can see the data type using the @code{ptype
5438 $_siginfo} command. On Unix systems, it typically corresponds to the
5439 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5442 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5443 referenced address that raised a segmentation fault.
5447 (@value{GDBP}) continue
5448 Program received signal SIGSEGV, Segmentation fault.
5449 0x0000000000400766 in main ()
5451 (@value{GDBP}) ptype $_siginfo
5458 struct @{...@} _kill;
5459 struct @{...@} _timer;
5461 struct @{...@} _sigchld;
5462 struct @{...@} _sigfault;
5463 struct @{...@} _sigpoll;
5466 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5470 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5471 $1 = (void *) 0x7ffff7ff7000
5475 Depending on target support, @code{$_siginfo} may also be writable.
5478 @section Stopping and Starting Multi-thread Programs
5480 @cindex stopped threads
5481 @cindex threads, stopped
5483 @cindex continuing threads
5484 @cindex threads, continuing
5486 @value{GDBN} supports debugging programs with multiple threads
5487 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5488 are two modes of controlling execution of your program within the
5489 debugger. In the default mode, referred to as @dfn{all-stop mode},
5490 when any thread in your program stops (for example, at a breakpoint
5491 or while being stepped), all other threads in the program are also stopped by
5492 @value{GDBN}. On some targets, @value{GDBN} also supports
5493 @dfn{non-stop mode}, in which other threads can continue to run freely while
5494 you examine the stopped thread in the debugger.
5497 * All-Stop Mode:: All threads stop when GDB takes control
5498 * Non-Stop Mode:: Other threads continue to execute
5499 * Background Execution:: Running your program asynchronously
5500 * Thread-Specific Breakpoints:: Controlling breakpoints
5501 * Interrupted System Calls:: GDB may interfere with system calls
5502 * Observer Mode:: GDB does not alter program behavior
5506 @subsection All-Stop Mode
5508 @cindex all-stop mode
5510 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5511 @emph{all} threads of execution stop, not just the current thread. This
5512 allows you to examine the overall state of the program, including
5513 switching between threads, without worrying that things may change
5516 Conversely, whenever you restart the program, @emph{all} threads start
5517 executing. @emph{This is true even when single-stepping} with commands
5518 like @code{step} or @code{next}.
5520 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5521 Since thread scheduling is up to your debugging target's operating
5522 system (not controlled by @value{GDBN}), other threads may
5523 execute more than one statement while the current thread completes a
5524 single step. Moreover, in general other threads stop in the middle of a
5525 statement, rather than at a clean statement boundary, when the program
5528 You might even find your program stopped in another thread after
5529 continuing or even single-stepping. This happens whenever some other
5530 thread runs into a breakpoint, a signal, or an exception before the
5531 first thread completes whatever you requested.
5533 @cindex automatic thread selection
5534 @cindex switching threads automatically
5535 @cindex threads, automatic switching
5536 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5537 signal, it automatically selects the thread where that breakpoint or
5538 signal happened. @value{GDBN} alerts you to the context switch with a
5539 message such as @samp{[Switching to Thread @var{n}]} to identify the
5542 On some OSes, you can modify @value{GDBN}'s default behavior by
5543 locking the OS scheduler to allow only a single thread to run.
5546 @item set scheduler-locking @var{mode}
5547 @cindex scheduler locking mode
5548 @cindex lock scheduler
5549 Set the scheduler locking mode. If it is @code{off}, then there is no
5550 locking and any thread may run at any time. If @code{on}, then only the
5551 current thread may run when the inferior is resumed. The @code{step}
5552 mode optimizes for single-stepping; it prevents other threads
5553 from preempting the current thread while you are stepping, so that
5554 the focus of debugging does not change unexpectedly.
5555 Other threads only rarely (or never) get a chance to run
5556 when you step. They are more likely to run when you @samp{next} over a
5557 function call, and they are completely free to run when you use commands
5558 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5559 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5560 the current thread away from the thread that you are debugging.
5562 @item show scheduler-locking
5563 Display the current scheduler locking mode.
5566 @cindex resume threads of multiple processes simultaneously
5567 By default, when you issue one of the execution commands such as
5568 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5569 threads of the current inferior to run. For example, if @value{GDBN}
5570 is attached to two inferiors, each with two threads, the
5571 @code{continue} command resumes only the two threads of the current
5572 inferior. This is useful, for example, when you debug a program that
5573 forks and you want to hold the parent stopped (so that, for instance,
5574 it doesn't run to exit), while you debug the child. In other
5575 situations, you may not be interested in inspecting the current state
5576 of any of the processes @value{GDBN} is attached to, and you may want
5577 to resume them all until some breakpoint is hit. In the latter case,
5578 you can instruct @value{GDBN} to allow all threads of all the
5579 inferiors to run with the @w{@code{set schedule-multiple}} command.
5582 @kindex set schedule-multiple
5583 @item set schedule-multiple
5584 Set the mode for allowing threads of multiple processes to be resumed
5585 when an execution command is issued. When @code{on}, all threads of
5586 all processes are allowed to run. When @code{off}, only the threads
5587 of the current process are resumed. The default is @code{off}. The
5588 @code{scheduler-locking} mode takes precedence when set to @code{on},
5589 or while you are stepping and set to @code{step}.
5591 @item show schedule-multiple
5592 Display the current mode for resuming the execution of threads of
5597 @subsection Non-Stop Mode
5599 @cindex non-stop mode
5601 @c This section is really only a place-holder, and needs to be expanded
5602 @c with more details.
5604 For some multi-threaded targets, @value{GDBN} supports an optional
5605 mode of operation in which you can examine stopped program threads in
5606 the debugger while other threads continue to execute freely. This
5607 minimizes intrusion when debugging live systems, such as programs
5608 where some threads have real-time constraints or must continue to
5609 respond to external events. This is referred to as @dfn{non-stop} mode.
5611 In non-stop mode, when a thread stops to report a debugging event,
5612 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5613 threads as well, in contrast to the all-stop mode behavior. Additionally,
5614 execution commands such as @code{continue} and @code{step} apply by default
5615 only to the current thread in non-stop mode, rather than all threads as
5616 in all-stop mode. This allows you to control threads explicitly in
5617 ways that are not possible in all-stop mode --- for example, stepping
5618 one thread while allowing others to run freely, stepping
5619 one thread while holding all others stopped, or stepping several threads
5620 independently and simultaneously.
5622 To enter non-stop mode, use this sequence of commands before you run
5623 or attach to your program:
5626 # Enable the async interface.
5629 # If using the CLI, pagination breaks non-stop.
5632 # Finally, turn it on!
5636 You can use these commands to manipulate the non-stop mode setting:
5639 @kindex set non-stop
5640 @item set non-stop on
5641 Enable selection of non-stop mode.
5642 @item set non-stop off
5643 Disable selection of non-stop mode.
5644 @kindex show non-stop
5646 Show the current non-stop enablement setting.
5649 Note these commands only reflect whether non-stop mode is enabled,
5650 not whether the currently-executing program is being run in non-stop mode.
5651 In particular, the @code{set non-stop} preference is only consulted when
5652 @value{GDBN} starts or connects to the target program, and it is generally
5653 not possible to switch modes once debugging has started. Furthermore,
5654 since not all targets support non-stop mode, even when you have enabled
5655 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5658 In non-stop mode, all execution commands apply only to the current thread
5659 by default. That is, @code{continue} only continues one thread.
5660 To continue all threads, issue @code{continue -a} or @code{c -a}.
5662 You can use @value{GDBN}'s background execution commands
5663 (@pxref{Background Execution}) to run some threads in the background
5664 while you continue to examine or step others from @value{GDBN}.
5665 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5666 always executed asynchronously in non-stop mode.
5668 Suspending execution is done with the @code{interrupt} command when
5669 running in the background, or @kbd{Ctrl-c} during foreground execution.
5670 In all-stop mode, this stops the whole process;
5671 but in non-stop mode the interrupt applies only to the current thread.
5672 To stop the whole program, use @code{interrupt -a}.
5674 Other execution commands do not currently support the @code{-a} option.
5676 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5677 that thread current, as it does in all-stop mode. This is because the
5678 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5679 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5680 changed to a different thread just as you entered a command to operate on the
5681 previously current thread.
5683 @node Background Execution
5684 @subsection Background Execution
5686 @cindex foreground execution
5687 @cindex background execution
5688 @cindex asynchronous execution
5689 @cindex execution, foreground, background and asynchronous
5691 @value{GDBN}'s execution commands have two variants: the normal
5692 foreground (synchronous) behavior, and a background
5693 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5694 the program to report that some thread has stopped before prompting for
5695 another command. In background execution, @value{GDBN} immediately gives
5696 a command prompt so that you can issue other commands while your program runs.
5698 You need to explicitly enable asynchronous mode before you can use
5699 background execution commands. You can use these commands to
5700 manipulate the asynchronous mode setting:
5703 @kindex set target-async
5704 @item set target-async on
5705 Enable asynchronous mode.
5706 @item set target-async off
5707 Disable asynchronous mode.
5708 @kindex show target-async
5709 @item show target-async
5710 Show the current target-async setting.
5713 If the target doesn't support async mode, @value{GDBN} issues an error
5714 message if you attempt to use the background execution commands.
5716 To specify background execution, add a @code{&} to the command. For example,
5717 the background form of the @code{continue} command is @code{continue&}, or
5718 just @code{c&}. The execution commands that accept background execution
5724 @xref{Starting, , Starting your Program}.
5728 @xref{Attach, , Debugging an Already-running Process}.
5732 @xref{Continuing and Stepping, step}.
5736 @xref{Continuing and Stepping, stepi}.
5740 @xref{Continuing and Stepping, next}.
5744 @xref{Continuing and Stepping, nexti}.
5748 @xref{Continuing and Stepping, continue}.
5752 @xref{Continuing and Stepping, finish}.
5756 @xref{Continuing and Stepping, until}.
5760 Background execution is especially useful in conjunction with non-stop
5761 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5762 However, you can also use these commands in the normal all-stop mode with
5763 the restriction that you cannot issue another execution command until the
5764 previous one finishes. Examples of commands that are valid in all-stop
5765 mode while the program is running include @code{help} and @code{info break}.
5767 You can interrupt your program while it is running in the background by
5768 using the @code{interrupt} command.
5775 Suspend execution of the running program. In all-stop mode,
5776 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5777 only the current thread. To stop the whole program in non-stop mode,
5778 use @code{interrupt -a}.
5781 @node Thread-Specific Breakpoints
5782 @subsection Thread-Specific Breakpoints
5784 When your program has multiple threads (@pxref{Threads,, Debugging
5785 Programs with Multiple Threads}), you can choose whether to set
5786 breakpoints on all threads, or on a particular thread.
5789 @cindex breakpoints and threads
5790 @cindex thread breakpoints
5791 @kindex break @dots{} thread @var{threadno}
5792 @item break @var{linespec} thread @var{threadno}
5793 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5794 @var{linespec} specifies source lines; there are several ways of
5795 writing them (@pxref{Specify Location}), but the effect is always to
5796 specify some source line.
5798 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5799 to specify that you only want @value{GDBN} to stop the program when a
5800 particular thread reaches this breakpoint. @var{threadno} is one of the
5801 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5802 column of the @samp{info threads} display.
5804 If you do not specify @samp{thread @var{threadno}} when you set a
5805 breakpoint, the breakpoint applies to @emph{all} threads of your
5808 You can use the @code{thread} qualifier on conditional breakpoints as
5809 well; in this case, place @samp{thread @var{threadno}} before or
5810 after the breakpoint condition, like this:
5813 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5818 @node Interrupted System Calls
5819 @subsection Interrupted System Calls
5821 @cindex thread breakpoints and system calls
5822 @cindex system calls and thread breakpoints
5823 @cindex premature return from system calls
5824 There is an unfortunate side effect when using @value{GDBN} to debug
5825 multi-threaded programs. If one thread stops for a
5826 breakpoint, or for some other reason, and another thread is blocked in a
5827 system call, then the system call may return prematurely. This is a
5828 consequence of the interaction between multiple threads and the signals
5829 that @value{GDBN} uses to implement breakpoints and other events that
5832 To handle this problem, your program should check the return value of
5833 each system call and react appropriately. This is good programming
5836 For example, do not write code like this:
5842 The call to @code{sleep} will return early if a different thread stops
5843 at a breakpoint or for some other reason.
5845 Instead, write this:
5850 unslept = sleep (unslept);
5853 A system call is allowed to return early, so the system is still
5854 conforming to its specification. But @value{GDBN} does cause your
5855 multi-threaded program to behave differently than it would without
5858 Also, @value{GDBN} uses internal breakpoints in the thread library to
5859 monitor certain events such as thread creation and thread destruction.
5860 When such an event happens, a system call in another thread may return
5861 prematurely, even though your program does not appear to stop.
5864 @subsection Observer Mode
5866 If you want to build on non-stop mode and observe program behavior
5867 without any chance of disruption by @value{GDBN}, you can set
5868 variables to disable all of the debugger's attempts to modify state,
5869 whether by writing memory, inserting breakpoints, etc. These operate
5870 at a low level, intercepting operations from all commands.
5872 When all of these are set to @code{off}, then @value{GDBN} is said to
5873 be @dfn{observer mode}. As a convenience, the variable
5874 @code{observer} can be set to disable these, plus enable non-stop
5877 Note that @value{GDBN} will not prevent you from making nonsensical
5878 combinations of these settings. For instance, if you have enabled
5879 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5880 then breakpoints that work by writing trap instructions into the code
5881 stream will still not be able to be placed.
5886 @item set observer on
5887 @itemx set observer off
5888 When set to @code{on}, this disables all the permission variables
5889 below (except for @code{insert-fast-tracepoints}), plus enables
5890 non-stop debugging. Setting this to @code{off} switches back to
5891 normal debugging, though remaining in non-stop mode.
5894 Show whether observer mode is on or off.
5896 @kindex may-write-registers
5897 @item set may-write-registers on
5898 @itemx set may-write-registers off
5899 This controls whether @value{GDBN} will attempt to alter the values of
5900 registers, such as with assignment expressions in @code{print}, or the
5901 @code{jump} command. It defaults to @code{on}.
5903 @item show may-write-registers
5904 Show the current permission to write registers.
5906 @kindex may-write-memory
5907 @item set may-write-memory on
5908 @itemx set may-write-memory off
5909 This controls whether @value{GDBN} will attempt to alter the contents
5910 of memory, such as with assignment expressions in @code{print}. It
5911 defaults to @code{on}.
5913 @item show may-write-memory
5914 Show the current permission to write memory.
5916 @kindex may-insert-breakpoints
5917 @item set may-insert-breakpoints on
5918 @itemx set may-insert-breakpoints off
5919 This controls whether @value{GDBN} will attempt to insert breakpoints.
5920 This affects all breakpoints, including internal breakpoints defined
5921 by @value{GDBN}. It defaults to @code{on}.
5923 @item show may-insert-breakpoints
5924 Show the current permission to insert breakpoints.
5926 @kindex may-insert-tracepoints
5927 @item set may-insert-tracepoints on
5928 @itemx set may-insert-tracepoints off
5929 This controls whether @value{GDBN} will attempt to insert (regular)
5930 tracepoints at the beginning of a tracing experiment. It affects only
5931 non-fast tracepoints, fast tracepoints being under the control of
5932 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5934 @item show may-insert-tracepoints
5935 Show the current permission to insert tracepoints.
5937 @kindex may-insert-fast-tracepoints
5938 @item set may-insert-fast-tracepoints on
5939 @itemx set may-insert-fast-tracepoints off
5940 This controls whether @value{GDBN} will attempt to insert fast
5941 tracepoints at the beginning of a tracing experiment. It affects only
5942 fast tracepoints, regular (non-fast) tracepoints being under the
5943 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5945 @item show may-insert-fast-tracepoints
5946 Show the current permission to insert fast tracepoints.
5948 @kindex may-interrupt
5949 @item set may-interrupt on
5950 @itemx set may-interrupt off
5951 This controls whether @value{GDBN} will attempt to interrupt or stop
5952 program execution. When this variable is @code{off}, the
5953 @code{interrupt} command will have no effect, nor will
5954 @kbd{Ctrl-c}. It defaults to @code{on}.
5956 @item show may-interrupt
5957 Show the current permission to interrupt or stop the program.
5961 @node Reverse Execution
5962 @chapter Running programs backward
5963 @cindex reverse execution
5964 @cindex running programs backward
5966 When you are debugging a program, it is not unusual to realize that
5967 you have gone too far, and some event of interest has already happened.
5968 If the target environment supports it, @value{GDBN} can allow you to
5969 ``rewind'' the program by running it backward.
5971 A target environment that supports reverse execution should be able
5972 to ``undo'' the changes in machine state that have taken place as the
5973 program was executing normally. Variables, registers etc.@: should
5974 revert to their previous values. Obviously this requires a great
5975 deal of sophistication on the part of the target environment; not
5976 all target environments can support reverse execution.
5978 When a program is executed in reverse, the instructions that
5979 have most recently been executed are ``un-executed'', in reverse
5980 order. The program counter runs backward, following the previous
5981 thread of execution in reverse. As each instruction is ``un-executed'',
5982 the values of memory and/or registers that were changed by that
5983 instruction are reverted to their previous states. After executing
5984 a piece of source code in reverse, all side effects of that code
5985 should be ``undone'', and all variables should be returned to their
5986 prior values@footnote{
5987 Note that some side effects are easier to undo than others. For instance,
5988 memory and registers are relatively easy, but device I/O is hard. Some
5989 targets may be able undo things like device I/O, and some may not.
5991 The contract between @value{GDBN} and the reverse executing target
5992 requires only that the target do something reasonable when
5993 @value{GDBN} tells it to execute backwards, and then report the
5994 results back to @value{GDBN}. Whatever the target reports back to
5995 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5996 assumes that the memory and registers that the target reports are in a
5997 consistant state, but @value{GDBN} accepts whatever it is given.
6000 If you are debugging in a target environment that supports
6001 reverse execution, @value{GDBN} provides the following commands.
6004 @kindex reverse-continue
6005 @kindex rc @r{(@code{reverse-continue})}
6006 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6007 @itemx rc @r{[}@var{ignore-count}@r{]}
6008 Beginning at the point where your program last stopped, start executing
6009 in reverse. Reverse execution will stop for breakpoints and synchronous
6010 exceptions (signals), just like normal execution. Behavior of
6011 asynchronous signals depends on the target environment.
6013 @kindex reverse-step
6014 @kindex rs @r{(@code{step})}
6015 @item reverse-step @r{[}@var{count}@r{]}
6016 Run the program backward until control reaches the start of a
6017 different source line; then stop it, and return control to @value{GDBN}.
6019 Like the @code{step} command, @code{reverse-step} will only stop
6020 at the beginning of a source line. It ``un-executes'' the previously
6021 executed source line. If the previous source line included calls to
6022 debuggable functions, @code{reverse-step} will step (backward) into
6023 the called function, stopping at the beginning of the @emph{last}
6024 statement in the called function (typically a return statement).
6026 Also, as with the @code{step} command, if non-debuggable functions are
6027 called, @code{reverse-step} will run thru them backward without stopping.
6029 @kindex reverse-stepi
6030 @kindex rsi @r{(@code{reverse-stepi})}
6031 @item reverse-stepi @r{[}@var{count}@r{]}
6032 Reverse-execute one machine instruction. Note that the instruction
6033 to be reverse-executed is @emph{not} the one pointed to by the program
6034 counter, but the instruction executed prior to that one. For instance,
6035 if the last instruction was a jump, @code{reverse-stepi} will take you
6036 back from the destination of the jump to the jump instruction itself.
6038 @kindex reverse-next
6039 @kindex rn @r{(@code{reverse-next})}
6040 @item reverse-next @r{[}@var{count}@r{]}
6041 Run backward to the beginning of the previous line executed in
6042 the current (innermost) stack frame. If the line contains function
6043 calls, they will be ``un-executed'' without stopping. Starting from
6044 the first line of a function, @code{reverse-next} will take you back
6045 to the caller of that function, @emph{before} the function was called,
6046 just as the normal @code{next} command would take you from the last
6047 line of a function back to its return to its caller
6048 @footnote{Unless the code is too heavily optimized.}.
6050 @kindex reverse-nexti
6051 @kindex rni @r{(@code{reverse-nexti})}
6052 @item reverse-nexti @r{[}@var{count}@r{]}
6053 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6054 in reverse, except that called functions are ``un-executed'' atomically.
6055 That is, if the previously executed instruction was a return from
6056 another function, @code{reverse-nexti} will continue to execute
6057 in reverse until the call to that function (from the current stack
6060 @kindex reverse-finish
6061 @item reverse-finish
6062 Just as the @code{finish} command takes you to the point where the
6063 current function returns, @code{reverse-finish} takes you to the point
6064 where it was called. Instead of ending up at the end of the current
6065 function invocation, you end up at the beginning.
6067 @kindex set exec-direction
6068 @item set exec-direction
6069 Set the direction of target execution.
6070 @item set exec-direction reverse
6071 @cindex execute forward or backward in time
6072 @value{GDBN} will perform all execution commands in reverse, until the
6073 exec-direction mode is changed to ``forward''. Affected commands include
6074 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6075 command cannot be used in reverse mode.
6076 @item set exec-direction forward
6077 @value{GDBN} will perform all execution commands in the normal fashion.
6078 This is the default.
6082 @node Process Record and Replay
6083 @chapter Recording Inferior's Execution and Replaying It
6084 @cindex process record and replay
6085 @cindex recording inferior's execution and replaying it
6087 On some platforms, @value{GDBN} provides a special @dfn{process record
6088 and replay} target that can record a log of the process execution, and
6089 replay it later with both forward and reverse execution commands.
6092 When this target is in use, if the execution log includes the record
6093 for the next instruction, @value{GDBN} will debug in @dfn{replay
6094 mode}. In the replay mode, the inferior does not really execute code
6095 instructions. Instead, all the events that normally happen during
6096 code execution are taken from the execution log. While code is not
6097 really executed in replay mode, the values of registers (including the
6098 program counter register) and the memory of the inferior are still
6099 changed as they normally would. Their contents are taken from the
6103 If the record for the next instruction is not in the execution log,
6104 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6105 inferior executes normally, and @value{GDBN} records the execution log
6108 The process record and replay target supports reverse execution
6109 (@pxref{Reverse Execution}), even if the platform on which the
6110 inferior runs does not. However, the reverse execution is limited in
6111 this case by the range of the instructions recorded in the execution
6112 log. In other words, reverse execution on platforms that don't
6113 support it directly can only be done in the replay mode.
6115 When debugging in the reverse direction, @value{GDBN} will work in
6116 replay mode as long as the execution log includes the record for the
6117 previous instruction; otherwise, it will work in record mode, if the
6118 platform supports reverse execution, or stop if not.
6120 For architecture environments that support process record and replay,
6121 @value{GDBN} provides the following commands:
6124 @kindex target record
6125 @kindex target record-full
6126 @kindex target record-btrace
6129 @kindex record btrace
6133 @item record @var{method}
6134 This command starts the process record and replay target. The
6135 recording method can be specified as parameter. Without a parameter
6136 the command uses the @code{full} recording method. The following
6137 recording methods are available:
6141 Full record/replay recording using @value{GDBN}'s software record and
6142 replay implementation. This method allows replaying and reverse
6146 Hardware-supported instruction recording. This method does not allow
6147 replaying and reverse execution.
6149 This recording method may not be available on all processors.
6152 The process record and replay target can only debug a process that is
6153 already running. Therefore, you need first to start the process with
6154 the @kbd{run} or @kbd{start} commands, and then start the recording
6155 with the @kbd{record @var{method}} command.
6157 Both @code{record @var{method}} and @code{rec @var{method}} are
6158 aliases of @code{target record-@var{method}}.
6160 @cindex displaced stepping, and process record and replay
6161 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6162 will be automatically disabled when process record and replay target
6163 is started. That's because the process record and replay target
6164 doesn't support displaced stepping.
6166 @cindex non-stop mode, and process record and replay
6167 @cindex asynchronous execution, and process record and replay
6168 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6169 the asynchronous execution mode (@pxref{Background Execution}), not
6170 all recording methods are available. The @code{full} recording method
6171 does not support these two modes.
6176 Stop the process record and replay target. When process record and
6177 replay target stops, the entire execution log will be deleted and the
6178 inferior will either be terminated, or will remain in its final state.
6180 When you stop the process record and replay target in record mode (at
6181 the end of the execution log), the inferior will be stopped at the
6182 next instruction that would have been recorded. In other words, if
6183 you record for a while and then stop recording, the inferior process
6184 will be left in the same state as if the recording never happened.
6186 On the other hand, if the process record and replay target is stopped
6187 while in replay mode (that is, not at the end of the execution log,
6188 but at some earlier point), the inferior process will become ``live''
6189 at that earlier state, and it will then be possible to continue the
6190 usual ``live'' debugging of the process from that state.
6192 When the inferior process exits, or @value{GDBN} detaches from it,
6193 process record and replay target will automatically stop itself.
6196 @item record save @var{filename}
6197 Save the execution log to a file @file{@var{filename}}.
6198 Default filename is @file{gdb_record.@var{process_id}}, where
6199 @var{process_id} is the process ID of the inferior.
6201 This command may not be available for all recording methods.
6203 @kindex record restore
6204 @item record restore @var{filename}
6205 Restore the execution log from a file @file{@var{filename}}.
6206 File must have been created with @code{record save}.
6208 @kindex set record full
6209 @item set record full insn-number-max @var{limit}
6210 @itemx set record full insn-number-max unlimited
6211 Set the limit of instructions to be recorded for the @code{full}
6212 recording method. Default value is 200000.
6214 If @var{limit} is a positive number, then @value{GDBN} will start
6215 deleting instructions from the log once the number of the record
6216 instructions becomes greater than @var{limit}. For every new recorded
6217 instruction, @value{GDBN} will delete the earliest recorded
6218 instruction to keep the number of recorded instructions at the limit.
6219 (Since deleting recorded instructions loses information, @value{GDBN}
6220 lets you control what happens when the limit is reached, by means of
6221 the @code{stop-at-limit} option, described below.)
6223 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6224 delete recorded instructions from the execution log. The number of
6225 recorded instructions is limited only by the available memory.
6227 @kindex show record full
6228 @item show record full insn-number-max
6229 Show the limit of instructions to be recorded with the @code{full}
6232 @item set record full stop-at-limit
6233 Control the behavior of the @code{full} recording method when the
6234 number of recorded instructions reaches the limit. If ON (the
6235 default), @value{GDBN} will stop when the limit is reached for the
6236 first time and ask you whether you want to stop the inferior or
6237 continue running it and recording the execution log. If you decide
6238 to continue recording, each new recorded instruction will cause the
6239 oldest one to be deleted.
6241 If this option is OFF, @value{GDBN} will automatically delete the
6242 oldest record to make room for each new one, without asking.
6244 @item show record full stop-at-limit
6245 Show the current setting of @code{stop-at-limit}.
6247 @item set record full memory-query
6248 Control the behavior when @value{GDBN} is unable to record memory
6249 changes caused by an instruction for the @code{full} recording method.
6250 If ON, @value{GDBN} will query whether to stop the inferior in that
6253 If this option is OFF (the default), @value{GDBN} will automatically
6254 ignore the effect of such instructions on memory. Later, when
6255 @value{GDBN} replays this execution log, it will mark the log of this
6256 instruction as not accessible, and it will not affect the replay
6259 @item show record full memory-query
6260 Show the current setting of @code{memory-query}.
6264 Show various statistics about the recording depending on the recording
6269 For the @code{full} recording method, it shows the state of process
6270 record and its in-memory execution log buffer, including:
6274 Whether in record mode or replay mode.
6276 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6278 Highest recorded instruction number.
6280 Current instruction about to be replayed (if in replay mode).
6282 Number of instructions contained in the execution log.
6284 Maximum number of instructions that may be contained in the execution log.
6288 For the @code{btrace} recording method, it shows the number of
6289 instructions that have been recorded and the number of blocks of
6290 sequential control-flow that is formed by the recorded instructions.
6293 @kindex record delete
6296 When record target runs in replay mode (``in the past''), delete the
6297 subsequent execution log and begin to record a new execution log starting
6298 from the current address. This means you will abandon the previously
6299 recorded ``future'' and begin recording a new ``future''.
6301 @kindex record instruction-history
6302 @kindex rec instruction-history
6303 @item record instruction-history
6304 Disassembles instructions from the recorded execution log. By
6305 default, ten instructions are disassembled. This can be changed using
6306 the @code{set record instruction-history-size} command. Instructions
6307 are printed in execution order. There are several ways to specify
6308 what part of the execution log to disassemble:
6311 @item record instruction-history @var{insn}
6312 Disassembles ten instructions starting from instruction number
6315 @item record instruction-history @var{insn}, +/-@var{n}
6316 Disassembles @var{n} instructions around instruction number
6317 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6318 @var{n} instructions after instruction number @var{insn}. If
6319 @var{n} is preceded with @code{-}, disassembles @var{n}
6320 instructions before instruction number @var{insn}.
6322 @item record instruction-history
6323 Disassembles ten more instructions after the last disassembly.
6325 @item record instruction-history -
6326 Disassembles ten more instructions before the last disassembly.
6328 @item record instruction-history @var{begin} @var{end}
6329 Disassembles instructions beginning with instruction number
6330 @var{begin} until instruction number @var{end}. The instruction
6331 number @var{end} is not included.
6334 This command may not be available for all recording methods.
6337 @item set record instruction-history-size @var{size}
6338 @itemx set record instruction-history-size unlimited
6339 Define how many instructions to disassemble in the @code{record
6340 instruction-history} command. The default value is 10.
6341 A @var{size} of @code{unlimited} means unlimited instructions.
6344 @item show record instruction-history-size
6345 Show how many instructions to disassemble in the @code{record
6346 instruction-history} command.
6348 @kindex record function-call-history
6349 @kindex rec function-call-history
6350 @item record function-call-history
6351 Prints the execution history at function granularity. It prints one
6352 line for each sequence of instructions that belong to the same
6353 function giving the name of that function, the source lines
6354 for this instruction sequence (if the @code{/l} modifier is
6355 specified), and the instructions numbers that form the sequence (if
6356 the @code{/i} modifier is specified).
6359 (@value{GDBP}) @b{list 1, 10}
6370 (@value{GDBP}) @b{record function-call-history /l}
6376 By default, ten lines are printed. This can be changed using the
6377 @code{set record function-call-history-size} command. Functions are
6378 printed in execution order. There are several ways to specify what
6382 @item record function-call-history @var{func}
6383 Prints ten functions starting from function number @var{func}.
6385 @item record function-call-history @var{func}, +/-@var{n}
6386 Prints @var{n} functions around function number @var{func}. If
6387 @var{n} is preceded with @code{+}, prints @var{n} functions after
6388 function number @var{func}. If @var{n} is preceded with @code{-},
6389 prints @var{n} functions before function number @var{func}.
6391 @item record function-call-history
6392 Prints ten more functions after the last ten-line print.
6394 @item record function-call-history -
6395 Prints ten more functions before the last ten-line print.
6397 @item record function-call-history @var{begin} @var{end}
6398 Prints functions beginning with function number @var{begin} until
6399 function number @var{end}. The function number @var{end} is not
6403 This command may not be available for all recording methods.
6405 @item set record function-call-history-size @var{size}
6406 @itemx set record function-call-history-size unlimited
6407 Define how many lines to print in the
6408 @code{record function-call-history} command. The default value is 10.
6409 A size of @code{unlimited} means unlimited lines.
6411 @item show record function-call-history-size
6412 Show how many lines to print in the
6413 @code{record function-call-history} command.
6418 @chapter Examining the Stack
6420 When your program has stopped, the first thing you need to know is where it
6421 stopped and how it got there.
6424 Each time your program performs a function call, information about the call
6426 That information includes the location of the call in your program,
6427 the arguments of the call,
6428 and the local variables of the function being called.
6429 The information is saved in a block of data called a @dfn{stack frame}.
6430 The stack frames are allocated in a region of memory called the @dfn{call
6433 When your program stops, the @value{GDBN} commands for examining the
6434 stack allow you to see all of this information.
6436 @cindex selected frame
6437 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6438 @value{GDBN} commands refer implicitly to the selected frame. In
6439 particular, whenever you ask @value{GDBN} for the value of a variable in
6440 your program, the value is found in the selected frame. There are
6441 special @value{GDBN} commands to select whichever frame you are
6442 interested in. @xref{Selection, ,Selecting a Frame}.
6444 When your program stops, @value{GDBN} automatically selects the
6445 currently executing frame and describes it briefly, similar to the
6446 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6449 * Frames:: Stack frames
6450 * Backtrace:: Backtraces
6451 * Selection:: Selecting a frame
6452 * Frame Info:: Information on a frame
6457 @section Stack Frames
6459 @cindex frame, definition
6461 The call stack is divided up into contiguous pieces called @dfn{stack
6462 frames}, or @dfn{frames} for short; each frame is the data associated
6463 with one call to one function. The frame contains the arguments given
6464 to the function, the function's local variables, and the address at
6465 which the function is executing.
6467 @cindex initial frame
6468 @cindex outermost frame
6469 @cindex innermost frame
6470 When your program is started, the stack has only one frame, that of the
6471 function @code{main}. This is called the @dfn{initial} frame or the
6472 @dfn{outermost} frame. Each time a function is called, a new frame is
6473 made. Each time a function returns, the frame for that function invocation
6474 is eliminated. If a function is recursive, there can be many frames for
6475 the same function. The frame for the function in which execution is
6476 actually occurring is called the @dfn{innermost} frame. This is the most
6477 recently created of all the stack frames that still exist.
6479 @cindex frame pointer
6480 Inside your program, stack frames are identified by their addresses. A
6481 stack frame consists of many bytes, each of which has its own address; each
6482 kind of computer has a convention for choosing one byte whose
6483 address serves as the address of the frame. Usually this address is kept
6484 in a register called the @dfn{frame pointer register}
6485 (@pxref{Registers, $fp}) while execution is going on in that frame.
6487 @cindex frame number
6488 @value{GDBN} assigns numbers to all existing stack frames, starting with
6489 zero for the innermost frame, one for the frame that called it,
6490 and so on upward. These numbers do not really exist in your program;
6491 they are assigned by @value{GDBN} to give you a way of designating stack
6492 frames in @value{GDBN} commands.
6494 @c The -fomit-frame-pointer below perennially causes hbox overflow
6495 @c underflow problems.
6496 @cindex frameless execution
6497 Some compilers provide a way to compile functions so that they operate
6498 without stack frames. (For example, the @value{NGCC} option
6500 @samp{-fomit-frame-pointer}
6502 generates functions without a frame.)
6503 This is occasionally done with heavily used library functions to save
6504 the frame setup time. @value{GDBN} has limited facilities for dealing
6505 with these function invocations. If the innermost function invocation
6506 has no stack frame, @value{GDBN} nevertheless regards it as though
6507 it had a separate frame, which is numbered zero as usual, allowing
6508 correct tracing of the function call chain. However, @value{GDBN} has
6509 no provision for frameless functions elsewhere in the stack.
6512 @kindex frame@r{, command}
6513 @cindex current stack frame
6514 @item frame @var{args}
6515 The @code{frame} command allows you to move from one stack frame to another,
6516 and to print the stack frame you select. @var{args} may be either the
6517 address of the frame or the stack frame number. Without an argument,
6518 @code{frame} prints the current stack frame.
6520 @kindex select-frame
6521 @cindex selecting frame silently
6523 The @code{select-frame} command allows you to move from one stack frame
6524 to another without printing the frame. This is the silent version of
6532 @cindex call stack traces
6533 A backtrace is a summary of how your program got where it is. It shows one
6534 line per frame, for many frames, starting with the currently executing
6535 frame (frame zero), followed by its caller (frame one), and on up the
6540 @kindex bt @r{(@code{backtrace})}
6543 Print a backtrace of the entire stack: one line per frame for all
6544 frames in the stack.
6546 You can stop the backtrace at any time by typing the system interrupt
6547 character, normally @kbd{Ctrl-c}.
6549 @item backtrace @var{n}
6551 Similar, but print only the innermost @var{n} frames.
6553 @item backtrace -@var{n}
6555 Similar, but print only the outermost @var{n} frames.
6557 @item backtrace full
6559 @itemx bt full @var{n}
6560 @itemx bt full -@var{n}
6561 Print the values of the local variables also. @var{n} specifies the
6562 number of frames to print, as described above.
6567 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6568 are additional aliases for @code{backtrace}.
6570 @cindex multiple threads, backtrace
6571 In a multi-threaded program, @value{GDBN} by default shows the
6572 backtrace only for the current thread. To display the backtrace for
6573 several or all of the threads, use the command @code{thread apply}
6574 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6575 apply all backtrace}, @value{GDBN} will display the backtrace for all
6576 the threads; this is handy when you debug a core dump of a
6577 multi-threaded program.
6579 Each line in the backtrace shows the frame number and the function name.
6580 The program counter value is also shown---unless you use @code{set
6581 print address off}. The backtrace also shows the source file name and
6582 line number, as well as the arguments to the function. The program
6583 counter value is omitted if it is at the beginning of the code for that
6586 Here is an example of a backtrace. It was made with the command
6587 @samp{bt 3}, so it shows the innermost three frames.
6591 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6593 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6594 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6596 (More stack frames follow...)
6601 The display for frame zero does not begin with a program counter
6602 value, indicating that your program has stopped at the beginning of the
6603 code for line @code{993} of @code{builtin.c}.
6606 The value of parameter @code{data} in frame 1 has been replaced by
6607 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6608 only if it is a scalar (integer, pointer, enumeration, etc). See command
6609 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6610 on how to configure the way function parameter values are printed.
6612 @cindex optimized out, in backtrace
6613 @cindex function call arguments, optimized out
6614 If your program was compiled with optimizations, some compilers will
6615 optimize away arguments passed to functions if those arguments are
6616 never used after the call. Such optimizations generate code that
6617 passes arguments through registers, but doesn't store those arguments
6618 in the stack frame. @value{GDBN} has no way of displaying such
6619 arguments in stack frames other than the innermost one. Here's what
6620 such a backtrace might look like:
6624 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6626 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6627 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6629 (More stack frames follow...)
6634 The values of arguments that were not saved in their stack frames are
6635 shown as @samp{<optimized out>}.
6637 If you need to display the values of such optimized-out arguments,
6638 either deduce that from other variables whose values depend on the one
6639 you are interested in, or recompile without optimizations.
6641 @cindex backtrace beyond @code{main} function
6642 @cindex program entry point
6643 @cindex startup code, and backtrace
6644 Most programs have a standard user entry point---a place where system
6645 libraries and startup code transition into user code. For C this is
6646 @code{main}@footnote{
6647 Note that embedded programs (the so-called ``free-standing''
6648 environment) are not required to have a @code{main} function as the
6649 entry point. They could even have multiple entry points.}.
6650 When @value{GDBN} finds the entry function in a backtrace
6651 it will terminate the backtrace, to avoid tracing into highly
6652 system-specific (and generally uninteresting) code.
6654 If you need to examine the startup code, or limit the number of levels
6655 in a backtrace, you can change this behavior:
6658 @item set backtrace past-main
6659 @itemx set backtrace past-main on
6660 @kindex set backtrace
6661 Backtraces will continue past the user entry point.
6663 @item set backtrace past-main off
6664 Backtraces will stop when they encounter the user entry point. This is the
6667 @item show backtrace past-main
6668 @kindex show backtrace
6669 Display the current user entry point backtrace policy.
6671 @item set backtrace past-entry
6672 @itemx set backtrace past-entry on
6673 Backtraces will continue past the internal entry point of an application.
6674 This entry point is encoded by the linker when the application is built,
6675 and is likely before the user entry point @code{main} (or equivalent) is called.
6677 @item set backtrace past-entry off
6678 Backtraces will stop when they encounter the internal entry point of an
6679 application. This is the default.
6681 @item show backtrace past-entry
6682 Display the current internal entry point backtrace policy.
6684 @item set backtrace limit @var{n}
6685 @itemx set backtrace limit 0
6686 @itemx set backtrace limit unlimited
6687 @cindex backtrace limit
6688 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6689 or zero means unlimited levels.
6691 @item show backtrace limit
6692 Display the current limit on backtrace levels.
6695 You can control how file names are displayed.
6698 @item set filename-display
6699 @itemx set filename-display relative
6700 @cindex filename-display
6701 Display file names relative to the compilation directory. This is the default.
6703 @item set filename-display basename
6704 Display only basename of a filename.
6706 @item set filename-display absolute
6707 Display an absolute filename.
6709 @item show filename-display
6710 Show the current way to display filenames.
6714 @section Selecting a Frame
6716 Most commands for examining the stack and other data in your program work on
6717 whichever stack frame is selected at the moment. Here are the commands for
6718 selecting a stack frame; all of them finish by printing a brief description
6719 of the stack frame just selected.
6722 @kindex frame@r{, selecting}
6723 @kindex f @r{(@code{frame})}
6726 Select frame number @var{n}. Recall that frame zero is the innermost
6727 (currently executing) frame, frame one is the frame that called the
6728 innermost one, and so on. The highest-numbered frame is the one for
6731 @item frame @var{addr}
6733 Select the frame at address @var{addr}. This is useful mainly if the
6734 chaining of stack frames has been damaged by a bug, making it
6735 impossible for @value{GDBN} to assign numbers properly to all frames. In
6736 addition, this can be useful when your program has multiple stacks and
6737 switches between them.
6739 On the SPARC architecture, @code{frame} needs two addresses to
6740 select an arbitrary frame: a frame pointer and a stack pointer.
6742 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6743 pointer and a program counter.
6745 On the 29k architecture, it needs three addresses: a register stack
6746 pointer, a program counter, and a memory stack pointer.
6750 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6751 advances toward the outermost frame, to higher frame numbers, to frames
6752 that have existed longer. @var{n} defaults to one.
6755 @kindex do @r{(@code{down})}
6757 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6758 advances toward the innermost frame, to lower frame numbers, to frames
6759 that were created more recently. @var{n} defaults to one. You may
6760 abbreviate @code{down} as @code{do}.
6763 All of these commands end by printing two lines of output describing the
6764 frame. The first line shows the frame number, the function name, the
6765 arguments, and the source file and line number of execution in that
6766 frame. The second line shows the text of that source line.
6774 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6776 10 read_input_file (argv[i]);
6780 After such a printout, the @code{list} command with no arguments
6781 prints ten lines centered on the point of execution in the frame.
6782 You can also edit the program at the point of execution with your favorite
6783 editing program by typing @code{edit}.
6784 @xref{List, ,Printing Source Lines},
6788 @kindex down-silently
6790 @item up-silently @var{n}
6791 @itemx down-silently @var{n}
6792 These two commands are variants of @code{up} and @code{down},
6793 respectively; they differ in that they do their work silently, without
6794 causing display of the new frame. They are intended primarily for use
6795 in @value{GDBN} command scripts, where the output might be unnecessary and
6800 @section Information About a Frame
6802 There are several other commands to print information about the selected
6808 When used without any argument, this command does not change which
6809 frame is selected, but prints a brief description of the currently
6810 selected stack frame. It can be abbreviated @code{f}. With an
6811 argument, this command is used to select a stack frame.
6812 @xref{Selection, ,Selecting a Frame}.
6815 @kindex info f @r{(@code{info frame})}
6818 This command prints a verbose description of the selected stack frame,
6823 the address of the frame
6825 the address of the next frame down (called by this frame)
6827 the address of the next frame up (caller of this frame)
6829 the language in which the source code corresponding to this frame is written
6831 the address of the frame's arguments
6833 the address of the frame's local variables
6835 the program counter saved in it (the address of execution in the caller frame)
6837 which registers were saved in the frame
6840 @noindent The verbose description is useful when
6841 something has gone wrong that has made the stack format fail to fit
6842 the usual conventions.
6844 @item info frame @var{addr}
6845 @itemx info f @var{addr}
6846 Print a verbose description of the frame at address @var{addr}, without
6847 selecting that frame. The selected frame remains unchanged by this
6848 command. This requires the same kind of address (more than one for some
6849 architectures) that you specify in the @code{frame} command.
6850 @xref{Selection, ,Selecting a Frame}.
6854 Print the arguments of the selected frame, each on a separate line.
6858 Print the local variables of the selected frame, each on a separate
6859 line. These are all variables (declared either static or automatic)
6860 accessible at the point of execution of the selected frame.
6866 @chapter Examining Source Files
6868 @value{GDBN} can print parts of your program's source, since the debugging
6869 information recorded in the program tells @value{GDBN} what source files were
6870 used to build it. When your program stops, @value{GDBN} spontaneously prints
6871 the line where it stopped. Likewise, when you select a stack frame
6872 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6873 execution in that frame has stopped. You can print other portions of
6874 source files by explicit command.
6876 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6877 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6878 @value{GDBN} under @sc{gnu} Emacs}.
6881 * List:: Printing source lines
6882 * Specify Location:: How to specify code locations
6883 * Edit:: Editing source files
6884 * Search:: Searching source files
6885 * Source Path:: Specifying source directories
6886 * Machine Code:: Source and machine code
6890 @section Printing Source Lines
6893 @kindex l @r{(@code{list})}
6894 To print lines from a source file, use the @code{list} command
6895 (abbreviated @code{l}). By default, ten lines are printed.
6896 There are several ways to specify what part of the file you want to
6897 print; see @ref{Specify Location}, for the full list.
6899 Here are the forms of the @code{list} command most commonly used:
6902 @item list @var{linenum}
6903 Print lines centered around line number @var{linenum} in the
6904 current source file.
6906 @item list @var{function}
6907 Print lines centered around the beginning of function
6911 Print more lines. If the last lines printed were printed with a
6912 @code{list} command, this prints lines following the last lines
6913 printed; however, if the last line printed was a solitary line printed
6914 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6915 Stack}), this prints lines centered around that line.
6918 Print lines just before the lines last printed.
6921 @cindex @code{list}, how many lines to display
6922 By default, @value{GDBN} prints ten source lines with any of these forms of
6923 the @code{list} command. You can change this using @code{set listsize}:
6926 @kindex set listsize
6927 @item set listsize @var{count}
6928 @itemx set listsize unlimited
6929 Make the @code{list} command display @var{count} source lines (unless
6930 the @code{list} argument explicitly specifies some other number).
6931 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
6933 @kindex show listsize
6935 Display the number of lines that @code{list} prints.
6938 Repeating a @code{list} command with @key{RET} discards the argument,
6939 so it is equivalent to typing just @code{list}. This is more useful
6940 than listing the same lines again. An exception is made for an
6941 argument of @samp{-}; that argument is preserved in repetition so that
6942 each repetition moves up in the source file.
6944 In general, the @code{list} command expects you to supply zero, one or two
6945 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6946 of writing them (@pxref{Specify Location}), but the effect is always
6947 to specify some source line.
6949 Here is a complete description of the possible arguments for @code{list}:
6952 @item list @var{linespec}
6953 Print lines centered around the line specified by @var{linespec}.
6955 @item list @var{first},@var{last}
6956 Print lines from @var{first} to @var{last}. Both arguments are
6957 linespecs. When a @code{list} command has two linespecs, and the
6958 source file of the second linespec is omitted, this refers to
6959 the same source file as the first linespec.
6961 @item list ,@var{last}
6962 Print lines ending with @var{last}.
6964 @item list @var{first},
6965 Print lines starting with @var{first}.
6968 Print lines just after the lines last printed.
6971 Print lines just before the lines last printed.
6974 As described in the preceding table.
6977 @node Specify Location
6978 @section Specifying a Location
6979 @cindex specifying location
6982 Several @value{GDBN} commands accept arguments that specify a location
6983 of your program's code. Since @value{GDBN} is a source-level
6984 debugger, a location usually specifies some line in the source code;
6985 for that reason, locations are also known as @dfn{linespecs}.
6987 Here are all the different ways of specifying a code location that
6988 @value{GDBN} understands:
6992 Specifies the line number @var{linenum} of the current source file.
6995 @itemx +@var{offset}
6996 Specifies the line @var{offset} lines before or after the @dfn{current
6997 line}. For the @code{list} command, the current line is the last one
6998 printed; for the breakpoint commands, this is the line at which
6999 execution stopped in the currently selected @dfn{stack frame}
7000 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7001 used as the second of the two linespecs in a @code{list} command,
7002 this specifies the line @var{offset} lines up or down from the first
7005 @item @var{filename}:@var{linenum}
7006 Specifies the line @var{linenum} in the source file @var{filename}.
7007 If @var{filename} is a relative file name, then it will match any
7008 source file name with the same trailing components. For example, if
7009 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7010 name of @file{/build/trunk/gcc/expr.c}, but not
7011 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7013 @item @var{function}
7014 Specifies the line that begins the body of the function @var{function}.
7015 For example, in C, this is the line with the open brace.
7017 @item @var{function}:@var{label}
7018 Specifies the line where @var{label} appears in @var{function}.
7020 @item @var{filename}:@var{function}
7021 Specifies the line that begins the body of the function @var{function}
7022 in the file @var{filename}. You only need the file name with a
7023 function name to avoid ambiguity when there are identically named
7024 functions in different source files.
7027 Specifies the line at which the label named @var{label} appears.
7028 @value{GDBN} searches for the label in the function corresponding to
7029 the currently selected stack frame. If there is no current selected
7030 stack frame (for instance, if the inferior is not running), then
7031 @value{GDBN} will not search for a label.
7033 @item *@var{address}
7034 Specifies the program address @var{address}. For line-oriented
7035 commands, such as @code{list} and @code{edit}, this specifies a source
7036 line that contains @var{address}. For @code{break} and other
7037 breakpoint oriented commands, this can be used to set breakpoints in
7038 parts of your program which do not have debugging information or
7041 Here @var{address} may be any expression valid in the current working
7042 language (@pxref{Languages, working language}) that specifies a code
7043 address. In addition, as a convenience, @value{GDBN} extends the
7044 semantics of expressions used in locations to cover the situations
7045 that frequently happen during debugging. Here are the various forms
7049 @item @var{expression}
7050 Any expression valid in the current working language.
7052 @item @var{funcaddr}
7053 An address of a function or procedure derived from its name. In C,
7054 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7055 simply the function's name @var{function} (and actually a special case
7056 of a valid expression). In Pascal and Modula-2, this is
7057 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7058 (although the Pascal form also works).
7060 This form specifies the address of the function's first instruction,
7061 before the stack frame and arguments have been set up.
7063 @item '@var{filename}'::@var{funcaddr}
7064 Like @var{funcaddr} above, but also specifies the name of the source
7065 file explicitly. This is useful if the name of the function does not
7066 specify the function unambiguously, e.g., if there are several
7067 functions with identical names in different source files.
7070 @cindex breakpoint at static probe point
7071 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7072 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7073 applications to embed static probes. @xref{Static Probe Points}, for more
7074 information on finding and using static probes. This form of linespec
7075 specifies the location of such a static probe.
7077 If @var{objfile} is given, only probes coming from that shared library
7078 or executable matching @var{objfile} as a regular expression are considered.
7079 If @var{provider} is given, then only probes from that provider are considered.
7080 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7081 each one of those probes.
7087 @section Editing Source Files
7088 @cindex editing source files
7091 @kindex e @r{(@code{edit})}
7092 To edit the lines in a source file, use the @code{edit} command.
7093 The editing program of your choice
7094 is invoked with the current line set to
7095 the active line in the program.
7096 Alternatively, there are several ways to specify what part of the file you
7097 want to print if you want to see other parts of the program:
7100 @item edit @var{location}
7101 Edit the source file specified by @code{location}. Editing starts at
7102 that @var{location}, e.g., at the specified source line of the
7103 specified file. @xref{Specify Location}, for all the possible forms
7104 of the @var{location} argument; here are the forms of the @code{edit}
7105 command most commonly used:
7108 @item edit @var{number}
7109 Edit the current source file with @var{number} as the active line number.
7111 @item edit @var{function}
7112 Edit the file containing @var{function} at the beginning of its definition.
7117 @subsection Choosing your Editor
7118 You can customize @value{GDBN} to use any editor you want
7120 The only restriction is that your editor (say @code{ex}), recognizes the
7121 following command-line syntax:
7123 ex +@var{number} file
7125 The optional numeric value +@var{number} specifies the number of the line in
7126 the file where to start editing.}.
7127 By default, it is @file{@value{EDITOR}}, but you can change this
7128 by setting the environment variable @code{EDITOR} before using
7129 @value{GDBN}. For example, to configure @value{GDBN} to use the
7130 @code{vi} editor, you could use these commands with the @code{sh} shell:
7136 or in the @code{csh} shell,
7138 setenv EDITOR /usr/bin/vi
7143 @section Searching Source Files
7144 @cindex searching source files
7146 There are two commands for searching through the current source file for a
7151 @kindex forward-search
7152 @kindex fo @r{(@code{forward-search})}
7153 @item forward-search @var{regexp}
7154 @itemx search @var{regexp}
7155 The command @samp{forward-search @var{regexp}} checks each line,
7156 starting with the one following the last line listed, for a match for
7157 @var{regexp}. It lists the line that is found. You can use the
7158 synonym @samp{search @var{regexp}} or abbreviate the command name as
7161 @kindex reverse-search
7162 @item reverse-search @var{regexp}
7163 The command @samp{reverse-search @var{regexp}} checks each line, starting
7164 with the one before the last line listed and going backward, for a match
7165 for @var{regexp}. It lists the line that is found. You can abbreviate
7166 this command as @code{rev}.
7170 @section Specifying Source Directories
7173 @cindex directories for source files
7174 Executable programs sometimes do not record the directories of the source
7175 files from which they were compiled, just the names. Even when they do,
7176 the directories could be moved between the compilation and your debugging
7177 session. @value{GDBN} has a list of directories to search for source files;
7178 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7179 it tries all the directories in the list, in the order they are present
7180 in the list, until it finds a file with the desired name.
7182 For example, suppose an executable references the file
7183 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7184 @file{/mnt/cross}. The file is first looked up literally; if this
7185 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7186 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7187 message is printed. @value{GDBN} does not look up the parts of the
7188 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7189 Likewise, the subdirectories of the source path are not searched: if
7190 the source path is @file{/mnt/cross}, and the binary refers to
7191 @file{foo.c}, @value{GDBN} would not find it under
7192 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7194 Plain file names, relative file names with leading directories, file
7195 names containing dots, etc.@: are all treated as described above; for
7196 instance, if the source path is @file{/mnt/cross}, and the source file
7197 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7198 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7199 that---@file{/mnt/cross/foo.c}.
7201 Note that the executable search path is @emph{not} used to locate the
7204 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7205 any information it has cached about where source files are found and where
7206 each line is in the file.
7210 When you start @value{GDBN}, its source path includes only @samp{cdir}
7211 and @samp{cwd}, in that order.
7212 To add other directories, use the @code{directory} command.
7214 The search path is used to find both program source files and @value{GDBN}
7215 script files (read using the @samp{-command} option and @samp{source} command).
7217 In addition to the source path, @value{GDBN} provides a set of commands
7218 that manage a list of source path substitution rules. A @dfn{substitution
7219 rule} specifies how to rewrite source directories stored in the program's
7220 debug information in case the sources were moved to a different
7221 directory between compilation and debugging. A rule is made of
7222 two strings, the first specifying what needs to be rewritten in
7223 the path, and the second specifying how it should be rewritten.
7224 In @ref{set substitute-path}, we name these two parts @var{from} and
7225 @var{to} respectively. @value{GDBN} does a simple string replacement
7226 of @var{from} with @var{to} at the start of the directory part of the
7227 source file name, and uses that result instead of the original file
7228 name to look up the sources.
7230 Using the previous example, suppose the @file{foo-1.0} tree has been
7231 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7232 @value{GDBN} to replace @file{/usr/src} in all source path names with
7233 @file{/mnt/cross}. The first lookup will then be
7234 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7235 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7236 substitution rule, use the @code{set substitute-path} command
7237 (@pxref{set substitute-path}).
7239 To avoid unexpected substitution results, a rule is applied only if the
7240 @var{from} part of the directory name ends at a directory separator.
7241 For instance, a rule substituting @file{/usr/source} into
7242 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7243 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7244 is applied only at the beginning of the directory name, this rule will
7245 not be applied to @file{/root/usr/source/baz.c} either.
7247 In many cases, you can achieve the same result using the @code{directory}
7248 command. However, @code{set substitute-path} can be more efficient in
7249 the case where the sources are organized in a complex tree with multiple
7250 subdirectories. With the @code{directory} command, you need to add each
7251 subdirectory of your project. If you moved the entire tree while
7252 preserving its internal organization, then @code{set substitute-path}
7253 allows you to direct the debugger to all the sources with one single
7256 @code{set substitute-path} is also more than just a shortcut command.
7257 The source path is only used if the file at the original location no
7258 longer exists. On the other hand, @code{set substitute-path} modifies
7259 the debugger behavior to look at the rewritten location instead. So, if
7260 for any reason a source file that is not relevant to your executable is
7261 located at the original location, a substitution rule is the only
7262 method available to point @value{GDBN} at the new location.
7264 @cindex @samp{--with-relocated-sources}
7265 @cindex default source path substitution
7266 You can configure a default source path substitution rule by
7267 configuring @value{GDBN} with the
7268 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7269 should be the name of a directory under @value{GDBN}'s configured
7270 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7271 directory names in debug information under @var{dir} will be adjusted
7272 automatically if the installed @value{GDBN} is moved to a new
7273 location. This is useful if @value{GDBN}, libraries or executables
7274 with debug information and corresponding source code are being moved
7278 @item directory @var{dirname} @dots{}
7279 @item dir @var{dirname} @dots{}
7280 Add directory @var{dirname} to the front of the source path. Several
7281 directory names may be given to this command, separated by @samp{:}
7282 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7283 part of absolute file names) or
7284 whitespace. You may specify a directory that is already in the source
7285 path; this moves it forward, so @value{GDBN} searches it sooner.
7289 @vindex $cdir@r{, convenience variable}
7290 @vindex $cwd@r{, convenience variable}
7291 @cindex compilation directory
7292 @cindex current directory
7293 @cindex working directory
7294 @cindex directory, current
7295 @cindex directory, compilation
7296 You can use the string @samp{$cdir} to refer to the compilation
7297 directory (if one is recorded), and @samp{$cwd} to refer to the current
7298 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7299 tracks the current working directory as it changes during your @value{GDBN}
7300 session, while the latter is immediately expanded to the current
7301 directory at the time you add an entry to the source path.
7304 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7306 @c RET-repeat for @code{directory} is explicitly disabled, but since
7307 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7309 @item set directories @var{path-list}
7310 @kindex set directories
7311 Set the source path to @var{path-list}.
7312 @samp{$cdir:$cwd} are added if missing.
7314 @item show directories
7315 @kindex show directories
7316 Print the source path: show which directories it contains.
7318 @anchor{set substitute-path}
7319 @item set substitute-path @var{from} @var{to}
7320 @kindex set substitute-path
7321 Define a source path substitution rule, and add it at the end of the
7322 current list of existing substitution rules. If a rule with the same
7323 @var{from} was already defined, then the old rule is also deleted.
7325 For example, if the file @file{/foo/bar/baz.c} was moved to
7326 @file{/mnt/cross/baz.c}, then the command
7329 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7333 will tell @value{GDBN} to replace @samp{/usr/src} with
7334 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7335 @file{baz.c} even though it was moved.
7337 In the case when more than one substitution rule have been defined,
7338 the rules are evaluated one by one in the order where they have been
7339 defined. The first one matching, if any, is selected to perform
7342 For instance, if we had entered the following commands:
7345 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7346 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7350 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7351 @file{/mnt/include/defs.h} by using the first rule. However, it would
7352 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7353 @file{/mnt/src/lib/foo.c}.
7356 @item unset substitute-path [path]
7357 @kindex unset substitute-path
7358 If a path is specified, search the current list of substitution rules
7359 for a rule that would rewrite that path. Delete that rule if found.
7360 A warning is emitted by the debugger if no rule could be found.
7362 If no path is specified, then all substitution rules are deleted.
7364 @item show substitute-path [path]
7365 @kindex show substitute-path
7366 If a path is specified, then print the source path substitution rule
7367 which would rewrite that path, if any.
7369 If no path is specified, then print all existing source path substitution
7374 If your source path is cluttered with directories that are no longer of
7375 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7376 versions of source. You can correct the situation as follows:
7380 Use @code{directory} with no argument to reset the source path to its default value.
7383 Use @code{directory} with suitable arguments to reinstall the
7384 directories you want in the source path. You can add all the
7385 directories in one command.
7389 @section Source and Machine Code
7390 @cindex source line and its code address
7392 You can use the command @code{info line} to map source lines to program
7393 addresses (and vice versa), and the command @code{disassemble} to display
7394 a range of addresses as machine instructions. You can use the command
7395 @code{set disassemble-next-line} to set whether to disassemble next
7396 source line when execution stops. When run under @sc{gnu} Emacs
7397 mode, the @code{info line} command causes the arrow to point to the
7398 line specified. Also, @code{info line} prints addresses in symbolic form as
7403 @item info line @var{linespec}
7404 Print the starting and ending addresses of the compiled code for
7405 source line @var{linespec}. You can specify source lines in any of
7406 the ways documented in @ref{Specify Location}.
7409 For example, we can use @code{info line} to discover the location of
7410 the object code for the first line of function
7411 @code{m4_changequote}:
7413 @c FIXME: I think this example should also show the addresses in
7414 @c symbolic form, as they usually would be displayed.
7416 (@value{GDBP}) info line m4_changequote
7417 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7421 @cindex code address and its source line
7422 We can also inquire (using @code{*@var{addr}} as the form for
7423 @var{linespec}) what source line covers a particular address:
7425 (@value{GDBP}) info line *0x63ff
7426 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7429 @cindex @code{$_} and @code{info line}
7430 @cindex @code{x} command, default address
7431 @kindex x@r{(examine), and} info line
7432 After @code{info line}, the default address for the @code{x} command
7433 is changed to the starting address of the line, so that @samp{x/i} is
7434 sufficient to begin examining the machine code (@pxref{Memory,
7435 ,Examining Memory}). Also, this address is saved as the value of the
7436 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7441 @cindex assembly instructions
7442 @cindex instructions, assembly
7443 @cindex machine instructions
7444 @cindex listing machine instructions
7446 @itemx disassemble /m
7447 @itemx disassemble /r
7448 This specialized command dumps a range of memory as machine
7449 instructions. It can also print mixed source+disassembly by specifying
7450 the @code{/m} modifier and print the raw instructions in hex as well as
7451 in symbolic form by specifying the @code{/r}.
7452 The default memory range is the function surrounding the
7453 program counter of the selected frame. A single argument to this
7454 command is a program counter value; @value{GDBN} dumps the function
7455 surrounding this value. When two arguments are given, they should
7456 be separated by a comma, possibly surrounded by whitespace. The
7457 arguments specify a range of addresses to dump, in one of two forms:
7460 @item @var{start},@var{end}
7461 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7462 @item @var{start},+@var{length}
7463 the addresses from @var{start} (inclusive) to
7464 @code{@var{start}+@var{length}} (exclusive).
7468 When 2 arguments are specified, the name of the function is also
7469 printed (since there could be several functions in the given range).
7471 The argument(s) can be any expression yielding a numeric value, such as
7472 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7474 If the range of memory being disassembled contains current program counter,
7475 the instruction at that location is shown with a @code{=>} marker.
7478 The following example shows the disassembly of a range of addresses of
7479 HP PA-RISC 2.0 code:
7482 (@value{GDBP}) disas 0x32c4, 0x32e4
7483 Dump of assembler code from 0x32c4 to 0x32e4:
7484 0x32c4 <main+204>: addil 0,dp
7485 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7486 0x32cc <main+212>: ldil 0x3000,r31
7487 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7488 0x32d4 <main+220>: ldo 0(r31),rp
7489 0x32d8 <main+224>: addil -0x800,dp
7490 0x32dc <main+228>: ldo 0x588(r1),r26
7491 0x32e0 <main+232>: ldil 0x3000,r31
7492 End of assembler dump.
7495 Here is an example showing mixed source+assembly for Intel x86, when the
7496 program is stopped just after function prologue:
7499 (@value{GDBP}) disas /m main
7500 Dump of assembler code for function main:
7502 0x08048330 <+0>: push %ebp
7503 0x08048331 <+1>: mov %esp,%ebp
7504 0x08048333 <+3>: sub $0x8,%esp
7505 0x08048336 <+6>: and $0xfffffff0,%esp
7506 0x08048339 <+9>: sub $0x10,%esp
7508 6 printf ("Hello.\n");
7509 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7510 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7514 0x08048348 <+24>: mov $0x0,%eax
7515 0x0804834d <+29>: leave
7516 0x0804834e <+30>: ret
7518 End of assembler dump.
7521 Here is another example showing raw instructions in hex for AMD x86-64,
7524 (gdb) disas /r 0x400281,+10
7525 Dump of assembler code from 0x400281 to 0x40028b:
7526 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7527 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7528 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7529 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7530 End of assembler dump.
7533 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7534 So, for example, if you want to disassemble function @code{bar}
7535 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7536 and not @samp{disassemble foo.c:bar}.
7538 Some architectures have more than one commonly-used set of instruction
7539 mnemonics or other syntax.
7541 For programs that were dynamically linked and use shared libraries,
7542 instructions that call functions or branch to locations in the shared
7543 libraries might show a seemingly bogus location---it's actually a
7544 location of the relocation table. On some architectures, @value{GDBN}
7545 might be able to resolve these to actual function names.
7548 @kindex set disassembly-flavor
7549 @cindex Intel disassembly flavor
7550 @cindex AT&T disassembly flavor
7551 @item set disassembly-flavor @var{instruction-set}
7552 Select the instruction set to use when disassembling the
7553 program via the @code{disassemble} or @code{x/i} commands.
7555 Currently this command is only defined for the Intel x86 family. You
7556 can set @var{instruction-set} to either @code{intel} or @code{att}.
7557 The default is @code{att}, the AT&T flavor used by default by Unix
7558 assemblers for x86-based targets.
7560 @kindex show disassembly-flavor
7561 @item show disassembly-flavor
7562 Show the current setting of the disassembly flavor.
7566 @kindex set disassemble-next-line
7567 @kindex show disassemble-next-line
7568 @item set disassemble-next-line
7569 @itemx show disassemble-next-line
7570 Control whether or not @value{GDBN} will disassemble the next source
7571 line or instruction when execution stops. If ON, @value{GDBN} will
7572 display disassembly of the next source line when execution of the
7573 program being debugged stops. This is @emph{in addition} to
7574 displaying the source line itself, which @value{GDBN} always does if
7575 possible. If the next source line cannot be displayed for some reason
7576 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7577 info in the debug info), @value{GDBN} will display disassembly of the
7578 next @emph{instruction} instead of showing the next source line. If
7579 AUTO, @value{GDBN} will display disassembly of next instruction only
7580 if the source line cannot be displayed. This setting causes
7581 @value{GDBN} to display some feedback when you step through a function
7582 with no line info or whose source file is unavailable. The default is
7583 OFF, which means never display the disassembly of the next line or
7589 @chapter Examining Data
7591 @cindex printing data
7592 @cindex examining data
7595 The usual way to examine data in your program is with the @code{print}
7596 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7597 evaluates and prints the value of an expression of the language your
7598 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7599 Different Languages}). It may also print the expression using a
7600 Python-based pretty-printer (@pxref{Pretty Printing}).
7603 @item print @var{expr}
7604 @itemx print /@var{f} @var{expr}
7605 @var{expr} is an expression (in the source language). By default the
7606 value of @var{expr} is printed in a format appropriate to its data type;
7607 you can choose a different format by specifying @samp{/@var{f}}, where
7608 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7612 @itemx print /@var{f}
7613 @cindex reprint the last value
7614 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7615 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7616 conveniently inspect the same value in an alternative format.
7619 A more low-level way of examining data is with the @code{x} command.
7620 It examines data in memory at a specified address and prints it in a
7621 specified format. @xref{Memory, ,Examining Memory}.
7623 If you are interested in information about types, or about how the
7624 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7625 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7628 @cindex exploring hierarchical data structures
7630 Another way of examining values of expressions and type information is
7631 through the Python extension command @code{explore} (available only if
7632 the @value{GDBN} build is configured with @code{--with-python}). It
7633 offers an interactive way to start at the highest level (or, the most
7634 abstract level) of the data type of an expression (or, the data type
7635 itself) and explore all the way down to leaf scalar values/fields
7636 embedded in the higher level data types.
7639 @item explore @var{arg}
7640 @var{arg} is either an expression (in the source language), or a type
7641 visible in the current context of the program being debugged.
7644 The working of the @code{explore} command can be illustrated with an
7645 example. If a data type @code{struct ComplexStruct} is defined in your
7655 struct ComplexStruct
7657 struct SimpleStruct *ss_p;
7663 followed by variable declarations as
7666 struct SimpleStruct ss = @{ 10, 1.11 @};
7667 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7671 then, the value of the variable @code{cs} can be explored using the
7672 @code{explore} command as follows.
7676 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7677 the following fields:
7679 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7680 arr = <Enter 1 to explore this field of type `int [10]'>
7682 Enter the field number of choice:
7686 Since the fields of @code{cs} are not scalar values, you are being
7687 prompted to chose the field you want to explore. Let's say you choose
7688 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7689 pointer, you will be asked if it is pointing to a single value. From
7690 the declaration of @code{cs} above, it is indeed pointing to a single
7691 value, hence you enter @code{y}. If you enter @code{n}, then you will
7692 be asked if it were pointing to an array of values, in which case this
7693 field will be explored as if it were an array.
7696 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7697 Continue exploring it as a pointer to a single value [y/n]: y
7698 The value of `*(cs.ss_p)' is a struct/class of type `struct
7699 SimpleStruct' with the following fields:
7701 i = 10 .. (Value of type `int')
7702 d = 1.1100000000000001 .. (Value of type `double')
7704 Press enter to return to parent value:
7708 If the field @code{arr} of @code{cs} was chosen for exploration by
7709 entering @code{1} earlier, then since it is as array, you will be
7710 prompted to enter the index of the element in the array that you want
7714 `cs.arr' is an array of `int'.
7715 Enter the index of the element you want to explore in `cs.arr': 5
7717 `(cs.arr)[5]' is a scalar value of type `int'.
7721 Press enter to return to parent value:
7724 In general, at any stage of exploration, you can go deeper towards the
7725 leaf values by responding to the prompts appropriately, or hit the
7726 return key to return to the enclosing data structure (the @i{higher}
7727 level data structure).
7729 Similar to exploring values, you can use the @code{explore} command to
7730 explore types. Instead of specifying a value (which is typically a
7731 variable name or an expression valid in the current context of the
7732 program being debugged), you specify a type name. If you consider the
7733 same example as above, your can explore the type
7734 @code{struct ComplexStruct} by passing the argument
7735 @code{struct ComplexStruct} to the @code{explore} command.
7738 (gdb) explore struct ComplexStruct
7742 By responding to the prompts appropriately in the subsequent interactive
7743 session, you can explore the type @code{struct ComplexStruct} in a
7744 manner similar to how the value @code{cs} was explored in the above
7747 The @code{explore} command also has two sub-commands,
7748 @code{explore value} and @code{explore type}. The former sub-command is
7749 a way to explicitly specify that value exploration of the argument is
7750 being invoked, while the latter is a way to explicitly specify that type
7751 exploration of the argument is being invoked.
7754 @item explore value @var{expr}
7755 @cindex explore value
7756 This sub-command of @code{explore} explores the value of the
7757 expression @var{expr} (if @var{expr} is an expression valid in the
7758 current context of the program being debugged). The behavior of this
7759 command is identical to that of the behavior of the @code{explore}
7760 command being passed the argument @var{expr}.
7762 @item explore type @var{arg}
7763 @cindex explore type
7764 This sub-command of @code{explore} explores the type of @var{arg} (if
7765 @var{arg} is a type visible in the current context of program being
7766 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7767 is an expression valid in the current context of the program being
7768 debugged). If @var{arg} is a type, then the behavior of this command is
7769 identical to that of the @code{explore} command being passed the
7770 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7771 this command will be identical to that of the @code{explore} command
7772 being passed the type of @var{arg} as the argument.
7776 * Expressions:: Expressions
7777 * Ambiguous Expressions:: Ambiguous Expressions
7778 * Variables:: Program variables
7779 * Arrays:: Artificial arrays
7780 * Output Formats:: Output formats
7781 * Memory:: Examining memory
7782 * Auto Display:: Automatic display
7783 * Print Settings:: Print settings
7784 * Pretty Printing:: Python pretty printing
7785 * Value History:: Value history
7786 * Convenience Vars:: Convenience variables
7787 * Convenience Funs:: Convenience functions
7788 * Registers:: Registers
7789 * Floating Point Hardware:: Floating point hardware
7790 * Vector Unit:: Vector Unit
7791 * OS Information:: Auxiliary data provided by operating system
7792 * Memory Region Attributes:: Memory region attributes
7793 * Dump/Restore Files:: Copy between memory and a file
7794 * Core File Generation:: Cause a program dump its core
7795 * Character Sets:: Debugging programs that use a different
7796 character set than GDB does
7797 * Caching Remote Data:: Data caching for remote targets
7798 * Searching Memory:: Searching memory for a sequence of bytes
7802 @section Expressions
7805 @code{print} and many other @value{GDBN} commands accept an expression and
7806 compute its value. Any kind of constant, variable or operator defined
7807 by the programming language you are using is valid in an expression in
7808 @value{GDBN}. This includes conditional expressions, function calls,
7809 casts, and string constants. It also includes preprocessor macros, if
7810 you compiled your program to include this information; see
7813 @cindex arrays in expressions
7814 @value{GDBN} supports array constants in expressions input by
7815 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7816 you can use the command @code{print @{1, 2, 3@}} to create an array
7817 of three integers. If you pass an array to a function or assign it
7818 to a program variable, @value{GDBN} copies the array to memory that
7819 is @code{malloc}ed in the target program.
7821 Because C is so widespread, most of the expressions shown in examples in
7822 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7823 Languages}, for information on how to use expressions in other
7826 In this section, we discuss operators that you can use in @value{GDBN}
7827 expressions regardless of your programming language.
7829 @cindex casts, in expressions
7830 Casts are supported in all languages, not just in C, because it is so
7831 useful to cast a number into a pointer in order to examine a structure
7832 at that address in memory.
7833 @c FIXME: casts supported---Mod2 true?
7835 @value{GDBN} supports these operators, in addition to those common
7836 to programming languages:
7840 @samp{@@} is a binary operator for treating parts of memory as arrays.
7841 @xref{Arrays, ,Artificial Arrays}, for more information.
7844 @samp{::} allows you to specify a variable in terms of the file or
7845 function where it is defined. @xref{Variables, ,Program Variables}.
7847 @cindex @{@var{type}@}
7848 @cindex type casting memory
7849 @cindex memory, viewing as typed object
7850 @cindex casts, to view memory
7851 @item @{@var{type}@} @var{addr}
7852 Refers to an object of type @var{type} stored at address @var{addr} in
7853 memory. @var{addr} may be any expression whose value is an integer or
7854 pointer (but parentheses are required around binary operators, just as in
7855 a cast). This construct is allowed regardless of what kind of data is
7856 normally supposed to reside at @var{addr}.
7859 @node Ambiguous Expressions
7860 @section Ambiguous Expressions
7861 @cindex ambiguous expressions
7863 Expressions can sometimes contain some ambiguous elements. For instance,
7864 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7865 a single function name to be defined several times, for application in
7866 different contexts. This is called @dfn{overloading}. Another example
7867 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7868 templates and is typically instantiated several times, resulting in
7869 the same function name being defined in different contexts.
7871 In some cases and depending on the language, it is possible to adjust
7872 the expression to remove the ambiguity. For instance in C@t{++}, you
7873 can specify the signature of the function you want to break on, as in
7874 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7875 qualified name of your function often makes the expression unambiguous
7878 When an ambiguity that needs to be resolved is detected, the debugger
7879 has the capability to display a menu of numbered choices for each
7880 possibility, and then waits for the selection with the prompt @samp{>}.
7881 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7882 aborts the current command. If the command in which the expression was
7883 used allows more than one choice to be selected, the next option in the
7884 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7887 For example, the following session excerpt shows an attempt to set a
7888 breakpoint at the overloaded symbol @code{String::after}.
7889 We choose three particular definitions of that function name:
7891 @c FIXME! This is likely to change to show arg type lists, at least
7894 (@value{GDBP}) b String::after
7897 [2] file:String.cc; line number:867
7898 [3] file:String.cc; line number:860
7899 [4] file:String.cc; line number:875
7900 [5] file:String.cc; line number:853
7901 [6] file:String.cc; line number:846
7902 [7] file:String.cc; line number:735
7904 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7905 Breakpoint 2 at 0xb344: file String.cc, line 875.
7906 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7907 Multiple breakpoints were set.
7908 Use the "delete" command to delete unwanted
7915 @kindex set multiple-symbols
7916 @item set multiple-symbols @var{mode}
7917 @cindex multiple-symbols menu
7919 This option allows you to adjust the debugger behavior when an expression
7922 By default, @var{mode} is set to @code{all}. If the command with which
7923 the expression is used allows more than one choice, then @value{GDBN}
7924 automatically selects all possible choices. For instance, inserting
7925 a breakpoint on a function using an ambiguous name results in a breakpoint
7926 inserted on each possible match. However, if a unique choice must be made,
7927 then @value{GDBN} uses the menu to help you disambiguate the expression.
7928 For instance, printing the address of an overloaded function will result
7929 in the use of the menu.
7931 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7932 when an ambiguity is detected.
7934 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7935 an error due to the ambiguity and the command is aborted.
7937 @kindex show multiple-symbols
7938 @item show multiple-symbols
7939 Show the current value of the @code{multiple-symbols} setting.
7943 @section Program Variables
7945 The most common kind of expression to use is the name of a variable
7948 Variables in expressions are understood in the selected stack frame
7949 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7953 global (or file-static)
7960 visible according to the scope rules of the
7961 programming language from the point of execution in that frame
7964 @noindent This means that in the function
7979 you can examine and use the variable @code{a} whenever your program is
7980 executing within the function @code{foo}, but you can only use or
7981 examine the variable @code{b} while your program is executing inside
7982 the block where @code{b} is declared.
7984 @cindex variable name conflict
7985 There is an exception: you can refer to a variable or function whose
7986 scope is a single source file even if the current execution point is not
7987 in this file. But it is possible to have more than one such variable or
7988 function with the same name (in different source files). If that
7989 happens, referring to that name has unpredictable effects. If you wish,
7990 you can specify a static variable in a particular function or file by
7991 using the colon-colon (@code{::}) notation:
7993 @cindex colon-colon, context for variables/functions
7995 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7996 @cindex @code{::}, context for variables/functions
7999 @var{file}::@var{variable}
8000 @var{function}::@var{variable}
8004 Here @var{file} or @var{function} is the name of the context for the
8005 static @var{variable}. In the case of file names, you can use quotes to
8006 make sure @value{GDBN} parses the file name as a single word---for example,
8007 to print a global value of @code{x} defined in @file{f2.c}:
8010 (@value{GDBP}) p 'f2.c'::x
8013 The @code{::} notation is normally used for referring to
8014 static variables, since you typically disambiguate uses of local variables
8015 in functions by selecting the appropriate frame and using the
8016 simple name of the variable. However, you may also use this notation
8017 to refer to local variables in frames enclosing the selected frame:
8026 process (a); /* Stop here */
8037 For example, if there is a breakpoint at the commented line,
8038 here is what you might see
8039 when the program stops after executing the call @code{bar(0)}:
8044 (@value{GDBP}) p bar::a
8047 #2 0x080483d0 in foo (a=5) at foobar.c:12
8050 (@value{GDBP}) p bar::a
8054 @cindex C@t{++} scope resolution
8055 These uses of @samp{::} are very rarely in conflict with the very similar
8056 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8057 scope resolution operator in @value{GDBN} expressions.
8058 @c FIXME: Um, so what happens in one of those rare cases where it's in
8061 @cindex wrong values
8062 @cindex variable values, wrong
8063 @cindex function entry/exit, wrong values of variables
8064 @cindex optimized code, wrong values of variables
8066 @emph{Warning:} Occasionally, a local variable may appear to have the
8067 wrong value at certain points in a function---just after entry to a new
8068 scope, and just before exit.
8070 You may see this problem when you are stepping by machine instructions.
8071 This is because, on most machines, it takes more than one instruction to
8072 set up a stack frame (including local variable definitions); if you are
8073 stepping by machine instructions, variables may appear to have the wrong
8074 values until the stack frame is completely built. On exit, it usually
8075 also takes more than one machine instruction to destroy a stack frame;
8076 after you begin stepping through that group of instructions, local
8077 variable definitions may be gone.
8079 This may also happen when the compiler does significant optimizations.
8080 To be sure of always seeing accurate values, turn off all optimization
8083 @cindex ``No symbol "foo" in current context''
8084 Another possible effect of compiler optimizations is to optimize
8085 unused variables out of existence, or assign variables to registers (as
8086 opposed to memory addresses). Depending on the support for such cases
8087 offered by the debug info format used by the compiler, @value{GDBN}
8088 might not be able to display values for such local variables. If that
8089 happens, @value{GDBN} will print a message like this:
8092 No symbol "foo" in current context.
8095 To solve such problems, either recompile without optimizations, or use a
8096 different debug info format, if the compiler supports several such
8097 formats. @xref{Compilation}, for more information on choosing compiler
8098 options. @xref{C, ,C and C@t{++}}, for more information about debug
8099 info formats that are best suited to C@t{++} programs.
8101 If you ask to print an object whose contents are unknown to
8102 @value{GDBN}, e.g., because its data type is not completely specified
8103 by the debug information, @value{GDBN} will say @samp{<incomplete
8104 type>}. @xref{Symbols, incomplete type}, for more about this.
8106 If you append @kbd{@@entry} string to a function parameter name you get its
8107 value at the time the function got called. If the value is not available an
8108 error message is printed. Entry values are available only with some compilers.
8109 Entry values are normally also printed at the function parameter list according
8110 to @ref{set print entry-values}.
8113 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8119 (gdb) print i@@entry
8123 Strings are identified as arrays of @code{char} values without specified
8124 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8125 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8126 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8127 defines literal string type @code{"char"} as @code{char} without a sign.
8132 signed char var1[] = "A";
8135 You get during debugging
8140 $2 = @{65 'A', 0 '\0'@}
8144 @section Artificial Arrays
8146 @cindex artificial array
8148 @kindex @@@r{, referencing memory as an array}
8149 It is often useful to print out several successive objects of the
8150 same type in memory; a section of an array, or an array of
8151 dynamically determined size for which only a pointer exists in the
8154 You can do this by referring to a contiguous span of memory as an
8155 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8156 operand of @samp{@@} should be the first element of the desired array
8157 and be an individual object. The right operand should be the desired length
8158 of the array. The result is an array value whose elements are all of
8159 the type of the left argument. The first element is actually the left
8160 argument; the second element comes from bytes of memory immediately
8161 following those that hold the first element, and so on. Here is an
8162 example. If a program says
8165 int *array = (int *) malloc (len * sizeof (int));
8169 you can print the contents of @code{array} with
8175 The left operand of @samp{@@} must reside in memory. Array values made
8176 with @samp{@@} in this way behave just like other arrays in terms of
8177 subscripting, and are coerced to pointers when used in expressions.
8178 Artificial arrays most often appear in expressions via the value history
8179 (@pxref{Value History, ,Value History}), after printing one out.
8181 Another way to create an artificial array is to use a cast.
8182 This re-interprets a value as if it were an array.
8183 The value need not be in memory:
8185 (@value{GDBP}) p/x (short[2])0x12345678
8186 $1 = @{0x1234, 0x5678@}
8189 As a convenience, if you leave the array length out (as in
8190 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8191 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8193 (@value{GDBP}) p/x (short[])0x12345678
8194 $2 = @{0x1234, 0x5678@}
8197 Sometimes the artificial array mechanism is not quite enough; in
8198 moderately complex data structures, the elements of interest may not
8199 actually be adjacent---for example, if you are interested in the values
8200 of pointers in an array. One useful work-around in this situation is
8201 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8202 Variables}) as a counter in an expression that prints the first
8203 interesting value, and then repeat that expression via @key{RET}. For
8204 instance, suppose you have an array @code{dtab} of pointers to
8205 structures, and you are interested in the values of a field @code{fv}
8206 in each structure. Here is an example of what you might type:
8216 @node Output Formats
8217 @section Output Formats
8219 @cindex formatted output
8220 @cindex output formats
8221 By default, @value{GDBN} prints a value according to its data type. Sometimes
8222 this is not what you want. For example, you might want to print a number
8223 in hex, or a pointer in decimal. Or you might want to view data in memory
8224 at a certain address as a character string or as an instruction. To do
8225 these things, specify an @dfn{output format} when you print a value.
8227 The simplest use of output formats is to say how to print a value
8228 already computed. This is done by starting the arguments of the
8229 @code{print} command with a slash and a format letter. The format
8230 letters supported are:
8234 Regard the bits of the value as an integer, and print the integer in
8238 Print as integer in signed decimal.
8241 Print as integer in unsigned decimal.
8244 Print as integer in octal.
8247 Print as integer in binary. The letter @samp{t} stands for ``two''.
8248 @footnote{@samp{b} cannot be used because these format letters are also
8249 used with the @code{x} command, where @samp{b} stands for ``byte'';
8250 see @ref{Memory,,Examining Memory}.}
8253 @cindex unknown address, locating
8254 @cindex locate address
8255 Print as an address, both absolute in hexadecimal and as an offset from
8256 the nearest preceding symbol. You can use this format used to discover
8257 where (in what function) an unknown address is located:
8260 (@value{GDBP}) p/a 0x54320
8261 $3 = 0x54320 <_initialize_vx+396>
8265 The command @code{info symbol 0x54320} yields similar results.
8266 @xref{Symbols, info symbol}.
8269 Regard as an integer and print it as a character constant. This
8270 prints both the numerical value and its character representation. The
8271 character representation is replaced with the octal escape @samp{\nnn}
8272 for characters outside the 7-bit @sc{ascii} range.
8274 Without this format, @value{GDBN} displays @code{char},
8275 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8276 constants. Single-byte members of vectors are displayed as integer
8280 Regard the bits of the value as a floating point number and print
8281 using typical floating point syntax.
8284 @cindex printing strings
8285 @cindex printing byte arrays
8286 Regard as a string, if possible. With this format, pointers to single-byte
8287 data are displayed as null-terminated strings and arrays of single-byte data
8288 are displayed as fixed-length strings. Other values are displayed in their
8291 Without this format, @value{GDBN} displays pointers to and arrays of
8292 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8293 strings. Single-byte members of a vector are displayed as an integer
8297 @cindex raw printing
8298 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8299 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8300 Printing}). This typically results in a higher-level display of the
8301 value's contents. The @samp{r} format bypasses any Python
8302 pretty-printer which might exist.
8305 For example, to print the program counter in hex (@pxref{Registers}), type
8312 Note that no space is required before the slash; this is because command
8313 names in @value{GDBN} cannot contain a slash.
8315 To reprint the last value in the value history with a different format,
8316 you can use the @code{print} command with just a format and no
8317 expression. For example, @samp{p/x} reprints the last value in hex.
8320 @section Examining Memory
8322 You can use the command @code{x} (for ``examine'') to examine memory in
8323 any of several formats, independently of your program's data types.
8325 @cindex examining memory
8327 @kindex x @r{(examine memory)}
8328 @item x/@var{nfu} @var{addr}
8331 Use the @code{x} command to examine memory.
8334 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8335 much memory to display and how to format it; @var{addr} is an
8336 expression giving the address where you want to start displaying memory.
8337 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8338 Several commands set convenient defaults for @var{addr}.
8341 @item @var{n}, the repeat count
8342 The repeat count is a decimal integer; the default is 1. It specifies
8343 how much memory (counting by units @var{u}) to display.
8344 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8347 @item @var{f}, the display format
8348 The display format is one of the formats used by @code{print}
8349 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8350 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8351 The default is @samp{x} (hexadecimal) initially. The default changes
8352 each time you use either @code{x} or @code{print}.
8354 @item @var{u}, the unit size
8355 The unit size is any of
8361 Halfwords (two bytes).
8363 Words (four bytes). This is the initial default.
8365 Giant words (eight bytes).
8368 Each time you specify a unit size with @code{x}, that size becomes the
8369 default unit the next time you use @code{x}. For the @samp{i} format,
8370 the unit size is ignored and is normally not written. For the @samp{s} format,
8371 the unit size defaults to @samp{b}, unless it is explicitly given.
8372 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8373 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8374 Note that the results depend on the programming language of the
8375 current compilation unit. If the language is C, the @samp{s}
8376 modifier will use the UTF-16 encoding while @samp{w} will use
8377 UTF-32. The encoding is set by the programming language and cannot
8380 @item @var{addr}, starting display address
8381 @var{addr} is the address where you want @value{GDBN} to begin displaying
8382 memory. The expression need not have a pointer value (though it may);
8383 it is always interpreted as an integer address of a byte of memory.
8384 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8385 @var{addr} is usually just after the last address examined---but several
8386 other commands also set the default address: @code{info breakpoints} (to
8387 the address of the last breakpoint listed), @code{info line} (to the
8388 starting address of a line), and @code{print} (if you use it to display
8389 a value from memory).
8392 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8393 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8394 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8395 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8396 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8398 Since the letters indicating unit sizes are all distinct from the
8399 letters specifying output formats, you do not have to remember whether
8400 unit size or format comes first; either order works. The output
8401 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8402 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8404 Even though the unit size @var{u} is ignored for the formats @samp{s}
8405 and @samp{i}, you might still want to use a count @var{n}; for example,
8406 @samp{3i} specifies that you want to see three machine instructions,
8407 including any operands. For convenience, especially when used with
8408 the @code{display} command, the @samp{i} format also prints branch delay
8409 slot instructions, if any, beyond the count specified, which immediately
8410 follow the last instruction that is within the count. The command
8411 @code{disassemble} gives an alternative way of inspecting machine
8412 instructions; see @ref{Machine Code,,Source and Machine Code}.
8414 All the defaults for the arguments to @code{x} are designed to make it
8415 easy to continue scanning memory with minimal specifications each time
8416 you use @code{x}. For example, after you have inspected three machine
8417 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8418 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8419 the repeat count @var{n} is used again; the other arguments default as
8420 for successive uses of @code{x}.
8422 When examining machine instructions, the instruction at current program
8423 counter is shown with a @code{=>} marker. For example:
8426 (@value{GDBP}) x/5i $pc-6
8427 0x804837f <main+11>: mov %esp,%ebp
8428 0x8048381 <main+13>: push %ecx
8429 0x8048382 <main+14>: sub $0x4,%esp
8430 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8431 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8434 @cindex @code{$_}, @code{$__}, and value history
8435 The addresses and contents printed by the @code{x} command are not saved
8436 in the value history because there is often too much of them and they
8437 would get in the way. Instead, @value{GDBN} makes these values available for
8438 subsequent use in expressions as values of the convenience variables
8439 @code{$_} and @code{$__}. After an @code{x} command, the last address
8440 examined is available for use in expressions in the convenience variable
8441 @code{$_}. The contents of that address, as examined, are available in
8442 the convenience variable @code{$__}.
8444 If the @code{x} command has a repeat count, the address and contents saved
8445 are from the last memory unit printed; this is not the same as the last
8446 address printed if several units were printed on the last line of output.
8448 @cindex remote memory comparison
8449 @cindex verify remote memory image
8450 When you are debugging a program running on a remote target machine
8451 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8452 remote machine's memory against the executable file you downloaded to
8453 the target. The @code{compare-sections} command is provided for such
8457 @kindex compare-sections
8458 @item compare-sections @r{[}@var{section-name}@r{]}
8459 Compare the data of a loadable section @var{section-name} in the
8460 executable file of the program being debugged with the same section in
8461 the remote machine's memory, and report any mismatches. With no
8462 arguments, compares all loadable sections. This command's
8463 availability depends on the target's support for the @code{"qCRC"}
8468 @section Automatic Display
8469 @cindex automatic display
8470 @cindex display of expressions
8472 If you find that you want to print the value of an expression frequently
8473 (to see how it changes), you might want to add it to the @dfn{automatic
8474 display list} so that @value{GDBN} prints its value each time your program stops.
8475 Each expression added to the list is given a number to identify it;
8476 to remove an expression from the list, you specify that number.
8477 The automatic display looks like this:
8481 3: bar[5] = (struct hack *) 0x3804
8485 This display shows item numbers, expressions and their current values. As with
8486 displays you request manually using @code{x} or @code{print}, you can
8487 specify the output format you prefer; in fact, @code{display} decides
8488 whether to use @code{print} or @code{x} depending your format
8489 specification---it uses @code{x} if you specify either the @samp{i}
8490 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8494 @item display @var{expr}
8495 Add the expression @var{expr} to the list of expressions to display
8496 each time your program stops. @xref{Expressions, ,Expressions}.
8498 @code{display} does not repeat if you press @key{RET} again after using it.
8500 @item display/@var{fmt} @var{expr}
8501 For @var{fmt} specifying only a display format and not a size or
8502 count, add the expression @var{expr} to the auto-display list but
8503 arrange to display it each time in the specified format @var{fmt}.
8504 @xref{Output Formats,,Output Formats}.
8506 @item display/@var{fmt} @var{addr}
8507 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8508 number of units, add the expression @var{addr} as a memory address to
8509 be examined each time your program stops. Examining means in effect
8510 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8513 For example, @samp{display/i $pc} can be helpful, to see the machine
8514 instruction about to be executed each time execution stops (@samp{$pc}
8515 is a common name for the program counter; @pxref{Registers, ,Registers}).
8518 @kindex delete display
8520 @item undisplay @var{dnums}@dots{}
8521 @itemx delete display @var{dnums}@dots{}
8522 Remove items from the list of expressions to display. Specify the
8523 numbers of the displays that you want affected with the command
8524 argument @var{dnums}. It can be a single display number, one of the
8525 numbers shown in the first field of the @samp{info display} display;
8526 or it could be a range of display numbers, as in @code{2-4}.
8528 @code{undisplay} does not repeat if you press @key{RET} after using it.
8529 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8531 @kindex disable display
8532 @item disable display @var{dnums}@dots{}
8533 Disable the display of item numbers @var{dnums}. A disabled display
8534 item is not printed automatically, but is not forgotten. It may be
8535 enabled again later. Specify the numbers of the displays that you
8536 want affected with the command argument @var{dnums}. It can be a
8537 single display number, one of the numbers shown in the first field of
8538 the @samp{info display} display; or it could be a range of display
8539 numbers, as in @code{2-4}.
8541 @kindex enable display
8542 @item enable display @var{dnums}@dots{}
8543 Enable display of item numbers @var{dnums}. It becomes effective once
8544 again in auto display of its expression, until you specify otherwise.
8545 Specify the numbers of the displays that you want affected with the
8546 command argument @var{dnums}. It can be a single display number, one
8547 of the numbers shown in the first field of the @samp{info display}
8548 display; or it could be a range of display numbers, as in @code{2-4}.
8551 Display the current values of the expressions on the list, just as is
8552 done when your program stops.
8554 @kindex info display
8556 Print the list of expressions previously set up to display
8557 automatically, each one with its item number, but without showing the
8558 values. This includes disabled expressions, which are marked as such.
8559 It also includes expressions which would not be displayed right now
8560 because they refer to automatic variables not currently available.
8563 @cindex display disabled out of scope
8564 If a display expression refers to local variables, then it does not make
8565 sense outside the lexical context for which it was set up. Such an
8566 expression is disabled when execution enters a context where one of its
8567 variables is not defined. For example, if you give the command
8568 @code{display last_char} while inside a function with an argument
8569 @code{last_char}, @value{GDBN} displays this argument while your program
8570 continues to stop inside that function. When it stops elsewhere---where
8571 there is no variable @code{last_char}---the display is disabled
8572 automatically. The next time your program stops where @code{last_char}
8573 is meaningful, you can enable the display expression once again.
8575 @node Print Settings
8576 @section Print Settings
8578 @cindex format options
8579 @cindex print settings
8580 @value{GDBN} provides the following ways to control how arrays, structures,
8581 and symbols are printed.
8584 These settings are useful for debugging programs in any language:
8588 @item set print address
8589 @itemx set print address on
8590 @cindex print/don't print memory addresses
8591 @value{GDBN} prints memory addresses showing the location of stack
8592 traces, structure values, pointer values, breakpoints, and so forth,
8593 even when it also displays the contents of those addresses. The default
8594 is @code{on}. For example, this is what a stack frame display looks like with
8595 @code{set print address on}:
8600 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8602 530 if (lquote != def_lquote)
8606 @item set print address off
8607 Do not print addresses when displaying their contents. For example,
8608 this is the same stack frame displayed with @code{set print address off}:
8612 (@value{GDBP}) set print addr off
8614 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8615 530 if (lquote != def_lquote)
8619 You can use @samp{set print address off} to eliminate all machine
8620 dependent displays from the @value{GDBN} interface. For example, with
8621 @code{print address off}, you should get the same text for backtraces on
8622 all machines---whether or not they involve pointer arguments.
8625 @item show print address
8626 Show whether or not addresses are to be printed.
8629 When @value{GDBN} prints a symbolic address, it normally prints the
8630 closest earlier symbol plus an offset. If that symbol does not uniquely
8631 identify the address (for example, it is a name whose scope is a single
8632 source file), you may need to clarify. One way to do this is with
8633 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8634 you can set @value{GDBN} to print the source file and line number when
8635 it prints a symbolic address:
8638 @item set print symbol-filename on
8639 @cindex source file and line of a symbol
8640 @cindex symbol, source file and line
8641 Tell @value{GDBN} to print the source file name and line number of a
8642 symbol in the symbolic form of an address.
8644 @item set print symbol-filename off
8645 Do not print source file name and line number of a symbol. This is the
8648 @item show print symbol-filename
8649 Show whether or not @value{GDBN} will print the source file name and
8650 line number of a symbol in the symbolic form of an address.
8653 Another situation where it is helpful to show symbol filenames and line
8654 numbers is when disassembling code; @value{GDBN} shows you the line
8655 number and source file that corresponds to each instruction.
8657 Also, you may wish to see the symbolic form only if the address being
8658 printed is reasonably close to the closest earlier symbol:
8661 @item set print max-symbolic-offset @var{max-offset}
8662 @itemx set print max-symbolic-offset unlimited
8663 @cindex maximum value for offset of closest symbol
8664 Tell @value{GDBN} to only display the symbolic form of an address if the
8665 offset between the closest earlier symbol and the address is less than
8666 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8667 to always print the symbolic form of an address if any symbol precedes
8668 it. Zero is equivalent to @code{unlimited}.
8670 @item show print max-symbolic-offset
8671 Ask how large the maximum offset is that @value{GDBN} prints in a
8675 @cindex wild pointer, interpreting
8676 @cindex pointer, finding referent
8677 If you have a pointer and you are not sure where it points, try
8678 @samp{set print symbol-filename on}. Then you can determine the name
8679 and source file location of the variable where it points, using
8680 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8681 For example, here @value{GDBN} shows that a variable @code{ptt} points
8682 at another variable @code{t}, defined in @file{hi2.c}:
8685 (@value{GDBP}) set print symbol-filename on
8686 (@value{GDBP}) p/a ptt
8687 $4 = 0xe008 <t in hi2.c>
8691 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8692 does not show the symbol name and filename of the referent, even with
8693 the appropriate @code{set print} options turned on.
8696 You can also enable @samp{/a}-like formatting all the time using
8697 @samp{set print symbol on}:
8700 @item set print symbol on
8701 Tell @value{GDBN} to print the symbol corresponding to an address, if
8704 @item set print symbol off
8705 Tell @value{GDBN} not to print the symbol corresponding to an
8706 address. In this mode, @value{GDBN} will still print the symbol
8707 corresponding to pointers to functions. This is the default.
8709 @item show print symbol
8710 Show whether @value{GDBN} will display the symbol corresponding to an
8714 Other settings control how different kinds of objects are printed:
8717 @item set print array
8718 @itemx set print array on
8719 @cindex pretty print arrays
8720 Pretty print arrays. This format is more convenient to read,
8721 but uses more space. The default is off.
8723 @item set print array off
8724 Return to compressed format for arrays.
8726 @item show print array
8727 Show whether compressed or pretty format is selected for displaying
8730 @cindex print array indexes
8731 @item set print array-indexes
8732 @itemx set print array-indexes on
8733 Print the index of each element when displaying arrays. May be more
8734 convenient to locate a given element in the array or quickly find the
8735 index of a given element in that printed array. The default is off.
8737 @item set print array-indexes off
8738 Stop printing element indexes when displaying arrays.
8740 @item show print array-indexes
8741 Show whether the index of each element is printed when displaying
8744 @item set print elements @var{number-of-elements}
8745 @itemx set print elements unlimited
8746 @cindex number of array elements to print
8747 @cindex limit on number of printed array elements
8748 Set a limit on how many elements of an array @value{GDBN} will print.
8749 If @value{GDBN} is printing a large array, it stops printing after it has
8750 printed the number of elements set by the @code{set print elements} command.
8751 This limit also applies to the display of strings.
8752 When @value{GDBN} starts, this limit is set to 200.
8753 Setting @var{number-of-elements} to @code{unlimited} or zero means
8754 that the number of elements to print is unlimited.
8756 @item show print elements
8757 Display the number of elements of a large array that @value{GDBN} will print.
8758 If the number is 0, then the printing is unlimited.
8760 @item set print frame-arguments @var{value}
8761 @kindex set print frame-arguments
8762 @cindex printing frame argument values
8763 @cindex print all frame argument values
8764 @cindex print frame argument values for scalars only
8765 @cindex do not print frame argument values
8766 This command allows to control how the values of arguments are printed
8767 when the debugger prints a frame (@pxref{Frames}). The possible
8772 The values of all arguments are printed.
8775 Print the value of an argument only if it is a scalar. The value of more
8776 complex arguments such as arrays, structures, unions, etc, is replaced
8777 by @code{@dots{}}. This is the default. Here is an example where
8778 only scalar arguments are shown:
8781 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8786 None of the argument values are printed. Instead, the value of each argument
8787 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8790 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8795 By default, only scalar arguments are printed. This command can be used
8796 to configure the debugger to print the value of all arguments, regardless
8797 of their type. However, it is often advantageous to not print the value
8798 of more complex parameters. For instance, it reduces the amount of
8799 information printed in each frame, making the backtrace more readable.
8800 Also, it improves performance when displaying Ada frames, because
8801 the computation of large arguments can sometimes be CPU-intensive,
8802 especially in large applications. Setting @code{print frame-arguments}
8803 to @code{scalars} (the default) or @code{none} avoids this computation,
8804 thus speeding up the display of each Ada frame.
8806 @item show print frame-arguments
8807 Show how the value of arguments should be displayed when printing a frame.
8809 @anchor{set print entry-values}
8810 @item set print entry-values @var{value}
8811 @kindex set print entry-values
8812 Set printing of frame argument values at function entry. In some cases
8813 @value{GDBN} can determine the value of function argument which was passed by
8814 the function caller, even if the value was modified inside the called function
8815 and therefore is different. With optimized code, the current value could be
8816 unavailable, but the entry value may still be known.
8818 The default value is @code{default} (see below for its description). Older
8819 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8820 this feature will behave in the @code{default} setting the same way as with the
8823 This functionality is currently supported only by DWARF 2 debugging format and
8824 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8825 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8828 The @var{value} parameter can be one of the following:
8832 Print only actual parameter values, never print values from function entry
8836 #0 different (val=6)
8837 #0 lost (val=<optimized out>)
8839 #0 invalid (val=<optimized out>)
8843 Print only parameter values from function entry point. The actual parameter
8844 values are never printed.
8846 #0 equal (val@@entry=5)
8847 #0 different (val@@entry=5)
8848 #0 lost (val@@entry=5)
8849 #0 born (val@@entry=<optimized out>)
8850 #0 invalid (val@@entry=<optimized out>)
8854 Print only parameter values from function entry point. If value from function
8855 entry point is not known while the actual value is known, print the actual
8856 value for such parameter.
8858 #0 equal (val@@entry=5)
8859 #0 different (val@@entry=5)
8860 #0 lost (val@@entry=5)
8862 #0 invalid (val@@entry=<optimized out>)
8866 Print actual parameter values. If actual parameter value is not known while
8867 value from function entry point is known, print the entry point value for such
8871 #0 different (val=6)
8872 #0 lost (val@@entry=5)
8874 #0 invalid (val=<optimized out>)
8878 Always print both the actual parameter value and its value from function entry
8879 point, even if values of one or both are not available due to compiler
8882 #0 equal (val=5, val@@entry=5)
8883 #0 different (val=6, val@@entry=5)
8884 #0 lost (val=<optimized out>, val@@entry=5)
8885 #0 born (val=10, val@@entry=<optimized out>)
8886 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8890 Print the actual parameter value if it is known and also its value from
8891 function entry point if it is known. If neither is known, print for the actual
8892 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8893 values are known and identical, print the shortened
8894 @code{param=param@@entry=VALUE} notation.
8896 #0 equal (val=val@@entry=5)
8897 #0 different (val=6, val@@entry=5)
8898 #0 lost (val@@entry=5)
8900 #0 invalid (val=<optimized out>)
8904 Always print the actual parameter value. Print also its value from function
8905 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8906 if both values are known and identical, print the shortened
8907 @code{param=param@@entry=VALUE} notation.
8909 #0 equal (val=val@@entry=5)
8910 #0 different (val=6, val@@entry=5)
8911 #0 lost (val=<optimized out>, val@@entry=5)
8913 #0 invalid (val=<optimized out>)
8917 For analysis messages on possible failures of frame argument values at function
8918 entry resolution see @ref{set debug entry-values}.
8920 @item show print entry-values
8921 Show the method being used for printing of frame argument values at function
8924 @item set print repeats @var{number-of-repeats}
8925 @itemx set print repeats unlimited
8926 @cindex repeated array elements
8927 Set the threshold for suppressing display of repeated array
8928 elements. When the number of consecutive identical elements of an
8929 array exceeds the threshold, @value{GDBN} prints the string
8930 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8931 identical repetitions, instead of displaying the identical elements
8932 themselves. Setting the threshold to @code{unlimited} or zero will
8933 cause all elements to be individually printed. The default threshold
8936 @item show print repeats
8937 Display the current threshold for printing repeated identical
8940 @item set print null-stop
8941 @cindex @sc{null} elements in arrays
8942 Cause @value{GDBN} to stop printing the characters of an array when the first
8943 @sc{null} is encountered. This is useful when large arrays actually
8944 contain only short strings.
8947 @item show print null-stop
8948 Show whether @value{GDBN} stops printing an array on the first
8949 @sc{null} character.
8951 @item set print pretty on
8952 @cindex print structures in indented form
8953 @cindex indentation in structure display
8954 Cause @value{GDBN} to print structures in an indented format with one member
8955 per line, like this:
8970 @item set print pretty off
8971 Cause @value{GDBN} to print structures in a compact format, like this:
8975 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8976 meat = 0x54 "Pork"@}
8981 This is the default format.
8983 @item show print pretty
8984 Show which format @value{GDBN} is using to print structures.
8986 @item set print sevenbit-strings on
8987 @cindex eight-bit characters in strings
8988 @cindex octal escapes in strings
8989 Print using only seven-bit characters; if this option is set,
8990 @value{GDBN} displays any eight-bit characters (in strings or
8991 character values) using the notation @code{\}@var{nnn}. This setting is
8992 best if you are working in English (@sc{ascii}) and you use the
8993 high-order bit of characters as a marker or ``meta'' bit.
8995 @item set print sevenbit-strings off
8996 Print full eight-bit characters. This allows the use of more
8997 international character sets, and is the default.
8999 @item show print sevenbit-strings
9000 Show whether or not @value{GDBN} is printing only seven-bit characters.
9002 @item set print union on
9003 @cindex unions in structures, printing
9004 Tell @value{GDBN} to print unions which are contained in structures
9005 and other unions. This is the default setting.
9007 @item set print union off
9008 Tell @value{GDBN} not to print unions which are contained in
9009 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9012 @item show print union
9013 Ask @value{GDBN} whether or not it will print unions which are contained in
9014 structures and other unions.
9016 For example, given the declarations
9019 typedef enum @{Tree, Bug@} Species;
9020 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9021 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9032 struct thing foo = @{Tree, @{Acorn@}@};
9036 with @code{set print union on} in effect @samp{p foo} would print
9039 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9043 and with @code{set print union off} in effect it would print
9046 $1 = @{it = Tree, form = @{...@}@}
9050 @code{set print union} affects programs written in C-like languages
9056 These settings are of interest when debugging C@t{++} programs:
9059 @cindex demangling C@t{++} names
9060 @item set print demangle
9061 @itemx set print demangle on
9062 Print C@t{++} names in their source form rather than in the encoded
9063 (``mangled'') form passed to the assembler and linker for type-safe
9064 linkage. The default is on.
9066 @item show print demangle
9067 Show whether C@t{++} names are printed in mangled or demangled form.
9069 @item set print asm-demangle
9070 @itemx set print asm-demangle on
9071 Print C@t{++} names in their source form rather than their mangled form, even
9072 in assembler code printouts such as instruction disassemblies.
9075 @item show print asm-demangle
9076 Show whether C@t{++} names in assembly listings are printed in mangled
9079 @cindex C@t{++} symbol decoding style
9080 @cindex symbol decoding style, C@t{++}
9081 @kindex set demangle-style
9082 @item set demangle-style @var{style}
9083 Choose among several encoding schemes used by different compilers to
9084 represent C@t{++} names. The choices for @var{style} are currently:
9088 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9089 This is the default.
9092 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9095 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9098 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9101 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9102 @strong{Warning:} this setting alone is not sufficient to allow
9103 debugging @code{cfront}-generated executables. @value{GDBN} would
9104 require further enhancement to permit that.
9107 If you omit @var{style}, you will see a list of possible formats.
9109 @item show demangle-style
9110 Display the encoding style currently in use for decoding C@t{++} symbols.
9112 @item set print object
9113 @itemx set print object on
9114 @cindex derived type of an object, printing
9115 @cindex display derived types
9116 When displaying a pointer to an object, identify the @emph{actual}
9117 (derived) type of the object rather than the @emph{declared} type, using
9118 the virtual function table. Note that the virtual function table is
9119 required---this feature can only work for objects that have run-time
9120 type identification; a single virtual method in the object's declared
9121 type is sufficient. Note that this setting is also taken into account when
9122 working with variable objects via MI (@pxref{GDB/MI}).
9124 @item set print object off
9125 Display only the declared type of objects, without reference to the
9126 virtual function table. This is the default setting.
9128 @item show print object
9129 Show whether actual, or declared, object types are displayed.
9131 @item set print static-members
9132 @itemx set print static-members on
9133 @cindex static members of C@t{++} objects
9134 Print static members when displaying a C@t{++} object. The default is on.
9136 @item set print static-members off
9137 Do not print static members when displaying a C@t{++} object.
9139 @item show print static-members
9140 Show whether C@t{++} static members are printed or not.
9142 @item set print pascal_static-members
9143 @itemx set print pascal_static-members on
9144 @cindex static members of Pascal objects
9145 @cindex Pascal objects, static members display
9146 Print static members when displaying a Pascal object. The default is on.
9148 @item set print pascal_static-members off
9149 Do not print static members when displaying a Pascal object.
9151 @item show print pascal_static-members
9152 Show whether Pascal static members are printed or not.
9154 @c These don't work with HP ANSI C++ yet.
9155 @item set print vtbl
9156 @itemx set print vtbl on
9157 @cindex pretty print C@t{++} virtual function tables
9158 @cindex virtual functions (C@t{++}) display
9159 @cindex VTBL display
9160 Pretty print C@t{++} virtual function tables. The default is off.
9161 (The @code{vtbl} commands do not work on programs compiled with the HP
9162 ANSI C@t{++} compiler (@code{aCC}).)
9164 @item set print vtbl off
9165 Do not pretty print C@t{++} virtual function tables.
9167 @item show print vtbl
9168 Show whether C@t{++} virtual function tables are pretty printed, or not.
9171 @node Pretty Printing
9172 @section Pretty Printing
9174 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9175 Python code. It greatly simplifies the display of complex objects. This
9176 mechanism works for both MI and the CLI.
9179 * Pretty-Printer Introduction:: Introduction to pretty-printers
9180 * Pretty-Printer Example:: An example pretty-printer
9181 * Pretty-Printer Commands:: Pretty-printer commands
9184 @node Pretty-Printer Introduction
9185 @subsection Pretty-Printer Introduction
9187 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9188 registered for the value. If there is then @value{GDBN} invokes the
9189 pretty-printer to print the value. Otherwise the value is printed normally.
9191 Pretty-printers are normally named. This makes them easy to manage.
9192 The @samp{info pretty-printer} command will list all the installed
9193 pretty-printers with their names.
9194 If a pretty-printer can handle multiple data types, then its
9195 @dfn{subprinters} are the printers for the individual data types.
9196 Each such subprinter has its own name.
9197 The format of the name is @var{printer-name};@var{subprinter-name}.
9199 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9200 Typically they are automatically loaded and registered when the corresponding
9201 debug information is loaded, thus making them available without having to
9202 do anything special.
9204 There are three places where a pretty-printer can be registered.
9208 Pretty-printers registered globally are available when debugging
9212 Pretty-printers registered with a program space are available only
9213 when debugging that program.
9214 @xref{Progspaces In Python}, for more details on program spaces in Python.
9217 Pretty-printers registered with an objfile are loaded and unloaded
9218 with the corresponding objfile (e.g., shared library).
9219 @xref{Objfiles In Python}, for more details on objfiles in Python.
9222 @xref{Selecting Pretty-Printers}, for further information on how
9223 pretty-printers are selected,
9225 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9228 @node Pretty-Printer Example
9229 @subsection Pretty-Printer Example
9231 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9234 (@value{GDBP}) print s
9236 static npos = 4294967295,
9238 <std::allocator<char>> = @{
9239 <__gnu_cxx::new_allocator<char>> = @{
9240 <No data fields>@}, <No data fields>
9242 members of std::basic_string<char, std::char_traits<char>,
9243 std::allocator<char> >::_Alloc_hider:
9244 _M_p = 0x804a014 "abcd"
9249 With a pretty-printer for @code{std::string} only the contents are printed:
9252 (@value{GDBP}) print s
9256 @node Pretty-Printer Commands
9257 @subsection Pretty-Printer Commands
9258 @cindex pretty-printer commands
9261 @kindex info pretty-printer
9262 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9263 Print the list of installed pretty-printers.
9264 This includes disabled pretty-printers, which are marked as such.
9266 @var{object-regexp} is a regular expression matching the objects
9267 whose pretty-printers to list.
9268 Objects can be @code{global}, the program space's file
9269 (@pxref{Progspaces In Python}),
9270 and the object files within that program space (@pxref{Objfiles In Python}).
9271 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9272 looks up a printer from these three objects.
9274 @var{name-regexp} is a regular expression matching the name of the printers
9277 @kindex disable pretty-printer
9278 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9279 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9280 A disabled pretty-printer is not forgotten, it may be enabled again later.
9282 @kindex enable pretty-printer
9283 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9284 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9289 Suppose we have three pretty-printers installed: one from library1.so
9290 named @code{foo} that prints objects of type @code{foo}, and
9291 another from library2.so named @code{bar} that prints two types of objects,
9292 @code{bar1} and @code{bar2}.
9295 (gdb) info pretty-printer
9302 (gdb) info pretty-printer library2
9307 (gdb) disable pretty-printer library1
9309 2 of 3 printers enabled
9310 (gdb) info pretty-printer
9317 (gdb) disable pretty-printer library2 bar:bar1
9319 1 of 3 printers enabled
9320 (gdb) info pretty-printer library2
9327 (gdb) disable pretty-printer library2 bar
9329 0 of 3 printers enabled
9330 (gdb) info pretty-printer library2
9339 Note that for @code{bar} the entire printer can be disabled,
9340 as can each individual subprinter.
9343 @section Value History
9345 @cindex value history
9346 @cindex history of values printed by @value{GDBN}
9347 Values printed by the @code{print} command are saved in the @value{GDBN}
9348 @dfn{value history}. This allows you to refer to them in other expressions.
9349 Values are kept until the symbol table is re-read or discarded
9350 (for example with the @code{file} or @code{symbol-file} commands).
9351 When the symbol table changes, the value history is discarded,
9352 since the values may contain pointers back to the types defined in the
9357 @cindex history number
9358 The values printed are given @dfn{history numbers} by which you can
9359 refer to them. These are successive integers starting with one.
9360 @code{print} shows you the history number assigned to a value by
9361 printing @samp{$@var{num} = } before the value; here @var{num} is the
9364 To refer to any previous value, use @samp{$} followed by the value's
9365 history number. The way @code{print} labels its output is designed to
9366 remind you of this. Just @code{$} refers to the most recent value in
9367 the history, and @code{$$} refers to the value before that.
9368 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9369 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9370 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9372 For example, suppose you have just printed a pointer to a structure and
9373 want to see the contents of the structure. It suffices to type
9379 If you have a chain of structures where the component @code{next} points
9380 to the next one, you can print the contents of the next one with this:
9387 You can print successive links in the chain by repeating this
9388 command---which you can do by just typing @key{RET}.
9390 Note that the history records values, not expressions. If the value of
9391 @code{x} is 4 and you type these commands:
9399 then the value recorded in the value history by the @code{print} command
9400 remains 4 even though the value of @code{x} has changed.
9405 Print the last ten values in the value history, with their item numbers.
9406 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9407 values} does not change the history.
9409 @item show values @var{n}
9410 Print ten history values centered on history item number @var{n}.
9413 Print ten history values just after the values last printed. If no more
9414 values are available, @code{show values +} produces no display.
9417 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9418 same effect as @samp{show values +}.
9420 @node Convenience Vars
9421 @section Convenience Variables
9423 @cindex convenience variables
9424 @cindex user-defined variables
9425 @value{GDBN} provides @dfn{convenience variables} that you can use within
9426 @value{GDBN} to hold on to a value and refer to it later. These variables
9427 exist entirely within @value{GDBN}; they are not part of your program, and
9428 setting a convenience variable has no direct effect on further execution
9429 of your program. That is why you can use them freely.
9431 Convenience variables are prefixed with @samp{$}. Any name preceded by
9432 @samp{$} can be used for a convenience variable, unless it is one of
9433 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9434 (Value history references, in contrast, are @emph{numbers} preceded
9435 by @samp{$}. @xref{Value History, ,Value History}.)
9437 You can save a value in a convenience variable with an assignment
9438 expression, just as you would set a variable in your program.
9442 set $foo = *object_ptr
9446 would save in @code{$foo} the value contained in the object pointed to by
9449 Using a convenience variable for the first time creates it, but its
9450 value is @code{void} until you assign a new value. You can alter the
9451 value with another assignment at any time.
9453 Convenience variables have no fixed types. You can assign a convenience
9454 variable any type of value, including structures and arrays, even if
9455 that variable already has a value of a different type. The convenience
9456 variable, when used as an expression, has the type of its current value.
9459 @kindex show convenience
9460 @cindex show all user variables and functions
9461 @item show convenience
9462 Print a list of convenience variables used so far, and their values,
9463 as well as a list of the convenience functions.
9464 Abbreviated @code{show conv}.
9466 @kindex init-if-undefined
9467 @cindex convenience variables, initializing
9468 @item init-if-undefined $@var{variable} = @var{expression}
9469 Set a convenience variable if it has not already been set. This is useful
9470 for user-defined commands that keep some state. It is similar, in concept,
9471 to using local static variables with initializers in C (except that
9472 convenience variables are global). It can also be used to allow users to
9473 override default values used in a command script.
9475 If the variable is already defined then the expression is not evaluated so
9476 any side-effects do not occur.
9479 One of the ways to use a convenience variable is as a counter to be
9480 incremented or a pointer to be advanced. For example, to print
9481 a field from successive elements of an array of structures:
9485 print bar[$i++]->contents
9489 Repeat that command by typing @key{RET}.
9491 Some convenience variables are created automatically by @value{GDBN} and given
9492 values likely to be useful.
9495 @vindex $_@r{, convenience variable}
9497 The variable @code{$_} is automatically set by the @code{x} command to
9498 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9499 commands which provide a default address for @code{x} to examine also
9500 set @code{$_} to that address; these commands include @code{info line}
9501 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9502 except when set by the @code{x} command, in which case it is a pointer
9503 to the type of @code{$__}.
9505 @vindex $__@r{, convenience variable}
9507 The variable @code{$__} is automatically set by the @code{x} command
9508 to the value found in the last address examined. Its type is chosen
9509 to match the format in which the data was printed.
9512 @vindex $_exitcode@r{, convenience variable}
9513 The variable @code{$_exitcode} is automatically set to the exit code when
9514 the program being debugged terminates.
9517 @itemx $_probe_arg0@dots{}$_probe_arg11
9518 Arguments to a static probe. @xref{Static Probe Points}.
9521 @vindex $_sdata@r{, inspect, convenience variable}
9522 The variable @code{$_sdata} contains extra collected static tracepoint
9523 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9524 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9525 if extra static tracepoint data has not been collected.
9528 @vindex $_siginfo@r{, convenience variable}
9529 The variable @code{$_siginfo} contains extra signal information
9530 (@pxref{extra signal information}). Note that @code{$_siginfo}
9531 could be empty, if the application has not yet received any signals.
9532 For example, it will be empty before you execute the @code{run} command.
9535 @vindex $_tlb@r{, convenience variable}
9536 The variable @code{$_tlb} is automatically set when debugging
9537 applications running on MS-Windows in native mode or connected to
9538 gdbserver that supports the @code{qGetTIBAddr} request.
9539 @xref{General Query Packets}.
9540 This variable contains the address of the thread information block.
9544 On HP-UX systems, if you refer to a function or variable name that
9545 begins with a dollar sign, @value{GDBN} searches for a user or system
9546 name first, before it searches for a convenience variable.
9548 @node Convenience Funs
9549 @section Convenience Functions
9551 @cindex convenience functions
9552 @value{GDBN} also supplies some @dfn{convenience functions}. These
9553 have a syntax similar to convenience variables. A convenience
9554 function can be used in an expression just like an ordinary function;
9555 however, a convenience function is implemented internally to
9558 These functions require @value{GDBN} to be configured with
9559 @code{Python} support.
9563 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9564 @findex $_memeq@r{, convenience function}
9565 Returns one if the @var{length} bytes at the addresses given by
9566 @var{buf1} and @var{buf2} are equal.
9567 Otherwise it returns zero.
9569 @item $_regex(@var{str}, @var{regex})
9570 @findex $_regex@r{, convenience function}
9571 Returns one if the string @var{str} matches the regular expression
9572 @var{regex}. Otherwise it returns zero.
9573 The syntax of the regular expression is that specified by @code{Python}'s
9574 regular expression support.
9576 @item $_streq(@var{str1}, @var{str2})
9577 @findex $_streq@r{, convenience function}
9578 Returns one if the strings @var{str1} and @var{str2} are equal.
9579 Otherwise it returns zero.
9581 @item $_strlen(@var{str})
9582 @findex $_strlen@r{, convenience function}
9583 Returns the length of string @var{str}.
9587 @value{GDBN} provides the ability to list and get help on
9588 convenience functions.
9592 @kindex help function
9593 @cindex show all convenience functions
9594 Print a list of all convenience functions.
9601 You can refer to machine register contents, in expressions, as variables
9602 with names starting with @samp{$}. The names of registers are different
9603 for each machine; use @code{info registers} to see the names used on
9607 @kindex info registers
9608 @item info registers
9609 Print the names and values of all registers except floating-point
9610 and vector registers (in the selected stack frame).
9612 @kindex info all-registers
9613 @cindex floating point registers
9614 @item info all-registers
9615 Print the names and values of all registers, including floating-point
9616 and vector registers (in the selected stack frame).
9618 @item info registers @var{regname} @dots{}
9619 Print the @dfn{relativized} value of each specified register @var{regname}.
9620 As discussed in detail below, register values are normally relative to
9621 the selected stack frame. @var{regname} may be any register name valid on
9622 the machine you are using, with or without the initial @samp{$}.
9625 @cindex stack pointer register
9626 @cindex program counter register
9627 @cindex process status register
9628 @cindex frame pointer register
9629 @cindex standard registers
9630 @value{GDBN} has four ``standard'' register names that are available (in
9631 expressions) on most machines---whenever they do not conflict with an
9632 architecture's canonical mnemonics for registers. The register names
9633 @code{$pc} and @code{$sp} are used for the program counter register and
9634 the stack pointer. @code{$fp} is used for a register that contains a
9635 pointer to the current stack frame, and @code{$ps} is used for a
9636 register that contains the processor status. For example,
9637 you could print the program counter in hex with
9644 or print the instruction to be executed next with
9651 or add four to the stack pointer@footnote{This is a way of removing
9652 one word from the stack, on machines where stacks grow downward in
9653 memory (most machines, nowadays). This assumes that the innermost
9654 stack frame is selected; setting @code{$sp} is not allowed when other
9655 stack frames are selected. To pop entire frames off the stack,
9656 regardless of machine architecture, use @code{return};
9657 see @ref{Returning, ,Returning from a Function}.} with
9663 Whenever possible, these four standard register names are available on
9664 your machine even though the machine has different canonical mnemonics,
9665 so long as there is no conflict. The @code{info registers} command
9666 shows the canonical names. For example, on the SPARC, @code{info
9667 registers} displays the processor status register as @code{$psr} but you
9668 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9669 is an alias for the @sc{eflags} register.
9671 @value{GDBN} always considers the contents of an ordinary register as an
9672 integer when the register is examined in this way. Some machines have
9673 special registers which can hold nothing but floating point; these
9674 registers are considered to have floating point values. There is no way
9675 to refer to the contents of an ordinary register as floating point value
9676 (although you can @emph{print} it as a floating point value with
9677 @samp{print/f $@var{regname}}).
9679 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9680 means that the data format in which the register contents are saved by
9681 the operating system is not the same one that your program normally
9682 sees. For example, the registers of the 68881 floating point
9683 coprocessor are always saved in ``extended'' (raw) format, but all C
9684 programs expect to work with ``double'' (virtual) format. In such
9685 cases, @value{GDBN} normally works with the virtual format only (the format
9686 that makes sense for your program), but the @code{info registers} command
9687 prints the data in both formats.
9689 @cindex SSE registers (x86)
9690 @cindex MMX registers (x86)
9691 Some machines have special registers whose contents can be interpreted
9692 in several different ways. For example, modern x86-based machines
9693 have SSE and MMX registers that can hold several values packed
9694 together in several different formats. @value{GDBN} refers to such
9695 registers in @code{struct} notation:
9698 (@value{GDBP}) print $xmm1
9700 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9701 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9702 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9703 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9704 v4_int32 = @{0, 20657912, 11, 13@},
9705 v2_int64 = @{88725056443645952, 55834574859@},
9706 uint128 = 0x0000000d0000000b013b36f800000000
9711 To set values of such registers, you need to tell @value{GDBN} which
9712 view of the register you wish to change, as if you were assigning
9713 value to a @code{struct} member:
9716 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9719 Normally, register values are relative to the selected stack frame
9720 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9721 value that the register would contain if all stack frames farther in
9722 were exited and their saved registers restored. In order to see the
9723 true contents of hardware registers, you must select the innermost
9724 frame (with @samp{frame 0}).
9726 However, @value{GDBN} must deduce where registers are saved, from the machine
9727 code generated by your compiler. If some registers are not saved, or if
9728 @value{GDBN} is unable to locate the saved registers, the selected stack
9729 frame makes no difference.
9731 @node Floating Point Hardware
9732 @section Floating Point Hardware
9733 @cindex floating point
9735 Depending on the configuration, @value{GDBN} may be able to give
9736 you more information about the status of the floating point hardware.
9741 Display hardware-dependent information about the floating
9742 point unit. The exact contents and layout vary depending on the
9743 floating point chip. Currently, @samp{info float} is supported on
9744 the ARM and x86 machines.
9748 @section Vector Unit
9751 Depending on the configuration, @value{GDBN} may be able to give you
9752 more information about the status of the vector unit.
9757 Display information about the vector unit. The exact contents and
9758 layout vary depending on the hardware.
9761 @node OS Information
9762 @section Operating System Auxiliary Information
9763 @cindex OS information
9765 @value{GDBN} provides interfaces to useful OS facilities that can help
9766 you debug your program.
9768 @cindex auxiliary vector
9769 @cindex vector, auxiliary
9770 Some operating systems supply an @dfn{auxiliary vector} to programs at
9771 startup. This is akin to the arguments and environment that you
9772 specify for a program, but contains a system-dependent variety of
9773 binary values that tell system libraries important details about the
9774 hardware, operating system, and process. Each value's purpose is
9775 identified by an integer tag; the meanings are well-known but system-specific.
9776 Depending on the configuration and operating system facilities,
9777 @value{GDBN} may be able to show you this information. For remote
9778 targets, this functionality may further depend on the remote stub's
9779 support of the @samp{qXfer:auxv:read} packet, see
9780 @ref{qXfer auxiliary vector read}.
9785 Display the auxiliary vector of the inferior, which can be either a
9786 live process or a core dump file. @value{GDBN} prints each tag value
9787 numerically, and also shows names and text descriptions for recognized
9788 tags. Some values in the vector are numbers, some bit masks, and some
9789 pointers to strings or other data. @value{GDBN} displays each value in the
9790 most appropriate form for a recognized tag, and in hexadecimal for
9791 an unrecognized tag.
9794 On some targets, @value{GDBN} can access operating system-specific
9795 information and show it to you. The types of information available
9796 will differ depending on the type of operating system running on the
9797 target. The mechanism used to fetch the data is described in
9798 @ref{Operating System Information}. For remote targets, this
9799 functionality depends on the remote stub's support of the
9800 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9804 @item info os @var{infotype}
9806 Display OS information of the requested type.
9808 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9810 @anchor{linux info os infotypes}
9812 @kindex info os processes
9814 Display the list of processes on the target. For each process,
9815 @value{GDBN} prints the process identifier, the name of the user, the
9816 command corresponding to the process, and the list of processor cores
9817 that the process is currently running on. (To understand what these
9818 properties mean, for this and the following info types, please consult
9819 the general @sc{gnu}/Linux documentation.)
9821 @kindex info os procgroups
9823 Display the list of process groups on the target. For each process,
9824 @value{GDBN} prints the identifier of the process group that it belongs
9825 to, the command corresponding to the process group leader, the process
9826 identifier, and the command line of the process. The list is sorted
9827 first by the process group identifier, then by the process identifier,
9828 so that processes belonging to the same process group are grouped together
9829 and the process group leader is listed first.
9831 @kindex info os threads
9833 Display the list of threads running on the target. For each thread,
9834 @value{GDBN} prints the identifier of the process that the thread
9835 belongs to, the command of the process, the thread identifier, and the
9836 processor core that it is currently running on. The main thread of a
9837 process is not listed.
9839 @kindex info os files
9841 Display the list of open file descriptors on the target. For each
9842 file descriptor, @value{GDBN} prints the identifier of the process
9843 owning the descriptor, the command of the owning process, the value
9844 of the descriptor, and the target of the descriptor.
9846 @kindex info os sockets
9848 Display the list of Internet-domain sockets on the target. For each
9849 socket, @value{GDBN} prints the address and port of the local and
9850 remote endpoints, the current state of the connection, the creator of
9851 the socket, the IP address family of the socket, and the type of the
9856 Display the list of all System V shared-memory regions on the target.
9857 For each shared-memory region, @value{GDBN} prints the region key,
9858 the shared-memory identifier, the access permissions, the size of the
9859 region, the process that created the region, the process that last
9860 attached to or detached from the region, the current number of live
9861 attaches to the region, and the times at which the region was last
9862 attached to, detach from, and changed.
9864 @kindex info os semaphores
9866 Display the list of all System V semaphore sets on the target. For each
9867 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9868 set identifier, the access permissions, the number of semaphores in the
9869 set, the user and group of the owner and creator of the semaphore set,
9870 and the times at which the semaphore set was operated upon and changed.
9874 Display the list of all System V message queues on the target. For each
9875 message queue, @value{GDBN} prints the message queue key, the message
9876 queue identifier, the access permissions, the current number of bytes
9877 on the queue, the current number of messages on the queue, the processes
9878 that last sent and received a message on the queue, the user and group
9879 of the owner and creator of the message queue, the times at which a
9880 message was last sent and received on the queue, and the time at which
9881 the message queue was last changed.
9883 @kindex info os modules
9885 Display the list of all loaded kernel modules on the target. For each
9886 module, @value{GDBN} prints the module name, the size of the module in
9887 bytes, the number of times the module is used, the dependencies of the
9888 module, the status of the module, and the address of the loaded module
9893 If @var{infotype} is omitted, then list the possible values for
9894 @var{infotype} and the kind of OS information available for each
9895 @var{infotype}. If the target does not return a list of possible
9896 types, this command will report an error.
9899 @node Memory Region Attributes
9900 @section Memory Region Attributes
9901 @cindex memory region attributes
9903 @dfn{Memory region attributes} allow you to describe special handling
9904 required by regions of your target's memory. @value{GDBN} uses
9905 attributes to determine whether to allow certain types of memory
9906 accesses; whether to use specific width accesses; and whether to cache
9907 target memory. By default the description of memory regions is
9908 fetched from the target (if the current target supports this), but the
9909 user can override the fetched regions.
9911 Defined memory regions can be individually enabled and disabled. When a
9912 memory region is disabled, @value{GDBN} uses the default attributes when
9913 accessing memory in that region. Similarly, if no memory regions have
9914 been defined, @value{GDBN} uses the default attributes when accessing
9917 When a memory region is defined, it is given a number to identify it;
9918 to enable, disable, or remove a memory region, you specify that number.
9922 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9923 Define a memory region bounded by @var{lower} and @var{upper} with
9924 attributes @var{attributes}@dots{}, and add it to the list of regions
9925 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9926 case: it is treated as the target's maximum memory address.
9927 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9930 Discard any user changes to the memory regions and use target-supplied
9931 regions, if available, or no regions if the target does not support.
9934 @item delete mem @var{nums}@dots{}
9935 Remove memory regions @var{nums}@dots{} from the list of regions
9936 monitored by @value{GDBN}.
9939 @item disable mem @var{nums}@dots{}
9940 Disable monitoring of memory regions @var{nums}@dots{}.
9941 A disabled memory region is not forgotten.
9942 It may be enabled again later.
9945 @item enable mem @var{nums}@dots{}
9946 Enable monitoring of memory regions @var{nums}@dots{}.
9950 Print a table of all defined memory regions, with the following columns
9954 @item Memory Region Number
9955 @item Enabled or Disabled.
9956 Enabled memory regions are marked with @samp{y}.
9957 Disabled memory regions are marked with @samp{n}.
9960 The address defining the inclusive lower bound of the memory region.
9963 The address defining the exclusive upper bound of the memory region.
9966 The list of attributes set for this memory region.
9971 @subsection Attributes
9973 @subsubsection Memory Access Mode
9974 The access mode attributes set whether @value{GDBN} may make read or
9975 write accesses to a memory region.
9977 While these attributes prevent @value{GDBN} from performing invalid
9978 memory accesses, they do nothing to prevent the target system, I/O DMA,
9979 etc.@: from accessing memory.
9983 Memory is read only.
9985 Memory is write only.
9987 Memory is read/write. This is the default.
9990 @subsubsection Memory Access Size
9991 The access size attribute tells @value{GDBN} to use specific sized
9992 accesses in the memory region. Often memory mapped device registers
9993 require specific sized accesses. If no access size attribute is
9994 specified, @value{GDBN} may use accesses of any size.
9998 Use 8 bit memory accesses.
10000 Use 16 bit memory accesses.
10002 Use 32 bit memory accesses.
10004 Use 64 bit memory accesses.
10007 @c @subsubsection Hardware/Software Breakpoints
10008 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10009 @c will use hardware or software breakpoints for the internal breakpoints
10010 @c used by the step, next, finish, until, etc. commands.
10014 @c Always use hardware breakpoints
10015 @c @item swbreak (default)
10018 @subsubsection Data Cache
10019 The data cache attributes set whether @value{GDBN} will cache target
10020 memory. While this generally improves performance by reducing debug
10021 protocol overhead, it can lead to incorrect results because @value{GDBN}
10022 does not know about volatile variables or memory mapped device
10027 Enable @value{GDBN} to cache target memory.
10029 Disable @value{GDBN} from caching target memory. This is the default.
10032 @subsection Memory Access Checking
10033 @value{GDBN} can be instructed to refuse accesses to memory that is
10034 not explicitly described. This can be useful if accessing such
10035 regions has undesired effects for a specific target, or to provide
10036 better error checking. The following commands control this behaviour.
10039 @kindex set mem inaccessible-by-default
10040 @item set mem inaccessible-by-default [on|off]
10041 If @code{on} is specified, make @value{GDBN} treat memory not
10042 explicitly described by the memory ranges as non-existent and refuse accesses
10043 to such memory. The checks are only performed if there's at least one
10044 memory range defined. If @code{off} is specified, make @value{GDBN}
10045 treat the memory not explicitly described by the memory ranges as RAM.
10046 The default value is @code{on}.
10047 @kindex show mem inaccessible-by-default
10048 @item show mem inaccessible-by-default
10049 Show the current handling of accesses to unknown memory.
10053 @c @subsubsection Memory Write Verification
10054 @c The memory write verification attributes set whether @value{GDBN}
10055 @c will re-reads data after each write to verify the write was successful.
10059 @c @item noverify (default)
10062 @node Dump/Restore Files
10063 @section Copy Between Memory and a File
10064 @cindex dump/restore files
10065 @cindex append data to a file
10066 @cindex dump data to a file
10067 @cindex restore data from a file
10069 You can use the commands @code{dump}, @code{append}, and
10070 @code{restore} to copy data between target memory and a file. The
10071 @code{dump} and @code{append} commands write data to a file, and the
10072 @code{restore} command reads data from a file back into the inferior's
10073 memory. Files may be in binary, Motorola S-record, Intel hex, or
10074 Tektronix Hex format; however, @value{GDBN} can only append to binary
10080 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10081 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10082 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10083 or the value of @var{expr}, to @var{filename} in the given format.
10085 The @var{format} parameter may be any one of:
10092 Motorola S-record format.
10094 Tektronix Hex format.
10097 @value{GDBN} uses the same definitions of these formats as the
10098 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10099 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10103 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10104 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10105 Append the contents of memory from @var{start_addr} to @var{end_addr},
10106 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10107 (@value{GDBN} can only append data to files in raw binary form.)
10110 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10111 Restore the contents of file @var{filename} into memory. The
10112 @code{restore} command can automatically recognize any known @sc{bfd}
10113 file format, except for raw binary. To restore a raw binary file you
10114 must specify the optional keyword @code{binary} after the filename.
10116 If @var{bias} is non-zero, its value will be added to the addresses
10117 contained in the file. Binary files always start at address zero, so
10118 they will be restored at address @var{bias}. Other bfd files have
10119 a built-in location; they will be restored at offset @var{bias}
10120 from that location.
10122 If @var{start} and/or @var{end} are non-zero, then only data between
10123 file offset @var{start} and file offset @var{end} will be restored.
10124 These offsets are relative to the addresses in the file, before
10125 the @var{bias} argument is applied.
10129 @node Core File Generation
10130 @section How to Produce a Core File from Your Program
10131 @cindex dump core from inferior
10133 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10134 image of a running process and its process status (register values
10135 etc.). Its primary use is post-mortem debugging of a program that
10136 crashed while it ran outside a debugger. A program that crashes
10137 automatically produces a core file, unless this feature is disabled by
10138 the user. @xref{Files}, for information on invoking @value{GDBN} in
10139 the post-mortem debugging mode.
10141 Occasionally, you may wish to produce a core file of the program you
10142 are debugging in order to preserve a snapshot of its state.
10143 @value{GDBN} has a special command for that.
10147 @kindex generate-core-file
10148 @item generate-core-file [@var{file}]
10149 @itemx gcore [@var{file}]
10150 Produce a core dump of the inferior process. The optional argument
10151 @var{file} specifies the file name where to put the core dump. If not
10152 specified, the file name defaults to @file{core.@var{pid}}, where
10153 @var{pid} is the inferior process ID.
10155 Note that this command is implemented only for some systems (as of
10156 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10159 @node Character Sets
10160 @section Character Sets
10161 @cindex character sets
10163 @cindex translating between character sets
10164 @cindex host character set
10165 @cindex target character set
10167 If the program you are debugging uses a different character set to
10168 represent characters and strings than the one @value{GDBN} uses itself,
10169 @value{GDBN} can automatically translate between the character sets for
10170 you. The character set @value{GDBN} uses we call the @dfn{host
10171 character set}; the one the inferior program uses we call the
10172 @dfn{target character set}.
10174 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10175 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10176 remote protocol (@pxref{Remote Debugging}) to debug a program
10177 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10178 then the host character set is Latin-1, and the target character set is
10179 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10180 target-charset EBCDIC-US}, then @value{GDBN} translates between
10181 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10182 character and string literals in expressions.
10184 @value{GDBN} has no way to automatically recognize which character set
10185 the inferior program uses; you must tell it, using the @code{set
10186 target-charset} command, described below.
10188 Here are the commands for controlling @value{GDBN}'s character set
10192 @item set target-charset @var{charset}
10193 @kindex set target-charset
10194 Set the current target character set to @var{charset}. To display the
10195 list of supported target character sets, type
10196 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10198 @item set host-charset @var{charset}
10199 @kindex set host-charset
10200 Set the current host character set to @var{charset}.
10202 By default, @value{GDBN} uses a host character set appropriate to the
10203 system it is running on; you can override that default using the
10204 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10205 automatically determine the appropriate host character set. In this
10206 case, @value{GDBN} uses @samp{UTF-8}.
10208 @value{GDBN} can only use certain character sets as its host character
10209 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10210 @value{GDBN} will list the host character sets it supports.
10212 @item set charset @var{charset}
10213 @kindex set charset
10214 Set the current host and target character sets to @var{charset}. As
10215 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10216 @value{GDBN} will list the names of the character sets that can be used
10217 for both host and target.
10220 @kindex show charset
10221 Show the names of the current host and target character sets.
10223 @item show host-charset
10224 @kindex show host-charset
10225 Show the name of the current host character set.
10227 @item show target-charset
10228 @kindex show target-charset
10229 Show the name of the current target character set.
10231 @item set target-wide-charset @var{charset}
10232 @kindex set target-wide-charset
10233 Set the current target's wide character set to @var{charset}. This is
10234 the character set used by the target's @code{wchar_t} type. To
10235 display the list of supported wide character sets, type
10236 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10238 @item show target-wide-charset
10239 @kindex show target-wide-charset
10240 Show the name of the current target's wide character set.
10243 Here is an example of @value{GDBN}'s character set support in action.
10244 Assume that the following source code has been placed in the file
10245 @file{charset-test.c}:
10251 = @{72, 101, 108, 108, 111, 44, 32, 119,
10252 111, 114, 108, 100, 33, 10, 0@};
10253 char ibm1047_hello[]
10254 = @{200, 133, 147, 147, 150, 107, 64, 166,
10255 150, 153, 147, 132, 90, 37, 0@};
10259 printf ("Hello, world!\n");
10263 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10264 containing the string @samp{Hello, world!} followed by a newline,
10265 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10267 We compile the program, and invoke the debugger on it:
10270 $ gcc -g charset-test.c -o charset-test
10271 $ gdb -nw charset-test
10272 GNU gdb 2001-12-19-cvs
10273 Copyright 2001 Free Software Foundation, Inc.
10278 We can use the @code{show charset} command to see what character sets
10279 @value{GDBN} is currently using to interpret and display characters and
10283 (@value{GDBP}) show charset
10284 The current host and target character set is `ISO-8859-1'.
10288 For the sake of printing this manual, let's use @sc{ascii} as our
10289 initial character set:
10291 (@value{GDBP}) set charset ASCII
10292 (@value{GDBP}) show charset
10293 The current host and target character set is `ASCII'.
10297 Let's assume that @sc{ascii} is indeed the correct character set for our
10298 host system --- in other words, let's assume that if @value{GDBN} prints
10299 characters using the @sc{ascii} character set, our terminal will display
10300 them properly. Since our current target character set is also
10301 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10304 (@value{GDBP}) print ascii_hello
10305 $1 = 0x401698 "Hello, world!\n"
10306 (@value{GDBP}) print ascii_hello[0]
10311 @value{GDBN} uses the target character set for character and string
10312 literals you use in expressions:
10315 (@value{GDBP}) print '+'
10320 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10323 @value{GDBN} relies on the user to tell it which character set the
10324 target program uses. If we print @code{ibm1047_hello} while our target
10325 character set is still @sc{ascii}, we get jibberish:
10328 (@value{GDBP}) print ibm1047_hello
10329 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10330 (@value{GDBP}) print ibm1047_hello[0]
10335 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10336 @value{GDBN} tells us the character sets it supports:
10339 (@value{GDBP}) set target-charset
10340 ASCII EBCDIC-US IBM1047 ISO-8859-1
10341 (@value{GDBP}) set target-charset
10344 We can select @sc{ibm1047} as our target character set, and examine the
10345 program's strings again. Now the @sc{ascii} string is wrong, but
10346 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10347 target character set, @sc{ibm1047}, to the host character set,
10348 @sc{ascii}, and they display correctly:
10351 (@value{GDBP}) set target-charset IBM1047
10352 (@value{GDBP}) show charset
10353 The current host character set is `ASCII'.
10354 The current target character set is `IBM1047'.
10355 (@value{GDBP}) print ascii_hello
10356 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10357 (@value{GDBP}) print ascii_hello[0]
10359 (@value{GDBP}) print ibm1047_hello
10360 $8 = 0x4016a8 "Hello, world!\n"
10361 (@value{GDBP}) print ibm1047_hello[0]
10366 As above, @value{GDBN} uses the target character set for character and
10367 string literals you use in expressions:
10370 (@value{GDBP}) print '+'
10375 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10378 @node Caching Remote Data
10379 @section Caching Data of Remote Targets
10380 @cindex caching data of remote targets
10382 @value{GDBN} caches data exchanged between the debugger and a
10383 remote target (@pxref{Remote Debugging}). Such caching generally improves
10384 performance, because it reduces the overhead of the remote protocol by
10385 bundling memory reads and writes into large chunks. Unfortunately, simply
10386 caching everything would lead to incorrect results, since @value{GDBN}
10387 does not necessarily know anything about volatile values, memory-mapped I/O
10388 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10389 memory can be changed @emph{while} a gdb command is executing.
10390 Therefore, by default, @value{GDBN} only caches data
10391 known to be on the stack@footnote{In non-stop mode, it is moderately
10392 rare for a running thread to modify the stack of a stopped thread
10393 in a way that would interfere with a backtrace, and caching of
10394 stack reads provides a significant speed up of remote backtraces.}.
10395 Other regions of memory can be explicitly marked as
10396 cacheable; see @pxref{Memory Region Attributes}.
10399 @kindex set remotecache
10400 @item set remotecache on
10401 @itemx set remotecache off
10402 This option no longer does anything; it exists for compatibility
10405 @kindex show remotecache
10406 @item show remotecache
10407 Show the current state of the obsolete remotecache flag.
10409 @kindex set stack-cache
10410 @item set stack-cache on
10411 @itemx set stack-cache off
10412 Enable or disable caching of stack accesses. When @code{ON}, use
10413 caching. By default, this option is @code{ON}.
10415 @kindex show stack-cache
10416 @item show stack-cache
10417 Show the current state of data caching for memory accesses.
10419 @kindex info dcache
10420 @item info dcache @r{[}line@r{]}
10421 Print the information about the data cache performance. The
10422 information displayed includes the dcache width and depth, and for
10423 each cache line, its number, address, and how many times it was
10424 referenced. This command is useful for debugging the data cache
10427 If a line number is specified, the contents of that line will be
10430 @item set dcache size @var{size}
10431 @cindex dcache size
10432 @kindex set dcache size
10433 Set maximum number of entries in dcache (dcache depth above).
10435 @item set dcache line-size @var{line-size}
10436 @cindex dcache line-size
10437 @kindex set dcache line-size
10438 Set number of bytes each dcache entry caches (dcache width above).
10439 Must be a power of 2.
10441 @item show dcache size
10442 @kindex show dcache size
10443 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10445 @item show dcache line-size
10446 @kindex show dcache line-size
10447 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10451 @node Searching Memory
10452 @section Search Memory
10453 @cindex searching memory
10455 Memory can be searched for a particular sequence of bytes with the
10456 @code{find} command.
10460 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10461 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10462 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10463 etc. The search begins at address @var{start_addr} and continues for either
10464 @var{len} bytes or through to @var{end_addr} inclusive.
10467 @var{s} and @var{n} are optional parameters.
10468 They may be specified in either order, apart or together.
10471 @item @var{s}, search query size
10472 The size of each search query value.
10478 halfwords (two bytes)
10482 giant words (eight bytes)
10485 All values are interpreted in the current language.
10486 This means, for example, that if the current source language is C/C@t{++}
10487 then searching for the string ``hello'' includes the trailing '\0'.
10489 If the value size is not specified, it is taken from the
10490 value's type in the current language.
10491 This is useful when one wants to specify the search
10492 pattern as a mixture of types.
10493 Note that this means, for example, that in the case of C-like languages
10494 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10495 which is typically four bytes.
10497 @item @var{n}, maximum number of finds
10498 The maximum number of matches to print. The default is to print all finds.
10501 You can use strings as search values. Quote them with double-quotes
10503 The string value is copied into the search pattern byte by byte,
10504 regardless of the endianness of the target and the size specification.
10506 The address of each match found is printed as well as a count of the
10507 number of matches found.
10509 The address of the last value found is stored in convenience variable
10511 A count of the number of matches is stored in @samp{$numfound}.
10513 For example, if stopped at the @code{printf} in this function:
10519 static char hello[] = "hello-hello";
10520 static struct @{ char c; short s; int i; @}
10521 __attribute__ ((packed)) mixed
10522 = @{ 'c', 0x1234, 0x87654321 @};
10523 printf ("%s\n", hello);
10528 you get during debugging:
10531 (gdb) find &hello[0], +sizeof(hello), "hello"
10532 0x804956d <hello.1620+6>
10534 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10535 0x8049567 <hello.1620>
10536 0x804956d <hello.1620+6>
10538 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10539 0x8049567 <hello.1620>
10541 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10542 0x8049560 <mixed.1625>
10544 (gdb) print $numfound
10547 $2 = (void *) 0x8049560
10550 @node Optimized Code
10551 @chapter Debugging Optimized Code
10552 @cindex optimized code, debugging
10553 @cindex debugging optimized code
10555 Almost all compilers support optimization. With optimization
10556 disabled, the compiler generates assembly code that corresponds
10557 directly to your source code, in a simplistic way. As the compiler
10558 applies more powerful optimizations, the generated assembly code
10559 diverges from your original source code. With help from debugging
10560 information generated by the compiler, @value{GDBN} can map from
10561 the running program back to constructs from your original source.
10563 @value{GDBN} is more accurate with optimization disabled. If you
10564 can recompile without optimization, it is easier to follow the
10565 progress of your program during debugging. But, there are many cases
10566 where you may need to debug an optimized version.
10568 When you debug a program compiled with @samp{-g -O}, remember that the
10569 optimizer has rearranged your code; the debugger shows you what is
10570 really there. Do not be too surprised when the execution path does not
10571 exactly match your source file! An extreme example: if you define a
10572 variable, but never use it, @value{GDBN} never sees that
10573 variable---because the compiler optimizes it out of existence.
10575 Some things do not work as well with @samp{-g -O} as with just
10576 @samp{-g}, particularly on machines with instruction scheduling. If in
10577 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10578 please report it to us as a bug (including a test case!).
10579 @xref{Variables}, for more information about debugging optimized code.
10582 * Inline Functions:: How @value{GDBN} presents inlining
10583 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10586 @node Inline Functions
10587 @section Inline Functions
10588 @cindex inline functions, debugging
10590 @dfn{Inlining} is an optimization that inserts a copy of the function
10591 body directly at each call site, instead of jumping to a shared
10592 routine. @value{GDBN} displays inlined functions just like
10593 non-inlined functions. They appear in backtraces. You can view their
10594 arguments and local variables, step into them with @code{step}, skip
10595 them with @code{next}, and escape from them with @code{finish}.
10596 You can check whether a function was inlined by using the
10597 @code{info frame} command.
10599 For @value{GDBN} to support inlined functions, the compiler must
10600 record information about inlining in the debug information ---
10601 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10602 other compilers do also. @value{GDBN} only supports inlined functions
10603 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10604 do not emit two required attributes (@samp{DW_AT_call_file} and
10605 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10606 function calls with earlier versions of @value{NGCC}. It instead
10607 displays the arguments and local variables of inlined functions as
10608 local variables in the caller.
10610 The body of an inlined function is directly included at its call site;
10611 unlike a non-inlined function, there are no instructions devoted to
10612 the call. @value{GDBN} still pretends that the call site and the
10613 start of the inlined function are different instructions. Stepping to
10614 the call site shows the call site, and then stepping again shows
10615 the first line of the inlined function, even though no additional
10616 instructions are executed.
10618 This makes source-level debugging much clearer; you can see both the
10619 context of the call and then the effect of the call. Only stepping by
10620 a single instruction using @code{stepi} or @code{nexti} does not do
10621 this; single instruction steps always show the inlined body.
10623 There are some ways that @value{GDBN} does not pretend that inlined
10624 function calls are the same as normal calls:
10628 Setting breakpoints at the call site of an inlined function may not
10629 work, because the call site does not contain any code. @value{GDBN}
10630 may incorrectly move the breakpoint to the next line of the enclosing
10631 function, after the call. This limitation will be removed in a future
10632 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10633 or inside the inlined function instead.
10636 @value{GDBN} cannot locate the return value of inlined calls after
10637 using the @code{finish} command. This is a limitation of compiler-generated
10638 debugging information; after @code{finish}, you can step to the next line
10639 and print a variable where your program stored the return value.
10643 @node Tail Call Frames
10644 @section Tail Call Frames
10645 @cindex tail call frames, debugging
10647 Function @code{B} can call function @code{C} in its very last statement. In
10648 unoptimized compilation the call of @code{C} is immediately followed by return
10649 instruction at the end of @code{B} code. Optimizing compiler may replace the
10650 call and return in function @code{B} into one jump to function @code{C}
10651 instead. Such use of a jump instruction is called @dfn{tail call}.
10653 During execution of function @code{C}, there will be no indication in the
10654 function call stack frames that it was tail-called from @code{B}. If function
10655 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10656 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10657 some cases @value{GDBN} can determine that @code{C} was tail-called from
10658 @code{B}, and it will then create fictitious call frame for that, with the
10659 return address set up as if @code{B} called @code{C} normally.
10661 This functionality is currently supported only by DWARF 2 debugging format and
10662 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10663 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10666 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10667 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10671 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10673 Stack level 1, frame at 0x7fffffffda30:
10674 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10675 tail call frame, caller of frame at 0x7fffffffda30
10676 source language c++.
10677 Arglist at unknown address.
10678 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10681 The detection of all the possible code path executions can find them ambiguous.
10682 There is no execution history stored (possible @ref{Reverse Execution} is never
10683 used for this purpose) and the last known caller could have reached the known
10684 callee by multiple different jump sequences. In such case @value{GDBN} still
10685 tries to show at least all the unambiguous top tail callers and all the
10686 unambiguous bottom tail calees, if any.
10689 @anchor{set debug entry-values}
10690 @item set debug entry-values
10691 @kindex set debug entry-values
10692 When set to on, enables printing of analysis messages for both frame argument
10693 values at function entry and tail calls. It will show all the possible valid
10694 tail calls code paths it has considered. It will also print the intersection
10695 of them with the final unambiguous (possibly partial or even empty) code path
10698 @item show debug entry-values
10699 @kindex show debug entry-values
10700 Show the current state of analysis messages printing for both frame argument
10701 values at function entry and tail calls.
10704 The analysis messages for tail calls can for example show why the virtual tail
10705 call frame for function @code{c} has not been recognized (due to the indirect
10706 reference by variable @code{x}):
10709 static void __attribute__((noinline, noclone)) c (void);
10710 void (*x) (void) = c;
10711 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10712 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10713 int main (void) @{ x (); return 0; @}
10715 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10716 DW_TAG_GNU_call_site 0x40039a in main
10718 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10721 #1 0x000000000040039a in main () at t.c:5
10724 Another possibility is an ambiguous virtual tail call frames resolution:
10728 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10729 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10730 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10731 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10732 static void __attribute__((noinline, noclone)) b (void)
10733 @{ if (i) c (); else e (); @}
10734 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10735 int main (void) @{ a (); return 0; @}
10737 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10738 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10739 tailcall: reduced: 0x4004d2(a) |
10742 #1 0x00000000004004d2 in a () at t.c:8
10743 #2 0x0000000000400395 in main () at t.c:9
10746 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10747 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10749 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10750 @ifset HAVE_MAKEINFO_CLICK
10751 @set ARROW @click{}
10752 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10753 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10755 @ifclear HAVE_MAKEINFO_CLICK
10757 @set CALLSEQ1B @value{CALLSEQ1A}
10758 @set CALLSEQ2B @value{CALLSEQ2A}
10761 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10762 The code can have possible execution paths @value{CALLSEQ1B} or
10763 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10765 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10766 has found. It then finds another possible calling sequcen - that one is
10767 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10768 printed as the @code{reduced:} calling sequence. That one could have many
10769 futher @code{compare:} and @code{reduced:} statements as long as there remain
10770 any non-ambiguous sequence entries.
10772 For the frame of function @code{b} in both cases there are different possible
10773 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10774 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10775 therefore this one is displayed to the user while the ambiguous frames are
10778 There can be also reasons why printing of frame argument values at function
10783 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10784 static void __attribute__((noinline, noclone)) a (int i);
10785 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10786 static void __attribute__((noinline, noclone)) a (int i)
10787 @{ if (i) b (i - 1); else c (0); @}
10788 int main (void) @{ a (5); return 0; @}
10791 #0 c (i=i@@entry=0) at t.c:2
10792 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10793 function "a" at 0x400420 can call itself via tail calls
10794 i=<optimized out>) at t.c:6
10795 #2 0x000000000040036e in main () at t.c:7
10798 @value{GDBN} cannot find out from the inferior state if and how many times did
10799 function @code{a} call itself (via function @code{b}) as these calls would be
10800 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10801 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10802 prints @code{<optimized out>} instead.
10805 @chapter C Preprocessor Macros
10807 Some languages, such as C and C@t{++}, provide a way to define and invoke
10808 ``preprocessor macros'' which expand into strings of tokens.
10809 @value{GDBN} can evaluate expressions containing macro invocations, show
10810 the result of macro expansion, and show a macro's definition, including
10811 where it was defined.
10813 You may need to compile your program specially to provide @value{GDBN}
10814 with information about preprocessor macros. Most compilers do not
10815 include macros in their debugging information, even when you compile
10816 with the @option{-g} flag. @xref{Compilation}.
10818 A program may define a macro at one point, remove that definition later,
10819 and then provide a different definition after that. Thus, at different
10820 points in the program, a macro may have different definitions, or have
10821 no definition at all. If there is a current stack frame, @value{GDBN}
10822 uses the macros in scope at that frame's source code line. Otherwise,
10823 @value{GDBN} uses the macros in scope at the current listing location;
10826 Whenever @value{GDBN} evaluates an expression, it always expands any
10827 macro invocations present in the expression. @value{GDBN} also provides
10828 the following commands for working with macros explicitly.
10832 @kindex macro expand
10833 @cindex macro expansion, showing the results of preprocessor
10834 @cindex preprocessor macro expansion, showing the results of
10835 @cindex expanding preprocessor macros
10836 @item macro expand @var{expression}
10837 @itemx macro exp @var{expression}
10838 Show the results of expanding all preprocessor macro invocations in
10839 @var{expression}. Since @value{GDBN} simply expands macros, but does
10840 not parse the result, @var{expression} need not be a valid expression;
10841 it can be any string of tokens.
10844 @item macro expand-once @var{expression}
10845 @itemx macro exp1 @var{expression}
10846 @cindex expand macro once
10847 @i{(This command is not yet implemented.)} Show the results of
10848 expanding those preprocessor macro invocations that appear explicitly in
10849 @var{expression}. Macro invocations appearing in that expansion are
10850 left unchanged. This command allows you to see the effect of a
10851 particular macro more clearly, without being confused by further
10852 expansions. Since @value{GDBN} simply expands macros, but does not
10853 parse the result, @var{expression} need not be a valid expression; it
10854 can be any string of tokens.
10857 @cindex macro definition, showing
10858 @cindex definition of a macro, showing
10859 @cindex macros, from debug info
10860 @item info macro [-a|-all] [--] @var{macro}
10861 Show the current definition or all definitions of the named @var{macro},
10862 and describe the source location or compiler command-line where that
10863 definition was established. The optional double dash is to signify the end of
10864 argument processing and the beginning of @var{macro} for non C-like macros where
10865 the macro may begin with a hyphen.
10867 @kindex info macros
10868 @item info macros @var{linespec}
10869 Show all macro definitions that are in effect at the location specified
10870 by @var{linespec}, and describe the source location or compiler
10871 command-line where those definitions were established.
10873 @kindex macro define
10874 @cindex user-defined macros
10875 @cindex defining macros interactively
10876 @cindex macros, user-defined
10877 @item macro define @var{macro} @var{replacement-list}
10878 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10879 Introduce a definition for a preprocessor macro named @var{macro},
10880 invocations of which are replaced by the tokens given in
10881 @var{replacement-list}. The first form of this command defines an
10882 ``object-like'' macro, which takes no arguments; the second form
10883 defines a ``function-like'' macro, which takes the arguments given in
10886 A definition introduced by this command is in scope in every
10887 expression evaluated in @value{GDBN}, until it is removed with the
10888 @code{macro undef} command, described below. The definition overrides
10889 all definitions for @var{macro} present in the program being debugged,
10890 as well as any previous user-supplied definition.
10892 @kindex macro undef
10893 @item macro undef @var{macro}
10894 Remove any user-supplied definition for the macro named @var{macro}.
10895 This command only affects definitions provided with the @code{macro
10896 define} command, described above; it cannot remove definitions present
10897 in the program being debugged.
10901 List all the macros defined using the @code{macro define} command.
10904 @cindex macros, example of debugging with
10905 Here is a transcript showing the above commands in action. First, we
10906 show our source files:
10911 #include "sample.h"
10914 #define ADD(x) (M + x)
10919 printf ("Hello, world!\n");
10921 printf ("We're so creative.\n");
10923 printf ("Goodbye, world!\n");
10930 Now, we compile the program using the @sc{gnu} C compiler,
10931 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10932 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10933 and @option{-gdwarf-4}; we recommend always choosing the most recent
10934 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10935 includes information about preprocessor macros in the debugging
10939 $ gcc -gdwarf-2 -g3 sample.c -o sample
10943 Now, we start @value{GDBN} on our sample program:
10947 GNU gdb 2002-05-06-cvs
10948 Copyright 2002 Free Software Foundation, Inc.
10949 GDB is free software, @dots{}
10953 We can expand macros and examine their definitions, even when the
10954 program is not running. @value{GDBN} uses the current listing position
10955 to decide which macro definitions are in scope:
10958 (@value{GDBP}) list main
10961 5 #define ADD(x) (M + x)
10966 10 printf ("Hello, world!\n");
10968 12 printf ("We're so creative.\n");
10969 (@value{GDBP}) info macro ADD
10970 Defined at /home/jimb/gdb/macros/play/sample.c:5
10971 #define ADD(x) (M + x)
10972 (@value{GDBP}) info macro Q
10973 Defined at /home/jimb/gdb/macros/play/sample.h:1
10974 included at /home/jimb/gdb/macros/play/sample.c:2
10976 (@value{GDBP}) macro expand ADD(1)
10977 expands to: (42 + 1)
10978 (@value{GDBP}) macro expand-once ADD(1)
10979 expands to: once (M + 1)
10983 In the example above, note that @code{macro expand-once} expands only
10984 the macro invocation explicit in the original text --- the invocation of
10985 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10986 which was introduced by @code{ADD}.
10988 Once the program is running, @value{GDBN} uses the macro definitions in
10989 force at the source line of the current stack frame:
10992 (@value{GDBP}) break main
10993 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10995 Starting program: /home/jimb/gdb/macros/play/sample
10997 Breakpoint 1, main () at sample.c:10
10998 10 printf ("Hello, world!\n");
11002 At line 10, the definition of the macro @code{N} at line 9 is in force:
11005 (@value{GDBP}) info macro N
11006 Defined at /home/jimb/gdb/macros/play/sample.c:9
11008 (@value{GDBP}) macro expand N Q M
11009 expands to: 28 < 42
11010 (@value{GDBP}) print N Q M
11015 As we step over directives that remove @code{N}'s definition, and then
11016 give it a new definition, @value{GDBN} finds the definition (or lack
11017 thereof) in force at each point:
11020 (@value{GDBP}) next
11022 12 printf ("We're so creative.\n");
11023 (@value{GDBP}) info macro N
11024 The symbol `N' has no definition as a C/C++ preprocessor macro
11025 at /home/jimb/gdb/macros/play/sample.c:12
11026 (@value{GDBP}) next
11028 14 printf ("Goodbye, world!\n");
11029 (@value{GDBP}) info macro N
11030 Defined at /home/jimb/gdb/macros/play/sample.c:13
11032 (@value{GDBP}) macro expand N Q M
11033 expands to: 1729 < 42
11034 (@value{GDBP}) print N Q M
11039 In addition to source files, macros can be defined on the compilation command
11040 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11041 such a way, @value{GDBN} displays the location of their definition as line zero
11042 of the source file submitted to the compiler.
11045 (@value{GDBP}) info macro __STDC__
11046 Defined at /home/jimb/gdb/macros/play/sample.c:0
11053 @chapter Tracepoints
11054 @c This chapter is based on the documentation written by Michael
11055 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11057 @cindex tracepoints
11058 In some applications, it is not feasible for the debugger to interrupt
11059 the program's execution long enough for the developer to learn
11060 anything helpful about its behavior. If the program's correctness
11061 depends on its real-time behavior, delays introduced by a debugger
11062 might cause the program to change its behavior drastically, or perhaps
11063 fail, even when the code itself is correct. It is useful to be able
11064 to observe the program's behavior without interrupting it.
11066 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11067 specify locations in the program, called @dfn{tracepoints}, and
11068 arbitrary expressions to evaluate when those tracepoints are reached.
11069 Later, using the @code{tfind} command, you can examine the values
11070 those expressions had when the program hit the tracepoints. The
11071 expressions may also denote objects in memory---structures or arrays,
11072 for example---whose values @value{GDBN} should record; while visiting
11073 a particular tracepoint, you may inspect those objects as if they were
11074 in memory at that moment. However, because @value{GDBN} records these
11075 values without interacting with you, it can do so quickly and
11076 unobtrusively, hopefully not disturbing the program's behavior.
11078 The tracepoint facility is currently available only for remote
11079 targets. @xref{Targets}. In addition, your remote target must know
11080 how to collect trace data. This functionality is implemented in the
11081 remote stub; however, none of the stubs distributed with @value{GDBN}
11082 support tracepoints as of this writing. The format of the remote
11083 packets used to implement tracepoints are described in @ref{Tracepoint
11086 It is also possible to get trace data from a file, in a manner reminiscent
11087 of corefiles; you specify the filename, and use @code{tfind} to search
11088 through the file. @xref{Trace Files}, for more details.
11090 This chapter describes the tracepoint commands and features.
11093 * Set Tracepoints::
11094 * Analyze Collected Data::
11095 * Tracepoint Variables::
11099 @node Set Tracepoints
11100 @section Commands to Set Tracepoints
11102 Before running such a @dfn{trace experiment}, an arbitrary number of
11103 tracepoints can be set. A tracepoint is actually a special type of
11104 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11105 standard breakpoint commands. For instance, as with breakpoints,
11106 tracepoint numbers are successive integers starting from one, and many
11107 of the commands associated with tracepoints take the tracepoint number
11108 as their argument, to identify which tracepoint to work on.
11110 For each tracepoint, you can specify, in advance, some arbitrary set
11111 of data that you want the target to collect in the trace buffer when
11112 it hits that tracepoint. The collected data can include registers,
11113 local variables, or global data. Later, you can use @value{GDBN}
11114 commands to examine the values these data had at the time the
11115 tracepoint was hit.
11117 Tracepoints do not support every breakpoint feature. Ignore counts on
11118 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11119 commands when they are hit. Tracepoints may not be thread-specific
11122 @cindex fast tracepoints
11123 Some targets may support @dfn{fast tracepoints}, which are inserted in
11124 a different way (such as with a jump instead of a trap), that is
11125 faster but possibly restricted in where they may be installed.
11127 @cindex static tracepoints
11128 @cindex markers, static tracepoints
11129 @cindex probing markers, static tracepoints
11130 Regular and fast tracepoints are dynamic tracing facilities, meaning
11131 that they can be used to insert tracepoints at (almost) any location
11132 in the target. Some targets may also support controlling @dfn{static
11133 tracepoints} from @value{GDBN}. With static tracing, a set of
11134 instrumentation points, also known as @dfn{markers}, are embedded in
11135 the target program, and can be activated or deactivated by name or
11136 address. These are usually placed at locations which facilitate
11137 investigating what the target is actually doing. @value{GDBN}'s
11138 support for static tracing includes being able to list instrumentation
11139 points, and attach them with @value{GDBN} defined high level
11140 tracepoints that expose the whole range of convenience of
11141 @value{GDBN}'s tracepoints support. Namely, support for collecting
11142 registers values and values of global or local (to the instrumentation
11143 point) variables; tracepoint conditions and trace state variables.
11144 The act of installing a @value{GDBN} static tracepoint on an
11145 instrumentation point, or marker, is referred to as @dfn{probing} a
11146 static tracepoint marker.
11148 @code{gdbserver} supports tracepoints on some target systems.
11149 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11151 This section describes commands to set tracepoints and associated
11152 conditions and actions.
11155 * Create and Delete Tracepoints::
11156 * Enable and Disable Tracepoints::
11157 * Tracepoint Passcounts::
11158 * Tracepoint Conditions::
11159 * Trace State Variables::
11160 * Tracepoint Actions::
11161 * Listing Tracepoints::
11162 * Listing Static Tracepoint Markers::
11163 * Starting and Stopping Trace Experiments::
11164 * Tracepoint Restrictions::
11167 @node Create and Delete Tracepoints
11168 @subsection Create and Delete Tracepoints
11171 @cindex set tracepoint
11173 @item trace @var{location}
11174 The @code{trace} command is very similar to the @code{break} command.
11175 Its argument @var{location} can be a source line, a function name, or
11176 an address in the target program. @xref{Specify Location}. The
11177 @code{trace} command defines a tracepoint, which is a point in the
11178 target program where the debugger will briefly stop, collect some
11179 data, and then allow the program to continue. Setting a tracepoint or
11180 changing its actions takes effect immediately if the remote stub
11181 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11183 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11184 these changes don't take effect until the next @code{tstart}
11185 command, and once a trace experiment is running, further changes will
11186 not have any effect until the next trace experiment starts. In addition,
11187 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11188 address is not yet resolved. (This is similar to pending breakpoints.)
11189 Pending tracepoints are not downloaded to the target and not installed
11190 until they are resolved. The resolution of pending tracepoints requires
11191 @value{GDBN} support---when debugging with the remote target, and
11192 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11193 tracing}), pending tracepoints can not be resolved (and downloaded to
11194 the remote stub) while @value{GDBN} is disconnected.
11196 Here are some examples of using the @code{trace} command:
11199 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11201 (@value{GDBP}) @b{trace +2} // 2 lines forward
11203 (@value{GDBP}) @b{trace my_function} // first source line of function
11205 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11207 (@value{GDBP}) @b{trace *0x2117c4} // an address
11211 You can abbreviate @code{trace} as @code{tr}.
11213 @item trace @var{location} if @var{cond}
11214 Set a tracepoint with condition @var{cond}; evaluate the expression
11215 @var{cond} each time the tracepoint is reached, and collect data only
11216 if the value is nonzero---that is, if @var{cond} evaluates as true.
11217 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11218 information on tracepoint conditions.
11220 @item ftrace @var{location} [ if @var{cond} ]
11221 @cindex set fast tracepoint
11222 @cindex fast tracepoints, setting
11224 The @code{ftrace} command sets a fast tracepoint. For targets that
11225 support them, fast tracepoints will use a more efficient but possibly
11226 less general technique to trigger data collection, such as a jump
11227 instruction instead of a trap, or some sort of hardware support. It
11228 may not be possible to create a fast tracepoint at the desired
11229 location, in which case the command will exit with an explanatory
11232 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11235 On 32-bit x86-architecture systems, fast tracepoints normally need to
11236 be placed at an instruction that is 5 bytes or longer, but can be
11237 placed at 4-byte instructions if the low 64K of memory of the target
11238 program is available to install trampolines. Some Unix-type systems,
11239 such as @sc{gnu}/Linux, exclude low addresses from the program's
11240 address space; but for instance with the Linux kernel it is possible
11241 to let @value{GDBN} use this area by doing a @command{sysctl} command
11242 to set the @code{mmap_min_addr} kernel parameter, as in
11245 sudo sysctl -w vm.mmap_min_addr=32768
11249 which sets the low address to 32K, which leaves plenty of room for
11250 trampolines. The minimum address should be set to a page boundary.
11252 @item strace @var{location} [ if @var{cond} ]
11253 @cindex set static tracepoint
11254 @cindex static tracepoints, setting
11255 @cindex probe static tracepoint marker
11257 The @code{strace} command sets a static tracepoint. For targets that
11258 support it, setting a static tracepoint probes a static
11259 instrumentation point, or marker, found at @var{location}. It may not
11260 be possible to set a static tracepoint at the desired location, in
11261 which case the command will exit with an explanatory message.
11263 @value{GDBN} handles arguments to @code{strace} exactly as for
11264 @code{trace}, with the addition that the user can also specify
11265 @code{-m @var{marker}} as @var{location}. This probes the marker
11266 identified by the @var{marker} string identifier. This identifier
11267 depends on the static tracepoint backend library your program is
11268 using. You can find all the marker identifiers in the @samp{ID} field
11269 of the @code{info static-tracepoint-markers} command output.
11270 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11271 Markers}. For example, in the following small program using the UST
11277 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11282 the marker id is composed of joining the first two arguments to the
11283 @code{trace_mark} call with a slash, which translates to:
11286 (@value{GDBP}) info static-tracepoint-markers
11287 Cnt Enb ID Address What
11288 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11294 so you may probe the marker above with:
11297 (@value{GDBP}) strace -m ust/bar33
11300 Static tracepoints accept an extra collect action --- @code{collect
11301 $_sdata}. This collects arbitrary user data passed in the probe point
11302 call to the tracing library. In the UST example above, you'll see
11303 that the third argument to @code{trace_mark} is a printf-like format
11304 string. The user data is then the result of running that formating
11305 string against the following arguments. Note that @code{info
11306 static-tracepoint-markers} command output lists that format string in
11307 the @samp{Data:} field.
11309 You can inspect this data when analyzing the trace buffer, by printing
11310 the $_sdata variable like any other variable available to
11311 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11314 @cindex last tracepoint number
11315 @cindex recent tracepoint number
11316 @cindex tracepoint number
11317 The convenience variable @code{$tpnum} records the tracepoint number
11318 of the most recently set tracepoint.
11320 @kindex delete tracepoint
11321 @cindex tracepoint deletion
11322 @item delete tracepoint @r{[}@var{num}@r{]}
11323 Permanently delete one or more tracepoints. With no argument, the
11324 default is to delete all tracepoints. Note that the regular
11325 @code{delete} command can remove tracepoints also.
11330 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11332 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11336 You can abbreviate this command as @code{del tr}.
11339 @node Enable and Disable Tracepoints
11340 @subsection Enable and Disable Tracepoints
11342 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11345 @kindex disable tracepoint
11346 @item disable tracepoint @r{[}@var{num}@r{]}
11347 Disable tracepoint @var{num}, or all tracepoints if no argument
11348 @var{num} is given. A disabled tracepoint will have no effect during
11349 a trace experiment, but it is not forgotten. You can re-enable
11350 a disabled tracepoint using the @code{enable tracepoint} command.
11351 If the command is issued during a trace experiment and the debug target
11352 has support for disabling tracepoints during a trace experiment, then the
11353 change will be effective immediately. Otherwise, it will be applied to the
11354 next trace experiment.
11356 @kindex enable tracepoint
11357 @item enable tracepoint @r{[}@var{num}@r{]}
11358 Enable tracepoint @var{num}, or all tracepoints. If this command is
11359 issued during a trace experiment and the debug target supports enabling
11360 tracepoints during a trace experiment, then the enabled tracepoints will
11361 become effective immediately. Otherwise, they will become effective the
11362 next time a trace experiment is run.
11365 @node Tracepoint Passcounts
11366 @subsection Tracepoint Passcounts
11370 @cindex tracepoint pass count
11371 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11372 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11373 automatically stop a trace experiment. If a tracepoint's passcount is
11374 @var{n}, then the trace experiment will be automatically stopped on
11375 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11376 @var{num} is not specified, the @code{passcount} command sets the
11377 passcount of the most recently defined tracepoint. If no passcount is
11378 given, the trace experiment will run until stopped explicitly by the
11384 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11385 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11387 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11388 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11389 (@value{GDBP}) @b{trace foo}
11390 (@value{GDBP}) @b{pass 3}
11391 (@value{GDBP}) @b{trace bar}
11392 (@value{GDBP}) @b{pass 2}
11393 (@value{GDBP}) @b{trace baz}
11394 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11395 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11396 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11397 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11401 @node Tracepoint Conditions
11402 @subsection Tracepoint Conditions
11403 @cindex conditional tracepoints
11404 @cindex tracepoint conditions
11406 The simplest sort of tracepoint collects data every time your program
11407 reaches a specified place. You can also specify a @dfn{condition} for
11408 a tracepoint. A condition is just a Boolean expression in your
11409 programming language (@pxref{Expressions, ,Expressions}). A
11410 tracepoint with a condition evaluates the expression each time your
11411 program reaches it, and data collection happens only if the condition
11414 Tracepoint conditions can be specified when a tracepoint is set, by
11415 using @samp{if} in the arguments to the @code{trace} command.
11416 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11417 also be set or changed at any time with the @code{condition} command,
11418 just as with breakpoints.
11420 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11421 the conditional expression itself. Instead, @value{GDBN} encodes the
11422 expression into an agent expression (@pxref{Agent Expressions})
11423 suitable for execution on the target, independently of @value{GDBN}.
11424 Global variables become raw memory locations, locals become stack
11425 accesses, and so forth.
11427 For instance, suppose you have a function that is usually called
11428 frequently, but should not be called after an error has occurred. You
11429 could use the following tracepoint command to collect data about calls
11430 of that function that happen while the error code is propagating
11431 through the program; an unconditional tracepoint could end up
11432 collecting thousands of useless trace frames that you would have to
11436 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11439 @node Trace State Variables
11440 @subsection Trace State Variables
11441 @cindex trace state variables
11443 A @dfn{trace state variable} is a special type of variable that is
11444 created and managed by target-side code. The syntax is the same as
11445 that for GDB's convenience variables (a string prefixed with ``$''),
11446 but they are stored on the target. They must be created explicitly,
11447 using a @code{tvariable} command. They are always 64-bit signed
11450 Trace state variables are remembered by @value{GDBN}, and downloaded
11451 to the target along with tracepoint information when the trace
11452 experiment starts. There are no intrinsic limits on the number of
11453 trace state variables, beyond memory limitations of the target.
11455 @cindex convenience variables, and trace state variables
11456 Although trace state variables are managed by the target, you can use
11457 them in print commands and expressions as if they were convenience
11458 variables; @value{GDBN} will get the current value from the target
11459 while the trace experiment is running. Trace state variables share
11460 the same namespace as other ``$'' variables, which means that you
11461 cannot have trace state variables with names like @code{$23} or
11462 @code{$pc}, nor can you have a trace state variable and a convenience
11463 variable with the same name.
11467 @item tvariable $@var{name} [ = @var{expression} ]
11469 The @code{tvariable} command creates a new trace state variable named
11470 @code{$@var{name}}, and optionally gives it an initial value of
11471 @var{expression}. @var{expression} is evaluated when this command is
11472 entered; the result will be converted to an integer if possible,
11473 otherwise @value{GDBN} will report an error. A subsequent
11474 @code{tvariable} command specifying the same name does not create a
11475 variable, but instead assigns the supplied initial value to the
11476 existing variable of that name, overwriting any previous initial
11477 value. The default initial value is 0.
11479 @item info tvariables
11480 @kindex info tvariables
11481 List all the trace state variables along with their initial values.
11482 Their current values may also be displayed, if the trace experiment is
11485 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11486 @kindex delete tvariable
11487 Delete the given trace state variables, or all of them if no arguments
11492 @node Tracepoint Actions
11493 @subsection Tracepoint Action Lists
11497 @cindex tracepoint actions
11498 @item actions @r{[}@var{num}@r{]}
11499 This command will prompt for a list of actions to be taken when the
11500 tracepoint is hit. If the tracepoint number @var{num} is not
11501 specified, this command sets the actions for the one that was most
11502 recently defined (so that you can define a tracepoint and then say
11503 @code{actions} without bothering about its number). You specify the
11504 actions themselves on the following lines, one action at a time, and
11505 terminate the actions list with a line containing just @code{end}. So
11506 far, the only defined actions are @code{collect}, @code{teval}, and
11507 @code{while-stepping}.
11509 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11510 Commands, ,Breakpoint Command Lists}), except that only the defined
11511 actions are allowed; any other @value{GDBN} command is rejected.
11513 @cindex remove actions from a tracepoint
11514 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11515 and follow it immediately with @samp{end}.
11518 (@value{GDBP}) @b{collect @var{data}} // collect some data
11520 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11522 (@value{GDBP}) @b{end} // signals the end of actions.
11525 In the following example, the action list begins with @code{collect}
11526 commands indicating the things to be collected when the tracepoint is
11527 hit. Then, in order to single-step and collect additional data
11528 following the tracepoint, a @code{while-stepping} command is used,
11529 followed by the list of things to be collected after each step in a
11530 sequence of single steps. The @code{while-stepping} command is
11531 terminated by its own separate @code{end} command. Lastly, the action
11532 list is terminated by an @code{end} command.
11535 (@value{GDBP}) @b{trace foo}
11536 (@value{GDBP}) @b{actions}
11537 Enter actions for tracepoint 1, one per line:
11540 > while-stepping 12
11541 > collect $pc, arr[i]
11546 @kindex collect @r{(tracepoints)}
11547 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11548 Collect values of the given expressions when the tracepoint is hit.
11549 This command accepts a comma-separated list of any valid expressions.
11550 In addition to global, static, or local variables, the following
11551 special arguments are supported:
11555 Collect all registers.
11558 Collect all function arguments.
11561 Collect all local variables.
11564 Collect the return address. This is helpful if you want to see more
11568 Collects the number of arguments from the static probe at which the
11569 tracepoint is located.
11570 @xref{Static Probe Points}.
11572 @item $_probe_arg@var{n}
11573 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11574 from the static probe at which the tracepoint is located.
11575 @xref{Static Probe Points}.
11578 @vindex $_sdata@r{, collect}
11579 Collect static tracepoint marker specific data. Only available for
11580 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11581 Lists}. On the UST static tracepoints library backend, an
11582 instrumentation point resembles a @code{printf} function call. The
11583 tracing library is able to collect user specified data formatted to a
11584 character string using the format provided by the programmer that
11585 instrumented the program. Other backends have similar mechanisms.
11586 Here's an example of a UST marker call:
11589 const char master_name[] = "$your_name";
11590 trace_mark(channel1, marker1, "hello %s", master_name)
11593 In this case, collecting @code{$_sdata} collects the string
11594 @samp{hello $yourname}. When analyzing the trace buffer, you can
11595 inspect @samp{$_sdata} like any other variable available to
11599 You can give several consecutive @code{collect} commands, each one
11600 with a single argument, or one @code{collect} command with several
11601 arguments separated by commas; the effect is the same.
11603 The optional @var{mods} changes the usual handling of the arguments.
11604 @code{s} requests that pointers to chars be handled as strings, in
11605 particular collecting the contents of the memory being pointed at, up
11606 to the first zero. The upper bound is by default the value of the
11607 @code{print elements} variable; if @code{s} is followed by a decimal
11608 number, that is the upper bound instead. So for instance
11609 @samp{collect/s25 mystr} collects as many as 25 characters at
11612 The command @code{info scope} (@pxref{Symbols, info scope}) is
11613 particularly useful for figuring out what data to collect.
11615 @kindex teval @r{(tracepoints)}
11616 @item teval @var{expr1}, @var{expr2}, @dots{}
11617 Evaluate the given expressions when the tracepoint is hit. This
11618 command accepts a comma-separated list of expressions. The results
11619 are discarded, so this is mainly useful for assigning values to trace
11620 state variables (@pxref{Trace State Variables}) without adding those
11621 values to the trace buffer, as would be the case if the @code{collect}
11624 @kindex while-stepping @r{(tracepoints)}
11625 @item while-stepping @var{n}
11626 Perform @var{n} single-step instruction traces after the tracepoint,
11627 collecting new data after each step. The @code{while-stepping}
11628 command is followed by the list of what to collect while stepping
11629 (followed by its own @code{end} command):
11632 > while-stepping 12
11633 > collect $regs, myglobal
11639 Note that @code{$pc} is not automatically collected by
11640 @code{while-stepping}; you need to explicitly collect that register if
11641 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11644 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11645 @kindex set default-collect
11646 @cindex default collection action
11647 This variable is a list of expressions to collect at each tracepoint
11648 hit. It is effectively an additional @code{collect} action prepended
11649 to every tracepoint action list. The expressions are parsed
11650 individually for each tracepoint, so for instance a variable named
11651 @code{xyz} may be interpreted as a global for one tracepoint, and a
11652 local for another, as appropriate to the tracepoint's location.
11654 @item show default-collect
11655 @kindex show default-collect
11656 Show the list of expressions that are collected by default at each
11661 @node Listing Tracepoints
11662 @subsection Listing Tracepoints
11665 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11666 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11667 @cindex information about tracepoints
11668 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11669 Display information about the tracepoint @var{num}. If you don't
11670 specify a tracepoint number, displays information about all the
11671 tracepoints defined so far. The format is similar to that used for
11672 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11673 command, simply restricting itself to tracepoints.
11675 A tracepoint's listing may include additional information specific to
11680 its passcount as given by the @code{passcount @var{n}} command
11683 the state about installed on target of each location
11687 (@value{GDBP}) @b{info trace}
11688 Num Type Disp Enb Address What
11689 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11691 collect globfoo, $regs
11696 2 tracepoint keep y <MULTIPLE>
11698 2.1 y 0x0804859c in func4 at change-loc.h:35
11699 installed on target
11700 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11701 installed on target
11702 2.3 y <PENDING> set_tracepoint
11703 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11704 not installed on target
11709 This command can be abbreviated @code{info tp}.
11712 @node Listing Static Tracepoint Markers
11713 @subsection Listing Static Tracepoint Markers
11716 @kindex info static-tracepoint-markers
11717 @cindex information about static tracepoint markers
11718 @item info static-tracepoint-markers
11719 Display information about all static tracepoint markers defined in the
11722 For each marker, the following columns are printed:
11726 An incrementing counter, output to help readability. This is not a
11729 The marker ID, as reported by the target.
11730 @item Enabled or Disabled
11731 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11732 that are not enabled.
11734 Where the marker is in your program, as a memory address.
11736 Where the marker is in the source for your program, as a file and line
11737 number. If the debug information included in the program does not
11738 allow @value{GDBN} to locate the source of the marker, this column
11739 will be left blank.
11743 In addition, the following information may be printed for each marker:
11747 User data passed to the tracing library by the marker call. In the
11748 UST backend, this is the format string passed as argument to the
11750 @item Static tracepoints probing the marker
11751 The list of static tracepoints attached to the marker.
11755 (@value{GDBP}) info static-tracepoint-markers
11756 Cnt ID Enb Address What
11757 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11758 Data: number1 %d number2 %d
11759 Probed by static tracepoints: #2
11760 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11766 @node Starting and Stopping Trace Experiments
11767 @subsection Starting and Stopping Trace Experiments
11770 @kindex tstart [ @var{notes} ]
11771 @cindex start a new trace experiment
11772 @cindex collected data discarded
11774 This command starts the trace experiment, and begins collecting data.
11775 It has the side effect of discarding all the data collected in the
11776 trace buffer during the previous trace experiment. If any arguments
11777 are supplied, they are taken as a note and stored with the trace
11778 experiment's state. The notes may be arbitrary text, and are
11779 especially useful with disconnected tracing in a multi-user context;
11780 the notes can explain what the trace is doing, supply user contact
11781 information, and so forth.
11783 @kindex tstop [ @var{notes} ]
11784 @cindex stop a running trace experiment
11786 This command stops the trace experiment. If any arguments are
11787 supplied, they are recorded with the experiment as a note. This is
11788 useful if you are stopping a trace started by someone else, for
11789 instance if the trace is interfering with the system's behavior and
11790 needs to be stopped quickly.
11792 @strong{Note}: a trace experiment and data collection may stop
11793 automatically if any tracepoint's passcount is reached
11794 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11797 @cindex status of trace data collection
11798 @cindex trace experiment, status of
11800 This command displays the status of the current trace data
11804 Here is an example of the commands we described so far:
11807 (@value{GDBP}) @b{trace gdb_c_test}
11808 (@value{GDBP}) @b{actions}
11809 Enter actions for tracepoint #1, one per line.
11810 > collect $regs,$locals,$args
11811 > while-stepping 11
11815 (@value{GDBP}) @b{tstart}
11816 [time passes @dots{}]
11817 (@value{GDBP}) @b{tstop}
11820 @anchor{disconnected tracing}
11821 @cindex disconnected tracing
11822 You can choose to continue running the trace experiment even if
11823 @value{GDBN} disconnects from the target, voluntarily or
11824 involuntarily. For commands such as @code{detach}, the debugger will
11825 ask what you want to do with the trace. But for unexpected
11826 terminations (@value{GDBN} crash, network outage), it would be
11827 unfortunate to lose hard-won trace data, so the variable
11828 @code{disconnected-tracing} lets you decide whether the trace should
11829 continue running without @value{GDBN}.
11832 @item set disconnected-tracing on
11833 @itemx set disconnected-tracing off
11834 @kindex set disconnected-tracing
11835 Choose whether a tracing run should continue to run if @value{GDBN}
11836 has disconnected from the target. Note that @code{detach} or
11837 @code{quit} will ask you directly what to do about a running trace no
11838 matter what this variable's setting, so the variable is mainly useful
11839 for handling unexpected situations, such as loss of the network.
11841 @item show disconnected-tracing
11842 @kindex show disconnected-tracing
11843 Show the current choice for disconnected tracing.
11847 When you reconnect to the target, the trace experiment may or may not
11848 still be running; it might have filled the trace buffer in the
11849 meantime, or stopped for one of the other reasons. If it is running,
11850 it will continue after reconnection.
11852 Upon reconnection, the target will upload information about the
11853 tracepoints in effect. @value{GDBN} will then compare that
11854 information to the set of tracepoints currently defined, and attempt
11855 to match them up, allowing for the possibility that the numbers may
11856 have changed due to creation and deletion in the meantime. If one of
11857 the target's tracepoints does not match any in @value{GDBN}, the
11858 debugger will create a new tracepoint, so that you have a number with
11859 which to specify that tracepoint. This matching-up process is
11860 necessarily heuristic, and it may result in useless tracepoints being
11861 created; you may simply delete them if they are of no use.
11863 @cindex circular trace buffer
11864 If your target agent supports a @dfn{circular trace buffer}, then you
11865 can run a trace experiment indefinitely without filling the trace
11866 buffer; when space runs out, the agent deletes already-collected trace
11867 frames, oldest first, until there is enough room to continue
11868 collecting. This is especially useful if your tracepoints are being
11869 hit too often, and your trace gets terminated prematurely because the
11870 buffer is full. To ask for a circular trace buffer, simply set
11871 @samp{circular-trace-buffer} to on. You can set this at any time,
11872 including during tracing; if the agent can do it, it will change
11873 buffer handling on the fly, otherwise it will not take effect until
11877 @item set circular-trace-buffer on
11878 @itemx set circular-trace-buffer off
11879 @kindex set circular-trace-buffer
11880 Choose whether a tracing run should use a linear or circular buffer
11881 for trace data. A linear buffer will not lose any trace data, but may
11882 fill up prematurely, while a circular buffer will discard old trace
11883 data, but it will have always room for the latest tracepoint hits.
11885 @item show circular-trace-buffer
11886 @kindex show circular-trace-buffer
11887 Show the current choice for the trace buffer. Note that this may not
11888 match the agent's current buffer handling, nor is it guaranteed to
11889 match the setting that might have been in effect during a past run,
11890 for instance if you are looking at frames from a trace file.
11895 @item set trace-buffer-size @var{n}
11896 @itemx set trace-buffer-size unlimited
11897 @kindex set trace-buffer-size
11898 Request that the target use a trace buffer of @var{n} bytes. Not all
11899 targets will honor the request; they may have a compiled-in size for
11900 the trace buffer, or some other limitation. Set to a value of
11901 @code{unlimited} or @code{-1} to let the target use whatever size it
11902 likes. This is also the default.
11904 @item show trace-buffer-size
11905 @kindex show trace-buffer-size
11906 Show the current requested size for the trace buffer. Note that this
11907 will only match the actual size if the target supports size-setting,
11908 and was able to handle the requested size. For instance, if the
11909 target can only change buffer size between runs, this variable will
11910 not reflect the change until the next run starts. Use @code{tstatus}
11911 to get a report of the actual buffer size.
11915 @item set trace-user @var{text}
11916 @kindex set trace-user
11918 @item show trace-user
11919 @kindex show trace-user
11921 @item set trace-notes @var{text}
11922 @kindex set trace-notes
11923 Set the trace run's notes.
11925 @item show trace-notes
11926 @kindex show trace-notes
11927 Show the trace run's notes.
11929 @item set trace-stop-notes @var{text}
11930 @kindex set trace-stop-notes
11931 Set the trace run's stop notes. The handling of the note is as for
11932 @code{tstop} arguments; the set command is convenient way to fix a
11933 stop note that is mistaken or incomplete.
11935 @item show trace-stop-notes
11936 @kindex show trace-stop-notes
11937 Show the trace run's stop notes.
11941 @node Tracepoint Restrictions
11942 @subsection Tracepoint Restrictions
11944 @cindex tracepoint restrictions
11945 There are a number of restrictions on the use of tracepoints. As
11946 described above, tracepoint data gathering occurs on the target
11947 without interaction from @value{GDBN}. Thus the full capabilities of
11948 the debugger are not available during data gathering, and then at data
11949 examination time, you will be limited by only having what was
11950 collected. The following items describe some common problems, but it
11951 is not exhaustive, and you may run into additional difficulties not
11957 Tracepoint expressions are intended to gather objects (lvalues). Thus
11958 the full flexibility of GDB's expression evaluator is not available.
11959 You cannot call functions, cast objects to aggregate types, access
11960 convenience variables or modify values (except by assignment to trace
11961 state variables). Some language features may implicitly call
11962 functions (for instance Objective-C fields with accessors), and therefore
11963 cannot be collected either.
11966 Collection of local variables, either individually or in bulk with
11967 @code{$locals} or @code{$args}, during @code{while-stepping} may
11968 behave erratically. The stepping action may enter a new scope (for
11969 instance by stepping into a function), or the location of the variable
11970 may change (for instance it is loaded into a register). The
11971 tracepoint data recorded uses the location information for the
11972 variables that is correct for the tracepoint location. When the
11973 tracepoint is created, it is not possible, in general, to determine
11974 where the steps of a @code{while-stepping} sequence will advance the
11975 program---particularly if a conditional branch is stepped.
11978 Collection of an incompletely-initialized or partially-destroyed object
11979 may result in something that @value{GDBN} cannot display, or displays
11980 in a misleading way.
11983 When @value{GDBN} displays a pointer to character it automatically
11984 dereferences the pointer to also display characters of the string
11985 being pointed to. However, collecting the pointer during tracing does
11986 not automatically collect the string. You need to explicitly
11987 dereference the pointer and provide size information if you want to
11988 collect not only the pointer, but the memory pointed to. For example,
11989 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11993 It is not possible to collect a complete stack backtrace at a
11994 tracepoint. Instead, you may collect the registers and a few hundred
11995 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11996 (adjust to use the name of the actual stack pointer register on your
11997 target architecture, and the amount of stack you wish to capture).
11998 Then the @code{backtrace} command will show a partial backtrace when
11999 using a trace frame. The number of stack frames that can be examined
12000 depends on the sizes of the frames in the collected stack. Note that
12001 if you ask for a block so large that it goes past the bottom of the
12002 stack, the target agent may report an error trying to read from an
12006 If you do not collect registers at a tracepoint, @value{GDBN} can
12007 infer that the value of @code{$pc} must be the same as the address of
12008 the tracepoint and use that when you are looking at a trace frame
12009 for that tracepoint. However, this cannot work if the tracepoint has
12010 multiple locations (for instance if it was set in a function that was
12011 inlined), or if it has a @code{while-stepping} loop. In those cases
12012 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12017 @node Analyze Collected Data
12018 @section Using the Collected Data
12020 After the tracepoint experiment ends, you use @value{GDBN} commands
12021 for examining the trace data. The basic idea is that each tracepoint
12022 collects a trace @dfn{snapshot} every time it is hit and another
12023 snapshot every time it single-steps. All these snapshots are
12024 consecutively numbered from zero and go into a buffer, and you can
12025 examine them later. The way you examine them is to @dfn{focus} on a
12026 specific trace snapshot. When the remote stub is focused on a trace
12027 snapshot, it will respond to all @value{GDBN} requests for memory and
12028 registers by reading from the buffer which belongs to that snapshot,
12029 rather than from @emph{real} memory or registers of the program being
12030 debugged. This means that @strong{all} @value{GDBN} commands
12031 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12032 behave as if we were currently debugging the program state as it was
12033 when the tracepoint occurred. Any requests for data that are not in
12034 the buffer will fail.
12037 * tfind:: How to select a trace snapshot
12038 * tdump:: How to display all data for a snapshot
12039 * save tracepoints:: How to save tracepoints for a future run
12043 @subsection @code{tfind @var{n}}
12046 @cindex select trace snapshot
12047 @cindex find trace snapshot
12048 The basic command for selecting a trace snapshot from the buffer is
12049 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12050 counting from zero. If no argument @var{n} is given, the next
12051 snapshot is selected.
12053 Here are the various forms of using the @code{tfind} command.
12057 Find the first snapshot in the buffer. This is a synonym for
12058 @code{tfind 0} (since 0 is the number of the first snapshot).
12061 Stop debugging trace snapshots, resume @emph{live} debugging.
12064 Same as @samp{tfind none}.
12067 No argument means find the next trace snapshot.
12070 Find the previous trace snapshot before the current one. This permits
12071 retracing earlier steps.
12073 @item tfind tracepoint @var{num}
12074 Find the next snapshot associated with tracepoint @var{num}. Search
12075 proceeds forward from the last examined trace snapshot. If no
12076 argument @var{num} is given, it means find the next snapshot collected
12077 for the same tracepoint as the current snapshot.
12079 @item tfind pc @var{addr}
12080 Find the next snapshot associated with the value @var{addr} of the
12081 program counter. Search proceeds forward from the last examined trace
12082 snapshot. If no argument @var{addr} is given, it means find the next
12083 snapshot with the same value of PC as the current snapshot.
12085 @item tfind outside @var{addr1}, @var{addr2}
12086 Find the next snapshot whose PC is outside the given range of
12087 addresses (exclusive).
12089 @item tfind range @var{addr1}, @var{addr2}
12090 Find the next snapshot whose PC is between @var{addr1} and
12091 @var{addr2} (inclusive).
12093 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12094 Find the next snapshot associated with the source line @var{n}. If
12095 the optional argument @var{file} is given, refer to line @var{n} in
12096 that source file. Search proceeds forward from the last examined
12097 trace snapshot. If no argument @var{n} is given, it means find the
12098 next line other than the one currently being examined; thus saying
12099 @code{tfind line} repeatedly can appear to have the same effect as
12100 stepping from line to line in a @emph{live} debugging session.
12103 The default arguments for the @code{tfind} commands are specifically
12104 designed to make it easy to scan through the trace buffer. For
12105 instance, @code{tfind} with no argument selects the next trace
12106 snapshot, and @code{tfind -} with no argument selects the previous
12107 trace snapshot. So, by giving one @code{tfind} command, and then
12108 simply hitting @key{RET} repeatedly you can examine all the trace
12109 snapshots in order. Or, by saying @code{tfind -} and then hitting
12110 @key{RET} repeatedly you can examine the snapshots in reverse order.
12111 The @code{tfind line} command with no argument selects the snapshot
12112 for the next source line executed. The @code{tfind pc} command with
12113 no argument selects the next snapshot with the same program counter
12114 (PC) as the current frame. The @code{tfind tracepoint} command with
12115 no argument selects the next trace snapshot collected by the same
12116 tracepoint as the current one.
12118 In addition to letting you scan through the trace buffer manually,
12119 these commands make it easy to construct @value{GDBN} scripts that
12120 scan through the trace buffer and print out whatever collected data
12121 you are interested in. Thus, if we want to examine the PC, FP, and SP
12122 registers from each trace frame in the buffer, we can say this:
12125 (@value{GDBP}) @b{tfind start}
12126 (@value{GDBP}) @b{while ($trace_frame != -1)}
12127 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12128 $trace_frame, $pc, $sp, $fp
12132 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12133 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12134 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12135 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12136 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12137 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12138 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12139 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12140 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12141 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12142 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12145 Or, if we want to examine the variable @code{X} at each source line in
12149 (@value{GDBP}) @b{tfind start}
12150 (@value{GDBP}) @b{while ($trace_frame != -1)}
12151 > printf "Frame %d, X == %d\n", $trace_frame, X
12161 @subsection @code{tdump}
12163 @cindex dump all data collected at tracepoint
12164 @cindex tracepoint data, display
12166 This command takes no arguments. It prints all the data collected at
12167 the current trace snapshot.
12170 (@value{GDBP}) @b{trace 444}
12171 (@value{GDBP}) @b{actions}
12172 Enter actions for tracepoint #2, one per line:
12173 > collect $regs, $locals, $args, gdb_long_test
12176 (@value{GDBP}) @b{tstart}
12178 (@value{GDBP}) @b{tfind line 444}
12179 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12181 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12183 (@value{GDBP}) @b{tdump}
12184 Data collected at tracepoint 2, trace frame 1:
12185 d0 0xc4aa0085 -995491707
12189 d4 0x71aea3d 119204413
12192 d7 0x380035 3670069
12193 a0 0x19e24a 1696330
12194 a1 0x3000668 50333288
12196 a3 0x322000 3284992
12197 a4 0x3000698 50333336
12198 a5 0x1ad3cc 1758156
12199 fp 0x30bf3c 0x30bf3c
12200 sp 0x30bf34 0x30bf34
12202 pc 0x20b2c8 0x20b2c8
12206 p = 0x20e5b4 "gdb-test"
12213 gdb_long_test = 17 '\021'
12218 @code{tdump} works by scanning the tracepoint's current collection
12219 actions and printing the value of each expression listed. So
12220 @code{tdump} can fail, if after a run, you change the tracepoint's
12221 actions to mention variables that were not collected during the run.
12223 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12224 uses the collected value of @code{$pc} to distinguish between trace
12225 frames that were collected at the tracepoint hit, and frames that were
12226 collected while stepping. This allows it to correctly choose whether
12227 to display the basic list of collections, or the collections from the
12228 body of the while-stepping loop. However, if @code{$pc} was not collected,
12229 then @code{tdump} will always attempt to dump using the basic collection
12230 list, and may fail if a while-stepping frame does not include all the
12231 same data that is collected at the tracepoint hit.
12232 @c This is getting pretty arcane, example would be good.
12234 @node save tracepoints
12235 @subsection @code{save tracepoints @var{filename}}
12236 @kindex save tracepoints
12237 @kindex save-tracepoints
12238 @cindex save tracepoints for future sessions
12240 This command saves all current tracepoint definitions together with
12241 their actions and passcounts, into a file @file{@var{filename}}
12242 suitable for use in a later debugging session. To read the saved
12243 tracepoint definitions, use the @code{source} command (@pxref{Command
12244 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12245 alias for @w{@code{save tracepoints}}
12247 @node Tracepoint Variables
12248 @section Convenience Variables for Tracepoints
12249 @cindex tracepoint variables
12250 @cindex convenience variables for tracepoints
12253 @vindex $trace_frame
12254 @item (int) $trace_frame
12255 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12256 snapshot is selected.
12258 @vindex $tracepoint
12259 @item (int) $tracepoint
12260 The tracepoint for the current trace snapshot.
12262 @vindex $trace_line
12263 @item (int) $trace_line
12264 The line number for the current trace snapshot.
12266 @vindex $trace_file
12267 @item (char []) $trace_file
12268 The source file for the current trace snapshot.
12270 @vindex $trace_func
12271 @item (char []) $trace_func
12272 The name of the function containing @code{$tracepoint}.
12275 Note: @code{$trace_file} is not suitable for use in @code{printf},
12276 use @code{output} instead.
12278 Here's a simple example of using these convenience variables for
12279 stepping through all the trace snapshots and printing some of their
12280 data. Note that these are not the same as trace state variables,
12281 which are managed by the target.
12284 (@value{GDBP}) @b{tfind start}
12286 (@value{GDBP}) @b{while $trace_frame != -1}
12287 > output $trace_file
12288 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12294 @section Using Trace Files
12295 @cindex trace files
12297 In some situations, the target running a trace experiment may no
12298 longer be available; perhaps it crashed, or the hardware was needed
12299 for a different activity. To handle these cases, you can arrange to
12300 dump the trace data into a file, and later use that file as a source
12301 of trace data, via the @code{target tfile} command.
12306 @item tsave [ -r ] @var{filename}
12307 @itemx tsave [-ctf] @var{dirname}
12308 Save the trace data to @var{filename}. By default, this command
12309 assumes that @var{filename} refers to the host filesystem, so if
12310 necessary @value{GDBN} will copy raw trace data up from the target and
12311 then save it. If the target supports it, you can also supply the
12312 optional argument @code{-r} (``remote'') to direct the target to save
12313 the data directly into @var{filename} in its own filesystem, which may be
12314 more efficient if the trace buffer is very large. (Note, however, that
12315 @code{target tfile} can only read from files accessible to the host.)
12316 By default, this command will save trace frame in tfile format.
12317 You can supply the optional argument @code{-ctf} to save date in CTF
12318 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12319 that can be shared by multiple debugging and tracing tools. Please go to
12320 @indicateurl{http://www.efficios.com/ctf} to get more information.
12322 @kindex target tfile
12326 @item target tfile @var{filename}
12327 @itemx target ctf @var{dirname}
12328 Use the file named @var{filename} or directory named @var{dirname} as
12329 a source of trace data. Commands that examine data work as they do with
12330 a live target, but it is not possible to run any new trace experiments.
12331 @code{tstatus} will report the state of the trace run at the moment
12332 the data was saved, as well as the current trace frame you are examining.
12333 @var{filename} or @var{dirname} must be on a filesystem accessible to
12337 (@value{GDBP}) target ctf ctf.ctf
12338 (@value{GDBP}) tfind
12339 Found trace frame 0, tracepoint 2
12340 39 ++a; /* set tracepoint 1 here */
12341 (@value{GDBP}) tdump
12342 Data collected at tracepoint 2, trace frame 0:
12346 c = @{"123", "456", "789", "123", "456", "789"@}
12347 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12355 @chapter Debugging Programs That Use Overlays
12358 If your program is too large to fit completely in your target system's
12359 memory, you can sometimes use @dfn{overlays} to work around this
12360 problem. @value{GDBN} provides some support for debugging programs that
12364 * How Overlays Work:: A general explanation of overlays.
12365 * Overlay Commands:: Managing overlays in @value{GDBN}.
12366 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12367 mapped by asking the inferior.
12368 * Overlay Sample Program:: A sample program using overlays.
12371 @node How Overlays Work
12372 @section How Overlays Work
12373 @cindex mapped overlays
12374 @cindex unmapped overlays
12375 @cindex load address, overlay's
12376 @cindex mapped address
12377 @cindex overlay area
12379 Suppose you have a computer whose instruction address space is only 64
12380 kilobytes long, but which has much more memory which can be accessed by
12381 other means: special instructions, segment registers, or memory
12382 management hardware, for example. Suppose further that you want to
12383 adapt a program which is larger than 64 kilobytes to run on this system.
12385 One solution is to identify modules of your program which are relatively
12386 independent, and need not call each other directly; call these modules
12387 @dfn{overlays}. Separate the overlays from the main program, and place
12388 their machine code in the larger memory. Place your main program in
12389 instruction memory, but leave at least enough space there to hold the
12390 largest overlay as well.
12392 Now, to call a function located in an overlay, you must first copy that
12393 overlay's machine code from the large memory into the space set aside
12394 for it in the instruction memory, and then jump to its entry point
12397 @c NB: In the below the mapped area's size is greater or equal to the
12398 @c size of all overlays. This is intentional to remind the developer
12399 @c that overlays don't necessarily need to be the same size.
12403 Data Instruction Larger
12404 Address Space Address Space Address Space
12405 +-----------+ +-----------+ +-----------+
12407 +-----------+ +-----------+ +-----------+<-- overlay 1
12408 | program | | main | .----| overlay 1 | load address
12409 | variables | | program | | +-----------+
12410 | and heap | | | | | |
12411 +-----------+ | | | +-----------+<-- overlay 2
12412 | | +-----------+ | | | load address
12413 +-----------+ | | | .-| overlay 2 |
12415 mapped --->+-----------+ | | +-----------+
12416 address | | | | | |
12417 | overlay | <-' | | |
12418 | area | <---' +-----------+<-- overlay 3
12419 | | <---. | | load address
12420 +-----------+ `--| overlay 3 |
12427 @anchor{A code overlay}A code overlay
12431 The diagram (@pxref{A code overlay}) shows a system with separate data
12432 and instruction address spaces. To map an overlay, the program copies
12433 its code from the larger address space to the instruction address space.
12434 Since the overlays shown here all use the same mapped address, only one
12435 may be mapped at a time. For a system with a single address space for
12436 data and instructions, the diagram would be similar, except that the
12437 program variables and heap would share an address space with the main
12438 program and the overlay area.
12440 An overlay loaded into instruction memory and ready for use is called a
12441 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12442 instruction memory. An overlay not present (or only partially present)
12443 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12444 is its address in the larger memory. The mapped address is also called
12445 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12446 called the @dfn{load memory address}, or @dfn{LMA}.
12448 Unfortunately, overlays are not a completely transparent way to adapt a
12449 program to limited instruction memory. They introduce a new set of
12450 global constraints you must keep in mind as you design your program:
12455 Before calling or returning to a function in an overlay, your program
12456 must make sure that overlay is actually mapped. Otherwise, the call or
12457 return will transfer control to the right address, but in the wrong
12458 overlay, and your program will probably crash.
12461 If the process of mapping an overlay is expensive on your system, you
12462 will need to choose your overlays carefully to minimize their effect on
12463 your program's performance.
12466 The executable file you load onto your system must contain each
12467 overlay's instructions, appearing at the overlay's load address, not its
12468 mapped address. However, each overlay's instructions must be relocated
12469 and its symbols defined as if the overlay were at its mapped address.
12470 You can use GNU linker scripts to specify different load and relocation
12471 addresses for pieces of your program; see @ref{Overlay Description,,,
12472 ld.info, Using ld: the GNU linker}.
12475 The procedure for loading executable files onto your system must be able
12476 to load their contents into the larger address space as well as the
12477 instruction and data spaces.
12481 The overlay system described above is rather simple, and could be
12482 improved in many ways:
12487 If your system has suitable bank switch registers or memory management
12488 hardware, you could use those facilities to make an overlay's load area
12489 contents simply appear at their mapped address in instruction space.
12490 This would probably be faster than copying the overlay to its mapped
12491 area in the usual way.
12494 If your overlays are small enough, you could set aside more than one
12495 overlay area, and have more than one overlay mapped at a time.
12498 You can use overlays to manage data, as well as instructions. In
12499 general, data overlays are even less transparent to your design than
12500 code overlays: whereas code overlays only require care when you call or
12501 return to functions, data overlays require care every time you access
12502 the data. Also, if you change the contents of a data overlay, you
12503 must copy its contents back out to its load address before you can copy a
12504 different data overlay into the same mapped area.
12509 @node Overlay Commands
12510 @section Overlay Commands
12512 To use @value{GDBN}'s overlay support, each overlay in your program must
12513 correspond to a separate section of the executable file. The section's
12514 virtual memory address and load memory address must be the overlay's
12515 mapped and load addresses. Identifying overlays with sections allows
12516 @value{GDBN} to determine the appropriate address of a function or
12517 variable, depending on whether the overlay is mapped or not.
12519 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12520 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12525 Disable @value{GDBN}'s overlay support. When overlay support is
12526 disabled, @value{GDBN} assumes that all functions and variables are
12527 always present at their mapped addresses. By default, @value{GDBN}'s
12528 overlay support is disabled.
12530 @item overlay manual
12531 @cindex manual overlay debugging
12532 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12533 relies on you to tell it which overlays are mapped, and which are not,
12534 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12535 commands described below.
12537 @item overlay map-overlay @var{overlay}
12538 @itemx overlay map @var{overlay}
12539 @cindex map an overlay
12540 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12541 be the name of the object file section containing the overlay. When an
12542 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12543 functions and variables at their mapped addresses. @value{GDBN} assumes
12544 that any other overlays whose mapped ranges overlap that of
12545 @var{overlay} are now unmapped.
12547 @item overlay unmap-overlay @var{overlay}
12548 @itemx overlay unmap @var{overlay}
12549 @cindex unmap an overlay
12550 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12551 must be the name of the object file section containing the overlay.
12552 When an overlay is unmapped, @value{GDBN} assumes it can find the
12553 overlay's functions and variables at their load addresses.
12556 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12557 consults a data structure the overlay manager maintains in the inferior
12558 to see which overlays are mapped. For details, see @ref{Automatic
12559 Overlay Debugging}.
12561 @item overlay load-target
12562 @itemx overlay load
12563 @cindex reloading the overlay table
12564 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12565 re-reads the table @value{GDBN} automatically each time the inferior
12566 stops, so this command should only be necessary if you have changed the
12567 overlay mapping yourself using @value{GDBN}. This command is only
12568 useful when using automatic overlay debugging.
12570 @item overlay list-overlays
12571 @itemx overlay list
12572 @cindex listing mapped overlays
12573 Display a list of the overlays currently mapped, along with their mapped
12574 addresses, load addresses, and sizes.
12578 Normally, when @value{GDBN} prints a code address, it includes the name
12579 of the function the address falls in:
12582 (@value{GDBP}) print main
12583 $3 = @{int ()@} 0x11a0 <main>
12586 When overlay debugging is enabled, @value{GDBN} recognizes code in
12587 unmapped overlays, and prints the names of unmapped functions with
12588 asterisks around them. For example, if @code{foo} is a function in an
12589 unmapped overlay, @value{GDBN} prints it this way:
12592 (@value{GDBP}) overlay list
12593 No sections are mapped.
12594 (@value{GDBP}) print foo
12595 $5 = @{int (int)@} 0x100000 <*foo*>
12598 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12602 (@value{GDBP}) overlay list
12603 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12604 mapped at 0x1016 - 0x104a
12605 (@value{GDBP}) print foo
12606 $6 = @{int (int)@} 0x1016 <foo>
12609 When overlay debugging is enabled, @value{GDBN} can find the correct
12610 address for functions and variables in an overlay, whether or not the
12611 overlay is mapped. This allows most @value{GDBN} commands, like
12612 @code{break} and @code{disassemble}, to work normally, even on unmapped
12613 code. However, @value{GDBN}'s breakpoint support has some limitations:
12617 @cindex breakpoints in overlays
12618 @cindex overlays, setting breakpoints in
12619 You can set breakpoints in functions in unmapped overlays, as long as
12620 @value{GDBN} can write to the overlay at its load address.
12622 @value{GDBN} can not set hardware or simulator-based breakpoints in
12623 unmapped overlays. However, if you set a breakpoint at the end of your
12624 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12625 you are using manual overlay management), @value{GDBN} will re-set its
12626 breakpoints properly.
12630 @node Automatic Overlay Debugging
12631 @section Automatic Overlay Debugging
12632 @cindex automatic overlay debugging
12634 @value{GDBN} can automatically track which overlays are mapped and which
12635 are not, given some simple co-operation from the overlay manager in the
12636 inferior. If you enable automatic overlay debugging with the
12637 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12638 looks in the inferior's memory for certain variables describing the
12639 current state of the overlays.
12641 Here are the variables your overlay manager must define to support
12642 @value{GDBN}'s automatic overlay debugging:
12646 @item @code{_ovly_table}:
12647 This variable must be an array of the following structures:
12652 /* The overlay's mapped address. */
12655 /* The size of the overlay, in bytes. */
12656 unsigned long size;
12658 /* The overlay's load address. */
12661 /* Non-zero if the overlay is currently mapped;
12663 unsigned long mapped;
12667 @item @code{_novlys}:
12668 This variable must be a four-byte signed integer, holding the total
12669 number of elements in @code{_ovly_table}.
12673 To decide whether a particular overlay is mapped or not, @value{GDBN}
12674 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12675 @code{lma} members equal the VMA and LMA of the overlay's section in the
12676 executable file. When @value{GDBN} finds a matching entry, it consults
12677 the entry's @code{mapped} member to determine whether the overlay is
12680 In addition, your overlay manager may define a function called
12681 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12682 will silently set a breakpoint there. If the overlay manager then
12683 calls this function whenever it has changed the overlay table, this
12684 will enable @value{GDBN} to accurately keep track of which overlays
12685 are in program memory, and update any breakpoints that may be set
12686 in overlays. This will allow breakpoints to work even if the
12687 overlays are kept in ROM or other non-writable memory while they
12688 are not being executed.
12690 @node Overlay Sample Program
12691 @section Overlay Sample Program
12692 @cindex overlay example program
12694 When linking a program which uses overlays, you must place the overlays
12695 at their load addresses, while relocating them to run at their mapped
12696 addresses. To do this, you must write a linker script (@pxref{Overlay
12697 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12698 since linker scripts are specific to a particular host system, target
12699 architecture, and target memory layout, this manual cannot provide
12700 portable sample code demonstrating @value{GDBN}'s overlay support.
12702 However, the @value{GDBN} source distribution does contain an overlaid
12703 program, with linker scripts for a few systems, as part of its test
12704 suite. The program consists of the following files from
12705 @file{gdb/testsuite/gdb.base}:
12709 The main program file.
12711 A simple overlay manager, used by @file{overlays.c}.
12716 Overlay modules, loaded and used by @file{overlays.c}.
12719 Linker scripts for linking the test program on the @code{d10v-elf}
12720 and @code{m32r-elf} targets.
12723 You can build the test program using the @code{d10v-elf} GCC
12724 cross-compiler like this:
12727 $ d10v-elf-gcc -g -c overlays.c
12728 $ d10v-elf-gcc -g -c ovlymgr.c
12729 $ d10v-elf-gcc -g -c foo.c
12730 $ d10v-elf-gcc -g -c bar.c
12731 $ d10v-elf-gcc -g -c baz.c
12732 $ d10v-elf-gcc -g -c grbx.c
12733 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12734 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12737 The build process is identical for any other architecture, except that
12738 you must substitute the appropriate compiler and linker script for the
12739 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12743 @chapter Using @value{GDBN} with Different Languages
12746 Although programming languages generally have common aspects, they are
12747 rarely expressed in the same manner. For instance, in ANSI C,
12748 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12749 Modula-2, it is accomplished by @code{p^}. Values can also be
12750 represented (and displayed) differently. Hex numbers in C appear as
12751 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12753 @cindex working language
12754 Language-specific information is built into @value{GDBN} for some languages,
12755 allowing you to express operations like the above in your program's
12756 native language, and allowing @value{GDBN} to output values in a manner
12757 consistent with the syntax of your program's native language. The
12758 language you use to build expressions is called the @dfn{working
12762 * Setting:: Switching between source languages
12763 * Show:: Displaying the language
12764 * Checks:: Type and range checks
12765 * Supported Languages:: Supported languages
12766 * Unsupported Languages:: Unsupported languages
12770 @section Switching Between Source Languages
12772 There are two ways to control the working language---either have @value{GDBN}
12773 set it automatically, or select it manually yourself. You can use the
12774 @code{set language} command for either purpose. On startup, @value{GDBN}
12775 defaults to setting the language automatically. The working language is
12776 used to determine how expressions you type are interpreted, how values
12779 In addition to the working language, every source file that
12780 @value{GDBN} knows about has its own working language. For some object
12781 file formats, the compiler might indicate which language a particular
12782 source file is in. However, most of the time @value{GDBN} infers the
12783 language from the name of the file. The language of a source file
12784 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12785 show each frame appropriately for its own language. There is no way to
12786 set the language of a source file from within @value{GDBN}, but you can
12787 set the language associated with a filename extension. @xref{Show, ,
12788 Displaying the Language}.
12790 This is most commonly a problem when you use a program, such
12791 as @code{cfront} or @code{f2c}, that generates C but is written in
12792 another language. In that case, make the
12793 program use @code{#line} directives in its C output; that way
12794 @value{GDBN} will know the correct language of the source code of the original
12795 program, and will display that source code, not the generated C code.
12798 * Filenames:: Filename extensions and languages.
12799 * Manually:: Setting the working language manually
12800 * Automatically:: Having @value{GDBN} infer the source language
12804 @subsection List of Filename Extensions and Languages
12806 If a source file name ends in one of the following extensions, then
12807 @value{GDBN} infers that its language is the one indicated.
12825 C@t{++} source file
12831 Objective-C source file
12835 Fortran source file
12838 Modula-2 source file
12842 Assembler source file. This actually behaves almost like C, but
12843 @value{GDBN} does not skip over function prologues when stepping.
12846 In addition, you may set the language associated with a filename
12847 extension. @xref{Show, , Displaying the Language}.
12850 @subsection Setting the Working Language
12852 If you allow @value{GDBN} to set the language automatically,
12853 expressions are interpreted the same way in your debugging session and
12856 @kindex set language
12857 If you wish, you may set the language manually. To do this, issue the
12858 command @samp{set language @var{lang}}, where @var{lang} is the name of
12859 a language, such as
12860 @code{c} or @code{modula-2}.
12861 For a list of the supported languages, type @samp{set language}.
12863 Setting the language manually prevents @value{GDBN} from updating the working
12864 language automatically. This can lead to confusion if you try
12865 to debug a program when the working language is not the same as the
12866 source language, when an expression is acceptable to both
12867 languages---but means different things. For instance, if the current
12868 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12876 might not have the effect you intended. In C, this means to add
12877 @code{b} and @code{c} and place the result in @code{a}. The result
12878 printed would be the value of @code{a}. In Modula-2, this means to compare
12879 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12881 @node Automatically
12882 @subsection Having @value{GDBN} Infer the Source Language
12884 To have @value{GDBN} set the working language automatically, use
12885 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12886 then infers the working language. That is, when your program stops in a
12887 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12888 working language to the language recorded for the function in that
12889 frame. If the language for a frame is unknown (that is, if the function
12890 or block corresponding to the frame was defined in a source file that
12891 does not have a recognized extension), the current working language is
12892 not changed, and @value{GDBN} issues a warning.
12894 This may not seem necessary for most programs, which are written
12895 entirely in one source language. However, program modules and libraries
12896 written in one source language can be used by a main program written in
12897 a different source language. Using @samp{set language auto} in this
12898 case frees you from having to set the working language manually.
12901 @section Displaying the Language
12903 The following commands help you find out which language is the
12904 working language, and also what language source files were written in.
12907 @item show language
12908 @kindex show language
12909 Display the current working language. This is the
12910 language you can use with commands such as @code{print} to
12911 build and compute expressions that may involve variables in your program.
12914 @kindex info frame@r{, show the source language}
12915 Display the source language for this frame. This language becomes the
12916 working language if you use an identifier from this frame.
12917 @xref{Frame Info, ,Information about a Frame}, to identify the other
12918 information listed here.
12921 @kindex info source@r{, show the source language}
12922 Display the source language of this source file.
12923 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12924 information listed here.
12927 In unusual circumstances, you may have source files with extensions
12928 not in the standard list. You can then set the extension associated
12929 with a language explicitly:
12932 @item set extension-language @var{ext} @var{language}
12933 @kindex set extension-language
12934 Tell @value{GDBN} that source files with extension @var{ext} are to be
12935 assumed as written in the source language @var{language}.
12937 @item info extensions
12938 @kindex info extensions
12939 List all the filename extensions and the associated languages.
12943 @section Type and Range Checking
12945 Some languages are designed to guard you against making seemingly common
12946 errors through a series of compile- and run-time checks. These include
12947 checking the type of arguments to functions and operators and making
12948 sure mathematical overflows are caught at run time. Checks such as
12949 these help to ensure a program's correctness once it has been compiled
12950 by eliminating type mismatches and providing active checks for range
12951 errors when your program is running.
12953 By default @value{GDBN} checks for these errors according to the
12954 rules of the current source language. Although @value{GDBN} does not check
12955 the statements in your program, it can check expressions entered directly
12956 into @value{GDBN} for evaluation via the @code{print} command, for example.
12959 * Type Checking:: An overview of type checking
12960 * Range Checking:: An overview of range checking
12963 @cindex type checking
12964 @cindex checks, type
12965 @node Type Checking
12966 @subsection An Overview of Type Checking
12968 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12969 arguments to operators and functions have to be of the correct type,
12970 otherwise an error occurs. These checks prevent type mismatch
12971 errors from ever causing any run-time problems. For example,
12974 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12976 (@value{GDBP}) print obj.my_method (0)
12979 (@value{GDBP}) print obj.my_method (0x1234)
12980 Cannot resolve method klass::my_method to any overloaded instance
12983 The second example fails because in C@t{++} the integer constant
12984 @samp{0x1234} is not type-compatible with the pointer parameter type.
12986 For the expressions you use in @value{GDBN} commands, you can tell
12987 @value{GDBN} to not enforce strict type checking or
12988 to treat any mismatches as errors and abandon the expression;
12989 When type checking is disabled, @value{GDBN} successfully evaluates
12990 expressions like the second example above.
12992 Even if type checking is off, there may be other reasons
12993 related to type that prevent @value{GDBN} from evaluating an expression.
12994 For instance, @value{GDBN} does not know how to add an @code{int} and
12995 a @code{struct foo}. These particular type errors have nothing to do
12996 with the language in use and usually arise from expressions which make
12997 little sense to evaluate anyway.
12999 @value{GDBN} provides some additional commands for controlling type checking:
13001 @kindex set check type
13002 @kindex show check type
13004 @item set check type on
13005 @itemx set check type off
13006 Set strict type checking on or off. If any type mismatches occur in
13007 evaluating an expression while type checking is on, @value{GDBN} prints a
13008 message and aborts evaluation of the expression.
13010 @item show check type
13011 Show the current setting of type checking and whether @value{GDBN}
13012 is enforcing strict type checking rules.
13015 @cindex range checking
13016 @cindex checks, range
13017 @node Range Checking
13018 @subsection An Overview of Range Checking
13020 In some languages (such as Modula-2), it is an error to exceed the
13021 bounds of a type; this is enforced with run-time checks. Such range
13022 checking is meant to ensure program correctness by making sure
13023 computations do not overflow, or indices on an array element access do
13024 not exceed the bounds of the array.
13026 For expressions you use in @value{GDBN} commands, you can tell
13027 @value{GDBN} to treat range errors in one of three ways: ignore them,
13028 always treat them as errors and abandon the expression, or issue
13029 warnings but evaluate the expression anyway.
13031 A range error can result from numerical overflow, from exceeding an
13032 array index bound, or when you type a constant that is not a member
13033 of any type. Some languages, however, do not treat overflows as an
13034 error. In many implementations of C, mathematical overflow causes the
13035 result to ``wrap around'' to lower values---for example, if @var{m} is
13036 the largest integer value, and @var{s} is the smallest, then
13039 @var{m} + 1 @result{} @var{s}
13042 This, too, is specific to individual languages, and in some cases
13043 specific to individual compilers or machines. @xref{Supported Languages, ,
13044 Supported Languages}, for further details on specific languages.
13046 @value{GDBN} provides some additional commands for controlling the range checker:
13048 @kindex set check range
13049 @kindex show check range
13051 @item set check range auto
13052 Set range checking on or off based on the current working language.
13053 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13056 @item set check range on
13057 @itemx set check range off
13058 Set range checking on or off, overriding the default setting for the
13059 current working language. A warning is issued if the setting does not
13060 match the language default. If a range error occurs and range checking is on,
13061 then a message is printed and evaluation of the expression is aborted.
13063 @item set check range warn
13064 Output messages when the @value{GDBN} range checker detects a range error,
13065 but attempt to evaluate the expression anyway. Evaluating the
13066 expression may still be impossible for other reasons, such as accessing
13067 memory that the process does not own (a typical example from many Unix
13071 Show the current setting of the range checker, and whether or not it is
13072 being set automatically by @value{GDBN}.
13075 @node Supported Languages
13076 @section Supported Languages
13078 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13079 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13080 @c This is false ...
13081 Some @value{GDBN} features may be used in expressions regardless of the
13082 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13083 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13084 ,Expressions}) can be used with the constructs of any supported
13087 The following sections detail to what degree each source language is
13088 supported by @value{GDBN}. These sections are not meant to be language
13089 tutorials or references, but serve only as a reference guide to what the
13090 @value{GDBN} expression parser accepts, and what input and output
13091 formats should look like for different languages. There are many good
13092 books written on each of these languages; please look to these for a
13093 language reference or tutorial.
13096 * C:: C and C@t{++}
13099 * Objective-C:: Objective-C
13100 * OpenCL C:: OpenCL C
13101 * Fortran:: Fortran
13103 * Modula-2:: Modula-2
13108 @subsection C and C@t{++}
13110 @cindex C and C@t{++}
13111 @cindex expressions in C or C@t{++}
13113 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13114 to both languages. Whenever this is the case, we discuss those languages
13118 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13119 @cindex @sc{gnu} C@t{++}
13120 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13121 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13122 effectively, you must compile your C@t{++} programs with a supported
13123 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13124 compiler (@code{aCC}).
13127 * C Operators:: C and C@t{++} operators
13128 * C Constants:: C and C@t{++} constants
13129 * C Plus Plus Expressions:: C@t{++} expressions
13130 * C Defaults:: Default settings for C and C@t{++}
13131 * C Checks:: C and C@t{++} type and range checks
13132 * Debugging C:: @value{GDBN} and C
13133 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13134 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13138 @subsubsection C and C@t{++} Operators
13140 @cindex C and C@t{++} operators
13142 Operators must be defined on values of specific types. For instance,
13143 @code{+} is defined on numbers, but not on structures. Operators are
13144 often defined on groups of types.
13146 For the purposes of C and C@t{++}, the following definitions hold:
13151 @emph{Integral types} include @code{int} with any of its storage-class
13152 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13155 @emph{Floating-point types} include @code{float}, @code{double}, and
13156 @code{long double} (if supported by the target platform).
13159 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13162 @emph{Scalar types} include all of the above.
13167 The following operators are supported. They are listed here
13168 in order of increasing precedence:
13172 The comma or sequencing operator. Expressions in a comma-separated list
13173 are evaluated from left to right, with the result of the entire
13174 expression being the last expression evaluated.
13177 Assignment. The value of an assignment expression is the value
13178 assigned. Defined on scalar types.
13181 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13182 and translated to @w{@code{@var{a} = @var{a op b}}}.
13183 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13184 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13185 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13188 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13189 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13193 Logical @sc{or}. Defined on integral types.
13196 Logical @sc{and}. Defined on integral types.
13199 Bitwise @sc{or}. Defined on integral types.
13202 Bitwise exclusive-@sc{or}. Defined on integral types.
13205 Bitwise @sc{and}. Defined on integral types.
13208 Equality and inequality. Defined on scalar types. The value of these
13209 expressions is 0 for false and non-zero for true.
13211 @item <@r{, }>@r{, }<=@r{, }>=
13212 Less than, greater than, less than or equal, greater than or equal.
13213 Defined on scalar types. The value of these expressions is 0 for false
13214 and non-zero for true.
13217 left shift, and right shift. Defined on integral types.
13220 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13223 Addition and subtraction. Defined on integral types, floating-point types and
13226 @item *@r{, }/@r{, }%
13227 Multiplication, division, and modulus. Multiplication and division are
13228 defined on integral and floating-point types. Modulus is defined on
13232 Increment and decrement. When appearing before a variable, the
13233 operation is performed before the variable is used in an expression;
13234 when appearing after it, the variable's value is used before the
13235 operation takes place.
13238 Pointer dereferencing. Defined on pointer types. Same precedence as
13242 Address operator. Defined on variables. Same precedence as @code{++}.
13244 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13245 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13246 to examine the address
13247 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13251 Negative. Defined on integral and floating-point types. Same
13252 precedence as @code{++}.
13255 Logical negation. Defined on integral types. Same precedence as
13259 Bitwise complement operator. Defined on integral types. Same precedence as
13264 Structure member, and pointer-to-structure member. For convenience,
13265 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13266 pointer based on the stored type information.
13267 Defined on @code{struct} and @code{union} data.
13270 Dereferences of pointers to members.
13273 Array indexing. @code{@var{a}[@var{i}]} is defined as
13274 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13277 Function parameter list. Same precedence as @code{->}.
13280 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13281 and @code{class} types.
13284 Doubled colons also represent the @value{GDBN} scope operator
13285 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13289 If an operator is redefined in the user code, @value{GDBN} usually
13290 attempts to invoke the redefined version instead of using the operator's
13291 predefined meaning.
13294 @subsubsection C and C@t{++} Constants
13296 @cindex C and C@t{++} constants
13298 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13303 Integer constants are a sequence of digits. Octal constants are
13304 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13305 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13306 @samp{l}, specifying that the constant should be treated as a
13310 Floating point constants are a sequence of digits, followed by a decimal
13311 point, followed by a sequence of digits, and optionally followed by an
13312 exponent. An exponent is of the form:
13313 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13314 sequence of digits. The @samp{+} is optional for positive exponents.
13315 A floating-point constant may also end with a letter @samp{f} or
13316 @samp{F}, specifying that the constant should be treated as being of
13317 the @code{float} (as opposed to the default @code{double}) type; or with
13318 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13322 Enumerated constants consist of enumerated identifiers, or their
13323 integral equivalents.
13326 Character constants are a single character surrounded by single quotes
13327 (@code{'}), or a number---the ordinal value of the corresponding character
13328 (usually its @sc{ascii} value). Within quotes, the single character may
13329 be represented by a letter or by @dfn{escape sequences}, which are of
13330 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13331 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13332 @samp{@var{x}} is a predefined special character---for example,
13333 @samp{\n} for newline.
13335 Wide character constants can be written by prefixing a character
13336 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13337 form of @samp{x}. The target wide character set is used when
13338 computing the value of this constant (@pxref{Character Sets}).
13341 String constants are a sequence of character constants surrounded by
13342 double quotes (@code{"}). Any valid character constant (as described
13343 above) may appear. Double quotes within the string must be preceded by
13344 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13347 Wide string constants can be written by prefixing a string constant
13348 with @samp{L}, as in C. The target wide character set is used when
13349 computing the value of this constant (@pxref{Character Sets}).
13352 Pointer constants are an integral value. You can also write pointers
13353 to constants using the C operator @samp{&}.
13356 Array constants are comma-separated lists surrounded by braces @samp{@{}
13357 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13358 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13359 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13362 @node C Plus Plus Expressions
13363 @subsubsection C@t{++} Expressions
13365 @cindex expressions in C@t{++}
13366 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13368 @cindex debugging C@t{++} programs
13369 @cindex C@t{++} compilers
13370 @cindex debug formats and C@t{++}
13371 @cindex @value{NGCC} and C@t{++}
13373 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13374 the proper compiler and the proper debug format. Currently,
13375 @value{GDBN} works best when debugging C@t{++} code that is compiled
13376 with the most recent version of @value{NGCC} possible. The DWARF
13377 debugging format is preferred; @value{NGCC} defaults to this on most
13378 popular platforms. Other compilers and/or debug formats are likely to
13379 work badly or not at all when using @value{GDBN} to debug C@t{++}
13380 code. @xref{Compilation}.
13385 @cindex member functions
13387 Member function calls are allowed; you can use expressions like
13390 count = aml->GetOriginal(x, y)
13393 @vindex this@r{, inside C@t{++} member functions}
13394 @cindex namespace in C@t{++}
13396 While a member function is active (in the selected stack frame), your
13397 expressions have the same namespace available as the member function;
13398 that is, @value{GDBN} allows implicit references to the class instance
13399 pointer @code{this} following the same rules as C@t{++}. @code{using}
13400 declarations in the current scope are also respected by @value{GDBN}.
13402 @cindex call overloaded functions
13403 @cindex overloaded functions, calling
13404 @cindex type conversions in C@t{++}
13406 You can call overloaded functions; @value{GDBN} resolves the function
13407 call to the right definition, with some restrictions. @value{GDBN} does not
13408 perform overload resolution involving user-defined type conversions,
13409 calls to constructors, or instantiations of templates that do not exist
13410 in the program. It also cannot handle ellipsis argument lists or
13413 It does perform integral conversions and promotions, floating-point
13414 promotions, arithmetic conversions, pointer conversions, conversions of
13415 class objects to base classes, and standard conversions such as those of
13416 functions or arrays to pointers; it requires an exact match on the
13417 number of function arguments.
13419 Overload resolution is always performed, unless you have specified
13420 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13421 ,@value{GDBN} Features for C@t{++}}.
13423 You must specify @code{set overload-resolution off} in order to use an
13424 explicit function signature to call an overloaded function, as in
13426 p 'foo(char,int)'('x', 13)
13429 The @value{GDBN} command-completion facility can simplify this;
13430 see @ref{Completion, ,Command Completion}.
13432 @cindex reference declarations
13434 @value{GDBN} understands variables declared as C@t{++} references; you can use
13435 them in expressions just as you do in C@t{++} source---they are automatically
13438 In the parameter list shown when @value{GDBN} displays a frame, the values of
13439 reference variables are not displayed (unlike other variables); this
13440 avoids clutter, since references are often used for large structures.
13441 The @emph{address} of a reference variable is always shown, unless
13442 you have specified @samp{set print address off}.
13445 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13446 expressions can use it just as expressions in your program do. Since
13447 one scope may be defined in another, you can use @code{::} repeatedly if
13448 necessary, for example in an expression like
13449 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13450 resolving name scope by reference to source files, in both C and C@t{++}
13451 debugging (@pxref{Variables, ,Program Variables}).
13454 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13459 @subsubsection C and C@t{++} Defaults
13461 @cindex C and C@t{++} defaults
13463 If you allow @value{GDBN} to set range checking automatically, it
13464 defaults to @code{off} whenever the working language changes to
13465 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13466 selects the working language.
13468 If you allow @value{GDBN} to set the language automatically, it
13469 recognizes source files whose names end with @file{.c}, @file{.C}, or
13470 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13471 these files, it sets the working language to C or C@t{++}.
13472 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13473 for further details.
13476 @subsubsection C and C@t{++} Type and Range Checks
13478 @cindex C and C@t{++} checks
13480 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13481 checking is used. However, if you turn type checking off, @value{GDBN}
13482 will allow certain non-standard conversions, such as promoting integer
13483 constants to pointers.
13485 Range checking, if turned on, is done on mathematical operations. Array
13486 indices are not checked, since they are often used to index a pointer
13487 that is not itself an array.
13490 @subsubsection @value{GDBN} and C
13492 The @code{set print union} and @code{show print union} commands apply to
13493 the @code{union} type. When set to @samp{on}, any @code{union} that is
13494 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13495 appears as @samp{@{...@}}.
13497 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13498 with pointers and a memory allocation function. @xref{Expressions,
13501 @node Debugging C Plus Plus
13502 @subsubsection @value{GDBN} Features for C@t{++}
13504 @cindex commands for C@t{++}
13506 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13507 designed specifically for use with C@t{++}. Here is a summary:
13510 @cindex break in overloaded functions
13511 @item @r{breakpoint menus}
13512 When you want a breakpoint in a function whose name is overloaded,
13513 @value{GDBN} has the capability to display a menu of possible breakpoint
13514 locations to help you specify which function definition you want.
13515 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13517 @cindex overloading in C@t{++}
13518 @item rbreak @var{regex}
13519 Setting breakpoints using regular expressions is helpful for setting
13520 breakpoints on overloaded functions that are not members of any special
13522 @xref{Set Breaks, ,Setting Breakpoints}.
13524 @cindex C@t{++} exception handling
13527 Debug C@t{++} exception handling using these commands. @xref{Set
13528 Catchpoints, , Setting Catchpoints}.
13530 @cindex inheritance
13531 @item ptype @var{typename}
13532 Print inheritance relationships as well as other information for type
13534 @xref{Symbols, ,Examining the Symbol Table}.
13536 @item info vtbl @var{expression}.
13537 The @code{info vtbl} command can be used to display the virtual
13538 method tables of the object computed by @var{expression}. This shows
13539 one entry per virtual table; there may be multiple virtual tables when
13540 multiple inheritance is in use.
13542 @cindex C@t{++} symbol display
13543 @item set print demangle
13544 @itemx show print demangle
13545 @itemx set print asm-demangle
13546 @itemx show print asm-demangle
13547 Control whether C@t{++} symbols display in their source form, both when
13548 displaying code as C@t{++} source and when displaying disassemblies.
13549 @xref{Print Settings, ,Print Settings}.
13551 @item set print object
13552 @itemx show print object
13553 Choose whether to print derived (actual) or declared types of objects.
13554 @xref{Print Settings, ,Print Settings}.
13556 @item set print vtbl
13557 @itemx show print vtbl
13558 Control the format for printing virtual function tables.
13559 @xref{Print Settings, ,Print Settings}.
13560 (The @code{vtbl} commands do not work on programs compiled with the HP
13561 ANSI C@t{++} compiler (@code{aCC}).)
13563 @kindex set overload-resolution
13564 @cindex overloaded functions, overload resolution
13565 @item set overload-resolution on
13566 Enable overload resolution for C@t{++} expression evaluation. The default
13567 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13568 and searches for a function whose signature matches the argument types,
13569 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13570 Expressions, ,C@t{++} Expressions}, for details).
13571 If it cannot find a match, it emits a message.
13573 @item set overload-resolution off
13574 Disable overload resolution for C@t{++} expression evaluation. For
13575 overloaded functions that are not class member functions, @value{GDBN}
13576 chooses the first function of the specified name that it finds in the
13577 symbol table, whether or not its arguments are of the correct type. For
13578 overloaded functions that are class member functions, @value{GDBN}
13579 searches for a function whose signature @emph{exactly} matches the
13582 @kindex show overload-resolution
13583 @item show overload-resolution
13584 Show the current setting of overload resolution.
13586 @item @r{Overloaded symbol names}
13587 You can specify a particular definition of an overloaded symbol, using
13588 the same notation that is used to declare such symbols in C@t{++}: type
13589 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13590 also use the @value{GDBN} command-line word completion facilities to list the
13591 available choices, or to finish the type list for you.
13592 @xref{Completion,, Command Completion}, for details on how to do this.
13595 @node Decimal Floating Point
13596 @subsubsection Decimal Floating Point format
13597 @cindex decimal floating point format
13599 @value{GDBN} can examine, set and perform computations with numbers in
13600 decimal floating point format, which in the C language correspond to the
13601 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13602 specified by the extension to support decimal floating-point arithmetic.
13604 There are two encodings in use, depending on the architecture: BID (Binary
13605 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13606 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13609 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13610 to manipulate decimal floating point numbers, it is not possible to convert
13611 (using a cast, for example) integers wider than 32-bit to decimal float.
13613 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13614 point computations, error checking in decimal float operations ignores
13615 underflow, overflow and divide by zero exceptions.
13617 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13618 to inspect @code{_Decimal128} values stored in floating point registers.
13619 See @ref{PowerPC,,PowerPC} for more details.
13625 @value{GDBN} can be used to debug programs written in D and compiled with
13626 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13627 specific feature --- dynamic arrays.
13632 @cindex Go (programming language)
13633 @value{GDBN} can be used to debug programs written in Go and compiled with
13634 @file{gccgo} or @file{6g} compilers.
13636 Here is a summary of the Go-specific features and restrictions:
13639 @cindex current Go package
13640 @item The current Go package
13641 The name of the current package does not need to be specified when
13642 specifying global variables and functions.
13644 For example, given the program:
13648 var myglob = "Shall we?"
13654 When stopped inside @code{main} either of these work:
13658 (gdb) p main.myglob
13661 @cindex builtin Go types
13662 @item Builtin Go types
13663 The @code{string} type is recognized by @value{GDBN} and is printed
13666 @cindex builtin Go functions
13667 @item Builtin Go functions
13668 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13669 function and handles it internally.
13671 @cindex restrictions on Go expressions
13672 @item Restrictions on Go expressions
13673 All Go operators are supported except @code{&^}.
13674 The Go @code{_} ``blank identifier'' is not supported.
13675 Automatic dereferencing of pointers is not supported.
13679 @subsection Objective-C
13681 @cindex Objective-C
13682 This section provides information about some commands and command
13683 options that are useful for debugging Objective-C code. See also
13684 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13685 few more commands specific to Objective-C support.
13688 * Method Names in Commands::
13689 * The Print Command with Objective-C::
13692 @node Method Names in Commands
13693 @subsubsection Method Names in Commands
13695 The following commands have been extended to accept Objective-C method
13696 names as line specifications:
13698 @kindex clear@r{, and Objective-C}
13699 @kindex break@r{, and Objective-C}
13700 @kindex info line@r{, and Objective-C}
13701 @kindex jump@r{, and Objective-C}
13702 @kindex list@r{, and Objective-C}
13706 @item @code{info line}
13711 A fully qualified Objective-C method name is specified as
13714 -[@var{Class} @var{methodName}]
13717 where the minus sign is used to indicate an instance method and a
13718 plus sign (not shown) is used to indicate a class method. The class
13719 name @var{Class} and method name @var{methodName} are enclosed in
13720 brackets, similar to the way messages are specified in Objective-C
13721 source code. For example, to set a breakpoint at the @code{create}
13722 instance method of class @code{Fruit} in the program currently being
13726 break -[Fruit create]
13729 To list ten program lines around the @code{initialize} class method,
13733 list +[NSText initialize]
13736 In the current version of @value{GDBN}, the plus or minus sign is
13737 required. In future versions of @value{GDBN}, the plus or minus
13738 sign will be optional, but you can use it to narrow the search. It
13739 is also possible to specify just a method name:
13745 You must specify the complete method name, including any colons. If
13746 your program's source files contain more than one @code{create} method,
13747 you'll be presented with a numbered list of classes that implement that
13748 method. Indicate your choice by number, or type @samp{0} to exit if
13751 As another example, to clear a breakpoint established at the
13752 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13755 clear -[NSWindow makeKeyAndOrderFront:]
13758 @node The Print Command with Objective-C
13759 @subsubsection The Print Command With Objective-C
13760 @cindex Objective-C, print objects
13761 @kindex print-object
13762 @kindex po @r{(@code{print-object})}
13764 The print command has also been extended to accept methods. For example:
13767 print -[@var{object} hash]
13770 @cindex print an Objective-C object description
13771 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13773 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13774 and print the result. Also, an additional command has been added,
13775 @code{print-object} or @code{po} for short, which is meant to print
13776 the description of an object. However, this command may only work
13777 with certain Objective-C libraries that have a particular hook
13778 function, @code{_NSPrintForDebugger}, defined.
13781 @subsection OpenCL C
13784 This section provides information about @value{GDBN}s OpenCL C support.
13787 * OpenCL C Datatypes::
13788 * OpenCL C Expressions::
13789 * OpenCL C Operators::
13792 @node OpenCL C Datatypes
13793 @subsubsection OpenCL C Datatypes
13795 @cindex OpenCL C Datatypes
13796 @value{GDBN} supports the builtin scalar and vector datatypes specified
13797 by OpenCL 1.1. In addition the half- and double-precision floating point
13798 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13799 extensions are also known to @value{GDBN}.
13801 @node OpenCL C Expressions
13802 @subsubsection OpenCL C Expressions
13804 @cindex OpenCL C Expressions
13805 @value{GDBN} supports accesses to vector components including the access as
13806 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13807 supported by @value{GDBN} can be used as well.
13809 @node OpenCL C Operators
13810 @subsubsection OpenCL C Operators
13812 @cindex OpenCL C Operators
13813 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13817 @subsection Fortran
13818 @cindex Fortran-specific support in @value{GDBN}
13820 @value{GDBN} can be used to debug programs written in Fortran, but it
13821 currently supports only the features of Fortran 77 language.
13823 @cindex trailing underscore, in Fortran symbols
13824 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13825 among them) append an underscore to the names of variables and
13826 functions. When you debug programs compiled by those compilers, you
13827 will need to refer to variables and functions with a trailing
13831 * Fortran Operators:: Fortran operators and expressions
13832 * Fortran Defaults:: Default settings for Fortran
13833 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13836 @node Fortran Operators
13837 @subsubsection Fortran Operators and Expressions
13839 @cindex Fortran operators and expressions
13841 Operators must be defined on values of specific types. For instance,
13842 @code{+} is defined on numbers, but not on characters or other non-
13843 arithmetic types. Operators are often defined on groups of types.
13847 The exponentiation operator. It raises the first operand to the power
13851 The range operator. Normally used in the form of array(low:high) to
13852 represent a section of array.
13855 The access component operator. Normally used to access elements in derived
13856 types. Also suitable for unions. As unions aren't part of regular Fortran,
13857 this can only happen when accessing a register that uses a gdbarch-defined
13861 @node Fortran Defaults
13862 @subsubsection Fortran Defaults
13864 @cindex Fortran Defaults
13866 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13867 default uses case-insensitive matches for Fortran symbols. You can
13868 change that with the @samp{set case-insensitive} command, see
13869 @ref{Symbols}, for the details.
13871 @node Special Fortran Commands
13872 @subsubsection Special Fortran Commands
13874 @cindex Special Fortran commands
13876 @value{GDBN} has some commands to support Fortran-specific features,
13877 such as displaying common blocks.
13880 @cindex @code{COMMON} blocks, Fortran
13881 @kindex info common
13882 @item info common @r{[}@var{common-name}@r{]}
13883 This command prints the values contained in the Fortran @code{COMMON}
13884 block whose name is @var{common-name}. With no argument, the names of
13885 all @code{COMMON} blocks visible at the current program location are
13892 @cindex Pascal support in @value{GDBN}, limitations
13893 Debugging Pascal programs which use sets, subranges, file variables, or
13894 nested functions does not currently work. @value{GDBN} does not support
13895 entering expressions, printing values, or similar features using Pascal
13898 The Pascal-specific command @code{set print pascal_static-members}
13899 controls whether static members of Pascal objects are displayed.
13900 @xref{Print Settings, pascal_static-members}.
13903 @subsection Modula-2
13905 @cindex Modula-2, @value{GDBN} support
13907 The extensions made to @value{GDBN} to support Modula-2 only support
13908 output from the @sc{gnu} Modula-2 compiler (which is currently being
13909 developed). Other Modula-2 compilers are not currently supported, and
13910 attempting to debug executables produced by them is most likely
13911 to give an error as @value{GDBN} reads in the executable's symbol
13914 @cindex expressions in Modula-2
13916 * M2 Operators:: Built-in operators
13917 * Built-In Func/Proc:: Built-in functions and procedures
13918 * M2 Constants:: Modula-2 constants
13919 * M2 Types:: Modula-2 types
13920 * M2 Defaults:: Default settings for Modula-2
13921 * Deviations:: Deviations from standard Modula-2
13922 * M2 Checks:: Modula-2 type and range checks
13923 * M2 Scope:: The scope operators @code{::} and @code{.}
13924 * GDB/M2:: @value{GDBN} and Modula-2
13928 @subsubsection Operators
13929 @cindex Modula-2 operators
13931 Operators must be defined on values of specific types. For instance,
13932 @code{+} is defined on numbers, but not on structures. Operators are
13933 often defined on groups of types. For the purposes of Modula-2, the
13934 following definitions hold:
13939 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13943 @emph{Character types} consist of @code{CHAR} and its subranges.
13946 @emph{Floating-point types} consist of @code{REAL}.
13949 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13953 @emph{Scalar types} consist of all of the above.
13956 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13959 @emph{Boolean types} consist of @code{BOOLEAN}.
13963 The following operators are supported, and appear in order of
13964 increasing precedence:
13968 Function argument or array index separator.
13971 Assignment. The value of @var{var} @code{:=} @var{value} is
13975 Less than, greater than on integral, floating-point, or enumerated
13979 Less than or equal to, greater than or equal to
13980 on integral, floating-point and enumerated types, or set inclusion on
13981 set types. Same precedence as @code{<}.
13983 @item =@r{, }<>@r{, }#
13984 Equality and two ways of expressing inequality, valid on scalar types.
13985 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13986 available for inequality, since @code{#} conflicts with the script
13990 Set membership. Defined on set types and the types of their members.
13991 Same precedence as @code{<}.
13994 Boolean disjunction. Defined on boolean types.
13997 Boolean conjunction. Defined on boolean types.
14000 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14003 Addition and subtraction on integral and floating-point types, or union
14004 and difference on set types.
14007 Multiplication on integral and floating-point types, or set intersection
14011 Division on floating-point types, or symmetric set difference on set
14012 types. Same precedence as @code{*}.
14015 Integer division and remainder. Defined on integral types. Same
14016 precedence as @code{*}.
14019 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14022 Pointer dereferencing. Defined on pointer types.
14025 Boolean negation. Defined on boolean types. Same precedence as
14029 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14030 precedence as @code{^}.
14033 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14036 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14040 @value{GDBN} and Modula-2 scope operators.
14044 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14045 treats the use of the operator @code{IN}, or the use of operators
14046 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14047 @code{<=}, and @code{>=} on sets as an error.
14051 @node Built-In Func/Proc
14052 @subsubsection Built-in Functions and Procedures
14053 @cindex Modula-2 built-ins
14055 Modula-2 also makes available several built-in procedures and functions.
14056 In describing these, the following metavariables are used:
14061 represents an @code{ARRAY} variable.
14064 represents a @code{CHAR} constant or variable.
14067 represents a variable or constant of integral type.
14070 represents an identifier that belongs to a set. Generally used in the
14071 same function with the metavariable @var{s}. The type of @var{s} should
14072 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14075 represents a variable or constant of integral or floating-point type.
14078 represents a variable or constant of floating-point type.
14084 represents a variable.
14087 represents a variable or constant of one of many types. See the
14088 explanation of the function for details.
14091 All Modula-2 built-in procedures also return a result, described below.
14095 Returns the absolute value of @var{n}.
14098 If @var{c} is a lower case letter, it returns its upper case
14099 equivalent, otherwise it returns its argument.
14102 Returns the character whose ordinal value is @var{i}.
14105 Decrements the value in the variable @var{v} by one. Returns the new value.
14107 @item DEC(@var{v},@var{i})
14108 Decrements the value in the variable @var{v} by @var{i}. Returns the
14111 @item EXCL(@var{m},@var{s})
14112 Removes the element @var{m} from the set @var{s}. Returns the new
14115 @item FLOAT(@var{i})
14116 Returns the floating point equivalent of the integer @var{i}.
14118 @item HIGH(@var{a})
14119 Returns the index of the last member of @var{a}.
14122 Increments the value in the variable @var{v} by one. Returns the new value.
14124 @item INC(@var{v},@var{i})
14125 Increments the value in the variable @var{v} by @var{i}. Returns the
14128 @item INCL(@var{m},@var{s})
14129 Adds the element @var{m} to the set @var{s} if it is not already
14130 there. Returns the new set.
14133 Returns the maximum value of the type @var{t}.
14136 Returns the minimum value of the type @var{t}.
14139 Returns boolean TRUE if @var{i} is an odd number.
14142 Returns the ordinal value of its argument. For example, the ordinal
14143 value of a character is its @sc{ascii} value (on machines supporting the
14144 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14145 integral, character and enumerated types.
14147 @item SIZE(@var{x})
14148 Returns the size of its argument. @var{x} can be a variable or a type.
14150 @item TRUNC(@var{r})
14151 Returns the integral part of @var{r}.
14153 @item TSIZE(@var{x})
14154 Returns the size of its argument. @var{x} can be a variable or a type.
14156 @item VAL(@var{t},@var{i})
14157 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14161 @emph{Warning:} Sets and their operations are not yet supported, so
14162 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14166 @cindex Modula-2 constants
14168 @subsubsection Constants
14170 @value{GDBN} allows you to express the constants of Modula-2 in the following
14176 Integer constants are simply a sequence of digits. When used in an
14177 expression, a constant is interpreted to be type-compatible with the
14178 rest of the expression. Hexadecimal integers are specified by a
14179 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14182 Floating point constants appear as a sequence of digits, followed by a
14183 decimal point and another sequence of digits. An optional exponent can
14184 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14185 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14186 digits of the floating point constant must be valid decimal (base 10)
14190 Character constants consist of a single character enclosed by a pair of
14191 like quotes, either single (@code{'}) or double (@code{"}). They may
14192 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14193 followed by a @samp{C}.
14196 String constants consist of a sequence of characters enclosed by a
14197 pair of like quotes, either single (@code{'}) or double (@code{"}).
14198 Escape sequences in the style of C are also allowed. @xref{C
14199 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14203 Enumerated constants consist of an enumerated identifier.
14206 Boolean constants consist of the identifiers @code{TRUE} and
14210 Pointer constants consist of integral values only.
14213 Set constants are not yet supported.
14217 @subsubsection Modula-2 Types
14218 @cindex Modula-2 types
14220 Currently @value{GDBN} can print the following data types in Modula-2
14221 syntax: array types, record types, set types, pointer types, procedure
14222 types, enumerated types, subrange types and base types. You can also
14223 print the contents of variables declared using these type.
14224 This section gives a number of simple source code examples together with
14225 sample @value{GDBN} sessions.
14227 The first example contains the following section of code:
14236 and you can request @value{GDBN} to interrogate the type and value of
14237 @code{r} and @code{s}.
14240 (@value{GDBP}) print s
14242 (@value{GDBP}) ptype s
14244 (@value{GDBP}) print r
14246 (@value{GDBP}) ptype r
14251 Likewise if your source code declares @code{s} as:
14255 s: SET ['A'..'Z'] ;
14259 then you may query the type of @code{s} by:
14262 (@value{GDBP}) ptype s
14263 type = SET ['A'..'Z']
14267 Note that at present you cannot interactively manipulate set
14268 expressions using the debugger.
14270 The following example shows how you might declare an array in Modula-2
14271 and how you can interact with @value{GDBN} to print its type and contents:
14275 s: ARRAY [-10..10] OF CHAR ;
14279 (@value{GDBP}) ptype s
14280 ARRAY [-10..10] OF CHAR
14283 Note that the array handling is not yet complete and although the type
14284 is printed correctly, expression handling still assumes that all
14285 arrays have a lower bound of zero and not @code{-10} as in the example
14288 Here are some more type related Modula-2 examples:
14292 colour = (blue, red, yellow, green) ;
14293 t = [blue..yellow] ;
14301 The @value{GDBN} interaction shows how you can query the data type
14302 and value of a variable.
14305 (@value{GDBP}) print s
14307 (@value{GDBP}) ptype t
14308 type = [blue..yellow]
14312 In this example a Modula-2 array is declared and its contents
14313 displayed. Observe that the contents are written in the same way as
14314 their @code{C} counterparts.
14318 s: ARRAY [1..5] OF CARDINAL ;
14324 (@value{GDBP}) print s
14325 $1 = @{1, 0, 0, 0, 0@}
14326 (@value{GDBP}) ptype s
14327 type = ARRAY [1..5] OF CARDINAL
14330 The Modula-2 language interface to @value{GDBN} also understands
14331 pointer types as shown in this example:
14335 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14342 and you can request that @value{GDBN} describes the type of @code{s}.
14345 (@value{GDBP}) ptype s
14346 type = POINTER TO ARRAY [1..5] OF CARDINAL
14349 @value{GDBN} handles compound types as we can see in this example.
14350 Here we combine array types, record types, pointer types and subrange
14361 myarray = ARRAY myrange OF CARDINAL ;
14362 myrange = [-2..2] ;
14364 s: POINTER TO ARRAY myrange OF foo ;
14368 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14372 (@value{GDBP}) ptype s
14373 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14376 f3 : ARRAY [-2..2] OF CARDINAL;
14381 @subsubsection Modula-2 Defaults
14382 @cindex Modula-2 defaults
14384 If type and range checking are set automatically by @value{GDBN}, they
14385 both default to @code{on} whenever the working language changes to
14386 Modula-2. This happens regardless of whether you or @value{GDBN}
14387 selected the working language.
14389 If you allow @value{GDBN} to set the language automatically, then entering
14390 code compiled from a file whose name ends with @file{.mod} sets the
14391 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14392 Infer the Source Language}, for further details.
14395 @subsubsection Deviations from Standard Modula-2
14396 @cindex Modula-2, deviations from
14398 A few changes have been made to make Modula-2 programs easier to debug.
14399 This is done primarily via loosening its type strictness:
14403 Unlike in standard Modula-2, pointer constants can be formed by
14404 integers. This allows you to modify pointer variables during
14405 debugging. (In standard Modula-2, the actual address contained in a
14406 pointer variable is hidden from you; it can only be modified
14407 through direct assignment to another pointer variable or expression that
14408 returned a pointer.)
14411 C escape sequences can be used in strings and characters to represent
14412 non-printable characters. @value{GDBN} prints out strings with these
14413 escape sequences embedded. Single non-printable characters are
14414 printed using the @samp{CHR(@var{nnn})} format.
14417 The assignment operator (@code{:=}) returns the value of its right-hand
14421 All built-in procedures both modify @emph{and} return their argument.
14425 @subsubsection Modula-2 Type and Range Checks
14426 @cindex Modula-2 checks
14429 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14432 @c FIXME remove warning when type/range checks added
14434 @value{GDBN} considers two Modula-2 variables type equivalent if:
14438 They are of types that have been declared equivalent via a @code{TYPE
14439 @var{t1} = @var{t2}} statement
14442 They have been declared on the same line. (Note: This is true of the
14443 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14446 As long as type checking is enabled, any attempt to combine variables
14447 whose types are not equivalent is an error.
14449 Range checking is done on all mathematical operations, assignment, array
14450 index bounds, and all built-in functions and procedures.
14453 @subsubsection The Scope Operators @code{::} and @code{.}
14455 @cindex @code{.}, Modula-2 scope operator
14456 @cindex colon, doubled as scope operator
14458 @vindex colon-colon@r{, in Modula-2}
14459 @c Info cannot handle :: but TeX can.
14462 @vindex ::@r{, in Modula-2}
14465 There are a few subtle differences between the Modula-2 scope operator
14466 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14471 @var{module} . @var{id}
14472 @var{scope} :: @var{id}
14476 where @var{scope} is the name of a module or a procedure,
14477 @var{module} the name of a module, and @var{id} is any declared
14478 identifier within your program, except another module.
14480 Using the @code{::} operator makes @value{GDBN} search the scope
14481 specified by @var{scope} for the identifier @var{id}. If it is not
14482 found in the specified scope, then @value{GDBN} searches all scopes
14483 enclosing the one specified by @var{scope}.
14485 Using the @code{.} operator makes @value{GDBN} search the current scope for
14486 the identifier specified by @var{id} that was imported from the
14487 definition module specified by @var{module}. With this operator, it is
14488 an error if the identifier @var{id} was not imported from definition
14489 module @var{module}, or if @var{id} is not an identifier in
14493 @subsubsection @value{GDBN} and Modula-2
14495 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14496 Five subcommands of @code{set print} and @code{show print} apply
14497 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14498 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14499 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14500 analogue in Modula-2.
14502 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14503 with any language, is not useful with Modula-2. Its
14504 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14505 created in Modula-2 as they can in C or C@t{++}. However, because an
14506 address can be specified by an integral constant, the construct
14507 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14509 @cindex @code{#} in Modula-2
14510 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14511 interpreted as the beginning of a comment. Use @code{<>} instead.
14517 The extensions made to @value{GDBN} for Ada only support
14518 output from the @sc{gnu} Ada (GNAT) compiler.
14519 Other Ada compilers are not currently supported, and
14520 attempting to debug executables produced by them is most likely
14524 @cindex expressions in Ada
14526 * Ada Mode Intro:: General remarks on the Ada syntax
14527 and semantics supported by Ada mode
14529 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14530 * Additions to Ada:: Extensions of the Ada expression syntax.
14531 * Stopping Before Main Program:: Debugging the program during elaboration.
14532 * Ada Tasks:: Listing and setting breakpoints in tasks.
14533 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14534 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14536 * Ada Glitches:: Known peculiarities of Ada mode.
14539 @node Ada Mode Intro
14540 @subsubsection Introduction
14541 @cindex Ada mode, general
14543 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14544 syntax, with some extensions.
14545 The philosophy behind the design of this subset is
14549 That @value{GDBN} should provide basic literals and access to operations for
14550 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14551 leaving more sophisticated computations to subprograms written into the
14552 program (which therefore may be called from @value{GDBN}).
14555 That type safety and strict adherence to Ada language restrictions
14556 are not particularly important to the @value{GDBN} user.
14559 That brevity is important to the @value{GDBN} user.
14562 Thus, for brevity, the debugger acts as if all names declared in
14563 user-written packages are directly visible, even if they are not visible
14564 according to Ada rules, thus making it unnecessary to fully qualify most
14565 names with their packages, regardless of context. Where this causes
14566 ambiguity, @value{GDBN} asks the user's intent.
14568 The debugger will start in Ada mode if it detects an Ada main program.
14569 As for other languages, it will enter Ada mode when stopped in a program that
14570 was translated from an Ada source file.
14572 While in Ada mode, you may use `@t{--}' for comments. This is useful
14573 mostly for documenting command files. The standard @value{GDBN} comment
14574 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14575 middle (to allow based literals).
14577 The debugger supports limited overloading. Given a subprogram call in which
14578 the function symbol has multiple definitions, it will use the number of
14579 actual parameters and some information about their types to attempt to narrow
14580 the set of definitions. It also makes very limited use of context, preferring
14581 procedures to functions in the context of the @code{call} command, and
14582 functions to procedures elsewhere.
14584 @node Omissions from Ada
14585 @subsubsection Omissions from Ada
14586 @cindex Ada, omissions from
14588 Here are the notable omissions from the subset:
14592 Only a subset of the attributes are supported:
14596 @t{'First}, @t{'Last}, and @t{'Length}
14597 on array objects (not on types and subtypes).
14600 @t{'Min} and @t{'Max}.
14603 @t{'Pos} and @t{'Val}.
14609 @t{'Range} on array objects (not subtypes), but only as the right
14610 operand of the membership (@code{in}) operator.
14613 @t{'Access}, @t{'Unchecked_Access}, and
14614 @t{'Unrestricted_Access} (a GNAT extension).
14622 @code{Characters.Latin_1} are not available and
14623 concatenation is not implemented. Thus, escape characters in strings are
14624 not currently available.
14627 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14628 equality of representations. They will generally work correctly
14629 for strings and arrays whose elements have integer or enumeration types.
14630 They may not work correctly for arrays whose element
14631 types have user-defined equality, for arrays of real values
14632 (in particular, IEEE-conformant floating point, because of negative
14633 zeroes and NaNs), and for arrays whose elements contain unused bits with
14634 indeterminate values.
14637 The other component-by-component array operations (@code{and}, @code{or},
14638 @code{xor}, @code{not}, and relational tests other than equality)
14639 are not implemented.
14642 @cindex array aggregates (Ada)
14643 @cindex record aggregates (Ada)
14644 @cindex aggregates (Ada)
14645 There is limited support for array and record aggregates. They are
14646 permitted only on the right sides of assignments, as in these examples:
14649 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14650 (@value{GDBP}) set An_Array := (1, others => 0)
14651 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14652 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14653 (@value{GDBP}) set A_Record := (1, "Peter", True);
14654 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14658 discriminant's value by assigning an aggregate has an
14659 undefined effect if that discriminant is used within the record.
14660 However, you can first modify discriminants by directly assigning to
14661 them (which normally would not be allowed in Ada), and then performing an
14662 aggregate assignment. For example, given a variable @code{A_Rec}
14663 declared to have a type such as:
14666 type Rec (Len : Small_Integer := 0) is record
14668 Vals : IntArray (1 .. Len);
14672 you can assign a value with a different size of @code{Vals} with two
14676 (@value{GDBP}) set A_Rec.Len := 4
14677 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14680 As this example also illustrates, @value{GDBN} is very loose about the usual
14681 rules concerning aggregates. You may leave out some of the
14682 components of an array or record aggregate (such as the @code{Len}
14683 component in the assignment to @code{A_Rec} above); they will retain their
14684 original values upon assignment. You may freely use dynamic values as
14685 indices in component associations. You may even use overlapping or
14686 redundant component associations, although which component values are
14687 assigned in such cases is not defined.
14690 Calls to dispatching subprograms are not implemented.
14693 The overloading algorithm is much more limited (i.e., less selective)
14694 than that of real Ada. It makes only limited use of the context in
14695 which a subexpression appears to resolve its meaning, and it is much
14696 looser in its rules for allowing type matches. As a result, some
14697 function calls will be ambiguous, and the user will be asked to choose
14698 the proper resolution.
14701 The @code{new} operator is not implemented.
14704 Entry calls are not implemented.
14707 Aside from printing, arithmetic operations on the native VAX floating-point
14708 formats are not supported.
14711 It is not possible to slice a packed array.
14714 The names @code{True} and @code{False}, when not part of a qualified name,
14715 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14717 Should your program
14718 redefine these names in a package or procedure (at best a dubious practice),
14719 you will have to use fully qualified names to access their new definitions.
14722 @node Additions to Ada
14723 @subsubsection Additions to Ada
14724 @cindex Ada, deviations from
14726 As it does for other languages, @value{GDBN} makes certain generic
14727 extensions to Ada (@pxref{Expressions}):
14731 If the expression @var{E} is a variable residing in memory (typically
14732 a local variable or array element) and @var{N} is a positive integer,
14733 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14734 @var{N}-1 adjacent variables following it in memory as an array. In
14735 Ada, this operator is generally not necessary, since its prime use is
14736 in displaying parts of an array, and slicing will usually do this in
14737 Ada. However, there are occasional uses when debugging programs in
14738 which certain debugging information has been optimized away.
14741 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14742 appears in function or file @var{B}.'' When @var{B} is a file name,
14743 you must typically surround it in single quotes.
14746 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14747 @var{type} that appears at address @var{addr}.''
14750 A name starting with @samp{$} is a convenience variable
14751 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14754 In addition, @value{GDBN} provides a few other shortcuts and outright
14755 additions specific to Ada:
14759 The assignment statement is allowed as an expression, returning
14760 its right-hand operand as its value. Thus, you may enter
14763 (@value{GDBP}) set x := y + 3
14764 (@value{GDBP}) print A(tmp := y + 1)
14768 The semicolon is allowed as an ``operator,'' returning as its value
14769 the value of its right-hand operand.
14770 This allows, for example,
14771 complex conditional breaks:
14774 (@value{GDBP}) break f
14775 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14779 Rather than use catenation and symbolic character names to introduce special
14780 characters into strings, one may instead use a special bracket notation,
14781 which is also used to print strings. A sequence of characters of the form
14782 @samp{["@var{XX}"]} within a string or character literal denotes the
14783 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14784 sequence of characters @samp{["""]} also denotes a single quotation mark
14785 in strings. For example,
14787 "One line.["0a"]Next line.["0a"]"
14790 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14794 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14795 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14799 (@value{GDBP}) print 'max(x, y)
14803 When printing arrays, @value{GDBN} uses positional notation when the
14804 array has a lower bound of 1, and uses a modified named notation otherwise.
14805 For example, a one-dimensional array of three integers with a lower bound
14806 of 3 might print as
14813 That is, in contrast to valid Ada, only the first component has a @code{=>}
14817 You may abbreviate attributes in expressions with any unique,
14818 multi-character subsequence of
14819 their names (an exact match gets preference).
14820 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14821 in place of @t{a'length}.
14824 @cindex quoting Ada internal identifiers
14825 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14826 to lower case. The GNAT compiler uses upper-case characters for
14827 some of its internal identifiers, which are normally of no interest to users.
14828 For the rare occasions when you actually have to look at them,
14829 enclose them in angle brackets to avoid the lower-case mapping.
14832 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14836 Printing an object of class-wide type or dereferencing an
14837 access-to-class-wide value will display all the components of the object's
14838 specific type (as indicated by its run-time tag). Likewise, component
14839 selection on such a value will operate on the specific type of the
14844 @node Stopping Before Main Program
14845 @subsubsection Stopping at the Very Beginning
14847 @cindex breakpointing Ada elaboration code
14848 It is sometimes necessary to debug the program during elaboration, and
14849 before reaching the main procedure.
14850 As defined in the Ada Reference
14851 Manual, the elaboration code is invoked from a procedure called
14852 @code{adainit}. To run your program up to the beginning of
14853 elaboration, simply use the following two commands:
14854 @code{tbreak adainit} and @code{run}.
14857 @subsubsection Extensions for Ada Tasks
14858 @cindex Ada, tasking
14860 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14861 @value{GDBN} provides the following task-related commands:
14866 This command shows a list of current Ada tasks, as in the following example:
14873 (@value{GDBP}) info tasks
14874 ID TID P-ID Pri State Name
14875 1 8088000 0 15 Child Activation Wait main_task
14876 2 80a4000 1 15 Accept Statement b
14877 3 809a800 1 15 Child Activation Wait a
14878 * 4 80ae800 3 15 Runnable c
14883 In this listing, the asterisk before the last task indicates it to be the
14884 task currently being inspected.
14888 Represents @value{GDBN}'s internal task number.
14894 The parent's task ID (@value{GDBN}'s internal task number).
14897 The base priority of the task.
14900 Current state of the task.
14904 The task has been created but has not been activated. It cannot be
14908 The task is not blocked for any reason known to Ada. (It may be waiting
14909 for a mutex, though.) It is conceptually "executing" in normal mode.
14912 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14913 that were waiting on terminate alternatives have been awakened and have
14914 terminated themselves.
14916 @item Child Activation Wait
14917 The task is waiting for created tasks to complete activation.
14919 @item Accept Statement
14920 The task is waiting on an accept or selective wait statement.
14922 @item Waiting on entry call
14923 The task is waiting on an entry call.
14925 @item Async Select Wait
14926 The task is waiting to start the abortable part of an asynchronous
14930 The task is waiting on a select statement with only a delay
14933 @item Child Termination Wait
14934 The task is sleeping having completed a master within itself, and is
14935 waiting for the tasks dependent on that master to become terminated or
14936 waiting on a terminate Phase.
14938 @item Wait Child in Term Alt
14939 The task is sleeping waiting for tasks on terminate alternatives to
14940 finish terminating.
14942 @item Accepting RV with @var{taskno}
14943 The task is accepting a rendez-vous with the task @var{taskno}.
14947 Name of the task in the program.
14951 @kindex info task @var{taskno}
14952 @item info task @var{taskno}
14953 This command shows detailled informations on the specified task, as in
14954 the following example:
14959 (@value{GDBP}) info tasks
14960 ID TID P-ID Pri State Name
14961 1 8077880 0 15 Child Activation Wait main_task
14962 * 2 807c468 1 15 Runnable task_1
14963 (@value{GDBP}) info task 2
14964 Ada Task: 0x807c468
14967 Parent: 1 (main_task)
14973 @kindex task@r{ (Ada)}
14974 @cindex current Ada task ID
14975 This command prints the ID of the current task.
14981 (@value{GDBP}) info tasks
14982 ID TID P-ID Pri State Name
14983 1 8077870 0 15 Child Activation Wait main_task
14984 * 2 807c458 1 15 Runnable t
14985 (@value{GDBP}) task
14986 [Current task is 2]
14989 @item task @var{taskno}
14990 @cindex Ada task switching
14991 This command is like the @code{thread @var{threadno}}
14992 command (@pxref{Threads}). It switches the context of debugging
14993 from the current task to the given task.
14999 (@value{GDBP}) info tasks
15000 ID TID P-ID Pri State Name
15001 1 8077870 0 15 Child Activation Wait main_task
15002 * 2 807c458 1 15 Runnable t
15003 (@value{GDBP}) task 1
15004 [Switching to task 1]
15005 #0 0x8067726 in pthread_cond_wait ()
15007 #0 0x8067726 in pthread_cond_wait ()
15008 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15009 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15010 #3 0x806153e in system.tasking.stages.activate_tasks ()
15011 #4 0x804aacc in un () at un.adb:5
15014 @item break @var{linespec} task @var{taskno}
15015 @itemx break @var{linespec} task @var{taskno} if @dots{}
15016 @cindex breakpoints and tasks, in Ada
15017 @cindex task breakpoints, in Ada
15018 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15019 These commands are like the @code{break @dots{} thread @dots{}}
15020 command (@pxref{Thread Stops}).
15021 @var{linespec} specifies source lines, as described
15022 in @ref{Specify Location}.
15024 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15025 to specify that you only want @value{GDBN} to stop the program when a
15026 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15027 numeric task identifiers assigned by @value{GDBN}, shown in the first
15028 column of the @samp{info tasks} display.
15030 If you do not specify @samp{task @var{taskno}} when you set a
15031 breakpoint, the breakpoint applies to @emph{all} tasks of your
15034 You can use the @code{task} qualifier on conditional breakpoints as
15035 well; in this case, place @samp{task @var{taskno}} before the
15036 breakpoint condition (before the @code{if}).
15044 (@value{GDBP}) info tasks
15045 ID TID P-ID Pri State Name
15046 1 140022020 0 15 Child Activation Wait main_task
15047 2 140045060 1 15 Accept/Select Wait t2
15048 3 140044840 1 15 Runnable t1
15049 * 4 140056040 1 15 Runnable t3
15050 (@value{GDBP}) b 15 task 2
15051 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15052 (@value{GDBP}) cont
15057 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15059 (@value{GDBP}) info tasks
15060 ID TID P-ID Pri State Name
15061 1 140022020 0 15 Child Activation Wait main_task
15062 * 2 140045060 1 15 Runnable t2
15063 3 140044840 1 15 Runnable t1
15064 4 140056040 1 15 Delay Sleep t3
15068 @node Ada Tasks and Core Files
15069 @subsubsection Tasking Support when Debugging Core Files
15070 @cindex Ada tasking and core file debugging
15072 When inspecting a core file, as opposed to debugging a live program,
15073 tasking support may be limited or even unavailable, depending on
15074 the platform being used.
15075 For instance, on x86-linux, the list of tasks is available, but task
15076 switching is not supported. On Tru64, however, task switching will work
15079 On certain platforms, including Tru64, the debugger needs to perform some
15080 memory writes in order to provide Ada tasking support. When inspecting
15081 a core file, this means that the core file must be opened with read-write
15082 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15083 Under these circumstances, you should make a backup copy of the core
15084 file before inspecting it with @value{GDBN}.
15086 @node Ravenscar Profile
15087 @subsubsection Tasking Support when using the Ravenscar Profile
15088 @cindex Ravenscar Profile
15090 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15091 specifically designed for systems with safety-critical real-time
15095 @kindex set ravenscar task-switching on
15096 @cindex task switching with program using Ravenscar Profile
15097 @item set ravenscar task-switching on
15098 Allows task switching when debugging a program that uses the Ravenscar
15099 Profile. This is the default.
15101 @kindex set ravenscar task-switching off
15102 @item set ravenscar task-switching off
15103 Turn off task switching when debugging a program that uses the Ravenscar
15104 Profile. This is mostly intended to disable the code that adds support
15105 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15106 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15107 To be effective, this command should be run before the program is started.
15109 @kindex show ravenscar task-switching
15110 @item show ravenscar task-switching
15111 Show whether it is possible to switch from task to task in a program
15112 using the Ravenscar Profile.
15117 @subsubsection Known Peculiarities of Ada Mode
15118 @cindex Ada, problems
15120 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15121 we know of several problems with and limitations of Ada mode in
15123 some of which will be fixed with planned future releases of the debugger
15124 and the GNU Ada compiler.
15128 Static constants that the compiler chooses not to materialize as objects in
15129 storage are invisible to the debugger.
15132 Named parameter associations in function argument lists are ignored (the
15133 argument lists are treated as positional).
15136 Many useful library packages are currently invisible to the debugger.
15139 Fixed-point arithmetic, conversions, input, and output is carried out using
15140 floating-point arithmetic, and may give results that only approximate those on
15144 The GNAT compiler never generates the prefix @code{Standard} for any of
15145 the standard symbols defined by the Ada language. @value{GDBN} knows about
15146 this: it will strip the prefix from names when you use it, and will never
15147 look for a name you have so qualified among local symbols, nor match against
15148 symbols in other packages or subprograms. If you have
15149 defined entities anywhere in your program other than parameters and
15150 local variables whose simple names match names in @code{Standard},
15151 GNAT's lack of qualification here can cause confusion. When this happens,
15152 you can usually resolve the confusion
15153 by qualifying the problematic names with package
15154 @code{Standard} explicitly.
15157 Older versions of the compiler sometimes generate erroneous debugging
15158 information, resulting in the debugger incorrectly printing the value
15159 of affected entities. In some cases, the debugger is able to work
15160 around an issue automatically. In other cases, the debugger is able
15161 to work around the issue, but the work-around has to be specifically
15164 @kindex set ada trust-PAD-over-XVS
15165 @kindex show ada trust-PAD-over-XVS
15168 @item set ada trust-PAD-over-XVS on
15169 Configure GDB to strictly follow the GNAT encoding when computing the
15170 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15171 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15172 a complete description of the encoding used by the GNAT compiler).
15173 This is the default.
15175 @item set ada trust-PAD-over-XVS off
15176 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15177 sometimes prints the wrong value for certain entities, changing @code{ada
15178 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15179 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15180 @code{off}, but this incurs a slight performance penalty, so it is
15181 recommended to leave this setting to @code{on} unless necessary.
15185 @node Unsupported Languages
15186 @section Unsupported Languages
15188 @cindex unsupported languages
15189 @cindex minimal language
15190 In addition to the other fully-supported programming languages,
15191 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15192 It does not represent a real programming language, but provides a set
15193 of capabilities close to what the C or assembly languages provide.
15194 This should allow most simple operations to be performed while debugging
15195 an application that uses a language currently not supported by @value{GDBN}.
15197 If the language is set to @code{auto}, @value{GDBN} will automatically
15198 select this language if the current frame corresponds to an unsupported
15202 @chapter Examining the Symbol Table
15204 The commands described in this chapter allow you to inquire about the
15205 symbols (names of variables, functions and types) defined in your
15206 program. This information is inherent in the text of your program and
15207 does not change as your program executes. @value{GDBN} finds it in your
15208 program's symbol table, in the file indicated when you started @value{GDBN}
15209 (@pxref{File Options, ,Choosing Files}), or by one of the
15210 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15212 @cindex symbol names
15213 @cindex names of symbols
15214 @cindex quoting names
15215 Occasionally, you may need to refer to symbols that contain unusual
15216 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15217 most frequent case is in referring to static variables in other
15218 source files (@pxref{Variables,,Program Variables}). File names
15219 are recorded in object files as debugging symbols, but @value{GDBN} would
15220 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15221 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15222 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15229 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15232 @cindex case-insensitive symbol names
15233 @cindex case sensitivity in symbol names
15234 @kindex set case-sensitive
15235 @item set case-sensitive on
15236 @itemx set case-sensitive off
15237 @itemx set case-sensitive auto
15238 Normally, when @value{GDBN} looks up symbols, it matches their names
15239 with case sensitivity determined by the current source language.
15240 Occasionally, you may wish to control that. The command @code{set
15241 case-sensitive} lets you do that by specifying @code{on} for
15242 case-sensitive matches or @code{off} for case-insensitive ones. If
15243 you specify @code{auto}, case sensitivity is reset to the default
15244 suitable for the source language. The default is case-sensitive
15245 matches for all languages except for Fortran, for which the default is
15246 case-insensitive matches.
15248 @kindex show case-sensitive
15249 @item show case-sensitive
15250 This command shows the current setting of case sensitivity for symbols
15253 @kindex set print type methods
15254 @item set print type methods
15255 @itemx set print type methods on
15256 @itemx set print type methods off
15257 Normally, when @value{GDBN} prints a class, it displays any methods
15258 declared in that class. You can control this behavior either by
15259 passing the appropriate flag to @code{ptype}, or using @command{set
15260 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15261 display the methods; this is the default. Specifying @code{off} will
15262 cause @value{GDBN} to omit the methods.
15264 @kindex show print type methods
15265 @item show print type methods
15266 This command shows the current setting of method display when printing
15269 @kindex set print type typedefs
15270 @item set print type typedefs
15271 @itemx set print type typedefs on
15272 @itemx set print type typedefs off
15274 Normally, when @value{GDBN} prints a class, it displays any typedefs
15275 defined in that class. You can control this behavior either by
15276 passing the appropriate flag to @code{ptype}, or using @command{set
15277 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15278 display the typedef definitions; this is the default. Specifying
15279 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15280 Note that this controls whether the typedef definition itself is
15281 printed, not whether typedef names are substituted when printing other
15284 @kindex show print type typedefs
15285 @item show print type typedefs
15286 This command shows the current setting of typedef display when
15289 @kindex info address
15290 @cindex address of a symbol
15291 @item info address @var{symbol}
15292 Describe where the data for @var{symbol} is stored. For a register
15293 variable, this says which register it is kept in. For a non-register
15294 local variable, this prints the stack-frame offset at which the variable
15297 Note the contrast with @samp{print &@var{symbol}}, which does not work
15298 at all for a register variable, and for a stack local variable prints
15299 the exact address of the current instantiation of the variable.
15301 @kindex info symbol
15302 @cindex symbol from address
15303 @cindex closest symbol and offset for an address
15304 @item info symbol @var{addr}
15305 Print the name of a symbol which is stored at the address @var{addr}.
15306 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15307 nearest symbol and an offset from it:
15310 (@value{GDBP}) info symbol 0x54320
15311 _initialize_vx + 396 in section .text
15315 This is the opposite of the @code{info address} command. You can use
15316 it to find out the name of a variable or a function given its address.
15318 For dynamically linked executables, the name of executable or shared
15319 library containing the symbol is also printed:
15322 (@value{GDBP}) info symbol 0x400225
15323 _start + 5 in section .text of /tmp/a.out
15324 (@value{GDBP}) info symbol 0x2aaaac2811cf
15325 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15329 @item whatis[/@var{flags}] [@var{arg}]
15330 Print the data type of @var{arg}, which can be either an expression
15331 or a name of a data type. With no argument, print the data type of
15332 @code{$}, the last value in the value history.
15334 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15335 is not actually evaluated, and any side-effecting operations (such as
15336 assignments or function calls) inside it do not take place.
15338 If @var{arg} is a variable or an expression, @code{whatis} prints its
15339 literal type as it is used in the source code. If the type was
15340 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15341 the data type underlying the @code{typedef}. If the type of the
15342 variable or the expression is a compound data type, such as
15343 @code{struct} or @code{class}, @code{whatis} never prints their
15344 fields or methods. It just prints the @code{struct}/@code{class}
15345 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15346 such a compound data type, use @code{ptype}.
15348 If @var{arg} is a type name that was defined using @code{typedef},
15349 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15350 Unrolling means that @code{whatis} will show the underlying type used
15351 in the @code{typedef} declaration of @var{arg}. However, if that
15352 underlying type is also a @code{typedef}, @code{whatis} will not
15355 For C code, the type names may also have the form @samp{class
15356 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15357 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15359 @var{flags} can be used to modify how the type is displayed.
15360 Available flags are:
15364 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15365 parameters and typedefs defined in a class when printing the class'
15366 members. The @code{/r} flag disables this.
15369 Do not print methods defined in the class.
15372 Print methods defined in the class. This is the default, but the flag
15373 exists in case you change the default with @command{set print type methods}.
15376 Do not print typedefs defined in the class. Note that this controls
15377 whether the typedef definition itself is printed, not whether typedef
15378 names are substituted when printing other types.
15381 Print typedefs defined in the class. This is the default, but the flag
15382 exists in case you change the default with @command{set print type typedefs}.
15386 @item ptype[/@var{flags}] [@var{arg}]
15387 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15388 detailed description of the type, instead of just the name of the type.
15389 @xref{Expressions, ,Expressions}.
15391 Contrary to @code{whatis}, @code{ptype} always unrolls any
15392 @code{typedef}s in its argument declaration, whether the argument is
15393 a variable, expression, or a data type. This means that @code{ptype}
15394 of a variable or an expression will not print literally its type as
15395 present in the source code---use @code{whatis} for that. @code{typedef}s at
15396 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15397 fields, methods and inner @code{class typedef}s of @code{struct}s,
15398 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15400 For example, for this variable declaration:
15403 typedef double real_t;
15404 struct complex @{ real_t real; double imag; @};
15405 typedef struct complex complex_t;
15407 real_t *real_pointer_var;
15411 the two commands give this output:
15415 (@value{GDBP}) whatis var
15417 (@value{GDBP}) ptype var
15418 type = struct complex @{
15422 (@value{GDBP}) whatis complex_t
15423 type = struct complex
15424 (@value{GDBP}) whatis struct complex
15425 type = struct complex
15426 (@value{GDBP}) ptype struct complex
15427 type = struct complex @{
15431 (@value{GDBP}) whatis real_pointer_var
15433 (@value{GDBP}) ptype real_pointer_var
15439 As with @code{whatis}, using @code{ptype} without an argument refers to
15440 the type of @code{$}, the last value in the value history.
15442 @cindex incomplete type
15443 Sometimes, programs use opaque data types or incomplete specifications
15444 of complex data structure. If the debug information included in the
15445 program does not allow @value{GDBN} to display a full declaration of
15446 the data type, it will say @samp{<incomplete type>}. For example,
15447 given these declarations:
15451 struct foo *fooptr;
15455 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15458 (@value{GDBP}) ptype foo
15459 $1 = <incomplete type>
15463 ``Incomplete type'' is C terminology for data types that are not
15464 completely specified.
15467 @item info types @var{regexp}
15469 Print a brief description of all types whose names match the regular
15470 expression @var{regexp} (or all types in your program, if you supply
15471 no argument). Each complete typename is matched as though it were a
15472 complete line; thus, @samp{i type value} gives information on all
15473 types in your program whose names include the string @code{value}, but
15474 @samp{i type ^value$} gives information only on types whose complete
15475 name is @code{value}.
15477 This command differs from @code{ptype} in two ways: first, like
15478 @code{whatis}, it does not print a detailed description; second, it
15479 lists all source files where a type is defined.
15481 @kindex info type-printers
15482 @item info type-printers
15483 Versions of @value{GDBN} that ship with Python scripting enabled may
15484 have ``type printers'' available. When using @command{ptype} or
15485 @command{whatis}, these printers are consulted when the name of a type
15486 is needed. @xref{Type Printing API}, for more information on writing
15489 @code{info type-printers} displays all the available type printers.
15491 @kindex enable type-printer
15492 @kindex disable type-printer
15493 @item enable type-printer @var{name}@dots{}
15494 @item disable type-printer @var{name}@dots{}
15495 These commands can be used to enable or disable type printers.
15498 @cindex local variables
15499 @item info scope @var{location}
15500 List all the variables local to a particular scope. This command
15501 accepts a @var{location} argument---a function name, a source line, or
15502 an address preceded by a @samp{*}, and prints all the variables local
15503 to the scope defined by that location. (@xref{Specify Location}, for
15504 details about supported forms of @var{location}.) For example:
15507 (@value{GDBP}) @b{info scope command_line_handler}
15508 Scope for command_line_handler:
15509 Symbol rl is an argument at stack/frame offset 8, length 4.
15510 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15511 Symbol linelength is in static storage at address 0x150a1c, length 4.
15512 Symbol p is a local variable in register $esi, length 4.
15513 Symbol p1 is a local variable in register $ebx, length 4.
15514 Symbol nline is a local variable in register $edx, length 4.
15515 Symbol repeat is a local variable at frame offset -8, length 4.
15519 This command is especially useful for determining what data to collect
15520 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15523 @kindex info source
15525 Show information about the current source file---that is, the source file for
15526 the function containing the current point of execution:
15529 the name of the source file, and the directory containing it,
15531 the directory it was compiled in,
15533 its length, in lines,
15535 which programming language it is written in,
15537 whether the executable includes debugging information for that file, and
15538 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15540 whether the debugging information includes information about
15541 preprocessor macros.
15545 @kindex info sources
15547 Print the names of all source files in your program for which there is
15548 debugging information, organized into two lists: files whose symbols
15549 have already been read, and files whose symbols will be read when needed.
15551 @kindex info functions
15552 @item info functions
15553 Print the names and data types of all defined functions.
15555 @item info functions @var{regexp}
15556 Print the names and data types of all defined functions
15557 whose names contain a match for regular expression @var{regexp}.
15558 Thus, @samp{info fun step} finds all functions whose names
15559 include @code{step}; @samp{info fun ^step} finds those whose names
15560 start with @code{step}. If a function name contains characters
15561 that conflict with the regular expression language (e.g.@:
15562 @samp{operator*()}), they may be quoted with a backslash.
15564 @kindex info variables
15565 @item info variables
15566 Print the names and data types of all variables that are defined
15567 outside of functions (i.e.@: excluding local variables).
15569 @item info variables @var{regexp}
15570 Print the names and data types of all variables (except for local
15571 variables) whose names contain a match for regular expression
15574 @kindex info classes
15575 @cindex Objective-C, classes and selectors
15577 @itemx info classes @var{regexp}
15578 Display all Objective-C classes in your program, or
15579 (with the @var{regexp} argument) all those matching a particular regular
15582 @kindex info selectors
15583 @item info selectors
15584 @itemx info selectors @var{regexp}
15585 Display all Objective-C selectors in your program, or
15586 (with the @var{regexp} argument) all those matching a particular regular
15590 This was never implemented.
15591 @kindex info methods
15593 @itemx info methods @var{regexp}
15594 The @code{info methods} command permits the user to examine all defined
15595 methods within C@t{++} program, or (with the @var{regexp} argument) a
15596 specific set of methods found in the various C@t{++} classes. Many
15597 C@t{++} classes provide a large number of methods. Thus, the output
15598 from the @code{ptype} command can be overwhelming and hard to use. The
15599 @code{info-methods} command filters the methods, printing only those
15600 which match the regular-expression @var{regexp}.
15603 @cindex opaque data types
15604 @kindex set opaque-type-resolution
15605 @item set opaque-type-resolution on
15606 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15607 declared as a pointer to a @code{struct}, @code{class}, or
15608 @code{union}---for example, @code{struct MyType *}---that is used in one
15609 source file although the full declaration of @code{struct MyType} is in
15610 another source file. The default is on.
15612 A change in the setting of this subcommand will not take effect until
15613 the next time symbols for a file are loaded.
15615 @item set opaque-type-resolution off
15616 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15617 is printed as follows:
15619 @{<no data fields>@}
15622 @kindex show opaque-type-resolution
15623 @item show opaque-type-resolution
15624 Show whether opaque types are resolved or not.
15626 @kindex maint print symbols
15627 @cindex symbol dump
15628 @kindex maint print psymbols
15629 @cindex partial symbol dump
15630 @item maint print symbols @var{filename}
15631 @itemx maint print psymbols @var{filename}
15632 @itemx maint print msymbols @var{filename}
15633 Write a dump of debugging symbol data into the file @var{filename}.
15634 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15635 symbols with debugging data are included. If you use @samp{maint print
15636 symbols}, @value{GDBN} includes all the symbols for which it has already
15637 collected full details: that is, @var{filename} reflects symbols for
15638 only those files whose symbols @value{GDBN} has read. You can use the
15639 command @code{info sources} to find out which files these are. If you
15640 use @samp{maint print psymbols} instead, the dump shows information about
15641 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15642 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15643 @samp{maint print msymbols} dumps just the minimal symbol information
15644 required for each object file from which @value{GDBN} has read some symbols.
15645 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15646 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15648 @kindex maint info symtabs
15649 @kindex maint info psymtabs
15650 @cindex listing @value{GDBN}'s internal symbol tables
15651 @cindex symbol tables, listing @value{GDBN}'s internal
15652 @cindex full symbol tables, listing @value{GDBN}'s internal
15653 @cindex partial symbol tables, listing @value{GDBN}'s internal
15654 @item maint info symtabs @r{[} @var{regexp} @r{]}
15655 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15657 List the @code{struct symtab} or @code{struct partial_symtab}
15658 structures whose names match @var{regexp}. If @var{regexp} is not
15659 given, list them all. The output includes expressions which you can
15660 copy into a @value{GDBN} debugging this one to examine a particular
15661 structure in more detail. For example:
15664 (@value{GDBP}) maint info psymtabs dwarf2read
15665 @{ objfile /home/gnu/build/gdb/gdb
15666 ((struct objfile *) 0x82e69d0)
15667 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15668 ((struct partial_symtab *) 0x8474b10)
15671 text addresses 0x814d3c8 -- 0x8158074
15672 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15673 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15674 dependencies (none)
15677 (@value{GDBP}) maint info symtabs
15681 We see that there is one partial symbol table whose filename contains
15682 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15683 and we see that @value{GDBN} has not read in any symtabs yet at all.
15684 If we set a breakpoint on a function, that will cause @value{GDBN} to
15685 read the symtab for the compilation unit containing that function:
15688 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15689 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15691 (@value{GDBP}) maint info symtabs
15692 @{ objfile /home/gnu/build/gdb/gdb
15693 ((struct objfile *) 0x82e69d0)
15694 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15695 ((struct symtab *) 0x86c1f38)
15698 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15699 linetable ((struct linetable *) 0x8370fa0)
15700 debugformat DWARF 2
15709 @chapter Altering Execution
15711 Once you think you have found an error in your program, you might want to
15712 find out for certain whether correcting the apparent error would lead to
15713 correct results in the rest of the run. You can find the answer by
15714 experiment, using the @value{GDBN} features for altering execution of the
15717 For example, you can store new values into variables or memory
15718 locations, give your program a signal, restart it at a different
15719 address, or even return prematurely from a function.
15722 * Assignment:: Assignment to variables
15723 * Jumping:: Continuing at a different address
15724 * Signaling:: Giving your program a signal
15725 * Returning:: Returning from a function
15726 * Calling:: Calling your program's functions
15727 * Patching:: Patching your program
15731 @section Assignment to Variables
15734 @cindex setting variables
15735 To alter the value of a variable, evaluate an assignment expression.
15736 @xref{Expressions, ,Expressions}. For example,
15743 stores the value 4 into the variable @code{x}, and then prints the
15744 value of the assignment expression (which is 4).
15745 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15746 information on operators in supported languages.
15748 @kindex set variable
15749 @cindex variables, setting
15750 If you are not interested in seeing the value of the assignment, use the
15751 @code{set} command instead of the @code{print} command. @code{set} is
15752 really the same as @code{print} except that the expression's value is
15753 not printed and is not put in the value history (@pxref{Value History,
15754 ,Value History}). The expression is evaluated only for its effects.
15756 If the beginning of the argument string of the @code{set} command
15757 appears identical to a @code{set} subcommand, use the @code{set
15758 variable} command instead of just @code{set}. This command is identical
15759 to @code{set} except for its lack of subcommands. For example, if your
15760 program has a variable @code{width}, you get an error if you try to set
15761 a new value with just @samp{set width=13}, because @value{GDBN} has the
15762 command @code{set width}:
15765 (@value{GDBP}) whatis width
15767 (@value{GDBP}) p width
15769 (@value{GDBP}) set width=47
15770 Invalid syntax in expression.
15774 The invalid expression, of course, is @samp{=47}. In
15775 order to actually set the program's variable @code{width}, use
15778 (@value{GDBP}) set var width=47
15781 Because the @code{set} command has many subcommands that can conflict
15782 with the names of program variables, it is a good idea to use the
15783 @code{set variable} command instead of just @code{set}. For example, if
15784 your program has a variable @code{g}, you run into problems if you try
15785 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15786 the command @code{set gnutarget}, abbreviated @code{set g}:
15790 (@value{GDBP}) whatis g
15794 (@value{GDBP}) set g=4
15798 The program being debugged has been started already.
15799 Start it from the beginning? (y or n) y
15800 Starting program: /home/smith/cc_progs/a.out
15801 "/home/smith/cc_progs/a.out": can't open to read symbols:
15802 Invalid bfd target.
15803 (@value{GDBP}) show g
15804 The current BFD target is "=4".
15809 The program variable @code{g} did not change, and you silently set the
15810 @code{gnutarget} to an invalid value. In order to set the variable
15814 (@value{GDBP}) set var g=4
15817 @value{GDBN} allows more implicit conversions in assignments than C; you can
15818 freely store an integer value into a pointer variable or vice versa,
15819 and you can convert any structure to any other structure that is the
15820 same length or shorter.
15821 @comment FIXME: how do structs align/pad in these conversions?
15822 @comment /doc@cygnus.com 18dec1990
15824 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15825 construct to generate a value of specified type at a specified address
15826 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15827 to memory location @code{0x83040} as an integer (which implies a certain size
15828 and representation in memory), and
15831 set @{int@}0x83040 = 4
15835 stores the value 4 into that memory location.
15838 @section Continuing at a Different Address
15840 Ordinarily, when you continue your program, you do so at the place where
15841 it stopped, with the @code{continue} command. You can instead continue at
15842 an address of your own choosing, with the following commands:
15846 @kindex j @r{(@code{jump})}
15847 @item jump @var{linespec}
15848 @itemx j @var{linespec}
15849 @itemx jump @var{location}
15850 @itemx j @var{location}
15851 Resume execution at line @var{linespec} or at address given by
15852 @var{location}. Execution stops again immediately if there is a
15853 breakpoint there. @xref{Specify Location}, for a description of the
15854 different forms of @var{linespec} and @var{location}. It is common
15855 practice to use the @code{tbreak} command in conjunction with
15856 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15858 The @code{jump} command does not change the current stack frame, or
15859 the stack pointer, or the contents of any memory location or any
15860 register other than the program counter. If line @var{linespec} is in
15861 a different function from the one currently executing, the results may
15862 be bizarre if the two functions expect different patterns of arguments or
15863 of local variables. For this reason, the @code{jump} command requests
15864 confirmation if the specified line is not in the function currently
15865 executing. However, even bizarre results are predictable if you are
15866 well acquainted with the machine-language code of your program.
15869 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15870 On many systems, you can get much the same effect as the @code{jump}
15871 command by storing a new value into the register @code{$pc}. The
15872 difference is that this does not start your program running; it only
15873 changes the address of where it @emph{will} run when you continue. For
15881 makes the next @code{continue} command or stepping command execute at
15882 address @code{0x485}, rather than at the address where your program stopped.
15883 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15885 The most common occasion to use the @code{jump} command is to back
15886 up---perhaps with more breakpoints set---over a portion of a program
15887 that has already executed, in order to examine its execution in more
15892 @section Giving your Program a Signal
15893 @cindex deliver a signal to a program
15897 @item signal @var{signal}
15898 Resume execution where your program stopped, but immediately give it the
15899 signal @var{signal}. @var{signal} can be the name or the number of a
15900 signal. For example, on many systems @code{signal 2} and @code{signal
15901 SIGINT} are both ways of sending an interrupt signal.
15903 Alternatively, if @var{signal} is zero, continue execution without
15904 giving a signal. This is useful when your program stopped on account of
15905 a signal and would ordinarily see the signal when resumed with the
15906 @code{continue} command; @samp{signal 0} causes it to resume without a
15909 @code{signal} does not repeat when you press @key{RET} a second time
15910 after executing the command.
15914 Invoking the @code{signal} command is not the same as invoking the
15915 @code{kill} utility from the shell. Sending a signal with @code{kill}
15916 causes @value{GDBN} to decide what to do with the signal depending on
15917 the signal handling tables (@pxref{Signals}). The @code{signal} command
15918 passes the signal directly to your program.
15922 @section Returning from a Function
15925 @cindex returning from a function
15928 @itemx return @var{expression}
15929 You can cancel execution of a function call with the @code{return}
15930 command. If you give an
15931 @var{expression} argument, its value is used as the function's return
15935 When you use @code{return}, @value{GDBN} discards the selected stack frame
15936 (and all frames within it). You can think of this as making the
15937 discarded frame return prematurely. If you wish to specify a value to
15938 be returned, give that value as the argument to @code{return}.
15940 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15941 Frame}), and any other frames inside of it, leaving its caller as the
15942 innermost remaining frame. That frame becomes selected. The
15943 specified value is stored in the registers used for returning values
15946 The @code{return} command does not resume execution; it leaves the
15947 program stopped in the state that would exist if the function had just
15948 returned. In contrast, the @code{finish} command (@pxref{Continuing
15949 and Stepping, ,Continuing and Stepping}) resumes execution until the
15950 selected stack frame returns naturally.
15952 @value{GDBN} needs to know how the @var{expression} argument should be set for
15953 the inferior. The concrete registers assignment depends on the OS ABI and the
15954 type being returned by the selected stack frame. For example it is common for
15955 OS ABI to return floating point values in FPU registers while integer values in
15956 CPU registers. Still some ABIs return even floating point values in CPU
15957 registers. Larger integer widths (such as @code{long long int}) also have
15958 specific placement rules. @value{GDBN} already knows the OS ABI from its
15959 current target so it needs to find out also the type being returned to make the
15960 assignment into the right register(s).
15962 Normally, the selected stack frame has debug info. @value{GDBN} will always
15963 use the debug info instead of the implicit type of @var{expression} when the
15964 debug info is available. For example, if you type @kbd{return -1}, and the
15965 function in the current stack frame is declared to return a @code{long long
15966 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15967 into a @code{long long int}:
15970 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15972 (@value{GDBP}) return -1
15973 Make func return now? (y or n) y
15974 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15975 43 printf ("result=%lld\n", func ());
15979 However, if the selected stack frame does not have a debug info, e.g., if the
15980 function was compiled without debug info, @value{GDBN} has to find out the type
15981 to return from user. Specifying a different type by mistake may set the value
15982 in different inferior registers than the caller code expects. For example,
15983 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15984 of a @code{long long int} result for a debug info less function (on 32-bit
15985 architectures). Therefore the user is required to specify the return type by
15986 an appropriate cast explicitly:
15989 Breakpoint 2, 0x0040050b in func ()
15990 (@value{GDBP}) return -1
15991 Return value type not available for selected stack frame.
15992 Please use an explicit cast of the value to return.
15993 (@value{GDBP}) return (long long int) -1
15994 Make selected stack frame return now? (y or n) y
15995 #0 0x00400526 in main ()
16000 @section Calling Program Functions
16003 @cindex calling functions
16004 @cindex inferior functions, calling
16005 @item print @var{expr}
16006 Evaluate the expression @var{expr} and display the resulting value.
16007 @var{expr} may include calls to functions in the program being
16011 @item call @var{expr}
16012 Evaluate the expression @var{expr} without displaying @code{void}
16015 You can use this variant of the @code{print} command if you want to
16016 execute a function from your program that does not return anything
16017 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16018 with @code{void} returned values that @value{GDBN} will otherwise
16019 print. If the result is not void, it is printed and saved in the
16023 It is possible for the function you call via the @code{print} or
16024 @code{call} command to generate a signal (e.g., if there's a bug in
16025 the function, or if you passed it incorrect arguments). What happens
16026 in that case is controlled by the @code{set unwindonsignal} command.
16028 Similarly, with a C@t{++} program it is possible for the function you
16029 call via the @code{print} or @code{call} command to generate an
16030 exception that is not handled due to the constraints of the dummy
16031 frame. In this case, any exception that is raised in the frame, but has
16032 an out-of-frame exception handler will not be found. GDB builds a
16033 dummy-frame for the inferior function call, and the unwinder cannot
16034 seek for exception handlers outside of this dummy-frame. What happens
16035 in that case is controlled by the
16036 @code{set unwind-on-terminating-exception} command.
16039 @item set unwindonsignal
16040 @kindex set unwindonsignal
16041 @cindex unwind stack in called functions
16042 @cindex call dummy stack unwinding
16043 Set unwinding of the stack if a signal is received while in a function
16044 that @value{GDBN} called in the program being debugged. If set to on,
16045 @value{GDBN} unwinds the stack it created for the call and restores
16046 the context to what it was before the call. If set to off (the
16047 default), @value{GDBN} stops in the frame where the signal was
16050 @item show unwindonsignal
16051 @kindex show unwindonsignal
16052 Show the current setting of stack unwinding in the functions called by
16055 @item set unwind-on-terminating-exception
16056 @kindex set unwind-on-terminating-exception
16057 @cindex unwind stack in called functions with unhandled exceptions
16058 @cindex call dummy stack unwinding on unhandled exception.
16059 Set unwinding of the stack if a C@t{++} exception is raised, but left
16060 unhandled while in a function that @value{GDBN} called in the program being
16061 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16062 it created for the call and restores the context to what it was before
16063 the call. If set to off, @value{GDBN} the exception is delivered to
16064 the default C@t{++} exception handler and the inferior terminated.
16066 @item show unwind-on-terminating-exception
16067 @kindex show unwind-on-terminating-exception
16068 Show the current setting of stack unwinding in the functions called by
16073 @cindex weak alias functions
16074 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16075 for another function. In such case, @value{GDBN} might not pick up
16076 the type information, including the types of the function arguments,
16077 which causes @value{GDBN} to call the inferior function incorrectly.
16078 As a result, the called function will function erroneously and may
16079 even crash. A solution to that is to use the name of the aliased
16083 @section Patching Programs
16085 @cindex patching binaries
16086 @cindex writing into executables
16087 @cindex writing into corefiles
16089 By default, @value{GDBN} opens the file containing your program's
16090 executable code (or the corefile) read-only. This prevents accidental
16091 alterations to machine code; but it also prevents you from intentionally
16092 patching your program's binary.
16094 If you'd like to be able to patch the binary, you can specify that
16095 explicitly with the @code{set write} command. For example, you might
16096 want to turn on internal debugging flags, or even to make emergency
16102 @itemx set write off
16103 If you specify @samp{set write on}, @value{GDBN} opens executable and
16104 core files for both reading and writing; if you specify @kbd{set write
16105 off} (the default), @value{GDBN} opens them read-only.
16107 If you have already loaded a file, you must load it again (using the
16108 @code{exec-file} or @code{core-file} command) after changing @code{set
16109 write}, for your new setting to take effect.
16113 Display whether executable files and core files are opened for writing
16114 as well as reading.
16118 @chapter @value{GDBN} Files
16120 @value{GDBN} needs to know the file name of the program to be debugged,
16121 both in order to read its symbol table and in order to start your
16122 program. To debug a core dump of a previous run, you must also tell
16123 @value{GDBN} the name of the core dump file.
16126 * Files:: Commands to specify files
16127 * Separate Debug Files:: Debugging information in separate files
16128 * MiniDebugInfo:: Debugging information in a special section
16129 * Index Files:: Index files speed up GDB
16130 * Symbol Errors:: Errors reading symbol files
16131 * Data Files:: GDB data files
16135 @section Commands to Specify Files
16137 @cindex symbol table
16138 @cindex core dump file
16140 You may want to specify executable and core dump file names. The usual
16141 way to do this is at start-up time, using the arguments to
16142 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16143 Out of @value{GDBN}}).
16145 Occasionally it is necessary to change to a different file during a
16146 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16147 specify a file you want to use. Or you are debugging a remote target
16148 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16149 Program}). In these situations the @value{GDBN} commands to specify
16150 new files are useful.
16153 @cindex executable file
16155 @item file @var{filename}
16156 Use @var{filename} as the program to be debugged. It is read for its
16157 symbols and for the contents of pure memory. It is also the program
16158 executed when you use the @code{run} command. If you do not specify a
16159 directory and the file is not found in the @value{GDBN} working directory,
16160 @value{GDBN} uses the environment variable @code{PATH} as a list of
16161 directories to search, just as the shell does when looking for a program
16162 to run. You can change the value of this variable, for both @value{GDBN}
16163 and your program, using the @code{path} command.
16165 @cindex unlinked object files
16166 @cindex patching object files
16167 You can load unlinked object @file{.o} files into @value{GDBN} using
16168 the @code{file} command. You will not be able to ``run'' an object
16169 file, but you can disassemble functions and inspect variables. Also,
16170 if the underlying BFD functionality supports it, you could use
16171 @kbd{gdb -write} to patch object files using this technique. Note
16172 that @value{GDBN} can neither interpret nor modify relocations in this
16173 case, so branches and some initialized variables will appear to go to
16174 the wrong place. But this feature is still handy from time to time.
16177 @code{file} with no argument makes @value{GDBN} discard any information it
16178 has on both executable file and the symbol table.
16181 @item exec-file @r{[} @var{filename} @r{]}
16182 Specify that the program to be run (but not the symbol table) is found
16183 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16184 if necessary to locate your program. Omitting @var{filename} means to
16185 discard information on the executable file.
16187 @kindex symbol-file
16188 @item symbol-file @r{[} @var{filename} @r{]}
16189 Read symbol table information from file @var{filename}. @code{PATH} is
16190 searched when necessary. Use the @code{file} command to get both symbol
16191 table and program to run from the same file.
16193 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16194 program's symbol table.
16196 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16197 some breakpoints and auto-display expressions. This is because they may
16198 contain pointers to the internal data recording symbols and data types,
16199 which are part of the old symbol table data being discarded inside
16202 @code{symbol-file} does not repeat if you press @key{RET} again after
16205 When @value{GDBN} is configured for a particular environment, it
16206 understands debugging information in whatever format is the standard
16207 generated for that environment; you may use either a @sc{gnu} compiler, or
16208 other compilers that adhere to the local conventions.
16209 Best results are usually obtained from @sc{gnu} compilers; for example,
16210 using @code{@value{NGCC}} you can generate debugging information for
16213 For most kinds of object files, with the exception of old SVR3 systems
16214 using COFF, the @code{symbol-file} command does not normally read the
16215 symbol table in full right away. Instead, it scans the symbol table
16216 quickly to find which source files and which symbols are present. The
16217 details are read later, one source file at a time, as they are needed.
16219 The purpose of this two-stage reading strategy is to make @value{GDBN}
16220 start up faster. For the most part, it is invisible except for
16221 occasional pauses while the symbol table details for a particular source
16222 file are being read. (The @code{set verbose} command can turn these
16223 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16224 Warnings and Messages}.)
16226 We have not implemented the two-stage strategy for COFF yet. When the
16227 symbol table is stored in COFF format, @code{symbol-file} reads the
16228 symbol table data in full right away. Note that ``stabs-in-COFF''
16229 still does the two-stage strategy, since the debug info is actually
16233 @cindex reading symbols immediately
16234 @cindex symbols, reading immediately
16235 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16236 @itemx file @r{[} -readnow @r{]} @var{filename}
16237 You can override the @value{GDBN} two-stage strategy for reading symbol
16238 tables by using the @samp{-readnow} option with any of the commands that
16239 load symbol table information, if you want to be sure @value{GDBN} has the
16240 entire symbol table available.
16242 @c FIXME: for now no mention of directories, since this seems to be in
16243 @c flux. 13mar1992 status is that in theory GDB would look either in
16244 @c current dir or in same dir as myprog; but issues like competing
16245 @c GDB's, or clutter in system dirs, mean that in practice right now
16246 @c only current dir is used. FFish says maybe a special GDB hierarchy
16247 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16251 @item core-file @r{[}@var{filename}@r{]}
16253 Specify the whereabouts of a core dump file to be used as the ``contents
16254 of memory''. Traditionally, core files contain only some parts of the
16255 address space of the process that generated them; @value{GDBN} can access the
16256 executable file itself for other parts.
16258 @code{core-file} with no argument specifies that no core file is
16261 Note that the core file is ignored when your program is actually running
16262 under @value{GDBN}. So, if you have been running your program and you
16263 wish to debug a core file instead, you must kill the subprocess in which
16264 the program is running. To do this, use the @code{kill} command
16265 (@pxref{Kill Process, ,Killing the Child Process}).
16267 @kindex add-symbol-file
16268 @cindex dynamic linking
16269 @item add-symbol-file @var{filename} @var{address}
16270 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16271 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16272 The @code{add-symbol-file} command reads additional symbol table
16273 information from the file @var{filename}. You would use this command
16274 when @var{filename} has been dynamically loaded (by some other means)
16275 into the program that is running. @var{address} should be the memory
16276 address at which the file has been loaded; @value{GDBN} cannot figure
16277 this out for itself. You can additionally specify an arbitrary number
16278 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16279 section name and base address for that section. You can specify any
16280 @var{address} as an expression.
16282 The symbol table of the file @var{filename} is added to the symbol table
16283 originally read with the @code{symbol-file} command. You can use the
16284 @code{add-symbol-file} command any number of times; the new symbol data
16285 thus read keeps adding to the old. To discard all old symbol data
16286 instead, use the @code{symbol-file} command without any arguments.
16288 @cindex relocatable object files, reading symbols from
16289 @cindex object files, relocatable, reading symbols from
16290 @cindex reading symbols from relocatable object files
16291 @cindex symbols, reading from relocatable object files
16292 @cindex @file{.o} files, reading symbols from
16293 Although @var{filename} is typically a shared library file, an
16294 executable file, or some other object file which has been fully
16295 relocated for loading into a process, you can also load symbolic
16296 information from relocatable @file{.o} files, as long as:
16300 the file's symbolic information refers only to linker symbols defined in
16301 that file, not to symbols defined by other object files,
16303 every section the file's symbolic information refers to has actually
16304 been loaded into the inferior, as it appears in the file, and
16306 you can determine the address at which every section was loaded, and
16307 provide these to the @code{add-symbol-file} command.
16311 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16312 relocatable files into an already running program; such systems
16313 typically make the requirements above easy to meet. However, it's
16314 important to recognize that many native systems use complex link
16315 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16316 assembly, for example) that make the requirements difficult to meet. In
16317 general, one cannot assume that using @code{add-symbol-file} to read a
16318 relocatable object file's symbolic information will have the same effect
16319 as linking the relocatable object file into the program in the normal
16322 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16324 @kindex add-symbol-file-from-memory
16325 @cindex @code{syscall DSO}
16326 @cindex load symbols from memory
16327 @item add-symbol-file-from-memory @var{address}
16328 Load symbols from the given @var{address} in a dynamically loaded
16329 object file whose image is mapped directly into the inferior's memory.
16330 For example, the Linux kernel maps a @code{syscall DSO} into each
16331 process's address space; this DSO provides kernel-specific code for
16332 some system calls. The argument can be any expression whose
16333 evaluation yields the address of the file's shared object file header.
16334 For this command to work, you must have used @code{symbol-file} or
16335 @code{exec-file} commands in advance.
16337 @kindex add-shared-symbol-files
16339 @item add-shared-symbol-files @var{library-file}
16340 @itemx assf @var{library-file}
16341 The @code{add-shared-symbol-files} command can currently be used only
16342 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16343 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16344 @value{GDBN} automatically looks for shared libraries, however if
16345 @value{GDBN} does not find yours, you can invoke
16346 @code{add-shared-symbol-files}. It takes one argument: the shared
16347 library's file name. @code{assf} is a shorthand alias for
16348 @code{add-shared-symbol-files}.
16351 @item section @var{section} @var{addr}
16352 The @code{section} command changes the base address of the named
16353 @var{section} of the exec file to @var{addr}. This can be used if the
16354 exec file does not contain section addresses, (such as in the
16355 @code{a.out} format), or when the addresses specified in the file
16356 itself are wrong. Each section must be changed separately. The
16357 @code{info files} command, described below, lists all the sections and
16361 @kindex info target
16364 @code{info files} and @code{info target} are synonymous; both print the
16365 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16366 including the names of the executable and core dump files currently in
16367 use by @value{GDBN}, and the files from which symbols were loaded. The
16368 command @code{help target} lists all possible targets rather than
16371 @kindex maint info sections
16372 @item maint info sections
16373 Another command that can give you extra information about program sections
16374 is @code{maint info sections}. In addition to the section information
16375 displayed by @code{info files}, this command displays the flags and file
16376 offset of each section in the executable and core dump files. In addition,
16377 @code{maint info sections} provides the following command options (which
16378 may be arbitrarily combined):
16382 Display sections for all loaded object files, including shared libraries.
16383 @item @var{sections}
16384 Display info only for named @var{sections}.
16385 @item @var{section-flags}
16386 Display info only for sections for which @var{section-flags} are true.
16387 The section flags that @value{GDBN} currently knows about are:
16390 Section will have space allocated in the process when loaded.
16391 Set for all sections except those containing debug information.
16393 Section will be loaded from the file into the child process memory.
16394 Set for pre-initialized code and data, clear for @code{.bss} sections.
16396 Section needs to be relocated before loading.
16398 Section cannot be modified by the child process.
16400 Section contains executable code only.
16402 Section contains data only (no executable code).
16404 Section will reside in ROM.
16406 Section contains data for constructor/destructor lists.
16408 Section is not empty.
16410 An instruction to the linker to not output the section.
16411 @item COFF_SHARED_LIBRARY
16412 A notification to the linker that the section contains
16413 COFF shared library information.
16415 Section contains common symbols.
16418 @kindex set trust-readonly-sections
16419 @cindex read-only sections
16420 @item set trust-readonly-sections on
16421 Tell @value{GDBN} that readonly sections in your object file
16422 really are read-only (i.e.@: that their contents will not change).
16423 In that case, @value{GDBN} can fetch values from these sections
16424 out of the object file, rather than from the target program.
16425 For some targets (notably embedded ones), this can be a significant
16426 enhancement to debugging performance.
16428 The default is off.
16430 @item set trust-readonly-sections off
16431 Tell @value{GDBN} not to trust readonly sections. This means that
16432 the contents of the section might change while the program is running,
16433 and must therefore be fetched from the target when needed.
16435 @item show trust-readonly-sections
16436 Show the current setting of trusting readonly sections.
16439 All file-specifying commands allow both absolute and relative file names
16440 as arguments. @value{GDBN} always converts the file name to an absolute file
16441 name and remembers it that way.
16443 @cindex shared libraries
16444 @anchor{Shared Libraries}
16445 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16446 and IBM RS/6000 AIX shared libraries.
16448 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16449 shared libraries. @xref{Expat}.
16451 @value{GDBN} automatically loads symbol definitions from shared libraries
16452 when you use the @code{run} command, or when you examine a core file.
16453 (Before you issue the @code{run} command, @value{GDBN} does not understand
16454 references to a function in a shared library, however---unless you are
16455 debugging a core file).
16457 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16458 automatically loads the symbols at the time of the @code{shl_load} call.
16460 @c FIXME: some @value{GDBN} release may permit some refs to undef
16461 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16462 @c FIXME...lib; check this from time to time when updating manual
16464 There are times, however, when you may wish to not automatically load
16465 symbol definitions from shared libraries, such as when they are
16466 particularly large or there are many of them.
16468 To control the automatic loading of shared library symbols, use the
16472 @kindex set auto-solib-add
16473 @item set auto-solib-add @var{mode}
16474 If @var{mode} is @code{on}, symbols from all shared object libraries
16475 will be loaded automatically when the inferior begins execution, you
16476 attach to an independently started inferior, or when the dynamic linker
16477 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16478 is @code{off}, symbols must be loaded manually, using the
16479 @code{sharedlibrary} command. The default value is @code{on}.
16481 @cindex memory used for symbol tables
16482 If your program uses lots of shared libraries with debug info that
16483 takes large amounts of memory, you can decrease the @value{GDBN}
16484 memory footprint by preventing it from automatically loading the
16485 symbols from shared libraries. To that end, type @kbd{set
16486 auto-solib-add off} before running the inferior, then load each
16487 library whose debug symbols you do need with @kbd{sharedlibrary
16488 @var{regexp}}, where @var{regexp} is a regular expression that matches
16489 the libraries whose symbols you want to be loaded.
16491 @kindex show auto-solib-add
16492 @item show auto-solib-add
16493 Display the current autoloading mode.
16496 @cindex load shared library
16497 To explicitly load shared library symbols, use the @code{sharedlibrary}
16501 @kindex info sharedlibrary
16503 @item info share @var{regex}
16504 @itemx info sharedlibrary @var{regex}
16505 Print the names of the shared libraries which are currently loaded
16506 that match @var{regex}. If @var{regex} is omitted then print
16507 all shared libraries that are loaded.
16509 @kindex sharedlibrary
16511 @item sharedlibrary @var{regex}
16512 @itemx share @var{regex}
16513 Load shared object library symbols for files matching a
16514 Unix regular expression.
16515 As with files loaded automatically, it only loads shared libraries
16516 required by your program for a core file or after typing @code{run}. If
16517 @var{regex} is omitted all shared libraries required by your program are
16520 @item nosharedlibrary
16521 @kindex nosharedlibrary
16522 @cindex unload symbols from shared libraries
16523 Unload all shared object library symbols. This discards all symbols
16524 that have been loaded from all shared libraries. Symbols from shared
16525 libraries that were loaded by explicit user requests are not
16529 Sometimes you may wish that @value{GDBN} stops and gives you control
16530 when any of shared library events happen. The best way to do this is
16531 to use @code{catch load} and @code{catch unload} (@pxref{Set
16534 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16535 command for this. This command exists for historical reasons. It is
16536 less useful than setting a catchpoint, because it does not allow for
16537 conditions or commands as a catchpoint does.
16540 @item set stop-on-solib-events
16541 @kindex set stop-on-solib-events
16542 This command controls whether @value{GDBN} should give you control
16543 when the dynamic linker notifies it about some shared library event.
16544 The most common event of interest is loading or unloading of a new
16547 @item show stop-on-solib-events
16548 @kindex show stop-on-solib-events
16549 Show whether @value{GDBN} stops and gives you control when shared
16550 library events happen.
16553 Shared libraries are also supported in many cross or remote debugging
16554 configurations. @value{GDBN} needs to have access to the target's libraries;
16555 this can be accomplished either by providing copies of the libraries
16556 on the host system, or by asking @value{GDBN} to automatically retrieve the
16557 libraries from the target. If copies of the target libraries are
16558 provided, they need to be the same as the target libraries, although the
16559 copies on the target can be stripped as long as the copies on the host are
16562 @cindex where to look for shared libraries
16563 For remote debugging, you need to tell @value{GDBN} where the target
16564 libraries are, so that it can load the correct copies---otherwise, it
16565 may try to load the host's libraries. @value{GDBN} has two variables
16566 to specify the search directories for target libraries.
16569 @cindex prefix for shared library file names
16570 @cindex system root, alternate
16571 @kindex set solib-absolute-prefix
16572 @kindex set sysroot
16573 @item set sysroot @var{path}
16574 Use @var{path} as the system root for the program being debugged. Any
16575 absolute shared library paths will be prefixed with @var{path}; many
16576 runtime loaders store the absolute paths to the shared library in the
16577 target program's memory. If you use @code{set sysroot} to find shared
16578 libraries, they need to be laid out in the same way that they are on
16579 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16582 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16583 retrieve the target libraries from the remote system. This is only
16584 supported when using a remote target that supports the @code{remote get}
16585 command (@pxref{File Transfer,,Sending files to a remote system}).
16586 The part of @var{path} following the initial @file{remote:}
16587 (if present) is used as system root prefix on the remote file system.
16588 @footnote{If you want to specify a local system root using a directory
16589 that happens to be named @file{remote:}, you need to use some equivalent
16590 variant of the name like @file{./remote:}.}
16592 For targets with an MS-DOS based filesystem, such as MS-Windows and
16593 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16594 absolute file name with @var{path}. But first, on Unix hosts,
16595 @value{GDBN} converts all backslash directory separators into forward
16596 slashes, because the backslash is not a directory separator on Unix:
16599 c:\foo\bar.dll @result{} c:/foo/bar.dll
16602 Then, @value{GDBN} attempts prefixing the target file name with
16603 @var{path}, and looks for the resulting file name in the host file
16607 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16610 If that does not find the shared library, @value{GDBN} tries removing
16611 the @samp{:} character from the drive spec, both for convenience, and,
16612 for the case of the host file system not supporting file names with
16616 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16619 This makes it possible to have a system root that mirrors a target
16620 with more than one drive. E.g., you may want to setup your local
16621 copies of the target system shared libraries like so (note @samp{c} vs
16625 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16626 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16627 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16631 and point the system root at @file{/path/to/sysroot}, so that
16632 @value{GDBN} can find the correct copies of both
16633 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16635 If that still does not find the shared library, @value{GDBN} tries
16636 removing the whole drive spec from the target file name:
16639 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16642 This last lookup makes it possible to not care about the drive name,
16643 if you don't want or need to.
16645 The @code{set solib-absolute-prefix} command is an alias for @code{set
16648 @cindex default system root
16649 @cindex @samp{--with-sysroot}
16650 You can set the default system root by using the configure-time
16651 @samp{--with-sysroot} option. If the system root is inside
16652 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16653 @samp{--exec-prefix}), then the default system root will be updated
16654 automatically if the installed @value{GDBN} is moved to a new
16657 @kindex show sysroot
16659 Display the current shared library prefix.
16661 @kindex set solib-search-path
16662 @item set solib-search-path @var{path}
16663 If this variable is set, @var{path} is a colon-separated list of
16664 directories to search for shared libraries. @samp{solib-search-path}
16665 is used after @samp{sysroot} fails to locate the library, or if the
16666 path to the library is relative instead of absolute. If you want to
16667 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16668 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16669 finding your host's libraries. @samp{sysroot} is preferred; setting
16670 it to a nonexistent directory may interfere with automatic loading
16671 of shared library symbols.
16673 @kindex show solib-search-path
16674 @item show solib-search-path
16675 Display the current shared library search path.
16677 @cindex DOS file-name semantics of file names.
16678 @kindex set target-file-system-kind (unix|dos-based|auto)
16679 @kindex show target-file-system-kind
16680 @item set target-file-system-kind @var{kind}
16681 Set assumed file system kind for target reported file names.
16683 Shared library file names as reported by the target system may not
16684 make sense as is on the system @value{GDBN} is running on. For
16685 example, when remote debugging a target that has MS-DOS based file
16686 system semantics, from a Unix host, the target may be reporting to
16687 @value{GDBN} a list of loaded shared libraries with file names such as
16688 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16689 drive letters, so the @samp{c:\} prefix is not normally understood as
16690 indicating an absolute file name, and neither is the backslash
16691 normally considered a directory separator character. In that case,
16692 the native file system would interpret this whole absolute file name
16693 as a relative file name with no directory components. This would make
16694 it impossible to point @value{GDBN} at a copy of the remote target's
16695 shared libraries on the host using @code{set sysroot}, and impractical
16696 with @code{set solib-search-path}. Setting
16697 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16698 to interpret such file names similarly to how the target would, and to
16699 map them to file names valid on @value{GDBN}'s native file system
16700 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16701 to one of the supported file system kinds. In that case, @value{GDBN}
16702 tries to determine the appropriate file system variant based on the
16703 current target's operating system (@pxref{ABI, ,Configuring the
16704 Current ABI}). The supported file system settings are:
16708 Instruct @value{GDBN} to assume the target file system is of Unix
16709 kind. Only file names starting the forward slash (@samp{/}) character
16710 are considered absolute, and the directory separator character is also
16714 Instruct @value{GDBN} to assume the target file system is DOS based.
16715 File names starting with either a forward slash, or a drive letter
16716 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16717 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16718 considered directory separators.
16721 Instruct @value{GDBN} to use the file system kind associated with the
16722 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16723 This is the default.
16727 @cindex file name canonicalization
16728 @cindex base name differences
16729 When processing file names provided by the user, @value{GDBN}
16730 frequently needs to compare them to the file names recorded in the
16731 program's debug info. Normally, @value{GDBN} compares just the
16732 @dfn{base names} of the files as strings, which is reasonably fast
16733 even for very large programs. (The base name of a file is the last
16734 portion of its name, after stripping all the leading directories.)
16735 This shortcut in comparison is based upon the assumption that files
16736 cannot have more than one base name. This is usually true, but
16737 references to files that use symlinks or similar filesystem
16738 facilities violate that assumption. If your program records files
16739 using such facilities, or if you provide file names to @value{GDBN}
16740 using symlinks etc., you can set @code{basenames-may-differ} to
16741 @code{true} to instruct @value{GDBN} to completely canonicalize each
16742 pair of file names it needs to compare. This will make file-name
16743 comparisons accurate, but at a price of a significant slowdown.
16746 @item set basenames-may-differ
16747 @kindex set basenames-may-differ
16748 Set whether a source file may have multiple base names.
16750 @item show basenames-may-differ
16751 @kindex show basenames-may-differ
16752 Show whether a source file may have multiple base names.
16755 @node Separate Debug Files
16756 @section Debugging Information in Separate Files
16757 @cindex separate debugging information files
16758 @cindex debugging information in separate files
16759 @cindex @file{.debug} subdirectories
16760 @cindex debugging information directory, global
16761 @cindex global debugging information directories
16762 @cindex build ID, and separate debugging files
16763 @cindex @file{.build-id} directory
16765 @value{GDBN} allows you to put a program's debugging information in a
16766 file separate from the executable itself, in a way that allows
16767 @value{GDBN} to find and load the debugging information automatically.
16768 Since debugging information can be very large---sometimes larger
16769 than the executable code itself---some systems distribute debugging
16770 information for their executables in separate files, which users can
16771 install only when they need to debug a problem.
16773 @value{GDBN} supports two ways of specifying the separate debug info
16778 The executable contains a @dfn{debug link} that specifies the name of
16779 the separate debug info file. The separate debug file's name is
16780 usually @file{@var{executable}.debug}, where @var{executable} is the
16781 name of the corresponding executable file without leading directories
16782 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16783 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16784 checksum for the debug file, which @value{GDBN} uses to validate that
16785 the executable and the debug file came from the same build.
16788 The executable contains a @dfn{build ID}, a unique bit string that is
16789 also present in the corresponding debug info file. (This is supported
16790 only on some operating systems, notably those which use the ELF format
16791 for binary files and the @sc{gnu} Binutils.) For more details about
16792 this feature, see the description of the @option{--build-id}
16793 command-line option in @ref{Options, , Command Line Options, ld.info,
16794 The GNU Linker}. The debug info file's name is not specified
16795 explicitly by the build ID, but can be computed from the build ID, see
16799 Depending on the way the debug info file is specified, @value{GDBN}
16800 uses two different methods of looking for the debug file:
16804 For the ``debug link'' method, @value{GDBN} looks up the named file in
16805 the directory of the executable file, then in a subdirectory of that
16806 directory named @file{.debug}, and finally under each one of the global debug
16807 directories, in a subdirectory whose name is identical to the leading
16808 directories of the executable's absolute file name.
16811 For the ``build ID'' method, @value{GDBN} looks in the
16812 @file{.build-id} subdirectory of each one of the global debug directories for
16813 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16814 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16815 are the rest of the bit string. (Real build ID strings are 32 or more
16816 hex characters, not 10.)
16819 So, for example, suppose you ask @value{GDBN} to debug
16820 @file{/usr/bin/ls}, which has a debug link that specifies the
16821 file @file{ls.debug}, and a build ID whose value in hex is
16822 @code{abcdef1234}. If the list of the global debug directories includes
16823 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16824 debug information files, in the indicated order:
16828 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16830 @file{/usr/bin/ls.debug}
16832 @file{/usr/bin/.debug/ls.debug}
16834 @file{/usr/lib/debug/usr/bin/ls.debug}.
16837 @anchor{debug-file-directory}
16838 Global debugging info directories default to what is set by @value{GDBN}
16839 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16840 you can also set the global debugging info directories, and view the list
16841 @value{GDBN} is currently using.
16845 @kindex set debug-file-directory
16846 @item set debug-file-directory @var{directories}
16847 Set the directories which @value{GDBN} searches for separate debugging
16848 information files to @var{directory}. Multiple path components can be set
16849 concatenating them by a path separator.
16851 @kindex show debug-file-directory
16852 @item show debug-file-directory
16853 Show the directories @value{GDBN} searches for separate debugging
16858 @cindex @code{.gnu_debuglink} sections
16859 @cindex debug link sections
16860 A debug link is a special section of the executable file named
16861 @code{.gnu_debuglink}. The section must contain:
16865 A filename, with any leading directory components removed, followed by
16868 zero to three bytes of padding, as needed to reach the next four-byte
16869 boundary within the section, and
16871 a four-byte CRC checksum, stored in the same endianness used for the
16872 executable file itself. The checksum is computed on the debugging
16873 information file's full contents by the function given below, passing
16874 zero as the @var{crc} argument.
16877 Any executable file format can carry a debug link, as long as it can
16878 contain a section named @code{.gnu_debuglink} with the contents
16881 @cindex @code{.note.gnu.build-id} sections
16882 @cindex build ID sections
16883 The build ID is a special section in the executable file (and in other
16884 ELF binary files that @value{GDBN} may consider). This section is
16885 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16886 It contains unique identification for the built files---the ID remains
16887 the same across multiple builds of the same build tree. The default
16888 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16889 content for the build ID string. The same section with an identical
16890 value is present in the original built binary with symbols, in its
16891 stripped variant, and in the separate debugging information file.
16893 The debugging information file itself should be an ordinary
16894 executable, containing a full set of linker symbols, sections, and
16895 debugging information. The sections of the debugging information file
16896 should have the same names, addresses, and sizes as the original file,
16897 but they need not contain any data---much like a @code{.bss} section
16898 in an ordinary executable.
16900 The @sc{gnu} binary utilities (Binutils) package includes the
16901 @samp{objcopy} utility that can produce
16902 the separated executable / debugging information file pairs using the
16903 following commands:
16906 @kbd{objcopy --only-keep-debug foo foo.debug}
16911 These commands remove the debugging
16912 information from the executable file @file{foo} and place it in the file
16913 @file{foo.debug}. You can use the first, second or both methods to link the
16918 The debug link method needs the following additional command to also leave
16919 behind a debug link in @file{foo}:
16922 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16925 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16926 a version of the @code{strip} command such that the command @kbd{strip foo -f
16927 foo.debug} has the same functionality as the two @code{objcopy} commands and
16928 the @code{ln -s} command above, together.
16931 Build ID gets embedded into the main executable using @code{ld --build-id} or
16932 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16933 compatibility fixes for debug files separation are present in @sc{gnu} binary
16934 utilities (Binutils) package since version 2.18.
16939 @cindex CRC algorithm definition
16940 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16941 IEEE 802.3 using the polynomial:
16943 @c TexInfo requires naked braces for multi-digit exponents for Tex
16944 @c output, but this causes HTML output to barf. HTML has to be set using
16945 @c raw commands. So we end up having to specify this equation in 2
16950 <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>
16951 + <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
16957 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16958 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16962 The function is computed byte at a time, taking the least
16963 significant bit of each byte first. The initial pattern
16964 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16965 the final result is inverted to ensure trailing zeros also affect the
16968 @emph{Note:} This is the same CRC polynomial as used in handling the
16969 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16970 , @value{GDBN} Remote Serial Protocol}). However in the
16971 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16972 significant bit first, and the result is not inverted, so trailing
16973 zeros have no effect on the CRC value.
16975 To complete the description, we show below the code of the function
16976 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16977 initially supplied @code{crc} argument means that an initial call to
16978 this function passing in zero will start computing the CRC using
16981 @kindex gnu_debuglink_crc32
16984 gnu_debuglink_crc32 (unsigned long crc,
16985 unsigned char *buf, size_t len)
16987 static const unsigned long crc32_table[256] =
16989 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16990 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16991 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16992 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16993 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16994 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16995 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16996 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16997 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16998 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16999 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17000 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17001 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17002 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17003 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17004 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17005 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17006 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17007 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17008 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17009 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17010 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17011 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17012 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17013 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17014 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17015 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17016 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17017 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17018 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17019 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17020 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17021 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17022 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17023 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17024 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17025 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17026 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17027 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17028 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17029 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17030 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17031 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17032 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17033 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17034 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17035 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17036 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17037 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17038 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17039 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17042 unsigned char *end;
17044 crc = ~crc & 0xffffffff;
17045 for (end = buf + len; buf < end; ++buf)
17046 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17047 return ~crc & 0xffffffff;
17052 This computation does not apply to the ``build ID'' method.
17054 @node MiniDebugInfo
17055 @section Debugging information in a special section
17056 @cindex separate debug sections
17057 @cindex @samp{.gnu_debugdata} section
17059 Some systems ship pre-built executables and libraries that have a
17060 special @samp{.gnu_debugdata} section. This feature is called
17061 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17062 is used to supply extra symbols for backtraces.
17064 The intent of this section is to provide extra minimal debugging
17065 information for use in simple backtraces. It is not intended to be a
17066 replacement for full separate debugging information (@pxref{Separate
17067 Debug Files}). The example below shows the intended use; however,
17068 @value{GDBN} does not currently put restrictions on what sort of
17069 debugging information might be included in the section.
17071 @value{GDBN} has support for this extension. If the section exists,
17072 then it is used provided that no other source of debugging information
17073 can be found, and that @value{GDBN} was configured with LZMA support.
17075 This section can be easily created using @command{objcopy} and other
17076 standard utilities:
17079 # Extract the dynamic symbols from the main binary, there is no need
17080 # to also have these in the normal symbol table
17081 nm -D @var{binary} --format=posix --defined-only \
17082 | awk '@{ print $1 @}' | sort > dynsyms
17084 # Extract all the text (i.e. function) symbols from the debuginfo .
17085 nm @var{binary} --format=posix --defined-only \
17086 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17089 # Keep all the function symbols not already in the dynamic symbol
17091 comm -13 dynsyms funcsyms > keep_symbols
17093 # Copy the full debuginfo, keeping only a minimal set of symbols and
17094 # removing some unnecessary sections.
17095 objcopy -S --remove-section .gdb_index --remove-section .comment \
17096 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17098 # Inject the compressed data into the .gnu_debugdata section of the
17101 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17105 @section Index Files Speed Up @value{GDBN}
17106 @cindex index files
17107 @cindex @samp{.gdb_index} section
17109 When @value{GDBN} finds a symbol file, it scans the symbols in the
17110 file in order to construct an internal symbol table. This lets most
17111 @value{GDBN} operations work quickly---at the cost of a delay early
17112 on. For large programs, this delay can be quite lengthy, so
17113 @value{GDBN} provides a way to build an index, which speeds up
17116 The index is stored as a section in the symbol file. @value{GDBN} can
17117 write the index to a file, then you can put it into the symbol file
17118 using @command{objcopy}.
17120 To create an index file, use the @code{save gdb-index} command:
17123 @item save gdb-index @var{directory}
17124 @kindex save gdb-index
17125 Create an index file for each symbol file currently known by
17126 @value{GDBN}. Each file is named after its corresponding symbol file,
17127 with @samp{.gdb-index} appended, and is written into the given
17131 Once you have created an index file you can merge it into your symbol
17132 file, here named @file{symfile}, using @command{objcopy}:
17135 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17136 --set-section-flags .gdb_index=readonly symfile symfile
17139 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17140 sections that have been deprecated. Usually they are deprecated because
17141 they are missing a new feature or have performance issues.
17142 To tell @value{GDBN} to use a deprecated index section anyway
17143 specify @code{set use-deprecated-index-sections on}.
17144 The default is @code{off}.
17145 This can speed up startup, but may result in some functionality being lost.
17146 @xref{Index Section Format}.
17148 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17149 must be done before gdb reads the file. The following will not work:
17152 $ gdb -ex "set use-deprecated-index-sections on" <program>
17155 Instead you must do, for example,
17158 $ gdb -iex "set use-deprecated-index-sections on" <program>
17161 There are currently some limitation on indices. They only work when
17162 for DWARF debugging information, not stabs. And, they do not
17163 currently work for programs using Ada.
17165 @node Symbol Errors
17166 @section Errors Reading Symbol Files
17168 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17169 such as symbol types it does not recognize, or known bugs in compiler
17170 output. By default, @value{GDBN} does not notify you of such problems, since
17171 they are relatively common and primarily of interest to people
17172 debugging compilers. If you are interested in seeing information
17173 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17174 only one message about each such type of problem, no matter how many
17175 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17176 to see how many times the problems occur, with the @code{set
17177 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17180 The messages currently printed, and their meanings, include:
17183 @item inner block not inside outer block in @var{symbol}
17185 The symbol information shows where symbol scopes begin and end
17186 (such as at the start of a function or a block of statements). This
17187 error indicates that an inner scope block is not fully contained
17188 in its outer scope blocks.
17190 @value{GDBN} circumvents the problem by treating the inner block as if it had
17191 the same scope as the outer block. In the error message, @var{symbol}
17192 may be shown as ``@code{(don't know)}'' if the outer block is not a
17195 @item block at @var{address} out of order
17197 The symbol information for symbol scope blocks should occur in
17198 order of increasing addresses. This error indicates that it does not
17201 @value{GDBN} does not circumvent this problem, and has trouble
17202 locating symbols in the source file whose symbols it is reading. (You
17203 can often determine what source file is affected by specifying
17204 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17207 @item bad block start address patched
17209 The symbol information for a symbol scope block has a start address
17210 smaller than the address of the preceding source line. This is known
17211 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17213 @value{GDBN} circumvents the problem by treating the symbol scope block as
17214 starting on the previous source line.
17216 @item bad string table offset in symbol @var{n}
17219 Symbol number @var{n} contains a pointer into the string table which is
17220 larger than the size of the string table.
17222 @value{GDBN} circumvents the problem by considering the symbol to have the
17223 name @code{foo}, which may cause other problems if many symbols end up
17226 @item unknown symbol type @code{0x@var{nn}}
17228 The symbol information contains new data types that @value{GDBN} does
17229 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17230 uncomprehended information, in hexadecimal.
17232 @value{GDBN} circumvents the error by ignoring this symbol information.
17233 This usually allows you to debug your program, though certain symbols
17234 are not accessible. If you encounter such a problem and feel like
17235 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17236 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17237 and examine @code{*bufp} to see the symbol.
17239 @item stub type has NULL name
17241 @value{GDBN} could not find the full definition for a struct or class.
17243 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17244 The symbol information for a C@t{++} member function is missing some
17245 information that recent versions of the compiler should have output for
17248 @item info mismatch between compiler and debugger
17250 @value{GDBN} could not parse a type specification output by the compiler.
17255 @section GDB Data Files
17257 @cindex prefix for data files
17258 @value{GDBN} will sometimes read an auxiliary data file. These files
17259 are kept in a directory known as the @dfn{data directory}.
17261 You can set the data directory's name, and view the name @value{GDBN}
17262 is currently using.
17265 @kindex set data-directory
17266 @item set data-directory @var{directory}
17267 Set the directory which @value{GDBN} searches for auxiliary data files
17268 to @var{directory}.
17270 @kindex show data-directory
17271 @item show data-directory
17272 Show the directory @value{GDBN} searches for auxiliary data files.
17275 @cindex default data directory
17276 @cindex @samp{--with-gdb-datadir}
17277 You can set the default data directory by using the configure-time
17278 @samp{--with-gdb-datadir} option. If the data directory is inside
17279 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17280 @samp{--exec-prefix}), then the default data directory will be updated
17281 automatically if the installed @value{GDBN} is moved to a new
17284 The data directory may also be specified with the
17285 @code{--data-directory} command line option.
17286 @xref{Mode Options}.
17289 @chapter Specifying a Debugging Target
17291 @cindex debugging target
17292 A @dfn{target} is the execution environment occupied by your program.
17294 Often, @value{GDBN} runs in the same host environment as your program;
17295 in that case, the debugging target is specified as a side effect when
17296 you use the @code{file} or @code{core} commands. When you need more
17297 flexibility---for example, running @value{GDBN} on a physically separate
17298 host, or controlling a standalone system over a serial port or a
17299 realtime system over a TCP/IP connection---you can use the @code{target}
17300 command to specify one of the target types configured for @value{GDBN}
17301 (@pxref{Target Commands, ,Commands for Managing Targets}).
17303 @cindex target architecture
17304 It is possible to build @value{GDBN} for several different @dfn{target
17305 architectures}. When @value{GDBN} is built like that, you can choose
17306 one of the available architectures with the @kbd{set architecture}
17310 @kindex set architecture
17311 @kindex show architecture
17312 @item set architecture @var{arch}
17313 This command sets the current target architecture to @var{arch}. The
17314 value of @var{arch} can be @code{"auto"}, in addition to one of the
17315 supported architectures.
17317 @item show architecture
17318 Show the current target architecture.
17320 @item set processor
17322 @kindex set processor
17323 @kindex show processor
17324 These are alias commands for, respectively, @code{set architecture}
17325 and @code{show architecture}.
17329 * Active Targets:: Active targets
17330 * Target Commands:: Commands for managing targets
17331 * Byte Order:: Choosing target byte order
17334 @node Active Targets
17335 @section Active Targets
17337 @cindex stacking targets
17338 @cindex active targets
17339 @cindex multiple targets
17341 There are multiple classes of targets such as: processes, executable files or
17342 recording sessions. Core files belong to the process class, making core file
17343 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17344 on multiple active targets, one in each class. This allows you to (for
17345 example) start a process and inspect its activity, while still having access to
17346 the executable file after the process finishes. Or if you start process
17347 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17348 presented a virtual layer of the recording target, while the process target
17349 remains stopped at the chronologically last point of the process execution.
17351 Use the @code{core-file} and @code{exec-file} commands to select a new core
17352 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17353 specify as a target a process that is already running, use the @code{attach}
17354 command (@pxref{Attach, ,Debugging an Already-running Process}).
17356 @node Target Commands
17357 @section Commands for Managing Targets
17360 @item target @var{type} @var{parameters}
17361 Connects the @value{GDBN} host environment to a target machine or
17362 process. A target is typically a protocol for talking to debugging
17363 facilities. You use the argument @var{type} to specify the type or
17364 protocol of the target machine.
17366 Further @var{parameters} are interpreted by the target protocol, but
17367 typically include things like device names or host names to connect
17368 with, process numbers, and baud rates.
17370 The @code{target} command does not repeat if you press @key{RET} again
17371 after executing the command.
17373 @kindex help target
17375 Displays the names of all targets available. To display targets
17376 currently selected, use either @code{info target} or @code{info files}
17377 (@pxref{Files, ,Commands to Specify Files}).
17379 @item help target @var{name}
17380 Describe a particular target, including any parameters necessary to
17383 @kindex set gnutarget
17384 @item set gnutarget @var{args}
17385 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17386 knows whether it is reading an @dfn{executable},
17387 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17388 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17389 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17392 @emph{Warning:} To specify a file format with @code{set gnutarget},
17393 you must know the actual BFD name.
17397 @xref{Files, , Commands to Specify Files}.
17399 @kindex show gnutarget
17400 @item show gnutarget
17401 Use the @code{show gnutarget} command to display what file format
17402 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17403 @value{GDBN} will determine the file format for each file automatically,
17404 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17407 @cindex common targets
17408 Here are some common targets (available, or not, depending on the GDB
17413 @item target exec @var{program}
17414 @cindex executable file target
17415 An executable file. @samp{target exec @var{program}} is the same as
17416 @samp{exec-file @var{program}}.
17418 @item target core @var{filename}
17419 @cindex core dump file target
17420 A core dump file. @samp{target core @var{filename}} is the same as
17421 @samp{core-file @var{filename}}.
17423 @item target remote @var{medium}
17424 @cindex remote target
17425 A remote system connected to @value{GDBN} via a serial line or network
17426 connection. This command tells @value{GDBN} to use its own remote
17427 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17429 For example, if you have a board connected to @file{/dev/ttya} on the
17430 machine running @value{GDBN}, you could say:
17433 target remote /dev/ttya
17436 @code{target remote} supports the @code{load} command. This is only
17437 useful if you have some other way of getting the stub to the target
17438 system, and you can put it somewhere in memory where it won't get
17439 clobbered by the download.
17441 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17442 @cindex built-in simulator target
17443 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17451 works; however, you cannot assume that a specific memory map, device
17452 drivers, or even basic I/O is available, although some simulators do
17453 provide these. For info about any processor-specific simulator details,
17454 see the appropriate section in @ref{Embedded Processors, ,Embedded
17459 Some configurations may include these targets as well:
17463 @item target nrom @var{dev}
17464 @cindex NetROM ROM emulator target
17465 NetROM ROM emulator. This target only supports downloading.
17469 Different targets are available on different configurations of @value{GDBN};
17470 your configuration may have more or fewer targets.
17472 Many remote targets require you to download the executable's code once
17473 you've successfully established a connection. You may wish to control
17474 various aspects of this process.
17479 @kindex set hash@r{, for remote monitors}
17480 @cindex hash mark while downloading
17481 This command controls whether a hash mark @samp{#} is displayed while
17482 downloading a file to the remote monitor. If on, a hash mark is
17483 displayed after each S-record is successfully downloaded to the
17487 @kindex show hash@r{, for remote monitors}
17488 Show the current status of displaying the hash mark.
17490 @item set debug monitor
17491 @kindex set debug monitor
17492 @cindex display remote monitor communications
17493 Enable or disable display of communications messages between
17494 @value{GDBN} and the remote monitor.
17496 @item show debug monitor
17497 @kindex show debug monitor
17498 Show the current status of displaying communications between
17499 @value{GDBN} and the remote monitor.
17504 @kindex load @var{filename}
17505 @item load @var{filename}
17507 Depending on what remote debugging facilities are configured into
17508 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17509 is meant to make @var{filename} (an executable) available for debugging
17510 on the remote system---by downloading, or dynamic linking, for example.
17511 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17512 the @code{add-symbol-file} command.
17514 If your @value{GDBN} does not have a @code{load} command, attempting to
17515 execute it gets the error message ``@code{You can't do that when your
17516 target is @dots{}}''
17518 The file is loaded at whatever address is specified in the executable.
17519 For some object file formats, you can specify the load address when you
17520 link the program; for other formats, like a.out, the object file format
17521 specifies a fixed address.
17522 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17524 Depending on the remote side capabilities, @value{GDBN} may be able to
17525 load programs into flash memory.
17527 @code{load} does not repeat if you press @key{RET} again after using it.
17531 @section Choosing Target Byte Order
17533 @cindex choosing target byte order
17534 @cindex target byte order
17536 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17537 offer the ability to run either big-endian or little-endian byte
17538 orders. Usually the executable or symbol will include a bit to
17539 designate the endian-ness, and you will not need to worry about
17540 which to use. However, you may still find it useful to adjust
17541 @value{GDBN}'s idea of processor endian-ness manually.
17545 @item set endian big
17546 Instruct @value{GDBN} to assume the target is big-endian.
17548 @item set endian little
17549 Instruct @value{GDBN} to assume the target is little-endian.
17551 @item set endian auto
17552 Instruct @value{GDBN} to use the byte order associated with the
17556 Display @value{GDBN}'s current idea of the target byte order.
17560 Note that these commands merely adjust interpretation of symbolic
17561 data on the host, and that they have absolutely no effect on the
17565 @node Remote Debugging
17566 @chapter Debugging Remote Programs
17567 @cindex remote debugging
17569 If you are trying to debug a program running on a machine that cannot run
17570 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17571 For example, you might use remote debugging on an operating system kernel,
17572 or on a small system which does not have a general purpose operating system
17573 powerful enough to run a full-featured debugger.
17575 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17576 to make this work with particular debugging targets. In addition,
17577 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17578 but not specific to any particular target system) which you can use if you
17579 write the remote stubs---the code that runs on the remote system to
17580 communicate with @value{GDBN}.
17582 Other remote targets may be available in your
17583 configuration of @value{GDBN}; use @code{help target} to list them.
17586 * Connecting:: Connecting to a remote target
17587 * File Transfer:: Sending files to a remote system
17588 * Server:: Using the gdbserver program
17589 * Remote Configuration:: Remote configuration
17590 * Remote Stub:: Implementing a remote stub
17594 @section Connecting to a Remote Target
17596 On the @value{GDBN} host machine, you will need an unstripped copy of
17597 your program, since @value{GDBN} needs symbol and debugging information.
17598 Start up @value{GDBN} as usual, using the name of the local copy of your
17599 program as the first argument.
17601 @cindex @code{target remote}
17602 @value{GDBN} can communicate with the target over a serial line, or
17603 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17604 each case, @value{GDBN} uses the same protocol for debugging your
17605 program; only the medium carrying the debugging packets varies. The
17606 @code{target remote} command establishes a connection to the target.
17607 Its arguments indicate which medium to use:
17611 @item target remote @var{serial-device}
17612 @cindex serial line, @code{target remote}
17613 Use @var{serial-device} to communicate with the target. For example,
17614 to use a serial line connected to the device named @file{/dev/ttyb}:
17617 target remote /dev/ttyb
17620 If you're using a serial line, you may want to give @value{GDBN} the
17621 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17622 (@pxref{Remote Configuration, set remotebaud}) before the
17623 @code{target} command.
17625 @item target remote @code{@var{host}:@var{port}}
17626 @itemx target remote @code{tcp:@var{host}:@var{port}}
17627 @cindex @acronym{TCP} port, @code{target remote}
17628 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17629 The @var{host} may be either a host name or a numeric @acronym{IP}
17630 address; @var{port} must be a decimal number. The @var{host} could be
17631 the target machine itself, if it is directly connected to the net, or
17632 it might be a terminal server which in turn has a serial line to the
17635 For example, to connect to port 2828 on a terminal server named
17639 target remote manyfarms:2828
17642 If your remote target is actually running on the same machine as your
17643 debugger session (e.g.@: a simulator for your target running on the
17644 same host), you can omit the hostname. For example, to connect to
17645 port 1234 on your local machine:
17648 target remote :1234
17652 Note that the colon is still required here.
17654 @item target remote @code{udp:@var{host}:@var{port}}
17655 @cindex @acronym{UDP} port, @code{target remote}
17656 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17657 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17660 target remote udp:manyfarms:2828
17663 When using a @acronym{UDP} connection for remote debugging, you should
17664 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17665 can silently drop packets on busy or unreliable networks, which will
17666 cause havoc with your debugging session.
17668 @item target remote | @var{command}
17669 @cindex pipe, @code{target remote} to
17670 Run @var{command} in the background and communicate with it using a
17671 pipe. The @var{command} is a shell command, to be parsed and expanded
17672 by the system's command shell, @code{/bin/sh}; it should expect remote
17673 protocol packets on its standard input, and send replies on its
17674 standard output. You could use this to run a stand-alone simulator
17675 that speaks the remote debugging protocol, to make net connections
17676 using programs like @code{ssh}, or for other similar tricks.
17678 If @var{command} closes its standard output (perhaps by exiting),
17679 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17680 program has already exited, this will have no effect.)
17684 Once the connection has been established, you can use all the usual
17685 commands to examine and change data. The remote program is already
17686 running; you can use @kbd{step} and @kbd{continue}, and you do not
17687 need to use @kbd{run}.
17689 @cindex interrupting remote programs
17690 @cindex remote programs, interrupting
17691 Whenever @value{GDBN} is waiting for the remote program, if you type the
17692 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17693 program. This may or may not succeed, depending in part on the hardware
17694 and the serial drivers the remote system uses. If you type the
17695 interrupt character once again, @value{GDBN} displays this prompt:
17698 Interrupted while waiting for the program.
17699 Give up (and stop debugging it)? (y or n)
17702 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17703 (If you decide you want to try again later, you can use @samp{target
17704 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17705 goes back to waiting.
17708 @kindex detach (remote)
17710 When you have finished debugging the remote program, you can use the
17711 @code{detach} command to release it from @value{GDBN} control.
17712 Detaching from the target normally resumes its execution, but the results
17713 will depend on your particular remote stub. After the @code{detach}
17714 command, @value{GDBN} is free to connect to another target.
17718 The @code{disconnect} command behaves like @code{detach}, except that
17719 the target is generally not resumed. It will wait for @value{GDBN}
17720 (this instance or another one) to connect and continue debugging. After
17721 the @code{disconnect} command, @value{GDBN} is again free to connect to
17724 @cindex send command to remote monitor
17725 @cindex extend @value{GDBN} for remote targets
17726 @cindex add new commands for external monitor
17728 @item monitor @var{cmd}
17729 This command allows you to send arbitrary commands directly to the
17730 remote monitor. Since @value{GDBN} doesn't care about the commands it
17731 sends like this, this command is the way to extend @value{GDBN}---you
17732 can add new commands that only the external monitor will understand
17736 @node File Transfer
17737 @section Sending files to a remote system
17738 @cindex remote target, file transfer
17739 @cindex file transfer
17740 @cindex sending files to remote systems
17742 Some remote targets offer the ability to transfer files over the same
17743 connection used to communicate with @value{GDBN}. This is convenient
17744 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17745 running @code{gdbserver} over a network interface. For other targets,
17746 e.g.@: embedded devices with only a single serial port, this may be
17747 the only way to upload or download files.
17749 Not all remote targets support these commands.
17753 @item remote put @var{hostfile} @var{targetfile}
17754 Copy file @var{hostfile} from the host system (the machine running
17755 @value{GDBN}) to @var{targetfile} on the target system.
17758 @item remote get @var{targetfile} @var{hostfile}
17759 Copy file @var{targetfile} from the target system to @var{hostfile}
17760 on the host system.
17762 @kindex remote delete
17763 @item remote delete @var{targetfile}
17764 Delete @var{targetfile} from the target system.
17769 @section Using the @code{gdbserver} Program
17772 @cindex remote connection without stubs
17773 @code{gdbserver} is a control program for Unix-like systems, which
17774 allows you to connect your program with a remote @value{GDBN} via
17775 @code{target remote}---but without linking in the usual debugging stub.
17777 @code{gdbserver} is not a complete replacement for the debugging stubs,
17778 because it requires essentially the same operating-system facilities
17779 that @value{GDBN} itself does. In fact, a system that can run
17780 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17781 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17782 because it is a much smaller program than @value{GDBN} itself. It is
17783 also easier to port than all of @value{GDBN}, so you may be able to get
17784 started more quickly on a new system by using @code{gdbserver}.
17785 Finally, if you develop code for real-time systems, you may find that
17786 the tradeoffs involved in real-time operation make it more convenient to
17787 do as much development work as possible on another system, for example
17788 by cross-compiling. You can use @code{gdbserver} to make a similar
17789 choice for debugging.
17791 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17792 or a TCP connection, using the standard @value{GDBN} remote serial
17796 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17797 Do not run @code{gdbserver} connected to any public network; a
17798 @value{GDBN} connection to @code{gdbserver} provides access to the
17799 target system with the same privileges as the user running
17803 @subsection Running @code{gdbserver}
17804 @cindex arguments, to @code{gdbserver}
17805 @cindex @code{gdbserver}, command-line arguments
17807 Run @code{gdbserver} on the target system. You need a copy of the
17808 program you want to debug, including any libraries it requires.
17809 @code{gdbserver} does not need your program's symbol table, so you can
17810 strip the program if necessary to save space. @value{GDBN} on the host
17811 system does all the symbol handling.
17813 To use the server, you must tell it how to communicate with @value{GDBN};
17814 the name of your program; and the arguments for your program. The usual
17818 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17821 @var{comm} is either a device name (to use a serial line), or a TCP
17822 hostname and portnumber, or @code{-} or @code{stdio} to use
17823 stdin/stdout of @code{gdbserver}.
17824 For example, to debug Emacs with the argument
17825 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17829 target> gdbserver /dev/com1 emacs foo.txt
17832 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17835 To use a TCP connection instead of a serial line:
17838 target> gdbserver host:2345 emacs foo.txt
17841 The only difference from the previous example is the first argument,
17842 specifying that you are communicating with the host @value{GDBN} via
17843 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17844 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17845 (Currently, the @samp{host} part is ignored.) You can choose any number
17846 you want for the port number as long as it does not conflict with any
17847 TCP ports already in use on the target system (for example, @code{23} is
17848 reserved for @code{telnet}).@footnote{If you choose a port number that
17849 conflicts with another service, @code{gdbserver} prints an error message
17850 and exits.} You must use the same port number with the host @value{GDBN}
17851 @code{target remote} command.
17853 The @code{stdio} connection is useful when starting @code{gdbserver}
17857 (gdb) target remote | ssh -T hostname gdbserver - hello
17860 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17861 and we don't want escape-character handling. Ssh does this by default when
17862 a command is provided, the flag is provided to make it explicit.
17863 You could elide it if you want to.
17865 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17866 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17867 display through a pipe connected to gdbserver.
17868 Both @code{stdout} and @code{stderr} use the same pipe.
17870 @subsubsection Attaching to a Running Program
17871 @cindex attach to a program, @code{gdbserver}
17872 @cindex @option{--attach}, @code{gdbserver} option
17874 On some targets, @code{gdbserver} can also attach to running programs.
17875 This is accomplished via the @code{--attach} argument. The syntax is:
17878 target> gdbserver --attach @var{comm} @var{pid}
17881 @var{pid} is the process ID of a currently running process. It isn't necessary
17882 to point @code{gdbserver} at a binary for the running process.
17885 You can debug processes by name instead of process ID if your target has the
17886 @code{pidof} utility:
17889 target> gdbserver --attach @var{comm} `pidof @var{program}`
17892 In case more than one copy of @var{program} is running, or @var{program}
17893 has multiple threads, most versions of @code{pidof} support the
17894 @code{-s} option to only return the first process ID.
17896 @subsubsection Multi-Process Mode for @code{gdbserver}
17897 @cindex @code{gdbserver}, multiple processes
17898 @cindex multiple processes with @code{gdbserver}
17900 When you connect to @code{gdbserver} using @code{target remote},
17901 @code{gdbserver} debugs the specified program only once. When the
17902 program exits, or you detach from it, @value{GDBN} closes the connection
17903 and @code{gdbserver} exits.
17905 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17906 enters multi-process mode. When the debugged program exits, or you
17907 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17908 though no program is running. The @code{run} and @code{attach}
17909 commands instruct @code{gdbserver} to run or attach to a new program.
17910 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17911 remote exec-file}) to select the program to run. Command line
17912 arguments are supported, except for wildcard expansion and I/O
17913 redirection (@pxref{Arguments}).
17915 @cindex @option{--multi}, @code{gdbserver} option
17916 To start @code{gdbserver} without supplying an initial command to run
17917 or process ID to attach, use the @option{--multi} command line option.
17918 Then you can connect using @kbd{target extended-remote} and start
17919 the program you want to debug.
17921 In multi-process mode @code{gdbserver} does not automatically exit unless you
17922 use the option @option{--once}. You can terminate it by using
17923 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17924 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17925 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17926 @option{--multi} option to @code{gdbserver} has no influence on that.
17928 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17930 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17932 @code{gdbserver} normally terminates after all of its debugged processes have
17933 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17934 extended-remote}, @code{gdbserver} stays running even with no processes left.
17935 @value{GDBN} normally terminates the spawned debugged process on its exit,
17936 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17937 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17938 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17939 stays running even in the @kbd{target remote} mode.
17941 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17942 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17943 completeness, at most one @value{GDBN} can be connected at a time.
17945 @cindex @option{--once}, @code{gdbserver} option
17946 By default, @code{gdbserver} keeps the listening TCP port open, so that
17947 additional connections are possible. However, if you start @code{gdbserver}
17948 with the @option{--once} option, it will stop listening for any further
17949 connection attempts after connecting to the first @value{GDBN} session. This
17950 means no further connections to @code{gdbserver} will be possible after the
17951 first one. It also means @code{gdbserver} will terminate after the first
17952 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17953 connections and even in the @kbd{target extended-remote} mode. The
17954 @option{--once} option allows reusing the same port number for connecting to
17955 multiple instances of @code{gdbserver} running on the same host, since each
17956 instance closes its port after the first connection.
17958 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17960 @cindex @option{--debug}, @code{gdbserver} option
17961 The @option{--debug} option tells @code{gdbserver} to display extra
17962 status information about the debugging process.
17963 @cindex @option{--remote-debug}, @code{gdbserver} option
17964 The @option{--remote-debug} option tells @code{gdbserver} to display
17965 remote protocol debug output. These options are intended for
17966 @code{gdbserver} development and for bug reports to the developers.
17968 @cindex @option{--wrapper}, @code{gdbserver} option
17969 The @option{--wrapper} option specifies a wrapper to launch programs
17970 for debugging. The option should be followed by the name of the
17971 wrapper, then any command-line arguments to pass to the wrapper, then
17972 @kbd{--} indicating the end of the wrapper arguments.
17974 @code{gdbserver} runs the specified wrapper program with a combined
17975 command line including the wrapper arguments, then the name of the
17976 program to debug, then any arguments to the program. The wrapper
17977 runs until it executes your program, and then @value{GDBN} gains control.
17979 You can use any program that eventually calls @code{execve} with
17980 its arguments as a wrapper. Several standard Unix utilities do
17981 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17982 with @code{exec "$@@"} will also work.
17984 For example, you can use @code{env} to pass an environment variable to
17985 the debugged program, without setting the variable in @code{gdbserver}'s
17989 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17992 @subsection Connecting to @code{gdbserver}
17994 Run @value{GDBN} on the host system.
17996 First make sure you have the necessary symbol files. Load symbols for
17997 your application using the @code{file} command before you connect. Use
17998 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17999 was compiled with the correct sysroot using @code{--with-sysroot}).
18001 The symbol file and target libraries must exactly match the executable
18002 and libraries on the target, with one exception: the files on the host
18003 system should not be stripped, even if the files on the target system
18004 are. Mismatched or missing files will lead to confusing results
18005 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18006 files may also prevent @code{gdbserver} from debugging multi-threaded
18009 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18010 For TCP connections, you must start up @code{gdbserver} prior to using
18011 the @code{target remote} command. Otherwise you may get an error whose
18012 text depends on the host system, but which usually looks something like
18013 @samp{Connection refused}. Don't use the @code{load}
18014 command in @value{GDBN} when using @code{gdbserver}, since the program is
18015 already on the target.
18017 @subsection Monitor Commands for @code{gdbserver}
18018 @cindex monitor commands, for @code{gdbserver}
18019 @anchor{Monitor Commands for gdbserver}
18021 During a @value{GDBN} session using @code{gdbserver}, you can use the
18022 @code{monitor} command to send special requests to @code{gdbserver}.
18023 Here are the available commands.
18027 List the available monitor commands.
18029 @item monitor set debug 0
18030 @itemx monitor set debug 1
18031 Disable or enable general debugging messages.
18033 @item monitor set remote-debug 0
18034 @itemx monitor set remote-debug 1
18035 Disable or enable specific debugging messages associated with the remote
18036 protocol (@pxref{Remote Protocol}).
18038 @item monitor set libthread-db-search-path [PATH]
18039 @cindex gdbserver, search path for @code{libthread_db}
18040 When this command is issued, @var{path} is a colon-separated list of
18041 directories to search for @code{libthread_db} (@pxref{Threads,,set
18042 libthread-db-search-path}). If you omit @var{path},
18043 @samp{libthread-db-search-path} will be reset to its default value.
18045 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18046 not supported in @code{gdbserver}.
18049 Tell gdbserver to exit immediately. This command should be followed by
18050 @code{disconnect} to close the debugging session. @code{gdbserver} will
18051 detach from any attached processes and kill any processes it created.
18052 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18053 of a multi-process mode debug session.
18057 @subsection Tracepoints support in @code{gdbserver}
18058 @cindex tracepoints support in @code{gdbserver}
18060 On some targets, @code{gdbserver} supports tracepoints, fast
18061 tracepoints and static tracepoints.
18063 For fast or static tracepoints to work, a special library called the
18064 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18065 This library is built and distributed as an integral part of
18066 @code{gdbserver}. In addition, support for static tracepoints
18067 requires building the in-process agent library with static tracepoints
18068 support. At present, the UST (LTTng Userspace Tracer,
18069 @url{http://lttng.org/ust}) tracing engine is supported. This support
18070 is automatically available if UST development headers are found in the
18071 standard include path when @code{gdbserver} is built, or if
18072 @code{gdbserver} was explicitly configured using @option{--with-ust}
18073 to point at such headers. You can explicitly disable the support
18074 using @option{--with-ust=no}.
18076 There are several ways to load the in-process agent in your program:
18079 @item Specifying it as dependency at link time
18081 You can link your program dynamically with the in-process agent
18082 library. On most systems, this is accomplished by adding
18083 @code{-linproctrace} to the link command.
18085 @item Using the system's preloading mechanisms
18087 You can force loading the in-process agent at startup time by using
18088 your system's support for preloading shared libraries. Many Unixes
18089 support the concept of preloading user defined libraries. In most
18090 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18091 in the environment. See also the description of @code{gdbserver}'s
18092 @option{--wrapper} command line option.
18094 @item Using @value{GDBN} to force loading the agent at run time
18096 On some systems, you can force the inferior to load a shared library,
18097 by calling a dynamic loader function in the inferior that takes care
18098 of dynamically looking up and loading a shared library. On most Unix
18099 systems, the function is @code{dlopen}. You'll use the @code{call}
18100 command for that. For example:
18103 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18106 Note that on most Unix systems, for the @code{dlopen} function to be
18107 available, the program needs to be linked with @code{-ldl}.
18110 On systems that have a userspace dynamic loader, like most Unix
18111 systems, when you connect to @code{gdbserver} using @code{target
18112 remote}, you'll find that the program is stopped at the dynamic
18113 loader's entry point, and no shared library has been loaded in the
18114 program's address space yet, including the in-process agent. In that
18115 case, before being able to use any of the fast or static tracepoints
18116 features, you need to let the loader run and load the shared
18117 libraries. The simplest way to do that is to run the program to the
18118 main procedure. E.g., if debugging a C or C@t{++} program, start
18119 @code{gdbserver} like so:
18122 $ gdbserver :9999 myprogram
18125 Start GDB and connect to @code{gdbserver} like so, and run to main:
18129 (@value{GDBP}) target remote myhost:9999
18130 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18131 (@value{GDBP}) b main
18132 (@value{GDBP}) continue
18135 The in-process tracing agent library should now be loaded into the
18136 process; you can confirm it with the @code{info sharedlibrary}
18137 command, which will list @file{libinproctrace.so} as loaded in the
18138 process. You are now ready to install fast tracepoints, list static
18139 tracepoint markers, probe static tracepoints markers, and start
18142 @node Remote Configuration
18143 @section Remote Configuration
18146 @kindex show remote
18147 This section documents the configuration options available when
18148 debugging remote programs. For the options related to the File I/O
18149 extensions of the remote protocol, see @ref{system,
18150 system-call-allowed}.
18153 @item set remoteaddresssize @var{bits}
18154 @cindex address size for remote targets
18155 @cindex bits in remote address
18156 Set the maximum size of address in a memory packet to the specified
18157 number of bits. @value{GDBN} will mask off the address bits above
18158 that number, when it passes addresses to the remote target. The
18159 default value is the number of bits in the target's address.
18161 @item show remoteaddresssize
18162 Show the current value of remote address size in bits.
18164 @item set remotebaud @var{n}
18165 @cindex baud rate for remote targets
18166 Set the baud rate for the remote serial I/O to @var{n} baud. The
18167 value is used to set the speed of the serial port used for debugging
18170 @item show remotebaud
18171 Show the current speed of the remote connection.
18173 @item set remotebreak
18174 @cindex interrupt remote programs
18175 @cindex BREAK signal instead of Ctrl-C
18176 @anchor{set remotebreak}
18177 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18178 when you type @kbd{Ctrl-c} to interrupt the program running
18179 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18180 character instead. The default is off, since most remote systems
18181 expect to see @samp{Ctrl-C} as the interrupt signal.
18183 @item show remotebreak
18184 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18185 interrupt the remote program.
18187 @item set remoteflow on
18188 @itemx set remoteflow off
18189 @kindex set remoteflow
18190 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18191 on the serial port used to communicate to the remote target.
18193 @item show remoteflow
18194 @kindex show remoteflow
18195 Show the current setting of hardware flow control.
18197 @item set remotelogbase @var{base}
18198 Set the base (a.k.a.@: radix) of logging serial protocol
18199 communications to @var{base}. Supported values of @var{base} are:
18200 @code{ascii}, @code{octal}, and @code{hex}. The default is
18203 @item show remotelogbase
18204 Show the current setting of the radix for logging remote serial
18207 @item set remotelogfile @var{file}
18208 @cindex record serial communications on file
18209 Record remote serial communications on the named @var{file}. The
18210 default is not to record at all.
18212 @item show remotelogfile.
18213 Show the current setting of the file name on which to record the
18214 serial communications.
18216 @item set remotetimeout @var{num}
18217 @cindex timeout for serial communications
18218 @cindex remote timeout
18219 Set the timeout limit to wait for the remote target to respond to
18220 @var{num} seconds. The default is 2 seconds.
18222 @item show remotetimeout
18223 Show the current number of seconds to wait for the remote target
18226 @cindex limit hardware breakpoints and watchpoints
18227 @cindex remote target, limit break- and watchpoints
18228 @anchor{set remote hardware-watchpoint-limit}
18229 @anchor{set remote hardware-breakpoint-limit}
18230 @item set remote hardware-watchpoint-limit @var{limit}
18231 @itemx set remote hardware-breakpoint-limit @var{limit}
18232 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18233 watchpoints. A limit of -1, the default, is treated as unlimited.
18235 @cindex limit hardware watchpoints length
18236 @cindex remote target, limit watchpoints length
18237 @anchor{set remote hardware-watchpoint-length-limit}
18238 @item set remote hardware-watchpoint-length-limit @var{limit}
18239 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18240 a remote hardware watchpoint. A limit of -1, the default, is treated
18243 @item show remote hardware-watchpoint-length-limit
18244 Show the current limit (in bytes) of the maximum length of
18245 a remote hardware watchpoint.
18247 @item set remote exec-file @var{filename}
18248 @itemx show remote exec-file
18249 @anchor{set remote exec-file}
18250 @cindex executable file, for remote target
18251 Select the file used for @code{run} with @code{target
18252 extended-remote}. This should be set to a filename valid on the
18253 target system. If it is not set, the target will use a default
18254 filename (e.g.@: the last program run).
18256 @item set remote interrupt-sequence
18257 @cindex interrupt remote programs
18258 @cindex select Ctrl-C, BREAK or BREAK-g
18259 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18260 @samp{BREAK-g} as the
18261 sequence to the remote target in order to interrupt the execution.
18262 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18263 is high level of serial line for some certain time.
18264 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18265 It is @code{BREAK} signal followed by character @code{g}.
18267 @item show interrupt-sequence
18268 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18269 is sent by @value{GDBN} to interrupt the remote program.
18270 @code{BREAK-g} is BREAK signal followed by @code{g} and
18271 also known as Magic SysRq g.
18273 @item set remote interrupt-on-connect
18274 @cindex send interrupt-sequence on start
18275 Specify whether interrupt-sequence is sent to remote target when
18276 @value{GDBN} connects to it. This is mostly needed when you debug
18277 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18278 which is known as Magic SysRq g in order to connect @value{GDBN}.
18280 @item show interrupt-on-connect
18281 Show whether interrupt-sequence is sent
18282 to remote target when @value{GDBN} connects to it.
18286 @item set tcp auto-retry on
18287 @cindex auto-retry, for remote TCP target
18288 Enable auto-retry for remote TCP connections. This is useful if the remote
18289 debugging agent is launched in parallel with @value{GDBN}; there is a race
18290 condition because the agent may not become ready to accept the connection
18291 before @value{GDBN} attempts to connect. When auto-retry is
18292 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18293 to establish the connection using the timeout specified by
18294 @code{set tcp connect-timeout}.
18296 @item set tcp auto-retry off
18297 Do not auto-retry failed TCP connections.
18299 @item show tcp auto-retry
18300 Show the current auto-retry setting.
18302 @item set tcp connect-timeout @var{seconds}
18303 @itemx set tcp connect-timeout unlimited
18304 @cindex connection timeout, for remote TCP target
18305 @cindex timeout, for remote target connection
18306 Set the timeout for establishing a TCP connection to the remote target to
18307 @var{seconds}. The timeout affects both polling to retry failed connections
18308 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18309 that are merely slow to complete, and represents an approximate cumulative
18310 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18311 @value{GDBN} will keep attempting to establish a connection forever,
18312 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18314 @item show tcp connect-timeout
18315 Show the current connection timeout setting.
18318 @cindex remote packets, enabling and disabling
18319 The @value{GDBN} remote protocol autodetects the packets supported by
18320 your debugging stub. If you need to override the autodetection, you
18321 can use these commands to enable or disable individual packets. Each
18322 packet can be set to @samp{on} (the remote target supports this
18323 packet), @samp{off} (the remote target does not support this packet),
18324 or @samp{auto} (detect remote target support for this packet). They
18325 all default to @samp{auto}. For more information about each packet,
18326 see @ref{Remote Protocol}.
18328 During normal use, you should not have to use any of these commands.
18329 If you do, that may be a bug in your remote debugging stub, or a bug
18330 in @value{GDBN}. You may want to report the problem to the
18331 @value{GDBN} developers.
18333 For each packet @var{name}, the command to enable or disable the
18334 packet is @code{set remote @var{name}-packet}. The available settings
18337 @multitable @columnfractions 0.28 0.32 0.25
18340 @tab Related Features
18342 @item @code{fetch-register}
18344 @tab @code{info registers}
18346 @item @code{set-register}
18350 @item @code{binary-download}
18352 @tab @code{load}, @code{set}
18354 @item @code{read-aux-vector}
18355 @tab @code{qXfer:auxv:read}
18356 @tab @code{info auxv}
18358 @item @code{symbol-lookup}
18359 @tab @code{qSymbol}
18360 @tab Detecting multiple threads
18362 @item @code{attach}
18363 @tab @code{vAttach}
18366 @item @code{verbose-resume}
18368 @tab Stepping or resuming multiple threads
18374 @item @code{software-breakpoint}
18378 @item @code{hardware-breakpoint}
18382 @item @code{write-watchpoint}
18386 @item @code{read-watchpoint}
18390 @item @code{access-watchpoint}
18394 @item @code{target-features}
18395 @tab @code{qXfer:features:read}
18396 @tab @code{set architecture}
18398 @item @code{library-info}
18399 @tab @code{qXfer:libraries:read}
18400 @tab @code{info sharedlibrary}
18402 @item @code{memory-map}
18403 @tab @code{qXfer:memory-map:read}
18404 @tab @code{info mem}
18406 @item @code{read-sdata-object}
18407 @tab @code{qXfer:sdata:read}
18408 @tab @code{print $_sdata}
18410 @item @code{read-spu-object}
18411 @tab @code{qXfer:spu:read}
18412 @tab @code{info spu}
18414 @item @code{write-spu-object}
18415 @tab @code{qXfer:spu:write}
18416 @tab @code{info spu}
18418 @item @code{read-siginfo-object}
18419 @tab @code{qXfer:siginfo:read}
18420 @tab @code{print $_siginfo}
18422 @item @code{write-siginfo-object}
18423 @tab @code{qXfer:siginfo:write}
18424 @tab @code{set $_siginfo}
18426 @item @code{threads}
18427 @tab @code{qXfer:threads:read}
18428 @tab @code{info threads}
18430 @item @code{get-thread-local-@*storage-address}
18431 @tab @code{qGetTLSAddr}
18432 @tab Displaying @code{__thread} variables
18434 @item @code{get-thread-information-block-address}
18435 @tab @code{qGetTIBAddr}
18436 @tab Display MS-Windows Thread Information Block.
18438 @item @code{search-memory}
18439 @tab @code{qSearch:memory}
18442 @item @code{supported-packets}
18443 @tab @code{qSupported}
18444 @tab Remote communications parameters
18446 @item @code{pass-signals}
18447 @tab @code{QPassSignals}
18448 @tab @code{handle @var{signal}}
18450 @item @code{program-signals}
18451 @tab @code{QProgramSignals}
18452 @tab @code{handle @var{signal}}
18454 @item @code{hostio-close-packet}
18455 @tab @code{vFile:close}
18456 @tab @code{remote get}, @code{remote put}
18458 @item @code{hostio-open-packet}
18459 @tab @code{vFile:open}
18460 @tab @code{remote get}, @code{remote put}
18462 @item @code{hostio-pread-packet}
18463 @tab @code{vFile:pread}
18464 @tab @code{remote get}, @code{remote put}
18466 @item @code{hostio-pwrite-packet}
18467 @tab @code{vFile:pwrite}
18468 @tab @code{remote get}, @code{remote put}
18470 @item @code{hostio-unlink-packet}
18471 @tab @code{vFile:unlink}
18472 @tab @code{remote delete}
18474 @item @code{hostio-readlink-packet}
18475 @tab @code{vFile:readlink}
18478 @item @code{noack-packet}
18479 @tab @code{QStartNoAckMode}
18480 @tab Packet acknowledgment
18482 @item @code{osdata}
18483 @tab @code{qXfer:osdata:read}
18484 @tab @code{info os}
18486 @item @code{query-attached}
18487 @tab @code{qAttached}
18488 @tab Querying remote process attach state.
18490 @item @code{trace-buffer-size}
18491 @tab @code{QTBuffer:size}
18492 @tab @code{set trace-buffer-size}
18494 @item @code{trace-status}
18495 @tab @code{qTStatus}
18496 @tab @code{tstatus}
18498 @item @code{traceframe-info}
18499 @tab @code{qXfer:traceframe-info:read}
18500 @tab Traceframe info
18502 @item @code{install-in-trace}
18503 @tab @code{InstallInTrace}
18504 @tab Install tracepoint in tracing
18506 @item @code{disable-randomization}
18507 @tab @code{QDisableRandomization}
18508 @tab @code{set disable-randomization}
18510 @item @code{conditional-breakpoints-packet}
18511 @tab @code{Z0 and Z1}
18512 @tab @code{Support for target-side breakpoint condition evaluation}
18516 @section Implementing a Remote Stub
18518 @cindex debugging stub, example
18519 @cindex remote stub, example
18520 @cindex stub example, remote debugging
18521 The stub files provided with @value{GDBN} implement the target side of the
18522 communication protocol, and the @value{GDBN} side is implemented in the
18523 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18524 these subroutines to communicate, and ignore the details. (If you're
18525 implementing your own stub file, you can still ignore the details: start
18526 with one of the existing stub files. @file{sparc-stub.c} is the best
18527 organized, and therefore the easiest to read.)
18529 @cindex remote serial debugging, overview
18530 To debug a program running on another machine (the debugging
18531 @dfn{target} machine), you must first arrange for all the usual
18532 prerequisites for the program to run by itself. For example, for a C
18537 A startup routine to set up the C runtime environment; these usually
18538 have a name like @file{crt0}. The startup routine may be supplied by
18539 your hardware supplier, or you may have to write your own.
18542 A C subroutine library to support your program's
18543 subroutine calls, notably managing input and output.
18546 A way of getting your program to the other machine---for example, a
18547 download program. These are often supplied by the hardware
18548 manufacturer, but you may have to write your own from hardware
18552 The next step is to arrange for your program to use a serial port to
18553 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18554 machine). In general terms, the scheme looks like this:
18558 @value{GDBN} already understands how to use this protocol; when everything
18559 else is set up, you can simply use the @samp{target remote} command
18560 (@pxref{Targets,,Specifying a Debugging Target}).
18562 @item On the target,
18563 you must link with your program a few special-purpose subroutines that
18564 implement the @value{GDBN} remote serial protocol. The file containing these
18565 subroutines is called a @dfn{debugging stub}.
18567 On certain remote targets, you can use an auxiliary program
18568 @code{gdbserver} instead of linking a stub into your program.
18569 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18572 The debugging stub is specific to the architecture of the remote
18573 machine; for example, use @file{sparc-stub.c} to debug programs on
18576 @cindex remote serial stub list
18577 These working remote stubs are distributed with @value{GDBN}:
18582 @cindex @file{i386-stub.c}
18585 For Intel 386 and compatible architectures.
18588 @cindex @file{m68k-stub.c}
18589 @cindex Motorola 680x0
18591 For Motorola 680x0 architectures.
18594 @cindex @file{sh-stub.c}
18597 For Renesas SH architectures.
18600 @cindex @file{sparc-stub.c}
18602 For @sc{sparc} architectures.
18604 @item sparcl-stub.c
18605 @cindex @file{sparcl-stub.c}
18608 For Fujitsu @sc{sparclite} architectures.
18612 The @file{README} file in the @value{GDBN} distribution may list other
18613 recently added stubs.
18616 * Stub Contents:: What the stub can do for you
18617 * Bootstrapping:: What you must do for the stub
18618 * Debug Session:: Putting it all together
18621 @node Stub Contents
18622 @subsection What the Stub Can Do for You
18624 @cindex remote serial stub
18625 The debugging stub for your architecture supplies these three
18629 @item set_debug_traps
18630 @findex set_debug_traps
18631 @cindex remote serial stub, initialization
18632 This routine arranges for @code{handle_exception} to run when your
18633 program stops. You must call this subroutine explicitly in your
18634 program's startup code.
18636 @item handle_exception
18637 @findex handle_exception
18638 @cindex remote serial stub, main routine
18639 This is the central workhorse, but your program never calls it
18640 explicitly---the setup code arranges for @code{handle_exception} to
18641 run when a trap is triggered.
18643 @code{handle_exception} takes control when your program stops during
18644 execution (for example, on a breakpoint), and mediates communications
18645 with @value{GDBN} on the host machine. This is where the communications
18646 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18647 representative on the target machine. It begins by sending summary
18648 information on the state of your program, then continues to execute,
18649 retrieving and transmitting any information @value{GDBN} needs, until you
18650 execute a @value{GDBN} command that makes your program resume; at that point,
18651 @code{handle_exception} returns control to your own code on the target
18655 @cindex @code{breakpoint} subroutine, remote
18656 Use this auxiliary subroutine to make your program contain a
18657 breakpoint. Depending on the particular situation, this may be the only
18658 way for @value{GDBN} to get control. For instance, if your target
18659 machine has some sort of interrupt button, you won't need to call this;
18660 pressing the interrupt button transfers control to
18661 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18662 simply receiving characters on the serial port may also trigger a trap;
18663 again, in that situation, you don't need to call @code{breakpoint} from
18664 your own program---simply running @samp{target remote} from the host
18665 @value{GDBN} session gets control.
18667 Call @code{breakpoint} if none of these is true, or if you simply want
18668 to make certain your program stops at a predetermined point for the
18669 start of your debugging session.
18672 @node Bootstrapping
18673 @subsection What You Must Do for the Stub
18675 @cindex remote stub, support routines
18676 The debugging stubs that come with @value{GDBN} are set up for a particular
18677 chip architecture, but they have no information about the rest of your
18678 debugging target machine.
18680 First of all you need to tell the stub how to communicate with the
18684 @item int getDebugChar()
18685 @findex getDebugChar
18686 Write this subroutine to read a single character from the serial port.
18687 It may be identical to @code{getchar} for your target system; a
18688 different name is used to allow you to distinguish the two if you wish.
18690 @item void putDebugChar(int)
18691 @findex putDebugChar
18692 Write this subroutine to write a single character to the serial port.
18693 It may be identical to @code{putchar} for your target system; a
18694 different name is used to allow you to distinguish the two if you wish.
18697 @cindex control C, and remote debugging
18698 @cindex interrupting remote targets
18699 If you want @value{GDBN} to be able to stop your program while it is
18700 running, you need to use an interrupt-driven serial driver, and arrange
18701 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18702 character). That is the character which @value{GDBN} uses to tell the
18703 remote system to stop.
18705 Getting the debugging target to return the proper status to @value{GDBN}
18706 probably requires changes to the standard stub; one quick and dirty way
18707 is to just execute a breakpoint instruction (the ``dirty'' part is that
18708 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18710 Other routines you need to supply are:
18713 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18714 @findex exceptionHandler
18715 Write this function to install @var{exception_address} in the exception
18716 handling tables. You need to do this because the stub does not have any
18717 way of knowing what the exception handling tables on your target system
18718 are like (for example, the processor's table might be in @sc{rom},
18719 containing entries which point to a table in @sc{ram}).
18720 @var{exception_number} is the exception number which should be changed;
18721 its meaning is architecture-dependent (for example, different numbers
18722 might represent divide by zero, misaligned access, etc). When this
18723 exception occurs, control should be transferred directly to
18724 @var{exception_address}, and the processor state (stack, registers,
18725 and so on) should be just as it is when a processor exception occurs. So if
18726 you want to use a jump instruction to reach @var{exception_address}, it
18727 should be a simple jump, not a jump to subroutine.
18729 For the 386, @var{exception_address} should be installed as an interrupt
18730 gate so that interrupts are masked while the handler runs. The gate
18731 should be at privilege level 0 (the most privileged level). The
18732 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18733 help from @code{exceptionHandler}.
18735 @item void flush_i_cache()
18736 @findex flush_i_cache
18737 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18738 instruction cache, if any, on your target machine. If there is no
18739 instruction cache, this subroutine may be a no-op.
18741 On target machines that have instruction caches, @value{GDBN} requires this
18742 function to make certain that the state of your program is stable.
18746 You must also make sure this library routine is available:
18749 @item void *memset(void *, int, int)
18751 This is the standard library function @code{memset} that sets an area of
18752 memory to a known value. If you have one of the free versions of
18753 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18754 either obtain it from your hardware manufacturer, or write your own.
18757 If you do not use the GNU C compiler, you may need other standard
18758 library subroutines as well; this varies from one stub to another,
18759 but in general the stubs are likely to use any of the common library
18760 subroutines which @code{@value{NGCC}} generates as inline code.
18763 @node Debug Session
18764 @subsection Putting it All Together
18766 @cindex remote serial debugging summary
18767 In summary, when your program is ready to debug, you must follow these
18772 Make sure you have defined the supporting low-level routines
18773 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18775 @code{getDebugChar}, @code{putDebugChar},
18776 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18780 Insert these lines in your program's startup code, before the main
18781 procedure is called:
18788 On some machines, when a breakpoint trap is raised, the hardware
18789 automatically makes the PC point to the instruction after the
18790 breakpoint. If your machine doesn't do that, you may need to adjust
18791 @code{handle_exception} to arrange for it to return to the instruction
18792 after the breakpoint on this first invocation, so that your program
18793 doesn't keep hitting the initial breakpoint instead of making
18797 For the 680x0 stub only, you need to provide a variable called
18798 @code{exceptionHook}. Normally you just use:
18801 void (*exceptionHook)() = 0;
18805 but if before calling @code{set_debug_traps}, you set it to point to a
18806 function in your program, that function is called when
18807 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18808 error). The function indicated by @code{exceptionHook} is called with
18809 one parameter: an @code{int} which is the exception number.
18812 Compile and link together: your program, the @value{GDBN} debugging stub for
18813 your target architecture, and the supporting subroutines.
18816 Make sure you have a serial connection between your target machine and
18817 the @value{GDBN} host, and identify the serial port on the host.
18820 @c The "remote" target now provides a `load' command, so we should
18821 @c document that. FIXME.
18822 Download your program to your target machine (or get it there by
18823 whatever means the manufacturer provides), and start it.
18826 Start @value{GDBN} on the host, and connect to the target
18827 (@pxref{Connecting,,Connecting to a Remote Target}).
18831 @node Configurations
18832 @chapter Configuration-Specific Information
18834 While nearly all @value{GDBN} commands are available for all native and
18835 cross versions of the debugger, there are some exceptions. This chapter
18836 describes things that are only available in certain configurations.
18838 There are three major categories of configurations: native
18839 configurations, where the host and target are the same, embedded
18840 operating system configurations, which are usually the same for several
18841 different processor architectures, and bare embedded processors, which
18842 are quite different from each other.
18847 * Embedded Processors::
18854 This section describes details specific to particular native
18859 * BSD libkvm Interface:: Debugging BSD kernel memory images
18860 * SVR4 Process Information:: SVR4 process information
18861 * DJGPP Native:: Features specific to the DJGPP port
18862 * Cygwin Native:: Features specific to the Cygwin port
18863 * Hurd Native:: Features specific to @sc{gnu} Hurd
18864 * Darwin:: Features specific to Darwin
18870 On HP-UX systems, if you refer to a function or variable name that
18871 begins with a dollar sign, @value{GDBN} searches for a user or system
18872 name first, before it searches for a convenience variable.
18875 @node BSD libkvm Interface
18876 @subsection BSD libkvm Interface
18879 @cindex kernel memory image
18880 @cindex kernel crash dump
18882 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18883 interface that provides a uniform interface for accessing kernel virtual
18884 memory images, including live systems and crash dumps. @value{GDBN}
18885 uses this interface to allow you to debug live kernels and kernel crash
18886 dumps on many native BSD configurations. This is implemented as a
18887 special @code{kvm} debugging target. For debugging a live system, load
18888 the currently running kernel into @value{GDBN} and connect to the
18892 (@value{GDBP}) @b{target kvm}
18895 For debugging crash dumps, provide the file name of the crash dump as an
18899 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18902 Once connected to the @code{kvm} target, the following commands are
18908 Set current context from the @dfn{Process Control Block} (PCB) address.
18911 Set current context from proc address. This command isn't available on
18912 modern FreeBSD systems.
18915 @node SVR4 Process Information
18916 @subsection SVR4 Process Information
18918 @cindex examine process image
18919 @cindex process info via @file{/proc}
18921 Many versions of SVR4 and compatible systems provide a facility called
18922 @samp{/proc} that can be used to examine the image of a running
18923 process using file-system subroutines.
18925 If @value{GDBN} is configured for an operating system with this
18926 facility, the command @code{info proc} is available to report
18927 information about the process running your program, or about any
18928 process running on your system. This includes, as of this writing,
18929 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18930 not HP-UX, for example.
18932 This command may also work on core files that were created on a system
18933 that has the @samp{/proc} facility.
18939 @itemx info proc @var{process-id}
18940 Summarize available information about any running process. If a
18941 process ID is specified by @var{process-id}, display information about
18942 that process; otherwise display information about the program being
18943 debugged. The summary includes the debugged process ID, the command
18944 line used to invoke it, its current working directory, and its
18945 executable file's absolute file name.
18947 On some systems, @var{process-id} can be of the form
18948 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18949 within a process. If the optional @var{pid} part is missing, it means
18950 a thread from the process being debugged (the leading @samp{/} still
18951 needs to be present, or else @value{GDBN} will interpret the number as
18952 a process ID rather than a thread ID).
18954 @item info proc cmdline
18955 @cindex info proc cmdline
18956 Show the original command line of the process. This command is
18957 specific to @sc{gnu}/Linux.
18959 @item info proc cwd
18960 @cindex info proc cwd
18961 Show the current working directory of the process. This command is
18962 specific to @sc{gnu}/Linux.
18964 @item info proc exe
18965 @cindex info proc exe
18966 Show the name of executable of the process. This command is specific
18969 @item info proc mappings
18970 @cindex memory address space mappings
18971 Report the memory address space ranges accessible in the program, with
18972 information on whether the process has read, write, or execute access
18973 rights to each range. On @sc{gnu}/Linux systems, each memory range
18974 includes the object file which is mapped to that range, instead of the
18975 memory access rights to that range.
18977 @item info proc stat
18978 @itemx info proc status
18979 @cindex process detailed status information
18980 These subcommands are specific to @sc{gnu}/Linux systems. They show
18981 the process-related information, including the user ID and group ID;
18982 how many threads are there in the process; its virtual memory usage;
18983 the signals that are pending, blocked, and ignored; its TTY; its
18984 consumption of system and user time; its stack size; its @samp{nice}
18985 value; etc. For more information, see the @samp{proc} man page
18986 (type @kbd{man 5 proc} from your shell prompt).
18988 @item info proc all
18989 Show all the information about the process described under all of the
18990 above @code{info proc} subcommands.
18993 @comment These sub-options of 'info proc' were not included when
18994 @comment procfs.c was re-written. Keep their descriptions around
18995 @comment against the day when someone finds the time to put them back in.
18996 @kindex info proc times
18997 @item info proc times
18998 Starting time, user CPU time, and system CPU time for your program and
19001 @kindex info proc id
19003 Report on the process IDs related to your program: its own process ID,
19004 the ID of its parent, the process group ID, and the session ID.
19007 @item set procfs-trace
19008 @kindex set procfs-trace
19009 @cindex @code{procfs} API calls
19010 This command enables and disables tracing of @code{procfs} API calls.
19012 @item show procfs-trace
19013 @kindex show procfs-trace
19014 Show the current state of @code{procfs} API call tracing.
19016 @item set procfs-file @var{file}
19017 @kindex set procfs-file
19018 Tell @value{GDBN} to write @code{procfs} API trace to the named
19019 @var{file}. @value{GDBN} appends the trace info to the previous
19020 contents of the file. The default is to display the trace on the
19023 @item show procfs-file
19024 @kindex show procfs-file
19025 Show the file to which @code{procfs} API trace is written.
19027 @item proc-trace-entry
19028 @itemx proc-trace-exit
19029 @itemx proc-untrace-entry
19030 @itemx proc-untrace-exit
19031 @kindex proc-trace-entry
19032 @kindex proc-trace-exit
19033 @kindex proc-untrace-entry
19034 @kindex proc-untrace-exit
19035 These commands enable and disable tracing of entries into and exits
19036 from the @code{syscall} interface.
19039 @kindex info pidlist
19040 @cindex process list, QNX Neutrino
19041 For QNX Neutrino only, this command displays the list of all the
19042 processes and all the threads within each process.
19045 @kindex info meminfo
19046 @cindex mapinfo list, QNX Neutrino
19047 For QNX Neutrino only, this command displays the list of all mapinfos.
19051 @subsection Features for Debugging @sc{djgpp} Programs
19052 @cindex @sc{djgpp} debugging
19053 @cindex native @sc{djgpp} debugging
19054 @cindex MS-DOS-specific commands
19057 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19058 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19059 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19060 top of real-mode DOS systems and their emulations.
19062 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19063 defines a few commands specific to the @sc{djgpp} port. This
19064 subsection describes those commands.
19069 This is a prefix of @sc{djgpp}-specific commands which print
19070 information about the target system and important OS structures.
19073 @cindex MS-DOS system info
19074 @cindex free memory information (MS-DOS)
19075 @item info dos sysinfo
19076 This command displays assorted information about the underlying
19077 platform: the CPU type and features, the OS version and flavor, the
19078 DPMI version, and the available conventional and DPMI memory.
19083 @cindex segment descriptor tables
19084 @cindex descriptor tables display
19086 @itemx info dos ldt
19087 @itemx info dos idt
19088 These 3 commands display entries from, respectively, Global, Local,
19089 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19090 tables are data structures which store a descriptor for each segment
19091 that is currently in use. The segment's selector is an index into a
19092 descriptor table; the table entry for that index holds the
19093 descriptor's base address and limit, and its attributes and access
19096 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19097 segment (used for both data and the stack), and a DOS segment (which
19098 allows access to DOS/BIOS data structures and absolute addresses in
19099 conventional memory). However, the DPMI host will usually define
19100 additional segments in order to support the DPMI environment.
19102 @cindex garbled pointers
19103 These commands allow to display entries from the descriptor tables.
19104 Without an argument, all entries from the specified table are
19105 displayed. An argument, which should be an integer expression, means
19106 display a single entry whose index is given by the argument. For
19107 example, here's a convenient way to display information about the
19108 debugged program's data segment:
19111 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19112 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19116 This comes in handy when you want to see whether a pointer is outside
19117 the data segment's limit (i.e.@: @dfn{garbled}).
19119 @cindex page tables display (MS-DOS)
19121 @itemx info dos pte
19122 These two commands display entries from, respectively, the Page
19123 Directory and the Page Tables. Page Directories and Page Tables are
19124 data structures which control how virtual memory addresses are mapped
19125 into physical addresses. A Page Table includes an entry for every
19126 page of memory that is mapped into the program's address space; there
19127 may be several Page Tables, each one holding up to 4096 entries. A
19128 Page Directory has up to 4096 entries, one each for every Page Table
19129 that is currently in use.
19131 Without an argument, @kbd{info dos pde} displays the entire Page
19132 Directory, and @kbd{info dos pte} displays all the entries in all of
19133 the Page Tables. An argument, an integer expression, given to the
19134 @kbd{info dos pde} command means display only that entry from the Page
19135 Directory table. An argument given to the @kbd{info dos pte} command
19136 means display entries from a single Page Table, the one pointed to by
19137 the specified entry in the Page Directory.
19139 @cindex direct memory access (DMA) on MS-DOS
19140 These commands are useful when your program uses @dfn{DMA} (Direct
19141 Memory Access), which needs physical addresses to program the DMA
19144 These commands are supported only with some DPMI servers.
19146 @cindex physical address from linear address
19147 @item info dos address-pte @var{addr}
19148 This command displays the Page Table entry for a specified linear
19149 address. The argument @var{addr} is a linear address which should
19150 already have the appropriate segment's base address added to it,
19151 because this command accepts addresses which may belong to @emph{any}
19152 segment. For example, here's how to display the Page Table entry for
19153 the page where a variable @code{i} is stored:
19156 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19157 @exdent @code{Page Table entry for address 0x11a00d30:}
19158 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19162 This says that @code{i} is stored at offset @code{0xd30} from the page
19163 whose physical base address is @code{0x02698000}, and shows all the
19164 attributes of that page.
19166 Note that you must cast the addresses of variables to a @code{char *},
19167 since otherwise the value of @code{__djgpp_base_address}, the base
19168 address of all variables and functions in a @sc{djgpp} program, will
19169 be added using the rules of C pointer arithmetics: if @code{i} is
19170 declared an @code{int}, @value{GDBN} will add 4 times the value of
19171 @code{__djgpp_base_address} to the address of @code{i}.
19173 Here's another example, it displays the Page Table entry for the
19177 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19178 @exdent @code{Page Table entry for address 0x29110:}
19179 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19183 (The @code{+ 3} offset is because the transfer buffer's address is the
19184 3rd member of the @code{_go32_info_block} structure.) The output
19185 clearly shows that this DPMI server maps the addresses in conventional
19186 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19187 linear (@code{0x29110}) addresses are identical.
19189 This command is supported only with some DPMI servers.
19192 @cindex DOS serial data link, remote debugging
19193 In addition to native debugging, the DJGPP port supports remote
19194 debugging via a serial data link. The following commands are specific
19195 to remote serial debugging in the DJGPP port of @value{GDBN}.
19198 @kindex set com1base
19199 @kindex set com1irq
19200 @kindex set com2base
19201 @kindex set com2irq
19202 @kindex set com3base
19203 @kindex set com3irq
19204 @kindex set com4base
19205 @kindex set com4irq
19206 @item set com1base @var{addr}
19207 This command sets the base I/O port address of the @file{COM1} serial
19210 @item set com1irq @var{irq}
19211 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19212 for the @file{COM1} serial port.
19214 There are similar commands @samp{set com2base}, @samp{set com3irq},
19215 etc.@: for setting the port address and the @code{IRQ} lines for the
19218 @kindex show com1base
19219 @kindex show com1irq
19220 @kindex show com2base
19221 @kindex show com2irq
19222 @kindex show com3base
19223 @kindex show com3irq
19224 @kindex show com4base
19225 @kindex show com4irq
19226 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19227 display the current settings of the base address and the @code{IRQ}
19228 lines used by the COM ports.
19231 @kindex info serial
19232 @cindex DOS serial port status
19233 This command prints the status of the 4 DOS serial ports. For each
19234 port, it prints whether it's active or not, its I/O base address and
19235 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19236 counts of various errors encountered so far.
19240 @node Cygwin Native
19241 @subsection Features for Debugging MS Windows PE Executables
19242 @cindex MS Windows debugging
19243 @cindex native Cygwin debugging
19244 @cindex Cygwin-specific commands
19246 @value{GDBN} supports native debugging of MS Windows programs, including
19247 DLLs with and without symbolic debugging information.
19249 @cindex Ctrl-BREAK, MS-Windows
19250 @cindex interrupt debuggee on MS-Windows
19251 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19252 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19253 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19254 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19255 sequence, which can be used to interrupt the debuggee even if it
19258 There are various additional Cygwin-specific commands, described in
19259 this section. Working with DLLs that have no debugging symbols is
19260 described in @ref{Non-debug DLL Symbols}.
19265 This is a prefix of MS Windows-specific commands which print
19266 information about the target system and important OS structures.
19268 @item info w32 selector
19269 This command displays information returned by
19270 the Win32 API @code{GetThreadSelectorEntry} function.
19271 It takes an optional argument that is evaluated to
19272 a long value to give the information about this given selector.
19273 Without argument, this command displays information
19274 about the six segment registers.
19276 @item info w32 thread-information-block
19277 This command displays thread specific information stored in the
19278 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19279 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19283 This is a Cygwin-specific alias of @code{info shared}.
19285 @kindex dll-symbols
19287 This command loads symbols from a dll similarly to
19288 add-sym command but without the need to specify a base address.
19290 @kindex set cygwin-exceptions
19291 @cindex debugging the Cygwin DLL
19292 @cindex Cygwin DLL, debugging
19293 @item set cygwin-exceptions @var{mode}
19294 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19295 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19296 @value{GDBN} will delay recognition of exceptions, and may ignore some
19297 exceptions which seem to be caused by internal Cygwin DLL
19298 ``bookkeeping''. This option is meant primarily for debugging the
19299 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19300 @value{GDBN} users with false @code{SIGSEGV} signals.
19302 @kindex show cygwin-exceptions
19303 @item show cygwin-exceptions
19304 Displays whether @value{GDBN} will break on exceptions that happen
19305 inside the Cygwin DLL itself.
19307 @kindex set new-console
19308 @item set new-console @var{mode}
19309 If @var{mode} is @code{on} the debuggee will
19310 be started in a new console on next start.
19311 If @var{mode} is @code{off}, the debuggee will
19312 be started in the same console as the debugger.
19314 @kindex show new-console
19315 @item show new-console
19316 Displays whether a new console is used
19317 when the debuggee is started.
19319 @kindex set new-group
19320 @item set new-group @var{mode}
19321 This boolean value controls whether the debuggee should
19322 start a new group or stay in the same group as the debugger.
19323 This affects the way the Windows OS handles
19326 @kindex show new-group
19327 @item show new-group
19328 Displays current value of new-group boolean.
19330 @kindex set debugevents
19331 @item set debugevents
19332 This boolean value adds debug output concerning kernel events related
19333 to the debuggee seen by the debugger. This includes events that
19334 signal thread and process creation and exit, DLL loading and
19335 unloading, console interrupts, and debugging messages produced by the
19336 Windows @code{OutputDebugString} API call.
19338 @kindex set debugexec
19339 @item set debugexec
19340 This boolean value adds debug output concerning execute events
19341 (such as resume thread) seen by the debugger.
19343 @kindex set debugexceptions
19344 @item set debugexceptions
19345 This boolean value adds debug output concerning exceptions in the
19346 debuggee seen by the debugger.
19348 @kindex set debugmemory
19349 @item set debugmemory
19350 This boolean value adds debug output concerning debuggee memory reads
19351 and writes by the debugger.
19355 This boolean values specifies whether the debuggee is called
19356 via a shell or directly (default value is on).
19360 Displays if the debuggee will be started with a shell.
19365 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19368 @node Non-debug DLL Symbols
19369 @subsubsection Support for DLLs without Debugging Symbols
19370 @cindex DLLs with no debugging symbols
19371 @cindex Minimal symbols and DLLs
19373 Very often on windows, some of the DLLs that your program relies on do
19374 not include symbolic debugging information (for example,
19375 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19376 symbols in a DLL, it relies on the minimal amount of symbolic
19377 information contained in the DLL's export table. This section
19378 describes working with such symbols, known internally to @value{GDBN} as
19379 ``minimal symbols''.
19381 Note that before the debugged program has started execution, no DLLs
19382 will have been loaded. The easiest way around this problem is simply to
19383 start the program --- either by setting a breakpoint or letting the
19384 program run once to completion. It is also possible to force
19385 @value{GDBN} to load a particular DLL before starting the executable ---
19386 see the shared library information in @ref{Files}, or the
19387 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19388 explicitly loading symbols from a DLL with no debugging information will
19389 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19390 which may adversely affect symbol lookup performance.
19392 @subsubsection DLL Name Prefixes
19394 In keeping with the naming conventions used by the Microsoft debugging
19395 tools, DLL export symbols are made available with a prefix based on the
19396 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19397 also entered into the symbol table, so @code{CreateFileA} is often
19398 sufficient. In some cases there will be name clashes within a program
19399 (particularly if the executable itself includes full debugging symbols)
19400 necessitating the use of the fully qualified name when referring to the
19401 contents of the DLL. Use single-quotes around the name to avoid the
19402 exclamation mark (``!'') being interpreted as a language operator.
19404 Note that the internal name of the DLL may be all upper-case, even
19405 though the file name of the DLL is lower-case, or vice-versa. Since
19406 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19407 some confusion. If in doubt, try the @code{info functions} and
19408 @code{info variables} commands or even @code{maint print msymbols}
19409 (@pxref{Symbols}). Here's an example:
19412 (@value{GDBP}) info function CreateFileA
19413 All functions matching regular expression "CreateFileA":
19415 Non-debugging symbols:
19416 0x77e885f4 CreateFileA
19417 0x77e885f4 KERNEL32!CreateFileA
19421 (@value{GDBP}) info function !
19422 All functions matching regular expression "!":
19424 Non-debugging symbols:
19425 0x6100114c cygwin1!__assert
19426 0x61004034 cygwin1!_dll_crt0@@0
19427 0x61004240 cygwin1!dll_crt0(per_process *)
19431 @subsubsection Working with Minimal Symbols
19433 Symbols extracted from a DLL's export table do not contain very much
19434 type information. All that @value{GDBN} can do is guess whether a symbol
19435 refers to a function or variable depending on the linker section that
19436 contains the symbol. Also note that the actual contents of the memory
19437 contained in a DLL are not available unless the program is running. This
19438 means that you cannot examine the contents of a variable or disassemble
19439 a function within a DLL without a running program.
19441 Variables are generally treated as pointers and dereferenced
19442 automatically. For this reason, it is often necessary to prefix a
19443 variable name with the address-of operator (``&'') and provide explicit
19444 type information in the command. Here's an example of the type of
19448 (@value{GDBP}) print 'cygwin1!__argv'
19453 (@value{GDBP}) x 'cygwin1!__argv'
19454 0x10021610: "\230y\""
19457 And two possible solutions:
19460 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19461 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19465 (@value{GDBP}) x/2x &'cygwin1!__argv'
19466 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19467 (@value{GDBP}) x/x 0x10021608
19468 0x10021608: 0x0022fd98
19469 (@value{GDBP}) x/s 0x0022fd98
19470 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19473 Setting a break point within a DLL is possible even before the program
19474 starts execution. However, under these circumstances, @value{GDBN} can't
19475 examine the initial instructions of the function in order to skip the
19476 function's frame set-up code. You can work around this by using ``*&''
19477 to set the breakpoint at a raw memory address:
19480 (@value{GDBP}) break *&'python22!PyOS_Readline'
19481 Breakpoint 1 at 0x1e04eff0
19484 The author of these extensions is not entirely convinced that setting a
19485 break point within a shared DLL like @file{kernel32.dll} is completely
19489 @subsection Commands Specific to @sc{gnu} Hurd Systems
19490 @cindex @sc{gnu} Hurd debugging
19492 This subsection describes @value{GDBN} commands specific to the
19493 @sc{gnu} Hurd native debugging.
19498 @kindex set signals@r{, Hurd command}
19499 @kindex set sigs@r{, Hurd command}
19500 This command toggles the state of inferior signal interception by
19501 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19502 affected by this command. @code{sigs} is a shorthand alias for
19507 @kindex show signals@r{, Hurd command}
19508 @kindex show sigs@r{, Hurd command}
19509 Show the current state of intercepting inferior's signals.
19511 @item set signal-thread
19512 @itemx set sigthread
19513 @kindex set signal-thread
19514 @kindex set sigthread
19515 This command tells @value{GDBN} which thread is the @code{libc} signal
19516 thread. That thread is run when a signal is delivered to a running
19517 process. @code{set sigthread} is the shorthand alias of @code{set
19520 @item show signal-thread
19521 @itemx show sigthread
19522 @kindex show signal-thread
19523 @kindex show sigthread
19524 These two commands show which thread will run when the inferior is
19525 delivered a signal.
19528 @kindex set stopped@r{, Hurd command}
19529 This commands tells @value{GDBN} that the inferior process is stopped,
19530 as with the @code{SIGSTOP} signal. The stopped process can be
19531 continued by delivering a signal to it.
19534 @kindex show stopped@r{, Hurd command}
19535 This command shows whether @value{GDBN} thinks the debuggee is
19538 @item set exceptions
19539 @kindex set exceptions@r{, Hurd command}
19540 Use this command to turn off trapping of exceptions in the inferior.
19541 When exception trapping is off, neither breakpoints nor
19542 single-stepping will work. To restore the default, set exception
19545 @item show exceptions
19546 @kindex show exceptions@r{, Hurd command}
19547 Show the current state of trapping exceptions in the inferior.
19549 @item set task pause
19550 @kindex set task@r{, Hurd commands}
19551 @cindex task attributes (@sc{gnu} Hurd)
19552 @cindex pause current task (@sc{gnu} Hurd)
19553 This command toggles task suspension when @value{GDBN} has control.
19554 Setting it to on takes effect immediately, and the task is suspended
19555 whenever @value{GDBN} gets control. Setting it to off will take
19556 effect the next time the inferior is continued. If this option is set
19557 to off, you can use @code{set thread default pause on} or @code{set
19558 thread pause on} (see below) to pause individual threads.
19560 @item show task pause
19561 @kindex show task@r{, Hurd commands}
19562 Show the current state of task suspension.
19564 @item set task detach-suspend-count
19565 @cindex task suspend count
19566 @cindex detach from task, @sc{gnu} Hurd
19567 This command sets the suspend count the task will be left with when
19568 @value{GDBN} detaches from it.
19570 @item show task detach-suspend-count
19571 Show the suspend count the task will be left with when detaching.
19573 @item set task exception-port
19574 @itemx set task excp
19575 @cindex task exception port, @sc{gnu} Hurd
19576 This command sets the task exception port to which @value{GDBN} will
19577 forward exceptions. The argument should be the value of the @dfn{send
19578 rights} of the task. @code{set task excp} is a shorthand alias.
19580 @item set noninvasive
19581 @cindex noninvasive task options
19582 This command switches @value{GDBN} to a mode that is the least
19583 invasive as far as interfering with the inferior is concerned. This
19584 is the same as using @code{set task pause}, @code{set exceptions}, and
19585 @code{set signals} to values opposite to the defaults.
19587 @item info send-rights
19588 @itemx info receive-rights
19589 @itemx info port-rights
19590 @itemx info port-sets
19591 @itemx info dead-names
19594 @cindex send rights, @sc{gnu} Hurd
19595 @cindex receive rights, @sc{gnu} Hurd
19596 @cindex port rights, @sc{gnu} Hurd
19597 @cindex port sets, @sc{gnu} Hurd
19598 @cindex dead names, @sc{gnu} Hurd
19599 These commands display information about, respectively, send rights,
19600 receive rights, port rights, port sets, and dead names of a task.
19601 There are also shorthand aliases: @code{info ports} for @code{info
19602 port-rights} and @code{info psets} for @code{info port-sets}.
19604 @item set thread pause
19605 @kindex set thread@r{, Hurd command}
19606 @cindex thread properties, @sc{gnu} Hurd
19607 @cindex pause current thread (@sc{gnu} Hurd)
19608 This command toggles current thread suspension when @value{GDBN} has
19609 control. Setting it to on takes effect immediately, and the current
19610 thread is suspended whenever @value{GDBN} gets control. Setting it to
19611 off will take effect the next time the inferior is continued.
19612 Normally, this command has no effect, since when @value{GDBN} has
19613 control, the whole task is suspended. However, if you used @code{set
19614 task pause off} (see above), this command comes in handy to suspend
19615 only the current thread.
19617 @item show thread pause
19618 @kindex show thread@r{, Hurd command}
19619 This command shows the state of current thread suspension.
19621 @item set thread run
19622 This command sets whether the current thread is allowed to run.
19624 @item show thread run
19625 Show whether the current thread is allowed to run.
19627 @item set thread detach-suspend-count
19628 @cindex thread suspend count, @sc{gnu} Hurd
19629 @cindex detach from thread, @sc{gnu} Hurd
19630 This command sets the suspend count @value{GDBN} will leave on a
19631 thread when detaching. This number is relative to the suspend count
19632 found by @value{GDBN} when it notices the thread; use @code{set thread
19633 takeover-suspend-count} to force it to an absolute value.
19635 @item show thread detach-suspend-count
19636 Show the suspend count @value{GDBN} will leave on the thread when
19639 @item set thread exception-port
19640 @itemx set thread excp
19641 Set the thread exception port to which to forward exceptions. This
19642 overrides the port set by @code{set task exception-port} (see above).
19643 @code{set thread excp} is the shorthand alias.
19645 @item set thread takeover-suspend-count
19646 Normally, @value{GDBN}'s thread suspend counts are relative to the
19647 value @value{GDBN} finds when it notices each thread. This command
19648 changes the suspend counts to be absolute instead.
19650 @item set thread default
19651 @itemx show thread default
19652 @cindex thread default settings, @sc{gnu} Hurd
19653 Each of the above @code{set thread} commands has a @code{set thread
19654 default} counterpart (e.g., @code{set thread default pause}, @code{set
19655 thread default exception-port}, etc.). The @code{thread default}
19656 variety of commands sets the default thread properties for all
19657 threads; you can then change the properties of individual threads with
19658 the non-default commands.
19665 @value{GDBN} provides the following commands specific to the Darwin target:
19668 @item set debug darwin @var{num}
19669 @kindex set debug darwin
19670 When set to a non zero value, enables debugging messages specific to
19671 the Darwin support. Higher values produce more verbose output.
19673 @item show debug darwin
19674 @kindex show debug darwin
19675 Show the current state of Darwin messages.
19677 @item set debug mach-o @var{num}
19678 @kindex set debug mach-o
19679 When set to a non zero value, enables debugging messages while
19680 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19681 file format used on Darwin for object and executable files.) Higher
19682 values produce more verbose output. This is a command to diagnose
19683 problems internal to @value{GDBN} and should not be needed in normal
19686 @item show debug mach-o
19687 @kindex show debug mach-o
19688 Show the current state of Mach-O file messages.
19690 @item set mach-exceptions on
19691 @itemx set mach-exceptions off
19692 @kindex set mach-exceptions
19693 On Darwin, faults are first reported as a Mach exception and are then
19694 mapped to a Posix signal. Use this command to turn on trapping of
19695 Mach exceptions in the inferior. This might be sometimes useful to
19696 better understand the cause of a fault. The default is off.
19698 @item show mach-exceptions
19699 @kindex show mach-exceptions
19700 Show the current state of exceptions trapping.
19705 @section Embedded Operating Systems
19707 This section describes configurations involving the debugging of
19708 embedded operating systems that are available for several different
19712 * VxWorks:: Using @value{GDBN} with VxWorks
19715 @value{GDBN} includes the ability to debug programs running on
19716 various real-time operating systems.
19719 @subsection Using @value{GDBN} with VxWorks
19725 @kindex target vxworks
19726 @item target vxworks @var{machinename}
19727 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19728 is the target system's machine name or IP address.
19732 On VxWorks, @code{load} links @var{filename} dynamically on the
19733 current target system as well as adding its symbols in @value{GDBN}.
19735 @value{GDBN} enables developers to spawn and debug tasks running on networked
19736 VxWorks targets from a Unix host. Already-running tasks spawned from
19737 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19738 both the Unix host and on the VxWorks target. The program
19739 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19740 installed with the name @code{vxgdb}, to distinguish it from a
19741 @value{GDBN} for debugging programs on the host itself.)
19744 @item VxWorks-timeout @var{args}
19745 @kindex vxworks-timeout
19746 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19747 This option is set by the user, and @var{args} represents the number of
19748 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19749 your VxWorks target is a slow software simulator or is on the far side
19750 of a thin network line.
19753 The following information on connecting to VxWorks was current when
19754 this manual was produced; newer releases of VxWorks may use revised
19757 @findex INCLUDE_RDB
19758 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19759 to include the remote debugging interface routines in the VxWorks
19760 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19761 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19762 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19763 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19764 information on configuring and remaking VxWorks, see the manufacturer's
19766 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19768 Once you have included @file{rdb.a} in your VxWorks system image and set
19769 your Unix execution search path to find @value{GDBN}, you are ready to
19770 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19771 @code{vxgdb}, depending on your installation).
19773 @value{GDBN} comes up showing the prompt:
19780 * VxWorks Connection:: Connecting to VxWorks
19781 * VxWorks Download:: VxWorks download
19782 * VxWorks Attach:: Running tasks
19785 @node VxWorks Connection
19786 @subsubsection Connecting to VxWorks
19788 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19789 network. To connect to a target whose host name is ``@code{tt}'', type:
19792 (vxgdb) target vxworks tt
19796 @value{GDBN} displays messages like these:
19799 Attaching remote machine across net...
19804 @value{GDBN} then attempts to read the symbol tables of any object modules
19805 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19806 these files by searching the directories listed in the command search
19807 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19808 to find an object file, it displays a message such as:
19811 prog.o: No such file or directory.
19814 When this happens, add the appropriate directory to the search path with
19815 the @value{GDBN} command @code{path}, and execute the @code{target}
19818 @node VxWorks Download
19819 @subsubsection VxWorks Download
19821 @cindex download to VxWorks
19822 If you have connected to the VxWorks target and you want to debug an
19823 object that has not yet been loaded, you can use the @value{GDBN}
19824 @code{load} command to download a file from Unix to VxWorks
19825 incrementally. The object file given as an argument to the @code{load}
19826 command is actually opened twice: first by the VxWorks target in order
19827 to download the code, then by @value{GDBN} in order to read the symbol
19828 table. This can lead to problems if the current working directories on
19829 the two systems differ. If both systems have NFS mounted the same
19830 filesystems, you can avoid these problems by using absolute paths.
19831 Otherwise, it is simplest to set the working directory on both systems
19832 to the directory in which the object file resides, and then to reference
19833 the file by its name, without any path. For instance, a program
19834 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19835 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19836 program, type this on VxWorks:
19839 -> cd "@var{vxpath}/vw/demo/rdb"
19843 Then, in @value{GDBN}, type:
19846 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19847 (vxgdb) load prog.o
19850 @value{GDBN} displays a response similar to this:
19853 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19856 You can also use the @code{load} command to reload an object module
19857 after editing and recompiling the corresponding source file. Note that
19858 this makes @value{GDBN} delete all currently-defined breakpoints,
19859 auto-displays, and convenience variables, and to clear the value
19860 history. (This is necessary in order to preserve the integrity of
19861 debugger's data structures that reference the target system's symbol
19864 @node VxWorks Attach
19865 @subsubsection Running Tasks
19867 @cindex running VxWorks tasks
19868 You can also attach to an existing task using the @code{attach} command as
19872 (vxgdb) attach @var{task}
19876 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19877 or suspended when you attach to it. Running tasks are suspended at
19878 the time of attachment.
19880 @node Embedded Processors
19881 @section Embedded Processors
19883 This section goes into details specific to particular embedded
19886 @cindex send command to simulator
19887 Whenever a specific embedded processor has a simulator, @value{GDBN}
19888 allows to send an arbitrary command to the simulator.
19891 @item sim @var{command}
19892 @kindex sim@r{, a command}
19893 Send an arbitrary @var{command} string to the simulator. Consult the
19894 documentation for the specific simulator in use for information about
19895 acceptable commands.
19901 * M32R/D:: Renesas M32R/D
19902 * M68K:: Motorola M68K
19903 * MicroBlaze:: Xilinx MicroBlaze
19904 * MIPS Embedded:: MIPS Embedded
19905 * PowerPC Embedded:: PowerPC Embedded
19906 * PA:: HP PA Embedded
19907 * Sparclet:: Tsqware Sparclet
19908 * Sparclite:: Fujitsu Sparclite
19909 * Z8000:: Zilog Z8000
19912 * Super-H:: Renesas Super-H
19921 @item target rdi @var{dev}
19922 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19923 use this target to communicate with both boards running the Angel
19924 monitor, or with the EmbeddedICE JTAG debug device.
19927 @item target rdp @var{dev}
19932 @value{GDBN} provides the following ARM-specific commands:
19935 @item set arm disassembler
19937 This commands selects from a list of disassembly styles. The
19938 @code{"std"} style is the standard style.
19940 @item show arm disassembler
19942 Show the current disassembly style.
19944 @item set arm apcs32
19945 @cindex ARM 32-bit mode
19946 This command toggles ARM operation mode between 32-bit and 26-bit.
19948 @item show arm apcs32
19949 Display the current usage of the ARM 32-bit mode.
19951 @item set arm fpu @var{fputype}
19952 This command sets the ARM floating-point unit (FPU) type. The
19953 argument @var{fputype} can be one of these:
19957 Determine the FPU type by querying the OS ABI.
19959 Software FPU, with mixed-endian doubles on little-endian ARM
19962 GCC-compiled FPA co-processor.
19964 Software FPU with pure-endian doubles.
19970 Show the current type of the FPU.
19973 This command forces @value{GDBN} to use the specified ABI.
19976 Show the currently used ABI.
19978 @item set arm fallback-mode (arm|thumb|auto)
19979 @value{GDBN} uses the symbol table, when available, to determine
19980 whether instructions are ARM or Thumb. This command controls
19981 @value{GDBN}'s default behavior when the symbol table is not
19982 available. The default is @samp{auto}, which causes @value{GDBN} to
19983 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19986 @item show arm fallback-mode
19987 Show the current fallback instruction mode.
19989 @item set arm force-mode (arm|thumb|auto)
19990 This command overrides use of the symbol table to determine whether
19991 instructions are ARM or Thumb. The default is @samp{auto}, which
19992 causes @value{GDBN} to use the symbol table and then the setting
19993 of @samp{set arm fallback-mode}.
19995 @item show arm force-mode
19996 Show the current forced instruction mode.
19998 @item set debug arm
19999 Toggle whether to display ARM-specific debugging messages from the ARM
20000 target support subsystem.
20002 @item show debug arm
20003 Show whether ARM-specific debugging messages are enabled.
20006 The following commands are available when an ARM target is debugged
20007 using the RDI interface:
20010 @item rdilogfile @r{[}@var{file}@r{]}
20012 @cindex ADP (Angel Debugger Protocol) logging
20013 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20014 With an argument, sets the log file to the specified @var{file}. With
20015 no argument, show the current log file name. The default log file is
20018 @item rdilogenable @r{[}@var{arg}@r{]}
20019 @kindex rdilogenable
20020 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20021 enables logging, with an argument 0 or @code{"no"} disables it. With
20022 no arguments displays the current setting. When logging is enabled,
20023 ADP packets exchanged between @value{GDBN} and the RDI target device
20024 are logged to a file.
20026 @item set rdiromatzero
20027 @kindex set rdiromatzero
20028 @cindex ROM at zero address, RDI
20029 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20030 vector catching is disabled, so that zero address can be used. If off
20031 (the default), vector catching is enabled. For this command to take
20032 effect, it needs to be invoked prior to the @code{target rdi} command.
20034 @item show rdiromatzero
20035 @kindex show rdiromatzero
20036 Show the current setting of ROM at zero address.
20038 @item set rdiheartbeat
20039 @kindex set rdiheartbeat
20040 @cindex RDI heartbeat
20041 Enable or disable RDI heartbeat packets. It is not recommended to
20042 turn on this option, since it confuses ARM and EPI JTAG interface, as
20043 well as the Angel monitor.
20045 @item show rdiheartbeat
20046 @kindex show rdiheartbeat
20047 Show the setting of RDI heartbeat packets.
20051 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20052 The @value{GDBN} ARM simulator accepts the following optional arguments.
20055 @item --swi-support=@var{type}
20056 Tell the simulator which SWI interfaces to support.
20057 @var{type} may be a comma separated list of the following values.
20058 The default value is @code{all}.
20071 @subsection Renesas M32R/D and M32R/SDI
20074 @kindex target m32r
20075 @item target m32r @var{dev}
20076 Renesas M32R/D ROM monitor.
20078 @kindex target m32rsdi
20079 @item target m32rsdi @var{dev}
20080 Renesas M32R SDI server, connected via parallel port to the board.
20083 The following @value{GDBN} commands are specific to the M32R monitor:
20086 @item set download-path @var{path}
20087 @kindex set download-path
20088 @cindex find downloadable @sc{srec} files (M32R)
20089 Set the default path for finding downloadable @sc{srec} files.
20091 @item show download-path
20092 @kindex show download-path
20093 Show the default path for downloadable @sc{srec} files.
20095 @item set board-address @var{addr}
20096 @kindex set board-address
20097 @cindex M32-EVA target board address
20098 Set the IP address for the M32R-EVA target board.
20100 @item show board-address
20101 @kindex show board-address
20102 Show the current IP address of the target board.
20104 @item set server-address @var{addr}
20105 @kindex set server-address
20106 @cindex download server address (M32R)
20107 Set the IP address for the download server, which is the @value{GDBN}'s
20110 @item show server-address
20111 @kindex show server-address
20112 Display the IP address of the download server.
20114 @item upload @r{[}@var{file}@r{]}
20115 @kindex upload@r{, M32R}
20116 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20117 upload capability. If no @var{file} argument is given, the current
20118 executable file is uploaded.
20120 @item tload @r{[}@var{file}@r{]}
20121 @kindex tload@r{, M32R}
20122 Test the @code{upload} command.
20125 The following commands are available for M32R/SDI:
20130 @cindex reset SDI connection, M32R
20131 This command resets the SDI connection.
20135 This command shows the SDI connection status.
20138 @kindex debug_chaos
20139 @cindex M32R/Chaos debugging
20140 Instructs the remote that M32R/Chaos debugging is to be used.
20142 @item use_debug_dma
20143 @kindex use_debug_dma
20144 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20147 @kindex use_mon_code
20148 Instructs the remote to use the MON_CODE method of accessing memory.
20151 @kindex use_ib_break
20152 Instructs the remote to set breakpoints by IB break.
20154 @item use_dbt_break
20155 @kindex use_dbt_break
20156 Instructs the remote to set breakpoints by DBT.
20162 The Motorola m68k configuration includes ColdFire support, and a
20163 target command for the following ROM monitor.
20167 @kindex target dbug
20168 @item target dbug @var{dev}
20169 dBUG ROM monitor for Motorola ColdFire.
20174 @subsection MicroBlaze
20175 @cindex Xilinx MicroBlaze
20176 @cindex XMD, Xilinx Microprocessor Debugger
20178 The MicroBlaze is a soft-core processor supported on various Xilinx
20179 FPGAs, such as Spartan or Virtex series. Boards with these processors
20180 usually have JTAG ports which connect to a host system running the Xilinx
20181 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20182 This host system is used to download the configuration bitstream to
20183 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20184 communicates with the target board using the JTAG interface and
20185 presents a @code{gdbserver} interface to the board. By default
20186 @code{xmd} uses port @code{1234}. (While it is possible to change
20187 this default port, it requires the use of undocumented @code{xmd}
20188 commands. Contact Xilinx support if you need to do this.)
20190 Use these GDB commands to connect to the MicroBlaze target processor.
20193 @item target remote :1234
20194 Use this command to connect to the target if you are running @value{GDBN}
20195 on the same system as @code{xmd}.
20197 @item target remote @var{xmd-host}:1234
20198 Use this command to connect to the target if it is connected to @code{xmd}
20199 running on a different system named @var{xmd-host}.
20202 Use this command to download a program to the MicroBlaze target.
20204 @item set debug microblaze @var{n}
20205 Enable MicroBlaze-specific debugging messages if non-zero.
20207 @item show debug microblaze @var{n}
20208 Show MicroBlaze-specific debugging level.
20211 @node MIPS Embedded
20212 @subsection @acronym{MIPS} Embedded
20214 @cindex @acronym{MIPS} boards
20215 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20216 @acronym{MIPS} board attached to a serial line. This is available when
20217 you configure @value{GDBN} with @samp{--target=mips-elf}.
20220 Use these @value{GDBN} commands to specify the connection to your target board:
20223 @item target mips @var{port}
20224 @kindex target mips @var{port}
20225 To run a program on the board, start up @code{@value{GDBP}} with the
20226 name of your program as the argument. To connect to the board, use the
20227 command @samp{target mips @var{port}}, where @var{port} is the name of
20228 the serial port connected to the board. If the program has not already
20229 been downloaded to the board, you may use the @code{load} command to
20230 download it. You can then use all the usual @value{GDBN} commands.
20232 For example, this sequence connects to the target board through a serial
20233 port, and loads and runs a program called @var{prog} through the
20237 host$ @value{GDBP} @var{prog}
20238 @value{GDBN} is free software and @dots{}
20239 (@value{GDBP}) target mips /dev/ttyb
20240 (@value{GDBP}) load @var{prog}
20244 @item target mips @var{hostname}:@var{portnumber}
20245 On some @value{GDBN} host configurations, you can specify a TCP
20246 connection (for instance, to a serial line managed by a terminal
20247 concentrator) instead of a serial port, using the syntax
20248 @samp{@var{hostname}:@var{portnumber}}.
20250 @item target pmon @var{port}
20251 @kindex target pmon @var{port}
20254 @item target ddb @var{port}
20255 @kindex target ddb @var{port}
20256 NEC's DDB variant of PMON for Vr4300.
20258 @item target lsi @var{port}
20259 @kindex target lsi @var{port}
20260 LSI variant of PMON.
20262 @kindex target r3900
20263 @item target r3900 @var{dev}
20264 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20266 @kindex target array
20267 @item target array @var{dev}
20268 Array Tech LSI33K RAID controller board.
20274 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20277 @item set mipsfpu double
20278 @itemx set mipsfpu single
20279 @itemx set mipsfpu none
20280 @itemx set mipsfpu auto
20281 @itemx show mipsfpu
20282 @kindex set mipsfpu
20283 @kindex show mipsfpu
20284 @cindex @acronym{MIPS} remote floating point
20285 @cindex floating point, @acronym{MIPS} remote
20286 If your target board does not support the @acronym{MIPS} floating point
20287 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20288 need this, you may wish to put the command in your @value{GDBN} init
20289 file). This tells @value{GDBN} how to find the return value of
20290 functions which return floating point values. It also allows
20291 @value{GDBN} to avoid saving the floating point registers when calling
20292 functions on the board. If you are using a floating point coprocessor
20293 with only single precision floating point support, as on the @sc{r4650}
20294 processor, use the command @samp{set mipsfpu single}. The default
20295 double precision floating point coprocessor may be selected using
20296 @samp{set mipsfpu double}.
20298 In previous versions the only choices were double precision or no
20299 floating point, so @samp{set mipsfpu on} will select double precision
20300 and @samp{set mipsfpu off} will select no floating point.
20302 As usual, you can inquire about the @code{mipsfpu} variable with
20303 @samp{show mipsfpu}.
20305 @item set timeout @var{seconds}
20306 @itemx set retransmit-timeout @var{seconds}
20307 @itemx show timeout
20308 @itemx show retransmit-timeout
20309 @cindex @code{timeout}, @acronym{MIPS} protocol
20310 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20311 @kindex set timeout
20312 @kindex show timeout
20313 @kindex set retransmit-timeout
20314 @kindex show retransmit-timeout
20315 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20316 remote protocol, with the @code{set timeout @var{seconds}} command. The
20317 default is 5 seconds. Similarly, you can control the timeout used while
20318 waiting for an acknowledgment of a packet with the @code{set
20319 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20320 You can inspect both values with @code{show timeout} and @code{show
20321 retransmit-timeout}. (These commands are @emph{only} available when
20322 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20324 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20325 is waiting for your program to stop. In that case, @value{GDBN} waits
20326 forever because it has no way of knowing how long the program is going
20327 to run before stopping.
20329 @item set syn-garbage-limit @var{num}
20330 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20331 @cindex synchronize with remote @acronym{MIPS} target
20332 Limit the maximum number of characters @value{GDBN} should ignore when
20333 it tries to synchronize with the remote target. The default is 10
20334 characters. Setting the limit to -1 means there's no limit.
20336 @item show syn-garbage-limit
20337 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20338 Show the current limit on the number of characters to ignore when
20339 trying to synchronize with the remote system.
20341 @item set monitor-prompt @var{prompt}
20342 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20343 @cindex remote monitor prompt
20344 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20345 remote monitor. The default depends on the target:
20355 @item show monitor-prompt
20356 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20357 Show the current strings @value{GDBN} expects as the prompt from the
20360 @item set monitor-warnings
20361 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20362 Enable or disable monitor warnings about hardware breakpoints. This
20363 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20364 display warning messages whose codes are returned by the @code{lsi}
20365 PMON monitor for breakpoint commands.
20367 @item show monitor-warnings
20368 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20369 Show the current setting of printing monitor warnings.
20371 @item pmon @var{command}
20372 @kindex pmon@r{, @acronym{MIPS} remote}
20373 @cindex send PMON command
20374 This command allows sending an arbitrary @var{command} string to the
20375 monitor. The monitor must be in debug mode for this to work.
20378 @node PowerPC Embedded
20379 @subsection PowerPC Embedded
20381 @cindex DVC register
20382 @value{GDBN} supports using the DVC (Data Value Compare) register to
20383 implement in hardware simple hardware watchpoint conditions of the form:
20386 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20387 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20390 The DVC register will be automatically used when @value{GDBN} detects
20391 such pattern in a condition expression, and the created watchpoint uses one
20392 debug register (either the @code{exact-watchpoints} option is on and the
20393 variable is scalar, or the variable has a length of one byte). This feature
20394 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20397 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20398 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20399 in which case watchpoints using only one debug register are created when
20400 watching variables of scalar types.
20402 You can create an artificial array to watch an arbitrary memory
20403 region using one of the following commands (@pxref{Expressions}):
20406 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20407 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20410 PowerPC embedded processors support masked watchpoints. See the discussion
20411 about the @code{mask} argument in @ref{Set Watchpoints}.
20413 @cindex ranged breakpoint
20414 PowerPC embedded processors support hardware accelerated
20415 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20416 the inferior whenever it executes an instruction at any address within
20417 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20418 use the @code{break-range} command.
20420 @value{GDBN} provides the following PowerPC-specific commands:
20423 @kindex break-range
20424 @item break-range @var{start-location}, @var{end-location}
20425 Set a breakpoint for an address range.
20426 @var{start-location} and @var{end-location} can specify a function name,
20427 a line number, an offset of lines from the current line or from the start
20428 location, or an address of an instruction (see @ref{Specify Location},
20429 for a list of all the possible ways to specify a @var{location}.)
20430 The breakpoint will stop execution of the inferior whenever it
20431 executes an instruction at any address within the specified range,
20432 (including @var{start-location} and @var{end-location}.)
20434 @kindex set powerpc
20435 @item set powerpc soft-float
20436 @itemx show powerpc soft-float
20437 Force @value{GDBN} to use (or not use) a software floating point calling
20438 convention. By default, @value{GDBN} selects the calling convention based
20439 on the selected architecture and the provided executable file.
20441 @item set powerpc vector-abi
20442 @itemx show powerpc vector-abi
20443 Force @value{GDBN} to use the specified calling convention for vector
20444 arguments and return values. The valid options are @samp{auto};
20445 @samp{generic}, to avoid vector registers even if they are present;
20446 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20447 registers. By default, @value{GDBN} selects the calling convention
20448 based on the selected architecture and the provided executable file.
20450 @item set powerpc exact-watchpoints
20451 @itemx show powerpc exact-watchpoints
20452 Allow @value{GDBN} to use only one debug register when watching a variable
20453 of scalar type, thus assuming that the variable is accessed through the
20454 address of its first byte.
20456 @kindex target dink32
20457 @item target dink32 @var{dev}
20458 DINK32 ROM monitor.
20460 @kindex target ppcbug
20461 @item target ppcbug @var{dev}
20462 @kindex target ppcbug1
20463 @item target ppcbug1 @var{dev}
20464 PPCBUG ROM monitor for PowerPC.
20467 @item target sds @var{dev}
20468 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20471 @cindex SDS protocol
20472 The following commands specific to the SDS protocol are supported
20476 @item set sdstimeout @var{nsec}
20477 @kindex set sdstimeout
20478 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20479 default is 2 seconds.
20481 @item show sdstimeout
20482 @kindex show sdstimeout
20483 Show the current value of the SDS timeout.
20485 @item sds @var{command}
20486 @kindex sds@r{, a command}
20487 Send the specified @var{command} string to the SDS monitor.
20492 @subsection HP PA Embedded
20496 @kindex target op50n
20497 @item target op50n @var{dev}
20498 OP50N monitor, running on an OKI HPPA board.
20500 @kindex target w89k
20501 @item target w89k @var{dev}
20502 W89K monitor, running on a Winbond HPPA board.
20507 @subsection Tsqware Sparclet
20511 @value{GDBN} enables developers to debug tasks running on
20512 Sparclet targets from a Unix host.
20513 @value{GDBN} uses code that runs on
20514 both the Unix host and on the Sparclet target. The program
20515 @code{@value{GDBP}} is installed and executed on the Unix host.
20518 @item remotetimeout @var{args}
20519 @kindex remotetimeout
20520 @value{GDBN} supports the option @code{remotetimeout}.
20521 This option is set by the user, and @var{args} represents the number of
20522 seconds @value{GDBN} waits for responses.
20525 @cindex compiling, on Sparclet
20526 When compiling for debugging, include the options @samp{-g} to get debug
20527 information and @samp{-Ttext} to relocate the program to where you wish to
20528 load it on the target. You may also want to add the options @samp{-n} or
20529 @samp{-N} in order to reduce the size of the sections. Example:
20532 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20535 You can use @code{objdump} to verify that the addresses are what you intended:
20538 sparclet-aout-objdump --headers --syms prog
20541 @cindex running, on Sparclet
20543 your Unix execution search path to find @value{GDBN}, you are ready to
20544 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20545 (or @code{sparclet-aout-gdb}, depending on your installation).
20547 @value{GDBN} comes up showing the prompt:
20554 * Sparclet File:: Setting the file to debug
20555 * Sparclet Connection:: Connecting to Sparclet
20556 * Sparclet Download:: Sparclet download
20557 * Sparclet Execution:: Running and debugging
20560 @node Sparclet File
20561 @subsubsection Setting File to Debug
20563 The @value{GDBN} command @code{file} lets you choose with program to debug.
20566 (gdbslet) file prog
20570 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20571 @value{GDBN} locates
20572 the file by searching the directories listed in the command search
20574 If the file was compiled with debug information (option @samp{-g}), source
20575 files will be searched as well.
20576 @value{GDBN} locates
20577 the source files by searching the directories listed in the directory search
20578 path (@pxref{Environment, ,Your Program's Environment}).
20580 to find a file, it displays a message such as:
20583 prog: No such file or directory.
20586 When this happens, add the appropriate directories to the search paths with
20587 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20588 @code{target} command again.
20590 @node Sparclet Connection
20591 @subsubsection Connecting to Sparclet
20593 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20594 To connect to a target on serial port ``@code{ttya}'', type:
20597 (gdbslet) target sparclet /dev/ttya
20598 Remote target sparclet connected to /dev/ttya
20599 main () at ../prog.c:3
20603 @value{GDBN} displays messages like these:
20609 @node Sparclet Download
20610 @subsubsection Sparclet Download
20612 @cindex download to Sparclet
20613 Once connected to the Sparclet target,
20614 you can use the @value{GDBN}
20615 @code{load} command to download the file from the host to the target.
20616 The file name and load offset should be given as arguments to the @code{load}
20618 Since the file format is aout, the program must be loaded to the starting
20619 address. You can use @code{objdump} to find out what this value is. The load
20620 offset is an offset which is added to the VMA (virtual memory address)
20621 of each of the file's sections.
20622 For instance, if the program
20623 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20624 and bss at 0x12010170, in @value{GDBN}, type:
20627 (gdbslet) load prog 0x12010000
20628 Loading section .text, size 0xdb0 vma 0x12010000
20631 If the code is loaded at a different address then what the program was linked
20632 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20633 to tell @value{GDBN} where to map the symbol table.
20635 @node Sparclet Execution
20636 @subsubsection Running and Debugging
20638 @cindex running and debugging Sparclet programs
20639 You can now begin debugging the task using @value{GDBN}'s execution control
20640 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20641 manual for the list of commands.
20645 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20647 Starting program: prog
20648 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20649 3 char *symarg = 0;
20651 4 char *execarg = "hello!";
20656 @subsection Fujitsu Sparclite
20660 @kindex target sparclite
20661 @item target sparclite @var{dev}
20662 Fujitsu sparclite boards, used only for the purpose of loading.
20663 You must use an additional command to debug the program.
20664 For example: target remote @var{dev} using @value{GDBN} standard
20670 @subsection Zilog Z8000
20673 @cindex simulator, Z8000
20674 @cindex Zilog Z8000 simulator
20676 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20679 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20680 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20681 segmented variant). The simulator recognizes which architecture is
20682 appropriate by inspecting the object code.
20685 @item target sim @var{args}
20687 @kindex target sim@r{, with Z8000}
20688 Debug programs on a simulated CPU. If the simulator supports setup
20689 options, specify them via @var{args}.
20693 After specifying this target, you can debug programs for the simulated
20694 CPU in the same style as programs for your host computer; use the
20695 @code{file} command to load a new program image, the @code{run} command
20696 to run your program, and so on.
20698 As well as making available all the usual machine registers
20699 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20700 additional items of information as specially named registers:
20705 Counts clock-ticks in the simulator.
20708 Counts instructions run in the simulator.
20711 Execution time in 60ths of a second.
20715 You can refer to these values in @value{GDBN} expressions with the usual
20716 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20717 conditional breakpoint that suspends only after at least 5000
20718 simulated clock ticks.
20721 @subsection Atmel AVR
20724 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20725 following AVR-specific commands:
20728 @item info io_registers
20729 @kindex info io_registers@r{, AVR}
20730 @cindex I/O registers (Atmel AVR)
20731 This command displays information about the AVR I/O registers. For
20732 each register, @value{GDBN} prints its number and value.
20739 When configured for debugging CRIS, @value{GDBN} provides the
20740 following CRIS-specific commands:
20743 @item set cris-version @var{ver}
20744 @cindex CRIS version
20745 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20746 The CRIS version affects register names and sizes. This command is useful in
20747 case autodetection of the CRIS version fails.
20749 @item show cris-version
20750 Show the current CRIS version.
20752 @item set cris-dwarf2-cfi
20753 @cindex DWARF-2 CFI and CRIS
20754 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20755 Change to @samp{off} when using @code{gcc-cris} whose version is below
20758 @item show cris-dwarf2-cfi
20759 Show the current state of using DWARF-2 CFI.
20761 @item set cris-mode @var{mode}
20763 Set the current CRIS mode to @var{mode}. It should only be changed when
20764 debugging in guru mode, in which case it should be set to
20765 @samp{guru} (the default is @samp{normal}).
20767 @item show cris-mode
20768 Show the current CRIS mode.
20772 @subsection Renesas Super-H
20775 For the Renesas Super-H processor, @value{GDBN} provides these
20779 @item set sh calling-convention @var{convention}
20780 @kindex set sh calling-convention
20781 Set the calling-convention used when calling functions from @value{GDBN}.
20782 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20783 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20784 convention. If the DWARF-2 information of the called function specifies
20785 that the function follows the Renesas calling convention, the function
20786 is called using the Renesas calling convention. If the calling convention
20787 is set to @samp{renesas}, the Renesas calling convention is always used,
20788 regardless of the DWARF-2 information. This can be used to override the
20789 default of @samp{gcc} if debug information is missing, or the compiler
20790 does not emit the DWARF-2 calling convention entry for a function.
20792 @item show sh calling-convention
20793 @kindex show sh calling-convention
20794 Show the current calling convention setting.
20799 @node Architectures
20800 @section Architectures
20802 This section describes characteristics of architectures that affect
20803 all uses of @value{GDBN} with the architecture, both native and cross.
20810 * HPPA:: HP PA architecture
20811 * SPU:: Cell Broadband Engine SPU architecture
20816 @subsection AArch64
20817 @cindex AArch64 support
20819 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20820 following special commands:
20823 @item set debug aarch64
20824 @kindex set debug aarch64
20825 This command determines whether AArch64 architecture-specific debugging
20826 messages are to be displayed.
20828 @item show debug aarch64
20829 Show whether AArch64 debugging messages are displayed.
20834 @subsection x86 Architecture-specific Issues
20837 @item set struct-convention @var{mode}
20838 @kindex set struct-convention
20839 @cindex struct return convention
20840 @cindex struct/union returned in registers
20841 Set the convention used by the inferior to return @code{struct}s and
20842 @code{union}s from functions to @var{mode}. Possible values of
20843 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20844 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20845 are returned on the stack, while @code{"reg"} means that a
20846 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20847 be returned in a register.
20849 @item show struct-convention
20850 @kindex show struct-convention
20851 Show the current setting of the convention to return @code{struct}s
20858 See the following section.
20861 @subsection @acronym{MIPS}
20863 @cindex stack on Alpha
20864 @cindex stack on @acronym{MIPS}
20865 @cindex Alpha stack
20866 @cindex @acronym{MIPS} stack
20867 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20868 sometimes requires @value{GDBN} to search backward in the object code to
20869 find the beginning of a function.
20871 @cindex response time, @acronym{MIPS} debugging
20872 To improve response time (especially for embedded applications, where
20873 @value{GDBN} may be restricted to a slow serial line for this search)
20874 you may want to limit the size of this search, using one of these
20878 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20879 @item set heuristic-fence-post @var{limit}
20880 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20881 search for the beginning of a function. A value of @var{0} (the
20882 default) means there is no limit. However, except for @var{0}, the
20883 larger the limit the more bytes @code{heuristic-fence-post} must search
20884 and therefore the longer it takes to run. You should only need to use
20885 this command when debugging a stripped executable.
20887 @item show heuristic-fence-post
20888 Display the current limit.
20892 These commands are available @emph{only} when @value{GDBN} is configured
20893 for debugging programs on Alpha or @acronym{MIPS} processors.
20895 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20899 @item set mips abi @var{arg}
20900 @kindex set mips abi
20901 @cindex set ABI for @acronym{MIPS}
20902 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20903 values of @var{arg} are:
20907 The default ABI associated with the current binary (this is the
20917 @item show mips abi
20918 @kindex show mips abi
20919 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20921 @item set mips compression @var{arg}
20922 @kindex set mips compression
20923 @cindex code compression, @acronym{MIPS}
20924 Tell @value{GDBN} which @acronym{MIPS} compressed
20925 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20926 inferior. @value{GDBN} uses this for code disassembly and other
20927 internal interpretation purposes. This setting is only referred to
20928 when no executable has been associated with the debugging session or
20929 the executable does not provide information about the encoding it uses.
20930 Otherwise this setting is automatically updated from information
20931 provided by the executable.
20933 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20934 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20935 executables containing @acronym{MIPS16} code frequently are not
20936 identified as such.
20938 This setting is ``sticky''; that is, it retains its value across
20939 debugging sessions until reset either explicitly with this command or
20940 implicitly from an executable.
20942 The compiler and/or assembler typically add symbol table annotations to
20943 identify functions compiled for the @acronym{MIPS16} or
20944 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20945 are present, @value{GDBN} uses them in preference to the global
20946 compressed @acronym{ISA} encoding setting.
20948 @item show mips compression
20949 @kindex show mips compression
20950 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20951 @value{GDBN} to debug the inferior.
20954 @itemx show mipsfpu
20955 @xref{MIPS Embedded, set mipsfpu}.
20957 @item set mips mask-address @var{arg}
20958 @kindex set mips mask-address
20959 @cindex @acronym{MIPS} addresses, masking
20960 This command determines whether the most-significant 32 bits of 64-bit
20961 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20962 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20963 setting, which lets @value{GDBN} determine the correct value.
20965 @item show mips mask-address
20966 @kindex show mips mask-address
20967 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20970 @item set remote-mips64-transfers-32bit-regs
20971 @kindex set remote-mips64-transfers-32bit-regs
20972 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20973 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20974 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20975 and 64 bits for other registers, set this option to @samp{on}.
20977 @item show remote-mips64-transfers-32bit-regs
20978 @kindex show remote-mips64-transfers-32bit-regs
20979 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20981 @item set debug mips
20982 @kindex set debug mips
20983 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20984 target code in @value{GDBN}.
20986 @item show debug mips
20987 @kindex show debug mips
20988 Show the current setting of @acronym{MIPS} debugging messages.
20994 @cindex HPPA support
20996 When @value{GDBN} is debugging the HP PA architecture, it provides the
20997 following special commands:
21000 @item set debug hppa
21001 @kindex set debug hppa
21002 This command determines whether HPPA architecture-specific debugging
21003 messages are to be displayed.
21005 @item show debug hppa
21006 Show whether HPPA debugging messages are displayed.
21008 @item maint print unwind @var{address}
21009 @kindex maint print unwind@r{, HPPA}
21010 This command displays the contents of the unwind table entry at the
21011 given @var{address}.
21017 @subsection Cell Broadband Engine SPU architecture
21018 @cindex Cell Broadband Engine
21021 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21022 it provides the following special commands:
21025 @item info spu event
21027 Display SPU event facility status. Shows current event mask
21028 and pending event status.
21030 @item info spu signal
21031 Display SPU signal notification facility status. Shows pending
21032 signal-control word and signal notification mode of both signal
21033 notification channels.
21035 @item info spu mailbox
21036 Display SPU mailbox facility status. Shows all pending entries,
21037 in order of processing, in each of the SPU Write Outbound,
21038 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21041 Display MFC DMA status. Shows all pending commands in the MFC
21042 DMA queue. For each entry, opcode, tag, class IDs, effective
21043 and local store addresses and transfer size are shown.
21045 @item info spu proxydma
21046 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21047 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21048 and local store addresses and transfer size are shown.
21052 When @value{GDBN} is debugging a combined PowerPC/SPU application
21053 on the Cell Broadband Engine, it provides in addition the following
21057 @item set spu stop-on-load @var{arg}
21059 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21060 will give control to the user when a new SPE thread enters its @code{main}
21061 function. The default is @code{off}.
21063 @item show spu stop-on-load
21065 Show whether to stop for new SPE threads.
21067 @item set spu auto-flush-cache @var{arg}
21068 Set whether to automatically flush the software-managed cache. When set to
21069 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21070 cache to be flushed whenever SPE execution stops. This provides a consistent
21071 view of PowerPC memory that is accessed via the cache. If an application
21072 does not use the software-managed cache, this option has no effect.
21074 @item show spu auto-flush-cache
21075 Show whether to automatically flush the software-managed cache.
21080 @subsection PowerPC
21081 @cindex PowerPC architecture
21083 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21084 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21085 numbers stored in the floating point registers. These values must be stored
21086 in two consecutive registers, always starting at an even register like
21087 @code{f0} or @code{f2}.
21089 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21090 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21091 @code{f2} and @code{f3} for @code{$dl1} and so on.
21093 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21094 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21097 @node Controlling GDB
21098 @chapter Controlling @value{GDBN}
21100 You can alter the way @value{GDBN} interacts with you by using the
21101 @code{set} command. For commands controlling how @value{GDBN} displays
21102 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21107 * Editing:: Command editing
21108 * Command History:: Command history
21109 * Screen Size:: Screen size
21110 * Numbers:: Numbers
21111 * ABI:: Configuring the current ABI
21112 * Auto-loading:: Automatically loading associated files
21113 * Messages/Warnings:: Optional warnings and messages
21114 * Debugging Output:: Optional messages about internal happenings
21115 * Other Misc Settings:: Other Miscellaneous Settings
21123 @value{GDBN} indicates its readiness to read a command by printing a string
21124 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21125 can change the prompt string with the @code{set prompt} command. For
21126 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21127 the prompt in one of the @value{GDBN} sessions so that you can always tell
21128 which one you are talking to.
21130 @emph{Note:} @code{set prompt} does not add a space for you after the
21131 prompt you set. This allows you to set a prompt which ends in a space
21132 or a prompt that does not.
21136 @item set prompt @var{newprompt}
21137 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21139 @kindex show prompt
21141 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21144 Versions of @value{GDBN} that ship with Python scripting enabled have
21145 prompt extensions. The commands for interacting with these extensions
21149 @kindex set extended-prompt
21150 @item set extended-prompt @var{prompt}
21151 Set an extended prompt that allows for substitutions.
21152 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21153 substitution. Any escape sequences specified as part of the prompt
21154 string are replaced with the corresponding strings each time the prompt
21160 set extended-prompt Current working directory: \w (gdb)
21163 Note that when an extended-prompt is set, it takes control of the
21164 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21166 @kindex show extended-prompt
21167 @item show extended-prompt
21168 Prints the extended prompt. Any escape sequences specified as part of
21169 the prompt string with @code{set extended-prompt}, are replaced with the
21170 corresponding strings each time the prompt is displayed.
21174 @section Command Editing
21176 @cindex command line editing
21178 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21179 @sc{gnu} library provides consistent behavior for programs which provide a
21180 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21181 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21182 substitution, and a storage and recall of command history across
21183 debugging sessions.
21185 You may control the behavior of command line editing in @value{GDBN} with the
21186 command @code{set}.
21189 @kindex set editing
21192 @itemx set editing on
21193 Enable command line editing (enabled by default).
21195 @item set editing off
21196 Disable command line editing.
21198 @kindex show editing
21200 Show whether command line editing is enabled.
21203 @ifset SYSTEM_READLINE
21204 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21206 @ifclear SYSTEM_READLINE
21207 @xref{Command Line Editing},
21209 for more details about the Readline
21210 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21211 encouraged to read that chapter.
21213 @node Command History
21214 @section Command History
21215 @cindex command history
21217 @value{GDBN} can keep track of the commands you type during your
21218 debugging sessions, so that you can be certain of precisely what
21219 happened. Use these commands to manage the @value{GDBN} command
21222 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21223 package, to provide the history facility.
21224 @ifset SYSTEM_READLINE
21225 @xref{Using History Interactively, , , history, GNU History Library},
21227 @ifclear SYSTEM_READLINE
21228 @xref{Using History Interactively},
21230 for the detailed description of the History library.
21232 To issue a command to @value{GDBN} without affecting certain aspects of
21233 the state which is seen by users, prefix it with @samp{server }
21234 (@pxref{Server Prefix}). This
21235 means that this command will not affect the command history, nor will it
21236 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21237 pressed on a line by itself.
21239 @cindex @code{server}, command prefix
21240 The server prefix does not affect the recording of values into the value
21241 history; to print a value without recording it into the value history,
21242 use the @code{output} command instead of the @code{print} command.
21244 Here is the description of @value{GDBN} commands related to command
21248 @cindex history substitution
21249 @cindex history file
21250 @kindex set history filename
21251 @cindex @env{GDBHISTFILE}, environment variable
21252 @item set history filename @var{fname}
21253 Set the name of the @value{GDBN} command history file to @var{fname}.
21254 This is the file where @value{GDBN} reads an initial command history
21255 list, and where it writes the command history from this session when it
21256 exits. You can access this list through history expansion or through
21257 the history command editing characters listed below. This file defaults
21258 to the value of the environment variable @code{GDBHISTFILE}, or to
21259 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21262 @cindex save command history
21263 @kindex set history save
21264 @item set history save
21265 @itemx set history save on
21266 Record command history in a file, whose name may be specified with the
21267 @code{set history filename} command. By default, this option is disabled.
21269 @item set history save off
21270 Stop recording command history in a file.
21272 @cindex history size
21273 @kindex set history size
21274 @cindex @env{HISTSIZE}, environment variable
21275 @item set history size @var{size}
21276 @itemx set history size unlimited
21277 Set the number of commands which @value{GDBN} keeps in its history list.
21278 This defaults to the value of the environment variable
21279 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21280 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21281 history list is unlimited.
21284 History expansion assigns special meaning to the character @kbd{!}.
21285 @ifset SYSTEM_READLINE
21286 @xref{Event Designators, , , history, GNU History Library},
21288 @ifclear SYSTEM_READLINE
21289 @xref{Event Designators},
21293 @cindex history expansion, turn on/off
21294 Since @kbd{!} is also the logical not operator in C, history expansion
21295 is off by default. If you decide to enable history expansion with the
21296 @code{set history expansion on} command, you may sometimes need to
21297 follow @kbd{!} (when it is used as logical not, in an expression) with
21298 a space or a tab to prevent it from being expanded. The readline
21299 history facilities do not attempt substitution on the strings
21300 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21302 The commands to control history expansion are:
21305 @item set history expansion on
21306 @itemx set history expansion
21307 @kindex set history expansion
21308 Enable history expansion. History expansion is off by default.
21310 @item set history expansion off
21311 Disable history expansion.
21314 @kindex show history
21316 @itemx show history filename
21317 @itemx show history save
21318 @itemx show history size
21319 @itemx show history expansion
21320 These commands display the state of the @value{GDBN} history parameters.
21321 @code{show history} by itself displays all four states.
21326 @kindex show commands
21327 @cindex show last commands
21328 @cindex display command history
21329 @item show commands
21330 Display the last ten commands in the command history.
21332 @item show commands @var{n}
21333 Print ten commands centered on command number @var{n}.
21335 @item show commands +
21336 Print ten commands just after the commands last printed.
21340 @section Screen Size
21341 @cindex size of screen
21342 @cindex pauses in output
21344 Certain commands to @value{GDBN} may produce large amounts of
21345 information output to the screen. To help you read all of it,
21346 @value{GDBN} pauses and asks you for input at the end of each page of
21347 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21348 to discard the remaining output. Also, the screen width setting
21349 determines when to wrap lines of output. Depending on what is being
21350 printed, @value{GDBN} tries to break the line at a readable place,
21351 rather than simply letting it overflow onto the following line.
21353 Normally @value{GDBN} knows the size of the screen from the terminal
21354 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21355 together with the value of the @code{TERM} environment variable and the
21356 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21357 you can override it with the @code{set height} and @code{set
21364 @kindex show height
21365 @item set height @var{lpp}
21366 @itemx set height unlimited
21368 @itemx set width @var{cpl}
21369 @itemx set width unlimited
21371 These @code{set} commands specify a screen height of @var{lpp} lines and
21372 a screen width of @var{cpl} characters. The associated @code{show}
21373 commands display the current settings.
21375 If you specify a height of either @code{unlimited} or zero lines,
21376 @value{GDBN} does not pause during output no matter how long the
21377 output is. This is useful if output is to a file or to an editor
21380 Likewise, you can specify @samp{set width unlimited} or @samp{set
21381 width 0} to prevent @value{GDBN} from wrapping its output.
21383 @item set pagination on
21384 @itemx set pagination off
21385 @kindex set pagination
21386 Turn the output pagination on or off; the default is on. Turning
21387 pagination off is the alternative to @code{set height unlimited}. Note that
21388 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21389 Options, -batch}) also automatically disables pagination.
21391 @item show pagination
21392 @kindex show pagination
21393 Show the current pagination mode.
21398 @cindex number representation
21399 @cindex entering numbers
21401 You can always enter numbers in octal, decimal, or hexadecimal in
21402 @value{GDBN} by the usual conventions: octal numbers begin with
21403 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21404 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21405 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21406 10; likewise, the default display for numbers---when no particular
21407 format is specified---is base 10. You can change the default base for
21408 both input and output with the commands described below.
21411 @kindex set input-radix
21412 @item set input-radix @var{base}
21413 Set the default base for numeric input. Supported choices
21414 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21415 specified either unambiguously or using the current input radix; for
21419 set input-radix 012
21420 set input-radix 10.
21421 set input-radix 0xa
21425 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21426 leaves the input radix unchanged, no matter what it was, since
21427 @samp{10}, being without any leading or trailing signs of its base, is
21428 interpreted in the current radix. Thus, if the current radix is 16,
21429 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21432 @kindex set output-radix
21433 @item set output-radix @var{base}
21434 Set the default base for numeric display. Supported choices
21435 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21436 specified either unambiguously or using the current input radix.
21438 @kindex show input-radix
21439 @item show input-radix
21440 Display the current default base for numeric input.
21442 @kindex show output-radix
21443 @item show output-radix
21444 Display the current default base for numeric display.
21446 @item set radix @r{[}@var{base}@r{]}
21450 These commands set and show the default base for both input and output
21451 of numbers. @code{set radix} sets the radix of input and output to
21452 the same base; without an argument, it resets the radix back to its
21453 default value of 10.
21458 @section Configuring the Current ABI
21460 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21461 application automatically. However, sometimes you need to override its
21462 conclusions. Use these commands to manage @value{GDBN}'s view of the
21468 @cindex Newlib OS ABI and its influence on the longjmp handling
21470 One @value{GDBN} configuration can debug binaries for multiple operating
21471 system targets, either via remote debugging or native emulation.
21472 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21473 but you can override its conclusion using the @code{set osabi} command.
21474 One example where this is useful is in debugging of binaries which use
21475 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21476 not have the same identifying marks that the standard C library for your
21479 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21480 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21481 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21482 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21486 Show the OS ABI currently in use.
21489 With no argument, show the list of registered available OS ABI's.
21491 @item set osabi @var{abi}
21492 Set the current OS ABI to @var{abi}.
21495 @cindex float promotion
21497 Generally, the way that an argument of type @code{float} is passed to a
21498 function depends on whether the function is prototyped. For a prototyped
21499 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21500 according to the architecture's convention for @code{float}. For unprototyped
21501 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21502 @code{double} and then passed.
21504 Unfortunately, some forms of debug information do not reliably indicate whether
21505 a function is prototyped. If @value{GDBN} calls a function that is not marked
21506 as prototyped, it consults @kbd{set coerce-float-to-double}.
21509 @kindex set coerce-float-to-double
21510 @item set coerce-float-to-double
21511 @itemx set coerce-float-to-double on
21512 Arguments of type @code{float} will be promoted to @code{double} when passed
21513 to an unprototyped function. This is the default setting.
21515 @item set coerce-float-to-double off
21516 Arguments of type @code{float} will be passed directly to unprototyped
21519 @kindex show coerce-float-to-double
21520 @item show coerce-float-to-double
21521 Show the current setting of promoting @code{float} to @code{double}.
21525 @kindex show cp-abi
21526 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21527 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21528 used to build your application. @value{GDBN} only fully supports
21529 programs with a single C@t{++} ABI; if your program contains code using
21530 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21531 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21532 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21533 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21534 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21535 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21540 Show the C@t{++} ABI currently in use.
21543 With no argument, show the list of supported C@t{++} ABI's.
21545 @item set cp-abi @var{abi}
21546 @itemx set cp-abi auto
21547 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21551 @section Automatically loading associated files
21552 @cindex auto-loading
21554 @value{GDBN} sometimes reads files with commands and settings automatically,
21555 without being explicitly told so by the user. We call this feature
21556 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21557 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21558 results or introduce security risks (e.g., if the file comes from untrusted
21561 Note that loading of these associated files (including the local @file{.gdbinit}
21562 file) requires accordingly configured @code{auto-load safe-path}
21563 (@pxref{Auto-loading safe path}).
21565 For these reasons, @value{GDBN} includes commands and options to let you
21566 control when to auto-load files and which files should be auto-loaded.
21569 @anchor{set auto-load off}
21570 @kindex set auto-load off
21571 @item set auto-load off
21572 Globally disable loading of all auto-loaded files.
21573 You may want to use this command with the @samp{-iex} option
21574 (@pxref{Option -init-eval-command}) such as:
21576 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21579 Be aware that system init file (@pxref{System-wide configuration})
21580 and init files from your home directory (@pxref{Home Directory Init File})
21581 still get read (as they come from generally trusted directories).
21582 To prevent @value{GDBN} from auto-loading even those init files, use the
21583 @option{-nx} option (@pxref{Mode Options}), in addition to
21584 @code{set auto-load no}.
21586 @anchor{show auto-load}
21587 @kindex show auto-load
21588 @item show auto-load
21589 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21593 (gdb) show auto-load
21594 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21595 libthread-db: Auto-loading of inferior specific libthread_db is on.
21596 local-gdbinit: Auto-loading of .gdbinit script from current directory
21598 python-scripts: Auto-loading of Python scripts is on.
21599 safe-path: List of directories from which it is safe to auto-load files
21600 is $debugdir:$datadir/auto-load.
21601 scripts-directory: List of directories from which to load auto-loaded scripts
21602 is $debugdir:$datadir/auto-load.
21605 @anchor{info auto-load}
21606 @kindex info auto-load
21607 @item info auto-load
21608 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21612 (gdb) info auto-load
21615 Yes /home/user/gdb/gdb-gdb.gdb
21616 libthread-db: No auto-loaded libthread-db.
21617 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21621 Yes /home/user/gdb/gdb-gdb.py
21625 These are various kinds of files @value{GDBN} can automatically load:
21629 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21631 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21633 @xref{dotdebug_gdb_scripts section},
21634 controlled by @ref{set auto-load python-scripts}.
21636 @xref{Init File in the Current Directory},
21637 controlled by @ref{set auto-load local-gdbinit}.
21639 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21642 These are @value{GDBN} control commands for the auto-loading:
21644 @multitable @columnfractions .5 .5
21645 @item @xref{set auto-load off}.
21646 @tab Disable auto-loading globally.
21647 @item @xref{show auto-load}.
21648 @tab Show setting of all kinds of files.
21649 @item @xref{info auto-load}.
21650 @tab Show state of all kinds of files.
21651 @item @xref{set auto-load gdb-scripts}.
21652 @tab Control for @value{GDBN} command scripts.
21653 @item @xref{show auto-load gdb-scripts}.
21654 @tab Show setting of @value{GDBN} command scripts.
21655 @item @xref{info auto-load gdb-scripts}.
21656 @tab Show state of @value{GDBN} command scripts.
21657 @item @xref{set auto-load python-scripts}.
21658 @tab Control for @value{GDBN} Python scripts.
21659 @item @xref{show auto-load python-scripts}.
21660 @tab Show setting of @value{GDBN} Python scripts.
21661 @item @xref{info auto-load python-scripts}.
21662 @tab Show state of @value{GDBN} Python scripts.
21663 @item @xref{set auto-load scripts-directory}.
21664 @tab Control for @value{GDBN} auto-loaded scripts location.
21665 @item @xref{show auto-load scripts-directory}.
21666 @tab Show @value{GDBN} auto-loaded scripts location.
21667 @item @xref{set auto-load local-gdbinit}.
21668 @tab Control for init file in the current directory.
21669 @item @xref{show auto-load local-gdbinit}.
21670 @tab Show setting of init file in the current directory.
21671 @item @xref{info auto-load local-gdbinit}.
21672 @tab Show state of init file in the current directory.
21673 @item @xref{set auto-load libthread-db}.
21674 @tab Control for thread debugging library.
21675 @item @xref{show auto-load libthread-db}.
21676 @tab Show setting of thread debugging library.
21677 @item @xref{info auto-load libthread-db}.
21678 @tab Show state of thread debugging library.
21679 @item @xref{set auto-load safe-path}.
21680 @tab Control directories trusted for automatic loading.
21681 @item @xref{show auto-load safe-path}.
21682 @tab Show directories trusted for automatic loading.
21683 @item @xref{add-auto-load-safe-path}.
21684 @tab Add directory trusted for automatic loading.
21688 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21689 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21690 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21691 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21692 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21693 @xref{Python Auto-loading}.
21696 @node Init File in the Current Directory
21697 @subsection Automatically loading init file in the current directory
21698 @cindex auto-loading init file in the current directory
21700 By default, @value{GDBN} reads and executes the canned sequences of commands
21701 from init file (if any) in the current working directory,
21702 see @ref{Init File in the Current Directory during Startup}.
21704 Note that loading of this local @file{.gdbinit} file also requires accordingly
21705 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21708 @anchor{set auto-load local-gdbinit}
21709 @kindex set auto-load local-gdbinit
21710 @item set auto-load local-gdbinit [on|off]
21711 Enable or disable the auto-loading of canned sequences of commands
21712 (@pxref{Sequences}) found in init file in the current directory.
21714 @anchor{show auto-load local-gdbinit}
21715 @kindex show auto-load local-gdbinit
21716 @item show auto-load local-gdbinit
21717 Show whether auto-loading of canned sequences of commands from init file in the
21718 current directory is enabled or disabled.
21720 @anchor{info auto-load local-gdbinit}
21721 @kindex info auto-load local-gdbinit
21722 @item info auto-load local-gdbinit
21723 Print whether canned sequences of commands from init file in the
21724 current directory have been auto-loaded.
21727 @node libthread_db.so.1 file
21728 @subsection Automatically loading thread debugging library
21729 @cindex auto-loading libthread_db.so.1
21731 This feature is currently present only on @sc{gnu}/Linux native hosts.
21733 @value{GDBN} reads in some cases thread debugging library from places specific
21734 to the inferior (@pxref{set libthread-db-search-path}).
21736 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21737 without checking this @samp{set auto-load libthread-db} switch as system
21738 libraries have to be trusted in general. In all other cases of
21739 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21740 auto-load libthread-db} is enabled before trying to open such thread debugging
21743 Note that loading of this debugging library also requires accordingly configured
21744 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21747 @anchor{set auto-load libthread-db}
21748 @kindex set auto-load libthread-db
21749 @item set auto-load libthread-db [on|off]
21750 Enable or disable the auto-loading of inferior specific thread debugging library.
21752 @anchor{show auto-load libthread-db}
21753 @kindex show auto-load libthread-db
21754 @item show auto-load libthread-db
21755 Show whether auto-loading of inferior specific thread debugging library is
21756 enabled or disabled.
21758 @anchor{info auto-load libthread-db}
21759 @kindex info auto-load libthread-db
21760 @item info auto-load libthread-db
21761 Print the list of all loaded inferior specific thread debugging libraries and
21762 for each such library print list of inferior @var{pid}s using it.
21765 @node objfile-gdb.gdb file
21766 @subsection The @file{@var{objfile}-gdb.gdb} file
21767 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21769 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21770 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21771 auto-load gdb-scripts} is set to @samp{on}.
21773 Note that loading of this script file also requires accordingly configured
21774 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21776 For more background refer to the similar Python scripts auto-loading
21777 description (@pxref{objfile-gdb.py file}).
21780 @anchor{set auto-load gdb-scripts}
21781 @kindex set auto-load gdb-scripts
21782 @item set auto-load gdb-scripts [on|off]
21783 Enable or disable the auto-loading of canned sequences of commands scripts.
21785 @anchor{show auto-load gdb-scripts}
21786 @kindex show auto-load gdb-scripts
21787 @item show auto-load gdb-scripts
21788 Show whether auto-loading of canned sequences of commands scripts is enabled or
21791 @anchor{info auto-load gdb-scripts}
21792 @kindex info auto-load gdb-scripts
21793 @cindex print list of auto-loaded canned sequences of commands scripts
21794 @item info auto-load gdb-scripts [@var{regexp}]
21795 Print the list of all canned sequences of commands scripts that @value{GDBN}
21799 If @var{regexp} is supplied only canned sequences of commands scripts with
21800 matching names are printed.
21802 @node Auto-loading safe path
21803 @subsection Security restriction for auto-loading
21804 @cindex auto-loading safe-path
21806 As the files of inferior can come from untrusted source (such as submitted by
21807 an application user) @value{GDBN} does not always load any files automatically.
21808 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21809 directories trusted for loading files not explicitly requested by user.
21810 Each directory can also be a shell wildcard pattern.
21812 If the path is not set properly you will see a warning and the file will not
21817 Reading symbols from /home/user/gdb/gdb...done.
21818 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21819 declined by your `auto-load safe-path' set
21820 to "$debugdir:$datadir/auto-load".
21821 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21822 declined by your `auto-load safe-path' set
21823 to "$debugdir:$datadir/auto-load".
21826 The list of trusted directories is controlled by the following commands:
21829 @anchor{set auto-load safe-path}
21830 @kindex set auto-load safe-path
21831 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21832 Set the list of directories (and their subdirectories) trusted for automatic
21833 loading and execution of scripts. You can also enter a specific trusted file.
21834 Each directory can also be a shell wildcard pattern; wildcards do not match
21835 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21836 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21837 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21838 its default value as specified during @value{GDBN} compilation.
21840 The list of directories uses path separator (@samp{:} on GNU and Unix
21841 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21842 to the @env{PATH} environment variable.
21844 @anchor{show auto-load safe-path}
21845 @kindex show auto-load safe-path
21846 @item show auto-load safe-path
21847 Show the list of directories trusted for automatic loading and execution of
21850 @anchor{add-auto-load-safe-path}
21851 @kindex add-auto-load-safe-path
21852 @item add-auto-load-safe-path
21853 Add an entry (or list of entries) the list of directories trusted for automatic
21854 loading and execution of scripts. Multiple entries may be delimited by the
21855 host platform path separator in use.
21858 This variable defaults to what @code{--with-auto-load-dir} has been configured
21859 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21860 substitution applies the same as for @ref{set auto-load scripts-directory}.
21861 The default @code{set auto-load safe-path} value can be also overriden by
21862 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21864 Setting this variable to @file{/} disables this security protection,
21865 corresponding @value{GDBN} configuration option is
21866 @option{--without-auto-load-safe-path}.
21867 This variable is supposed to be set to the system directories writable by the
21868 system superuser only. Users can add their source directories in init files in
21869 their home directories (@pxref{Home Directory Init File}). See also deprecated
21870 init file in the current directory
21871 (@pxref{Init File in the Current Directory during Startup}).
21873 To force @value{GDBN} to load the files it declined to load in the previous
21874 example, you could use one of the following ways:
21877 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21878 Specify this trusted directory (or a file) as additional component of the list.
21879 You have to specify also any existing directories displayed by
21880 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21882 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21883 Specify this directory as in the previous case but just for a single
21884 @value{GDBN} session.
21886 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21887 Disable auto-loading safety for a single @value{GDBN} session.
21888 This assumes all the files you debug during this @value{GDBN} session will come
21889 from trusted sources.
21891 @item @kbd{./configure --without-auto-load-safe-path}
21892 During compilation of @value{GDBN} you may disable any auto-loading safety.
21893 This assumes all the files you will ever debug with this @value{GDBN} come from
21897 On the other hand you can also explicitly forbid automatic files loading which
21898 also suppresses any such warning messages:
21901 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21902 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21904 @item @file{~/.gdbinit}: @samp{set auto-load no}
21905 Disable auto-loading globally for the user
21906 (@pxref{Home Directory Init File}). While it is improbable, you could also
21907 use system init file instead (@pxref{System-wide configuration}).
21910 This setting applies to the file names as entered by user. If no entry matches
21911 @value{GDBN} tries as a last resort to also resolve all the file names into
21912 their canonical form (typically resolving symbolic links) and compare the
21913 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21914 own before starting the comparison so a canonical form of directories is
21915 recommended to be entered.
21917 @node Auto-loading verbose mode
21918 @subsection Displaying files tried for auto-load
21919 @cindex auto-loading verbose mode
21921 For better visibility of all the file locations where you can place scripts to
21922 be auto-loaded with inferior --- or to protect yourself against accidental
21923 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21924 all the files attempted to be loaded. Both existing and non-existing files may
21927 For example the list of directories from which it is safe to auto-load files
21928 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21929 may not be too obvious while setting it up.
21932 (gdb) set debug auto-load on
21933 (gdb) file ~/src/t/true
21934 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21935 for objfile "/tmp/true".
21936 auto-load: Updating directories of "/usr:/opt".
21937 auto-load: Using directory "/usr".
21938 auto-load: Using directory "/opt".
21939 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21940 by your `auto-load safe-path' set to "/usr:/opt".
21944 @anchor{set debug auto-load}
21945 @kindex set debug auto-load
21946 @item set debug auto-load [on|off]
21947 Set whether to print the filenames attempted to be auto-loaded.
21949 @anchor{show debug auto-load}
21950 @kindex show debug auto-load
21951 @item show debug auto-load
21952 Show whether printing of the filenames attempted to be auto-loaded is turned
21956 @node Messages/Warnings
21957 @section Optional Warnings and Messages
21959 @cindex verbose operation
21960 @cindex optional warnings
21961 By default, @value{GDBN} is silent about its inner workings. If you are
21962 running on a slow machine, you may want to use the @code{set verbose}
21963 command. This makes @value{GDBN} tell you when it does a lengthy
21964 internal operation, so you will not think it has crashed.
21966 Currently, the messages controlled by @code{set verbose} are those
21967 which announce that the symbol table for a source file is being read;
21968 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21971 @kindex set verbose
21972 @item set verbose on
21973 Enables @value{GDBN} output of certain informational messages.
21975 @item set verbose off
21976 Disables @value{GDBN} output of certain informational messages.
21978 @kindex show verbose
21980 Displays whether @code{set verbose} is on or off.
21983 By default, if @value{GDBN} encounters bugs in the symbol table of an
21984 object file, it is silent; but if you are debugging a compiler, you may
21985 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21990 @kindex set complaints
21991 @item set complaints @var{limit}
21992 Permits @value{GDBN} to output @var{limit} complaints about each type of
21993 unusual symbols before becoming silent about the problem. Set
21994 @var{limit} to zero to suppress all complaints; set it to a large number
21995 to prevent complaints from being suppressed.
21997 @kindex show complaints
21998 @item show complaints
21999 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22003 @anchor{confirmation requests}
22004 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22005 lot of stupid questions to confirm certain commands. For example, if
22006 you try to run a program which is already running:
22010 The program being debugged has been started already.
22011 Start it from the beginning? (y or n)
22014 If you are willing to unflinchingly face the consequences of your own
22015 commands, you can disable this ``feature'':
22019 @kindex set confirm
22021 @cindex confirmation
22022 @cindex stupid questions
22023 @item set confirm off
22024 Disables confirmation requests. Note that running @value{GDBN} with
22025 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22026 automatically disables confirmation requests.
22028 @item set confirm on
22029 Enables confirmation requests (the default).
22031 @kindex show confirm
22033 Displays state of confirmation requests.
22037 @cindex command tracing
22038 If you need to debug user-defined commands or sourced files you may find it
22039 useful to enable @dfn{command tracing}. In this mode each command will be
22040 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22041 quantity denoting the call depth of each command.
22044 @kindex set trace-commands
22045 @cindex command scripts, debugging
22046 @item set trace-commands on
22047 Enable command tracing.
22048 @item set trace-commands off
22049 Disable command tracing.
22050 @item show trace-commands
22051 Display the current state of command tracing.
22054 @node Debugging Output
22055 @section Optional Messages about Internal Happenings
22056 @cindex optional debugging messages
22058 @value{GDBN} has commands that enable optional debugging messages from
22059 various @value{GDBN} subsystems; normally these commands are of
22060 interest to @value{GDBN} maintainers, or when reporting a bug. This
22061 section documents those commands.
22064 @kindex set exec-done-display
22065 @item set exec-done-display
22066 Turns on or off the notification of asynchronous commands'
22067 completion. When on, @value{GDBN} will print a message when an
22068 asynchronous command finishes its execution. The default is off.
22069 @kindex show exec-done-display
22070 @item show exec-done-display
22071 Displays the current setting of asynchronous command completion
22074 @cindex ARM AArch64
22075 @item set debug aarch64
22076 Turns on or off display of debugging messages related to ARM AArch64.
22077 The default is off.
22079 @item show debug aarch64
22080 Displays the current state of displaying debugging messages related to
22082 @cindex gdbarch debugging info
22083 @cindex architecture debugging info
22084 @item set debug arch
22085 Turns on or off display of gdbarch debugging info. The default is off
22086 @item show debug arch
22087 Displays the current state of displaying gdbarch debugging info.
22088 @item set debug aix-thread
22089 @cindex AIX threads
22090 Display debugging messages about inner workings of the AIX thread
22092 @item show debug aix-thread
22093 Show the current state of AIX thread debugging info display.
22094 @item set debug check-physname
22096 Check the results of the ``physname'' computation. When reading DWARF
22097 debugging information for C@t{++}, @value{GDBN} attempts to compute
22098 each entity's name. @value{GDBN} can do this computation in two
22099 different ways, depending on exactly what information is present.
22100 When enabled, this setting causes @value{GDBN} to compute the names
22101 both ways and display any discrepancies.
22102 @item show debug check-physname
22103 Show the current state of ``physname'' checking.
22104 @item set debug coff-pe-read
22105 @cindex COFF/PE exported symbols
22106 Control display of debugging messages related to reading of COFF/PE
22107 exported symbols. The default is off.
22108 @item show debug coff-pe-read
22109 Displays the current state of displaying debugging messages related to
22110 reading of COFF/PE exported symbols.
22111 @item set debug dwarf2-die
22112 @cindex DWARF2 DIEs
22113 Dump DWARF2 DIEs after they are read in.
22114 The value is the number of nesting levels to print.
22115 A value of zero turns off the display.
22116 @item show debug dwarf2-die
22117 Show the current state of DWARF2 DIE debugging.
22118 @item set debug dwarf2-read
22119 @cindex DWARF2 Reading
22120 Turns on or off display of debugging messages related to reading
22121 DWARF debug info. The default is off.
22122 @item show debug dwarf2-read
22123 Show the current state of DWARF2 reader debugging.
22124 @item set debug displaced
22125 @cindex displaced stepping debugging info
22126 Turns on or off display of @value{GDBN} debugging info for the
22127 displaced stepping support. The default is off.
22128 @item show debug displaced
22129 Displays the current state of displaying @value{GDBN} debugging info
22130 related to displaced stepping.
22131 @item set debug event
22132 @cindex event debugging info
22133 Turns on or off display of @value{GDBN} event debugging info. The
22135 @item show debug event
22136 Displays the current state of displaying @value{GDBN} event debugging
22138 @item set debug expression
22139 @cindex expression debugging info
22140 Turns on or off display of debugging info about @value{GDBN}
22141 expression parsing. The default is off.
22142 @item show debug expression
22143 Displays the current state of displaying debugging info about
22144 @value{GDBN} expression parsing.
22145 @item set debug frame
22146 @cindex frame debugging info
22147 Turns on or off display of @value{GDBN} frame debugging info. The
22149 @item show debug frame
22150 Displays the current state of displaying @value{GDBN} frame debugging
22152 @item set debug gnu-nat
22153 @cindex @sc{gnu}/Hurd debug messages
22154 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22155 @item show debug gnu-nat
22156 Show the current state of @sc{gnu}/Hurd debugging messages.
22157 @item set debug infrun
22158 @cindex inferior debugging info
22159 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22160 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22161 for implementing operations such as single-stepping the inferior.
22162 @item show debug infrun
22163 Displays the current state of @value{GDBN} inferior debugging.
22164 @item set debug jit
22165 @cindex just-in-time compilation, debugging messages
22166 Turns on or off debugging messages from JIT debug support.
22167 @item show debug jit
22168 Displays the current state of @value{GDBN} JIT debugging.
22169 @item set debug lin-lwp
22170 @cindex @sc{gnu}/Linux LWP debug messages
22171 @cindex Linux lightweight processes
22172 Turns on or off debugging messages from the Linux LWP debug support.
22173 @item show debug lin-lwp
22174 Show the current state of Linux LWP debugging messages.
22175 @item set debug mach-o
22176 @cindex Mach-O symbols processing
22177 Control display of debugging messages related to Mach-O symbols
22178 processing. The default is off.
22179 @item show debug mach-o
22180 Displays the current state of displaying debugging messages related to
22181 reading of COFF/PE exported symbols.
22182 @item set debug notification
22183 @cindex remote async notification debugging info
22184 Turns on or off debugging messages about remote async notification.
22185 The default is off.
22186 @item show debug notification
22187 Displays the current state of remote async notification debugging messages.
22188 @item set debug observer
22189 @cindex observer debugging info
22190 Turns on or off display of @value{GDBN} observer debugging. This
22191 includes info such as the notification of observable events.
22192 @item show debug observer
22193 Displays the current state of observer debugging.
22194 @item set debug overload
22195 @cindex C@t{++} overload debugging info
22196 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22197 info. This includes info such as ranking of functions, etc. The default
22199 @item show debug overload
22200 Displays the current state of displaying @value{GDBN} C@t{++} overload
22202 @cindex expression parser, debugging info
22203 @cindex debug expression parser
22204 @item set debug parser
22205 Turns on or off the display of expression parser debugging output.
22206 Internally, this sets the @code{yydebug} variable in the expression
22207 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22208 details. The default is off.
22209 @item show debug parser
22210 Show the current state of expression parser debugging.
22211 @cindex packets, reporting on stdout
22212 @cindex serial connections, debugging
22213 @cindex debug remote protocol
22214 @cindex remote protocol debugging
22215 @cindex display remote packets
22216 @item set debug remote
22217 Turns on or off display of reports on all packets sent back and forth across
22218 the serial line to the remote machine. The info is printed on the
22219 @value{GDBN} standard output stream. The default is off.
22220 @item show debug remote
22221 Displays the state of display of remote packets.
22222 @item set debug serial
22223 Turns on or off display of @value{GDBN} serial debugging info. The
22225 @item show debug serial
22226 Displays the current state of displaying @value{GDBN} serial debugging
22228 @item set debug solib-frv
22229 @cindex FR-V shared-library debugging
22230 Turns on or off debugging messages for FR-V shared-library code.
22231 @item show debug solib-frv
22232 Display the current state of FR-V shared-library code debugging
22234 @item set debug symtab-create
22235 @cindex symbol table creation
22236 Turns on or off display of debugging messages related to symbol table creation.
22237 The default is off.
22238 @item show debug symtab-create
22239 Show the current state of symbol table creation debugging.
22240 @item set debug target
22241 @cindex target debugging info
22242 Turns on or off display of @value{GDBN} target debugging info. This info
22243 includes what is going on at the target level of GDB, as it happens. The
22244 default is 0. Set it to 1 to track events, and to 2 to also track the
22245 value of large memory transfers. Changes to this flag do not take effect
22246 until the next time you connect to a target or use the @code{run} command.
22247 @item show debug target
22248 Displays the current state of displaying @value{GDBN} target debugging
22250 @item set debug timestamp
22251 @cindex timestampping debugging info
22252 Turns on or off display of timestamps with @value{GDBN} debugging info.
22253 When enabled, seconds and microseconds are displayed before each debugging
22255 @item show debug timestamp
22256 Displays the current state of displaying timestamps with @value{GDBN}
22258 @item set debugvarobj
22259 @cindex variable object debugging info
22260 Turns on or off display of @value{GDBN} variable object debugging
22261 info. The default is off.
22262 @item show debugvarobj
22263 Displays the current state of displaying @value{GDBN} variable object
22265 @item set debug xml
22266 @cindex XML parser debugging
22267 Turns on or off debugging messages for built-in XML parsers.
22268 @item show debug xml
22269 Displays the current state of XML debugging messages.
22272 @node Other Misc Settings
22273 @section Other Miscellaneous Settings
22274 @cindex miscellaneous settings
22277 @kindex set interactive-mode
22278 @item set interactive-mode
22279 If @code{on}, forces @value{GDBN} to assume that GDB was started
22280 in a terminal. In practice, this means that @value{GDBN} should wait
22281 for the user to answer queries generated by commands entered at
22282 the command prompt. If @code{off}, forces @value{GDBN} to operate
22283 in the opposite mode, and it uses the default answers to all queries.
22284 If @code{auto} (the default), @value{GDBN} tries to determine whether
22285 its standard input is a terminal, and works in interactive-mode if it
22286 is, non-interactively otherwise.
22288 In the vast majority of cases, the debugger should be able to guess
22289 correctly which mode should be used. But this setting can be useful
22290 in certain specific cases, such as running a MinGW @value{GDBN}
22291 inside a cygwin window.
22293 @kindex show interactive-mode
22294 @item show interactive-mode
22295 Displays whether the debugger is operating in interactive mode or not.
22298 @node Extending GDB
22299 @chapter Extending @value{GDBN}
22300 @cindex extending GDB
22302 @value{GDBN} provides three mechanisms for extension. The first is based
22303 on composition of @value{GDBN} commands, the second is based on the
22304 Python scripting language, and the third is for defining new aliases of
22307 To facilitate the use of the first two extensions, @value{GDBN} is capable
22308 of evaluating the contents of a file. When doing so, @value{GDBN}
22309 can recognize which scripting language is being used by looking at
22310 the filename extension. Files with an unrecognized filename extension
22311 are always treated as a @value{GDBN} Command Files.
22312 @xref{Command Files,, Command files}.
22314 You can control how @value{GDBN} evaluates these files with the following
22318 @kindex set script-extension
22319 @kindex show script-extension
22320 @item set script-extension off
22321 All scripts are always evaluated as @value{GDBN} Command Files.
22323 @item set script-extension soft
22324 The debugger determines the scripting language based on filename
22325 extension. If this scripting language is supported, @value{GDBN}
22326 evaluates the script using that language. Otherwise, it evaluates
22327 the file as a @value{GDBN} Command File.
22329 @item set script-extension strict
22330 The debugger determines the scripting language based on filename
22331 extension, and evaluates the script using that language. If the
22332 language is not supported, then the evaluation fails.
22334 @item show script-extension
22335 Display the current value of the @code{script-extension} option.
22340 * Sequences:: Canned Sequences of Commands
22341 * Python:: Scripting @value{GDBN} using Python
22342 * Aliases:: Creating new spellings of existing commands
22346 @section Canned Sequences of Commands
22348 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22349 Command Lists}), @value{GDBN} provides two ways to store sequences of
22350 commands for execution as a unit: user-defined commands and command
22354 * Define:: How to define your own commands
22355 * Hooks:: Hooks for user-defined commands
22356 * Command Files:: How to write scripts of commands to be stored in a file
22357 * Output:: Commands for controlled output
22361 @subsection User-defined Commands
22363 @cindex user-defined command
22364 @cindex arguments, to user-defined commands
22365 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22366 which you assign a new name as a command. This is done with the
22367 @code{define} command. User commands may accept up to 10 arguments
22368 separated by whitespace. Arguments are accessed within the user command
22369 via @code{$arg0@dots{}$arg9}. A trivial example:
22373 print $arg0 + $arg1 + $arg2
22378 To execute the command use:
22385 This defines the command @code{adder}, which prints the sum of
22386 its three arguments. Note the arguments are text substitutions, so they may
22387 reference variables, use complex expressions, or even perform inferior
22390 @cindex argument count in user-defined commands
22391 @cindex how many arguments (user-defined commands)
22392 In addition, @code{$argc} may be used to find out how many arguments have
22393 been passed. This expands to a number in the range 0@dots{}10.
22398 print $arg0 + $arg1
22401 print $arg0 + $arg1 + $arg2
22409 @item define @var{commandname}
22410 Define a command named @var{commandname}. If there is already a command
22411 by that name, you are asked to confirm that you want to redefine it.
22412 @var{commandname} may be a bare command name consisting of letters,
22413 numbers, dashes, and underscores. It may also start with any predefined
22414 prefix command. For example, @samp{define target my-target} creates
22415 a user-defined @samp{target my-target} command.
22417 The definition of the command is made up of other @value{GDBN} command lines,
22418 which are given following the @code{define} command. The end of these
22419 commands is marked by a line containing @code{end}.
22422 @kindex end@r{ (user-defined commands)}
22423 @item document @var{commandname}
22424 Document the user-defined command @var{commandname}, so that it can be
22425 accessed by @code{help}. The command @var{commandname} must already be
22426 defined. This command reads lines of documentation just as @code{define}
22427 reads the lines of the command definition, ending with @code{end}.
22428 After the @code{document} command is finished, @code{help} on command
22429 @var{commandname} displays the documentation you have written.
22431 You may use the @code{document} command again to change the
22432 documentation of a command. Redefining the command with @code{define}
22433 does not change the documentation.
22435 @kindex dont-repeat
22436 @cindex don't repeat command
22438 Used inside a user-defined command, this tells @value{GDBN} that this
22439 command should not be repeated when the user hits @key{RET}
22440 (@pxref{Command Syntax, repeat last command}).
22442 @kindex help user-defined
22443 @item help user-defined
22444 List all user-defined commands and all python commands defined in class
22445 COMAND_USER. The first line of the documentation or docstring is
22450 @itemx show user @var{commandname}
22451 Display the @value{GDBN} commands used to define @var{commandname} (but
22452 not its documentation). If no @var{commandname} is given, display the
22453 definitions for all user-defined commands.
22454 This does not work for user-defined python commands.
22456 @cindex infinite recursion in user-defined commands
22457 @kindex show max-user-call-depth
22458 @kindex set max-user-call-depth
22459 @item show max-user-call-depth
22460 @itemx set max-user-call-depth
22461 The value of @code{max-user-call-depth} controls how many recursion
22462 levels are allowed in user-defined commands before @value{GDBN} suspects an
22463 infinite recursion and aborts the command.
22464 This does not apply to user-defined python commands.
22467 In addition to the above commands, user-defined commands frequently
22468 use control flow commands, described in @ref{Command Files}.
22470 When user-defined commands are executed, the
22471 commands of the definition are not printed. An error in any command
22472 stops execution of the user-defined command.
22474 If used interactively, commands that would ask for confirmation proceed
22475 without asking when used inside a user-defined command. Many @value{GDBN}
22476 commands that normally print messages to say what they are doing omit the
22477 messages when used in a user-defined command.
22480 @subsection User-defined Command Hooks
22481 @cindex command hooks
22482 @cindex hooks, for commands
22483 @cindex hooks, pre-command
22486 You may define @dfn{hooks}, which are a special kind of user-defined
22487 command. Whenever you run the command @samp{foo}, if the user-defined
22488 command @samp{hook-foo} exists, it is executed (with no arguments)
22489 before that command.
22491 @cindex hooks, post-command
22493 A hook may also be defined which is run after the command you executed.
22494 Whenever you run the command @samp{foo}, if the user-defined command
22495 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22496 that command. Post-execution hooks may exist simultaneously with
22497 pre-execution hooks, for the same command.
22499 It is valid for a hook to call the command which it hooks. If this
22500 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22502 @c It would be nice if hookpost could be passed a parameter indicating
22503 @c if the command it hooks executed properly or not. FIXME!
22505 @kindex stop@r{, a pseudo-command}
22506 In addition, a pseudo-command, @samp{stop} exists. Defining
22507 (@samp{hook-stop}) makes the associated commands execute every time
22508 execution stops in your program: before breakpoint commands are run,
22509 displays are printed, or the stack frame is printed.
22511 For example, to ignore @code{SIGALRM} signals while
22512 single-stepping, but treat them normally during normal execution,
22517 handle SIGALRM nopass
22521 handle SIGALRM pass
22524 define hook-continue
22525 handle SIGALRM pass
22529 As a further example, to hook at the beginning and end of the @code{echo}
22530 command, and to add extra text to the beginning and end of the message,
22538 define hookpost-echo
22542 (@value{GDBP}) echo Hello World
22543 <<<---Hello World--->>>
22548 You can define a hook for any single-word command in @value{GDBN}, but
22549 not for command aliases; you should define a hook for the basic command
22550 name, e.g.@: @code{backtrace} rather than @code{bt}.
22551 @c FIXME! So how does Joe User discover whether a command is an alias
22553 You can hook a multi-word command by adding @code{hook-} or
22554 @code{hookpost-} to the last word of the command, e.g.@:
22555 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22557 If an error occurs during the execution of your hook, execution of
22558 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22559 (before the command that you actually typed had a chance to run).
22561 If you try to define a hook which does not match any known command, you
22562 get a warning from the @code{define} command.
22564 @node Command Files
22565 @subsection Command Files
22567 @cindex command files
22568 @cindex scripting commands
22569 A command file for @value{GDBN} is a text file made of lines that are
22570 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22571 also be included. An empty line in a command file does nothing; it
22572 does not mean to repeat the last command, as it would from the
22575 You can request the execution of a command file with the @code{source}
22576 command. Note that the @code{source} command is also used to evaluate
22577 scripts that are not Command Files. The exact behavior can be configured
22578 using the @code{script-extension} setting.
22579 @xref{Extending GDB,, Extending GDB}.
22583 @cindex execute commands from a file
22584 @item source [-s] [-v] @var{filename}
22585 Execute the command file @var{filename}.
22588 The lines in a command file are generally executed sequentially,
22589 unless the order of execution is changed by one of the
22590 @emph{flow-control commands} described below. The commands are not
22591 printed as they are executed. An error in any command terminates
22592 execution of the command file and control is returned to the console.
22594 @value{GDBN} first searches for @var{filename} in the current directory.
22595 If the file is not found there, and @var{filename} does not specify a
22596 directory, then @value{GDBN} also looks for the file on the source search path
22597 (specified with the @samp{directory} command);
22598 except that @file{$cdir} is not searched because the compilation directory
22599 is not relevant to scripts.
22601 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22602 on the search path even if @var{filename} specifies a directory.
22603 The search is done by appending @var{filename} to each element of the
22604 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22605 and the search path contains @file{/home/user} then @value{GDBN} will
22606 look for the script @file{/home/user/mylib/myscript}.
22607 The search is also done if @var{filename} is an absolute path.
22608 For example, if @var{filename} is @file{/tmp/myscript} and
22609 the search path contains @file{/home/user} then @value{GDBN} will
22610 look for the script @file{/home/user/tmp/myscript}.
22611 For DOS-like systems, if @var{filename} contains a drive specification,
22612 it is stripped before concatenation. For example, if @var{filename} is
22613 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22614 will look for the script @file{c:/tmp/myscript}.
22616 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22617 each command as it is executed. The option must be given before
22618 @var{filename}, and is interpreted as part of the filename anywhere else.
22620 Commands that would ask for confirmation if used interactively proceed
22621 without asking when used in a command file. Many @value{GDBN} commands that
22622 normally print messages to say what they are doing omit the messages
22623 when called from command files.
22625 @value{GDBN} also accepts command input from standard input. In this
22626 mode, normal output goes to standard output and error output goes to
22627 standard error. Errors in a command file supplied on standard input do
22628 not terminate execution of the command file---execution continues with
22632 gdb < cmds > log 2>&1
22635 (The syntax above will vary depending on the shell used.) This example
22636 will execute commands from the file @file{cmds}. All output and errors
22637 would be directed to @file{log}.
22639 Since commands stored on command files tend to be more general than
22640 commands typed interactively, they frequently need to deal with
22641 complicated situations, such as different or unexpected values of
22642 variables and symbols, changes in how the program being debugged is
22643 built, etc. @value{GDBN} provides a set of flow-control commands to
22644 deal with these complexities. Using these commands, you can write
22645 complex scripts that loop over data structures, execute commands
22646 conditionally, etc.
22653 This command allows to include in your script conditionally executed
22654 commands. The @code{if} command takes a single argument, which is an
22655 expression to evaluate. It is followed by a series of commands that
22656 are executed only if the expression is true (its value is nonzero).
22657 There can then optionally be an @code{else} line, followed by a series
22658 of commands that are only executed if the expression was false. The
22659 end of the list is marked by a line containing @code{end}.
22663 This command allows to write loops. Its syntax is similar to
22664 @code{if}: the command takes a single argument, which is an expression
22665 to evaluate, and must be followed by the commands to execute, one per
22666 line, terminated by an @code{end}. These commands are called the
22667 @dfn{body} of the loop. The commands in the body of @code{while} are
22668 executed repeatedly as long as the expression evaluates to true.
22672 This command exits the @code{while} loop in whose body it is included.
22673 Execution of the script continues after that @code{while}s @code{end}
22676 @kindex loop_continue
22677 @item loop_continue
22678 This command skips the execution of the rest of the body of commands
22679 in the @code{while} loop in whose body it is included. Execution
22680 branches to the beginning of the @code{while} loop, where it evaluates
22681 the controlling expression.
22683 @kindex end@r{ (if/else/while commands)}
22685 Terminate the block of commands that are the body of @code{if},
22686 @code{else}, or @code{while} flow-control commands.
22691 @subsection Commands for Controlled Output
22693 During the execution of a command file or a user-defined command, normal
22694 @value{GDBN} output is suppressed; the only output that appears is what is
22695 explicitly printed by the commands in the definition. This section
22696 describes three commands useful for generating exactly the output you
22701 @item echo @var{text}
22702 @c I do not consider backslash-space a standard C escape sequence
22703 @c because it is not in ANSI.
22704 Print @var{text}. Nonprinting characters can be included in
22705 @var{text} using C escape sequences, such as @samp{\n} to print a
22706 newline. @strong{No newline is printed unless you specify one.}
22707 In addition to the standard C escape sequences, a backslash followed
22708 by a space stands for a space. This is useful for displaying a
22709 string with spaces at the beginning or the end, since leading and
22710 trailing spaces are otherwise trimmed from all arguments.
22711 To print @samp{@w{ }and foo =@w{ }}, use the command
22712 @samp{echo \@w{ }and foo = \@w{ }}.
22714 A backslash at the end of @var{text} can be used, as in C, to continue
22715 the command onto subsequent lines. For example,
22718 echo This is some text\n\
22719 which is continued\n\
22720 onto several lines.\n
22723 produces the same output as
22726 echo This is some text\n
22727 echo which is continued\n
22728 echo onto several lines.\n
22732 @item output @var{expression}
22733 Print the value of @var{expression} and nothing but that value: no
22734 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22735 value history either. @xref{Expressions, ,Expressions}, for more information
22738 @item output/@var{fmt} @var{expression}
22739 Print the value of @var{expression} in format @var{fmt}. You can use
22740 the same formats as for @code{print}. @xref{Output Formats,,Output
22741 Formats}, for more information.
22744 @item printf @var{template}, @var{expressions}@dots{}
22745 Print the values of one or more @var{expressions} under the control of
22746 the string @var{template}. To print several values, make
22747 @var{expressions} be a comma-separated list of individual expressions,
22748 which may be either numbers or pointers. Their values are printed as
22749 specified by @var{template}, exactly as a C program would do by
22750 executing the code below:
22753 printf (@var{template}, @var{expressions}@dots{});
22756 As in @code{C} @code{printf}, ordinary characters in @var{template}
22757 are printed verbatim, while @dfn{conversion specification} introduced
22758 by the @samp{%} character cause subsequent @var{expressions} to be
22759 evaluated, their values converted and formatted according to type and
22760 style information encoded in the conversion specifications, and then
22763 For example, you can print two values in hex like this:
22766 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22769 @code{printf} supports all the standard @code{C} conversion
22770 specifications, including the flags and modifiers between the @samp{%}
22771 character and the conversion letter, with the following exceptions:
22775 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22778 The modifier @samp{*} is not supported for specifying precision or
22782 The @samp{'} flag (for separation of digits into groups according to
22783 @code{LC_NUMERIC'}) is not supported.
22786 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22790 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22793 The conversion letters @samp{a} and @samp{A} are not supported.
22797 Note that the @samp{ll} type modifier is supported only if the
22798 underlying @code{C} implementation used to build @value{GDBN} supports
22799 the @code{long long int} type, and the @samp{L} type modifier is
22800 supported only if @code{long double} type is available.
22802 As in @code{C}, @code{printf} supports simple backslash-escape
22803 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22804 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22805 single character. Octal and hexadecimal escape sequences are not
22808 Additionally, @code{printf} supports conversion specifications for DFP
22809 (@dfn{Decimal Floating Point}) types using the following length modifiers
22810 together with a floating point specifier.
22815 @samp{H} for printing @code{Decimal32} types.
22818 @samp{D} for printing @code{Decimal64} types.
22821 @samp{DD} for printing @code{Decimal128} types.
22824 If the underlying @code{C} implementation used to build @value{GDBN} has
22825 support for the three length modifiers for DFP types, other modifiers
22826 such as width and precision will also be available for @value{GDBN} to use.
22828 In case there is no such @code{C} support, no additional modifiers will be
22829 available and the value will be printed in the standard way.
22831 Here's an example of printing DFP types using the above conversion letters:
22833 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22837 @item eval @var{template}, @var{expressions}@dots{}
22838 Convert the values of one or more @var{expressions} under the control of
22839 the string @var{template} to a command line, and call it.
22844 @section Scripting @value{GDBN} using Python
22845 @cindex python scripting
22846 @cindex scripting with python
22848 You can script @value{GDBN} using the @uref{http://www.python.org/,
22849 Python programming language}. This feature is available only if
22850 @value{GDBN} was configured using @option{--with-python}.
22852 @cindex python directory
22853 Python scripts used by @value{GDBN} should be installed in
22854 @file{@var{data-directory}/python}, where @var{data-directory} is
22855 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22856 This directory, known as the @dfn{python directory},
22857 is automatically added to the Python Search Path in order to allow
22858 the Python interpreter to locate all scripts installed at this location.
22860 Additionally, @value{GDBN} commands and convenience functions which
22861 are written in Python and are located in the
22862 @file{@var{data-directory}/python/gdb/command} or
22863 @file{@var{data-directory}/python/gdb/function} directories are
22864 automatically imported when @value{GDBN} starts.
22867 * Python Commands:: Accessing Python from @value{GDBN}.
22868 * Python API:: Accessing @value{GDBN} from Python.
22869 * Python Auto-loading:: Automatically loading Python code.
22870 * Python modules:: Python modules provided by @value{GDBN}.
22873 @node Python Commands
22874 @subsection Python Commands
22875 @cindex python commands
22876 @cindex commands to access python
22878 @value{GDBN} provides two commands for accessing the Python interpreter,
22879 and one related setting:
22882 @kindex python-interactive
22884 @item python-interactive @r{[}@var{command}@r{]}
22885 @itemx pi @r{[}@var{command}@r{]}
22886 Without an argument, the @code{python-interactive} command can be used
22887 to start an interactive Python prompt. To return to @value{GDBN},
22888 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22890 Alternatively, a single-line Python command can be given as an
22891 argument and evaluated. If the command is an expression, the result
22892 will be printed; otherwise, nothing will be printed. For example:
22895 (@value{GDBP}) python-interactive 2 + 3
22901 @item python @r{[}@var{command}@r{]}
22902 @itemx py @r{[}@var{command}@r{]}
22903 The @code{python} command can be used to evaluate Python code.
22905 If given an argument, the @code{python} command will evaluate the
22906 argument as a Python command. For example:
22909 (@value{GDBP}) python print 23
22913 If you do not provide an argument to @code{python}, it will act as a
22914 multi-line command, like @code{define}. In this case, the Python
22915 script is made up of subsequent command lines, given after the
22916 @code{python} command. This command list is terminated using a line
22917 containing @code{end}. For example:
22920 (@value{GDBP}) python
22922 End with a line saying just "end".
22928 @kindex set python print-stack
22929 @item set python print-stack
22930 By default, @value{GDBN} will print only the message component of a
22931 Python exception when an error occurs in a Python script. This can be
22932 controlled using @code{set python print-stack}: if @code{full}, then
22933 full Python stack printing is enabled; if @code{none}, then Python stack
22934 and message printing is disabled; if @code{message}, the default, only
22935 the message component of the error is printed.
22938 It is also possible to execute a Python script from the @value{GDBN}
22942 @item source @file{script-name}
22943 The script name must end with @samp{.py} and @value{GDBN} must be configured
22944 to recognize the script language based on filename extension using
22945 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22947 @item python execfile ("script-name")
22948 This method is based on the @code{execfile} Python built-in function,
22949 and thus is always available.
22953 @subsection Python API
22955 @cindex programming in python
22957 @cindex python stdout
22958 @cindex python pagination
22959 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22960 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22961 A Python program which outputs to one of these streams may have its
22962 output interrupted by the user (@pxref{Screen Size}). In this
22963 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22966 * Basic Python:: Basic Python Functions.
22967 * Exception Handling:: How Python exceptions are translated.
22968 * Values From Inferior:: Python representation of values.
22969 * Types In Python:: Python representation of types.
22970 * Pretty Printing API:: Pretty-printing values.
22971 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22972 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22973 * Type Printing API:: Pretty-printing types.
22974 * Inferiors In Python:: Python representation of inferiors (processes)
22975 * Events In Python:: Listening for events from @value{GDBN}.
22976 * Threads In Python:: Accessing inferior threads from Python.
22977 * Commands In Python:: Implementing new commands in Python.
22978 * Parameters In Python:: Adding new @value{GDBN} parameters.
22979 * Functions In Python:: Writing new convenience functions.
22980 * Progspaces In Python:: Program spaces.
22981 * Objfiles In Python:: Object files.
22982 * Frames In Python:: Accessing inferior stack frames from Python.
22983 * Blocks In Python:: Accessing frame blocks from Python.
22984 * Symbols In Python:: Python representation of symbols.
22985 * Symbol Tables In Python:: Python representation of symbol tables.
22986 * Breakpoints In Python:: Manipulating breakpoints using Python.
22987 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22989 * Lazy Strings In Python:: Python representation of lazy strings.
22990 * Architectures In Python:: Python representation of architectures.
22994 @subsubsection Basic Python
22996 @cindex python functions
22997 @cindex python module
22999 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23000 methods and classes added by @value{GDBN} are placed in this module.
23001 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23002 use in all scripts evaluated by the @code{python} command.
23004 @findex gdb.PYTHONDIR
23005 @defvar gdb.PYTHONDIR
23006 A string containing the python directory (@pxref{Python}).
23009 @findex gdb.execute
23010 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23011 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23012 If a GDB exception happens while @var{command} runs, it is
23013 translated as described in @ref{Exception Handling,,Exception Handling}.
23015 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23016 command as having originated from the user invoking it interactively.
23017 It must be a boolean value. If omitted, it defaults to @code{False}.
23019 By default, any output produced by @var{command} is sent to
23020 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23021 @code{True}, then output will be collected by @code{gdb.execute} and
23022 returned as a string. The default is @code{False}, in which case the
23023 return value is @code{None}. If @var{to_string} is @code{True}, the
23024 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23025 and height, and its pagination will be disabled; @pxref{Screen Size}.
23028 @findex gdb.breakpoints
23029 @defun gdb.breakpoints ()
23030 Return a sequence holding all of @value{GDBN}'s breakpoints.
23031 @xref{Breakpoints In Python}, for more information.
23034 @findex gdb.parameter
23035 @defun gdb.parameter (parameter)
23036 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23037 string naming the parameter to look up; @var{parameter} may contain
23038 spaces if the parameter has a multi-part name. For example,
23039 @samp{print object} is a valid parameter name.
23041 If the named parameter does not exist, this function throws a
23042 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23043 parameter's value is converted to a Python value of the appropriate
23044 type, and returned.
23047 @findex gdb.history
23048 @defun gdb.history (number)
23049 Return a value from @value{GDBN}'s value history (@pxref{Value
23050 History}). @var{number} indicates which history element to return.
23051 If @var{number} is negative, then @value{GDBN} will take its absolute value
23052 and count backward from the last element (i.e., the most recent element) to
23053 find the value to return. If @var{number} is zero, then @value{GDBN} will
23054 return the most recent element. If the element specified by @var{number}
23055 doesn't exist in the value history, a @code{gdb.error} exception will be
23058 If no exception is raised, the return value is always an instance of
23059 @code{gdb.Value} (@pxref{Values From Inferior}).
23062 @findex gdb.parse_and_eval
23063 @defun gdb.parse_and_eval (expression)
23064 Parse @var{expression} as an expression in the current language,
23065 evaluate it, and return the result as a @code{gdb.Value}.
23066 @var{expression} must be a string.
23068 This function can be useful when implementing a new command
23069 (@pxref{Commands In Python}), as it provides a way to parse the
23070 command's argument as an expression. It is also useful simply to
23071 compute values, for example, it is the only way to get the value of a
23072 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23075 @findex gdb.find_pc_line
23076 @defun gdb.find_pc_line (pc)
23077 Return the @code{gdb.Symtab_and_line} object corresponding to the
23078 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23079 value of @var{pc} is passed as an argument, then the @code{symtab} and
23080 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23081 will be @code{None} and 0 respectively.
23084 @findex gdb.post_event
23085 @defun gdb.post_event (event)
23086 Put @var{event}, a callable object taking no arguments, into
23087 @value{GDBN}'s internal event queue. This callable will be invoked at
23088 some later point, during @value{GDBN}'s event processing. Events
23089 posted using @code{post_event} will be run in the order in which they
23090 were posted; however, there is no way to know when they will be
23091 processed relative to other events inside @value{GDBN}.
23093 @value{GDBN} is not thread-safe. If your Python program uses multiple
23094 threads, you must be careful to only call @value{GDBN}-specific
23095 functions in the main @value{GDBN} thread. @code{post_event} ensures
23099 (@value{GDBP}) python
23103 > def __init__(self, message):
23104 > self.message = message;
23105 > def __call__(self):
23106 > gdb.write(self.message)
23108 >class MyThread1 (threading.Thread):
23110 > gdb.post_event(Writer("Hello "))
23112 >class MyThread2 (threading.Thread):
23114 > gdb.post_event(Writer("World\n"))
23116 >MyThread1().start()
23117 >MyThread2().start()
23119 (@value{GDBP}) Hello World
23124 @defun gdb.write (string @r{[}, stream{]})
23125 Print a string to @value{GDBN}'s paginated output stream. The
23126 optional @var{stream} determines the stream to print to. The default
23127 stream is @value{GDBN}'s standard output stream. Possible stream
23134 @value{GDBN}'s standard output stream.
23139 @value{GDBN}'s standard error stream.
23144 @value{GDBN}'s log stream (@pxref{Logging Output}).
23147 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23148 call this function and will automatically direct the output to the
23153 @defun gdb.flush ()
23154 Flush the buffer of a @value{GDBN} paginated stream so that the
23155 contents are displayed immediately. @value{GDBN} will flush the
23156 contents of a stream automatically when it encounters a newline in the
23157 buffer. The optional @var{stream} determines the stream to flush. The
23158 default stream is @value{GDBN}'s standard output stream. Possible
23165 @value{GDBN}'s standard output stream.
23170 @value{GDBN}'s standard error stream.
23175 @value{GDBN}'s log stream (@pxref{Logging Output}).
23179 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23180 call this function for the relevant stream.
23183 @findex gdb.target_charset
23184 @defun gdb.target_charset ()
23185 Return the name of the current target character set (@pxref{Character
23186 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23187 that @samp{auto} is never returned.
23190 @findex gdb.target_wide_charset
23191 @defun gdb.target_wide_charset ()
23192 Return the name of the current target wide character set
23193 (@pxref{Character Sets}). This differs from
23194 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23198 @findex gdb.solib_name
23199 @defun gdb.solib_name (address)
23200 Return the name of the shared library holding the given @var{address}
23201 as a string, or @code{None}.
23204 @findex gdb.decode_line
23205 @defun gdb.decode_line @r{[}expression@r{]}
23206 Return locations of the line specified by @var{expression}, or of the
23207 current line if no argument was given. This function returns a Python
23208 tuple containing two elements. The first element contains a string
23209 holding any unparsed section of @var{expression} (or @code{None} if
23210 the expression has been fully parsed). The second element contains
23211 either @code{None} or another tuple that contains all the locations
23212 that match the expression represented as @code{gdb.Symtab_and_line}
23213 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23214 provided, it is decoded the way that @value{GDBN}'s inbuilt
23215 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23218 @defun gdb.prompt_hook (current_prompt)
23219 @anchor{prompt_hook}
23221 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23222 assigned to this operation before a prompt is displayed by
23225 The parameter @code{current_prompt} contains the current @value{GDBN}
23226 prompt. This method must return a Python string, or @code{None}. If
23227 a string is returned, the @value{GDBN} prompt will be set to that
23228 string. If @code{None} is returned, @value{GDBN} will continue to use
23229 the current prompt.
23231 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23232 such as those used by readline for command input, and annotation
23233 related prompts are prohibited from being changed.
23236 @node Exception Handling
23237 @subsubsection Exception Handling
23238 @cindex python exceptions
23239 @cindex exceptions, python
23241 When executing the @code{python} command, Python exceptions
23242 uncaught within the Python code are translated to calls to
23243 @value{GDBN} error-reporting mechanism. If the command that called
23244 @code{python} does not handle the error, @value{GDBN} will
23245 terminate it and print an error message containing the Python
23246 exception name, the associated value, and the Python call stack
23247 backtrace at the point where the exception was raised. Example:
23250 (@value{GDBP}) python print foo
23251 Traceback (most recent call last):
23252 File "<string>", line 1, in <module>
23253 NameError: name 'foo' is not defined
23256 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23257 Python code are converted to Python exceptions. The type of the
23258 Python exception depends on the error.
23262 This is the base class for most exceptions generated by @value{GDBN}.
23263 It is derived from @code{RuntimeError}, for compatibility with earlier
23264 versions of @value{GDBN}.
23266 If an error occurring in @value{GDBN} does not fit into some more
23267 specific category, then the generated exception will have this type.
23269 @item gdb.MemoryError
23270 This is a subclass of @code{gdb.error} which is thrown when an
23271 operation tried to access invalid memory in the inferior.
23273 @item KeyboardInterrupt
23274 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23275 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23278 In all cases, your exception handler will see the @value{GDBN} error
23279 message as its value and the Python call stack backtrace at the Python
23280 statement closest to where the @value{GDBN} error occured as the
23283 @findex gdb.GdbError
23284 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23285 it is useful to be able to throw an exception that doesn't cause a
23286 traceback to be printed. For example, the user may have invoked the
23287 command incorrectly. Use the @code{gdb.GdbError} exception
23288 to handle this case. Example:
23292 >class HelloWorld (gdb.Command):
23293 > """Greet the whole world."""
23294 > def __init__ (self):
23295 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23296 > def invoke (self, args, from_tty):
23297 > argv = gdb.string_to_argv (args)
23298 > if len (argv) != 0:
23299 > raise gdb.GdbError ("hello-world takes no arguments")
23300 > print "Hello, World!"
23303 (gdb) hello-world 42
23304 hello-world takes no arguments
23307 @node Values From Inferior
23308 @subsubsection Values From Inferior
23309 @cindex values from inferior, with Python
23310 @cindex python, working with values from inferior
23312 @cindex @code{gdb.Value}
23313 @value{GDBN} provides values it obtains from the inferior program in
23314 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23315 for its internal bookkeeping of the inferior's values, and for
23316 fetching values when necessary.
23318 Inferior values that are simple scalars can be used directly in
23319 Python expressions that are valid for the value's data type. Here's
23320 an example for an integer or floating-point value @code{some_val}:
23327 As result of this, @code{bar} will also be a @code{gdb.Value} object
23328 whose values are of the same type as those of @code{some_val}.
23330 Inferior values that are structures or instances of some class can
23331 be accessed using the Python @dfn{dictionary syntax}. For example, if
23332 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23333 can access its @code{foo} element with:
23336 bar = some_val['foo']
23339 Again, @code{bar} will also be a @code{gdb.Value} object.
23341 A @code{gdb.Value} that represents a function can be executed via
23342 inferior function call. Any arguments provided to the call must match
23343 the function's prototype, and must be provided in the order specified
23346 For example, @code{some_val} is a @code{gdb.Value} instance
23347 representing a function that takes two integers as arguments. To
23348 execute this function, call it like so:
23351 result = some_val (10,20)
23354 Any values returned from a function call will be stored as a
23357 The following attributes are provided:
23359 @defvar Value.address
23360 If this object is addressable, this read-only attribute holds a
23361 @code{gdb.Value} object representing the address. Otherwise,
23362 this attribute holds @code{None}.
23365 @cindex optimized out value in Python
23366 @defvar Value.is_optimized_out
23367 This read-only boolean attribute is true if the compiler optimized out
23368 this value, thus it is not available for fetching from the inferior.
23372 The type of this @code{gdb.Value}. The value of this attribute is a
23373 @code{gdb.Type} object (@pxref{Types In Python}).
23376 @defvar Value.dynamic_type
23377 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23378 type information (@acronym{RTTI}) to determine the dynamic type of the
23379 value. If this value is of class type, it will return the class in
23380 which the value is embedded, if any. If this value is of pointer or
23381 reference to a class type, it will compute the dynamic type of the
23382 referenced object, and return a pointer or reference to that type,
23383 respectively. In all other cases, it will return the value's static
23386 Note that this feature will only work when debugging a C@t{++} program
23387 that includes @acronym{RTTI} for the object in question. Otherwise,
23388 it will just return the static type of the value as in @kbd{ptype foo}
23389 (@pxref{Symbols, ptype}).
23392 @defvar Value.is_lazy
23393 The value of this read-only boolean attribute is @code{True} if this
23394 @code{gdb.Value} has not yet been fetched from the inferior.
23395 @value{GDBN} does not fetch values until necessary, for efficiency.
23399 myval = gdb.parse_and_eval ('somevar')
23402 The value of @code{somevar} is not fetched at this time. It will be
23403 fetched when the value is needed, or when the @code{fetch_lazy}
23407 The following methods are provided:
23409 @defun Value.__init__ (@var{val})
23410 Many Python values can be converted directly to a @code{gdb.Value} via
23411 this object initializer. Specifically:
23414 @item Python boolean
23415 A Python boolean is converted to the boolean type from the current
23418 @item Python integer
23419 A Python integer is converted to the C @code{long} type for the
23420 current architecture.
23423 A Python long is converted to the C @code{long long} type for the
23424 current architecture.
23427 A Python float is converted to the C @code{double} type for the
23428 current architecture.
23430 @item Python string
23431 A Python string is converted to a target string, using the current
23434 @item @code{gdb.Value}
23435 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23437 @item @code{gdb.LazyString}
23438 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23439 Python}), then the lazy string's @code{value} method is called, and
23440 its result is used.
23444 @defun Value.cast (type)
23445 Return a new instance of @code{gdb.Value} that is the result of
23446 casting this instance to the type described by @var{type}, which must
23447 be a @code{gdb.Type} object. If the cast cannot be performed for some
23448 reason, this method throws an exception.
23451 @defun Value.dereference ()
23452 For pointer data types, this method returns a new @code{gdb.Value} object
23453 whose contents is the object pointed to by the pointer. For example, if
23454 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23461 then you can use the corresponding @code{gdb.Value} to access what
23462 @code{foo} points to like this:
23465 bar = foo.dereference ()
23468 The result @code{bar} will be a @code{gdb.Value} object holding the
23469 value pointed to by @code{foo}.
23471 A similar function @code{Value.referenced_value} exists which also
23472 returns @code{gdb.Value} objects corresonding to the values pointed to
23473 by pointer values (and additionally, values referenced by reference
23474 values). However, the behavior of @code{Value.dereference}
23475 differs from @code{Value.referenced_value} by the fact that the
23476 behavior of @code{Value.dereference} is identical to applying the C
23477 unary operator @code{*} on a given value. For example, consider a
23478 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23482 typedef int *intptr;
23486 intptr &ptrref = ptr;
23489 Though @code{ptrref} is a reference value, one can apply the method
23490 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23491 to it and obtain a @code{gdb.Value} which is identical to that
23492 corresponding to @code{val}. However, if you apply the method
23493 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23494 object identical to that corresponding to @code{ptr}.
23497 py_ptrref = gdb.parse_and_eval ("ptrref")
23498 py_val = py_ptrref.dereference ()
23499 py_ptr = py_ptrref.referenced_value ()
23502 The @code{gdb.Value} object @code{py_val} is identical to that
23503 corresponding to @code{val}, and @code{py_ptr} is identical to that
23504 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23505 be applied whenever the C unary operator @code{*} can be applied
23506 to the corresponding C value. For those cases where applying both
23507 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23508 the results obtained need not be identical (as we have seen in the above
23509 example). The results are however identical when applied on
23510 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23511 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23514 @defun Value.referenced_value ()
23515 For pointer or reference data types, this method returns a new
23516 @code{gdb.Value} object corresponding to the value referenced by the
23517 pointer/reference value. For pointer data types,
23518 @code{Value.dereference} and @code{Value.referenced_value} produce
23519 identical results. The difference between these methods is that
23520 @code{Value.dereference} cannot get the values referenced by reference
23521 values. For example, consider a reference to an @code{int}, declared
23522 in your C@t{++} program as
23530 then applying @code{Value.dereference} to the @code{gdb.Value} object
23531 corresponding to @code{ref} will result in an error, while applying
23532 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23533 identical to that corresponding to @code{val}.
23536 py_ref = gdb.parse_and_eval ("ref")
23537 er_ref = py_ref.dereference () # Results in error
23538 py_val = py_ref.referenced_value () # Returns the referenced value
23541 The @code{gdb.Value} object @code{py_val} is identical to that
23542 corresponding to @code{val}.
23545 @defun Value.dynamic_cast (type)
23546 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23547 operator were used. Consult a C@t{++} reference for details.
23550 @defun Value.reinterpret_cast (type)
23551 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23552 operator were used. Consult a C@t{++} reference for details.
23555 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23556 If this @code{gdb.Value} represents a string, then this method
23557 converts the contents to a Python string. Otherwise, this method will
23558 throw an exception.
23560 Strings are recognized in a language-specific way; whether a given
23561 @code{gdb.Value} represents a string is determined by the current
23564 For C-like languages, a value is a string if it is a pointer to or an
23565 array of characters or ints. The string is assumed to be terminated
23566 by a zero of the appropriate width. However if the optional length
23567 argument is given, the string will be converted to that given length,
23568 ignoring any embedded zeros that the string may contain.
23570 If the optional @var{encoding} argument is given, it must be a string
23571 naming the encoding of the string in the @code{gdb.Value}, such as
23572 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23573 the same encodings as the corresponding argument to Python's
23574 @code{string.decode} method, and the Python codec machinery will be used
23575 to convert the string. If @var{encoding} is not given, or if
23576 @var{encoding} is the empty string, then either the @code{target-charset}
23577 (@pxref{Character Sets}) will be used, or a language-specific encoding
23578 will be used, if the current language is able to supply one.
23580 The optional @var{errors} argument is the same as the corresponding
23581 argument to Python's @code{string.decode} method.
23583 If the optional @var{length} argument is given, the string will be
23584 fetched and converted to the given length.
23587 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23588 If this @code{gdb.Value} represents a string, then this method
23589 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23590 In Python}). Otherwise, this method will throw an exception.
23592 If the optional @var{encoding} argument is given, it must be a string
23593 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23594 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23595 @var{encoding} argument is an encoding that @value{GDBN} does
23596 recognize, @value{GDBN} will raise an error.
23598 When a lazy string is printed, the @value{GDBN} encoding machinery is
23599 used to convert the string during printing. If the optional
23600 @var{encoding} argument is not provided, or is an empty string,
23601 @value{GDBN} will automatically select the encoding most suitable for
23602 the string type. For further information on encoding in @value{GDBN}
23603 please see @ref{Character Sets}.
23605 If the optional @var{length} argument is given, the string will be
23606 fetched and encoded to the length of characters specified. If
23607 the @var{length} argument is not provided, the string will be fetched
23608 and encoded until a null of appropriate width is found.
23611 @defun Value.fetch_lazy ()
23612 If the @code{gdb.Value} object is currently a lazy value
23613 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23614 fetched from the inferior. Any errors that occur in the process
23615 will produce a Python exception.
23617 If the @code{gdb.Value} object is not a lazy value, this method
23620 This method does not return a value.
23624 @node Types In Python
23625 @subsubsection Types In Python
23626 @cindex types in Python
23627 @cindex Python, working with types
23630 @value{GDBN} represents types from the inferior using the class
23633 The following type-related functions are available in the @code{gdb}
23636 @findex gdb.lookup_type
23637 @defun gdb.lookup_type (name @r{[}, block@r{]})
23638 This function looks up a type by name. @var{name} is the name of the
23639 type to look up. It must be a string.
23641 If @var{block} is given, then @var{name} is looked up in that scope.
23642 Otherwise, it is searched for globally.
23644 Ordinarily, this function will return an instance of @code{gdb.Type}.
23645 If the named type cannot be found, it will throw an exception.
23648 If the type is a structure or class type, or an enum type, the fields
23649 of that type can be accessed using the Python @dfn{dictionary syntax}.
23650 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23651 a structure type, you can access its @code{foo} field with:
23654 bar = some_type['foo']
23657 @code{bar} will be a @code{gdb.Field} object; see below under the
23658 description of the @code{Type.fields} method for a description of the
23659 @code{gdb.Field} class.
23661 An instance of @code{Type} has the following attributes:
23664 The type code for this type. The type code will be one of the
23665 @code{TYPE_CODE_} constants defined below.
23668 @defvar Type.sizeof
23669 The size of this type, in target @code{char} units. Usually, a
23670 target's @code{char} type will be an 8-bit byte. However, on some
23671 unusual platforms, this type may have a different size.
23675 The tag name for this type. The tag name is the name after
23676 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23677 languages have this concept. If this type has no tag name, then
23678 @code{None} is returned.
23681 The following methods are provided:
23683 @defun Type.fields ()
23684 For structure and union types, this method returns the fields. Range
23685 types have two fields, the minimum and maximum values. Enum types
23686 have one field per enum constant. Function and method types have one
23687 field per parameter. The base types of C@t{++} classes are also
23688 represented as fields. If the type has no fields, or does not fit
23689 into one of these categories, an empty sequence will be returned.
23691 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23694 This attribute is not available for @code{static} fields (as in
23695 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23696 position of the field. For @code{enum} fields, the value is the
23697 enumeration member's integer representation.
23700 The name of the field, or @code{None} for anonymous fields.
23703 This is @code{True} if the field is artificial, usually meaning that
23704 it was provided by the compiler and not the user. This attribute is
23705 always provided, and is @code{False} if the field is not artificial.
23707 @item is_base_class
23708 This is @code{True} if the field represents a base class of a C@t{++}
23709 structure. This attribute is always provided, and is @code{False}
23710 if the field is not a base class of the type that is the argument of
23711 @code{fields}, or if that type was not a C@t{++} class.
23714 If the field is packed, or is a bitfield, then this will have a
23715 non-zero value, which is the size of the field in bits. Otherwise,
23716 this will be zero; in this case the field's size is given by its type.
23719 The type of the field. This is usually an instance of @code{Type},
23720 but it can be @code{None} in some situations.
23724 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23725 Return a new @code{gdb.Type} object which represents an array of this
23726 type. If one argument is given, it is the inclusive upper bound of
23727 the array; in this case the lower bound is zero. If two arguments are
23728 given, the first argument is the lower bound of the array, and the
23729 second argument is the upper bound of the array. An array's length
23730 must not be negative, but the bounds can be.
23733 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23734 Return a new @code{gdb.Type} object which represents a vector of this
23735 type. If one argument is given, it is the inclusive upper bound of
23736 the vector; in this case the lower bound is zero. If two arguments are
23737 given, the first argument is the lower bound of the vector, and the
23738 second argument is the upper bound of the vector. A vector's length
23739 must not be negative, but the bounds can be.
23741 The difference between an @code{array} and a @code{vector} is that
23742 arrays behave like in C: when used in expressions they decay to a pointer
23743 to the first element whereas vectors are treated as first class values.
23746 @defun Type.const ()
23747 Return a new @code{gdb.Type} object which represents a
23748 @code{const}-qualified variant of this type.
23751 @defun Type.volatile ()
23752 Return a new @code{gdb.Type} object which represents a
23753 @code{volatile}-qualified variant of this type.
23756 @defun Type.unqualified ()
23757 Return a new @code{gdb.Type} object which represents an unqualified
23758 variant of this type. That is, the result is neither @code{const} nor
23762 @defun Type.range ()
23763 Return a Python @code{Tuple} object that contains two elements: the
23764 low bound of the argument type and the high bound of that type. If
23765 the type does not have a range, @value{GDBN} will raise a
23766 @code{gdb.error} exception (@pxref{Exception Handling}).
23769 @defun Type.reference ()
23770 Return a new @code{gdb.Type} object which represents a reference to this
23774 @defun Type.pointer ()
23775 Return a new @code{gdb.Type} object which represents a pointer to this
23779 @defun Type.strip_typedefs ()
23780 Return a new @code{gdb.Type} that represents the real type,
23781 after removing all layers of typedefs.
23784 @defun Type.target ()
23785 Return a new @code{gdb.Type} object which represents the target type
23788 For a pointer type, the target type is the type of the pointed-to
23789 object. For an array type (meaning C-like arrays), the target type is
23790 the type of the elements of the array. For a function or method type,
23791 the target type is the type of the return value. For a complex type,
23792 the target type is the type of the elements. For a typedef, the
23793 target type is the aliased type.
23795 If the type does not have a target, this method will throw an
23799 @defun Type.template_argument (n @r{[}, block@r{]})
23800 If this @code{gdb.Type} is an instantiation of a template, this will
23801 return a new @code{gdb.Type} which represents the type of the
23802 @var{n}th template argument.
23804 If this @code{gdb.Type} is not a template type, this will throw an
23805 exception. Ordinarily, only C@t{++} code will have template types.
23807 If @var{block} is given, then @var{name} is looked up in that scope.
23808 Otherwise, it is searched for globally.
23812 Each type has a code, which indicates what category this type falls
23813 into. The available type categories are represented by constants
23814 defined in the @code{gdb} module:
23817 @findex TYPE_CODE_PTR
23818 @findex gdb.TYPE_CODE_PTR
23819 @item gdb.TYPE_CODE_PTR
23820 The type is a pointer.
23822 @findex TYPE_CODE_ARRAY
23823 @findex gdb.TYPE_CODE_ARRAY
23824 @item gdb.TYPE_CODE_ARRAY
23825 The type is an array.
23827 @findex TYPE_CODE_STRUCT
23828 @findex gdb.TYPE_CODE_STRUCT
23829 @item gdb.TYPE_CODE_STRUCT
23830 The type is a structure.
23832 @findex TYPE_CODE_UNION
23833 @findex gdb.TYPE_CODE_UNION
23834 @item gdb.TYPE_CODE_UNION
23835 The type is a union.
23837 @findex TYPE_CODE_ENUM
23838 @findex gdb.TYPE_CODE_ENUM
23839 @item gdb.TYPE_CODE_ENUM
23840 The type is an enum.
23842 @findex TYPE_CODE_FLAGS
23843 @findex gdb.TYPE_CODE_FLAGS
23844 @item gdb.TYPE_CODE_FLAGS
23845 A bit flags type, used for things such as status registers.
23847 @findex TYPE_CODE_FUNC
23848 @findex gdb.TYPE_CODE_FUNC
23849 @item gdb.TYPE_CODE_FUNC
23850 The type is a function.
23852 @findex TYPE_CODE_INT
23853 @findex gdb.TYPE_CODE_INT
23854 @item gdb.TYPE_CODE_INT
23855 The type is an integer type.
23857 @findex TYPE_CODE_FLT
23858 @findex gdb.TYPE_CODE_FLT
23859 @item gdb.TYPE_CODE_FLT
23860 A floating point type.
23862 @findex TYPE_CODE_VOID
23863 @findex gdb.TYPE_CODE_VOID
23864 @item gdb.TYPE_CODE_VOID
23865 The special type @code{void}.
23867 @findex TYPE_CODE_SET
23868 @findex gdb.TYPE_CODE_SET
23869 @item gdb.TYPE_CODE_SET
23872 @findex TYPE_CODE_RANGE
23873 @findex gdb.TYPE_CODE_RANGE
23874 @item gdb.TYPE_CODE_RANGE
23875 A range type, that is, an integer type with bounds.
23877 @findex TYPE_CODE_STRING
23878 @findex gdb.TYPE_CODE_STRING
23879 @item gdb.TYPE_CODE_STRING
23880 A string type. Note that this is only used for certain languages with
23881 language-defined string types; C strings are not represented this way.
23883 @findex TYPE_CODE_BITSTRING
23884 @findex gdb.TYPE_CODE_BITSTRING
23885 @item gdb.TYPE_CODE_BITSTRING
23886 A string of bits. It is deprecated.
23888 @findex TYPE_CODE_ERROR
23889 @findex gdb.TYPE_CODE_ERROR
23890 @item gdb.TYPE_CODE_ERROR
23891 An unknown or erroneous type.
23893 @findex TYPE_CODE_METHOD
23894 @findex gdb.TYPE_CODE_METHOD
23895 @item gdb.TYPE_CODE_METHOD
23896 A method type, as found in C@t{++} or Java.
23898 @findex TYPE_CODE_METHODPTR
23899 @findex gdb.TYPE_CODE_METHODPTR
23900 @item gdb.TYPE_CODE_METHODPTR
23901 A pointer-to-member-function.
23903 @findex TYPE_CODE_MEMBERPTR
23904 @findex gdb.TYPE_CODE_MEMBERPTR
23905 @item gdb.TYPE_CODE_MEMBERPTR
23906 A pointer-to-member.
23908 @findex TYPE_CODE_REF
23909 @findex gdb.TYPE_CODE_REF
23910 @item gdb.TYPE_CODE_REF
23913 @findex TYPE_CODE_CHAR
23914 @findex gdb.TYPE_CODE_CHAR
23915 @item gdb.TYPE_CODE_CHAR
23918 @findex TYPE_CODE_BOOL
23919 @findex gdb.TYPE_CODE_BOOL
23920 @item gdb.TYPE_CODE_BOOL
23923 @findex TYPE_CODE_COMPLEX
23924 @findex gdb.TYPE_CODE_COMPLEX
23925 @item gdb.TYPE_CODE_COMPLEX
23926 A complex float type.
23928 @findex TYPE_CODE_TYPEDEF
23929 @findex gdb.TYPE_CODE_TYPEDEF
23930 @item gdb.TYPE_CODE_TYPEDEF
23931 A typedef to some other type.
23933 @findex TYPE_CODE_NAMESPACE
23934 @findex gdb.TYPE_CODE_NAMESPACE
23935 @item gdb.TYPE_CODE_NAMESPACE
23936 A C@t{++} namespace.
23938 @findex TYPE_CODE_DECFLOAT
23939 @findex gdb.TYPE_CODE_DECFLOAT
23940 @item gdb.TYPE_CODE_DECFLOAT
23941 A decimal floating point type.
23943 @findex TYPE_CODE_INTERNAL_FUNCTION
23944 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23945 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23946 A function internal to @value{GDBN}. This is the type used to represent
23947 convenience functions.
23950 Further support for types is provided in the @code{gdb.types}
23951 Python module (@pxref{gdb.types}).
23953 @node Pretty Printing API
23954 @subsubsection Pretty Printing API
23956 An example output is provided (@pxref{Pretty Printing}).
23958 A pretty-printer is just an object that holds a value and implements a
23959 specific interface, defined here.
23961 @defun pretty_printer.children (self)
23962 @value{GDBN} will call this method on a pretty-printer to compute the
23963 children of the pretty-printer's value.
23965 This method must return an object conforming to the Python iterator
23966 protocol. Each item returned by the iterator must be a tuple holding
23967 two elements. The first element is the ``name'' of the child; the
23968 second element is the child's value. The value can be any Python
23969 object which is convertible to a @value{GDBN} value.
23971 This method is optional. If it does not exist, @value{GDBN} will act
23972 as though the value has no children.
23975 @defun pretty_printer.display_hint (self)
23976 The CLI may call this method and use its result to change the
23977 formatting of a value. The result will also be supplied to an MI
23978 consumer as a @samp{displayhint} attribute of the variable being
23981 This method is optional. If it does exist, this method must return a
23984 Some display hints are predefined by @value{GDBN}:
23988 Indicate that the object being printed is ``array-like''. The CLI
23989 uses this to respect parameters such as @code{set print elements} and
23990 @code{set print array}.
23993 Indicate that the object being printed is ``map-like'', and that the
23994 children of this value can be assumed to alternate between keys and
23998 Indicate that the object being printed is ``string-like''. If the
23999 printer's @code{to_string} method returns a Python string of some
24000 kind, then @value{GDBN} will call its internal language-specific
24001 string-printing function to format the string. For the CLI this means
24002 adding quotation marks, possibly escaping some characters, respecting
24003 @code{set print elements}, and the like.
24007 @defun pretty_printer.to_string (self)
24008 @value{GDBN} will call this method to display the string
24009 representation of the value passed to the object's constructor.
24011 When printing from the CLI, if the @code{to_string} method exists,
24012 then @value{GDBN} will prepend its result to the values returned by
24013 @code{children}. Exactly how this formatting is done is dependent on
24014 the display hint, and may change as more hints are added. Also,
24015 depending on the print settings (@pxref{Print Settings}), the CLI may
24016 print just the result of @code{to_string} in a stack trace, omitting
24017 the result of @code{children}.
24019 If this method returns a string, it is printed verbatim.
24021 Otherwise, if this method returns an instance of @code{gdb.Value},
24022 then @value{GDBN} prints this value. This may result in a call to
24023 another pretty-printer.
24025 If instead the method returns a Python value which is convertible to a
24026 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24027 the resulting value. Again, this may result in a call to another
24028 pretty-printer. Python scalars (integers, floats, and booleans) and
24029 strings are convertible to @code{gdb.Value}; other types are not.
24031 Finally, if this method returns @code{None} then no further operations
24032 are peformed in this method and nothing is printed.
24034 If the result is not one of these types, an exception is raised.
24037 @value{GDBN} provides a function which can be used to look up the
24038 default pretty-printer for a @code{gdb.Value}:
24040 @findex gdb.default_visualizer
24041 @defun gdb.default_visualizer (value)
24042 This function takes a @code{gdb.Value} object as an argument. If a
24043 pretty-printer for this value exists, then it is returned. If no such
24044 printer exists, then this returns @code{None}.
24047 @node Selecting Pretty-Printers
24048 @subsubsection Selecting Pretty-Printers
24050 The Python list @code{gdb.pretty_printers} contains an array of
24051 functions or callable objects that have been registered via addition
24052 as a pretty-printer. Printers in this list are called @code{global}
24053 printers, they're available when debugging all inferiors.
24054 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24055 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24058 Each function on these lists is passed a single @code{gdb.Value}
24059 argument and should return a pretty-printer object conforming to the
24060 interface definition above (@pxref{Pretty Printing API}). If a function
24061 cannot create a pretty-printer for the value, it should return
24064 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24065 @code{gdb.Objfile} in the current program space and iteratively calls
24066 each enabled lookup routine in the list for that @code{gdb.Objfile}
24067 until it receives a pretty-printer object.
24068 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24069 searches the pretty-printer list of the current program space,
24070 calling each enabled function until an object is returned.
24071 After these lists have been exhausted, it tries the global
24072 @code{gdb.pretty_printers} list, again calling each enabled function until an
24073 object is returned.
24075 The order in which the objfiles are searched is not specified. For a
24076 given list, functions are always invoked from the head of the list,
24077 and iterated over sequentially until the end of the list, or a printer
24078 object is returned.
24080 For various reasons a pretty-printer may not work.
24081 For example, the underlying data structure may have changed and
24082 the pretty-printer is out of date.
24084 The consequences of a broken pretty-printer are severe enough that
24085 @value{GDBN} provides support for enabling and disabling individual
24086 printers. For example, if @code{print frame-arguments} is on,
24087 a backtrace can become highly illegible if any argument is printed
24088 with a broken printer.
24090 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24091 attribute to the registered function or callable object. If this attribute
24092 is present and its value is @code{False}, the printer is disabled, otherwise
24093 the printer is enabled.
24095 @node Writing a Pretty-Printer
24096 @subsubsection Writing a Pretty-Printer
24097 @cindex writing a pretty-printer
24099 A pretty-printer consists of two parts: a lookup function to detect
24100 if the type is supported, and the printer itself.
24102 Here is an example showing how a @code{std::string} printer might be
24103 written. @xref{Pretty Printing API}, for details on the API this class
24107 class StdStringPrinter(object):
24108 "Print a std::string"
24110 def __init__(self, val):
24113 def to_string(self):
24114 return self.val['_M_dataplus']['_M_p']
24116 def display_hint(self):
24120 And here is an example showing how a lookup function for the printer
24121 example above might be written.
24124 def str_lookup_function(val):
24125 lookup_tag = val.type.tag
24126 if lookup_tag == None:
24128 regex = re.compile("^std::basic_string<char,.*>$")
24129 if regex.match(lookup_tag):
24130 return StdStringPrinter(val)
24134 The example lookup function extracts the value's type, and attempts to
24135 match it to a type that it can pretty-print. If it is a type the
24136 printer can pretty-print, it will return a printer object. If not, it
24137 returns @code{None}.
24139 We recommend that you put your core pretty-printers into a Python
24140 package. If your pretty-printers are for use with a library, we
24141 further recommend embedding a version number into the package name.
24142 This practice will enable @value{GDBN} to load multiple versions of
24143 your pretty-printers at the same time, because they will have
24146 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24147 can be evaluated multiple times without changing its meaning. An
24148 ideal auto-load file will consist solely of @code{import}s of your
24149 printer modules, followed by a call to a register pretty-printers with
24150 the current objfile.
24152 Taken as a whole, this approach will scale nicely to multiple
24153 inferiors, each potentially using a different library version.
24154 Embedding a version number in the Python package name will ensure that
24155 @value{GDBN} is able to load both sets of printers simultaneously.
24156 Then, because the search for pretty-printers is done by objfile, and
24157 because your auto-loaded code took care to register your library's
24158 printers with a specific objfile, @value{GDBN} will find the correct
24159 printers for the specific version of the library used by each
24162 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24163 this code might appear in @code{gdb.libstdcxx.v6}:
24166 def register_printers(objfile):
24167 objfile.pretty_printers.append(str_lookup_function)
24171 And then the corresponding contents of the auto-load file would be:
24174 import gdb.libstdcxx.v6
24175 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24178 The previous example illustrates a basic pretty-printer.
24179 There are a few things that can be improved on.
24180 The printer doesn't have a name, making it hard to identify in a
24181 list of installed printers. The lookup function has a name, but
24182 lookup functions can have arbitrary, even identical, names.
24184 Second, the printer only handles one type, whereas a library typically has
24185 several types. One could install a lookup function for each desired type
24186 in the library, but one could also have a single lookup function recognize
24187 several types. The latter is the conventional way this is handled.
24188 If a pretty-printer can handle multiple data types, then its
24189 @dfn{subprinters} are the printers for the individual data types.
24191 The @code{gdb.printing} module provides a formal way of solving these
24192 problems (@pxref{gdb.printing}).
24193 Here is another example that handles multiple types.
24195 These are the types we are going to pretty-print:
24198 struct foo @{ int a, b; @};
24199 struct bar @{ struct foo x, y; @};
24202 Here are the printers:
24206 """Print a foo object."""
24208 def __init__(self, val):
24211 def to_string(self):
24212 return ("a=<" + str(self.val["a"]) +
24213 "> b=<" + str(self.val["b"]) + ">")
24216 """Print a bar object."""
24218 def __init__(self, val):
24221 def to_string(self):
24222 return ("x=<" + str(self.val["x"]) +
24223 "> y=<" + str(self.val["y"]) + ">")
24226 This example doesn't need a lookup function, that is handled by the
24227 @code{gdb.printing} module. Instead a function is provided to build up
24228 the object that handles the lookup.
24231 import gdb.printing
24233 def build_pretty_printer():
24234 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24236 pp.add_printer('foo', '^foo$', fooPrinter)
24237 pp.add_printer('bar', '^bar$', barPrinter)
24241 And here is the autoload support:
24244 import gdb.printing
24246 gdb.printing.register_pretty_printer(
24247 gdb.current_objfile(),
24248 my_library.build_pretty_printer())
24251 Finally, when this printer is loaded into @value{GDBN}, here is the
24252 corresponding output of @samp{info pretty-printer}:
24255 (gdb) info pretty-printer
24262 @node Type Printing API
24263 @subsubsection Type Printing API
24264 @cindex type printing API for Python
24266 @value{GDBN} provides a way for Python code to customize type display.
24267 This is mainly useful for substituting canonical typedef names for
24270 @cindex type printer
24271 A @dfn{type printer} is just a Python object conforming to a certain
24272 protocol. A simple base class implementing the protocol is provided;
24273 see @ref{gdb.types}. A type printer must supply at least:
24275 @defivar type_printer enabled
24276 A boolean which is True if the printer is enabled, and False
24277 otherwise. This is manipulated by the @code{enable type-printer}
24278 and @code{disable type-printer} commands.
24281 @defivar type_printer name
24282 The name of the type printer. This must be a string. This is used by
24283 the @code{enable type-printer} and @code{disable type-printer}
24287 @defmethod type_printer instantiate (self)
24288 This is called by @value{GDBN} at the start of type-printing. It is
24289 only called if the type printer is enabled. This method must return a
24290 new object that supplies a @code{recognize} method, as described below.
24294 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24295 will compute a list of type recognizers. This is done by iterating
24296 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24297 followed by the per-progspace type printers (@pxref{Progspaces In
24298 Python}), and finally the global type printers.
24300 @value{GDBN} will call the @code{instantiate} method of each enabled
24301 type printer. If this method returns @code{None}, then the result is
24302 ignored; otherwise, it is appended to the list of recognizers.
24304 Then, when @value{GDBN} is going to display a type name, it iterates
24305 over the list of recognizers. For each one, it calls the recognition
24306 function, stopping if the function returns a non-@code{None} value.
24307 The recognition function is defined as:
24309 @defmethod type_recognizer recognize (self, type)
24310 If @var{type} is not recognized, return @code{None}. Otherwise,
24311 return a string which is to be printed as the name of @var{type}.
24312 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24316 @value{GDBN} uses this two-pass approach so that type printers can
24317 efficiently cache information without holding on to it too long. For
24318 example, it can be convenient to look up type information in a type
24319 printer and hold it for a recognizer's lifetime; if a single pass were
24320 done then type printers would have to make use of the event system in
24321 order to avoid holding information that could become stale as the
24324 @node Inferiors In Python
24325 @subsubsection Inferiors In Python
24326 @cindex inferiors in Python
24328 @findex gdb.Inferior
24329 Programs which are being run under @value{GDBN} are called inferiors
24330 (@pxref{Inferiors and Programs}). Python scripts can access
24331 information about and manipulate inferiors controlled by @value{GDBN}
24332 via objects of the @code{gdb.Inferior} class.
24334 The following inferior-related functions are available in the @code{gdb}
24337 @defun gdb.inferiors ()
24338 Return a tuple containing all inferior objects.
24341 @defun gdb.selected_inferior ()
24342 Return an object representing the current inferior.
24345 A @code{gdb.Inferior} object has the following attributes:
24347 @defvar Inferior.num
24348 ID of inferior, as assigned by GDB.
24351 @defvar Inferior.pid
24352 Process ID of the inferior, as assigned by the underlying operating
24356 @defvar Inferior.was_attached
24357 Boolean signaling whether the inferior was created using `attach', or
24358 started by @value{GDBN} itself.
24361 A @code{gdb.Inferior} object has the following methods:
24363 @defun Inferior.is_valid ()
24364 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24365 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24366 if the inferior no longer exists within @value{GDBN}. All other
24367 @code{gdb.Inferior} methods will throw an exception if it is invalid
24368 at the time the method is called.
24371 @defun Inferior.threads ()
24372 This method returns a tuple holding all the threads which are valid
24373 when it is called. If there are no valid threads, the method will
24374 return an empty tuple.
24377 @findex Inferior.read_memory
24378 @defun Inferior.read_memory (address, length)
24379 Read @var{length} bytes of memory from the inferior, starting at
24380 @var{address}. Returns a buffer object, which behaves much like an array
24381 or a string. It can be modified and given to the
24382 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24383 value is a @code{memoryview} object.
24386 @findex Inferior.write_memory
24387 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24388 Write the contents of @var{buffer} to the inferior, starting at
24389 @var{address}. The @var{buffer} parameter must be a Python object
24390 which supports the buffer protocol, i.e., a string, an array or the
24391 object returned from @code{Inferior.read_memory}. If given, @var{length}
24392 determines the number of bytes from @var{buffer} to be written.
24395 @findex gdb.search_memory
24396 @defun Inferior.search_memory (address, length, pattern)
24397 Search a region of the inferior memory starting at @var{address} with
24398 the given @var{length} using the search pattern supplied in
24399 @var{pattern}. The @var{pattern} parameter must be a Python object
24400 which supports the buffer protocol, i.e., a string, an array or the
24401 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24402 containing the address where the pattern was found, or @code{None} if
24403 the pattern could not be found.
24406 @node Events In Python
24407 @subsubsection Events In Python
24408 @cindex inferior events in Python
24410 @value{GDBN} provides a general event facility so that Python code can be
24411 notified of various state changes, particularly changes that occur in
24414 An @dfn{event} is just an object that describes some state change. The
24415 type of the object and its attributes will vary depending on the details
24416 of the change. All the existing events are described below.
24418 In order to be notified of an event, you must register an event handler
24419 with an @dfn{event registry}. An event registry is an object in the
24420 @code{gdb.events} module which dispatches particular events. A registry
24421 provides methods to register and unregister event handlers:
24423 @defun EventRegistry.connect (object)
24424 Add the given callable @var{object} to the registry. This object will be
24425 called when an event corresponding to this registry occurs.
24428 @defun EventRegistry.disconnect (object)
24429 Remove the given @var{object} from the registry. Once removed, the object
24430 will no longer receive notifications of events.
24433 Here is an example:
24436 def exit_handler (event):
24437 print "event type: exit"
24438 print "exit code: %d" % (event.exit_code)
24440 gdb.events.exited.connect (exit_handler)
24443 In the above example we connect our handler @code{exit_handler} to the
24444 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24445 called when the inferior exits. The argument @dfn{event} in this example is
24446 of type @code{gdb.ExitedEvent}. As you can see in the example the
24447 @code{ExitedEvent} object has an attribute which indicates the exit code of
24450 The following is a listing of the event registries that are available and
24451 details of the events they emit:
24456 Emits @code{gdb.ThreadEvent}.
24458 Some events can be thread specific when @value{GDBN} is running in non-stop
24459 mode. When represented in Python, these events all extend
24460 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24461 events which are emitted by this or other modules might extend this event.
24462 Examples of these events are @code{gdb.BreakpointEvent} and
24463 @code{gdb.ContinueEvent}.
24465 @defvar ThreadEvent.inferior_thread
24466 In non-stop mode this attribute will be set to the specific thread which was
24467 involved in the emitted event. Otherwise, it will be set to @code{None}.
24470 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24472 This event indicates that the inferior has been continued after a stop. For
24473 inherited attribute refer to @code{gdb.ThreadEvent} above.
24475 @item events.exited
24476 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24477 @code{events.ExitedEvent} has two attributes:
24478 @defvar ExitedEvent.exit_code
24479 An integer representing the exit code, if available, which the inferior
24480 has returned. (The exit code could be unavailable if, for example,
24481 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24482 the attribute does not exist.
24484 @defvar ExitedEvent inferior
24485 A reference to the inferior which triggered the @code{exited} event.
24489 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24491 Indicates that the inferior has stopped. All events emitted by this registry
24492 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24493 will indicate the stopped thread when @value{GDBN} is running in non-stop
24494 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24496 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24498 This event indicates that the inferior or one of its threads has received as
24499 signal. @code{gdb.SignalEvent} has the following attributes:
24501 @defvar SignalEvent.stop_signal
24502 A string representing the signal received by the inferior. A list of possible
24503 signal values can be obtained by running the command @code{info signals} in
24504 the @value{GDBN} command prompt.
24507 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24509 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24510 been hit, and has the following attributes:
24512 @defvar BreakpointEvent.breakpoints
24513 A sequence containing references to all the breakpoints (type
24514 @code{gdb.Breakpoint}) that were hit.
24515 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24517 @defvar BreakpointEvent.breakpoint
24518 A reference to the first breakpoint that was hit.
24519 This function is maintained for backward compatibility and is now deprecated
24520 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24523 @item events.new_objfile
24524 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24525 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24527 @defvar NewObjFileEvent.new_objfile
24528 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24529 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24534 @node Threads In Python
24535 @subsubsection Threads In Python
24536 @cindex threads in python
24538 @findex gdb.InferiorThread
24539 Python scripts can access information about, and manipulate inferior threads
24540 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24542 The following thread-related functions are available in the @code{gdb}
24545 @findex gdb.selected_thread
24546 @defun gdb.selected_thread ()
24547 This function returns the thread object for the selected thread. If there
24548 is no selected thread, this will return @code{None}.
24551 A @code{gdb.InferiorThread} object has the following attributes:
24553 @defvar InferiorThread.name
24554 The name of the thread. If the user specified a name using
24555 @code{thread name}, then this returns that name. Otherwise, if an
24556 OS-supplied name is available, then it is returned. Otherwise, this
24557 returns @code{None}.
24559 This attribute can be assigned to. The new value must be a string
24560 object, which sets the new name, or @code{None}, which removes any
24561 user-specified thread name.
24564 @defvar InferiorThread.num
24565 ID of the thread, as assigned by GDB.
24568 @defvar InferiorThread.ptid
24569 ID of the thread, as assigned by the operating system. This attribute is a
24570 tuple containing three integers. The first is the Process ID (PID); the second
24571 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24572 Either the LWPID or TID may be 0, which indicates that the operating system
24573 does not use that identifier.
24576 A @code{gdb.InferiorThread} object has the following methods:
24578 @defun InferiorThread.is_valid ()
24579 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24580 @code{False} if not. A @code{gdb.InferiorThread} object will become
24581 invalid if the thread exits, or the inferior that the thread belongs
24582 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24583 exception if it is invalid at the time the method is called.
24586 @defun InferiorThread.switch ()
24587 This changes @value{GDBN}'s currently selected thread to the one represented
24591 @defun InferiorThread.is_stopped ()
24592 Return a Boolean indicating whether the thread is stopped.
24595 @defun InferiorThread.is_running ()
24596 Return a Boolean indicating whether the thread is running.
24599 @defun InferiorThread.is_exited ()
24600 Return a Boolean indicating whether the thread is exited.
24603 @node Commands In Python
24604 @subsubsection Commands In Python
24606 @cindex commands in python
24607 @cindex python commands
24608 You can implement new @value{GDBN} CLI commands in Python. A CLI
24609 command is implemented using an instance of the @code{gdb.Command}
24610 class, most commonly using a subclass.
24612 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24613 The object initializer for @code{Command} registers the new command
24614 with @value{GDBN}. This initializer is normally invoked from the
24615 subclass' own @code{__init__} method.
24617 @var{name} is the name of the command. If @var{name} consists of
24618 multiple words, then the initial words are looked for as prefix
24619 commands. In this case, if one of the prefix commands does not exist,
24620 an exception is raised.
24622 There is no support for multi-line commands.
24624 @var{command_class} should be one of the @samp{COMMAND_} constants
24625 defined below. This argument tells @value{GDBN} how to categorize the
24626 new command in the help system.
24628 @var{completer_class} is an optional argument. If given, it should be
24629 one of the @samp{COMPLETE_} constants defined below. This argument
24630 tells @value{GDBN} how to perform completion for this command. If not
24631 given, @value{GDBN} will attempt to complete using the object's
24632 @code{complete} method (see below); if no such method is found, an
24633 error will occur when completion is attempted.
24635 @var{prefix} is an optional argument. If @code{True}, then the new
24636 command is a prefix command; sub-commands of this command may be
24639 The help text for the new command is taken from the Python
24640 documentation string for the command's class, if there is one. If no
24641 documentation string is provided, the default value ``This command is
24642 not documented.'' is used.
24645 @cindex don't repeat Python command
24646 @defun Command.dont_repeat ()
24647 By default, a @value{GDBN} command is repeated when the user enters a
24648 blank line at the command prompt. A command can suppress this
24649 behavior by invoking the @code{dont_repeat} method. This is similar
24650 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24653 @defun Command.invoke (argument, from_tty)
24654 This method is called by @value{GDBN} when this command is invoked.
24656 @var{argument} is a string. It is the argument to the command, after
24657 leading and trailing whitespace has been stripped.
24659 @var{from_tty} is a boolean argument. When true, this means that the
24660 command was entered by the user at the terminal; when false it means
24661 that the command came from elsewhere.
24663 If this method throws an exception, it is turned into a @value{GDBN}
24664 @code{error} call. Otherwise, the return value is ignored.
24666 @findex gdb.string_to_argv
24667 To break @var{argument} up into an argv-like string use
24668 @code{gdb.string_to_argv}. This function behaves identically to
24669 @value{GDBN}'s internal argument lexer @code{buildargv}.
24670 It is recommended to use this for consistency.
24671 Arguments are separated by spaces and may be quoted.
24675 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24676 ['1', '2 "3', '4 "5', "6 '7"]
24681 @cindex completion of Python commands
24682 @defun Command.complete (text, word)
24683 This method is called by @value{GDBN} when the user attempts
24684 completion on this command. All forms of completion are handled by
24685 this method, that is, the @key{TAB} and @key{M-?} key bindings
24686 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24689 The arguments @var{text} and @var{word} are both strings. @var{text}
24690 holds the complete command line up to the cursor's location.
24691 @var{word} holds the last word of the command line; this is computed
24692 using a word-breaking heuristic.
24694 The @code{complete} method can return several values:
24697 If the return value is a sequence, the contents of the sequence are
24698 used as the completions. It is up to @code{complete} to ensure that the
24699 contents actually do complete the word. A zero-length sequence is
24700 allowed, it means that there were no completions available. Only
24701 string elements of the sequence are used; other elements in the
24702 sequence are ignored.
24705 If the return value is one of the @samp{COMPLETE_} constants defined
24706 below, then the corresponding @value{GDBN}-internal completion
24707 function is invoked, and its result is used.
24710 All other results are treated as though there were no available
24715 When a new command is registered, it must be declared as a member of
24716 some general class of commands. This is used to classify top-level
24717 commands in the on-line help system; note that prefix commands are not
24718 listed under their own category but rather that of their top-level
24719 command. The available classifications are represented by constants
24720 defined in the @code{gdb} module:
24723 @findex COMMAND_NONE
24724 @findex gdb.COMMAND_NONE
24725 @item gdb.COMMAND_NONE
24726 The command does not belong to any particular class. A command in
24727 this category will not be displayed in any of the help categories.
24729 @findex COMMAND_RUNNING
24730 @findex gdb.COMMAND_RUNNING
24731 @item gdb.COMMAND_RUNNING
24732 The command is related to running the inferior. For example,
24733 @code{start}, @code{step}, and @code{continue} are in this category.
24734 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24735 commands in this category.
24737 @findex COMMAND_DATA
24738 @findex gdb.COMMAND_DATA
24739 @item gdb.COMMAND_DATA
24740 The command is related to data or variables. For example,
24741 @code{call}, @code{find}, and @code{print} are in this category. Type
24742 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24745 @findex COMMAND_STACK
24746 @findex gdb.COMMAND_STACK
24747 @item gdb.COMMAND_STACK
24748 The command has to do with manipulation of the stack. For example,
24749 @code{backtrace}, @code{frame}, and @code{return} are in this
24750 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24751 list of commands in this category.
24753 @findex COMMAND_FILES
24754 @findex gdb.COMMAND_FILES
24755 @item gdb.COMMAND_FILES
24756 This class is used for file-related commands. For example,
24757 @code{file}, @code{list} and @code{section} are in this category.
24758 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24759 commands in this category.
24761 @findex COMMAND_SUPPORT
24762 @findex gdb.COMMAND_SUPPORT
24763 @item gdb.COMMAND_SUPPORT
24764 This should be used for ``support facilities'', generally meaning
24765 things that are useful to the user when interacting with @value{GDBN},
24766 but not related to the state of the inferior. For example,
24767 @code{help}, @code{make}, and @code{shell} are in this category. Type
24768 @kbd{help support} at the @value{GDBN} prompt to see a list of
24769 commands in this category.
24771 @findex COMMAND_STATUS
24772 @findex gdb.COMMAND_STATUS
24773 @item gdb.COMMAND_STATUS
24774 The command is an @samp{info}-related command, that is, related to the
24775 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24776 and @code{show} are in this category. Type @kbd{help status} at the
24777 @value{GDBN} prompt to see a list of commands in this category.
24779 @findex COMMAND_BREAKPOINTS
24780 @findex gdb.COMMAND_BREAKPOINTS
24781 @item gdb.COMMAND_BREAKPOINTS
24782 The command has to do with breakpoints. For example, @code{break},
24783 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24784 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24787 @findex COMMAND_TRACEPOINTS
24788 @findex gdb.COMMAND_TRACEPOINTS
24789 @item gdb.COMMAND_TRACEPOINTS
24790 The command has to do with tracepoints. For example, @code{trace},
24791 @code{actions}, and @code{tfind} are in this category. Type
24792 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24793 commands in this category.
24795 @findex COMMAND_USER
24796 @findex gdb.COMMAND_USER
24797 @item gdb.COMMAND_USER
24798 The command is a general purpose command for the user, and typically
24799 does not fit in one of the other categories.
24800 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24801 a list of commands in this category, as well as the list of gdb macros
24802 (@pxref{Sequences}).
24804 @findex COMMAND_OBSCURE
24805 @findex gdb.COMMAND_OBSCURE
24806 @item gdb.COMMAND_OBSCURE
24807 The command is only used in unusual circumstances, or is not of
24808 general interest to users. For example, @code{checkpoint},
24809 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24810 obscure} at the @value{GDBN} prompt to see a list of commands in this
24813 @findex COMMAND_MAINTENANCE
24814 @findex gdb.COMMAND_MAINTENANCE
24815 @item gdb.COMMAND_MAINTENANCE
24816 The command is only useful to @value{GDBN} maintainers. The
24817 @code{maintenance} and @code{flushregs} commands are in this category.
24818 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24819 commands in this category.
24822 A new command can use a predefined completion function, either by
24823 specifying it via an argument at initialization, or by returning it
24824 from the @code{complete} method. These predefined completion
24825 constants are all defined in the @code{gdb} module:
24828 @findex COMPLETE_NONE
24829 @findex gdb.COMPLETE_NONE
24830 @item gdb.COMPLETE_NONE
24831 This constant means that no completion should be done.
24833 @findex COMPLETE_FILENAME
24834 @findex gdb.COMPLETE_FILENAME
24835 @item gdb.COMPLETE_FILENAME
24836 This constant means that filename completion should be performed.
24838 @findex COMPLETE_LOCATION
24839 @findex gdb.COMPLETE_LOCATION
24840 @item gdb.COMPLETE_LOCATION
24841 This constant means that location completion should be done.
24842 @xref{Specify Location}.
24844 @findex COMPLETE_COMMAND
24845 @findex gdb.COMPLETE_COMMAND
24846 @item gdb.COMPLETE_COMMAND
24847 This constant means that completion should examine @value{GDBN}
24850 @findex COMPLETE_SYMBOL
24851 @findex gdb.COMPLETE_SYMBOL
24852 @item gdb.COMPLETE_SYMBOL
24853 This constant means that completion should be done using symbol names
24857 The following code snippet shows how a trivial CLI command can be
24858 implemented in Python:
24861 class HelloWorld (gdb.Command):
24862 """Greet the whole world."""
24864 def __init__ (self):
24865 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24867 def invoke (self, arg, from_tty):
24868 print "Hello, World!"
24873 The last line instantiates the class, and is necessary to trigger the
24874 registration of the command with @value{GDBN}. Depending on how the
24875 Python code is read into @value{GDBN}, you may need to import the
24876 @code{gdb} module explicitly.
24878 @node Parameters In Python
24879 @subsubsection Parameters In Python
24881 @cindex parameters in python
24882 @cindex python parameters
24883 @tindex gdb.Parameter
24885 You can implement new @value{GDBN} parameters using Python. A new
24886 parameter is implemented as an instance of the @code{gdb.Parameter}
24889 Parameters are exposed to the user via the @code{set} and
24890 @code{show} commands. @xref{Help}.
24892 There are many parameters that already exist and can be set in
24893 @value{GDBN}. Two examples are: @code{set follow fork} and
24894 @code{set charset}. Setting these parameters influences certain
24895 behavior in @value{GDBN}. Similarly, you can define parameters that
24896 can be used to influence behavior in custom Python scripts and commands.
24898 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24899 The object initializer for @code{Parameter} registers the new
24900 parameter with @value{GDBN}. This initializer is normally invoked
24901 from the subclass' own @code{__init__} method.
24903 @var{name} is the name of the new parameter. If @var{name} consists
24904 of multiple words, then the initial words are looked for as prefix
24905 parameters. An example of this can be illustrated with the
24906 @code{set print} set of parameters. If @var{name} is
24907 @code{print foo}, then @code{print} will be searched as the prefix
24908 parameter. In this case the parameter can subsequently be accessed in
24909 @value{GDBN} as @code{set print foo}.
24911 If @var{name} consists of multiple words, and no prefix parameter group
24912 can be found, an exception is raised.
24914 @var{command-class} should be one of the @samp{COMMAND_} constants
24915 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24916 categorize the new parameter in the help system.
24918 @var{parameter-class} should be one of the @samp{PARAM_} constants
24919 defined below. This argument tells @value{GDBN} the type of the new
24920 parameter; this information is used for input validation and
24923 If @var{parameter-class} is @code{PARAM_ENUM}, then
24924 @var{enum-sequence} must be a sequence of strings. These strings
24925 represent the possible values for the parameter.
24927 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24928 of a fourth argument will cause an exception to be thrown.
24930 The help text for the new parameter is taken from the Python
24931 documentation string for the parameter's class, if there is one. If
24932 there is no documentation string, a default value is used.
24935 @defvar Parameter.set_doc
24936 If this attribute exists, and is a string, then its value is used as
24937 the help text for this parameter's @code{set} command. The value is
24938 examined when @code{Parameter.__init__} is invoked; subsequent changes
24942 @defvar Parameter.show_doc
24943 If this attribute exists, and is a string, then its value is used as
24944 the help text for this parameter's @code{show} command. The value is
24945 examined when @code{Parameter.__init__} is invoked; subsequent changes
24949 @defvar Parameter.value
24950 The @code{value} attribute holds the underlying value of the
24951 parameter. It can be read and assigned to just as any other
24952 attribute. @value{GDBN} does validation when assignments are made.
24955 There are two methods that should be implemented in any
24956 @code{Parameter} class. These are:
24958 @defun Parameter.get_set_string (self)
24959 @value{GDBN} will call this method when a @var{parameter}'s value has
24960 been changed via the @code{set} API (for example, @kbd{set foo off}).
24961 The @code{value} attribute has already been populated with the new
24962 value and may be used in output. This method must return a string.
24965 @defun Parameter.get_show_string (self, svalue)
24966 @value{GDBN} will call this method when a @var{parameter}'s
24967 @code{show} API has been invoked (for example, @kbd{show foo}). The
24968 argument @code{svalue} receives the string representation of the
24969 current value. This method must return a string.
24972 When a new parameter is defined, its type must be specified. The
24973 available types are represented by constants defined in the @code{gdb}
24977 @findex PARAM_BOOLEAN
24978 @findex gdb.PARAM_BOOLEAN
24979 @item gdb.PARAM_BOOLEAN
24980 The value is a plain boolean. The Python boolean values, @code{True}
24981 and @code{False} are the only valid values.
24983 @findex PARAM_AUTO_BOOLEAN
24984 @findex gdb.PARAM_AUTO_BOOLEAN
24985 @item gdb.PARAM_AUTO_BOOLEAN
24986 The value has three possible states: true, false, and @samp{auto}. In
24987 Python, true and false are represented using boolean constants, and
24988 @samp{auto} is represented using @code{None}.
24990 @findex PARAM_UINTEGER
24991 @findex gdb.PARAM_UINTEGER
24992 @item gdb.PARAM_UINTEGER
24993 The value is an unsigned integer. The value of 0 should be
24994 interpreted to mean ``unlimited''.
24996 @findex PARAM_INTEGER
24997 @findex gdb.PARAM_INTEGER
24998 @item gdb.PARAM_INTEGER
24999 The value is a signed integer. The value of 0 should be interpreted
25000 to mean ``unlimited''.
25002 @findex PARAM_STRING
25003 @findex gdb.PARAM_STRING
25004 @item gdb.PARAM_STRING
25005 The value is a string. When the user modifies the string, any escape
25006 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25007 translated into corresponding characters and encoded into the current
25010 @findex PARAM_STRING_NOESCAPE
25011 @findex gdb.PARAM_STRING_NOESCAPE
25012 @item gdb.PARAM_STRING_NOESCAPE
25013 The value is a string. When the user modifies the string, escapes are
25014 passed through untranslated.
25016 @findex PARAM_OPTIONAL_FILENAME
25017 @findex gdb.PARAM_OPTIONAL_FILENAME
25018 @item gdb.PARAM_OPTIONAL_FILENAME
25019 The value is a either a filename (a string), or @code{None}.
25021 @findex PARAM_FILENAME
25022 @findex gdb.PARAM_FILENAME
25023 @item gdb.PARAM_FILENAME
25024 The value is a filename. This is just like
25025 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25027 @findex PARAM_ZINTEGER
25028 @findex gdb.PARAM_ZINTEGER
25029 @item gdb.PARAM_ZINTEGER
25030 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25031 is interpreted as itself.
25034 @findex gdb.PARAM_ENUM
25035 @item gdb.PARAM_ENUM
25036 The value is a string, which must be one of a collection string
25037 constants provided when the parameter is created.
25040 @node Functions In Python
25041 @subsubsection Writing new convenience functions
25043 @cindex writing convenience functions
25044 @cindex convenience functions in python
25045 @cindex python convenience functions
25046 @tindex gdb.Function
25048 You can implement new convenience functions (@pxref{Convenience Vars})
25049 in Python. A convenience function is an instance of a subclass of the
25050 class @code{gdb.Function}.
25052 @defun Function.__init__ (name)
25053 The initializer for @code{Function} registers the new function with
25054 @value{GDBN}. The argument @var{name} is the name of the function,
25055 a string. The function will be visible to the user as a convenience
25056 variable of type @code{internal function}, whose name is the same as
25057 the given @var{name}.
25059 The documentation for the new function is taken from the documentation
25060 string for the new class.
25063 @defun Function.invoke (@var{*args})
25064 When a convenience function is evaluated, its arguments are converted
25065 to instances of @code{gdb.Value}, and then the function's
25066 @code{invoke} method is called. Note that @value{GDBN} does not
25067 predetermine the arity of convenience functions. Instead, all
25068 available arguments are passed to @code{invoke}, following the
25069 standard Python calling convention. In particular, a convenience
25070 function can have default values for parameters without ill effect.
25072 The return value of this method is used as its value in the enclosing
25073 expression. If an ordinary Python value is returned, it is converted
25074 to a @code{gdb.Value} following the usual rules.
25077 The following code snippet shows how a trivial convenience function can
25078 be implemented in Python:
25081 class Greet (gdb.Function):
25082 """Return string to greet someone.
25083 Takes a name as argument."""
25085 def __init__ (self):
25086 super (Greet, self).__init__ ("greet")
25088 def invoke (self, name):
25089 return "Hello, %s!" % name.string ()
25094 The last line instantiates the class, and is necessary to trigger the
25095 registration of the function with @value{GDBN}. Depending on how the
25096 Python code is read into @value{GDBN}, you may need to import the
25097 @code{gdb} module explicitly.
25099 Now you can use the function in an expression:
25102 (gdb) print $greet("Bob")
25106 @node Progspaces In Python
25107 @subsubsection Program Spaces In Python
25109 @cindex progspaces in python
25110 @tindex gdb.Progspace
25112 A program space, or @dfn{progspace}, represents a symbolic view
25113 of an address space.
25114 It consists of all of the objfiles of the program.
25115 @xref{Objfiles In Python}.
25116 @xref{Inferiors and Programs, program spaces}, for more details
25117 about program spaces.
25119 The following progspace-related functions are available in the
25122 @findex gdb.current_progspace
25123 @defun gdb.current_progspace ()
25124 This function returns the program space of the currently selected inferior.
25125 @xref{Inferiors and Programs}.
25128 @findex gdb.progspaces
25129 @defun gdb.progspaces ()
25130 Return a sequence of all the progspaces currently known to @value{GDBN}.
25133 Each progspace is represented by an instance of the @code{gdb.Progspace}
25136 @defvar Progspace.filename
25137 The file name of the progspace as a string.
25140 @defvar Progspace.pretty_printers
25141 The @code{pretty_printers} attribute is a list of functions. It is
25142 used to look up pretty-printers. A @code{Value} is passed to each
25143 function in order; if the function returns @code{None}, then the
25144 search continues. Otherwise, the return value should be an object
25145 which is used to format the value. @xref{Pretty Printing API}, for more
25149 @defvar Progspace.type_printers
25150 The @code{type_printers} attribute is a list of type printer objects.
25151 @xref{Type Printing API}, for more information.
25154 @node Objfiles In Python
25155 @subsubsection Objfiles In Python
25157 @cindex objfiles in python
25158 @tindex gdb.Objfile
25160 @value{GDBN} loads symbols for an inferior from various
25161 symbol-containing files (@pxref{Files}). These include the primary
25162 executable file, any shared libraries used by the inferior, and any
25163 separate debug info files (@pxref{Separate Debug Files}).
25164 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25166 The following objfile-related functions are available in the
25169 @findex gdb.current_objfile
25170 @defun gdb.current_objfile ()
25171 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25172 sets the ``current objfile'' to the corresponding objfile. This
25173 function returns the current objfile. If there is no current objfile,
25174 this function returns @code{None}.
25177 @findex gdb.objfiles
25178 @defun gdb.objfiles ()
25179 Return a sequence of all the objfiles current known to @value{GDBN}.
25180 @xref{Objfiles In Python}.
25183 Each objfile is represented by an instance of the @code{gdb.Objfile}
25186 @defvar Objfile.filename
25187 The file name of the objfile as a string.
25190 @defvar Objfile.pretty_printers
25191 The @code{pretty_printers} attribute is a list of functions. It is
25192 used to look up pretty-printers. A @code{Value} is passed to each
25193 function in order; if the function returns @code{None}, then the
25194 search continues. Otherwise, the return value should be an object
25195 which is used to format the value. @xref{Pretty Printing API}, for more
25199 @defvar Objfile.type_printers
25200 The @code{type_printers} attribute is a list of type printer objects.
25201 @xref{Type Printing API}, for more information.
25204 A @code{gdb.Objfile} object has the following methods:
25206 @defun Objfile.is_valid ()
25207 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25208 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25209 if the object file it refers to is not loaded in @value{GDBN} any
25210 longer. All other @code{gdb.Objfile} methods will throw an exception
25211 if it is invalid at the time the method is called.
25214 @node Frames In Python
25215 @subsubsection Accessing inferior stack frames from Python.
25217 @cindex frames in python
25218 When the debugged program stops, @value{GDBN} is able to analyze its call
25219 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25220 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25221 while its corresponding frame exists in the inferior's stack. If you try
25222 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25223 exception (@pxref{Exception Handling}).
25225 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25229 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25233 The following frame-related functions are available in the @code{gdb} module:
25235 @findex gdb.selected_frame
25236 @defun gdb.selected_frame ()
25237 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25240 @findex gdb.newest_frame
25241 @defun gdb.newest_frame ()
25242 Return the newest frame object for the selected thread.
25245 @defun gdb.frame_stop_reason_string (reason)
25246 Return a string explaining the reason why @value{GDBN} stopped unwinding
25247 frames, as expressed by the given @var{reason} code (an integer, see the
25248 @code{unwind_stop_reason} method further down in this section).
25251 A @code{gdb.Frame} object has the following methods:
25253 @defun Frame.is_valid ()
25254 Returns true if the @code{gdb.Frame} object is valid, false if not.
25255 A frame object can become invalid if the frame it refers to doesn't
25256 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25257 an exception if it is invalid at the time the method is called.
25260 @defun Frame.name ()
25261 Returns the function name of the frame, or @code{None} if it can't be
25265 @defun Frame.architecture ()
25266 Returns the @code{gdb.Architecture} object corresponding to the frame's
25267 architecture. @xref{Architectures In Python}.
25270 @defun Frame.type ()
25271 Returns the type of the frame. The value can be one of:
25273 @item gdb.NORMAL_FRAME
25274 An ordinary stack frame.
25276 @item gdb.DUMMY_FRAME
25277 A fake stack frame that was created by @value{GDBN} when performing an
25278 inferior function call.
25280 @item gdb.INLINE_FRAME
25281 A frame representing an inlined function. The function was inlined
25282 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25284 @item gdb.TAILCALL_FRAME
25285 A frame representing a tail call. @xref{Tail Call Frames}.
25287 @item gdb.SIGTRAMP_FRAME
25288 A signal trampoline frame. This is the frame created by the OS when
25289 it calls into a signal handler.
25291 @item gdb.ARCH_FRAME
25292 A fake stack frame representing a cross-architecture call.
25294 @item gdb.SENTINEL_FRAME
25295 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25300 @defun Frame.unwind_stop_reason ()
25301 Return an integer representing the reason why it's not possible to find
25302 more frames toward the outermost frame. Use
25303 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25304 function to a string. The value can be one of:
25307 @item gdb.FRAME_UNWIND_NO_REASON
25308 No particular reason (older frames should be available).
25310 @item gdb.FRAME_UNWIND_NULL_ID
25311 The previous frame's analyzer returns an invalid result.
25313 @item gdb.FRAME_UNWIND_OUTERMOST
25314 This frame is the outermost.
25316 @item gdb.FRAME_UNWIND_UNAVAILABLE
25317 Cannot unwind further, because that would require knowing the
25318 values of registers or memory that have not been collected.
25320 @item gdb.FRAME_UNWIND_INNER_ID
25321 This frame ID looks like it ought to belong to a NEXT frame,
25322 but we got it for a PREV frame. Normally, this is a sign of
25323 unwinder failure. It could also indicate stack corruption.
25325 @item gdb.FRAME_UNWIND_SAME_ID
25326 This frame has the same ID as the previous one. That means
25327 that unwinding further would almost certainly give us another
25328 frame with exactly the same ID, so break the chain. Normally,
25329 this is a sign of unwinder failure. It could also indicate
25332 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25333 The frame unwinder did not find any saved PC, but we needed
25334 one to unwind further.
25336 @item gdb.FRAME_UNWIND_FIRST_ERROR
25337 Any stop reason greater or equal to this value indicates some kind
25338 of error. This special value facilitates writing code that tests
25339 for errors in unwinding in a way that will work correctly even if
25340 the list of the other values is modified in future @value{GDBN}
25341 versions. Using it, you could write:
25343 reason = gdb.selected_frame().unwind_stop_reason ()
25344 reason_str = gdb.frame_stop_reason_string (reason)
25345 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25346 print "An error occured: %s" % reason_str
25353 Returns the frame's resume address.
25356 @defun Frame.block ()
25357 Return the frame's code block. @xref{Blocks In Python}.
25360 @defun Frame.function ()
25361 Return the symbol for the function corresponding to this frame.
25362 @xref{Symbols In Python}.
25365 @defun Frame.older ()
25366 Return the frame that called this frame.
25369 @defun Frame.newer ()
25370 Return the frame called by this frame.
25373 @defun Frame.find_sal ()
25374 Return the frame's symtab and line object.
25375 @xref{Symbol Tables In Python}.
25378 @defun Frame.read_var (variable @r{[}, block@r{]})
25379 Return the value of @var{variable} in this frame. If the optional
25380 argument @var{block} is provided, search for the variable from that
25381 block; otherwise start at the frame's current block (which is
25382 determined by the frame's current program counter). @var{variable}
25383 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25384 @code{gdb.Block} object.
25387 @defun Frame.select ()
25388 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25392 @node Blocks In Python
25393 @subsubsection Accessing frame blocks from Python.
25395 @cindex blocks in python
25398 Within each frame, @value{GDBN} maintains information on each block
25399 stored in that frame. These blocks are organized hierarchically, and
25400 are represented individually in Python as a @code{gdb.Block}.
25401 Please see @ref{Frames In Python}, for a more in-depth discussion on
25402 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25403 detailed technical information on @value{GDBN}'s book-keeping of the
25406 A @code{gdb.Block} is iterable. The iterator returns the symbols
25407 (@pxref{Symbols In Python}) local to the block. Python programs
25408 should not assume that a specific block object will always contain a
25409 given symbol, since changes in @value{GDBN} features and
25410 infrastructure may cause symbols move across blocks in a symbol
25413 The following block-related functions are available in the @code{gdb}
25416 @findex gdb.block_for_pc
25417 @defun gdb.block_for_pc (pc)
25418 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25419 block cannot be found for the @var{pc} value specified, the function
25420 will return @code{None}.
25423 A @code{gdb.Block} object has the following methods:
25425 @defun Block.is_valid ()
25426 Returns @code{True} if the @code{gdb.Block} object is valid,
25427 @code{False} if not. A block object can become invalid if the block it
25428 refers to doesn't exist anymore in the inferior. All other
25429 @code{gdb.Block} methods will throw an exception if it is invalid at
25430 the time the method is called. The block's validity is also checked
25431 during iteration over symbols of the block.
25434 A @code{gdb.Block} object has the following attributes:
25436 @defvar Block.start
25437 The start address of the block. This attribute is not writable.
25441 The end address of the block. This attribute is not writable.
25444 @defvar Block.function
25445 The name of the block represented as a @code{gdb.Symbol}. If the
25446 block is not named, then this attribute holds @code{None}. This
25447 attribute is not writable.
25450 @defvar Block.superblock
25451 The block containing this block. If this parent block does not exist,
25452 this attribute holds @code{None}. This attribute is not writable.
25455 @defvar Block.global_block
25456 The global block associated with this block. This attribute is not
25460 @defvar Block.static_block
25461 The static block associated with this block. This attribute is not
25465 @defvar Block.is_global
25466 @code{True} if the @code{gdb.Block} object is a global block,
25467 @code{False} if not. This attribute is not
25471 @defvar Block.is_static
25472 @code{True} if the @code{gdb.Block} object is a static block,
25473 @code{False} if not. This attribute is not writable.
25476 @node Symbols In Python
25477 @subsubsection Python representation of Symbols.
25479 @cindex symbols in python
25482 @value{GDBN} represents every variable, function and type as an
25483 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25484 Similarly, Python represents these symbols in @value{GDBN} with the
25485 @code{gdb.Symbol} object.
25487 The following symbol-related functions are available in the @code{gdb}
25490 @findex gdb.lookup_symbol
25491 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25492 This function searches for a symbol by name. The search scope can be
25493 restricted to the parameters defined in the optional domain and block
25496 @var{name} is the name of the symbol. It must be a string. The
25497 optional @var{block} argument restricts the search to symbols visible
25498 in that @var{block}. The @var{block} argument must be a
25499 @code{gdb.Block} object. If omitted, the block for the current frame
25500 is used. The optional @var{domain} argument restricts
25501 the search to the domain type. The @var{domain} argument must be a
25502 domain constant defined in the @code{gdb} module and described later
25505 The result is a tuple of two elements.
25506 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25508 If the symbol is found, the second element is @code{True} if the symbol
25509 is a field of a method's object (e.g., @code{this} in C@t{++}),
25510 otherwise it is @code{False}.
25511 If the symbol is not found, the second element is @code{False}.
25514 @findex gdb.lookup_global_symbol
25515 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25516 This function searches for a global symbol by name.
25517 The search scope can be restricted to by the domain argument.
25519 @var{name} is the name of the symbol. It must be a string.
25520 The optional @var{domain} argument restricts the search to the domain type.
25521 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25522 module and described later in this chapter.
25524 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25528 A @code{gdb.Symbol} object has the following attributes:
25530 @defvar Symbol.type
25531 The type of the symbol or @code{None} if no type is recorded.
25532 This attribute is represented as a @code{gdb.Type} object.
25533 @xref{Types In Python}. This attribute is not writable.
25536 @defvar Symbol.symtab
25537 The symbol table in which the symbol appears. This attribute is
25538 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25539 Python}. This attribute is not writable.
25542 @defvar Symbol.line
25543 The line number in the source code at which the symbol was defined.
25544 This is an integer.
25547 @defvar Symbol.name
25548 The name of the symbol as a string. This attribute is not writable.
25551 @defvar Symbol.linkage_name
25552 The name of the symbol, as used by the linker (i.e., may be mangled).
25553 This attribute is not writable.
25556 @defvar Symbol.print_name
25557 The name of the symbol in a form suitable for output. This is either
25558 @code{name} or @code{linkage_name}, depending on whether the user
25559 asked @value{GDBN} to display demangled or mangled names.
25562 @defvar Symbol.addr_class
25563 The address class of the symbol. This classifies how to find the value
25564 of a symbol. Each address class is a constant defined in the
25565 @code{gdb} module and described later in this chapter.
25568 @defvar Symbol.needs_frame
25569 This is @code{True} if evaluating this symbol's value requires a frame
25570 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25571 local variables will require a frame, but other symbols will not.
25574 @defvar Symbol.is_argument
25575 @code{True} if the symbol is an argument of a function.
25578 @defvar Symbol.is_constant
25579 @code{True} if the symbol is a constant.
25582 @defvar Symbol.is_function
25583 @code{True} if the symbol is a function or a method.
25586 @defvar Symbol.is_variable
25587 @code{True} if the symbol is a variable.
25590 A @code{gdb.Symbol} object has the following methods:
25592 @defun Symbol.is_valid ()
25593 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25594 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25595 the symbol it refers to does not exist in @value{GDBN} any longer.
25596 All other @code{gdb.Symbol} methods will throw an exception if it is
25597 invalid at the time the method is called.
25600 @defun Symbol.value (@r{[}frame@r{]})
25601 Compute the value of the symbol, as a @code{gdb.Value}. For
25602 functions, this computes the address of the function, cast to the
25603 appropriate type. If the symbol requires a frame in order to compute
25604 its value, then @var{frame} must be given. If @var{frame} is not
25605 given, or if @var{frame} is invalid, then this method will throw an
25609 The available domain categories in @code{gdb.Symbol} are represented
25610 as constants in the @code{gdb} module:
25613 @findex SYMBOL_UNDEF_DOMAIN
25614 @findex gdb.SYMBOL_UNDEF_DOMAIN
25615 @item gdb.SYMBOL_UNDEF_DOMAIN
25616 This is used when a domain has not been discovered or none of the
25617 following domains apply. This usually indicates an error either
25618 in the symbol information or in @value{GDBN}'s handling of symbols.
25619 @findex SYMBOL_VAR_DOMAIN
25620 @findex gdb.SYMBOL_VAR_DOMAIN
25621 @item gdb.SYMBOL_VAR_DOMAIN
25622 This domain contains variables, function names, typedef names and enum
25624 @findex SYMBOL_STRUCT_DOMAIN
25625 @findex gdb.SYMBOL_STRUCT_DOMAIN
25626 @item gdb.SYMBOL_STRUCT_DOMAIN
25627 This domain holds struct, union and enum type names.
25628 @findex SYMBOL_LABEL_DOMAIN
25629 @findex gdb.SYMBOL_LABEL_DOMAIN
25630 @item gdb.SYMBOL_LABEL_DOMAIN
25631 This domain contains names of labels (for gotos).
25632 @findex SYMBOL_VARIABLES_DOMAIN
25633 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25634 @item gdb.SYMBOL_VARIABLES_DOMAIN
25635 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25636 contains everything minus functions and types.
25637 @findex SYMBOL_FUNCTIONS_DOMAIN
25638 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25639 @item gdb.SYMBOL_FUNCTION_DOMAIN
25640 This domain contains all functions.
25641 @findex SYMBOL_TYPES_DOMAIN
25642 @findex gdb.SYMBOL_TYPES_DOMAIN
25643 @item gdb.SYMBOL_TYPES_DOMAIN
25644 This domain contains all types.
25647 The available address class categories in @code{gdb.Symbol} are represented
25648 as constants in the @code{gdb} module:
25651 @findex SYMBOL_LOC_UNDEF
25652 @findex gdb.SYMBOL_LOC_UNDEF
25653 @item gdb.SYMBOL_LOC_UNDEF
25654 If this is returned by address class, it indicates an error either in
25655 the symbol information or in @value{GDBN}'s handling of symbols.
25656 @findex SYMBOL_LOC_CONST
25657 @findex gdb.SYMBOL_LOC_CONST
25658 @item gdb.SYMBOL_LOC_CONST
25659 Value is constant int.
25660 @findex SYMBOL_LOC_STATIC
25661 @findex gdb.SYMBOL_LOC_STATIC
25662 @item gdb.SYMBOL_LOC_STATIC
25663 Value is at a fixed address.
25664 @findex SYMBOL_LOC_REGISTER
25665 @findex gdb.SYMBOL_LOC_REGISTER
25666 @item gdb.SYMBOL_LOC_REGISTER
25667 Value is in a register.
25668 @findex SYMBOL_LOC_ARG
25669 @findex gdb.SYMBOL_LOC_ARG
25670 @item gdb.SYMBOL_LOC_ARG
25671 Value is an argument. This value is at the offset stored within the
25672 symbol inside the frame's argument list.
25673 @findex SYMBOL_LOC_REF_ARG
25674 @findex gdb.SYMBOL_LOC_REF_ARG
25675 @item gdb.SYMBOL_LOC_REF_ARG
25676 Value address is stored in the frame's argument list. Just like
25677 @code{LOC_ARG} except that the value's address is stored at the
25678 offset, not the value itself.
25679 @findex SYMBOL_LOC_REGPARM_ADDR
25680 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25681 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25682 Value is a specified register. Just like @code{LOC_REGISTER} except
25683 the register holds the address of the argument instead of the argument
25685 @findex SYMBOL_LOC_LOCAL
25686 @findex gdb.SYMBOL_LOC_LOCAL
25687 @item gdb.SYMBOL_LOC_LOCAL
25688 Value is a local variable.
25689 @findex SYMBOL_LOC_TYPEDEF
25690 @findex gdb.SYMBOL_LOC_TYPEDEF
25691 @item gdb.SYMBOL_LOC_TYPEDEF
25692 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25694 @findex SYMBOL_LOC_BLOCK
25695 @findex gdb.SYMBOL_LOC_BLOCK
25696 @item gdb.SYMBOL_LOC_BLOCK
25698 @findex SYMBOL_LOC_CONST_BYTES
25699 @findex gdb.SYMBOL_LOC_CONST_BYTES
25700 @item gdb.SYMBOL_LOC_CONST_BYTES
25701 Value is a byte-sequence.
25702 @findex SYMBOL_LOC_UNRESOLVED
25703 @findex gdb.SYMBOL_LOC_UNRESOLVED
25704 @item gdb.SYMBOL_LOC_UNRESOLVED
25705 Value is at a fixed address, but the address of the variable has to be
25706 determined from the minimal symbol table whenever the variable is
25708 @findex SYMBOL_LOC_OPTIMIZED_OUT
25709 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25710 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25711 The value does not actually exist in the program.
25712 @findex SYMBOL_LOC_COMPUTED
25713 @findex gdb.SYMBOL_LOC_COMPUTED
25714 @item gdb.SYMBOL_LOC_COMPUTED
25715 The value's address is a computed location.
25718 @node Symbol Tables In Python
25719 @subsubsection Symbol table representation in Python.
25721 @cindex symbol tables in python
25723 @tindex gdb.Symtab_and_line
25725 Access to symbol table data maintained by @value{GDBN} on the inferior
25726 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25727 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25728 from the @code{find_sal} method in @code{gdb.Frame} object.
25729 @xref{Frames In Python}.
25731 For more information on @value{GDBN}'s symbol table management, see
25732 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25734 A @code{gdb.Symtab_and_line} object has the following attributes:
25736 @defvar Symtab_and_line.symtab
25737 The symbol table object (@code{gdb.Symtab}) for this frame.
25738 This attribute is not writable.
25741 @defvar Symtab_and_line.pc
25742 Indicates the start of the address range occupied by code for the
25743 current source line. This attribute is not writable.
25746 @defvar Symtab_and_line.last
25747 Indicates the end of the address range occupied by code for the current
25748 source line. This attribute is not writable.
25751 @defvar Symtab_and_line.line
25752 Indicates the current line number for this object. This
25753 attribute is not writable.
25756 A @code{gdb.Symtab_and_line} object has the following methods:
25758 @defun Symtab_and_line.is_valid ()
25759 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25760 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25761 invalid if the Symbol table and line object it refers to does not
25762 exist in @value{GDBN} any longer. All other
25763 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25764 invalid at the time the method is called.
25767 A @code{gdb.Symtab} object has the following attributes:
25769 @defvar Symtab.filename
25770 The symbol table's source filename. This attribute is not writable.
25773 @defvar Symtab.objfile
25774 The symbol table's backing object file. @xref{Objfiles In Python}.
25775 This attribute is not writable.
25778 A @code{gdb.Symtab} object has the following methods:
25780 @defun Symtab.is_valid ()
25781 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25782 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25783 the symbol table it refers to does not exist in @value{GDBN} any
25784 longer. All other @code{gdb.Symtab} methods will throw an exception
25785 if it is invalid at the time the method is called.
25788 @defun Symtab.fullname ()
25789 Return the symbol table's source absolute file name.
25792 @defun Symtab.global_block ()
25793 Return the global block of the underlying symbol table.
25794 @xref{Blocks In Python}.
25797 @defun Symtab.static_block ()
25798 Return the static block of the underlying symbol table.
25799 @xref{Blocks In Python}.
25802 @node Breakpoints In Python
25803 @subsubsection Manipulating breakpoints using Python
25805 @cindex breakpoints in python
25806 @tindex gdb.Breakpoint
25808 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25811 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25812 Create a new breakpoint. @var{spec} is a string naming the
25813 location of the breakpoint, or an expression that defines a
25814 watchpoint. The contents can be any location recognized by the
25815 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25816 command. The optional @var{type} denotes the breakpoint to create
25817 from the types defined later in this chapter. This argument can be
25818 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25819 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25820 allows the breakpoint to become invisible to the user. The breakpoint
25821 will neither be reported when created, nor will it be listed in the
25822 output from @code{info breakpoints} (but will be listed with the
25823 @code{maint info breakpoints} command). The optional @var{wp_class}
25824 argument defines the class of watchpoint to create, if @var{type} is
25825 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25826 assumed to be a @code{gdb.WP_WRITE} class.
25829 @defun Breakpoint.stop (self)
25830 The @code{gdb.Breakpoint} class can be sub-classed and, in
25831 particular, you may choose to implement the @code{stop} method.
25832 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25833 it will be called when the inferior reaches any location of a
25834 breakpoint which instantiates that sub-class. If the method returns
25835 @code{True}, the inferior will be stopped at the location of the
25836 breakpoint, otherwise the inferior will continue.
25838 If there are multiple breakpoints at the same location with a
25839 @code{stop} method, each one will be called regardless of the
25840 return status of the previous. This ensures that all @code{stop}
25841 methods have a chance to execute at that location. In this scenario
25842 if one of the methods returns @code{True} but the others return
25843 @code{False}, the inferior will still be stopped.
25845 You should not alter the execution state of the inferior (i.e.@:, step,
25846 next, etc.), alter the current frame context (i.e.@:, change the current
25847 active frame), or alter, add or delete any breakpoint. As a general
25848 rule, you should not alter any data within @value{GDBN} or the inferior
25851 Example @code{stop} implementation:
25854 class MyBreakpoint (gdb.Breakpoint):
25856 inf_val = gdb.parse_and_eval("foo")
25863 The available watchpoint types represented by constants are defined in the
25868 @findex gdb.WP_READ
25870 Read only watchpoint.
25873 @findex gdb.WP_WRITE
25875 Write only watchpoint.
25878 @findex gdb.WP_ACCESS
25879 @item gdb.WP_ACCESS
25880 Read/Write watchpoint.
25883 @defun Breakpoint.is_valid ()
25884 Return @code{True} if this @code{Breakpoint} object is valid,
25885 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25886 if the user deletes the breakpoint. In this case, the object still
25887 exists, but the underlying breakpoint does not. In the cases of
25888 watchpoint scope, the watchpoint remains valid even if execution of the
25889 inferior leaves the scope of that watchpoint.
25892 @defun Breakpoint.delete
25893 Permanently deletes the @value{GDBN} breakpoint. This also
25894 invalidates the Python @code{Breakpoint} object. Any further access
25895 to this object's attributes or methods will raise an error.
25898 @defvar Breakpoint.enabled
25899 This attribute is @code{True} if the breakpoint is enabled, and
25900 @code{False} otherwise. This attribute is writable.
25903 @defvar Breakpoint.silent
25904 This attribute is @code{True} if the breakpoint is silent, and
25905 @code{False} otherwise. This attribute is writable.
25907 Note that a breakpoint can also be silent if it has commands and the
25908 first command is @code{silent}. This is not reported by the
25909 @code{silent} attribute.
25912 @defvar Breakpoint.thread
25913 If the breakpoint is thread-specific, this attribute holds the thread
25914 id. If the breakpoint is not thread-specific, this attribute is
25915 @code{None}. This attribute is writable.
25918 @defvar Breakpoint.task
25919 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25920 id. If the breakpoint is not task-specific (or the underlying
25921 language is not Ada), this attribute is @code{None}. This attribute
25925 @defvar Breakpoint.ignore_count
25926 This attribute holds the ignore count for the breakpoint, an integer.
25927 This attribute is writable.
25930 @defvar Breakpoint.number
25931 This attribute holds the breakpoint's number --- the identifier used by
25932 the user to manipulate the breakpoint. This attribute is not writable.
25935 @defvar Breakpoint.type
25936 This attribute holds the breakpoint's type --- the identifier used to
25937 determine the actual breakpoint type or use-case. This attribute is not
25941 @defvar Breakpoint.visible
25942 This attribute tells whether the breakpoint is visible to the user
25943 when set, or when the @samp{info breakpoints} command is run. This
25944 attribute is not writable.
25947 The available types are represented by constants defined in the @code{gdb}
25951 @findex BP_BREAKPOINT
25952 @findex gdb.BP_BREAKPOINT
25953 @item gdb.BP_BREAKPOINT
25954 Normal code breakpoint.
25956 @findex BP_WATCHPOINT
25957 @findex gdb.BP_WATCHPOINT
25958 @item gdb.BP_WATCHPOINT
25959 Watchpoint breakpoint.
25961 @findex BP_HARDWARE_WATCHPOINT
25962 @findex gdb.BP_HARDWARE_WATCHPOINT
25963 @item gdb.BP_HARDWARE_WATCHPOINT
25964 Hardware assisted watchpoint.
25966 @findex BP_READ_WATCHPOINT
25967 @findex gdb.BP_READ_WATCHPOINT
25968 @item gdb.BP_READ_WATCHPOINT
25969 Hardware assisted read watchpoint.
25971 @findex BP_ACCESS_WATCHPOINT
25972 @findex gdb.BP_ACCESS_WATCHPOINT
25973 @item gdb.BP_ACCESS_WATCHPOINT
25974 Hardware assisted access watchpoint.
25977 @defvar Breakpoint.hit_count
25978 This attribute holds the hit count for the breakpoint, an integer.
25979 This attribute is writable, but currently it can only be set to zero.
25982 @defvar Breakpoint.location
25983 This attribute holds the location of the breakpoint, as specified by
25984 the user. It is a string. If the breakpoint does not have a location
25985 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25986 attribute is not writable.
25989 @defvar Breakpoint.expression
25990 This attribute holds a breakpoint expression, as specified by
25991 the user. It is a string. If the breakpoint does not have an
25992 expression (the breakpoint is not a watchpoint) the attribute's value
25993 is @code{None}. This attribute is not writable.
25996 @defvar Breakpoint.condition
25997 This attribute holds the condition of the breakpoint, as specified by
25998 the user. It is a string. If there is no condition, this attribute's
25999 value is @code{None}. This attribute is writable.
26002 @defvar Breakpoint.commands
26003 This attribute holds the commands attached to the breakpoint. If
26004 there are commands, this attribute's value is a string holding all the
26005 commands, separated by newlines. If there are no commands, this
26006 attribute is @code{None}. This attribute is not writable.
26009 @node Finish Breakpoints in Python
26010 @subsubsection Finish Breakpoints
26012 @cindex python finish breakpoints
26013 @tindex gdb.FinishBreakpoint
26015 A finish breakpoint is a temporary breakpoint set at the return address of
26016 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26017 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26018 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26019 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26020 Finish breakpoints are thread specific and must be create with the right
26023 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26024 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26025 object @var{frame}. If @var{frame} is not provided, this defaults to the
26026 newest frame. The optional @var{internal} argument allows the breakpoint to
26027 become invisible to the user. @xref{Breakpoints In Python}, for further
26028 details about this argument.
26031 @defun FinishBreakpoint.out_of_scope (self)
26032 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26033 @code{return} command, @dots{}), a function may not properly terminate, and
26034 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26035 situation, the @code{out_of_scope} callback will be triggered.
26037 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26041 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26043 print "normal finish"
26046 def out_of_scope ():
26047 print "abnormal finish"
26051 @defvar FinishBreakpoint.return_value
26052 When @value{GDBN} is stopped at a finish breakpoint and the frame
26053 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26054 attribute will contain a @code{gdb.Value} object corresponding to the return
26055 value of the function. The value will be @code{None} if the function return
26056 type is @code{void} or if the return value was not computable. This attribute
26060 @node Lazy Strings In Python
26061 @subsubsection Python representation of lazy strings.
26063 @cindex lazy strings in python
26064 @tindex gdb.LazyString
26066 A @dfn{lazy string} is a string whose contents is not retrieved or
26067 encoded until it is needed.
26069 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26070 @code{address} that points to a region of memory, an @code{encoding}
26071 that will be used to encode that region of memory, and a @code{length}
26072 to delimit the region of memory that represents the string. The
26073 difference between a @code{gdb.LazyString} and a string wrapped within
26074 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26075 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26076 retrieved and encoded during printing, while a @code{gdb.Value}
26077 wrapping a string is immediately retrieved and encoded on creation.
26079 A @code{gdb.LazyString} object has the following functions:
26081 @defun LazyString.value ()
26082 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26083 will point to the string in memory, but will lose all the delayed
26084 retrieval, encoding and handling that @value{GDBN} applies to a
26085 @code{gdb.LazyString}.
26088 @defvar LazyString.address
26089 This attribute holds the address of the string. This attribute is not
26093 @defvar LazyString.length
26094 This attribute holds the length of the string in characters. If the
26095 length is -1, then the string will be fetched and encoded up to the
26096 first null of appropriate width. This attribute is not writable.
26099 @defvar LazyString.encoding
26100 This attribute holds the encoding that will be applied to the string
26101 when the string is printed by @value{GDBN}. If the encoding is not
26102 set, or contains an empty string, then @value{GDBN} will select the
26103 most appropriate encoding when the string is printed. This attribute
26107 @defvar LazyString.type
26108 This attribute holds the type that is represented by the lazy string's
26109 type. For a lazy string this will always be a pointer type. To
26110 resolve this to the lazy string's character type, use the type's
26111 @code{target} method. @xref{Types In Python}. This attribute is not
26115 @node Architectures In Python
26116 @subsubsection Python representation of architectures
26117 @cindex Python architectures
26119 @value{GDBN} uses architecture specific parameters and artifacts in a
26120 number of its various computations. An architecture is represented
26121 by an instance of the @code{gdb.Architecture} class.
26123 A @code{gdb.Architecture} class has the following methods:
26125 @defun Architecture.name ()
26126 Return the name (string value) of the architecture.
26129 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26130 Return a list of disassembled instructions starting from the memory
26131 address @var{start_pc}. The optional arguments @var{end_pc} and
26132 @var{count} determine the number of instructions in the returned list.
26133 If both the optional arguments @var{end_pc} and @var{count} are
26134 specified, then a list of at most @var{count} disassembled instructions
26135 whose start address falls in the closed memory address interval from
26136 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26137 specified, but @var{count} is specified, then @var{count} number of
26138 instructions starting from the address @var{start_pc} are returned. If
26139 @var{count} is not specified but @var{end_pc} is specified, then all
26140 instructions whose start address falls in the closed memory address
26141 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26142 @var{end_pc} nor @var{count} are specified, then a single instruction at
26143 @var{start_pc} is returned. For all of these cases, each element of the
26144 returned list is a Python @code{dict} with the following string keys:
26149 The value corresponding to this key is a Python long integer capturing
26150 the memory address of the instruction.
26153 The value corresponding to this key is a string value which represents
26154 the instruction with assembly language mnemonics. The assembly
26155 language flavor used is the same as that specified by the current CLI
26156 variable @code{disassembly-flavor}. @xref{Machine Code}.
26159 The value corresponding to this key is the length (integer value) of the
26160 instruction in bytes.
26165 @node Python Auto-loading
26166 @subsection Python Auto-loading
26167 @cindex Python auto-loading
26169 When a new object file is read (for example, due to the @code{file}
26170 command, or because the inferior has loaded a shared library),
26171 @value{GDBN} will look for Python support scripts in several ways:
26172 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26173 and @code{.debug_gdb_scripts} section
26174 (@pxref{dotdebug_gdb_scripts section}).
26176 The auto-loading feature is useful for supplying application-specific
26177 debugging commands and scripts.
26179 Auto-loading can be enabled or disabled,
26180 and the list of auto-loaded scripts can be printed.
26183 @anchor{set auto-load python-scripts}
26184 @kindex set auto-load python-scripts
26185 @item set auto-load python-scripts [on|off]
26186 Enable or disable the auto-loading of Python scripts.
26188 @anchor{show auto-load python-scripts}
26189 @kindex show auto-load python-scripts
26190 @item show auto-load python-scripts
26191 Show whether auto-loading of Python scripts is enabled or disabled.
26193 @anchor{info auto-load python-scripts}
26194 @kindex info auto-load python-scripts
26195 @cindex print list of auto-loaded Python scripts
26196 @item info auto-load python-scripts [@var{regexp}]
26197 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26199 Also printed is the list of Python scripts that were mentioned in
26200 the @code{.debug_gdb_scripts} section and were not found
26201 (@pxref{dotdebug_gdb_scripts section}).
26202 This is useful because their names are not printed when @value{GDBN}
26203 tries to load them and fails. There may be many of them, and printing
26204 an error message for each one is problematic.
26206 If @var{regexp} is supplied only Python scripts with matching names are printed.
26211 (gdb) info auto-load python-scripts
26213 Yes py-section-script.py
26214 full name: /tmp/py-section-script.py
26215 No my-foo-pretty-printers.py
26219 When reading an auto-loaded file, @value{GDBN} sets the
26220 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26221 function (@pxref{Objfiles In Python}). This can be useful for
26222 registering objfile-specific pretty-printers.
26225 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26226 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26227 * Which flavor to choose?::
26230 @node objfile-gdb.py file
26231 @subsubsection The @file{@var{objfile}-gdb.py} file
26232 @cindex @file{@var{objfile}-gdb.py}
26234 When a new object file is read, @value{GDBN} looks for
26235 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26236 where @var{objfile} is the object file's real name, formed by ensuring
26237 that the file name is absolute, following all symlinks, and resolving
26238 @code{.} and @code{..} components. If this file exists and is
26239 readable, @value{GDBN} will evaluate it as a Python script.
26241 If this file does not exist, then @value{GDBN} will look for
26242 @var{script-name} file in all of the directories as specified below.
26244 Note that loading of this script file also requires accordingly configured
26245 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26247 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26248 scripts normally according to its @file{.exe} filename. But if no scripts are
26249 found @value{GDBN} also tries script filenames matching the object file without
26250 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26251 is attempted on any platform. This makes the script filenames compatible
26252 between Unix and MS-Windows hosts.
26255 @anchor{set auto-load scripts-directory}
26256 @kindex set auto-load scripts-directory
26257 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26258 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26259 may be delimited by the host platform path separator in use
26260 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26262 Each entry here needs to be covered also by the security setting
26263 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26265 @anchor{with-auto-load-dir}
26266 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26267 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26268 configuration option @option{--with-auto-load-dir}.
26270 Any reference to @file{$debugdir} will get replaced by
26271 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26272 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26273 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26274 @file{$datadir} must be placed as a directory component --- either alone or
26275 delimited by @file{/} or @file{\} directory separators, depending on the host
26278 The list of directories uses path separator (@samp{:} on GNU and Unix
26279 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26280 to the @env{PATH} environment variable.
26282 @anchor{show auto-load scripts-directory}
26283 @kindex show auto-load scripts-directory
26284 @item show auto-load scripts-directory
26285 Show @value{GDBN} auto-loaded scripts location.
26288 @value{GDBN} does not track which files it has already auto-loaded this way.
26289 @value{GDBN} will load the associated script every time the corresponding
26290 @var{objfile} is opened.
26291 So your @file{-gdb.py} file should be careful to avoid errors if it
26292 is evaluated more than once.
26294 @node dotdebug_gdb_scripts section
26295 @subsubsection The @code{.debug_gdb_scripts} section
26296 @cindex @code{.debug_gdb_scripts} section
26298 For systems using file formats like ELF and COFF,
26299 when @value{GDBN} loads a new object file
26300 it will look for a special section named @samp{.debug_gdb_scripts}.
26301 If this section exists, its contents is a list of names of scripts to load.
26303 @value{GDBN} will look for each specified script file first in the
26304 current directory and then along the source search path
26305 (@pxref{Source Path, ,Specifying Source Directories}),
26306 except that @file{$cdir} is not searched, since the compilation
26307 directory is not relevant to scripts.
26309 Entries can be placed in section @code{.debug_gdb_scripts} with,
26310 for example, this GCC macro:
26313 /* Note: The "MS" section flags are to remove duplicates. */
26314 #define DEFINE_GDB_SCRIPT(script_name) \
26316 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26318 .asciz \"" script_name "\"\n\
26324 Then one can reference the macro in a header or source file like this:
26327 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26330 The script name may include directories if desired.
26332 Note that loading of this script file also requires accordingly configured
26333 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26335 If the macro is put in a header, any application or library
26336 using this header will get a reference to the specified script.
26338 @node Which flavor to choose?
26339 @subsubsection Which flavor to choose?
26341 Given the multiple ways of auto-loading Python scripts, it might not always
26342 be clear which one to choose. This section provides some guidance.
26344 Benefits of the @file{-gdb.py} way:
26348 Can be used with file formats that don't support multiple sections.
26351 Ease of finding scripts for public libraries.
26353 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26354 in the source search path.
26355 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26356 isn't a source directory in which to find the script.
26359 Doesn't require source code additions.
26362 Benefits of the @code{.debug_gdb_scripts} way:
26366 Works with static linking.
26368 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26369 trigger their loading. When an application is statically linked the only
26370 objfile available is the executable, and it is cumbersome to attach all the
26371 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26374 Works with classes that are entirely inlined.
26376 Some classes can be entirely inlined, and thus there may not be an associated
26377 shared library to attach a @file{-gdb.py} script to.
26380 Scripts needn't be copied out of the source tree.
26382 In some circumstances, apps can be built out of large collections of internal
26383 libraries, and the build infrastructure necessary to install the
26384 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26385 cumbersome. It may be easier to specify the scripts in the
26386 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26387 top of the source tree to the source search path.
26390 @node Python modules
26391 @subsection Python modules
26392 @cindex python modules
26394 @value{GDBN} comes with several modules to assist writing Python code.
26397 * gdb.printing:: Building and registering pretty-printers.
26398 * gdb.types:: Utilities for working with types.
26399 * gdb.prompt:: Utilities for prompt value substitution.
26403 @subsubsection gdb.printing
26404 @cindex gdb.printing
26406 This module provides a collection of utilities for working with
26410 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26411 This class specifies the API that makes @samp{info pretty-printer},
26412 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26413 Pretty-printers should generally inherit from this class.
26415 @item SubPrettyPrinter (@var{name})
26416 For printers that handle multiple types, this class specifies the
26417 corresponding API for the subprinters.
26419 @item RegexpCollectionPrettyPrinter (@var{name})
26420 Utility class for handling multiple printers, all recognized via
26421 regular expressions.
26422 @xref{Writing a Pretty-Printer}, for an example.
26424 @item FlagEnumerationPrinter (@var{name})
26425 A pretty-printer which handles printing of @code{enum} values. Unlike
26426 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26427 work properly when there is some overlap between the enumeration
26428 constants. @var{name} is the name of the printer and also the name of
26429 the @code{enum} type to look up.
26431 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26432 Register @var{printer} with the pretty-printer list of @var{obj}.
26433 If @var{replace} is @code{True} then any existing copy of the printer
26434 is replaced. Otherwise a @code{RuntimeError} exception is raised
26435 if a printer with the same name already exists.
26439 @subsubsection gdb.types
26442 This module provides a collection of utilities for working with
26443 @code{gdb.Type} objects.
26446 @item get_basic_type (@var{type})
26447 Return @var{type} with const and volatile qualifiers stripped,
26448 and with typedefs and C@t{++} references converted to the underlying type.
26453 typedef const int const_int;
26455 const_int& foo_ref (foo);
26456 int main () @{ return 0; @}
26463 (gdb) python import gdb.types
26464 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26465 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26469 @item has_field (@var{type}, @var{field})
26470 Return @code{True} if @var{type}, assumed to be a type with fields
26471 (e.g., a structure or union), has field @var{field}.
26473 @item make_enum_dict (@var{enum_type})
26474 Return a Python @code{dictionary} type produced from @var{enum_type}.
26476 @item deep_items (@var{type})
26477 Returns a Python iterator similar to the standard
26478 @code{gdb.Type.iteritems} method, except that the iterator returned
26479 by @code{deep_items} will recursively traverse anonymous struct or
26480 union fields. For example:
26494 Then in @value{GDBN}:
26496 (@value{GDBP}) python import gdb.types
26497 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26498 (@value{GDBP}) python print struct_a.keys ()
26500 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26501 @{['a', 'b0', 'b1']@}
26504 @item get_type_recognizers ()
26505 Return a list of the enabled type recognizers for the current context.
26506 This is called by @value{GDBN} during the type-printing process
26507 (@pxref{Type Printing API}).
26509 @item apply_type_recognizers (recognizers, type_obj)
26510 Apply the type recognizers, @var{recognizers}, to the type object
26511 @var{type_obj}. If any recognizer returns a string, return that
26512 string. Otherwise, return @code{None}. This is called by
26513 @value{GDBN} during the type-printing process (@pxref{Type Printing
26516 @item register_type_printer (locus, printer)
26517 This is a convenience function to register a type printer.
26518 @var{printer} is the type printer to register. It must implement the
26519 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26520 which case the printer is registered with that objfile; a
26521 @code{gdb.Progspace}, in which case the printer is registered with
26522 that progspace; or @code{None}, in which case the printer is
26523 registered globally.
26526 This is a base class that implements the type printer protocol. Type
26527 printers are encouraged, but not required, to derive from this class.
26528 It defines a constructor:
26530 @defmethod TypePrinter __init__ (self, name)
26531 Initialize the type printer with the given name. The new printer
26532 starts in the enabled state.
26538 @subsubsection gdb.prompt
26541 This module provides a method for prompt value-substitution.
26544 @item substitute_prompt (@var{string})
26545 Return @var{string} with escape sequences substituted by values. Some
26546 escape sequences take arguments. You can specify arguments inside
26547 ``@{@}'' immediately following the escape sequence.
26549 The escape sequences you can pass to this function are:
26553 Substitute a backslash.
26555 Substitute an ESC character.
26557 Substitute the selected frame; an argument names a frame parameter.
26559 Substitute a newline.
26561 Substitute a parameter's value; the argument names the parameter.
26563 Substitute a carriage return.
26565 Substitute the selected thread; an argument names a thread parameter.
26567 Substitute the version of GDB.
26569 Substitute the current working directory.
26571 Begin a sequence of non-printing characters. These sequences are
26572 typically used with the ESC character, and are not counted in the string
26573 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26574 blue-colored ``(gdb)'' prompt where the length is five.
26576 End a sequence of non-printing characters.
26582 substitute_prompt (``frame: \f,
26583 print arguments: \p@{print frame-arguments@}'')
26586 @exdent will return the string:
26589 "frame: main, print arguments: scalars"
26594 @section Creating new spellings of existing commands
26595 @cindex aliases for commands
26597 It is often useful to define alternate spellings of existing commands.
26598 For example, if a new @value{GDBN} command defined in Python has
26599 a long name to type, it is handy to have an abbreviated version of it
26600 that involves less typing.
26602 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26603 of the @samp{step} command even though it is otherwise an ambiguous
26604 abbreviation of other commands like @samp{set} and @samp{show}.
26606 Aliases are also used to provide shortened or more common versions
26607 of multi-word commands. For example, @value{GDBN} provides the
26608 @samp{tty} alias of the @samp{set inferior-tty} command.
26610 You can define a new alias with the @samp{alias} command.
26615 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26619 @var{ALIAS} specifies the name of the new alias.
26620 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26623 @var{COMMAND} specifies the name of an existing command
26624 that is being aliased.
26626 The @samp{-a} option specifies that the new alias is an abbreviation
26627 of the command. Abbreviations are not shown in command
26628 lists displayed by the @samp{help} command.
26630 The @samp{--} option specifies the end of options,
26631 and is useful when @var{ALIAS} begins with a dash.
26633 Here is a simple example showing how to make an abbreviation
26634 of a command so that there is less to type.
26635 Suppose you were tired of typing @samp{disas}, the current
26636 shortest unambiguous abbreviation of the @samp{disassemble} command
26637 and you wanted an even shorter version named @samp{di}.
26638 The following will accomplish this.
26641 (gdb) alias -a di = disas
26644 Note that aliases are different from user-defined commands.
26645 With a user-defined command, you also need to write documentation
26646 for it with the @samp{document} command.
26647 An alias automatically picks up the documentation of the existing command.
26649 Here is an example where we make @samp{elms} an abbreviation of
26650 @samp{elements} in the @samp{set print elements} command.
26651 This is to show that you can make an abbreviation of any part
26655 (gdb) alias -a set print elms = set print elements
26656 (gdb) alias -a show print elms = show print elements
26657 (gdb) set p elms 20
26659 Limit on string chars or array elements to print is 200.
26662 Note that if you are defining an alias of a @samp{set} command,
26663 and you want to have an alias for the corresponding @samp{show}
26664 command, then you need to define the latter separately.
26666 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26667 @var{ALIAS}, just as they are normally.
26670 (gdb) alias -a set pr elms = set p ele
26673 Finally, here is an example showing the creation of a one word
26674 alias for a more complex command.
26675 This creates alias @samp{spe} of the command @samp{set print elements}.
26678 (gdb) alias spe = set print elements
26683 @chapter Command Interpreters
26684 @cindex command interpreters
26686 @value{GDBN} supports multiple command interpreters, and some command
26687 infrastructure to allow users or user interface writers to switch
26688 between interpreters or run commands in other interpreters.
26690 @value{GDBN} currently supports two command interpreters, the console
26691 interpreter (sometimes called the command-line interpreter or @sc{cli})
26692 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26693 describes both of these interfaces in great detail.
26695 By default, @value{GDBN} will start with the console interpreter.
26696 However, the user may choose to start @value{GDBN} with another
26697 interpreter by specifying the @option{-i} or @option{--interpreter}
26698 startup options. Defined interpreters include:
26702 @cindex console interpreter
26703 The traditional console or command-line interpreter. This is the most often
26704 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26705 @value{GDBN} will use this interpreter.
26708 @cindex mi interpreter
26709 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26710 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26711 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26715 @cindex mi2 interpreter
26716 The current @sc{gdb/mi} interface.
26719 @cindex mi1 interpreter
26720 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26724 @cindex invoke another interpreter
26725 The interpreter being used by @value{GDBN} may not be dynamically
26726 switched at runtime. Although possible, this could lead to a very
26727 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26728 enters the command "interpreter-set console" in a console view,
26729 @value{GDBN} would switch to using the console interpreter, rendering
26730 the IDE inoperable!
26732 @kindex interpreter-exec
26733 Although you may only choose a single interpreter at startup, you may execute
26734 commands in any interpreter from the current interpreter using the appropriate
26735 command. If you are running the console interpreter, simply use the
26736 @code{interpreter-exec} command:
26739 interpreter-exec mi "-data-list-register-names"
26742 @sc{gdb/mi} has a similar command, although it is only available in versions of
26743 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26746 @chapter @value{GDBN} Text User Interface
26748 @cindex Text User Interface
26751 * TUI Overview:: TUI overview
26752 * TUI Keys:: TUI key bindings
26753 * TUI Single Key Mode:: TUI single key mode
26754 * TUI Commands:: TUI-specific commands
26755 * TUI Configuration:: TUI configuration variables
26758 The @value{GDBN} Text User Interface (TUI) is a terminal
26759 interface which uses the @code{curses} library to show the source
26760 file, the assembly output, the program registers and @value{GDBN}
26761 commands in separate text windows. The TUI mode is supported only
26762 on platforms where a suitable version of the @code{curses} library
26765 The TUI mode is enabled by default when you invoke @value{GDBN} as
26766 @samp{@value{GDBP} -tui}.
26767 You can also switch in and out of TUI mode while @value{GDBN} runs by
26768 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26769 @xref{TUI Keys, ,TUI Key Bindings}.
26772 @section TUI Overview
26774 In TUI mode, @value{GDBN} can display several text windows:
26778 This window is the @value{GDBN} command window with the @value{GDBN}
26779 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26780 managed using readline.
26783 The source window shows the source file of the program. The current
26784 line and active breakpoints are displayed in this window.
26787 The assembly window shows the disassembly output of the program.
26790 This window shows the processor registers. Registers are highlighted
26791 when their values change.
26794 The source and assembly windows show the current program position
26795 by highlighting the current line and marking it with a @samp{>} marker.
26796 Breakpoints are indicated with two markers. The first marker
26797 indicates the breakpoint type:
26801 Breakpoint which was hit at least once.
26804 Breakpoint which was never hit.
26807 Hardware breakpoint which was hit at least once.
26810 Hardware breakpoint which was never hit.
26813 The second marker indicates whether the breakpoint is enabled or not:
26817 Breakpoint is enabled.
26820 Breakpoint is disabled.
26823 The source, assembly and register windows are updated when the current
26824 thread changes, when the frame changes, or when the program counter
26827 These windows are not all visible at the same time. The command
26828 window is always visible. The others can be arranged in several
26839 source and assembly,
26842 source and registers, or
26845 assembly and registers.
26848 A status line above the command window shows the following information:
26852 Indicates the current @value{GDBN} target.
26853 (@pxref{Targets, ,Specifying a Debugging Target}).
26856 Gives the current process or thread number.
26857 When no process is being debugged, this field is set to @code{No process}.
26860 Gives the current function name for the selected frame.
26861 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26862 When there is no symbol corresponding to the current program counter,
26863 the string @code{??} is displayed.
26866 Indicates the current line number for the selected frame.
26867 When the current line number is not known, the string @code{??} is displayed.
26870 Indicates the current program counter address.
26874 @section TUI Key Bindings
26875 @cindex TUI key bindings
26877 The TUI installs several key bindings in the readline keymaps
26878 @ifset SYSTEM_READLINE
26879 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26881 @ifclear SYSTEM_READLINE
26882 (@pxref{Command Line Editing}).
26884 The following key bindings are installed for both TUI mode and the
26885 @value{GDBN} standard mode.
26894 Enter or leave the TUI mode. When leaving the TUI mode,
26895 the curses window management stops and @value{GDBN} operates using
26896 its standard mode, writing on the terminal directly. When reentering
26897 the TUI mode, control is given back to the curses windows.
26898 The screen is then refreshed.
26902 Use a TUI layout with only one window. The layout will
26903 either be @samp{source} or @samp{assembly}. When the TUI mode
26904 is not active, it will switch to the TUI mode.
26906 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26910 Use a TUI layout with at least two windows. When the current
26911 layout already has two windows, the next layout with two windows is used.
26912 When a new layout is chosen, one window will always be common to the
26913 previous layout and the new one.
26915 Think of it as the Emacs @kbd{C-x 2} binding.
26919 Change the active window. The TUI associates several key bindings
26920 (like scrolling and arrow keys) with the active window. This command
26921 gives the focus to the next TUI window.
26923 Think of it as the Emacs @kbd{C-x o} binding.
26927 Switch in and out of the TUI SingleKey mode that binds single
26928 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26931 The following key bindings only work in the TUI mode:
26936 Scroll the active window one page up.
26940 Scroll the active window one page down.
26944 Scroll the active window one line up.
26948 Scroll the active window one line down.
26952 Scroll the active window one column left.
26956 Scroll the active window one column right.
26960 Refresh the screen.
26963 Because the arrow keys scroll the active window in the TUI mode, they
26964 are not available for their normal use by readline unless the command
26965 window has the focus. When another window is active, you must use
26966 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26967 and @kbd{C-f} to control the command window.
26969 @node TUI Single Key Mode
26970 @section TUI Single Key Mode
26971 @cindex TUI single key mode
26973 The TUI also provides a @dfn{SingleKey} mode, which binds several
26974 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26975 switch into this mode, where the following key bindings are used:
26978 @kindex c @r{(SingleKey TUI key)}
26982 @kindex d @r{(SingleKey TUI key)}
26986 @kindex f @r{(SingleKey TUI key)}
26990 @kindex n @r{(SingleKey TUI key)}
26994 @kindex q @r{(SingleKey TUI key)}
26996 exit the SingleKey mode.
26998 @kindex r @r{(SingleKey TUI key)}
27002 @kindex s @r{(SingleKey TUI key)}
27006 @kindex u @r{(SingleKey TUI key)}
27010 @kindex v @r{(SingleKey TUI key)}
27014 @kindex w @r{(SingleKey TUI key)}
27019 Other keys temporarily switch to the @value{GDBN} command prompt.
27020 The key that was pressed is inserted in the editing buffer so that
27021 it is possible to type most @value{GDBN} commands without interaction
27022 with the TUI SingleKey mode. Once the command is entered the TUI
27023 SingleKey mode is restored. The only way to permanently leave
27024 this mode is by typing @kbd{q} or @kbd{C-x s}.
27028 @section TUI-specific Commands
27029 @cindex TUI commands
27031 The TUI has specific commands to control the text windows.
27032 These commands are always available, even when @value{GDBN} is not in
27033 the TUI mode. When @value{GDBN} is in the standard mode, most
27034 of these commands will automatically switch to the TUI mode.
27036 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27037 terminal, or @value{GDBN} has been started with the machine interface
27038 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27039 these commands will fail with an error, because it would not be
27040 possible or desirable to enable curses window management.
27045 List and give the size of all displayed windows.
27049 Display the next layout.
27052 Display the previous layout.
27055 Display the source window only.
27058 Display the assembly window only.
27061 Display the source and assembly window.
27064 Display the register window together with the source or assembly window.
27068 Make the next window active for scrolling.
27071 Make the previous window active for scrolling.
27074 Make the source window active for scrolling.
27077 Make the assembly window active for scrolling.
27080 Make the register window active for scrolling.
27083 Make the command window active for scrolling.
27087 Refresh the screen. This is similar to typing @kbd{C-L}.
27089 @item tui reg float
27091 Show the floating point registers in the register window.
27093 @item tui reg general
27094 Show the general registers in the register window.
27097 Show the next register group. The list of register groups as well as
27098 their order is target specific. The predefined register groups are the
27099 following: @code{general}, @code{float}, @code{system}, @code{vector},
27100 @code{all}, @code{save}, @code{restore}.
27102 @item tui reg system
27103 Show the system registers in the register window.
27107 Update the source window and the current execution point.
27109 @item winheight @var{name} +@var{count}
27110 @itemx winheight @var{name} -@var{count}
27112 Change the height of the window @var{name} by @var{count}
27113 lines. Positive counts increase the height, while negative counts
27116 @item tabset @var{nchars}
27118 Set the width of tab stops to be @var{nchars} characters.
27121 @node TUI Configuration
27122 @section TUI Configuration Variables
27123 @cindex TUI configuration variables
27125 Several configuration variables control the appearance of TUI windows.
27128 @item set tui border-kind @var{kind}
27129 @kindex set tui border-kind
27130 Select the border appearance for the source, assembly and register windows.
27131 The possible values are the following:
27134 Use a space character to draw the border.
27137 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27140 Use the Alternate Character Set to draw the border. The border is
27141 drawn using character line graphics if the terminal supports them.
27144 @item set tui border-mode @var{mode}
27145 @kindex set tui border-mode
27146 @itemx set tui active-border-mode @var{mode}
27147 @kindex set tui active-border-mode
27148 Select the display attributes for the borders of the inactive windows
27149 or the active window. The @var{mode} can be one of the following:
27152 Use normal attributes to display the border.
27158 Use reverse video mode.
27161 Use half bright mode.
27163 @item half-standout
27164 Use half bright and standout mode.
27167 Use extra bright or bold mode.
27169 @item bold-standout
27170 Use extra bright or bold and standout mode.
27175 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27178 @cindex @sc{gnu} Emacs
27179 A special interface allows you to use @sc{gnu} Emacs to view (and
27180 edit) the source files for the program you are debugging with
27183 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27184 executable file you want to debug as an argument. This command starts
27185 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27186 created Emacs buffer.
27187 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27189 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27194 All ``terminal'' input and output goes through an Emacs buffer, called
27197 This applies both to @value{GDBN} commands and their output, and to the input
27198 and output done by the program you are debugging.
27200 This is useful because it means that you can copy the text of previous
27201 commands and input them again; you can even use parts of the output
27204 All the facilities of Emacs' Shell mode are available for interacting
27205 with your program. In particular, you can send signals the usual
27206 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27210 @value{GDBN} displays source code through Emacs.
27212 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27213 source file for that frame and puts an arrow (@samp{=>}) at the
27214 left margin of the current line. Emacs uses a separate buffer for
27215 source display, and splits the screen to show both your @value{GDBN} session
27218 Explicit @value{GDBN} @code{list} or search commands still produce output as
27219 usual, but you probably have no reason to use them from Emacs.
27222 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27223 a graphical mode, enabled by default, which provides further buffers
27224 that can control the execution and describe the state of your program.
27225 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27227 If you specify an absolute file name when prompted for the @kbd{M-x
27228 gdb} argument, then Emacs sets your current working directory to where
27229 your program resides. If you only specify the file name, then Emacs
27230 sets your current working directory to the directory associated
27231 with the previous buffer. In this case, @value{GDBN} may find your
27232 program by searching your environment's @code{PATH} variable, but on
27233 some operating systems it might not find the source. So, although the
27234 @value{GDBN} input and output session proceeds normally, the auxiliary
27235 buffer does not display the current source and line of execution.
27237 The initial working directory of @value{GDBN} is printed on the top
27238 line of the GUD buffer and this serves as a default for the commands
27239 that specify files for @value{GDBN} to operate on. @xref{Files,
27240 ,Commands to Specify Files}.
27242 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27243 need to call @value{GDBN} by a different name (for example, if you
27244 keep several configurations around, with different names) you can
27245 customize the Emacs variable @code{gud-gdb-command-name} to run the
27248 In the GUD buffer, you can use these special Emacs commands in
27249 addition to the standard Shell mode commands:
27253 Describe the features of Emacs' GUD Mode.
27256 Execute to another source line, like the @value{GDBN} @code{step} command; also
27257 update the display window to show the current file and location.
27260 Execute to next source line in this function, skipping all function
27261 calls, like the @value{GDBN} @code{next} command. Then update the display window
27262 to show the current file and location.
27265 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27266 display window accordingly.
27269 Execute until exit from the selected stack frame, like the @value{GDBN}
27270 @code{finish} command.
27273 Continue execution of your program, like the @value{GDBN} @code{continue}
27277 Go up the number of frames indicated by the numeric argument
27278 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27279 like the @value{GDBN} @code{up} command.
27282 Go down the number of frames indicated by the numeric argument, like the
27283 @value{GDBN} @code{down} command.
27286 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27287 tells @value{GDBN} to set a breakpoint on the source line point is on.
27289 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27290 separate frame which shows a backtrace when the GUD buffer is current.
27291 Move point to any frame in the stack and type @key{RET} to make it
27292 become the current frame and display the associated source in the
27293 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27294 selected frame become the current one. In graphical mode, the
27295 speedbar displays watch expressions.
27297 If you accidentally delete the source-display buffer, an easy way to get
27298 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27299 request a frame display; when you run under Emacs, this recreates
27300 the source buffer if necessary to show you the context of the current
27303 The source files displayed in Emacs are in ordinary Emacs buffers
27304 which are visiting the source files in the usual way. You can edit
27305 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27306 communicates with Emacs in terms of line numbers. If you add or
27307 delete lines from the text, the line numbers that @value{GDBN} knows cease
27308 to correspond properly with the code.
27310 A more detailed description of Emacs' interaction with @value{GDBN} is
27311 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27315 @chapter The @sc{gdb/mi} Interface
27317 @unnumberedsec Function and Purpose
27319 @cindex @sc{gdb/mi}, its purpose
27320 @sc{gdb/mi} is a line based machine oriented text interface to
27321 @value{GDBN} and is activated by specifying using the
27322 @option{--interpreter} command line option (@pxref{Mode Options}). It
27323 is specifically intended to support the development of systems which
27324 use the debugger as just one small component of a larger system.
27326 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27327 in the form of a reference manual.
27329 Note that @sc{gdb/mi} is still under construction, so some of the
27330 features described below are incomplete and subject to change
27331 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27333 @unnumberedsec Notation and Terminology
27335 @cindex notational conventions, for @sc{gdb/mi}
27336 This chapter uses the following notation:
27340 @code{|} separates two alternatives.
27343 @code{[ @var{something} ]} indicates that @var{something} is optional:
27344 it may or may not be given.
27347 @code{( @var{group} )*} means that @var{group} inside the parentheses
27348 may repeat zero or more times.
27351 @code{( @var{group} )+} means that @var{group} inside the parentheses
27352 may repeat one or more times.
27355 @code{"@var{string}"} means a literal @var{string}.
27359 @heading Dependencies
27363 * GDB/MI General Design::
27364 * GDB/MI Command Syntax::
27365 * GDB/MI Compatibility with CLI::
27366 * GDB/MI Development and Front Ends::
27367 * GDB/MI Output Records::
27368 * GDB/MI Simple Examples::
27369 * GDB/MI Command Description Format::
27370 * GDB/MI Breakpoint Commands::
27371 * GDB/MI Catchpoint Commands::
27372 * GDB/MI Program Context::
27373 * GDB/MI Thread Commands::
27374 * GDB/MI Ada Tasking Commands::
27375 * GDB/MI Program Execution::
27376 * GDB/MI Stack Manipulation::
27377 * GDB/MI Variable Objects::
27378 * GDB/MI Data Manipulation::
27379 * GDB/MI Tracepoint Commands::
27380 * GDB/MI Symbol Query::
27381 * GDB/MI File Commands::
27383 * GDB/MI Kod Commands::
27384 * GDB/MI Memory Overlay Commands::
27385 * GDB/MI Signal Handling Commands::
27387 * GDB/MI Target Manipulation::
27388 * GDB/MI File Transfer Commands::
27389 * GDB/MI Miscellaneous Commands::
27392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27393 @node GDB/MI General Design
27394 @section @sc{gdb/mi} General Design
27395 @cindex GDB/MI General Design
27397 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27398 parts---commands sent to @value{GDBN}, responses to those commands
27399 and notifications. Each command results in exactly one response,
27400 indicating either successful completion of the command, or an error.
27401 For the commands that do not resume the target, the response contains the
27402 requested information. For the commands that resume the target, the
27403 response only indicates whether the target was successfully resumed.
27404 Notifications is the mechanism for reporting changes in the state of the
27405 target, or in @value{GDBN} state, that cannot conveniently be associated with
27406 a command and reported as part of that command response.
27408 The important examples of notifications are:
27412 Exec notifications. These are used to report changes in
27413 target state---when a target is resumed, or stopped. It would not
27414 be feasible to include this information in response of resuming
27415 commands, because one resume commands can result in multiple events in
27416 different threads. Also, quite some time may pass before any event
27417 happens in the target, while a frontend needs to know whether the resuming
27418 command itself was successfully executed.
27421 Console output, and status notifications. Console output
27422 notifications are used to report output of CLI commands, as well as
27423 diagnostics for other commands. Status notifications are used to
27424 report the progress of a long-running operation. Naturally, including
27425 this information in command response would mean no output is produced
27426 until the command is finished, which is undesirable.
27429 General notifications. Commands may have various side effects on
27430 the @value{GDBN} or target state beyond their official purpose. For example,
27431 a command may change the selected thread. Although such changes can
27432 be included in command response, using notification allows for more
27433 orthogonal frontend design.
27437 There's no guarantee that whenever an MI command reports an error,
27438 @value{GDBN} or the target are in any specific state, and especially,
27439 the state is not reverted to the state before the MI command was
27440 processed. Therefore, whenever an MI command results in an error,
27441 we recommend that the frontend refreshes all the information shown in
27442 the user interface.
27446 * Context management::
27447 * Asynchronous and non-stop modes::
27451 @node Context management
27452 @subsection Context management
27454 In most cases when @value{GDBN} accesses the target, this access is
27455 done in context of a specific thread and frame (@pxref{Frames}).
27456 Often, even when accessing global data, the target requires that a thread
27457 be specified. The CLI interface maintains the selected thread and frame,
27458 and supplies them to target on each command. This is convenient,
27459 because a command line user would not want to specify that information
27460 explicitly on each command, and because user interacts with
27461 @value{GDBN} via a single terminal, so no confusion is possible as
27462 to what thread and frame are the current ones.
27464 In the case of MI, the concept of selected thread and frame is less
27465 useful. First, a frontend can easily remember this information
27466 itself. Second, a graphical frontend can have more than one window,
27467 each one used for debugging a different thread, and the frontend might
27468 want to access additional threads for internal purposes. This
27469 increases the risk that by relying on implicitly selected thread, the
27470 frontend may be operating on a wrong one. Therefore, each MI command
27471 should explicitly specify which thread and frame to operate on. To
27472 make it possible, each MI command accepts the @samp{--thread} and
27473 @samp{--frame} options, the value to each is @value{GDBN} identifier
27474 for thread and frame to operate on.
27476 Usually, each top-level window in a frontend allows the user to select
27477 a thread and a frame, and remembers the user selection for further
27478 operations. However, in some cases @value{GDBN} may suggest that the
27479 current thread be changed. For example, when stopping on a breakpoint
27480 it is reasonable to switch to the thread where breakpoint is hit. For
27481 another example, if the user issues the CLI @samp{thread} command via
27482 the frontend, it is desirable to change the frontend's selected thread to the
27483 one specified by user. @value{GDBN} communicates the suggestion to
27484 change current thread using the @samp{=thread-selected} notification.
27485 No such notification is available for the selected frame at the moment.
27487 Note that historically, MI shares the selected thread with CLI, so
27488 frontends used the @code{-thread-select} to execute commands in the
27489 right context. However, getting this to work right is cumbersome. The
27490 simplest way is for frontend to emit @code{-thread-select} command
27491 before every command. This doubles the number of commands that need
27492 to be sent. The alternative approach is to suppress @code{-thread-select}
27493 if the selected thread in @value{GDBN} is supposed to be identical to the
27494 thread the frontend wants to operate on. However, getting this
27495 optimization right can be tricky. In particular, if the frontend
27496 sends several commands to @value{GDBN}, and one of the commands changes the
27497 selected thread, then the behaviour of subsequent commands will
27498 change. So, a frontend should either wait for response from such
27499 problematic commands, or explicitly add @code{-thread-select} for
27500 all subsequent commands. No frontend is known to do this exactly
27501 right, so it is suggested to just always pass the @samp{--thread} and
27502 @samp{--frame} options.
27504 @node Asynchronous and non-stop modes
27505 @subsection Asynchronous command execution and non-stop mode
27507 On some targets, @value{GDBN} is capable of processing MI commands
27508 even while the target is running. This is called @dfn{asynchronous
27509 command execution} (@pxref{Background Execution}). The frontend may
27510 specify a preferrence for asynchronous execution using the
27511 @code{-gdb-set target-async 1} command, which should be emitted before
27512 either running the executable or attaching to the target. After the
27513 frontend has started the executable or attached to the target, it can
27514 find if asynchronous execution is enabled using the
27515 @code{-list-target-features} command.
27517 Even if @value{GDBN} can accept a command while target is running,
27518 many commands that access the target do not work when the target is
27519 running. Therefore, asynchronous command execution is most useful
27520 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27521 it is possible to examine the state of one thread, while other threads
27524 When a given thread is running, MI commands that try to access the
27525 target in the context of that thread may not work, or may work only on
27526 some targets. In particular, commands that try to operate on thread's
27527 stack will not work, on any target. Commands that read memory, or
27528 modify breakpoints, may work or not work, depending on the target. Note
27529 that even commands that operate on global state, such as @code{print},
27530 @code{set}, and breakpoint commands, still access the target in the
27531 context of a specific thread, so frontend should try to find a
27532 stopped thread and perform the operation on that thread (using the
27533 @samp{--thread} option).
27535 Which commands will work in the context of a running thread is
27536 highly target dependent. However, the two commands
27537 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27538 to find the state of a thread, will always work.
27540 @node Thread groups
27541 @subsection Thread groups
27542 @value{GDBN} may be used to debug several processes at the same time.
27543 On some platfroms, @value{GDBN} may support debugging of several
27544 hardware systems, each one having several cores with several different
27545 processes running on each core. This section describes the MI
27546 mechanism to support such debugging scenarios.
27548 The key observation is that regardless of the structure of the
27549 target, MI can have a global list of threads, because most commands that
27550 accept the @samp{--thread} option do not need to know what process that
27551 thread belongs to. Therefore, it is not necessary to introduce
27552 neither additional @samp{--process} option, nor an notion of the
27553 current process in the MI interface. The only strictly new feature
27554 that is required is the ability to find how the threads are grouped
27557 To allow the user to discover such grouping, and to support arbitrary
27558 hierarchy of machines/cores/processes, MI introduces the concept of a
27559 @dfn{thread group}. Thread group is a collection of threads and other
27560 thread groups. A thread group always has a string identifier, a type,
27561 and may have additional attributes specific to the type. A new
27562 command, @code{-list-thread-groups}, returns the list of top-level
27563 thread groups, which correspond to processes that @value{GDBN} is
27564 debugging at the moment. By passing an identifier of a thread group
27565 to the @code{-list-thread-groups} command, it is possible to obtain
27566 the members of specific thread group.
27568 To allow the user to easily discover processes, and other objects, he
27569 wishes to debug, a concept of @dfn{available thread group} is
27570 introduced. Available thread group is an thread group that
27571 @value{GDBN} is not debugging, but that can be attached to, using the
27572 @code{-target-attach} command. The list of available top-level thread
27573 groups can be obtained using @samp{-list-thread-groups --available}.
27574 In general, the content of a thread group may be only retrieved only
27575 after attaching to that thread group.
27577 Thread groups are related to inferiors (@pxref{Inferiors and
27578 Programs}). Each inferior corresponds to a thread group of a special
27579 type @samp{process}, and some additional operations are permitted on
27580 such thread groups.
27582 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27583 @node GDB/MI Command Syntax
27584 @section @sc{gdb/mi} Command Syntax
27587 * GDB/MI Input Syntax::
27588 * GDB/MI Output Syntax::
27591 @node GDB/MI Input Syntax
27592 @subsection @sc{gdb/mi} Input Syntax
27594 @cindex input syntax for @sc{gdb/mi}
27595 @cindex @sc{gdb/mi}, input syntax
27597 @item @var{command} @expansion{}
27598 @code{@var{cli-command} | @var{mi-command}}
27600 @item @var{cli-command} @expansion{}
27601 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27602 @var{cli-command} is any existing @value{GDBN} CLI command.
27604 @item @var{mi-command} @expansion{}
27605 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27606 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27608 @item @var{token} @expansion{}
27609 "any sequence of digits"
27611 @item @var{option} @expansion{}
27612 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27614 @item @var{parameter} @expansion{}
27615 @code{@var{non-blank-sequence} | @var{c-string}}
27617 @item @var{operation} @expansion{}
27618 @emph{any of the operations described in this chapter}
27620 @item @var{non-blank-sequence} @expansion{}
27621 @emph{anything, provided it doesn't contain special characters such as
27622 "-", @var{nl}, """ and of course " "}
27624 @item @var{c-string} @expansion{}
27625 @code{""" @var{seven-bit-iso-c-string-content} """}
27627 @item @var{nl} @expansion{}
27636 The CLI commands are still handled by the @sc{mi} interpreter; their
27637 output is described below.
27640 The @code{@var{token}}, when present, is passed back when the command
27644 Some @sc{mi} commands accept optional arguments as part of the parameter
27645 list. Each option is identified by a leading @samp{-} (dash) and may be
27646 followed by an optional argument parameter. Options occur first in the
27647 parameter list and can be delimited from normal parameters using
27648 @samp{--} (this is useful when some parameters begin with a dash).
27655 We want easy access to the existing CLI syntax (for debugging).
27658 We want it to be easy to spot a @sc{mi} operation.
27661 @node GDB/MI Output Syntax
27662 @subsection @sc{gdb/mi} Output Syntax
27664 @cindex output syntax of @sc{gdb/mi}
27665 @cindex @sc{gdb/mi}, output syntax
27666 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27667 followed, optionally, by a single result record. This result record
27668 is for the most recent command. The sequence of output records is
27669 terminated by @samp{(gdb)}.
27671 If an input command was prefixed with a @code{@var{token}} then the
27672 corresponding output for that command will also be prefixed by that same
27676 @item @var{output} @expansion{}
27677 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27679 @item @var{result-record} @expansion{}
27680 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27682 @item @var{out-of-band-record} @expansion{}
27683 @code{@var{async-record} | @var{stream-record}}
27685 @item @var{async-record} @expansion{}
27686 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27688 @item @var{exec-async-output} @expansion{}
27689 @code{[ @var{token} ] "*" @var{async-output}}
27691 @item @var{status-async-output} @expansion{}
27692 @code{[ @var{token} ] "+" @var{async-output}}
27694 @item @var{notify-async-output} @expansion{}
27695 @code{[ @var{token} ] "=" @var{async-output}}
27697 @item @var{async-output} @expansion{}
27698 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27700 @item @var{result-class} @expansion{}
27701 @code{"done" | "running" | "connected" | "error" | "exit"}
27703 @item @var{async-class} @expansion{}
27704 @code{"stopped" | @var{others}} (where @var{others} will be added
27705 depending on the needs---this is still in development).
27707 @item @var{result} @expansion{}
27708 @code{ @var{variable} "=" @var{value}}
27710 @item @var{variable} @expansion{}
27711 @code{ @var{string} }
27713 @item @var{value} @expansion{}
27714 @code{ @var{const} | @var{tuple} | @var{list} }
27716 @item @var{const} @expansion{}
27717 @code{@var{c-string}}
27719 @item @var{tuple} @expansion{}
27720 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27722 @item @var{list} @expansion{}
27723 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27724 @var{result} ( "," @var{result} )* "]" }
27726 @item @var{stream-record} @expansion{}
27727 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27729 @item @var{console-stream-output} @expansion{}
27730 @code{"~" @var{c-string}}
27732 @item @var{target-stream-output} @expansion{}
27733 @code{"@@" @var{c-string}}
27735 @item @var{log-stream-output} @expansion{}
27736 @code{"&" @var{c-string}}
27738 @item @var{nl} @expansion{}
27741 @item @var{token} @expansion{}
27742 @emph{any sequence of digits}.
27750 All output sequences end in a single line containing a period.
27753 The @code{@var{token}} is from the corresponding request. Note that
27754 for all async output, while the token is allowed by the grammar and
27755 may be output by future versions of @value{GDBN} for select async
27756 output messages, it is generally omitted. Frontends should treat
27757 all async output as reporting general changes in the state of the
27758 target and there should be no need to associate async output to any
27762 @cindex status output in @sc{gdb/mi}
27763 @var{status-async-output} contains on-going status information about the
27764 progress of a slow operation. It can be discarded. All status output is
27765 prefixed by @samp{+}.
27768 @cindex async output in @sc{gdb/mi}
27769 @var{exec-async-output} contains asynchronous state change on the target
27770 (stopped, started, disappeared). All async output is prefixed by
27774 @cindex notify output in @sc{gdb/mi}
27775 @var{notify-async-output} contains supplementary information that the
27776 client should handle (e.g., a new breakpoint information). All notify
27777 output is prefixed by @samp{=}.
27780 @cindex console output in @sc{gdb/mi}
27781 @var{console-stream-output} is output that should be displayed as is in the
27782 console. It is the textual response to a CLI command. All the console
27783 output is prefixed by @samp{~}.
27786 @cindex target output in @sc{gdb/mi}
27787 @var{target-stream-output} is the output produced by the target program.
27788 All the target output is prefixed by @samp{@@}.
27791 @cindex log output in @sc{gdb/mi}
27792 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27793 instance messages that should be displayed as part of an error log. All
27794 the log output is prefixed by @samp{&}.
27797 @cindex list output in @sc{gdb/mi}
27798 New @sc{gdb/mi} commands should only output @var{lists} containing
27804 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27805 details about the various output records.
27807 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27808 @node GDB/MI Compatibility with CLI
27809 @section @sc{gdb/mi} Compatibility with CLI
27811 @cindex compatibility, @sc{gdb/mi} and CLI
27812 @cindex @sc{gdb/mi}, compatibility with CLI
27814 For the developers convenience CLI commands can be entered directly,
27815 but there may be some unexpected behaviour. For example, commands
27816 that query the user will behave as if the user replied yes, breakpoint
27817 command lists are not executed and some CLI commands, such as
27818 @code{if}, @code{when} and @code{define}, prompt for further input with
27819 @samp{>}, which is not valid MI output.
27821 This feature may be removed at some stage in the future and it is
27822 recommended that front ends use the @code{-interpreter-exec} command
27823 (@pxref{-interpreter-exec}).
27825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27826 @node GDB/MI Development and Front Ends
27827 @section @sc{gdb/mi} Development and Front Ends
27828 @cindex @sc{gdb/mi} development
27830 The application which takes the MI output and presents the state of the
27831 program being debugged to the user is called a @dfn{front end}.
27833 Although @sc{gdb/mi} is still incomplete, it is currently being used
27834 by a variety of front ends to @value{GDBN}. This makes it difficult
27835 to introduce new functionality without breaking existing usage. This
27836 section tries to minimize the problems by describing how the protocol
27839 Some changes in MI need not break a carefully designed front end, and
27840 for these the MI version will remain unchanged. The following is a
27841 list of changes that may occur within one level, so front ends should
27842 parse MI output in a way that can handle them:
27846 New MI commands may be added.
27849 New fields may be added to the output of any MI command.
27852 The range of values for fields with specified values, e.g.,
27853 @code{in_scope} (@pxref{-var-update}) may be extended.
27855 @c The format of field's content e.g type prefix, may change so parse it
27856 @c at your own risk. Yes, in general?
27858 @c The order of fields may change? Shouldn't really matter but it might
27859 @c resolve inconsistencies.
27862 If the changes are likely to break front ends, the MI version level
27863 will be increased by one. This will allow the front end to parse the
27864 output according to the MI version. Apart from mi0, new versions of
27865 @value{GDBN} will not support old versions of MI and it will be the
27866 responsibility of the front end to work with the new one.
27868 @c Starting with mi3, add a new command -mi-version that prints the MI
27871 The best way to avoid unexpected changes in MI that might break your front
27872 end is to make your project known to @value{GDBN} developers and
27873 follow development on @email{gdb@@sourceware.org} and
27874 @email{gdb-patches@@sourceware.org}.
27875 @cindex mailing lists
27877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27878 @node GDB/MI Output Records
27879 @section @sc{gdb/mi} Output Records
27882 * GDB/MI Result Records::
27883 * GDB/MI Stream Records::
27884 * GDB/MI Async Records::
27885 * GDB/MI Breakpoint Information::
27886 * GDB/MI Frame Information::
27887 * GDB/MI Thread Information::
27888 * GDB/MI Ada Exception Information::
27891 @node GDB/MI Result Records
27892 @subsection @sc{gdb/mi} Result Records
27894 @cindex result records in @sc{gdb/mi}
27895 @cindex @sc{gdb/mi}, result records
27896 In addition to a number of out-of-band notifications, the response to a
27897 @sc{gdb/mi} command includes one of the following result indications:
27901 @item "^done" [ "," @var{results} ]
27902 The synchronous operation was successful, @code{@var{results}} are the return
27907 This result record is equivalent to @samp{^done}. Historically, it
27908 was output instead of @samp{^done} if the command has resumed the
27909 target. This behaviour is maintained for backward compatibility, but
27910 all frontends should treat @samp{^done} and @samp{^running}
27911 identically and rely on the @samp{*running} output record to determine
27912 which threads are resumed.
27916 @value{GDBN} has connected to a remote target.
27918 @item "^error" "," @var{c-string}
27920 The operation failed. The @code{@var{c-string}} contains the corresponding
27925 @value{GDBN} has terminated.
27929 @node GDB/MI Stream Records
27930 @subsection @sc{gdb/mi} Stream Records
27932 @cindex @sc{gdb/mi}, stream records
27933 @cindex stream records in @sc{gdb/mi}
27934 @value{GDBN} internally maintains a number of output streams: the console, the
27935 target, and the log. The output intended for each of these streams is
27936 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27938 Each stream record begins with a unique @dfn{prefix character} which
27939 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27940 Syntax}). In addition to the prefix, each stream record contains a
27941 @code{@var{string-output}}. This is either raw text (with an implicit new
27942 line) or a quoted C string (which does not contain an implicit newline).
27945 @item "~" @var{string-output}
27946 The console output stream contains text that should be displayed in the
27947 CLI console window. It contains the textual responses to CLI commands.
27949 @item "@@" @var{string-output}
27950 The target output stream contains any textual output from the running
27951 target. This is only present when GDB's event loop is truly
27952 asynchronous, which is currently only the case for remote targets.
27954 @item "&" @var{string-output}
27955 The log stream contains debugging messages being produced by @value{GDBN}'s
27959 @node GDB/MI Async Records
27960 @subsection @sc{gdb/mi} Async Records
27962 @cindex async records in @sc{gdb/mi}
27963 @cindex @sc{gdb/mi}, async records
27964 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27965 additional changes that have occurred. Those changes can either be a
27966 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27967 target activity (e.g., target stopped).
27969 The following is the list of possible async records:
27973 @item *running,thread-id="@var{thread}"
27974 The target is now running. The @var{thread} field tells which
27975 specific thread is now running, and can be @samp{all} if all threads
27976 are running. The frontend should assume that no interaction with a
27977 running thread is possible after this notification is produced.
27978 The frontend should not assume that this notification is output
27979 only once for any command. @value{GDBN} may emit this notification
27980 several times, either for different threads, because it cannot resume
27981 all threads together, or even for a single thread, if the thread must
27982 be stepped though some code before letting it run freely.
27984 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27985 The target has stopped. The @var{reason} field can have one of the
27989 @item breakpoint-hit
27990 A breakpoint was reached.
27991 @item watchpoint-trigger
27992 A watchpoint was triggered.
27993 @item read-watchpoint-trigger
27994 A read watchpoint was triggered.
27995 @item access-watchpoint-trigger
27996 An access watchpoint was triggered.
27997 @item function-finished
27998 An -exec-finish or similar CLI command was accomplished.
27999 @item location-reached
28000 An -exec-until or similar CLI command was accomplished.
28001 @item watchpoint-scope
28002 A watchpoint has gone out of scope.
28003 @item end-stepping-range
28004 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28005 similar CLI command was accomplished.
28006 @item exited-signalled
28007 The inferior exited because of a signal.
28009 The inferior exited.
28010 @item exited-normally
28011 The inferior exited normally.
28012 @item signal-received
28013 A signal was received by the inferior.
28015 The inferior has stopped due to a library being loaded or unloaded.
28016 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28017 set or when a @code{catch load} or @code{catch unload} catchpoint is
28018 in use (@pxref{Set Catchpoints}).
28020 The inferior has forked. This is reported when @code{catch fork}
28021 (@pxref{Set Catchpoints}) has been used.
28023 The inferior has vforked. This is reported in when @code{catch vfork}
28024 (@pxref{Set Catchpoints}) has been used.
28025 @item syscall-entry
28026 The inferior entered a system call. This is reported when @code{catch
28027 syscall} (@pxref{Set Catchpoints}) has been used.
28028 @item syscall-entry
28029 The inferior returned from a system call. This is reported when
28030 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28032 The inferior called @code{exec}. This is reported when @code{catch exec}
28033 (@pxref{Set Catchpoints}) has been used.
28036 The @var{id} field identifies the thread that directly caused the stop
28037 -- for example by hitting a breakpoint. Depending on whether all-stop
28038 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28039 stop all threads, or only the thread that directly triggered the stop.
28040 If all threads are stopped, the @var{stopped} field will have the
28041 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28042 field will be a list of thread identifiers. Presently, this list will
28043 always include a single thread, but frontend should be prepared to see
28044 several threads in the list. The @var{core} field reports the
28045 processor core on which the stop event has happened. This field may be absent
28046 if such information is not available.
28048 @item =thread-group-added,id="@var{id}"
28049 @itemx =thread-group-removed,id="@var{id}"
28050 A thread group was either added or removed. The @var{id} field
28051 contains the @value{GDBN} identifier of the thread group. When a thread
28052 group is added, it generally might not be associated with a running
28053 process. When a thread group is removed, its id becomes invalid and
28054 cannot be used in any way.
28056 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28057 A thread group became associated with a running program,
28058 either because the program was just started or the thread group
28059 was attached to a program. The @var{id} field contains the
28060 @value{GDBN} identifier of the thread group. The @var{pid} field
28061 contains process identifier, specific to the operating system.
28063 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28064 A thread group is no longer associated with a running program,
28065 either because the program has exited, or because it was detached
28066 from. The @var{id} field contains the @value{GDBN} identifier of the
28067 thread group. @var{code} is the exit code of the inferior; it exists
28068 only when the inferior exited with some code.
28070 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28071 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28072 A thread either was created, or has exited. The @var{id} field
28073 contains the @value{GDBN} identifier of the thread. The @var{gid}
28074 field identifies the thread group this thread belongs to.
28076 @item =thread-selected,id="@var{id}"
28077 Informs that the selected thread was changed as result of the last
28078 command. This notification is not emitted as result of @code{-thread-select}
28079 command but is emitted whenever an MI command that is not documented
28080 to change the selected thread actually changes it. In particular,
28081 invoking, directly or indirectly (via user-defined command), the CLI
28082 @code{thread} command, will generate this notification.
28084 We suggest that in response to this notification, front ends
28085 highlight the selected thread and cause subsequent commands to apply to
28088 @item =library-loaded,...
28089 Reports that a new library file was loaded by the program. This
28090 notification has 4 fields---@var{id}, @var{target-name},
28091 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28092 opaque identifier of the library. For remote debugging case,
28093 @var{target-name} and @var{host-name} fields give the name of the
28094 library file on the target, and on the host respectively. For native
28095 debugging, both those fields have the same value. The
28096 @var{symbols-loaded} field is emitted only for backward compatibility
28097 and should not be relied on to convey any useful information. The
28098 @var{thread-group} field, if present, specifies the id of the thread
28099 group in whose context the library was loaded. If the field is
28100 absent, it means the library was loaded in the context of all present
28103 @item =library-unloaded,...
28104 Reports that a library was unloaded by the program. This notification
28105 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28106 the same meaning as for the @code{=library-loaded} notification.
28107 The @var{thread-group} field, if present, specifies the id of the
28108 thread group in whose context the library was unloaded. If the field is
28109 absent, it means the library was unloaded in the context of all present
28112 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28113 @itemx =traceframe-changed,end
28114 Reports that the trace frame was changed and its new number is
28115 @var{tfnum}. The number of the tracepoint associated with this trace
28116 frame is @var{tpnum}.
28118 @item =tsv-created,name=@var{name},initial=@var{initial}
28119 Reports that the new trace state variable @var{name} is created with
28120 initial value @var{initial}.
28122 @item =tsv-deleted,name=@var{name}
28123 @itemx =tsv-deleted
28124 Reports that the trace state variable @var{name} is deleted or all
28125 trace state variables are deleted.
28127 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28128 Reports that the trace state variable @var{name} is modified with
28129 the initial value @var{initial}. The current value @var{current} of
28130 trace state variable is optional and is reported if the current
28131 value of trace state variable is known.
28133 @item =breakpoint-created,bkpt=@{...@}
28134 @itemx =breakpoint-modified,bkpt=@{...@}
28135 @itemx =breakpoint-deleted,id=@var{number}
28136 Reports that a breakpoint was created, modified, or deleted,
28137 respectively. Only user-visible breakpoints are reported to the MI
28140 The @var{bkpt} argument is of the same form as returned by the various
28141 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28142 @var{number} is the ordinal number of the breakpoint.
28144 Note that if a breakpoint is emitted in the result record of a
28145 command, then it will not also be emitted in an async record.
28147 @item =record-started,thread-group="@var{id}"
28148 @itemx =record-stopped,thread-group="@var{id}"
28149 Execution log recording was either started or stopped on an
28150 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28151 group corresponding to the affected inferior.
28153 @item =cmd-param-changed,param=@var{param},value=@var{value}
28154 Reports that a parameter of the command @code{set @var{param}} is
28155 changed to @var{value}. In the multi-word @code{set} command,
28156 the @var{param} is the whole parameter list to @code{set} command.
28157 For example, In command @code{set check type on}, @var{param}
28158 is @code{check type} and @var{value} is @code{on}.
28160 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28161 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28162 written in an inferior. The @var{id} is the identifier of the
28163 thread group corresponding to the affected inferior. The optional
28164 @code{type="code"} part is reported if the memory written to holds
28168 @node GDB/MI Breakpoint Information
28169 @subsection @sc{gdb/mi} Breakpoint Information
28171 When @value{GDBN} reports information about a breakpoint, a
28172 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28177 The breakpoint number. For a breakpoint that represents one location
28178 of a multi-location breakpoint, this will be a dotted pair, like
28182 The type of the breakpoint. For ordinary breakpoints this will be
28183 @samp{breakpoint}, but many values are possible.
28186 If the type of the breakpoint is @samp{catchpoint}, then this
28187 indicates the exact type of catchpoint.
28190 This is the breakpoint disposition---either @samp{del}, meaning that
28191 the breakpoint will be deleted at the next stop, or @samp{keep},
28192 meaning that the breakpoint will not be deleted.
28195 This indicates whether the breakpoint is enabled, in which case the
28196 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28197 Note that this is not the same as the field @code{enable}.
28200 The address of the breakpoint. This may be a hexidecimal number,
28201 giving the address; or the string @samp{<PENDING>}, for a pending
28202 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28203 multiple locations. This field will not be present if no address can
28204 be determined. For example, a watchpoint does not have an address.
28207 If known, the function in which the breakpoint appears.
28208 If not known, this field is not present.
28211 The name of the source file which contains this function, if known.
28212 If not known, this field is not present.
28215 The full file name of the source file which contains this function, if
28216 known. If not known, this field is not present.
28219 The line number at which this breakpoint appears, if known.
28220 If not known, this field is not present.
28223 If the source file is not known, this field may be provided. If
28224 provided, this holds the address of the breakpoint, possibly followed
28228 If this breakpoint is pending, this field is present and holds the
28229 text used to set the breakpoint, as entered by the user.
28232 Where this breakpoint's condition is evaluated, either @samp{host} or
28236 If this is a thread-specific breakpoint, then this identifies the
28237 thread in which the breakpoint can trigger.
28240 If this breakpoint is restricted to a particular Ada task, then this
28241 field will hold the task identifier.
28244 If the breakpoint is conditional, this is the condition expression.
28247 The ignore count of the breakpoint.
28250 The enable count of the breakpoint.
28252 @item traceframe-usage
28255 @item static-tracepoint-marker-string-id
28256 For a static tracepoint, the name of the static tracepoint marker.
28259 For a masked watchpoint, this is the mask.
28262 A tracepoint's pass count.
28264 @item original-location
28265 The location of the breakpoint as originally specified by the user.
28266 This field is optional.
28269 The number of times the breakpoint has been hit.
28272 This field is only given for tracepoints. This is either @samp{y},
28273 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28277 Some extra data, the exact contents of which are type-dependent.
28281 For example, here is what the output of @code{-break-insert}
28282 (@pxref{GDB/MI Breakpoint Commands}) might be:
28285 -> -break-insert main
28286 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28287 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28288 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28293 @node GDB/MI Frame Information
28294 @subsection @sc{gdb/mi} Frame Information
28296 Response from many MI commands includes an information about stack
28297 frame. This information is a tuple that may have the following
28302 The level of the stack frame. The innermost frame has the level of
28303 zero. This field is always present.
28306 The name of the function corresponding to the frame. This field may
28307 be absent if @value{GDBN} is unable to determine the function name.
28310 The code address for the frame. This field is always present.
28313 The name of the source files that correspond to the frame's code
28314 address. This field may be absent.
28317 The source line corresponding to the frames' code address. This field
28321 The name of the binary file (either executable or shared library) the
28322 corresponds to the frame's code address. This field may be absent.
28326 @node GDB/MI Thread Information
28327 @subsection @sc{gdb/mi} Thread Information
28329 Whenever @value{GDBN} has to report an information about a thread, it
28330 uses a tuple with the following fields:
28334 The numeric id assigned to the thread by @value{GDBN}. This field is
28338 Target-specific string identifying the thread. This field is always present.
28341 Additional information about the thread provided by the target.
28342 It is supposed to be human-readable and not interpreted by the
28343 frontend. This field is optional.
28346 Either @samp{stopped} or @samp{running}, depending on whether the
28347 thread is presently running. This field is always present.
28350 The value of this field is an integer number of the processor core the
28351 thread was last seen on. This field is optional.
28354 @node GDB/MI Ada Exception Information
28355 @subsection @sc{gdb/mi} Ada Exception Information
28357 Whenever a @code{*stopped} record is emitted because the program
28358 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28359 @value{GDBN} provides the name of the exception that was raised via
28360 the @code{exception-name} field.
28362 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28363 @node GDB/MI Simple Examples
28364 @section Simple Examples of @sc{gdb/mi} Interaction
28365 @cindex @sc{gdb/mi}, simple examples
28367 This subsection presents several simple examples of interaction using
28368 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28369 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28370 the output received from @sc{gdb/mi}.
28372 Note the line breaks shown in the examples are here only for
28373 readability, they don't appear in the real output.
28375 @subheading Setting a Breakpoint
28377 Setting a breakpoint generates synchronous output which contains detailed
28378 information of the breakpoint.
28381 -> -break-insert main
28382 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28383 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28384 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28389 @subheading Program Execution
28391 Program execution generates asynchronous records and MI gives the
28392 reason that execution stopped.
28398 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28399 frame=@{addr="0x08048564",func="main",
28400 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28401 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28406 <- *stopped,reason="exited-normally"
28410 @subheading Quitting @value{GDBN}
28412 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28420 Please note that @samp{^exit} is printed immediately, but it might
28421 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28422 performs necessary cleanups, including killing programs being debugged
28423 or disconnecting from debug hardware, so the frontend should wait till
28424 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28425 fails to exit in reasonable time.
28427 @subheading A Bad Command
28429 Here's what happens if you pass a non-existent command:
28433 <- ^error,msg="Undefined MI command: rubbish"
28438 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28439 @node GDB/MI Command Description Format
28440 @section @sc{gdb/mi} Command Description Format
28442 The remaining sections describe blocks of commands. Each block of
28443 commands is laid out in a fashion similar to this section.
28445 @subheading Motivation
28447 The motivation for this collection of commands.
28449 @subheading Introduction
28451 A brief introduction to this collection of commands as a whole.
28453 @subheading Commands
28455 For each command in the block, the following is described:
28457 @subsubheading Synopsis
28460 -command @var{args}@dots{}
28463 @subsubheading Result
28465 @subsubheading @value{GDBN} Command
28467 The corresponding @value{GDBN} CLI command(s), if any.
28469 @subsubheading Example
28471 Example(s) formatted for readability. Some of the described commands have
28472 not been implemented yet and these are labeled N.A.@: (not available).
28475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28476 @node GDB/MI Breakpoint Commands
28477 @section @sc{gdb/mi} Breakpoint Commands
28479 @cindex breakpoint commands for @sc{gdb/mi}
28480 @cindex @sc{gdb/mi}, breakpoint commands
28481 This section documents @sc{gdb/mi} commands for manipulating
28484 @subheading The @code{-break-after} Command
28485 @findex -break-after
28487 @subsubheading Synopsis
28490 -break-after @var{number} @var{count}
28493 The breakpoint number @var{number} is not in effect until it has been
28494 hit @var{count} times. To see how this is reflected in the output of
28495 the @samp{-break-list} command, see the description of the
28496 @samp{-break-list} command below.
28498 @subsubheading @value{GDBN} Command
28500 The corresponding @value{GDBN} command is @samp{ignore}.
28502 @subsubheading Example
28507 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28508 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28509 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28517 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28518 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28519 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28520 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28521 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28522 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28523 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28524 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28525 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28526 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28531 @subheading The @code{-break-catch} Command
28532 @findex -break-catch
28535 @subheading The @code{-break-commands} Command
28536 @findex -break-commands
28538 @subsubheading Synopsis
28541 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28544 Specifies the CLI commands that should be executed when breakpoint
28545 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28546 are the commands. If no command is specified, any previously-set
28547 commands are cleared. @xref{Break Commands}. Typical use of this
28548 functionality is tracing a program, that is, printing of values of
28549 some variables whenever breakpoint is hit and then continuing.
28551 @subsubheading @value{GDBN} Command
28553 The corresponding @value{GDBN} command is @samp{commands}.
28555 @subsubheading Example
28560 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28561 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28562 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28565 -break-commands 1 "print v" "continue"
28570 @subheading The @code{-break-condition} Command
28571 @findex -break-condition
28573 @subsubheading Synopsis
28576 -break-condition @var{number} @var{expr}
28579 Breakpoint @var{number} will stop the program only if the condition in
28580 @var{expr} is true. The condition becomes part of the
28581 @samp{-break-list} output (see the description of the @samp{-break-list}
28584 @subsubheading @value{GDBN} Command
28586 The corresponding @value{GDBN} command is @samp{condition}.
28588 @subsubheading Example
28592 -break-condition 1 1
28596 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28597 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28598 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28599 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28600 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28601 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28602 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28603 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28604 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28605 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28609 @subheading The @code{-break-delete} Command
28610 @findex -break-delete
28612 @subsubheading Synopsis
28615 -break-delete ( @var{breakpoint} )+
28618 Delete the breakpoint(s) whose number(s) are specified in the argument
28619 list. This is obviously reflected in the breakpoint list.
28621 @subsubheading @value{GDBN} Command
28623 The corresponding @value{GDBN} command is @samp{delete}.
28625 @subsubheading Example
28633 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28634 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28635 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28636 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28637 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28638 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28639 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28644 @subheading The @code{-break-disable} Command
28645 @findex -break-disable
28647 @subsubheading Synopsis
28650 -break-disable ( @var{breakpoint} )+
28653 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28654 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28656 @subsubheading @value{GDBN} Command
28658 The corresponding @value{GDBN} command is @samp{disable}.
28660 @subsubheading Example
28668 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28669 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28670 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28671 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28672 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28673 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28674 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28675 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28676 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28677 line="5",thread-groups=["i1"],times="0"@}]@}
28681 @subheading The @code{-break-enable} Command
28682 @findex -break-enable
28684 @subsubheading Synopsis
28687 -break-enable ( @var{breakpoint} )+
28690 Enable (previously disabled) @var{breakpoint}(s).
28692 @subsubheading @value{GDBN} Command
28694 The corresponding @value{GDBN} command is @samp{enable}.
28696 @subsubheading Example
28704 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28705 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28706 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28707 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28708 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28709 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28710 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28711 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28712 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28713 line="5",thread-groups=["i1"],times="0"@}]@}
28717 @subheading The @code{-break-info} Command
28718 @findex -break-info
28720 @subsubheading Synopsis
28723 -break-info @var{breakpoint}
28727 Get information about a single breakpoint.
28729 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28730 Information}, for details on the format of each breakpoint in the
28733 @subsubheading @value{GDBN} Command
28735 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28737 @subsubheading Example
28740 @subheading The @code{-break-insert} Command
28741 @findex -break-insert
28743 @subsubheading Synopsis
28746 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28747 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28748 [ -p @var{thread-id} ] [ @var{location} ]
28752 If specified, @var{location}, can be one of:
28759 @item filename:linenum
28760 @item filename:function
28764 The possible optional parameters of this command are:
28768 Insert a temporary breakpoint.
28770 Insert a hardware breakpoint.
28772 If @var{location} cannot be parsed (for example if it
28773 refers to unknown files or functions), create a pending
28774 breakpoint. Without this flag, @value{GDBN} will report
28775 an error, and won't create a breakpoint, if @var{location}
28778 Create a disabled breakpoint.
28780 Create a tracepoint. @xref{Tracepoints}. When this parameter
28781 is used together with @samp{-h}, a fast tracepoint is created.
28782 @item -c @var{condition}
28783 Make the breakpoint conditional on @var{condition}.
28784 @item -i @var{ignore-count}
28785 Initialize the @var{ignore-count}.
28786 @item -p @var{thread-id}
28787 Restrict the breakpoint to the specified @var{thread-id}.
28790 @subsubheading Result
28792 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28793 resulting breakpoint.
28795 Note: this format is open to change.
28796 @c An out-of-band breakpoint instead of part of the result?
28798 @subsubheading @value{GDBN} Command
28800 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28801 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28803 @subsubheading Example
28808 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28809 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28812 -break-insert -t foo
28813 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28814 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28818 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28819 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28820 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28821 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28822 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28823 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28824 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28825 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28826 addr="0x0001072c", func="main",file="recursive2.c",
28827 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28829 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28830 addr="0x00010774",func="foo",file="recursive2.c",
28831 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28834 @c -break-insert -r foo.*
28835 @c ~int foo(int, int);
28836 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28837 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28842 @subheading The @code{-break-list} Command
28843 @findex -break-list
28845 @subsubheading Synopsis
28851 Displays the list of inserted breakpoints, showing the following fields:
28855 number of the breakpoint
28857 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28859 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28862 is the breakpoint enabled or no: @samp{y} or @samp{n}
28864 memory location at which the breakpoint is set
28866 logical location of the breakpoint, expressed by function name, file
28868 @item Thread-groups
28869 list of thread groups to which this breakpoint applies
28871 number of times the breakpoint has been hit
28874 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28875 @code{body} field is an empty list.
28877 @subsubheading @value{GDBN} Command
28879 The corresponding @value{GDBN} command is @samp{info break}.
28881 @subsubheading Example
28886 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28887 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28888 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28889 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28890 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28891 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28892 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28893 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28894 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28896 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28897 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28898 line="13",thread-groups=["i1"],times="0"@}]@}
28902 Here's an example of the result when there are no breakpoints:
28907 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28908 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28909 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28910 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28911 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28912 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28913 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28918 @subheading The @code{-break-passcount} Command
28919 @findex -break-passcount
28921 @subsubheading Synopsis
28924 -break-passcount @var{tracepoint-number} @var{passcount}
28927 Set the passcount for tracepoint @var{tracepoint-number} to
28928 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28929 is not a tracepoint, error is emitted. This corresponds to CLI
28930 command @samp{passcount}.
28932 @subheading The @code{-break-watch} Command
28933 @findex -break-watch
28935 @subsubheading Synopsis
28938 -break-watch [ -a | -r ]
28941 Create a watchpoint. With the @samp{-a} option it will create an
28942 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28943 read from or on a write to the memory location. With the @samp{-r}
28944 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28945 trigger only when the memory location is accessed for reading. Without
28946 either of the options, the watchpoint created is a regular watchpoint,
28947 i.e., it will trigger when the memory location is accessed for writing.
28948 @xref{Set Watchpoints, , Setting Watchpoints}.
28950 Note that @samp{-break-list} will report a single list of watchpoints and
28951 breakpoints inserted.
28953 @subsubheading @value{GDBN} Command
28955 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28958 @subsubheading Example
28960 Setting a watchpoint on a variable in the @code{main} function:
28965 ^done,wpt=@{number="2",exp="x"@}
28970 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28971 value=@{old="-268439212",new="55"@},
28972 frame=@{func="main",args=[],file="recursive2.c",
28973 fullname="/home/foo/bar/recursive2.c",line="5"@}
28977 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28978 the program execution twice: first for the variable changing value, then
28979 for the watchpoint going out of scope.
28984 ^done,wpt=@{number="5",exp="C"@}
28989 *stopped,reason="watchpoint-trigger",
28990 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28991 frame=@{func="callee4",args=[],
28992 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28993 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28998 *stopped,reason="watchpoint-scope",wpnum="5",
28999 frame=@{func="callee3",args=[@{name="strarg",
29000 value="0x11940 \"A string argument.\""@}],
29001 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29002 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29006 Listing breakpoints and watchpoints, at different points in the program
29007 execution. Note that once the watchpoint goes out of scope, it is
29013 ^done,wpt=@{number="2",exp="C"@}
29016 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29017 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29018 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29019 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29020 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29021 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29022 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29023 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29024 addr="0x00010734",func="callee4",
29025 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29026 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29028 bkpt=@{number="2",type="watchpoint",disp="keep",
29029 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29034 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29035 value=@{old="-276895068",new="3"@},
29036 frame=@{func="callee4",args=[],
29037 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29038 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29041 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29042 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29043 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29044 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29045 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29046 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29047 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29048 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29049 addr="0x00010734",func="callee4",
29050 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29051 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29053 bkpt=@{number="2",type="watchpoint",disp="keep",
29054 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29058 ^done,reason="watchpoint-scope",wpnum="2",
29059 frame=@{func="callee3",args=[@{name="strarg",
29060 value="0x11940 \"A string argument.\""@}],
29061 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29062 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29065 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29066 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29067 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29068 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29069 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29070 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29071 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29072 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29073 addr="0x00010734",func="callee4",
29074 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29075 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29076 thread-groups=["i1"],times="1"@}]@}
29081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29082 @node GDB/MI Catchpoint Commands
29083 @section @sc{gdb/mi} Catchpoint Commands
29085 This section documents @sc{gdb/mi} commands for manipulating
29088 @subheading The @code{-catch-load} Command
29089 @findex -catch-load
29091 @subsubheading Synopsis
29094 -catch-load [ -t ] [ -d ] @var{regexp}
29097 Add a catchpoint for library load events. If the @samp{-t} option is used,
29098 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29099 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29100 in a disabled state. The @samp{regexp} argument is a regular
29101 expression used to match the name of the loaded library.
29104 @subsubheading @value{GDBN} Command
29106 The corresponding @value{GDBN} command is @samp{catch load}.
29108 @subsubheading Example
29111 -catch-load -t foo.so
29112 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29113 what="load of library matching foo.so",catch-type="load",times="0"@}
29118 @subheading The @code{-catch-unload} Command
29119 @findex -catch-unload
29121 @subsubheading Synopsis
29124 -catch-unload [ -t ] [ -d ] @var{regexp}
29127 Add a catchpoint for library unload events. If the @samp{-t} option is
29128 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29129 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29130 created in a disabled state. The @samp{regexp} argument is a regular
29131 expression used to match the name of the unloaded library.
29133 @subsubheading @value{GDBN} Command
29135 The corresponding @value{GDBN} command is @samp{catch unload}.
29137 @subsubheading Example
29140 -catch-unload -d bar.so
29141 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29142 what="load of library matching bar.so",catch-type="unload",times="0"@}
29147 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29148 @node GDB/MI Program Context
29149 @section @sc{gdb/mi} Program Context
29151 @subheading The @code{-exec-arguments} Command
29152 @findex -exec-arguments
29155 @subsubheading Synopsis
29158 -exec-arguments @var{args}
29161 Set the inferior program arguments, to be used in the next
29164 @subsubheading @value{GDBN} Command
29166 The corresponding @value{GDBN} command is @samp{set args}.
29168 @subsubheading Example
29172 -exec-arguments -v word
29179 @subheading The @code{-exec-show-arguments} Command
29180 @findex -exec-show-arguments
29182 @subsubheading Synopsis
29185 -exec-show-arguments
29188 Print the arguments of the program.
29190 @subsubheading @value{GDBN} Command
29192 The corresponding @value{GDBN} command is @samp{show args}.
29194 @subsubheading Example
29199 @subheading The @code{-environment-cd} Command
29200 @findex -environment-cd
29202 @subsubheading Synopsis
29205 -environment-cd @var{pathdir}
29208 Set @value{GDBN}'s working directory.
29210 @subsubheading @value{GDBN} Command
29212 The corresponding @value{GDBN} command is @samp{cd}.
29214 @subsubheading Example
29218 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29224 @subheading The @code{-environment-directory} Command
29225 @findex -environment-directory
29227 @subsubheading Synopsis
29230 -environment-directory [ -r ] [ @var{pathdir} ]+
29233 Add directories @var{pathdir} to beginning of search path for source files.
29234 If the @samp{-r} option is used, the search path is reset to the default
29235 search path. If directories @var{pathdir} are supplied in addition to the
29236 @samp{-r} option, the search path is first reset and then addition
29238 Multiple directories may be specified, separated by blanks. Specifying
29239 multiple directories in a single command
29240 results in the directories added to the beginning of the
29241 search path in the same order they were presented in the command.
29242 If blanks are needed as
29243 part of a directory name, double-quotes should be used around
29244 the name. In the command output, the path will show up separated
29245 by the system directory-separator character. The directory-separator
29246 character must not be used
29247 in any directory name.
29248 If no directories are specified, the current search path is displayed.
29250 @subsubheading @value{GDBN} Command
29252 The corresponding @value{GDBN} command is @samp{dir}.
29254 @subsubheading Example
29258 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29259 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29261 -environment-directory ""
29262 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29264 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29265 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29267 -environment-directory -r
29268 ^done,source-path="$cdir:$cwd"
29273 @subheading The @code{-environment-path} Command
29274 @findex -environment-path
29276 @subsubheading Synopsis
29279 -environment-path [ -r ] [ @var{pathdir} ]+
29282 Add directories @var{pathdir} to beginning of search path for object files.
29283 If the @samp{-r} option is used, the search path is reset to the original
29284 search path that existed at gdb start-up. If directories @var{pathdir} are
29285 supplied in addition to the
29286 @samp{-r} option, the search path is first reset and then addition
29288 Multiple directories may be specified, separated by blanks. Specifying
29289 multiple directories in a single command
29290 results in the directories added to the beginning of the
29291 search path in the same order they were presented in the command.
29292 If blanks are needed as
29293 part of a directory name, double-quotes should be used around
29294 the name. In the command output, the path will show up separated
29295 by the system directory-separator character. The directory-separator
29296 character must not be used
29297 in any directory name.
29298 If no directories are specified, the current path is displayed.
29301 @subsubheading @value{GDBN} Command
29303 The corresponding @value{GDBN} command is @samp{path}.
29305 @subsubheading Example
29310 ^done,path="/usr/bin"
29312 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29313 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29315 -environment-path -r /usr/local/bin
29316 ^done,path="/usr/local/bin:/usr/bin"
29321 @subheading The @code{-environment-pwd} Command
29322 @findex -environment-pwd
29324 @subsubheading Synopsis
29330 Show the current working directory.
29332 @subsubheading @value{GDBN} Command
29334 The corresponding @value{GDBN} command is @samp{pwd}.
29336 @subsubheading Example
29341 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29345 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29346 @node GDB/MI Thread Commands
29347 @section @sc{gdb/mi} Thread Commands
29350 @subheading The @code{-thread-info} Command
29351 @findex -thread-info
29353 @subsubheading Synopsis
29356 -thread-info [ @var{thread-id} ]
29359 Reports information about either a specific thread, if
29360 the @var{thread-id} parameter is present, or about all
29361 threads. When printing information about all threads,
29362 also reports the current thread.
29364 @subsubheading @value{GDBN} Command
29366 The @samp{info thread} command prints the same information
29369 @subsubheading Result
29371 The result is a list of threads. The following attributes are
29372 defined for a given thread:
29376 This field exists only for the current thread. It has the value @samp{*}.
29379 The identifier that @value{GDBN} uses to refer to the thread.
29382 The identifier that the target uses to refer to the thread.
29385 Extra information about the thread, in a target-specific format. This
29389 The name of the thread. If the user specified a name using the
29390 @code{thread name} command, then this name is given. Otherwise, if
29391 @value{GDBN} can extract the thread name from the target, then that
29392 name is given. If @value{GDBN} cannot find the thread name, then this
29396 The stack frame currently executing in the thread.
29399 The thread's state. The @samp{state} field may have the following
29404 The thread is stopped. Frame information is available for stopped
29408 The thread is running. There's no frame information for running
29414 If @value{GDBN} can find the CPU core on which this thread is running,
29415 then this field is the core identifier. This field is optional.
29419 @subsubheading Example
29424 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29425 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29426 args=[]@},state="running"@},
29427 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29428 frame=@{level="0",addr="0x0804891f",func="foo",
29429 args=[@{name="i",value="10"@}],
29430 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29431 state="running"@}],
29432 current-thread-id="1"
29436 @subheading The @code{-thread-list-ids} Command
29437 @findex -thread-list-ids
29439 @subsubheading Synopsis
29445 Produces a list of the currently known @value{GDBN} thread ids. At the
29446 end of the list it also prints the total number of such threads.
29448 This command is retained for historical reasons, the
29449 @code{-thread-info} command should be used instead.
29451 @subsubheading @value{GDBN} Command
29453 Part of @samp{info threads} supplies the same information.
29455 @subsubheading Example
29460 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29461 current-thread-id="1",number-of-threads="3"
29466 @subheading The @code{-thread-select} Command
29467 @findex -thread-select
29469 @subsubheading Synopsis
29472 -thread-select @var{threadnum}
29475 Make @var{threadnum} the current thread. It prints the number of the new
29476 current thread, and the topmost frame for that thread.
29478 This command is deprecated in favor of explicitly using the
29479 @samp{--thread} option to each command.
29481 @subsubheading @value{GDBN} Command
29483 The corresponding @value{GDBN} command is @samp{thread}.
29485 @subsubheading Example
29492 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29493 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29497 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29498 number-of-threads="3"
29501 ^done,new-thread-id="3",
29502 frame=@{level="0",func="vprintf",
29503 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29504 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29508 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29509 @node GDB/MI Ada Tasking Commands
29510 @section @sc{gdb/mi} Ada Tasking Commands
29512 @subheading The @code{-ada-task-info} Command
29513 @findex -ada-task-info
29515 @subsubheading Synopsis
29518 -ada-task-info [ @var{task-id} ]
29521 Reports information about either a specific Ada task, if the
29522 @var{task-id} parameter is present, or about all Ada tasks.
29524 @subsubheading @value{GDBN} Command
29526 The @samp{info tasks} command prints the same information
29527 about all Ada tasks (@pxref{Ada Tasks}).
29529 @subsubheading Result
29531 The result is a table of Ada tasks. The following columns are
29532 defined for each Ada task:
29536 This field exists only for the current thread. It has the value @samp{*}.
29539 The identifier that @value{GDBN} uses to refer to the Ada task.
29542 The identifier that the target uses to refer to the Ada task.
29545 The identifier of the thread corresponding to the Ada task.
29547 This field should always exist, as Ada tasks are always implemented
29548 on top of a thread. But if @value{GDBN} cannot find this corresponding
29549 thread for any reason, the field is omitted.
29552 This field exists only when the task was created by another task.
29553 In this case, it provides the ID of the parent task.
29556 The base priority of the task.
29559 The current state of the task. For a detailed description of the
29560 possible states, see @ref{Ada Tasks}.
29563 The name of the task.
29567 @subsubheading Example
29571 ^done,tasks=@{nr_rows="3",nr_cols="8",
29572 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29573 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29574 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29575 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29576 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29577 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29578 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29579 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29580 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29581 state="Child Termination Wait",name="main_task"@}]@}
29585 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29586 @node GDB/MI Program Execution
29587 @section @sc{gdb/mi} Program Execution
29589 These are the asynchronous commands which generate the out-of-band
29590 record @samp{*stopped}. Currently @value{GDBN} only really executes
29591 asynchronously with remote targets and this interaction is mimicked in
29594 @subheading The @code{-exec-continue} Command
29595 @findex -exec-continue
29597 @subsubheading Synopsis
29600 -exec-continue [--reverse] [--all|--thread-group N]
29603 Resumes the execution of the inferior program, which will continue
29604 to execute until it reaches a debugger stop event. If the
29605 @samp{--reverse} option is specified, execution resumes in reverse until
29606 it reaches a stop event. Stop events may include
29609 breakpoints or watchpoints
29611 signals or exceptions
29613 the end of the process (or its beginning under @samp{--reverse})
29615 the end or beginning of a replay log if one is being used.
29617 In all-stop mode (@pxref{All-Stop
29618 Mode}), may resume only one thread, or all threads, depending on the
29619 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29620 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29621 ignored in all-stop mode. If the @samp{--thread-group} options is
29622 specified, then all threads in that thread group are resumed.
29624 @subsubheading @value{GDBN} Command
29626 The corresponding @value{GDBN} corresponding is @samp{continue}.
29628 @subsubheading Example
29635 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29636 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29642 @subheading The @code{-exec-finish} Command
29643 @findex -exec-finish
29645 @subsubheading Synopsis
29648 -exec-finish [--reverse]
29651 Resumes the execution of the inferior program until the current
29652 function is exited. Displays the results returned by the function.
29653 If the @samp{--reverse} option is specified, resumes the reverse
29654 execution of the inferior program until the point where current
29655 function was called.
29657 @subsubheading @value{GDBN} Command
29659 The corresponding @value{GDBN} command is @samp{finish}.
29661 @subsubheading Example
29663 Function returning @code{void}.
29670 *stopped,reason="function-finished",frame=@{func="main",args=[],
29671 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29675 Function returning other than @code{void}. The name of the internal
29676 @value{GDBN} variable storing the result is printed, together with the
29683 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29684 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29686 gdb-result-var="$1",return-value="0"
29691 @subheading The @code{-exec-interrupt} Command
29692 @findex -exec-interrupt
29694 @subsubheading Synopsis
29697 -exec-interrupt [--all|--thread-group N]
29700 Interrupts the background execution of the target. Note how the token
29701 associated with the stop message is the one for the execution command
29702 that has been interrupted. The token for the interrupt itself only
29703 appears in the @samp{^done} output. If the user is trying to
29704 interrupt a non-running program, an error message will be printed.
29706 Note that when asynchronous execution is enabled, this command is
29707 asynchronous just like other execution commands. That is, first the
29708 @samp{^done} response will be printed, and the target stop will be
29709 reported after that using the @samp{*stopped} notification.
29711 In non-stop mode, only the context thread is interrupted by default.
29712 All threads (in all inferiors) will be interrupted if the
29713 @samp{--all} option is specified. If the @samp{--thread-group}
29714 option is specified, all threads in that group will be interrupted.
29716 @subsubheading @value{GDBN} Command
29718 The corresponding @value{GDBN} command is @samp{interrupt}.
29720 @subsubheading Example
29731 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29732 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29733 fullname="/home/foo/bar/try.c",line="13"@}
29738 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29742 @subheading The @code{-exec-jump} Command
29745 @subsubheading Synopsis
29748 -exec-jump @var{location}
29751 Resumes execution of the inferior program at the location specified by
29752 parameter. @xref{Specify Location}, for a description of the
29753 different forms of @var{location}.
29755 @subsubheading @value{GDBN} Command
29757 The corresponding @value{GDBN} command is @samp{jump}.
29759 @subsubheading Example
29762 -exec-jump foo.c:10
29763 *running,thread-id="all"
29768 @subheading The @code{-exec-next} Command
29771 @subsubheading Synopsis
29774 -exec-next [--reverse]
29777 Resumes execution of the inferior program, stopping when the beginning
29778 of the next source line is reached.
29780 If the @samp{--reverse} option is specified, resumes reverse execution
29781 of the inferior program, stopping at the beginning of the previous
29782 source line. If you issue this command on the first line of a
29783 function, it will take you back to the caller of that function, to the
29784 source line where the function was called.
29787 @subsubheading @value{GDBN} Command
29789 The corresponding @value{GDBN} command is @samp{next}.
29791 @subsubheading Example
29797 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29802 @subheading The @code{-exec-next-instruction} Command
29803 @findex -exec-next-instruction
29805 @subsubheading Synopsis
29808 -exec-next-instruction [--reverse]
29811 Executes one machine instruction. If the instruction is a function
29812 call, continues until the function returns. If the program stops at an
29813 instruction in the middle of a source line, the address will be
29816 If the @samp{--reverse} option is specified, resumes reverse execution
29817 of the inferior program, stopping at the previous instruction. If the
29818 previously executed instruction was a return from another function,
29819 it will continue to execute in reverse until the call to that function
29820 (from the current stack frame) is reached.
29822 @subsubheading @value{GDBN} Command
29824 The corresponding @value{GDBN} command is @samp{nexti}.
29826 @subsubheading Example
29830 -exec-next-instruction
29834 *stopped,reason="end-stepping-range",
29835 addr="0x000100d4",line="5",file="hello.c"
29840 @subheading The @code{-exec-return} Command
29841 @findex -exec-return
29843 @subsubheading Synopsis
29849 Makes current function return immediately. Doesn't execute the inferior.
29850 Displays the new current frame.
29852 @subsubheading @value{GDBN} Command
29854 The corresponding @value{GDBN} command is @samp{return}.
29856 @subsubheading Example
29860 200-break-insert callee4
29861 200^done,bkpt=@{number="1",addr="0x00010734",
29862 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29867 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29868 frame=@{func="callee4",args=[],
29869 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29870 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29876 111^done,frame=@{level="0",func="callee3",
29877 args=[@{name="strarg",
29878 value="0x11940 \"A string argument.\""@}],
29879 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29880 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29885 @subheading The @code{-exec-run} Command
29888 @subsubheading Synopsis
29891 -exec-run [--all | --thread-group N]
29894 Starts execution of the inferior from the beginning. The inferior
29895 executes until either a breakpoint is encountered or the program
29896 exits. In the latter case the output will include an exit code, if
29897 the program has exited exceptionally.
29899 When no option is specified, the current inferior is started. If the
29900 @samp{--thread-group} option is specified, it should refer to a thread
29901 group of type @samp{process}, and that thread group will be started.
29902 If the @samp{--all} option is specified, then all inferiors will be started.
29904 @subsubheading @value{GDBN} Command
29906 The corresponding @value{GDBN} command is @samp{run}.
29908 @subsubheading Examples
29913 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29918 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29919 frame=@{func="main",args=[],file="recursive2.c",
29920 fullname="/home/foo/bar/recursive2.c",line="4"@}
29925 Program exited normally:
29933 *stopped,reason="exited-normally"
29938 Program exited exceptionally:
29946 *stopped,reason="exited",exit-code="01"
29950 Another way the program can terminate is if it receives a signal such as
29951 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29955 *stopped,reason="exited-signalled",signal-name="SIGINT",
29956 signal-meaning="Interrupt"
29960 @c @subheading -exec-signal
29963 @subheading The @code{-exec-step} Command
29966 @subsubheading Synopsis
29969 -exec-step [--reverse]
29972 Resumes execution of the inferior program, stopping when the beginning
29973 of the next source line is reached, if the next source line is not a
29974 function call. If it is, stop at the first instruction of the called
29975 function. If the @samp{--reverse} option is specified, resumes reverse
29976 execution of the inferior program, stopping at the beginning of the
29977 previously executed source line.
29979 @subsubheading @value{GDBN} Command
29981 The corresponding @value{GDBN} command is @samp{step}.
29983 @subsubheading Example
29985 Stepping into a function:
29991 *stopped,reason="end-stepping-range",
29992 frame=@{func="foo",args=[@{name="a",value="10"@},
29993 @{name="b",value="0"@}],file="recursive2.c",
29994 fullname="/home/foo/bar/recursive2.c",line="11"@}
30004 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30009 @subheading The @code{-exec-step-instruction} Command
30010 @findex -exec-step-instruction
30012 @subsubheading Synopsis
30015 -exec-step-instruction [--reverse]
30018 Resumes the inferior which executes one machine instruction. If the
30019 @samp{--reverse} option is specified, resumes reverse execution of the
30020 inferior program, stopping at the previously executed instruction.
30021 The output, once @value{GDBN} has stopped, will vary depending on
30022 whether we have stopped in the middle of a source line or not. In the
30023 former case, the address at which the program stopped will be printed
30026 @subsubheading @value{GDBN} Command
30028 The corresponding @value{GDBN} command is @samp{stepi}.
30030 @subsubheading Example
30034 -exec-step-instruction
30038 *stopped,reason="end-stepping-range",
30039 frame=@{func="foo",args=[],file="try.c",
30040 fullname="/home/foo/bar/try.c",line="10"@}
30042 -exec-step-instruction
30046 *stopped,reason="end-stepping-range",
30047 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30048 fullname="/home/foo/bar/try.c",line="10"@}
30053 @subheading The @code{-exec-until} Command
30054 @findex -exec-until
30056 @subsubheading Synopsis
30059 -exec-until [ @var{location} ]
30062 Executes the inferior until the @var{location} specified in the
30063 argument is reached. If there is no argument, the inferior executes
30064 until a source line greater than the current one is reached. The
30065 reason for stopping in this case will be @samp{location-reached}.
30067 @subsubheading @value{GDBN} Command
30069 The corresponding @value{GDBN} command is @samp{until}.
30071 @subsubheading Example
30075 -exec-until recursive2.c:6
30079 *stopped,reason="location-reached",frame=@{func="main",args=[],
30080 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30085 @subheading -file-clear
30086 Is this going away????
30089 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30090 @node GDB/MI Stack Manipulation
30091 @section @sc{gdb/mi} Stack Manipulation Commands
30094 @subheading The @code{-stack-info-frame} Command
30095 @findex -stack-info-frame
30097 @subsubheading Synopsis
30103 Get info on the selected frame.
30105 @subsubheading @value{GDBN} Command
30107 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30108 (without arguments).
30110 @subsubheading Example
30115 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30116 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30117 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30121 @subheading The @code{-stack-info-depth} Command
30122 @findex -stack-info-depth
30124 @subsubheading Synopsis
30127 -stack-info-depth [ @var{max-depth} ]
30130 Return the depth of the stack. If the integer argument @var{max-depth}
30131 is specified, do not count beyond @var{max-depth} frames.
30133 @subsubheading @value{GDBN} Command
30135 There's no equivalent @value{GDBN} command.
30137 @subsubheading Example
30139 For a stack with frame levels 0 through 11:
30146 -stack-info-depth 4
30149 -stack-info-depth 12
30152 -stack-info-depth 11
30155 -stack-info-depth 13
30160 @subheading The @code{-stack-list-arguments} Command
30161 @findex -stack-list-arguments
30163 @subsubheading Synopsis
30166 -stack-list-arguments @var{print-values}
30167 [ @var{low-frame} @var{high-frame} ]
30170 Display a list of the arguments for the frames between @var{low-frame}
30171 and @var{high-frame} (inclusive). If @var{low-frame} and
30172 @var{high-frame} are not provided, list the arguments for the whole
30173 call stack. If the two arguments are equal, show the single frame
30174 at the corresponding level. It is an error if @var{low-frame} is
30175 larger than the actual number of frames. On the other hand,
30176 @var{high-frame} may be larger than the actual number of frames, in
30177 which case only existing frames will be returned.
30179 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30180 the variables; if it is 1 or @code{--all-values}, print also their
30181 values; and if it is 2 or @code{--simple-values}, print the name,
30182 type and value for simple data types, and the name and type for arrays,
30183 structures and unions.
30185 Use of this command to obtain arguments in a single frame is
30186 deprecated in favor of the @samp{-stack-list-variables} command.
30188 @subsubheading @value{GDBN} Command
30190 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30191 @samp{gdb_get_args} command which partially overlaps with the
30192 functionality of @samp{-stack-list-arguments}.
30194 @subsubheading Example
30201 frame=@{level="0",addr="0x00010734",func="callee4",
30202 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30203 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30204 frame=@{level="1",addr="0x0001076c",func="callee3",
30205 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30206 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30207 frame=@{level="2",addr="0x0001078c",func="callee2",
30208 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30209 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30210 frame=@{level="3",addr="0x000107b4",func="callee1",
30211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30212 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30213 frame=@{level="4",addr="0x000107e0",func="main",
30214 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30215 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30217 -stack-list-arguments 0
30220 frame=@{level="0",args=[]@},
30221 frame=@{level="1",args=[name="strarg"]@},
30222 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30223 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30224 frame=@{level="4",args=[]@}]
30226 -stack-list-arguments 1
30229 frame=@{level="0",args=[]@},
30231 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30232 frame=@{level="2",args=[
30233 @{name="intarg",value="2"@},
30234 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30235 @{frame=@{level="3",args=[
30236 @{name="intarg",value="2"@},
30237 @{name="strarg",value="0x11940 \"A string argument.\""@},
30238 @{name="fltarg",value="3.5"@}]@},
30239 frame=@{level="4",args=[]@}]
30241 -stack-list-arguments 0 2 2
30242 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30244 -stack-list-arguments 1 2 2
30245 ^done,stack-args=[frame=@{level="2",
30246 args=[@{name="intarg",value="2"@},
30247 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30251 @c @subheading -stack-list-exception-handlers
30254 @subheading The @code{-stack-list-frames} Command
30255 @findex -stack-list-frames
30257 @subsubheading Synopsis
30260 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30263 List the frames currently on the stack. For each frame it displays the
30268 The frame number, 0 being the topmost frame, i.e., the innermost function.
30270 The @code{$pc} value for that frame.
30274 File name of the source file where the function lives.
30275 @item @var{fullname}
30276 The full file name of the source file where the function lives.
30278 Line number corresponding to the @code{$pc}.
30280 The shared library where this function is defined. This is only given
30281 if the frame's function is not known.
30284 If invoked without arguments, this command prints a backtrace for the
30285 whole stack. If given two integer arguments, it shows the frames whose
30286 levels are between the two arguments (inclusive). If the two arguments
30287 are equal, it shows the single frame at the corresponding level. It is
30288 an error if @var{low-frame} is larger than the actual number of
30289 frames. On the other hand, @var{high-frame} may be larger than the
30290 actual number of frames, in which case only existing frames will be returned.
30292 @subsubheading @value{GDBN} Command
30294 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30296 @subsubheading Example
30298 Full stack backtrace:
30304 [frame=@{level="0",addr="0x0001076c",func="foo",
30305 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30306 frame=@{level="1",addr="0x000107a4",func="foo",
30307 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30308 frame=@{level="2",addr="0x000107a4",func="foo",
30309 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30310 frame=@{level="3",addr="0x000107a4",func="foo",
30311 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30312 frame=@{level="4",addr="0x000107a4",func="foo",
30313 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30314 frame=@{level="5",addr="0x000107a4",func="foo",
30315 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30316 frame=@{level="6",addr="0x000107a4",func="foo",
30317 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30318 frame=@{level="7",addr="0x000107a4",func="foo",
30319 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30320 frame=@{level="8",addr="0x000107a4",func="foo",
30321 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30322 frame=@{level="9",addr="0x000107a4",func="foo",
30323 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30324 frame=@{level="10",addr="0x000107a4",func="foo",
30325 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30326 frame=@{level="11",addr="0x00010738",func="main",
30327 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30331 Show frames between @var{low_frame} and @var{high_frame}:
30335 -stack-list-frames 3 5
30337 [frame=@{level="3",addr="0x000107a4",func="foo",
30338 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30339 frame=@{level="4",addr="0x000107a4",func="foo",
30340 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30341 frame=@{level="5",addr="0x000107a4",func="foo",
30342 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30346 Show a single frame:
30350 -stack-list-frames 3 3
30352 [frame=@{level="3",addr="0x000107a4",func="foo",
30353 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30358 @subheading The @code{-stack-list-locals} Command
30359 @findex -stack-list-locals
30361 @subsubheading Synopsis
30364 -stack-list-locals @var{print-values}
30367 Display the local variable names for the selected frame. If
30368 @var{print-values} is 0 or @code{--no-values}, print only the names of
30369 the variables; if it is 1 or @code{--all-values}, print also their
30370 values; and if it is 2 or @code{--simple-values}, print the name,
30371 type and value for simple data types, and the name and type for arrays,
30372 structures and unions. In this last case, a frontend can immediately
30373 display the value of simple data types and create variable objects for
30374 other data types when the user wishes to explore their values in
30377 This command is deprecated in favor of the
30378 @samp{-stack-list-variables} command.
30380 @subsubheading @value{GDBN} Command
30382 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30384 @subsubheading Example
30388 -stack-list-locals 0
30389 ^done,locals=[name="A",name="B",name="C"]
30391 -stack-list-locals --all-values
30392 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30393 @{name="C",value="@{1, 2, 3@}"@}]
30394 -stack-list-locals --simple-values
30395 ^done,locals=[@{name="A",type="int",value="1"@},
30396 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30400 @subheading The @code{-stack-list-variables} Command
30401 @findex -stack-list-variables
30403 @subsubheading Synopsis
30406 -stack-list-variables @var{print-values}
30409 Display the names of local variables and function arguments for the selected frame. If
30410 @var{print-values} is 0 or @code{--no-values}, print only the names of
30411 the variables; if it is 1 or @code{--all-values}, print also their
30412 values; and if it is 2 or @code{--simple-values}, print the name,
30413 type and value for simple data types, and the name and type for arrays,
30414 structures and unions.
30416 @subsubheading Example
30420 -stack-list-variables --thread 1 --frame 0 --all-values
30421 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30426 @subheading The @code{-stack-select-frame} Command
30427 @findex -stack-select-frame
30429 @subsubheading Synopsis
30432 -stack-select-frame @var{framenum}
30435 Change the selected frame. Select a different frame @var{framenum} on
30438 This command in deprecated in favor of passing the @samp{--frame}
30439 option to every command.
30441 @subsubheading @value{GDBN} Command
30443 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30444 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30446 @subsubheading Example
30450 -stack-select-frame 2
30455 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30456 @node GDB/MI Variable Objects
30457 @section @sc{gdb/mi} Variable Objects
30461 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30463 For the implementation of a variable debugger window (locals, watched
30464 expressions, etc.), we are proposing the adaptation of the existing code
30465 used by @code{Insight}.
30467 The two main reasons for that are:
30471 It has been proven in practice (it is already on its second generation).
30474 It will shorten development time (needless to say how important it is
30478 The original interface was designed to be used by Tcl code, so it was
30479 slightly changed so it could be used through @sc{gdb/mi}. This section
30480 describes the @sc{gdb/mi} operations that will be available and gives some
30481 hints about their use.
30483 @emph{Note}: In addition to the set of operations described here, we
30484 expect the @sc{gui} implementation of a variable window to require, at
30485 least, the following operations:
30488 @item @code{-gdb-show} @code{output-radix}
30489 @item @code{-stack-list-arguments}
30490 @item @code{-stack-list-locals}
30491 @item @code{-stack-select-frame}
30496 @subheading Introduction to Variable Objects
30498 @cindex variable objects in @sc{gdb/mi}
30500 Variable objects are "object-oriented" MI interface for examining and
30501 changing values of expressions. Unlike some other MI interfaces that
30502 work with expressions, variable objects are specifically designed for
30503 simple and efficient presentation in the frontend. A variable object
30504 is identified by string name. When a variable object is created, the
30505 frontend specifies the expression for that variable object. The
30506 expression can be a simple variable, or it can be an arbitrary complex
30507 expression, and can even involve CPU registers. After creating a
30508 variable object, the frontend can invoke other variable object
30509 operations---for example to obtain or change the value of a variable
30510 object, or to change display format.
30512 Variable objects have hierarchical tree structure. Any variable object
30513 that corresponds to a composite type, such as structure in C, has
30514 a number of child variable objects, for example corresponding to each
30515 element of a structure. A child variable object can itself have
30516 children, recursively. Recursion ends when we reach
30517 leaf variable objects, which always have built-in types. Child variable
30518 objects are created only by explicit request, so if a frontend
30519 is not interested in the children of a particular variable object, no
30520 child will be created.
30522 For a leaf variable object it is possible to obtain its value as a
30523 string, or set the value from a string. String value can be also
30524 obtained for a non-leaf variable object, but it's generally a string
30525 that only indicates the type of the object, and does not list its
30526 contents. Assignment to a non-leaf variable object is not allowed.
30528 A frontend does not need to read the values of all variable objects each time
30529 the program stops. Instead, MI provides an update command that lists all
30530 variable objects whose values has changed since the last update
30531 operation. This considerably reduces the amount of data that must
30532 be transferred to the frontend. As noted above, children variable
30533 objects are created on demand, and only leaf variable objects have a
30534 real value. As result, gdb will read target memory only for leaf
30535 variables that frontend has created.
30537 The automatic update is not always desirable. For example, a frontend
30538 might want to keep a value of some expression for future reference,
30539 and never update it. For another example, fetching memory is
30540 relatively slow for embedded targets, so a frontend might want
30541 to disable automatic update for the variables that are either not
30542 visible on the screen, or ``closed''. This is possible using so
30543 called ``frozen variable objects''. Such variable objects are never
30544 implicitly updated.
30546 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30547 fixed variable object, the expression is parsed when the variable
30548 object is created, including associating identifiers to specific
30549 variables. The meaning of expression never changes. For a floating
30550 variable object the values of variables whose names appear in the
30551 expressions are re-evaluated every time in the context of the current
30552 frame. Consider this example:
30557 struct work_state state;
30564 If a fixed variable object for the @code{state} variable is created in
30565 this function, and we enter the recursive call, the variable
30566 object will report the value of @code{state} in the top-level
30567 @code{do_work} invocation. On the other hand, a floating variable
30568 object will report the value of @code{state} in the current frame.
30570 If an expression specified when creating a fixed variable object
30571 refers to a local variable, the variable object becomes bound to the
30572 thread and frame in which the variable object is created. When such
30573 variable object is updated, @value{GDBN} makes sure that the
30574 thread/frame combination the variable object is bound to still exists,
30575 and re-evaluates the variable object in context of that thread/frame.
30577 The following is the complete set of @sc{gdb/mi} operations defined to
30578 access this functionality:
30580 @multitable @columnfractions .4 .6
30581 @item @strong{Operation}
30582 @tab @strong{Description}
30584 @item @code{-enable-pretty-printing}
30585 @tab enable Python-based pretty-printing
30586 @item @code{-var-create}
30587 @tab create a variable object
30588 @item @code{-var-delete}
30589 @tab delete the variable object and/or its children
30590 @item @code{-var-set-format}
30591 @tab set the display format of this variable
30592 @item @code{-var-show-format}
30593 @tab show the display format of this variable
30594 @item @code{-var-info-num-children}
30595 @tab tells how many children this object has
30596 @item @code{-var-list-children}
30597 @tab return a list of the object's children
30598 @item @code{-var-info-type}
30599 @tab show the type of this variable object
30600 @item @code{-var-info-expression}
30601 @tab print parent-relative expression that this variable object represents
30602 @item @code{-var-info-path-expression}
30603 @tab print full expression that this variable object represents
30604 @item @code{-var-show-attributes}
30605 @tab is this variable editable? does it exist here?
30606 @item @code{-var-evaluate-expression}
30607 @tab get the value of this variable
30608 @item @code{-var-assign}
30609 @tab set the value of this variable
30610 @item @code{-var-update}
30611 @tab update the variable and its children
30612 @item @code{-var-set-frozen}
30613 @tab set frozeness attribute
30614 @item @code{-var-set-update-range}
30615 @tab set range of children to display on update
30618 In the next subsection we describe each operation in detail and suggest
30619 how it can be used.
30621 @subheading Description And Use of Operations on Variable Objects
30623 @subheading The @code{-enable-pretty-printing} Command
30624 @findex -enable-pretty-printing
30627 -enable-pretty-printing
30630 @value{GDBN} allows Python-based visualizers to affect the output of the
30631 MI variable object commands. However, because there was no way to
30632 implement this in a fully backward-compatible way, a front end must
30633 request that this functionality be enabled.
30635 Once enabled, this feature cannot be disabled.
30637 Note that if Python support has not been compiled into @value{GDBN},
30638 this command will still succeed (and do nothing).
30640 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30641 may work differently in future versions of @value{GDBN}.
30643 @subheading The @code{-var-create} Command
30644 @findex -var-create
30646 @subsubheading Synopsis
30649 -var-create @{@var{name} | "-"@}
30650 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30653 This operation creates a variable object, which allows the monitoring of
30654 a variable, the result of an expression, a memory cell or a CPU
30657 The @var{name} parameter is the string by which the object can be
30658 referenced. It must be unique. If @samp{-} is specified, the varobj
30659 system will generate a string ``varNNNNNN'' automatically. It will be
30660 unique provided that one does not specify @var{name} of that format.
30661 The command fails if a duplicate name is found.
30663 The frame under which the expression should be evaluated can be
30664 specified by @var{frame-addr}. A @samp{*} indicates that the current
30665 frame should be used. A @samp{@@} indicates that a floating variable
30666 object must be created.
30668 @var{expression} is any expression valid on the current language set (must not
30669 begin with a @samp{*}), or one of the following:
30673 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30676 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30679 @samp{$@var{regname}} --- a CPU register name
30682 @cindex dynamic varobj
30683 A varobj's contents may be provided by a Python-based pretty-printer. In this
30684 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30685 have slightly different semantics in some cases. If the
30686 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30687 will never create a dynamic varobj. This ensures backward
30688 compatibility for existing clients.
30690 @subsubheading Result
30692 This operation returns attributes of the newly-created varobj. These
30697 The name of the varobj.
30700 The number of children of the varobj. This number is not necessarily
30701 reliable for a dynamic varobj. Instead, you must examine the
30702 @samp{has_more} attribute.
30705 The varobj's scalar value. For a varobj whose type is some sort of
30706 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30707 will not be interesting.
30710 The varobj's type. This is a string representation of the type, as
30711 would be printed by the @value{GDBN} CLI. If @samp{print object}
30712 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30713 @emph{actual} (derived) type of the object is shown rather than the
30714 @emph{declared} one.
30717 If a variable object is bound to a specific thread, then this is the
30718 thread's identifier.
30721 For a dynamic varobj, this indicates whether there appear to be any
30722 children available. For a non-dynamic varobj, this will be 0.
30725 This attribute will be present and have the value @samp{1} if the
30726 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30727 then this attribute will not be present.
30730 A dynamic varobj can supply a display hint to the front end. The
30731 value comes directly from the Python pretty-printer object's
30732 @code{display_hint} method. @xref{Pretty Printing API}.
30735 Typical output will look like this:
30738 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30739 has_more="@var{has_more}"
30743 @subheading The @code{-var-delete} Command
30744 @findex -var-delete
30746 @subsubheading Synopsis
30749 -var-delete [ -c ] @var{name}
30752 Deletes a previously created variable object and all of its children.
30753 With the @samp{-c} option, just deletes the children.
30755 Returns an error if the object @var{name} is not found.
30758 @subheading The @code{-var-set-format} Command
30759 @findex -var-set-format
30761 @subsubheading Synopsis
30764 -var-set-format @var{name} @var{format-spec}
30767 Sets the output format for the value of the object @var{name} to be
30770 @anchor{-var-set-format}
30771 The syntax for the @var{format-spec} is as follows:
30774 @var{format-spec} @expansion{}
30775 @{binary | decimal | hexadecimal | octal | natural@}
30778 The natural format is the default format choosen automatically
30779 based on the variable type (like decimal for an @code{int}, hex
30780 for pointers, etc.).
30782 For a variable with children, the format is set only on the
30783 variable itself, and the children are not affected.
30785 @subheading The @code{-var-show-format} Command
30786 @findex -var-show-format
30788 @subsubheading Synopsis
30791 -var-show-format @var{name}
30794 Returns the format used to display the value of the object @var{name}.
30797 @var{format} @expansion{}
30802 @subheading The @code{-var-info-num-children} Command
30803 @findex -var-info-num-children
30805 @subsubheading Synopsis
30808 -var-info-num-children @var{name}
30811 Returns the number of children of a variable object @var{name}:
30817 Note that this number is not completely reliable for a dynamic varobj.
30818 It will return the current number of children, but more children may
30822 @subheading The @code{-var-list-children} Command
30823 @findex -var-list-children
30825 @subsubheading Synopsis
30828 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30830 @anchor{-var-list-children}
30832 Return a list of the children of the specified variable object and
30833 create variable objects for them, if they do not already exist. With
30834 a single argument or if @var{print-values} has a value of 0 or
30835 @code{--no-values}, print only the names of the variables; if
30836 @var{print-values} is 1 or @code{--all-values}, also print their
30837 values; and if it is 2 or @code{--simple-values} print the name and
30838 value for simple data types and just the name for arrays, structures
30841 @var{from} and @var{to}, if specified, indicate the range of children
30842 to report. If @var{from} or @var{to} is less than zero, the range is
30843 reset and all children will be reported. Otherwise, children starting
30844 at @var{from} (zero-based) and up to and excluding @var{to} will be
30847 If a child range is requested, it will only affect the current call to
30848 @code{-var-list-children}, but not future calls to @code{-var-update}.
30849 For this, you must instead use @code{-var-set-update-range}. The
30850 intent of this approach is to enable a front end to implement any
30851 update approach it likes; for example, scrolling a view may cause the
30852 front end to request more children with @code{-var-list-children}, and
30853 then the front end could call @code{-var-set-update-range} with a
30854 different range to ensure that future updates are restricted to just
30857 For each child the following results are returned:
30862 Name of the variable object created for this child.
30865 The expression to be shown to the user by the front end to designate this child.
30866 For example this may be the name of a structure member.
30868 For a dynamic varobj, this value cannot be used to form an
30869 expression. There is no way to do this at all with a dynamic varobj.
30871 For C/C@t{++} structures there are several pseudo children returned to
30872 designate access qualifiers. For these pseudo children @var{exp} is
30873 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30874 type and value are not present.
30876 A dynamic varobj will not report the access qualifying
30877 pseudo-children, regardless of the language. This information is not
30878 available at all with a dynamic varobj.
30881 Number of children this child has. For a dynamic varobj, this will be
30885 The type of the child. If @samp{print object}
30886 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30887 @emph{actual} (derived) type of the object is shown rather than the
30888 @emph{declared} one.
30891 If values were requested, this is the value.
30894 If this variable object is associated with a thread, this is the thread id.
30895 Otherwise this result is not present.
30898 If the variable object is frozen, this variable will be present with a value of 1.
30901 The result may have its own attributes:
30905 A dynamic varobj can supply a display hint to the front end. The
30906 value comes directly from the Python pretty-printer object's
30907 @code{display_hint} method. @xref{Pretty Printing API}.
30910 This is an integer attribute which is nonzero if there are children
30911 remaining after the end of the selected range.
30914 @subsubheading Example
30918 -var-list-children n
30919 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30920 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30922 -var-list-children --all-values n
30923 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30924 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30928 @subheading The @code{-var-info-type} Command
30929 @findex -var-info-type
30931 @subsubheading Synopsis
30934 -var-info-type @var{name}
30937 Returns the type of the specified variable @var{name}. The type is
30938 returned as a string in the same format as it is output by the
30942 type=@var{typename}
30946 @subheading The @code{-var-info-expression} Command
30947 @findex -var-info-expression
30949 @subsubheading Synopsis
30952 -var-info-expression @var{name}
30955 Returns a string that is suitable for presenting this
30956 variable object in user interface. The string is generally
30957 not valid expression in the current language, and cannot be evaluated.
30959 For example, if @code{a} is an array, and variable object
30960 @code{A} was created for @code{a}, then we'll get this output:
30963 (gdb) -var-info-expression A.1
30964 ^done,lang="C",exp="1"
30968 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30970 Note that the output of the @code{-var-list-children} command also
30971 includes those expressions, so the @code{-var-info-expression} command
30974 @subheading The @code{-var-info-path-expression} Command
30975 @findex -var-info-path-expression
30977 @subsubheading Synopsis
30980 -var-info-path-expression @var{name}
30983 Returns an expression that can be evaluated in the current
30984 context and will yield the same value that a variable object has.
30985 Compare this with the @code{-var-info-expression} command, which
30986 result can be used only for UI presentation. Typical use of
30987 the @code{-var-info-path-expression} command is creating a
30988 watchpoint from a variable object.
30990 This command is currently not valid for children of a dynamic varobj,
30991 and will give an error when invoked on one.
30993 For example, suppose @code{C} is a C@t{++} class, derived from class
30994 @code{Base}, and that the @code{Base} class has a member called
30995 @code{m_size}. Assume a variable @code{c} is has the type of
30996 @code{C} and a variable object @code{C} was created for variable
30997 @code{c}. Then, we'll get this output:
30999 (gdb) -var-info-path-expression C.Base.public.m_size
31000 ^done,path_expr=((Base)c).m_size)
31003 @subheading The @code{-var-show-attributes} Command
31004 @findex -var-show-attributes
31006 @subsubheading Synopsis
31009 -var-show-attributes @var{name}
31012 List attributes of the specified variable object @var{name}:
31015 status=@var{attr} [ ( ,@var{attr} )* ]
31019 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31021 @subheading The @code{-var-evaluate-expression} Command
31022 @findex -var-evaluate-expression
31024 @subsubheading Synopsis
31027 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31030 Evaluates the expression that is represented by the specified variable
31031 object and returns its value as a string. The format of the string
31032 can be specified with the @samp{-f} option. The possible values of
31033 this option are the same as for @code{-var-set-format}
31034 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31035 the current display format will be used. The current display format
31036 can be changed using the @code{-var-set-format} command.
31042 Note that one must invoke @code{-var-list-children} for a variable
31043 before the value of a child variable can be evaluated.
31045 @subheading The @code{-var-assign} Command
31046 @findex -var-assign
31048 @subsubheading Synopsis
31051 -var-assign @var{name} @var{expression}
31054 Assigns the value of @var{expression} to the variable object specified
31055 by @var{name}. The object must be @samp{editable}. If the variable's
31056 value is altered by the assign, the variable will show up in any
31057 subsequent @code{-var-update} list.
31059 @subsubheading Example
31067 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31071 @subheading The @code{-var-update} Command
31072 @findex -var-update
31074 @subsubheading Synopsis
31077 -var-update [@var{print-values}] @{@var{name} | "*"@}
31080 Reevaluate the expressions corresponding to the variable object
31081 @var{name} and all its direct and indirect children, and return the
31082 list of variable objects whose values have changed; @var{name} must
31083 be a root variable object. Here, ``changed'' means that the result of
31084 @code{-var-evaluate-expression} before and after the
31085 @code{-var-update} is different. If @samp{*} is used as the variable
31086 object names, all existing variable objects are updated, except
31087 for frozen ones (@pxref{-var-set-frozen}). The option
31088 @var{print-values} determines whether both names and values, or just
31089 names are printed. The possible values of this option are the same
31090 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31091 recommended to use the @samp{--all-values} option, to reduce the
31092 number of MI commands needed on each program stop.
31094 With the @samp{*} parameter, if a variable object is bound to a
31095 currently running thread, it will not be updated, without any
31098 If @code{-var-set-update-range} was previously used on a varobj, then
31099 only the selected range of children will be reported.
31101 @code{-var-update} reports all the changed varobjs in a tuple named
31104 Each item in the change list is itself a tuple holding:
31108 The name of the varobj.
31111 If values were requested for this update, then this field will be
31112 present and will hold the value of the varobj.
31115 @anchor{-var-update}
31116 This field is a string which may take one of three values:
31120 The variable object's current value is valid.
31123 The variable object does not currently hold a valid value but it may
31124 hold one in the future if its associated expression comes back into
31128 The variable object no longer holds a valid value.
31129 This can occur when the executable file being debugged has changed,
31130 either through recompilation or by using the @value{GDBN} @code{file}
31131 command. The front end should normally choose to delete these variable
31135 In the future new values may be added to this list so the front should
31136 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31139 This is only present if the varobj is still valid. If the type
31140 changed, then this will be the string @samp{true}; otherwise it will
31143 When a varobj's type changes, its children are also likely to have
31144 become incorrect. Therefore, the varobj's children are automatically
31145 deleted when this attribute is @samp{true}. Also, the varobj's update
31146 range, when set using the @code{-var-set-update-range} command, is
31150 If the varobj's type changed, then this field will be present and will
31153 @item new_num_children
31154 For a dynamic varobj, if the number of children changed, or if the
31155 type changed, this will be the new number of children.
31157 The @samp{numchild} field in other varobj responses is generally not
31158 valid for a dynamic varobj -- it will show the number of children that
31159 @value{GDBN} knows about, but because dynamic varobjs lazily
31160 instantiate their children, this will not reflect the number of
31161 children which may be available.
31163 The @samp{new_num_children} attribute only reports changes to the
31164 number of children known by @value{GDBN}. This is the only way to
31165 detect whether an update has removed children (which necessarily can
31166 only happen at the end of the update range).
31169 The display hint, if any.
31172 This is an integer value, which will be 1 if there are more children
31173 available outside the varobj's update range.
31176 This attribute will be present and have the value @samp{1} if the
31177 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31178 then this attribute will not be present.
31181 If new children were added to a dynamic varobj within the selected
31182 update range (as set by @code{-var-set-update-range}), then they will
31183 be listed in this attribute.
31186 @subsubheading Example
31193 -var-update --all-values var1
31194 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31195 type_changed="false"@}]
31199 @subheading The @code{-var-set-frozen} Command
31200 @findex -var-set-frozen
31201 @anchor{-var-set-frozen}
31203 @subsubheading Synopsis
31206 -var-set-frozen @var{name} @var{flag}
31209 Set the frozenness flag on the variable object @var{name}. The
31210 @var{flag} parameter should be either @samp{1} to make the variable
31211 frozen or @samp{0} to make it unfrozen. If a variable object is
31212 frozen, then neither itself, nor any of its children, are
31213 implicitly updated by @code{-var-update} of
31214 a parent variable or by @code{-var-update *}. Only
31215 @code{-var-update} of the variable itself will update its value and
31216 values of its children. After a variable object is unfrozen, it is
31217 implicitly updated by all subsequent @code{-var-update} operations.
31218 Unfreezing a variable does not update it, only subsequent
31219 @code{-var-update} does.
31221 @subsubheading Example
31225 -var-set-frozen V 1
31230 @subheading The @code{-var-set-update-range} command
31231 @findex -var-set-update-range
31232 @anchor{-var-set-update-range}
31234 @subsubheading Synopsis
31237 -var-set-update-range @var{name} @var{from} @var{to}
31240 Set the range of children to be returned by future invocations of
31241 @code{-var-update}.
31243 @var{from} and @var{to} indicate the range of children to report. If
31244 @var{from} or @var{to} is less than zero, the range is reset and all
31245 children will be reported. Otherwise, children starting at @var{from}
31246 (zero-based) and up to and excluding @var{to} will be reported.
31248 @subsubheading Example
31252 -var-set-update-range V 1 2
31256 @subheading The @code{-var-set-visualizer} command
31257 @findex -var-set-visualizer
31258 @anchor{-var-set-visualizer}
31260 @subsubheading Synopsis
31263 -var-set-visualizer @var{name} @var{visualizer}
31266 Set a visualizer for the variable object @var{name}.
31268 @var{visualizer} is the visualizer to use. The special value
31269 @samp{None} means to disable any visualizer in use.
31271 If not @samp{None}, @var{visualizer} must be a Python expression.
31272 This expression must evaluate to a callable object which accepts a
31273 single argument. @value{GDBN} will call this object with the value of
31274 the varobj @var{name} as an argument (this is done so that the same
31275 Python pretty-printing code can be used for both the CLI and MI).
31276 When called, this object must return an object which conforms to the
31277 pretty-printing interface (@pxref{Pretty Printing API}).
31279 The pre-defined function @code{gdb.default_visualizer} may be used to
31280 select a visualizer by following the built-in process
31281 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31282 a varobj is created, and so ordinarily is not needed.
31284 This feature is only available if Python support is enabled. The MI
31285 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31286 can be used to check this.
31288 @subsubheading Example
31290 Resetting the visualizer:
31294 -var-set-visualizer V None
31298 Reselecting the default (type-based) visualizer:
31302 -var-set-visualizer V gdb.default_visualizer
31306 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31307 can be used to instantiate this class for a varobj:
31311 -var-set-visualizer V "lambda val: SomeClass()"
31315 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31316 @node GDB/MI Data Manipulation
31317 @section @sc{gdb/mi} Data Manipulation
31319 @cindex data manipulation, in @sc{gdb/mi}
31320 @cindex @sc{gdb/mi}, data manipulation
31321 This section describes the @sc{gdb/mi} commands that manipulate data:
31322 examine memory and registers, evaluate expressions, etc.
31324 @c REMOVED FROM THE INTERFACE.
31325 @c @subheading -data-assign
31326 @c Change the value of a program variable. Plenty of side effects.
31327 @c @subsubheading GDB Command
31329 @c @subsubheading Example
31332 @subheading The @code{-data-disassemble} Command
31333 @findex -data-disassemble
31335 @subsubheading Synopsis
31339 [ -s @var{start-addr} -e @var{end-addr} ]
31340 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31348 @item @var{start-addr}
31349 is the beginning address (or @code{$pc})
31350 @item @var{end-addr}
31352 @item @var{filename}
31353 is the name of the file to disassemble
31354 @item @var{linenum}
31355 is the line number to disassemble around
31357 is the number of disassembly lines to be produced. If it is -1,
31358 the whole function will be disassembled, in case no @var{end-addr} is
31359 specified. If @var{end-addr} is specified as a non-zero value, and
31360 @var{lines} is lower than the number of disassembly lines between
31361 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31362 displayed; if @var{lines} is higher than the number of lines between
31363 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31366 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31367 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31368 mixed source and disassembly with raw opcodes).
31371 @subsubheading Result
31373 The result of the @code{-data-disassemble} command will be a list named
31374 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31375 used with the @code{-data-disassemble} command.
31377 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31382 The address at which this instruction was disassembled.
31385 The name of the function this instruction is within.
31388 The decimal offset in bytes from the start of @samp{func-name}.
31391 The text disassembly for this @samp{address}.
31394 This field is only present for mode 2. This contains the raw opcode
31395 bytes for the @samp{inst} field.
31399 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31400 @samp{src_and_asm_line}, each of which has the following fields:
31404 The line number within @samp{file}.
31407 The file name from the compilation unit. This might be an absolute
31408 file name or a relative file name depending on the compile command
31412 Absolute file name of @samp{file}. It is converted to a canonical form
31413 using the source file search path
31414 (@pxref{Source Path, ,Specifying Source Directories})
31415 and after resolving all the symbolic links.
31417 If the source file is not found this field will contain the path as
31418 present in the debug information.
31420 @item line_asm_insn
31421 This is a list of tuples containing the disassembly for @samp{line} in
31422 @samp{file}. The fields of each tuple are the same as for
31423 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31424 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31429 Note that whatever included in the @samp{inst} field, is not
31430 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31433 @subsubheading @value{GDBN} Command
31435 The corresponding @value{GDBN} command is @samp{disassemble}.
31437 @subsubheading Example
31439 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31443 -data-disassemble -s $pc -e "$pc + 20" -- 0
31446 @{address="0x000107c0",func-name="main",offset="4",
31447 inst="mov 2, %o0"@},
31448 @{address="0x000107c4",func-name="main",offset="8",
31449 inst="sethi %hi(0x11800), %o2"@},
31450 @{address="0x000107c8",func-name="main",offset="12",
31451 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31452 @{address="0x000107cc",func-name="main",offset="16",
31453 inst="sethi %hi(0x11800), %o2"@},
31454 @{address="0x000107d0",func-name="main",offset="20",
31455 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31459 Disassemble the whole @code{main} function. Line 32 is part of
31463 -data-disassemble -f basics.c -l 32 -- 0
31465 @{address="0x000107bc",func-name="main",offset="0",
31466 inst="save %sp, -112, %sp"@},
31467 @{address="0x000107c0",func-name="main",offset="4",
31468 inst="mov 2, %o0"@},
31469 @{address="0x000107c4",func-name="main",offset="8",
31470 inst="sethi %hi(0x11800), %o2"@},
31472 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31473 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31477 Disassemble 3 instructions from the start of @code{main}:
31481 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31483 @{address="0x000107bc",func-name="main",offset="0",
31484 inst="save %sp, -112, %sp"@},
31485 @{address="0x000107c0",func-name="main",offset="4",
31486 inst="mov 2, %o0"@},
31487 @{address="0x000107c4",func-name="main",offset="8",
31488 inst="sethi %hi(0x11800), %o2"@}]
31492 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31496 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31498 src_and_asm_line=@{line="31",
31499 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31500 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31501 line_asm_insn=[@{address="0x000107bc",
31502 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31503 src_and_asm_line=@{line="32",
31504 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31505 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31506 line_asm_insn=[@{address="0x000107c0",
31507 func-name="main",offset="4",inst="mov 2, %o0"@},
31508 @{address="0x000107c4",func-name="main",offset="8",
31509 inst="sethi %hi(0x11800), %o2"@}]@}]
31514 @subheading The @code{-data-evaluate-expression} Command
31515 @findex -data-evaluate-expression
31517 @subsubheading Synopsis
31520 -data-evaluate-expression @var{expr}
31523 Evaluate @var{expr} as an expression. The expression could contain an
31524 inferior function call. The function call will execute synchronously.
31525 If the expression contains spaces, it must be enclosed in double quotes.
31527 @subsubheading @value{GDBN} Command
31529 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31530 @samp{call}. In @code{gdbtk} only, there's a corresponding
31531 @samp{gdb_eval} command.
31533 @subsubheading Example
31535 In the following example, the numbers that precede the commands are the
31536 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31537 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31541 211-data-evaluate-expression A
31544 311-data-evaluate-expression &A
31545 311^done,value="0xefffeb7c"
31547 411-data-evaluate-expression A+3
31550 511-data-evaluate-expression "A + 3"
31556 @subheading The @code{-data-list-changed-registers} Command
31557 @findex -data-list-changed-registers
31559 @subsubheading Synopsis
31562 -data-list-changed-registers
31565 Display a list of the registers that have changed.
31567 @subsubheading @value{GDBN} Command
31569 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31570 has the corresponding command @samp{gdb_changed_register_list}.
31572 @subsubheading Example
31574 On a PPC MBX board:
31582 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31583 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31586 -data-list-changed-registers
31587 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31588 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31589 "24","25","26","27","28","30","31","64","65","66","67","69"]
31594 @subheading The @code{-data-list-register-names} Command
31595 @findex -data-list-register-names
31597 @subsubheading Synopsis
31600 -data-list-register-names [ ( @var{regno} )+ ]
31603 Show a list of register names for the current target. If no arguments
31604 are given, it shows a list of the names of all the registers. If
31605 integer numbers are given as arguments, it will print a list of the
31606 names of the registers corresponding to the arguments. To ensure
31607 consistency between a register name and its number, the output list may
31608 include empty register names.
31610 @subsubheading @value{GDBN} Command
31612 @value{GDBN} does not have a command which corresponds to
31613 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31614 corresponding command @samp{gdb_regnames}.
31616 @subsubheading Example
31618 For the PPC MBX board:
31621 -data-list-register-names
31622 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31623 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31624 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31625 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31626 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31627 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31628 "", "pc","ps","cr","lr","ctr","xer"]
31630 -data-list-register-names 1 2 3
31631 ^done,register-names=["r1","r2","r3"]
31635 @subheading The @code{-data-list-register-values} Command
31636 @findex -data-list-register-values
31638 @subsubheading Synopsis
31641 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31644 Display the registers' contents. @var{fmt} is the format according to
31645 which the registers' contents are to be returned, followed by an optional
31646 list of numbers specifying the registers to display. A missing list of
31647 numbers indicates that the contents of all the registers must be returned.
31649 Allowed formats for @var{fmt} are:
31666 @subsubheading @value{GDBN} Command
31668 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31669 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31671 @subsubheading Example
31673 For a PPC MBX board (note: line breaks are for readability only, they
31674 don't appear in the actual output):
31678 -data-list-register-values r 64 65
31679 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31680 @{number="65",value="0x00029002"@}]
31682 -data-list-register-values x
31683 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31684 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31685 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31686 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31687 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31688 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31689 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31690 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31691 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31692 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31693 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31694 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31695 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31696 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31697 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31698 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31699 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31700 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31701 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31702 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31703 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31704 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31705 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31706 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31707 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31708 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31709 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31710 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31711 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31712 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31713 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31714 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31715 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31716 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31717 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31718 @{number="69",value="0x20002b03"@}]
31723 @subheading The @code{-data-read-memory} Command
31724 @findex -data-read-memory
31726 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31728 @subsubheading Synopsis
31731 -data-read-memory [ -o @var{byte-offset} ]
31732 @var{address} @var{word-format} @var{word-size}
31733 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31740 @item @var{address}
31741 An expression specifying the address of the first memory word to be
31742 read. Complex expressions containing embedded white space should be
31743 quoted using the C convention.
31745 @item @var{word-format}
31746 The format to be used to print the memory words. The notation is the
31747 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31750 @item @var{word-size}
31751 The size of each memory word in bytes.
31753 @item @var{nr-rows}
31754 The number of rows in the output table.
31756 @item @var{nr-cols}
31757 The number of columns in the output table.
31760 If present, indicates that each row should include an @sc{ascii} dump. The
31761 value of @var{aschar} is used as a padding character when a byte is not a
31762 member of the printable @sc{ascii} character set (printable @sc{ascii}
31763 characters are those whose code is between 32 and 126, inclusively).
31765 @item @var{byte-offset}
31766 An offset to add to the @var{address} before fetching memory.
31769 This command displays memory contents as a table of @var{nr-rows} by
31770 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31771 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31772 (returned as @samp{total-bytes}). Should less than the requested number
31773 of bytes be returned by the target, the missing words are identified
31774 using @samp{N/A}. The number of bytes read from the target is returned
31775 in @samp{nr-bytes} and the starting address used to read memory in
31778 The address of the next/previous row or page is available in
31779 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31782 @subsubheading @value{GDBN} Command
31784 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31785 @samp{gdb_get_mem} memory read command.
31787 @subsubheading Example
31789 Read six bytes of memory starting at @code{bytes+6} but then offset by
31790 @code{-6} bytes. Format as three rows of two columns. One byte per
31791 word. Display each word in hex.
31795 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31796 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31797 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31798 prev-page="0x0000138a",memory=[
31799 @{addr="0x00001390",data=["0x00","0x01"]@},
31800 @{addr="0x00001392",data=["0x02","0x03"]@},
31801 @{addr="0x00001394",data=["0x04","0x05"]@}]
31805 Read two bytes of memory starting at address @code{shorts + 64} and
31806 display as a single word formatted in decimal.
31810 5-data-read-memory shorts+64 d 2 1 1
31811 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31812 next-row="0x00001512",prev-row="0x0000150e",
31813 next-page="0x00001512",prev-page="0x0000150e",memory=[
31814 @{addr="0x00001510",data=["128"]@}]
31818 Read thirty two bytes of memory starting at @code{bytes+16} and format
31819 as eight rows of four columns. Include a string encoding with @samp{x}
31820 used as the non-printable character.
31824 4-data-read-memory bytes+16 x 1 8 4 x
31825 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31826 next-row="0x000013c0",prev-row="0x0000139c",
31827 next-page="0x000013c0",prev-page="0x00001380",memory=[
31828 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31829 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31830 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31831 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31832 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31833 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31834 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31835 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31839 @subheading The @code{-data-read-memory-bytes} Command
31840 @findex -data-read-memory-bytes
31842 @subsubheading Synopsis
31845 -data-read-memory-bytes [ -o @var{byte-offset} ]
31846 @var{address} @var{count}
31853 @item @var{address}
31854 An expression specifying the address of the first memory word to be
31855 read. Complex expressions containing embedded white space should be
31856 quoted using the C convention.
31859 The number of bytes to read. This should be an integer literal.
31861 @item @var{byte-offset}
31862 The offsets in bytes relative to @var{address} at which to start
31863 reading. This should be an integer literal. This option is provided
31864 so that a frontend is not required to first evaluate address and then
31865 perform address arithmetics itself.
31869 This command attempts to read all accessible memory regions in the
31870 specified range. First, all regions marked as unreadable in the memory
31871 map (if one is defined) will be skipped. @xref{Memory Region
31872 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31873 regions. For each one, if reading full region results in an errors,
31874 @value{GDBN} will try to read a subset of the region.
31876 In general, every single byte in the region may be readable or not,
31877 and the only way to read every readable byte is to try a read at
31878 every address, which is not practical. Therefore, @value{GDBN} will
31879 attempt to read all accessible bytes at either beginning or the end
31880 of the region, using a binary division scheme. This heuristic works
31881 well for reading accross a memory map boundary. Note that if a region
31882 has a readable range that is neither at the beginning or the end,
31883 @value{GDBN} will not read it.
31885 The result record (@pxref{GDB/MI Result Records}) that is output of
31886 the command includes a field named @samp{memory} whose content is a
31887 list of tuples. Each tuple represent a successfully read memory block
31888 and has the following fields:
31892 The start address of the memory block, as hexadecimal literal.
31895 The end address of the memory block, as hexadecimal literal.
31898 The offset of the memory block, as hexadecimal literal, relative to
31899 the start address passed to @code{-data-read-memory-bytes}.
31902 The contents of the memory block, in hex.
31908 @subsubheading @value{GDBN} Command
31910 The corresponding @value{GDBN} command is @samp{x}.
31912 @subsubheading Example
31916 -data-read-memory-bytes &a 10
31917 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31919 contents="01000000020000000300"@}]
31924 @subheading The @code{-data-write-memory-bytes} Command
31925 @findex -data-write-memory-bytes
31927 @subsubheading Synopsis
31930 -data-write-memory-bytes @var{address} @var{contents}
31931 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31938 @item @var{address}
31939 An expression specifying the address of the first memory word to be
31940 read. Complex expressions containing embedded white space should be
31941 quoted using the C convention.
31943 @item @var{contents}
31944 The hex-encoded bytes to write.
31947 Optional argument indicating the number of bytes to be written. If @var{count}
31948 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31949 write @var{contents} until it fills @var{count} bytes.
31953 @subsubheading @value{GDBN} Command
31955 There's no corresponding @value{GDBN} command.
31957 @subsubheading Example
31961 -data-write-memory-bytes &a "aabbccdd"
31968 -data-write-memory-bytes &a "aabbccdd" 16e
31973 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31974 @node GDB/MI Tracepoint Commands
31975 @section @sc{gdb/mi} Tracepoint Commands
31977 The commands defined in this section implement MI support for
31978 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31980 @subheading The @code{-trace-find} Command
31981 @findex -trace-find
31983 @subsubheading Synopsis
31986 -trace-find @var{mode} [@var{parameters}@dots{}]
31989 Find a trace frame using criteria defined by @var{mode} and
31990 @var{parameters}. The following table lists permissible
31991 modes and their parameters. For details of operation, see @ref{tfind}.
31996 No parameters are required. Stops examining trace frames.
31999 An integer is required as parameter. Selects tracepoint frame with
32002 @item tracepoint-number
32003 An integer is required as parameter. Finds next
32004 trace frame that corresponds to tracepoint with the specified number.
32007 An address is required as parameter. Finds
32008 next trace frame that corresponds to any tracepoint at the specified
32011 @item pc-inside-range
32012 Two addresses are required as parameters. Finds next trace
32013 frame that corresponds to a tracepoint at an address inside the
32014 specified range. Both bounds are considered to be inside the range.
32016 @item pc-outside-range
32017 Two addresses are required as parameters. Finds
32018 next trace frame that corresponds to a tracepoint at an address outside
32019 the specified range. Both bounds are considered to be inside the range.
32022 Line specification is required as parameter. @xref{Specify Location}.
32023 Finds next trace frame that corresponds to a tracepoint at
32024 the specified location.
32028 If @samp{none} was passed as @var{mode}, the response does not
32029 have fields. Otherwise, the response may have the following fields:
32033 This field has either @samp{0} or @samp{1} as the value, depending
32034 on whether a matching tracepoint was found.
32037 The index of the found traceframe. This field is present iff
32038 the @samp{found} field has value of @samp{1}.
32041 The index of the found tracepoint. This field is present iff
32042 the @samp{found} field has value of @samp{1}.
32045 The information about the frame corresponding to the found trace
32046 frame. This field is present only if a trace frame was found.
32047 @xref{GDB/MI Frame Information}, for description of this field.
32051 @subsubheading @value{GDBN} Command
32053 The corresponding @value{GDBN} command is @samp{tfind}.
32055 @subheading -trace-define-variable
32056 @findex -trace-define-variable
32058 @subsubheading Synopsis
32061 -trace-define-variable @var{name} [ @var{value} ]
32064 Create trace variable @var{name} if it does not exist. If
32065 @var{value} is specified, sets the initial value of the specified
32066 trace variable to that value. Note that the @var{name} should start
32067 with the @samp{$} character.
32069 @subsubheading @value{GDBN} Command
32071 The corresponding @value{GDBN} command is @samp{tvariable}.
32073 @subheading -trace-list-variables
32074 @findex -trace-list-variables
32076 @subsubheading Synopsis
32079 -trace-list-variables
32082 Return a table of all defined trace variables. Each element of the
32083 table has the following fields:
32087 The name of the trace variable. This field is always present.
32090 The initial value. This is a 64-bit signed integer. This
32091 field is always present.
32094 The value the trace variable has at the moment. This is a 64-bit
32095 signed integer. This field is absent iff current value is
32096 not defined, for example if the trace was never run, or is
32101 @subsubheading @value{GDBN} Command
32103 The corresponding @value{GDBN} command is @samp{tvariables}.
32105 @subsubheading Example
32109 -trace-list-variables
32110 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32111 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32112 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32113 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32114 body=[variable=@{name="$trace_timestamp",initial="0"@}
32115 variable=@{name="$foo",initial="10",current="15"@}]@}
32119 @subheading -trace-save
32120 @findex -trace-save
32122 @subsubheading Synopsis
32125 -trace-save [-r ] @var{filename}
32128 Saves the collected trace data to @var{filename}. Without the
32129 @samp{-r} option, the data is downloaded from the target and saved
32130 in a local file. With the @samp{-r} option the target is asked
32131 to perform the save.
32133 @subsubheading @value{GDBN} Command
32135 The corresponding @value{GDBN} command is @samp{tsave}.
32138 @subheading -trace-start
32139 @findex -trace-start
32141 @subsubheading Synopsis
32147 Starts a tracing experiments. The result of this command does not
32150 @subsubheading @value{GDBN} Command
32152 The corresponding @value{GDBN} command is @samp{tstart}.
32154 @subheading -trace-status
32155 @findex -trace-status
32157 @subsubheading Synopsis
32163 Obtains the status of a tracing experiment. The result may include
32164 the following fields:
32169 May have a value of either @samp{0}, when no tracing operations are
32170 supported, @samp{1}, when all tracing operations are supported, or
32171 @samp{file} when examining trace file. In the latter case, examining
32172 of trace frame is possible but new tracing experiement cannot be
32173 started. This field is always present.
32176 May have a value of either @samp{0} or @samp{1} depending on whether
32177 tracing experiement is in progress on target. This field is present
32178 if @samp{supported} field is not @samp{0}.
32181 Report the reason why the tracing was stopped last time. This field
32182 may be absent iff tracing was never stopped on target yet. The
32183 value of @samp{request} means the tracing was stopped as result of
32184 the @code{-trace-stop} command. The value of @samp{overflow} means
32185 the tracing buffer is full. The value of @samp{disconnection} means
32186 tracing was automatically stopped when @value{GDBN} has disconnected.
32187 The value of @samp{passcount} means tracing was stopped when a
32188 tracepoint was passed a maximal number of times for that tracepoint.
32189 This field is present if @samp{supported} field is not @samp{0}.
32191 @item stopping-tracepoint
32192 The number of tracepoint whose passcount as exceeded. This field is
32193 present iff the @samp{stop-reason} field has the value of
32197 @itemx frames-created
32198 The @samp{frames} field is a count of the total number of trace frames
32199 in the trace buffer, while @samp{frames-created} is the total created
32200 during the run, including ones that were discarded, such as when a
32201 circular trace buffer filled up. Both fields are optional.
32205 These fields tell the current size of the tracing buffer and the
32206 remaining space. These fields are optional.
32209 The value of the circular trace buffer flag. @code{1} means that the
32210 trace buffer is circular and old trace frames will be discarded if
32211 necessary to make room, @code{0} means that the trace buffer is linear
32215 The value of the disconnected tracing flag. @code{1} means that
32216 tracing will continue after @value{GDBN} disconnects, @code{0} means
32217 that the trace run will stop.
32220 The filename of the trace file being examined. This field is
32221 optional, and only present when examining a trace file.
32225 @subsubheading @value{GDBN} Command
32227 The corresponding @value{GDBN} command is @samp{tstatus}.
32229 @subheading -trace-stop
32230 @findex -trace-stop
32232 @subsubheading Synopsis
32238 Stops a tracing experiment. The result of this command has the same
32239 fields as @code{-trace-status}, except that the @samp{supported} and
32240 @samp{running} fields are not output.
32242 @subsubheading @value{GDBN} Command
32244 The corresponding @value{GDBN} command is @samp{tstop}.
32247 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32248 @node GDB/MI Symbol Query
32249 @section @sc{gdb/mi} Symbol Query Commands
32253 @subheading The @code{-symbol-info-address} Command
32254 @findex -symbol-info-address
32256 @subsubheading Synopsis
32259 -symbol-info-address @var{symbol}
32262 Describe where @var{symbol} is stored.
32264 @subsubheading @value{GDBN} Command
32266 The corresponding @value{GDBN} command is @samp{info address}.
32268 @subsubheading Example
32272 @subheading The @code{-symbol-info-file} Command
32273 @findex -symbol-info-file
32275 @subsubheading Synopsis
32281 Show the file for the symbol.
32283 @subsubheading @value{GDBN} Command
32285 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32286 @samp{gdb_find_file}.
32288 @subsubheading Example
32292 @subheading The @code{-symbol-info-function} Command
32293 @findex -symbol-info-function
32295 @subsubheading Synopsis
32298 -symbol-info-function
32301 Show which function the symbol lives in.
32303 @subsubheading @value{GDBN} Command
32305 @samp{gdb_get_function} in @code{gdbtk}.
32307 @subsubheading Example
32311 @subheading The @code{-symbol-info-line} Command
32312 @findex -symbol-info-line
32314 @subsubheading Synopsis
32320 Show the core addresses of the code for a source line.
32322 @subsubheading @value{GDBN} Command
32324 The corresponding @value{GDBN} command is @samp{info line}.
32325 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32327 @subsubheading Example
32331 @subheading The @code{-symbol-info-symbol} Command
32332 @findex -symbol-info-symbol
32334 @subsubheading Synopsis
32337 -symbol-info-symbol @var{addr}
32340 Describe what symbol is at location @var{addr}.
32342 @subsubheading @value{GDBN} Command
32344 The corresponding @value{GDBN} command is @samp{info symbol}.
32346 @subsubheading Example
32350 @subheading The @code{-symbol-list-functions} Command
32351 @findex -symbol-list-functions
32353 @subsubheading Synopsis
32356 -symbol-list-functions
32359 List the functions in the executable.
32361 @subsubheading @value{GDBN} Command
32363 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32364 @samp{gdb_search} in @code{gdbtk}.
32366 @subsubheading Example
32371 @subheading The @code{-symbol-list-lines} Command
32372 @findex -symbol-list-lines
32374 @subsubheading Synopsis
32377 -symbol-list-lines @var{filename}
32380 Print the list of lines that contain code and their associated program
32381 addresses for the given source filename. The entries are sorted in
32382 ascending PC order.
32384 @subsubheading @value{GDBN} Command
32386 There is no corresponding @value{GDBN} command.
32388 @subsubheading Example
32391 -symbol-list-lines basics.c
32392 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32398 @subheading The @code{-symbol-list-types} Command
32399 @findex -symbol-list-types
32401 @subsubheading Synopsis
32407 List all the type names.
32409 @subsubheading @value{GDBN} Command
32411 The corresponding commands are @samp{info types} in @value{GDBN},
32412 @samp{gdb_search} in @code{gdbtk}.
32414 @subsubheading Example
32418 @subheading The @code{-symbol-list-variables} Command
32419 @findex -symbol-list-variables
32421 @subsubheading Synopsis
32424 -symbol-list-variables
32427 List all the global and static variable names.
32429 @subsubheading @value{GDBN} Command
32431 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32433 @subsubheading Example
32437 @subheading The @code{-symbol-locate} Command
32438 @findex -symbol-locate
32440 @subsubheading Synopsis
32446 @subsubheading @value{GDBN} Command
32448 @samp{gdb_loc} in @code{gdbtk}.
32450 @subsubheading Example
32454 @subheading The @code{-symbol-type} Command
32455 @findex -symbol-type
32457 @subsubheading Synopsis
32460 -symbol-type @var{variable}
32463 Show type of @var{variable}.
32465 @subsubheading @value{GDBN} Command
32467 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32468 @samp{gdb_obj_variable}.
32470 @subsubheading Example
32475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32476 @node GDB/MI File Commands
32477 @section @sc{gdb/mi} File Commands
32479 This section describes the GDB/MI commands to specify executable file names
32480 and to read in and obtain symbol table information.
32482 @subheading The @code{-file-exec-and-symbols} Command
32483 @findex -file-exec-and-symbols
32485 @subsubheading Synopsis
32488 -file-exec-and-symbols @var{file}
32491 Specify the executable file to be debugged. This file is the one from
32492 which the symbol table is also read. If no file is specified, the
32493 command clears the executable and symbol information. If breakpoints
32494 are set when using this command with no arguments, @value{GDBN} will produce
32495 error messages. Otherwise, no output is produced, except a completion
32498 @subsubheading @value{GDBN} Command
32500 The corresponding @value{GDBN} command is @samp{file}.
32502 @subsubheading Example
32506 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32512 @subheading The @code{-file-exec-file} Command
32513 @findex -file-exec-file
32515 @subsubheading Synopsis
32518 -file-exec-file @var{file}
32521 Specify the executable file to be debugged. Unlike
32522 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32523 from this file. If used without argument, @value{GDBN} clears the information
32524 about the executable file. No output is produced, except a completion
32527 @subsubheading @value{GDBN} Command
32529 The corresponding @value{GDBN} command is @samp{exec-file}.
32531 @subsubheading Example
32535 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32542 @subheading The @code{-file-list-exec-sections} Command
32543 @findex -file-list-exec-sections
32545 @subsubheading Synopsis
32548 -file-list-exec-sections
32551 List the sections of the current executable file.
32553 @subsubheading @value{GDBN} Command
32555 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32556 information as this command. @code{gdbtk} has a corresponding command
32557 @samp{gdb_load_info}.
32559 @subsubheading Example
32564 @subheading The @code{-file-list-exec-source-file} Command
32565 @findex -file-list-exec-source-file
32567 @subsubheading Synopsis
32570 -file-list-exec-source-file
32573 List the line number, the current source file, and the absolute path
32574 to the current source file for the current executable. The macro
32575 information field has a value of @samp{1} or @samp{0} depending on
32576 whether or not the file includes preprocessor macro information.
32578 @subsubheading @value{GDBN} Command
32580 The @value{GDBN} equivalent is @samp{info source}
32582 @subsubheading Example
32586 123-file-list-exec-source-file
32587 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32592 @subheading The @code{-file-list-exec-source-files} Command
32593 @findex -file-list-exec-source-files
32595 @subsubheading Synopsis
32598 -file-list-exec-source-files
32601 List the source files for the current executable.
32603 It will always output both the filename and fullname (absolute file
32604 name) of a source file.
32606 @subsubheading @value{GDBN} Command
32608 The @value{GDBN} equivalent is @samp{info sources}.
32609 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32611 @subsubheading Example
32614 -file-list-exec-source-files
32616 @{file=foo.c,fullname=/home/foo.c@},
32617 @{file=/home/bar.c,fullname=/home/bar.c@},
32618 @{file=gdb_could_not_find_fullpath.c@}]
32623 @subheading The @code{-file-list-shared-libraries} Command
32624 @findex -file-list-shared-libraries
32626 @subsubheading Synopsis
32629 -file-list-shared-libraries
32632 List the shared libraries in the program.
32634 @subsubheading @value{GDBN} Command
32636 The corresponding @value{GDBN} command is @samp{info shared}.
32638 @subsubheading Example
32642 @subheading The @code{-file-list-symbol-files} Command
32643 @findex -file-list-symbol-files
32645 @subsubheading Synopsis
32648 -file-list-symbol-files
32653 @subsubheading @value{GDBN} Command
32655 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32657 @subsubheading Example
32662 @subheading The @code{-file-symbol-file} Command
32663 @findex -file-symbol-file
32665 @subsubheading Synopsis
32668 -file-symbol-file @var{file}
32671 Read symbol table info from the specified @var{file} argument. When
32672 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32673 produced, except for a completion notification.
32675 @subsubheading @value{GDBN} Command
32677 The corresponding @value{GDBN} command is @samp{symbol-file}.
32679 @subsubheading Example
32683 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32689 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32690 @node GDB/MI Memory Overlay Commands
32691 @section @sc{gdb/mi} Memory Overlay Commands
32693 The memory overlay commands are not implemented.
32695 @c @subheading -overlay-auto
32697 @c @subheading -overlay-list-mapping-state
32699 @c @subheading -overlay-list-overlays
32701 @c @subheading -overlay-map
32703 @c @subheading -overlay-off
32705 @c @subheading -overlay-on
32707 @c @subheading -overlay-unmap
32709 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32710 @node GDB/MI Signal Handling Commands
32711 @section @sc{gdb/mi} Signal Handling Commands
32713 Signal handling commands are not implemented.
32715 @c @subheading -signal-handle
32717 @c @subheading -signal-list-handle-actions
32719 @c @subheading -signal-list-signal-types
32723 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32724 @node GDB/MI Target Manipulation
32725 @section @sc{gdb/mi} Target Manipulation Commands
32728 @subheading The @code{-target-attach} Command
32729 @findex -target-attach
32731 @subsubheading Synopsis
32734 -target-attach @var{pid} | @var{gid} | @var{file}
32737 Attach to a process @var{pid} or a file @var{file} outside of
32738 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32739 group, the id previously returned by
32740 @samp{-list-thread-groups --available} must be used.
32742 @subsubheading @value{GDBN} Command
32744 The corresponding @value{GDBN} command is @samp{attach}.
32746 @subsubheading Example
32750 =thread-created,id="1"
32751 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32757 @subheading The @code{-target-compare-sections} Command
32758 @findex -target-compare-sections
32760 @subsubheading Synopsis
32763 -target-compare-sections [ @var{section} ]
32766 Compare data of section @var{section} on target to the exec file.
32767 Without the argument, all sections are compared.
32769 @subsubheading @value{GDBN} Command
32771 The @value{GDBN} equivalent is @samp{compare-sections}.
32773 @subsubheading Example
32778 @subheading The @code{-target-detach} Command
32779 @findex -target-detach
32781 @subsubheading Synopsis
32784 -target-detach [ @var{pid} | @var{gid} ]
32787 Detach from the remote target which normally resumes its execution.
32788 If either @var{pid} or @var{gid} is specified, detaches from either
32789 the specified process, or specified thread group. There's no output.
32791 @subsubheading @value{GDBN} Command
32793 The corresponding @value{GDBN} command is @samp{detach}.
32795 @subsubheading Example
32805 @subheading The @code{-target-disconnect} Command
32806 @findex -target-disconnect
32808 @subsubheading Synopsis
32814 Disconnect from the remote target. There's no output and the target is
32815 generally not resumed.
32817 @subsubheading @value{GDBN} Command
32819 The corresponding @value{GDBN} command is @samp{disconnect}.
32821 @subsubheading Example
32831 @subheading The @code{-target-download} Command
32832 @findex -target-download
32834 @subsubheading Synopsis
32840 Loads the executable onto the remote target.
32841 It prints out an update message every half second, which includes the fields:
32845 The name of the section.
32847 The size of what has been sent so far for that section.
32849 The size of the section.
32851 The total size of what was sent so far (the current and the previous sections).
32853 The size of the overall executable to download.
32857 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32858 @sc{gdb/mi} Output Syntax}).
32860 In addition, it prints the name and size of the sections, as they are
32861 downloaded. These messages include the following fields:
32865 The name of the section.
32867 The size of the section.
32869 The size of the overall executable to download.
32873 At the end, a summary is printed.
32875 @subsubheading @value{GDBN} Command
32877 The corresponding @value{GDBN} command is @samp{load}.
32879 @subsubheading Example
32881 Note: each status message appears on a single line. Here the messages
32882 have been broken down so that they can fit onto a page.
32887 +download,@{section=".text",section-size="6668",total-size="9880"@}
32888 +download,@{section=".text",section-sent="512",section-size="6668",
32889 total-sent="512",total-size="9880"@}
32890 +download,@{section=".text",section-sent="1024",section-size="6668",
32891 total-sent="1024",total-size="9880"@}
32892 +download,@{section=".text",section-sent="1536",section-size="6668",
32893 total-sent="1536",total-size="9880"@}
32894 +download,@{section=".text",section-sent="2048",section-size="6668",
32895 total-sent="2048",total-size="9880"@}
32896 +download,@{section=".text",section-sent="2560",section-size="6668",
32897 total-sent="2560",total-size="9880"@}
32898 +download,@{section=".text",section-sent="3072",section-size="6668",
32899 total-sent="3072",total-size="9880"@}
32900 +download,@{section=".text",section-sent="3584",section-size="6668",
32901 total-sent="3584",total-size="9880"@}
32902 +download,@{section=".text",section-sent="4096",section-size="6668",
32903 total-sent="4096",total-size="9880"@}
32904 +download,@{section=".text",section-sent="4608",section-size="6668",
32905 total-sent="4608",total-size="9880"@}
32906 +download,@{section=".text",section-sent="5120",section-size="6668",
32907 total-sent="5120",total-size="9880"@}
32908 +download,@{section=".text",section-sent="5632",section-size="6668",
32909 total-sent="5632",total-size="9880"@}
32910 +download,@{section=".text",section-sent="6144",section-size="6668",
32911 total-sent="6144",total-size="9880"@}
32912 +download,@{section=".text",section-sent="6656",section-size="6668",
32913 total-sent="6656",total-size="9880"@}
32914 +download,@{section=".init",section-size="28",total-size="9880"@}
32915 +download,@{section=".fini",section-size="28",total-size="9880"@}
32916 +download,@{section=".data",section-size="3156",total-size="9880"@}
32917 +download,@{section=".data",section-sent="512",section-size="3156",
32918 total-sent="7236",total-size="9880"@}
32919 +download,@{section=".data",section-sent="1024",section-size="3156",
32920 total-sent="7748",total-size="9880"@}
32921 +download,@{section=".data",section-sent="1536",section-size="3156",
32922 total-sent="8260",total-size="9880"@}
32923 +download,@{section=".data",section-sent="2048",section-size="3156",
32924 total-sent="8772",total-size="9880"@}
32925 +download,@{section=".data",section-sent="2560",section-size="3156",
32926 total-sent="9284",total-size="9880"@}
32927 +download,@{section=".data",section-sent="3072",section-size="3156",
32928 total-sent="9796",total-size="9880"@}
32929 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32936 @subheading The @code{-target-exec-status} Command
32937 @findex -target-exec-status
32939 @subsubheading Synopsis
32942 -target-exec-status
32945 Provide information on the state of the target (whether it is running or
32946 not, for instance).
32948 @subsubheading @value{GDBN} Command
32950 There's no equivalent @value{GDBN} command.
32952 @subsubheading Example
32956 @subheading The @code{-target-list-available-targets} Command
32957 @findex -target-list-available-targets
32959 @subsubheading Synopsis
32962 -target-list-available-targets
32965 List the possible targets to connect to.
32967 @subsubheading @value{GDBN} Command
32969 The corresponding @value{GDBN} command is @samp{help target}.
32971 @subsubheading Example
32975 @subheading The @code{-target-list-current-targets} Command
32976 @findex -target-list-current-targets
32978 @subsubheading Synopsis
32981 -target-list-current-targets
32984 Describe the current target.
32986 @subsubheading @value{GDBN} Command
32988 The corresponding information is printed by @samp{info file} (among
32991 @subsubheading Example
32995 @subheading The @code{-target-list-parameters} Command
32996 @findex -target-list-parameters
32998 @subsubheading Synopsis
33001 -target-list-parameters
33007 @subsubheading @value{GDBN} Command
33011 @subsubheading Example
33015 @subheading The @code{-target-select} Command
33016 @findex -target-select
33018 @subsubheading Synopsis
33021 -target-select @var{type} @var{parameters @dots{}}
33024 Connect @value{GDBN} to the remote target. This command takes two args:
33028 The type of target, for instance @samp{remote}, etc.
33029 @item @var{parameters}
33030 Device names, host names and the like. @xref{Target Commands, ,
33031 Commands for Managing Targets}, for more details.
33034 The output is a connection notification, followed by the address at
33035 which the target program is, in the following form:
33038 ^connected,addr="@var{address}",func="@var{function name}",
33039 args=[@var{arg list}]
33042 @subsubheading @value{GDBN} Command
33044 The corresponding @value{GDBN} command is @samp{target}.
33046 @subsubheading Example
33050 -target-select remote /dev/ttya
33051 ^connected,addr="0xfe00a300",func="??",args=[]
33055 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33056 @node GDB/MI File Transfer Commands
33057 @section @sc{gdb/mi} File Transfer Commands
33060 @subheading The @code{-target-file-put} Command
33061 @findex -target-file-put
33063 @subsubheading Synopsis
33066 -target-file-put @var{hostfile} @var{targetfile}
33069 Copy file @var{hostfile} from the host system (the machine running
33070 @value{GDBN}) to @var{targetfile} on the target system.
33072 @subsubheading @value{GDBN} Command
33074 The corresponding @value{GDBN} command is @samp{remote put}.
33076 @subsubheading Example
33080 -target-file-put localfile remotefile
33086 @subheading The @code{-target-file-get} Command
33087 @findex -target-file-get
33089 @subsubheading Synopsis
33092 -target-file-get @var{targetfile} @var{hostfile}
33095 Copy file @var{targetfile} from the target system to @var{hostfile}
33096 on the host system.
33098 @subsubheading @value{GDBN} Command
33100 The corresponding @value{GDBN} command is @samp{remote get}.
33102 @subsubheading Example
33106 -target-file-get remotefile localfile
33112 @subheading The @code{-target-file-delete} Command
33113 @findex -target-file-delete
33115 @subsubheading Synopsis
33118 -target-file-delete @var{targetfile}
33121 Delete @var{targetfile} from the target system.
33123 @subsubheading @value{GDBN} Command
33125 The corresponding @value{GDBN} command is @samp{remote delete}.
33127 @subsubheading Example
33131 -target-file-delete remotefile
33137 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33138 @node GDB/MI Miscellaneous Commands
33139 @section Miscellaneous @sc{gdb/mi} Commands
33141 @c @subheading -gdb-complete
33143 @subheading The @code{-gdb-exit} Command
33146 @subsubheading Synopsis
33152 Exit @value{GDBN} immediately.
33154 @subsubheading @value{GDBN} Command
33156 Approximately corresponds to @samp{quit}.
33158 @subsubheading Example
33168 @subheading The @code{-exec-abort} Command
33169 @findex -exec-abort
33171 @subsubheading Synopsis
33177 Kill the inferior running program.
33179 @subsubheading @value{GDBN} Command
33181 The corresponding @value{GDBN} command is @samp{kill}.
33183 @subsubheading Example
33188 @subheading The @code{-gdb-set} Command
33191 @subsubheading Synopsis
33197 Set an internal @value{GDBN} variable.
33198 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33200 @subsubheading @value{GDBN} Command
33202 The corresponding @value{GDBN} command is @samp{set}.
33204 @subsubheading Example
33214 @subheading The @code{-gdb-show} Command
33217 @subsubheading Synopsis
33223 Show the current value of a @value{GDBN} variable.
33225 @subsubheading @value{GDBN} Command
33227 The corresponding @value{GDBN} command is @samp{show}.
33229 @subsubheading Example
33238 @c @subheading -gdb-source
33241 @subheading The @code{-gdb-version} Command
33242 @findex -gdb-version
33244 @subsubheading Synopsis
33250 Show version information for @value{GDBN}. Used mostly in testing.
33252 @subsubheading @value{GDBN} Command
33254 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33255 default shows this information when you start an interactive session.
33257 @subsubheading Example
33259 @c This example modifies the actual output from GDB to avoid overfull
33265 ~Copyright 2000 Free Software Foundation, Inc.
33266 ~GDB is free software, covered by the GNU General Public License, and
33267 ~you are welcome to change it and/or distribute copies of it under
33268 ~ certain conditions.
33269 ~Type "show copying" to see the conditions.
33270 ~There is absolutely no warranty for GDB. Type "show warranty" for
33272 ~This GDB was configured as
33273 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33278 @subheading The @code{-list-features} Command
33279 @findex -list-features
33281 Returns a list of particular features of the MI protocol that
33282 this version of gdb implements. A feature can be a command,
33283 or a new field in an output of some command, or even an
33284 important bugfix. While a frontend can sometimes detect presence
33285 of a feature at runtime, it is easier to perform detection at debugger
33288 The command returns a list of strings, with each string naming an
33289 available feature. Each returned string is just a name, it does not
33290 have any internal structure. The list of possible feature names
33296 (gdb) -list-features
33297 ^done,result=["feature1","feature2"]
33300 The current list of features is:
33303 @item frozen-varobjs
33304 Indicates support for the @code{-var-set-frozen} command, as well
33305 as possible presense of the @code{frozen} field in the output
33306 of @code{-varobj-create}.
33307 @item pending-breakpoints
33308 Indicates support for the @option{-f} option to the @code{-break-insert}
33311 Indicates Python scripting support, Python-based
33312 pretty-printing commands, and possible presence of the
33313 @samp{display_hint} field in the output of @code{-var-list-children}
33315 Indicates support for the @code{-thread-info} command.
33316 @item data-read-memory-bytes
33317 Indicates support for the @code{-data-read-memory-bytes} and the
33318 @code{-data-write-memory-bytes} commands.
33319 @item breakpoint-notifications
33320 Indicates that changes to breakpoints and breakpoints created via the
33321 CLI will be announced via async records.
33322 @item ada-task-info
33323 Indicates support for the @code{-ada-task-info} command.
33326 @subheading The @code{-list-target-features} Command
33327 @findex -list-target-features
33329 Returns a list of particular features that are supported by the
33330 target. Those features affect the permitted MI commands, but
33331 unlike the features reported by the @code{-list-features} command, the
33332 features depend on which target GDB is using at the moment. Whenever
33333 a target can change, due to commands such as @code{-target-select},
33334 @code{-target-attach} or @code{-exec-run}, the list of target features
33335 may change, and the frontend should obtain it again.
33339 (gdb) -list-features
33340 ^done,result=["async"]
33343 The current list of features is:
33347 Indicates that the target is capable of asynchronous command
33348 execution, which means that @value{GDBN} will accept further commands
33349 while the target is running.
33352 Indicates that the target is capable of reverse execution.
33353 @xref{Reverse Execution}, for more information.
33357 @subheading The @code{-list-thread-groups} Command
33358 @findex -list-thread-groups
33360 @subheading Synopsis
33363 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33366 Lists thread groups (@pxref{Thread groups}). When a single thread
33367 group is passed as the argument, lists the children of that group.
33368 When several thread group are passed, lists information about those
33369 thread groups. Without any parameters, lists information about all
33370 top-level thread groups.
33372 Normally, thread groups that are being debugged are reported.
33373 With the @samp{--available} option, @value{GDBN} reports thread groups
33374 available on the target.
33376 The output of this command may have either a @samp{threads} result or
33377 a @samp{groups} result. The @samp{thread} result has a list of tuples
33378 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33379 Information}). The @samp{groups} result has a list of tuples as value,
33380 each tuple describing a thread group. If top-level groups are
33381 requested (that is, no parameter is passed), or when several groups
33382 are passed, the output always has a @samp{groups} result. The format
33383 of the @samp{group} result is described below.
33385 To reduce the number of roundtrips it's possible to list thread groups
33386 together with their children, by passing the @samp{--recurse} option
33387 and the recursion depth. Presently, only recursion depth of 1 is
33388 permitted. If this option is present, then every reported thread group
33389 will also include its children, either as @samp{group} or
33390 @samp{threads} field.
33392 In general, any combination of option and parameters is permitted, with
33393 the following caveats:
33397 When a single thread group is passed, the output will typically
33398 be the @samp{threads} result. Because threads may not contain
33399 anything, the @samp{recurse} option will be ignored.
33402 When the @samp{--available} option is passed, limited information may
33403 be available. In particular, the list of threads of a process might
33404 be inaccessible. Further, specifying specific thread groups might
33405 not give any performance advantage over listing all thread groups.
33406 The frontend should assume that @samp{-list-thread-groups --available}
33407 is always an expensive operation and cache the results.
33411 The @samp{groups} result is a list of tuples, where each tuple may
33412 have the following fields:
33416 Identifier of the thread group. This field is always present.
33417 The identifier is an opaque string; frontends should not try to
33418 convert it to an integer, even though it might look like one.
33421 The type of the thread group. At present, only @samp{process} is a
33425 The target-specific process identifier. This field is only present
33426 for thread groups of type @samp{process} and only if the process exists.
33429 The number of children this thread group has. This field may be
33430 absent for an available thread group.
33433 This field has a list of tuples as value, each tuple describing a
33434 thread. It may be present if the @samp{--recurse} option is
33435 specified, and it's actually possible to obtain the threads.
33438 This field is a list of integers, each identifying a core that one
33439 thread of the group is running on. This field may be absent if
33440 such information is not available.
33443 The name of the executable file that corresponds to this thread group.
33444 The field is only present for thread groups of type @samp{process},
33445 and only if there is a corresponding executable file.
33449 @subheading Example
33453 -list-thread-groups
33454 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33455 -list-thread-groups 17
33456 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33457 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33458 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33459 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33460 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33461 -list-thread-groups --available
33462 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33463 -list-thread-groups --available --recurse 1
33464 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33465 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33466 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33467 -list-thread-groups --available --recurse 1 17 18
33468 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33469 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33470 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33473 @subheading The @code{-info-os} Command
33476 @subsubheading Synopsis
33479 -info-os [ @var{type} ]
33482 If no argument is supplied, the command returns a table of available
33483 operating-system-specific information types. If one of these types is
33484 supplied as an argument @var{type}, then the command returns a table
33485 of data of that type.
33487 The types of information available depend on the target operating
33490 @subsubheading @value{GDBN} Command
33492 The corresponding @value{GDBN} command is @samp{info os}.
33494 @subsubheading Example
33496 When run on a @sc{gnu}/Linux system, the output will look something
33502 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33503 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33504 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33505 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33506 body=[item=@{col0="processes",col1="Listing of all processes",
33507 col2="Processes"@},
33508 item=@{col0="procgroups",col1="Listing of all process groups",
33509 col2="Process groups"@},
33510 item=@{col0="threads",col1="Listing of all threads",
33512 item=@{col0="files",col1="Listing of all file descriptors",
33513 col2="File descriptors"@},
33514 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33516 item=@{col0="shm",col1="Listing of all shared-memory regions",
33517 col2="Shared-memory regions"@},
33518 item=@{col0="semaphores",col1="Listing of all semaphores",
33519 col2="Semaphores"@},
33520 item=@{col0="msg",col1="Listing of all message queues",
33521 col2="Message queues"@},
33522 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33523 col2="Kernel modules"@}]@}
33526 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33527 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33528 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33529 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33530 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33531 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33532 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33533 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33535 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33536 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33540 (Note that the MI output here includes a @code{"Title"} column that
33541 does not appear in command-line @code{info os}; this column is useful
33542 for MI clients that want to enumerate the types of data, such as in a
33543 popup menu, but is needless clutter on the command line, and
33544 @code{info os} omits it.)
33546 @subheading The @code{-add-inferior} Command
33547 @findex -add-inferior
33549 @subheading Synopsis
33555 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33556 inferior is not associated with any executable. Such association may
33557 be established with the @samp{-file-exec-and-symbols} command
33558 (@pxref{GDB/MI File Commands}). The command response has a single
33559 field, @samp{thread-group}, whose value is the identifier of the
33560 thread group corresponding to the new inferior.
33562 @subheading Example
33567 ^done,thread-group="i3"
33570 @subheading The @code{-interpreter-exec} Command
33571 @findex -interpreter-exec
33573 @subheading Synopsis
33576 -interpreter-exec @var{interpreter} @var{command}
33578 @anchor{-interpreter-exec}
33580 Execute the specified @var{command} in the given @var{interpreter}.
33582 @subheading @value{GDBN} Command
33584 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33586 @subheading Example
33590 -interpreter-exec console "break main"
33591 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33592 &"During symbol reading, bad structure-type format.\n"
33593 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33598 @subheading The @code{-inferior-tty-set} Command
33599 @findex -inferior-tty-set
33601 @subheading Synopsis
33604 -inferior-tty-set /dev/pts/1
33607 Set terminal for future runs of the program being debugged.
33609 @subheading @value{GDBN} Command
33611 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33613 @subheading Example
33617 -inferior-tty-set /dev/pts/1
33622 @subheading The @code{-inferior-tty-show} Command
33623 @findex -inferior-tty-show
33625 @subheading Synopsis
33631 Show terminal for future runs of program being debugged.
33633 @subheading @value{GDBN} Command
33635 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33637 @subheading Example
33641 -inferior-tty-set /dev/pts/1
33645 ^done,inferior_tty_terminal="/dev/pts/1"
33649 @subheading The @code{-enable-timings} Command
33650 @findex -enable-timings
33652 @subheading Synopsis
33655 -enable-timings [yes | no]
33658 Toggle the printing of the wallclock, user and system times for an MI
33659 command as a field in its output. This command is to help frontend
33660 developers optimize the performance of their code. No argument is
33661 equivalent to @samp{yes}.
33663 @subheading @value{GDBN} Command
33667 @subheading Example
33675 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33676 addr="0x080484ed",func="main",file="myprog.c",
33677 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33679 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33687 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33688 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33689 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33690 fullname="/home/nickrob/myprog.c",line="73"@}
33695 @chapter @value{GDBN} Annotations
33697 This chapter describes annotations in @value{GDBN}. Annotations were
33698 designed to interface @value{GDBN} to graphical user interfaces or other
33699 similar programs which want to interact with @value{GDBN} at a
33700 relatively high level.
33702 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33706 This is Edition @value{EDITION}, @value{DATE}.
33710 * Annotations Overview:: What annotations are; the general syntax.
33711 * Server Prefix:: Issuing a command without affecting user state.
33712 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33713 * Errors:: Annotations for error messages.
33714 * Invalidation:: Some annotations describe things now invalid.
33715 * Annotations for Running::
33716 Whether the program is running, how it stopped, etc.
33717 * Source Annotations:: Annotations describing source code.
33720 @node Annotations Overview
33721 @section What is an Annotation?
33722 @cindex annotations
33724 Annotations start with a newline character, two @samp{control-z}
33725 characters, and the name of the annotation. If there is no additional
33726 information associated with this annotation, the name of the annotation
33727 is followed immediately by a newline. If there is additional
33728 information, the name of the annotation is followed by a space, the
33729 additional information, and a newline. The additional information
33730 cannot contain newline characters.
33732 Any output not beginning with a newline and two @samp{control-z}
33733 characters denotes literal output from @value{GDBN}. Currently there is
33734 no need for @value{GDBN} to output a newline followed by two
33735 @samp{control-z} characters, but if there was such a need, the
33736 annotations could be extended with an @samp{escape} annotation which
33737 means those three characters as output.
33739 The annotation @var{level}, which is specified using the
33740 @option{--annotate} command line option (@pxref{Mode Options}), controls
33741 how much information @value{GDBN} prints together with its prompt,
33742 values of expressions, source lines, and other types of output. Level 0
33743 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33744 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33745 for programs that control @value{GDBN}, and level 2 annotations have
33746 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33747 Interface, annotate, GDB's Obsolete Annotations}).
33750 @kindex set annotate
33751 @item set annotate @var{level}
33752 The @value{GDBN} command @code{set annotate} sets the level of
33753 annotations to the specified @var{level}.
33755 @item show annotate
33756 @kindex show annotate
33757 Show the current annotation level.
33760 This chapter describes level 3 annotations.
33762 A simple example of starting up @value{GDBN} with annotations is:
33765 $ @kbd{gdb --annotate=3}
33767 Copyright 2003 Free Software Foundation, Inc.
33768 GDB is free software, covered by the GNU General Public License,
33769 and you are welcome to change it and/or distribute copies of it
33770 under certain conditions.
33771 Type "show copying" to see the conditions.
33772 There is absolutely no warranty for GDB. Type "show warranty"
33774 This GDB was configured as "i386-pc-linux-gnu"
33785 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33786 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33787 denotes a @samp{control-z} character) are annotations; the rest is
33788 output from @value{GDBN}.
33790 @node Server Prefix
33791 @section The Server Prefix
33792 @cindex server prefix
33794 If you prefix a command with @samp{server } then it will not affect
33795 the command history, nor will it affect @value{GDBN}'s notion of which
33796 command to repeat if @key{RET} is pressed on a line by itself. This
33797 means that commands can be run behind a user's back by a front-end in
33798 a transparent manner.
33800 The @code{server } prefix does not affect the recording of values into
33801 the value history; to print a value without recording it into the
33802 value history, use the @code{output} command instead of the
33803 @code{print} command.
33805 Using this prefix also disables confirmation requests
33806 (@pxref{confirmation requests}).
33809 @section Annotation for @value{GDBN} Input
33811 @cindex annotations for prompts
33812 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33813 to know when to send output, when the output from a given command is
33816 Different kinds of input each have a different @dfn{input type}. Each
33817 input type has three annotations: a @code{pre-} annotation, which
33818 denotes the beginning of any prompt which is being output, a plain
33819 annotation, which denotes the end of the prompt, and then a @code{post-}
33820 annotation which denotes the end of any echo which may (or may not) be
33821 associated with the input. For example, the @code{prompt} input type
33822 features the following annotations:
33830 The input types are
33833 @findex pre-prompt annotation
33834 @findex prompt annotation
33835 @findex post-prompt annotation
33837 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33839 @findex pre-commands annotation
33840 @findex commands annotation
33841 @findex post-commands annotation
33843 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33844 command. The annotations are repeated for each command which is input.
33846 @findex pre-overload-choice annotation
33847 @findex overload-choice annotation
33848 @findex post-overload-choice annotation
33849 @item overload-choice
33850 When @value{GDBN} wants the user to select between various overloaded functions.
33852 @findex pre-query annotation
33853 @findex query annotation
33854 @findex post-query annotation
33856 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33858 @findex pre-prompt-for-continue annotation
33859 @findex prompt-for-continue annotation
33860 @findex post-prompt-for-continue annotation
33861 @item prompt-for-continue
33862 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33863 expect this to work well; instead use @code{set height 0} to disable
33864 prompting. This is because the counting of lines is buggy in the
33865 presence of annotations.
33870 @cindex annotations for errors, warnings and interrupts
33872 @findex quit annotation
33877 This annotation occurs right before @value{GDBN} responds to an interrupt.
33879 @findex error annotation
33884 This annotation occurs right before @value{GDBN} responds to an error.
33886 Quit and error annotations indicate that any annotations which @value{GDBN} was
33887 in the middle of may end abruptly. For example, if a
33888 @code{value-history-begin} annotation is followed by a @code{error}, one
33889 cannot expect to receive the matching @code{value-history-end}. One
33890 cannot expect not to receive it either, however; an error annotation
33891 does not necessarily mean that @value{GDBN} is immediately returning all the way
33894 @findex error-begin annotation
33895 A quit or error annotation may be preceded by
33901 Any output between that and the quit or error annotation is the error
33904 Warning messages are not yet annotated.
33905 @c If we want to change that, need to fix warning(), type_error(),
33906 @c range_error(), and possibly other places.
33909 @section Invalidation Notices
33911 @cindex annotations for invalidation messages
33912 The following annotations say that certain pieces of state may have
33916 @findex frames-invalid annotation
33917 @item ^Z^Zframes-invalid
33919 The frames (for example, output from the @code{backtrace} command) may
33922 @findex breakpoints-invalid annotation
33923 @item ^Z^Zbreakpoints-invalid
33925 The breakpoints may have changed. For example, the user just added or
33926 deleted a breakpoint.
33929 @node Annotations for Running
33930 @section Running the Program
33931 @cindex annotations for running programs
33933 @findex starting annotation
33934 @findex stopping annotation
33935 When the program starts executing due to a @value{GDBN} command such as
33936 @code{step} or @code{continue},
33942 is output. When the program stops,
33948 is output. Before the @code{stopped} annotation, a variety of
33949 annotations describe how the program stopped.
33952 @findex exited annotation
33953 @item ^Z^Zexited @var{exit-status}
33954 The program exited, and @var{exit-status} is the exit status (zero for
33955 successful exit, otherwise nonzero).
33957 @findex signalled annotation
33958 @findex signal-name annotation
33959 @findex signal-name-end annotation
33960 @findex signal-string annotation
33961 @findex signal-string-end annotation
33962 @item ^Z^Zsignalled
33963 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33964 annotation continues:
33970 ^Z^Zsignal-name-end
33974 ^Z^Zsignal-string-end
33979 where @var{name} is the name of the signal, such as @code{SIGILL} or
33980 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33981 as @code{Illegal Instruction} or @code{Segmentation fault}.
33982 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33983 user's benefit and have no particular format.
33985 @findex signal annotation
33987 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33988 just saying that the program received the signal, not that it was
33989 terminated with it.
33991 @findex breakpoint annotation
33992 @item ^Z^Zbreakpoint @var{number}
33993 The program hit breakpoint number @var{number}.
33995 @findex watchpoint annotation
33996 @item ^Z^Zwatchpoint @var{number}
33997 The program hit watchpoint number @var{number}.
34000 @node Source Annotations
34001 @section Displaying Source
34002 @cindex annotations for source display
34004 @findex source annotation
34005 The following annotation is used instead of displaying source code:
34008 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34011 where @var{filename} is an absolute file name indicating which source
34012 file, @var{line} is the line number within that file (where 1 is the
34013 first line in the file), @var{character} is the character position
34014 within the file (where 0 is the first character in the file) (for most
34015 debug formats this will necessarily point to the beginning of a line),
34016 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34017 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34018 @var{addr} is the address in the target program associated with the
34019 source which is being displayed. @var{addr} is in the form @samp{0x}
34020 followed by one or more lowercase hex digits (note that this does not
34021 depend on the language).
34023 @node JIT Interface
34024 @chapter JIT Compilation Interface
34025 @cindex just-in-time compilation
34026 @cindex JIT compilation interface
34028 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34029 interface. A JIT compiler is a program or library that generates native
34030 executable code at runtime and executes it, usually in order to achieve good
34031 performance while maintaining platform independence.
34033 Programs that use JIT compilation are normally difficult to debug because
34034 portions of their code are generated at runtime, instead of being loaded from
34035 object files, which is where @value{GDBN} normally finds the program's symbols
34036 and debug information. In order to debug programs that use JIT compilation,
34037 @value{GDBN} has an interface that allows the program to register in-memory
34038 symbol files with @value{GDBN} at runtime.
34040 If you are using @value{GDBN} to debug a program that uses this interface, then
34041 it should work transparently so long as you have not stripped the binary. If
34042 you are developing a JIT compiler, then the interface is documented in the rest
34043 of this chapter. At this time, the only known client of this interface is the
34046 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34047 JIT compiler communicates with @value{GDBN} by writing data into a global
34048 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34049 attaches, it reads a linked list of symbol files from the global variable to
34050 find existing code, and puts a breakpoint in the function so that it can find
34051 out about additional code.
34054 * Declarations:: Relevant C struct declarations
34055 * Registering Code:: Steps to register code
34056 * Unregistering Code:: Steps to unregister code
34057 * Custom Debug Info:: Emit debug information in a custom format
34061 @section JIT Declarations
34063 These are the relevant struct declarations that a C program should include to
34064 implement the interface:
34074 struct jit_code_entry
34076 struct jit_code_entry *next_entry;
34077 struct jit_code_entry *prev_entry;
34078 const char *symfile_addr;
34079 uint64_t symfile_size;
34082 struct jit_descriptor
34085 /* This type should be jit_actions_t, but we use uint32_t
34086 to be explicit about the bitwidth. */
34087 uint32_t action_flag;
34088 struct jit_code_entry *relevant_entry;
34089 struct jit_code_entry *first_entry;
34092 /* GDB puts a breakpoint in this function. */
34093 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34095 /* Make sure to specify the version statically, because the
34096 debugger may check the version before we can set it. */
34097 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34100 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34101 modifications to this global data properly, which can easily be done by putting
34102 a global mutex around modifications to these structures.
34104 @node Registering Code
34105 @section Registering Code
34107 To register code with @value{GDBN}, the JIT should follow this protocol:
34111 Generate an object file in memory with symbols and other desired debug
34112 information. The file must include the virtual addresses of the sections.
34115 Create a code entry for the file, which gives the start and size of the symbol
34119 Add it to the linked list in the JIT descriptor.
34122 Point the relevant_entry field of the descriptor at the entry.
34125 Set @code{action_flag} to @code{JIT_REGISTER} and call
34126 @code{__jit_debug_register_code}.
34129 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34130 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34131 new code. However, the linked list must still be maintained in order to allow
34132 @value{GDBN} to attach to a running process and still find the symbol files.
34134 @node Unregistering Code
34135 @section Unregistering Code
34137 If code is freed, then the JIT should use the following protocol:
34141 Remove the code entry corresponding to the code from the linked list.
34144 Point the @code{relevant_entry} field of the descriptor at the code entry.
34147 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34148 @code{__jit_debug_register_code}.
34151 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34152 and the JIT will leak the memory used for the associated symbol files.
34154 @node Custom Debug Info
34155 @section Custom Debug Info
34156 @cindex custom JIT debug info
34157 @cindex JIT debug info reader
34159 Generating debug information in platform-native file formats (like ELF
34160 or COFF) may be an overkill for JIT compilers; especially if all the
34161 debug info is used for is displaying a meaningful backtrace. The
34162 issue can be resolved by having the JIT writers decide on a debug info
34163 format and also provide a reader that parses the debug info generated
34164 by the JIT compiler. This section gives a brief overview on writing
34165 such a parser. More specific details can be found in the source file
34166 @file{gdb/jit-reader.in}, which is also installed as a header at
34167 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34169 The reader is implemented as a shared object (so this functionality is
34170 not available on platforms which don't allow loading shared objects at
34171 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34172 @code{jit-reader-unload} are provided, to be used to load and unload
34173 the readers from a preconfigured directory. Once loaded, the shared
34174 object is used the parse the debug information emitted by the JIT
34178 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34179 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34182 @node Using JIT Debug Info Readers
34183 @subsection Using JIT Debug Info Readers
34184 @kindex jit-reader-load
34185 @kindex jit-reader-unload
34187 Readers can be loaded and unloaded using the @code{jit-reader-load}
34188 and @code{jit-reader-unload} commands.
34191 @item jit-reader-load @var{reader}
34192 Load the JIT reader named @var{reader}. @var{reader} is a shared
34193 object specified as either an absolute or a relative file name. In
34194 the latter case, @value{GDBN} will try to load the reader from a
34195 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34196 system (here @var{libdir} is the system library directory, often
34197 @file{/usr/local/lib}).
34199 Only one reader can be active at a time; trying to load a second
34200 reader when one is already loaded will result in @value{GDBN}
34201 reporting an error. A new JIT reader can be loaded by first unloading
34202 the current one using @code{jit-reader-unload} and then invoking
34203 @code{jit-reader-load}.
34205 @item jit-reader-unload
34206 Unload the currently loaded JIT reader.
34210 @node Writing JIT Debug Info Readers
34211 @subsection Writing JIT Debug Info Readers
34212 @cindex writing JIT debug info readers
34214 As mentioned, a reader is essentially a shared object conforming to a
34215 certain ABI. This ABI is described in @file{jit-reader.h}.
34217 @file{jit-reader.h} defines the structures, macros and functions
34218 required to write a reader. It is installed (along with
34219 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34220 the system include directory.
34222 Readers need to be released under a GPL compatible license. A reader
34223 can be declared as released under such a license by placing the macro
34224 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34226 The entry point for readers is the symbol @code{gdb_init_reader},
34227 which is expected to be a function with the prototype
34229 @findex gdb_init_reader
34231 extern struct gdb_reader_funcs *gdb_init_reader (void);
34234 @cindex @code{struct gdb_reader_funcs}
34236 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34237 functions. These functions are executed to read the debug info
34238 generated by the JIT compiler (@code{read}), to unwind stack frames
34239 (@code{unwind}) and to create canonical frame IDs
34240 (@code{get_Frame_id}). It also has a callback that is called when the
34241 reader is being unloaded (@code{destroy}). The struct looks like this
34244 struct gdb_reader_funcs
34246 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34247 int reader_version;
34249 /* For use by the reader. */
34252 gdb_read_debug_info *read;
34253 gdb_unwind_frame *unwind;
34254 gdb_get_frame_id *get_frame_id;
34255 gdb_destroy_reader *destroy;
34259 @cindex @code{struct gdb_symbol_callbacks}
34260 @cindex @code{struct gdb_unwind_callbacks}
34262 The callbacks are provided with another set of callbacks by
34263 @value{GDBN} to do their job. For @code{read}, these callbacks are
34264 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34265 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34266 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34267 files and new symbol tables inside those object files. @code{struct
34268 gdb_unwind_callbacks} has callbacks to read registers off the current
34269 frame and to write out the values of the registers in the previous
34270 frame. Both have a callback (@code{target_read}) to read bytes off the
34271 target's address space.
34273 @node In-Process Agent
34274 @chapter In-Process Agent
34275 @cindex debugging agent
34276 The traditional debugging model is conceptually low-speed, but works fine,
34277 because most bugs can be reproduced in debugging-mode execution. However,
34278 as multi-core or many-core processors are becoming mainstream, and
34279 multi-threaded programs become more and more popular, there should be more
34280 and more bugs that only manifest themselves at normal-mode execution, for
34281 example, thread races, because debugger's interference with the program's
34282 timing may conceal the bugs. On the other hand, in some applications,
34283 it is not feasible for the debugger to interrupt the program's execution
34284 long enough for the developer to learn anything helpful about its behavior.
34285 If the program's correctness depends on its real-time behavior, delays
34286 introduced by a debugger might cause the program to fail, even when the
34287 code itself is correct. It is useful to be able to observe the program's
34288 behavior without interrupting it.
34290 Therefore, traditional debugging model is too intrusive to reproduce
34291 some bugs. In order to reduce the interference with the program, we can
34292 reduce the number of operations performed by debugger. The
34293 @dfn{In-Process Agent}, a shared library, is running within the same
34294 process with inferior, and is able to perform some debugging operations
34295 itself. As a result, debugger is only involved when necessary, and
34296 performance of debugging can be improved accordingly. Note that
34297 interference with program can be reduced but can't be removed completely,
34298 because the in-process agent will still stop or slow down the program.
34300 The in-process agent can interpret and execute Agent Expressions
34301 (@pxref{Agent Expressions}) during performing debugging operations. The
34302 agent expressions can be used for different purposes, such as collecting
34303 data in tracepoints, and condition evaluation in breakpoints.
34305 @anchor{Control Agent}
34306 You can control whether the in-process agent is used as an aid for
34307 debugging with the following commands:
34310 @kindex set agent on
34312 Causes the in-process agent to perform some operations on behalf of the
34313 debugger. Just which operations requested by the user will be done
34314 by the in-process agent depends on the its capabilities. For example,
34315 if you request to evaluate breakpoint conditions in the in-process agent,
34316 and the in-process agent has such capability as well, then breakpoint
34317 conditions will be evaluated in the in-process agent.
34319 @kindex set agent off
34320 @item set agent off
34321 Disables execution of debugging operations by the in-process agent. All
34322 of the operations will be performed by @value{GDBN}.
34326 Display the current setting of execution of debugging operations by
34327 the in-process agent.
34331 * In-Process Agent Protocol::
34334 @node In-Process Agent Protocol
34335 @section In-Process Agent Protocol
34336 @cindex in-process agent protocol
34338 The in-process agent is able to communicate with both @value{GDBN} and
34339 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34340 used for communications between @value{GDBN} or GDBserver and the IPA.
34341 In general, @value{GDBN} or GDBserver sends commands
34342 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34343 in-process agent replies back with the return result of the command, or
34344 some other information. The data sent to in-process agent is composed
34345 of primitive data types, such as 4-byte or 8-byte type, and composite
34346 types, which are called objects (@pxref{IPA Protocol Objects}).
34349 * IPA Protocol Objects::
34350 * IPA Protocol Commands::
34353 @node IPA Protocol Objects
34354 @subsection IPA Protocol Objects
34355 @cindex ipa protocol objects
34357 The commands sent to and results received from agent may contain some
34358 complex data types called @dfn{objects}.
34360 The in-process agent is running on the same machine with @value{GDBN}
34361 or GDBserver, so it doesn't have to handle as much differences between
34362 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34363 However, there are still some differences of two ends in two processes:
34367 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34368 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34370 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34371 GDBserver is compiled with one, and in-process agent is compiled with
34375 Here are the IPA Protocol Objects:
34379 agent expression object. It represents an agent expression
34380 (@pxref{Agent Expressions}).
34381 @anchor{agent expression object}
34383 tracepoint action object. It represents a tracepoint action
34384 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34385 memory, static trace data and to evaluate expression.
34386 @anchor{tracepoint action object}
34388 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34389 @anchor{tracepoint object}
34393 The following table describes important attributes of each IPA protocol
34396 @multitable @columnfractions .30 .20 .50
34397 @headitem Name @tab Size @tab Description
34398 @item @emph{agent expression object} @tab @tab
34399 @item length @tab 4 @tab length of bytes code
34400 @item byte code @tab @var{length} @tab contents of byte code
34401 @item @emph{tracepoint action for collecting memory} @tab @tab
34402 @item 'M' @tab 1 @tab type of tracepoint action
34403 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34404 address of the lowest byte to collect, otherwise @var{addr} is the offset
34405 of @var{basereg} for memory collecting.
34406 @item len @tab 8 @tab length of memory for collecting
34407 @item basereg @tab 4 @tab the register number containing the starting
34408 memory address for collecting.
34409 @item @emph{tracepoint action for collecting registers} @tab @tab
34410 @item 'R' @tab 1 @tab type of tracepoint action
34411 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34412 @item 'L' @tab 1 @tab type of tracepoint action
34413 @item @emph{tracepoint action for expression evaluation} @tab @tab
34414 @item 'X' @tab 1 @tab type of tracepoint action
34415 @item agent expression @tab length of @tab @ref{agent expression object}
34416 @item @emph{tracepoint object} @tab @tab
34417 @item number @tab 4 @tab number of tracepoint
34418 @item address @tab 8 @tab address of tracepoint inserted on
34419 @item type @tab 4 @tab type of tracepoint
34420 @item enabled @tab 1 @tab enable or disable of tracepoint
34421 @item step_count @tab 8 @tab step
34422 @item pass_count @tab 8 @tab pass
34423 @item numactions @tab 4 @tab number of tracepoint actions
34424 @item hit count @tab 8 @tab hit count
34425 @item trace frame usage @tab 8 @tab trace frame usage
34426 @item compiled_cond @tab 8 @tab compiled condition
34427 @item orig_size @tab 8 @tab orig size
34428 @item condition @tab 4 if condition is NULL otherwise length of
34429 @ref{agent expression object}
34430 @tab zero if condition is NULL, otherwise is
34431 @ref{agent expression object}
34432 @item actions @tab variable
34433 @tab numactions number of @ref{tracepoint action object}
34436 @node IPA Protocol Commands
34437 @subsection IPA Protocol Commands
34438 @cindex ipa protocol commands
34440 The spaces in each command are delimiters to ease reading this commands
34441 specification. They don't exist in real commands.
34445 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34446 Installs a new fast tracepoint described by @var{tracepoint_object}
34447 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34448 head of @dfn{jumppad}, which is used to jump to data collection routine
34453 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34454 @var{target_address} is address of tracepoint in the inferior.
34455 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34456 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34457 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34458 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34465 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34466 is about to kill inferiors.
34474 @item probe_marker_at:@var{address}
34475 Asks in-process agent to probe the marker at @var{address}.
34482 @item unprobe_marker_at:@var{address}
34483 Asks in-process agent to unprobe the marker at @var{address}.
34487 @chapter Reporting Bugs in @value{GDBN}
34488 @cindex bugs in @value{GDBN}
34489 @cindex reporting bugs in @value{GDBN}
34491 Your bug reports play an essential role in making @value{GDBN} reliable.
34493 Reporting a bug may help you by bringing a solution to your problem, or it
34494 may not. But in any case the principal function of a bug report is to help
34495 the entire community by making the next version of @value{GDBN} work better. Bug
34496 reports are your contribution to the maintenance of @value{GDBN}.
34498 In order for a bug report to serve its purpose, you must include the
34499 information that enables us to fix the bug.
34502 * Bug Criteria:: Have you found a bug?
34503 * Bug Reporting:: How to report bugs
34507 @section Have You Found a Bug?
34508 @cindex bug criteria
34510 If you are not sure whether you have found a bug, here are some guidelines:
34513 @cindex fatal signal
34514 @cindex debugger crash
34515 @cindex crash of debugger
34517 If the debugger gets a fatal signal, for any input whatever, that is a
34518 @value{GDBN} bug. Reliable debuggers never crash.
34520 @cindex error on valid input
34522 If @value{GDBN} produces an error message for valid input, that is a
34523 bug. (Note that if you're cross debugging, the problem may also be
34524 somewhere in the connection to the target.)
34526 @cindex invalid input
34528 If @value{GDBN} does not produce an error message for invalid input,
34529 that is a bug. However, you should note that your idea of
34530 ``invalid input'' might be our idea of ``an extension'' or ``support
34531 for traditional practice''.
34534 If you are an experienced user of debugging tools, your suggestions
34535 for improvement of @value{GDBN} are welcome in any case.
34538 @node Bug Reporting
34539 @section How to Report Bugs
34540 @cindex bug reports
34541 @cindex @value{GDBN} bugs, reporting
34543 A number of companies and individuals offer support for @sc{gnu} products.
34544 If you obtained @value{GDBN} from a support organization, we recommend you
34545 contact that organization first.
34547 You can find contact information for many support companies and
34548 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34550 @c should add a web page ref...
34553 @ifset BUGURL_DEFAULT
34554 In any event, we also recommend that you submit bug reports for
34555 @value{GDBN}. The preferred method is to submit them directly using
34556 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34557 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34560 @strong{Do not send bug reports to @samp{info-gdb}, or to
34561 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34562 not want to receive bug reports. Those that do have arranged to receive
34565 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34566 serves as a repeater. The mailing list and the newsgroup carry exactly
34567 the same messages. Often people think of posting bug reports to the
34568 newsgroup instead of mailing them. This appears to work, but it has one
34569 problem which can be crucial: a newsgroup posting often lacks a mail
34570 path back to the sender. Thus, if we need to ask for more information,
34571 we may be unable to reach you. For this reason, it is better to send
34572 bug reports to the mailing list.
34574 @ifclear BUGURL_DEFAULT
34575 In any event, we also recommend that you submit bug reports for
34576 @value{GDBN} to @value{BUGURL}.
34580 The fundamental principle of reporting bugs usefully is this:
34581 @strong{report all the facts}. If you are not sure whether to state a
34582 fact or leave it out, state it!
34584 Often people omit facts because they think they know what causes the
34585 problem and assume that some details do not matter. Thus, you might
34586 assume that the name of the variable you use in an example does not matter.
34587 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34588 stray memory reference which happens to fetch from the location where that
34589 name is stored in memory; perhaps, if the name were different, the contents
34590 of that location would fool the debugger into doing the right thing despite
34591 the bug. Play it safe and give a specific, complete example. That is the
34592 easiest thing for you to do, and the most helpful.
34594 Keep in mind that the purpose of a bug report is to enable us to fix the
34595 bug. It may be that the bug has been reported previously, but neither
34596 you nor we can know that unless your bug report is complete and
34599 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34600 bell?'' Those bug reports are useless, and we urge everyone to
34601 @emph{refuse to respond to them} except to chide the sender to report
34604 To enable us to fix the bug, you should include all these things:
34608 The version of @value{GDBN}. @value{GDBN} announces it if you start
34609 with no arguments; you can also print it at any time using @code{show
34612 Without this, we will not know whether there is any point in looking for
34613 the bug in the current version of @value{GDBN}.
34616 The type of machine you are using, and the operating system name and
34620 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34621 ``@value{GCC}--2.8.1''.
34624 What compiler (and its version) was used to compile the program you are
34625 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34626 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34627 to get this information; for other compilers, see the documentation for
34631 The command arguments you gave the compiler to compile your example and
34632 observe the bug. For example, did you use @samp{-O}? To guarantee
34633 you will not omit something important, list them all. A copy of the
34634 Makefile (or the output from make) is sufficient.
34636 If we were to try to guess the arguments, we would probably guess wrong
34637 and then we might not encounter the bug.
34640 A complete input script, and all necessary source files, that will
34644 A description of what behavior you observe that you believe is
34645 incorrect. For example, ``It gets a fatal signal.''
34647 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34648 will certainly notice it. But if the bug is incorrect output, we might
34649 not notice unless it is glaringly wrong. You might as well not give us
34650 a chance to make a mistake.
34652 Even if the problem you experience is a fatal signal, you should still
34653 say so explicitly. Suppose something strange is going on, such as, your
34654 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34655 the C library on your system. (This has happened!) Your copy might
34656 crash and ours would not. If you told us to expect a crash, then when
34657 ours fails to crash, we would know that the bug was not happening for
34658 us. If you had not told us to expect a crash, then we would not be able
34659 to draw any conclusion from our observations.
34662 @cindex recording a session script
34663 To collect all this information, you can use a session recording program
34664 such as @command{script}, which is available on many Unix systems.
34665 Just run your @value{GDBN} session inside @command{script} and then
34666 include the @file{typescript} file with your bug report.
34668 Another way to record a @value{GDBN} session is to run @value{GDBN}
34669 inside Emacs and then save the entire buffer to a file.
34672 If you wish to suggest changes to the @value{GDBN} source, send us context
34673 diffs. If you even discuss something in the @value{GDBN} source, refer to
34674 it by context, not by line number.
34676 The line numbers in our development sources will not match those in your
34677 sources. Your line numbers would convey no useful information to us.
34681 Here are some things that are not necessary:
34685 A description of the envelope of the bug.
34687 Often people who encounter a bug spend a lot of time investigating
34688 which changes to the input file will make the bug go away and which
34689 changes will not affect it.
34691 This is often time consuming and not very useful, because the way we
34692 will find the bug is by running a single example under the debugger
34693 with breakpoints, not by pure deduction from a series of examples.
34694 We recommend that you save your time for something else.
34696 Of course, if you can find a simpler example to report @emph{instead}
34697 of the original one, that is a convenience for us. Errors in the
34698 output will be easier to spot, running under the debugger will take
34699 less time, and so on.
34701 However, simplification is not vital; if you do not want to do this,
34702 report the bug anyway and send us the entire test case you used.
34705 A patch for the bug.
34707 A patch for the bug does help us if it is a good one. But do not omit
34708 the necessary information, such as the test case, on the assumption that
34709 a patch is all we need. We might see problems with your patch and decide
34710 to fix the problem another way, or we might not understand it at all.
34712 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34713 construct an example that will make the program follow a certain path
34714 through the code. If you do not send us the example, we will not be able
34715 to construct one, so we will not be able to verify that the bug is fixed.
34717 And if we cannot understand what bug you are trying to fix, or why your
34718 patch should be an improvement, we will not install it. A test case will
34719 help us to understand.
34722 A guess about what the bug is or what it depends on.
34724 Such guesses are usually wrong. Even we cannot guess right about such
34725 things without first using the debugger to find the facts.
34728 @c The readline documentation is distributed with the readline code
34729 @c and consists of the two following files:
34732 @c Use -I with makeinfo to point to the appropriate directory,
34733 @c environment var TEXINPUTS with TeX.
34734 @ifclear SYSTEM_READLINE
34735 @include rluser.texi
34736 @include hsuser.texi
34740 @appendix In Memoriam
34742 The @value{GDBN} project mourns the loss of the following long-time
34747 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34748 to Free Software in general. Outside of @value{GDBN}, he was known in
34749 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34751 @item Michael Snyder
34752 Michael was one of the Global Maintainers of the @value{GDBN} project,
34753 with contributions recorded as early as 1996, until 2011. In addition
34754 to his day to day participation, he was a large driving force behind
34755 adding Reverse Debugging to @value{GDBN}.
34758 Beyond their technical contributions to the project, they were also
34759 enjoyable members of the Free Software Community. We will miss them.
34761 @node Formatting Documentation
34762 @appendix Formatting Documentation
34764 @cindex @value{GDBN} reference card
34765 @cindex reference card
34766 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34767 for printing with PostScript or Ghostscript, in the @file{gdb}
34768 subdirectory of the main source directory@footnote{In
34769 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34770 release.}. If you can use PostScript or Ghostscript with your printer,
34771 you can print the reference card immediately with @file{refcard.ps}.
34773 The release also includes the source for the reference card. You
34774 can format it, using @TeX{}, by typing:
34780 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34781 mode on US ``letter'' size paper;
34782 that is, on a sheet 11 inches wide by 8.5 inches
34783 high. You will need to specify this form of printing as an option to
34784 your @sc{dvi} output program.
34786 @cindex documentation
34788 All the documentation for @value{GDBN} comes as part of the machine-readable
34789 distribution. The documentation is written in Texinfo format, which is
34790 a documentation system that uses a single source file to produce both
34791 on-line information and a printed manual. You can use one of the Info
34792 formatting commands to create the on-line version of the documentation
34793 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34795 @value{GDBN} includes an already formatted copy of the on-line Info
34796 version of this manual in the @file{gdb} subdirectory. The main Info
34797 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34798 subordinate files matching @samp{gdb.info*} in the same directory. If
34799 necessary, you can print out these files, or read them with any editor;
34800 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34801 Emacs or the standalone @code{info} program, available as part of the
34802 @sc{gnu} Texinfo distribution.
34804 If you want to format these Info files yourself, you need one of the
34805 Info formatting programs, such as @code{texinfo-format-buffer} or
34808 If you have @code{makeinfo} installed, and are in the top level
34809 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34810 version @value{GDBVN}), you can make the Info file by typing:
34817 If you want to typeset and print copies of this manual, you need @TeX{},
34818 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34819 Texinfo definitions file.
34821 @TeX{} is a typesetting program; it does not print files directly, but
34822 produces output files called @sc{dvi} files. To print a typeset
34823 document, you need a program to print @sc{dvi} files. If your system
34824 has @TeX{} installed, chances are it has such a program. The precise
34825 command to use depends on your system; @kbd{lpr -d} is common; another
34826 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34827 require a file name without any extension or a @samp{.dvi} extension.
34829 @TeX{} also requires a macro definitions file called
34830 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34831 written in Texinfo format. On its own, @TeX{} cannot either read or
34832 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34833 and is located in the @file{gdb-@var{version-number}/texinfo}
34836 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34837 typeset and print this manual. First switch to the @file{gdb}
34838 subdirectory of the main source directory (for example, to
34839 @file{gdb-@value{GDBVN}/gdb}) and type:
34845 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34847 @node Installing GDB
34848 @appendix Installing @value{GDBN}
34849 @cindex installation
34852 * Requirements:: Requirements for building @value{GDBN}
34853 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34854 * Separate Objdir:: Compiling @value{GDBN} in another directory
34855 * Config Names:: Specifying names for hosts and targets
34856 * Configure Options:: Summary of options for configure
34857 * System-wide configuration:: Having a system-wide init file
34861 @section Requirements for Building @value{GDBN}
34862 @cindex building @value{GDBN}, requirements for
34864 Building @value{GDBN} requires various tools and packages to be available.
34865 Other packages will be used only if they are found.
34867 @heading Tools/Packages Necessary for Building @value{GDBN}
34869 @item ISO C90 compiler
34870 @value{GDBN} is written in ISO C90. It should be buildable with any
34871 working C90 compiler, e.g.@: GCC.
34875 @heading Tools/Packages Optional for Building @value{GDBN}
34879 @value{GDBN} can use the Expat XML parsing library. This library may be
34880 included with your operating system distribution; if it is not, you
34881 can get the latest version from @url{http://expat.sourceforge.net}.
34882 The @file{configure} script will search for this library in several
34883 standard locations; if it is installed in an unusual path, you can
34884 use the @option{--with-libexpat-prefix} option to specify its location.
34890 Remote protocol memory maps (@pxref{Memory Map Format})
34892 Target descriptions (@pxref{Target Descriptions})
34894 Remote shared library lists (@xref{Library List Format},
34895 or alternatively @pxref{Library List Format for SVR4 Targets})
34897 MS-Windows shared libraries (@pxref{Shared Libraries})
34899 Traceframe info (@pxref{Traceframe Info Format})
34901 Branch trace (@pxref{Branch Trace Format})
34905 @cindex compressed debug sections
34906 @value{GDBN} will use the @samp{zlib} library, if available, to read
34907 compressed debug sections. Some linkers, such as GNU gold, are capable
34908 of producing binaries with compressed debug sections. If @value{GDBN}
34909 is compiled with @samp{zlib}, it will be able to read the debug
34910 information in such binaries.
34912 The @samp{zlib} library is likely included with your operating system
34913 distribution; if it is not, you can get the latest version from
34914 @url{http://zlib.net}.
34917 @value{GDBN}'s features related to character sets (@pxref{Character
34918 Sets}) require a functioning @code{iconv} implementation. If you are
34919 on a GNU system, then this is provided by the GNU C Library. Some
34920 other systems also provide a working @code{iconv}.
34922 If @value{GDBN} is using the @code{iconv} program which is installed
34923 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34924 This is done with @option{--with-iconv-bin} which specifies the
34925 directory that contains the @code{iconv} program.
34927 On systems without @code{iconv}, you can install GNU Libiconv. If you
34928 have previously installed Libiconv, you can use the
34929 @option{--with-libiconv-prefix} option to configure.
34931 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34932 arrange to build Libiconv if a directory named @file{libiconv} appears
34933 in the top-most source directory. If Libiconv is built this way, and
34934 if the operating system does not provide a suitable @code{iconv}
34935 implementation, then the just-built library will automatically be used
34936 by @value{GDBN}. One easy way to set this up is to download GNU
34937 Libiconv, unpack it, and then rename the directory holding the
34938 Libiconv source code to @samp{libiconv}.
34941 @node Running Configure
34942 @section Invoking the @value{GDBN} @file{configure} Script
34943 @cindex configuring @value{GDBN}
34944 @value{GDBN} comes with a @file{configure} script that automates the process
34945 of preparing @value{GDBN} for installation; you can then use @code{make} to
34946 build the @code{gdb} program.
34948 @c irrelevant in info file; it's as current as the code it lives with.
34949 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34950 look at the @file{README} file in the sources; we may have improved the
34951 installation procedures since publishing this manual.}
34954 The @value{GDBN} distribution includes all the source code you need for
34955 @value{GDBN} in a single directory, whose name is usually composed by
34956 appending the version number to @samp{gdb}.
34958 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34959 @file{gdb-@value{GDBVN}} directory. That directory contains:
34962 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34963 script for configuring @value{GDBN} and all its supporting libraries
34965 @item gdb-@value{GDBVN}/gdb
34966 the source specific to @value{GDBN} itself
34968 @item gdb-@value{GDBVN}/bfd
34969 source for the Binary File Descriptor library
34971 @item gdb-@value{GDBVN}/include
34972 @sc{gnu} include files
34974 @item gdb-@value{GDBVN}/libiberty
34975 source for the @samp{-liberty} free software library
34977 @item gdb-@value{GDBVN}/opcodes
34978 source for the library of opcode tables and disassemblers
34980 @item gdb-@value{GDBVN}/readline
34981 source for the @sc{gnu} command-line interface
34983 @item gdb-@value{GDBVN}/glob
34984 source for the @sc{gnu} filename pattern-matching subroutine
34986 @item gdb-@value{GDBVN}/mmalloc
34987 source for the @sc{gnu} memory-mapped malloc package
34990 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34991 from the @file{gdb-@var{version-number}} source directory, which in
34992 this example is the @file{gdb-@value{GDBVN}} directory.
34994 First switch to the @file{gdb-@var{version-number}} source directory
34995 if you are not already in it; then run @file{configure}. Pass the
34996 identifier for the platform on which @value{GDBN} will run as an
35002 cd gdb-@value{GDBVN}
35003 ./configure @var{host}
35008 where @var{host} is an identifier such as @samp{sun4} or
35009 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35010 (You can often leave off @var{host}; @file{configure} tries to guess the
35011 correct value by examining your system.)
35013 Running @samp{configure @var{host}} and then running @code{make} builds the
35014 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35015 libraries, then @code{gdb} itself. The configured source files, and the
35016 binaries, are left in the corresponding source directories.
35019 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35020 system does not recognize this automatically when you run a different
35021 shell, you may need to run @code{sh} on it explicitly:
35024 sh configure @var{host}
35027 If you run @file{configure} from a directory that contains source
35028 directories for multiple libraries or programs, such as the
35029 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35031 creates configuration files for every directory level underneath (unless
35032 you tell it not to, with the @samp{--norecursion} option).
35034 You should run the @file{configure} script from the top directory in the
35035 source tree, the @file{gdb-@var{version-number}} directory. If you run
35036 @file{configure} from one of the subdirectories, you will configure only
35037 that subdirectory. That is usually not what you want. In particular,
35038 if you run the first @file{configure} from the @file{gdb} subdirectory
35039 of the @file{gdb-@var{version-number}} directory, you will omit the
35040 configuration of @file{bfd}, @file{readline}, and other sibling
35041 directories of the @file{gdb} subdirectory. This leads to build errors
35042 about missing include files such as @file{bfd/bfd.h}.
35044 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35045 However, you should make sure that the shell on your path (named by
35046 the @samp{SHELL} environment variable) is publicly readable. Remember
35047 that @value{GDBN} uses the shell to start your program---some systems refuse to
35048 let @value{GDBN} debug child processes whose programs are not readable.
35050 @node Separate Objdir
35051 @section Compiling @value{GDBN} in Another Directory
35053 If you want to run @value{GDBN} versions for several host or target machines,
35054 you need a different @code{gdb} compiled for each combination of
35055 host and target. @file{configure} is designed to make this easy by
35056 allowing you to generate each configuration in a separate subdirectory,
35057 rather than in the source directory. If your @code{make} program
35058 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35059 @code{make} in each of these directories builds the @code{gdb}
35060 program specified there.
35062 To build @code{gdb} in a separate directory, run @file{configure}
35063 with the @samp{--srcdir} option to specify where to find the source.
35064 (You also need to specify a path to find @file{configure}
35065 itself from your working directory. If the path to @file{configure}
35066 would be the same as the argument to @samp{--srcdir}, you can leave out
35067 the @samp{--srcdir} option; it is assumed.)
35069 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35070 separate directory for a Sun 4 like this:
35074 cd gdb-@value{GDBVN}
35077 ../gdb-@value{GDBVN}/configure sun4
35082 When @file{configure} builds a configuration using a remote source
35083 directory, it creates a tree for the binaries with the same structure
35084 (and using the same names) as the tree under the source directory. In
35085 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35086 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35087 @file{gdb-sun4/gdb}.
35089 Make sure that your path to the @file{configure} script has just one
35090 instance of @file{gdb} in it. If your path to @file{configure} looks
35091 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35092 one subdirectory of @value{GDBN}, not the whole package. This leads to
35093 build errors about missing include files such as @file{bfd/bfd.h}.
35095 One popular reason to build several @value{GDBN} configurations in separate
35096 directories is to configure @value{GDBN} for cross-compiling (where
35097 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35098 programs that run on another machine---the @dfn{target}).
35099 You specify a cross-debugging target by
35100 giving the @samp{--target=@var{target}} option to @file{configure}.
35102 When you run @code{make} to build a program or library, you must run
35103 it in a configured directory---whatever directory you were in when you
35104 called @file{configure} (or one of its subdirectories).
35106 The @code{Makefile} that @file{configure} generates in each source
35107 directory also runs recursively. If you type @code{make} in a source
35108 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35109 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35110 will build all the required libraries, and then build GDB.
35112 When you have multiple hosts or targets configured in separate
35113 directories, you can run @code{make} on them in parallel (for example,
35114 if they are NFS-mounted on each of the hosts); they will not interfere
35118 @section Specifying Names for Hosts and Targets
35120 The specifications used for hosts and targets in the @file{configure}
35121 script are based on a three-part naming scheme, but some short predefined
35122 aliases are also supported. The full naming scheme encodes three pieces
35123 of information in the following pattern:
35126 @var{architecture}-@var{vendor}-@var{os}
35129 For example, you can use the alias @code{sun4} as a @var{host} argument,
35130 or as the value for @var{target} in a @code{--target=@var{target}}
35131 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35133 The @file{configure} script accompanying @value{GDBN} does not provide
35134 any query facility to list all supported host and target names or
35135 aliases. @file{configure} calls the Bourne shell script
35136 @code{config.sub} to map abbreviations to full names; you can read the
35137 script, if you wish, or you can use it to test your guesses on
35138 abbreviations---for example:
35141 % sh config.sub i386-linux
35143 % sh config.sub alpha-linux
35144 alpha-unknown-linux-gnu
35145 % sh config.sub hp9k700
35147 % sh config.sub sun4
35148 sparc-sun-sunos4.1.1
35149 % sh config.sub sun3
35150 m68k-sun-sunos4.1.1
35151 % sh config.sub i986v
35152 Invalid configuration `i986v': machine `i986v' not recognized
35156 @code{config.sub} is also distributed in the @value{GDBN} source
35157 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35159 @node Configure Options
35160 @section @file{configure} Options
35162 Here is a summary of the @file{configure} options and arguments that
35163 are most often useful for building @value{GDBN}. @file{configure} also has
35164 several other options not listed here. @inforef{What Configure
35165 Does,,configure.info}, for a full explanation of @file{configure}.
35168 configure @r{[}--help@r{]}
35169 @r{[}--prefix=@var{dir}@r{]}
35170 @r{[}--exec-prefix=@var{dir}@r{]}
35171 @r{[}--srcdir=@var{dirname}@r{]}
35172 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35173 @r{[}--target=@var{target}@r{]}
35178 You may introduce options with a single @samp{-} rather than
35179 @samp{--} if you prefer; but you may abbreviate option names if you use
35184 Display a quick summary of how to invoke @file{configure}.
35186 @item --prefix=@var{dir}
35187 Configure the source to install programs and files under directory
35190 @item --exec-prefix=@var{dir}
35191 Configure the source to install programs under directory
35194 @c avoid splitting the warning from the explanation:
35196 @item --srcdir=@var{dirname}
35197 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35198 @code{make} that implements the @code{VPATH} feature.}@*
35199 Use this option to make configurations in directories separate from the
35200 @value{GDBN} source directories. Among other things, you can use this to
35201 build (or maintain) several configurations simultaneously, in separate
35202 directories. @file{configure} writes configuration-specific files in
35203 the current directory, but arranges for them to use the source in the
35204 directory @var{dirname}. @file{configure} creates directories under
35205 the working directory in parallel to the source directories below
35208 @item --norecursion
35209 Configure only the directory level where @file{configure} is executed; do not
35210 propagate configuration to subdirectories.
35212 @item --target=@var{target}
35213 Configure @value{GDBN} for cross-debugging programs running on the specified
35214 @var{target}. Without this option, @value{GDBN} is configured to debug
35215 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35217 There is no convenient way to generate a list of all available targets.
35219 @item @var{host} @dots{}
35220 Configure @value{GDBN} to run on the specified @var{host}.
35222 There is no convenient way to generate a list of all available hosts.
35225 There are many other options available as well, but they are generally
35226 needed for special purposes only.
35228 @node System-wide configuration
35229 @section System-wide configuration and settings
35230 @cindex system-wide init file
35232 @value{GDBN} can be configured to have a system-wide init file;
35233 this file will be read and executed at startup (@pxref{Startup, , What
35234 @value{GDBN} does during startup}).
35236 Here is the corresponding configure option:
35239 @item --with-system-gdbinit=@var{file}
35240 Specify that the default location of the system-wide init file is
35244 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35245 it may be subject to relocation. Two possible cases:
35249 If the default location of this init file contains @file{$prefix},
35250 it will be subject to relocation. Suppose that the configure options
35251 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35252 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35253 init file is looked for as @file{$install/etc/gdbinit} instead of
35254 @file{$prefix/etc/gdbinit}.
35257 By contrast, if the default location does not contain the prefix,
35258 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35259 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35260 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35261 wherever @value{GDBN} is installed.
35264 If the configured location of the system-wide init file (as given by the
35265 @option{--with-system-gdbinit} option at configure time) is in the
35266 data-directory (as specified by @option{--with-gdb-datadir} at configure
35267 time) or in one of its subdirectories, then @value{GDBN} will look for the
35268 system-wide init file in the directory specified by the
35269 @option{--data-directory} command-line option.
35270 Note that the system-wide init file is only read once, during @value{GDBN}
35271 initialization. If the data-directory is changed after @value{GDBN} has
35272 started with the @code{set data-directory} command, the file will not be
35275 @node Maintenance Commands
35276 @appendix Maintenance Commands
35277 @cindex maintenance commands
35278 @cindex internal commands
35280 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35281 includes a number of commands intended for @value{GDBN} developers,
35282 that are not documented elsewhere in this manual. These commands are
35283 provided here for reference. (For commands that turn on debugging
35284 messages, see @ref{Debugging Output}.)
35287 @kindex maint agent
35288 @kindex maint agent-eval
35289 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35290 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35291 Translate the given @var{expression} into remote agent bytecodes.
35292 This command is useful for debugging the Agent Expression mechanism
35293 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35294 expression useful for data collection, such as by tracepoints, while
35295 @samp{maint agent-eval} produces an expression that evaluates directly
35296 to a result. For instance, a collection expression for @code{globa +
35297 globb} will include bytecodes to record four bytes of memory at each
35298 of the addresses of @code{globa} and @code{globb}, while discarding
35299 the result of the addition, while an evaluation expression will do the
35300 addition and return the sum.
35301 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35302 If not, generate remote agent bytecode for current frame PC address.
35304 @kindex maint agent-printf
35305 @item maint agent-printf @var{format},@var{expr},...
35306 Translate the given format string and list of argument expressions
35307 into remote agent bytecodes and display them as a disassembled list.
35308 This command is useful for debugging the agent version of dynamic
35309 printf (@pxref{Dynamic Printf}).
35311 @kindex maint info breakpoints
35312 @item @anchor{maint info breakpoints}maint info breakpoints
35313 Using the same format as @samp{info breakpoints}, display both the
35314 breakpoints you've set explicitly, and those @value{GDBN} is using for
35315 internal purposes. Internal breakpoints are shown with negative
35316 breakpoint numbers. The type column identifies what kind of breakpoint
35321 Normal, explicitly set breakpoint.
35324 Normal, explicitly set watchpoint.
35327 Internal breakpoint, used to handle correctly stepping through
35328 @code{longjmp} calls.
35330 @item longjmp resume
35331 Internal breakpoint at the target of a @code{longjmp}.
35334 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35337 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35340 Shared library events.
35344 @kindex maint info bfds
35345 @item maint info bfds
35346 This prints information about each @code{bfd} object that is known to
35347 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35349 @kindex set displaced-stepping
35350 @kindex show displaced-stepping
35351 @cindex displaced stepping support
35352 @cindex out-of-line single-stepping
35353 @item set displaced-stepping
35354 @itemx show displaced-stepping
35355 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35356 if the target supports it. Displaced stepping is a way to single-step
35357 over breakpoints without removing them from the inferior, by executing
35358 an out-of-line copy of the instruction that was originally at the
35359 breakpoint location. It is also known as out-of-line single-stepping.
35362 @item set displaced-stepping on
35363 If the target architecture supports it, @value{GDBN} will use
35364 displaced stepping to step over breakpoints.
35366 @item set displaced-stepping off
35367 @value{GDBN} will not use displaced stepping to step over breakpoints,
35368 even if such is supported by the target architecture.
35370 @cindex non-stop mode, and @samp{set displaced-stepping}
35371 @item set displaced-stepping auto
35372 This is the default mode. @value{GDBN} will use displaced stepping
35373 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35374 architecture supports displaced stepping.
35377 @kindex maint check-symtabs
35378 @item maint check-symtabs
35379 Check the consistency of psymtabs and symtabs.
35381 @kindex maint cplus first_component
35382 @item maint cplus first_component @var{name}
35383 Print the first C@t{++} class/namespace component of @var{name}.
35385 @kindex maint cplus namespace
35386 @item maint cplus namespace
35387 Print the list of possible C@t{++} namespaces.
35389 @kindex maint demangle
35390 @item maint demangle @var{name}
35391 Demangle a C@t{++} or Objective-C mangled @var{name}.
35393 @kindex maint deprecate
35394 @kindex maint undeprecate
35395 @cindex deprecated commands
35396 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35397 @itemx maint undeprecate @var{command}
35398 Deprecate or undeprecate the named @var{command}. Deprecated commands
35399 cause @value{GDBN} to issue a warning when you use them. The optional
35400 argument @var{replacement} says which newer command should be used in
35401 favor of the deprecated one; if it is given, @value{GDBN} will mention
35402 the replacement as part of the warning.
35404 @kindex maint dump-me
35405 @item maint dump-me
35406 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35407 Cause a fatal signal in the debugger and force it to dump its core.
35408 This is supported only on systems which support aborting a program
35409 with the @code{SIGQUIT} signal.
35411 @kindex maint internal-error
35412 @kindex maint internal-warning
35413 @item maint internal-error @r{[}@var{message-text}@r{]}
35414 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35415 Cause @value{GDBN} to call the internal function @code{internal_error}
35416 or @code{internal_warning} and hence behave as though an internal error
35417 or internal warning has been detected. In addition to reporting the
35418 internal problem, these functions give the user the opportunity to
35419 either quit @value{GDBN} or create a core file of the current
35420 @value{GDBN} session.
35422 These commands take an optional parameter @var{message-text} that is
35423 used as the text of the error or warning message.
35425 Here's an example of using @code{internal-error}:
35428 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35429 @dots{}/maint.c:121: internal-error: testing, 1, 2
35430 A problem internal to GDB has been detected. Further
35431 debugging may prove unreliable.
35432 Quit this debugging session? (y or n) @kbd{n}
35433 Create a core file? (y or n) @kbd{n}
35437 @cindex @value{GDBN} internal error
35438 @cindex internal errors, control of @value{GDBN} behavior
35440 @kindex maint set internal-error
35441 @kindex maint show internal-error
35442 @kindex maint set internal-warning
35443 @kindex maint show internal-warning
35444 @item maint set internal-error @var{action} [ask|yes|no]
35445 @itemx maint show internal-error @var{action}
35446 @itemx maint set internal-warning @var{action} [ask|yes|no]
35447 @itemx maint show internal-warning @var{action}
35448 When @value{GDBN} reports an internal problem (error or warning) it
35449 gives the user the opportunity to both quit @value{GDBN} and create a
35450 core file of the current @value{GDBN} session. These commands let you
35451 override the default behaviour for each particular @var{action},
35452 described in the table below.
35456 You can specify that @value{GDBN} should always (yes) or never (no)
35457 quit. The default is to ask the user what to do.
35460 You can specify that @value{GDBN} should always (yes) or never (no)
35461 create a core file. The default is to ask the user what to do.
35464 @kindex maint packet
35465 @item maint packet @var{text}
35466 If @value{GDBN} is talking to an inferior via the serial protocol,
35467 then this command sends the string @var{text} to the inferior, and
35468 displays the response packet. @value{GDBN} supplies the initial
35469 @samp{$} character, the terminating @samp{#} character, and the
35472 @kindex maint print architecture
35473 @item maint print architecture @r{[}@var{file}@r{]}
35474 Print the entire architecture configuration. The optional argument
35475 @var{file} names the file where the output goes.
35477 @kindex maint print c-tdesc
35478 @item maint print c-tdesc
35479 Print the current target description (@pxref{Target Descriptions}) as
35480 a C source file. The created source file can be used in @value{GDBN}
35481 when an XML parser is not available to parse the description.
35483 @kindex maint print dummy-frames
35484 @item maint print dummy-frames
35485 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35488 (@value{GDBP}) @kbd{b add}
35490 (@value{GDBP}) @kbd{print add(2,3)}
35491 Breakpoint 2, add (a=2, b=3) at @dots{}
35493 The program being debugged stopped while in a function called from GDB.
35495 (@value{GDBP}) @kbd{maint print dummy-frames}
35496 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35497 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35498 call_lo=0x01014000 call_hi=0x01014001
35502 Takes an optional file parameter.
35504 @kindex maint print registers
35505 @kindex maint print raw-registers
35506 @kindex maint print cooked-registers
35507 @kindex maint print register-groups
35508 @kindex maint print remote-registers
35509 @item maint print registers @r{[}@var{file}@r{]}
35510 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35511 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35512 @itemx maint print register-groups @r{[}@var{file}@r{]}
35513 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35514 Print @value{GDBN}'s internal register data structures.
35516 The command @code{maint print raw-registers} includes the contents of
35517 the raw register cache; the command @code{maint print
35518 cooked-registers} includes the (cooked) value of all registers,
35519 including registers which aren't available on the target nor visible
35520 to user; the command @code{maint print register-groups} includes the
35521 groups that each register is a member of; and the command @code{maint
35522 print remote-registers} includes the remote target's register numbers
35523 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35524 @value{GDBN} Internals}.
35526 These commands take an optional parameter, a file name to which to
35527 write the information.
35529 @kindex maint print reggroups
35530 @item maint print reggroups @r{[}@var{file}@r{]}
35531 Print @value{GDBN}'s internal register group data structures. The
35532 optional argument @var{file} tells to what file to write the
35535 The register groups info looks like this:
35538 (@value{GDBP}) @kbd{maint print reggroups}
35551 This command forces @value{GDBN} to flush its internal register cache.
35553 @kindex maint print objfiles
35554 @cindex info for known object files
35555 @item maint print objfiles
35556 Print a dump of all known object files. For each object file, this
35557 command prints its name, address in memory, and all of its psymtabs
35560 @kindex maint print section-scripts
35561 @cindex info for known .debug_gdb_scripts-loaded scripts
35562 @item maint print section-scripts [@var{regexp}]
35563 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35564 If @var{regexp} is specified, only print scripts loaded by object files
35565 matching @var{regexp}.
35566 For each script, this command prints its name as specified in the objfile,
35567 and the full path if known.
35568 @xref{dotdebug_gdb_scripts section}.
35570 @kindex maint print statistics
35571 @cindex bcache statistics
35572 @item maint print statistics
35573 This command prints, for each object file in the program, various data
35574 about that object file followed by the byte cache (@dfn{bcache})
35575 statistics for the object file. The objfile data includes the number
35576 of minimal, partial, full, and stabs symbols, the number of types
35577 defined by the objfile, the number of as yet unexpanded psym tables,
35578 the number of line tables and string tables, and the amount of memory
35579 used by the various tables. The bcache statistics include the counts,
35580 sizes, and counts of duplicates of all and unique objects, max,
35581 average, and median entry size, total memory used and its overhead and
35582 savings, and various measures of the hash table size and chain
35585 @kindex maint print target-stack
35586 @cindex target stack description
35587 @item maint print target-stack
35588 A @dfn{target} is an interface between the debugger and a particular
35589 kind of file or process. Targets can be stacked in @dfn{strata},
35590 so that more than one target can potentially respond to a request.
35591 In particular, memory accesses will walk down the stack of targets
35592 until they find a target that is interested in handling that particular
35595 This command prints a short description of each layer that was pushed on
35596 the @dfn{target stack}, starting from the top layer down to the bottom one.
35598 @kindex maint print type
35599 @cindex type chain of a data type
35600 @item maint print type @var{expr}
35601 Print the type chain for a type specified by @var{expr}. The argument
35602 can be either a type name or a symbol. If it is a symbol, the type of
35603 that symbol is described. The type chain produced by this command is
35604 a recursive definition of the data type as stored in @value{GDBN}'s
35605 data structures, including its flags and contained types.
35607 @kindex maint set dwarf2 always-disassemble
35608 @kindex maint show dwarf2 always-disassemble
35609 @item maint set dwarf2 always-disassemble
35610 @item maint show dwarf2 always-disassemble
35611 Control the behavior of @code{info address} when using DWARF debugging
35614 The default is @code{off}, which means that @value{GDBN} should try to
35615 describe a variable's location in an easily readable format. When
35616 @code{on}, @value{GDBN} will instead display the DWARF location
35617 expression in an assembly-like format. Note that some locations are
35618 too complex for @value{GDBN} to describe simply; in this case you will
35619 always see the disassembly form.
35621 Here is an example of the resulting disassembly:
35624 (gdb) info addr argc
35625 Symbol "argc" is a complex DWARF expression:
35629 For more information on these expressions, see
35630 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35632 @kindex maint set dwarf2 max-cache-age
35633 @kindex maint show dwarf2 max-cache-age
35634 @item maint set dwarf2 max-cache-age
35635 @itemx maint show dwarf2 max-cache-age
35636 Control the DWARF 2 compilation unit cache.
35638 @cindex DWARF 2 compilation units cache
35639 In object files with inter-compilation-unit references, such as those
35640 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35641 reader needs to frequently refer to previously read compilation units.
35642 This setting controls how long a compilation unit will remain in the
35643 cache if it is not referenced. A higher limit means that cached
35644 compilation units will be stored in memory longer, and more total
35645 memory will be used. Setting it to zero disables caching, which will
35646 slow down @value{GDBN} startup, but reduce memory consumption.
35648 @kindex maint set profile
35649 @kindex maint show profile
35650 @cindex profiling GDB
35651 @item maint set profile
35652 @itemx maint show profile
35653 Control profiling of @value{GDBN}.
35655 Profiling will be disabled until you use the @samp{maint set profile}
35656 command to enable it. When you enable profiling, the system will begin
35657 collecting timing and execution count data; when you disable profiling or
35658 exit @value{GDBN}, the results will be written to a log file. Remember that
35659 if you use profiling, @value{GDBN} will overwrite the profiling log file
35660 (often called @file{gmon.out}). If you have a record of important profiling
35661 data in a @file{gmon.out} file, be sure to move it to a safe location.
35663 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35664 compiled with the @samp{-pg} compiler option.
35666 @kindex maint set show-debug-regs
35667 @kindex maint show show-debug-regs
35668 @cindex hardware debug registers
35669 @item maint set show-debug-regs
35670 @itemx maint show show-debug-regs
35671 Control whether to show variables that mirror the hardware debug
35672 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35673 enabled, the debug registers values are shown when @value{GDBN} inserts or
35674 removes a hardware breakpoint or watchpoint, and when the inferior
35675 triggers a hardware-assisted breakpoint or watchpoint.
35677 @kindex maint set show-all-tib
35678 @kindex maint show show-all-tib
35679 @item maint set show-all-tib
35680 @itemx maint show show-all-tib
35681 Control whether to show all non zero areas within a 1k block starting
35682 at thread local base, when using the @samp{info w32 thread-information-block}
35685 @kindex maint set per-command
35686 @kindex maint show per-command
35687 @item maint set per-command
35688 @itemx maint show per-command
35689 @cindex resources used by commands
35691 @value{GDBN} can display the resources used by each command.
35692 This is useful in debugging performance problems.
35695 @item maint set per-command space [on|off]
35696 @itemx maint show per-command space
35697 Enable or disable the printing of the memory used by GDB for each command.
35698 If enabled, @value{GDBN} will display how much memory each command
35699 took, following the command's own output.
35700 This can also be requested by invoking @value{GDBN} with the
35701 @option{--statistics} command-line switch (@pxref{Mode Options}).
35703 @item maint set per-command time [on|off]
35704 @itemx maint show per-command time
35705 Enable or disable the printing of the execution time of @value{GDBN}
35707 If enabled, @value{GDBN} will display how much time it
35708 took to execute each command, following the command's own output.
35709 Both CPU time and wallclock time are printed.
35710 Printing both is useful when trying to determine whether the cost is
35711 CPU or, e.g., disk/network latency.
35712 Note that the CPU time printed is for @value{GDBN} only, it does not include
35713 the execution time of the inferior because there's no mechanism currently
35714 to compute how much time was spent by @value{GDBN} and how much time was
35715 spent by the program been debugged.
35716 This can also be requested by invoking @value{GDBN} with the
35717 @option{--statistics} command-line switch (@pxref{Mode Options}).
35719 @item maint set per-command symtab [on|off]
35720 @itemx maint show per-command symtab
35721 Enable or disable the printing of basic symbol table statistics
35723 If enabled, @value{GDBN} will display the following information:
35727 number of symbol tables
35729 number of primary symbol tables
35731 number of blocks in the blockvector
35735 @kindex maint space
35736 @cindex memory used by commands
35737 @item maint space @var{value}
35738 An alias for @code{maint set per-command space}.
35739 A non-zero value enables it, zero disables it.
35742 @cindex time of command execution
35743 @item maint time @var{value}
35744 An alias for @code{maint set per-command time}.
35745 A non-zero value enables it, zero disables it.
35747 @kindex maint translate-address
35748 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35749 Find the symbol stored at the location specified by the address
35750 @var{addr} and an optional section name @var{section}. If found,
35751 @value{GDBN} prints the name of the closest symbol and an offset from
35752 the symbol's location to the specified address. This is similar to
35753 the @code{info address} command (@pxref{Symbols}), except that this
35754 command also allows to find symbols in other sections.
35756 If section was not specified, the section in which the symbol was found
35757 is also printed. For dynamically linked executables, the name of
35758 executable or shared library containing the symbol is printed as well.
35762 The following command is useful for non-interactive invocations of
35763 @value{GDBN}, such as in the test suite.
35766 @item set watchdog @var{nsec}
35767 @kindex set watchdog
35768 @cindex watchdog timer
35769 @cindex timeout for commands
35770 Set the maximum number of seconds @value{GDBN} will wait for the
35771 target operation to finish. If this time expires, @value{GDBN}
35772 reports and error and the command is aborted.
35774 @item show watchdog
35775 Show the current setting of the target wait timeout.
35778 @node Remote Protocol
35779 @appendix @value{GDBN} Remote Serial Protocol
35784 * Stop Reply Packets::
35785 * General Query Packets::
35786 * Architecture-Specific Protocol Details::
35787 * Tracepoint Packets::
35788 * Host I/O Packets::
35790 * Notification Packets::
35791 * Remote Non-Stop::
35792 * Packet Acknowledgment::
35794 * File-I/O Remote Protocol Extension::
35795 * Library List Format::
35796 * Library List Format for SVR4 Targets::
35797 * Memory Map Format::
35798 * Thread List Format::
35799 * Traceframe Info Format::
35800 * Branch Trace Format::
35806 There may be occasions when you need to know something about the
35807 protocol---for example, if there is only one serial port to your target
35808 machine, you might want your program to do something special if it
35809 recognizes a packet meant for @value{GDBN}.
35811 In the examples below, @samp{->} and @samp{<-} are used to indicate
35812 transmitted and received data, respectively.
35814 @cindex protocol, @value{GDBN} remote serial
35815 @cindex serial protocol, @value{GDBN} remote
35816 @cindex remote serial protocol
35817 All @value{GDBN} commands and responses (other than acknowledgments
35818 and notifications, see @ref{Notification Packets}) are sent as a
35819 @var{packet}. A @var{packet} is introduced with the character
35820 @samp{$}, the actual @var{packet-data}, and the terminating character
35821 @samp{#} followed by a two-digit @var{checksum}:
35824 @code{$}@var{packet-data}@code{#}@var{checksum}
35828 @cindex checksum, for @value{GDBN} remote
35830 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35831 characters between the leading @samp{$} and the trailing @samp{#} (an
35832 eight bit unsigned checksum).
35834 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35835 specification also included an optional two-digit @var{sequence-id}:
35838 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35841 @cindex sequence-id, for @value{GDBN} remote
35843 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35844 has never output @var{sequence-id}s. Stubs that handle packets added
35845 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35847 When either the host or the target machine receives a packet, the first
35848 response expected is an acknowledgment: either @samp{+} (to indicate
35849 the package was received correctly) or @samp{-} (to request
35853 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35858 The @samp{+}/@samp{-} acknowledgments can be disabled
35859 once a connection is established.
35860 @xref{Packet Acknowledgment}, for details.
35862 The host (@value{GDBN}) sends @var{command}s, and the target (the
35863 debugging stub incorporated in your program) sends a @var{response}. In
35864 the case of step and continue @var{command}s, the response is only sent
35865 when the operation has completed, and the target has again stopped all
35866 threads in all attached processes. This is the default all-stop mode
35867 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35868 execution mode; see @ref{Remote Non-Stop}, for details.
35870 @var{packet-data} consists of a sequence of characters with the
35871 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35874 @cindex remote protocol, field separator
35875 Fields within the packet should be separated using @samp{,} @samp{;} or
35876 @samp{:}. Except where otherwise noted all numbers are represented in
35877 @sc{hex} with leading zeros suppressed.
35879 Implementors should note that prior to @value{GDBN} 5.0, the character
35880 @samp{:} could not appear as the third character in a packet (as it
35881 would potentially conflict with the @var{sequence-id}).
35883 @cindex remote protocol, binary data
35884 @anchor{Binary Data}
35885 Binary data in most packets is encoded either as two hexadecimal
35886 digits per byte of binary data. This allowed the traditional remote
35887 protocol to work over connections which were only seven-bit clean.
35888 Some packets designed more recently assume an eight-bit clean
35889 connection, and use a more efficient encoding to send and receive
35892 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35893 as an escape character. Any escaped byte is transmitted as the escape
35894 character followed by the original character XORed with @code{0x20}.
35895 For example, the byte @code{0x7d} would be transmitted as the two
35896 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35897 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35898 @samp{@}}) must always be escaped. Responses sent by the stub
35899 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35900 is not interpreted as the start of a run-length encoded sequence
35903 Response @var{data} can be run-length encoded to save space.
35904 Run-length encoding replaces runs of identical characters with one
35905 instance of the repeated character, followed by a @samp{*} and a
35906 repeat count. The repeat count is itself sent encoded, to avoid
35907 binary characters in @var{data}: a value of @var{n} is sent as
35908 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35909 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35910 code 32) for a repeat count of 3. (This is because run-length
35911 encoding starts to win for counts 3 or more.) Thus, for example,
35912 @samp{0* } is a run-length encoding of ``0000'': the space character
35913 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35916 The printable characters @samp{#} and @samp{$} or with a numeric value
35917 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35918 seven repeats (@samp{$}) can be expanded using a repeat count of only
35919 five (@samp{"}). For example, @samp{00000000} can be encoded as
35922 The error response returned for some packets includes a two character
35923 error number. That number is not well defined.
35925 @cindex empty response, for unsupported packets
35926 For any @var{command} not supported by the stub, an empty response
35927 (@samp{$#00}) should be returned. That way it is possible to extend the
35928 protocol. A newer @value{GDBN} can tell if a packet is supported based
35931 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35932 commands for register access, and the @samp{m} and @samp{M} commands
35933 for memory access. Stubs that only control single-threaded targets
35934 can implement run control with the @samp{c} (continue), and @samp{s}
35935 (step) commands. Stubs that support multi-threading targets should
35936 support the @samp{vCont} command. All other commands are optional.
35941 The following table provides a complete list of all currently defined
35942 @var{command}s and their corresponding response @var{data}.
35943 @xref{File-I/O Remote Protocol Extension}, for details about the File
35944 I/O extension of the remote protocol.
35946 Each packet's description has a template showing the packet's overall
35947 syntax, followed by an explanation of the packet's meaning. We
35948 include spaces in some of the templates for clarity; these are not
35949 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35950 separate its components. For example, a template like @samp{foo
35951 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35952 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35953 @var{baz}. @value{GDBN} does not transmit a space character between the
35954 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35957 @cindex @var{thread-id}, in remote protocol
35958 @anchor{thread-id syntax}
35959 Several packets and replies include a @var{thread-id} field to identify
35960 a thread. Normally these are positive numbers with a target-specific
35961 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35962 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35965 In addition, the remote protocol supports a multiprocess feature in
35966 which the @var{thread-id} syntax is extended to optionally include both
35967 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35968 The @var{pid} (process) and @var{tid} (thread) components each have the
35969 format described above: a positive number with target-specific
35970 interpretation formatted as a big-endian hex string, literal @samp{-1}
35971 to indicate all processes or threads (respectively), or @samp{0} to
35972 indicate an arbitrary process or thread. Specifying just a process, as
35973 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35974 error to specify all processes but a specific thread, such as
35975 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35976 for those packets and replies explicitly documented to include a process
35977 ID, rather than a @var{thread-id}.
35979 The multiprocess @var{thread-id} syntax extensions are only used if both
35980 @value{GDBN} and the stub report support for the @samp{multiprocess}
35981 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35984 Note that all packet forms beginning with an upper- or lower-case
35985 letter, other than those described here, are reserved for future use.
35987 Here are the packet descriptions.
35992 @cindex @samp{!} packet
35993 @anchor{extended mode}
35994 Enable extended mode. In extended mode, the remote server is made
35995 persistent. The @samp{R} packet is used to restart the program being
36001 The remote target both supports and has enabled extended mode.
36005 @cindex @samp{?} packet
36006 Indicate the reason the target halted. The reply is the same as for
36007 step and continue. This packet has a special interpretation when the
36008 target is in non-stop mode; see @ref{Remote Non-Stop}.
36011 @xref{Stop Reply Packets}, for the reply specifications.
36013 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36014 @cindex @samp{A} packet
36015 Initialized @code{argv[]} array passed into program. @var{arglen}
36016 specifies the number of bytes in the hex encoded byte stream
36017 @var{arg}. See @code{gdbserver} for more details.
36022 The arguments were set.
36028 @cindex @samp{b} packet
36029 (Don't use this packet; its behavior is not well-defined.)
36030 Change the serial line speed to @var{baud}.
36032 JTC: @emph{When does the transport layer state change? When it's
36033 received, or after the ACK is transmitted. In either case, there are
36034 problems if the command or the acknowledgment packet is dropped.}
36036 Stan: @emph{If people really wanted to add something like this, and get
36037 it working for the first time, they ought to modify ser-unix.c to send
36038 some kind of out-of-band message to a specially-setup stub and have the
36039 switch happen "in between" packets, so that from remote protocol's point
36040 of view, nothing actually happened.}
36042 @item B @var{addr},@var{mode}
36043 @cindex @samp{B} packet
36044 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36045 breakpoint at @var{addr}.
36047 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36048 (@pxref{insert breakpoint or watchpoint packet}).
36050 @cindex @samp{bc} packet
36053 Backward continue. Execute the target system in reverse. No parameter.
36054 @xref{Reverse Execution}, for more information.
36057 @xref{Stop Reply Packets}, for the reply specifications.
36059 @cindex @samp{bs} packet
36062 Backward single step. Execute one instruction in reverse. No parameter.
36063 @xref{Reverse Execution}, for more information.
36066 @xref{Stop Reply Packets}, for the reply specifications.
36068 @item c @r{[}@var{addr}@r{]}
36069 @cindex @samp{c} packet
36070 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36071 resume at current address.
36073 This packet is deprecated for multi-threading support. @xref{vCont
36077 @xref{Stop Reply Packets}, for the reply specifications.
36079 @item C @var{sig}@r{[};@var{addr}@r{]}
36080 @cindex @samp{C} packet
36081 Continue with signal @var{sig} (hex signal number). If
36082 @samp{;@var{addr}} is omitted, resume at same address.
36084 This packet is deprecated for multi-threading support. @xref{vCont
36088 @xref{Stop Reply Packets}, for the reply specifications.
36091 @cindex @samp{d} packet
36094 Don't use this packet; instead, define a general set packet
36095 (@pxref{General Query Packets}).
36099 @cindex @samp{D} packet
36100 The first form of the packet is used to detach @value{GDBN} from the
36101 remote system. It is sent to the remote target
36102 before @value{GDBN} disconnects via the @code{detach} command.
36104 The second form, including a process ID, is used when multiprocess
36105 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36106 detach only a specific process. The @var{pid} is specified as a
36107 big-endian hex string.
36117 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36118 @cindex @samp{F} packet
36119 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36120 This is part of the File-I/O protocol extension. @xref{File-I/O
36121 Remote Protocol Extension}, for the specification.
36124 @anchor{read registers packet}
36125 @cindex @samp{g} packet
36126 Read general registers.
36130 @item @var{XX@dots{}}
36131 Each byte of register data is described by two hex digits. The bytes
36132 with the register are transmitted in target byte order. The size of
36133 each register and their position within the @samp{g} packet are
36134 determined by the @value{GDBN} internal gdbarch functions
36135 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36136 specification of several standard @samp{g} packets is specified below.
36138 When reading registers from a trace frame (@pxref{Analyze Collected
36139 Data,,Using the Collected Data}), the stub may also return a string of
36140 literal @samp{x}'s in place of the register data digits, to indicate
36141 that the corresponding register has not been collected, thus its value
36142 is unavailable. For example, for an architecture with 4 registers of
36143 4 bytes each, the following reply indicates to @value{GDBN} that
36144 registers 0 and 2 have not been collected, while registers 1 and 3
36145 have been collected, and both have zero value:
36149 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36156 @item G @var{XX@dots{}}
36157 @cindex @samp{G} packet
36158 Write general registers. @xref{read registers packet}, for a
36159 description of the @var{XX@dots{}} data.
36169 @item H @var{op} @var{thread-id}
36170 @cindex @samp{H} packet
36171 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36172 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36173 it should be @samp{c} for step and continue operations (note that this
36174 is deprecated, supporting the @samp{vCont} command is a better
36175 option), @samp{g} for other operations. The thread designator
36176 @var{thread-id} has the format and interpretation described in
36177 @ref{thread-id syntax}.
36188 @c 'H': How restrictive (or permissive) is the thread model. If a
36189 @c thread is selected and stopped, are other threads allowed
36190 @c to continue to execute? As I mentioned above, I think the
36191 @c semantics of each command when a thread is selected must be
36192 @c described. For example:
36194 @c 'g': If the stub supports threads and a specific thread is
36195 @c selected, returns the register block from that thread;
36196 @c otherwise returns current registers.
36198 @c 'G' If the stub supports threads and a specific thread is
36199 @c selected, sets the registers of the register block of
36200 @c that thread; otherwise sets current registers.
36202 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36203 @anchor{cycle step packet}
36204 @cindex @samp{i} packet
36205 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36206 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36207 step starting at that address.
36210 @cindex @samp{I} packet
36211 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36215 @cindex @samp{k} packet
36218 FIXME: @emph{There is no description of how to operate when a specific
36219 thread context has been selected (i.e.@: does 'k' kill only that
36222 @item m @var{addr},@var{length}
36223 @cindex @samp{m} packet
36224 Read @var{length} bytes of memory starting at address @var{addr}.
36225 Note that @var{addr} may not be aligned to any particular boundary.
36227 The stub need not use any particular size or alignment when gathering
36228 data from memory for the response; even if @var{addr} is word-aligned
36229 and @var{length} is a multiple of the word size, the stub is free to
36230 use byte accesses, or not. For this reason, this packet may not be
36231 suitable for accessing memory-mapped I/O devices.
36232 @cindex alignment of remote memory accesses
36233 @cindex size of remote memory accesses
36234 @cindex memory, alignment and size of remote accesses
36238 @item @var{XX@dots{}}
36239 Memory contents; each byte is transmitted as a two-digit hexadecimal
36240 number. The reply may contain fewer bytes than requested if the
36241 server was able to read only part of the region of memory.
36246 @item M @var{addr},@var{length}:@var{XX@dots{}}
36247 @cindex @samp{M} packet
36248 Write @var{length} bytes of memory starting at address @var{addr}.
36249 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36250 hexadecimal number.
36257 for an error (this includes the case where only part of the data was
36262 @cindex @samp{p} packet
36263 Read the value of register @var{n}; @var{n} is in hex.
36264 @xref{read registers packet}, for a description of how the returned
36265 register value is encoded.
36269 @item @var{XX@dots{}}
36270 the register's value
36274 Indicating an unrecognized @var{query}.
36277 @item P @var{n@dots{}}=@var{r@dots{}}
36278 @anchor{write register packet}
36279 @cindex @samp{P} packet
36280 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36281 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36282 digits for each byte in the register (target byte order).
36292 @item q @var{name} @var{params}@dots{}
36293 @itemx Q @var{name} @var{params}@dots{}
36294 @cindex @samp{q} packet
36295 @cindex @samp{Q} packet
36296 General query (@samp{q}) and set (@samp{Q}). These packets are
36297 described fully in @ref{General Query Packets}.
36300 @cindex @samp{r} packet
36301 Reset the entire system.
36303 Don't use this packet; use the @samp{R} packet instead.
36306 @cindex @samp{R} packet
36307 Restart the program being debugged. @var{XX}, while needed, is ignored.
36308 This packet is only available in extended mode (@pxref{extended mode}).
36310 The @samp{R} packet has no reply.
36312 @item s @r{[}@var{addr}@r{]}
36313 @cindex @samp{s} packet
36314 Single step. @var{addr} is the address at which to resume. If
36315 @var{addr} is omitted, resume at same address.
36317 This packet is deprecated for multi-threading support. @xref{vCont
36321 @xref{Stop Reply Packets}, for the reply specifications.
36323 @item S @var{sig}@r{[};@var{addr}@r{]}
36324 @anchor{step with signal packet}
36325 @cindex @samp{S} packet
36326 Step with signal. This is analogous to the @samp{C} packet, but
36327 requests a single-step, rather than a normal resumption of execution.
36329 This packet is deprecated for multi-threading support. @xref{vCont
36333 @xref{Stop Reply Packets}, for the reply specifications.
36335 @item t @var{addr}:@var{PP},@var{MM}
36336 @cindex @samp{t} packet
36337 Search backwards starting at address @var{addr} for a match with pattern
36338 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36339 @var{addr} must be at least 3 digits.
36341 @item T @var{thread-id}
36342 @cindex @samp{T} packet
36343 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36348 thread is still alive
36354 Packets starting with @samp{v} are identified by a multi-letter name,
36355 up to the first @samp{;} or @samp{?} (or the end of the packet).
36357 @item vAttach;@var{pid}
36358 @cindex @samp{vAttach} packet
36359 Attach to a new process with the specified process ID @var{pid}.
36360 The process ID is a
36361 hexadecimal integer identifying the process. In all-stop mode, all
36362 threads in the attached process are stopped; in non-stop mode, it may be
36363 attached without being stopped if that is supported by the target.
36365 @c In non-stop mode, on a successful vAttach, the stub should set the
36366 @c current thread to a thread of the newly-attached process. After
36367 @c attaching, GDB queries for the attached process's thread ID with qC.
36368 @c Also note that, from a user perspective, whether or not the
36369 @c target is stopped on attach in non-stop mode depends on whether you
36370 @c use the foreground or background version of the attach command, not
36371 @c on what vAttach does; GDB does the right thing with respect to either
36372 @c stopping or restarting threads.
36374 This packet is only available in extended mode (@pxref{extended mode}).
36380 @item @r{Any stop packet}
36381 for success in all-stop mode (@pxref{Stop Reply Packets})
36383 for success in non-stop mode (@pxref{Remote Non-Stop})
36386 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36387 @cindex @samp{vCont} packet
36388 @anchor{vCont packet}
36389 Resume the inferior, specifying different actions for each thread.
36390 If an action is specified with no @var{thread-id}, then it is applied to any
36391 threads that don't have a specific action specified; if no default action is
36392 specified then other threads should remain stopped in all-stop mode and
36393 in their current state in non-stop mode.
36394 Specifying multiple
36395 default actions is an error; specifying no actions is also an error.
36396 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36398 Currently supported actions are:
36404 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36408 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36413 The optional argument @var{addr} normally associated with the
36414 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36415 not supported in @samp{vCont}.
36417 The @samp{t} action is only relevant in non-stop mode
36418 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36419 A stop reply should be generated for any affected thread not already stopped.
36420 When a thread is stopped by means of a @samp{t} action,
36421 the corresponding stop reply should indicate that the thread has stopped with
36422 signal @samp{0}, regardless of whether the target uses some other signal
36423 as an implementation detail.
36425 The stub must support @samp{vCont} if it reports support for
36426 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36427 this case @samp{vCont} actions can be specified to apply to all threads
36428 in a process by using the @samp{p@var{pid}.-1} form of the
36432 @xref{Stop Reply Packets}, for the reply specifications.
36435 @cindex @samp{vCont?} packet
36436 Request a list of actions supported by the @samp{vCont} packet.
36440 @item vCont@r{[};@var{action}@dots{}@r{]}
36441 The @samp{vCont} packet is supported. Each @var{action} is a supported
36442 command in the @samp{vCont} packet.
36444 The @samp{vCont} packet is not supported.
36447 @item vFile:@var{operation}:@var{parameter}@dots{}
36448 @cindex @samp{vFile} packet
36449 Perform a file operation on the target system. For details,
36450 see @ref{Host I/O Packets}.
36452 @item vFlashErase:@var{addr},@var{length}
36453 @cindex @samp{vFlashErase} packet
36454 Direct the stub to erase @var{length} bytes of flash starting at
36455 @var{addr}. The region may enclose any number of flash blocks, but
36456 its start and end must fall on block boundaries, as indicated by the
36457 flash block size appearing in the memory map (@pxref{Memory Map
36458 Format}). @value{GDBN} groups flash memory programming operations
36459 together, and sends a @samp{vFlashDone} request after each group; the
36460 stub is allowed to delay erase operation until the @samp{vFlashDone}
36461 packet is received.
36471 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36472 @cindex @samp{vFlashWrite} packet
36473 Direct the stub to write data to flash address @var{addr}. The data
36474 is passed in binary form using the same encoding as for the @samp{X}
36475 packet (@pxref{Binary Data}). The memory ranges specified by
36476 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36477 not overlap, and must appear in order of increasing addresses
36478 (although @samp{vFlashErase} packets for higher addresses may already
36479 have been received; the ordering is guaranteed only between
36480 @samp{vFlashWrite} packets). If a packet writes to an address that was
36481 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36482 target-specific method, the results are unpredictable.
36490 for vFlashWrite addressing non-flash memory
36496 @cindex @samp{vFlashDone} packet
36497 Indicate to the stub that flash programming operation is finished.
36498 The stub is permitted to delay or batch the effects of a group of
36499 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36500 @samp{vFlashDone} packet is received. The contents of the affected
36501 regions of flash memory are unpredictable until the @samp{vFlashDone}
36502 request is completed.
36504 @item vKill;@var{pid}
36505 @cindex @samp{vKill} packet
36506 Kill the process with the specified process ID. @var{pid} is a
36507 hexadecimal integer identifying the process. This packet is used in
36508 preference to @samp{k} when multiprocess protocol extensions are
36509 supported; see @ref{multiprocess extensions}.
36519 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36520 @cindex @samp{vRun} packet
36521 Run the program @var{filename}, passing it each @var{argument} on its
36522 command line. The file and arguments are hex-encoded strings. If
36523 @var{filename} is an empty string, the stub may use a default program
36524 (e.g.@: the last program run). The program is created in the stopped
36527 @c FIXME: What about non-stop mode?
36529 This packet is only available in extended mode (@pxref{extended mode}).
36535 @item @r{Any stop packet}
36536 for success (@pxref{Stop Reply Packets})
36540 @cindex @samp{vStopped} packet
36541 @xref{Notification Packets}.
36543 @item X @var{addr},@var{length}:@var{XX@dots{}}
36545 @cindex @samp{X} packet
36546 Write data to memory, where the data is transmitted in binary.
36547 @var{addr} is address, @var{length} is number of bytes,
36548 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36558 @item z @var{type},@var{addr},@var{kind}
36559 @itemx Z @var{type},@var{addr},@var{kind}
36560 @anchor{insert breakpoint or watchpoint packet}
36561 @cindex @samp{z} packet
36562 @cindex @samp{Z} packets
36563 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36564 watchpoint starting at address @var{address} of kind @var{kind}.
36566 Each breakpoint and watchpoint packet @var{type} is documented
36569 @emph{Implementation notes: A remote target shall return an empty string
36570 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36571 remote target shall support either both or neither of a given
36572 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36573 avoid potential problems with duplicate packets, the operations should
36574 be implemented in an idempotent way.}
36576 @item z0,@var{addr},@var{kind}
36577 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36578 @cindex @samp{z0} packet
36579 @cindex @samp{Z0} packet
36580 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36581 @var{addr} of type @var{kind}.
36583 A memory breakpoint is implemented by replacing the instruction at
36584 @var{addr} with a software breakpoint or trap instruction. The
36585 @var{kind} is target-specific and typically indicates the size of
36586 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36587 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36588 architectures have additional meanings for @var{kind};
36589 @var{cond_list} is an optional list of conditional expressions in bytecode
36590 form that should be evaluated on the target's side. These are the
36591 conditions that should be taken into consideration when deciding if
36592 the breakpoint trigger should be reported back to @var{GDBN}.
36594 The @var{cond_list} parameter is comprised of a series of expressions,
36595 concatenated without separators. Each expression has the following form:
36599 @item X @var{len},@var{expr}
36600 @var{len} is the length of the bytecode expression and @var{expr} is the
36601 actual conditional expression in bytecode form.
36605 The optional @var{cmd_list} parameter introduces commands that may be
36606 run on the target, rather than being reported back to @value{GDBN}.
36607 The parameter starts with a numeric flag @var{persist}; if the flag is
36608 nonzero, then the breakpoint may remain active and the commands
36609 continue to be run even when @value{GDBN} disconnects from the target.
36610 Following this flag is a series of expressions concatenated with no
36611 separators. Each expression has the following form:
36615 @item X @var{len},@var{expr}
36616 @var{len} is the length of the bytecode expression and @var{expr} is the
36617 actual conditional expression in bytecode form.
36621 see @ref{Architecture-Specific Protocol Details}.
36623 @emph{Implementation note: It is possible for a target to copy or move
36624 code that contains memory breakpoints (e.g., when implementing
36625 overlays). The behavior of this packet, in the presence of such a
36626 target, is not defined.}
36638 @item z1,@var{addr},@var{kind}
36639 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36640 @cindex @samp{z1} packet
36641 @cindex @samp{Z1} packet
36642 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36643 address @var{addr}.
36645 A hardware breakpoint is implemented using a mechanism that is not
36646 dependant on being able to modify the target's memory. @var{kind}
36647 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36649 @emph{Implementation note: A hardware breakpoint is not affected by code
36662 @item z2,@var{addr},@var{kind}
36663 @itemx Z2,@var{addr},@var{kind}
36664 @cindex @samp{z2} packet
36665 @cindex @samp{Z2} packet
36666 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36667 @var{kind} is interpreted as the number of bytes to watch.
36679 @item z3,@var{addr},@var{kind}
36680 @itemx Z3,@var{addr},@var{kind}
36681 @cindex @samp{z3} packet
36682 @cindex @samp{Z3} packet
36683 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36684 @var{kind} is interpreted as the number of bytes to watch.
36696 @item z4,@var{addr},@var{kind}
36697 @itemx Z4,@var{addr},@var{kind}
36698 @cindex @samp{z4} packet
36699 @cindex @samp{Z4} packet
36700 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36701 @var{kind} is interpreted as the number of bytes to watch.
36715 @node Stop Reply Packets
36716 @section Stop Reply Packets
36717 @cindex stop reply packets
36719 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36720 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36721 receive any of the below as a reply. Except for @samp{?}
36722 and @samp{vStopped}, that reply is only returned
36723 when the target halts. In the below the exact meaning of @dfn{signal
36724 number} is defined by the header @file{include/gdb/signals.h} in the
36725 @value{GDBN} source code.
36727 As in the description of request packets, we include spaces in the
36728 reply templates for clarity; these are not part of the reply packet's
36729 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36735 The program received signal number @var{AA} (a two-digit hexadecimal
36736 number). This is equivalent to a @samp{T} response with no
36737 @var{n}:@var{r} pairs.
36739 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36740 @cindex @samp{T} packet reply
36741 The program received signal number @var{AA} (a two-digit hexadecimal
36742 number). This is equivalent to an @samp{S} response, except that the
36743 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36744 and other information directly in the stop reply packet, reducing
36745 round-trip latency. Single-step and breakpoint traps are reported
36746 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36750 If @var{n} is a hexadecimal number, it is a register number, and the
36751 corresponding @var{r} gives that register's value. @var{r} is a
36752 series of bytes in target byte order, with each byte given by a
36753 two-digit hex number.
36756 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36757 the stopped thread, as specified in @ref{thread-id syntax}.
36760 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36761 the core on which the stop event was detected.
36764 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36765 specific event that stopped the target. The currently defined stop
36766 reasons are listed below. @var{aa} should be @samp{05}, the trap
36767 signal. At most one stop reason should be present.
36770 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36771 and go on to the next; this allows us to extend the protocol in the
36775 The currently defined stop reasons are:
36781 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36784 @cindex shared library events, remote reply
36786 The packet indicates that the loaded libraries have changed.
36787 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36788 list of loaded libraries. @var{r} is ignored.
36790 @cindex replay log events, remote reply
36792 The packet indicates that the target cannot continue replaying
36793 logged execution events, because it has reached the end (or the
36794 beginning when executing backward) of the log. The value of @var{r}
36795 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36796 for more information.
36800 @itemx W @var{AA} ; process:@var{pid}
36801 The process exited, and @var{AA} is the exit status. This is only
36802 applicable to certain targets.
36804 The second form of the response, including the process ID of the exited
36805 process, can be used only when @value{GDBN} has reported support for
36806 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36807 The @var{pid} is formatted as a big-endian hex string.
36810 @itemx X @var{AA} ; process:@var{pid}
36811 The process terminated with signal @var{AA}.
36813 The second form of the response, including the process ID of the
36814 terminated process, can be used only when @value{GDBN} has reported
36815 support for multiprocess protocol extensions; see @ref{multiprocess
36816 extensions}. The @var{pid} is formatted as a big-endian hex string.
36818 @item O @var{XX}@dots{}
36819 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36820 written as the program's console output. This can happen at any time
36821 while the program is running and the debugger should continue to wait
36822 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36824 @item F @var{call-id},@var{parameter}@dots{}
36825 @var{call-id} is the identifier which says which host system call should
36826 be called. This is just the name of the function. Translation into the
36827 correct system call is only applicable as it's defined in @value{GDBN}.
36828 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36831 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36832 this very system call.
36834 The target replies with this packet when it expects @value{GDBN} to
36835 call a host system call on behalf of the target. @value{GDBN} replies
36836 with an appropriate @samp{F} packet and keeps up waiting for the next
36837 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36838 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36839 Protocol Extension}, for more details.
36843 @node General Query Packets
36844 @section General Query Packets
36845 @cindex remote query requests
36847 Packets starting with @samp{q} are @dfn{general query packets};
36848 packets starting with @samp{Q} are @dfn{general set packets}. General
36849 query and set packets are a semi-unified form for retrieving and
36850 sending information to and from the stub.
36852 The initial letter of a query or set packet is followed by a name
36853 indicating what sort of thing the packet applies to. For example,
36854 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36855 definitions with the stub. These packet names follow some
36860 The name must not contain commas, colons or semicolons.
36862 Most @value{GDBN} query and set packets have a leading upper case
36865 The names of custom vendor packets should use a company prefix, in
36866 lower case, followed by a period. For example, packets designed at
36867 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36868 foos) or @samp{Qacme.bar} (for setting bars).
36871 The name of a query or set packet should be separated from any
36872 parameters by a @samp{:}; the parameters themselves should be
36873 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36874 full packet name, and check for a separator or the end of the packet,
36875 in case two packet names share a common prefix. New packets should not begin
36876 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36877 packets predate these conventions, and have arguments without any terminator
36878 for the packet name; we suspect they are in widespread use in places that
36879 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36880 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36883 Like the descriptions of the other packets, each description here
36884 has a template showing the packet's overall syntax, followed by an
36885 explanation of the packet's meaning. We include spaces in some of the
36886 templates for clarity; these are not part of the packet's syntax. No
36887 @value{GDBN} packet uses spaces to separate its components.
36889 Here are the currently defined query and set packets:
36895 Turn on or off the agent as a helper to perform some debugging operations
36896 delegated from @value{GDBN} (@pxref{Control Agent}).
36898 @item QAllow:@var{op}:@var{val}@dots{}
36899 @cindex @samp{QAllow} packet
36900 Specify which operations @value{GDBN} expects to request of the
36901 target, as a semicolon-separated list of operation name and value
36902 pairs. Possible values for @var{op} include @samp{WriteReg},
36903 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36904 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36905 indicating that @value{GDBN} will not request the operation, or 1,
36906 indicating that it may. (The target can then use this to set up its
36907 own internals optimally, for instance if the debugger never expects to
36908 insert breakpoints, it may not need to install its own trap handler.)
36911 @cindex current thread, remote request
36912 @cindex @samp{qC} packet
36913 Return the current thread ID.
36917 @item QC @var{thread-id}
36918 Where @var{thread-id} is a thread ID as documented in
36919 @ref{thread-id syntax}.
36920 @item @r{(anything else)}
36921 Any other reply implies the old thread ID.
36924 @item qCRC:@var{addr},@var{length}
36925 @cindex CRC of memory block, remote request
36926 @cindex @samp{qCRC} packet
36927 Compute the CRC checksum of a block of memory using CRC-32 defined in
36928 IEEE 802.3. The CRC is computed byte at a time, taking the most
36929 significant bit of each byte first. The initial pattern code
36930 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36932 @emph{Note:} This is the same CRC used in validating separate debug
36933 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36934 Files}). However the algorithm is slightly different. When validating
36935 separate debug files, the CRC is computed taking the @emph{least}
36936 significant bit of each byte first, and the final result is inverted to
36937 detect trailing zeros.
36942 An error (such as memory fault)
36943 @item C @var{crc32}
36944 The specified memory region's checksum is @var{crc32}.
36947 @item QDisableRandomization:@var{value}
36948 @cindex disable address space randomization, remote request
36949 @cindex @samp{QDisableRandomization} packet
36950 Some target operating systems will randomize the virtual address space
36951 of the inferior process as a security feature, but provide a feature
36952 to disable such randomization, e.g.@: to allow for a more deterministic
36953 debugging experience. On such systems, this packet with a @var{value}
36954 of 1 directs the target to disable address space randomization for
36955 processes subsequently started via @samp{vRun} packets, while a packet
36956 with a @var{value} of 0 tells the target to enable address space
36959 This packet is only available in extended mode (@pxref{extended mode}).
36964 The request succeeded.
36967 An error occurred. @var{nn} are hex digits.
36970 An empty reply indicates that @samp{QDisableRandomization} is not supported
36974 This packet is not probed by default; the remote stub must request it,
36975 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36976 This should only be done on targets that actually support disabling
36977 address space randomization.
36980 @itemx qsThreadInfo
36981 @cindex list active threads, remote request
36982 @cindex @samp{qfThreadInfo} packet
36983 @cindex @samp{qsThreadInfo} packet
36984 Obtain a list of all active thread IDs from the target (OS). Since there
36985 may be too many active threads to fit into one reply packet, this query
36986 works iteratively: it may require more than one query/reply sequence to
36987 obtain the entire list of threads. The first query of the sequence will
36988 be the @samp{qfThreadInfo} query; subsequent queries in the
36989 sequence will be the @samp{qsThreadInfo} query.
36991 NOTE: This packet replaces the @samp{qL} query (see below).
36995 @item m @var{thread-id}
36997 @item m @var{thread-id},@var{thread-id}@dots{}
36998 a comma-separated list of thread IDs
37000 (lower case letter @samp{L}) denotes end of list.
37003 In response to each query, the target will reply with a list of one or
37004 more thread IDs, separated by commas.
37005 @value{GDBN} will respond to each reply with a request for more thread
37006 ids (using the @samp{qs} form of the query), until the target responds
37007 with @samp{l} (lower-case ell, for @dfn{last}).
37008 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37011 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37012 @cindex get thread-local storage address, remote request
37013 @cindex @samp{qGetTLSAddr} packet
37014 Fetch the address associated with thread local storage specified
37015 by @var{thread-id}, @var{offset}, and @var{lm}.
37017 @var{thread-id} is the thread ID associated with the
37018 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37020 @var{offset} is the (big endian, hex encoded) offset associated with the
37021 thread local variable. (This offset is obtained from the debug
37022 information associated with the variable.)
37024 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37025 load module associated with the thread local storage. For example,
37026 a @sc{gnu}/Linux system will pass the link map address of the shared
37027 object associated with the thread local storage under consideration.
37028 Other operating environments may choose to represent the load module
37029 differently, so the precise meaning of this parameter will vary.
37033 @item @var{XX}@dots{}
37034 Hex encoded (big endian) bytes representing the address of the thread
37035 local storage requested.
37038 An error occurred. @var{nn} are hex digits.
37041 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37044 @item qGetTIBAddr:@var{thread-id}
37045 @cindex get thread information block address
37046 @cindex @samp{qGetTIBAddr} packet
37047 Fetch address of the Windows OS specific Thread Information Block.
37049 @var{thread-id} is the thread ID associated with the thread.
37053 @item @var{XX}@dots{}
37054 Hex encoded (big endian) bytes representing the linear address of the
37055 thread information block.
37058 An error occured. This means that either the thread was not found, or the
37059 address could not be retrieved.
37062 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37065 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37066 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37067 digit) is one to indicate the first query and zero to indicate a
37068 subsequent query; @var{threadcount} (two hex digits) is the maximum
37069 number of threads the response packet can contain; and @var{nextthread}
37070 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37071 returned in the response as @var{argthread}.
37073 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37077 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37078 Where: @var{count} (two hex digits) is the number of threads being
37079 returned; @var{done} (one hex digit) is zero to indicate more threads
37080 and one indicates no further threads; @var{argthreadid} (eight hex
37081 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37082 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37083 digits). See @code{remote.c:parse_threadlist_response()}.
37087 @cindex section offsets, remote request
37088 @cindex @samp{qOffsets} packet
37089 Get section offsets that the target used when relocating the downloaded
37094 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37095 Relocate the @code{Text} section by @var{xxx} from its original address.
37096 Relocate the @code{Data} section by @var{yyy} from its original address.
37097 If the object file format provides segment information (e.g.@: @sc{elf}
37098 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37099 segments by the supplied offsets.
37101 @emph{Note: while a @code{Bss} offset may be included in the response,
37102 @value{GDBN} ignores this and instead applies the @code{Data} offset
37103 to the @code{Bss} section.}
37105 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37106 Relocate the first segment of the object file, which conventionally
37107 contains program code, to a starting address of @var{xxx}. If
37108 @samp{DataSeg} is specified, relocate the second segment, which
37109 conventionally contains modifiable data, to a starting address of
37110 @var{yyy}. @value{GDBN} will report an error if the object file
37111 does not contain segment information, or does not contain at least
37112 as many segments as mentioned in the reply. Extra segments are
37113 kept at fixed offsets relative to the last relocated segment.
37116 @item qP @var{mode} @var{thread-id}
37117 @cindex thread information, remote request
37118 @cindex @samp{qP} packet
37119 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37120 encoded 32 bit mode; @var{thread-id} is a thread ID
37121 (@pxref{thread-id syntax}).
37123 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37126 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37130 @cindex non-stop mode, remote request
37131 @cindex @samp{QNonStop} packet
37133 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37134 @xref{Remote Non-Stop}, for more information.
37139 The request succeeded.
37142 An error occurred. @var{nn} are hex digits.
37145 An empty reply indicates that @samp{QNonStop} is not supported by
37149 This packet is not probed by default; the remote stub must request it,
37150 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37151 Use of this packet is controlled by the @code{set non-stop} command;
37152 @pxref{Non-Stop Mode}.
37154 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37155 @cindex pass signals to inferior, remote request
37156 @cindex @samp{QPassSignals} packet
37157 @anchor{QPassSignals}
37158 Each listed @var{signal} should be passed directly to the inferior process.
37159 Signals are numbered identically to continue packets and stop replies
37160 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37161 strictly greater than the previous item. These signals do not need to stop
37162 the inferior, or be reported to @value{GDBN}. All other signals should be
37163 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37164 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37165 new list. This packet improves performance when using @samp{handle
37166 @var{signal} nostop noprint pass}.
37171 The request succeeded.
37174 An error occurred. @var{nn} are hex digits.
37177 An empty reply indicates that @samp{QPassSignals} is not supported by
37181 Use of this packet is controlled by the @code{set remote pass-signals}
37182 command (@pxref{Remote Configuration, set remote pass-signals}).
37183 This packet is not probed by default; the remote stub must request it,
37184 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37186 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37187 @cindex signals the inferior may see, remote request
37188 @cindex @samp{QProgramSignals} packet
37189 @anchor{QProgramSignals}
37190 Each listed @var{signal} may be delivered to the inferior process.
37191 Others should be silently discarded.
37193 In some cases, the remote stub may need to decide whether to deliver a
37194 signal to the program or not without @value{GDBN} involvement. One
37195 example of that is while detaching --- the program's threads may have
37196 stopped for signals that haven't yet had a chance of being reported to
37197 @value{GDBN}, and so the remote stub can use the signal list specified
37198 by this packet to know whether to deliver or ignore those pending
37201 This does not influence whether to deliver a signal as requested by a
37202 resumption packet (@pxref{vCont packet}).
37204 Signals are numbered identically to continue packets and stop replies
37205 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37206 strictly greater than the previous item. Multiple
37207 @samp{QProgramSignals} packets do not combine; any earlier
37208 @samp{QProgramSignals} list is completely replaced by the new list.
37213 The request succeeded.
37216 An error occurred. @var{nn} are hex digits.
37219 An empty reply indicates that @samp{QProgramSignals} is not supported
37223 Use of this packet is controlled by the @code{set remote program-signals}
37224 command (@pxref{Remote Configuration, set remote program-signals}).
37225 This packet is not probed by default; the remote stub must request it,
37226 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37228 @item qRcmd,@var{command}
37229 @cindex execute remote command, remote request
37230 @cindex @samp{qRcmd} packet
37231 @var{command} (hex encoded) is passed to the local interpreter for
37232 execution. Invalid commands should be reported using the output
37233 string. Before the final result packet, the target may also respond
37234 with a number of intermediate @samp{O@var{output}} console output
37235 packets. @emph{Implementors should note that providing access to a
37236 stubs's interpreter may have security implications}.
37241 A command response with no output.
37243 A command response with the hex encoded output string @var{OUTPUT}.
37245 Indicate a badly formed request.
37247 An empty reply indicates that @samp{qRcmd} is not recognized.
37250 (Note that the @code{qRcmd} packet's name is separated from the
37251 command by a @samp{,}, not a @samp{:}, contrary to the naming
37252 conventions above. Please don't use this packet as a model for new
37255 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37256 @cindex searching memory, in remote debugging
37258 @cindex @samp{qSearch:memory} packet
37260 @cindex @samp{qSearch memory} packet
37261 @anchor{qSearch memory}
37262 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37263 @var{address} and @var{length} are encoded in hex.
37264 @var{search-pattern} is a sequence of bytes, hex encoded.
37269 The pattern was not found.
37271 The pattern was found at @var{address}.
37273 A badly formed request or an error was encountered while searching memory.
37275 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37278 @item QStartNoAckMode
37279 @cindex @samp{QStartNoAckMode} packet
37280 @anchor{QStartNoAckMode}
37281 Request that the remote stub disable the normal @samp{+}/@samp{-}
37282 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37287 The stub has switched to no-acknowledgment mode.
37288 @value{GDBN} acknowledges this reponse,
37289 but neither the stub nor @value{GDBN} shall send or expect further
37290 @samp{+}/@samp{-} acknowledgments in the current connection.
37292 An empty reply indicates that the stub does not support no-acknowledgment mode.
37295 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37296 @cindex supported packets, remote query
37297 @cindex features of the remote protocol
37298 @cindex @samp{qSupported} packet
37299 @anchor{qSupported}
37300 Tell the remote stub about features supported by @value{GDBN}, and
37301 query the stub for features it supports. This packet allows
37302 @value{GDBN} and the remote stub to take advantage of each others'
37303 features. @samp{qSupported} also consolidates multiple feature probes
37304 at startup, to improve @value{GDBN} performance---a single larger
37305 packet performs better than multiple smaller probe packets on
37306 high-latency links. Some features may enable behavior which must not
37307 be on by default, e.g.@: because it would confuse older clients or
37308 stubs. Other features may describe packets which could be
37309 automatically probed for, but are not. These features must be
37310 reported before @value{GDBN} will use them. This ``default
37311 unsupported'' behavior is not appropriate for all packets, but it
37312 helps to keep the initial connection time under control with new
37313 versions of @value{GDBN} which support increasing numbers of packets.
37317 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37318 The stub supports or does not support each returned @var{stubfeature},
37319 depending on the form of each @var{stubfeature} (see below for the
37322 An empty reply indicates that @samp{qSupported} is not recognized,
37323 or that no features needed to be reported to @value{GDBN}.
37326 The allowed forms for each feature (either a @var{gdbfeature} in the
37327 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37331 @item @var{name}=@var{value}
37332 The remote protocol feature @var{name} is supported, and associated
37333 with the specified @var{value}. The format of @var{value} depends
37334 on the feature, but it must not include a semicolon.
37336 The remote protocol feature @var{name} is supported, and does not
37337 need an associated value.
37339 The remote protocol feature @var{name} is not supported.
37341 The remote protocol feature @var{name} may be supported, and
37342 @value{GDBN} should auto-detect support in some other way when it is
37343 needed. This form will not be used for @var{gdbfeature} notifications,
37344 but may be used for @var{stubfeature} responses.
37347 Whenever the stub receives a @samp{qSupported} request, the
37348 supplied set of @value{GDBN} features should override any previous
37349 request. This allows @value{GDBN} to put the stub in a known
37350 state, even if the stub had previously been communicating with
37351 a different version of @value{GDBN}.
37353 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37358 This feature indicates whether @value{GDBN} supports multiprocess
37359 extensions to the remote protocol. @value{GDBN} does not use such
37360 extensions unless the stub also reports that it supports them by
37361 including @samp{multiprocess+} in its @samp{qSupported} reply.
37362 @xref{multiprocess extensions}, for details.
37365 This feature indicates that @value{GDBN} supports the XML target
37366 description. If the stub sees @samp{xmlRegisters=} with target
37367 specific strings separated by a comma, it will report register
37371 This feature indicates whether @value{GDBN} supports the
37372 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37373 instruction reply packet}).
37376 Stubs should ignore any unknown values for
37377 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37378 packet supports receiving packets of unlimited length (earlier
37379 versions of @value{GDBN} may reject overly long responses). Additional values
37380 for @var{gdbfeature} may be defined in the future to let the stub take
37381 advantage of new features in @value{GDBN}, e.g.@: incompatible
37382 improvements in the remote protocol---the @samp{multiprocess} feature is
37383 an example of such a feature. The stub's reply should be independent
37384 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37385 describes all the features it supports, and then the stub replies with
37386 all the features it supports.
37388 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37389 responses, as long as each response uses one of the standard forms.
37391 Some features are flags. A stub which supports a flag feature
37392 should respond with a @samp{+} form response. Other features
37393 require values, and the stub should respond with an @samp{=}
37396 Each feature has a default value, which @value{GDBN} will use if
37397 @samp{qSupported} is not available or if the feature is not mentioned
37398 in the @samp{qSupported} response. The default values are fixed; a
37399 stub is free to omit any feature responses that match the defaults.
37401 Not all features can be probed, but for those which can, the probing
37402 mechanism is useful: in some cases, a stub's internal
37403 architecture may not allow the protocol layer to know some information
37404 about the underlying target in advance. This is especially common in
37405 stubs which may be configured for multiple targets.
37407 These are the currently defined stub features and their properties:
37409 @multitable @columnfractions 0.35 0.2 0.12 0.2
37410 @c NOTE: The first row should be @headitem, but we do not yet require
37411 @c a new enough version of Texinfo (4.7) to use @headitem.
37413 @tab Value Required
37417 @item @samp{PacketSize}
37422 @item @samp{qXfer:auxv:read}
37427 @item @samp{qXfer:btrace:read}
37432 @item @samp{qXfer:features:read}
37437 @item @samp{qXfer:libraries:read}
37442 @item @samp{qXfer:memory-map:read}
37447 @item @samp{qXfer:sdata:read}
37452 @item @samp{qXfer:spu:read}
37457 @item @samp{qXfer:spu:write}
37462 @item @samp{qXfer:siginfo:read}
37467 @item @samp{qXfer:siginfo:write}
37472 @item @samp{qXfer:threads:read}
37477 @item @samp{qXfer:traceframe-info:read}
37482 @item @samp{qXfer:uib:read}
37487 @item @samp{qXfer:fdpic:read}
37492 @item @samp{Qbtrace:off}
37497 @item @samp{Qbtrace:bts}
37502 @item @samp{QNonStop}
37507 @item @samp{QPassSignals}
37512 @item @samp{QStartNoAckMode}
37517 @item @samp{multiprocess}
37522 @item @samp{ConditionalBreakpoints}
37527 @item @samp{ConditionalTracepoints}
37532 @item @samp{ReverseContinue}
37537 @item @samp{ReverseStep}
37542 @item @samp{TracepointSource}
37547 @item @samp{QAgent}
37552 @item @samp{QAllow}
37557 @item @samp{QDisableRandomization}
37562 @item @samp{EnableDisableTracepoints}
37567 @item @samp{QTBuffer:size}
37572 @item @samp{tracenz}
37577 @item @samp{BreakpointCommands}
37584 These are the currently defined stub features, in more detail:
37587 @cindex packet size, remote protocol
37588 @item PacketSize=@var{bytes}
37589 The remote stub can accept packets up to at least @var{bytes} in
37590 length. @value{GDBN} will send packets up to this size for bulk
37591 transfers, and will never send larger packets. This is a limit on the
37592 data characters in the packet, including the frame and checksum.
37593 There is no trailing NUL byte in a remote protocol packet; if the stub
37594 stores packets in a NUL-terminated format, it should allow an extra
37595 byte in its buffer for the NUL. If this stub feature is not supported,
37596 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37598 @item qXfer:auxv:read
37599 The remote stub understands the @samp{qXfer:auxv:read} packet
37600 (@pxref{qXfer auxiliary vector read}).
37602 @item qXfer:btrace:read
37603 The remote stub understands the @samp{qXfer:btrace:read}
37604 packet (@pxref{qXfer btrace read}).
37606 @item qXfer:features:read
37607 The remote stub understands the @samp{qXfer:features:read} packet
37608 (@pxref{qXfer target description read}).
37610 @item qXfer:libraries:read
37611 The remote stub understands the @samp{qXfer:libraries:read} packet
37612 (@pxref{qXfer library list read}).
37614 @item qXfer:libraries-svr4:read
37615 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37616 (@pxref{qXfer svr4 library list read}).
37618 @item qXfer:memory-map:read
37619 The remote stub understands the @samp{qXfer:memory-map:read} packet
37620 (@pxref{qXfer memory map read}).
37622 @item qXfer:sdata:read
37623 The remote stub understands the @samp{qXfer:sdata:read} packet
37624 (@pxref{qXfer sdata read}).
37626 @item qXfer:spu:read
37627 The remote stub understands the @samp{qXfer:spu:read} packet
37628 (@pxref{qXfer spu read}).
37630 @item qXfer:spu:write
37631 The remote stub understands the @samp{qXfer:spu:write} packet
37632 (@pxref{qXfer spu write}).
37634 @item qXfer:siginfo:read
37635 The remote stub understands the @samp{qXfer:siginfo:read} packet
37636 (@pxref{qXfer siginfo read}).
37638 @item qXfer:siginfo:write
37639 The remote stub understands the @samp{qXfer:siginfo:write} packet
37640 (@pxref{qXfer siginfo write}).
37642 @item qXfer:threads:read
37643 The remote stub understands the @samp{qXfer:threads:read} packet
37644 (@pxref{qXfer threads read}).
37646 @item qXfer:traceframe-info:read
37647 The remote stub understands the @samp{qXfer:traceframe-info:read}
37648 packet (@pxref{qXfer traceframe info read}).
37650 @item qXfer:uib:read
37651 The remote stub understands the @samp{qXfer:uib:read}
37652 packet (@pxref{qXfer unwind info block}).
37654 @item qXfer:fdpic:read
37655 The remote stub understands the @samp{qXfer:fdpic:read}
37656 packet (@pxref{qXfer fdpic loadmap read}).
37659 The remote stub understands the @samp{QNonStop} packet
37660 (@pxref{QNonStop}).
37663 The remote stub understands the @samp{QPassSignals} packet
37664 (@pxref{QPassSignals}).
37666 @item QStartNoAckMode
37667 The remote stub understands the @samp{QStartNoAckMode} packet and
37668 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37671 @anchor{multiprocess extensions}
37672 @cindex multiprocess extensions, in remote protocol
37673 The remote stub understands the multiprocess extensions to the remote
37674 protocol syntax. The multiprocess extensions affect the syntax of
37675 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37676 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37677 replies. Note that reporting this feature indicates support for the
37678 syntactic extensions only, not that the stub necessarily supports
37679 debugging of more than one process at a time. The stub must not use
37680 multiprocess extensions in packet replies unless @value{GDBN} has also
37681 indicated it supports them in its @samp{qSupported} request.
37683 @item qXfer:osdata:read
37684 The remote stub understands the @samp{qXfer:osdata:read} packet
37685 ((@pxref{qXfer osdata read}).
37687 @item ConditionalBreakpoints
37688 The target accepts and implements evaluation of conditional expressions
37689 defined for breakpoints. The target will only report breakpoint triggers
37690 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37692 @item ConditionalTracepoints
37693 The remote stub accepts and implements conditional expressions defined
37694 for tracepoints (@pxref{Tracepoint Conditions}).
37696 @item ReverseContinue
37697 The remote stub accepts and implements the reverse continue packet
37701 The remote stub accepts and implements the reverse step packet
37704 @item TracepointSource
37705 The remote stub understands the @samp{QTDPsrc} packet that supplies
37706 the source form of tracepoint definitions.
37709 The remote stub understands the @samp{QAgent} packet.
37712 The remote stub understands the @samp{QAllow} packet.
37714 @item QDisableRandomization
37715 The remote stub understands the @samp{QDisableRandomization} packet.
37717 @item StaticTracepoint
37718 @cindex static tracepoints, in remote protocol
37719 The remote stub supports static tracepoints.
37721 @item InstallInTrace
37722 @anchor{install tracepoint in tracing}
37723 The remote stub supports installing tracepoint in tracing.
37725 @item EnableDisableTracepoints
37726 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37727 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37728 to be enabled and disabled while a trace experiment is running.
37730 @item QTBuffer:size
37731 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37732 packet that allows to change the size of the trace buffer.
37735 @cindex string tracing, in remote protocol
37736 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37737 See @ref{Bytecode Descriptions} for details about the bytecode.
37739 @item BreakpointCommands
37740 @cindex breakpoint commands, in remote protocol
37741 The remote stub supports running a breakpoint's command list itself,
37742 rather than reporting the hit to @value{GDBN}.
37745 The remote stub understands the @samp{Qbtrace:off} packet.
37748 The remote stub understands the @samp{Qbtrace:bts} packet.
37753 @cindex symbol lookup, remote request
37754 @cindex @samp{qSymbol} packet
37755 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37756 requests. Accept requests from the target for the values of symbols.
37761 The target does not need to look up any (more) symbols.
37762 @item qSymbol:@var{sym_name}
37763 The target requests the value of symbol @var{sym_name} (hex encoded).
37764 @value{GDBN} may provide the value by using the
37765 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37769 @item qSymbol:@var{sym_value}:@var{sym_name}
37770 Set the value of @var{sym_name} to @var{sym_value}.
37772 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37773 target has previously requested.
37775 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37776 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37782 The target does not need to look up any (more) symbols.
37783 @item qSymbol:@var{sym_name}
37784 The target requests the value of a new symbol @var{sym_name} (hex
37785 encoded). @value{GDBN} will continue to supply the values of symbols
37786 (if available), until the target ceases to request them.
37791 @itemx QTDisconnected
37798 @itemx qTMinFTPILen
37800 @xref{Tracepoint Packets}.
37802 @item qThreadExtraInfo,@var{thread-id}
37803 @cindex thread attributes info, remote request
37804 @cindex @samp{qThreadExtraInfo} packet
37805 Obtain a printable string description of a thread's attributes from
37806 the target OS. @var{thread-id} is a thread ID;
37807 see @ref{thread-id syntax}. This
37808 string may contain anything that the target OS thinks is interesting
37809 for @value{GDBN} to tell the user about the thread. The string is
37810 displayed in @value{GDBN}'s @code{info threads} display. Some
37811 examples of possible thread extra info strings are @samp{Runnable}, or
37812 @samp{Blocked on Mutex}.
37816 @item @var{XX}@dots{}
37817 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37818 comprising the printable string containing the extra information about
37819 the thread's attributes.
37822 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37823 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37824 conventions above. Please don't use this packet as a model for new
37843 @xref{Tracepoint Packets}.
37845 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37846 @cindex read special object, remote request
37847 @cindex @samp{qXfer} packet
37848 @anchor{qXfer read}
37849 Read uninterpreted bytes from the target's special data area
37850 identified by the keyword @var{object}. Request @var{length} bytes
37851 starting at @var{offset} bytes into the data. The content and
37852 encoding of @var{annex} is specific to @var{object}; it can supply
37853 additional details about what data to access.
37855 Here are the specific requests of this form defined so far. All
37856 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37857 formats, listed below.
37860 @item qXfer:auxv:read::@var{offset},@var{length}
37861 @anchor{qXfer auxiliary vector read}
37862 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37863 auxiliary vector}. Note @var{annex} must be empty.
37865 This packet is not probed by default; the remote stub must request it,
37866 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37868 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37869 @anchor{qXfer btrace read}
37871 Return a description of the current branch trace.
37872 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37873 packet may have one of the following values:
37877 Returns all available branch trace.
37880 Returns all available branch trace if the branch trace changed since
37881 the last read request.
37884 This packet is not probed by default; the remote stub must request it
37885 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37887 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37888 @anchor{qXfer target description read}
37889 Access the @dfn{target description}. @xref{Target Descriptions}. The
37890 annex specifies which XML document to access. The main description is
37891 always loaded from the @samp{target.xml} annex.
37893 This packet is not probed by default; the remote stub must request it,
37894 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37896 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37897 @anchor{qXfer library list read}
37898 Access the target's list of loaded libraries. @xref{Library List Format}.
37899 The annex part of the generic @samp{qXfer} packet must be empty
37900 (@pxref{qXfer read}).
37902 Targets which maintain a list of libraries in the program's memory do
37903 not need to implement this packet; it is designed for platforms where
37904 the operating system manages the list of loaded libraries.
37906 This packet is not probed by default; the remote stub must request it,
37907 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37909 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37910 @anchor{qXfer svr4 library list read}
37911 Access the target's list of loaded libraries when the target is an SVR4
37912 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37913 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37915 This packet is optional for better performance on SVR4 targets.
37916 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37918 This packet is not probed by default; the remote stub must request it,
37919 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37921 @item qXfer:memory-map:read::@var{offset},@var{length}
37922 @anchor{qXfer memory map read}
37923 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37924 annex part of the generic @samp{qXfer} packet must be empty
37925 (@pxref{qXfer read}).
37927 This packet is not probed by default; the remote stub must request it,
37928 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37930 @item qXfer:sdata:read::@var{offset},@var{length}
37931 @anchor{qXfer sdata read}
37933 Read contents of the extra collected static tracepoint marker
37934 information. The annex part of the generic @samp{qXfer} packet must
37935 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37938 This packet is not probed by default; the remote stub must request it,
37939 by supplying an appropriate @samp{qSupported} response
37940 (@pxref{qSupported}).
37942 @item qXfer:siginfo:read::@var{offset},@var{length}
37943 @anchor{qXfer siginfo read}
37944 Read contents of the extra signal information on the target
37945 system. The annex part of the generic @samp{qXfer} packet must be
37946 empty (@pxref{qXfer read}).
37948 This packet is not probed by default; the remote stub must request it,
37949 by supplying an appropriate @samp{qSupported} response
37950 (@pxref{qSupported}).
37952 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37953 @anchor{qXfer spu read}
37954 Read contents of an @code{spufs} file on the target system. The
37955 annex specifies which file to read; it must be of the form
37956 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37957 in the target process, and @var{name} identifes the @code{spufs} file
37958 in that context to be accessed.
37960 This packet is not probed by default; the remote stub must request it,
37961 by supplying an appropriate @samp{qSupported} response
37962 (@pxref{qSupported}).
37964 @item qXfer:threads:read::@var{offset},@var{length}
37965 @anchor{qXfer threads read}
37966 Access the list of threads on target. @xref{Thread List Format}. The
37967 annex part of the generic @samp{qXfer} packet must be empty
37968 (@pxref{qXfer read}).
37970 This packet is not probed by default; the remote stub must request it,
37971 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37973 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37974 @anchor{qXfer traceframe info read}
37976 Return a description of the current traceframe's contents.
37977 @xref{Traceframe Info Format}. The annex part of the generic
37978 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37980 This packet is not probed by default; the remote stub must request it,
37981 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37983 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37984 @anchor{qXfer unwind info block}
37986 Return the unwind information block for @var{pc}. This packet is used
37987 on OpenVMS/ia64 to ask the kernel unwind information.
37989 This packet is not probed by default.
37991 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37992 @anchor{qXfer fdpic loadmap read}
37993 Read contents of @code{loadmap}s on the target system. The
37994 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37995 executable @code{loadmap} or interpreter @code{loadmap} to read.
37997 This packet is not probed by default; the remote stub must request it,
37998 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38000 @item qXfer:osdata:read::@var{offset},@var{length}
38001 @anchor{qXfer osdata read}
38002 Access the target's @dfn{operating system information}.
38003 @xref{Operating System Information}.
38010 Data @var{data} (@pxref{Binary Data}) has been read from the
38011 target. There may be more data at a higher address (although
38012 it is permitted to return @samp{m} even for the last valid
38013 block of data, as long as at least one byte of data was read).
38014 @var{data} may have fewer bytes than the @var{length} in the
38018 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38019 There is no more data to be read. @var{data} may have fewer bytes
38020 than the @var{length} in the request.
38023 The @var{offset} in the request is at the end of the data.
38024 There is no more data to be read.
38027 The request was malformed, or @var{annex} was invalid.
38030 The offset was invalid, or there was an error encountered reading the data.
38031 @var{nn} is a hex-encoded @code{errno} value.
38034 An empty reply indicates the @var{object} string was not recognized by
38035 the stub, or that the object does not support reading.
38038 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38039 @cindex write data into object, remote request
38040 @anchor{qXfer write}
38041 Write uninterpreted bytes into the target's special data area
38042 identified by the keyword @var{object}, starting at @var{offset} bytes
38043 into the data. @var{data}@dots{} is the binary-encoded data
38044 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38045 is specific to @var{object}; it can supply additional details about what data
38048 Here are the specific requests of this form defined so far. All
38049 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38050 formats, listed below.
38053 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38054 @anchor{qXfer siginfo write}
38055 Write @var{data} to the extra signal information on the target system.
38056 The annex part of the generic @samp{qXfer} packet must be
38057 empty (@pxref{qXfer write}).
38059 This packet is not probed by default; the remote stub must request it,
38060 by supplying an appropriate @samp{qSupported} response
38061 (@pxref{qSupported}).
38063 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38064 @anchor{qXfer spu write}
38065 Write @var{data} to an @code{spufs} file on the target system. The
38066 annex specifies which file to write; it must be of the form
38067 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38068 in the target process, and @var{name} identifes the @code{spufs} file
38069 in that context to be accessed.
38071 This packet is not probed by default; the remote stub must request it,
38072 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38078 @var{nn} (hex encoded) is the number of bytes written.
38079 This may be fewer bytes than supplied in the request.
38082 The request was malformed, or @var{annex} was invalid.
38085 The offset was invalid, or there was an error encountered writing the data.
38086 @var{nn} is a hex-encoded @code{errno} value.
38089 An empty reply indicates the @var{object} string was not
38090 recognized by the stub, or that the object does not support writing.
38093 @item qXfer:@var{object}:@var{operation}:@dots{}
38094 Requests of this form may be added in the future. When a stub does
38095 not recognize the @var{object} keyword, or its support for
38096 @var{object} does not recognize the @var{operation} keyword, the stub
38097 must respond with an empty packet.
38099 @item qAttached:@var{pid}
38100 @cindex query attached, remote request
38101 @cindex @samp{qAttached} packet
38102 Return an indication of whether the remote server attached to an
38103 existing process or created a new process. When the multiprocess
38104 protocol extensions are supported (@pxref{multiprocess extensions}),
38105 @var{pid} is an integer in hexadecimal format identifying the target
38106 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38107 the query packet will be simplified as @samp{qAttached}.
38109 This query is used, for example, to know whether the remote process
38110 should be detached or killed when a @value{GDBN} session is ended with
38111 the @code{quit} command.
38116 The remote server attached to an existing process.
38118 The remote server created a new process.
38120 A badly formed request or an error was encountered.
38124 Enable branch tracing for the current thread using bts tracing.
38129 Branch tracing has been enabled.
38131 A badly formed request or an error was encountered.
38135 Disable branch tracing for the current thread.
38140 Branch tracing has been disabled.
38142 A badly formed request or an error was encountered.
38147 @node Architecture-Specific Protocol Details
38148 @section Architecture-Specific Protocol Details
38150 This section describes how the remote protocol is applied to specific
38151 target architectures. Also see @ref{Standard Target Features}, for
38152 details of XML target descriptions for each architecture.
38155 * ARM-Specific Protocol Details::
38156 * MIPS-Specific Protocol Details::
38159 @node ARM-Specific Protocol Details
38160 @subsection @acronym{ARM}-specific Protocol Details
38163 * ARM Breakpoint Kinds::
38166 @node ARM Breakpoint Kinds
38167 @subsubsection @acronym{ARM} Breakpoint Kinds
38168 @cindex breakpoint kinds, @acronym{ARM}
38170 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38175 16-bit Thumb mode breakpoint.
38178 32-bit Thumb mode (Thumb-2) breakpoint.
38181 32-bit @acronym{ARM} mode breakpoint.
38185 @node MIPS-Specific Protocol Details
38186 @subsection @acronym{MIPS}-specific Protocol Details
38189 * MIPS Register packet Format::
38190 * MIPS Breakpoint Kinds::
38193 @node MIPS Register packet Format
38194 @subsubsection @acronym{MIPS} Register Packet Format
38195 @cindex register packet format, @acronym{MIPS}
38197 The following @code{g}/@code{G} packets have previously been defined.
38198 In the below, some thirty-two bit registers are transferred as
38199 sixty-four bits. Those registers should be zero/sign extended (which?)
38200 to fill the space allocated. Register bytes are transferred in target
38201 byte order. The two nibbles within a register byte are transferred
38202 most-significant -- least-significant.
38207 All registers are transferred as thirty-two bit quantities in the order:
38208 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38209 registers; fsr; fir; fp.
38212 All registers are transferred as sixty-four bit quantities (including
38213 thirty-two bit registers such as @code{sr}). The ordering is the same
38218 @node MIPS Breakpoint Kinds
38219 @subsubsection @acronym{MIPS} Breakpoint Kinds
38220 @cindex breakpoint kinds, @acronym{MIPS}
38222 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38227 16-bit @acronym{MIPS16} mode breakpoint.
38230 16-bit @acronym{microMIPS} mode breakpoint.
38233 32-bit standard @acronym{MIPS} mode breakpoint.
38236 32-bit @acronym{microMIPS} mode breakpoint.
38240 @node Tracepoint Packets
38241 @section Tracepoint Packets
38242 @cindex tracepoint packets
38243 @cindex packets, tracepoint
38245 Here we describe the packets @value{GDBN} uses to implement
38246 tracepoints (@pxref{Tracepoints}).
38250 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38251 @cindex @samp{QTDP} packet
38252 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38253 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38254 the tracepoint is disabled. @var{step} is the tracepoint's step
38255 count, and @var{pass} is its pass count. If an @samp{F} is present,
38256 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38257 the number of bytes that the target should copy elsewhere to make room
38258 for the tracepoint. If an @samp{X} is present, it introduces a
38259 tracepoint condition, which consists of a hexadecimal length, followed
38260 by a comma and hex-encoded bytes, in a manner similar to action
38261 encodings as described below. If the trailing @samp{-} is present,
38262 further @samp{QTDP} packets will follow to specify this tracepoint's
38268 The packet was understood and carried out.
38270 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38272 The packet was not recognized.
38275 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38276 Define actions to be taken when a tracepoint is hit. @var{n} and
38277 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38278 this tracepoint. This packet may only be sent immediately after
38279 another @samp{QTDP} packet that ended with a @samp{-}. If the
38280 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38281 specifying more actions for this tracepoint.
38283 In the series of action packets for a given tracepoint, at most one
38284 can have an @samp{S} before its first @var{action}. If such a packet
38285 is sent, it and the following packets define ``while-stepping''
38286 actions. Any prior packets define ordinary actions --- that is, those
38287 taken when the tracepoint is first hit. If no action packet has an
38288 @samp{S}, then all the packets in the series specify ordinary
38289 tracepoint actions.
38291 The @samp{@var{action}@dots{}} portion of the packet is a series of
38292 actions, concatenated without separators. Each action has one of the
38298 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38299 a hexadecimal number whose @var{i}'th bit is set if register number
38300 @var{i} should be collected. (The least significant bit is numbered
38301 zero.) Note that @var{mask} may be any number of digits long; it may
38302 not fit in a 32-bit word.
38304 @item M @var{basereg},@var{offset},@var{len}
38305 Collect @var{len} bytes of memory starting at the address in register
38306 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38307 @samp{-1}, then the range has a fixed address: @var{offset} is the
38308 address of the lowest byte to collect. The @var{basereg},
38309 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38310 values (the @samp{-1} value for @var{basereg} is a special case).
38312 @item X @var{len},@var{expr}
38313 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38314 it directs. @var{expr} is an agent expression, as described in
38315 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38316 two-digit hex number in the packet; @var{len} is the number of bytes
38317 in the expression (and thus one-half the number of hex digits in the
38322 Any number of actions may be packed together in a single @samp{QTDP}
38323 packet, as long as the packet does not exceed the maximum packet
38324 length (400 bytes, for many stubs). There may be only one @samp{R}
38325 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38326 actions. Any registers referred to by @samp{M} and @samp{X} actions
38327 must be collected by a preceding @samp{R} action. (The
38328 ``while-stepping'' actions are treated as if they were attached to a
38329 separate tracepoint, as far as these restrictions are concerned.)
38334 The packet was understood and carried out.
38336 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38338 The packet was not recognized.
38341 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38342 @cindex @samp{QTDPsrc} packet
38343 Specify a source string of tracepoint @var{n} at address @var{addr}.
38344 This is useful to get accurate reproduction of the tracepoints
38345 originally downloaded at the beginning of the trace run. @var{type}
38346 is the name of the tracepoint part, such as @samp{cond} for the
38347 tracepoint's conditional expression (see below for a list of types), while
38348 @var{bytes} is the string, encoded in hexadecimal.
38350 @var{start} is the offset of the @var{bytes} within the overall source
38351 string, while @var{slen} is the total length of the source string.
38352 This is intended for handling source strings that are longer than will
38353 fit in a single packet.
38354 @c Add detailed example when this info is moved into a dedicated
38355 @c tracepoint descriptions section.
38357 The available string types are @samp{at} for the location,
38358 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38359 @value{GDBN} sends a separate packet for each command in the action
38360 list, in the same order in which the commands are stored in the list.
38362 The target does not need to do anything with source strings except
38363 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38366 Although this packet is optional, and @value{GDBN} will only send it
38367 if the target replies with @samp{TracepointSource} @xref{General
38368 Query Packets}, it makes both disconnected tracing and trace files
38369 much easier to use. Otherwise the user must be careful that the
38370 tracepoints in effect while looking at trace frames are identical to
38371 the ones in effect during the trace run; even a small discrepancy
38372 could cause @samp{tdump} not to work, or a particular trace frame not
38375 @item QTDV:@var{n}:@var{value}
38376 @cindex define trace state variable, remote request
38377 @cindex @samp{QTDV} packet
38378 Create a new trace state variable, number @var{n}, with an initial
38379 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38380 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38381 the option of not using this packet for initial values of zero; the
38382 target should simply create the trace state variables as they are
38383 mentioned in expressions.
38385 @item QTFrame:@var{n}
38386 @cindex @samp{QTFrame} packet
38387 Select the @var{n}'th tracepoint frame from the buffer, and use the
38388 register and memory contents recorded there to answer subsequent
38389 request packets from @value{GDBN}.
38391 A successful reply from the stub indicates that the stub has found the
38392 requested frame. The response is a series of parts, concatenated
38393 without separators, describing the frame we selected. Each part has
38394 one of the following forms:
38398 The selected frame is number @var{n} in the trace frame buffer;
38399 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38400 was no frame matching the criteria in the request packet.
38403 The selected trace frame records a hit of tracepoint number @var{t};
38404 @var{t} is a hexadecimal number.
38408 @item QTFrame:pc:@var{addr}
38409 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38410 currently selected frame whose PC is @var{addr};
38411 @var{addr} is a hexadecimal number.
38413 @item QTFrame:tdp:@var{t}
38414 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38415 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38416 is a hexadecimal number.
38418 @item QTFrame:range:@var{start}:@var{end}
38419 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38420 currently selected frame whose PC is between @var{start} (inclusive)
38421 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38424 @item QTFrame:outside:@var{start}:@var{end}
38425 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38426 frame @emph{outside} the given range of addresses (exclusive).
38429 @cindex @samp{qTMinFTPILen} packet
38430 This packet requests the minimum length of instruction at which a fast
38431 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38432 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38433 it depends on the target system being able to create trampolines in
38434 the first 64K of memory, which might or might not be possible for that
38435 system. So the reply to this packet will be 4 if it is able to
38442 The minimum instruction length is currently unknown.
38444 The minimum instruction length is @var{length}, where @var{length} is greater
38445 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38446 that a fast tracepoint may be placed on any instruction regardless of size.
38448 An error has occurred.
38450 An empty reply indicates that the request is not supported by the stub.
38454 @cindex @samp{QTStart} packet
38455 Begin the tracepoint experiment. Begin collecting data from
38456 tracepoint hits in the trace frame buffer. This packet supports the
38457 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38458 instruction reply packet}).
38461 @cindex @samp{QTStop} packet
38462 End the tracepoint experiment. Stop collecting trace frames.
38464 @item QTEnable:@var{n}:@var{addr}
38466 @cindex @samp{QTEnable} packet
38467 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38468 experiment. If the tracepoint was previously disabled, then collection
38469 of data from it will resume.
38471 @item QTDisable:@var{n}:@var{addr}
38473 @cindex @samp{QTDisable} packet
38474 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38475 experiment. No more data will be collected from the tracepoint unless
38476 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38479 @cindex @samp{QTinit} packet
38480 Clear the table of tracepoints, and empty the trace frame buffer.
38482 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38483 @cindex @samp{QTro} packet
38484 Establish the given ranges of memory as ``transparent''. The stub
38485 will answer requests for these ranges from memory's current contents,
38486 if they were not collected as part of the tracepoint hit.
38488 @value{GDBN} uses this to mark read-only regions of memory, like those
38489 containing program code. Since these areas never change, they should
38490 still have the same contents they did when the tracepoint was hit, so
38491 there's no reason for the stub to refuse to provide their contents.
38493 @item QTDisconnected:@var{value}
38494 @cindex @samp{QTDisconnected} packet
38495 Set the choice to what to do with the tracing run when @value{GDBN}
38496 disconnects from the target. A @var{value} of 1 directs the target to
38497 continue the tracing run, while 0 tells the target to stop tracing if
38498 @value{GDBN} is no longer in the picture.
38501 @cindex @samp{qTStatus} packet
38502 Ask the stub if there is a trace experiment running right now.
38504 The reply has the form:
38508 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38509 @var{running} is a single digit @code{1} if the trace is presently
38510 running, or @code{0} if not. It is followed by semicolon-separated
38511 optional fields that an agent may use to report additional status.
38515 If the trace is not running, the agent may report any of several
38516 explanations as one of the optional fields:
38521 No trace has been run yet.
38523 @item tstop[:@var{text}]:0
38524 The trace was stopped by a user-originated stop command. The optional
38525 @var{text} field is a user-supplied string supplied as part of the
38526 stop command (for instance, an explanation of why the trace was
38527 stopped manually). It is hex-encoded.
38530 The trace stopped because the trace buffer filled up.
38532 @item tdisconnected:0
38533 The trace stopped because @value{GDBN} disconnected from the target.
38535 @item tpasscount:@var{tpnum}
38536 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38538 @item terror:@var{text}:@var{tpnum}
38539 The trace stopped because tracepoint @var{tpnum} had an error. The
38540 string @var{text} is available to describe the nature of the error
38541 (for instance, a divide by zero in the condition expression).
38542 @var{text} is hex encoded.
38545 The trace stopped for some other reason.
38549 Additional optional fields supply statistical and other information.
38550 Although not required, they are extremely useful for users monitoring
38551 the progress of a trace run. If a trace has stopped, and these
38552 numbers are reported, they must reflect the state of the just-stopped
38557 @item tframes:@var{n}
38558 The number of trace frames in the buffer.
38560 @item tcreated:@var{n}
38561 The total number of trace frames created during the run. This may
38562 be larger than the trace frame count, if the buffer is circular.
38564 @item tsize:@var{n}
38565 The total size of the trace buffer, in bytes.
38567 @item tfree:@var{n}
38568 The number of bytes still unused in the buffer.
38570 @item circular:@var{n}
38571 The value of the circular trace buffer flag. @code{1} means that the
38572 trace buffer is circular and old trace frames will be discarded if
38573 necessary to make room, @code{0} means that the trace buffer is linear
38576 @item disconn:@var{n}
38577 The value of the disconnected tracing flag. @code{1} means that
38578 tracing will continue after @value{GDBN} disconnects, @code{0} means
38579 that the trace run will stop.
38583 @item qTP:@var{tp}:@var{addr}
38584 @cindex tracepoint status, remote request
38585 @cindex @samp{qTP} packet
38586 Ask the stub for the current state of tracepoint number @var{tp} at
38587 address @var{addr}.
38591 @item V@var{hits}:@var{usage}
38592 The tracepoint has been hit @var{hits} times so far during the trace
38593 run, and accounts for @var{usage} in the trace buffer. Note that
38594 @code{while-stepping} steps are not counted as separate hits, but the
38595 steps' space consumption is added into the usage number.
38599 @item qTV:@var{var}
38600 @cindex trace state variable value, remote request
38601 @cindex @samp{qTV} packet
38602 Ask the stub for the value of the trace state variable number @var{var}.
38607 The value of the variable is @var{value}. This will be the current
38608 value of the variable if the user is examining a running target, or a
38609 saved value if the variable was collected in the trace frame that the
38610 user is looking at. Note that multiple requests may result in
38611 different reply values, such as when requesting values while the
38612 program is running.
38615 The value of the variable is unknown. This would occur, for example,
38616 if the user is examining a trace frame in which the requested variable
38621 @cindex @samp{qTfP} packet
38623 @cindex @samp{qTsP} packet
38624 These packets request data about tracepoints that are being used by
38625 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38626 of data, and multiple @code{qTsP} to get additional pieces. Replies
38627 to these packets generally take the form of the @code{QTDP} packets
38628 that define tracepoints. (FIXME add detailed syntax)
38631 @cindex @samp{qTfV} packet
38633 @cindex @samp{qTsV} packet
38634 These packets request data about trace state variables that are on the
38635 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38636 and multiple @code{qTsV} to get additional variables. Replies to
38637 these packets follow the syntax of the @code{QTDV} packets that define
38638 trace state variables.
38644 @cindex @samp{qTfSTM} packet
38645 @cindex @samp{qTsSTM} packet
38646 These packets request data about static tracepoint markers that exist
38647 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38648 first piece of data, and multiple @code{qTsSTM} to get additional
38649 pieces. Replies to these packets take the following form:
38653 @item m @var{address}:@var{id}:@var{extra}
38655 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38656 a comma-separated list of markers
38658 (lower case letter @samp{L}) denotes end of list.
38660 An error occurred. @var{nn} are hex digits.
38662 An empty reply indicates that the request is not supported by the
38666 @var{address} is encoded in hex.
38667 @var{id} and @var{extra} are strings encoded in hex.
38669 In response to each query, the target will reply with a list of one or
38670 more markers, separated by commas. @value{GDBN} will respond to each
38671 reply with a request for more markers (using the @samp{qs} form of the
38672 query), until the target responds with @samp{l} (lower-case ell, for
38675 @item qTSTMat:@var{address}
38677 @cindex @samp{qTSTMat} packet
38678 This packets requests data about static tracepoint markers in the
38679 target program at @var{address}. Replies to this packet follow the
38680 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38681 tracepoint markers.
38683 @item QTSave:@var{filename}
38684 @cindex @samp{QTSave} packet
38685 This packet directs the target to save trace data to the file name
38686 @var{filename} in the target's filesystem. @var{filename} is encoded
38687 as a hex string; the interpretation of the file name (relative vs
38688 absolute, wild cards, etc) is up to the target.
38690 @item qTBuffer:@var{offset},@var{len}
38691 @cindex @samp{qTBuffer} packet
38692 Return up to @var{len} bytes of the current contents of trace buffer,
38693 starting at @var{offset}. The trace buffer is treated as if it were
38694 a contiguous collection of traceframes, as per the trace file format.
38695 The reply consists as many hex-encoded bytes as the target can deliver
38696 in a packet; it is not an error to return fewer than were asked for.
38697 A reply consisting of just @code{l} indicates that no bytes are
38700 @item QTBuffer:circular:@var{value}
38701 This packet directs the target to use a circular trace buffer if
38702 @var{value} is 1, or a linear buffer if the value is 0.
38704 @item QTBuffer:size:@var{size}
38705 @anchor{QTBuffer-size}
38706 @cindex @samp{QTBuffer size} packet
38707 This packet directs the target to make the trace buffer be of size
38708 @var{size} if possible. A value of @code{-1} tells the target to
38709 use whatever size it prefers.
38711 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38712 @cindex @samp{QTNotes} packet
38713 This packet adds optional textual notes to the trace run. Allowable
38714 types include @code{user}, @code{notes}, and @code{tstop}, the
38715 @var{text} fields are arbitrary strings, hex-encoded.
38719 @subsection Relocate instruction reply packet
38720 When installing fast tracepoints in memory, the target may need to
38721 relocate the instruction currently at the tracepoint address to a
38722 different address in memory. For most instructions, a simple copy is
38723 enough, but, for example, call instructions that implicitly push the
38724 return address on the stack, and relative branches or other
38725 PC-relative instructions require offset adjustment, so that the effect
38726 of executing the instruction at a different address is the same as if
38727 it had executed in the original location.
38729 In response to several of the tracepoint packets, the target may also
38730 respond with a number of intermediate @samp{qRelocInsn} request
38731 packets before the final result packet, to have @value{GDBN} handle
38732 this relocation operation. If a packet supports this mechanism, its
38733 documentation will explicitly say so. See for example the above
38734 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38735 format of the request is:
38738 @item qRelocInsn:@var{from};@var{to}
38740 This requests @value{GDBN} to copy instruction at address @var{from}
38741 to address @var{to}, possibly adjusted so that executing the
38742 instruction at @var{to} has the same effect as executing it at
38743 @var{from}. @value{GDBN} writes the adjusted instruction to target
38744 memory starting at @var{to}.
38749 @item qRelocInsn:@var{adjusted_size}
38750 Informs the stub the relocation is complete. @var{adjusted_size} is
38751 the length in bytes of resulting relocated instruction sequence.
38753 A badly formed request was detected, or an error was encountered while
38754 relocating the instruction.
38757 @node Host I/O Packets
38758 @section Host I/O Packets
38759 @cindex Host I/O, remote protocol
38760 @cindex file transfer, remote protocol
38762 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38763 operations on the far side of a remote link. For example, Host I/O is
38764 used to upload and download files to a remote target with its own
38765 filesystem. Host I/O uses the same constant values and data structure
38766 layout as the target-initiated File-I/O protocol. However, the
38767 Host I/O packets are structured differently. The target-initiated
38768 protocol relies on target memory to store parameters and buffers.
38769 Host I/O requests are initiated by @value{GDBN}, and the
38770 target's memory is not involved. @xref{File-I/O Remote Protocol
38771 Extension}, for more details on the target-initiated protocol.
38773 The Host I/O request packets all encode a single operation along with
38774 its arguments. They have this format:
38778 @item vFile:@var{operation}: @var{parameter}@dots{}
38779 @var{operation} is the name of the particular request; the target
38780 should compare the entire packet name up to the second colon when checking
38781 for a supported operation. The format of @var{parameter} depends on
38782 the operation. Numbers are always passed in hexadecimal. Negative
38783 numbers have an explicit minus sign (i.e.@: two's complement is not
38784 used). Strings (e.g.@: filenames) are encoded as a series of
38785 hexadecimal bytes. The last argument to a system call may be a
38786 buffer of escaped binary data (@pxref{Binary Data}).
38790 The valid responses to Host I/O packets are:
38794 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38795 @var{result} is the integer value returned by this operation, usually
38796 non-negative for success and -1 for errors. If an error has occured,
38797 @var{errno} will be included in the result. @var{errno} will have a
38798 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38799 operations which return data, @var{attachment} supplies the data as a
38800 binary buffer. Binary buffers in response packets are escaped in the
38801 normal way (@pxref{Binary Data}). See the individual packet
38802 documentation for the interpretation of @var{result} and
38806 An empty response indicates that this operation is not recognized.
38810 These are the supported Host I/O operations:
38813 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38814 Open a file at @var{pathname} and return a file descriptor for it, or
38815 return -1 if an error occurs. @var{pathname} is a string,
38816 @var{flags} is an integer indicating a mask of open flags
38817 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38818 of mode bits to use if the file is created (@pxref{mode_t Values}).
38819 @xref{open}, for details of the open flags and mode values.
38821 @item vFile:close: @var{fd}
38822 Close the open file corresponding to @var{fd} and return 0, or
38823 -1 if an error occurs.
38825 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38826 Read data from the open file corresponding to @var{fd}. Up to
38827 @var{count} bytes will be read from the file, starting at @var{offset}
38828 relative to the start of the file. The target may read fewer bytes;
38829 common reasons include packet size limits and an end-of-file
38830 condition. The number of bytes read is returned. Zero should only be
38831 returned for a successful read at the end of the file, or if
38832 @var{count} was zero.
38834 The data read should be returned as a binary attachment on success.
38835 If zero bytes were read, the response should include an empty binary
38836 attachment (i.e.@: a trailing semicolon). The return value is the
38837 number of target bytes read; the binary attachment may be longer if
38838 some characters were escaped.
38840 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38841 Write @var{data} (a binary buffer) to the open file corresponding
38842 to @var{fd}. Start the write at @var{offset} from the start of the
38843 file. Unlike many @code{write} system calls, there is no
38844 separate @var{count} argument; the length of @var{data} in the
38845 packet is used. @samp{vFile:write} returns the number of bytes written,
38846 which may be shorter than the length of @var{data}, or -1 if an
38849 @item vFile:unlink: @var{pathname}
38850 Delete the file at @var{pathname} on the target. Return 0,
38851 or -1 if an error occurs. @var{pathname} is a string.
38853 @item vFile:readlink: @var{filename}
38854 Read value of symbolic link @var{filename} on the target. Return
38855 the number of bytes read, or -1 if an error occurs.
38857 The data read should be returned as a binary attachment on success.
38858 If zero bytes were read, the response should include an empty binary
38859 attachment (i.e.@: a trailing semicolon). The return value is the
38860 number of target bytes read; the binary attachment may be longer if
38861 some characters were escaped.
38866 @section Interrupts
38867 @cindex interrupts (remote protocol)
38869 When a program on the remote target is running, @value{GDBN} may
38870 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38871 a @code{BREAK} followed by @code{g},
38872 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38874 The precise meaning of @code{BREAK} is defined by the transport
38875 mechanism and may, in fact, be undefined. @value{GDBN} does not
38876 currently define a @code{BREAK} mechanism for any of the network
38877 interfaces except for TCP, in which case @value{GDBN} sends the
38878 @code{telnet} BREAK sequence.
38880 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38881 transport mechanisms. It is represented by sending the single byte
38882 @code{0x03} without any of the usual packet overhead described in
38883 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38884 transmitted as part of a packet, it is considered to be packet data
38885 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38886 (@pxref{X packet}), used for binary downloads, may include an unescaped
38887 @code{0x03} as part of its packet.
38889 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38890 When Linux kernel receives this sequence from serial port,
38891 it stops execution and connects to gdb.
38893 Stubs are not required to recognize these interrupt mechanisms and the
38894 precise meaning associated with receipt of the interrupt is
38895 implementation defined. If the target supports debugging of multiple
38896 threads and/or processes, it should attempt to interrupt all
38897 currently-executing threads and processes.
38898 If the stub is successful at interrupting the
38899 running program, it should send one of the stop
38900 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38901 of successfully stopping the program in all-stop mode, and a stop reply
38902 for each stopped thread in non-stop mode.
38903 Interrupts received while the
38904 program is stopped are discarded.
38906 @node Notification Packets
38907 @section Notification Packets
38908 @cindex notification packets
38909 @cindex packets, notification
38911 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38912 packets that require no acknowledgment. Both the GDB and the stub
38913 may send notifications (although the only notifications defined at
38914 present are sent by the stub). Notifications carry information
38915 without incurring the round-trip latency of an acknowledgment, and so
38916 are useful for low-impact communications where occasional packet loss
38919 A notification packet has the form @samp{% @var{data} #
38920 @var{checksum}}, where @var{data} is the content of the notification,
38921 and @var{checksum} is a checksum of @var{data}, computed and formatted
38922 as for ordinary @value{GDBN} packets. A notification's @var{data}
38923 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38924 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38925 to acknowledge the notification's receipt or to report its corruption.
38927 Every notification's @var{data} begins with a name, which contains no
38928 colon characters, followed by a colon character.
38930 Recipients should silently ignore corrupted notifications and
38931 notifications they do not understand. Recipients should restart
38932 timeout periods on receipt of a well-formed notification, whether or
38933 not they understand it.
38935 Senders should only send the notifications described here when this
38936 protocol description specifies that they are permitted. In the
38937 future, we may extend the protocol to permit existing notifications in
38938 new contexts; this rule helps older senders avoid confusing newer
38941 (Older versions of @value{GDBN} ignore bytes received until they see
38942 the @samp{$} byte that begins an ordinary packet, so new stubs may
38943 transmit notifications without fear of confusing older clients. There
38944 are no notifications defined for @value{GDBN} to send at the moment, but we
38945 assume that most older stubs would ignore them, as well.)
38947 Each notification is comprised of three parts:
38949 @item @var{name}:@var{event}
38950 The notification packet is sent by the side that initiates the
38951 exchange (currently, only the stub does that), with @var{event}
38952 carrying the specific information about the notification.
38953 @var{name} is the name of the notification.
38955 The acknowledge sent by the other side, usually @value{GDBN}, to
38956 acknowledge the exchange and request the event.
38959 The purpose of an asynchronous notification mechanism is to report to
38960 @value{GDBN} that something interesting happened in the remote stub.
38962 The remote stub may send notification @var{name}:@var{event}
38963 at any time, but @value{GDBN} acknowledges the notification when
38964 appropriate. The notification event is pending before @value{GDBN}
38965 acknowledges. Only one notification at a time may be pending; if
38966 additional events occur before @value{GDBN} has acknowledged the
38967 previous notification, they must be queued by the stub for later
38968 synchronous transmission in response to @var{ack} packets from
38969 @value{GDBN}. Because the notification mechanism is unreliable,
38970 the stub is permitted to resend a notification if it believes
38971 @value{GDBN} may not have received it.
38973 Specifically, notifications may appear when @value{GDBN} is not
38974 otherwise reading input from the stub, or when @value{GDBN} is
38975 expecting to read a normal synchronous response or a
38976 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38977 Notification packets are distinct from any other communication from
38978 the stub so there is no ambiguity.
38980 After receiving a notification, @value{GDBN} shall acknowledge it by
38981 sending a @var{ack} packet as a regular, synchronous request to the
38982 stub. Such acknowledgment is not required to happen immediately, as
38983 @value{GDBN} is permitted to send other, unrelated packets to the
38984 stub first, which the stub should process normally.
38986 Upon receiving a @var{ack} packet, if the stub has other queued
38987 events to report to @value{GDBN}, it shall respond by sending a
38988 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38989 packet to solicit further responses; again, it is permitted to send
38990 other, unrelated packets as well which the stub should process
38993 If the stub receives a @var{ack} packet and there are no additional
38994 @var{event} to report, the stub shall return an @samp{OK} response.
38995 At this point, @value{GDBN} has finished processing a notification
38996 and the stub has completed sending any queued events. @value{GDBN}
38997 won't accept any new notifications until the final @samp{OK} is
38998 received . If further notification events occur, the stub shall send
38999 a new notification, @value{GDBN} shall accept the notification, and
39000 the process shall be repeated.
39002 The process of asynchronous notification can be illustrated by the
39005 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39008 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39010 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39015 The following notifications are defined:
39016 @multitable @columnfractions 0.12 0.12 0.38 0.38
39025 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39026 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39027 for information on how these notifications are acknowledged by
39029 @tab Report an asynchronous stop event in non-stop mode.
39033 @node Remote Non-Stop
39034 @section Remote Protocol Support for Non-Stop Mode
39036 @value{GDBN}'s remote protocol supports non-stop debugging of
39037 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39038 supports non-stop mode, it should report that to @value{GDBN} by including
39039 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39041 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39042 establishing a new connection with the stub. Entering non-stop mode
39043 does not alter the state of any currently-running threads, but targets
39044 must stop all threads in any already-attached processes when entering
39045 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39046 probe the target state after a mode change.
39048 In non-stop mode, when an attached process encounters an event that
39049 would otherwise be reported with a stop reply, it uses the
39050 asynchronous notification mechanism (@pxref{Notification Packets}) to
39051 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39052 in all processes are stopped when a stop reply is sent, in non-stop
39053 mode only the thread reporting the stop event is stopped. That is,
39054 when reporting a @samp{S} or @samp{T} response to indicate completion
39055 of a step operation, hitting a breakpoint, or a fault, only the
39056 affected thread is stopped; any other still-running threads continue
39057 to run. When reporting a @samp{W} or @samp{X} response, all running
39058 threads belonging to other attached processes continue to run.
39060 In non-stop mode, the target shall respond to the @samp{?} packet as
39061 follows. First, any incomplete stop reply notification/@samp{vStopped}
39062 sequence in progress is abandoned. The target must begin a new
39063 sequence reporting stop events for all stopped threads, whether or not
39064 it has previously reported those events to @value{GDBN}. The first
39065 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39066 subsequent stop replies are sent as responses to @samp{vStopped} packets
39067 using the mechanism described above. The target must not send
39068 asynchronous stop reply notifications until the sequence is complete.
39069 If all threads are running when the target receives the @samp{?} packet,
39070 or if the target is not attached to any process, it shall respond
39073 @node Packet Acknowledgment
39074 @section Packet Acknowledgment
39076 @cindex acknowledgment, for @value{GDBN} remote
39077 @cindex packet acknowledgment, for @value{GDBN} remote
39078 By default, when either the host or the target machine receives a packet,
39079 the first response expected is an acknowledgment: either @samp{+} (to indicate
39080 the package was received correctly) or @samp{-} (to request retransmission).
39081 This mechanism allows the @value{GDBN} remote protocol to operate over
39082 unreliable transport mechanisms, such as a serial line.
39084 In cases where the transport mechanism is itself reliable (such as a pipe or
39085 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39086 It may be desirable to disable them in that case to reduce communication
39087 overhead, or for other reasons. This can be accomplished by means of the
39088 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39090 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39091 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39092 and response format still includes the normal checksum, as described in
39093 @ref{Overview}, but the checksum may be ignored by the receiver.
39095 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39096 no-acknowledgment mode, it should report that to @value{GDBN}
39097 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39098 @pxref{qSupported}.
39099 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39100 disabled via the @code{set remote noack-packet off} command
39101 (@pxref{Remote Configuration}),
39102 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39103 Only then may the stub actually turn off packet acknowledgments.
39104 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39105 response, which can be safely ignored by the stub.
39107 Note that @code{set remote noack-packet} command only affects negotiation
39108 between @value{GDBN} and the stub when subsequent connections are made;
39109 it does not affect the protocol acknowledgment state for any current
39111 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39112 new connection is established,
39113 there is also no protocol request to re-enable the acknowledgments
39114 for the current connection, once disabled.
39119 Example sequence of a target being re-started. Notice how the restart
39120 does not get any direct output:
39125 @emph{target restarts}
39128 <- @code{T001:1234123412341234}
39132 Example sequence of a target being stepped by a single instruction:
39135 -> @code{G1445@dots{}}
39140 <- @code{T001:1234123412341234}
39144 <- @code{1455@dots{}}
39148 @node File-I/O Remote Protocol Extension
39149 @section File-I/O Remote Protocol Extension
39150 @cindex File-I/O remote protocol extension
39153 * File-I/O Overview::
39154 * Protocol Basics::
39155 * The F Request Packet::
39156 * The F Reply Packet::
39157 * The Ctrl-C Message::
39159 * List of Supported Calls::
39160 * Protocol-specific Representation of Datatypes::
39162 * File-I/O Examples::
39165 @node File-I/O Overview
39166 @subsection File-I/O Overview
39167 @cindex file-i/o overview
39169 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39170 target to use the host's file system and console I/O to perform various
39171 system calls. System calls on the target system are translated into a
39172 remote protocol packet to the host system, which then performs the needed
39173 actions and returns a response packet to the target system.
39174 This simulates file system operations even on targets that lack file systems.
39176 The protocol is defined to be independent of both the host and target systems.
39177 It uses its own internal representation of datatypes and values. Both
39178 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39179 translating the system-dependent value representations into the internal
39180 protocol representations when data is transmitted.
39182 The communication is synchronous. A system call is possible only when
39183 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39184 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39185 the target is stopped to allow deterministic access to the target's
39186 memory. Therefore File-I/O is not interruptible by target signals. On
39187 the other hand, it is possible to interrupt File-I/O by a user interrupt
39188 (@samp{Ctrl-C}) within @value{GDBN}.
39190 The target's request to perform a host system call does not finish
39191 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39192 after finishing the system call, the target returns to continuing the
39193 previous activity (continue, step). No additional continue or step
39194 request from @value{GDBN} is required.
39197 (@value{GDBP}) continue
39198 <- target requests 'system call X'
39199 target is stopped, @value{GDBN} executes system call
39200 -> @value{GDBN} returns result
39201 ... target continues, @value{GDBN} returns to wait for the target
39202 <- target hits breakpoint and sends a Txx packet
39205 The protocol only supports I/O on the console and to regular files on
39206 the host file system. Character or block special devices, pipes,
39207 named pipes, sockets or any other communication method on the host
39208 system are not supported by this protocol.
39210 File I/O is not supported in non-stop mode.
39212 @node Protocol Basics
39213 @subsection Protocol Basics
39214 @cindex protocol basics, file-i/o
39216 The File-I/O protocol uses the @code{F} packet as the request as well
39217 as reply packet. Since a File-I/O system call can only occur when
39218 @value{GDBN} is waiting for a response from the continuing or stepping target,
39219 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39220 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39221 This @code{F} packet contains all information needed to allow @value{GDBN}
39222 to call the appropriate host system call:
39226 A unique identifier for the requested system call.
39229 All parameters to the system call. Pointers are given as addresses
39230 in the target memory address space. Pointers to strings are given as
39231 pointer/length pair. Numerical values are given as they are.
39232 Numerical control flags are given in a protocol-specific representation.
39236 At this point, @value{GDBN} has to perform the following actions.
39240 If the parameters include pointer values to data needed as input to a
39241 system call, @value{GDBN} requests this data from the target with a
39242 standard @code{m} packet request. This additional communication has to be
39243 expected by the target implementation and is handled as any other @code{m}
39247 @value{GDBN} translates all value from protocol representation to host
39248 representation as needed. Datatypes are coerced into the host types.
39251 @value{GDBN} calls the system call.
39254 It then coerces datatypes back to protocol representation.
39257 If the system call is expected to return data in buffer space specified
39258 by pointer parameters to the call, the data is transmitted to the
39259 target using a @code{M} or @code{X} packet. This packet has to be expected
39260 by the target implementation and is handled as any other @code{M} or @code{X}
39265 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39266 necessary information for the target to continue. This at least contains
39273 @code{errno}, if has been changed by the system call.
39280 After having done the needed type and value coercion, the target continues
39281 the latest continue or step action.
39283 @node The F Request Packet
39284 @subsection The @code{F} Request Packet
39285 @cindex file-i/o request packet
39286 @cindex @code{F} request packet
39288 The @code{F} request packet has the following format:
39291 @item F@var{call-id},@var{parameter@dots{}}
39293 @var{call-id} is the identifier to indicate the host system call to be called.
39294 This is just the name of the function.
39296 @var{parameter@dots{}} are the parameters to the system call.
39297 Parameters are hexadecimal integer values, either the actual values in case
39298 of scalar datatypes, pointers to target buffer space in case of compound
39299 datatypes and unspecified memory areas, or pointer/length pairs in case
39300 of string parameters. These are appended to the @var{call-id} as a
39301 comma-delimited list. All values are transmitted in ASCII
39302 string representation, pointer/length pairs separated by a slash.
39308 @node The F Reply Packet
39309 @subsection The @code{F} Reply Packet
39310 @cindex file-i/o reply packet
39311 @cindex @code{F} reply packet
39313 The @code{F} reply packet has the following format:
39317 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39319 @var{retcode} is the return code of the system call as hexadecimal value.
39321 @var{errno} is the @code{errno} set by the call, in protocol-specific
39323 This parameter can be omitted if the call was successful.
39325 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39326 case, @var{errno} must be sent as well, even if the call was successful.
39327 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39334 or, if the call was interrupted before the host call has been performed:
39341 assuming 4 is the protocol-specific representation of @code{EINTR}.
39346 @node The Ctrl-C Message
39347 @subsection The @samp{Ctrl-C} Message
39348 @cindex ctrl-c message, in file-i/o protocol
39350 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39351 reply packet (@pxref{The F Reply Packet}),
39352 the target should behave as if it had
39353 gotten a break message. The meaning for the target is ``system call
39354 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39355 (as with a break message) and return to @value{GDBN} with a @code{T02}
39358 It's important for the target to know in which
39359 state the system call was interrupted. There are two possible cases:
39363 The system call hasn't been performed on the host yet.
39366 The system call on the host has been finished.
39370 These two states can be distinguished by the target by the value of the
39371 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39372 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39373 on POSIX systems. In any other case, the target may presume that the
39374 system call has been finished --- successfully or not --- and should behave
39375 as if the break message arrived right after the system call.
39377 @value{GDBN} must behave reliably. If the system call has not been called
39378 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39379 @code{errno} in the packet. If the system call on the host has been finished
39380 before the user requests a break, the full action must be finished by
39381 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39382 The @code{F} packet may only be sent when either nothing has happened
39383 or the full action has been completed.
39386 @subsection Console I/O
39387 @cindex console i/o as part of file-i/o
39389 By default and if not explicitly closed by the target system, the file
39390 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39391 on the @value{GDBN} console is handled as any other file output operation
39392 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39393 by @value{GDBN} so that after the target read request from file descriptor
39394 0 all following typing is buffered until either one of the following
39399 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39401 system call is treated as finished.
39404 The user presses @key{RET}. This is treated as end of input with a trailing
39408 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39409 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39413 If the user has typed more characters than fit in the buffer given to
39414 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39415 either another @code{read(0, @dots{})} is requested by the target, or debugging
39416 is stopped at the user's request.
39419 @node List of Supported Calls
39420 @subsection List of Supported Calls
39421 @cindex list of supported file-i/o calls
39438 @unnumberedsubsubsec open
39439 @cindex open, file-i/o system call
39444 int open(const char *pathname, int flags);
39445 int open(const char *pathname, int flags, mode_t mode);
39449 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39452 @var{flags} is the bitwise @code{OR} of the following values:
39456 If the file does not exist it will be created. The host
39457 rules apply as far as file ownership and time stamps
39461 When used with @code{O_CREAT}, if the file already exists it is
39462 an error and open() fails.
39465 If the file already exists and the open mode allows
39466 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39467 truncated to zero length.
39470 The file is opened in append mode.
39473 The file is opened for reading only.
39476 The file is opened for writing only.
39479 The file is opened for reading and writing.
39483 Other bits are silently ignored.
39487 @var{mode} is the bitwise @code{OR} of the following values:
39491 User has read permission.
39494 User has write permission.
39497 Group has read permission.
39500 Group has write permission.
39503 Others have read permission.
39506 Others have write permission.
39510 Other bits are silently ignored.
39513 @item Return value:
39514 @code{open} returns the new file descriptor or -1 if an error
39521 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39524 @var{pathname} refers to a directory.
39527 The requested access is not allowed.
39530 @var{pathname} was too long.
39533 A directory component in @var{pathname} does not exist.
39536 @var{pathname} refers to a device, pipe, named pipe or socket.
39539 @var{pathname} refers to a file on a read-only filesystem and
39540 write access was requested.
39543 @var{pathname} is an invalid pointer value.
39546 No space on device to create the file.
39549 The process already has the maximum number of files open.
39552 The limit on the total number of files open on the system
39556 The call was interrupted by the user.
39562 @unnumberedsubsubsec close
39563 @cindex close, file-i/o system call
39572 @samp{Fclose,@var{fd}}
39574 @item Return value:
39575 @code{close} returns zero on success, or -1 if an error occurred.
39581 @var{fd} isn't a valid open file descriptor.
39584 The call was interrupted by the user.
39590 @unnumberedsubsubsec read
39591 @cindex read, file-i/o system call
39596 int read(int fd, void *buf, unsigned int count);
39600 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39602 @item Return value:
39603 On success, the number of bytes read is returned.
39604 Zero indicates end of file. If count is zero, read
39605 returns zero as well. On error, -1 is returned.
39611 @var{fd} is not a valid file descriptor or is not open for
39615 @var{bufptr} is an invalid pointer value.
39618 The call was interrupted by the user.
39624 @unnumberedsubsubsec write
39625 @cindex write, file-i/o system call
39630 int write(int fd, const void *buf, unsigned int count);
39634 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39636 @item Return value:
39637 On success, the number of bytes written are returned.
39638 Zero indicates nothing was written. On error, -1
39645 @var{fd} is not a valid file descriptor or is not open for
39649 @var{bufptr} is an invalid pointer value.
39652 An attempt was made to write a file that exceeds the
39653 host-specific maximum file size allowed.
39656 No space on device to write the data.
39659 The call was interrupted by the user.
39665 @unnumberedsubsubsec lseek
39666 @cindex lseek, file-i/o system call
39671 long lseek (int fd, long offset, int flag);
39675 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39677 @var{flag} is one of:
39681 The offset is set to @var{offset} bytes.
39684 The offset is set to its current location plus @var{offset}
39688 The offset is set to the size of the file plus @var{offset}
39692 @item Return value:
39693 On success, the resulting unsigned offset in bytes from
39694 the beginning of the file is returned. Otherwise, a
39695 value of -1 is returned.
39701 @var{fd} is not a valid open file descriptor.
39704 @var{fd} is associated with the @value{GDBN} console.
39707 @var{flag} is not a proper value.
39710 The call was interrupted by the user.
39716 @unnumberedsubsubsec rename
39717 @cindex rename, file-i/o system call
39722 int rename(const char *oldpath, const char *newpath);
39726 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39728 @item Return value:
39729 On success, zero is returned. On error, -1 is returned.
39735 @var{newpath} is an existing directory, but @var{oldpath} is not a
39739 @var{newpath} is a non-empty directory.
39742 @var{oldpath} or @var{newpath} is a directory that is in use by some
39746 An attempt was made to make a directory a subdirectory
39750 A component used as a directory in @var{oldpath} or new
39751 path is not a directory. Or @var{oldpath} is a directory
39752 and @var{newpath} exists but is not a directory.
39755 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39758 No access to the file or the path of the file.
39762 @var{oldpath} or @var{newpath} was too long.
39765 A directory component in @var{oldpath} or @var{newpath} does not exist.
39768 The file is on a read-only filesystem.
39771 The device containing the file has no room for the new
39775 The call was interrupted by the user.
39781 @unnumberedsubsubsec unlink
39782 @cindex unlink, file-i/o system call
39787 int unlink(const char *pathname);
39791 @samp{Funlink,@var{pathnameptr}/@var{len}}
39793 @item Return value:
39794 On success, zero is returned. On error, -1 is returned.
39800 No access to the file or the path of the file.
39803 The system does not allow unlinking of directories.
39806 The file @var{pathname} cannot be unlinked because it's
39807 being used by another process.
39810 @var{pathnameptr} is an invalid pointer value.
39813 @var{pathname} was too long.
39816 A directory component in @var{pathname} does not exist.
39819 A component of the path is not a directory.
39822 The file is on a read-only filesystem.
39825 The call was interrupted by the user.
39831 @unnumberedsubsubsec stat/fstat
39832 @cindex fstat, file-i/o system call
39833 @cindex stat, file-i/o system call
39838 int stat(const char *pathname, struct stat *buf);
39839 int fstat(int fd, struct stat *buf);
39843 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39844 @samp{Ffstat,@var{fd},@var{bufptr}}
39846 @item Return value:
39847 On success, zero is returned. On error, -1 is returned.
39853 @var{fd} is not a valid open file.
39856 A directory component in @var{pathname} does not exist or the
39857 path is an empty string.
39860 A component of the path is not a directory.
39863 @var{pathnameptr} is an invalid pointer value.
39866 No access to the file or the path of the file.
39869 @var{pathname} was too long.
39872 The call was interrupted by the user.
39878 @unnumberedsubsubsec gettimeofday
39879 @cindex gettimeofday, file-i/o system call
39884 int gettimeofday(struct timeval *tv, void *tz);
39888 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39890 @item Return value:
39891 On success, 0 is returned, -1 otherwise.
39897 @var{tz} is a non-NULL pointer.
39900 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39906 @unnumberedsubsubsec isatty
39907 @cindex isatty, file-i/o system call
39912 int isatty(int fd);
39916 @samp{Fisatty,@var{fd}}
39918 @item Return value:
39919 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39925 The call was interrupted by the user.
39930 Note that the @code{isatty} call is treated as a special case: it returns
39931 1 to the target if the file descriptor is attached
39932 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39933 would require implementing @code{ioctl} and would be more complex than
39938 @unnumberedsubsubsec system
39939 @cindex system, file-i/o system call
39944 int system(const char *command);
39948 @samp{Fsystem,@var{commandptr}/@var{len}}
39950 @item Return value:
39951 If @var{len} is zero, the return value indicates whether a shell is
39952 available. A zero return value indicates a shell is not available.
39953 For non-zero @var{len}, the value returned is -1 on error and the
39954 return status of the command otherwise. Only the exit status of the
39955 command is returned, which is extracted from the host's @code{system}
39956 return value by calling @code{WEXITSTATUS(retval)}. In case
39957 @file{/bin/sh} could not be executed, 127 is returned.
39963 The call was interrupted by the user.
39968 @value{GDBN} takes over the full task of calling the necessary host calls
39969 to perform the @code{system} call. The return value of @code{system} on
39970 the host is simplified before it's returned
39971 to the target. Any termination signal information from the child process
39972 is discarded, and the return value consists
39973 entirely of the exit status of the called command.
39975 Due to security concerns, the @code{system} call is by default refused
39976 by @value{GDBN}. The user has to allow this call explicitly with the
39977 @code{set remote system-call-allowed 1} command.
39980 @item set remote system-call-allowed
39981 @kindex set remote system-call-allowed
39982 Control whether to allow the @code{system} calls in the File I/O
39983 protocol for the remote target. The default is zero (disabled).
39985 @item show remote system-call-allowed
39986 @kindex show remote system-call-allowed
39987 Show whether the @code{system} calls are allowed in the File I/O
39991 @node Protocol-specific Representation of Datatypes
39992 @subsection Protocol-specific Representation of Datatypes
39993 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39996 * Integral Datatypes::
39998 * Memory Transfer::
40003 @node Integral Datatypes
40004 @unnumberedsubsubsec Integral Datatypes
40005 @cindex integral datatypes, in file-i/o protocol
40007 The integral datatypes used in the system calls are @code{int},
40008 @code{unsigned int}, @code{long}, @code{unsigned long},
40009 @code{mode_t}, and @code{time_t}.
40011 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40012 implemented as 32 bit values in this protocol.
40014 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40016 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40017 in @file{limits.h}) to allow range checking on host and target.
40019 @code{time_t} datatypes are defined as seconds since the Epoch.
40021 All integral datatypes transferred as part of a memory read or write of a
40022 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40025 @node Pointer Values
40026 @unnumberedsubsubsec Pointer Values
40027 @cindex pointer values, in file-i/o protocol
40029 Pointers to target data are transmitted as they are. An exception
40030 is made for pointers to buffers for which the length isn't
40031 transmitted as part of the function call, namely strings. Strings
40032 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40039 which is a pointer to data of length 18 bytes at position 0x1aaf.
40040 The length is defined as the full string length in bytes, including
40041 the trailing null byte. For example, the string @code{"hello world"}
40042 at address 0x123456 is transmitted as
40048 @node Memory Transfer
40049 @unnumberedsubsubsec Memory Transfer
40050 @cindex memory transfer, in file-i/o protocol
40052 Structured data which is transferred using a memory read or write (for
40053 example, a @code{struct stat}) is expected to be in a protocol-specific format
40054 with all scalar multibyte datatypes being big endian. Translation to
40055 this representation needs to be done both by the target before the @code{F}
40056 packet is sent, and by @value{GDBN} before
40057 it transfers memory to the target. Transferred pointers to structured
40058 data should point to the already-coerced data at any time.
40062 @unnumberedsubsubsec struct stat
40063 @cindex struct stat, in file-i/o protocol
40065 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40066 is defined as follows:
40070 unsigned int st_dev; /* device */
40071 unsigned int st_ino; /* inode */
40072 mode_t st_mode; /* protection */
40073 unsigned int st_nlink; /* number of hard links */
40074 unsigned int st_uid; /* user ID of owner */
40075 unsigned int st_gid; /* group ID of owner */
40076 unsigned int st_rdev; /* device type (if inode device) */
40077 unsigned long st_size; /* total size, in bytes */
40078 unsigned long st_blksize; /* blocksize for filesystem I/O */
40079 unsigned long st_blocks; /* number of blocks allocated */
40080 time_t st_atime; /* time of last access */
40081 time_t st_mtime; /* time of last modification */
40082 time_t st_ctime; /* time of last change */
40086 The integral datatypes conform to the definitions given in the
40087 appropriate section (see @ref{Integral Datatypes}, for details) so this
40088 structure is of size 64 bytes.
40090 The values of several fields have a restricted meaning and/or
40096 A value of 0 represents a file, 1 the console.
40099 No valid meaning for the target. Transmitted unchanged.
40102 Valid mode bits are described in @ref{Constants}. Any other
40103 bits have currently no meaning for the target.
40108 No valid meaning for the target. Transmitted unchanged.
40113 These values have a host and file system dependent
40114 accuracy. Especially on Windows hosts, the file system may not
40115 support exact timing values.
40118 The target gets a @code{struct stat} of the above representation and is
40119 responsible for coercing it to the target representation before
40122 Note that due to size differences between the host, target, and protocol
40123 representations of @code{struct stat} members, these members could eventually
40124 get truncated on the target.
40126 @node struct timeval
40127 @unnumberedsubsubsec struct timeval
40128 @cindex struct timeval, in file-i/o protocol
40130 The buffer of type @code{struct timeval} used by the File-I/O protocol
40131 is defined as follows:
40135 time_t tv_sec; /* second */
40136 long tv_usec; /* microsecond */
40140 The integral datatypes conform to the definitions given in the
40141 appropriate section (see @ref{Integral Datatypes}, for details) so this
40142 structure is of size 8 bytes.
40145 @subsection Constants
40146 @cindex constants, in file-i/o protocol
40148 The following values are used for the constants inside of the
40149 protocol. @value{GDBN} and target are responsible for translating these
40150 values before and after the call as needed.
40161 @unnumberedsubsubsec Open Flags
40162 @cindex open flags, in file-i/o protocol
40164 All values are given in hexadecimal representation.
40176 @node mode_t Values
40177 @unnumberedsubsubsec mode_t Values
40178 @cindex mode_t values, in file-i/o protocol
40180 All values are given in octal representation.
40197 @unnumberedsubsubsec Errno Values
40198 @cindex errno values, in file-i/o protocol
40200 All values are given in decimal representation.
40225 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40226 any error value not in the list of supported error numbers.
40229 @unnumberedsubsubsec Lseek Flags
40230 @cindex lseek flags, in file-i/o protocol
40239 @unnumberedsubsubsec Limits
40240 @cindex limits, in file-i/o protocol
40242 All values are given in decimal representation.
40245 INT_MIN -2147483648
40247 UINT_MAX 4294967295
40248 LONG_MIN -9223372036854775808
40249 LONG_MAX 9223372036854775807
40250 ULONG_MAX 18446744073709551615
40253 @node File-I/O Examples
40254 @subsection File-I/O Examples
40255 @cindex file-i/o examples
40257 Example sequence of a write call, file descriptor 3, buffer is at target
40258 address 0x1234, 6 bytes should be written:
40261 <- @code{Fwrite,3,1234,6}
40262 @emph{request memory read from target}
40265 @emph{return "6 bytes written"}
40269 Example sequence of a read call, file descriptor 3, buffer is at target
40270 address 0x1234, 6 bytes should be read:
40273 <- @code{Fread,3,1234,6}
40274 @emph{request memory write to target}
40275 -> @code{X1234,6:XXXXXX}
40276 @emph{return "6 bytes read"}
40280 Example sequence of a read call, call fails on the host due to invalid
40281 file descriptor (@code{EBADF}):
40284 <- @code{Fread,3,1234,6}
40288 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40292 <- @code{Fread,3,1234,6}
40297 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40301 <- @code{Fread,3,1234,6}
40302 -> @code{X1234,6:XXXXXX}
40306 @node Library List Format
40307 @section Library List Format
40308 @cindex library list format, remote protocol
40310 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40311 same process as your application to manage libraries. In this case,
40312 @value{GDBN} can use the loader's symbol table and normal memory
40313 operations to maintain a list of shared libraries. On other
40314 platforms, the operating system manages loaded libraries.
40315 @value{GDBN} can not retrieve the list of currently loaded libraries
40316 through memory operations, so it uses the @samp{qXfer:libraries:read}
40317 packet (@pxref{qXfer library list read}) instead. The remote stub
40318 queries the target's operating system and reports which libraries
40321 The @samp{qXfer:libraries:read} packet returns an XML document which
40322 lists loaded libraries and their offsets. Each library has an
40323 associated name and one or more segment or section base addresses,
40324 which report where the library was loaded in memory.
40326 For the common case of libraries that are fully linked binaries, the
40327 library should have a list of segments. If the target supports
40328 dynamic linking of a relocatable object file, its library XML element
40329 should instead include a list of allocated sections. The segment or
40330 section bases are start addresses, not relocation offsets; they do not
40331 depend on the library's link-time base addresses.
40333 @value{GDBN} must be linked with the Expat library to support XML
40334 library lists. @xref{Expat}.
40336 A simple memory map, with one loaded library relocated by a single
40337 offset, looks like this:
40341 <library name="/lib/libc.so.6">
40342 <segment address="0x10000000"/>
40347 Another simple memory map, with one loaded library with three
40348 allocated sections (.text, .data, .bss), looks like this:
40352 <library name="sharedlib.o">
40353 <section address="0x10000000"/>
40354 <section address="0x20000000"/>
40355 <section address="0x30000000"/>
40360 The format of a library list is described by this DTD:
40363 <!-- library-list: Root element with versioning -->
40364 <!ELEMENT library-list (library)*>
40365 <!ATTLIST library-list version CDATA #FIXED "1.0">
40366 <!ELEMENT library (segment*, section*)>
40367 <!ATTLIST library name CDATA #REQUIRED>
40368 <!ELEMENT segment EMPTY>
40369 <!ATTLIST segment address CDATA #REQUIRED>
40370 <!ELEMENT section EMPTY>
40371 <!ATTLIST section address CDATA #REQUIRED>
40374 In addition, segments and section descriptors cannot be mixed within a
40375 single library element, and you must supply at least one segment or
40376 section for each library.
40378 @node Library List Format for SVR4 Targets
40379 @section Library List Format for SVR4 Targets
40380 @cindex library list format, remote protocol
40382 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40383 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40384 shared libraries. Still a special library list provided by this packet is
40385 more efficient for the @value{GDBN} remote protocol.
40387 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40388 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40389 target, the following parameters are reported:
40393 @code{name}, the absolute file name from the @code{l_name} field of
40394 @code{struct link_map}.
40396 @code{lm} with address of @code{struct link_map} used for TLS
40397 (Thread Local Storage) access.
40399 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40400 @code{struct link_map}. For prelinked libraries this is not an absolute
40401 memory address. It is a displacement of absolute memory address against
40402 address the file was prelinked to during the library load.
40404 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40407 Additionally the single @code{main-lm} attribute specifies address of
40408 @code{struct link_map} used for the main executable. This parameter is used
40409 for TLS access and its presence is optional.
40411 @value{GDBN} must be linked with the Expat library to support XML
40412 SVR4 library lists. @xref{Expat}.
40414 A simple memory map, with two loaded libraries (which do not use prelink),
40418 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40419 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40421 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40423 </library-list-svr>
40426 The format of an SVR4 library list is described by this DTD:
40429 <!-- library-list-svr4: Root element with versioning -->
40430 <!ELEMENT library-list-svr4 (library)*>
40431 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40432 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40433 <!ELEMENT library EMPTY>
40434 <!ATTLIST library name CDATA #REQUIRED>
40435 <!ATTLIST library lm CDATA #REQUIRED>
40436 <!ATTLIST library l_addr CDATA #REQUIRED>
40437 <!ATTLIST library l_ld CDATA #REQUIRED>
40440 @node Memory Map Format
40441 @section Memory Map Format
40442 @cindex memory map format
40444 To be able to write into flash memory, @value{GDBN} needs to obtain a
40445 memory map from the target. This section describes the format of the
40448 The memory map is obtained using the @samp{qXfer:memory-map:read}
40449 (@pxref{qXfer memory map read}) packet and is an XML document that
40450 lists memory regions.
40452 @value{GDBN} must be linked with the Expat library to support XML
40453 memory maps. @xref{Expat}.
40455 The top-level structure of the document is shown below:
40458 <?xml version="1.0"?>
40459 <!DOCTYPE memory-map
40460 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40461 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40467 Each region can be either:
40472 A region of RAM starting at @var{addr} and extending for @var{length}
40476 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40481 A region of read-only memory:
40484 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40489 A region of flash memory, with erasure blocks @var{blocksize}
40493 <memory type="flash" start="@var{addr}" length="@var{length}">
40494 <property name="blocksize">@var{blocksize}</property>
40500 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40501 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40502 packets to write to addresses in such ranges.
40504 The formal DTD for memory map format is given below:
40507 <!-- ................................................... -->
40508 <!-- Memory Map XML DTD ................................ -->
40509 <!-- File: memory-map.dtd .............................. -->
40510 <!-- .................................... .............. -->
40511 <!-- memory-map.dtd -->
40512 <!-- memory-map: Root element with versioning -->
40513 <!ELEMENT memory-map (memory | property)>
40514 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40515 <!ELEMENT memory (property)>
40516 <!-- memory: Specifies a memory region,
40517 and its type, or device. -->
40518 <!ATTLIST memory type CDATA #REQUIRED
40519 start CDATA #REQUIRED
40520 length CDATA #REQUIRED
40521 device CDATA #IMPLIED>
40522 <!-- property: Generic attribute tag -->
40523 <!ELEMENT property (#PCDATA | property)*>
40524 <!ATTLIST property name CDATA #REQUIRED>
40527 @node Thread List Format
40528 @section Thread List Format
40529 @cindex thread list format
40531 To efficiently update the list of threads and their attributes,
40532 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40533 (@pxref{qXfer threads read}) and obtains the XML document with
40534 the following structure:
40537 <?xml version="1.0"?>
40539 <thread id="id" core="0">
40540 ... description ...
40545 Each @samp{thread} element must have the @samp{id} attribute that
40546 identifies the thread (@pxref{thread-id syntax}). The
40547 @samp{core} attribute, if present, specifies which processor core
40548 the thread was last executing on. The content of the of @samp{thread}
40549 element is interpreted as human-readable auxilliary information.
40551 @node Traceframe Info Format
40552 @section Traceframe Info Format
40553 @cindex traceframe info format
40555 To be able to know which objects in the inferior can be examined when
40556 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40557 memory ranges, registers and trace state variables that have been
40558 collected in a traceframe.
40560 This list is obtained using the @samp{qXfer:traceframe-info:read}
40561 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40563 @value{GDBN} must be linked with the Expat library to support XML
40564 traceframe info discovery. @xref{Expat}.
40566 The top-level structure of the document is shown below:
40569 <?xml version="1.0"?>
40570 <!DOCTYPE traceframe-info
40571 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40572 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40578 Each traceframe block can be either:
40583 A region of collected memory starting at @var{addr} and extending for
40584 @var{length} bytes from there:
40587 <memory start="@var{addr}" length="@var{length}"/>
40592 The formal DTD for the traceframe info format is given below:
40595 <!ELEMENT traceframe-info (memory)* >
40596 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40598 <!ELEMENT memory EMPTY>
40599 <!ATTLIST memory start CDATA #REQUIRED
40600 length CDATA #REQUIRED>
40603 @node Branch Trace Format
40604 @section Branch Trace Format
40605 @cindex branch trace format
40607 In order to display the branch trace of an inferior thread,
40608 @value{GDBN} needs to obtain the list of branches. This list is
40609 represented as list of sequential code blocks that are connected via
40610 branches. The code in each block has been executed sequentially.
40612 This list is obtained using the @samp{qXfer:btrace:read}
40613 (@pxref{qXfer btrace read}) packet and is an XML document.
40615 @value{GDBN} must be linked with the Expat library to support XML
40616 traceframe info discovery. @xref{Expat}.
40618 The top-level structure of the document is shown below:
40621 <?xml version="1.0"?>
40623 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40624 "http://sourceware.org/gdb/gdb-btrace.dtd">
40633 A block of sequentially executed instructions starting at @var{begin}
40634 and ending at @var{end}:
40637 <block begin="@var{begin}" end="@var{end}"/>
40642 The formal DTD for the branch trace format is given below:
40645 <!ELEMENT btrace (block)* >
40646 <!ATTLIST btrace version CDATA #FIXED "1.0">
40648 <!ELEMENT block EMPTY>
40649 <!ATTLIST block begin CDATA #REQUIRED
40650 end CDATA #REQUIRED>
40653 @include agentexpr.texi
40655 @node Target Descriptions
40656 @appendix Target Descriptions
40657 @cindex target descriptions
40659 One of the challenges of using @value{GDBN} to debug embedded systems
40660 is that there are so many minor variants of each processor
40661 architecture in use. It is common practice for vendors to start with
40662 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40663 and then make changes to adapt it to a particular market niche. Some
40664 architectures have hundreds of variants, available from dozens of
40665 vendors. This leads to a number of problems:
40669 With so many different customized processors, it is difficult for
40670 the @value{GDBN} maintainers to keep up with the changes.
40672 Since individual variants may have short lifetimes or limited
40673 audiences, it may not be worthwhile to carry information about every
40674 variant in the @value{GDBN} source tree.
40676 When @value{GDBN} does support the architecture of the embedded system
40677 at hand, the task of finding the correct architecture name to give the
40678 @command{set architecture} command can be error-prone.
40681 To address these problems, the @value{GDBN} remote protocol allows a
40682 target system to not only identify itself to @value{GDBN}, but to
40683 actually describe its own features. This lets @value{GDBN} support
40684 processor variants it has never seen before --- to the extent that the
40685 descriptions are accurate, and that @value{GDBN} understands them.
40687 @value{GDBN} must be linked with the Expat library to support XML
40688 target descriptions. @xref{Expat}.
40691 * Retrieving Descriptions:: How descriptions are fetched from a target.
40692 * Target Description Format:: The contents of a target description.
40693 * Predefined Target Types:: Standard types available for target
40695 * Standard Target Features:: Features @value{GDBN} knows about.
40698 @node Retrieving Descriptions
40699 @section Retrieving Descriptions
40701 Target descriptions can be read from the target automatically, or
40702 specified by the user manually. The default behavior is to read the
40703 description from the target. @value{GDBN} retrieves it via the remote
40704 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40705 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40706 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40707 XML document, of the form described in @ref{Target Description
40710 Alternatively, you can specify a file to read for the target description.
40711 If a file is set, the target will not be queried. The commands to
40712 specify a file are:
40715 @cindex set tdesc filename
40716 @item set tdesc filename @var{path}
40717 Read the target description from @var{path}.
40719 @cindex unset tdesc filename
40720 @item unset tdesc filename
40721 Do not read the XML target description from a file. @value{GDBN}
40722 will use the description supplied by the current target.
40724 @cindex show tdesc filename
40725 @item show tdesc filename
40726 Show the filename to read for a target description, if any.
40730 @node Target Description Format
40731 @section Target Description Format
40732 @cindex target descriptions, XML format
40734 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40735 document which complies with the Document Type Definition provided in
40736 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40737 means you can use generally available tools like @command{xmllint} to
40738 check that your feature descriptions are well-formed and valid.
40739 However, to help people unfamiliar with XML write descriptions for
40740 their targets, we also describe the grammar here.
40742 Target descriptions can identify the architecture of the remote target
40743 and (for some architectures) provide information about custom register
40744 sets. They can also identify the OS ABI of the remote target.
40745 @value{GDBN} can use this information to autoconfigure for your
40746 target, or to warn you if you connect to an unsupported target.
40748 Here is a simple target description:
40751 <target version="1.0">
40752 <architecture>i386:x86-64</architecture>
40757 This minimal description only says that the target uses
40758 the x86-64 architecture.
40760 A target description has the following overall form, with [ ] marking
40761 optional elements and @dots{} marking repeatable elements. The elements
40762 are explained further below.
40765 <?xml version="1.0"?>
40766 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40767 <target version="1.0">
40768 @r{[}@var{architecture}@r{]}
40769 @r{[}@var{osabi}@r{]}
40770 @r{[}@var{compatible}@r{]}
40771 @r{[}@var{feature}@dots{}@r{]}
40776 The description is generally insensitive to whitespace and line
40777 breaks, under the usual common-sense rules. The XML version
40778 declaration and document type declaration can generally be omitted
40779 (@value{GDBN} does not require them), but specifying them may be
40780 useful for XML validation tools. The @samp{version} attribute for
40781 @samp{<target>} may also be omitted, but we recommend
40782 including it; if future versions of @value{GDBN} use an incompatible
40783 revision of @file{gdb-target.dtd}, they will detect and report
40784 the version mismatch.
40786 @subsection Inclusion
40787 @cindex target descriptions, inclusion
40790 @cindex <xi:include>
40793 It can sometimes be valuable to split a target description up into
40794 several different annexes, either for organizational purposes, or to
40795 share files between different possible target descriptions. You can
40796 divide a description into multiple files by replacing any element of
40797 the target description with an inclusion directive of the form:
40800 <xi:include href="@var{document}"/>
40804 When @value{GDBN} encounters an element of this form, it will retrieve
40805 the named XML @var{document}, and replace the inclusion directive with
40806 the contents of that document. If the current description was read
40807 using @samp{qXfer}, then so will be the included document;
40808 @var{document} will be interpreted as the name of an annex. If the
40809 current description was read from a file, @value{GDBN} will look for
40810 @var{document} as a file in the same directory where it found the
40811 original description.
40813 @subsection Architecture
40814 @cindex <architecture>
40816 An @samp{<architecture>} element has this form:
40819 <architecture>@var{arch}</architecture>
40822 @var{arch} is one of the architectures from the set accepted by
40823 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40826 @cindex @code{<osabi>}
40828 This optional field was introduced in @value{GDBN} version 7.0.
40829 Previous versions of @value{GDBN} ignore it.
40831 An @samp{<osabi>} element has this form:
40834 <osabi>@var{abi-name}</osabi>
40837 @var{abi-name} is an OS ABI name from the same selection accepted by
40838 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40840 @subsection Compatible Architecture
40841 @cindex @code{<compatible>}
40843 This optional field was introduced in @value{GDBN} version 7.0.
40844 Previous versions of @value{GDBN} ignore it.
40846 A @samp{<compatible>} element has this form:
40849 <compatible>@var{arch}</compatible>
40852 @var{arch} is one of the architectures from the set accepted by
40853 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40855 A @samp{<compatible>} element is used to specify that the target
40856 is able to run binaries in some other than the main target architecture
40857 given by the @samp{<architecture>} element. For example, on the
40858 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40859 or @code{powerpc:common64}, but the system is able to run binaries
40860 in the @code{spu} architecture as well. The way to describe this
40861 capability with @samp{<compatible>} is as follows:
40864 <architecture>powerpc:common</architecture>
40865 <compatible>spu</compatible>
40868 @subsection Features
40871 Each @samp{<feature>} describes some logical portion of the target
40872 system. Features are currently used to describe available CPU
40873 registers and the types of their contents. A @samp{<feature>} element
40877 <feature name="@var{name}">
40878 @r{[}@var{type}@dots{}@r{]}
40884 Each feature's name should be unique within the description. The name
40885 of a feature does not matter unless @value{GDBN} has some special
40886 knowledge of the contents of that feature; if it does, the feature
40887 should have its standard name. @xref{Standard Target Features}.
40891 Any register's value is a collection of bits which @value{GDBN} must
40892 interpret. The default interpretation is a two's complement integer,
40893 but other types can be requested by name in the register description.
40894 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40895 Target Types}), and the description can define additional composite types.
40897 Each type element must have an @samp{id} attribute, which gives
40898 a unique (within the containing @samp{<feature>}) name to the type.
40899 Types must be defined before they are used.
40902 Some targets offer vector registers, which can be treated as arrays
40903 of scalar elements. These types are written as @samp{<vector>} elements,
40904 specifying the array element type, @var{type}, and the number of elements,
40908 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40912 If a register's value is usefully viewed in multiple ways, define it
40913 with a union type containing the useful representations. The
40914 @samp{<union>} element contains one or more @samp{<field>} elements,
40915 each of which has a @var{name} and a @var{type}:
40918 <union id="@var{id}">
40919 <field name="@var{name}" type="@var{type}"/>
40925 If a register's value is composed from several separate values, define
40926 it with a structure type. There are two forms of the @samp{<struct>}
40927 element; a @samp{<struct>} element must either contain only bitfields
40928 or contain no bitfields. If the structure contains only bitfields,
40929 its total size in bytes must be specified, each bitfield must have an
40930 explicit start and end, and bitfields are automatically assigned an
40931 integer type. The field's @var{start} should be less than or
40932 equal to its @var{end}, and zero represents the least significant bit.
40935 <struct id="@var{id}" size="@var{size}">
40936 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40941 If the structure contains no bitfields, then each field has an
40942 explicit type, and no implicit padding is added.
40945 <struct id="@var{id}">
40946 <field name="@var{name}" type="@var{type}"/>
40952 If a register's value is a series of single-bit flags, define it with
40953 a flags type. The @samp{<flags>} element has an explicit @var{size}
40954 and contains one or more @samp{<field>} elements. Each field has a
40955 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40959 <flags id="@var{id}" size="@var{size}">
40960 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40965 @subsection Registers
40968 Each register is represented as an element with this form:
40971 <reg name="@var{name}"
40972 bitsize="@var{size}"
40973 @r{[}regnum="@var{num}"@r{]}
40974 @r{[}save-restore="@var{save-restore}"@r{]}
40975 @r{[}type="@var{type}"@r{]}
40976 @r{[}group="@var{group}"@r{]}/>
40980 The components are as follows:
40985 The register's name; it must be unique within the target description.
40988 The register's size, in bits.
40991 The register's number. If omitted, a register's number is one greater
40992 than that of the previous register (either in the current feature or in
40993 a preceding feature); the first register in the target description
40994 defaults to zero. This register number is used to read or write
40995 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40996 packets, and registers appear in the @code{g} and @code{G} packets
40997 in order of increasing register number.
41000 Whether the register should be preserved across inferior function
41001 calls; this must be either @code{yes} or @code{no}. The default is
41002 @code{yes}, which is appropriate for most registers except for
41003 some system control registers; this is not related to the target's
41007 The type of the register. @var{type} may be a predefined type, a type
41008 defined in the current feature, or one of the special types @code{int}
41009 and @code{float}. @code{int} is an integer type of the correct size
41010 for @var{bitsize}, and @code{float} is a floating point type (in the
41011 architecture's normal floating point format) of the correct size for
41012 @var{bitsize}. The default is @code{int}.
41015 The register group to which this register belongs. @var{group} must
41016 be either @code{general}, @code{float}, or @code{vector}. If no
41017 @var{group} is specified, @value{GDBN} will not display the register
41018 in @code{info registers}.
41022 @node Predefined Target Types
41023 @section Predefined Target Types
41024 @cindex target descriptions, predefined types
41026 Type definitions in the self-description can build up composite types
41027 from basic building blocks, but can not define fundamental types. Instead,
41028 standard identifiers are provided by @value{GDBN} for the fundamental
41029 types. The currently supported types are:
41038 Signed integer types holding the specified number of bits.
41045 Unsigned integer types holding the specified number of bits.
41049 Pointers to unspecified code and data. The program counter and
41050 any dedicated return address register may be marked as code
41051 pointers; printing a code pointer converts it into a symbolic
41052 address. The stack pointer and any dedicated address registers
41053 may be marked as data pointers.
41056 Single precision IEEE floating point.
41059 Double precision IEEE floating point.
41062 The 12-byte extended precision format used by ARM FPA registers.
41065 The 10-byte extended precision format used by x87 registers.
41068 32bit @sc{eflags} register used by x86.
41071 32bit @sc{mxcsr} register used by x86.
41075 @node Standard Target Features
41076 @section Standard Target Features
41077 @cindex target descriptions, standard features
41079 A target description must contain either no registers or all the
41080 target's registers. If the description contains no registers, then
41081 @value{GDBN} will assume a default register layout, selected based on
41082 the architecture. If the description contains any registers, the
41083 default layout will not be used; the standard registers must be
41084 described in the target description, in such a way that @value{GDBN}
41085 can recognize them.
41087 This is accomplished by giving specific names to feature elements
41088 which contain standard registers. @value{GDBN} will look for features
41089 with those names and verify that they contain the expected registers;
41090 if any known feature is missing required registers, or if any required
41091 feature is missing, @value{GDBN} will reject the target
41092 description. You can add additional registers to any of the
41093 standard features --- @value{GDBN} will display them just as if
41094 they were added to an unrecognized feature.
41096 This section lists the known features and their expected contents.
41097 Sample XML documents for these features are included in the
41098 @value{GDBN} source tree, in the directory @file{gdb/features}.
41100 Names recognized by @value{GDBN} should include the name of the
41101 company or organization which selected the name, and the overall
41102 architecture to which the feature applies; so e.g.@: the feature
41103 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41105 The names of registers are not case sensitive for the purpose
41106 of recognizing standard features, but @value{GDBN} will only display
41107 registers using the capitalization used in the description.
41110 * AArch64 Features::
41115 * PowerPC Features::
41120 @node AArch64 Features
41121 @subsection AArch64 Features
41122 @cindex target descriptions, AArch64 features
41124 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41125 targets. It should contain registers @samp{x0} through @samp{x30},
41126 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41128 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41129 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41133 @subsection ARM Features
41134 @cindex target descriptions, ARM features
41136 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41138 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41139 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41141 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41142 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41143 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41146 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41147 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41149 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41150 it should contain at least registers @samp{wR0} through @samp{wR15} and
41151 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41152 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41154 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41155 should contain at least registers @samp{d0} through @samp{d15}. If
41156 they are present, @samp{d16} through @samp{d31} should also be included.
41157 @value{GDBN} will synthesize the single-precision registers from
41158 halves of the double-precision registers.
41160 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41161 need to contain registers; it instructs @value{GDBN} to display the
41162 VFP double-precision registers as vectors and to synthesize the
41163 quad-precision registers from pairs of double-precision registers.
41164 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41165 be present and include 32 double-precision registers.
41167 @node i386 Features
41168 @subsection i386 Features
41169 @cindex target descriptions, i386 features
41171 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41172 targets. It should describe the following registers:
41176 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41178 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41180 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41181 @samp{fs}, @samp{gs}
41183 @samp{st0} through @samp{st7}
41185 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41186 @samp{foseg}, @samp{fooff} and @samp{fop}
41189 The register sets may be different, depending on the target.
41191 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41192 describe registers:
41196 @samp{xmm0} through @samp{xmm7} for i386
41198 @samp{xmm0} through @samp{xmm15} for amd64
41203 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41204 @samp{org.gnu.gdb.i386.sse} feature. It should
41205 describe the upper 128 bits of @sc{ymm} registers:
41209 @samp{ymm0h} through @samp{ymm7h} for i386
41211 @samp{ymm0h} through @samp{ymm15h} for amd64
41214 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41215 describe a single register, @samp{orig_eax}.
41217 @node MIPS Features
41218 @subsection @acronym{MIPS} Features
41219 @cindex target descriptions, @acronym{MIPS} features
41221 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41222 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41223 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41226 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41227 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41228 registers. They may be 32-bit or 64-bit depending on the target.
41230 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41231 it may be optional in a future version of @value{GDBN}. It should
41232 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41233 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41235 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41236 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41237 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41238 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41240 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41241 contain a single register, @samp{restart}, which is used by the
41242 Linux kernel to control restartable syscalls.
41244 @node M68K Features
41245 @subsection M68K Features
41246 @cindex target descriptions, M68K features
41249 @item @samp{org.gnu.gdb.m68k.core}
41250 @itemx @samp{org.gnu.gdb.coldfire.core}
41251 @itemx @samp{org.gnu.gdb.fido.core}
41252 One of those features must be always present.
41253 The feature that is present determines which flavor of m68k is
41254 used. The feature that is present should contain registers
41255 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41256 @samp{sp}, @samp{ps} and @samp{pc}.
41258 @item @samp{org.gnu.gdb.coldfire.fp}
41259 This feature is optional. If present, it should contain registers
41260 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41264 @node PowerPC Features
41265 @subsection PowerPC Features
41266 @cindex target descriptions, PowerPC features
41268 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41269 targets. It should contain registers @samp{r0} through @samp{r31},
41270 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41271 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41273 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41274 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41276 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41277 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41280 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41281 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41282 will combine these registers with the floating point registers
41283 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41284 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41285 through @samp{vs63}, the set of vector registers for POWER7.
41287 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41288 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41289 @samp{spefscr}. SPE targets should provide 32-bit registers in
41290 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41291 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41292 these to present registers @samp{ev0} through @samp{ev31} to the
41295 @node TIC6x Features
41296 @subsection TMS320C6x Features
41297 @cindex target descriptions, TIC6x features
41298 @cindex target descriptions, TMS320C6x features
41299 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41300 targets. It should contain registers @samp{A0} through @samp{A15},
41301 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41303 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41304 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41305 through @samp{B31}.
41307 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41308 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41310 @node Operating System Information
41311 @appendix Operating System Information
41312 @cindex operating system information
41318 Users of @value{GDBN} often wish to obtain information about the state of
41319 the operating system running on the target---for example the list of
41320 processes, or the list of open files. This section describes the
41321 mechanism that makes it possible. This mechanism is similar to the
41322 target features mechanism (@pxref{Target Descriptions}), but focuses
41323 on a different aspect of target.
41325 Operating system information is retrived from the target via the
41326 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41327 read}). The object name in the request should be @samp{osdata}, and
41328 the @var{annex} identifies the data to be fetched.
41331 @appendixsection Process list
41332 @cindex operating system information, process list
41334 When requesting the process list, the @var{annex} field in the
41335 @samp{qXfer} request should be @samp{processes}. The returned data is
41336 an XML document. The formal syntax of this document is defined in
41337 @file{gdb/features/osdata.dtd}.
41339 An example document is:
41342 <?xml version="1.0"?>
41343 <!DOCTYPE target SYSTEM "osdata.dtd">
41344 <osdata type="processes">
41346 <column name="pid">1</column>
41347 <column name="user">root</column>
41348 <column name="command">/sbin/init</column>
41349 <column name="cores">1,2,3</column>
41354 Each item should include a column whose name is @samp{pid}. The value
41355 of that column should identify the process on the target. The
41356 @samp{user} and @samp{command} columns are optional, and will be
41357 displayed by @value{GDBN}. The @samp{cores} column, if present,
41358 should contain a comma-separated list of cores that this process
41359 is running on. Target may provide additional columns,
41360 which @value{GDBN} currently ignores.
41362 @node Trace File Format
41363 @appendix Trace File Format
41364 @cindex trace file format
41366 The trace file comes in three parts: a header, a textual description
41367 section, and a trace frame section with binary data.
41369 The header has the form @code{\x7fTRACE0\n}. The first byte is
41370 @code{0x7f} so as to indicate that the file contains binary data,
41371 while the @code{0} is a version number that may have different values
41374 The description section consists of multiple lines of @sc{ascii} text
41375 separated by newline characters (@code{0xa}). The lines may include a
41376 variety of optional descriptive or context-setting information, such
41377 as tracepoint definitions or register set size. @value{GDBN} will
41378 ignore any line that it does not recognize. An empty line marks the end
41381 @c FIXME add some specific types of data
41383 The trace frame section consists of a number of consecutive frames.
41384 Each frame begins with a two-byte tracepoint number, followed by a
41385 four-byte size giving the amount of data in the frame. The data in
41386 the frame consists of a number of blocks, each introduced by a
41387 character indicating its type (at least register, memory, and trace
41388 state variable). The data in this section is raw binary, not a
41389 hexadecimal or other encoding; its endianness matches the target's
41392 @c FIXME bi-arch may require endianness/arch info in description section
41395 @item R @var{bytes}
41396 Register block. The number and ordering of bytes matches that of a
41397 @code{g} packet in the remote protocol. Note that these are the
41398 actual bytes, in target order and @value{GDBN} register order, not a
41399 hexadecimal encoding.
41401 @item M @var{address} @var{length} @var{bytes}...
41402 Memory block. This is a contiguous block of memory, at the 8-byte
41403 address @var{address}, with a 2-byte length @var{length}, followed by
41404 @var{length} bytes.
41406 @item V @var{number} @var{value}
41407 Trace state variable block. This records the 8-byte signed value
41408 @var{value} of trace state variable numbered @var{number}.
41412 Future enhancements of the trace file format may include additional types
41415 @node Index Section Format
41416 @appendix @code{.gdb_index} section format
41417 @cindex .gdb_index section format
41418 @cindex index section format
41420 This section documents the index section that is created by @code{save
41421 gdb-index} (@pxref{Index Files}). The index section is
41422 DWARF-specific; some knowledge of DWARF is assumed in this
41425 The mapped index file format is designed to be directly
41426 @code{mmap}able on any architecture. In most cases, a datum is
41427 represented using a little-endian 32-bit integer value, called an
41428 @code{offset_type}. Big endian machines must byte-swap the values
41429 before using them. Exceptions to this rule are noted. The data is
41430 laid out such that alignment is always respected.
41432 A mapped index consists of several areas, laid out in order.
41436 The file header. This is a sequence of values, of @code{offset_type}
41437 unless otherwise noted:
41441 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41442 Version 4 uses a different hashing function from versions 5 and 6.
41443 Version 6 includes symbols for inlined functions, whereas versions 4
41444 and 5 do not. Version 7 adds attributes to the CU indices in the
41445 symbol table. Version 8 specifies that symbols from DWARF type units
41446 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41447 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41449 @value{GDBN} will only read version 4, 5, or 6 indices
41450 by specifying @code{set use-deprecated-index-sections on}.
41451 GDB has a workaround for potentially broken version 7 indices so it is
41452 currently not flagged as deprecated.
41455 The offset, from the start of the file, of the CU list.
41458 The offset, from the start of the file, of the types CU list. Note
41459 that this area can be empty, in which case this offset will be equal
41460 to the next offset.
41463 The offset, from the start of the file, of the address area.
41466 The offset, from the start of the file, of the symbol table.
41469 The offset, from the start of the file, of the constant pool.
41473 The CU list. This is a sequence of pairs of 64-bit little-endian
41474 values, sorted by the CU offset. The first element in each pair is
41475 the offset of a CU in the @code{.debug_info} section. The second
41476 element in each pair is the length of that CU. References to a CU
41477 elsewhere in the map are done using a CU index, which is just the
41478 0-based index into this table. Note that if there are type CUs, then
41479 conceptually CUs and type CUs form a single list for the purposes of
41483 The types CU list. This is a sequence of triplets of 64-bit
41484 little-endian values. In a triplet, the first value is the CU offset,
41485 the second value is the type offset in the CU, and the third value is
41486 the type signature. The types CU list is not sorted.
41489 The address area. The address area consists of a sequence of address
41490 entries. Each address entry has three elements:
41494 The low address. This is a 64-bit little-endian value.
41497 The high address. This is a 64-bit little-endian value. Like
41498 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41501 The CU index. This is an @code{offset_type} value.
41505 The symbol table. This is an open-addressed hash table. The size of
41506 the hash table is always a power of 2.
41508 Each slot in the hash table consists of a pair of @code{offset_type}
41509 values. The first value is the offset of the symbol's name in the
41510 constant pool. The second value is the offset of the CU vector in the
41513 If both values are 0, then this slot in the hash table is empty. This
41514 is ok because while 0 is a valid constant pool index, it cannot be a
41515 valid index for both a string and a CU vector.
41517 The hash value for a table entry is computed by applying an
41518 iterative hash function to the symbol's name. Starting with an
41519 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41520 the string is incorporated into the hash using the formula depending on the
41525 The formula is @code{r = r * 67 + c - 113}.
41527 @item Versions 5 to 7
41528 The formula is @code{r = r * 67 + tolower (c) - 113}.
41531 The terminating @samp{\0} is not incorporated into the hash.
41533 The step size used in the hash table is computed via
41534 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41535 value, and @samp{size} is the size of the hash table. The step size
41536 is used to find the next candidate slot when handling a hash
41539 The names of C@t{++} symbols in the hash table are canonicalized. We
41540 don't currently have a simple description of the canonicalization
41541 algorithm; if you intend to create new index sections, you must read
41545 The constant pool. This is simply a bunch of bytes. It is organized
41546 so that alignment is correct: CU vectors are stored first, followed by
41549 A CU vector in the constant pool is a sequence of @code{offset_type}
41550 values. The first value is the number of CU indices in the vector.
41551 Each subsequent value is the index and symbol attributes of a CU in
41552 the CU list. This element in the hash table is used to indicate which
41553 CUs define the symbol and how the symbol is used.
41554 See below for the format of each CU index+attributes entry.
41556 A string in the constant pool is zero-terminated.
41559 Attributes were added to CU index values in @code{.gdb_index} version 7.
41560 If a symbol has multiple uses within a CU then there is one
41561 CU index+attributes value for each use.
41563 The format of each CU index+attributes entry is as follows
41569 This is the index of the CU in the CU list.
41571 These bits are reserved for future purposes and must be zero.
41573 The kind of the symbol in the CU.
41577 This value is reserved and should not be used.
41578 By reserving zero the full @code{offset_type} value is backwards compatible
41579 with previous versions of the index.
41581 The symbol is a type.
41583 The symbol is a variable or an enum value.
41585 The symbol is a function.
41587 Any other kind of symbol.
41589 These values are reserved.
41593 This bit is zero if the value is global and one if it is static.
41595 The determination of whether a symbol is global or static is complicated.
41596 The authorative reference is the file @file{dwarf2read.c} in
41597 @value{GDBN} sources.
41601 This pseudo-code describes the computation of a symbol's kind and
41602 global/static attributes in the index.
41605 is_external = get_attribute (die, DW_AT_external);
41606 language = get_attribute (cu_die, DW_AT_language);
41609 case DW_TAG_typedef:
41610 case DW_TAG_base_type:
41611 case DW_TAG_subrange_type:
41615 case DW_TAG_enumerator:
41617 is_static = (language != CPLUS && language != JAVA);
41619 case DW_TAG_subprogram:
41621 is_static = ! (is_external || language == ADA);
41623 case DW_TAG_constant:
41625 is_static = ! is_external;
41627 case DW_TAG_variable:
41629 is_static = ! is_external;
41631 case DW_TAG_namespace:
41635 case DW_TAG_class_type:
41636 case DW_TAG_interface_type:
41637 case DW_TAG_structure_type:
41638 case DW_TAG_union_type:
41639 case DW_TAG_enumeration_type:
41641 is_static = (language != CPLUS && language != JAVA);
41649 @appendix Manual pages
41653 * gdb man:: The GNU Debugger man page
41654 * gdbserver man:: Remote Server for the GNU Debugger man page
41655 * gcore man:: Generate a core file of a running program
41656 * gdbinit man:: gdbinit scripts
41662 @c man title gdb The GNU Debugger
41664 @c man begin SYNOPSIS gdb
41665 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41666 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41667 [@option{-b}@w{ }@var{bps}]
41668 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41669 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41670 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41671 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41672 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41675 @c man begin DESCRIPTION gdb
41676 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41677 going on ``inside'' another program while it executes -- or what another
41678 program was doing at the moment it crashed.
41680 @value{GDBN} can do four main kinds of things (plus other things in support of
41681 these) to help you catch bugs in the act:
41685 Start your program, specifying anything that might affect its behavior.
41688 Make your program stop on specified conditions.
41691 Examine what has happened, when your program has stopped.
41694 Change things in your program, so you can experiment with correcting the
41695 effects of one bug and go on to learn about another.
41698 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41701 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41702 commands from the terminal until you tell it to exit with the @value{GDBN}
41703 command @code{quit}. You can get online help from @value{GDBN} itself
41704 by using the command @code{help}.
41706 You can run @code{gdb} with no arguments or options; but the most
41707 usual way to start @value{GDBN} is with one argument or two, specifying an
41708 executable program as the argument:
41714 You can also start with both an executable program and a core file specified:
41720 You can, instead, specify a process ID as a second argument, if you want
41721 to debug a running process:
41729 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41730 named @file{1234}; @value{GDBN} does check for a core file first).
41731 With option @option{-p} you can omit the @var{program} filename.
41733 Here are some of the most frequently needed @value{GDBN} commands:
41735 @c pod2man highlights the right hand side of the @item lines.
41737 @item break [@var{file}:]@var{functiop}
41738 Set a breakpoint at @var{function} (in @var{file}).
41740 @item run [@var{arglist}]
41741 Start your program (with @var{arglist}, if specified).
41744 Backtrace: display the program stack.
41746 @item print @var{expr}
41747 Display the value of an expression.
41750 Continue running your program (after stopping, e.g. at a breakpoint).
41753 Execute next program line (after stopping); step @emph{over} any
41754 function calls in the line.
41756 @item edit [@var{file}:]@var{function}
41757 look at the program line where it is presently stopped.
41759 @item list [@var{file}:]@var{function}
41760 type the text of the program in the vicinity of where it is presently stopped.
41763 Execute next program line (after stopping); step @emph{into} any
41764 function calls in the line.
41766 @item help [@var{name}]
41767 Show information about @value{GDBN} command @var{name}, or general information
41768 about using @value{GDBN}.
41771 Exit from @value{GDBN}.
41775 For full details on @value{GDBN},
41776 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41777 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41778 as the @code{gdb} entry in the @code{info} program.
41782 @c man begin OPTIONS gdb
41783 Any arguments other than options specify an executable
41784 file and core file (or process ID); that is, the first argument
41785 encountered with no
41786 associated option flag is equivalent to a @option{-se} option, and the second,
41787 if any, is equivalent to a @option{-c} option if it's the name of a file.
41789 both long and short forms; both are shown here. The long forms are also
41790 recognized if you truncate them, so long as enough of the option is
41791 present to be unambiguous. (If you prefer, you can flag option
41792 arguments with @option{+} rather than @option{-}, though we illustrate the
41793 more usual convention.)
41795 All the options and command line arguments you give are processed
41796 in sequential order. The order makes a difference when the @option{-x}
41802 List all options, with brief explanations.
41804 @item -symbols=@var{file}
41805 @itemx -s @var{file}
41806 Read symbol table from file @var{file}.
41809 Enable writing into executable and core files.
41811 @item -exec=@var{file}
41812 @itemx -e @var{file}
41813 Use file @var{file} as the executable file to execute when
41814 appropriate, and for examining pure data in conjunction with a core
41817 @item -se=@var{file}
41818 Read symbol table from file @var{file} and use it as the executable
41821 @item -core=@var{file}
41822 @itemx -c @var{file}
41823 Use file @var{file} as a core dump to examine.
41825 @item -command=@var{file}
41826 @itemx -x @var{file}
41827 Execute @value{GDBN} commands from file @var{file}.
41829 @item -ex @var{command}
41830 Execute given @value{GDBN} @var{command}.
41832 @item -directory=@var{directory}
41833 @itemx -d @var{directory}
41834 Add @var{directory} to the path to search for source files.
41837 Do not execute commands from @file{~/.gdbinit}.
41841 Do not execute commands from any @file{.gdbinit} initialization files.
41845 ``Quiet''. Do not print the introductory and copyright messages. These
41846 messages are also suppressed in batch mode.
41849 Run in batch mode. Exit with status @code{0} after processing all the command
41850 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41851 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41852 commands in the command files.
41854 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41855 download and run a program on another computer; in order to make this
41856 more useful, the message
41859 Program exited normally.
41863 (which is ordinarily issued whenever a program running under @value{GDBN} control
41864 terminates) is not issued when running in batch mode.
41866 @item -cd=@var{directory}
41867 Run @value{GDBN} using @var{directory} as its working directory,
41868 instead of the current directory.
41872 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41873 @value{GDBN} to output the full file name and line number in a standard,
41874 recognizable fashion each time a stack frame is displayed (which
41875 includes each time the program stops). This recognizable format looks
41876 like two @samp{\032} characters, followed by the file name, line number
41877 and character position separated by colons, and a newline. The
41878 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41879 characters as a signal to display the source code for the frame.
41882 Set the line speed (baud rate or bits per second) of any serial
41883 interface used by @value{GDBN} for remote debugging.
41885 @item -tty=@var{device}
41886 Run using @var{device} for your program's standard input and output.
41890 @c man begin SEEALSO gdb
41892 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41893 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41894 documentation are properly installed at your site, the command
41901 should give you access to the complete manual.
41903 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41904 Richard M. Stallman and Roland H. Pesch, July 1991.
41908 @node gdbserver man
41909 @heading gdbserver man
41911 @c man title gdbserver Remote Server for the GNU Debugger
41913 @c man begin SYNOPSIS gdbserver
41914 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41916 gdbserver --attach @var{comm} @var{pid}
41918 gdbserver --multi @var{comm}
41922 @c man begin DESCRIPTION gdbserver
41923 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41924 than the one which is running the program being debugged.
41927 @subheading Usage (server (target) side)
41930 Usage (server (target) side):
41933 First, you need to have a copy of the program you want to debug put onto
41934 the target system. The program can be stripped to save space if needed, as
41935 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41936 the @value{GDBN} running on the host system.
41938 To use the server, you log on to the target system, and run the @command{gdbserver}
41939 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41940 your program, and (c) its arguments. The general syntax is:
41943 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41946 For example, using a serial port, you might say:
41950 @c @file would wrap it as F</dev/com1>.
41951 target> gdbserver /dev/com1 emacs foo.txt
41954 target> gdbserver @file{/dev/com1} emacs foo.txt
41958 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41959 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41960 waits patiently for the host @value{GDBN} to communicate with it.
41962 To use a TCP connection, you could say:
41965 target> gdbserver host:2345 emacs foo.txt
41968 This says pretty much the same thing as the last example, except that we are
41969 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41970 that we are expecting to see a TCP connection from @code{host} to local TCP port
41971 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41972 want for the port number as long as it does not conflict with any existing TCP
41973 ports on the target system. This same port number must be used in the host
41974 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41975 you chose a port number that conflicts with another service, @command{gdbserver} will
41976 print an error message and exit.
41978 @command{gdbserver} can also attach to running programs.
41979 This is accomplished via the @option{--attach} argument. The syntax is:
41982 target> gdbserver --attach @var{comm} @var{pid}
41985 @var{pid} is the process ID of a currently running process. It isn't
41986 necessary to point @command{gdbserver} at a binary for the running process.
41988 To start @code{gdbserver} without supplying an initial command to run
41989 or process ID to attach, use the @option{--multi} command line option.
41990 In such case you should connect using @kbd{target extended-remote} to start
41991 the program you want to debug.
41994 target> gdbserver --multi @var{comm}
41998 @subheading Usage (host side)
42004 You need an unstripped copy of the target program on your host system, since
42005 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42006 would, with the target program as the first argument. (You may need to use the
42007 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42008 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42009 new command you need to know about is @code{target remote}
42010 (or @code{target extended-remote}). Its argument is either
42011 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42012 descriptor. For example:
42016 @c @file would wrap it as F</dev/ttyb>.
42017 (gdb) target remote /dev/ttyb
42020 (gdb) target remote @file{/dev/ttyb}
42025 communicates with the server via serial line @file{/dev/ttyb}, and:
42028 (gdb) target remote the-target:2345
42032 communicates via a TCP connection to port 2345 on host `the-target', where
42033 you previously started up @command{gdbserver} with the same port number. Note that for
42034 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42035 command, otherwise you may get an error that looks something like
42036 `Connection refused'.
42038 @command{gdbserver} can also debug multiple inferiors at once,
42041 the @value{GDBN} manual in node @code{Inferiors and Programs}
42042 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42045 @ref{Inferiors and Programs}.
42047 In such case use the @code{extended-remote} @value{GDBN} command variant:
42050 (gdb) target extended-remote the-target:2345
42053 The @command{gdbserver} option @option{--multi} may or may not be used in such
42057 @c man begin OPTIONS gdbserver
42058 There are three different modes for invoking @command{gdbserver}:
42063 Debug a specific program specified by its program name:
42066 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42069 The @var{comm} parameter specifies how should the server communicate
42070 with @value{GDBN}; it is either a device name (to use a serial line),
42071 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42072 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42073 debug in @var{prog}. Any remaining arguments will be passed to the
42074 program verbatim. When the program exits, @value{GDBN} will close the
42075 connection, and @code{gdbserver} will exit.
42078 Debug a specific program by specifying the process ID of a running
42082 gdbserver --attach @var{comm} @var{pid}
42085 The @var{comm} parameter is as described above. Supply the process ID
42086 of a running program in @var{pid}; @value{GDBN} will do everything
42087 else. Like with the previous mode, when the process @var{pid} exits,
42088 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42091 Multi-process mode -- debug more than one program/process:
42094 gdbserver --multi @var{comm}
42097 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42098 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42099 close the connection when a process being debugged exits, so you can
42100 debug several processes in the same session.
42103 In each of the modes you may specify these options:
42108 List all options, with brief explanations.
42111 This option causes @command{gdbserver} to print its version number and exit.
42114 @command{gdbserver} will attach to a running program. The syntax is:
42117 target> gdbserver --attach @var{comm} @var{pid}
42120 @var{pid} is the process ID of a currently running process. It isn't
42121 necessary to point @command{gdbserver} at a binary for the running process.
42124 To start @code{gdbserver} without supplying an initial command to run
42125 or process ID to attach, use this command line option.
42126 Then you can connect using @kbd{target extended-remote} and start
42127 the program you want to debug. The syntax is:
42130 target> gdbserver --multi @var{comm}
42134 Instruct @code{gdbserver} to display extra status information about the debugging
42136 This option is intended for @code{gdbserver} development and for bug reports to
42139 @item --remote-debug
42140 Instruct @code{gdbserver} to display remote protocol debug output.
42141 This option is intended for @code{gdbserver} development and for bug reports to
42145 Specify a wrapper to launch programs
42146 for debugging. The option should be followed by the name of the
42147 wrapper, then any command-line arguments to pass to the wrapper, then
42148 @kbd{--} indicating the end of the wrapper arguments.
42151 By default, @command{gdbserver} keeps the listening TCP port open, so that
42152 additional connections are possible. However, if you start @code{gdbserver}
42153 with the @option{--once} option, it will stop listening for any further
42154 connection attempts after connecting to the first @value{GDBN} session.
42156 @c --disable-packet is not documented for users.
42158 @c --disable-randomization and --no-disable-randomization are superseded by
42159 @c QDisableRandomization.
42164 @c man begin SEEALSO gdbserver
42166 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42167 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42168 documentation are properly installed at your site, the command
42174 should give you access to the complete manual.
42176 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42177 Richard M. Stallman and Roland H. Pesch, July 1991.
42184 @c man title gcore Generate a core file of a running program
42187 @c man begin SYNOPSIS gcore
42188 gcore [-o @var{filename}] @var{pid}
42192 @c man begin DESCRIPTION gcore
42193 Generate a core dump of a running program with process ID @var{pid}.
42194 Produced file is equivalent to a kernel produced core file as if the process
42195 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42196 limit). Unlike after a crash, after @command{gcore} the program remains
42197 running without any change.
42200 @c man begin OPTIONS gcore
42202 @item -o @var{filename}
42203 The optional argument
42204 @var{filename} specifies the file name where to put the core dump.
42205 If not specified, the file name defaults to @file{core.@var{pid}},
42206 where @var{pid} is the running program process ID.
42210 @c man begin SEEALSO gcore
42212 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42213 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42214 documentation are properly installed at your site, the command
42221 should give you access to the complete manual.
42223 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42224 Richard M. Stallman and Roland H. Pesch, July 1991.
42231 @c man title gdbinit GDB initialization scripts
42234 @c man begin SYNOPSIS gdbinit
42235 @ifset SYSTEM_GDBINIT
42236 @value{SYSTEM_GDBINIT}
42245 @c man begin DESCRIPTION gdbinit
42246 These files contain @value{GDBN} commands to automatically execute during
42247 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42250 the @value{GDBN} manual in node @code{Sequences}
42251 -- shell command @code{info -f gdb -n Sequences}.
42257 Please read more in
42259 the @value{GDBN} manual in node @code{Startup}
42260 -- shell command @code{info -f gdb -n Startup}.
42267 @ifset SYSTEM_GDBINIT
42268 @item @value{SYSTEM_GDBINIT}
42270 @ifclear SYSTEM_GDBINIT
42271 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42273 System-wide initialization file. It is executed unless user specified
42274 @value{GDBN} option @code{-nx} or @code{-n}.
42277 the @value{GDBN} manual in node @code{System-wide configuration}
42278 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42281 @ref{System-wide configuration}.
42285 User initialization file. It is executed unless user specified
42286 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42289 Initialization file for current directory. It may need to be enabled with
42290 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42293 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42294 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42297 @ref{Init File in the Current Directory}.
42302 @c man begin SEEALSO gdbinit
42304 gdb(1), @code{info -f gdb -n Startup}
42306 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42307 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42308 documentation are properly installed at your site, the command
42314 should give you access to the complete manual.
42316 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42317 Richard M. Stallman and Roland H. Pesch, July 1991.
42323 @node GNU Free Documentation License
42324 @appendix GNU Free Documentation License
42327 @node Concept Index
42328 @unnumbered Concept Index
42332 @node Command and Variable Index
42333 @unnumbered Command, Variable, and Function Index
42338 % I think something like @@colophon should be in texinfo. In the
42340 \long\def\colophon{\hbox to0pt{}\vfill
42341 \centerline{The body of this manual is set in}
42342 \centerline{\fontname\tenrm,}
42343 \centerline{with headings in {\bf\fontname\tenbf}}
42344 \centerline{and examples in {\tt\fontname\tentt}.}
42345 \centerline{{\it\fontname\tenit\/},}
42346 \centerline{{\bf\fontname\tenbf}, and}
42347 \centerline{{\sl\fontname\tensl\/}}
42348 \centerline{are used for emphasis.}\vfill}
42350 % Blame: doc@@cygnus.com, 1991.