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.
1271 @item -configuration
1272 @cindex @code{--configuration}
1273 This option causes @value{GDBN} to print details about its build-time
1274 configuration parameters, and then exit. These details can be
1275 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1280 @subsection What @value{GDBN} Does During Startup
1281 @cindex @value{GDBN} startup
1283 Here's the description of what @value{GDBN} does during session startup:
1287 Sets up the command interpreter as specified by the command line
1288 (@pxref{Mode Options, interpreter}).
1292 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1293 used when building @value{GDBN}; @pxref{System-wide configuration,
1294 ,System-wide configuration and settings}) and executes all the commands in
1297 @anchor{Home Directory Init File}
1299 Reads the init file (if any) in your home directory@footnote{On
1300 DOS/Windows systems, the home directory is the one pointed to by the
1301 @code{HOME} environment variable.} and executes all the commands in
1304 @anchor{Option -init-eval-command}
1306 Executes commands and command files specified by the @samp{-iex} and
1307 @samp{-ix} options in their specified order. Usually you should use the
1308 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1309 settings before @value{GDBN} init files get executed and before inferior
1313 Processes command line options and operands.
1315 @anchor{Init File in the Current Directory during Startup}
1317 Reads and executes the commands from init file (if any) in the current
1318 working directory as long as @samp{set auto-load local-gdbinit} is set to
1319 @samp{on} (@pxref{Init File in the Current Directory}).
1320 This is only done if the current directory is
1321 different from your home directory. Thus, you can have more than one
1322 init file, one generic in your home directory, and another, specific
1323 to the program you are debugging, in the directory where you invoke
1327 If the command line specified a program to debug, or a process to
1328 attach to, or a core file, @value{GDBN} loads any auto-loaded
1329 scripts provided for the program or for its loaded shared libraries.
1330 @xref{Auto-loading}.
1332 If you wish to disable the auto-loading during startup,
1333 you must do something like the following:
1336 $ gdb -iex "set auto-load python-scripts off" myprogram
1339 Option @samp{-ex} does not work because the auto-loading is then turned
1343 Executes commands and command files specified by the @samp{-ex} and
1344 @samp{-x} options in their specified order. @xref{Command Files}, for
1345 more details about @value{GDBN} command files.
1348 Reads the command history recorded in the @dfn{history file}.
1349 @xref{Command History}, for more details about the command history and the
1350 files where @value{GDBN} records it.
1353 Init files use the same syntax as @dfn{command files} (@pxref{Command
1354 Files}) and are processed by @value{GDBN} in the same way. The init
1355 file in your home directory can set options (such as @samp{set
1356 complaints}) that affect subsequent processing of command line options
1357 and operands. Init files are not executed if you use the @samp{-nx}
1358 option (@pxref{Mode Options, ,Choosing Modes}).
1360 To display the list of init files loaded by gdb at startup, you
1361 can use @kbd{gdb --help}.
1363 @cindex init file name
1364 @cindex @file{.gdbinit}
1365 @cindex @file{gdb.ini}
1366 The @value{GDBN} init files are normally called @file{.gdbinit}.
1367 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1368 the limitations of file names imposed by DOS filesystems. The Windows
1369 port of @value{GDBN} uses the standard name, but if it finds a
1370 @file{gdb.ini} file in your home directory, it warns you about that
1371 and suggests to rename the file to the standard name.
1375 @section Quitting @value{GDBN}
1376 @cindex exiting @value{GDBN}
1377 @cindex leaving @value{GDBN}
1380 @kindex quit @r{[}@var{expression}@r{]}
1381 @kindex q @r{(@code{quit})}
1382 @item quit @r{[}@var{expression}@r{]}
1384 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1385 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1386 do not supply @var{expression}, @value{GDBN} will terminate normally;
1387 otherwise it will terminate using the result of @var{expression} as the
1392 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1393 terminates the action of any @value{GDBN} command that is in progress and
1394 returns to @value{GDBN} command level. It is safe to type the interrupt
1395 character at any time because @value{GDBN} does not allow it to take effect
1396 until a time when it is safe.
1398 If you have been using @value{GDBN} to control an attached process or
1399 device, you can release it with the @code{detach} command
1400 (@pxref{Attach, ,Debugging an Already-running Process}).
1402 @node Shell Commands
1403 @section Shell Commands
1405 If you need to execute occasional shell commands during your
1406 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1407 just use the @code{shell} command.
1412 @cindex shell escape
1413 @item shell @var{command-string}
1414 @itemx !@var{command-string}
1415 Invoke a standard shell to execute @var{command-string}.
1416 Note that no space is needed between @code{!} and @var{command-string}.
1417 If it exists, the environment variable @code{SHELL} determines which
1418 shell to run. Otherwise @value{GDBN} uses the default shell
1419 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1422 The utility @code{make} is often needed in development environments.
1423 You do not have to use the @code{shell} command for this purpose in
1428 @cindex calling make
1429 @item make @var{make-args}
1430 Execute the @code{make} program with the specified
1431 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1434 @node Logging Output
1435 @section Logging Output
1436 @cindex logging @value{GDBN} output
1437 @cindex save @value{GDBN} output to a file
1439 You may want to save the output of @value{GDBN} commands to a file.
1440 There are several commands to control @value{GDBN}'s logging.
1444 @item set logging on
1446 @item set logging off
1448 @cindex logging file name
1449 @item set logging file @var{file}
1450 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1451 @item set logging overwrite [on|off]
1452 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1453 you want @code{set logging on} to overwrite the logfile instead.
1454 @item set logging redirect [on|off]
1455 By default, @value{GDBN} output will go to both the terminal and the logfile.
1456 Set @code{redirect} if you want output to go only to the log file.
1457 @kindex show logging
1459 Show the current values of the logging settings.
1463 @chapter @value{GDBN} Commands
1465 You can abbreviate a @value{GDBN} command to the first few letters of the command
1466 name, if that abbreviation is unambiguous; and you can repeat certain
1467 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1468 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1469 show you the alternatives available, if there is more than one possibility).
1472 * Command Syntax:: How to give commands to @value{GDBN}
1473 * Completion:: Command completion
1474 * Help:: How to ask @value{GDBN} for help
1477 @node Command Syntax
1478 @section Command Syntax
1480 A @value{GDBN} command is a single line of input. There is no limit on
1481 how long it can be. It starts with a command name, which is followed by
1482 arguments whose meaning depends on the command name. For example, the
1483 command @code{step} accepts an argument which is the number of times to
1484 step, as in @samp{step 5}. You can also use the @code{step} command
1485 with no arguments. Some commands do not allow any arguments.
1487 @cindex abbreviation
1488 @value{GDBN} command names may always be truncated if that abbreviation is
1489 unambiguous. Other possible command abbreviations are listed in the
1490 documentation for individual commands. In some cases, even ambiguous
1491 abbreviations are allowed; for example, @code{s} is specially defined as
1492 equivalent to @code{step} even though there are other commands whose
1493 names start with @code{s}. You can test abbreviations by using them as
1494 arguments to the @code{help} command.
1496 @cindex repeating commands
1497 @kindex RET @r{(repeat last command)}
1498 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1499 repeat the previous command. Certain commands (for example, @code{run})
1500 will not repeat this way; these are commands whose unintentional
1501 repetition might cause trouble and which you are unlikely to want to
1502 repeat. User-defined commands can disable this feature; see
1503 @ref{Define, dont-repeat}.
1505 The @code{list} and @code{x} commands, when you repeat them with
1506 @key{RET}, construct new arguments rather than repeating
1507 exactly as typed. This permits easy scanning of source or memory.
1509 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1510 output, in a way similar to the common utility @code{more}
1511 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1512 @key{RET} too many in this situation, @value{GDBN} disables command
1513 repetition after any command that generates this sort of display.
1515 @kindex # @r{(a comment)}
1517 Any text from a @kbd{#} to the end of the line is a comment; it does
1518 nothing. This is useful mainly in command files (@pxref{Command
1519 Files,,Command Files}).
1521 @cindex repeating command sequences
1522 @kindex Ctrl-o @r{(operate-and-get-next)}
1523 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1524 commands. This command accepts the current line, like @key{RET}, and
1525 then fetches the next line relative to the current line from the history
1529 @section Command Completion
1532 @cindex word completion
1533 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1534 only one possibility; it can also show you what the valid possibilities
1535 are for the next word in a command, at any time. This works for @value{GDBN}
1536 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1538 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1539 of a word. If there is only one possibility, @value{GDBN} fills in the
1540 word, and waits for you to finish the command (or press @key{RET} to
1541 enter it). For example, if you type
1543 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1544 @c complete accuracy in these examples; space introduced for clarity.
1545 @c If texinfo enhancements make it unnecessary, it would be nice to
1546 @c replace " @key" by "@key" in the following...
1548 (@value{GDBP}) info bre @key{TAB}
1552 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1553 the only @code{info} subcommand beginning with @samp{bre}:
1556 (@value{GDBP}) info breakpoints
1560 You can either press @key{RET} at this point, to run the @code{info
1561 breakpoints} command, or backspace and enter something else, if
1562 @samp{breakpoints} does not look like the command you expected. (If you
1563 were sure you wanted @code{info breakpoints} in the first place, you
1564 might as well just type @key{RET} immediately after @samp{info bre},
1565 to exploit command abbreviations rather than command completion).
1567 If there is more than one possibility for the next word when you press
1568 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1569 characters and try again, or just press @key{TAB} a second time;
1570 @value{GDBN} displays all the possible completions for that word. For
1571 example, you might want to set a breakpoint on a subroutine whose name
1572 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1573 just sounds the bell. Typing @key{TAB} again displays all the
1574 function names in your program that begin with those characters, for
1578 (@value{GDBP}) b make_ @key{TAB}
1579 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1580 make_a_section_from_file make_environ
1581 make_abs_section make_function_type
1582 make_blockvector make_pointer_type
1583 make_cleanup make_reference_type
1584 make_command make_symbol_completion_list
1585 (@value{GDBP}) b make_
1589 After displaying the available possibilities, @value{GDBN} copies your
1590 partial input (@samp{b make_} in the example) so you can finish the
1593 If you just want to see the list of alternatives in the first place, you
1594 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1595 means @kbd{@key{META} ?}. You can type this either by holding down a
1596 key designated as the @key{META} shift on your keyboard (if there is
1597 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1599 @cindex quotes in commands
1600 @cindex completion of quoted strings
1601 Sometimes the string you need, while logically a ``word'', may contain
1602 parentheses or other characters that @value{GDBN} normally excludes from
1603 its notion of a word. To permit word completion to work in this
1604 situation, you may enclose words in @code{'} (single quote marks) in
1605 @value{GDBN} commands.
1607 The most likely situation where you might need this is in typing the
1608 name of a C@t{++} function. This is because C@t{++} allows function
1609 overloading (multiple definitions of the same function, distinguished
1610 by argument type). For example, when you want to set a breakpoint you
1611 may need to distinguish whether you mean the version of @code{name}
1612 that takes an @code{int} parameter, @code{name(int)}, or the version
1613 that takes a @code{float} parameter, @code{name(float)}. To use the
1614 word-completion facilities in this situation, type a single quote
1615 @code{'} at the beginning of the function name. This alerts
1616 @value{GDBN} that it may need to consider more information than usual
1617 when you press @key{TAB} or @kbd{M-?} to request word completion:
1620 (@value{GDBP}) b 'bubble( @kbd{M-?}
1621 bubble(double,double) bubble(int,int)
1622 (@value{GDBP}) b 'bubble(
1625 In some cases, @value{GDBN} can tell that completing a name requires using
1626 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1627 completing as much as it can) if you do not type the quote in the first
1631 (@value{GDBP}) b bub @key{TAB}
1632 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1633 (@value{GDBP}) b 'bubble(
1637 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1638 you have not yet started typing the argument list when you ask for
1639 completion on an overloaded symbol.
1641 For more information about overloaded functions, see @ref{C Plus Plus
1642 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1643 overload-resolution off} to disable overload resolution;
1644 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1646 @cindex completion of structure field names
1647 @cindex structure field name completion
1648 @cindex completion of union field names
1649 @cindex union field name completion
1650 When completing in an expression which looks up a field in a
1651 structure, @value{GDBN} also tries@footnote{The completer can be
1652 confused by certain kinds of invalid expressions. Also, it only
1653 examines the static type of the expression, not the dynamic type.} to
1654 limit completions to the field names available in the type of the
1658 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1659 magic to_fputs to_rewind
1660 to_data to_isatty to_write
1661 to_delete to_put to_write_async_safe
1666 This is because the @code{gdb_stdout} is a variable of the type
1667 @code{struct ui_file} that is defined in @value{GDBN} sources as
1674 ui_file_flush_ftype *to_flush;
1675 ui_file_write_ftype *to_write;
1676 ui_file_write_async_safe_ftype *to_write_async_safe;
1677 ui_file_fputs_ftype *to_fputs;
1678 ui_file_read_ftype *to_read;
1679 ui_file_delete_ftype *to_delete;
1680 ui_file_isatty_ftype *to_isatty;
1681 ui_file_rewind_ftype *to_rewind;
1682 ui_file_put_ftype *to_put;
1689 @section Getting Help
1690 @cindex online documentation
1693 You can always ask @value{GDBN} itself for information on its commands,
1694 using the command @code{help}.
1697 @kindex h @r{(@code{help})}
1700 You can use @code{help} (abbreviated @code{h}) with no arguments to
1701 display a short list of named classes of commands:
1705 List of classes of commands:
1707 aliases -- Aliases of other commands
1708 breakpoints -- Making program stop at certain points
1709 data -- Examining data
1710 files -- Specifying and examining files
1711 internals -- Maintenance commands
1712 obscure -- Obscure features
1713 running -- Running the program
1714 stack -- Examining the stack
1715 status -- Status inquiries
1716 support -- Support facilities
1717 tracepoints -- Tracing of program execution without
1718 stopping the program
1719 user-defined -- User-defined commands
1721 Type "help" followed by a class name for a list of
1722 commands in that class.
1723 Type "help" followed by command name for full
1725 Command name abbreviations are allowed if unambiguous.
1728 @c the above line break eliminates huge line overfull...
1730 @item help @var{class}
1731 Using one of the general help classes as an argument, you can get a
1732 list of the individual commands in that class. For example, here is the
1733 help display for the class @code{status}:
1736 (@value{GDBP}) help status
1741 @c Line break in "show" line falsifies real output, but needed
1742 @c to fit in smallbook page size.
1743 info -- Generic command for showing things
1744 about the program being debugged
1745 show -- Generic command for showing things
1748 Type "help" followed by command name for full
1750 Command name abbreviations are allowed if unambiguous.
1754 @item help @var{command}
1755 With a command name as @code{help} argument, @value{GDBN} displays a
1756 short paragraph on how to use that command.
1759 @item apropos @var{args}
1760 The @code{apropos} command searches through all of the @value{GDBN}
1761 commands, and their documentation, for the regular expression specified in
1762 @var{args}. It prints out all matches found. For example:
1773 alias -- Define a new command that is an alias of an existing command
1774 aliases -- Aliases of other commands
1775 d -- Delete some breakpoints or auto-display expressions
1776 del -- Delete some breakpoints or auto-display expressions
1777 delete -- Delete some breakpoints or auto-display expressions
1782 @item complete @var{args}
1783 The @code{complete @var{args}} command lists all the possible completions
1784 for the beginning of a command. Use @var{args} to specify the beginning of the
1785 command you want completed. For example:
1791 @noindent results in:
1802 @noindent This is intended for use by @sc{gnu} Emacs.
1805 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1806 and @code{show} to inquire about the state of your program, or the state
1807 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1808 manual introduces each of them in the appropriate context. The listings
1809 under @code{info} and under @code{show} in the Command, Variable, and
1810 Function Index point to all the sub-commands. @xref{Command and Variable
1816 @kindex i @r{(@code{info})}
1818 This command (abbreviated @code{i}) is for describing the state of your
1819 program. For example, you can show the arguments passed to a function
1820 with @code{info args}, list the registers currently in use with @code{info
1821 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1822 You can get a complete list of the @code{info} sub-commands with
1823 @w{@code{help info}}.
1827 You can assign the result of an expression to an environment variable with
1828 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1829 @code{set prompt $}.
1833 In contrast to @code{info}, @code{show} is for describing the state of
1834 @value{GDBN} itself.
1835 You can change most of the things you can @code{show}, by using the
1836 related command @code{set}; for example, you can control what number
1837 system is used for displays with @code{set radix}, or simply inquire
1838 which is currently in use with @code{show radix}.
1841 To display all the settable parameters and their current
1842 values, you can use @code{show} with no arguments; you may also use
1843 @code{info set}. Both commands produce the same display.
1844 @c FIXME: "info set" violates the rule that "info" is for state of
1845 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1846 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1850 Here are several miscellaneous @code{show} subcommands, all of which are
1851 exceptional in lacking corresponding @code{set} commands:
1854 @kindex show version
1855 @cindex @value{GDBN} version number
1857 Show what version of @value{GDBN} is running. You should include this
1858 information in @value{GDBN} bug-reports. If multiple versions of
1859 @value{GDBN} are in use at your site, you may need to determine which
1860 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1861 commands are introduced, and old ones may wither away. Also, many
1862 system vendors ship variant versions of @value{GDBN}, and there are
1863 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1864 The version number is the same as the one announced when you start
1867 @kindex show copying
1868 @kindex info copying
1869 @cindex display @value{GDBN} copyright
1872 Display information about permission for copying @value{GDBN}.
1874 @kindex show warranty
1875 @kindex info warranty
1877 @itemx info warranty
1878 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1879 if your version of @value{GDBN} comes with one.
1881 @kindex show configuration
1882 @item show configuration
1883 Display detailed information about the way @value{GDBN} was configured
1884 when it was built. This displays the optional arguments passed to the
1885 @file{configure} script and also configuration parameters detected
1886 automatically by @command{configure}. When reporting a @value{GDBN}
1887 bug (@pxref{GDB Bugs}), it is important to include this information in
1893 @chapter Running Programs Under @value{GDBN}
1895 When you run a program under @value{GDBN}, you must first generate
1896 debugging information when you compile it.
1898 You may start @value{GDBN} with its arguments, if any, in an environment
1899 of your choice. If you are doing native debugging, you may redirect
1900 your program's input and output, debug an already running process, or
1901 kill a child process.
1904 * Compilation:: Compiling for debugging
1905 * Starting:: Starting your program
1906 * Arguments:: Your program's arguments
1907 * Environment:: Your program's environment
1909 * Working Directory:: Your program's working directory
1910 * Input/Output:: Your program's input and output
1911 * Attach:: Debugging an already-running process
1912 * Kill Process:: Killing the child process
1914 * Inferiors and Programs:: Debugging multiple inferiors and programs
1915 * Threads:: Debugging programs with multiple threads
1916 * Forks:: Debugging forks
1917 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1921 @section Compiling for Debugging
1923 In order to debug a program effectively, you need to generate
1924 debugging information when you compile it. This debugging information
1925 is stored in the object file; it describes the data type of each
1926 variable or function and the correspondence between source line numbers
1927 and addresses in the executable code.
1929 To request debugging information, specify the @samp{-g} option when you run
1932 Programs that are to be shipped to your customers are compiled with
1933 optimizations, using the @samp{-O} compiler option. However, some
1934 compilers are unable to handle the @samp{-g} and @samp{-O} options
1935 together. Using those compilers, you cannot generate optimized
1936 executables containing debugging information.
1938 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1939 without @samp{-O}, making it possible to debug optimized code. We
1940 recommend that you @emph{always} use @samp{-g} whenever you compile a
1941 program. You may think your program is correct, but there is no sense
1942 in pushing your luck. For more information, see @ref{Optimized Code}.
1944 Older versions of the @sc{gnu} C compiler permitted a variant option
1945 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1946 format; if your @sc{gnu} C compiler has this option, do not use it.
1948 @value{GDBN} knows about preprocessor macros and can show you their
1949 expansion (@pxref{Macros}). Most compilers do not include information
1950 about preprocessor macros in the debugging information if you specify
1951 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1952 the @sc{gnu} C compiler, provides macro information if you are using
1953 the DWARF debugging format, and specify the option @option{-g3}.
1955 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1956 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1957 information on @value{NGCC} options affecting debug information.
1959 You will have the best debugging experience if you use the latest
1960 version of the DWARF debugging format that your compiler supports.
1961 DWARF is currently the most expressive and best supported debugging
1962 format in @value{GDBN}.
1966 @section Starting your Program
1972 @kindex r @r{(@code{run})}
1975 Use the @code{run} command to start your program under @value{GDBN}.
1976 You must first specify the program name (except on VxWorks) with an
1977 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1978 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1979 (@pxref{Files, ,Commands to Specify Files}).
1983 If you are running your program in an execution environment that
1984 supports processes, @code{run} creates an inferior process and makes
1985 that process run your program. In some environments without processes,
1986 @code{run} jumps to the start of your program. Other targets,
1987 like @samp{remote}, are always running. If you get an error
1988 message like this one:
1991 The "remote" target does not support "run".
1992 Try "help target" or "continue".
1996 then use @code{continue} to run your program. You may need @code{load}
1997 first (@pxref{load}).
1999 The execution of a program is affected by certain information it
2000 receives from its superior. @value{GDBN} provides ways to specify this
2001 information, which you must do @emph{before} starting your program. (You
2002 can change it after starting your program, but such changes only affect
2003 your program the next time you start it.) This information may be
2004 divided into four categories:
2007 @item The @emph{arguments.}
2008 Specify the arguments to give your program as the arguments of the
2009 @code{run} command. If a shell is available on your target, the shell
2010 is used to pass the arguments, so that you may use normal conventions
2011 (such as wildcard expansion or variable substitution) in describing
2013 In Unix systems, you can control which shell is used with the
2014 @code{SHELL} environment variable.
2015 @xref{Arguments, ,Your Program's Arguments}.
2017 @item The @emph{environment.}
2018 Your program normally inherits its environment from @value{GDBN}, but you can
2019 use the @value{GDBN} commands @code{set environment} and @code{unset
2020 environment} to change parts of the environment that affect
2021 your program. @xref{Environment, ,Your Program's Environment}.
2023 @item The @emph{working directory.}
2024 Your program inherits its working directory from @value{GDBN}. You can set
2025 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2026 @xref{Working Directory, ,Your Program's Working Directory}.
2028 @item The @emph{standard input and output.}
2029 Your program normally uses the same device for standard input and
2030 standard output as @value{GDBN} is using. You can redirect input and output
2031 in the @code{run} command line, or you can use the @code{tty} command to
2032 set a different device for your program.
2033 @xref{Input/Output, ,Your Program's Input and Output}.
2036 @emph{Warning:} While input and output redirection work, you cannot use
2037 pipes to pass the output of the program you are debugging to another
2038 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2042 When you issue the @code{run} command, your program begins to execute
2043 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2044 of how to arrange for your program to stop. Once your program has
2045 stopped, you may call functions in your program, using the @code{print}
2046 or @code{call} commands. @xref{Data, ,Examining Data}.
2048 If the modification time of your symbol file has changed since the last
2049 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2050 table, and reads it again. When it does this, @value{GDBN} tries to retain
2051 your current breakpoints.
2056 @cindex run to main procedure
2057 The name of the main procedure can vary from language to language.
2058 With C or C@t{++}, the main procedure name is always @code{main}, but
2059 other languages such as Ada do not require a specific name for their
2060 main procedure. The debugger provides a convenient way to start the
2061 execution of the program and to stop at the beginning of the main
2062 procedure, depending on the language used.
2064 The @samp{start} command does the equivalent of setting a temporary
2065 breakpoint at the beginning of the main procedure and then invoking
2066 the @samp{run} command.
2068 @cindex elaboration phase
2069 Some programs contain an @dfn{elaboration} phase where some startup code is
2070 executed before the main procedure is called. This depends on the
2071 languages used to write your program. In C@t{++}, for instance,
2072 constructors for static and global objects are executed before
2073 @code{main} is called. It is therefore possible that the debugger stops
2074 before reaching the main procedure. However, the temporary breakpoint
2075 will remain to halt execution.
2077 Specify the arguments to give to your program as arguments to the
2078 @samp{start} command. These arguments will be given verbatim to the
2079 underlying @samp{run} command. Note that the same arguments will be
2080 reused if no argument is provided during subsequent calls to
2081 @samp{start} or @samp{run}.
2083 It is sometimes necessary to debug the program during elaboration. In
2084 these cases, using the @code{start} command would stop the execution of
2085 your program too late, as the program would have already completed the
2086 elaboration phase. Under these circumstances, insert breakpoints in your
2087 elaboration code before running your program.
2089 @kindex set exec-wrapper
2090 @item set exec-wrapper @var{wrapper}
2091 @itemx show exec-wrapper
2092 @itemx unset exec-wrapper
2093 When @samp{exec-wrapper} is set, the specified wrapper is used to
2094 launch programs for debugging. @value{GDBN} starts your program
2095 with a shell command of the form @kbd{exec @var{wrapper}
2096 @var{program}}. Quoting is added to @var{program} and its
2097 arguments, but not to @var{wrapper}, so you should add quotes if
2098 appropriate for your shell. The wrapper runs until it executes
2099 your program, and then @value{GDBN} takes control.
2101 You can use any program that eventually calls @code{execve} with
2102 its arguments as a wrapper. Several standard Unix utilities do
2103 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2104 with @code{exec "$@@"} will also work.
2106 For example, you can use @code{env} to pass an environment variable to
2107 the debugged program, without setting the variable in your shell's
2111 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2115 This command is available when debugging locally on most targets, excluding
2116 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2118 @kindex set disable-randomization
2119 @item set disable-randomization
2120 @itemx set disable-randomization on
2121 This option (enabled by default in @value{GDBN}) will turn off the native
2122 randomization of the virtual address space of the started program. This option
2123 is useful for multiple debugging sessions to make the execution better
2124 reproducible and memory addresses reusable across debugging sessions.
2126 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2127 On @sc{gnu}/Linux you can get the same behavior using
2130 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2133 @item set disable-randomization off
2134 Leave the behavior of the started executable unchanged. Some bugs rear their
2135 ugly heads only when the program is loaded at certain addresses. If your bug
2136 disappears when you run the program under @value{GDBN}, that might be because
2137 @value{GDBN} by default disables the address randomization on platforms, such
2138 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2139 disable-randomization off} to try to reproduce such elusive bugs.
2141 On targets where it is available, virtual address space randomization
2142 protects the programs against certain kinds of security attacks. In these
2143 cases the attacker needs to know the exact location of a concrete executable
2144 code. Randomizing its location makes it impossible to inject jumps misusing
2145 a code at its expected addresses.
2147 Prelinking shared libraries provides a startup performance advantage but it
2148 makes addresses in these libraries predictable for privileged processes by
2149 having just unprivileged access at the target system. Reading the shared
2150 library binary gives enough information for assembling the malicious code
2151 misusing it. Still even a prelinked shared library can get loaded at a new
2152 random address just requiring the regular relocation process during the
2153 startup. Shared libraries not already prelinked are always loaded at
2154 a randomly chosen address.
2156 Position independent executables (PIE) contain position independent code
2157 similar to the shared libraries and therefore such executables get loaded at
2158 a randomly chosen address upon startup. PIE executables always load even
2159 already prelinked shared libraries at a random address. You can build such
2160 executable using @command{gcc -fPIE -pie}.
2162 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2163 (as long as the randomization is enabled).
2165 @item show disable-randomization
2166 Show the current setting of the explicit disable of the native randomization of
2167 the virtual address space of the started program.
2172 @section Your Program's Arguments
2174 @cindex arguments (to your program)
2175 The arguments to your program can be specified by the arguments of the
2177 They are passed to a shell, which expands wildcard characters and
2178 performs redirection of I/O, and thence to your program. Your
2179 @code{SHELL} environment variable (if it exists) specifies what shell
2180 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2181 the default shell (@file{/bin/sh} on Unix).
2183 On non-Unix systems, the program is usually invoked directly by
2184 @value{GDBN}, which emulates I/O redirection via the appropriate system
2185 calls, and the wildcard characters are expanded by the startup code of
2186 the program, not by the shell.
2188 @code{run} with no arguments uses the same arguments used by the previous
2189 @code{run}, or those set by the @code{set args} command.
2194 Specify the arguments to be used the next time your program is run. If
2195 @code{set args} has no arguments, @code{run} executes your program
2196 with no arguments. Once you have run your program with arguments,
2197 using @code{set args} before the next @code{run} is the only way to run
2198 it again without arguments.
2202 Show the arguments to give your program when it is started.
2206 @section Your Program's Environment
2208 @cindex environment (of your program)
2209 The @dfn{environment} consists of a set of environment variables and
2210 their values. Environment variables conventionally record such things as
2211 your user name, your home directory, your terminal type, and your search
2212 path for programs to run. Usually you set up environment variables with
2213 the shell and they are inherited by all the other programs you run. When
2214 debugging, it can be useful to try running your program with a modified
2215 environment without having to start @value{GDBN} over again.
2219 @item path @var{directory}
2220 Add @var{directory} to the front of the @code{PATH} environment variable
2221 (the search path for executables) that will be passed to your program.
2222 The value of @code{PATH} used by @value{GDBN} does not change.
2223 You may specify several directory names, separated by whitespace or by a
2224 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2225 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2226 is moved to the front, so it is searched sooner.
2228 You can use the string @samp{$cwd} to refer to whatever is the current
2229 working directory at the time @value{GDBN} searches the path. If you
2230 use @samp{.} instead, it refers to the directory where you executed the
2231 @code{path} command. @value{GDBN} replaces @samp{.} in the
2232 @var{directory} argument (with the current path) before adding
2233 @var{directory} to the search path.
2234 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2235 @c document that, since repeating it would be a no-op.
2239 Display the list of search paths for executables (the @code{PATH}
2240 environment variable).
2242 @kindex show environment
2243 @item show environment @r{[}@var{varname}@r{]}
2244 Print the value of environment variable @var{varname} to be given to
2245 your program when it starts. If you do not supply @var{varname},
2246 print the names and values of all environment variables to be given to
2247 your program. You can abbreviate @code{environment} as @code{env}.
2249 @kindex set environment
2250 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2251 Set environment variable @var{varname} to @var{value}. The value
2252 changes for your program only, not for @value{GDBN} itself. @var{value} may
2253 be any string; the values of environment variables are just strings, and
2254 any interpretation is supplied by your program itself. The @var{value}
2255 parameter is optional; if it is eliminated, the variable is set to a
2257 @c "any string" here does not include leading, trailing
2258 @c blanks. Gnu asks: does anyone care?
2260 For example, this command:
2267 tells the debugged program, when subsequently run, that its user is named
2268 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2269 are not actually required.)
2271 @kindex unset environment
2272 @item unset environment @var{varname}
2273 Remove variable @var{varname} from the environment to be passed to your
2274 program. This is different from @samp{set env @var{varname} =};
2275 @code{unset environment} removes the variable from the environment,
2276 rather than assigning it an empty value.
2279 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2281 by your @code{SHELL} environment variable if it exists (or
2282 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2283 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2284 @file{.bashrc} for BASH---any variables you set in that file affect
2285 your program. You may wish to move setting of environment variables to
2286 files that are only run when you sign on, such as @file{.login} or
2289 @node Working Directory
2290 @section Your Program's Working Directory
2292 @cindex working directory (of your program)
2293 Each time you start your program with @code{run}, it inherits its
2294 working directory from the current working directory of @value{GDBN}.
2295 The @value{GDBN} working directory is initially whatever it inherited
2296 from its parent process (typically the shell), but you can specify a new
2297 working directory in @value{GDBN} with the @code{cd} command.
2299 The @value{GDBN} working directory also serves as a default for the commands
2300 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2305 @cindex change working directory
2306 @item cd @r{[}@var{directory}@r{]}
2307 Set the @value{GDBN} working directory to @var{directory}. If not
2308 given, @var{directory} uses @file{'~'}.
2312 Print the @value{GDBN} working directory.
2315 It is generally impossible to find the current working directory of
2316 the process being debugged (since a program can change its directory
2317 during its run). If you work on a system where @value{GDBN} is
2318 configured with the @file{/proc} support, you can use the @code{info
2319 proc} command (@pxref{SVR4 Process Information}) to find out the
2320 current working directory of the debuggee.
2323 @section Your Program's Input and Output
2328 By default, the program you run under @value{GDBN} does input and output to
2329 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2330 to its own terminal modes to interact with you, but it records the terminal
2331 modes your program was using and switches back to them when you continue
2332 running your program.
2335 @kindex info terminal
2337 Displays information recorded by @value{GDBN} about the terminal modes your
2341 You can redirect your program's input and/or output using shell
2342 redirection with the @code{run} command. For example,
2349 starts your program, diverting its output to the file @file{outfile}.
2352 @cindex controlling terminal
2353 Another way to specify where your program should do input and output is
2354 with the @code{tty} command. This command accepts a file name as
2355 argument, and causes this file to be the default for future @code{run}
2356 commands. It also resets the controlling terminal for the child
2357 process, for future @code{run} commands. For example,
2364 directs that processes started with subsequent @code{run} commands
2365 default to do input and output on the terminal @file{/dev/ttyb} and have
2366 that as their controlling terminal.
2368 An explicit redirection in @code{run} overrides the @code{tty} command's
2369 effect on the input/output device, but not its effect on the controlling
2372 When you use the @code{tty} command or redirect input in the @code{run}
2373 command, only the input @emph{for your program} is affected. The input
2374 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2375 for @code{set inferior-tty}.
2377 @cindex inferior tty
2378 @cindex set inferior controlling terminal
2379 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2380 display the name of the terminal that will be used for future runs of your
2384 @item set inferior-tty /dev/ttyb
2385 @kindex set inferior-tty
2386 Set the tty for the program being debugged to /dev/ttyb.
2388 @item show inferior-tty
2389 @kindex show inferior-tty
2390 Show the current tty for the program being debugged.
2394 @section Debugging an Already-running Process
2399 @item attach @var{process-id}
2400 This command attaches to a running process---one that was started
2401 outside @value{GDBN}. (@code{info files} shows your active
2402 targets.) The command takes as argument a process ID. The usual way to
2403 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2404 or with the @samp{jobs -l} shell command.
2406 @code{attach} does not repeat if you press @key{RET} a second time after
2407 executing the command.
2410 To use @code{attach}, your program must be running in an environment
2411 which supports processes; for example, @code{attach} does not work for
2412 programs on bare-board targets that lack an operating system. You must
2413 also have permission to send the process a signal.
2415 When you use @code{attach}, the debugger finds the program running in
2416 the process first by looking in the current working directory, then (if
2417 the program is not found) by using the source file search path
2418 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2419 the @code{file} command to load the program. @xref{Files, ,Commands to
2422 The first thing @value{GDBN} does after arranging to debug the specified
2423 process is to stop it. You can examine and modify an attached process
2424 with all the @value{GDBN} commands that are ordinarily available when
2425 you start processes with @code{run}. You can insert breakpoints; you
2426 can step and continue; you can modify storage. If you would rather the
2427 process continue running, you may use the @code{continue} command after
2428 attaching @value{GDBN} to the process.
2433 When you have finished debugging the attached process, you can use the
2434 @code{detach} command to release it from @value{GDBN} control. Detaching
2435 the process continues its execution. After the @code{detach} command,
2436 that process and @value{GDBN} become completely independent once more, and you
2437 are ready to @code{attach} another process or start one with @code{run}.
2438 @code{detach} does not repeat if you press @key{RET} again after
2439 executing the command.
2442 If you exit @value{GDBN} while you have an attached process, you detach
2443 that process. If you use the @code{run} command, you kill that process.
2444 By default, @value{GDBN} asks for confirmation if you try to do either of these
2445 things; you can control whether or not you need to confirm by using the
2446 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2450 @section Killing the Child Process
2455 Kill the child process in which your program is running under @value{GDBN}.
2458 This command is useful if you wish to debug a core dump instead of a
2459 running process. @value{GDBN} ignores any core dump file while your program
2462 On some operating systems, a program cannot be executed outside @value{GDBN}
2463 while you have breakpoints set on it inside @value{GDBN}. You can use the
2464 @code{kill} command in this situation to permit running your program
2465 outside the debugger.
2467 The @code{kill} command is also useful if you wish to recompile and
2468 relink your program, since on many systems it is impossible to modify an
2469 executable file while it is running in a process. In this case, when you
2470 next type @code{run}, @value{GDBN} notices that the file has changed, and
2471 reads the symbol table again (while trying to preserve your current
2472 breakpoint settings).
2474 @node Inferiors and Programs
2475 @section Debugging Multiple Inferiors and Programs
2477 @value{GDBN} lets you run and debug multiple programs in a single
2478 session. In addition, @value{GDBN} on some systems may let you run
2479 several programs simultaneously (otherwise you have to exit from one
2480 before starting another). In the most general case, you can have
2481 multiple threads of execution in each of multiple processes, launched
2482 from multiple executables.
2485 @value{GDBN} represents the state of each program execution with an
2486 object called an @dfn{inferior}. An inferior typically corresponds to
2487 a process, but is more general and applies also to targets that do not
2488 have processes. Inferiors may be created before a process runs, and
2489 may be retained after a process exits. Inferiors have unique
2490 identifiers that are different from process ids. Usually each
2491 inferior will also have its own distinct address space, although some
2492 embedded targets may have several inferiors running in different parts
2493 of a single address space. Each inferior may in turn have multiple
2494 threads running in it.
2496 To find out what inferiors exist at any moment, use @w{@code{info
2500 @kindex info inferiors
2501 @item info inferiors
2502 Print a list of all inferiors currently being managed by @value{GDBN}.
2504 @value{GDBN} displays for each inferior (in this order):
2508 the inferior number assigned by @value{GDBN}
2511 the target system's inferior identifier
2514 the name of the executable the inferior is running.
2519 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2520 indicates the current inferior.
2524 @c end table here to get a little more width for example
2527 (@value{GDBP}) info inferiors
2528 Num Description Executable
2529 2 process 2307 hello
2530 * 1 process 3401 goodbye
2533 To switch focus between inferiors, use the @code{inferior} command:
2536 @kindex inferior @var{infno}
2537 @item inferior @var{infno}
2538 Make inferior number @var{infno} the current inferior. The argument
2539 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2540 in the first field of the @samp{info inferiors} display.
2544 You can get multiple executables into a debugging session via the
2545 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2546 systems @value{GDBN} can add inferiors to the debug session
2547 automatically by following calls to @code{fork} and @code{exec}. To
2548 remove inferiors from the debugging session use the
2549 @w{@code{remove-inferiors}} command.
2552 @kindex add-inferior
2553 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2554 Adds @var{n} inferiors to be run using @var{executable} as the
2555 executable. @var{n} defaults to 1. If no executable is specified,
2556 the inferiors begins empty, with no program. You can still assign or
2557 change the program assigned to the inferior at any time by using the
2558 @code{file} command with the executable name as its argument.
2560 @kindex clone-inferior
2561 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2562 Adds @var{n} inferiors ready to execute the same program as inferior
2563 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2564 number of the current inferior. This is a convenient command when you
2565 want to run another instance of the inferior you are debugging.
2568 (@value{GDBP}) info inferiors
2569 Num Description Executable
2570 * 1 process 29964 helloworld
2571 (@value{GDBP}) clone-inferior
2574 (@value{GDBP}) info inferiors
2575 Num Description Executable
2577 * 1 process 29964 helloworld
2580 You can now simply switch focus to inferior 2 and run it.
2582 @kindex remove-inferiors
2583 @item remove-inferiors @var{infno}@dots{}
2584 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2585 possible to remove an inferior that is running with this command. For
2586 those, use the @code{kill} or @code{detach} command first.
2590 To quit debugging one of the running inferiors that is not the current
2591 inferior, you can either detach from it by using the @w{@code{detach
2592 inferior}} command (allowing it to run independently), or kill it
2593 using the @w{@code{kill inferiors}} command:
2596 @kindex detach inferiors @var{infno}@dots{}
2597 @item detach inferior @var{infno}@dots{}
2598 Detach from the inferior or inferiors identified by @value{GDBN}
2599 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2600 still stays on the list of inferiors shown by @code{info inferiors},
2601 but its Description will show @samp{<null>}.
2603 @kindex kill inferiors @var{infno}@dots{}
2604 @item kill inferiors @var{infno}@dots{}
2605 Kill the inferior or inferiors identified by @value{GDBN} inferior
2606 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2607 stays on the list of inferiors shown by @code{info inferiors}, but its
2608 Description will show @samp{<null>}.
2611 After the successful completion of a command such as @code{detach},
2612 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2613 a normal process exit, the inferior is still valid and listed with
2614 @code{info inferiors}, ready to be restarted.
2617 To be notified when inferiors are started or exit under @value{GDBN}'s
2618 control use @w{@code{set print inferior-events}}:
2621 @kindex set print inferior-events
2622 @cindex print messages on inferior start and exit
2623 @item set print inferior-events
2624 @itemx set print inferior-events on
2625 @itemx set print inferior-events off
2626 The @code{set print inferior-events} command allows you to enable or
2627 disable printing of messages when @value{GDBN} notices that new
2628 inferiors have started or that inferiors have exited or have been
2629 detached. By default, these messages will not be printed.
2631 @kindex show print inferior-events
2632 @item show print inferior-events
2633 Show whether messages will be printed when @value{GDBN} detects that
2634 inferiors have started, exited or have been detached.
2637 Many commands will work the same with multiple programs as with a
2638 single program: e.g., @code{print myglobal} will simply display the
2639 value of @code{myglobal} in the current inferior.
2642 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2643 get more info about the relationship of inferiors, programs, address
2644 spaces in a debug session. You can do that with the @w{@code{maint
2645 info program-spaces}} command.
2648 @kindex maint info program-spaces
2649 @item maint info program-spaces
2650 Print a list of all program spaces currently being managed by
2653 @value{GDBN} displays for each program space (in this order):
2657 the program space number assigned by @value{GDBN}
2660 the name of the executable loaded into the program space, with e.g.,
2661 the @code{file} command.
2666 An asterisk @samp{*} preceding the @value{GDBN} program space number
2667 indicates the current program space.
2669 In addition, below each program space line, @value{GDBN} prints extra
2670 information that isn't suitable to display in tabular form. For
2671 example, the list of inferiors bound to the program space.
2674 (@value{GDBP}) maint info program-spaces
2677 Bound inferiors: ID 1 (process 21561)
2681 Here we can see that no inferior is running the program @code{hello},
2682 while @code{process 21561} is running the program @code{goodbye}. On
2683 some targets, it is possible that multiple inferiors are bound to the
2684 same program space. The most common example is that of debugging both
2685 the parent and child processes of a @code{vfork} call. For example,
2688 (@value{GDBP}) maint info program-spaces
2691 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2694 Here, both inferior 2 and inferior 1 are running in the same program
2695 space as a result of inferior 1 having executed a @code{vfork} call.
2699 @section Debugging Programs with Multiple Threads
2701 @cindex threads of execution
2702 @cindex multiple threads
2703 @cindex switching threads
2704 In some operating systems, such as HP-UX and Solaris, a single program
2705 may have more than one @dfn{thread} of execution. The precise semantics
2706 of threads differ from one operating system to another, but in general
2707 the threads of a single program are akin to multiple processes---except
2708 that they share one address space (that is, they can all examine and
2709 modify the same variables). On the other hand, each thread has its own
2710 registers and execution stack, and perhaps private memory.
2712 @value{GDBN} provides these facilities for debugging multi-thread
2716 @item automatic notification of new threads
2717 @item @samp{thread @var{threadno}}, a command to switch among threads
2718 @item @samp{info threads}, a command to inquire about existing threads
2719 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2720 a command to apply a command to a list of threads
2721 @item thread-specific breakpoints
2722 @item @samp{set print thread-events}, which controls printing of
2723 messages on thread start and exit.
2724 @item @samp{set libthread-db-search-path @var{path}}, which lets
2725 the user specify which @code{libthread_db} to use if the default choice
2726 isn't compatible with the program.
2730 @emph{Warning:} These facilities are not yet available on every
2731 @value{GDBN} configuration where the operating system supports threads.
2732 If your @value{GDBN} does not support threads, these commands have no
2733 effect. For example, a system without thread support shows no output
2734 from @samp{info threads}, and always rejects the @code{thread} command,
2738 (@value{GDBP}) info threads
2739 (@value{GDBP}) thread 1
2740 Thread ID 1 not known. Use the "info threads" command to
2741 see the IDs of currently known threads.
2743 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2744 @c doesn't support threads"?
2747 @cindex focus of debugging
2748 @cindex current thread
2749 The @value{GDBN} thread debugging facility allows you to observe all
2750 threads while your program runs---but whenever @value{GDBN} takes
2751 control, one thread in particular is always the focus of debugging.
2752 This thread is called the @dfn{current thread}. Debugging commands show
2753 program information from the perspective of the current thread.
2755 @cindex @code{New} @var{systag} message
2756 @cindex thread identifier (system)
2757 @c FIXME-implementors!! It would be more helpful if the [New...] message
2758 @c included GDB's numeric thread handle, so you could just go to that
2759 @c thread without first checking `info threads'.
2760 Whenever @value{GDBN} detects a new thread in your program, it displays
2761 the target system's identification for the thread with a message in the
2762 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2763 whose form varies depending on the particular system. For example, on
2764 @sc{gnu}/Linux, you might see
2767 [New Thread 0x41e02940 (LWP 25582)]
2771 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2772 the @var{systag} is simply something like @samp{process 368}, with no
2775 @c FIXME!! (1) Does the [New...] message appear even for the very first
2776 @c thread of a program, or does it only appear for the
2777 @c second---i.e.@: when it becomes obvious we have a multithread
2779 @c (2) *Is* there necessarily a first thread always? Or do some
2780 @c multithread systems permit starting a program with multiple
2781 @c threads ab initio?
2783 @cindex thread number
2784 @cindex thread identifier (GDB)
2785 For debugging purposes, @value{GDBN} associates its own thread
2786 number---always a single integer---with each thread in your program.
2789 @kindex info threads
2790 @item info threads @r{[}@var{id}@dots{}@r{]}
2791 Display a summary of all threads currently in your program. Optional
2792 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2793 means to print information only about the specified thread or threads.
2794 @value{GDBN} displays for each thread (in this order):
2798 the thread number assigned by @value{GDBN}
2801 the target system's thread identifier (@var{systag})
2804 the thread's name, if one is known. A thread can either be named by
2805 the user (see @code{thread name}, below), or, in some cases, by the
2809 the current stack frame summary for that thread
2813 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2814 indicates the current thread.
2818 @c end table here to get a little more width for example
2821 (@value{GDBP}) info threads
2823 3 process 35 thread 27 0x34e5 in sigpause ()
2824 2 process 35 thread 23 0x34e5 in sigpause ()
2825 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2829 On Solaris, you can display more information about user threads with a
2830 Solaris-specific command:
2833 @item maint info sol-threads
2834 @kindex maint info sol-threads
2835 @cindex thread info (Solaris)
2836 Display info on Solaris user threads.
2840 @kindex thread @var{threadno}
2841 @item thread @var{threadno}
2842 Make thread number @var{threadno} the current thread. The command
2843 argument @var{threadno} is the internal @value{GDBN} thread number, as
2844 shown in the first field of the @samp{info threads} display.
2845 @value{GDBN} responds by displaying the system identifier of the thread
2846 you selected, and its current stack frame summary:
2849 (@value{GDBP}) thread 2
2850 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2851 #0 some_function (ignore=0x0) at example.c:8
2852 8 printf ("hello\n");
2856 As with the @samp{[New @dots{}]} message, the form of the text after
2857 @samp{Switching to} depends on your system's conventions for identifying
2860 @vindex $_thread@r{, convenience variable}
2861 The debugger convenience variable @samp{$_thread} contains the number
2862 of the current thread. You may find this useful in writing breakpoint
2863 conditional expressions, command scripts, and so forth. See
2864 @xref{Convenience Vars,, Convenience Variables}, for general
2865 information on convenience variables.
2867 @kindex thread apply
2868 @cindex apply command to several threads
2869 @item thread apply [@var{threadno} | all] @var{command}
2870 The @code{thread apply} command allows you to apply the named
2871 @var{command} to one or more threads. Specify the numbers of the
2872 threads that you want affected with the command argument
2873 @var{threadno}. It can be a single thread number, one of the numbers
2874 shown in the first field of the @samp{info threads} display; or it
2875 could be a range of thread numbers, as in @code{2-4}. To apply a
2876 command to all threads, type @kbd{thread apply all @var{command}}.
2879 @cindex name a thread
2880 @item thread name [@var{name}]
2881 This command assigns a name to the current thread. If no argument is
2882 given, any existing user-specified name is removed. The thread name
2883 appears in the @samp{info threads} display.
2885 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2886 determine the name of the thread as given by the OS. On these
2887 systems, a name specified with @samp{thread name} will override the
2888 system-give name, and removing the user-specified name will cause
2889 @value{GDBN} to once again display the system-specified name.
2892 @cindex search for a thread
2893 @item thread find [@var{regexp}]
2894 Search for and display thread ids whose name or @var{systag}
2895 matches the supplied regular expression.
2897 As well as being the complement to the @samp{thread name} command,
2898 this command also allows you to identify a thread by its target
2899 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2903 (@value{GDBN}) thread find 26688
2904 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2905 (@value{GDBN}) info thread 4
2907 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2910 @kindex set print thread-events
2911 @cindex print messages on thread start and exit
2912 @item set print thread-events
2913 @itemx set print thread-events on
2914 @itemx set print thread-events off
2915 The @code{set print thread-events} command allows you to enable or
2916 disable printing of messages when @value{GDBN} notices that new threads have
2917 started or that threads have exited. By default, these messages will
2918 be printed if detection of these events is supported by the target.
2919 Note that these messages cannot be disabled on all targets.
2921 @kindex show print thread-events
2922 @item show print thread-events
2923 Show whether messages will be printed when @value{GDBN} detects that threads
2924 have started and exited.
2927 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2928 more information about how @value{GDBN} behaves when you stop and start
2929 programs with multiple threads.
2931 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2932 watchpoints in programs with multiple threads.
2934 @anchor{set libthread-db-search-path}
2936 @kindex set libthread-db-search-path
2937 @cindex search path for @code{libthread_db}
2938 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2939 If this variable is set, @var{path} is a colon-separated list of
2940 directories @value{GDBN} will use to search for @code{libthread_db}.
2941 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2942 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2943 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2946 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2947 @code{libthread_db} library to obtain information about threads in the
2948 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2949 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2950 specific thread debugging library loading is enabled
2951 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2953 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2954 refers to the default system directories that are
2955 normally searched for loading shared libraries. The @samp{$sdir} entry
2956 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2957 (@pxref{libthread_db.so.1 file}).
2959 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2960 refers to the directory from which @code{libpthread}
2961 was loaded in the inferior process.
2963 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2964 @value{GDBN} attempts to initialize it with the current inferior process.
2965 If this initialization fails (which could happen because of a version
2966 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2967 will unload @code{libthread_db}, and continue with the next directory.
2968 If none of @code{libthread_db} libraries initialize successfully,
2969 @value{GDBN} will issue a warning and thread debugging will be disabled.
2971 Setting @code{libthread-db-search-path} is currently implemented
2972 only on some platforms.
2974 @kindex show libthread-db-search-path
2975 @item show libthread-db-search-path
2976 Display current libthread_db search path.
2978 @kindex set debug libthread-db
2979 @kindex show debug libthread-db
2980 @cindex debugging @code{libthread_db}
2981 @item set debug libthread-db
2982 @itemx show debug libthread-db
2983 Turns on or off display of @code{libthread_db}-related events.
2984 Use @code{1} to enable, @code{0} to disable.
2988 @section Debugging Forks
2990 @cindex fork, debugging programs which call
2991 @cindex multiple processes
2992 @cindex processes, multiple
2993 On most systems, @value{GDBN} has no special support for debugging
2994 programs which create additional processes using the @code{fork}
2995 function. When a program forks, @value{GDBN} will continue to debug the
2996 parent process and the child process will run unimpeded. If you have
2997 set a breakpoint in any code which the child then executes, the child
2998 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2999 will cause it to terminate.
3001 However, if you want to debug the child process there is a workaround
3002 which isn't too painful. Put a call to @code{sleep} in the code which
3003 the child process executes after the fork. It may be useful to sleep
3004 only if a certain environment variable is set, or a certain file exists,
3005 so that the delay need not occur when you don't want to run @value{GDBN}
3006 on the child. While the child is sleeping, use the @code{ps} program to
3007 get its process ID. Then tell @value{GDBN} (a new invocation of
3008 @value{GDBN} if you are also debugging the parent process) to attach to
3009 the child process (@pxref{Attach}). From that point on you can debug
3010 the child process just like any other process which you attached to.
3012 On some systems, @value{GDBN} provides support for debugging programs that
3013 create additional processes using the @code{fork} or @code{vfork} functions.
3014 Currently, the only platforms with this feature are HP-UX (11.x and later
3015 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3017 By default, when a program forks, @value{GDBN} will continue to debug
3018 the parent process and the child process will run unimpeded.
3020 If you want to follow the child process instead of the parent process,
3021 use the command @w{@code{set follow-fork-mode}}.
3024 @kindex set follow-fork-mode
3025 @item set follow-fork-mode @var{mode}
3026 Set the debugger response to a program call of @code{fork} or
3027 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3028 process. The @var{mode} argument can be:
3032 The original process is debugged after a fork. The child process runs
3033 unimpeded. This is the default.
3036 The new process is debugged after a fork. The parent process runs
3041 @kindex show follow-fork-mode
3042 @item show follow-fork-mode
3043 Display the current debugger response to a @code{fork} or @code{vfork} call.
3046 @cindex debugging multiple processes
3047 On Linux, if you want to debug both the parent and child processes, use the
3048 command @w{@code{set detach-on-fork}}.
3051 @kindex set detach-on-fork
3052 @item set detach-on-fork @var{mode}
3053 Tells gdb whether to detach one of the processes after a fork, or
3054 retain debugger control over them both.
3058 The child process (or parent process, depending on the value of
3059 @code{follow-fork-mode}) will be detached and allowed to run
3060 independently. This is the default.
3063 Both processes will be held under the control of @value{GDBN}.
3064 One process (child or parent, depending on the value of
3065 @code{follow-fork-mode}) is debugged as usual, while the other
3070 @kindex show detach-on-fork
3071 @item show detach-on-fork
3072 Show whether detach-on-fork mode is on/off.
3075 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3076 will retain control of all forked processes (including nested forks).
3077 You can list the forked processes under the control of @value{GDBN} by
3078 using the @w{@code{info inferiors}} command, and switch from one fork
3079 to another by using the @code{inferior} command (@pxref{Inferiors and
3080 Programs, ,Debugging Multiple Inferiors and Programs}).
3082 To quit debugging one of the forked processes, you can either detach
3083 from it by using the @w{@code{detach inferiors}} command (allowing it
3084 to run independently), or kill it using the @w{@code{kill inferiors}}
3085 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3088 If you ask to debug a child process and a @code{vfork} is followed by an
3089 @code{exec}, @value{GDBN} executes the new target up to the first
3090 breakpoint in the new target. If you have a breakpoint set on
3091 @code{main} in your original program, the breakpoint will also be set on
3092 the child process's @code{main}.
3094 On some systems, when a child process is spawned by @code{vfork}, you
3095 cannot debug the child or parent until an @code{exec} call completes.
3097 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3098 call executes, the new target restarts. To restart the parent
3099 process, use the @code{file} command with the parent executable name
3100 as its argument. By default, after an @code{exec} call executes,
3101 @value{GDBN} discards the symbols of the previous executable image.
3102 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3106 @kindex set follow-exec-mode
3107 @item set follow-exec-mode @var{mode}
3109 Set debugger response to a program call of @code{exec}. An
3110 @code{exec} call replaces the program image of a process.
3112 @code{follow-exec-mode} can be:
3116 @value{GDBN} creates a new inferior and rebinds the process to this
3117 new inferior. The program the process was running before the
3118 @code{exec} call can be restarted afterwards by restarting the
3124 (@value{GDBP}) info inferiors
3126 Id Description Executable
3129 process 12020 is executing new program: prog2
3130 Program exited normally.
3131 (@value{GDBP}) info inferiors
3132 Id Description Executable
3138 @value{GDBN} keeps the process bound to the same inferior. The new
3139 executable image replaces the previous executable loaded in the
3140 inferior. Restarting the inferior after the @code{exec} call, with
3141 e.g., the @code{run} command, restarts the executable the process was
3142 running after the @code{exec} call. This is the default mode.
3147 (@value{GDBP}) info inferiors
3148 Id Description Executable
3151 process 12020 is executing new program: prog2
3152 Program exited normally.
3153 (@value{GDBP}) info inferiors
3154 Id Description Executable
3161 You can use the @code{catch} command to make @value{GDBN} stop whenever
3162 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3163 Catchpoints, ,Setting Catchpoints}.
3165 @node Checkpoint/Restart
3166 @section Setting a @emph{Bookmark} to Return to Later
3171 @cindex snapshot of a process
3172 @cindex rewind program state
3174 On certain operating systems@footnote{Currently, only
3175 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3176 program's state, called a @dfn{checkpoint}, and come back to it
3179 Returning to a checkpoint effectively undoes everything that has
3180 happened in the program since the @code{checkpoint} was saved. This
3181 includes changes in memory, registers, and even (within some limits)
3182 system state. Effectively, it is like going back in time to the
3183 moment when the checkpoint was saved.
3185 Thus, if you're stepping thru a program and you think you're
3186 getting close to the point where things go wrong, you can save
3187 a checkpoint. Then, if you accidentally go too far and miss
3188 the critical statement, instead of having to restart your program
3189 from the beginning, you can just go back to the checkpoint and
3190 start again from there.
3192 This can be especially useful if it takes a lot of time or
3193 steps to reach the point where you think the bug occurs.
3195 To use the @code{checkpoint}/@code{restart} method of debugging:
3200 Save a snapshot of the debugged program's current execution state.
3201 The @code{checkpoint} command takes no arguments, but each checkpoint
3202 is assigned a small integer id, similar to a breakpoint id.
3204 @kindex info checkpoints
3205 @item info checkpoints
3206 List the checkpoints that have been saved in the current debugging
3207 session. For each checkpoint, the following information will be
3214 @item Source line, or label
3217 @kindex restart @var{checkpoint-id}
3218 @item restart @var{checkpoint-id}
3219 Restore the program state that was saved as checkpoint number
3220 @var{checkpoint-id}. All program variables, registers, stack frames
3221 etc.@: will be returned to the values that they had when the checkpoint
3222 was saved. In essence, gdb will ``wind back the clock'' to the point
3223 in time when the checkpoint was saved.
3225 Note that breakpoints, @value{GDBN} variables, command history etc.
3226 are not affected by restoring a checkpoint. In general, a checkpoint
3227 only restores things that reside in the program being debugged, not in
3230 @kindex delete checkpoint @var{checkpoint-id}
3231 @item delete checkpoint @var{checkpoint-id}
3232 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3236 Returning to a previously saved checkpoint will restore the user state
3237 of the program being debugged, plus a significant subset of the system
3238 (OS) state, including file pointers. It won't ``un-write'' data from
3239 a file, but it will rewind the file pointer to the previous location,
3240 so that the previously written data can be overwritten. For files
3241 opened in read mode, the pointer will also be restored so that the
3242 previously read data can be read again.
3244 Of course, characters that have been sent to a printer (or other
3245 external device) cannot be ``snatched back'', and characters received
3246 from eg.@: a serial device can be removed from internal program buffers,
3247 but they cannot be ``pushed back'' into the serial pipeline, ready to
3248 be received again. Similarly, the actual contents of files that have
3249 been changed cannot be restored (at this time).
3251 However, within those constraints, you actually can ``rewind'' your
3252 program to a previously saved point in time, and begin debugging it
3253 again --- and you can change the course of events so as to debug a
3254 different execution path this time.
3256 @cindex checkpoints and process id
3257 Finally, there is one bit of internal program state that will be
3258 different when you return to a checkpoint --- the program's process
3259 id. Each checkpoint will have a unique process id (or @var{pid}),
3260 and each will be different from the program's original @var{pid}.
3261 If your program has saved a local copy of its process id, this could
3262 potentially pose a problem.
3264 @subsection A Non-obvious Benefit of Using Checkpoints
3266 On some systems such as @sc{gnu}/Linux, address space randomization
3267 is performed on new processes for security reasons. This makes it
3268 difficult or impossible to set a breakpoint, or watchpoint, on an
3269 absolute address if you have to restart the program, since the
3270 absolute location of a symbol will change from one execution to the
3273 A checkpoint, however, is an @emph{identical} copy of a process.
3274 Therefore if you create a checkpoint at (eg.@:) the start of main,
3275 and simply return to that checkpoint instead of restarting the
3276 process, you can avoid the effects of address randomization and
3277 your symbols will all stay in the same place.
3280 @chapter Stopping and Continuing
3282 The principal purposes of using a debugger are so that you can stop your
3283 program before it terminates; or so that, if your program runs into
3284 trouble, you can investigate and find out why.
3286 Inside @value{GDBN}, your program may stop for any of several reasons,
3287 such as a signal, a breakpoint, or reaching a new line after a
3288 @value{GDBN} command such as @code{step}. You may then examine and
3289 change variables, set new breakpoints or remove old ones, and then
3290 continue execution. Usually, the messages shown by @value{GDBN} provide
3291 ample explanation of the status of your program---but you can also
3292 explicitly request this information at any time.
3295 @kindex info program
3297 Display information about the status of your program: whether it is
3298 running or not, what process it is, and why it stopped.
3302 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3303 * Continuing and Stepping:: Resuming execution
3304 * Skipping Over Functions and Files::
3305 Skipping over functions and files
3307 * Thread Stops:: Stopping and starting multi-thread programs
3311 @section Breakpoints, Watchpoints, and Catchpoints
3314 A @dfn{breakpoint} makes your program stop whenever a certain point in
3315 the program is reached. For each breakpoint, you can add conditions to
3316 control in finer detail whether your program stops. You can set
3317 breakpoints with the @code{break} command and its variants (@pxref{Set
3318 Breaks, ,Setting Breakpoints}), to specify the place where your program
3319 should stop by line number, function name or exact address in the
3322 On some systems, you can set breakpoints in shared libraries before
3323 the executable is run. There is a minor limitation on HP-UX systems:
3324 you must wait until the executable is run in order to set breakpoints
3325 in shared library routines that are not called directly by the program
3326 (for example, routines that are arguments in a @code{pthread_create}
3330 @cindex data breakpoints
3331 @cindex memory tracing
3332 @cindex breakpoint on memory address
3333 @cindex breakpoint on variable modification
3334 A @dfn{watchpoint} is a special breakpoint that stops your program
3335 when the value of an expression changes. The expression may be a value
3336 of a variable, or it could involve values of one or more variables
3337 combined by operators, such as @samp{a + b}. This is sometimes called
3338 @dfn{data breakpoints}. You must use a different command to set
3339 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3340 from that, you can manage a watchpoint like any other breakpoint: you
3341 enable, disable, and delete both breakpoints and watchpoints using the
3344 You can arrange to have values from your program displayed automatically
3345 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3349 @cindex breakpoint on events
3350 A @dfn{catchpoint} is another special breakpoint that stops your program
3351 when a certain kind of event occurs, such as the throwing of a C@t{++}
3352 exception or the loading of a library. As with watchpoints, you use a
3353 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3354 Catchpoints}), but aside from that, you can manage a catchpoint like any
3355 other breakpoint. (To stop when your program receives a signal, use the
3356 @code{handle} command; see @ref{Signals, ,Signals}.)
3358 @cindex breakpoint numbers
3359 @cindex numbers for breakpoints
3360 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3361 catchpoint when you create it; these numbers are successive integers
3362 starting with one. In many of the commands for controlling various
3363 features of breakpoints you use the breakpoint number to say which
3364 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3365 @dfn{disabled}; if disabled, it has no effect on your program until you
3368 @cindex breakpoint ranges
3369 @cindex ranges of breakpoints
3370 Some @value{GDBN} commands accept a range of breakpoints on which to
3371 operate. A breakpoint range is either a single breakpoint number, like
3372 @samp{5}, or two such numbers, in increasing order, separated by a
3373 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3374 all breakpoints in that range are operated on.
3377 * Set Breaks:: Setting breakpoints
3378 * Set Watchpoints:: Setting watchpoints
3379 * Set Catchpoints:: Setting catchpoints
3380 * Delete Breaks:: Deleting breakpoints
3381 * Disabling:: Disabling breakpoints
3382 * Conditions:: Break conditions
3383 * Break Commands:: Breakpoint command lists
3384 * Dynamic Printf:: Dynamic printf
3385 * Save Breakpoints:: How to save breakpoints in a file
3386 * Static Probe Points:: Listing static probe points
3387 * Error in Breakpoints:: ``Cannot insert breakpoints''
3388 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3392 @subsection Setting Breakpoints
3394 @c FIXME LMB what does GDB do if no code on line of breakpt?
3395 @c consider in particular declaration with/without initialization.
3397 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3400 @kindex b @r{(@code{break})}
3401 @vindex $bpnum@r{, convenience variable}
3402 @cindex latest breakpoint
3403 Breakpoints are set with the @code{break} command (abbreviated
3404 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3405 number of the breakpoint you've set most recently; see @ref{Convenience
3406 Vars,, Convenience Variables}, for a discussion of what you can do with
3407 convenience variables.
3410 @item break @var{location}
3411 Set a breakpoint at the given @var{location}, which can specify a
3412 function name, a line number, or an address of an instruction.
3413 (@xref{Specify Location}, for a list of all the possible ways to
3414 specify a @var{location}.) The breakpoint will stop your program just
3415 before it executes any of the code in the specified @var{location}.
3417 When using source languages that permit overloading of symbols, such as
3418 C@t{++}, a function name may refer to more than one possible place to break.
3419 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3422 It is also possible to insert a breakpoint that will stop the program
3423 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3424 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3427 When called without any arguments, @code{break} sets a breakpoint at
3428 the next instruction to be executed in the selected stack frame
3429 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3430 innermost, this makes your program stop as soon as control
3431 returns to that frame. This is similar to the effect of a
3432 @code{finish} command in the frame inside the selected frame---except
3433 that @code{finish} does not leave an active breakpoint. If you use
3434 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3435 the next time it reaches the current location; this may be useful
3438 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3439 least one instruction has been executed. If it did not do this, you
3440 would be unable to proceed past a breakpoint without first disabling the
3441 breakpoint. This rule applies whether or not the breakpoint already
3442 existed when your program stopped.
3444 @item break @dots{} if @var{cond}
3445 Set a breakpoint with condition @var{cond}; evaluate the expression
3446 @var{cond} each time the breakpoint is reached, and stop only if the
3447 value is nonzero---that is, if @var{cond} evaluates as true.
3448 @samp{@dots{}} stands for one of the possible arguments described
3449 above (or no argument) specifying where to break. @xref{Conditions,
3450 ,Break Conditions}, for more information on breakpoint conditions.
3453 @item tbreak @var{args}
3454 Set a breakpoint enabled only for one stop. @var{args} are the
3455 same as for the @code{break} command, and the breakpoint is set in the same
3456 way, but the breakpoint is automatically deleted after the first time your
3457 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3460 @cindex hardware breakpoints
3461 @item hbreak @var{args}
3462 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3463 @code{break} command and the breakpoint is set in the same way, but the
3464 breakpoint requires hardware support and some target hardware may not
3465 have this support. The main purpose of this is EPROM/ROM code
3466 debugging, so you can set a breakpoint at an instruction without
3467 changing the instruction. This can be used with the new trap-generation
3468 provided by SPARClite DSU and most x86-based targets. These targets
3469 will generate traps when a program accesses some data or instruction
3470 address that is assigned to the debug registers. However the hardware
3471 breakpoint registers can take a limited number of breakpoints. For
3472 example, on the DSU, only two data breakpoints can be set at a time, and
3473 @value{GDBN} will reject this command if more than two are used. Delete
3474 or disable unused hardware breakpoints before setting new ones
3475 (@pxref{Disabling, ,Disabling Breakpoints}).
3476 @xref{Conditions, ,Break Conditions}.
3477 For remote targets, you can restrict the number of hardware
3478 breakpoints @value{GDBN} will use, see @ref{set remote
3479 hardware-breakpoint-limit}.
3482 @item thbreak @var{args}
3483 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3484 are the same as for the @code{hbreak} command and the breakpoint is set in
3485 the same way. However, like the @code{tbreak} command,
3486 the breakpoint is automatically deleted after the
3487 first time your program stops there. Also, like the @code{hbreak}
3488 command, the breakpoint requires hardware support and some target hardware
3489 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3490 See also @ref{Conditions, ,Break Conditions}.
3493 @cindex regular expression
3494 @cindex breakpoints at functions matching a regexp
3495 @cindex set breakpoints in many functions
3496 @item rbreak @var{regex}
3497 Set breakpoints on all functions matching the regular expression
3498 @var{regex}. This command sets an unconditional breakpoint on all
3499 matches, printing a list of all breakpoints it set. Once these
3500 breakpoints are set, they are treated just like the breakpoints set with
3501 the @code{break} command. You can delete them, disable them, or make
3502 them conditional the same way as any other breakpoint.
3504 The syntax of the regular expression is the standard one used with tools
3505 like @file{grep}. Note that this is different from the syntax used by
3506 shells, so for instance @code{foo*} matches all functions that include
3507 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3508 @code{.*} leading and trailing the regular expression you supply, so to
3509 match only functions that begin with @code{foo}, use @code{^foo}.
3511 @cindex non-member C@t{++} functions, set breakpoint in
3512 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3513 breakpoints on overloaded functions that are not members of any special
3516 @cindex set breakpoints on all functions
3517 The @code{rbreak} command can be used to set breakpoints in
3518 @strong{all} the functions in a program, like this:
3521 (@value{GDBP}) rbreak .
3524 @item rbreak @var{file}:@var{regex}
3525 If @code{rbreak} is called with a filename qualification, it limits
3526 the search for functions matching the given regular expression to the
3527 specified @var{file}. This can be used, for example, to set breakpoints on
3528 every function in a given file:
3531 (@value{GDBP}) rbreak file.c:.
3534 The colon separating the filename qualifier from the regex may
3535 optionally be surrounded by spaces.
3537 @kindex info breakpoints
3538 @cindex @code{$_} and @code{info breakpoints}
3539 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3540 @itemx info break @r{[}@var{n}@dots{}@r{]}
3541 Print a table of all breakpoints, watchpoints, and catchpoints set and
3542 not deleted. Optional argument @var{n} means print information only
3543 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3544 For each breakpoint, following columns are printed:
3547 @item Breakpoint Numbers
3549 Breakpoint, watchpoint, or catchpoint.
3551 Whether the breakpoint is marked to be disabled or deleted when hit.
3552 @item Enabled or Disabled
3553 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3554 that are not enabled.
3556 Where the breakpoint is in your program, as a memory address. For a
3557 pending breakpoint whose address is not yet known, this field will
3558 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3559 library that has the symbol or line referred by breakpoint is loaded.
3560 See below for details. A breakpoint with several locations will
3561 have @samp{<MULTIPLE>} in this field---see below for details.
3563 Where the breakpoint is in the source for your program, as a file and
3564 line number. For a pending breakpoint, the original string passed to
3565 the breakpoint command will be listed as it cannot be resolved until
3566 the appropriate shared library is loaded in the future.
3570 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3571 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3572 @value{GDBN} on the host's side. If it is ``target'', then the condition
3573 is evaluated by the target. The @code{info break} command shows
3574 the condition on the line following the affected breakpoint, together with
3575 its condition evaluation mode in between parentheses.
3577 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3578 allowed to have a condition specified for it. The condition is not parsed for
3579 validity until a shared library is loaded that allows the pending
3580 breakpoint to resolve to a valid location.
3583 @code{info break} with a breakpoint
3584 number @var{n} as argument lists only that breakpoint. The
3585 convenience variable @code{$_} and the default examining-address for
3586 the @code{x} command are set to the address of the last breakpoint
3587 listed (@pxref{Memory, ,Examining Memory}).
3590 @code{info break} displays a count of the number of times the breakpoint
3591 has been hit. This is especially useful in conjunction with the
3592 @code{ignore} command. You can ignore a large number of breakpoint
3593 hits, look at the breakpoint info to see how many times the breakpoint
3594 was hit, and then run again, ignoring one less than that number. This
3595 will get you quickly to the last hit of that breakpoint.
3598 For a breakpoints with an enable count (xref) greater than 1,
3599 @code{info break} also displays that count.
3603 @value{GDBN} allows you to set any number of breakpoints at the same place in
3604 your program. There is nothing silly or meaningless about this. When
3605 the breakpoints are conditional, this is even useful
3606 (@pxref{Conditions, ,Break Conditions}).
3608 @cindex multiple locations, breakpoints
3609 @cindex breakpoints, multiple locations
3610 It is possible that a breakpoint corresponds to several locations
3611 in your program. Examples of this situation are:
3615 Multiple functions in the program may have the same name.
3618 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3619 instances of the function body, used in different cases.
3622 For a C@t{++} template function, a given line in the function can
3623 correspond to any number of instantiations.
3626 For an inlined function, a given source line can correspond to
3627 several places where that function is inlined.
3630 In all those cases, @value{GDBN} will insert a breakpoint at all
3631 the relevant locations.
3633 A breakpoint with multiple locations is displayed in the breakpoint
3634 table using several rows---one header row, followed by one row for
3635 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3636 address column. The rows for individual locations contain the actual
3637 addresses for locations, and show the functions to which those
3638 locations belong. The number column for a location is of the form
3639 @var{breakpoint-number}.@var{location-number}.
3644 Num Type Disp Enb Address What
3645 1 breakpoint keep y <MULTIPLE>
3647 breakpoint already hit 1 time
3648 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3649 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3652 Each location can be individually enabled or disabled by passing
3653 @var{breakpoint-number}.@var{location-number} as argument to the
3654 @code{enable} and @code{disable} commands. Note that you cannot
3655 delete the individual locations from the list, you can only delete the
3656 entire list of locations that belong to their parent breakpoint (with
3657 the @kbd{delete @var{num}} command, where @var{num} is the number of
3658 the parent breakpoint, 1 in the above example). Disabling or enabling
3659 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3660 that belong to that breakpoint.
3662 @cindex pending breakpoints
3663 It's quite common to have a breakpoint inside a shared library.
3664 Shared libraries can be loaded and unloaded explicitly,
3665 and possibly repeatedly, as the program is executed. To support
3666 this use case, @value{GDBN} updates breakpoint locations whenever
3667 any shared library is loaded or unloaded. Typically, you would
3668 set a breakpoint in a shared library at the beginning of your
3669 debugging session, when the library is not loaded, and when the
3670 symbols from the library are not available. When you try to set
3671 breakpoint, @value{GDBN} will ask you if you want to set
3672 a so called @dfn{pending breakpoint}---breakpoint whose address
3673 is not yet resolved.
3675 After the program is run, whenever a new shared library is loaded,
3676 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3677 shared library contains the symbol or line referred to by some
3678 pending breakpoint, that breakpoint is resolved and becomes an
3679 ordinary breakpoint. When a library is unloaded, all breakpoints
3680 that refer to its symbols or source lines become pending again.
3682 This logic works for breakpoints with multiple locations, too. For
3683 example, if you have a breakpoint in a C@t{++} template function, and
3684 a newly loaded shared library has an instantiation of that template,
3685 a new location is added to the list of locations for the breakpoint.
3687 Except for having unresolved address, pending breakpoints do not
3688 differ from regular breakpoints. You can set conditions or commands,
3689 enable and disable them and perform other breakpoint operations.
3691 @value{GDBN} provides some additional commands for controlling what
3692 happens when the @samp{break} command cannot resolve breakpoint
3693 address specification to an address:
3695 @kindex set breakpoint pending
3696 @kindex show breakpoint pending
3698 @item set breakpoint pending auto
3699 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3700 location, it queries you whether a pending breakpoint should be created.
3702 @item set breakpoint pending on
3703 This indicates that an unrecognized breakpoint location should automatically
3704 result in a pending breakpoint being created.
3706 @item set breakpoint pending off
3707 This indicates that pending breakpoints are not to be created. Any
3708 unrecognized breakpoint location results in an error. This setting does
3709 not affect any pending breakpoints previously created.
3711 @item show breakpoint pending
3712 Show the current behavior setting for creating pending breakpoints.
3715 The settings above only affect the @code{break} command and its
3716 variants. Once breakpoint is set, it will be automatically updated
3717 as shared libraries are loaded and unloaded.
3719 @cindex automatic hardware breakpoints
3720 For some targets, @value{GDBN} can automatically decide if hardware or
3721 software breakpoints should be used, depending on whether the
3722 breakpoint address is read-only or read-write. This applies to
3723 breakpoints set with the @code{break} command as well as to internal
3724 breakpoints set by commands like @code{next} and @code{finish}. For
3725 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3728 You can control this automatic behaviour with the following commands::
3730 @kindex set breakpoint auto-hw
3731 @kindex show breakpoint auto-hw
3733 @item set breakpoint auto-hw on
3734 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3735 will try to use the target memory map to decide if software or hardware
3736 breakpoint must be used.
3738 @item set breakpoint auto-hw off
3739 This indicates @value{GDBN} should not automatically select breakpoint
3740 type. If the target provides a memory map, @value{GDBN} will warn when
3741 trying to set software breakpoint at a read-only address.
3744 @value{GDBN} normally implements breakpoints by replacing the program code
3745 at the breakpoint address with a special instruction, which, when
3746 executed, given control to the debugger. By default, the program
3747 code is so modified only when the program is resumed. As soon as
3748 the program stops, @value{GDBN} restores the original instructions. This
3749 behaviour guards against leaving breakpoints inserted in the
3750 target should gdb abrubptly disconnect. However, with slow remote
3751 targets, inserting and removing breakpoint can reduce the performance.
3752 This behavior can be controlled with the following commands::
3754 @kindex set breakpoint always-inserted
3755 @kindex show breakpoint always-inserted
3757 @item set breakpoint always-inserted off
3758 All breakpoints, including newly added by the user, are inserted in
3759 the target only when the target is resumed. All breakpoints are
3760 removed from the target when it stops.
3762 @item set breakpoint always-inserted on
3763 Causes all breakpoints to be inserted in the target at all times. If
3764 the user adds a new breakpoint, or changes an existing breakpoint, the
3765 breakpoints in the target are updated immediately. A breakpoint is
3766 removed from the target only when breakpoint itself is removed.
3768 @cindex non-stop mode, and @code{breakpoint always-inserted}
3769 @item set breakpoint always-inserted auto
3770 This is the default mode. If @value{GDBN} is controlling the inferior
3771 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3772 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3773 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3774 @code{breakpoint always-inserted} mode is off.
3777 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3778 when a breakpoint breaks. If the condition is true, then the process being
3779 debugged stops, otherwise the process is resumed.
3781 If the target supports evaluating conditions on its end, @value{GDBN} may
3782 download the breakpoint, together with its conditions, to it.
3784 This feature can be controlled via the following commands:
3786 @kindex set breakpoint condition-evaluation
3787 @kindex show breakpoint condition-evaluation
3789 @item set breakpoint condition-evaluation host
3790 This option commands @value{GDBN} to evaluate the breakpoint
3791 conditions on the host's side. Unconditional breakpoints are sent to
3792 the target which in turn receives the triggers and reports them back to GDB
3793 for condition evaluation. This is the standard evaluation mode.
3795 @item set breakpoint condition-evaluation target
3796 This option commands @value{GDBN} to download breakpoint conditions
3797 to the target at the moment of their insertion. The target
3798 is responsible for evaluating the conditional expression and reporting
3799 breakpoint stop events back to @value{GDBN} whenever the condition
3800 is true. Due to limitations of target-side evaluation, some conditions
3801 cannot be evaluated there, e.g., conditions that depend on local data
3802 that is only known to the host. Examples include
3803 conditional expressions involving convenience variables, complex types
3804 that cannot be handled by the agent expression parser and expressions
3805 that are too long to be sent over to the target, specially when the
3806 target is a remote system. In these cases, the conditions will be
3807 evaluated by @value{GDBN}.
3809 @item set breakpoint condition-evaluation auto
3810 This is the default mode. If the target supports evaluating breakpoint
3811 conditions on its end, @value{GDBN} will download breakpoint conditions to
3812 the target (limitations mentioned previously apply). If the target does
3813 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3814 to evaluating all these conditions on the host's side.
3818 @cindex negative breakpoint numbers
3819 @cindex internal @value{GDBN} breakpoints
3820 @value{GDBN} itself sometimes sets breakpoints in your program for
3821 special purposes, such as proper handling of @code{longjmp} (in C
3822 programs). These internal breakpoints are assigned negative numbers,
3823 starting with @code{-1}; @samp{info breakpoints} does not display them.
3824 You can see these breakpoints with the @value{GDBN} maintenance command
3825 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3828 @node Set Watchpoints
3829 @subsection Setting Watchpoints
3831 @cindex setting watchpoints
3832 You can use a watchpoint to stop execution whenever the value of an
3833 expression changes, without having to predict a particular place where
3834 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3835 The expression may be as simple as the value of a single variable, or
3836 as complex as many variables combined by operators. Examples include:
3840 A reference to the value of a single variable.
3843 An address cast to an appropriate data type. For example,
3844 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3845 address (assuming an @code{int} occupies 4 bytes).
3848 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3849 expression can use any operators valid in the program's native
3850 language (@pxref{Languages}).
3853 You can set a watchpoint on an expression even if the expression can
3854 not be evaluated yet. For instance, you can set a watchpoint on
3855 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3856 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3857 the expression produces a valid value. If the expression becomes
3858 valid in some other way than changing a variable (e.g.@: if the memory
3859 pointed to by @samp{*global_ptr} becomes readable as the result of a
3860 @code{malloc} call), @value{GDBN} may not stop until the next time
3861 the expression changes.
3863 @cindex software watchpoints
3864 @cindex hardware watchpoints
3865 Depending on your system, watchpoints may be implemented in software or
3866 hardware. @value{GDBN} does software watchpointing by single-stepping your
3867 program and testing the variable's value each time, which is hundreds of
3868 times slower than normal execution. (But this may still be worth it, to
3869 catch errors where you have no clue what part of your program is the
3872 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3873 x86-based targets, @value{GDBN} includes support for hardware
3874 watchpoints, which do not slow down the running of your program.
3878 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3879 Set a watchpoint for an expression. @value{GDBN} will break when the
3880 expression @var{expr} is written into by the program and its value
3881 changes. The simplest (and the most popular) use of this command is
3882 to watch the value of a single variable:
3885 (@value{GDBP}) watch foo
3888 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3889 argument, @value{GDBN} breaks only when the thread identified by
3890 @var{threadnum} changes the value of @var{expr}. If any other threads
3891 change the value of @var{expr}, @value{GDBN} will not break. Note
3892 that watchpoints restricted to a single thread in this way only work
3893 with Hardware Watchpoints.
3895 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3896 (see below). The @code{-location} argument tells @value{GDBN} to
3897 instead watch the memory referred to by @var{expr}. In this case,
3898 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3899 and watch the memory at that address. The type of the result is used
3900 to determine the size of the watched memory. If the expression's
3901 result does not have an address, then @value{GDBN} will print an
3904 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3905 of masked watchpoints, if the current architecture supports this
3906 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3907 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3908 to an address to watch. The mask specifies that some bits of an address
3909 (the bits which are reset in the mask) should be ignored when matching
3910 the address accessed by the inferior against the watchpoint address.
3911 Thus, a masked watchpoint watches many addresses simultaneously---those
3912 addresses whose unmasked bits are identical to the unmasked bits in the
3913 watchpoint address. The @code{mask} argument implies @code{-location}.
3917 (@value{GDBP}) watch foo mask 0xffff00ff
3918 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3922 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3923 Set a watchpoint that will break when the value of @var{expr} is read
3927 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3928 Set a watchpoint that will break when @var{expr} is either read from
3929 or written into by the program.
3931 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3932 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3933 This command prints a list of watchpoints, using the same format as
3934 @code{info break} (@pxref{Set Breaks}).
3937 If you watch for a change in a numerically entered address you need to
3938 dereference it, as the address itself is just a constant number which will
3939 never change. @value{GDBN} refuses to create a watchpoint that watches
3940 a never-changing value:
3943 (@value{GDBP}) watch 0x600850
3944 Cannot watch constant value 0x600850.
3945 (@value{GDBP}) watch *(int *) 0x600850
3946 Watchpoint 1: *(int *) 6293584
3949 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3950 watchpoints execute very quickly, and the debugger reports a change in
3951 value at the exact instruction where the change occurs. If @value{GDBN}
3952 cannot set a hardware watchpoint, it sets a software watchpoint, which
3953 executes more slowly and reports the change in value at the next
3954 @emph{statement}, not the instruction, after the change occurs.
3956 @cindex use only software watchpoints
3957 You can force @value{GDBN} to use only software watchpoints with the
3958 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3959 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3960 the underlying system supports them. (Note that hardware-assisted
3961 watchpoints that were set @emph{before} setting
3962 @code{can-use-hw-watchpoints} to zero will still use the hardware
3963 mechanism of watching expression values.)
3966 @item set can-use-hw-watchpoints
3967 @kindex set can-use-hw-watchpoints
3968 Set whether or not to use hardware watchpoints.
3970 @item show can-use-hw-watchpoints
3971 @kindex show can-use-hw-watchpoints
3972 Show the current mode of using hardware watchpoints.
3975 For remote targets, you can restrict the number of hardware
3976 watchpoints @value{GDBN} will use, see @ref{set remote
3977 hardware-breakpoint-limit}.
3979 When you issue the @code{watch} command, @value{GDBN} reports
3982 Hardware watchpoint @var{num}: @var{expr}
3986 if it was able to set a hardware watchpoint.
3988 Currently, the @code{awatch} and @code{rwatch} commands can only set
3989 hardware watchpoints, because accesses to data that don't change the
3990 value of the watched expression cannot be detected without examining
3991 every instruction as it is being executed, and @value{GDBN} does not do
3992 that currently. If @value{GDBN} finds that it is unable to set a
3993 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3994 will print a message like this:
3997 Expression cannot be implemented with read/access watchpoint.
4000 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4001 data type of the watched expression is wider than what a hardware
4002 watchpoint on the target machine can handle. For example, some systems
4003 can only watch regions that are up to 4 bytes wide; on such systems you
4004 cannot set hardware watchpoints for an expression that yields a
4005 double-precision floating-point number (which is typically 8 bytes
4006 wide). As a work-around, it might be possible to break the large region
4007 into a series of smaller ones and watch them with separate watchpoints.
4009 If you set too many hardware watchpoints, @value{GDBN} might be unable
4010 to insert all of them when you resume the execution of your program.
4011 Since the precise number of active watchpoints is unknown until such
4012 time as the program is about to be resumed, @value{GDBN} might not be
4013 able to warn you about this when you set the watchpoints, and the
4014 warning will be printed only when the program is resumed:
4017 Hardware watchpoint @var{num}: Could not insert watchpoint
4021 If this happens, delete or disable some of the watchpoints.
4023 Watching complex expressions that reference many variables can also
4024 exhaust the resources available for hardware-assisted watchpoints.
4025 That's because @value{GDBN} needs to watch every variable in the
4026 expression with separately allocated resources.
4028 If you call a function interactively using @code{print} or @code{call},
4029 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4030 kind of breakpoint or the call completes.
4032 @value{GDBN} automatically deletes watchpoints that watch local
4033 (automatic) variables, or expressions that involve such variables, when
4034 they go out of scope, that is, when the execution leaves the block in
4035 which these variables were defined. In particular, when the program
4036 being debugged terminates, @emph{all} local variables go out of scope,
4037 and so only watchpoints that watch global variables remain set. If you
4038 rerun the program, you will need to set all such watchpoints again. One
4039 way of doing that would be to set a code breakpoint at the entry to the
4040 @code{main} function and when it breaks, set all the watchpoints.
4042 @cindex watchpoints and threads
4043 @cindex threads and watchpoints
4044 In multi-threaded programs, watchpoints will detect changes to the
4045 watched expression from every thread.
4048 @emph{Warning:} In multi-threaded programs, software watchpoints
4049 have only limited usefulness. If @value{GDBN} creates a software
4050 watchpoint, it can only watch the value of an expression @emph{in a
4051 single thread}. If you are confident that the expression can only
4052 change due to the current thread's activity (and if you are also
4053 confident that no other thread can become current), then you can use
4054 software watchpoints as usual. However, @value{GDBN} may not notice
4055 when a non-current thread's activity changes the expression. (Hardware
4056 watchpoints, in contrast, watch an expression in all threads.)
4059 @xref{set remote hardware-watchpoint-limit}.
4061 @node Set Catchpoints
4062 @subsection Setting Catchpoints
4063 @cindex catchpoints, setting
4064 @cindex exception handlers
4065 @cindex event handling
4067 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4068 kinds of program events, such as C@t{++} exceptions or the loading of a
4069 shared library. Use the @code{catch} command to set a catchpoint.
4073 @item catch @var{event}
4074 Stop when @var{event} occurs. @var{event} can be any of the following:
4080 @cindex stop on C@t{++} exceptions
4081 The throwing, re-throwing, or catching of a C@t{++} exception.
4083 There are currently some limitations to C@t{++} exception handling in
4088 The support for these commands is system-dependent. Currently, only
4089 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4093 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4094 location in the system library which implements runtime exception
4095 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4096 (@pxref{Selection}) to get to your code.
4099 If you call a function interactively, @value{GDBN} normally returns
4100 control to you when the function has finished executing. If the call
4101 raises an exception, however, the call may bypass the mechanism that
4102 returns control to you and cause your program either to abort or to
4103 simply continue running until it hits a breakpoint, catches a signal
4104 that @value{GDBN} is listening for, or exits. This is the case even if
4105 you set a catchpoint for the exception; catchpoints on exceptions are
4106 disabled within interactive calls. @xref{Calling}, for information on
4107 controlling this with @code{set unwind-on-terminating-exception}.
4110 You cannot raise an exception interactively.
4113 You cannot install an exception handler interactively.
4117 @cindex Ada exception catching
4118 @cindex catch Ada exceptions
4119 An Ada exception being raised. If an exception name is specified
4120 at the end of the command (eg @code{catch exception Program_Error}),
4121 the debugger will stop only when this specific exception is raised.
4122 Otherwise, the debugger stops execution when any Ada exception is raised.
4124 When inserting an exception catchpoint on a user-defined exception whose
4125 name is identical to one of the exceptions defined by the language, the
4126 fully qualified name must be used as the exception name. Otherwise,
4127 @value{GDBN} will assume that it should stop on the pre-defined exception
4128 rather than the user-defined one. For instance, assuming an exception
4129 called @code{Constraint_Error} is defined in package @code{Pck}, then
4130 the command to use to catch such exceptions is @kbd{catch exception
4131 Pck.Constraint_Error}.
4133 @item exception unhandled
4134 An exception that was raised but is not handled by the program.
4137 A failed Ada assertion.
4140 @cindex break on fork/exec
4141 A call to @code{exec}. This is currently only available for HP-UX
4145 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4146 @cindex break on a system call.
4147 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4148 syscall is a mechanism for application programs to request a service
4149 from the operating system (OS) or one of the OS system services.
4150 @value{GDBN} can catch some or all of the syscalls issued by the
4151 debuggee, and show the related information for each syscall. If no
4152 argument is specified, calls to and returns from all system calls
4155 @var{name} can be any system call name that is valid for the
4156 underlying OS. Just what syscalls are valid depends on the OS. On
4157 GNU and Unix systems, you can find the full list of valid syscall
4158 names on @file{/usr/include/asm/unistd.h}.
4160 @c For MS-Windows, the syscall names and the corresponding numbers
4161 @c can be found, e.g., on this URL:
4162 @c http://www.metasploit.com/users/opcode/syscalls.html
4163 @c but we don't support Windows syscalls yet.
4165 Normally, @value{GDBN} knows in advance which syscalls are valid for
4166 each OS, so you can use the @value{GDBN} command-line completion
4167 facilities (@pxref{Completion,, command completion}) to list the
4170 You may also specify the system call numerically. A syscall's
4171 number is the value passed to the OS's syscall dispatcher to
4172 identify the requested service. When you specify the syscall by its
4173 name, @value{GDBN} uses its database of syscalls to convert the name
4174 into the corresponding numeric code, but using the number directly
4175 may be useful if @value{GDBN}'s database does not have the complete
4176 list of syscalls on your system (e.g., because @value{GDBN} lags
4177 behind the OS upgrades).
4179 The example below illustrates how this command works if you don't provide
4183 (@value{GDBP}) catch syscall
4184 Catchpoint 1 (syscall)
4186 Starting program: /tmp/catch-syscall
4188 Catchpoint 1 (call to syscall 'close'), \
4189 0xffffe424 in __kernel_vsyscall ()
4193 Catchpoint 1 (returned from syscall 'close'), \
4194 0xffffe424 in __kernel_vsyscall ()
4198 Here is an example of catching a system call by name:
4201 (@value{GDBP}) catch syscall chroot
4202 Catchpoint 1 (syscall 'chroot' [61])
4204 Starting program: /tmp/catch-syscall
4206 Catchpoint 1 (call to syscall 'chroot'), \
4207 0xffffe424 in __kernel_vsyscall ()
4211 Catchpoint 1 (returned from syscall 'chroot'), \
4212 0xffffe424 in __kernel_vsyscall ()
4216 An example of specifying a system call numerically. In the case
4217 below, the syscall number has a corresponding entry in the XML
4218 file, so @value{GDBN} finds its name and prints it:
4221 (@value{GDBP}) catch syscall 252
4222 Catchpoint 1 (syscall(s) 'exit_group')
4224 Starting program: /tmp/catch-syscall
4226 Catchpoint 1 (call to syscall 'exit_group'), \
4227 0xffffe424 in __kernel_vsyscall ()
4231 Program exited normally.
4235 However, there can be situations when there is no corresponding name
4236 in XML file for that syscall number. In this case, @value{GDBN} prints
4237 a warning message saying that it was not able to find the syscall name,
4238 but the catchpoint will be set anyway. See the example below:
4241 (@value{GDBP}) catch syscall 764
4242 warning: The number '764' does not represent a known syscall.
4243 Catchpoint 2 (syscall 764)
4247 If you configure @value{GDBN} using the @samp{--without-expat} option,
4248 it will not be able to display syscall names. Also, if your
4249 architecture does not have an XML file describing its system calls,
4250 you will not be able to see the syscall names. It is important to
4251 notice that these two features are used for accessing the syscall
4252 name database. In either case, you will see a warning like this:
4255 (@value{GDBP}) catch syscall
4256 warning: Could not open "syscalls/i386-linux.xml"
4257 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4258 GDB will not be able to display syscall names.
4259 Catchpoint 1 (syscall)
4263 Of course, the file name will change depending on your architecture and system.
4265 Still using the example above, you can also try to catch a syscall by its
4266 number. In this case, you would see something like:
4269 (@value{GDBP}) catch syscall 252
4270 Catchpoint 1 (syscall(s) 252)
4273 Again, in this case @value{GDBN} would not be able to display syscall's names.
4276 A call to @code{fork}. This is currently only available for HP-UX
4280 A call to @code{vfork}. This is currently only available for HP-UX
4283 @item load @r{[}regexp@r{]}
4284 @itemx unload @r{[}regexp@r{]}
4285 The loading or unloading of a shared library. If @var{regexp} is
4286 given, then the catchpoint will stop only if the regular expression
4287 matches one of the affected libraries.
4289 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4290 The delivery of a signal.
4292 With no arguments, this catchpoint will catch any signal that is not
4293 used internally by @value{GDBN}, specifically, all signals except
4294 @samp{SIGTRAP} and @samp{SIGINT}.
4296 With the argument @samp{all}, all signals, including those used by
4297 @value{GDBN}, will be caught. This argument cannot be used with other
4300 Otherwise, the arguments are a list of signal names as given to
4301 @code{handle} (@pxref{Signals}). Only signals specified in this list
4304 One reason that @code{catch signal} can be more useful than
4305 @code{handle} is that you can attach commands and conditions to the
4308 When a signal is caught by a catchpoint, the signal's @code{stop} and
4309 @code{print} settings, as specified by @code{handle}, are ignored.
4310 However, whether the signal is still delivered to the inferior depends
4311 on the @code{pass} setting; this can be changed in the catchpoint's
4316 @item tcatch @var{event}
4317 Set a catchpoint that is enabled only for one stop. The catchpoint is
4318 automatically deleted after the first time the event is caught.
4322 Use the @code{info break} command to list the current catchpoints.
4326 @subsection Deleting Breakpoints
4328 @cindex clearing breakpoints, watchpoints, catchpoints
4329 @cindex deleting breakpoints, watchpoints, catchpoints
4330 It is often necessary to eliminate a breakpoint, watchpoint, or
4331 catchpoint once it has done its job and you no longer want your program
4332 to stop there. This is called @dfn{deleting} the breakpoint. A
4333 breakpoint that has been deleted no longer exists; it is forgotten.
4335 With the @code{clear} command you can delete breakpoints according to
4336 where they are in your program. With the @code{delete} command you can
4337 delete individual breakpoints, watchpoints, or catchpoints by specifying
4338 their breakpoint numbers.
4340 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4341 automatically ignores breakpoints on the first instruction to be executed
4342 when you continue execution without changing the execution address.
4347 Delete any breakpoints at the next instruction to be executed in the
4348 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4349 the innermost frame is selected, this is a good way to delete a
4350 breakpoint where your program just stopped.
4352 @item clear @var{location}
4353 Delete any breakpoints set at the specified @var{location}.
4354 @xref{Specify Location}, for the various forms of @var{location}; the
4355 most useful ones are listed below:
4358 @item clear @var{function}
4359 @itemx clear @var{filename}:@var{function}
4360 Delete any breakpoints set at entry to the named @var{function}.
4362 @item clear @var{linenum}
4363 @itemx clear @var{filename}:@var{linenum}
4364 Delete any breakpoints set at or within the code of the specified
4365 @var{linenum} of the specified @var{filename}.
4368 @cindex delete breakpoints
4370 @kindex d @r{(@code{delete})}
4371 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4372 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4373 ranges specified as arguments. If no argument is specified, delete all
4374 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4375 confirm off}). You can abbreviate this command as @code{d}.
4379 @subsection Disabling Breakpoints
4381 @cindex enable/disable a breakpoint
4382 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4383 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4384 it had been deleted, but remembers the information on the breakpoint so
4385 that you can @dfn{enable} it again later.
4387 You disable and enable breakpoints, watchpoints, and catchpoints with
4388 the @code{enable} and @code{disable} commands, optionally specifying
4389 one or more breakpoint numbers as arguments. Use @code{info break} to
4390 print a list of all breakpoints, watchpoints, and catchpoints if you
4391 do not know which numbers to use.
4393 Disabling and enabling a breakpoint that has multiple locations
4394 affects all of its locations.
4396 A breakpoint, watchpoint, or catchpoint can have any of several
4397 different states of enablement:
4401 Enabled. The breakpoint stops your program. A breakpoint set
4402 with the @code{break} command starts out in this state.
4404 Disabled. The breakpoint has no effect on your program.
4406 Enabled once. The breakpoint stops your program, but then becomes
4409 Enabled for a count. The breakpoint stops your program for the next
4410 N times, then becomes disabled.
4412 Enabled for deletion. The breakpoint stops your program, but
4413 immediately after it does so it is deleted permanently. A breakpoint
4414 set with the @code{tbreak} command starts out in this state.
4417 You can use the following commands to enable or disable breakpoints,
4418 watchpoints, and catchpoints:
4422 @kindex dis @r{(@code{disable})}
4423 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4424 Disable the specified breakpoints---or all breakpoints, if none are
4425 listed. A disabled breakpoint has no effect but is not forgotten. All
4426 options such as ignore-counts, conditions and commands are remembered in
4427 case the breakpoint is enabled again later. You may abbreviate
4428 @code{disable} as @code{dis}.
4431 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4432 Enable the specified breakpoints (or all defined breakpoints). They
4433 become effective once again in stopping your program.
4435 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4436 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4437 of these breakpoints immediately after stopping your program.
4439 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4440 Enable the specified breakpoints temporarily. @value{GDBN} records
4441 @var{count} with each of the specified breakpoints, and decrements a
4442 breakpoint's count when it is hit. When any count reaches 0,
4443 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4444 count (@pxref{Conditions, ,Break Conditions}), that will be
4445 decremented to 0 before @var{count} is affected.
4447 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4448 Enable the specified breakpoints to work once, then die. @value{GDBN}
4449 deletes any of these breakpoints as soon as your program stops there.
4450 Breakpoints set by the @code{tbreak} command start out in this state.
4453 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4454 @c confusing: tbreak is also initially enabled.
4455 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4456 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4457 subsequently, they become disabled or enabled only when you use one of
4458 the commands above. (The command @code{until} can set and delete a
4459 breakpoint of its own, but it does not change the state of your other
4460 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4464 @subsection Break Conditions
4465 @cindex conditional breakpoints
4466 @cindex breakpoint conditions
4468 @c FIXME what is scope of break condition expr? Context where wanted?
4469 @c in particular for a watchpoint?
4470 The simplest sort of breakpoint breaks every time your program reaches a
4471 specified place. You can also specify a @dfn{condition} for a
4472 breakpoint. A condition is just a Boolean expression in your
4473 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4474 a condition evaluates the expression each time your program reaches it,
4475 and your program stops only if the condition is @emph{true}.
4477 This is the converse of using assertions for program validation; in that
4478 situation, you want to stop when the assertion is violated---that is,
4479 when the condition is false. In C, if you want to test an assertion expressed
4480 by the condition @var{assert}, you should set the condition
4481 @samp{! @var{assert}} on the appropriate breakpoint.
4483 Conditions are also accepted for watchpoints; you may not need them,
4484 since a watchpoint is inspecting the value of an expression anyhow---but
4485 it might be simpler, say, to just set a watchpoint on a variable name,
4486 and specify a condition that tests whether the new value is an interesting
4489 Break conditions can have side effects, and may even call functions in
4490 your program. This can be useful, for example, to activate functions
4491 that log program progress, or to use your own print functions to
4492 format special data structures. The effects are completely predictable
4493 unless there is another enabled breakpoint at the same address. (In
4494 that case, @value{GDBN} might see the other breakpoint first and stop your
4495 program without checking the condition of this one.) Note that
4496 breakpoint commands are usually more convenient and flexible than break
4498 purpose of performing side effects when a breakpoint is reached
4499 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4501 Breakpoint conditions can also be evaluated on the target's side if
4502 the target supports it. Instead of evaluating the conditions locally,
4503 @value{GDBN} encodes the expression into an agent expression
4504 (@pxref{Agent Expressions}) suitable for execution on the target,
4505 independently of @value{GDBN}. Global variables become raw memory
4506 locations, locals become stack accesses, and so forth.
4508 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4509 when its condition evaluates to true. This mechanism may provide faster
4510 response times depending on the performance characteristics of the target
4511 since it does not need to keep @value{GDBN} informed about
4512 every breakpoint trigger, even those with false conditions.
4514 Break conditions can be specified when a breakpoint is set, by using
4515 @samp{if} in the arguments to the @code{break} command. @xref{Set
4516 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4517 with the @code{condition} command.
4519 You can also use the @code{if} keyword with the @code{watch} command.
4520 The @code{catch} command does not recognize the @code{if} keyword;
4521 @code{condition} is the only way to impose a further condition on a
4526 @item condition @var{bnum} @var{expression}
4527 Specify @var{expression} as the break condition for breakpoint,
4528 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4529 breakpoint @var{bnum} stops your program only if the value of
4530 @var{expression} is true (nonzero, in C). When you use
4531 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4532 syntactic correctness, and to determine whether symbols in it have
4533 referents in the context of your breakpoint. If @var{expression} uses
4534 symbols not referenced in the context of the breakpoint, @value{GDBN}
4535 prints an error message:
4538 No symbol "foo" in current context.
4543 not actually evaluate @var{expression} at the time the @code{condition}
4544 command (or a command that sets a breakpoint with a condition, like
4545 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4547 @item condition @var{bnum}
4548 Remove the condition from breakpoint number @var{bnum}. It becomes
4549 an ordinary unconditional breakpoint.
4552 @cindex ignore count (of breakpoint)
4553 A special case of a breakpoint condition is to stop only when the
4554 breakpoint has been reached a certain number of times. This is so
4555 useful that there is a special way to do it, using the @dfn{ignore
4556 count} of the breakpoint. Every breakpoint has an ignore count, which
4557 is an integer. Most of the time, the ignore count is zero, and
4558 therefore has no effect. But if your program reaches a breakpoint whose
4559 ignore count is positive, then instead of stopping, it just decrements
4560 the ignore count by one and continues. As a result, if the ignore count
4561 value is @var{n}, the breakpoint does not stop the next @var{n} times
4562 your program reaches it.
4566 @item ignore @var{bnum} @var{count}
4567 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4568 The next @var{count} times the breakpoint is reached, your program's
4569 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4572 To make the breakpoint stop the next time it is reached, specify
4575 When you use @code{continue} to resume execution of your program from a
4576 breakpoint, you can specify an ignore count directly as an argument to
4577 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4578 Stepping,,Continuing and Stepping}.
4580 If a breakpoint has a positive ignore count and a condition, the
4581 condition is not checked. Once the ignore count reaches zero,
4582 @value{GDBN} resumes checking the condition.
4584 You could achieve the effect of the ignore count with a condition such
4585 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4586 is decremented each time. @xref{Convenience Vars, ,Convenience
4590 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4593 @node Break Commands
4594 @subsection Breakpoint Command Lists
4596 @cindex breakpoint commands
4597 You can give any breakpoint (or watchpoint or catchpoint) a series of
4598 commands to execute when your program stops due to that breakpoint. For
4599 example, you might want to print the values of certain expressions, or
4600 enable other breakpoints.
4604 @kindex end@r{ (breakpoint commands)}
4605 @item commands @r{[}@var{range}@dots{}@r{]}
4606 @itemx @dots{} @var{command-list} @dots{}
4608 Specify a list of commands for the given breakpoints. The commands
4609 themselves appear on the following lines. Type a line containing just
4610 @code{end} to terminate the commands.
4612 To remove all commands from a breakpoint, type @code{commands} and
4613 follow it immediately with @code{end}; that is, give no commands.
4615 With no argument, @code{commands} refers to the last breakpoint,
4616 watchpoint, or catchpoint set (not to the breakpoint most recently
4617 encountered). If the most recent breakpoints were set with a single
4618 command, then the @code{commands} will apply to all the breakpoints
4619 set by that command. This applies to breakpoints set by
4620 @code{rbreak}, and also applies when a single @code{break} command
4621 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4625 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4626 disabled within a @var{command-list}.
4628 You can use breakpoint commands to start your program up again. Simply
4629 use the @code{continue} command, or @code{step}, or any other command
4630 that resumes execution.
4632 Any other commands in the command list, after a command that resumes
4633 execution, are ignored. This is because any time you resume execution
4634 (even with a simple @code{next} or @code{step}), you may encounter
4635 another breakpoint---which could have its own command list, leading to
4636 ambiguities about which list to execute.
4639 If the first command you specify in a command list is @code{silent}, the
4640 usual message about stopping at a breakpoint is not printed. This may
4641 be desirable for breakpoints that are to print a specific message and
4642 then continue. If none of the remaining commands print anything, you
4643 see no sign that the breakpoint was reached. @code{silent} is
4644 meaningful only at the beginning of a breakpoint command list.
4646 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4647 print precisely controlled output, and are often useful in silent
4648 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4650 For example, here is how you could use breakpoint commands to print the
4651 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4657 printf "x is %d\n",x
4662 One application for breakpoint commands is to compensate for one bug so
4663 you can test for another. Put a breakpoint just after the erroneous line
4664 of code, give it a condition to detect the case in which something
4665 erroneous has been done, and give it commands to assign correct values
4666 to any variables that need them. End with the @code{continue} command
4667 so that your program does not stop, and start with the @code{silent}
4668 command so that no output is produced. Here is an example:
4679 @node Dynamic Printf
4680 @subsection Dynamic Printf
4682 @cindex dynamic printf
4684 The dynamic printf command @code{dprintf} combines a breakpoint with
4685 formatted printing of your program's data to give you the effect of
4686 inserting @code{printf} calls into your program on-the-fly, without
4687 having to recompile it.
4689 In its most basic form, the output goes to the GDB console. However,
4690 you can set the variable @code{dprintf-style} for alternate handling.
4691 For instance, you can ask to format the output by calling your
4692 program's @code{printf} function. This has the advantage that the
4693 characters go to the program's output device, so they can recorded in
4694 redirects to files and so forth.
4696 If you are doing remote debugging with a stub or agent, you can also
4697 ask to have the printf handled by the remote agent. In addition to
4698 ensuring that the output goes to the remote program's device along
4699 with any other output the program might produce, you can also ask that
4700 the dprintf remain active even after disconnecting from the remote
4701 target. Using the stub/agent is also more efficient, as it can do
4702 everything without needing to communicate with @value{GDBN}.
4706 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4707 Whenever execution reaches @var{location}, print the values of one or
4708 more @var{expressions} under the control of the string @var{template}.
4709 To print several values, separate them with commas.
4711 @item set dprintf-style @var{style}
4712 Set the dprintf output to be handled in one of several different
4713 styles enumerated below. A change of style affects all existing
4714 dynamic printfs immediately. (If you need individual control over the
4715 print commands, simply define normal breakpoints with
4716 explicitly-supplied command lists.)
4719 @kindex dprintf-style gdb
4720 Handle the output using the @value{GDBN} @code{printf} command.
4723 @kindex dprintf-style call
4724 Handle the output by calling a function in your program (normally
4728 @kindex dprintf-style agent
4729 Have the remote debugging agent (such as @code{gdbserver}) handle
4730 the output itself. This style is only available for agents that
4731 support running commands on the target.
4733 @item set dprintf-function @var{function}
4734 Set the function to call if the dprintf style is @code{call}. By
4735 default its value is @code{printf}. You may set it to any expression.
4736 that @value{GDBN} can evaluate to a function, as per the @code{call}
4739 @item set dprintf-channel @var{channel}
4740 Set a ``channel'' for dprintf. If set to a non-empty value,
4741 @value{GDBN} will evaluate it as an expression and pass the result as
4742 a first argument to the @code{dprintf-function}, in the manner of
4743 @code{fprintf} and similar functions. Otherwise, the dprintf format
4744 string will be the first argument, in the manner of @code{printf}.
4746 As an example, if you wanted @code{dprintf} output to go to a logfile
4747 that is a standard I/O stream assigned to the variable @code{mylog},
4748 you could do the following:
4751 (gdb) set dprintf-style call
4752 (gdb) set dprintf-function fprintf
4753 (gdb) set dprintf-channel mylog
4754 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4755 Dprintf 1 at 0x123456: file main.c, line 25.
4757 1 dprintf keep y 0x00123456 in main at main.c:25
4758 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4763 Note that the @code{info break} displays the dynamic printf commands
4764 as normal breakpoint commands; you can thus easily see the effect of
4765 the variable settings.
4767 @item set disconnected-dprintf on
4768 @itemx set disconnected-dprintf off
4769 @kindex set disconnected-dprintf
4770 Choose whether @code{dprintf} commands should continue to run if
4771 @value{GDBN} has disconnected from the target. This only applies
4772 if the @code{dprintf-style} is @code{agent}.
4774 @item show disconnected-dprintf off
4775 @kindex show disconnected-dprintf
4776 Show the current choice for disconnected @code{dprintf}.
4780 @value{GDBN} does not check the validity of function and channel,
4781 relying on you to supply values that are meaningful for the contexts
4782 in which they are being used. For instance, the function and channel
4783 may be the values of local variables, but if that is the case, then
4784 all enabled dynamic prints must be at locations within the scope of
4785 those locals. If evaluation fails, @value{GDBN} will report an error.
4787 @node Save Breakpoints
4788 @subsection How to save breakpoints to a file
4790 To save breakpoint definitions to a file use the @w{@code{save
4791 breakpoints}} command.
4794 @kindex save breakpoints
4795 @cindex save breakpoints to a file for future sessions
4796 @item save breakpoints [@var{filename}]
4797 This command saves all current breakpoint definitions together with
4798 their commands and ignore counts, into a file @file{@var{filename}}
4799 suitable for use in a later debugging session. This includes all
4800 types of breakpoints (breakpoints, watchpoints, catchpoints,
4801 tracepoints). To read the saved breakpoint definitions, use the
4802 @code{source} command (@pxref{Command Files}). Note that watchpoints
4803 with expressions involving local variables may fail to be recreated
4804 because it may not be possible to access the context where the
4805 watchpoint is valid anymore. Because the saved breakpoint definitions
4806 are simply a sequence of @value{GDBN} commands that recreate the
4807 breakpoints, you can edit the file in your favorite editing program,
4808 and remove the breakpoint definitions you're not interested in, or
4809 that can no longer be recreated.
4812 @node Static Probe Points
4813 @subsection Static Probe Points
4815 @cindex static probe point, SystemTap
4816 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4817 for Statically Defined Tracing, and the probes are designed to have a tiny
4818 runtime code and data footprint, and no dynamic relocations. They are
4819 usable from assembly, C and C@t{++} languages. See
4820 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4821 for a good reference on how the @acronym{SDT} probes are implemented.
4823 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4824 @acronym{SDT} probes are supported on ELF-compatible systems. See
4825 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4826 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4827 in your applications.
4829 @cindex semaphores on static probe points
4830 Some probes have an associated semaphore variable; for instance, this
4831 happens automatically if you defined your probe using a DTrace-style
4832 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4833 automatically enable it when you specify a breakpoint using the
4834 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4835 location by some other method (e.g., @code{break file:line}), then
4836 @value{GDBN} will not automatically set the semaphore.
4838 You can examine the available static static probes using @code{info
4839 probes}, with optional arguments:
4843 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4844 If given, @var{provider} is a regular expression used to match against provider
4845 names when selecting which probes to list. If omitted, probes by all
4846 probes from all providers are listed.
4848 If given, @var{name} is a regular expression to match against probe names
4849 when selecting which probes to list. If omitted, probe names are not
4850 considered when deciding whether to display them.
4852 If given, @var{objfile} is a regular expression used to select which
4853 object files (executable or shared libraries) to examine. If not
4854 given, all object files are considered.
4856 @item info probes all
4857 List the available static probes, from all types.
4860 @vindex $_probe_arg@r{, convenience variable}
4861 A probe may specify up to twelve arguments. These are available at the
4862 point at which the probe is defined---that is, when the current PC is
4863 at the probe's location. The arguments are available using the
4864 convenience variables (@pxref{Convenience Vars})
4865 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4866 an integer of the appropriate size; types are not preserved. The
4867 convenience variable @code{$_probe_argc} holds the number of arguments
4868 at the current probe point.
4870 These variables are always available, but attempts to access them at
4871 any location other than a probe point will cause @value{GDBN} to give
4875 @c @ifclear BARETARGET
4876 @node Error in Breakpoints
4877 @subsection ``Cannot insert breakpoints''
4879 If you request too many active hardware-assisted breakpoints and
4880 watchpoints, you will see this error message:
4882 @c FIXME: the precise wording of this message may change; the relevant
4883 @c source change is not committed yet (Sep 3, 1999).
4885 Stopped; cannot insert breakpoints.
4886 You may have requested too many hardware breakpoints and watchpoints.
4890 This message is printed when you attempt to resume the program, since
4891 only then @value{GDBN} knows exactly how many hardware breakpoints and
4892 watchpoints it needs to insert.
4894 When this message is printed, you need to disable or remove some of the
4895 hardware-assisted breakpoints and watchpoints, and then continue.
4897 @node Breakpoint-related Warnings
4898 @subsection ``Breakpoint address adjusted...''
4899 @cindex breakpoint address adjusted
4901 Some processor architectures place constraints on the addresses at
4902 which breakpoints may be placed. For architectures thus constrained,
4903 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4904 with the constraints dictated by the architecture.
4906 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4907 a VLIW architecture in which a number of RISC-like instructions may be
4908 bundled together for parallel execution. The FR-V architecture
4909 constrains the location of a breakpoint instruction within such a
4910 bundle to the instruction with the lowest address. @value{GDBN}
4911 honors this constraint by adjusting a breakpoint's address to the
4912 first in the bundle.
4914 It is not uncommon for optimized code to have bundles which contain
4915 instructions from different source statements, thus it may happen that
4916 a breakpoint's address will be adjusted from one source statement to
4917 another. Since this adjustment may significantly alter @value{GDBN}'s
4918 breakpoint related behavior from what the user expects, a warning is
4919 printed when the breakpoint is first set and also when the breakpoint
4922 A warning like the one below is printed when setting a breakpoint
4923 that's been subject to address adjustment:
4926 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4929 Such warnings are printed both for user settable and @value{GDBN}'s
4930 internal breakpoints. If you see one of these warnings, you should
4931 verify that a breakpoint set at the adjusted address will have the
4932 desired affect. If not, the breakpoint in question may be removed and
4933 other breakpoints may be set which will have the desired behavior.
4934 E.g., it may be sufficient to place the breakpoint at a later
4935 instruction. A conditional breakpoint may also be useful in some
4936 cases to prevent the breakpoint from triggering too often.
4938 @value{GDBN} will also issue a warning when stopping at one of these
4939 adjusted breakpoints:
4942 warning: Breakpoint 1 address previously adjusted from 0x00010414
4946 When this warning is encountered, it may be too late to take remedial
4947 action except in cases where the breakpoint is hit earlier or more
4948 frequently than expected.
4950 @node Continuing and Stepping
4951 @section Continuing and Stepping
4955 @cindex resuming execution
4956 @dfn{Continuing} means resuming program execution until your program
4957 completes normally. In contrast, @dfn{stepping} means executing just
4958 one more ``step'' of your program, where ``step'' may mean either one
4959 line of source code, or one machine instruction (depending on what
4960 particular command you use). Either when continuing or when stepping,
4961 your program may stop even sooner, due to a breakpoint or a signal. (If
4962 it stops due to a signal, you may want to use @code{handle}, or use
4963 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4967 @kindex c @r{(@code{continue})}
4968 @kindex fg @r{(resume foreground execution)}
4969 @item continue @r{[}@var{ignore-count}@r{]}
4970 @itemx c @r{[}@var{ignore-count}@r{]}
4971 @itemx fg @r{[}@var{ignore-count}@r{]}
4972 Resume program execution, at the address where your program last stopped;
4973 any breakpoints set at that address are bypassed. The optional argument
4974 @var{ignore-count} allows you to specify a further number of times to
4975 ignore a breakpoint at this location; its effect is like that of
4976 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4978 The argument @var{ignore-count} is meaningful only when your program
4979 stopped due to a breakpoint. At other times, the argument to
4980 @code{continue} is ignored.
4982 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4983 debugged program is deemed to be the foreground program) are provided
4984 purely for convenience, and have exactly the same behavior as
4988 To resume execution at a different place, you can use @code{return}
4989 (@pxref{Returning, ,Returning from a Function}) to go back to the
4990 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4991 Different Address}) to go to an arbitrary location in your program.
4993 A typical technique for using stepping is to set a breakpoint
4994 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4995 beginning of the function or the section of your program where a problem
4996 is believed to lie, run your program until it stops at that breakpoint,
4997 and then step through the suspect area, examining the variables that are
4998 interesting, until you see the problem happen.
5002 @kindex s @r{(@code{step})}
5004 Continue running your program until control reaches a different source
5005 line, then stop it and return control to @value{GDBN}. This command is
5006 abbreviated @code{s}.
5009 @c "without debugging information" is imprecise; actually "without line
5010 @c numbers in the debugging information". (gcc -g1 has debugging info but
5011 @c not line numbers). But it seems complex to try to make that
5012 @c distinction here.
5013 @emph{Warning:} If you use the @code{step} command while control is
5014 within a function that was compiled without debugging information,
5015 execution proceeds until control reaches a function that does have
5016 debugging information. Likewise, it will not step into a function which
5017 is compiled without debugging information. To step through functions
5018 without debugging information, use the @code{stepi} command, described
5022 The @code{step} command only stops at the first instruction of a source
5023 line. This prevents the multiple stops that could otherwise occur in
5024 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5025 to stop if a function that has debugging information is called within
5026 the line. In other words, @code{step} @emph{steps inside} any functions
5027 called within the line.
5029 Also, the @code{step} command only enters a function if there is line
5030 number information for the function. Otherwise it acts like the
5031 @code{next} command. This avoids problems when using @code{cc -gl}
5032 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5033 was any debugging information about the routine.
5035 @item step @var{count}
5036 Continue running as in @code{step}, but do so @var{count} times. If a
5037 breakpoint is reached, or a signal not related to stepping occurs before
5038 @var{count} steps, stepping stops right away.
5041 @kindex n @r{(@code{next})}
5042 @item next @r{[}@var{count}@r{]}
5043 Continue to the next source line in the current (innermost) stack frame.
5044 This is similar to @code{step}, but function calls that appear within
5045 the line of code are executed without stopping. Execution stops when
5046 control reaches a different line of code at the original stack level
5047 that was executing when you gave the @code{next} command. This command
5048 is abbreviated @code{n}.
5050 An argument @var{count} is a repeat count, as for @code{step}.
5053 @c FIX ME!! Do we delete this, or is there a way it fits in with
5054 @c the following paragraph? --- Vctoria
5056 @c @code{next} within a function that lacks debugging information acts like
5057 @c @code{step}, but any function calls appearing within the code of the
5058 @c function are executed without stopping.
5060 The @code{next} command only stops at the first instruction of a
5061 source line. This prevents multiple stops that could otherwise occur in
5062 @code{switch} statements, @code{for} loops, etc.
5064 @kindex set step-mode
5066 @cindex functions without line info, and stepping
5067 @cindex stepping into functions with no line info
5068 @itemx set step-mode on
5069 The @code{set step-mode on} command causes the @code{step} command to
5070 stop at the first instruction of a function which contains no debug line
5071 information rather than stepping over it.
5073 This is useful in cases where you may be interested in inspecting the
5074 machine instructions of a function which has no symbolic info and do not
5075 want @value{GDBN} to automatically skip over this function.
5077 @item set step-mode off
5078 Causes the @code{step} command to step over any functions which contains no
5079 debug information. This is the default.
5081 @item show step-mode
5082 Show whether @value{GDBN} will stop in or step over functions without
5083 source line debug information.
5086 @kindex fin @r{(@code{finish})}
5088 Continue running until just after function in the selected stack frame
5089 returns. Print the returned value (if any). This command can be
5090 abbreviated as @code{fin}.
5092 Contrast this with the @code{return} command (@pxref{Returning,
5093 ,Returning from a Function}).
5096 @kindex u @r{(@code{until})}
5097 @cindex run until specified location
5100 Continue running until a source line past the current line, in the
5101 current stack frame, is reached. This command is used to avoid single
5102 stepping through a loop more than once. It is like the @code{next}
5103 command, except that when @code{until} encounters a jump, it
5104 automatically continues execution until the program counter is greater
5105 than the address of the jump.
5107 This means that when you reach the end of a loop after single stepping
5108 though it, @code{until} makes your program continue execution until it
5109 exits the loop. In contrast, a @code{next} command at the end of a loop
5110 simply steps back to the beginning of the loop, which forces you to step
5111 through the next iteration.
5113 @code{until} always stops your program if it attempts to exit the current
5116 @code{until} may produce somewhat counterintuitive results if the order
5117 of machine code does not match the order of the source lines. For
5118 example, in the following excerpt from a debugging session, the @code{f}
5119 (@code{frame}) command shows that execution is stopped at line
5120 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5124 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5126 (@value{GDBP}) until
5127 195 for ( ; argc > 0; NEXTARG) @{
5130 This happened because, for execution efficiency, the compiler had
5131 generated code for the loop closure test at the end, rather than the
5132 start, of the loop---even though the test in a C @code{for}-loop is
5133 written before the body of the loop. The @code{until} command appeared
5134 to step back to the beginning of the loop when it advanced to this
5135 expression; however, it has not really gone to an earlier
5136 statement---not in terms of the actual machine code.
5138 @code{until} with no argument works by means of single
5139 instruction stepping, and hence is slower than @code{until} with an
5142 @item until @var{location}
5143 @itemx u @var{location}
5144 Continue running your program until either the specified location is
5145 reached, or the current stack frame returns. @var{location} is any of
5146 the forms described in @ref{Specify Location}.
5147 This form of the command uses temporary breakpoints, and
5148 hence is quicker than @code{until} without an argument. The specified
5149 location is actually reached only if it is in the current frame. This
5150 implies that @code{until} can be used to skip over recursive function
5151 invocations. For instance in the code below, if the current location is
5152 line @code{96}, issuing @code{until 99} will execute the program up to
5153 line @code{99} in the same invocation of factorial, i.e., after the inner
5154 invocations have returned.
5157 94 int factorial (int value)
5159 96 if (value > 1) @{
5160 97 value *= factorial (value - 1);
5167 @kindex advance @var{location}
5168 @item advance @var{location}
5169 Continue running the program up to the given @var{location}. An argument is
5170 required, which should be of one of the forms described in
5171 @ref{Specify Location}.
5172 Execution will also stop upon exit from the current stack
5173 frame. This command is similar to @code{until}, but @code{advance} will
5174 not skip over recursive function calls, and the target location doesn't
5175 have to be in the same frame as the current one.
5179 @kindex si @r{(@code{stepi})}
5181 @itemx stepi @var{arg}
5183 Execute one machine instruction, then stop and return to the debugger.
5185 It is often useful to do @samp{display/i $pc} when stepping by machine
5186 instructions. This makes @value{GDBN} automatically display the next
5187 instruction to be executed, each time your program stops. @xref{Auto
5188 Display,, Automatic Display}.
5190 An argument is a repeat count, as in @code{step}.
5194 @kindex ni @r{(@code{nexti})}
5196 @itemx nexti @var{arg}
5198 Execute one machine instruction, but if it is a function call,
5199 proceed until the function returns.
5201 An argument is a repeat count, as in @code{next}.
5204 @node Skipping Over Functions and Files
5205 @section Skipping Over Functions and Files
5206 @cindex skipping over functions and files
5208 The program you are debugging may contain some functions which are
5209 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5210 skip a function or all functions in a file when stepping.
5212 For example, consider the following C function:
5223 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5224 are not interested in stepping through @code{boring}. If you run @code{step}
5225 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5226 step over both @code{foo} and @code{boring}!
5228 One solution is to @code{step} into @code{boring} and use the @code{finish}
5229 command to immediately exit it. But this can become tedious if @code{boring}
5230 is called from many places.
5232 A more flexible solution is to execute @kbd{skip boring}. This instructs
5233 @value{GDBN} never to step into @code{boring}. Now when you execute
5234 @code{step} at line 103, you'll step over @code{boring} and directly into
5237 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5238 example, @code{skip file boring.c}.
5241 @kindex skip function
5242 @item skip @r{[}@var{linespec}@r{]}
5243 @itemx skip function @r{[}@var{linespec}@r{]}
5244 After running this command, the function named by @var{linespec} or the
5245 function containing the line named by @var{linespec} will be skipped over when
5246 stepping. @xref{Specify Location}.
5248 If you do not specify @var{linespec}, the function you're currently debugging
5251 (If you have a function called @code{file} that you want to skip, use
5252 @kbd{skip function file}.)
5255 @item skip file @r{[}@var{filename}@r{]}
5256 After running this command, any function whose source lives in @var{filename}
5257 will be skipped over when stepping.
5259 If you do not specify @var{filename}, functions whose source lives in the file
5260 you're currently debugging will be skipped.
5263 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5264 These are the commands for managing your list of skips:
5268 @item info skip @r{[}@var{range}@r{]}
5269 Print details about the specified skip(s). If @var{range} is not specified,
5270 print a table with details about all functions and files marked for skipping.
5271 @code{info skip} prints the following information about each skip:
5275 A number identifying this skip.
5277 The type of this skip, either @samp{function} or @samp{file}.
5278 @item Enabled or Disabled
5279 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5281 For function skips, this column indicates the address in memory of the function
5282 being skipped. If you've set a function skip on a function which has not yet
5283 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5284 which has the function is loaded, @code{info skip} will show the function's
5287 For file skips, this field contains the filename being skipped. For functions
5288 skips, this field contains the function name and its line number in the file
5289 where it is defined.
5293 @item skip delete @r{[}@var{range}@r{]}
5294 Delete the specified skip(s). If @var{range} is not specified, delete all
5298 @item skip enable @r{[}@var{range}@r{]}
5299 Enable the specified skip(s). If @var{range} is not specified, enable all
5302 @kindex skip disable
5303 @item skip disable @r{[}@var{range}@r{]}
5304 Disable the specified skip(s). If @var{range} is not specified, disable all
5313 A signal is an asynchronous event that can happen in a program. The
5314 operating system defines the possible kinds of signals, and gives each
5315 kind a name and a number. For example, in Unix @code{SIGINT} is the
5316 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5317 @code{SIGSEGV} is the signal a program gets from referencing a place in
5318 memory far away from all the areas in use; @code{SIGALRM} occurs when
5319 the alarm clock timer goes off (which happens only if your program has
5320 requested an alarm).
5322 @cindex fatal signals
5323 Some signals, including @code{SIGALRM}, are a normal part of the
5324 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5325 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5326 program has not specified in advance some other way to handle the signal.
5327 @code{SIGINT} does not indicate an error in your program, but it is normally
5328 fatal so it can carry out the purpose of the interrupt: to kill the program.
5330 @value{GDBN} has the ability to detect any occurrence of a signal in your
5331 program. You can tell @value{GDBN} in advance what to do for each kind of
5334 @cindex handling signals
5335 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5336 @code{SIGALRM} be silently passed to your program
5337 (so as not to interfere with their role in the program's functioning)
5338 but to stop your program immediately whenever an error signal happens.
5339 You can change these settings with the @code{handle} command.
5342 @kindex info signals
5346 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5347 handle each one. You can use this to see the signal numbers of all
5348 the defined types of signals.
5350 @item info signals @var{sig}
5351 Similar, but print information only about the specified signal number.
5353 @code{info handle} is an alias for @code{info signals}.
5355 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5356 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5357 for details about this command.
5360 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5361 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5362 can be the number of a signal or its name (with or without the
5363 @samp{SIG} at the beginning); a list of signal numbers of the form
5364 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5365 known signals. Optional arguments @var{keywords}, described below,
5366 say what change to make.
5370 The keywords allowed by the @code{handle} command can be abbreviated.
5371 Their full names are:
5375 @value{GDBN} should not stop your program when this signal happens. It may
5376 still print a message telling you that the signal has come in.
5379 @value{GDBN} should stop your program when this signal happens. This implies
5380 the @code{print} keyword as well.
5383 @value{GDBN} should print a message when this signal happens.
5386 @value{GDBN} should not mention the occurrence of the signal at all. This
5387 implies the @code{nostop} keyword as well.
5391 @value{GDBN} should allow your program to see this signal; your program
5392 can handle the signal, or else it may terminate if the signal is fatal
5393 and not handled. @code{pass} and @code{noignore} are synonyms.
5397 @value{GDBN} should not allow your program to see this signal.
5398 @code{nopass} and @code{ignore} are synonyms.
5402 When a signal stops your program, the signal is not visible to the
5404 continue. Your program sees the signal then, if @code{pass} is in
5405 effect for the signal in question @emph{at that time}. In other words,
5406 after @value{GDBN} reports a signal, you can use the @code{handle}
5407 command with @code{pass} or @code{nopass} to control whether your
5408 program sees that signal when you continue.
5410 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5411 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5412 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5415 You can also use the @code{signal} command to prevent your program from
5416 seeing a signal, or cause it to see a signal it normally would not see,
5417 or to give it any signal at any time. For example, if your program stopped
5418 due to some sort of memory reference error, you might store correct
5419 values into the erroneous variables and continue, hoping to see more
5420 execution; but your program would probably terminate immediately as
5421 a result of the fatal signal once it saw the signal. To prevent this,
5422 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5425 @cindex extra signal information
5426 @anchor{extra signal information}
5428 On some targets, @value{GDBN} can inspect extra signal information
5429 associated with the intercepted signal, before it is actually
5430 delivered to the program being debugged. This information is exported
5431 by the convenience variable @code{$_siginfo}, and consists of data
5432 that is passed by the kernel to the signal handler at the time of the
5433 receipt of a signal. The data type of the information itself is
5434 target dependent. You can see the data type using the @code{ptype
5435 $_siginfo} command. On Unix systems, it typically corresponds to the
5436 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5439 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5440 referenced address that raised a segmentation fault.
5444 (@value{GDBP}) continue
5445 Program received signal SIGSEGV, Segmentation fault.
5446 0x0000000000400766 in main ()
5448 (@value{GDBP}) ptype $_siginfo
5455 struct @{...@} _kill;
5456 struct @{...@} _timer;
5458 struct @{...@} _sigchld;
5459 struct @{...@} _sigfault;
5460 struct @{...@} _sigpoll;
5463 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5467 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5468 $1 = (void *) 0x7ffff7ff7000
5472 Depending on target support, @code{$_siginfo} may also be writable.
5475 @section Stopping and Starting Multi-thread Programs
5477 @cindex stopped threads
5478 @cindex threads, stopped
5480 @cindex continuing threads
5481 @cindex threads, continuing
5483 @value{GDBN} supports debugging programs with multiple threads
5484 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5485 are two modes of controlling execution of your program within the
5486 debugger. In the default mode, referred to as @dfn{all-stop mode},
5487 when any thread in your program stops (for example, at a breakpoint
5488 or while being stepped), all other threads in the program are also stopped by
5489 @value{GDBN}. On some targets, @value{GDBN} also supports
5490 @dfn{non-stop mode}, in which other threads can continue to run freely while
5491 you examine the stopped thread in the debugger.
5494 * All-Stop Mode:: All threads stop when GDB takes control
5495 * Non-Stop Mode:: Other threads continue to execute
5496 * Background Execution:: Running your program asynchronously
5497 * Thread-Specific Breakpoints:: Controlling breakpoints
5498 * Interrupted System Calls:: GDB may interfere with system calls
5499 * Observer Mode:: GDB does not alter program behavior
5503 @subsection All-Stop Mode
5505 @cindex all-stop mode
5507 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5508 @emph{all} threads of execution stop, not just the current thread. This
5509 allows you to examine the overall state of the program, including
5510 switching between threads, without worrying that things may change
5513 Conversely, whenever you restart the program, @emph{all} threads start
5514 executing. @emph{This is true even when single-stepping} with commands
5515 like @code{step} or @code{next}.
5517 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5518 Since thread scheduling is up to your debugging target's operating
5519 system (not controlled by @value{GDBN}), other threads may
5520 execute more than one statement while the current thread completes a
5521 single step. Moreover, in general other threads stop in the middle of a
5522 statement, rather than at a clean statement boundary, when the program
5525 You might even find your program stopped in another thread after
5526 continuing or even single-stepping. This happens whenever some other
5527 thread runs into a breakpoint, a signal, or an exception before the
5528 first thread completes whatever you requested.
5530 @cindex automatic thread selection
5531 @cindex switching threads automatically
5532 @cindex threads, automatic switching
5533 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5534 signal, it automatically selects the thread where that breakpoint or
5535 signal happened. @value{GDBN} alerts you to the context switch with a
5536 message such as @samp{[Switching to Thread @var{n}]} to identify the
5539 On some OSes, you can modify @value{GDBN}'s default behavior by
5540 locking the OS scheduler to allow only a single thread to run.
5543 @item set scheduler-locking @var{mode}
5544 @cindex scheduler locking mode
5545 @cindex lock scheduler
5546 Set the scheduler locking mode. If it is @code{off}, then there is no
5547 locking and any thread may run at any time. If @code{on}, then only the
5548 current thread may run when the inferior is resumed. The @code{step}
5549 mode optimizes for single-stepping; it prevents other threads
5550 from preempting the current thread while you are stepping, so that
5551 the focus of debugging does not change unexpectedly.
5552 Other threads only rarely (or never) get a chance to run
5553 when you step. They are more likely to run when you @samp{next} over a
5554 function call, and they are completely free to run when you use commands
5555 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5556 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5557 the current thread away from the thread that you are debugging.
5559 @item show scheduler-locking
5560 Display the current scheduler locking mode.
5563 @cindex resume threads of multiple processes simultaneously
5564 By default, when you issue one of the execution commands such as
5565 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5566 threads of the current inferior to run. For example, if @value{GDBN}
5567 is attached to two inferiors, each with two threads, the
5568 @code{continue} command resumes only the two threads of the current
5569 inferior. This is useful, for example, when you debug a program that
5570 forks and you want to hold the parent stopped (so that, for instance,
5571 it doesn't run to exit), while you debug the child. In other
5572 situations, you may not be interested in inspecting the current state
5573 of any of the processes @value{GDBN} is attached to, and you may want
5574 to resume them all until some breakpoint is hit. In the latter case,
5575 you can instruct @value{GDBN} to allow all threads of all the
5576 inferiors to run with the @w{@code{set schedule-multiple}} command.
5579 @kindex set schedule-multiple
5580 @item set schedule-multiple
5581 Set the mode for allowing threads of multiple processes to be resumed
5582 when an execution command is issued. When @code{on}, all threads of
5583 all processes are allowed to run. When @code{off}, only the threads
5584 of the current process are resumed. The default is @code{off}. The
5585 @code{scheduler-locking} mode takes precedence when set to @code{on},
5586 or while you are stepping and set to @code{step}.
5588 @item show schedule-multiple
5589 Display the current mode for resuming the execution of threads of
5594 @subsection Non-Stop Mode
5596 @cindex non-stop mode
5598 @c This section is really only a place-holder, and needs to be expanded
5599 @c with more details.
5601 For some multi-threaded targets, @value{GDBN} supports an optional
5602 mode of operation in which you can examine stopped program threads in
5603 the debugger while other threads continue to execute freely. This
5604 minimizes intrusion when debugging live systems, such as programs
5605 where some threads have real-time constraints or must continue to
5606 respond to external events. This is referred to as @dfn{non-stop} mode.
5608 In non-stop mode, when a thread stops to report a debugging event,
5609 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5610 threads as well, in contrast to the all-stop mode behavior. Additionally,
5611 execution commands such as @code{continue} and @code{step} apply by default
5612 only to the current thread in non-stop mode, rather than all threads as
5613 in all-stop mode. This allows you to control threads explicitly in
5614 ways that are not possible in all-stop mode --- for example, stepping
5615 one thread while allowing others to run freely, stepping
5616 one thread while holding all others stopped, or stepping several threads
5617 independently and simultaneously.
5619 To enter non-stop mode, use this sequence of commands before you run
5620 or attach to your program:
5623 # Enable the async interface.
5626 # If using the CLI, pagination breaks non-stop.
5629 # Finally, turn it on!
5633 You can use these commands to manipulate the non-stop mode setting:
5636 @kindex set non-stop
5637 @item set non-stop on
5638 Enable selection of non-stop mode.
5639 @item set non-stop off
5640 Disable selection of non-stop mode.
5641 @kindex show non-stop
5643 Show the current non-stop enablement setting.
5646 Note these commands only reflect whether non-stop mode is enabled,
5647 not whether the currently-executing program is being run in non-stop mode.
5648 In particular, the @code{set non-stop} preference is only consulted when
5649 @value{GDBN} starts or connects to the target program, and it is generally
5650 not possible to switch modes once debugging has started. Furthermore,
5651 since not all targets support non-stop mode, even when you have enabled
5652 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5655 In non-stop mode, all execution commands apply only to the current thread
5656 by default. That is, @code{continue} only continues one thread.
5657 To continue all threads, issue @code{continue -a} or @code{c -a}.
5659 You can use @value{GDBN}'s background execution commands
5660 (@pxref{Background Execution}) to run some threads in the background
5661 while you continue to examine or step others from @value{GDBN}.
5662 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5663 always executed asynchronously in non-stop mode.
5665 Suspending execution is done with the @code{interrupt} command when
5666 running in the background, or @kbd{Ctrl-c} during foreground execution.
5667 In all-stop mode, this stops the whole process;
5668 but in non-stop mode the interrupt applies only to the current thread.
5669 To stop the whole program, use @code{interrupt -a}.
5671 Other execution commands do not currently support the @code{-a} option.
5673 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5674 that thread current, as it does in all-stop mode. This is because the
5675 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5676 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5677 changed to a different thread just as you entered a command to operate on the
5678 previously current thread.
5680 @node Background Execution
5681 @subsection Background Execution
5683 @cindex foreground execution
5684 @cindex background execution
5685 @cindex asynchronous execution
5686 @cindex execution, foreground, background and asynchronous
5688 @value{GDBN}'s execution commands have two variants: the normal
5689 foreground (synchronous) behavior, and a background
5690 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5691 the program to report that some thread has stopped before prompting for
5692 another command. In background execution, @value{GDBN} immediately gives
5693 a command prompt so that you can issue other commands while your program runs.
5695 You need to explicitly enable asynchronous mode before you can use
5696 background execution commands. You can use these commands to
5697 manipulate the asynchronous mode setting:
5700 @kindex set target-async
5701 @item set target-async on
5702 Enable asynchronous mode.
5703 @item set target-async off
5704 Disable asynchronous mode.
5705 @kindex show target-async
5706 @item show target-async
5707 Show the current target-async setting.
5710 If the target doesn't support async mode, @value{GDBN} issues an error
5711 message if you attempt to use the background execution commands.
5713 To specify background execution, add a @code{&} to the command. For example,
5714 the background form of the @code{continue} command is @code{continue&}, or
5715 just @code{c&}. The execution commands that accept background execution
5721 @xref{Starting, , Starting your Program}.
5725 @xref{Attach, , Debugging an Already-running Process}.
5729 @xref{Continuing and Stepping, step}.
5733 @xref{Continuing and Stepping, stepi}.
5737 @xref{Continuing and Stepping, next}.
5741 @xref{Continuing and Stepping, nexti}.
5745 @xref{Continuing and Stepping, continue}.
5749 @xref{Continuing and Stepping, finish}.
5753 @xref{Continuing and Stepping, until}.
5757 Background execution is especially useful in conjunction with non-stop
5758 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5759 However, you can also use these commands in the normal all-stop mode with
5760 the restriction that you cannot issue another execution command until the
5761 previous one finishes. Examples of commands that are valid in all-stop
5762 mode while the program is running include @code{help} and @code{info break}.
5764 You can interrupt your program while it is running in the background by
5765 using the @code{interrupt} command.
5772 Suspend execution of the running program. In all-stop mode,
5773 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5774 only the current thread. To stop the whole program in non-stop mode,
5775 use @code{interrupt -a}.
5778 @node Thread-Specific Breakpoints
5779 @subsection Thread-Specific Breakpoints
5781 When your program has multiple threads (@pxref{Threads,, Debugging
5782 Programs with Multiple Threads}), you can choose whether to set
5783 breakpoints on all threads, or on a particular thread.
5786 @cindex breakpoints and threads
5787 @cindex thread breakpoints
5788 @kindex break @dots{} thread @var{threadno}
5789 @item break @var{linespec} thread @var{threadno}
5790 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5791 @var{linespec} specifies source lines; there are several ways of
5792 writing them (@pxref{Specify Location}), but the effect is always to
5793 specify some source line.
5795 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5796 to specify that you only want @value{GDBN} to stop the program when a
5797 particular thread reaches this breakpoint. @var{threadno} is one of the
5798 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5799 column of the @samp{info threads} display.
5801 If you do not specify @samp{thread @var{threadno}} when you set a
5802 breakpoint, the breakpoint applies to @emph{all} threads of your
5805 You can use the @code{thread} qualifier on conditional breakpoints as
5806 well; in this case, place @samp{thread @var{threadno}} before or
5807 after the breakpoint condition, like this:
5810 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5815 @node Interrupted System Calls
5816 @subsection Interrupted System Calls
5818 @cindex thread breakpoints and system calls
5819 @cindex system calls and thread breakpoints
5820 @cindex premature return from system calls
5821 There is an unfortunate side effect when using @value{GDBN} to debug
5822 multi-threaded programs. If one thread stops for a
5823 breakpoint, or for some other reason, and another thread is blocked in a
5824 system call, then the system call may return prematurely. This is a
5825 consequence of the interaction between multiple threads and the signals
5826 that @value{GDBN} uses to implement breakpoints and other events that
5829 To handle this problem, your program should check the return value of
5830 each system call and react appropriately. This is good programming
5833 For example, do not write code like this:
5839 The call to @code{sleep} will return early if a different thread stops
5840 at a breakpoint or for some other reason.
5842 Instead, write this:
5847 unslept = sleep (unslept);
5850 A system call is allowed to return early, so the system is still
5851 conforming to its specification. But @value{GDBN} does cause your
5852 multi-threaded program to behave differently than it would without
5855 Also, @value{GDBN} uses internal breakpoints in the thread library to
5856 monitor certain events such as thread creation and thread destruction.
5857 When such an event happens, a system call in another thread may return
5858 prematurely, even though your program does not appear to stop.
5861 @subsection Observer Mode
5863 If you want to build on non-stop mode and observe program behavior
5864 without any chance of disruption by @value{GDBN}, you can set
5865 variables to disable all of the debugger's attempts to modify state,
5866 whether by writing memory, inserting breakpoints, etc. These operate
5867 at a low level, intercepting operations from all commands.
5869 When all of these are set to @code{off}, then @value{GDBN} is said to
5870 be @dfn{observer mode}. As a convenience, the variable
5871 @code{observer} can be set to disable these, plus enable non-stop
5874 Note that @value{GDBN} will not prevent you from making nonsensical
5875 combinations of these settings. For instance, if you have enabled
5876 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5877 then breakpoints that work by writing trap instructions into the code
5878 stream will still not be able to be placed.
5883 @item set observer on
5884 @itemx set observer off
5885 When set to @code{on}, this disables all the permission variables
5886 below (except for @code{insert-fast-tracepoints}), plus enables
5887 non-stop debugging. Setting this to @code{off} switches back to
5888 normal debugging, though remaining in non-stop mode.
5891 Show whether observer mode is on or off.
5893 @kindex may-write-registers
5894 @item set may-write-registers on
5895 @itemx set may-write-registers off
5896 This controls whether @value{GDBN} will attempt to alter the values of
5897 registers, such as with assignment expressions in @code{print}, or the
5898 @code{jump} command. It defaults to @code{on}.
5900 @item show may-write-registers
5901 Show the current permission to write registers.
5903 @kindex may-write-memory
5904 @item set may-write-memory on
5905 @itemx set may-write-memory off
5906 This controls whether @value{GDBN} will attempt to alter the contents
5907 of memory, such as with assignment expressions in @code{print}. It
5908 defaults to @code{on}.
5910 @item show may-write-memory
5911 Show the current permission to write memory.
5913 @kindex may-insert-breakpoints
5914 @item set may-insert-breakpoints on
5915 @itemx set may-insert-breakpoints off
5916 This controls whether @value{GDBN} will attempt to insert breakpoints.
5917 This affects all breakpoints, including internal breakpoints defined
5918 by @value{GDBN}. It defaults to @code{on}.
5920 @item show may-insert-breakpoints
5921 Show the current permission to insert breakpoints.
5923 @kindex may-insert-tracepoints
5924 @item set may-insert-tracepoints on
5925 @itemx set may-insert-tracepoints off
5926 This controls whether @value{GDBN} will attempt to insert (regular)
5927 tracepoints at the beginning of a tracing experiment. It affects only
5928 non-fast tracepoints, fast tracepoints being under the control of
5929 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5931 @item show may-insert-tracepoints
5932 Show the current permission to insert tracepoints.
5934 @kindex may-insert-fast-tracepoints
5935 @item set may-insert-fast-tracepoints on
5936 @itemx set may-insert-fast-tracepoints off
5937 This controls whether @value{GDBN} will attempt to insert fast
5938 tracepoints at the beginning of a tracing experiment. It affects only
5939 fast tracepoints, regular (non-fast) tracepoints being under the
5940 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5942 @item show may-insert-fast-tracepoints
5943 Show the current permission to insert fast tracepoints.
5945 @kindex may-interrupt
5946 @item set may-interrupt on
5947 @itemx set may-interrupt off
5948 This controls whether @value{GDBN} will attempt to interrupt or stop
5949 program execution. When this variable is @code{off}, the
5950 @code{interrupt} command will have no effect, nor will
5951 @kbd{Ctrl-c}. It defaults to @code{on}.
5953 @item show may-interrupt
5954 Show the current permission to interrupt or stop the program.
5958 @node Reverse Execution
5959 @chapter Running programs backward
5960 @cindex reverse execution
5961 @cindex running programs backward
5963 When you are debugging a program, it is not unusual to realize that
5964 you have gone too far, and some event of interest has already happened.
5965 If the target environment supports it, @value{GDBN} can allow you to
5966 ``rewind'' the program by running it backward.
5968 A target environment that supports reverse execution should be able
5969 to ``undo'' the changes in machine state that have taken place as the
5970 program was executing normally. Variables, registers etc.@: should
5971 revert to their previous values. Obviously this requires a great
5972 deal of sophistication on the part of the target environment; not
5973 all target environments can support reverse execution.
5975 When a program is executed in reverse, the instructions that
5976 have most recently been executed are ``un-executed'', in reverse
5977 order. The program counter runs backward, following the previous
5978 thread of execution in reverse. As each instruction is ``un-executed'',
5979 the values of memory and/or registers that were changed by that
5980 instruction are reverted to their previous states. After executing
5981 a piece of source code in reverse, all side effects of that code
5982 should be ``undone'', and all variables should be returned to their
5983 prior values@footnote{
5984 Note that some side effects are easier to undo than others. For instance,
5985 memory and registers are relatively easy, but device I/O is hard. Some
5986 targets may be able undo things like device I/O, and some may not.
5988 The contract between @value{GDBN} and the reverse executing target
5989 requires only that the target do something reasonable when
5990 @value{GDBN} tells it to execute backwards, and then report the
5991 results back to @value{GDBN}. Whatever the target reports back to
5992 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5993 assumes that the memory and registers that the target reports are in a
5994 consistant state, but @value{GDBN} accepts whatever it is given.
5997 If you are debugging in a target environment that supports
5998 reverse execution, @value{GDBN} provides the following commands.
6001 @kindex reverse-continue
6002 @kindex rc @r{(@code{reverse-continue})}
6003 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6004 @itemx rc @r{[}@var{ignore-count}@r{]}
6005 Beginning at the point where your program last stopped, start executing
6006 in reverse. Reverse execution will stop for breakpoints and synchronous
6007 exceptions (signals), just like normal execution. Behavior of
6008 asynchronous signals depends on the target environment.
6010 @kindex reverse-step
6011 @kindex rs @r{(@code{step})}
6012 @item reverse-step @r{[}@var{count}@r{]}
6013 Run the program backward until control reaches the start of a
6014 different source line; then stop it, and return control to @value{GDBN}.
6016 Like the @code{step} command, @code{reverse-step} will only stop
6017 at the beginning of a source line. It ``un-executes'' the previously
6018 executed source line. If the previous source line included calls to
6019 debuggable functions, @code{reverse-step} will step (backward) into
6020 the called function, stopping at the beginning of the @emph{last}
6021 statement in the called function (typically a return statement).
6023 Also, as with the @code{step} command, if non-debuggable functions are
6024 called, @code{reverse-step} will run thru them backward without stopping.
6026 @kindex reverse-stepi
6027 @kindex rsi @r{(@code{reverse-stepi})}
6028 @item reverse-stepi @r{[}@var{count}@r{]}
6029 Reverse-execute one machine instruction. Note that the instruction
6030 to be reverse-executed is @emph{not} the one pointed to by the program
6031 counter, but the instruction executed prior to that one. For instance,
6032 if the last instruction was a jump, @code{reverse-stepi} will take you
6033 back from the destination of the jump to the jump instruction itself.
6035 @kindex reverse-next
6036 @kindex rn @r{(@code{reverse-next})}
6037 @item reverse-next @r{[}@var{count}@r{]}
6038 Run backward to the beginning of the previous line executed in
6039 the current (innermost) stack frame. If the line contains function
6040 calls, they will be ``un-executed'' without stopping. Starting from
6041 the first line of a function, @code{reverse-next} will take you back
6042 to the caller of that function, @emph{before} the function was called,
6043 just as the normal @code{next} command would take you from the last
6044 line of a function back to its return to its caller
6045 @footnote{Unless the code is too heavily optimized.}.
6047 @kindex reverse-nexti
6048 @kindex rni @r{(@code{reverse-nexti})}
6049 @item reverse-nexti @r{[}@var{count}@r{]}
6050 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6051 in reverse, except that called functions are ``un-executed'' atomically.
6052 That is, if the previously executed instruction was a return from
6053 another function, @code{reverse-nexti} will continue to execute
6054 in reverse until the call to that function (from the current stack
6057 @kindex reverse-finish
6058 @item reverse-finish
6059 Just as the @code{finish} command takes you to the point where the
6060 current function returns, @code{reverse-finish} takes you to the point
6061 where it was called. Instead of ending up at the end of the current
6062 function invocation, you end up at the beginning.
6064 @kindex set exec-direction
6065 @item set exec-direction
6066 Set the direction of target execution.
6067 @item set exec-direction reverse
6068 @cindex execute forward or backward in time
6069 @value{GDBN} will perform all execution commands in reverse, until the
6070 exec-direction mode is changed to ``forward''. Affected commands include
6071 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6072 command cannot be used in reverse mode.
6073 @item set exec-direction forward
6074 @value{GDBN} will perform all execution commands in the normal fashion.
6075 This is the default.
6079 @node Process Record and Replay
6080 @chapter Recording Inferior's Execution and Replaying It
6081 @cindex process record and replay
6082 @cindex recording inferior's execution and replaying it
6084 On some platforms, @value{GDBN} provides a special @dfn{process record
6085 and replay} target that can record a log of the process execution, and
6086 replay it later with both forward and reverse execution commands.
6089 When this target is in use, if the execution log includes the record
6090 for the next instruction, @value{GDBN} will debug in @dfn{replay
6091 mode}. In the replay mode, the inferior does not really execute code
6092 instructions. Instead, all the events that normally happen during
6093 code execution are taken from the execution log. While code is not
6094 really executed in replay mode, the values of registers (including the
6095 program counter register) and the memory of the inferior are still
6096 changed as they normally would. Their contents are taken from the
6100 If the record for the next instruction is not in the execution log,
6101 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6102 inferior executes normally, and @value{GDBN} records the execution log
6105 The process record and replay target supports reverse execution
6106 (@pxref{Reverse Execution}), even if the platform on which the
6107 inferior runs does not. However, the reverse execution is limited in
6108 this case by the range of the instructions recorded in the execution
6109 log. In other words, reverse execution on platforms that don't
6110 support it directly can only be done in the replay mode.
6112 When debugging in the reverse direction, @value{GDBN} will work in
6113 replay mode as long as the execution log includes the record for the
6114 previous instruction; otherwise, it will work in record mode, if the
6115 platform supports reverse execution, or stop if not.
6117 For architecture environments that support process record and replay,
6118 @value{GDBN} provides the following commands:
6121 @kindex target record
6122 @kindex target record-full
6123 @kindex target record-btrace
6126 @kindex record btrace
6130 @item record @var{method}
6131 This command starts the process record and replay target. The
6132 recording method can be specified as parameter. Without a parameter
6133 the command uses the @code{full} recording method. The following
6134 recording methods are available:
6138 Full record/replay recording using @value{GDBN}'s software record and
6139 replay implementation. This method allows replaying and reverse
6143 Hardware-supported instruction recording. This method does not allow
6144 replaying and reverse execution.
6146 This recording method may not be available on all processors.
6149 The process record and replay target can only debug a process that is
6150 already running. Therefore, you need first to start the process with
6151 the @kbd{run} or @kbd{start} commands, and then start the recording
6152 with the @kbd{record @var{method}} command.
6154 Both @code{record @var{method}} and @code{rec @var{method}} are
6155 aliases of @code{target record-@var{method}}.
6157 @cindex displaced stepping, and process record and replay
6158 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6159 will be automatically disabled when process record and replay target
6160 is started. That's because the process record and replay target
6161 doesn't support displaced stepping.
6163 @cindex non-stop mode, and process record and replay
6164 @cindex asynchronous execution, and process record and replay
6165 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6166 the asynchronous execution mode (@pxref{Background Execution}), not
6167 all recording methods are available. The @code{full} recording method
6168 does not support these two modes.
6173 Stop the process record and replay target. When process record and
6174 replay target stops, the entire execution log will be deleted and the
6175 inferior will either be terminated, or will remain in its final state.
6177 When you stop the process record and replay target in record mode (at
6178 the end of the execution log), the inferior will be stopped at the
6179 next instruction that would have been recorded. In other words, if
6180 you record for a while and then stop recording, the inferior process
6181 will be left in the same state as if the recording never happened.
6183 On the other hand, if the process record and replay target is stopped
6184 while in replay mode (that is, not at the end of the execution log,
6185 but at some earlier point), the inferior process will become ``live''
6186 at that earlier state, and it will then be possible to continue the
6187 usual ``live'' debugging of the process from that state.
6189 When the inferior process exits, or @value{GDBN} detaches from it,
6190 process record and replay target will automatically stop itself.
6193 @item record save @var{filename}
6194 Save the execution log to a file @file{@var{filename}}.
6195 Default filename is @file{gdb_record.@var{process_id}}, where
6196 @var{process_id} is the process ID of the inferior.
6198 This command may not be available for all recording methods.
6200 @kindex record restore
6201 @item record restore @var{filename}
6202 Restore the execution log from a file @file{@var{filename}}.
6203 File must have been created with @code{record save}.
6205 @kindex set record full
6206 @item set record full insn-number-max @var{limit}
6207 @itemx set record full insn-number-max unlimited
6208 Set the limit of instructions to be recorded for the @code{full}
6209 recording method. Default value is 200000.
6211 If @var{limit} is a positive number, then @value{GDBN} will start
6212 deleting instructions from the log once the number of the record
6213 instructions becomes greater than @var{limit}. For every new recorded
6214 instruction, @value{GDBN} will delete the earliest recorded
6215 instruction to keep the number of recorded instructions at the limit.
6216 (Since deleting recorded instructions loses information, @value{GDBN}
6217 lets you control what happens when the limit is reached, by means of
6218 the @code{stop-at-limit} option, described below.)
6220 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6221 delete recorded instructions from the execution log. The number of
6222 recorded instructions is limited only by the available memory.
6224 @kindex show record full
6225 @item show record full insn-number-max
6226 Show the limit of instructions to be recorded with the @code{full}
6229 @item set record full stop-at-limit
6230 Control the behavior of the @code{full} recording method when the
6231 number of recorded instructions reaches the limit. If ON (the
6232 default), @value{GDBN} will stop when the limit is reached for the
6233 first time and ask you whether you want to stop the inferior or
6234 continue running it and recording the execution log. If you decide
6235 to continue recording, each new recorded instruction will cause the
6236 oldest one to be deleted.
6238 If this option is OFF, @value{GDBN} will automatically delete the
6239 oldest record to make room for each new one, without asking.
6241 @item show record full stop-at-limit
6242 Show the current setting of @code{stop-at-limit}.
6244 @item set record full memory-query
6245 Control the behavior when @value{GDBN} is unable to record memory
6246 changes caused by an instruction for the @code{full} recording method.
6247 If ON, @value{GDBN} will query whether to stop the inferior in that
6250 If this option is OFF (the default), @value{GDBN} will automatically
6251 ignore the effect of such instructions on memory. Later, when
6252 @value{GDBN} replays this execution log, it will mark the log of this
6253 instruction as not accessible, and it will not affect the replay
6256 @item show record full memory-query
6257 Show the current setting of @code{memory-query}.
6261 Show various statistics about the recording depending on the recording
6266 For the @code{full} recording method, it shows the state of process
6267 record and its in-memory execution log buffer, including:
6271 Whether in record mode or replay mode.
6273 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6275 Highest recorded instruction number.
6277 Current instruction about to be replayed (if in replay mode).
6279 Number of instructions contained in the execution log.
6281 Maximum number of instructions that may be contained in the execution log.
6285 For the @code{btrace} recording method, it shows the number of
6286 instructions that have been recorded and the number of blocks of
6287 sequential control-flow that is formed by the recorded instructions.
6290 @kindex record delete
6293 When record target runs in replay mode (``in the past''), delete the
6294 subsequent execution log and begin to record a new execution log starting
6295 from the current address. This means you will abandon the previously
6296 recorded ``future'' and begin recording a new ``future''.
6298 @kindex record instruction-history
6299 @kindex rec instruction-history
6300 @item record instruction-history
6301 Disassembles instructions from the recorded execution log. By
6302 default, ten instructions are disassembled. This can be changed using
6303 the @code{set record instruction-history-size} command. Instructions
6304 are printed in execution order. There are several ways to specify
6305 what part of the execution log to disassemble:
6308 @item record instruction-history @var{insn}
6309 Disassembles ten instructions starting from instruction number
6312 @item record instruction-history @var{insn}, +/-@var{n}
6313 Disassembles @var{n} instructions around instruction number
6314 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6315 @var{n} instructions after instruction number @var{insn}. If
6316 @var{n} is preceded with @code{-}, disassembles @var{n}
6317 instructions before instruction number @var{insn}.
6319 @item record instruction-history
6320 Disassembles ten more instructions after the last disassembly.
6322 @item record instruction-history -
6323 Disassembles ten more instructions before the last disassembly.
6325 @item record instruction-history @var{begin} @var{end}
6326 Disassembles instructions beginning with instruction number
6327 @var{begin} until instruction number @var{end}. The instruction
6328 number @var{end} is not included.
6331 This command may not be available for all recording methods.
6334 @item set record instruction-history-size @var{size}
6335 @itemx set record instruction-history-size unlimited
6336 Define how many instructions to disassemble in the @code{record
6337 instruction-history} command. The default value is 10.
6338 A @var{size} of @code{unlimited} means unlimited instructions.
6341 @item show record instruction-history-size
6342 Show how many instructions to disassemble in the @code{record
6343 instruction-history} command.
6345 @kindex record function-call-history
6346 @kindex rec function-call-history
6347 @item record function-call-history
6348 Prints the execution history at function granularity. It prints one
6349 line for each sequence of instructions that belong to the same
6350 function giving the name of that function, the source lines
6351 for this instruction sequence (if the @code{/l} modifier is
6352 specified), and the instructions numbers that form the sequence (if
6353 the @code{/i} modifier is specified).
6356 (@value{GDBP}) @b{list 1, 10}
6367 (@value{GDBP}) @b{record function-call-history /l}
6373 By default, ten lines are printed. This can be changed using the
6374 @code{set record function-call-history-size} command. Functions are
6375 printed in execution order. There are several ways to specify what
6379 @item record function-call-history @var{func}
6380 Prints ten functions starting from function number @var{func}.
6382 @item record function-call-history @var{func}, +/-@var{n}
6383 Prints @var{n} functions around function number @var{func}. If
6384 @var{n} is preceded with @code{+}, prints @var{n} functions after
6385 function number @var{func}. If @var{n} is preceded with @code{-},
6386 prints @var{n} functions before function number @var{func}.
6388 @item record function-call-history
6389 Prints ten more functions after the last ten-line print.
6391 @item record function-call-history -
6392 Prints ten more functions before the last ten-line print.
6394 @item record function-call-history @var{begin} @var{end}
6395 Prints functions beginning with function number @var{begin} until
6396 function number @var{end}. The function number @var{end} is not
6400 This command may not be available for all recording methods.
6402 @item set record function-call-history-size @var{size}
6403 @itemx set record function-call-history-size unlimited
6404 Define how many lines to print in the
6405 @code{record function-call-history} command. The default value is 10.
6406 A size of @code{unlimited} means unlimited lines.
6408 @item show record function-call-history-size
6409 Show how many lines to print in the
6410 @code{record function-call-history} command.
6415 @chapter Examining the Stack
6417 When your program has stopped, the first thing you need to know is where it
6418 stopped and how it got there.
6421 Each time your program performs a function call, information about the call
6423 That information includes the location of the call in your program,
6424 the arguments of the call,
6425 and the local variables of the function being called.
6426 The information is saved in a block of data called a @dfn{stack frame}.
6427 The stack frames are allocated in a region of memory called the @dfn{call
6430 When your program stops, the @value{GDBN} commands for examining the
6431 stack allow you to see all of this information.
6433 @cindex selected frame
6434 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6435 @value{GDBN} commands refer implicitly to the selected frame. In
6436 particular, whenever you ask @value{GDBN} for the value of a variable in
6437 your program, the value is found in the selected frame. There are
6438 special @value{GDBN} commands to select whichever frame you are
6439 interested in. @xref{Selection, ,Selecting a Frame}.
6441 When your program stops, @value{GDBN} automatically selects the
6442 currently executing frame and describes it briefly, similar to the
6443 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6446 * Frames:: Stack frames
6447 * Backtrace:: Backtraces
6448 * Selection:: Selecting a frame
6449 * Frame Info:: Information on a frame
6454 @section Stack Frames
6456 @cindex frame, definition
6458 The call stack is divided up into contiguous pieces called @dfn{stack
6459 frames}, or @dfn{frames} for short; each frame is the data associated
6460 with one call to one function. The frame contains the arguments given
6461 to the function, the function's local variables, and the address at
6462 which the function is executing.
6464 @cindex initial frame
6465 @cindex outermost frame
6466 @cindex innermost frame
6467 When your program is started, the stack has only one frame, that of the
6468 function @code{main}. This is called the @dfn{initial} frame or the
6469 @dfn{outermost} frame. Each time a function is called, a new frame is
6470 made. Each time a function returns, the frame for that function invocation
6471 is eliminated. If a function is recursive, there can be many frames for
6472 the same function. The frame for the function in which execution is
6473 actually occurring is called the @dfn{innermost} frame. This is the most
6474 recently created of all the stack frames that still exist.
6476 @cindex frame pointer
6477 Inside your program, stack frames are identified by their addresses. A
6478 stack frame consists of many bytes, each of which has its own address; each
6479 kind of computer has a convention for choosing one byte whose
6480 address serves as the address of the frame. Usually this address is kept
6481 in a register called the @dfn{frame pointer register}
6482 (@pxref{Registers, $fp}) while execution is going on in that frame.
6484 @cindex frame number
6485 @value{GDBN} assigns numbers to all existing stack frames, starting with
6486 zero for the innermost frame, one for the frame that called it,
6487 and so on upward. These numbers do not really exist in your program;
6488 they are assigned by @value{GDBN} to give you a way of designating stack
6489 frames in @value{GDBN} commands.
6491 @c The -fomit-frame-pointer below perennially causes hbox overflow
6492 @c underflow problems.
6493 @cindex frameless execution
6494 Some compilers provide a way to compile functions so that they operate
6495 without stack frames. (For example, the @value{NGCC} option
6497 @samp{-fomit-frame-pointer}
6499 generates functions without a frame.)
6500 This is occasionally done with heavily used library functions to save
6501 the frame setup time. @value{GDBN} has limited facilities for dealing
6502 with these function invocations. If the innermost function invocation
6503 has no stack frame, @value{GDBN} nevertheless regards it as though
6504 it had a separate frame, which is numbered zero as usual, allowing
6505 correct tracing of the function call chain. However, @value{GDBN} has
6506 no provision for frameless functions elsewhere in the stack.
6509 @kindex frame@r{, command}
6510 @cindex current stack frame
6511 @item frame @var{args}
6512 The @code{frame} command allows you to move from one stack frame to another,
6513 and to print the stack frame you select. @var{args} may be either the
6514 address of the frame or the stack frame number. Without an argument,
6515 @code{frame} prints the current stack frame.
6517 @kindex select-frame
6518 @cindex selecting frame silently
6520 The @code{select-frame} command allows you to move from one stack frame
6521 to another without printing the frame. This is the silent version of
6529 @cindex call stack traces
6530 A backtrace is a summary of how your program got where it is. It shows one
6531 line per frame, for many frames, starting with the currently executing
6532 frame (frame zero), followed by its caller (frame one), and on up the
6537 @kindex bt @r{(@code{backtrace})}
6540 Print a backtrace of the entire stack: one line per frame for all
6541 frames in the stack.
6543 You can stop the backtrace at any time by typing the system interrupt
6544 character, normally @kbd{Ctrl-c}.
6546 @item backtrace @var{n}
6548 Similar, but print only the innermost @var{n} frames.
6550 @item backtrace -@var{n}
6552 Similar, but print only the outermost @var{n} frames.
6554 @item backtrace full
6556 @itemx bt full @var{n}
6557 @itemx bt full -@var{n}
6558 Print the values of the local variables also. @var{n} specifies the
6559 number of frames to print, as described above.
6564 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6565 are additional aliases for @code{backtrace}.
6567 @cindex multiple threads, backtrace
6568 In a multi-threaded program, @value{GDBN} by default shows the
6569 backtrace only for the current thread. To display the backtrace for
6570 several or all of the threads, use the command @code{thread apply}
6571 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6572 apply all backtrace}, @value{GDBN} will display the backtrace for all
6573 the threads; this is handy when you debug a core dump of a
6574 multi-threaded program.
6576 Each line in the backtrace shows the frame number and the function name.
6577 The program counter value is also shown---unless you use @code{set
6578 print address off}. The backtrace also shows the source file name and
6579 line number, as well as the arguments to the function. The program
6580 counter value is omitted if it is at the beginning of the code for that
6583 Here is an example of a backtrace. It was made with the command
6584 @samp{bt 3}, so it shows the innermost three frames.
6588 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6590 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6591 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6593 (More stack frames follow...)
6598 The display for frame zero does not begin with a program counter
6599 value, indicating that your program has stopped at the beginning of the
6600 code for line @code{993} of @code{builtin.c}.
6603 The value of parameter @code{data} in frame 1 has been replaced by
6604 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6605 only if it is a scalar (integer, pointer, enumeration, etc). See command
6606 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6607 on how to configure the way function parameter values are printed.
6609 @cindex optimized out, in backtrace
6610 @cindex function call arguments, optimized out
6611 If your program was compiled with optimizations, some compilers will
6612 optimize away arguments passed to functions if those arguments are
6613 never used after the call. Such optimizations generate code that
6614 passes arguments through registers, but doesn't store those arguments
6615 in the stack frame. @value{GDBN} has no way of displaying such
6616 arguments in stack frames other than the innermost one. Here's what
6617 such a backtrace might look like:
6621 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6623 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6624 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6626 (More stack frames follow...)
6631 The values of arguments that were not saved in their stack frames are
6632 shown as @samp{<optimized out>}.
6634 If you need to display the values of such optimized-out arguments,
6635 either deduce that from other variables whose values depend on the one
6636 you are interested in, or recompile without optimizations.
6638 @cindex backtrace beyond @code{main} function
6639 @cindex program entry point
6640 @cindex startup code, and backtrace
6641 Most programs have a standard user entry point---a place where system
6642 libraries and startup code transition into user code. For C this is
6643 @code{main}@footnote{
6644 Note that embedded programs (the so-called ``free-standing''
6645 environment) are not required to have a @code{main} function as the
6646 entry point. They could even have multiple entry points.}.
6647 When @value{GDBN} finds the entry function in a backtrace
6648 it will terminate the backtrace, to avoid tracing into highly
6649 system-specific (and generally uninteresting) code.
6651 If you need to examine the startup code, or limit the number of levels
6652 in a backtrace, you can change this behavior:
6655 @item set backtrace past-main
6656 @itemx set backtrace past-main on
6657 @kindex set backtrace
6658 Backtraces will continue past the user entry point.
6660 @item set backtrace past-main off
6661 Backtraces will stop when they encounter the user entry point. This is the
6664 @item show backtrace past-main
6665 @kindex show backtrace
6666 Display the current user entry point backtrace policy.
6668 @item set backtrace past-entry
6669 @itemx set backtrace past-entry on
6670 Backtraces will continue past the internal entry point of an application.
6671 This entry point is encoded by the linker when the application is built,
6672 and is likely before the user entry point @code{main} (or equivalent) is called.
6674 @item set backtrace past-entry off
6675 Backtraces will stop when they encounter the internal entry point of an
6676 application. This is the default.
6678 @item show backtrace past-entry
6679 Display the current internal entry point backtrace policy.
6681 @item set backtrace limit @var{n}
6682 @itemx set backtrace limit 0
6683 @itemx set backtrace limit unlimited
6684 @cindex backtrace limit
6685 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6686 or zero means unlimited levels.
6688 @item show backtrace limit
6689 Display the current limit on backtrace levels.
6692 You can control how file names are displayed.
6695 @item set filename-display
6696 @itemx set filename-display relative
6697 @cindex filename-display
6698 Display file names relative to the compilation directory. This is the default.
6700 @item set filename-display basename
6701 Display only basename of a filename.
6703 @item set filename-display absolute
6704 Display an absolute filename.
6706 @item show filename-display
6707 Show the current way to display filenames.
6711 @section Selecting a Frame
6713 Most commands for examining the stack and other data in your program work on
6714 whichever stack frame is selected at the moment. Here are the commands for
6715 selecting a stack frame; all of them finish by printing a brief description
6716 of the stack frame just selected.
6719 @kindex frame@r{, selecting}
6720 @kindex f @r{(@code{frame})}
6723 Select frame number @var{n}. Recall that frame zero is the innermost
6724 (currently executing) frame, frame one is the frame that called the
6725 innermost one, and so on. The highest-numbered frame is the one for
6728 @item frame @var{addr}
6730 Select the frame at address @var{addr}. This is useful mainly if the
6731 chaining of stack frames has been damaged by a bug, making it
6732 impossible for @value{GDBN} to assign numbers properly to all frames. In
6733 addition, this can be useful when your program has multiple stacks and
6734 switches between them.
6736 On the SPARC architecture, @code{frame} needs two addresses to
6737 select an arbitrary frame: a frame pointer and a stack pointer.
6739 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6740 pointer and a program counter.
6742 On the 29k architecture, it needs three addresses: a register stack
6743 pointer, a program counter, and a memory stack pointer.
6747 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6748 advances toward the outermost frame, to higher frame numbers, to frames
6749 that have existed longer. @var{n} defaults to one.
6752 @kindex do @r{(@code{down})}
6754 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6755 advances toward the innermost frame, to lower frame numbers, to frames
6756 that were created more recently. @var{n} defaults to one. You may
6757 abbreviate @code{down} as @code{do}.
6760 All of these commands end by printing two lines of output describing the
6761 frame. The first line shows the frame number, the function name, the
6762 arguments, and the source file and line number of execution in that
6763 frame. The second line shows the text of that source line.
6771 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6773 10 read_input_file (argv[i]);
6777 After such a printout, the @code{list} command with no arguments
6778 prints ten lines centered on the point of execution in the frame.
6779 You can also edit the program at the point of execution with your favorite
6780 editing program by typing @code{edit}.
6781 @xref{List, ,Printing Source Lines},
6785 @kindex down-silently
6787 @item up-silently @var{n}
6788 @itemx down-silently @var{n}
6789 These two commands are variants of @code{up} and @code{down},
6790 respectively; they differ in that they do their work silently, without
6791 causing display of the new frame. They are intended primarily for use
6792 in @value{GDBN} command scripts, where the output might be unnecessary and
6797 @section Information About a Frame
6799 There are several other commands to print information about the selected
6805 When used without any argument, this command does not change which
6806 frame is selected, but prints a brief description of the currently
6807 selected stack frame. It can be abbreviated @code{f}. With an
6808 argument, this command is used to select a stack frame.
6809 @xref{Selection, ,Selecting a Frame}.
6812 @kindex info f @r{(@code{info frame})}
6815 This command prints a verbose description of the selected stack frame,
6820 the address of the frame
6822 the address of the next frame down (called by this frame)
6824 the address of the next frame up (caller of this frame)
6826 the language in which the source code corresponding to this frame is written
6828 the address of the frame's arguments
6830 the address of the frame's local variables
6832 the program counter saved in it (the address of execution in the caller frame)
6834 which registers were saved in the frame
6837 @noindent The verbose description is useful when
6838 something has gone wrong that has made the stack format fail to fit
6839 the usual conventions.
6841 @item info frame @var{addr}
6842 @itemx info f @var{addr}
6843 Print a verbose description of the frame at address @var{addr}, without
6844 selecting that frame. The selected frame remains unchanged by this
6845 command. This requires the same kind of address (more than one for some
6846 architectures) that you specify in the @code{frame} command.
6847 @xref{Selection, ,Selecting a Frame}.
6851 Print the arguments of the selected frame, each on a separate line.
6855 Print the local variables of the selected frame, each on a separate
6856 line. These are all variables (declared either static or automatic)
6857 accessible at the point of execution of the selected frame.
6863 @chapter Examining Source Files
6865 @value{GDBN} can print parts of your program's source, since the debugging
6866 information recorded in the program tells @value{GDBN} what source files were
6867 used to build it. When your program stops, @value{GDBN} spontaneously prints
6868 the line where it stopped. Likewise, when you select a stack frame
6869 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6870 execution in that frame has stopped. You can print other portions of
6871 source files by explicit command.
6873 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6874 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6875 @value{GDBN} under @sc{gnu} Emacs}.
6878 * List:: Printing source lines
6879 * Specify Location:: How to specify code locations
6880 * Edit:: Editing source files
6881 * Search:: Searching source files
6882 * Source Path:: Specifying source directories
6883 * Machine Code:: Source and machine code
6887 @section Printing Source Lines
6890 @kindex l @r{(@code{list})}
6891 To print lines from a source file, use the @code{list} command
6892 (abbreviated @code{l}). By default, ten lines are printed.
6893 There are several ways to specify what part of the file you want to
6894 print; see @ref{Specify Location}, for the full list.
6896 Here are the forms of the @code{list} command most commonly used:
6899 @item list @var{linenum}
6900 Print lines centered around line number @var{linenum} in the
6901 current source file.
6903 @item list @var{function}
6904 Print lines centered around the beginning of function
6908 Print more lines. If the last lines printed were printed with a
6909 @code{list} command, this prints lines following the last lines
6910 printed; however, if the last line printed was a solitary line printed
6911 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6912 Stack}), this prints lines centered around that line.
6915 Print lines just before the lines last printed.
6918 @cindex @code{list}, how many lines to display
6919 By default, @value{GDBN} prints ten source lines with any of these forms of
6920 the @code{list} command. You can change this using @code{set listsize}:
6923 @kindex set listsize
6924 @item set listsize @var{count}
6925 @itemx set listsize unlimited
6926 Make the @code{list} command display @var{count} source lines (unless
6927 the @code{list} argument explicitly specifies some other number).
6928 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
6930 @kindex show listsize
6932 Display the number of lines that @code{list} prints.
6935 Repeating a @code{list} command with @key{RET} discards the argument,
6936 so it is equivalent to typing just @code{list}. This is more useful
6937 than listing the same lines again. An exception is made for an
6938 argument of @samp{-}; that argument is preserved in repetition so that
6939 each repetition moves up in the source file.
6941 In general, the @code{list} command expects you to supply zero, one or two
6942 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6943 of writing them (@pxref{Specify Location}), but the effect is always
6944 to specify some source line.
6946 Here is a complete description of the possible arguments for @code{list}:
6949 @item list @var{linespec}
6950 Print lines centered around the line specified by @var{linespec}.
6952 @item list @var{first},@var{last}
6953 Print lines from @var{first} to @var{last}. Both arguments are
6954 linespecs. When a @code{list} command has two linespecs, and the
6955 source file of the second linespec is omitted, this refers to
6956 the same source file as the first linespec.
6958 @item list ,@var{last}
6959 Print lines ending with @var{last}.
6961 @item list @var{first},
6962 Print lines starting with @var{first}.
6965 Print lines just after the lines last printed.
6968 Print lines just before the lines last printed.
6971 As described in the preceding table.
6974 @node Specify Location
6975 @section Specifying a Location
6976 @cindex specifying location
6979 Several @value{GDBN} commands accept arguments that specify a location
6980 of your program's code. Since @value{GDBN} is a source-level
6981 debugger, a location usually specifies some line in the source code;
6982 for that reason, locations are also known as @dfn{linespecs}.
6984 Here are all the different ways of specifying a code location that
6985 @value{GDBN} understands:
6989 Specifies the line number @var{linenum} of the current source file.
6992 @itemx +@var{offset}
6993 Specifies the line @var{offset} lines before or after the @dfn{current
6994 line}. For the @code{list} command, the current line is the last one
6995 printed; for the breakpoint commands, this is the line at which
6996 execution stopped in the currently selected @dfn{stack frame}
6997 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6998 used as the second of the two linespecs in a @code{list} command,
6999 this specifies the line @var{offset} lines up or down from the first
7002 @item @var{filename}:@var{linenum}
7003 Specifies the line @var{linenum} in the source file @var{filename}.
7004 If @var{filename} is a relative file name, then it will match any
7005 source file name with the same trailing components. For example, if
7006 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7007 name of @file{/build/trunk/gcc/expr.c}, but not
7008 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7010 @item @var{function}
7011 Specifies the line that begins the body of the function @var{function}.
7012 For example, in C, this is the line with the open brace.
7014 @item @var{function}:@var{label}
7015 Specifies the line where @var{label} appears in @var{function}.
7017 @item @var{filename}:@var{function}
7018 Specifies the line that begins the body of the function @var{function}
7019 in the file @var{filename}. You only need the file name with a
7020 function name to avoid ambiguity when there are identically named
7021 functions in different source files.
7024 Specifies the line at which the label named @var{label} appears.
7025 @value{GDBN} searches for the label in the function corresponding to
7026 the currently selected stack frame. If there is no current selected
7027 stack frame (for instance, if the inferior is not running), then
7028 @value{GDBN} will not search for a label.
7030 @item *@var{address}
7031 Specifies the program address @var{address}. For line-oriented
7032 commands, such as @code{list} and @code{edit}, this specifies a source
7033 line that contains @var{address}. For @code{break} and other
7034 breakpoint oriented commands, this can be used to set breakpoints in
7035 parts of your program which do not have debugging information or
7038 Here @var{address} may be any expression valid in the current working
7039 language (@pxref{Languages, working language}) that specifies a code
7040 address. In addition, as a convenience, @value{GDBN} extends the
7041 semantics of expressions used in locations to cover the situations
7042 that frequently happen during debugging. Here are the various forms
7046 @item @var{expression}
7047 Any expression valid in the current working language.
7049 @item @var{funcaddr}
7050 An address of a function or procedure derived from its name. In C,
7051 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7052 simply the function's name @var{function} (and actually a special case
7053 of a valid expression). In Pascal and Modula-2, this is
7054 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7055 (although the Pascal form also works).
7057 This form specifies the address of the function's first instruction,
7058 before the stack frame and arguments have been set up.
7060 @item '@var{filename}'::@var{funcaddr}
7061 Like @var{funcaddr} above, but also specifies the name of the source
7062 file explicitly. This is useful if the name of the function does not
7063 specify the function unambiguously, e.g., if there are several
7064 functions with identical names in different source files.
7067 @cindex breakpoint at static probe point
7068 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7069 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7070 applications to embed static probes. @xref{Static Probe Points}, for more
7071 information on finding and using static probes. This form of linespec
7072 specifies the location of such a static probe.
7074 If @var{objfile} is given, only probes coming from that shared library
7075 or executable matching @var{objfile} as a regular expression are considered.
7076 If @var{provider} is given, then only probes from that provider are considered.
7077 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7078 each one of those probes.
7084 @section Editing Source Files
7085 @cindex editing source files
7088 @kindex e @r{(@code{edit})}
7089 To edit the lines in a source file, use the @code{edit} command.
7090 The editing program of your choice
7091 is invoked with the current line set to
7092 the active line in the program.
7093 Alternatively, there are several ways to specify what part of the file you
7094 want to print if you want to see other parts of the program:
7097 @item edit @var{location}
7098 Edit the source file specified by @code{location}. Editing starts at
7099 that @var{location}, e.g., at the specified source line of the
7100 specified file. @xref{Specify Location}, for all the possible forms
7101 of the @var{location} argument; here are the forms of the @code{edit}
7102 command most commonly used:
7105 @item edit @var{number}
7106 Edit the current source file with @var{number} as the active line number.
7108 @item edit @var{function}
7109 Edit the file containing @var{function} at the beginning of its definition.
7114 @subsection Choosing your Editor
7115 You can customize @value{GDBN} to use any editor you want
7117 The only restriction is that your editor (say @code{ex}), recognizes the
7118 following command-line syntax:
7120 ex +@var{number} file
7122 The optional numeric value +@var{number} specifies the number of the line in
7123 the file where to start editing.}.
7124 By default, it is @file{@value{EDITOR}}, but you can change this
7125 by setting the environment variable @code{EDITOR} before using
7126 @value{GDBN}. For example, to configure @value{GDBN} to use the
7127 @code{vi} editor, you could use these commands with the @code{sh} shell:
7133 or in the @code{csh} shell,
7135 setenv EDITOR /usr/bin/vi
7140 @section Searching Source Files
7141 @cindex searching source files
7143 There are two commands for searching through the current source file for a
7148 @kindex forward-search
7149 @kindex fo @r{(@code{forward-search})}
7150 @item forward-search @var{regexp}
7151 @itemx search @var{regexp}
7152 The command @samp{forward-search @var{regexp}} checks each line,
7153 starting with the one following the last line listed, for a match for
7154 @var{regexp}. It lists the line that is found. You can use the
7155 synonym @samp{search @var{regexp}} or abbreviate the command name as
7158 @kindex reverse-search
7159 @item reverse-search @var{regexp}
7160 The command @samp{reverse-search @var{regexp}} checks each line, starting
7161 with the one before the last line listed and going backward, for a match
7162 for @var{regexp}. It lists the line that is found. You can abbreviate
7163 this command as @code{rev}.
7167 @section Specifying Source Directories
7170 @cindex directories for source files
7171 Executable programs sometimes do not record the directories of the source
7172 files from which they were compiled, just the names. Even when they do,
7173 the directories could be moved between the compilation and your debugging
7174 session. @value{GDBN} has a list of directories to search for source files;
7175 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7176 it tries all the directories in the list, in the order they are present
7177 in the list, until it finds a file with the desired name.
7179 For example, suppose an executable references the file
7180 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7181 @file{/mnt/cross}. The file is first looked up literally; if this
7182 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7183 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7184 message is printed. @value{GDBN} does not look up the parts of the
7185 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7186 Likewise, the subdirectories of the source path are not searched: if
7187 the source path is @file{/mnt/cross}, and the binary refers to
7188 @file{foo.c}, @value{GDBN} would not find it under
7189 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7191 Plain file names, relative file names with leading directories, file
7192 names containing dots, etc.@: are all treated as described above; for
7193 instance, if the source path is @file{/mnt/cross}, and the source file
7194 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7195 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7196 that---@file{/mnt/cross/foo.c}.
7198 Note that the executable search path is @emph{not} used to locate the
7201 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7202 any information it has cached about where source files are found and where
7203 each line is in the file.
7207 When you start @value{GDBN}, its source path includes only @samp{cdir}
7208 and @samp{cwd}, in that order.
7209 To add other directories, use the @code{directory} command.
7211 The search path is used to find both program source files and @value{GDBN}
7212 script files (read using the @samp{-command} option and @samp{source} command).
7214 In addition to the source path, @value{GDBN} provides a set of commands
7215 that manage a list of source path substitution rules. A @dfn{substitution
7216 rule} specifies how to rewrite source directories stored in the program's
7217 debug information in case the sources were moved to a different
7218 directory between compilation and debugging. A rule is made of
7219 two strings, the first specifying what needs to be rewritten in
7220 the path, and the second specifying how it should be rewritten.
7221 In @ref{set substitute-path}, we name these two parts @var{from} and
7222 @var{to} respectively. @value{GDBN} does a simple string replacement
7223 of @var{from} with @var{to} at the start of the directory part of the
7224 source file name, and uses that result instead of the original file
7225 name to look up the sources.
7227 Using the previous example, suppose the @file{foo-1.0} tree has been
7228 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7229 @value{GDBN} to replace @file{/usr/src} in all source path names with
7230 @file{/mnt/cross}. The first lookup will then be
7231 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7232 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7233 substitution rule, use the @code{set substitute-path} command
7234 (@pxref{set substitute-path}).
7236 To avoid unexpected substitution results, a rule is applied only if the
7237 @var{from} part of the directory name ends at a directory separator.
7238 For instance, a rule substituting @file{/usr/source} into
7239 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7240 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7241 is applied only at the beginning of the directory name, this rule will
7242 not be applied to @file{/root/usr/source/baz.c} either.
7244 In many cases, you can achieve the same result using the @code{directory}
7245 command. However, @code{set substitute-path} can be more efficient in
7246 the case where the sources are organized in a complex tree with multiple
7247 subdirectories. With the @code{directory} command, you need to add each
7248 subdirectory of your project. If you moved the entire tree while
7249 preserving its internal organization, then @code{set substitute-path}
7250 allows you to direct the debugger to all the sources with one single
7253 @code{set substitute-path} is also more than just a shortcut command.
7254 The source path is only used if the file at the original location no
7255 longer exists. On the other hand, @code{set substitute-path} modifies
7256 the debugger behavior to look at the rewritten location instead. So, if
7257 for any reason a source file that is not relevant to your executable is
7258 located at the original location, a substitution rule is the only
7259 method available to point @value{GDBN} at the new location.
7261 @cindex @samp{--with-relocated-sources}
7262 @cindex default source path substitution
7263 You can configure a default source path substitution rule by
7264 configuring @value{GDBN} with the
7265 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7266 should be the name of a directory under @value{GDBN}'s configured
7267 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7268 directory names in debug information under @var{dir} will be adjusted
7269 automatically if the installed @value{GDBN} is moved to a new
7270 location. This is useful if @value{GDBN}, libraries or executables
7271 with debug information and corresponding source code are being moved
7275 @item directory @var{dirname} @dots{}
7276 @item dir @var{dirname} @dots{}
7277 Add directory @var{dirname} to the front of the source path. Several
7278 directory names may be given to this command, separated by @samp{:}
7279 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7280 part of absolute file names) or
7281 whitespace. You may specify a directory that is already in the source
7282 path; this moves it forward, so @value{GDBN} searches it sooner.
7286 @vindex $cdir@r{, convenience variable}
7287 @vindex $cwd@r{, convenience variable}
7288 @cindex compilation directory
7289 @cindex current directory
7290 @cindex working directory
7291 @cindex directory, current
7292 @cindex directory, compilation
7293 You can use the string @samp{$cdir} to refer to the compilation
7294 directory (if one is recorded), and @samp{$cwd} to refer to the current
7295 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7296 tracks the current working directory as it changes during your @value{GDBN}
7297 session, while the latter is immediately expanded to the current
7298 directory at the time you add an entry to the source path.
7301 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7303 @c RET-repeat for @code{directory} is explicitly disabled, but since
7304 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7306 @item set directories @var{path-list}
7307 @kindex set directories
7308 Set the source path to @var{path-list}.
7309 @samp{$cdir:$cwd} are added if missing.
7311 @item show directories
7312 @kindex show directories
7313 Print the source path: show which directories it contains.
7315 @anchor{set substitute-path}
7316 @item set substitute-path @var{from} @var{to}
7317 @kindex set substitute-path
7318 Define a source path substitution rule, and add it at the end of the
7319 current list of existing substitution rules. If a rule with the same
7320 @var{from} was already defined, then the old rule is also deleted.
7322 For example, if the file @file{/foo/bar/baz.c} was moved to
7323 @file{/mnt/cross/baz.c}, then the command
7326 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7330 will tell @value{GDBN} to replace @samp{/usr/src} with
7331 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7332 @file{baz.c} even though it was moved.
7334 In the case when more than one substitution rule have been defined,
7335 the rules are evaluated one by one in the order where they have been
7336 defined. The first one matching, if any, is selected to perform
7339 For instance, if we had entered the following commands:
7342 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7343 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7347 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7348 @file{/mnt/include/defs.h} by using the first rule. However, it would
7349 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7350 @file{/mnt/src/lib/foo.c}.
7353 @item unset substitute-path [path]
7354 @kindex unset substitute-path
7355 If a path is specified, search the current list of substitution rules
7356 for a rule that would rewrite that path. Delete that rule if found.
7357 A warning is emitted by the debugger if no rule could be found.
7359 If no path is specified, then all substitution rules are deleted.
7361 @item show substitute-path [path]
7362 @kindex show substitute-path
7363 If a path is specified, then print the source path substitution rule
7364 which would rewrite that path, if any.
7366 If no path is specified, then print all existing source path substitution
7371 If your source path is cluttered with directories that are no longer of
7372 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7373 versions of source. You can correct the situation as follows:
7377 Use @code{directory} with no argument to reset the source path to its default value.
7380 Use @code{directory} with suitable arguments to reinstall the
7381 directories you want in the source path. You can add all the
7382 directories in one command.
7386 @section Source and Machine Code
7387 @cindex source line and its code address
7389 You can use the command @code{info line} to map source lines to program
7390 addresses (and vice versa), and the command @code{disassemble} to display
7391 a range of addresses as machine instructions. You can use the command
7392 @code{set disassemble-next-line} to set whether to disassemble next
7393 source line when execution stops. When run under @sc{gnu} Emacs
7394 mode, the @code{info line} command causes the arrow to point to the
7395 line specified. Also, @code{info line} prints addresses in symbolic form as
7400 @item info line @var{linespec}
7401 Print the starting and ending addresses of the compiled code for
7402 source line @var{linespec}. You can specify source lines in any of
7403 the ways documented in @ref{Specify Location}.
7406 For example, we can use @code{info line} to discover the location of
7407 the object code for the first line of function
7408 @code{m4_changequote}:
7410 @c FIXME: I think this example should also show the addresses in
7411 @c symbolic form, as they usually would be displayed.
7413 (@value{GDBP}) info line m4_changequote
7414 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7418 @cindex code address and its source line
7419 We can also inquire (using @code{*@var{addr}} as the form for
7420 @var{linespec}) what source line covers a particular address:
7422 (@value{GDBP}) info line *0x63ff
7423 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7426 @cindex @code{$_} and @code{info line}
7427 @cindex @code{x} command, default address
7428 @kindex x@r{(examine), and} info line
7429 After @code{info line}, the default address for the @code{x} command
7430 is changed to the starting address of the line, so that @samp{x/i} is
7431 sufficient to begin examining the machine code (@pxref{Memory,
7432 ,Examining Memory}). Also, this address is saved as the value of the
7433 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7438 @cindex assembly instructions
7439 @cindex instructions, assembly
7440 @cindex machine instructions
7441 @cindex listing machine instructions
7443 @itemx disassemble /m
7444 @itemx disassemble /r
7445 This specialized command dumps a range of memory as machine
7446 instructions. It can also print mixed source+disassembly by specifying
7447 the @code{/m} modifier and print the raw instructions in hex as well as
7448 in symbolic form by specifying the @code{/r}.
7449 The default memory range is the function surrounding the
7450 program counter of the selected frame. A single argument to this
7451 command is a program counter value; @value{GDBN} dumps the function
7452 surrounding this value. When two arguments are given, they should
7453 be separated by a comma, possibly surrounded by whitespace. The
7454 arguments specify a range of addresses to dump, in one of two forms:
7457 @item @var{start},@var{end}
7458 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7459 @item @var{start},+@var{length}
7460 the addresses from @var{start} (inclusive) to
7461 @code{@var{start}+@var{length}} (exclusive).
7465 When 2 arguments are specified, the name of the function is also
7466 printed (since there could be several functions in the given range).
7468 The argument(s) can be any expression yielding a numeric value, such as
7469 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7471 If the range of memory being disassembled contains current program counter,
7472 the instruction at that location is shown with a @code{=>} marker.
7475 The following example shows the disassembly of a range of addresses of
7476 HP PA-RISC 2.0 code:
7479 (@value{GDBP}) disas 0x32c4, 0x32e4
7480 Dump of assembler code from 0x32c4 to 0x32e4:
7481 0x32c4 <main+204>: addil 0,dp
7482 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7483 0x32cc <main+212>: ldil 0x3000,r31
7484 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7485 0x32d4 <main+220>: ldo 0(r31),rp
7486 0x32d8 <main+224>: addil -0x800,dp
7487 0x32dc <main+228>: ldo 0x588(r1),r26
7488 0x32e0 <main+232>: ldil 0x3000,r31
7489 End of assembler dump.
7492 Here is an example showing mixed source+assembly for Intel x86, when the
7493 program is stopped just after function prologue:
7496 (@value{GDBP}) disas /m main
7497 Dump of assembler code for function main:
7499 0x08048330 <+0>: push %ebp
7500 0x08048331 <+1>: mov %esp,%ebp
7501 0x08048333 <+3>: sub $0x8,%esp
7502 0x08048336 <+6>: and $0xfffffff0,%esp
7503 0x08048339 <+9>: sub $0x10,%esp
7505 6 printf ("Hello.\n");
7506 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7507 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7511 0x08048348 <+24>: mov $0x0,%eax
7512 0x0804834d <+29>: leave
7513 0x0804834e <+30>: ret
7515 End of assembler dump.
7518 Here is another example showing raw instructions in hex for AMD x86-64,
7521 (gdb) disas /r 0x400281,+10
7522 Dump of assembler code from 0x400281 to 0x40028b:
7523 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7524 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7525 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7526 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7527 End of assembler dump.
7530 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7531 So, for example, if you want to disassemble function @code{bar}
7532 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7533 and not @samp{disassemble foo.c:bar}.
7535 Some architectures have more than one commonly-used set of instruction
7536 mnemonics or other syntax.
7538 For programs that were dynamically linked and use shared libraries,
7539 instructions that call functions or branch to locations in the shared
7540 libraries might show a seemingly bogus location---it's actually a
7541 location of the relocation table. On some architectures, @value{GDBN}
7542 might be able to resolve these to actual function names.
7545 @kindex set disassembly-flavor
7546 @cindex Intel disassembly flavor
7547 @cindex AT&T disassembly flavor
7548 @item set disassembly-flavor @var{instruction-set}
7549 Select the instruction set to use when disassembling the
7550 program via the @code{disassemble} or @code{x/i} commands.
7552 Currently this command is only defined for the Intel x86 family. You
7553 can set @var{instruction-set} to either @code{intel} or @code{att}.
7554 The default is @code{att}, the AT&T flavor used by default by Unix
7555 assemblers for x86-based targets.
7557 @kindex show disassembly-flavor
7558 @item show disassembly-flavor
7559 Show the current setting of the disassembly flavor.
7563 @kindex set disassemble-next-line
7564 @kindex show disassemble-next-line
7565 @item set disassemble-next-line
7566 @itemx show disassemble-next-line
7567 Control whether or not @value{GDBN} will disassemble the next source
7568 line or instruction when execution stops. If ON, @value{GDBN} will
7569 display disassembly of the next source line when execution of the
7570 program being debugged stops. This is @emph{in addition} to
7571 displaying the source line itself, which @value{GDBN} always does if
7572 possible. If the next source line cannot be displayed for some reason
7573 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7574 info in the debug info), @value{GDBN} will display disassembly of the
7575 next @emph{instruction} instead of showing the next source line. If
7576 AUTO, @value{GDBN} will display disassembly of next instruction only
7577 if the source line cannot be displayed. This setting causes
7578 @value{GDBN} to display some feedback when you step through a function
7579 with no line info or whose source file is unavailable. The default is
7580 OFF, which means never display the disassembly of the next line or
7586 @chapter Examining Data
7588 @cindex printing data
7589 @cindex examining data
7592 The usual way to examine data in your program is with the @code{print}
7593 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7594 evaluates and prints the value of an expression of the language your
7595 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7596 Different Languages}). It may also print the expression using a
7597 Python-based pretty-printer (@pxref{Pretty Printing}).
7600 @item print @var{expr}
7601 @itemx print /@var{f} @var{expr}
7602 @var{expr} is an expression (in the source language). By default the
7603 value of @var{expr} is printed in a format appropriate to its data type;
7604 you can choose a different format by specifying @samp{/@var{f}}, where
7605 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7609 @itemx print /@var{f}
7610 @cindex reprint the last value
7611 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7612 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7613 conveniently inspect the same value in an alternative format.
7616 A more low-level way of examining data is with the @code{x} command.
7617 It examines data in memory at a specified address and prints it in a
7618 specified format. @xref{Memory, ,Examining Memory}.
7620 If you are interested in information about types, or about how the
7621 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7622 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7625 @cindex exploring hierarchical data structures
7627 Another way of examining values of expressions and type information is
7628 through the Python extension command @code{explore} (available only if
7629 the @value{GDBN} build is configured with @code{--with-python}). It
7630 offers an interactive way to start at the highest level (or, the most
7631 abstract level) of the data type of an expression (or, the data type
7632 itself) and explore all the way down to leaf scalar values/fields
7633 embedded in the higher level data types.
7636 @item explore @var{arg}
7637 @var{arg} is either an expression (in the source language), or a type
7638 visible in the current context of the program being debugged.
7641 The working of the @code{explore} command can be illustrated with an
7642 example. If a data type @code{struct ComplexStruct} is defined in your
7652 struct ComplexStruct
7654 struct SimpleStruct *ss_p;
7660 followed by variable declarations as
7663 struct SimpleStruct ss = @{ 10, 1.11 @};
7664 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7668 then, the value of the variable @code{cs} can be explored using the
7669 @code{explore} command as follows.
7673 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7674 the following fields:
7676 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7677 arr = <Enter 1 to explore this field of type `int [10]'>
7679 Enter the field number of choice:
7683 Since the fields of @code{cs} are not scalar values, you are being
7684 prompted to chose the field you want to explore. Let's say you choose
7685 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7686 pointer, you will be asked if it is pointing to a single value. From
7687 the declaration of @code{cs} above, it is indeed pointing to a single
7688 value, hence you enter @code{y}. If you enter @code{n}, then you will
7689 be asked if it were pointing to an array of values, in which case this
7690 field will be explored as if it were an array.
7693 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7694 Continue exploring it as a pointer to a single value [y/n]: y
7695 The value of `*(cs.ss_p)' is a struct/class of type `struct
7696 SimpleStruct' with the following fields:
7698 i = 10 .. (Value of type `int')
7699 d = 1.1100000000000001 .. (Value of type `double')
7701 Press enter to return to parent value:
7705 If the field @code{arr} of @code{cs} was chosen for exploration by
7706 entering @code{1} earlier, then since it is as array, you will be
7707 prompted to enter the index of the element in the array that you want
7711 `cs.arr' is an array of `int'.
7712 Enter the index of the element you want to explore in `cs.arr': 5
7714 `(cs.arr)[5]' is a scalar value of type `int'.
7718 Press enter to return to parent value:
7721 In general, at any stage of exploration, you can go deeper towards the
7722 leaf values by responding to the prompts appropriately, or hit the
7723 return key to return to the enclosing data structure (the @i{higher}
7724 level data structure).
7726 Similar to exploring values, you can use the @code{explore} command to
7727 explore types. Instead of specifying a value (which is typically a
7728 variable name or an expression valid in the current context of the
7729 program being debugged), you specify a type name. If you consider the
7730 same example as above, your can explore the type
7731 @code{struct ComplexStruct} by passing the argument
7732 @code{struct ComplexStruct} to the @code{explore} command.
7735 (gdb) explore struct ComplexStruct
7739 By responding to the prompts appropriately in the subsequent interactive
7740 session, you can explore the type @code{struct ComplexStruct} in a
7741 manner similar to how the value @code{cs} was explored in the above
7744 The @code{explore} command also has two sub-commands,
7745 @code{explore value} and @code{explore type}. The former sub-command is
7746 a way to explicitly specify that value exploration of the argument is
7747 being invoked, while the latter is a way to explicitly specify that type
7748 exploration of the argument is being invoked.
7751 @item explore value @var{expr}
7752 @cindex explore value
7753 This sub-command of @code{explore} explores the value of the
7754 expression @var{expr} (if @var{expr} is an expression valid in the
7755 current context of the program being debugged). The behavior of this
7756 command is identical to that of the behavior of the @code{explore}
7757 command being passed the argument @var{expr}.
7759 @item explore type @var{arg}
7760 @cindex explore type
7761 This sub-command of @code{explore} explores the type of @var{arg} (if
7762 @var{arg} is a type visible in the current context of program being
7763 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7764 is an expression valid in the current context of the program being
7765 debugged). If @var{arg} is a type, then the behavior of this command is
7766 identical to that of the @code{explore} command being passed the
7767 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7768 this command will be identical to that of the @code{explore} command
7769 being passed the type of @var{arg} as the argument.
7773 * Expressions:: Expressions
7774 * Ambiguous Expressions:: Ambiguous Expressions
7775 * Variables:: Program variables
7776 * Arrays:: Artificial arrays
7777 * Output Formats:: Output formats
7778 * Memory:: Examining memory
7779 * Auto Display:: Automatic display
7780 * Print Settings:: Print settings
7781 * Pretty Printing:: Python pretty printing
7782 * Value History:: Value history
7783 * Convenience Vars:: Convenience variables
7784 * Convenience Funs:: Convenience functions
7785 * Registers:: Registers
7786 * Floating Point Hardware:: Floating point hardware
7787 * Vector Unit:: Vector Unit
7788 * OS Information:: Auxiliary data provided by operating system
7789 * Memory Region Attributes:: Memory region attributes
7790 * Dump/Restore Files:: Copy between memory and a file
7791 * Core File Generation:: Cause a program dump its core
7792 * Character Sets:: Debugging programs that use a different
7793 character set than GDB does
7794 * Caching Remote Data:: Data caching for remote targets
7795 * Searching Memory:: Searching memory for a sequence of bytes
7799 @section Expressions
7802 @code{print} and many other @value{GDBN} commands accept an expression and
7803 compute its value. Any kind of constant, variable or operator defined
7804 by the programming language you are using is valid in an expression in
7805 @value{GDBN}. This includes conditional expressions, function calls,
7806 casts, and string constants. It also includes preprocessor macros, if
7807 you compiled your program to include this information; see
7810 @cindex arrays in expressions
7811 @value{GDBN} supports array constants in expressions input by
7812 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7813 you can use the command @code{print @{1, 2, 3@}} to create an array
7814 of three integers. If you pass an array to a function or assign it
7815 to a program variable, @value{GDBN} copies the array to memory that
7816 is @code{malloc}ed in the target program.
7818 Because C is so widespread, most of the expressions shown in examples in
7819 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7820 Languages}, for information on how to use expressions in other
7823 In this section, we discuss operators that you can use in @value{GDBN}
7824 expressions regardless of your programming language.
7826 @cindex casts, in expressions
7827 Casts are supported in all languages, not just in C, because it is so
7828 useful to cast a number into a pointer in order to examine a structure
7829 at that address in memory.
7830 @c FIXME: casts supported---Mod2 true?
7832 @value{GDBN} supports these operators, in addition to those common
7833 to programming languages:
7837 @samp{@@} is a binary operator for treating parts of memory as arrays.
7838 @xref{Arrays, ,Artificial Arrays}, for more information.
7841 @samp{::} allows you to specify a variable in terms of the file or
7842 function where it is defined. @xref{Variables, ,Program Variables}.
7844 @cindex @{@var{type}@}
7845 @cindex type casting memory
7846 @cindex memory, viewing as typed object
7847 @cindex casts, to view memory
7848 @item @{@var{type}@} @var{addr}
7849 Refers to an object of type @var{type} stored at address @var{addr} in
7850 memory. @var{addr} may be any expression whose value is an integer or
7851 pointer (but parentheses are required around binary operators, just as in
7852 a cast). This construct is allowed regardless of what kind of data is
7853 normally supposed to reside at @var{addr}.
7856 @node Ambiguous Expressions
7857 @section Ambiguous Expressions
7858 @cindex ambiguous expressions
7860 Expressions can sometimes contain some ambiguous elements. For instance,
7861 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7862 a single function name to be defined several times, for application in
7863 different contexts. This is called @dfn{overloading}. Another example
7864 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7865 templates and is typically instantiated several times, resulting in
7866 the same function name being defined in different contexts.
7868 In some cases and depending on the language, it is possible to adjust
7869 the expression to remove the ambiguity. For instance in C@t{++}, you
7870 can specify the signature of the function you want to break on, as in
7871 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7872 qualified name of your function often makes the expression unambiguous
7875 When an ambiguity that needs to be resolved is detected, the debugger
7876 has the capability to display a menu of numbered choices for each
7877 possibility, and then waits for the selection with the prompt @samp{>}.
7878 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7879 aborts the current command. If the command in which the expression was
7880 used allows more than one choice to be selected, the next option in the
7881 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7884 For example, the following session excerpt shows an attempt to set a
7885 breakpoint at the overloaded symbol @code{String::after}.
7886 We choose three particular definitions of that function name:
7888 @c FIXME! This is likely to change to show arg type lists, at least
7891 (@value{GDBP}) b String::after
7894 [2] file:String.cc; line number:867
7895 [3] file:String.cc; line number:860
7896 [4] file:String.cc; line number:875
7897 [5] file:String.cc; line number:853
7898 [6] file:String.cc; line number:846
7899 [7] file:String.cc; line number:735
7901 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7902 Breakpoint 2 at 0xb344: file String.cc, line 875.
7903 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7904 Multiple breakpoints were set.
7905 Use the "delete" command to delete unwanted
7912 @kindex set multiple-symbols
7913 @item set multiple-symbols @var{mode}
7914 @cindex multiple-symbols menu
7916 This option allows you to adjust the debugger behavior when an expression
7919 By default, @var{mode} is set to @code{all}. If the command with which
7920 the expression is used allows more than one choice, then @value{GDBN}
7921 automatically selects all possible choices. For instance, inserting
7922 a breakpoint on a function using an ambiguous name results in a breakpoint
7923 inserted on each possible match. However, if a unique choice must be made,
7924 then @value{GDBN} uses the menu to help you disambiguate the expression.
7925 For instance, printing the address of an overloaded function will result
7926 in the use of the menu.
7928 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7929 when an ambiguity is detected.
7931 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7932 an error due to the ambiguity and the command is aborted.
7934 @kindex show multiple-symbols
7935 @item show multiple-symbols
7936 Show the current value of the @code{multiple-symbols} setting.
7940 @section Program Variables
7942 The most common kind of expression to use is the name of a variable
7945 Variables in expressions are understood in the selected stack frame
7946 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7950 global (or file-static)
7957 visible according to the scope rules of the
7958 programming language from the point of execution in that frame
7961 @noindent This means that in the function
7976 you can examine and use the variable @code{a} whenever your program is
7977 executing within the function @code{foo}, but you can only use or
7978 examine the variable @code{b} while your program is executing inside
7979 the block where @code{b} is declared.
7981 @cindex variable name conflict
7982 There is an exception: you can refer to a variable or function whose
7983 scope is a single source file even if the current execution point is not
7984 in this file. But it is possible to have more than one such variable or
7985 function with the same name (in different source files). If that
7986 happens, referring to that name has unpredictable effects. If you wish,
7987 you can specify a static variable in a particular function or file by
7988 using the colon-colon (@code{::}) notation:
7990 @cindex colon-colon, context for variables/functions
7992 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7993 @cindex @code{::}, context for variables/functions
7996 @var{file}::@var{variable}
7997 @var{function}::@var{variable}
8001 Here @var{file} or @var{function} is the name of the context for the
8002 static @var{variable}. In the case of file names, you can use quotes to
8003 make sure @value{GDBN} parses the file name as a single word---for example,
8004 to print a global value of @code{x} defined in @file{f2.c}:
8007 (@value{GDBP}) p 'f2.c'::x
8010 The @code{::} notation is normally used for referring to
8011 static variables, since you typically disambiguate uses of local variables
8012 in functions by selecting the appropriate frame and using the
8013 simple name of the variable. However, you may also use this notation
8014 to refer to local variables in frames enclosing the selected frame:
8023 process (a); /* Stop here */
8034 For example, if there is a breakpoint at the commented line,
8035 here is what you might see
8036 when the program stops after executing the call @code{bar(0)}:
8041 (@value{GDBP}) p bar::a
8044 #2 0x080483d0 in foo (a=5) at foobar.c:12
8047 (@value{GDBP}) p bar::a
8051 @cindex C@t{++} scope resolution
8052 These uses of @samp{::} are very rarely in conflict with the very similar
8053 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8054 scope resolution operator in @value{GDBN} expressions.
8055 @c FIXME: Um, so what happens in one of those rare cases where it's in
8058 @cindex wrong values
8059 @cindex variable values, wrong
8060 @cindex function entry/exit, wrong values of variables
8061 @cindex optimized code, wrong values of variables
8063 @emph{Warning:} Occasionally, a local variable may appear to have the
8064 wrong value at certain points in a function---just after entry to a new
8065 scope, and just before exit.
8067 You may see this problem when you are stepping by machine instructions.
8068 This is because, on most machines, it takes more than one instruction to
8069 set up a stack frame (including local variable definitions); if you are
8070 stepping by machine instructions, variables may appear to have the wrong
8071 values until the stack frame is completely built. On exit, it usually
8072 also takes more than one machine instruction to destroy a stack frame;
8073 after you begin stepping through that group of instructions, local
8074 variable definitions may be gone.
8076 This may also happen when the compiler does significant optimizations.
8077 To be sure of always seeing accurate values, turn off all optimization
8080 @cindex ``No symbol "foo" in current context''
8081 Another possible effect of compiler optimizations is to optimize
8082 unused variables out of existence, or assign variables to registers (as
8083 opposed to memory addresses). Depending on the support for such cases
8084 offered by the debug info format used by the compiler, @value{GDBN}
8085 might not be able to display values for such local variables. If that
8086 happens, @value{GDBN} will print a message like this:
8089 No symbol "foo" in current context.
8092 To solve such problems, either recompile without optimizations, or use a
8093 different debug info format, if the compiler supports several such
8094 formats. @xref{Compilation}, for more information on choosing compiler
8095 options. @xref{C, ,C and C@t{++}}, for more information about debug
8096 info formats that are best suited to C@t{++} programs.
8098 If you ask to print an object whose contents are unknown to
8099 @value{GDBN}, e.g., because its data type is not completely specified
8100 by the debug information, @value{GDBN} will say @samp{<incomplete
8101 type>}. @xref{Symbols, incomplete type}, for more about this.
8103 If you append @kbd{@@entry} string to a function parameter name you get its
8104 value at the time the function got called. If the value is not available an
8105 error message is printed. Entry values are available only with some compilers.
8106 Entry values are normally also printed at the function parameter list according
8107 to @ref{set print entry-values}.
8110 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8116 (gdb) print i@@entry
8120 Strings are identified as arrays of @code{char} values without specified
8121 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8122 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8123 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8124 defines literal string type @code{"char"} as @code{char} without a sign.
8129 signed char var1[] = "A";
8132 You get during debugging
8137 $2 = @{65 'A', 0 '\0'@}
8141 @section Artificial Arrays
8143 @cindex artificial array
8145 @kindex @@@r{, referencing memory as an array}
8146 It is often useful to print out several successive objects of the
8147 same type in memory; a section of an array, or an array of
8148 dynamically determined size for which only a pointer exists in the
8151 You can do this by referring to a contiguous span of memory as an
8152 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8153 operand of @samp{@@} should be the first element of the desired array
8154 and be an individual object. The right operand should be the desired length
8155 of the array. The result is an array value whose elements are all of
8156 the type of the left argument. The first element is actually the left
8157 argument; the second element comes from bytes of memory immediately
8158 following those that hold the first element, and so on. Here is an
8159 example. If a program says
8162 int *array = (int *) malloc (len * sizeof (int));
8166 you can print the contents of @code{array} with
8172 The left operand of @samp{@@} must reside in memory. Array values made
8173 with @samp{@@} in this way behave just like other arrays in terms of
8174 subscripting, and are coerced to pointers when used in expressions.
8175 Artificial arrays most often appear in expressions via the value history
8176 (@pxref{Value History, ,Value History}), after printing one out.
8178 Another way to create an artificial array is to use a cast.
8179 This re-interprets a value as if it were an array.
8180 The value need not be in memory:
8182 (@value{GDBP}) p/x (short[2])0x12345678
8183 $1 = @{0x1234, 0x5678@}
8186 As a convenience, if you leave the array length out (as in
8187 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8188 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8190 (@value{GDBP}) p/x (short[])0x12345678
8191 $2 = @{0x1234, 0x5678@}
8194 Sometimes the artificial array mechanism is not quite enough; in
8195 moderately complex data structures, the elements of interest may not
8196 actually be adjacent---for example, if you are interested in the values
8197 of pointers in an array. One useful work-around in this situation is
8198 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8199 Variables}) as a counter in an expression that prints the first
8200 interesting value, and then repeat that expression via @key{RET}. For
8201 instance, suppose you have an array @code{dtab} of pointers to
8202 structures, and you are interested in the values of a field @code{fv}
8203 in each structure. Here is an example of what you might type:
8213 @node Output Formats
8214 @section Output Formats
8216 @cindex formatted output
8217 @cindex output formats
8218 By default, @value{GDBN} prints a value according to its data type. Sometimes
8219 this is not what you want. For example, you might want to print a number
8220 in hex, or a pointer in decimal. Or you might want to view data in memory
8221 at a certain address as a character string or as an instruction. To do
8222 these things, specify an @dfn{output format} when you print a value.
8224 The simplest use of output formats is to say how to print a value
8225 already computed. This is done by starting the arguments of the
8226 @code{print} command with a slash and a format letter. The format
8227 letters supported are:
8231 Regard the bits of the value as an integer, and print the integer in
8235 Print as integer in signed decimal.
8238 Print as integer in unsigned decimal.
8241 Print as integer in octal.
8244 Print as integer in binary. The letter @samp{t} stands for ``two''.
8245 @footnote{@samp{b} cannot be used because these format letters are also
8246 used with the @code{x} command, where @samp{b} stands for ``byte'';
8247 see @ref{Memory,,Examining Memory}.}
8250 @cindex unknown address, locating
8251 @cindex locate address
8252 Print as an address, both absolute in hexadecimal and as an offset from
8253 the nearest preceding symbol. You can use this format used to discover
8254 where (in what function) an unknown address is located:
8257 (@value{GDBP}) p/a 0x54320
8258 $3 = 0x54320 <_initialize_vx+396>
8262 The command @code{info symbol 0x54320} yields similar results.
8263 @xref{Symbols, info symbol}.
8266 Regard as an integer and print it as a character constant. This
8267 prints both the numerical value and its character representation. The
8268 character representation is replaced with the octal escape @samp{\nnn}
8269 for characters outside the 7-bit @sc{ascii} range.
8271 Without this format, @value{GDBN} displays @code{char},
8272 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8273 constants. Single-byte members of vectors are displayed as integer
8277 Regard the bits of the value as a floating point number and print
8278 using typical floating point syntax.
8281 @cindex printing strings
8282 @cindex printing byte arrays
8283 Regard as a string, if possible. With this format, pointers to single-byte
8284 data are displayed as null-terminated strings and arrays of single-byte data
8285 are displayed as fixed-length strings. Other values are displayed in their
8288 Without this format, @value{GDBN} displays pointers to and arrays of
8289 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8290 strings. Single-byte members of a vector are displayed as an integer
8294 @cindex raw printing
8295 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8296 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8297 Printing}). This typically results in a higher-level display of the
8298 value's contents. The @samp{r} format bypasses any Python
8299 pretty-printer which might exist.
8302 For example, to print the program counter in hex (@pxref{Registers}), type
8309 Note that no space is required before the slash; this is because command
8310 names in @value{GDBN} cannot contain a slash.
8312 To reprint the last value in the value history with a different format,
8313 you can use the @code{print} command with just a format and no
8314 expression. For example, @samp{p/x} reprints the last value in hex.
8317 @section Examining Memory
8319 You can use the command @code{x} (for ``examine'') to examine memory in
8320 any of several formats, independently of your program's data types.
8322 @cindex examining memory
8324 @kindex x @r{(examine memory)}
8325 @item x/@var{nfu} @var{addr}
8328 Use the @code{x} command to examine memory.
8331 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8332 much memory to display and how to format it; @var{addr} is an
8333 expression giving the address where you want to start displaying memory.
8334 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8335 Several commands set convenient defaults for @var{addr}.
8338 @item @var{n}, the repeat count
8339 The repeat count is a decimal integer; the default is 1. It specifies
8340 how much memory (counting by units @var{u}) to display.
8341 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8344 @item @var{f}, the display format
8345 The display format is one of the formats used by @code{print}
8346 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8347 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8348 The default is @samp{x} (hexadecimal) initially. The default changes
8349 each time you use either @code{x} or @code{print}.
8351 @item @var{u}, the unit size
8352 The unit size is any of
8358 Halfwords (two bytes).
8360 Words (four bytes). This is the initial default.
8362 Giant words (eight bytes).
8365 Each time you specify a unit size with @code{x}, that size becomes the
8366 default unit the next time you use @code{x}. For the @samp{i} format,
8367 the unit size is ignored and is normally not written. For the @samp{s} format,
8368 the unit size defaults to @samp{b}, unless it is explicitly given.
8369 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8370 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8371 Note that the results depend on the programming language of the
8372 current compilation unit. If the language is C, the @samp{s}
8373 modifier will use the UTF-16 encoding while @samp{w} will use
8374 UTF-32. The encoding is set by the programming language and cannot
8377 @item @var{addr}, starting display address
8378 @var{addr} is the address where you want @value{GDBN} to begin displaying
8379 memory. The expression need not have a pointer value (though it may);
8380 it is always interpreted as an integer address of a byte of memory.
8381 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8382 @var{addr} is usually just after the last address examined---but several
8383 other commands also set the default address: @code{info breakpoints} (to
8384 the address of the last breakpoint listed), @code{info line} (to the
8385 starting address of a line), and @code{print} (if you use it to display
8386 a value from memory).
8389 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8390 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8391 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8392 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8393 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8395 Since the letters indicating unit sizes are all distinct from the
8396 letters specifying output formats, you do not have to remember whether
8397 unit size or format comes first; either order works. The output
8398 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8399 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8401 Even though the unit size @var{u} is ignored for the formats @samp{s}
8402 and @samp{i}, you might still want to use a count @var{n}; for example,
8403 @samp{3i} specifies that you want to see three machine instructions,
8404 including any operands. For convenience, especially when used with
8405 the @code{display} command, the @samp{i} format also prints branch delay
8406 slot instructions, if any, beyond the count specified, which immediately
8407 follow the last instruction that is within the count. The command
8408 @code{disassemble} gives an alternative way of inspecting machine
8409 instructions; see @ref{Machine Code,,Source and Machine Code}.
8411 All the defaults for the arguments to @code{x} are designed to make it
8412 easy to continue scanning memory with minimal specifications each time
8413 you use @code{x}. For example, after you have inspected three machine
8414 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8415 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8416 the repeat count @var{n} is used again; the other arguments default as
8417 for successive uses of @code{x}.
8419 When examining machine instructions, the instruction at current program
8420 counter is shown with a @code{=>} marker. For example:
8423 (@value{GDBP}) x/5i $pc-6
8424 0x804837f <main+11>: mov %esp,%ebp
8425 0x8048381 <main+13>: push %ecx
8426 0x8048382 <main+14>: sub $0x4,%esp
8427 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8428 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8431 @cindex @code{$_}, @code{$__}, and value history
8432 The addresses and contents printed by the @code{x} command are not saved
8433 in the value history because there is often too much of them and they
8434 would get in the way. Instead, @value{GDBN} makes these values available for
8435 subsequent use in expressions as values of the convenience variables
8436 @code{$_} and @code{$__}. After an @code{x} command, the last address
8437 examined is available for use in expressions in the convenience variable
8438 @code{$_}. The contents of that address, as examined, are available in
8439 the convenience variable @code{$__}.
8441 If the @code{x} command has a repeat count, the address and contents saved
8442 are from the last memory unit printed; this is not the same as the last
8443 address printed if several units were printed on the last line of output.
8445 @cindex remote memory comparison
8446 @cindex verify remote memory image
8447 When you are debugging a program running on a remote target machine
8448 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8449 remote machine's memory against the executable file you downloaded to
8450 the target. The @code{compare-sections} command is provided for such
8454 @kindex compare-sections
8455 @item compare-sections @r{[}@var{section-name}@r{]}
8456 Compare the data of a loadable section @var{section-name} in the
8457 executable file of the program being debugged with the same section in
8458 the remote machine's memory, and report any mismatches. With no
8459 arguments, compares all loadable sections. This command's
8460 availability depends on the target's support for the @code{"qCRC"}
8465 @section Automatic Display
8466 @cindex automatic display
8467 @cindex display of expressions
8469 If you find that you want to print the value of an expression frequently
8470 (to see how it changes), you might want to add it to the @dfn{automatic
8471 display list} so that @value{GDBN} prints its value each time your program stops.
8472 Each expression added to the list is given a number to identify it;
8473 to remove an expression from the list, you specify that number.
8474 The automatic display looks like this:
8478 3: bar[5] = (struct hack *) 0x3804
8482 This display shows item numbers, expressions and their current values. As with
8483 displays you request manually using @code{x} or @code{print}, you can
8484 specify the output format you prefer; in fact, @code{display} decides
8485 whether to use @code{print} or @code{x} depending your format
8486 specification---it uses @code{x} if you specify either the @samp{i}
8487 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8491 @item display @var{expr}
8492 Add the expression @var{expr} to the list of expressions to display
8493 each time your program stops. @xref{Expressions, ,Expressions}.
8495 @code{display} does not repeat if you press @key{RET} again after using it.
8497 @item display/@var{fmt} @var{expr}
8498 For @var{fmt} specifying only a display format and not a size or
8499 count, add the expression @var{expr} to the auto-display list but
8500 arrange to display it each time in the specified format @var{fmt}.
8501 @xref{Output Formats,,Output Formats}.
8503 @item display/@var{fmt} @var{addr}
8504 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8505 number of units, add the expression @var{addr} as a memory address to
8506 be examined each time your program stops. Examining means in effect
8507 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8510 For example, @samp{display/i $pc} can be helpful, to see the machine
8511 instruction about to be executed each time execution stops (@samp{$pc}
8512 is a common name for the program counter; @pxref{Registers, ,Registers}).
8515 @kindex delete display
8517 @item undisplay @var{dnums}@dots{}
8518 @itemx delete display @var{dnums}@dots{}
8519 Remove items from the list of expressions to display. Specify the
8520 numbers of the displays that you want affected with the command
8521 argument @var{dnums}. It can be a single display number, one of the
8522 numbers shown in the first field of the @samp{info display} display;
8523 or it could be a range of display numbers, as in @code{2-4}.
8525 @code{undisplay} does not repeat if you press @key{RET} after using it.
8526 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8528 @kindex disable display
8529 @item disable display @var{dnums}@dots{}
8530 Disable the display of item numbers @var{dnums}. A disabled display
8531 item is not printed automatically, but is not forgotten. It may be
8532 enabled again later. Specify the numbers of the displays that you
8533 want affected with the command argument @var{dnums}. It can be a
8534 single display number, one of the numbers shown in the first field of
8535 the @samp{info display} display; or it could be a range of display
8536 numbers, as in @code{2-4}.
8538 @kindex enable display
8539 @item enable display @var{dnums}@dots{}
8540 Enable display of item numbers @var{dnums}. It becomes effective once
8541 again in auto display of its expression, until you specify otherwise.
8542 Specify the numbers of the displays that you want affected with the
8543 command argument @var{dnums}. It can be a single display number, one
8544 of the numbers shown in the first field of the @samp{info display}
8545 display; or it could be a range of display numbers, as in @code{2-4}.
8548 Display the current values of the expressions on the list, just as is
8549 done when your program stops.
8551 @kindex info display
8553 Print the list of expressions previously set up to display
8554 automatically, each one with its item number, but without showing the
8555 values. This includes disabled expressions, which are marked as such.
8556 It also includes expressions which would not be displayed right now
8557 because they refer to automatic variables not currently available.
8560 @cindex display disabled out of scope
8561 If a display expression refers to local variables, then it does not make
8562 sense outside the lexical context for which it was set up. Such an
8563 expression is disabled when execution enters a context where one of its
8564 variables is not defined. For example, if you give the command
8565 @code{display last_char} while inside a function with an argument
8566 @code{last_char}, @value{GDBN} displays this argument while your program
8567 continues to stop inside that function. When it stops elsewhere---where
8568 there is no variable @code{last_char}---the display is disabled
8569 automatically. The next time your program stops where @code{last_char}
8570 is meaningful, you can enable the display expression once again.
8572 @node Print Settings
8573 @section Print Settings
8575 @cindex format options
8576 @cindex print settings
8577 @value{GDBN} provides the following ways to control how arrays, structures,
8578 and symbols are printed.
8581 These settings are useful for debugging programs in any language:
8585 @item set print address
8586 @itemx set print address on
8587 @cindex print/don't print memory addresses
8588 @value{GDBN} prints memory addresses showing the location of stack
8589 traces, structure values, pointer values, breakpoints, and so forth,
8590 even when it also displays the contents of those addresses. The default
8591 is @code{on}. For example, this is what a stack frame display looks like with
8592 @code{set print address on}:
8597 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8599 530 if (lquote != def_lquote)
8603 @item set print address off
8604 Do not print addresses when displaying their contents. For example,
8605 this is the same stack frame displayed with @code{set print address off}:
8609 (@value{GDBP}) set print addr off
8611 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8612 530 if (lquote != def_lquote)
8616 You can use @samp{set print address off} to eliminate all machine
8617 dependent displays from the @value{GDBN} interface. For example, with
8618 @code{print address off}, you should get the same text for backtraces on
8619 all machines---whether or not they involve pointer arguments.
8622 @item show print address
8623 Show whether or not addresses are to be printed.
8626 When @value{GDBN} prints a symbolic address, it normally prints the
8627 closest earlier symbol plus an offset. If that symbol does not uniquely
8628 identify the address (for example, it is a name whose scope is a single
8629 source file), you may need to clarify. One way to do this is with
8630 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8631 you can set @value{GDBN} to print the source file and line number when
8632 it prints a symbolic address:
8635 @item set print symbol-filename on
8636 @cindex source file and line of a symbol
8637 @cindex symbol, source file and line
8638 Tell @value{GDBN} to print the source file name and line number of a
8639 symbol in the symbolic form of an address.
8641 @item set print symbol-filename off
8642 Do not print source file name and line number of a symbol. This is the
8645 @item show print symbol-filename
8646 Show whether or not @value{GDBN} will print the source file name and
8647 line number of a symbol in the symbolic form of an address.
8650 Another situation where it is helpful to show symbol filenames and line
8651 numbers is when disassembling code; @value{GDBN} shows you the line
8652 number and source file that corresponds to each instruction.
8654 Also, you may wish to see the symbolic form only if the address being
8655 printed is reasonably close to the closest earlier symbol:
8658 @item set print max-symbolic-offset @var{max-offset}
8659 @itemx set print max-symbolic-offset unlimited
8660 @cindex maximum value for offset of closest symbol
8661 Tell @value{GDBN} to only display the symbolic form of an address if the
8662 offset between the closest earlier symbol and the address is less than
8663 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8664 to always print the symbolic form of an address if any symbol precedes
8665 it. Zero is equivalent to @code{unlimited}.
8667 @item show print max-symbolic-offset
8668 Ask how large the maximum offset is that @value{GDBN} prints in a
8672 @cindex wild pointer, interpreting
8673 @cindex pointer, finding referent
8674 If you have a pointer and you are not sure where it points, try
8675 @samp{set print symbol-filename on}. Then you can determine the name
8676 and source file location of the variable where it points, using
8677 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8678 For example, here @value{GDBN} shows that a variable @code{ptt} points
8679 at another variable @code{t}, defined in @file{hi2.c}:
8682 (@value{GDBP}) set print symbol-filename on
8683 (@value{GDBP}) p/a ptt
8684 $4 = 0xe008 <t in hi2.c>
8688 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8689 does not show the symbol name and filename of the referent, even with
8690 the appropriate @code{set print} options turned on.
8693 You can also enable @samp{/a}-like formatting all the time using
8694 @samp{set print symbol on}:
8697 @item set print symbol on
8698 Tell @value{GDBN} to print the symbol corresponding to an address, if
8701 @item set print symbol off
8702 Tell @value{GDBN} not to print the symbol corresponding to an
8703 address. In this mode, @value{GDBN} will still print the symbol
8704 corresponding to pointers to functions. This is the default.
8706 @item show print symbol
8707 Show whether @value{GDBN} will display the symbol corresponding to an
8711 Other settings control how different kinds of objects are printed:
8714 @item set print array
8715 @itemx set print array on
8716 @cindex pretty print arrays
8717 Pretty print arrays. This format is more convenient to read,
8718 but uses more space. The default is off.
8720 @item set print array off
8721 Return to compressed format for arrays.
8723 @item show print array
8724 Show whether compressed or pretty format is selected for displaying
8727 @cindex print array indexes
8728 @item set print array-indexes
8729 @itemx set print array-indexes on
8730 Print the index of each element when displaying arrays. May be more
8731 convenient to locate a given element in the array or quickly find the
8732 index of a given element in that printed array. The default is off.
8734 @item set print array-indexes off
8735 Stop printing element indexes when displaying arrays.
8737 @item show print array-indexes
8738 Show whether the index of each element is printed when displaying
8741 @item set print elements @var{number-of-elements}
8742 @itemx set print elements unlimited
8743 @cindex number of array elements to print
8744 @cindex limit on number of printed array elements
8745 Set a limit on how many elements of an array @value{GDBN} will print.
8746 If @value{GDBN} is printing a large array, it stops printing after it has
8747 printed the number of elements set by the @code{set print elements} command.
8748 This limit also applies to the display of strings.
8749 When @value{GDBN} starts, this limit is set to 200.
8750 Setting @var{number-of-elements} to @code{unlimited} or zero means
8751 that the number of elements to print is unlimited.
8753 @item show print elements
8754 Display the number of elements of a large array that @value{GDBN} will print.
8755 If the number is 0, then the printing is unlimited.
8757 @item set print frame-arguments @var{value}
8758 @kindex set print frame-arguments
8759 @cindex printing frame argument values
8760 @cindex print all frame argument values
8761 @cindex print frame argument values for scalars only
8762 @cindex do not print frame argument values
8763 This command allows to control how the values of arguments are printed
8764 when the debugger prints a frame (@pxref{Frames}). The possible
8769 The values of all arguments are printed.
8772 Print the value of an argument only if it is a scalar. The value of more
8773 complex arguments such as arrays, structures, unions, etc, is replaced
8774 by @code{@dots{}}. This is the default. Here is an example where
8775 only scalar arguments are shown:
8778 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8783 None of the argument values are printed. Instead, the value of each argument
8784 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8787 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8792 By default, only scalar arguments are printed. This command can be used
8793 to configure the debugger to print the value of all arguments, regardless
8794 of their type. However, it is often advantageous to not print the value
8795 of more complex parameters. For instance, it reduces the amount of
8796 information printed in each frame, making the backtrace more readable.
8797 Also, it improves performance when displaying Ada frames, because
8798 the computation of large arguments can sometimes be CPU-intensive,
8799 especially in large applications. Setting @code{print frame-arguments}
8800 to @code{scalars} (the default) or @code{none} avoids this computation,
8801 thus speeding up the display of each Ada frame.
8803 @item show print frame-arguments
8804 Show how the value of arguments should be displayed when printing a frame.
8806 @anchor{set print entry-values}
8807 @item set print entry-values @var{value}
8808 @kindex set print entry-values
8809 Set printing of frame argument values at function entry. In some cases
8810 @value{GDBN} can determine the value of function argument which was passed by
8811 the function caller, even if the value was modified inside the called function
8812 and therefore is different. With optimized code, the current value could be
8813 unavailable, but the entry value may still be known.
8815 The default value is @code{default} (see below for its description). Older
8816 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8817 this feature will behave in the @code{default} setting the same way as with the
8820 This functionality is currently supported only by DWARF 2 debugging format and
8821 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8822 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8825 The @var{value} parameter can be one of the following:
8829 Print only actual parameter values, never print values from function entry
8833 #0 different (val=6)
8834 #0 lost (val=<optimized out>)
8836 #0 invalid (val=<optimized out>)
8840 Print only parameter values from function entry point. The actual parameter
8841 values are never printed.
8843 #0 equal (val@@entry=5)
8844 #0 different (val@@entry=5)
8845 #0 lost (val@@entry=5)
8846 #0 born (val@@entry=<optimized out>)
8847 #0 invalid (val@@entry=<optimized out>)
8851 Print only parameter values from function entry point. If value from function
8852 entry point is not known while the actual value is known, print the actual
8853 value for such parameter.
8855 #0 equal (val@@entry=5)
8856 #0 different (val@@entry=5)
8857 #0 lost (val@@entry=5)
8859 #0 invalid (val@@entry=<optimized out>)
8863 Print actual parameter values. If actual parameter value is not known while
8864 value from function entry point is known, print the entry point value for such
8868 #0 different (val=6)
8869 #0 lost (val@@entry=5)
8871 #0 invalid (val=<optimized out>)
8875 Always print both the actual parameter value and its value from function entry
8876 point, even if values of one or both are not available due to compiler
8879 #0 equal (val=5, val@@entry=5)
8880 #0 different (val=6, val@@entry=5)
8881 #0 lost (val=<optimized out>, val@@entry=5)
8882 #0 born (val=10, val@@entry=<optimized out>)
8883 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8887 Print the actual parameter value if it is known and also its value from
8888 function entry point if it is known. If neither is known, print for the actual
8889 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8890 values are known and identical, print the shortened
8891 @code{param=param@@entry=VALUE} notation.
8893 #0 equal (val=val@@entry=5)
8894 #0 different (val=6, val@@entry=5)
8895 #0 lost (val@@entry=5)
8897 #0 invalid (val=<optimized out>)
8901 Always print the actual parameter value. Print also its value from function
8902 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8903 if both values are known and identical, print the shortened
8904 @code{param=param@@entry=VALUE} notation.
8906 #0 equal (val=val@@entry=5)
8907 #0 different (val=6, val@@entry=5)
8908 #0 lost (val=<optimized out>, val@@entry=5)
8910 #0 invalid (val=<optimized out>)
8914 For analysis messages on possible failures of frame argument values at function
8915 entry resolution see @ref{set debug entry-values}.
8917 @item show print entry-values
8918 Show the method being used for printing of frame argument values at function
8921 @item set print repeats @var{number-of-repeats}
8922 @itemx set print repeats unlimited
8923 @cindex repeated array elements
8924 Set the threshold for suppressing display of repeated array
8925 elements. When the number of consecutive identical elements of an
8926 array exceeds the threshold, @value{GDBN} prints the string
8927 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8928 identical repetitions, instead of displaying the identical elements
8929 themselves. Setting the threshold to @code{unlimited} or zero will
8930 cause all elements to be individually printed. The default threshold
8933 @item show print repeats
8934 Display the current threshold for printing repeated identical
8937 @item set print null-stop
8938 @cindex @sc{null} elements in arrays
8939 Cause @value{GDBN} to stop printing the characters of an array when the first
8940 @sc{null} is encountered. This is useful when large arrays actually
8941 contain only short strings.
8944 @item show print null-stop
8945 Show whether @value{GDBN} stops printing an array on the first
8946 @sc{null} character.
8948 @item set print pretty on
8949 @cindex print structures in indented form
8950 @cindex indentation in structure display
8951 Cause @value{GDBN} to print structures in an indented format with one member
8952 per line, like this:
8967 @item set print pretty off
8968 Cause @value{GDBN} to print structures in a compact format, like this:
8972 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8973 meat = 0x54 "Pork"@}
8978 This is the default format.
8980 @item show print pretty
8981 Show which format @value{GDBN} is using to print structures.
8983 @item set print sevenbit-strings on
8984 @cindex eight-bit characters in strings
8985 @cindex octal escapes in strings
8986 Print using only seven-bit characters; if this option is set,
8987 @value{GDBN} displays any eight-bit characters (in strings or
8988 character values) using the notation @code{\}@var{nnn}. This setting is
8989 best if you are working in English (@sc{ascii}) and you use the
8990 high-order bit of characters as a marker or ``meta'' bit.
8992 @item set print sevenbit-strings off
8993 Print full eight-bit characters. This allows the use of more
8994 international character sets, and is the default.
8996 @item show print sevenbit-strings
8997 Show whether or not @value{GDBN} is printing only seven-bit characters.
8999 @item set print union on
9000 @cindex unions in structures, printing
9001 Tell @value{GDBN} to print unions which are contained in structures
9002 and other unions. This is the default setting.
9004 @item set print union off
9005 Tell @value{GDBN} not to print unions which are contained in
9006 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9009 @item show print union
9010 Ask @value{GDBN} whether or not it will print unions which are contained in
9011 structures and other unions.
9013 For example, given the declarations
9016 typedef enum @{Tree, Bug@} Species;
9017 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9018 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9029 struct thing foo = @{Tree, @{Acorn@}@};
9033 with @code{set print union on} in effect @samp{p foo} would print
9036 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9040 and with @code{set print union off} in effect it would print
9043 $1 = @{it = Tree, form = @{...@}@}
9047 @code{set print union} affects programs written in C-like languages
9053 These settings are of interest when debugging C@t{++} programs:
9056 @cindex demangling C@t{++} names
9057 @item set print demangle
9058 @itemx set print demangle on
9059 Print C@t{++} names in their source form rather than in the encoded
9060 (``mangled'') form passed to the assembler and linker for type-safe
9061 linkage. The default is on.
9063 @item show print demangle
9064 Show whether C@t{++} names are printed in mangled or demangled form.
9066 @item set print asm-demangle
9067 @itemx set print asm-demangle on
9068 Print C@t{++} names in their source form rather than their mangled form, even
9069 in assembler code printouts such as instruction disassemblies.
9072 @item show print asm-demangle
9073 Show whether C@t{++} names in assembly listings are printed in mangled
9076 @cindex C@t{++} symbol decoding style
9077 @cindex symbol decoding style, C@t{++}
9078 @kindex set demangle-style
9079 @item set demangle-style @var{style}
9080 Choose among several encoding schemes used by different compilers to
9081 represent C@t{++} names. The choices for @var{style} are currently:
9085 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9086 This is the default.
9089 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9092 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9095 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9098 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9099 @strong{Warning:} this setting alone is not sufficient to allow
9100 debugging @code{cfront}-generated executables. @value{GDBN} would
9101 require further enhancement to permit that.
9104 If you omit @var{style}, you will see a list of possible formats.
9106 @item show demangle-style
9107 Display the encoding style currently in use for decoding C@t{++} symbols.
9109 @item set print object
9110 @itemx set print object on
9111 @cindex derived type of an object, printing
9112 @cindex display derived types
9113 When displaying a pointer to an object, identify the @emph{actual}
9114 (derived) type of the object rather than the @emph{declared} type, using
9115 the virtual function table. Note that the virtual function table is
9116 required---this feature can only work for objects that have run-time
9117 type identification; a single virtual method in the object's declared
9118 type is sufficient. Note that this setting is also taken into account when
9119 working with variable objects via MI (@pxref{GDB/MI}).
9121 @item set print object off
9122 Display only the declared type of objects, without reference to the
9123 virtual function table. This is the default setting.
9125 @item show print object
9126 Show whether actual, or declared, object types are displayed.
9128 @item set print static-members
9129 @itemx set print static-members on
9130 @cindex static members of C@t{++} objects
9131 Print static members when displaying a C@t{++} object. The default is on.
9133 @item set print static-members off
9134 Do not print static members when displaying a C@t{++} object.
9136 @item show print static-members
9137 Show whether C@t{++} static members are printed or not.
9139 @item set print pascal_static-members
9140 @itemx set print pascal_static-members on
9141 @cindex static members of Pascal objects
9142 @cindex Pascal objects, static members display
9143 Print static members when displaying a Pascal object. The default is on.
9145 @item set print pascal_static-members off
9146 Do not print static members when displaying a Pascal object.
9148 @item show print pascal_static-members
9149 Show whether Pascal static members are printed or not.
9151 @c These don't work with HP ANSI C++ yet.
9152 @item set print vtbl
9153 @itemx set print vtbl on
9154 @cindex pretty print C@t{++} virtual function tables
9155 @cindex virtual functions (C@t{++}) display
9156 @cindex VTBL display
9157 Pretty print C@t{++} virtual function tables. The default is off.
9158 (The @code{vtbl} commands do not work on programs compiled with the HP
9159 ANSI C@t{++} compiler (@code{aCC}).)
9161 @item set print vtbl off
9162 Do not pretty print C@t{++} virtual function tables.
9164 @item show print vtbl
9165 Show whether C@t{++} virtual function tables are pretty printed, or not.
9168 @node Pretty Printing
9169 @section Pretty Printing
9171 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9172 Python code. It greatly simplifies the display of complex objects. This
9173 mechanism works for both MI and the CLI.
9176 * Pretty-Printer Introduction:: Introduction to pretty-printers
9177 * Pretty-Printer Example:: An example pretty-printer
9178 * Pretty-Printer Commands:: Pretty-printer commands
9181 @node Pretty-Printer Introduction
9182 @subsection Pretty-Printer Introduction
9184 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9185 registered for the value. If there is then @value{GDBN} invokes the
9186 pretty-printer to print the value. Otherwise the value is printed normally.
9188 Pretty-printers are normally named. This makes them easy to manage.
9189 The @samp{info pretty-printer} command will list all the installed
9190 pretty-printers with their names.
9191 If a pretty-printer can handle multiple data types, then its
9192 @dfn{subprinters} are the printers for the individual data types.
9193 Each such subprinter has its own name.
9194 The format of the name is @var{printer-name};@var{subprinter-name}.
9196 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9197 Typically they are automatically loaded and registered when the corresponding
9198 debug information is loaded, thus making them available without having to
9199 do anything special.
9201 There are three places where a pretty-printer can be registered.
9205 Pretty-printers registered globally are available when debugging
9209 Pretty-printers registered with a program space are available only
9210 when debugging that program.
9211 @xref{Progspaces In Python}, for more details on program spaces in Python.
9214 Pretty-printers registered with an objfile are loaded and unloaded
9215 with the corresponding objfile (e.g., shared library).
9216 @xref{Objfiles In Python}, for more details on objfiles in Python.
9219 @xref{Selecting Pretty-Printers}, for further information on how
9220 pretty-printers are selected,
9222 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9225 @node Pretty-Printer Example
9226 @subsection Pretty-Printer Example
9228 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9231 (@value{GDBP}) print s
9233 static npos = 4294967295,
9235 <std::allocator<char>> = @{
9236 <__gnu_cxx::new_allocator<char>> = @{
9237 <No data fields>@}, <No data fields>
9239 members of std::basic_string<char, std::char_traits<char>,
9240 std::allocator<char> >::_Alloc_hider:
9241 _M_p = 0x804a014 "abcd"
9246 With a pretty-printer for @code{std::string} only the contents are printed:
9249 (@value{GDBP}) print s
9253 @node Pretty-Printer Commands
9254 @subsection Pretty-Printer Commands
9255 @cindex pretty-printer commands
9258 @kindex info pretty-printer
9259 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9260 Print the list of installed pretty-printers.
9261 This includes disabled pretty-printers, which are marked as such.
9263 @var{object-regexp} is a regular expression matching the objects
9264 whose pretty-printers to list.
9265 Objects can be @code{global}, the program space's file
9266 (@pxref{Progspaces In Python}),
9267 and the object files within that program space (@pxref{Objfiles In Python}).
9268 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9269 looks up a printer from these three objects.
9271 @var{name-regexp} is a regular expression matching the name of the printers
9274 @kindex disable pretty-printer
9275 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9276 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9277 A disabled pretty-printer is not forgotten, it may be enabled again later.
9279 @kindex enable pretty-printer
9280 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9281 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9286 Suppose we have three pretty-printers installed: one from library1.so
9287 named @code{foo} that prints objects of type @code{foo}, and
9288 another from library2.so named @code{bar} that prints two types of objects,
9289 @code{bar1} and @code{bar2}.
9292 (gdb) info pretty-printer
9299 (gdb) info pretty-printer library2
9304 (gdb) disable pretty-printer library1
9306 2 of 3 printers enabled
9307 (gdb) info pretty-printer
9314 (gdb) disable pretty-printer library2 bar:bar1
9316 1 of 3 printers enabled
9317 (gdb) info pretty-printer library2
9324 (gdb) disable pretty-printer library2 bar
9326 0 of 3 printers enabled
9327 (gdb) info pretty-printer library2
9336 Note that for @code{bar} the entire printer can be disabled,
9337 as can each individual subprinter.
9340 @section Value History
9342 @cindex value history
9343 @cindex history of values printed by @value{GDBN}
9344 Values printed by the @code{print} command are saved in the @value{GDBN}
9345 @dfn{value history}. This allows you to refer to them in other expressions.
9346 Values are kept until the symbol table is re-read or discarded
9347 (for example with the @code{file} or @code{symbol-file} commands).
9348 When the symbol table changes, the value history is discarded,
9349 since the values may contain pointers back to the types defined in the
9354 @cindex history number
9355 The values printed are given @dfn{history numbers} by which you can
9356 refer to them. These are successive integers starting with one.
9357 @code{print} shows you the history number assigned to a value by
9358 printing @samp{$@var{num} = } before the value; here @var{num} is the
9361 To refer to any previous value, use @samp{$} followed by the value's
9362 history number. The way @code{print} labels its output is designed to
9363 remind you of this. Just @code{$} refers to the most recent value in
9364 the history, and @code{$$} refers to the value before that.
9365 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9366 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9367 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9369 For example, suppose you have just printed a pointer to a structure and
9370 want to see the contents of the structure. It suffices to type
9376 If you have a chain of structures where the component @code{next} points
9377 to the next one, you can print the contents of the next one with this:
9384 You can print successive links in the chain by repeating this
9385 command---which you can do by just typing @key{RET}.
9387 Note that the history records values, not expressions. If the value of
9388 @code{x} is 4 and you type these commands:
9396 then the value recorded in the value history by the @code{print} command
9397 remains 4 even though the value of @code{x} has changed.
9402 Print the last ten values in the value history, with their item numbers.
9403 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9404 values} does not change the history.
9406 @item show values @var{n}
9407 Print ten history values centered on history item number @var{n}.
9410 Print ten history values just after the values last printed. If no more
9411 values are available, @code{show values +} produces no display.
9414 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9415 same effect as @samp{show values +}.
9417 @node Convenience Vars
9418 @section Convenience Variables
9420 @cindex convenience variables
9421 @cindex user-defined variables
9422 @value{GDBN} provides @dfn{convenience variables} that you can use within
9423 @value{GDBN} to hold on to a value and refer to it later. These variables
9424 exist entirely within @value{GDBN}; they are not part of your program, and
9425 setting a convenience variable has no direct effect on further execution
9426 of your program. That is why you can use them freely.
9428 Convenience variables are prefixed with @samp{$}. Any name preceded by
9429 @samp{$} can be used for a convenience variable, unless it is one of
9430 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9431 (Value history references, in contrast, are @emph{numbers} preceded
9432 by @samp{$}. @xref{Value History, ,Value History}.)
9434 You can save a value in a convenience variable with an assignment
9435 expression, just as you would set a variable in your program.
9439 set $foo = *object_ptr
9443 would save in @code{$foo} the value contained in the object pointed to by
9446 Using a convenience variable for the first time creates it, but its
9447 value is @code{void} until you assign a new value. You can alter the
9448 value with another assignment at any time.
9450 Convenience variables have no fixed types. You can assign a convenience
9451 variable any type of value, including structures and arrays, even if
9452 that variable already has a value of a different type. The convenience
9453 variable, when used as an expression, has the type of its current value.
9456 @kindex show convenience
9457 @cindex show all user variables and functions
9458 @item show convenience
9459 Print a list of convenience variables used so far, and their values,
9460 as well as a list of the convenience functions.
9461 Abbreviated @code{show conv}.
9463 @kindex init-if-undefined
9464 @cindex convenience variables, initializing
9465 @item init-if-undefined $@var{variable} = @var{expression}
9466 Set a convenience variable if it has not already been set. This is useful
9467 for user-defined commands that keep some state. It is similar, in concept,
9468 to using local static variables with initializers in C (except that
9469 convenience variables are global). It can also be used to allow users to
9470 override default values used in a command script.
9472 If the variable is already defined then the expression is not evaluated so
9473 any side-effects do not occur.
9476 One of the ways to use a convenience variable is as a counter to be
9477 incremented or a pointer to be advanced. For example, to print
9478 a field from successive elements of an array of structures:
9482 print bar[$i++]->contents
9486 Repeat that command by typing @key{RET}.
9488 Some convenience variables are created automatically by @value{GDBN} and given
9489 values likely to be useful.
9492 @vindex $_@r{, convenience variable}
9494 The variable @code{$_} is automatically set by the @code{x} command to
9495 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9496 commands which provide a default address for @code{x} to examine also
9497 set @code{$_} to that address; these commands include @code{info line}
9498 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9499 except when set by the @code{x} command, in which case it is a pointer
9500 to the type of @code{$__}.
9502 @vindex $__@r{, convenience variable}
9504 The variable @code{$__} is automatically set by the @code{x} command
9505 to the value found in the last address examined. Its type is chosen
9506 to match the format in which the data was printed.
9509 @vindex $_exitcode@r{, convenience variable}
9510 The variable @code{$_exitcode} is automatically set to the exit code when
9511 the program being debugged terminates.
9514 @itemx $_probe_arg0@dots{}$_probe_arg11
9515 Arguments to a static probe. @xref{Static Probe Points}.
9518 @vindex $_sdata@r{, inspect, convenience variable}
9519 The variable @code{$_sdata} contains extra collected static tracepoint
9520 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9521 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9522 if extra static tracepoint data has not been collected.
9525 @vindex $_siginfo@r{, convenience variable}
9526 The variable @code{$_siginfo} contains extra signal information
9527 (@pxref{extra signal information}). Note that @code{$_siginfo}
9528 could be empty, if the application has not yet received any signals.
9529 For example, it will be empty before you execute the @code{run} command.
9532 @vindex $_tlb@r{, convenience variable}
9533 The variable @code{$_tlb} is automatically set when debugging
9534 applications running on MS-Windows in native mode or connected to
9535 gdbserver that supports the @code{qGetTIBAddr} request.
9536 @xref{General Query Packets}.
9537 This variable contains the address of the thread information block.
9541 On HP-UX systems, if you refer to a function or variable name that
9542 begins with a dollar sign, @value{GDBN} searches for a user or system
9543 name first, before it searches for a convenience variable.
9545 @node Convenience Funs
9546 @section Convenience Functions
9548 @cindex convenience functions
9549 @value{GDBN} also supplies some @dfn{convenience functions}. These
9550 have a syntax similar to convenience variables. A convenience
9551 function can be used in an expression just like an ordinary function;
9552 however, a convenience function is implemented internally to
9555 These functions require @value{GDBN} to be configured with
9556 @code{Python} support.
9560 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9561 @findex $_memeq@r{, convenience function}
9562 Returns one if the @var{length} bytes at the addresses given by
9563 @var{buf1} and @var{buf2} are equal.
9564 Otherwise it returns zero.
9566 @item $_regex(@var{str}, @var{regex})
9567 @findex $_regex@r{, convenience function}
9568 Returns one if the string @var{str} matches the regular expression
9569 @var{regex}. Otherwise it returns zero.
9570 The syntax of the regular expression is that specified by @code{Python}'s
9571 regular expression support.
9573 @item $_streq(@var{str1}, @var{str2})
9574 @findex $_streq@r{, convenience function}
9575 Returns one if the strings @var{str1} and @var{str2} are equal.
9576 Otherwise it returns zero.
9578 @item $_strlen(@var{str})
9579 @findex $_strlen@r{, convenience function}
9580 Returns the length of string @var{str}.
9584 @value{GDBN} provides the ability to list and get help on
9585 convenience functions.
9589 @kindex help function
9590 @cindex show all convenience functions
9591 Print a list of all convenience functions.
9598 You can refer to machine register contents, in expressions, as variables
9599 with names starting with @samp{$}. The names of registers are different
9600 for each machine; use @code{info registers} to see the names used on
9604 @kindex info registers
9605 @item info registers
9606 Print the names and values of all registers except floating-point
9607 and vector registers (in the selected stack frame).
9609 @kindex info all-registers
9610 @cindex floating point registers
9611 @item info all-registers
9612 Print the names and values of all registers, including floating-point
9613 and vector registers (in the selected stack frame).
9615 @item info registers @var{regname} @dots{}
9616 Print the @dfn{relativized} value of each specified register @var{regname}.
9617 As discussed in detail below, register values are normally relative to
9618 the selected stack frame. @var{regname} may be any register name valid on
9619 the machine you are using, with or without the initial @samp{$}.
9622 @cindex stack pointer register
9623 @cindex program counter register
9624 @cindex process status register
9625 @cindex frame pointer register
9626 @cindex standard registers
9627 @value{GDBN} has four ``standard'' register names that are available (in
9628 expressions) on most machines---whenever they do not conflict with an
9629 architecture's canonical mnemonics for registers. The register names
9630 @code{$pc} and @code{$sp} are used for the program counter register and
9631 the stack pointer. @code{$fp} is used for a register that contains a
9632 pointer to the current stack frame, and @code{$ps} is used for a
9633 register that contains the processor status. For example,
9634 you could print the program counter in hex with
9641 or print the instruction to be executed next with
9648 or add four to the stack pointer@footnote{This is a way of removing
9649 one word from the stack, on machines where stacks grow downward in
9650 memory (most machines, nowadays). This assumes that the innermost
9651 stack frame is selected; setting @code{$sp} is not allowed when other
9652 stack frames are selected. To pop entire frames off the stack,
9653 regardless of machine architecture, use @code{return};
9654 see @ref{Returning, ,Returning from a Function}.} with
9660 Whenever possible, these four standard register names are available on
9661 your machine even though the machine has different canonical mnemonics,
9662 so long as there is no conflict. The @code{info registers} command
9663 shows the canonical names. For example, on the SPARC, @code{info
9664 registers} displays the processor status register as @code{$psr} but you
9665 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9666 is an alias for the @sc{eflags} register.
9668 @value{GDBN} always considers the contents of an ordinary register as an
9669 integer when the register is examined in this way. Some machines have
9670 special registers which can hold nothing but floating point; these
9671 registers are considered to have floating point values. There is no way
9672 to refer to the contents of an ordinary register as floating point value
9673 (although you can @emph{print} it as a floating point value with
9674 @samp{print/f $@var{regname}}).
9676 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9677 means that the data format in which the register contents are saved by
9678 the operating system is not the same one that your program normally
9679 sees. For example, the registers of the 68881 floating point
9680 coprocessor are always saved in ``extended'' (raw) format, but all C
9681 programs expect to work with ``double'' (virtual) format. In such
9682 cases, @value{GDBN} normally works with the virtual format only (the format
9683 that makes sense for your program), but the @code{info registers} command
9684 prints the data in both formats.
9686 @cindex SSE registers (x86)
9687 @cindex MMX registers (x86)
9688 Some machines have special registers whose contents can be interpreted
9689 in several different ways. For example, modern x86-based machines
9690 have SSE and MMX registers that can hold several values packed
9691 together in several different formats. @value{GDBN} refers to such
9692 registers in @code{struct} notation:
9695 (@value{GDBP}) print $xmm1
9697 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9698 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9699 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9700 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9701 v4_int32 = @{0, 20657912, 11, 13@},
9702 v2_int64 = @{88725056443645952, 55834574859@},
9703 uint128 = 0x0000000d0000000b013b36f800000000
9708 To set values of such registers, you need to tell @value{GDBN} which
9709 view of the register you wish to change, as if you were assigning
9710 value to a @code{struct} member:
9713 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9716 Normally, register values are relative to the selected stack frame
9717 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9718 value that the register would contain if all stack frames farther in
9719 were exited and their saved registers restored. In order to see the
9720 true contents of hardware registers, you must select the innermost
9721 frame (with @samp{frame 0}).
9723 However, @value{GDBN} must deduce where registers are saved, from the machine
9724 code generated by your compiler. If some registers are not saved, or if
9725 @value{GDBN} is unable to locate the saved registers, the selected stack
9726 frame makes no difference.
9728 @node Floating Point Hardware
9729 @section Floating Point Hardware
9730 @cindex floating point
9732 Depending on the configuration, @value{GDBN} may be able to give
9733 you more information about the status of the floating point hardware.
9738 Display hardware-dependent information about the floating
9739 point unit. The exact contents and layout vary depending on the
9740 floating point chip. Currently, @samp{info float} is supported on
9741 the ARM and x86 machines.
9745 @section Vector Unit
9748 Depending on the configuration, @value{GDBN} may be able to give you
9749 more information about the status of the vector unit.
9754 Display information about the vector unit. The exact contents and
9755 layout vary depending on the hardware.
9758 @node OS Information
9759 @section Operating System Auxiliary Information
9760 @cindex OS information
9762 @value{GDBN} provides interfaces to useful OS facilities that can help
9763 you debug your program.
9765 @cindex auxiliary vector
9766 @cindex vector, auxiliary
9767 Some operating systems supply an @dfn{auxiliary vector} to programs at
9768 startup. This is akin to the arguments and environment that you
9769 specify for a program, but contains a system-dependent variety of
9770 binary values that tell system libraries important details about the
9771 hardware, operating system, and process. Each value's purpose is
9772 identified by an integer tag; the meanings are well-known but system-specific.
9773 Depending on the configuration and operating system facilities,
9774 @value{GDBN} may be able to show you this information. For remote
9775 targets, this functionality may further depend on the remote stub's
9776 support of the @samp{qXfer:auxv:read} packet, see
9777 @ref{qXfer auxiliary vector read}.
9782 Display the auxiliary vector of the inferior, which can be either a
9783 live process or a core dump file. @value{GDBN} prints each tag value
9784 numerically, and also shows names and text descriptions for recognized
9785 tags. Some values in the vector are numbers, some bit masks, and some
9786 pointers to strings or other data. @value{GDBN} displays each value in the
9787 most appropriate form for a recognized tag, and in hexadecimal for
9788 an unrecognized tag.
9791 On some targets, @value{GDBN} can access operating system-specific
9792 information and show it to you. The types of information available
9793 will differ depending on the type of operating system running on the
9794 target. The mechanism used to fetch the data is described in
9795 @ref{Operating System Information}. For remote targets, this
9796 functionality depends on the remote stub's support of the
9797 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9801 @item info os @var{infotype}
9803 Display OS information of the requested type.
9805 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9807 @anchor{linux info os infotypes}
9809 @kindex info os processes
9811 Display the list of processes on the target. For each process,
9812 @value{GDBN} prints the process identifier, the name of the user, the
9813 command corresponding to the process, and the list of processor cores
9814 that the process is currently running on. (To understand what these
9815 properties mean, for this and the following info types, please consult
9816 the general @sc{gnu}/Linux documentation.)
9818 @kindex info os procgroups
9820 Display the list of process groups on the target. For each process,
9821 @value{GDBN} prints the identifier of the process group that it belongs
9822 to, the command corresponding to the process group leader, the process
9823 identifier, and the command line of the process. The list is sorted
9824 first by the process group identifier, then by the process identifier,
9825 so that processes belonging to the same process group are grouped together
9826 and the process group leader is listed first.
9828 @kindex info os threads
9830 Display the list of threads running on the target. For each thread,
9831 @value{GDBN} prints the identifier of the process that the thread
9832 belongs to, the command of the process, the thread identifier, and the
9833 processor core that it is currently running on. The main thread of a
9834 process is not listed.
9836 @kindex info os files
9838 Display the list of open file descriptors on the target. For each
9839 file descriptor, @value{GDBN} prints the identifier of the process
9840 owning the descriptor, the command of the owning process, the value
9841 of the descriptor, and the target of the descriptor.
9843 @kindex info os sockets
9845 Display the list of Internet-domain sockets on the target. For each
9846 socket, @value{GDBN} prints the address and port of the local and
9847 remote endpoints, the current state of the connection, the creator of
9848 the socket, the IP address family of the socket, and the type of the
9853 Display the list of all System V shared-memory regions on the target.
9854 For each shared-memory region, @value{GDBN} prints the region key,
9855 the shared-memory identifier, the access permissions, the size of the
9856 region, the process that created the region, the process that last
9857 attached to or detached from the region, the current number of live
9858 attaches to the region, and the times at which the region was last
9859 attached to, detach from, and changed.
9861 @kindex info os semaphores
9863 Display the list of all System V semaphore sets on the target. For each
9864 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9865 set identifier, the access permissions, the number of semaphores in the
9866 set, the user and group of the owner and creator of the semaphore set,
9867 and the times at which the semaphore set was operated upon and changed.
9871 Display the list of all System V message queues on the target. For each
9872 message queue, @value{GDBN} prints the message queue key, the message
9873 queue identifier, the access permissions, the current number of bytes
9874 on the queue, the current number of messages on the queue, the processes
9875 that last sent and received a message on the queue, the user and group
9876 of the owner and creator of the message queue, the times at which a
9877 message was last sent and received on the queue, and the time at which
9878 the message queue was last changed.
9880 @kindex info os modules
9882 Display the list of all loaded kernel modules on the target. For each
9883 module, @value{GDBN} prints the module name, the size of the module in
9884 bytes, the number of times the module is used, the dependencies of the
9885 module, the status of the module, and the address of the loaded module
9890 If @var{infotype} is omitted, then list the possible values for
9891 @var{infotype} and the kind of OS information available for each
9892 @var{infotype}. If the target does not return a list of possible
9893 types, this command will report an error.
9896 @node Memory Region Attributes
9897 @section Memory Region Attributes
9898 @cindex memory region attributes
9900 @dfn{Memory region attributes} allow you to describe special handling
9901 required by regions of your target's memory. @value{GDBN} uses
9902 attributes to determine whether to allow certain types of memory
9903 accesses; whether to use specific width accesses; and whether to cache
9904 target memory. By default the description of memory regions is
9905 fetched from the target (if the current target supports this), but the
9906 user can override the fetched regions.
9908 Defined memory regions can be individually enabled and disabled. When a
9909 memory region is disabled, @value{GDBN} uses the default attributes when
9910 accessing memory in that region. Similarly, if no memory regions have
9911 been defined, @value{GDBN} uses the default attributes when accessing
9914 When a memory region is defined, it is given a number to identify it;
9915 to enable, disable, or remove a memory region, you specify that number.
9919 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9920 Define a memory region bounded by @var{lower} and @var{upper} with
9921 attributes @var{attributes}@dots{}, and add it to the list of regions
9922 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9923 case: it is treated as the target's maximum memory address.
9924 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9927 Discard any user changes to the memory regions and use target-supplied
9928 regions, if available, or no regions if the target does not support.
9931 @item delete mem @var{nums}@dots{}
9932 Remove memory regions @var{nums}@dots{} from the list of regions
9933 monitored by @value{GDBN}.
9936 @item disable mem @var{nums}@dots{}
9937 Disable monitoring of memory regions @var{nums}@dots{}.
9938 A disabled memory region is not forgotten.
9939 It may be enabled again later.
9942 @item enable mem @var{nums}@dots{}
9943 Enable monitoring of memory regions @var{nums}@dots{}.
9947 Print a table of all defined memory regions, with the following columns
9951 @item Memory Region Number
9952 @item Enabled or Disabled.
9953 Enabled memory regions are marked with @samp{y}.
9954 Disabled memory regions are marked with @samp{n}.
9957 The address defining the inclusive lower bound of the memory region.
9960 The address defining the exclusive upper bound of the memory region.
9963 The list of attributes set for this memory region.
9968 @subsection Attributes
9970 @subsubsection Memory Access Mode
9971 The access mode attributes set whether @value{GDBN} may make read or
9972 write accesses to a memory region.
9974 While these attributes prevent @value{GDBN} from performing invalid
9975 memory accesses, they do nothing to prevent the target system, I/O DMA,
9976 etc.@: from accessing memory.
9980 Memory is read only.
9982 Memory is write only.
9984 Memory is read/write. This is the default.
9987 @subsubsection Memory Access Size
9988 The access size attribute tells @value{GDBN} to use specific sized
9989 accesses in the memory region. Often memory mapped device registers
9990 require specific sized accesses. If no access size attribute is
9991 specified, @value{GDBN} may use accesses of any size.
9995 Use 8 bit memory accesses.
9997 Use 16 bit memory accesses.
9999 Use 32 bit memory accesses.
10001 Use 64 bit memory accesses.
10004 @c @subsubsection Hardware/Software Breakpoints
10005 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10006 @c will use hardware or software breakpoints for the internal breakpoints
10007 @c used by the step, next, finish, until, etc. commands.
10011 @c Always use hardware breakpoints
10012 @c @item swbreak (default)
10015 @subsubsection Data Cache
10016 The data cache attributes set whether @value{GDBN} will cache target
10017 memory. While this generally improves performance by reducing debug
10018 protocol overhead, it can lead to incorrect results because @value{GDBN}
10019 does not know about volatile variables or memory mapped device
10024 Enable @value{GDBN} to cache target memory.
10026 Disable @value{GDBN} from caching target memory. This is the default.
10029 @subsection Memory Access Checking
10030 @value{GDBN} can be instructed to refuse accesses to memory that is
10031 not explicitly described. This can be useful if accessing such
10032 regions has undesired effects for a specific target, or to provide
10033 better error checking. The following commands control this behaviour.
10036 @kindex set mem inaccessible-by-default
10037 @item set mem inaccessible-by-default [on|off]
10038 If @code{on} is specified, make @value{GDBN} treat memory not
10039 explicitly described by the memory ranges as non-existent and refuse accesses
10040 to such memory. The checks are only performed if there's at least one
10041 memory range defined. If @code{off} is specified, make @value{GDBN}
10042 treat the memory not explicitly described by the memory ranges as RAM.
10043 The default value is @code{on}.
10044 @kindex show mem inaccessible-by-default
10045 @item show mem inaccessible-by-default
10046 Show the current handling of accesses to unknown memory.
10050 @c @subsubsection Memory Write Verification
10051 @c The memory write verification attributes set whether @value{GDBN}
10052 @c will re-reads data after each write to verify the write was successful.
10056 @c @item noverify (default)
10059 @node Dump/Restore Files
10060 @section Copy Between Memory and a File
10061 @cindex dump/restore files
10062 @cindex append data to a file
10063 @cindex dump data to a file
10064 @cindex restore data from a file
10066 You can use the commands @code{dump}, @code{append}, and
10067 @code{restore} to copy data between target memory and a file. The
10068 @code{dump} and @code{append} commands write data to a file, and the
10069 @code{restore} command reads data from a file back into the inferior's
10070 memory. Files may be in binary, Motorola S-record, Intel hex, or
10071 Tektronix Hex format; however, @value{GDBN} can only append to binary
10077 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10078 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10079 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10080 or the value of @var{expr}, to @var{filename} in the given format.
10082 The @var{format} parameter may be any one of:
10089 Motorola S-record format.
10091 Tektronix Hex format.
10094 @value{GDBN} uses the same definitions of these formats as the
10095 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10096 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10100 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10101 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10102 Append the contents of memory from @var{start_addr} to @var{end_addr},
10103 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10104 (@value{GDBN} can only append data to files in raw binary form.)
10107 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10108 Restore the contents of file @var{filename} into memory. The
10109 @code{restore} command can automatically recognize any known @sc{bfd}
10110 file format, except for raw binary. To restore a raw binary file you
10111 must specify the optional keyword @code{binary} after the filename.
10113 If @var{bias} is non-zero, its value will be added to the addresses
10114 contained in the file. Binary files always start at address zero, so
10115 they will be restored at address @var{bias}. Other bfd files have
10116 a built-in location; they will be restored at offset @var{bias}
10117 from that location.
10119 If @var{start} and/or @var{end} are non-zero, then only data between
10120 file offset @var{start} and file offset @var{end} will be restored.
10121 These offsets are relative to the addresses in the file, before
10122 the @var{bias} argument is applied.
10126 @node Core File Generation
10127 @section How to Produce a Core File from Your Program
10128 @cindex dump core from inferior
10130 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10131 image of a running process and its process status (register values
10132 etc.). Its primary use is post-mortem debugging of a program that
10133 crashed while it ran outside a debugger. A program that crashes
10134 automatically produces a core file, unless this feature is disabled by
10135 the user. @xref{Files}, for information on invoking @value{GDBN} in
10136 the post-mortem debugging mode.
10138 Occasionally, you may wish to produce a core file of the program you
10139 are debugging in order to preserve a snapshot of its state.
10140 @value{GDBN} has a special command for that.
10144 @kindex generate-core-file
10145 @item generate-core-file [@var{file}]
10146 @itemx gcore [@var{file}]
10147 Produce a core dump of the inferior process. The optional argument
10148 @var{file} specifies the file name where to put the core dump. If not
10149 specified, the file name defaults to @file{core.@var{pid}}, where
10150 @var{pid} is the inferior process ID.
10152 Note that this command is implemented only for some systems (as of
10153 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10156 @node Character Sets
10157 @section Character Sets
10158 @cindex character sets
10160 @cindex translating between character sets
10161 @cindex host character set
10162 @cindex target character set
10164 If the program you are debugging uses a different character set to
10165 represent characters and strings than the one @value{GDBN} uses itself,
10166 @value{GDBN} can automatically translate between the character sets for
10167 you. The character set @value{GDBN} uses we call the @dfn{host
10168 character set}; the one the inferior program uses we call the
10169 @dfn{target character set}.
10171 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10172 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10173 remote protocol (@pxref{Remote Debugging}) to debug a program
10174 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10175 then the host character set is Latin-1, and the target character set is
10176 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10177 target-charset EBCDIC-US}, then @value{GDBN} translates between
10178 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10179 character and string literals in expressions.
10181 @value{GDBN} has no way to automatically recognize which character set
10182 the inferior program uses; you must tell it, using the @code{set
10183 target-charset} command, described below.
10185 Here are the commands for controlling @value{GDBN}'s character set
10189 @item set target-charset @var{charset}
10190 @kindex set target-charset
10191 Set the current target character set to @var{charset}. To display the
10192 list of supported target character sets, type
10193 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10195 @item set host-charset @var{charset}
10196 @kindex set host-charset
10197 Set the current host character set to @var{charset}.
10199 By default, @value{GDBN} uses a host character set appropriate to the
10200 system it is running on; you can override that default using the
10201 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10202 automatically determine the appropriate host character set. In this
10203 case, @value{GDBN} uses @samp{UTF-8}.
10205 @value{GDBN} can only use certain character sets as its host character
10206 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10207 @value{GDBN} will list the host character sets it supports.
10209 @item set charset @var{charset}
10210 @kindex set charset
10211 Set the current host and target character sets to @var{charset}. As
10212 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10213 @value{GDBN} will list the names of the character sets that can be used
10214 for both host and target.
10217 @kindex show charset
10218 Show the names of the current host and target character sets.
10220 @item show host-charset
10221 @kindex show host-charset
10222 Show the name of the current host character set.
10224 @item show target-charset
10225 @kindex show target-charset
10226 Show the name of the current target character set.
10228 @item set target-wide-charset @var{charset}
10229 @kindex set target-wide-charset
10230 Set the current target's wide character set to @var{charset}. This is
10231 the character set used by the target's @code{wchar_t} type. To
10232 display the list of supported wide character sets, type
10233 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10235 @item show target-wide-charset
10236 @kindex show target-wide-charset
10237 Show the name of the current target's wide character set.
10240 Here is an example of @value{GDBN}'s character set support in action.
10241 Assume that the following source code has been placed in the file
10242 @file{charset-test.c}:
10248 = @{72, 101, 108, 108, 111, 44, 32, 119,
10249 111, 114, 108, 100, 33, 10, 0@};
10250 char ibm1047_hello[]
10251 = @{200, 133, 147, 147, 150, 107, 64, 166,
10252 150, 153, 147, 132, 90, 37, 0@};
10256 printf ("Hello, world!\n");
10260 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10261 containing the string @samp{Hello, world!} followed by a newline,
10262 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10264 We compile the program, and invoke the debugger on it:
10267 $ gcc -g charset-test.c -o charset-test
10268 $ gdb -nw charset-test
10269 GNU gdb 2001-12-19-cvs
10270 Copyright 2001 Free Software Foundation, Inc.
10275 We can use the @code{show charset} command to see what character sets
10276 @value{GDBN} is currently using to interpret and display characters and
10280 (@value{GDBP}) show charset
10281 The current host and target character set is `ISO-8859-1'.
10285 For the sake of printing this manual, let's use @sc{ascii} as our
10286 initial character set:
10288 (@value{GDBP}) set charset ASCII
10289 (@value{GDBP}) show charset
10290 The current host and target character set is `ASCII'.
10294 Let's assume that @sc{ascii} is indeed the correct character set for our
10295 host system --- in other words, let's assume that if @value{GDBN} prints
10296 characters using the @sc{ascii} character set, our terminal will display
10297 them properly. Since our current target character set is also
10298 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10301 (@value{GDBP}) print ascii_hello
10302 $1 = 0x401698 "Hello, world!\n"
10303 (@value{GDBP}) print ascii_hello[0]
10308 @value{GDBN} uses the target character set for character and string
10309 literals you use in expressions:
10312 (@value{GDBP}) print '+'
10317 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10320 @value{GDBN} relies on the user to tell it which character set the
10321 target program uses. If we print @code{ibm1047_hello} while our target
10322 character set is still @sc{ascii}, we get jibberish:
10325 (@value{GDBP}) print ibm1047_hello
10326 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10327 (@value{GDBP}) print ibm1047_hello[0]
10332 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10333 @value{GDBN} tells us the character sets it supports:
10336 (@value{GDBP}) set target-charset
10337 ASCII EBCDIC-US IBM1047 ISO-8859-1
10338 (@value{GDBP}) set target-charset
10341 We can select @sc{ibm1047} as our target character set, and examine the
10342 program's strings again. Now the @sc{ascii} string is wrong, but
10343 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10344 target character set, @sc{ibm1047}, to the host character set,
10345 @sc{ascii}, and they display correctly:
10348 (@value{GDBP}) set target-charset IBM1047
10349 (@value{GDBP}) show charset
10350 The current host character set is `ASCII'.
10351 The current target character set is `IBM1047'.
10352 (@value{GDBP}) print ascii_hello
10353 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10354 (@value{GDBP}) print ascii_hello[0]
10356 (@value{GDBP}) print ibm1047_hello
10357 $8 = 0x4016a8 "Hello, world!\n"
10358 (@value{GDBP}) print ibm1047_hello[0]
10363 As above, @value{GDBN} uses the target character set for character and
10364 string literals you use in expressions:
10367 (@value{GDBP}) print '+'
10372 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10375 @node Caching Remote Data
10376 @section Caching Data of Remote Targets
10377 @cindex caching data of remote targets
10379 @value{GDBN} caches data exchanged between the debugger and a
10380 remote target (@pxref{Remote Debugging}). Such caching generally improves
10381 performance, because it reduces the overhead of the remote protocol by
10382 bundling memory reads and writes into large chunks. Unfortunately, simply
10383 caching everything would lead to incorrect results, since @value{GDBN}
10384 does not necessarily know anything about volatile values, memory-mapped I/O
10385 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10386 memory can be changed @emph{while} a gdb command is executing.
10387 Therefore, by default, @value{GDBN} only caches data
10388 known to be on the stack@footnote{In non-stop mode, it is moderately
10389 rare for a running thread to modify the stack of a stopped thread
10390 in a way that would interfere with a backtrace, and caching of
10391 stack reads provides a significant speed up of remote backtraces.}.
10392 Other regions of memory can be explicitly marked as
10393 cacheable; see @pxref{Memory Region Attributes}.
10396 @kindex set remotecache
10397 @item set remotecache on
10398 @itemx set remotecache off
10399 This option no longer does anything; it exists for compatibility
10402 @kindex show remotecache
10403 @item show remotecache
10404 Show the current state of the obsolete remotecache flag.
10406 @kindex set stack-cache
10407 @item set stack-cache on
10408 @itemx set stack-cache off
10409 Enable or disable caching of stack accesses. When @code{ON}, use
10410 caching. By default, this option is @code{ON}.
10412 @kindex show stack-cache
10413 @item show stack-cache
10414 Show the current state of data caching for memory accesses.
10416 @kindex info dcache
10417 @item info dcache @r{[}line@r{]}
10418 Print the information about the data cache performance. The
10419 information displayed includes the dcache width and depth, and for
10420 each cache line, its number, address, and how many times it was
10421 referenced. This command is useful for debugging the data cache
10424 If a line number is specified, the contents of that line will be
10427 @item set dcache size @var{size}
10428 @cindex dcache size
10429 @kindex set dcache size
10430 Set maximum number of entries in dcache (dcache depth above).
10432 @item set dcache line-size @var{line-size}
10433 @cindex dcache line-size
10434 @kindex set dcache line-size
10435 Set number of bytes each dcache entry caches (dcache width above).
10436 Must be a power of 2.
10438 @item show dcache size
10439 @kindex show dcache size
10440 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10442 @item show dcache line-size
10443 @kindex show dcache line-size
10444 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10448 @node Searching Memory
10449 @section Search Memory
10450 @cindex searching memory
10452 Memory can be searched for a particular sequence of bytes with the
10453 @code{find} command.
10457 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10458 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10459 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10460 etc. The search begins at address @var{start_addr} and continues for either
10461 @var{len} bytes or through to @var{end_addr} inclusive.
10464 @var{s} and @var{n} are optional parameters.
10465 They may be specified in either order, apart or together.
10468 @item @var{s}, search query size
10469 The size of each search query value.
10475 halfwords (two bytes)
10479 giant words (eight bytes)
10482 All values are interpreted in the current language.
10483 This means, for example, that if the current source language is C/C@t{++}
10484 then searching for the string ``hello'' includes the trailing '\0'.
10486 If the value size is not specified, it is taken from the
10487 value's type in the current language.
10488 This is useful when one wants to specify the search
10489 pattern as a mixture of types.
10490 Note that this means, for example, that in the case of C-like languages
10491 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10492 which is typically four bytes.
10494 @item @var{n}, maximum number of finds
10495 The maximum number of matches to print. The default is to print all finds.
10498 You can use strings as search values. Quote them with double-quotes
10500 The string value is copied into the search pattern byte by byte,
10501 regardless of the endianness of the target and the size specification.
10503 The address of each match found is printed as well as a count of the
10504 number of matches found.
10506 The address of the last value found is stored in convenience variable
10508 A count of the number of matches is stored in @samp{$numfound}.
10510 For example, if stopped at the @code{printf} in this function:
10516 static char hello[] = "hello-hello";
10517 static struct @{ char c; short s; int i; @}
10518 __attribute__ ((packed)) mixed
10519 = @{ 'c', 0x1234, 0x87654321 @};
10520 printf ("%s\n", hello);
10525 you get during debugging:
10528 (gdb) find &hello[0], +sizeof(hello), "hello"
10529 0x804956d <hello.1620+6>
10531 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10532 0x8049567 <hello.1620>
10533 0x804956d <hello.1620+6>
10535 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10536 0x8049567 <hello.1620>
10538 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10539 0x8049560 <mixed.1625>
10541 (gdb) print $numfound
10544 $2 = (void *) 0x8049560
10547 @node Optimized Code
10548 @chapter Debugging Optimized Code
10549 @cindex optimized code, debugging
10550 @cindex debugging optimized code
10552 Almost all compilers support optimization. With optimization
10553 disabled, the compiler generates assembly code that corresponds
10554 directly to your source code, in a simplistic way. As the compiler
10555 applies more powerful optimizations, the generated assembly code
10556 diverges from your original source code. With help from debugging
10557 information generated by the compiler, @value{GDBN} can map from
10558 the running program back to constructs from your original source.
10560 @value{GDBN} is more accurate with optimization disabled. If you
10561 can recompile without optimization, it is easier to follow the
10562 progress of your program during debugging. But, there are many cases
10563 where you may need to debug an optimized version.
10565 When you debug a program compiled with @samp{-g -O}, remember that the
10566 optimizer has rearranged your code; the debugger shows you what is
10567 really there. Do not be too surprised when the execution path does not
10568 exactly match your source file! An extreme example: if you define a
10569 variable, but never use it, @value{GDBN} never sees that
10570 variable---because the compiler optimizes it out of existence.
10572 Some things do not work as well with @samp{-g -O} as with just
10573 @samp{-g}, particularly on machines with instruction scheduling. If in
10574 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10575 please report it to us as a bug (including a test case!).
10576 @xref{Variables}, for more information about debugging optimized code.
10579 * Inline Functions:: How @value{GDBN} presents inlining
10580 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10583 @node Inline Functions
10584 @section Inline Functions
10585 @cindex inline functions, debugging
10587 @dfn{Inlining} is an optimization that inserts a copy of the function
10588 body directly at each call site, instead of jumping to a shared
10589 routine. @value{GDBN} displays inlined functions just like
10590 non-inlined functions. They appear in backtraces. You can view their
10591 arguments and local variables, step into them with @code{step}, skip
10592 them with @code{next}, and escape from them with @code{finish}.
10593 You can check whether a function was inlined by using the
10594 @code{info frame} command.
10596 For @value{GDBN} to support inlined functions, the compiler must
10597 record information about inlining in the debug information ---
10598 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10599 other compilers do also. @value{GDBN} only supports inlined functions
10600 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10601 do not emit two required attributes (@samp{DW_AT_call_file} and
10602 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10603 function calls with earlier versions of @value{NGCC}. It instead
10604 displays the arguments and local variables of inlined functions as
10605 local variables in the caller.
10607 The body of an inlined function is directly included at its call site;
10608 unlike a non-inlined function, there are no instructions devoted to
10609 the call. @value{GDBN} still pretends that the call site and the
10610 start of the inlined function are different instructions. Stepping to
10611 the call site shows the call site, and then stepping again shows
10612 the first line of the inlined function, even though no additional
10613 instructions are executed.
10615 This makes source-level debugging much clearer; you can see both the
10616 context of the call and then the effect of the call. Only stepping by
10617 a single instruction using @code{stepi} or @code{nexti} does not do
10618 this; single instruction steps always show the inlined body.
10620 There are some ways that @value{GDBN} does not pretend that inlined
10621 function calls are the same as normal calls:
10625 Setting breakpoints at the call site of an inlined function may not
10626 work, because the call site does not contain any code. @value{GDBN}
10627 may incorrectly move the breakpoint to the next line of the enclosing
10628 function, after the call. This limitation will be removed in a future
10629 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10630 or inside the inlined function instead.
10633 @value{GDBN} cannot locate the return value of inlined calls after
10634 using the @code{finish} command. This is a limitation of compiler-generated
10635 debugging information; after @code{finish}, you can step to the next line
10636 and print a variable where your program stored the return value.
10640 @node Tail Call Frames
10641 @section Tail Call Frames
10642 @cindex tail call frames, debugging
10644 Function @code{B} can call function @code{C} in its very last statement. In
10645 unoptimized compilation the call of @code{C} is immediately followed by return
10646 instruction at the end of @code{B} code. Optimizing compiler may replace the
10647 call and return in function @code{B} into one jump to function @code{C}
10648 instead. Such use of a jump instruction is called @dfn{tail call}.
10650 During execution of function @code{C}, there will be no indication in the
10651 function call stack frames that it was tail-called from @code{B}. If function
10652 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10653 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10654 some cases @value{GDBN} can determine that @code{C} was tail-called from
10655 @code{B}, and it will then create fictitious call frame for that, with the
10656 return address set up as if @code{B} called @code{C} normally.
10658 This functionality is currently supported only by DWARF 2 debugging format and
10659 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10660 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10663 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10664 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10668 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10670 Stack level 1, frame at 0x7fffffffda30:
10671 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10672 tail call frame, caller of frame at 0x7fffffffda30
10673 source language c++.
10674 Arglist at unknown address.
10675 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10678 The detection of all the possible code path executions can find them ambiguous.
10679 There is no execution history stored (possible @ref{Reverse Execution} is never
10680 used for this purpose) and the last known caller could have reached the known
10681 callee by multiple different jump sequences. In such case @value{GDBN} still
10682 tries to show at least all the unambiguous top tail callers and all the
10683 unambiguous bottom tail calees, if any.
10686 @anchor{set debug entry-values}
10687 @item set debug entry-values
10688 @kindex set debug entry-values
10689 When set to on, enables printing of analysis messages for both frame argument
10690 values at function entry and tail calls. It will show all the possible valid
10691 tail calls code paths it has considered. It will also print the intersection
10692 of them with the final unambiguous (possibly partial or even empty) code path
10695 @item show debug entry-values
10696 @kindex show debug entry-values
10697 Show the current state of analysis messages printing for both frame argument
10698 values at function entry and tail calls.
10701 The analysis messages for tail calls can for example show why the virtual tail
10702 call frame for function @code{c} has not been recognized (due to the indirect
10703 reference by variable @code{x}):
10706 static void __attribute__((noinline, noclone)) c (void);
10707 void (*x) (void) = c;
10708 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10709 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10710 int main (void) @{ x (); return 0; @}
10712 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10713 DW_TAG_GNU_call_site 0x40039a in main
10715 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10718 #1 0x000000000040039a in main () at t.c:5
10721 Another possibility is an ambiguous virtual tail call frames resolution:
10725 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10726 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10727 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10728 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10729 static void __attribute__((noinline, noclone)) b (void)
10730 @{ if (i) c (); else e (); @}
10731 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10732 int main (void) @{ a (); return 0; @}
10734 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10735 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10736 tailcall: reduced: 0x4004d2(a) |
10739 #1 0x00000000004004d2 in a () at t.c:8
10740 #2 0x0000000000400395 in main () at t.c:9
10743 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10744 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10746 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10747 @ifset HAVE_MAKEINFO_CLICK
10748 @set ARROW @click{}
10749 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10750 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10752 @ifclear HAVE_MAKEINFO_CLICK
10754 @set CALLSEQ1B @value{CALLSEQ1A}
10755 @set CALLSEQ2B @value{CALLSEQ2A}
10758 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10759 The code can have possible execution paths @value{CALLSEQ1B} or
10760 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10762 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10763 has found. It then finds another possible calling sequcen - that one is
10764 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10765 printed as the @code{reduced:} calling sequence. That one could have many
10766 futher @code{compare:} and @code{reduced:} statements as long as there remain
10767 any non-ambiguous sequence entries.
10769 For the frame of function @code{b} in both cases there are different possible
10770 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10771 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10772 therefore this one is displayed to the user while the ambiguous frames are
10775 There can be also reasons why printing of frame argument values at function
10780 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10781 static void __attribute__((noinline, noclone)) a (int i);
10782 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10783 static void __attribute__((noinline, noclone)) a (int i)
10784 @{ if (i) b (i - 1); else c (0); @}
10785 int main (void) @{ a (5); return 0; @}
10788 #0 c (i=i@@entry=0) at t.c:2
10789 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10790 function "a" at 0x400420 can call itself via tail calls
10791 i=<optimized out>) at t.c:6
10792 #2 0x000000000040036e in main () at t.c:7
10795 @value{GDBN} cannot find out from the inferior state if and how many times did
10796 function @code{a} call itself (via function @code{b}) as these calls would be
10797 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10798 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10799 prints @code{<optimized out>} instead.
10802 @chapter C Preprocessor Macros
10804 Some languages, such as C and C@t{++}, provide a way to define and invoke
10805 ``preprocessor macros'' which expand into strings of tokens.
10806 @value{GDBN} can evaluate expressions containing macro invocations, show
10807 the result of macro expansion, and show a macro's definition, including
10808 where it was defined.
10810 You may need to compile your program specially to provide @value{GDBN}
10811 with information about preprocessor macros. Most compilers do not
10812 include macros in their debugging information, even when you compile
10813 with the @option{-g} flag. @xref{Compilation}.
10815 A program may define a macro at one point, remove that definition later,
10816 and then provide a different definition after that. Thus, at different
10817 points in the program, a macro may have different definitions, or have
10818 no definition at all. If there is a current stack frame, @value{GDBN}
10819 uses the macros in scope at that frame's source code line. Otherwise,
10820 @value{GDBN} uses the macros in scope at the current listing location;
10823 Whenever @value{GDBN} evaluates an expression, it always expands any
10824 macro invocations present in the expression. @value{GDBN} also provides
10825 the following commands for working with macros explicitly.
10829 @kindex macro expand
10830 @cindex macro expansion, showing the results of preprocessor
10831 @cindex preprocessor macro expansion, showing the results of
10832 @cindex expanding preprocessor macros
10833 @item macro expand @var{expression}
10834 @itemx macro exp @var{expression}
10835 Show the results of expanding all preprocessor macro invocations in
10836 @var{expression}. Since @value{GDBN} simply expands macros, but does
10837 not parse the result, @var{expression} need not be a valid expression;
10838 it can be any string of tokens.
10841 @item macro expand-once @var{expression}
10842 @itemx macro exp1 @var{expression}
10843 @cindex expand macro once
10844 @i{(This command is not yet implemented.)} Show the results of
10845 expanding those preprocessor macro invocations that appear explicitly in
10846 @var{expression}. Macro invocations appearing in that expansion are
10847 left unchanged. This command allows you to see the effect of a
10848 particular macro more clearly, without being confused by further
10849 expansions. Since @value{GDBN} simply expands macros, but does not
10850 parse the result, @var{expression} need not be a valid expression; it
10851 can be any string of tokens.
10854 @cindex macro definition, showing
10855 @cindex definition of a macro, showing
10856 @cindex macros, from debug info
10857 @item info macro [-a|-all] [--] @var{macro}
10858 Show the current definition or all definitions of the named @var{macro},
10859 and describe the source location or compiler command-line where that
10860 definition was established. The optional double dash is to signify the end of
10861 argument processing and the beginning of @var{macro} for non C-like macros where
10862 the macro may begin with a hyphen.
10864 @kindex info macros
10865 @item info macros @var{linespec}
10866 Show all macro definitions that are in effect at the location specified
10867 by @var{linespec}, and describe the source location or compiler
10868 command-line where those definitions were established.
10870 @kindex macro define
10871 @cindex user-defined macros
10872 @cindex defining macros interactively
10873 @cindex macros, user-defined
10874 @item macro define @var{macro} @var{replacement-list}
10875 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10876 Introduce a definition for a preprocessor macro named @var{macro},
10877 invocations of which are replaced by the tokens given in
10878 @var{replacement-list}. The first form of this command defines an
10879 ``object-like'' macro, which takes no arguments; the second form
10880 defines a ``function-like'' macro, which takes the arguments given in
10883 A definition introduced by this command is in scope in every
10884 expression evaluated in @value{GDBN}, until it is removed with the
10885 @code{macro undef} command, described below. The definition overrides
10886 all definitions for @var{macro} present in the program being debugged,
10887 as well as any previous user-supplied definition.
10889 @kindex macro undef
10890 @item macro undef @var{macro}
10891 Remove any user-supplied definition for the macro named @var{macro}.
10892 This command only affects definitions provided with the @code{macro
10893 define} command, described above; it cannot remove definitions present
10894 in the program being debugged.
10898 List all the macros defined using the @code{macro define} command.
10901 @cindex macros, example of debugging with
10902 Here is a transcript showing the above commands in action. First, we
10903 show our source files:
10908 #include "sample.h"
10911 #define ADD(x) (M + x)
10916 printf ("Hello, world!\n");
10918 printf ("We're so creative.\n");
10920 printf ("Goodbye, world!\n");
10927 Now, we compile the program using the @sc{gnu} C compiler,
10928 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10929 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10930 and @option{-gdwarf-4}; we recommend always choosing the most recent
10931 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10932 includes information about preprocessor macros in the debugging
10936 $ gcc -gdwarf-2 -g3 sample.c -o sample
10940 Now, we start @value{GDBN} on our sample program:
10944 GNU gdb 2002-05-06-cvs
10945 Copyright 2002 Free Software Foundation, Inc.
10946 GDB is free software, @dots{}
10950 We can expand macros and examine their definitions, even when the
10951 program is not running. @value{GDBN} uses the current listing position
10952 to decide which macro definitions are in scope:
10955 (@value{GDBP}) list main
10958 5 #define ADD(x) (M + x)
10963 10 printf ("Hello, world!\n");
10965 12 printf ("We're so creative.\n");
10966 (@value{GDBP}) info macro ADD
10967 Defined at /home/jimb/gdb/macros/play/sample.c:5
10968 #define ADD(x) (M + x)
10969 (@value{GDBP}) info macro Q
10970 Defined at /home/jimb/gdb/macros/play/sample.h:1
10971 included at /home/jimb/gdb/macros/play/sample.c:2
10973 (@value{GDBP}) macro expand ADD(1)
10974 expands to: (42 + 1)
10975 (@value{GDBP}) macro expand-once ADD(1)
10976 expands to: once (M + 1)
10980 In the example above, note that @code{macro expand-once} expands only
10981 the macro invocation explicit in the original text --- the invocation of
10982 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10983 which was introduced by @code{ADD}.
10985 Once the program is running, @value{GDBN} uses the macro definitions in
10986 force at the source line of the current stack frame:
10989 (@value{GDBP}) break main
10990 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10992 Starting program: /home/jimb/gdb/macros/play/sample
10994 Breakpoint 1, main () at sample.c:10
10995 10 printf ("Hello, world!\n");
10999 At line 10, the definition of the macro @code{N} at line 9 is in force:
11002 (@value{GDBP}) info macro N
11003 Defined at /home/jimb/gdb/macros/play/sample.c:9
11005 (@value{GDBP}) macro expand N Q M
11006 expands to: 28 < 42
11007 (@value{GDBP}) print N Q M
11012 As we step over directives that remove @code{N}'s definition, and then
11013 give it a new definition, @value{GDBN} finds the definition (or lack
11014 thereof) in force at each point:
11017 (@value{GDBP}) next
11019 12 printf ("We're so creative.\n");
11020 (@value{GDBP}) info macro N
11021 The symbol `N' has no definition as a C/C++ preprocessor macro
11022 at /home/jimb/gdb/macros/play/sample.c:12
11023 (@value{GDBP}) next
11025 14 printf ("Goodbye, world!\n");
11026 (@value{GDBP}) info macro N
11027 Defined at /home/jimb/gdb/macros/play/sample.c:13
11029 (@value{GDBP}) macro expand N Q M
11030 expands to: 1729 < 42
11031 (@value{GDBP}) print N Q M
11036 In addition to source files, macros can be defined on the compilation command
11037 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11038 such a way, @value{GDBN} displays the location of their definition as line zero
11039 of the source file submitted to the compiler.
11042 (@value{GDBP}) info macro __STDC__
11043 Defined at /home/jimb/gdb/macros/play/sample.c:0
11050 @chapter Tracepoints
11051 @c This chapter is based on the documentation written by Michael
11052 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11054 @cindex tracepoints
11055 In some applications, it is not feasible for the debugger to interrupt
11056 the program's execution long enough for the developer to learn
11057 anything helpful about its behavior. If the program's correctness
11058 depends on its real-time behavior, delays introduced by a debugger
11059 might cause the program to change its behavior drastically, or perhaps
11060 fail, even when the code itself is correct. It is useful to be able
11061 to observe the program's behavior without interrupting it.
11063 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11064 specify locations in the program, called @dfn{tracepoints}, and
11065 arbitrary expressions to evaluate when those tracepoints are reached.
11066 Later, using the @code{tfind} command, you can examine the values
11067 those expressions had when the program hit the tracepoints. The
11068 expressions may also denote objects in memory---structures or arrays,
11069 for example---whose values @value{GDBN} should record; while visiting
11070 a particular tracepoint, you may inspect those objects as if they were
11071 in memory at that moment. However, because @value{GDBN} records these
11072 values without interacting with you, it can do so quickly and
11073 unobtrusively, hopefully not disturbing the program's behavior.
11075 The tracepoint facility is currently available only for remote
11076 targets. @xref{Targets}. In addition, your remote target must know
11077 how to collect trace data. This functionality is implemented in the
11078 remote stub; however, none of the stubs distributed with @value{GDBN}
11079 support tracepoints as of this writing. The format of the remote
11080 packets used to implement tracepoints are described in @ref{Tracepoint
11083 It is also possible to get trace data from a file, in a manner reminiscent
11084 of corefiles; you specify the filename, and use @code{tfind} to search
11085 through the file. @xref{Trace Files}, for more details.
11087 This chapter describes the tracepoint commands and features.
11090 * Set Tracepoints::
11091 * Analyze Collected Data::
11092 * Tracepoint Variables::
11096 @node Set Tracepoints
11097 @section Commands to Set Tracepoints
11099 Before running such a @dfn{trace experiment}, an arbitrary number of
11100 tracepoints can be set. A tracepoint is actually a special type of
11101 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11102 standard breakpoint commands. For instance, as with breakpoints,
11103 tracepoint numbers are successive integers starting from one, and many
11104 of the commands associated with tracepoints take the tracepoint number
11105 as their argument, to identify which tracepoint to work on.
11107 For each tracepoint, you can specify, in advance, some arbitrary set
11108 of data that you want the target to collect in the trace buffer when
11109 it hits that tracepoint. The collected data can include registers,
11110 local variables, or global data. Later, you can use @value{GDBN}
11111 commands to examine the values these data had at the time the
11112 tracepoint was hit.
11114 Tracepoints do not support every breakpoint feature. Ignore counts on
11115 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11116 commands when they are hit. Tracepoints may not be thread-specific
11119 @cindex fast tracepoints
11120 Some targets may support @dfn{fast tracepoints}, which are inserted in
11121 a different way (such as with a jump instead of a trap), that is
11122 faster but possibly restricted in where they may be installed.
11124 @cindex static tracepoints
11125 @cindex markers, static tracepoints
11126 @cindex probing markers, static tracepoints
11127 Regular and fast tracepoints are dynamic tracing facilities, meaning
11128 that they can be used to insert tracepoints at (almost) any location
11129 in the target. Some targets may also support controlling @dfn{static
11130 tracepoints} from @value{GDBN}. With static tracing, a set of
11131 instrumentation points, also known as @dfn{markers}, are embedded in
11132 the target program, and can be activated or deactivated by name or
11133 address. These are usually placed at locations which facilitate
11134 investigating what the target is actually doing. @value{GDBN}'s
11135 support for static tracing includes being able to list instrumentation
11136 points, and attach them with @value{GDBN} defined high level
11137 tracepoints that expose the whole range of convenience of
11138 @value{GDBN}'s tracepoints support. Namely, support for collecting
11139 registers values and values of global or local (to the instrumentation
11140 point) variables; tracepoint conditions and trace state variables.
11141 The act of installing a @value{GDBN} static tracepoint on an
11142 instrumentation point, or marker, is referred to as @dfn{probing} a
11143 static tracepoint marker.
11145 @code{gdbserver} supports tracepoints on some target systems.
11146 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11148 This section describes commands to set tracepoints and associated
11149 conditions and actions.
11152 * Create and Delete Tracepoints::
11153 * Enable and Disable Tracepoints::
11154 * Tracepoint Passcounts::
11155 * Tracepoint Conditions::
11156 * Trace State Variables::
11157 * Tracepoint Actions::
11158 * Listing Tracepoints::
11159 * Listing Static Tracepoint Markers::
11160 * Starting and Stopping Trace Experiments::
11161 * Tracepoint Restrictions::
11164 @node Create and Delete Tracepoints
11165 @subsection Create and Delete Tracepoints
11168 @cindex set tracepoint
11170 @item trace @var{location}
11171 The @code{trace} command is very similar to the @code{break} command.
11172 Its argument @var{location} can be a source line, a function name, or
11173 an address in the target program. @xref{Specify Location}. The
11174 @code{trace} command defines a tracepoint, which is a point in the
11175 target program where the debugger will briefly stop, collect some
11176 data, and then allow the program to continue. Setting a tracepoint or
11177 changing its actions takes effect immediately if the remote stub
11178 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11180 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11181 these changes don't take effect until the next @code{tstart}
11182 command, and once a trace experiment is running, further changes will
11183 not have any effect until the next trace experiment starts. In addition,
11184 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11185 address is not yet resolved. (This is similar to pending breakpoints.)
11186 Pending tracepoints are not downloaded to the target and not installed
11187 until they are resolved. The resolution of pending tracepoints requires
11188 @value{GDBN} support---when debugging with the remote target, and
11189 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11190 tracing}), pending tracepoints can not be resolved (and downloaded to
11191 the remote stub) while @value{GDBN} is disconnected.
11193 Here are some examples of using the @code{trace} command:
11196 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11198 (@value{GDBP}) @b{trace +2} // 2 lines forward
11200 (@value{GDBP}) @b{trace my_function} // first source line of function
11202 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11204 (@value{GDBP}) @b{trace *0x2117c4} // an address
11208 You can abbreviate @code{trace} as @code{tr}.
11210 @item trace @var{location} if @var{cond}
11211 Set a tracepoint with condition @var{cond}; evaluate the expression
11212 @var{cond} each time the tracepoint is reached, and collect data only
11213 if the value is nonzero---that is, if @var{cond} evaluates as true.
11214 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11215 information on tracepoint conditions.
11217 @item ftrace @var{location} [ if @var{cond} ]
11218 @cindex set fast tracepoint
11219 @cindex fast tracepoints, setting
11221 The @code{ftrace} command sets a fast tracepoint. For targets that
11222 support them, fast tracepoints will use a more efficient but possibly
11223 less general technique to trigger data collection, such as a jump
11224 instruction instead of a trap, or some sort of hardware support. It
11225 may not be possible to create a fast tracepoint at the desired
11226 location, in which case the command will exit with an explanatory
11229 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11232 On 32-bit x86-architecture systems, fast tracepoints normally need to
11233 be placed at an instruction that is 5 bytes or longer, but can be
11234 placed at 4-byte instructions if the low 64K of memory of the target
11235 program is available to install trampolines. Some Unix-type systems,
11236 such as @sc{gnu}/Linux, exclude low addresses from the program's
11237 address space; but for instance with the Linux kernel it is possible
11238 to let @value{GDBN} use this area by doing a @command{sysctl} command
11239 to set the @code{mmap_min_addr} kernel parameter, as in
11242 sudo sysctl -w vm.mmap_min_addr=32768
11246 which sets the low address to 32K, which leaves plenty of room for
11247 trampolines. The minimum address should be set to a page boundary.
11249 @item strace @var{location} [ if @var{cond} ]
11250 @cindex set static tracepoint
11251 @cindex static tracepoints, setting
11252 @cindex probe static tracepoint marker
11254 The @code{strace} command sets a static tracepoint. For targets that
11255 support it, setting a static tracepoint probes a static
11256 instrumentation point, or marker, found at @var{location}. It may not
11257 be possible to set a static tracepoint at the desired location, in
11258 which case the command will exit with an explanatory message.
11260 @value{GDBN} handles arguments to @code{strace} exactly as for
11261 @code{trace}, with the addition that the user can also specify
11262 @code{-m @var{marker}} as @var{location}. This probes the marker
11263 identified by the @var{marker} string identifier. This identifier
11264 depends on the static tracepoint backend library your program is
11265 using. You can find all the marker identifiers in the @samp{ID} field
11266 of the @code{info static-tracepoint-markers} command output.
11267 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11268 Markers}. For example, in the following small program using the UST
11274 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11279 the marker id is composed of joining the first two arguments to the
11280 @code{trace_mark} call with a slash, which translates to:
11283 (@value{GDBP}) info static-tracepoint-markers
11284 Cnt Enb ID Address What
11285 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11291 so you may probe the marker above with:
11294 (@value{GDBP}) strace -m ust/bar33
11297 Static tracepoints accept an extra collect action --- @code{collect
11298 $_sdata}. This collects arbitrary user data passed in the probe point
11299 call to the tracing library. In the UST example above, you'll see
11300 that the third argument to @code{trace_mark} is a printf-like format
11301 string. The user data is then the result of running that formating
11302 string against the following arguments. Note that @code{info
11303 static-tracepoint-markers} command output lists that format string in
11304 the @samp{Data:} field.
11306 You can inspect this data when analyzing the trace buffer, by printing
11307 the $_sdata variable like any other variable available to
11308 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11311 @cindex last tracepoint number
11312 @cindex recent tracepoint number
11313 @cindex tracepoint number
11314 The convenience variable @code{$tpnum} records the tracepoint number
11315 of the most recently set tracepoint.
11317 @kindex delete tracepoint
11318 @cindex tracepoint deletion
11319 @item delete tracepoint @r{[}@var{num}@r{]}
11320 Permanently delete one or more tracepoints. With no argument, the
11321 default is to delete all tracepoints. Note that the regular
11322 @code{delete} command can remove tracepoints also.
11327 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11329 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11333 You can abbreviate this command as @code{del tr}.
11336 @node Enable and Disable Tracepoints
11337 @subsection Enable and Disable Tracepoints
11339 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11342 @kindex disable tracepoint
11343 @item disable tracepoint @r{[}@var{num}@r{]}
11344 Disable tracepoint @var{num}, or all tracepoints if no argument
11345 @var{num} is given. A disabled tracepoint will have no effect during
11346 a trace experiment, but it is not forgotten. You can re-enable
11347 a disabled tracepoint using the @code{enable tracepoint} command.
11348 If the command is issued during a trace experiment and the debug target
11349 has support for disabling tracepoints during a trace experiment, then the
11350 change will be effective immediately. Otherwise, it will be applied to the
11351 next trace experiment.
11353 @kindex enable tracepoint
11354 @item enable tracepoint @r{[}@var{num}@r{]}
11355 Enable tracepoint @var{num}, or all tracepoints. If this command is
11356 issued during a trace experiment and the debug target supports enabling
11357 tracepoints during a trace experiment, then the enabled tracepoints will
11358 become effective immediately. Otherwise, they will become effective the
11359 next time a trace experiment is run.
11362 @node Tracepoint Passcounts
11363 @subsection Tracepoint Passcounts
11367 @cindex tracepoint pass count
11368 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11369 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11370 automatically stop a trace experiment. If a tracepoint's passcount is
11371 @var{n}, then the trace experiment will be automatically stopped on
11372 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11373 @var{num} is not specified, the @code{passcount} command sets the
11374 passcount of the most recently defined tracepoint. If no passcount is
11375 given, the trace experiment will run until stopped explicitly by the
11381 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11382 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11384 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11385 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11386 (@value{GDBP}) @b{trace foo}
11387 (@value{GDBP}) @b{pass 3}
11388 (@value{GDBP}) @b{trace bar}
11389 (@value{GDBP}) @b{pass 2}
11390 (@value{GDBP}) @b{trace baz}
11391 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11392 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11393 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11394 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11398 @node Tracepoint Conditions
11399 @subsection Tracepoint Conditions
11400 @cindex conditional tracepoints
11401 @cindex tracepoint conditions
11403 The simplest sort of tracepoint collects data every time your program
11404 reaches a specified place. You can also specify a @dfn{condition} for
11405 a tracepoint. A condition is just a Boolean expression in your
11406 programming language (@pxref{Expressions, ,Expressions}). A
11407 tracepoint with a condition evaluates the expression each time your
11408 program reaches it, and data collection happens only if the condition
11411 Tracepoint conditions can be specified when a tracepoint is set, by
11412 using @samp{if} in the arguments to the @code{trace} command.
11413 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11414 also be set or changed at any time with the @code{condition} command,
11415 just as with breakpoints.
11417 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11418 the conditional expression itself. Instead, @value{GDBN} encodes the
11419 expression into an agent expression (@pxref{Agent Expressions})
11420 suitable for execution on the target, independently of @value{GDBN}.
11421 Global variables become raw memory locations, locals become stack
11422 accesses, and so forth.
11424 For instance, suppose you have a function that is usually called
11425 frequently, but should not be called after an error has occurred. You
11426 could use the following tracepoint command to collect data about calls
11427 of that function that happen while the error code is propagating
11428 through the program; an unconditional tracepoint could end up
11429 collecting thousands of useless trace frames that you would have to
11433 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11436 @node Trace State Variables
11437 @subsection Trace State Variables
11438 @cindex trace state variables
11440 A @dfn{trace state variable} is a special type of variable that is
11441 created and managed by target-side code. The syntax is the same as
11442 that for GDB's convenience variables (a string prefixed with ``$''),
11443 but they are stored on the target. They must be created explicitly,
11444 using a @code{tvariable} command. They are always 64-bit signed
11447 Trace state variables are remembered by @value{GDBN}, and downloaded
11448 to the target along with tracepoint information when the trace
11449 experiment starts. There are no intrinsic limits on the number of
11450 trace state variables, beyond memory limitations of the target.
11452 @cindex convenience variables, and trace state variables
11453 Although trace state variables are managed by the target, you can use
11454 them in print commands and expressions as if they were convenience
11455 variables; @value{GDBN} will get the current value from the target
11456 while the trace experiment is running. Trace state variables share
11457 the same namespace as other ``$'' variables, which means that you
11458 cannot have trace state variables with names like @code{$23} or
11459 @code{$pc}, nor can you have a trace state variable and a convenience
11460 variable with the same name.
11464 @item tvariable $@var{name} [ = @var{expression} ]
11466 The @code{tvariable} command creates a new trace state variable named
11467 @code{$@var{name}}, and optionally gives it an initial value of
11468 @var{expression}. @var{expression} is evaluated when this command is
11469 entered; the result will be converted to an integer if possible,
11470 otherwise @value{GDBN} will report an error. A subsequent
11471 @code{tvariable} command specifying the same name does not create a
11472 variable, but instead assigns the supplied initial value to the
11473 existing variable of that name, overwriting any previous initial
11474 value. The default initial value is 0.
11476 @item info tvariables
11477 @kindex info tvariables
11478 List all the trace state variables along with their initial values.
11479 Their current values may also be displayed, if the trace experiment is
11482 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11483 @kindex delete tvariable
11484 Delete the given trace state variables, or all of them if no arguments
11489 @node Tracepoint Actions
11490 @subsection Tracepoint Action Lists
11494 @cindex tracepoint actions
11495 @item actions @r{[}@var{num}@r{]}
11496 This command will prompt for a list of actions to be taken when the
11497 tracepoint is hit. If the tracepoint number @var{num} is not
11498 specified, this command sets the actions for the one that was most
11499 recently defined (so that you can define a tracepoint and then say
11500 @code{actions} without bothering about its number). You specify the
11501 actions themselves on the following lines, one action at a time, and
11502 terminate the actions list with a line containing just @code{end}. So
11503 far, the only defined actions are @code{collect}, @code{teval}, and
11504 @code{while-stepping}.
11506 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11507 Commands, ,Breakpoint Command Lists}), except that only the defined
11508 actions are allowed; any other @value{GDBN} command is rejected.
11510 @cindex remove actions from a tracepoint
11511 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11512 and follow it immediately with @samp{end}.
11515 (@value{GDBP}) @b{collect @var{data}} // collect some data
11517 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11519 (@value{GDBP}) @b{end} // signals the end of actions.
11522 In the following example, the action list begins with @code{collect}
11523 commands indicating the things to be collected when the tracepoint is
11524 hit. Then, in order to single-step and collect additional data
11525 following the tracepoint, a @code{while-stepping} command is used,
11526 followed by the list of things to be collected after each step in a
11527 sequence of single steps. The @code{while-stepping} command is
11528 terminated by its own separate @code{end} command. Lastly, the action
11529 list is terminated by an @code{end} command.
11532 (@value{GDBP}) @b{trace foo}
11533 (@value{GDBP}) @b{actions}
11534 Enter actions for tracepoint 1, one per line:
11537 > while-stepping 12
11538 > collect $pc, arr[i]
11543 @kindex collect @r{(tracepoints)}
11544 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11545 Collect values of the given expressions when the tracepoint is hit.
11546 This command accepts a comma-separated list of any valid expressions.
11547 In addition to global, static, or local variables, the following
11548 special arguments are supported:
11552 Collect all registers.
11555 Collect all function arguments.
11558 Collect all local variables.
11561 Collect the return address. This is helpful if you want to see more
11565 Collects the number of arguments from the static probe at which the
11566 tracepoint is located.
11567 @xref{Static Probe Points}.
11569 @item $_probe_arg@var{n}
11570 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11571 from the static probe at which the tracepoint is located.
11572 @xref{Static Probe Points}.
11575 @vindex $_sdata@r{, collect}
11576 Collect static tracepoint marker specific data. Only available for
11577 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11578 Lists}. On the UST static tracepoints library backend, an
11579 instrumentation point resembles a @code{printf} function call. The
11580 tracing library is able to collect user specified data formatted to a
11581 character string using the format provided by the programmer that
11582 instrumented the program. Other backends have similar mechanisms.
11583 Here's an example of a UST marker call:
11586 const char master_name[] = "$your_name";
11587 trace_mark(channel1, marker1, "hello %s", master_name)
11590 In this case, collecting @code{$_sdata} collects the string
11591 @samp{hello $yourname}. When analyzing the trace buffer, you can
11592 inspect @samp{$_sdata} like any other variable available to
11596 You can give several consecutive @code{collect} commands, each one
11597 with a single argument, or one @code{collect} command with several
11598 arguments separated by commas; the effect is the same.
11600 The optional @var{mods} changes the usual handling of the arguments.
11601 @code{s} requests that pointers to chars be handled as strings, in
11602 particular collecting the contents of the memory being pointed at, up
11603 to the first zero. The upper bound is by default the value of the
11604 @code{print elements} variable; if @code{s} is followed by a decimal
11605 number, that is the upper bound instead. So for instance
11606 @samp{collect/s25 mystr} collects as many as 25 characters at
11609 The command @code{info scope} (@pxref{Symbols, info scope}) is
11610 particularly useful for figuring out what data to collect.
11612 @kindex teval @r{(tracepoints)}
11613 @item teval @var{expr1}, @var{expr2}, @dots{}
11614 Evaluate the given expressions when the tracepoint is hit. This
11615 command accepts a comma-separated list of expressions. The results
11616 are discarded, so this is mainly useful for assigning values to trace
11617 state variables (@pxref{Trace State Variables}) without adding those
11618 values to the trace buffer, as would be the case if the @code{collect}
11621 @kindex while-stepping @r{(tracepoints)}
11622 @item while-stepping @var{n}
11623 Perform @var{n} single-step instruction traces after the tracepoint,
11624 collecting new data after each step. The @code{while-stepping}
11625 command is followed by the list of what to collect while stepping
11626 (followed by its own @code{end} command):
11629 > while-stepping 12
11630 > collect $regs, myglobal
11636 Note that @code{$pc} is not automatically collected by
11637 @code{while-stepping}; you need to explicitly collect that register if
11638 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11641 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11642 @kindex set default-collect
11643 @cindex default collection action
11644 This variable is a list of expressions to collect at each tracepoint
11645 hit. It is effectively an additional @code{collect} action prepended
11646 to every tracepoint action list. The expressions are parsed
11647 individually for each tracepoint, so for instance a variable named
11648 @code{xyz} may be interpreted as a global for one tracepoint, and a
11649 local for another, as appropriate to the tracepoint's location.
11651 @item show default-collect
11652 @kindex show default-collect
11653 Show the list of expressions that are collected by default at each
11658 @node Listing Tracepoints
11659 @subsection Listing Tracepoints
11662 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11663 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11664 @cindex information about tracepoints
11665 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11666 Display information about the tracepoint @var{num}. If you don't
11667 specify a tracepoint number, displays information about all the
11668 tracepoints defined so far. The format is similar to that used for
11669 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11670 command, simply restricting itself to tracepoints.
11672 A tracepoint's listing may include additional information specific to
11677 its passcount as given by the @code{passcount @var{n}} command
11680 the state about installed on target of each location
11684 (@value{GDBP}) @b{info trace}
11685 Num Type Disp Enb Address What
11686 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11688 collect globfoo, $regs
11693 2 tracepoint keep y <MULTIPLE>
11695 2.1 y 0x0804859c in func4 at change-loc.h:35
11696 installed on target
11697 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11698 installed on target
11699 2.3 y <PENDING> set_tracepoint
11700 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11701 not installed on target
11706 This command can be abbreviated @code{info tp}.
11709 @node Listing Static Tracepoint Markers
11710 @subsection Listing Static Tracepoint Markers
11713 @kindex info static-tracepoint-markers
11714 @cindex information about static tracepoint markers
11715 @item info static-tracepoint-markers
11716 Display information about all static tracepoint markers defined in the
11719 For each marker, the following columns are printed:
11723 An incrementing counter, output to help readability. This is not a
11726 The marker ID, as reported by the target.
11727 @item Enabled or Disabled
11728 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11729 that are not enabled.
11731 Where the marker is in your program, as a memory address.
11733 Where the marker is in the source for your program, as a file and line
11734 number. If the debug information included in the program does not
11735 allow @value{GDBN} to locate the source of the marker, this column
11736 will be left blank.
11740 In addition, the following information may be printed for each marker:
11744 User data passed to the tracing library by the marker call. In the
11745 UST backend, this is the format string passed as argument to the
11747 @item Static tracepoints probing the marker
11748 The list of static tracepoints attached to the marker.
11752 (@value{GDBP}) info static-tracepoint-markers
11753 Cnt ID Enb Address What
11754 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11755 Data: number1 %d number2 %d
11756 Probed by static tracepoints: #2
11757 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11763 @node Starting and Stopping Trace Experiments
11764 @subsection Starting and Stopping Trace Experiments
11767 @kindex tstart [ @var{notes} ]
11768 @cindex start a new trace experiment
11769 @cindex collected data discarded
11771 This command starts the trace experiment, and begins collecting data.
11772 It has the side effect of discarding all the data collected in the
11773 trace buffer during the previous trace experiment. If any arguments
11774 are supplied, they are taken as a note and stored with the trace
11775 experiment's state. The notes may be arbitrary text, and are
11776 especially useful with disconnected tracing in a multi-user context;
11777 the notes can explain what the trace is doing, supply user contact
11778 information, and so forth.
11780 @kindex tstop [ @var{notes} ]
11781 @cindex stop a running trace experiment
11783 This command stops the trace experiment. If any arguments are
11784 supplied, they are recorded with the experiment as a note. This is
11785 useful if you are stopping a trace started by someone else, for
11786 instance if the trace is interfering with the system's behavior and
11787 needs to be stopped quickly.
11789 @strong{Note}: a trace experiment and data collection may stop
11790 automatically if any tracepoint's passcount is reached
11791 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11794 @cindex status of trace data collection
11795 @cindex trace experiment, status of
11797 This command displays the status of the current trace data
11801 Here is an example of the commands we described so far:
11804 (@value{GDBP}) @b{trace gdb_c_test}
11805 (@value{GDBP}) @b{actions}
11806 Enter actions for tracepoint #1, one per line.
11807 > collect $regs,$locals,$args
11808 > while-stepping 11
11812 (@value{GDBP}) @b{tstart}
11813 [time passes @dots{}]
11814 (@value{GDBP}) @b{tstop}
11817 @anchor{disconnected tracing}
11818 @cindex disconnected tracing
11819 You can choose to continue running the trace experiment even if
11820 @value{GDBN} disconnects from the target, voluntarily or
11821 involuntarily. For commands such as @code{detach}, the debugger will
11822 ask what you want to do with the trace. But for unexpected
11823 terminations (@value{GDBN} crash, network outage), it would be
11824 unfortunate to lose hard-won trace data, so the variable
11825 @code{disconnected-tracing} lets you decide whether the trace should
11826 continue running without @value{GDBN}.
11829 @item set disconnected-tracing on
11830 @itemx set disconnected-tracing off
11831 @kindex set disconnected-tracing
11832 Choose whether a tracing run should continue to run if @value{GDBN}
11833 has disconnected from the target. Note that @code{detach} or
11834 @code{quit} will ask you directly what to do about a running trace no
11835 matter what this variable's setting, so the variable is mainly useful
11836 for handling unexpected situations, such as loss of the network.
11838 @item show disconnected-tracing
11839 @kindex show disconnected-tracing
11840 Show the current choice for disconnected tracing.
11844 When you reconnect to the target, the trace experiment may or may not
11845 still be running; it might have filled the trace buffer in the
11846 meantime, or stopped for one of the other reasons. If it is running,
11847 it will continue after reconnection.
11849 Upon reconnection, the target will upload information about the
11850 tracepoints in effect. @value{GDBN} will then compare that
11851 information to the set of tracepoints currently defined, and attempt
11852 to match them up, allowing for the possibility that the numbers may
11853 have changed due to creation and deletion in the meantime. If one of
11854 the target's tracepoints does not match any in @value{GDBN}, the
11855 debugger will create a new tracepoint, so that you have a number with
11856 which to specify that tracepoint. This matching-up process is
11857 necessarily heuristic, and it may result in useless tracepoints being
11858 created; you may simply delete them if they are of no use.
11860 @cindex circular trace buffer
11861 If your target agent supports a @dfn{circular trace buffer}, then you
11862 can run a trace experiment indefinitely without filling the trace
11863 buffer; when space runs out, the agent deletes already-collected trace
11864 frames, oldest first, until there is enough room to continue
11865 collecting. This is especially useful if your tracepoints are being
11866 hit too often, and your trace gets terminated prematurely because the
11867 buffer is full. To ask for a circular trace buffer, simply set
11868 @samp{circular-trace-buffer} to on. You can set this at any time,
11869 including during tracing; if the agent can do it, it will change
11870 buffer handling on the fly, otherwise it will not take effect until
11874 @item set circular-trace-buffer on
11875 @itemx set circular-trace-buffer off
11876 @kindex set circular-trace-buffer
11877 Choose whether a tracing run should use a linear or circular buffer
11878 for trace data. A linear buffer will not lose any trace data, but may
11879 fill up prematurely, while a circular buffer will discard old trace
11880 data, but it will have always room for the latest tracepoint hits.
11882 @item show circular-trace-buffer
11883 @kindex show circular-trace-buffer
11884 Show the current choice for the trace buffer. Note that this may not
11885 match the agent's current buffer handling, nor is it guaranteed to
11886 match the setting that might have been in effect during a past run,
11887 for instance if you are looking at frames from a trace file.
11892 @item set trace-buffer-size @var{n}
11893 @itemx set trace-buffer-size unlimited
11894 @kindex set trace-buffer-size
11895 Request that the target use a trace buffer of @var{n} bytes. Not all
11896 targets will honor the request; they may have a compiled-in size for
11897 the trace buffer, or some other limitation. Set to a value of
11898 @code{unlimited} or @code{-1} to let the target use whatever size it
11899 likes. This is also the default.
11901 @item show trace-buffer-size
11902 @kindex show trace-buffer-size
11903 Show the current requested size for the trace buffer. Note that this
11904 will only match the actual size if the target supports size-setting,
11905 and was able to handle the requested size. For instance, if the
11906 target can only change buffer size between runs, this variable will
11907 not reflect the change until the next run starts. Use @code{tstatus}
11908 to get a report of the actual buffer size.
11912 @item set trace-user @var{text}
11913 @kindex set trace-user
11915 @item show trace-user
11916 @kindex show trace-user
11918 @item set trace-notes @var{text}
11919 @kindex set trace-notes
11920 Set the trace run's notes.
11922 @item show trace-notes
11923 @kindex show trace-notes
11924 Show the trace run's notes.
11926 @item set trace-stop-notes @var{text}
11927 @kindex set trace-stop-notes
11928 Set the trace run's stop notes. The handling of the note is as for
11929 @code{tstop} arguments; the set command is convenient way to fix a
11930 stop note that is mistaken or incomplete.
11932 @item show trace-stop-notes
11933 @kindex show trace-stop-notes
11934 Show the trace run's stop notes.
11938 @node Tracepoint Restrictions
11939 @subsection Tracepoint Restrictions
11941 @cindex tracepoint restrictions
11942 There are a number of restrictions on the use of tracepoints. As
11943 described above, tracepoint data gathering occurs on the target
11944 without interaction from @value{GDBN}. Thus the full capabilities of
11945 the debugger are not available during data gathering, and then at data
11946 examination time, you will be limited by only having what was
11947 collected. The following items describe some common problems, but it
11948 is not exhaustive, and you may run into additional difficulties not
11954 Tracepoint expressions are intended to gather objects (lvalues). Thus
11955 the full flexibility of GDB's expression evaluator is not available.
11956 You cannot call functions, cast objects to aggregate types, access
11957 convenience variables or modify values (except by assignment to trace
11958 state variables). Some language features may implicitly call
11959 functions (for instance Objective-C fields with accessors), and therefore
11960 cannot be collected either.
11963 Collection of local variables, either individually or in bulk with
11964 @code{$locals} or @code{$args}, during @code{while-stepping} may
11965 behave erratically. The stepping action may enter a new scope (for
11966 instance by stepping into a function), or the location of the variable
11967 may change (for instance it is loaded into a register). The
11968 tracepoint data recorded uses the location information for the
11969 variables that is correct for the tracepoint location. When the
11970 tracepoint is created, it is not possible, in general, to determine
11971 where the steps of a @code{while-stepping} sequence will advance the
11972 program---particularly if a conditional branch is stepped.
11975 Collection of an incompletely-initialized or partially-destroyed object
11976 may result in something that @value{GDBN} cannot display, or displays
11977 in a misleading way.
11980 When @value{GDBN} displays a pointer to character it automatically
11981 dereferences the pointer to also display characters of the string
11982 being pointed to. However, collecting the pointer during tracing does
11983 not automatically collect the string. You need to explicitly
11984 dereference the pointer and provide size information if you want to
11985 collect not only the pointer, but the memory pointed to. For example,
11986 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11990 It is not possible to collect a complete stack backtrace at a
11991 tracepoint. Instead, you may collect the registers and a few hundred
11992 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11993 (adjust to use the name of the actual stack pointer register on your
11994 target architecture, and the amount of stack you wish to capture).
11995 Then the @code{backtrace} command will show a partial backtrace when
11996 using a trace frame. The number of stack frames that can be examined
11997 depends on the sizes of the frames in the collected stack. Note that
11998 if you ask for a block so large that it goes past the bottom of the
11999 stack, the target agent may report an error trying to read from an
12003 If you do not collect registers at a tracepoint, @value{GDBN} can
12004 infer that the value of @code{$pc} must be the same as the address of
12005 the tracepoint and use that when you are looking at a trace frame
12006 for that tracepoint. However, this cannot work if the tracepoint has
12007 multiple locations (for instance if it was set in a function that was
12008 inlined), or if it has a @code{while-stepping} loop. In those cases
12009 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12014 @node Analyze Collected Data
12015 @section Using the Collected Data
12017 After the tracepoint experiment ends, you use @value{GDBN} commands
12018 for examining the trace data. The basic idea is that each tracepoint
12019 collects a trace @dfn{snapshot} every time it is hit and another
12020 snapshot every time it single-steps. All these snapshots are
12021 consecutively numbered from zero and go into a buffer, and you can
12022 examine them later. The way you examine them is to @dfn{focus} on a
12023 specific trace snapshot. When the remote stub is focused on a trace
12024 snapshot, it will respond to all @value{GDBN} requests for memory and
12025 registers by reading from the buffer which belongs to that snapshot,
12026 rather than from @emph{real} memory or registers of the program being
12027 debugged. This means that @strong{all} @value{GDBN} commands
12028 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12029 behave as if we were currently debugging the program state as it was
12030 when the tracepoint occurred. Any requests for data that are not in
12031 the buffer will fail.
12034 * tfind:: How to select a trace snapshot
12035 * tdump:: How to display all data for a snapshot
12036 * save tracepoints:: How to save tracepoints for a future run
12040 @subsection @code{tfind @var{n}}
12043 @cindex select trace snapshot
12044 @cindex find trace snapshot
12045 The basic command for selecting a trace snapshot from the buffer is
12046 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12047 counting from zero. If no argument @var{n} is given, the next
12048 snapshot is selected.
12050 Here are the various forms of using the @code{tfind} command.
12054 Find the first snapshot in the buffer. This is a synonym for
12055 @code{tfind 0} (since 0 is the number of the first snapshot).
12058 Stop debugging trace snapshots, resume @emph{live} debugging.
12061 Same as @samp{tfind none}.
12064 No argument means find the next trace snapshot.
12067 Find the previous trace snapshot before the current one. This permits
12068 retracing earlier steps.
12070 @item tfind tracepoint @var{num}
12071 Find the next snapshot associated with tracepoint @var{num}. Search
12072 proceeds forward from the last examined trace snapshot. If no
12073 argument @var{num} is given, it means find the next snapshot collected
12074 for the same tracepoint as the current snapshot.
12076 @item tfind pc @var{addr}
12077 Find the next snapshot associated with the value @var{addr} of the
12078 program counter. Search proceeds forward from the last examined trace
12079 snapshot. If no argument @var{addr} is given, it means find the next
12080 snapshot with the same value of PC as the current snapshot.
12082 @item tfind outside @var{addr1}, @var{addr2}
12083 Find the next snapshot whose PC is outside the given range of
12084 addresses (exclusive).
12086 @item tfind range @var{addr1}, @var{addr2}
12087 Find the next snapshot whose PC is between @var{addr1} and
12088 @var{addr2} (inclusive).
12090 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12091 Find the next snapshot associated with the source line @var{n}. If
12092 the optional argument @var{file} is given, refer to line @var{n} in
12093 that source file. Search proceeds forward from the last examined
12094 trace snapshot. If no argument @var{n} is given, it means find the
12095 next line other than the one currently being examined; thus saying
12096 @code{tfind line} repeatedly can appear to have the same effect as
12097 stepping from line to line in a @emph{live} debugging session.
12100 The default arguments for the @code{tfind} commands are specifically
12101 designed to make it easy to scan through the trace buffer. For
12102 instance, @code{tfind} with no argument selects the next trace
12103 snapshot, and @code{tfind -} with no argument selects the previous
12104 trace snapshot. So, by giving one @code{tfind} command, and then
12105 simply hitting @key{RET} repeatedly you can examine all the trace
12106 snapshots in order. Or, by saying @code{tfind -} and then hitting
12107 @key{RET} repeatedly you can examine the snapshots in reverse order.
12108 The @code{tfind line} command with no argument selects the snapshot
12109 for the next source line executed. The @code{tfind pc} command with
12110 no argument selects the next snapshot with the same program counter
12111 (PC) as the current frame. The @code{tfind tracepoint} command with
12112 no argument selects the next trace snapshot collected by the same
12113 tracepoint as the current one.
12115 In addition to letting you scan through the trace buffer manually,
12116 these commands make it easy to construct @value{GDBN} scripts that
12117 scan through the trace buffer and print out whatever collected data
12118 you are interested in. Thus, if we want to examine the PC, FP, and SP
12119 registers from each trace frame in the buffer, we can say this:
12122 (@value{GDBP}) @b{tfind start}
12123 (@value{GDBP}) @b{while ($trace_frame != -1)}
12124 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12125 $trace_frame, $pc, $sp, $fp
12129 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12130 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12131 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12132 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12133 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12134 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12135 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12136 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12137 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12138 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12139 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12142 Or, if we want to examine the variable @code{X} at each source line in
12146 (@value{GDBP}) @b{tfind start}
12147 (@value{GDBP}) @b{while ($trace_frame != -1)}
12148 > printf "Frame %d, X == %d\n", $trace_frame, X
12158 @subsection @code{tdump}
12160 @cindex dump all data collected at tracepoint
12161 @cindex tracepoint data, display
12163 This command takes no arguments. It prints all the data collected at
12164 the current trace snapshot.
12167 (@value{GDBP}) @b{trace 444}
12168 (@value{GDBP}) @b{actions}
12169 Enter actions for tracepoint #2, one per line:
12170 > collect $regs, $locals, $args, gdb_long_test
12173 (@value{GDBP}) @b{tstart}
12175 (@value{GDBP}) @b{tfind line 444}
12176 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12178 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12180 (@value{GDBP}) @b{tdump}
12181 Data collected at tracepoint 2, trace frame 1:
12182 d0 0xc4aa0085 -995491707
12186 d4 0x71aea3d 119204413
12189 d7 0x380035 3670069
12190 a0 0x19e24a 1696330
12191 a1 0x3000668 50333288
12193 a3 0x322000 3284992
12194 a4 0x3000698 50333336
12195 a5 0x1ad3cc 1758156
12196 fp 0x30bf3c 0x30bf3c
12197 sp 0x30bf34 0x30bf34
12199 pc 0x20b2c8 0x20b2c8
12203 p = 0x20e5b4 "gdb-test"
12210 gdb_long_test = 17 '\021'
12215 @code{tdump} works by scanning the tracepoint's current collection
12216 actions and printing the value of each expression listed. So
12217 @code{tdump} can fail, if after a run, you change the tracepoint's
12218 actions to mention variables that were not collected during the run.
12220 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12221 uses the collected value of @code{$pc} to distinguish between trace
12222 frames that were collected at the tracepoint hit, and frames that were
12223 collected while stepping. This allows it to correctly choose whether
12224 to display the basic list of collections, or the collections from the
12225 body of the while-stepping loop. However, if @code{$pc} was not collected,
12226 then @code{tdump} will always attempt to dump using the basic collection
12227 list, and may fail if a while-stepping frame does not include all the
12228 same data that is collected at the tracepoint hit.
12229 @c This is getting pretty arcane, example would be good.
12231 @node save tracepoints
12232 @subsection @code{save tracepoints @var{filename}}
12233 @kindex save tracepoints
12234 @kindex save-tracepoints
12235 @cindex save tracepoints for future sessions
12237 This command saves all current tracepoint definitions together with
12238 their actions and passcounts, into a file @file{@var{filename}}
12239 suitable for use in a later debugging session. To read the saved
12240 tracepoint definitions, use the @code{source} command (@pxref{Command
12241 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12242 alias for @w{@code{save tracepoints}}
12244 @node Tracepoint Variables
12245 @section Convenience Variables for Tracepoints
12246 @cindex tracepoint variables
12247 @cindex convenience variables for tracepoints
12250 @vindex $trace_frame
12251 @item (int) $trace_frame
12252 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12253 snapshot is selected.
12255 @vindex $tracepoint
12256 @item (int) $tracepoint
12257 The tracepoint for the current trace snapshot.
12259 @vindex $trace_line
12260 @item (int) $trace_line
12261 The line number for the current trace snapshot.
12263 @vindex $trace_file
12264 @item (char []) $trace_file
12265 The source file for the current trace snapshot.
12267 @vindex $trace_func
12268 @item (char []) $trace_func
12269 The name of the function containing @code{$tracepoint}.
12272 Note: @code{$trace_file} is not suitable for use in @code{printf},
12273 use @code{output} instead.
12275 Here's a simple example of using these convenience variables for
12276 stepping through all the trace snapshots and printing some of their
12277 data. Note that these are not the same as trace state variables,
12278 which are managed by the target.
12281 (@value{GDBP}) @b{tfind start}
12283 (@value{GDBP}) @b{while $trace_frame != -1}
12284 > output $trace_file
12285 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12291 @section Using Trace Files
12292 @cindex trace files
12294 In some situations, the target running a trace experiment may no
12295 longer be available; perhaps it crashed, or the hardware was needed
12296 for a different activity. To handle these cases, you can arrange to
12297 dump the trace data into a file, and later use that file as a source
12298 of trace data, via the @code{target tfile} command.
12303 @item tsave [ -r ] @var{filename}
12304 @itemx tsave [-ctf] @var{dirname}
12305 Save the trace data to @var{filename}. By default, this command
12306 assumes that @var{filename} refers to the host filesystem, so if
12307 necessary @value{GDBN} will copy raw trace data up from the target and
12308 then save it. If the target supports it, you can also supply the
12309 optional argument @code{-r} (``remote'') to direct the target to save
12310 the data directly into @var{filename} in its own filesystem, which may be
12311 more efficient if the trace buffer is very large. (Note, however, that
12312 @code{target tfile} can only read from files accessible to the host.)
12313 By default, this command will save trace frame in tfile format.
12314 You can supply the optional argument @code{-ctf} to save date in CTF
12315 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12316 that can be shared by multiple debugging and tracing tools. Please go to
12317 @indicateurl{http://www.efficios.com/ctf} to get more information.
12319 @kindex target tfile
12323 @item target tfile @var{filename}
12324 @itemx target ctf @var{dirname}
12325 Use the file named @var{filename} or directory named @var{dirname} as
12326 a source of trace data. Commands that examine data work as they do with
12327 a live target, but it is not possible to run any new trace experiments.
12328 @code{tstatus} will report the state of the trace run at the moment
12329 the data was saved, as well as the current trace frame you are examining.
12330 @var{filename} or @var{dirname} must be on a filesystem accessible to
12334 (@value{GDBP}) target ctf ctf.ctf
12335 (@value{GDBP}) tfind
12336 Found trace frame 0, tracepoint 2
12337 39 ++a; /* set tracepoint 1 here */
12338 (@value{GDBP}) tdump
12339 Data collected at tracepoint 2, trace frame 0:
12343 c = @{"123", "456", "789", "123", "456", "789"@}
12344 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12352 @chapter Debugging Programs That Use Overlays
12355 If your program is too large to fit completely in your target system's
12356 memory, you can sometimes use @dfn{overlays} to work around this
12357 problem. @value{GDBN} provides some support for debugging programs that
12361 * How Overlays Work:: A general explanation of overlays.
12362 * Overlay Commands:: Managing overlays in @value{GDBN}.
12363 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12364 mapped by asking the inferior.
12365 * Overlay Sample Program:: A sample program using overlays.
12368 @node How Overlays Work
12369 @section How Overlays Work
12370 @cindex mapped overlays
12371 @cindex unmapped overlays
12372 @cindex load address, overlay's
12373 @cindex mapped address
12374 @cindex overlay area
12376 Suppose you have a computer whose instruction address space is only 64
12377 kilobytes long, but which has much more memory which can be accessed by
12378 other means: special instructions, segment registers, or memory
12379 management hardware, for example. Suppose further that you want to
12380 adapt a program which is larger than 64 kilobytes to run on this system.
12382 One solution is to identify modules of your program which are relatively
12383 independent, and need not call each other directly; call these modules
12384 @dfn{overlays}. Separate the overlays from the main program, and place
12385 their machine code in the larger memory. Place your main program in
12386 instruction memory, but leave at least enough space there to hold the
12387 largest overlay as well.
12389 Now, to call a function located in an overlay, you must first copy that
12390 overlay's machine code from the large memory into the space set aside
12391 for it in the instruction memory, and then jump to its entry point
12394 @c NB: In the below the mapped area's size is greater or equal to the
12395 @c size of all overlays. This is intentional to remind the developer
12396 @c that overlays don't necessarily need to be the same size.
12400 Data Instruction Larger
12401 Address Space Address Space Address Space
12402 +-----------+ +-----------+ +-----------+
12404 +-----------+ +-----------+ +-----------+<-- overlay 1
12405 | program | | main | .----| overlay 1 | load address
12406 | variables | | program | | +-----------+
12407 | and heap | | | | | |
12408 +-----------+ | | | +-----------+<-- overlay 2
12409 | | +-----------+ | | | load address
12410 +-----------+ | | | .-| overlay 2 |
12412 mapped --->+-----------+ | | +-----------+
12413 address | | | | | |
12414 | overlay | <-' | | |
12415 | area | <---' +-----------+<-- overlay 3
12416 | | <---. | | load address
12417 +-----------+ `--| overlay 3 |
12424 @anchor{A code overlay}A code overlay
12428 The diagram (@pxref{A code overlay}) shows a system with separate data
12429 and instruction address spaces. To map an overlay, the program copies
12430 its code from the larger address space to the instruction address space.
12431 Since the overlays shown here all use the same mapped address, only one
12432 may be mapped at a time. For a system with a single address space for
12433 data and instructions, the diagram would be similar, except that the
12434 program variables and heap would share an address space with the main
12435 program and the overlay area.
12437 An overlay loaded into instruction memory and ready for use is called a
12438 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12439 instruction memory. An overlay not present (or only partially present)
12440 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12441 is its address in the larger memory. The mapped address is also called
12442 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12443 called the @dfn{load memory address}, or @dfn{LMA}.
12445 Unfortunately, overlays are not a completely transparent way to adapt a
12446 program to limited instruction memory. They introduce a new set of
12447 global constraints you must keep in mind as you design your program:
12452 Before calling or returning to a function in an overlay, your program
12453 must make sure that overlay is actually mapped. Otherwise, the call or
12454 return will transfer control to the right address, but in the wrong
12455 overlay, and your program will probably crash.
12458 If the process of mapping an overlay is expensive on your system, you
12459 will need to choose your overlays carefully to minimize their effect on
12460 your program's performance.
12463 The executable file you load onto your system must contain each
12464 overlay's instructions, appearing at the overlay's load address, not its
12465 mapped address. However, each overlay's instructions must be relocated
12466 and its symbols defined as if the overlay were at its mapped address.
12467 You can use GNU linker scripts to specify different load and relocation
12468 addresses for pieces of your program; see @ref{Overlay Description,,,
12469 ld.info, Using ld: the GNU linker}.
12472 The procedure for loading executable files onto your system must be able
12473 to load their contents into the larger address space as well as the
12474 instruction and data spaces.
12478 The overlay system described above is rather simple, and could be
12479 improved in many ways:
12484 If your system has suitable bank switch registers or memory management
12485 hardware, you could use those facilities to make an overlay's load area
12486 contents simply appear at their mapped address in instruction space.
12487 This would probably be faster than copying the overlay to its mapped
12488 area in the usual way.
12491 If your overlays are small enough, you could set aside more than one
12492 overlay area, and have more than one overlay mapped at a time.
12495 You can use overlays to manage data, as well as instructions. In
12496 general, data overlays are even less transparent to your design than
12497 code overlays: whereas code overlays only require care when you call or
12498 return to functions, data overlays require care every time you access
12499 the data. Also, if you change the contents of a data overlay, you
12500 must copy its contents back out to its load address before you can copy a
12501 different data overlay into the same mapped area.
12506 @node Overlay Commands
12507 @section Overlay Commands
12509 To use @value{GDBN}'s overlay support, each overlay in your program must
12510 correspond to a separate section of the executable file. The section's
12511 virtual memory address and load memory address must be the overlay's
12512 mapped and load addresses. Identifying overlays with sections allows
12513 @value{GDBN} to determine the appropriate address of a function or
12514 variable, depending on whether the overlay is mapped or not.
12516 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12517 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12522 Disable @value{GDBN}'s overlay support. When overlay support is
12523 disabled, @value{GDBN} assumes that all functions and variables are
12524 always present at their mapped addresses. By default, @value{GDBN}'s
12525 overlay support is disabled.
12527 @item overlay manual
12528 @cindex manual overlay debugging
12529 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12530 relies on you to tell it which overlays are mapped, and which are not,
12531 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12532 commands described below.
12534 @item overlay map-overlay @var{overlay}
12535 @itemx overlay map @var{overlay}
12536 @cindex map an overlay
12537 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12538 be the name of the object file section containing the overlay. When an
12539 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12540 functions and variables at their mapped addresses. @value{GDBN} assumes
12541 that any other overlays whose mapped ranges overlap that of
12542 @var{overlay} are now unmapped.
12544 @item overlay unmap-overlay @var{overlay}
12545 @itemx overlay unmap @var{overlay}
12546 @cindex unmap an overlay
12547 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12548 must be the name of the object file section containing the overlay.
12549 When an overlay is unmapped, @value{GDBN} assumes it can find the
12550 overlay's functions and variables at their load addresses.
12553 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12554 consults a data structure the overlay manager maintains in the inferior
12555 to see which overlays are mapped. For details, see @ref{Automatic
12556 Overlay Debugging}.
12558 @item overlay load-target
12559 @itemx overlay load
12560 @cindex reloading the overlay table
12561 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12562 re-reads the table @value{GDBN} automatically each time the inferior
12563 stops, so this command should only be necessary if you have changed the
12564 overlay mapping yourself using @value{GDBN}. This command is only
12565 useful when using automatic overlay debugging.
12567 @item overlay list-overlays
12568 @itemx overlay list
12569 @cindex listing mapped overlays
12570 Display a list of the overlays currently mapped, along with their mapped
12571 addresses, load addresses, and sizes.
12575 Normally, when @value{GDBN} prints a code address, it includes the name
12576 of the function the address falls in:
12579 (@value{GDBP}) print main
12580 $3 = @{int ()@} 0x11a0 <main>
12583 When overlay debugging is enabled, @value{GDBN} recognizes code in
12584 unmapped overlays, and prints the names of unmapped functions with
12585 asterisks around them. For example, if @code{foo} is a function in an
12586 unmapped overlay, @value{GDBN} prints it this way:
12589 (@value{GDBP}) overlay list
12590 No sections are mapped.
12591 (@value{GDBP}) print foo
12592 $5 = @{int (int)@} 0x100000 <*foo*>
12595 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12599 (@value{GDBP}) overlay list
12600 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12601 mapped at 0x1016 - 0x104a
12602 (@value{GDBP}) print foo
12603 $6 = @{int (int)@} 0x1016 <foo>
12606 When overlay debugging is enabled, @value{GDBN} can find the correct
12607 address for functions and variables in an overlay, whether or not the
12608 overlay is mapped. This allows most @value{GDBN} commands, like
12609 @code{break} and @code{disassemble}, to work normally, even on unmapped
12610 code. However, @value{GDBN}'s breakpoint support has some limitations:
12614 @cindex breakpoints in overlays
12615 @cindex overlays, setting breakpoints in
12616 You can set breakpoints in functions in unmapped overlays, as long as
12617 @value{GDBN} can write to the overlay at its load address.
12619 @value{GDBN} can not set hardware or simulator-based breakpoints in
12620 unmapped overlays. However, if you set a breakpoint at the end of your
12621 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12622 you are using manual overlay management), @value{GDBN} will re-set its
12623 breakpoints properly.
12627 @node Automatic Overlay Debugging
12628 @section Automatic Overlay Debugging
12629 @cindex automatic overlay debugging
12631 @value{GDBN} can automatically track which overlays are mapped and which
12632 are not, given some simple co-operation from the overlay manager in the
12633 inferior. If you enable automatic overlay debugging with the
12634 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12635 looks in the inferior's memory for certain variables describing the
12636 current state of the overlays.
12638 Here are the variables your overlay manager must define to support
12639 @value{GDBN}'s automatic overlay debugging:
12643 @item @code{_ovly_table}:
12644 This variable must be an array of the following structures:
12649 /* The overlay's mapped address. */
12652 /* The size of the overlay, in bytes. */
12653 unsigned long size;
12655 /* The overlay's load address. */
12658 /* Non-zero if the overlay is currently mapped;
12660 unsigned long mapped;
12664 @item @code{_novlys}:
12665 This variable must be a four-byte signed integer, holding the total
12666 number of elements in @code{_ovly_table}.
12670 To decide whether a particular overlay is mapped or not, @value{GDBN}
12671 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12672 @code{lma} members equal the VMA and LMA of the overlay's section in the
12673 executable file. When @value{GDBN} finds a matching entry, it consults
12674 the entry's @code{mapped} member to determine whether the overlay is
12677 In addition, your overlay manager may define a function called
12678 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12679 will silently set a breakpoint there. If the overlay manager then
12680 calls this function whenever it has changed the overlay table, this
12681 will enable @value{GDBN} to accurately keep track of which overlays
12682 are in program memory, and update any breakpoints that may be set
12683 in overlays. This will allow breakpoints to work even if the
12684 overlays are kept in ROM or other non-writable memory while they
12685 are not being executed.
12687 @node Overlay Sample Program
12688 @section Overlay Sample Program
12689 @cindex overlay example program
12691 When linking a program which uses overlays, you must place the overlays
12692 at their load addresses, while relocating them to run at their mapped
12693 addresses. To do this, you must write a linker script (@pxref{Overlay
12694 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12695 since linker scripts are specific to a particular host system, target
12696 architecture, and target memory layout, this manual cannot provide
12697 portable sample code demonstrating @value{GDBN}'s overlay support.
12699 However, the @value{GDBN} source distribution does contain an overlaid
12700 program, with linker scripts for a few systems, as part of its test
12701 suite. The program consists of the following files from
12702 @file{gdb/testsuite/gdb.base}:
12706 The main program file.
12708 A simple overlay manager, used by @file{overlays.c}.
12713 Overlay modules, loaded and used by @file{overlays.c}.
12716 Linker scripts for linking the test program on the @code{d10v-elf}
12717 and @code{m32r-elf} targets.
12720 You can build the test program using the @code{d10v-elf} GCC
12721 cross-compiler like this:
12724 $ d10v-elf-gcc -g -c overlays.c
12725 $ d10v-elf-gcc -g -c ovlymgr.c
12726 $ d10v-elf-gcc -g -c foo.c
12727 $ d10v-elf-gcc -g -c bar.c
12728 $ d10v-elf-gcc -g -c baz.c
12729 $ d10v-elf-gcc -g -c grbx.c
12730 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12731 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12734 The build process is identical for any other architecture, except that
12735 you must substitute the appropriate compiler and linker script for the
12736 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12740 @chapter Using @value{GDBN} with Different Languages
12743 Although programming languages generally have common aspects, they are
12744 rarely expressed in the same manner. For instance, in ANSI C,
12745 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12746 Modula-2, it is accomplished by @code{p^}. Values can also be
12747 represented (and displayed) differently. Hex numbers in C appear as
12748 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12750 @cindex working language
12751 Language-specific information is built into @value{GDBN} for some languages,
12752 allowing you to express operations like the above in your program's
12753 native language, and allowing @value{GDBN} to output values in a manner
12754 consistent with the syntax of your program's native language. The
12755 language you use to build expressions is called the @dfn{working
12759 * Setting:: Switching between source languages
12760 * Show:: Displaying the language
12761 * Checks:: Type and range checks
12762 * Supported Languages:: Supported languages
12763 * Unsupported Languages:: Unsupported languages
12767 @section Switching Between Source Languages
12769 There are two ways to control the working language---either have @value{GDBN}
12770 set it automatically, or select it manually yourself. You can use the
12771 @code{set language} command for either purpose. On startup, @value{GDBN}
12772 defaults to setting the language automatically. The working language is
12773 used to determine how expressions you type are interpreted, how values
12776 In addition to the working language, every source file that
12777 @value{GDBN} knows about has its own working language. For some object
12778 file formats, the compiler might indicate which language a particular
12779 source file is in. However, most of the time @value{GDBN} infers the
12780 language from the name of the file. The language of a source file
12781 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12782 show each frame appropriately for its own language. There is no way to
12783 set the language of a source file from within @value{GDBN}, but you can
12784 set the language associated with a filename extension. @xref{Show, ,
12785 Displaying the Language}.
12787 This is most commonly a problem when you use a program, such
12788 as @code{cfront} or @code{f2c}, that generates C but is written in
12789 another language. In that case, make the
12790 program use @code{#line} directives in its C output; that way
12791 @value{GDBN} will know the correct language of the source code of the original
12792 program, and will display that source code, not the generated C code.
12795 * Filenames:: Filename extensions and languages.
12796 * Manually:: Setting the working language manually
12797 * Automatically:: Having @value{GDBN} infer the source language
12801 @subsection List of Filename Extensions and Languages
12803 If a source file name ends in one of the following extensions, then
12804 @value{GDBN} infers that its language is the one indicated.
12822 C@t{++} source file
12828 Objective-C source file
12832 Fortran source file
12835 Modula-2 source file
12839 Assembler source file. This actually behaves almost like C, but
12840 @value{GDBN} does not skip over function prologues when stepping.
12843 In addition, you may set the language associated with a filename
12844 extension. @xref{Show, , Displaying the Language}.
12847 @subsection Setting the Working Language
12849 If you allow @value{GDBN} to set the language automatically,
12850 expressions are interpreted the same way in your debugging session and
12853 @kindex set language
12854 If you wish, you may set the language manually. To do this, issue the
12855 command @samp{set language @var{lang}}, where @var{lang} is the name of
12856 a language, such as
12857 @code{c} or @code{modula-2}.
12858 For a list of the supported languages, type @samp{set language}.
12860 Setting the language manually prevents @value{GDBN} from updating the working
12861 language automatically. This can lead to confusion if you try
12862 to debug a program when the working language is not the same as the
12863 source language, when an expression is acceptable to both
12864 languages---but means different things. For instance, if the current
12865 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12873 might not have the effect you intended. In C, this means to add
12874 @code{b} and @code{c} and place the result in @code{a}. The result
12875 printed would be the value of @code{a}. In Modula-2, this means to compare
12876 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12878 @node Automatically
12879 @subsection Having @value{GDBN} Infer the Source Language
12881 To have @value{GDBN} set the working language automatically, use
12882 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12883 then infers the working language. That is, when your program stops in a
12884 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12885 working language to the language recorded for the function in that
12886 frame. If the language for a frame is unknown (that is, if the function
12887 or block corresponding to the frame was defined in a source file that
12888 does not have a recognized extension), the current working language is
12889 not changed, and @value{GDBN} issues a warning.
12891 This may not seem necessary for most programs, which are written
12892 entirely in one source language. However, program modules and libraries
12893 written in one source language can be used by a main program written in
12894 a different source language. Using @samp{set language auto} in this
12895 case frees you from having to set the working language manually.
12898 @section Displaying the Language
12900 The following commands help you find out which language is the
12901 working language, and also what language source files were written in.
12904 @item show language
12905 @kindex show language
12906 Display the current working language. This is the
12907 language you can use with commands such as @code{print} to
12908 build and compute expressions that may involve variables in your program.
12911 @kindex info frame@r{, show the source language}
12912 Display the source language for this frame. This language becomes the
12913 working language if you use an identifier from this frame.
12914 @xref{Frame Info, ,Information about a Frame}, to identify the other
12915 information listed here.
12918 @kindex info source@r{, show the source language}
12919 Display the source language of this source file.
12920 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12921 information listed here.
12924 In unusual circumstances, you may have source files with extensions
12925 not in the standard list. You can then set the extension associated
12926 with a language explicitly:
12929 @item set extension-language @var{ext} @var{language}
12930 @kindex set extension-language
12931 Tell @value{GDBN} that source files with extension @var{ext} are to be
12932 assumed as written in the source language @var{language}.
12934 @item info extensions
12935 @kindex info extensions
12936 List all the filename extensions and the associated languages.
12940 @section Type and Range Checking
12942 Some languages are designed to guard you against making seemingly common
12943 errors through a series of compile- and run-time checks. These include
12944 checking the type of arguments to functions and operators and making
12945 sure mathematical overflows are caught at run time. Checks such as
12946 these help to ensure a program's correctness once it has been compiled
12947 by eliminating type mismatches and providing active checks for range
12948 errors when your program is running.
12950 By default @value{GDBN} checks for these errors according to the
12951 rules of the current source language. Although @value{GDBN} does not check
12952 the statements in your program, it can check expressions entered directly
12953 into @value{GDBN} for evaluation via the @code{print} command, for example.
12956 * Type Checking:: An overview of type checking
12957 * Range Checking:: An overview of range checking
12960 @cindex type checking
12961 @cindex checks, type
12962 @node Type Checking
12963 @subsection An Overview of Type Checking
12965 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12966 arguments to operators and functions have to be of the correct type,
12967 otherwise an error occurs. These checks prevent type mismatch
12968 errors from ever causing any run-time problems. For example,
12971 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12973 (@value{GDBP}) print obj.my_method (0)
12976 (@value{GDBP}) print obj.my_method (0x1234)
12977 Cannot resolve method klass::my_method to any overloaded instance
12980 The second example fails because in C@t{++} the integer constant
12981 @samp{0x1234} is not type-compatible with the pointer parameter type.
12983 For the expressions you use in @value{GDBN} commands, you can tell
12984 @value{GDBN} to not enforce strict type checking or
12985 to treat any mismatches as errors and abandon the expression;
12986 When type checking is disabled, @value{GDBN} successfully evaluates
12987 expressions like the second example above.
12989 Even if type checking is off, there may be other reasons
12990 related to type that prevent @value{GDBN} from evaluating an expression.
12991 For instance, @value{GDBN} does not know how to add an @code{int} and
12992 a @code{struct foo}. These particular type errors have nothing to do
12993 with the language in use and usually arise from expressions which make
12994 little sense to evaluate anyway.
12996 @value{GDBN} provides some additional commands for controlling type checking:
12998 @kindex set check type
12999 @kindex show check type
13001 @item set check type on
13002 @itemx set check type off
13003 Set strict type checking on or off. If any type mismatches occur in
13004 evaluating an expression while type checking is on, @value{GDBN} prints a
13005 message and aborts evaluation of the expression.
13007 @item show check type
13008 Show the current setting of type checking and whether @value{GDBN}
13009 is enforcing strict type checking rules.
13012 @cindex range checking
13013 @cindex checks, range
13014 @node Range Checking
13015 @subsection An Overview of Range Checking
13017 In some languages (such as Modula-2), it is an error to exceed the
13018 bounds of a type; this is enforced with run-time checks. Such range
13019 checking is meant to ensure program correctness by making sure
13020 computations do not overflow, or indices on an array element access do
13021 not exceed the bounds of the array.
13023 For expressions you use in @value{GDBN} commands, you can tell
13024 @value{GDBN} to treat range errors in one of three ways: ignore them,
13025 always treat them as errors and abandon the expression, or issue
13026 warnings but evaluate the expression anyway.
13028 A range error can result from numerical overflow, from exceeding an
13029 array index bound, or when you type a constant that is not a member
13030 of any type. Some languages, however, do not treat overflows as an
13031 error. In many implementations of C, mathematical overflow causes the
13032 result to ``wrap around'' to lower values---for example, if @var{m} is
13033 the largest integer value, and @var{s} is the smallest, then
13036 @var{m} + 1 @result{} @var{s}
13039 This, too, is specific to individual languages, and in some cases
13040 specific to individual compilers or machines. @xref{Supported Languages, ,
13041 Supported Languages}, for further details on specific languages.
13043 @value{GDBN} provides some additional commands for controlling the range checker:
13045 @kindex set check range
13046 @kindex show check range
13048 @item set check range auto
13049 Set range checking on or off based on the current working language.
13050 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13053 @item set check range on
13054 @itemx set check range off
13055 Set range checking on or off, overriding the default setting for the
13056 current working language. A warning is issued if the setting does not
13057 match the language default. If a range error occurs and range checking is on,
13058 then a message is printed and evaluation of the expression is aborted.
13060 @item set check range warn
13061 Output messages when the @value{GDBN} range checker detects a range error,
13062 but attempt to evaluate the expression anyway. Evaluating the
13063 expression may still be impossible for other reasons, such as accessing
13064 memory that the process does not own (a typical example from many Unix
13068 Show the current setting of the range checker, and whether or not it is
13069 being set automatically by @value{GDBN}.
13072 @node Supported Languages
13073 @section Supported Languages
13075 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13076 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13077 @c This is false ...
13078 Some @value{GDBN} features may be used in expressions regardless of the
13079 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13080 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13081 ,Expressions}) can be used with the constructs of any supported
13084 The following sections detail to what degree each source language is
13085 supported by @value{GDBN}. These sections are not meant to be language
13086 tutorials or references, but serve only as a reference guide to what the
13087 @value{GDBN} expression parser accepts, and what input and output
13088 formats should look like for different languages. There are many good
13089 books written on each of these languages; please look to these for a
13090 language reference or tutorial.
13093 * C:: C and C@t{++}
13096 * Objective-C:: Objective-C
13097 * OpenCL C:: OpenCL C
13098 * Fortran:: Fortran
13100 * Modula-2:: Modula-2
13105 @subsection C and C@t{++}
13107 @cindex C and C@t{++}
13108 @cindex expressions in C or C@t{++}
13110 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13111 to both languages. Whenever this is the case, we discuss those languages
13115 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13116 @cindex @sc{gnu} C@t{++}
13117 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13118 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13119 effectively, you must compile your C@t{++} programs with a supported
13120 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13121 compiler (@code{aCC}).
13124 * C Operators:: C and C@t{++} operators
13125 * C Constants:: C and C@t{++} constants
13126 * C Plus Plus Expressions:: C@t{++} expressions
13127 * C Defaults:: Default settings for C and C@t{++}
13128 * C Checks:: C and C@t{++} type and range checks
13129 * Debugging C:: @value{GDBN} and C
13130 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13131 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13135 @subsubsection C and C@t{++} Operators
13137 @cindex C and C@t{++} operators
13139 Operators must be defined on values of specific types. For instance,
13140 @code{+} is defined on numbers, but not on structures. Operators are
13141 often defined on groups of types.
13143 For the purposes of C and C@t{++}, the following definitions hold:
13148 @emph{Integral types} include @code{int} with any of its storage-class
13149 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13152 @emph{Floating-point types} include @code{float}, @code{double}, and
13153 @code{long double} (if supported by the target platform).
13156 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13159 @emph{Scalar types} include all of the above.
13164 The following operators are supported. They are listed here
13165 in order of increasing precedence:
13169 The comma or sequencing operator. Expressions in a comma-separated list
13170 are evaluated from left to right, with the result of the entire
13171 expression being the last expression evaluated.
13174 Assignment. The value of an assignment expression is the value
13175 assigned. Defined on scalar types.
13178 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13179 and translated to @w{@code{@var{a} = @var{a op b}}}.
13180 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13181 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13182 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13185 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13186 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13190 Logical @sc{or}. Defined on integral types.
13193 Logical @sc{and}. Defined on integral types.
13196 Bitwise @sc{or}. Defined on integral types.
13199 Bitwise exclusive-@sc{or}. Defined on integral types.
13202 Bitwise @sc{and}. Defined on integral types.
13205 Equality and inequality. Defined on scalar types. The value of these
13206 expressions is 0 for false and non-zero for true.
13208 @item <@r{, }>@r{, }<=@r{, }>=
13209 Less than, greater than, less than or equal, greater than or equal.
13210 Defined on scalar types. The value of these expressions is 0 for false
13211 and non-zero for true.
13214 left shift, and right shift. Defined on integral types.
13217 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13220 Addition and subtraction. Defined on integral types, floating-point types and
13223 @item *@r{, }/@r{, }%
13224 Multiplication, division, and modulus. Multiplication and division are
13225 defined on integral and floating-point types. Modulus is defined on
13229 Increment and decrement. When appearing before a variable, the
13230 operation is performed before the variable is used in an expression;
13231 when appearing after it, the variable's value is used before the
13232 operation takes place.
13235 Pointer dereferencing. Defined on pointer types. Same precedence as
13239 Address operator. Defined on variables. Same precedence as @code{++}.
13241 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13242 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13243 to examine the address
13244 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13248 Negative. Defined on integral and floating-point types. Same
13249 precedence as @code{++}.
13252 Logical negation. Defined on integral types. Same precedence as
13256 Bitwise complement operator. Defined on integral types. Same precedence as
13261 Structure member, and pointer-to-structure member. For convenience,
13262 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13263 pointer based on the stored type information.
13264 Defined on @code{struct} and @code{union} data.
13267 Dereferences of pointers to members.
13270 Array indexing. @code{@var{a}[@var{i}]} is defined as
13271 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13274 Function parameter list. Same precedence as @code{->}.
13277 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13278 and @code{class} types.
13281 Doubled colons also represent the @value{GDBN} scope operator
13282 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13286 If an operator is redefined in the user code, @value{GDBN} usually
13287 attempts to invoke the redefined version instead of using the operator's
13288 predefined meaning.
13291 @subsubsection C and C@t{++} Constants
13293 @cindex C and C@t{++} constants
13295 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13300 Integer constants are a sequence of digits. Octal constants are
13301 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13302 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13303 @samp{l}, specifying that the constant should be treated as a
13307 Floating point constants are a sequence of digits, followed by a decimal
13308 point, followed by a sequence of digits, and optionally followed by an
13309 exponent. An exponent is of the form:
13310 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13311 sequence of digits. The @samp{+} is optional for positive exponents.
13312 A floating-point constant may also end with a letter @samp{f} or
13313 @samp{F}, specifying that the constant should be treated as being of
13314 the @code{float} (as opposed to the default @code{double}) type; or with
13315 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13319 Enumerated constants consist of enumerated identifiers, or their
13320 integral equivalents.
13323 Character constants are a single character surrounded by single quotes
13324 (@code{'}), or a number---the ordinal value of the corresponding character
13325 (usually its @sc{ascii} value). Within quotes, the single character may
13326 be represented by a letter or by @dfn{escape sequences}, which are of
13327 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13328 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13329 @samp{@var{x}} is a predefined special character---for example,
13330 @samp{\n} for newline.
13332 Wide character constants can be written by prefixing a character
13333 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13334 form of @samp{x}. The target wide character set is used when
13335 computing the value of this constant (@pxref{Character Sets}).
13338 String constants are a sequence of character constants surrounded by
13339 double quotes (@code{"}). Any valid character constant (as described
13340 above) may appear. Double quotes within the string must be preceded by
13341 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13344 Wide string constants can be written by prefixing a string constant
13345 with @samp{L}, as in C. The target wide character set is used when
13346 computing the value of this constant (@pxref{Character Sets}).
13349 Pointer constants are an integral value. You can also write pointers
13350 to constants using the C operator @samp{&}.
13353 Array constants are comma-separated lists surrounded by braces @samp{@{}
13354 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13355 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13356 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13359 @node C Plus Plus Expressions
13360 @subsubsection C@t{++} Expressions
13362 @cindex expressions in C@t{++}
13363 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13365 @cindex debugging C@t{++} programs
13366 @cindex C@t{++} compilers
13367 @cindex debug formats and C@t{++}
13368 @cindex @value{NGCC} and C@t{++}
13370 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13371 the proper compiler and the proper debug format. Currently,
13372 @value{GDBN} works best when debugging C@t{++} code that is compiled
13373 with the most recent version of @value{NGCC} possible. The DWARF
13374 debugging format is preferred; @value{NGCC} defaults to this on most
13375 popular platforms. Other compilers and/or debug formats are likely to
13376 work badly or not at all when using @value{GDBN} to debug C@t{++}
13377 code. @xref{Compilation}.
13382 @cindex member functions
13384 Member function calls are allowed; you can use expressions like
13387 count = aml->GetOriginal(x, y)
13390 @vindex this@r{, inside C@t{++} member functions}
13391 @cindex namespace in C@t{++}
13393 While a member function is active (in the selected stack frame), your
13394 expressions have the same namespace available as the member function;
13395 that is, @value{GDBN} allows implicit references to the class instance
13396 pointer @code{this} following the same rules as C@t{++}. @code{using}
13397 declarations in the current scope are also respected by @value{GDBN}.
13399 @cindex call overloaded functions
13400 @cindex overloaded functions, calling
13401 @cindex type conversions in C@t{++}
13403 You can call overloaded functions; @value{GDBN} resolves the function
13404 call to the right definition, with some restrictions. @value{GDBN} does not
13405 perform overload resolution involving user-defined type conversions,
13406 calls to constructors, or instantiations of templates that do not exist
13407 in the program. It also cannot handle ellipsis argument lists or
13410 It does perform integral conversions and promotions, floating-point
13411 promotions, arithmetic conversions, pointer conversions, conversions of
13412 class objects to base classes, and standard conversions such as those of
13413 functions or arrays to pointers; it requires an exact match on the
13414 number of function arguments.
13416 Overload resolution is always performed, unless you have specified
13417 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13418 ,@value{GDBN} Features for C@t{++}}.
13420 You must specify @code{set overload-resolution off} in order to use an
13421 explicit function signature to call an overloaded function, as in
13423 p 'foo(char,int)'('x', 13)
13426 The @value{GDBN} command-completion facility can simplify this;
13427 see @ref{Completion, ,Command Completion}.
13429 @cindex reference declarations
13431 @value{GDBN} understands variables declared as C@t{++} references; you can use
13432 them in expressions just as you do in C@t{++} source---they are automatically
13435 In the parameter list shown when @value{GDBN} displays a frame, the values of
13436 reference variables are not displayed (unlike other variables); this
13437 avoids clutter, since references are often used for large structures.
13438 The @emph{address} of a reference variable is always shown, unless
13439 you have specified @samp{set print address off}.
13442 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13443 expressions can use it just as expressions in your program do. Since
13444 one scope may be defined in another, you can use @code{::} repeatedly if
13445 necessary, for example in an expression like
13446 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13447 resolving name scope by reference to source files, in both C and C@t{++}
13448 debugging (@pxref{Variables, ,Program Variables}).
13451 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13456 @subsubsection C and C@t{++} Defaults
13458 @cindex C and C@t{++} defaults
13460 If you allow @value{GDBN} to set range checking automatically, it
13461 defaults to @code{off} whenever the working language changes to
13462 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13463 selects the working language.
13465 If you allow @value{GDBN} to set the language automatically, it
13466 recognizes source files whose names end with @file{.c}, @file{.C}, or
13467 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13468 these files, it sets the working language to C or C@t{++}.
13469 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13470 for further details.
13473 @subsubsection C and C@t{++} Type and Range Checks
13475 @cindex C and C@t{++} checks
13477 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13478 checking is used. However, if you turn type checking off, @value{GDBN}
13479 will allow certain non-standard conversions, such as promoting integer
13480 constants to pointers.
13482 Range checking, if turned on, is done on mathematical operations. Array
13483 indices are not checked, since they are often used to index a pointer
13484 that is not itself an array.
13487 @subsubsection @value{GDBN} and C
13489 The @code{set print union} and @code{show print union} commands apply to
13490 the @code{union} type. When set to @samp{on}, any @code{union} that is
13491 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13492 appears as @samp{@{...@}}.
13494 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13495 with pointers and a memory allocation function. @xref{Expressions,
13498 @node Debugging C Plus Plus
13499 @subsubsection @value{GDBN} Features for C@t{++}
13501 @cindex commands for C@t{++}
13503 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13504 designed specifically for use with C@t{++}. Here is a summary:
13507 @cindex break in overloaded functions
13508 @item @r{breakpoint menus}
13509 When you want a breakpoint in a function whose name is overloaded,
13510 @value{GDBN} has the capability to display a menu of possible breakpoint
13511 locations to help you specify which function definition you want.
13512 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13514 @cindex overloading in C@t{++}
13515 @item rbreak @var{regex}
13516 Setting breakpoints using regular expressions is helpful for setting
13517 breakpoints on overloaded functions that are not members of any special
13519 @xref{Set Breaks, ,Setting Breakpoints}.
13521 @cindex C@t{++} exception handling
13523 @itemx catch rethrow
13525 Debug C@t{++} exception handling using these commands. @xref{Set
13526 Catchpoints, , Setting Catchpoints}.
13528 @cindex inheritance
13529 @item ptype @var{typename}
13530 Print inheritance relationships as well as other information for type
13532 @xref{Symbols, ,Examining the Symbol Table}.
13534 @item info vtbl @var{expression}.
13535 The @code{info vtbl} command can be used to display the virtual
13536 method tables of the object computed by @var{expression}. This shows
13537 one entry per virtual table; there may be multiple virtual tables when
13538 multiple inheritance is in use.
13540 @cindex C@t{++} symbol display
13541 @item set print demangle
13542 @itemx show print demangle
13543 @itemx set print asm-demangle
13544 @itemx show print asm-demangle
13545 Control whether C@t{++} symbols display in their source form, both when
13546 displaying code as C@t{++} source and when displaying disassemblies.
13547 @xref{Print Settings, ,Print Settings}.
13549 @item set print object
13550 @itemx show print object
13551 Choose whether to print derived (actual) or declared types of objects.
13552 @xref{Print Settings, ,Print Settings}.
13554 @item set print vtbl
13555 @itemx show print vtbl
13556 Control the format for printing virtual function tables.
13557 @xref{Print Settings, ,Print Settings}.
13558 (The @code{vtbl} commands do not work on programs compiled with the HP
13559 ANSI C@t{++} compiler (@code{aCC}).)
13561 @kindex set overload-resolution
13562 @cindex overloaded functions, overload resolution
13563 @item set overload-resolution on
13564 Enable overload resolution for C@t{++} expression evaluation. The default
13565 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13566 and searches for a function whose signature matches the argument types,
13567 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13568 Expressions, ,C@t{++} Expressions}, for details).
13569 If it cannot find a match, it emits a message.
13571 @item set overload-resolution off
13572 Disable overload resolution for C@t{++} expression evaluation. For
13573 overloaded functions that are not class member functions, @value{GDBN}
13574 chooses the first function of the specified name that it finds in the
13575 symbol table, whether or not its arguments are of the correct type. For
13576 overloaded functions that are class member functions, @value{GDBN}
13577 searches for a function whose signature @emph{exactly} matches the
13580 @kindex show overload-resolution
13581 @item show overload-resolution
13582 Show the current setting of overload resolution.
13584 @item @r{Overloaded symbol names}
13585 You can specify a particular definition of an overloaded symbol, using
13586 the same notation that is used to declare such symbols in C@t{++}: type
13587 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13588 also use the @value{GDBN} command-line word completion facilities to list the
13589 available choices, or to finish the type list for you.
13590 @xref{Completion,, Command Completion}, for details on how to do this.
13593 @node Decimal Floating Point
13594 @subsubsection Decimal Floating Point format
13595 @cindex decimal floating point format
13597 @value{GDBN} can examine, set and perform computations with numbers in
13598 decimal floating point format, which in the C language correspond to the
13599 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13600 specified by the extension to support decimal floating-point arithmetic.
13602 There are two encodings in use, depending on the architecture: BID (Binary
13603 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13604 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13607 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13608 to manipulate decimal floating point numbers, it is not possible to convert
13609 (using a cast, for example) integers wider than 32-bit to decimal float.
13611 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13612 point computations, error checking in decimal float operations ignores
13613 underflow, overflow and divide by zero exceptions.
13615 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13616 to inspect @code{_Decimal128} values stored in floating point registers.
13617 See @ref{PowerPC,,PowerPC} for more details.
13623 @value{GDBN} can be used to debug programs written in D and compiled with
13624 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13625 specific feature --- dynamic arrays.
13630 @cindex Go (programming language)
13631 @value{GDBN} can be used to debug programs written in Go and compiled with
13632 @file{gccgo} or @file{6g} compilers.
13634 Here is a summary of the Go-specific features and restrictions:
13637 @cindex current Go package
13638 @item The current Go package
13639 The name of the current package does not need to be specified when
13640 specifying global variables and functions.
13642 For example, given the program:
13646 var myglob = "Shall we?"
13652 When stopped inside @code{main} either of these work:
13656 (gdb) p main.myglob
13659 @cindex builtin Go types
13660 @item Builtin Go types
13661 The @code{string} type is recognized by @value{GDBN} and is printed
13664 @cindex builtin Go functions
13665 @item Builtin Go functions
13666 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13667 function and handles it internally.
13669 @cindex restrictions on Go expressions
13670 @item Restrictions on Go expressions
13671 All Go operators are supported except @code{&^}.
13672 The Go @code{_} ``blank identifier'' is not supported.
13673 Automatic dereferencing of pointers is not supported.
13677 @subsection Objective-C
13679 @cindex Objective-C
13680 This section provides information about some commands and command
13681 options that are useful for debugging Objective-C code. See also
13682 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13683 few more commands specific to Objective-C support.
13686 * Method Names in Commands::
13687 * The Print Command with Objective-C::
13690 @node Method Names in Commands
13691 @subsubsection Method Names in Commands
13693 The following commands have been extended to accept Objective-C method
13694 names as line specifications:
13696 @kindex clear@r{, and Objective-C}
13697 @kindex break@r{, and Objective-C}
13698 @kindex info line@r{, and Objective-C}
13699 @kindex jump@r{, and Objective-C}
13700 @kindex list@r{, and Objective-C}
13704 @item @code{info line}
13709 A fully qualified Objective-C method name is specified as
13712 -[@var{Class} @var{methodName}]
13715 where the minus sign is used to indicate an instance method and a
13716 plus sign (not shown) is used to indicate a class method. The class
13717 name @var{Class} and method name @var{methodName} are enclosed in
13718 brackets, similar to the way messages are specified in Objective-C
13719 source code. For example, to set a breakpoint at the @code{create}
13720 instance method of class @code{Fruit} in the program currently being
13724 break -[Fruit create]
13727 To list ten program lines around the @code{initialize} class method,
13731 list +[NSText initialize]
13734 In the current version of @value{GDBN}, the plus or minus sign is
13735 required. In future versions of @value{GDBN}, the plus or minus
13736 sign will be optional, but you can use it to narrow the search. It
13737 is also possible to specify just a method name:
13743 You must specify the complete method name, including any colons. If
13744 your program's source files contain more than one @code{create} method,
13745 you'll be presented with a numbered list of classes that implement that
13746 method. Indicate your choice by number, or type @samp{0} to exit if
13749 As another example, to clear a breakpoint established at the
13750 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13753 clear -[NSWindow makeKeyAndOrderFront:]
13756 @node The Print Command with Objective-C
13757 @subsubsection The Print Command With Objective-C
13758 @cindex Objective-C, print objects
13759 @kindex print-object
13760 @kindex po @r{(@code{print-object})}
13762 The print command has also been extended to accept methods. For example:
13765 print -[@var{object} hash]
13768 @cindex print an Objective-C object description
13769 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13771 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13772 and print the result. Also, an additional command has been added,
13773 @code{print-object} or @code{po} for short, which is meant to print
13774 the description of an object. However, this command may only work
13775 with certain Objective-C libraries that have a particular hook
13776 function, @code{_NSPrintForDebugger}, defined.
13779 @subsection OpenCL C
13782 This section provides information about @value{GDBN}s OpenCL C support.
13785 * OpenCL C Datatypes::
13786 * OpenCL C Expressions::
13787 * OpenCL C Operators::
13790 @node OpenCL C Datatypes
13791 @subsubsection OpenCL C Datatypes
13793 @cindex OpenCL C Datatypes
13794 @value{GDBN} supports the builtin scalar and vector datatypes specified
13795 by OpenCL 1.1. In addition the half- and double-precision floating point
13796 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13797 extensions are also known to @value{GDBN}.
13799 @node OpenCL C Expressions
13800 @subsubsection OpenCL C Expressions
13802 @cindex OpenCL C Expressions
13803 @value{GDBN} supports accesses to vector components including the access as
13804 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13805 supported by @value{GDBN} can be used as well.
13807 @node OpenCL C Operators
13808 @subsubsection OpenCL C Operators
13810 @cindex OpenCL C Operators
13811 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13815 @subsection Fortran
13816 @cindex Fortran-specific support in @value{GDBN}
13818 @value{GDBN} can be used to debug programs written in Fortran, but it
13819 currently supports only the features of Fortran 77 language.
13821 @cindex trailing underscore, in Fortran symbols
13822 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13823 among them) append an underscore to the names of variables and
13824 functions. When you debug programs compiled by those compilers, you
13825 will need to refer to variables and functions with a trailing
13829 * Fortran Operators:: Fortran operators and expressions
13830 * Fortran Defaults:: Default settings for Fortran
13831 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13834 @node Fortran Operators
13835 @subsubsection Fortran Operators and Expressions
13837 @cindex Fortran operators and expressions
13839 Operators must be defined on values of specific types. For instance,
13840 @code{+} is defined on numbers, but not on characters or other non-
13841 arithmetic types. Operators are often defined on groups of types.
13845 The exponentiation operator. It raises the first operand to the power
13849 The range operator. Normally used in the form of array(low:high) to
13850 represent a section of array.
13853 The access component operator. Normally used to access elements in derived
13854 types. Also suitable for unions. As unions aren't part of regular Fortran,
13855 this can only happen when accessing a register that uses a gdbarch-defined
13859 @node Fortran Defaults
13860 @subsubsection Fortran Defaults
13862 @cindex Fortran Defaults
13864 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13865 default uses case-insensitive matches for Fortran symbols. You can
13866 change that with the @samp{set case-insensitive} command, see
13867 @ref{Symbols}, for the details.
13869 @node Special Fortran Commands
13870 @subsubsection Special Fortran Commands
13872 @cindex Special Fortran commands
13874 @value{GDBN} has some commands to support Fortran-specific features,
13875 such as displaying common blocks.
13878 @cindex @code{COMMON} blocks, Fortran
13879 @kindex info common
13880 @item info common @r{[}@var{common-name}@r{]}
13881 This command prints the values contained in the Fortran @code{COMMON}
13882 block whose name is @var{common-name}. With no argument, the names of
13883 all @code{COMMON} blocks visible at the current program location are
13890 @cindex Pascal support in @value{GDBN}, limitations
13891 Debugging Pascal programs which use sets, subranges, file variables, or
13892 nested functions does not currently work. @value{GDBN} does not support
13893 entering expressions, printing values, or similar features using Pascal
13896 The Pascal-specific command @code{set print pascal_static-members}
13897 controls whether static members of Pascal objects are displayed.
13898 @xref{Print Settings, pascal_static-members}.
13901 @subsection Modula-2
13903 @cindex Modula-2, @value{GDBN} support
13905 The extensions made to @value{GDBN} to support Modula-2 only support
13906 output from the @sc{gnu} Modula-2 compiler (which is currently being
13907 developed). Other Modula-2 compilers are not currently supported, and
13908 attempting to debug executables produced by them is most likely
13909 to give an error as @value{GDBN} reads in the executable's symbol
13912 @cindex expressions in Modula-2
13914 * M2 Operators:: Built-in operators
13915 * Built-In Func/Proc:: Built-in functions and procedures
13916 * M2 Constants:: Modula-2 constants
13917 * M2 Types:: Modula-2 types
13918 * M2 Defaults:: Default settings for Modula-2
13919 * Deviations:: Deviations from standard Modula-2
13920 * M2 Checks:: Modula-2 type and range checks
13921 * M2 Scope:: The scope operators @code{::} and @code{.}
13922 * GDB/M2:: @value{GDBN} and Modula-2
13926 @subsubsection Operators
13927 @cindex Modula-2 operators
13929 Operators must be defined on values of specific types. For instance,
13930 @code{+} is defined on numbers, but not on structures. Operators are
13931 often defined on groups of types. For the purposes of Modula-2, the
13932 following definitions hold:
13937 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13941 @emph{Character types} consist of @code{CHAR} and its subranges.
13944 @emph{Floating-point types} consist of @code{REAL}.
13947 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13951 @emph{Scalar types} consist of all of the above.
13954 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13957 @emph{Boolean types} consist of @code{BOOLEAN}.
13961 The following operators are supported, and appear in order of
13962 increasing precedence:
13966 Function argument or array index separator.
13969 Assignment. The value of @var{var} @code{:=} @var{value} is
13973 Less than, greater than on integral, floating-point, or enumerated
13977 Less than or equal to, greater than or equal to
13978 on integral, floating-point and enumerated types, or set inclusion on
13979 set types. Same precedence as @code{<}.
13981 @item =@r{, }<>@r{, }#
13982 Equality and two ways of expressing inequality, valid on scalar types.
13983 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13984 available for inequality, since @code{#} conflicts with the script
13988 Set membership. Defined on set types and the types of their members.
13989 Same precedence as @code{<}.
13992 Boolean disjunction. Defined on boolean types.
13995 Boolean conjunction. Defined on boolean types.
13998 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14001 Addition and subtraction on integral and floating-point types, or union
14002 and difference on set types.
14005 Multiplication on integral and floating-point types, or set intersection
14009 Division on floating-point types, or symmetric set difference on set
14010 types. Same precedence as @code{*}.
14013 Integer division and remainder. Defined on integral types. Same
14014 precedence as @code{*}.
14017 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14020 Pointer dereferencing. Defined on pointer types.
14023 Boolean negation. Defined on boolean types. Same precedence as
14027 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14028 precedence as @code{^}.
14031 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14034 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14038 @value{GDBN} and Modula-2 scope operators.
14042 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14043 treats the use of the operator @code{IN}, or the use of operators
14044 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14045 @code{<=}, and @code{>=} on sets as an error.
14049 @node Built-In Func/Proc
14050 @subsubsection Built-in Functions and Procedures
14051 @cindex Modula-2 built-ins
14053 Modula-2 also makes available several built-in procedures and functions.
14054 In describing these, the following metavariables are used:
14059 represents an @code{ARRAY} variable.
14062 represents a @code{CHAR} constant or variable.
14065 represents a variable or constant of integral type.
14068 represents an identifier that belongs to a set. Generally used in the
14069 same function with the metavariable @var{s}. The type of @var{s} should
14070 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14073 represents a variable or constant of integral or floating-point type.
14076 represents a variable or constant of floating-point type.
14082 represents a variable.
14085 represents a variable or constant of one of many types. See the
14086 explanation of the function for details.
14089 All Modula-2 built-in procedures also return a result, described below.
14093 Returns the absolute value of @var{n}.
14096 If @var{c} is a lower case letter, it returns its upper case
14097 equivalent, otherwise it returns its argument.
14100 Returns the character whose ordinal value is @var{i}.
14103 Decrements the value in the variable @var{v} by one. Returns the new value.
14105 @item DEC(@var{v},@var{i})
14106 Decrements the value in the variable @var{v} by @var{i}. Returns the
14109 @item EXCL(@var{m},@var{s})
14110 Removes the element @var{m} from the set @var{s}. Returns the new
14113 @item FLOAT(@var{i})
14114 Returns the floating point equivalent of the integer @var{i}.
14116 @item HIGH(@var{a})
14117 Returns the index of the last member of @var{a}.
14120 Increments the value in the variable @var{v} by one. Returns the new value.
14122 @item INC(@var{v},@var{i})
14123 Increments the value in the variable @var{v} by @var{i}. Returns the
14126 @item INCL(@var{m},@var{s})
14127 Adds the element @var{m} to the set @var{s} if it is not already
14128 there. Returns the new set.
14131 Returns the maximum value of the type @var{t}.
14134 Returns the minimum value of the type @var{t}.
14137 Returns boolean TRUE if @var{i} is an odd number.
14140 Returns the ordinal value of its argument. For example, the ordinal
14141 value of a character is its @sc{ascii} value (on machines supporting the
14142 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14143 integral, character and enumerated types.
14145 @item SIZE(@var{x})
14146 Returns the size of its argument. @var{x} can be a variable or a type.
14148 @item TRUNC(@var{r})
14149 Returns the integral part of @var{r}.
14151 @item TSIZE(@var{x})
14152 Returns the size of its argument. @var{x} can be a variable or a type.
14154 @item VAL(@var{t},@var{i})
14155 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14159 @emph{Warning:} Sets and their operations are not yet supported, so
14160 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14164 @cindex Modula-2 constants
14166 @subsubsection Constants
14168 @value{GDBN} allows you to express the constants of Modula-2 in the following
14174 Integer constants are simply a sequence of digits. When used in an
14175 expression, a constant is interpreted to be type-compatible with the
14176 rest of the expression. Hexadecimal integers are specified by a
14177 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14180 Floating point constants appear as a sequence of digits, followed by a
14181 decimal point and another sequence of digits. An optional exponent can
14182 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14183 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14184 digits of the floating point constant must be valid decimal (base 10)
14188 Character constants consist of a single character enclosed by a pair of
14189 like quotes, either single (@code{'}) or double (@code{"}). They may
14190 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14191 followed by a @samp{C}.
14194 String constants consist of a sequence of characters enclosed by a
14195 pair of like quotes, either single (@code{'}) or double (@code{"}).
14196 Escape sequences in the style of C are also allowed. @xref{C
14197 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14201 Enumerated constants consist of an enumerated identifier.
14204 Boolean constants consist of the identifiers @code{TRUE} and
14208 Pointer constants consist of integral values only.
14211 Set constants are not yet supported.
14215 @subsubsection Modula-2 Types
14216 @cindex Modula-2 types
14218 Currently @value{GDBN} can print the following data types in Modula-2
14219 syntax: array types, record types, set types, pointer types, procedure
14220 types, enumerated types, subrange types and base types. You can also
14221 print the contents of variables declared using these type.
14222 This section gives a number of simple source code examples together with
14223 sample @value{GDBN} sessions.
14225 The first example contains the following section of code:
14234 and you can request @value{GDBN} to interrogate the type and value of
14235 @code{r} and @code{s}.
14238 (@value{GDBP}) print s
14240 (@value{GDBP}) ptype s
14242 (@value{GDBP}) print r
14244 (@value{GDBP}) ptype r
14249 Likewise if your source code declares @code{s} as:
14253 s: SET ['A'..'Z'] ;
14257 then you may query the type of @code{s} by:
14260 (@value{GDBP}) ptype s
14261 type = SET ['A'..'Z']
14265 Note that at present you cannot interactively manipulate set
14266 expressions using the debugger.
14268 The following example shows how you might declare an array in Modula-2
14269 and how you can interact with @value{GDBN} to print its type and contents:
14273 s: ARRAY [-10..10] OF CHAR ;
14277 (@value{GDBP}) ptype s
14278 ARRAY [-10..10] OF CHAR
14281 Note that the array handling is not yet complete and although the type
14282 is printed correctly, expression handling still assumes that all
14283 arrays have a lower bound of zero and not @code{-10} as in the example
14286 Here are some more type related Modula-2 examples:
14290 colour = (blue, red, yellow, green) ;
14291 t = [blue..yellow] ;
14299 The @value{GDBN} interaction shows how you can query the data type
14300 and value of a variable.
14303 (@value{GDBP}) print s
14305 (@value{GDBP}) ptype t
14306 type = [blue..yellow]
14310 In this example a Modula-2 array is declared and its contents
14311 displayed. Observe that the contents are written in the same way as
14312 their @code{C} counterparts.
14316 s: ARRAY [1..5] OF CARDINAL ;
14322 (@value{GDBP}) print s
14323 $1 = @{1, 0, 0, 0, 0@}
14324 (@value{GDBP}) ptype s
14325 type = ARRAY [1..5] OF CARDINAL
14328 The Modula-2 language interface to @value{GDBN} also understands
14329 pointer types as shown in this example:
14333 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14340 and you can request that @value{GDBN} describes the type of @code{s}.
14343 (@value{GDBP}) ptype s
14344 type = POINTER TO ARRAY [1..5] OF CARDINAL
14347 @value{GDBN} handles compound types as we can see in this example.
14348 Here we combine array types, record types, pointer types and subrange
14359 myarray = ARRAY myrange OF CARDINAL ;
14360 myrange = [-2..2] ;
14362 s: POINTER TO ARRAY myrange OF foo ;
14366 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14370 (@value{GDBP}) ptype s
14371 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14374 f3 : ARRAY [-2..2] OF CARDINAL;
14379 @subsubsection Modula-2 Defaults
14380 @cindex Modula-2 defaults
14382 If type and range checking are set automatically by @value{GDBN}, they
14383 both default to @code{on} whenever the working language changes to
14384 Modula-2. This happens regardless of whether you or @value{GDBN}
14385 selected the working language.
14387 If you allow @value{GDBN} to set the language automatically, then entering
14388 code compiled from a file whose name ends with @file{.mod} sets the
14389 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14390 Infer the Source Language}, for further details.
14393 @subsubsection Deviations from Standard Modula-2
14394 @cindex Modula-2, deviations from
14396 A few changes have been made to make Modula-2 programs easier to debug.
14397 This is done primarily via loosening its type strictness:
14401 Unlike in standard Modula-2, pointer constants can be formed by
14402 integers. This allows you to modify pointer variables during
14403 debugging. (In standard Modula-2, the actual address contained in a
14404 pointer variable is hidden from you; it can only be modified
14405 through direct assignment to another pointer variable or expression that
14406 returned a pointer.)
14409 C escape sequences can be used in strings and characters to represent
14410 non-printable characters. @value{GDBN} prints out strings with these
14411 escape sequences embedded. Single non-printable characters are
14412 printed using the @samp{CHR(@var{nnn})} format.
14415 The assignment operator (@code{:=}) returns the value of its right-hand
14419 All built-in procedures both modify @emph{and} return their argument.
14423 @subsubsection Modula-2 Type and Range Checks
14424 @cindex Modula-2 checks
14427 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14430 @c FIXME remove warning when type/range checks added
14432 @value{GDBN} considers two Modula-2 variables type equivalent if:
14436 They are of types that have been declared equivalent via a @code{TYPE
14437 @var{t1} = @var{t2}} statement
14440 They have been declared on the same line. (Note: This is true of the
14441 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14444 As long as type checking is enabled, any attempt to combine variables
14445 whose types are not equivalent is an error.
14447 Range checking is done on all mathematical operations, assignment, array
14448 index bounds, and all built-in functions and procedures.
14451 @subsubsection The Scope Operators @code{::} and @code{.}
14453 @cindex @code{.}, Modula-2 scope operator
14454 @cindex colon, doubled as scope operator
14456 @vindex colon-colon@r{, in Modula-2}
14457 @c Info cannot handle :: but TeX can.
14460 @vindex ::@r{, in Modula-2}
14463 There are a few subtle differences between the Modula-2 scope operator
14464 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14469 @var{module} . @var{id}
14470 @var{scope} :: @var{id}
14474 where @var{scope} is the name of a module or a procedure,
14475 @var{module} the name of a module, and @var{id} is any declared
14476 identifier within your program, except another module.
14478 Using the @code{::} operator makes @value{GDBN} search the scope
14479 specified by @var{scope} for the identifier @var{id}. If it is not
14480 found in the specified scope, then @value{GDBN} searches all scopes
14481 enclosing the one specified by @var{scope}.
14483 Using the @code{.} operator makes @value{GDBN} search the current scope for
14484 the identifier specified by @var{id} that was imported from the
14485 definition module specified by @var{module}. With this operator, it is
14486 an error if the identifier @var{id} was not imported from definition
14487 module @var{module}, or if @var{id} is not an identifier in
14491 @subsubsection @value{GDBN} and Modula-2
14493 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14494 Five subcommands of @code{set print} and @code{show print} apply
14495 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14496 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14497 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14498 analogue in Modula-2.
14500 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14501 with any language, is not useful with Modula-2. Its
14502 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14503 created in Modula-2 as they can in C or C@t{++}. However, because an
14504 address can be specified by an integral constant, the construct
14505 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14507 @cindex @code{#} in Modula-2
14508 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14509 interpreted as the beginning of a comment. Use @code{<>} instead.
14515 The extensions made to @value{GDBN} for Ada only support
14516 output from the @sc{gnu} Ada (GNAT) compiler.
14517 Other Ada compilers are not currently supported, and
14518 attempting to debug executables produced by them is most likely
14522 @cindex expressions in Ada
14524 * Ada Mode Intro:: General remarks on the Ada syntax
14525 and semantics supported by Ada mode
14527 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14528 * Additions to Ada:: Extensions of the Ada expression syntax.
14529 * Stopping Before Main Program:: Debugging the program during elaboration.
14530 * Ada Tasks:: Listing and setting breakpoints in tasks.
14531 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14532 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14534 * Ada Glitches:: Known peculiarities of Ada mode.
14537 @node Ada Mode Intro
14538 @subsubsection Introduction
14539 @cindex Ada mode, general
14541 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14542 syntax, with some extensions.
14543 The philosophy behind the design of this subset is
14547 That @value{GDBN} should provide basic literals and access to operations for
14548 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14549 leaving more sophisticated computations to subprograms written into the
14550 program (which therefore may be called from @value{GDBN}).
14553 That type safety and strict adherence to Ada language restrictions
14554 are not particularly important to the @value{GDBN} user.
14557 That brevity is important to the @value{GDBN} user.
14560 Thus, for brevity, the debugger acts as if all names declared in
14561 user-written packages are directly visible, even if they are not visible
14562 according to Ada rules, thus making it unnecessary to fully qualify most
14563 names with their packages, regardless of context. Where this causes
14564 ambiguity, @value{GDBN} asks the user's intent.
14566 The debugger will start in Ada mode if it detects an Ada main program.
14567 As for other languages, it will enter Ada mode when stopped in a program that
14568 was translated from an Ada source file.
14570 While in Ada mode, you may use `@t{--}' for comments. This is useful
14571 mostly for documenting command files. The standard @value{GDBN} comment
14572 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14573 middle (to allow based literals).
14575 The debugger supports limited overloading. Given a subprogram call in which
14576 the function symbol has multiple definitions, it will use the number of
14577 actual parameters and some information about their types to attempt to narrow
14578 the set of definitions. It also makes very limited use of context, preferring
14579 procedures to functions in the context of the @code{call} command, and
14580 functions to procedures elsewhere.
14582 @node Omissions from Ada
14583 @subsubsection Omissions from Ada
14584 @cindex Ada, omissions from
14586 Here are the notable omissions from the subset:
14590 Only a subset of the attributes are supported:
14594 @t{'First}, @t{'Last}, and @t{'Length}
14595 on array objects (not on types and subtypes).
14598 @t{'Min} and @t{'Max}.
14601 @t{'Pos} and @t{'Val}.
14607 @t{'Range} on array objects (not subtypes), but only as the right
14608 operand of the membership (@code{in}) operator.
14611 @t{'Access}, @t{'Unchecked_Access}, and
14612 @t{'Unrestricted_Access} (a GNAT extension).
14620 @code{Characters.Latin_1} are not available and
14621 concatenation is not implemented. Thus, escape characters in strings are
14622 not currently available.
14625 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14626 equality of representations. They will generally work correctly
14627 for strings and arrays whose elements have integer or enumeration types.
14628 They may not work correctly for arrays whose element
14629 types have user-defined equality, for arrays of real values
14630 (in particular, IEEE-conformant floating point, because of negative
14631 zeroes and NaNs), and for arrays whose elements contain unused bits with
14632 indeterminate values.
14635 The other component-by-component array operations (@code{and}, @code{or},
14636 @code{xor}, @code{not}, and relational tests other than equality)
14637 are not implemented.
14640 @cindex array aggregates (Ada)
14641 @cindex record aggregates (Ada)
14642 @cindex aggregates (Ada)
14643 There is limited support for array and record aggregates. They are
14644 permitted only on the right sides of assignments, as in these examples:
14647 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14648 (@value{GDBP}) set An_Array := (1, others => 0)
14649 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14650 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14651 (@value{GDBP}) set A_Record := (1, "Peter", True);
14652 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14656 discriminant's value by assigning an aggregate has an
14657 undefined effect if that discriminant is used within the record.
14658 However, you can first modify discriminants by directly assigning to
14659 them (which normally would not be allowed in Ada), and then performing an
14660 aggregate assignment. For example, given a variable @code{A_Rec}
14661 declared to have a type such as:
14664 type Rec (Len : Small_Integer := 0) is record
14666 Vals : IntArray (1 .. Len);
14670 you can assign a value with a different size of @code{Vals} with two
14674 (@value{GDBP}) set A_Rec.Len := 4
14675 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14678 As this example also illustrates, @value{GDBN} is very loose about the usual
14679 rules concerning aggregates. You may leave out some of the
14680 components of an array or record aggregate (such as the @code{Len}
14681 component in the assignment to @code{A_Rec} above); they will retain their
14682 original values upon assignment. You may freely use dynamic values as
14683 indices in component associations. You may even use overlapping or
14684 redundant component associations, although which component values are
14685 assigned in such cases is not defined.
14688 Calls to dispatching subprograms are not implemented.
14691 The overloading algorithm is much more limited (i.e., less selective)
14692 than that of real Ada. It makes only limited use of the context in
14693 which a subexpression appears to resolve its meaning, and it is much
14694 looser in its rules for allowing type matches. As a result, some
14695 function calls will be ambiguous, and the user will be asked to choose
14696 the proper resolution.
14699 The @code{new} operator is not implemented.
14702 Entry calls are not implemented.
14705 Aside from printing, arithmetic operations on the native VAX floating-point
14706 formats are not supported.
14709 It is not possible to slice a packed array.
14712 The names @code{True} and @code{False}, when not part of a qualified name,
14713 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14715 Should your program
14716 redefine these names in a package or procedure (at best a dubious practice),
14717 you will have to use fully qualified names to access their new definitions.
14720 @node Additions to Ada
14721 @subsubsection Additions to Ada
14722 @cindex Ada, deviations from
14724 As it does for other languages, @value{GDBN} makes certain generic
14725 extensions to Ada (@pxref{Expressions}):
14729 If the expression @var{E} is a variable residing in memory (typically
14730 a local variable or array element) and @var{N} is a positive integer,
14731 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14732 @var{N}-1 adjacent variables following it in memory as an array. In
14733 Ada, this operator is generally not necessary, since its prime use is
14734 in displaying parts of an array, and slicing will usually do this in
14735 Ada. However, there are occasional uses when debugging programs in
14736 which certain debugging information has been optimized away.
14739 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14740 appears in function or file @var{B}.'' When @var{B} is a file name,
14741 you must typically surround it in single quotes.
14744 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14745 @var{type} that appears at address @var{addr}.''
14748 A name starting with @samp{$} is a convenience variable
14749 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14752 In addition, @value{GDBN} provides a few other shortcuts and outright
14753 additions specific to Ada:
14757 The assignment statement is allowed as an expression, returning
14758 its right-hand operand as its value. Thus, you may enter
14761 (@value{GDBP}) set x := y + 3
14762 (@value{GDBP}) print A(tmp := y + 1)
14766 The semicolon is allowed as an ``operator,'' returning as its value
14767 the value of its right-hand operand.
14768 This allows, for example,
14769 complex conditional breaks:
14772 (@value{GDBP}) break f
14773 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14777 Rather than use catenation and symbolic character names to introduce special
14778 characters into strings, one may instead use a special bracket notation,
14779 which is also used to print strings. A sequence of characters of the form
14780 @samp{["@var{XX}"]} within a string or character literal denotes the
14781 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14782 sequence of characters @samp{["""]} also denotes a single quotation mark
14783 in strings. For example,
14785 "One line.["0a"]Next line.["0a"]"
14788 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14792 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14793 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14797 (@value{GDBP}) print 'max(x, y)
14801 When printing arrays, @value{GDBN} uses positional notation when the
14802 array has a lower bound of 1, and uses a modified named notation otherwise.
14803 For example, a one-dimensional array of three integers with a lower bound
14804 of 3 might print as
14811 That is, in contrast to valid Ada, only the first component has a @code{=>}
14815 You may abbreviate attributes in expressions with any unique,
14816 multi-character subsequence of
14817 their names (an exact match gets preference).
14818 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14819 in place of @t{a'length}.
14822 @cindex quoting Ada internal identifiers
14823 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14824 to lower case. The GNAT compiler uses upper-case characters for
14825 some of its internal identifiers, which are normally of no interest to users.
14826 For the rare occasions when you actually have to look at them,
14827 enclose them in angle brackets to avoid the lower-case mapping.
14830 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14834 Printing an object of class-wide type or dereferencing an
14835 access-to-class-wide value will display all the components of the object's
14836 specific type (as indicated by its run-time tag). Likewise, component
14837 selection on such a value will operate on the specific type of the
14842 @node Stopping Before Main Program
14843 @subsubsection Stopping at the Very Beginning
14845 @cindex breakpointing Ada elaboration code
14846 It is sometimes necessary to debug the program during elaboration, and
14847 before reaching the main procedure.
14848 As defined in the Ada Reference
14849 Manual, the elaboration code is invoked from a procedure called
14850 @code{adainit}. To run your program up to the beginning of
14851 elaboration, simply use the following two commands:
14852 @code{tbreak adainit} and @code{run}.
14855 @subsubsection Extensions for Ada Tasks
14856 @cindex Ada, tasking
14858 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14859 @value{GDBN} provides the following task-related commands:
14864 This command shows a list of current Ada tasks, as in the following example:
14871 (@value{GDBP}) info tasks
14872 ID TID P-ID Pri State Name
14873 1 8088000 0 15 Child Activation Wait main_task
14874 2 80a4000 1 15 Accept Statement b
14875 3 809a800 1 15 Child Activation Wait a
14876 * 4 80ae800 3 15 Runnable c
14881 In this listing, the asterisk before the last task indicates it to be the
14882 task currently being inspected.
14886 Represents @value{GDBN}'s internal task number.
14892 The parent's task ID (@value{GDBN}'s internal task number).
14895 The base priority of the task.
14898 Current state of the task.
14902 The task has been created but has not been activated. It cannot be
14906 The task is not blocked for any reason known to Ada. (It may be waiting
14907 for a mutex, though.) It is conceptually "executing" in normal mode.
14910 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14911 that were waiting on terminate alternatives have been awakened and have
14912 terminated themselves.
14914 @item Child Activation Wait
14915 The task is waiting for created tasks to complete activation.
14917 @item Accept Statement
14918 The task is waiting on an accept or selective wait statement.
14920 @item Waiting on entry call
14921 The task is waiting on an entry call.
14923 @item Async Select Wait
14924 The task is waiting to start the abortable part of an asynchronous
14928 The task is waiting on a select statement with only a delay
14931 @item Child Termination Wait
14932 The task is sleeping having completed a master within itself, and is
14933 waiting for the tasks dependent on that master to become terminated or
14934 waiting on a terminate Phase.
14936 @item Wait Child in Term Alt
14937 The task is sleeping waiting for tasks on terminate alternatives to
14938 finish terminating.
14940 @item Accepting RV with @var{taskno}
14941 The task is accepting a rendez-vous with the task @var{taskno}.
14945 Name of the task in the program.
14949 @kindex info task @var{taskno}
14950 @item info task @var{taskno}
14951 This command shows detailled informations on the specified task, as in
14952 the following example:
14957 (@value{GDBP}) info tasks
14958 ID TID P-ID Pri State Name
14959 1 8077880 0 15 Child Activation Wait main_task
14960 * 2 807c468 1 15 Runnable task_1
14961 (@value{GDBP}) info task 2
14962 Ada Task: 0x807c468
14965 Parent: 1 (main_task)
14971 @kindex task@r{ (Ada)}
14972 @cindex current Ada task ID
14973 This command prints the ID of the current task.
14979 (@value{GDBP}) info tasks
14980 ID TID P-ID Pri State Name
14981 1 8077870 0 15 Child Activation Wait main_task
14982 * 2 807c458 1 15 Runnable t
14983 (@value{GDBP}) task
14984 [Current task is 2]
14987 @item task @var{taskno}
14988 @cindex Ada task switching
14989 This command is like the @code{thread @var{threadno}}
14990 command (@pxref{Threads}). It switches the context of debugging
14991 from the current task to the given task.
14997 (@value{GDBP}) info tasks
14998 ID TID P-ID Pri State Name
14999 1 8077870 0 15 Child Activation Wait main_task
15000 * 2 807c458 1 15 Runnable t
15001 (@value{GDBP}) task 1
15002 [Switching to task 1]
15003 #0 0x8067726 in pthread_cond_wait ()
15005 #0 0x8067726 in pthread_cond_wait ()
15006 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15007 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15008 #3 0x806153e in system.tasking.stages.activate_tasks ()
15009 #4 0x804aacc in un () at un.adb:5
15012 @item break @var{linespec} task @var{taskno}
15013 @itemx break @var{linespec} task @var{taskno} if @dots{}
15014 @cindex breakpoints and tasks, in Ada
15015 @cindex task breakpoints, in Ada
15016 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15017 These commands are like the @code{break @dots{} thread @dots{}}
15018 command (@pxref{Thread Stops}).
15019 @var{linespec} specifies source lines, as described
15020 in @ref{Specify Location}.
15022 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15023 to specify that you only want @value{GDBN} to stop the program when a
15024 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15025 numeric task identifiers assigned by @value{GDBN}, shown in the first
15026 column of the @samp{info tasks} display.
15028 If you do not specify @samp{task @var{taskno}} when you set a
15029 breakpoint, the breakpoint applies to @emph{all} tasks of your
15032 You can use the @code{task} qualifier on conditional breakpoints as
15033 well; in this case, place @samp{task @var{taskno}} before the
15034 breakpoint condition (before the @code{if}).
15042 (@value{GDBP}) info tasks
15043 ID TID P-ID Pri State Name
15044 1 140022020 0 15 Child Activation Wait main_task
15045 2 140045060 1 15 Accept/Select Wait t2
15046 3 140044840 1 15 Runnable t1
15047 * 4 140056040 1 15 Runnable t3
15048 (@value{GDBP}) b 15 task 2
15049 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15050 (@value{GDBP}) cont
15055 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15057 (@value{GDBP}) info tasks
15058 ID TID P-ID Pri State Name
15059 1 140022020 0 15 Child Activation Wait main_task
15060 * 2 140045060 1 15 Runnable t2
15061 3 140044840 1 15 Runnable t1
15062 4 140056040 1 15 Delay Sleep t3
15066 @node Ada Tasks and Core Files
15067 @subsubsection Tasking Support when Debugging Core Files
15068 @cindex Ada tasking and core file debugging
15070 When inspecting a core file, as opposed to debugging a live program,
15071 tasking support may be limited or even unavailable, depending on
15072 the platform being used.
15073 For instance, on x86-linux, the list of tasks is available, but task
15074 switching is not supported. On Tru64, however, task switching will work
15077 On certain platforms, including Tru64, the debugger needs to perform some
15078 memory writes in order to provide Ada tasking support. When inspecting
15079 a core file, this means that the core file must be opened with read-write
15080 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15081 Under these circumstances, you should make a backup copy of the core
15082 file before inspecting it with @value{GDBN}.
15084 @node Ravenscar Profile
15085 @subsubsection Tasking Support when using the Ravenscar Profile
15086 @cindex Ravenscar Profile
15088 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15089 specifically designed for systems with safety-critical real-time
15093 @kindex set ravenscar task-switching on
15094 @cindex task switching with program using Ravenscar Profile
15095 @item set ravenscar task-switching on
15096 Allows task switching when debugging a program that uses the Ravenscar
15097 Profile. This is the default.
15099 @kindex set ravenscar task-switching off
15100 @item set ravenscar task-switching off
15101 Turn off task switching when debugging a program that uses the Ravenscar
15102 Profile. This is mostly intended to disable the code that adds support
15103 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15104 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15105 To be effective, this command should be run before the program is started.
15107 @kindex show ravenscar task-switching
15108 @item show ravenscar task-switching
15109 Show whether it is possible to switch from task to task in a program
15110 using the Ravenscar Profile.
15115 @subsubsection Known Peculiarities of Ada Mode
15116 @cindex Ada, problems
15118 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15119 we know of several problems with and limitations of Ada mode in
15121 some of which will be fixed with planned future releases of the debugger
15122 and the GNU Ada compiler.
15126 Static constants that the compiler chooses not to materialize as objects in
15127 storage are invisible to the debugger.
15130 Named parameter associations in function argument lists are ignored (the
15131 argument lists are treated as positional).
15134 Many useful library packages are currently invisible to the debugger.
15137 Fixed-point arithmetic, conversions, input, and output is carried out using
15138 floating-point arithmetic, and may give results that only approximate those on
15142 The GNAT compiler never generates the prefix @code{Standard} for any of
15143 the standard symbols defined by the Ada language. @value{GDBN} knows about
15144 this: it will strip the prefix from names when you use it, and will never
15145 look for a name you have so qualified among local symbols, nor match against
15146 symbols in other packages or subprograms. If you have
15147 defined entities anywhere in your program other than parameters and
15148 local variables whose simple names match names in @code{Standard},
15149 GNAT's lack of qualification here can cause confusion. When this happens,
15150 you can usually resolve the confusion
15151 by qualifying the problematic names with package
15152 @code{Standard} explicitly.
15155 Older versions of the compiler sometimes generate erroneous debugging
15156 information, resulting in the debugger incorrectly printing the value
15157 of affected entities. In some cases, the debugger is able to work
15158 around an issue automatically. In other cases, the debugger is able
15159 to work around the issue, but the work-around has to be specifically
15162 @kindex set ada trust-PAD-over-XVS
15163 @kindex show ada trust-PAD-over-XVS
15166 @item set ada trust-PAD-over-XVS on
15167 Configure GDB to strictly follow the GNAT encoding when computing the
15168 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15169 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15170 a complete description of the encoding used by the GNAT compiler).
15171 This is the default.
15173 @item set ada trust-PAD-over-XVS off
15174 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15175 sometimes prints the wrong value for certain entities, changing @code{ada
15176 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15177 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15178 @code{off}, but this incurs a slight performance penalty, so it is
15179 recommended to leave this setting to @code{on} unless necessary.
15183 @node Unsupported Languages
15184 @section Unsupported Languages
15186 @cindex unsupported languages
15187 @cindex minimal language
15188 In addition to the other fully-supported programming languages,
15189 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15190 It does not represent a real programming language, but provides a set
15191 of capabilities close to what the C or assembly languages provide.
15192 This should allow most simple operations to be performed while debugging
15193 an application that uses a language currently not supported by @value{GDBN}.
15195 If the language is set to @code{auto}, @value{GDBN} will automatically
15196 select this language if the current frame corresponds to an unsupported
15200 @chapter Examining the Symbol Table
15202 The commands described in this chapter allow you to inquire about the
15203 symbols (names of variables, functions and types) defined in your
15204 program. This information is inherent in the text of your program and
15205 does not change as your program executes. @value{GDBN} finds it in your
15206 program's symbol table, in the file indicated when you started @value{GDBN}
15207 (@pxref{File Options, ,Choosing Files}), or by one of the
15208 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15210 @cindex symbol names
15211 @cindex names of symbols
15212 @cindex quoting names
15213 Occasionally, you may need to refer to symbols that contain unusual
15214 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15215 most frequent case is in referring to static variables in other
15216 source files (@pxref{Variables,,Program Variables}). File names
15217 are recorded in object files as debugging symbols, but @value{GDBN} would
15218 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15219 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15220 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15227 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15230 @cindex case-insensitive symbol names
15231 @cindex case sensitivity in symbol names
15232 @kindex set case-sensitive
15233 @item set case-sensitive on
15234 @itemx set case-sensitive off
15235 @itemx set case-sensitive auto
15236 Normally, when @value{GDBN} looks up symbols, it matches their names
15237 with case sensitivity determined by the current source language.
15238 Occasionally, you may wish to control that. The command @code{set
15239 case-sensitive} lets you do that by specifying @code{on} for
15240 case-sensitive matches or @code{off} for case-insensitive ones. If
15241 you specify @code{auto}, case sensitivity is reset to the default
15242 suitable for the source language. The default is case-sensitive
15243 matches for all languages except for Fortran, for which the default is
15244 case-insensitive matches.
15246 @kindex show case-sensitive
15247 @item show case-sensitive
15248 This command shows the current setting of case sensitivity for symbols
15251 @kindex set print type methods
15252 @item set print type methods
15253 @itemx set print type methods on
15254 @itemx set print type methods off
15255 Normally, when @value{GDBN} prints a class, it displays any methods
15256 declared in that class. You can control this behavior either by
15257 passing the appropriate flag to @code{ptype}, or using @command{set
15258 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15259 display the methods; this is the default. Specifying @code{off} will
15260 cause @value{GDBN} to omit the methods.
15262 @kindex show print type methods
15263 @item show print type methods
15264 This command shows the current setting of method display when printing
15267 @kindex set print type typedefs
15268 @item set print type typedefs
15269 @itemx set print type typedefs on
15270 @itemx set print type typedefs off
15272 Normally, when @value{GDBN} prints a class, it displays any typedefs
15273 defined in that class. You can control this behavior either by
15274 passing the appropriate flag to @code{ptype}, or using @command{set
15275 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15276 display the typedef definitions; this is the default. Specifying
15277 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15278 Note that this controls whether the typedef definition itself is
15279 printed, not whether typedef names are substituted when printing other
15282 @kindex show print type typedefs
15283 @item show print type typedefs
15284 This command shows the current setting of typedef display when
15287 @kindex info address
15288 @cindex address of a symbol
15289 @item info address @var{symbol}
15290 Describe where the data for @var{symbol} is stored. For a register
15291 variable, this says which register it is kept in. For a non-register
15292 local variable, this prints the stack-frame offset at which the variable
15295 Note the contrast with @samp{print &@var{symbol}}, which does not work
15296 at all for a register variable, and for a stack local variable prints
15297 the exact address of the current instantiation of the variable.
15299 @kindex info symbol
15300 @cindex symbol from address
15301 @cindex closest symbol and offset for an address
15302 @item info symbol @var{addr}
15303 Print the name of a symbol which is stored at the address @var{addr}.
15304 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15305 nearest symbol and an offset from it:
15308 (@value{GDBP}) info symbol 0x54320
15309 _initialize_vx + 396 in section .text
15313 This is the opposite of the @code{info address} command. You can use
15314 it to find out the name of a variable or a function given its address.
15316 For dynamically linked executables, the name of executable or shared
15317 library containing the symbol is also printed:
15320 (@value{GDBP}) info symbol 0x400225
15321 _start + 5 in section .text of /tmp/a.out
15322 (@value{GDBP}) info symbol 0x2aaaac2811cf
15323 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15327 @item whatis[/@var{flags}] [@var{arg}]
15328 Print the data type of @var{arg}, which can be either an expression
15329 or a name of a data type. With no argument, print the data type of
15330 @code{$}, the last value in the value history.
15332 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15333 is not actually evaluated, and any side-effecting operations (such as
15334 assignments or function calls) inside it do not take place.
15336 If @var{arg} is a variable or an expression, @code{whatis} prints its
15337 literal type as it is used in the source code. If the type was
15338 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15339 the data type underlying the @code{typedef}. If the type of the
15340 variable or the expression is a compound data type, such as
15341 @code{struct} or @code{class}, @code{whatis} never prints their
15342 fields or methods. It just prints the @code{struct}/@code{class}
15343 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15344 such a compound data type, use @code{ptype}.
15346 If @var{arg} is a type name that was defined using @code{typedef},
15347 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15348 Unrolling means that @code{whatis} will show the underlying type used
15349 in the @code{typedef} declaration of @var{arg}. However, if that
15350 underlying type is also a @code{typedef}, @code{whatis} will not
15353 For C code, the type names may also have the form @samp{class
15354 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15355 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15357 @var{flags} can be used to modify how the type is displayed.
15358 Available flags are:
15362 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15363 parameters and typedefs defined in a class when printing the class'
15364 members. The @code{/r} flag disables this.
15367 Do not print methods defined in the class.
15370 Print methods defined in the class. This is the default, but the flag
15371 exists in case you change the default with @command{set print type methods}.
15374 Do not print typedefs defined in the class. Note that this controls
15375 whether the typedef definition itself is printed, not whether typedef
15376 names are substituted when printing other types.
15379 Print typedefs defined in the class. This is the default, but the flag
15380 exists in case you change the default with @command{set print type typedefs}.
15384 @item ptype[/@var{flags}] [@var{arg}]
15385 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15386 detailed description of the type, instead of just the name of the type.
15387 @xref{Expressions, ,Expressions}.
15389 Contrary to @code{whatis}, @code{ptype} always unrolls any
15390 @code{typedef}s in its argument declaration, whether the argument is
15391 a variable, expression, or a data type. This means that @code{ptype}
15392 of a variable or an expression will not print literally its type as
15393 present in the source code---use @code{whatis} for that. @code{typedef}s at
15394 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15395 fields, methods and inner @code{class typedef}s of @code{struct}s,
15396 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15398 For example, for this variable declaration:
15401 typedef double real_t;
15402 struct complex @{ real_t real; double imag; @};
15403 typedef struct complex complex_t;
15405 real_t *real_pointer_var;
15409 the two commands give this output:
15413 (@value{GDBP}) whatis var
15415 (@value{GDBP}) ptype var
15416 type = struct complex @{
15420 (@value{GDBP}) whatis complex_t
15421 type = struct complex
15422 (@value{GDBP}) whatis struct complex
15423 type = struct complex
15424 (@value{GDBP}) ptype struct complex
15425 type = struct complex @{
15429 (@value{GDBP}) whatis real_pointer_var
15431 (@value{GDBP}) ptype real_pointer_var
15437 As with @code{whatis}, using @code{ptype} without an argument refers to
15438 the type of @code{$}, the last value in the value history.
15440 @cindex incomplete type
15441 Sometimes, programs use opaque data types or incomplete specifications
15442 of complex data structure. If the debug information included in the
15443 program does not allow @value{GDBN} to display a full declaration of
15444 the data type, it will say @samp{<incomplete type>}. For example,
15445 given these declarations:
15449 struct foo *fooptr;
15453 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15456 (@value{GDBP}) ptype foo
15457 $1 = <incomplete type>
15461 ``Incomplete type'' is C terminology for data types that are not
15462 completely specified.
15465 @item info types @var{regexp}
15467 Print a brief description of all types whose names match the regular
15468 expression @var{regexp} (or all types in your program, if you supply
15469 no argument). Each complete typename is matched as though it were a
15470 complete line; thus, @samp{i type value} gives information on all
15471 types in your program whose names include the string @code{value}, but
15472 @samp{i type ^value$} gives information only on types whose complete
15473 name is @code{value}.
15475 This command differs from @code{ptype} in two ways: first, like
15476 @code{whatis}, it does not print a detailed description; second, it
15477 lists all source files where a type is defined.
15479 @kindex info type-printers
15480 @item info type-printers
15481 Versions of @value{GDBN} that ship with Python scripting enabled may
15482 have ``type printers'' available. When using @command{ptype} or
15483 @command{whatis}, these printers are consulted when the name of a type
15484 is needed. @xref{Type Printing API}, for more information on writing
15487 @code{info type-printers} displays all the available type printers.
15489 @kindex enable type-printer
15490 @kindex disable type-printer
15491 @item enable type-printer @var{name}@dots{}
15492 @item disable type-printer @var{name}@dots{}
15493 These commands can be used to enable or disable type printers.
15496 @cindex local variables
15497 @item info scope @var{location}
15498 List all the variables local to a particular scope. This command
15499 accepts a @var{location} argument---a function name, a source line, or
15500 an address preceded by a @samp{*}, and prints all the variables local
15501 to the scope defined by that location. (@xref{Specify Location}, for
15502 details about supported forms of @var{location}.) For example:
15505 (@value{GDBP}) @b{info scope command_line_handler}
15506 Scope for command_line_handler:
15507 Symbol rl is an argument at stack/frame offset 8, length 4.
15508 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15509 Symbol linelength is in static storage at address 0x150a1c, length 4.
15510 Symbol p is a local variable in register $esi, length 4.
15511 Symbol p1 is a local variable in register $ebx, length 4.
15512 Symbol nline is a local variable in register $edx, length 4.
15513 Symbol repeat is a local variable at frame offset -8, length 4.
15517 This command is especially useful for determining what data to collect
15518 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15521 @kindex info source
15523 Show information about the current source file---that is, the source file for
15524 the function containing the current point of execution:
15527 the name of the source file, and the directory containing it,
15529 the directory it was compiled in,
15531 its length, in lines,
15533 which programming language it is written in,
15535 whether the executable includes debugging information for that file, and
15536 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15538 whether the debugging information includes information about
15539 preprocessor macros.
15543 @kindex info sources
15545 Print the names of all source files in your program for which there is
15546 debugging information, organized into two lists: files whose symbols
15547 have already been read, and files whose symbols will be read when needed.
15549 @kindex info functions
15550 @item info functions
15551 Print the names and data types of all defined functions.
15553 @item info functions @var{regexp}
15554 Print the names and data types of all defined functions
15555 whose names contain a match for regular expression @var{regexp}.
15556 Thus, @samp{info fun step} finds all functions whose names
15557 include @code{step}; @samp{info fun ^step} finds those whose names
15558 start with @code{step}. If a function name contains characters
15559 that conflict with the regular expression language (e.g.@:
15560 @samp{operator*()}), they may be quoted with a backslash.
15562 @kindex info variables
15563 @item info variables
15564 Print the names and data types of all variables that are defined
15565 outside of functions (i.e.@: excluding local variables).
15567 @item info variables @var{regexp}
15568 Print the names and data types of all variables (except for local
15569 variables) whose names contain a match for regular expression
15572 @kindex info classes
15573 @cindex Objective-C, classes and selectors
15575 @itemx info classes @var{regexp}
15576 Display all Objective-C classes in your program, or
15577 (with the @var{regexp} argument) all those matching a particular regular
15580 @kindex info selectors
15581 @item info selectors
15582 @itemx info selectors @var{regexp}
15583 Display all Objective-C selectors in your program, or
15584 (with the @var{regexp} argument) all those matching a particular regular
15588 This was never implemented.
15589 @kindex info methods
15591 @itemx info methods @var{regexp}
15592 The @code{info methods} command permits the user to examine all defined
15593 methods within C@t{++} program, or (with the @var{regexp} argument) a
15594 specific set of methods found in the various C@t{++} classes. Many
15595 C@t{++} classes provide a large number of methods. Thus, the output
15596 from the @code{ptype} command can be overwhelming and hard to use. The
15597 @code{info-methods} command filters the methods, printing only those
15598 which match the regular-expression @var{regexp}.
15601 @cindex opaque data types
15602 @kindex set opaque-type-resolution
15603 @item set opaque-type-resolution on
15604 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15605 declared as a pointer to a @code{struct}, @code{class}, or
15606 @code{union}---for example, @code{struct MyType *}---that is used in one
15607 source file although the full declaration of @code{struct MyType} is in
15608 another source file. The default is on.
15610 A change in the setting of this subcommand will not take effect until
15611 the next time symbols for a file are loaded.
15613 @item set opaque-type-resolution off
15614 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15615 is printed as follows:
15617 @{<no data fields>@}
15620 @kindex show opaque-type-resolution
15621 @item show opaque-type-resolution
15622 Show whether opaque types are resolved or not.
15624 @kindex maint print symbols
15625 @cindex symbol dump
15626 @kindex maint print psymbols
15627 @cindex partial symbol dump
15628 @item maint print symbols @var{filename}
15629 @itemx maint print psymbols @var{filename}
15630 @itemx maint print msymbols @var{filename}
15631 Write a dump of debugging symbol data into the file @var{filename}.
15632 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15633 symbols with debugging data are included. If you use @samp{maint print
15634 symbols}, @value{GDBN} includes all the symbols for which it has already
15635 collected full details: that is, @var{filename} reflects symbols for
15636 only those files whose symbols @value{GDBN} has read. You can use the
15637 command @code{info sources} to find out which files these are. If you
15638 use @samp{maint print psymbols} instead, the dump shows information about
15639 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15640 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15641 @samp{maint print msymbols} dumps just the minimal symbol information
15642 required for each object file from which @value{GDBN} has read some symbols.
15643 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15644 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15646 @kindex maint info symtabs
15647 @kindex maint info psymtabs
15648 @cindex listing @value{GDBN}'s internal symbol tables
15649 @cindex symbol tables, listing @value{GDBN}'s internal
15650 @cindex full symbol tables, listing @value{GDBN}'s internal
15651 @cindex partial symbol tables, listing @value{GDBN}'s internal
15652 @item maint info symtabs @r{[} @var{regexp} @r{]}
15653 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15655 List the @code{struct symtab} or @code{struct partial_symtab}
15656 structures whose names match @var{regexp}. If @var{regexp} is not
15657 given, list them all. The output includes expressions which you can
15658 copy into a @value{GDBN} debugging this one to examine a particular
15659 structure in more detail. For example:
15662 (@value{GDBP}) maint info psymtabs dwarf2read
15663 @{ objfile /home/gnu/build/gdb/gdb
15664 ((struct objfile *) 0x82e69d0)
15665 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15666 ((struct partial_symtab *) 0x8474b10)
15669 text addresses 0x814d3c8 -- 0x8158074
15670 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15671 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15672 dependencies (none)
15675 (@value{GDBP}) maint info symtabs
15679 We see that there is one partial symbol table whose filename contains
15680 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15681 and we see that @value{GDBN} has not read in any symtabs yet at all.
15682 If we set a breakpoint on a function, that will cause @value{GDBN} to
15683 read the symtab for the compilation unit containing that function:
15686 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15687 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15689 (@value{GDBP}) maint info symtabs
15690 @{ objfile /home/gnu/build/gdb/gdb
15691 ((struct objfile *) 0x82e69d0)
15692 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15693 ((struct symtab *) 0x86c1f38)
15696 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15697 linetable ((struct linetable *) 0x8370fa0)
15698 debugformat DWARF 2
15707 @chapter Altering Execution
15709 Once you think you have found an error in your program, you might want to
15710 find out for certain whether correcting the apparent error would lead to
15711 correct results in the rest of the run. You can find the answer by
15712 experiment, using the @value{GDBN} features for altering execution of the
15715 For example, you can store new values into variables or memory
15716 locations, give your program a signal, restart it at a different
15717 address, or even return prematurely from a function.
15720 * Assignment:: Assignment to variables
15721 * Jumping:: Continuing at a different address
15722 * Signaling:: Giving your program a signal
15723 * Returning:: Returning from a function
15724 * Calling:: Calling your program's functions
15725 * Patching:: Patching your program
15729 @section Assignment to Variables
15732 @cindex setting variables
15733 To alter the value of a variable, evaluate an assignment expression.
15734 @xref{Expressions, ,Expressions}. For example,
15741 stores the value 4 into the variable @code{x}, and then prints the
15742 value of the assignment expression (which is 4).
15743 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15744 information on operators in supported languages.
15746 @kindex set variable
15747 @cindex variables, setting
15748 If you are not interested in seeing the value of the assignment, use the
15749 @code{set} command instead of the @code{print} command. @code{set} is
15750 really the same as @code{print} except that the expression's value is
15751 not printed and is not put in the value history (@pxref{Value History,
15752 ,Value History}). The expression is evaluated only for its effects.
15754 If the beginning of the argument string of the @code{set} command
15755 appears identical to a @code{set} subcommand, use the @code{set
15756 variable} command instead of just @code{set}. This command is identical
15757 to @code{set} except for its lack of subcommands. For example, if your
15758 program has a variable @code{width}, you get an error if you try to set
15759 a new value with just @samp{set width=13}, because @value{GDBN} has the
15760 command @code{set width}:
15763 (@value{GDBP}) whatis width
15765 (@value{GDBP}) p width
15767 (@value{GDBP}) set width=47
15768 Invalid syntax in expression.
15772 The invalid expression, of course, is @samp{=47}. In
15773 order to actually set the program's variable @code{width}, use
15776 (@value{GDBP}) set var width=47
15779 Because the @code{set} command has many subcommands that can conflict
15780 with the names of program variables, it is a good idea to use the
15781 @code{set variable} command instead of just @code{set}. For example, if
15782 your program has a variable @code{g}, you run into problems if you try
15783 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15784 the command @code{set gnutarget}, abbreviated @code{set g}:
15788 (@value{GDBP}) whatis g
15792 (@value{GDBP}) set g=4
15796 The program being debugged has been started already.
15797 Start it from the beginning? (y or n) y
15798 Starting program: /home/smith/cc_progs/a.out
15799 "/home/smith/cc_progs/a.out": can't open to read symbols:
15800 Invalid bfd target.
15801 (@value{GDBP}) show g
15802 The current BFD target is "=4".
15807 The program variable @code{g} did not change, and you silently set the
15808 @code{gnutarget} to an invalid value. In order to set the variable
15812 (@value{GDBP}) set var g=4
15815 @value{GDBN} allows more implicit conversions in assignments than C; you can
15816 freely store an integer value into a pointer variable or vice versa,
15817 and you can convert any structure to any other structure that is the
15818 same length or shorter.
15819 @comment FIXME: how do structs align/pad in these conversions?
15820 @comment /doc@cygnus.com 18dec1990
15822 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15823 construct to generate a value of specified type at a specified address
15824 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15825 to memory location @code{0x83040} as an integer (which implies a certain size
15826 and representation in memory), and
15829 set @{int@}0x83040 = 4
15833 stores the value 4 into that memory location.
15836 @section Continuing at a Different Address
15838 Ordinarily, when you continue your program, you do so at the place where
15839 it stopped, with the @code{continue} command. You can instead continue at
15840 an address of your own choosing, with the following commands:
15844 @kindex j @r{(@code{jump})}
15845 @item jump @var{linespec}
15846 @itemx j @var{linespec}
15847 @itemx jump @var{location}
15848 @itemx j @var{location}
15849 Resume execution at line @var{linespec} or at address given by
15850 @var{location}. Execution stops again immediately if there is a
15851 breakpoint there. @xref{Specify Location}, for a description of the
15852 different forms of @var{linespec} and @var{location}. It is common
15853 practice to use the @code{tbreak} command in conjunction with
15854 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15856 The @code{jump} command does not change the current stack frame, or
15857 the stack pointer, or the contents of any memory location or any
15858 register other than the program counter. If line @var{linespec} is in
15859 a different function from the one currently executing, the results may
15860 be bizarre if the two functions expect different patterns of arguments or
15861 of local variables. For this reason, the @code{jump} command requests
15862 confirmation if the specified line is not in the function currently
15863 executing. However, even bizarre results are predictable if you are
15864 well acquainted with the machine-language code of your program.
15867 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15868 On many systems, you can get much the same effect as the @code{jump}
15869 command by storing a new value into the register @code{$pc}. The
15870 difference is that this does not start your program running; it only
15871 changes the address of where it @emph{will} run when you continue. For
15879 makes the next @code{continue} command or stepping command execute at
15880 address @code{0x485}, rather than at the address where your program stopped.
15881 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15883 The most common occasion to use the @code{jump} command is to back
15884 up---perhaps with more breakpoints set---over a portion of a program
15885 that has already executed, in order to examine its execution in more
15890 @section Giving your Program a Signal
15891 @cindex deliver a signal to a program
15895 @item signal @var{signal}
15896 Resume execution where your program stopped, but immediately give it the
15897 signal @var{signal}. @var{signal} can be the name or the number of a
15898 signal. For example, on many systems @code{signal 2} and @code{signal
15899 SIGINT} are both ways of sending an interrupt signal.
15901 Alternatively, if @var{signal} is zero, continue execution without
15902 giving a signal. This is useful when your program stopped on account of
15903 a signal and would ordinarily see the signal when resumed with the
15904 @code{continue} command; @samp{signal 0} causes it to resume without a
15907 @code{signal} does not repeat when you press @key{RET} a second time
15908 after executing the command.
15912 Invoking the @code{signal} command is not the same as invoking the
15913 @code{kill} utility from the shell. Sending a signal with @code{kill}
15914 causes @value{GDBN} to decide what to do with the signal depending on
15915 the signal handling tables (@pxref{Signals}). The @code{signal} command
15916 passes the signal directly to your program.
15920 @section Returning from a Function
15923 @cindex returning from a function
15926 @itemx return @var{expression}
15927 You can cancel execution of a function call with the @code{return}
15928 command. If you give an
15929 @var{expression} argument, its value is used as the function's return
15933 When you use @code{return}, @value{GDBN} discards the selected stack frame
15934 (and all frames within it). You can think of this as making the
15935 discarded frame return prematurely. If you wish to specify a value to
15936 be returned, give that value as the argument to @code{return}.
15938 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15939 Frame}), and any other frames inside of it, leaving its caller as the
15940 innermost remaining frame. That frame becomes selected. The
15941 specified value is stored in the registers used for returning values
15944 The @code{return} command does not resume execution; it leaves the
15945 program stopped in the state that would exist if the function had just
15946 returned. In contrast, the @code{finish} command (@pxref{Continuing
15947 and Stepping, ,Continuing and Stepping}) resumes execution until the
15948 selected stack frame returns naturally.
15950 @value{GDBN} needs to know how the @var{expression} argument should be set for
15951 the inferior. The concrete registers assignment depends on the OS ABI and the
15952 type being returned by the selected stack frame. For example it is common for
15953 OS ABI to return floating point values in FPU registers while integer values in
15954 CPU registers. Still some ABIs return even floating point values in CPU
15955 registers. Larger integer widths (such as @code{long long int}) also have
15956 specific placement rules. @value{GDBN} already knows the OS ABI from its
15957 current target so it needs to find out also the type being returned to make the
15958 assignment into the right register(s).
15960 Normally, the selected stack frame has debug info. @value{GDBN} will always
15961 use the debug info instead of the implicit type of @var{expression} when the
15962 debug info is available. For example, if you type @kbd{return -1}, and the
15963 function in the current stack frame is declared to return a @code{long long
15964 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15965 into a @code{long long int}:
15968 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15970 (@value{GDBP}) return -1
15971 Make func return now? (y or n) y
15972 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15973 43 printf ("result=%lld\n", func ());
15977 However, if the selected stack frame does not have a debug info, e.g., if the
15978 function was compiled without debug info, @value{GDBN} has to find out the type
15979 to return from user. Specifying a different type by mistake may set the value
15980 in different inferior registers than the caller code expects. For example,
15981 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15982 of a @code{long long int} result for a debug info less function (on 32-bit
15983 architectures). Therefore the user is required to specify the return type by
15984 an appropriate cast explicitly:
15987 Breakpoint 2, 0x0040050b in func ()
15988 (@value{GDBP}) return -1
15989 Return value type not available for selected stack frame.
15990 Please use an explicit cast of the value to return.
15991 (@value{GDBP}) return (long long int) -1
15992 Make selected stack frame return now? (y or n) y
15993 #0 0x00400526 in main ()
15998 @section Calling Program Functions
16001 @cindex calling functions
16002 @cindex inferior functions, calling
16003 @item print @var{expr}
16004 Evaluate the expression @var{expr} and display the resulting value.
16005 @var{expr} may include calls to functions in the program being
16009 @item call @var{expr}
16010 Evaluate the expression @var{expr} without displaying @code{void}
16013 You can use this variant of the @code{print} command if you want to
16014 execute a function from your program that does not return anything
16015 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16016 with @code{void} returned values that @value{GDBN} will otherwise
16017 print. If the result is not void, it is printed and saved in the
16021 It is possible for the function you call via the @code{print} or
16022 @code{call} command to generate a signal (e.g., if there's a bug in
16023 the function, or if you passed it incorrect arguments). What happens
16024 in that case is controlled by the @code{set unwindonsignal} command.
16026 Similarly, with a C@t{++} program it is possible for the function you
16027 call via the @code{print} or @code{call} command to generate an
16028 exception that is not handled due to the constraints of the dummy
16029 frame. In this case, any exception that is raised in the frame, but has
16030 an out-of-frame exception handler will not be found. GDB builds a
16031 dummy-frame for the inferior function call, and the unwinder cannot
16032 seek for exception handlers outside of this dummy-frame. What happens
16033 in that case is controlled by the
16034 @code{set unwind-on-terminating-exception} command.
16037 @item set unwindonsignal
16038 @kindex set unwindonsignal
16039 @cindex unwind stack in called functions
16040 @cindex call dummy stack unwinding
16041 Set unwinding of the stack if a signal is received while in a function
16042 that @value{GDBN} called in the program being debugged. If set to on,
16043 @value{GDBN} unwinds the stack it created for the call and restores
16044 the context to what it was before the call. If set to off (the
16045 default), @value{GDBN} stops in the frame where the signal was
16048 @item show unwindonsignal
16049 @kindex show unwindonsignal
16050 Show the current setting of stack unwinding in the functions called by
16053 @item set unwind-on-terminating-exception
16054 @kindex set unwind-on-terminating-exception
16055 @cindex unwind stack in called functions with unhandled exceptions
16056 @cindex call dummy stack unwinding on unhandled exception.
16057 Set unwinding of the stack if a C@t{++} exception is raised, but left
16058 unhandled while in a function that @value{GDBN} called in the program being
16059 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16060 it created for the call and restores the context to what it was before
16061 the call. If set to off, @value{GDBN} the exception is delivered to
16062 the default C@t{++} exception handler and the inferior terminated.
16064 @item show unwind-on-terminating-exception
16065 @kindex show unwind-on-terminating-exception
16066 Show the current setting of stack unwinding in the functions called by
16071 @cindex weak alias functions
16072 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16073 for another function. In such case, @value{GDBN} might not pick up
16074 the type information, including the types of the function arguments,
16075 which causes @value{GDBN} to call the inferior function incorrectly.
16076 As a result, the called function will function erroneously and may
16077 even crash. A solution to that is to use the name of the aliased
16081 @section Patching Programs
16083 @cindex patching binaries
16084 @cindex writing into executables
16085 @cindex writing into corefiles
16087 By default, @value{GDBN} opens the file containing your program's
16088 executable code (or the corefile) read-only. This prevents accidental
16089 alterations to machine code; but it also prevents you from intentionally
16090 patching your program's binary.
16092 If you'd like to be able to patch the binary, you can specify that
16093 explicitly with the @code{set write} command. For example, you might
16094 want to turn on internal debugging flags, or even to make emergency
16100 @itemx set write off
16101 If you specify @samp{set write on}, @value{GDBN} opens executable and
16102 core files for both reading and writing; if you specify @kbd{set write
16103 off} (the default), @value{GDBN} opens them read-only.
16105 If you have already loaded a file, you must load it again (using the
16106 @code{exec-file} or @code{core-file} command) after changing @code{set
16107 write}, for your new setting to take effect.
16111 Display whether executable files and core files are opened for writing
16112 as well as reading.
16116 @chapter @value{GDBN} Files
16118 @value{GDBN} needs to know the file name of the program to be debugged,
16119 both in order to read its symbol table and in order to start your
16120 program. To debug a core dump of a previous run, you must also tell
16121 @value{GDBN} the name of the core dump file.
16124 * Files:: Commands to specify files
16125 * Separate Debug Files:: Debugging information in separate files
16126 * MiniDebugInfo:: Debugging information in a special section
16127 * Index Files:: Index files speed up GDB
16128 * Symbol Errors:: Errors reading symbol files
16129 * Data Files:: GDB data files
16133 @section Commands to Specify Files
16135 @cindex symbol table
16136 @cindex core dump file
16138 You may want to specify executable and core dump file names. The usual
16139 way to do this is at start-up time, using the arguments to
16140 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16141 Out of @value{GDBN}}).
16143 Occasionally it is necessary to change to a different file during a
16144 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16145 specify a file you want to use. Or you are debugging a remote target
16146 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16147 Program}). In these situations the @value{GDBN} commands to specify
16148 new files are useful.
16151 @cindex executable file
16153 @item file @var{filename}
16154 Use @var{filename} as the program to be debugged. It is read for its
16155 symbols and for the contents of pure memory. It is also the program
16156 executed when you use the @code{run} command. If you do not specify a
16157 directory and the file is not found in the @value{GDBN} working directory,
16158 @value{GDBN} uses the environment variable @code{PATH} as a list of
16159 directories to search, just as the shell does when looking for a program
16160 to run. You can change the value of this variable, for both @value{GDBN}
16161 and your program, using the @code{path} command.
16163 @cindex unlinked object files
16164 @cindex patching object files
16165 You can load unlinked object @file{.o} files into @value{GDBN} using
16166 the @code{file} command. You will not be able to ``run'' an object
16167 file, but you can disassemble functions and inspect variables. Also,
16168 if the underlying BFD functionality supports it, you could use
16169 @kbd{gdb -write} to patch object files using this technique. Note
16170 that @value{GDBN} can neither interpret nor modify relocations in this
16171 case, so branches and some initialized variables will appear to go to
16172 the wrong place. But this feature is still handy from time to time.
16175 @code{file} with no argument makes @value{GDBN} discard any information it
16176 has on both executable file and the symbol table.
16179 @item exec-file @r{[} @var{filename} @r{]}
16180 Specify that the program to be run (but not the symbol table) is found
16181 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16182 if necessary to locate your program. Omitting @var{filename} means to
16183 discard information on the executable file.
16185 @kindex symbol-file
16186 @item symbol-file @r{[} @var{filename} @r{]}
16187 Read symbol table information from file @var{filename}. @code{PATH} is
16188 searched when necessary. Use the @code{file} command to get both symbol
16189 table and program to run from the same file.
16191 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16192 program's symbol table.
16194 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16195 some breakpoints and auto-display expressions. This is because they may
16196 contain pointers to the internal data recording symbols and data types,
16197 which are part of the old symbol table data being discarded inside
16200 @code{symbol-file} does not repeat if you press @key{RET} again after
16203 When @value{GDBN} is configured for a particular environment, it
16204 understands debugging information in whatever format is the standard
16205 generated for that environment; you may use either a @sc{gnu} compiler, or
16206 other compilers that adhere to the local conventions.
16207 Best results are usually obtained from @sc{gnu} compilers; for example,
16208 using @code{@value{NGCC}} you can generate debugging information for
16211 For most kinds of object files, with the exception of old SVR3 systems
16212 using COFF, the @code{symbol-file} command does not normally read the
16213 symbol table in full right away. Instead, it scans the symbol table
16214 quickly to find which source files and which symbols are present. The
16215 details are read later, one source file at a time, as they are needed.
16217 The purpose of this two-stage reading strategy is to make @value{GDBN}
16218 start up faster. For the most part, it is invisible except for
16219 occasional pauses while the symbol table details for a particular source
16220 file are being read. (The @code{set verbose} command can turn these
16221 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16222 Warnings and Messages}.)
16224 We have not implemented the two-stage strategy for COFF yet. When the
16225 symbol table is stored in COFF format, @code{symbol-file} reads the
16226 symbol table data in full right away. Note that ``stabs-in-COFF''
16227 still does the two-stage strategy, since the debug info is actually
16231 @cindex reading symbols immediately
16232 @cindex symbols, reading immediately
16233 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16234 @itemx file @r{[} -readnow @r{]} @var{filename}
16235 You can override the @value{GDBN} two-stage strategy for reading symbol
16236 tables by using the @samp{-readnow} option with any of the commands that
16237 load symbol table information, if you want to be sure @value{GDBN} has the
16238 entire symbol table available.
16240 @c FIXME: for now no mention of directories, since this seems to be in
16241 @c flux. 13mar1992 status is that in theory GDB would look either in
16242 @c current dir or in same dir as myprog; but issues like competing
16243 @c GDB's, or clutter in system dirs, mean that in practice right now
16244 @c only current dir is used. FFish says maybe a special GDB hierarchy
16245 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16249 @item core-file @r{[}@var{filename}@r{]}
16251 Specify the whereabouts of a core dump file to be used as the ``contents
16252 of memory''. Traditionally, core files contain only some parts of the
16253 address space of the process that generated them; @value{GDBN} can access the
16254 executable file itself for other parts.
16256 @code{core-file} with no argument specifies that no core file is
16259 Note that the core file is ignored when your program is actually running
16260 under @value{GDBN}. So, if you have been running your program and you
16261 wish to debug a core file instead, you must kill the subprocess in which
16262 the program is running. To do this, use the @code{kill} command
16263 (@pxref{Kill Process, ,Killing the Child Process}).
16265 @kindex add-symbol-file
16266 @cindex dynamic linking
16267 @item add-symbol-file @var{filename} @var{address}
16268 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16269 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16270 The @code{add-symbol-file} command reads additional symbol table
16271 information from the file @var{filename}. You would use this command
16272 when @var{filename} has been dynamically loaded (by some other means)
16273 into the program that is running. @var{address} should be the memory
16274 address at which the file has been loaded; @value{GDBN} cannot figure
16275 this out for itself. You can additionally specify an arbitrary number
16276 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16277 section name and base address for that section. You can specify any
16278 @var{address} as an expression.
16280 The symbol table of the file @var{filename} is added to the symbol table
16281 originally read with the @code{symbol-file} command. You can use the
16282 @code{add-symbol-file} command any number of times; the new symbol data
16283 thus read keeps adding to the old. To discard all old symbol data
16284 instead, use the @code{symbol-file} command without any arguments.
16286 @cindex relocatable object files, reading symbols from
16287 @cindex object files, relocatable, reading symbols from
16288 @cindex reading symbols from relocatable object files
16289 @cindex symbols, reading from relocatable object files
16290 @cindex @file{.o} files, reading symbols from
16291 Although @var{filename} is typically a shared library file, an
16292 executable file, or some other object file which has been fully
16293 relocated for loading into a process, you can also load symbolic
16294 information from relocatable @file{.o} files, as long as:
16298 the file's symbolic information refers only to linker symbols defined in
16299 that file, not to symbols defined by other object files,
16301 every section the file's symbolic information refers to has actually
16302 been loaded into the inferior, as it appears in the file, and
16304 you can determine the address at which every section was loaded, and
16305 provide these to the @code{add-symbol-file} command.
16309 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16310 relocatable files into an already running program; such systems
16311 typically make the requirements above easy to meet. However, it's
16312 important to recognize that many native systems use complex link
16313 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16314 assembly, for example) that make the requirements difficult to meet. In
16315 general, one cannot assume that using @code{add-symbol-file} to read a
16316 relocatable object file's symbolic information will have the same effect
16317 as linking the relocatable object file into the program in the normal
16320 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16322 @kindex add-symbol-file-from-memory
16323 @cindex @code{syscall DSO}
16324 @cindex load symbols from memory
16325 @item add-symbol-file-from-memory @var{address}
16326 Load symbols from the given @var{address} in a dynamically loaded
16327 object file whose image is mapped directly into the inferior's memory.
16328 For example, the Linux kernel maps a @code{syscall DSO} into each
16329 process's address space; this DSO provides kernel-specific code for
16330 some system calls. The argument can be any expression whose
16331 evaluation yields the address of the file's shared object file header.
16332 For this command to work, you must have used @code{symbol-file} or
16333 @code{exec-file} commands in advance.
16335 @kindex add-shared-symbol-files
16337 @item add-shared-symbol-files @var{library-file}
16338 @itemx assf @var{library-file}
16339 The @code{add-shared-symbol-files} command can currently be used only
16340 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16341 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16342 @value{GDBN} automatically looks for shared libraries, however if
16343 @value{GDBN} does not find yours, you can invoke
16344 @code{add-shared-symbol-files}. It takes one argument: the shared
16345 library's file name. @code{assf} is a shorthand alias for
16346 @code{add-shared-symbol-files}.
16349 @item section @var{section} @var{addr}
16350 The @code{section} command changes the base address of the named
16351 @var{section} of the exec file to @var{addr}. This can be used if the
16352 exec file does not contain section addresses, (such as in the
16353 @code{a.out} format), or when the addresses specified in the file
16354 itself are wrong. Each section must be changed separately. The
16355 @code{info files} command, described below, lists all the sections and
16359 @kindex info target
16362 @code{info files} and @code{info target} are synonymous; both print the
16363 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16364 including the names of the executable and core dump files currently in
16365 use by @value{GDBN}, and the files from which symbols were loaded. The
16366 command @code{help target} lists all possible targets rather than
16369 @kindex maint info sections
16370 @item maint info sections
16371 Another command that can give you extra information about program sections
16372 is @code{maint info sections}. In addition to the section information
16373 displayed by @code{info files}, this command displays the flags and file
16374 offset of each section in the executable and core dump files. In addition,
16375 @code{maint info sections} provides the following command options (which
16376 may be arbitrarily combined):
16380 Display sections for all loaded object files, including shared libraries.
16381 @item @var{sections}
16382 Display info only for named @var{sections}.
16383 @item @var{section-flags}
16384 Display info only for sections for which @var{section-flags} are true.
16385 The section flags that @value{GDBN} currently knows about are:
16388 Section will have space allocated in the process when loaded.
16389 Set for all sections except those containing debug information.
16391 Section will be loaded from the file into the child process memory.
16392 Set for pre-initialized code and data, clear for @code{.bss} sections.
16394 Section needs to be relocated before loading.
16396 Section cannot be modified by the child process.
16398 Section contains executable code only.
16400 Section contains data only (no executable code).
16402 Section will reside in ROM.
16404 Section contains data for constructor/destructor lists.
16406 Section is not empty.
16408 An instruction to the linker to not output the section.
16409 @item COFF_SHARED_LIBRARY
16410 A notification to the linker that the section contains
16411 COFF shared library information.
16413 Section contains common symbols.
16416 @kindex set trust-readonly-sections
16417 @cindex read-only sections
16418 @item set trust-readonly-sections on
16419 Tell @value{GDBN} that readonly sections in your object file
16420 really are read-only (i.e.@: that their contents will not change).
16421 In that case, @value{GDBN} can fetch values from these sections
16422 out of the object file, rather than from the target program.
16423 For some targets (notably embedded ones), this can be a significant
16424 enhancement to debugging performance.
16426 The default is off.
16428 @item set trust-readonly-sections off
16429 Tell @value{GDBN} not to trust readonly sections. This means that
16430 the contents of the section might change while the program is running,
16431 and must therefore be fetched from the target when needed.
16433 @item show trust-readonly-sections
16434 Show the current setting of trusting readonly sections.
16437 All file-specifying commands allow both absolute and relative file names
16438 as arguments. @value{GDBN} always converts the file name to an absolute file
16439 name and remembers it that way.
16441 @cindex shared libraries
16442 @anchor{Shared Libraries}
16443 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16444 and IBM RS/6000 AIX shared libraries.
16446 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16447 shared libraries. @xref{Expat}.
16449 @value{GDBN} automatically loads symbol definitions from shared libraries
16450 when you use the @code{run} command, or when you examine a core file.
16451 (Before you issue the @code{run} command, @value{GDBN} does not understand
16452 references to a function in a shared library, however---unless you are
16453 debugging a core file).
16455 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16456 automatically loads the symbols at the time of the @code{shl_load} call.
16458 @c FIXME: some @value{GDBN} release may permit some refs to undef
16459 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16460 @c FIXME...lib; check this from time to time when updating manual
16462 There are times, however, when you may wish to not automatically load
16463 symbol definitions from shared libraries, such as when they are
16464 particularly large or there are many of them.
16466 To control the automatic loading of shared library symbols, use the
16470 @kindex set auto-solib-add
16471 @item set auto-solib-add @var{mode}
16472 If @var{mode} is @code{on}, symbols from all shared object libraries
16473 will be loaded automatically when the inferior begins execution, you
16474 attach to an independently started inferior, or when the dynamic linker
16475 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16476 is @code{off}, symbols must be loaded manually, using the
16477 @code{sharedlibrary} command. The default value is @code{on}.
16479 @cindex memory used for symbol tables
16480 If your program uses lots of shared libraries with debug info that
16481 takes large amounts of memory, you can decrease the @value{GDBN}
16482 memory footprint by preventing it from automatically loading the
16483 symbols from shared libraries. To that end, type @kbd{set
16484 auto-solib-add off} before running the inferior, then load each
16485 library whose debug symbols you do need with @kbd{sharedlibrary
16486 @var{regexp}}, where @var{regexp} is a regular expression that matches
16487 the libraries whose symbols you want to be loaded.
16489 @kindex show auto-solib-add
16490 @item show auto-solib-add
16491 Display the current autoloading mode.
16494 @cindex load shared library
16495 To explicitly load shared library symbols, use the @code{sharedlibrary}
16499 @kindex info sharedlibrary
16501 @item info share @var{regex}
16502 @itemx info sharedlibrary @var{regex}
16503 Print the names of the shared libraries which are currently loaded
16504 that match @var{regex}. If @var{regex} is omitted then print
16505 all shared libraries that are loaded.
16507 @kindex sharedlibrary
16509 @item sharedlibrary @var{regex}
16510 @itemx share @var{regex}
16511 Load shared object library symbols for files matching a
16512 Unix regular expression.
16513 As with files loaded automatically, it only loads shared libraries
16514 required by your program for a core file or after typing @code{run}. If
16515 @var{regex} is omitted all shared libraries required by your program are
16518 @item nosharedlibrary
16519 @kindex nosharedlibrary
16520 @cindex unload symbols from shared libraries
16521 Unload all shared object library symbols. This discards all symbols
16522 that have been loaded from all shared libraries. Symbols from shared
16523 libraries that were loaded by explicit user requests are not
16527 Sometimes you may wish that @value{GDBN} stops and gives you control
16528 when any of shared library events happen. The best way to do this is
16529 to use @code{catch load} and @code{catch unload} (@pxref{Set
16532 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16533 command for this. This command exists for historical reasons. It is
16534 less useful than setting a catchpoint, because it does not allow for
16535 conditions or commands as a catchpoint does.
16538 @item set stop-on-solib-events
16539 @kindex set stop-on-solib-events
16540 This command controls whether @value{GDBN} should give you control
16541 when the dynamic linker notifies it about some shared library event.
16542 The most common event of interest is loading or unloading of a new
16545 @item show stop-on-solib-events
16546 @kindex show stop-on-solib-events
16547 Show whether @value{GDBN} stops and gives you control when shared
16548 library events happen.
16551 Shared libraries are also supported in many cross or remote debugging
16552 configurations. @value{GDBN} needs to have access to the target's libraries;
16553 this can be accomplished either by providing copies of the libraries
16554 on the host system, or by asking @value{GDBN} to automatically retrieve the
16555 libraries from the target. If copies of the target libraries are
16556 provided, they need to be the same as the target libraries, although the
16557 copies on the target can be stripped as long as the copies on the host are
16560 @cindex where to look for shared libraries
16561 For remote debugging, you need to tell @value{GDBN} where the target
16562 libraries are, so that it can load the correct copies---otherwise, it
16563 may try to load the host's libraries. @value{GDBN} has two variables
16564 to specify the search directories for target libraries.
16567 @cindex prefix for shared library file names
16568 @cindex system root, alternate
16569 @kindex set solib-absolute-prefix
16570 @kindex set sysroot
16571 @item set sysroot @var{path}
16572 Use @var{path} as the system root for the program being debugged. Any
16573 absolute shared library paths will be prefixed with @var{path}; many
16574 runtime loaders store the absolute paths to the shared library in the
16575 target program's memory. If you use @code{set sysroot} to find shared
16576 libraries, they need to be laid out in the same way that they are on
16577 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16580 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16581 retrieve the target libraries from the remote system. This is only
16582 supported when using a remote target that supports the @code{remote get}
16583 command (@pxref{File Transfer,,Sending files to a remote system}).
16584 The part of @var{path} following the initial @file{remote:}
16585 (if present) is used as system root prefix on the remote file system.
16586 @footnote{If you want to specify a local system root using a directory
16587 that happens to be named @file{remote:}, you need to use some equivalent
16588 variant of the name like @file{./remote:}.}
16590 For targets with an MS-DOS based filesystem, such as MS-Windows and
16591 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16592 absolute file name with @var{path}. But first, on Unix hosts,
16593 @value{GDBN} converts all backslash directory separators into forward
16594 slashes, because the backslash is not a directory separator on Unix:
16597 c:\foo\bar.dll @result{} c:/foo/bar.dll
16600 Then, @value{GDBN} attempts prefixing the target file name with
16601 @var{path}, and looks for the resulting file name in the host file
16605 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16608 If that does not find the shared library, @value{GDBN} tries removing
16609 the @samp{:} character from the drive spec, both for convenience, and,
16610 for the case of the host file system not supporting file names with
16614 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16617 This makes it possible to have a system root that mirrors a target
16618 with more than one drive. E.g., you may want to setup your local
16619 copies of the target system shared libraries like so (note @samp{c} vs
16623 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16624 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16625 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16629 and point the system root at @file{/path/to/sysroot}, so that
16630 @value{GDBN} can find the correct copies of both
16631 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16633 If that still does not find the shared library, @value{GDBN} tries
16634 removing the whole drive spec from the target file name:
16637 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16640 This last lookup makes it possible to not care about the drive name,
16641 if you don't want or need to.
16643 The @code{set solib-absolute-prefix} command is an alias for @code{set
16646 @cindex default system root
16647 @cindex @samp{--with-sysroot}
16648 You can set the default system root by using the configure-time
16649 @samp{--with-sysroot} option. If the system root is inside
16650 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16651 @samp{--exec-prefix}), then the default system root will be updated
16652 automatically if the installed @value{GDBN} is moved to a new
16655 @kindex show sysroot
16657 Display the current shared library prefix.
16659 @kindex set solib-search-path
16660 @item set solib-search-path @var{path}
16661 If this variable is set, @var{path} is a colon-separated list of
16662 directories to search for shared libraries. @samp{solib-search-path}
16663 is used after @samp{sysroot} fails to locate the library, or if the
16664 path to the library is relative instead of absolute. If you want to
16665 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16666 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16667 finding your host's libraries. @samp{sysroot} is preferred; setting
16668 it to a nonexistent directory may interfere with automatic loading
16669 of shared library symbols.
16671 @kindex show solib-search-path
16672 @item show solib-search-path
16673 Display the current shared library search path.
16675 @cindex DOS file-name semantics of file names.
16676 @kindex set target-file-system-kind (unix|dos-based|auto)
16677 @kindex show target-file-system-kind
16678 @item set target-file-system-kind @var{kind}
16679 Set assumed file system kind for target reported file names.
16681 Shared library file names as reported by the target system may not
16682 make sense as is on the system @value{GDBN} is running on. For
16683 example, when remote debugging a target that has MS-DOS based file
16684 system semantics, from a Unix host, the target may be reporting to
16685 @value{GDBN} a list of loaded shared libraries with file names such as
16686 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16687 drive letters, so the @samp{c:\} prefix is not normally understood as
16688 indicating an absolute file name, and neither is the backslash
16689 normally considered a directory separator character. In that case,
16690 the native file system would interpret this whole absolute file name
16691 as a relative file name with no directory components. This would make
16692 it impossible to point @value{GDBN} at a copy of the remote target's
16693 shared libraries on the host using @code{set sysroot}, and impractical
16694 with @code{set solib-search-path}. Setting
16695 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16696 to interpret such file names similarly to how the target would, and to
16697 map them to file names valid on @value{GDBN}'s native file system
16698 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16699 to one of the supported file system kinds. In that case, @value{GDBN}
16700 tries to determine the appropriate file system variant based on the
16701 current target's operating system (@pxref{ABI, ,Configuring the
16702 Current ABI}). The supported file system settings are:
16706 Instruct @value{GDBN} to assume the target file system is of Unix
16707 kind. Only file names starting the forward slash (@samp{/}) character
16708 are considered absolute, and the directory separator character is also
16712 Instruct @value{GDBN} to assume the target file system is DOS based.
16713 File names starting with either a forward slash, or a drive letter
16714 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16715 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16716 considered directory separators.
16719 Instruct @value{GDBN} to use the file system kind associated with the
16720 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16721 This is the default.
16725 @cindex file name canonicalization
16726 @cindex base name differences
16727 When processing file names provided by the user, @value{GDBN}
16728 frequently needs to compare them to the file names recorded in the
16729 program's debug info. Normally, @value{GDBN} compares just the
16730 @dfn{base names} of the files as strings, which is reasonably fast
16731 even for very large programs. (The base name of a file is the last
16732 portion of its name, after stripping all the leading directories.)
16733 This shortcut in comparison is based upon the assumption that files
16734 cannot have more than one base name. This is usually true, but
16735 references to files that use symlinks or similar filesystem
16736 facilities violate that assumption. If your program records files
16737 using such facilities, or if you provide file names to @value{GDBN}
16738 using symlinks etc., you can set @code{basenames-may-differ} to
16739 @code{true} to instruct @value{GDBN} to completely canonicalize each
16740 pair of file names it needs to compare. This will make file-name
16741 comparisons accurate, but at a price of a significant slowdown.
16744 @item set basenames-may-differ
16745 @kindex set basenames-may-differ
16746 Set whether a source file may have multiple base names.
16748 @item show basenames-may-differ
16749 @kindex show basenames-may-differ
16750 Show whether a source file may have multiple base names.
16753 @node Separate Debug Files
16754 @section Debugging Information in Separate Files
16755 @cindex separate debugging information files
16756 @cindex debugging information in separate files
16757 @cindex @file{.debug} subdirectories
16758 @cindex debugging information directory, global
16759 @cindex global debugging information directories
16760 @cindex build ID, and separate debugging files
16761 @cindex @file{.build-id} directory
16763 @value{GDBN} allows you to put a program's debugging information in a
16764 file separate from the executable itself, in a way that allows
16765 @value{GDBN} to find and load the debugging information automatically.
16766 Since debugging information can be very large---sometimes larger
16767 than the executable code itself---some systems distribute debugging
16768 information for their executables in separate files, which users can
16769 install only when they need to debug a problem.
16771 @value{GDBN} supports two ways of specifying the separate debug info
16776 The executable contains a @dfn{debug link} that specifies the name of
16777 the separate debug info file. The separate debug file's name is
16778 usually @file{@var{executable}.debug}, where @var{executable} is the
16779 name of the corresponding executable file without leading directories
16780 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16781 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16782 checksum for the debug file, which @value{GDBN} uses to validate that
16783 the executable and the debug file came from the same build.
16786 The executable contains a @dfn{build ID}, a unique bit string that is
16787 also present in the corresponding debug info file. (This is supported
16788 only on some operating systems, notably those which use the ELF format
16789 for binary files and the @sc{gnu} Binutils.) For more details about
16790 this feature, see the description of the @option{--build-id}
16791 command-line option in @ref{Options, , Command Line Options, ld.info,
16792 The GNU Linker}. The debug info file's name is not specified
16793 explicitly by the build ID, but can be computed from the build ID, see
16797 Depending on the way the debug info file is specified, @value{GDBN}
16798 uses two different methods of looking for the debug file:
16802 For the ``debug link'' method, @value{GDBN} looks up the named file in
16803 the directory of the executable file, then in a subdirectory of that
16804 directory named @file{.debug}, and finally under each one of the global debug
16805 directories, in a subdirectory whose name is identical to the leading
16806 directories of the executable's absolute file name.
16809 For the ``build ID'' method, @value{GDBN} looks in the
16810 @file{.build-id} subdirectory of each one of the global debug directories for
16811 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16812 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16813 are the rest of the bit string. (Real build ID strings are 32 or more
16814 hex characters, not 10.)
16817 So, for example, suppose you ask @value{GDBN} to debug
16818 @file{/usr/bin/ls}, which has a debug link that specifies the
16819 file @file{ls.debug}, and a build ID whose value in hex is
16820 @code{abcdef1234}. If the list of the global debug directories includes
16821 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16822 debug information files, in the indicated order:
16826 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16828 @file{/usr/bin/ls.debug}
16830 @file{/usr/bin/.debug/ls.debug}
16832 @file{/usr/lib/debug/usr/bin/ls.debug}.
16835 @anchor{debug-file-directory}
16836 Global debugging info directories default to what is set by @value{GDBN}
16837 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16838 you can also set the global debugging info directories, and view the list
16839 @value{GDBN} is currently using.
16843 @kindex set debug-file-directory
16844 @item set debug-file-directory @var{directories}
16845 Set the directories which @value{GDBN} searches for separate debugging
16846 information files to @var{directory}. Multiple path components can be set
16847 concatenating them by a path separator.
16849 @kindex show debug-file-directory
16850 @item show debug-file-directory
16851 Show the directories @value{GDBN} searches for separate debugging
16856 @cindex @code{.gnu_debuglink} sections
16857 @cindex debug link sections
16858 A debug link is a special section of the executable file named
16859 @code{.gnu_debuglink}. The section must contain:
16863 A filename, with any leading directory components removed, followed by
16866 zero to three bytes of padding, as needed to reach the next four-byte
16867 boundary within the section, and
16869 a four-byte CRC checksum, stored in the same endianness used for the
16870 executable file itself. The checksum is computed on the debugging
16871 information file's full contents by the function given below, passing
16872 zero as the @var{crc} argument.
16875 Any executable file format can carry a debug link, as long as it can
16876 contain a section named @code{.gnu_debuglink} with the contents
16879 @cindex @code{.note.gnu.build-id} sections
16880 @cindex build ID sections
16881 The build ID is a special section in the executable file (and in other
16882 ELF binary files that @value{GDBN} may consider). This section is
16883 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16884 It contains unique identification for the built files---the ID remains
16885 the same across multiple builds of the same build tree. The default
16886 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16887 content for the build ID string. The same section with an identical
16888 value is present in the original built binary with symbols, in its
16889 stripped variant, and in the separate debugging information file.
16891 The debugging information file itself should be an ordinary
16892 executable, containing a full set of linker symbols, sections, and
16893 debugging information. The sections of the debugging information file
16894 should have the same names, addresses, and sizes as the original file,
16895 but they need not contain any data---much like a @code{.bss} section
16896 in an ordinary executable.
16898 The @sc{gnu} binary utilities (Binutils) package includes the
16899 @samp{objcopy} utility that can produce
16900 the separated executable / debugging information file pairs using the
16901 following commands:
16904 @kbd{objcopy --only-keep-debug foo foo.debug}
16909 These commands remove the debugging
16910 information from the executable file @file{foo} and place it in the file
16911 @file{foo.debug}. You can use the first, second or both methods to link the
16916 The debug link method needs the following additional command to also leave
16917 behind a debug link in @file{foo}:
16920 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16923 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16924 a version of the @code{strip} command such that the command @kbd{strip foo -f
16925 foo.debug} has the same functionality as the two @code{objcopy} commands and
16926 the @code{ln -s} command above, together.
16929 Build ID gets embedded into the main executable using @code{ld --build-id} or
16930 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16931 compatibility fixes for debug files separation are present in @sc{gnu} binary
16932 utilities (Binutils) package since version 2.18.
16937 @cindex CRC algorithm definition
16938 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16939 IEEE 802.3 using the polynomial:
16941 @c TexInfo requires naked braces for multi-digit exponents for Tex
16942 @c output, but this causes HTML output to barf. HTML has to be set using
16943 @c raw commands. So we end up having to specify this equation in 2
16948 <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>
16949 + <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
16955 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16956 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16960 The function is computed byte at a time, taking the least
16961 significant bit of each byte first. The initial pattern
16962 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16963 the final result is inverted to ensure trailing zeros also affect the
16966 @emph{Note:} This is the same CRC polynomial as used in handling the
16967 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16968 , @value{GDBN} Remote Serial Protocol}). However in the
16969 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16970 significant bit first, and the result is not inverted, so trailing
16971 zeros have no effect on the CRC value.
16973 To complete the description, we show below the code of the function
16974 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16975 initially supplied @code{crc} argument means that an initial call to
16976 this function passing in zero will start computing the CRC using
16979 @kindex gnu_debuglink_crc32
16982 gnu_debuglink_crc32 (unsigned long crc,
16983 unsigned char *buf, size_t len)
16985 static const unsigned long crc32_table[256] =
16987 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16988 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16989 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16990 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16991 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16992 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16993 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16994 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16995 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16996 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16997 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16998 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16999 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17000 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17001 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17002 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17003 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17004 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17005 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17006 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17007 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17008 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17009 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17010 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17011 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17012 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17013 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17014 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17015 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17016 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17017 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17018 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17019 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17020 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17021 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17022 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17023 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17024 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17025 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17026 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17027 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17028 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17029 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17030 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17031 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17032 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17033 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17034 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17035 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17036 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17037 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17040 unsigned char *end;
17042 crc = ~crc & 0xffffffff;
17043 for (end = buf + len; buf < end; ++buf)
17044 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17045 return ~crc & 0xffffffff;
17050 This computation does not apply to the ``build ID'' method.
17052 @node MiniDebugInfo
17053 @section Debugging information in a special section
17054 @cindex separate debug sections
17055 @cindex @samp{.gnu_debugdata} section
17057 Some systems ship pre-built executables and libraries that have a
17058 special @samp{.gnu_debugdata} section. This feature is called
17059 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17060 is used to supply extra symbols for backtraces.
17062 The intent of this section is to provide extra minimal debugging
17063 information for use in simple backtraces. It is not intended to be a
17064 replacement for full separate debugging information (@pxref{Separate
17065 Debug Files}). The example below shows the intended use; however,
17066 @value{GDBN} does not currently put restrictions on what sort of
17067 debugging information might be included in the section.
17069 @value{GDBN} has support for this extension. If the section exists,
17070 then it is used provided that no other source of debugging information
17071 can be found, and that @value{GDBN} was configured with LZMA support.
17073 This section can be easily created using @command{objcopy} and other
17074 standard utilities:
17077 # Extract the dynamic symbols from the main binary, there is no need
17078 # to also have these in the normal symbol table
17079 nm -D @var{binary} --format=posix --defined-only \
17080 | awk '@{ print $1 @}' | sort > dynsyms
17082 # Extract all the text (i.e. function) symbols from the debuginfo .
17083 nm @var{binary} --format=posix --defined-only \
17084 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17087 # Keep all the function symbols not already in the dynamic symbol
17089 comm -13 dynsyms funcsyms > keep_symbols
17091 # Copy the full debuginfo, keeping only a minimal set of symbols and
17092 # removing some unnecessary sections.
17093 objcopy -S --remove-section .gdb_index --remove-section .comment \
17094 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17096 # Inject the compressed data into the .gnu_debugdata section of the
17099 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17103 @section Index Files Speed Up @value{GDBN}
17104 @cindex index files
17105 @cindex @samp{.gdb_index} section
17107 When @value{GDBN} finds a symbol file, it scans the symbols in the
17108 file in order to construct an internal symbol table. This lets most
17109 @value{GDBN} operations work quickly---at the cost of a delay early
17110 on. For large programs, this delay can be quite lengthy, so
17111 @value{GDBN} provides a way to build an index, which speeds up
17114 The index is stored as a section in the symbol file. @value{GDBN} can
17115 write the index to a file, then you can put it into the symbol file
17116 using @command{objcopy}.
17118 To create an index file, use the @code{save gdb-index} command:
17121 @item save gdb-index @var{directory}
17122 @kindex save gdb-index
17123 Create an index file for each symbol file currently known by
17124 @value{GDBN}. Each file is named after its corresponding symbol file,
17125 with @samp{.gdb-index} appended, and is written into the given
17129 Once you have created an index file you can merge it into your symbol
17130 file, here named @file{symfile}, using @command{objcopy}:
17133 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17134 --set-section-flags .gdb_index=readonly symfile symfile
17137 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17138 sections that have been deprecated. Usually they are deprecated because
17139 they are missing a new feature or have performance issues.
17140 To tell @value{GDBN} to use a deprecated index section anyway
17141 specify @code{set use-deprecated-index-sections on}.
17142 The default is @code{off}.
17143 This can speed up startup, but may result in some functionality being lost.
17144 @xref{Index Section Format}.
17146 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17147 must be done before gdb reads the file. The following will not work:
17150 $ gdb -ex "set use-deprecated-index-sections on" <program>
17153 Instead you must do, for example,
17156 $ gdb -iex "set use-deprecated-index-sections on" <program>
17159 There are currently some limitation on indices. They only work when
17160 for DWARF debugging information, not stabs. And, they do not
17161 currently work for programs using Ada.
17163 @node Symbol Errors
17164 @section Errors Reading Symbol Files
17166 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17167 such as symbol types it does not recognize, or known bugs in compiler
17168 output. By default, @value{GDBN} does not notify you of such problems, since
17169 they are relatively common and primarily of interest to people
17170 debugging compilers. If you are interested in seeing information
17171 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17172 only one message about each such type of problem, no matter how many
17173 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17174 to see how many times the problems occur, with the @code{set
17175 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17178 The messages currently printed, and their meanings, include:
17181 @item inner block not inside outer block in @var{symbol}
17183 The symbol information shows where symbol scopes begin and end
17184 (such as at the start of a function or a block of statements). This
17185 error indicates that an inner scope block is not fully contained
17186 in its outer scope blocks.
17188 @value{GDBN} circumvents the problem by treating the inner block as if it had
17189 the same scope as the outer block. In the error message, @var{symbol}
17190 may be shown as ``@code{(don't know)}'' if the outer block is not a
17193 @item block at @var{address} out of order
17195 The symbol information for symbol scope blocks should occur in
17196 order of increasing addresses. This error indicates that it does not
17199 @value{GDBN} does not circumvent this problem, and has trouble
17200 locating symbols in the source file whose symbols it is reading. (You
17201 can often determine what source file is affected by specifying
17202 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17205 @item bad block start address patched
17207 The symbol information for a symbol scope block has a start address
17208 smaller than the address of the preceding source line. This is known
17209 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17211 @value{GDBN} circumvents the problem by treating the symbol scope block as
17212 starting on the previous source line.
17214 @item bad string table offset in symbol @var{n}
17217 Symbol number @var{n} contains a pointer into the string table which is
17218 larger than the size of the string table.
17220 @value{GDBN} circumvents the problem by considering the symbol to have the
17221 name @code{foo}, which may cause other problems if many symbols end up
17224 @item unknown symbol type @code{0x@var{nn}}
17226 The symbol information contains new data types that @value{GDBN} does
17227 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17228 uncomprehended information, in hexadecimal.
17230 @value{GDBN} circumvents the error by ignoring this symbol information.
17231 This usually allows you to debug your program, though certain symbols
17232 are not accessible. If you encounter such a problem and feel like
17233 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17234 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17235 and examine @code{*bufp} to see the symbol.
17237 @item stub type has NULL name
17239 @value{GDBN} could not find the full definition for a struct or class.
17241 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17242 The symbol information for a C@t{++} member function is missing some
17243 information that recent versions of the compiler should have output for
17246 @item info mismatch between compiler and debugger
17248 @value{GDBN} could not parse a type specification output by the compiler.
17253 @section GDB Data Files
17255 @cindex prefix for data files
17256 @value{GDBN} will sometimes read an auxiliary data file. These files
17257 are kept in a directory known as the @dfn{data directory}.
17259 You can set the data directory's name, and view the name @value{GDBN}
17260 is currently using.
17263 @kindex set data-directory
17264 @item set data-directory @var{directory}
17265 Set the directory which @value{GDBN} searches for auxiliary data files
17266 to @var{directory}.
17268 @kindex show data-directory
17269 @item show data-directory
17270 Show the directory @value{GDBN} searches for auxiliary data files.
17273 @cindex default data directory
17274 @cindex @samp{--with-gdb-datadir}
17275 You can set the default data directory by using the configure-time
17276 @samp{--with-gdb-datadir} option. If the data directory is inside
17277 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17278 @samp{--exec-prefix}), then the default data directory will be updated
17279 automatically if the installed @value{GDBN} is moved to a new
17282 The data directory may also be specified with the
17283 @code{--data-directory} command line option.
17284 @xref{Mode Options}.
17287 @chapter Specifying a Debugging Target
17289 @cindex debugging target
17290 A @dfn{target} is the execution environment occupied by your program.
17292 Often, @value{GDBN} runs in the same host environment as your program;
17293 in that case, the debugging target is specified as a side effect when
17294 you use the @code{file} or @code{core} commands. When you need more
17295 flexibility---for example, running @value{GDBN} on a physically separate
17296 host, or controlling a standalone system over a serial port or a
17297 realtime system over a TCP/IP connection---you can use the @code{target}
17298 command to specify one of the target types configured for @value{GDBN}
17299 (@pxref{Target Commands, ,Commands for Managing Targets}).
17301 @cindex target architecture
17302 It is possible to build @value{GDBN} for several different @dfn{target
17303 architectures}. When @value{GDBN} is built like that, you can choose
17304 one of the available architectures with the @kbd{set architecture}
17308 @kindex set architecture
17309 @kindex show architecture
17310 @item set architecture @var{arch}
17311 This command sets the current target architecture to @var{arch}. The
17312 value of @var{arch} can be @code{"auto"}, in addition to one of the
17313 supported architectures.
17315 @item show architecture
17316 Show the current target architecture.
17318 @item set processor
17320 @kindex set processor
17321 @kindex show processor
17322 These are alias commands for, respectively, @code{set architecture}
17323 and @code{show architecture}.
17327 * Active Targets:: Active targets
17328 * Target Commands:: Commands for managing targets
17329 * Byte Order:: Choosing target byte order
17332 @node Active Targets
17333 @section Active Targets
17335 @cindex stacking targets
17336 @cindex active targets
17337 @cindex multiple targets
17339 There are multiple classes of targets such as: processes, executable files or
17340 recording sessions. Core files belong to the process class, making core file
17341 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17342 on multiple active targets, one in each class. This allows you to (for
17343 example) start a process and inspect its activity, while still having access to
17344 the executable file after the process finishes. Or if you start process
17345 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17346 presented a virtual layer of the recording target, while the process target
17347 remains stopped at the chronologically last point of the process execution.
17349 Use the @code{core-file} and @code{exec-file} commands to select a new core
17350 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17351 specify as a target a process that is already running, use the @code{attach}
17352 command (@pxref{Attach, ,Debugging an Already-running Process}).
17354 @node Target Commands
17355 @section Commands for Managing Targets
17358 @item target @var{type} @var{parameters}
17359 Connects the @value{GDBN} host environment to a target machine or
17360 process. A target is typically a protocol for talking to debugging
17361 facilities. You use the argument @var{type} to specify the type or
17362 protocol of the target machine.
17364 Further @var{parameters} are interpreted by the target protocol, but
17365 typically include things like device names or host names to connect
17366 with, process numbers, and baud rates.
17368 The @code{target} command does not repeat if you press @key{RET} again
17369 after executing the command.
17371 @kindex help target
17373 Displays the names of all targets available. To display targets
17374 currently selected, use either @code{info target} or @code{info files}
17375 (@pxref{Files, ,Commands to Specify Files}).
17377 @item help target @var{name}
17378 Describe a particular target, including any parameters necessary to
17381 @kindex set gnutarget
17382 @item set gnutarget @var{args}
17383 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17384 knows whether it is reading an @dfn{executable},
17385 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17386 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17387 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17390 @emph{Warning:} To specify a file format with @code{set gnutarget},
17391 you must know the actual BFD name.
17395 @xref{Files, , Commands to Specify Files}.
17397 @kindex show gnutarget
17398 @item show gnutarget
17399 Use the @code{show gnutarget} command to display what file format
17400 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17401 @value{GDBN} will determine the file format for each file automatically,
17402 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17405 @cindex common targets
17406 Here are some common targets (available, or not, depending on the GDB
17411 @item target exec @var{program}
17412 @cindex executable file target
17413 An executable file. @samp{target exec @var{program}} is the same as
17414 @samp{exec-file @var{program}}.
17416 @item target core @var{filename}
17417 @cindex core dump file target
17418 A core dump file. @samp{target core @var{filename}} is the same as
17419 @samp{core-file @var{filename}}.
17421 @item target remote @var{medium}
17422 @cindex remote target
17423 A remote system connected to @value{GDBN} via a serial line or network
17424 connection. This command tells @value{GDBN} to use its own remote
17425 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17427 For example, if you have a board connected to @file{/dev/ttya} on the
17428 machine running @value{GDBN}, you could say:
17431 target remote /dev/ttya
17434 @code{target remote} supports the @code{load} command. This is only
17435 useful if you have some other way of getting the stub to the target
17436 system, and you can put it somewhere in memory where it won't get
17437 clobbered by the download.
17439 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17440 @cindex built-in simulator target
17441 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17449 works; however, you cannot assume that a specific memory map, device
17450 drivers, or even basic I/O is available, although some simulators do
17451 provide these. For info about any processor-specific simulator details,
17452 see the appropriate section in @ref{Embedded Processors, ,Embedded
17457 Some configurations may include these targets as well:
17461 @item target nrom @var{dev}
17462 @cindex NetROM ROM emulator target
17463 NetROM ROM emulator. This target only supports downloading.
17467 Different targets are available on different configurations of @value{GDBN};
17468 your configuration may have more or fewer targets.
17470 Many remote targets require you to download the executable's code once
17471 you've successfully established a connection. You may wish to control
17472 various aspects of this process.
17477 @kindex set hash@r{, for remote monitors}
17478 @cindex hash mark while downloading
17479 This command controls whether a hash mark @samp{#} is displayed while
17480 downloading a file to the remote monitor. If on, a hash mark is
17481 displayed after each S-record is successfully downloaded to the
17485 @kindex show hash@r{, for remote monitors}
17486 Show the current status of displaying the hash mark.
17488 @item set debug monitor
17489 @kindex set debug monitor
17490 @cindex display remote monitor communications
17491 Enable or disable display of communications messages between
17492 @value{GDBN} and the remote monitor.
17494 @item show debug monitor
17495 @kindex show debug monitor
17496 Show the current status of displaying communications between
17497 @value{GDBN} and the remote monitor.
17502 @kindex load @var{filename}
17503 @item load @var{filename}
17505 Depending on what remote debugging facilities are configured into
17506 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17507 is meant to make @var{filename} (an executable) available for debugging
17508 on the remote system---by downloading, or dynamic linking, for example.
17509 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17510 the @code{add-symbol-file} command.
17512 If your @value{GDBN} does not have a @code{load} command, attempting to
17513 execute it gets the error message ``@code{You can't do that when your
17514 target is @dots{}}''
17516 The file is loaded at whatever address is specified in the executable.
17517 For some object file formats, you can specify the load address when you
17518 link the program; for other formats, like a.out, the object file format
17519 specifies a fixed address.
17520 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17522 Depending on the remote side capabilities, @value{GDBN} may be able to
17523 load programs into flash memory.
17525 @code{load} does not repeat if you press @key{RET} again after using it.
17529 @section Choosing Target Byte Order
17531 @cindex choosing target byte order
17532 @cindex target byte order
17534 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17535 offer the ability to run either big-endian or little-endian byte
17536 orders. Usually the executable or symbol will include a bit to
17537 designate the endian-ness, and you will not need to worry about
17538 which to use. However, you may still find it useful to adjust
17539 @value{GDBN}'s idea of processor endian-ness manually.
17543 @item set endian big
17544 Instruct @value{GDBN} to assume the target is big-endian.
17546 @item set endian little
17547 Instruct @value{GDBN} to assume the target is little-endian.
17549 @item set endian auto
17550 Instruct @value{GDBN} to use the byte order associated with the
17554 Display @value{GDBN}'s current idea of the target byte order.
17558 Note that these commands merely adjust interpretation of symbolic
17559 data on the host, and that they have absolutely no effect on the
17563 @node Remote Debugging
17564 @chapter Debugging Remote Programs
17565 @cindex remote debugging
17567 If you are trying to debug a program running on a machine that cannot run
17568 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17569 For example, you might use remote debugging on an operating system kernel,
17570 or on a small system which does not have a general purpose operating system
17571 powerful enough to run a full-featured debugger.
17573 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17574 to make this work with particular debugging targets. In addition,
17575 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17576 but not specific to any particular target system) which you can use if you
17577 write the remote stubs---the code that runs on the remote system to
17578 communicate with @value{GDBN}.
17580 Other remote targets may be available in your
17581 configuration of @value{GDBN}; use @code{help target} to list them.
17584 * Connecting:: Connecting to a remote target
17585 * File Transfer:: Sending files to a remote system
17586 * Server:: Using the gdbserver program
17587 * Remote Configuration:: Remote configuration
17588 * Remote Stub:: Implementing a remote stub
17592 @section Connecting to a Remote Target
17594 On the @value{GDBN} host machine, you will need an unstripped copy of
17595 your program, since @value{GDBN} needs symbol and debugging information.
17596 Start up @value{GDBN} as usual, using the name of the local copy of your
17597 program as the first argument.
17599 @cindex @code{target remote}
17600 @value{GDBN} can communicate with the target over a serial line, or
17601 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17602 each case, @value{GDBN} uses the same protocol for debugging your
17603 program; only the medium carrying the debugging packets varies. The
17604 @code{target remote} command establishes a connection to the target.
17605 Its arguments indicate which medium to use:
17609 @item target remote @var{serial-device}
17610 @cindex serial line, @code{target remote}
17611 Use @var{serial-device} to communicate with the target. For example,
17612 to use a serial line connected to the device named @file{/dev/ttyb}:
17615 target remote /dev/ttyb
17618 If you're using a serial line, you may want to give @value{GDBN} the
17619 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17620 (@pxref{Remote Configuration, set remotebaud}) before the
17621 @code{target} command.
17623 @item target remote @code{@var{host}:@var{port}}
17624 @itemx target remote @code{tcp:@var{host}:@var{port}}
17625 @cindex @acronym{TCP} port, @code{target remote}
17626 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17627 The @var{host} may be either a host name or a numeric @acronym{IP}
17628 address; @var{port} must be a decimal number. The @var{host} could be
17629 the target machine itself, if it is directly connected to the net, or
17630 it might be a terminal server which in turn has a serial line to the
17633 For example, to connect to port 2828 on a terminal server named
17637 target remote manyfarms:2828
17640 If your remote target is actually running on the same machine as your
17641 debugger session (e.g.@: a simulator for your target running on the
17642 same host), you can omit the hostname. For example, to connect to
17643 port 1234 on your local machine:
17646 target remote :1234
17650 Note that the colon is still required here.
17652 @item target remote @code{udp:@var{host}:@var{port}}
17653 @cindex @acronym{UDP} port, @code{target remote}
17654 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17655 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17658 target remote udp:manyfarms:2828
17661 When using a @acronym{UDP} connection for remote debugging, you should
17662 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17663 can silently drop packets on busy or unreliable networks, which will
17664 cause havoc with your debugging session.
17666 @item target remote | @var{command}
17667 @cindex pipe, @code{target remote} to
17668 Run @var{command} in the background and communicate with it using a
17669 pipe. The @var{command} is a shell command, to be parsed and expanded
17670 by the system's command shell, @code{/bin/sh}; it should expect remote
17671 protocol packets on its standard input, and send replies on its
17672 standard output. You could use this to run a stand-alone simulator
17673 that speaks the remote debugging protocol, to make net connections
17674 using programs like @code{ssh}, or for other similar tricks.
17676 If @var{command} closes its standard output (perhaps by exiting),
17677 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17678 program has already exited, this will have no effect.)
17682 Once the connection has been established, you can use all the usual
17683 commands to examine and change data. The remote program is already
17684 running; you can use @kbd{step} and @kbd{continue}, and you do not
17685 need to use @kbd{run}.
17687 @cindex interrupting remote programs
17688 @cindex remote programs, interrupting
17689 Whenever @value{GDBN} is waiting for the remote program, if you type the
17690 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17691 program. This may or may not succeed, depending in part on the hardware
17692 and the serial drivers the remote system uses. If you type the
17693 interrupt character once again, @value{GDBN} displays this prompt:
17696 Interrupted while waiting for the program.
17697 Give up (and stop debugging it)? (y or n)
17700 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17701 (If you decide you want to try again later, you can use @samp{target
17702 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17703 goes back to waiting.
17706 @kindex detach (remote)
17708 When you have finished debugging the remote program, you can use the
17709 @code{detach} command to release it from @value{GDBN} control.
17710 Detaching from the target normally resumes its execution, but the results
17711 will depend on your particular remote stub. After the @code{detach}
17712 command, @value{GDBN} is free to connect to another target.
17716 The @code{disconnect} command behaves like @code{detach}, except that
17717 the target is generally not resumed. It will wait for @value{GDBN}
17718 (this instance or another one) to connect and continue debugging. After
17719 the @code{disconnect} command, @value{GDBN} is again free to connect to
17722 @cindex send command to remote monitor
17723 @cindex extend @value{GDBN} for remote targets
17724 @cindex add new commands for external monitor
17726 @item monitor @var{cmd}
17727 This command allows you to send arbitrary commands directly to the
17728 remote monitor. Since @value{GDBN} doesn't care about the commands it
17729 sends like this, this command is the way to extend @value{GDBN}---you
17730 can add new commands that only the external monitor will understand
17734 @node File Transfer
17735 @section Sending files to a remote system
17736 @cindex remote target, file transfer
17737 @cindex file transfer
17738 @cindex sending files to remote systems
17740 Some remote targets offer the ability to transfer files over the same
17741 connection used to communicate with @value{GDBN}. This is convenient
17742 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17743 running @code{gdbserver} over a network interface. For other targets,
17744 e.g.@: embedded devices with only a single serial port, this may be
17745 the only way to upload or download files.
17747 Not all remote targets support these commands.
17751 @item remote put @var{hostfile} @var{targetfile}
17752 Copy file @var{hostfile} from the host system (the machine running
17753 @value{GDBN}) to @var{targetfile} on the target system.
17756 @item remote get @var{targetfile} @var{hostfile}
17757 Copy file @var{targetfile} from the target system to @var{hostfile}
17758 on the host system.
17760 @kindex remote delete
17761 @item remote delete @var{targetfile}
17762 Delete @var{targetfile} from the target system.
17767 @section Using the @code{gdbserver} Program
17770 @cindex remote connection without stubs
17771 @code{gdbserver} is a control program for Unix-like systems, which
17772 allows you to connect your program with a remote @value{GDBN} via
17773 @code{target remote}---but without linking in the usual debugging stub.
17775 @code{gdbserver} is not a complete replacement for the debugging stubs,
17776 because it requires essentially the same operating-system facilities
17777 that @value{GDBN} itself does. In fact, a system that can run
17778 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17779 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17780 because it is a much smaller program than @value{GDBN} itself. It is
17781 also easier to port than all of @value{GDBN}, so you may be able to get
17782 started more quickly on a new system by using @code{gdbserver}.
17783 Finally, if you develop code for real-time systems, you may find that
17784 the tradeoffs involved in real-time operation make it more convenient to
17785 do as much development work as possible on another system, for example
17786 by cross-compiling. You can use @code{gdbserver} to make a similar
17787 choice for debugging.
17789 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17790 or a TCP connection, using the standard @value{GDBN} remote serial
17794 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17795 Do not run @code{gdbserver} connected to any public network; a
17796 @value{GDBN} connection to @code{gdbserver} provides access to the
17797 target system with the same privileges as the user running
17801 @subsection Running @code{gdbserver}
17802 @cindex arguments, to @code{gdbserver}
17803 @cindex @code{gdbserver}, command-line arguments
17805 Run @code{gdbserver} on the target system. You need a copy of the
17806 program you want to debug, including any libraries it requires.
17807 @code{gdbserver} does not need your program's symbol table, so you can
17808 strip the program if necessary to save space. @value{GDBN} on the host
17809 system does all the symbol handling.
17811 To use the server, you must tell it how to communicate with @value{GDBN};
17812 the name of your program; and the arguments for your program. The usual
17816 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17819 @var{comm} is either a device name (to use a serial line), or a TCP
17820 hostname and portnumber, or @code{-} or @code{stdio} to use
17821 stdin/stdout of @code{gdbserver}.
17822 For example, to debug Emacs with the argument
17823 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17827 target> gdbserver /dev/com1 emacs foo.txt
17830 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17833 To use a TCP connection instead of a serial line:
17836 target> gdbserver host:2345 emacs foo.txt
17839 The only difference from the previous example is the first argument,
17840 specifying that you are communicating with the host @value{GDBN} via
17841 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17842 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17843 (Currently, the @samp{host} part is ignored.) You can choose any number
17844 you want for the port number as long as it does not conflict with any
17845 TCP ports already in use on the target system (for example, @code{23} is
17846 reserved for @code{telnet}).@footnote{If you choose a port number that
17847 conflicts with another service, @code{gdbserver} prints an error message
17848 and exits.} You must use the same port number with the host @value{GDBN}
17849 @code{target remote} command.
17851 The @code{stdio} connection is useful when starting @code{gdbserver}
17855 (gdb) target remote | ssh -T hostname gdbserver - hello
17858 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17859 and we don't want escape-character handling. Ssh does this by default when
17860 a command is provided, the flag is provided to make it explicit.
17861 You could elide it if you want to.
17863 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17864 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17865 display through a pipe connected to gdbserver.
17866 Both @code{stdout} and @code{stderr} use the same pipe.
17868 @subsubsection Attaching to a Running Program
17869 @cindex attach to a program, @code{gdbserver}
17870 @cindex @option{--attach}, @code{gdbserver} option
17872 On some targets, @code{gdbserver} can also attach to running programs.
17873 This is accomplished via the @code{--attach} argument. The syntax is:
17876 target> gdbserver --attach @var{comm} @var{pid}
17879 @var{pid} is the process ID of a currently running process. It isn't necessary
17880 to point @code{gdbserver} at a binary for the running process.
17883 You can debug processes by name instead of process ID if your target has the
17884 @code{pidof} utility:
17887 target> gdbserver --attach @var{comm} `pidof @var{program}`
17890 In case more than one copy of @var{program} is running, or @var{program}
17891 has multiple threads, most versions of @code{pidof} support the
17892 @code{-s} option to only return the first process ID.
17894 @subsubsection Multi-Process Mode for @code{gdbserver}
17895 @cindex @code{gdbserver}, multiple processes
17896 @cindex multiple processes with @code{gdbserver}
17898 When you connect to @code{gdbserver} using @code{target remote},
17899 @code{gdbserver} debugs the specified program only once. When the
17900 program exits, or you detach from it, @value{GDBN} closes the connection
17901 and @code{gdbserver} exits.
17903 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17904 enters multi-process mode. When the debugged program exits, or you
17905 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17906 though no program is running. The @code{run} and @code{attach}
17907 commands instruct @code{gdbserver} to run or attach to a new program.
17908 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17909 remote exec-file}) to select the program to run. Command line
17910 arguments are supported, except for wildcard expansion and I/O
17911 redirection (@pxref{Arguments}).
17913 @cindex @option{--multi}, @code{gdbserver} option
17914 To start @code{gdbserver} without supplying an initial command to run
17915 or process ID to attach, use the @option{--multi} command line option.
17916 Then you can connect using @kbd{target extended-remote} and start
17917 the program you want to debug.
17919 In multi-process mode @code{gdbserver} does not automatically exit unless you
17920 use the option @option{--once}. You can terminate it by using
17921 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17922 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17923 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17924 @option{--multi} option to @code{gdbserver} has no influence on that.
17926 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17928 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17930 @code{gdbserver} normally terminates after all of its debugged processes have
17931 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17932 extended-remote}, @code{gdbserver} stays running even with no processes left.
17933 @value{GDBN} normally terminates the spawned debugged process on its exit,
17934 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17935 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17936 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17937 stays running even in the @kbd{target remote} mode.
17939 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17940 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17941 completeness, at most one @value{GDBN} can be connected at a time.
17943 @cindex @option{--once}, @code{gdbserver} option
17944 By default, @code{gdbserver} keeps the listening TCP port open, so that
17945 additional connections are possible. However, if you start @code{gdbserver}
17946 with the @option{--once} option, it will stop listening for any further
17947 connection attempts after connecting to the first @value{GDBN} session. This
17948 means no further connections to @code{gdbserver} will be possible after the
17949 first one. It also means @code{gdbserver} will terminate after the first
17950 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17951 connections and even in the @kbd{target extended-remote} mode. The
17952 @option{--once} option allows reusing the same port number for connecting to
17953 multiple instances of @code{gdbserver} running on the same host, since each
17954 instance closes its port after the first connection.
17956 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17958 @cindex @option{--debug}, @code{gdbserver} option
17959 The @option{--debug} option tells @code{gdbserver} to display extra
17960 status information about the debugging process.
17961 @cindex @option{--remote-debug}, @code{gdbserver} option
17962 The @option{--remote-debug} option tells @code{gdbserver} to display
17963 remote protocol debug output. These options are intended for
17964 @code{gdbserver} development and for bug reports to the developers.
17966 @cindex @option{--wrapper}, @code{gdbserver} option
17967 The @option{--wrapper} option specifies a wrapper to launch programs
17968 for debugging. The option should be followed by the name of the
17969 wrapper, then any command-line arguments to pass to the wrapper, then
17970 @kbd{--} indicating the end of the wrapper arguments.
17972 @code{gdbserver} runs the specified wrapper program with a combined
17973 command line including the wrapper arguments, then the name of the
17974 program to debug, then any arguments to the program. The wrapper
17975 runs until it executes your program, and then @value{GDBN} gains control.
17977 You can use any program that eventually calls @code{execve} with
17978 its arguments as a wrapper. Several standard Unix utilities do
17979 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17980 with @code{exec "$@@"} will also work.
17982 For example, you can use @code{env} to pass an environment variable to
17983 the debugged program, without setting the variable in @code{gdbserver}'s
17987 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17990 @subsection Connecting to @code{gdbserver}
17992 Run @value{GDBN} on the host system.
17994 First make sure you have the necessary symbol files. Load symbols for
17995 your application using the @code{file} command before you connect. Use
17996 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17997 was compiled with the correct sysroot using @code{--with-sysroot}).
17999 The symbol file and target libraries must exactly match the executable
18000 and libraries on the target, with one exception: the files on the host
18001 system should not be stripped, even if the files on the target system
18002 are. Mismatched or missing files will lead to confusing results
18003 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18004 files may also prevent @code{gdbserver} from debugging multi-threaded
18007 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18008 For TCP connections, you must start up @code{gdbserver} prior to using
18009 the @code{target remote} command. Otherwise you may get an error whose
18010 text depends on the host system, but which usually looks something like
18011 @samp{Connection refused}. Don't use the @code{load}
18012 command in @value{GDBN} when using @code{gdbserver}, since the program is
18013 already on the target.
18015 @subsection Monitor Commands for @code{gdbserver}
18016 @cindex monitor commands, for @code{gdbserver}
18017 @anchor{Monitor Commands for gdbserver}
18019 During a @value{GDBN} session using @code{gdbserver}, you can use the
18020 @code{monitor} command to send special requests to @code{gdbserver}.
18021 Here are the available commands.
18025 List the available monitor commands.
18027 @item monitor set debug 0
18028 @itemx monitor set debug 1
18029 Disable or enable general debugging messages.
18031 @item monitor set remote-debug 0
18032 @itemx monitor set remote-debug 1
18033 Disable or enable specific debugging messages associated with the remote
18034 protocol (@pxref{Remote Protocol}).
18036 @item monitor set libthread-db-search-path [PATH]
18037 @cindex gdbserver, search path for @code{libthread_db}
18038 When this command is issued, @var{path} is a colon-separated list of
18039 directories to search for @code{libthread_db} (@pxref{Threads,,set
18040 libthread-db-search-path}). If you omit @var{path},
18041 @samp{libthread-db-search-path} will be reset to its default value.
18043 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18044 not supported in @code{gdbserver}.
18047 Tell gdbserver to exit immediately. This command should be followed by
18048 @code{disconnect} to close the debugging session. @code{gdbserver} will
18049 detach from any attached processes and kill any processes it created.
18050 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18051 of a multi-process mode debug session.
18055 @subsection Tracepoints support in @code{gdbserver}
18056 @cindex tracepoints support in @code{gdbserver}
18058 On some targets, @code{gdbserver} supports tracepoints, fast
18059 tracepoints and static tracepoints.
18061 For fast or static tracepoints to work, a special library called the
18062 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18063 This library is built and distributed as an integral part of
18064 @code{gdbserver}. In addition, support for static tracepoints
18065 requires building the in-process agent library with static tracepoints
18066 support. At present, the UST (LTTng Userspace Tracer,
18067 @url{http://lttng.org/ust}) tracing engine is supported. This support
18068 is automatically available if UST development headers are found in the
18069 standard include path when @code{gdbserver} is built, or if
18070 @code{gdbserver} was explicitly configured using @option{--with-ust}
18071 to point at such headers. You can explicitly disable the support
18072 using @option{--with-ust=no}.
18074 There are several ways to load the in-process agent in your program:
18077 @item Specifying it as dependency at link time
18079 You can link your program dynamically with the in-process agent
18080 library. On most systems, this is accomplished by adding
18081 @code{-linproctrace} to the link command.
18083 @item Using the system's preloading mechanisms
18085 You can force loading the in-process agent at startup time by using
18086 your system's support for preloading shared libraries. Many Unixes
18087 support the concept of preloading user defined libraries. In most
18088 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18089 in the environment. See also the description of @code{gdbserver}'s
18090 @option{--wrapper} command line option.
18092 @item Using @value{GDBN} to force loading the agent at run time
18094 On some systems, you can force the inferior to load a shared library,
18095 by calling a dynamic loader function in the inferior that takes care
18096 of dynamically looking up and loading a shared library. On most Unix
18097 systems, the function is @code{dlopen}. You'll use the @code{call}
18098 command for that. For example:
18101 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18104 Note that on most Unix systems, for the @code{dlopen} function to be
18105 available, the program needs to be linked with @code{-ldl}.
18108 On systems that have a userspace dynamic loader, like most Unix
18109 systems, when you connect to @code{gdbserver} using @code{target
18110 remote}, you'll find that the program is stopped at the dynamic
18111 loader's entry point, and no shared library has been loaded in the
18112 program's address space yet, including the in-process agent. In that
18113 case, before being able to use any of the fast or static tracepoints
18114 features, you need to let the loader run and load the shared
18115 libraries. The simplest way to do that is to run the program to the
18116 main procedure. E.g., if debugging a C or C@t{++} program, start
18117 @code{gdbserver} like so:
18120 $ gdbserver :9999 myprogram
18123 Start GDB and connect to @code{gdbserver} like so, and run to main:
18127 (@value{GDBP}) target remote myhost:9999
18128 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18129 (@value{GDBP}) b main
18130 (@value{GDBP}) continue
18133 The in-process tracing agent library should now be loaded into the
18134 process; you can confirm it with the @code{info sharedlibrary}
18135 command, which will list @file{libinproctrace.so} as loaded in the
18136 process. You are now ready to install fast tracepoints, list static
18137 tracepoint markers, probe static tracepoints markers, and start
18140 @node Remote Configuration
18141 @section Remote Configuration
18144 @kindex show remote
18145 This section documents the configuration options available when
18146 debugging remote programs. For the options related to the File I/O
18147 extensions of the remote protocol, see @ref{system,
18148 system-call-allowed}.
18151 @item set remoteaddresssize @var{bits}
18152 @cindex address size for remote targets
18153 @cindex bits in remote address
18154 Set the maximum size of address in a memory packet to the specified
18155 number of bits. @value{GDBN} will mask off the address bits above
18156 that number, when it passes addresses to the remote target. The
18157 default value is the number of bits in the target's address.
18159 @item show remoteaddresssize
18160 Show the current value of remote address size in bits.
18162 @item set remotebaud @var{n}
18163 @cindex baud rate for remote targets
18164 Set the baud rate for the remote serial I/O to @var{n} baud. The
18165 value is used to set the speed of the serial port used for debugging
18168 @item show remotebaud
18169 Show the current speed of the remote connection.
18171 @item set remotebreak
18172 @cindex interrupt remote programs
18173 @cindex BREAK signal instead of Ctrl-C
18174 @anchor{set remotebreak}
18175 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18176 when you type @kbd{Ctrl-c} to interrupt the program running
18177 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18178 character instead. The default is off, since most remote systems
18179 expect to see @samp{Ctrl-C} as the interrupt signal.
18181 @item show remotebreak
18182 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18183 interrupt the remote program.
18185 @item set remoteflow on
18186 @itemx set remoteflow off
18187 @kindex set remoteflow
18188 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18189 on the serial port used to communicate to the remote target.
18191 @item show remoteflow
18192 @kindex show remoteflow
18193 Show the current setting of hardware flow control.
18195 @item set remotelogbase @var{base}
18196 Set the base (a.k.a.@: radix) of logging serial protocol
18197 communications to @var{base}. Supported values of @var{base} are:
18198 @code{ascii}, @code{octal}, and @code{hex}. The default is
18201 @item show remotelogbase
18202 Show the current setting of the radix for logging remote serial
18205 @item set remotelogfile @var{file}
18206 @cindex record serial communications on file
18207 Record remote serial communications on the named @var{file}. The
18208 default is not to record at all.
18210 @item show remotelogfile.
18211 Show the current setting of the file name on which to record the
18212 serial communications.
18214 @item set remotetimeout @var{num}
18215 @cindex timeout for serial communications
18216 @cindex remote timeout
18217 Set the timeout limit to wait for the remote target to respond to
18218 @var{num} seconds. The default is 2 seconds.
18220 @item show remotetimeout
18221 Show the current number of seconds to wait for the remote target
18224 @cindex limit hardware breakpoints and watchpoints
18225 @cindex remote target, limit break- and watchpoints
18226 @anchor{set remote hardware-watchpoint-limit}
18227 @anchor{set remote hardware-breakpoint-limit}
18228 @item set remote hardware-watchpoint-limit @var{limit}
18229 @itemx set remote hardware-breakpoint-limit @var{limit}
18230 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18231 watchpoints. A limit of -1, the default, is treated as unlimited.
18233 @cindex limit hardware watchpoints length
18234 @cindex remote target, limit watchpoints length
18235 @anchor{set remote hardware-watchpoint-length-limit}
18236 @item set remote hardware-watchpoint-length-limit @var{limit}
18237 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18238 a remote hardware watchpoint. A limit of -1, the default, is treated
18241 @item show remote hardware-watchpoint-length-limit
18242 Show the current limit (in bytes) of the maximum length of
18243 a remote hardware watchpoint.
18245 @item set remote exec-file @var{filename}
18246 @itemx show remote exec-file
18247 @anchor{set remote exec-file}
18248 @cindex executable file, for remote target
18249 Select the file used for @code{run} with @code{target
18250 extended-remote}. This should be set to a filename valid on the
18251 target system. If it is not set, the target will use a default
18252 filename (e.g.@: the last program run).
18254 @item set remote interrupt-sequence
18255 @cindex interrupt remote programs
18256 @cindex select Ctrl-C, BREAK or BREAK-g
18257 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18258 @samp{BREAK-g} as the
18259 sequence to the remote target in order to interrupt the execution.
18260 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18261 is high level of serial line for some certain time.
18262 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18263 It is @code{BREAK} signal followed by character @code{g}.
18265 @item show interrupt-sequence
18266 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18267 is sent by @value{GDBN} to interrupt the remote program.
18268 @code{BREAK-g} is BREAK signal followed by @code{g} and
18269 also known as Magic SysRq g.
18271 @item set remote interrupt-on-connect
18272 @cindex send interrupt-sequence on start
18273 Specify whether interrupt-sequence is sent to remote target when
18274 @value{GDBN} connects to it. This is mostly needed when you debug
18275 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18276 which is known as Magic SysRq g in order to connect @value{GDBN}.
18278 @item show interrupt-on-connect
18279 Show whether interrupt-sequence is sent
18280 to remote target when @value{GDBN} connects to it.
18284 @item set tcp auto-retry on
18285 @cindex auto-retry, for remote TCP target
18286 Enable auto-retry for remote TCP connections. This is useful if the remote
18287 debugging agent is launched in parallel with @value{GDBN}; there is a race
18288 condition because the agent may not become ready to accept the connection
18289 before @value{GDBN} attempts to connect. When auto-retry is
18290 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18291 to establish the connection using the timeout specified by
18292 @code{set tcp connect-timeout}.
18294 @item set tcp auto-retry off
18295 Do not auto-retry failed TCP connections.
18297 @item show tcp auto-retry
18298 Show the current auto-retry setting.
18300 @item set tcp connect-timeout @var{seconds}
18301 @itemx set tcp connect-timeout unlimited
18302 @cindex connection timeout, for remote TCP target
18303 @cindex timeout, for remote target connection
18304 Set the timeout for establishing a TCP connection to the remote target to
18305 @var{seconds}. The timeout affects both polling to retry failed connections
18306 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18307 that are merely slow to complete, and represents an approximate cumulative
18308 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18309 @value{GDBN} will keep attempting to establish a connection forever,
18310 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18312 @item show tcp connect-timeout
18313 Show the current connection timeout setting.
18316 @cindex remote packets, enabling and disabling
18317 The @value{GDBN} remote protocol autodetects the packets supported by
18318 your debugging stub. If you need to override the autodetection, you
18319 can use these commands to enable or disable individual packets. Each
18320 packet can be set to @samp{on} (the remote target supports this
18321 packet), @samp{off} (the remote target does not support this packet),
18322 or @samp{auto} (detect remote target support for this packet). They
18323 all default to @samp{auto}. For more information about each packet,
18324 see @ref{Remote Protocol}.
18326 During normal use, you should not have to use any of these commands.
18327 If you do, that may be a bug in your remote debugging stub, or a bug
18328 in @value{GDBN}. You may want to report the problem to the
18329 @value{GDBN} developers.
18331 For each packet @var{name}, the command to enable or disable the
18332 packet is @code{set remote @var{name}-packet}. The available settings
18335 @multitable @columnfractions 0.28 0.32 0.25
18338 @tab Related Features
18340 @item @code{fetch-register}
18342 @tab @code{info registers}
18344 @item @code{set-register}
18348 @item @code{binary-download}
18350 @tab @code{load}, @code{set}
18352 @item @code{read-aux-vector}
18353 @tab @code{qXfer:auxv:read}
18354 @tab @code{info auxv}
18356 @item @code{symbol-lookup}
18357 @tab @code{qSymbol}
18358 @tab Detecting multiple threads
18360 @item @code{attach}
18361 @tab @code{vAttach}
18364 @item @code{verbose-resume}
18366 @tab Stepping or resuming multiple threads
18372 @item @code{software-breakpoint}
18376 @item @code{hardware-breakpoint}
18380 @item @code{write-watchpoint}
18384 @item @code{read-watchpoint}
18388 @item @code{access-watchpoint}
18392 @item @code{target-features}
18393 @tab @code{qXfer:features:read}
18394 @tab @code{set architecture}
18396 @item @code{library-info}
18397 @tab @code{qXfer:libraries:read}
18398 @tab @code{info sharedlibrary}
18400 @item @code{memory-map}
18401 @tab @code{qXfer:memory-map:read}
18402 @tab @code{info mem}
18404 @item @code{read-sdata-object}
18405 @tab @code{qXfer:sdata:read}
18406 @tab @code{print $_sdata}
18408 @item @code{read-spu-object}
18409 @tab @code{qXfer:spu:read}
18410 @tab @code{info spu}
18412 @item @code{write-spu-object}
18413 @tab @code{qXfer:spu:write}
18414 @tab @code{info spu}
18416 @item @code{read-siginfo-object}
18417 @tab @code{qXfer:siginfo:read}
18418 @tab @code{print $_siginfo}
18420 @item @code{write-siginfo-object}
18421 @tab @code{qXfer:siginfo:write}
18422 @tab @code{set $_siginfo}
18424 @item @code{threads}
18425 @tab @code{qXfer:threads:read}
18426 @tab @code{info threads}
18428 @item @code{get-thread-local-@*storage-address}
18429 @tab @code{qGetTLSAddr}
18430 @tab Displaying @code{__thread} variables
18432 @item @code{get-thread-information-block-address}
18433 @tab @code{qGetTIBAddr}
18434 @tab Display MS-Windows Thread Information Block.
18436 @item @code{search-memory}
18437 @tab @code{qSearch:memory}
18440 @item @code{supported-packets}
18441 @tab @code{qSupported}
18442 @tab Remote communications parameters
18444 @item @code{pass-signals}
18445 @tab @code{QPassSignals}
18446 @tab @code{handle @var{signal}}
18448 @item @code{program-signals}
18449 @tab @code{QProgramSignals}
18450 @tab @code{handle @var{signal}}
18452 @item @code{hostio-close-packet}
18453 @tab @code{vFile:close}
18454 @tab @code{remote get}, @code{remote put}
18456 @item @code{hostio-open-packet}
18457 @tab @code{vFile:open}
18458 @tab @code{remote get}, @code{remote put}
18460 @item @code{hostio-pread-packet}
18461 @tab @code{vFile:pread}
18462 @tab @code{remote get}, @code{remote put}
18464 @item @code{hostio-pwrite-packet}
18465 @tab @code{vFile:pwrite}
18466 @tab @code{remote get}, @code{remote put}
18468 @item @code{hostio-unlink-packet}
18469 @tab @code{vFile:unlink}
18470 @tab @code{remote delete}
18472 @item @code{hostio-readlink-packet}
18473 @tab @code{vFile:readlink}
18476 @item @code{noack-packet}
18477 @tab @code{QStartNoAckMode}
18478 @tab Packet acknowledgment
18480 @item @code{osdata}
18481 @tab @code{qXfer:osdata:read}
18482 @tab @code{info os}
18484 @item @code{query-attached}
18485 @tab @code{qAttached}
18486 @tab Querying remote process attach state.
18488 @item @code{trace-buffer-size}
18489 @tab @code{QTBuffer:size}
18490 @tab @code{set trace-buffer-size}
18492 @item @code{trace-status}
18493 @tab @code{qTStatus}
18494 @tab @code{tstatus}
18496 @item @code{traceframe-info}
18497 @tab @code{qXfer:traceframe-info:read}
18498 @tab Traceframe info
18500 @item @code{install-in-trace}
18501 @tab @code{InstallInTrace}
18502 @tab Install tracepoint in tracing
18504 @item @code{disable-randomization}
18505 @tab @code{QDisableRandomization}
18506 @tab @code{set disable-randomization}
18508 @item @code{conditional-breakpoints-packet}
18509 @tab @code{Z0 and Z1}
18510 @tab @code{Support for target-side breakpoint condition evaluation}
18514 @section Implementing a Remote Stub
18516 @cindex debugging stub, example
18517 @cindex remote stub, example
18518 @cindex stub example, remote debugging
18519 The stub files provided with @value{GDBN} implement the target side of the
18520 communication protocol, and the @value{GDBN} side is implemented in the
18521 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18522 these subroutines to communicate, and ignore the details. (If you're
18523 implementing your own stub file, you can still ignore the details: start
18524 with one of the existing stub files. @file{sparc-stub.c} is the best
18525 organized, and therefore the easiest to read.)
18527 @cindex remote serial debugging, overview
18528 To debug a program running on another machine (the debugging
18529 @dfn{target} machine), you must first arrange for all the usual
18530 prerequisites for the program to run by itself. For example, for a C
18535 A startup routine to set up the C runtime environment; these usually
18536 have a name like @file{crt0}. The startup routine may be supplied by
18537 your hardware supplier, or you may have to write your own.
18540 A C subroutine library to support your program's
18541 subroutine calls, notably managing input and output.
18544 A way of getting your program to the other machine---for example, a
18545 download program. These are often supplied by the hardware
18546 manufacturer, but you may have to write your own from hardware
18550 The next step is to arrange for your program to use a serial port to
18551 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18552 machine). In general terms, the scheme looks like this:
18556 @value{GDBN} already understands how to use this protocol; when everything
18557 else is set up, you can simply use the @samp{target remote} command
18558 (@pxref{Targets,,Specifying a Debugging Target}).
18560 @item On the target,
18561 you must link with your program a few special-purpose subroutines that
18562 implement the @value{GDBN} remote serial protocol. The file containing these
18563 subroutines is called a @dfn{debugging stub}.
18565 On certain remote targets, you can use an auxiliary program
18566 @code{gdbserver} instead of linking a stub into your program.
18567 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18570 The debugging stub is specific to the architecture of the remote
18571 machine; for example, use @file{sparc-stub.c} to debug programs on
18574 @cindex remote serial stub list
18575 These working remote stubs are distributed with @value{GDBN}:
18580 @cindex @file{i386-stub.c}
18583 For Intel 386 and compatible architectures.
18586 @cindex @file{m68k-stub.c}
18587 @cindex Motorola 680x0
18589 For Motorola 680x0 architectures.
18592 @cindex @file{sh-stub.c}
18595 For Renesas SH architectures.
18598 @cindex @file{sparc-stub.c}
18600 For @sc{sparc} architectures.
18602 @item sparcl-stub.c
18603 @cindex @file{sparcl-stub.c}
18606 For Fujitsu @sc{sparclite} architectures.
18610 The @file{README} file in the @value{GDBN} distribution may list other
18611 recently added stubs.
18614 * Stub Contents:: What the stub can do for you
18615 * Bootstrapping:: What you must do for the stub
18616 * Debug Session:: Putting it all together
18619 @node Stub Contents
18620 @subsection What the Stub Can Do for You
18622 @cindex remote serial stub
18623 The debugging stub for your architecture supplies these three
18627 @item set_debug_traps
18628 @findex set_debug_traps
18629 @cindex remote serial stub, initialization
18630 This routine arranges for @code{handle_exception} to run when your
18631 program stops. You must call this subroutine explicitly in your
18632 program's startup code.
18634 @item handle_exception
18635 @findex handle_exception
18636 @cindex remote serial stub, main routine
18637 This is the central workhorse, but your program never calls it
18638 explicitly---the setup code arranges for @code{handle_exception} to
18639 run when a trap is triggered.
18641 @code{handle_exception} takes control when your program stops during
18642 execution (for example, on a breakpoint), and mediates communications
18643 with @value{GDBN} on the host machine. This is where the communications
18644 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18645 representative on the target machine. It begins by sending summary
18646 information on the state of your program, then continues to execute,
18647 retrieving and transmitting any information @value{GDBN} needs, until you
18648 execute a @value{GDBN} command that makes your program resume; at that point,
18649 @code{handle_exception} returns control to your own code on the target
18653 @cindex @code{breakpoint} subroutine, remote
18654 Use this auxiliary subroutine to make your program contain a
18655 breakpoint. Depending on the particular situation, this may be the only
18656 way for @value{GDBN} to get control. For instance, if your target
18657 machine has some sort of interrupt button, you won't need to call this;
18658 pressing the interrupt button transfers control to
18659 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18660 simply receiving characters on the serial port may also trigger a trap;
18661 again, in that situation, you don't need to call @code{breakpoint} from
18662 your own program---simply running @samp{target remote} from the host
18663 @value{GDBN} session gets control.
18665 Call @code{breakpoint} if none of these is true, or if you simply want
18666 to make certain your program stops at a predetermined point for the
18667 start of your debugging session.
18670 @node Bootstrapping
18671 @subsection What You Must Do for the Stub
18673 @cindex remote stub, support routines
18674 The debugging stubs that come with @value{GDBN} are set up for a particular
18675 chip architecture, but they have no information about the rest of your
18676 debugging target machine.
18678 First of all you need to tell the stub how to communicate with the
18682 @item int getDebugChar()
18683 @findex getDebugChar
18684 Write this subroutine to read a single character from the serial port.
18685 It may be identical to @code{getchar} for your target system; a
18686 different name is used to allow you to distinguish the two if you wish.
18688 @item void putDebugChar(int)
18689 @findex putDebugChar
18690 Write this subroutine to write a single character to the serial port.
18691 It may be identical to @code{putchar} for your target system; a
18692 different name is used to allow you to distinguish the two if you wish.
18695 @cindex control C, and remote debugging
18696 @cindex interrupting remote targets
18697 If you want @value{GDBN} to be able to stop your program while it is
18698 running, you need to use an interrupt-driven serial driver, and arrange
18699 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18700 character). That is the character which @value{GDBN} uses to tell the
18701 remote system to stop.
18703 Getting the debugging target to return the proper status to @value{GDBN}
18704 probably requires changes to the standard stub; one quick and dirty way
18705 is to just execute a breakpoint instruction (the ``dirty'' part is that
18706 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18708 Other routines you need to supply are:
18711 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18712 @findex exceptionHandler
18713 Write this function to install @var{exception_address} in the exception
18714 handling tables. You need to do this because the stub does not have any
18715 way of knowing what the exception handling tables on your target system
18716 are like (for example, the processor's table might be in @sc{rom},
18717 containing entries which point to a table in @sc{ram}).
18718 @var{exception_number} is the exception number which should be changed;
18719 its meaning is architecture-dependent (for example, different numbers
18720 might represent divide by zero, misaligned access, etc). When this
18721 exception occurs, control should be transferred directly to
18722 @var{exception_address}, and the processor state (stack, registers,
18723 and so on) should be just as it is when a processor exception occurs. So if
18724 you want to use a jump instruction to reach @var{exception_address}, it
18725 should be a simple jump, not a jump to subroutine.
18727 For the 386, @var{exception_address} should be installed as an interrupt
18728 gate so that interrupts are masked while the handler runs. The gate
18729 should be at privilege level 0 (the most privileged level). The
18730 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18731 help from @code{exceptionHandler}.
18733 @item void flush_i_cache()
18734 @findex flush_i_cache
18735 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18736 instruction cache, if any, on your target machine. If there is no
18737 instruction cache, this subroutine may be a no-op.
18739 On target machines that have instruction caches, @value{GDBN} requires this
18740 function to make certain that the state of your program is stable.
18744 You must also make sure this library routine is available:
18747 @item void *memset(void *, int, int)
18749 This is the standard library function @code{memset} that sets an area of
18750 memory to a known value. If you have one of the free versions of
18751 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18752 either obtain it from your hardware manufacturer, or write your own.
18755 If you do not use the GNU C compiler, you may need other standard
18756 library subroutines as well; this varies from one stub to another,
18757 but in general the stubs are likely to use any of the common library
18758 subroutines which @code{@value{NGCC}} generates as inline code.
18761 @node Debug Session
18762 @subsection Putting it All Together
18764 @cindex remote serial debugging summary
18765 In summary, when your program is ready to debug, you must follow these
18770 Make sure you have defined the supporting low-level routines
18771 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18773 @code{getDebugChar}, @code{putDebugChar},
18774 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18778 Insert these lines in your program's startup code, before the main
18779 procedure is called:
18786 On some machines, when a breakpoint trap is raised, the hardware
18787 automatically makes the PC point to the instruction after the
18788 breakpoint. If your machine doesn't do that, you may need to adjust
18789 @code{handle_exception} to arrange for it to return to the instruction
18790 after the breakpoint on this first invocation, so that your program
18791 doesn't keep hitting the initial breakpoint instead of making
18795 For the 680x0 stub only, you need to provide a variable called
18796 @code{exceptionHook}. Normally you just use:
18799 void (*exceptionHook)() = 0;
18803 but if before calling @code{set_debug_traps}, you set it to point to a
18804 function in your program, that function is called when
18805 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18806 error). The function indicated by @code{exceptionHook} is called with
18807 one parameter: an @code{int} which is the exception number.
18810 Compile and link together: your program, the @value{GDBN} debugging stub for
18811 your target architecture, and the supporting subroutines.
18814 Make sure you have a serial connection between your target machine and
18815 the @value{GDBN} host, and identify the serial port on the host.
18818 @c The "remote" target now provides a `load' command, so we should
18819 @c document that. FIXME.
18820 Download your program to your target machine (or get it there by
18821 whatever means the manufacturer provides), and start it.
18824 Start @value{GDBN} on the host, and connect to the target
18825 (@pxref{Connecting,,Connecting to a Remote Target}).
18829 @node Configurations
18830 @chapter Configuration-Specific Information
18832 While nearly all @value{GDBN} commands are available for all native and
18833 cross versions of the debugger, there are some exceptions. This chapter
18834 describes things that are only available in certain configurations.
18836 There are three major categories of configurations: native
18837 configurations, where the host and target are the same, embedded
18838 operating system configurations, which are usually the same for several
18839 different processor architectures, and bare embedded processors, which
18840 are quite different from each other.
18845 * Embedded Processors::
18852 This section describes details specific to particular native
18857 * BSD libkvm Interface:: Debugging BSD kernel memory images
18858 * SVR4 Process Information:: SVR4 process information
18859 * DJGPP Native:: Features specific to the DJGPP port
18860 * Cygwin Native:: Features specific to the Cygwin port
18861 * Hurd Native:: Features specific to @sc{gnu} Hurd
18862 * Darwin:: Features specific to Darwin
18868 On HP-UX systems, if you refer to a function or variable name that
18869 begins with a dollar sign, @value{GDBN} searches for a user or system
18870 name first, before it searches for a convenience variable.
18873 @node BSD libkvm Interface
18874 @subsection BSD libkvm Interface
18877 @cindex kernel memory image
18878 @cindex kernel crash dump
18880 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18881 interface that provides a uniform interface for accessing kernel virtual
18882 memory images, including live systems and crash dumps. @value{GDBN}
18883 uses this interface to allow you to debug live kernels and kernel crash
18884 dumps on many native BSD configurations. This is implemented as a
18885 special @code{kvm} debugging target. For debugging a live system, load
18886 the currently running kernel into @value{GDBN} and connect to the
18890 (@value{GDBP}) @b{target kvm}
18893 For debugging crash dumps, provide the file name of the crash dump as an
18897 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18900 Once connected to the @code{kvm} target, the following commands are
18906 Set current context from the @dfn{Process Control Block} (PCB) address.
18909 Set current context from proc address. This command isn't available on
18910 modern FreeBSD systems.
18913 @node SVR4 Process Information
18914 @subsection SVR4 Process Information
18916 @cindex examine process image
18917 @cindex process info via @file{/proc}
18919 Many versions of SVR4 and compatible systems provide a facility called
18920 @samp{/proc} that can be used to examine the image of a running
18921 process using file-system subroutines.
18923 If @value{GDBN} is configured for an operating system with this
18924 facility, the command @code{info proc} is available to report
18925 information about the process running your program, or about any
18926 process running on your system. This includes, as of this writing,
18927 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18928 not HP-UX, for example.
18930 This command may also work on core files that were created on a system
18931 that has the @samp{/proc} facility.
18937 @itemx info proc @var{process-id}
18938 Summarize available information about any running process. If a
18939 process ID is specified by @var{process-id}, display information about
18940 that process; otherwise display information about the program being
18941 debugged. The summary includes the debugged process ID, the command
18942 line used to invoke it, its current working directory, and its
18943 executable file's absolute file name.
18945 On some systems, @var{process-id} can be of the form
18946 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18947 within a process. If the optional @var{pid} part is missing, it means
18948 a thread from the process being debugged (the leading @samp{/} still
18949 needs to be present, or else @value{GDBN} will interpret the number as
18950 a process ID rather than a thread ID).
18952 @item info proc cmdline
18953 @cindex info proc cmdline
18954 Show the original command line of the process. This command is
18955 specific to @sc{gnu}/Linux.
18957 @item info proc cwd
18958 @cindex info proc cwd
18959 Show the current working directory of the process. This command is
18960 specific to @sc{gnu}/Linux.
18962 @item info proc exe
18963 @cindex info proc exe
18964 Show the name of executable of the process. This command is specific
18967 @item info proc mappings
18968 @cindex memory address space mappings
18969 Report the memory address space ranges accessible in the program, with
18970 information on whether the process has read, write, or execute access
18971 rights to each range. On @sc{gnu}/Linux systems, each memory range
18972 includes the object file which is mapped to that range, instead of the
18973 memory access rights to that range.
18975 @item info proc stat
18976 @itemx info proc status
18977 @cindex process detailed status information
18978 These subcommands are specific to @sc{gnu}/Linux systems. They show
18979 the process-related information, including the user ID and group ID;
18980 how many threads are there in the process; its virtual memory usage;
18981 the signals that are pending, blocked, and ignored; its TTY; its
18982 consumption of system and user time; its stack size; its @samp{nice}
18983 value; etc. For more information, see the @samp{proc} man page
18984 (type @kbd{man 5 proc} from your shell prompt).
18986 @item info proc all
18987 Show all the information about the process described under all of the
18988 above @code{info proc} subcommands.
18991 @comment These sub-options of 'info proc' were not included when
18992 @comment procfs.c was re-written. Keep their descriptions around
18993 @comment against the day when someone finds the time to put them back in.
18994 @kindex info proc times
18995 @item info proc times
18996 Starting time, user CPU time, and system CPU time for your program and
18999 @kindex info proc id
19001 Report on the process IDs related to your program: its own process ID,
19002 the ID of its parent, the process group ID, and the session ID.
19005 @item set procfs-trace
19006 @kindex set procfs-trace
19007 @cindex @code{procfs} API calls
19008 This command enables and disables tracing of @code{procfs} API calls.
19010 @item show procfs-trace
19011 @kindex show procfs-trace
19012 Show the current state of @code{procfs} API call tracing.
19014 @item set procfs-file @var{file}
19015 @kindex set procfs-file
19016 Tell @value{GDBN} to write @code{procfs} API trace to the named
19017 @var{file}. @value{GDBN} appends the trace info to the previous
19018 contents of the file. The default is to display the trace on the
19021 @item show procfs-file
19022 @kindex show procfs-file
19023 Show the file to which @code{procfs} API trace is written.
19025 @item proc-trace-entry
19026 @itemx proc-trace-exit
19027 @itemx proc-untrace-entry
19028 @itemx proc-untrace-exit
19029 @kindex proc-trace-entry
19030 @kindex proc-trace-exit
19031 @kindex proc-untrace-entry
19032 @kindex proc-untrace-exit
19033 These commands enable and disable tracing of entries into and exits
19034 from the @code{syscall} interface.
19037 @kindex info pidlist
19038 @cindex process list, QNX Neutrino
19039 For QNX Neutrino only, this command displays the list of all the
19040 processes and all the threads within each process.
19043 @kindex info meminfo
19044 @cindex mapinfo list, QNX Neutrino
19045 For QNX Neutrino only, this command displays the list of all mapinfos.
19049 @subsection Features for Debugging @sc{djgpp} Programs
19050 @cindex @sc{djgpp} debugging
19051 @cindex native @sc{djgpp} debugging
19052 @cindex MS-DOS-specific commands
19055 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19056 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19057 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19058 top of real-mode DOS systems and their emulations.
19060 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19061 defines a few commands specific to the @sc{djgpp} port. This
19062 subsection describes those commands.
19067 This is a prefix of @sc{djgpp}-specific commands which print
19068 information about the target system and important OS structures.
19071 @cindex MS-DOS system info
19072 @cindex free memory information (MS-DOS)
19073 @item info dos sysinfo
19074 This command displays assorted information about the underlying
19075 platform: the CPU type and features, the OS version and flavor, the
19076 DPMI version, and the available conventional and DPMI memory.
19081 @cindex segment descriptor tables
19082 @cindex descriptor tables display
19084 @itemx info dos ldt
19085 @itemx info dos idt
19086 These 3 commands display entries from, respectively, Global, Local,
19087 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19088 tables are data structures which store a descriptor for each segment
19089 that is currently in use. The segment's selector is an index into a
19090 descriptor table; the table entry for that index holds the
19091 descriptor's base address and limit, and its attributes and access
19094 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19095 segment (used for both data and the stack), and a DOS segment (which
19096 allows access to DOS/BIOS data structures and absolute addresses in
19097 conventional memory). However, the DPMI host will usually define
19098 additional segments in order to support the DPMI environment.
19100 @cindex garbled pointers
19101 These commands allow to display entries from the descriptor tables.
19102 Without an argument, all entries from the specified table are
19103 displayed. An argument, which should be an integer expression, means
19104 display a single entry whose index is given by the argument. For
19105 example, here's a convenient way to display information about the
19106 debugged program's data segment:
19109 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19110 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19114 This comes in handy when you want to see whether a pointer is outside
19115 the data segment's limit (i.e.@: @dfn{garbled}).
19117 @cindex page tables display (MS-DOS)
19119 @itemx info dos pte
19120 These two commands display entries from, respectively, the Page
19121 Directory and the Page Tables. Page Directories and Page Tables are
19122 data structures which control how virtual memory addresses are mapped
19123 into physical addresses. A Page Table includes an entry for every
19124 page of memory that is mapped into the program's address space; there
19125 may be several Page Tables, each one holding up to 4096 entries. A
19126 Page Directory has up to 4096 entries, one each for every Page Table
19127 that is currently in use.
19129 Without an argument, @kbd{info dos pde} displays the entire Page
19130 Directory, and @kbd{info dos pte} displays all the entries in all of
19131 the Page Tables. An argument, an integer expression, given to the
19132 @kbd{info dos pde} command means display only that entry from the Page
19133 Directory table. An argument given to the @kbd{info dos pte} command
19134 means display entries from a single Page Table, the one pointed to by
19135 the specified entry in the Page Directory.
19137 @cindex direct memory access (DMA) on MS-DOS
19138 These commands are useful when your program uses @dfn{DMA} (Direct
19139 Memory Access), which needs physical addresses to program the DMA
19142 These commands are supported only with some DPMI servers.
19144 @cindex physical address from linear address
19145 @item info dos address-pte @var{addr}
19146 This command displays the Page Table entry for a specified linear
19147 address. The argument @var{addr} is a linear address which should
19148 already have the appropriate segment's base address added to it,
19149 because this command accepts addresses which may belong to @emph{any}
19150 segment. For example, here's how to display the Page Table entry for
19151 the page where a variable @code{i} is stored:
19154 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19155 @exdent @code{Page Table entry for address 0x11a00d30:}
19156 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19160 This says that @code{i} is stored at offset @code{0xd30} from the page
19161 whose physical base address is @code{0x02698000}, and shows all the
19162 attributes of that page.
19164 Note that you must cast the addresses of variables to a @code{char *},
19165 since otherwise the value of @code{__djgpp_base_address}, the base
19166 address of all variables and functions in a @sc{djgpp} program, will
19167 be added using the rules of C pointer arithmetics: if @code{i} is
19168 declared an @code{int}, @value{GDBN} will add 4 times the value of
19169 @code{__djgpp_base_address} to the address of @code{i}.
19171 Here's another example, it displays the Page Table entry for the
19175 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19176 @exdent @code{Page Table entry for address 0x29110:}
19177 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19181 (The @code{+ 3} offset is because the transfer buffer's address is the
19182 3rd member of the @code{_go32_info_block} structure.) The output
19183 clearly shows that this DPMI server maps the addresses in conventional
19184 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19185 linear (@code{0x29110}) addresses are identical.
19187 This command is supported only with some DPMI servers.
19190 @cindex DOS serial data link, remote debugging
19191 In addition to native debugging, the DJGPP port supports remote
19192 debugging via a serial data link. The following commands are specific
19193 to remote serial debugging in the DJGPP port of @value{GDBN}.
19196 @kindex set com1base
19197 @kindex set com1irq
19198 @kindex set com2base
19199 @kindex set com2irq
19200 @kindex set com3base
19201 @kindex set com3irq
19202 @kindex set com4base
19203 @kindex set com4irq
19204 @item set com1base @var{addr}
19205 This command sets the base I/O port address of the @file{COM1} serial
19208 @item set com1irq @var{irq}
19209 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19210 for the @file{COM1} serial port.
19212 There are similar commands @samp{set com2base}, @samp{set com3irq},
19213 etc.@: for setting the port address and the @code{IRQ} lines for the
19216 @kindex show com1base
19217 @kindex show com1irq
19218 @kindex show com2base
19219 @kindex show com2irq
19220 @kindex show com3base
19221 @kindex show com3irq
19222 @kindex show com4base
19223 @kindex show com4irq
19224 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19225 display the current settings of the base address and the @code{IRQ}
19226 lines used by the COM ports.
19229 @kindex info serial
19230 @cindex DOS serial port status
19231 This command prints the status of the 4 DOS serial ports. For each
19232 port, it prints whether it's active or not, its I/O base address and
19233 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19234 counts of various errors encountered so far.
19238 @node Cygwin Native
19239 @subsection Features for Debugging MS Windows PE Executables
19240 @cindex MS Windows debugging
19241 @cindex native Cygwin debugging
19242 @cindex Cygwin-specific commands
19244 @value{GDBN} supports native debugging of MS Windows programs, including
19245 DLLs with and without symbolic debugging information.
19247 @cindex Ctrl-BREAK, MS-Windows
19248 @cindex interrupt debuggee on MS-Windows
19249 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19250 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19251 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19252 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19253 sequence, which can be used to interrupt the debuggee even if it
19256 There are various additional Cygwin-specific commands, described in
19257 this section. Working with DLLs that have no debugging symbols is
19258 described in @ref{Non-debug DLL Symbols}.
19263 This is a prefix of MS Windows-specific commands which print
19264 information about the target system and important OS structures.
19266 @item info w32 selector
19267 This command displays information returned by
19268 the Win32 API @code{GetThreadSelectorEntry} function.
19269 It takes an optional argument that is evaluated to
19270 a long value to give the information about this given selector.
19271 Without argument, this command displays information
19272 about the six segment registers.
19274 @item info w32 thread-information-block
19275 This command displays thread specific information stored in the
19276 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19277 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19281 This is a Cygwin-specific alias of @code{info shared}.
19283 @kindex dll-symbols
19285 This command loads symbols from a dll similarly to
19286 add-sym command but without the need to specify a base address.
19288 @kindex set cygwin-exceptions
19289 @cindex debugging the Cygwin DLL
19290 @cindex Cygwin DLL, debugging
19291 @item set cygwin-exceptions @var{mode}
19292 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19293 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19294 @value{GDBN} will delay recognition of exceptions, and may ignore some
19295 exceptions which seem to be caused by internal Cygwin DLL
19296 ``bookkeeping''. This option is meant primarily for debugging the
19297 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19298 @value{GDBN} users with false @code{SIGSEGV} signals.
19300 @kindex show cygwin-exceptions
19301 @item show cygwin-exceptions
19302 Displays whether @value{GDBN} will break on exceptions that happen
19303 inside the Cygwin DLL itself.
19305 @kindex set new-console
19306 @item set new-console @var{mode}
19307 If @var{mode} is @code{on} the debuggee will
19308 be started in a new console on next start.
19309 If @var{mode} is @code{off}, the debuggee will
19310 be started in the same console as the debugger.
19312 @kindex show new-console
19313 @item show new-console
19314 Displays whether a new console is used
19315 when the debuggee is started.
19317 @kindex set new-group
19318 @item set new-group @var{mode}
19319 This boolean value controls whether the debuggee should
19320 start a new group or stay in the same group as the debugger.
19321 This affects the way the Windows OS handles
19324 @kindex show new-group
19325 @item show new-group
19326 Displays current value of new-group boolean.
19328 @kindex set debugevents
19329 @item set debugevents
19330 This boolean value adds debug output concerning kernel events related
19331 to the debuggee seen by the debugger. This includes events that
19332 signal thread and process creation and exit, DLL loading and
19333 unloading, console interrupts, and debugging messages produced by the
19334 Windows @code{OutputDebugString} API call.
19336 @kindex set debugexec
19337 @item set debugexec
19338 This boolean value adds debug output concerning execute events
19339 (such as resume thread) seen by the debugger.
19341 @kindex set debugexceptions
19342 @item set debugexceptions
19343 This boolean value adds debug output concerning exceptions in the
19344 debuggee seen by the debugger.
19346 @kindex set debugmemory
19347 @item set debugmemory
19348 This boolean value adds debug output concerning debuggee memory reads
19349 and writes by the debugger.
19353 This boolean values specifies whether the debuggee is called
19354 via a shell or directly (default value is on).
19358 Displays if the debuggee will be started with a shell.
19363 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19366 @node Non-debug DLL Symbols
19367 @subsubsection Support for DLLs without Debugging Symbols
19368 @cindex DLLs with no debugging symbols
19369 @cindex Minimal symbols and DLLs
19371 Very often on windows, some of the DLLs that your program relies on do
19372 not include symbolic debugging information (for example,
19373 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19374 symbols in a DLL, it relies on the minimal amount of symbolic
19375 information contained in the DLL's export table. This section
19376 describes working with such symbols, known internally to @value{GDBN} as
19377 ``minimal symbols''.
19379 Note that before the debugged program has started execution, no DLLs
19380 will have been loaded. The easiest way around this problem is simply to
19381 start the program --- either by setting a breakpoint or letting the
19382 program run once to completion. It is also possible to force
19383 @value{GDBN} to load a particular DLL before starting the executable ---
19384 see the shared library information in @ref{Files}, or the
19385 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19386 explicitly loading symbols from a DLL with no debugging information will
19387 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19388 which may adversely affect symbol lookup performance.
19390 @subsubsection DLL Name Prefixes
19392 In keeping with the naming conventions used by the Microsoft debugging
19393 tools, DLL export symbols are made available with a prefix based on the
19394 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19395 also entered into the symbol table, so @code{CreateFileA} is often
19396 sufficient. In some cases there will be name clashes within a program
19397 (particularly if the executable itself includes full debugging symbols)
19398 necessitating the use of the fully qualified name when referring to the
19399 contents of the DLL. Use single-quotes around the name to avoid the
19400 exclamation mark (``!'') being interpreted as a language operator.
19402 Note that the internal name of the DLL may be all upper-case, even
19403 though the file name of the DLL is lower-case, or vice-versa. Since
19404 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19405 some confusion. If in doubt, try the @code{info functions} and
19406 @code{info variables} commands or even @code{maint print msymbols}
19407 (@pxref{Symbols}). Here's an example:
19410 (@value{GDBP}) info function CreateFileA
19411 All functions matching regular expression "CreateFileA":
19413 Non-debugging symbols:
19414 0x77e885f4 CreateFileA
19415 0x77e885f4 KERNEL32!CreateFileA
19419 (@value{GDBP}) info function !
19420 All functions matching regular expression "!":
19422 Non-debugging symbols:
19423 0x6100114c cygwin1!__assert
19424 0x61004034 cygwin1!_dll_crt0@@0
19425 0x61004240 cygwin1!dll_crt0(per_process *)
19429 @subsubsection Working with Minimal Symbols
19431 Symbols extracted from a DLL's export table do not contain very much
19432 type information. All that @value{GDBN} can do is guess whether a symbol
19433 refers to a function or variable depending on the linker section that
19434 contains the symbol. Also note that the actual contents of the memory
19435 contained in a DLL are not available unless the program is running. This
19436 means that you cannot examine the contents of a variable or disassemble
19437 a function within a DLL without a running program.
19439 Variables are generally treated as pointers and dereferenced
19440 automatically. For this reason, it is often necessary to prefix a
19441 variable name with the address-of operator (``&'') and provide explicit
19442 type information in the command. Here's an example of the type of
19446 (@value{GDBP}) print 'cygwin1!__argv'
19451 (@value{GDBP}) x 'cygwin1!__argv'
19452 0x10021610: "\230y\""
19455 And two possible solutions:
19458 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19459 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19463 (@value{GDBP}) x/2x &'cygwin1!__argv'
19464 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19465 (@value{GDBP}) x/x 0x10021608
19466 0x10021608: 0x0022fd98
19467 (@value{GDBP}) x/s 0x0022fd98
19468 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19471 Setting a break point within a DLL is possible even before the program
19472 starts execution. However, under these circumstances, @value{GDBN} can't
19473 examine the initial instructions of the function in order to skip the
19474 function's frame set-up code. You can work around this by using ``*&''
19475 to set the breakpoint at a raw memory address:
19478 (@value{GDBP}) break *&'python22!PyOS_Readline'
19479 Breakpoint 1 at 0x1e04eff0
19482 The author of these extensions is not entirely convinced that setting a
19483 break point within a shared DLL like @file{kernel32.dll} is completely
19487 @subsection Commands Specific to @sc{gnu} Hurd Systems
19488 @cindex @sc{gnu} Hurd debugging
19490 This subsection describes @value{GDBN} commands specific to the
19491 @sc{gnu} Hurd native debugging.
19496 @kindex set signals@r{, Hurd command}
19497 @kindex set sigs@r{, Hurd command}
19498 This command toggles the state of inferior signal interception by
19499 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19500 affected by this command. @code{sigs} is a shorthand alias for
19505 @kindex show signals@r{, Hurd command}
19506 @kindex show sigs@r{, Hurd command}
19507 Show the current state of intercepting inferior's signals.
19509 @item set signal-thread
19510 @itemx set sigthread
19511 @kindex set signal-thread
19512 @kindex set sigthread
19513 This command tells @value{GDBN} which thread is the @code{libc} signal
19514 thread. That thread is run when a signal is delivered to a running
19515 process. @code{set sigthread} is the shorthand alias of @code{set
19518 @item show signal-thread
19519 @itemx show sigthread
19520 @kindex show signal-thread
19521 @kindex show sigthread
19522 These two commands show which thread will run when the inferior is
19523 delivered a signal.
19526 @kindex set stopped@r{, Hurd command}
19527 This commands tells @value{GDBN} that the inferior process is stopped,
19528 as with the @code{SIGSTOP} signal. The stopped process can be
19529 continued by delivering a signal to it.
19532 @kindex show stopped@r{, Hurd command}
19533 This command shows whether @value{GDBN} thinks the debuggee is
19536 @item set exceptions
19537 @kindex set exceptions@r{, Hurd command}
19538 Use this command to turn off trapping of exceptions in the inferior.
19539 When exception trapping is off, neither breakpoints nor
19540 single-stepping will work. To restore the default, set exception
19543 @item show exceptions
19544 @kindex show exceptions@r{, Hurd command}
19545 Show the current state of trapping exceptions in the inferior.
19547 @item set task pause
19548 @kindex set task@r{, Hurd commands}
19549 @cindex task attributes (@sc{gnu} Hurd)
19550 @cindex pause current task (@sc{gnu} Hurd)
19551 This command toggles task suspension when @value{GDBN} has control.
19552 Setting it to on takes effect immediately, and the task is suspended
19553 whenever @value{GDBN} gets control. Setting it to off will take
19554 effect the next time the inferior is continued. If this option is set
19555 to off, you can use @code{set thread default pause on} or @code{set
19556 thread pause on} (see below) to pause individual threads.
19558 @item show task pause
19559 @kindex show task@r{, Hurd commands}
19560 Show the current state of task suspension.
19562 @item set task detach-suspend-count
19563 @cindex task suspend count
19564 @cindex detach from task, @sc{gnu} Hurd
19565 This command sets the suspend count the task will be left with when
19566 @value{GDBN} detaches from it.
19568 @item show task detach-suspend-count
19569 Show the suspend count the task will be left with when detaching.
19571 @item set task exception-port
19572 @itemx set task excp
19573 @cindex task exception port, @sc{gnu} Hurd
19574 This command sets the task exception port to which @value{GDBN} will
19575 forward exceptions. The argument should be the value of the @dfn{send
19576 rights} of the task. @code{set task excp} is a shorthand alias.
19578 @item set noninvasive
19579 @cindex noninvasive task options
19580 This command switches @value{GDBN} to a mode that is the least
19581 invasive as far as interfering with the inferior is concerned. This
19582 is the same as using @code{set task pause}, @code{set exceptions}, and
19583 @code{set signals} to values opposite to the defaults.
19585 @item info send-rights
19586 @itemx info receive-rights
19587 @itemx info port-rights
19588 @itemx info port-sets
19589 @itemx info dead-names
19592 @cindex send rights, @sc{gnu} Hurd
19593 @cindex receive rights, @sc{gnu} Hurd
19594 @cindex port rights, @sc{gnu} Hurd
19595 @cindex port sets, @sc{gnu} Hurd
19596 @cindex dead names, @sc{gnu} Hurd
19597 These commands display information about, respectively, send rights,
19598 receive rights, port rights, port sets, and dead names of a task.
19599 There are also shorthand aliases: @code{info ports} for @code{info
19600 port-rights} and @code{info psets} for @code{info port-sets}.
19602 @item set thread pause
19603 @kindex set thread@r{, Hurd command}
19604 @cindex thread properties, @sc{gnu} Hurd
19605 @cindex pause current thread (@sc{gnu} Hurd)
19606 This command toggles current thread suspension when @value{GDBN} has
19607 control. Setting it to on takes effect immediately, and the current
19608 thread is suspended whenever @value{GDBN} gets control. Setting it to
19609 off will take effect the next time the inferior is continued.
19610 Normally, this command has no effect, since when @value{GDBN} has
19611 control, the whole task is suspended. However, if you used @code{set
19612 task pause off} (see above), this command comes in handy to suspend
19613 only the current thread.
19615 @item show thread pause
19616 @kindex show thread@r{, Hurd command}
19617 This command shows the state of current thread suspension.
19619 @item set thread run
19620 This command sets whether the current thread is allowed to run.
19622 @item show thread run
19623 Show whether the current thread is allowed to run.
19625 @item set thread detach-suspend-count
19626 @cindex thread suspend count, @sc{gnu} Hurd
19627 @cindex detach from thread, @sc{gnu} Hurd
19628 This command sets the suspend count @value{GDBN} will leave on a
19629 thread when detaching. This number is relative to the suspend count
19630 found by @value{GDBN} when it notices the thread; use @code{set thread
19631 takeover-suspend-count} to force it to an absolute value.
19633 @item show thread detach-suspend-count
19634 Show the suspend count @value{GDBN} will leave on the thread when
19637 @item set thread exception-port
19638 @itemx set thread excp
19639 Set the thread exception port to which to forward exceptions. This
19640 overrides the port set by @code{set task exception-port} (see above).
19641 @code{set thread excp} is the shorthand alias.
19643 @item set thread takeover-suspend-count
19644 Normally, @value{GDBN}'s thread suspend counts are relative to the
19645 value @value{GDBN} finds when it notices each thread. This command
19646 changes the suspend counts to be absolute instead.
19648 @item set thread default
19649 @itemx show thread default
19650 @cindex thread default settings, @sc{gnu} Hurd
19651 Each of the above @code{set thread} commands has a @code{set thread
19652 default} counterpart (e.g., @code{set thread default pause}, @code{set
19653 thread default exception-port}, etc.). The @code{thread default}
19654 variety of commands sets the default thread properties for all
19655 threads; you can then change the properties of individual threads with
19656 the non-default commands.
19663 @value{GDBN} provides the following commands specific to the Darwin target:
19666 @item set debug darwin @var{num}
19667 @kindex set debug darwin
19668 When set to a non zero value, enables debugging messages specific to
19669 the Darwin support. Higher values produce more verbose output.
19671 @item show debug darwin
19672 @kindex show debug darwin
19673 Show the current state of Darwin messages.
19675 @item set debug mach-o @var{num}
19676 @kindex set debug mach-o
19677 When set to a non zero value, enables debugging messages while
19678 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19679 file format used on Darwin for object and executable files.) Higher
19680 values produce more verbose output. This is a command to diagnose
19681 problems internal to @value{GDBN} and should not be needed in normal
19684 @item show debug mach-o
19685 @kindex show debug mach-o
19686 Show the current state of Mach-O file messages.
19688 @item set mach-exceptions on
19689 @itemx set mach-exceptions off
19690 @kindex set mach-exceptions
19691 On Darwin, faults are first reported as a Mach exception and are then
19692 mapped to a Posix signal. Use this command to turn on trapping of
19693 Mach exceptions in the inferior. This might be sometimes useful to
19694 better understand the cause of a fault. The default is off.
19696 @item show mach-exceptions
19697 @kindex show mach-exceptions
19698 Show the current state of exceptions trapping.
19703 @section Embedded Operating Systems
19705 This section describes configurations involving the debugging of
19706 embedded operating systems that are available for several different
19710 * VxWorks:: Using @value{GDBN} with VxWorks
19713 @value{GDBN} includes the ability to debug programs running on
19714 various real-time operating systems.
19717 @subsection Using @value{GDBN} with VxWorks
19723 @kindex target vxworks
19724 @item target vxworks @var{machinename}
19725 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19726 is the target system's machine name or IP address.
19730 On VxWorks, @code{load} links @var{filename} dynamically on the
19731 current target system as well as adding its symbols in @value{GDBN}.
19733 @value{GDBN} enables developers to spawn and debug tasks running on networked
19734 VxWorks targets from a Unix host. Already-running tasks spawned from
19735 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19736 both the Unix host and on the VxWorks target. The program
19737 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19738 installed with the name @code{vxgdb}, to distinguish it from a
19739 @value{GDBN} for debugging programs on the host itself.)
19742 @item VxWorks-timeout @var{args}
19743 @kindex vxworks-timeout
19744 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19745 This option is set by the user, and @var{args} represents the number of
19746 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19747 your VxWorks target is a slow software simulator or is on the far side
19748 of a thin network line.
19751 The following information on connecting to VxWorks was current when
19752 this manual was produced; newer releases of VxWorks may use revised
19755 @findex INCLUDE_RDB
19756 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19757 to include the remote debugging interface routines in the VxWorks
19758 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19759 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19760 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19761 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19762 information on configuring and remaking VxWorks, see the manufacturer's
19764 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19766 Once you have included @file{rdb.a} in your VxWorks system image and set
19767 your Unix execution search path to find @value{GDBN}, you are ready to
19768 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19769 @code{vxgdb}, depending on your installation).
19771 @value{GDBN} comes up showing the prompt:
19778 * VxWorks Connection:: Connecting to VxWorks
19779 * VxWorks Download:: VxWorks download
19780 * VxWorks Attach:: Running tasks
19783 @node VxWorks Connection
19784 @subsubsection Connecting to VxWorks
19786 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19787 network. To connect to a target whose host name is ``@code{tt}'', type:
19790 (vxgdb) target vxworks tt
19794 @value{GDBN} displays messages like these:
19797 Attaching remote machine across net...
19802 @value{GDBN} then attempts to read the symbol tables of any object modules
19803 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19804 these files by searching the directories listed in the command search
19805 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19806 to find an object file, it displays a message such as:
19809 prog.o: No such file or directory.
19812 When this happens, add the appropriate directory to the search path with
19813 the @value{GDBN} command @code{path}, and execute the @code{target}
19816 @node VxWorks Download
19817 @subsubsection VxWorks Download
19819 @cindex download to VxWorks
19820 If you have connected to the VxWorks target and you want to debug an
19821 object that has not yet been loaded, you can use the @value{GDBN}
19822 @code{load} command to download a file from Unix to VxWorks
19823 incrementally. The object file given as an argument to the @code{load}
19824 command is actually opened twice: first by the VxWorks target in order
19825 to download the code, then by @value{GDBN} in order to read the symbol
19826 table. This can lead to problems if the current working directories on
19827 the two systems differ. If both systems have NFS mounted the same
19828 filesystems, you can avoid these problems by using absolute paths.
19829 Otherwise, it is simplest to set the working directory on both systems
19830 to the directory in which the object file resides, and then to reference
19831 the file by its name, without any path. For instance, a program
19832 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19833 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19834 program, type this on VxWorks:
19837 -> cd "@var{vxpath}/vw/demo/rdb"
19841 Then, in @value{GDBN}, type:
19844 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19845 (vxgdb) load prog.o
19848 @value{GDBN} displays a response similar to this:
19851 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19854 You can also use the @code{load} command to reload an object module
19855 after editing and recompiling the corresponding source file. Note that
19856 this makes @value{GDBN} delete all currently-defined breakpoints,
19857 auto-displays, and convenience variables, and to clear the value
19858 history. (This is necessary in order to preserve the integrity of
19859 debugger's data structures that reference the target system's symbol
19862 @node VxWorks Attach
19863 @subsubsection Running Tasks
19865 @cindex running VxWorks tasks
19866 You can also attach to an existing task using the @code{attach} command as
19870 (vxgdb) attach @var{task}
19874 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19875 or suspended when you attach to it. Running tasks are suspended at
19876 the time of attachment.
19878 @node Embedded Processors
19879 @section Embedded Processors
19881 This section goes into details specific to particular embedded
19884 @cindex send command to simulator
19885 Whenever a specific embedded processor has a simulator, @value{GDBN}
19886 allows to send an arbitrary command to the simulator.
19889 @item sim @var{command}
19890 @kindex sim@r{, a command}
19891 Send an arbitrary @var{command} string to the simulator. Consult the
19892 documentation for the specific simulator in use for information about
19893 acceptable commands.
19899 * M32R/D:: Renesas M32R/D
19900 * M68K:: Motorola M68K
19901 * MicroBlaze:: Xilinx MicroBlaze
19902 * MIPS Embedded:: MIPS Embedded
19903 * PowerPC Embedded:: PowerPC Embedded
19904 * PA:: HP PA Embedded
19905 * Sparclet:: Tsqware Sparclet
19906 * Sparclite:: Fujitsu Sparclite
19907 * Z8000:: Zilog Z8000
19910 * Super-H:: Renesas Super-H
19919 @item target rdi @var{dev}
19920 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19921 use this target to communicate with both boards running the Angel
19922 monitor, or with the EmbeddedICE JTAG debug device.
19925 @item target rdp @var{dev}
19930 @value{GDBN} provides the following ARM-specific commands:
19933 @item set arm disassembler
19935 This commands selects from a list of disassembly styles. The
19936 @code{"std"} style is the standard style.
19938 @item show arm disassembler
19940 Show the current disassembly style.
19942 @item set arm apcs32
19943 @cindex ARM 32-bit mode
19944 This command toggles ARM operation mode between 32-bit and 26-bit.
19946 @item show arm apcs32
19947 Display the current usage of the ARM 32-bit mode.
19949 @item set arm fpu @var{fputype}
19950 This command sets the ARM floating-point unit (FPU) type. The
19951 argument @var{fputype} can be one of these:
19955 Determine the FPU type by querying the OS ABI.
19957 Software FPU, with mixed-endian doubles on little-endian ARM
19960 GCC-compiled FPA co-processor.
19962 Software FPU with pure-endian doubles.
19968 Show the current type of the FPU.
19971 This command forces @value{GDBN} to use the specified ABI.
19974 Show the currently used ABI.
19976 @item set arm fallback-mode (arm|thumb|auto)
19977 @value{GDBN} uses the symbol table, when available, to determine
19978 whether instructions are ARM or Thumb. This command controls
19979 @value{GDBN}'s default behavior when the symbol table is not
19980 available. The default is @samp{auto}, which causes @value{GDBN} to
19981 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19984 @item show arm fallback-mode
19985 Show the current fallback instruction mode.
19987 @item set arm force-mode (arm|thumb|auto)
19988 This command overrides use of the symbol table to determine whether
19989 instructions are ARM or Thumb. The default is @samp{auto}, which
19990 causes @value{GDBN} to use the symbol table and then the setting
19991 of @samp{set arm fallback-mode}.
19993 @item show arm force-mode
19994 Show the current forced instruction mode.
19996 @item set debug arm
19997 Toggle whether to display ARM-specific debugging messages from the ARM
19998 target support subsystem.
20000 @item show debug arm
20001 Show whether ARM-specific debugging messages are enabled.
20004 The following commands are available when an ARM target is debugged
20005 using the RDI interface:
20008 @item rdilogfile @r{[}@var{file}@r{]}
20010 @cindex ADP (Angel Debugger Protocol) logging
20011 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20012 With an argument, sets the log file to the specified @var{file}. With
20013 no argument, show the current log file name. The default log file is
20016 @item rdilogenable @r{[}@var{arg}@r{]}
20017 @kindex rdilogenable
20018 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20019 enables logging, with an argument 0 or @code{"no"} disables it. With
20020 no arguments displays the current setting. When logging is enabled,
20021 ADP packets exchanged between @value{GDBN} and the RDI target device
20022 are logged to a file.
20024 @item set rdiromatzero
20025 @kindex set rdiromatzero
20026 @cindex ROM at zero address, RDI
20027 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20028 vector catching is disabled, so that zero address can be used. If off
20029 (the default), vector catching is enabled. For this command to take
20030 effect, it needs to be invoked prior to the @code{target rdi} command.
20032 @item show rdiromatzero
20033 @kindex show rdiromatzero
20034 Show the current setting of ROM at zero address.
20036 @item set rdiheartbeat
20037 @kindex set rdiheartbeat
20038 @cindex RDI heartbeat
20039 Enable or disable RDI heartbeat packets. It is not recommended to
20040 turn on this option, since it confuses ARM and EPI JTAG interface, as
20041 well as the Angel monitor.
20043 @item show rdiheartbeat
20044 @kindex show rdiheartbeat
20045 Show the setting of RDI heartbeat packets.
20049 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20050 The @value{GDBN} ARM simulator accepts the following optional arguments.
20053 @item --swi-support=@var{type}
20054 Tell the simulator which SWI interfaces to support.
20055 @var{type} may be a comma separated list of the following values.
20056 The default value is @code{all}.
20069 @subsection Renesas M32R/D and M32R/SDI
20072 @kindex target m32r
20073 @item target m32r @var{dev}
20074 Renesas M32R/D ROM monitor.
20076 @kindex target m32rsdi
20077 @item target m32rsdi @var{dev}
20078 Renesas M32R SDI server, connected via parallel port to the board.
20081 The following @value{GDBN} commands are specific to the M32R monitor:
20084 @item set download-path @var{path}
20085 @kindex set download-path
20086 @cindex find downloadable @sc{srec} files (M32R)
20087 Set the default path for finding downloadable @sc{srec} files.
20089 @item show download-path
20090 @kindex show download-path
20091 Show the default path for downloadable @sc{srec} files.
20093 @item set board-address @var{addr}
20094 @kindex set board-address
20095 @cindex M32-EVA target board address
20096 Set the IP address for the M32R-EVA target board.
20098 @item show board-address
20099 @kindex show board-address
20100 Show the current IP address of the target board.
20102 @item set server-address @var{addr}
20103 @kindex set server-address
20104 @cindex download server address (M32R)
20105 Set the IP address for the download server, which is the @value{GDBN}'s
20108 @item show server-address
20109 @kindex show server-address
20110 Display the IP address of the download server.
20112 @item upload @r{[}@var{file}@r{]}
20113 @kindex upload@r{, M32R}
20114 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20115 upload capability. If no @var{file} argument is given, the current
20116 executable file is uploaded.
20118 @item tload @r{[}@var{file}@r{]}
20119 @kindex tload@r{, M32R}
20120 Test the @code{upload} command.
20123 The following commands are available for M32R/SDI:
20128 @cindex reset SDI connection, M32R
20129 This command resets the SDI connection.
20133 This command shows the SDI connection status.
20136 @kindex debug_chaos
20137 @cindex M32R/Chaos debugging
20138 Instructs the remote that M32R/Chaos debugging is to be used.
20140 @item use_debug_dma
20141 @kindex use_debug_dma
20142 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20145 @kindex use_mon_code
20146 Instructs the remote to use the MON_CODE method of accessing memory.
20149 @kindex use_ib_break
20150 Instructs the remote to set breakpoints by IB break.
20152 @item use_dbt_break
20153 @kindex use_dbt_break
20154 Instructs the remote to set breakpoints by DBT.
20160 The Motorola m68k configuration includes ColdFire support, and a
20161 target command for the following ROM monitor.
20165 @kindex target dbug
20166 @item target dbug @var{dev}
20167 dBUG ROM monitor for Motorola ColdFire.
20172 @subsection MicroBlaze
20173 @cindex Xilinx MicroBlaze
20174 @cindex XMD, Xilinx Microprocessor Debugger
20176 The MicroBlaze is a soft-core processor supported on various Xilinx
20177 FPGAs, such as Spartan or Virtex series. Boards with these processors
20178 usually have JTAG ports which connect to a host system running the Xilinx
20179 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20180 This host system is used to download the configuration bitstream to
20181 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20182 communicates with the target board using the JTAG interface and
20183 presents a @code{gdbserver} interface to the board. By default
20184 @code{xmd} uses port @code{1234}. (While it is possible to change
20185 this default port, it requires the use of undocumented @code{xmd}
20186 commands. Contact Xilinx support if you need to do this.)
20188 Use these GDB commands to connect to the MicroBlaze target processor.
20191 @item target remote :1234
20192 Use this command to connect to the target if you are running @value{GDBN}
20193 on the same system as @code{xmd}.
20195 @item target remote @var{xmd-host}:1234
20196 Use this command to connect to the target if it is connected to @code{xmd}
20197 running on a different system named @var{xmd-host}.
20200 Use this command to download a program to the MicroBlaze target.
20202 @item set debug microblaze @var{n}
20203 Enable MicroBlaze-specific debugging messages if non-zero.
20205 @item show debug microblaze @var{n}
20206 Show MicroBlaze-specific debugging level.
20209 @node MIPS Embedded
20210 @subsection @acronym{MIPS} Embedded
20212 @cindex @acronym{MIPS} boards
20213 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20214 @acronym{MIPS} board attached to a serial line. This is available when
20215 you configure @value{GDBN} with @samp{--target=mips-elf}.
20218 Use these @value{GDBN} commands to specify the connection to your target board:
20221 @item target mips @var{port}
20222 @kindex target mips @var{port}
20223 To run a program on the board, start up @code{@value{GDBP}} with the
20224 name of your program as the argument. To connect to the board, use the
20225 command @samp{target mips @var{port}}, where @var{port} is the name of
20226 the serial port connected to the board. If the program has not already
20227 been downloaded to the board, you may use the @code{load} command to
20228 download it. You can then use all the usual @value{GDBN} commands.
20230 For example, this sequence connects to the target board through a serial
20231 port, and loads and runs a program called @var{prog} through the
20235 host$ @value{GDBP} @var{prog}
20236 @value{GDBN} is free software and @dots{}
20237 (@value{GDBP}) target mips /dev/ttyb
20238 (@value{GDBP}) load @var{prog}
20242 @item target mips @var{hostname}:@var{portnumber}
20243 On some @value{GDBN} host configurations, you can specify a TCP
20244 connection (for instance, to a serial line managed by a terminal
20245 concentrator) instead of a serial port, using the syntax
20246 @samp{@var{hostname}:@var{portnumber}}.
20248 @item target pmon @var{port}
20249 @kindex target pmon @var{port}
20252 @item target ddb @var{port}
20253 @kindex target ddb @var{port}
20254 NEC's DDB variant of PMON for Vr4300.
20256 @item target lsi @var{port}
20257 @kindex target lsi @var{port}
20258 LSI variant of PMON.
20260 @kindex target r3900
20261 @item target r3900 @var{dev}
20262 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20264 @kindex target array
20265 @item target array @var{dev}
20266 Array Tech LSI33K RAID controller board.
20272 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20275 @item set mipsfpu double
20276 @itemx set mipsfpu single
20277 @itemx set mipsfpu none
20278 @itemx set mipsfpu auto
20279 @itemx show mipsfpu
20280 @kindex set mipsfpu
20281 @kindex show mipsfpu
20282 @cindex @acronym{MIPS} remote floating point
20283 @cindex floating point, @acronym{MIPS} remote
20284 If your target board does not support the @acronym{MIPS} floating point
20285 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20286 need this, you may wish to put the command in your @value{GDBN} init
20287 file). This tells @value{GDBN} how to find the return value of
20288 functions which return floating point values. It also allows
20289 @value{GDBN} to avoid saving the floating point registers when calling
20290 functions on the board. If you are using a floating point coprocessor
20291 with only single precision floating point support, as on the @sc{r4650}
20292 processor, use the command @samp{set mipsfpu single}. The default
20293 double precision floating point coprocessor may be selected using
20294 @samp{set mipsfpu double}.
20296 In previous versions the only choices were double precision or no
20297 floating point, so @samp{set mipsfpu on} will select double precision
20298 and @samp{set mipsfpu off} will select no floating point.
20300 As usual, you can inquire about the @code{mipsfpu} variable with
20301 @samp{show mipsfpu}.
20303 @item set timeout @var{seconds}
20304 @itemx set retransmit-timeout @var{seconds}
20305 @itemx show timeout
20306 @itemx show retransmit-timeout
20307 @cindex @code{timeout}, @acronym{MIPS} protocol
20308 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20309 @kindex set timeout
20310 @kindex show timeout
20311 @kindex set retransmit-timeout
20312 @kindex show retransmit-timeout
20313 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20314 remote protocol, with the @code{set timeout @var{seconds}} command. The
20315 default is 5 seconds. Similarly, you can control the timeout used while
20316 waiting for an acknowledgment of a packet with the @code{set
20317 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20318 You can inspect both values with @code{show timeout} and @code{show
20319 retransmit-timeout}. (These commands are @emph{only} available when
20320 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20322 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20323 is waiting for your program to stop. In that case, @value{GDBN} waits
20324 forever because it has no way of knowing how long the program is going
20325 to run before stopping.
20327 @item set syn-garbage-limit @var{num}
20328 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20329 @cindex synchronize with remote @acronym{MIPS} target
20330 Limit the maximum number of characters @value{GDBN} should ignore when
20331 it tries to synchronize with the remote target. The default is 10
20332 characters. Setting the limit to -1 means there's no limit.
20334 @item show syn-garbage-limit
20335 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20336 Show the current limit on the number of characters to ignore when
20337 trying to synchronize with the remote system.
20339 @item set monitor-prompt @var{prompt}
20340 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20341 @cindex remote monitor prompt
20342 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20343 remote monitor. The default depends on the target:
20353 @item show monitor-prompt
20354 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20355 Show the current strings @value{GDBN} expects as the prompt from the
20358 @item set monitor-warnings
20359 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20360 Enable or disable monitor warnings about hardware breakpoints. This
20361 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20362 display warning messages whose codes are returned by the @code{lsi}
20363 PMON monitor for breakpoint commands.
20365 @item show monitor-warnings
20366 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20367 Show the current setting of printing monitor warnings.
20369 @item pmon @var{command}
20370 @kindex pmon@r{, @acronym{MIPS} remote}
20371 @cindex send PMON command
20372 This command allows sending an arbitrary @var{command} string to the
20373 monitor. The monitor must be in debug mode for this to work.
20376 @node PowerPC Embedded
20377 @subsection PowerPC Embedded
20379 @cindex DVC register
20380 @value{GDBN} supports using the DVC (Data Value Compare) register to
20381 implement in hardware simple hardware watchpoint conditions of the form:
20384 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20385 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20388 The DVC register will be automatically used when @value{GDBN} detects
20389 such pattern in a condition expression, and the created watchpoint uses one
20390 debug register (either the @code{exact-watchpoints} option is on and the
20391 variable is scalar, or the variable has a length of one byte). This feature
20392 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20395 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20396 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20397 in which case watchpoints using only one debug register are created when
20398 watching variables of scalar types.
20400 You can create an artificial array to watch an arbitrary memory
20401 region using one of the following commands (@pxref{Expressions}):
20404 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20405 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20408 PowerPC embedded processors support masked watchpoints. See the discussion
20409 about the @code{mask} argument in @ref{Set Watchpoints}.
20411 @cindex ranged breakpoint
20412 PowerPC embedded processors support hardware accelerated
20413 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20414 the inferior whenever it executes an instruction at any address within
20415 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20416 use the @code{break-range} command.
20418 @value{GDBN} provides the following PowerPC-specific commands:
20421 @kindex break-range
20422 @item break-range @var{start-location}, @var{end-location}
20423 Set a breakpoint for an address range.
20424 @var{start-location} and @var{end-location} can specify a function name,
20425 a line number, an offset of lines from the current line or from the start
20426 location, or an address of an instruction (see @ref{Specify Location},
20427 for a list of all the possible ways to specify a @var{location}.)
20428 The breakpoint will stop execution of the inferior whenever it
20429 executes an instruction at any address within the specified range,
20430 (including @var{start-location} and @var{end-location}.)
20432 @kindex set powerpc
20433 @item set powerpc soft-float
20434 @itemx show powerpc soft-float
20435 Force @value{GDBN} to use (or not use) a software floating point calling
20436 convention. By default, @value{GDBN} selects the calling convention based
20437 on the selected architecture and the provided executable file.
20439 @item set powerpc vector-abi
20440 @itemx show powerpc vector-abi
20441 Force @value{GDBN} to use the specified calling convention for vector
20442 arguments and return values. The valid options are @samp{auto};
20443 @samp{generic}, to avoid vector registers even if they are present;
20444 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20445 registers. By default, @value{GDBN} selects the calling convention
20446 based on the selected architecture and the provided executable file.
20448 @item set powerpc exact-watchpoints
20449 @itemx show powerpc exact-watchpoints
20450 Allow @value{GDBN} to use only one debug register when watching a variable
20451 of scalar type, thus assuming that the variable is accessed through the
20452 address of its first byte.
20454 @kindex target dink32
20455 @item target dink32 @var{dev}
20456 DINK32 ROM monitor.
20458 @kindex target ppcbug
20459 @item target ppcbug @var{dev}
20460 @kindex target ppcbug1
20461 @item target ppcbug1 @var{dev}
20462 PPCBUG ROM monitor for PowerPC.
20465 @item target sds @var{dev}
20466 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20469 @cindex SDS protocol
20470 The following commands specific to the SDS protocol are supported
20474 @item set sdstimeout @var{nsec}
20475 @kindex set sdstimeout
20476 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20477 default is 2 seconds.
20479 @item show sdstimeout
20480 @kindex show sdstimeout
20481 Show the current value of the SDS timeout.
20483 @item sds @var{command}
20484 @kindex sds@r{, a command}
20485 Send the specified @var{command} string to the SDS monitor.
20490 @subsection HP PA Embedded
20494 @kindex target op50n
20495 @item target op50n @var{dev}
20496 OP50N monitor, running on an OKI HPPA board.
20498 @kindex target w89k
20499 @item target w89k @var{dev}
20500 W89K monitor, running on a Winbond HPPA board.
20505 @subsection Tsqware Sparclet
20509 @value{GDBN} enables developers to debug tasks running on
20510 Sparclet targets from a Unix host.
20511 @value{GDBN} uses code that runs on
20512 both the Unix host and on the Sparclet target. The program
20513 @code{@value{GDBP}} is installed and executed on the Unix host.
20516 @item remotetimeout @var{args}
20517 @kindex remotetimeout
20518 @value{GDBN} supports the option @code{remotetimeout}.
20519 This option is set by the user, and @var{args} represents the number of
20520 seconds @value{GDBN} waits for responses.
20523 @cindex compiling, on Sparclet
20524 When compiling for debugging, include the options @samp{-g} to get debug
20525 information and @samp{-Ttext} to relocate the program to where you wish to
20526 load it on the target. You may also want to add the options @samp{-n} or
20527 @samp{-N} in order to reduce the size of the sections. Example:
20530 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20533 You can use @code{objdump} to verify that the addresses are what you intended:
20536 sparclet-aout-objdump --headers --syms prog
20539 @cindex running, on Sparclet
20541 your Unix execution search path to find @value{GDBN}, you are ready to
20542 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20543 (or @code{sparclet-aout-gdb}, depending on your installation).
20545 @value{GDBN} comes up showing the prompt:
20552 * Sparclet File:: Setting the file to debug
20553 * Sparclet Connection:: Connecting to Sparclet
20554 * Sparclet Download:: Sparclet download
20555 * Sparclet Execution:: Running and debugging
20558 @node Sparclet File
20559 @subsubsection Setting File to Debug
20561 The @value{GDBN} command @code{file} lets you choose with program to debug.
20564 (gdbslet) file prog
20568 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20569 @value{GDBN} locates
20570 the file by searching the directories listed in the command search
20572 If the file was compiled with debug information (option @samp{-g}), source
20573 files will be searched as well.
20574 @value{GDBN} locates
20575 the source files by searching the directories listed in the directory search
20576 path (@pxref{Environment, ,Your Program's Environment}).
20578 to find a file, it displays a message such as:
20581 prog: No such file or directory.
20584 When this happens, add the appropriate directories to the search paths with
20585 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20586 @code{target} command again.
20588 @node Sparclet Connection
20589 @subsubsection Connecting to Sparclet
20591 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20592 To connect to a target on serial port ``@code{ttya}'', type:
20595 (gdbslet) target sparclet /dev/ttya
20596 Remote target sparclet connected to /dev/ttya
20597 main () at ../prog.c:3
20601 @value{GDBN} displays messages like these:
20607 @node Sparclet Download
20608 @subsubsection Sparclet Download
20610 @cindex download to Sparclet
20611 Once connected to the Sparclet target,
20612 you can use the @value{GDBN}
20613 @code{load} command to download the file from the host to the target.
20614 The file name and load offset should be given as arguments to the @code{load}
20616 Since the file format is aout, the program must be loaded to the starting
20617 address. You can use @code{objdump} to find out what this value is. The load
20618 offset is an offset which is added to the VMA (virtual memory address)
20619 of each of the file's sections.
20620 For instance, if the program
20621 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20622 and bss at 0x12010170, in @value{GDBN}, type:
20625 (gdbslet) load prog 0x12010000
20626 Loading section .text, size 0xdb0 vma 0x12010000
20629 If the code is loaded at a different address then what the program was linked
20630 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20631 to tell @value{GDBN} where to map the symbol table.
20633 @node Sparclet Execution
20634 @subsubsection Running and Debugging
20636 @cindex running and debugging Sparclet programs
20637 You can now begin debugging the task using @value{GDBN}'s execution control
20638 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20639 manual for the list of commands.
20643 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20645 Starting program: prog
20646 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20647 3 char *symarg = 0;
20649 4 char *execarg = "hello!";
20654 @subsection Fujitsu Sparclite
20658 @kindex target sparclite
20659 @item target sparclite @var{dev}
20660 Fujitsu sparclite boards, used only for the purpose of loading.
20661 You must use an additional command to debug the program.
20662 For example: target remote @var{dev} using @value{GDBN} standard
20668 @subsection Zilog Z8000
20671 @cindex simulator, Z8000
20672 @cindex Zilog Z8000 simulator
20674 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20677 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20678 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20679 segmented variant). The simulator recognizes which architecture is
20680 appropriate by inspecting the object code.
20683 @item target sim @var{args}
20685 @kindex target sim@r{, with Z8000}
20686 Debug programs on a simulated CPU. If the simulator supports setup
20687 options, specify them via @var{args}.
20691 After specifying this target, you can debug programs for the simulated
20692 CPU in the same style as programs for your host computer; use the
20693 @code{file} command to load a new program image, the @code{run} command
20694 to run your program, and so on.
20696 As well as making available all the usual machine registers
20697 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20698 additional items of information as specially named registers:
20703 Counts clock-ticks in the simulator.
20706 Counts instructions run in the simulator.
20709 Execution time in 60ths of a second.
20713 You can refer to these values in @value{GDBN} expressions with the usual
20714 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20715 conditional breakpoint that suspends only after at least 5000
20716 simulated clock ticks.
20719 @subsection Atmel AVR
20722 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20723 following AVR-specific commands:
20726 @item info io_registers
20727 @kindex info io_registers@r{, AVR}
20728 @cindex I/O registers (Atmel AVR)
20729 This command displays information about the AVR I/O registers. For
20730 each register, @value{GDBN} prints its number and value.
20737 When configured for debugging CRIS, @value{GDBN} provides the
20738 following CRIS-specific commands:
20741 @item set cris-version @var{ver}
20742 @cindex CRIS version
20743 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20744 The CRIS version affects register names and sizes. This command is useful in
20745 case autodetection of the CRIS version fails.
20747 @item show cris-version
20748 Show the current CRIS version.
20750 @item set cris-dwarf2-cfi
20751 @cindex DWARF-2 CFI and CRIS
20752 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20753 Change to @samp{off} when using @code{gcc-cris} whose version is below
20756 @item show cris-dwarf2-cfi
20757 Show the current state of using DWARF-2 CFI.
20759 @item set cris-mode @var{mode}
20761 Set the current CRIS mode to @var{mode}. It should only be changed when
20762 debugging in guru mode, in which case it should be set to
20763 @samp{guru} (the default is @samp{normal}).
20765 @item show cris-mode
20766 Show the current CRIS mode.
20770 @subsection Renesas Super-H
20773 For the Renesas Super-H processor, @value{GDBN} provides these
20777 @item set sh calling-convention @var{convention}
20778 @kindex set sh calling-convention
20779 Set the calling-convention used when calling functions from @value{GDBN}.
20780 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20781 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20782 convention. If the DWARF-2 information of the called function specifies
20783 that the function follows the Renesas calling convention, the function
20784 is called using the Renesas calling convention. If the calling convention
20785 is set to @samp{renesas}, the Renesas calling convention is always used,
20786 regardless of the DWARF-2 information. This can be used to override the
20787 default of @samp{gcc} if debug information is missing, or the compiler
20788 does not emit the DWARF-2 calling convention entry for a function.
20790 @item show sh calling-convention
20791 @kindex show sh calling-convention
20792 Show the current calling convention setting.
20797 @node Architectures
20798 @section Architectures
20800 This section describes characteristics of architectures that affect
20801 all uses of @value{GDBN} with the architecture, both native and cross.
20808 * HPPA:: HP PA architecture
20809 * SPU:: Cell Broadband Engine SPU architecture
20814 @subsection AArch64
20815 @cindex AArch64 support
20817 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20818 following special commands:
20821 @item set debug aarch64
20822 @kindex set debug aarch64
20823 This command determines whether AArch64 architecture-specific debugging
20824 messages are to be displayed.
20826 @item show debug aarch64
20827 Show whether AArch64 debugging messages are displayed.
20832 @subsection x86 Architecture-specific Issues
20835 @item set struct-convention @var{mode}
20836 @kindex set struct-convention
20837 @cindex struct return convention
20838 @cindex struct/union returned in registers
20839 Set the convention used by the inferior to return @code{struct}s and
20840 @code{union}s from functions to @var{mode}. Possible values of
20841 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20842 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20843 are returned on the stack, while @code{"reg"} means that a
20844 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20845 be returned in a register.
20847 @item show struct-convention
20848 @kindex show struct-convention
20849 Show the current setting of the convention to return @code{struct}s
20856 See the following section.
20859 @subsection @acronym{MIPS}
20861 @cindex stack on Alpha
20862 @cindex stack on @acronym{MIPS}
20863 @cindex Alpha stack
20864 @cindex @acronym{MIPS} stack
20865 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20866 sometimes requires @value{GDBN} to search backward in the object code to
20867 find the beginning of a function.
20869 @cindex response time, @acronym{MIPS} debugging
20870 To improve response time (especially for embedded applications, where
20871 @value{GDBN} may be restricted to a slow serial line for this search)
20872 you may want to limit the size of this search, using one of these
20876 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20877 @item set heuristic-fence-post @var{limit}
20878 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20879 search for the beginning of a function. A value of @var{0} (the
20880 default) means there is no limit. However, except for @var{0}, the
20881 larger the limit the more bytes @code{heuristic-fence-post} must search
20882 and therefore the longer it takes to run. You should only need to use
20883 this command when debugging a stripped executable.
20885 @item show heuristic-fence-post
20886 Display the current limit.
20890 These commands are available @emph{only} when @value{GDBN} is configured
20891 for debugging programs on Alpha or @acronym{MIPS} processors.
20893 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20897 @item set mips abi @var{arg}
20898 @kindex set mips abi
20899 @cindex set ABI for @acronym{MIPS}
20900 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20901 values of @var{arg} are:
20905 The default ABI associated with the current binary (this is the
20915 @item show mips abi
20916 @kindex show mips abi
20917 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20919 @item set mips compression @var{arg}
20920 @kindex set mips compression
20921 @cindex code compression, @acronym{MIPS}
20922 Tell @value{GDBN} which @acronym{MIPS} compressed
20923 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20924 inferior. @value{GDBN} uses this for code disassembly and other
20925 internal interpretation purposes. This setting is only referred to
20926 when no executable has been associated with the debugging session or
20927 the executable does not provide information about the encoding it uses.
20928 Otherwise this setting is automatically updated from information
20929 provided by the executable.
20931 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20932 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20933 executables containing @acronym{MIPS16} code frequently are not
20934 identified as such.
20936 This setting is ``sticky''; that is, it retains its value across
20937 debugging sessions until reset either explicitly with this command or
20938 implicitly from an executable.
20940 The compiler and/or assembler typically add symbol table annotations to
20941 identify functions compiled for the @acronym{MIPS16} or
20942 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20943 are present, @value{GDBN} uses them in preference to the global
20944 compressed @acronym{ISA} encoding setting.
20946 @item show mips compression
20947 @kindex show mips compression
20948 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20949 @value{GDBN} to debug the inferior.
20952 @itemx show mipsfpu
20953 @xref{MIPS Embedded, set mipsfpu}.
20955 @item set mips mask-address @var{arg}
20956 @kindex set mips mask-address
20957 @cindex @acronym{MIPS} addresses, masking
20958 This command determines whether the most-significant 32 bits of 64-bit
20959 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20960 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20961 setting, which lets @value{GDBN} determine the correct value.
20963 @item show mips mask-address
20964 @kindex show mips mask-address
20965 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20968 @item set remote-mips64-transfers-32bit-regs
20969 @kindex set remote-mips64-transfers-32bit-regs
20970 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20971 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20972 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20973 and 64 bits for other registers, set this option to @samp{on}.
20975 @item show remote-mips64-transfers-32bit-regs
20976 @kindex show remote-mips64-transfers-32bit-regs
20977 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20979 @item set debug mips
20980 @kindex set debug mips
20981 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20982 target code in @value{GDBN}.
20984 @item show debug mips
20985 @kindex show debug mips
20986 Show the current setting of @acronym{MIPS} debugging messages.
20992 @cindex HPPA support
20994 When @value{GDBN} is debugging the HP PA architecture, it provides the
20995 following special commands:
20998 @item set debug hppa
20999 @kindex set debug hppa
21000 This command determines whether HPPA architecture-specific debugging
21001 messages are to be displayed.
21003 @item show debug hppa
21004 Show whether HPPA debugging messages are displayed.
21006 @item maint print unwind @var{address}
21007 @kindex maint print unwind@r{, HPPA}
21008 This command displays the contents of the unwind table entry at the
21009 given @var{address}.
21015 @subsection Cell Broadband Engine SPU architecture
21016 @cindex Cell Broadband Engine
21019 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21020 it provides the following special commands:
21023 @item info spu event
21025 Display SPU event facility status. Shows current event mask
21026 and pending event status.
21028 @item info spu signal
21029 Display SPU signal notification facility status. Shows pending
21030 signal-control word and signal notification mode of both signal
21031 notification channels.
21033 @item info spu mailbox
21034 Display SPU mailbox facility status. Shows all pending entries,
21035 in order of processing, in each of the SPU Write Outbound,
21036 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21039 Display MFC DMA status. Shows all pending commands in the MFC
21040 DMA queue. For each entry, opcode, tag, class IDs, effective
21041 and local store addresses and transfer size are shown.
21043 @item info spu proxydma
21044 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21045 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21046 and local store addresses and transfer size are shown.
21050 When @value{GDBN} is debugging a combined PowerPC/SPU application
21051 on the Cell Broadband Engine, it provides in addition the following
21055 @item set spu stop-on-load @var{arg}
21057 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21058 will give control to the user when a new SPE thread enters its @code{main}
21059 function. The default is @code{off}.
21061 @item show spu stop-on-load
21063 Show whether to stop for new SPE threads.
21065 @item set spu auto-flush-cache @var{arg}
21066 Set whether to automatically flush the software-managed cache. When set to
21067 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21068 cache to be flushed whenever SPE execution stops. This provides a consistent
21069 view of PowerPC memory that is accessed via the cache. If an application
21070 does not use the software-managed cache, this option has no effect.
21072 @item show spu auto-flush-cache
21073 Show whether to automatically flush the software-managed cache.
21078 @subsection PowerPC
21079 @cindex PowerPC architecture
21081 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21082 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21083 numbers stored in the floating point registers. These values must be stored
21084 in two consecutive registers, always starting at an even register like
21085 @code{f0} or @code{f2}.
21087 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21088 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21089 @code{f2} and @code{f3} for @code{$dl1} and so on.
21091 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21092 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21095 @node Controlling GDB
21096 @chapter Controlling @value{GDBN}
21098 You can alter the way @value{GDBN} interacts with you by using the
21099 @code{set} command. For commands controlling how @value{GDBN} displays
21100 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21105 * Editing:: Command editing
21106 * Command History:: Command history
21107 * Screen Size:: Screen size
21108 * Numbers:: Numbers
21109 * ABI:: Configuring the current ABI
21110 * Auto-loading:: Automatically loading associated files
21111 * Messages/Warnings:: Optional warnings and messages
21112 * Debugging Output:: Optional messages about internal happenings
21113 * Other Misc Settings:: Other Miscellaneous Settings
21121 @value{GDBN} indicates its readiness to read a command by printing a string
21122 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21123 can change the prompt string with the @code{set prompt} command. For
21124 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21125 the prompt in one of the @value{GDBN} sessions so that you can always tell
21126 which one you are talking to.
21128 @emph{Note:} @code{set prompt} does not add a space for you after the
21129 prompt you set. This allows you to set a prompt which ends in a space
21130 or a prompt that does not.
21134 @item set prompt @var{newprompt}
21135 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21137 @kindex show prompt
21139 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21142 Versions of @value{GDBN} that ship with Python scripting enabled have
21143 prompt extensions. The commands for interacting with these extensions
21147 @kindex set extended-prompt
21148 @item set extended-prompt @var{prompt}
21149 Set an extended prompt that allows for substitutions.
21150 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21151 substitution. Any escape sequences specified as part of the prompt
21152 string are replaced with the corresponding strings each time the prompt
21158 set extended-prompt Current working directory: \w (gdb)
21161 Note that when an extended-prompt is set, it takes control of the
21162 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21164 @kindex show extended-prompt
21165 @item show extended-prompt
21166 Prints the extended prompt. Any escape sequences specified as part of
21167 the prompt string with @code{set extended-prompt}, are replaced with the
21168 corresponding strings each time the prompt is displayed.
21172 @section Command Editing
21174 @cindex command line editing
21176 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21177 @sc{gnu} library provides consistent behavior for programs which provide a
21178 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21179 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21180 substitution, and a storage and recall of command history across
21181 debugging sessions.
21183 You may control the behavior of command line editing in @value{GDBN} with the
21184 command @code{set}.
21187 @kindex set editing
21190 @itemx set editing on
21191 Enable command line editing (enabled by default).
21193 @item set editing off
21194 Disable command line editing.
21196 @kindex show editing
21198 Show whether command line editing is enabled.
21201 @ifset SYSTEM_READLINE
21202 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21204 @ifclear SYSTEM_READLINE
21205 @xref{Command Line Editing},
21207 for more details about the Readline
21208 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21209 encouraged to read that chapter.
21211 @node Command History
21212 @section Command History
21213 @cindex command history
21215 @value{GDBN} can keep track of the commands you type during your
21216 debugging sessions, so that you can be certain of precisely what
21217 happened. Use these commands to manage the @value{GDBN} command
21220 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21221 package, to provide the history facility.
21222 @ifset SYSTEM_READLINE
21223 @xref{Using History Interactively, , , history, GNU History Library},
21225 @ifclear SYSTEM_READLINE
21226 @xref{Using History Interactively},
21228 for the detailed description of the History library.
21230 To issue a command to @value{GDBN} without affecting certain aspects of
21231 the state which is seen by users, prefix it with @samp{server }
21232 (@pxref{Server Prefix}). This
21233 means that this command will not affect the command history, nor will it
21234 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21235 pressed on a line by itself.
21237 @cindex @code{server}, command prefix
21238 The server prefix does not affect the recording of values into the value
21239 history; to print a value without recording it into the value history,
21240 use the @code{output} command instead of the @code{print} command.
21242 Here is the description of @value{GDBN} commands related to command
21246 @cindex history substitution
21247 @cindex history file
21248 @kindex set history filename
21249 @cindex @env{GDBHISTFILE}, environment variable
21250 @item set history filename @var{fname}
21251 Set the name of the @value{GDBN} command history file to @var{fname}.
21252 This is the file where @value{GDBN} reads an initial command history
21253 list, and where it writes the command history from this session when it
21254 exits. You can access this list through history expansion or through
21255 the history command editing characters listed below. This file defaults
21256 to the value of the environment variable @code{GDBHISTFILE}, or to
21257 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21260 @cindex save command history
21261 @kindex set history save
21262 @item set history save
21263 @itemx set history save on
21264 Record command history in a file, whose name may be specified with the
21265 @code{set history filename} command. By default, this option is disabled.
21267 @item set history save off
21268 Stop recording command history in a file.
21270 @cindex history size
21271 @kindex set history size
21272 @cindex @env{HISTSIZE}, environment variable
21273 @item set history size @var{size}
21274 @itemx set history size unlimited
21275 Set the number of commands which @value{GDBN} keeps in its history list.
21276 This defaults to the value of the environment variable
21277 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21278 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21279 history list is unlimited.
21282 History expansion assigns special meaning to the character @kbd{!}.
21283 @ifset SYSTEM_READLINE
21284 @xref{Event Designators, , , history, GNU History Library},
21286 @ifclear SYSTEM_READLINE
21287 @xref{Event Designators},
21291 @cindex history expansion, turn on/off
21292 Since @kbd{!} is also the logical not operator in C, history expansion
21293 is off by default. If you decide to enable history expansion with the
21294 @code{set history expansion on} command, you may sometimes need to
21295 follow @kbd{!} (when it is used as logical not, in an expression) with
21296 a space or a tab to prevent it from being expanded. The readline
21297 history facilities do not attempt substitution on the strings
21298 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21300 The commands to control history expansion are:
21303 @item set history expansion on
21304 @itemx set history expansion
21305 @kindex set history expansion
21306 Enable history expansion. History expansion is off by default.
21308 @item set history expansion off
21309 Disable history expansion.
21312 @kindex show history
21314 @itemx show history filename
21315 @itemx show history save
21316 @itemx show history size
21317 @itemx show history expansion
21318 These commands display the state of the @value{GDBN} history parameters.
21319 @code{show history} by itself displays all four states.
21324 @kindex show commands
21325 @cindex show last commands
21326 @cindex display command history
21327 @item show commands
21328 Display the last ten commands in the command history.
21330 @item show commands @var{n}
21331 Print ten commands centered on command number @var{n}.
21333 @item show commands +
21334 Print ten commands just after the commands last printed.
21338 @section Screen Size
21339 @cindex size of screen
21340 @cindex pauses in output
21342 Certain commands to @value{GDBN} may produce large amounts of
21343 information output to the screen. To help you read all of it,
21344 @value{GDBN} pauses and asks you for input at the end of each page of
21345 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21346 to discard the remaining output. Also, the screen width setting
21347 determines when to wrap lines of output. Depending on what is being
21348 printed, @value{GDBN} tries to break the line at a readable place,
21349 rather than simply letting it overflow onto the following line.
21351 Normally @value{GDBN} knows the size of the screen from the terminal
21352 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21353 together with the value of the @code{TERM} environment variable and the
21354 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21355 you can override it with the @code{set height} and @code{set
21362 @kindex show height
21363 @item set height @var{lpp}
21364 @itemx set height unlimited
21366 @itemx set width @var{cpl}
21367 @itemx set width unlimited
21369 These @code{set} commands specify a screen height of @var{lpp} lines and
21370 a screen width of @var{cpl} characters. The associated @code{show}
21371 commands display the current settings.
21373 If you specify a height of either @code{unlimited} or zero lines,
21374 @value{GDBN} does not pause during output no matter how long the
21375 output is. This is useful if output is to a file or to an editor
21378 Likewise, you can specify @samp{set width unlimited} or @samp{set
21379 width 0} to prevent @value{GDBN} from wrapping its output.
21381 @item set pagination on
21382 @itemx set pagination off
21383 @kindex set pagination
21384 Turn the output pagination on or off; the default is on. Turning
21385 pagination off is the alternative to @code{set height unlimited}. Note that
21386 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21387 Options, -batch}) also automatically disables pagination.
21389 @item show pagination
21390 @kindex show pagination
21391 Show the current pagination mode.
21396 @cindex number representation
21397 @cindex entering numbers
21399 You can always enter numbers in octal, decimal, or hexadecimal in
21400 @value{GDBN} by the usual conventions: octal numbers begin with
21401 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21402 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21403 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21404 10; likewise, the default display for numbers---when no particular
21405 format is specified---is base 10. You can change the default base for
21406 both input and output with the commands described below.
21409 @kindex set input-radix
21410 @item set input-radix @var{base}
21411 Set the default base for numeric input. Supported choices
21412 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21413 specified either unambiguously or using the current input radix; for
21417 set input-radix 012
21418 set input-radix 10.
21419 set input-radix 0xa
21423 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21424 leaves the input radix unchanged, no matter what it was, since
21425 @samp{10}, being without any leading or trailing signs of its base, is
21426 interpreted in the current radix. Thus, if the current radix is 16,
21427 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21430 @kindex set output-radix
21431 @item set output-radix @var{base}
21432 Set the default base for numeric display. Supported choices
21433 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21434 specified either unambiguously or using the current input radix.
21436 @kindex show input-radix
21437 @item show input-radix
21438 Display the current default base for numeric input.
21440 @kindex show output-radix
21441 @item show output-radix
21442 Display the current default base for numeric display.
21444 @item set radix @r{[}@var{base}@r{]}
21448 These commands set and show the default base for both input and output
21449 of numbers. @code{set radix} sets the radix of input and output to
21450 the same base; without an argument, it resets the radix back to its
21451 default value of 10.
21456 @section Configuring the Current ABI
21458 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21459 application automatically. However, sometimes you need to override its
21460 conclusions. Use these commands to manage @value{GDBN}'s view of the
21466 @cindex Newlib OS ABI and its influence on the longjmp handling
21468 One @value{GDBN} configuration can debug binaries for multiple operating
21469 system targets, either via remote debugging or native emulation.
21470 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21471 but you can override its conclusion using the @code{set osabi} command.
21472 One example where this is useful is in debugging of binaries which use
21473 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21474 not have the same identifying marks that the standard C library for your
21477 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21478 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21479 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21480 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21484 Show the OS ABI currently in use.
21487 With no argument, show the list of registered available OS ABI's.
21489 @item set osabi @var{abi}
21490 Set the current OS ABI to @var{abi}.
21493 @cindex float promotion
21495 Generally, the way that an argument of type @code{float} is passed to a
21496 function depends on whether the function is prototyped. For a prototyped
21497 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21498 according to the architecture's convention for @code{float}. For unprototyped
21499 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21500 @code{double} and then passed.
21502 Unfortunately, some forms of debug information do not reliably indicate whether
21503 a function is prototyped. If @value{GDBN} calls a function that is not marked
21504 as prototyped, it consults @kbd{set coerce-float-to-double}.
21507 @kindex set coerce-float-to-double
21508 @item set coerce-float-to-double
21509 @itemx set coerce-float-to-double on
21510 Arguments of type @code{float} will be promoted to @code{double} when passed
21511 to an unprototyped function. This is the default setting.
21513 @item set coerce-float-to-double off
21514 Arguments of type @code{float} will be passed directly to unprototyped
21517 @kindex show coerce-float-to-double
21518 @item show coerce-float-to-double
21519 Show the current setting of promoting @code{float} to @code{double}.
21523 @kindex show cp-abi
21524 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21525 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21526 used to build your application. @value{GDBN} only fully supports
21527 programs with a single C@t{++} ABI; if your program contains code using
21528 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21529 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21530 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21531 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21532 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21533 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21538 Show the C@t{++} ABI currently in use.
21541 With no argument, show the list of supported C@t{++} ABI's.
21543 @item set cp-abi @var{abi}
21544 @itemx set cp-abi auto
21545 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21549 @section Automatically loading associated files
21550 @cindex auto-loading
21552 @value{GDBN} sometimes reads files with commands and settings automatically,
21553 without being explicitly told so by the user. We call this feature
21554 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21555 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21556 results or introduce security risks (e.g., if the file comes from untrusted
21559 Note that loading of these associated files (including the local @file{.gdbinit}
21560 file) requires accordingly configured @code{auto-load safe-path}
21561 (@pxref{Auto-loading safe path}).
21563 For these reasons, @value{GDBN} includes commands and options to let you
21564 control when to auto-load files and which files should be auto-loaded.
21567 @anchor{set auto-load off}
21568 @kindex set auto-load off
21569 @item set auto-load off
21570 Globally disable loading of all auto-loaded files.
21571 You may want to use this command with the @samp{-iex} option
21572 (@pxref{Option -init-eval-command}) such as:
21574 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21577 Be aware that system init file (@pxref{System-wide configuration})
21578 and init files from your home directory (@pxref{Home Directory Init File})
21579 still get read (as they come from generally trusted directories).
21580 To prevent @value{GDBN} from auto-loading even those init files, use the
21581 @option{-nx} option (@pxref{Mode Options}), in addition to
21582 @code{set auto-load no}.
21584 @anchor{show auto-load}
21585 @kindex show auto-load
21586 @item show auto-load
21587 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21591 (gdb) show auto-load
21592 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21593 libthread-db: Auto-loading of inferior specific libthread_db is on.
21594 local-gdbinit: Auto-loading of .gdbinit script from current directory
21596 python-scripts: Auto-loading of Python scripts is on.
21597 safe-path: List of directories from which it is safe to auto-load files
21598 is $debugdir:$datadir/auto-load.
21599 scripts-directory: List of directories from which to load auto-loaded scripts
21600 is $debugdir:$datadir/auto-load.
21603 @anchor{info auto-load}
21604 @kindex info auto-load
21605 @item info auto-load
21606 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21610 (gdb) info auto-load
21613 Yes /home/user/gdb/gdb-gdb.gdb
21614 libthread-db: No auto-loaded libthread-db.
21615 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21619 Yes /home/user/gdb/gdb-gdb.py
21623 These are various kinds of files @value{GDBN} can automatically load:
21627 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21629 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21631 @xref{dotdebug_gdb_scripts section},
21632 controlled by @ref{set auto-load python-scripts}.
21634 @xref{Init File in the Current Directory},
21635 controlled by @ref{set auto-load local-gdbinit}.
21637 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21640 These are @value{GDBN} control commands for the auto-loading:
21642 @multitable @columnfractions .5 .5
21643 @item @xref{set auto-load off}.
21644 @tab Disable auto-loading globally.
21645 @item @xref{show auto-load}.
21646 @tab Show setting of all kinds of files.
21647 @item @xref{info auto-load}.
21648 @tab Show state of all kinds of files.
21649 @item @xref{set auto-load gdb-scripts}.
21650 @tab Control for @value{GDBN} command scripts.
21651 @item @xref{show auto-load gdb-scripts}.
21652 @tab Show setting of @value{GDBN} command scripts.
21653 @item @xref{info auto-load gdb-scripts}.
21654 @tab Show state of @value{GDBN} command scripts.
21655 @item @xref{set auto-load python-scripts}.
21656 @tab Control for @value{GDBN} Python scripts.
21657 @item @xref{show auto-load python-scripts}.
21658 @tab Show setting of @value{GDBN} Python scripts.
21659 @item @xref{info auto-load python-scripts}.
21660 @tab Show state of @value{GDBN} Python scripts.
21661 @item @xref{set auto-load scripts-directory}.
21662 @tab Control for @value{GDBN} auto-loaded scripts location.
21663 @item @xref{show auto-load scripts-directory}.
21664 @tab Show @value{GDBN} auto-loaded scripts location.
21665 @item @xref{set auto-load local-gdbinit}.
21666 @tab Control for init file in the current directory.
21667 @item @xref{show auto-load local-gdbinit}.
21668 @tab Show setting of init file in the current directory.
21669 @item @xref{info auto-load local-gdbinit}.
21670 @tab Show state of init file in the current directory.
21671 @item @xref{set auto-load libthread-db}.
21672 @tab Control for thread debugging library.
21673 @item @xref{show auto-load libthread-db}.
21674 @tab Show setting of thread debugging library.
21675 @item @xref{info auto-load libthread-db}.
21676 @tab Show state of thread debugging library.
21677 @item @xref{set auto-load safe-path}.
21678 @tab Control directories trusted for automatic loading.
21679 @item @xref{show auto-load safe-path}.
21680 @tab Show directories trusted for automatic loading.
21681 @item @xref{add-auto-load-safe-path}.
21682 @tab Add directory trusted for automatic loading.
21686 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21687 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21688 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21689 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21690 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21691 @xref{Python Auto-loading}.
21694 @node Init File in the Current Directory
21695 @subsection Automatically loading init file in the current directory
21696 @cindex auto-loading init file in the current directory
21698 By default, @value{GDBN} reads and executes the canned sequences of commands
21699 from init file (if any) in the current working directory,
21700 see @ref{Init File in the Current Directory during Startup}.
21702 Note that loading of this local @file{.gdbinit} file also requires accordingly
21703 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21706 @anchor{set auto-load local-gdbinit}
21707 @kindex set auto-load local-gdbinit
21708 @item set auto-load local-gdbinit [on|off]
21709 Enable or disable the auto-loading of canned sequences of commands
21710 (@pxref{Sequences}) found in init file in the current directory.
21712 @anchor{show auto-load local-gdbinit}
21713 @kindex show auto-load local-gdbinit
21714 @item show auto-load local-gdbinit
21715 Show whether auto-loading of canned sequences of commands from init file in the
21716 current directory is enabled or disabled.
21718 @anchor{info auto-load local-gdbinit}
21719 @kindex info auto-load local-gdbinit
21720 @item info auto-load local-gdbinit
21721 Print whether canned sequences of commands from init file in the
21722 current directory have been auto-loaded.
21725 @node libthread_db.so.1 file
21726 @subsection Automatically loading thread debugging library
21727 @cindex auto-loading libthread_db.so.1
21729 This feature is currently present only on @sc{gnu}/Linux native hosts.
21731 @value{GDBN} reads in some cases thread debugging library from places specific
21732 to the inferior (@pxref{set libthread-db-search-path}).
21734 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21735 without checking this @samp{set auto-load libthread-db} switch as system
21736 libraries have to be trusted in general. In all other cases of
21737 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21738 auto-load libthread-db} is enabled before trying to open such thread debugging
21741 Note that loading of this debugging library also requires accordingly configured
21742 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21745 @anchor{set auto-load libthread-db}
21746 @kindex set auto-load libthread-db
21747 @item set auto-load libthread-db [on|off]
21748 Enable or disable the auto-loading of inferior specific thread debugging library.
21750 @anchor{show auto-load libthread-db}
21751 @kindex show auto-load libthread-db
21752 @item show auto-load libthread-db
21753 Show whether auto-loading of inferior specific thread debugging library is
21754 enabled or disabled.
21756 @anchor{info auto-load libthread-db}
21757 @kindex info auto-load libthread-db
21758 @item info auto-load libthread-db
21759 Print the list of all loaded inferior specific thread debugging libraries and
21760 for each such library print list of inferior @var{pid}s using it.
21763 @node objfile-gdb.gdb file
21764 @subsection The @file{@var{objfile}-gdb.gdb} file
21765 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21767 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21768 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21769 auto-load gdb-scripts} is set to @samp{on}.
21771 Note that loading of this script file also requires accordingly configured
21772 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21774 For more background refer to the similar Python scripts auto-loading
21775 description (@pxref{objfile-gdb.py file}).
21778 @anchor{set auto-load gdb-scripts}
21779 @kindex set auto-load gdb-scripts
21780 @item set auto-load gdb-scripts [on|off]
21781 Enable or disable the auto-loading of canned sequences of commands scripts.
21783 @anchor{show auto-load gdb-scripts}
21784 @kindex show auto-load gdb-scripts
21785 @item show auto-load gdb-scripts
21786 Show whether auto-loading of canned sequences of commands scripts is enabled or
21789 @anchor{info auto-load gdb-scripts}
21790 @kindex info auto-load gdb-scripts
21791 @cindex print list of auto-loaded canned sequences of commands scripts
21792 @item info auto-load gdb-scripts [@var{regexp}]
21793 Print the list of all canned sequences of commands scripts that @value{GDBN}
21797 If @var{regexp} is supplied only canned sequences of commands scripts with
21798 matching names are printed.
21800 @node Auto-loading safe path
21801 @subsection Security restriction for auto-loading
21802 @cindex auto-loading safe-path
21804 As the files of inferior can come from untrusted source (such as submitted by
21805 an application user) @value{GDBN} does not always load any files automatically.
21806 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21807 directories trusted for loading files not explicitly requested by user.
21808 Each directory can also be a shell wildcard pattern.
21810 If the path is not set properly you will see a warning and the file will not
21815 Reading symbols from /home/user/gdb/gdb...done.
21816 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21817 declined by your `auto-load safe-path' set
21818 to "$debugdir:$datadir/auto-load".
21819 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21820 declined by your `auto-load safe-path' set
21821 to "$debugdir:$datadir/auto-load".
21825 To instruct @value{GDBN} to go ahead and use the init files anyway,
21826 invoke @value{GDBN} like this:
21829 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
21832 The list of trusted directories is controlled by the following commands:
21835 @anchor{set auto-load safe-path}
21836 @kindex set auto-load safe-path
21837 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21838 Set the list of directories (and their subdirectories) trusted for automatic
21839 loading and execution of scripts. You can also enter a specific trusted file.
21840 Each directory can also be a shell wildcard pattern; wildcards do not match
21841 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21842 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21843 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21844 its default value as specified during @value{GDBN} compilation.
21846 The list of directories uses path separator (@samp{:} on GNU and Unix
21847 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21848 to the @env{PATH} environment variable.
21850 @anchor{show auto-load safe-path}
21851 @kindex show auto-load safe-path
21852 @item show auto-load safe-path
21853 Show the list of directories trusted for automatic loading and execution of
21856 @anchor{add-auto-load-safe-path}
21857 @kindex add-auto-load-safe-path
21858 @item add-auto-load-safe-path
21859 Add an entry (or list of entries) the list of directories trusted for automatic
21860 loading and execution of scripts. Multiple entries may be delimited by the
21861 host platform path separator in use.
21864 This variable defaults to what @code{--with-auto-load-dir} has been configured
21865 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21866 substitution applies the same as for @ref{set auto-load scripts-directory}.
21867 The default @code{set auto-load safe-path} value can be also overriden by
21868 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21870 Setting this variable to @file{/} disables this security protection,
21871 corresponding @value{GDBN} configuration option is
21872 @option{--without-auto-load-safe-path}.
21873 This variable is supposed to be set to the system directories writable by the
21874 system superuser only. Users can add their source directories in init files in
21875 their home directories (@pxref{Home Directory Init File}). See also deprecated
21876 init file in the current directory
21877 (@pxref{Init File in the Current Directory during Startup}).
21879 To force @value{GDBN} to load the files it declined to load in the previous
21880 example, you could use one of the following ways:
21883 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21884 Specify this trusted directory (or a file) as additional component of the list.
21885 You have to specify also any existing directories displayed by
21886 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21888 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21889 Specify this directory as in the previous case but just for a single
21890 @value{GDBN} session.
21892 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21893 Disable auto-loading safety for a single @value{GDBN} session.
21894 This assumes all the files you debug during this @value{GDBN} session will come
21895 from trusted sources.
21897 @item @kbd{./configure --without-auto-load-safe-path}
21898 During compilation of @value{GDBN} you may disable any auto-loading safety.
21899 This assumes all the files you will ever debug with this @value{GDBN} come from
21903 On the other hand you can also explicitly forbid automatic files loading which
21904 also suppresses any such warning messages:
21907 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21908 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21910 @item @file{~/.gdbinit}: @samp{set auto-load no}
21911 Disable auto-loading globally for the user
21912 (@pxref{Home Directory Init File}). While it is improbable, you could also
21913 use system init file instead (@pxref{System-wide configuration}).
21916 This setting applies to the file names as entered by user. If no entry matches
21917 @value{GDBN} tries as a last resort to also resolve all the file names into
21918 their canonical form (typically resolving symbolic links) and compare the
21919 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21920 own before starting the comparison so a canonical form of directories is
21921 recommended to be entered.
21923 @node Auto-loading verbose mode
21924 @subsection Displaying files tried for auto-load
21925 @cindex auto-loading verbose mode
21927 For better visibility of all the file locations where you can place scripts to
21928 be auto-loaded with inferior --- or to protect yourself against accidental
21929 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21930 all the files attempted to be loaded. Both existing and non-existing files may
21933 For example the list of directories from which it is safe to auto-load files
21934 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21935 may not be too obvious while setting it up.
21938 (gdb) set debug auto-load on
21939 (gdb) file ~/src/t/true
21940 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21941 for objfile "/tmp/true".
21942 auto-load: Updating directories of "/usr:/opt".
21943 auto-load: Using directory "/usr".
21944 auto-load: Using directory "/opt".
21945 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21946 by your `auto-load safe-path' set to "/usr:/opt".
21950 @anchor{set debug auto-load}
21951 @kindex set debug auto-load
21952 @item set debug auto-load [on|off]
21953 Set whether to print the filenames attempted to be auto-loaded.
21955 @anchor{show debug auto-load}
21956 @kindex show debug auto-load
21957 @item show debug auto-load
21958 Show whether printing of the filenames attempted to be auto-loaded is turned
21962 @node Messages/Warnings
21963 @section Optional Warnings and Messages
21965 @cindex verbose operation
21966 @cindex optional warnings
21967 By default, @value{GDBN} is silent about its inner workings. If you are
21968 running on a slow machine, you may want to use the @code{set verbose}
21969 command. This makes @value{GDBN} tell you when it does a lengthy
21970 internal operation, so you will not think it has crashed.
21972 Currently, the messages controlled by @code{set verbose} are those
21973 which announce that the symbol table for a source file is being read;
21974 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21977 @kindex set verbose
21978 @item set verbose on
21979 Enables @value{GDBN} output of certain informational messages.
21981 @item set verbose off
21982 Disables @value{GDBN} output of certain informational messages.
21984 @kindex show verbose
21986 Displays whether @code{set verbose} is on or off.
21989 By default, if @value{GDBN} encounters bugs in the symbol table of an
21990 object file, it is silent; but if you are debugging a compiler, you may
21991 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21996 @kindex set complaints
21997 @item set complaints @var{limit}
21998 Permits @value{GDBN} to output @var{limit} complaints about each type of
21999 unusual symbols before becoming silent about the problem. Set
22000 @var{limit} to zero to suppress all complaints; set it to a large number
22001 to prevent complaints from being suppressed.
22003 @kindex show complaints
22004 @item show complaints
22005 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22009 @anchor{confirmation requests}
22010 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22011 lot of stupid questions to confirm certain commands. For example, if
22012 you try to run a program which is already running:
22016 The program being debugged has been started already.
22017 Start it from the beginning? (y or n)
22020 If you are willing to unflinchingly face the consequences of your own
22021 commands, you can disable this ``feature'':
22025 @kindex set confirm
22027 @cindex confirmation
22028 @cindex stupid questions
22029 @item set confirm off
22030 Disables confirmation requests. Note that running @value{GDBN} with
22031 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22032 automatically disables confirmation requests.
22034 @item set confirm on
22035 Enables confirmation requests (the default).
22037 @kindex show confirm
22039 Displays state of confirmation requests.
22043 @cindex command tracing
22044 If you need to debug user-defined commands or sourced files you may find it
22045 useful to enable @dfn{command tracing}. In this mode each command will be
22046 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22047 quantity denoting the call depth of each command.
22050 @kindex set trace-commands
22051 @cindex command scripts, debugging
22052 @item set trace-commands on
22053 Enable command tracing.
22054 @item set trace-commands off
22055 Disable command tracing.
22056 @item show trace-commands
22057 Display the current state of command tracing.
22060 @node Debugging Output
22061 @section Optional Messages about Internal Happenings
22062 @cindex optional debugging messages
22064 @value{GDBN} has commands that enable optional debugging messages from
22065 various @value{GDBN} subsystems; normally these commands are of
22066 interest to @value{GDBN} maintainers, or when reporting a bug. This
22067 section documents those commands.
22070 @kindex set exec-done-display
22071 @item set exec-done-display
22072 Turns on or off the notification of asynchronous commands'
22073 completion. When on, @value{GDBN} will print a message when an
22074 asynchronous command finishes its execution. The default is off.
22075 @kindex show exec-done-display
22076 @item show exec-done-display
22077 Displays the current setting of asynchronous command completion
22080 @cindex ARM AArch64
22081 @item set debug aarch64
22082 Turns on or off display of debugging messages related to ARM AArch64.
22083 The default is off.
22085 @item show debug aarch64
22086 Displays the current state of displaying debugging messages related to
22088 @cindex gdbarch debugging info
22089 @cindex architecture debugging info
22090 @item set debug arch
22091 Turns on or off display of gdbarch debugging info. The default is off
22092 @item show debug arch
22093 Displays the current state of displaying gdbarch debugging info.
22094 @item set debug aix-thread
22095 @cindex AIX threads
22096 Display debugging messages about inner workings of the AIX thread
22098 @item show debug aix-thread
22099 Show the current state of AIX thread debugging info display.
22100 @item set debug check-physname
22102 Check the results of the ``physname'' computation. When reading DWARF
22103 debugging information for C@t{++}, @value{GDBN} attempts to compute
22104 each entity's name. @value{GDBN} can do this computation in two
22105 different ways, depending on exactly what information is present.
22106 When enabled, this setting causes @value{GDBN} to compute the names
22107 both ways and display any discrepancies.
22108 @item show debug check-physname
22109 Show the current state of ``physname'' checking.
22110 @item set debug coff-pe-read
22111 @cindex COFF/PE exported symbols
22112 Control display of debugging messages related to reading of COFF/PE
22113 exported symbols. The default is off.
22114 @item show debug coff-pe-read
22115 Displays the current state of displaying debugging messages related to
22116 reading of COFF/PE exported symbols.
22117 @item set debug dwarf2-die
22118 @cindex DWARF2 DIEs
22119 Dump DWARF2 DIEs after they are read in.
22120 The value is the number of nesting levels to print.
22121 A value of zero turns off the display.
22122 @item show debug dwarf2-die
22123 Show the current state of DWARF2 DIE debugging.
22124 @item set debug dwarf2-read
22125 @cindex DWARF2 Reading
22126 Turns on or off display of debugging messages related to reading
22127 DWARF debug info. The default is off.
22128 @item show debug dwarf2-read
22129 Show the current state of DWARF2 reader debugging.
22130 @item set debug displaced
22131 @cindex displaced stepping debugging info
22132 Turns on or off display of @value{GDBN} debugging info for the
22133 displaced stepping support. The default is off.
22134 @item show debug displaced
22135 Displays the current state of displaying @value{GDBN} debugging info
22136 related to displaced stepping.
22137 @item set debug event
22138 @cindex event debugging info
22139 Turns on or off display of @value{GDBN} event debugging info. The
22141 @item show debug event
22142 Displays the current state of displaying @value{GDBN} event debugging
22144 @item set debug expression
22145 @cindex expression debugging info
22146 Turns on or off display of debugging info about @value{GDBN}
22147 expression parsing. The default is off.
22148 @item show debug expression
22149 Displays the current state of displaying debugging info about
22150 @value{GDBN} expression parsing.
22151 @item set debug frame
22152 @cindex frame debugging info
22153 Turns on or off display of @value{GDBN} frame debugging info. The
22155 @item show debug frame
22156 Displays the current state of displaying @value{GDBN} frame debugging
22158 @item set debug gnu-nat
22159 @cindex @sc{gnu}/Hurd debug messages
22160 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22161 @item show debug gnu-nat
22162 Show the current state of @sc{gnu}/Hurd debugging messages.
22163 @item set debug infrun
22164 @cindex inferior debugging info
22165 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22166 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22167 for implementing operations such as single-stepping the inferior.
22168 @item show debug infrun
22169 Displays the current state of @value{GDBN} inferior debugging.
22170 @item set debug jit
22171 @cindex just-in-time compilation, debugging messages
22172 Turns on or off debugging messages from JIT debug support.
22173 @item show debug jit
22174 Displays the current state of @value{GDBN} JIT debugging.
22175 @item set debug lin-lwp
22176 @cindex @sc{gnu}/Linux LWP debug messages
22177 @cindex Linux lightweight processes
22178 Turns on or off debugging messages from the Linux LWP debug support.
22179 @item show debug lin-lwp
22180 Show the current state of Linux LWP debugging messages.
22181 @item set debug mach-o
22182 @cindex Mach-O symbols processing
22183 Control display of debugging messages related to Mach-O symbols
22184 processing. The default is off.
22185 @item show debug mach-o
22186 Displays the current state of displaying debugging messages related to
22187 reading of COFF/PE exported symbols.
22188 @item set debug notification
22189 @cindex remote async notification debugging info
22190 Turns on or off debugging messages about remote async notification.
22191 The default is off.
22192 @item show debug notification
22193 Displays the current state of remote async notification debugging messages.
22194 @item set debug observer
22195 @cindex observer debugging info
22196 Turns on or off display of @value{GDBN} observer debugging. This
22197 includes info such as the notification of observable events.
22198 @item show debug observer
22199 Displays the current state of observer debugging.
22200 @item set debug overload
22201 @cindex C@t{++} overload debugging info
22202 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22203 info. This includes info such as ranking of functions, etc. The default
22205 @item show debug overload
22206 Displays the current state of displaying @value{GDBN} C@t{++} overload
22208 @cindex expression parser, debugging info
22209 @cindex debug expression parser
22210 @item set debug parser
22211 Turns on or off the display of expression parser debugging output.
22212 Internally, this sets the @code{yydebug} variable in the expression
22213 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22214 details. The default is off.
22215 @item show debug parser
22216 Show the current state of expression parser debugging.
22217 @cindex packets, reporting on stdout
22218 @cindex serial connections, debugging
22219 @cindex debug remote protocol
22220 @cindex remote protocol debugging
22221 @cindex display remote packets
22222 @item set debug remote
22223 Turns on or off display of reports on all packets sent back and forth across
22224 the serial line to the remote machine. The info is printed on the
22225 @value{GDBN} standard output stream. The default is off.
22226 @item show debug remote
22227 Displays the state of display of remote packets.
22228 @item set debug serial
22229 Turns on or off display of @value{GDBN} serial debugging info. The
22231 @item show debug serial
22232 Displays the current state of displaying @value{GDBN} serial debugging
22234 @item set debug solib-frv
22235 @cindex FR-V shared-library debugging
22236 Turns on or off debugging messages for FR-V shared-library code.
22237 @item show debug solib-frv
22238 Display the current state of FR-V shared-library code debugging
22240 @item set debug symtab-create
22241 @cindex symbol table creation
22242 Turns on or off display of debugging messages related to symbol table creation.
22243 The default is off.
22244 @item show debug symtab-create
22245 Show the current state of symbol table creation debugging.
22246 @item set debug target
22247 @cindex target debugging info
22248 Turns on or off display of @value{GDBN} target debugging info. This info
22249 includes what is going on at the target level of GDB, as it happens. The
22250 default is 0. Set it to 1 to track events, and to 2 to also track the
22251 value of large memory transfers. Changes to this flag do not take effect
22252 until the next time you connect to a target or use the @code{run} command.
22253 @item show debug target
22254 Displays the current state of displaying @value{GDBN} target debugging
22256 @item set debug timestamp
22257 @cindex timestampping debugging info
22258 Turns on or off display of timestamps with @value{GDBN} debugging info.
22259 When enabled, seconds and microseconds are displayed before each debugging
22261 @item show debug timestamp
22262 Displays the current state of displaying timestamps with @value{GDBN}
22264 @item set debugvarobj
22265 @cindex variable object debugging info
22266 Turns on or off display of @value{GDBN} variable object debugging
22267 info. The default is off.
22268 @item show debugvarobj
22269 Displays the current state of displaying @value{GDBN} variable object
22271 @item set debug xml
22272 @cindex XML parser debugging
22273 Turns on or off debugging messages for built-in XML parsers.
22274 @item show debug xml
22275 Displays the current state of XML debugging messages.
22278 @node Other Misc Settings
22279 @section Other Miscellaneous Settings
22280 @cindex miscellaneous settings
22283 @kindex set interactive-mode
22284 @item set interactive-mode
22285 If @code{on}, forces @value{GDBN} to assume that GDB was started
22286 in a terminal. In practice, this means that @value{GDBN} should wait
22287 for the user to answer queries generated by commands entered at
22288 the command prompt. If @code{off}, forces @value{GDBN} to operate
22289 in the opposite mode, and it uses the default answers to all queries.
22290 If @code{auto} (the default), @value{GDBN} tries to determine whether
22291 its standard input is a terminal, and works in interactive-mode if it
22292 is, non-interactively otherwise.
22294 In the vast majority of cases, the debugger should be able to guess
22295 correctly which mode should be used. But this setting can be useful
22296 in certain specific cases, such as running a MinGW @value{GDBN}
22297 inside a cygwin window.
22299 @kindex show interactive-mode
22300 @item show interactive-mode
22301 Displays whether the debugger is operating in interactive mode or not.
22304 @node Extending GDB
22305 @chapter Extending @value{GDBN}
22306 @cindex extending GDB
22308 @value{GDBN} provides three mechanisms for extension. The first is based
22309 on composition of @value{GDBN} commands, the second is based on the
22310 Python scripting language, and the third is for defining new aliases of
22313 To facilitate the use of the first two extensions, @value{GDBN} is capable
22314 of evaluating the contents of a file. When doing so, @value{GDBN}
22315 can recognize which scripting language is being used by looking at
22316 the filename extension. Files with an unrecognized filename extension
22317 are always treated as a @value{GDBN} Command Files.
22318 @xref{Command Files,, Command files}.
22320 You can control how @value{GDBN} evaluates these files with the following
22324 @kindex set script-extension
22325 @kindex show script-extension
22326 @item set script-extension off
22327 All scripts are always evaluated as @value{GDBN} Command Files.
22329 @item set script-extension soft
22330 The debugger determines the scripting language based on filename
22331 extension. If this scripting language is supported, @value{GDBN}
22332 evaluates the script using that language. Otherwise, it evaluates
22333 the file as a @value{GDBN} Command File.
22335 @item set script-extension strict
22336 The debugger determines the scripting language based on filename
22337 extension, and evaluates the script using that language. If the
22338 language is not supported, then the evaluation fails.
22340 @item show script-extension
22341 Display the current value of the @code{script-extension} option.
22346 * Sequences:: Canned Sequences of Commands
22347 * Python:: Scripting @value{GDBN} using Python
22348 * Aliases:: Creating new spellings of existing commands
22352 @section Canned Sequences of Commands
22354 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22355 Command Lists}), @value{GDBN} provides two ways to store sequences of
22356 commands for execution as a unit: user-defined commands and command
22360 * Define:: How to define your own commands
22361 * Hooks:: Hooks for user-defined commands
22362 * Command Files:: How to write scripts of commands to be stored in a file
22363 * Output:: Commands for controlled output
22367 @subsection User-defined Commands
22369 @cindex user-defined command
22370 @cindex arguments, to user-defined commands
22371 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22372 which you assign a new name as a command. This is done with the
22373 @code{define} command. User commands may accept up to 10 arguments
22374 separated by whitespace. Arguments are accessed within the user command
22375 via @code{$arg0@dots{}$arg9}. A trivial example:
22379 print $arg0 + $arg1 + $arg2
22384 To execute the command use:
22391 This defines the command @code{adder}, which prints the sum of
22392 its three arguments. Note the arguments are text substitutions, so they may
22393 reference variables, use complex expressions, or even perform inferior
22396 @cindex argument count in user-defined commands
22397 @cindex how many arguments (user-defined commands)
22398 In addition, @code{$argc} may be used to find out how many arguments have
22399 been passed. This expands to a number in the range 0@dots{}10.
22404 print $arg0 + $arg1
22407 print $arg0 + $arg1 + $arg2
22415 @item define @var{commandname}
22416 Define a command named @var{commandname}. If there is already a command
22417 by that name, you are asked to confirm that you want to redefine it.
22418 @var{commandname} may be a bare command name consisting of letters,
22419 numbers, dashes, and underscores. It may also start with any predefined
22420 prefix command. For example, @samp{define target my-target} creates
22421 a user-defined @samp{target my-target} command.
22423 The definition of the command is made up of other @value{GDBN} command lines,
22424 which are given following the @code{define} command. The end of these
22425 commands is marked by a line containing @code{end}.
22428 @kindex end@r{ (user-defined commands)}
22429 @item document @var{commandname}
22430 Document the user-defined command @var{commandname}, so that it can be
22431 accessed by @code{help}. The command @var{commandname} must already be
22432 defined. This command reads lines of documentation just as @code{define}
22433 reads the lines of the command definition, ending with @code{end}.
22434 After the @code{document} command is finished, @code{help} on command
22435 @var{commandname} displays the documentation you have written.
22437 You may use the @code{document} command again to change the
22438 documentation of a command. Redefining the command with @code{define}
22439 does not change the documentation.
22441 @kindex dont-repeat
22442 @cindex don't repeat command
22444 Used inside a user-defined command, this tells @value{GDBN} that this
22445 command should not be repeated when the user hits @key{RET}
22446 (@pxref{Command Syntax, repeat last command}).
22448 @kindex help user-defined
22449 @item help user-defined
22450 List all user-defined commands and all python commands defined in class
22451 COMAND_USER. The first line of the documentation or docstring is
22456 @itemx show user @var{commandname}
22457 Display the @value{GDBN} commands used to define @var{commandname} (but
22458 not its documentation). If no @var{commandname} is given, display the
22459 definitions for all user-defined commands.
22460 This does not work for user-defined python commands.
22462 @cindex infinite recursion in user-defined commands
22463 @kindex show max-user-call-depth
22464 @kindex set max-user-call-depth
22465 @item show max-user-call-depth
22466 @itemx set max-user-call-depth
22467 The value of @code{max-user-call-depth} controls how many recursion
22468 levels are allowed in user-defined commands before @value{GDBN} suspects an
22469 infinite recursion and aborts the command.
22470 This does not apply to user-defined python commands.
22473 In addition to the above commands, user-defined commands frequently
22474 use control flow commands, described in @ref{Command Files}.
22476 When user-defined commands are executed, the
22477 commands of the definition are not printed. An error in any command
22478 stops execution of the user-defined command.
22480 If used interactively, commands that would ask for confirmation proceed
22481 without asking when used inside a user-defined command. Many @value{GDBN}
22482 commands that normally print messages to say what they are doing omit the
22483 messages when used in a user-defined command.
22486 @subsection User-defined Command Hooks
22487 @cindex command hooks
22488 @cindex hooks, for commands
22489 @cindex hooks, pre-command
22492 You may define @dfn{hooks}, which are a special kind of user-defined
22493 command. Whenever you run the command @samp{foo}, if the user-defined
22494 command @samp{hook-foo} exists, it is executed (with no arguments)
22495 before that command.
22497 @cindex hooks, post-command
22499 A hook may also be defined which is run after the command you executed.
22500 Whenever you run the command @samp{foo}, if the user-defined command
22501 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22502 that command. Post-execution hooks may exist simultaneously with
22503 pre-execution hooks, for the same command.
22505 It is valid for a hook to call the command which it hooks. If this
22506 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22508 @c It would be nice if hookpost could be passed a parameter indicating
22509 @c if the command it hooks executed properly or not. FIXME!
22511 @kindex stop@r{, a pseudo-command}
22512 In addition, a pseudo-command, @samp{stop} exists. Defining
22513 (@samp{hook-stop}) makes the associated commands execute every time
22514 execution stops in your program: before breakpoint commands are run,
22515 displays are printed, or the stack frame is printed.
22517 For example, to ignore @code{SIGALRM} signals while
22518 single-stepping, but treat them normally during normal execution,
22523 handle SIGALRM nopass
22527 handle SIGALRM pass
22530 define hook-continue
22531 handle SIGALRM pass
22535 As a further example, to hook at the beginning and end of the @code{echo}
22536 command, and to add extra text to the beginning and end of the message,
22544 define hookpost-echo
22548 (@value{GDBP}) echo Hello World
22549 <<<---Hello World--->>>
22554 You can define a hook for any single-word command in @value{GDBN}, but
22555 not for command aliases; you should define a hook for the basic command
22556 name, e.g.@: @code{backtrace} rather than @code{bt}.
22557 @c FIXME! So how does Joe User discover whether a command is an alias
22559 You can hook a multi-word command by adding @code{hook-} or
22560 @code{hookpost-} to the last word of the command, e.g.@:
22561 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22563 If an error occurs during the execution of your hook, execution of
22564 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22565 (before the command that you actually typed had a chance to run).
22567 If you try to define a hook which does not match any known command, you
22568 get a warning from the @code{define} command.
22570 @node Command Files
22571 @subsection Command Files
22573 @cindex command files
22574 @cindex scripting commands
22575 A command file for @value{GDBN} is a text file made of lines that are
22576 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22577 also be included. An empty line in a command file does nothing; it
22578 does not mean to repeat the last command, as it would from the
22581 You can request the execution of a command file with the @code{source}
22582 command. Note that the @code{source} command is also used to evaluate
22583 scripts that are not Command Files. The exact behavior can be configured
22584 using the @code{script-extension} setting.
22585 @xref{Extending GDB,, Extending GDB}.
22589 @cindex execute commands from a file
22590 @item source [-s] [-v] @var{filename}
22591 Execute the command file @var{filename}.
22594 The lines in a command file are generally executed sequentially,
22595 unless the order of execution is changed by one of the
22596 @emph{flow-control commands} described below. The commands are not
22597 printed as they are executed. An error in any command terminates
22598 execution of the command file and control is returned to the console.
22600 @value{GDBN} first searches for @var{filename} in the current directory.
22601 If the file is not found there, and @var{filename} does not specify a
22602 directory, then @value{GDBN} also looks for the file on the source search path
22603 (specified with the @samp{directory} command);
22604 except that @file{$cdir} is not searched because the compilation directory
22605 is not relevant to scripts.
22607 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22608 on the search path even if @var{filename} specifies a directory.
22609 The search is done by appending @var{filename} to each element of the
22610 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22611 and the search path contains @file{/home/user} then @value{GDBN} will
22612 look for the script @file{/home/user/mylib/myscript}.
22613 The search is also done if @var{filename} is an absolute path.
22614 For example, if @var{filename} is @file{/tmp/myscript} and
22615 the search path contains @file{/home/user} then @value{GDBN} will
22616 look for the script @file{/home/user/tmp/myscript}.
22617 For DOS-like systems, if @var{filename} contains a drive specification,
22618 it is stripped before concatenation. For example, if @var{filename} is
22619 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22620 will look for the script @file{c:/tmp/myscript}.
22622 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22623 each command as it is executed. The option must be given before
22624 @var{filename}, and is interpreted as part of the filename anywhere else.
22626 Commands that would ask for confirmation if used interactively proceed
22627 without asking when used in a command file. Many @value{GDBN} commands that
22628 normally print messages to say what they are doing omit the messages
22629 when called from command files.
22631 @value{GDBN} also accepts command input from standard input. In this
22632 mode, normal output goes to standard output and error output goes to
22633 standard error. Errors in a command file supplied on standard input do
22634 not terminate execution of the command file---execution continues with
22638 gdb < cmds > log 2>&1
22641 (The syntax above will vary depending on the shell used.) This example
22642 will execute commands from the file @file{cmds}. All output and errors
22643 would be directed to @file{log}.
22645 Since commands stored on command files tend to be more general than
22646 commands typed interactively, they frequently need to deal with
22647 complicated situations, such as different or unexpected values of
22648 variables and symbols, changes in how the program being debugged is
22649 built, etc. @value{GDBN} provides a set of flow-control commands to
22650 deal with these complexities. Using these commands, you can write
22651 complex scripts that loop over data structures, execute commands
22652 conditionally, etc.
22659 This command allows to include in your script conditionally executed
22660 commands. The @code{if} command takes a single argument, which is an
22661 expression to evaluate. It is followed by a series of commands that
22662 are executed only if the expression is true (its value is nonzero).
22663 There can then optionally be an @code{else} line, followed by a series
22664 of commands that are only executed if the expression was false. The
22665 end of the list is marked by a line containing @code{end}.
22669 This command allows to write loops. Its syntax is similar to
22670 @code{if}: the command takes a single argument, which is an expression
22671 to evaluate, and must be followed by the commands to execute, one per
22672 line, terminated by an @code{end}. These commands are called the
22673 @dfn{body} of the loop. The commands in the body of @code{while} are
22674 executed repeatedly as long as the expression evaluates to true.
22678 This command exits the @code{while} loop in whose body it is included.
22679 Execution of the script continues after that @code{while}s @code{end}
22682 @kindex loop_continue
22683 @item loop_continue
22684 This command skips the execution of the rest of the body of commands
22685 in the @code{while} loop in whose body it is included. Execution
22686 branches to the beginning of the @code{while} loop, where it evaluates
22687 the controlling expression.
22689 @kindex end@r{ (if/else/while commands)}
22691 Terminate the block of commands that are the body of @code{if},
22692 @code{else}, or @code{while} flow-control commands.
22697 @subsection Commands for Controlled Output
22699 During the execution of a command file or a user-defined command, normal
22700 @value{GDBN} output is suppressed; the only output that appears is what is
22701 explicitly printed by the commands in the definition. This section
22702 describes three commands useful for generating exactly the output you
22707 @item echo @var{text}
22708 @c I do not consider backslash-space a standard C escape sequence
22709 @c because it is not in ANSI.
22710 Print @var{text}. Nonprinting characters can be included in
22711 @var{text} using C escape sequences, such as @samp{\n} to print a
22712 newline. @strong{No newline is printed unless you specify one.}
22713 In addition to the standard C escape sequences, a backslash followed
22714 by a space stands for a space. This is useful for displaying a
22715 string with spaces at the beginning or the end, since leading and
22716 trailing spaces are otherwise trimmed from all arguments.
22717 To print @samp{@w{ }and foo =@w{ }}, use the command
22718 @samp{echo \@w{ }and foo = \@w{ }}.
22720 A backslash at the end of @var{text} can be used, as in C, to continue
22721 the command onto subsequent lines. For example,
22724 echo This is some text\n\
22725 which is continued\n\
22726 onto several lines.\n
22729 produces the same output as
22732 echo This is some text\n
22733 echo which is continued\n
22734 echo onto several lines.\n
22738 @item output @var{expression}
22739 Print the value of @var{expression} and nothing but that value: no
22740 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22741 value history either. @xref{Expressions, ,Expressions}, for more information
22744 @item output/@var{fmt} @var{expression}
22745 Print the value of @var{expression} in format @var{fmt}. You can use
22746 the same formats as for @code{print}. @xref{Output Formats,,Output
22747 Formats}, for more information.
22750 @item printf @var{template}, @var{expressions}@dots{}
22751 Print the values of one or more @var{expressions} under the control of
22752 the string @var{template}. To print several values, make
22753 @var{expressions} be a comma-separated list of individual expressions,
22754 which may be either numbers or pointers. Their values are printed as
22755 specified by @var{template}, exactly as a C program would do by
22756 executing the code below:
22759 printf (@var{template}, @var{expressions}@dots{});
22762 As in @code{C} @code{printf}, ordinary characters in @var{template}
22763 are printed verbatim, while @dfn{conversion specification} introduced
22764 by the @samp{%} character cause subsequent @var{expressions} to be
22765 evaluated, their values converted and formatted according to type and
22766 style information encoded in the conversion specifications, and then
22769 For example, you can print two values in hex like this:
22772 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22775 @code{printf} supports all the standard @code{C} conversion
22776 specifications, including the flags and modifiers between the @samp{%}
22777 character and the conversion letter, with the following exceptions:
22781 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22784 The modifier @samp{*} is not supported for specifying precision or
22788 The @samp{'} flag (for separation of digits into groups according to
22789 @code{LC_NUMERIC'}) is not supported.
22792 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22796 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22799 The conversion letters @samp{a} and @samp{A} are not supported.
22803 Note that the @samp{ll} type modifier is supported only if the
22804 underlying @code{C} implementation used to build @value{GDBN} supports
22805 the @code{long long int} type, and the @samp{L} type modifier is
22806 supported only if @code{long double} type is available.
22808 As in @code{C}, @code{printf} supports simple backslash-escape
22809 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22810 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22811 single character. Octal and hexadecimal escape sequences are not
22814 Additionally, @code{printf} supports conversion specifications for DFP
22815 (@dfn{Decimal Floating Point}) types using the following length modifiers
22816 together with a floating point specifier.
22821 @samp{H} for printing @code{Decimal32} types.
22824 @samp{D} for printing @code{Decimal64} types.
22827 @samp{DD} for printing @code{Decimal128} types.
22830 If the underlying @code{C} implementation used to build @value{GDBN} has
22831 support for the three length modifiers for DFP types, other modifiers
22832 such as width and precision will also be available for @value{GDBN} to use.
22834 In case there is no such @code{C} support, no additional modifiers will be
22835 available and the value will be printed in the standard way.
22837 Here's an example of printing DFP types using the above conversion letters:
22839 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22843 @item eval @var{template}, @var{expressions}@dots{}
22844 Convert the values of one or more @var{expressions} under the control of
22845 the string @var{template} to a command line, and call it.
22850 @section Scripting @value{GDBN} using Python
22851 @cindex python scripting
22852 @cindex scripting with python
22854 You can script @value{GDBN} using the @uref{http://www.python.org/,
22855 Python programming language}. This feature is available only if
22856 @value{GDBN} was configured using @option{--with-python}.
22858 @cindex python directory
22859 Python scripts used by @value{GDBN} should be installed in
22860 @file{@var{data-directory}/python}, where @var{data-directory} is
22861 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22862 This directory, known as the @dfn{python directory},
22863 is automatically added to the Python Search Path in order to allow
22864 the Python interpreter to locate all scripts installed at this location.
22866 Additionally, @value{GDBN} commands and convenience functions which
22867 are written in Python and are located in the
22868 @file{@var{data-directory}/python/gdb/command} or
22869 @file{@var{data-directory}/python/gdb/function} directories are
22870 automatically imported when @value{GDBN} starts.
22873 * Python Commands:: Accessing Python from @value{GDBN}.
22874 * Python API:: Accessing @value{GDBN} from Python.
22875 * Python Auto-loading:: Automatically loading Python code.
22876 * Python modules:: Python modules provided by @value{GDBN}.
22879 @node Python Commands
22880 @subsection Python Commands
22881 @cindex python commands
22882 @cindex commands to access python
22884 @value{GDBN} provides two commands for accessing the Python interpreter,
22885 and one related setting:
22888 @kindex python-interactive
22890 @item python-interactive @r{[}@var{command}@r{]}
22891 @itemx pi @r{[}@var{command}@r{]}
22892 Without an argument, the @code{python-interactive} command can be used
22893 to start an interactive Python prompt. To return to @value{GDBN},
22894 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22896 Alternatively, a single-line Python command can be given as an
22897 argument and evaluated. If the command is an expression, the result
22898 will be printed; otherwise, nothing will be printed. For example:
22901 (@value{GDBP}) python-interactive 2 + 3
22907 @item python @r{[}@var{command}@r{]}
22908 @itemx py @r{[}@var{command}@r{]}
22909 The @code{python} command can be used to evaluate Python code.
22911 If given an argument, the @code{python} command will evaluate the
22912 argument as a Python command. For example:
22915 (@value{GDBP}) python print 23
22919 If you do not provide an argument to @code{python}, it will act as a
22920 multi-line command, like @code{define}. In this case, the Python
22921 script is made up of subsequent command lines, given after the
22922 @code{python} command. This command list is terminated using a line
22923 containing @code{end}. For example:
22926 (@value{GDBP}) python
22928 End with a line saying just "end".
22934 @kindex set python print-stack
22935 @item set python print-stack
22936 By default, @value{GDBN} will print only the message component of a
22937 Python exception when an error occurs in a Python script. This can be
22938 controlled using @code{set python print-stack}: if @code{full}, then
22939 full Python stack printing is enabled; if @code{none}, then Python stack
22940 and message printing is disabled; if @code{message}, the default, only
22941 the message component of the error is printed.
22944 It is also possible to execute a Python script from the @value{GDBN}
22948 @item source @file{script-name}
22949 The script name must end with @samp{.py} and @value{GDBN} must be configured
22950 to recognize the script language based on filename extension using
22951 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22953 @item python execfile ("script-name")
22954 This method is based on the @code{execfile} Python built-in function,
22955 and thus is always available.
22959 @subsection Python API
22961 @cindex programming in python
22963 @cindex python stdout
22964 @cindex python pagination
22965 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22966 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22967 A Python program which outputs to one of these streams may have its
22968 output interrupted by the user (@pxref{Screen Size}). In this
22969 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22972 * Basic Python:: Basic Python Functions.
22973 * Exception Handling:: How Python exceptions are translated.
22974 * Values From Inferior:: Python representation of values.
22975 * Types In Python:: Python representation of types.
22976 * Pretty Printing API:: Pretty-printing values.
22977 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22978 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22979 * Type Printing API:: Pretty-printing types.
22980 * Inferiors In Python:: Python representation of inferiors (processes)
22981 * Events In Python:: Listening for events from @value{GDBN}.
22982 * Threads In Python:: Accessing inferior threads from Python.
22983 * Commands In Python:: Implementing new commands in Python.
22984 * Parameters In Python:: Adding new @value{GDBN} parameters.
22985 * Functions In Python:: Writing new convenience functions.
22986 * Progspaces In Python:: Program spaces.
22987 * Objfiles In Python:: Object files.
22988 * Frames In Python:: Accessing inferior stack frames from Python.
22989 * Blocks In Python:: Accessing frame blocks from Python.
22990 * Symbols In Python:: Python representation of symbols.
22991 * Symbol Tables In Python:: Python representation of symbol tables.
22992 * Breakpoints In Python:: Manipulating breakpoints using Python.
22993 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22995 * Lazy Strings In Python:: Python representation of lazy strings.
22996 * Architectures In Python:: Python representation of architectures.
23000 @subsubsection Basic Python
23002 @cindex python functions
23003 @cindex python module
23005 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23006 methods and classes added by @value{GDBN} are placed in this module.
23007 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23008 use in all scripts evaluated by the @code{python} command.
23010 @findex gdb.PYTHONDIR
23011 @defvar gdb.PYTHONDIR
23012 A string containing the python directory (@pxref{Python}).
23015 @findex gdb.execute
23016 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23017 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23018 If a GDB exception happens while @var{command} runs, it is
23019 translated as described in @ref{Exception Handling,,Exception Handling}.
23021 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23022 command as having originated from the user invoking it interactively.
23023 It must be a boolean value. If omitted, it defaults to @code{False}.
23025 By default, any output produced by @var{command} is sent to
23026 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23027 @code{True}, then output will be collected by @code{gdb.execute} and
23028 returned as a string. The default is @code{False}, in which case the
23029 return value is @code{None}. If @var{to_string} is @code{True}, the
23030 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23031 and height, and its pagination will be disabled; @pxref{Screen Size}.
23034 @findex gdb.breakpoints
23035 @defun gdb.breakpoints ()
23036 Return a sequence holding all of @value{GDBN}'s breakpoints.
23037 @xref{Breakpoints In Python}, for more information.
23040 @findex gdb.parameter
23041 @defun gdb.parameter (parameter)
23042 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23043 string naming the parameter to look up; @var{parameter} may contain
23044 spaces if the parameter has a multi-part name. For example,
23045 @samp{print object} is a valid parameter name.
23047 If the named parameter does not exist, this function throws a
23048 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23049 parameter's value is converted to a Python value of the appropriate
23050 type, and returned.
23053 @findex gdb.history
23054 @defun gdb.history (number)
23055 Return a value from @value{GDBN}'s value history (@pxref{Value
23056 History}). @var{number} indicates which history element to return.
23057 If @var{number} is negative, then @value{GDBN} will take its absolute value
23058 and count backward from the last element (i.e., the most recent element) to
23059 find the value to return. If @var{number} is zero, then @value{GDBN} will
23060 return the most recent element. If the element specified by @var{number}
23061 doesn't exist in the value history, a @code{gdb.error} exception will be
23064 If no exception is raised, the return value is always an instance of
23065 @code{gdb.Value} (@pxref{Values From Inferior}).
23068 @findex gdb.parse_and_eval
23069 @defun gdb.parse_and_eval (expression)
23070 Parse @var{expression} as an expression in the current language,
23071 evaluate it, and return the result as a @code{gdb.Value}.
23072 @var{expression} must be a string.
23074 This function can be useful when implementing a new command
23075 (@pxref{Commands In Python}), as it provides a way to parse the
23076 command's argument as an expression. It is also useful simply to
23077 compute values, for example, it is the only way to get the value of a
23078 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23081 @findex gdb.find_pc_line
23082 @defun gdb.find_pc_line (pc)
23083 Return the @code{gdb.Symtab_and_line} object corresponding to the
23084 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23085 value of @var{pc} is passed as an argument, then the @code{symtab} and
23086 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23087 will be @code{None} and 0 respectively.
23090 @findex gdb.post_event
23091 @defun gdb.post_event (event)
23092 Put @var{event}, a callable object taking no arguments, into
23093 @value{GDBN}'s internal event queue. This callable will be invoked at
23094 some later point, during @value{GDBN}'s event processing. Events
23095 posted using @code{post_event} will be run in the order in which they
23096 were posted; however, there is no way to know when they will be
23097 processed relative to other events inside @value{GDBN}.
23099 @value{GDBN} is not thread-safe. If your Python program uses multiple
23100 threads, you must be careful to only call @value{GDBN}-specific
23101 functions in the main @value{GDBN} thread. @code{post_event} ensures
23105 (@value{GDBP}) python
23109 > def __init__(self, message):
23110 > self.message = message;
23111 > def __call__(self):
23112 > gdb.write(self.message)
23114 >class MyThread1 (threading.Thread):
23116 > gdb.post_event(Writer("Hello "))
23118 >class MyThread2 (threading.Thread):
23120 > gdb.post_event(Writer("World\n"))
23122 >MyThread1().start()
23123 >MyThread2().start()
23125 (@value{GDBP}) Hello World
23130 @defun gdb.write (string @r{[}, stream{]})
23131 Print a string to @value{GDBN}'s paginated output stream. The
23132 optional @var{stream} determines the stream to print to. The default
23133 stream is @value{GDBN}'s standard output stream. Possible stream
23140 @value{GDBN}'s standard output stream.
23145 @value{GDBN}'s standard error stream.
23150 @value{GDBN}'s log stream (@pxref{Logging Output}).
23153 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23154 call this function and will automatically direct the output to the
23159 @defun gdb.flush ()
23160 Flush the buffer of a @value{GDBN} paginated stream so that the
23161 contents are displayed immediately. @value{GDBN} will flush the
23162 contents of a stream automatically when it encounters a newline in the
23163 buffer. The optional @var{stream} determines the stream to flush. The
23164 default stream is @value{GDBN}'s standard output stream. Possible
23171 @value{GDBN}'s standard output stream.
23176 @value{GDBN}'s standard error stream.
23181 @value{GDBN}'s log stream (@pxref{Logging Output}).
23185 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23186 call this function for the relevant stream.
23189 @findex gdb.target_charset
23190 @defun gdb.target_charset ()
23191 Return the name of the current target character set (@pxref{Character
23192 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23193 that @samp{auto} is never returned.
23196 @findex gdb.target_wide_charset
23197 @defun gdb.target_wide_charset ()
23198 Return the name of the current target wide character set
23199 (@pxref{Character Sets}). This differs from
23200 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23204 @findex gdb.solib_name
23205 @defun gdb.solib_name (address)
23206 Return the name of the shared library holding the given @var{address}
23207 as a string, or @code{None}.
23210 @findex gdb.decode_line
23211 @defun gdb.decode_line @r{[}expression@r{]}
23212 Return locations of the line specified by @var{expression}, or of the
23213 current line if no argument was given. This function returns a Python
23214 tuple containing two elements. The first element contains a string
23215 holding any unparsed section of @var{expression} (or @code{None} if
23216 the expression has been fully parsed). The second element contains
23217 either @code{None} or another tuple that contains all the locations
23218 that match the expression represented as @code{gdb.Symtab_and_line}
23219 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23220 provided, it is decoded the way that @value{GDBN}'s inbuilt
23221 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23224 @defun gdb.prompt_hook (current_prompt)
23225 @anchor{prompt_hook}
23227 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23228 assigned to this operation before a prompt is displayed by
23231 The parameter @code{current_prompt} contains the current @value{GDBN}
23232 prompt. This method must return a Python string, or @code{None}. If
23233 a string is returned, the @value{GDBN} prompt will be set to that
23234 string. If @code{None} is returned, @value{GDBN} will continue to use
23235 the current prompt.
23237 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23238 such as those used by readline for command input, and annotation
23239 related prompts are prohibited from being changed.
23242 @node Exception Handling
23243 @subsubsection Exception Handling
23244 @cindex python exceptions
23245 @cindex exceptions, python
23247 When executing the @code{python} command, Python exceptions
23248 uncaught within the Python code are translated to calls to
23249 @value{GDBN} error-reporting mechanism. If the command that called
23250 @code{python} does not handle the error, @value{GDBN} will
23251 terminate it and print an error message containing the Python
23252 exception name, the associated value, and the Python call stack
23253 backtrace at the point where the exception was raised. Example:
23256 (@value{GDBP}) python print foo
23257 Traceback (most recent call last):
23258 File "<string>", line 1, in <module>
23259 NameError: name 'foo' is not defined
23262 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23263 Python code are converted to Python exceptions. The type of the
23264 Python exception depends on the error.
23268 This is the base class for most exceptions generated by @value{GDBN}.
23269 It is derived from @code{RuntimeError}, for compatibility with earlier
23270 versions of @value{GDBN}.
23272 If an error occurring in @value{GDBN} does not fit into some more
23273 specific category, then the generated exception will have this type.
23275 @item gdb.MemoryError
23276 This is a subclass of @code{gdb.error} which is thrown when an
23277 operation tried to access invalid memory in the inferior.
23279 @item KeyboardInterrupt
23280 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23281 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23284 In all cases, your exception handler will see the @value{GDBN} error
23285 message as its value and the Python call stack backtrace at the Python
23286 statement closest to where the @value{GDBN} error occured as the
23289 @findex gdb.GdbError
23290 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23291 it is useful to be able to throw an exception that doesn't cause a
23292 traceback to be printed. For example, the user may have invoked the
23293 command incorrectly. Use the @code{gdb.GdbError} exception
23294 to handle this case. Example:
23298 >class HelloWorld (gdb.Command):
23299 > """Greet the whole world."""
23300 > def __init__ (self):
23301 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23302 > def invoke (self, args, from_tty):
23303 > argv = gdb.string_to_argv (args)
23304 > if len (argv) != 0:
23305 > raise gdb.GdbError ("hello-world takes no arguments")
23306 > print "Hello, World!"
23309 (gdb) hello-world 42
23310 hello-world takes no arguments
23313 @node Values From Inferior
23314 @subsubsection Values From Inferior
23315 @cindex values from inferior, with Python
23316 @cindex python, working with values from inferior
23318 @cindex @code{gdb.Value}
23319 @value{GDBN} provides values it obtains from the inferior program in
23320 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23321 for its internal bookkeeping of the inferior's values, and for
23322 fetching values when necessary.
23324 Inferior values that are simple scalars can be used directly in
23325 Python expressions that are valid for the value's data type. Here's
23326 an example for an integer or floating-point value @code{some_val}:
23333 As result of this, @code{bar} will also be a @code{gdb.Value} object
23334 whose values are of the same type as those of @code{some_val}.
23336 Inferior values that are structures or instances of some class can
23337 be accessed using the Python @dfn{dictionary syntax}. For example, if
23338 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23339 can access its @code{foo} element with:
23342 bar = some_val['foo']
23345 Again, @code{bar} will also be a @code{gdb.Value} object.
23347 A @code{gdb.Value} that represents a function can be executed via
23348 inferior function call. Any arguments provided to the call must match
23349 the function's prototype, and must be provided in the order specified
23352 For example, @code{some_val} is a @code{gdb.Value} instance
23353 representing a function that takes two integers as arguments. To
23354 execute this function, call it like so:
23357 result = some_val (10,20)
23360 Any values returned from a function call will be stored as a
23363 The following attributes are provided:
23365 @defvar Value.address
23366 If this object is addressable, this read-only attribute holds a
23367 @code{gdb.Value} object representing the address. Otherwise,
23368 this attribute holds @code{None}.
23371 @cindex optimized out value in Python
23372 @defvar Value.is_optimized_out
23373 This read-only boolean attribute is true if the compiler optimized out
23374 this value, thus it is not available for fetching from the inferior.
23378 The type of this @code{gdb.Value}. The value of this attribute is a
23379 @code{gdb.Type} object (@pxref{Types In Python}).
23382 @defvar Value.dynamic_type
23383 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23384 type information (@acronym{RTTI}) to determine the dynamic type of the
23385 value. If this value is of class type, it will return the class in
23386 which the value is embedded, if any. If this value is of pointer or
23387 reference to a class type, it will compute the dynamic type of the
23388 referenced object, and return a pointer or reference to that type,
23389 respectively. In all other cases, it will return the value's static
23392 Note that this feature will only work when debugging a C@t{++} program
23393 that includes @acronym{RTTI} for the object in question. Otherwise,
23394 it will just return the static type of the value as in @kbd{ptype foo}
23395 (@pxref{Symbols, ptype}).
23398 @defvar Value.is_lazy
23399 The value of this read-only boolean attribute is @code{True} if this
23400 @code{gdb.Value} has not yet been fetched from the inferior.
23401 @value{GDBN} does not fetch values until necessary, for efficiency.
23405 myval = gdb.parse_and_eval ('somevar')
23408 The value of @code{somevar} is not fetched at this time. It will be
23409 fetched when the value is needed, or when the @code{fetch_lazy}
23413 The following methods are provided:
23415 @defun Value.__init__ (@var{val})
23416 Many Python values can be converted directly to a @code{gdb.Value} via
23417 this object initializer. Specifically:
23420 @item Python boolean
23421 A Python boolean is converted to the boolean type from the current
23424 @item Python integer
23425 A Python integer is converted to the C @code{long} type for the
23426 current architecture.
23429 A Python long is converted to the C @code{long long} type for the
23430 current architecture.
23433 A Python float is converted to the C @code{double} type for the
23434 current architecture.
23436 @item Python string
23437 A Python string is converted to a target string, using the current
23440 @item @code{gdb.Value}
23441 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23443 @item @code{gdb.LazyString}
23444 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23445 Python}), then the lazy string's @code{value} method is called, and
23446 its result is used.
23450 @defun Value.cast (type)
23451 Return a new instance of @code{gdb.Value} that is the result of
23452 casting this instance to the type described by @var{type}, which must
23453 be a @code{gdb.Type} object. If the cast cannot be performed for some
23454 reason, this method throws an exception.
23457 @defun Value.dereference ()
23458 For pointer data types, this method returns a new @code{gdb.Value} object
23459 whose contents is the object pointed to by the pointer. For example, if
23460 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23467 then you can use the corresponding @code{gdb.Value} to access what
23468 @code{foo} points to like this:
23471 bar = foo.dereference ()
23474 The result @code{bar} will be a @code{gdb.Value} object holding the
23475 value pointed to by @code{foo}.
23477 A similar function @code{Value.referenced_value} exists which also
23478 returns @code{gdb.Value} objects corresonding to the values pointed to
23479 by pointer values (and additionally, values referenced by reference
23480 values). However, the behavior of @code{Value.dereference}
23481 differs from @code{Value.referenced_value} by the fact that the
23482 behavior of @code{Value.dereference} is identical to applying the C
23483 unary operator @code{*} on a given value. For example, consider a
23484 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23488 typedef int *intptr;
23492 intptr &ptrref = ptr;
23495 Though @code{ptrref} is a reference value, one can apply the method
23496 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23497 to it and obtain a @code{gdb.Value} which is identical to that
23498 corresponding to @code{val}. However, if you apply the method
23499 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23500 object identical to that corresponding to @code{ptr}.
23503 py_ptrref = gdb.parse_and_eval ("ptrref")
23504 py_val = py_ptrref.dereference ()
23505 py_ptr = py_ptrref.referenced_value ()
23508 The @code{gdb.Value} object @code{py_val} is identical to that
23509 corresponding to @code{val}, and @code{py_ptr} is identical to that
23510 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23511 be applied whenever the C unary operator @code{*} can be applied
23512 to the corresponding C value. For those cases where applying both
23513 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23514 the results obtained need not be identical (as we have seen in the above
23515 example). The results are however identical when applied on
23516 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23517 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23520 @defun Value.referenced_value ()
23521 For pointer or reference data types, this method returns a new
23522 @code{gdb.Value} object corresponding to the value referenced by the
23523 pointer/reference value. For pointer data types,
23524 @code{Value.dereference} and @code{Value.referenced_value} produce
23525 identical results. The difference between these methods is that
23526 @code{Value.dereference} cannot get the values referenced by reference
23527 values. For example, consider a reference to an @code{int}, declared
23528 in your C@t{++} program as
23536 then applying @code{Value.dereference} to the @code{gdb.Value} object
23537 corresponding to @code{ref} will result in an error, while applying
23538 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23539 identical to that corresponding to @code{val}.
23542 py_ref = gdb.parse_and_eval ("ref")
23543 er_ref = py_ref.dereference () # Results in error
23544 py_val = py_ref.referenced_value () # Returns the referenced value
23547 The @code{gdb.Value} object @code{py_val} is identical to that
23548 corresponding to @code{val}.
23551 @defun Value.dynamic_cast (type)
23552 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23553 operator were used. Consult a C@t{++} reference for details.
23556 @defun Value.reinterpret_cast (type)
23557 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23558 operator were used. Consult a C@t{++} reference for details.
23561 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23562 If this @code{gdb.Value} represents a string, then this method
23563 converts the contents to a Python string. Otherwise, this method will
23564 throw an exception.
23566 Strings are recognized in a language-specific way; whether a given
23567 @code{gdb.Value} represents a string is determined by the current
23570 For C-like languages, a value is a string if it is a pointer to or an
23571 array of characters or ints. The string is assumed to be terminated
23572 by a zero of the appropriate width. However if the optional length
23573 argument is given, the string will be converted to that given length,
23574 ignoring any embedded zeros that the string may contain.
23576 If the optional @var{encoding} argument is given, it must be a string
23577 naming the encoding of the string in the @code{gdb.Value}, such as
23578 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23579 the same encodings as the corresponding argument to Python's
23580 @code{string.decode} method, and the Python codec machinery will be used
23581 to convert the string. If @var{encoding} is not given, or if
23582 @var{encoding} is the empty string, then either the @code{target-charset}
23583 (@pxref{Character Sets}) will be used, or a language-specific encoding
23584 will be used, if the current language is able to supply one.
23586 The optional @var{errors} argument is the same as the corresponding
23587 argument to Python's @code{string.decode} method.
23589 If the optional @var{length} argument is given, the string will be
23590 fetched and converted to the given length.
23593 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23594 If this @code{gdb.Value} represents a string, then this method
23595 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23596 In Python}). Otherwise, this method will throw an exception.
23598 If the optional @var{encoding} argument is given, it must be a string
23599 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23600 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23601 @var{encoding} argument is an encoding that @value{GDBN} does
23602 recognize, @value{GDBN} will raise an error.
23604 When a lazy string is printed, the @value{GDBN} encoding machinery is
23605 used to convert the string during printing. If the optional
23606 @var{encoding} argument is not provided, or is an empty string,
23607 @value{GDBN} will automatically select the encoding most suitable for
23608 the string type. For further information on encoding in @value{GDBN}
23609 please see @ref{Character Sets}.
23611 If the optional @var{length} argument is given, the string will be
23612 fetched and encoded to the length of characters specified. If
23613 the @var{length} argument is not provided, the string will be fetched
23614 and encoded until a null of appropriate width is found.
23617 @defun Value.fetch_lazy ()
23618 If the @code{gdb.Value} object is currently a lazy value
23619 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23620 fetched from the inferior. Any errors that occur in the process
23621 will produce a Python exception.
23623 If the @code{gdb.Value} object is not a lazy value, this method
23626 This method does not return a value.
23630 @node Types In Python
23631 @subsubsection Types In Python
23632 @cindex types in Python
23633 @cindex Python, working with types
23636 @value{GDBN} represents types from the inferior using the class
23639 The following type-related functions are available in the @code{gdb}
23642 @findex gdb.lookup_type
23643 @defun gdb.lookup_type (name @r{[}, block@r{]})
23644 This function looks up a type by name. @var{name} is the name of the
23645 type to look up. It must be a string.
23647 If @var{block} is given, then @var{name} is looked up in that scope.
23648 Otherwise, it is searched for globally.
23650 Ordinarily, this function will return an instance of @code{gdb.Type}.
23651 If the named type cannot be found, it will throw an exception.
23654 If the type is a structure or class type, or an enum type, the fields
23655 of that type can be accessed using the Python @dfn{dictionary syntax}.
23656 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23657 a structure type, you can access its @code{foo} field with:
23660 bar = some_type['foo']
23663 @code{bar} will be a @code{gdb.Field} object; see below under the
23664 description of the @code{Type.fields} method for a description of the
23665 @code{gdb.Field} class.
23667 An instance of @code{Type} has the following attributes:
23670 The type code for this type. The type code will be one of the
23671 @code{TYPE_CODE_} constants defined below.
23674 @defvar Type.sizeof
23675 The size of this type, in target @code{char} units. Usually, a
23676 target's @code{char} type will be an 8-bit byte. However, on some
23677 unusual platforms, this type may have a different size.
23681 The tag name for this type. The tag name is the name after
23682 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23683 languages have this concept. If this type has no tag name, then
23684 @code{None} is returned.
23687 The following methods are provided:
23689 @defun Type.fields ()
23690 For structure and union types, this method returns the fields. Range
23691 types have two fields, the minimum and maximum values. Enum types
23692 have one field per enum constant. Function and method types have one
23693 field per parameter. The base types of C@t{++} classes are also
23694 represented as fields. If the type has no fields, or does not fit
23695 into one of these categories, an empty sequence will be returned.
23697 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23700 This attribute is not available for @code{static} fields (as in
23701 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23702 position of the field. For @code{enum} fields, the value is the
23703 enumeration member's integer representation.
23706 The name of the field, or @code{None} for anonymous fields.
23709 This is @code{True} if the field is artificial, usually meaning that
23710 it was provided by the compiler and not the user. This attribute is
23711 always provided, and is @code{False} if the field is not artificial.
23713 @item is_base_class
23714 This is @code{True} if the field represents a base class of a C@t{++}
23715 structure. This attribute is always provided, and is @code{False}
23716 if the field is not a base class of the type that is the argument of
23717 @code{fields}, or if that type was not a C@t{++} class.
23720 If the field is packed, or is a bitfield, then this will have a
23721 non-zero value, which is the size of the field in bits. Otherwise,
23722 this will be zero; in this case the field's size is given by its type.
23725 The type of the field. This is usually an instance of @code{Type},
23726 but it can be @code{None} in some situations.
23730 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23731 Return a new @code{gdb.Type} object which represents an array of this
23732 type. If one argument is given, it is the inclusive upper bound of
23733 the array; in this case the lower bound is zero. If two arguments are
23734 given, the first argument is the lower bound of the array, and the
23735 second argument is the upper bound of the array. An array's length
23736 must not be negative, but the bounds can be.
23739 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23740 Return a new @code{gdb.Type} object which represents a vector of this
23741 type. If one argument is given, it is the inclusive upper bound of
23742 the vector; in this case the lower bound is zero. If two arguments are
23743 given, the first argument is the lower bound of the vector, and the
23744 second argument is the upper bound of the vector. A vector's length
23745 must not be negative, but the bounds can be.
23747 The difference between an @code{array} and a @code{vector} is that
23748 arrays behave like in C: when used in expressions they decay to a pointer
23749 to the first element whereas vectors are treated as first class values.
23752 @defun Type.const ()
23753 Return a new @code{gdb.Type} object which represents a
23754 @code{const}-qualified variant of this type.
23757 @defun Type.volatile ()
23758 Return a new @code{gdb.Type} object which represents a
23759 @code{volatile}-qualified variant of this type.
23762 @defun Type.unqualified ()
23763 Return a new @code{gdb.Type} object which represents an unqualified
23764 variant of this type. That is, the result is neither @code{const} nor
23768 @defun Type.range ()
23769 Return a Python @code{Tuple} object that contains two elements: the
23770 low bound of the argument type and the high bound of that type. If
23771 the type does not have a range, @value{GDBN} will raise a
23772 @code{gdb.error} exception (@pxref{Exception Handling}).
23775 @defun Type.reference ()
23776 Return a new @code{gdb.Type} object which represents a reference to this
23780 @defun Type.pointer ()
23781 Return a new @code{gdb.Type} object which represents a pointer to this
23785 @defun Type.strip_typedefs ()
23786 Return a new @code{gdb.Type} that represents the real type,
23787 after removing all layers of typedefs.
23790 @defun Type.target ()
23791 Return a new @code{gdb.Type} object which represents the target type
23794 For a pointer type, the target type is the type of the pointed-to
23795 object. For an array type (meaning C-like arrays), the target type is
23796 the type of the elements of the array. For a function or method type,
23797 the target type is the type of the return value. For a complex type,
23798 the target type is the type of the elements. For a typedef, the
23799 target type is the aliased type.
23801 If the type does not have a target, this method will throw an
23805 @defun Type.template_argument (n @r{[}, block@r{]})
23806 If this @code{gdb.Type} is an instantiation of a template, this will
23807 return a new @code{gdb.Type} which represents the type of the
23808 @var{n}th template argument.
23810 If this @code{gdb.Type} is not a template type, this will throw an
23811 exception. Ordinarily, only C@t{++} code will have template types.
23813 If @var{block} is given, then @var{name} is looked up in that scope.
23814 Otherwise, it is searched for globally.
23818 Each type has a code, which indicates what category this type falls
23819 into. The available type categories are represented by constants
23820 defined in the @code{gdb} module:
23823 @findex TYPE_CODE_PTR
23824 @findex gdb.TYPE_CODE_PTR
23825 @item gdb.TYPE_CODE_PTR
23826 The type is a pointer.
23828 @findex TYPE_CODE_ARRAY
23829 @findex gdb.TYPE_CODE_ARRAY
23830 @item gdb.TYPE_CODE_ARRAY
23831 The type is an array.
23833 @findex TYPE_CODE_STRUCT
23834 @findex gdb.TYPE_CODE_STRUCT
23835 @item gdb.TYPE_CODE_STRUCT
23836 The type is a structure.
23838 @findex TYPE_CODE_UNION
23839 @findex gdb.TYPE_CODE_UNION
23840 @item gdb.TYPE_CODE_UNION
23841 The type is a union.
23843 @findex TYPE_CODE_ENUM
23844 @findex gdb.TYPE_CODE_ENUM
23845 @item gdb.TYPE_CODE_ENUM
23846 The type is an enum.
23848 @findex TYPE_CODE_FLAGS
23849 @findex gdb.TYPE_CODE_FLAGS
23850 @item gdb.TYPE_CODE_FLAGS
23851 A bit flags type, used for things such as status registers.
23853 @findex TYPE_CODE_FUNC
23854 @findex gdb.TYPE_CODE_FUNC
23855 @item gdb.TYPE_CODE_FUNC
23856 The type is a function.
23858 @findex TYPE_CODE_INT
23859 @findex gdb.TYPE_CODE_INT
23860 @item gdb.TYPE_CODE_INT
23861 The type is an integer type.
23863 @findex TYPE_CODE_FLT
23864 @findex gdb.TYPE_CODE_FLT
23865 @item gdb.TYPE_CODE_FLT
23866 A floating point type.
23868 @findex TYPE_CODE_VOID
23869 @findex gdb.TYPE_CODE_VOID
23870 @item gdb.TYPE_CODE_VOID
23871 The special type @code{void}.
23873 @findex TYPE_CODE_SET
23874 @findex gdb.TYPE_CODE_SET
23875 @item gdb.TYPE_CODE_SET
23878 @findex TYPE_CODE_RANGE
23879 @findex gdb.TYPE_CODE_RANGE
23880 @item gdb.TYPE_CODE_RANGE
23881 A range type, that is, an integer type with bounds.
23883 @findex TYPE_CODE_STRING
23884 @findex gdb.TYPE_CODE_STRING
23885 @item gdb.TYPE_CODE_STRING
23886 A string type. Note that this is only used for certain languages with
23887 language-defined string types; C strings are not represented this way.
23889 @findex TYPE_CODE_BITSTRING
23890 @findex gdb.TYPE_CODE_BITSTRING
23891 @item gdb.TYPE_CODE_BITSTRING
23892 A string of bits. It is deprecated.
23894 @findex TYPE_CODE_ERROR
23895 @findex gdb.TYPE_CODE_ERROR
23896 @item gdb.TYPE_CODE_ERROR
23897 An unknown or erroneous type.
23899 @findex TYPE_CODE_METHOD
23900 @findex gdb.TYPE_CODE_METHOD
23901 @item gdb.TYPE_CODE_METHOD
23902 A method type, as found in C@t{++} or Java.
23904 @findex TYPE_CODE_METHODPTR
23905 @findex gdb.TYPE_CODE_METHODPTR
23906 @item gdb.TYPE_CODE_METHODPTR
23907 A pointer-to-member-function.
23909 @findex TYPE_CODE_MEMBERPTR
23910 @findex gdb.TYPE_CODE_MEMBERPTR
23911 @item gdb.TYPE_CODE_MEMBERPTR
23912 A pointer-to-member.
23914 @findex TYPE_CODE_REF
23915 @findex gdb.TYPE_CODE_REF
23916 @item gdb.TYPE_CODE_REF
23919 @findex TYPE_CODE_CHAR
23920 @findex gdb.TYPE_CODE_CHAR
23921 @item gdb.TYPE_CODE_CHAR
23924 @findex TYPE_CODE_BOOL
23925 @findex gdb.TYPE_CODE_BOOL
23926 @item gdb.TYPE_CODE_BOOL
23929 @findex TYPE_CODE_COMPLEX
23930 @findex gdb.TYPE_CODE_COMPLEX
23931 @item gdb.TYPE_CODE_COMPLEX
23932 A complex float type.
23934 @findex TYPE_CODE_TYPEDEF
23935 @findex gdb.TYPE_CODE_TYPEDEF
23936 @item gdb.TYPE_CODE_TYPEDEF
23937 A typedef to some other type.
23939 @findex TYPE_CODE_NAMESPACE
23940 @findex gdb.TYPE_CODE_NAMESPACE
23941 @item gdb.TYPE_CODE_NAMESPACE
23942 A C@t{++} namespace.
23944 @findex TYPE_CODE_DECFLOAT
23945 @findex gdb.TYPE_CODE_DECFLOAT
23946 @item gdb.TYPE_CODE_DECFLOAT
23947 A decimal floating point type.
23949 @findex TYPE_CODE_INTERNAL_FUNCTION
23950 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23951 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23952 A function internal to @value{GDBN}. This is the type used to represent
23953 convenience functions.
23956 Further support for types is provided in the @code{gdb.types}
23957 Python module (@pxref{gdb.types}).
23959 @node Pretty Printing API
23960 @subsubsection Pretty Printing API
23962 An example output is provided (@pxref{Pretty Printing}).
23964 A pretty-printer is just an object that holds a value and implements a
23965 specific interface, defined here.
23967 @defun pretty_printer.children (self)
23968 @value{GDBN} will call this method on a pretty-printer to compute the
23969 children of the pretty-printer's value.
23971 This method must return an object conforming to the Python iterator
23972 protocol. Each item returned by the iterator must be a tuple holding
23973 two elements. The first element is the ``name'' of the child; the
23974 second element is the child's value. The value can be any Python
23975 object which is convertible to a @value{GDBN} value.
23977 This method is optional. If it does not exist, @value{GDBN} will act
23978 as though the value has no children.
23981 @defun pretty_printer.display_hint (self)
23982 The CLI may call this method and use its result to change the
23983 formatting of a value. The result will also be supplied to an MI
23984 consumer as a @samp{displayhint} attribute of the variable being
23987 This method is optional. If it does exist, this method must return a
23990 Some display hints are predefined by @value{GDBN}:
23994 Indicate that the object being printed is ``array-like''. The CLI
23995 uses this to respect parameters such as @code{set print elements} and
23996 @code{set print array}.
23999 Indicate that the object being printed is ``map-like'', and that the
24000 children of this value can be assumed to alternate between keys and
24004 Indicate that the object being printed is ``string-like''. If the
24005 printer's @code{to_string} method returns a Python string of some
24006 kind, then @value{GDBN} will call its internal language-specific
24007 string-printing function to format the string. For the CLI this means
24008 adding quotation marks, possibly escaping some characters, respecting
24009 @code{set print elements}, and the like.
24013 @defun pretty_printer.to_string (self)
24014 @value{GDBN} will call this method to display the string
24015 representation of the value passed to the object's constructor.
24017 When printing from the CLI, if the @code{to_string} method exists,
24018 then @value{GDBN} will prepend its result to the values returned by
24019 @code{children}. Exactly how this formatting is done is dependent on
24020 the display hint, and may change as more hints are added. Also,
24021 depending on the print settings (@pxref{Print Settings}), the CLI may
24022 print just the result of @code{to_string} in a stack trace, omitting
24023 the result of @code{children}.
24025 If this method returns a string, it is printed verbatim.
24027 Otherwise, if this method returns an instance of @code{gdb.Value},
24028 then @value{GDBN} prints this value. This may result in a call to
24029 another pretty-printer.
24031 If instead the method returns a Python value which is convertible to a
24032 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24033 the resulting value. Again, this may result in a call to another
24034 pretty-printer. Python scalars (integers, floats, and booleans) and
24035 strings are convertible to @code{gdb.Value}; other types are not.
24037 Finally, if this method returns @code{None} then no further operations
24038 are peformed in this method and nothing is printed.
24040 If the result is not one of these types, an exception is raised.
24043 @value{GDBN} provides a function which can be used to look up the
24044 default pretty-printer for a @code{gdb.Value}:
24046 @findex gdb.default_visualizer
24047 @defun gdb.default_visualizer (value)
24048 This function takes a @code{gdb.Value} object as an argument. If a
24049 pretty-printer for this value exists, then it is returned. If no such
24050 printer exists, then this returns @code{None}.
24053 @node Selecting Pretty-Printers
24054 @subsubsection Selecting Pretty-Printers
24056 The Python list @code{gdb.pretty_printers} contains an array of
24057 functions or callable objects that have been registered via addition
24058 as a pretty-printer. Printers in this list are called @code{global}
24059 printers, they're available when debugging all inferiors.
24060 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24061 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24064 Each function on these lists is passed a single @code{gdb.Value}
24065 argument and should return a pretty-printer object conforming to the
24066 interface definition above (@pxref{Pretty Printing API}). If a function
24067 cannot create a pretty-printer for the value, it should return
24070 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24071 @code{gdb.Objfile} in the current program space and iteratively calls
24072 each enabled lookup routine in the list for that @code{gdb.Objfile}
24073 until it receives a pretty-printer object.
24074 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24075 searches the pretty-printer list of the current program space,
24076 calling each enabled function until an object is returned.
24077 After these lists have been exhausted, it tries the global
24078 @code{gdb.pretty_printers} list, again calling each enabled function until an
24079 object is returned.
24081 The order in which the objfiles are searched is not specified. For a
24082 given list, functions are always invoked from the head of the list,
24083 and iterated over sequentially until the end of the list, or a printer
24084 object is returned.
24086 For various reasons a pretty-printer may not work.
24087 For example, the underlying data structure may have changed and
24088 the pretty-printer is out of date.
24090 The consequences of a broken pretty-printer are severe enough that
24091 @value{GDBN} provides support for enabling and disabling individual
24092 printers. For example, if @code{print frame-arguments} is on,
24093 a backtrace can become highly illegible if any argument is printed
24094 with a broken printer.
24096 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24097 attribute to the registered function or callable object. If this attribute
24098 is present and its value is @code{False}, the printer is disabled, otherwise
24099 the printer is enabled.
24101 @node Writing a Pretty-Printer
24102 @subsubsection Writing a Pretty-Printer
24103 @cindex writing a pretty-printer
24105 A pretty-printer consists of two parts: a lookup function to detect
24106 if the type is supported, and the printer itself.
24108 Here is an example showing how a @code{std::string} printer might be
24109 written. @xref{Pretty Printing API}, for details on the API this class
24113 class StdStringPrinter(object):
24114 "Print a std::string"
24116 def __init__(self, val):
24119 def to_string(self):
24120 return self.val['_M_dataplus']['_M_p']
24122 def display_hint(self):
24126 And here is an example showing how a lookup function for the printer
24127 example above might be written.
24130 def str_lookup_function(val):
24131 lookup_tag = val.type.tag
24132 if lookup_tag == None:
24134 regex = re.compile("^std::basic_string<char,.*>$")
24135 if regex.match(lookup_tag):
24136 return StdStringPrinter(val)
24140 The example lookup function extracts the value's type, and attempts to
24141 match it to a type that it can pretty-print. If it is a type the
24142 printer can pretty-print, it will return a printer object. If not, it
24143 returns @code{None}.
24145 We recommend that you put your core pretty-printers into a Python
24146 package. If your pretty-printers are for use with a library, we
24147 further recommend embedding a version number into the package name.
24148 This practice will enable @value{GDBN} to load multiple versions of
24149 your pretty-printers at the same time, because they will have
24152 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24153 can be evaluated multiple times without changing its meaning. An
24154 ideal auto-load file will consist solely of @code{import}s of your
24155 printer modules, followed by a call to a register pretty-printers with
24156 the current objfile.
24158 Taken as a whole, this approach will scale nicely to multiple
24159 inferiors, each potentially using a different library version.
24160 Embedding a version number in the Python package name will ensure that
24161 @value{GDBN} is able to load both sets of printers simultaneously.
24162 Then, because the search for pretty-printers is done by objfile, and
24163 because your auto-loaded code took care to register your library's
24164 printers with a specific objfile, @value{GDBN} will find the correct
24165 printers for the specific version of the library used by each
24168 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24169 this code might appear in @code{gdb.libstdcxx.v6}:
24172 def register_printers(objfile):
24173 objfile.pretty_printers.append(str_lookup_function)
24177 And then the corresponding contents of the auto-load file would be:
24180 import gdb.libstdcxx.v6
24181 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24184 The previous example illustrates a basic pretty-printer.
24185 There are a few things that can be improved on.
24186 The printer doesn't have a name, making it hard to identify in a
24187 list of installed printers. The lookup function has a name, but
24188 lookup functions can have arbitrary, even identical, names.
24190 Second, the printer only handles one type, whereas a library typically has
24191 several types. One could install a lookup function for each desired type
24192 in the library, but one could also have a single lookup function recognize
24193 several types. The latter is the conventional way this is handled.
24194 If a pretty-printer can handle multiple data types, then its
24195 @dfn{subprinters} are the printers for the individual data types.
24197 The @code{gdb.printing} module provides a formal way of solving these
24198 problems (@pxref{gdb.printing}).
24199 Here is another example that handles multiple types.
24201 These are the types we are going to pretty-print:
24204 struct foo @{ int a, b; @};
24205 struct bar @{ struct foo x, y; @};
24208 Here are the printers:
24212 """Print a foo object."""
24214 def __init__(self, val):
24217 def to_string(self):
24218 return ("a=<" + str(self.val["a"]) +
24219 "> b=<" + str(self.val["b"]) + ">")
24222 """Print a bar object."""
24224 def __init__(self, val):
24227 def to_string(self):
24228 return ("x=<" + str(self.val["x"]) +
24229 "> y=<" + str(self.val["y"]) + ">")
24232 This example doesn't need a lookup function, that is handled by the
24233 @code{gdb.printing} module. Instead a function is provided to build up
24234 the object that handles the lookup.
24237 import gdb.printing
24239 def build_pretty_printer():
24240 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24242 pp.add_printer('foo', '^foo$', fooPrinter)
24243 pp.add_printer('bar', '^bar$', barPrinter)
24247 And here is the autoload support:
24250 import gdb.printing
24252 gdb.printing.register_pretty_printer(
24253 gdb.current_objfile(),
24254 my_library.build_pretty_printer())
24257 Finally, when this printer is loaded into @value{GDBN}, here is the
24258 corresponding output of @samp{info pretty-printer}:
24261 (gdb) info pretty-printer
24268 @node Type Printing API
24269 @subsubsection Type Printing API
24270 @cindex type printing API for Python
24272 @value{GDBN} provides a way for Python code to customize type display.
24273 This is mainly useful for substituting canonical typedef names for
24276 @cindex type printer
24277 A @dfn{type printer} is just a Python object conforming to a certain
24278 protocol. A simple base class implementing the protocol is provided;
24279 see @ref{gdb.types}. A type printer must supply at least:
24281 @defivar type_printer enabled
24282 A boolean which is True if the printer is enabled, and False
24283 otherwise. This is manipulated by the @code{enable type-printer}
24284 and @code{disable type-printer} commands.
24287 @defivar type_printer name
24288 The name of the type printer. This must be a string. This is used by
24289 the @code{enable type-printer} and @code{disable type-printer}
24293 @defmethod type_printer instantiate (self)
24294 This is called by @value{GDBN} at the start of type-printing. It is
24295 only called if the type printer is enabled. This method must return a
24296 new object that supplies a @code{recognize} method, as described below.
24300 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24301 will compute a list of type recognizers. This is done by iterating
24302 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24303 followed by the per-progspace type printers (@pxref{Progspaces In
24304 Python}), and finally the global type printers.
24306 @value{GDBN} will call the @code{instantiate} method of each enabled
24307 type printer. If this method returns @code{None}, then the result is
24308 ignored; otherwise, it is appended to the list of recognizers.
24310 Then, when @value{GDBN} is going to display a type name, it iterates
24311 over the list of recognizers. For each one, it calls the recognition
24312 function, stopping if the function returns a non-@code{None} value.
24313 The recognition function is defined as:
24315 @defmethod type_recognizer recognize (self, type)
24316 If @var{type} is not recognized, return @code{None}. Otherwise,
24317 return a string which is to be printed as the name of @var{type}.
24318 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24322 @value{GDBN} uses this two-pass approach so that type printers can
24323 efficiently cache information without holding on to it too long. For
24324 example, it can be convenient to look up type information in a type
24325 printer and hold it for a recognizer's lifetime; if a single pass were
24326 done then type printers would have to make use of the event system in
24327 order to avoid holding information that could become stale as the
24330 @node Inferiors In Python
24331 @subsubsection Inferiors In Python
24332 @cindex inferiors in Python
24334 @findex gdb.Inferior
24335 Programs which are being run under @value{GDBN} are called inferiors
24336 (@pxref{Inferiors and Programs}). Python scripts can access
24337 information about and manipulate inferiors controlled by @value{GDBN}
24338 via objects of the @code{gdb.Inferior} class.
24340 The following inferior-related functions are available in the @code{gdb}
24343 @defun gdb.inferiors ()
24344 Return a tuple containing all inferior objects.
24347 @defun gdb.selected_inferior ()
24348 Return an object representing the current inferior.
24351 A @code{gdb.Inferior} object has the following attributes:
24353 @defvar Inferior.num
24354 ID of inferior, as assigned by GDB.
24357 @defvar Inferior.pid
24358 Process ID of the inferior, as assigned by the underlying operating
24362 @defvar Inferior.was_attached
24363 Boolean signaling whether the inferior was created using `attach', or
24364 started by @value{GDBN} itself.
24367 A @code{gdb.Inferior} object has the following methods:
24369 @defun Inferior.is_valid ()
24370 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24371 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24372 if the inferior no longer exists within @value{GDBN}. All other
24373 @code{gdb.Inferior} methods will throw an exception if it is invalid
24374 at the time the method is called.
24377 @defun Inferior.threads ()
24378 This method returns a tuple holding all the threads which are valid
24379 when it is called. If there are no valid threads, the method will
24380 return an empty tuple.
24383 @findex Inferior.read_memory
24384 @defun Inferior.read_memory (address, length)
24385 Read @var{length} bytes of memory from the inferior, starting at
24386 @var{address}. Returns a buffer object, which behaves much like an array
24387 or a string. It can be modified and given to the
24388 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24389 value is a @code{memoryview} object.
24392 @findex Inferior.write_memory
24393 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24394 Write the contents of @var{buffer} to the inferior, starting at
24395 @var{address}. The @var{buffer} parameter must be a Python object
24396 which supports the buffer protocol, i.e., a string, an array or the
24397 object returned from @code{Inferior.read_memory}. If given, @var{length}
24398 determines the number of bytes from @var{buffer} to be written.
24401 @findex gdb.search_memory
24402 @defun Inferior.search_memory (address, length, pattern)
24403 Search a region of the inferior memory starting at @var{address} with
24404 the given @var{length} using the search pattern supplied in
24405 @var{pattern}. The @var{pattern} parameter must be a Python object
24406 which supports the buffer protocol, i.e., a string, an array or the
24407 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24408 containing the address where the pattern was found, or @code{None} if
24409 the pattern could not be found.
24412 @node Events In Python
24413 @subsubsection Events In Python
24414 @cindex inferior events in Python
24416 @value{GDBN} provides a general event facility so that Python code can be
24417 notified of various state changes, particularly changes that occur in
24420 An @dfn{event} is just an object that describes some state change. The
24421 type of the object and its attributes will vary depending on the details
24422 of the change. All the existing events are described below.
24424 In order to be notified of an event, you must register an event handler
24425 with an @dfn{event registry}. An event registry is an object in the
24426 @code{gdb.events} module which dispatches particular events. A registry
24427 provides methods to register and unregister event handlers:
24429 @defun EventRegistry.connect (object)
24430 Add the given callable @var{object} to the registry. This object will be
24431 called when an event corresponding to this registry occurs.
24434 @defun EventRegistry.disconnect (object)
24435 Remove the given @var{object} from the registry. Once removed, the object
24436 will no longer receive notifications of events.
24439 Here is an example:
24442 def exit_handler (event):
24443 print "event type: exit"
24444 print "exit code: %d" % (event.exit_code)
24446 gdb.events.exited.connect (exit_handler)
24449 In the above example we connect our handler @code{exit_handler} to the
24450 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24451 called when the inferior exits. The argument @dfn{event} in this example is
24452 of type @code{gdb.ExitedEvent}. As you can see in the example the
24453 @code{ExitedEvent} object has an attribute which indicates the exit code of
24456 The following is a listing of the event registries that are available and
24457 details of the events they emit:
24462 Emits @code{gdb.ThreadEvent}.
24464 Some events can be thread specific when @value{GDBN} is running in non-stop
24465 mode. When represented in Python, these events all extend
24466 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24467 events which are emitted by this or other modules might extend this event.
24468 Examples of these events are @code{gdb.BreakpointEvent} and
24469 @code{gdb.ContinueEvent}.
24471 @defvar ThreadEvent.inferior_thread
24472 In non-stop mode this attribute will be set to the specific thread which was
24473 involved in the emitted event. Otherwise, it will be set to @code{None}.
24476 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24478 This event indicates that the inferior has been continued after a stop. For
24479 inherited attribute refer to @code{gdb.ThreadEvent} above.
24481 @item events.exited
24482 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24483 @code{events.ExitedEvent} has two attributes:
24484 @defvar ExitedEvent.exit_code
24485 An integer representing the exit code, if available, which the inferior
24486 has returned. (The exit code could be unavailable if, for example,
24487 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24488 the attribute does not exist.
24490 @defvar ExitedEvent inferior
24491 A reference to the inferior which triggered the @code{exited} event.
24495 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24497 Indicates that the inferior has stopped. All events emitted by this registry
24498 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24499 will indicate the stopped thread when @value{GDBN} is running in non-stop
24500 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24502 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24504 This event indicates that the inferior or one of its threads has received as
24505 signal. @code{gdb.SignalEvent} has the following attributes:
24507 @defvar SignalEvent.stop_signal
24508 A string representing the signal received by the inferior. A list of possible
24509 signal values can be obtained by running the command @code{info signals} in
24510 the @value{GDBN} command prompt.
24513 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24515 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24516 been hit, and has the following attributes:
24518 @defvar BreakpointEvent.breakpoints
24519 A sequence containing references to all the breakpoints (type
24520 @code{gdb.Breakpoint}) that were hit.
24521 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24523 @defvar BreakpointEvent.breakpoint
24524 A reference to the first breakpoint that was hit.
24525 This function is maintained for backward compatibility and is now deprecated
24526 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24529 @item events.new_objfile
24530 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24531 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24533 @defvar NewObjFileEvent.new_objfile
24534 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24535 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24540 @node Threads In Python
24541 @subsubsection Threads In Python
24542 @cindex threads in python
24544 @findex gdb.InferiorThread
24545 Python scripts can access information about, and manipulate inferior threads
24546 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24548 The following thread-related functions are available in the @code{gdb}
24551 @findex gdb.selected_thread
24552 @defun gdb.selected_thread ()
24553 This function returns the thread object for the selected thread. If there
24554 is no selected thread, this will return @code{None}.
24557 A @code{gdb.InferiorThread} object has the following attributes:
24559 @defvar InferiorThread.name
24560 The name of the thread. If the user specified a name using
24561 @code{thread name}, then this returns that name. Otherwise, if an
24562 OS-supplied name is available, then it is returned. Otherwise, this
24563 returns @code{None}.
24565 This attribute can be assigned to. The new value must be a string
24566 object, which sets the new name, or @code{None}, which removes any
24567 user-specified thread name.
24570 @defvar InferiorThread.num
24571 ID of the thread, as assigned by GDB.
24574 @defvar InferiorThread.ptid
24575 ID of the thread, as assigned by the operating system. This attribute is a
24576 tuple containing three integers. The first is the Process ID (PID); the second
24577 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24578 Either the LWPID or TID may be 0, which indicates that the operating system
24579 does not use that identifier.
24582 A @code{gdb.InferiorThread} object has the following methods:
24584 @defun InferiorThread.is_valid ()
24585 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24586 @code{False} if not. A @code{gdb.InferiorThread} object will become
24587 invalid if the thread exits, or the inferior that the thread belongs
24588 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24589 exception if it is invalid at the time the method is called.
24592 @defun InferiorThread.switch ()
24593 This changes @value{GDBN}'s currently selected thread to the one represented
24597 @defun InferiorThread.is_stopped ()
24598 Return a Boolean indicating whether the thread is stopped.
24601 @defun InferiorThread.is_running ()
24602 Return a Boolean indicating whether the thread is running.
24605 @defun InferiorThread.is_exited ()
24606 Return a Boolean indicating whether the thread is exited.
24609 @node Commands In Python
24610 @subsubsection Commands In Python
24612 @cindex commands in python
24613 @cindex python commands
24614 You can implement new @value{GDBN} CLI commands in Python. A CLI
24615 command is implemented using an instance of the @code{gdb.Command}
24616 class, most commonly using a subclass.
24618 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24619 The object initializer for @code{Command} registers the new command
24620 with @value{GDBN}. This initializer is normally invoked from the
24621 subclass' own @code{__init__} method.
24623 @var{name} is the name of the command. If @var{name} consists of
24624 multiple words, then the initial words are looked for as prefix
24625 commands. In this case, if one of the prefix commands does not exist,
24626 an exception is raised.
24628 There is no support for multi-line commands.
24630 @var{command_class} should be one of the @samp{COMMAND_} constants
24631 defined below. This argument tells @value{GDBN} how to categorize the
24632 new command in the help system.
24634 @var{completer_class} is an optional argument. If given, it should be
24635 one of the @samp{COMPLETE_} constants defined below. This argument
24636 tells @value{GDBN} how to perform completion for this command. If not
24637 given, @value{GDBN} will attempt to complete using the object's
24638 @code{complete} method (see below); if no such method is found, an
24639 error will occur when completion is attempted.
24641 @var{prefix} is an optional argument. If @code{True}, then the new
24642 command is a prefix command; sub-commands of this command may be
24645 The help text for the new command is taken from the Python
24646 documentation string for the command's class, if there is one. If no
24647 documentation string is provided, the default value ``This command is
24648 not documented.'' is used.
24651 @cindex don't repeat Python command
24652 @defun Command.dont_repeat ()
24653 By default, a @value{GDBN} command is repeated when the user enters a
24654 blank line at the command prompt. A command can suppress this
24655 behavior by invoking the @code{dont_repeat} method. This is similar
24656 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24659 @defun Command.invoke (argument, from_tty)
24660 This method is called by @value{GDBN} when this command is invoked.
24662 @var{argument} is a string. It is the argument to the command, after
24663 leading and trailing whitespace has been stripped.
24665 @var{from_tty} is a boolean argument. When true, this means that the
24666 command was entered by the user at the terminal; when false it means
24667 that the command came from elsewhere.
24669 If this method throws an exception, it is turned into a @value{GDBN}
24670 @code{error} call. Otherwise, the return value is ignored.
24672 @findex gdb.string_to_argv
24673 To break @var{argument} up into an argv-like string use
24674 @code{gdb.string_to_argv}. This function behaves identically to
24675 @value{GDBN}'s internal argument lexer @code{buildargv}.
24676 It is recommended to use this for consistency.
24677 Arguments are separated by spaces and may be quoted.
24681 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24682 ['1', '2 "3', '4 "5', "6 '7"]
24687 @cindex completion of Python commands
24688 @defun Command.complete (text, word)
24689 This method is called by @value{GDBN} when the user attempts
24690 completion on this command. All forms of completion are handled by
24691 this method, that is, the @key{TAB} and @key{M-?} key bindings
24692 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24695 The arguments @var{text} and @var{word} are both strings. @var{text}
24696 holds the complete command line up to the cursor's location.
24697 @var{word} holds the last word of the command line; this is computed
24698 using a word-breaking heuristic.
24700 The @code{complete} method can return several values:
24703 If the return value is a sequence, the contents of the sequence are
24704 used as the completions. It is up to @code{complete} to ensure that the
24705 contents actually do complete the word. A zero-length sequence is
24706 allowed, it means that there were no completions available. Only
24707 string elements of the sequence are used; other elements in the
24708 sequence are ignored.
24711 If the return value is one of the @samp{COMPLETE_} constants defined
24712 below, then the corresponding @value{GDBN}-internal completion
24713 function is invoked, and its result is used.
24716 All other results are treated as though there were no available
24721 When a new command is registered, it must be declared as a member of
24722 some general class of commands. This is used to classify top-level
24723 commands in the on-line help system; note that prefix commands are not
24724 listed under their own category but rather that of their top-level
24725 command. The available classifications are represented by constants
24726 defined in the @code{gdb} module:
24729 @findex COMMAND_NONE
24730 @findex gdb.COMMAND_NONE
24731 @item gdb.COMMAND_NONE
24732 The command does not belong to any particular class. A command in
24733 this category will not be displayed in any of the help categories.
24735 @findex COMMAND_RUNNING
24736 @findex gdb.COMMAND_RUNNING
24737 @item gdb.COMMAND_RUNNING
24738 The command is related to running the inferior. For example,
24739 @code{start}, @code{step}, and @code{continue} are in this category.
24740 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24741 commands in this category.
24743 @findex COMMAND_DATA
24744 @findex gdb.COMMAND_DATA
24745 @item gdb.COMMAND_DATA
24746 The command is related to data or variables. For example,
24747 @code{call}, @code{find}, and @code{print} are in this category. Type
24748 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24751 @findex COMMAND_STACK
24752 @findex gdb.COMMAND_STACK
24753 @item gdb.COMMAND_STACK
24754 The command has to do with manipulation of the stack. For example,
24755 @code{backtrace}, @code{frame}, and @code{return} are in this
24756 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24757 list of commands in this category.
24759 @findex COMMAND_FILES
24760 @findex gdb.COMMAND_FILES
24761 @item gdb.COMMAND_FILES
24762 This class is used for file-related commands. For example,
24763 @code{file}, @code{list} and @code{section} are in this category.
24764 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24765 commands in this category.
24767 @findex COMMAND_SUPPORT
24768 @findex gdb.COMMAND_SUPPORT
24769 @item gdb.COMMAND_SUPPORT
24770 This should be used for ``support facilities'', generally meaning
24771 things that are useful to the user when interacting with @value{GDBN},
24772 but not related to the state of the inferior. For example,
24773 @code{help}, @code{make}, and @code{shell} are in this category. Type
24774 @kbd{help support} at the @value{GDBN} prompt to see a list of
24775 commands in this category.
24777 @findex COMMAND_STATUS
24778 @findex gdb.COMMAND_STATUS
24779 @item gdb.COMMAND_STATUS
24780 The command is an @samp{info}-related command, that is, related to the
24781 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24782 and @code{show} are in this category. Type @kbd{help status} at the
24783 @value{GDBN} prompt to see a list of commands in this category.
24785 @findex COMMAND_BREAKPOINTS
24786 @findex gdb.COMMAND_BREAKPOINTS
24787 @item gdb.COMMAND_BREAKPOINTS
24788 The command has to do with breakpoints. For example, @code{break},
24789 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24790 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24793 @findex COMMAND_TRACEPOINTS
24794 @findex gdb.COMMAND_TRACEPOINTS
24795 @item gdb.COMMAND_TRACEPOINTS
24796 The command has to do with tracepoints. For example, @code{trace},
24797 @code{actions}, and @code{tfind} are in this category. Type
24798 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24799 commands in this category.
24801 @findex COMMAND_USER
24802 @findex gdb.COMMAND_USER
24803 @item gdb.COMMAND_USER
24804 The command is a general purpose command for the user, and typically
24805 does not fit in one of the other categories.
24806 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24807 a list of commands in this category, as well as the list of gdb macros
24808 (@pxref{Sequences}).
24810 @findex COMMAND_OBSCURE
24811 @findex gdb.COMMAND_OBSCURE
24812 @item gdb.COMMAND_OBSCURE
24813 The command is only used in unusual circumstances, or is not of
24814 general interest to users. For example, @code{checkpoint},
24815 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24816 obscure} at the @value{GDBN} prompt to see a list of commands in this
24819 @findex COMMAND_MAINTENANCE
24820 @findex gdb.COMMAND_MAINTENANCE
24821 @item gdb.COMMAND_MAINTENANCE
24822 The command is only useful to @value{GDBN} maintainers. The
24823 @code{maintenance} and @code{flushregs} commands are in this category.
24824 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24825 commands in this category.
24828 A new command can use a predefined completion function, either by
24829 specifying it via an argument at initialization, or by returning it
24830 from the @code{complete} method. These predefined completion
24831 constants are all defined in the @code{gdb} module:
24834 @findex COMPLETE_NONE
24835 @findex gdb.COMPLETE_NONE
24836 @item gdb.COMPLETE_NONE
24837 This constant means that no completion should be done.
24839 @findex COMPLETE_FILENAME
24840 @findex gdb.COMPLETE_FILENAME
24841 @item gdb.COMPLETE_FILENAME
24842 This constant means that filename completion should be performed.
24844 @findex COMPLETE_LOCATION
24845 @findex gdb.COMPLETE_LOCATION
24846 @item gdb.COMPLETE_LOCATION
24847 This constant means that location completion should be done.
24848 @xref{Specify Location}.
24850 @findex COMPLETE_COMMAND
24851 @findex gdb.COMPLETE_COMMAND
24852 @item gdb.COMPLETE_COMMAND
24853 This constant means that completion should examine @value{GDBN}
24856 @findex COMPLETE_SYMBOL
24857 @findex gdb.COMPLETE_SYMBOL
24858 @item gdb.COMPLETE_SYMBOL
24859 This constant means that completion should be done using symbol names
24863 The following code snippet shows how a trivial CLI command can be
24864 implemented in Python:
24867 class HelloWorld (gdb.Command):
24868 """Greet the whole world."""
24870 def __init__ (self):
24871 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24873 def invoke (self, arg, from_tty):
24874 print "Hello, World!"
24879 The last line instantiates the class, and is necessary to trigger the
24880 registration of the command with @value{GDBN}. Depending on how the
24881 Python code is read into @value{GDBN}, you may need to import the
24882 @code{gdb} module explicitly.
24884 @node Parameters In Python
24885 @subsubsection Parameters In Python
24887 @cindex parameters in python
24888 @cindex python parameters
24889 @tindex gdb.Parameter
24891 You can implement new @value{GDBN} parameters using Python. A new
24892 parameter is implemented as an instance of the @code{gdb.Parameter}
24895 Parameters are exposed to the user via the @code{set} and
24896 @code{show} commands. @xref{Help}.
24898 There are many parameters that already exist and can be set in
24899 @value{GDBN}. Two examples are: @code{set follow fork} and
24900 @code{set charset}. Setting these parameters influences certain
24901 behavior in @value{GDBN}. Similarly, you can define parameters that
24902 can be used to influence behavior in custom Python scripts and commands.
24904 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24905 The object initializer for @code{Parameter} registers the new
24906 parameter with @value{GDBN}. This initializer is normally invoked
24907 from the subclass' own @code{__init__} method.
24909 @var{name} is the name of the new parameter. If @var{name} consists
24910 of multiple words, then the initial words are looked for as prefix
24911 parameters. An example of this can be illustrated with the
24912 @code{set print} set of parameters. If @var{name} is
24913 @code{print foo}, then @code{print} will be searched as the prefix
24914 parameter. In this case the parameter can subsequently be accessed in
24915 @value{GDBN} as @code{set print foo}.
24917 If @var{name} consists of multiple words, and no prefix parameter group
24918 can be found, an exception is raised.
24920 @var{command-class} should be one of the @samp{COMMAND_} constants
24921 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24922 categorize the new parameter in the help system.
24924 @var{parameter-class} should be one of the @samp{PARAM_} constants
24925 defined below. This argument tells @value{GDBN} the type of the new
24926 parameter; this information is used for input validation and
24929 If @var{parameter-class} is @code{PARAM_ENUM}, then
24930 @var{enum-sequence} must be a sequence of strings. These strings
24931 represent the possible values for the parameter.
24933 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24934 of a fourth argument will cause an exception to be thrown.
24936 The help text for the new parameter is taken from the Python
24937 documentation string for the parameter's class, if there is one. If
24938 there is no documentation string, a default value is used.
24941 @defvar Parameter.set_doc
24942 If this attribute exists, and is a string, then its value is used as
24943 the help text for this parameter's @code{set} command. The value is
24944 examined when @code{Parameter.__init__} is invoked; subsequent changes
24948 @defvar Parameter.show_doc
24949 If this attribute exists, and is a string, then its value is used as
24950 the help text for this parameter's @code{show} command. The value is
24951 examined when @code{Parameter.__init__} is invoked; subsequent changes
24955 @defvar Parameter.value
24956 The @code{value} attribute holds the underlying value of the
24957 parameter. It can be read and assigned to just as any other
24958 attribute. @value{GDBN} does validation when assignments are made.
24961 There are two methods that should be implemented in any
24962 @code{Parameter} class. These are:
24964 @defun Parameter.get_set_string (self)
24965 @value{GDBN} will call this method when a @var{parameter}'s value has
24966 been changed via the @code{set} API (for example, @kbd{set foo off}).
24967 The @code{value} attribute has already been populated with the new
24968 value and may be used in output. This method must return a string.
24971 @defun Parameter.get_show_string (self, svalue)
24972 @value{GDBN} will call this method when a @var{parameter}'s
24973 @code{show} API has been invoked (for example, @kbd{show foo}). The
24974 argument @code{svalue} receives the string representation of the
24975 current value. This method must return a string.
24978 When a new parameter is defined, its type must be specified. The
24979 available types are represented by constants defined in the @code{gdb}
24983 @findex PARAM_BOOLEAN
24984 @findex gdb.PARAM_BOOLEAN
24985 @item gdb.PARAM_BOOLEAN
24986 The value is a plain boolean. The Python boolean values, @code{True}
24987 and @code{False} are the only valid values.
24989 @findex PARAM_AUTO_BOOLEAN
24990 @findex gdb.PARAM_AUTO_BOOLEAN
24991 @item gdb.PARAM_AUTO_BOOLEAN
24992 The value has three possible states: true, false, and @samp{auto}. In
24993 Python, true and false are represented using boolean constants, and
24994 @samp{auto} is represented using @code{None}.
24996 @findex PARAM_UINTEGER
24997 @findex gdb.PARAM_UINTEGER
24998 @item gdb.PARAM_UINTEGER
24999 The value is an unsigned integer. The value of 0 should be
25000 interpreted to mean ``unlimited''.
25002 @findex PARAM_INTEGER
25003 @findex gdb.PARAM_INTEGER
25004 @item gdb.PARAM_INTEGER
25005 The value is a signed integer. The value of 0 should be interpreted
25006 to mean ``unlimited''.
25008 @findex PARAM_STRING
25009 @findex gdb.PARAM_STRING
25010 @item gdb.PARAM_STRING
25011 The value is a string. When the user modifies the string, any escape
25012 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25013 translated into corresponding characters and encoded into the current
25016 @findex PARAM_STRING_NOESCAPE
25017 @findex gdb.PARAM_STRING_NOESCAPE
25018 @item gdb.PARAM_STRING_NOESCAPE
25019 The value is a string. When the user modifies the string, escapes are
25020 passed through untranslated.
25022 @findex PARAM_OPTIONAL_FILENAME
25023 @findex gdb.PARAM_OPTIONAL_FILENAME
25024 @item gdb.PARAM_OPTIONAL_FILENAME
25025 The value is a either a filename (a string), or @code{None}.
25027 @findex PARAM_FILENAME
25028 @findex gdb.PARAM_FILENAME
25029 @item gdb.PARAM_FILENAME
25030 The value is a filename. This is just like
25031 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25033 @findex PARAM_ZINTEGER
25034 @findex gdb.PARAM_ZINTEGER
25035 @item gdb.PARAM_ZINTEGER
25036 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25037 is interpreted as itself.
25040 @findex gdb.PARAM_ENUM
25041 @item gdb.PARAM_ENUM
25042 The value is a string, which must be one of a collection string
25043 constants provided when the parameter is created.
25046 @node Functions In Python
25047 @subsubsection Writing new convenience functions
25049 @cindex writing convenience functions
25050 @cindex convenience functions in python
25051 @cindex python convenience functions
25052 @tindex gdb.Function
25054 You can implement new convenience functions (@pxref{Convenience Vars})
25055 in Python. A convenience function is an instance of a subclass of the
25056 class @code{gdb.Function}.
25058 @defun Function.__init__ (name)
25059 The initializer for @code{Function} registers the new function with
25060 @value{GDBN}. The argument @var{name} is the name of the function,
25061 a string. The function will be visible to the user as a convenience
25062 variable of type @code{internal function}, whose name is the same as
25063 the given @var{name}.
25065 The documentation for the new function is taken from the documentation
25066 string for the new class.
25069 @defun Function.invoke (@var{*args})
25070 When a convenience function is evaluated, its arguments are converted
25071 to instances of @code{gdb.Value}, and then the function's
25072 @code{invoke} method is called. Note that @value{GDBN} does not
25073 predetermine the arity of convenience functions. Instead, all
25074 available arguments are passed to @code{invoke}, following the
25075 standard Python calling convention. In particular, a convenience
25076 function can have default values for parameters without ill effect.
25078 The return value of this method is used as its value in the enclosing
25079 expression. If an ordinary Python value is returned, it is converted
25080 to a @code{gdb.Value} following the usual rules.
25083 The following code snippet shows how a trivial convenience function can
25084 be implemented in Python:
25087 class Greet (gdb.Function):
25088 """Return string to greet someone.
25089 Takes a name as argument."""
25091 def __init__ (self):
25092 super (Greet, self).__init__ ("greet")
25094 def invoke (self, name):
25095 return "Hello, %s!" % name.string ()
25100 The last line instantiates the class, and is necessary to trigger the
25101 registration of the function with @value{GDBN}. Depending on how the
25102 Python code is read into @value{GDBN}, you may need to import the
25103 @code{gdb} module explicitly.
25105 Now you can use the function in an expression:
25108 (gdb) print $greet("Bob")
25112 @node Progspaces In Python
25113 @subsubsection Program Spaces In Python
25115 @cindex progspaces in python
25116 @tindex gdb.Progspace
25118 A program space, or @dfn{progspace}, represents a symbolic view
25119 of an address space.
25120 It consists of all of the objfiles of the program.
25121 @xref{Objfiles In Python}.
25122 @xref{Inferiors and Programs, program spaces}, for more details
25123 about program spaces.
25125 The following progspace-related functions are available in the
25128 @findex gdb.current_progspace
25129 @defun gdb.current_progspace ()
25130 This function returns the program space of the currently selected inferior.
25131 @xref{Inferiors and Programs}.
25134 @findex gdb.progspaces
25135 @defun gdb.progspaces ()
25136 Return a sequence of all the progspaces currently known to @value{GDBN}.
25139 Each progspace is represented by an instance of the @code{gdb.Progspace}
25142 @defvar Progspace.filename
25143 The file name of the progspace as a string.
25146 @defvar Progspace.pretty_printers
25147 The @code{pretty_printers} attribute is a list of functions. It is
25148 used to look up pretty-printers. A @code{Value} is passed to each
25149 function in order; if the function returns @code{None}, then the
25150 search continues. Otherwise, the return value should be an object
25151 which is used to format the value. @xref{Pretty Printing API}, for more
25155 @defvar Progspace.type_printers
25156 The @code{type_printers} attribute is a list of type printer objects.
25157 @xref{Type Printing API}, for more information.
25160 @node Objfiles In Python
25161 @subsubsection Objfiles In Python
25163 @cindex objfiles in python
25164 @tindex gdb.Objfile
25166 @value{GDBN} loads symbols for an inferior from various
25167 symbol-containing files (@pxref{Files}). These include the primary
25168 executable file, any shared libraries used by the inferior, and any
25169 separate debug info files (@pxref{Separate Debug Files}).
25170 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25172 The following objfile-related functions are available in the
25175 @findex gdb.current_objfile
25176 @defun gdb.current_objfile ()
25177 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25178 sets the ``current objfile'' to the corresponding objfile. This
25179 function returns the current objfile. If there is no current objfile,
25180 this function returns @code{None}.
25183 @findex gdb.objfiles
25184 @defun gdb.objfiles ()
25185 Return a sequence of all the objfiles current known to @value{GDBN}.
25186 @xref{Objfiles In Python}.
25189 Each objfile is represented by an instance of the @code{gdb.Objfile}
25192 @defvar Objfile.filename
25193 The file name of the objfile as a string.
25196 @defvar Objfile.pretty_printers
25197 The @code{pretty_printers} attribute is a list of functions. It is
25198 used to look up pretty-printers. A @code{Value} is passed to each
25199 function in order; if the function returns @code{None}, then the
25200 search continues. Otherwise, the return value should be an object
25201 which is used to format the value. @xref{Pretty Printing API}, for more
25205 @defvar Objfile.type_printers
25206 The @code{type_printers} attribute is a list of type printer objects.
25207 @xref{Type Printing API}, for more information.
25210 A @code{gdb.Objfile} object has the following methods:
25212 @defun Objfile.is_valid ()
25213 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25214 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25215 if the object file it refers to is not loaded in @value{GDBN} any
25216 longer. All other @code{gdb.Objfile} methods will throw an exception
25217 if it is invalid at the time the method is called.
25220 @node Frames In Python
25221 @subsubsection Accessing inferior stack frames from Python.
25223 @cindex frames in python
25224 When the debugged program stops, @value{GDBN} is able to analyze its call
25225 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25226 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25227 while its corresponding frame exists in the inferior's stack. If you try
25228 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25229 exception (@pxref{Exception Handling}).
25231 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25235 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25239 The following frame-related functions are available in the @code{gdb} module:
25241 @findex gdb.selected_frame
25242 @defun gdb.selected_frame ()
25243 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25246 @findex gdb.newest_frame
25247 @defun gdb.newest_frame ()
25248 Return the newest frame object for the selected thread.
25251 @defun gdb.frame_stop_reason_string (reason)
25252 Return a string explaining the reason why @value{GDBN} stopped unwinding
25253 frames, as expressed by the given @var{reason} code (an integer, see the
25254 @code{unwind_stop_reason} method further down in this section).
25257 A @code{gdb.Frame} object has the following methods:
25259 @defun Frame.is_valid ()
25260 Returns true if the @code{gdb.Frame} object is valid, false if not.
25261 A frame object can become invalid if the frame it refers to doesn't
25262 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25263 an exception if it is invalid at the time the method is called.
25266 @defun Frame.name ()
25267 Returns the function name of the frame, or @code{None} if it can't be
25271 @defun Frame.architecture ()
25272 Returns the @code{gdb.Architecture} object corresponding to the frame's
25273 architecture. @xref{Architectures In Python}.
25276 @defun Frame.type ()
25277 Returns the type of the frame. The value can be one of:
25279 @item gdb.NORMAL_FRAME
25280 An ordinary stack frame.
25282 @item gdb.DUMMY_FRAME
25283 A fake stack frame that was created by @value{GDBN} when performing an
25284 inferior function call.
25286 @item gdb.INLINE_FRAME
25287 A frame representing an inlined function. The function was inlined
25288 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25290 @item gdb.TAILCALL_FRAME
25291 A frame representing a tail call. @xref{Tail Call Frames}.
25293 @item gdb.SIGTRAMP_FRAME
25294 A signal trampoline frame. This is the frame created by the OS when
25295 it calls into a signal handler.
25297 @item gdb.ARCH_FRAME
25298 A fake stack frame representing a cross-architecture call.
25300 @item gdb.SENTINEL_FRAME
25301 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25306 @defun Frame.unwind_stop_reason ()
25307 Return an integer representing the reason why it's not possible to find
25308 more frames toward the outermost frame. Use
25309 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25310 function to a string. The value can be one of:
25313 @item gdb.FRAME_UNWIND_NO_REASON
25314 No particular reason (older frames should be available).
25316 @item gdb.FRAME_UNWIND_NULL_ID
25317 The previous frame's analyzer returns an invalid result.
25319 @item gdb.FRAME_UNWIND_OUTERMOST
25320 This frame is the outermost.
25322 @item gdb.FRAME_UNWIND_UNAVAILABLE
25323 Cannot unwind further, because that would require knowing the
25324 values of registers or memory that have not been collected.
25326 @item gdb.FRAME_UNWIND_INNER_ID
25327 This frame ID looks like it ought to belong to a NEXT frame,
25328 but we got it for a PREV frame. Normally, this is a sign of
25329 unwinder failure. It could also indicate stack corruption.
25331 @item gdb.FRAME_UNWIND_SAME_ID
25332 This frame has the same ID as the previous one. That means
25333 that unwinding further would almost certainly give us another
25334 frame with exactly the same ID, so break the chain. Normally,
25335 this is a sign of unwinder failure. It could also indicate
25338 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25339 The frame unwinder did not find any saved PC, but we needed
25340 one to unwind further.
25342 @item gdb.FRAME_UNWIND_FIRST_ERROR
25343 Any stop reason greater or equal to this value indicates some kind
25344 of error. This special value facilitates writing code that tests
25345 for errors in unwinding in a way that will work correctly even if
25346 the list of the other values is modified in future @value{GDBN}
25347 versions. Using it, you could write:
25349 reason = gdb.selected_frame().unwind_stop_reason ()
25350 reason_str = gdb.frame_stop_reason_string (reason)
25351 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25352 print "An error occured: %s" % reason_str
25359 Returns the frame's resume address.
25362 @defun Frame.block ()
25363 Return the frame's code block. @xref{Blocks In Python}.
25366 @defun Frame.function ()
25367 Return the symbol for the function corresponding to this frame.
25368 @xref{Symbols In Python}.
25371 @defun Frame.older ()
25372 Return the frame that called this frame.
25375 @defun Frame.newer ()
25376 Return the frame called by this frame.
25379 @defun Frame.find_sal ()
25380 Return the frame's symtab and line object.
25381 @xref{Symbol Tables In Python}.
25384 @defun Frame.read_var (variable @r{[}, block@r{]})
25385 Return the value of @var{variable} in this frame. If the optional
25386 argument @var{block} is provided, search for the variable from that
25387 block; otherwise start at the frame's current block (which is
25388 determined by the frame's current program counter). @var{variable}
25389 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25390 @code{gdb.Block} object.
25393 @defun Frame.select ()
25394 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25398 @node Blocks In Python
25399 @subsubsection Accessing frame blocks from Python.
25401 @cindex blocks in python
25404 Within each frame, @value{GDBN} maintains information on each block
25405 stored in that frame. These blocks are organized hierarchically, and
25406 are represented individually in Python as a @code{gdb.Block}.
25407 Please see @ref{Frames In Python}, for a more in-depth discussion on
25408 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25409 detailed technical information on @value{GDBN}'s book-keeping of the
25412 A @code{gdb.Block} is iterable. The iterator returns the symbols
25413 (@pxref{Symbols In Python}) local to the block. Python programs
25414 should not assume that a specific block object will always contain a
25415 given symbol, since changes in @value{GDBN} features and
25416 infrastructure may cause symbols move across blocks in a symbol
25419 The following block-related functions are available in the @code{gdb}
25422 @findex gdb.block_for_pc
25423 @defun gdb.block_for_pc (pc)
25424 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25425 block cannot be found for the @var{pc} value specified, the function
25426 will return @code{None}.
25429 A @code{gdb.Block} object has the following methods:
25431 @defun Block.is_valid ()
25432 Returns @code{True} if the @code{gdb.Block} object is valid,
25433 @code{False} if not. A block object can become invalid if the block it
25434 refers to doesn't exist anymore in the inferior. All other
25435 @code{gdb.Block} methods will throw an exception if it is invalid at
25436 the time the method is called. The block's validity is also checked
25437 during iteration over symbols of the block.
25440 A @code{gdb.Block} object has the following attributes:
25442 @defvar Block.start
25443 The start address of the block. This attribute is not writable.
25447 The end address of the block. This attribute is not writable.
25450 @defvar Block.function
25451 The name of the block represented as a @code{gdb.Symbol}. If the
25452 block is not named, then this attribute holds @code{None}. This
25453 attribute is not writable.
25456 @defvar Block.superblock
25457 The block containing this block. If this parent block does not exist,
25458 this attribute holds @code{None}. This attribute is not writable.
25461 @defvar Block.global_block
25462 The global block associated with this block. This attribute is not
25466 @defvar Block.static_block
25467 The static block associated with this block. This attribute is not
25471 @defvar Block.is_global
25472 @code{True} if the @code{gdb.Block} object is a global block,
25473 @code{False} if not. This attribute is not
25477 @defvar Block.is_static
25478 @code{True} if the @code{gdb.Block} object is a static block,
25479 @code{False} if not. This attribute is not writable.
25482 @node Symbols In Python
25483 @subsubsection Python representation of Symbols.
25485 @cindex symbols in python
25488 @value{GDBN} represents every variable, function and type as an
25489 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25490 Similarly, Python represents these symbols in @value{GDBN} with the
25491 @code{gdb.Symbol} object.
25493 The following symbol-related functions are available in the @code{gdb}
25496 @findex gdb.lookup_symbol
25497 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25498 This function searches for a symbol by name. The search scope can be
25499 restricted to the parameters defined in the optional domain and block
25502 @var{name} is the name of the symbol. It must be a string. The
25503 optional @var{block} argument restricts the search to symbols visible
25504 in that @var{block}. The @var{block} argument must be a
25505 @code{gdb.Block} object. If omitted, the block for the current frame
25506 is used. The optional @var{domain} argument restricts
25507 the search to the domain type. The @var{domain} argument must be a
25508 domain constant defined in the @code{gdb} module and described later
25511 The result is a tuple of two elements.
25512 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25514 If the symbol is found, the second element is @code{True} if the symbol
25515 is a field of a method's object (e.g., @code{this} in C@t{++}),
25516 otherwise it is @code{False}.
25517 If the symbol is not found, the second element is @code{False}.
25520 @findex gdb.lookup_global_symbol
25521 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25522 This function searches for a global symbol by name.
25523 The search scope can be restricted to by the domain argument.
25525 @var{name} is the name of the symbol. It must be a string.
25526 The optional @var{domain} argument restricts the search to the domain type.
25527 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25528 module and described later in this chapter.
25530 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25534 A @code{gdb.Symbol} object has the following attributes:
25536 @defvar Symbol.type
25537 The type of the symbol or @code{None} if no type is recorded.
25538 This attribute is represented as a @code{gdb.Type} object.
25539 @xref{Types In Python}. This attribute is not writable.
25542 @defvar Symbol.symtab
25543 The symbol table in which the symbol appears. This attribute is
25544 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25545 Python}. This attribute is not writable.
25548 @defvar Symbol.line
25549 The line number in the source code at which the symbol was defined.
25550 This is an integer.
25553 @defvar Symbol.name
25554 The name of the symbol as a string. This attribute is not writable.
25557 @defvar Symbol.linkage_name
25558 The name of the symbol, as used by the linker (i.e., may be mangled).
25559 This attribute is not writable.
25562 @defvar Symbol.print_name
25563 The name of the symbol in a form suitable for output. This is either
25564 @code{name} or @code{linkage_name}, depending on whether the user
25565 asked @value{GDBN} to display demangled or mangled names.
25568 @defvar Symbol.addr_class
25569 The address class of the symbol. This classifies how to find the value
25570 of a symbol. Each address class is a constant defined in the
25571 @code{gdb} module and described later in this chapter.
25574 @defvar Symbol.needs_frame
25575 This is @code{True} if evaluating this symbol's value requires a frame
25576 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25577 local variables will require a frame, but other symbols will not.
25580 @defvar Symbol.is_argument
25581 @code{True} if the symbol is an argument of a function.
25584 @defvar Symbol.is_constant
25585 @code{True} if the symbol is a constant.
25588 @defvar Symbol.is_function
25589 @code{True} if the symbol is a function or a method.
25592 @defvar Symbol.is_variable
25593 @code{True} if the symbol is a variable.
25596 A @code{gdb.Symbol} object has the following methods:
25598 @defun Symbol.is_valid ()
25599 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25600 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25601 the symbol it refers to does not exist in @value{GDBN} any longer.
25602 All other @code{gdb.Symbol} methods will throw an exception if it is
25603 invalid at the time the method is called.
25606 @defun Symbol.value (@r{[}frame@r{]})
25607 Compute the value of the symbol, as a @code{gdb.Value}. For
25608 functions, this computes the address of the function, cast to the
25609 appropriate type. If the symbol requires a frame in order to compute
25610 its value, then @var{frame} must be given. If @var{frame} is not
25611 given, or if @var{frame} is invalid, then this method will throw an
25615 The available domain categories in @code{gdb.Symbol} are represented
25616 as constants in the @code{gdb} module:
25619 @findex SYMBOL_UNDEF_DOMAIN
25620 @findex gdb.SYMBOL_UNDEF_DOMAIN
25621 @item gdb.SYMBOL_UNDEF_DOMAIN
25622 This is used when a domain has not been discovered or none of the
25623 following domains apply. This usually indicates an error either
25624 in the symbol information or in @value{GDBN}'s handling of symbols.
25625 @findex SYMBOL_VAR_DOMAIN
25626 @findex gdb.SYMBOL_VAR_DOMAIN
25627 @item gdb.SYMBOL_VAR_DOMAIN
25628 This domain contains variables, function names, typedef names and enum
25630 @findex SYMBOL_STRUCT_DOMAIN
25631 @findex gdb.SYMBOL_STRUCT_DOMAIN
25632 @item gdb.SYMBOL_STRUCT_DOMAIN
25633 This domain holds struct, union and enum type names.
25634 @findex SYMBOL_LABEL_DOMAIN
25635 @findex gdb.SYMBOL_LABEL_DOMAIN
25636 @item gdb.SYMBOL_LABEL_DOMAIN
25637 This domain contains names of labels (for gotos).
25638 @findex SYMBOL_VARIABLES_DOMAIN
25639 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25640 @item gdb.SYMBOL_VARIABLES_DOMAIN
25641 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25642 contains everything minus functions and types.
25643 @findex SYMBOL_FUNCTIONS_DOMAIN
25644 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25645 @item gdb.SYMBOL_FUNCTION_DOMAIN
25646 This domain contains all functions.
25647 @findex SYMBOL_TYPES_DOMAIN
25648 @findex gdb.SYMBOL_TYPES_DOMAIN
25649 @item gdb.SYMBOL_TYPES_DOMAIN
25650 This domain contains all types.
25653 The available address class categories in @code{gdb.Symbol} are represented
25654 as constants in the @code{gdb} module:
25657 @findex SYMBOL_LOC_UNDEF
25658 @findex gdb.SYMBOL_LOC_UNDEF
25659 @item gdb.SYMBOL_LOC_UNDEF
25660 If this is returned by address class, it indicates an error either in
25661 the symbol information or in @value{GDBN}'s handling of symbols.
25662 @findex SYMBOL_LOC_CONST
25663 @findex gdb.SYMBOL_LOC_CONST
25664 @item gdb.SYMBOL_LOC_CONST
25665 Value is constant int.
25666 @findex SYMBOL_LOC_STATIC
25667 @findex gdb.SYMBOL_LOC_STATIC
25668 @item gdb.SYMBOL_LOC_STATIC
25669 Value is at a fixed address.
25670 @findex SYMBOL_LOC_REGISTER
25671 @findex gdb.SYMBOL_LOC_REGISTER
25672 @item gdb.SYMBOL_LOC_REGISTER
25673 Value is in a register.
25674 @findex SYMBOL_LOC_ARG
25675 @findex gdb.SYMBOL_LOC_ARG
25676 @item gdb.SYMBOL_LOC_ARG
25677 Value is an argument. This value is at the offset stored within the
25678 symbol inside the frame's argument list.
25679 @findex SYMBOL_LOC_REF_ARG
25680 @findex gdb.SYMBOL_LOC_REF_ARG
25681 @item gdb.SYMBOL_LOC_REF_ARG
25682 Value address is stored in the frame's argument list. Just like
25683 @code{LOC_ARG} except that the value's address is stored at the
25684 offset, not the value itself.
25685 @findex SYMBOL_LOC_REGPARM_ADDR
25686 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25687 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25688 Value is a specified register. Just like @code{LOC_REGISTER} except
25689 the register holds the address of the argument instead of the argument
25691 @findex SYMBOL_LOC_LOCAL
25692 @findex gdb.SYMBOL_LOC_LOCAL
25693 @item gdb.SYMBOL_LOC_LOCAL
25694 Value is a local variable.
25695 @findex SYMBOL_LOC_TYPEDEF
25696 @findex gdb.SYMBOL_LOC_TYPEDEF
25697 @item gdb.SYMBOL_LOC_TYPEDEF
25698 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25700 @findex SYMBOL_LOC_BLOCK
25701 @findex gdb.SYMBOL_LOC_BLOCK
25702 @item gdb.SYMBOL_LOC_BLOCK
25704 @findex SYMBOL_LOC_CONST_BYTES
25705 @findex gdb.SYMBOL_LOC_CONST_BYTES
25706 @item gdb.SYMBOL_LOC_CONST_BYTES
25707 Value is a byte-sequence.
25708 @findex SYMBOL_LOC_UNRESOLVED
25709 @findex gdb.SYMBOL_LOC_UNRESOLVED
25710 @item gdb.SYMBOL_LOC_UNRESOLVED
25711 Value is at a fixed address, but the address of the variable has to be
25712 determined from the minimal symbol table whenever the variable is
25714 @findex SYMBOL_LOC_OPTIMIZED_OUT
25715 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25716 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25717 The value does not actually exist in the program.
25718 @findex SYMBOL_LOC_COMPUTED
25719 @findex gdb.SYMBOL_LOC_COMPUTED
25720 @item gdb.SYMBOL_LOC_COMPUTED
25721 The value's address is a computed location.
25724 @node Symbol Tables In Python
25725 @subsubsection Symbol table representation in Python.
25727 @cindex symbol tables in python
25729 @tindex gdb.Symtab_and_line
25731 Access to symbol table data maintained by @value{GDBN} on the inferior
25732 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25733 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25734 from the @code{find_sal} method in @code{gdb.Frame} object.
25735 @xref{Frames In Python}.
25737 For more information on @value{GDBN}'s symbol table management, see
25738 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25740 A @code{gdb.Symtab_and_line} object has the following attributes:
25742 @defvar Symtab_and_line.symtab
25743 The symbol table object (@code{gdb.Symtab}) for this frame.
25744 This attribute is not writable.
25747 @defvar Symtab_and_line.pc
25748 Indicates the start of the address range occupied by code for the
25749 current source line. This attribute is not writable.
25752 @defvar Symtab_and_line.last
25753 Indicates the end of the address range occupied by code for the current
25754 source line. This attribute is not writable.
25757 @defvar Symtab_and_line.line
25758 Indicates the current line number for this object. This
25759 attribute is not writable.
25762 A @code{gdb.Symtab_and_line} object has the following methods:
25764 @defun Symtab_and_line.is_valid ()
25765 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25766 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25767 invalid if the Symbol table and line object it refers to does not
25768 exist in @value{GDBN} any longer. All other
25769 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25770 invalid at the time the method is called.
25773 A @code{gdb.Symtab} object has the following attributes:
25775 @defvar Symtab.filename
25776 The symbol table's source filename. This attribute is not writable.
25779 @defvar Symtab.objfile
25780 The symbol table's backing object file. @xref{Objfiles In Python}.
25781 This attribute is not writable.
25784 A @code{gdb.Symtab} object has the following methods:
25786 @defun Symtab.is_valid ()
25787 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25788 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25789 the symbol table it refers to does not exist in @value{GDBN} any
25790 longer. All other @code{gdb.Symtab} methods will throw an exception
25791 if it is invalid at the time the method is called.
25794 @defun Symtab.fullname ()
25795 Return the symbol table's source absolute file name.
25798 @defun Symtab.global_block ()
25799 Return the global block of the underlying symbol table.
25800 @xref{Blocks In Python}.
25803 @defun Symtab.static_block ()
25804 Return the static block of the underlying symbol table.
25805 @xref{Blocks In Python}.
25808 @node Breakpoints In Python
25809 @subsubsection Manipulating breakpoints using Python
25811 @cindex breakpoints in python
25812 @tindex gdb.Breakpoint
25814 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25817 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25818 Create a new breakpoint. @var{spec} is a string naming the
25819 location of the breakpoint, or an expression that defines a
25820 watchpoint. The contents can be any location recognized by the
25821 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25822 command. The optional @var{type} denotes the breakpoint to create
25823 from the types defined later in this chapter. This argument can be
25824 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25825 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25826 allows the breakpoint to become invisible to the user. The breakpoint
25827 will neither be reported when created, nor will it be listed in the
25828 output from @code{info breakpoints} (but will be listed with the
25829 @code{maint info breakpoints} command). The optional @var{wp_class}
25830 argument defines the class of watchpoint to create, if @var{type} is
25831 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25832 assumed to be a @code{gdb.WP_WRITE} class.
25835 @defun Breakpoint.stop (self)
25836 The @code{gdb.Breakpoint} class can be sub-classed and, in
25837 particular, you may choose to implement the @code{stop} method.
25838 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25839 it will be called when the inferior reaches any location of a
25840 breakpoint which instantiates that sub-class. If the method returns
25841 @code{True}, the inferior will be stopped at the location of the
25842 breakpoint, otherwise the inferior will continue.
25844 If there are multiple breakpoints at the same location with a
25845 @code{stop} method, each one will be called regardless of the
25846 return status of the previous. This ensures that all @code{stop}
25847 methods have a chance to execute at that location. In this scenario
25848 if one of the methods returns @code{True} but the others return
25849 @code{False}, the inferior will still be stopped.
25851 You should not alter the execution state of the inferior (i.e.@:, step,
25852 next, etc.), alter the current frame context (i.e.@:, change the current
25853 active frame), or alter, add or delete any breakpoint. As a general
25854 rule, you should not alter any data within @value{GDBN} or the inferior
25857 Example @code{stop} implementation:
25860 class MyBreakpoint (gdb.Breakpoint):
25862 inf_val = gdb.parse_and_eval("foo")
25869 The available watchpoint types represented by constants are defined in the
25874 @findex gdb.WP_READ
25876 Read only watchpoint.
25879 @findex gdb.WP_WRITE
25881 Write only watchpoint.
25884 @findex gdb.WP_ACCESS
25885 @item gdb.WP_ACCESS
25886 Read/Write watchpoint.
25889 @defun Breakpoint.is_valid ()
25890 Return @code{True} if this @code{Breakpoint} object is valid,
25891 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25892 if the user deletes the breakpoint. In this case, the object still
25893 exists, but the underlying breakpoint does not. In the cases of
25894 watchpoint scope, the watchpoint remains valid even if execution of the
25895 inferior leaves the scope of that watchpoint.
25898 @defun Breakpoint.delete
25899 Permanently deletes the @value{GDBN} breakpoint. This also
25900 invalidates the Python @code{Breakpoint} object. Any further access
25901 to this object's attributes or methods will raise an error.
25904 @defvar Breakpoint.enabled
25905 This attribute is @code{True} if the breakpoint is enabled, and
25906 @code{False} otherwise. This attribute is writable.
25909 @defvar Breakpoint.silent
25910 This attribute is @code{True} if the breakpoint is silent, and
25911 @code{False} otherwise. This attribute is writable.
25913 Note that a breakpoint can also be silent if it has commands and the
25914 first command is @code{silent}. This is not reported by the
25915 @code{silent} attribute.
25918 @defvar Breakpoint.thread
25919 If the breakpoint is thread-specific, this attribute holds the thread
25920 id. If the breakpoint is not thread-specific, this attribute is
25921 @code{None}. This attribute is writable.
25924 @defvar Breakpoint.task
25925 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25926 id. If the breakpoint is not task-specific (or the underlying
25927 language is not Ada), this attribute is @code{None}. This attribute
25931 @defvar Breakpoint.ignore_count
25932 This attribute holds the ignore count for the breakpoint, an integer.
25933 This attribute is writable.
25936 @defvar Breakpoint.number
25937 This attribute holds the breakpoint's number --- the identifier used by
25938 the user to manipulate the breakpoint. This attribute is not writable.
25941 @defvar Breakpoint.type
25942 This attribute holds the breakpoint's type --- the identifier used to
25943 determine the actual breakpoint type or use-case. This attribute is not
25947 @defvar Breakpoint.visible
25948 This attribute tells whether the breakpoint is visible to the user
25949 when set, or when the @samp{info breakpoints} command is run. This
25950 attribute is not writable.
25953 The available types are represented by constants defined in the @code{gdb}
25957 @findex BP_BREAKPOINT
25958 @findex gdb.BP_BREAKPOINT
25959 @item gdb.BP_BREAKPOINT
25960 Normal code breakpoint.
25962 @findex BP_WATCHPOINT
25963 @findex gdb.BP_WATCHPOINT
25964 @item gdb.BP_WATCHPOINT
25965 Watchpoint breakpoint.
25967 @findex BP_HARDWARE_WATCHPOINT
25968 @findex gdb.BP_HARDWARE_WATCHPOINT
25969 @item gdb.BP_HARDWARE_WATCHPOINT
25970 Hardware assisted watchpoint.
25972 @findex BP_READ_WATCHPOINT
25973 @findex gdb.BP_READ_WATCHPOINT
25974 @item gdb.BP_READ_WATCHPOINT
25975 Hardware assisted read watchpoint.
25977 @findex BP_ACCESS_WATCHPOINT
25978 @findex gdb.BP_ACCESS_WATCHPOINT
25979 @item gdb.BP_ACCESS_WATCHPOINT
25980 Hardware assisted access watchpoint.
25983 @defvar Breakpoint.hit_count
25984 This attribute holds the hit count for the breakpoint, an integer.
25985 This attribute is writable, but currently it can only be set to zero.
25988 @defvar Breakpoint.location
25989 This attribute holds the location of the breakpoint, as specified by
25990 the user. It is a string. If the breakpoint does not have a location
25991 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25992 attribute is not writable.
25995 @defvar Breakpoint.expression
25996 This attribute holds a breakpoint expression, as specified by
25997 the user. It is a string. If the breakpoint does not have an
25998 expression (the breakpoint is not a watchpoint) the attribute's value
25999 is @code{None}. This attribute is not writable.
26002 @defvar Breakpoint.condition
26003 This attribute holds the condition of the breakpoint, as specified by
26004 the user. It is a string. If there is no condition, this attribute's
26005 value is @code{None}. This attribute is writable.
26008 @defvar Breakpoint.commands
26009 This attribute holds the commands attached to the breakpoint. If
26010 there are commands, this attribute's value is a string holding all the
26011 commands, separated by newlines. If there are no commands, this
26012 attribute is @code{None}. This attribute is not writable.
26015 @node Finish Breakpoints in Python
26016 @subsubsection Finish Breakpoints
26018 @cindex python finish breakpoints
26019 @tindex gdb.FinishBreakpoint
26021 A finish breakpoint is a temporary breakpoint set at the return address of
26022 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26023 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26024 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26025 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26026 Finish breakpoints are thread specific and must be create with the right
26029 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26030 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26031 object @var{frame}. If @var{frame} is not provided, this defaults to the
26032 newest frame. The optional @var{internal} argument allows the breakpoint to
26033 become invisible to the user. @xref{Breakpoints In Python}, for further
26034 details about this argument.
26037 @defun FinishBreakpoint.out_of_scope (self)
26038 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26039 @code{return} command, @dots{}), a function may not properly terminate, and
26040 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26041 situation, the @code{out_of_scope} callback will be triggered.
26043 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26047 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26049 print "normal finish"
26052 def out_of_scope ():
26053 print "abnormal finish"
26057 @defvar FinishBreakpoint.return_value
26058 When @value{GDBN} is stopped at a finish breakpoint and the frame
26059 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26060 attribute will contain a @code{gdb.Value} object corresponding to the return
26061 value of the function. The value will be @code{None} if the function return
26062 type is @code{void} or if the return value was not computable. This attribute
26066 @node Lazy Strings In Python
26067 @subsubsection Python representation of lazy strings.
26069 @cindex lazy strings in python
26070 @tindex gdb.LazyString
26072 A @dfn{lazy string} is a string whose contents is not retrieved or
26073 encoded until it is needed.
26075 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26076 @code{address} that points to a region of memory, an @code{encoding}
26077 that will be used to encode that region of memory, and a @code{length}
26078 to delimit the region of memory that represents the string. The
26079 difference between a @code{gdb.LazyString} and a string wrapped within
26080 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26081 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26082 retrieved and encoded during printing, while a @code{gdb.Value}
26083 wrapping a string is immediately retrieved and encoded on creation.
26085 A @code{gdb.LazyString} object has the following functions:
26087 @defun LazyString.value ()
26088 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26089 will point to the string in memory, but will lose all the delayed
26090 retrieval, encoding and handling that @value{GDBN} applies to a
26091 @code{gdb.LazyString}.
26094 @defvar LazyString.address
26095 This attribute holds the address of the string. This attribute is not
26099 @defvar LazyString.length
26100 This attribute holds the length of the string in characters. If the
26101 length is -1, then the string will be fetched and encoded up to the
26102 first null of appropriate width. This attribute is not writable.
26105 @defvar LazyString.encoding
26106 This attribute holds the encoding that will be applied to the string
26107 when the string is printed by @value{GDBN}. If the encoding is not
26108 set, or contains an empty string, then @value{GDBN} will select the
26109 most appropriate encoding when the string is printed. This attribute
26113 @defvar LazyString.type
26114 This attribute holds the type that is represented by the lazy string's
26115 type. For a lazy string this will always be a pointer type. To
26116 resolve this to the lazy string's character type, use the type's
26117 @code{target} method. @xref{Types In Python}. This attribute is not
26121 @node Architectures In Python
26122 @subsubsection Python representation of architectures
26123 @cindex Python architectures
26125 @value{GDBN} uses architecture specific parameters and artifacts in a
26126 number of its various computations. An architecture is represented
26127 by an instance of the @code{gdb.Architecture} class.
26129 A @code{gdb.Architecture} class has the following methods:
26131 @defun Architecture.name ()
26132 Return the name (string value) of the architecture.
26135 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26136 Return a list of disassembled instructions starting from the memory
26137 address @var{start_pc}. The optional arguments @var{end_pc} and
26138 @var{count} determine the number of instructions in the returned list.
26139 If both the optional arguments @var{end_pc} and @var{count} are
26140 specified, then a list of at most @var{count} disassembled instructions
26141 whose start address falls in the closed memory address interval from
26142 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26143 specified, but @var{count} is specified, then @var{count} number of
26144 instructions starting from the address @var{start_pc} are returned. If
26145 @var{count} is not specified but @var{end_pc} is specified, then all
26146 instructions whose start address falls in the closed memory address
26147 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26148 @var{end_pc} nor @var{count} are specified, then a single instruction at
26149 @var{start_pc} is returned. For all of these cases, each element of the
26150 returned list is a Python @code{dict} with the following string keys:
26155 The value corresponding to this key is a Python long integer capturing
26156 the memory address of the instruction.
26159 The value corresponding to this key is a string value which represents
26160 the instruction with assembly language mnemonics. The assembly
26161 language flavor used is the same as that specified by the current CLI
26162 variable @code{disassembly-flavor}. @xref{Machine Code}.
26165 The value corresponding to this key is the length (integer value) of the
26166 instruction in bytes.
26171 @node Python Auto-loading
26172 @subsection Python Auto-loading
26173 @cindex Python auto-loading
26175 When a new object file is read (for example, due to the @code{file}
26176 command, or because the inferior has loaded a shared library),
26177 @value{GDBN} will look for Python support scripts in several ways:
26178 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26179 and @code{.debug_gdb_scripts} section
26180 (@pxref{dotdebug_gdb_scripts section}).
26182 The auto-loading feature is useful for supplying application-specific
26183 debugging commands and scripts.
26185 Auto-loading can be enabled or disabled,
26186 and the list of auto-loaded scripts can be printed.
26189 @anchor{set auto-load python-scripts}
26190 @kindex set auto-load python-scripts
26191 @item set auto-load python-scripts [on|off]
26192 Enable or disable the auto-loading of Python scripts.
26194 @anchor{show auto-load python-scripts}
26195 @kindex show auto-load python-scripts
26196 @item show auto-load python-scripts
26197 Show whether auto-loading of Python scripts is enabled or disabled.
26199 @anchor{info auto-load python-scripts}
26200 @kindex info auto-load python-scripts
26201 @cindex print list of auto-loaded Python scripts
26202 @item info auto-load python-scripts [@var{regexp}]
26203 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26205 Also printed is the list of Python scripts that were mentioned in
26206 the @code{.debug_gdb_scripts} section and were not found
26207 (@pxref{dotdebug_gdb_scripts section}).
26208 This is useful because their names are not printed when @value{GDBN}
26209 tries to load them and fails. There may be many of them, and printing
26210 an error message for each one is problematic.
26212 If @var{regexp} is supplied only Python scripts with matching names are printed.
26217 (gdb) info auto-load python-scripts
26219 Yes py-section-script.py
26220 full name: /tmp/py-section-script.py
26221 No my-foo-pretty-printers.py
26225 When reading an auto-loaded file, @value{GDBN} sets the
26226 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26227 function (@pxref{Objfiles In Python}). This can be useful for
26228 registering objfile-specific pretty-printers.
26231 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26232 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26233 * Which flavor to choose?::
26236 @node objfile-gdb.py file
26237 @subsubsection The @file{@var{objfile}-gdb.py} file
26238 @cindex @file{@var{objfile}-gdb.py}
26240 When a new object file is read, @value{GDBN} looks for
26241 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26242 where @var{objfile} is the object file's real name, formed by ensuring
26243 that the file name is absolute, following all symlinks, and resolving
26244 @code{.} and @code{..} components. If this file exists and is
26245 readable, @value{GDBN} will evaluate it as a Python script.
26247 If this file does not exist, then @value{GDBN} will look for
26248 @var{script-name} file in all of the directories as specified below.
26250 Note that loading of this script file also requires accordingly configured
26251 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26253 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26254 scripts normally according to its @file{.exe} filename. But if no scripts are
26255 found @value{GDBN} also tries script filenames matching the object file without
26256 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26257 is attempted on any platform. This makes the script filenames compatible
26258 between Unix and MS-Windows hosts.
26261 @anchor{set auto-load scripts-directory}
26262 @kindex set auto-load scripts-directory
26263 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26264 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26265 may be delimited by the host platform path separator in use
26266 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26268 Each entry here needs to be covered also by the security setting
26269 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26271 @anchor{with-auto-load-dir}
26272 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26273 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26274 configuration option @option{--with-auto-load-dir}.
26276 Any reference to @file{$debugdir} will get replaced by
26277 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26278 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26279 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26280 @file{$datadir} must be placed as a directory component --- either alone or
26281 delimited by @file{/} or @file{\} directory separators, depending on the host
26284 The list of directories uses path separator (@samp{:} on GNU and Unix
26285 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26286 to the @env{PATH} environment variable.
26288 @anchor{show auto-load scripts-directory}
26289 @kindex show auto-load scripts-directory
26290 @item show auto-load scripts-directory
26291 Show @value{GDBN} auto-loaded scripts location.
26294 @value{GDBN} does not track which files it has already auto-loaded this way.
26295 @value{GDBN} will load the associated script every time the corresponding
26296 @var{objfile} is opened.
26297 So your @file{-gdb.py} file should be careful to avoid errors if it
26298 is evaluated more than once.
26300 @node dotdebug_gdb_scripts section
26301 @subsubsection The @code{.debug_gdb_scripts} section
26302 @cindex @code{.debug_gdb_scripts} section
26304 For systems using file formats like ELF and COFF,
26305 when @value{GDBN} loads a new object file
26306 it will look for a special section named @samp{.debug_gdb_scripts}.
26307 If this section exists, its contents is a list of names of scripts to load.
26309 @value{GDBN} will look for each specified script file first in the
26310 current directory and then along the source search path
26311 (@pxref{Source Path, ,Specifying Source Directories}),
26312 except that @file{$cdir} is not searched, since the compilation
26313 directory is not relevant to scripts.
26315 Entries can be placed in section @code{.debug_gdb_scripts} with,
26316 for example, this GCC macro:
26319 /* Note: The "MS" section flags are to remove duplicates. */
26320 #define DEFINE_GDB_SCRIPT(script_name) \
26322 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26324 .asciz \"" script_name "\"\n\
26330 Then one can reference the macro in a header or source file like this:
26333 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26336 The script name may include directories if desired.
26338 Note that loading of this script file also requires accordingly configured
26339 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26341 If the macro is put in a header, any application or library
26342 using this header will get a reference to the specified script.
26344 @node Which flavor to choose?
26345 @subsubsection Which flavor to choose?
26347 Given the multiple ways of auto-loading Python scripts, it might not always
26348 be clear which one to choose. This section provides some guidance.
26350 Benefits of the @file{-gdb.py} way:
26354 Can be used with file formats that don't support multiple sections.
26357 Ease of finding scripts for public libraries.
26359 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26360 in the source search path.
26361 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26362 isn't a source directory in which to find the script.
26365 Doesn't require source code additions.
26368 Benefits of the @code{.debug_gdb_scripts} way:
26372 Works with static linking.
26374 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26375 trigger their loading. When an application is statically linked the only
26376 objfile available is the executable, and it is cumbersome to attach all the
26377 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26380 Works with classes that are entirely inlined.
26382 Some classes can be entirely inlined, and thus there may not be an associated
26383 shared library to attach a @file{-gdb.py} script to.
26386 Scripts needn't be copied out of the source tree.
26388 In some circumstances, apps can be built out of large collections of internal
26389 libraries, and the build infrastructure necessary to install the
26390 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26391 cumbersome. It may be easier to specify the scripts in the
26392 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26393 top of the source tree to the source search path.
26396 @node Python modules
26397 @subsection Python modules
26398 @cindex python modules
26400 @value{GDBN} comes with several modules to assist writing Python code.
26403 * gdb.printing:: Building and registering pretty-printers.
26404 * gdb.types:: Utilities for working with types.
26405 * gdb.prompt:: Utilities for prompt value substitution.
26409 @subsubsection gdb.printing
26410 @cindex gdb.printing
26412 This module provides a collection of utilities for working with
26416 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26417 This class specifies the API that makes @samp{info pretty-printer},
26418 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26419 Pretty-printers should generally inherit from this class.
26421 @item SubPrettyPrinter (@var{name})
26422 For printers that handle multiple types, this class specifies the
26423 corresponding API for the subprinters.
26425 @item RegexpCollectionPrettyPrinter (@var{name})
26426 Utility class for handling multiple printers, all recognized via
26427 regular expressions.
26428 @xref{Writing a Pretty-Printer}, for an example.
26430 @item FlagEnumerationPrinter (@var{name})
26431 A pretty-printer which handles printing of @code{enum} values. Unlike
26432 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26433 work properly when there is some overlap between the enumeration
26434 constants. @var{name} is the name of the printer and also the name of
26435 the @code{enum} type to look up.
26437 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26438 Register @var{printer} with the pretty-printer list of @var{obj}.
26439 If @var{replace} is @code{True} then any existing copy of the printer
26440 is replaced. Otherwise a @code{RuntimeError} exception is raised
26441 if a printer with the same name already exists.
26445 @subsubsection gdb.types
26448 This module provides a collection of utilities for working with
26449 @code{gdb.Type} objects.
26452 @item get_basic_type (@var{type})
26453 Return @var{type} with const and volatile qualifiers stripped,
26454 and with typedefs and C@t{++} references converted to the underlying type.
26459 typedef const int const_int;
26461 const_int& foo_ref (foo);
26462 int main () @{ return 0; @}
26469 (gdb) python import gdb.types
26470 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26471 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26475 @item has_field (@var{type}, @var{field})
26476 Return @code{True} if @var{type}, assumed to be a type with fields
26477 (e.g., a structure or union), has field @var{field}.
26479 @item make_enum_dict (@var{enum_type})
26480 Return a Python @code{dictionary} type produced from @var{enum_type}.
26482 @item deep_items (@var{type})
26483 Returns a Python iterator similar to the standard
26484 @code{gdb.Type.iteritems} method, except that the iterator returned
26485 by @code{deep_items} will recursively traverse anonymous struct or
26486 union fields. For example:
26500 Then in @value{GDBN}:
26502 (@value{GDBP}) python import gdb.types
26503 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26504 (@value{GDBP}) python print struct_a.keys ()
26506 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26507 @{['a', 'b0', 'b1']@}
26510 @item get_type_recognizers ()
26511 Return a list of the enabled type recognizers for the current context.
26512 This is called by @value{GDBN} during the type-printing process
26513 (@pxref{Type Printing API}).
26515 @item apply_type_recognizers (recognizers, type_obj)
26516 Apply the type recognizers, @var{recognizers}, to the type object
26517 @var{type_obj}. If any recognizer returns a string, return that
26518 string. Otherwise, return @code{None}. This is called by
26519 @value{GDBN} during the type-printing process (@pxref{Type Printing
26522 @item register_type_printer (locus, printer)
26523 This is a convenience function to register a type printer.
26524 @var{printer} is the type printer to register. It must implement the
26525 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26526 which case the printer is registered with that objfile; a
26527 @code{gdb.Progspace}, in which case the printer is registered with
26528 that progspace; or @code{None}, in which case the printer is
26529 registered globally.
26532 This is a base class that implements the type printer protocol. Type
26533 printers are encouraged, but not required, to derive from this class.
26534 It defines a constructor:
26536 @defmethod TypePrinter __init__ (self, name)
26537 Initialize the type printer with the given name. The new printer
26538 starts in the enabled state.
26544 @subsubsection gdb.prompt
26547 This module provides a method for prompt value-substitution.
26550 @item substitute_prompt (@var{string})
26551 Return @var{string} with escape sequences substituted by values. Some
26552 escape sequences take arguments. You can specify arguments inside
26553 ``@{@}'' immediately following the escape sequence.
26555 The escape sequences you can pass to this function are:
26559 Substitute a backslash.
26561 Substitute an ESC character.
26563 Substitute the selected frame; an argument names a frame parameter.
26565 Substitute a newline.
26567 Substitute a parameter's value; the argument names the parameter.
26569 Substitute a carriage return.
26571 Substitute the selected thread; an argument names a thread parameter.
26573 Substitute the version of GDB.
26575 Substitute the current working directory.
26577 Begin a sequence of non-printing characters. These sequences are
26578 typically used with the ESC character, and are not counted in the string
26579 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26580 blue-colored ``(gdb)'' prompt where the length is five.
26582 End a sequence of non-printing characters.
26588 substitute_prompt (``frame: \f,
26589 print arguments: \p@{print frame-arguments@}'')
26592 @exdent will return the string:
26595 "frame: main, print arguments: scalars"
26600 @section Creating new spellings of existing commands
26601 @cindex aliases for commands
26603 It is often useful to define alternate spellings of existing commands.
26604 For example, if a new @value{GDBN} command defined in Python has
26605 a long name to type, it is handy to have an abbreviated version of it
26606 that involves less typing.
26608 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26609 of the @samp{step} command even though it is otherwise an ambiguous
26610 abbreviation of other commands like @samp{set} and @samp{show}.
26612 Aliases are also used to provide shortened or more common versions
26613 of multi-word commands. For example, @value{GDBN} provides the
26614 @samp{tty} alias of the @samp{set inferior-tty} command.
26616 You can define a new alias with the @samp{alias} command.
26621 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26625 @var{ALIAS} specifies the name of the new alias.
26626 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26629 @var{COMMAND} specifies the name of an existing command
26630 that is being aliased.
26632 The @samp{-a} option specifies that the new alias is an abbreviation
26633 of the command. Abbreviations are not shown in command
26634 lists displayed by the @samp{help} command.
26636 The @samp{--} option specifies the end of options,
26637 and is useful when @var{ALIAS} begins with a dash.
26639 Here is a simple example showing how to make an abbreviation
26640 of a command so that there is less to type.
26641 Suppose you were tired of typing @samp{disas}, the current
26642 shortest unambiguous abbreviation of the @samp{disassemble} command
26643 and you wanted an even shorter version named @samp{di}.
26644 The following will accomplish this.
26647 (gdb) alias -a di = disas
26650 Note that aliases are different from user-defined commands.
26651 With a user-defined command, you also need to write documentation
26652 for it with the @samp{document} command.
26653 An alias automatically picks up the documentation of the existing command.
26655 Here is an example where we make @samp{elms} an abbreviation of
26656 @samp{elements} in the @samp{set print elements} command.
26657 This is to show that you can make an abbreviation of any part
26661 (gdb) alias -a set print elms = set print elements
26662 (gdb) alias -a show print elms = show print elements
26663 (gdb) set p elms 20
26665 Limit on string chars or array elements to print is 200.
26668 Note that if you are defining an alias of a @samp{set} command,
26669 and you want to have an alias for the corresponding @samp{show}
26670 command, then you need to define the latter separately.
26672 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26673 @var{ALIAS}, just as they are normally.
26676 (gdb) alias -a set pr elms = set p ele
26679 Finally, here is an example showing the creation of a one word
26680 alias for a more complex command.
26681 This creates alias @samp{spe} of the command @samp{set print elements}.
26684 (gdb) alias spe = set print elements
26689 @chapter Command Interpreters
26690 @cindex command interpreters
26692 @value{GDBN} supports multiple command interpreters, and some command
26693 infrastructure to allow users or user interface writers to switch
26694 between interpreters or run commands in other interpreters.
26696 @value{GDBN} currently supports two command interpreters, the console
26697 interpreter (sometimes called the command-line interpreter or @sc{cli})
26698 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26699 describes both of these interfaces in great detail.
26701 By default, @value{GDBN} will start with the console interpreter.
26702 However, the user may choose to start @value{GDBN} with another
26703 interpreter by specifying the @option{-i} or @option{--interpreter}
26704 startup options. Defined interpreters include:
26708 @cindex console interpreter
26709 The traditional console or command-line interpreter. This is the most often
26710 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26711 @value{GDBN} will use this interpreter.
26714 @cindex mi interpreter
26715 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26716 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26717 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26721 @cindex mi2 interpreter
26722 The current @sc{gdb/mi} interface.
26725 @cindex mi1 interpreter
26726 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26730 @cindex invoke another interpreter
26731 The interpreter being used by @value{GDBN} may not be dynamically
26732 switched at runtime. Although possible, this could lead to a very
26733 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26734 enters the command "interpreter-set console" in a console view,
26735 @value{GDBN} would switch to using the console interpreter, rendering
26736 the IDE inoperable!
26738 @kindex interpreter-exec
26739 Although you may only choose a single interpreter at startup, you may execute
26740 commands in any interpreter from the current interpreter using the appropriate
26741 command. If you are running the console interpreter, simply use the
26742 @code{interpreter-exec} command:
26745 interpreter-exec mi "-data-list-register-names"
26748 @sc{gdb/mi} has a similar command, although it is only available in versions of
26749 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26752 @chapter @value{GDBN} Text User Interface
26754 @cindex Text User Interface
26757 * TUI Overview:: TUI overview
26758 * TUI Keys:: TUI key bindings
26759 * TUI Single Key Mode:: TUI single key mode
26760 * TUI Commands:: TUI-specific commands
26761 * TUI Configuration:: TUI configuration variables
26764 The @value{GDBN} Text User Interface (TUI) is a terminal
26765 interface which uses the @code{curses} library to show the source
26766 file, the assembly output, the program registers and @value{GDBN}
26767 commands in separate text windows. The TUI mode is supported only
26768 on platforms where a suitable version of the @code{curses} library
26771 The TUI mode is enabled by default when you invoke @value{GDBN} as
26772 @samp{@value{GDBP} -tui}.
26773 You can also switch in and out of TUI mode while @value{GDBN} runs by
26774 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26775 @xref{TUI Keys, ,TUI Key Bindings}.
26778 @section TUI Overview
26780 In TUI mode, @value{GDBN} can display several text windows:
26784 This window is the @value{GDBN} command window with the @value{GDBN}
26785 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26786 managed using readline.
26789 The source window shows the source file of the program. The current
26790 line and active breakpoints are displayed in this window.
26793 The assembly window shows the disassembly output of the program.
26796 This window shows the processor registers. Registers are highlighted
26797 when their values change.
26800 The source and assembly windows show the current program position
26801 by highlighting the current line and marking it with a @samp{>} marker.
26802 Breakpoints are indicated with two markers. The first marker
26803 indicates the breakpoint type:
26807 Breakpoint which was hit at least once.
26810 Breakpoint which was never hit.
26813 Hardware breakpoint which was hit at least once.
26816 Hardware breakpoint which was never hit.
26819 The second marker indicates whether the breakpoint is enabled or not:
26823 Breakpoint is enabled.
26826 Breakpoint is disabled.
26829 The source, assembly and register windows are updated when the current
26830 thread changes, when the frame changes, or when the program counter
26833 These windows are not all visible at the same time. The command
26834 window is always visible. The others can be arranged in several
26845 source and assembly,
26848 source and registers, or
26851 assembly and registers.
26854 A status line above the command window shows the following information:
26858 Indicates the current @value{GDBN} target.
26859 (@pxref{Targets, ,Specifying a Debugging Target}).
26862 Gives the current process or thread number.
26863 When no process is being debugged, this field is set to @code{No process}.
26866 Gives the current function name for the selected frame.
26867 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26868 When there is no symbol corresponding to the current program counter,
26869 the string @code{??} is displayed.
26872 Indicates the current line number for the selected frame.
26873 When the current line number is not known, the string @code{??} is displayed.
26876 Indicates the current program counter address.
26880 @section TUI Key Bindings
26881 @cindex TUI key bindings
26883 The TUI installs several key bindings in the readline keymaps
26884 @ifset SYSTEM_READLINE
26885 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26887 @ifclear SYSTEM_READLINE
26888 (@pxref{Command Line Editing}).
26890 The following key bindings are installed for both TUI mode and the
26891 @value{GDBN} standard mode.
26900 Enter or leave the TUI mode. When leaving the TUI mode,
26901 the curses window management stops and @value{GDBN} operates using
26902 its standard mode, writing on the terminal directly. When reentering
26903 the TUI mode, control is given back to the curses windows.
26904 The screen is then refreshed.
26908 Use a TUI layout with only one window. The layout will
26909 either be @samp{source} or @samp{assembly}. When the TUI mode
26910 is not active, it will switch to the TUI mode.
26912 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26916 Use a TUI layout with at least two windows. When the current
26917 layout already has two windows, the next layout with two windows is used.
26918 When a new layout is chosen, one window will always be common to the
26919 previous layout and the new one.
26921 Think of it as the Emacs @kbd{C-x 2} binding.
26925 Change the active window. The TUI associates several key bindings
26926 (like scrolling and arrow keys) with the active window. This command
26927 gives the focus to the next TUI window.
26929 Think of it as the Emacs @kbd{C-x o} binding.
26933 Switch in and out of the TUI SingleKey mode that binds single
26934 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26937 The following key bindings only work in the TUI mode:
26942 Scroll the active window one page up.
26946 Scroll the active window one page down.
26950 Scroll the active window one line up.
26954 Scroll the active window one line down.
26958 Scroll the active window one column left.
26962 Scroll the active window one column right.
26966 Refresh the screen.
26969 Because the arrow keys scroll the active window in the TUI mode, they
26970 are not available for their normal use by readline unless the command
26971 window has the focus. When another window is active, you must use
26972 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26973 and @kbd{C-f} to control the command window.
26975 @node TUI Single Key Mode
26976 @section TUI Single Key Mode
26977 @cindex TUI single key mode
26979 The TUI also provides a @dfn{SingleKey} mode, which binds several
26980 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26981 switch into this mode, where the following key bindings are used:
26984 @kindex c @r{(SingleKey TUI key)}
26988 @kindex d @r{(SingleKey TUI key)}
26992 @kindex f @r{(SingleKey TUI key)}
26996 @kindex n @r{(SingleKey TUI key)}
27000 @kindex q @r{(SingleKey TUI key)}
27002 exit the SingleKey mode.
27004 @kindex r @r{(SingleKey TUI key)}
27008 @kindex s @r{(SingleKey TUI key)}
27012 @kindex u @r{(SingleKey TUI key)}
27016 @kindex v @r{(SingleKey TUI key)}
27020 @kindex w @r{(SingleKey TUI key)}
27025 Other keys temporarily switch to the @value{GDBN} command prompt.
27026 The key that was pressed is inserted in the editing buffer so that
27027 it is possible to type most @value{GDBN} commands without interaction
27028 with the TUI SingleKey mode. Once the command is entered the TUI
27029 SingleKey mode is restored. The only way to permanently leave
27030 this mode is by typing @kbd{q} or @kbd{C-x s}.
27034 @section TUI-specific Commands
27035 @cindex TUI commands
27037 The TUI has specific commands to control the text windows.
27038 These commands are always available, even when @value{GDBN} is not in
27039 the TUI mode. When @value{GDBN} is in the standard mode, most
27040 of these commands will automatically switch to the TUI mode.
27042 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27043 terminal, or @value{GDBN} has been started with the machine interface
27044 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27045 these commands will fail with an error, because it would not be
27046 possible or desirable to enable curses window management.
27051 List and give the size of all displayed windows.
27055 Display the next layout.
27058 Display the previous layout.
27061 Display the source window only.
27064 Display the assembly window only.
27067 Display the source and assembly window.
27070 Display the register window together with the source or assembly window.
27074 Make the next window active for scrolling.
27077 Make the previous window active for scrolling.
27080 Make the source window active for scrolling.
27083 Make the assembly window active for scrolling.
27086 Make the register window active for scrolling.
27089 Make the command window active for scrolling.
27093 Refresh the screen. This is similar to typing @kbd{C-L}.
27095 @item tui reg float
27097 Show the floating point registers in the register window.
27099 @item tui reg general
27100 Show the general registers in the register window.
27103 Show the next register group. The list of register groups as well as
27104 their order is target specific. The predefined register groups are the
27105 following: @code{general}, @code{float}, @code{system}, @code{vector},
27106 @code{all}, @code{save}, @code{restore}.
27108 @item tui reg system
27109 Show the system registers in the register window.
27113 Update the source window and the current execution point.
27115 @item winheight @var{name} +@var{count}
27116 @itemx winheight @var{name} -@var{count}
27118 Change the height of the window @var{name} by @var{count}
27119 lines. Positive counts increase the height, while negative counts
27122 @item tabset @var{nchars}
27124 Set the width of tab stops to be @var{nchars} characters.
27127 @node TUI Configuration
27128 @section TUI Configuration Variables
27129 @cindex TUI configuration variables
27131 Several configuration variables control the appearance of TUI windows.
27134 @item set tui border-kind @var{kind}
27135 @kindex set tui border-kind
27136 Select the border appearance for the source, assembly and register windows.
27137 The possible values are the following:
27140 Use a space character to draw the border.
27143 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27146 Use the Alternate Character Set to draw the border. The border is
27147 drawn using character line graphics if the terminal supports them.
27150 @item set tui border-mode @var{mode}
27151 @kindex set tui border-mode
27152 @itemx set tui active-border-mode @var{mode}
27153 @kindex set tui active-border-mode
27154 Select the display attributes for the borders of the inactive windows
27155 or the active window. The @var{mode} can be one of the following:
27158 Use normal attributes to display the border.
27164 Use reverse video mode.
27167 Use half bright mode.
27169 @item half-standout
27170 Use half bright and standout mode.
27173 Use extra bright or bold mode.
27175 @item bold-standout
27176 Use extra bright or bold and standout mode.
27181 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27184 @cindex @sc{gnu} Emacs
27185 A special interface allows you to use @sc{gnu} Emacs to view (and
27186 edit) the source files for the program you are debugging with
27189 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27190 executable file you want to debug as an argument. This command starts
27191 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27192 created Emacs buffer.
27193 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27195 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27200 All ``terminal'' input and output goes through an Emacs buffer, called
27203 This applies both to @value{GDBN} commands and their output, and to the input
27204 and output done by the program you are debugging.
27206 This is useful because it means that you can copy the text of previous
27207 commands and input them again; you can even use parts of the output
27210 All the facilities of Emacs' Shell mode are available for interacting
27211 with your program. In particular, you can send signals the usual
27212 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27216 @value{GDBN} displays source code through Emacs.
27218 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27219 source file for that frame and puts an arrow (@samp{=>}) at the
27220 left margin of the current line. Emacs uses a separate buffer for
27221 source display, and splits the screen to show both your @value{GDBN} session
27224 Explicit @value{GDBN} @code{list} or search commands still produce output as
27225 usual, but you probably have no reason to use them from Emacs.
27228 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27229 a graphical mode, enabled by default, which provides further buffers
27230 that can control the execution and describe the state of your program.
27231 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27233 If you specify an absolute file name when prompted for the @kbd{M-x
27234 gdb} argument, then Emacs sets your current working directory to where
27235 your program resides. If you only specify the file name, then Emacs
27236 sets your current working directory to the directory associated
27237 with the previous buffer. In this case, @value{GDBN} may find your
27238 program by searching your environment's @code{PATH} variable, but on
27239 some operating systems it might not find the source. So, although the
27240 @value{GDBN} input and output session proceeds normally, the auxiliary
27241 buffer does not display the current source and line of execution.
27243 The initial working directory of @value{GDBN} is printed on the top
27244 line of the GUD buffer and this serves as a default for the commands
27245 that specify files for @value{GDBN} to operate on. @xref{Files,
27246 ,Commands to Specify Files}.
27248 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27249 need to call @value{GDBN} by a different name (for example, if you
27250 keep several configurations around, with different names) you can
27251 customize the Emacs variable @code{gud-gdb-command-name} to run the
27254 In the GUD buffer, you can use these special Emacs commands in
27255 addition to the standard Shell mode commands:
27259 Describe the features of Emacs' GUD Mode.
27262 Execute to another source line, like the @value{GDBN} @code{step} command; also
27263 update the display window to show the current file and location.
27266 Execute to next source line in this function, skipping all function
27267 calls, like the @value{GDBN} @code{next} command. Then update the display window
27268 to show the current file and location.
27271 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27272 display window accordingly.
27275 Execute until exit from the selected stack frame, like the @value{GDBN}
27276 @code{finish} command.
27279 Continue execution of your program, like the @value{GDBN} @code{continue}
27283 Go up the number of frames indicated by the numeric argument
27284 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27285 like the @value{GDBN} @code{up} command.
27288 Go down the number of frames indicated by the numeric argument, like the
27289 @value{GDBN} @code{down} command.
27292 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27293 tells @value{GDBN} to set a breakpoint on the source line point is on.
27295 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27296 separate frame which shows a backtrace when the GUD buffer is current.
27297 Move point to any frame in the stack and type @key{RET} to make it
27298 become the current frame and display the associated source in the
27299 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27300 selected frame become the current one. In graphical mode, the
27301 speedbar displays watch expressions.
27303 If you accidentally delete the source-display buffer, an easy way to get
27304 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27305 request a frame display; when you run under Emacs, this recreates
27306 the source buffer if necessary to show you the context of the current
27309 The source files displayed in Emacs are in ordinary Emacs buffers
27310 which are visiting the source files in the usual way. You can edit
27311 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27312 communicates with Emacs in terms of line numbers. If you add or
27313 delete lines from the text, the line numbers that @value{GDBN} knows cease
27314 to correspond properly with the code.
27316 A more detailed description of Emacs' interaction with @value{GDBN} is
27317 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27321 @chapter The @sc{gdb/mi} Interface
27323 @unnumberedsec Function and Purpose
27325 @cindex @sc{gdb/mi}, its purpose
27326 @sc{gdb/mi} is a line based machine oriented text interface to
27327 @value{GDBN} and is activated by specifying using the
27328 @option{--interpreter} command line option (@pxref{Mode Options}). It
27329 is specifically intended to support the development of systems which
27330 use the debugger as just one small component of a larger system.
27332 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27333 in the form of a reference manual.
27335 Note that @sc{gdb/mi} is still under construction, so some of the
27336 features described below are incomplete and subject to change
27337 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27339 @unnumberedsec Notation and Terminology
27341 @cindex notational conventions, for @sc{gdb/mi}
27342 This chapter uses the following notation:
27346 @code{|} separates two alternatives.
27349 @code{[ @var{something} ]} indicates that @var{something} is optional:
27350 it may or may not be given.
27353 @code{( @var{group} )*} means that @var{group} inside the parentheses
27354 may repeat zero or more times.
27357 @code{( @var{group} )+} means that @var{group} inside the parentheses
27358 may repeat one or more times.
27361 @code{"@var{string}"} means a literal @var{string}.
27365 @heading Dependencies
27369 * GDB/MI General Design::
27370 * GDB/MI Command Syntax::
27371 * GDB/MI Compatibility with CLI::
27372 * GDB/MI Development and Front Ends::
27373 * GDB/MI Output Records::
27374 * GDB/MI Simple Examples::
27375 * GDB/MI Command Description Format::
27376 * GDB/MI Breakpoint Commands::
27377 * GDB/MI Catchpoint Commands::
27378 * GDB/MI Program Context::
27379 * GDB/MI Thread Commands::
27380 * GDB/MI Ada Tasking Commands::
27381 * GDB/MI Program Execution::
27382 * GDB/MI Stack Manipulation::
27383 * GDB/MI Variable Objects::
27384 * GDB/MI Data Manipulation::
27385 * GDB/MI Tracepoint Commands::
27386 * GDB/MI Symbol Query::
27387 * GDB/MI File Commands::
27389 * GDB/MI Kod Commands::
27390 * GDB/MI Memory Overlay Commands::
27391 * GDB/MI Signal Handling Commands::
27393 * GDB/MI Target Manipulation::
27394 * GDB/MI File Transfer Commands::
27395 * GDB/MI Miscellaneous Commands::
27398 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27399 @node GDB/MI General Design
27400 @section @sc{gdb/mi} General Design
27401 @cindex GDB/MI General Design
27403 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27404 parts---commands sent to @value{GDBN}, responses to those commands
27405 and notifications. Each command results in exactly one response,
27406 indicating either successful completion of the command, or an error.
27407 For the commands that do not resume the target, the response contains the
27408 requested information. For the commands that resume the target, the
27409 response only indicates whether the target was successfully resumed.
27410 Notifications is the mechanism for reporting changes in the state of the
27411 target, or in @value{GDBN} state, that cannot conveniently be associated with
27412 a command and reported as part of that command response.
27414 The important examples of notifications are:
27418 Exec notifications. These are used to report changes in
27419 target state---when a target is resumed, or stopped. It would not
27420 be feasible to include this information in response of resuming
27421 commands, because one resume commands can result in multiple events in
27422 different threads. Also, quite some time may pass before any event
27423 happens in the target, while a frontend needs to know whether the resuming
27424 command itself was successfully executed.
27427 Console output, and status notifications. Console output
27428 notifications are used to report output of CLI commands, as well as
27429 diagnostics for other commands. Status notifications are used to
27430 report the progress of a long-running operation. Naturally, including
27431 this information in command response would mean no output is produced
27432 until the command is finished, which is undesirable.
27435 General notifications. Commands may have various side effects on
27436 the @value{GDBN} or target state beyond their official purpose. For example,
27437 a command may change the selected thread. Although such changes can
27438 be included in command response, using notification allows for more
27439 orthogonal frontend design.
27443 There's no guarantee that whenever an MI command reports an error,
27444 @value{GDBN} or the target are in any specific state, and especially,
27445 the state is not reverted to the state before the MI command was
27446 processed. Therefore, whenever an MI command results in an error,
27447 we recommend that the frontend refreshes all the information shown in
27448 the user interface.
27452 * Context management::
27453 * Asynchronous and non-stop modes::
27457 @node Context management
27458 @subsection Context management
27460 In most cases when @value{GDBN} accesses the target, this access is
27461 done in context of a specific thread and frame (@pxref{Frames}).
27462 Often, even when accessing global data, the target requires that a thread
27463 be specified. The CLI interface maintains the selected thread and frame,
27464 and supplies them to target on each command. This is convenient,
27465 because a command line user would not want to specify that information
27466 explicitly on each command, and because user interacts with
27467 @value{GDBN} via a single terminal, so no confusion is possible as
27468 to what thread and frame are the current ones.
27470 In the case of MI, the concept of selected thread and frame is less
27471 useful. First, a frontend can easily remember this information
27472 itself. Second, a graphical frontend can have more than one window,
27473 each one used for debugging a different thread, and the frontend might
27474 want to access additional threads for internal purposes. This
27475 increases the risk that by relying on implicitly selected thread, the
27476 frontend may be operating on a wrong one. Therefore, each MI command
27477 should explicitly specify which thread and frame to operate on. To
27478 make it possible, each MI command accepts the @samp{--thread} and
27479 @samp{--frame} options, the value to each is @value{GDBN} identifier
27480 for thread and frame to operate on.
27482 Usually, each top-level window in a frontend allows the user to select
27483 a thread and a frame, and remembers the user selection for further
27484 operations. However, in some cases @value{GDBN} may suggest that the
27485 current thread be changed. For example, when stopping on a breakpoint
27486 it is reasonable to switch to the thread where breakpoint is hit. For
27487 another example, if the user issues the CLI @samp{thread} command via
27488 the frontend, it is desirable to change the frontend's selected thread to the
27489 one specified by user. @value{GDBN} communicates the suggestion to
27490 change current thread using the @samp{=thread-selected} notification.
27491 No such notification is available for the selected frame at the moment.
27493 Note that historically, MI shares the selected thread with CLI, so
27494 frontends used the @code{-thread-select} to execute commands in the
27495 right context. However, getting this to work right is cumbersome. The
27496 simplest way is for frontend to emit @code{-thread-select} command
27497 before every command. This doubles the number of commands that need
27498 to be sent. The alternative approach is to suppress @code{-thread-select}
27499 if the selected thread in @value{GDBN} is supposed to be identical to the
27500 thread the frontend wants to operate on. However, getting this
27501 optimization right can be tricky. In particular, if the frontend
27502 sends several commands to @value{GDBN}, and one of the commands changes the
27503 selected thread, then the behaviour of subsequent commands will
27504 change. So, a frontend should either wait for response from such
27505 problematic commands, or explicitly add @code{-thread-select} for
27506 all subsequent commands. No frontend is known to do this exactly
27507 right, so it is suggested to just always pass the @samp{--thread} and
27508 @samp{--frame} options.
27510 @node Asynchronous and non-stop modes
27511 @subsection Asynchronous command execution and non-stop mode
27513 On some targets, @value{GDBN} is capable of processing MI commands
27514 even while the target is running. This is called @dfn{asynchronous
27515 command execution} (@pxref{Background Execution}). The frontend may
27516 specify a preferrence for asynchronous execution using the
27517 @code{-gdb-set target-async 1} command, which should be emitted before
27518 either running the executable or attaching to the target. After the
27519 frontend has started the executable or attached to the target, it can
27520 find if asynchronous execution is enabled using the
27521 @code{-list-target-features} command.
27523 Even if @value{GDBN} can accept a command while target is running,
27524 many commands that access the target do not work when the target is
27525 running. Therefore, asynchronous command execution is most useful
27526 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27527 it is possible to examine the state of one thread, while other threads
27530 When a given thread is running, MI commands that try to access the
27531 target in the context of that thread may not work, or may work only on
27532 some targets. In particular, commands that try to operate on thread's
27533 stack will not work, on any target. Commands that read memory, or
27534 modify breakpoints, may work or not work, depending on the target. Note
27535 that even commands that operate on global state, such as @code{print},
27536 @code{set}, and breakpoint commands, still access the target in the
27537 context of a specific thread, so frontend should try to find a
27538 stopped thread and perform the operation on that thread (using the
27539 @samp{--thread} option).
27541 Which commands will work in the context of a running thread is
27542 highly target dependent. However, the two commands
27543 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27544 to find the state of a thread, will always work.
27546 @node Thread groups
27547 @subsection Thread groups
27548 @value{GDBN} may be used to debug several processes at the same time.
27549 On some platfroms, @value{GDBN} may support debugging of several
27550 hardware systems, each one having several cores with several different
27551 processes running on each core. This section describes the MI
27552 mechanism to support such debugging scenarios.
27554 The key observation is that regardless of the structure of the
27555 target, MI can have a global list of threads, because most commands that
27556 accept the @samp{--thread} option do not need to know what process that
27557 thread belongs to. Therefore, it is not necessary to introduce
27558 neither additional @samp{--process} option, nor an notion of the
27559 current process in the MI interface. The only strictly new feature
27560 that is required is the ability to find how the threads are grouped
27563 To allow the user to discover such grouping, and to support arbitrary
27564 hierarchy of machines/cores/processes, MI introduces the concept of a
27565 @dfn{thread group}. Thread group is a collection of threads and other
27566 thread groups. A thread group always has a string identifier, a type,
27567 and may have additional attributes specific to the type. A new
27568 command, @code{-list-thread-groups}, returns the list of top-level
27569 thread groups, which correspond to processes that @value{GDBN} is
27570 debugging at the moment. By passing an identifier of a thread group
27571 to the @code{-list-thread-groups} command, it is possible to obtain
27572 the members of specific thread group.
27574 To allow the user to easily discover processes, and other objects, he
27575 wishes to debug, a concept of @dfn{available thread group} is
27576 introduced. Available thread group is an thread group that
27577 @value{GDBN} is not debugging, but that can be attached to, using the
27578 @code{-target-attach} command. The list of available top-level thread
27579 groups can be obtained using @samp{-list-thread-groups --available}.
27580 In general, the content of a thread group may be only retrieved only
27581 after attaching to that thread group.
27583 Thread groups are related to inferiors (@pxref{Inferiors and
27584 Programs}). Each inferior corresponds to a thread group of a special
27585 type @samp{process}, and some additional operations are permitted on
27586 such thread groups.
27588 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27589 @node GDB/MI Command Syntax
27590 @section @sc{gdb/mi} Command Syntax
27593 * GDB/MI Input Syntax::
27594 * GDB/MI Output Syntax::
27597 @node GDB/MI Input Syntax
27598 @subsection @sc{gdb/mi} Input Syntax
27600 @cindex input syntax for @sc{gdb/mi}
27601 @cindex @sc{gdb/mi}, input syntax
27603 @item @var{command} @expansion{}
27604 @code{@var{cli-command} | @var{mi-command}}
27606 @item @var{cli-command} @expansion{}
27607 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27608 @var{cli-command} is any existing @value{GDBN} CLI command.
27610 @item @var{mi-command} @expansion{}
27611 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27612 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27614 @item @var{token} @expansion{}
27615 "any sequence of digits"
27617 @item @var{option} @expansion{}
27618 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27620 @item @var{parameter} @expansion{}
27621 @code{@var{non-blank-sequence} | @var{c-string}}
27623 @item @var{operation} @expansion{}
27624 @emph{any of the operations described in this chapter}
27626 @item @var{non-blank-sequence} @expansion{}
27627 @emph{anything, provided it doesn't contain special characters such as
27628 "-", @var{nl}, """ and of course " "}
27630 @item @var{c-string} @expansion{}
27631 @code{""" @var{seven-bit-iso-c-string-content} """}
27633 @item @var{nl} @expansion{}
27642 The CLI commands are still handled by the @sc{mi} interpreter; their
27643 output is described below.
27646 The @code{@var{token}}, when present, is passed back when the command
27650 Some @sc{mi} commands accept optional arguments as part of the parameter
27651 list. Each option is identified by a leading @samp{-} (dash) and may be
27652 followed by an optional argument parameter. Options occur first in the
27653 parameter list and can be delimited from normal parameters using
27654 @samp{--} (this is useful when some parameters begin with a dash).
27661 We want easy access to the existing CLI syntax (for debugging).
27664 We want it to be easy to spot a @sc{mi} operation.
27667 @node GDB/MI Output Syntax
27668 @subsection @sc{gdb/mi} Output Syntax
27670 @cindex output syntax of @sc{gdb/mi}
27671 @cindex @sc{gdb/mi}, output syntax
27672 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27673 followed, optionally, by a single result record. This result record
27674 is for the most recent command. The sequence of output records is
27675 terminated by @samp{(gdb)}.
27677 If an input command was prefixed with a @code{@var{token}} then the
27678 corresponding output for that command will also be prefixed by that same
27682 @item @var{output} @expansion{}
27683 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27685 @item @var{result-record} @expansion{}
27686 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27688 @item @var{out-of-band-record} @expansion{}
27689 @code{@var{async-record} | @var{stream-record}}
27691 @item @var{async-record} @expansion{}
27692 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27694 @item @var{exec-async-output} @expansion{}
27695 @code{[ @var{token} ] "*" @var{async-output}}
27697 @item @var{status-async-output} @expansion{}
27698 @code{[ @var{token} ] "+" @var{async-output}}
27700 @item @var{notify-async-output} @expansion{}
27701 @code{[ @var{token} ] "=" @var{async-output}}
27703 @item @var{async-output} @expansion{}
27704 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27706 @item @var{result-class} @expansion{}
27707 @code{"done" | "running" | "connected" | "error" | "exit"}
27709 @item @var{async-class} @expansion{}
27710 @code{"stopped" | @var{others}} (where @var{others} will be added
27711 depending on the needs---this is still in development).
27713 @item @var{result} @expansion{}
27714 @code{ @var{variable} "=" @var{value}}
27716 @item @var{variable} @expansion{}
27717 @code{ @var{string} }
27719 @item @var{value} @expansion{}
27720 @code{ @var{const} | @var{tuple} | @var{list} }
27722 @item @var{const} @expansion{}
27723 @code{@var{c-string}}
27725 @item @var{tuple} @expansion{}
27726 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27728 @item @var{list} @expansion{}
27729 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27730 @var{result} ( "," @var{result} )* "]" }
27732 @item @var{stream-record} @expansion{}
27733 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27735 @item @var{console-stream-output} @expansion{}
27736 @code{"~" @var{c-string}}
27738 @item @var{target-stream-output} @expansion{}
27739 @code{"@@" @var{c-string}}
27741 @item @var{log-stream-output} @expansion{}
27742 @code{"&" @var{c-string}}
27744 @item @var{nl} @expansion{}
27747 @item @var{token} @expansion{}
27748 @emph{any sequence of digits}.
27756 All output sequences end in a single line containing a period.
27759 The @code{@var{token}} is from the corresponding request. Note that
27760 for all async output, while the token is allowed by the grammar and
27761 may be output by future versions of @value{GDBN} for select async
27762 output messages, it is generally omitted. Frontends should treat
27763 all async output as reporting general changes in the state of the
27764 target and there should be no need to associate async output to any
27768 @cindex status output in @sc{gdb/mi}
27769 @var{status-async-output} contains on-going status information about the
27770 progress of a slow operation. It can be discarded. All status output is
27771 prefixed by @samp{+}.
27774 @cindex async output in @sc{gdb/mi}
27775 @var{exec-async-output} contains asynchronous state change on the target
27776 (stopped, started, disappeared). All async output is prefixed by
27780 @cindex notify output in @sc{gdb/mi}
27781 @var{notify-async-output} contains supplementary information that the
27782 client should handle (e.g., a new breakpoint information). All notify
27783 output is prefixed by @samp{=}.
27786 @cindex console output in @sc{gdb/mi}
27787 @var{console-stream-output} is output that should be displayed as is in the
27788 console. It is the textual response to a CLI command. All the console
27789 output is prefixed by @samp{~}.
27792 @cindex target output in @sc{gdb/mi}
27793 @var{target-stream-output} is the output produced by the target program.
27794 All the target output is prefixed by @samp{@@}.
27797 @cindex log output in @sc{gdb/mi}
27798 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27799 instance messages that should be displayed as part of an error log. All
27800 the log output is prefixed by @samp{&}.
27803 @cindex list output in @sc{gdb/mi}
27804 New @sc{gdb/mi} commands should only output @var{lists} containing
27810 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27811 details about the various output records.
27813 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27814 @node GDB/MI Compatibility with CLI
27815 @section @sc{gdb/mi} Compatibility with CLI
27817 @cindex compatibility, @sc{gdb/mi} and CLI
27818 @cindex @sc{gdb/mi}, compatibility with CLI
27820 For the developers convenience CLI commands can be entered directly,
27821 but there may be some unexpected behaviour. For example, commands
27822 that query the user will behave as if the user replied yes, breakpoint
27823 command lists are not executed and some CLI commands, such as
27824 @code{if}, @code{when} and @code{define}, prompt for further input with
27825 @samp{>}, which is not valid MI output.
27827 This feature may be removed at some stage in the future and it is
27828 recommended that front ends use the @code{-interpreter-exec} command
27829 (@pxref{-interpreter-exec}).
27831 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27832 @node GDB/MI Development and Front Ends
27833 @section @sc{gdb/mi} Development and Front Ends
27834 @cindex @sc{gdb/mi} development
27836 The application which takes the MI output and presents the state of the
27837 program being debugged to the user is called a @dfn{front end}.
27839 Although @sc{gdb/mi} is still incomplete, it is currently being used
27840 by a variety of front ends to @value{GDBN}. This makes it difficult
27841 to introduce new functionality without breaking existing usage. This
27842 section tries to minimize the problems by describing how the protocol
27845 Some changes in MI need not break a carefully designed front end, and
27846 for these the MI version will remain unchanged. The following is a
27847 list of changes that may occur within one level, so front ends should
27848 parse MI output in a way that can handle them:
27852 New MI commands may be added.
27855 New fields may be added to the output of any MI command.
27858 The range of values for fields with specified values, e.g.,
27859 @code{in_scope} (@pxref{-var-update}) may be extended.
27861 @c The format of field's content e.g type prefix, may change so parse it
27862 @c at your own risk. Yes, in general?
27864 @c The order of fields may change? Shouldn't really matter but it might
27865 @c resolve inconsistencies.
27868 If the changes are likely to break front ends, the MI version level
27869 will be increased by one. This will allow the front end to parse the
27870 output according to the MI version. Apart from mi0, new versions of
27871 @value{GDBN} will not support old versions of MI and it will be the
27872 responsibility of the front end to work with the new one.
27874 @c Starting with mi3, add a new command -mi-version that prints the MI
27877 The best way to avoid unexpected changes in MI that might break your front
27878 end is to make your project known to @value{GDBN} developers and
27879 follow development on @email{gdb@@sourceware.org} and
27880 @email{gdb-patches@@sourceware.org}.
27881 @cindex mailing lists
27883 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27884 @node GDB/MI Output Records
27885 @section @sc{gdb/mi} Output Records
27888 * GDB/MI Result Records::
27889 * GDB/MI Stream Records::
27890 * GDB/MI Async Records::
27891 * GDB/MI Breakpoint Information::
27892 * GDB/MI Frame Information::
27893 * GDB/MI Thread Information::
27894 * GDB/MI Ada Exception Information::
27897 @node GDB/MI Result Records
27898 @subsection @sc{gdb/mi} Result Records
27900 @cindex result records in @sc{gdb/mi}
27901 @cindex @sc{gdb/mi}, result records
27902 In addition to a number of out-of-band notifications, the response to a
27903 @sc{gdb/mi} command includes one of the following result indications:
27907 @item "^done" [ "," @var{results} ]
27908 The synchronous operation was successful, @code{@var{results}} are the return
27913 This result record is equivalent to @samp{^done}. Historically, it
27914 was output instead of @samp{^done} if the command has resumed the
27915 target. This behaviour is maintained for backward compatibility, but
27916 all frontends should treat @samp{^done} and @samp{^running}
27917 identically and rely on the @samp{*running} output record to determine
27918 which threads are resumed.
27922 @value{GDBN} has connected to a remote target.
27924 @item "^error" "," @var{c-string}
27926 The operation failed. The @code{@var{c-string}} contains the corresponding
27931 @value{GDBN} has terminated.
27935 @node GDB/MI Stream Records
27936 @subsection @sc{gdb/mi} Stream Records
27938 @cindex @sc{gdb/mi}, stream records
27939 @cindex stream records in @sc{gdb/mi}
27940 @value{GDBN} internally maintains a number of output streams: the console, the
27941 target, and the log. The output intended for each of these streams is
27942 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27944 Each stream record begins with a unique @dfn{prefix character} which
27945 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27946 Syntax}). In addition to the prefix, each stream record contains a
27947 @code{@var{string-output}}. This is either raw text (with an implicit new
27948 line) or a quoted C string (which does not contain an implicit newline).
27951 @item "~" @var{string-output}
27952 The console output stream contains text that should be displayed in the
27953 CLI console window. It contains the textual responses to CLI commands.
27955 @item "@@" @var{string-output}
27956 The target output stream contains any textual output from the running
27957 target. This is only present when GDB's event loop is truly
27958 asynchronous, which is currently only the case for remote targets.
27960 @item "&" @var{string-output}
27961 The log stream contains debugging messages being produced by @value{GDBN}'s
27965 @node GDB/MI Async Records
27966 @subsection @sc{gdb/mi} Async Records
27968 @cindex async records in @sc{gdb/mi}
27969 @cindex @sc{gdb/mi}, async records
27970 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27971 additional changes that have occurred. Those changes can either be a
27972 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27973 target activity (e.g., target stopped).
27975 The following is the list of possible async records:
27979 @item *running,thread-id="@var{thread}"
27980 The target is now running. The @var{thread} field tells which
27981 specific thread is now running, and can be @samp{all} if all threads
27982 are running. The frontend should assume that no interaction with a
27983 running thread is possible after this notification is produced.
27984 The frontend should not assume that this notification is output
27985 only once for any command. @value{GDBN} may emit this notification
27986 several times, either for different threads, because it cannot resume
27987 all threads together, or even for a single thread, if the thread must
27988 be stepped though some code before letting it run freely.
27990 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27991 The target has stopped. The @var{reason} field can have one of the
27995 @item breakpoint-hit
27996 A breakpoint was reached.
27997 @item watchpoint-trigger
27998 A watchpoint was triggered.
27999 @item read-watchpoint-trigger
28000 A read watchpoint was triggered.
28001 @item access-watchpoint-trigger
28002 An access watchpoint was triggered.
28003 @item function-finished
28004 An -exec-finish or similar CLI command was accomplished.
28005 @item location-reached
28006 An -exec-until or similar CLI command was accomplished.
28007 @item watchpoint-scope
28008 A watchpoint has gone out of scope.
28009 @item end-stepping-range
28010 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28011 similar CLI command was accomplished.
28012 @item exited-signalled
28013 The inferior exited because of a signal.
28015 The inferior exited.
28016 @item exited-normally
28017 The inferior exited normally.
28018 @item signal-received
28019 A signal was received by the inferior.
28021 The inferior has stopped due to a library being loaded or unloaded.
28022 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28023 set or when a @code{catch load} or @code{catch unload} catchpoint is
28024 in use (@pxref{Set Catchpoints}).
28026 The inferior has forked. This is reported when @code{catch fork}
28027 (@pxref{Set Catchpoints}) has been used.
28029 The inferior has vforked. This is reported in when @code{catch vfork}
28030 (@pxref{Set Catchpoints}) has been used.
28031 @item syscall-entry
28032 The inferior entered a system call. This is reported when @code{catch
28033 syscall} (@pxref{Set Catchpoints}) has been used.
28034 @item syscall-entry
28035 The inferior returned from a system call. This is reported when
28036 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28038 The inferior called @code{exec}. This is reported when @code{catch exec}
28039 (@pxref{Set Catchpoints}) has been used.
28042 The @var{id} field identifies the thread that directly caused the stop
28043 -- for example by hitting a breakpoint. Depending on whether all-stop
28044 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28045 stop all threads, or only the thread that directly triggered the stop.
28046 If all threads are stopped, the @var{stopped} field will have the
28047 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28048 field will be a list of thread identifiers. Presently, this list will
28049 always include a single thread, but frontend should be prepared to see
28050 several threads in the list. The @var{core} field reports the
28051 processor core on which the stop event has happened. This field may be absent
28052 if such information is not available.
28054 @item =thread-group-added,id="@var{id}"
28055 @itemx =thread-group-removed,id="@var{id}"
28056 A thread group was either added or removed. The @var{id} field
28057 contains the @value{GDBN} identifier of the thread group. When a thread
28058 group is added, it generally might not be associated with a running
28059 process. When a thread group is removed, its id becomes invalid and
28060 cannot be used in any way.
28062 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28063 A thread group became associated with a running program,
28064 either because the program was just started or the thread group
28065 was attached to a program. The @var{id} field contains the
28066 @value{GDBN} identifier of the thread group. The @var{pid} field
28067 contains process identifier, specific to the operating system.
28069 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28070 A thread group is no longer associated with a running program,
28071 either because the program has exited, or because it was detached
28072 from. The @var{id} field contains the @value{GDBN} identifier of the
28073 thread group. @var{code} is the exit code of the inferior; it exists
28074 only when the inferior exited with some code.
28076 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28077 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28078 A thread either was created, or has exited. The @var{id} field
28079 contains the @value{GDBN} identifier of the thread. The @var{gid}
28080 field identifies the thread group this thread belongs to.
28082 @item =thread-selected,id="@var{id}"
28083 Informs that the selected thread was changed as result of the last
28084 command. This notification is not emitted as result of @code{-thread-select}
28085 command but is emitted whenever an MI command that is not documented
28086 to change the selected thread actually changes it. In particular,
28087 invoking, directly or indirectly (via user-defined command), the CLI
28088 @code{thread} command, will generate this notification.
28090 We suggest that in response to this notification, front ends
28091 highlight the selected thread and cause subsequent commands to apply to
28094 @item =library-loaded,...
28095 Reports that a new library file was loaded by the program. This
28096 notification has 4 fields---@var{id}, @var{target-name},
28097 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28098 opaque identifier of the library. For remote debugging case,
28099 @var{target-name} and @var{host-name} fields give the name of the
28100 library file on the target, and on the host respectively. For native
28101 debugging, both those fields have the same value. The
28102 @var{symbols-loaded} field is emitted only for backward compatibility
28103 and should not be relied on to convey any useful information. The
28104 @var{thread-group} field, if present, specifies the id of the thread
28105 group in whose context the library was loaded. If the field is
28106 absent, it means the library was loaded in the context of all present
28109 @item =library-unloaded,...
28110 Reports that a library was unloaded by the program. This notification
28111 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28112 the same meaning as for the @code{=library-loaded} notification.
28113 The @var{thread-group} field, if present, specifies the id of the
28114 thread group in whose context the library was unloaded. If the field is
28115 absent, it means the library was unloaded in the context of all present
28118 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28119 @itemx =traceframe-changed,end
28120 Reports that the trace frame was changed and its new number is
28121 @var{tfnum}. The number of the tracepoint associated with this trace
28122 frame is @var{tpnum}.
28124 @item =tsv-created,name=@var{name},initial=@var{initial}
28125 Reports that the new trace state variable @var{name} is created with
28126 initial value @var{initial}.
28128 @item =tsv-deleted,name=@var{name}
28129 @itemx =tsv-deleted
28130 Reports that the trace state variable @var{name} is deleted or all
28131 trace state variables are deleted.
28133 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28134 Reports that the trace state variable @var{name} is modified with
28135 the initial value @var{initial}. The current value @var{current} of
28136 trace state variable is optional and is reported if the current
28137 value of trace state variable is known.
28139 @item =breakpoint-created,bkpt=@{...@}
28140 @itemx =breakpoint-modified,bkpt=@{...@}
28141 @itemx =breakpoint-deleted,id=@var{number}
28142 Reports that a breakpoint was created, modified, or deleted,
28143 respectively. Only user-visible breakpoints are reported to the MI
28146 The @var{bkpt} argument is of the same form as returned by the various
28147 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28148 @var{number} is the ordinal number of the breakpoint.
28150 Note that if a breakpoint is emitted in the result record of a
28151 command, then it will not also be emitted in an async record.
28153 @item =record-started,thread-group="@var{id}"
28154 @itemx =record-stopped,thread-group="@var{id}"
28155 Execution log recording was either started or stopped on an
28156 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28157 group corresponding to the affected inferior.
28159 @item =cmd-param-changed,param=@var{param},value=@var{value}
28160 Reports that a parameter of the command @code{set @var{param}} is
28161 changed to @var{value}. In the multi-word @code{set} command,
28162 the @var{param} is the whole parameter list to @code{set} command.
28163 For example, In command @code{set check type on}, @var{param}
28164 is @code{check type} and @var{value} is @code{on}.
28166 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28167 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28168 written in an inferior. The @var{id} is the identifier of the
28169 thread group corresponding to the affected inferior. The optional
28170 @code{type="code"} part is reported if the memory written to holds
28174 @node GDB/MI Breakpoint Information
28175 @subsection @sc{gdb/mi} Breakpoint Information
28177 When @value{GDBN} reports information about a breakpoint, a
28178 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28183 The breakpoint number. For a breakpoint that represents one location
28184 of a multi-location breakpoint, this will be a dotted pair, like
28188 The type of the breakpoint. For ordinary breakpoints this will be
28189 @samp{breakpoint}, but many values are possible.
28192 If the type of the breakpoint is @samp{catchpoint}, then this
28193 indicates the exact type of catchpoint.
28196 This is the breakpoint disposition---either @samp{del}, meaning that
28197 the breakpoint will be deleted at the next stop, or @samp{keep},
28198 meaning that the breakpoint will not be deleted.
28201 This indicates whether the breakpoint is enabled, in which case the
28202 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28203 Note that this is not the same as the field @code{enable}.
28206 The address of the breakpoint. This may be a hexidecimal number,
28207 giving the address; or the string @samp{<PENDING>}, for a pending
28208 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28209 multiple locations. This field will not be present if no address can
28210 be determined. For example, a watchpoint does not have an address.
28213 If known, the function in which the breakpoint appears.
28214 If not known, this field is not present.
28217 The name of the source file which contains this function, if known.
28218 If not known, this field is not present.
28221 The full file name of the source file which contains this function, if
28222 known. If not known, this field is not present.
28225 The line number at which this breakpoint appears, if known.
28226 If not known, this field is not present.
28229 If the source file is not known, this field may be provided. If
28230 provided, this holds the address of the breakpoint, possibly followed
28234 If this breakpoint is pending, this field is present and holds the
28235 text used to set the breakpoint, as entered by the user.
28238 Where this breakpoint's condition is evaluated, either @samp{host} or
28242 If this is a thread-specific breakpoint, then this identifies the
28243 thread in which the breakpoint can trigger.
28246 If this breakpoint is restricted to a particular Ada task, then this
28247 field will hold the task identifier.
28250 If the breakpoint is conditional, this is the condition expression.
28253 The ignore count of the breakpoint.
28256 The enable count of the breakpoint.
28258 @item traceframe-usage
28261 @item static-tracepoint-marker-string-id
28262 For a static tracepoint, the name of the static tracepoint marker.
28265 For a masked watchpoint, this is the mask.
28268 A tracepoint's pass count.
28270 @item original-location
28271 The location of the breakpoint as originally specified by the user.
28272 This field is optional.
28275 The number of times the breakpoint has been hit.
28278 This field is only given for tracepoints. This is either @samp{y},
28279 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28283 Some extra data, the exact contents of which are type-dependent.
28287 For example, here is what the output of @code{-break-insert}
28288 (@pxref{GDB/MI Breakpoint Commands}) might be:
28291 -> -break-insert main
28292 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28293 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28294 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28299 @node GDB/MI Frame Information
28300 @subsection @sc{gdb/mi} Frame Information
28302 Response from many MI commands includes an information about stack
28303 frame. This information is a tuple that may have the following
28308 The level of the stack frame. The innermost frame has the level of
28309 zero. This field is always present.
28312 The name of the function corresponding to the frame. This field may
28313 be absent if @value{GDBN} is unable to determine the function name.
28316 The code address for the frame. This field is always present.
28319 The name of the source files that correspond to the frame's code
28320 address. This field may be absent.
28323 The source line corresponding to the frames' code address. This field
28327 The name of the binary file (either executable or shared library) the
28328 corresponds to the frame's code address. This field may be absent.
28332 @node GDB/MI Thread Information
28333 @subsection @sc{gdb/mi} Thread Information
28335 Whenever @value{GDBN} has to report an information about a thread, it
28336 uses a tuple with the following fields:
28340 The numeric id assigned to the thread by @value{GDBN}. This field is
28344 Target-specific string identifying the thread. This field is always present.
28347 Additional information about the thread provided by the target.
28348 It is supposed to be human-readable and not interpreted by the
28349 frontend. This field is optional.
28352 Either @samp{stopped} or @samp{running}, depending on whether the
28353 thread is presently running. This field is always present.
28356 The value of this field is an integer number of the processor core the
28357 thread was last seen on. This field is optional.
28360 @node GDB/MI Ada Exception Information
28361 @subsection @sc{gdb/mi} Ada Exception Information
28363 Whenever a @code{*stopped} record is emitted because the program
28364 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28365 @value{GDBN} provides the name of the exception that was raised via
28366 the @code{exception-name} field.
28368 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28369 @node GDB/MI Simple Examples
28370 @section Simple Examples of @sc{gdb/mi} Interaction
28371 @cindex @sc{gdb/mi}, simple examples
28373 This subsection presents several simple examples of interaction using
28374 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28375 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28376 the output received from @sc{gdb/mi}.
28378 Note the line breaks shown in the examples are here only for
28379 readability, they don't appear in the real output.
28381 @subheading Setting a Breakpoint
28383 Setting a breakpoint generates synchronous output which contains detailed
28384 information of the breakpoint.
28387 -> -break-insert main
28388 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28389 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28390 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28395 @subheading Program Execution
28397 Program execution generates asynchronous records and MI gives the
28398 reason that execution stopped.
28404 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28405 frame=@{addr="0x08048564",func="main",
28406 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28407 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28412 <- *stopped,reason="exited-normally"
28416 @subheading Quitting @value{GDBN}
28418 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28426 Please note that @samp{^exit} is printed immediately, but it might
28427 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28428 performs necessary cleanups, including killing programs being debugged
28429 or disconnecting from debug hardware, so the frontend should wait till
28430 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28431 fails to exit in reasonable time.
28433 @subheading A Bad Command
28435 Here's what happens if you pass a non-existent command:
28439 <- ^error,msg="Undefined MI command: rubbish"
28444 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28445 @node GDB/MI Command Description Format
28446 @section @sc{gdb/mi} Command Description Format
28448 The remaining sections describe blocks of commands. Each block of
28449 commands is laid out in a fashion similar to this section.
28451 @subheading Motivation
28453 The motivation for this collection of commands.
28455 @subheading Introduction
28457 A brief introduction to this collection of commands as a whole.
28459 @subheading Commands
28461 For each command in the block, the following is described:
28463 @subsubheading Synopsis
28466 -command @var{args}@dots{}
28469 @subsubheading Result
28471 @subsubheading @value{GDBN} Command
28473 The corresponding @value{GDBN} CLI command(s), if any.
28475 @subsubheading Example
28477 Example(s) formatted for readability. Some of the described commands have
28478 not been implemented yet and these are labeled N.A.@: (not available).
28481 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28482 @node GDB/MI Breakpoint Commands
28483 @section @sc{gdb/mi} Breakpoint Commands
28485 @cindex breakpoint commands for @sc{gdb/mi}
28486 @cindex @sc{gdb/mi}, breakpoint commands
28487 This section documents @sc{gdb/mi} commands for manipulating
28490 @subheading The @code{-break-after} Command
28491 @findex -break-after
28493 @subsubheading Synopsis
28496 -break-after @var{number} @var{count}
28499 The breakpoint number @var{number} is not in effect until it has been
28500 hit @var{count} times. To see how this is reflected in the output of
28501 the @samp{-break-list} command, see the description of the
28502 @samp{-break-list} command below.
28504 @subsubheading @value{GDBN} Command
28506 The corresponding @value{GDBN} command is @samp{ignore}.
28508 @subsubheading Example
28513 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28514 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28515 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28523 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28524 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28525 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28526 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28527 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28528 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28529 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28530 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28531 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28532 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28537 @subheading The @code{-break-catch} Command
28538 @findex -break-catch
28541 @subheading The @code{-break-commands} Command
28542 @findex -break-commands
28544 @subsubheading Synopsis
28547 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28550 Specifies the CLI commands that should be executed when breakpoint
28551 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28552 are the commands. If no command is specified, any previously-set
28553 commands are cleared. @xref{Break Commands}. Typical use of this
28554 functionality is tracing a program, that is, printing of values of
28555 some variables whenever breakpoint is hit and then continuing.
28557 @subsubheading @value{GDBN} Command
28559 The corresponding @value{GDBN} command is @samp{commands}.
28561 @subsubheading Example
28566 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28567 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28568 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28571 -break-commands 1 "print v" "continue"
28576 @subheading The @code{-break-condition} Command
28577 @findex -break-condition
28579 @subsubheading Synopsis
28582 -break-condition @var{number} @var{expr}
28585 Breakpoint @var{number} will stop the program only if the condition in
28586 @var{expr} is true. The condition becomes part of the
28587 @samp{-break-list} output (see the description of the @samp{-break-list}
28590 @subsubheading @value{GDBN} Command
28592 The corresponding @value{GDBN} command is @samp{condition}.
28594 @subsubheading Example
28598 -break-condition 1 1
28602 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28603 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28604 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28605 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28606 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28607 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28608 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28609 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28610 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28611 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28615 @subheading The @code{-break-delete} Command
28616 @findex -break-delete
28618 @subsubheading Synopsis
28621 -break-delete ( @var{breakpoint} )+
28624 Delete the breakpoint(s) whose number(s) are specified in the argument
28625 list. This is obviously reflected in the breakpoint list.
28627 @subsubheading @value{GDBN} Command
28629 The corresponding @value{GDBN} command is @samp{delete}.
28631 @subsubheading Example
28639 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28640 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28641 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28642 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28643 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28644 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28645 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28650 @subheading The @code{-break-disable} Command
28651 @findex -break-disable
28653 @subsubheading Synopsis
28656 -break-disable ( @var{breakpoint} )+
28659 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28660 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28662 @subsubheading @value{GDBN} Command
28664 The corresponding @value{GDBN} command is @samp{disable}.
28666 @subsubheading Example
28674 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28675 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28676 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28677 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28678 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28679 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28680 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28681 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28682 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28683 line="5",thread-groups=["i1"],times="0"@}]@}
28687 @subheading The @code{-break-enable} Command
28688 @findex -break-enable
28690 @subsubheading Synopsis
28693 -break-enable ( @var{breakpoint} )+
28696 Enable (previously disabled) @var{breakpoint}(s).
28698 @subsubheading @value{GDBN} Command
28700 The corresponding @value{GDBN} command is @samp{enable}.
28702 @subsubheading Example
28710 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28711 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28712 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28713 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28714 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28715 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28716 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28717 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28718 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28719 line="5",thread-groups=["i1"],times="0"@}]@}
28723 @subheading The @code{-break-info} Command
28724 @findex -break-info
28726 @subsubheading Synopsis
28729 -break-info @var{breakpoint}
28733 Get information about a single breakpoint.
28735 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28736 Information}, for details on the format of each breakpoint in the
28739 @subsubheading @value{GDBN} Command
28741 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28743 @subsubheading Example
28746 @subheading The @code{-break-insert} Command
28747 @findex -break-insert
28749 @subsubheading Synopsis
28752 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28753 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28754 [ -p @var{thread-id} ] [ @var{location} ]
28758 If specified, @var{location}, can be one of:
28765 @item filename:linenum
28766 @item filename:function
28770 The possible optional parameters of this command are:
28774 Insert a temporary breakpoint.
28776 Insert a hardware breakpoint.
28778 If @var{location} cannot be parsed (for example if it
28779 refers to unknown files or functions), create a pending
28780 breakpoint. Without this flag, @value{GDBN} will report
28781 an error, and won't create a breakpoint, if @var{location}
28784 Create a disabled breakpoint.
28786 Create a tracepoint. @xref{Tracepoints}. When this parameter
28787 is used together with @samp{-h}, a fast tracepoint is created.
28788 @item -c @var{condition}
28789 Make the breakpoint conditional on @var{condition}.
28790 @item -i @var{ignore-count}
28791 Initialize the @var{ignore-count}.
28792 @item -p @var{thread-id}
28793 Restrict the breakpoint to the specified @var{thread-id}.
28796 @subsubheading Result
28798 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28799 resulting breakpoint.
28801 Note: this format is open to change.
28802 @c An out-of-band breakpoint instead of part of the result?
28804 @subsubheading @value{GDBN} Command
28806 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28807 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28809 @subsubheading Example
28814 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28815 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28818 -break-insert -t foo
28819 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28820 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28824 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28825 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28826 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28827 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28828 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28829 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28830 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28831 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28832 addr="0x0001072c", func="main",file="recursive2.c",
28833 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28835 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28836 addr="0x00010774",func="foo",file="recursive2.c",
28837 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28840 @c -break-insert -r foo.*
28841 @c ~int foo(int, int);
28842 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28843 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28848 @subheading The @code{-break-list} Command
28849 @findex -break-list
28851 @subsubheading Synopsis
28857 Displays the list of inserted breakpoints, showing the following fields:
28861 number of the breakpoint
28863 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28865 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28868 is the breakpoint enabled or no: @samp{y} or @samp{n}
28870 memory location at which the breakpoint is set
28872 logical location of the breakpoint, expressed by function name, file
28874 @item Thread-groups
28875 list of thread groups to which this breakpoint applies
28877 number of times the breakpoint has been hit
28880 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28881 @code{body} field is an empty list.
28883 @subsubheading @value{GDBN} Command
28885 The corresponding @value{GDBN} command is @samp{info break}.
28887 @subsubheading Example
28892 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28893 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28894 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28895 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28896 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28897 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28898 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28899 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28900 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28902 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28903 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28904 line="13",thread-groups=["i1"],times="0"@}]@}
28908 Here's an example of the result when there are no breakpoints:
28913 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28914 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28915 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28916 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28917 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28918 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28919 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28924 @subheading The @code{-break-passcount} Command
28925 @findex -break-passcount
28927 @subsubheading Synopsis
28930 -break-passcount @var{tracepoint-number} @var{passcount}
28933 Set the passcount for tracepoint @var{tracepoint-number} to
28934 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28935 is not a tracepoint, error is emitted. This corresponds to CLI
28936 command @samp{passcount}.
28938 @subheading The @code{-break-watch} Command
28939 @findex -break-watch
28941 @subsubheading Synopsis
28944 -break-watch [ -a | -r ]
28947 Create a watchpoint. With the @samp{-a} option it will create an
28948 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28949 read from or on a write to the memory location. With the @samp{-r}
28950 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28951 trigger only when the memory location is accessed for reading. Without
28952 either of the options, the watchpoint created is a regular watchpoint,
28953 i.e., it will trigger when the memory location is accessed for writing.
28954 @xref{Set Watchpoints, , Setting Watchpoints}.
28956 Note that @samp{-break-list} will report a single list of watchpoints and
28957 breakpoints inserted.
28959 @subsubheading @value{GDBN} Command
28961 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28964 @subsubheading Example
28966 Setting a watchpoint on a variable in the @code{main} function:
28971 ^done,wpt=@{number="2",exp="x"@}
28976 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28977 value=@{old="-268439212",new="55"@},
28978 frame=@{func="main",args=[],file="recursive2.c",
28979 fullname="/home/foo/bar/recursive2.c",line="5"@}
28983 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28984 the program execution twice: first for the variable changing value, then
28985 for the watchpoint going out of scope.
28990 ^done,wpt=@{number="5",exp="C"@}
28995 *stopped,reason="watchpoint-trigger",
28996 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28997 frame=@{func="callee4",args=[],
28998 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28999 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29004 *stopped,reason="watchpoint-scope",wpnum="5",
29005 frame=@{func="callee3",args=[@{name="strarg",
29006 value="0x11940 \"A string argument.\""@}],
29007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29012 Listing breakpoints and watchpoints, at different points in the program
29013 execution. Note that once the watchpoint goes out of scope, it is
29019 ^done,wpt=@{number="2",exp="C"@}
29022 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29029 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29030 addr="0x00010734",func="callee4",
29031 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29032 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29034 bkpt=@{number="2",type="watchpoint",disp="keep",
29035 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29040 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29041 value=@{old="-276895068",new="3"@},
29042 frame=@{func="callee4",args=[],
29043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29044 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29047 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29048 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29049 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29050 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29051 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29052 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29053 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29054 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29055 addr="0x00010734",func="callee4",
29056 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29057 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29059 bkpt=@{number="2",type="watchpoint",disp="keep",
29060 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29064 ^done,reason="watchpoint-scope",wpnum="2",
29065 frame=@{func="callee3",args=[@{name="strarg",
29066 value="0x11940 \"A string argument.\""@}],
29067 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29068 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29071 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29072 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29073 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29074 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29075 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29076 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29077 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29078 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29079 addr="0x00010734",func="callee4",
29080 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29081 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29082 thread-groups=["i1"],times="1"@}]@}
29087 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29088 @node GDB/MI Catchpoint Commands
29089 @section @sc{gdb/mi} Catchpoint Commands
29091 This section documents @sc{gdb/mi} commands for manipulating
29094 @subheading The @code{-catch-load} Command
29095 @findex -catch-load
29097 @subsubheading Synopsis
29100 -catch-load [ -t ] [ -d ] @var{regexp}
29103 Add a catchpoint for library load events. If the @samp{-t} option is used,
29104 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29105 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29106 in a disabled state. The @samp{regexp} argument is a regular
29107 expression used to match the name of the loaded library.
29110 @subsubheading @value{GDBN} Command
29112 The corresponding @value{GDBN} command is @samp{catch load}.
29114 @subsubheading Example
29117 -catch-load -t foo.so
29118 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29119 what="load of library matching foo.so",catch-type="load",times="0"@}
29124 @subheading The @code{-catch-unload} Command
29125 @findex -catch-unload
29127 @subsubheading Synopsis
29130 -catch-unload [ -t ] [ -d ] @var{regexp}
29133 Add a catchpoint for library unload events. If the @samp{-t} option is
29134 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29135 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29136 created in a disabled state. The @samp{regexp} argument is a regular
29137 expression used to match the name of the unloaded library.
29139 @subsubheading @value{GDBN} Command
29141 The corresponding @value{GDBN} command is @samp{catch unload}.
29143 @subsubheading Example
29146 -catch-unload -d bar.so
29147 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29148 what="load of library matching bar.so",catch-type="unload",times="0"@}
29153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29154 @node GDB/MI Program Context
29155 @section @sc{gdb/mi} Program Context
29157 @subheading The @code{-exec-arguments} Command
29158 @findex -exec-arguments
29161 @subsubheading Synopsis
29164 -exec-arguments @var{args}
29167 Set the inferior program arguments, to be used in the next
29170 @subsubheading @value{GDBN} Command
29172 The corresponding @value{GDBN} command is @samp{set args}.
29174 @subsubheading Example
29178 -exec-arguments -v word
29185 @subheading The @code{-exec-show-arguments} Command
29186 @findex -exec-show-arguments
29188 @subsubheading Synopsis
29191 -exec-show-arguments
29194 Print the arguments of the program.
29196 @subsubheading @value{GDBN} Command
29198 The corresponding @value{GDBN} command is @samp{show args}.
29200 @subsubheading Example
29205 @subheading The @code{-environment-cd} Command
29206 @findex -environment-cd
29208 @subsubheading Synopsis
29211 -environment-cd @var{pathdir}
29214 Set @value{GDBN}'s working directory.
29216 @subsubheading @value{GDBN} Command
29218 The corresponding @value{GDBN} command is @samp{cd}.
29220 @subsubheading Example
29224 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29230 @subheading The @code{-environment-directory} Command
29231 @findex -environment-directory
29233 @subsubheading Synopsis
29236 -environment-directory [ -r ] [ @var{pathdir} ]+
29239 Add directories @var{pathdir} to beginning of search path for source files.
29240 If the @samp{-r} option is used, the search path is reset to the default
29241 search path. If directories @var{pathdir} are supplied in addition to the
29242 @samp{-r} option, the search path is first reset and then addition
29244 Multiple directories may be specified, separated by blanks. Specifying
29245 multiple directories in a single command
29246 results in the directories added to the beginning of the
29247 search path in the same order they were presented in the command.
29248 If blanks are needed as
29249 part of a directory name, double-quotes should be used around
29250 the name. In the command output, the path will show up separated
29251 by the system directory-separator character. The directory-separator
29252 character must not be used
29253 in any directory name.
29254 If no directories are specified, the current search path is displayed.
29256 @subsubheading @value{GDBN} Command
29258 The corresponding @value{GDBN} command is @samp{dir}.
29260 @subsubheading Example
29264 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29265 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29267 -environment-directory ""
29268 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29270 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29271 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29273 -environment-directory -r
29274 ^done,source-path="$cdir:$cwd"
29279 @subheading The @code{-environment-path} Command
29280 @findex -environment-path
29282 @subsubheading Synopsis
29285 -environment-path [ -r ] [ @var{pathdir} ]+
29288 Add directories @var{pathdir} to beginning of search path for object files.
29289 If the @samp{-r} option is used, the search path is reset to the original
29290 search path that existed at gdb start-up. If directories @var{pathdir} are
29291 supplied in addition to the
29292 @samp{-r} option, the search path is first reset and then addition
29294 Multiple directories may be specified, separated by blanks. Specifying
29295 multiple directories in a single command
29296 results in the directories added to the beginning of the
29297 search path in the same order they were presented in the command.
29298 If blanks are needed as
29299 part of a directory name, double-quotes should be used around
29300 the name. In the command output, the path will show up separated
29301 by the system directory-separator character. The directory-separator
29302 character must not be used
29303 in any directory name.
29304 If no directories are specified, the current path is displayed.
29307 @subsubheading @value{GDBN} Command
29309 The corresponding @value{GDBN} command is @samp{path}.
29311 @subsubheading Example
29316 ^done,path="/usr/bin"
29318 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29319 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29321 -environment-path -r /usr/local/bin
29322 ^done,path="/usr/local/bin:/usr/bin"
29327 @subheading The @code{-environment-pwd} Command
29328 @findex -environment-pwd
29330 @subsubheading Synopsis
29336 Show the current working directory.
29338 @subsubheading @value{GDBN} Command
29340 The corresponding @value{GDBN} command is @samp{pwd}.
29342 @subsubheading Example
29347 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29351 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29352 @node GDB/MI Thread Commands
29353 @section @sc{gdb/mi} Thread Commands
29356 @subheading The @code{-thread-info} Command
29357 @findex -thread-info
29359 @subsubheading Synopsis
29362 -thread-info [ @var{thread-id} ]
29365 Reports information about either a specific thread, if
29366 the @var{thread-id} parameter is present, or about all
29367 threads. When printing information about all threads,
29368 also reports the current thread.
29370 @subsubheading @value{GDBN} Command
29372 The @samp{info thread} command prints the same information
29375 @subsubheading Result
29377 The result is a list of threads. The following attributes are
29378 defined for a given thread:
29382 This field exists only for the current thread. It has the value @samp{*}.
29385 The identifier that @value{GDBN} uses to refer to the thread.
29388 The identifier that the target uses to refer to the thread.
29391 Extra information about the thread, in a target-specific format. This
29395 The name of the thread. If the user specified a name using the
29396 @code{thread name} command, then this name is given. Otherwise, if
29397 @value{GDBN} can extract the thread name from the target, then that
29398 name is given. If @value{GDBN} cannot find the thread name, then this
29402 The stack frame currently executing in the thread.
29405 The thread's state. The @samp{state} field may have the following
29410 The thread is stopped. Frame information is available for stopped
29414 The thread is running. There's no frame information for running
29420 If @value{GDBN} can find the CPU core on which this thread is running,
29421 then this field is the core identifier. This field is optional.
29425 @subsubheading Example
29430 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29431 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29432 args=[]@},state="running"@},
29433 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29434 frame=@{level="0",addr="0x0804891f",func="foo",
29435 args=[@{name="i",value="10"@}],
29436 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29437 state="running"@}],
29438 current-thread-id="1"
29442 @subheading The @code{-thread-list-ids} Command
29443 @findex -thread-list-ids
29445 @subsubheading Synopsis
29451 Produces a list of the currently known @value{GDBN} thread ids. At the
29452 end of the list it also prints the total number of such threads.
29454 This command is retained for historical reasons, the
29455 @code{-thread-info} command should be used instead.
29457 @subsubheading @value{GDBN} Command
29459 Part of @samp{info threads} supplies the same information.
29461 @subsubheading Example
29466 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29467 current-thread-id="1",number-of-threads="3"
29472 @subheading The @code{-thread-select} Command
29473 @findex -thread-select
29475 @subsubheading Synopsis
29478 -thread-select @var{threadnum}
29481 Make @var{threadnum} the current thread. It prints the number of the new
29482 current thread, and the topmost frame for that thread.
29484 This command is deprecated in favor of explicitly using the
29485 @samp{--thread} option to each command.
29487 @subsubheading @value{GDBN} Command
29489 The corresponding @value{GDBN} command is @samp{thread}.
29491 @subsubheading Example
29498 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29499 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29503 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29504 number-of-threads="3"
29507 ^done,new-thread-id="3",
29508 frame=@{level="0",func="vprintf",
29509 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29510 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29514 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29515 @node GDB/MI Ada Tasking Commands
29516 @section @sc{gdb/mi} Ada Tasking Commands
29518 @subheading The @code{-ada-task-info} Command
29519 @findex -ada-task-info
29521 @subsubheading Synopsis
29524 -ada-task-info [ @var{task-id} ]
29527 Reports information about either a specific Ada task, if the
29528 @var{task-id} parameter is present, or about all Ada tasks.
29530 @subsubheading @value{GDBN} Command
29532 The @samp{info tasks} command prints the same information
29533 about all Ada tasks (@pxref{Ada Tasks}).
29535 @subsubheading Result
29537 The result is a table of Ada tasks. The following columns are
29538 defined for each Ada task:
29542 This field exists only for the current thread. It has the value @samp{*}.
29545 The identifier that @value{GDBN} uses to refer to the Ada task.
29548 The identifier that the target uses to refer to the Ada task.
29551 The identifier of the thread corresponding to the Ada task.
29553 This field should always exist, as Ada tasks are always implemented
29554 on top of a thread. But if @value{GDBN} cannot find this corresponding
29555 thread for any reason, the field is omitted.
29558 This field exists only when the task was created by another task.
29559 In this case, it provides the ID of the parent task.
29562 The base priority of the task.
29565 The current state of the task. For a detailed description of the
29566 possible states, see @ref{Ada Tasks}.
29569 The name of the task.
29573 @subsubheading Example
29577 ^done,tasks=@{nr_rows="3",nr_cols="8",
29578 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29579 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29580 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29581 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29582 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29583 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29584 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29585 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29586 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29587 state="Child Termination Wait",name="main_task"@}]@}
29591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29592 @node GDB/MI Program Execution
29593 @section @sc{gdb/mi} Program Execution
29595 These are the asynchronous commands which generate the out-of-band
29596 record @samp{*stopped}. Currently @value{GDBN} only really executes
29597 asynchronously with remote targets and this interaction is mimicked in
29600 @subheading The @code{-exec-continue} Command
29601 @findex -exec-continue
29603 @subsubheading Synopsis
29606 -exec-continue [--reverse] [--all|--thread-group N]
29609 Resumes the execution of the inferior program, which will continue
29610 to execute until it reaches a debugger stop event. If the
29611 @samp{--reverse} option is specified, execution resumes in reverse until
29612 it reaches a stop event. Stop events may include
29615 breakpoints or watchpoints
29617 signals or exceptions
29619 the end of the process (or its beginning under @samp{--reverse})
29621 the end or beginning of a replay log if one is being used.
29623 In all-stop mode (@pxref{All-Stop
29624 Mode}), may resume only one thread, or all threads, depending on the
29625 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29626 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29627 ignored in all-stop mode. If the @samp{--thread-group} options is
29628 specified, then all threads in that thread group are resumed.
29630 @subsubheading @value{GDBN} Command
29632 The corresponding @value{GDBN} corresponding is @samp{continue}.
29634 @subsubheading Example
29641 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29642 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29648 @subheading The @code{-exec-finish} Command
29649 @findex -exec-finish
29651 @subsubheading Synopsis
29654 -exec-finish [--reverse]
29657 Resumes the execution of the inferior program until the current
29658 function is exited. Displays the results returned by the function.
29659 If the @samp{--reverse} option is specified, resumes the reverse
29660 execution of the inferior program until the point where current
29661 function was called.
29663 @subsubheading @value{GDBN} Command
29665 The corresponding @value{GDBN} command is @samp{finish}.
29667 @subsubheading Example
29669 Function returning @code{void}.
29676 *stopped,reason="function-finished",frame=@{func="main",args=[],
29677 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29681 Function returning other than @code{void}. The name of the internal
29682 @value{GDBN} variable storing the result is printed, together with the
29689 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29690 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29691 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29692 gdb-result-var="$1",return-value="0"
29697 @subheading The @code{-exec-interrupt} Command
29698 @findex -exec-interrupt
29700 @subsubheading Synopsis
29703 -exec-interrupt [--all|--thread-group N]
29706 Interrupts the background execution of the target. Note how the token
29707 associated with the stop message is the one for the execution command
29708 that has been interrupted. The token for the interrupt itself only
29709 appears in the @samp{^done} output. If the user is trying to
29710 interrupt a non-running program, an error message will be printed.
29712 Note that when asynchronous execution is enabled, this command is
29713 asynchronous just like other execution commands. That is, first the
29714 @samp{^done} response will be printed, and the target stop will be
29715 reported after that using the @samp{*stopped} notification.
29717 In non-stop mode, only the context thread is interrupted by default.
29718 All threads (in all inferiors) will be interrupted if the
29719 @samp{--all} option is specified. If the @samp{--thread-group}
29720 option is specified, all threads in that group will be interrupted.
29722 @subsubheading @value{GDBN} Command
29724 The corresponding @value{GDBN} command is @samp{interrupt}.
29726 @subsubheading Example
29737 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29738 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29739 fullname="/home/foo/bar/try.c",line="13"@}
29744 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29748 @subheading The @code{-exec-jump} Command
29751 @subsubheading Synopsis
29754 -exec-jump @var{location}
29757 Resumes execution of the inferior program at the location specified by
29758 parameter. @xref{Specify Location}, for a description of the
29759 different forms of @var{location}.
29761 @subsubheading @value{GDBN} Command
29763 The corresponding @value{GDBN} command is @samp{jump}.
29765 @subsubheading Example
29768 -exec-jump foo.c:10
29769 *running,thread-id="all"
29774 @subheading The @code{-exec-next} Command
29777 @subsubheading Synopsis
29780 -exec-next [--reverse]
29783 Resumes execution of the inferior program, stopping when the beginning
29784 of the next source line is reached.
29786 If the @samp{--reverse} option is specified, resumes reverse execution
29787 of the inferior program, stopping at the beginning of the previous
29788 source line. If you issue this command on the first line of a
29789 function, it will take you back to the caller of that function, to the
29790 source line where the function was called.
29793 @subsubheading @value{GDBN} Command
29795 The corresponding @value{GDBN} command is @samp{next}.
29797 @subsubheading Example
29803 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29808 @subheading The @code{-exec-next-instruction} Command
29809 @findex -exec-next-instruction
29811 @subsubheading Synopsis
29814 -exec-next-instruction [--reverse]
29817 Executes one machine instruction. If the instruction is a function
29818 call, continues until the function returns. If the program stops at an
29819 instruction in the middle of a source line, the address will be
29822 If the @samp{--reverse} option is specified, resumes reverse execution
29823 of the inferior program, stopping at the previous instruction. If the
29824 previously executed instruction was a return from another function,
29825 it will continue to execute in reverse until the call to that function
29826 (from the current stack frame) is reached.
29828 @subsubheading @value{GDBN} Command
29830 The corresponding @value{GDBN} command is @samp{nexti}.
29832 @subsubheading Example
29836 -exec-next-instruction
29840 *stopped,reason="end-stepping-range",
29841 addr="0x000100d4",line="5",file="hello.c"
29846 @subheading The @code{-exec-return} Command
29847 @findex -exec-return
29849 @subsubheading Synopsis
29855 Makes current function return immediately. Doesn't execute the inferior.
29856 Displays the new current frame.
29858 @subsubheading @value{GDBN} Command
29860 The corresponding @value{GDBN} command is @samp{return}.
29862 @subsubheading Example
29866 200-break-insert callee4
29867 200^done,bkpt=@{number="1",addr="0x00010734",
29868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29873 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29874 frame=@{func="callee4",args=[],
29875 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29876 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29882 111^done,frame=@{level="0",func="callee3",
29883 args=[@{name="strarg",
29884 value="0x11940 \"A string argument.\""@}],
29885 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29886 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29891 @subheading The @code{-exec-run} Command
29894 @subsubheading Synopsis
29897 -exec-run [--all | --thread-group N]
29900 Starts execution of the inferior from the beginning. The inferior
29901 executes until either a breakpoint is encountered or the program
29902 exits. In the latter case the output will include an exit code, if
29903 the program has exited exceptionally.
29905 When no option is specified, the current inferior is started. If the
29906 @samp{--thread-group} option is specified, it should refer to a thread
29907 group of type @samp{process}, and that thread group will be started.
29908 If the @samp{--all} option is specified, then all inferiors will be started.
29910 @subsubheading @value{GDBN} Command
29912 The corresponding @value{GDBN} command is @samp{run}.
29914 @subsubheading Examples
29919 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29924 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29925 frame=@{func="main",args=[],file="recursive2.c",
29926 fullname="/home/foo/bar/recursive2.c",line="4"@}
29931 Program exited normally:
29939 *stopped,reason="exited-normally"
29944 Program exited exceptionally:
29952 *stopped,reason="exited",exit-code="01"
29956 Another way the program can terminate is if it receives a signal such as
29957 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29961 *stopped,reason="exited-signalled",signal-name="SIGINT",
29962 signal-meaning="Interrupt"
29966 @c @subheading -exec-signal
29969 @subheading The @code{-exec-step} Command
29972 @subsubheading Synopsis
29975 -exec-step [--reverse]
29978 Resumes execution of the inferior program, stopping when the beginning
29979 of the next source line is reached, if the next source line is not a
29980 function call. If it is, stop at the first instruction of the called
29981 function. If the @samp{--reverse} option is specified, resumes reverse
29982 execution of the inferior program, stopping at the beginning of the
29983 previously executed source line.
29985 @subsubheading @value{GDBN} Command
29987 The corresponding @value{GDBN} command is @samp{step}.
29989 @subsubheading Example
29991 Stepping into a function:
29997 *stopped,reason="end-stepping-range",
29998 frame=@{func="foo",args=[@{name="a",value="10"@},
29999 @{name="b",value="0"@}],file="recursive2.c",
30000 fullname="/home/foo/bar/recursive2.c",line="11"@}
30010 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30015 @subheading The @code{-exec-step-instruction} Command
30016 @findex -exec-step-instruction
30018 @subsubheading Synopsis
30021 -exec-step-instruction [--reverse]
30024 Resumes the inferior which executes one machine instruction. If the
30025 @samp{--reverse} option is specified, resumes reverse execution of the
30026 inferior program, stopping at the previously executed instruction.
30027 The output, once @value{GDBN} has stopped, will vary depending on
30028 whether we have stopped in the middle of a source line or not. In the
30029 former case, the address at which the program stopped will be printed
30032 @subsubheading @value{GDBN} Command
30034 The corresponding @value{GDBN} command is @samp{stepi}.
30036 @subsubheading Example
30040 -exec-step-instruction
30044 *stopped,reason="end-stepping-range",
30045 frame=@{func="foo",args=[],file="try.c",
30046 fullname="/home/foo/bar/try.c",line="10"@}
30048 -exec-step-instruction
30052 *stopped,reason="end-stepping-range",
30053 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30054 fullname="/home/foo/bar/try.c",line="10"@}
30059 @subheading The @code{-exec-until} Command
30060 @findex -exec-until
30062 @subsubheading Synopsis
30065 -exec-until [ @var{location} ]
30068 Executes the inferior until the @var{location} specified in the
30069 argument is reached. If there is no argument, the inferior executes
30070 until a source line greater than the current one is reached. The
30071 reason for stopping in this case will be @samp{location-reached}.
30073 @subsubheading @value{GDBN} Command
30075 The corresponding @value{GDBN} command is @samp{until}.
30077 @subsubheading Example
30081 -exec-until recursive2.c:6
30085 *stopped,reason="location-reached",frame=@{func="main",args=[],
30086 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30091 @subheading -file-clear
30092 Is this going away????
30095 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30096 @node GDB/MI Stack Manipulation
30097 @section @sc{gdb/mi} Stack Manipulation Commands
30100 @subheading The @code{-stack-info-frame} Command
30101 @findex -stack-info-frame
30103 @subsubheading Synopsis
30109 Get info on the selected frame.
30111 @subsubheading @value{GDBN} Command
30113 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30114 (without arguments).
30116 @subsubheading Example
30121 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30122 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30123 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30127 @subheading The @code{-stack-info-depth} Command
30128 @findex -stack-info-depth
30130 @subsubheading Synopsis
30133 -stack-info-depth [ @var{max-depth} ]
30136 Return the depth of the stack. If the integer argument @var{max-depth}
30137 is specified, do not count beyond @var{max-depth} frames.
30139 @subsubheading @value{GDBN} Command
30141 There's no equivalent @value{GDBN} command.
30143 @subsubheading Example
30145 For a stack with frame levels 0 through 11:
30152 -stack-info-depth 4
30155 -stack-info-depth 12
30158 -stack-info-depth 11
30161 -stack-info-depth 13
30166 @subheading The @code{-stack-list-arguments} Command
30167 @findex -stack-list-arguments
30169 @subsubheading Synopsis
30172 -stack-list-arguments @var{print-values}
30173 [ @var{low-frame} @var{high-frame} ]
30176 Display a list of the arguments for the frames between @var{low-frame}
30177 and @var{high-frame} (inclusive). If @var{low-frame} and
30178 @var{high-frame} are not provided, list the arguments for the whole
30179 call stack. If the two arguments are equal, show the single frame
30180 at the corresponding level. It is an error if @var{low-frame} is
30181 larger than the actual number of frames. On the other hand,
30182 @var{high-frame} may be larger than the actual number of frames, in
30183 which case only existing frames will be returned.
30185 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30186 the variables; if it is 1 or @code{--all-values}, print also their
30187 values; and if it is 2 or @code{--simple-values}, print the name,
30188 type and value for simple data types, and the name and type for arrays,
30189 structures and unions.
30191 Use of this command to obtain arguments in a single frame is
30192 deprecated in favor of the @samp{-stack-list-variables} command.
30194 @subsubheading @value{GDBN} Command
30196 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30197 @samp{gdb_get_args} command which partially overlaps with the
30198 functionality of @samp{-stack-list-arguments}.
30200 @subsubheading Example
30207 frame=@{level="0",addr="0x00010734",func="callee4",
30208 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30209 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30210 frame=@{level="1",addr="0x0001076c",func="callee3",
30211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30212 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30213 frame=@{level="2",addr="0x0001078c",func="callee2",
30214 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30215 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30216 frame=@{level="3",addr="0x000107b4",func="callee1",
30217 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30218 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30219 frame=@{level="4",addr="0x000107e0",func="main",
30220 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30221 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30223 -stack-list-arguments 0
30226 frame=@{level="0",args=[]@},
30227 frame=@{level="1",args=[name="strarg"]@},
30228 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30229 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30230 frame=@{level="4",args=[]@}]
30232 -stack-list-arguments 1
30235 frame=@{level="0",args=[]@},
30237 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30238 frame=@{level="2",args=[
30239 @{name="intarg",value="2"@},
30240 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30241 @{frame=@{level="3",args=[
30242 @{name="intarg",value="2"@},
30243 @{name="strarg",value="0x11940 \"A string argument.\""@},
30244 @{name="fltarg",value="3.5"@}]@},
30245 frame=@{level="4",args=[]@}]
30247 -stack-list-arguments 0 2 2
30248 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30250 -stack-list-arguments 1 2 2
30251 ^done,stack-args=[frame=@{level="2",
30252 args=[@{name="intarg",value="2"@},
30253 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30257 @c @subheading -stack-list-exception-handlers
30260 @subheading The @code{-stack-list-frames} Command
30261 @findex -stack-list-frames
30263 @subsubheading Synopsis
30266 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30269 List the frames currently on the stack. For each frame it displays the
30274 The frame number, 0 being the topmost frame, i.e., the innermost function.
30276 The @code{$pc} value for that frame.
30280 File name of the source file where the function lives.
30281 @item @var{fullname}
30282 The full file name of the source file where the function lives.
30284 Line number corresponding to the @code{$pc}.
30286 The shared library where this function is defined. This is only given
30287 if the frame's function is not known.
30290 If invoked without arguments, this command prints a backtrace for the
30291 whole stack. If given two integer arguments, it shows the frames whose
30292 levels are between the two arguments (inclusive). If the two arguments
30293 are equal, it shows the single frame at the corresponding level. It is
30294 an error if @var{low-frame} is larger than the actual number of
30295 frames. On the other hand, @var{high-frame} may be larger than the
30296 actual number of frames, in which case only existing frames will be returned.
30298 @subsubheading @value{GDBN} Command
30300 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30302 @subsubheading Example
30304 Full stack backtrace:
30310 [frame=@{level="0",addr="0x0001076c",func="foo",
30311 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30312 frame=@{level="1",addr="0x000107a4",func="foo",
30313 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30314 frame=@{level="2",addr="0x000107a4",func="foo",
30315 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30316 frame=@{level="3",addr="0x000107a4",func="foo",
30317 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30318 frame=@{level="4",addr="0x000107a4",func="foo",
30319 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30320 frame=@{level="5",addr="0x000107a4",func="foo",
30321 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30322 frame=@{level="6",addr="0x000107a4",func="foo",
30323 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30324 frame=@{level="7",addr="0x000107a4",func="foo",
30325 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30326 frame=@{level="8",addr="0x000107a4",func="foo",
30327 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30328 frame=@{level="9",addr="0x000107a4",func="foo",
30329 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30330 frame=@{level="10",addr="0x000107a4",func="foo",
30331 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30332 frame=@{level="11",addr="0x00010738",func="main",
30333 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30337 Show frames between @var{low_frame} and @var{high_frame}:
30341 -stack-list-frames 3 5
30343 [frame=@{level="3",addr="0x000107a4",func="foo",
30344 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30345 frame=@{level="4",addr="0x000107a4",func="foo",
30346 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30347 frame=@{level="5",addr="0x000107a4",func="foo",
30348 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30352 Show a single frame:
30356 -stack-list-frames 3 3
30358 [frame=@{level="3",addr="0x000107a4",func="foo",
30359 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30364 @subheading The @code{-stack-list-locals} Command
30365 @findex -stack-list-locals
30367 @subsubheading Synopsis
30370 -stack-list-locals @var{print-values}
30373 Display the local variable names for the selected frame. If
30374 @var{print-values} is 0 or @code{--no-values}, print only the names of
30375 the variables; if it is 1 or @code{--all-values}, print also their
30376 values; and if it is 2 or @code{--simple-values}, print the name,
30377 type and value for simple data types, and the name and type for arrays,
30378 structures and unions. In this last case, a frontend can immediately
30379 display the value of simple data types and create variable objects for
30380 other data types when the user wishes to explore their values in
30383 This command is deprecated in favor of the
30384 @samp{-stack-list-variables} command.
30386 @subsubheading @value{GDBN} Command
30388 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30390 @subsubheading Example
30394 -stack-list-locals 0
30395 ^done,locals=[name="A",name="B",name="C"]
30397 -stack-list-locals --all-values
30398 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30399 @{name="C",value="@{1, 2, 3@}"@}]
30400 -stack-list-locals --simple-values
30401 ^done,locals=[@{name="A",type="int",value="1"@},
30402 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30406 @subheading The @code{-stack-list-variables} Command
30407 @findex -stack-list-variables
30409 @subsubheading Synopsis
30412 -stack-list-variables @var{print-values}
30415 Display the names of local variables and function arguments for the selected frame. If
30416 @var{print-values} is 0 or @code{--no-values}, print only the names of
30417 the variables; if it is 1 or @code{--all-values}, print also their
30418 values; and if it is 2 or @code{--simple-values}, print the name,
30419 type and value for simple data types, and the name and type for arrays,
30420 structures and unions.
30422 @subsubheading Example
30426 -stack-list-variables --thread 1 --frame 0 --all-values
30427 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30432 @subheading The @code{-stack-select-frame} Command
30433 @findex -stack-select-frame
30435 @subsubheading Synopsis
30438 -stack-select-frame @var{framenum}
30441 Change the selected frame. Select a different frame @var{framenum} on
30444 This command in deprecated in favor of passing the @samp{--frame}
30445 option to every command.
30447 @subsubheading @value{GDBN} Command
30449 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30450 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30452 @subsubheading Example
30456 -stack-select-frame 2
30461 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30462 @node GDB/MI Variable Objects
30463 @section @sc{gdb/mi} Variable Objects
30467 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30469 For the implementation of a variable debugger window (locals, watched
30470 expressions, etc.), we are proposing the adaptation of the existing code
30471 used by @code{Insight}.
30473 The two main reasons for that are:
30477 It has been proven in practice (it is already on its second generation).
30480 It will shorten development time (needless to say how important it is
30484 The original interface was designed to be used by Tcl code, so it was
30485 slightly changed so it could be used through @sc{gdb/mi}. This section
30486 describes the @sc{gdb/mi} operations that will be available and gives some
30487 hints about their use.
30489 @emph{Note}: In addition to the set of operations described here, we
30490 expect the @sc{gui} implementation of a variable window to require, at
30491 least, the following operations:
30494 @item @code{-gdb-show} @code{output-radix}
30495 @item @code{-stack-list-arguments}
30496 @item @code{-stack-list-locals}
30497 @item @code{-stack-select-frame}
30502 @subheading Introduction to Variable Objects
30504 @cindex variable objects in @sc{gdb/mi}
30506 Variable objects are "object-oriented" MI interface for examining and
30507 changing values of expressions. Unlike some other MI interfaces that
30508 work with expressions, variable objects are specifically designed for
30509 simple and efficient presentation in the frontend. A variable object
30510 is identified by string name. When a variable object is created, the
30511 frontend specifies the expression for that variable object. The
30512 expression can be a simple variable, or it can be an arbitrary complex
30513 expression, and can even involve CPU registers. After creating a
30514 variable object, the frontend can invoke other variable object
30515 operations---for example to obtain or change the value of a variable
30516 object, or to change display format.
30518 Variable objects have hierarchical tree structure. Any variable object
30519 that corresponds to a composite type, such as structure in C, has
30520 a number of child variable objects, for example corresponding to each
30521 element of a structure. A child variable object can itself have
30522 children, recursively. Recursion ends when we reach
30523 leaf variable objects, which always have built-in types. Child variable
30524 objects are created only by explicit request, so if a frontend
30525 is not interested in the children of a particular variable object, no
30526 child will be created.
30528 For a leaf variable object it is possible to obtain its value as a
30529 string, or set the value from a string. String value can be also
30530 obtained for a non-leaf variable object, but it's generally a string
30531 that only indicates the type of the object, and does not list its
30532 contents. Assignment to a non-leaf variable object is not allowed.
30534 A frontend does not need to read the values of all variable objects each time
30535 the program stops. Instead, MI provides an update command that lists all
30536 variable objects whose values has changed since the last update
30537 operation. This considerably reduces the amount of data that must
30538 be transferred to the frontend. As noted above, children variable
30539 objects are created on demand, and only leaf variable objects have a
30540 real value. As result, gdb will read target memory only for leaf
30541 variables that frontend has created.
30543 The automatic update is not always desirable. For example, a frontend
30544 might want to keep a value of some expression for future reference,
30545 and never update it. For another example, fetching memory is
30546 relatively slow for embedded targets, so a frontend might want
30547 to disable automatic update for the variables that are either not
30548 visible on the screen, or ``closed''. This is possible using so
30549 called ``frozen variable objects''. Such variable objects are never
30550 implicitly updated.
30552 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30553 fixed variable object, the expression is parsed when the variable
30554 object is created, including associating identifiers to specific
30555 variables. The meaning of expression never changes. For a floating
30556 variable object the values of variables whose names appear in the
30557 expressions are re-evaluated every time in the context of the current
30558 frame. Consider this example:
30563 struct work_state state;
30570 If a fixed variable object for the @code{state} variable is created in
30571 this function, and we enter the recursive call, the variable
30572 object will report the value of @code{state} in the top-level
30573 @code{do_work} invocation. On the other hand, a floating variable
30574 object will report the value of @code{state} in the current frame.
30576 If an expression specified when creating a fixed variable object
30577 refers to a local variable, the variable object becomes bound to the
30578 thread and frame in which the variable object is created. When such
30579 variable object is updated, @value{GDBN} makes sure that the
30580 thread/frame combination the variable object is bound to still exists,
30581 and re-evaluates the variable object in context of that thread/frame.
30583 The following is the complete set of @sc{gdb/mi} operations defined to
30584 access this functionality:
30586 @multitable @columnfractions .4 .6
30587 @item @strong{Operation}
30588 @tab @strong{Description}
30590 @item @code{-enable-pretty-printing}
30591 @tab enable Python-based pretty-printing
30592 @item @code{-var-create}
30593 @tab create a variable object
30594 @item @code{-var-delete}
30595 @tab delete the variable object and/or its children
30596 @item @code{-var-set-format}
30597 @tab set the display format of this variable
30598 @item @code{-var-show-format}
30599 @tab show the display format of this variable
30600 @item @code{-var-info-num-children}
30601 @tab tells how many children this object has
30602 @item @code{-var-list-children}
30603 @tab return a list of the object's children
30604 @item @code{-var-info-type}
30605 @tab show the type of this variable object
30606 @item @code{-var-info-expression}
30607 @tab print parent-relative expression that this variable object represents
30608 @item @code{-var-info-path-expression}
30609 @tab print full expression that this variable object represents
30610 @item @code{-var-show-attributes}
30611 @tab is this variable editable? does it exist here?
30612 @item @code{-var-evaluate-expression}
30613 @tab get the value of this variable
30614 @item @code{-var-assign}
30615 @tab set the value of this variable
30616 @item @code{-var-update}
30617 @tab update the variable and its children
30618 @item @code{-var-set-frozen}
30619 @tab set frozeness attribute
30620 @item @code{-var-set-update-range}
30621 @tab set range of children to display on update
30624 In the next subsection we describe each operation in detail and suggest
30625 how it can be used.
30627 @subheading Description And Use of Operations on Variable Objects
30629 @subheading The @code{-enable-pretty-printing} Command
30630 @findex -enable-pretty-printing
30633 -enable-pretty-printing
30636 @value{GDBN} allows Python-based visualizers to affect the output of the
30637 MI variable object commands. However, because there was no way to
30638 implement this in a fully backward-compatible way, a front end must
30639 request that this functionality be enabled.
30641 Once enabled, this feature cannot be disabled.
30643 Note that if Python support has not been compiled into @value{GDBN},
30644 this command will still succeed (and do nothing).
30646 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30647 may work differently in future versions of @value{GDBN}.
30649 @subheading The @code{-var-create} Command
30650 @findex -var-create
30652 @subsubheading Synopsis
30655 -var-create @{@var{name} | "-"@}
30656 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30659 This operation creates a variable object, which allows the monitoring of
30660 a variable, the result of an expression, a memory cell or a CPU
30663 The @var{name} parameter is the string by which the object can be
30664 referenced. It must be unique. If @samp{-} is specified, the varobj
30665 system will generate a string ``varNNNNNN'' automatically. It will be
30666 unique provided that one does not specify @var{name} of that format.
30667 The command fails if a duplicate name is found.
30669 The frame under which the expression should be evaluated can be
30670 specified by @var{frame-addr}. A @samp{*} indicates that the current
30671 frame should be used. A @samp{@@} indicates that a floating variable
30672 object must be created.
30674 @var{expression} is any expression valid on the current language set (must not
30675 begin with a @samp{*}), or one of the following:
30679 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30682 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30685 @samp{$@var{regname}} --- a CPU register name
30688 @cindex dynamic varobj
30689 A varobj's contents may be provided by a Python-based pretty-printer. In this
30690 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30691 have slightly different semantics in some cases. If the
30692 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30693 will never create a dynamic varobj. This ensures backward
30694 compatibility for existing clients.
30696 @subsubheading Result
30698 This operation returns attributes of the newly-created varobj. These
30703 The name of the varobj.
30706 The number of children of the varobj. This number is not necessarily
30707 reliable for a dynamic varobj. Instead, you must examine the
30708 @samp{has_more} attribute.
30711 The varobj's scalar value. For a varobj whose type is some sort of
30712 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30713 will not be interesting.
30716 The varobj's type. This is a string representation of the type, as
30717 would be printed by the @value{GDBN} CLI. If @samp{print object}
30718 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30719 @emph{actual} (derived) type of the object is shown rather than the
30720 @emph{declared} one.
30723 If a variable object is bound to a specific thread, then this is the
30724 thread's identifier.
30727 For a dynamic varobj, this indicates whether there appear to be any
30728 children available. For a non-dynamic varobj, this will be 0.
30731 This attribute will be present and have the value @samp{1} if the
30732 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30733 then this attribute will not be present.
30736 A dynamic varobj can supply a display hint to the front end. The
30737 value comes directly from the Python pretty-printer object's
30738 @code{display_hint} method. @xref{Pretty Printing API}.
30741 Typical output will look like this:
30744 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30745 has_more="@var{has_more}"
30749 @subheading The @code{-var-delete} Command
30750 @findex -var-delete
30752 @subsubheading Synopsis
30755 -var-delete [ -c ] @var{name}
30758 Deletes a previously created variable object and all of its children.
30759 With the @samp{-c} option, just deletes the children.
30761 Returns an error if the object @var{name} is not found.
30764 @subheading The @code{-var-set-format} Command
30765 @findex -var-set-format
30767 @subsubheading Synopsis
30770 -var-set-format @var{name} @var{format-spec}
30773 Sets the output format for the value of the object @var{name} to be
30776 @anchor{-var-set-format}
30777 The syntax for the @var{format-spec} is as follows:
30780 @var{format-spec} @expansion{}
30781 @{binary | decimal | hexadecimal | octal | natural@}
30784 The natural format is the default format choosen automatically
30785 based on the variable type (like decimal for an @code{int}, hex
30786 for pointers, etc.).
30788 For a variable with children, the format is set only on the
30789 variable itself, and the children are not affected.
30791 @subheading The @code{-var-show-format} Command
30792 @findex -var-show-format
30794 @subsubheading Synopsis
30797 -var-show-format @var{name}
30800 Returns the format used to display the value of the object @var{name}.
30803 @var{format} @expansion{}
30808 @subheading The @code{-var-info-num-children} Command
30809 @findex -var-info-num-children
30811 @subsubheading Synopsis
30814 -var-info-num-children @var{name}
30817 Returns the number of children of a variable object @var{name}:
30823 Note that this number is not completely reliable for a dynamic varobj.
30824 It will return the current number of children, but more children may
30828 @subheading The @code{-var-list-children} Command
30829 @findex -var-list-children
30831 @subsubheading Synopsis
30834 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30836 @anchor{-var-list-children}
30838 Return a list of the children of the specified variable object and
30839 create variable objects for them, if they do not already exist. With
30840 a single argument or if @var{print-values} has a value of 0 or
30841 @code{--no-values}, print only the names of the variables; if
30842 @var{print-values} is 1 or @code{--all-values}, also print their
30843 values; and if it is 2 or @code{--simple-values} print the name and
30844 value for simple data types and just the name for arrays, structures
30847 @var{from} and @var{to}, if specified, indicate the range of children
30848 to report. If @var{from} or @var{to} is less than zero, the range is
30849 reset and all children will be reported. Otherwise, children starting
30850 at @var{from} (zero-based) and up to and excluding @var{to} will be
30853 If a child range is requested, it will only affect the current call to
30854 @code{-var-list-children}, but not future calls to @code{-var-update}.
30855 For this, you must instead use @code{-var-set-update-range}. The
30856 intent of this approach is to enable a front end to implement any
30857 update approach it likes; for example, scrolling a view may cause the
30858 front end to request more children with @code{-var-list-children}, and
30859 then the front end could call @code{-var-set-update-range} with a
30860 different range to ensure that future updates are restricted to just
30863 For each child the following results are returned:
30868 Name of the variable object created for this child.
30871 The expression to be shown to the user by the front end to designate this child.
30872 For example this may be the name of a structure member.
30874 For a dynamic varobj, this value cannot be used to form an
30875 expression. There is no way to do this at all with a dynamic varobj.
30877 For C/C@t{++} structures there are several pseudo children returned to
30878 designate access qualifiers. For these pseudo children @var{exp} is
30879 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30880 type and value are not present.
30882 A dynamic varobj will not report the access qualifying
30883 pseudo-children, regardless of the language. This information is not
30884 available at all with a dynamic varobj.
30887 Number of children this child has. For a dynamic varobj, this will be
30891 The type of the child. If @samp{print object}
30892 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30893 @emph{actual} (derived) type of the object is shown rather than the
30894 @emph{declared} one.
30897 If values were requested, this is the value.
30900 If this variable object is associated with a thread, this is the thread id.
30901 Otherwise this result is not present.
30904 If the variable object is frozen, this variable will be present with a value of 1.
30907 The result may have its own attributes:
30911 A dynamic varobj can supply a display hint to the front end. The
30912 value comes directly from the Python pretty-printer object's
30913 @code{display_hint} method. @xref{Pretty Printing API}.
30916 This is an integer attribute which is nonzero if there are children
30917 remaining after the end of the selected range.
30920 @subsubheading Example
30924 -var-list-children n
30925 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30926 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30928 -var-list-children --all-values n
30929 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30930 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30934 @subheading The @code{-var-info-type} Command
30935 @findex -var-info-type
30937 @subsubheading Synopsis
30940 -var-info-type @var{name}
30943 Returns the type of the specified variable @var{name}. The type is
30944 returned as a string in the same format as it is output by the
30948 type=@var{typename}
30952 @subheading The @code{-var-info-expression} Command
30953 @findex -var-info-expression
30955 @subsubheading Synopsis
30958 -var-info-expression @var{name}
30961 Returns a string that is suitable for presenting this
30962 variable object in user interface. The string is generally
30963 not valid expression in the current language, and cannot be evaluated.
30965 For example, if @code{a} is an array, and variable object
30966 @code{A} was created for @code{a}, then we'll get this output:
30969 (gdb) -var-info-expression A.1
30970 ^done,lang="C",exp="1"
30974 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30976 Note that the output of the @code{-var-list-children} command also
30977 includes those expressions, so the @code{-var-info-expression} command
30980 @subheading The @code{-var-info-path-expression} Command
30981 @findex -var-info-path-expression
30983 @subsubheading Synopsis
30986 -var-info-path-expression @var{name}
30989 Returns an expression that can be evaluated in the current
30990 context and will yield the same value that a variable object has.
30991 Compare this with the @code{-var-info-expression} command, which
30992 result can be used only for UI presentation. Typical use of
30993 the @code{-var-info-path-expression} command is creating a
30994 watchpoint from a variable object.
30996 This command is currently not valid for children of a dynamic varobj,
30997 and will give an error when invoked on one.
30999 For example, suppose @code{C} is a C@t{++} class, derived from class
31000 @code{Base}, and that the @code{Base} class has a member called
31001 @code{m_size}. Assume a variable @code{c} is has the type of
31002 @code{C} and a variable object @code{C} was created for variable
31003 @code{c}. Then, we'll get this output:
31005 (gdb) -var-info-path-expression C.Base.public.m_size
31006 ^done,path_expr=((Base)c).m_size)
31009 @subheading The @code{-var-show-attributes} Command
31010 @findex -var-show-attributes
31012 @subsubheading Synopsis
31015 -var-show-attributes @var{name}
31018 List attributes of the specified variable object @var{name}:
31021 status=@var{attr} [ ( ,@var{attr} )* ]
31025 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31027 @subheading The @code{-var-evaluate-expression} Command
31028 @findex -var-evaluate-expression
31030 @subsubheading Synopsis
31033 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31036 Evaluates the expression that is represented by the specified variable
31037 object and returns its value as a string. The format of the string
31038 can be specified with the @samp{-f} option. The possible values of
31039 this option are the same as for @code{-var-set-format}
31040 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31041 the current display format will be used. The current display format
31042 can be changed using the @code{-var-set-format} command.
31048 Note that one must invoke @code{-var-list-children} for a variable
31049 before the value of a child variable can be evaluated.
31051 @subheading The @code{-var-assign} Command
31052 @findex -var-assign
31054 @subsubheading Synopsis
31057 -var-assign @var{name} @var{expression}
31060 Assigns the value of @var{expression} to the variable object specified
31061 by @var{name}. The object must be @samp{editable}. If the variable's
31062 value is altered by the assign, the variable will show up in any
31063 subsequent @code{-var-update} list.
31065 @subsubheading Example
31073 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31077 @subheading The @code{-var-update} Command
31078 @findex -var-update
31080 @subsubheading Synopsis
31083 -var-update [@var{print-values}] @{@var{name} | "*"@}
31086 Reevaluate the expressions corresponding to the variable object
31087 @var{name} and all its direct and indirect children, and return the
31088 list of variable objects whose values have changed; @var{name} must
31089 be a root variable object. Here, ``changed'' means that the result of
31090 @code{-var-evaluate-expression} before and after the
31091 @code{-var-update} is different. If @samp{*} is used as the variable
31092 object names, all existing variable objects are updated, except
31093 for frozen ones (@pxref{-var-set-frozen}). The option
31094 @var{print-values} determines whether both names and values, or just
31095 names are printed. The possible values of this option are the same
31096 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31097 recommended to use the @samp{--all-values} option, to reduce the
31098 number of MI commands needed on each program stop.
31100 With the @samp{*} parameter, if a variable object is bound to a
31101 currently running thread, it will not be updated, without any
31104 If @code{-var-set-update-range} was previously used on a varobj, then
31105 only the selected range of children will be reported.
31107 @code{-var-update} reports all the changed varobjs in a tuple named
31110 Each item in the change list is itself a tuple holding:
31114 The name of the varobj.
31117 If values were requested for this update, then this field will be
31118 present and will hold the value of the varobj.
31121 @anchor{-var-update}
31122 This field is a string which may take one of three values:
31126 The variable object's current value is valid.
31129 The variable object does not currently hold a valid value but it may
31130 hold one in the future if its associated expression comes back into
31134 The variable object no longer holds a valid value.
31135 This can occur when the executable file being debugged has changed,
31136 either through recompilation or by using the @value{GDBN} @code{file}
31137 command. The front end should normally choose to delete these variable
31141 In the future new values may be added to this list so the front should
31142 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31145 This is only present if the varobj is still valid. If the type
31146 changed, then this will be the string @samp{true}; otherwise it will
31149 When a varobj's type changes, its children are also likely to have
31150 become incorrect. Therefore, the varobj's children are automatically
31151 deleted when this attribute is @samp{true}. Also, the varobj's update
31152 range, when set using the @code{-var-set-update-range} command, is
31156 If the varobj's type changed, then this field will be present and will
31159 @item new_num_children
31160 For a dynamic varobj, if the number of children changed, or if the
31161 type changed, this will be the new number of children.
31163 The @samp{numchild} field in other varobj responses is generally not
31164 valid for a dynamic varobj -- it will show the number of children that
31165 @value{GDBN} knows about, but because dynamic varobjs lazily
31166 instantiate their children, this will not reflect the number of
31167 children which may be available.
31169 The @samp{new_num_children} attribute only reports changes to the
31170 number of children known by @value{GDBN}. This is the only way to
31171 detect whether an update has removed children (which necessarily can
31172 only happen at the end of the update range).
31175 The display hint, if any.
31178 This is an integer value, which will be 1 if there are more children
31179 available outside the varobj's update range.
31182 This attribute will be present and have the value @samp{1} if the
31183 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31184 then this attribute will not be present.
31187 If new children were added to a dynamic varobj within the selected
31188 update range (as set by @code{-var-set-update-range}), then they will
31189 be listed in this attribute.
31192 @subsubheading Example
31199 -var-update --all-values var1
31200 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31201 type_changed="false"@}]
31205 @subheading The @code{-var-set-frozen} Command
31206 @findex -var-set-frozen
31207 @anchor{-var-set-frozen}
31209 @subsubheading Synopsis
31212 -var-set-frozen @var{name} @var{flag}
31215 Set the frozenness flag on the variable object @var{name}. The
31216 @var{flag} parameter should be either @samp{1} to make the variable
31217 frozen or @samp{0} to make it unfrozen. If a variable object is
31218 frozen, then neither itself, nor any of its children, are
31219 implicitly updated by @code{-var-update} of
31220 a parent variable or by @code{-var-update *}. Only
31221 @code{-var-update} of the variable itself will update its value and
31222 values of its children. After a variable object is unfrozen, it is
31223 implicitly updated by all subsequent @code{-var-update} operations.
31224 Unfreezing a variable does not update it, only subsequent
31225 @code{-var-update} does.
31227 @subsubheading Example
31231 -var-set-frozen V 1
31236 @subheading The @code{-var-set-update-range} command
31237 @findex -var-set-update-range
31238 @anchor{-var-set-update-range}
31240 @subsubheading Synopsis
31243 -var-set-update-range @var{name} @var{from} @var{to}
31246 Set the range of children to be returned by future invocations of
31247 @code{-var-update}.
31249 @var{from} and @var{to} indicate the range of children to report. If
31250 @var{from} or @var{to} is less than zero, the range is reset and all
31251 children will be reported. Otherwise, children starting at @var{from}
31252 (zero-based) and up to and excluding @var{to} will be reported.
31254 @subsubheading Example
31258 -var-set-update-range V 1 2
31262 @subheading The @code{-var-set-visualizer} command
31263 @findex -var-set-visualizer
31264 @anchor{-var-set-visualizer}
31266 @subsubheading Synopsis
31269 -var-set-visualizer @var{name} @var{visualizer}
31272 Set a visualizer for the variable object @var{name}.
31274 @var{visualizer} is the visualizer to use. The special value
31275 @samp{None} means to disable any visualizer in use.
31277 If not @samp{None}, @var{visualizer} must be a Python expression.
31278 This expression must evaluate to a callable object which accepts a
31279 single argument. @value{GDBN} will call this object with the value of
31280 the varobj @var{name} as an argument (this is done so that the same
31281 Python pretty-printing code can be used for both the CLI and MI).
31282 When called, this object must return an object which conforms to the
31283 pretty-printing interface (@pxref{Pretty Printing API}).
31285 The pre-defined function @code{gdb.default_visualizer} may be used to
31286 select a visualizer by following the built-in process
31287 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31288 a varobj is created, and so ordinarily is not needed.
31290 This feature is only available if Python support is enabled. The MI
31291 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31292 can be used to check this.
31294 @subsubheading Example
31296 Resetting the visualizer:
31300 -var-set-visualizer V None
31304 Reselecting the default (type-based) visualizer:
31308 -var-set-visualizer V gdb.default_visualizer
31312 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31313 can be used to instantiate this class for a varobj:
31317 -var-set-visualizer V "lambda val: SomeClass()"
31321 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31322 @node GDB/MI Data Manipulation
31323 @section @sc{gdb/mi} Data Manipulation
31325 @cindex data manipulation, in @sc{gdb/mi}
31326 @cindex @sc{gdb/mi}, data manipulation
31327 This section describes the @sc{gdb/mi} commands that manipulate data:
31328 examine memory and registers, evaluate expressions, etc.
31330 @c REMOVED FROM THE INTERFACE.
31331 @c @subheading -data-assign
31332 @c Change the value of a program variable. Plenty of side effects.
31333 @c @subsubheading GDB Command
31335 @c @subsubheading Example
31338 @subheading The @code{-data-disassemble} Command
31339 @findex -data-disassemble
31341 @subsubheading Synopsis
31345 [ -s @var{start-addr} -e @var{end-addr} ]
31346 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31354 @item @var{start-addr}
31355 is the beginning address (or @code{$pc})
31356 @item @var{end-addr}
31358 @item @var{filename}
31359 is the name of the file to disassemble
31360 @item @var{linenum}
31361 is the line number to disassemble around
31363 is the number of disassembly lines to be produced. If it is -1,
31364 the whole function will be disassembled, in case no @var{end-addr} is
31365 specified. If @var{end-addr} is specified as a non-zero value, and
31366 @var{lines} is lower than the number of disassembly lines between
31367 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31368 displayed; if @var{lines} is higher than the number of lines between
31369 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31372 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31373 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31374 mixed source and disassembly with raw opcodes).
31377 @subsubheading Result
31379 The result of the @code{-data-disassemble} command will be a list named
31380 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31381 used with the @code{-data-disassemble} command.
31383 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31388 The address at which this instruction was disassembled.
31391 The name of the function this instruction is within.
31394 The decimal offset in bytes from the start of @samp{func-name}.
31397 The text disassembly for this @samp{address}.
31400 This field is only present for mode 2. This contains the raw opcode
31401 bytes for the @samp{inst} field.
31405 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31406 @samp{src_and_asm_line}, each of which has the following fields:
31410 The line number within @samp{file}.
31413 The file name from the compilation unit. This might be an absolute
31414 file name or a relative file name depending on the compile command
31418 Absolute file name of @samp{file}. It is converted to a canonical form
31419 using the source file search path
31420 (@pxref{Source Path, ,Specifying Source Directories})
31421 and after resolving all the symbolic links.
31423 If the source file is not found this field will contain the path as
31424 present in the debug information.
31426 @item line_asm_insn
31427 This is a list of tuples containing the disassembly for @samp{line} in
31428 @samp{file}. The fields of each tuple are the same as for
31429 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31430 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31435 Note that whatever included in the @samp{inst} field, is not
31436 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31439 @subsubheading @value{GDBN} Command
31441 The corresponding @value{GDBN} command is @samp{disassemble}.
31443 @subsubheading Example
31445 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31449 -data-disassemble -s $pc -e "$pc + 20" -- 0
31452 @{address="0x000107c0",func-name="main",offset="4",
31453 inst="mov 2, %o0"@},
31454 @{address="0x000107c4",func-name="main",offset="8",
31455 inst="sethi %hi(0x11800), %o2"@},
31456 @{address="0x000107c8",func-name="main",offset="12",
31457 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31458 @{address="0x000107cc",func-name="main",offset="16",
31459 inst="sethi %hi(0x11800), %o2"@},
31460 @{address="0x000107d0",func-name="main",offset="20",
31461 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31465 Disassemble the whole @code{main} function. Line 32 is part of
31469 -data-disassemble -f basics.c -l 32 -- 0
31471 @{address="0x000107bc",func-name="main",offset="0",
31472 inst="save %sp, -112, %sp"@},
31473 @{address="0x000107c0",func-name="main",offset="4",
31474 inst="mov 2, %o0"@},
31475 @{address="0x000107c4",func-name="main",offset="8",
31476 inst="sethi %hi(0x11800), %o2"@},
31478 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31479 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31483 Disassemble 3 instructions from the start of @code{main}:
31487 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31489 @{address="0x000107bc",func-name="main",offset="0",
31490 inst="save %sp, -112, %sp"@},
31491 @{address="0x000107c0",func-name="main",offset="4",
31492 inst="mov 2, %o0"@},
31493 @{address="0x000107c4",func-name="main",offset="8",
31494 inst="sethi %hi(0x11800), %o2"@}]
31498 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31502 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31504 src_and_asm_line=@{line="31",
31505 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31506 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31507 line_asm_insn=[@{address="0x000107bc",
31508 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31509 src_and_asm_line=@{line="32",
31510 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31511 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31512 line_asm_insn=[@{address="0x000107c0",
31513 func-name="main",offset="4",inst="mov 2, %o0"@},
31514 @{address="0x000107c4",func-name="main",offset="8",
31515 inst="sethi %hi(0x11800), %o2"@}]@}]
31520 @subheading The @code{-data-evaluate-expression} Command
31521 @findex -data-evaluate-expression
31523 @subsubheading Synopsis
31526 -data-evaluate-expression @var{expr}
31529 Evaluate @var{expr} as an expression. The expression could contain an
31530 inferior function call. The function call will execute synchronously.
31531 If the expression contains spaces, it must be enclosed in double quotes.
31533 @subsubheading @value{GDBN} Command
31535 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31536 @samp{call}. In @code{gdbtk} only, there's a corresponding
31537 @samp{gdb_eval} command.
31539 @subsubheading Example
31541 In the following example, the numbers that precede the commands are the
31542 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31543 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31547 211-data-evaluate-expression A
31550 311-data-evaluate-expression &A
31551 311^done,value="0xefffeb7c"
31553 411-data-evaluate-expression A+3
31556 511-data-evaluate-expression "A + 3"
31562 @subheading The @code{-data-list-changed-registers} Command
31563 @findex -data-list-changed-registers
31565 @subsubheading Synopsis
31568 -data-list-changed-registers
31571 Display a list of the registers that have changed.
31573 @subsubheading @value{GDBN} Command
31575 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31576 has the corresponding command @samp{gdb_changed_register_list}.
31578 @subsubheading Example
31580 On a PPC MBX board:
31588 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31589 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31592 -data-list-changed-registers
31593 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31594 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31595 "24","25","26","27","28","30","31","64","65","66","67","69"]
31600 @subheading The @code{-data-list-register-names} Command
31601 @findex -data-list-register-names
31603 @subsubheading Synopsis
31606 -data-list-register-names [ ( @var{regno} )+ ]
31609 Show a list of register names for the current target. If no arguments
31610 are given, it shows a list of the names of all the registers. If
31611 integer numbers are given as arguments, it will print a list of the
31612 names of the registers corresponding to the arguments. To ensure
31613 consistency between a register name and its number, the output list may
31614 include empty register names.
31616 @subsubheading @value{GDBN} Command
31618 @value{GDBN} does not have a command which corresponds to
31619 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31620 corresponding command @samp{gdb_regnames}.
31622 @subsubheading Example
31624 For the PPC MBX board:
31627 -data-list-register-names
31628 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31629 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31630 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31631 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31632 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31633 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31634 "", "pc","ps","cr","lr","ctr","xer"]
31636 -data-list-register-names 1 2 3
31637 ^done,register-names=["r1","r2","r3"]
31641 @subheading The @code{-data-list-register-values} Command
31642 @findex -data-list-register-values
31644 @subsubheading Synopsis
31647 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31650 Display the registers' contents. @var{fmt} is the format according to
31651 which the registers' contents are to be returned, followed by an optional
31652 list of numbers specifying the registers to display. A missing list of
31653 numbers indicates that the contents of all the registers must be returned.
31655 Allowed formats for @var{fmt} are:
31672 @subsubheading @value{GDBN} Command
31674 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31675 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31677 @subsubheading Example
31679 For a PPC MBX board (note: line breaks are for readability only, they
31680 don't appear in the actual output):
31684 -data-list-register-values r 64 65
31685 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31686 @{number="65",value="0x00029002"@}]
31688 -data-list-register-values x
31689 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31690 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31691 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31692 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31693 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31694 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31695 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31696 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31697 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31698 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31699 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31700 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31701 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31702 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31703 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31704 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31705 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31706 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31707 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31708 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31709 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31710 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31711 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31712 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31713 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31714 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31715 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31716 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31717 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31718 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31719 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31720 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31721 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31722 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31723 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31724 @{number="69",value="0x20002b03"@}]
31729 @subheading The @code{-data-read-memory} Command
31730 @findex -data-read-memory
31732 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31734 @subsubheading Synopsis
31737 -data-read-memory [ -o @var{byte-offset} ]
31738 @var{address} @var{word-format} @var{word-size}
31739 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31746 @item @var{address}
31747 An expression specifying the address of the first memory word to be
31748 read. Complex expressions containing embedded white space should be
31749 quoted using the C convention.
31751 @item @var{word-format}
31752 The format to be used to print the memory words. The notation is the
31753 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31756 @item @var{word-size}
31757 The size of each memory word in bytes.
31759 @item @var{nr-rows}
31760 The number of rows in the output table.
31762 @item @var{nr-cols}
31763 The number of columns in the output table.
31766 If present, indicates that each row should include an @sc{ascii} dump. The
31767 value of @var{aschar} is used as a padding character when a byte is not a
31768 member of the printable @sc{ascii} character set (printable @sc{ascii}
31769 characters are those whose code is between 32 and 126, inclusively).
31771 @item @var{byte-offset}
31772 An offset to add to the @var{address} before fetching memory.
31775 This command displays memory contents as a table of @var{nr-rows} by
31776 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31777 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31778 (returned as @samp{total-bytes}). Should less than the requested number
31779 of bytes be returned by the target, the missing words are identified
31780 using @samp{N/A}. The number of bytes read from the target is returned
31781 in @samp{nr-bytes} and the starting address used to read memory in
31784 The address of the next/previous row or page is available in
31785 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31788 @subsubheading @value{GDBN} Command
31790 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31791 @samp{gdb_get_mem} memory read command.
31793 @subsubheading Example
31795 Read six bytes of memory starting at @code{bytes+6} but then offset by
31796 @code{-6} bytes. Format as three rows of two columns. One byte per
31797 word. Display each word in hex.
31801 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31802 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31803 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31804 prev-page="0x0000138a",memory=[
31805 @{addr="0x00001390",data=["0x00","0x01"]@},
31806 @{addr="0x00001392",data=["0x02","0x03"]@},
31807 @{addr="0x00001394",data=["0x04","0x05"]@}]
31811 Read two bytes of memory starting at address @code{shorts + 64} and
31812 display as a single word formatted in decimal.
31816 5-data-read-memory shorts+64 d 2 1 1
31817 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31818 next-row="0x00001512",prev-row="0x0000150e",
31819 next-page="0x00001512",prev-page="0x0000150e",memory=[
31820 @{addr="0x00001510",data=["128"]@}]
31824 Read thirty two bytes of memory starting at @code{bytes+16} and format
31825 as eight rows of four columns. Include a string encoding with @samp{x}
31826 used as the non-printable character.
31830 4-data-read-memory bytes+16 x 1 8 4 x
31831 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31832 next-row="0x000013c0",prev-row="0x0000139c",
31833 next-page="0x000013c0",prev-page="0x00001380",memory=[
31834 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31835 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31836 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31837 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31838 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31839 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31840 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31841 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31845 @subheading The @code{-data-read-memory-bytes} Command
31846 @findex -data-read-memory-bytes
31848 @subsubheading Synopsis
31851 -data-read-memory-bytes [ -o @var{byte-offset} ]
31852 @var{address} @var{count}
31859 @item @var{address}
31860 An expression specifying the address of the first memory word to be
31861 read. Complex expressions containing embedded white space should be
31862 quoted using the C convention.
31865 The number of bytes to read. This should be an integer literal.
31867 @item @var{byte-offset}
31868 The offsets in bytes relative to @var{address} at which to start
31869 reading. This should be an integer literal. This option is provided
31870 so that a frontend is not required to first evaluate address and then
31871 perform address arithmetics itself.
31875 This command attempts to read all accessible memory regions in the
31876 specified range. First, all regions marked as unreadable in the memory
31877 map (if one is defined) will be skipped. @xref{Memory Region
31878 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31879 regions. For each one, if reading full region results in an errors,
31880 @value{GDBN} will try to read a subset of the region.
31882 In general, every single byte in the region may be readable or not,
31883 and the only way to read every readable byte is to try a read at
31884 every address, which is not practical. Therefore, @value{GDBN} will
31885 attempt to read all accessible bytes at either beginning or the end
31886 of the region, using a binary division scheme. This heuristic works
31887 well for reading accross a memory map boundary. Note that if a region
31888 has a readable range that is neither at the beginning or the end,
31889 @value{GDBN} will not read it.
31891 The result record (@pxref{GDB/MI Result Records}) that is output of
31892 the command includes a field named @samp{memory} whose content is a
31893 list of tuples. Each tuple represent a successfully read memory block
31894 and has the following fields:
31898 The start address of the memory block, as hexadecimal literal.
31901 The end address of the memory block, as hexadecimal literal.
31904 The offset of the memory block, as hexadecimal literal, relative to
31905 the start address passed to @code{-data-read-memory-bytes}.
31908 The contents of the memory block, in hex.
31914 @subsubheading @value{GDBN} Command
31916 The corresponding @value{GDBN} command is @samp{x}.
31918 @subsubheading Example
31922 -data-read-memory-bytes &a 10
31923 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31925 contents="01000000020000000300"@}]
31930 @subheading The @code{-data-write-memory-bytes} Command
31931 @findex -data-write-memory-bytes
31933 @subsubheading Synopsis
31936 -data-write-memory-bytes @var{address} @var{contents}
31937 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31944 @item @var{address}
31945 An expression specifying the address of the first memory word to be
31946 read. Complex expressions containing embedded white space should be
31947 quoted using the C convention.
31949 @item @var{contents}
31950 The hex-encoded bytes to write.
31953 Optional argument indicating the number of bytes to be written. If @var{count}
31954 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31955 write @var{contents} until it fills @var{count} bytes.
31959 @subsubheading @value{GDBN} Command
31961 There's no corresponding @value{GDBN} command.
31963 @subsubheading Example
31967 -data-write-memory-bytes &a "aabbccdd"
31974 -data-write-memory-bytes &a "aabbccdd" 16e
31979 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31980 @node GDB/MI Tracepoint Commands
31981 @section @sc{gdb/mi} Tracepoint Commands
31983 The commands defined in this section implement MI support for
31984 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31986 @subheading The @code{-trace-find} Command
31987 @findex -trace-find
31989 @subsubheading Synopsis
31992 -trace-find @var{mode} [@var{parameters}@dots{}]
31995 Find a trace frame using criteria defined by @var{mode} and
31996 @var{parameters}. The following table lists permissible
31997 modes and their parameters. For details of operation, see @ref{tfind}.
32002 No parameters are required. Stops examining trace frames.
32005 An integer is required as parameter. Selects tracepoint frame with
32008 @item tracepoint-number
32009 An integer is required as parameter. Finds next
32010 trace frame that corresponds to tracepoint with the specified number.
32013 An address is required as parameter. Finds
32014 next trace frame that corresponds to any tracepoint at the specified
32017 @item pc-inside-range
32018 Two addresses are required as parameters. Finds next trace
32019 frame that corresponds to a tracepoint at an address inside the
32020 specified range. Both bounds are considered to be inside the range.
32022 @item pc-outside-range
32023 Two addresses are required as parameters. Finds
32024 next trace frame that corresponds to a tracepoint at an address outside
32025 the specified range. Both bounds are considered to be inside the range.
32028 Line specification is required as parameter. @xref{Specify Location}.
32029 Finds next trace frame that corresponds to a tracepoint at
32030 the specified location.
32034 If @samp{none} was passed as @var{mode}, the response does not
32035 have fields. Otherwise, the response may have the following fields:
32039 This field has either @samp{0} or @samp{1} as the value, depending
32040 on whether a matching tracepoint was found.
32043 The index of the found traceframe. This field is present iff
32044 the @samp{found} field has value of @samp{1}.
32047 The index of the found tracepoint. This field is present iff
32048 the @samp{found} field has value of @samp{1}.
32051 The information about the frame corresponding to the found trace
32052 frame. This field is present only if a trace frame was found.
32053 @xref{GDB/MI Frame Information}, for description of this field.
32057 @subsubheading @value{GDBN} Command
32059 The corresponding @value{GDBN} command is @samp{tfind}.
32061 @subheading -trace-define-variable
32062 @findex -trace-define-variable
32064 @subsubheading Synopsis
32067 -trace-define-variable @var{name} [ @var{value} ]
32070 Create trace variable @var{name} if it does not exist. If
32071 @var{value} is specified, sets the initial value of the specified
32072 trace variable to that value. Note that the @var{name} should start
32073 with the @samp{$} character.
32075 @subsubheading @value{GDBN} Command
32077 The corresponding @value{GDBN} command is @samp{tvariable}.
32079 @subheading -trace-list-variables
32080 @findex -trace-list-variables
32082 @subsubheading Synopsis
32085 -trace-list-variables
32088 Return a table of all defined trace variables. Each element of the
32089 table has the following fields:
32093 The name of the trace variable. This field is always present.
32096 The initial value. This is a 64-bit signed integer. This
32097 field is always present.
32100 The value the trace variable has at the moment. This is a 64-bit
32101 signed integer. This field is absent iff current value is
32102 not defined, for example if the trace was never run, or is
32107 @subsubheading @value{GDBN} Command
32109 The corresponding @value{GDBN} command is @samp{tvariables}.
32111 @subsubheading Example
32115 -trace-list-variables
32116 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32117 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32118 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32119 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32120 body=[variable=@{name="$trace_timestamp",initial="0"@}
32121 variable=@{name="$foo",initial="10",current="15"@}]@}
32125 @subheading -trace-save
32126 @findex -trace-save
32128 @subsubheading Synopsis
32131 -trace-save [-r ] @var{filename}
32134 Saves the collected trace data to @var{filename}. Without the
32135 @samp{-r} option, the data is downloaded from the target and saved
32136 in a local file. With the @samp{-r} option the target is asked
32137 to perform the save.
32139 @subsubheading @value{GDBN} Command
32141 The corresponding @value{GDBN} command is @samp{tsave}.
32144 @subheading -trace-start
32145 @findex -trace-start
32147 @subsubheading Synopsis
32153 Starts a tracing experiments. The result of this command does not
32156 @subsubheading @value{GDBN} Command
32158 The corresponding @value{GDBN} command is @samp{tstart}.
32160 @subheading -trace-status
32161 @findex -trace-status
32163 @subsubheading Synopsis
32169 Obtains the status of a tracing experiment. The result may include
32170 the following fields:
32175 May have a value of either @samp{0}, when no tracing operations are
32176 supported, @samp{1}, when all tracing operations are supported, or
32177 @samp{file} when examining trace file. In the latter case, examining
32178 of trace frame is possible but new tracing experiement cannot be
32179 started. This field is always present.
32182 May have a value of either @samp{0} or @samp{1} depending on whether
32183 tracing experiement is in progress on target. This field is present
32184 if @samp{supported} field is not @samp{0}.
32187 Report the reason why the tracing was stopped last time. This field
32188 may be absent iff tracing was never stopped on target yet. The
32189 value of @samp{request} means the tracing was stopped as result of
32190 the @code{-trace-stop} command. The value of @samp{overflow} means
32191 the tracing buffer is full. The value of @samp{disconnection} means
32192 tracing was automatically stopped when @value{GDBN} has disconnected.
32193 The value of @samp{passcount} means tracing was stopped when a
32194 tracepoint was passed a maximal number of times for that tracepoint.
32195 This field is present if @samp{supported} field is not @samp{0}.
32197 @item stopping-tracepoint
32198 The number of tracepoint whose passcount as exceeded. This field is
32199 present iff the @samp{stop-reason} field has the value of
32203 @itemx frames-created
32204 The @samp{frames} field is a count of the total number of trace frames
32205 in the trace buffer, while @samp{frames-created} is the total created
32206 during the run, including ones that were discarded, such as when a
32207 circular trace buffer filled up. Both fields are optional.
32211 These fields tell the current size of the tracing buffer and the
32212 remaining space. These fields are optional.
32215 The value of the circular trace buffer flag. @code{1} means that the
32216 trace buffer is circular and old trace frames will be discarded if
32217 necessary to make room, @code{0} means that the trace buffer is linear
32221 The value of the disconnected tracing flag. @code{1} means that
32222 tracing will continue after @value{GDBN} disconnects, @code{0} means
32223 that the trace run will stop.
32226 The filename of the trace file being examined. This field is
32227 optional, and only present when examining a trace file.
32231 @subsubheading @value{GDBN} Command
32233 The corresponding @value{GDBN} command is @samp{tstatus}.
32235 @subheading -trace-stop
32236 @findex -trace-stop
32238 @subsubheading Synopsis
32244 Stops a tracing experiment. The result of this command has the same
32245 fields as @code{-trace-status}, except that the @samp{supported} and
32246 @samp{running} fields are not output.
32248 @subsubheading @value{GDBN} Command
32250 The corresponding @value{GDBN} command is @samp{tstop}.
32253 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32254 @node GDB/MI Symbol Query
32255 @section @sc{gdb/mi} Symbol Query Commands
32259 @subheading The @code{-symbol-info-address} Command
32260 @findex -symbol-info-address
32262 @subsubheading Synopsis
32265 -symbol-info-address @var{symbol}
32268 Describe where @var{symbol} is stored.
32270 @subsubheading @value{GDBN} Command
32272 The corresponding @value{GDBN} command is @samp{info address}.
32274 @subsubheading Example
32278 @subheading The @code{-symbol-info-file} Command
32279 @findex -symbol-info-file
32281 @subsubheading Synopsis
32287 Show the file for the symbol.
32289 @subsubheading @value{GDBN} Command
32291 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32292 @samp{gdb_find_file}.
32294 @subsubheading Example
32298 @subheading The @code{-symbol-info-function} Command
32299 @findex -symbol-info-function
32301 @subsubheading Synopsis
32304 -symbol-info-function
32307 Show which function the symbol lives in.
32309 @subsubheading @value{GDBN} Command
32311 @samp{gdb_get_function} in @code{gdbtk}.
32313 @subsubheading Example
32317 @subheading The @code{-symbol-info-line} Command
32318 @findex -symbol-info-line
32320 @subsubheading Synopsis
32326 Show the core addresses of the code for a source line.
32328 @subsubheading @value{GDBN} Command
32330 The corresponding @value{GDBN} command is @samp{info line}.
32331 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32333 @subsubheading Example
32337 @subheading The @code{-symbol-info-symbol} Command
32338 @findex -symbol-info-symbol
32340 @subsubheading Synopsis
32343 -symbol-info-symbol @var{addr}
32346 Describe what symbol is at location @var{addr}.
32348 @subsubheading @value{GDBN} Command
32350 The corresponding @value{GDBN} command is @samp{info symbol}.
32352 @subsubheading Example
32356 @subheading The @code{-symbol-list-functions} Command
32357 @findex -symbol-list-functions
32359 @subsubheading Synopsis
32362 -symbol-list-functions
32365 List the functions in the executable.
32367 @subsubheading @value{GDBN} Command
32369 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32370 @samp{gdb_search} in @code{gdbtk}.
32372 @subsubheading Example
32377 @subheading The @code{-symbol-list-lines} Command
32378 @findex -symbol-list-lines
32380 @subsubheading Synopsis
32383 -symbol-list-lines @var{filename}
32386 Print the list of lines that contain code and their associated program
32387 addresses for the given source filename. The entries are sorted in
32388 ascending PC order.
32390 @subsubheading @value{GDBN} Command
32392 There is no corresponding @value{GDBN} command.
32394 @subsubheading Example
32397 -symbol-list-lines basics.c
32398 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32404 @subheading The @code{-symbol-list-types} Command
32405 @findex -symbol-list-types
32407 @subsubheading Synopsis
32413 List all the type names.
32415 @subsubheading @value{GDBN} Command
32417 The corresponding commands are @samp{info types} in @value{GDBN},
32418 @samp{gdb_search} in @code{gdbtk}.
32420 @subsubheading Example
32424 @subheading The @code{-symbol-list-variables} Command
32425 @findex -symbol-list-variables
32427 @subsubheading Synopsis
32430 -symbol-list-variables
32433 List all the global and static variable names.
32435 @subsubheading @value{GDBN} Command
32437 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32439 @subsubheading Example
32443 @subheading The @code{-symbol-locate} Command
32444 @findex -symbol-locate
32446 @subsubheading Synopsis
32452 @subsubheading @value{GDBN} Command
32454 @samp{gdb_loc} in @code{gdbtk}.
32456 @subsubheading Example
32460 @subheading The @code{-symbol-type} Command
32461 @findex -symbol-type
32463 @subsubheading Synopsis
32466 -symbol-type @var{variable}
32469 Show type of @var{variable}.
32471 @subsubheading @value{GDBN} Command
32473 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32474 @samp{gdb_obj_variable}.
32476 @subsubheading Example
32481 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32482 @node GDB/MI File Commands
32483 @section @sc{gdb/mi} File Commands
32485 This section describes the GDB/MI commands to specify executable file names
32486 and to read in and obtain symbol table information.
32488 @subheading The @code{-file-exec-and-symbols} Command
32489 @findex -file-exec-and-symbols
32491 @subsubheading Synopsis
32494 -file-exec-and-symbols @var{file}
32497 Specify the executable file to be debugged. This file is the one from
32498 which the symbol table is also read. If no file is specified, the
32499 command clears the executable and symbol information. If breakpoints
32500 are set when using this command with no arguments, @value{GDBN} will produce
32501 error messages. Otherwise, no output is produced, except a completion
32504 @subsubheading @value{GDBN} Command
32506 The corresponding @value{GDBN} command is @samp{file}.
32508 @subsubheading Example
32512 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32518 @subheading The @code{-file-exec-file} Command
32519 @findex -file-exec-file
32521 @subsubheading Synopsis
32524 -file-exec-file @var{file}
32527 Specify the executable file to be debugged. Unlike
32528 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32529 from this file. If used without argument, @value{GDBN} clears the information
32530 about the executable file. No output is produced, except a completion
32533 @subsubheading @value{GDBN} Command
32535 The corresponding @value{GDBN} command is @samp{exec-file}.
32537 @subsubheading Example
32541 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32548 @subheading The @code{-file-list-exec-sections} Command
32549 @findex -file-list-exec-sections
32551 @subsubheading Synopsis
32554 -file-list-exec-sections
32557 List the sections of the current executable file.
32559 @subsubheading @value{GDBN} Command
32561 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32562 information as this command. @code{gdbtk} has a corresponding command
32563 @samp{gdb_load_info}.
32565 @subsubheading Example
32570 @subheading The @code{-file-list-exec-source-file} Command
32571 @findex -file-list-exec-source-file
32573 @subsubheading Synopsis
32576 -file-list-exec-source-file
32579 List the line number, the current source file, and the absolute path
32580 to the current source file for the current executable. The macro
32581 information field has a value of @samp{1} or @samp{0} depending on
32582 whether or not the file includes preprocessor macro information.
32584 @subsubheading @value{GDBN} Command
32586 The @value{GDBN} equivalent is @samp{info source}
32588 @subsubheading Example
32592 123-file-list-exec-source-file
32593 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32598 @subheading The @code{-file-list-exec-source-files} Command
32599 @findex -file-list-exec-source-files
32601 @subsubheading Synopsis
32604 -file-list-exec-source-files
32607 List the source files for the current executable.
32609 It will always output both the filename and fullname (absolute file
32610 name) of a source file.
32612 @subsubheading @value{GDBN} Command
32614 The @value{GDBN} equivalent is @samp{info sources}.
32615 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32617 @subsubheading Example
32620 -file-list-exec-source-files
32622 @{file=foo.c,fullname=/home/foo.c@},
32623 @{file=/home/bar.c,fullname=/home/bar.c@},
32624 @{file=gdb_could_not_find_fullpath.c@}]
32629 @subheading The @code{-file-list-shared-libraries} Command
32630 @findex -file-list-shared-libraries
32632 @subsubheading Synopsis
32635 -file-list-shared-libraries
32638 List the shared libraries in the program.
32640 @subsubheading @value{GDBN} Command
32642 The corresponding @value{GDBN} command is @samp{info shared}.
32644 @subsubheading Example
32648 @subheading The @code{-file-list-symbol-files} Command
32649 @findex -file-list-symbol-files
32651 @subsubheading Synopsis
32654 -file-list-symbol-files
32659 @subsubheading @value{GDBN} Command
32661 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32663 @subsubheading Example
32668 @subheading The @code{-file-symbol-file} Command
32669 @findex -file-symbol-file
32671 @subsubheading Synopsis
32674 -file-symbol-file @var{file}
32677 Read symbol table info from the specified @var{file} argument. When
32678 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32679 produced, except for a completion notification.
32681 @subsubheading @value{GDBN} Command
32683 The corresponding @value{GDBN} command is @samp{symbol-file}.
32685 @subsubheading Example
32689 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32695 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32696 @node GDB/MI Memory Overlay Commands
32697 @section @sc{gdb/mi} Memory Overlay Commands
32699 The memory overlay commands are not implemented.
32701 @c @subheading -overlay-auto
32703 @c @subheading -overlay-list-mapping-state
32705 @c @subheading -overlay-list-overlays
32707 @c @subheading -overlay-map
32709 @c @subheading -overlay-off
32711 @c @subheading -overlay-on
32713 @c @subheading -overlay-unmap
32715 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32716 @node GDB/MI Signal Handling Commands
32717 @section @sc{gdb/mi} Signal Handling Commands
32719 Signal handling commands are not implemented.
32721 @c @subheading -signal-handle
32723 @c @subheading -signal-list-handle-actions
32725 @c @subheading -signal-list-signal-types
32729 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32730 @node GDB/MI Target Manipulation
32731 @section @sc{gdb/mi} Target Manipulation Commands
32734 @subheading The @code{-target-attach} Command
32735 @findex -target-attach
32737 @subsubheading Synopsis
32740 -target-attach @var{pid} | @var{gid} | @var{file}
32743 Attach to a process @var{pid} or a file @var{file} outside of
32744 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32745 group, the id previously returned by
32746 @samp{-list-thread-groups --available} must be used.
32748 @subsubheading @value{GDBN} Command
32750 The corresponding @value{GDBN} command is @samp{attach}.
32752 @subsubheading Example
32756 =thread-created,id="1"
32757 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32763 @subheading The @code{-target-compare-sections} Command
32764 @findex -target-compare-sections
32766 @subsubheading Synopsis
32769 -target-compare-sections [ @var{section} ]
32772 Compare data of section @var{section} on target to the exec file.
32773 Without the argument, all sections are compared.
32775 @subsubheading @value{GDBN} Command
32777 The @value{GDBN} equivalent is @samp{compare-sections}.
32779 @subsubheading Example
32784 @subheading The @code{-target-detach} Command
32785 @findex -target-detach
32787 @subsubheading Synopsis
32790 -target-detach [ @var{pid} | @var{gid} ]
32793 Detach from the remote target which normally resumes its execution.
32794 If either @var{pid} or @var{gid} is specified, detaches from either
32795 the specified process, or specified thread group. There's no output.
32797 @subsubheading @value{GDBN} Command
32799 The corresponding @value{GDBN} command is @samp{detach}.
32801 @subsubheading Example
32811 @subheading The @code{-target-disconnect} Command
32812 @findex -target-disconnect
32814 @subsubheading Synopsis
32820 Disconnect from the remote target. There's no output and the target is
32821 generally not resumed.
32823 @subsubheading @value{GDBN} Command
32825 The corresponding @value{GDBN} command is @samp{disconnect}.
32827 @subsubheading Example
32837 @subheading The @code{-target-download} Command
32838 @findex -target-download
32840 @subsubheading Synopsis
32846 Loads the executable onto the remote target.
32847 It prints out an update message every half second, which includes the fields:
32851 The name of the section.
32853 The size of what has been sent so far for that section.
32855 The size of the section.
32857 The total size of what was sent so far (the current and the previous sections).
32859 The size of the overall executable to download.
32863 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32864 @sc{gdb/mi} Output Syntax}).
32866 In addition, it prints the name and size of the sections, as they are
32867 downloaded. These messages include the following fields:
32871 The name of the section.
32873 The size of the section.
32875 The size of the overall executable to download.
32879 At the end, a summary is printed.
32881 @subsubheading @value{GDBN} Command
32883 The corresponding @value{GDBN} command is @samp{load}.
32885 @subsubheading Example
32887 Note: each status message appears on a single line. Here the messages
32888 have been broken down so that they can fit onto a page.
32893 +download,@{section=".text",section-size="6668",total-size="9880"@}
32894 +download,@{section=".text",section-sent="512",section-size="6668",
32895 total-sent="512",total-size="9880"@}
32896 +download,@{section=".text",section-sent="1024",section-size="6668",
32897 total-sent="1024",total-size="9880"@}
32898 +download,@{section=".text",section-sent="1536",section-size="6668",
32899 total-sent="1536",total-size="9880"@}
32900 +download,@{section=".text",section-sent="2048",section-size="6668",
32901 total-sent="2048",total-size="9880"@}
32902 +download,@{section=".text",section-sent="2560",section-size="6668",
32903 total-sent="2560",total-size="9880"@}
32904 +download,@{section=".text",section-sent="3072",section-size="6668",
32905 total-sent="3072",total-size="9880"@}
32906 +download,@{section=".text",section-sent="3584",section-size="6668",
32907 total-sent="3584",total-size="9880"@}
32908 +download,@{section=".text",section-sent="4096",section-size="6668",
32909 total-sent="4096",total-size="9880"@}
32910 +download,@{section=".text",section-sent="4608",section-size="6668",
32911 total-sent="4608",total-size="9880"@}
32912 +download,@{section=".text",section-sent="5120",section-size="6668",
32913 total-sent="5120",total-size="9880"@}
32914 +download,@{section=".text",section-sent="5632",section-size="6668",
32915 total-sent="5632",total-size="9880"@}
32916 +download,@{section=".text",section-sent="6144",section-size="6668",
32917 total-sent="6144",total-size="9880"@}
32918 +download,@{section=".text",section-sent="6656",section-size="6668",
32919 total-sent="6656",total-size="9880"@}
32920 +download,@{section=".init",section-size="28",total-size="9880"@}
32921 +download,@{section=".fini",section-size="28",total-size="9880"@}
32922 +download,@{section=".data",section-size="3156",total-size="9880"@}
32923 +download,@{section=".data",section-sent="512",section-size="3156",
32924 total-sent="7236",total-size="9880"@}
32925 +download,@{section=".data",section-sent="1024",section-size="3156",
32926 total-sent="7748",total-size="9880"@}
32927 +download,@{section=".data",section-sent="1536",section-size="3156",
32928 total-sent="8260",total-size="9880"@}
32929 +download,@{section=".data",section-sent="2048",section-size="3156",
32930 total-sent="8772",total-size="9880"@}
32931 +download,@{section=".data",section-sent="2560",section-size="3156",
32932 total-sent="9284",total-size="9880"@}
32933 +download,@{section=".data",section-sent="3072",section-size="3156",
32934 total-sent="9796",total-size="9880"@}
32935 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32942 @subheading The @code{-target-exec-status} Command
32943 @findex -target-exec-status
32945 @subsubheading Synopsis
32948 -target-exec-status
32951 Provide information on the state of the target (whether it is running or
32952 not, for instance).
32954 @subsubheading @value{GDBN} Command
32956 There's no equivalent @value{GDBN} command.
32958 @subsubheading Example
32962 @subheading The @code{-target-list-available-targets} Command
32963 @findex -target-list-available-targets
32965 @subsubheading Synopsis
32968 -target-list-available-targets
32971 List the possible targets to connect to.
32973 @subsubheading @value{GDBN} Command
32975 The corresponding @value{GDBN} command is @samp{help target}.
32977 @subsubheading Example
32981 @subheading The @code{-target-list-current-targets} Command
32982 @findex -target-list-current-targets
32984 @subsubheading Synopsis
32987 -target-list-current-targets
32990 Describe the current target.
32992 @subsubheading @value{GDBN} Command
32994 The corresponding information is printed by @samp{info file} (among
32997 @subsubheading Example
33001 @subheading The @code{-target-list-parameters} Command
33002 @findex -target-list-parameters
33004 @subsubheading Synopsis
33007 -target-list-parameters
33013 @subsubheading @value{GDBN} Command
33017 @subsubheading Example
33021 @subheading The @code{-target-select} Command
33022 @findex -target-select
33024 @subsubheading Synopsis
33027 -target-select @var{type} @var{parameters @dots{}}
33030 Connect @value{GDBN} to the remote target. This command takes two args:
33034 The type of target, for instance @samp{remote}, etc.
33035 @item @var{parameters}
33036 Device names, host names and the like. @xref{Target Commands, ,
33037 Commands for Managing Targets}, for more details.
33040 The output is a connection notification, followed by the address at
33041 which the target program is, in the following form:
33044 ^connected,addr="@var{address}",func="@var{function name}",
33045 args=[@var{arg list}]
33048 @subsubheading @value{GDBN} Command
33050 The corresponding @value{GDBN} command is @samp{target}.
33052 @subsubheading Example
33056 -target-select remote /dev/ttya
33057 ^connected,addr="0xfe00a300",func="??",args=[]
33061 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33062 @node GDB/MI File Transfer Commands
33063 @section @sc{gdb/mi} File Transfer Commands
33066 @subheading The @code{-target-file-put} Command
33067 @findex -target-file-put
33069 @subsubheading Synopsis
33072 -target-file-put @var{hostfile} @var{targetfile}
33075 Copy file @var{hostfile} from the host system (the machine running
33076 @value{GDBN}) to @var{targetfile} on the target system.
33078 @subsubheading @value{GDBN} Command
33080 The corresponding @value{GDBN} command is @samp{remote put}.
33082 @subsubheading Example
33086 -target-file-put localfile remotefile
33092 @subheading The @code{-target-file-get} Command
33093 @findex -target-file-get
33095 @subsubheading Synopsis
33098 -target-file-get @var{targetfile} @var{hostfile}
33101 Copy file @var{targetfile} from the target system to @var{hostfile}
33102 on the host system.
33104 @subsubheading @value{GDBN} Command
33106 The corresponding @value{GDBN} command is @samp{remote get}.
33108 @subsubheading Example
33112 -target-file-get remotefile localfile
33118 @subheading The @code{-target-file-delete} Command
33119 @findex -target-file-delete
33121 @subsubheading Synopsis
33124 -target-file-delete @var{targetfile}
33127 Delete @var{targetfile} from the target system.
33129 @subsubheading @value{GDBN} Command
33131 The corresponding @value{GDBN} command is @samp{remote delete}.
33133 @subsubheading Example
33137 -target-file-delete remotefile
33143 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33144 @node GDB/MI Miscellaneous Commands
33145 @section Miscellaneous @sc{gdb/mi} Commands
33147 @c @subheading -gdb-complete
33149 @subheading The @code{-gdb-exit} Command
33152 @subsubheading Synopsis
33158 Exit @value{GDBN} immediately.
33160 @subsubheading @value{GDBN} Command
33162 Approximately corresponds to @samp{quit}.
33164 @subsubheading Example
33174 @subheading The @code{-exec-abort} Command
33175 @findex -exec-abort
33177 @subsubheading Synopsis
33183 Kill the inferior running program.
33185 @subsubheading @value{GDBN} Command
33187 The corresponding @value{GDBN} command is @samp{kill}.
33189 @subsubheading Example
33194 @subheading The @code{-gdb-set} Command
33197 @subsubheading Synopsis
33203 Set an internal @value{GDBN} variable.
33204 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33206 @subsubheading @value{GDBN} Command
33208 The corresponding @value{GDBN} command is @samp{set}.
33210 @subsubheading Example
33220 @subheading The @code{-gdb-show} Command
33223 @subsubheading Synopsis
33229 Show the current value of a @value{GDBN} variable.
33231 @subsubheading @value{GDBN} Command
33233 The corresponding @value{GDBN} command is @samp{show}.
33235 @subsubheading Example
33244 @c @subheading -gdb-source
33247 @subheading The @code{-gdb-version} Command
33248 @findex -gdb-version
33250 @subsubheading Synopsis
33256 Show version information for @value{GDBN}. Used mostly in testing.
33258 @subsubheading @value{GDBN} Command
33260 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33261 default shows this information when you start an interactive session.
33263 @subsubheading Example
33265 @c This example modifies the actual output from GDB to avoid overfull
33271 ~Copyright 2000 Free Software Foundation, Inc.
33272 ~GDB is free software, covered by the GNU General Public License, and
33273 ~you are welcome to change it and/or distribute copies of it under
33274 ~ certain conditions.
33275 ~Type "show copying" to see the conditions.
33276 ~There is absolutely no warranty for GDB. Type "show warranty" for
33278 ~This GDB was configured as
33279 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33284 @subheading The @code{-list-features} Command
33285 @findex -list-features
33287 Returns a list of particular features of the MI protocol that
33288 this version of gdb implements. A feature can be a command,
33289 or a new field in an output of some command, or even an
33290 important bugfix. While a frontend can sometimes detect presence
33291 of a feature at runtime, it is easier to perform detection at debugger
33294 The command returns a list of strings, with each string naming an
33295 available feature. Each returned string is just a name, it does not
33296 have any internal structure. The list of possible feature names
33302 (gdb) -list-features
33303 ^done,result=["feature1","feature2"]
33306 The current list of features is:
33309 @item frozen-varobjs
33310 Indicates support for the @code{-var-set-frozen} command, as well
33311 as possible presense of the @code{frozen} field in the output
33312 of @code{-varobj-create}.
33313 @item pending-breakpoints
33314 Indicates support for the @option{-f} option to the @code{-break-insert}
33317 Indicates Python scripting support, Python-based
33318 pretty-printing commands, and possible presence of the
33319 @samp{display_hint} field in the output of @code{-var-list-children}
33321 Indicates support for the @code{-thread-info} command.
33322 @item data-read-memory-bytes
33323 Indicates support for the @code{-data-read-memory-bytes} and the
33324 @code{-data-write-memory-bytes} commands.
33325 @item breakpoint-notifications
33326 Indicates that changes to breakpoints and breakpoints created via the
33327 CLI will be announced via async records.
33328 @item ada-task-info
33329 Indicates support for the @code{-ada-task-info} command.
33332 @subheading The @code{-list-target-features} Command
33333 @findex -list-target-features
33335 Returns a list of particular features that are supported by the
33336 target. Those features affect the permitted MI commands, but
33337 unlike the features reported by the @code{-list-features} command, the
33338 features depend on which target GDB is using at the moment. Whenever
33339 a target can change, due to commands such as @code{-target-select},
33340 @code{-target-attach} or @code{-exec-run}, the list of target features
33341 may change, and the frontend should obtain it again.
33345 (gdb) -list-features
33346 ^done,result=["async"]
33349 The current list of features is:
33353 Indicates that the target is capable of asynchronous command
33354 execution, which means that @value{GDBN} will accept further commands
33355 while the target is running.
33358 Indicates that the target is capable of reverse execution.
33359 @xref{Reverse Execution}, for more information.
33363 @subheading The @code{-list-thread-groups} Command
33364 @findex -list-thread-groups
33366 @subheading Synopsis
33369 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33372 Lists thread groups (@pxref{Thread groups}). When a single thread
33373 group is passed as the argument, lists the children of that group.
33374 When several thread group are passed, lists information about those
33375 thread groups. Without any parameters, lists information about all
33376 top-level thread groups.
33378 Normally, thread groups that are being debugged are reported.
33379 With the @samp{--available} option, @value{GDBN} reports thread groups
33380 available on the target.
33382 The output of this command may have either a @samp{threads} result or
33383 a @samp{groups} result. The @samp{thread} result has a list of tuples
33384 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33385 Information}). The @samp{groups} result has a list of tuples as value,
33386 each tuple describing a thread group. If top-level groups are
33387 requested (that is, no parameter is passed), or when several groups
33388 are passed, the output always has a @samp{groups} result. The format
33389 of the @samp{group} result is described below.
33391 To reduce the number of roundtrips it's possible to list thread groups
33392 together with their children, by passing the @samp{--recurse} option
33393 and the recursion depth. Presently, only recursion depth of 1 is
33394 permitted. If this option is present, then every reported thread group
33395 will also include its children, either as @samp{group} or
33396 @samp{threads} field.
33398 In general, any combination of option and parameters is permitted, with
33399 the following caveats:
33403 When a single thread group is passed, the output will typically
33404 be the @samp{threads} result. Because threads may not contain
33405 anything, the @samp{recurse} option will be ignored.
33408 When the @samp{--available} option is passed, limited information may
33409 be available. In particular, the list of threads of a process might
33410 be inaccessible. Further, specifying specific thread groups might
33411 not give any performance advantage over listing all thread groups.
33412 The frontend should assume that @samp{-list-thread-groups --available}
33413 is always an expensive operation and cache the results.
33417 The @samp{groups} result is a list of tuples, where each tuple may
33418 have the following fields:
33422 Identifier of the thread group. This field is always present.
33423 The identifier is an opaque string; frontends should not try to
33424 convert it to an integer, even though it might look like one.
33427 The type of the thread group. At present, only @samp{process} is a
33431 The target-specific process identifier. This field is only present
33432 for thread groups of type @samp{process} and only if the process exists.
33435 The number of children this thread group has. This field may be
33436 absent for an available thread group.
33439 This field has a list of tuples as value, each tuple describing a
33440 thread. It may be present if the @samp{--recurse} option is
33441 specified, and it's actually possible to obtain the threads.
33444 This field is a list of integers, each identifying a core that one
33445 thread of the group is running on. This field may be absent if
33446 such information is not available.
33449 The name of the executable file that corresponds to this thread group.
33450 The field is only present for thread groups of type @samp{process},
33451 and only if there is a corresponding executable file.
33455 @subheading Example
33459 -list-thread-groups
33460 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33461 -list-thread-groups 17
33462 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33463 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33464 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33465 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33466 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33467 -list-thread-groups --available
33468 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33469 -list-thread-groups --available --recurse 1
33470 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33471 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33472 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33473 -list-thread-groups --available --recurse 1 17 18
33474 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33475 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33476 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33479 @subheading The @code{-info-os} Command
33482 @subsubheading Synopsis
33485 -info-os [ @var{type} ]
33488 If no argument is supplied, the command returns a table of available
33489 operating-system-specific information types. If one of these types is
33490 supplied as an argument @var{type}, then the command returns a table
33491 of data of that type.
33493 The types of information available depend on the target operating
33496 @subsubheading @value{GDBN} Command
33498 The corresponding @value{GDBN} command is @samp{info os}.
33500 @subsubheading Example
33502 When run on a @sc{gnu}/Linux system, the output will look something
33508 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33509 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33510 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33511 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33512 body=[item=@{col0="processes",col1="Listing of all processes",
33513 col2="Processes"@},
33514 item=@{col0="procgroups",col1="Listing of all process groups",
33515 col2="Process groups"@},
33516 item=@{col0="threads",col1="Listing of all threads",
33518 item=@{col0="files",col1="Listing of all file descriptors",
33519 col2="File descriptors"@},
33520 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33522 item=@{col0="shm",col1="Listing of all shared-memory regions",
33523 col2="Shared-memory regions"@},
33524 item=@{col0="semaphores",col1="Listing of all semaphores",
33525 col2="Semaphores"@},
33526 item=@{col0="msg",col1="Listing of all message queues",
33527 col2="Message queues"@},
33528 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33529 col2="Kernel modules"@}]@}
33532 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33533 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33534 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33535 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33536 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33537 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33538 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33539 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33541 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33542 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33546 (Note that the MI output here includes a @code{"Title"} column that
33547 does not appear in command-line @code{info os}; this column is useful
33548 for MI clients that want to enumerate the types of data, such as in a
33549 popup menu, but is needless clutter on the command line, and
33550 @code{info os} omits it.)
33552 @subheading The @code{-add-inferior} Command
33553 @findex -add-inferior
33555 @subheading Synopsis
33561 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33562 inferior is not associated with any executable. Such association may
33563 be established with the @samp{-file-exec-and-symbols} command
33564 (@pxref{GDB/MI File Commands}). The command response has a single
33565 field, @samp{thread-group}, whose value is the identifier of the
33566 thread group corresponding to the new inferior.
33568 @subheading Example
33573 ^done,thread-group="i3"
33576 @subheading The @code{-interpreter-exec} Command
33577 @findex -interpreter-exec
33579 @subheading Synopsis
33582 -interpreter-exec @var{interpreter} @var{command}
33584 @anchor{-interpreter-exec}
33586 Execute the specified @var{command} in the given @var{interpreter}.
33588 @subheading @value{GDBN} Command
33590 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33592 @subheading Example
33596 -interpreter-exec console "break main"
33597 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33598 &"During symbol reading, bad structure-type format.\n"
33599 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33604 @subheading The @code{-inferior-tty-set} Command
33605 @findex -inferior-tty-set
33607 @subheading Synopsis
33610 -inferior-tty-set /dev/pts/1
33613 Set terminal for future runs of the program being debugged.
33615 @subheading @value{GDBN} Command
33617 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33619 @subheading Example
33623 -inferior-tty-set /dev/pts/1
33628 @subheading The @code{-inferior-tty-show} Command
33629 @findex -inferior-tty-show
33631 @subheading Synopsis
33637 Show terminal for future runs of program being debugged.
33639 @subheading @value{GDBN} Command
33641 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33643 @subheading Example
33647 -inferior-tty-set /dev/pts/1
33651 ^done,inferior_tty_terminal="/dev/pts/1"
33655 @subheading The @code{-enable-timings} Command
33656 @findex -enable-timings
33658 @subheading Synopsis
33661 -enable-timings [yes | no]
33664 Toggle the printing of the wallclock, user and system times for an MI
33665 command as a field in its output. This command is to help frontend
33666 developers optimize the performance of their code. No argument is
33667 equivalent to @samp{yes}.
33669 @subheading @value{GDBN} Command
33673 @subheading Example
33681 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33682 addr="0x080484ed",func="main",file="myprog.c",
33683 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33685 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33693 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33694 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33695 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33696 fullname="/home/nickrob/myprog.c",line="73"@}
33701 @chapter @value{GDBN} Annotations
33703 This chapter describes annotations in @value{GDBN}. Annotations were
33704 designed to interface @value{GDBN} to graphical user interfaces or other
33705 similar programs which want to interact with @value{GDBN} at a
33706 relatively high level.
33708 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33712 This is Edition @value{EDITION}, @value{DATE}.
33716 * Annotations Overview:: What annotations are; the general syntax.
33717 * Server Prefix:: Issuing a command without affecting user state.
33718 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33719 * Errors:: Annotations for error messages.
33720 * Invalidation:: Some annotations describe things now invalid.
33721 * Annotations for Running::
33722 Whether the program is running, how it stopped, etc.
33723 * Source Annotations:: Annotations describing source code.
33726 @node Annotations Overview
33727 @section What is an Annotation?
33728 @cindex annotations
33730 Annotations start with a newline character, two @samp{control-z}
33731 characters, and the name of the annotation. If there is no additional
33732 information associated with this annotation, the name of the annotation
33733 is followed immediately by a newline. If there is additional
33734 information, the name of the annotation is followed by a space, the
33735 additional information, and a newline. The additional information
33736 cannot contain newline characters.
33738 Any output not beginning with a newline and two @samp{control-z}
33739 characters denotes literal output from @value{GDBN}. Currently there is
33740 no need for @value{GDBN} to output a newline followed by two
33741 @samp{control-z} characters, but if there was such a need, the
33742 annotations could be extended with an @samp{escape} annotation which
33743 means those three characters as output.
33745 The annotation @var{level}, which is specified using the
33746 @option{--annotate} command line option (@pxref{Mode Options}), controls
33747 how much information @value{GDBN} prints together with its prompt,
33748 values of expressions, source lines, and other types of output. Level 0
33749 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33750 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33751 for programs that control @value{GDBN}, and level 2 annotations have
33752 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33753 Interface, annotate, GDB's Obsolete Annotations}).
33756 @kindex set annotate
33757 @item set annotate @var{level}
33758 The @value{GDBN} command @code{set annotate} sets the level of
33759 annotations to the specified @var{level}.
33761 @item show annotate
33762 @kindex show annotate
33763 Show the current annotation level.
33766 This chapter describes level 3 annotations.
33768 A simple example of starting up @value{GDBN} with annotations is:
33771 $ @kbd{gdb --annotate=3}
33773 Copyright 2003 Free Software Foundation, Inc.
33774 GDB is free software, covered by the GNU General Public License,
33775 and you are welcome to change it and/or distribute copies of it
33776 under certain conditions.
33777 Type "show copying" to see the conditions.
33778 There is absolutely no warranty for GDB. Type "show warranty"
33780 This GDB was configured as "i386-pc-linux-gnu"
33791 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33792 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33793 denotes a @samp{control-z} character) are annotations; the rest is
33794 output from @value{GDBN}.
33796 @node Server Prefix
33797 @section The Server Prefix
33798 @cindex server prefix
33800 If you prefix a command with @samp{server } then it will not affect
33801 the command history, nor will it affect @value{GDBN}'s notion of which
33802 command to repeat if @key{RET} is pressed on a line by itself. This
33803 means that commands can be run behind a user's back by a front-end in
33804 a transparent manner.
33806 The @code{server } prefix does not affect the recording of values into
33807 the value history; to print a value without recording it into the
33808 value history, use the @code{output} command instead of the
33809 @code{print} command.
33811 Using this prefix also disables confirmation requests
33812 (@pxref{confirmation requests}).
33815 @section Annotation for @value{GDBN} Input
33817 @cindex annotations for prompts
33818 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33819 to know when to send output, when the output from a given command is
33822 Different kinds of input each have a different @dfn{input type}. Each
33823 input type has three annotations: a @code{pre-} annotation, which
33824 denotes the beginning of any prompt which is being output, a plain
33825 annotation, which denotes the end of the prompt, and then a @code{post-}
33826 annotation which denotes the end of any echo which may (or may not) be
33827 associated with the input. For example, the @code{prompt} input type
33828 features the following annotations:
33836 The input types are
33839 @findex pre-prompt annotation
33840 @findex prompt annotation
33841 @findex post-prompt annotation
33843 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33845 @findex pre-commands annotation
33846 @findex commands annotation
33847 @findex post-commands annotation
33849 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33850 command. The annotations are repeated for each command which is input.
33852 @findex pre-overload-choice annotation
33853 @findex overload-choice annotation
33854 @findex post-overload-choice annotation
33855 @item overload-choice
33856 When @value{GDBN} wants the user to select between various overloaded functions.
33858 @findex pre-query annotation
33859 @findex query annotation
33860 @findex post-query annotation
33862 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33864 @findex pre-prompt-for-continue annotation
33865 @findex prompt-for-continue annotation
33866 @findex post-prompt-for-continue annotation
33867 @item prompt-for-continue
33868 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33869 expect this to work well; instead use @code{set height 0} to disable
33870 prompting. This is because the counting of lines is buggy in the
33871 presence of annotations.
33876 @cindex annotations for errors, warnings and interrupts
33878 @findex quit annotation
33883 This annotation occurs right before @value{GDBN} responds to an interrupt.
33885 @findex error annotation
33890 This annotation occurs right before @value{GDBN} responds to an error.
33892 Quit and error annotations indicate that any annotations which @value{GDBN} was
33893 in the middle of may end abruptly. For example, if a
33894 @code{value-history-begin} annotation is followed by a @code{error}, one
33895 cannot expect to receive the matching @code{value-history-end}. One
33896 cannot expect not to receive it either, however; an error annotation
33897 does not necessarily mean that @value{GDBN} is immediately returning all the way
33900 @findex error-begin annotation
33901 A quit or error annotation may be preceded by
33907 Any output between that and the quit or error annotation is the error
33910 Warning messages are not yet annotated.
33911 @c If we want to change that, need to fix warning(), type_error(),
33912 @c range_error(), and possibly other places.
33915 @section Invalidation Notices
33917 @cindex annotations for invalidation messages
33918 The following annotations say that certain pieces of state may have
33922 @findex frames-invalid annotation
33923 @item ^Z^Zframes-invalid
33925 The frames (for example, output from the @code{backtrace} command) may
33928 @findex breakpoints-invalid annotation
33929 @item ^Z^Zbreakpoints-invalid
33931 The breakpoints may have changed. For example, the user just added or
33932 deleted a breakpoint.
33935 @node Annotations for Running
33936 @section Running the Program
33937 @cindex annotations for running programs
33939 @findex starting annotation
33940 @findex stopping annotation
33941 When the program starts executing due to a @value{GDBN} command such as
33942 @code{step} or @code{continue},
33948 is output. When the program stops,
33954 is output. Before the @code{stopped} annotation, a variety of
33955 annotations describe how the program stopped.
33958 @findex exited annotation
33959 @item ^Z^Zexited @var{exit-status}
33960 The program exited, and @var{exit-status} is the exit status (zero for
33961 successful exit, otherwise nonzero).
33963 @findex signalled annotation
33964 @findex signal-name annotation
33965 @findex signal-name-end annotation
33966 @findex signal-string annotation
33967 @findex signal-string-end annotation
33968 @item ^Z^Zsignalled
33969 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33970 annotation continues:
33976 ^Z^Zsignal-name-end
33980 ^Z^Zsignal-string-end
33985 where @var{name} is the name of the signal, such as @code{SIGILL} or
33986 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33987 as @code{Illegal Instruction} or @code{Segmentation fault}.
33988 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33989 user's benefit and have no particular format.
33991 @findex signal annotation
33993 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33994 just saying that the program received the signal, not that it was
33995 terminated with it.
33997 @findex breakpoint annotation
33998 @item ^Z^Zbreakpoint @var{number}
33999 The program hit breakpoint number @var{number}.
34001 @findex watchpoint annotation
34002 @item ^Z^Zwatchpoint @var{number}
34003 The program hit watchpoint number @var{number}.
34006 @node Source Annotations
34007 @section Displaying Source
34008 @cindex annotations for source display
34010 @findex source annotation
34011 The following annotation is used instead of displaying source code:
34014 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34017 where @var{filename} is an absolute file name indicating which source
34018 file, @var{line} is the line number within that file (where 1 is the
34019 first line in the file), @var{character} is the character position
34020 within the file (where 0 is the first character in the file) (for most
34021 debug formats this will necessarily point to the beginning of a line),
34022 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34023 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34024 @var{addr} is the address in the target program associated with the
34025 source which is being displayed. @var{addr} is in the form @samp{0x}
34026 followed by one or more lowercase hex digits (note that this does not
34027 depend on the language).
34029 @node JIT Interface
34030 @chapter JIT Compilation Interface
34031 @cindex just-in-time compilation
34032 @cindex JIT compilation interface
34034 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34035 interface. A JIT compiler is a program or library that generates native
34036 executable code at runtime and executes it, usually in order to achieve good
34037 performance while maintaining platform independence.
34039 Programs that use JIT compilation are normally difficult to debug because
34040 portions of their code are generated at runtime, instead of being loaded from
34041 object files, which is where @value{GDBN} normally finds the program's symbols
34042 and debug information. In order to debug programs that use JIT compilation,
34043 @value{GDBN} has an interface that allows the program to register in-memory
34044 symbol files with @value{GDBN} at runtime.
34046 If you are using @value{GDBN} to debug a program that uses this interface, then
34047 it should work transparently so long as you have not stripped the binary. If
34048 you are developing a JIT compiler, then the interface is documented in the rest
34049 of this chapter. At this time, the only known client of this interface is the
34052 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34053 JIT compiler communicates with @value{GDBN} by writing data into a global
34054 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34055 attaches, it reads a linked list of symbol files from the global variable to
34056 find existing code, and puts a breakpoint in the function so that it can find
34057 out about additional code.
34060 * Declarations:: Relevant C struct declarations
34061 * Registering Code:: Steps to register code
34062 * Unregistering Code:: Steps to unregister code
34063 * Custom Debug Info:: Emit debug information in a custom format
34067 @section JIT Declarations
34069 These are the relevant struct declarations that a C program should include to
34070 implement the interface:
34080 struct jit_code_entry
34082 struct jit_code_entry *next_entry;
34083 struct jit_code_entry *prev_entry;
34084 const char *symfile_addr;
34085 uint64_t symfile_size;
34088 struct jit_descriptor
34091 /* This type should be jit_actions_t, but we use uint32_t
34092 to be explicit about the bitwidth. */
34093 uint32_t action_flag;
34094 struct jit_code_entry *relevant_entry;
34095 struct jit_code_entry *first_entry;
34098 /* GDB puts a breakpoint in this function. */
34099 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34101 /* Make sure to specify the version statically, because the
34102 debugger may check the version before we can set it. */
34103 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34106 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34107 modifications to this global data properly, which can easily be done by putting
34108 a global mutex around modifications to these structures.
34110 @node Registering Code
34111 @section Registering Code
34113 To register code with @value{GDBN}, the JIT should follow this protocol:
34117 Generate an object file in memory with symbols and other desired debug
34118 information. The file must include the virtual addresses of the sections.
34121 Create a code entry for the file, which gives the start and size of the symbol
34125 Add it to the linked list in the JIT descriptor.
34128 Point the relevant_entry field of the descriptor at the entry.
34131 Set @code{action_flag} to @code{JIT_REGISTER} and call
34132 @code{__jit_debug_register_code}.
34135 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34136 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34137 new code. However, the linked list must still be maintained in order to allow
34138 @value{GDBN} to attach to a running process and still find the symbol files.
34140 @node Unregistering Code
34141 @section Unregistering Code
34143 If code is freed, then the JIT should use the following protocol:
34147 Remove the code entry corresponding to the code from the linked list.
34150 Point the @code{relevant_entry} field of the descriptor at the code entry.
34153 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34154 @code{__jit_debug_register_code}.
34157 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34158 and the JIT will leak the memory used for the associated symbol files.
34160 @node Custom Debug Info
34161 @section Custom Debug Info
34162 @cindex custom JIT debug info
34163 @cindex JIT debug info reader
34165 Generating debug information in platform-native file formats (like ELF
34166 or COFF) may be an overkill for JIT compilers; especially if all the
34167 debug info is used for is displaying a meaningful backtrace. The
34168 issue can be resolved by having the JIT writers decide on a debug info
34169 format and also provide a reader that parses the debug info generated
34170 by the JIT compiler. This section gives a brief overview on writing
34171 such a parser. More specific details can be found in the source file
34172 @file{gdb/jit-reader.in}, which is also installed as a header at
34173 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34175 The reader is implemented as a shared object (so this functionality is
34176 not available on platforms which don't allow loading shared objects at
34177 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34178 @code{jit-reader-unload} are provided, to be used to load and unload
34179 the readers from a preconfigured directory. Once loaded, the shared
34180 object is used the parse the debug information emitted by the JIT
34184 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34185 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34188 @node Using JIT Debug Info Readers
34189 @subsection Using JIT Debug Info Readers
34190 @kindex jit-reader-load
34191 @kindex jit-reader-unload
34193 Readers can be loaded and unloaded using the @code{jit-reader-load}
34194 and @code{jit-reader-unload} commands.
34197 @item jit-reader-load @var{reader}
34198 Load the JIT reader named @var{reader}. @var{reader} is a shared
34199 object specified as either an absolute or a relative file name. In
34200 the latter case, @value{GDBN} will try to load the reader from a
34201 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34202 system (here @var{libdir} is the system library directory, often
34203 @file{/usr/local/lib}).
34205 Only one reader can be active at a time; trying to load a second
34206 reader when one is already loaded will result in @value{GDBN}
34207 reporting an error. A new JIT reader can be loaded by first unloading
34208 the current one using @code{jit-reader-unload} and then invoking
34209 @code{jit-reader-load}.
34211 @item jit-reader-unload
34212 Unload the currently loaded JIT reader.
34216 @node Writing JIT Debug Info Readers
34217 @subsection Writing JIT Debug Info Readers
34218 @cindex writing JIT debug info readers
34220 As mentioned, a reader is essentially a shared object conforming to a
34221 certain ABI. This ABI is described in @file{jit-reader.h}.
34223 @file{jit-reader.h} defines the structures, macros and functions
34224 required to write a reader. It is installed (along with
34225 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34226 the system include directory.
34228 Readers need to be released under a GPL compatible license. A reader
34229 can be declared as released under such a license by placing the macro
34230 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34232 The entry point for readers is the symbol @code{gdb_init_reader},
34233 which is expected to be a function with the prototype
34235 @findex gdb_init_reader
34237 extern struct gdb_reader_funcs *gdb_init_reader (void);
34240 @cindex @code{struct gdb_reader_funcs}
34242 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34243 functions. These functions are executed to read the debug info
34244 generated by the JIT compiler (@code{read}), to unwind stack frames
34245 (@code{unwind}) and to create canonical frame IDs
34246 (@code{get_Frame_id}). It also has a callback that is called when the
34247 reader is being unloaded (@code{destroy}). The struct looks like this
34250 struct gdb_reader_funcs
34252 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34253 int reader_version;
34255 /* For use by the reader. */
34258 gdb_read_debug_info *read;
34259 gdb_unwind_frame *unwind;
34260 gdb_get_frame_id *get_frame_id;
34261 gdb_destroy_reader *destroy;
34265 @cindex @code{struct gdb_symbol_callbacks}
34266 @cindex @code{struct gdb_unwind_callbacks}
34268 The callbacks are provided with another set of callbacks by
34269 @value{GDBN} to do their job. For @code{read}, these callbacks are
34270 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34271 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34272 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34273 files and new symbol tables inside those object files. @code{struct
34274 gdb_unwind_callbacks} has callbacks to read registers off the current
34275 frame and to write out the values of the registers in the previous
34276 frame. Both have a callback (@code{target_read}) to read bytes off the
34277 target's address space.
34279 @node In-Process Agent
34280 @chapter In-Process Agent
34281 @cindex debugging agent
34282 The traditional debugging model is conceptually low-speed, but works fine,
34283 because most bugs can be reproduced in debugging-mode execution. However,
34284 as multi-core or many-core processors are becoming mainstream, and
34285 multi-threaded programs become more and more popular, there should be more
34286 and more bugs that only manifest themselves at normal-mode execution, for
34287 example, thread races, because debugger's interference with the program's
34288 timing may conceal the bugs. On the other hand, in some applications,
34289 it is not feasible for the debugger to interrupt the program's execution
34290 long enough for the developer to learn anything helpful about its behavior.
34291 If the program's correctness depends on its real-time behavior, delays
34292 introduced by a debugger might cause the program to fail, even when the
34293 code itself is correct. It is useful to be able to observe the program's
34294 behavior without interrupting it.
34296 Therefore, traditional debugging model is too intrusive to reproduce
34297 some bugs. In order to reduce the interference with the program, we can
34298 reduce the number of operations performed by debugger. The
34299 @dfn{In-Process Agent}, a shared library, is running within the same
34300 process with inferior, and is able to perform some debugging operations
34301 itself. As a result, debugger is only involved when necessary, and
34302 performance of debugging can be improved accordingly. Note that
34303 interference with program can be reduced but can't be removed completely,
34304 because the in-process agent will still stop or slow down the program.
34306 The in-process agent can interpret and execute Agent Expressions
34307 (@pxref{Agent Expressions}) during performing debugging operations. The
34308 agent expressions can be used for different purposes, such as collecting
34309 data in tracepoints, and condition evaluation in breakpoints.
34311 @anchor{Control Agent}
34312 You can control whether the in-process agent is used as an aid for
34313 debugging with the following commands:
34316 @kindex set agent on
34318 Causes the in-process agent to perform some operations on behalf of the
34319 debugger. Just which operations requested by the user will be done
34320 by the in-process agent depends on the its capabilities. For example,
34321 if you request to evaluate breakpoint conditions in the in-process agent,
34322 and the in-process agent has such capability as well, then breakpoint
34323 conditions will be evaluated in the in-process agent.
34325 @kindex set agent off
34326 @item set agent off
34327 Disables execution of debugging operations by the in-process agent. All
34328 of the operations will be performed by @value{GDBN}.
34332 Display the current setting of execution of debugging operations by
34333 the in-process agent.
34337 * In-Process Agent Protocol::
34340 @node In-Process Agent Protocol
34341 @section In-Process Agent Protocol
34342 @cindex in-process agent protocol
34344 The in-process agent is able to communicate with both @value{GDBN} and
34345 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34346 used for communications between @value{GDBN} or GDBserver and the IPA.
34347 In general, @value{GDBN} or GDBserver sends commands
34348 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34349 in-process agent replies back with the return result of the command, or
34350 some other information. The data sent to in-process agent is composed
34351 of primitive data types, such as 4-byte or 8-byte type, and composite
34352 types, which are called objects (@pxref{IPA Protocol Objects}).
34355 * IPA Protocol Objects::
34356 * IPA Protocol Commands::
34359 @node IPA Protocol Objects
34360 @subsection IPA Protocol Objects
34361 @cindex ipa protocol objects
34363 The commands sent to and results received from agent may contain some
34364 complex data types called @dfn{objects}.
34366 The in-process agent is running on the same machine with @value{GDBN}
34367 or GDBserver, so it doesn't have to handle as much differences between
34368 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34369 However, there are still some differences of two ends in two processes:
34373 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34374 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34376 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34377 GDBserver is compiled with one, and in-process agent is compiled with
34381 Here are the IPA Protocol Objects:
34385 agent expression object. It represents an agent expression
34386 (@pxref{Agent Expressions}).
34387 @anchor{agent expression object}
34389 tracepoint action object. It represents a tracepoint action
34390 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34391 memory, static trace data and to evaluate expression.
34392 @anchor{tracepoint action object}
34394 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34395 @anchor{tracepoint object}
34399 The following table describes important attributes of each IPA protocol
34402 @multitable @columnfractions .30 .20 .50
34403 @headitem Name @tab Size @tab Description
34404 @item @emph{agent expression object} @tab @tab
34405 @item length @tab 4 @tab length of bytes code
34406 @item byte code @tab @var{length} @tab contents of byte code
34407 @item @emph{tracepoint action for collecting memory} @tab @tab
34408 @item 'M' @tab 1 @tab type of tracepoint action
34409 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34410 address of the lowest byte to collect, otherwise @var{addr} is the offset
34411 of @var{basereg} for memory collecting.
34412 @item len @tab 8 @tab length of memory for collecting
34413 @item basereg @tab 4 @tab the register number containing the starting
34414 memory address for collecting.
34415 @item @emph{tracepoint action for collecting registers} @tab @tab
34416 @item 'R' @tab 1 @tab type of tracepoint action
34417 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34418 @item 'L' @tab 1 @tab type of tracepoint action
34419 @item @emph{tracepoint action for expression evaluation} @tab @tab
34420 @item 'X' @tab 1 @tab type of tracepoint action
34421 @item agent expression @tab length of @tab @ref{agent expression object}
34422 @item @emph{tracepoint object} @tab @tab
34423 @item number @tab 4 @tab number of tracepoint
34424 @item address @tab 8 @tab address of tracepoint inserted on
34425 @item type @tab 4 @tab type of tracepoint
34426 @item enabled @tab 1 @tab enable or disable of tracepoint
34427 @item step_count @tab 8 @tab step
34428 @item pass_count @tab 8 @tab pass
34429 @item numactions @tab 4 @tab number of tracepoint actions
34430 @item hit count @tab 8 @tab hit count
34431 @item trace frame usage @tab 8 @tab trace frame usage
34432 @item compiled_cond @tab 8 @tab compiled condition
34433 @item orig_size @tab 8 @tab orig size
34434 @item condition @tab 4 if condition is NULL otherwise length of
34435 @ref{agent expression object}
34436 @tab zero if condition is NULL, otherwise is
34437 @ref{agent expression object}
34438 @item actions @tab variable
34439 @tab numactions number of @ref{tracepoint action object}
34442 @node IPA Protocol Commands
34443 @subsection IPA Protocol Commands
34444 @cindex ipa protocol commands
34446 The spaces in each command are delimiters to ease reading this commands
34447 specification. They don't exist in real commands.
34451 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34452 Installs a new fast tracepoint described by @var{tracepoint_object}
34453 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34454 head of @dfn{jumppad}, which is used to jump to data collection routine
34459 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34460 @var{target_address} is address of tracepoint in the inferior.
34461 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34462 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34463 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34464 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34471 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34472 is about to kill inferiors.
34480 @item probe_marker_at:@var{address}
34481 Asks in-process agent to probe the marker at @var{address}.
34488 @item unprobe_marker_at:@var{address}
34489 Asks in-process agent to unprobe the marker at @var{address}.
34493 @chapter Reporting Bugs in @value{GDBN}
34494 @cindex bugs in @value{GDBN}
34495 @cindex reporting bugs in @value{GDBN}
34497 Your bug reports play an essential role in making @value{GDBN} reliable.
34499 Reporting a bug may help you by bringing a solution to your problem, or it
34500 may not. But in any case the principal function of a bug report is to help
34501 the entire community by making the next version of @value{GDBN} work better. Bug
34502 reports are your contribution to the maintenance of @value{GDBN}.
34504 In order for a bug report to serve its purpose, you must include the
34505 information that enables us to fix the bug.
34508 * Bug Criteria:: Have you found a bug?
34509 * Bug Reporting:: How to report bugs
34513 @section Have You Found a Bug?
34514 @cindex bug criteria
34516 If you are not sure whether you have found a bug, here are some guidelines:
34519 @cindex fatal signal
34520 @cindex debugger crash
34521 @cindex crash of debugger
34523 If the debugger gets a fatal signal, for any input whatever, that is a
34524 @value{GDBN} bug. Reliable debuggers never crash.
34526 @cindex error on valid input
34528 If @value{GDBN} produces an error message for valid input, that is a
34529 bug. (Note that if you're cross debugging, the problem may also be
34530 somewhere in the connection to the target.)
34532 @cindex invalid input
34534 If @value{GDBN} does not produce an error message for invalid input,
34535 that is a bug. However, you should note that your idea of
34536 ``invalid input'' might be our idea of ``an extension'' or ``support
34537 for traditional practice''.
34540 If you are an experienced user of debugging tools, your suggestions
34541 for improvement of @value{GDBN} are welcome in any case.
34544 @node Bug Reporting
34545 @section How to Report Bugs
34546 @cindex bug reports
34547 @cindex @value{GDBN} bugs, reporting
34549 A number of companies and individuals offer support for @sc{gnu} products.
34550 If you obtained @value{GDBN} from a support organization, we recommend you
34551 contact that organization first.
34553 You can find contact information for many support companies and
34554 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34556 @c should add a web page ref...
34559 @ifset BUGURL_DEFAULT
34560 In any event, we also recommend that you submit bug reports for
34561 @value{GDBN}. The preferred method is to submit them directly using
34562 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34563 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34566 @strong{Do not send bug reports to @samp{info-gdb}, or to
34567 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34568 not want to receive bug reports. Those that do have arranged to receive
34571 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34572 serves as a repeater. The mailing list and the newsgroup carry exactly
34573 the same messages. Often people think of posting bug reports to the
34574 newsgroup instead of mailing them. This appears to work, but it has one
34575 problem which can be crucial: a newsgroup posting often lacks a mail
34576 path back to the sender. Thus, if we need to ask for more information,
34577 we may be unable to reach you. For this reason, it is better to send
34578 bug reports to the mailing list.
34580 @ifclear BUGURL_DEFAULT
34581 In any event, we also recommend that you submit bug reports for
34582 @value{GDBN} to @value{BUGURL}.
34586 The fundamental principle of reporting bugs usefully is this:
34587 @strong{report all the facts}. If you are not sure whether to state a
34588 fact or leave it out, state it!
34590 Often people omit facts because they think they know what causes the
34591 problem and assume that some details do not matter. Thus, you might
34592 assume that the name of the variable you use in an example does not matter.
34593 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34594 stray memory reference which happens to fetch from the location where that
34595 name is stored in memory; perhaps, if the name were different, the contents
34596 of that location would fool the debugger into doing the right thing despite
34597 the bug. Play it safe and give a specific, complete example. That is the
34598 easiest thing for you to do, and the most helpful.
34600 Keep in mind that the purpose of a bug report is to enable us to fix the
34601 bug. It may be that the bug has been reported previously, but neither
34602 you nor we can know that unless your bug report is complete and
34605 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34606 bell?'' Those bug reports are useless, and we urge everyone to
34607 @emph{refuse to respond to them} except to chide the sender to report
34610 To enable us to fix the bug, you should include all these things:
34614 The version of @value{GDBN}. @value{GDBN} announces it if you start
34615 with no arguments; you can also print it at any time using @code{show
34618 Without this, we will not know whether there is any point in looking for
34619 the bug in the current version of @value{GDBN}.
34622 The type of machine you are using, and the operating system name and
34626 The details of the @value{GDBN} build-time configuration.
34627 @value{GDBN} shows these details if you invoke it with the
34628 @option{--configuration} command-line option, or if you type
34629 @code{show configuration} at @value{GDBN}'s prompt.
34632 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34633 ``@value{GCC}--2.8.1''.
34636 What compiler (and its version) was used to compile the program you are
34637 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34638 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34639 to get this information; for other compilers, see the documentation for
34643 The command arguments you gave the compiler to compile your example and
34644 observe the bug. For example, did you use @samp{-O}? To guarantee
34645 you will not omit something important, list them all. A copy of the
34646 Makefile (or the output from make) is sufficient.
34648 If we were to try to guess the arguments, we would probably guess wrong
34649 and then we might not encounter the bug.
34652 A complete input script, and all necessary source files, that will
34656 A description of what behavior you observe that you believe is
34657 incorrect. For example, ``It gets a fatal signal.''
34659 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34660 will certainly notice it. But if the bug is incorrect output, we might
34661 not notice unless it is glaringly wrong. You might as well not give us
34662 a chance to make a mistake.
34664 Even if the problem you experience is a fatal signal, you should still
34665 say so explicitly. Suppose something strange is going on, such as, your
34666 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34667 the C library on your system. (This has happened!) Your copy might
34668 crash and ours would not. If you told us to expect a crash, then when
34669 ours fails to crash, we would know that the bug was not happening for
34670 us. If you had not told us to expect a crash, then we would not be able
34671 to draw any conclusion from our observations.
34674 @cindex recording a session script
34675 To collect all this information, you can use a session recording program
34676 such as @command{script}, which is available on many Unix systems.
34677 Just run your @value{GDBN} session inside @command{script} and then
34678 include the @file{typescript} file with your bug report.
34680 Another way to record a @value{GDBN} session is to run @value{GDBN}
34681 inside Emacs and then save the entire buffer to a file.
34684 If you wish to suggest changes to the @value{GDBN} source, send us context
34685 diffs. If you even discuss something in the @value{GDBN} source, refer to
34686 it by context, not by line number.
34688 The line numbers in our development sources will not match those in your
34689 sources. Your line numbers would convey no useful information to us.
34693 Here are some things that are not necessary:
34697 A description of the envelope of the bug.
34699 Often people who encounter a bug spend a lot of time investigating
34700 which changes to the input file will make the bug go away and which
34701 changes will not affect it.
34703 This is often time consuming and not very useful, because the way we
34704 will find the bug is by running a single example under the debugger
34705 with breakpoints, not by pure deduction from a series of examples.
34706 We recommend that you save your time for something else.
34708 Of course, if you can find a simpler example to report @emph{instead}
34709 of the original one, that is a convenience for us. Errors in the
34710 output will be easier to spot, running under the debugger will take
34711 less time, and so on.
34713 However, simplification is not vital; if you do not want to do this,
34714 report the bug anyway and send us the entire test case you used.
34717 A patch for the bug.
34719 A patch for the bug does help us if it is a good one. But do not omit
34720 the necessary information, such as the test case, on the assumption that
34721 a patch is all we need. We might see problems with your patch and decide
34722 to fix the problem another way, or we might not understand it at all.
34724 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34725 construct an example that will make the program follow a certain path
34726 through the code. If you do not send us the example, we will not be able
34727 to construct one, so we will not be able to verify that the bug is fixed.
34729 And if we cannot understand what bug you are trying to fix, or why your
34730 patch should be an improvement, we will not install it. A test case will
34731 help us to understand.
34734 A guess about what the bug is or what it depends on.
34736 Such guesses are usually wrong. Even we cannot guess right about such
34737 things without first using the debugger to find the facts.
34740 @c The readline documentation is distributed with the readline code
34741 @c and consists of the two following files:
34744 @c Use -I with makeinfo to point to the appropriate directory,
34745 @c environment var TEXINPUTS with TeX.
34746 @ifclear SYSTEM_READLINE
34747 @include rluser.texi
34748 @include hsuser.texi
34752 @appendix In Memoriam
34754 The @value{GDBN} project mourns the loss of the following long-time
34759 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34760 to Free Software in general. Outside of @value{GDBN}, he was known in
34761 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34763 @item Michael Snyder
34764 Michael was one of the Global Maintainers of the @value{GDBN} project,
34765 with contributions recorded as early as 1996, until 2011. In addition
34766 to his day to day participation, he was a large driving force behind
34767 adding Reverse Debugging to @value{GDBN}.
34770 Beyond their technical contributions to the project, they were also
34771 enjoyable members of the Free Software Community. We will miss them.
34773 @node Formatting Documentation
34774 @appendix Formatting Documentation
34776 @cindex @value{GDBN} reference card
34777 @cindex reference card
34778 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34779 for printing with PostScript or Ghostscript, in the @file{gdb}
34780 subdirectory of the main source directory@footnote{In
34781 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34782 release.}. If you can use PostScript or Ghostscript with your printer,
34783 you can print the reference card immediately with @file{refcard.ps}.
34785 The release also includes the source for the reference card. You
34786 can format it, using @TeX{}, by typing:
34792 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34793 mode on US ``letter'' size paper;
34794 that is, on a sheet 11 inches wide by 8.5 inches
34795 high. You will need to specify this form of printing as an option to
34796 your @sc{dvi} output program.
34798 @cindex documentation
34800 All the documentation for @value{GDBN} comes as part of the machine-readable
34801 distribution. The documentation is written in Texinfo format, which is
34802 a documentation system that uses a single source file to produce both
34803 on-line information and a printed manual. You can use one of the Info
34804 formatting commands to create the on-line version of the documentation
34805 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34807 @value{GDBN} includes an already formatted copy of the on-line Info
34808 version of this manual in the @file{gdb} subdirectory. The main Info
34809 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34810 subordinate files matching @samp{gdb.info*} in the same directory. If
34811 necessary, you can print out these files, or read them with any editor;
34812 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34813 Emacs or the standalone @code{info} program, available as part of the
34814 @sc{gnu} Texinfo distribution.
34816 If you want to format these Info files yourself, you need one of the
34817 Info formatting programs, such as @code{texinfo-format-buffer} or
34820 If you have @code{makeinfo} installed, and are in the top level
34821 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34822 version @value{GDBVN}), you can make the Info file by typing:
34829 If you want to typeset and print copies of this manual, you need @TeX{},
34830 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34831 Texinfo definitions file.
34833 @TeX{} is a typesetting program; it does not print files directly, but
34834 produces output files called @sc{dvi} files. To print a typeset
34835 document, you need a program to print @sc{dvi} files. If your system
34836 has @TeX{} installed, chances are it has such a program. The precise
34837 command to use depends on your system; @kbd{lpr -d} is common; another
34838 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34839 require a file name without any extension or a @samp{.dvi} extension.
34841 @TeX{} also requires a macro definitions file called
34842 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34843 written in Texinfo format. On its own, @TeX{} cannot either read or
34844 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34845 and is located in the @file{gdb-@var{version-number}/texinfo}
34848 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34849 typeset and print this manual. First switch to the @file{gdb}
34850 subdirectory of the main source directory (for example, to
34851 @file{gdb-@value{GDBVN}/gdb}) and type:
34857 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34859 @node Installing GDB
34860 @appendix Installing @value{GDBN}
34861 @cindex installation
34864 * Requirements:: Requirements for building @value{GDBN}
34865 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34866 * Separate Objdir:: Compiling @value{GDBN} in another directory
34867 * Config Names:: Specifying names for hosts and targets
34868 * Configure Options:: Summary of options for configure
34869 * System-wide configuration:: Having a system-wide init file
34873 @section Requirements for Building @value{GDBN}
34874 @cindex building @value{GDBN}, requirements for
34876 Building @value{GDBN} requires various tools and packages to be available.
34877 Other packages will be used only if they are found.
34879 @heading Tools/Packages Necessary for Building @value{GDBN}
34881 @item ISO C90 compiler
34882 @value{GDBN} is written in ISO C90. It should be buildable with any
34883 working C90 compiler, e.g.@: GCC.
34887 @heading Tools/Packages Optional for Building @value{GDBN}
34891 @value{GDBN} can use the Expat XML parsing library. This library may be
34892 included with your operating system distribution; if it is not, you
34893 can get the latest version from @url{http://expat.sourceforge.net}.
34894 The @file{configure} script will search for this library in several
34895 standard locations; if it is installed in an unusual path, you can
34896 use the @option{--with-libexpat-prefix} option to specify its location.
34902 Remote protocol memory maps (@pxref{Memory Map Format})
34904 Target descriptions (@pxref{Target Descriptions})
34906 Remote shared library lists (@xref{Library List Format},
34907 or alternatively @pxref{Library List Format for SVR4 Targets})
34909 MS-Windows shared libraries (@pxref{Shared Libraries})
34911 Traceframe info (@pxref{Traceframe Info Format})
34913 Branch trace (@pxref{Branch Trace Format})
34917 @cindex compressed debug sections
34918 @value{GDBN} will use the @samp{zlib} library, if available, to read
34919 compressed debug sections. Some linkers, such as GNU gold, are capable
34920 of producing binaries with compressed debug sections. If @value{GDBN}
34921 is compiled with @samp{zlib}, it will be able to read the debug
34922 information in such binaries.
34924 The @samp{zlib} library is likely included with your operating system
34925 distribution; if it is not, you can get the latest version from
34926 @url{http://zlib.net}.
34929 @value{GDBN}'s features related to character sets (@pxref{Character
34930 Sets}) require a functioning @code{iconv} implementation. If you are
34931 on a GNU system, then this is provided by the GNU C Library. Some
34932 other systems also provide a working @code{iconv}.
34934 If @value{GDBN} is using the @code{iconv} program which is installed
34935 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34936 This is done with @option{--with-iconv-bin} which specifies the
34937 directory that contains the @code{iconv} program.
34939 On systems without @code{iconv}, you can install GNU Libiconv. If you
34940 have previously installed Libiconv, you can use the
34941 @option{--with-libiconv-prefix} option to configure.
34943 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34944 arrange to build Libiconv if a directory named @file{libiconv} appears
34945 in the top-most source directory. If Libiconv is built this way, and
34946 if the operating system does not provide a suitable @code{iconv}
34947 implementation, then the just-built library will automatically be used
34948 by @value{GDBN}. One easy way to set this up is to download GNU
34949 Libiconv, unpack it, and then rename the directory holding the
34950 Libiconv source code to @samp{libiconv}.
34953 @node Running Configure
34954 @section Invoking the @value{GDBN} @file{configure} Script
34955 @cindex configuring @value{GDBN}
34956 @value{GDBN} comes with a @file{configure} script that automates the process
34957 of preparing @value{GDBN} for installation; you can then use @code{make} to
34958 build the @code{gdb} program.
34960 @c irrelevant in info file; it's as current as the code it lives with.
34961 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34962 look at the @file{README} file in the sources; we may have improved the
34963 installation procedures since publishing this manual.}
34966 The @value{GDBN} distribution includes all the source code you need for
34967 @value{GDBN} in a single directory, whose name is usually composed by
34968 appending the version number to @samp{gdb}.
34970 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34971 @file{gdb-@value{GDBVN}} directory. That directory contains:
34974 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34975 script for configuring @value{GDBN} and all its supporting libraries
34977 @item gdb-@value{GDBVN}/gdb
34978 the source specific to @value{GDBN} itself
34980 @item gdb-@value{GDBVN}/bfd
34981 source for the Binary File Descriptor library
34983 @item gdb-@value{GDBVN}/include
34984 @sc{gnu} include files
34986 @item gdb-@value{GDBVN}/libiberty
34987 source for the @samp{-liberty} free software library
34989 @item gdb-@value{GDBVN}/opcodes
34990 source for the library of opcode tables and disassemblers
34992 @item gdb-@value{GDBVN}/readline
34993 source for the @sc{gnu} command-line interface
34995 @item gdb-@value{GDBVN}/glob
34996 source for the @sc{gnu} filename pattern-matching subroutine
34998 @item gdb-@value{GDBVN}/mmalloc
34999 source for the @sc{gnu} memory-mapped malloc package
35002 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35003 from the @file{gdb-@var{version-number}} source directory, which in
35004 this example is the @file{gdb-@value{GDBVN}} directory.
35006 First switch to the @file{gdb-@var{version-number}} source directory
35007 if you are not already in it; then run @file{configure}. Pass the
35008 identifier for the platform on which @value{GDBN} will run as an
35014 cd gdb-@value{GDBVN}
35015 ./configure @var{host}
35020 where @var{host} is an identifier such as @samp{sun4} or
35021 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35022 (You can often leave off @var{host}; @file{configure} tries to guess the
35023 correct value by examining your system.)
35025 Running @samp{configure @var{host}} and then running @code{make} builds the
35026 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35027 libraries, then @code{gdb} itself. The configured source files, and the
35028 binaries, are left in the corresponding source directories.
35031 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35032 system does not recognize this automatically when you run a different
35033 shell, you may need to run @code{sh} on it explicitly:
35036 sh configure @var{host}
35039 If you run @file{configure} from a directory that contains source
35040 directories for multiple libraries or programs, such as the
35041 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35043 creates configuration files for every directory level underneath (unless
35044 you tell it not to, with the @samp{--norecursion} option).
35046 You should run the @file{configure} script from the top directory in the
35047 source tree, the @file{gdb-@var{version-number}} directory. If you run
35048 @file{configure} from one of the subdirectories, you will configure only
35049 that subdirectory. That is usually not what you want. In particular,
35050 if you run the first @file{configure} from the @file{gdb} subdirectory
35051 of the @file{gdb-@var{version-number}} directory, you will omit the
35052 configuration of @file{bfd}, @file{readline}, and other sibling
35053 directories of the @file{gdb} subdirectory. This leads to build errors
35054 about missing include files such as @file{bfd/bfd.h}.
35056 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35057 However, you should make sure that the shell on your path (named by
35058 the @samp{SHELL} environment variable) is publicly readable. Remember
35059 that @value{GDBN} uses the shell to start your program---some systems refuse to
35060 let @value{GDBN} debug child processes whose programs are not readable.
35062 @node Separate Objdir
35063 @section Compiling @value{GDBN} in Another Directory
35065 If you want to run @value{GDBN} versions for several host or target machines,
35066 you need a different @code{gdb} compiled for each combination of
35067 host and target. @file{configure} is designed to make this easy by
35068 allowing you to generate each configuration in a separate subdirectory,
35069 rather than in the source directory. If your @code{make} program
35070 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35071 @code{make} in each of these directories builds the @code{gdb}
35072 program specified there.
35074 To build @code{gdb} in a separate directory, run @file{configure}
35075 with the @samp{--srcdir} option to specify where to find the source.
35076 (You also need to specify a path to find @file{configure}
35077 itself from your working directory. If the path to @file{configure}
35078 would be the same as the argument to @samp{--srcdir}, you can leave out
35079 the @samp{--srcdir} option; it is assumed.)
35081 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35082 separate directory for a Sun 4 like this:
35086 cd gdb-@value{GDBVN}
35089 ../gdb-@value{GDBVN}/configure sun4
35094 When @file{configure} builds a configuration using a remote source
35095 directory, it creates a tree for the binaries with the same structure
35096 (and using the same names) as the tree under the source directory. In
35097 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35098 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35099 @file{gdb-sun4/gdb}.
35101 Make sure that your path to the @file{configure} script has just one
35102 instance of @file{gdb} in it. If your path to @file{configure} looks
35103 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35104 one subdirectory of @value{GDBN}, not the whole package. This leads to
35105 build errors about missing include files such as @file{bfd/bfd.h}.
35107 One popular reason to build several @value{GDBN} configurations in separate
35108 directories is to configure @value{GDBN} for cross-compiling (where
35109 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35110 programs that run on another machine---the @dfn{target}).
35111 You specify a cross-debugging target by
35112 giving the @samp{--target=@var{target}} option to @file{configure}.
35114 When you run @code{make} to build a program or library, you must run
35115 it in a configured directory---whatever directory you were in when you
35116 called @file{configure} (or one of its subdirectories).
35118 The @code{Makefile} that @file{configure} generates in each source
35119 directory also runs recursively. If you type @code{make} in a source
35120 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35121 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35122 will build all the required libraries, and then build GDB.
35124 When you have multiple hosts or targets configured in separate
35125 directories, you can run @code{make} on them in parallel (for example,
35126 if they are NFS-mounted on each of the hosts); they will not interfere
35130 @section Specifying Names for Hosts and Targets
35132 The specifications used for hosts and targets in the @file{configure}
35133 script are based on a three-part naming scheme, but some short predefined
35134 aliases are also supported. The full naming scheme encodes three pieces
35135 of information in the following pattern:
35138 @var{architecture}-@var{vendor}-@var{os}
35141 For example, you can use the alias @code{sun4} as a @var{host} argument,
35142 or as the value for @var{target} in a @code{--target=@var{target}}
35143 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35145 The @file{configure} script accompanying @value{GDBN} does not provide
35146 any query facility to list all supported host and target names or
35147 aliases. @file{configure} calls the Bourne shell script
35148 @code{config.sub} to map abbreviations to full names; you can read the
35149 script, if you wish, or you can use it to test your guesses on
35150 abbreviations---for example:
35153 % sh config.sub i386-linux
35155 % sh config.sub alpha-linux
35156 alpha-unknown-linux-gnu
35157 % sh config.sub hp9k700
35159 % sh config.sub sun4
35160 sparc-sun-sunos4.1.1
35161 % sh config.sub sun3
35162 m68k-sun-sunos4.1.1
35163 % sh config.sub i986v
35164 Invalid configuration `i986v': machine `i986v' not recognized
35168 @code{config.sub} is also distributed in the @value{GDBN} source
35169 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35171 @node Configure Options
35172 @section @file{configure} Options
35174 Here is a summary of the @file{configure} options and arguments that
35175 are most often useful for building @value{GDBN}. @file{configure} also has
35176 several other options not listed here. @inforef{What Configure
35177 Does,,configure.info}, for a full explanation of @file{configure}.
35180 configure @r{[}--help@r{]}
35181 @r{[}--prefix=@var{dir}@r{]}
35182 @r{[}--exec-prefix=@var{dir}@r{]}
35183 @r{[}--srcdir=@var{dirname}@r{]}
35184 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35185 @r{[}--target=@var{target}@r{]}
35190 You may introduce options with a single @samp{-} rather than
35191 @samp{--} if you prefer; but you may abbreviate option names if you use
35196 Display a quick summary of how to invoke @file{configure}.
35198 @item --prefix=@var{dir}
35199 Configure the source to install programs and files under directory
35202 @item --exec-prefix=@var{dir}
35203 Configure the source to install programs under directory
35206 @c avoid splitting the warning from the explanation:
35208 @item --srcdir=@var{dirname}
35209 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35210 @code{make} that implements the @code{VPATH} feature.}@*
35211 Use this option to make configurations in directories separate from the
35212 @value{GDBN} source directories. Among other things, you can use this to
35213 build (or maintain) several configurations simultaneously, in separate
35214 directories. @file{configure} writes configuration-specific files in
35215 the current directory, but arranges for them to use the source in the
35216 directory @var{dirname}. @file{configure} creates directories under
35217 the working directory in parallel to the source directories below
35220 @item --norecursion
35221 Configure only the directory level where @file{configure} is executed; do not
35222 propagate configuration to subdirectories.
35224 @item --target=@var{target}
35225 Configure @value{GDBN} for cross-debugging programs running on the specified
35226 @var{target}. Without this option, @value{GDBN} is configured to debug
35227 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35229 There is no convenient way to generate a list of all available targets.
35231 @item @var{host} @dots{}
35232 Configure @value{GDBN} to run on the specified @var{host}.
35234 There is no convenient way to generate a list of all available hosts.
35237 There are many other options available as well, but they are generally
35238 needed for special purposes only.
35240 @node System-wide configuration
35241 @section System-wide configuration and settings
35242 @cindex system-wide init file
35244 @value{GDBN} can be configured to have a system-wide init file;
35245 this file will be read and executed at startup (@pxref{Startup, , What
35246 @value{GDBN} does during startup}).
35248 Here is the corresponding configure option:
35251 @item --with-system-gdbinit=@var{file}
35252 Specify that the default location of the system-wide init file is
35256 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35257 it may be subject to relocation. Two possible cases:
35261 If the default location of this init file contains @file{$prefix},
35262 it will be subject to relocation. Suppose that the configure options
35263 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35264 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35265 init file is looked for as @file{$install/etc/gdbinit} instead of
35266 @file{$prefix/etc/gdbinit}.
35269 By contrast, if the default location does not contain the prefix,
35270 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35271 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35272 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35273 wherever @value{GDBN} is installed.
35276 If the configured location of the system-wide init file (as given by the
35277 @option{--with-system-gdbinit} option at configure time) is in the
35278 data-directory (as specified by @option{--with-gdb-datadir} at configure
35279 time) or in one of its subdirectories, then @value{GDBN} will look for the
35280 system-wide init file in the directory specified by the
35281 @option{--data-directory} command-line option.
35282 Note that the system-wide init file is only read once, during @value{GDBN}
35283 initialization. If the data-directory is changed after @value{GDBN} has
35284 started with the @code{set data-directory} command, the file will not be
35287 @node Maintenance Commands
35288 @appendix Maintenance Commands
35289 @cindex maintenance commands
35290 @cindex internal commands
35292 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35293 includes a number of commands intended for @value{GDBN} developers,
35294 that are not documented elsewhere in this manual. These commands are
35295 provided here for reference. (For commands that turn on debugging
35296 messages, see @ref{Debugging Output}.)
35299 @kindex maint agent
35300 @kindex maint agent-eval
35301 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35302 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35303 Translate the given @var{expression} into remote agent bytecodes.
35304 This command is useful for debugging the Agent Expression mechanism
35305 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35306 expression useful for data collection, such as by tracepoints, while
35307 @samp{maint agent-eval} produces an expression that evaluates directly
35308 to a result. For instance, a collection expression for @code{globa +
35309 globb} will include bytecodes to record four bytes of memory at each
35310 of the addresses of @code{globa} and @code{globb}, while discarding
35311 the result of the addition, while an evaluation expression will do the
35312 addition and return the sum.
35313 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35314 If not, generate remote agent bytecode for current frame PC address.
35316 @kindex maint agent-printf
35317 @item maint agent-printf @var{format},@var{expr},...
35318 Translate the given format string and list of argument expressions
35319 into remote agent bytecodes and display them as a disassembled list.
35320 This command is useful for debugging the agent version of dynamic
35321 printf (@pxref{Dynamic Printf}).
35323 @kindex maint info breakpoints
35324 @item @anchor{maint info breakpoints}maint info breakpoints
35325 Using the same format as @samp{info breakpoints}, display both the
35326 breakpoints you've set explicitly, and those @value{GDBN} is using for
35327 internal purposes. Internal breakpoints are shown with negative
35328 breakpoint numbers. The type column identifies what kind of breakpoint
35333 Normal, explicitly set breakpoint.
35336 Normal, explicitly set watchpoint.
35339 Internal breakpoint, used to handle correctly stepping through
35340 @code{longjmp} calls.
35342 @item longjmp resume
35343 Internal breakpoint at the target of a @code{longjmp}.
35346 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35349 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35352 Shared library events.
35356 @kindex maint info bfds
35357 @item maint info bfds
35358 This prints information about each @code{bfd} object that is known to
35359 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35361 @kindex set displaced-stepping
35362 @kindex show displaced-stepping
35363 @cindex displaced stepping support
35364 @cindex out-of-line single-stepping
35365 @item set displaced-stepping
35366 @itemx show displaced-stepping
35367 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35368 if the target supports it. Displaced stepping is a way to single-step
35369 over breakpoints without removing them from the inferior, by executing
35370 an out-of-line copy of the instruction that was originally at the
35371 breakpoint location. It is also known as out-of-line single-stepping.
35374 @item set displaced-stepping on
35375 If the target architecture supports it, @value{GDBN} will use
35376 displaced stepping to step over breakpoints.
35378 @item set displaced-stepping off
35379 @value{GDBN} will not use displaced stepping to step over breakpoints,
35380 even if such is supported by the target architecture.
35382 @cindex non-stop mode, and @samp{set displaced-stepping}
35383 @item set displaced-stepping auto
35384 This is the default mode. @value{GDBN} will use displaced stepping
35385 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35386 architecture supports displaced stepping.
35389 @kindex maint check-symtabs
35390 @item maint check-symtabs
35391 Check the consistency of psymtabs and symtabs.
35393 @kindex maint cplus first_component
35394 @item maint cplus first_component @var{name}
35395 Print the first C@t{++} class/namespace component of @var{name}.
35397 @kindex maint cplus namespace
35398 @item maint cplus namespace
35399 Print the list of possible C@t{++} namespaces.
35401 @kindex maint demangle
35402 @item maint demangle @var{name}
35403 Demangle a C@t{++} or Objective-C mangled @var{name}.
35405 @kindex maint deprecate
35406 @kindex maint undeprecate
35407 @cindex deprecated commands
35408 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35409 @itemx maint undeprecate @var{command}
35410 Deprecate or undeprecate the named @var{command}. Deprecated commands
35411 cause @value{GDBN} to issue a warning when you use them. The optional
35412 argument @var{replacement} says which newer command should be used in
35413 favor of the deprecated one; if it is given, @value{GDBN} will mention
35414 the replacement as part of the warning.
35416 @kindex maint dump-me
35417 @item maint dump-me
35418 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35419 Cause a fatal signal in the debugger and force it to dump its core.
35420 This is supported only on systems which support aborting a program
35421 with the @code{SIGQUIT} signal.
35423 @kindex maint internal-error
35424 @kindex maint internal-warning
35425 @item maint internal-error @r{[}@var{message-text}@r{]}
35426 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35427 Cause @value{GDBN} to call the internal function @code{internal_error}
35428 or @code{internal_warning} and hence behave as though an internal error
35429 or internal warning has been detected. In addition to reporting the
35430 internal problem, these functions give the user the opportunity to
35431 either quit @value{GDBN} or create a core file of the current
35432 @value{GDBN} session.
35434 These commands take an optional parameter @var{message-text} that is
35435 used as the text of the error or warning message.
35437 Here's an example of using @code{internal-error}:
35440 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35441 @dots{}/maint.c:121: internal-error: testing, 1, 2
35442 A problem internal to GDB has been detected. Further
35443 debugging may prove unreliable.
35444 Quit this debugging session? (y or n) @kbd{n}
35445 Create a core file? (y or n) @kbd{n}
35449 @cindex @value{GDBN} internal error
35450 @cindex internal errors, control of @value{GDBN} behavior
35452 @kindex maint set internal-error
35453 @kindex maint show internal-error
35454 @kindex maint set internal-warning
35455 @kindex maint show internal-warning
35456 @item maint set internal-error @var{action} [ask|yes|no]
35457 @itemx maint show internal-error @var{action}
35458 @itemx maint set internal-warning @var{action} [ask|yes|no]
35459 @itemx maint show internal-warning @var{action}
35460 When @value{GDBN} reports an internal problem (error or warning) it
35461 gives the user the opportunity to both quit @value{GDBN} and create a
35462 core file of the current @value{GDBN} session. These commands let you
35463 override the default behaviour for each particular @var{action},
35464 described in the table below.
35468 You can specify that @value{GDBN} should always (yes) or never (no)
35469 quit. The default is to ask the user what to do.
35472 You can specify that @value{GDBN} should always (yes) or never (no)
35473 create a core file. The default is to ask the user what to do.
35476 @kindex maint packet
35477 @item maint packet @var{text}
35478 If @value{GDBN} is talking to an inferior via the serial protocol,
35479 then this command sends the string @var{text} to the inferior, and
35480 displays the response packet. @value{GDBN} supplies the initial
35481 @samp{$} character, the terminating @samp{#} character, and the
35484 @kindex maint print architecture
35485 @item maint print architecture @r{[}@var{file}@r{]}
35486 Print the entire architecture configuration. The optional argument
35487 @var{file} names the file where the output goes.
35489 @kindex maint print c-tdesc
35490 @item maint print c-tdesc
35491 Print the current target description (@pxref{Target Descriptions}) as
35492 a C source file. The created source file can be used in @value{GDBN}
35493 when an XML parser is not available to parse the description.
35495 @kindex maint print dummy-frames
35496 @item maint print dummy-frames
35497 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35500 (@value{GDBP}) @kbd{b add}
35502 (@value{GDBP}) @kbd{print add(2,3)}
35503 Breakpoint 2, add (a=2, b=3) at @dots{}
35505 The program being debugged stopped while in a function called from GDB.
35507 (@value{GDBP}) @kbd{maint print dummy-frames}
35508 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35509 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35510 call_lo=0x01014000 call_hi=0x01014001
35514 Takes an optional file parameter.
35516 @kindex maint print registers
35517 @kindex maint print raw-registers
35518 @kindex maint print cooked-registers
35519 @kindex maint print register-groups
35520 @kindex maint print remote-registers
35521 @item maint print registers @r{[}@var{file}@r{]}
35522 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35523 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35524 @itemx maint print register-groups @r{[}@var{file}@r{]}
35525 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35526 Print @value{GDBN}'s internal register data structures.
35528 The command @code{maint print raw-registers} includes the contents of
35529 the raw register cache; the command @code{maint print
35530 cooked-registers} includes the (cooked) value of all registers,
35531 including registers which aren't available on the target nor visible
35532 to user; the command @code{maint print register-groups} includes the
35533 groups that each register is a member of; and the command @code{maint
35534 print remote-registers} includes the remote target's register numbers
35535 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35536 @value{GDBN} Internals}.
35538 These commands take an optional parameter, a file name to which to
35539 write the information.
35541 @kindex maint print reggroups
35542 @item maint print reggroups @r{[}@var{file}@r{]}
35543 Print @value{GDBN}'s internal register group data structures. The
35544 optional argument @var{file} tells to what file to write the
35547 The register groups info looks like this:
35550 (@value{GDBP}) @kbd{maint print reggroups}
35563 This command forces @value{GDBN} to flush its internal register cache.
35565 @kindex maint print objfiles
35566 @cindex info for known object files
35567 @item maint print objfiles
35568 Print a dump of all known object files. For each object file, this
35569 command prints its name, address in memory, and all of its psymtabs
35572 @kindex maint print section-scripts
35573 @cindex info for known .debug_gdb_scripts-loaded scripts
35574 @item maint print section-scripts [@var{regexp}]
35575 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35576 If @var{regexp} is specified, only print scripts loaded by object files
35577 matching @var{regexp}.
35578 For each script, this command prints its name as specified in the objfile,
35579 and the full path if known.
35580 @xref{dotdebug_gdb_scripts section}.
35582 @kindex maint print statistics
35583 @cindex bcache statistics
35584 @item maint print statistics
35585 This command prints, for each object file in the program, various data
35586 about that object file followed by the byte cache (@dfn{bcache})
35587 statistics for the object file. The objfile data includes the number
35588 of minimal, partial, full, and stabs symbols, the number of types
35589 defined by the objfile, the number of as yet unexpanded psym tables,
35590 the number of line tables and string tables, and the amount of memory
35591 used by the various tables. The bcache statistics include the counts,
35592 sizes, and counts of duplicates of all and unique objects, max,
35593 average, and median entry size, total memory used and its overhead and
35594 savings, and various measures of the hash table size and chain
35597 @kindex maint print target-stack
35598 @cindex target stack description
35599 @item maint print target-stack
35600 A @dfn{target} is an interface between the debugger and a particular
35601 kind of file or process. Targets can be stacked in @dfn{strata},
35602 so that more than one target can potentially respond to a request.
35603 In particular, memory accesses will walk down the stack of targets
35604 until they find a target that is interested in handling that particular
35607 This command prints a short description of each layer that was pushed on
35608 the @dfn{target stack}, starting from the top layer down to the bottom one.
35610 @kindex maint print type
35611 @cindex type chain of a data type
35612 @item maint print type @var{expr}
35613 Print the type chain for a type specified by @var{expr}. The argument
35614 can be either a type name or a symbol. If it is a symbol, the type of
35615 that symbol is described. The type chain produced by this command is
35616 a recursive definition of the data type as stored in @value{GDBN}'s
35617 data structures, including its flags and contained types.
35619 @kindex maint set dwarf2 always-disassemble
35620 @kindex maint show dwarf2 always-disassemble
35621 @item maint set dwarf2 always-disassemble
35622 @item maint show dwarf2 always-disassemble
35623 Control the behavior of @code{info address} when using DWARF debugging
35626 The default is @code{off}, which means that @value{GDBN} should try to
35627 describe a variable's location in an easily readable format. When
35628 @code{on}, @value{GDBN} will instead display the DWARF location
35629 expression in an assembly-like format. Note that some locations are
35630 too complex for @value{GDBN} to describe simply; in this case you will
35631 always see the disassembly form.
35633 Here is an example of the resulting disassembly:
35636 (gdb) info addr argc
35637 Symbol "argc" is a complex DWARF expression:
35641 For more information on these expressions, see
35642 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35644 @kindex maint set dwarf2 max-cache-age
35645 @kindex maint show dwarf2 max-cache-age
35646 @item maint set dwarf2 max-cache-age
35647 @itemx maint show dwarf2 max-cache-age
35648 Control the DWARF 2 compilation unit cache.
35650 @cindex DWARF 2 compilation units cache
35651 In object files with inter-compilation-unit references, such as those
35652 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35653 reader needs to frequently refer to previously read compilation units.
35654 This setting controls how long a compilation unit will remain in the
35655 cache if it is not referenced. A higher limit means that cached
35656 compilation units will be stored in memory longer, and more total
35657 memory will be used. Setting it to zero disables caching, which will
35658 slow down @value{GDBN} startup, but reduce memory consumption.
35660 @kindex maint set profile
35661 @kindex maint show profile
35662 @cindex profiling GDB
35663 @item maint set profile
35664 @itemx maint show profile
35665 Control profiling of @value{GDBN}.
35667 Profiling will be disabled until you use the @samp{maint set profile}
35668 command to enable it. When you enable profiling, the system will begin
35669 collecting timing and execution count data; when you disable profiling or
35670 exit @value{GDBN}, the results will be written to a log file. Remember that
35671 if you use profiling, @value{GDBN} will overwrite the profiling log file
35672 (often called @file{gmon.out}). If you have a record of important profiling
35673 data in a @file{gmon.out} file, be sure to move it to a safe location.
35675 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35676 compiled with the @samp{-pg} compiler option.
35678 @kindex maint set show-debug-regs
35679 @kindex maint show show-debug-regs
35680 @cindex hardware debug registers
35681 @item maint set show-debug-regs
35682 @itemx maint show show-debug-regs
35683 Control whether to show variables that mirror the hardware debug
35684 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35685 enabled, the debug registers values are shown when @value{GDBN} inserts or
35686 removes a hardware breakpoint or watchpoint, and when the inferior
35687 triggers a hardware-assisted breakpoint or watchpoint.
35689 @kindex maint set show-all-tib
35690 @kindex maint show show-all-tib
35691 @item maint set show-all-tib
35692 @itemx maint show show-all-tib
35693 Control whether to show all non zero areas within a 1k block starting
35694 at thread local base, when using the @samp{info w32 thread-information-block}
35697 @kindex maint set per-command
35698 @kindex maint show per-command
35699 @item maint set per-command
35700 @itemx maint show per-command
35701 @cindex resources used by commands
35703 @value{GDBN} can display the resources used by each command.
35704 This is useful in debugging performance problems.
35707 @item maint set per-command space [on|off]
35708 @itemx maint show per-command space
35709 Enable or disable the printing of the memory used by GDB for each command.
35710 If enabled, @value{GDBN} will display how much memory each command
35711 took, following the command's own output.
35712 This can also be requested by invoking @value{GDBN} with the
35713 @option{--statistics} command-line switch (@pxref{Mode Options}).
35715 @item maint set per-command time [on|off]
35716 @itemx maint show per-command time
35717 Enable or disable the printing of the execution time of @value{GDBN}
35719 If enabled, @value{GDBN} will display how much time it
35720 took to execute each command, following the command's own output.
35721 Both CPU time and wallclock time are printed.
35722 Printing both is useful when trying to determine whether the cost is
35723 CPU or, e.g., disk/network latency.
35724 Note that the CPU time printed is for @value{GDBN} only, it does not include
35725 the execution time of the inferior because there's no mechanism currently
35726 to compute how much time was spent by @value{GDBN} and how much time was
35727 spent by the program been debugged.
35728 This can also be requested by invoking @value{GDBN} with the
35729 @option{--statistics} command-line switch (@pxref{Mode Options}).
35731 @item maint set per-command symtab [on|off]
35732 @itemx maint show per-command symtab
35733 Enable or disable the printing of basic symbol table statistics
35735 If enabled, @value{GDBN} will display the following information:
35739 number of symbol tables
35741 number of primary symbol tables
35743 number of blocks in the blockvector
35747 @kindex maint space
35748 @cindex memory used by commands
35749 @item maint space @var{value}
35750 An alias for @code{maint set per-command space}.
35751 A non-zero value enables it, zero disables it.
35754 @cindex time of command execution
35755 @item maint time @var{value}
35756 An alias for @code{maint set per-command time}.
35757 A non-zero value enables it, zero disables it.
35759 @kindex maint translate-address
35760 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35761 Find the symbol stored at the location specified by the address
35762 @var{addr} and an optional section name @var{section}. If found,
35763 @value{GDBN} prints the name of the closest symbol and an offset from
35764 the symbol's location to the specified address. This is similar to
35765 the @code{info address} command (@pxref{Symbols}), except that this
35766 command also allows to find symbols in other sections.
35768 If section was not specified, the section in which the symbol was found
35769 is also printed. For dynamically linked executables, the name of
35770 executable or shared library containing the symbol is printed as well.
35774 The following command is useful for non-interactive invocations of
35775 @value{GDBN}, such as in the test suite.
35778 @item set watchdog @var{nsec}
35779 @kindex set watchdog
35780 @cindex watchdog timer
35781 @cindex timeout for commands
35782 Set the maximum number of seconds @value{GDBN} will wait for the
35783 target operation to finish. If this time expires, @value{GDBN}
35784 reports and error and the command is aborted.
35786 @item show watchdog
35787 Show the current setting of the target wait timeout.
35790 @node Remote Protocol
35791 @appendix @value{GDBN} Remote Serial Protocol
35796 * Stop Reply Packets::
35797 * General Query Packets::
35798 * Architecture-Specific Protocol Details::
35799 * Tracepoint Packets::
35800 * Host I/O Packets::
35802 * Notification Packets::
35803 * Remote Non-Stop::
35804 * Packet Acknowledgment::
35806 * File-I/O Remote Protocol Extension::
35807 * Library List Format::
35808 * Library List Format for SVR4 Targets::
35809 * Memory Map Format::
35810 * Thread List Format::
35811 * Traceframe Info Format::
35812 * Branch Trace Format::
35818 There may be occasions when you need to know something about the
35819 protocol---for example, if there is only one serial port to your target
35820 machine, you might want your program to do something special if it
35821 recognizes a packet meant for @value{GDBN}.
35823 In the examples below, @samp{->} and @samp{<-} are used to indicate
35824 transmitted and received data, respectively.
35826 @cindex protocol, @value{GDBN} remote serial
35827 @cindex serial protocol, @value{GDBN} remote
35828 @cindex remote serial protocol
35829 All @value{GDBN} commands and responses (other than acknowledgments
35830 and notifications, see @ref{Notification Packets}) are sent as a
35831 @var{packet}. A @var{packet} is introduced with the character
35832 @samp{$}, the actual @var{packet-data}, and the terminating character
35833 @samp{#} followed by a two-digit @var{checksum}:
35836 @code{$}@var{packet-data}@code{#}@var{checksum}
35840 @cindex checksum, for @value{GDBN} remote
35842 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35843 characters between the leading @samp{$} and the trailing @samp{#} (an
35844 eight bit unsigned checksum).
35846 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35847 specification also included an optional two-digit @var{sequence-id}:
35850 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35853 @cindex sequence-id, for @value{GDBN} remote
35855 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35856 has never output @var{sequence-id}s. Stubs that handle packets added
35857 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35859 When either the host or the target machine receives a packet, the first
35860 response expected is an acknowledgment: either @samp{+} (to indicate
35861 the package was received correctly) or @samp{-} (to request
35865 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35870 The @samp{+}/@samp{-} acknowledgments can be disabled
35871 once a connection is established.
35872 @xref{Packet Acknowledgment}, for details.
35874 The host (@value{GDBN}) sends @var{command}s, and the target (the
35875 debugging stub incorporated in your program) sends a @var{response}. In
35876 the case of step and continue @var{command}s, the response is only sent
35877 when the operation has completed, and the target has again stopped all
35878 threads in all attached processes. This is the default all-stop mode
35879 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35880 execution mode; see @ref{Remote Non-Stop}, for details.
35882 @var{packet-data} consists of a sequence of characters with the
35883 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35886 @cindex remote protocol, field separator
35887 Fields within the packet should be separated using @samp{,} @samp{;} or
35888 @samp{:}. Except where otherwise noted all numbers are represented in
35889 @sc{hex} with leading zeros suppressed.
35891 Implementors should note that prior to @value{GDBN} 5.0, the character
35892 @samp{:} could not appear as the third character in a packet (as it
35893 would potentially conflict with the @var{sequence-id}).
35895 @cindex remote protocol, binary data
35896 @anchor{Binary Data}
35897 Binary data in most packets is encoded either as two hexadecimal
35898 digits per byte of binary data. This allowed the traditional remote
35899 protocol to work over connections which were only seven-bit clean.
35900 Some packets designed more recently assume an eight-bit clean
35901 connection, and use a more efficient encoding to send and receive
35904 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35905 as an escape character. Any escaped byte is transmitted as the escape
35906 character followed by the original character XORed with @code{0x20}.
35907 For example, the byte @code{0x7d} would be transmitted as the two
35908 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35909 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35910 @samp{@}}) must always be escaped. Responses sent by the stub
35911 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35912 is not interpreted as the start of a run-length encoded sequence
35915 Response @var{data} can be run-length encoded to save space.
35916 Run-length encoding replaces runs of identical characters with one
35917 instance of the repeated character, followed by a @samp{*} and a
35918 repeat count. The repeat count is itself sent encoded, to avoid
35919 binary characters in @var{data}: a value of @var{n} is sent as
35920 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35921 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35922 code 32) for a repeat count of 3. (This is because run-length
35923 encoding starts to win for counts 3 or more.) Thus, for example,
35924 @samp{0* } is a run-length encoding of ``0000'': the space character
35925 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35928 The printable characters @samp{#} and @samp{$} or with a numeric value
35929 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35930 seven repeats (@samp{$}) can be expanded using a repeat count of only
35931 five (@samp{"}). For example, @samp{00000000} can be encoded as
35934 The error response returned for some packets includes a two character
35935 error number. That number is not well defined.
35937 @cindex empty response, for unsupported packets
35938 For any @var{command} not supported by the stub, an empty response
35939 (@samp{$#00}) should be returned. That way it is possible to extend the
35940 protocol. A newer @value{GDBN} can tell if a packet is supported based
35943 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35944 commands for register access, and the @samp{m} and @samp{M} commands
35945 for memory access. Stubs that only control single-threaded targets
35946 can implement run control with the @samp{c} (continue), and @samp{s}
35947 (step) commands. Stubs that support multi-threading targets should
35948 support the @samp{vCont} command. All other commands are optional.
35953 The following table provides a complete list of all currently defined
35954 @var{command}s and their corresponding response @var{data}.
35955 @xref{File-I/O Remote Protocol Extension}, for details about the File
35956 I/O extension of the remote protocol.
35958 Each packet's description has a template showing the packet's overall
35959 syntax, followed by an explanation of the packet's meaning. We
35960 include spaces in some of the templates for clarity; these are not
35961 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35962 separate its components. For example, a template like @samp{foo
35963 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35964 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35965 @var{baz}. @value{GDBN} does not transmit a space character between the
35966 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35969 @cindex @var{thread-id}, in remote protocol
35970 @anchor{thread-id syntax}
35971 Several packets and replies include a @var{thread-id} field to identify
35972 a thread. Normally these are positive numbers with a target-specific
35973 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35974 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35977 In addition, the remote protocol supports a multiprocess feature in
35978 which the @var{thread-id} syntax is extended to optionally include both
35979 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35980 The @var{pid} (process) and @var{tid} (thread) components each have the
35981 format described above: a positive number with target-specific
35982 interpretation formatted as a big-endian hex string, literal @samp{-1}
35983 to indicate all processes or threads (respectively), or @samp{0} to
35984 indicate an arbitrary process or thread. Specifying just a process, as
35985 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35986 error to specify all processes but a specific thread, such as
35987 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35988 for those packets and replies explicitly documented to include a process
35989 ID, rather than a @var{thread-id}.
35991 The multiprocess @var{thread-id} syntax extensions are only used if both
35992 @value{GDBN} and the stub report support for the @samp{multiprocess}
35993 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35996 Note that all packet forms beginning with an upper- or lower-case
35997 letter, other than those described here, are reserved for future use.
35999 Here are the packet descriptions.
36004 @cindex @samp{!} packet
36005 @anchor{extended mode}
36006 Enable extended mode. In extended mode, the remote server is made
36007 persistent. The @samp{R} packet is used to restart the program being
36013 The remote target both supports and has enabled extended mode.
36017 @cindex @samp{?} packet
36018 Indicate the reason the target halted. The reply is the same as for
36019 step and continue. This packet has a special interpretation when the
36020 target is in non-stop mode; see @ref{Remote Non-Stop}.
36023 @xref{Stop Reply Packets}, for the reply specifications.
36025 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36026 @cindex @samp{A} packet
36027 Initialized @code{argv[]} array passed into program. @var{arglen}
36028 specifies the number of bytes in the hex encoded byte stream
36029 @var{arg}. See @code{gdbserver} for more details.
36034 The arguments were set.
36040 @cindex @samp{b} packet
36041 (Don't use this packet; its behavior is not well-defined.)
36042 Change the serial line speed to @var{baud}.
36044 JTC: @emph{When does the transport layer state change? When it's
36045 received, or after the ACK is transmitted. In either case, there are
36046 problems if the command or the acknowledgment packet is dropped.}
36048 Stan: @emph{If people really wanted to add something like this, and get
36049 it working for the first time, they ought to modify ser-unix.c to send
36050 some kind of out-of-band message to a specially-setup stub and have the
36051 switch happen "in between" packets, so that from remote protocol's point
36052 of view, nothing actually happened.}
36054 @item B @var{addr},@var{mode}
36055 @cindex @samp{B} packet
36056 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36057 breakpoint at @var{addr}.
36059 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36060 (@pxref{insert breakpoint or watchpoint packet}).
36062 @cindex @samp{bc} packet
36065 Backward continue. Execute the target system in reverse. No parameter.
36066 @xref{Reverse Execution}, for more information.
36069 @xref{Stop Reply Packets}, for the reply specifications.
36071 @cindex @samp{bs} packet
36074 Backward single step. Execute one instruction in reverse. No parameter.
36075 @xref{Reverse Execution}, for more information.
36078 @xref{Stop Reply Packets}, for the reply specifications.
36080 @item c @r{[}@var{addr}@r{]}
36081 @cindex @samp{c} packet
36082 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36083 resume at current address.
36085 This packet is deprecated for multi-threading support. @xref{vCont
36089 @xref{Stop Reply Packets}, for the reply specifications.
36091 @item C @var{sig}@r{[};@var{addr}@r{]}
36092 @cindex @samp{C} packet
36093 Continue with signal @var{sig} (hex signal number). If
36094 @samp{;@var{addr}} is omitted, resume at same address.
36096 This packet is deprecated for multi-threading support. @xref{vCont
36100 @xref{Stop Reply Packets}, for the reply specifications.
36103 @cindex @samp{d} packet
36106 Don't use this packet; instead, define a general set packet
36107 (@pxref{General Query Packets}).
36111 @cindex @samp{D} packet
36112 The first form of the packet is used to detach @value{GDBN} from the
36113 remote system. It is sent to the remote target
36114 before @value{GDBN} disconnects via the @code{detach} command.
36116 The second form, including a process ID, is used when multiprocess
36117 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36118 detach only a specific process. The @var{pid} is specified as a
36119 big-endian hex string.
36129 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36130 @cindex @samp{F} packet
36131 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36132 This is part of the File-I/O protocol extension. @xref{File-I/O
36133 Remote Protocol Extension}, for the specification.
36136 @anchor{read registers packet}
36137 @cindex @samp{g} packet
36138 Read general registers.
36142 @item @var{XX@dots{}}
36143 Each byte of register data is described by two hex digits. The bytes
36144 with the register are transmitted in target byte order. The size of
36145 each register and their position within the @samp{g} packet are
36146 determined by the @value{GDBN} internal gdbarch functions
36147 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36148 specification of several standard @samp{g} packets is specified below.
36150 When reading registers from a trace frame (@pxref{Analyze Collected
36151 Data,,Using the Collected Data}), the stub may also return a string of
36152 literal @samp{x}'s in place of the register data digits, to indicate
36153 that the corresponding register has not been collected, thus its value
36154 is unavailable. For example, for an architecture with 4 registers of
36155 4 bytes each, the following reply indicates to @value{GDBN} that
36156 registers 0 and 2 have not been collected, while registers 1 and 3
36157 have been collected, and both have zero value:
36161 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36168 @item G @var{XX@dots{}}
36169 @cindex @samp{G} packet
36170 Write general registers. @xref{read registers packet}, for a
36171 description of the @var{XX@dots{}} data.
36181 @item H @var{op} @var{thread-id}
36182 @cindex @samp{H} packet
36183 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36184 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36185 it should be @samp{c} for step and continue operations (note that this
36186 is deprecated, supporting the @samp{vCont} command is a better
36187 option), @samp{g} for other operations. The thread designator
36188 @var{thread-id} has the format and interpretation described in
36189 @ref{thread-id syntax}.
36200 @c 'H': How restrictive (or permissive) is the thread model. If a
36201 @c thread is selected and stopped, are other threads allowed
36202 @c to continue to execute? As I mentioned above, I think the
36203 @c semantics of each command when a thread is selected must be
36204 @c described. For example:
36206 @c 'g': If the stub supports threads and a specific thread is
36207 @c selected, returns the register block from that thread;
36208 @c otherwise returns current registers.
36210 @c 'G' If the stub supports threads and a specific thread is
36211 @c selected, sets the registers of the register block of
36212 @c that thread; otherwise sets current registers.
36214 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36215 @anchor{cycle step packet}
36216 @cindex @samp{i} packet
36217 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36218 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36219 step starting at that address.
36222 @cindex @samp{I} packet
36223 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36227 @cindex @samp{k} packet
36230 FIXME: @emph{There is no description of how to operate when a specific
36231 thread context has been selected (i.e.@: does 'k' kill only that
36234 @item m @var{addr},@var{length}
36235 @cindex @samp{m} packet
36236 Read @var{length} bytes of memory starting at address @var{addr}.
36237 Note that @var{addr} may not be aligned to any particular boundary.
36239 The stub need not use any particular size or alignment when gathering
36240 data from memory for the response; even if @var{addr} is word-aligned
36241 and @var{length} is a multiple of the word size, the stub is free to
36242 use byte accesses, or not. For this reason, this packet may not be
36243 suitable for accessing memory-mapped I/O devices.
36244 @cindex alignment of remote memory accesses
36245 @cindex size of remote memory accesses
36246 @cindex memory, alignment and size of remote accesses
36250 @item @var{XX@dots{}}
36251 Memory contents; each byte is transmitted as a two-digit hexadecimal
36252 number. The reply may contain fewer bytes than requested if the
36253 server was able to read only part of the region of memory.
36258 @item M @var{addr},@var{length}:@var{XX@dots{}}
36259 @cindex @samp{M} packet
36260 Write @var{length} bytes of memory starting at address @var{addr}.
36261 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36262 hexadecimal number.
36269 for an error (this includes the case where only part of the data was
36274 @cindex @samp{p} packet
36275 Read the value of register @var{n}; @var{n} is in hex.
36276 @xref{read registers packet}, for a description of how the returned
36277 register value is encoded.
36281 @item @var{XX@dots{}}
36282 the register's value
36286 Indicating an unrecognized @var{query}.
36289 @item P @var{n@dots{}}=@var{r@dots{}}
36290 @anchor{write register packet}
36291 @cindex @samp{P} packet
36292 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36293 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36294 digits for each byte in the register (target byte order).
36304 @item q @var{name} @var{params}@dots{}
36305 @itemx Q @var{name} @var{params}@dots{}
36306 @cindex @samp{q} packet
36307 @cindex @samp{Q} packet
36308 General query (@samp{q}) and set (@samp{Q}). These packets are
36309 described fully in @ref{General Query Packets}.
36312 @cindex @samp{r} packet
36313 Reset the entire system.
36315 Don't use this packet; use the @samp{R} packet instead.
36318 @cindex @samp{R} packet
36319 Restart the program being debugged. @var{XX}, while needed, is ignored.
36320 This packet is only available in extended mode (@pxref{extended mode}).
36322 The @samp{R} packet has no reply.
36324 @item s @r{[}@var{addr}@r{]}
36325 @cindex @samp{s} packet
36326 Single step. @var{addr} is the address at which to resume. If
36327 @var{addr} is omitted, resume at same address.
36329 This packet is deprecated for multi-threading support. @xref{vCont
36333 @xref{Stop Reply Packets}, for the reply specifications.
36335 @item S @var{sig}@r{[};@var{addr}@r{]}
36336 @anchor{step with signal packet}
36337 @cindex @samp{S} packet
36338 Step with signal. This is analogous to the @samp{C} packet, but
36339 requests a single-step, rather than a normal resumption of execution.
36341 This packet is deprecated for multi-threading support. @xref{vCont
36345 @xref{Stop Reply Packets}, for the reply specifications.
36347 @item t @var{addr}:@var{PP},@var{MM}
36348 @cindex @samp{t} packet
36349 Search backwards starting at address @var{addr} for a match with pattern
36350 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36351 @var{addr} must be at least 3 digits.
36353 @item T @var{thread-id}
36354 @cindex @samp{T} packet
36355 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36360 thread is still alive
36366 Packets starting with @samp{v} are identified by a multi-letter name,
36367 up to the first @samp{;} or @samp{?} (or the end of the packet).
36369 @item vAttach;@var{pid}
36370 @cindex @samp{vAttach} packet
36371 Attach to a new process with the specified process ID @var{pid}.
36372 The process ID is a
36373 hexadecimal integer identifying the process. In all-stop mode, all
36374 threads in the attached process are stopped; in non-stop mode, it may be
36375 attached without being stopped if that is supported by the target.
36377 @c In non-stop mode, on a successful vAttach, the stub should set the
36378 @c current thread to a thread of the newly-attached process. After
36379 @c attaching, GDB queries for the attached process's thread ID with qC.
36380 @c Also note that, from a user perspective, whether or not the
36381 @c target is stopped on attach in non-stop mode depends on whether you
36382 @c use the foreground or background version of the attach command, not
36383 @c on what vAttach does; GDB does the right thing with respect to either
36384 @c stopping or restarting threads.
36386 This packet is only available in extended mode (@pxref{extended mode}).
36392 @item @r{Any stop packet}
36393 for success in all-stop mode (@pxref{Stop Reply Packets})
36395 for success in non-stop mode (@pxref{Remote Non-Stop})
36398 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36399 @cindex @samp{vCont} packet
36400 @anchor{vCont packet}
36401 Resume the inferior, specifying different actions for each thread.
36402 If an action is specified with no @var{thread-id}, then it is applied to any
36403 threads that don't have a specific action specified; if no default action is
36404 specified then other threads should remain stopped in all-stop mode and
36405 in their current state in non-stop mode.
36406 Specifying multiple
36407 default actions is an error; specifying no actions is also an error.
36408 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36410 Currently supported actions are:
36416 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36420 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36425 The optional argument @var{addr} normally associated with the
36426 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36427 not supported in @samp{vCont}.
36429 The @samp{t} action is only relevant in non-stop mode
36430 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36431 A stop reply should be generated for any affected thread not already stopped.
36432 When a thread is stopped by means of a @samp{t} action,
36433 the corresponding stop reply should indicate that the thread has stopped with
36434 signal @samp{0}, regardless of whether the target uses some other signal
36435 as an implementation detail.
36437 The stub must support @samp{vCont} if it reports support for
36438 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36439 this case @samp{vCont} actions can be specified to apply to all threads
36440 in a process by using the @samp{p@var{pid}.-1} form of the
36444 @xref{Stop Reply Packets}, for the reply specifications.
36447 @cindex @samp{vCont?} packet
36448 Request a list of actions supported by the @samp{vCont} packet.
36452 @item vCont@r{[};@var{action}@dots{}@r{]}
36453 The @samp{vCont} packet is supported. Each @var{action} is a supported
36454 command in the @samp{vCont} packet.
36456 The @samp{vCont} packet is not supported.
36459 @item vFile:@var{operation}:@var{parameter}@dots{}
36460 @cindex @samp{vFile} packet
36461 Perform a file operation on the target system. For details,
36462 see @ref{Host I/O Packets}.
36464 @item vFlashErase:@var{addr},@var{length}
36465 @cindex @samp{vFlashErase} packet
36466 Direct the stub to erase @var{length} bytes of flash starting at
36467 @var{addr}. The region may enclose any number of flash blocks, but
36468 its start and end must fall on block boundaries, as indicated by the
36469 flash block size appearing in the memory map (@pxref{Memory Map
36470 Format}). @value{GDBN} groups flash memory programming operations
36471 together, and sends a @samp{vFlashDone} request after each group; the
36472 stub is allowed to delay erase operation until the @samp{vFlashDone}
36473 packet is received.
36483 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36484 @cindex @samp{vFlashWrite} packet
36485 Direct the stub to write data to flash address @var{addr}. The data
36486 is passed in binary form using the same encoding as for the @samp{X}
36487 packet (@pxref{Binary Data}). The memory ranges specified by
36488 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36489 not overlap, and must appear in order of increasing addresses
36490 (although @samp{vFlashErase} packets for higher addresses may already
36491 have been received; the ordering is guaranteed only between
36492 @samp{vFlashWrite} packets). If a packet writes to an address that was
36493 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36494 target-specific method, the results are unpredictable.
36502 for vFlashWrite addressing non-flash memory
36508 @cindex @samp{vFlashDone} packet
36509 Indicate to the stub that flash programming operation is finished.
36510 The stub is permitted to delay or batch the effects of a group of
36511 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36512 @samp{vFlashDone} packet is received. The contents of the affected
36513 regions of flash memory are unpredictable until the @samp{vFlashDone}
36514 request is completed.
36516 @item vKill;@var{pid}
36517 @cindex @samp{vKill} packet
36518 Kill the process with the specified process ID. @var{pid} is a
36519 hexadecimal integer identifying the process. This packet is used in
36520 preference to @samp{k} when multiprocess protocol extensions are
36521 supported; see @ref{multiprocess extensions}.
36531 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36532 @cindex @samp{vRun} packet
36533 Run the program @var{filename}, passing it each @var{argument} on its
36534 command line. The file and arguments are hex-encoded strings. If
36535 @var{filename} is an empty string, the stub may use a default program
36536 (e.g.@: the last program run). The program is created in the stopped
36539 @c FIXME: What about non-stop mode?
36541 This packet is only available in extended mode (@pxref{extended mode}).
36547 @item @r{Any stop packet}
36548 for success (@pxref{Stop Reply Packets})
36552 @cindex @samp{vStopped} packet
36553 @xref{Notification Packets}.
36555 @item X @var{addr},@var{length}:@var{XX@dots{}}
36557 @cindex @samp{X} packet
36558 Write data to memory, where the data is transmitted in binary.
36559 @var{addr} is address, @var{length} is number of bytes,
36560 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36570 @item z @var{type},@var{addr},@var{kind}
36571 @itemx Z @var{type},@var{addr},@var{kind}
36572 @anchor{insert breakpoint or watchpoint packet}
36573 @cindex @samp{z} packet
36574 @cindex @samp{Z} packets
36575 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36576 watchpoint starting at address @var{address} of kind @var{kind}.
36578 Each breakpoint and watchpoint packet @var{type} is documented
36581 @emph{Implementation notes: A remote target shall return an empty string
36582 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36583 remote target shall support either both or neither of a given
36584 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36585 avoid potential problems with duplicate packets, the operations should
36586 be implemented in an idempotent way.}
36588 @item z0,@var{addr},@var{kind}
36589 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36590 @cindex @samp{z0} packet
36591 @cindex @samp{Z0} packet
36592 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36593 @var{addr} of type @var{kind}.
36595 A memory breakpoint is implemented by replacing the instruction at
36596 @var{addr} with a software breakpoint or trap instruction. The
36597 @var{kind} is target-specific and typically indicates the size of
36598 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36599 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36600 architectures have additional meanings for @var{kind};
36601 @var{cond_list} is an optional list of conditional expressions in bytecode
36602 form that should be evaluated on the target's side. These are the
36603 conditions that should be taken into consideration when deciding if
36604 the breakpoint trigger should be reported back to @var{GDBN}.
36606 The @var{cond_list} parameter is comprised of a series of expressions,
36607 concatenated without separators. Each expression has the following form:
36611 @item X @var{len},@var{expr}
36612 @var{len} is the length of the bytecode expression and @var{expr} is the
36613 actual conditional expression in bytecode form.
36617 The optional @var{cmd_list} parameter introduces commands that may be
36618 run on the target, rather than being reported back to @value{GDBN}.
36619 The parameter starts with a numeric flag @var{persist}; if the flag is
36620 nonzero, then the breakpoint may remain active and the commands
36621 continue to be run even when @value{GDBN} disconnects from the target.
36622 Following this flag is a series of expressions concatenated with no
36623 separators. Each expression has the following form:
36627 @item X @var{len},@var{expr}
36628 @var{len} is the length of the bytecode expression and @var{expr} is the
36629 actual conditional expression in bytecode form.
36633 see @ref{Architecture-Specific Protocol Details}.
36635 @emph{Implementation note: It is possible for a target to copy or move
36636 code that contains memory breakpoints (e.g., when implementing
36637 overlays). The behavior of this packet, in the presence of such a
36638 target, is not defined.}
36650 @item z1,@var{addr},@var{kind}
36651 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36652 @cindex @samp{z1} packet
36653 @cindex @samp{Z1} packet
36654 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36655 address @var{addr}.
36657 A hardware breakpoint is implemented using a mechanism that is not
36658 dependant on being able to modify the target's memory. @var{kind}
36659 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36661 @emph{Implementation note: A hardware breakpoint is not affected by code
36674 @item z2,@var{addr},@var{kind}
36675 @itemx Z2,@var{addr},@var{kind}
36676 @cindex @samp{z2} packet
36677 @cindex @samp{Z2} packet
36678 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36679 @var{kind} is interpreted as the number of bytes to watch.
36691 @item z3,@var{addr},@var{kind}
36692 @itemx Z3,@var{addr},@var{kind}
36693 @cindex @samp{z3} packet
36694 @cindex @samp{Z3} packet
36695 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36696 @var{kind} is interpreted as the number of bytes to watch.
36708 @item z4,@var{addr},@var{kind}
36709 @itemx Z4,@var{addr},@var{kind}
36710 @cindex @samp{z4} packet
36711 @cindex @samp{Z4} packet
36712 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36713 @var{kind} is interpreted as the number of bytes to watch.
36727 @node Stop Reply Packets
36728 @section Stop Reply Packets
36729 @cindex stop reply packets
36731 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36732 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36733 receive any of the below as a reply. Except for @samp{?}
36734 and @samp{vStopped}, that reply is only returned
36735 when the target halts. In the below the exact meaning of @dfn{signal
36736 number} is defined by the header @file{include/gdb/signals.h} in the
36737 @value{GDBN} source code.
36739 As in the description of request packets, we include spaces in the
36740 reply templates for clarity; these are not part of the reply packet's
36741 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36747 The program received signal number @var{AA} (a two-digit hexadecimal
36748 number). This is equivalent to a @samp{T} response with no
36749 @var{n}:@var{r} pairs.
36751 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36752 @cindex @samp{T} packet reply
36753 The program received signal number @var{AA} (a two-digit hexadecimal
36754 number). This is equivalent to an @samp{S} response, except that the
36755 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36756 and other information directly in the stop reply packet, reducing
36757 round-trip latency. Single-step and breakpoint traps are reported
36758 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36762 If @var{n} is a hexadecimal number, it is a register number, and the
36763 corresponding @var{r} gives that register's value. @var{r} is a
36764 series of bytes in target byte order, with each byte given by a
36765 two-digit hex number.
36768 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36769 the stopped thread, as specified in @ref{thread-id syntax}.
36772 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36773 the core on which the stop event was detected.
36776 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36777 specific event that stopped the target. The currently defined stop
36778 reasons are listed below. @var{aa} should be @samp{05}, the trap
36779 signal. At most one stop reason should be present.
36782 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36783 and go on to the next; this allows us to extend the protocol in the
36787 The currently defined stop reasons are:
36793 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36796 @cindex shared library events, remote reply
36798 The packet indicates that the loaded libraries have changed.
36799 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36800 list of loaded libraries. @var{r} is ignored.
36802 @cindex replay log events, remote reply
36804 The packet indicates that the target cannot continue replaying
36805 logged execution events, because it has reached the end (or the
36806 beginning when executing backward) of the log. The value of @var{r}
36807 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36808 for more information.
36812 @itemx W @var{AA} ; process:@var{pid}
36813 The process exited, and @var{AA} is the exit status. This is only
36814 applicable to certain targets.
36816 The second form of the response, including the process ID of the exited
36817 process, can be used only when @value{GDBN} has reported support for
36818 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36819 The @var{pid} is formatted as a big-endian hex string.
36822 @itemx X @var{AA} ; process:@var{pid}
36823 The process terminated with signal @var{AA}.
36825 The second form of the response, including the process ID of the
36826 terminated process, can be used only when @value{GDBN} has reported
36827 support for multiprocess protocol extensions; see @ref{multiprocess
36828 extensions}. The @var{pid} is formatted as a big-endian hex string.
36830 @item O @var{XX}@dots{}
36831 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36832 written as the program's console output. This can happen at any time
36833 while the program is running and the debugger should continue to wait
36834 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36836 @item F @var{call-id},@var{parameter}@dots{}
36837 @var{call-id} is the identifier which says which host system call should
36838 be called. This is just the name of the function. Translation into the
36839 correct system call is only applicable as it's defined in @value{GDBN}.
36840 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36843 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36844 this very system call.
36846 The target replies with this packet when it expects @value{GDBN} to
36847 call a host system call on behalf of the target. @value{GDBN} replies
36848 with an appropriate @samp{F} packet and keeps up waiting for the next
36849 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36850 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36851 Protocol Extension}, for more details.
36855 @node General Query Packets
36856 @section General Query Packets
36857 @cindex remote query requests
36859 Packets starting with @samp{q} are @dfn{general query packets};
36860 packets starting with @samp{Q} are @dfn{general set packets}. General
36861 query and set packets are a semi-unified form for retrieving and
36862 sending information to and from the stub.
36864 The initial letter of a query or set packet is followed by a name
36865 indicating what sort of thing the packet applies to. For example,
36866 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36867 definitions with the stub. These packet names follow some
36872 The name must not contain commas, colons or semicolons.
36874 Most @value{GDBN} query and set packets have a leading upper case
36877 The names of custom vendor packets should use a company prefix, in
36878 lower case, followed by a period. For example, packets designed at
36879 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36880 foos) or @samp{Qacme.bar} (for setting bars).
36883 The name of a query or set packet should be separated from any
36884 parameters by a @samp{:}; the parameters themselves should be
36885 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36886 full packet name, and check for a separator or the end of the packet,
36887 in case two packet names share a common prefix. New packets should not begin
36888 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36889 packets predate these conventions, and have arguments without any terminator
36890 for the packet name; we suspect they are in widespread use in places that
36891 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36892 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36895 Like the descriptions of the other packets, each description here
36896 has a template showing the packet's overall syntax, followed by an
36897 explanation of the packet's meaning. We include spaces in some of the
36898 templates for clarity; these are not part of the packet's syntax. No
36899 @value{GDBN} packet uses spaces to separate its components.
36901 Here are the currently defined query and set packets:
36907 Turn on or off the agent as a helper to perform some debugging operations
36908 delegated from @value{GDBN} (@pxref{Control Agent}).
36910 @item QAllow:@var{op}:@var{val}@dots{}
36911 @cindex @samp{QAllow} packet
36912 Specify which operations @value{GDBN} expects to request of the
36913 target, as a semicolon-separated list of operation name and value
36914 pairs. Possible values for @var{op} include @samp{WriteReg},
36915 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36916 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36917 indicating that @value{GDBN} will not request the operation, or 1,
36918 indicating that it may. (The target can then use this to set up its
36919 own internals optimally, for instance if the debugger never expects to
36920 insert breakpoints, it may not need to install its own trap handler.)
36923 @cindex current thread, remote request
36924 @cindex @samp{qC} packet
36925 Return the current thread ID.
36929 @item QC @var{thread-id}
36930 Where @var{thread-id} is a thread ID as documented in
36931 @ref{thread-id syntax}.
36932 @item @r{(anything else)}
36933 Any other reply implies the old thread ID.
36936 @item qCRC:@var{addr},@var{length}
36937 @cindex CRC of memory block, remote request
36938 @cindex @samp{qCRC} packet
36939 Compute the CRC checksum of a block of memory using CRC-32 defined in
36940 IEEE 802.3. The CRC is computed byte at a time, taking the most
36941 significant bit of each byte first. The initial pattern code
36942 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36944 @emph{Note:} This is the same CRC used in validating separate debug
36945 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36946 Files}). However the algorithm is slightly different. When validating
36947 separate debug files, the CRC is computed taking the @emph{least}
36948 significant bit of each byte first, and the final result is inverted to
36949 detect trailing zeros.
36954 An error (such as memory fault)
36955 @item C @var{crc32}
36956 The specified memory region's checksum is @var{crc32}.
36959 @item QDisableRandomization:@var{value}
36960 @cindex disable address space randomization, remote request
36961 @cindex @samp{QDisableRandomization} packet
36962 Some target operating systems will randomize the virtual address space
36963 of the inferior process as a security feature, but provide a feature
36964 to disable such randomization, e.g.@: to allow for a more deterministic
36965 debugging experience. On such systems, this packet with a @var{value}
36966 of 1 directs the target to disable address space randomization for
36967 processes subsequently started via @samp{vRun} packets, while a packet
36968 with a @var{value} of 0 tells the target to enable address space
36971 This packet is only available in extended mode (@pxref{extended mode}).
36976 The request succeeded.
36979 An error occurred. @var{nn} are hex digits.
36982 An empty reply indicates that @samp{QDisableRandomization} is not supported
36986 This packet is not probed by default; the remote stub must request it,
36987 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36988 This should only be done on targets that actually support disabling
36989 address space randomization.
36992 @itemx qsThreadInfo
36993 @cindex list active threads, remote request
36994 @cindex @samp{qfThreadInfo} packet
36995 @cindex @samp{qsThreadInfo} packet
36996 Obtain a list of all active thread IDs from the target (OS). Since there
36997 may be too many active threads to fit into one reply packet, this query
36998 works iteratively: it may require more than one query/reply sequence to
36999 obtain the entire list of threads. The first query of the sequence will
37000 be the @samp{qfThreadInfo} query; subsequent queries in the
37001 sequence will be the @samp{qsThreadInfo} query.
37003 NOTE: This packet replaces the @samp{qL} query (see below).
37007 @item m @var{thread-id}
37009 @item m @var{thread-id},@var{thread-id}@dots{}
37010 a comma-separated list of thread IDs
37012 (lower case letter @samp{L}) denotes end of list.
37015 In response to each query, the target will reply with a list of one or
37016 more thread IDs, separated by commas.
37017 @value{GDBN} will respond to each reply with a request for more thread
37018 ids (using the @samp{qs} form of the query), until the target responds
37019 with @samp{l} (lower-case ell, for @dfn{last}).
37020 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37023 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37024 @cindex get thread-local storage address, remote request
37025 @cindex @samp{qGetTLSAddr} packet
37026 Fetch the address associated with thread local storage specified
37027 by @var{thread-id}, @var{offset}, and @var{lm}.
37029 @var{thread-id} is the thread ID associated with the
37030 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37032 @var{offset} is the (big endian, hex encoded) offset associated with the
37033 thread local variable. (This offset is obtained from the debug
37034 information associated with the variable.)
37036 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37037 load module associated with the thread local storage. For example,
37038 a @sc{gnu}/Linux system will pass the link map address of the shared
37039 object associated with the thread local storage under consideration.
37040 Other operating environments may choose to represent the load module
37041 differently, so the precise meaning of this parameter will vary.
37045 @item @var{XX}@dots{}
37046 Hex encoded (big endian) bytes representing the address of the thread
37047 local storage requested.
37050 An error occurred. @var{nn} are hex digits.
37053 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37056 @item qGetTIBAddr:@var{thread-id}
37057 @cindex get thread information block address
37058 @cindex @samp{qGetTIBAddr} packet
37059 Fetch address of the Windows OS specific Thread Information Block.
37061 @var{thread-id} is the thread ID associated with the thread.
37065 @item @var{XX}@dots{}
37066 Hex encoded (big endian) bytes representing the linear address of the
37067 thread information block.
37070 An error occured. This means that either the thread was not found, or the
37071 address could not be retrieved.
37074 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37077 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37078 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37079 digit) is one to indicate the first query and zero to indicate a
37080 subsequent query; @var{threadcount} (two hex digits) is the maximum
37081 number of threads the response packet can contain; and @var{nextthread}
37082 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37083 returned in the response as @var{argthread}.
37085 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37089 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37090 Where: @var{count} (two hex digits) is the number of threads being
37091 returned; @var{done} (one hex digit) is zero to indicate more threads
37092 and one indicates no further threads; @var{argthreadid} (eight hex
37093 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37094 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37095 digits). See @code{remote.c:parse_threadlist_response()}.
37099 @cindex section offsets, remote request
37100 @cindex @samp{qOffsets} packet
37101 Get section offsets that the target used when relocating the downloaded
37106 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37107 Relocate the @code{Text} section by @var{xxx} from its original address.
37108 Relocate the @code{Data} section by @var{yyy} from its original address.
37109 If the object file format provides segment information (e.g.@: @sc{elf}
37110 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37111 segments by the supplied offsets.
37113 @emph{Note: while a @code{Bss} offset may be included in the response,
37114 @value{GDBN} ignores this and instead applies the @code{Data} offset
37115 to the @code{Bss} section.}
37117 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37118 Relocate the first segment of the object file, which conventionally
37119 contains program code, to a starting address of @var{xxx}. If
37120 @samp{DataSeg} is specified, relocate the second segment, which
37121 conventionally contains modifiable data, to a starting address of
37122 @var{yyy}. @value{GDBN} will report an error if the object file
37123 does not contain segment information, or does not contain at least
37124 as many segments as mentioned in the reply. Extra segments are
37125 kept at fixed offsets relative to the last relocated segment.
37128 @item qP @var{mode} @var{thread-id}
37129 @cindex thread information, remote request
37130 @cindex @samp{qP} packet
37131 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37132 encoded 32 bit mode; @var{thread-id} is a thread ID
37133 (@pxref{thread-id syntax}).
37135 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37138 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37142 @cindex non-stop mode, remote request
37143 @cindex @samp{QNonStop} packet
37145 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37146 @xref{Remote Non-Stop}, for more information.
37151 The request succeeded.
37154 An error occurred. @var{nn} are hex digits.
37157 An empty reply indicates that @samp{QNonStop} is not supported by
37161 This packet is not probed by default; the remote stub must request it,
37162 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37163 Use of this packet is controlled by the @code{set non-stop} command;
37164 @pxref{Non-Stop Mode}.
37166 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37167 @cindex pass signals to inferior, remote request
37168 @cindex @samp{QPassSignals} packet
37169 @anchor{QPassSignals}
37170 Each listed @var{signal} should be passed directly to the inferior process.
37171 Signals are numbered identically to continue packets and stop replies
37172 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37173 strictly greater than the previous item. These signals do not need to stop
37174 the inferior, or be reported to @value{GDBN}. All other signals should be
37175 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37176 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37177 new list. This packet improves performance when using @samp{handle
37178 @var{signal} nostop noprint pass}.
37183 The request succeeded.
37186 An error occurred. @var{nn} are hex digits.
37189 An empty reply indicates that @samp{QPassSignals} is not supported by
37193 Use of this packet is controlled by the @code{set remote pass-signals}
37194 command (@pxref{Remote Configuration, set remote pass-signals}).
37195 This packet is not probed by default; the remote stub must request it,
37196 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37198 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37199 @cindex signals the inferior may see, remote request
37200 @cindex @samp{QProgramSignals} packet
37201 @anchor{QProgramSignals}
37202 Each listed @var{signal} may be delivered to the inferior process.
37203 Others should be silently discarded.
37205 In some cases, the remote stub may need to decide whether to deliver a
37206 signal to the program or not without @value{GDBN} involvement. One
37207 example of that is while detaching --- the program's threads may have
37208 stopped for signals that haven't yet had a chance of being reported to
37209 @value{GDBN}, and so the remote stub can use the signal list specified
37210 by this packet to know whether to deliver or ignore those pending
37213 This does not influence whether to deliver a signal as requested by a
37214 resumption packet (@pxref{vCont packet}).
37216 Signals are numbered identically to continue packets and stop replies
37217 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37218 strictly greater than the previous item. Multiple
37219 @samp{QProgramSignals} packets do not combine; any earlier
37220 @samp{QProgramSignals} list is completely replaced by the new list.
37225 The request succeeded.
37228 An error occurred. @var{nn} are hex digits.
37231 An empty reply indicates that @samp{QProgramSignals} is not supported
37235 Use of this packet is controlled by the @code{set remote program-signals}
37236 command (@pxref{Remote Configuration, set remote program-signals}).
37237 This packet is not probed by default; the remote stub must request it,
37238 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37240 @item qRcmd,@var{command}
37241 @cindex execute remote command, remote request
37242 @cindex @samp{qRcmd} packet
37243 @var{command} (hex encoded) is passed to the local interpreter for
37244 execution. Invalid commands should be reported using the output
37245 string. Before the final result packet, the target may also respond
37246 with a number of intermediate @samp{O@var{output}} console output
37247 packets. @emph{Implementors should note that providing access to a
37248 stubs's interpreter may have security implications}.
37253 A command response with no output.
37255 A command response with the hex encoded output string @var{OUTPUT}.
37257 Indicate a badly formed request.
37259 An empty reply indicates that @samp{qRcmd} is not recognized.
37262 (Note that the @code{qRcmd} packet's name is separated from the
37263 command by a @samp{,}, not a @samp{:}, contrary to the naming
37264 conventions above. Please don't use this packet as a model for new
37267 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37268 @cindex searching memory, in remote debugging
37270 @cindex @samp{qSearch:memory} packet
37272 @cindex @samp{qSearch memory} packet
37273 @anchor{qSearch memory}
37274 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37275 @var{address} and @var{length} are encoded in hex.
37276 @var{search-pattern} is a sequence of bytes, hex encoded.
37281 The pattern was not found.
37283 The pattern was found at @var{address}.
37285 A badly formed request or an error was encountered while searching memory.
37287 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37290 @item QStartNoAckMode
37291 @cindex @samp{QStartNoAckMode} packet
37292 @anchor{QStartNoAckMode}
37293 Request that the remote stub disable the normal @samp{+}/@samp{-}
37294 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37299 The stub has switched to no-acknowledgment mode.
37300 @value{GDBN} acknowledges this reponse,
37301 but neither the stub nor @value{GDBN} shall send or expect further
37302 @samp{+}/@samp{-} acknowledgments in the current connection.
37304 An empty reply indicates that the stub does not support no-acknowledgment mode.
37307 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37308 @cindex supported packets, remote query
37309 @cindex features of the remote protocol
37310 @cindex @samp{qSupported} packet
37311 @anchor{qSupported}
37312 Tell the remote stub about features supported by @value{GDBN}, and
37313 query the stub for features it supports. This packet allows
37314 @value{GDBN} and the remote stub to take advantage of each others'
37315 features. @samp{qSupported} also consolidates multiple feature probes
37316 at startup, to improve @value{GDBN} performance---a single larger
37317 packet performs better than multiple smaller probe packets on
37318 high-latency links. Some features may enable behavior which must not
37319 be on by default, e.g.@: because it would confuse older clients or
37320 stubs. Other features may describe packets which could be
37321 automatically probed for, but are not. These features must be
37322 reported before @value{GDBN} will use them. This ``default
37323 unsupported'' behavior is not appropriate for all packets, but it
37324 helps to keep the initial connection time under control with new
37325 versions of @value{GDBN} which support increasing numbers of packets.
37329 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37330 The stub supports or does not support each returned @var{stubfeature},
37331 depending on the form of each @var{stubfeature} (see below for the
37334 An empty reply indicates that @samp{qSupported} is not recognized,
37335 or that no features needed to be reported to @value{GDBN}.
37338 The allowed forms for each feature (either a @var{gdbfeature} in the
37339 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37343 @item @var{name}=@var{value}
37344 The remote protocol feature @var{name} is supported, and associated
37345 with the specified @var{value}. The format of @var{value} depends
37346 on the feature, but it must not include a semicolon.
37348 The remote protocol feature @var{name} is supported, and does not
37349 need an associated value.
37351 The remote protocol feature @var{name} is not supported.
37353 The remote protocol feature @var{name} may be supported, and
37354 @value{GDBN} should auto-detect support in some other way when it is
37355 needed. This form will not be used for @var{gdbfeature} notifications,
37356 but may be used for @var{stubfeature} responses.
37359 Whenever the stub receives a @samp{qSupported} request, the
37360 supplied set of @value{GDBN} features should override any previous
37361 request. This allows @value{GDBN} to put the stub in a known
37362 state, even if the stub had previously been communicating with
37363 a different version of @value{GDBN}.
37365 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37370 This feature indicates whether @value{GDBN} supports multiprocess
37371 extensions to the remote protocol. @value{GDBN} does not use such
37372 extensions unless the stub also reports that it supports them by
37373 including @samp{multiprocess+} in its @samp{qSupported} reply.
37374 @xref{multiprocess extensions}, for details.
37377 This feature indicates that @value{GDBN} supports the XML target
37378 description. If the stub sees @samp{xmlRegisters=} with target
37379 specific strings separated by a comma, it will report register
37383 This feature indicates whether @value{GDBN} supports the
37384 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37385 instruction reply packet}).
37388 Stubs should ignore any unknown values for
37389 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37390 packet supports receiving packets of unlimited length (earlier
37391 versions of @value{GDBN} may reject overly long responses). Additional values
37392 for @var{gdbfeature} may be defined in the future to let the stub take
37393 advantage of new features in @value{GDBN}, e.g.@: incompatible
37394 improvements in the remote protocol---the @samp{multiprocess} feature is
37395 an example of such a feature. The stub's reply should be independent
37396 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37397 describes all the features it supports, and then the stub replies with
37398 all the features it supports.
37400 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37401 responses, as long as each response uses one of the standard forms.
37403 Some features are flags. A stub which supports a flag feature
37404 should respond with a @samp{+} form response. Other features
37405 require values, and the stub should respond with an @samp{=}
37408 Each feature has a default value, which @value{GDBN} will use if
37409 @samp{qSupported} is not available or if the feature is not mentioned
37410 in the @samp{qSupported} response. The default values are fixed; a
37411 stub is free to omit any feature responses that match the defaults.
37413 Not all features can be probed, but for those which can, the probing
37414 mechanism is useful: in some cases, a stub's internal
37415 architecture may not allow the protocol layer to know some information
37416 about the underlying target in advance. This is especially common in
37417 stubs which may be configured for multiple targets.
37419 These are the currently defined stub features and their properties:
37421 @multitable @columnfractions 0.35 0.2 0.12 0.2
37422 @c NOTE: The first row should be @headitem, but we do not yet require
37423 @c a new enough version of Texinfo (4.7) to use @headitem.
37425 @tab Value Required
37429 @item @samp{PacketSize}
37434 @item @samp{qXfer:auxv:read}
37439 @item @samp{qXfer:btrace:read}
37444 @item @samp{qXfer:features:read}
37449 @item @samp{qXfer:libraries:read}
37454 @item @samp{qXfer:memory-map:read}
37459 @item @samp{qXfer:sdata:read}
37464 @item @samp{qXfer:spu:read}
37469 @item @samp{qXfer:spu:write}
37474 @item @samp{qXfer:siginfo:read}
37479 @item @samp{qXfer:siginfo:write}
37484 @item @samp{qXfer:threads:read}
37489 @item @samp{qXfer:traceframe-info:read}
37494 @item @samp{qXfer:uib:read}
37499 @item @samp{qXfer:fdpic:read}
37504 @item @samp{Qbtrace:off}
37509 @item @samp{Qbtrace:bts}
37514 @item @samp{QNonStop}
37519 @item @samp{QPassSignals}
37524 @item @samp{QStartNoAckMode}
37529 @item @samp{multiprocess}
37534 @item @samp{ConditionalBreakpoints}
37539 @item @samp{ConditionalTracepoints}
37544 @item @samp{ReverseContinue}
37549 @item @samp{ReverseStep}
37554 @item @samp{TracepointSource}
37559 @item @samp{QAgent}
37564 @item @samp{QAllow}
37569 @item @samp{QDisableRandomization}
37574 @item @samp{EnableDisableTracepoints}
37579 @item @samp{QTBuffer:size}
37584 @item @samp{tracenz}
37589 @item @samp{BreakpointCommands}
37596 These are the currently defined stub features, in more detail:
37599 @cindex packet size, remote protocol
37600 @item PacketSize=@var{bytes}
37601 The remote stub can accept packets up to at least @var{bytes} in
37602 length. @value{GDBN} will send packets up to this size for bulk
37603 transfers, and will never send larger packets. This is a limit on the
37604 data characters in the packet, including the frame and checksum.
37605 There is no trailing NUL byte in a remote protocol packet; if the stub
37606 stores packets in a NUL-terminated format, it should allow an extra
37607 byte in its buffer for the NUL. If this stub feature is not supported,
37608 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37610 @item qXfer:auxv:read
37611 The remote stub understands the @samp{qXfer:auxv:read} packet
37612 (@pxref{qXfer auxiliary vector read}).
37614 @item qXfer:btrace:read
37615 The remote stub understands the @samp{qXfer:btrace:read}
37616 packet (@pxref{qXfer btrace read}).
37618 @item qXfer:features:read
37619 The remote stub understands the @samp{qXfer:features:read} packet
37620 (@pxref{qXfer target description read}).
37622 @item qXfer:libraries:read
37623 The remote stub understands the @samp{qXfer:libraries:read} packet
37624 (@pxref{qXfer library list read}).
37626 @item qXfer:libraries-svr4:read
37627 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37628 (@pxref{qXfer svr4 library list read}).
37630 @item qXfer:memory-map:read
37631 The remote stub understands the @samp{qXfer:memory-map:read} packet
37632 (@pxref{qXfer memory map read}).
37634 @item qXfer:sdata:read
37635 The remote stub understands the @samp{qXfer:sdata:read} packet
37636 (@pxref{qXfer sdata read}).
37638 @item qXfer:spu:read
37639 The remote stub understands the @samp{qXfer:spu:read} packet
37640 (@pxref{qXfer spu read}).
37642 @item qXfer:spu:write
37643 The remote stub understands the @samp{qXfer:spu:write} packet
37644 (@pxref{qXfer spu write}).
37646 @item qXfer:siginfo:read
37647 The remote stub understands the @samp{qXfer:siginfo:read} packet
37648 (@pxref{qXfer siginfo read}).
37650 @item qXfer:siginfo:write
37651 The remote stub understands the @samp{qXfer:siginfo:write} packet
37652 (@pxref{qXfer siginfo write}).
37654 @item qXfer:threads:read
37655 The remote stub understands the @samp{qXfer:threads:read} packet
37656 (@pxref{qXfer threads read}).
37658 @item qXfer:traceframe-info:read
37659 The remote stub understands the @samp{qXfer:traceframe-info:read}
37660 packet (@pxref{qXfer traceframe info read}).
37662 @item qXfer:uib:read
37663 The remote stub understands the @samp{qXfer:uib:read}
37664 packet (@pxref{qXfer unwind info block}).
37666 @item qXfer:fdpic:read
37667 The remote stub understands the @samp{qXfer:fdpic:read}
37668 packet (@pxref{qXfer fdpic loadmap read}).
37671 The remote stub understands the @samp{QNonStop} packet
37672 (@pxref{QNonStop}).
37675 The remote stub understands the @samp{QPassSignals} packet
37676 (@pxref{QPassSignals}).
37678 @item QStartNoAckMode
37679 The remote stub understands the @samp{QStartNoAckMode} packet and
37680 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37683 @anchor{multiprocess extensions}
37684 @cindex multiprocess extensions, in remote protocol
37685 The remote stub understands the multiprocess extensions to the remote
37686 protocol syntax. The multiprocess extensions affect the syntax of
37687 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37688 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37689 replies. Note that reporting this feature indicates support for the
37690 syntactic extensions only, not that the stub necessarily supports
37691 debugging of more than one process at a time. The stub must not use
37692 multiprocess extensions in packet replies unless @value{GDBN} has also
37693 indicated it supports them in its @samp{qSupported} request.
37695 @item qXfer:osdata:read
37696 The remote stub understands the @samp{qXfer:osdata:read} packet
37697 ((@pxref{qXfer osdata read}).
37699 @item ConditionalBreakpoints
37700 The target accepts and implements evaluation of conditional expressions
37701 defined for breakpoints. The target will only report breakpoint triggers
37702 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37704 @item ConditionalTracepoints
37705 The remote stub accepts and implements conditional expressions defined
37706 for tracepoints (@pxref{Tracepoint Conditions}).
37708 @item ReverseContinue
37709 The remote stub accepts and implements the reverse continue packet
37713 The remote stub accepts and implements the reverse step packet
37716 @item TracepointSource
37717 The remote stub understands the @samp{QTDPsrc} packet that supplies
37718 the source form of tracepoint definitions.
37721 The remote stub understands the @samp{QAgent} packet.
37724 The remote stub understands the @samp{QAllow} packet.
37726 @item QDisableRandomization
37727 The remote stub understands the @samp{QDisableRandomization} packet.
37729 @item StaticTracepoint
37730 @cindex static tracepoints, in remote protocol
37731 The remote stub supports static tracepoints.
37733 @item InstallInTrace
37734 @anchor{install tracepoint in tracing}
37735 The remote stub supports installing tracepoint in tracing.
37737 @item EnableDisableTracepoints
37738 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37739 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37740 to be enabled and disabled while a trace experiment is running.
37742 @item QTBuffer:size
37743 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37744 packet that allows to change the size of the trace buffer.
37747 @cindex string tracing, in remote protocol
37748 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37749 See @ref{Bytecode Descriptions} for details about the bytecode.
37751 @item BreakpointCommands
37752 @cindex breakpoint commands, in remote protocol
37753 The remote stub supports running a breakpoint's command list itself,
37754 rather than reporting the hit to @value{GDBN}.
37757 The remote stub understands the @samp{Qbtrace:off} packet.
37760 The remote stub understands the @samp{Qbtrace:bts} packet.
37765 @cindex symbol lookup, remote request
37766 @cindex @samp{qSymbol} packet
37767 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37768 requests. Accept requests from the target for the values of symbols.
37773 The target does not need to look up any (more) symbols.
37774 @item qSymbol:@var{sym_name}
37775 The target requests the value of symbol @var{sym_name} (hex encoded).
37776 @value{GDBN} may provide the value by using the
37777 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37781 @item qSymbol:@var{sym_value}:@var{sym_name}
37782 Set the value of @var{sym_name} to @var{sym_value}.
37784 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37785 target has previously requested.
37787 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37788 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37794 The target does not need to look up any (more) symbols.
37795 @item qSymbol:@var{sym_name}
37796 The target requests the value of a new symbol @var{sym_name} (hex
37797 encoded). @value{GDBN} will continue to supply the values of symbols
37798 (if available), until the target ceases to request them.
37803 @itemx QTDisconnected
37810 @itemx qTMinFTPILen
37812 @xref{Tracepoint Packets}.
37814 @item qThreadExtraInfo,@var{thread-id}
37815 @cindex thread attributes info, remote request
37816 @cindex @samp{qThreadExtraInfo} packet
37817 Obtain a printable string description of a thread's attributes from
37818 the target OS. @var{thread-id} is a thread ID;
37819 see @ref{thread-id syntax}. This
37820 string may contain anything that the target OS thinks is interesting
37821 for @value{GDBN} to tell the user about the thread. The string is
37822 displayed in @value{GDBN}'s @code{info threads} display. Some
37823 examples of possible thread extra info strings are @samp{Runnable}, or
37824 @samp{Blocked on Mutex}.
37828 @item @var{XX}@dots{}
37829 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37830 comprising the printable string containing the extra information about
37831 the thread's attributes.
37834 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37835 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37836 conventions above. Please don't use this packet as a model for new
37855 @xref{Tracepoint Packets}.
37857 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37858 @cindex read special object, remote request
37859 @cindex @samp{qXfer} packet
37860 @anchor{qXfer read}
37861 Read uninterpreted bytes from the target's special data area
37862 identified by the keyword @var{object}. Request @var{length} bytes
37863 starting at @var{offset} bytes into the data. The content and
37864 encoding of @var{annex} is specific to @var{object}; it can supply
37865 additional details about what data to access.
37867 Here are the specific requests of this form defined so far. All
37868 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37869 formats, listed below.
37872 @item qXfer:auxv:read::@var{offset},@var{length}
37873 @anchor{qXfer auxiliary vector read}
37874 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37875 auxiliary vector}. Note @var{annex} must be empty.
37877 This packet is not probed by default; the remote stub must request it,
37878 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37880 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37881 @anchor{qXfer btrace read}
37883 Return a description of the current branch trace.
37884 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37885 packet may have one of the following values:
37889 Returns all available branch trace.
37892 Returns all available branch trace if the branch trace changed since
37893 the last read request.
37896 This packet is not probed by default; the remote stub must request it
37897 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37899 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37900 @anchor{qXfer target description read}
37901 Access the @dfn{target description}. @xref{Target Descriptions}. The
37902 annex specifies which XML document to access. The main description is
37903 always loaded from the @samp{target.xml} annex.
37905 This packet is not probed by default; the remote stub must request it,
37906 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37908 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37909 @anchor{qXfer library list read}
37910 Access the target's list of loaded libraries. @xref{Library List Format}.
37911 The annex part of the generic @samp{qXfer} packet must be empty
37912 (@pxref{qXfer read}).
37914 Targets which maintain a list of libraries in the program's memory do
37915 not need to implement this packet; it is designed for platforms where
37916 the operating system manages the list of loaded libraries.
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:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37922 @anchor{qXfer svr4 library list read}
37923 Access the target's list of loaded libraries when the target is an SVR4
37924 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37925 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37927 This packet is optional for better performance on SVR4 targets.
37928 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37930 This packet is not probed by default; the remote stub must request it,
37931 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37933 @item qXfer:memory-map:read::@var{offset},@var{length}
37934 @anchor{qXfer memory map read}
37935 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37936 annex part of the generic @samp{qXfer} packet must be empty
37937 (@pxref{qXfer read}).
37939 This packet is not probed by default; the remote stub must request it,
37940 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37942 @item qXfer:sdata:read::@var{offset},@var{length}
37943 @anchor{qXfer sdata read}
37945 Read contents of the extra collected static tracepoint marker
37946 information. The annex part of the generic @samp{qXfer} packet must
37947 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37950 This packet is not probed by default; the remote stub must request it,
37951 by supplying an appropriate @samp{qSupported} response
37952 (@pxref{qSupported}).
37954 @item qXfer:siginfo:read::@var{offset},@var{length}
37955 @anchor{qXfer siginfo read}
37956 Read contents of the extra signal information on the target
37957 system. The annex part of the generic @samp{qXfer} packet must be
37958 empty (@pxref{qXfer read}).
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:spu:read:@var{annex}:@var{offset},@var{length}
37965 @anchor{qXfer spu read}
37966 Read contents of an @code{spufs} file on the target system. The
37967 annex specifies which file to read; it must be of the form
37968 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37969 in the target process, and @var{name} identifes the @code{spufs} file
37970 in that context to be accessed.
37972 This packet is not probed by default; the remote stub must request it,
37973 by supplying an appropriate @samp{qSupported} response
37974 (@pxref{qSupported}).
37976 @item qXfer:threads:read::@var{offset},@var{length}
37977 @anchor{qXfer threads read}
37978 Access the list of threads on target. @xref{Thread List Format}. The
37979 annex part of the generic @samp{qXfer} packet must be empty
37980 (@pxref{qXfer read}).
37982 This packet is not probed by default; the remote stub must request it,
37983 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37985 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37986 @anchor{qXfer traceframe info read}
37988 Return a description of the current traceframe's contents.
37989 @xref{Traceframe Info Format}. The annex part of the generic
37990 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37992 This packet is not probed by default; the remote stub must request it,
37993 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37995 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37996 @anchor{qXfer unwind info block}
37998 Return the unwind information block for @var{pc}. This packet is used
37999 on OpenVMS/ia64 to ask the kernel unwind information.
38001 This packet is not probed by default.
38003 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38004 @anchor{qXfer fdpic loadmap read}
38005 Read contents of @code{loadmap}s on the target system. The
38006 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38007 executable @code{loadmap} or interpreter @code{loadmap} to read.
38009 This packet is not probed by default; the remote stub must request it,
38010 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38012 @item qXfer:osdata:read::@var{offset},@var{length}
38013 @anchor{qXfer osdata read}
38014 Access the target's @dfn{operating system information}.
38015 @xref{Operating System Information}.
38022 Data @var{data} (@pxref{Binary Data}) has been read from the
38023 target. There may be more data at a higher address (although
38024 it is permitted to return @samp{m} even for the last valid
38025 block of data, as long as at least one byte of data was read).
38026 @var{data} may have fewer bytes than the @var{length} in the
38030 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38031 There is no more data to be read. @var{data} may have fewer bytes
38032 than the @var{length} in the request.
38035 The @var{offset} in the request is at the end of the data.
38036 There is no more data to be read.
38039 The request was malformed, or @var{annex} was invalid.
38042 The offset was invalid, or there was an error encountered reading the data.
38043 @var{nn} is a hex-encoded @code{errno} value.
38046 An empty reply indicates the @var{object} string was not recognized by
38047 the stub, or that the object does not support reading.
38050 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38051 @cindex write data into object, remote request
38052 @anchor{qXfer write}
38053 Write uninterpreted bytes into the target's special data area
38054 identified by the keyword @var{object}, starting at @var{offset} bytes
38055 into the data. @var{data}@dots{} is the binary-encoded data
38056 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38057 is specific to @var{object}; it can supply additional details about what data
38060 Here are the specific requests of this form defined so far. All
38061 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38062 formats, listed below.
38065 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38066 @anchor{qXfer siginfo write}
38067 Write @var{data} to the extra signal information on the target system.
38068 The annex part of the generic @samp{qXfer} packet must be
38069 empty (@pxref{qXfer write}).
38071 This packet is not probed by default; the remote stub must request it,
38072 by supplying an appropriate @samp{qSupported} response
38073 (@pxref{qSupported}).
38075 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38076 @anchor{qXfer spu write}
38077 Write @var{data} to an @code{spufs} file on the target system. The
38078 annex specifies which file to write; it must be of the form
38079 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38080 in the target process, and @var{name} identifes the @code{spufs} file
38081 in that context to be accessed.
38083 This packet is not probed by default; the remote stub must request it,
38084 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38090 @var{nn} (hex encoded) is the number of bytes written.
38091 This may be fewer bytes than supplied in the request.
38094 The request was malformed, or @var{annex} was invalid.
38097 The offset was invalid, or there was an error encountered writing the data.
38098 @var{nn} is a hex-encoded @code{errno} value.
38101 An empty reply indicates the @var{object} string was not
38102 recognized by the stub, or that the object does not support writing.
38105 @item qXfer:@var{object}:@var{operation}:@dots{}
38106 Requests of this form may be added in the future. When a stub does
38107 not recognize the @var{object} keyword, or its support for
38108 @var{object} does not recognize the @var{operation} keyword, the stub
38109 must respond with an empty packet.
38111 @item qAttached:@var{pid}
38112 @cindex query attached, remote request
38113 @cindex @samp{qAttached} packet
38114 Return an indication of whether the remote server attached to an
38115 existing process or created a new process. When the multiprocess
38116 protocol extensions are supported (@pxref{multiprocess extensions}),
38117 @var{pid} is an integer in hexadecimal format identifying the target
38118 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38119 the query packet will be simplified as @samp{qAttached}.
38121 This query is used, for example, to know whether the remote process
38122 should be detached or killed when a @value{GDBN} session is ended with
38123 the @code{quit} command.
38128 The remote server attached to an existing process.
38130 The remote server created a new process.
38132 A badly formed request or an error was encountered.
38136 Enable branch tracing for the current thread using bts tracing.
38141 Branch tracing has been enabled.
38143 A badly formed request or an error was encountered.
38147 Disable branch tracing for the current thread.
38152 Branch tracing has been disabled.
38154 A badly formed request or an error was encountered.
38159 @node Architecture-Specific Protocol Details
38160 @section Architecture-Specific Protocol Details
38162 This section describes how the remote protocol is applied to specific
38163 target architectures. Also see @ref{Standard Target Features}, for
38164 details of XML target descriptions for each architecture.
38167 * ARM-Specific Protocol Details::
38168 * MIPS-Specific Protocol Details::
38171 @node ARM-Specific Protocol Details
38172 @subsection @acronym{ARM}-specific Protocol Details
38175 * ARM Breakpoint Kinds::
38178 @node ARM Breakpoint Kinds
38179 @subsubsection @acronym{ARM} Breakpoint Kinds
38180 @cindex breakpoint kinds, @acronym{ARM}
38182 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38187 16-bit Thumb mode breakpoint.
38190 32-bit Thumb mode (Thumb-2) breakpoint.
38193 32-bit @acronym{ARM} mode breakpoint.
38197 @node MIPS-Specific Protocol Details
38198 @subsection @acronym{MIPS}-specific Protocol Details
38201 * MIPS Register packet Format::
38202 * MIPS Breakpoint Kinds::
38205 @node MIPS Register packet Format
38206 @subsubsection @acronym{MIPS} Register Packet Format
38207 @cindex register packet format, @acronym{MIPS}
38209 The following @code{g}/@code{G} packets have previously been defined.
38210 In the below, some thirty-two bit registers are transferred as
38211 sixty-four bits. Those registers should be zero/sign extended (which?)
38212 to fill the space allocated. Register bytes are transferred in target
38213 byte order. The two nibbles within a register byte are transferred
38214 most-significant -- least-significant.
38219 All registers are transferred as thirty-two bit quantities in the order:
38220 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38221 registers; fsr; fir; fp.
38224 All registers are transferred as sixty-four bit quantities (including
38225 thirty-two bit registers such as @code{sr}). The ordering is the same
38230 @node MIPS Breakpoint Kinds
38231 @subsubsection @acronym{MIPS} Breakpoint Kinds
38232 @cindex breakpoint kinds, @acronym{MIPS}
38234 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38239 16-bit @acronym{MIPS16} mode breakpoint.
38242 16-bit @acronym{microMIPS} mode breakpoint.
38245 32-bit standard @acronym{MIPS} mode breakpoint.
38248 32-bit @acronym{microMIPS} mode breakpoint.
38252 @node Tracepoint Packets
38253 @section Tracepoint Packets
38254 @cindex tracepoint packets
38255 @cindex packets, tracepoint
38257 Here we describe the packets @value{GDBN} uses to implement
38258 tracepoints (@pxref{Tracepoints}).
38262 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38263 @cindex @samp{QTDP} packet
38264 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38265 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38266 the tracepoint is disabled. @var{step} is the tracepoint's step
38267 count, and @var{pass} is its pass count. If an @samp{F} is present,
38268 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38269 the number of bytes that the target should copy elsewhere to make room
38270 for the tracepoint. If an @samp{X} is present, it introduces a
38271 tracepoint condition, which consists of a hexadecimal length, followed
38272 by a comma and hex-encoded bytes, in a manner similar to action
38273 encodings as described below. If the trailing @samp{-} is present,
38274 further @samp{QTDP} packets will follow to specify this tracepoint's
38280 The packet was understood and carried out.
38282 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38284 The packet was not recognized.
38287 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38288 Define actions to be taken when a tracepoint is hit. @var{n} and
38289 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38290 this tracepoint. This packet may only be sent immediately after
38291 another @samp{QTDP} packet that ended with a @samp{-}. If the
38292 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38293 specifying more actions for this tracepoint.
38295 In the series of action packets for a given tracepoint, at most one
38296 can have an @samp{S} before its first @var{action}. If such a packet
38297 is sent, it and the following packets define ``while-stepping''
38298 actions. Any prior packets define ordinary actions --- that is, those
38299 taken when the tracepoint is first hit. If no action packet has an
38300 @samp{S}, then all the packets in the series specify ordinary
38301 tracepoint actions.
38303 The @samp{@var{action}@dots{}} portion of the packet is a series of
38304 actions, concatenated without separators. Each action has one of the
38310 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38311 a hexadecimal number whose @var{i}'th bit is set if register number
38312 @var{i} should be collected. (The least significant bit is numbered
38313 zero.) Note that @var{mask} may be any number of digits long; it may
38314 not fit in a 32-bit word.
38316 @item M @var{basereg},@var{offset},@var{len}
38317 Collect @var{len} bytes of memory starting at the address in register
38318 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38319 @samp{-1}, then the range has a fixed address: @var{offset} is the
38320 address of the lowest byte to collect. The @var{basereg},
38321 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38322 values (the @samp{-1} value for @var{basereg} is a special case).
38324 @item X @var{len},@var{expr}
38325 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38326 it directs. @var{expr} is an agent expression, as described in
38327 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38328 two-digit hex number in the packet; @var{len} is the number of bytes
38329 in the expression (and thus one-half the number of hex digits in the
38334 Any number of actions may be packed together in a single @samp{QTDP}
38335 packet, as long as the packet does not exceed the maximum packet
38336 length (400 bytes, for many stubs). There may be only one @samp{R}
38337 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38338 actions. Any registers referred to by @samp{M} and @samp{X} actions
38339 must be collected by a preceding @samp{R} action. (The
38340 ``while-stepping'' actions are treated as if they were attached to a
38341 separate tracepoint, as far as these restrictions are concerned.)
38346 The packet was understood and carried out.
38348 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38350 The packet was not recognized.
38353 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38354 @cindex @samp{QTDPsrc} packet
38355 Specify a source string of tracepoint @var{n} at address @var{addr}.
38356 This is useful to get accurate reproduction of the tracepoints
38357 originally downloaded at the beginning of the trace run. @var{type}
38358 is the name of the tracepoint part, such as @samp{cond} for the
38359 tracepoint's conditional expression (see below for a list of types), while
38360 @var{bytes} is the string, encoded in hexadecimal.
38362 @var{start} is the offset of the @var{bytes} within the overall source
38363 string, while @var{slen} is the total length of the source string.
38364 This is intended for handling source strings that are longer than will
38365 fit in a single packet.
38366 @c Add detailed example when this info is moved into a dedicated
38367 @c tracepoint descriptions section.
38369 The available string types are @samp{at} for the location,
38370 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38371 @value{GDBN} sends a separate packet for each command in the action
38372 list, in the same order in which the commands are stored in the list.
38374 The target does not need to do anything with source strings except
38375 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38378 Although this packet is optional, and @value{GDBN} will only send it
38379 if the target replies with @samp{TracepointSource} @xref{General
38380 Query Packets}, it makes both disconnected tracing and trace files
38381 much easier to use. Otherwise the user must be careful that the
38382 tracepoints in effect while looking at trace frames are identical to
38383 the ones in effect during the trace run; even a small discrepancy
38384 could cause @samp{tdump} not to work, or a particular trace frame not
38387 @item QTDV:@var{n}:@var{value}
38388 @cindex define trace state variable, remote request
38389 @cindex @samp{QTDV} packet
38390 Create a new trace state variable, number @var{n}, with an initial
38391 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38392 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38393 the option of not using this packet for initial values of zero; the
38394 target should simply create the trace state variables as they are
38395 mentioned in expressions.
38397 @item QTFrame:@var{n}
38398 @cindex @samp{QTFrame} packet
38399 Select the @var{n}'th tracepoint frame from the buffer, and use the
38400 register and memory contents recorded there to answer subsequent
38401 request packets from @value{GDBN}.
38403 A successful reply from the stub indicates that the stub has found the
38404 requested frame. The response is a series of parts, concatenated
38405 without separators, describing the frame we selected. Each part has
38406 one of the following forms:
38410 The selected frame is number @var{n} in the trace frame buffer;
38411 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38412 was no frame matching the criteria in the request packet.
38415 The selected trace frame records a hit of tracepoint number @var{t};
38416 @var{t} is a hexadecimal number.
38420 @item QTFrame:pc:@var{addr}
38421 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38422 currently selected frame whose PC is @var{addr};
38423 @var{addr} is a hexadecimal number.
38425 @item QTFrame:tdp:@var{t}
38426 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38427 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38428 is a hexadecimal number.
38430 @item QTFrame:range:@var{start}:@var{end}
38431 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38432 currently selected frame whose PC is between @var{start} (inclusive)
38433 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38436 @item QTFrame:outside:@var{start}:@var{end}
38437 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38438 frame @emph{outside} the given range of addresses (exclusive).
38441 @cindex @samp{qTMinFTPILen} packet
38442 This packet requests the minimum length of instruction at which a fast
38443 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38444 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38445 it depends on the target system being able to create trampolines in
38446 the first 64K of memory, which might or might not be possible for that
38447 system. So the reply to this packet will be 4 if it is able to
38454 The minimum instruction length is currently unknown.
38456 The minimum instruction length is @var{length}, where @var{length} is greater
38457 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38458 that a fast tracepoint may be placed on any instruction regardless of size.
38460 An error has occurred.
38462 An empty reply indicates that the request is not supported by the stub.
38466 @cindex @samp{QTStart} packet
38467 Begin the tracepoint experiment. Begin collecting data from
38468 tracepoint hits in the trace frame buffer. This packet supports the
38469 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38470 instruction reply packet}).
38473 @cindex @samp{QTStop} packet
38474 End the tracepoint experiment. Stop collecting trace frames.
38476 @item QTEnable:@var{n}:@var{addr}
38478 @cindex @samp{QTEnable} packet
38479 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38480 experiment. If the tracepoint was previously disabled, then collection
38481 of data from it will resume.
38483 @item QTDisable:@var{n}:@var{addr}
38485 @cindex @samp{QTDisable} packet
38486 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38487 experiment. No more data will be collected from the tracepoint unless
38488 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38491 @cindex @samp{QTinit} packet
38492 Clear the table of tracepoints, and empty the trace frame buffer.
38494 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38495 @cindex @samp{QTro} packet
38496 Establish the given ranges of memory as ``transparent''. The stub
38497 will answer requests for these ranges from memory's current contents,
38498 if they were not collected as part of the tracepoint hit.
38500 @value{GDBN} uses this to mark read-only regions of memory, like those
38501 containing program code. Since these areas never change, they should
38502 still have the same contents they did when the tracepoint was hit, so
38503 there's no reason for the stub to refuse to provide their contents.
38505 @item QTDisconnected:@var{value}
38506 @cindex @samp{QTDisconnected} packet
38507 Set the choice to what to do with the tracing run when @value{GDBN}
38508 disconnects from the target. A @var{value} of 1 directs the target to
38509 continue the tracing run, while 0 tells the target to stop tracing if
38510 @value{GDBN} is no longer in the picture.
38513 @cindex @samp{qTStatus} packet
38514 Ask the stub if there is a trace experiment running right now.
38516 The reply has the form:
38520 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38521 @var{running} is a single digit @code{1} if the trace is presently
38522 running, or @code{0} if not. It is followed by semicolon-separated
38523 optional fields that an agent may use to report additional status.
38527 If the trace is not running, the agent may report any of several
38528 explanations as one of the optional fields:
38533 No trace has been run yet.
38535 @item tstop[:@var{text}]:0
38536 The trace was stopped by a user-originated stop command. The optional
38537 @var{text} field is a user-supplied string supplied as part of the
38538 stop command (for instance, an explanation of why the trace was
38539 stopped manually). It is hex-encoded.
38542 The trace stopped because the trace buffer filled up.
38544 @item tdisconnected:0
38545 The trace stopped because @value{GDBN} disconnected from the target.
38547 @item tpasscount:@var{tpnum}
38548 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38550 @item terror:@var{text}:@var{tpnum}
38551 The trace stopped because tracepoint @var{tpnum} had an error. The
38552 string @var{text} is available to describe the nature of the error
38553 (for instance, a divide by zero in the condition expression).
38554 @var{text} is hex encoded.
38557 The trace stopped for some other reason.
38561 Additional optional fields supply statistical and other information.
38562 Although not required, they are extremely useful for users monitoring
38563 the progress of a trace run. If a trace has stopped, and these
38564 numbers are reported, they must reflect the state of the just-stopped
38569 @item tframes:@var{n}
38570 The number of trace frames in the buffer.
38572 @item tcreated:@var{n}
38573 The total number of trace frames created during the run. This may
38574 be larger than the trace frame count, if the buffer is circular.
38576 @item tsize:@var{n}
38577 The total size of the trace buffer, in bytes.
38579 @item tfree:@var{n}
38580 The number of bytes still unused in the buffer.
38582 @item circular:@var{n}
38583 The value of the circular trace buffer flag. @code{1} means that the
38584 trace buffer is circular and old trace frames will be discarded if
38585 necessary to make room, @code{0} means that the trace buffer is linear
38588 @item disconn:@var{n}
38589 The value of the disconnected tracing flag. @code{1} means that
38590 tracing will continue after @value{GDBN} disconnects, @code{0} means
38591 that the trace run will stop.
38595 @item qTP:@var{tp}:@var{addr}
38596 @cindex tracepoint status, remote request
38597 @cindex @samp{qTP} packet
38598 Ask the stub for the current state of tracepoint number @var{tp} at
38599 address @var{addr}.
38603 @item V@var{hits}:@var{usage}
38604 The tracepoint has been hit @var{hits} times so far during the trace
38605 run, and accounts for @var{usage} in the trace buffer. Note that
38606 @code{while-stepping} steps are not counted as separate hits, but the
38607 steps' space consumption is added into the usage number.
38611 @item qTV:@var{var}
38612 @cindex trace state variable value, remote request
38613 @cindex @samp{qTV} packet
38614 Ask the stub for the value of the trace state variable number @var{var}.
38619 The value of the variable is @var{value}. This will be the current
38620 value of the variable if the user is examining a running target, or a
38621 saved value if the variable was collected in the trace frame that the
38622 user is looking at. Note that multiple requests may result in
38623 different reply values, such as when requesting values while the
38624 program is running.
38627 The value of the variable is unknown. This would occur, for example,
38628 if the user is examining a trace frame in which the requested variable
38633 @cindex @samp{qTfP} packet
38635 @cindex @samp{qTsP} packet
38636 These packets request data about tracepoints that are being used by
38637 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38638 of data, and multiple @code{qTsP} to get additional pieces. Replies
38639 to these packets generally take the form of the @code{QTDP} packets
38640 that define tracepoints. (FIXME add detailed syntax)
38643 @cindex @samp{qTfV} packet
38645 @cindex @samp{qTsV} packet
38646 These packets request data about trace state variables that are on the
38647 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38648 and multiple @code{qTsV} to get additional variables. Replies to
38649 these packets follow the syntax of the @code{QTDV} packets that define
38650 trace state variables.
38656 @cindex @samp{qTfSTM} packet
38657 @cindex @samp{qTsSTM} packet
38658 These packets request data about static tracepoint markers that exist
38659 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38660 first piece of data, and multiple @code{qTsSTM} to get additional
38661 pieces. Replies to these packets take the following form:
38665 @item m @var{address}:@var{id}:@var{extra}
38667 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38668 a comma-separated list of markers
38670 (lower case letter @samp{L}) denotes end of list.
38672 An error occurred. @var{nn} are hex digits.
38674 An empty reply indicates that the request is not supported by the
38678 @var{address} is encoded in hex.
38679 @var{id} and @var{extra} are strings encoded in hex.
38681 In response to each query, the target will reply with a list of one or
38682 more markers, separated by commas. @value{GDBN} will respond to each
38683 reply with a request for more markers (using the @samp{qs} form of the
38684 query), until the target responds with @samp{l} (lower-case ell, for
38687 @item qTSTMat:@var{address}
38689 @cindex @samp{qTSTMat} packet
38690 This packets requests data about static tracepoint markers in the
38691 target program at @var{address}. Replies to this packet follow the
38692 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38693 tracepoint markers.
38695 @item QTSave:@var{filename}
38696 @cindex @samp{QTSave} packet
38697 This packet directs the target to save trace data to the file name
38698 @var{filename} in the target's filesystem. @var{filename} is encoded
38699 as a hex string; the interpretation of the file name (relative vs
38700 absolute, wild cards, etc) is up to the target.
38702 @item qTBuffer:@var{offset},@var{len}
38703 @cindex @samp{qTBuffer} packet
38704 Return up to @var{len} bytes of the current contents of trace buffer,
38705 starting at @var{offset}. The trace buffer is treated as if it were
38706 a contiguous collection of traceframes, as per the trace file format.
38707 The reply consists as many hex-encoded bytes as the target can deliver
38708 in a packet; it is not an error to return fewer than were asked for.
38709 A reply consisting of just @code{l} indicates that no bytes are
38712 @item QTBuffer:circular:@var{value}
38713 This packet directs the target to use a circular trace buffer if
38714 @var{value} is 1, or a linear buffer if the value is 0.
38716 @item QTBuffer:size:@var{size}
38717 @anchor{QTBuffer-size}
38718 @cindex @samp{QTBuffer size} packet
38719 This packet directs the target to make the trace buffer be of size
38720 @var{size} if possible. A value of @code{-1} tells the target to
38721 use whatever size it prefers.
38723 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38724 @cindex @samp{QTNotes} packet
38725 This packet adds optional textual notes to the trace run. Allowable
38726 types include @code{user}, @code{notes}, and @code{tstop}, the
38727 @var{text} fields are arbitrary strings, hex-encoded.
38731 @subsection Relocate instruction reply packet
38732 When installing fast tracepoints in memory, the target may need to
38733 relocate the instruction currently at the tracepoint address to a
38734 different address in memory. For most instructions, a simple copy is
38735 enough, but, for example, call instructions that implicitly push the
38736 return address on the stack, and relative branches or other
38737 PC-relative instructions require offset adjustment, so that the effect
38738 of executing the instruction at a different address is the same as if
38739 it had executed in the original location.
38741 In response to several of the tracepoint packets, the target may also
38742 respond with a number of intermediate @samp{qRelocInsn} request
38743 packets before the final result packet, to have @value{GDBN} handle
38744 this relocation operation. If a packet supports this mechanism, its
38745 documentation will explicitly say so. See for example the above
38746 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38747 format of the request is:
38750 @item qRelocInsn:@var{from};@var{to}
38752 This requests @value{GDBN} to copy instruction at address @var{from}
38753 to address @var{to}, possibly adjusted so that executing the
38754 instruction at @var{to} has the same effect as executing it at
38755 @var{from}. @value{GDBN} writes the adjusted instruction to target
38756 memory starting at @var{to}.
38761 @item qRelocInsn:@var{adjusted_size}
38762 Informs the stub the relocation is complete. @var{adjusted_size} is
38763 the length in bytes of resulting relocated instruction sequence.
38765 A badly formed request was detected, or an error was encountered while
38766 relocating the instruction.
38769 @node Host I/O Packets
38770 @section Host I/O Packets
38771 @cindex Host I/O, remote protocol
38772 @cindex file transfer, remote protocol
38774 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38775 operations on the far side of a remote link. For example, Host I/O is
38776 used to upload and download files to a remote target with its own
38777 filesystem. Host I/O uses the same constant values and data structure
38778 layout as the target-initiated File-I/O protocol. However, the
38779 Host I/O packets are structured differently. The target-initiated
38780 protocol relies on target memory to store parameters and buffers.
38781 Host I/O requests are initiated by @value{GDBN}, and the
38782 target's memory is not involved. @xref{File-I/O Remote Protocol
38783 Extension}, for more details on the target-initiated protocol.
38785 The Host I/O request packets all encode a single operation along with
38786 its arguments. They have this format:
38790 @item vFile:@var{operation}: @var{parameter}@dots{}
38791 @var{operation} is the name of the particular request; the target
38792 should compare the entire packet name up to the second colon when checking
38793 for a supported operation. The format of @var{parameter} depends on
38794 the operation. Numbers are always passed in hexadecimal. Negative
38795 numbers have an explicit minus sign (i.e.@: two's complement is not
38796 used). Strings (e.g.@: filenames) are encoded as a series of
38797 hexadecimal bytes. The last argument to a system call may be a
38798 buffer of escaped binary data (@pxref{Binary Data}).
38802 The valid responses to Host I/O packets are:
38806 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38807 @var{result} is the integer value returned by this operation, usually
38808 non-negative for success and -1 for errors. If an error has occured,
38809 @var{errno} will be included in the result. @var{errno} will have a
38810 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38811 operations which return data, @var{attachment} supplies the data as a
38812 binary buffer. Binary buffers in response packets are escaped in the
38813 normal way (@pxref{Binary Data}). See the individual packet
38814 documentation for the interpretation of @var{result} and
38818 An empty response indicates that this operation is not recognized.
38822 These are the supported Host I/O operations:
38825 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38826 Open a file at @var{pathname} and return a file descriptor for it, or
38827 return -1 if an error occurs. @var{pathname} is a string,
38828 @var{flags} is an integer indicating a mask of open flags
38829 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38830 of mode bits to use if the file is created (@pxref{mode_t Values}).
38831 @xref{open}, for details of the open flags and mode values.
38833 @item vFile:close: @var{fd}
38834 Close the open file corresponding to @var{fd} and return 0, or
38835 -1 if an error occurs.
38837 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38838 Read data from the open file corresponding to @var{fd}. Up to
38839 @var{count} bytes will be read from the file, starting at @var{offset}
38840 relative to the start of the file. The target may read fewer bytes;
38841 common reasons include packet size limits and an end-of-file
38842 condition. The number of bytes read is returned. Zero should only be
38843 returned for a successful read at the end of the file, or if
38844 @var{count} was zero.
38846 The data read should be returned as a binary attachment on success.
38847 If zero bytes were read, the response should include an empty binary
38848 attachment (i.e.@: a trailing semicolon). The return value is the
38849 number of target bytes read; the binary attachment may be longer if
38850 some characters were escaped.
38852 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38853 Write @var{data} (a binary buffer) to the open file corresponding
38854 to @var{fd}. Start the write at @var{offset} from the start of the
38855 file. Unlike many @code{write} system calls, there is no
38856 separate @var{count} argument; the length of @var{data} in the
38857 packet is used. @samp{vFile:write} returns the number of bytes written,
38858 which may be shorter than the length of @var{data}, or -1 if an
38861 @item vFile:unlink: @var{pathname}
38862 Delete the file at @var{pathname} on the target. Return 0,
38863 or -1 if an error occurs. @var{pathname} is a string.
38865 @item vFile:readlink: @var{filename}
38866 Read value of symbolic link @var{filename} on the target. Return
38867 the number of bytes read, or -1 if an error occurs.
38869 The data read should be returned as a binary attachment on success.
38870 If zero bytes were read, the response should include an empty binary
38871 attachment (i.e.@: a trailing semicolon). The return value is the
38872 number of target bytes read; the binary attachment may be longer if
38873 some characters were escaped.
38878 @section Interrupts
38879 @cindex interrupts (remote protocol)
38881 When a program on the remote target is running, @value{GDBN} may
38882 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38883 a @code{BREAK} followed by @code{g},
38884 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38886 The precise meaning of @code{BREAK} is defined by the transport
38887 mechanism and may, in fact, be undefined. @value{GDBN} does not
38888 currently define a @code{BREAK} mechanism for any of the network
38889 interfaces except for TCP, in which case @value{GDBN} sends the
38890 @code{telnet} BREAK sequence.
38892 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38893 transport mechanisms. It is represented by sending the single byte
38894 @code{0x03} without any of the usual packet overhead described in
38895 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38896 transmitted as part of a packet, it is considered to be packet data
38897 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38898 (@pxref{X packet}), used for binary downloads, may include an unescaped
38899 @code{0x03} as part of its packet.
38901 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38902 When Linux kernel receives this sequence from serial port,
38903 it stops execution and connects to gdb.
38905 Stubs are not required to recognize these interrupt mechanisms and the
38906 precise meaning associated with receipt of the interrupt is
38907 implementation defined. If the target supports debugging of multiple
38908 threads and/or processes, it should attempt to interrupt all
38909 currently-executing threads and processes.
38910 If the stub is successful at interrupting the
38911 running program, it should send one of the stop
38912 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38913 of successfully stopping the program in all-stop mode, and a stop reply
38914 for each stopped thread in non-stop mode.
38915 Interrupts received while the
38916 program is stopped are discarded.
38918 @node Notification Packets
38919 @section Notification Packets
38920 @cindex notification packets
38921 @cindex packets, notification
38923 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38924 packets that require no acknowledgment. Both the GDB and the stub
38925 may send notifications (although the only notifications defined at
38926 present are sent by the stub). Notifications carry information
38927 without incurring the round-trip latency of an acknowledgment, and so
38928 are useful for low-impact communications where occasional packet loss
38931 A notification packet has the form @samp{% @var{data} #
38932 @var{checksum}}, where @var{data} is the content of the notification,
38933 and @var{checksum} is a checksum of @var{data}, computed and formatted
38934 as for ordinary @value{GDBN} packets. A notification's @var{data}
38935 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38936 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38937 to acknowledge the notification's receipt or to report its corruption.
38939 Every notification's @var{data} begins with a name, which contains no
38940 colon characters, followed by a colon character.
38942 Recipients should silently ignore corrupted notifications and
38943 notifications they do not understand. Recipients should restart
38944 timeout periods on receipt of a well-formed notification, whether or
38945 not they understand it.
38947 Senders should only send the notifications described here when this
38948 protocol description specifies that they are permitted. In the
38949 future, we may extend the protocol to permit existing notifications in
38950 new contexts; this rule helps older senders avoid confusing newer
38953 (Older versions of @value{GDBN} ignore bytes received until they see
38954 the @samp{$} byte that begins an ordinary packet, so new stubs may
38955 transmit notifications without fear of confusing older clients. There
38956 are no notifications defined for @value{GDBN} to send at the moment, but we
38957 assume that most older stubs would ignore them, as well.)
38959 Each notification is comprised of three parts:
38961 @item @var{name}:@var{event}
38962 The notification packet is sent by the side that initiates the
38963 exchange (currently, only the stub does that), with @var{event}
38964 carrying the specific information about the notification.
38965 @var{name} is the name of the notification.
38967 The acknowledge sent by the other side, usually @value{GDBN}, to
38968 acknowledge the exchange and request the event.
38971 The purpose of an asynchronous notification mechanism is to report to
38972 @value{GDBN} that something interesting happened in the remote stub.
38974 The remote stub may send notification @var{name}:@var{event}
38975 at any time, but @value{GDBN} acknowledges the notification when
38976 appropriate. The notification event is pending before @value{GDBN}
38977 acknowledges. Only one notification at a time may be pending; if
38978 additional events occur before @value{GDBN} has acknowledged the
38979 previous notification, they must be queued by the stub for later
38980 synchronous transmission in response to @var{ack} packets from
38981 @value{GDBN}. Because the notification mechanism is unreliable,
38982 the stub is permitted to resend a notification if it believes
38983 @value{GDBN} may not have received it.
38985 Specifically, notifications may appear when @value{GDBN} is not
38986 otherwise reading input from the stub, or when @value{GDBN} is
38987 expecting to read a normal synchronous response or a
38988 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38989 Notification packets are distinct from any other communication from
38990 the stub so there is no ambiguity.
38992 After receiving a notification, @value{GDBN} shall acknowledge it by
38993 sending a @var{ack} packet as a regular, synchronous request to the
38994 stub. Such acknowledgment is not required to happen immediately, as
38995 @value{GDBN} is permitted to send other, unrelated packets to the
38996 stub first, which the stub should process normally.
38998 Upon receiving a @var{ack} packet, if the stub has other queued
38999 events to report to @value{GDBN}, it shall respond by sending a
39000 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39001 packet to solicit further responses; again, it is permitted to send
39002 other, unrelated packets as well which the stub should process
39005 If the stub receives a @var{ack} packet and there are no additional
39006 @var{event} to report, the stub shall return an @samp{OK} response.
39007 At this point, @value{GDBN} has finished processing a notification
39008 and the stub has completed sending any queued events. @value{GDBN}
39009 won't accept any new notifications until the final @samp{OK} is
39010 received . If further notification events occur, the stub shall send
39011 a new notification, @value{GDBN} shall accept the notification, and
39012 the process shall be repeated.
39014 The process of asynchronous notification can be illustrated by the
39017 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39020 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39022 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39027 The following notifications are defined:
39028 @multitable @columnfractions 0.12 0.12 0.38 0.38
39037 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39038 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39039 for information on how these notifications are acknowledged by
39041 @tab Report an asynchronous stop event in non-stop mode.
39045 @node Remote Non-Stop
39046 @section Remote Protocol Support for Non-Stop Mode
39048 @value{GDBN}'s remote protocol supports non-stop debugging of
39049 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39050 supports non-stop mode, it should report that to @value{GDBN} by including
39051 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39053 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39054 establishing a new connection with the stub. Entering non-stop mode
39055 does not alter the state of any currently-running threads, but targets
39056 must stop all threads in any already-attached processes when entering
39057 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39058 probe the target state after a mode change.
39060 In non-stop mode, when an attached process encounters an event that
39061 would otherwise be reported with a stop reply, it uses the
39062 asynchronous notification mechanism (@pxref{Notification Packets}) to
39063 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39064 in all processes are stopped when a stop reply is sent, in non-stop
39065 mode only the thread reporting the stop event is stopped. That is,
39066 when reporting a @samp{S} or @samp{T} response to indicate completion
39067 of a step operation, hitting a breakpoint, or a fault, only the
39068 affected thread is stopped; any other still-running threads continue
39069 to run. When reporting a @samp{W} or @samp{X} response, all running
39070 threads belonging to other attached processes continue to run.
39072 In non-stop mode, the target shall respond to the @samp{?} packet as
39073 follows. First, any incomplete stop reply notification/@samp{vStopped}
39074 sequence in progress is abandoned. The target must begin a new
39075 sequence reporting stop events for all stopped threads, whether or not
39076 it has previously reported those events to @value{GDBN}. The first
39077 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39078 subsequent stop replies are sent as responses to @samp{vStopped} packets
39079 using the mechanism described above. The target must not send
39080 asynchronous stop reply notifications until the sequence is complete.
39081 If all threads are running when the target receives the @samp{?} packet,
39082 or if the target is not attached to any process, it shall respond
39085 @node Packet Acknowledgment
39086 @section Packet Acknowledgment
39088 @cindex acknowledgment, for @value{GDBN} remote
39089 @cindex packet acknowledgment, for @value{GDBN} remote
39090 By default, when either the host or the target machine receives a packet,
39091 the first response expected is an acknowledgment: either @samp{+} (to indicate
39092 the package was received correctly) or @samp{-} (to request retransmission).
39093 This mechanism allows the @value{GDBN} remote protocol to operate over
39094 unreliable transport mechanisms, such as a serial line.
39096 In cases where the transport mechanism is itself reliable (such as a pipe or
39097 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39098 It may be desirable to disable them in that case to reduce communication
39099 overhead, or for other reasons. This can be accomplished by means of the
39100 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39102 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39103 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39104 and response format still includes the normal checksum, as described in
39105 @ref{Overview}, but the checksum may be ignored by the receiver.
39107 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39108 no-acknowledgment mode, it should report that to @value{GDBN}
39109 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39110 @pxref{qSupported}.
39111 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39112 disabled via the @code{set remote noack-packet off} command
39113 (@pxref{Remote Configuration}),
39114 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39115 Only then may the stub actually turn off packet acknowledgments.
39116 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39117 response, which can be safely ignored by the stub.
39119 Note that @code{set remote noack-packet} command only affects negotiation
39120 between @value{GDBN} and the stub when subsequent connections are made;
39121 it does not affect the protocol acknowledgment state for any current
39123 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39124 new connection is established,
39125 there is also no protocol request to re-enable the acknowledgments
39126 for the current connection, once disabled.
39131 Example sequence of a target being re-started. Notice how the restart
39132 does not get any direct output:
39137 @emph{target restarts}
39140 <- @code{T001:1234123412341234}
39144 Example sequence of a target being stepped by a single instruction:
39147 -> @code{G1445@dots{}}
39152 <- @code{T001:1234123412341234}
39156 <- @code{1455@dots{}}
39160 @node File-I/O Remote Protocol Extension
39161 @section File-I/O Remote Protocol Extension
39162 @cindex File-I/O remote protocol extension
39165 * File-I/O Overview::
39166 * Protocol Basics::
39167 * The F Request Packet::
39168 * The F Reply Packet::
39169 * The Ctrl-C Message::
39171 * List of Supported Calls::
39172 * Protocol-specific Representation of Datatypes::
39174 * File-I/O Examples::
39177 @node File-I/O Overview
39178 @subsection File-I/O Overview
39179 @cindex file-i/o overview
39181 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39182 target to use the host's file system and console I/O to perform various
39183 system calls. System calls on the target system are translated into a
39184 remote protocol packet to the host system, which then performs the needed
39185 actions and returns a response packet to the target system.
39186 This simulates file system operations even on targets that lack file systems.
39188 The protocol is defined to be independent of both the host and target systems.
39189 It uses its own internal representation of datatypes and values. Both
39190 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39191 translating the system-dependent value representations into the internal
39192 protocol representations when data is transmitted.
39194 The communication is synchronous. A system call is possible only when
39195 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39196 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39197 the target is stopped to allow deterministic access to the target's
39198 memory. Therefore File-I/O is not interruptible by target signals. On
39199 the other hand, it is possible to interrupt File-I/O by a user interrupt
39200 (@samp{Ctrl-C}) within @value{GDBN}.
39202 The target's request to perform a host system call does not finish
39203 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39204 after finishing the system call, the target returns to continuing the
39205 previous activity (continue, step). No additional continue or step
39206 request from @value{GDBN} is required.
39209 (@value{GDBP}) continue
39210 <- target requests 'system call X'
39211 target is stopped, @value{GDBN} executes system call
39212 -> @value{GDBN} returns result
39213 ... target continues, @value{GDBN} returns to wait for the target
39214 <- target hits breakpoint and sends a Txx packet
39217 The protocol only supports I/O on the console and to regular files on
39218 the host file system. Character or block special devices, pipes,
39219 named pipes, sockets or any other communication method on the host
39220 system are not supported by this protocol.
39222 File I/O is not supported in non-stop mode.
39224 @node Protocol Basics
39225 @subsection Protocol Basics
39226 @cindex protocol basics, file-i/o
39228 The File-I/O protocol uses the @code{F} packet as the request as well
39229 as reply packet. Since a File-I/O system call can only occur when
39230 @value{GDBN} is waiting for a response from the continuing or stepping target,
39231 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39232 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39233 This @code{F} packet contains all information needed to allow @value{GDBN}
39234 to call the appropriate host system call:
39238 A unique identifier for the requested system call.
39241 All parameters to the system call. Pointers are given as addresses
39242 in the target memory address space. Pointers to strings are given as
39243 pointer/length pair. Numerical values are given as they are.
39244 Numerical control flags are given in a protocol-specific representation.
39248 At this point, @value{GDBN} has to perform the following actions.
39252 If the parameters include pointer values to data needed as input to a
39253 system call, @value{GDBN} requests this data from the target with a
39254 standard @code{m} packet request. This additional communication has to be
39255 expected by the target implementation and is handled as any other @code{m}
39259 @value{GDBN} translates all value from protocol representation to host
39260 representation as needed. Datatypes are coerced into the host types.
39263 @value{GDBN} calls the system call.
39266 It then coerces datatypes back to protocol representation.
39269 If the system call is expected to return data in buffer space specified
39270 by pointer parameters to the call, the data is transmitted to the
39271 target using a @code{M} or @code{X} packet. This packet has to be expected
39272 by the target implementation and is handled as any other @code{M} or @code{X}
39277 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39278 necessary information for the target to continue. This at least contains
39285 @code{errno}, if has been changed by the system call.
39292 After having done the needed type and value coercion, the target continues
39293 the latest continue or step action.
39295 @node The F Request Packet
39296 @subsection The @code{F} Request Packet
39297 @cindex file-i/o request packet
39298 @cindex @code{F} request packet
39300 The @code{F} request packet has the following format:
39303 @item F@var{call-id},@var{parameter@dots{}}
39305 @var{call-id} is the identifier to indicate the host system call to be called.
39306 This is just the name of the function.
39308 @var{parameter@dots{}} are the parameters to the system call.
39309 Parameters are hexadecimal integer values, either the actual values in case
39310 of scalar datatypes, pointers to target buffer space in case of compound
39311 datatypes and unspecified memory areas, or pointer/length pairs in case
39312 of string parameters. These are appended to the @var{call-id} as a
39313 comma-delimited list. All values are transmitted in ASCII
39314 string representation, pointer/length pairs separated by a slash.
39320 @node The F Reply Packet
39321 @subsection The @code{F} Reply Packet
39322 @cindex file-i/o reply packet
39323 @cindex @code{F} reply packet
39325 The @code{F} reply packet has the following format:
39329 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39331 @var{retcode} is the return code of the system call as hexadecimal value.
39333 @var{errno} is the @code{errno} set by the call, in protocol-specific
39335 This parameter can be omitted if the call was successful.
39337 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39338 case, @var{errno} must be sent as well, even if the call was successful.
39339 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39346 or, if the call was interrupted before the host call has been performed:
39353 assuming 4 is the protocol-specific representation of @code{EINTR}.
39358 @node The Ctrl-C Message
39359 @subsection The @samp{Ctrl-C} Message
39360 @cindex ctrl-c message, in file-i/o protocol
39362 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39363 reply packet (@pxref{The F Reply Packet}),
39364 the target should behave as if it had
39365 gotten a break message. The meaning for the target is ``system call
39366 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39367 (as with a break message) and return to @value{GDBN} with a @code{T02}
39370 It's important for the target to know in which
39371 state the system call was interrupted. There are two possible cases:
39375 The system call hasn't been performed on the host yet.
39378 The system call on the host has been finished.
39382 These two states can be distinguished by the target by the value of the
39383 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39384 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39385 on POSIX systems. In any other case, the target may presume that the
39386 system call has been finished --- successfully or not --- and should behave
39387 as if the break message arrived right after the system call.
39389 @value{GDBN} must behave reliably. If the system call has not been called
39390 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39391 @code{errno} in the packet. If the system call on the host has been finished
39392 before the user requests a break, the full action must be finished by
39393 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39394 The @code{F} packet may only be sent when either nothing has happened
39395 or the full action has been completed.
39398 @subsection Console I/O
39399 @cindex console i/o as part of file-i/o
39401 By default and if not explicitly closed by the target system, the file
39402 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39403 on the @value{GDBN} console is handled as any other file output operation
39404 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39405 by @value{GDBN} so that after the target read request from file descriptor
39406 0 all following typing is buffered until either one of the following
39411 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39413 system call is treated as finished.
39416 The user presses @key{RET}. This is treated as end of input with a trailing
39420 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39421 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39425 If the user has typed more characters than fit in the buffer given to
39426 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39427 either another @code{read(0, @dots{})} is requested by the target, or debugging
39428 is stopped at the user's request.
39431 @node List of Supported Calls
39432 @subsection List of Supported Calls
39433 @cindex list of supported file-i/o calls
39450 @unnumberedsubsubsec open
39451 @cindex open, file-i/o system call
39456 int open(const char *pathname, int flags);
39457 int open(const char *pathname, int flags, mode_t mode);
39461 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39464 @var{flags} is the bitwise @code{OR} of the following values:
39468 If the file does not exist it will be created. The host
39469 rules apply as far as file ownership and time stamps
39473 When used with @code{O_CREAT}, if the file already exists it is
39474 an error and open() fails.
39477 If the file already exists and the open mode allows
39478 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39479 truncated to zero length.
39482 The file is opened in append mode.
39485 The file is opened for reading only.
39488 The file is opened for writing only.
39491 The file is opened for reading and writing.
39495 Other bits are silently ignored.
39499 @var{mode} is the bitwise @code{OR} of the following values:
39503 User has read permission.
39506 User has write permission.
39509 Group has read permission.
39512 Group has write permission.
39515 Others have read permission.
39518 Others have write permission.
39522 Other bits are silently ignored.
39525 @item Return value:
39526 @code{open} returns the new file descriptor or -1 if an error
39533 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39536 @var{pathname} refers to a directory.
39539 The requested access is not allowed.
39542 @var{pathname} was too long.
39545 A directory component in @var{pathname} does not exist.
39548 @var{pathname} refers to a device, pipe, named pipe or socket.
39551 @var{pathname} refers to a file on a read-only filesystem and
39552 write access was requested.
39555 @var{pathname} is an invalid pointer value.
39558 No space on device to create the file.
39561 The process already has the maximum number of files open.
39564 The limit on the total number of files open on the system
39568 The call was interrupted by the user.
39574 @unnumberedsubsubsec close
39575 @cindex close, file-i/o system call
39584 @samp{Fclose,@var{fd}}
39586 @item Return value:
39587 @code{close} returns zero on success, or -1 if an error occurred.
39593 @var{fd} isn't a valid open file descriptor.
39596 The call was interrupted by the user.
39602 @unnumberedsubsubsec read
39603 @cindex read, file-i/o system call
39608 int read(int fd, void *buf, unsigned int count);
39612 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39614 @item Return value:
39615 On success, the number of bytes read is returned.
39616 Zero indicates end of file. If count is zero, read
39617 returns zero as well. On error, -1 is returned.
39623 @var{fd} is not a valid file descriptor or is not open for
39627 @var{bufptr} is an invalid pointer value.
39630 The call was interrupted by the user.
39636 @unnumberedsubsubsec write
39637 @cindex write, file-i/o system call
39642 int write(int fd, const void *buf, unsigned int count);
39646 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39648 @item Return value:
39649 On success, the number of bytes written are returned.
39650 Zero indicates nothing was written. On error, -1
39657 @var{fd} is not a valid file descriptor or is not open for
39661 @var{bufptr} is an invalid pointer value.
39664 An attempt was made to write a file that exceeds the
39665 host-specific maximum file size allowed.
39668 No space on device to write the data.
39671 The call was interrupted by the user.
39677 @unnumberedsubsubsec lseek
39678 @cindex lseek, file-i/o system call
39683 long lseek (int fd, long offset, int flag);
39687 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39689 @var{flag} is one of:
39693 The offset is set to @var{offset} bytes.
39696 The offset is set to its current location plus @var{offset}
39700 The offset is set to the size of the file plus @var{offset}
39704 @item Return value:
39705 On success, the resulting unsigned offset in bytes from
39706 the beginning of the file is returned. Otherwise, a
39707 value of -1 is returned.
39713 @var{fd} is not a valid open file descriptor.
39716 @var{fd} is associated with the @value{GDBN} console.
39719 @var{flag} is not a proper value.
39722 The call was interrupted by the user.
39728 @unnumberedsubsubsec rename
39729 @cindex rename, file-i/o system call
39734 int rename(const char *oldpath, const char *newpath);
39738 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39740 @item Return value:
39741 On success, zero is returned. On error, -1 is returned.
39747 @var{newpath} is an existing directory, but @var{oldpath} is not a
39751 @var{newpath} is a non-empty directory.
39754 @var{oldpath} or @var{newpath} is a directory that is in use by some
39758 An attempt was made to make a directory a subdirectory
39762 A component used as a directory in @var{oldpath} or new
39763 path is not a directory. Or @var{oldpath} is a directory
39764 and @var{newpath} exists but is not a directory.
39767 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39770 No access to the file or the path of the file.
39774 @var{oldpath} or @var{newpath} was too long.
39777 A directory component in @var{oldpath} or @var{newpath} does not exist.
39780 The file is on a read-only filesystem.
39783 The device containing the file has no room for the new
39787 The call was interrupted by the user.
39793 @unnumberedsubsubsec unlink
39794 @cindex unlink, file-i/o system call
39799 int unlink(const char *pathname);
39803 @samp{Funlink,@var{pathnameptr}/@var{len}}
39805 @item Return value:
39806 On success, zero is returned. On error, -1 is returned.
39812 No access to the file or the path of the file.
39815 The system does not allow unlinking of directories.
39818 The file @var{pathname} cannot be unlinked because it's
39819 being used by another process.
39822 @var{pathnameptr} is an invalid pointer value.
39825 @var{pathname} was too long.
39828 A directory component in @var{pathname} does not exist.
39831 A component of the path is not a directory.
39834 The file is on a read-only filesystem.
39837 The call was interrupted by the user.
39843 @unnumberedsubsubsec stat/fstat
39844 @cindex fstat, file-i/o system call
39845 @cindex stat, file-i/o system call
39850 int stat(const char *pathname, struct stat *buf);
39851 int fstat(int fd, struct stat *buf);
39855 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39856 @samp{Ffstat,@var{fd},@var{bufptr}}
39858 @item Return value:
39859 On success, zero is returned. On error, -1 is returned.
39865 @var{fd} is not a valid open file.
39868 A directory component in @var{pathname} does not exist or the
39869 path is an empty string.
39872 A component of the path is not a directory.
39875 @var{pathnameptr} is an invalid pointer value.
39878 No access to the file or the path of the file.
39881 @var{pathname} was too long.
39884 The call was interrupted by the user.
39890 @unnumberedsubsubsec gettimeofday
39891 @cindex gettimeofday, file-i/o system call
39896 int gettimeofday(struct timeval *tv, void *tz);
39900 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39902 @item Return value:
39903 On success, 0 is returned, -1 otherwise.
39909 @var{tz} is a non-NULL pointer.
39912 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39918 @unnumberedsubsubsec isatty
39919 @cindex isatty, file-i/o system call
39924 int isatty(int fd);
39928 @samp{Fisatty,@var{fd}}
39930 @item Return value:
39931 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39937 The call was interrupted by the user.
39942 Note that the @code{isatty} call is treated as a special case: it returns
39943 1 to the target if the file descriptor is attached
39944 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39945 would require implementing @code{ioctl} and would be more complex than
39950 @unnumberedsubsubsec system
39951 @cindex system, file-i/o system call
39956 int system(const char *command);
39960 @samp{Fsystem,@var{commandptr}/@var{len}}
39962 @item Return value:
39963 If @var{len} is zero, the return value indicates whether a shell is
39964 available. A zero return value indicates a shell is not available.
39965 For non-zero @var{len}, the value returned is -1 on error and the
39966 return status of the command otherwise. Only the exit status of the
39967 command is returned, which is extracted from the host's @code{system}
39968 return value by calling @code{WEXITSTATUS(retval)}. In case
39969 @file{/bin/sh} could not be executed, 127 is returned.
39975 The call was interrupted by the user.
39980 @value{GDBN} takes over the full task of calling the necessary host calls
39981 to perform the @code{system} call. The return value of @code{system} on
39982 the host is simplified before it's returned
39983 to the target. Any termination signal information from the child process
39984 is discarded, and the return value consists
39985 entirely of the exit status of the called command.
39987 Due to security concerns, the @code{system} call is by default refused
39988 by @value{GDBN}. The user has to allow this call explicitly with the
39989 @code{set remote system-call-allowed 1} command.
39992 @item set remote system-call-allowed
39993 @kindex set remote system-call-allowed
39994 Control whether to allow the @code{system} calls in the File I/O
39995 protocol for the remote target. The default is zero (disabled).
39997 @item show remote system-call-allowed
39998 @kindex show remote system-call-allowed
39999 Show whether the @code{system} calls are allowed in the File I/O
40003 @node Protocol-specific Representation of Datatypes
40004 @subsection Protocol-specific Representation of Datatypes
40005 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40008 * Integral Datatypes::
40010 * Memory Transfer::
40015 @node Integral Datatypes
40016 @unnumberedsubsubsec Integral Datatypes
40017 @cindex integral datatypes, in file-i/o protocol
40019 The integral datatypes used in the system calls are @code{int},
40020 @code{unsigned int}, @code{long}, @code{unsigned long},
40021 @code{mode_t}, and @code{time_t}.
40023 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40024 implemented as 32 bit values in this protocol.
40026 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40028 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40029 in @file{limits.h}) to allow range checking on host and target.
40031 @code{time_t} datatypes are defined as seconds since the Epoch.
40033 All integral datatypes transferred as part of a memory read or write of a
40034 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40037 @node Pointer Values
40038 @unnumberedsubsubsec Pointer Values
40039 @cindex pointer values, in file-i/o protocol
40041 Pointers to target data are transmitted as they are. An exception
40042 is made for pointers to buffers for which the length isn't
40043 transmitted as part of the function call, namely strings. Strings
40044 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40051 which is a pointer to data of length 18 bytes at position 0x1aaf.
40052 The length is defined as the full string length in bytes, including
40053 the trailing null byte. For example, the string @code{"hello world"}
40054 at address 0x123456 is transmitted as
40060 @node Memory Transfer
40061 @unnumberedsubsubsec Memory Transfer
40062 @cindex memory transfer, in file-i/o protocol
40064 Structured data which is transferred using a memory read or write (for
40065 example, a @code{struct stat}) is expected to be in a protocol-specific format
40066 with all scalar multibyte datatypes being big endian. Translation to
40067 this representation needs to be done both by the target before the @code{F}
40068 packet is sent, and by @value{GDBN} before
40069 it transfers memory to the target. Transferred pointers to structured
40070 data should point to the already-coerced data at any time.
40074 @unnumberedsubsubsec struct stat
40075 @cindex struct stat, in file-i/o protocol
40077 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40078 is defined as follows:
40082 unsigned int st_dev; /* device */
40083 unsigned int st_ino; /* inode */
40084 mode_t st_mode; /* protection */
40085 unsigned int st_nlink; /* number of hard links */
40086 unsigned int st_uid; /* user ID of owner */
40087 unsigned int st_gid; /* group ID of owner */
40088 unsigned int st_rdev; /* device type (if inode device) */
40089 unsigned long st_size; /* total size, in bytes */
40090 unsigned long st_blksize; /* blocksize for filesystem I/O */
40091 unsigned long st_blocks; /* number of blocks allocated */
40092 time_t st_atime; /* time of last access */
40093 time_t st_mtime; /* time of last modification */
40094 time_t st_ctime; /* time of last change */
40098 The integral datatypes conform to the definitions given in the
40099 appropriate section (see @ref{Integral Datatypes}, for details) so this
40100 structure is of size 64 bytes.
40102 The values of several fields have a restricted meaning and/or
40108 A value of 0 represents a file, 1 the console.
40111 No valid meaning for the target. Transmitted unchanged.
40114 Valid mode bits are described in @ref{Constants}. Any other
40115 bits have currently no meaning for the target.
40120 No valid meaning for the target. Transmitted unchanged.
40125 These values have a host and file system dependent
40126 accuracy. Especially on Windows hosts, the file system may not
40127 support exact timing values.
40130 The target gets a @code{struct stat} of the above representation and is
40131 responsible for coercing it to the target representation before
40134 Note that due to size differences between the host, target, and protocol
40135 representations of @code{struct stat} members, these members could eventually
40136 get truncated on the target.
40138 @node struct timeval
40139 @unnumberedsubsubsec struct timeval
40140 @cindex struct timeval, in file-i/o protocol
40142 The buffer of type @code{struct timeval} used by the File-I/O protocol
40143 is defined as follows:
40147 time_t tv_sec; /* second */
40148 long tv_usec; /* microsecond */
40152 The integral datatypes conform to the definitions given in the
40153 appropriate section (see @ref{Integral Datatypes}, for details) so this
40154 structure is of size 8 bytes.
40157 @subsection Constants
40158 @cindex constants, in file-i/o protocol
40160 The following values are used for the constants inside of the
40161 protocol. @value{GDBN} and target are responsible for translating these
40162 values before and after the call as needed.
40173 @unnumberedsubsubsec Open Flags
40174 @cindex open flags, in file-i/o protocol
40176 All values are given in hexadecimal representation.
40188 @node mode_t Values
40189 @unnumberedsubsubsec mode_t Values
40190 @cindex mode_t values, in file-i/o protocol
40192 All values are given in octal representation.
40209 @unnumberedsubsubsec Errno Values
40210 @cindex errno values, in file-i/o protocol
40212 All values are given in decimal representation.
40237 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40238 any error value not in the list of supported error numbers.
40241 @unnumberedsubsubsec Lseek Flags
40242 @cindex lseek flags, in file-i/o protocol
40251 @unnumberedsubsubsec Limits
40252 @cindex limits, in file-i/o protocol
40254 All values are given in decimal representation.
40257 INT_MIN -2147483648
40259 UINT_MAX 4294967295
40260 LONG_MIN -9223372036854775808
40261 LONG_MAX 9223372036854775807
40262 ULONG_MAX 18446744073709551615
40265 @node File-I/O Examples
40266 @subsection File-I/O Examples
40267 @cindex file-i/o examples
40269 Example sequence of a write call, file descriptor 3, buffer is at target
40270 address 0x1234, 6 bytes should be written:
40273 <- @code{Fwrite,3,1234,6}
40274 @emph{request memory read from target}
40277 @emph{return "6 bytes written"}
40281 Example sequence of a read call, file descriptor 3, buffer is at target
40282 address 0x1234, 6 bytes should be read:
40285 <- @code{Fread,3,1234,6}
40286 @emph{request memory write to target}
40287 -> @code{X1234,6:XXXXXX}
40288 @emph{return "6 bytes read"}
40292 Example sequence of a read call, call fails on the host due to invalid
40293 file descriptor (@code{EBADF}):
40296 <- @code{Fread,3,1234,6}
40300 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40304 <- @code{Fread,3,1234,6}
40309 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40313 <- @code{Fread,3,1234,6}
40314 -> @code{X1234,6:XXXXXX}
40318 @node Library List Format
40319 @section Library List Format
40320 @cindex library list format, remote protocol
40322 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40323 same process as your application to manage libraries. In this case,
40324 @value{GDBN} can use the loader's symbol table and normal memory
40325 operations to maintain a list of shared libraries. On other
40326 platforms, the operating system manages loaded libraries.
40327 @value{GDBN} can not retrieve the list of currently loaded libraries
40328 through memory operations, so it uses the @samp{qXfer:libraries:read}
40329 packet (@pxref{qXfer library list read}) instead. The remote stub
40330 queries the target's operating system and reports which libraries
40333 The @samp{qXfer:libraries:read} packet returns an XML document which
40334 lists loaded libraries and their offsets. Each library has an
40335 associated name and one or more segment or section base addresses,
40336 which report where the library was loaded in memory.
40338 For the common case of libraries that are fully linked binaries, the
40339 library should have a list of segments. If the target supports
40340 dynamic linking of a relocatable object file, its library XML element
40341 should instead include a list of allocated sections. The segment or
40342 section bases are start addresses, not relocation offsets; they do not
40343 depend on the library's link-time base addresses.
40345 @value{GDBN} must be linked with the Expat library to support XML
40346 library lists. @xref{Expat}.
40348 A simple memory map, with one loaded library relocated by a single
40349 offset, looks like this:
40353 <library name="/lib/libc.so.6">
40354 <segment address="0x10000000"/>
40359 Another simple memory map, with one loaded library with three
40360 allocated sections (.text, .data, .bss), looks like this:
40364 <library name="sharedlib.o">
40365 <section address="0x10000000"/>
40366 <section address="0x20000000"/>
40367 <section address="0x30000000"/>
40372 The format of a library list is described by this DTD:
40375 <!-- library-list: Root element with versioning -->
40376 <!ELEMENT library-list (library)*>
40377 <!ATTLIST library-list version CDATA #FIXED "1.0">
40378 <!ELEMENT library (segment*, section*)>
40379 <!ATTLIST library name CDATA #REQUIRED>
40380 <!ELEMENT segment EMPTY>
40381 <!ATTLIST segment address CDATA #REQUIRED>
40382 <!ELEMENT section EMPTY>
40383 <!ATTLIST section address CDATA #REQUIRED>
40386 In addition, segments and section descriptors cannot be mixed within a
40387 single library element, and you must supply at least one segment or
40388 section for each library.
40390 @node Library List Format for SVR4 Targets
40391 @section Library List Format for SVR4 Targets
40392 @cindex library list format, remote protocol
40394 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40395 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40396 shared libraries. Still a special library list provided by this packet is
40397 more efficient for the @value{GDBN} remote protocol.
40399 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40400 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40401 target, the following parameters are reported:
40405 @code{name}, the absolute file name from the @code{l_name} field of
40406 @code{struct link_map}.
40408 @code{lm} with address of @code{struct link_map} used for TLS
40409 (Thread Local Storage) access.
40411 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40412 @code{struct link_map}. For prelinked libraries this is not an absolute
40413 memory address. It is a displacement of absolute memory address against
40414 address the file was prelinked to during the library load.
40416 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40419 Additionally the single @code{main-lm} attribute specifies address of
40420 @code{struct link_map} used for the main executable. This parameter is used
40421 for TLS access and its presence is optional.
40423 @value{GDBN} must be linked with the Expat library to support XML
40424 SVR4 library lists. @xref{Expat}.
40426 A simple memory map, with two loaded libraries (which do not use prelink),
40430 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40431 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40433 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40435 </library-list-svr>
40438 The format of an SVR4 library list is described by this DTD:
40441 <!-- library-list-svr4: Root element with versioning -->
40442 <!ELEMENT library-list-svr4 (library)*>
40443 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40444 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40445 <!ELEMENT library EMPTY>
40446 <!ATTLIST library name CDATA #REQUIRED>
40447 <!ATTLIST library lm CDATA #REQUIRED>
40448 <!ATTLIST library l_addr CDATA #REQUIRED>
40449 <!ATTLIST library l_ld CDATA #REQUIRED>
40452 @node Memory Map Format
40453 @section Memory Map Format
40454 @cindex memory map format
40456 To be able to write into flash memory, @value{GDBN} needs to obtain a
40457 memory map from the target. This section describes the format of the
40460 The memory map is obtained using the @samp{qXfer:memory-map:read}
40461 (@pxref{qXfer memory map read}) packet and is an XML document that
40462 lists memory regions.
40464 @value{GDBN} must be linked with the Expat library to support XML
40465 memory maps. @xref{Expat}.
40467 The top-level structure of the document is shown below:
40470 <?xml version="1.0"?>
40471 <!DOCTYPE memory-map
40472 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40473 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40479 Each region can be either:
40484 A region of RAM starting at @var{addr} and extending for @var{length}
40488 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40493 A region of read-only memory:
40496 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40501 A region of flash memory, with erasure blocks @var{blocksize}
40505 <memory type="flash" start="@var{addr}" length="@var{length}">
40506 <property name="blocksize">@var{blocksize}</property>
40512 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40513 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40514 packets to write to addresses in such ranges.
40516 The formal DTD for memory map format is given below:
40519 <!-- ................................................... -->
40520 <!-- Memory Map XML DTD ................................ -->
40521 <!-- File: memory-map.dtd .............................. -->
40522 <!-- .................................... .............. -->
40523 <!-- memory-map.dtd -->
40524 <!-- memory-map: Root element with versioning -->
40525 <!ELEMENT memory-map (memory | property)>
40526 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40527 <!ELEMENT memory (property)>
40528 <!-- memory: Specifies a memory region,
40529 and its type, or device. -->
40530 <!ATTLIST memory type CDATA #REQUIRED
40531 start CDATA #REQUIRED
40532 length CDATA #REQUIRED
40533 device CDATA #IMPLIED>
40534 <!-- property: Generic attribute tag -->
40535 <!ELEMENT property (#PCDATA | property)*>
40536 <!ATTLIST property name CDATA #REQUIRED>
40539 @node Thread List Format
40540 @section Thread List Format
40541 @cindex thread list format
40543 To efficiently update the list of threads and their attributes,
40544 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40545 (@pxref{qXfer threads read}) and obtains the XML document with
40546 the following structure:
40549 <?xml version="1.0"?>
40551 <thread id="id" core="0">
40552 ... description ...
40557 Each @samp{thread} element must have the @samp{id} attribute that
40558 identifies the thread (@pxref{thread-id syntax}). The
40559 @samp{core} attribute, if present, specifies which processor core
40560 the thread was last executing on. The content of the of @samp{thread}
40561 element is interpreted as human-readable auxilliary information.
40563 @node Traceframe Info Format
40564 @section Traceframe Info Format
40565 @cindex traceframe info format
40567 To be able to know which objects in the inferior can be examined when
40568 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40569 memory ranges, registers and trace state variables that have been
40570 collected in a traceframe.
40572 This list is obtained using the @samp{qXfer:traceframe-info:read}
40573 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40575 @value{GDBN} must be linked with the Expat library to support XML
40576 traceframe info discovery. @xref{Expat}.
40578 The top-level structure of the document is shown below:
40581 <?xml version="1.0"?>
40582 <!DOCTYPE traceframe-info
40583 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40584 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40590 Each traceframe block can be either:
40595 A region of collected memory starting at @var{addr} and extending for
40596 @var{length} bytes from there:
40599 <memory start="@var{addr}" length="@var{length}"/>
40604 The formal DTD for the traceframe info format is given below:
40607 <!ELEMENT traceframe-info (memory)* >
40608 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40610 <!ELEMENT memory EMPTY>
40611 <!ATTLIST memory start CDATA #REQUIRED
40612 length CDATA #REQUIRED>
40615 @node Branch Trace Format
40616 @section Branch Trace Format
40617 @cindex branch trace format
40619 In order to display the branch trace of an inferior thread,
40620 @value{GDBN} needs to obtain the list of branches. This list is
40621 represented as list of sequential code blocks that are connected via
40622 branches. The code in each block has been executed sequentially.
40624 This list is obtained using the @samp{qXfer:btrace:read}
40625 (@pxref{qXfer btrace read}) packet and is an XML document.
40627 @value{GDBN} must be linked with the Expat library to support XML
40628 traceframe info discovery. @xref{Expat}.
40630 The top-level structure of the document is shown below:
40633 <?xml version="1.0"?>
40635 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40636 "http://sourceware.org/gdb/gdb-btrace.dtd">
40645 A block of sequentially executed instructions starting at @var{begin}
40646 and ending at @var{end}:
40649 <block begin="@var{begin}" end="@var{end}"/>
40654 The formal DTD for the branch trace format is given below:
40657 <!ELEMENT btrace (block)* >
40658 <!ATTLIST btrace version CDATA #FIXED "1.0">
40660 <!ELEMENT block EMPTY>
40661 <!ATTLIST block begin CDATA #REQUIRED
40662 end CDATA #REQUIRED>
40665 @include agentexpr.texi
40667 @node Target Descriptions
40668 @appendix Target Descriptions
40669 @cindex target descriptions
40671 One of the challenges of using @value{GDBN} to debug embedded systems
40672 is that there are so many minor variants of each processor
40673 architecture in use. It is common practice for vendors to start with
40674 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40675 and then make changes to adapt it to a particular market niche. Some
40676 architectures have hundreds of variants, available from dozens of
40677 vendors. This leads to a number of problems:
40681 With so many different customized processors, it is difficult for
40682 the @value{GDBN} maintainers to keep up with the changes.
40684 Since individual variants may have short lifetimes or limited
40685 audiences, it may not be worthwhile to carry information about every
40686 variant in the @value{GDBN} source tree.
40688 When @value{GDBN} does support the architecture of the embedded system
40689 at hand, the task of finding the correct architecture name to give the
40690 @command{set architecture} command can be error-prone.
40693 To address these problems, the @value{GDBN} remote protocol allows a
40694 target system to not only identify itself to @value{GDBN}, but to
40695 actually describe its own features. This lets @value{GDBN} support
40696 processor variants it has never seen before --- to the extent that the
40697 descriptions are accurate, and that @value{GDBN} understands them.
40699 @value{GDBN} must be linked with the Expat library to support XML
40700 target descriptions. @xref{Expat}.
40703 * Retrieving Descriptions:: How descriptions are fetched from a target.
40704 * Target Description Format:: The contents of a target description.
40705 * Predefined Target Types:: Standard types available for target
40707 * Standard Target Features:: Features @value{GDBN} knows about.
40710 @node Retrieving Descriptions
40711 @section Retrieving Descriptions
40713 Target descriptions can be read from the target automatically, or
40714 specified by the user manually. The default behavior is to read the
40715 description from the target. @value{GDBN} retrieves it via the remote
40716 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40717 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40718 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40719 XML document, of the form described in @ref{Target Description
40722 Alternatively, you can specify a file to read for the target description.
40723 If a file is set, the target will not be queried. The commands to
40724 specify a file are:
40727 @cindex set tdesc filename
40728 @item set tdesc filename @var{path}
40729 Read the target description from @var{path}.
40731 @cindex unset tdesc filename
40732 @item unset tdesc filename
40733 Do not read the XML target description from a file. @value{GDBN}
40734 will use the description supplied by the current target.
40736 @cindex show tdesc filename
40737 @item show tdesc filename
40738 Show the filename to read for a target description, if any.
40742 @node Target Description Format
40743 @section Target Description Format
40744 @cindex target descriptions, XML format
40746 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40747 document which complies with the Document Type Definition provided in
40748 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40749 means you can use generally available tools like @command{xmllint} to
40750 check that your feature descriptions are well-formed and valid.
40751 However, to help people unfamiliar with XML write descriptions for
40752 their targets, we also describe the grammar here.
40754 Target descriptions can identify the architecture of the remote target
40755 and (for some architectures) provide information about custom register
40756 sets. They can also identify the OS ABI of the remote target.
40757 @value{GDBN} can use this information to autoconfigure for your
40758 target, or to warn you if you connect to an unsupported target.
40760 Here is a simple target description:
40763 <target version="1.0">
40764 <architecture>i386:x86-64</architecture>
40769 This minimal description only says that the target uses
40770 the x86-64 architecture.
40772 A target description has the following overall form, with [ ] marking
40773 optional elements and @dots{} marking repeatable elements. The elements
40774 are explained further below.
40777 <?xml version="1.0"?>
40778 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40779 <target version="1.0">
40780 @r{[}@var{architecture}@r{]}
40781 @r{[}@var{osabi}@r{]}
40782 @r{[}@var{compatible}@r{]}
40783 @r{[}@var{feature}@dots{}@r{]}
40788 The description is generally insensitive to whitespace and line
40789 breaks, under the usual common-sense rules. The XML version
40790 declaration and document type declaration can generally be omitted
40791 (@value{GDBN} does not require them), but specifying them may be
40792 useful for XML validation tools. The @samp{version} attribute for
40793 @samp{<target>} may also be omitted, but we recommend
40794 including it; if future versions of @value{GDBN} use an incompatible
40795 revision of @file{gdb-target.dtd}, they will detect and report
40796 the version mismatch.
40798 @subsection Inclusion
40799 @cindex target descriptions, inclusion
40802 @cindex <xi:include>
40805 It can sometimes be valuable to split a target description up into
40806 several different annexes, either for organizational purposes, or to
40807 share files between different possible target descriptions. You can
40808 divide a description into multiple files by replacing any element of
40809 the target description with an inclusion directive of the form:
40812 <xi:include href="@var{document}"/>
40816 When @value{GDBN} encounters an element of this form, it will retrieve
40817 the named XML @var{document}, and replace the inclusion directive with
40818 the contents of that document. If the current description was read
40819 using @samp{qXfer}, then so will be the included document;
40820 @var{document} will be interpreted as the name of an annex. If the
40821 current description was read from a file, @value{GDBN} will look for
40822 @var{document} as a file in the same directory where it found the
40823 original description.
40825 @subsection Architecture
40826 @cindex <architecture>
40828 An @samp{<architecture>} element has this form:
40831 <architecture>@var{arch}</architecture>
40834 @var{arch} is one of the architectures from the set accepted by
40835 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40838 @cindex @code{<osabi>}
40840 This optional field was introduced in @value{GDBN} version 7.0.
40841 Previous versions of @value{GDBN} ignore it.
40843 An @samp{<osabi>} element has this form:
40846 <osabi>@var{abi-name}</osabi>
40849 @var{abi-name} is an OS ABI name from the same selection accepted by
40850 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40852 @subsection Compatible Architecture
40853 @cindex @code{<compatible>}
40855 This optional field was introduced in @value{GDBN} version 7.0.
40856 Previous versions of @value{GDBN} ignore it.
40858 A @samp{<compatible>} element has this form:
40861 <compatible>@var{arch}</compatible>
40864 @var{arch} is one of the architectures from the set accepted by
40865 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40867 A @samp{<compatible>} element is used to specify that the target
40868 is able to run binaries in some other than the main target architecture
40869 given by the @samp{<architecture>} element. For example, on the
40870 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40871 or @code{powerpc:common64}, but the system is able to run binaries
40872 in the @code{spu} architecture as well. The way to describe this
40873 capability with @samp{<compatible>} is as follows:
40876 <architecture>powerpc:common</architecture>
40877 <compatible>spu</compatible>
40880 @subsection Features
40883 Each @samp{<feature>} describes some logical portion of the target
40884 system. Features are currently used to describe available CPU
40885 registers and the types of their contents. A @samp{<feature>} element
40889 <feature name="@var{name}">
40890 @r{[}@var{type}@dots{}@r{]}
40896 Each feature's name should be unique within the description. The name
40897 of a feature does not matter unless @value{GDBN} has some special
40898 knowledge of the contents of that feature; if it does, the feature
40899 should have its standard name. @xref{Standard Target Features}.
40903 Any register's value is a collection of bits which @value{GDBN} must
40904 interpret. The default interpretation is a two's complement integer,
40905 but other types can be requested by name in the register description.
40906 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40907 Target Types}), and the description can define additional composite types.
40909 Each type element must have an @samp{id} attribute, which gives
40910 a unique (within the containing @samp{<feature>}) name to the type.
40911 Types must be defined before they are used.
40914 Some targets offer vector registers, which can be treated as arrays
40915 of scalar elements. These types are written as @samp{<vector>} elements,
40916 specifying the array element type, @var{type}, and the number of elements,
40920 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40924 If a register's value is usefully viewed in multiple ways, define it
40925 with a union type containing the useful representations. The
40926 @samp{<union>} element contains one or more @samp{<field>} elements,
40927 each of which has a @var{name} and a @var{type}:
40930 <union id="@var{id}">
40931 <field name="@var{name}" type="@var{type}"/>
40937 If a register's value is composed from several separate values, define
40938 it with a structure type. There are two forms of the @samp{<struct>}
40939 element; a @samp{<struct>} element must either contain only bitfields
40940 or contain no bitfields. If the structure contains only bitfields,
40941 its total size in bytes must be specified, each bitfield must have an
40942 explicit start and end, and bitfields are automatically assigned an
40943 integer type. The field's @var{start} should be less than or
40944 equal to its @var{end}, and zero represents the least significant bit.
40947 <struct id="@var{id}" size="@var{size}">
40948 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40953 If the structure contains no bitfields, then each field has an
40954 explicit type, and no implicit padding is added.
40957 <struct id="@var{id}">
40958 <field name="@var{name}" type="@var{type}"/>
40964 If a register's value is a series of single-bit flags, define it with
40965 a flags type. The @samp{<flags>} element has an explicit @var{size}
40966 and contains one or more @samp{<field>} elements. Each field has a
40967 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40971 <flags id="@var{id}" size="@var{size}">
40972 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40977 @subsection Registers
40980 Each register is represented as an element with this form:
40983 <reg name="@var{name}"
40984 bitsize="@var{size}"
40985 @r{[}regnum="@var{num}"@r{]}
40986 @r{[}save-restore="@var{save-restore}"@r{]}
40987 @r{[}type="@var{type}"@r{]}
40988 @r{[}group="@var{group}"@r{]}/>
40992 The components are as follows:
40997 The register's name; it must be unique within the target description.
41000 The register's size, in bits.
41003 The register's number. If omitted, a register's number is one greater
41004 than that of the previous register (either in the current feature or in
41005 a preceding feature); the first register in the target description
41006 defaults to zero. This register number is used to read or write
41007 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41008 packets, and registers appear in the @code{g} and @code{G} packets
41009 in order of increasing register number.
41012 Whether the register should be preserved across inferior function
41013 calls; this must be either @code{yes} or @code{no}. The default is
41014 @code{yes}, which is appropriate for most registers except for
41015 some system control registers; this is not related to the target's
41019 The type of the register. @var{type} may be a predefined type, a type
41020 defined in the current feature, or one of the special types @code{int}
41021 and @code{float}. @code{int} is an integer type of the correct size
41022 for @var{bitsize}, and @code{float} is a floating point type (in the
41023 architecture's normal floating point format) of the correct size for
41024 @var{bitsize}. The default is @code{int}.
41027 The register group to which this register belongs. @var{group} must
41028 be either @code{general}, @code{float}, or @code{vector}. If no
41029 @var{group} is specified, @value{GDBN} will not display the register
41030 in @code{info registers}.
41034 @node Predefined Target Types
41035 @section Predefined Target Types
41036 @cindex target descriptions, predefined types
41038 Type definitions in the self-description can build up composite types
41039 from basic building blocks, but can not define fundamental types. Instead,
41040 standard identifiers are provided by @value{GDBN} for the fundamental
41041 types. The currently supported types are:
41050 Signed integer types holding the specified number of bits.
41057 Unsigned integer types holding the specified number of bits.
41061 Pointers to unspecified code and data. The program counter and
41062 any dedicated return address register may be marked as code
41063 pointers; printing a code pointer converts it into a symbolic
41064 address. The stack pointer and any dedicated address registers
41065 may be marked as data pointers.
41068 Single precision IEEE floating point.
41071 Double precision IEEE floating point.
41074 The 12-byte extended precision format used by ARM FPA registers.
41077 The 10-byte extended precision format used by x87 registers.
41080 32bit @sc{eflags} register used by x86.
41083 32bit @sc{mxcsr} register used by x86.
41087 @node Standard Target Features
41088 @section Standard Target Features
41089 @cindex target descriptions, standard features
41091 A target description must contain either no registers or all the
41092 target's registers. If the description contains no registers, then
41093 @value{GDBN} will assume a default register layout, selected based on
41094 the architecture. If the description contains any registers, the
41095 default layout will not be used; the standard registers must be
41096 described in the target description, in such a way that @value{GDBN}
41097 can recognize them.
41099 This is accomplished by giving specific names to feature elements
41100 which contain standard registers. @value{GDBN} will look for features
41101 with those names and verify that they contain the expected registers;
41102 if any known feature is missing required registers, or if any required
41103 feature is missing, @value{GDBN} will reject the target
41104 description. You can add additional registers to any of the
41105 standard features --- @value{GDBN} will display them just as if
41106 they were added to an unrecognized feature.
41108 This section lists the known features and their expected contents.
41109 Sample XML documents for these features are included in the
41110 @value{GDBN} source tree, in the directory @file{gdb/features}.
41112 Names recognized by @value{GDBN} should include the name of the
41113 company or organization which selected the name, and the overall
41114 architecture to which the feature applies; so e.g.@: the feature
41115 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41117 The names of registers are not case sensitive for the purpose
41118 of recognizing standard features, but @value{GDBN} will only display
41119 registers using the capitalization used in the description.
41122 * AArch64 Features::
41127 * PowerPC Features::
41132 @node AArch64 Features
41133 @subsection AArch64 Features
41134 @cindex target descriptions, AArch64 features
41136 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41137 targets. It should contain registers @samp{x0} through @samp{x30},
41138 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41140 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41141 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41145 @subsection ARM Features
41146 @cindex target descriptions, ARM features
41148 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41150 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41151 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41153 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41154 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41155 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41158 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41159 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41161 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41162 it should contain at least registers @samp{wR0} through @samp{wR15} and
41163 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41164 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41166 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41167 should contain at least registers @samp{d0} through @samp{d15}. If
41168 they are present, @samp{d16} through @samp{d31} should also be included.
41169 @value{GDBN} will synthesize the single-precision registers from
41170 halves of the double-precision registers.
41172 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41173 need to contain registers; it instructs @value{GDBN} to display the
41174 VFP double-precision registers as vectors and to synthesize the
41175 quad-precision registers from pairs of double-precision registers.
41176 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41177 be present and include 32 double-precision registers.
41179 @node i386 Features
41180 @subsection i386 Features
41181 @cindex target descriptions, i386 features
41183 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41184 targets. It should describe the following registers:
41188 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41190 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41192 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41193 @samp{fs}, @samp{gs}
41195 @samp{st0} through @samp{st7}
41197 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41198 @samp{foseg}, @samp{fooff} and @samp{fop}
41201 The register sets may be different, depending on the target.
41203 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41204 describe registers:
41208 @samp{xmm0} through @samp{xmm7} for i386
41210 @samp{xmm0} through @samp{xmm15} for amd64
41215 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41216 @samp{org.gnu.gdb.i386.sse} feature. It should
41217 describe the upper 128 bits of @sc{ymm} registers:
41221 @samp{ymm0h} through @samp{ymm7h} for i386
41223 @samp{ymm0h} through @samp{ymm15h} for amd64
41226 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41227 describe a single register, @samp{orig_eax}.
41229 @node MIPS Features
41230 @subsection @acronym{MIPS} Features
41231 @cindex target descriptions, @acronym{MIPS} features
41233 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41234 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41235 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41238 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41239 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41240 registers. They may be 32-bit or 64-bit depending on the target.
41242 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41243 it may be optional in a future version of @value{GDBN}. It should
41244 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41245 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41247 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41248 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41249 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41250 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41252 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41253 contain a single register, @samp{restart}, which is used by the
41254 Linux kernel to control restartable syscalls.
41256 @node M68K Features
41257 @subsection M68K Features
41258 @cindex target descriptions, M68K features
41261 @item @samp{org.gnu.gdb.m68k.core}
41262 @itemx @samp{org.gnu.gdb.coldfire.core}
41263 @itemx @samp{org.gnu.gdb.fido.core}
41264 One of those features must be always present.
41265 The feature that is present determines which flavor of m68k is
41266 used. The feature that is present should contain registers
41267 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41268 @samp{sp}, @samp{ps} and @samp{pc}.
41270 @item @samp{org.gnu.gdb.coldfire.fp}
41271 This feature is optional. If present, it should contain registers
41272 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41276 @node PowerPC Features
41277 @subsection PowerPC Features
41278 @cindex target descriptions, PowerPC features
41280 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41281 targets. It should contain registers @samp{r0} through @samp{r31},
41282 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41283 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41285 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41286 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41288 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41289 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41292 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41293 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41294 will combine these registers with the floating point registers
41295 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41296 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41297 through @samp{vs63}, the set of vector registers for POWER7.
41299 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41300 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41301 @samp{spefscr}. SPE targets should provide 32-bit registers in
41302 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41303 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41304 these to present registers @samp{ev0} through @samp{ev31} to the
41307 @node TIC6x Features
41308 @subsection TMS320C6x Features
41309 @cindex target descriptions, TIC6x features
41310 @cindex target descriptions, TMS320C6x features
41311 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41312 targets. It should contain registers @samp{A0} through @samp{A15},
41313 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41315 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41316 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41317 through @samp{B31}.
41319 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41320 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41322 @node Operating System Information
41323 @appendix Operating System Information
41324 @cindex operating system information
41330 Users of @value{GDBN} often wish to obtain information about the state of
41331 the operating system running on the target---for example the list of
41332 processes, or the list of open files. This section describes the
41333 mechanism that makes it possible. This mechanism is similar to the
41334 target features mechanism (@pxref{Target Descriptions}), but focuses
41335 on a different aspect of target.
41337 Operating system information is retrived from the target via the
41338 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41339 read}). The object name in the request should be @samp{osdata}, and
41340 the @var{annex} identifies the data to be fetched.
41343 @appendixsection Process list
41344 @cindex operating system information, process list
41346 When requesting the process list, the @var{annex} field in the
41347 @samp{qXfer} request should be @samp{processes}. The returned data is
41348 an XML document. The formal syntax of this document is defined in
41349 @file{gdb/features/osdata.dtd}.
41351 An example document is:
41354 <?xml version="1.0"?>
41355 <!DOCTYPE target SYSTEM "osdata.dtd">
41356 <osdata type="processes">
41358 <column name="pid">1</column>
41359 <column name="user">root</column>
41360 <column name="command">/sbin/init</column>
41361 <column name="cores">1,2,3</column>
41366 Each item should include a column whose name is @samp{pid}. The value
41367 of that column should identify the process on the target. The
41368 @samp{user} and @samp{command} columns are optional, and will be
41369 displayed by @value{GDBN}. The @samp{cores} column, if present,
41370 should contain a comma-separated list of cores that this process
41371 is running on. Target may provide additional columns,
41372 which @value{GDBN} currently ignores.
41374 @node Trace File Format
41375 @appendix Trace File Format
41376 @cindex trace file format
41378 The trace file comes in three parts: a header, a textual description
41379 section, and a trace frame section with binary data.
41381 The header has the form @code{\x7fTRACE0\n}. The first byte is
41382 @code{0x7f} so as to indicate that the file contains binary data,
41383 while the @code{0} is a version number that may have different values
41386 The description section consists of multiple lines of @sc{ascii} text
41387 separated by newline characters (@code{0xa}). The lines may include a
41388 variety of optional descriptive or context-setting information, such
41389 as tracepoint definitions or register set size. @value{GDBN} will
41390 ignore any line that it does not recognize. An empty line marks the end
41393 @c FIXME add some specific types of data
41395 The trace frame section consists of a number of consecutive frames.
41396 Each frame begins with a two-byte tracepoint number, followed by a
41397 four-byte size giving the amount of data in the frame. The data in
41398 the frame consists of a number of blocks, each introduced by a
41399 character indicating its type (at least register, memory, and trace
41400 state variable). The data in this section is raw binary, not a
41401 hexadecimal or other encoding; its endianness matches the target's
41404 @c FIXME bi-arch may require endianness/arch info in description section
41407 @item R @var{bytes}
41408 Register block. The number and ordering of bytes matches that of a
41409 @code{g} packet in the remote protocol. Note that these are the
41410 actual bytes, in target order and @value{GDBN} register order, not a
41411 hexadecimal encoding.
41413 @item M @var{address} @var{length} @var{bytes}...
41414 Memory block. This is a contiguous block of memory, at the 8-byte
41415 address @var{address}, with a 2-byte length @var{length}, followed by
41416 @var{length} bytes.
41418 @item V @var{number} @var{value}
41419 Trace state variable block. This records the 8-byte signed value
41420 @var{value} of trace state variable numbered @var{number}.
41424 Future enhancements of the trace file format may include additional types
41427 @node Index Section Format
41428 @appendix @code{.gdb_index} section format
41429 @cindex .gdb_index section format
41430 @cindex index section format
41432 This section documents the index section that is created by @code{save
41433 gdb-index} (@pxref{Index Files}). The index section is
41434 DWARF-specific; some knowledge of DWARF is assumed in this
41437 The mapped index file format is designed to be directly
41438 @code{mmap}able on any architecture. In most cases, a datum is
41439 represented using a little-endian 32-bit integer value, called an
41440 @code{offset_type}. Big endian machines must byte-swap the values
41441 before using them. Exceptions to this rule are noted. The data is
41442 laid out such that alignment is always respected.
41444 A mapped index consists of several areas, laid out in order.
41448 The file header. This is a sequence of values, of @code{offset_type}
41449 unless otherwise noted:
41453 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41454 Version 4 uses a different hashing function from versions 5 and 6.
41455 Version 6 includes symbols for inlined functions, whereas versions 4
41456 and 5 do not. Version 7 adds attributes to the CU indices in the
41457 symbol table. Version 8 specifies that symbols from DWARF type units
41458 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41459 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41461 @value{GDBN} will only read version 4, 5, or 6 indices
41462 by specifying @code{set use-deprecated-index-sections on}.
41463 GDB has a workaround for potentially broken version 7 indices so it is
41464 currently not flagged as deprecated.
41467 The offset, from the start of the file, of the CU list.
41470 The offset, from the start of the file, of the types CU list. Note
41471 that this area can be empty, in which case this offset will be equal
41472 to the next offset.
41475 The offset, from the start of the file, of the address area.
41478 The offset, from the start of the file, of the symbol table.
41481 The offset, from the start of the file, of the constant pool.
41485 The CU list. This is a sequence of pairs of 64-bit little-endian
41486 values, sorted by the CU offset. The first element in each pair is
41487 the offset of a CU in the @code{.debug_info} section. The second
41488 element in each pair is the length of that CU. References to a CU
41489 elsewhere in the map are done using a CU index, which is just the
41490 0-based index into this table. Note that if there are type CUs, then
41491 conceptually CUs and type CUs form a single list for the purposes of
41495 The types CU list. This is a sequence of triplets of 64-bit
41496 little-endian values. In a triplet, the first value is the CU offset,
41497 the second value is the type offset in the CU, and the third value is
41498 the type signature. The types CU list is not sorted.
41501 The address area. The address area consists of a sequence of address
41502 entries. Each address entry has three elements:
41506 The low address. This is a 64-bit little-endian value.
41509 The high address. This is a 64-bit little-endian value. Like
41510 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41513 The CU index. This is an @code{offset_type} value.
41517 The symbol table. This is an open-addressed hash table. The size of
41518 the hash table is always a power of 2.
41520 Each slot in the hash table consists of a pair of @code{offset_type}
41521 values. The first value is the offset of the symbol's name in the
41522 constant pool. The second value is the offset of the CU vector in the
41525 If both values are 0, then this slot in the hash table is empty. This
41526 is ok because while 0 is a valid constant pool index, it cannot be a
41527 valid index for both a string and a CU vector.
41529 The hash value for a table entry is computed by applying an
41530 iterative hash function to the symbol's name. Starting with an
41531 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41532 the string is incorporated into the hash using the formula depending on the
41537 The formula is @code{r = r * 67 + c - 113}.
41539 @item Versions 5 to 7
41540 The formula is @code{r = r * 67 + tolower (c) - 113}.
41543 The terminating @samp{\0} is not incorporated into the hash.
41545 The step size used in the hash table is computed via
41546 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41547 value, and @samp{size} is the size of the hash table. The step size
41548 is used to find the next candidate slot when handling a hash
41551 The names of C@t{++} symbols in the hash table are canonicalized. We
41552 don't currently have a simple description of the canonicalization
41553 algorithm; if you intend to create new index sections, you must read
41557 The constant pool. This is simply a bunch of bytes. It is organized
41558 so that alignment is correct: CU vectors are stored first, followed by
41561 A CU vector in the constant pool is a sequence of @code{offset_type}
41562 values. The first value is the number of CU indices in the vector.
41563 Each subsequent value is the index and symbol attributes of a CU in
41564 the CU list. This element in the hash table is used to indicate which
41565 CUs define the symbol and how the symbol is used.
41566 See below for the format of each CU index+attributes entry.
41568 A string in the constant pool is zero-terminated.
41571 Attributes were added to CU index values in @code{.gdb_index} version 7.
41572 If a symbol has multiple uses within a CU then there is one
41573 CU index+attributes value for each use.
41575 The format of each CU index+attributes entry is as follows
41581 This is the index of the CU in the CU list.
41583 These bits are reserved for future purposes and must be zero.
41585 The kind of the symbol in the CU.
41589 This value is reserved and should not be used.
41590 By reserving zero the full @code{offset_type} value is backwards compatible
41591 with previous versions of the index.
41593 The symbol is a type.
41595 The symbol is a variable or an enum value.
41597 The symbol is a function.
41599 Any other kind of symbol.
41601 These values are reserved.
41605 This bit is zero if the value is global and one if it is static.
41607 The determination of whether a symbol is global or static is complicated.
41608 The authorative reference is the file @file{dwarf2read.c} in
41609 @value{GDBN} sources.
41613 This pseudo-code describes the computation of a symbol's kind and
41614 global/static attributes in the index.
41617 is_external = get_attribute (die, DW_AT_external);
41618 language = get_attribute (cu_die, DW_AT_language);
41621 case DW_TAG_typedef:
41622 case DW_TAG_base_type:
41623 case DW_TAG_subrange_type:
41627 case DW_TAG_enumerator:
41629 is_static = (language != CPLUS && language != JAVA);
41631 case DW_TAG_subprogram:
41633 is_static = ! (is_external || language == ADA);
41635 case DW_TAG_constant:
41637 is_static = ! is_external;
41639 case DW_TAG_variable:
41641 is_static = ! is_external;
41643 case DW_TAG_namespace:
41647 case DW_TAG_class_type:
41648 case DW_TAG_interface_type:
41649 case DW_TAG_structure_type:
41650 case DW_TAG_union_type:
41651 case DW_TAG_enumeration_type:
41653 is_static = (language != CPLUS && language != JAVA);
41661 @appendix Manual pages
41665 * gdb man:: The GNU Debugger man page
41666 * gdbserver man:: Remote Server for the GNU Debugger man page
41667 * gcore man:: Generate a core file of a running program
41668 * gdbinit man:: gdbinit scripts
41674 @c man title gdb The GNU Debugger
41676 @c man begin SYNOPSIS gdb
41677 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41678 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41679 [@option{-b}@w{ }@var{bps}]
41680 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41681 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41682 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41683 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41684 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41687 @c man begin DESCRIPTION gdb
41688 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41689 going on ``inside'' another program while it executes -- or what another
41690 program was doing at the moment it crashed.
41692 @value{GDBN} can do four main kinds of things (plus other things in support of
41693 these) to help you catch bugs in the act:
41697 Start your program, specifying anything that might affect its behavior.
41700 Make your program stop on specified conditions.
41703 Examine what has happened, when your program has stopped.
41706 Change things in your program, so you can experiment with correcting the
41707 effects of one bug and go on to learn about another.
41710 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41713 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41714 commands from the terminal until you tell it to exit with the @value{GDBN}
41715 command @code{quit}. You can get online help from @value{GDBN} itself
41716 by using the command @code{help}.
41718 You can run @code{gdb} with no arguments or options; but the most
41719 usual way to start @value{GDBN} is with one argument or two, specifying an
41720 executable program as the argument:
41726 You can also start with both an executable program and a core file specified:
41732 You can, instead, specify a process ID as a second argument, if you want
41733 to debug a running process:
41741 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41742 named @file{1234}; @value{GDBN} does check for a core file first).
41743 With option @option{-p} you can omit the @var{program} filename.
41745 Here are some of the most frequently needed @value{GDBN} commands:
41747 @c pod2man highlights the right hand side of the @item lines.
41749 @item break [@var{file}:]@var{functiop}
41750 Set a breakpoint at @var{function} (in @var{file}).
41752 @item run [@var{arglist}]
41753 Start your program (with @var{arglist}, if specified).
41756 Backtrace: display the program stack.
41758 @item print @var{expr}
41759 Display the value of an expression.
41762 Continue running your program (after stopping, e.g. at a breakpoint).
41765 Execute next program line (after stopping); step @emph{over} any
41766 function calls in the line.
41768 @item edit [@var{file}:]@var{function}
41769 look at the program line where it is presently stopped.
41771 @item list [@var{file}:]@var{function}
41772 type the text of the program in the vicinity of where it is presently stopped.
41775 Execute next program line (after stopping); step @emph{into} any
41776 function calls in the line.
41778 @item help [@var{name}]
41779 Show information about @value{GDBN} command @var{name}, or general information
41780 about using @value{GDBN}.
41783 Exit from @value{GDBN}.
41787 For full details on @value{GDBN},
41788 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41789 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41790 as the @code{gdb} entry in the @code{info} program.
41794 @c man begin OPTIONS gdb
41795 Any arguments other than options specify an executable
41796 file and core file (or process ID); that is, the first argument
41797 encountered with no
41798 associated option flag is equivalent to a @option{-se} option, and the second,
41799 if any, is equivalent to a @option{-c} option if it's the name of a file.
41801 both long and short forms; both are shown here. The long forms are also
41802 recognized if you truncate them, so long as enough of the option is
41803 present to be unambiguous. (If you prefer, you can flag option
41804 arguments with @option{+} rather than @option{-}, though we illustrate the
41805 more usual convention.)
41807 All the options and command line arguments you give are processed
41808 in sequential order. The order makes a difference when the @option{-x}
41814 List all options, with brief explanations.
41816 @item -symbols=@var{file}
41817 @itemx -s @var{file}
41818 Read symbol table from file @var{file}.
41821 Enable writing into executable and core files.
41823 @item -exec=@var{file}
41824 @itemx -e @var{file}
41825 Use file @var{file} as the executable file to execute when
41826 appropriate, and for examining pure data in conjunction with a core
41829 @item -se=@var{file}
41830 Read symbol table from file @var{file} and use it as the executable
41833 @item -core=@var{file}
41834 @itemx -c @var{file}
41835 Use file @var{file} as a core dump to examine.
41837 @item -command=@var{file}
41838 @itemx -x @var{file}
41839 Execute @value{GDBN} commands from file @var{file}.
41841 @item -ex @var{command}
41842 Execute given @value{GDBN} @var{command}.
41844 @item -directory=@var{directory}
41845 @itemx -d @var{directory}
41846 Add @var{directory} to the path to search for source files.
41849 Do not execute commands from @file{~/.gdbinit}.
41853 Do not execute commands from any @file{.gdbinit} initialization files.
41857 ``Quiet''. Do not print the introductory and copyright messages. These
41858 messages are also suppressed in batch mode.
41861 Run in batch mode. Exit with status @code{0} after processing all the command
41862 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41863 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41864 commands in the command files.
41866 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41867 download and run a program on another computer; in order to make this
41868 more useful, the message
41871 Program exited normally.
41875 (which is ordinarily issued whenever a program running under @value{GDBN} control
41876 terminates) is not issued when running in batch mode.
41878 @item -cd=@var{directory}
41879 Run @value{GDBN} using @var{directory} as its working directory,
41880 instead of the current directory.
41884 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41885 @value{GDBN} to output the full file name and line number in a standard,
41886 recognizable fashion each time a stack frame is displayed (which
41887 includes each time the program stops). This recognizable format looks
41888 like two @samp{\032} characters, followed by the file name, line number
41889 and character position separated by colons, and a newline. The
41890 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41891 characters as a signal to display the source code for the frame.
41894 Set the line speed (baud rate or bits per second) of any serial
41895 interface used by @value{GDBN} for remote debugging.
41897 @item -tty=@var{device}
41898 Run using @var{device} for your program's standard input and output.
41902 @c man begin SEEALSO gdb
41904 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41905 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41906 documentation are properly installed at your site, the command
41913 should give you access to the complete manual.
41915 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41916 Richard M. Stallman and Roland H. Pesch, July 1991.
41920 @node gdbserver man
41921 @heading gdbserver man
41923 @c man title gdbserver Remote Server for the GNU Debugger
41925 @c man begin SYNOPSIS gdbserver
41926 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41928 gdbserver --attach @var{comm} @var{pid}
41930 gdbserver --multi @var{comm}
41934 @c man begin DESCRIPTION gdbserver
41935 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41936 than the one which is running the program being debugged.
41939 @subheading Usage (server (target) side)
41942 Usage (server (target) side):
41945 First, you need to have a copy of the program you want to debug put onto
41946 the target system. The program can be stripped to save space if needed, as
41947 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41948 the @value{GDBN} running on the host system.
41950 To use the server, you log on to the target system, and run the @command{gdbserver}
41951 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41952 your program, and (c) its arguments. The general syntax is:
41955 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41958 For example, using a serial port, you might say:
41962 @c @file would wrap it as F</dev/com1>.
41963 target> gdbserver /dev/com1 emacs foo.txt
41966 target> gdbserver @file{/dev/com1} emacs foo.txt
41970 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41971 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41972 waits patiently for the host @value{GDBN} to communicate with it.
41974 To use a TCP connection, you could say:
41977 target> gdbserver host:2345 emacs foo.txt
41980 This says pretty much the same thing as the last example, except that we are
41981 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41982 that we are expecting to see a TCP connection from @code{host} to local TCP port
41983 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41984 want for the port number as long as it does not conflict with any existing TCP
41985 ports on the target system. This same port number must be used in the host
41986 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41987 you chose a port number that conflicts with another service, @command{gdbserver} will
41988 print an error message and exit.
41990 @command{gdbserver} can also attach to running programs.
41991 This is accomplished via the @option{--attach} argument. The syntax is:
41994 target> gdbserver --attach @var{comm} @var{pid}
41997 @var{pid} is the process ID of a currently running process. It isn't
41998 necessary to point @command{gdbserver} at a binary for the running process.
42000 To start @code{gdbserver} without supplying an initial command to run
42001 or process ID to attach, use the @option{--multi} command line option.
42002 In such case you should connect using @kbd{target extended-remote} to start
42003 the program you want to debug.
42006 target> gdbserver --multi @var{comm}
42010 @subheading Usage (host side)
42016 You need an unstripped copy of the target program on your host system, since
42017 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42018 would, with the target program as the first argument. (You may need to use the
42019 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42020 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42021 new command you need to know about is @code{target remote}
42022 (or @code{target extended-remote}). Its argument is either
42023 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42024 descriptor. For example:
42028 @c @file would wrap it as F</dev/ttyb>.
42029 (gdb) target remote /dev/ttyb
42032 (gdb) target remote @file{/dev/ttyb}
42037 communicates with the server via serial line @file{/dev/ttyb}, and:
42040 (gdb) target remote the-target:2345
42044 communicates via a TCP connection to port 2345 on host `the-target', where
42045 you previously started up @command{gdbserver} with the same port number. Note that for
42046 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42047 command, otherwise you may get an error that looks something like
42048 `Connection refused'.
42050 @command{gdbserver} can also debug multiple inferiors at once,
42053 the @value{GDBN} manual in node @code{Inferiors and Programs}
42054 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42057 @ref{Inferiors and Programs}.
42059 In such case use the @code{extended-remote} @value{GDBN} command variant:
42062 (gdb) target extended-remote the-target:2345
42065 The @command{gdbserver} option @option{--multi} may or may not be used in such
42069 @c man begin OPTIONS gdbserver
42070 There are three different modes for invoking @command{gdbserver}:
42075 Debug a specific program specified by its program name:
42078 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42081 The @var{comm} parameter specifies how should the server communicate
42082 with @value{GDBN}; it is either a device name (to use a serial line),
42083 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42084 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42085 debug in @var{prog}. Any remaining arguments will be passed to the
42086 program verbatim. When the program exits, @value{GDBN} will close the
42087 connection, and @code{gdbserver} will exit.
42090 Debug a specific program by specifying the process ID of a running
42094 gdbserver --attach @var{comm} @var{pid}
42097 The @var{comm} parameter is as described above. Supply the process ID
42098 of a running program in @var{pid}; @value{GDBN} will do everything
42099 else. Like with the previous mode, when the process @var{pid} exits,
42100 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42103 Multi-process mode -- debug more than one program/process:
42106 gdbserver --multi @var{comm}
42109 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42110 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42111 close the connection when a process being debugged exits, so you can
42112 debug several processes in the same session.
42115 In each of the modes you may specify these options:
42120 List all options, with brief explanations.
42123 This option causes @command{gdbserver} to print its version number and exit.
42126 @command{gdbserver} will attach to a running program. The syntax is:
42129 target> gdbserver --attach @var{comm} @var{pid}
42132 @var{pid} is the process ID of a currently running process. It isn't
42133 necessary to point @command{gdbserver} at a binary for the running process.
42136 To start @code{gdbserver} without supplying an initial command to run
42137 or process ID to attach, use this command line option.
42138 Then you can connect using @kbd{target extended-remote} and start
42139 the program you want to debug. The syntax is:
42142 target> gdbserver --multi @var{comm}
42146 Instruct @code{gdbserver} to display extra status information about the debugging
42148 This option is intended for @code{gdbserver} development and for bug reports to
42151 @item --remote-debug
42152 Instruct @code{gdbserver} to display remote protocol debug output.
42153 This option is intended for @code{gdbserver} development and for bug reports to
42157 Specify a wrapper to launch programs
42158 for debugging. The option should be followed by the name of the
42159 wrapper, then any command-line arguments to pass to the wrapper, then
42160 @kbd{--} indicating the end of the wrapper arguments.
42163 By default, @command{gdbserver} keeps the listening TCP port open, so that
42164 additional connections are possible. However, if you start @code{gdbserver}
42165 with the @option{--once} option, it will stop listening for any further
42166 connection attempts after connecting to the first @value{GDBN} session.
42168 @c --disable-packet is not documented for users.
42170 @c --disable-randomization and --no-disable-randomization are superseded by
42171 @c QDisableRandomization.
42176 @c man begin SEEALSO gdbserver
42178 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42179 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42180 documentation are properly installed at your site, the command
42186 should give you access to the complete manual.
42188 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42189 Richard M. Stallman and Roland H. Pesch, July 1991.
42196 @c man title gcore Generate a core file of a running program
42199 @c man begin SYNOPSIS gcore
42200 gcore [-o @var{filename}] @var{pid}
42204 @c man begin DESCRIPTION gcore
42205 Generate a core dump of a running program with process ID @var{pid}.
42206 Produced file is equivalent to a kernel produced core file as if the process
42207 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42208 limit). Unlike after a crash, after @command{gcore} the program remains
42209 running without any change.
42212 @c man begin OPTIONS gcore
42214 @item -o @var{filename}
42215 The optional argument
42216 @var{filename} specifies the file name where to put the core dump.
42217 If not specified, the file name defaults to @file{core.@var{pid}},
42218 where @var{pid} is the running program process ID.
42222 @c man begin SEEALSO gcore
42224 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42225 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42226 documentation are properly installed at your site, the command
42233 should give you access to the complete manual.
42235 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42236 Richard M. Stallman and Roland H. Pesch, July 1991.
42243 @c man title gdbinit GDB initialization scripts
42246 @c man begin SYNOPSIS gdbinit
42247 @ifset SYSTEM_GDBINIT
42248 @value{SYSTEM_GDBINIT}
42257 @c man begin DESCRIPTION gdbinit
42258 These files contain @value{GDBN} commands to automatically execute during
42259 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42262 the @value{GDBN} manual in node @code{Sequences}
42263 -- shell command @code{info -f gdb -n Sequences}.
42269 Please read more in
42271 the @value{GDBN} manual in node @code{Startup}
42272 -- shell command @code{info -f gdb -n Startup}.
42279 @ifset SYSTEM_GDBINIT
42280 @item @value{SYSTEM_GDBINIT}
42282 @ifclear SYSTEM_GDBINIT
42283 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42285 System-wide initialization file. It is executed unless user specified
42286 @value{GDBN} option @code{-nx} or @code{-n}.
42289 the @value{GDBN} manual in node @code{System-wide configuration}
42290 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42293 @ref{System-wide configuration}.
42297 User initialization file. It is executed unless user specified
42298 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42301 Initialization file for current directory. It may need to be enabled with
42302 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42305 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42306 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42309 @ref{Init File in the Current Directory}.
42314 @c man begin SEEALSO gdbinit
42316 gdb(1), @code{info -f gdb -n Startup}
42318 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42319 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42320 documentation are properly installed at your site, the command
42326 should give you access to the complete manual.
42328 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42329 Richard M. Stallman and Roland H. Pesch, July 1991.
42335 @node GNU Free Documentation License
42336 @appendix GNU Free Documentation License
42339 @node Concept Index
42340 @unnumbered Concept Index
42344 @node Command and Variable Index
42345 @unnumbered Command, Variable, and Function Index
42350 % I think something like @@colophon should be in texinfo. In the
42352 \long\def\colophon{\hbox to0pt{}\vfill
42353 \centerline{The body of this manual is set in}
42354 \centerline{\fontname\tenrm,}
42355 \centerline{with headings in {\bf\fontname\tenbf}}
42356 \centerline{and examples in {\tt\fontname\tentt}.}
42357 \centerline{{\it\fontname\tenit\/},}
42358 \centerline{{\bf\fontname\tenbf}, and}
42359 \centerline{{\sl\fontname\tensl\/}}
42360 \centerline{are used for emphasis.}\vfill}
42362 % Blame: doc@@cygnus.com, 1991.